Dimethyl terephthalate ethylene glycol polyester

Dimethyl terephthalate + ethylene glycol Polyester resin Ediylene glycol Various 320-570 Distillation of solvent and recovery of the polymer as a melt... 

Fig. 1 Effect of acidic catalysts on acetal-containing polyesters. , Dimethyl terephthalate-ethylene glycol polyester , dimethyl terephthalate-pentaerythritol acetal-ethylene glycol...

Unlike poly(ethylene terephthalate), the polyester from dimethyl terephthalate and cyclohexane-1,4-dimethylol can be manufactured with initially equivalent monomer quantities. It has improved dyeability, just as in the case of the copolymer of dimethyl terephthalate, ethylene glycol, and 5-10% p-hydroxybenzoic or isophthalic acid. 

PET is the polyester of terephthalic acid and ethylene glycol. Polyesters are prepared by either direct esterification or transesterification reactions. In the direct esterification process, terephthalic acid is reacted with ethylene glycol to produce PET and water as a by-product. Transesterification involves the reaction of dimethyl terephthalate (DMT) with ethylene glycol in the presence of a catalyst (usually a metal carboxylate) to form bis(hydroxyethyl)terephthalate (BHET) and methyl alcohol as a by-product. In the second step of transesterification, BHET... 

Table 13 2 lists the average commercial specifications of terephthalic acid and dimethyl terephthalate used to manufacture fibers. Terephthalic acid and its methyl ester are utilized chiefly in the form of ethylene glycol polyester for fibers, films, and resins. They are also used in the manufacture of polyesters of butylene glycol (PBT). Among the various applications is the manufacture of additives for lubricants, plasticizers and adhesives. Uses in Western Europe, the United States and Japan in 1984 are given in Table 13.3. This table also gives the. production- capacities -of. terephthalic. acid and dimethyl terephthalate in Western Europe, the United States and Japan in 1984.

Reactions of the Methyl Groups. These reactions include oxidation, polycondensation, and ammoxidation. PX can be oxidized to both terephthahc acid and dimethyl terephthalate, which ate then condensed with ethylene glycol to form polyesters. Oxidation of OX yields phthaUc anhydride, which is used in the production of esters. These ate used as plasticizers for synthetic polymers. MX is oxidized to isophthaUc acid, which is also converted to esters and eventually used in plasticizers and resins (see Phthalic acids and otherbenzenepolycarboxylic acids). 

Manufacture. The manufacture of 1,4-cyclohexanedimethanol can be accompHshed by the catalytic reduction under pressure of dimethyl terephthalate ia a methanol solution (47,65). This glycol also may be prepared by the depolymerization and catalytic reduction of linear polyesters that have alkylene terephthalates as primary constituents. Poly(ethylene terephthalate) may be hydrogenated ia the presence of methanol under pressure and heat to give good yields of the glycol (see Polyesters) (66,67). 

Manufacture and Processing. Terephthalic acid and dimethyl terephthalate did not become large-volume industrial chemicals until after World War II. Imperial Chemical Industries in the United Kingdom in 1949 and Du Pont in the United States in 1953 commercialized fibers made from poly(ethylene terephthalate). Dimethyl terephthalate and ethylene glycol were the comonomers used by both companies (see Fibers, polyester). 

Polyethylene terephthalate [25038-59-9] (8) is a polyester produced by the condensation polymerization of dimethyl terephthalate and ethylene glycol. Polyethylene terephthalate sutures are available white (undyed), or dyed green with D C Green No. 6, or blue with D C Blue No. 6. These may be coated with polybutylene adipate (polybutilate), polyydimethylsiloxane, or polytetrafiuoroethylene [9002-84-0]. The sutures are distributed under the trade names Ethibond Exel, Mersdene, Polydek, Silky II Polydek, Surgidac, Tevdek II, Polyester, and Tl.Cron. 

Polyester Polyols. Initially polyester polyols were the preferred raw materials for polyurethanes, but in the 1990s the less expensive polyether polyols dominate the polyurethane market. Inexpensive aromatic polyester polyols have been introduced for rigid foam appHcations. These are obtained from residues of terephthaHc acid production or by transesterification of dimethyl terephthalate (DMT) or poly(ethylene terephthalate) (PET) scrap with glycols. 

On the basis of bulk production (10), poly(ethylene terephthalate) manufacture is the most important ester producing process. This polymer is produced by either the direct esterification of terephthaHc acid and ethylene glycol, or by the transesterification of dimethyl terephthalate with ethylene glycol. In 1990, poly(ethylene terephthalate) manufacture exceeded 3.47 x 10 t/yr (see Polyesters). Dimethyl terephthalate is produced by the direct esterification of terephthaHc acid and methanol. 

The most generally useful polyester is that made by reaction between dimethyl terephthalate (dimethyl 1,4-benzenedicarboxylate) and ethylene glycol (1,2-ethanediol). The product is used under the trade name Dacron to make clothing fiber and tire cord and under the name Mylar to make recording tape. The tensile strength of polyethylene terephthalate) film is nearly equal to that of steel. 

Both terephthalic acid (TPA) and dimethyl terephthalate (DMT) are used exclusively for the manufacture of polyesters for textile fibers (e.g,. Dacron ), films, soft-drink bottles, and engineering resins for automotive applications. The glycol used for most TPA-based polyesters is ethylene glycol. The polyester is then known as polyethylene terephthalate, or PET. 

Polyester has become a mainstay commodity material. This is one material that everyone comes in contact with daily for example, it is used in clothing, bedding, upholstery and carpeting. The first patent to cover polyesters was filed in 1941 by Whinfield and Dickson, with the material defined as a polymer formed by the combination of a diacid and a diol [1]. Following this discovery, the first commercial polyester, polyethylene 1,4-terephthalate) (PET), was produced by condensation polymerization of terephthalic acid (TA) (or dimethyl terephthalate (DMT)) as the diacid moiety and ethylene glycol as the diol. PET is now a well-known and widely utilized polymer material that is used throughout the world to manufacture films and fibers. 

The sole use for para-xylene is to make terephthalic acid (TPA) and its derivative, dimethyl terephthalate (DMT). When DMT is copolymerized with ethylene glycol, chemists call it polyethylene terephthalate. On Seventh Avenue in New York, they call it polyester. On the labels, it is sometimes called Dacron. 

Prior to polymerization, p-xylene is first oxidized to terephthalic acid (TA) or dimethyl terephtalate (DMT). These diacid or dimethyl ester monomers are then polymerized via a condensation reaction with ethylene glycol to form the polyester. Prior to the development of a method to purify TA to make purified terephtahc acid (PTA, >99% pure) by the Mid-Century Corporation in the 1950s [10], DMT was the primary way to obtain the purified dicarboxylate. The Amoco Oil Company, now part of BP International, made several improvements to the PTA process since its inception [11]. Since the advent of the availability of PTA, it has become the monomer of choice over DMT. PTA avoids the complications of including methanol to enable purification and handling the methanol evolved during the polymerization to polyester. 

The methanolysis begins with reasonably clean PET scrap to which a catalyst and methanol are added. This mixture is heated under pressure to force the PET to depolym-erize. The end products are ethylene glycol and dimethyl terephthalate (DMT). Pure DMT and ethylene glycol are obtained through reciystallization and distillation, respectively. These pure materials can be used as feedstocks for the synthesis of new polyesters. 

Preparation of a Polyester from Ethylene Glycol and Dimethyl Terephthalate by Melt Condensation... 

Terephthalic acid and dimethyl terephthalate are used to produce polyester fibers, polyester resins, and polyester film. Terephthalic acid or dimethyl terephthalate is usually reacted with ethylene glycol to give polyethylene terephthalate) but sometimes it is combined with 1,4-butanediol to yield poly (butylene terephthalale). Polyester fibers are used in the textile industry. Films find applications as magnetic tapes, electrical insulation, photographic film, packaging, and polyester bottles. 

The concept of transesterifications was used for polymerization reactions by Hedrick and colleagues [76]. Various biodegradable polyesters were synthesized with the l,3-dimethylimidazol-2-ylidene carbene in THF at 25 °C. Polymers such as poly(e-caprolactone) were obtained with no need of organometallic catalysts, as in classical methods. Poly(ethylene terephthalate) (PET) 97 was synthesized in the ionic liquid 98, which functions as the reaction medium and, at the same time, as a precatalyst that is activated (99) with KOt-Bu. Dimethyl terephthalate (DMT) 100 was condensed with an excess of ethylene glycol 101 to generate 102. The melt condensation of 102 was performed under vacuum using a heating ramp to 280 °C. 

In the case of condensation polymers such as PET, it is often possible to reverse the polymerization process and convert the polymer back to its constituent monomers. The monomers can then be purified and used to prepare new polymer. PET is converted back to ethylene glycol and dimethyl terephthalate by heating the polymer with methanol. This is exactly the reverse of the reaction that is used to prepare the polyester ... 

Recall that we discussed the reversibility of polyester formation in Chapters 4 and 5. Polyester producers have worked out a process called metbanolysis in which shredded PET bottles are heated with methanol and catalysts, causing depolymerization of the polyester and producing dimethyl terephthalate (DMT) and ethylene glycol, the two starting materials from which the PET was prepared originally ... 

In the polyurethane industry, the polymeric glycols are prepared by anionic polymerization of epoxides such as ethylene oxide and propylene oxide. Poly(tetra-methylene glycol), which was prepared by polymerization of tetrahydrofuran, was subjected to chain extension by reaction with diisocyanate (polyurethane formation) and with dimethyl terephthalate (polyester by alcoholysis). 

All these plastics are essentially the same compound, composed of terephthalic acid (para-phthalic acid) esterified with ethylene glycol. This polyester is made by a base-catalyzed transesterification of dimethyl terephthalate with ethylene glycol at a temperature around 150 °C. At this temperature, methanol escapes as a gas, driving the reaction to completion. We will study polyesters and other polymers in more detail in Chapter 26. 

Polyethylene terephthalate) in short PET is a polyester. It is mainly used in the garment industry with or without natural cotton and has trade names such as Terylene , Dacron , etc. As the name indicates, it is a polymer between terephthalic acid (PT) and ethylene glycol. Both terephthalic acid and dimethyl terephthalate (DMT) can be used to make the polymer. A majority of the modem plants tend to use PT as the starting material because of the availability of high-purity PT on a large scale. Both PT and DMT are first converted to bis(hydroxy ethyl) terephthalate 8.17 (see reaction 8.26). For PT this is effected by a straightforward esterification reaction. For DMT a transesterification reaction catalyzed by zinc and manganese acetate is used. 

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