Recycling of PET wastes

Recycling of PET Wastes. Hoechst Celanese has built a 70 000 t/a plant at Wilmington, Delaware, to recycle poly(ethylene terephthalate) wastes by methanolysis. 

FIGURE 6.3 Flow diagram of a typical system for glycolytic recycling of PET waste. (After Richard, R., ACS Polym. Prepr., 32(2), 144, 1991. With permission.)... 

Shukla SR, Harad AM, Jawale LS. Chemical recycling of PET waste into hydrophobic textile dyestuffs. Polym Degrad Stab 2009 94 (4) 604-609. 

A method for removing the contaminants in the recycling of PET waste has also been devised. In this process, PET is transesterified by heating with ethylene glycol to give a solution containing short chain PET and bis(2-hydroxyethyl) terephthalate. By hydrolysis of this mixture at elevated pressure and temperature, ethylene glycol and terephthalic acid crystals are produced. Activated carbon and clay are used to absorb contaminants for separation by filtration. ... 

PET recycling represents one of the most successful and widespread examples of polymer recycling. The recycling of PET waste can be carried out in many ways. 

Contamination problems act as a barrier to the recycling of PET bottle waste. The presence of impurities that generate acid compounds at the high temperatures reached during the extrusion process prior to blow molding is a major problem in the reprocessing of PET because chain cleavage reactions are acid catalyzed. EVA... 

Rieckmann, Th., Poly condensation and recycling of PET fibres and other PET waste by continuous processes, presentation given at the 5th Conference on Man-Made Fibres, Beijing, China, 1994. 

Originally, PET methanolysis was developed by PET manufacturers as a process aimed at the recovery and treatment of polyester wastes generated during the production cycle in order to increase the polyester yield. However, with the increase in environmental public concern, methanolysis began to be considered as a feasible alternative for the recycling of PET residues present in the solid waste stream. 

A practicable reextrusion process was worked out and described by Syntex Chemie nearly forty 30 years ago [23]. This method—with some modifications—is still being used. The greatest recycler of fiber waste in the U.S. is Wellman they recover PET fiber and bottle waste for home furnishing and nonwoven materials by a similar method. 

The larger use of PET film is as a photographic film base, which accounts for over 50% of the PET film produced in the world. The manufacturers of these materials, mainly Agfa-Gaevert, Eastman Kodak, du Pont de Nemours, Fuji, 3M, and Konishiroku, have long been interested in the recovery of PET film because of its content of rather expensive silver derivatives. Recycling of PET-film waste in production, which may amount to 25-30% of the total output, is almost complete by these manufacturers. 

Asahi Carry out chemical recycling of PET bottles and post-industrial fibre waste. A methanolysis process termed Ecosensor is used to produce DMTA and EG, and is claimed to provide high-purity products which are used in fibre applications ( bottle to fleece system). No intellectual property has been found directly assigned to this company, which suggests that the process may be licensed from another concern. The website is tvtvw.ashai-kasei.co.jp. 

Petcore, Guidelines on Acceptability of Additives and Barrier Materials in the PET Waste Stream for an Effective Recycling of PET, http //www.petcore.org/chargement/publications/ Guidelines.pdf. 

PET recycling technologies have become well known and represent one of the most successful and widespread examples of polymer recycling. There are two methods of recycling PET waste one method involves physical recycling to produce PET flakes which are reused in a resin, and the other method involves chemical recycling via the depolymerisation of PET wastes. 

---