Recycling Polyesters by Chemical Depolymerization

Abstract

In the presented paper, two basic strategies that can be used in the processes of chemical recycling of polyester material were described. The first of them involves increasing the molar mass of recycled materials in the solid-state polycondensation (SSP) process and/or joining their chains with various types of substances easily reacting with the end groups of polyesters (so-called extending agents). The essence of the second strategy is the degradation of the material under the influence of various protogenic agents (such as water, alcohols, glycols and amines) to obtain low-molecular products or oligomers that can be used as raw materials in the synthesis of many classes of polymers. The methods that are already used in PET [poly(ethylene terephthalate)] recycling and the possibility of their extension to other types of polyesters are both shown.

Degradation and Recyclability of Poly (Ethylene Terephthalate)

“…Chemical recycling of polyethylene terephthalate into yarn through a process where part of the virgin raw materials are replaced by washed post consumer polyester which is partially depolymerized before repolymerization [42]. Controlled hydrolysis of polyethylene terephthalate using dilute HNO3 as catalyst is shown to produce cation exchange sites based on acidic groups and the acid sites are shown to adsorb heavy metal cations like Cd + + , large cationic dye molecules and the acid hydrolysis is shown to be much more efficient compared to neutral and alkaline hydrolysis [43].…”

100th Anniversary of Macromolecular Science Viewpoint: Needs for Plastics Packaging Circularity

“…Patel et al calculated that for PET, depolymerization by either methanolysis or ethanolysis, followed by repolymerization, is environmentally advantageous over virgin PET production . Polyethylene terephthalate recycling by depolymerization has been demonstrated as industrially viable several times over the last 50-plus years. , In fact, Eastman Kodak built a PET depolymerization plant as early as the 1970s to recover dimethyl terephthalate (DMT). At that time, the drive to recycle was due to the expense of producing virgin DMT.…”

Systems Analysis Approach to Polyethylene Terephthalate and Olefin Plastics Supply Chains in the Circular Economy: A Review of Data Sets and Models

“…Depending on the type of depolymerizing technology, capital costs for a depolymerization facility processing 22 700 tonnes/year could range from $0.98− $1.41/kg of annual product, while that for simple glycolysis without purification of the product was $0.39/kg of product. 181 Data Sets and Models for Landfills. Landfilling is possibly the lowest-value end-of-life management process for plastics, in that it generates no economic return and costing municipalities money to permanently store the material.…”

“…The commercial economic success of depolymerization technologies of PET bottles to produce food grade articles depends on desired products and quality and quantity of the feedstock. Depending on the type of depolymerizing technology, capital costs for a depolymerization facility processing 22 700 tonnes/year could range from $0.98–$1.41/kg of annual product, while that for simple glycolysis without purification of the product was $0.39/kg of product …”