Plasticizers terephthalate esters

Terephthalate esters are not as compatible as phthalates with PVC and are more difficult to process. Today there is essentially only one important terephthalate plasticizer commercially available, DEHTP, as terephthalate esters of C9 and CIO alcohols have compatibility issues. The diisoheptyl terephthalate ester was shown [27] to have advantages in processabihty and plasticizing efficiency over DEHTP, but with hmited availability of isoheptanol, this product was never commercialized. The terephthalate ester based on C4 alcohols, dibutyl terephthalate (DBTP) is now commercially available for use in plasticizer blends to help improve processability [28] of DEHTP. Although DEHTP is very similar to the structure of DEHP, the structural difference yields important effects in the plasticizer toxicity profile. Extensive testing of DEHTP confirms that it is a safer product than DEHP [24]. 

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). 

Phthahc anhydride (1) is the commercial form of phthaUc acid (2). The worldwide production capacity for the anhydride was ca 3.5 x 10 metric tons ia 1993, and it was used ia the manufacture of plasticizers (qv), unsaturated polyesters, and alkyd resins (qv) (see Polyesters, unsaturated). Sales of terephthahc acid (3) and its dimethyl ester are by far the largest of any of the benzenepolycarboxyhc acids 14.3 x 10 t were produced in 1993. This is 80% of the total toimage of ah. commercial forms of the benzenepolycarboxyhc acids. Terephthahc acid is used almost exclusively for the manufacture of poly(ethylene terephthalate), which then is formed into textiles, films, containers, and molded articles. Isophthahc acid (4) and trimehitic anhydride (5) are commercial products, but their worldwide production capacities are an order of magnitude smaller than for terephthahc acid and its dimethyl ester. Isophthahc acid is used primarily in the production of unsaturated polyesters and as a comonomer in saturated polyesters. Trimehitic anhydride is used mainly to make esters for high performance poly(vinyl chloride) plasticizers. Trimesic acid (6), pyromehitic dianhydride (7), and hernimehitic acid (8) have specialized commercial apphcations. The rest of the benzenepolycarboxyhc acids are not available commercially. 

Derivatives. In general, the esters of terephthaHc acid derived from saturated alcohols undergo the same reactions as dimethyl terephthalate. Some physical properties of six of these esters are Hsted in Table 23. The di- -butyl and di-2-ethyIhexyl esters find use as plasticizers (qv). Terephthaloyl chloride, which is prepared by reaction of terephthaHc acid and thionyl chloride, is used to prepare derivatives of terephthaHc acid. 

Commodity Phthalate Esters. The family of phthalate esters are by far the most abundandy produced woddwide. Both orthophthaUc and terephthahc acid and anhydrides are manufactured. The plasticizer esters are produced from these materials by reaction with an appropriate alcohol (eq. 1) terephthalate esterification for plasticizers is performed more abundandy in the United States. Phthalate esters are manufactured from methanol (C ) up to Qyj alcohols, although phthalate use as PVC plasticizers is generally in the range to The lower molecular weight phthalates find use in nitrocellulose the higher phthalates as synthetic lubricants for the automotive industries. 

Poly(ethylene terephthalate). PET is a crystalline material and hence difficult to plasticize. Additionally, since PET is used as a high strength film and textile fiber, plasticization is not usually required although esters showing plasticizing properties with PVC may be used in small amounts as processing aids and external lubricants. Plasticizers have also been used to aid the injection mol ding of PET, but only at low concentrations. 

Transesterification has a number of important commercial uses. Methyl esters of fatty acids are produced from fats and oils. Transesterification is also the basis of recycling technology to break up poly(ethylene terephthalate) [25038-59-9] to monomer for reuse (29) (see Recycling, plastics). Because vinyl alcohol does not exist, poly(vinyl alcohol) [9002-89-5] is produced commercially by base-cataly2ed alcoholysis of poly(vinyl acetate) [9003-20-7] (see Vinyl polymers). An industrial example of acidolysis is the reaction of poly(vinyl acetate) with butyric acid to form poly(vinyl butyrate) [24991-31-9]. 

Plasticizers. Plasticizers are materials that soften and flexibilize inherently rigid, and even britde polymers. Organic esters are widely used as plasticizers in polymers (97,98). These esters include the benzoats, phthalates, terephthalates, and trimeUitates, and aUphatic dibasic acid esters. Eor example, triethylene glycol bis(2-ethylbutyrate) [95-08-9] is a plasticizer for poly(vinyl butyral) [63148-65-2] which is used in laminated safety glass (see Vinyl POLYMERS, poly(vinyl acetals)). Di(2-ethyUiexyl)phthalate [117-81-7] (DOP) is a preeminent plasticizer. Variation of acid and/or alcohol component(s) modifies the efficacy of the resultant ester as a plasticizer. In phthalate plasticizers, molecular sizes of the alcohol moiety can be varied from methyl to tridecyl to control permanence, compatibiUty, and efficiency branched (eg, 2-ethylhexyl, isodecyl) for rapid absorption and fusion linear (C6—Cll) for low temperature flexibiUty and low volatility and aromatic (benzyl) for solvating. Terephthalates are recognized for their migration resistance, and trimeUitates for their low volatility in plasticizer appHcations. 

With the expiry of the basic ICI patents on poly(ethylene terephthalate) there was considerable development in terephthalate polymers in the early 1970s. More than a dozen companies introduced poly(butylene terephthalate) as an engineering plastics material whilst a polyether-ester thermoplastic rubber was introduced by Du Pont as Hytrel. Polyfethylene terephthalate) was also the basis of the glass-filled engineering polymer (Rynite) introduced by Du Pont in the late 1970s. Towards the end of the 1970s poly(ethylene terephthalate) was used for the manufacture of biaxially oriented bottles for beer, colas and other carbonated drinks, and this application has since become of major importance. Similar processes are now used for making wide-neck Jars. 

RPLC-PDA is frequently used for quality control, such as the determination of free Irganox 1098 in PA4.6 (at 278 nm after dissolution/precipitation), of free Irganox 1010/1076 in PP (at 278 nm after extraction with MTBE, thus avoiding dissolution of polymer waxes), of Luperco 802 in PP (at 218 nm, after extraction with HCC13), and of Tinuvin 122 in HDPE (at 225 nm as diol). The advantages of the use of HSLC over conventional LC in QC of plastics and additives have been demonstrated, e.g. for AOs in PE, mixed phthalate esters and residual terephthalic acid in PET and partially cured epoxy resins [557],... 

Copoly(ether ester)s consisting of short-chain crystalline segments of PBT and amorphous poly(ether ester) of poly(tetramethylene terephthalate) exhibit a two-phase structure and can be used for the production of high-impact-strength engineering plastics. These very interesting materials with their outstanding properties understandably require stabilization to heat and UV exposure [45],... 

Uses Solvent for nitrocellulose, ethyl cellulose, polyvinyl butyral, rosin, shellac, manila resin, dyes fuel for utility plants home heating oil extender preparation of methyl esters, formaldehyde, methacrylates, methylamines, dimethyl terephthalate, polyformaldehydes methyl halides, ethylene glycol in gasoline and diesel oil antifreezes octane booster in gasoline source of hydrocarbon for fuel cells extractant for animal and vegetable oils denaturant for ethanol in formaldehyde solutions to inhibit polymerization softening agent for certain plastics dehydrator for natural gas intermediate in production of methyl terLbutyl ether. 

Polymerization of esters to produce polyesters is an important commercial process. Polyethylene terephthalate or PET is one of the most common plastics used in food containers (Table 15.4). This ester is formed by the reaction of ethylene glycol and terephthalic acid (Figure 15.17). PET and other polyesters consist of esters linked together. Notice that both terephthalic acid and ethylene glycol have two carboxyls and two hydroxyls, respectively. When a polyester such as PET is formed, a monomer con-... 

Polyesters [2] find use in fibers [poly(ethylene terephthalate), poly(ethylene oxybenzoate), poly(ester ethers), poly(ester amides), etc.] [1], coatings (especially unsaturated polyesters) [4], plasticizers, adhesives, polyurethane base resins, films, etc. Cross-linked polyesters prepared from glycerol and phthalic anhydride (alkyd resins) have been reviewed [20], High-melting poly aryl esters have been investigated for high-temperature applications. 

Results obtained for two mixed plastics are summarized in Table 4. A balance exists between process temperature, plastics feed rate, and product yields (67). For example, lower temperatures increase wax formation due to incomplete depolymerization. Slower feed rates and increased residence times reduce wax formation and increase the yield of liquids. The data summarized in Table 4 illustrate that the addition of PET to a HDPE PP PS mixture changes the performance of the Conrad process. Compared to the reference HDPE PP PS mixture, increased amounts of solids are formed. These are 95% terephthalic acid and 5% mono- and bis-hydroxyethyl esters. At higher temperatures, apparendy enough water remains to promote decarboxylation. 

Because the monomers above are all joined by ester linkages, the polymer chain is a polyester. This one is called PET, which stands for poly(ethylene terephthalate). (PET is used to make soft-drink bottles, magnetic tape, and many other plastic products.)... 

Acetic acid is used in the manufacture of a wide variety of products including adhesives, polyester fibres, plastics, paints, resins and solvents. About 40% of the acetic acid made industrially is used in the manufacture of vinyl acetate monomer for the plastics industry other large uses are to make cellulose acetate, a variety of acetate esters that are used as solvents, as well as monochloracetic acid, a pesticide. Acetic acid is also used as a solvent for the oxidation of p-xylene to terephthalic acid, a precursor to the important polyester, polyethylene terephthalate (PET). A minor, but important use is as non-brewed condiment, a vinegar substitute widely used in British fish and chip shops this is made using food-grade industrial acetic acid and is less expensive than fermentation vinegar. 

Benzenedicarboxylic acids have trivial names. Benzene-1,4-dicarboxylic acid (terephthalic acid, 3) is used in the manufacture of commercially important polyesters. Esters of benzene-1,2-dicarboxylic acid (phthalic acid) are used for plasticizing polymers. 

Phthalic anhydride is used in the preparation of alkyd and other resins, as well as in the preparation of esters (e.g., di-2-ethylhexyl phthalate) which serve as plasticizers for polyvinyl chloride. It can also be converted to terephthalic acid for the preparation of polyethylene terephthalate)... 

Poly(ester-imide)s useful as molding plastics are made from terephthalic acid, trimellitic anhydride, 4-(aminomethyl)cyclohexanemethanol, and 1,4-cy-clohexanedimethanol [244]. Blends of this poly(ester-imide) with polycarbonate are also patent protected [245]. An amorphous polymer containing units derived from N-3-hydroxyphenyl trimellitimide and units derived from p-hy-droxybenzoic acid [246] and another having units derived from 9,9-bis(4-ami-nophenyl)fluorene [247] have similar claims. 

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