Polyethylene terephthalate manufacture

The first step in manufacturing polyethylene terephthalate is to react terephthalic acid with a large excess of ethylene glycol to form diglycol terephthalate ... 

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. 

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]. 

That fall, Carothers assistant Edgar W. Spanagel discovered polyethylene terephthalate, the polyester that Du Pont later manufactured under license as Dacron fiber and Mylar film. Carothers had made most of the polyesters, but he and others in his group assumed that Spanagel s polyester, like their earlier ones, melted at too low a temperature to be practical. As a result, Carothers did not have this one tested for spinnability. British scientists later used it to make Terylene. When Du Pont executives had to buy a license from the British to make Spanagel s fiber, their faces were bright red with embarrassment. 

Here the polymer grows by successive esterification with elimination of water and no termination step. Polymers formed by linking monomers with carboxylic acid groups and those that have alcohol groups are known as polyesters. Polymers of this type are widely used for the manufacture of artificial fibers. For example, the esterification of terephthalic acid with ethylene glycol produces polyethylene terephthalate. 

When the new product to be manufactured is the same as what it started as, for example a new bottle made from bottle scrap, the recycling is referred to as closed-loop. When the new application is different from the starting one, the process is referred to as open-loop recycling, as is the case when the polyethylene terephthalate bottle is used to produce polyester fiber for carpeting. 

Why do polyethylene terephthalate bottle manufacturers not use any polyvinyl chloride for closures or labels on the bottle ... 

Figure 24.3 Two-step polymerization process for the manufacture of polyethylene terephthalate ...

In addition to the desired polymerization reaction, the dialcohol reactants can participate in deleterious side reactions. Ethylene glycol, used in the manufacture of polyethylene terephthalate, can react with itself to form a dialcohol ether and water as shown in Fig. 24.4a). This dialcohol ether can incorporate into the growing polymer chain because it contains terminal alcohol units. Unfortunately, this incorporation lowers the crystallinity of the polyester on cooling which alters the polymer s physical properties. 1,4 butanediol, the dialcohol used to manufacture polybutylene terephthalate, can form tetrahydrofuran and water as shown in Fig. 24.4b). Both the tetrahydrofuran and water can be easily removed from the melt but this reaction reduces the efficiency of the process since reactants are lost. 

Injection molding grades of polyethylene terephthalate and polybutylene terephthalate have low melt viscosities. Because of this, they can be used to manufacture intricate parts within... 

Polyethylene terephthalate is the dominant material for the manufacture of carbonated beverage bottles Why are the bottles clear despite the tendency for this polymer to form crystalline domains ... 

Manufacture. The manufacture of 1,4-cyclohexanedimethanol can be accomplished by the catalytic reduction under pressure of dimethyl terephthalate in 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. Polyethylene terephthalate) may be hydrogenated in the presence of methanol under pressure and heat to give good yields of the glycol (see Polyesters) (66,67). 

Ethylene Glycol. Well over 50% of the ethylene oxide produced is used in the manufacture of ethylene glycol. Ethylene glycol [107-21-1] is used in two significant applications as a raw material for polyethylene terephthalate) for use in polyester fiber, film, and containers, and as an automotive... 

The first really successful artificial material used in the manufacture of synthetic blood vessels was Dacron , a polyester fiber made from polyethylene terephthalate (PET). The material is woven or knitted into thin tubes with dimensions similar to those of a natural blood vessel. The tubes are then treated with coagulated blood or with albumin, an important blood protein, to block the tiny holes in the fabric of which they are made. Over time, cells migrate into the blood or albumin trapped within the Dacron matrix and deposit collagen. As the blood or albumin degrades, it is replaced by the collagen, producing a vessel with some properties similar to those of natural blood vessels. 

Ethylene oxide is used for manufacture of ethylene glycol, the latter being an antifreeze compound as well as a raw material for production of polyethylene terephthalate used in the manufacture of polyester fibers for preparation of surfactants for the manufacture of ethanolamines for production of ethylene glycols used in plasticizers, solvents, and lubricants and for making glycol ethers used as jet-fuel additives and solvents. 

Polyesters are manufactured in one of two ways by direct reaction of a di-acid and a diol or by ester interchange of a di-ester and a diol. By far the most commercially useful polyester is polyethylene terephthalate). 

Dimethyl terephthalate (DMT) is produced either by the esterification of terephthalic acid or the esterification of monomethyl terephthalate produced by oxidation of methyl p-toluate. DMT is consumed in the production of polyethylene terephthalate, the polymer used in the manufacture of polyester fibers, films and bottle resins. Terephthalic acid (TPA) is also used in the production of polyethylene terephthalate but does not consume methanol. Since TPA is continuing to increase its share of the market, DMT is expected to exhibit slower growth than the overall market for polyethylene terephthalate. 

Condensation fibers such as nylon and polyethylene terephthalate are formed when two or more different monomers react, releasing small molecules such as water, and forming amide or ester bonds between the monomers. Nylon, first produced by DuPont in 1938, became a mainstay of the hosiery industry and is now the most widely used fiber in carpet manufacture. Polyethylene terephthalate, produced by formation of an ester bond between terephthalic acid and ethylene glycol, is by far the most widely used synthetic fiber. 

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