Recycling of Polyethylene Terephthalate

Martin J. Forrest

• Publisher: De Gruyter
• Year: 2019
• ISBN:
  9783110640458
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Ingénierie de la chimie et de la biochimie

Polyethylene terephthalate (PET) is the most recycled plastic in the world. This book covers all from the world market of PET to the many technologies and processes developed for separation, decontamination, recycling and manufacturing into food-grade and non-food-grade products of PET. Also, regulations, testing methods and analytical procedures according to the current regulatory framework are presented.

1 Introduction to polyethylene terephthalate recycling

The recycling of polyethylene terephthalate (PET) has been carried out for many years, with Saint Jude Polymers reported as being the first company in the USA to set up a process to recycle PET bottles in 1976. In this process, the bottles were recycled into plastic strapping and paintbrush bristles, and 1 year later the company began to produce pelletised recycled polyethylene terephthalate (rPET) for the general market. Other companies, particularly Wellman Incorporated, started to recycle PET into other products (e.g., carpet fibres) and the rPET industry continued to expand throughout the 1980s and 1990s. Given its large-scale use for food-packaging products, it was only a matter of time before this market was targeted. By the 1990s, with the appropriate recycling technology now available, ‘letters of no objection’ started to be issued by the US Food and Drug Administration for the use of rPET in food contact packaging applications [1].

However, in common with other major manufacturing industries, such as the rubber industry, the pressure on the plastics industry and the many users of its products to recycle plastic has increased dramatically over the last 25 years or so due to a combination of economic, environmental, societal and legislative factors. The need to conserve natural resources, coupled with the publication of important legislation, such as the Landfill Directive (1999/31/EC) and the Packaging and Packaging Waste Directive (94/62/EC) in the European Union (EU), have stimulated the search for technologies and manufacturing processes that can recycle and re-use waste plastic. When it comes to recycling, the significant advantage that plastics, such as PET, have over thermoset materials, such as rubber and thermosetting resins (e.g., phenolics and epoxies) is that, once separated and decontaminated, they can be reprocessed using the same processing techniques as their virgin equivalents.

In the EU, the debate on how to continue to increase the amount of plastic that is recycled and re-used for the benefit of the community is continuing. A demonstration of the intention to increase the focus on plastic recycling was provided by the recent green paper by the European Commission (EC) indicating that it planned to revise legislation affecting this sector [2]. The main focus of this legislation is likely to be greater emphasis on recycling targets, solving the problem of the landfilling of plastics and increasing the quality of recyclates. Some of the proposals in this green paper were:

• – Phasing out landfilling by 2025 for recyclable materials (e.g., plastics, metals, paper, and bio-waste).
• – Recycling and preparing for re-use of packaging waste to be increased to 80% by 2030, with material-specific targets set to increase gradually between 2020 and 2030, to reach:
• – 60% for plastics by the end of 2030.
• – 80% for wood and 90% ferrous metal, aluminium and glass by the end of 2030.
• – 90% for paper by the end of 2025.
• – Recycling and preparing for re-use of municipal waste to be increased to 70% by 2030.

It has been reported [3] that the comments that were received by the EC after the publication of this green paper showed that there was strong support for promoting monomaterials and improving the design of plastics to increase recyclability. In addition, the responses obtained showed that there were split views about biodegradable and bio-based plastics, that more consumer information on plastics recycling was needed, and that better waste collection and sorting infrastructure was required.

Due to these considerations, increased funding has become available from several sources, including national and regional governments, and the area of plastics recycling is now an extremely active one with areas such as improved sorting and identification systems and the production of food-grade recyclate being of particular interest to researchers. It is possible to divide different types of recycling activities and processes for waste plastics into four broad generic categories:

• – Primary: Reprocessing into materials and products having properties that are the same (or at least comparable) to the original material or product.
• – Secondary: Where the recycled plastic is made into products that do not have (or need to have) properties that are the same or comparable to the original product.
• – Tertiary: The reduction of the recycled plastic into small chemical units (i.e., molecules) that can then be recycled into new materials and products by routes such as re-polymerisation.
• – Quaternary: The recovery of the energy inherently present in recycled plastic by methods such as incineration or the burning of fuel products that are derived from pyrolysis processes.

As this book demonstrates, all four of the recycling routes described above have been explored in the search for new and effective ways to recycle PET. The relative ease with which PET can be depolymerised by hydrolysis has resulted in variants of the Tertiary route often being used as part of the purification process in order to produce food grade rPET. Evidently, in this case, because the purpose is to re-create high-quality, high-molecular weight rPET [e.g., for bottle-to-bottle (B2B) recycling], this particular recycling stream could also be regarded as a form of the Primary route.

PET is an important class of plastic material and it is used for several applications (Chapters 8 and 9), including:

• – Food packaging (e.g., bottles, trays and film)
• – Non-food packaging (e.g., containers for cosmetics, healthcare, and detergents)
• – Strapping products
• – Fibres (e.g., for clothing and bags)
• – Non-woven fabrics
• – Carpets

Of the end-applications for PET, packaging, both food [4] (Figure 1.1) and non-food, is the most important. It is in this area that most of the recycling effort has been concentrated, particularly in the food-packaging sector, where several new technologies (often referred to as ‘super-clean’ recycling processes) have been developed to enable post-consumer waste (particularly PET bottles) to be re-recycled back into food grade pellets and products (Chapter 6). The market in Europe and the rest of the world for PET B2B recycling is growing rapidly due to several factors, including government initiatives intended to facilitate the meeting of recycling targets, and technological advances which have seen the development of several chemical and physical processes that can regenerate food-grade PET. In Europe, there are many super-clean recycling processes (mostly for PET) that are awaiting consideration by the European Food Safety Authority (EFSA). This fact has not stopped them being used commercially as the dossiers to show that they meet the EU Plastics Recycling for Food Use Regulation 282/2008/EC were compiled for these submissions, and EFSA permits the processes to be used while the assessment is being carried out. EFSA adopted its first three scientific opinions on the safety of processes to recycle PET for use in food contact materials in 2012 [5]. These processes were considered by EFSA not to give rise to safety concerns if operated under well-defined and controlled conditions as outlined in 282/2008/EC. These three ‘opinions’, which were to be the first in a series to be published by EFSA (Chapter 6), covered ten recycling processes, which were grouped according to the particular type of recycling technology that they employed, as shown below:

• – Four recycling processes based on VACUREMA Prime® technology.
• – Five recycling processes based on Starlinger IV+® technology.
• – Recycling process ‘PETUK SSP’.

Figure 1.1: Typical PET food tray packaging in the UK. Reproduced with permission from the Waste and Resources Action Programme (WRAP), Banbury, UK. ©WRAP.

The relative importance of PET in the packaging market is shown in data provided by Mergers Alliance [6]. They have described the overall market structure for plastic packaging in the EU (Table 1.1) and, of the ≈18 million tonnes of plastic that are converted into all types of packaging (i.e., food and non-food), PET has an overall share of 8.6%.

Table 1.1: Types of plastic used in the packaging industry within the EU [6].

Plastic type	Share of total packaging (%)
PS	4.7
Polyurethane	6.7
PET	8.6
PVC	11.3
Low-density PE	11.5
HDPE	17.9
PP	18.6
Other	20.7

PE: Polyethylene

PP: Polypropylene

PS: Polystyrene

PVC: Polyvinyl chloride

Reproduced with permission from Mergers Alliance, Plastics Europe MRG, Rexam, 2012. ©2012, Mergers Alliance [6] http://www.mergers-alliance.com

The average rate of recycling for plastic packaging in the EU is 26% and, as described in Chapters 2 and 3, plastic bottles are the leading source of plastic for recycling, accounting for more than half of all plastic recycled in 2012, and the biggest growth opportunities for recycled plastics in packaging will come from PET. This scenario was illustrated by Mergers Alliance [6] who estimated in 2012 that, at the end of its life, 66% of the ≈18 million tonnes of plastic packaging was recycled (into new products or energy recovery), but that 34% was sent to landfill.

Industry is assisting the growth of rPET in food packaging by developing new equipment that can tackle production issues. For exam...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• Preface
• Acknowledgements
• Contents
• 1 Introduction to polyethylene terephthalate recycling
• 2 Overview of the world market for recycled polyethylene terephthalate
• 3 Brief history of the recycling of polyethylene terephthalate
• 4 Regulations and guidance documents from the european union and US food and drug administration
• 5 Separation and sorting technologies
• 6 Recycling technologies for polyethylene terephthalate
• 7 Testing and characterisation of recycled polyethylene terephthalate products
• 8 Food-grade products made from recycled polyethylene terephthalate
• 9 Other products manufactured from recycled polyethylene terephthalate
• 10 Conclusion
• Abbreviations
• Index