PET-waste

By depolymerizing PET waste with a polyol and subsequently condensing the oligomeric product with a polycarboxylic acid or anhydride, polyester resins are produced which have wide industrial applications. Depending on the polyol and polycarboxylic acid or anhydride used, saturated resins, alkyd resins, or unsaturated resins are obtained. PET wastes have been used for the production of alkyd resins in water thinnable paints. The materials obtained from the reaction of PET with a mixture of fatty acids high in linoleic acid content and trimethylolethane have been used in the preparation of water-dispersible coatings. Products of the depolymerization of PET with trimethylolpropane and pentaerythritol are used in the manufacture of high-solids paints. In the first step, PET is depolymerized with trimethylopropane and pentaerythritol at temperatures of 230-240°C. The final paint compositions contain 30-50% of PET depolymerization products.12... 

PET waste has been used in the manufacture of terephthalic electroinsulation lacquers. Here PET is heated in a mixture of a triol and glycol at temperatures of 230-260°C followed by catalytic transesterification and distillation of low-molecular-weight products of degradation until a polyester with the required softening temperature (ca. 60-100°C) is obtained. 

Methanolysis products are separated and purified by distillation. BHET, the monomer obtained by PET glycolysis, is normally purified by melt filtration under pressure. One of the problems encountered in neutral hydrolysis of PET is that the terephthalic acid isolated contains most of the impurities initially present in the PET waste. Hence very elaborate purification processes are required to obtain terephthalic acid of commercial purity. 

PET waste was glycolyzed at different weight ratios of PET to propylene glycol in die presence of 0.5% (w/w) zinc acetate, based on the weight of PET, as the catalyst. The reaction was carried out at about 200°C under redux in a nitrogen atmosphere for 4 h in a four-necked round-bottom dask fitted widi a redux condenser, gas bubbler, thermometer, and stirrer. 

Glycolyzed PET waste, polyester polyols from, 559-560 Glyptal resins, 18... 

Unsaturated polyesters (UPs), 4, 18, 19 from PET waste, 560-561 Unsaturated polyester/styrene resin, preparation and cure of, 101 Unsaturated polyester thermosetting resins, syntheses of, 101-103 Unstirred interfacial process, 155 U-Polymer, 77... 

Macromolecular Materials and Engineering 286, No.ll, 30thNov.2001, p.695-704 UV CURABILITY AND MECHANICAL PROPERTIES OF NOVEL BINDER SYSTEMS DERIVED FROM POLY(ETHYLENE TEREPHTHALATE)(PET) WASTE FOR SOLVENTLESS MAGNETIC TAPE MANUFACTURING. I. ACRYLATED OLIGOESTERS Farahat M S Nikles D E Alabama,University... 

The effect of incorporating p-hydroxybenzoic acid (I) into the structures of various unsaturated polyesters synthesised from polyethylene terephthalate (PET) waste depolymerised by glycolysis at three different diethylene glycol (DEG) ratios with Mn acetate as transesterification catalyst, was studied. Copolyesters of PET modified using various I mole ratios showed excellent mechanical and chemical properties because of their liquid crystalline behaviour. The oligoesters obtained from the twelve modified unsaturated polyesters (MUP) were reacted with I and maleic anhydride, with variation of the I ratio with a view to determining the effect on mechanical... 

UNSATURATED POLYESTER RESINS ON THE BASE OF CHEMICAL DEGRADATION PRODUCTS OF PET WASTE FOR VARNISHES... 

Davos, 14th-18th March 1994, paper 55. 8(13) CHEMICAL RECYCLING STARTING FROM POST CONSUMER PET WASTE TO POLYMER QUALITY PTA Benzaria J Recopet... 

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. 

Long-term durability of the PET waste form is not known. 

The activation of PET waste produce carbon materials suitable for using as active carbons, with very high BET apparent surface areas -up to 2468 m g" -. These active carbons are mainly microporous, with low meso and macroporosity. It was observed that the increase in the activation degree (i.e., bum-off) produces a gradual increase in the volume of total micropores, probably by enlarging the small micropores besides creating new porosity. Further studies on this topic are ongoing. 

The high cost of resins used in the production of polymer concrete (PC) makes the material expensive relative to cement-based materials. Not surprisingly, a recent survey ranked lower cost resins as the most important future need for PC [1], Recently, some work has been done on the production of unsaturated polyester resins based on recycled poly (ethylene terephthalate), PET [2], The PET wastes are typically found in used beverage bottles, and many states have passed legislation to collect and recycle these bottles. If specially formulated, the unsaturated polyester could be used in the production of PC [3],... 

PET wastes, proved to be an excellent raw material for low cost aromatic polyester polyols. By transesterification with DEG and (or) propylene glycol or dipropyleneglycol (DPG), liquid, low viscosity and low functionality aromatic polyester polyols were obtained. Due to the low cost, DEG is the preferred glycol for transesterification (reaction 16.3) [4, 6-8, 12]. 

The reaction between PET and DEG takes place at higher temperatures, around 200-230 °C, without catalysts or better still in the presence of the usual catalysts for polyester synthesis (lead, manganese, tin, titanium or zinc compounds). In the situation of transesterification without catalyst, the catalyst existing in PET wastes acts as the catalyst for glycolysis, but the reaction needs longer times. The time for liquefaction of PET with DEG varies from 6-14 hours [2, 4]. 

The characteristics of some aromatic polyester polyols derived from the glycolysis of PET wastes are presented next ... 

The reaction of polyethylene terephthalate) (PET) with diethanolamine, followed by propoxylation, gives liquid amidic polyols useful in rigid PU foam fabrication. This method is an efficient variant of PET waste chemical recovery (bottles, x-ray films, fibres and so on) [1]. 

Glycolysis is the simplest and oldest method of PET depolymerization. The first patents on PET glycolysis were filed more than 30 years ago.3-9 The method involves the reaction of PET, under pressure and at temperatures in the range 180-240 °C, with an excess of glycol, usually ethylene glycol, which promotes the formation of BHET.10-13 This monomer has to be purified, normally by melt filtration under pressure, prior to its use in the production of new PET polymer. Colours present in the starting PET wastes are not usually removed by glycolysis. The depolymerization is carried out in the presence of a transesterification catalyst, usually zinc or lithium acetate. 

The following phenomena have been proposed to describe the mechanism of PET glycolysis 14,15 glycol diffusion into the polymer, polymer swelling which increases the diffusion rate, and reaction of the glycol with an ester bond in the chain. Because the reaction rate is proportional to the polymer surface area, it is advisable to first reduce the size of the raw PET waste to small particles by grinding, cutting, etc. 

The reaction temperature can be reached by heating and melting the PET wastes in a first step, which are subsequently contacted with methanol. In other... 

One of the major problems associated with the neutral hydrolysis method is that most of the impurities initially present in the PET waste remain in the TPA produced by the reaction. Therefore, complex and intensive purification operations are needed to obtain TPA with properties similar to the commercial grades. A hydrogenation step has been proposed as a method for the removal of impurities and colour found in the TPA produced by PET neutral hydrolysis.60 TPA precipitated from the hydrolysis medium is slurried in water and cata-lytically hydrogenated at 260-290 °C and a pressure of 65-82 atm for around 1 h. Palladium supported on carbon is one of the preferred catalysts for this hydrogenation step. This treatment leads to a colour level and fluorescence properties in the produced TPA similar to those of the commercially available virgin PET. 

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