PET production

Processing is similar to other engineering plastic resins. Drying is necessary before extmsion or molding. Special drying precautions are required for PET products to prevent degradation and splay. 

Depolymerization mechanisms, 456 Depolymerized PET products, applications of, 531-532 Deuterium NMR, 328 Dexon, 28... 

PET industrial synthesis, 70 PET monomers, recycling of, 539-541 PET products, recycled and depolymerized, 531-532 PETRA, 532... 

Terephthalic acid (p-TA or TA), a raw material for polyethylene terephthalate (PET) production, is one of the most important chemicals in petrochemical industry. Crude terephthalic acid (CTA), commonly produced by homogeneous liquid phase p-xylene oxidation, contains impurities such as 4-carboxybenzaldehyde (4-CBA, 2000-5000 ppm) and several colored polyaromatics that should be removed to obtain purified terephthalic acid (PTA). PTA is manufactured by hydropurification of CTA over carbon supported palladium catalyst (Pd/C) in current industry [1]. 

Area occupied by PET production ca. 4 ha Assume area needed for infrastructure (raw material/energy provision, processing) for chemicals production and sheep-rearing are similar... 

Transesterification is a crucial step in several industrial processes such as (i) production of higher acrylates from methylmethacrylate (for applications in resins and paints), (ii) polyethene terephthalate (PET) production from dimethyl terephthalate (DMT) and ethene glycol (in polyester manufacturing),... 

PET production in, 20 20 petrochemical industry in, 24 254 petroleum refineries in, 24 258 phenol producers in, 18 752t phenolic resin manufacturers in, 18 774 phosphate rock production by, 19 17 phosphate rock statistics for, 19 15t phosphorus compound production in, 19 67t, 68t... 

The formation of prepolymer can also be achieved by transesterification of dimethyl terephthalate (DMT) with EG, releasing the by-product methanol. High-purity DMT is easily obtained by distillation and in the early years of PET production, all processes were based on this feedstock. During the late 1960s, highly purified TPA was produced for the first time on an industrial scale by re-crystallization. Since then, more and more processes have shifted to TPA as the feedstock and today more than 70 % of global PET production is based on TPA. The TPA-based PET production saves approximately 8 % of total capital investment and 15% of feedstock cost (Figure 2.1). 

In the next sections, we will discuss the chemical and kinetic details of the main reactions and the product-quality relevant side reactions. This information is the basis for a proper understanding of reactor and process design in PET production. The compounds and functional groups which have to be considered are given in Table 2.2. 

Transesterification is the main reaction of PET polycondensation in both the melt phase and the solid state. It is the dominant reaction in the second and subsequent stages of PET production, but also occurs to a significant extent during esterification. As mentioned above, polycondensation is an equilibrium reaction and the reverse reaction is glycolysis. The temperature-dependent equilibrium constant of transesterification has already been discussed in Section 2.1. The polycondensation process in the melt phase involves a gas phase and a homogeneous liquid phase, while the SSP process involves a gas phase and two solid phases. The respective phase equilibria, which have to be considered for process modelling, will be discussed below in Section 3.1. 

Many studies on the modelling of esterification, melt polycondensation, or solid-state polycondensation refer to the reaction scheme and kinetic data published by Ravindranath and co-workers. Therefore, we will examine the data sources they have used over the years. The first paper concerned with reactor modelling of PET production was published by Ravindranath el al. in 1981 [88], The reaction scheme was taken from Ank and Mellichamps [89] and from Dijkman and Duvekot [90], The kinetics for DEG formation are based on data published by Hovenkamp and Munting [60], while the kinetics for esterification were deduced... 

The production of PET is a well-known industrial process. Early patents on PET synthesis refer to the 1940s. Esterification and transesterification reactions have been investigated since the end of the 19th century. PET production plants have been optimized over the last few decades based on well-established production know-how . PET is now a commodity product with unusually rapid growth and further nearly unlimited future growth perspectives. 

Furthermore, the environmental impact of PET production should be reduced by substituting the commonly used antimony-based catalyst for an antimony-free catalyst leg, for a titanium-based catalyst. The pollution by liquid effluents could be reduced by installing a reverse-osmosis unit on top of the glycol distillation unit for the purification of water from the esterification process. 

Figure 5.22 Scattering in the degree of polycondensation of the PET product, as a result of variations in the particle size and intrinsic viscosity in the virgin polymer s/mp, standard deviation of the particle mass [12b]. From Weger, F., Solid-state postcondensation of polyesters and polyamides, presentation given at the FrankI and Thomas Polymer Seminar, June 16,1994, Greenville, SC, USA, and reproduced with permission of EMS Inventa-Fischer, GmbH Co. KG...

Although PBT has many desirable properties, its rapid crystallization almost always renders it opaque. While transparent PET products are quite common, PBT crystallization can rarely be quenched to the extent necessary for the formation of transparent articles. Thin films of PBT are translucent, allowing some light to penetrate, but are almost never clear. 

Thiele, U., Which criteria of polymer lines of PET Production determine quality and purity of the melt (in German), presentation given at the 3rd Plastic Symposium ofGneufi Bad Oeynhausen, Germany, 15-16 September, 1999. 

PET producers have had to deal with recovery of scrap polymer since the 1950s, particularly when raw materials were rather expensive. Glycolysis has been and is practiced within the production setting on material of known composition and acceptable purity. Methanolysis was practiced in the United States and Europe until about 1980 as most PET production was then based on DMT and EG. Methanolysis is still practiced on post-consumer and pre-consumer X-ray film by the Eastman Kodak Company which uses the DMT and EG to make more film. Other than an occasional use of glycolysis, no other large-scale, on-going commercial use of post-consumer PET is made in developed countries. 

The 1-2 order of magnitude decrease of the rate constant for the recombination of PET products, in comparison with the homogeneous solution, was also observed by Matsuo and co-workers [167, 168]. In their studies one of these products was hydrophilic and thus located in the aqueous phase, while the other was hydrophobic and thus immersed in the membrane. Such a decrease of the rate is, apparently, a common feature of the reactions providing electron transfer across the membrane // water interface between the reagents with substantially different hydro-phobidty. 

Polyethylene Terephthalate (PET) A plastic resin of the polyester family and one of the most common thermoformed plastics. Plastic soda bottle are a common PET product. PET is also fully recyclable. 

Glycols manufactured by this process are among the highest quality in the world these products easily and consistently meet the most stringent specifications used in polyester fiber and PET production. 

Indoor exposure assessments can be more complex than outdoor assessments. The indoor assessments are often complicated by the fact that pesticide application methods and their placement within the indoor environments are very diverse and include, for example, crack and crevice treatment, carpet treatment, room loggers, moth repellents, residual termiticides, disinfectants and pet products. This diversity also means that potential human contact with the residues may range from a low probability (crack and crevice treatment) to a higher probability (indoor broadcast treatment such as an indoor total release logger) because of the nature of the application and the variability in activities that may bring individuals in contact with treated areas. Furthermore, the varied characteristics of the source (e.g. formulation type, application methods, room of application and duration of emission) and the indoor residential environment (e.g. room size, air exchange rates, temperature and types of surfaces, such as carpet, upholstery, vinyl, etc.) significantly influence exposure pofenfial. 

To comply with the general requirements of Article 3 of the EU Regulation 1935/2004 sufficient sensory inermess of the PCR PET products as food contact articles needs to be assured. Therefore appropriate sensory testing of food contact articles made from super-clean products is recommended. As worse case test conditions for this purpose, storage of the article in direct contact with water for ten days at 40 °C have been generally accepted. However, depending on the particular application, modified tests may be more suitable. 

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