Polymeric foams structure-property-performance: a design guide 9781455777556, 1455777552

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PLASTICS DESIGN LIBRARY (PDL) PDL HANDBOOK SERIES Series Editor: Sina Ebnesajjad, PhD ([email protected]) President, FluoroConsultants Group, LLC, Chadds Ford, PA, United States www.FluoroConsultants.com The PDL Handbook Series is aimed at a wide range of engineers and other professionals working in the plastics industry, and related sectors using plastics and adhesives. PDL is a series of data books, reference works and practical guides covering plastics engineering, applications, processing, and manufacturing, and applied aspects of polymer science, elastomers, and adhesives. Recent titles in the series Polymeric Foams Structure-Property-Performance, Obi (ISBN: 9781455777556) Technology and Applications of Polymers Derived From Biomass, Ashter (ISBN: 9780323511155) Fluoropolymer Applications in the Chemical Processing Industries, 2e, Ebnesajjad & Khaladkar (ISBN: 9780323447164) Reactive Polymers, 3e, Fink (ISBN: 9780128145098) Service Life Prediction of Polymers and Plastics Exposed to Outdoor Weathering, White, White & Pickett (ISBN: 9780323497763) Polylactide Foams, Nofar & Park (ISBN: 9780128139912) Designing Successful Products With Plastics, Maclean-Blevins (ISBN: 9780323445016) Waste Management of Marine Plastics Debris, Niaounakis (ISBN: 9780323443548) Film Properties of Plastics and Elastomers, 4e, McKeen (ISBN: 9780128132920) Anticorrosive Rubber Lining, Chandrasekaran (ISBN: 9780323443715) Shape-Memory Polymer Device Design Safranski & Griffis (ISBN: 9780323377973) A Guide to the Manufacture, Performance, and Potential of Plastics in Agriculture, Orzolek (ISBN: 9780081021705) Plastics in Medical Devices for Cardiovascular Applications, Padsalgikar (ISBN: 9780323358859) Industrial Applications of Renewable Plastics, Biron (ISBN: 9780323480659) Permeability Properties of Plastics and Elastomers, 4e, McKeen (ISBN: 9780323508599) Expanded PTFE Applications Handbook, Ebnesajjad (ISBN: 9781437778557) Applied Plastics Engineering Handbook, 2e, Kutz (ISBN: 9780323390408) Modification of Polymer Properties, Jasso-Gastinel & Kenny (ISBN: 9780323443531) The Science and Technology of Flexible Packaging, Morris (ISBN: 9780323242738) Stretch Blow Molding, 3e, Brandau (ISBN: 9780323461771) Chemical Resistance of Engineering Thermoplastics, Baur, Ruhrberg & Woishnis (ISBN: 9780323473576) Chemical Resistance of Commodity Thermoplastics, Baur, Ruhrberg & Woishnis (ISBN: 9780323473583) Color Trends and Selection for Product Design, Becker (ISBN: 9780323393959) Fluoroelastomers Handbook, 2e, Drobny (ISBN: 9780323394802) Introduction to Bioplastics Engineering, Ashter (ISBN: 9780323393966) Multilayer Flexible Packaging, 2e, Wagner, Jr. (ISBN: 9780323371001) Fatigue and Tribological Properties of Plastics and Elastomers, 3e, McKeen (ISBN: 9780323442015) Emerging Trends in Medical Plastic Engineering and Manufacturing, Scho¨nberger & Hoffstetter (ISBN: 9780323370233) Manufacturing and Novel Applications of Multilayer Polymer Films, Langhe & Ponting (ISBN: 9780323371254) PEEK Biomaterials Handbook, 2e, Kurtz (ISBN: 9780128125243) Fluoropolymer Additives, 2e, Ebnesajjad (ISBN: 9780128137840) The Effect of UV Light and Weather on Plastics and Elastomers, 4e, McKeen (ISBN: 9780128164570) To submit a new book proposal for the series, or place an order, please contact Edward Payne, Acquisitions Editor at [email protected]

RECYCLING OF FLEXIBLE PLASTIC PACKAGING Michael Niaounakis

William Andrew is an imprint of Elsevier The Boulevard, Langford Lane, Kidlington, Oxford, OX5 1GB, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States Copyright Ó 2020 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Statement The views and opinions expressed in this book are those of the author and do not represent the views of the European Patent Office (EPO). Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN: 978-0-12-816335-1 For information on all William Andrew publications visit our website at https://www.elsevier.com/books-and-journals Publisher: Matthew Deans Acquisition Editor: Edward Payne Editorial Project Manager: Emily Thomson Production Project Manager: Anitha Sivaraj Cover Designer: Victoria Pearson Typeset by TNQ Technologies

Preface Flexible plastic packaging is the fastest growing segment of packaging worldwide. Its increasing popularity is attributed to the many benefits flexible plastic packaging offers when compared with traditional packaging formats. Flexible plastic packaging extends food shelf life and minimizes spoilage; reduces waste by preserving and protecting products until they are consumed; reduces material use; minimizes overall size and weight; lowers shipping costs; generates less greenhouse gases (GHG) than alternative packaging; provides easy printing; and provides an attractive appearance. Flexible plastic packaging takes the shape of a bag, pouch, liner, or overwrap. Most types of flexible plastic packaging have complex structures (e.g., laminates), such as pouches. Nowadays, pouches are the most preferred format and account for the majority of the flexible plastic packaging. Food is the largest end-use industry accounting for nearly half of the flexible packaging used. Despite all its positive attributes, the disposal of flexible plastic packaging poses a threat to the environment. A substantial amount of flexible plastic packaging materials are made into disposable items, which are typically discarded within a year of manufacture. Most of the discarded flexible packaging ends up in the mainstream of municipal waste and is disposed in a landfill or incinerated. Improperly disposed packaging films and plastic bags often end up in the sea creating an environment menace because of their bulkiness and nonbiodegradability. Negative image publicity with upsetting images of dead marine animals after ingesting or being entangled in plastic packaging debris heightened the awareness of the public about the impacts of plastic packaging on marine life. Current flexible plastic packaging materials are neither sustainable, as they are derived from fossil fuelebased resources, nor recyclable, as most of them are made of multilayer structures (e.g. pouches). Existing lifecycle assessments (LCAs) often ignore disposal of flexible plastic packaging in the environment and pay more attention to GHG emissions than to end-of-life impacts. Among the proposed solutions to tackle the disposal problem of flexible plastic packaging waste is the use of biodegradable plastics, thermal decomposition, and recycling (i.e. recovery of the polymer(s) or monomer(s)). Biodegradable plastics has the potential to improve

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environmental performance, but it might be half the solution because the favorable degradation conditions required for the composting of these materials are not always achieved in the sea and in other natural environments. Thermal decomposition involves pollution risks as result of gas emissions generated during incineration/pyrolysis, while conversion of the plastic waste to fuel has not yet reached optimal reusability. For most applications, recycling seems to be the obvious choice in terms of saving resources and reducing pollution. However, recycling is not without problems. Flexible plastic packaging is usually made of multiple layers. Multilayer packaging is very difficult to recycle because it contains many incompatible polymers. The proposed book aims to give a thorough and detailed presentation of the issues surrounding the management of flexible plastic packaging waste and investigate feasible methods and viable technologies to increase the recycling and diversion of this type of waste from disposal. It provides all the current developments and trends towards a sustainable and recyclable flexible plastic packaging. The book consists of eleven chapters: Chapter 1 gives a general overview of flexible plastic packaging. It also presents the benefits and limitations of flexible plastic packaging as they are reflected in LCA studies. Flexible packaging is also compared with rigid packaging. Emphasis is given to the recycling problem of flexible multilayer plastic packaging. Further, it describes the various options of recycling and the waste management hierarchies used by EU and US EPA. Chapter 2 studies the environmental and socio-economic effects of flexible plastic packaging. At first, the various degradation modes including hydrolytic degradation, thermooxidative degradation, photodegradation, biodegradation, and mechanical degradation by which plastics can be degraded in the environment are presented. Further, the dire consequences that the uncontrolled disposal of flexible plastic packaging can have in land and at sea are discussed. The damages inflicted to marine animals (mammals, turtles, birds, and fishes) by entanglement in and ingestion of plastic packaging debris are also discussed. Finally, the social and economic impacts of plastic packaging litter on to marine ecosystems and various human activities such as fishing and aquaculture, shipping, recreational activities, and tourism are examined. Chapter 3 examines the main polymers used in flexible packaging as films, coatings, sealants, adhesives/tie layers, and inks, in terms of sustainability and recyclability. While there many polymers utilized in the flexible packaging industry, the most common ones are polyolefins,

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including the various types of polyethylene and polypropylene, poly(ethylene terephthalate) and poly(vinyl chloride), and secondarily polyamides, ethylene vinyl alcohol, poly(vinylidene chloride), ethylenevinyl acetate, and ionomers. The used polymers are homopolymers, copolymers, or polymer blends and are usually compounded with various additives (e.g., antioxidants, plasticizers, moisture absorbers, colorants, and the like) to improve certain properties of the flexible packaging materials. Chapter 4 examines the various types, forms, and uses of flexible plastic packaging. The two main types of flexible plastic packaging are single film or monolayer and multilayer packaging. The main forms of flexible plastic packaging are bags, wraps, pouches and sachets, air pillows and envelopes, labels and sleeves, straps, tapes and six pack rings, net bags, and woven bags. Flexible plastic packaging finds multiple uses in food and beverage, cleaning products, pharmaceuticals, medical, personal care and cosmetics, construction and building, e-commerce, and others. Chapter 5 examines the main strategies employed for the collection of flexible plastic packaging. The three main sources of flexible plastic packaging waste are postconsumer (residential or household) derived from residences, postcommercial generated by businesses, and postindustrial generated during processing. Curbside collection is currently the least preferred manner for the collection of flexible packaging materials. Return collection centers or drop-off sites are the principal means for collecting films and bags. A considerable amount of scrap is generated in the course of manufacture of packaging films, such scrap coming from trimming from roll ends (edge trims or off-cuts), film breakages, filling custom orders involving less than the full width of rolls of the film, or rolls out of specification. It is an industry practice to feedback at least part of this type of flexible plastic packaging waste. Reprocessing of scrap film can take place either on the site of film production or at a remote location. Chapter 6 examines the main technologies used for the separation and sorting of flexible plastic packaging in material recovery facilities (MRFs) and/or plastic recovery facilities (PRFs), including manual and vacuumassisted manual sorting, air separators, screens, mainly ballistic screens, grabbers, marking and labeling systems, optical sorters, fluorescent additives, robotic sorters, eddy current separators, volume reduction, and baling. Chapter 7 examines the solvent and/or chemical agent technology for the separation or delamination of multilayer packaging films. Stripping solvents are used for the dissolution or swelling of the interlayer binder

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(tie layer) and separation of the individual layers from a multilayer packaging film and/or chemical agents for the separation or delamination of the aluminum foil from plastic layers. Cleaning systems, which use solvent and/or aqueous surfactant solutions for removing printing inks, film additives, impurities, etc, from flexible plastic packaging waste are also described. Further, selective dissolutionebased processes in organic solvents for the separation of commingled and multilayer postconsumer plastic packaging products, which usually are mixtures of polyolefins, such as polyethylenes, with other polymers are described. Solvent-based recycling is selective for polyolefins and generates pure and high-quality recovered polymers from mixed postconsumer waste. A large number of patents have been disclosed for this technology, which are applicable to both flexible and rigid multilayer plastic packaging. Despite the large number of disclosed patents and research and industrial projects with promising preliminary results, the solvent and/or chemical agent technology is still not commercially used. Chapter 8 examines the main stages of postprocessing of flexible plastic packaging comprising size deduction using shredders and granulators; mechanical cleaning including wet cleaning and dry cleaning for the removal of residual contamination; sorting of the different polymers by density/gravity techniques including float sink, hydrocyclones, and centrifuge; extrusion; blending including compatibilization and solid-state shear pulverization; and compounding. In addition, it describes various recycled products disclosed in patent literature and reviews the available commercial uses of recycled flexible plastic packaging materials. Chapter 9 examines the chemical (or tertiary) plastic recycling technology by which at least one polymer of a plastic article is depolymerized to yield repolymerizable monomers and/or oligomers, which are recovered for producing new polymers. The chemical recycling of polymers aims mainly at saving the material resources and less at reducing the amount of waste generated by slowly degrading polymers. The main types of chemical recycling are solvolysis and thermolysis. A special type of chemical recycling is enzymatic depolymerization. The available processes for the depolymerization of rigid plastic packaging and nonpackaging films (e.g., agricultural films), fibers, foams, etc., can be equally applied to the depolymerization of flexible plastic packaging. Chemical recycling is a promising option to recycle mixed, multilayer, or other complex plastics. However, the technology is still at early stages of development and is not expected to be fully operational before 2025.

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Chapter 10 examines the EU legislation (directives and regulations) related to flexible packaging and packaging waste. It also briefly reviews the legislation and regulative measures taken in selected countries and regions including the United States, the United Kingdom, China, India, and Southeast Asia. The two main frameworks that are applied in the packaging industry for the effective control of waste, namely the Sustainable Materials Management (SMM) and the Circular Economy (CE) are also examined. Further, the Extended Producer Responsibility (EPR) environmental policy approach is discussed, as well the obligations of the producers for the removal of single-use plastic products pursuant to the EPR provisions as described in Directive 2019/904/EU. Another policy framework that is considered is the Corporate Social Responsibility (CSR) that holds accountable the manufacturers of goods that create postconsumer waste. Finally, the various programs, initiatives, and campaigns to raise awareness and encourage consumers to recycle packaging films and plastic bags are presented. Chapter 11 reviews the global market of flexible plastic packaging and the markets of the main types of recycled film. Further, it investigates the main trends toward a sustainable and recyclable flexible plastic packaging including redesign, increase collection, improve sorting, new recycling technologies (e.g. use of compatibilizers, solvent separation and chemical recycling), alternative materials, such as bioplastics, the proposed measures to stimulate the market for recycled flexible packaging, and the four reuse models to reduce the need for single-use packaging. It also presents some legislative initiatives and recommendations for future legislation. Finally, a summary of the major programs/projects and reports for the recycling of flexible plastic packaging is given. In this book, recycling is understood as the recovery of several components from flexible plastic packaging waste by mechanical, physical, chemical, and biological processes or their combination to convert them into monomers, oligomers, and/or polymers, which can be used, optionally in combination with virgin polymers, for the making of new products. Decomposition (or destruction) recovery options such as incineration, pyrolysis, and gasification that convert flexible plastic packaging materials into energy, fuel, or chemicals do not fall under this recycling definition and are commented only in short. Further, agricultural films and their recycling are outside the scope of this book.

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Waste plastic bagsda form of flexible plastic packagingdhave already been dealt in the author’s previous book: “Management of Marine Plastic Debris.” In the present book, only the collection and recycling options of plastic bags are examined. The writing of the book started in late autumn 2017. Till its completion in summer 2019, there were many changes in the waste management of flexible plastic packaging. Sustainable packaging materials, such as bioplastics, gained ground, and there were significant breakthroughs in recycling technologies and the design of recyclable flexible plastic packaging materials. At the same time, there were many coordinated efforts for the efficient collection of large amounts of flexible packaging waste. New legislation addressing the issue of single-use plastic packaging was launched by the EU, namely Directive 2019/904/EU, and regulative measures with far reaching consequences were taken by China and Southeast Asia countries in banning the import of plastic waste. SMM, CE, EPR and CSR are used nowadays for the effective control of flexible packaging waste. Michael Niaounakis July 2019, Rijswijk

1 Flexible Plastic Packaging and Recycling 1.1 Definition of Flexible Packaging The expression “flexible packaging” refers to packaging structures that are capable of being flexed or bent, such that they are pliant and yieldable in response to externally applied forces. Accordingly, the term “flexible” is substantially opposite in meaning to the terms inflexible, rigid, or unyielding. A packaging structure that is flexible, therefore, may be altered in shape to accommodate external forces and to conform to the shape of objects brought into contact with them without losing their integrity. As one of the fastest growing segments of the packaging industry, flexible packaging delivers a broad range of protective properties while employing a minimum amount of material. It typically takes the shape of a bag, pouch, liner, or overwrap.

1.2 Flexible Packaging Categories Flexible packaging is typically described in relation to the type of product being packaged, for example, retail food, medical devices, pharmaceuticals, etc. It can also be categorized by layer/function. It is convenient to categorize packaging by layer or function:
primary packagingdthe material that first envelops the product and is in direct contact with the contents;
secondary packagingdthe material that is outside the primary packaging, often used to group primary packages together. Film wrappers around the primary packaging are examples of secondary packaging; and
tertiary packagingdthe material that is used for bulk handling, warehouse storage, and transport shipping. The most common form is a palletized unit that packs into containers.

Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00001-3 Copyright © 2020 Elsevier Inc. All rights reserved.

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These broad categories are arbitrary. For example, depending on the use, a shrink wrap can be primary packaging when applied directly to the product, secondary packaging when bundling smaller packages, and tertiary packaging on some palletized distribution packs.

1.3 Selection Criteria of Flexible Packaging The main selection criteria for an optimum flexible packaging could be summarized as follows:
product protection (performance)
packaging cost
usage benefits and
environmental impact Flexible packaging protects the enclosed product from damages (breakages, spoilages, contamination), extends shelf/usage life, safeguards hygiene, and provides an attractive appearance. Most flexible packaging has been optimized for minimum material usage for a given functionality. Flexible packaging reduces overall package size and weight, reduces shipping costs, and promotes fitting more products on a delivery truck. In most cases, flexible packaging materials are intended for single use. Flexible packaging can be monolayer, coated monolayer, or multilayer. The layers are different material with specific functions in the structure and can include outer bulk layers, barrier layers, tie layers, and seal layers. Polyethylene, including low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE), is by far the most used polymer in the flexible packaging industry. Other polymers are polypropylene, including cast polypropylene and biaxially oriented polypropylene (BOPP), poly(ethylene terephthalate) (PET), and poly(vinyl chloride) (PVC). Polyethylene gives the packaging its bulk and structural integrity. For tougher packaging, a packaging company might opt for PET. Polyethylene can also be used to seal the package. But often lower melting point ethylene-vinyl acetate (EVA) is the better choice for that. And if the food inside the packaging is greasy, a food company might opt for a higher-end sealant ionomer, such as SurlynÒ (DuPont, ex-Dow). Most food packaging needs a barrier layer to protect against oxygen. Ethylene-vinyl alcohol (EVOH) and poly(vinylidene chloride) (PVDC) are effective in blocking

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oxygen. If even more barrier is needed, a package might incorporate a metallized film [1]. Metalized films provide optimal protection for high oxygen, gas and water vapor barrier levels, aroma, and flavor retention. Metalized films can also provide special optical properties or a metal look for decorative applications. There is demand to replace part of these films, especially those used for packaging goods with a short shelf life (e.g., food packaging, waste bags) with films made of biodegradable polymers. The most commonly used polymers in plastic packaging are made of fossil fuelebased resources and degrade very slowly in the environment. Packaging materials made of biobased polymers address the concerns about depletion of natural resources and greenhouse gas (GHG) generation effects. Bio-based polymers are expecteddonce fully scaled-updto help reduce reliance on fossil fuels, reduce production of GHGs, and be biodegradable or compostable as well. Packaging is the biggest application for bio-based and biodegradable polymers nowadays [2].

1.4 Benefits of Flexible Plastic Packaging The food and beverage market is flexible packaging’s largest end user segment, although healthcare has become the fastest growing. Flexible packaging is used in almost every consumer goods section. The benefits of flexible plastic packaging can be summarized as follows [3]:
Less material needed for production.
Uses less energy to produce and less plastic than rigid containers.
Lighter weight allowing transport of higher volumes of product.
Generates less CO2 during transportation.
Creates less waste and takes up less space in the landfill.
Extends the shelf life of many products, especially food.
Maintains freshness.
Provides efficient product-to-package ratios.
Reduces food waste.
Creates self-appeal.
Enables visibility of the contents.
Easy to open, carry, store, and reseal (convenience).
Extensible into diverse product categories.

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1.5 Flexible Packaging versus Rigid Packaging Consumer, retail, and technology trends have contributed to a gradual replacement of rigid formats by flexible packaging types, mainly pouches, during the last decade. Flexible plastic packaging is widely used instead of (semi-)rigid plastic packaging because of its flexible convenient format, low weight, durability, cost effectiveness, attractiveness, and its easiness to be shaped. In particular, flexible packaging uses less energy and fewer resources, helps extend food shelf life, minimizes spoilage, brings savings in transportation costs and gas emissions, and reduces food waste. To the consumer it takes up less space when empty than rigid packaging [4]. According to the Flexible Packaging Association (FPA), the flexible packaging uses 50% less energy to produce and 60% less plastic than rigid bottles [5] (see Fig. 1.1). With flexible packaging such as pouches, the converting of the pouch generally includes full printing features along with the lamination of the films, if necessary. This printing only marginally increases the cost of the pouch and has no effect on the filling process itself. Printing options for flexible packaging are numerous and can be changed if required. On the other hand, part of the total cost of rigid packaging is the labels, which are applied as part of the filling process. Labels are supplied from a different supplier than the bottles, meaning that they often become a bottleneck in the filling process [7]. Further, flexible packaging can be printed with security or brand identity graphics. This technology includes pigment additives that only appear under certain lighting and inks that disappear and reappear depending on environmental conditions. Such technology is not possible with rigid packaging [7].

50 % less energy in producon

60 % less plasc

68 % decrease in weight of packaging

Figure 1.1 Flexible plastic packaging versus rigid packaging. Courtesy of Enval Ltd., 2019. The Enval process [6].

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One of the main advantages of flexible packaging over rigid packaging is the ability to fine-tune the appropriate barrier level for the product and end use. Bottles made from PET, glass, or multilayer paperboard laminates provide a barrier for all products whether it is required or not. A flexible package can be supplied with barrier properties that can provide anything from moisture and aroma protection to essentially the same barriers as glass [7]. As far as recycling is concerned, the main differences between flexible plastic packaging and rigid plastic packaging can be summarized as follows:
Most households have access to a rigid plastics packaging recovery system (e.g., PET bottles), while similar services for domestic consumers of flexible plastic packaging are still in their infancy [8].
Many municipalities do not accept flexible packaging in curbside recycling bins. Plastic films and bags must be taken to a drop-off location, such as a grocery or other retail store, to be collected for recycling (see also Chapter 5; Section 5.2.2).
Multilayer flexible packaging structures, such as pouches, are not recyclable.
The recycling rate of flexible packaging is less than 1%, while the rigid packaging is around 40% [8].

1.6 Limitations of Flexible Plastic Packaging The most commonly used polymers in plastic packaging are made of fossil fuelebased resources and degrade very slowly in the environment. Unlike rigid plastic packaging (e.g., PET bottles), there is no established recovery facilities for flexible packaging. The lack of recycling infrastructure, largely because of problems of collection, sorting, and recycling of films and multilayer structures, particularly arising from postconsumer waste, is the main limitation of flexible plastic packaging. Actually, lack of recycling is the Achilles’ heel of flexible plastic packaging. The problem of disposal is especially acute with the flexible multilayer packaging waste. Up to date, packaging films can be recovered from plastic waste streams by recycling technologies requiring sorting of the commingled plastic materials. Sorting can require use of costly techniques, such as

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video cameras, electronic devices, infrared detectors, and organic” markers”, to provide effective segregation of like plastics. However, even sorted scrap film can present problems in processing as a result of density and chemical differences among polymers falling in the same general class and made by different plastics manufacturers. Further, sorted scrap film must be subjected to shredding and/or grinding to produce flake scrap material that, then, must be pelletized and ground again to provide powder feedstock for blow molding, rotational molding, extruding, spray coating, and other melt processing techniques that require powder feedstock. The high cost of sorting has greatly limited widespread use of recycling approaches that require a sorting step. In particular, collected and sorted postconsumer plastic materials are usually more expensive than the corresponding virgin plastic materials. Thus, users of plastic materials are discouraged from using sorted, recycled plastic materials. While flexible packaging films are favored by brands for their ability to efficiently transport products with minimal packaging waste, they are rejected by recyclers because of their sorting difficulties at material recovery facilities (MRFs) [9]. Recyclers do not accept postconsumer flexible packaging, due to the fact that 80% of the flexibles are food contaminateddfood waste contamination levels are often 10%e20% of package weightdand as such unsuitable to go into their existing recycling stream as it will contaminate the final recyclate. This contamination makes the recyclate unacceptable for first-grade applications [10]. Further, packaging films have the tendency to get tangled and clogged in the sortation equipment at MRFs (see Chapter 6, Section 6.1).

1.6.1 The Problem of Flexible Multilayer Plastic Packaging Up to today, there is no proper system or technology available for the economical recycling of disposed multilayer flexible packaging [10]. There are several reasons for this:
large variety of materials used for each layer;
large differences in the processing properties of the polymers used for multilayer films;

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lack of systems for identification of multilayer film;
lack of system solutions for the collection of these materials;
lack of economically viable systems of separation of the various materials; and
lack of standard research of the properties, processing, and applications of composites based on recycled multicomponent materials. In principle, it is not the technology that makes it difficult to recycle flexible multilayer packaging, but the selection process. In other words, every single flexible packaging layer has to be analyzed and categorized, separated, and recycled individually to recover a maximum of every component to further convert into a recyclate, which increases the overall recycling cost; especially, the different material components used in flexible pouches makes their recycling practically impossible to implement, too complicated, and too risky in terms of investment [10]. There is as yet no commercial facility in the world that can recycle flexible multilayer packaging or metalized films. For example, while PET recycling industry has been established for several decades and accepted as the most leading recycled material, metalized PET films are discarded as waste and end up in the landfill. Multilayer packaging is composed of a mixture of incompatible polymers and cannot be recompounded without the use of expensive modifiers. In addition to that, the products obtained by recompounding such materials exhibit worse mechanical properties than pure polymers and their compatible polymer blends. The bulk of flexible plastic packaging are printed, labeled, or decorated for providing usage instructions to meeting statutory requirements (labeling, price details, manufacture details, ingredients, trademarks, and safety information among others) or for esthetic, branding, and differentiation reasons. The removal of the inks, adhesives, coatings, or labels used is not an easy task.

1.7 Recycling Recycling refers to the recovery of several components from a waste flexible plastic packaging by mechanical, physical, chemical, and

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biological processes or their combination to convert them into monomers, oligomers, and polymers, which can be used, optionally in combination with virgin polymers, for the making of new products. This process is often, although not quite correctly, called a “cradle-tocradle” recycling. The EU’s waste management hierarchy [11] (Fig. 1.2) places prevention, reuse, and recycling (including composting) clearly above recovery options (e.g. waste to energy and incineration), while waste disposal (e.g. landfilling) is the very last resort. The US EPA waste management hierarchy [12] (Fig. 1.3) places source reduction first and recycling/composting second on its list of preferable waste management strategies. Dumping the flexible plastic packaging waste in landfills is impractical. Plastic waste degrades very slowly and takes up a significant amount of landfill space. Further, the land available for waste disposal is quickly disappearing. Therefore, burying such waste does not significantly contribute to the elimination of disposed plastic packaging products. Incineration is also impractical. It is expensive, and not all of the toxic or near toxic emissions can be captured or scrubbed out of the resulting fumes. This is especially true of packaging materials composed of a variety of different plastics. Beyond the obvious environmental benefits, there are practical gains to companies that recycle flexible packaging films. The removal and recycling of flexible packaging films from the waste stream reduces the volume needed to be taken away from their facility and their waste bill.

Figure 1.2 Waste management hierarchy of the European Union (EU) [11].

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Source Reduction & Reuse

Recycling / composting Energy Recovery

Treatment & Disposal

Figure 1.3 Waste management hierarchy of US Environmental Protection Agency (EPA). Courtesy of United States Environmental Protection Agency (EPA) [13].

Many recycling companies pay for the used packaging film. Flexible packaging film waste takes up less space than other types of packaging such as corrugate paper waste, meaning less frequent deliveries and recycling pickups and, therefore, less transport costs. Because the bulk of plastic packaging is made of polyethylene, which is derived from natural gas, it uses less energy to produce and recycle compared, for example, with corrugate paper [14]. According to the Association of Plastic Recyclers (APR), an item is “recyclable per APR definition” when the following three conditions are met [15]:
at least 60% of consumers or communities have access to a collection system that accepts the item;
the item is most likely sorted correctly into a market-ready bale of a particular plastic meeting industry standard specifications, through commonly used MRFs and plastic recovery facilities (PRFs), including single-stream and dual-stream MRFs’ and PRFs’, systems that handle deposit system containers, grocery store rigid plastic, and film collection systems; and
the item can be further processed through a typical recycling process cost effectively into a postconsumer plastic feedstock suitable for use in identifiable new products.

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According to the Global Plastics Outreach Alliance definition [16], an item is considered recyclable if it meets the following conditions:
the item must be made with a plastic that is collected for recycling, has market value, and/or is supported by a legislatively mandated program;
the item must be sorted and aggregated into defined streams for recycling processes;
the item can be processed and reclaimed/recycled with commercial recycling processes; and
the recycled plastic becomes a raw material that is used in the production of new products. The properties of the discarded plastics are varied widely due to numerous suppliers, each of which uses proprietary additive packages, fillers, etc. It has been established that it is not possible to control the consistency of the discarded feedstocks before recycling. Because mixed (commingled) plastics are incompatible with one another, their reprocessing presents numerous challenges, including phase separation in the melt, delamination of molded parts, and inconsistent color, among others.

1.7.1 Types of Recycling Recycling processes for plastics can be classified in a variety of ways. Depending on the final product (polymer, monomer/oligomer), the recycling processes of plastic waste can be classified into four categories (see Table 1.1). Primary recycling involves the recycling of preconsumer industrial (inplant) plastic scrap (see Chapter 5, Section 5.2.3.1). The recycled scrap or waste is either mixed with virgin plastic or used as second-grade material with less demanding specifications. Secondary recycling involves the recycling of postconsumer and postcommercial plastic waste. Tertiary recycling involves the chemical treatment of plastic waste, whereby the recovered chemical compounds are used for making new polymers (see Chapter 9). Biological recycling involves the depolymerization by enzymes or microorganisms of plastic waste and use of the recovered chemical compounds for making new polymers. Quaternary recycling or energy recovery or valorization is not considered to be true recycling and is outside the scope of the book.

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Table 1.1 Categories of Plastic Waste Recycling Types of Plastic Recycling

Synonyms

Primary recycling

Mechanical recycling Physical reprocessing

Closed-loop recycling

Secondary recycling

Mechanical recycling Physical reprocessing

Downgrading

Tertiary recycling

Chemical recycling  Chemical modification

Feedstock recycling

 Chemical depolymerization Biological recycling

Enzymatic depolymerization

Quaternary recycling

Energy recovery

Valorization

An alternative categorization is mechanical and chemical or feedstock recycling [18]. Mechanical recycling uses mechanical processes to convert the plastic to a useable form, thus encompassing the primary and secondary processes outlined above. In mechanical recycling, plastics stay intact, and this permits, in theory, for multiple reuse of plastics in the same or similar productdeffectively creating a closed-loop. To mechanically recycle postconsumer flexible plastic packaging, the waste has to be collected, separated/sorted, baled, shipped, washed, shredded/ground, and reprocessed before it can be mixed with virgin plastics of the same type for molding new products or used on its own for alternative (usually lower value) products (see Chapters 5, 6, and 8). In practice, the mechanical recycling of the recycled product over repeated cycles downgrades its physical and mechanical properties. When plastic material that has been recycled only once is mixed with virgin plastic, only minor impairments are caused in the film properties. The slight impairments of the film may be compensated by reducing the proportion of plastic material that has been recycled once. Further, there are limitations in the use of recycled polymers in the food contact compliance area where certain end use applications are temperature restricted [19] (see Chapter 10, Section 10.2). When processing biodegradable plastics, special attention must be paid to low and uniform processing temperatures

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(avoiding temperature peaks), increased sensitivity to shearing, and oxidation [20]. Chemical or feedstock recycling is essentially equivalent to tertiary recycling, using the recycled plastic as a chemical raw material, generally for the production of new polymers [18] (see Chapter 9). A special subcategory of chemical recycling can be considered the chemical modification of the polymers of a plastic waste. It can include modification of incompatible polymers with reactive compatibilizers (see Chapter 8, Section 8.7.1.1).

1.8 Life Cycle Analysis The packaging sector is using life cycle assessment (LCA) to evaluate the potential environmental impacts of flexible plastic packaging throughout its life cycle from the production of raw materials to the disposal of finished products. The rules for conducting an LCA analysis are defined by ISO (International Standard Organization) standards 14040 and 14044. From a general LCA perspective, flexible film packaging is a highly efficient form of packagingdeven when it is not able to be recycled, it typically results in less global warming potential, energy use, and quantity landfilled than recyclable rigid package alternatives [21]. Six different LCA case studies, commissioned by the FPA, were developed by PTIS using the EcoImpact-COMPASSÒ LCA software, comparing flexible packaging to other formats across a range of products (see Table 1.2). The case studies included coffee, motor oil, baby food, laundry detergent pods, cat litter, and beverages (single-serve juiceflavored beverages). The results from the case studies showed that flexible plastic packaging has more preferable environmental attributes for carbon impact, fossil fuel usage, water usage, product-to-package ratio, and material to landfill, when compared with other package formats. This is due to the efficient use of resources enabled by flexible packaging. This further supports the close alignment of flexible packaging with Sustainable Materials Management (SMM), which focus on the efficient use of resources, and minimizing associated environmental impacts [13,17,22]. Flexible Packaging Europe (FPE) had a number of full LCA studies carried out by independent third party LCA specialist institutes to evaluate the environmental impacts of flexible packaging in different packed food products [23]. The three main objectives of these studies were to

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Table 1.2 Six Life Cycle Assessment (LCA) Case Studies of Flexible Plastic Packaging Versus Other Packaging Formats [17] Case Study

Formats

Results

Ground coffee

Stand-up flexible pouch Steel can HDPE canister

Stand-up flexible pouch has a number of significant benefits than steel can and HDPE canister. This is attributed mainly to the reduced amount of material being used and the favorable product-to-package ratio. Other general benefits include product protection, brand message, and ease of use

Motor oil

Stand-up pouch with fitment DPE bottle

Large benefit across all SMM attributes for flexible packaging optiondin a new product category.

Baby food

Pouch with fitment Thermoformed tub Glass jar

Flexible packaging offers better environmental attributes than glass and thermoform tub and overall less material to landfill.

Laundry detergent pods

Stand-up pouch with zipper Rigid PET container

Stand-up pouch has a number of significant benefits (fossil fuel usage, carbon impact, water consumption, and municipal solid waste) over the PET rigid container, even when taking the current (Continued)

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Table 1.2 Six Life Cycle Assessment (LCA) Case Studies of Flexible Plastic Packaging Versus Other Packaging Formats [17] (Continued) Case Study

Formats

Results recycling rate of the rigid container into consideration.

Cat litter

Stand-up bag Barrier carton Rigid pail

Stand-up bag has a number of significant benefits (fossil fuel usage, carbon impact, water consumption, and municipal solid waste) over the rigid pail and barrier carton, even when taking the current recycling rate of the rigid container into consideration.

Single-serve juiceflavored beverages

Drink pouch Composite carton PET bottle Aluminum can Glass bottle

Drink pouch has a number of significant benefits (fossil fuel usage, carbon impact, water consumption) over the other formats when considering these environmental indicators. The drink pouch also results in much less municipal solid waste than all of the package formats, except for the aluminum can, which has a slight advantage based on its relatively high recycling rate.

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- understand the environmental impact of flexible packaging with respect to its function within the life cycle of the product; - quantify the contribution of flexible packaging to increasing the use of that resource efficiently, e.g., through the prevention of spoilage of the product and efficient pack design; and - show how flexible packaging adds value by helping consumers to consume more sustainably, e.g., by considering aspects such as consumption occasions and portion sizes and contrasting these benefits with the increase in environmental impact due to the packaging. The packed food products included butter [24], coffee [25], goulash [26], and spinach [27]. The different LCA studies showed that flexible packaging actively contributes to minimizing the overall environmental impact of the product by reducing spoilage, over consumption, and/or by facilitating more sustainable lifestyles [23]. An LCA study compared retort pouches (made from a laminate of flexible plastic and metal foil) and cups to metal cans for the packaging of tuna products. Retort cup system possessed a significant advantage over metal cans and retort pouch systems in terms of overall GHG emissions [28]. In another study, two series of five LCAs corresponding to five EU countries were conducted on three olive packaging solutions: doypacks (sealed plastic bags that are designed to stand upright), glass jars, and steel cans. The environmental performance of each packaging type differs from one country to another. The plastic packaging (nonrenewable and nonrecyclable) has the lowest environmental impact, while glass has the greatest [29]. The evaluation of flexible packaging’s environmental performance usually concentrates on a comparison of different packaging materials or designs. Another important aspect in LCA studies on packaging is the recycling or treatment of packaging waste. LCA studies of packed food include the packaging with specific focus on the contribution of the packaging to the total results. The consumption behavior is often assessed only roughly. Broader approaches, which focus on the life cycle of packed goods, including the entire supply system and the consumption of goods, are necessary to get an environmental footprint of the system with respect to sustainable production and consumption [30]. There is also too much emphasis of LCA on GHG emissions and too little on end-of-life impacts. The result is complex packaging design,

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such as pouches, which cannot be recycled, and end up either in landfills or destined for incineration or disposed in the environment [31]. Existing LCAs often ignore disposal of flexible packaging in the environment. LCAs should consider the waste treatment in the field to develop measures to reduce marine litter and other forms of pollution [31]. LCA should take into account the gained expertise on food waste drivers, as many food waste drivers (e.g., overpurchasing and preparation techniques) are not linked to packaging, and some packaging practices (e.g., trimming and multipacks) can actually increase food waste [32]. The environmental performance of flexible plastic packaging is difficult to ascertain, given the complex trade-offs and competing interests [32]. According to the Australian Packaging Covenant [8], the LCA-related considerations in favor of flexible plastic packaging can be summarized as follows:
Plastic packaging has high strength-to-weight ratio and can provide excellent packaging-to-product weight ratio.
Plastic packaging manufacturing usually generates little solid or liquid waste.
Life cycle studies comparing the use of flexible plastic containers with rigid plastic, fiber, glass, or metal alternatives have found that the flexible packs perform as well or better across most areas of environmental impact.
Bags and pouches use a lot less material than rigid alternatives, resulting in significant energy and water savings in production (often up to 75%).
Flexible plastic packaging is lightweight and saves energy in transport.
Flexible plastic packaging is versatile and inexpensive and provides reasonable product protection.
There is a low risk of food contamination from the packaging. However, the use of recycled plastic is avoided for some food contact applications out of caution.
Plastic packaging, if disposed to landfill, will not decompose. This results in the continuing long-term sequestration (storage) of the fossil carbon in the plastic, rather than this being released to the atmosphere as a GHG.

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The corresponding LCA-related considerations against flexible plastic packaging are as follows [8]:
Plastic packaging is generally made from nonrenewable fossil fuel resources.
The extraction of nonrenewable hydrocarbons results in the direct emission of GHG and is a significant source of risk for pollution of the local environment.
Flexible plastic packaging is not collected by most curbside collection systems.
Plastics films and bags are generally more difficult to sort from commingled curbside recycling streams at MRFs.
Flexible plastic packaging is more challenging to recover because it often involves multiple polymer layers and/or a layer of aluminum, which are difficult to separate.
Being lightweight and more likely to be blown away by wind, flexible packaging films and bags have a higher tendency to become part of the litter stream, particularly when disposed in the environment [33].
Most plastic packaging can take hundreds of years to fully degrade and bring damage to the ecosystem.
Virgin polymer production is energy- and chemical-intensive.
Flexible plastics containing recycled content are uncommon and difficult to source.
If plastic reprocessing is undertaken, it can be water-intensive (due to the washing and separation process steps).

References [1] c&en. The cost of plastic packaging. https://cenacsorg/articles/94/i41/ cost-plastic-packaginghtml. 17-10-2017, 94(41):32e37. [2] Institute for Bioplastics and Biocomposites n-I. Global production capacities of bioplastics 2013 (by market segment); 2014. http://biobased.eu/markets/. [3] Flexible Packaging Association (FPA), Advantages of flexible packaging. Retrieved June 6, 2018. https://www.flexpack.org/advantages/.

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[4] Smithers - PIRA. What’s causing a shift from traditional materials to flexible packaging types? https://www.smitherspira.com/resources/ 2018/january/shift-to-flexible-packaging; 2018. [5] Packaging Digest. Is 100% recyclable flexible packaging possible?. 08-8-2014. https://www.packagingdigest.com/flexible-packaging/is100-recyclable-flexible-packaging-possible140807. [6] Enval Ltd. The Enval process. 2019. http://www.enval.com/process/. [7] Flexible Packaging, Flexible Packaging Association (FPA). Shifting From Rigid to Flexible Packaging. Information from the Smithers - Pira report. The Future of Global Flexible Packaging to 2018; 25-02-2014. [8] O’Farrell K, Lewis H. Design smart material guide - Australian packaging covenant - flexible plastic packaging, No.4. Sydney. 2013. http://www.helenlewisresearch.com.au/wp-content/uploads/2014/ 03/Flexible_Plastic-DSMG-082013.pdf. [9] Edington J. Advancements in mechanical recycling j Unraveling film recovery. Sustainable packaging SolutionÒ. 15-10-2018. https:// sustainablepackaging.org/advancements-in-mechanical-recyclingunraveling-film-recovery/. [10] Steenman A. Flexible packaging and its recycling problems. 28-072013. https://bestinpackaging.com/2013/07/28/flexible-packagingand-its-recycling-problems/. [11] Official Journal of the European Communities. Directive 2008/98/EC of the European Parliament and of the council on waste and repealing certain directives. EUR-Lex; 19 November 2008. EUR-Lex, https:// eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri¼CELEX:32008 L0098&from¼EN. [12] European Commission. Waste management hierarchy. 09-06-2016. http://ec.europa.eu/environment/waste/framework/. [13] United States Environmental Protection Agency (EPA). Sustainable materials management: non-hazardous materials and waste management hierarchy. 10-08-2017. https://www.epa.gov/smm/ sustainable-materials-management-non-hazardous-materials-andwaste-management-hierarchy. [14] Danex Plast, How does the process work? Retrieved July 11, 2019. http://www.danexplast.com.my/about-us/. [15] APR - Association of Plastic Recyclers. The APR DesignÒ guide for plastics recyclability. 06-01-2018. http://www.plasticsrecycling.org/ images/pdf/design-guide/PE_Film_APR_Design_Guide.pdf.

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[16] Plastics Recyclers Europe. Design for recycling. 2018. https://www. plasticsrecyclers.eu/design-recycling. [17] Bukowski T, PTIS PTIS. A holistic view of the role of flexible packaging in a sustainable world. 25-02-2019. https://www. eiseverywhere.com/eselectv2/backendfileapi/download/358894?id¼ 06a7ad01aa9dd64bfc8a5e4122bd6f6c-MjAxOS0wMiM1YzVjNG M1NTZhM2I3. [18] Recycling Processes. In: Harper CA, editor. Handbook of plastics technologies: the complete guide to properties and performance. McGraw-Hill; 2006. [19] DuPont Teijin Films. DuPont Teijin Films introduces polyester films range with up to 50 percent post-consumer recycled rPET content. 03-01-2019. https://ceflex.eu/wp-content/uploads/2019/03/PressRelease.pdf. [20] Next Generation Recyclingmaschinen GmbH. Mechanical recycling of bioplastics - Part I. Bioplastics Magazine 2018;13:02e18. [21] Reclay StewardEdge. Product stewardship solutions, resource recovery systems, Moore Recycling Associates Inc. Analysis of flexible film plastics packaging diversion systems - Canadian Plastics Industry Association continuous improvement fund stewardship Ontario. Feb. 2013. [22] Bukowski T, Richmond M, PTIS. A holistic view of the role of flexible packaging in a sustainable world. Flexible Packaging Association; 0904-2018. [23] Flexible Packaging Europe (FPE). Understanding Life Cycle Assessment (LCA) of flexible packaging. July 14, 2019. https://www. flexpack-europe.org/en/sustainability/food-lcas.html. [24] Bu¨sser S, Steiner R, Jungbluth N. LCA of packed food products e the function of flexible packaging e case study: butter. Flexible Packaging Europe (FPE); Jan. 2008. https://www.flexpack-europe.org/ files/FPE/sustainability/ESU-Butter_2008-ExecSum.pdf. [25] Bu¨sser S, Steiner R, Jungbluth N. LCA of packed food products e the function of flexible packaging e case study: coffee. Flexible Packaging Europe (FPE); Jan. 2008. https://www.flexpack-europe.org/ files/FPE/sustainability/ESU-Coffee2008-ExecSum.pdf. [26] Bu¨sser S, Jungbluth N. LCA of ready-to-serve goulash soup packed in stand-up pouches. Flexible Packaging Europe (FPE); Feb. 2011. https://www.flexpack-europe.org/files/FPE/sustainability/ESUGoulash2011%20ExecSum.pdf.

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[27] Bu¨sser S, Steiner R, Jungbluth N. LCA of packed food products e the function of flexible packaging e case study: spinach. Flexible Packaging Europe (FPE); Jan. 2008. https://www.flexpack-europe.org/ files/FPE/sustainability/ESU-Spinach_2008-%20ExecSum.pdf. [28] Poovarodom N, Ponnak C, Manatphrom N. Comparative carbon footprint of packaging systems for tuna products. Packaging Technology and Science 2012;25(5):249e57. [29] Bertoluci G, Leroy Y, Olsson A. Exploring the environmental impacts of olive packaging solutions for the European food market. Journal of Cleaner Production 2014;64:234e43. [30] Bu¨sser S, Jungbluth N. The role of flexible packaging in the life cycle of coffee and butter. The International Journal of Life Cycle Assessment 2009;14(Suppl. 1):80e91. [31] Schweitzer J-P, Petsinaris F, Gionfra C. Justifying plastic pollution: how Life Cycle Assessments are misused in food packaging policy. Brussels: Institute for European Environmental Policy (IEEP); 2018. A study by Zero Waste Europe and Friends of the Earth Europe for the Rethink Plastic Alliance. https://ieep.eu/uploads/articles/ attachments/d028bd51-4f3d-48e2-8573-72bd33697dcf/ Shortcomings%20of%20LCA%20in%20food%20packaging% 20policy%20-%20Unwrapped%20Packaging%20and%20Food% 20Waste%20IEEP%202018.pdf?v¼63690511118%20. [32] Schweitzer J-P, Gionfra S, Pantzar M, Mottershead D, Watkins E, Petsinaris F, et al. Unwrapped: how throwaway plastic is failing to solve Europe’s food waste problem (and what we need to do instead). Brussels: Institute for European Environmental Policy (IEEP); 2018. A study by Zero Waste Europe and Friends of the Earth Europe for the Rethink Plastic Alliance, https://www.foeeurope.org/sites/default/ files/materials_and_waste/2018/unwrapped_-_throwaway_plastic_ failing_to_solve_europes_food_waste_problem.pdf. [33] Barnes DK, Galgani F, Thompson RC, Barlaz M. Accumulation and fragmentation of plastic debris in global environments. Philosophical Transactions of the Royal Society B: Biological Sciences 2009;364(1526):1985e98.

2 Environmental and Socio-Economic Effects 2.1 Description of the Problem In its quest to solve a big environmental problem, namely food waste, the packaging industry created another one. Flexible plastic packaging offers many benefits: extends food shelf life and minimizes spoilage; reduces waste by preserving and protecting products until they are consumed; reduces material use; minimizes overall size and weight; lowers shipping costs; and generates fewer greenhouse gases (GHG) than alternative packaging. At the same time, the growth in consumption and disposal of flexible plastic packaging raises environmental concerns. Flexible plastic packaging, like rigid plastic packaging, is derived from nonrenewable resources, and increased amounts of waste end up in landfills and the environment. It is estimated that about 300 million metric tons (MMT) of plastic are produced annually, and half of this is used once; about 40% of the total sum of the plastic produced is used for packaging. A large part of that amount ends up in nature [1]. The uncontrolled disposal of flexible plastic packaging, and the lack of legislation and effective recycling technologies can have dire consequences on the environment. Because of its longevity, sheer volume, and difficulty to be recycled profitably, plastic packaging in general, and flexible packaging in particular, has become a global environmental problem [2]. According to Barlow and Morgan [3] the environmental impact of packaging is more dependent on material volume than recyclability. Thin-film products, such as plastic wrap and shopping bags, are a particular subset of flexible packaging items that are frequently littered. These items are extremely light and mostly enter the marine environment through wind transfer into oceans or rivers when incorrectly or poorly disposed of [4]. Another subset of flexible packaging is pouches and sachets. Both of them are currently used in the packaging of a wide variety of products, from food and beverage to cleaning supplies and other household items. Despite their numerous benefits, pouches and sachets pose a serious waste problem. These multilayer flexible packaging materials are used once and thrown away, ending up in landfill or in Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00002-5 Copyright © 2020 Elsevier Inc. All rights reserved.

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waterways and oceans [5]. It is estimated that single-use plastics, such as crisp packets and sweet wrappers, food containers, and cutlery, make up about 60% of the plastics found in beaches worldwide [6]. Most types of flexible plastic packaging have complex structures (e.g., laminates), and with the exception of clean monolayer polyethylene films, they are not currently recycled and have little or no economic value. In spite of the damage flexible plastic packaging causes to marine ecosystems and human activities, such as fishing, shipping, recreational activities, and tourism, there is no much literature on the fate of these plastic items in seawater [7]. Bioplastics (including biodegradable and/or biobased plastics) are alternative materials to conventional plastics (e.g., polyolefins) in flexible packaging with the potential to improve environmental performance. However, biodegradable plastics might be half the solution, because the favorable degradation conditions required for the composting of these materials are not always achieved in the sea and other natural environments. A further complication arises from the fact that although the bioplastics should degrade rapidly in natural environments, they should not degrade during their shelf and service life [8]. Biodegradable plastic packaging may also release methane when disposed of in a landfill, whereas nonbiodegradable packaging is inert. Further, biobased polymers, which are not biodegradable, have to be recycled in the same way as their counterparts [9].

2.2 Degradation of Plastics in the Environment1 2.2.1 Environmental Degradation Modes Degradation is the partial or complete breakdown of a plastic under the influence of one or more environmental factors, such as water, heat, light, microbes, and mechanical action. There are five degradation modes by which plastics can degrade in the environment:
hydrolytic degradation;
thermooxidative degradation;
photodegradation; 1

This section is based on Chapter 3 of the book “Management of Marine Plastic Debris”, Niaounakis M. William Andrew-Elsevier, 2017.

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biodegradation; and
mechanical degradation. In the diverse marine habitats, including beaches, the sea surface, the water column, and the seafloor, plastic debris is exposed to different environmental conditions that either accelerate or decelerate the degradation of plastics. The degradation of plastics in the sea or on the beach is affected by many factors, such as exposure time, the intensity of UV radiation, temperature, biological degradation, and physical abrasion. The degradation is more intensive on the beach and to a lesser degree at the sea surface as the result of solar UV-radiation-induced photooxidation. The degradation of plastic materials occurs slower in the sea than on land, because seawater, which is a good heat sink, inhibits the thermal loading that accelerates degradation on land. In the water column, plastics degrade very slowly, especially at the seafloor [10]. The length of time that the various plastic materials persist in the sea is not reliably known [11]. The degradation times of most flexible plastic debris, such as plastic bags, films, and six-pack rings, is estimated to be tens of years. Most of the estimated life spans of the various plastic debris are hypothetical, and they do not reflect the actual lifetime of plastic debris in the marine environment. Most of these estimations are based on degradation studies of various plastics exposed in different environments and are focused on the early stages of degradation that impact the useful lifetime of the product [12]. Furthermore, there is limited or fragmented information on the weathering of plastic debris floating in seawater, stranded on shorelines, submerged in seawater or sediment [13,14]. The effects of variables, such as mechanical impact, salinity, temperature, hydrostatic pressure, presence of pollutants, such as oil in seawater and biofouling (reducing UV exposure) on the degradation rates of various types of plastic items are virtually unknown [12]. While a pure polymer can be more degradable than others, its overall degradation behavior can be altered by the incorporation of additives (e.g., antioxidants, UV stabilizers, and the like), blending of other polymers, after-treatment processing, etc.

2.2.2 Hydrolytic Degradation Polyolefins, including polyethylene, polypropylene, and most of their copolymers, are hydrophobic and are not expected to hydrolyze in the water environment. In general, polymers with pure carbon backbones are particularly resistant to most types of degradation, including hydrolysis,

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while vinyl polymers carrying aromatic carbocyclic rings, such as polystyrene tend to be more resistant to hydrolysis [15]. Polymers that contain heteroatoms in the backbone, including various polyaddition or condensation polymers, such as polyesters and polyamides show higher susceptibility to hydrolysis. While this is often true, aromatic polymers tend to be resistant to degradation, despite the presence of bonds that are normally readily hydrolyzed [15,16]. Poly(ethylene terephthalate) (PET) is a typical example of such a polymer; the ester bonds that form part of the polymer chain are potentially hydrolyzable, however, due to its aromatic groups, the polymer is essentially nondegradable under normal conditions [17]. Hydrolysis is usually not a significant mechanism in seawater for the degradation of most commercial fossil fuel-derived plastics [13].

2.2.3 Thermooxidative Degradation The temperatures and oxygen levels encountered in seawater are not adequate to initiate thermooxidative degradation. The relatively low temperatures and low oxygen concentration in water environments, as well as the biofouling of plastics, inhibit the heat build-up and retard the thermooxidative degradation [13,18]. The situation is different when the same plastic is stranded on the beach where it is subjected to higher temperatures. Certain plastics will fragment more rapidly in regions subject to higher temperatures, such as those in tropical beaches. High temperatures increase the rate of chemical reaction, generating greater degradation. Given the relatively low specific heat of sand (664 J/kg- C), sandy beach surfaces and the plastic debris on it can heat up to temperatures of about 40  C in summer. In dark-colored plastic debris, the heat build-up due to solar infrared absorption can raise the temperature even higher [19]. The light-initiated oxidative degradation is accelerated at higher temperatures by a factor depending on the activation energy (Ea) of the process; for example, for an Ea of about 50 kJ/mol, the rate of degradation doubles when the temperature rises by only 10  C [13].

2.2.4 Photodegradation Photodegradation is the dominant environmental degradation mode of most plastic debris. The ultraviolet (UV) radiation portion (400e10 nm) of sunlight plays a key role in plastic degradation through photooxidation. It is primarily the UV-B radiation (280e315 nm) in sunlight that initiates the photooxidative degradation of common polymers, such as low-density

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polyethylene (LDPE), high-density polyethylene (HDPE, polypropylene and aliphatic polyamides (nylons) that are exposed to the marine environment. The mechanism of photodegradation is one of photooxidative degradation rather than of direct photolysis [20]. Once initiated, the degradation can also proceed through thermooxidative mechanisms for some time without the need for further exposure to UV radiation. The autocatalytic degradation reaction sequence can progress as long as oxygen is available to the system. In photodegradation, the molecular weight of the polymer is decreased, and oxygen-rich functional groups are generated in the polymer. Higher temperatures and oxygen levels both increase the rate of fragmentation, as does mechanical abrasion [21]. However, the other types of environmental degradation are several orders of magnitude slower compared to UV-induced degradation. The initial photooxidative degradation of plastic debris usually starts at the outer surface of the plastic [13]. This localized degradation is because of the high extinction coefficient of UV-B radiation in plastics, the diffusion-controlled nature of oxidation reaction [22] and the presence of fillers that impede oxygen diffusion in the plastic [23,24]. The deterioration of the surface takes the form of discoloration, pitting, crazing or cracking, erosion or embrittlement. This degraded fragile surface is susceptible to fracture by stress, induced by humidity or temperature changes, as well abrasion against sand [25], which may result in the fragmentation of plastic into smaller pieces [13,26]. The extent of photodegradation depends primarily on the presence within the polymer of light-absorbing structures. Polymers containing aromatic or carbonyl groups in their backbone are likely to absorb the sunlight (wavelength, l > 290 nm), and usually become photosensitive materials. On the other hand, polymers that do not possess any chromophore group in their backbone, absorbing above 250 nm, like polyolefins, still appear to be degraded by sunlight during outdoor exposure. This finding implies that those polymers must contain chromophore groups absorbing the solar radiation either as impurities (catalyst residues, organic contaminants, and thermal oxidation products, such as hydroperoxides) or as functional groups incorporated into the polymer backbone [27]. Actually, many aliphatic polymers are more sensitive to UV radiation than most aromatic polymers in spite of the fact that the latter is capable of absorbing much more solar UV radiation; for example, polyolefins and poly(vinyl chloride) (PVC) are less stable than aromatic polyesters, like PET [28]. PVC exhibits the highest sensitivity toward UV radiation. The UV sensitivity of PVC is attributed mainly to the CeCl bond, which together

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with the saturated bonds CeC and CeH, absorb in the far ultraviolet region, at wavelength below 200 nm. PVC articles exposed to UV radiation degrade and become embrittled and readily crack or shatter. Moreover, as photodegradation is primarily a superficial process due to the limited penetration of UV radiation, the surface properties of the degraded polymer are substantially modified. Most commercial PVC products are effectively protected by the incorporation of adequate stabilizers [27]. Polypropylene is liable to chain degradation from exposure to UV and will become brittle and weak if left for long periods in the sun. Degradation shows up as a network of fine cracks and crazes that become deeper and more severe with exposure over time [29]. Little is known about the fate of plastics that sink to the seafloor. It is postulated that the plastics at the seafloor are largely impervious to photodegradation once shielded from UV radiation [30]. The lack of UV-B (rapidly attenuated in seawater) to initiate the process, the low temperatures and the lower oxygen concentration relative to that in air, makes extensive degradation far less likely than for the floating plastic debris [31]. On the other hand, plastic debris stranded on the beach, and exposed to high levels of UV radiation, degrade more readily [32,33]. In most cases, the photodegradation of plastics is accompanied by a change in color turning them into yellow, brown, or even white, or acquiring gray tons [34e38]. Yellowing of plastic debris is most likely the result of quenching, which derives from the capture of free radicals on the plastic surface by the action of UV light stabilizers, particularly phenolic antioxidants, which absorb UV radiation, quench the free radicals that are generated in the polymer and prevent oxidation. The action of quenching leads to the formation of yellow byproducts, such as quinonoid structures [35]. Yellowing may constitute a qualitative measure to determine exposure time in the marine environment [36]. For white plastics, it should not be assumed that this color pertains exclusively to plastic debris with a short residence time in the marine environment. Plastic debris, which appears to have turned white, may correspond to plastics that have been exposed for a long period of time in the marine environment and have been subjected to extensive degradation [34]. Pigmented plastics usually lose some of their original colors and become lighter. Sometimes, surface darkening gives plastics a gray ton, likely owing to the progress of oxidation that fosters small cracks and holes. These facilitate the adhesion of various kinds of materials that end up darkening the plastic surface. In general, paints, pigments, and dyes on plastic surfaces provide protection from UV radiation and diminish the

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extent of photooxidation. Photooxidative processes, however, were found to degrade polymers when artificial fractures (scoring) were induced on colored polymer surfaces [39].

2.2.5 Biodegradation Most conventional polymers used in packagings like polyethylene, polypropylene, PET, nylons, and PVC have very slow biodegradation rates, and thus, remain semi-permanent when disposed of in the sea [10]. The microbial species that can metabolize these polymers are rare in nature. Several features of polyethylene make it resistant to biodegradation. Among these features are: (1) polyethylene’s highly stable CeC and CeH covalent bonds; (2) its high molecular weight, which makes it too large to penetrate the cell walls of microbes; (3) its lack of readily oxidizable and/ or hydrolyzable groups; and (4) its highly hydrophobic nature [40,41]. The biodegradation of polyethylene can be compared with the biodegradation of paraffin. The biodegradation of the latter starts with the oxidation of the alkane chain to a carboxylic acid, which later undergoes b-oxidation [42]. An initial necessary abiotic step is the oxidation of the polymer chain; once hydroperoxides have been introduced, a gradual increase in keto groups in the polymer is followed by a decrease in keto groups when short-chain carboxylic acids are released as degradation products to the surroundings [8e10]. Photooxidation enhances the rate of biodegradation of polyethylene. It leads to the scission of the main chain in the polymer, thereby leading to the formation of low molecular weight products. This results in the generation of large surface area due to its embrittlement and also a greater degree of hydrophilicity due to the introduction of carbonyl groups. All these factors further promote the biodegradation of polyethylene [43]. However, the biodegradation proceeds at a very slow rate. A laboratory study reported degradation rates of LDPE of 1, 1.5, and 1.75 wt% after 30 days of incubation with Kocuria palustris M16, Bacillus pumilus M27, and Bacillus subtilis H1584, respectively, isolated from marine waters present at high microbial densities [44]. A field study reported degradation rates of LDPE, HDPE, and polypropylene after 1 year in seawater off the Indian coast of 1.9 w, 1.6 wt, and 0.65 wt%, respectively [45]. Synthetic polyamides, and in particular aliphatic polyamides (nylons), are resistant to degradation in the natural environment because of the high symmetry of their molecular structures and strong intermolecular hydrogen bonds [46].

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Unlike fossil fuel-derived plastics, which have very slow rates of biodegradation, biodegradable polymers have been designed to degrade in compost under specific conditions within a certain time span. However, the extent to which these bioplastics decompose in the sea has not been adequately investigated. There is no concrete evidence that they will degrade readily in seawater [47], where the average temperature of the ocean surface water is about 17  C, while the deep ocean water is between 0 and 3  C at least in the time span foreseen by the relevant international standards [7]. Most bioplastics, such as PLA, are heavier than seawater and will sink, where the low water temperature, the lack of UV, and the lower oxygen concentration are expected to further retard their degradation. Biodegradable plastic packaging may also release methane when disposed of in a landfill, whereas nonbiodegradable packaging is inert. The most versatile bioplastic, poly(lactic acid) (PLA), degrades slowly in water over a period from several weeks up to about 1 year. Compared to water-soluble or water-swelled polymers, which fall apart quickly in water, PLA-based polymers can only be classified as moisture-sensitive because they degrade slowly. For instance, after a month’s immersion in water, PLA and certain copolymers thereof show no reduction in molecular weight; but after 6 months, the physical properties drop significantly. Poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3valerate) (PHBV) films disposed of in seawater disappeared within 8 weeks [48]. PHBV and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) solvent-cast films exposed in seawater for a 3-week period (22 þ 3  C) were degraded via surface dissolution. The rate of surface erosion was almost independent of the copolymer compositions of PHBV and P3HBP4HB samples, but markedly dependent upon the temperature of the seawater. A simple hydrolytic degradation process did not contribute to the degradation of the polyhydroxyalkanoates in the marine environment [49]. Several microorganisms have been identified that can degrade polyhydroxyalkanoates (e.g., PHB, PHBV) in freshwater [50,51] and marine environments [49,50,52e54]. Among them are the bacteria Pseudoalteromonas sp. NRRL B-30083, Marinobacter sp. NK-1, Alcaligenes faecalis AE122, and the actinomycetes Nocardiopsis aegyptia and Streptomyces sp. SNG9. The biodegradabilities of eight aliphatic polyester films: PHB, PHBV, P3HB4HB, poly(ε-caprolactone) (PCL), poly(ethylene succinate) (PES), poly(ethylene adipate) (PEA), poly(butylene succinate) (PBS), and poly(butylene adipate) (PBA) were studied in different natural waters from

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a river and a lake, and in seawater, from bay and ocean for 28 days at 25  C under aerobic conditions [55]. PHB films were eroded at a relatively fast rate in freshwater from river and lake, and the weight loss was almost 100% after 28 days. By contrast, the biodegradation rate of PHB in seawater, from both the bay and the ocean, were slower than those in freshwater. PHBV films were degraded at a rapid rate in all the natural waters used, and the weight-loss and BOD (biochemical oxygen demand) of the PHBV films were 100 and 78  8% for 28 days, respectively. PES films were eroded completely in freshwater within 10 days, whereas the PES films were hardly eroded after 28 days in seawater. PCL films were degraded in freshwater from river and lake, and in seawater from the bay, in which, the weight-loss and BOD were 100 and 80%, respectively. PEA films were completely degraded in freshwater and seawater from a bay, and the weight-loss were almost 100%. PBS films were hardly eroded in natural water, except for freshwater from lake, in which, the weight-loss and BOD were 22  14 and 12  8%, respectively. The weight-loss and BOD of PBA films in freshwater from the lake were 80  13 and 50  10%, respectively. The biodegradation rates of PBA films in freshwater from the river and in seawater from the bay and ocean were slower than that in freshwater from the lake [55]. A series of studies compared the deterioration of carrier bags made of Mater-BiÒ (Novamont), which is believed to consist of corn starch, vegetable oils, and poly(butylene adipate-co-terephthalate) (PBAT), in two aquatic ecosystems, a littoral marsh and seawater, in soil and compost. Little deterioration was observed in specimens exposed to water of a littoral marsh and of the Adriatic Sea or buried in soil under field conditions. Conversely, results from the laboratory study indicated that after 3 months of incubation Mater-BiÒ carrier bags were rapidly deteriorated in soil and compost with weight loss of specimens of 37 and 43%, respectively [56]. A Mater-BiÒ film, thought to contain corn starch and PCL, underwent a severe deterioration in its tensile properties during aging in seawater for at least 8 months [7]. A further study investigated the degradation of oxodegradable, compostable, and conventional plastic carrier bags in the marine environment [57]. Four types of polymers that are used as carrier bags were compared. The first two bags were made from two oxodegradable polyethylenes. The first polyethylene used the d2wÔ self-destruct oxodegradable plastic additive manufactured by Symphony Plastics (UK), and the second polyethylene used the Totally Degradable Plastics Additives (TDPAÒ) manufactured by EPI Environmental Products, Inc. The third bag was made from Mater-BiÒ. The fourth bag was made from standard

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polyethylene containing 33% recycled material. Tensile strength of all materials decreased during exposure, but at different rates. Mater-BiÒ degraded more than all the other polymers with 100% surface area loss between 16 and 24 weeks, while the other polymers lost only approximately 2% after 40 weeks. Some polymers required UV light to degrade. The transmittance of UV light through oxodegradable and standard polyethylene decreased as a consequence of fouling, such that, these materials received approximately 90% less UV light after 40 weeks. The data indicate that Mater-BiÒ degrades relatively quickly compared to oxodegradable polyethylene and conventional polyethylene. While biodegradable polymers offer waste management solutions, there are limitations to their effectiveness in reducing hazards associated with plastic debris; some biodegradable polymers may not degrade quickly in natural habitats. On the other hand, oxodegradable formulations could merely disintegrate into small pieces that are not in themselves any more degradable than conventional polymers. Another study examined the degradation of oxodegradable, compostable, and conventional shopping bags in the gastrointestinal fluids of sea turtles [48]. The conventional plastic bags were made of HDPE; the oxodegradable plastic bags were made of polyethylene with prooxidant (d2wÔ ); and the compostable plastic bags were made of Mater-BiÒ and manufactured by BioBag (US). After 49 days, the weight losses of the HDPE and oxodegradable plastic bags were negligible. The compostable bags showed a weight loss between 3 and 9 wt%. This is much slower than the degradation rates claimed by the manufacturers for industrial composting.

2.2.5.1 Biofouling Biofouling is the colonization of an interface by a diverse array of organisms affecting the surfaces, the materials they are made of and their properties. Biofilm formation leading to biofouling develops in four stages: (1) adsorption of dissolved organic molecules; (2) attachment of bacterial cells; (3) attachment of unicellular eukaryotes; and (4) attachment of larvae and spores [58]. Bacterial attachment is a highly controlled and regulated process whereby attached cells produce extracellular polymers to form structured and complex matrixes [59]. Microbial biofilms can subsequently trigger the attachment of specific invertebrates and algae, which increases the degree of biofouling [14,60]. Biofouling depends on the surface properties of the plastic debris, such as surface roughness, surface energy, and hydrophobicity [45]. Biofouling

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also depends on the concentration of bacteria and nutrients in the marine environment. Biofouling fluctuates depending upon the season, geographic location, substrate, and age. Cursory calculations estimate a range of 1000e15,000 MT of microbial biomass harbored on plastic debris. The biofouling of plastic surfaces is more extensive in warmer climates [39]. Most of the plastic debris consists of hydrophobic plastics, such as polyethylene and polypropylene that promote microbial colonization and biofilm formation. With a hydrophobic surface rapidly stimulating biofilm formation in the water column, plastic debris can function as an artificial “microbial reef” [61]. The accumulation of micro and macroorganisms covering the surface of floating plastic debris, substantially, reduces the amount of UV-light reaching the plastic and increases its density, which decreases the plastic buoyancy. Using nitrogen as a proxy for biomass, which is absent in virgin polyethylene and polypropylene, it has been shown that the change in density is caused by the attached biomass. Initial rate of biofouling depends on the surface energy of the plastic; materials with surface energy between 5 and 25 mN/m are minimally fouled [62]. Once the density of biofouled plastic debris reaches that of seawater, it can sink well below the water surface. Microbial biofilms that developed early on plastic debris would become less hydrophobic and more neutrally buoyant so as to sink below the sea surface [63]. Polyethylene food bags (20 cm  28 cm) submerged in seawater displayed a well-developed biofilm within 1 week, which continued to increase throughout a 3 week exposure period. By the third week, the polyethylene food bags had started to sink below the sea surface, indicating neutral buoyancy [63]. Typically, the density of seawater increases with depth. Therefore, neutrally drifting or slowly sinking plastic debris would remain suspended at a certain depth in which density is equal to that of plastic debris. Field experiments, however, have shown that biofouled plastic debris would undergo rapid defouling by other organisms or other mechanisms when submerged that can decrease its density causing the plastic debris to return back to the surface [64]. Fouled plastic debris may increase in density enough to ultimately reach benthic regions [65e67]. There are early indications that the formation of a biofilm on the surface of plastic debris may promote the biodegradation process. Bacterial diversity upon polyethylene and polypropylene samples collected from geographically distinct areas from the North Atlantic Subtropical Gyre and analyzed with scanning electron microscopy (SEM) and nextgeneration sequencing (pyrotag sequencing) revealed a diverse microbial community of heterotrophs, autotrophs, predators, and symbionts

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[61]. Pits visualized in the plastic debris surface conformed to bacterial shapes suggesting active hydrolysis of the polyolefins. Small-subunit rRNA gene surveys identified several hydrocarbon-degrading bacteria, supporting the possibility that microbes play a role in degrading plastic debris. Some of the microbes may be opportunistic pathogens, such as specific members of the genus Vibrio that dominated one of the plastic samples. SEM has also been used to explore how microbial diversity (measured in terms of morphology) on polyethylene, polystyrene, and polypropylene particles from the North Pacific Gyre varies with location and polymer type, showing “Bacillus” bacteria and pennate diatoms to be most abundant on the plastic, with highest abundances on expanded polystyrene [68]. Despite the reports of plastic degrading microbes in biofouled plastic debris, the degradation rates are extremely slow.

2.2.6 Mechanical Degradation Mechanical shearing has been suggested as a possible degradation mechanism of plastic debris [69]. The mechanical forces exerted on plastic debris are more intense on the beach than at sea [70]. Mechanical degradation may happen through the combined efforts of wave and tide action, and abrasion from sediment particles, which can scratch the surface of plastic debris and increase its rate of fragmentation. Surface alterations in plastic fragments resulting from environmental erosion increase the overall surface area and polarity and can facilitate the sorption of persistent organic pollutants (POPs) [37,71] (see Section 2.4.5.1). Plastic debris particles sampled from the beaches of Kauai, Hawaii, and analyzed by SEM were found to contain fractures, horizontal notches, flakes, pits, grooves, and vermiculate textures. The mechanically produced textures provide favorable sites for oxidative processes to occur, which further weaken the polymer surface leading to embrittlement. Fourier transform infrared spectroscopy (FTIR) results suggest that, compared to polypropylene, polyethylene marine debris are more liable to surface oxidation, which occurs in pits and fractures created during collisions [72].

2.2.7 Combined Degradation Processes The degradation of most common plastics encountered in the marine environment is attributed to the combined action of sunlight, atmospheric oxygen, and seawater [69]. Among the degradation processes involved,

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the most important is photooxidation, followed by mechanical action, and thermal oxidation, and to a lesser degree biodegradation and hydrolysis. Andrady [73] compared the loss of mechanical integrity of several common packaging and fish gear-related plasticsdincluding LDPE film, polypropylene stripping tape, rubber latex balloons, expanded polystyrene sheet, and rapidly degradable polyethylene2 and six-pack ringdexposed while floating in seawater with those exposed in air at the same sites. LDPE film and polypropylene tape were found to degrade at a significantly slower rate on seawater, with marked differences in elongation at break after 1 year of exposure. The marked retardation of the degradation process in these types of plastic materials might be attributed to lack of heat buildup in samples exposed on seawater and the shielding action of surface biofouling, which reduces the light availability [13,28]. Enhanced degradable polyethylene six-pack ring material is degraded in about the same time scale under both air and seawater exposure. Plastic debris stranded on the beach degrades more readily through the combined action of exposure to high levels of UV radiation, and particleparticle collisions associated with physical processes as saltation and dragging. Polyethylene marine debris appears to be more conducive to breakdown via both weathering processes than polypropylene, which occur in pits and fractures created during collisions [28]. While IR spectra of sampled and experimentally degraded polymers indicate that polypropylene is more conducive to photooxidative degradation relative to polyethylene, SEM results indicate that the combined effects of chemical and mechanical degradation processes may degrade polyethylene preferentially to polypropylene [39]. According to Rochman [74], the prolonged weathering of plastic debris can increase its surface area, generate oxygen groups (i.e., increase polarity) [37,75], and induce biofouling (increase electrical charge, roughness, and porosity) [45], and allow plastic debris to accumulate increasingly larger concentrations of chemical contaminants, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and trace metals [37,76e78], the longer the plastic is exposed in the marine environment, the higher the concentration of adsorbed contaminants [79]. Presently, there are no reliable methodologies to assess the exposure time of plastic debris in the marine environment. While the degree of degradation of plastic debris can be quantified by FTIR, the duration of its exposure cannot be deduced from such information [12].

2

Ethylene-carbon monoxide copolymer.

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2.3 Environmental Effects in Land According to Flexible Packaging Association (FPA), the estimated amount of flexible packaging waste generated in the United States is 5.8 MMT per year. After a single use, 95% of flexible plastic packaging material ends up in landfills, as roadside litter, and eventually in the sea. Nearly, a third of this plastic packaging waste does not even make it to landfill, and instead, is littered on land or swept into the ocean, while only 14% of the plastic packaging waste is recycled. Flexible plastic packaging films and bags are thin and lightweight, and it is easy for flexible packaging material to become airborne after use, and scatter on land or be washed into storm drains, and pollute water bodies and aquatic ecosystems. Consigning plastic waste to landfill is one of the most traditional methods of waste disposal, and it remains a common practice in most countries. However, older, poorly managed landfills can create a number of adverse environmental impacts, such as wind-blown litter, attraction of vermin, and generation of landfill gas, mainly composed of carbon dioxide and methane, which is produced as organic waste from food waste breaks down anaerobically. For overcoming these problems, many landfills are covered with earth to prevent attracting vermin and to reduce the amount of wind-blown litter. Furthermore, space in landfills is at a premium, and the cost of dumping waste material is calculated on a weight basis. It is disadvantageous to dispose of untreated flexible plastic waste materials in a landfill because these waste materials are bulky, and therefore, the cost of transporting them to the landfill is high.

2.4 Environmental Effects at Sea3 More than 8 MMT of plastic waste enters the oceans every year wreaking havoc on the wildlife and generally degrading the landscape [80]. Flexible plastic packaging films and plastic bags are the most prevalently found marine plastic pollution. Plastic bags have the tendency to float because of entrapped air. Approximately 70% of the carry plastic bags make their way to the ocean floor, where conditions are such that they prevent plastic bags from biodegrading [47]. A plastic bag and sweet wrappers were found even on the seabed of the Mariana Trench, the 3

This section is based on Chapter 2 of the book “Management of Marine Plastic Debris”, Niaounakis M. William Andrew-Elsevier, 2017.

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deepest place in the Pacific Ocean [81]. It is estimated that 150 MMT of plastics are currently residing in the world’s oceans. Plastic packaging accounts for more than 60% of the plastics recovered in coastal cleanup operations [82]. Plastic bags and food plastic packaging are the next most common item, after cigarettes butts, removed from beaches during the annual International Coastal Cleanup campaigns, but they have a much greater potential impact than cigarettes butts [83]. The bulk of flexible plastic packaging debris found floating in the sea is composed mainly of LDPE, linear low-density polyethylene (LLDPE) and HDPE (e.g., plastic shopping bags, packaging films, or six-pack rings); polypropylene (e.g., films, or food containers) because of their inherent buoyancy, broad utility, and high production volumes. Floatable plastic debris items, once they enter the ocean, are carried away via oceanic currents and atmospheric winds. Oceanic features, such as gyres, eddies, and frontal meanders, trap marine debris in accumulation zones, often referred to as “garbage patch,” “plastic soup,” “trash island,” or “ocean landfill.” Because of the longevity of plastic debris, once it enters a gyre system, it can remain for long periods of time. The largest garbage patch is the “Great Pacific Ocean Garbage Patch” also known as “Eastern Garbage Patch.” The size of the patch has been estimated to be from 700,000 km2 (270,000 mi2) to more than 15,000,000 km2 (0.4e8% of the size of the Pacific Ocean). Polyethylene is the most common type of plastic packaging debris and has recently been recognized as a major threat to marine life. There are reports that polyethylene fragments and particles cause blockages in the intestines of fish, birds, and marine mammals. In addition, the entanglement of marine animals in polyethylene packaging debris, such as carrier bags and films, has endangered hundreds of marine species [47]. Negative media publicity with upsetting images of dead marine animals after ingesting or being entangled in plastic debris heightened the awareness about the negative impacts of plastic debris on marine life.

2.4.1 Entanglement Polypropylene packaging straps, HDPE six-pack rings, and LDPE bags are also a major source of entanglement found around the bodies (neckcollars) of marine animals. Although the packaging straps and six-pack rings account for only a tiny fraction of the marine plastic debris, they are responsible for the deaths of hundreds to thousands of seabirds and marine mammals [84].

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2.4.1.1 Mammals It is estimated that 45e46% (52e53 of 115) of all marine mammals have been entangled in plastic debris. The pinniped with the most references to plastic debris entanglement in the U.S. waters is the northern fur seal (Callorhinus ursinus) followed by the Hawaiian monk seal (Monachus schauinslandi), the California sea lion, and the northern elephant seal (Mirounga angustirostris). Pinnipeds were generally observed to be entangled around the head and appendages in net fragments, monofilament line, packing straps, rope, and rubber products [85]. The decline in the populations of the northern sea lion (Eumetopias jubatus), endangered Hawaiian monk seal [86,87] and northern fur seal [88] seems at least aggravated by the entanglement of young animals in derelict fishing nets and packing bands. Page et al. [89] reported that New Zealand fur seals were commonly entangled in loops of packing tape.

2.4.1.2 Sea Turtles Sea turtles tend to align themselves with oceanic fronts, convergences, rip and drift lines, where marine debris often occur [90]. As such, sea turtles are susceptible to entanglement in marine debris that can form loops and openings that could catch on and appendages [85]. Hawksbill turtles show a tendency to entangle in plastic bags and sacks [91]. Entanglement accounts for 10e11.8% of all turtles (including brackish turtles) species. Bjorndal et al. [92] reported that 5% of 1500 observed sea turtles worldwide were entangled in marine debris.

2.4.1.3 Birds It is estimated that 25e26% (79e80 of 312) of all marine birds have been entangled in plastic debris [93]. Besides the risk of entanglement from derelict nets and fishing gear, marine birds are also susceptible to entanglement from plastics and other synthetic materials that they may gather for making nests [85].

2.4.2 Ingestion The negative effects of ingested plastic debris can be divided into three categories [31]: physical damage to the digestive system [32,33]; impairment of digestive and foraging efficiency [34]; and the release of

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toxic chemicals [35e37]. Most of plastics found in the stomachs of marine animals are characterized by shape (e.g., plastic fragments, pellets, pieces of films, threads or nets) and/or color.

2.4.2.1 Mammals Baulch and Perry [94] listed 48 cetacean species (56% of all) having ingested marine debris, with rates of ingestion as high as 31% in some populations. Items ingested by cetaceans were most commonly plastic (47%), with fishing gear (e.g., nets, hooks, lines, etc.) (25%), and miscellaneous items (28%) constituting the remainder [95]. Flexible plastic packaging debris (films, bags, and bands) was also found in the ingestion system of 68 Franiscana dolphins (Pontoporia blainvillei) out of 106 examined (64%) [96]. A Cuvier’s beaked whale (Ziphius cavirostris) found on the west coast of Norway in January 2017 had its stomach filled with 30 plastic bags, and many smaller pieces of plastic (see Fig. 2.1). Another dead whale that swallowed 40 kg of plastic was found in the Philippines in March 2019. The stomach of this juvenile Cuvier’s beaked whale contained 16 rice sacks, 4 banana plantation-style bags, and many plastic bags [98]. A pregnant sperm whale washed ashore in Italy’s island of Sardinia in April 2019 with almost 23 kg of plastic in its stomach, including plastic bags, plastic plates, fishing lines, etc. [99].

2.4.2.2 Turtles Marine turtles are known for consuming plastic bags at sea. It is assumed that these neutrally buoyant bags are mistaken by the turtles for food items, such as salps and medusa (jellyfish), the major food items of leatherback turtles [100e102]. Mrosovsky et al. [103] studied the autopsy records of 408 leatherback turtles (Dermochelys coriacea), spanning 123 years (1885e2007). The first mention of plastic in the gastrointestinal tract was for 1968. Of the 371 autopsies from that year and onwards, 37.1% revealed the presence of plastics. Blockage of the gut by plastic was mentioned in some accounts [7]. Balazs [90] listed 79 cases of turtles whose guts were full of various sorts of plastic debris. Plotkin and Amos [91] necropsied 111 turtles that were found stranded on the south Texas coast from 1986 through 1988.

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Figure 2.1 Plastic films and bags found in the stomach of a whale stranded at Sotra, Bergen, in January 2017 (the University of Bergen Copyright) [97]. Photo: Christoph Noever.

Plastic debris was found in the stomachs or intestinal tracts of 60 (54%) of the turtles. Plastic debris was present in 52% of the loggerhead turtles (Caretta caretta), 47% of the green turtles (Chelonia mydas), and 87.5% of the hawksbill turtles. Lazar and Gracan [104] analyzed the gastrointestinal tract of 54 loggerhead sea turtles found stranded or incidentally captured dead by fisheries in the Adriatic Sea. Plastic debris was present in about 35% of turtles, 68% of which have ingested soft plastics. Santos et al. [105] analyzed the impact of plastic debris ingestion in 265 green turtles (Chelonia mydas) over a large geographical area and different habitats along the Brazilian coast. It was found that a surprisingly small amount of debris (about 0.5 g for juveniles and about 47% of adults) was sufficient to block the digestive tract and cause the death of juvenile green turtles. A large part of the ingested debris might come from disposable and short-lived plastic products.

2.4.2.3 Fishes Davison and Asch [106] reported that at least 9.2% of fish in and below the Great Pacific Garbage Patch had plastic debris in their stomachs, and

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the researchers estimated that fish in the North Pacific are ingesting 12,000 to 24,000 tons of plastic every year. The occurrence of microplastics in the stomachs of fish poses several environmental concerns. Ingested microplastics are passed through in the feces, retained in the digestive tract, or translocated from the gut into body tissues via the epithelial lining [107,108]. Negative effects on fish health are due to the plastic itself and to other pollutants in the marine environment absorbed by plastic debris.

2.4.3 Rafting Floating and submerged marine plastic debris were reported to act as rafts for the transport of alien and invasive species to distant or remote areas. Some types of debris, such as plastic bags and films, are completely submerged and remain just below the surface where they are transported by currents. Furthermore, because of their hydrophobic nature, plastics act as “sponges” and absorb a wide range of inorganic and organic compounds from the marine environment [77]. A wide variety of POPs can sorb from the marine environment (i.e., seawater and sediment) on and/or in the plastic matrix. These contaminants have a greater affinity for the plastic matrix than the surrounding seawater leading to an accumulation onto the plastic particle. Polymer type plays an important role in this contamination accumulation: under identical sorption conditions, PCBs and PAHs are consistently found in a higher concentration on HDPE, LDPE, and polypropylene, compared to PET and PVC [77]. In this way, marine plastic debris may act as a transport vector of chemical pollutants to marine organisms [75,109].

2.4.4 Loss of Biodiversity and Habitat Plastic debris poses a serious threat to marine habitats and wildlife. When settled on the seafloor marine debris alters the habitat, either by introducing substrates where none was available before or by overlaying the sediment, inhibiting gas exchange and interfering with life on the seabed. If relatively static on the seabed, or buoyant but retained in oceanic gyres, plastic debris will still become colonized, providing additional habitat having the potential to influence the relative abundance of organisms within local assemblages [110]. Ecosystem impacts can also occur in the intertidal. For example, microplastics and debris fragments on beaches have been reported to alter the porosity of the sediment and its heat transfer capacity. It has been suggested that increased plastic debris loads could lead to reduced

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subsurface temperatures, potentially affecting organisms, such as sea turtles whose sex-determination relies on temperature [38]. Nesting beaches for sea turtles, frequently, are sinks for plastic debris. As a result, nesting females may have difficulty in ascending to lay their eggs, or debris could act as obstacles for emerging hatchlings. Moreover, the physical properties of nesting beaches, particularly, the permeability and temperature of sediments, are known to be altered by the presence of plastic fragments. Such alterations could ultimately have implications for sex ratios, which are influenced by nest conditions, and for nest success rates when pollution is severe [111].

2.4.5 Toxicity The plastic polymers are considered to be biochemically inert due to their large molecular weight, and are, therefore, not considered to be hazardous for the marine environment. However, unreacted monomers, oligomers, residual catalysts, and solvents can be found in plastic products as a result of incomplete polymerization [112]. Plastics also contain several additives that have been added to endow the plastics with certain desirable properties. While at sea, several of these chemical compounds and additives can be released from the plastic in the marine environment as a result of degradation and/or incomplete polymerization. As mentioned earlier, plastic debris has the tendency to adsorb contaminants that are present in water, particularly those that are hydrophobic. Many of the hydrophobic contaminants are concentrated at the sea surface, and their levels are up to 500 times greater than in the underlying water column [113]. The plastic debris can either transport the contaminants to other areas and if washed up, the contaminants could be transferred to shoreline sediment or could be ingested by marine organisms and potentially transferred to their tissues and further up the food chain. Plastic debris could be subject to fouling and then sink to the bottom, where it becomes part of the sediment or is eaten by benthic organisms that live on the sea bottom [114].

2.4.5.1 Persistent Organic Pollutants A wide variety of POPs can sorb from the marine environment (i.e., seawater and sediment) on/in the plastic matrix. The presence of such POPS on plastic debris has been demonstrated for a wide variety of chemicals and for different geographic areas [75,115]. These contaminants have a greater affinity for the plastic matrix than the surrounding

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seawater leading to an accumulation onto the plastic. Polymer type plays an important role in this contamination accumulation: under identical sorption conditions, PCBs and PAHs are consistently found in a higher concentration on HDPE, LDPE, and polypropylene, compared to poly(ethylene terephthalate) (PET) and poly(vinyl chloride) (PVC), while phenanthrene sorbs more to polyethylene than polypropylene or PVC [77,116]. As a result, the possible effects of both the polymer and associated contaminants have to be considered when assessing the potential risks of plastic debris. Rochman et al. [77] measured sorption of PCBs and PAHs throughout a 12-month period to the five most common types of mass-produced plastic: HDPE, LDPE, polypropylene, PVC, and PET. For PAHs and PCBs, PET and PVC reach equilibrium in the marine environment much faster than HDPE, LDPE, and polypropylene. Most importantly, concentrations of PAHs and PCBs sorbed to HDPE, LDPE, and polypropylene were consistently much greater than concentrations sorbed to PET and PVC. These data imply that products made from HDPE, LDPE, and polypropylene pose a greater risk than products made from PET and PVC of concentrating these hazardous chemicals onto fragmented plastic debris ingested by marine animals. Plastic fragments (w10 mm) collected from the open ocean and from remote and urban beaches were analyzed for organic micropollutants. PCBs, PAHs, DDE and its metabolites (DDTs), polybrominated diphenyl ethers (PBDEs), alkylphenols and bisphenol A were detected in the fragments at concentrations from 1 to 10,000 ng/g. Concentrations showed large piece-to-piece variability. Hydrophobic organic compounds, such as PCBs and PAHs were sorbed from seawater to the plastic fragments. PCBs are most probably derived from legacy pollution. Nonylphenol, bisphenol A, and PBDEs came mainly from additives and were detected at high concentrations in some fragments both from remote and urban beaches and the open ocean [115].

2.5 Socio-Economic Effects The social impacts of plastic litter include a deterioration in the quality of human life, reduced recreational opportunities, loss of aesthetic value, and loss of nonuse or vicarious value4 [117]. Socially, the plastic garbage 4

Knowledge that quality coastal ecosystems exist.

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patches affect the health and lives of people living along coasts that border the ocean gyres [118]. Most of the socio-economic impacts of plastic debris are intertwined, and it is not always easy to distinguish one from another [119].

2.5.1 Tourism There are few studies in the literature to consider the economic effects of marine plastic debris on tourism. Ofiara and Brown [120,121] found that marine debris wash-ups in New Jersey, United States, decreased beach attendance by 8.9e18.7% in 1987 and by 7.9e32.9% in 1988. A study in South Africa found that a decrease in beach cleanliness could decrease tourism spending by up to 52% [122]. It is further estimated that the tourism on the Skagerrak coast of Bohusla¨n in West Sweden decreased by 1e5% as a result of beach litter, resulting in a calculated annual loss of $23.4 million [123]. In the Goeje Island of South Korea, marine debris led to lost revenue of V29e37 from tourism in 2011. The number of people visiting the island decreased by 63% from 2010 to 2011 were probably due to the marine debris pollution [124]. Cleanups of beaches and waterways can be expensive. The cost of cleaning the beaches in Bohusla¨n, in just 1 year was reportedly at least $1,550,200 (or 10 million SEK). In the Netherlands and Belgium, about $13.65 million per year is spent on removing beach litter. The annual cleanup costs for municipalities in the UK amounted to $23.62 million in 2011 [119]. The municipality of Ventanillas in Peru has calculated that it would have to invest around $400,000 a year in order to clean its coastline, while its annual budget for cleaning all public areas is only half that amount [125]. A cost analysis on a hypothetical cleanup scenario was developed by NOAA (National Oceanic and Atmospheric Administration) based on the following assumptions [126]: - cleaning up less than 1% of the North Pacific Ocean (a 3-degree swath between 30 and 35 N and 150 to 180 W), which would be about 1,000,000 km2 - using nets or net-like devices to collect the plastic debris - hiring a boat with an 18 ft (5.5 m) beam and surveying an area within 100 m off of each side of the ship. If the ship travels at 11 knots (20 km/h), and surveys during daylight hours (about 10 h a day), it would take 67 ships 1 year to cover that area.

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At a cost of $5000e20,000 per day, it would cost between $122 million and $489 million per year only for boat time, without taking into account equipment or labor costs; and yet, not all debris can be swept up with a net [126]. The costs for cleaning the seafloor of the coasts are also especially expensive. The deposit of macro- and microplastics along beaches, aside from having an ecological impact, has a significant economic impact on local businesses and property owners there along. Ocean resorts and hotels must maintain their property for guests, keeping up the appearance of the beach for continued use and for aesthetic reasons. Therefore, the burden of cleanup of these microplastic deposits shifts to the local businesses and property owners, which can be both incredibly costly and time-consuming. Tourism and recreational usage of beaches can be a significant source of litter to the marine environment, especially during summer, when seaside resorts receive their greatest number of visitors. A study correlated the debris levels with visitor density on beaches in Brazil and found that the daily litter input to the beach was significantly higher in the regions frequented by people with lower annual income and literacy [127].

2.5.2 Aesthetics The social cost of marine plastic debris is not known, but it seems likely that the largest component of this cost is the reduced aesthetic value of fouled shorelines. The presence of floating, submerged, and stranded plastic debris can negatively affect the aesthetic appeal of beaches, reduce its recreational value [128], and lead to serious economic problems for regions that are dependent on tourism and marine activities [120]. The degradation of the aesthetic appeal of beaches has a serious effect on many user groups, such as recreational fishers and boaters, sport divers and tourists, who visit and enjoy these areas, and value the coastal scenery and landscape [129]. Floating plastic debris is an aesthetic issue for swimmers, mariners, coastal, and inland water body dwellers, and submerged debris is an aesthetic issue for divers [130]. The absence of marine litter has been identified as a desirable beach quality in beach users priorities [131,132]. A survey assessing the value of clean beaches to users and the socioeconomic impacts of beach litter on South Africa beaches found that 85% of both tourist and residents would not visit beaches if they had more than two items of debris per meter [133]. Although it is difficult to convert the aesthetic value into a monetary equivalent, coastal litter causes economic losses, including the decline of tourism and generation of cleanup costs, and furthermore, may be

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translated into a social issue, such as distrust of governments [117]. The effects of aesthetic issues on the amenity value of marine and riverine environments have been defined by the World Health Organization (WHO) as loss of tourist days; resultant damage to leisure/tourism infrastructure; damage to commercial activities dependent on tourism; damage to fishery activities and fishery-dependent activities; and damage to the local, national, and international image of a resort [134].

2.5.3 Human Health Flexible plastic packaging debris, such as film residues, plastic bags, and straps, can be a navigational hazard to boats and can threaten the safety of the occupants. Film fragments carrying or adsorbing toxic compounds, such as PCBs or pathogenic pollutants and being ingested by fishes and shellfishes can enter the human food chain and may (might) affect the health of the food consumers [135].

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[98] Borunda A. This young whale died with 88 pounds of plastic in its stomach. national Geographic; 18-03-2019. https://www. nationalgeographic.com/environment/2019/03/whale-dies-88-poundsplastic-philippines/. [99] Borunda A. This pregnant whale died with 50 pounds of plastic in her stomach. national Geographic; 02-04-2019. https://www. nationalgeographic.com/environment/2019/04/dead-pregnant-whaleplastic-italy/. [100] Wehle D, Coleman FC. A naturalis at large-plastics at sea. Natural History 1983;92(2). 20-&. [101] Fritts TH. Plastic bags in the intestinal tracts of leatherback marine turtles. Herpetological Review 1982;13(3):72e3. [102] Schuyler QA, Wilcox C, Townsend K, Hardesty BD, Marshall NJ. Mistaken identity? Visual similarities of marine debris to natural prey items of sea turtles. BMC Ecology 2014;14(1):14. [103] Mrosovsky N, Ryan GD, James MC. Leatherback turtles: the menace of plastic. Marine Pollution Bulletin 2009;58(2):287e9. [104] Lazar B, Gracan R. Ingestion of marine debris by loggerhead sea turtles, Caretta caretta, in the Adriatic Sea. Marine Pollution Bulletin 2011;62(1):43e7. [105] Santos RG, Andrades R, Boldrini MA, Martins AS. Debris ingestion by juvenile marine turtles: an underestimated problem. Marine Pollution Bulletin 2015;93(1e2):37e43. [106] Davison P, Asch RG. Plastic ingestion by mesopelagic fishes in the north Pacific Subtropical Gyre. Marine Ecology Progress Series 2011;432:173e80. [107] Browne MA, Galloway TS, Thompson RC. Spatial patterns of plastic debris along estuarine shorelines. Environmental Science and Technology 2010;44(9):3404e9. [108] Browne MA, Dissanayake A, Galloway TS, Lowe DM, Thompson RC. Ingested microscopic plastic translocates to the circulatory system of the mussel, Mytilus edulis (L.). Environmental Science and Technology 2008;42(13):5026e31. [109] Karapanagioti HK, Klontza I. Testing phenanthrene distribution properties of virgin plastic pellets and plastic eroded pellets found on Lesvos island beaches (Greece). Marine Environmental Research 2008;65(4):283e90. [110] Secretariat of the Convention on Biological Diversity and the Scientific and Technical Advisory PaneldGEF. Impacts of marine

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debris on biodiversity: current status and potential solutions. CBD Technical Series No 67. Montreal. 2012. p. 61. Duncan E. SWOT Report. Turtles and plastic, vol. XI; 2015. p. 6e7. ˚ , Dave G. Environmental and health hazard Lithner D, Larsson A ranking and assessment of plastic polymers based on chemical composition. The Science of the Total Environment 2011;409(18):3309e24. Teuten EL, Rowland SJ, Galloway TS, Thompson RC. Potential for plastics to transport hydrophobic contaminants. Environmental Science and Technology 2007;41(22):7759e64. European Commission’s Directorate-General Environment. Science for environment policy j in-depth reports j plastic waste: ecological and human health impacts. DG Environment News Alert Service; November 2011. Hirai H, Takada H, Ogata Y, Yamashita R, Mizukawa K, Saha M, et al. Organic micropollutants in marine plastics debris from the open ocean and remote and urban beaches. Marine Pollution Bulletin 2011;62(8):1683e92. Bakir A, Rowland SJ, Thompson RC. Enhanced desorption of persistent organic pollutants from microplastics under simulated physiological conditions. Environmental Pollution 2014;185: 16e23. NOWPAP MERRAC. Negative impacts of marine litter in the NOWPAP region: case studies. Republic of Korea; 2013. Leous JP, Parry NB. Who is responsible for marine debris? The international politics of cleaning our oceans. Journal of International Affairs 2005;59(1):257e69. Thompson R, La Belle B, Bouwman H, Neretin L. Marine debris: defining a global environmental challenge. UNEP Science and Technical Advisory Panel (STAP). Advisory document. 2011. http:// www.opc.ca.gov/webmaster/ftp/pdf/public_comment/20110909_ MCaldwell_att1.pdf. Ofiara DD, Brown B. Assessment of economic losses to recreational activities from 1988 marine pollution events and assessment of Economic Losses from long-term contamination of fish within the New York Bight to New Jersey. Marine Pollution Bulletin 1999;38(11):990e1004. Ofiara D, Brown B. Marine pollution events of 1988 and their effect on travel, tourism, and recreational activities in New Jersey. In:

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Conference of floatable wastes in the ocean: social, economic, and public health implications; March 1989. p. 21e2. Ballance A, Ryan PG, Turpie JK. How much is a clean beach worth? The impact of litter on beach users in the Cape Peninsula, South Africa. South African Journal of Science 2000;96(5):210e30. Marine Litter Task Team (MaLiTT). The impacts of marine litter marine pollution monitoring management group. In: Fanshawe T, Everard M, editors; May 2002. http://www.gov.scot/Uploads/ Documents/Impacts%20of%20Marine%20Litter.pdf. Jang YC, Hong S, Lee J, Lee MJ, Shim WJ. Estimation of lost tourism revenue in Geoje Island from the 2011 marine debris pollution event in South Korea. Marine Pollution Bulletin 2014;81(1):49e54. UNEP - United Nations Environmental Programme. Report brings to the surface the growing global problem of marine litter. Nairobi. http://www.unep.org/climatechange/News/PressRelease/tabid/416/ language/en-US/Default.aspx?DocumentId¼589&ArticleId¼6214;08-06-2009. Office of Response and Restoration j NOAA’s Ocean Service j National Oceanic and Atmospheric Administration j US Department of Commerce j USA.gov. How much would it cost to clean up the Pacific garbage patches? http://response.restoration.noaa.gov/about/ media/how-much-would-it-cost-clean-pacific-garbage-patches.html; 21/12/2015revised. Santos IR, Friedrich AC, Wallner-Kersanach M, Fillmann G. Influence of socio-economic characteristics of beach users on litter generation. Ocean and Coastal Management 2005;48(9e10):742e52. Pendleton L, Martin N, Webster DG. Public perceptions of environmental quality: a survey study of beach use and perceptions in Los Angeles County. Marine Pollution Bulletin 2001;42(11):1155e60. Debrot AO, Nagelkerken I. User perceptions on coastal resource state and management options in Curac¸ao. Revista de Biologia Tropical 2000;48(1):95e106. Moore CJ. Synthetic polymers in the marine environment: a rapidly increasing, long-term threat. Environmental Research 2008;108(2):131e9. Morgan R, Jones TC, Williams AT. Opinions and perceptions of England and Wales Heritage coast beach users: some management

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implications from the Glamorgan Heritage coast, Wales. Journal of Coastal Research 1993;9(4):1083e93. Oldridge S. Bathing water quality: a local authority perspective. In: Kay D, editor. Recreational water quality management. Chichester: Ellis Horwood Ltd.; 1992. p. 33e47. Ballance A, Ryan PG, Turpie JK. How much is a clean beach worth? The impact of litter on beach users in the Cape Peninsula, South Africa. South African Journal of Science 2000;96(5):210e3. Williams AT, Pond K, Pablo R. Chapter 12: Aesthetic aspects. In: Bartram J, Rees G, editors. Monitoring bathing waters - a practical guide to the design and implementation of assessments and monitoring programmes: WHO-World Health Organization; 2000. http:// www.who.int/water_sanitation_health/bathing/monbathwat.pdf. Bouwmeester H, Hollman PCH, Peters RJB. Potential health impact of environmentally released micro- and nanoplastics in the human food production chain: experiences from nanotoxicology. Environmental Science and Technology 2015;49(15):8932e47.

3 Polymers Used in Flexible Packaging 3.1 Types of Polymers Flexible packaging uses a wide range of materials, including plastic films, paper, and aluminum. The plastic films include various types of vinyl polymers, polyesters, and polyamides. The used polymers are homopolymers, copolymers, or polymer blends, and are usually compounded with various additives (e.g., antioxidants, plasticizers, moisture absorbers, colorants, and the like) to improve certain properties. The films are used either as a single layer or as coextruded multilayers. The films are also commonly coated, metalized, or otherwise treated to enhance the performance of the resulting package. Flexible packaging materials are selected based on a variety of factors, including desired barrier properties, mechanical performance, cost, sealing properties, appearance, physical feel, printability, and easy opening/reclosing features. While there are many polymers utilized in the flexible packaging industry, the most common ones are polyolefins, including the various types of polyethylene and polypropylene, poly(ethylene terephthalate) (PET) and poly(vinyl chloride) (PVC) [1,2]. Each polymer used in flexible packaging is examined in terms of sustainability and recyclability.

3.2 Polyolefins The polyolefins1 is a group of vinyl polymers, which comprise more than 50 wt% monomers based on the weight of the polymer derived from one or more olefin monomers, for example, ethylene or propylene, and, optionally, may contain at least one comonomer. They are produced mainly from nonrenewable fossil fuel-based resources. Their easy processability, low price, chemical inertness, good optical properties, flexibility, and toughness have made them the most versatile polymers in the packaging industry and distribution of products. Polyolefins are suitable 1

They are also called polyalkenes.

Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00003-7 Copyright © 2020 Elsevier Inc. All rights reserved.

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for packaging of single or bundle packaging of food and other products, such as cosmetics, toys, stationery, confectionery, chemicals for households, etc. They are also prone to thermo-fusion welding. Flexible polyolefin packaging films have the disadvantage that they are not receptive to printing inks. Therefore, practical films of this type have coatings or surfaces specially treated (e.g., by corona treatment). Polyolefins are naturally hydrophobic, and they do not decompose in the environment.

3.2.1 Polyethylenes Polyethylenes are a group of ethylene polymers, which comprise more than 50 wt% ethylene monomer. Polyethylene films are by far the largest volume flexible packaging film family accounting to more than 32% of the total market share. Polyethylenes are available with a wide range of properties combining transparency (low-density types), toughness, heat seal-ability, low water vapor transmission rate, low-temperature performance, and low cost. Polyethylene films are highly permeable to oxygen and other nonpolar gases and have high viscoelastic flow properties. Polyethylene has the lowest softening point of the basic packaging polymers. The lower softening point results in lower processing energy costs. Polyethylene can be clear or translucent depending on density. It is a tough, waxy solid that is unaffected by water and is inert to a large range of chemicals. The properties of polyethylene are highly dependent on type and number of chain branches. Polyethylene is marketed in three general categories: low, medium, and high density.

3.2.1.1 Low-Density Polyethylene Low-density polyethylene (LDPE), also referred as “high pressure polyethylene” or “highly branched polyethylene”, is characterized by a high degree of short- and long-chain branching, which contributes to its relative processing ease. It has a density in the range of 0.916e0.930 g/ cm3 and a melting temperature of 105e115
C and can be processed at low temperatures and pressures while maintaining a good melt strength. LDPE is blown, slit, and wound to create film rolls, which is increasingly used by product manufacturers for a variety of packaging purposes, such as plastic bags and shrink film. Most stock poly bags used to wrap a large variety of products are made from LDPE. LDPE is widely used for shrink bundling, offering low shrink temperature and excellent clarity. One of the most common uses for LDPE bundling film is for wrapping

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water bottles and canned goods. The LDPE bundling film is thicker and offers more strength than PVC shrink film. LDPE film is used mainly for its heat-seal ability and bulk in packaging. LDPE film is flexible and tough. The toughness and durability of LPDE film offer several advantages: - stability for unsupported and bundled products; - good tear resistance; - a coefficient of friction that helps the film form to the product’s shape and holds it in place during stacking or stretch wrapping prior to distribution; - low cost and recyclability that makes it a sustainable option for many manufacturers [3]. LDPE film also has some limitations to consider: - poor weathering resistance; - poor gas barrier properties; - low tensile strength; - limited possibilities for down-gauging (reducing the thickness), due to a low draw ratio, and low stiffness of the polymer; - can appear cloudy, depending on the level of technology used during its manufacture [3]. LDPE film can be collected and recycled to create new products, such as piping, trash bags, sheeting, and films for building and agricultural applications, composite lumber, and other products [3].

3.2.1.2 Linear Low-Density Polyethylene Linear low-density polyethylene (LLDPE) includes linear, substantially linear or heterogeneous copolymers of ethylene with a-olefins, usually 1-butene, 1-hexene, or 1-octene. LLDPE contains less long chain branching than LDPE and is tougher and has better heat-seal strength than LDPE. It has a density in the range of 0.915e0.934 g/cm3 and a melting temperature of 115e125
C. Its stiffness, however, remains low and its processability is well below that of LDPE. Also, conventional LLDPE’s optical properties do not match those of LDPE. Optical properties of LLDPE have been improved by using metallocene-catalyzed LLDPE

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(mLLDPE); however, the processability of these grades is generally worse than that of conventional LLDPE (2000, US6114456, FINA RESEARCH). Most stretch films are made from either cast or blown extruded LLDPE. LLDPE offers the high stretch rate needed for stretch film. Because of the strength and stretch characteristics of LLDPE, such film is used as a baling material and wrap material for palletized loads or bailing processes. LLDPE film wraps and secures bottles, other containers, or similar items on a pallet during shipping. The LLDPE film typically is wrapped around the materials on the pallets several times so that there are layers upon layers of the film. Upon arrival at a given destination, the LLDPE is removed from the palletized materials and scrapped. LLDPE film is also used to baling waste material. When LLDPE film is removed from the pallets or other bales, because of the high level of contamination, such as dirt, oil, biological material, layering, label adhesives, etc. the LLDPE film is either disposed in a landfill or processed as a filler for other plastic products. Reuse of the LLDPE film as a viable blown film product for use as an industrial film or a bag product has generally not been instituted. Typically, such used film has limited use due to high level of contamination present which, in turn, causes severe processing issues as well as unpleasant properties in the finished product, for example, odor, discoloration and “pitted” appearance (2014, WO2014158316 A1, WISCONSIN FILM & BAG INC).

3.2.1.3 Very Low-Density Polyethylene Very low-density polyethylene (VLDPE)2 is a substantially linear polyethylene comprising, like LLDPE, only copolymers of ethylene with a-olefins, usually 1-butene, 1-hexene or 1-octene, and having a high degree of linearity of structure with short branching rather than the long side branches characteristic of LDPE. Today’s commercially available VLDPEs are metallocene-catalyzed (mVLDPEs) of narrow molecular weight distribution; they are produced in a gas phase process and provide high film toughness (Dart Impact Strength > 450 g/mil for a 1 mil monolayer film), but tend to have a number of drawbacks. Due to their narrow molecular weight distribution, mVLDPEs have difficulty in conversion to finished products, and the prepared films have the tendency to split in the machine direction. In addition, both the mVLDPEs and the 2

Also called ultra low-density polyethylene (ULDPE).

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ZieglereNatta catalyzed (z-nVLDPEs) demonstrate nonhomogeneous melting of the VLDPE copolymer, i.e., exhibiting at least two peaks in the Differential Scanning Calorimetry (DSC) measurement (2016, WO2016027194 A1, NOVA CHEM INT SA). VLDPE has been used for making shrinkable mono- or multilayer films for food packaging (1996, EP0374783 A2, VISKASE CORP). A commercial VLDPE for flexible packaging is ExceedÔ 1012 CA of Exxon Mobil Chemical Company, which is an mVLDPE having a density of 0.912 g/cm3 and outstanding toughness [4].

3.2.1.4 Medium-Density Polyethylene Medium-density polyethylene (MDPE) has a density in the range of 0.926e0.940 g/cm3 and a molecular weight distribution greater than 2.5. MDPE offers much improved rigidity and down-gauging possibilities. MDPE is translucent, lacking the good optical properties of LDPE or LLDPE (1998, EP0870802 A1; and 2000, US6114456, FINA RESEARCH). MDPE is the least commonly used polyethylene for flexible film.

3.2.1.5 High-Density Polyethylene High-density polyethylene (HDPE) has little branching, which gives it stronger intermolecular forces and tensile strength than LDPE. It has a density in the range of 0.941e0.970 g/cm3 and melting temperature of 125e135
C. Further, it has excellent puncture resistance, low stretch, reduced tearing, and moisture protection. HDPE has much higher stiffness, higher temperature resistance, and much better water vapor barrier properties than LDPE, but it is more opaque and can withstand somewhat higher temperatures (120
C for short periods) [5]. HDPE finds uses in industrial wrapping and packaging. Many retail bags are made from extruded HDPE (2e10 mils thick). Common products include grocery bags, T-shirt bags, packaging films, trash bags, bags with sealed air for packaging (e.g., air cushion), and a large selection of retail packaging bags. HDPE is also used for making woven sacks/bags. Recycled HDPE film is primarily used for composite lumber and plastic bags [3].

3.2.1.6 Ethylene-Vinyl Acetate Ethylene-vinyl acetate (EVA) is a polar copolymer of ethylene and vinyl acetate, retaining some of the properties of polyethylene, but with

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increased flexibility, elongation, and impact resistance. EVA is often used as extrusion coating on polypropylene, aluminum foil, and PET, to provide good heat-sealing at high converting rates, or as an adhesion layer in some laminates. Important applications in flexible packaging include sealants in meat and dairy packaging structures. ElvaxÒ EVA (Dow, ex DuPont) is an inherently flexible, tough and clear resin that is used as a heat seal layer, coextrusion tie layer, or structural layer. It can be made into blown or cast monolayer and coextruded films [6]. ElvaxÒ can be blended into polyethylene to improve enduse properties, especially at low temperatures, for frozen food and readyto-eat food packaging applications. Its low seal initiation temperature and ability to seal to themselves and other substrates allow for higher line speeds and help reduce package failures. Typical structures for fresh meat barrier packaging and block cheese packaging are EVA/PVDC/EVA and PE/EVA/PVDC/EVA/PE [7].

3.2.1.7 Ethylene-Vinyl Alcohol Ethylene-vinyl alcohol copolymer (EVOH) is a flexible, crystal clear, and glossy thermoplastic ethylene copolymer in which varying amounts of the eOH functional group have been incorporated. A typical packaging EVOH consists of about 20%e35% ethylene. It has excellent flex-crack resistance, and very high resistance to hydrocarbons, oils, and organic solvents. EVOH has been one of the most effective gas barrier materials known to the flexible packaging industry, especially in providing an excellent barrier for oxygen and aroma. EVOH is extensively used in modified atmosphere packaging (MAP), where a certain atmosphere is needed inside the package to improve the shelf life of food products. Other applications include medical and pharmaceutical packaging. A multilayer packaging film, including an EVOH layer, is often subject to a heating treatment (retort treatment or boiling treatment) with hot water or water vapor for a long time period, often carried out after filling the packaging materials with contents, such as foods. EVOH results in a problem through the heating treatment involving resin whitening and/or deterioration of the capability to keep the shape of the vacuum-packed contents. Various techniques have been developed to address this problem (2017, EP3144349 A1, KURARAY CO LTD). EVOH loses its gas barrier property when exposed to a high moisture environment. Therefore, EVOH requires a moisture barrier layer for protection, such as a nonpolar layer or metalized layer. In order to optimize both cost and performance, EVOH is frequently used in

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multilayer, coextruded films, such as LDPE, HDPE, polypropylene, and PET, which have superior moisture barrier properties. However, the polar EVOH is not compatible with a nonpolar polyolefin film, such as biaxially oriented polypropylene (BOPP). Thus, it requires an adhesion promoter or tie-layer resin, such as anhydride-modified polyolefin in order to adhere to a nonpolar polyolefin substrate. EVOH has a melting temperature of 165e185
C. This can cause problems in the recycling process if different materials melt at different temperatures [8]. An EVOH barrier layer sandwiched between polyethylene layers has the tendency to gum up when reprocessed, resulting in holes in the recycled polyethylene film [9]. Kuraray’s EVOH filmgrades of EVALÔ combine the humidity resistance and easy processing of ethylene with the exceptional gas barrier and resistance to organic solvents of poly(vinyl alcohol) (PVOH) [10]. Representative flexible multilayer structures of EVALÔ finding applications in food packaging are: fresh meat shrink wrap: PA/EVALÔ /PA/tie/PE; sliced ham: PET/tie/EVAÔ L/PA/tie/EVA; MAP with long-lasting gas mix: PET/PE/tie/EVALÔ /tie/EVA; UHT3 milk pouch: PE/tie/EVALÔ /tie/PE; and transparent packs for sensitive foods: OPP/EVALÔ /PE. Another commercial EVOH for flexible packaging is SoarnolÔ developed by Nippon Gohsei and owned by Mitsubishi [11]; and EvasinÒ EVOH copolymers of Chang Chun Petrochemicals, marketed by Arkema [12].

3.2.2 Polypropylene Polypropylene is a tough and rigid thermoplastic polymer with properties similar to polyethylene. It has a low cost and is the second-most widely produced commodity plastic (after polyethylene). It has a density in the range of 0.895e0.92 g/cm3, the lowest among commodity polymers, and a melting point of 130e170
C; commercial isotactic polypropylene has a density in the range of 0.900e0.905 g/cm3 and a melting point in the range of 160e166
C. Depending on the desired 3

Ultra-high temperature or ultra-heat treatment, or ultra-pasteurization.

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properties, different types of polypropylene are used, including homopolymers, random, heterophasic and random heterophasic co-polymers (Rahecos). Polypropylene homopolymers are characterized by high stiffness, excellent heat deflection temperatures, excellent moisture barrier, and good transparency, as well as high tensile strength for film applications. Random propylene copolymers with statistically incorporated ethylene monomer into the isotactic polypropylene chain are very soft and have excellent heat sealing properties at low sealing initiation temperature, very low-stress whitening and the best optical properties (gloss and haze) of all polypropylene grades. Heterophasic propylene copolymers have an ethylene-propylene rubber as a separate phase dispersed in a polypropylene homo- or copolymer matrix, and the films are characterized by a matt surface and low transparency. The high toughness and good stiffness over a very wide temperature range, are the dominant properties of this material. Rahecos comprise a propylene random copolymer matrix and an ethylene-propylene rubber and combine the properties of both previously mentioned propylene copolymers (2009, WO2009019277 A1, BOREALIS TECH OY). A commercial product of the Rahecos propylene copolymers is BorsoftÔ of Borealis, which can produce films with extreme softness and toughness [13]. The two most important types of polypropylene films are cast (unoriented) polypropylene (CPP) and biaxially oriented polypropylene (BOPP). Both types have a high gloss, exceptional optics, good or excellent heat-sealing performance, better heat resistance than polyethylene, and good moisture barrier properties. Nowadays, the majority of polypropylene films for packaging applications are made using the casting process, in particular, the chill roll process. Polypropylene films can be metalized, which results in improved gas barrier properties for demanding applications where long product shelf life is important. Polypropylene is also used for making packaging straps and woven sacks/bags. Polypropylene film composes over 20% of all film generated, and it is estimated that about 70% of it is generated in the residential sector [14]. Although industrial woven polypropylene slit film products are currently recycled, polypropylene films are not.

3.2.2.1 Cast Polypropylene The main characteristics of cast polypropylene (CPP) film are high gloss finish, high clarity (transparency), increased rigidity, and high moisture barrier. Due to its unoriented manufacturing process, it is

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resistant to impact and low temperatures. The CPP film properties can be customized to meet specific packaging, performance, and processing requirements. In general, CPP has higher tear and impact resistance, better cold-temperature performance, and heat-sealing properties than BOPP. CPP generally finds fewer applications than BOPP. However, CPP has been steadily gaining ground as an alternative material in many traditional flexible packaging applications. CPP requires lesser fixed investment compared to BOPP film and is, thus, preferred by the packaging industry [15]. CPP films of 20e80 mm thick are widely used in the flexible packaging industry for applications, such as food (e.g., bread, snacks, and dried food), confectionery, beverage, textiles, cosmetics, pharmaceuticals, and others. Some typical packaging applications of polypropylene cast films are listed in Table 3.1.

3.2.2.2 Oriented Polypropylene Polypropylene films are oriented or stretched in one direction (OPP) or in two directions (BOPP). This orientation of the film brings about several changes in the film, such as lower elongation, higher tensile strength, greater stiffness, improved optical properties, and better barrier to moisture/gases. Both OPP and BOPP are used in a wide variety of packaging applications, including use as packaging films and labels employed on plastic bottles. An OPP film has linear and parallel tear properties. This property is used to open packaging films easily and conveniently. A commercial OPP film is Nowostraight of Nowofol Kunststoffprodukte GmbH & Co. KG. The notch on the side ensures that the film always tears in a linear and parallel direction [16,17]. The BOPP film is used for the purpose of various flexible packaging films or labels with high strength and excellent tensile, transparency, and water vapor barrier properties. These key properties, combined with an excellent cost/performance ratio, have made BOPP one of the most popular and highly demanded film packaging material for form-fill-seal packaging of food and nonfood. BOPP films are mainly used for the packaging of food products, such as snacks, bakery, confectionery, dried foods, and pasta/noodles. Dried food dominated the global BOPP film market in 2014 [18]. Some of the main players in the global BOPP film market include: Taghleef Industries, Jindal Poly Films, Nan Ya Plastics, Treofan, Vibac, Vitopel, Jiangsu Shukang Packing Material Co., Ltd., Futamura, Cosmo

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Table 3.1 Typical Packaging Applications of Polypropylene (PP) Cast Films Film Packaging

Type of Polypropylene

Properties

Textile

Random copolymers with high C2content

Excellent sealing and optical properties

Flower

Mono- or threelayer coextruded films with PP homopolymers and PP random copolymers

PP homopolymers: stiffness; PP random copolymers: sealing, optics

Food

PP homopolymers, random copolymers, hetero-phasic copolymers, depending on required properties like

Good mechanical properties, excellent optics, lowtemperature resistance, good sealing properties

Laminating films

PP random copolymers and heterophasic copolymers for lamination with aluminum, other plastics films (PET, PA, PE)

Good sealing properties

Exemplary Applications

Courtesy of Borealis A/S. Polypropylene cast film; 2006. https://www.fist.si/datoteke/ navigacija/PP-Cast-film.pdf.

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Films, Kopa Films, Dow (ex DuPont; masterbatches for BOPP), Innovia Films, and Ampacet Corp. (masterbatches for BOPP) [18]. A variety of structures and compositions employed in commercial BOPP flexible packaging and label applications can be recycled, including structures based on clear, white, coated, or metalized films. The streams of reclaimed BOPP flexible packaging and label structures most often include inks, lacquers, coatings, and adhesives, which generally have been considered to render them undesirable for use as recycled material in plastic film structures; particularly, when a gray tint or hue is unacceptable (2007, US2007120283 A1; and 2008, US2008233413 A1, APPLIED EXTRUSION TECHNOLOGIES).

3.3 Polystyrene Polystyrene, also known commercially as crystal polystyrene or general-purpose polystyrene, is an amorphous polymer and has the particular properties of high clarity, being colorless, hard, but rather brittle. Polystyrene film can be biaxially oriented, in this form maintains clarity, and overcomes some of the brittleness of unstretched plastic. Biaxially oriented polystyrene films in thin gauges are used for food packaging carton windows. They have also been used as breathable films for over-wrapping fresh produce, such as lettuce [19]. Polystyrene represents a niche market (160
C). Hence, PVC is compounded with various additives to improve its processing and performance characteristics. By the inclusion of plasticizers, PVC can be made soft and flexible. In this form, known as

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plasticized PVC (PVC-P), it can form films. PVC-P can be fabricated into a tough, puncture-resistant, clear, and low-cost packaging film product. The film has good cling and heat-seal properties. It is mainly used as cling and stretch film and in closures and repeat-use flexible tube applications [22]. Because PVC has a comparable low permeability to oxygen, it keeps food, such as meat and cheese fresh. A representative example of commercial PVC for the manufacture of cling film is SolVinÒ S-PVC of Solvay [23]. PVC has been under pressure on the grounds of health and safety concerns. Attention has been focused on the migration of residual vinyl chloride monomer and plasticizers from flexible PVC food packaging into the edible material. There have also been environmental concerns on the waste management of PVC [22]. The costs for the recycling of PVC films in packaging waste are considerably high. Generally, the collection of PVC packaging films and other PVC products in the EU is included in the existing packaging recycling systems. For the packaging recycling systems in Austria and Germany, the costs for the plastics fraction are between 700 and more than 1.000 V/ton. This is far from economic profitability [24]. Flexible PVC is also harmful to the incineration process, and in the Nordic countries, it is currently landfilled [25]. A major problem in the recycling of flexible PVC is the high chlorine content in raw PVC (about 56% of the polymer’s weight) and the high level of plasticizer added to the polymer. As a result, PVC requires separation from other plastics before mechanical recycling.

3.4.2 Poly(Vinylidene Chloride) Poly(vinylidene chloride) (PVDC) is a chloropolymer that has excellent barrier properties to a wide variety of gases and liquids due to the combination of high density and high crystallinity. Coated or extruded PVDC with superior resistance to most gases, particularly oxygen and moisture vapor, is used in packaging. An OPP film-coated or coextruded with PDVC is a particularly good flexible packaging material for products, which tend to be sensitive to attack by oxygen, such as, for example, coffee and cheese, or snack foods, such as corn-based products and potato chips. Additionally, PVDC top-coating materials promote the heat sealability of such oriented film structures which, in an uncoated state, tend to seal only with great difficulty, if at all (1994, US5286424 A, MOBIL OIL CORP).

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PVDC has a number of limitations due to its poor thermal stability. Its degradation begins at about 120
C, and its extrusion temperature is in the range of 150e180
C. It is prone to gel and black spec formation during high-temperature extrusion, and evolves corrosive by-products, which require special materials of construction and good ventilation, and is known to discolor when exposed to radiation [26]. The PVDC must be stabilized and plasticized in order to be successfully extruded at commercial rates; typically used stabilizers-plasticizers are epoxidized oils. Although PVDC is an excellent gas barrier polymer, it is being phased out of many packaging applications because of environmental concerns [27]. PVDC layers and coatings render a flexible plastic packaging, nonrecyclable according to APR (Association of Plastic Recyclers) test protocols [28]. Specifically, PVDC is not compatible with polypropylene films or labels into which the plastic films are intended to be recycled (see also Table 3.4), and tends to release chlorine or HCI when melted causing all the other materials to degrade besides causing atmospheric pollution. The removal of PVDC from the plastic films prior to recycling them is costly, and therefore, economically not feasible (2007, US2007120283 A1; and 2008, US2008233413 A1, APPLIED EXTRUSION TECHNOLOGIES). The main producers of PVDC are SK Global Chemical4 [29], Solvay [30], Kureha [31], Asahi Kasei [32], Juhua Group, Nantong SKT and Keguan Polymer.

3.5 Poly(Vinyl Alcohol) Poly(vinyl alcohol) (PVOH) is a biodegradable fossil fuel-based vinyl polymer used in food packaging applications because of its high barrier properties to oxygen and carbon dioxide. On the other hand, its mechanical and water resistance is limited. PVOH is water-soluble, and therefore, is sometimes combined with other polymers and put in the core layer of a multilayer packaging structure. PVOH, as well EVOH, are highly hygroscopic materials and lose their barrier properties when they absorb water. PVOH has been replaced by EVOH because it is more expensive and its processability is more challenging than EVOH.

4

SK Global Chemical, the chemical unit of SK Innovation, acquired in 2017 Dow’s PVDC unit.

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Detergent packaging is the dominant application of PVOH because of its water solubility, and nonhazardous and nontoxic properties. Laundry detergents are, nowadays, packaged in PVOH films in the form of small packs named water-soluble pods. PVOH films are also suitable for manufacturing bags for agrochemicals. Main manufacturers of PVOH films include Nippon Synthetic Chemical Industry Co., Ltd., Kuraray Co., Ltd., and Sekisui Chemical Co., Ltd., and others. During the past few years, the global market has observed a considerable rise in the production capacity of PVOH films [33].

3.6 Polyesters Aromatic, semi-aromatic and aliphatic polyesters are used in flexible packaging as mono- or multilayers, coatings, and adhesives.

3.6.1 Aromatic Polyesters Among the aromatic polyesters, the most widely used polyester in flexible packaging is PET.

3.6.1.1 Poly(Ethylene Terephthalate) PET possesses excellent high-temperature properties, high strength, and clarity, and has moderate oxygen and carbon dioxide barrier properties. In particular, biaxially oriented polyester (BOPET) film is an important material in the field of flexible packaging because of excellent balance between cost and mechanical strength, heat resistance, dimensional stability, chemical resistance, and optical properties. BOPET films find applications in flexible packagings, such as bags and pouches for food products, wrapping of food and confectionery, or shrink labels for bottles.

3.6.1.2 Poly(Ethylene Furanoate) Poly(ethylene furanoate) (PEF) is a 100% biobased polyester, which has the potential to replace PET in the future. A PEF film has better gas barrier properties than PET (at least six times for oxygen, three times for carbon dioxide, and two times for moisture vapor). PEF is currently in the development stage. At present, the focus is on soda and water bottles, but applications for flexible films with a good gas and odor barrier will follow (2016, WO2016032330 A1, FURANIX TECHNOLOGIES BV). Toyobo (JP) and Avantium (NL) (FURANIX,

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SYNVINA) developed PEF-based thin films about 10 mm thick, which can be applied for food packaging, and in industrial and medical packages (2018, EP3398768 A1, TOYO CO LTD; SYNVINA CV). PEF can be mixed with its fossil fuel-based counterparts, e.g., industrial PET, and recycled in existing recycling facilities. PEF would be compatible in an amount up to 2% in the existing PET recycling stream [16,17].

3.6.1.3 Semi-Aromatic Polyesters These biodegradable polyesters are predominantly derived from fossil fuel-based resources. The most commonly used semi-aromatic polyester is poly(butylene adipate-co-terephthalate) (PBAT), which is nonbiobased and fully biodegradable. The PBAT produced by BASF under the trademark of Ecoflex is a flexible plastic designed for film extrusion and extrusion coating. PBAT is used for the toughening of PLA and starch while maintaining biodegradability. Ecovio produced by BASF is a blend of Ecoflex and PLA used in film applications, such as cling film, shopping bags, and compost bags. PBAT reduces the stiffness and improves the tear strength of a PLA-based flexible film [34]. PBAT improves the processability, water resistance, and tear strength of starch-based flexible films [34]. Origo-Bi produced by Novamont is a blend of PBAT with starch.

3.6.2 Aliphatic Polyesters Aliphatic polyesters are biodegradable polymers derived from either renewable (biobased) or fossil-fuel (nonbiobased) resources. The most important group of biodegradable aliphatic polyesters are the biobased ones.

3.6.2.1 Poly(hydroxy acid)s The poly(hydroxy acid)s are biodegradable aliphatic polyesters synthesized from hydroxy acids and/or esters or by ring-opening polymerization of cyclic esters. The most widely used poly(hydroxy acid) is the biobased poly(lactic acid) or polylactide (PLA) that is derived from lactic acid, or preferably from lactide (a lactic acid dimer). There are two forms of lactic acid (D- or L-lactic acid). The properties of PLA can be varied by adjusting the relative amounts of the two lactic acid isomers in the polymer. A PLA formulation of about 90% L-lactic acid and 10% D-lactic acid is commonly

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used for the production of packaging films. PLA has reasonable moisture and oxygen properties and is suitable for various flexible packaging, such as blown and cast film. PLA films are not as flexible as LPDE films, but rather stiff (comparable to PET and cellophane). PLA is currently used in wraps for bakery and confectionery products, containers for fresh produce, etc. [35]. The rate of degradation of PLA depends on the degree of crystallinity. Increasing the amount of D-isomer in predominantly LPLA tends to suppress crystallinity and therefore increase the rate of biodegradation [36] (see also Chapter 10, Section 10.2.4). Nativia films is a range of bio-based and biodegradable (PLA) packaging films produced by Taghleef Industries. The film is used for the packaging of products ranging from bakery items to pet food [37]. Nativia Ness of Taghleef Industries is a potato starch- and PLA-based white voided biobased film. The film was originally designed for wrapping chocolate bars of Mars in cooperation with Mondi and Rodenburg Biopolymers.5 The starch-based candy wrapping of Mars can replace the current BOPP film used in chocolate bar wrappers [38].

3.6.2.2 Polyhydroxyalkanoates Polyhydroxyalkanoates (PHAs) is a family of biodegradable aliphatic polyesters produced by microorganisms. The properties of a PHA can be altered by copolymerization with more than 150 different monomers within this family. PHAs are limited to very small-scale applications in packaging, mainly because of their higher price versus fossil fuel-based polymers. In addition, most PHAs types are brittle. The most common PHA is poly(3-hydroxybutyrate) (PHB). The structure of PHB is comparable with that of isotactic polypropylene, and hence, it has many similar properties similar to polypropylene. The isotacticity combined with the linear nature of the chain results in a highly crystalline material with very attractive strength and modulus, but very poor elongation (3%). PHB films cannot be made by conventional processing due to their low elongation. PBAT was blended with PHB to increase its elongation, and thus, make it feasible to process blown film and also the addition of flexible PBAT to PHB was successful in increasing the toughness. The challenges in processing PHB into flexible, thin films is one of the main factors that prevent its widespread application. Its high melting 5

This film won the 11th Global Bioplastics Award, 2016 for a chocolate bar wrapper developed for Mars and Snickers bars packaging.

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temperature (about 175e180
C) and low degradation temperature (220
C) limit the possibility of thermal processing to prepare PHB films. Approaches, such as heat treatment, copolymerization, blending (e.g., with PBAT) and the addition of plasticizers have been used to improve thermal processability and toughness. By using a combination of approaches mentioned above, PHB can be extruded, rolled or pressed into films having reasonably good mechanical properties (2016, US2016230039 A1, UNIV ALBERTA). Another PHA is PHBV (poly(3-hydroxybutyrate-co-3hydroxyvalerate)), that is less stiff and tougher, and it may be used as packaging material. Processability, impact strength, and flexibility can be improved, for example, by increasing the valerate content in a PHB copolymer.

3.7 Polyamides Polyamides are used for the production of flexible plastic packaging due to their unique combination of properties:  good barrier properties to oxygen, chemicals, and aroma substances;  high mechanical strength (strength, stiffness, puncture resistance);  high toughness;  high heat distortion temperature;  high transparency; and  good thermoformability. Polyamides can be processed as cast (CPA) and blown films and can be used for extrusion coating, and the production of biaxially oriented (BOPA) films. BOPA may be produced by both blown film process (“double bubble”) and cast film (“tenter frame”) process with simultaneous or sequential orientation. CPA is used mostly for thermoformable packaging applications. BOPA film can be used for a wide variety of applications, especially where high gas barrier properties are required [39]. BOPA films have excellent barrier to gas, fat, and transmission of aroma, exceptional mechanical strength and also high resistance to impact, puncture, and pin holing. The most commonly used polyamides for the production of flexible plastic packaging are poly(ε-caprolactam) (nynlon 6) and poly(hexamethylene adipamide) (nylon 66), especially nylon 6/66 [39]. Nylon 66

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has much higher melting temperature, thus better temperature resistance, but the nylon 6 is easier to process, and it is cheaper. These types of nylon have good oxygen and aroma barrier properties, but they are poor barriers to water vapor. Another interesting polyamide to be used as a packaging material is poly(metaxylylene adipamide) (nylon-MXD6). The majority of polyamide films are mostly used as component layers of coextruded or laminated multilayer films for packaging of oxygensensitive food, such as meat and processed meat (sausage, bacon), cheese, dairy products, smoked fish, cereals, and semi-cooked meals.

3.7.1 Polyamide 6 Polyamide 6 (or nylon 6 or PA6), synthesized by ring opening of ε-caprolactam (see Fig. 3.1), is considered the ideal component for packaging with the best combination of barrier properties as well as mechanical strength. It is used for the packaging of high-value food products, including meat, cheese, pasta, and convenience food [39]. However, the majority of such applications combine nylon 6 with commodity plastics (mainly polyethylene) in multilayer films to make up for nylon’s poor moisture barriers [40]. The recycling of multilayer films containing nylon 6 is problematic [8,40]. Nylon 6 is a tough material that becomes fluffy when shredded. It also has a high melting temperature, 220
C, which means it will often create lumps in the recyclate if the melting temperature of other materials is lower [8]. Representative examples of commercial nylon 6 products that are suitable for flexible plastic packaging are Ultramid B (BASF) and Akulon 6 (DSM). UltramidÒ B is an all-purpose nylon 6 (m.pt 220
C), which can be used as gas and aroma barrier in flexible plastic packaging, for example in sausage skins. BASF’s UltramidÒ B grades are processed into biaxially

Figure 3.1 Chemical formulas of nylon 6, nylon 66, and nylon MXD6.

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oriented (BOPA) and/or coextruded films for laminates/nonlaminates or thermoforming films. In high barrier EVOH-based structures, layers of UltramidÒ film grades support and protect the EVOH, and thus, enhance its barrier performance [41]. AkulonÒ 6 (DSM) is a nylon 6 (m.pt 220
C), which has high-range processing (high-temperature resistance and high-viscosity extrusion grade), superior mechanical attributes, viscosity, low gel count, and ability to preserve moisture. It is used as a flexible barrier film in food packaging, protecting both fresh and processed food from spoilage aging and discoloration, as well as medical and industrial packaging [42]. AkulonÒ XS6 (DMS) is a new type of nylon 6, which crystallizes much slower in the film bubble than conventional polyamide 6dmatching the crystallization rate of other material layers. This creates a more stable bubble and extends the processing window, with no need to augment production with expensive, amorphous polyamides or polyamide copolymers. Importantly, the look and feel of AkulonÒ XS manufactured film are comparable to traditional film-grade polymers, despite being made from larger crystals. In fact, all its properties are the same [42].

3.7.2 Polyamide 66 Polyamide 66 (or nylon 66 or PA66), synthesized by step-growth polymerization of hexamethylene diamine and adipic acid (see Fig. 3.1), is quite similar to nylon 6, but it has slightly different characteristics. Nylon 66 has higher mechanical strength, stiffness, heat and wear resistance than nylon 6. It also has a better creep resistance, but lower impact strength and is approved for food contact. Nylon 66 benefits over nylon 6 extruded: Higher temperature rating, lower impact strength, and mechanical damping. Higher wear resistance and easier to machine. Representative examples of commercial nylon 66 materials that are suitable for flexible plastic packaging are AkulonÒ 66 (DSM) and UltramidÒ A (BASF) (melting point, m.pt, 260
C). Nylon 6/66 (PA6/66) is a copolyamide made from nylon 6 and nylon 66 (m.pt 190e195
C). Nylon 6/66 is suitable for film applications due to their good balance of properties, including easy processing, flexibility, strength, good optics, and barrier properties. A representative example of commercial nylon 6/66 is UltramidÒ C37LC (BASF) [41]. However, the supply chain for nylon 66 and nylon 6/66 is under extreme, long-term 6

Frost & Sullivan’s 2016 European Barrier Films in Flexible Packaging Product Leadership Award.

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pressure due to a lack of the key raw material 66 salt. Since the global supply of 66 salt is in shortage, it is placing pressure on the pricing and availability of both nylon 66 and nylon 6/66. A good alternative for nylon 6/66 is DSM’s AkulonÒ XS [43].

3.7.3 Nylon-MXD6 Poly(m-xylylene adipamide) (nylon-MXD6) is a crystalline polyamide produced by Mitsubishi Gas Chemical Co., Ind. (see Fig. 3.1). A suitable grade of nynlon-MXD6 for the production of monolayers or multilayer films is S6007 of Mitsubishi [44]. Compared to nylon 6, nylon-MXD6 has the following favorable characteristics:  greater tensile strength and tensile modulus of elasticity (Table 3.2);  high Tg;  low water absorption and moisture permeability;  favorable crystallization speed and ease of molding and fabrication; and  excellent gas-barrier properties against oxygen and carbon dioxide. These features lead to greatly varied applications for nylon-MXD6 as a packaging material. Under certain conditions, its gas-barrier quality exceeds that of EVOH, PVDC, and polyacrylonitrile.

3.8 Polysaccharides Polysaccharides are known for their complex structure and functional diversity. Film-forming polysaccharides include cellulose, starch (native and modified), dextran, pectins, seaweed extracts (alginates, carrageenan, agar), gums (acacia, tragacanth, guar), pullulan, and chitin/chitosan The linear structure present in cellulose (1,4-b-D-glucan), amylose (a component of starch 1,4-a-D-glucan), and chitosan (1,4-b-D-carbohydrate polymer) provide the films with hardness, flexibility, and transparency; the films are also resistant to fats and oils (2013, WO2013042083 A1, UNIV DEL CAUCA; CT REGIONAL DE PRODUCTIVIDAD E INNOVACION DEL CAUCA CREPIC). Polysaccharide-based films usually show poor moisture barrier properties, but selective permeability to O2 and CO2 and resistance to oils [46,47]. The interest for films from polysaccharides

Property

Measuring Method ASTM

PET

Thickness (mm)

15

15

15

Specific gravity

1.22

1.14

1.38

Haze

3.1

2.0

2.5

220(22)

200(20)

160(16)

220(20)

220(20)

190(19)

75

90

140

76

90

60

3.8(385)

1.7(170)

3.4(350)

3.8(390)

1.5(150)

3.9(400)

Tensile strength (MPa [kgf/mm2])

MD

Tensile elongation (%)

MD

Tensile modulus (GPa [kgf/mm2])

MD

D882

TD D882

TD D882

TD

Impact strength (J kgf$cm)

D781

0.5(5)

1.0(10)

0.4(4)

Water vapor permeability (g/m2$24 h)

JIS-Z0208 (B)

41

260

40

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IN

Nylon-MXD6

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Table 3.2 Properties of Biaxially Oriented Film of nylon-MXD6 Versus nylon 6 and PET [45].

Nylon-MXD6 films: stretch ratio of nylon-MXD6: 4  4.

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has grown in recent years because of their edibility, low permeability to oxygen, and contribution to quality preservation.

3.8.1 Cellulose and its Derivatives Cellulose was one of the first materials to be used in packaging. Cellulose derivatives, i.e., cellulose functionalized in a solvent state with various side groups, are an important source of biopolymers for food packaging. Cellophane, methylcellulose, and carboxymethylcellulose are the three traditional film-forming cellulose derivatives in flexible food packaging. The most commonly used cellulose-based food packaging film is cellophane, a versatile thin transparent film made from plant cellulose [48]. The trademark “cellophane” is owned by Futamura (JP), which is the leading producer of cellophane packaging films worldwide. Cellophane offers inherent benefits, such as excellent transparency and clarity in a broad range of colors, high gloss, heat resistance, naturally antistatic, and excellent dead-fold. It is used in food packaging, particularly when high stiffness is preferred to allow bags to stand upright. It is also used for nonfood applications where easy tearing is needed (see also Chapter 10; Section 10.2.4, Table 10.2). Several grades of cellophane are available in various formats, including: - uncoated; - vinyl chloride/vinyl acetate copolymer coated (semipermeable); - nitrocellulose coated (semipermeable); and - PVDC coated (good barrier, but not fully biodegradable). Cellophane finds applications in specialty markets, including twistwrapped confectionery, “breathable” packaging for baked goods, “live” yeast and cheese products and CelloThermÔ ovenable and microwaveable packaging [49]. Although cellophane is biodegradable, the way in which it is made results in a lot of other kinds of pollution. The last years, cellophane has been replaced by polypropylene in food packaging, mainly because of its poor performance at low temperature, limited shelf life, and high cost. A range of cellulose-based packaging films is NatureFlexÔ , developed by Futamura [50]. The NatureFlexÔ film types are available as uncoated, semipermeable, barrier and metalized films, and as labels for food packaging applications.

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3.8.2 Starch Starch is one of the most abundant, inexpensive, and commonly used natural polysaccharides. In its granular form, starch is normally a mixture of amylose and amylopectin polymers. Most starches, such as those from wheat, corn, and potato, contain about 25% amylose and 75% amylopectin. A high-amylose (>25%e75%) starch (from high-amylose rice, corn or peas) is a very useful film-forming material because it normally improves tensile strength, flexibility, and gas barrier properties [51]; see also WO2008003165 A1 (2008, UNIV MANITOBA). A starch-based film is produced from thermoplastic starch (TPS), which is obtained by mixing starch with water or plasticizer (glycerol, sorbitol) under shear at an elevated temperature. Starch is used in the formulation of biodegradable, edible films for the packaging of food (2008, WO2008003165 A1, UNIV MANITOBA). Different starch formulations may lead to the formation of edible films with particular characteristics and properties. Among starches, cassava, corn, and wheat starches have been proposed for the formulation of edible films thanks to their availability and relatively low price [52]. Starch is blended with biodegradable polymers to improve its water resistance, processing properties, and mechanical properties. Typically, the starch content of these starch-based blends is lower than 50% [34] (see also Section 3.6.1.3). The starch-based grades of Mater-BiÒ of Novamont containing various amounts of biodegradable polymers find applications in food packaging (e.g., bags, pouches, sealing films, cling film, or shopping bags) and cosmetic overwrap. The starch-based grades of Bioplast of Biotec contain potato-starch and other biologically sourced polymers. Bioplast film grades are suitable for blown-film extrusion applications, especially ultra-lightweight films with a thickness of about 10 mm, and are used as bags, fruit and vegetable bags, films and mailing films [53].

3.8.3 Chitin/Chitosan Chitin is the second most common biopolymer and can be found in the exoskeleton of crustaceans, such as the shells of shrimps, and mollusks, but also in insects and fungi. It is in ample supply from by-products of the shellfish food industry. A film was made from chitin and cellulose that has the potential to replace flexible plastic packaging. The chitin is derived from crab shells, and the cellulose is derived from tree fibers. A largescale manufacturing process has to be developed to make the new film competitive with the plastic film on cost. While there are plenty of

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industrial processes available to produce cellulose, methods to produce chitin are still developing [54]. Chitosan is a polysaccharide derived by the alkaline deacetylation of chitin. It has great potential for applications in food technology, owing to its biocompatibility, nontoxicity, short time biodegradability, and excellent film-forming ability. Chitosan also has inherent antimicrobial, antifungal, and barrier properties. Further, it has the ability to form edible films that can carry and release compounds with antimicrobial or antioxidant abilities [46,55e57]. Chitosan could also be used as a sensing film in food packaging to detect the quality of the food. It can be combined with other biomaterials to develop sensing films, which could be sensitive to pH, microbial enzyme, and microbial metabolism [57].

3.9 Blends of Polymers A polymer blend is a mixture of at least two polymers having different physical properties than the constituting polymers. A polymer blend forms either a single phase (with a single Tg), and is called miscible, or multiple phases (with at least 2 Tgs), and is called immiscible. The vast majority of polymer blends are immiscible. In practice, the term compatibility is used instead, which describes the degree to which polymers interact. Compatibility creates a disperse phase with size and stability determined by interfacial interactions. A compatible polymer blend is an immiscible blend that exhibits macroscopically uniform physical properties. Miscibility is of maximum compatibility. However, compatibility is a relative term and is not well defined. The compatibility of two polymers is better when their solubility parameters (see Table 3.3) are close to each other depending on their interaction strength (e.g., presence of hydrogen bonding and polar interactions) [58]. Most polymers used in flexible multilayer plastic packaging are incompatible as can be seen in Table 3.4. Even chemically similar polymers like polyethylene and polypropylene are incompatible to each other. The provided compatibility indicators are purely indicative. Commercial packaging films contain specific polymer grades and additives which affect the compatibility of the polymers constituting the blend. Polymers, even in the same family, may not readily mix if their densities are substantially different [62]. A compatible blend is PLA/PBAT, the biodegradable plastic EcovioÒ (BASF) made from PLA and EcoflexÒ (BASF) (see Section 3.6.1.3). Its first application area is in flexible packaging films, e.g., for the production of shopping bags.

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Table 3.3 Average Solubility Parameter (dh) of Selected Polymers Used in Flexible Multilayer Packaging [58e61]. Polymer

dh (MPa1/2)

PE (LDPE, LLDPE, HDPE)

16.4e16.7

PP

16.2e16.6

PVC

19.5e19.6

PVDC

18.9e21.3

PET

20.5e21.2

PA6

25.5e26.0

PA66

26.0e28.0

PVOH

30.5

EVOH (32 mol%)

38.9

EVOH, ethylene-vinyl alcohol; HDPE, high density polyethylene; LDPE, low- density polyethylene; LLDPE, linear low- density polyethylene; PA6, polyamide 6; PA66, polyamide 66; PE, polyethylene; PET, poly(ethylene terephthalate); PP, polypropylene; PVC, poly(vinyl chloride); PVDC, poly(vinylidene chloride); PVOH, poly(vinyl alcohol).

The major problem in the recycling of used flexible multilayer plastic packaging is connected to a great inhomogeneity of the polymers present in the waste. The eventual incompatibility of the different layers is the most important reason of the difficult processing and inferior mechanical properties of the resulting products from mixed, chemically different polymers If the waste stream includes incompatible polymers, such as in a multilayer structure, the incompatible portion will move to the outside of the extrudate and result in die build-up. One possible solution is the use of compatibilizers. Theses additives are responsible for enhancing the phase dispersion and stability; especially, polymer compatibilizers have shown to be a useful tool for the recycling of multilayer packaging based on incompatible polymers (e.g., polyethylene, PET and nylon). However, despite of presenting good physico-mechanical properties, care must be taken when analyzing the viability of recycling the compatibilized film waste from an economic perspective. The use of higher amounts of compatibilizer (as in the case of 10 or 15 w%) is not a common practice among the recycling industry, due to the high costs of the compatibilizers [63]; see also Chapter 8, Section 8.7.1.1.

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Table 3.4 Compatibility of Commonly Used Polymers in Flexible Packaging PE Polymer

LDPE

LLDPE

HDPE

PP

PVC

PET

PA6, PA66

PVDC

EVOH

M

M

*

*

*

*

*

*

LDPE

M

M

M

M

*

*

*

*

*

*

LLDPE

M

M

M

M

*

*

*

*

*

*

HDPE

M

M

M

M

*

*

*

*

*

*

PP

*

*

*

*

M

*

*

*

*

*

PVC

*

*

*

*

*

M

*

*

**

*

PET

*

*

*

*

*

*

M

*

*

*

PA (PA6, PA66)

*

*

*

*

*

*

**

M

*

**

PVDC

*

*

*

*

*

**

*

*

M

*

EVOH

*

*

*

*

*

*

*

**

*

M

*, incompatible; **, semi-compatible; ***, compatible. M, miscible different grades. Adjusted from Merrington A. Recycling of plastics. In: Kutz M, editor. Applied plastics engineering handbook. Elsevier; 2017. p. 167e189.

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M

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3.10 Polymers Used as Adhesives and Tie Layers Tie layers are special adhesives that are used to bond the incompatible layers of a flexible multilayer plastic packaging, mainly in coextrusion. The vast majority of the polymers used in coextrusion as tie layers are maleic anhydride grafted polyolefins, such as ByneÒ l (Dow, ex Dupont), AdmerÔ (Mitsui), and OrevacÒ (Arkema). Adhesives are also used to attach labels and closure systems on flexible plastic packaging. Most commonly used polymers as adhesives for flexible food packaging are polyurethane and acrylics. Solvent-based polyurethane adhesives are used for dry bond lamination (e.g., HI-THANEÔ of Singwon); polyurethane aqueous dispersions are used for wet-bond adhesion (e.g., EpotalÒ P 100 ECO and EpotalÒ FLX 3621 of BASF); see also Chapter 4, Section 4.1.2. Some of the main players in global flexible packaging laminating adhesives market include 3M, Henkel, H.B. Fuller, Dural Industries, Bond Tech Industries, and DIC Corporation [64]. Stripping agents are used for the dissolution or swelling of the tie layers and separation of the individual layers from a multilayer packaging film (see Chapter 7, Section 7.1).

3.11 Polymers Used as Coatings/Sealants Coatings are applied to the inside or outside (e.g., food contact layer), outside (e.g., nonfood contact layer) or in between layers to either alter the physical properties or enhance the aesthetics of the packaging. The various types of coating include protective coatings, primers, sealants, release coatings, gas barriers, antimist coatings, etc. Many applications in the area of flexible packaging require the use of a primer. The primer task of a primer is to enable the adhesion of layers (e.g., inks, adhesives, other film types). The various types of coatings used in flexible multilayer plastic food packaging are shown in Table 3.5. Representative combinations of layers and coatings used in the manufacture of flexible multilayer plastic packaging are shown in Table 3.6. A typical beverage flexible package has the structure: PET/print/primer coating/LDPE/foil/LDPE (heat seal). A typical retort flexible package has the structure: PET/print/primer coating/LDPE/foil/LDPE (heat seal). The

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Table 3.5 Coatings Used in Flexible Multilayer Plastic Food Packaging Coating Material

Type of Coating

Function

Nitrocellulose, reactive polyurethane systems, ionomers (e.g., SurlynÒ of Dow [ex DuPont])

Protective coating

Protects the surface from mechanical damage

Polyacrylate dispersion (e.g., EpotalÒ A 816 of BASF); polyesterpolyurethane dispersion (LuphenÒ 700 of BASF)

Top coatings

Top coat for polymeric film

EEA, EAA, EVA, PVDC, ionomersa

Heat sealable coating

Allow heat sealability for nonsealable materials

Water-based acrylate dispersion (e.g., AquatackÒ , 1422 of Paramelt); waterbased polyurethane (e.g., EmuldurÒ 381 A, EpotalÒ P 350 and LuphenÒ 700 of BASF; AquatackÒ , 1411 & 1467 of Paramelt)

Primer

Improves the bond between a polyolefin film and an otherwise incompatible coating

Blends of acrylic resins and latex; synthetic rubber

Cold sealable coating

Coatings that can be sealed self-to-self using just pressure (e.g., for flowwrapping heatsensitive products like chocolate or ice cream)

Polyamide (Nylon)

Release lacquers

Applied to the opposite surface of a plastic film that is

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Table 3.5 Coatings Used in Flexible Multilayer Plastic Food Packaging (Continued) Coating Material

Type of Coating

Function coated with cold seal to prevent sticking and to promote easy unwinding from the reel

PVDC

Antimist

Prevents formation of condensate droplets/ fogging on the food contact side (e.g., in fresh salad packaging)

PVDC, AlOx vapor coating

Gas barrier

Barrier to oxygen/ moisture/odors/ flavors

EAA, ethylene-acrylic acid; EEA, ethylene-ethyl acrylate; EVA, ethylene-vinyl acetate; PVDC, poly(vinylidene chloride). a EAA or EMA neutralized with cations (e.g., Naþ, Zn2þ, Liþ). Adjusted from Mieth A, Hoekstra E, Simoneau C. Guidance for the identification of polymers in multilayer films used in food contact materials: user guide of selected practices to determine the nature of layers; EUR 27816 EN. Joint Research Centre (JRC) Technical Report, JRC100835. European Commission; 2016. https://doi.org/10.2788/10593.

Table 3.6 Substrates and Coatings Used in Flexible Plastic Packaging [66]. Layer

Coating

PET

Primers

Polyethylene

Adhesive coating

OPP/BOPP

Wash coats

CPP

PVOH

Nylon

Lacquers

MetPET

Varnishes

Cellophane

Acrylic polyurethanes

Aluminum foil

PVDC

BOPP, biaxially oriented polypropylene; CPP, cast polypropylene; MetPET, metalized PET; OPP, oriented polypropylene; PET, poly(ethylene terephthalate); PVDC, poly(vinylidene chloride); PVOH, poly(vinyl alcohol).

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foil is a barrier layer and may be substituted with metalized PET, nylon of EVOH depending on the type of barrier required. Sealant layers provide low-temperature sealability for fast packing line speeds and may also contribute to barrier performance. EVA, EEA, LDPE, LLDPE, polyethylene plastomers, and ionomers are standardly used, among which ionomers additionally provide exceptional oil and grease resistance [26,67]. Metallocene catalyzed polyethylene provides better fast-tack than EVA without the odor and taste transfer associated with EVA [68].

3.12 Polymers Used as Inks Many different types of resins are used in the ink formulations for printing on flexible packaging, including styrene, acrylics (e.g., JoncrylÒ acrylics of BASF), polyurethanes (e.g., VersamidÒ PUR of BASF) e.g., polyamides (e.g., VersamidÒ 970 series of BASF), nitrocellulose, etc. The use of nitrocellulose is not recommended in retort packaging due to the formation of nitrosamines caused by the exposure of it in the packaging to high temperatures. Polyurethane resins create a flexible film and provide superior lamination bond strengths that prevent delamination of the packaging; they are not as effective as other resins when it comes to pigment dispersion and also tend to be harder to print with. For this reason, polyurethanes tend to require a coresin to help improve the pigment dispersion [69].

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FURANIX TECHNOLOGIES BV

Process for producing an oriented film comprising poly(ethylene-2,5furandicarboxylate).

4 Types, Forms, and Uses of Flexible Plastic Packaging 4.1 Types of Flexible Plastic Packaging Flexible plastic packaging refers to a package or container made of flexible or easily yielding plastic materials that when wrapped up or filled and closed with a product can be readily changed in shape. The term is used to describe monolayer and multilayer packaging films having a thickness less than 250 mm and applies generally to bags, pouches, or wraps [1]. Flexible packaging has played an increasing role in containing a wide variety of products ranging from liquid and dry chemicals to food products. Because of this wide variety of products, the flexible packaging industry is constantly changing the characteristics of the packaging structures to meet the needs of the packers and consumers. Desired flexible packaging characteristics include optical clarity, rigidity, toughness, heat resistance, and recyclability. Some of the key market converters in the flexible packaging industry are Amcor Ltd., Sealed Air Corporation, Sigma Plastics Group, American Packaging Corporation, Amerplast, ProAmpac, Bischof þ Klein SE and Co. KG, Bryce Corporation, Clondalkin, Constantia Flexibles International GmbH, Coveris, Dai Nippon Printing, Flextrus AB (Part of AR Packaging Group), Huhtamaki Group, Innovia Films, Mondi Group, Printpack, Schur Flexibles Group, and Sonoco Products [2]. The main types of flexible plastic packaging are single film or monolayer and multilayer packaging. All types of flexible plastic packaging create a large amount of waste that must be disposed of or recycled.

4.1.1 Monolayers A monolayer film is produced with a single film layer typically comprising low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), or polypropylene. The monolayer film is made from either a single polymer or a blend of several polymers. A monolayer film is an economical choice when single Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00004-9 Copyright © 2020 Elsevier Inc. All rights reserved.

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layer film properties are sufficient to protect the product from oxygen transfer, water vapor transfer, or other gaseous or greasy substances. Monolayer, single material flexible packaging is commonly found in plastic bags, produce bags, and self-sealed food storage bags. Monolayer, single material flexible packaging constitutes about half of flexible packaging waste. It is currently collected and mechanically recycled using store drop-off programs or in limited municipal curbside collection programs.

4.1.2 Multilayers Most packaging, especially that involved in the flexible packaging, is made up of a plurality of layers (ranging from 3 up to 20 layers) of a variety of plastic films, adhesives, inks, and metals. These layers are firmly adhered together by either the inherent bonding action of the polymers themselves or adhesives. A multilayer packaging film can be coextruded or laminated. There is, currently, no practical method of disposing of or recycling this heterogeneous, multi-ply packaging material after use. There has, thus, been a difficulty in recycling multilayer flexible plastic packaging due to the combination of different materials in the laminate. Flexible plastic packaging cannot be readily separated back into the individual components. In the combined form, certain layers melt at different process temperatures than other polymer layers, and some layers such as an aluminum coating do not melt at all at polymer processing temperatures. Most discarded multilayer packaging films are not accepted in Material Recycling Facilities (MRFs) and are disposed of by incineration or burial in landfills.

4.1.2.1 Coextruded Films In coextrusion, separate extruders are used to produce layers of different polymers. The layers join together in the molten state in the extrusion die. The combined layers then pass through the die to be cast or blown into one multilayer film. The combination of several layers of different materials improves the mechanical and physical properties of the film including puncture, tear, and heat resistance, as well as moisture and oxygen barrier properties. Multilayer films find many applications in the high-volume food packaging industry. The combination of several polymer layers significantly increases shelf-life by controlling the transmission rate of oxygen,

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carbon dioxide, and moisture, which is a key factor in preserving the freshness of fresh produce for longer period of time. Multilayer films constitute about 17% of all produced packaging films [3]. The majority of today’s packaging films include more than one polyethylene layer. LLDPE layer, which is widely used in food packaging, is sometimes combined with HDPE, which is stiffer, harder, and has higher tensile and bursting strength but lower impact and tear strength than LLDPE. The combination of LLDPE and HDPE provides superior mechanical properties and allows for thinner films. Because the polyethylene films have poor gas barrier properties, they are often combined with polar polymers such as polyamide, ethylene vinyl alcohol (EVOH), or poly(vinylidene chloride) (PVDC). For example, a barrier cereal liner film (bag-in-box) consists of several layers of HDPE (as moisture barrier), EVOH (as aroma barrier) and ethylene vinyl acetate (EVA) (as sealant), e.g., HDPE-tie layer-EVOH-tie-EVA [4]; whereas films that require higher mechanical strength and/or improved heat resistance (microwavable and hot-filled food packaging) often include a layer of polypropylene. Besides superior heat resistance, polypropylene provides the basic strength of the packaging and contributes to the moisture barrier. Many multilayer barrier films for food packaging consist of a combination of polyethylene and polyamide 6 (nylon 6 or PA6), where polyethylene acts as a barrier for moisture and polyamide 6 as a barrier for oxygen, thus significantly extending the shelf life of the packaged food. Such packaging cannot be produced with a monomaterial polyethylene film, as the layer thickness to achieve sufficient barrier properties would become too high. The addition of polyamide 6 in the multimaterial solution reduces the total layer thickness and improves the mechanical integrity of the film resulting in less rupture during transportation and logistics. This leads to a lower food waste percentage and, thus, to a significantly better carbon footprint in a life-cycle analysis [5]. However, the recycling of the multilayer packaging films has several problems. The hydrophilic polyamide and hydrophobic polyethylene are not compatible with each other and there is a 40e50 C difference between their processing temperatures. Thus, the conventional compounding methods are not suitable for their homogenization, and their separation is not feasible. DSM and APK developed a solvent-based process, the so-called NewcyclingÒ technology (see Chapter 7, Section 7.3), for the recycling of multilayer polyethylene/polyamide 6 packaging waste [5]. Further, the coextrusion of dissimilar polymers requires tie resins because the different layers do not adhere well to each other. A typical packaging film for fresh produce consists of 4 to 7 layers. Two examples

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are LLDPE-tie-EVOH-tie-LLDPE and LLDPE-HDPE-tie-EVOH-tieHDPE-LLDPE among many others. Most of these multilayer films consist of at least 50% olefins (see Table 4.1).

4.1.2.1.1 Tie Layers To improve adhesion between poorly adhering layers, special adhesive polymers or tie resins have been developed. Tie layers are functional polymers coextruded between two chemically different polymers to improve the adhesive strength of a multilayer structure. These resins are commonly ethylene copolymers of polar and nonpolar monomers and with or without functional reactive groups [7] (see Table 4.2). Typical nonreactive tie resins include EVA and ethylene methyl acrylate. Other important tie resins include acid-modified olefin copolymers Table 4.1 Common Coextruded (Multilayer) Flexible Packaging Films Multilayer

Structure

Application

LLDPE/HDPE/LLDPE

15/70/15

Grocery bags

HDPE/LLDPE/HDPE/ EVA

30/30/30/10

Cereal liners

Paper-LDPE-AlLDPE

Laminated packaging

Liquid/paste packaging (juice, milk cartons)

PET/Tie/LDPE/Al/ LDPE

Laminated packaging

Liquid/paste packaging (juice, milk cartons)

LLDPE-Tie-EVOHTie-LLDPE

Fresh meat

LLDPE-Tie-PA-TieLLDPE

40/5/10/5/40

Fresh meat

LLDPE-Tie-PAEVOH-PA-TieLLDPE

30/5/10/10/10/5/30

Fresh meat

LLDPE-HDPE-TieEVOH-Tie-HDPELLDPE

20/20/5/10/5/20/20

Processed meat

Al, aluminum; EVA, Ethylene vinyl acetate; EVOH, Ethylene vinyl alcohol; HDPE, Highdensity polyethylene; LDPE, Low-density polyethylene; LLDPE, Linear low-density polyethylene; PA, Polyamide; PET, Poly(ethylene terephthalate).

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Table 4.2 Typical Tie Layer Resins Tie Layer Resin

Adherent Layer

Ethylene vinyl acetate (EVA)

HDPE, LDPE, PP, PS, PVDC

Ethylene methyl acrylate (EMA)

HDPE, LDPE, PP, PS, PVDC

Ethylene acrylic acid (EAA)

PA, PET, ionomers, LDPE, EVA, EMA, Al

Ethylene-grafted maleic anhydride (AMP)

PA, Al, EVOH, cellulose

such as ethylene acrylic acid (EAA) and ethylene methacrylic acid (EMAA). They are considered nonreactive as no or only a small portion of the acid groups undergo chemical reactions such as esterification. These resins still provide excellent adhesion to many polar polymers because they form strong hydrogen and polar bonds with many polar polymers such as nylon and polyesters. The most important reactive tie layer resin is anhydride-modified polyethylene (AMP).1 This adhesive resin is frequently employed when polyolefins have to be bonded to polyamides (nylons) or to EVOH copolymers. The anhydride reacts with amine end groups to form imides and with alcohols to form ester crosslinks. A very important parameter is the amount of functionality in the tie resin. The anhydride level is usually less than 1% because a higher percentage is often cost prohibitive and/or does not yield enough improvements in performance and adhesion (peel strength) to justify the higher cost. AMPs can also be employed when no chemical reaction between the two resin layers takes place, as it is the case with PET and PVDC. In the case of metalized films or aluminum foils, tie resins with acid functionalities are used. Typically, copolymers of ethylene and acrylic acid and/or methacrylic acid (EAA, EMAA) are employed for these applications that also bond well to nylon, whereas acrylate-modified olefin resins are a good choice when the film has to adhere to inks and polyesters.

1

Anhydrides are usually grafted onto a polyethylene backbone. These resins are much more reactive than ordinary anhydrideeethylene copolymers with same percentage of anhydride because there is less steric hindrance involved, that is, the grafted anhydride groups are more accessible.

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4.1.2.2 Laminates Lamination adheres multiple film layers together with a bonding agent. Adhesive is applied to the less absorbent layer. A second layer is then pressed against the first to produce a multilayer film. The process is repeated for additional layers.

4.1.2.3 Adhesives The different types of adhesives currently used to laminate flexible packing layers include: (1) one component solvent-based; (2) two component solvent-based; (3) one component water-based; (4) two component water-based; and (5) two component solvent-free type adhesives (2005, US2005163960 A1, NORTHWEST COATINGS, LLC). Solvent-based adhesives have inherent limitations that include: (1) emission of volatile organic compounds (VOCs); (2) high cost of solvent recovery equipment; (3) flammability; and (4) analysis and control of residual solvents in the package. Water-based adhesives have inherent limitations that include: (1) need for extended drying equipment; (2) effect of heat used in drying on thermally sensitive packaging films; (3) variable drying rates dependent on ambient humidity level; and (4) difficulty in starting and stopping due to adhesive drying on the application equipment (2005, US2005163960 A1, NORTHWEST COATINGS, LLC). Any two component system (solvent-based, water-based, or solventfree) has inherent disadvantages that include: (1) the need for accurate mixing of the two components; (2) limited pot life of the mixed components; and (3) the time delay (typically 2e5 days) required for the two components to react to achieve the final adhesive properties. Other limitations associated with two component solvent-free adhesives include: (1) the need for heated application equipment and (2) residual toxic aromatic amines, which are by-products of isocyanate-based curing systems (2005, US2005163960 A1, NORTHWEST COATINGS, LLC). Radiation-curable adhesives can potentially be used as flexible packaging laminating adhesives. They may offer: (1) stable one-part compositions; (2) little or no VOCs; and (3) full adhesive performance immediately on cure. UV-curable laminating adhesives require at least one layer of packing material that is sufficiently transparent to allow penetration of UV light to cure the adhesive. Electron beam curing has the added advantage of being able to penetrate opaque or printed packaging materials to cure the adhesive (2005, US2005163960 A1, NORTHWEST COATINGS, LLC).

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4.1.3 Metalized and Metal Foil Containing Films For more demanding packaging applications, plastic films are metal˚ ), usually ized with a very thin metal coating layer (about 400e500 A aluminum, deposited on the film as a vapor. The most commonly used polymers for metalized films are polypropylene and PET. The aluminum layer greatly reduces the moisture and oxygen transmission rate and also provides a metallic and glossy appearance. Flexible packaging films are often laminated to a metal foil, typically of a thickness of about 6e10 mm, so that a desired combination of properties of both materials can be obtained. Aluminum foil laminated with plastic films is also used as labels in flexible plastic packaging. These labels should not be confused with metalized film. Metal foil labels are extremely problematic in two areas. First, they alarm metal detectors that are employed at the beginning of the recycling process to protect machinery. When this occurs, the entire package containing the offending part is discarded and landfilled. Secondly, if they happen to pass through the process into the extruder, they can quickly blind a melt filter causing a pressure upset, which automatically shuts down the process for safety [7a]. The applications of these films in flexible packaging include packaging of food products, medical items, and industrial products, such as household electrical appliances and electronic items. Aluminum cannot be microwaved and is not recyclable [6]. In recent years, the amount of aluminum foil used in packaging has decreased to reduce recycling problems.

4.1.3.1 Metalized Polypropylene The surface of polypropylene film is nonpolar with a low surface energy or tension of about 30 mN/m (dyne/cm) and, hence, lacks strong adhesion to metals. To improve adhesive properties, the polypropylene film is, thus, often treated with corona discharge plasma to increase the surface energy to a minimum surface energy of 38 mN/m [8]. The applications of metalized polypropylene film are numerous. Metalized biaxially oriented polypropylene (BOPP) is used in food packaging for meat, potato chips, biscuits, and other food products. Metalized BOPP is also used for decorative packaging or gift wrapping as metalized BOPP lends a sparkle to packages that paper and others do not. Personal care industries use metalized BOPP films to create containers

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lined with water-resistant and gas-resistant packages for preservation and protection [9]. Characteristically, a multilayer potato chip bag is composed of a metalized BOPP (inside layer), LDPE (middle layer), BOPP (middle layer), and SurlynÒ (outermost layer and sealant). Major companies operating in the global metalized BOPP market include Jindal Poly Films, VacMet, Uflex, Formosa Plastics Group, DK Enterprises, Mondi Group, Viam Films, Vitophel, and General Binding [9]. Metallized cast polypropylene film (CPP film) with good bonding between a metallized layer and CPP provides excellent barrier properties to oxygen and moisture. Retort CPP film has strong heat sealing properties, good heat resistance, and low temperature impact performance. Indicative applications include bread or noodle packaging, retort pouch, dry fruit packaging, and meat product packaging. Metalized polypropylene packaging films, such as crinkly bags and wraps, are not currently recycled and put in the trash bin.

4.1.3.2 Metalized Poly(ethylene terephthalate) Metalized PET films cover an ever-growing range of applications, making it one of the fastest growing segments in the flexible packaging market. Metalized PET films provide an optimal solution for high oxygen and general gas barrier levels, aroma and flavor retention, and significant improvement in water vapor barrier. Metalized PET film is also proven to achieve special optical properties or a metal look for decorative applications. Although the metalized PET film market continues to grow, there are no established sustainable solutions to recover and recycle postconsumer and postindustrial metalized PET films waste. Unlike PET bottle recycling, which is a viable and profitable business, metalized PET films are discarded as waste and end up in the landfill. Similarly, trim scrap generated during the process of making metalized PET films has traditionally been discarded. The absence of collection schemes for metalized PET films makes a poor business case for the technology to be designed for this material. Currently, there are no recycling facilities for metalized PET films (2014, WO2014162238 A2, JAIN PRANAY). There are numerous issues that make recycling of PET films difficult. The intrinsic viscosity of metalized PET film is typically less than 0.6 dL/ g, making it unsuitable for many applications such as sheet extrusion/ thermoforming after recycling (2014, WO2014162238 A, JAIN PRANAY).

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4.2 Forms of Flexible Plastic Packaging The most common forms of flexible plastic packaging are: bags, T-shirt bags, wave top bags, soft loop handle bags, die cut handle bags, wraps, shrink wraps, stretch wraps, bubble wraps, twist wraps, pouches/sachets, stand-up pouches (SUPs), lay flat/pillow pouches, labels and sleeves.

4.2.1 Bags Plastic bags (of thin film) are usually made of LDPE or HDPE and also of polypropylene. Common uses include bags for shopping, household garbage, dry cleaning, newspapers, frozen foods, fresh produce, agricultural products, medical and biohazard waste, antistatic bags, etc. Plastic bags are inexpensive to mass produce, relatively easy to transport due to their lightweight, and have the ability to fold up to a small size. They are water resistant and add virtually no weight to the goods they carry. Plastic bags are used once and discarded as trash, typically ending up in landfills or incinerated, adding to air pollution. Many plastic bags escaping the disposal process end up in gutters, sewers, waterways, or in the sea creating a modern menace for the environment [10].

4.2.2 Wraps Plastic wrap is a generic term commonly used to describe a variety of flexible packaging products. Plastic wrap is most often referring to industrial plastic wrap for securing pallets or food grade plastic wrap.

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Food plastic wrap, also known as cling film, or food wrap, is a thin plastic film commonly used for sealing and securing food items in containers to keep fresh. Food plastic wrap is sold in rolls or more typically sold with a roll in a box that has a cutting edge on it. Most monolayer film wraps range in thickness from 0.5 to 2 mil, and at such low thickness, they are highly flexible and generally not able to support their own weight.

4.2.2.1 Shrink Wraps A shrink wrap film is a heat-activated LDPE film that wraps around an object or a cluster of objects such as cans or bottles (see Fig. 4.1). Shrinkage occurs when the film absorbs energy, typically through the form of heat energy (e.g., a heat gun), causing the molecule chains to return to a more natural arrangement. The manufacturing process of LDPE film allows the shrink potential around a product to be between 50 and 70% in the machine direction (MD), or length of the film, and 5 to 25% in the transverse direction (TD), or width of film. The film casts to the product, creating a tight unitized pack. This provides additional shipping, palletizing, and handling benefits compared with unitizing and packaging products within a corrugated box.

Figure 4.1 Cluster pack having six bottles encased by a shrink film (2014, DE102012016340 A, KHS GMBH). 1, Cluster pack; 2, Six PET bottles; 3, Shrink film (LDPE); 4, Shrink holes; 5, Carrying plastic strip; and 14, Corner container.

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The following types of shrink wraps are used [11]: Centerfold shrink wrap: This is one of the most common types of shrink wrap for retail packaging. Centerfold shrink wrap is folded in half length ways and placed on a roll. This allows users to slide the product being wrapped between the film, seal the open ends, and then apply heat. Centerfold shrink wrap is most commonly made from polyolefin and PVC. Shrink sleeves: This is another very common type of shrink wrap for retail packaging. Shrink sleeves are often printed on and placed over bottles to brand products. Shrink sleeves often have a lower maximum shrink rate to keep from distorting printing. Shrink tubing: The main difference between shrink tubing and shrink sleeves is that shrink tubing is often on a continuous roll. Shrink sleeves are precut to fit the product being packaged. Shrink tubing is often made from polyethylene or PVC. Tubing made from PVC is often used for retail packaging longer objects, while polyethylene tubing is often used for packaging cases of liquids and canned products. Shrink banding: This is another form of tubing or sleeve except much smaller. Most people are familiar with shrink banding as a safety seal wrapped around over-the-counter medicines and toiletries. Shrink banding is often made from a PVC shrink wrap and requires a low shrink temperature. Shrink banding often comes with easy-to-open perforations. Most shrink banding is custom made to fit the specific bottle being packaged, but some companies do stock a lot of different banding sizes. Shrink Bags: These have three enclosed sides and one open side. Users insert a product inside the bag, seal the open end, and apply heat. Shrink bags are most commonly available in polyethylene or PVC. Pallet shrink wrap bags: Before the popularity of stretch film, pallet shrink bags used to be the preferred method of stabilizing and protecting pallet loads of products. Pallet bags are normally made from 3e6 mil clear LDPE shrink wrap. Pallet bags are often shrunk with a propane heat gun. They are used to stabilize and protect products during transport.

4.2.2.2 Stretch Wraps Stretch wrap or stretch film is a highly stretchable plastic film that is used in packaging and shipping to wrap around items to keep them in place. The elastic recovery of stretch wrap keeps the items tightly bound. In contrast, shrink wrap is applied loosely around an item and shrinks tightly with heat. Stretch film is frequently used to unitize pallet loads, and it may also be used for bundling smaller items such as food (e.g., fruits).

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Stretch film also finds applications as diverse as wrapping of furniture and airport luggage. Stretch wrap is usually made from LLDPE. Some of the most important types of stretch wraps, as described by IPS Packaging [11a] are: Cast stretch film, like blown stretch film, is created using an extensive manufacturing process known as cast extrusion. This process requires the continuous propelling of thermoplastic material through a flat die onto a chilled roll. The film thickness is then determined by how fast the casting roll pulls the plastic away from the die. This process causes cast films to have excellent clarity, which allows users the ability to see the wrapped products. This film, unlike blown film, is extremely quiet when coming off the roll and is easier to stretch. Cast stretch film also offers two-sided cling that allows products to stay securely wrapped during shipping processes. While cast film has excellent qualities, including a lower price tag from blown film, it does not stand up to blown film in holding power and tear resistance. Cast stretch film is initially easier to stretch, but because it is less dense, the film does not have as strong of a stretch memory. Blown stretch film is manufactured by a process known as blown extrusion. This process consists of plastic melt being pumped through a circular slit die, to create a thin walled tube. Air is then introduced to the tube, allowing the volume of air contained to stretch the tube to the desired width. On top of the tube, an air ring blows onto the film to cool it. This process of cooling the film allows the blown film to be tougher and more resilient to other types of film. Because blown film is tougher than most other films, it also has a higher tear resistance. This becomes an advantage when securing loads that may have sharper edges susceptible to breaking through less dense films. Blown films also have a higher degree of memory once stretched, which allows for packages to stay better secured. While blown film has the advantage of higher tear resistance and strength due to its manufacturing process, this also results in higher costs to consumers and poorer film clarity. Blown film is also a bit noisier than most films, including cast film. Hand stretch film is designed specifically to be applied manually. It is also referred to as hand film, hand stretch wrap, hand wrap, or manual pallet wrap. It is typically utilized in lower capacity packaging operations. However, the efficiency of manual stretch wrap packaging should be regularly reevaluated against potential benefits of upgrading to a machine wrapper. Choosing the right stretch applicator will result in more efficient and cost-effective packaging operations.

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Machine stretch film is designed to be applied with a stretch wrap machine. It provides many advantages over hand film including faster and more efficient packaging, reduced packaging material costs, safer application, more secure loads, and more. Common machine stretch film types are cast machine stretch film, blown machine film, and prestretched films. Prestretched film is stretched close to its ultimate breaking point before being wound onto rolls. As a result, the film does not require as much stretching energy as the standard stretch film to accomplish the same wrapping force. Prestretched film consumption can be one half of that of traditional stretch films, allowing for vast cost savings. Stretch wrap films can only be recycled in a special process and therefore cannot be put in the curbside recycling bin.

4.2.2.3 Bubble Wrap Bubble wrap is a flexible plastic film made from LDPE containing numerous small air pockets, and is used in cushioning items during shipment. Standard average bubble diameter is 6.0e25.4 mm and height is about 4 mm. Bubble wrap is commonly used for packing fragile items. Bubble wrap must be flattened before it can be recycled. The bubble wrap needs to be a flat sheet to be processed with other types of similar stretch plastics. Once flattened, the bubble wraps and similar plastics are taken to a facility to be ground up and turned into plastic pellets. Those pellets can then be reused to create other plastic products.

4.2.2.4 Twist Wraps Twist wrapping is a particular method of closing complete wrappings for packaging of goods. A prerequisite for the use of twist wrapping is that the film must exhibit neither tear starting nor tearing-off at the twist points, but on the other hand, it must be sufficiently stiff so that no shrinkage or crumpling occurs during twisting. While early twist wrappers were made mostly from cellophane, modern twist wrappers are made of nonoriented (cast) polypropylene film. This packaging method is used for the complete wrapping of relatively small goods items, including round articles such as candies, bottles, candles, rolls of circular candies, chocolate bars, marzipan bars, or the like (1987, EP0217388 A2, HOECHST AG). This type of packaging is very large in piece count, but it represents a small weight percentage of the total flexible plastic packaging.

4.2.3 Pouches, Sachets Pouches and sachets are small bags comprising two side flat sheets that are flexible and sealed along the edges to form a compartment, whose

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volume is dependent on the relative position of the walls. There is no clear distinction between a pouch and a sachet other than the common understanding that a sachet is smaller. There are mainly two types of pouches: stand-up pouches (SUPs) or free-standing pouches and lay flat or pillow pouches. Conventional SUPs are generally constructed by forming a gusset in the bottom to provide a flat bottom surface or base for the upper portion of the pouch. SUPs are fabricated from two or more layers of laminated materials such as PET, BOPP, nylon, polyethylene, and other polymers, aluminum foil, and specialty materials. The PET, nylon, or BOPP offers good clarity, rigidity, and heat resistance, while the polyethylene offers a sealant layer to seal the bag closed using heat and pressure. The heat resistance on the outer layer is used to resist sticking to the high temperature sealing jaws of the packer machine. A printed layer is applied inside on the contact surface either on the outer film or the inner film in such a laminate before adhesion of the inner film to the outer film and is then visible through the transparent outer film. The pouch’s walls have a thickness in the range from 2 to 5 mil (0.002e0.005 in or 0.051e0.127 mm), and while flexible, they have a degree of stiffness. SUPs dominate the types segment in terms of both revenue and growth rate. On the basis of product type, the SUPs can be distinguished into aseptic, standard, retort, and hot-filled pouches. Aseptic segment is anticipated to dominate the global market in terms of revenue over the period 2018 to 2025. In terms of form, the SUPs can be distinguished into round bottom, rollstock, K-style, plow/folded bottom, flat bottom, and others. Round bottom SUPs are popularly used across several application industries as they are ideal for packaging products weighing less than one pound. K-style is the second most popular segment after round bottom pouches. SUPs are available in three closure types, namely, top notch, zipper, and spout. Top notch pouches dominate the global market due to the ease of usage and reclosability [12]. Flexible pouches are currently used in the packaging of a broad variety of products, from food and beverage products to cleaning supplies and other household items. Single-use plastic sachets allow low-income consumers in developing countries to buy small amounts of quality products that would otherwise be unaffordable to them. These products tend to provide hygiene or nutrition benefits. Despite the numerous benefits, pouches and sachets also pose a serious waste challenge. These multilayer flexible packaging materials are not currently recycled and have little or no economic value, so they leak into the environment. Huge

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amounts of pouches and sachets are used once and just thrown away, all over the world, ending up in landfill or in waterways and oceans [13]. In the last few years, there are intense efforts to develop recyclable pouches. The trend is to make a pouch from a monocomponent material, namely polyethylene that will allow recycling [14]. Nowadays, many recycling facilities are able to recycle a coextruded or laminated film that contains at least 95% polyethylene. However, polyethylene suffers from some disadvantages that make it difficult to design an SUP using polyethylene as the only material of construction. For example, HDPE provides the stiffness that is required for a SUP, but the physical and optical properties of HDPE (such as haze and gloss) are comparatively poor. In contrast, LLDPE provides very good physical and optical properties but poor stiffness. The physical and optical properties of mediumdensity polyethylene (MLDPE) generally fall in between those of HDPE and LLDPE. Accordingly, a simple “all-polyethylene” SUP design will not have the combination of optical and stiffness properties that are provided by the prior art design that contains a layer of PET and a layer of polyethylene (2016, WO2016128865 A1, NOVA CHEMICALS (INTERNATIONAL) S A). Mondi and Werner & Mertz developed a 100% recyclable pouch made of polyethylene monomaterial, with detachable decorative panels. The pouch is free of glue or adhesive. Spout and cap are also made of polyethylene. The pouch replaces conventional flexible packaging for Frosch products. The monomaterial pouch is disclosed in EP3168169 A1 (2017, MONDI CONSUMER PACKAGING TECH GMBH; WERNER & MERTZ GMBH) which describes a pouch (see Fig. 4.2) having front (2) and back face panels formed of a body film and each having two generally parallel and normally vertical side edges bridging ends of respective upper and lower edges, respective longitudinal side welds (3) fixing the side edges of the front panel to the side edges of the back panel; a separate piece of label film (6) different from the body film, covering a mid-portion of one of the face panels between the respective longitudinal edges (3), and spaced downward from the upper edge of the one face panel (2) and upward from the lower edge of the one face panel (2), and structure at the longitudinal edges holding the piece of label film (6) on the one face pane (2)l without surface bonding of the piece of label film (6) to the one face panel (2) between the respective longitudinal edges (3). According to the invention, the additional piece of label film and the body film are not fully attached to one another. Preferably, large

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Figure 4.2 Front view of a pouch having a body made from a monocomponent film and a separate piece of label film (2017, EP3168169 A1, MONDI CONSUMER PACKAGING TECH GMBH; WERNER & MERTZ GMBH). 1, Pouch body; 2, Face panel; 3, Longitudinal welds; 4, Stamped-out handle; 5, Reclosable spout; 6, Label film; 7, Printing; and 11, Tear lines.

unattached areas remain so that the particles resulting from shredding can then be fully separated from one another. To allow for good recycling of the pouch body (1), this is made from a monocomponent material. Polyolefins such as polyethylene or polypropylene are preferred. The body film is then labeled as single-origin, in particular, if it can be classified according to the German Ordinance of the Avoidance and Recovery of Packaging Waste (Packaging OrdinancedVerpack V) according to appendix IV, in which recycling number 02 HDPE, recycling number 04 LDPE, and recycling number 05 polypropylene are allocated, for example. Depending on the intended use, however, polyethylenes or polypropylenes with differing densities can be used as a blend or in a multilayer body film. The label film is preferably a multilayer laminate. Furthermore, the body film and the label film have different densities with a difference of at least 0.02 g/cm3. The materials can therefore be separated from one another using a suitable density separation in a liquid technique. In the simplest case, separation can occur in a liquid bath, thanks to the different

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densities. If, for example, the body film has a density greater than 1 g/cm3, which is the density of water, and the piece of label film has a density greater than 1 g/cm3according to a preferred design of the invention, separation can occur in a simple water bath using a float-sink process. Another approach is to use flexible pouches, whose constituent parts can be easily deconstructed and placed into appropriate recycling streams. US2018009587 A1 (2018, NESTEC SA) discloses such a recyclable flexible pouch (10), as shown in Fig. 4.3, comprising a flexible pouch body defining a chamber into which a product may be disposed, the pouch body having a front wall (14) and a rear wall (16) each formed of a plurality of flexible layers of different materials so as to form at least an inner layer (60, 66), an intermediate layer (66, 68), and an outer layer (64, 70) connected with one another; the connection of the intermediate layer and the outer layer having a connection strength less than the strength of the connection between the intermediate layer and the inner layer such that the intermediate layer and the outer layer can be selectively peeled from the inner layer; and means for assisting in the removal of one or more

Figure 4.3 A perspective view of a flexible pouch in a partially deconstructed configuration (2018, US2018009587 A1, NESTEC SA).10, Flexible pouch; 14, Front wall; 16, Rear wall; 30, First side edge; 32, Second side edge; 34, Upper edge; 52, Cap; 58, Dispensing device; 60, 66, Inner layers; 62, 68, Intermediate layers; and 64, 70, Outer layers.

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of the inner layer, the intermediate layer, and the outer layer from one another. The means for assisting in the removal of one or more of the inner layer, the intermediate layer, and the outer layer from one another comprises an unconnected portion or a cut associated with at least one of the inner layer, the intermediate layer, and the outer layer. EP3059061 A1 (2016, MONDI CONSUMER PACKAGING TECHNOLOGIES GMBH) discloses a recyclable flexible pouch, wherein the first surface of the pouch wall is formed of a transparent outer film, preferably PET, and the second surface of the pouch wall is formed of an inner film, preferably polyethylene or polypropylene. The inner film and the outer film are connected to each other with a water-soluble pressure adhesive applied only at the side edges of the pouch body. When the pouch is cut or shredded into particles after being used for recycling, the particles formed by the outer film separate easily from the particles of the inner film (see also Chapter 8, Section 8.2.1). Avantium’s business unit Synvina produced pouches from biaxially oriented poly(ethylene furanoate) (BOPEF), which is a biobased polyester. The pouches consist of a two-layer laminate of a BOPEF layer and commercial 55% biobased polyethylene (bio-PE) sealing layer. BOPEF/ bio-PE’s inherent oxygen permeability of about 10 cm3/m2$day$atm fits well with oxygen-sensitive products such as cheese and dairy, dry snacks, sauces, and cosmetics, which, today, employ more complex multilayer structures such as PVDC-coated BOPET or EVOH-containing sealant layer. Besides the reduced complexity, BOPEF/bio-PE pouches offer excellent toughness and clarity and are suitable for dry and liquid products [15].

4.2.4 Air Pillows and Envelopes Packaging air pillows or air cushions are inflatable plastic bags that are made out of two layers of polyethylene (LDPE and HDPE). They are used extensively in e-commerce, thanks to their ease-of-use, low cost, product protection, and convenience. They are more environmentally friendly when compared with alternative forms of void fill such as foam peanuts made of expanded polystyrene. In fact, many disposal companies will not even accept packaging peanuts for disposal anymore due to the complexity of disposal and their harmful effects on the environment (see also Section 4.3.5). Plastic shipping envelopes that have bubble wrap inside of them cannot be placed in the curbside recycling bin. They must be put instead in the curbside trash bin. Plastic shipping envelopes having the labels removed, air pillows, and bubble wraps can go into the curbside recycling bin.

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4.2.5 Labels and Sleeves Labels (or stickers) and sleeves are essential components of plastic packaging, especially plastic containers. They are used for informational and promotional purposes, giving details relating to the brand, product composition, use-by date, usage precautions where applicable, and the procedure to follow for recycling the packaging after use. The labels can be mono- or multilayers comprising one or more polymers, typically produced by coextrusion, while some labels are aluminized. A label is known as “dry” if adhesive has to be applied before it is stuck to the product or “self-adhesive” if it is supplied precoated with an adhesive [16]. There are two types of sleeve: stretch and shrink (wrap) sleeves. The sleeves do not require an adhesive to attach them to a plastic bottle. The polymers used for labels and sleeves are polypropylene, oriented polypropylene (OPP), glycol-modified PET (PET-G), LDPE, PVC, and polystyrene. PET-G is the preferred material for shrink wrap labels and sleeves for PET containers because of its optimum shrink properties or printability. Label and sleeve made of the same or compatible polymer as the film or the plastic container do not become contaminates and are recycled with the film [17]; for example, OPP-based labels can be recycled with HDPE and polypropylene bottles. If the label and the shrink wrap sleeve are made of a polymer that is incompatible to the film and the plastic container, it is necessary to remove the label from the flexible plastic packaging and the shrink wrap sleeve from the plastic container to allow recycling. OPP-based labels and sleeves are easily separated from their commercially used PET food and beverage containers before recycling the containers to recover the PET for subsequent use in other plastic products. In connection with this recycling process, the OPP-based labels that are separated from the PET plastic containers generally are disposed of by incineration, by being transported to landfills or by being used in low-quality molding applications. Shrink sleeve separation from PET containers is typically achieved in float-sink tanks as part of the overall PET recycling. However, shrink sleeve flakes of PET-G have a high density (about 1.3), which hinders their separation from PET flakes in float-sink tanks. The effect the plastic labels and sleeves can have on the recycling of PET, HDPE, and polypropylene bottles are summarized in Table 4.3. When the labels and sleeves are not easily separable from the containers, many containers are not recycled that otherwise would be, and

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Table 4.3 Effect of Plastic Labels and Sleeves on the Various Processing Steps of the Recycling of Plastic Bottles

Polymer

Recycling Step

Effect

Evaluation

Sorting on bottles

PVC L/S detected ¼ up to 3 bottles without PVC L/S ejected

Increase in losses and waste to be processed

Float-sink

Undetected PVC flakes cannot be separated from PET flakes by flotation (density of the two materials >1)

Recycling stream pollution

Sorting on pellets

PVC flake detected ¼ up to 100 flakes ejected

Recycling stream pollution and increase in losses

Granulation/ recycling

Decomposition of PVC into carbon residues at PET conversion temperature: Clogging of extruder filters and/or quality problems with the granules

Increase in machine stoppages, increase in losses, quality problems, and increase in waste to be processed

Float-sink

Depending on their density, PS flakes are sent into the

Pollution of the recycling stream and the

PET stream PVC

PS

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Table 4.3 Effect of Plastic Labels and Sleeves on the Various Processing Steps of the Recycling of Plastic Bottles (Continued ) Polymer

Recycling Step

Effect

Evaluation

PET stream (d > 1 g/cm3) or polyolefin stream (d < 1 g/cm3)

polyolefin stream

With a fusion temperature well below that of PET, deterioration of the PS during shaping

Creation of impurities and yellowing of pale-colored materials (not visible in dark materials), and quality problems

None

Favorable

Float-sink

PEGT flakes not separated from PET flakes (density of the two materials >1 g/ cm3)

PET stream pollution

Washing

Tendency of PEGT to stick to the walls of the machines during drying and transfer

Blocking of pipes

Granulation/ recycling

Yellowing of pale-colored PET streams over a certain concentration

Quality problems

None

Favorable

Granulation/ recycling

Stretch LDPE PET-G

PP/OPP

(Continued)

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Table 4.3 Effect of Plastic Labels and Sleeves on the Various Processing Steps of the Recycling of Plastic Bottles (Continued ) Polymer

Recycling Step

Effect

Evaluation

HDPE/PP stream PVC

Granulation/ recycling

Traces of PVC create black stains during recycling

Quality problems

PS

Float-sink

Depending on their density, flakes are sent into the HDPE/ PP stream (d < 1 g/cm3) or into postsorted waste (d > 1 g/ cm3)

Recycling stream pollution and increase in losses

Granulation/ recycling

Given their conversion temperatures close to those of PS, PP, and HDPE, the shaping process is identical. PS incompatible with HDPE and PP

Tendency to agglomerate and impair the final properties of the material (creation of areas of weakness, incipient breaks)

Stretch LDPE

None

Favorable

PP

None

Favorable

HDPE, High-density polyethylene, LDPE, Low-density polyethylene, L/S, Labels or sleeves, OPP, Oriented polypropylene, PET, Poly(ethylene terephthalate), PET-G, Glycol-modified PET, PP, Polypropylene, PS, Polystyrene, PVC, Poly(vinyl chloride). Adapted from Cotrep (Comite´ Technique pour le Recyclage des Emballages Plastiques). General notice 12 e the behaviour of labels and sleeves during the recycling of PET, HDPE and PP bottles; February 3, 2012. https://www.mondigroup.com/en/newsroom/mondi-flexiblepackaging-leapfrogs-ahead-in-the-recycling-game/.

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recycling yields are reduced. This is the case with the full wrap sleeve of PET bottles, which tend to obscure the automated detection systems during the sorting process [18]. To alleviate the problems with sorting, recyclers and brand owners tend to recommend paper labels, or partial sleeves made with low-density thermoplastic materials, such as polyolefins. However, such materials do not have the desirable shrink properties or printability of higher density substrates such as PET-G. If the density of the sleeve before printing is not low enough, it is possible for the printed sleeve to become too dense and therefore unable to be separated from the standard PET to be recycled (2017, US2017213484 A1; 2018, WO2018187203 A1, SUN CHEMICAL CORP). Several film/resin suppliers (including Exxon, Topas, and Cryovac or converters such as Fuji Seal) have introduced low-density films or coextruded film structures with low density (below 1.0 or at least below 1.05 g/cm3) based on mono- or multilayer structures including polymers built around a low-density core, such as polyolefins, or microvoided polymer, optionally wrapped by a PET-G skin, and, if needed, a tie layer between the core and the PET-G. The overall density of the film is designed to make it floatable in a float-sink tank (2015, WO2015026479 A1; 2017, US2017213484 A1; 2018, WO2018187203 A1, SUN CHEMICAL). The National Association for PET Container Resources is looking at a combination of solutions including the addition of perforations to the labels or sleeves to help them come off during the normal bailing processes, providing recycle facilities with delabeling equipment and making labels from materials that float. This last idea is promoted by the Association of Postconsumer Plastic Recyclers because PET flakes sink in a float-sink separation process, as do other common shrink sleeve materials such as poly(lactic acid) (PLA) or PVC. Using a floatable label makes the separation process much more successful. WO2015026479 A1 (2015), US2017213484 A1 (2017), and WO2018187203 A1 (2018) of SUN CHEMICAL disclose a coating composition for use with labels, including wrap around and sleeve labels, particularly shrink wrap labels, for containers that will allow for an easy separation of the label from the container during recycling. The coating composition comprises at least a first resin with a Tg or a softening point from 25 to 115 C, a second resin having a Tg or a softening point lower than the Tg or softening point of the first resin, and in some instances, a third resin having a Tg or a softening point lower than the first resin but higher than the second resin. At least one of the first and second resins is a polyester resin, while the third resin is preferably a hydrogenated rosin.

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The coating composition provides good bond strength in the seam area of the label, and the coating composition and/or each of the resins thereof may be at least partially hydrolyzable but not solutionable in a hot caustic bath, enabling separation of the label from the article during recycling. Aluminized labels are problematic to recycling and have a negative effect on the purity of the recovered polymer.

4.2.6 Straps/Tapes/Six-Pack Rings Packaging straps and tapes are strapping thin, flat pieces of plastic bands used to preserve the integrity of a package or bundle numerous packages during transportation and storage. They are usually made of polypropylene or PET. Polypropylene strapping is the most common form of strapping for unitizing and protecting smaller containers and boxes. Polypropylene strapping is often used to complement stretch film during load stabilization. Polypropylene strapping is also used to secure crates, bales of netting, frozen bait, and bundle products together for retail sales. Six-pack rings are composed of a semiflexible LDPE. They are used in the packaging of beer cans, sodas, etc. Although six-pack rings account for only a tiny fraction of the marine plastic debris, they are responsible for the deaths of hundreds thousands of seabirds and marine mammals [19] (see also Chapter 2, Section 2.4.1). Both, packaging straps and six-pack rings, are not mechanically recycled and are not accepted in return collection centers or drop-off sites.

4.2.7 Net Bags and Woven Bags/Sacks Net bags (or mesh bags or poly bags) are used for transport and retail packaging of agricultural products (e.g., onions, oranges lemons, limes, nuts, and the like), chocolate coins, or as reusable shopping bags. Transport packaging includes knitted (raschel) and woven (leno) net bags. Retail packaging includes extruded and knitted tubular net bags. Because the net bags are usually used for packaging vegetables, fruits, or chocolates, it is likely to be discarded after use. However, net bags are made of HDPE, polypropylene, PET, or nylon, which do not decompose naturally and tend to cause environmental problems. Woven bags or sacks are flexible containers with a single opening of strong, coarse material for storing and handling various products. Plastic woven bags are mainly made of HDPE or polypropylene. Polypropylene woven bags are the highly preferred choice for packaging purposes. One

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of the latest trends in the packaging industry is the manufacture of BOPP laminated woven polypropylene bags. Polypropylene woven bags are used in the construction and building industry (e.g., for packing cement) and agrochemical industry (e.g., for packing chemicals, fertilizers, vegetables, and fruits) because of their high strength, inertness toward moisture, chemical resistance, and low cost. Polypropylene woven bags are also increasingly used in food packaging. Common food woven bags include rice woven bags, flour woven bags, maize woven bags, etc. Key companies operating in the global market for polypropylene woven bags and sacks include Mondi Group plc, United Bags, Inc., Berry Global, Inc., Muscat Polymers Pvt. Ltd., Al-Tawfiq Company, Emmbi Industries Limited, Uflex Ltd., Palmetto Industries, and Printpak Inc., among others [20]. Industrial woven polypropylene slit film products are currently recycled (e.g., industrial bulk sacks) [21].

4.2.8 Coated/Printed Films Coatings and inks add functional benefits and aesthetics to flexible packaging. The most common type of coating is PVDC, which is used to improve the gas barrier properties of transparent films as well as the gloss of printed films. The printing of flexible plastic packaging requires a printing ink spectrum that is suitable for a large variety of flexible plastic substrates, ranging from construction industry films and peat bags all the way through to food packaging. The printing inks used must be as flexible as the packaging types themselves and have to offer good printability for very low up to extremely high printing speeds (see also Chapter 3, Section 3.12). Multilayer packaging structures, especially in food packaging, incorporate reverse printing on the outer layer of packaging and laminating to an internal layer. The selection of inks to be used in such packaging applications requires careful consideration [22]. The main printing technologies used in flexible plastic packaging are  flexography,  rotogravure,  digital printing, and  others. Flexography is the preferred printing technology for flexible plastic packaging. It is used for printing on a wide range of flexible plastic

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packaging forms such as SUPs, flat pouches, roll stocks, gusseted bags, wicketed bags, and wraps. Flexography printing technology has several benefits such as the flexographic ink requires extremely less drying time and allows for printing both the nonporous and porous surfaces. Also, its simple plate-manufacturing process allows for printing huge quantities of images with just one template; and the technology allows for printing continuous image patterns [23]. The process of printing on a flexible packaging involves the application of a liquid ink on a plastic film. The solvent used (normally organic compounds or water), which volatilizes, is then removed by means of a drying process. The desired drawing is printed on the film after evaporation, and it is ready for use as packaging for various products. It is common practice to adjust the parameters of the printing machine and to adjust the different colors used during printing to obtain quality printing that has no imperfections. The plastic film circulates through the printer at speeds that can reach up to 500 m/min during machine adjustment. Large amounts of defect plastic film (5e10% of the total packaging film production) are generated due to this speed (2013, WO2013144400 A1, UNIV ALICANTE) (see also Chapter 7, Section 7.2). Coating and printing on flexible plastic packaging are significant sources of contamination that reduce the value of plastic materials at the end of packaging life cycle [24]. The coatings are not easily removed in the film recycling process and are either melted or blended together with the film material. Heavily printed film of dark colors is detrimental to recycling as the dark colors affect a large amount of polymer, limiting its potential for reuse. Further, high levels of ink volatize in the extruder and may cause gels in the final product, even if most recyclers use vented extruders [17]. Currently, the scrap film is recovered for recycling by means of processes in which the printed ink is not removed. A lowquality brownish or black film is thus obtained, so its price is significantly lower than the price of films free of starting ink. Therefore, the recycled film is usually used for the preparation of trash bags or applications of low visual quality.

4.3 Applications of Flexible Plastic Packaging The flexible packaging market is segmented on the basis of application in industries of:  food and beverage;  cleaning products;

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 pharmaceutical;  medical and personal care;  construction and building; and  others.

4.3.1 Food and Beverage Food and beverage are the largest application market segments of flexible plastic packaging [23]. Flexible food packaging for perishable foodstuffs is prepared from multilayers comprising aluminum foil and polyolefins, such as polyethylene, polypropylene, or condensation polymers, such as PET or polyamide (nylon) films. These films are often coated with barrier coatings such as PVDC to improve oxygen barrier properties and may be provided with a heat sealing material such as wax or hot melt adhesive. The multilayer flexible plastic packaging is one of the fastest growing packaging types on the food market. Table 4.4 gives a representative list of flexible plastic packaging forms for food.

4.3.2 Cleaning Products Soaps and detergents are available in a variety of forms. Common examples of detergent and soap packaging include: soap wrappers; laundry detergent pods; liquid detergent pouches; liquid hand soap tubes; powder soap pouches; dishwater pouches; dishwater pods; natural bar soaps; septic system cleaning soap packets; and pouch packing for cleaning chemicals, etc. Flexible containers allow a more controlled dispensing of soap, and the packaging can be rolled up to squeeze out nearly every last drop. SUPs manufactured from multilayers are primarily used to package liquid detergents and cleaning materials. Resealable spouts or pouring devices

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Table 4.4 Forms of Flexible Plastic Packaging for Food [25] Packaging Form

Exemplary Food Products

Stand-up pouches

Frozen prawns, scallops, fish fillets; frozen fruits; and vegetables; Frozen prepared food such as chicken wings, shrimps; Baby food; Pet food

Zipper lock pouches

Sugar, oatmeal, grated cheese, rice, grain, coffee, dried fruits and nuts, candies

Zipper lock bags

Grape bags, deli meat, and cheese bags

Crinkly bags

Chips, candies, dried pasta, cereal, and cookie bags

Crinkly wrappers (nonstretchable);

Cheese wrappers, vacuum seal packaging, plastic safety seal on bottles and jars, plastic inner seal on yogurt

Crinkly wrappers

Cheese slice wrappers, snack and chocolate wrappers, candy wrappers, individual cookie wrappers

Cellophane

Flower and gift wrapping

Flexible packaging with plastic seal

Fresh pasta, prepackage deli meat, prepackage cheese packaging

Net plastic bags

Oranges, lemons, limes, avocado, nuts, onions

Woven plastic bags

Rice

Shrink wrap

Meat, poultry, cheese, vegetables

are ideal for both refill packaging and for primary packaging. Today, nearly all the big names in laundry detergent packaging are using SUPs as their preferred method to ship their products. Water-soluble films are used by packaging manufacturers to package laundry detergents, dish wash,

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other products, such as shaving creams, cosmetics for spa services, etc. These products are packaged in poly(vinyl alcohol) (PVOH) films in the form of small packs termed as water-soluble pods. Henkel sells its Megaperls powder laundry pods in a flexible package, called a Quadro Seal Bag that consists of an OPP/polyethylene laminate. At present, 30% of the package’s polyethylene layer consists of industrial waste reclaimed from Mondi. That means the overall package structure contains approximately 10% reground material (see also Chapter 8, Section 8.7).

4.3.3 Medical/Personal Care/Cosmetics The major end users in the flexible packaging market are pharmaceutical manufacturing, contract packaging, implant manufacturing, and medical device manufacturing. The packaging of these medical products is of great importance because it increases their shelf life. The global medical flexible packaging market size was estimated at $20.14 billion in 2016 and is expected to witness rapid growth owing to the rising demand from the pharmaceutical and medical deviceemanufacturing industries. Flexible packaging provides various advantages such as low waste, reduction of the overall weight by around 70%, and product protection [9]. Flexible plastic packaging is used to protect various pharmaceuticals such as tablets, pills, capsules, and powders. According to Gupta [27], almost 75% of oral tablets and powders in the United States are packaged in flexible materials. The most common forms of flexible packaging for pharmaceutical use include blisters, sachets, pouches, and strips. A blister package is generally composed of two layers: a forming film and a lid. The lid is usually a multilayer material including a barrier layer (e.g., aluminum foil) with a print primer on one side and a sealing material on the other side (see Fig. 4.4). The forming film may be a single film, a coated film, or a multilayer. LDPE, LLDPE, BOPP, OPP, PET, polyamide, PVC, and PVDC used in single- or multilayer form are the main components in forming the film and coating layers of a pharmaceutical package. Blister packets are classed as hazardous waste and are usually either landfilled, which has environmental consequence if the aluminum leaks into the environment, or incinerated, which can produce gas and ash exhausts that also have a negative environmental impact [28]. The major products that come under medical flexible packaging are seals, high barrier films, wraps, pouches and bags, lids, labels, and others.

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Figure 4.4 Example of a blister type flexible plastic packaging card (1996, US5549204, TOREN CONSULTING PTY LTD). 1, Flexible plastic sheet; 2, Thermoformed blisters or pockets; 3, Round tablets and pills; 4, Aluminum foil; 5, Perforated hinge line; 6, 7, Resealable fastening means; and 88, 9, Ribs.

Pouches and bags are the major products in the market and expected to remain the largest segment over the forecast period, recording a CAGR2 of 5.9% from 2017 to 2025. Pouches and bags cater to wide variety of applications in the healthcare sector [9]. The use of flexible pouches is much more developed in the medical field where flexibility is particularly important as it makes it possible to obtain zero-volume chambers (i.e., empty of gas and particularly of ambient air) in the absence of internal liquid. As such, flexible pouches make it possible to retain the asepsis of the products contained (blood, solutions, medicinal products) throughout the use thereof. All flexible pouches of the medical pouch type are produced with high frequency or heat sealing, using thermoplastic films. More specifically, a medical pouch is produced by sealing from three sides, and one side is left open for filling and sealing thereafter. In general, the films are made of PVC or polypropylene, and the pouches may have different sizes to exhibit a content volume between 50 and 1000 mL. Flexible pouches and squeeze tubes allow for improved product evacuation, which can reduce waste, while maintaining visibility. There is also a growing trend toward flexible packaging for cosmetics and personal care. According to Smithers-Pira [29], pharmaceuticals, 2

Compound annual growth rate.

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medical, cosmetics, and toiletries are the largest nonfood markets for flexible packaging. Flexible plastic packaging keeps cosmetic and personal care products fresh and safe from contamination and extends their shelf life. Some examples of personal care packaging are lay flat pouches for shampoos and conditioners; packets and sachets for baby wipes; sample sachets; SUPs (or doypacks) for liquid soap refill and shower gel; shrink sleeves for cleansers, creams, and lotions; and roll-fed labels films. Commonly used polymers include polyethylene (LDPE or LLDPE), polypropylene, and PET. Often, multilayer packaging is used for cosmetic products. TerraCycleÒ and GarnierÒ have partnered to create a free recycling program for personal care and cosmetic product packaging, as well as a fundraising opportunity for participants [30]. The program accepts waste from (semi)rigid and flexible packaging for hair care, skin care, and cosmetics as follows: Hair care packaging such as shampoo caps, conditioner caps, hair gel tubes and caps, hair spray triggers, and hair paste caps. Skin care packaging such as lip balm tubes and caps, soap dispensers and tubes, body wash caps, lotion dispensers, and caps. Cosmetics packaging such as lipstick cases, lip gloss tubes, mascara tubes, eye shadow cases, bronzer cases, foundation packaging, powder cases, eyeliner cases, eyeliner pencils, eye shadow tubes, concealer tubes, concealer sticks, and lip liner pencils.

4.3.4 Construction and Building Products for construction (such as bricks, brickwork, tiling, paving, roofing, beams, truss structures) and building materials (such as mortar and plaster mixtures, lime, cement, and other construction materials) they need industrial packaging, which reliably ensures the products and the materials during transport and storage. Stretch films are commonly employed, for example, to wrap goods and products of various types positioned on a pallet, the film wholly or partially covering the goods or products and also typically applied to the pallet itself to secure the pallet to the items positioned. Stretch films, typically made from LLDPE, are used to protect and unitize construction products on a pallet. For heavier construction loads (such as bricks, cement blocks, bags, drums, steel tubes, pipes, etc.), highstrength stretch films are being continuously wrapped around the pallets to achieve load retention. Currently, the safety concerns are strong enough that the stretch film has to be wrapped with heavier gage material, such as

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Figure 4.5 Perspective view of a reinforced stretch film being wrapped around bricks on a pallet through use of a stretch wrapping machine (2017, US2017313020 A1, GRUBBS JR RONALD; LOPEZ LUIS ARURO). 10, Reinforced stretch film; 28, Folded edges; 50, Reinforcement strips; 55, Roll of reinforced stretch film; 60, Stretch film wrapping machine; 62, Pallet.

straps, bags, or stretch hoods, or a large amount of film with low prestretch is used to keep the heavy product secure. However, both of these options clearly increase packaging and/or shipping costs. Fig. 4.5 shows a reinforced stretch film being wrapped around bricks positioned on a pallet through use of a stretch wrapping machine. Woven polypropylene bags and sacks are used for carrying sand, bricks, rubble, and cement bags (see also Section 4.2.7). Polypropylene aggregate rubble sacks are used for carrying debris, bricks, rubble, sharp items, metal, etc. Polypropylene or PET straps are used for strapping of packed construction material, e.g., ceramic tiles of layers of pavers and building blocks with or without pallet. In construction, demolition, and renovation, plastic packaging films are voluminous waste. Plastic films are readily compactable and permit easy transport. Most commonly used means of collection are containers, preferably containers with a press for the packaging films, big bags, and special bags. Some systems make it possible to deposit these bags free of charge at the building materials dealer. The packaging is, then, sent to a recycling center. Some packaging is supported by a “take-back

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obligation” (obligation for any party responsible for packaging to attain a certain percentage of recycling for the packaging he puts on the market). Other types of flexible plastic packaging such as woven bags can be reused [31]. Total (BE) and several partners (Valipac, Oerlemans Packaging, Morssinkhof Rymoplast Group, Wienerberger, and Fema) along the construction value chain have formed the Clean Site Circular Project that aims at recycling films used for protection and stabilization of goods during storage and transport on pallet (shrink hoods) wastes from the construction sector in closed system without film performances degradation. Total has developed a film recipe showing that a closed loop “shrink hood to shrink hood” is industrially feasible and can technically match virgin solutions. It uses Lumicene SupertoughÒ 22ST05 of Total as a “booster” for the recyclate. Lumicene SupertoughÒ 22ST05 is a metallocene-polymerized polyethylene multilayer film for flexible packaging [32].

4.3.5 E-Commerce E-commerce represents 8.5% of the overall retail market, but it is growing at a rate of 18e20% annually, and it is likely to accelerate [33]. The growing e-commerce sales are subsequently creating a demand for safe packaging for the entire supply chain duration. Flexible plastic packaging plays a significant role in e-commerce in that respect. Because shippers charge based on dimensional weight (volume þ weight), flexible packaging can reduce shipping costs and allow more items to fit on delivery trucks compared with corrugated cardboard boxes. The last years, Amazon has reduced the portion of shipments it packs in its cardboard boxes in favor of lightweight plastic mailers, which enable the retailing company to squeeze more packages in delivery trucks and planes. Amazon is by far the biggest shipper and producer of flexible packaging and a trendsetter, meaning that their switch to plastic mailers could signal a shift across the industry. Some of the common types of packaging bags used for the shipment of items to customers by online shopping websites, and for the transportation of documents and valuable papers are plastic courier bags and envelopes, bubble courier bags, festive courier packing bags, tamper evident security bags and envelopes, poly bags with POD (proof of delivery) jackets, and premium courier bags. The courier bags and envelopes are made from multilayer film manufactured by a coextrusion process. The multiple linings make the

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courier bag durable and printable. Multiple linings in courier bags are made of layers of LDPE and HDPE (see also Section 4.2.4). They are milky white in the outside layer and black inside to ensure confidentiality of the content. Hot melt adhesive seal on top ensures that once it is sealed, it cannot be opened without tearing. Some plastic bags have a bubble lining on the inner surface of the bag, which protects the valuables inside from the outside pressure or load and even provides light protection when in transition. The bubble wrap is most often made from LDPE. E-commerce flexible plastic packaging and its disposal has unaccountable environmental costs. Shipping envelopes, such as those having a bubble wrap inside of them, cannot be put in a curbside recycling bin. They need to be recycled separately, and if they end up in the usual stream, they gum up recycling systems and prevent larger bundles of materials from being recycled. Another problem with the new padded plastic mailers is that retailers affix a paper address label that renders them unfit to be recycled, even at a store drop-off location. The label needs to be removed, separating the paper from the plastic, for the material to be recyclable [34].

References [1] Dunn T. Manufacturing flexible packaging: materials, machinery, and techniques. William Andrew; 2014. [2] Market Researchcom. Global flexible packaging market forecast 2018e2026. Inkwood Research; September 2018. https://www. marketresearch.com/Inkwood-Research-v4104/Global-FlexiblePackaging-Forecast-11838789/. [3] Tartakowski Z. Recycling of packaging multilayer films: new materials for technical products. Resources, Conservation and Recycling 2010;55(2):167e70. [4] Morris BA. The science and technology of flexible packaging. Multilayer films from resin and process to end use. Elsevier e William Andrew; 2016. [5] DSM Media Relations. DSM and APK cooperate on recycling multilayer food packaging films. July 24, 2018. https://www.dsm. com/corporate/media/informationcenter-news/2018/07/2018-07-24dsm-and-apk-cooperate-on-recycling-multilayer-food-packagingfilms.html.

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[6] Sekisui Chemical Co.,Ltd.. Reduce layers in flexible packaging using selvol ultiloc. Retrieved January 1, 2019. https://www.sekisui-sc.com/ flexpack/. [7] Polymer Properties Database. Adhesive layers and tie resins. Retrieved March 28, 2019. http://polymerdatabase.com/Films/Tie% 20Layers.html. [7a] APR e Association of Plastics Recyclers. APR news and Media. 2018. http://www.plasticsrecycling.org/news-and-media/142-apr-designguide/quick-links/pe-film-tabs/534-labels-inks-and-adhesives. [8] Borealis A/S. Polypropylene cast film. 2006. https://www.fist.si/ datoteke/navigacija/PP-Cast-film.pdf. [9] Grand View Research. Market research report - metalized biaxially oriented polypropylene (BOPP) films market analysis, market size, application analysis, regional outlook, competitive strategies, and segment forecasts, 2015 to 2022. 2015. https://www.grandviewresearch. com/industry-analysis/metalized-biaxially-orient ed-polypropylene-films-market. [10] Niaounakis M. Management of marine plastic debris. William Andrew, Elsevier; 2017. [11] Packaging Blog. Different types of shrink wrap. U.S. Packaging & Wrapping; January 29, 2016. https://packagingblog.org/2016/01/29/ different-types-of-shrink-wrap/. [11a] IPS Packaging. Stretch Film Types. July 23, 2018. https://www. ipack.com/solutions/stretch-film-types/. [12] Grand View Research. Stand-up pouches market analysis, market size, by product, by application analysis, regional outlook, competitive strategies, and segment forecasts, 2018 to 2025. 2018. https:// www.grandviewresearch.com/industry-analysis/stand-up-pouchesmarket. [13] Unilever. Unilever develops new technology to tackle the global issue of plastic sachet waste. May 11, 2017. https://www.unilever.com/news/ press-releases/2017/Unilever-developsnew-technology-to-takle-theglobal-issue-of-plastic-sachet-waste.html. [14] Mondi Newsroom. Mondi flexible packaging “leapfrogs” ahead in the recycling game. September 10, 2010. https://www.mondigroup.com/ en/newsroom/mondi-flexible-packaging-leapfrogs-ahead-in-therecycling-game/. [15] Berkel van J, Avantium. BU Synvina. First plant-based pouches with BOPEF film. Bioplastics Magazine 2019;14(02):23.

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[16] Cotrep (Comite´ Technique pour le Recyclage des Emballages Plastiques). General Notice 12 e the behaviour of labels and sleeves during the recycling of PET, HDPE and PP bottles. February 3, 2012. http://www.cotrep.fr/fileadmin/contribution/mediatheque/avisgeneraux/anglais/labels-and-sleeves/Cotrep_AG12_Label_and_ sleeve.pdf. [17] APReAssociation of Plastic Recyclers. The APR DesignÒ guide for plastics recyclability. January 6, 2018. http://www.plasticsrecycling. org/images/pdf/design-guide/PE_Film_APR_Design_Guide.pdf. [18] Holbrook J. Recyclers to address label issues. Plastic News May 13, 2013;25(9):0001. [19] National Conference of State Legislatures. State plastic and paper bag legislation e fees, Taxes and bans j recycling and reuse. September 11, 2016. http://www.ncsl.org/research/environment-andnatural-resources/plastic-bag-legislation.aspx. [20] Fact. MR. Polypropylene woven bags and sacks market forecast, trend analysis & competition tracking - global market insights 2018 to 2028. July 2018. https://www.factmr.com/report/1203/polypropylenewoven-bags-and-sacks-market. [21] RSE USA. The closed loop foundation e film recycling investment report. 2016. http://www.closedlooppartners.com/wp-content/ uploads/2017/09/FilmRecyclingInvestmentReport_Final.pdf. [22] Chavannavar S. Polyurethane ink resins: technology for the future of flexible packaging. BASF; November 30, 2018. https://insights.basf. com/home/article/read/polyurethane-ink-resins-technology-for-thefuture-of-flexible-packaging. [23] Inkwood research. Global flexible packaging market forecast 2019e2027. 2018. https://www.inkwoodresearch.com/reports/ flexible-packaging-market/. [24] Gabriel DS, Maulana J. Impact of plastic labelling, coloring and printing on material value conservation in the products of secondary recycling. In: 3rd International conference on applied engineering, materials and mechanics, ICAEMM key engineering materials e applied engineering, materials and mechanics II, vol. 773; 2018. p. 384e9. [25] RecycleBC. Other flexible plastic packaging material list. January 18, 2019. https://recyclebc.ca/wp-content/uploads/2018/06/MaterialList_Other-Flexible-Plastic-Packaging.pdf. [26] Grand View Research. Medical flexible packaging market report medical flexible packaging market analysis by material (plastics,

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paper, aluminum), by product seals, high barrier films, pouches & bags, lids & labels) by end-use, and segment forecasts, 2018 - 2025. Report ID: GVR-1-68038-893-0. August 2017. p. 1e145. https:// www.grandviewresearch.com/industry-analysis/medical-flexiblepackaging-market. Gupta RM, Perfect Pharmaceutical Consultants Pvt. Ltd. U.S. regulations for flexible pharmaceutical packaging materials. http://www. perfectdossier.com/pdf/US%20Regulations%20for%20%20Flexible %20Packaging%20Materials.pdf. Yousef S, Mumladze T, Tatariants M, Kri
ukien_e R, Makarevicius V, Bendikiene R, et al. Cleaner and profitable industrial technology for full recovery of metallic and non-metallic fraction of waste pharmaceutical blisters using switchable hydrophilicity solvents. Journal of Cleaner Production 2018;197:379e92. SmithersePIRA. Paper and board have key roles in the future of packaging. 2017. https://www.smitherspira.com/resources/2018/ february/the-future-of-packaging-trends. TerraCycleÒ . Personal care and beauty recycling program. 2019. https:// www.terracycle.com/en-US/brigades/personal-care-and-beautybrigade-r. Project APPRICOD. Waste management on the building site e Towards a sustainable management of plastic construction and demolition wastes in Europe. In: Co-funded by the European commission’s LIFE-environment programme. February 28, 2019. http://ec.europa.eu/environment/life/project/Projects/index.cfm?fuse action¼home.showFile&rep¼file&fil¼APRICOD_toolbox_brochure .pdf. Total Polymers Press Release. Total associates with partners to create a closed loop recycling chain in construction films. March 13, 2019. https://www.polymers.total.com/total-associates-partners-createclosed-loop-recycling-chain-construction-films. Armstrong J. The extremes of e-commerce. Recycling today. December 2017. https://www.recyclingtoday.com/article/ecommerce-occ-supply-demand/. Young KM. Why Amazon’s new streamlined packaging is jamming up recycling centers. The Washington Post; February 11, 2019. https:// www.washingtonpost.com/technology/2019/02/11/why-amazonsnew-streamlined-packaging-is-jamming-up-recycling-centers/?utm_ term¼.71048b35ddf5.

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STUHLMANN CHRISTOPHER

KHS GMBH

Gebinde und Verfahren zur Bildung von Gebinden. “Cluster pack and method for forming cluster packs."

EP0217388 A2

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CRASS GUENTHER; BOTHE LOTHAR

HOECHST AG

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PERICK MATTHIAS

MONDI CONSUMER PACKAGING TECHNOLOGIES GMBH

Verfahren zur Wiederverwertung von Kunststoff aus einem Folienverpackungsbeutel, Folienverpackungsbeutel sowie Folienverbundbahn zur Herstellung eines Folienverpackungsbeutel. “Method for recycling plastics from a film packaging bag, a film packaging bag and a method of preparing a film packaging bag."

EP3168169 A1

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EP20150194573 20151113

LUCCESE MICHELE; SANDER IMMO; PERICK MATTHIAS; ¨ STERS JENS KO

MONDI CONSUMER PACKAGING TECH GMBH; WERNER & MERTZ GMBH

Folienbeutel. “Film bag."

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LAPIN STEPHEN C

NORTHWEST COATINGS, LLC

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Laminated structure and stand up pouch made thereof.

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SUN CHEMICAL CORP

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5 Collection and Feedback 5.1 Collection Collection is the first stage of a multistage procedure leading to the recycling, reuse, or disposal of flexible plastic packaging waste. Flexible plastic packaging is not widely collected for recycling around the world, and the collected volume remains considerably lower than is feasible. One key imitation is that the packaging waste is often difficult and costly to collect. Another key limitation is the awareness of the public. Collection is a prerequisite for higher recycling. The CEFLEX project makes a number of recommendations aiming at increasing collection [1]:
proper collection at all levels is required for successful recycling;
collection prevents packaging from leaking into the environment;
to avoid cherry-picking of easy recyclables, mandatory separate collection of all packaging is needed;
without mandatory collection, flexible packaging may not generate sufficient material volumes to make recycling commercially viable; and
mandatory collection is the basis of more investment in infrastructure for sorting and recycling of flexible packaging. The expansion of film collection is dependent on the creation of new end-use markets that will increase demand for recycled film [2].

5.2 Sources of Flexible Plastic Packaging Waste There are generally three sources of flexible plastic packaging waste1: postconsumer (residential or household) derived from residences, postcommercial generated by businesses, and postindustrial generated during processing.

1

Agricultural film is outside the scope of the book.

Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00005-0 Copyright © 2020 Elsevier Inc. All rights reserved.

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5.2.1 Postconsumer Flexible Plastic Packaging In terms of volumes, one of the largest sections in film recycling is postconsumer film waste. Postconsumer film quality can significantly vary according to the market conditions, and mainly depends on the type of collecting and presorting systems that are employed by the recyclers. The material collected may present different degrees of humidity and contamination. In addition, film waste is often in very different printing conditions and shapes. The main contaminations to be treated in postconsumer film are a high quantity of organics as well as different polymers, such as multilayers; multilayer films are composed of a variety of materials, and often, they even contain metallic components. For these films to be treated, a preliminary sorting section should be foreseen. Postconsumer flexible plastic packaging includes a mixture of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and polypropylene films and a growing number of multilayer packaging films [3]. It has been estimated that some 1.1 million tons of packaging film arises in the UK waste stream every year. This is about 44% of all plastic packaging. Of this amount, about 560,000 t are postconsumer plastic film [4]. More than 50% of plastics in household in Norway and Sweden are packaging films, mainly LDPE films. A large part of these films consists of multiple layers [5]. Residential postconsumer flexible plastic packaging shows the lowest recycling rates mainly because of inefficient sorting technologies [6]. Postconsumer multilayer packaging is not a targeted material and is not currently recycled. It is estimated that 97% of postconsumer plastic films end up in landfills and oceans [7]. TerraCycle promotes the Zero Waste Bags to collect and recycle virtually any type of residential waste including flexible plastic packaging. The consumer must purchase Zero Waste Shipping boxes to send the Plastic Packaging Zero Waste Bags back to TerraCycle [8]. In the European Union, it is envisaged that by 2025, there will be an established collection, sorting, and reprocessing infrastructure developed for postconsumer flexible packaging, based on end-of-life technologies and processes that deliver the best economic, technical, and environmental outcome for a circular economy [9]. The two main routes for the collection of residential postconsumer films are through local authority curbside recycling schemes and front of store recycling points (generally located at larger supermarkets).

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5.2.1.1 Curbside Collection Flexible film and plastic bags from curbside collection are usually considered as contaminants and a source of problems for the machinery of Materials Recovery Facilities (MRFs) and are removed from the waste stream. At best, they are intended for energy recovery, but, often, they end up in landfills [6]. Very few MRFs accept curbside polyethylene film because of the cost to process it and lack of markets for curbside film, while there are no MRFs that accept majority polypropylene bags and multilayer pouches. The MRFs that handle curbside collected recyclables use complex machinery to sort a variety of recyclables; film clogs (jams) the machines wheels, and its removal is problematic and costly [10]. Of the total amount of collected film in the United States in 2016 (0.59 MMT), less than 2% was obtained from curbside recycling programs and processed through MRFs [2]. Bales of curbside polyethylene film are traded at a much lower price than mixed film that comes from retail collection programs due to the contamination of curbside film collected during collection and processing in MRFs [11] (see Chapter 11, Section 11.3). The Hefty® EnergyBagÔ program is an initiative that collects hard-torecycle materials, including flexible plastic packaging and materials contaminated with food waste, at curbside and converts them into valuable resources [12]. The program is built on learnings from a 2014 pilot sponsored by Dow, the Flexible Packaging Association and Republic Services, along with the City of Citrus Heights. The first permanent Hefty® EnergyBag® program was launched in the U.S. in 2016 in Omaha, Nebraska and now there are a number of active, self-sustaining programs in the U.S., with plans to launch the first program in Canada in late 2019. All materials collected have been diverted from the landfill and are helping to create end-of-life solutions for plastics and advancing the development of a plastics circular economy. The goal is to turn plastic waste resources into higher value applications that are in the Recycle and Recovery categories of the EPA’s Waste Management Hierarchy such as supplying valuable raw materials to industry, remanufacturing the recycled raw materials into new products, conversion of non-recyclable waste materials into useable fuel (Reference [X]: United States Environmental Protection Agency (EPA). Sustainable Materials Management: NonHazardous Materials and Waste Management Hierarchy. 10-08-2017. https:// www.epa.gov/smm/sustainable-materials-management-non-hazardousmaterials-and-waste-management-hierarchy). Consumers use an easily identifiable orange bag into which they place hard to recycle plastic packaging such as bags, pouches and wrapper (see

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Figure 5.1 Orange bags filled with hard-to-recycle plastic packaging (The Hefty® EnergyBag® program) [12].

Fig. 5.1). The bag is then placed in the single stream recycling bin or next to the bin for collection and pulled off the sortation line at the MRF. Flexible packaging items that can be collected as part of the program include flexible drink pouches, candy bar wrappers, plastic pet food bags, and shredded cheese bags. Other plastic packaging that is not usually recycled but collected as part of the program may include plastic meat packaging, straws/stirrers, and plastic service ware (plates and cups) (see also Chapter 11, section 11.14). The bag-in-bag system, where plastic bags and film are collected in a larger plastic bag before bringing to a local retailer, is gaining ground. However, the success of the system depends on the degree to which curbside recycling program participants place film inside of one film bag and tie it off. For example, one film bag containing 20 pieces of film has only 5% of the direct manual sorting cost of film set out for recycling as individual pieces. Even when film is bagged, collection truck compaction and metering equipment at the MRF can cause bags to break open and their contents to be scattered. MRF scrap film value is much lower than the cost to sort and bale it [7]. The following best practices for curbside collection of bagged film are recommended by Reclay StewardEdge [11]:

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- extensive and continued education on what are acceptable packaging materials; - collect films in specially assigned plastic bags to reduce contamination of other materials and sorting costs at the MRF; - monitor/reduce truck compaction to reduce bag breakage; - utilize carts to reduce moisture; and - curbside-collecting loose film is not recommended. There is emerging evidence that postconsumer multimaterial flexible packaging may eventually be collected and sorted through a curbside system. There are various scenarios for the collection of multilayer flexible packaging materials at curbside [13]: - Multilayer packaging materials could be “bagged” and collected at curbside. Bagged multilayers would be easier to presort at the MRF. However, loose laminates would be easier for the consumer and potentially increase the collection rate. - A separate pickup could go directly to the processor, removing the sorting challenge, but collection cost could be higher. - Multilayers collected at a drop-off would bypass the MRF and sortation challenge but would require more effort on the part of the consumer. A multimaterial laminate collection pilot is currently being explored. Materials Recovery for the Future (MRFF), a project of the American Chemistry Council Foundation for Chemistry Research and Initiatives, is a collaboration of brand owners and trade associations to undertake research to determine how flexible packaging of all types (i.e., not just polyethylene) can be collected in curbside recycling programs and sorted by MRFs. The increased convenience of curbside recycling collection offers the possibility for much higher recycling rates than is found in retail return programs [14] (see also Chapter 11, Section 11.14). Return collection centers or drop-off sites are the principal means for collecting flexible plastic packaging. Collection sites that accept film for recycling include retail, municipal, nonprofit, and commercial program drop-off facilities. The most common drop-off flexible packaging material

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is polyethylene. It is relatively pure (75e90%) and includes LDPE, LLDPE, and HDPE. Common contaminants found in drop-offs include receipts, paper labels (metalized), bonus tickets, and the like, which are detrimental to recycling [3]. The majority of locations are retail drop-offs. There are more than 18,000 retail collection or drop-off centers throughout the United States. Examples of flexible plastic packaging films and bags that can be brought to drop-off locations include [15]: - shopping bags: grocery, retail, carryout, produce, newspaper, bread, and dry cleaning bags (clean, dry, and free of receipts and clothes hangers); - zip-top food storage bags and pouches (clean and dry); - plastic shipping envelopes (free of labels), bubble wrap, and air shipping pillows (deflated); - product wrap of water/soda bottles, toilet paper, paper towels, napkins, disposable cups, bathroom tissue, diapers, and female sanitary products; - furniture and electronic wrap; and - plastic cereal box liners (not containing paper). Examples of flexible plastic packaging that cannot be brought to dropoff locations include: - cling wrap (or cling film); - candy bar wrappers (multilayer); - flower and gift wrapping (cellophane, polypropylene); - chip or cookie bags; - salad and green bags; - plastic squeeze tubes; - paper-lined plastic; - plastic straps; - six-pack rings; - biodegradable packaging; - oxodegradable packaging; and - PVC packaging (e.g., zipper bedsheet bags).

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The consumer returned packaging material (e.g., bags, sacks, and wraps) is often combined with film generated through business operations (e.g., polyethylene stretch wrap) to make bales, which are sold to reprocessors or recyclers that make new products [10]. The main obstacles in the collection of flexible plastic packaging in retail shopping centers are [16]: - the activity of recycling is disconnected from the activity of retail shopping; - consumers rarely return small plastic bags to a source whereby they can be recycled; - in areas that have banned plastic shopping bags, stores have removed bag and film recycling bins; - discerning a multilayer film from a pure polyethylene film is impossible; - odor and leakage from residual food packaging may be an issue when accumulating and storing materials for sale to recyclers; - traditional polyethylene processors may reject mixed materials; - retail recycling centers are inconsistent among different stores with regard to bin placement, signage, and materials accepted; and - the volume of space that must be dedicated to store precompacted flexible plastic packaging waste is usually impractical for most businesses; for example, the amount of shrink wrapped film or garment bags necessary to fill a single bale of only plastic may take weeks or months to accumulate, requiring great expense to store a significant amount of uncompacted packaging film. An important issue is that consumers do not always know which packaging can and cannot be recycled. Another problem is throwing items in the wrong recycling bins. Not only does this take time to separate at a recycling facility but it can also contaminate other items in the same bin. CleanRobotics, a Pittsburgh-based start-up, developed the so-called TrashBot to address the aforementioned issue [17]. TrashBot is a robotic trash can system embedded with artificial intelligence. Once a consumer throws a packaging item into the bin, the system uses a set of sensors and machine learning to identify the type of packaging. It will also weigh it, drain any liquids, and place it into the right bin, while providing 90% accuracy. Because of the great capacity, TrashBot can be deployed at

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airports, shopping malls, stadiums, office buildings, and other businesses that handle large quantities of packaging waste. CleanRobotics plans to add LEDs to the system to let the user know whether the item they throw away is recyclable [18]. Bin-e, a Polish tech start-up, developed the “smart waste bin” designed to recognize and sort packaging waste according to its category [19]. The smart waste bin is equipped with a camera and sensors, and it relies on machine learning to detect and identify the waste that is thrown in it. After it recognizes the packaging item, it directs the item into the right chamber. When the chambers are full, it notifies the maintenance team to take the packaging waste to the recycling plant. Every time a consumer throws a packaging item into the bin, its computer system will collect information such as the brand and quantity of items, and the data will be automatically uploaded to the cloud [18].

5.2.2 Postcommercial Flexible Plastic Packaging Postcommercial polyethylene film, also known as polyethylene clear film (see Chapter 11, Section 11.3), primarily comes from large commercial generators and includes mainly clear bags and stretch wrap film. This type of film contains lower amounts of contaminants compared with postconsumer waste film and in many cases does not require washing before recycling. Postcommercial polyethylene film represents the majority of film that is currently recycled, with an estimated 21% recycling rate. Much of this film is recycled into trash bags and thicker commercial films [7]. Postcommercial mixed color film, also known as polyethylene color film, also comes from commercial sources and includes stretch wrap. A special type of postcommercial flexible plastic packaging that is recycled is woven polypropylene bags.

5.2.3 Postindustrial Flexible Plastic Packaging A considerable amount of scrap is generated in the course of manufacture of flexible plastic packaging films, such scrap coming from trimming from roll ends (edge trims or offcuts), film breakages, filling custom orders involving less than the full width of rolls of the film, or rolls out of specification (1991, WO9117886 A1; 1992, US5128212 A, DUPONT). Experience shows that still in most of the cases, 2e10% of the production materials are lost due to process reasons [20]. It is estimated that 79% of postindustrial plastic films end up in landfills and oceans [7].

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5.2.3.1 Feedback of Scrap Film The feedback of plastic scrap generated during processing corresponds to the first out of three recognized types of plastic recycling.2 In primary (or preconsumption) recycling, preconsumer industrial scrap and salvage is collected by the plastics producer at the site of manufacture and fed back into the processing apparatus to thereby effectively use the scrap material. It is a general practice to recycle at least part of this type of flexible plastic packaging waste generated in a film-forming extrusion process back into the extruder to, thereby, effectively use the scrap film in the formation of extruded film from which the waste material was generated. The reutilization of scrap films, which exist in considerable quantities as rejects or cuttings, by direct processing in an extruder is possible only to a very limited extent because of their voluminous nature and poor flow property. Such plastic waste must first be pretreated appropriately by comminution, and the plastic particles, which have thereby become flakelike, are then agglomerated into highly compacted, free-flowing, and abrasion-resistant granules. The granules obtained in this way must have the same quality as the granules of virgin material, so that they can be proportionately admixed with the latter (see Chapter 8, Section 8.3). In the case of monolayer plastic film, it is safe to recycle scrap film with virgin polymer because the composition of the scrap film and the virgin polymer is the same. Reprocessing of scrap film can take place either on the site of film production or at a remote location. For economic reasons, scrap film recycling most commonly takes place at the location of film production. In on-site recycle processing, the edge trim that is slit from the film is immediately conveyed to a cutter that cuts the trims into small pieces (chips) in preparation for further processing (1992, US5170949 A, SPROUT BAUER INC ANDRITZ); see also Chapter 8, Section 8.2.2.

2

The other two types of plastic recycling include secondary (or postconsumption) recycling, which involves sorting out postconsumer and postcommercial plastic waste and physically reprocessing the waste by shredding/grinding, melting, and/or reforming the plastic (see Chapters 6 and 8Chapter 6Chapter 8), and tertiary (chemical) recycling, which involves depolymerizing a polymer into repolymerizable monomers and oligomers (see Chapter 9). A fourth type of plastic recycling could be considered the quaternary (energy) recycling, where energy recovery of plastic waste occurs by controlled incineration (see Chapter 8, Section 8.4).

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Figure 5.2 Schematic drawing of a rotary knife cutter with a roll-off cover (1988, US4738404 A, SPROUT-BAUER, INC). 12, Cylindrical rotor; 14, Rotor shaft; 18, Base portion of the cutter housing; 20, Cover portion of the cutter housing; 24, Bearing bushing; 40, Feeder; 42, Feed rolls; 44, Variable speed motor; 54, Laterally spaced rails; 60, Hinge pin means; and 70, Laterally extending side flanges.

It is often necessary to open the rotary knife cutter and clean any film fragments that may have accumulated in cracks or crevices within the working chamber of the cutter housing before changing plastic composition or color to prevent contamination of the new batch when recycling the scrap material. However, such a process can be laborious and timeconsuming in that it commonly takes two men from 1 to 6 hours, depending on the machine design and location, to open a prior art rotary knife cutter for cleaning or service (1988, US4738404 A, SPROUTBAUER, INC). This problem has been addressed by US4738404 A (1988, SPROUTBAUER, INC), which discloses a rotary knife cutter provided with a roll-off cover, which can be readily translated to facilitate access to the cutter rotor for cleaning and maintenance (see Fig. 5.2). US5170949 A (1992, SPROUT BAUER INC ANDRITZ) discloses a method and an apparatus, shown in Fig. 5.3, for reprocessing scrap film generated in the film-forming process. The apparatus (10) includes a filmeair separation chamber (14) for separating air from incoming strips of scrap film, a cutter (20) for cutting the strips into small pieces, and a storage tank (26) or further reprocessing means to which the cut pieces of scrap film are conveyed. An air bypass line (36) having a computercontrolled valve (38) conveys air directly from the filmeair separation

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Figure 5.3 Schematic side view of an apparatus for reprocessing scrap film (1992, US5170949 A, SPROUT BAUER INC ANDRITZ). 10, Scrap film reprocessing apparatus; 11, Edge slitter; 12, Scrap film inlet line; 14, Filmeair separation chamber; 16, Film outlet opening; 18, Inlet opening of 20; 20, Scrap film cutter; 21, Motor; 22, Cutter outlet end; 23, Tubular cutter outlet line or discharge conduit; 24, Fan; 26, Fluff storage tank; 28, Cyclone; 30, Bin discharge line; 32, Pelletizer; 34, Pellet outlet line; 36, Air bypass line; 38, Control valve; 40, Valve controller; and 42, Solid-state motor power sensor.

chamber (14) to the cutter outlet (22) when the valve is in an open position and causes all of the air to flow into the cutter inlet when the valve is in a closed position. The open or closed position of the air bypass valve depends on the cutter motor power, which varies as the volume of scrap film in the cutter varies. Because of the inclusion of the accurately controlled air bypass valve (38), only a single fan (24) is needed to convey the film into and out of both the filmeair separation chamber (14) and the cutter (20). The cost and energy consumption of the single fan were about half of the cost and energy consumption of two fans used in the conventional system. Example: Narrow strips of polyethylene scrap film trimmed from a roll of film product by a conventional slitter were conveyed through a 5 inches pipe at a rate of 5000 ft/min (25.4 m/s) through a filmeair separator and into a film cutter, model DSF 1512 from Andritz Sprout-Bauer, Inc.

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having a 30 hp (22.4 kW) motor, and outward from the cutter to a fluff storage tank. The strips of scrap film were conveyed from the slitter to the fluff storage tank by a single fan located downstream from the cutter and upstream from the fluff bin. During start-up, when the power of the cutter exceeded about 18 hp (13.4 kW), the control valve on the air bypass line was closed, resulting in an air flow rate of about 800 ft3/min (0.38 m3/s) from the top of the separator to the cutter outlet. This air flow pulled the film out of the cutter through the cutter outlet and onward to the fluff bin. The motor power was sensed by monitoring each of the three power phases with a voltmeter, and the amperage of one leg was monitored in order to determine horsepower. The valve controller was a combination of commercially available components commonly used to monitor electrical power and energizes an air-operated valve. The practice of refeeding the granules or chips to the process together with virgin material can lead to process difficulties including:
inconsistent feeding performance of the production extruder;
air inclusion in the melt that leads to defects of the finished products; and
no way to remove process materials such as printing inks, coatings, and adhesives [20]. In the case of multilayer film of layers having different composition, the scrap film has a different composition from any individual layer of the film (1991, WO9117886 A1; 1992, US5128212 A, DUPONT). It is industry practice to take scrap trim and defect material generated in the multilayer film-forming process, such as coextrusion, and comminute the scrap trim into flakes pelletize the flakes through a secondary extrusion process, crystallize those pellets, so that they do not agglomerate during further processing, and use these pellets as part of the resin feed to form a layer, such as a core or skin of a multilayer film (2011, WO2011140317 A1, TORAY PLASTICS AMERICA INC). WO9117886 (1991, DUPONT) relates to the use of scrap heat shrinkable multilayer film along with virgin polymer to form new multilayer heat-shrinkable film. TThe scrap film is derived from a multilayer film comprising a core composed of 50-90 wt% on the weight of said core of LLDPE and 10-50 wt% based on the weight of said core of highly branched polyethylene. The scrap multilayer film is incorporated into the core layer of the new co-extruded film in an amount of about 25 to 40 wt% on the weight of the core layer. Various methods are available for

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incorporating the scrap film into the coextruded core of the heat shrinkable film. Most conveniently, the scrap film can be cut up into flakes no larger than about 4 mm. The flakes can be preblended with molding granules of virgin polymer to form the coextruded core and then added to the extruder, or the preblending can be carried out by simultaneously adding the desired proportions of scrap and virgin polymer to the extruder, which extrudes the core. It has been found that despite the different shapes of the recycle polymer film and the virgin polymer feeds to the extruder, and despite the fact that the recycled polymer is formed from multilayer film of different overall composition from the core layer, the coextruded blend portion of the core is provided as a homogeneous blend of recycled polymer and virgin polymer. Tie layer(s) of recycled film can be formed by using one or more extruders to melt process the recycled film and coextrude the tie layer(s) along with the coextrusion of the rest of the multilayer film. EP0679487 A1 (1995, GRACE W R & CO) discloses a process for the manufacture of a multilayer crosslinked heat shrinkable film by recycling industrial scrap of the same film, generated at different stages of the production of the film, in an amount of up to 10 wt% in the core of the new crosslinked film. Particularly, the process is applied to an oriented, heatsealable, multilayer crosslinked film comprising a core layer, consisting essentially of LLDPE and two outer layers each comprising a three component blend of LLDPE, medium-density polyethylene (MDPE), and EVA. The process of making metalized plastic films also generates waste of scrap trim. Scrap trim results from slitting rolls to custom product widths or from recovered metalized plastic film, such as poly(ethylene terephthalate) (PET) film that has defects, which cause rejection (e.g., wrinkles, creases, or poor metallization). However, metalized plastic films have not been recycled. The metal particles can potentially cause web breaks during film formation processing if, for example, reclaimed metallized PET film is fed in a similar manner to reclaimed nonmetallized PET film. The tendency for web breaks to occur is attributed due to the difference in crystallinity. Accordingly, trim and defect-containing metalized PET waste has traditionally been discarded at cost of materials, processing cost, and disposal and environmental costs (2011, WO2011140317 A1, TORAY PLASTICS AMERICA INC); see also Chapter 8, Section 8.8. WO2011140317 A1 (2011, TORAY PLASTICS AMERICA INC) discloses the use of metalized film that has been shredded, pelletized or densified, and dried/crystallized as a component for either the core or skin layer in a PET film. By appropriate processing conditions in the

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pelletizing operation, sufficiently small particles of the aluminum layer can be formed and dispersed in the PET. It is contemplated that other metalized films such as oriented polypropylen (OPP), oriented HDPE, and oriented polyamide can also be reused. For example, shredded and pelletized metalized OPP film can then be used as a portion or the whole of the core and/or skin layer of a newly made OPP film. The reclaimed metalized OPP replaces at least a portion of the virgin polypropylene in such a film for cost reduction purposes. Sources of such waste material include scrap product generated during deviations from normal operating conditions that occur at production line start-ups, shutdowns, and unexpected machine failures. Also in film production, it is typical to generate scrap product by trimming film product to specification sizes. Example: Reclaimed metalized PET was obtained by trimming PET film on which had been deposited a layer of aluminum of about 3.0 nominal optical density. The PET of this film contained no metalized reclaim material, i.e., there was no aluminum in the PET. This metalized film was shredded into flakes and densified to form pellets. The densified reclaimed metalized PET contained 0.33 wt% aluminum. The reclaimed metalized PET pellets were melt blended with nonmetalized reclaimed PET film at a 1:9 weight ratio. The melt blend was cast and stretched to form PET film containing 10 wt% of metalized reclaimed PET. This oriented PET sheet was plasma treated on one side, and then aluminum was placed by vapor deposition on the treated side to a nominal thickness of about 3.0 optical density. In the production of biaxially oriented polyamide film (BOPA), a large amount of edge trims is also produced. CN203156973 U (2013) and CN104070617 A (2014) of FANGCHENGGANG CITY GANGKOU DISTR HONGDA PLASTIC FACTORY disclose a recovery system of BOPA film edge trims, shown in Fig. 5.4, comprising a fan (5), a shredder (7), and an air direction converter (1), wherein an air pipe is connected between the fan (5) and the air direction converter (1); a material pipe (3) is connected between the air direction converter (1) and the shredder (7); one end of the material pipe (3) near to the air direction converter (1) is connected with an edge trim suction feeder (2); one section of the material pipe (3) near to the shredder (7) is at an elevating position; a connecting pipe (6) is between the elevating section and the shredder (7); and the upper part of the connecting pipe (6) is provided with an air outlet. In practical use, the high-pressure air flow generated by the fan (5) is sent from the air duct (4) to the air direction converter (1). After the air direction is converted, the edge material is sucked into the material pipe

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Figure 5.4 Schematic view of a recovery system of biaxially oriented polyamide film (BOPA) film edge trims (2013, CN203156973 U; 2014, CN104070617 A, ANGCHENGGANG CITY GANGKOU DISTR HONGDA PLASTIC FACTORY). 1, Air direction converter; 2, Suction material feeder; 3, Material pipe; 4, Air duct; 5, Fan; 6, Connecting pipe; and 7, Shredder.

(3) by the suction material feeder (2), and, then, the edge material is blown to the connecting pipe (6). The edge material is slid down by the connecting pipe (6) into the shredder (7), and the shredded edge material can be recycled. The system is claimed to be able to recover edge trims generated in a BOPA production process without the need of a granulator at a reduced production cost. US3797702 A (1974), US4014462 A (1977), and US4340347 A (1982) of ROBERTSON J disclose various versions of a waste recovery and feed system, wherein plastic edge trims obtained during the manufacture of films or sheets are cut and fed back to the processing machine along with the base material, such as a virgin plastic and various additives. The plastic waste is fed with an auger from an upper hopper toward the outlet opening of a lower hopper containing the base material. The materials are mixed just before entry in the extruder or other processing machine. An inducer blower and forced air, preferably an adjustable vacuum-pressure air stream, are used to blow plastic edge trims along an open conduit into a grinder. After grinding, a separator separates the waste from the air stream, where the ground waste falls into a feed hopper. The feed hopper is continuously filled with base material and processes trim material to an extruder. In plastic-blown film extrusion processes, it is known that the equipment cannot directly reutilize ground trim material and feed that trim directly back to the process material input section. Simple grinders do not produce the correct pelletized form required to begin the extrusion process,

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Figure 5.5 Schematic view of a plastic trim reclaim process in-line with an existing extrusion process (2012, US2012258189 A1, WILHELM MICHAEL BRANDON). 12, Reclaim apparatus; 11, Thermoplastic extrusion process; 13, Feed line; 14, Edge trims; 15, Inlet section; 16, Bricker section; 17, Extruder/pelletizer section; 18, Forced air standpipe; 19, Upstanding separator; 20, Container; and 21, Driven ram.

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therefore such trim is generally discarded or sold, creating a loss of material and a process by-product. Common practice is to ship out scrap to be repelitized with different types of plastics; consequently, when the repelitized material is blended back into extruders, problems such as gels, discoloration, carbon buildup, and esthetic errors occur in the extruded output (2012, US2012258189 A1, WILHELM MICHAEL BRANDON). To solve these issues, US2012258189 A1 (2012, WILHELM MICHAEL BRANDON) disclosed a process for recycling waste trim from a typical blown film extrusion process that takes in-line trim and reprocesses it into either a pellet or elongated composite brick. The apparatus, shown in Fig. 5.5, combines four sections to process waste trims: an input and feed section, a grinding and presizing section, a compaction and sizing section, and a repelletizing and recovery section. The final product takes one of two forms: a compacted plastic brick or pellet-sized beads that can be directly reused in a new extrusion process. The compaction and sizing section utilizes a heating chamber and ram to force ground trim through an extruder, which is then cut into sections to form brick. The repelletizing and recovery section utilizes an extrusion process that feeds into a cutting plate, whereafter the sized pellets are cooled to solidify their structure before being vacuum transported into a container for reuse.

Figure 5.6 E:GRAN chopperefeedereextruder combination. Sample stand-alone application: Feeding defective film via a roll feeder. Courtesy of Next Generation Recyclingmachinen GmbH. NGR, Plastic recycling technologies. E:GRAN. https://www.ngr-world.com/product/egran/.

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Figure 5.7 Schematic diagram of the Intarema® K system. Courtesy of Erema Engineering Recycling - Machinen und Anlagen Ges.m.b.H.. INTAREMA® K. https://www.erema.com/en/intarema_k/) 1, Cyclones; 2, Conveyor belt; 3, Feed rollers; 4, Preconditioning Unit; 5, Extruder; and 6, Pelletizing system.

Next Generation Recyclingmaschinen developed the E:GRAN series of recycling machines for the processing of defective films and film edge trims [21]. All models of the E:GRAN series feature a shredder/feeder/ extruder combination (see Fig. 5.6). Plastic film and film edge trims are shredded directly in the extruder feed section. The conically shaped conveying area of the screw compresses the material as it enters the extruder. In the extruder, the material is brought to a uniform melt temperature and subsequently pelletized. The feed section (where the material is shredded), the conveying area, and the extruder all lie along a single shaft. The resulting design requires only one energy-efficient drive. All the components are positioned in close proximity to prevent oxidation of the material and to make optimal use of heat from the shredding process. Erema developed the Intarema® K recycling system for transforming plastic film edge trim efficiently into high quality, clean pellets [22]. The Intarema® K recycling system, shown in Fig. 5.7, works as follows: Feeding with edge trim is automatic and direct via pipes and cyclone (1). Loose waste material can also be fed into the machine by conveyor belt (2) or feed rollers (3). In the patented Preconditioning Unit (4), the material is cut, mixed, heated, dried, precompacted, and buffered. Next, the

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tangentially connected extruder with its extremely short screw is filled continuously with hot, precompacted material. The innovative Counter Current technology enables optimized intake action across an extended temperature range. The Counter Current technology changes the direction of rotation inside the cutter/compactor: the plastic material thus moves in the opposite direction to that of the extruder screw. In this special, patented extruder (5), the material is melted at an extremely low temperature and turned into pellets in an air-cooled pelletizing system (6). Intarema® K can be used to recycle several types of clean plastic scrap, including polyethylene mono- or multilayer films; polyethylene films with polypropylene, polyamide, ethylene vinyl alcohol; and breathable films such as polyethylene with calcium carbonate.

References [1] CEFLEX. Flexible packaging Europe sustainability key facts. 2018. https://ceflex.eu/wp-content/uploads/2019/04/FPE-sustainabilitykey-messages-factsheet-small-GB_web.pdf. [2] 2016 More Recycling American Chemistry Council. National postconsumer plastic bag & film recycling report. February 2018. https://plastics.americanchemistry.com/2016-National-PostConsumer-Plastic-Bag-and-Film-Recycling-Report.pdf. [3] APReAssociation of Plastic Recyclers. The APR design® guide for plastics recyclability. January 6, 2018. http://www.plasticsrecycling. org/images/pdf/design-guide/PE_Film_APR_Design_Guide.pdf. [4] AMEC Environment & Infrastructure UK, Axion Consulting. Collection and recycling of household plastic film packaging. Waste & Resources Action Programme (WRAP). Retrieved September 2, 2019, http://www.wrap.org.uk/sites/files/wrap/MST1445_Plastic_ Film_Breifing_Note_final%20for%20web.pdf. [5] Mepex Consult AS. Basic facts report on design for plastic packaging recyclability. April 7, 2017. https://www.grontpunkt.no/media/2777/ report-gpn-design-for-recycling-0704174.pdf. [6] Horodytska O, Valde´s FJ, Fullana A. Plastic flexible films waste management e a state of art review. Waste Management 2018;77: 413e25. [7] RSE USA. The closed loop foundation - film recycling investment report. 2016. http://www.closedlooppartners.com/wp-content/ uploads/2017/09/FilmRecyclingInvestmentReport_Final.pdf. [8] Terracycle. Zero waste bags. 2019. https://zerowasteboxes.terracycle. com/collections/zero-waste-bags.

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[9] CEFLEX. Driving towards circular economy. Retrieved April 6, 2019, https://ceflex.eu/. [10] Plastic Film Recycling.org, Flexible Film Recycling Group (FFRG), American Chemistry Council. Recycling plastic film e opportunity. 2018. https://www.plasticfilmrecycling.org/recycling-commercialfilm/value-chain-case-study/#pmcs_showHomeAndWork. [11] Reclay StewardEdge. Product stewardship solutions, resource recovery systems , Moore recycling associates Inc. Analysis of flexible film plastics diversion systems e Canadian plastics industry association continuous improvement fund stewardship ontario. February 2013. [12] Hefty® EnergyBagÔ program. September 2016. Omaha, Nebraska, http://www.hefty.com/hefty-energybag/hefty-energybag-program/. [13] Flexible Packaging Association (FPA). Flexible Packaging Resource Recovery: A work-in-progress e summary report: Continuing evaluation of resource recovery infrastructures and processes. Retrieved June 6, 2018, https://www.flexpack.org/flexible-packaging-resourcerecovery-a-work-in-progress-brochure/. [14] RRS, Recycle.com. Flexible packaging sortation at materials recovery facilities e research report. Materials Recovery For the Future (MRFF). September 21, 2016. https://www.materialsrecoveryforthefuture.com/ wp-content/uploads/2016/09/Flexible-Packaging-Sortation-at-MaterialsRecovery-Facilities-RRS-Research-Report.pdf. [15] PlasticFilmRecycling.org, Flexible Film Recycling Group (FFRG). American Chemistry Council. Learn what’s recyclable. 2018. https:// www.plasticfilmrecycling.org/recycling-bags-and-wraps/plastic-filmeducation-individuals/learn-whats-recyclable/. [16] APReAssociation of Plastic Recyclers. The APR Design® guide for plastics recyclability - film and flexible packaging. https://www. eiseverywhere.com/eselectv2/backendfileapi/download/358894? id¼37b3e1bf5a2bcbdab4d6cf68e04fefc8-MjAxOS0wMiM1YzY0 MzE0NDAwNTNl&csrf¼db64eea30f41a7b93e77510e2649162f915ff 16947926e1161; 25-02-2019. [17] CleanRobotics. Introducing Trashbot e the first ever smart trash can that uses AI to sort recyclables from landfill waste. 2017. http://www. cleanrobotics.com/. [18] Hooijdonk van R. The holy grail of recycling: AI-powered robots. PreScouter; December 2018. https://www.prescouter.com/2018/12/ the-holy-grail-of-recycling-ai-powered-robots/. [19] Bin-e. Smart waste bin. 2017. http://bine.world/.

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[20] Next Generation Recyclingmaschinen GmbH. Mechanical recycling of bioplastics e Part I. Bioplastics Magazine 2018;13:02e18. [21] NGR, Plastic Recycling Technologies. E:GRAN. Retrieved June 14, 2019, https://www.ngr-world.com/product/egran/. [22] Erema engineering recycling maschinen and anlagen. INTAREMA® K. Retrieved May 5, 2019, https://www.erema.com/en/intarema_k/.

Patents Patent number

Publication Date

CN104070617 A

Family members

Priority numbers

Inventors

Applicants

Title

20141001

CN20131099371 20130326

ZHANG XUEYUN

FANGCHENGGANG CITY PORT DISTR HONGDA PLASTIC FACTORY

BOPA production marginal material recovery system.

CN203156973 U

20130828

CN20132141412U 20130326

ZHANG XUEYUN

FANGCHENGGANG CITY PORT DISTR HONGDA PLASTIC FACTORY

BOPA (biaxially oriented polyamide) production leftover recovery system.

EP0679487 A1

19951102

EP19940106672 19940428

BUONGIORNO LIVIO; CIOCCA PAOLO

GRACE W R & CO

Multi-layer polyolefin film containing recycle polymer from cross-linked films.

KR100361735 B1

20021107

KR20020009924 20020225

LEE YOUNG CHUL

KOREA IND TECH INST

Method for recycling multilayered film waste for packing.

US2006060586 A1

20060323

US7571870 B2 20090811

US20050110290 20050420; US20040611661P 20040921

LANGSTON JODY

LANGSTON JODY

Apparatus, system, and method for condensing, separating and storing recyclable material.

US2012258189 A1

20121011

US8932043 B2 20150113

US201213442745 20120409; US201161473455P 20110408

WILHELM MICHAEL BRANDON

WILHELM MICHAEL BRANDON

Plastic trim pelletizer and bricker reclaim device.

AU1774495 A 19951109; AU688863 B2 19980319; BR9501861 A 19951121; CA2148072 A1 19951029; EP0679487 A1 19951102; JPH0852781 A 19960227; NZ270984 A 19960625; US5605660 A 19970225; US5928798 A 19990727

US3797702 A

19740319

US19710128973 19710329

ROBERTSON J

ROBERTSON J

Scrap recovery and feed system.

US4014462 A

19770329

US19750629070 19751105; US19710128973 19710329; US19740439029 19740204

ROBERTSON J

ROBERTSON J

Scrap recovery and feed system.

US4340347 A

19820720

US19800211751 19801201

ROBERTSON J

ROBERTSON J

Scrap recovery system.

US4738404 A

19880419

US19870010048 19870202

MITCHELL WAYNE R

SPROUT-BAUER, INC ANDRITZ

Rotary knife cutter having rolloff cover.

US5128212 A

19920707

US19900525020 19900518

KNEALE TIMOTHY M; ROBERTS RICHARD KENNETH; SNYDER JOHN DOUGLAS

DUPONT

Multilayer heat shrinkable polymeric film containing recycle polymer.

US5170949 A

19921215

AU1825892 A 19930218; AU643145 B2 19931104; CA2069771 A1 19930217; CA2069771 C 19960416; CN1069675 A 19930310; CN1025161 C 19940629; EP0528184 A1 19930224; KR950010976 B1 19950926; MX9204733 A 19930701; PH05277464 A 19931026; US5307998 A 19940503

US19910746357 19910816

BUCK RAY A; SMITH KIMBER; WILSON LARRY J

ANDRITZ SPROUT BAUER INC

Apparatus and method for processing scrap film.

WO2011140317 A1

20111110

EP2566690 A1 20130313; EP2566690 A4 20131030; TW201141695 A 20111201; US2011274796 A1 20111110; US2014147561 A1 20140529; US8642145 B2 20140204; US9676122 B2 20170613

US20100332528P 20100507

BOWER DOUGLAS JAMES; PEGUERO LARISSA MARIE

TORAY PLASTICS AMERICA INC

Barrier film with reclaimed metalized polyester.

AU1242588 A 19880824; CA1295594 C 19920211; CN1004859 B 19890726; CN88100480 A 19880817; EP0344198 A1 19891206; EP0344198 B1 19911127; ES2009525 A6 19891001; JPH01503213 A 19891102; KR900008673 B1 19901126; MX159798 A 19890830; WO8805695 A1 19880811

(Continued )

(Continued ) Patent number

Publication Date

Family members

Priority numbers

Inventors

Applicants

Title

WO9117886 A1

19911128

CA2083258 A1 19911119; DE69129230 T2 19981126; EP0528980 A1 19930303; EP0528980 A4 19930317; EP0528980 B1 19980408; JPH06500963 A 19940127

US19900525020 19900518; US19910692147 19910502

KNEALE TIMOTHY M; ROBERTS RICHARD KENNETH; SNYDER JOHN DOUGLAS

DUPONT

Multilayer heat shrinkable polymeric film containing recycle polymer.

US2009148629 A1

20090611

US20080333175 20081211; US20060482356 20060707; US20050299442 20051212; US20050166516 20050624

SASINE JOHN; JONGERT CHARLES ACEY MARVIN; ASHBY JEFFERY A

PAPER AND PLASTIC PARTNERSHIP, LLC

Systems, methods and devices for collecting, packaging, and processing recyclable waste.

6 Separation/Sorting and Volume Reduction 6.1 Separation/Sorting The term separation is interpreted as meaning separation of one class of materials from another, such as plastics from metals. Separation is performed either at the source by the generator or at a material(s) recovery facility (MRF) [1]. An MRF1 is a solid waste management plant that uses a combination of equipment and manual labor to separate and densify recyclable materials in preparation for shipment to reprocessors or recyclers of the particular materials recovered. An MRF that is designed to process source separated/commingled dry recyclables is sometimes referred to as a “clean MRF,” while an MRF that handles commingled wastes including decomposable solid organic matter is often called a “dirty MRF.” Once classes of materials have been separated from each other, sorting is also generally needed to separate the films by polymer type from mixed flexible packaging. Sorting is a crucial and often neglected step in the recycling process. Failure to sort the collected packaging into material streams that recyclers can use leads to downcycling, that is, the production of recycled material no longer suitable for its original application. Sorting is most commonly performed at MRFs. Some MRFs produce single polymeretype film grade from a large size separation stream, which is mostly composed of polyethylene bags; however, the technology and logistics are in their infancy [2]. One of the challenges MRFs face is contamination in the material they receive with metals, paper, and other plastics, all of which can negatively affect the final recycled product, for example, a single allen wrench carelessly thrown into a bale of film could wreak havoc if it passed through the metal detection equipment and made it into the reprocessing equipment undetected [3]. Most MRFs in the United States consider flexible plastic films as a contaminant because the films can easily get

1

Also known as materia(s)l reclamation facility or material(s) recycling facility.

Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00006-2 Copyright © 2020 Elsevier Inc. All rights reserved.

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tangled in sortation equipment at MRFs, causing the lines to shut down so that workers can remove the clogged (jammed) film [3]. For plastics that make up small percentages of incoming MRF materials or materials that require costly specialized equipment for sorting, sorting may be performed at plastic recovery facilities (PRFs). A PRF can be considered as a plastic-specific MRF. It is a facility where the mixed plastics are separated into different formats and/or polymers by manual, mechanical, and optical means (see Chapter 8). Currently, there are no PRFs for mixed types of plastic film in the United States. Once film has been sorted into market grades of compatible types, either by the generator or by MRFs/PRFs, it is sent to a reprocessor or recycler for cleaning and processing, followed by sale to end users that can use it as a raw material in recycled content product manufacturing [1]. The main technologies used for the separation and sorting of flexible plastic packaging are discussed in the following subsections.

6.1.1 Manual and Vacuum-Assisted Manual Sorting In manual (or visual) sorting, targeted materials are removed by hand on the basis of shape, size, and/or color and redirected into storage bins. Manual sorting is the most widely used method to separate packaging films from a waste mixture in any size facility. Manual sorting is suitable when a large amount of a plastic packaging component is present, but it is a laborintensive and costly process. The cost of manually sorting film in the United States is at least $150/ton, not including the cost that film adds to additional quality control (e.g., to remove stray film) from other product grades and the cost of removing film from screens [1]. Low labor costs in Asian countries make the manual sorting of packaging waste an attractive option [4]. In vacuum-assisted manual sorting, laborers lift flexible plastic packaging into a vacuum system positioned above the belt at picking stations and redirect other material into storage bins. Retrofitted large-scale MRFs commonly utilize overhead suction tubes at manual sort stations to collect and convey plastic film from multiple points in the MRF to one central point. Manual sorters snatch and lift plastic film to the suction tubes. The plastic film is pulled in by the suction and conveyed to a storage bin. Older or smaller facilities may manually pick out film at only one point in the MRF and drop it down a chute into a bin [5]. The vacuum-assisted manual sorting improves the recovery volume by 40% and the quality of flexible plastic packaging materials removed manually at picking stations. Although the vacuum-assisted manual sorting is more efficient than

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Figure 6.1 The FilmVac System [7]. Courtesy of Impact Air Systems.

unassisted manual, the volume of material that can be handled by each sorter is limited [6]. Impact Air Systems developed the FilmVac System for collecting and conveying handpicked material, such as plastic film, during the manual sorting process [7]. The FilmVac System consists of a series of specially designed material collection hoods that are typically mounted in the ceiling of the sorting cabin above the waste belts (see Fig. 6.1). A series of collection hoods can be connected together via a range of ductwork, meaning all material is transported to a single point within the MRF, eliminating the need for transfer stations and additional storage bunkers.

Figure 6.2 The Nihot Film Vacuum System (FVS) [8]. Courtesy of NIHOT.

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Material is typically fed directly into a bale press or compacted in the socalled Impact Film Screw to reduce the film’s volume (see Section 6.2.1). For manually sorted plastic film, Nihot has developed the Film Vacuum System consisting of one or more suction points above a sorting belt, a recirculation fan, and a material/air separator. The complete system works in a closed loop (see Fig. 6.2). The film, which is manually brought to the suction point, is sucked into a suction hood and conveyed pneumatically to a rotary air separator, where the air and film are separated. The film is dropped pressure less into a baler, press container, bay, or onto a conveyor. The aspirated air is recirculated by the fan and led back to the opening of the suction point [9]. Manual sorting can promote the collection of all types of packaging films and sorting into more than one film grade. This could be achieved by adopting the following processing steps:
separate film from no-film materials (the best practice for manually sorting film is for all film to be “bags-in-bags,” i.e., all film stuffed inside a tied-off bag);
open bags-in-bags so each piece of film is individualized;
sort out bags and film that are only polyethylene into a one grade; and
leave all remaining film as a mixed film/laminate grade [5].

6.1.2 Air Separators An air separator removes light or heavy items from a waste stream. Other names used for an air separator are air classifier, wind sifter, wind shifter, or aeraulic separator. Using an airflow, the materials from one stream are separated into various streams depending on the size, shape, and weight of the waste items. An air separator is typically situated at the beginning of the waste material stream to preseparate the lighter material (plastic bags, plastic film, light packaging) from the heavier materials (plastic bottles, plastic containers, heavy objects). In modern systems, packaging films are presorted either by air separators (1- or 2-stage) or ballistic separators. Several manufacturers, including Ken Mills Engineering (partner of Krause Manufacturing Inc., of the CP group), Bollegraaf, Nihot, Bezner (of the Heilig Group), Parini s.r.l, and Waste Sorting Line, build air separator systems, which can be used for the separation of packaging films. Ken Mills Engineering developed the Air Drum Separator (ADS), which separates light flexible two-dimensional (2D) material from rigid three-dimensional (3D) material streams in any MRF [10]. ADS applies

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Figure 6.3 Schematic diagram of an aspirator air separator [11]. Courtesy of PARINI S.R.L.

vacuum technology through a rotating, perforated drum to draw the flexible 2D material against the drum, separating it from the rigid, 3D material that bounces off. A schematic diagram of an air separator built by Parini s.r.l. is shown in Fig. 6.3. The input material to the air separator conveyed by a belt conveyor ends up in an extractor hood (black arrow or “material input”). Here, thanks to the controlled airflow generated by the fan (blue arrow or “air”), the light fraction is aspirated upwards and continues its path in a series of piping (red arrow or “air with material”), while the heavy fraction is discharged on a second conveyor. The light fraction then reaches the rotary valve, in which, thanks to the movement of the rotor and the consequent reduction of the air speed, the lightweight material is unloaded on another conveyor. The air then continues its path toward the fan, after which there is a dust suppression filter, thus closing the air recirculation. DE9417627 U1 (1994, PAALS PACKPRESSEN FABRIK GMBH) discloses a system and a method, in which a waste stream of a material to be sorted is fed to an inclined sorting track constituted by a portion of a circulating, air-permeable conveyor member under which a vacuum is generated and maintained. Under the influence of the vacuum, flat material, such as plastic film and paper, adheres to the conveyor member and is entrained from the drop zone to the upper end of the sorting track. Other material, which is less susceptible to be held by suction through the airpermeable belt, such as bottles, cans, and other not generally flat material, does not adhere to the sorting track belt and descends to the lower end of the sorting track. Thus, plastic film and paper are sorted out of the waste stream.

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Such a sorting step is of particular use in situations in which a dry waste consisting mainly of paper, metal, and plastic waste is collected in combination for efficient collection of waste. The flat material consists mainly of paper, and the plastic film can be sorted out of the paper in a separate sorting step, for instance, employing the apparatus disclosed in EP1970130 (2008, MACHF BOLLEGRAAF APPINGEDAM B). However, a problem of such a sorting apparatus and method is that some nonflat materials are nevertheless entrained to the upper end of the sorting track, in particular, if waste is supplied at a high rate or irregularly so that high peak rates occur. This problem can to a large extent be solved by avoiding high waste supply rates, but this entails a reduced sorting capacity (2011, EP2314387, BOLLEGRAAF PATENTS AND BRANDS B V). EP2314387 A1 (2011, BOLLEGRAAF PATENTS AND BRANDS B V) discloses a method and an apparatus, shown in Fig. 6.4, for sorting a flat material such as plastic film or paper from a stream of waste material, comprising a circulating air-permeable conveyor member (6) of which a portion constitutes a sorting track (7), extending and inclined from a lower end (8) to an upper end (9); means for maintaining a vacuum underneath the sorting track (11); and a motor (12) for driving the circulation of the conveyor member (6) in a sense of transport; wherein the sorting track (7) is arranged for entraining a portion of the material to be sorted with the conveyor member from a drop zone (15) of the sorting track (7) toward the upper end (9) of the sorting track and allowing another portion of the material to be sorted to descend from the drop zone (15) toward the lower end (8) of the sorting track (7) and further comprising a sweeper (2) between the drop zone (15) and the upper end (9) for sweeping flat material entrapping nonflat material off the entrapped nonflat material. Most of the flat items (42) in the waste material (37) are engaged by the circulating conveyor belt (6) and transported upwardly from the drop zone (15); some of the flat items (42) may initially slide downwardly over some distance until being engaged by a portion of the sorting track (7) not covered by other material and then be transported upwardly toward the upper end (9) of the sorting track (7) and discharged into a flat item collecting bin (17). As at least most of the nonflat items (43) are not engaged by the circulating conveyor belt (6), at least most of the nonflat items (43) roll and slide from the drop zone (15) toward the lower end (8) of the sorting track (7) and drop into a nonflat item collecting bin (19). Air separators offer multiple advantages to the sorting of plastic waste including: (1) effective separation of bulky plastic film waste from a two

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Figure 6.4 Schematic diagram of the apparatus for sorting flat material from a stream of waste (2011, EP2314387 A1, BOLLEGRAAF PATENTS AND BRANDS B V). a, Angle; 1, Transport conveyor; 2, Sweeper in the form of a rotor; 3, Feeding conveyor; 6, Circulating conveyor member; 7, Conveyor sorting track; 8, Lower end of 7; 9, Upper end of 7; 11, Fan; 12, Motor; 14, Direction of transport; 15, Drop zone; 16, Air hose; 17, First discharge site; 18, Scraper; 19, Collecting bin; 21, Radially projecting flexible sweeping blades of 2; 22, Rotation; 25, Grader; 26, Drop zone; 27, Vacuum chamber; 28, Rotation axis; 32, Orifice; 34, Roller; 35, Roller; 37, Stream of waste material; 38, Feeding path; 39, Downstream end of 38; 41, Obliquely upwardly facing side; 42, Flat items; and 43, Nonflat items.

stream MRF; (2) reduction of wear parts; (3) the waste does not interact with the generator of the airflow, avoiding wear and clogging; (4) low maintenance; (5) high reliability and versatility (it can process very different waste streams); and (6) low dust emission [11]. The limitations of an air separator are: (1) it cannot distinguish plastic film from paper; (2) it cannot separate a polyethylene film from other polymer films or multilayers; (3) the separation of a film from a mixed containers stream would require quality control checking to produce film that meets recycling specifications [5]; and (4) when using the air

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separators with an optical sorter, the films do not stick well to the fast conveyor belts, and the jets of air used for separation have difficulty controlling the exit direction of the ejected flexible plastic. However, given the large range of size and shapes of flexible plastic packaging, several parallel processing lines and methods will likely be needed [12].

6.1.3 Screens Screens are used to separate materials by size. The purpose of each screen is to agitate and spread out the material to break up loosely bound items and to separate smaller items from larger ones. There are four main types of screens: vibrating screens, trommel screens, disc screens, and ballistic screens. Some disc screens, as well as ballistic screens, are designed to screen small material as well as separate flat, 2D items such as film from 3D items such as plastic containers [13].

6.1.3.1 Ballistic Screens A ballistic screen or separator is in many ways a combination of a vibrating screen with a disc screen. It has a small incline in the deck causing heavy materials to fall to the lower level of the deck, while lighter materials such as plastic films are transported upwards. Fine materials fall through the perforated bottom. A ballistic separator is a 2De3D sorting apparatus and is used to separate rigid plastics (which tend to be threedimensional) from plastics films, which are two-dimensional. Ballistic separation is used to do three distinct separations: flexible materials, rigid materials, and to screen out a certain size fraction of material. Similar to a conventional disc screen, the 3D rigid items will tumble back, and the flat/flexible items will climb to the top front portion of the machine. Finally, the ballistic separator’s paddles are fitted with replaceable screening plates that are used to screen out material of a certain size as determined by the application [14]. The ballistic separator has multiple advantages over a conventional rubber star screen.2 The most appreciated benefit is certainly the lower operational cost of the machine. There are no rubber discs to wear out, and the elliptical movement does not result in the wrapping of long and stringy flexible items, which is what happens on the spinning shaft of a regular screen. Together, these two main aspects translate to more uptime with 2

Named after star-shaped rubber discs located on the shafts.

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lower, almost nonexistent, wear parts replacement and much lower labor costs related to cleaning the screen. Further, the ballistic separator has a compact footprint that makes it easy to integrate and retrofit within sorting systems, and it does a better and more constant job at separation than a regular star screen and also consumes less energy than a comparable capacity star screen [14].

6.1.4 Grabbers Film grabbers (or grippers) are designed to capture plastic films and bags. The hooks (spokes, spikes, piercing needles, protruding fingers, or teeth) of a grabber pass very close to the conveyor belt to grab the films or bags and then retract and redirect them into bins. Large 3D objects must be removed before the grabber. Patents US4067506 A (1978, R.UTI.R s.r.l), BE867777 A (1978), US4207986 A(1980), and BR7805346 A (1980) of SORAIN CECCHINI SPA disclose a series of apparatuses in which plastic films are separated from waste by bringing the waste in contact with circulating hooks that engage plastic films more than other waste materials brought in contact with the hooks. The circulating hooks displace engaged films away from other waste materials, and the engaged films are subsequently disengaged from the hooks and transported away for further processing and storage. In particular, US4067506 A (1978, R.UTI.R s.r.l) discloses an apparatus, shown in Fig. 6.5, for tearing open small bags containing city solid waste material and for separating out plastic film material and/or the bags,

Figure 6.5 Schematic diagram of an apparatus for tearing small plastic bags (1978, US4067506 A, R.UTI.R s.r.l). A, Direction; 11, Conveyor belt; 12, Hooks (aculei); 13, Blades; 130 , Hinges; 14, Blade’s teeth; 15, Shaft; 16, Front transmission pulley; and 17, Rear transmission pulley.

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comprising an endless conveyor belt (11), which carries on the surface thereof a plurality of hooks (or aculei) (12), which engage the bags placed on the surface of the conveyor belt (11). The belt follows a path of a first straight or rectilinear length and a second or return straight or rectilinear length. The transition between the first straight length and the second straight length follows a mild curve about a drive pulley having a relatively large diameter (16), whereas the transition between the return straight length and the first straight length follows a relatively sharp curve about a drive pulley having a relatively small diameter (17) so that such transition is sufficiently sudden; a plurality of toothed (serrated) blades (13) is pivotally carried on a shaft above the conveyor belt (11) so that the blades (13) are placed in proximity to the surface of the belt for engaging and tearing the bags carried thereon. Hook-like projections having a hook portion bent in a direction opposite to the direction of travel of the belt may be substituted for the hooks (12) for engaging the bags. According to the invention, an important and essential feature of the apparatus is that the front transmission pulley (16) has a diameter that is substantially larger than the rear pulley (17). The difference between the diameter of the front pulley and the rear one, with respect to the direction of travel of the belt, is significant not only for the tearing of little bags but also for the other important workings of the apparatus. When the belt reaches the rear transmission roller (17) having a small diameter, about which the belt follows a relatively sharp curve, the plastic films that are being carried on the hooks, as a consequence of the sharp movement of the belt, will fall off so as to be conveniently collected. BE867777 A (1978), US4207986 A (1980), and BR7805346 A (1980) of SORAIN CECCHINI SPA disclose an apparatus, shown in Fig. 6.6, for separating waste material (10) composed mainly of plastic film and paper including a conveyor belt (1) for moving the waste material along a substantially horizontal path in a given direction and a reel device (2) having a plurality of spokes or hooked members (11) extending therefrom rotating to move the spokes through the waste material at a portion of the horizontal path, with the spokes moving in the same direction in which the waste material is moving while being passed there through. The spokes of the reel device engage plastic film contained in the waste material to separate the plastic film therefrom. In another variation of the apparatus, the reel device (2) may be formed by a plurality of generally linear belt type conveyors each extending at an oblique angle to the horizontal direction of travel of the waste material and each having an end overlapping an adjacent reel device so that engaged plastic material may be serially deposited between reel devices in an upstream direction taken

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Figure 6.6 Schematic diagram of the separation apparatus (1978, BE867777 A; 1980 US4207986 A; 1980. BR7805346 A of SORAIN CECCHINI SPA). 1, Conveyor belt; 2, Reel device; 3, Intake mouth; 4, Decanting or settling cyclone; 6, Fans; 10, Waste material; and 11, Spokes of the reel (2).

relative to the direction of travel of the composite material until it is removed from or released by the reel device that is furthest upstream. JPS5422477 A (1979, NIPPON KOKAN KK) discloses an apparatus and a method for separating plastic films from paper, by piercing the plastic with a hole by heating and hooking and conveying the plastic with a hook. The apparatus, shown in Fig. 6.7, comprises: 1) a rotary drum (2) having a top inlet opening (4) and a bottom outlet (23); a series of electrode hooks (7) projecting from an inner surface of the drum and spaced from each other angularly; 2) a fixed semicircular electric current carrying rail connected to the electrodes; 3) a cooling air nozzle (17) arranged in the drum at the opposite side with reference to the electric current carrying rail; and 4) a conveyor belt (5) arranged in the drum (2) below a top end of the rail. Specifically, the electrodes are heated when they come into contact with the rail, so that they fuse the plastic waste and make a hole thereon to hang it upwards. During this lifting motion, electric current is stopped and cold air is blown from the nozzle (17). At the top, electric current reenters the electrodes to fuse the hole and then the plastic waste falls onto the conveyor belt.

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Figure 6.7 Apparatus for separating plastics from paper (1979, JPS5422477 A, NIPPON KOKAN KK). A, Direction line; 1, Roller; 2, Rotary drum; 3, Waste mixture; 4, Top inlet; 5, Conveyor belt; 6, Chute; 7, Electrode hook; 17, Cooling air nozzle; 18, Holes; 19, Pipe; 20, Rotating cylinder; 21, Hood; 22, Plastic outlet; 23, Bottom outlet; 24, Plastic discharge conveyor; and 26, Skirt plate.

Figure 6.8 Schematic diagram of an apparatus for the sorting out of plastic film from a mixture of waste (1982, EP0050259 A2, VOELSKOW PETER). 1, Mixture of waste; 3, Spikes; 4, Spiked roller; 5, Brush bands; 6, Brush rollers; 7, Remaining refuse; 8, Textile refuse; and 9, Combingoff rollers.

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EP0050259 A2 (1982, VOELSKOW PETER) discloses a method and apparatus for the sorting out of plastic film from a mixture of waste from which heavy components, such as small pieces of stone, glass, and metal, have already been removed (see Fig. 6.8). The waste (1) descending in a thin layer is swept by the brushes (5) of a brush roller (6) onto sharp spikes (3) moving in the opposite direction; only those articles that have high tensile strength are spiked, whereas components with lower tensile strength such as paper are torn by the spikes (3) and are further conveyed by the brooms or brushes (5) together with the components that are not seized by the spikes, such as leather, cardboard, and wood, and which slide away across the spikes. Combing-off rollers (9), e.g. spiked rollers or brush rollers, may be used, rotating at higher velocity and in opposite direction to the spiked rollers (4), to loosen hanged plastic films from the spikes. Plastic film and any textile waste present are effectively removed by the spikes with a minimum amount of other accompanying materials, such as paper.

Figure 6.9 Schematic side view of the apparatus for separating plastic film from waste (2008, EP1970130 A1; 2008, US2008223770 A1, MACHF BOLLEGRAAF APPINGEDAM B). 1, Supply track; 2, Waste; 3, Supply direction (arrow); 4, Downstream end; 5, Hooks; 6, Drum; 7, Sense of circulation (arrow); 8, Engagement area; 9, Disengagement area; 10, Blower; 11, Upward airflow; 12, Fraction of the waste (2); 13, Remainder of the waste (2); 14, Discharge conveyor; 15, Blower; 16, Counter airflow; 17, Discharge channel; 18, Inlet; 19, and Ventilator.

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EP1970130 A1 (2008) and US2008223770 A1 (2008) of MACHF BOLLEGRAAF APPINGEDAM B disclose an apparatus, shown in Fig. 6.9, and a method for separating plastic film from waste (2) comprising a plurality of hooks (5) mounted on a drum (6) for circulating the hooks (5) along a trajectory through an engagement area (8) near a supply track (1) and through a disengagement area (9) downstream of the engagement area (8). The engagement area (8) is located higher than the supply track (1) and/ or in supply direction (3) beyond the downstream end of the supply track (1), such that, in operation, a remainder of the waste (13) passes by the trajectory of the hooks (5) without contacting the hooks (5). By an upward airflow (11) generated by a blower (10), a fraction (12) of the waste (2) that is easily entrained by the airflow, such as a flexible plastic film, is separated from the waste (2) and blown against the hooks (5) in the engagement area (8). The remainder of the waste (13), such as paper that is not engaged by the hooks (5) once it is outside the upward airflow (11), drops onto the discharge conveyor (14). The hooks (5) project from the drum (6) via openings in the circumferential surface of the drum (6) and are retractable into a circumferential surface of the drum (6). Because the hooks (5) that are rotated along with the drum (6) are retracted, no separate members for stripping caught film material are required, and the construction can be relatively light and simple and is suitable for rotation at relatively high rotational speeds. Moreover, the openings in the drum via which the hooks project and retract only need to be small so that the inside of the drum can be well shielded from the waste material. According to FR3009211 A1 (2015, NEOS), the aforementioned separation apparatus is very sensitive to fine particles of waste, which will be driven by the airflow produced by the first nozzle and obstruct the drum. This requires to provide upstream of the separation apparatus a device for removing the fine particles from the waste stream, which increases the cost. Also, this separation apparatus does not enable the separation of the so-called “heavy” films, which are films that have been wrapped at least partially on other nonflexible solid waste or films in which solid waste is trapped. Another disadvantage of this separation apparatus is that it will be easily rendered inoperative in the event of aberrant waste in the waste stream, such as hard metal pieces. Indeed, the hooks will be bent by such aberrant waste and cannot be returned to their retracted position, forcing a stop of the separation apparatus and the entire sorting chain of which forms a part. CN201760985 U (2011, WUXI CHANGJIANG MECHANICAL and ELECTRICAL CO LTD) discloses a flexible plastic film collecting device

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Figure 6.10 Schematic diagram of the flexible plastic film collecting device (2011, CN201760985 U, WUXI CHANGJIANG MECHANICAL and ELECTRICAL CO LTD). 2, Aggregate conveyor belt; 4, Crochet hook (needle) conveying device; 5, Water channel; and 41, Conveying belt of 4.

of a water-sorting waste treatment apparatus, shown in Fig. 6.10, comprising a conveying water channel (5), a crochet needle (or hook) conveying device (4), and a material collecting and conveyor belt (2). The crochet needle conveying device (4) is used to hook the flexible plastic film on the water surface and is composed of a closed loop conveyor belt (41) with crochet needles on the surface and runs against water flow; the material collecting and conveyor belt (2) is arranged between the end of the conveyor belt and the water surface, and the conveying water channel (5) is particularly a nonstage water channel without level difference. Viewed from the side site, the circulating conveying belt (41) in the crochet needle conveying device (4) presents a trapezoid-similar structure. When the flexible plastic film floats on the water surface and flows from the left side of the conveying water channel (5) to the right side, it is picked up by the crochets of the conveyor belt (41) and transported to the aggregate conveyor belt terminal (2), whereon the film is dropped and carried away. CN201816154 U (2011, HUBEI HEJIA ENVIRONMENT EQUIPMENT CO LTD) discloses a sorting apparatus, shown in Fig. 6.11, for separating flexible plastic in a household refuse treatment plant. The flexible plastic sorting apparatus comprises a rack (2), a driving device (8), a lower guide shaft (4), a rotating device (6), grabbing hooks (5), a lower baffle plate (1), nozzles (3), and an air source supply device (not shown). The driving device (8) and the lower guide shaft (4) are respectively

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Figure 6.11 Schematic diagram of the flexible plastic sorting apparatus (2011, CN201816154 U, HUBEI HEJIA ENVIRONMENT EQUIPMENT CO LTD). 1, Lower baffle plate; 2, Rack; 3, Nozzles; 4, Lower guide shaft; 5, Grabbing hooks (flukes); 6, Rotating device; 7, Air source connecting pipe; 8, Driving device; 9, Flexible plastic; 10, Drive spindle; 11, Outer cover; 31, Nozzles; and 32, Nozzles.

arranged on the rack (2); the rotating device (6) is arranged on the driving device (8) and the lower guide shaft (4); the driving device (8) drives the rotating device (6) to rotate; the rotating device (6) is provided with grabbing hooks (5); the lower baffle plate (1) is arranged on the rack (2) corresponding to the lower end of the rotating device (6); and a plurality of nozzles (3) is arranged and divided into three groups, two groups are respectively arranged on the rack (2) corresponding to the lower baffle plate (1), one group is arranged on the rack below the driving device (8), and the nozzles are respectively connected with an air source supply device. The flexible plastic sorting apparatus combines air separation with mechanical movement, and it is claimed to have the following advantages: improved efficiency of plastic sorting; less impurity in the recycled plastic; better quality of the recycled plastic; and economic and environmental benefits. AT515429 A4 (2015) and DE202015102117 U1 (2015) of HILLEBRAND JOSEF disclose an apparatus, shown in Fig. 6.12, for separating large plastic films and bags from mixed waste. The apparatus has an inclined supply surface comprising roller chains from which protrude pins (22), which revolve in a direction opposite to the slope of the supply surface, i.e., from bottom to top. Plates (25) are provided

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Figure 6.12 Schematic diagram of the separation apparatus (2015, AT515429 A; 2015, DE202015102117 U1 HILLEBRAND JOSEF). 14,14’, Fittings; 16, Frame; 17, Drive shaft; 18, Clamping shaft; 19, Deflection shaft; 20, Motor; 21, Chains; 22, Pins; 25, Plates; and 27, 28 Lateral guides.

between the pins. The apparatus functions as follows: The waste to be separated is introduced to the first section. The waste slides down on the metal plates (25) but is plowed by the pins (22). Films larger than the distance between the chains (21) will stick to the pins (22) and will be carried up. The remaining waste slides down between the pins (22) and received by a conveyor belt. The guides (27, 28) prevent the material escaping sideways; the material can leave the apparatus only forward and backward. The inclination angle of the supply surface relative to the horizontal surface is 55e65 . The length of the pins is at least 250 mm. FR3009211 A1 (2015, NEOS) discloses an apparatus (6), shown in Fig. 6.13, for separating films (4) from waste (2) moving in a supply conveyor (1) comprising retractable teeth (8); means for circulating the moving part along a path comprising a zone of gripping the films and a zone of disengaging the films (4) from the teeth (8); means for controlling the projection and retraction of the teeth so that, in the gripping zone, the teeth (8) are projected; and means for maintaining the teeth (8) in the projected position in the gripping zone, characterized in that the holding means comprise rigid support means secured to the teeth (8) and at least one rail (not shown) positioned such that when the teeth (8) are in the projected position, the rigid support means is in contact with at least one rail and prevents the teeth (8) from being retracted.

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Figure 6.13 Schematic diagram of the separation apparatus placed at an end of a supply conveyer for pouring a mass of waste (2015, FR3009211 A1, NEOS). 1, Supply conveyor; 2, Waste; 3, Various types of waste; 4, Films; 5, Bin; 6, Separation apparatus; 7, Circumferential surface of a drum; 8, Teeth; 9, Bin; and 10, Inclined baffle plate.

Film grabbers work well for individualized plastic bags and other very thin and highly flexible materials, but they are not effective in separating bags-in-bags or thicker polyethylene films and multilayer plastic packaging, and their effectiveness with films and bags is between 40 and 60% [6]. When this technology is used on a fiber or single-stream line, this system also captures some paper that would need to be manually separated later [5]. The base price of a film grabber is about $450,000, but with the addition of an air system, storage container, and installation costs, the total installed cost can be over $500,000 [5]. Reclay StewardEdge estimated the costs to sort curbside collected film from other recyclables using three different, commercially available MRF sorting technologies, namely manual sorting, air separator, and film grabber that could be considered under single- and dual-stream collection systems. Air separation had the lowest cost; however, output will likely be lower quality than other more costly methods [5].

6.1.5 Marking and Labeling Systems 6.1.5.1 Resin Identification Codes The Resin Identification Code (RIC) system is a voluntary labeling system to allow consumers and recyclers to differentiate different types of

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Table 6.1 Resin Identification Codes (RICs) for the Seven Most Commonly Used Resin Types According to ASTM D7611-13e1 [15]

plastics used in the manufacture of the product or packaging while providing manufacturers a consistent uniform coding system. The RIC system assigns each of the seven most common resins a number from 1 to 7, which is encircled by the recycle logo, a triangle of arrows (see Table 6.1). The code is molded, formed, or imprinted on all containers and bottles that are large enough to accept the 0.5 in minimum size symbol. The code is placed in an inconspicuous location on the manufactured article, such as the bottom or back, and is usually accompanied by the abbreviation symbol of the plastic. Coding enables consumers to perform sorting before recycling, ensuring that the recycled plastic is as homogenous as possible to meet the

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needs of the end markets. Another potential benefit of coding is that it may facilitate the recovery of plastics not currently collected for recycling. The higher the recycling code number, the more difficult the plastic is to profitably be deployed into useful postconsumer applications other than by burning it for energy recovery or for disposal in landfills, which can create environmental problems. The RICs are used solely to identify the resin a plastic article is made of as detailed in ASTM D7611/D7611M13e1 [15]. The RICs are not “recycle codes.” The use of a RIC on a manufactured plastic article does not imply that the article is recycled or that there are systems in place to effectively process the article for reclamation or reuse. Their purpose is to assist recyclers with sorting the collected materials, but they do not necessarily mean that the product/ packaging can be recycled either through domestic curbside collection or industrial collections. The RIC system is not considered accurate for the identification and (pre)sorting of packaging materials from a waste mixture. Further, the identification code on the surface of plastic moldings such as bottles or large plastic fragments that have been exposed for long periods to the sun or in the sea becomes often illegible as a result of erosion caused by sandblasting, wave action, and wind or UV degradation. For plastic-based multilayers, the identification codes 81e90 are used. The identification codes of selected multilayers are presented in Table 6.2.

6.1.5.2 Marker Systems Examples of environmental and recycling symbols include the universal recycling symbol (see Fig. 6.14) and the “Green Dot”. The universal recycling symbol is in the public domain and is not a trademark. The Green Dot (German: Der Gru¨ne Punkt) is the license symbol of a European network of industry-funded systems for recycling the packaging materials of consumer goods [16]. The logo is trademark protected worldwide. The “Green Dot” on packaging means that for such packaging, a financial contribution has been paid to a national packaging recovery company that has been set up in accordance with the principles defined in European Directive 94/62/EC and its national law. The logo informs the consumer that the manufacturer of the product contributes to the cost of recovery and recycling. This can be with household waste collected by the authorities (e.g., in special bags or in containers in public places such as car parks and outside supermarkets). The Green Dot logo

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Table 6.2 Resin Identification Codes (RICs) for Selected Multilayers Symbol

Description

Exemplary Uses

Paper þ PET

Consumer packaging, pet food bags, cold store grocery bags, ice-cream containers

Paper and cardboard/plastic/ aluminium

Liquid storage containers, juice boxes, cardboard cans, cigarette pack liners, gum wrappers

LDPE/aluminium

Food packaging

indicates that a company has joined the Green Dot scheme, and not necessarily that the package is fully recyclable.

6.1.5.3 Other Marking/Labeling Schemes The How2Recycle label, shown in Fig. 6.15, is a voluntary standardized labeling system on packaging that clearly communicates recycling

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Figure 6.14 The universal recycling symbol.

instructions to the consumer. It involves a coalition of forward thinking brands that want their packaging to be recycled and are empowering consumers through smart packaging labels [17]. The How2Recycle label provides information for the identification of the packaging material (plastic), and the packaging parts (bags/film/wrap) need to be recycled. Another innovative solution for advanced sorting is digital watermarking, which could allow much better sorting and traceability of materials, with few retrofitting costs [18]. Radio frequency identification tags implemented in packaging products will also cause new challenges

Figure 6.15 The How2Recycle label [17]. From How2RecycleÒ.

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for the waste management of plastics in the future [19]; see also Chapter 11, Section 11.4.3.

6.1.6 Optical Sorters The two main optical (spectroscopic) sorting technologies are visible light (VIS) 3 sorting and near-infrared (NIR)4 sorting. Visible light sorting uses a high-speed camera or other light sensor, equipped with a visible range spectrometer to detect different plastic items. It does not identify plastics by chemical nature. NIR sorting uses the wavelength fingerprint in the NIR region of specific polymers to distinguish from one another. It does not distinguish colored and multilayer packaging materials. NIR sorting is used in both MRFs and PRFs. The most common and widely used optical sorter is a device that combines visible light and NIR to detect plastics. With this optical sorter, the spectrum of light is reflected off the plastic surface to identify polymer type and color and then the components are sorted, often by plastic grade. A representative patent for the sorting of packaging materials is WO0138012 A2 (2001, DER GRUENE PUNKT DUALES SYST), which discloses a method and an apparatus for automatically sorting films, e.g., packaging films, equipped with an NIR device (see Fig. 6.16). The films are conveyed through a 3D measuring zone (26) of an NIR device (20) in an air stream (L) at a known flow velocity and are identified. The films are removed from the air current at a site different from that of the measuring device according to the nature of the identified material. The films can be made of polyethylene or polypropylene. The main limitations of optical sorters can be summarized as follows:
optical sorters can only be applied to monomaterials. However, most flexible plastic packages are made of many different materials;
optical sorters scan only the material at the surface layer (ignoring deeper materials within a multilayer composite);
there is no optical sorter system that could identify multiple, specific materials or their location on a conveyor belt;
materials must be physically separated before they are scanned;
optical sorters require their own special belts; 3

Visible light refers to a wavelength spectrum in a range between 380 and 740 nm. 4 NIR refers to a wavelength spectrum in a range between 760 and 2500 nm.

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Figure 6.16 Schematic representation of a plastic film sorting apparatus equipped with a near-infrared (NIR) device (2001, WO0138012 A2, DER GRUENE PUNKT DUALES SYST). L, Air stream; L1, L2, Partial air streams; S1, S2, Control lines; W, Short distance; 10, Wind tunnel; 12, 14, Removal tunnels; 20, NIR device; 22, Sensor; 24, While light; 26, 3D measuring zone; 28, Reflecting tube; 30, Control device; 32, 34, Blow nozzles; and 36, 38, Baffles.


optical sorters cannot identify black colored films;
as plastic films have a very low surface weight, sorting with optical sensors on acceleration belts is often inefficient;
most types of optical sorters are unable to adequately distinguish material types when they have highly glossy, dark colored surfaces, paints, and coatings [12,20]. Another issue is created by the full wrap sleeve labels, which tend to obscure the automated detection systems during the sorting process. As a result, PET recycling facilities have seen decreasing yields as sleeved

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bottles tend to end up being separated from clear PET containers and discarded (see also Chapter 4, Section 4.2.5).

6.1.6.1 Fluorescent Light Fluorescent additives have been used for the identification and separation of various polymers from a plastic waste. Dyes in the plastic to be sorted are excited by an irradiation source producing scattered emitted light that is intercepted by a detector and recorded. Machine-readable inks (including fluorescent pigments) have shown great potential for the identification and separation of plastic packaging. Unlike NIR sorting practices, these technologies are not polymer specific and could be applied to targeted streams such as food contact plastic packaging, using commercial labeling and decoration methods and sorted using MRF infrastructure with only minor modifications [21]. A method of marking plastics consists of applying a lacquer, containing fluorescent markers, on a surface of a plastic packaging in the final step of its production [21]. In this method, it is also possible to apply the lacquer on labels. A nitrocellulose lacquer, with addition of organic and inorganic markers, is used as a coating. This method allows for efficient macrosorting of waste, but there is no possibility of sorting flakes. A weakness of this method is the lack of possibility to mark plastics before they are thermoformed. It is also necessary to use UV stabilizers due to marker aging. Because of the use of large concentrations of markers in the lacquer, in the range of 0.5e5%, and the use of expensive inorganic markers containing rare earth metals, the described method is costly (2018, WO2018182437 A1, ERGIS S A; INNOVALAB SP Z O O). Fluorescent markers as plastics recycling aids have been widely reported in the patent literature. Some recent patents on the fluorescent marking and sorting of plastic packaging waste are presented below. WO2018182437 A1 (2018, ERGIS S A; INNOVALAB SP Z O O) discloses components of a system for marking plastics with fluorescent additives and their application in identification and sorting of plastic waste, including waste of multilayer and multicomponent plastics, using the fluorescent radiation emitted by plastic item after its excitation. The coating material for marking plastics contains a base and fluorescent markers dissolved or dispersed and also in a form chemically immobilized

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on a spherical polymer matrix with a diameter below 2 mm, in the base of the coating material. The base of the coating material can be an aqueous dispersion of appropriate resins (e.g., acrylic, alkyd, silicones) or it can contain ethyl acetate, 2-(2-butoxyethanol), 2-butanone, and their mixtures. The coating composition or the way it is printed constitutes an arbitrary code, consistent with the adopted marking system. The coating material can be washed off from the surface of marked material with a washing agent. Alternatively, the coating material can be fixed to the surface of plastics. The code contained in the composition of the coating material or in the way it is printed is readable after irradiating with appropriate wavelength. The use of printed graphic or text patterns with at least two coating materials containing different fluorescent markers allows the creation of a practically unlimited number of individual identification codes. The proposed technology claims be able to sort multilayer materials into appropriate clean streams of various types of plastics, suitable for later reprocessing, and is complementary with other technologies, used at present on the market, for separating individual layers of multilayer material. Some polymers such as poly(vinyl chloride) (PVC) fluoresce under black light and an enclosed black light manual sorting station can be used to separate out PVC and other polymers that fluoresce from either a polyethylene stream or a stream of film to be sent for recovery. Because polymers such as polypropylene, PET, or poly(lactic acid) (PLA) do not fluoresce naturally, manual sorting under black light is not effective for separating those polymers from polyethylene or each other. DE102017118601 A1 (2019, TAILORLUX GMBH) discloses a sorting method for packaging materials comprising a base material and a marking material that absorbs and/or emits infrared radiation, preferably NIR. The method is particularly suitable for the separation of polyethylene film from an ethylene vinyl alcohol (EVOH) barrier film. The marking material is preferably a luminescent organic, inorganic, and/or organometallic dye, a pigment, and/or a complex compound. The luminescent marking material can emit radiation with a wavelength deviating from the excitation radiation, wherein the excitation radiation has a wavelength preferably in the UV, VIS, or infrared range, while the emission radiation has a wavelength preferably lying in the infrared range. The marking material is partially destroyed and/or removed before or during the processing step. The sorting method comprises the steps of irradiating the unsorted packaging material with electromagnetic irradiation; recording and analyzing the emission and/or absorption spectra with a defined wavelength range;

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identifying and separating packaging materials provided with the marking material; and processing the separated packaging materials.

6.1.7 Robotic Sorters The robotic sorter is a promising technology that could assist and eventually replace optical sorters in the detection and separation of specific materials. Currently, several companies are testing proprietary robotic sorters in MRFs for the sorting of flexible packaging films from commingled waste streams. AMP5 Robotics, a start-up company founded in 2015 by Matanya Horowitz, has developed a robotic system that can rapidly pick recyclable materials off a conveyor belt for recovery [22]. The robotic system, called the AMP Cortex Robotic Sorter, comes with Neuron the artificial intelligence that peers into the recyclable stream to identify individual pieces of recoverable material in piled, mixed waste. The Neuron software transforms the material on the recovery belt into valuable data using computer vision to distinguish features in much the same way as the human eye (see Fig. 6.17B). The AMP’s system can figure out different combinations of featuresdfor instance, shapes and the specific shininess of aluminum. Features of new materials are added to the learning algorithms of Neuron. The robotic system shows the potential to be able to identify virtually any item it has yet to encounter. Once the APM’s robot moved from the lab and put to the test in MRFs, there were hurdles to overcome. A big one was improving the ability to grip a wide variety of materials, which is still being fine-tuned. AMP’s robotic system is claimed to have the following advantages:
cuts sorting costs by 50%;
stabilizes labor spend by fixing labor rate for sorting stations, while lowering labor needs;
exceeds the return on investment offered by legacy recycling equipment;
designed to detect and separate multiple materials;
improves bale quality by reducing contamination levels;
can be installed with practically no retrofit on existing conveyor belts; and 5

“AMP” stands for autonomous manipulation and perception.

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provides higher throughput yields greater recovery rates and more revenue. Some of the disadvantages of the APM’s robotic technology are:
technology is not yet mature and more testing is needed in the realword conditions of an MRF; and
need to improve the ability to grip a wide variety of materials, which is still being fine-tuned. EP1829621 A1 (2007) and US2007208455 A1 (2007) of MACHINEFABRIEK BOLLEGRAAF APPINGEDAM B.V. disclose a sorting system (see Fig. 6.17) for extracting recyclable items from waste material comprising a conveyor (4) for transporting waste material (6); a detector (8) for identifying and locating items of the waste material (6) on the conveyor (4); depositing openings (11, 12, 14, 15, 17) along the conveyor (4); eight robots (1.1e1.8) along the conveyor (4); and a control circuitry (32) that is equipped with a central control unit (41) that communicates with the detector (8) and the robot motors. Each robot has arms (34, 35, 39) driven by corresponding motors. The central control unit (41) determines control signals for the motors from signal obtained from the detector. Bollegraaf’s robotic system has been testing for the sorting of flexible plastic packaging out of waste material. The design application of this technology is for quality control sorting and for production sorting in low- to medium-throughput applications. Units developed so far consist of an optical scanner over a conveyor belt followed by a robotic arm that picks low percentage contaminants from a conveyor and deposits them into a bin, chute, or onto another conveyor [5]. Compared to manual sorting at 50 picks per minute, a robot arm can make over 200 picks per minute. A single scanner can support multiple arms on a single conveyor, so theoretically, rates of over 1000 picks per minute are possible. Also, robot arms have the capability of picking items that overlap other items, something that air separators and optical sorters that use air jets for sorting cannot do well. Another advantage of robot sorters is the potential to sort multiple products with a single-robot system. As applied to plastic film, the limitations will be throughput

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Figure 6.17 Robotic system for sorting items out of waste material (2007, EP1829621 A1; and US2007208455 A1, MACHINEFABRIEK BOLLEGRAAF APPINGEDAM B.V.). 1.1e1.8, Eight robots; 4, Conveyor; 5, Conveyor track; 6, Waste material; 7, Transport direction; 8, Detector unit; 10, Frame; 11, 12, 14, 15, and 17 Depositing openings; 20, 21, 23, 24, and 26, Chutes; 29, 31, Outer tracks; 30, Central track; 32, Control circuitry; 34, 35, 39, Robot arms; 36, 37, Hinged carrier bags; 38, Linear motor; 40, Gripper; 41, Central control unit; and 43, Valve.

(because of the low weight of each pick) and sufficient discrimination between products. According to Reclay StewardEdge [5], a robot sorter with a single sorting arm is estimated to cost less than an air jet optical sorter (about $400,000 installed), but until commercial production units are available, pricing remains uncertain. Additionally, operational costs are very uncertain, not knowing the true efficiency of a unit in sorting film in an MRF environment. Based on 100 picks per minute and the above capital costs, the range of allocated capital and operating costs may prove to range from $250e$400 per ton once this future technology is commercialized. However, it could also be significantly higher if the system cannot accurately handle bags-in-bags, if the burden depth is deep or if manual quality control after the machines is still required [5].

6.1.8 Eddy Current Separators An eddy current separator (ESC) is used to remove nonferrous metals such as aluminum, brass, and copper from the waste stream. The material

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is separated in an ECS on the basis of eddy currents being generated in nonferrous materials by rapidly rotating permanent magnets. These eddy currents in turn cause the material to be repulsed by the magnet field of the ECS, and the nonferrous material is diverted from the waste stream and is ejected into a separate hopper or conveyor. Trials have demonstrated that ECS is effective at separating a significant proportion of multilayer packaging from the waste stream, alongside other nonferrous materials such as aluminum used beverage cans (UBCs) and aluminum foil [23]. ECS has been used in combination with other separating devices such as ballistic or angled disc screen separator and optical systems for the separation of plastic films and/or paper from other recyclables (2017, US9713812 B1; US2017253891 A1, ORGANIC ENERGY CORP). It has been proposed to use ECS as an additional separating device in the processing line of an MRF for the separation of pouches from the waste stream [24].

6.2 Volume Reduction A problem with flexible plastic packaging waste is that it is bulky and takes up a large amount of space if left unprocessed. Volume reduction processes involve the transformation of this type of waste (including printed films and bags, coextruded barrier films, metalized films, and the like) into high bulk density products that can be easily handled or stacked. High bulk density products can be transported more efficiently to recycling facilities.

6.2.1 Compacting Compactors are used to reduce the volume of flexible plastic packaging waste. Compactors reduce operating and housekeeping costs and can be located close to any process area. A known type of compactor, typically referred to as a hydraulic compactor, is disclosed in WO9407688 A1 (1994, MARSHALL SPV LTD). The compactor comprises a rotating shaft having a screw vane located in a conical chamber, wherein the waste material is driven through the chamber by the rotating shaft and is deformed and compressed before finally being discharged through a nozzle. Hydraulic compactors are generally slow in operation, and the compacted material can create dust

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and other airborne or surface waste pollution (2008, WO2008135757 A1, TAYLOR PRODUCTS LTD). US5452492 A (1995, HAMILTON ROBIN) discloses an alternative compaction method and apparatus, which utilizes a compaction chamber and a vane for conveying the waste material through the passage and includes an exit nozzle, which defines an internal transverse cross-sectional area that enlarges and reduces respectively in response to increasing and decreasing material pressure. Effectively, a plurality of fingers is provided at the outlet to control the size of the extrudate. However, such an apparatus puts severe force and stresses in the shaft and, furthermore, the waste reexpands once it is passed through the nozzle (2008, WO2008135757 A1, TAYLOR PRODUCTS LTD; 2012, WO2012035308 A2, MASSMELT LTD). Compactors should not be confused with extrusion devices, which force a uniform homogeneous feedstock into alignment guides and specifically shaped dies to produce lengths of stock cross-sectional shapes, such as polymer pipes, rods or tracks. Extrusion machines are constructed similarly to the compacting apparatus mentioned above, except that they are only designed to handle throughput of a constant and consistent plastic material, and they are not compactors as such (2008, WO2008135757 A1, TAYLOR PRODUCTS LTD). DE4140577 A1 (1992, PAVEL WILFRIED MASCHINENBAU) discloses an apparatus for compacting used plastic films and/or plastic film waste into blocks designed as a mobile compactor. The compacted plastic film takes during transport only a relatively small space. Sources of scrap film are packaging films such as garments’ plastic protective covers. However, because of air pockets often trapped between the films and the air-filled nubs in the films, compressing the films into a compact block requires a relatively large amount of time and energy (2003, DE20308945 U1, PAVEL WILFRIED). Impact Air Systems developed the Film Screw Compactor System to compress waste materials collected by the company’s Filmvac System into manageable plastic [25] (see Section 6.1.1). The unit comprises a single screw auger within trough, which compacts the material into a circular outlet spigot. The unit achieves its compaction by means of combination of the length of the outlet spigot and the rubber tension clamping ring, which retains the expanding spool of plastic waste bag to provide a variable length sausage-like bale for ease of handling (see Fig. 6.18).

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Figure 6.18 Sausage-like bale obtained by the Film Screw Compactor [25]. Courtesy of Impact Air Systems.

6.2.2 Softening or Melting the Outer Surface of Compacted Waste DE2261678 A1 (1973) and CH557763 A (1975) of FLUMS AG MASCHF disclose an apparatus, shown in Fig. 6.19, for compacting scrap wrapping film by feeding film trims into a compressing chamber having a funnel-shaped outlet end whose walls are heated with electrical heaters to a temperature sufficient to fuse together those trims coming into contact with the walls. A piston ram operating at regular intervals compresses the film trims into a compact mass, which is discharged from the outlet in the form of a continuous sausage having an outer skin formed from the fused film trims. The apparatus is designed to operate in conjunction with a packing station, where the plastic wrapping film is welded and trimmed. FR2294037 A1 (1976, ALDES ATEL LYONNAIS EMBOUTISSA) discloses a method for compacting scrap film into a shaped block comprising compacted material enclosed in a shaped skin of heat shrunk and chilled material. The method is carried out in the apparatus shown in Fig. 6.20, wherein a container (2) for receiving the plastic waste to be processed into a block comprises a horizontally arranged tubular chamber (3), which on both sides is provided with pistons, of which one piston (7) is connected with a guide system (8) and a spring mechanism (10), whereas the other piston (5) is connected with a hydraulic jack (6). The chamber walls are heated and the walls and pistons have passages for circulating coolant. The cooling of the plastic waste to be compressed into a block occurs by means of a coolant, which is run through canals positioned in the walls of the tubular chamber and/or of the pistons. The load opening and

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Figure 6.19 Cross-sectional view of the compacting apparatus (1973, DE2261678 FLUMS AG MASCHF). A, Axis; IA, Line; M, Scraps of polyethylene film; S, Sheath; T, Thermostat; W, Compact sausage-like body; 1, Housing/compressing cylinder; 2, Ram/compressing piston; 3, Hydraulic cylinder/drive; 4, Funnel; 5, Feed casing; 6, Conveyor belt; 6a, Horizontal transport belt; 6b, 6c, Rolls; 6d, Electric motor; 7, Feed rollers; 70 , Electric motor; 10 Circular disc; 21, Cylindrical plunger/projection; 34, Chamber; 35, Inlet; 36, Outlet; 38, Piston rod; 39, Pump; and 41, Heater.

discharge opening (4) are the same. The apparatus is suitable for compacting scrap film, especially polyethylene film, for recovery and reuse; it increases the material bulk density for economic transport without causing mechanical or thermal degradation of the molecular structure. According to EP0397280 A1 (1990, PWR RECYCLING BV), the aforementioned apparatus has the disadvantage that the processing of the plastic waste into a block is very complicated and, therefore, expensive. The walls of the tubular chamber as well as the inner surfaces of the pistons are not provided with a coating resulting in the adhering of the obtained plastic waste blocks to the walls, with the consequence that on the one hand, the removal of the blocks is difficult, and on the other hand, the walls have to be cleaned repeatedly. The apparatus has also the disadvantage that the plastic waste may get stuck easily during compressing. Further, the plastic waste to be compacted is transported by means of a piston to a funnel-like device, which is open at its tapered end, so that subsequent to heating and compacting, the material leaves the apparatus in the form of a continuous sausage, i.e., no blocks are obtained.

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Figure 6.20 Apparatus for compacting thermoplastic sheet or film (1976, FR2294037 A1, ALDES ATEL LYONNAIS EMBOUTISSA). 2, Container; 3, Tubular chamber; 4, Opening (load and discharge); 5, Piston; 6, Hydraulic jack; 7, Piston; 8, Guide system/rod; 9, Fixed support; 10, Helical spring; 11, Heating plugs; 12, Circuit for the circulation coolant; 13, Stopper; 14, Plastic materials; 15, Chamber of 6; and 16, Pressure regulator.

EP0397280 A1 (1990, PWR RECYCLING BV) and US5263841 A (1993, THERMOPERS BV) disclose a method and an apparatus, shown in Fig. 6.21, for compacting plastic waste into blocks claiming to overcome the aforementioned problems. Plastic waste, such as packaging film of PVC, polyethylene, or polypropylene, is introduced into a container and compressed, whereas the walls and bottom of the container are heated by means of electrical heating elements to soften the surface of the plastic waste, followed by cooling, wherein the outer layer solidifies and the obtained compressed block-like plastic waste is removed. The compressing of the plastic waste takes place by means of a punch at a temperature of 120e180 C (preferably, 140e160 C) and a pressure of 250e400 g/cm2 (preferably 260e290 g/cm2), followed by cooling by introducing air in the container with a fan for 5e15 min (preferably 8e10 min). The inner surfaces of the container and/or the punch are provided with a coating (e.g., of Teflon) to prevent the softened and compressed plastic waste from adhering to the walls. Although the aforementioned method and apparatus are able to achieve a substantial volume reduction of the plastic waste film, both are too laborious in industrial or semiindustrial scale. In particular, in the claimed apparatus, the plastic waste must be loaded and unloaded manually. This not only disturbs the throughput of plastic waste but also renders the apparatus less suitable for the processing of contaminated plastic waste (1997, NL1002391 C2, ICORDE). US3831340 A (1993, TULKOFF M) discloses a method for compacting a scrap film being bulky due to incorporation of air pockets of air.

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Figure 6.21 Apparatus for compacting plastic waste (1993, US5263841 A, THERMOPERS BV). 1, 2, Side walls; 3, Bottom wall; 4, Plastic waste load; 5, Punch; 6, Heating elements; 13, Teflon coating; 14, Orifices; and 15, Air fan.

The scrap film is oftentimes in the form of thermoplastic bags of fairly heavy gauge and large size. The bag is used to enclose a stack of a plurality of boxes that have been positioned on a pallet. The bulky film is loaded into a receptacle of relatively large size, shown in Fig. 6.22, having a plurality of openings along all of its surfaces. The receptacle is then subjected to a heat treatment at a temperature of at least 240 F (116 C) in an oven that surrounds the receptacle along its sides and top, while the receptacle is on the floor. The oven employed is essentially a housing having an open bottom with a plurality of electric heating elements positioned internally with respect to the inner walls thereof. The oven is relatively movable to encompass the bag containing receptacle. The bags are melted or fused within the receptacle during its dwell time in the confines of the oven. To prevent sticking of the bags to any of the surfaces

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Figure 6.22 Schematic perspective of a rectangular receptacle loaded with waste bags (1993, US3831340 A, TULKOFF M). 11, Rectangular receptacle; 12, End walls of the receptacle; 13, Side walls of the receptacle; 14, Skids; 15, 16, Top hinged doors; 17, Hinges; 19, Rectangular metal frame; and 20, Grid of wire.

of the receptacle, at least the inside of the receptacle is given a coating treatment with a plastic release material. WO2008135757 A1 (2008, TAYLOR PRODUCTS LTD) discloses a method and an apparatus for processing heterogeneous waste, such as domestic waste comprising: 1) feeding the heterogeneous waste material into a compaction compartment, wherein the compaction compartment defines a progressively tapering waste processing path that diminishes in diameter as waste proceeds along the processing path; 2) transporting and compacting the waste material through the compaction compartment toward an outlet; 3) heating the compacted waste in a heating zone to a temperature that facilitates melting of low molecular weight polymers located within the waste but which is below the carbonization temperature of either the polymers or the organic matter within the waste; and 4) extruding the compacted and heated waste from the heating zone through an extrusion nozzle to produce compacted and sterilized waste, which is encapsulated within the melted polymers comprised within the waste. Low melting point polymers include, for example, film waste and bottles comprising high-density polyethylene, low-density polyethylene, polypropylene, and PVC. WO2012035308 A2 (2012, MASSMELT LTD) discloses an alternative method and apparatus comprising further

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a cooling zone including a cooling arrangement for cooling the waste material received from the heating zone. Although the aforementioned apparatuses are designed to handle a diverse heterogeneous waste stream, it is also possible for homogeneous waste material to be processed and compacted. The type of waste to be compacted will largely depend on the location of the apparatus. For example, a compactor located on a cruise ship may be required to process significant quantities of generally plastic waste, whereas a compactor situated behind a supermarket or shopping mall may be used to process single-use plastic packaging such as carrier bags or shrink wrap film used to wrap pallets of goods.

6.2.3 Bales Flexible plastic packaging waste that is to be recycled is often pressed into bales for transportation. The baling of plastic film into large, compact bundles is a standard practice for most recycling centers, where films are consolidated and trucked or shipped to processing facilities. By baling the loose films, recycling centers can save on space and lower logistic cost. Plastic film bales vary in size, depending on the type of baling equipment used and the experience of the operator; however, most bales are about 1e1.5 m in length, width, and height with each bale weighting about 200e700 kg [26]. Mixed flexible plastic bales have lower economic value than completely segregated material. This leads to a lower incentive for MRFs and recyclers to focus on multimaterial flexible packaging that is very lightweight and does not take up much volume. Bales of curbside film have about one-sixth of the value of mixed film that comes from retail collection programs, due to contamination of curbside film during collection and processing in MRF [5]. Odors and leakage from residual food packaging is a potential issue when accumulating and storing materials for sale to recyclers. Occasionally, collected mixed flexible film bales are shipped to a PRF where the plastics are sorted by polymer type and formed into bales of higher purity. Most plastic recyclers are currently experiencing sharp decreases in bale quality and yields. It is very difficult to evaluate the contents of a bale of flexible packaging films simply by looking at it, so creating and implementing bale specifications will improve separation selectivity, which is a prerequisite for obtaining recyclates of high and constant quality. Plastics Recyclers Europe released a set of bale quality guidelines to drive market transformation toward circularity. The guidelines aim at improving the quality of the collected and sorted plastics, and in turn increasing the quality of input that reaches the recycling plants. The guidelines serve as information

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benchmarks to suppliers of any collected waste. There are bales characterization guidelines for polyethylene [27] and polypropylene films [27]. The Association of Plastic Recyclers (APR), representing over 90% of the postconsumer plastics recycling capacity in North America, has also developed model bale specifications for plastic films. APR’s Model Bale Specifications have seven standard components:
bale content overview;
acceptable levels of contaminants;
contaminants not acceptable at any level;
warnings;
bale size/minimum shipping weight; and
bale wire. There are model bale specifications for specific plastic films6:
MRF curbside film [29];
polyethylene clear film [30];
polyethylene retail bags and film [31]; and
LDPE furniture mix film [32]. The bales are typically tied using strings such as steel wires, tapes, strips, cords of twined or otherwise mutually engaged filaments, and the like. When processing the plastic waste, string material tends to become entangled in machinery, thereby reducing effectivity and/or efficiency of operation and causing damage to the machinery. In particular, in sorting screens, string material tends to be wound-up around shafts and rotor bodies of the sorting screen. Although it has been attempted to reduce the tendency of string material to wind-up in sorting screens by providing special rotor designs, winding of string material still occurs and removal of string material from sorting screens is cumbersome and requires the sorting screen to be stopped, which reduces productivity (2017, EP3165291 A1, BOLLEGRAAF PATENTS AND BRANDS B V). Some types of flexible plastic packaging are highly compressible such that when compacted in a baler the volume the waste occupies in the bale can be significantly reduced. For example, used plastic bags and plastic 6

Model specifications for agricultural films have been omitted as falling outside the scope of this book.

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shrink wrap are pliable and also highly compressible. Other types of flexible plastic packaging, however, may be less compressible. However, there is the problem that compressed bales of waste material with polyethylene films include air pockets. These cause after tying special expansion forces in the bale, which can lead to the tearing of the wires. For this reason, these bales are currently not so highly compressed, which has the disadvantage of transporting low-density bales (1994, DE9407754 U1; 1995, WO9531374 A1, LINDEMANN MASCHFAB GMBH). There are two general types of balers: vertical, or downstroke, and horizontal. Some representative commercial balers for flexible packaging waste such as plastic bags and plastic films are: - Bollegraaf’s bales (HBC series) [33]. - Maren’s plastic film recycling horizontal automatic tie balers; the plastic film recycling two ram baler; and closed door manual tie balers [34]. - HSM’s vertical balers (HSM V series) [34]. - The horizontal balers (both manual tie and automatic tie) and standard mill size balers of Ningbo Sinobaler Machinery Co. Ltd. [36]. US2007020410 A (2007), CA2593836 A1 (2008), and US2009148629 of PAPER AND PLASTIC PARTNERSHIP describe various approaches that are used to track the weight of recyclable waste that is pressed into a bale. One efficient way is to measure the thickness of each layer of a distinct type of recyclable material and multiply that thickness times other known constants such as the dimensions of the bale to determine an approximate volume. This number is particularly helpful for use in determining the value of the recyclable plastic film that has been recovered. For example, it is currently known that every 3 in of compacted plastic film in a bale measuring 60 in  48 in  30 in weighs about 50 lb (22.7 kg). A 72 in  48 in  30 in bale in turn weighs about 65 lb (29.5 kg). Thus, on the formation of the bale, the thickness of a layer of plastic film can be approximately measured in inches and a weight estimate can be made. In another way, the thickness of a recyclable waste layer can be estimated as a fraction of the bale thickness. Regardless, the entire bale can also be weighed so that the correct fractional portion of the load is assigned to the recyclable waste. In yet another alternative, past measurements of the various types of recyclable waste by-products included in the composite bales can be used. For instance, for a particular size of bag, historical averages for the various types of recyclable waste can be calculated and used to estimate the weight of each type of waste material in the bale. Accordingly, on creation of the bale,

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the retailer can indicate on the bale, or on the shipping documents, the number of bags of each type of recyclable waste by-product that is in the bale. In this manner, when the bale is received by the processing facility, the processing facility can calculate the approximate weight of each recyclable material even without separating the bale. The processing or recycling facility can also separate the bale and count the bags of each type of product to, verify, for example, the retailer’s count and/or to update historical average data. The historical weight averages may also be used even without an indication by the retailer of the number of each type of product in the bale. For instance, the processing facility may merely separate the bale and count each type of bag. To facilitate such counting, each bag may contain only one type of recyclable waste by-product. Further, each type of byproduct may be enclosed in a different color bag such that the byproduct therein can easily be identified by the processing facility even without opening the bag. Alternatively, indicia may be provided on the container enclosing the by-product (e.g., a description or picture of the byproduct) to facilitate identification, or the bags may not include any indicia or other method for distinguishing between types of content. For a more accurate measurement of the recovered waste products, the whole bale can be weighed at the processing or recycling facility. Thereafter, after the bale is broken open and the various types of recyclable waste are separated, each bag can once more be weighed to get a final accurate measurement of the recovered amount.

References [1] RSE USA. The closed loop foundation - film recycling investment report. 2016. http://www.closedlooppartners.com/wp-content/ uploads/2017/09/FilmRecyclingInvestmentReport_Final.pdf. [2] APR - Association of Plastic Recyclers. The APR designÒ guide for plastics recyclability. January 6, 2018. http://www.plasticsrecycling. org/images/pdf/design-guide/PE_Film_APR_Design_Guide.pdf. [3] Edington J. Advancements in mechanical recyclingjunraveling film recovery. Sustainable packaging solutionÒ. October 15, 2018. https:// sustainablepackaging.org/advancements-in-mechanical-recycling-un raveling-film-recovery/. [4] Hestin M, Mitsios A, Ait Said S, Fouret F, Berwald A, Senlis V. Deloitte sustainability e blueprint for plastics packaging waste: quality sorting & recycling - final report. Deloitte and plastics recyclers Europe. 2017. https://www.plasticsrecyclers.eu/sites/default/ files/PRE_blueprint%20packaging%20waste_Final%20report% 202017.pdf.

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[5] Reclay StewardEdge. Product stewardship solutions, resource recovery systems, Moore recycling associates Inc. Analysis of flexible film plastics packaging diversion systems e Canadian plastics industry association continuous improvement fund stewardship Ontario. February 2013. [6] Flexible Packaging Association (FPA). tFlexible packaging resource recovery: a work-in-progress e summary report: continuing evaluation of resource recovery infrastructures and processes. Retrieved June 6, 2018. https://www.flexpack.org/flexible-packaging-resourcerecovery-a-work-in-progress-brochure/. [7] Impact Air Systems. Film vacuum system. Retrieved May 30, 2019. https://www.impactairsystems.com/separation-solutions/film-vacuumsystem-plastic-bags-film-separation-manual-sorting.html. [8] NIHOT Recycling Technology BV. Nihot film vacuum system. Retrieved May 30, 2019. https://www.nihot.co.uk/products/filmvacuum-system/. [9] NIHOT Recycling Technology BV. AirconomyÒ. Retrieved May 30, 2019. https://www.bulkhandlingsystems.com/wp/wp-content/uploads/ 2014/09/Nihot.pdf. [10] Krause Manufacturing Inc. Plastic recycling equipment. Retrieved May 30, 2019. http://www.krausemanufacturing.com/recyclingequipment/recycling-sorting-equipment/plastic-recycling-equipment/. [11] PARINI SRL. Air separator. 2014. http://www.parinisrl.it/en/ portfolio/air-separator/. [12] Reed DW, Lacey JA, Thompson VS. Separation and processing of plastic films. Idaho Falls, Idaho: Idaho National Laboratory Biological & Chemical Processing; May 2018. 83415, https:// inldigitallibrary.inl.gov/sites/sti/sti/Sort_5444.pdf. [13] Gershman, Brickner & Bratton Inc. Supplemental report: the evolution of mixed waste processing facilities e technology and equipment guide. May 2016. https://plastics.americanchemistry.com/EducationResources/Publications/The-Evolution-of-Mixed-Waste-ProcessingFacilities-Technology-and-Equipment-Guide.pdf. [14] Roy S. 5 Questions about ballistic separators e Se´bastien Roy of machinex answers questions about ballistic separators. Recycling Today; October 2018. https://wwwrecyclingtodaycom/article/5questions-about-ballistic-separators/. [15] ASTM International./D7611M e 13e1 e Standard practice for coding plastic manufactured articles for resin identification. https://www. astm.org/Standards/D7611.htm.

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[16] Packaging Recovery Organisation (PRO) Europe. The green dot trademark. Retrieved June 10, 2019. https://www.pro-e.org/the-greendot-trademark. [17] How2Recycle. A cleaner world starts with us. 2018. http://www. how2recycle.info/. [18] European Commission. Communication from the commission to the European parliament, the council, the European economic and social committee and the committee of the regions - a European strategy for plastics in a circular economy EUR-lex. January 2018. https://eur-lex. europa.eu/legal-content/EN/TXT/HTML/?uri¼CELEX: 52018DC0028&from¼EN16. [19] Plastic Zero. Action 4.1: market conditions for plastic recycling. Public Private Cooperations for Avoiding Plastic as a Waste; January 02, 2013. http://www.plastic-zero.com/media/30825/action_4_1_ market_for_recycled_polymers_final_report.pdf. [20] Sustainable Packaging Coalition. Lessons learned about multimaterial flexible packaging recovery. 2019. https:// sustainablepackaging.org/multi-material-lessons-learned/. [21] Kosior E, Davies K, Kay M, Mitchell J, Ahmad R, Billiet E, et al. Final report - optimizing the use of machine readable inks for food packaging sorting e WRAP Project: IMT003-106. September 19, 2014. http://www.wrap.org.uk/sites/files/wrap/Optimising_the_use_of_mac hine_readable_inks_for_food_packaging_sorting.pdf. [22] AMP Robotics. Robots for recycling. 2017. https://www. amprobotics.com/. [23] Bains M, Robinson L. Project report e recovery of laminated packaging from black bag waste. WRAP (Waste & Resources Action Programme) and URS; JanuaryeMarch 2012. http://www.wrap.org. uk/sites/files/wrap/Recovery%20of%20laminated%20packaging%20 from%20black%20bag%20waste.pdf. [24] Slatter S, Trevor C. Project report e recycling of laminated packaging. WRAP (Waste & Resources Action Programme) and Oakdene Hollins Ltd; September 2011. http://www.wrap.org.uk/sites/files/wrap/ Recycling%20of%20laminated%20packaging.pdf. [25] Impact Air Systems. Film screw compactor. Retrieved May 30, 2019. https://www.impactairsystems.com/files/film-screw-compactor.pdf. [26] ASG Recycling. Plastic film washing line. 2013. http://www. plasticrecyclingmachine.net/plastic-film-washing-line/. [27] Plastics Recyclers Europe. Bales characterization guidelines: PE films e version: 1.0. December 30, 2017. https://www.plasticsrecyclers.eu/

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[28]

[29]

[30]

[31]

[32]

[33] [34]

[35]

[36]

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sites/default/files/2018-06/PRE%20PE%20Film%20Bales%20Guide lines%2030-11-2017.pdf. Plastics Recyclers Europe. Bales characterization guidelines: PP films e Version: 1.0. November 30, 2017. 30-12-2017, https://www. plasticsrecyclers.eu/sites/default/files/2018-06/PRE%20PP%20Film %20Bales%20Guidelines%2030-11-2017.pdf. APR - Association of Plastic Recyclers. Model bale specifications: MRF curbside film. Retrieved June 6, 2019. http://www. plasticsrecycling.org/images/pdf/Markets/MRF_Curbside_Film.pdf. APR - Association of Plastic Recyclers. Model bale specifications: PE clear film. Retrieved June 6, 2019. http://www.plasticsrecycling.org/ images/pdf/Markets/PE_Clear_Film_.pdf. APR - Association of Plastic Recyclers. Model bale specifications: PE retail bags and film. Retrieved June 6, 2019. http://www. plasticsrecycling.org/images/pdf/Markets/PE_Retail_Bags_Film_.pdf. APR - Association of Plastic Recyclers. Model bale specifications: LDPE furniture mix film. Retrieved June 6, 2019. http://www. plasticsrecycling.org/images/pdf/Markets/LDPE_Furniture_Mix_ Film.pdf. Bollegraaf Recycling Machinery B.V. Balers. Retrieved February 21, 2019. https://www.bollegraaf.com/technologies/balers. Maren Balers & Shredders. Plastic film recycling balers. Retrieved February 24, 2019. https://www.marenengineering.com/choose-yourmaterial/plastic-film/. HSM. Retrieved February 14, 2019. https://us.hsm.eu/c/ verticalBalingPresses?q¼%3Apriority%3Afeature-V0032-M_0005 79%3ARecyclingþ%26þDisposal%3Afeature-V0032-M_00585% 3APlasticþfilm. Ningbo Sinobaler Machinery Co Ltd. Plastic film e prosino shredders. Retrieved January 14, 2019. http://www.sinoshredder.com/ application/plastic-film-shredder-for-sale/.

Patents

Patent Number

Publication Date

CA2593836 A1

Family Members

Priority Numbers

Inventors

Applicants

Title

20080107

US20060482356 20060707

ASHBY JEFFERY A; JONGERT CHARLES; ACEY MARVIN; SASINE JOHN

PAPER AND PLASTIC PARTNERSHIP, LLC

Method and process of collecting, packaging and processing recyclable waste.

CH557763 A

19750115

CH19720015834 19721031

MATZINGER AUGUST

FLUMS AG MASCHF

Komprimieranlage. ”Compacting system.”

DE102017118601 A1

20190221

DE201710118601 20170815

DEITERMANN ALEX; ¨ NING JOHANN LO

TAILORLUX GMBH

Sortierverfahren fu¨r Verpackungsmaterialien. “Sorting method for packaging material.”

DE20308945 U1

20031218

DE20032008945U 20030607

PAVEL WILFRIED

PAVEL WILFRIED MASCHINENBAU

Vorrichtung zum Zerkleinern von gebrauchten Kunststoff-Folien und Folienabfa¨llen. “Apparatus for shredding of used plastic films and film waste.”

DE2261678 A1

19730719

FR2166003 A1 19730810; FR2166003 B3 19760213; GB1378340 A 19741227; US3827213 A 19740806

CH19720015834 19721031; CH19710019009 19711227

MATZINGER AUGUST

FLUMS AG MASCHF

Komprimieranlage. ”Compacting system.”

DE4140577 A1

19921022

DE4140577 C2 19941013; EP0510313 A1 19921028

DE19914140577 19911210; DE19914112267 19910415

PAVEL WILFRIED

PAVEL WILFRIED MASCHINENBAU

Vorrichtung zur bildung einer kompakten kunststoffmasse aus gebrauchten kunststoffolien und/oder kunststoffolien-abfa¨llen. “Apparatus for building a compacted plastic mass from used plastic films and/or plastic film waste."

DE9407754 U1

19940728

DE19940007754U 19940511

EP0397280 A1

19901114

AT125745 T 19950815; AU5493690 A 19901115; AU627876 B2 19920903; CA2016540 A1 19901112; DE69021259 T2 19960404; DK0397280 T3 19951211; EP0397280 B1 19950802; ES2077629 T3 19951201; GR3017961 T3 19960229; JPH0330918 A 19910208; JP2933353 B2 19990809; NL8901198 A 19901203; NZ233662 A 19930428

NL19890001198 19890512

EP3165291 A1

20170510

CA2947550 A1 20170505; US2017129637 A1 20170511

EP20150193296 20151105

FR2294037 A1

19760709

FR19740041679 19741209

NL1002391 C2

19970821

NL19961002391 19960220

US2007020410

20070125

US20060482356 20060707; US20050299442 20051212; US20050166516 20050624; US20040617971P 20041011

US7784399 B2 20100831

LINDEMANN MASCHFAB GMBH

Ballenpresse. “Baler."

DE SOET ANTONIUS HENDRIKUS

THERMOPERS BV

A process and device for processing plastic waste into blocks.

BENJAMINS JAN

BOLLEGRAAF PATENTS AND BRANDS B V

Apparatus and method for sorting string material from waste.

ALDES ATEL LYONNAIS EMBOUTISSA

Chamber for consolidating thermoplastic sheet or film - for economic transport and recovery of scrap.

BARSINGERHORN BEA

ICORDE

The automatic treatment of plastic waste by volume reduction.

SASINE JOHN; JONGERT CHARLES; ACEY MARVIN; ASHBY JEFFERY A

PAPER AND PLASTIC PARTNERSHIP, LLC

Method and process of collecting, packaging and processing recyclable waste.

(Continued )

(Continued ) Patent Number

Publication Date

Family Members

Priority Numbers

Inventors

Applicants

Title

US3831340 A

19740827

US19730344624 19730326

TULKOFF M

TULKOFF M

Method for compacting thermoplastic film material and apparatus therefor.

US5263841 A

19931123

US19910814250 19911223; NL19890001198 19890512; US19900522521 19900511

DE SOET ANTONIUS H

THERMOPERS BV

Device for processing plastic waste into blocks.

US5452492 A

19950926

EP0790122 A2 19970820; EP0790122 A3 19980107; EP0790122 B1 20020515; EP1193045 A1 20020403; US5768744 A 19980623

GB19920020382 19920926

HAMILTON ROBIN

HAMILTON ROBIN

Material collection.

WO2008135757 A1

20081113

GB2448925 A 20081105; GB2462560 A 20100217; GB2462560 B 20121219; WO2008135757 A9 20090205

GB20070008628 20070504

SCHEERES DAVID

TAYLOR PRODUCTS LTD

Waste processing apparatus and methods.

WO2012035308 A2

20120322

CA2811251 A1 20120322; CN103108734 A 20130515; EP2616222 A2 20130724; EP2616222 B1 20170426; GB2483851 A 20120328; GB2483851 B 20150218; GB2517615 A 20150225; GB2517615 B 20150422; US2014007783 A1 20140109; US9956736 B2 20180501; WO2012035308 A3 20120510

GB20100015495 20100916

SCHEERES DAVID

MASSMELT LTD

Waste processing apparatus and methods.

WO2018182437 A1

20181004

PL421008 A1 20181008

PL20170421008 20170327

NOWICKI TADEUSZ; SAWICZ-KRYNIGER KATARZYNA; TABAK DOMINIK

ERGIS S A; INNOVALAB SP Z O O

Coating material for marking artificial materials, method for marking artificial materials, method of identification of marked artificial materials and their application for sorting of plastic waste.

WO9407688 A1

19940414

AU4828093 A 19940426; AU681596 B2 19970904; CA2144987 A1 19940414; CA2144987 C 20041207; DE69314802 T2 19980514; DE69331937 T2 20021114; EP0662043 A1 19950712; EP0662043 B1 19971022; ES2111181 T3 19980301; ES2173376 T3 20021016; GB2286361 A 19950816; GB2286361 B 19970625; JP3426233 B2 20030714; JPH08503915 A 19960430; US5611268 A 19970318

GB19920020382 19920926; GB19930006462 19930329

HAMILTON ROBIN

MARSHALL SPV LTD

Compaction methods and apparatus.

WO9531374 A1

19951123

DE4416584 A1 19951116; EP0758976 A1 19970226; EP0758976 B1 19980930

DE19944416584 19940511

GONSCHOREK HELMUT

LINDEMANN MASCHFAB GMBH

Verfahren zum Betreiben einer Ballenpresse und Ballenpresse. “Bale press and method of operating it."

7 Solvent- and/or Chemical Agent-Based Separation Multilayer plastic packaging films cannot be recycled properly, as the different plastic layers (3 up to 20) and/or metal foils cannot be separated with mechanical technologies. Solvent and/or chemical agent technology is a promising approach for the separation of multilayer packaging films. A large number of patents have been disclosed for this technology, which are applicable to both flexible and rigid multilayer plastic packaging. Despite the large number of disclosed patents, scientific publications, research and industrial projects with promising preliminary results, the solvent and/or chemical agent technology is still not commercially used.

7.1 Stripping Stripping agents are solvents for the dissolution or swelling of the interlayer binder (tie layer), or for the delamination and separation of the individual layers from a multilayer packaging film and/or chemical agents for the separation or delamination of the aluminum foil from plastic layers. DE4215573 A1 (1993, HOECHST AG) discloses a method for separating a multilayer film into its individual layers by treating the film with an organic liquid, which acts as a solvent or swelling agent for the adhesive or which, in the case of heat-laminated composites, can penetrate between the different layers and split them apart. Preferably, the multilayer film is first pulverized by grinding and then stirred with the organic solvent, or the solvent can be added during the grinding stage. The different film components are then separated on the basis of their different densities. The organic solvent must be a nonsolvent for the film components; preferred solvents are ethyl acetate, toluene, and gasoline. The treated film components are then separated, e.g., in a hydrocyclone or by stream classification. It is also possible first to separate off the organic liquid in a known manner, such as filtration or centrifugation, to redisperse the residue in water and to effect separation by the treatment of heavy liquids (addition of soluble or insoluble substances).The method enables the separation of multilayer films into the individual layers (e.g., PVC and aluminum; polyester and polyethylene; PVC and polyethylene, etc.), Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00007-4 Copyright © 2020 Elsevier Inc. All rights reserved.

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which can then be recovered separately in a sufficiently pure form for recycling in high-grade products. WO9304116 A1 (1993, SCHERING AG) discloses a method for separating layers bonded together by an adhesive from waste packaging materials by immersing the packaging material, preferably with agitation, in a solvent for the adhesive with optional flotation to save the separated layers. The adhesive is dissolved by a solvent in which the bonded layers are themselves insoluble. The packaging material is preferably first cut into pieces of 10 cm2, preferably 2 cm2, and then immersed in or sprayed with a solvent. The invention can be used for the separation of packaging materials such as aluminum blister packs of aluminum and PVC, and toothpaste tubes, for material recovery and reuse. The selection of the solvent system depends on the type of the adhesive. Suitable solvents are methyl formate, methyl acetate, toluene, or chloroform. A preferred solvent system is a mixture of acetone with water (1%e20%). The patent is claimed to have the following advantages: providing a simple and flexible separation process; saving raw material; avoiding the problems of incineration and consequent fume disposal; and reducing need for dumping. On the other hand, acetone has a very low flash point (
20 C), and it is highly flammable and prone to accidents. The plastics are also fairly flammable. In industrial application, where a large amount will be required, the hazard of an accident is very high (2004, WO2004031274 A1, MUKHOPADHYAY ASHUTOSH). US5246116 A (1993, REYNOLDS METALS CO) discloses a method of recovering the components from an aluminum foilecontaining laminate used in packaging comprising the steps of 1) providing an aluminum foilecontaining laminate in a predetermined size, said foil-containing laminate comprising foil/plastic laminate or a foil/plastic/paper laminate; 2) combining the foil-containing laminate with a polyalkylene glycol aqueous solution to form a mixture; 3) agitating the mixture; 4) heating the mixture to at least about 80  C for a predetermined period of time to delaminate the foil-containing laminate; 5) cooling the mixture; 6) separating the plastic from the mixture by flotation; 7) separating foil and recovering the foil from the polyalkylene glycol aqueous solution;

7: S OLVENT-

AND / OR

C HEMICAL AGENT-BASED S EPARATION

213

8) heating the remaining polyalkylene glycol solution to at least 90  C to separate and recover the polyalkylene glycol polymer from the remaining polyalkylene glycol solution; and 9) reusing the recovered polyalkylene glycol in step (2). The polyalkylene glycol is believed to function in one mode as a type of solvent to separate or delaminate the aluminum foil from plastic or paper components, especially where adhesive is used for bonding of foil with another component. Where pressure type bonding, as in extrusion, is used to laminate the components together, the polyalkylene glycol softens the nonfoil components to facilitate delamination. In a preferred embodiment, the polyalkylene glycol includes linear polymers of equal amounts of ethylene oxide and propylene oxide started with butanol. The molecular weight is dependent on the chain length. The preferred molecular weights vary from 270 to 1230. The overall range extends from about 200 to 10,000. The polyalkylene glycol is water soluble at temperature below 40  C. Because of ethoxylation, these compounds exhibit reverse solubility. At temperatures above 40  C, a solution of the polyalkylene glycol separates into two layers, the top being the polyalkylene glycol polymer and the bottom layer being water. This separation characteristic of the glycol fluid permits recycling of the polyalkylene glycol solution after foil separation. Utilization of the polyalkylene glycol fluids also minimizes any adverse effect on the environment during processing of the foilcontaining laminates. The polyalkylene glycol fluids have low vapor pressures, e.g., less than 0.01 torr (1.33 Pa) at 100  C. Thus, there are no volatile organic compounds associated during separation and recovery of the aluminum foil from the laminate. Suitable commercial polyalkylene glycols are Carbowax and UCON-HB (Union Carbide Corporation) and Pluronic and Tetronic (BASF). EP0538730 A (1993, NORDENIA VERPACKUNG) discloses a method and an apparatus for the separation of the various layers from a used multilayer packaging film comprising at least one first layer made of polyethylene and at least one second layer made of the same polyethylene, a similar polyethylene, another polymer, or another material, for example, aluminum (see Fig. 7.1). The used packaging film is shredded into pieces, and the pieces are brought into at least one solvent bath containing an organic solvent under vigorous agitation. Packaging films containing a bonding agent (adhesion promoter) between the individual layers of the film, which comprises relatively high-percentage copolymers or terpolymers of polyethylene with acrylic acid and derivatives thereof,

214

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Figure 7.1 Schematic diagram of the process flow (B) for transforming polyethylene multilayer film (A) into reusable raw materials (1993, EP0538730 A, NORDENIA VERPACKUNG). 1, Polyethylene; 2, Aluminum; 3, Polyethylene; 4, 5, Bonding agents; 6, Shredding station; 7, 10, 11, 14, 16, and 17, Indicating arrow; 8, Solvent; 9, Solvent bath; 12, Cleaning station; 13, Mixing device; 15, Separation station

and relatively high-percentage ethylene vinyl acetate (EVA) copolymers, are bought into contact with a solvent, which causes the coupling agent to swell, for example, low-boiling esters of acetic acid (e.g., ethyl acetate and isopropyl acetate) or aliphatic ethers (e.g., propylene glycol monomethyl ether). The process often results in decomposition of the packaging components, long processing times, and insufficient separation. Further, the

7: S OLVENT-

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215

pigments present in the films are not removed, and residues of adhesion promoters always remain on the separate film layers, which largely consist of nitrocellulose. In subsequent processing, these residues result in charring so that high-quality films cannot be obtained (2002, WO02100932 A1, DER GRUENE PUNKT DUALES SYST; 2017, WO2017108014 A1, USTAV CHEMICKYCH PROCESU AV CR V V I). US2004129372 A1 (2004, HUANG CHAO-KUO; SHAO CHUNGHSING) discloses a method for separating and recycling an aluminum foil containing composite packaging material using an acid solution containing nitric acid as a stripping agent to soak the foil-laminated material (see Fig. 7.2). The nitric acid in the stripping agent permeates

Figure 7.2 Block diagram of a separating method for recycling aluminum foilelaminated packaging material (2004, US2004129372 A1, HUANG CHAO-KUO; SHAO CHUNG-HSING).

216

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the plastic layer (made mostly of polyethylene) and into the interfaces between the aluminum foil layer and the plastic layer to dissolve the alumina (Al2O3) and separate the layers. After separating the different layers of the Al2O3 foilelaminated material, the striping agent remaining on the separated layers is drained out and neutralized; the separated layers are cleaned, dried, and classified for a subsequent recycling process. The concentration of the nitric acid in the acid solution of the striping agent is 15%e68%. Acetic acid and phosphoric acid can be added to nitric acid solution to increase the efficiency of the striping agent. Optionally, a heating process is carried out within a temperature range of 40e70 C when soaking the foil-laminated material to accelerate stripping speed. The concentration of the stripping agent and the heating temperature are determined according to thickness of the plastic layer. Practically, when the concentration of the stripping agent is 68% and the heating temperature is 60 C, a soaking time in the stripping agent for the foil-laminated material is about 40 min. When the concentration of the nitric acid is 34% and the heating temperature is 65 C, the soaking time for the foillaminated material in the stripping agent is 60 min. If the stripping is carried out without heating, the operational conditions are when the stripping agent is 30%e34%, the soaking time is 7 h; and when the stripping agent is 20%e30%, the soaking time is 15 h. The method is suitable for treating foil-laminated material in large quantity batches and has lower operation cost. WO0250175 A2 (2002, MUKHOPADHYAY ASHUTOSH) discloses a method for the recovery of aluminum foil and polyethylene from multilayer fragments from packaging industrial refuse in sheet, strip, tube, or shredded form. The multilayer fragments are treated with an inorganic acid solution being 50%e70% concentrated nitric acid for about 4e7 h, so as to loosen the bonding of the constituents; the constituents are stripped physically and washed. The washing step is carried out with dilute lime water followed by one or more water baths for total removal of adhered acid from the delaminated fragments. The delaminated fragments are physically separated into polyethylene and aluminum. The constituents are further dried, preferably by conventional centrifuge, optionally followed by drying under the sun or in a conventional dryer. WO2004031274 A1 (2004, MUKHOPADHYAY ASHUTOSH) discloses a method for the recovery of aluminum foil and polyethylene from multilayer fragments of packaging industrial refuse in sheet, tube, or shredded form as separate constituents by treating the comminuted fragments with an inorganic base solution, in particular sodium hydroxide (NaOH), so as to dissolve the aluminum foil to subsequent recoverable

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217

aluminum salts, namely sodium aluminate (NaAlO2), and polyethylene retained in its physical form. From the recovered sodium aluminate, aluminum hydroxide gel (Al(OH)3) is obtained. From the aluminum hydroxide gel, dried powder of alumina (Al2O3) or other aluminum salts can also be obtained. According to the invention, the method is relatively economical and efficient than that of the applicant’s earlier patent application WO0250175 A2 (2002) also because sodium aluminate (either concentrated solution or dried powder) is the main recovery product of the process. Example: In a 1000 ml clear conical flask were added 66 g of pure dried sodium hydroxide flakes. Clear water was poured to make 800 ml of 2M sodium hydroxide solution. A few pieces of laminated toiletry tubes were added to the flask. The shoulder and tail end seal of the tubes were shredded out through manual cutting with scissors. Then taking 0.25 cm breadth-wisely, the tubes were longitudinally shredded, and all the contaminants were cleared and washed out. The shredded fragments (0.25 cm) of the laminated tubes were dipped into the conical flask. The flask was closed with stopcock and allowed to stand for 48e84 h with inbetween stirring. When all aluminum was dissolved, the two layers of plastics that were released from lamination floated in the solution. The released plastics were taken out from the resultant very dilute solution of sodium aluminate and dipped in a dilute nitric acid solution for 0.5e2 min with fast stirring and washed with water. The resulting mixture was further processed to yield pure sodium chloride as a by-product having its own specific market. WO03104315 A1 (2004, MASSURA ANDERSON CROVADOR; CROCHEMORE GUILHERME BALTAR; MARCAL DE SOUZA EDSON ALEXANDR) discloses a method for the separation of polymer, aluminum, and/or paper from multilayered films, from pack- and decorative-type food packaging, by introducing the films in heated baths of organic solvents, protonic carboxylic acid, and water at temperature ranging from 20 to 140 C and time between 5 s and 2 h. Preferred organic solvents include tetrahydrofuran, xylene, toluene, carbon tetrachloride, acetone, and chloroform. A preferred protonic carboxylic acid is acetic acid. The complete recovery of each component film is enabled by the solubilization of the adhesive used among the layers. According to Hildebrand’s law, the nearer the solubility parameters of the adhesive and the solvent, the more easily the solubilization will occur; in particular, if the difference of absolute values between the two solubility parameters is lower than 1.7 Hildebrand, the solubilization is assured. Another parameter to be taken into consideration is the cohesive energy density, which

218

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especially depends on the temperature in general; the greater the cohesive energy density, the greater is the difficulty to make the polymer or any type of organic molecule with lower molecular weight soluble, as it happens with adhesives. The higher the temperature, the greater the thermal agitation state of adhesive molecules and, therefore, the lower is its cohesive energy density, thereby enabling solubilization thereof. Solubilization of polyurethane adhesive joining the polyethylene film with PET film, polypropylene film, aluminum, or paper sheet can be performed in chloroform bath at atmospheric pressure with temperature in the range of 20e61  C within a time between 30 s and 1 h. Solubilization of poly(vinyl alcohol) (PVOH) adhesive joining the different polymeric films each other or to aluminum or paper sheet is performed in protonic carboxylic acid bath at atmospheric pressure with temperature in the range of 20e115  C within a time between 30 s and 2 h or further in water bath at atmospheric pressure with temperature in the range of 15e100  C within a time between 5 s and 1 h. The recovered films can be reused in the manufacture of several articles by usual recycling processes. The use of organic solvents, like halogenated media, in this method has, however, a negative environmental impact (2018, WO2018109147 A2, SAPERATEC GMBH). BRPI0402112 A (2006, MARCAL DE SOUZA EDSON ALEXANDR; MASSURA ANDERSON CROVADOR) discloses a method for recycling flexible multilayer comprising oxidation, solubilization, and defunctionalization of the polyurethane (polyether- or polyester-based), polyester, hot melt, PVOH, and dextrin base adhesives, which bind the laminated layers formed of polymer films (metallized or not), aluminum foil, and paper to be separated, using a bath of a chemical solution containing acetic acid (of concentration 70%e90%) and formaldehyde (of concentration 0.1%e10%) heated at a temperature ranging from 85 to 95  C, for a time period between 5 and 100 min. WO2014162238 A (2014, JAIN PRANAY) discloses a method for recycling metalized PET film including a washing step for removing aluminum. Metalized PET film or flakes are washed in a hot washing water bath tank or at room temperature with an alkaline solution, such as a solution containing caustic soda or in a solvent such as a hydrocarbon solvent. The desired level of caustic soda is in the range of 0.5%e3% in a water solution at room temperature to 90  C or any other suitable alkali solution. Keeping the metalized film in 1% caustic soda solution at a water temperature of 80e85  C, the alumimum was removed within few seconds. The time required to remove aluminum from the metalized PET film for similar caustic soda solution was 2 min at room

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219

temperature water. The aluminum completely dissolves and the water acts as an acid. The aluminum layer from metalized PET film is removed, and clear PET film is obtained after multiple washing steps varying from 2 to 10 times. CN104744724 A (2015, DAI XIANGHUI) discloses a method for separating the layers of an aluminumeplastic multilayer packaging with the use of a separating agent prepared by mixing 40e200 pbw, preferably 42 pbw, formic acid, 5e10 pbw, preferably 6 pbw, dichloromethane (methylene dichloride) and further 1e4 pbw, preferably 3 pbw, nonionic surfactant. The separating method comprises the following steps: mixing the separating agent with water to obtain the separating agent, and soaking a pulverized cleaned aluminumeplastic composite film in the separating agent for 4e12 h; pulling out the fragments of the composite film, cleaning, centrifuging, and drying. The separating agent that is used in this patent application is highly volatile and also contains components that are harmful to the environment (2018, WO2018109147 A2, SAPERATEC GMBH). CN104669467 A (2015, XU CHAO; ZHANG QIUHUA; CHEN GUANG) discloses a stripping agent to separate plastic, such as PVC, and aluminum foil from waste pharmaceuticals packaging materials. The stripping agent comprises 10%e40% tetrahydrofuran, 30%e50% ethyl acetate, 15%e30% ethanol (ethyl alcohol), and 5%e20% n-hexane. KR20060000247 A (2006, HEA SONG COMMERCIAL FIRM) discloses a method for recovering EVA copolymer and PET from a waste laminate film comprising the following steps: (1) pulverizing the laminate; (2) precipitating the pulverized laminate film in a settling tank containing a 35%, or preferably 50%, hydrogen peroxide solution for a predetermined time; (3) transferring the pulverized film from the precipitation tank into an extruder; (4) discharge the pulverized to a precipitation separation tank and separating the EVA floating at an upper layer and the PET precipitated at a lower layer owing to the difference of specific gravity; and (5) dehydrating the separated EVA and PET. GB2525858 A (2015, SAPERATEC GMBH) discloses a method and an apparatus for recovering individual material components from multilayer packaging waste comprising a metal layer at least one polymer layer and, optionally, a paperboard layer. In one nonlimiting example of the invention, the polymer layers are made of low-density polyethylene (LDPE) and the metal layer is made of aluminum. The multilayer packaging waste is collected together as bales. The bales are placed into a first vat to remove a substantial portion of the paper layer as a slurry and thus to produce residual waste, subsequently placing the residual waste in

220

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a second vat comprising a separation fluid to produce a mixture of aluminum shreds, plastic shreds, and residual components. The separation fluid is a microemulsion comprising a carboxylic acid, a swelling agent for the polymer, and a surfactant. The carboxylic acid is selected from the group of short chain carboxylic acids consisting of acetic acid, formic acid, or propanoic acid, or mixtures thereof. The swelling agent used is a hydrocarbon solvent selected from the group of aromatic hydrocarbons, such as toluene, xylene, ethylbenzene, or solvents of the naphtha types, alicyclic hydrocarbons, such as cyclohexane or decalin, olefins, terpenes, and acyclic aliphatic hydrocarbons, or mixtures thereof. Additional swelling agents include aprotic solvents, such as ketones, esters, or ethers. In a further aspect of the invention, the separation fluid further comprises water and at least one anionic surfactant and is a microemulsion. The microemulsion must be stable in the temperature range at which the second vat is operating (20e50 C). This can be achieved by combining anionic surfactants with cosurfactants or with hydrotropes, such as phosphoric acid decyl ester. The anionic surfactants are selected from alkyl sulfates, alkylbenzene sulfonates, and olefin sulfonates, or mixtures thereof. An exemplary cosurfactant is caprylic acid, and an exemplary hydrotrope is phosphoric acid decyl ester. The pros and cons of Saperatec’s microemulsion technology can be summarized as follows: Pros: The only currently available technology that can separate plastic layers from a multilayer plastic packaging material to obtain raw materials of high purity. The recovered raw materials can be reclaimed as secondary raw materials, thus fully preserving the cycle of materials. The separation process functions well at room temperature. The microemulsion can be reconditioned and reused [1]. Cons: Higher water and energy demand than alternatives as a result of washing and drying requirements. It still requires an understanding of structure composition before beginning the process. This makes it unfeasible for curbside collection programs and limits processing to one structure format at a time [2]. WO2018109147 A2 (2018, SAPERATEC GMBH) discloses a method for recycling a multilayer packaging material comprising a metal layer and at least one polymer layer using a separation fluid that is a mixture of water, a short-chained carboxylic acid, phosphoric acid, and an alkali metal hydroxide solution. The short-chain carboxylic acid and the phosphoric acid react partially with the alkali metal hydroxide to produce alkali metal phosphates and alkali metal carboxylates. The short-chain carboxylic acids used are water miscible C1eC4 monocarboxylic acids,

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Table 7.1 Composition of a Separation Liquid (2018, WO2018109147 A2, SAPERATEC GMBH) Components

Content (wt%)

Water

45.7

Glacial acetic acid

45.0

Phosphoric acid, 30% solution

3.0

Sodium hydroxide, 33% solution

6.3

such as formic acid, acetic acid, propionic acid, and butyric acid. In one aspect of the invention, formic or acetic acid is used. The alkali metal hydroxides include hydroxides of lithium, sodium, and potassium. In general, other hydroxides can be used if the other hydroxides do not form insoluble phosphate salts because these insoluble salts would interfere with passivation of aluminum. In the following examples, flakes of flexible multilayer plastic packaging used for drinks, food, and coffee packaging are stirred in a separation liquid (see Table 7.1) at 70 C. The detachment of the plastic layer from the aluminum is complete within 2e5 h (see Table 7.2). WO2017108014 A1 (2017, USTAV CHEMICKYCH PROCESU AV CR V V I) discloses a method for the separation of individual components from a multilayer packaging material, wherein the multilayer packaging material is crushed and combined with an organic separation agent in weight ratio material/agent 1/5 to 1/10; the resulting mixture is heated to a temperature in the range of 40e100  C and left to react at stirring until separation of the individual components occurs, and the individual components are then isolated by a method based on their different specific weights. The organic separation agent is a mixture of crude oil fraction with distillation curve from 50 to 200  C with an organic solvent selected from toluene, xylene, acetone, N-methyl pyrrolidone, N-ethyl pyrrolidone, and formic acid. The composite packaging material contains the following components: LDPE/polypropylene, LDPE/aluminum/PET, polyethylene/aluminum/polyethylene, or polyethylene/aluminum/ polypropylene. WO2017037260 A1 (2017, CENTRE NAT RECH SCIENT) discloses a method and an apparatus for delaminating multilayer systems including at least one polymeric layer, the layers being separated by interfaces, comprising at least the following steps: mixing the multilayer system with

222 Table 7.2 Separation of Aluminum Foil from Multilayer Plastic Packaging Materials by Treatment With the Separation Liquid of Table 7.1 (2018, WO2018109147 A2, SAPERATEC GMBH) Amount of Packaging Material (g)

Amount of Separation Liquid (g)

Detachment Time (h)

Beverage standup pouches

LDPE/Al/PET

1

60

1000

4

Snack food packaging

LDPE/Al/PET

3

30

30

4

Toothpaste tubes

LDPE/Al/LDPE

2

60

1000

2

Coffee packaging

PP/Al/PET

1

20

5

e

Al, Aluminum; LDPE, Low-density polyethylene; PET, Poly(ethylene terephthalate); PP, Polypropylene.

F LEXIBLE P LASTIC PACKAGING

Multilayer Type

OF

Packaging

R ECYCLING

Flakes’ Surface Area (cm2)

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223

a fluid made up of at least one gas having the capacity of causing at least one of the layers to swell and one or more nonreactive liquids having the capacity of allowing each layer individually or subsets of layers to be disconnected without damaging the components of the layers, the gas/ liquid fluid being brought to the required temperature and pressure, and separately recovering at least one or more layers or a subset of layers which are undamaged. The fluid is preferably a mixture of CO2, water, and acetone. The volume proportion of the liquid mixture with respect to the gas is at least 15%. The volume proportions of the constituents of the acetone/water mixture are, for example, 80% acetone and 20% water or with a proportion of water relative to acetone ranging from 0% to 100%. The method allows the separation of layers without the need for mechanical action. The method can be used for the recycling of multilayer packaging waste, for example, food packaging, cosmetic, or pharmaceutical packaging composed of at least a polymer layer coated with an aluminum foil. Particular examples include chewing gum packaging comprising an assembly of polymeric layers and an aluminum foil, and fresh cream package consisting of polyethylene/cardboard/polyethylene/ aluminum/polyethylene. Yousef et al. [3,4] developed a process that uses a switchable hydrophilicity solvent to delaminate the layers of a multilayer flexible packaging and uses ultrasonic treatment to accelerate the separation process. The solvent used is N, N-dimethylcyclohexylamine (DMCHA). The delamination was conducted on six common types of multilayer flexible packaging from food wrapping (crisps, chocolate bars, bakery products, ground coffee, ice cream, and biscuits) and six different types of waste pharmaceutical blister packets. The polarity of the solvent is switched by adding water and CO2, allowing the remaining dissolved adhesives and inks to be recovered. The recycling rate using this method is >99%, and the recovered materials are aluminum flakes, PVC films, EVA films, PET films, and polyethylene powder. The solvent can also be recycled by heating it overnight to remove the CO2 and to evaporate water that has been added. The main stripping agents used for the delamination of flexible plastic multilayer packaging films are listed in Table 7.3. A new development uses supercritical liquids for the delamination of multilayer packaging films. An application of this technology can be found in WO2017037260 A1 (2017, CENTRE NAT RECH SCIENT), which discloses a method for delaminating a multilayer system used in food packaging, cosmetic or pharmaceutical packaging, and photovoltaic module by treating the multilayer system with a gas/liquid mixture fluid, preferably CO2/water/acetone, at a temperature that is greater than the

224

Table 7.3 Stripping Agents for the Delamination of Flexible Plastic Multilayer Packaging Films Multilayer Packaging Material

Use

Adhesive; thermal lamination

Ethyl acetate, toluene, and gasoline

DE4215573 A1 (1993, HOECHST AG)

Adhesive

Acetone (90%) and water (10%)

WO9304116 A1 (1993, SCHERING AG)

(PE, PP)/Al

Adhesive; pressure bonding

Polyalkylene glycol (Carbowax and UCONHB, Union Carbide Corporation; Pluronic and Tetronic, BASF)

US5246116 A (1993, REYNOLDS METALS CO)

PE/Al/PE

Copolymers or terpolymers of polyethylene with acrylic acid and derivatives and ethylene vinyl acetate copolymers

Swelling agent: ethyl acetate and isopropyl acetate) or aliphatic ethers (e.g., propylene glycol monomethyl ether)

EP0538730 A (1993, NORDENIA VERPACKUNG)

PVC and Al; PVC and PE; PET and PE PE/Al, PVC/Al

Al blister packs of Al and PVC and toothpaste tubes

F LEXIBLE P LASTIC PACKAGING

Patent

OF

Stripping Agent

R ECYCLING

Bonding System

PE/Al

US2004129372 A1 (2004, HUA NG CHAO-KUO; SHAO CHUNG-HSING) WO0250175 (2002, MUKHOPADHYAY ASHUTOSH)

PE/Al

Medicinal strips or blister type packs, toiletry tubes

Sodium hydroxide; nitric acid

WO2004031274 A1 (2004, MUKHOPADHYAY ASHUTOSH)

PE-PET/PP-Alpaper; BOPP/OPP-Alpaper

Pack- and decorative-type food packaging

PU, PVOH

Chloroform, xylene, tetrahydrofuran; acetic acid

WO03104315 A1 (2004, MASSURA ANDERSON CROVADOR; CROCHEMORE GUILHERME BALTAR; MARCAL DE SOUZA EDSON ALEXANDR)

PU, PVOH, dextrin

Acetic acid

BRPI0402112 A (2006, SOUZA EDSON ALEXANDRE MARCAL D; MASSURA ANDERSON

(PE, PP, PET, PA)/ Al, paper/Al

(Continued )

225

Nitric acid (50%e70%)

C HEMICAL AGENT-BASED S EPARATION

Medicinal strips or blister type packs, toiletry tubes

AND / OR

PE/Al

7: S OLVENT-

Nitric acid; optionally acetic acid and phosphoric acid

226

Table 7.3 Stripping Agents for the Delamination of Flexible Plastic Multilayer Packaging Films (Continued ) Multilayer Packaging Material

Use

Bonding System

Stripping Agent

Patent KR20060000247 A (2006, HEA SONG COMMERCIAL FIRM)

PET/Al

Film

Caustic soda (0.5%e3% in water solution, 25e90  C)

WO2014162238 A (2014, JAIN PRANAY)

PVC/Al

Packaging of pharmaceuticals (tablets, capsules, suppositories, etc.)

Tetrahydrofuran (10%e40%), ethyl acetate (30%e50%), ethanol (15%e30%), and n-hexane (5%e20%)

CN104669467 A (2015, XU CHAO; ZHANG QIUHUA; CHEN GUANG)

Formic acid (40e200 pbm), dichloromethane (5e10 pbm) and

CN104744724 A (2015, DAI XIANGHUI)

Plastic/Al

F LEXIBLE P LASTIC PACKAGING

Hydrogen peroxide solution (35%e50%)

OF

Coating films, printing materials, or labels

R ECYCLING

PET/EVA

PE/adhesive/Al

Chewing gum packaging, fresh cream package

Mixture of CO2, water (e.g., 20%) and acetone (e.g., 80%)

WO2017037260 A1 (2017, CENTER NAT RECH SCIENT)

PE/Al/PET; PP/Al/PET

Coffee packaging, drinks packaging, pet food packaging

Microemulsion: acetic acid (6.0%e12.0%); xylene isomers (20.0%e21.7%) or naphtha, heavy aromatic, naphthalene depleted (25.0%); sulfonic acids, C14-17-sec-alkane sodium salts (12%e14.4%); caprylic acid (3.3%e4.8%) or phosphoric acid decyl

GB2525858 A (2015, SAPERATEC GMBH)

227

PE/Al/PE; PE/cardboard/PE/Al/ PE

C HEMICAL AGENT-BASED S EPARATION

CN107599234 A (2018, ANHUI TENGYUE ALUMINUM PLASTIC CO LTD)

AND / OR

First stage in organic solvent (acetone, chloroform, ethyl ether, benzene. and toluene); second stage in 1e2 mol/l hydrochloric acid solution, 2e5 h, at 30e70 C

7: S OLVENT-

nonionic surfactant (5 e10 pbm)

(Continued )

Multilayer Packaging Material

Use

Bonding System

Stripping Agent

228

Table 7.3 Stripping Agents for the Delamination of Flexible Plastic Multilayer Packaging Films (Continued ) Patent

ester, sodium salt (1.8%); water (51.4%e53.4%) WO2018109147 A2 (2018, SAPERATEC GMBH)

PE/Al/PET; PVC, PP/Al/EVA

Pharmaceutical blister packets, food products (crisps, chocolate bars, bakery products, ground coffee, ice cream, and biscuits)

DMCHA (40e80  C)

[3,4]

Al, Aluminum; BOPP/OPP, Biooriented/oriented polypropylene; DMCHA, N, N-Dimethylcyclohexylamine; EVA, Ethylene vinyl acetate; PE, Polyethylene; PET, Poly(ethylene terephthalate); PP, Polypropylene; PVOH, Poly(vinyl alcohol); PU, Polyurethane.

F LEXIBLE P LASTIC PACKAGING

Water (45.7%), glacial acetic acid (45.0%); phosphoric acid 30% solution, (3.0%); sodium hydroxide 33% solution (6.3%)

OF

Beverage stand-up pouches, snack food packaging, tooth paste tubes, coffee packaging

R ECYCLING

LDPE/Al/PET; LDPE/Al/LDPE; PP/Al/PET

7: S OLVENT-

AND / OR

C HEMICAL AGENT-BASED S EPARATION

229

critical temperature1 of the gas (CO2) and lower than the degradation temperature of the layers of the multilayer system and at a pressure that is higher than the critical pressure of the gas, and the volume proportion of the mixture of liquids (water and acetone) with respect to the gas is at least 15%. Some processes use chemical separating agent(s) in combination with water or organic solvent(s) for the separation of layers and/or metal foils. WO2015159301 A2 (2015, PATEL KETAN MAHADEV; VAVIYA MAHESH MAHADEV; PATEL MAHESH HARJI) discloses a method for recovering LDPE from flexible packaging material comprising at least polyester and LDPE by treating the flexible packaging material in an acidic environment having sulfuric acid, thereby removing at least the polyester component in the packaging material and extracting at least the LDPE component from the acidic environment by washing with water to remove traces of at least the sulfuric acid. The flexible packaging material includes packaging material for food products, agricultural products, medicinal products, pharmaceutical products, and detergents. Example 1: 30 g of a detergent packaging made up of polyester and LDPE was treated with 500 g of 68% sulfuric acid for 2 min. The color gradually turned to dark brown on mixing detergent packaging with sulfuric acid. No further color change was observed for around 2 min, which indicated the end point of the reaction. The sulfuric acid burnt the polyester component, and the LDPE component was retained. LDPE was extracted from the acidic environment by a physical method and washed with water to remove traces of sulfuric acid. 6 g of polyester was burnt, and 24 g of LDPE was extracted. CN107599234 A (2018, ANHUI TENGYUE ALUMINUM PLASTIC CO LTD) discloses a method for separating and recycling waste aluminum and plastic from a composite packaging by combining an organic solvent method and a chemical separating method. The method comprises the steps of; 1) putting a waste aluminum plastic composite packaging material into a shredder; placing the shredded aluminum plastic material in a stirring barrel; adding an organic solvent (acetone, chloroform, ethyl ether, benzene, and toluene) in the stirring barrel till the aluminum

1

The critical temperature of a substance is the temperature at and above which vapor of the substance cannot be liquefied, no matter how much pressure is applied.

230

R ECYCLING

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plastic packaging material is fully immersed and stirring the mixture at a rotating speed of 200e500 r/min for 2e8 h; separately washing the plastic floating on the surface of the organic solvent and the aluminum foil precipitated in the bottom of the stirring barrel with clean water; 2) drying, pelletizing, and remolding the plastic; drying the precipitated aluminum foil and transferring it to a reaction container for secondary separation; 3) adding a 1e2 mol/l hydrochloric acid solution into the reaction container, stirring the mixture for 2e5 h at 30e70  C; filtering and washing to obtain a filtrate for later use; 4) adding 1e2 mol/l sodium hydroxide solution to the filtrate obtained in step (3); stirring the mixture at 60e90 C for 3e5 h to obtain polyaluminum chloride; 5) adding ammonia/water to the filtrate obtained in step (3) until the pH of the solution is 10 and then filtered; adding 0.3e1 mol/l sodium hydroxide solution to the precipitate obtained by filtration until the precipitate is completely dissolved; charging the dissolved solution with carbon dioxide until the pH of the solution is 5e7; after aging for 18e48 h, the solution is filtered, washed, and dried to obtain precipitated aluminum hydroxide; and 6) calcining the precipitated aluminum hydroxide at a high temperature of 1200  C to obtain an alumina solid. CN106832393 A (2017, HENAN WANBANG HIGHLY-EFFICIENT AGRICULTURAL DEV CO LTD) discloses a method of separating the layers of a polyethylene/aluminum/PET film comprising the following steps: (1) slitting the packaging film, putting the slitted film into a stainless steel tank; (2) adding water and a surfactant into the stainless steel tank, and heating to a preset temperature to soak the slitted film; (3) taking out the soaked slitted film, and separating the polyethylene film; (4) packing the residue mixed material where the polyethylene film is separated and soaking it in a PVC tank at room temperature; (5) hot-dipping the soaked residue mixed material in the stainless steel tank; (6) subjecting the residue mixed material subjected to hot dipping to separate aluminum and PET film; (7) drying the separated aluminum. The film separation method has the following beneficial effects: the problem of air pollution in the traditional separation method is avoided; the separation method provided

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by the invention realizes the safe production at the normal temperature in the whole process; no pollution waste is produced; and the method is favorable for environmental protection.

7.2 Cleaning Solutions Cleaning systems using solvent and/or an aqueous surfactant solution are used for removing printing inks, film additives, impurities, etc., from flexible plastic packaging waste. These cleaning systems are distinguished from wet cleaning or washing using water (see Chapter 8, Section 8.1.1). EP0521418 A1 (1993, NORDENIA VERPACKUNG GMBH) discloses a method and an apparatus for removing film additives, nonpolar polyethylene waxes, and adhering printing inks from used packaging films made of polyethylene, such as shrinking films, bags, and pouches manufactured from the films. The method comprises the steps of: (1) shredding the polyethylene films and washing the shreds with water to remove dirt followed by drying; (2) placing the shreds in a first solvent bath containing boiling solvent and intensively stirring mechanically for about 30 min to rub the shreds on one another and remove the printing inks adhering to the shreds by friction; (3) removing the shreds from the first solvent bath, which is loaded with printing inks, placing the shreds in a second solvent bath so that the shreds are acted on by fresh solvent, and boiling and intensively stirring again for 30 min; (4) placing the shreds in a third solvent bath and boiling and intensively stirring for about 30e60 min; (5) removing the shreds from the third solvent bath and dripping off the solvent; (6) drying the dripped-off shreds under evaporation of solvent residues adhering thereto; and (7) subsequently, melting and shaping the shreds into granulates as reusable raw material. Preferably, a solvent is used having a boiling temperature that is significantly below the softening temperature of polyethylene. When using such a solvent, it is avoided during the regeneration that the polyethylene shreds soften to a high degree or that they melt to a lesser or higher degree and stick to one another. At the same time, printing ink particles are prevented from irreversibly embedding in the polyethylene shreds, which might lead to dyeing of the recycling product. Furthermore, advantageously, a solvent is used having a density that is lower than the density of the shreds to be regenerated. In this way, the polyethylene shreds are prevented from floating up. Because of their higher specific weight, the shreds sink and are in this way subjected more intensively to mutual friction for rubbing off the printing inks adhering thereto.

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Particularly, suitable solvents are low-boiling acetic acid esters such as methyl acetate, ethyl acetate, and isopropyl acetate or also alcohols such as ethanol. In this connection, the esters have advantages over ethanol only with respect to their power of extracting film ingredients. The shreds treated under heat with an organic solvent, following mechanical separation of the solvent, still contain about 50e60 wt% solvent, for example, in the case of ethyl acetate. The solvent can be found both on the surfaces of the shreds and diffused into the interior of the shreds. The surfaces of the shreds contain also residues of nitrocellulose, the preferred vehicle for flexographic printing inks. Such residual amounts of nitrocellulose, even though low, lead to carbonization during regranulation and, thus, to black spots in the recycled film (1994, EP0602658 A1, NORDENIA VERPACKUNG GMBH). Further, the solvent is contaminated with water, which makes the process considerably more expensive. In addition, the color pigments contained in the film chips are not easily removed (2002, WO02100932 A1, DER GRUENE PUNKT DUALES SYST). EP0602658 A1 (1994, NORDENIA VERPACKUNG) discloses a method for the removal of solvent and/or nitrocellulose residues from precleaned polyolefin, particularly from precleaned polyethylene recycled shreds comprising the steps of: (1) mixing the polyolefin shreds with washing water in a weight ratio of 1/9 to 1/10; (2) removing the solvent, preferably ethyl acetate, by heating the water to a temperature above the boiling temperature of the solvent (77  C), preferably 85e90  C; (3) washing the nitrocellulose residues from each surface of the polyolefin shreds; (4) using the washing water for precipitating nitrocellulose from the solvent; and (5) collecting solvent in the form of vapors during washing and passing said vapors into a solvent tank and using the collected solvent as circulation solvent. The disadvantage of this method is the resulting three-phase mixture of solvent, water, and nitrocellulose, which again must be separated. Also, the rinse water must be cleaned with ultrafine filters, which increases the total cost (2002, WO02100932 A1, DER GRUENE PUNKT DUALES SYST). WO2013144400 A1 (2013, UNIV ALICANTE) discloses a method using a number of devices for removing ink printed on a plastic film (see Fig. 7.3). The method comprises the following steps: 1) conditioning the input printed material in a plunger obtaining a film free of impurities; 2) grinding the film free of impurities in a grinder;

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Figure 7.3 Diagram of the method and the devices used for removing ink from the printed film (2013, WO2013144400 A1, UNIV ALICANTE). 1, Conditioning the film; 2, Grinding the film; 3, Removing ink from the film; 4, Washing the film; 5, Recovering the cleaning solution; 6, Recovering the pigment; 7, Drying the film; 101, Plunger; 102, Blade grinder; 103, Cleaning system; 104, Centrifuge; 105, Ink thermal treatment reactor; and 106, Briquette machine

3) removing ink from the film in a cleaning system with a cleaning solution consisting of surfactants in water at basic pH, where a cleaning tank stirred with vanes generates a treated plastic film containing part of that cleaning solution and the dispersed ink residues, and in addition, the cleaning solution together with the ink removed from the film; 4) washing the treated plastic film in the preceding cleaning system where at least two washing tanks obtain a clean film free of ink and cleaning solution residues; 5) recovering the cleaning solution in a centrifuge; 6) recovering the pigment in a thermal treatment reactor; and 7) drying the film for obtaining a ground film free of ink and cleaning solution in a drying element. The input printed material can be polyethylene, polypropylene, polyester, or polyamide. The cleaning solution contains hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, or dodecyl sulfate as surfactants.

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7.3 Selective Dissolution In a selective dissolution process, the solvent and process conditions are selected in such a way that only the targeted plastic is dissolved, so that all the other composite components can be removed from the solution by means of the known solid/liquid separation techniques (filters, centrifuges, decanters), before the polymer is isolated again from the solution and processed further to form a new plastic (2010, DE102008056311 A1, APK ALUMINIUM UND KUNSTSTOFFE). Selective dissolutionebased processes in organic solvents have been used to separate commingled and multilayer postconsumer plastic packaging products, which usually are mixtures of polyolefins, such as polyethylenes, with other polymers. Solvent-based recycling is selective for polyolefins and generates pure and high-quality, recovered polymers from mixed postconsumer waste. The main advantages of the dissolution-based method in organic solvents are as follows: the input consisting of a heterogeneous mixture of multilayer and nonmultilayer packaging material does not have to run through a complex sorting process, and the precipitated polymer is expected to be of very high quality. The main disadvantages of the dissolution-based method are as follows: the energy-intensive drying of the polymer and the fact that all polymer components that do not dissolve remain as a residue of little value [5]. An overview of the solvents and acids suitable to dissolve the most common polymers used for the production of flexible packaging is given in Table 7.4. US5286424 A (1994, MOBIL OIL CORP) discloses a method for the recycling of biaxially oriented polypropylene (BOPP) film, coated with a chlorine-containing polymer, such as poly(vinylidene chloride) (PVDC), and having a primer, such as polyethyleneimine, there between. First, a caustic solution is formulated containing from about 0.1 to about 50 wt % of a caustic compound, such as potassium hydroxide, calcium hydroxide, and sodium hydroxide, and from about 0.05 to about 1.0 wt% of a wetting agent, such as sodium lauryl sulfate. The formulated caustic solution is heated to a temperature from about 25 to about 140 C. Pieces of BOPP film are soaked in the heated caustic solution until the PVDC is separated from the BOPP film. After separating the BOPP film from the PVDC, the BOPP material is reprocessed into desired product by extrusion, molding, or other product-forming process. US4031039 A (1977, MITSUBISHI HEAVY IND LTD) discloses a method for treating waste of plastic laminates by fractionating the waste

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Table 7.4 Solvents and Acids Suitable to Dissolve Polymers Used in Flexible Plastic Packaging [6] Polymer/Coating/Adhesive

Solvent/Acid

Polyethylene

Boiling p-xylene, boiling toluene, boiling dimethyl sulfoxide

Polypropylene

Boiling toluene, boiling dimethyl sulfoxide

Ethylene vinyl alcohol (EVOH)

Boiling N,N-dimethylformamide, hot concentrated sulfuric acid (turns black)

Ethylene vinyl acetate (EVA)

Toluene

Polyacrylates

Boiling xylene, toluene, methylene chloride, acetone, ethyl acetate

Poly(vinylidene chloride) (PVDC)

Boiling xylene, boiling N,Ndimethylacetamide, boiling cycloheptanone, di-n-butyl sulfoxide

Polyamide (PA)

Hot concentrated formic acid (95%), hydrochloric acid (37%), hot concentrated sulfuric acid (96%), boiling N,Ndimethylformamide

Poly(ethylene terephthalate) (PET)

Boiling N,N-dimethylformamide (swells), hot concentrated sulfuric acid

Polyurethane

Formic acid, methylene chloride (swells), acetone (swells), ethyl acetate (swells)

consisting essentially of polyolefins, polystyrene, PVC, thermosetting polymers, and natural polymers (e.g., pulp, paper, and cellophane), taking advantage of their dissimilar solubilities in different organic solvents. The method comprises the steps of bringing the mixture into contact with oxylene, p-xylene, or m-xylene, the isomers being used either singly or in a combination of two or more, at a temperature of 5e50 C to dissolve and fractionate the polystyrene, and then at a temperature of 90e150 C to

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dissolve and fractionate the polyolefins such as polyethylenes and polypropylenes, and finally dissolving and fractionating the PVC by heating the remainder by use of at least one solvent selected from the group consisting of tetrahydrofuran, cyclohexanone, dioxane, and methyl ethyl ketone, at a temperature of 5e60 C, whereby the waste mixture is fractionated into polyolefins, polystyrene, PVC, and thermosetting and natural polymers. Example: 100 g of plastic waste of a flexible laminated film composed of cellophane2 and polyethylene fractured in size of less than 50 mm and 1 l of industrial xylene were placed in a separable flask having a content volume of 2 l equipped with a thermometer, a cooler, and a stirrer. Under stirring, the materials were heated to 120e130 C in an oil bath thereby to dissolve polyethylene. Then, the dissolved material and undissolved material were separated by use of a wire screen, and cellophane remaining on the wire screen was freed from solvent by a vacuum drier. The other solution was cooled to room temperature to phase separate xylene and polyethylene completely. The separated polyethylene was filtered under reduced pressure by a Buchner funnel and then freed from solvent by a vacuum drier. The amounts of cellophane and polyethylene recovered were 40 and 60 g, respectively. Cellophane could not be detected in the recovered polyethylene. The aforementioned solvents are either aromatic or flammable low boiling (b.pt. < 115 C) and do not show very high electrical conductivities and are hazardous due to the risk of electrostatic charging and/or explosion. Thus, these organic solventebased techniques require strict and expensive safety measurements to protect human health and environment. Another disadvantage is the low selectivity of the disclosed solvents for the target polyolefins that make preextraction necessary. A further disadvantage is that the residual solvent traces, which are foreign substances for virgin polyolefin qualities, have a negative impact on the applicability of the recovered polymer (2018, EP3305839 A1, FRAUNHOFER GES FORSCHUNG). Although there are efforts to preextract nonpolyolefins or to use more selective solvents or solvent mixtures, there are still traces of codissolved nonpolyolefins, which will be concentrated (together with the target polymer) during the drying process in which the filtered polymers are separated from the solvent. At locally higher concentrations, the

2

Cellophane is a thin, flexible, translucent film made of regenerated cellulose. Cellophane is a registered trademark in Europe and elsewhere and a generic term in the United States.

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nonpolyolefins are incompatible with the target polymer and result in undesired impurities, such as stickies, crusts, or gel particles, in the recovered polymer, in particular during melt drying and extrusion with high temperature and friction (2018, EP3305839 A1, FRAUNHOFER GES FORSCHUNG). Such a melt filtration of target polymer gel after a first solvent separation is known from WO2011082802 A1 (2011, FRAUNHOFER GES FORSCHUNG). In an embodiment, the method comprises treating a flexible multilayer packaging waste with a swelling agent to swell the target polymer to a polymer gel as the first phase having a polymer content of at least 20 wt% and forming a liquid phase, which is immiscible with the polymer gel and in which the substance to be separated, such as other polymers, is dissolved. The substance is separated from the polymer gel by sedimentation or filtration, using preferably a screen or a split filter with a mesh size of 1e1000 mm. The method requires a low amount of solvent based on the polymer flow rate, is simple to operate and it does not require cleaning of the dissolved polymer at molecular level and also it reduces costs and energy consumption associated with the complex multistage process for the recovery of the solvent and the further treatment of the polymer and the solvent. WO9103515 A1 (1991, RENSSELAER POLYTECH INST) discloses a method for separating polymers from a physically commingled solid mixture containing at least three polymers by selective dissolution comprising: (1) dissolving at least one first polymer of the mixture in a selected solvent at a first temperature to form a first solution and a first remaining solid component that contains at least two polymers of the mixture, which are insoluble in the selected solvent at the first temperature but soluble in the selected solvent at higher temperatures; (2) separating the first solution from the first remaining solid component (e.g., by filtration); (3) separating the at least one first polymer from the selected solvent of the first solution; (4) dissolving at least one second polymer from the first remaining solid component in the selected solvent at a second temperature to form a second solution and a second remaining solid component that contains at least one third polymer of the mixture that is insoluble in the selected solvent at the second temperature but soluble in the selected solvent at a third higher temperature; (5) separating the second solution from the second remaining solid component; separating the at least one second polymer from the selected solvent of the second solution; dissolving at least one third polymer from the second remaining solid component in the selected solvent at the third higher

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temperature to form a third solution; and (6) separating the at least one third polymer from the selected solvent of the third solution. Each of the first, second, and third solutions initially contain a solid concentration of polymer of from 5 to about 20 wt% and dissolve at least two of the polymers in the solvent at a single temperature simultaneously, one of the simultaneously dissolved polymers being present at concentrations of less than about 10 wt% of the other one of the simultaneously dissolved polymers, the simultaneously dissolved polymers forming a single-phase solution. The tested solvents were xylene, tetrahydrofuran, and toluene (see Table 7.5). The method was also tested for multilayer packaging structures. The selective dissolution method will work for bilayer packaging as both polymers will be in contact with the solvent. It will not work, or at least not as well, in multilayer packaging when an inner layer or dispersed phase would normally dissolve at a lower temperature than the outer material. In this case, the entire packaging would dissolve at the higher temperature and a cosolution would result. WO0077082 A1 (2000, LINDNER WOLFGANG) discloses a method for separating postconsumer plastic material using a starting material that consists of a polyolefin fraction or another plastic material mixture. The Table 7.5 Dissolution Temperatures of the Six Major Polymers Used in Packaging and Solvents (1991, WO9103515 A1, RENSSELAER POLYTECH INST) Polymer

Xylene

Tetrahydrofuran

Toluene

LDPE

75

65

50

HDPE

105

160

105

PP

118

160

105

PS

RT

RT

RT

PET

NS

190

NS

PVC

138

RT

NS

NS, Not soluble; RT, Room temperature; LDPE, Low-density polyethylene; HDPE, High-density polyethylene; PET, Poly(ethylene terephthalate); PS, Polystyrene; PVC, Poly(vinyl chloride); THF, Tetrahydrofuran.

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starting material is brought into contact with a solvent, and the temperature of the solution, and preferably also the proportion of solvent to volume of plastic material, is adjusted in such a manner that at least one of the polymer types and preferably several of the polymer types from the plastic material batch dissolve and the solution as a whole has sufficiently low viscosity for the final solideliquid separation. Finally, at least the single dissolved polymer type is sheared and precipitated from the solution to separate the polymer type from all other components in the solution, including the additional types of polymers contained in the solution. To separate each polymer type, the solution passes through one or multiple precipitation steps. Each precipitation step could include several cooling steps to cool the solution to a transportation temperature at which no polymer will be precipitated and finally, to cool the solution in the next or, as the case may be, last, cooling step, to a precipitation temperature at which each specific polymer type is sheared and precipitated. A preferred embodiment of the invention is shown in Fig. 7.4. A mixture of polypropylene, LDPE, linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE) is used as starting material, as shown in step 10. This starting material is put into contact with a solvent, such as petroleum spirits or n-hexane, and is completely dissolved at an elevated temperature, for example, approximately 140  C, as shown in step 12. Instead of petroleum spirits or n- hexane, decalin or xylene could also be used as a solvent. An advantageous value for the adjustment of the polymer concentration in the solvent is about 20%. Finally, the solution is cleaned of undissolved compounds in one or several steps, using filtration, centrifugion, or other mechanical separation techniques, as shown in step 14. In this particular case, when used plastic packaging material is employed, the insoluble compounds are usually inorganic contaminants, undissolved cellulose parts, PVC, PET or polystyrene packaging materials, paper fibers, nonpolyolefin packaging, inorganic filling, and the like. Following this mechanical cleaning step, the solution consists 99% or more of the solvent and the dissolved polyolefin plastic materials polypropylene, HDPE, LDPE, and LLDPE. Each polymer type is precipitated one after the other from the solution using crystallization under simultaneous shearing action to separate each polymer type and to keep waxes, polymer chain fragments, and as many coloring agents and filling materials as possible in the solution. When shearing and precipitating, it must be considered that the choice of solvent to be used and the shearing rate will strongly influence the exact precipitation temperature of each polymer type. It should be noted that the precipitation temperatures for the different polymer types must be

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PP, LDPE, LLDPE, HDPE

10

Dissolving in solvent to give 20% solution

12

Mechanical sepeation of insoluble components

14

Shearing crystallization of the solution at temperature T1 for the precipitation of HDPE

Solid-liquid seperation HDPE/solvent suspension

16

18

20

HDPE degassing in bypass extruder

Shearing crystallization of remaining solution at temperature T2 for the precipitation of PP

22

95% HDPE with PP content of ≤ 3%

Solid-liquid seperation of PP solvent suspension

28

PP degassing in bypass extruder

95% PP with ≤ 3% HDPE content

30

38

95% LDPE

26

Shearing crystallization of the LDPE remaining solution at LLDPE temperature T3 for precipitation Solid-liquid seperation of LDPE/solvent suspension

LDPE degassing in bypass extruder

24

32

34

Solvent processing for the Seperation of waxes. Solvent and additives

40

36

Figure 7.4 Schematic diagram showing a sequence of operations of a preferred embodiment of the invention (2000, WO0077082 A1, LINDNER WOLFGANG).

sufficiently different to ensure definite separation of the different polymer. In the case of the polyolefin fraction consisting of LDPE, HDPE, and polypropylene, a separation method using crystallization and simultaneous shearing provides a better separation of the plastic fractions into each different component than the selective dissolving method from the abovementioned patent WO9103515 A1, as can easily be inferred from Table 7.6. It is clear from the above table that the temperature ranges for dissolving HDPE and polypropylene overlap in the selective dissolving method from WO9103515 A1 (1991, RENSSELAER POLYTECH INST) so that selective dissolving is virtually impossible. However, the precipitation temperatures for the different polymer types HDPE and

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LDPE

HDPE

PP

LDPE

HDPE

PP

Petroleum spirits

70e75

96e103

100e113

67e70

95e100

78e86

Decalin

80e90

115e130

130e140

50e60

90e100

70e80

N-hexane

>100

>100

>100

70e80

100e110

80e110

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Dissolving Temperature in Method according to WO9103515 A1 (1991, RENSSELAER Precipitation Temperature according to POLYTECH INST) WO0077082 A1 (2000, LINDNER WOLFGANG)

AND / OR

Table 7.6 Dissolution and Precipitation Temperatures of Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE), and Polypropylene Used in Packaging (2000, WO0077082 A1, LINDNER WOLFGANG)

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polypropylene in the method from the invention WO0077082 A1 (2000, LINDNER WOLFGANG) differ by approximately 9e10  C, while the precipitation temperatures for polymer types polypropylene and LDPE using the same solvents would show a difference of approximately 8e9  C. EP0543302 A1 (1993, KERSTING JOHANNES) discloses a method for separating aluminum foil from a plastic film, in particular polyethylene film, to enable the recycling of the aluminum. The composite film is placed in a 20% solution of a lower fatty acid CnH2nþ1(COOH), where n4 (e.g., acetic acid, propionic acid, formic acid, butyric acid) and heated at 100  C for 10e20 min. The method is preferably carried out in a closed vessel to operate the liquid at and/or above its boiling point. After cooling, the detached plastic film is separated from the aluminum foil. Cooling preferably takes 3e4 h and is carried out in a tightly sealed vessel in such a way that a reduced pressure, up to 80% of the natural air pressure, is formed on cooling. Used films made of polyethylene are shredded and subjected in a solvent bath containing an organic solvent, under intensive motion, for example, through mechanical stirring, to a frictional surface cleaning, and simultaneously to an extraction without dissolving the plastic material. By the extraction, ingredients added to the foils and PE waxes are separated from the shreds and the printing inks are removed especially through the frictional surface cleaning. Used polyethylene films are shredded and subjected to frictional surface cleaning and simultaneously, without dissolving the plastic, to extraction in a solvent bath containing an organic solvent with intensive movement, for example, by mechanical agitation. The extraction dissolves out added ingredients of the films and PE waxes from the shreds as well as, specifically by the frictional surface cleaning, removs printing inks. Example: 10 g of a multicolor printed polyethyleneepolyamide composite film for cheese packaging was shredded into about 3  3 cm2 large slices of film, placed in a conventional Soxhlet extraction apparatus and extracted with a normal paraffin fraction (paraffin wax) with an initial boiling point of about 180  C. In the extraction sleeve remained 5.5 g of polyamide content including the majority of the printing. The resulting green-colored polyethylene solution was mixed with 0.5 g of bleaching earth and 0.5 g of active coal, stirred for 30 min at 120  C and then filtered at about 100  C. After cooling of the colorless filtrate to room temperature, the precipitated polyethylene was filtered and largely freed from the solvent by vacuum drying at 50  C. The remaining solvent odor in the polyethylene powder was removed by treatment with 50 g of acetone at

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room temperature and subsequent removal of the acetone by vacuum drying at 20  C resulting in an odorless product of pure white color. According to WO2018109147 A2 (2018, SAPERATEC GMBH), the industrial feasibility of the above method is questionable, as the whole waste material in the form of aluminum foil and plastic layers together with the solution has to be heated and cooled for every charging cycle. This can be difficult to implement fast enough with large vessels and requires vast amounts of energy. EP0644230 A1 (1995, VAW VER ALUMINIUM WERKE AG) discloses a method for the extraction of polyolefins, especially polyethylenes, from a composite packaging using organic solvents. The solvents used are cycloalkanes (e.g., cyclohexane), C₉ to C₁₆ n-alkanes and C₁₀-C₂₅ iso-alkanes, or their mixture. After the insoluble components have been separated off, the polyolefin solution and an aqueous surfactant solution are dispersed in one another. The obtained dispersion comprising precipitated polyolefin, an aqueous phase and an organic phase is then separated into its constituents in a manner known per se. At a temperature between 30 and 60 C, a polyolefin concentration of 5e30 wt%, and a surfactant concentration of 0.025 wt%, polyolefin particles of a size of 2e8 mm are obtained. The precipitation of the polyolefin is nearly quantitative, and the particles have a very smooth surface. A further advantage of the method is that the number of washing steps, and also the costs and time expenditure, can be reduced. EP0849312 A1 (1998, PARAFFINWERK WEBAU GMBH) discloses a method for the production of impurity-free, colorless, and odorless polyolefin from polyolefin-containing plastic packaging waste, comprising: (1) extraction of the plastic packaging waste with a hydrocarbon fraction in the petrol or diesel fuel range with a boiling point above 90  C, by heating to a temperature between 90  C and the boiling range of the hydrocarbon; (2) separation of the hot primary polyolefin solution from the extraction residue and treatment of the solution by intensive contact with active earth and/or active carbon and then removing the earth and/or carbon with the adsorbed impurities; and 3) cooling to below 70  C and isolating the crystallized polyolefin. The invention is claimed to be economically feasible on an industrial scale due to its simple procedure and inexpensive feedstocks. WO02100932 A1 (2002, DER GRUENE PUNKT DUALES SYST) discloses a method for the recovery of LDPE from used packaging films comprising the following steps: (1) washing the film material in a first organic solvent, wherein a suspension is formed and printing inks adhering to the surface of the film material are washed off; (2) dissolving

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the film in a second organic solvent and extracting low molecular weight components from the film; (3) dissolving selectively in at least one third organic solvent; (4) precipitating of at least one disruptive polymer from the solution by applying shearing forces to said solution; and (5) recovering the LDPE from the remaining polymer solution. The starting material can be ground film arising from dry or wet treatment. If the ground film arises from dry treatment, the step wherein the film material is washed in a first organic solvent, resulting in a suspension, and printing ink adhering to the surface is washed, is performed at an earlier stage. The organic solvents used for suspension washing, extraction, and selective solution can be the same or different; preferably, the same solvent is used for extraction and selective solution, i.e., commercial hexane. KR100361735 B1 (2002, KOREA IND TECH INST) discloses a method for separating polyethylene, polypropylene, PET, and aluminum from a multilayer packaging film waste comprising the steps of: (1) introducing the multilayer packaging film waste to a reactor and treating it with an organic solvent; (2) separating the different polymers of the multilayer film waste on the basis of their different solubilities in the organic solvent at a temperature range of 60e135  C; (3) adding an alkali aqueous solution or an acid aqueous solution (e.g., HCl, H2SO4 or H2NO3) to the organic solution and dissolving aluminum by heating as needed to obtain a solution; and (4) separating and recovering the polymers and aluminum from the discharged material and the residue in the reactor. The organic solvent is selected from hydrocarbons, halogenated hydrocarbons, esters, and ketones. In an embodiment, a multilayer packaging film made of LDPE, polypropylene, PET, and aluminum is heated at the temperature range of 75e95  C for 30 min in xylene to dissolve LDPE. After the dissolved LDPE passed through a mesh box, the remaining material is heated at the temperature range of 115e135  C for 30 min to dissolve the polypropylene. The undissolved residue consisting of PET and aluminum is treated with an aqueous solution of NaOH for 5 min at room temperature (20  C) to remove the aluminum from the residue; see also EP1683829 A1 (2006, KOREA IND TECH INST). EP3305839 A1 (2018, FRAUNHOFER GES FORSCHUNG) discloses a method for recycling polyolefin containing waste by using a solvent with a specific Hansen parameter and contacting this mixture with a liquid filtration aid before separating the polyolefin from the mixture. The Hansen parameter (dH) is an acknowledged parameter that characterizes the solubility of a compound [7]. The recycling method comprises the following steps:

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1) mixing the polyolefin containing waste with a solvent having a Hansen parameter dH from 0.0 to 3.0 MPa1/2; 2) contacting this mixture with a liquid filtration aid having a Hansen parameter dH > 4.0 MPa1/2; and 3) separating the polyolefin from the mixture. The polyolefin containing waste is selected from the group consisting of Green Dot collection waste, industrial waste, household-waste, bulky waste, and especially postuse flexible multilayer film packaging waste. The solvent is selected from the group consisting of hydrocarbons, preferably aliphatic hydrocarbon, more preferably cycloaliphatic, linear, or branched hydrocarbon, in particular cycloaliphatic, linear, or branched hydrocarbons with 5e18 carbon atoms and mixtures of those. The liquid filtration aid contains at least one fluid with a Hansen parameter dH from 4.0 to 38.0 MPa1/2, preferably from 10.0 to 35.0 MPa1/2, and more preferably from 20.0 to 33.0 MPa1/2 that preferably forms a miscibility gap with the solvent and more preferably shows complete immiscibility with the solvent, in particular at least one fluid selected from the group consisting of mono-/polyhydroxy hydrocarbons with 2e12 carbon atoms, preferably with 3e5 carbon atoms, 3-pentanol, 1,2-propanediol, 1,3propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,2,3propanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, 2-(hydroxymethyl)-1,3propanediol, 1,3,5-pentanetriol, 2,3,4-pentanetriol, 2-(hydroxymethyl)2-methyl-propanediol, 2-propene-1-ol, propene-2-ol, 3-butene-1-ol, 2buten-1-ol, 3-buten-2-ol, 1-butene-2-ol, (E)-2-buten-1-ol, (Z)-2-buten-1ol, 2-methyl-2-propen-1-ol, 2-methyl-prop-1-en-1-ol, cyclopropylcarbinol, cyclobutanol, 1-penten-3-ol, 3-methyl-3-buten-1-ol, (Z)2-penten-1-ol, 3-methyl-2-buten-1-ol, 2-methyl-3-buten-2-ol, (E)-2penten-1-ol, 2-methyl-2-buten-1-ol, 4-penten-1-ol, 3-penten-2-ol, 2penten-1-ol, 4-penten-2-ol, (Z)-2-penten-1-ol, (Z)-3-penten-1-ol, 3methyl-3-buten-2-ol, 3-penten-1-ol, (E)-2-penten-1-ol, (E)- 3-penten-1ol, 2-methyl-3-buten-1-ol, 2-penten-1-ol, pent-2-en-1-ol, 2-methyl-(E)2-butenol, trans-3-penten-2-ol, 1-penten-3-ol, (Z)-pent-3-en-2-ol, (E)pent-3-en-2-ol, prop-1-en-1,2-dimethyl-1-ol, 1-ethylcyclopropanol, 1methylcyclopropane-methanol, cyclopentanol, cyclobutanemethanol, cyclopropylmethylcarbinol, 1,2-cyclopentanediol, and mixtures of those. The aforementioned patent forms the basis for the development by Fraunhofer Institute for Process Engineering and Packaging IVV in collaboration with CreaCycle GmbH of a technology called CreaSolv

246

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Process, which allows the recovery of high-quality plastic recyclates from plastic waste [8]. The technology can be applied to waste plastics from the production of laminates and composites. Unilever implements the CreaSolv Process into its supply chain for the recycling of plastic sachet waste [9]. WO2016209094 A (2016, 23 RS CORAS SP Z O O) discloses a method outlined in Fig. 7.5 for the separation of components from composite packaging materials including polymer film, aluminum, and/or cellulose comprising the following steps: (1) cutting the waste packaging materials into 10  10 cm or smaller pieces; (2) extracting the polymer fraction using xylene or other organic solvents such as benzene, toluene,

Waste loading into the rank reactor Polyethylene flushing using hot xylene

Xylene tank

PE solution seperation

Xylene regeneration

Xylene residues evaporation

Product 1 : Polyethylene

Cooling the mixture down with

Water tank

Mechanical seperation of the mixture using a mixer. Water filtration and drying Pouring carbon tetrachloride and fraction seperation

Carbon tetrachloride tank

Upper fraction filtration

Lower Fraction filtration

Washing aluminium precipitate with water

Washing cellulose precipitate with water

Aluminium drying

Cellulose drying

Product 2: Aluminium

Product 3: Cellulose

Figure 7.5 Flowchart of the method for the separation of components from composite packaging materials (2016, WO2016209094 A, 23 RS CORAS SP Z O O).

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cumene, ethylbenzene, naphthalene, chlorobenzene, dichlorobenzene, and bromotoluene; (3) separating the insoluble ingredients by fragmenting them in an agitator; (4) forming a slurry from the aluminum and cellulose particles, wherein said slurry has a higher density than the cellulose density and lower than the aluminum density; (5) dosing said slurry into a separator, while evaporating the polymer solutions to recover the solvent; and (6) separating the initial polymer component from the processed packaging waste. According to the invention, the used solvents may be recycled, and thanks to correct design of the entire process, maximum heat recuperation and minimization of operation costs is ensured, thus making the method profitable. DSM and APK cooperate on recycling multilayer food packaging films using APK’s NewcyclingÒ process, a solvent-based technique to separate and recover the different polymer types in high-quality regranulates with properties close to virgin polymers (see Fig. 7.6). With conventional recycling systems that is not possible. NewcyclingÒ allows the pelletized recyclates to be used in demanding applications, such as flexible packaging, again. The focus is on polyethylene, polypropylene, and polyamide, but also PET, polystyrene, PLA, and aluminum, could be technically recovered. APK is building a plant in Merseburg (DE) for recycling multilayer polyethylene/polyamide 6 (PE/PA6) packaging waste from postindustrial origin, using the NewcyclingÒ process, which is planned to start up in 2019 [11]. The APK’s technology is based on the following patents: DE102016015198 A1 (2018, APK AG) discloses a solvent (L) and a method of dissolving a plastic (K) present in and/or on a solid (F) within a waste suspension (S) (see Fig. 7.7). The method involves heating or superheating the suspension (S) within a gastight system to a dissolving temperature (T1) within a temperature range of 5  C around the boiling temperature (T2) of the solvent (L). The solvent is selected from a group consisting of alkanes, isooctane, or cycloalkanes, such as methylcyclohexane. Cyclohexanes are particularly suitable for dissolving polyethylene. DE102016015199 A1 (2018, APK AG), which is a modification of the above patent, discloses a solvent (L) and a method of dissolving at least two plastics (K1, K2) present in and/or on a solid (F) within a waste suspension (S) (see Fig. 7.8). The solvent (L) has a temperature-dependent dissolving effect on the two plastics. The suspension (S) is heated in several stages to different dissolving temperatures (T1, T2), wherein in a first stage at a first dissolving temperature (T1), the first plastic (K1) is dissolved, and in a second stage at a second dissolving temperature (T2),

248 R ECYCLING OF

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Figure 7.6 NewcyclingÒ process overview, e.g., for polyethylene/polyamide (PE/PA) [10].

7: S OLVENT-

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249

Figure 7.7 Schematic diagram of the method of a waste separation plant (2018, DE102016015198 A1, APK AG). F, Solid; K, Plastic; L, Solvent; P, Polymer solution (¼K þ L); T, Inert gas; S, Suspension (¼F þ K þ L); T1, Dissolving temperature; T2, Boiling temperature of solvent; 1, Waste separation plant; 2, Dissolving station; 3, Inerting device; 4, Separation station; 5, Inlet; 7, Outlet; 8, Outflow; 9, Sluice; 10, Solvent separation; 11, Outflow; and 12, Return

the second plastic (K2) is dissolved. In the preferred composition, the plastic K1 is polyethylene, and the plastic K2 is polypropylene. The dissolving temperature, T1, is 80e100  C. The dissolving temperature, T2, is 120e180  C. The difference between the dissolving temperature T1 and the dissolving temperature T2 is 20  C. DE102016015197 A1 (2018, APK AG) discloses a centrifuge for separating at least one solid (F) from a waste material suspension (S), the suspension comprising the solid (F), and a polymer solution (P) with at least one solvent (L) and at least one plastic (K) dissolved therein (see Fig. 7.9). The centrifuge has a housing (3) with a rotating insert (4) mounted therein and is characterized by a design of the housing (3), which encompasses the rotating insert (4) such that the suspension (S) can be gas tightly centrifuged inside the housing (3). The housing is provided with an inlet (10) for introducing the suspension and outlets (11, 12) for

250

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OF

F LEXIBLE P LASTIC PACKAGING

Figure 7.8 Schematic diagram of the method of dissolving at least two plastics from a solid within a waste suspension (2018, DE102016015199 A1, APK AG). 1, Waste separation plant; 2, First dissolving station; 3, Separation station; 4, Inlet; 5, Outlet; 6, Second dissolving station; 7, Solid processing; F, Solid; K1, First plastic; K2, Second plastic; L, Solvent; S, Suspension; T1, First dissolving temperature; T2, Second dissolving temperature; ST, Boiling temperature; DT, Temperature difference

discharging the polymer solution (P) and the centrifuged solid (F). The plastic can go into solution within a very short time, while the solids due to their inertia by means of centrifuging of the polymer solution are removed in a controlled manner. The consistency of the polymer solution can be adjusted so that it has the lowest possible viscosity. In this way, unlike its separation by pure heating, the dissolved polymer can be separated without appreciable resistance by the remaining centrifuging material. The gastight construction of the centrifuge enables safe handling even of flammable solvents. WO2016077904 A1 (2016, OLIVEIRA JUAREZ SOUZA DE) discloses a process for the recycling of aluminized and plastic packaging, cartooned or not, by means of an apparatus for extracting and separating the constituents of polyethylene or polypropylene film with aluminum by dissolving the polymer in a compatible primary solvent, at a temperature

7: S OLVENT-

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251

Figure 7.9 Waste separation apparatus with a gastight centrifuge for separating solid from a waste suspension (2018, DE102016015197 A1, APK AG). A, Cross section; F, Solid; K, Centrifuged plastic; L, Solvent; P, Polymer solution; S, Suspension; T, Inert gas; x, Axis of rotation; 1, Waste separation apparatus; 2, Centrifuge; 3, Housing; 4, Rotating insert; 5, Hollow cylindrical surface; 6, Centrifuge compartment; 7, Shaft; 8, Location; 9, Sealing member; 10, Inlet; 11, First outlet; 12, Second outlet; 13, Container; 14, Front opening; 15, First container; 16, Second container; 17, Inserting device; 18, Connecting line; 19, Rear wall; and 20, Through opening

below the polymer softening temperature and under pressure followed by insolubilization via reduction of temperature, separation of the solvent from the polymer, and finally filtration and reuse of the solvent in the step of dissolution. The process comprises at least 11 steps. The dissolving solvent is selected from hexane, kerosene, or mineral oil. In the case of a packaging made only with nonpaper aluminized polymer films containing polypropylene and polyethylene, and if the process is conducted at 100  C, then, only the polyethylene is dissolved, while the polypropylene remains insoluble. Further, the hot solution is filtered and the undissolved solid components, polypropylene and aluminum are washed with petroleum ether and subsequently with ethanol, in an aluminum crusher. The aluminum is crushed leaving the polypropylene in a larger size, thus allowing easy separation by sieve filtration.

252

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References [1] Saperatec. Technologye Principle and Function. Saperatec GmbH. Retrieved October 2, 2019 https://www.saperatec.de/en/technology.html. [2] The Sustainable Packaging Coalition (SPC). GREENBLUEÒ. Mechanical recycling options. 2018. https://sustainablepackaging. org/mechanical-recycling-options/. [3] Yousef S, Mumladze T, Tatariants M, Kri
ukien_e R, Makarevicius V, Bendikiene R, et al. Cleaner and profitable industrial technology for full recovery of metallic and non-metallic fraction of waste pharmaceutical blisters using switchable hydrophilicity solvents. Journal of Cleaner Production 2018;197:379e92. [4] Mumladze T, Yousef S, Tatariants M, Kri
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ut_e S-I, et al. Sustainable approach to recycling of multilayer flexible packaging using switchable hydrophilicity solvents. Green Chemistry 2018;20(15):3604e18. [5] Kaiser K, Schmid M, Schlummer M. Recycling of polymer-based multilayer packaging: a review. Recycling 2017;3(1):1. [6] Mieth A, Hoekstra E, Simoneau C. Guidance for the identification of polymers in multilayer films used in food contact materials: user guide of selected practices to determine the nature of layers; EUR 27816 EN. Joint Research Centre (JRC) Technical Report, JRC100835. European Commission; 2016. https://doi.org/10.2788/10593. [7] Hansen C. Hansen solubility parameters: a user’s handbook. 2nd ed. Boca Raton, FL: CRC Press; 2007. [8] Ma¨urer A. High-quality injection plastic moldings from shredder residues e Poly-Ressource. Fraunhofer IVV. https://www.ivv. fraunhofer.de/en/forschung/verfahrensentwicklung-polymer-recycling/poly-ressource.html; Project term: 1.9.2010 to 30.11.2012. [9] Unilever. Develops new technology to tackle the global issue of plastic sachet waste. May 11, 2017. https://www.unilever.com/news/pressreleases/2017/Unilever-develops-new-technology-to-tackle-theglobal-issue-of-plastic-sachet-waste.html. [10] Wohnig K. APK. From recycling to NewcyclingÒ gpca e PLASTICON - sustainable plastic innovation: closing the loop. March 14e15, 2018. Dubai, UAE. [11] DSM Media Relations. DSM and APK cooperate on recycling multilayer food packaging films. July 24, 2018. https://www.dsm. com/corporate/media/informationcenter-news/2018/07/2018-07-24dsm-and-apk-cooperate-on-recycling-multilayer-food-packagingfilms.html.

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Processo para reciclagem de embalagens flexı`veis multicamadas laminadas. "Process for recycling flexible laminated packaging."

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XU CHAO; ZHANG QIUHUA; CHEN GUANG

XU CHAO; ZHANG QIUHUA; CHEN GUANG

Separating agent for medical waste aluminium-plastic packaging materials and preparation method of separating agent.

CN104744724 A

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DAI XIANGHUI; MU ZHENJIANG

DAI XIANGHUI

Aluminium-plastic separating agent and method for carrying out aluminium-plastic separation by utilizing aluminium-plastic separating agent.

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CN20171180865 20170324

MENG WEIYU; MENG ZIBO; CUI ZIXING

HENAN WANBANG HIGHLYEFFICIENT AGRICULTURAL DEV CO LTD

Aluminum-plastic compound film separation method.

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ZHANG SONGFENG

ANHUI TENGYUE ALUMINUM PLASTIC CO LTD

Waste aluminum and plastic separating and recycling process.

BRPI0921209 A2 20160223; CN102256761 A 20111123; CN102256761 B 20150930; EP2364246 A 20110914; EP2364246 B1 20161109; ES2621228 T3 20170703; US2011266377 A1 20111103; US9469049 B2 20161018; WO2010052016 A2 20100514

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LINDNER WOLFGANG

APK ALUMINIUM UND KUNSTSTOFFE

Verfahren zum Abtrennen einzelner Wertstoffe aus gemischtem, insbesondere zerkleinertem Kunststoffabfall. “Method for separating individual valuable materials from mixed, in particular milled, plastic waste."

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WOHIG KLAUS; KALNA MIKE; FLEIG MICHAEL; JESCHKE JANINE

APK AG

Gasdichte Zentrifuge zur Feststoffabtrennung aus einer Polymerlo¨sung sowie Verfahren zur Feststoffabtrennung aus einer Polymerlo¨sung. "Gas-tight centrifuge for separating solids from a polymer solution and method for separating solids from a polymer solution."

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WOHNIG KLAUS; KAINA MIKE; FLEIG MICHAEL; HANEL HAGEN

APK AG

Lo¨sungsmittel sowie Verfahren zum Lo¨sen eines Kunststoffs von einem Feststoff innerhalb einer Suspension. "Solvent and method of dissolving a plastic from a solid within a suspension."

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WOHNIG KLAUS; KAINA MIKE; FLEIG MICHAEL; HANEL HAGEN

APK AG

Lo¨sungsmittel sowie Verfahren zum Lo¨sen wenigstens zweier Kunststoffe von einem Feststoff innerhalb einer Suspension. "Solvent and method of dissolving at least two plastics from a solid within a suspension."

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LORENZ ARNULF; WALSER HANS PETER

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DE102016015198 A1

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BRAUER JOCHEN; LORENZ ARNULF

NORDENIA VERPACKUNG

Verfahren zur Aufbereitung von insbesondere PolyethylenVerbundfolien, zu wiederverwendbaren Rohstoffen. "Process for the transforming in particular polyethylene composite films into reusable raw materials."

EP0543302 A1

19930526

AT144784 T 19961115; CZ9203394 A3 19930616; DE4137895 C1 19930325; DE4137895 C2 20000210; DK0543302 T3 19970414; EP0543302 A1 19930526; EP0543302 B1 19961030; ES2095385 T3 19970216; PL170192 B1 19961129; PL296612 A1 19930726

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PARAFFINWERK WEBAU GMBH

Verfahren zur Gewinnung von Polyolefinen aus polyolefinhaltigen Kunststof-Ggemischen oder polyolefinhaltigen Abfa¨llen. "Process for recovering polyolefins from polymer compositions or from waste materials." (Continued )

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Method for recycling multi-layered film waste for packing.

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KO BYONG CHUL; KO SUNG CHUN

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FULLANA FONT ANDRES; LOZANO MORCILLO AGUSTIN

UNIV ALICANTE

Procedimiento para la eliminatio´n de tinta impresa en films de pla´stico. "Method for removing ink printed on a plastic films."

(Continued )

(Continued ) Patent Number

Publication Date

Family Members

Priority Numbers

Inventors

Applicants

Title

ES2427019 A1 20131028; ES2427019 B2 20140509; IN2109MUMNP2014 A 20150904; JP2015520684 A 20150723; JP6190446 B2 20170830; KR20150006427 A 20150116; MA20150353 A1 20151030; MA37447 B1 20160531; MX2014011432 A 20150814; MX357125 B 20180627; PE21552014 A1 20150114; PL2832459 T3 20170929; US2015298360 A1 20151022; US9616595 B2 20170411; PT2832459T T 20170713; RU2014142594 A 20160520; RU2630819 C2 20170913; SI2832459T T1 20171030; ZA201407763 B 20160525 WO2014162238 A

20141009

US2016039992 A1 20160211; WO2014162238 A3 20150402

IN2012DEL3342 20130331

JAIN PRANAY

JAIN PRANAY

A process for recycling a metalized polyester film.

WO2015159301 A2

20151022

IN3143MU2013 A 20150703; WO2015159301 A3 20160121

IN2013MUM3143 20131003

PATEL KETAN MAHADEV; VAVIYA MAHESH MAHADEV; PATEL MAHESH HARJI

PATEL KETAN MAHADEV; VAVIYA MAHESH MAHADEV; PATEL MAHESH HARJI

Process for recovering low-density polyethylene from flexible packaging material.

WO2016077904 A1

20160526

AU2015349557 A1 20170706; CA2968244 A1 20160526; CN107001683 A 20170801; EA201700269 A1 20180531; EP3222657 A1 20170927; EP3222657 A4 20180822; KR20170097046 A 20170825; MX2017006613 A 20180126; SG10201806145P A 20180830; SG11201704074R A 20170629; US2017342233 A1 20171130

BR20141028989 20141120; BR20151028864 20151117

OLIVEIRA JUAREZ SOUZA DE

OLIVEIRA JUAREZ SOUZA DE

Process for recycling by separating the constituents of aluminized and plasticized, optionally carton, containers, and respective equipment.

WO2016209094 A1

20161229

PL412820 A1 20170102

PL20150412820 20150623

GRZYBOWSKI PIOTR

23 RS CORAS SP Z OO

Device and method for separation of components of composite packaging materials.

WO2017037260 A1

20170309

CA2998513 A1 20170309; EP3344690 A1 20180711; FR3040704 A1 20170310; JP2018528853 A 20181004; KR20180064377 A 20180614; US2018257267 A1 20180913

FR20150058185 20150903

AYMONIER CYRIL; SLOSTOWSKI CE´DRIC

CENTRE NAT RECH SCIENT

Proce´de´ et dispositif de de´montage de syste`mes multicouches comprenant au moins un composant organique. "Method and device for dismantling multilayer systems including at least one organic component."

WO2017108014 A1

20170629

CZ20150931 A3 20170707; CZ307054 B6 20171220

CZ20150000931 20151222

SOBEK JIRI; POLAK JIRI; HAJEK MILAN

USTAV CHEMICKYCH PROCESU AV CR V VI

Method for separating composite packaging materials.

WO2018109147 A2

20180621

GB2557682 A 20180627; WO2018109147 A3 20180726

GB20160021371 20161215

LOVIS FLORIAN; SCHULZE MARCUS

SAPERATEC GMBH

Method and apparatus for recycling packaging material. (Continued )

(Continued ) Patent Number

Publication Date

WO9103515 A1

WO9304116 A1

Family Members

Priority Numbers

Inventors

Applicants

Title

19910321

AU6420490 A 19910408; BR9007650 A 19920818; CA2065046 A1 19910312; CA2065046 C 20010327; DE69026829 T2 19961121; DE69033888 T2 20021031; EP0491836 A1 19920701; EP0491836 A4 19920826; EP0491836 B1 19960501; EP0664314 A1 19950726; EP0664314 B1 20020102; JP2968998 B2 19991102; JPH05500186 A 19930121; US5198471 A 19930330; US5278282 A 19940111

US19890406087 19890911

NAUMAN E BRUCE; LYNCH JERRY C

RENSSELAER POLYTECH INST

Polymer recycling by selective dissolution.

19930304

AT186314 T 19991115; CA2116217 A1 19930304; DE4127705 A1 19930225; EP0599905 A1 19940608; EP0599905 B1 19991103; ES2141724 T3 20000401; JPH07501348 A 19950209; MX9204850 A 19930401

DE19914127705 19910823

GARTZEN JOHANNES; HEIL GUENTER; MANG THOMAS

SCHERING AG

Verfahren zum Behandeln von miteinander mittels Haftvermittler verbundenen Materialien. "Process for treating materials bonded together by an adhesive agent."

8 Post-processing and Reuse 8.1 Cleaning Plastic packaging film cleaning is an integral part of the plastic film recycling process. Cleaning can run simultaneously with or follow the size reduction and usually involves a succession of cleaning steps to remove solid and liquid waste residues adhering to the film. Cleaning can be carried either in a wet state or in a dry state.

8.1.1 Wet Cleaning The wet cleaning of scrap films is mainly performed with water, optionally in combination with a surfactant. An alternative type of wet cleaning is using solvent (see Chapter 7, Section 7.2). The cleaning with water (washing) performs several tasks, including [1]:
removal of food residues;
removal of dirt, dust, and glass grit the film picks up during processing at a material recovery facility (MRF);
pulping and removal of paper and stripping of plastic labels adhered by water-soluble adhesives;
preliminary separation of polymers that have a higher density (e.g., PET, PLA) from those that have a lower density than water (e.g., polyethylene, polypropylene). Washing plastic film includes size reduction, followed by washing in (heated) water containing detergents and wetting agents, taking place under agitation in a series of containers. Washing is followed by drying of the packaging film. A typical washing line of a scrap film comprises the following steps and/or equipment [2]: 1) Size reduction of the scrap film carried out by a shredder or wet granulator, which also has the effect of washing away some of the dirt. Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00008-6 Copyright © 2020 Elsevier Inc. All rights reserved.

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2) Transport the film through a friction washer/dryer; this is similar to a screw conveyor, which transports the material up the screw, while water is introduced at the top and drains from the bottom. The countercurrent flow of the water further cleans the plastic, while the agitation of the screw loosens any adhered items such as labels and also dries the plastic to a moisture level of about 30e40%. 3) Immerse the scrap film into a tank containing either hot water or (rarely) a hot caustic solution and agitate it. The heat and agitation remove labels from the film and dissolve the glue. This can either be done in batches or continuously. Washing can also remove surfaceprinted inks; washing does not remove inks that are reverse printed on the inside of multilayer bags and pouches [3]. 4) Use of a screw press conveyor to mechanically squeeze more water out, leaving 8e15% moisture, before a hot air or friction drying system is used to reduce the moisture content to below 2e3%, so it is suitable for extrusion. 5) Treatment of the generated wastewater [2]. The main disadvantages of scrap film washing can be summarized as follows: 1) The rate at which scrap film can be conveyed throughout the system, the rate at which the extruder can process, and the volume of wastewater that the attached treatment plant can deal with. 2) The large amount of water needed for the cleaning of scrap film. Some plants use dry cleaning equipment ahead of the wet washing process to remove contamination as much as possible before the material enters the water bath. This reduces the load on the wastewater treatment. 3) The large amount of energy required for drying the washed film. The annual cost (capital and O&M1) of washing and drying is estimated to about $400/ton [3]. 4) Greater capital equipment cost compared with dry cleaning. However, it is estimated that the capital equipment cost and associated labor cost will decrease as film is recycled in larger volume throughput facilities. This means that unlike dry recycling facilities,

1

Operation and Maintenance.

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there are cost advantages to large film washing facilities compared with small ones [3]. Water quality and energy consumption are of paramount importance in plastic film washing. The presence of contaminated or not appropriately filtered and treated water will compromise the quality of the washing process, the floating efficiency, and wear of machine parts. A representative example of wet washing is the Sorema film recycling process, which is considered to be “best practice” for plastic film wet washing [2]. Sorema’s washing lines are equipped with specific in-line systems for water recirculation and filtration (see also Section 8.6). The energy cost required to dry the film on a cost per lb basis is constant, irrespectively of whether larger volumes are processed by bigger facilities. Some film recycling equipment suppliers have designed integrated film recycling lines that do not require separate pieces of equipment for drying, densifying, and extruding film. Such an equipment supplier is Erema that developed an integrated film recycling equipment that can accept film with 12% residual moisture, which the equipment then dries, densifies, and extrudes (energy is still required by this piece of equipment to evaporate the residual moisture) [3]. Flexible multilayer packaging films may either sink or float during washing depending on the relative amounts and densities of the constituting polymers. Washing cannot remove labels that are adhered by waterinsoluble adhesives. Certain polyethylene retail sacks imported from Asia contain more than 10% fillers and would rather sink than float, reducing the total amount of polyethylene film that is washed [1] (see also Section 8.4.1). In the conventional process of washing a discarded flexible plastic packaging composed of wrapping materials covered with organic wastes from food rests, there has been used, for example, an apparatus capable of separating therein the flexible plastic packaging into the wrapping materials and the adherents, washing the wrapping materials, and outputting them in a separate manner. Such an apparatus as disclosed in JP2003320264 A (2003, KANEMIYA KK) has a feed port through which the flexible plastic packaging is loaded; a cylindrical process tank communicated with the feed port and allowing therein separation of the flexible plastic packaging into the wrapping materials and foods; a discharge port and a discharge path, provided to the process tank, through which the adherent and the wrapping materials, after being separated, are respectively discharged; a drive shaft provided in the process tank and rotated by a motor; and a plurality of rotating blades

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having the base ends thereof, respectively fixed on the drive shaft, and having the tip ends located so as to be opposed with the inner circumferential surface of the process tank. In the process tank of this apparatus, there are provided jetting nozzles through which a treatment agent (water, oil, or water/oil mixture) is jetted into the process tank. The treatment agent jetted through the jetting nozzles into the process tank prevents the undesirable kneading of the adherent foods, even if the enclosed foods were raw pasta, such as Japanese wheat pasta (udon) or Japanese rice cake (mochi), and facilitates their discharge. According to US2012160282 A1 (2012, HASEGAWA TOSHIHIRO), the wrapping materials separated by the apparatus of JP2003320264 A had residues of foods remained thereon, so that putrefaction of the residues have often resulted in offensive odor. JP2005058845 A (2005, KANEMIYA KK) discloses an apparatus aiming at solving the aforementioned problems having washing brushes attached to the ends of the rotating blades. The apparatus is configured to fix the washing brushes so that the ends thereof are positioned close to the inner circumferential surface of the process tank and are allowed to be brought into sliding contact with the wrapping materials as the drive shaft rotates. The apparatus is aimed at forcedly separating residues previously adhered on the wrapping materials, making use of washing water jetted through the jetting nozzles and the washing brushes and, thereby, preventing the offensive odor. The apparatus of JP2005058845 A has been suffering from a problem that the offensive odor could not completely be removed even after the adherents were separated from the flexible plastic packaging. This is because the treatment agent jetted through the jetting nozzles is water, oil, or water/oil mixture, having no sterilizing activity, so that the wrapping materials, even visually judged as being clean without any recognizable adherent, may still carry destructive fungi contained in the organic wastes. Accordingly, any efforts of recycling the plastic, previously composing the wrapping materials output from the conventional washing apparatus, after being pelletized for the purpose of recycling them as source materials for new products, have been successful only in a limited range of products due to offensive odor possibly emitted from the new products. The efforts have alternatively resulted in large devaluation of the source plastics to be recycled, due to the offensive odor (2012, US2012160282 A1, HASEGAWA TOSHIHIRO). US2012160282 A1 (2012, HASEGAWA TOSHIHIRO) discloses a washing apparatus aiming at solving the aforementioned odor problem by effectively cleaning and deodorizing deposits attached to flexible

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plastic packaging. The flexible plastic packaging is a film-, sheet-, or baglike product previously used as a wrapping material for foods or as an agricultural material, and it is composed of poly(vinyl chloride) (PVC), PET, or the like. The washing apparatus (1) according to an embodiment shown in Fig. 8.1 includes a feeding port (11) through which the flexible plastic packaging is loaded; a processing tank (31) laid while horizontally aligning the longitudinal axis thereof, having one end thereof communicated with the feeding port (11), having therein a housing space for housing the flexible plastic packaging, and a plurality of openings formed in the bottom surface thereof; a rotating shaft (72) arranged in the processing tank (31) and rotated by a drive motor (21); a plurality of rotating blades (81e84, 86e89) having the base ends thereof respectively fixed on the rotating shaft (72) and the tip ends are positioned inside the processing tank (31); a discharge passage (69) formed at the other end side of the processing tank (31) and through which the washed plastic packaging is discharged; a washing water spraying nozzle (not shown) for spraying washing water to the upstream side in the processing tank (31); and a sterilizing water spraying nozzle (not shown) for spraying sterilizing water to the downstream side in the process tank (31), relative to the position of the washing water jetting nozzle. The washing apparatus (1) is a constituent of a washing facility (110) shown in Fig. 8.2. CN103240809 A (2012, NANTONG INT PLASTIC ENG CO LTD) discloses a plastic film recovery and cleaning apparatus, shown in Fig. 8.3, comprising a tank body (1); a feeding port (2) arranged on the upper portion of the tank body; a water inlet (3) arranged on one side of the tank body (1); a discharge port (4) arranged on the other side of the tank body (1); a drain port (water outlet) (5) arranged at the bottom end of the tank body; a rotating drum (6) arranged inside the tank body (1) and connected with an electric motor (8) through a rotating shaft (7). A plurality of tapered tines (9) are disposed outside the rotating drum (6), a plurality of fins (10) are disposed in the discharge port (4), and a filter screen (11) is disposed at the drain port (5). The apparatus is claimed to be effective in cleaning and easy to use. The apparatus is claimed to have the following disadvantages: (1) because of the limited space inside the tank, the plastic film cannot be completely unfolded, and as the film is light, it will float on the water surface, and a part of the plastic film will be exposed on the water surface, resulting in a smaller contact area between the film and the water; as a result, the plastic film cannot be thoroughly washed; (2) the clean water entering the water inlet and the wastewater generated during the cleaning

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Figure 8.1 Schematic diagram of an apparatus for washing a discarded flexible plastic packaging according to an embodiment of the invention (2012, US2012160282 A1, HASEGAWA TOSHIHIRO). A, Direction line; B, Direction line; 1, Washing apparatus; 2, Six casters; 3, Frame; 3a, Four support columns; 3b, Cross beams; 3d, Base frame of 3; 3p, Upstream-side bearing frame; 3q, Downstream-side bearing frame; 5, Upstream cover; 5a, Top plate; 5c, Side plate; 6, Downstream-side cove; 6a, Top plate of 6; 6e, Downstream-side plate of 6; 11, Feeding port; 21, Drive motor; 21a, Output shaft; 22, Mounting base; 23, Hopper; 23a, Flow path; 25, Motor frame; 31, Processing tank; 32, Open-top process tank body; 33, Feed frame; 34, Rid; 34i, Discharge frame; 48, Opposing gutter; 49, Drain; 56, Funnel; 56a, Main body; 56b, Inclined portion; 57, Reservoir tank; 57a, Four casters; 61e65, Guide ribs; 66, V-pulley; 67, Driven side; V-pulley; 68, Three V-belts; 69, Discharge path; 72, Rotating shaft; 72a, Square portion; 73, Rolling bearing; 74, Rolling bearing; 81e84, Rotating blades; 86e88, Rotating blades; and 91, 93, 96, and 98, Comb-like elements.

process of the plastic film are mixed in the tank body, wherein the plastic film is cleaned by the mixed water. Because the film is confined in the tank body, more wrinkles are formed, the dirt in the mixed water enters the

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Figure 8.2 Schematic diagram of a washing facility equipped with an apparatus for washing a discarded flexible plastic packaging (2012, US2012160282 A1, HASEGAWA TOSHIHIRO). 1, Washing apparatus; 5, Upstream-side cover; 6, Downstream-side cover; 13, Aqueous HClO solution feed pipe (tube); 23, Hopper; 23a, Flow path; 33, Feed frame; 40, Two locking components; 42, Locking component; 42c, Handle bar; 70, Discharge duct; 110, Washing facility; 111, Conveyor unit; 112, Weakly acidic aqueous HClO solution production unit; 114, Feed port; 115, Circulating conveyor belt; and 116, Anti-slipping ribs.

wrinkles, and the dirt cannot be completely taken out during draining, so that the plastic film is not adequately cleaned (2017, CN106738455 A, CHONGQING YAOHONG FOOD CO LTD). CN106738455 A (2017, CHONGQING YAOHONG FOOD CO LTD) discloses a plastic film cleaning and recycling apparatus claiming to overcome the aforementioned problems (see Fig. 8.4). The apparatus comprises a tank body (1) internally provided with a rotating drum (4). An electric motor (3) is arranged below the tank (1). A feeding port (5) is formed at the top of the rotating drum. A rotating shaft (7) is arranged in

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Figure 8.3 Schematic view of a plastic film recycling and cleaning apparatus (2012, CN103240809 A, NANTONG INT PLASTIC ENG CO LTD). 1, Tank body; 2, Feeding port; 3, Water inlet; 4, Discharge port; 5, Drain port; 6, Rotating drum; 7, Rotating shaft; 8, Electric motor; 9, Tapered tines; 10, Fins; and 11, Filter screen. 5

1

4

2 7

6

11

10 8

9

3

Figure 8.4 Schematic view of a plastic film recycling and cleaning apparatus (2017, CN106738455 A, CHONGQING YAOHONG FOOD CO LTD). 1, Tank body; 2, Water inlet; 3, Electric motor; 4, Rotating drum; 5, Feeding port; 6, Tapered tines; 7, Rotating shaft; 8, Drain port; 9, Filter screen; 10, Discharge port; and 11, Fins.

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the rotating drum. The rotating drum is connected with the motor through the rotating shaft. Water inlet holes (not shown) are formed in the two sides of the wall of the rotating drum. Water outlet holes are formed in the bottom of the rotating drum. A drain port (8) is formed in the lower portion of the rotating drum. Further, a plurality of tapered tines are provided on both sides of the inside of the rotaring drum. Tapered tines can tear the plastic film into small pieces for easy cleaning. The apparatus is claimed to have the following advantages: 1) the clean water enters into the rotating drum from the inlet holes, and the impact force of the water in the multidirectional direction of the inlet holes immerses completely the plastic film in the water, and the plastic film does not float on the water surface; 2) as the plastic film is cleaned in the rotating drum, the clean water in the tank and the wastewater after cleaning the plastic film in the rotating drum are separated, and the wastewater flows out from the water outlet hole at the bottom of the rotating drum, thereby improving the cleaning quality. CN106426638 A (2017, SUZHOU DEGRADATION PLASTIC MACHINERY COMPANY) is a modification of the above apparatus; it discloses a waste film cleaning and recycling process comprising the steps of: 1) conveying the waste film into a size reduction device, so that the film is cut to small pieces; 2) conveying the film pieces into a double-screw cleaning machine and cleaning with water at a temperature of 25e35 C for 10e20 min, so that impurities in the film pieces are removed; 3) feeding the cleaned film pieces into a centrifugal dewatering machine, so that moisture is removed from the film pieces; 4) introducing the obtained film pieces into a dryer and discharging the recycled product into a material bin. The disclosed process is claimed to clean the waste film efficiently and rapidly.

8.1.1.1 Friction Washer A friction washer or friction separator is a water high-speed cleaning machine for mixed plastics. The system cleans materials with a high contamination or persistent dirt, for instance, film flakes. BþB (DE) manufactures friction washers, which are optimum combined with hot washers. The friction washer, equipped with a high-speed revolving rotor, conveys the polluted ground material through the housing. A cleaning solution that is constantly refreshed flows in the opposite direction. The rapid rotations allow the contaminants to rub off and break down into small particles. The inner screen tube functions as

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dewatering device and filter for contaminants. B þ B’s friction washer follows the (plastic) hot washer as a rinsing unit in the plastic recycling process [4]. The Neue Herbold (DE) manufactures the friction washers FW Series, shown in Fig. 8.5, which are used to intensively wash plastic materials such as film flakes [5]. The friction washers are mounted on an inclined frame. The material enters at the lower end of the washer with vertical infeed. The special angular flights in conjunction with the high rpm of the shaft transport the material in an inclined direction toward the top of the unit and simultaneously executes the washing phase. Fines, water, and soaked fibrous paper are separated through the perforated screen cage that surrounds the high-speed shaft and allows the separated material to flow down through the friction washer housing to the lower discharge pipe. The device is equipped with water injection nozzles that spray the fresh water

Figure 8.5 The Neue Herbold friction washers FW Series [5]. Courtesy of Neue Herbold.

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or recycled water directly at the screen cage to assist in screen cage cleaning and prevent clogging. In conjunction with the water spray, the friction washer is manufactured with a pneumatically operated mechanical screen cleaner. A high-speed friction washer manufactured by ASG Environmental Science Research and Development Institute (CN) comprises a long, fastrotating shaft (1000 rpm) mounted with many tilted panels or paddles. Surrounding this rotating shaft is a mesh screen tunnel used for dewatering. These are then encased within a rectangular box where water jets and nozzles are mounted and directed at the mesh screen. The entire machine is set at an incline with plastic films being fed into a vertical feeder located on the lower end and cleaned plastic films exiting at the top. The spinning panels constantly hit the film pieces at high speeds causing friction to occur. As the film pieces are rubbing against each other, debris is scrubbed off and thrown at the mesh screen via centrifugal force. Finer particles of dust, dirt, and water exit the chamber at this time. The water jets continuously spray water at the mesh screen reducing clogging and adding water into the friction chamber [6].

8.1.1.2 Drying Drying of the wet film is usually accomplished by first squeezing the water out and, then, evaporating it through direct application of heat, heating through friction, or application of vacuum [1]. Shreds of film tend to trap and sandwich water between the sheets, unlike bottle flakes that are rigid and more easily shed water droplets. This makes drying film harder and more costly than drying rigid plastics [3]. In general, washing and drying, especially of postconsumer flexible plastic packaging, have highenergy demands. There are two generally accepted methods of drying plastic films in a washing line. The first and more common method is via a dewatering machine or horizontal centrifuge accompanied with thermal heaters. The dewatering machine removes excess water via centrifugal force. Dewatering can bring the water content of wet plastic films down to about 20e30%. The rest of the water is removed via a thermal dryer, much like a hair dryer. The second, more economical method, uses a screw press to mechanically squeeze and twist the plastic film. A dewatering screw press has a screw shaft of increasing diameter. The screw shaft is most narrow at the opening where the plastic film first enters via a vertical

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feeder. Surrounding the screw shaft is a thick-walled, constant diameter outer tube lined with tiny holes for water outlet. The common dewatering screw press for plastic film washing lines is 4e6 m long, but can be increased or decreased based on application. As the wet plastic film enters the screw press, the screw shaft slowly rotates moving the plastic film forward. As the screw shaft becomes thicker in diameter, the plastic film becomes more and more compacted against the outer casing wall. The water from the plastic film is squeezed out and discharged via the tiny holes [6]. At the end of the horizontal screw press, the diameter of the screw shaft is only slightly smaller than the inside diameter of the outer casing. It is through this narrow gap that the dried plastic film exits the screw press. A screw press can bring moisture content down to or below 15% [6].

8.1.2 Dry Cleaning In dry cleaning, the scrap film is subject to shearing from high-speed rotating blades within a confined space in the absence of water. Dry cleaning is used for relatively clean monomaterial films. Where levels of contamination are relatively low, dry cleaning can be used as a stand-alone process. Dry cleaning can also be used either upstream or downstream of washing [2]. Dry cleaning can remove 80e90% of contamination [7]. The annual cost (capital and O&M) of dry cleaning is estimated to about $200/ton. The main advantage of dry cleaning is that it eliminates the use of water or chemical agents, and as a result, it does not have the problems associated with drying and wastewater treatment. In addition, there is not a lot of capital equipment required by film recyclers for the dry approach, especially for very clean film, so small-scale facilities can enter the business and be competitive with large-scale facilities. There is not a large economy-of-scale advantage for larger dry film recyclers compared with smaller dry film recyclers [3]. CN201776854 U (2010) and CN101954677 A (2011) of ZHANGJIAGANG LIANGUAN ENVIRONMENTAL PROT TECHNOLOGY CO LTD disclose a cleaning apparatus, which can remove impurities and dust from waste plastic films in a water-free manner (see Fig. 8.6). The water-free cleaning apparatus comprises: a rotary drum (2) and a housing (3), wherein the rotating drum (2) is arranged on a centrifugal separator (1), and the housing (3) is disposed above the rotating drum (2); a feed inlet (4) is arranged at the bottom of the rotating drum (2), the

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Figure 8.6 Schematic diagram of a waste plastic film, water-free cleaning apparatus (2010, CN201776854 U, ZHANGJIAGANG LIANGUAN ENVIRONMENTAL PROT TECHNOLOGY CO LTD). 1, Centrifugal separator; 2, Rotating drum; 3, Housing; 4, Feed inlet; 5, Conical screen; 6, Screen; 7, Vent pipelines; 9, Material outlet hole; 10, Pipeline; 11, Storage bin; 12, Dust suction opening; 13, Waste discharge pipeline; and 14, Waste discharge bin.

rotating drum is provided with a conical screen (5) with a frequently enlarged aperture from bottom to top, a separating space is formed among the screen (5), the housing (3), and the rotating drum (2); a plurality of vent pipelines (7) are disposed on the inner wall of the screen (5) and respectively provided with a plurality of air outlet holes (not shown); a discharge hole arranged on the side wall of the housing (3) is communicated with a storage bin (11) through a pipe; and a dust suction opening (12) is disposed at the top of the housing (3) and communicated with a waste discharge bin (14) through a waste discharge pipeline (13). The water-free cleaning apparatus is claimed to be simple and functional, saving a great amount of water resources, and avoiding secondary pollution after cleaning the waste plastic films. The main disadvantages of dry cleaning are [3]:

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1) Film subject to dry cleaning needs to be clean. Polyethylene film requires careful manual quality control on the front end to remove other polymer films and in some cases perform color sorts. 2) Inks are not removed, so any printing on film results in impurities in and discoloration of the recycled polymer produced from the film. 3) Contaminants, including dirt and tapes, if not removed manually, magnetically, or by air classification, they should be removed, e.g. by screening at the end of the process. Dry cleaning is also used for the removal of shrink full wrap shrink sleeves from PET bottles [8].

8.2 Size Reduction Size reduction is the primary step in the flexible plastic packaging’s recycling process. Shredders and/or wet granulators are the main equipment of choice for reducing the plastic film into small free-flowing pieces. Size reduction performs a number of tasks that facilitate the recycling of plastic films: 1) Breaks up large bales of plastic film. Spinning blades mechanically break the compacted bundles of film apart and unwrap stuck together films. 2) Reduces the danger posed by large strips of plastic film and plastic bags of tangling angle conveyors and rotary-based washing equipment, slowing production and damaging the equipment. 3) Improves the free flow of the film from one recycling process equipment to another [6].

8.2.1 Shredders A shredder is a single-stage, low-speed (3.6e83 rpm), high-torque size reduction machine, which cuts films and high volumes of film feedstock into smaller pieces of about 1- 5 in. A shredder is initially used to cut through entire bales of plastic film into hand-sized pieces. The shredder reduces the volume needed for storage, drops the cost of transportation,

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and facilitates further processing of the flexible plastic packaging waste by generating a stable flow of the incoming waste. Especially for dual-shaft shredder, which has no screen at the outlet, there could be a wide variation in particle size and shape [6]. Flexible plastic film is difficult to tear. The film has the tendency to wrap around the rotor shafts or rotating blades in string fashion and jam the throughput of the shredder causing poor performance or blockage. The tearing, stretching, and jamming also wears and dulls the blades and further reduces cutting or shredding efficiency. In the case of rotating parallel shafts having blades on them, the plastic material drawn between the shafts results in a high-pressure wedging there between, which tends to cause the shafts to spread. The plastic, thus, passes through the machine without cutting. A sufficient build-up of wound up plastic film can cause friction within the machine, excessive heat buildup, and subsequent meltdown of the plastic material. Removal of the melted plastic requires complete shutdown and disassembly of the apparatus (1994, US5285973, ADVANCED ENVIRONMENTAL RECYCLING TECHNOLOGIES). Special shredding machines have been developed to handle plastic film streams. Such machines are equipped with a water-cooled rotor, which keeps frictional heat to a minimum and prevents meltdown. A typical film shredder will reduce the size of the film down to about 40 mm with a feed rate of about 2.5 ton/h [7]. Individual requirements vary greatly according to the type of film to be shredded. Stretch wrap film is easy to process as it tends to ball up and react more like a rigid plastic purging than a film. Because the material sticks to itself so tightly, it does not unravel in the shredder to pose a wrapping risk but simply shreds into chunks. In this case, a standard rotor is all that is required. On the other hand, in cases of self-feeding films, a specially designed film rotor is required. These rotors ensure that every strand or tail is cut before fully wrapping 360 degrees around the rotor. One such rotor forces each strand or film tail into the valley of its corrugated rotor, where a nip cutter ensures it does not wrap more than 180 degrees. By cutting each tail that attempts to wrap the rotor, the self-feeding of the film is minimized, so it will run efficiently and without issue [9]. The primary criterion for the selection of the proper type of rotor for film shredding is the extent to which the film will stretch, rather than break, during the shredding process. If the film does not stretch much before breaking, it should shred without problem. On the other hand, if the film is very difficult to break because it tends to stretch, a specialized rotor designed for this purpose will be required [9].

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The pros and cons of using a shredder for reducing the size of a plastic film can be summarized as follows [6]: Pro 1: Shredders can cut though entire bales of plastic film reducing the amount of manual labor required. Pro 2: Shredders operate at low speeds and are much quieter, produce less dust and fines and have low rate of wear and tear (applies to dualshaft and quad-shaft shredders). Con 1: Shredders are more difficult to maintain; sharpening and replacing blades can be difficult and time consuming. Con 2: The size and shape of film shreds are not optimal; the shreds are not uniform and relatively large. Several apparatuses for and methods of shredding plastic films have been disclosed in the patent literature. US3545686 A (1970, DUPONT) discloses an apparatus, shown in Fig. 8.7, for shredding plastic films (24) comprising a support frame (11), a movable cutting blade (14) having a sawtooth cutting edge rotatably mounted on the frame, a stationary cutting blade (18) having a sawtooth cutting edge (19), wherein the movable cutting blade, and the cutting edge of the stationary cutting blade are separated from each other by a gap of about 1/16 and 1/4 in and interdigitated on rotation of the movable cutting blade (18) to pierce and tear a plastic film (24) advanced across the stationary cutting blade (18). Plastic film (24) fed into the slot is shredded by the interacting blades and carried away by a suction fan connected to an outlet duct (23) in the lower part of the cutting cylinder housing (22). US5257740 A (1993) and WO9407671 A1 (1994) of SPROUT BAUER INC ANDRITZ disclose a method and an apparatus for recycling scrap film, comprising the steps of: 1) wetting the scrap film with a liquid, such as water; 2) removing particulate impurities from the wet scrap film by gravity; 3) washing and shredding the wet scrap film with a washer shredder having a pair of counterrotating, intermeshed rotors; 4) removing particulate impurities including at least one of dirt, metal, wood, glass, heavy plastic, and heavy paper from the washed and shredded scrap film; 5) cutting the scrap film with a rotary knife cutter described in US4738404 A (1988, SPROUT-BAUER, INC); and 6) rinsing the cut scrap film in multistage gravity fed screen sieves using a rinse liquid to remove additional impurities and form a scrap film product stream and a plurality of rinse liquid streams. The apparatus of WO9407671 shown in Fig. 8.8 includes a washer-shredder unit (10) upstream from a film cutter (14) to

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Figure 8.7 Schematic overview of the shredding apparatus (1970, US3545686 A, DU PONT). A, Direction arrow; 10, Upper housing assembly; 11, Frame assembly; 14, Cutting blades; 15, Recessed shoulders of cylinder; 14, Rotating cutting blades; 17, V-shaped teeth; 18, Stationary cutting blade; 19, V-shaped teeth; 20, Laterally extending flange; 21, Entrance slot; 22, Lower housing assembly; 23, Outlet duct; and 24, Film material.

remove impurities from the film before cutting. Before the scrap film enters the washer-shredder unit (10), it is pre-shredded into strips that are about 1-2 in wide by about 6e12 in long. The pre-shredded scrap film is delivered to the washer-shredder unit (10) by a belt conveyor (20). The apparatus includes wetting means for wetting the film with a liquid. The wetting means includes a wetting tank and means for supplying a washing liquid and a surfactant to the wetting tank. The cutter (14) cuts the washed film into 1/8 to 3/8 in pieces to allow further separation of the dirt from the film. Furthermore, violent agitation is provided during the cutting action to loosen fine dirt particles from the film. The cut film is removed from the cutter (14) through line (40) and is conveyed to further film processing units for rinsing. The method and the apparatus substantially reduce conventional problems with the film cutter (14) caused by impurities that customarily are present in unwashed film. The apparatus is claimed to be particularly useful for recycling very thin scrap film. US5285973 A (1994, ADVANCED ENVIRONMENTAL RECYCLING TECHNOLOGIES, INC) discloses a shredder including a shredder housing (12) having an inside, an outside, opposed side walls,

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Figure 8.8 Side view of an apparatus for washing and shredding contaminated scrap film (1994, WO9407671 A1, SPROUT BAUER INC ANDRITZ). 10, Washer-shredder unit; 14, Cutter; 20, Belt conveyor; 26, Wetting-settling zone, 27; Wash water-surfactant inlet line; 28, Wettingsettling tank; 30, 31, Paddle wheel agitators; 32, Washing-shredding zone; 34a, 34b, Pair of interlocking, counterrotating high-speed toothed shredder rotors; 35, Settling zone; 36, Settling tanks; 37, Double dump valves; 38, Down-stream paddle; 40, Remove line; 41, Discharge line; 140, Large blades; 142, Small blades; and 144, Central shaft mounting blades 140 and 142.

and opposed end walls, such that the end walls and side walls are engineered and joined together to maintain tight tolerance within the shredder (see Fig. 8.9). The end walls and side walls define a top inlet opening and a bottom outlet opening. Two parallel, spaced-apart shafts (24, 28) are horizontally aligned with each other and rotationally mounted through the end walls for receiving rotational power. Adjustable speed rotational motors (22, 26) engage each of the shafts for rotating them in counterrotational directions. A plurality of uniform thickness disk-shaped blades is alternatingly positioned with interposed disk-shaped spacers placed there between. The spacers have a thickness slightly thicker than the blades. The blades and spacers are arranged on the shafts and mounted for counterrotation with the shafts in an interdigitated fashion so that the blades on one of the shafts are aligned with the spacers on the other shaft such that the blades pass side-by-side closely spaced with the blades on the counterrotating shafts in a way that close tolerance cutting occurs

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Figure 8.9 Side plan view of a shredder and a hopper (1994, US5285973 A, ADVANCED ENVIRONMENTAL RECYCLING TECHNOLOGIES). 3e3, Section line; 4e4, Section line; 12, Shredder housing; 16, Feed hopper; 18, Hopper mouth; 20, Housing opening; 22, First hydraulic motor; 24, First shaft; 26, Second hydraulic motor; 28, Second shaft; 30, 32, Pump assemblies; 34, First hydraulic input tubing; 36, First outlet tubing; 38, First input flow and pressure sensor; 40, Second input flow and pressure sensor; 42, First outlet sensor; 44, Second outlet sensor; 46, Second hydraulic input tubing; 48, Second outlet tubing; 50, First control system; 51, 52, Control panels; 53, Computer control panel; 54, Second control system; 56, Bearings; 60, First coupler; 68, First parallel end plate; 72, First side of housing 12; 76, Side opening; 82, Removable side plate; 84, 90, Standard threaded fasteners; 92, First top adjuster; 94, Second bottom adjuster; 104, Second spray nozzle; 106, Coolant supply line; and 154, Conveyor.

between the blades. Close spacing between blade teeth edges and the interior sides of casing further facilitates cutting of thin gauge plastic, including plastic film, such as grocery bags, shrink wrap film, and the like. A conveyor (154) or other means for carrying the shredded plastic for further processing may be positioned below the shredder. To maintain the temperature of the blades and the shearing process below the melting temperature of the plastic material, spray nozzles are provided attached ahead of the input opening as, for example, a spray nozzle (104) at one end

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of hopper (16) and are supplied with a coolant supply line (106). Keeping the shredder cool facilitates shredding without melting the shredded pieces along the sheared edges. Also, the coolant mist is preferably water that is adjusted to evaporate completely so that dirt particles may be shaken off of the shredded plastic to facilitate recycling processes. Further, melting that might entrap dirt particles at the shear edges is reduced and avoided. DE29803922 U1 (1998, HOSOKAWA ALPINE AG) discloses an apparatus, shown in Fig. 8.10, for drawing in and feeding strips, films, and plastic bands of different materials into a film shredder comprising a pair of equal diameter, parallel rolls (1, 2) rotating in opposite directions and forming a gap between them (12). Stripper plates (3, 4) located below the rolls on both sides of the gap have internal air channels (5) through which a pressurized gas flows to nozzle openings (6) feeding the gas directly onto the rolls. The pressurized gas prevents film from adhering to the roll surfaces, and efficient use of pressurized gas reduces costs. DE20308945 U1 (2003, PAVEL WILFRIED) discloses a plastic film and scrap film shredder, shown in Fig. 8.11, having upper and lower converging faces with retractable rows of pins for forward movement and light compression of film. A frame forms a conveying channel (30) for films and has on its base (34) a row of pins (36) that move backward and forward along the length of the channel and can be raised above or lowered below the base surface. A second row of pins (52) above the first row

Figure 8.10 Side view of a film shredder (1998, DE29803922 U1, HOSOKAWA ALPINE AG). 1, 2, Pair of equal diameter, parallel rolls; 3, 4, Stripper plates; 5, Internal air channels; 6, Nozzle opening; and 12, Feed gap.

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Figure 8.11 Side view of the shredding apparatus (2003, DE20308945 U1, PAVEL WILFRIED). 10, 12, 14, Longitudinal struts; 18, 22, Vertical connectors; 30, Conveying channel; 32, Collecting groove/channel; 34, Base; 36, Pin row; 38, Supporting bar; 40, 42, Swiveling levers; 44, 46, Slides; 50, Guiding wall; 52, Pin row; 54, Supporting bar; 56, 58, Swiveling levers; 60, 62, Axes; 64, 66, Axes; 68, 70, Slides; 72, Connecting bar; 74, Frame; 76, Knife; 78, Crank mechanism; 80, Motor; and 82, Belt.

and toward the downstream end is raised and lowered by a guiding wall (50) and can also move backward and forward along the channel length. A cutting blade moving across the conveying direction is located at the downstream end. The rows of pins (36, 52) are mounted on common bars (38, 54) each of which is supported on two parallel swiveling levers (40, 42, 56, 58) that raise and lower the bars relative to the base (34). The parallel levers are mounted on two parallel slides (44, 46, 68, 70) that move backward and forward on the frame. Downward inclination of the upper guiding wall (50) in the film conveying direction may be varied by a swiveling action. The shredder is used, in particular, for shredding and recycling of plastic films or scrap film, in particular protective film covers for clothing or packaging films. A compacted block of film is created

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quickly using low energy levels, and the resulting small cut pieces are less prone to holding air pockets. CN103240811 A (2013, NANTONG INT PLASTIC ENG CO LTD) discloses an apparatus for cleaning and recovering scrap film shown in Fig. 8.12 comprising a recycling tank (1) with a feeding port (2) that is equipped with cutting blades (3), a first cyclone separator (4), and a discharge pipe (5). A side wall of the recycling tank (1) is connected with a suction pipe (6) that is provided with a suction blower fan (7). The suction pipe (6) is connected with a shredding chamber (8). The upper part of the shredding chamber is provided with a shredder (9); the lower part of the shredding chamber (8) is provided with a second cyclone separator (10); and the bottom part of the shredding chamber (8) is connected with the discharging pipe (11). The apparatus is claimed to have the following advantages: 1) better film recovery; 2) high degree of automation and high efficiency; 3) reduced labor intensity; 4) low manufacturing cost; and

Figure 8.12 Apparatus for cleaning and recovering scrap film (2013, CN103240811 A, NANTONG INT PLASTIC ENG CO LTD). 1, Recycling tank; 2, Feeding port; 3, Cutting blades; 4, First cyclone separator; 5, Discharge pipe; 6, Suction pipe; 7, Suction blower fan; 8, Shredding chamber; 9, Shredder; 10, Second cyclone separator; 11, Discharge pipe; 12, Collecting bin; and 13, Valve.

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5) small floor area. Further, the apparatus can work continuously, is stable and reliable, simple in operation, and convenient to use. _ PL406201 A1 (2015, KUTA PAWEq; KUTA LESZEK; ZMIJEWSKI TOMASZ; MAJCHER MONIKA) discloses a method and an apparatus for washing and shredding plastic packaging films. The apparatus has a shredder and a flotation bath that are fixed with a dynamic pressure washer, i.e., a washer tandem. The film is shredded to a size of 100 mm and then is washed in the floatation bath for the removal of impurities. After washing, the film is shredded again to a size of 40 mm. EP3059061 A1 (2016, MONDI CONSUMER PACKAGING TECHNOLOGIES GMBH) discloses a method for recycling a flexible pouch, comprising the steps of: providing a pouch, as shown in Fig. 8.13A, with a pouch body (1) formed by a pouch wall, wherein the first surface of the pouch wall is formed of a transparent outer film (2) made of PET and the second surface of the pouch wall is formed of a nonperforated inner film (not shown) made of polyethylene or polypropylene, and a visible pressure layer (4) is arranged between the outer film (2) and the inner film through the transparent outer film (2), wherein the inner film and the outer film (2) are connected to each other only at the side edges of the pouch body (5); shredding the pouch, as shown in Fig. 8.13B, wherein at the noninterconnected first pouch wall sections of the outer film and the inner film separated particles (Pi, Pa) are formed; and forming at least a first sorted fraction of particles (Pi, Pa), which are recycled. The recycled particles are used to make new pouches (see Section 8.7). Representative commercial shredders for flexible plastic packaging waste are: - Bollegraaf’s shredders [10]. - Vecoplan’s plastic film and fiber shredders, e.g., RG42K-XL F based on patented SureCut shredding system that delivers built-in two-stage auxiliary size reduction in a single pass [11] (2012, US2012325950 A1, VECOPLAN LLC); and - Prosino plastic film shredders [12].

8.2.2 Granulators Hand-sized pieces of plastic film obtained by a shredder are fed into a granulator, where they are further reduced in size. A plastic granulator (also known as crusher or grinder), unlike a shredder, operates at much higher speeds, around 200e800 rpm, at relatively low torque. A typical

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Figure 8.13 Schematic diagram of the method (B) for recycling plastic from a film packaging pouch (A) with a shredder (2016, EP3059061 A1, MONDI CONSUMER PACKAGING TECHNOLOGIES GMBH). 1, Bag body; 2, Transparent outer film; 4, Visible pressure layer; 5, Side edges; 10, Shredder; and Pa, Pi, Separated particles.

plastic granulator is exemplified by rotating cutting blades housed in a chamber enclosure. Heavy duty knives are mounted at an adjustable angle on an open, hollow rotor in various arrays. When the blades on the fast spinning rotor contact the stationary blades on the granulator housing, the feed stock is cut into relatively fine flakes or regrinds. At the bottom or surrounding the spinning rotor is a sizing screen, a metal screen with holes of about 6e12 mm. A granulator can repeatedly reduce the size of the scrap film until it passes through the holes of the sizing screen, and it is considered the most suitable equipment to produce uniform granules consistently. Although plastic granulators are able to produce smaller sized outputs, the fast rotating parts are noisy and produce high amounts of dust or fines.

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For the purpose of washing plastic films, wet granulators are used. In wet granulators, a constant stream of water is sprayed into the cutting chamber. This setup accomplishes size reduction, and at the same time, it cleans dirty films before they reach another set of washing equipment. The added water also acts as a lubricant for the rotating blades to reduce generated heat and friction. A high-speed friction washer is usually placed after a wet granulator [6] (see Section 8.1.1.1). A wet granulator chamber includes a water spray composed of a plurality of nozzles mounted in the chamber and oriented to direct the spray onto the cutting blades during comminution. However, oftentimes, significant amounts of solid and liquid contaminants are not removed by the clean water spray, and, thus, the flakes that are produced by the granulator are not clean enough for use in an extruder. To remove a sufficient amount of the solid and liquid contaminants from the plastic flakes for such usage, the prior art processes typically employ several repetitive steps of washing and rinsing the flakes with clean water following granulation. If the number of times the flakes are required to be washed and rinsed during the recycling process could be reduced while nonetheless yielding a sufficiently clean flake for end-use requirements, the recycling process would require less clean water and otherwise be more resource-conserving and efficient. RU2116196 C1 (1998, PANOV ALEKSANDR KONSTANTINOVIC; BIKTIMIROV FARIT VAGIZOVICH; PETROV PAVEL IVANOVICH; IBRAKOV MINNULA SHAJAKHMETOVIC; SHULAEV NIKOLAJ SERGEEVICH; BELOBORODOVA TAT JANA GENNAD E) discloses a grinder for the disintegration of films, sacs, plastic bands, cords, and plastic bundles. The grinding apparatus, shown in Fig. 8.14, comprises a housing (1), a rotor with a set of large (2), with a diameter of 300 mm, and small diameter (3) disc cutters, with a diameter of 285 mm (with teeth similar to a circular saw), mounted on a shaft (4) and fixed with a key (5). A stationary cutter (blade) (6) with a total length of 400 mm is fixed to the housing with a screw (7). The grinding apparatus operates as follows: The plastic waste is fed to the receiving hopper (15). Foreign metallic debris are removed by magnetic traps (16), and the plastic waste is captured by the protrusions of the rollers (10). The protrusions and recesses of the rollers have a special profile (13) to compact the plastic waste and form a web (rather than cut) convenient for grinding with disc cutters. The formed web is then sent to a connecting tube (14) and into the rotor rotation zone, where it is cut to pieces, which then fall through a grid (8), and sucked off by a blower. Pieces of a film with a size of 6.5  7.5 mm

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Figure 8.14 Side view of a grinding apparatus (1998, RU2116196 C1, PANOV ALEKSANDR KONSTANTINOVIC; BIKTIMIROV FARIT VAGIZOVICH; PETROV PAVEL IVANOVICH; IBRAKOV MINNULA SHAJAKHMETOVIC; SHULAEV NIKOLAJ SERGEEVICH; BELOBORODOVA TAT JANA GENNAD E). 1, Housing; 2, Large diameter disc cutter; 3, Small diameter disc cutters; 4, Shaft; 5, Key; 6, Stationary cutter (blade); 7, Screw; 8, Grid; 9, Housing; 10, Rollers; 11, Rods; 12, Springs; 13, Roller’s special profile of protrusions and recesses; 14, Connecting tube; 15, Hopper; and 16, Magnetic trap.

were obtained, which were then passed through an extruder to be converted into pellets. PL414258 A1 (2017, POLIMER COMPOMAX PRZED´ W KOMPOZYTOSIE˛BIORSTWO PRODUKCJI PREFABRYKATO ´ WYCH SPOqKA Z OGRANIC) discloses a method for the recycling of polyolefins, in particular, LDPE packaging films, from municipal waste. The packaging films are separated from municipal waste on the basis of thickness and color and cut into pieces whose longest side is less than 5 mm, preferably 2 mm, more preferably 1 mm; further, the film pieces, depending on their purpose, are washed with water by adding 1-4 wt% detergent and dried in the open air or at 40e70 C, preferably at 50 C. The cleaned film pieces are subject to granulation to obtain granules with a size 0.5e2 mm.

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The pros and cons of using a granulator in plastic film size reduction can be summarized as follows [6]: Pro 1: Plastic film cut using a granulator is optimum; the cut pieces are relatively uniform and small. Pro 2: Granulators are easy to maintain; blades can be easily mounted and taken out for sharpening. Con 1: Granulators cannot take whole film bales; instead, baled films must first be manually loosened and feed into the machine piece by piece. A “bale opener” or “debaler” machine can be added to washing lines to automate this process. Con 2: Granulators have much higher wear and tear because they operate in high speeds. Operators must be careful about accidently putting hard objects such as metals (nuts and bolts) into the cutting chamber as this will easily damage the blades. The fast-spinning blades may also propel these hard objects causing potential hazards in the working environment. Con 3: Wet granulator partially cleans and “pretreats” the plastic film.

8.2.2.1 Cryogenic Systems Cryogenic recycling can be used to separate an embrittled polymer from a more ductile polymer. Cooling can also embrittle the adhesive used in a multilayer plastic packaging. Separation of foils from polymer coatings is especially aided by cryogenics [13]. Many conventional cryogenic recycling processes and apparatuses require the use of liquid nitrogen or solid carbon dioxide to lower the temperature of the material to be recycled to a point where a subsequent impact or cutting produces a powder or granular material. These cryogenic processes are expensive to implement and operate due to the need for a large plant to produce the liquid nitrogen or solid carbon dioxide and the cost of energy required to operate the system.

8.3 Agglomeration Scrap films cannot be ground up at all or only unsatisfactorily. In many cases, the films are thinner than the grinding gap between the grinding discs such that they pass through the grinder without being frayed. Only

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compacting of the two-dimensional scrap films into a three-dimensional agglomerate enables a satisfactory grinding process. A proven technology for this is the agglomeration by agitation using a pan agglomerator, which leads to the increase in a transport-optimal apparent bulk density in the form of a granular agglomerate. However, other methods for compacting scrap film into an agglomerate are also available. Thus, for example, a targeted heating, which does not exceed the melting point of the carrier film (sintering), leads to a shrinking of the flakes, which in the process are compacted into an agglomerate on their own, moved in a drum, or passed through in a discharge chute by hot air (2006, WO2006100044 A1, CVP CLEAN VALUE PLASTICS GMBH). During the heat treatment required for the agglomeration, the thermoplastics must not be thermally damaged, i.e., they must not be heated above their typespecific melting point as, when this is exceeded, they decompose chemically with release of gases, which are harmful in most cases and cause the scrap film to become useless for technological reutilization. Such an agglomeration of plastic particles is effected in the agglomerator known DE2614730 A1 (1977, PALLMANN WILHELM); it refers to a polyethylene and polypropylene film disintegrator in such a way that the plastic particles fed into the disk-shaped annular chamber are gripped therein by the rotating pressing blades and are drawn into the plasticizing chambers that are formed by the inside wall of the annular perforated die and the active flank of the pressing blades and revolve with the latter. In the plasticizing chambers, the voluminous mass of particles is first precompacted with simultaneous venting and then plasticized within fractions of a second by the frictional heat caused by the pressing blades. Because of the shape of the blades, the plasticizing chambers in front of the rotating blades steadily narrow, and the mass is also intensively subjected to increasing thrust forces and shear forces. However, the thermoplastic mass softened in this way can then not escape through the perforated die until the pressure exerted on them by the pressing blades is sufficient to overcome the flow resistance in the die holes. When pressed through the perforated die, the thermoplastic particles, which have become tacky due to softening, are formed into compact extrudates or filaments that are cut up immediately after their emergence from the die by knives rotating on the outside wall thereof, into uniform lengths whereby uniform free-flowing granules are obtained. US3510067 A (1970, BECK ERICH; SCHULZ HEINRICH) discloses a method and an apparatus for converting scrap film, particularly from polyethylene films, to a flowable granular material by comminuting the scrap film into small particles and thereafter densifying and agglomerating

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Figure 8.15 Side view of the agglomerating apparatus being taken along the line II-II (1972, US3510067 A, BECK ERICH; SCHULZ HEINRICH). a4b, double-headed vertical direction arrow; c4d, double-headed horizontal direction arrow; 1, Frame structure; 2, Drive motor; 3, Hub; 4, Beater members; 5, Beater ledges; 6, Clamping plates; 7, Clamping plate; 8, Plates; 9, Outlet; 10, Cover; 11, Inlet opening of 10; 12, Bottom of the container; 13, Cylindrical container; 14, Sealing plate; 15, Nozzles; 16, Duct; 17, Thermometer; and 18, Flap.

the particles to produce granules. The apparatus, shown in Fig. 8.15, comprises a substantially cylindrical container (13) having a vertical axis (a4b) and forming a processing chamber for receiving a batch of scrap film to be converted and the container having an inlet (11) for the scrap film and an outlet (9) for discharging the resulting granular material; beater members (4) disposed in the bottom portion (12) of the container

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chamber and rotatable about the axis, the beater members comprising radial beater arms axially displaceable relative to the container, and radially adjustable beater ledges (5) mounted on the respective arms; fixed comminuting members in the shape of plates, blades, or pins (8) mounted on the container and protruding inwardly into the chamber into proximity of the rotatable beater members for comminuting and granulating the scrap film in coaction with the beater members; and coolant supply means communicating with the chamber for cooling the granulated material. Example: An apparatus was used having a cylindrical container of 1.1 m diameter and a height of 1.5 m. The beater arms extended into the immediate vicinity of the fixed comminuting plates. A quantity of 60 kg polyethylene scrap film was filled into the container. The comminution by tearing of the scrap film between beater arms and plates was effected at a peripheral speed of about 70 m/sec within about 4 min. The beater rotor was continued to be driven for an additional period of about 3 min during which most of the mechanical power supplied was converted into heat with the result that the scrap film was densified and agglomerated. During such continued running of the beater arms, about 1.5 L water of 20 C was injected for a short interval of time. After one additional minute, the solidified and cooled granular mass was discharged and was found to have no tendency to stick together. DE1454877 B1 (1972, ULTREX CHEMIE GMBH) discloses an apparatus for the continuous granulation of flakes of scrap films. Scrap films of polypropylene or PVC are fed into the apparatus, shown in Fig. 8.16, consisting of a cutting mill (1) with a feeding equipment, a blower (7) with a feed pipeline (9), an air separator (27) and an agglomerating installation with a screw feeding device (2) manufactured according to DE1454875 A1 (1969, ULTREX CHEMIE GMBH). The agglomerating plant is connected to a free granules discharge outlet (29) by a suction return pipe (90 ), so that the granules can be separated from nongranular remnants, which are sucked back to the agglomerating installation. Variations of the apparatus can be found in CA793191 A (1968) and DE1454873 A1 (1970) of ULTREX CHEMIE GMBH.

8.4 Density/Gravity Techniques Separation of different plastic materials can be performed by density/ gravity sorting with a range of different technologies. The most commonly used density sorting technologies for the separation of flexible plastic

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Figure 8.16 Apparatus for the continuous compressing of thermoplastic films into granules (1972, DE1454877 B1, ULTREX CHEMIE GMBH). 1, Cutting mill; 2, Agglomerator; 7, Blower; 9, Feed pipeline; 90 , Suction return pipeline; 12, Feed hopper; 20, Feed pipeline; 27, Air separator; 29, Granules discharge outlet; and 30, Storage bin.

packaging materials are float-sink, air sifting (see Chapter 6, Section 6.1.2), and to a lesser extent, hydrocyclones and centrifuge. Separation of different plastic phases or fractions is more difficult for mixed plastic waste because in addition to a multitude of different plastic types also composite materials and varying impurities exist in that waste. Systems for separating plastic mixtures include several float-sink stages and/or hydrocyclone stages that are successively connected. This leads to higher consumption of water and energy, whereby the losses of valuable plastic increase with each stage. Density sorting techniques are not successful for the separation of multilayer plastic packaging materials due to the complexity of these structures.

8.4.1 Float-Sink In the float-sink separation technique, pieces of plastic packaging shredded to predetermined sizes are immersed in a tank containing a liquid that has a density in between the constituting materials making it possible for less dense material to float and heavier to sink. Such facilities,

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Table 8.1 Densities of Common Polymers and Aluminum Used in Flexible Packaging Polymers

Density (g/cm3)

Polypropylene (isotactic)

0.900e0.905

Low-density polyethylene (LDPE)

0.916e0.930

Linear low-density polyethylene (LLDPE)

0.915e0.934

Medium-density polyethylene (MDPE)

0.926e0.940

High-density polyethylene (HDPE)

0.941e0.970

Water

1.000

Nylons

1.020e1.140

Poly(vinyl chloride) (PVC)

1.290e1.440

Poly(ethylene terephthalate) (PET)

1.380e1.390

Aluminum

2.690e2.713

referred to as float-sink tanks, can separate, for example, PET, nylon, or PVC majority films with a density greater than 1.000 g/cm3 from standard polyolefins (see Table 8.1). Typically, the density ranges of selective polyolefins are 0.900e0.905 g/cm3 for polypropylene, 0.916e0.930 g/ cm3 for low-density polyethylene (LDPE), and 0.941e0.970 g/cm3; for high-density polyethylene (HDPE). In contrast, the density of the aluminum foils normally used in the packaging industry ranges from 2.690 to 2.713 g/cm3 (1993, US5246116 A, REYNOLDS METALS CO). Float-sink tanks are critical separation tools used by film recyclers, who use a wet wash process [14]. The separation of multilayer plastic packaging materials by the floatsink technique gives often erroneous results for the following reasons: The effective density of a multilayer piece (e.g., flake or chip) depends on the ratio and the types of polymer used in a multilayer packaging material. A polyethylene, which is the main constituent of most flexible plastic packaging, is typically mixed with a number of additives and fillers, which increase the overall density of the film. When the additive/filler concentration reaches the point that the film density is greater than 1.000 g/cm3,

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the film sinks in water rendering the packaging film nonrecyclable. Further, if air bubbles are attached to a surface of the PET layer with a density of 1.380 g/cm3, or if the PET layer is positioned on a plurality of polypropylene or polyethylene (0.900e0.970 g/cm3) films, it will float on water. If a polyolefin layer is positioned under a plurality of PET layers, it will sink in water. These mistakes can be reduced through the addition of a surfactant or through the repetition of the separation process using the specific gravity differences [15]. The separation of labels and shrink wrap sleeves from PET containers is typically achieved in float-sink tanks as part of the overall PET recycling (see Chapter 4, Section 4.2.5). DE102008056311 A1 (2010, APK ALUMINUM UND KUNSTSTOFFE) discloses a method and an installation for separating individual valuable materials from mixed, in particular milled, plastic waste, comprising films, multilayer films and hard plastic parts, and optionally impurities. The method, outlined in Fig. 8.17, comprises the following basis steps: 1) plastic waste is separated into hard plastics and films as well as laminates; 2) the hard plastics are separated from the films; and 3) the hard plastics are separated into the different types of plastic. The hard plastics and films on the one hand and the laminated films on the other hand are separated by means of float-sink separation, and, for this purpose, the optimum density of the separation medium is adjusted by means of a measured density distribution curve of one or more fractions selected from the group consisting of the hard plastics and films and the laminated films. The films predominantly comprise LDPE, the multilayer films comprise aluminum foil and LDPE film, and the hard plastics from the lips and closure caps of drink carton rejects comprise HDPE and to a lesser extent polypropylene.

8.4.2 Hydrocyclones Hydrocyclones can also be used for plastic film washing and separation. They serve the same purpose as float-sink tanks, where pieces of plastic films are separated from heavier contaminants, however, in a more efficient manner with a much higher separation effect, about 20 times earth’s gravity. A hydrocyclone utilizes a centrifugal force to separate pieces of plastic film according to size, shape, and gravity (specific weight). The plastic waste is fed into the hydrocyclone in a suspension. Pressure jets excel the water mixture of films and contaminants within a cylindrical apparatus. The cyclone generated pushes the lighter plastic films outward and upward, while heavier contaminants move inward and downward to the bottom of the hydrocyclone. The hydrocyclone’s sensitivity and selectivity can be adjusted by choosing the nozzle sizes of the exiting outlets at both the top and the bottom.

(A)

1

from first part (a) 4

grinding mill

3

19

wet purification

20

determination of seperation density

21

sink-or-float seperation

air sifting 4

5

LPDE and AI/PE

9

hard plastics

8

6

impurities

sink-or-float seperation

10

7

22

LDPE

AI/PE

24

drying

solvent treatment

25

agglomeration

26

extruslon

seperation of hydrocarbons

38

end product

degassing and extrusion of PE

39

23

28

29 PP

HDPE

12

drying

drying

14

15

granulation

granulation

16

17

end product

end product

18

27

end product

Fig. 3

40

Figure 8.17 First part (A) and second part (B) of the flow diagram of the method for separation of individual materials from plastic waste comprising films, multilayer films, and hard plastics (2010, DE102008056311 A1, APK ALUMINUM UND KUNSTSTOFFE). Al, Aluminum; HDPE, High-density polyethylene; LDPE, Low-density polyethylene; PE, Polyethylene; and PP, Polypropylene.

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impurity seperation

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2

(B)

plastic waste

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Heavier plastic components can be separated from the polyolefin, which is the desired material of a film washing line. A further advantage of the hydrocyclone separation step is the high amount of water present in the water circuit, ensuring together with the revolving forces arising due to the hydrocyclone a very good washing result of the films. Deposits of organic substances, a frequent feature of film from household waste, are easily removed by washing. In contrast, films from supermarkets often have a high percentage of paper in the form of affixed labels. It is a real challenge to separate this paper from the film as these linear low-density polyethylene (LLDPE) films from supermarkets are ideal as feeding material for recyclate used for the production of new film. DE2900666 A1 (1980, BAHR ALBERT) discloses a method for the separation of mixed plastic waste composed of polymers of different densities (e.g., a mixture of granulates of polyethylene, polystyrene, and films of plasticized PVC) by reducing their size to a maximum 20 mm (preferably 5 mm long), washing, and suspending the polymers in a liquid. Successive hydrocyclones are arranged in stages, with upper cylindrical parts through which the suspended materials are dropped; the ratio of the diameter of the overflow/underflow outlets is 1e4 (preferably 1e2.5) and the ratio of the length/diameter of the top cylindrical part is 1e10 but increases with decrease in difference in density between the polymers and liquid. If the polymer’s density exceeds that of the liquid, and if they are mainly plastic films, the angle of the cyclone cone is 120e180 degrees; if the density of the polymers is only partly above that of the liquid, this angle is 5e40 degrees. According to EP0791396 A2 (1997, DEUTZ AG), a disadvantage of the above method is the unsatisfactory separation effect, which leads to loss of solid material. Also, the required separation of the liquid from the solid matter fraction suspensions must be implemented downstream. These disadvantages are largely avoided in the separating centrifuge disclosed in EP0553793 A2 (1993, KLOECKNER HUMBOLDT DEUTZ AG), in which the separation ensues in the generated centrifugal field of a rotating container. EP0791396 A2 (1997, DEUTZ AG) discloses a method for the separation of mixed plastic waste containing heavy contaminants, e.g., sand or metal residues, according to their density, wherein some of the heavy impurities are separated off in a hydrocyclone (15), and the plastic mixture (e.g., polyethylene and PVC films) is separated from the rotating suspension in a following sorting centrifuge (20). The method apparatus, shown in Fig. 8.18, comprises a mixing vessel (10) for combining the solids (12) and a separating liquid (11), connected via a pump (24) to

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Figure 8.18 Flow diagram with direct successive connection of the hydrocyclone and the separating centrifuge (1997, DE19606415 A1, DEUTZ AG). 10, Mixing vessel; 11, Separating liquid; 12, Solid materials; 14, Inlet; 15, Hydrocyclone; 16, Overflow; 17, Underflow,; 18, Heavy goods; 19, Light goods; 20, Sorting centrifuge; 24, Conveyor pump; 26, Mixing apparatus; 27, Sluice; and 28, Line.

a hydrocyclone (15) and a sorting centrifuge (20) whose feed (14) is connected to the overflow (16) from the hydrocyclone. Wear on components of the separating centrifuge caused by these heavy materials can be avoided, and in some applications, a second separating stage at a higher separation density can be eliminated. Herbold Meckesheim GmbH assists its customers retrofit their film washing lines by introducing a hydrocyclone separation step in place of the common separation tank [16]. The new step improves the quality of film flakes extrusion. Herbold Meckesheim GmbH has installed a model line for Rodepa Plastics B.V. in the Netherlands that was launched at the beginning of 2018. High-quality granulate for film thicknesses lower than

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30 mm is produced from a mixture of plastic waste. This mixture consists of commercial films and LDPE film waste from sorting postconsumer packaging waste as is the case with automatic waste sorting plants [16]. This plant can cope with highly contaminated films as well as with very thin gauge films. The wet shredder integrated into the washing plant and the hydrocyclone separation technology are the outstanding construction features of Herbold Meckesheim GmbH (see Fig. 8.19). To separate the contamination from the film, in the washing line as early as the presize reduction step, a wet shredder especially designed for this purpose is used with Rodepa Plastics B.V. The feeding materials consist of a mixture of different plastics.

8.5 Extrusion The recycling of plastic films involves grinding of the films and transforming the ground material either by an agglomeration treatment in the pasty state or by twin-screw vacuum extrusion. Sometimes the ground material is obtained with equipment operating on the “Vacurema” principle (extrusion from flakes, agglomerates, or granules) using four stages of transformation integrated in the same machine: 1) compacting, sending the pasty product to the feed orifice of the screw extruder;

Figure 8.19 Hydrocyclone and dryer, in the background a prewashing unit [16]. Courtesy of Herbold Meckesheim GmbH.

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2) transport and start of extrusion in a double-diameter single-screw extruder; 3) degassing; and 4) extrusion. WO2010118447 A1 (2010, EREMA) discloses a method for recycling plastics comprising the following processing steps: 1) reprocessing the raw material whereby the material is comminuted, if necessary, and brought to a fluid form and then heated and permanently mixed while retaining its particulate and flowable form and, if need, be degassed, softened, dried, increased in viscosity, and/or crystallized; 2) melting the reprocessed material at least to a point where filtration is possible; 3) filtering the melt to remove impurities; 4) homogenizing the filtered melt; 5) degassing the homogenized melt; and 6) discharging and/or subsequently processing the melt, for example, by granulation or blow-extrusion treatment,whereby these processing steps are implemented consecutively and directly in chronological and spatial order without intermediate steps. It was found to be particularly advantageous when the homogenization step is carried out after filtration, but before the degassing of the melt, as in that manner, homogenization is not negatively affected by any coarse contaminants or solid impurities or nonmolten plastic clusters, while at the same time the subsequent degassing can be carried out effectively, whereby the gas bubbles can be removed completely from the melt. In that manner, a final product of high quality can be achieved, which can be used for many different subsequent processing applications. Contaminated packaging films that were printed or had adhesive labels were processed in comparative experiments, namely once with an arrangement known from prior art without homogenization according to the conventional method and parallel to it with the inventive arrangement of the claimed method with homogenization. It was found that in the conventional method, the material is not completely degassed, but that small gas bubbles, caused by the decomposed printer inks, remain in the final product. With the claimed

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method, in particular through homogenization before degassing, the degassing result is further improved and hardly any gas bubbles can be seen. Ò Ò Erema developed the Intarema TVEplus system especially for the processing of postconsumer materials [17]. Heavily contaminated film can Ò Ò be processed with the recycling duo Intarema TVEplus and Erema Laserfilter to make high-quality recyclates. Ò Ò The Intarema TVEplus system, shown in Fig. 8.20, works as follows: Automatic feeding (1) of the material according to customer requirements. The material is cut, mixed, heated, dried, precompacted, and buffered in the cutter/compactor (2). Next, the tangentially connected extruder is filled continuously with hot, precompacted material. The patented Counter Current technology changes the direction of rotation inside the cutter/compactor and enables optimized intake action across an extended temperature range. The material is plasticized and degassed in reverse in the extruder screw (3). At the end of the plasticizing zone, the melt is directed out of the extruder, cleaned in the fully automatic, self-cleaning filter (4), and returned to the extruder again. The final homogenization of the melt (5) takes place after the melt filter. The filtered and homogenized material is degassed in the subsequent degassing zone (6). Following this, and with the help of the discharge zone (7), the melt is conveyed to the respective tool (8) (e.g., pelletizer) at extremely low pressure [17]. The patented extruder system Intarema TVEplus sets new standards in the recycling of materials that are difficult to process such as heavily printed polyethylene and polypropylene films, very moist materials (e.g., washed polyethylene film flakes), polyethylene films with paper

Figure 8.20 Schematic diagram of the Intarema TVEplus system [17]. 1, Feeding; 2, Cutter/compactor; 3, Extruder screw; 4, Self-cleaning filter; 5, Melt; 6, Degassing zone; 7, Discharge zone; and 8, Pelletizer. Courtesy of EREMA.

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contamination, and metalized biaxially oriented polypropylene (BOPP) films. This is made possible through ultrafine filtration, thorough melt homogenization, and high-performance degassing in a single step. WO2007076165 A2 (2007), US2007120283 A1 (2007), and US2008233413 A1 (2008) of APPLIED EXTRUSION TECHNOLOGIES disclose a method for making a multilayer film including a core layer with recycled oriented polypropylene (OPP) film therein comprising the following steps: 1) bales of OPP flexible packaging or label stock including inks either with or without an adhesive in the product are fed into a granulator where large sheets of recycled material are reduced in size to flakes of about (1/8) to (1/4) in2; 2) the flakes are then processed through a densifier to produce compressed pellets of unmelted film; heat generated in this process is an important first step in reducing the volatiles from the inks and adhesives in the label stock; and 3) the pellets are fed into an extruder, which is equipped with a vacuum vent; vacuum venting the extruder is very important to further reduce volatiles from the inks and adhesives, as well as moisture and entrained air in the feed. A commercial processing aid, such as a compound of calcium oxide in polyethylene (e.g., ML1803, ML Plastics GmbH), is fed with the scrap at a 3 wt% level, to aid in reducing the volatiles by chemical reaction. Finally, the melt is pumped through a fine mesh filter and into a standard underwater pelletizer. In some cases, the product is directed through a fine mesh filter before vacuum venting. The pellets then are introduced into an extruder for incorporation into the core layer of a new, multilayer, opaque plastic film, either uniaxially oriented or biaxially oriented (see also Section 8.9.1). WO2014162238 A (2014, JAIN PRANAY) discloses a method for converting waste or used metalized (aluminum coated) PET film to recycled PET pellets with enhanced physical, mechanical, optical, and aesthetic properties comprising the steps of: 1) collecting waste/used metalized PET film; 2) reducing the size of waste or used metalized PET film in flakes either before or after washing by a grinder or granulator or by cutter compactor; 3) washing the film of step (1) and/or flakes of step (2) in a hot water bath or in alkaline (e.g., caustic soda) or in alkali solution having a concentration in the range of 0.5e3 wt% in water solution at room temperature to 90 C;

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4) densifying the film or flakes of step (3) in an agglomerator to increase the bulk density of the film or flakes; 5) feeding the obtained film or flakes of step (4) into an extruder for devolatilizing, homogenizing, and converting the same into melt; 6) conveying the melt of step (5) into a pelletizer to obtain recycled PET pellets having intrinsic viscosity less than 0.55 dL/g; and 7) increasing the intrinsic viscosity of the pellets obtained in step (6) from 0.55 dL/g up to 1.00 dL/g by solid-state polymerization (SSP) to obtain recycled PET pellets suitable for making highquality strapping or monofilament yarn or sheets. PET straps, monofilaments, yarns, or sheets were made from pellets of recycled metalized PET film.

8.6 Integrated Systems An early study describes an integrated system for the recovery of polyolefin films from packaging and industrial wastes in the form of very clean recycled film flakes from even the dirtiest of scrap film. The feedstock is provided in form of baled film, which has had metal or plastic strapping removed, wherein the scrap film is reduced to smaller stripes in a shredder, which are carried under an electronic metal detector and then fed with other impurities into a water-filled separation tank where the polyolefin films float while the heavier fractions sink to the bottom of the separation tank for removal. The floating stream is then fed in a wet granulator where it is intensively washed. Water recycling circuits from tanks are also provided [18]. US2012199675 A1 (2012), US2013186573 A (2013), and US2014048631 A (2014) of WISCONSIN FILM and BAG INC disclose a method (see Fig. 8.21) and an apparatus (see Fig. 8.22) for processing a supply of postconsumer scrap LLDPE or LDPE film. The method includes tearing the supply of film in a shredder, wherein the surface area of the film is exposed, including delamination of the film. The torn supply of film is washed in a water bath including a surfactant and agitated to remove contaminants from the film. The washed film is ground into smaller pieces, and additional washing of the ground film in a rotating friction washer occurs wherein additional contaminants are removed from the film. The ground film is then dried and compacted without addition of water into granules of near-virgin quality polyetylene.

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Figure 8.21 Flowchart of the method for recycling postconsumer scrap film (2014, US2014048631 A, WISCONSIN FILM and BAG INC).

US2013119575 A1 (2013) and US2013119171 A1 (2013) of NEXTLIFE ENTERPRISES, LLC disclose a process (see Fig. 8.23) and an apparatus (see Fig. 8.24) for recycling plastic waste material, including shredding the waste material in a universal shredder apparatus and washing the waste material. The apparatus includes a dryer for drying substantially all moisture from the plastic, and an agglomerator that

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Figure 8.22 Schematic top view of an apparatus configured to process scrap film in accordance with the flowchart of Fig. 8.21 (2014, US2014048631 A, WISCONSIN FILM and BAG INC).

receives the dry film material from the dryer and creates a course mix of cut material. Multiple in-line extruders process the cleaned plastic with filter screens positioned after each extruder to mix and filter the plastic into a final uniform mixed mass, which is sent to a pelletizer. CN106994756 A (2017, GUANGZHOU HONGTAI PLASTIC TECH CO LTD) discloses a scrap plastic film recycling and treating apparatus. The apparatus comprises a shredder, a cooling device, a blow-drying device, a granulator, and a collecting bin. The granules can be used for producing new film. Some representative commercial integrated film recycling systems are the following: Sorema’s film recycling process is outlined in Fig. 8.25 [19]. The first step in film recycling is generating a stable flow of the incoming waste through a shredder. Prewash then takes place, initially by agitation and decontamination and subsequently in float-sink tanks to remove heavier contaminants. This operation reduces machinery wear in the remaining part of the line. Precleaned film shreds are sent to a wet granulator followed by a centrifuge for the removal of water and pulp. A stirring and separation tank follow, for further decontamination. Additional centrifugation steps follow to remove fine contaminants and water. Specially

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Figure 8.23 Block diagram view of the process for recycling film and rigid plastic (2013, US2013119575 A1; 2013, US2013119171 A1, NEXTLIFE ENTERPRISES, LLC).

designed thermal drying with hot air allows to remove efficiently final moisture. Polystar’s plastic recycling apparatus Repro-Flex is designed for the reprocessing of polyethylene (HDPE, LDPE, LLDPE) and polypropylene flexible packaging material, printed and nonprinted. This cutter-integrated pelletizing system eliminates the need of precutting the material and requires less space and energy consumption, while producing high quality plastic pellets at a productive rate [20]. The Repro-Flex plastic recycling apparatus combines cutting, extrusion, and pelletizing into one compact and efficient recycling line. The

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Figure 8.24 Perspective view of an apparatus depicting the initial shredding operation and the separate conveying of shredded material to a separate grinding apparatus (2013, US2013119575 A; 2013, US2013119171 A1, NEXTLIFE ENTERPRISES, LLC). W, Waste material; 10, Apparatus; 12, Single plastic waste intake; 14, Initial universal shredder; 16, Conveyor belt; 18, Shredded plastic material; 20, Conveyor assembly; 24, Film recycling line; 26, Rigid plastic recycling line; 30, Shredder housing; 66, Rigid processing line; 68, Rigid material; 70, Film processing line; 72, Film material; 74, Metal separation assembly; 76, Rigid material grinder; 78, Eddy current metal separation unit; 80, Ferrous metal separator; 82, Fines separator; 84, Blower assembly; 86, Fines collector; 88, Passageway; 94, Film grinder; 108, Transport duct; and 110, Agitation process.

cutter compactor of the recycling machine prepares (preconditions) the material into an ideal condition for the extrusion process and feeds the material directly into the extruder with a centrifugal force. Comparing with the conventional recycling machines, this integrated system does not require a separate crusher and, therefore, eliminates the problem of inconsistent feeding (overfeeding or insufficient feeding). The apparatus

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Figure 8.25 Schematic diagram of the Sorema film recycling process [19]. 1, Feeding; 2, Primary shredding; 3, Metal separation; 4, Buffer storage; 5, Prewashing; 6, Wet grinding; 7, Final washing; 8, Mechanical drying; 9, Thermal drying and aerodynamic separation; 10, Buffer for extrusion; and 11, In-line water filtration. Courtesy of Sorema.

can be used for the processing of printed and nonprinted polyethylene and polypropylene monolayer and multilayer scrap film.

8.7 Blending Blending of at least two polymers at various ratios makes possible to achieve desired property combinations of the resulting material [21]. Blending is often used to provide tailored product properties for a specific application such as barrier properties to layers in a multilayer structure. Polymer blends exhibit synergistic physical properties when the minor phase is effectively dispersed in the matrix phase (see also Chapter 3, Section 3.9). However, there are technical limitations in achieving such well-dispersed morphologies with conventional melt processing techniques. In incompatible polymer blends, a large viscosity difference and/ or interfacial tension often prevents the dispersed phase from developing fine domains, and coarsening of these domains at typical processing temperatures leads to a noncompatibilized blend structure [22]. Addition of compatibilizers and prefunctionalization of the materials have yielded some success in producing well-dispersed blends; however, they are neither applicable to all polymer systems nor the most desired route of production. A continuous processing technique, called solid-state shear pulverization (SSSP) has proven to yield polymer blends with compatibilized, sub-micron-size dispersed domains [23].

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Polypropylene/LLDPE chip bags can be blended with other recycled polypropylene streams to dilute the LLDPE portion. This needs not be done to simply dilute (hide) impurities in the majority polymer matrix. Sometimes, careful blends of incompatible polymers can enhance performance of the majority polymer. One drawback of polypropylene is its low impact strength, particularly, at low temperatures. If LLDPE from polypropylene/LLDPE chip bags is blended into polypropylene in a proper amount (e.g., up to about 30%), it can improve the impact strength of the polypropylene. Henkel in cooperation with Mondi have developed a technology for incorporating more of its scrap plastic into an environmentally flexible OPP/polyethylene multilayer packaging for its laundry detergents. Henkel has begun selling its Megaperls washing powder in the resulting flexible package called “quadro seal bag” (see Fig. 8.26); 30% of the package’s polyethylene layer consists of industrial waste reclaimed from Mondi’s factory in Halle, Germany. This means that the overall structure contains about 10% regrind material. Mondi aims to achieve a 50% regranulate in the full OPP/polyethylene multilayer structure, which consists entirely of polyolefin materials [24].

8.7.1 Compatibilization The greatest challenge in recycling multilayer plastic packaging waste is that most plastic layers are incompatible with one another, producing phase-separated mixtures with diminished properties. For years,

Figure 8.26 Henkel’s Megaperls washing powder in a flexible package called “quadro seal bag” [24]. Courtesy of Henkel.

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a considerable amount of flexible multilayer barrier packaging films is being disposed by landfill or incineration, due to the difficulty of dispersing typical functional barrier polymers such as ethylene vinyl alcohol (EVOH) or polyamide within a more conventional polyolefin waste stream for further recycling (see also Chapter 3, Table 3.9).

8.7.1.1 Compatibilizers A potential solution to the problem of immiscibility is through the use of compatibilizers that control the phase behavior of polymer mixtures. Flexible film converters and recyclers get value out of postindustrial packaging waste by submitting the material to a compatibility process, in which a recycling compatibilizer is added to the waste stream for further conversion of the material into pellets, allowing its reuse. However, when a postconsumer barrier film is collected and mixed with a conventional polyolefin waste stream, it is very difficult to know when to use such compatibilizers and the amounts required (2016, EP3040199 A1, DOW GLOBAL TECHNOLOGIES LLC). Several compatibilizers are commercially available (see Table 8.2), and, if used correctly, allow a noncompatible polymer in smaller percentage to blend with a primary polymer without negative effects. Compatibilizers work best with polymer blends that can be processed at similar temperatures, e.g., multilayer films of polyethylene, polypropylene, and EVOH. On the other hand, for multilayer films composed of polyolefin layers and polyamide 6 (nylon 6) or PET layer having a 40e50 C difference between their processing temperatures the compatibilization is less efficient. A drawback of the compatibilizers is that they are expensive; however, they need not be used in large quantities to be effective [3]. In general, while there are available compatibilizers capable of providing compatibilization of binary polymeric blends, such materials are specific for the blend desired. Acceptable compatibilizers for polymeric blends of three or more components simply do not exist (2002, WO0211963 A2, MATERIAL SCIENCES CORP). DE4223864 A1 (1994, BAYER AG) relates to polyamide mixtures containing (1) 40e98 wt% polyamide, (2) 0.5e50 wt% scrap polyamide/ polyolefin film, (3) 1e50 wt% compatibilizer, and (4) 0e60 wt% normal additives. The polyolefin in (2) is polyethylene and the polyamide in (2) is nylon 6 or a copolyamide containing at least 60% caprolactam, with a weight ratio polyethylene/polyamide of (9/1)e(1/1); preferably, (2) contains 5e50 wt% polyamide. The polyamide in (1) is preferably nylon

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Table 8.2 Commercial Compatibilizers for Recycling Multilayer Flexible Packaging [25] Target Resins for Blending

Supplier

Commercial Name

Arkema

LotaderÒ AX8840, LotaderÒ AX8900

PET, PBT, PPS

Arkema

LotaderÒ 3210, LotaderÒ 3410

PA/polyolefin

Dowa

RetainÒ

PE/EVOH or PA/ EVOH/PE

Dow

IntuneÒ

PE/PP

a

FusabondÒ M603

PE/PA, PE/EVOH, PA, EVOH/PE

Dowa

FusabonÒ d E226

PE/PA, Surlyn, EVOH, or PA

Dowa

BynelÒ 41E710

PE/EVOH or PA/ EVOH/PE

Dowa

SurlynÒ 1650

EVOH or PA

Dow

Ò

a

Fusabond P353

PP/PA or PP/EVOH/ PP

Dowa

ElvaloyÒ PTW, Elvaloy 3427 A C

Polyesters/PE

Struktol

StruktolÒ TR 219

PA, PET

Dow

Struktol

Ò

Strukto l TR 229

PA, PC, PC/ABS

ABS, acrylonitrile butadiene styrene; EVOH, ethylene vinyl alcohol; PA, polyamide; PBT, poly(butylene terephthalate); PC, polycarbonate; PE, polyethylene; PET, poly(ethylene terephthalate); PP, polypropylene; PPS, poly(phenylene sulfide); Surlyn, ionomer of ethylene acid copolymer. a ex DuPont.

6, nylon 66 or a copolyamide of nylon 6 and nylon 66, or a copolyamide of at least 70 wt% caprolactam. Addition of small amounts of compatibilizer (3) to mixtures of (1) and (2) gives products with impact strength at least as good as that of high-impact polyamides containing no recycled polyamide/polyolefin multilayer film. Exemplary compatibilizers (3) are copolymers of ethylene/n-butyl acrylate/glycidyl acrylate and ethylene/

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acrylic acid t-butylester/acrylic acid. ‘’Downrecycling’’ of such scrap film from food packaging therefore becomes unnecessary. EP3040199 A1 (2016, DOW GLOBAL TECHNOLOGIES LLC) discloses a self-recyclable barrier packaging film comprising (1) at least one polyolefin layer comprising (1a) 60e94 wt% of a first component selected from the group consisting of ethylene homopolymer (e.g., DMDA-8007 NT 7 of Dow Chemical Co.), ethylene copolymer (e.g., LLDPE such as DowlexÒ 5056G of Dow Chemical Co.), polypropylene homopolymer (e.g., H110-02N of Braskem), polypropylene copolymer (e.g., DS6D81 of Braskem), and combinations thereof; (1b) 0e35 wt% of a functional polymer component (e.g., AmplifyÒ TY 1353 of Dow Chemical Co.); and (1c) 1e35 wt% of a compatibilizer component comprising an anhydride and/or carboxylic acid functionalized ethylene/ a-olefin interpolymer having a melt viscosity (177 C) less than, or equal to, 200,000 mPa s (cP) and a density from 0.855 to 0.94 g/cm3 (e.g., RetainÒ 3000 of Dow); (2) at least one tie layer comprising maleicanhydride grafted polymer with a melt index of less than 50 dg/min, wherein the tie layer does not contain the compatibilizer; and (3) at least one polar layer comprising a polar polymer selected from EVOH (such as EVALÒ H171B of Kuraray) or polyamide (such as nylon 6, nylon 66, and nylon 6/66 of DuPont) and combinations thereof. JP2006298960 A (2006, NABATA and CO LTD; KANSAI KOBUNSHI KOGYO KK) discloses a low-cost reclaimed film by recycling polyethylene or polypropylene contained in wastes such as waste plastic containers and packages. The reclaimed film is obtained by adding a compatibilizer (B1) for polyethylene and polypropylene (C) to a recovered plastic mixture (A) comprising 40e60 wt% polyethylene, 40e60 wt% polypropylene, and 0e10 wt% other plastics, the total of these being 100 wt%, and subjecting the resulting mixture to inflation molding. A preferred compatibilizer is a modified polyolefin type adhesive resin of the same type as the polyolefin waste having an acid functional group (e.g., ModicÔ -AP 908 of Mitsubishi Chemical Corp.) or a hydrogenated block copolymer2 (DynaronÒ 6200P of JSR Co., Ltd). KR20050005631 A (2005) and KR100733941 B1 (2007) of KOREA INST SCI and TECH disclose a method for recycling waste aluminumdeposited multilayer packaging films comprising the steps of: 1) introducing the waste multilayer packaging films through the main hopper of a first extruder and introducing a compatibilizer through a second hopper

2

Crystalline blocke(ethylene/butylene)ecrystalline block copolymer.

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to conduct a first stage melting, mixing, and extrusion; 2) cooling and pulverizing the extrudate; 3) conducting a second stage melting and extrusion in a secondary extruder of the pulverized material; and 4) injection molding the secondary extrudate. The reaction temperature in the first extruder is at least 250 C and the residual time period is not less than 3 min. The waste multilayer packaging film includes a polypropylene/polyethylene-based multilayer packaging film and a nylon/ polyethylene-based packaging film. The polypropylene is a highly crystalline polypropylene, and the polyethylene is LDPE or LLDPE. The waste packaging film mixture comprises 50e80 wt% polypropylene, 10e50 wt% nylon, 5e20 wt% polyethylene, 3e5 wt% polyester, and 1e2 wt% polystyrene. The compatibilizer is selected from the group consisting of a polyethylene copolymer grafted with maleic anhydride, a polypropylene copolymer grafted with maleic anhydride, a hydrogenated polystyreneepolybutadiene copolymer, a hydrogenated polystyrene-polybutadiene copolymer having maleic anhydride attached to its main chain, and a polyisopreneepolystyreneepolyisoprene triblock copolymer wherein maleic anhydride is substituted on both ends, and mixtures thereof, preferably a polyisopreneepolystyreneepolyisoprene triblock copolymer having maleic anhydride substituted at both ends thereof is used after mixing with a radical initiator. JP2008000908 A (2008, NPO HIROSHIMA JUNKANGATA SHAKA; HIROSHIMA PREFECTURE) discloses a recycling method for the conversion of thin wall plastic products such as plastic bags by mixing the waste plastic with a modification resin, dispersing uniformly and granulating. The granulates are extruded to form new thin wall products. The waste plastics contain at least 70 wt% of both polyethylene and polypropylene as main components. The modification resin is regenerated polyethylene or polypropylene recovered from industrial waste. Heterogeneous plastics, such as polystyrene, and dissimilar materials are further added during the recycling process. A compatibilizer is further added to the modification resin to improve the compatibility between dissimilar materials and polyolefin. A preferred nonreactive compatibilizer is styreneeethylene/butyleneestyrene block copolymer, and a preferred reactive compatibilizer is maleic anhydride grafted styreneeethylene/ butyleneestyrene block copolymer. ´ GER INVEST KERESKEDELMI WO2015177580 A2 (2015, JA ´ ´ ´ SZOLGALTATO ES INGATLANHASZNOSITO KFT) describes polymer blends and homogeneous polymer agglomerates containing coextruded polyolefin/polyamide packaging film waste and glass fiber reinforced plastic waste and a low molecular weight compatibilizing

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additive. The low molecular weight compatibilizing additive is a dicarboxylic acid anhydride, preferably maleic acid anhydride. The film waste usually contains 40e49 wt% polypropylene, 49e58 wt% polyamide, and about 2 wt% EVOH, and it is usually contaminated with prepreg or materials of pharmaceutical or food industrial sources. In one embodiment, the coextruded film is in the form of granules, and the fiber reinforced plastic is present in the form of waste SMC3 grinds; optionally, a compatibilizing polymer such as polypropylene EPDM (ethyleneepropyleneediene monomer) elastomer and a property modifying polymer such as EPDM or TPU (thermoplastic polyurethane) are used. DE3938552 A1 (1991, DIESEN HERMANN) discloses the recycling of polyamide/polyethylene (PAPE) (50/50e99/1) film by compatibilizing the different polymer types with peroxides of formula R-O-O-R, wherein R is phenyl-aralkoxy-, aroyl-, alkoxy and/or alkyl, preferably 1,3-bis(tbutylperoxyisopropy l)benzene, and/or coagents containing preferably triple carbon bonds, such as 2-butyne-1,4-diol. The diol reacts with the secondary amine of the polyamide, and the triple bond promotes radical crosslinking with the polyethylene. The process gives a uniform melt, which can be reprocessed.

8.7.2 Solid-State Shear Pulverization SSSP is a process in which polymer blends are sheared together at temperatures below their melting points. SSSP utilizes a modified twinscrew extruder to exert high shear forces and pressures onto a polymer blend while maintaining the solid state through continuous cooling. SSSP has proven to yield polymer blends with compatibilized, submicron-size dispersed domains. Its solid-state nature allows for morphology development to take place without regard to limitations in viscosity, thermodynamics, and kinetics. It does not require heat, monomer, solvent, or chemical premodification and, thus, is a practical and advantageous alternative for making effective polymer blends [23]. WO0211963 A2 (2002, MATERIAL SCIENCES CORP) discloses a method of making polymeric particulates (e.g., powder) from a waste stream of multicomponent scrap film comprising at least 50 wt% LDPE comprising the steps of: 1) comminuting the scrap film to chips or flakes by shredding or grinding using conventional equipment; 2) feeding the comminuted scrap film (M) to a twin-screw pulverizer (10) shown in Fig. 8.27 equipped with intermeshing pulverizer screws (14), which are 3

Sheet molding compound.

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Figure 8.27 Schematic sectional view of a twin-screw pulverizer for the solid-state polymerization (SSP) of a multicomponent scrap film (2002, WO0211963 A2, MATERIAL SCIENCES CORP). BC, Coolant bands; BH, Heating bands; M, Flake scrap material feedstock; P, Pulverized polymeric particulates; 12, Feeder; 10, Twin-screw pulverizer; 14, Intermeshing, corotating screws; 16, Pulverizer barrel; 16a, Discharge end; 18, Drive motor; and 16, Extrusion barrel.

rotated to transport the comminuted scrap film along their length, and subject it to SSSP and in situ polymer compatibilization; and 3) discharging the resulting pulverized polymeric particulates (P). Uniform pulverized particulates are produced without addition of a compatibilizing agent. The pulverized particulates (P) are directly melt processable by conventional blow molding, rotational molding, extrusion, spray coating, and other melt processing techniques requiring a powder feedstock. Scrap film containing high proportions of LDPE yield molded articles of superior notched Izod impact strength (5 ft-lb/in or 266.8 J/m) and elongation. Zzyzx Polymers, a spinning company from Northwestern University, has developed an SSSP process known as continuous mechanochemical compatibilization (CMC), which could be used for the recycling of multilayer flexible plastic packaging. CMC differs from traditional compatibilization as it does not rely on melting. CMC cools plastics below the plastic’s melting and/or glass transition temperature to maintain a solid state and then subjects them to high shear and compressive forces in a twin-screw extruder. This causes repeated fragmentation and fusion of the polymers in the solid-state leading to polymer morphology changes such as chain scission, branching, and free radical formation. Polymers are then chemically recombined, allowing compositions to bind with other polymers or fillers. Although the extruder is cooled, CMC is not an expensive cryogenic process. The plastic is processed near ambient temperature, and overall energy use remains below that for standard

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recycling process that requires additional washing, drying, and separation steps. Only in the final step of the process is the compatibilized powder heated so that standard plastic pellets are prepared [26]. Zzyzx Polymers’ technology is based on patents WO2014127133 A1 (2014, UNIV NORTHWESTERN) and US2015065616 A1 (2015, ZZYZX POLYMERS LLC). In 2016, one of the inventors, Philip Brunner, left the company putting the development in jeopardy [27]. The pros and cons of Zzyzx technology can be summarized as follows: Pros: When it comes to processing multilayer flexible packaging, the Zzyzx method compatibilizes different polymers quite effectively. It reduces impurities to particle fillers of size around 1 mm, disperses them, and eliminates air gaps between the particle fillers and the polymer(s). The result is a polymer composition with good mechanical properties. The process does not require high sortation or cleaning which reduces time, costs, and efforts. Additionally, the process is environmentally benign because it does not require monomers, solvents, or processing aids. Furthermore, unlike other solid-state processes such as ball milling, pan milling, and cryogenic milling, CMC is a continuous production process that is industrially applicable and scalable like traditional twin-screw extruder. Cons: The application of this technology to multilayer flexible packaging still requires an understanding of the polymers within the structure. This makes collection at the curbside currently impossible [28]. Further, it is doubtful whether manufacturers of recycled polymers produced through this process would be able to offer much if any scrap value to MRFs and/or could afford to transport materials at long distances [3].

8.8 Compounding Some reprocessors compound the recycled packaging material with additives or fillers at the reextruding phase to improve the properties of the material. FR2870477 A1 (2005, J and M COMPOUND SOC PAR ACTION) discloses a method for recycling waste of printed polyolefin films by compounding extrusion with a mineral load. The polyolefin film waste is converted to shreds, lamellae, or flakes by grinding and densification and is then fed into a twin-screw extruder, in which addition of mineral filler or other additives takes place. The disclosed method leads to the production of a masterbatch, which is easily used in the formation of a good quality thin film having a thickness of less than 30 nm.

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Example: 5 ton of production waste films, from heavily printed (over 80% of the surface) LDPE films intended for frozen food packaging, were shredded. The films were produced by coextrusion with an interior layer of LLDPE and were 50 mm thick. The films were formulated with TiO2 to provide opacity and white background. The flakes of film had been recycled in a conventional monoscrew extruder before being introduced into the feed zone of a corotating twin-screw extruder 96 mm wide with a screw length 40 times the diameter. The mineral filler used was calcium Ò carbonate (Omyafilm 707) surface treated with calcium stearate. The filler was introduced into the principal extruder by two laterally mounted force feed extruders. Dosage was regulated by two gravimetric balances. The extruded product contained 50 wt% of filler introduced 60% by the first extruder and 40% by the second. The extruder speed was maintained at 380 rpm to give a final output 1200 kg/h. IrganoxÒ 1010 was introduced as an antioxidant stabilizer. The recycled masterbatch with density 1.384 g/cm3 wasÒ then used to produce waste sacks with an 80 mm screw diameter Kiefel extruder, equipped with two 120 mmÒ extruder heads. Extrusion was carried out on line with a Roll-o-Matic double-channel sack machine. Garbage bags 700 mm wide and 950 mm long with varying thicknesses of 75e30 mm were produced. When a recycled material produced by known methods from heavily printed film with density 0.932 g/cm3 and colored with 2 wt% dark gray colorant was used without virgin LLDPE, it was not possible to produce a film below 75 mm thick. A formulation containing 53 wt% recycled LLDPE, 25 wt% of the recycled masterbatch, 2 wt% gray colorant, and 20 wt% virgin LLDPE produced a film of 35 mm thickness. US2015240041 A1 (2015, TORAY FILMS EUROP) discloses a method of recycling by “compounding” extrusion of metalized polyester and/or polyolefin film comprising the following stages: 1) grinding the metalized film, preferably by means of a grinding mill with metal or ceramic blades, to obtain flakes; 2) optionally, compacting the flakes resulting from grinding to form agglomerates; 3) melting the flakes or agglomerates resulting from compacting, preferably followed by filtration to remove the particles of metal and/or of at least one metal oxide, the largest dimension of which is greater than or equal to 10 mm, preferably greater than or equal to 5 mm, and even more preferably greater than or equal to 3 mm; 4) cooling/solidifying the molten mass;

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5) transforming the solidified mass into discrete elements, preferably into granules; 6) manufacturing the film by melt extrusion, in which granules of a polymer (polyester, preferably PET, and/or polyolefin) and the polymer/lamellar filler obtained in stages (3), (4) and (5) are fed into an extruder; 7) cooling the obtained film; and, optionally 8) stretching the film; and 9) heat-setting the film, preferably between 180 and 250 C. The produced films can be used for the heat treatment of various products, in particular food products, as they are extremely resistant to high temperatures (e.g., above 120 C). The heat treatments envisaged are, among others, sterilization, pasteurization, and cooking or reheating of foods in a microwave oven or steam. CN101722639 A (2010) and CN101857691 A (2010) of QINGDAO JIEXIN RENEWABLE RESOURCE TECHNOLOGY DEV CO LTD disclose a method for producing a recyclable composite molding from a discarded plastic/paper/aluminum flexible packaging container comprising the following steps: 1) shredding the plastic/paper/aluminum flexible packaging container into shreds of less than 10 mm in diameter; 2) adding auxiliary agents; 3) kneading the skin shreds and the auxiliary agents in the temperature range 100e125 C; 4) strengthening the kneading effect further by screw-rod shearing; and 5) extruding and molding the material by the screw rod. According to a preferred embodiment, the recyclable composite material comprises 100 Kg of pulverized packaging material; 15e45 Kg of calcium carbonate; 1e4 Kg of polyethylene wax; 0.5e2 Kg of paraffin wax; 1e3 Kg of stearic acid; and 0.2e0.3 Kg of coupling agent. Up to date, the recycling of plastic films having a coating film, e.g., metallic, has not been used successfully in the manufacture of new films. In fact, the metalized films have increased mechanical characteristics of rigidity, and consequently, the resultant ground material is coarse (fragments with a size of about 10 mm in the plane of the coating) and quickly damages the blades of a grinder. Moreover, this coarse ground material quickly clogs the polymer filters (e.g., Vacurema of Erema) causing large production losses. Furthermore, the coarse ground material inevitably leads to film breakages on the film-making machines. Consequently, machine operating time is greatly reduced and the production costs are

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substantially increased. This has curtailed the recycling of metalized plastic films in film manufacture (2009, WO2009124989 A1, TORAY PLASTICS EUROPE). One of the well-known methods of recycling PAPE film waste is compounding it in a double-screw extruder, during which the wastes are melted, property-enhancing additives are introduced into them, and then they are “kneaded” to obtain a homogeneous material, after which the obtained material is granulated. Because of the high melting point of polyamide, this process should be performed at a temperature around 250 C; however, the processing temperature of polyolefins is only 190 C, and at temperature higher than this, polyethylene becomes highly degraded. Furthermore, any extra heat transfer step taken during the process leads to the partial degradation and property impairment of the ´ GER INVEST KERESKEpolyethylene (2015, WO2015177580 A2, JA ´ ´ ´ DELMI SZOLGALTATO ES INGATLANHASZNOSITO KFT). A composite material was produced by Tartakowski [29] from recycled five-layered PAPE, recycled polyethylene (25e75 wt%) obtained from mixed polyethylene HDPE and LDPE, and fillers in form of fly ashes (up to 30 wt%) with a particle size up to 41 mm. The PAPE film was comminuted in a knife mill with a vertical rotor and then agglomerated in a single screw extruder to obtain a regranulate (diameter 3e5 mm, length up to 5 mm). The recyclate of PAPE was modified with fly ashes, which are waste from the combustion of coal in power plants. Modification of PAPE recyclates with fly ashes increases the resistance to electric arc and improves the dimensional stability of the products, which is important especially for precision products such as sliding elements in electronic devices (e.g., bearings and electric motors).

8.9 Reuse 8.9.1 Recycled Products DE3110254 A1 (1982, RIES WALTER) and DE4412959 A1 (1995, RIES ANDREAS) disclose a method for the recycling of blister packaging from the pharmaceutical industry. The aluminum foil/PVC film waste is granulated in a pulverizer, for example, to grain sizes of 1.5e3 mm. The granules obtained are mixed with at least one plastic additive, for example, 50 wt% of untreated rigid-PVC granules, or waste chemical additive(s) together with waste fiber, latex and stone dust, and the mixture is used as starting material for producing thermoplastics. The aluminum/PVC film waste granules may also be added to wood chips for the production of

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chipboards. They may also be used as filler in mold construction for polyurethane foam molds and as filling material for adhesives in the construction industry. According to the invention, the plastic products produced by the claimed method have a high heat conductivity and a low capability, if any at all, to build up an electrostatic charge. Separate recovery of plastic and aluminum is not possible with this method. GB2350083 A (2000, GREENAWAY HANNAH) describes a sheet material (see Fig. 8.28) produced by compression molding recycled polyethylene plastic bags. Preferably, the polyethylene bags (3) are arranged in layers, and the sheet material may be built up in successive layers, which are each subjected to heat and pressure between two heated plates (1, 4). The appearance of the sheet material may be enhanced by using dyes and/or ensuring that specific elements, e.g., of a specific color, are located on the surface when the polythene bags are arranged in their layers. The heated plates (1, 4) may be provided with a protective coating (2, 5), e.g., glass or Teflon. The produced sheets have a thickness of 1e3 mm and are colored and can be either patterned or printed. The produced sheets are claimed to be lightweight, strong, wear-resistant, durable, flexible, moldable, and are water-proof. The sheets can be used as packaging material, construction material, and as substitute for paper.

Figure 8.28 Schematic diagram of a sheet from used polyethylene bags (2000, GB2350083 A, GREENAWAY HANNAH). 1, Heated plate; 2, Protective coating; 3, Plastic material; 4, lower plate; 5, Protective sheet; and 6, Sheet material.

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JP2008213395 A (2008, NOZOE KAZUO) discloses a protective sheet made of discarded stretch films of industrial waste. The discarded stretch films are collected and pulverized, then the pulverized stretch films are heat melted and pressurized at about 200 C, and extruded in a string-like shape from an extruder. The string-like shaped plastic body is cut into pellets. The pellets are blown up by an inflation molding machine at a temperature of about 180 C. The obtained tubular body is cut and spared in one, two, or more sections along its longitudinal direction and reeled as a single sheet or one-way spread sheet. The obtained sheet is used for protecting surfaces of passages and stairways of buildings, e.g., of public institutions or factories. WO2010066398 A1 (2010, TREOFAN GERMANY GMBH and CO KG) discloses a method for producing a BOPP film, comprising at least one layer made of virgin polypropylene and 0.5e40 wt% of OPP filmebased flexible packaging and labels that have been recycled once. The film can be used as dielectric in capacitors. WO2007076165 A2 (2007), US2007120283 A1 (2007), and US2008233413 A1 (2008) of APPLIED EXTRUSION TECHNOLOGIES disclose the use of recycled OPP-based flexible packaging film or label stock as part of the composition of the core layer of a multilayer opaque OPP film. The labels may be collected as scrap or second quality material subsequent to the label making process, or the labels may be separated from plastic bottles, preferably PET bottles, as part of a typical PET container recycling process. In all cases, the reclaimed material is ground up and melt extruded into pellets for inclusion into at least the core layer of a multilayer opaque film. The multilayer OPP film includes at least one skin layer containing whitening agent or other pigmenting agent therein to mask any undesired coloration created by the presence of inks and/or adhesives in the reclaimed material. The benefits of reutilizing postconsumer OPP flexible packaging films and labels as part of the composition of a newly produced OPP film are numerous. It is envisioned that the overall economics for a process that utilizes recycled OPP film and labels would operate at a reduced material cost compared with the utilization of all new materials. The other benefits to the use of recycled OPP film and labels as part of a composition of newly produced OPP films are the environmental benefits from a recycle perspective and enhanced sustainability life cycle. CN102909210 A (2013, HAIBO ON TO THE SDECIAL TRADE CO LTD) discloses a method for recycling discarded aluminum foil/plastic/ paper packaging by combining extrusion and cold press technology in

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one-time molding to obtain a composite aluminum foil material product. The method comprises the following steps: 1) shredding the composite material to a particle size of 5 cm; 2) extruding the composite material at a temperature of 250e270 C for 3e4 min; 3) cold pressing the extruded material in a mold at a pressure of 25e28 MPa for 4 min so that the plastic components are wrapped on the surface of the paper and the aluminum foil. Through the above process, products such as student desks and chairs, stools, household sorting trash cans, outdoor trash cans, covers, etc., can be produced. JP2017222425 A (2017, GREEN PLA CO LTD; DAN SANGYO KK) discloses a plastic stretch band made from a postconsumer flexible container. A postconsumer flexible container composed of polypropylene, polyethylene, and PET is shredded, melted and stretched. The obtained product is preferably composed of polypropylene in an amount of 80e90 wt% and has a melt flow index of 15 g/10 min (JIS-K7210). The composition further comprises calcium stearate, magnesium stearate, zinc stearate, calcium carbonate and talc, and/or a compatibilizing agent having affinity for at least one compound of the composition. The plastic stretch band is 0.2e0.75 mm and 0.2e0.75 wide. The plastic stretch band can be used for packing newspapers. WO2014039479 A1 (2014) and US2016244598 A1 (2016) of CPG INT LLC disclose a polymer composite and its method of manufacture using a recycled multilayer packaging (e.g., used beverage pouches). Examples of the recycled multilayer material comprise polyethylene/PET/ aluminum film or polyethylene/polyamide/aluminum film that is extruded with an organic filler (e.g., wood flour) in an amount of 40e60 wt% to make wood-substitute products such as deck boards, railing, fencing, pergolas, residential cladding/siding, sheet products, and other applications. According to the invention, predrying the cellulosic filler and the multilayer material, using coupling agent including olefinic maleic anhydride type coupling agents such as PolybondÔ of Chemtura, and/or using higher processing temperatures may facilitate the optimization of the properties of the composite (e.g., to obtain properties that are the same, similar, or improved relative to a comparable product comprising polyethylene, polypropylene, other polyolefin, or ionomer instead of recycled multilayer materials). BRPI0804756 A2 (2010, COSMO ANTONIO EUFRASIO DE ARAUJO) discloses an asphalt pavement formed from an asphalt matrix reinforced by fragments of flexible multilayer and/or monolayer plastic packaging in an amount of 0.1e40 wt% relative to the weight of the

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Figure 8.29 Asphalt pavement formed from an asphalt matrix (2) reinforced by fragments of flexible multilayer and/or monolayer plastic packaging (1) (2010, BRPI0804756 A2, COSMO ANTONIO EUFRASIO DE ARAUJO).

asphalt matrix (see Fig. 8.29). The asphalt pavement can be used in transport, architecture, engineering, urban planning, design, and related areas.

8.9.2 Commercial Uses Currently, most recycled flexible packaging is reused in applications that are different to their initial use. The major end uses of recycled plastic films in the United States include composite lumber (43%) for applications such as decking and park benches, film/sheet, e.g., plastic bags (37%) and other uses (20%), such as containers, crates, pipes, pallets, and playground sets [30]. Composite lumber remains the dominant domestic end-use market for postconsumer plastic films [31]. In the United States and Canada, recycled film from commercial, mixed polyethylene film, and curbside film is used to produce recycled content film and sheet products such as trash bags and thicker gage commercial film. Film and sheet markets sourced about 16% of the available supply of recycled film in the United States in 2011. Additional end uses in Canada and the United States reported in 2011 were automotive applications, pipe, lawn and garden products, and some injection molding articles [1]. Multilayer films are considered contamination and are used in lowvalue applications such as fishing floats depending on the type of materials and volume. The percentage of film-to-film (37%) recycling could be increased if the demand for postconsumer recycled film (PCR) is also increased. Currently, the processing capacity of PCR is lower than the amount of film that is collected. This limited capacity to process PCR film was compounded so far by the fact that Europe and the United States used to

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export more than 50% of its collected film to China, but China is no longer accepting this material (see Chapter 10, Section 10.3). An increased demand for PCR film will allow recyclers to invest in more advanced equipment that can produce high quality PCR to be used in more applications [32]. Turning flexible plastic packaging into other applications is a viable way to reuse flexible packaging secondary materials. Producing more recycled material from flexible packaging would intensify competition and a greater availability of products would bring down the prices [33]. TerraCycle is a US recycling company working with many of the world’s best companies to bring upcycling4 solutions to many forms of waste. They convert flexible plastic packaging waste into a range of innovative products, for example, by sewing juice pouches together into backpacks, chip bags into casual shoes, and even granola wrappers into shower curtains. Many of these products are available to buy in major retailers around the world as well as online [34].

References [1] Reclay StewardEdge e product stewardship solutions, resource recovery systems, Moore Recycling Associates Inc. Analysis of flexible film plastics packaging diversion systems e Canadian plastics industry association continuous improvement fund stewardship Ontario. February 2013. [2] Haig S, Morrish L, Mortonand R, Wilkinson S. Axion consulting. Final report e film reprocessing technologies and collection schemes e project code: IMT006-002. WRAP; July 2012. http://www.wrap. org.uk/sites/files/wrap/Film%20reprocessing%20technologies% 20and%20collection%20schemes.pdf. [3] RSE USA. The closed loop foundation e film recycling investment report. 2016. http://www.closedlooppartners.com/wp-content/ uploads/2017/09/FilmRecyclingInvestmentReport_Final.pdf. [4] BþB Anlagenbau. Machines for washing, separating and drying. 2019. http://www.bub-anlagenbau.de/products/washing/frictionwasher/.

4

The key difference between upcycling and reusing waste is that with upcycling the original intention of the object changes.

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[5] Neue Herbold, Maschinen- und Anlagenbau GmbH. Friction Washer FW. Retrieved May 19, 2019. https://neue-herbold.com/en/frictionwasher/. [6] ASG Recycling. Plastic film washing line. 2013. http://www. plasticrecyclingmachine.net/plastic-film-washing-line/. [7] AMEC Environment & Infrastructure UK, Axion Consulting. Collection and recycling of household plastic film packaging. Waste & Resources Action Programme (WRAP). Retrieved February 9, 2019. http://www.wrap.org.uk/sites/files/wrap/MST1445_Plastic_ Film_Breifing_Note_final%20for%20web.pdf. [8] Sorema Plastics Recycling Ssstems. Plastic dry cleaning process. Retrieved February 24, 2019. http://sorema.it/en_US/applications/ dry-cleaning-process/. [9] Parent G. Shredding thin film: how to do it right. Plastics Technology. April 27, 2017. https://www.ptonline.com/articles/shredding-thinfilm-how-to-do-it-right. [10] Bollegraaf Recycling Machinery B.V. Shredders. Retrieved February 21, 2019. https://www.bollegraaf.com/technologies/shredders-2. [11] Vecoplan. Vecoplan plastic film and fiber shredder. May 03, 2010. https://www.vecoplanllc.com/blog/vecoplan-plastic-film-and-fibershredder.html. [12] Ningbo Sinobaler Machinery Co Ltd. Plastic film - Prosino shredders. Retrieved January 14, 2019. http://www.sinoshredder.com/ application/plastic-film-shredder-for-sale/. [13] Koutsky J. Chapter 8: the uses of cryogenically recycled rubber. In: Braton NR, editor. Cryogenic recycling and processing. CRC Press; 2018. [14] APR - Association of Plastic Recyclers. The APR Design Guide for plastics recyclability. January 06, 2018. http://www.plasticsrecycling. org/images/pdf/design-guide/PE_Film_APR_Design_Guide.pdf. [15] Kaiser K, Schmid M, Schlummer M. Recycling of polymer-based multilayer packaging: a review. Recycling 2017;3(1):1. [16] Meckesheim GmbH Herbold. Success story for Rodepa plastics B.V. And Herbold Meckesheim GmbH recycling post-consumer waste and film waste. September 27, 2018. https://www.herbold.com/en/ erfolgsgeschichte-im-recycling-fuer-post-consumer-undfolienabfaelle-mit-rodepa-plastics-b-v-und-herbold-meckesheimgmbh/. [17] EREMA Engineering Recycling Maschinen und Anlagen. INTAREMAÒ TVEplusÒ . Retrieved January 1, 2019. https://www.

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Polypropylene films employing recycled commercially used polypropylene based films and labels.

WO2009124989 A1

20091015

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FR20080052394 20080409

Penache MARIA CRISTINA; MARZE ALAIN JEANMARIE; Lacrampe VALERIE; MAITRE ERIC JEAN; CASATI PIERRE

Toray Plastics Europe

Film plastique extrude´ charge´ en particules metalliques, proce´dee´ d’obtention et utilisations dudit film. "Extruded plastic film filled with metal particles, method of obtaining same and uses of said film."

WO2010066398 A1

20100617

BRPI0922267 A2 20160802; CN102245363 A 20111116; CN102245363 B 20150506; EP2376265 A1 20111019; JP2012511446 A 20120524; JP2015143029 A 20150806; JP5726746 B2 20150603; KR101807191 B1 20171208; KR20110128783 A 20111130; MX2011005987 A 20110915; RU2011128394 A 20130120; RU2480330 C2 20130427; US2011236702 A1 20110929; US2014370312 A1 20141218; US8980144 B2 20150317

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BUSCH DETLEF; EIDEN HARALD; PETERS CHRISTIAN; SCHAAN JOSEF

Treofan Germany GMBH and CO KG

Verfahren zur Herstellung von Polypropylenfolien. "Method for producing polypropylene films."

WO2010118447 A1

20101021

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AT20090000599 20090417

FEICHTINGER KLAUS; HACKL MANFRED; WENDELIN GERHARD

EREMA

Verfahren zur Recyclierung von Kunststoffen. "Method for recycling plastic materials."

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US201261696476P 20120904

STANHOPE BRUCE; ZEHNER BURCH E; BUHRTS BRYAN K

CPG INT LLC

Use of recycled packaging in polymer composite products.

WO2014127133 A1

20140821

US2015051339 A1 20150219

US201361764384P 20130213

BRUNNER PHILIP J; TORKELSON JOHN M; WAKABAYASHI KATSUYUKI

UNIV NORTHWESTERN

Method for processing polymers and/or polymer blends from virgin and/or recycled materials via solid-state/melt extrusion.

WO2014162238 A2

20141009

US2016039992 A1 20160211; WO2014162238 A3 20150402

IN2012DEL3342 20130331

JAIN PRANAY

JAIN PRANAY

A process for recycling a metalized polyester film.

WO2015177580 A2

20151126

CA2949927 A1 20151126; EP3145995 A 20170329 EP3145995 A4 20180214; HU1400262 A2 20151130; US2017174883 A1 20170622; WO2015177580 A3 20160428

HU20140000262 20140523

´ ´ RI LA ´ SZLO CSATA

´ GER INVEST JA KERESKEDELMI ´ E´S ´ LTATO SZOLGA INGATLANHASZNOSITO KFT

Polymer blend and polymer agglomerate containing recycled multilayer film waste and fiber reinforced plastic waste and process for preparing said agglomerate.

WO9407671 A1

19940414

TW221392 B 19940301

US19920953473 19920929

PREW STANLEY R

SPROUT BAUER INC ANDRITZ

Apparatus and process for washing and shredding film.

9 Chemical Recycling 9.1 Types of Chemical Recycling Chemical (or tertiary) plastic recycling refers to processes by which at least one polymer of a plastic article is depolymerized to yield repolymerizable monomers and/or oligomers, which are recovered for producing new polymers. The chemical recycling of polymers aims mainly at saving the material resources and less at reducing the amount of waste generated by slowly degrading polymers. Chemical recycling can replace fossil fuel resources for chemical production of monomers and/or oligomers with recycled material from plastic waste. Directive (EU) 2018/852 amending Directive 94/62/EC on packaging and packaging waste (see Chapter 10, Section 10.1) states that plastic waste can be considered as (chemically) recycled only if it is not subject to energy recovery and is processed into new materials that are not to be used as fuels (see Section 9.6) [1]. The main types of chemical recycling are solvolysis and thermolysis. A special type of chemical recycling is enzymatic depolymerization. The available processes for the depolymerization of rigid plastic packaging and nonpackaging films (e.g., agricultural films), fibers, foams, etc., can be equally applied to the depolymerization of flexible plastic packaging. In principle, chemical recycling can enable the recovery of various polymers from multilayer flexible packaging reducing the need for the complex separation processes employed by mechanical recycling. Further, the mechanical recycling of plastics produces materials with inferior properties, and the recycling process, with the progressive degradation of the products, cannot be conducted endlessly. On the other hand, chemical recycling has not been applied so far to the depolymerization of polymers of flexible packaging because of economic considerations and other processing challenges. Chemical depolymerization has the highest product value; however, the feed for this process requires a pure plastic stream and, therefore, presorting. Chemical recycling processes are energy demanding requiring in general high temperature and/or pressure and/or the presence of catalysts. There is no technology available for the depolymerization of polyolefins, namely polyethylenes, contained in flexible plastic packaging Recycling of Flexible Plastic Packaging https://doi.org/10.1016/B978-0-12-816335-1.00009-8 Copyright © 2020 Elsevier Inc. All rights reserved.

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materials to monomers and/or oligomers with the purpose of obtaining new polymers. Most of the available technologies apply to the depolymerization of PET films and are borrowed from the chemical recycling of PET bottles. Currently, chemical recycling represents only a marginal share of recycling (