Terephthalic acid, esters

Table 23. Properties of terephthalic acid ester and Terephthaloyl Chloride...

Because PET has a melting point Tm of 240 C, it is difficult to mold. The difficulty in processing and the low ductility of PET have been overcome by the production of terephthalic acid esters with higher-molecular-weight dihydric alcohols, such as butylene glycol. 

Acids Phosphoric acid, FFAP (carbowax-20m-terephthalic acid ester), trimer acid These modifiers will act as subtractive agents for basic components in the sample FFAP will selectively abstract aldehydes phosphoric acid may convert amides to the nitrile (of the same carbon number), desulfonate sulfur compounds, and may esterify or dehydrate alcohols... 

Plamitic, stearic, oleic acid Terephthalic acid Alkyl terephthalic acid esters... 

NFPA Health 0, Flammability 1, Reactivity 0 Uses Comonomer for alkyds and unsat. polyester resins chemical intermediate for paints, in polyester bottle resins, fibers, and films in prod, of terephthalic acid esters forms polyesters with glycols in analytical chemistry reagent for alkali in wool as poultry food additive... 

Diamino-1,2,4-triazole is a component in polyester imide coatings with increased hardness that is used for thermosetting insulating varnishes for coating of electric wires [69,70]. Acid components are terephthalic acid esters and trimellitic acid anhydride. 

Phthalic acid esters Plamitic, stearic, oleic acid Terephthalic acid Alkyl terephthalic acid esters 2,6-bis-( 1, l-methylethyl)-4-ethyl phenol Pyrogallol... 

Ethylene glycol + terephthalic acid(ester) PET PET PET PETP PETE... 

Ester interchange is favored for terephthalates because the free acid is very insoluble and difficult to incorporate into a reaction system. Two stages are used In the first, methanol is displaced from the terephthalic acid ester by the diol, and in the second, the excess diol is driven off at high temperatures and low pressures. A continuous process (Figure 17.1) starts with a molar ratio of dimethyl terephthal-ate to glycol of 1 1.7. Methanol is removed from the horizontally sectioned vessel over a period of 4 h with a rise in temperature to 245°C at a pressure of 1 atm. In two polycondensation reactors, the pressures are about 0.020 and 0.001 atm, and the exit temperatures are 270°C and 280°C, respectively. The resultant polymer melt is low enough in viscosity that pumps can be used to extrude fibers directly or to make chips as an intermediate form for storage. 

PET in fibers and bottles and polycarbonates in compact discs represent large-volume markets. As with most polymer families, there is a wide diversity of applications, many of which involve combinations with other materials. Aliphatic polyesters have been used as lubricants and vinyl plasticizers. Hydrolytic stability is a factor to be considered in many applications. As a rule, aryl acids and branched-chain diols resist hydrolysis. Fibers and films of terephthalic acid esters and polycarbonates are not particularly sensitive to moisture. Alkyd resins are so highly cross-linked in the final coating that water is not a major problem, although alkaline solutions of soaps and detergents can cause film failure. It is in the urethane foams that hydrolytic stability... 

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. 

Polyester—any long-chain synthetic polymer composed of at least 85% hy weight of an ester of a dihydric alcohol and terephthalic acid (p—HOOC—C6H4—COOH). 2.2-7.8 E-G G G-F G G 1.38 300... 

The high yields of ethyl ester obtainable from the product attest its purity. A mixture of 50 g. of terephthalic acid, 500 ml. of absolute ethyl alcohol, and 25 ml. of sulfuric acid was boiled for 16 hours and then distilled to half its volume and poured into dilute aqueous sodium carbonate. There was obtained 56.7 g. of diethyl terephthalate (m.p. 42-44°), and from the wash water there was recovered 4.6 g. of terephthalic acid these materials account for 93.3% of the original substance. 

The oldest of these materials, a poly (trimethylhexamethylene terephthal-amide) was first marketed by Dynamit Nobel in the mid-1960s (Trogamid T). It is a condensation product of trimethylhexamethylenediamine and terephthalic acid (or its dimethyl ester) (Figure 18.25). In practice a 1 1 mixture of 2,2,4- and 2,4,4-trimethyldiamines is used, this being produced from acetone via iso-phorone, trimethyladipic acid and trimethyladiponitrile. 

In many cases simple esters are more easily purified than their intractable parent acids. For example, /7-xylene is difficult to obtain in pure form because of the closeness of its boiling point to the other isomeric xylenes (o-144°C m- 138.8°C p- 138.5°C). It is thus difficult to produce terephthalic acid, which sublimes at 300°C, in a pure form. 

In recent years, however, the ester exchange reaction has been decreasingly used, with manufacturers now usually preferring to use direct acid glycol condensation with purified terephthalic acid. 

Chemical Designations - Synonyms Terephthalic Acid, Dimethyl Ester Chemical Formula 1,4-CH3OOCC5H4COOCH3. 

Note-. Bisphenol-A and the diaryl esters of terephthalic acid and isophthalic acid are nonvolatile compounds, so that any excess of these components cannot completely be removed, resulting in a low-molar-mass, unusable polyester. Moreover, excess bisphenol-A causes a strong discoloration of the polyester melt due to thermal degradation at the high reaction temperature used. This can be avoided if the diaryl esters are mixed with 5 mol% of diphenyl carbonate. Any excess of this compound can easily be removed in vacuum at the polycondensation temperature. 

Aromatic polyesters were efficiently synthesized from aromatic diacid divinyl esters. Lipase CA induced the polymerization of divinyl esters of isoph-thalic acid, terephthalic acid, and p-phenylene diacetic acid with glycols to give polyesters containing aromatic moiety in the main chain. The highest molecular weight (7.2 x 10 ) was attained from a combination of divinyl isophthalate and 1,10-decanediol. Enzymatic polymerization of divinyl esters and aromatic diols also afforded the aromatic polyesters. ... 

Polymerisation of a diol with a dicarboxylic acid is exemplified by the production of a polyester from ethylene glycol and terephthalic acid either by direct esterification or by a catalysed ester-interchange reaction. The resulting polyester Terylene) is used for the manufacture of fibres and fabrics, and has high tensile strength and resiliency its structure is probably ... 

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],... 

Oxidation is the first step for producing molecules with a very wide range of functional groups because oxygenated compounds are precursors to many other products. For example, alcohols may be converted to ethers, esters, alkenes, and, via nucleophilic substitution, to halogenated or amine products. Ketones and aldehydes may be used in condensation reactions to form new C-C double bonds, epoxides may be ring opened to form diols and polymers, and, finally, carboxylic acids are routinely converted to esters, amides, acid chlorides and acid anhydrides. Oxidation reactions are some of the largest scale industrial processes in synthetic chemistry, and the production of alcohols, ketones, aldehydes, epoxides and carboxylic acids is performed on a mammoth scale. For example, world production of ethylene oxide is estimated at 58 million tonnes, 2 million tonnes of adipic acid are made, mainly as a precursor in the synthesis of nylons, and 8 million tonnes of terephthalic acid are produced each year, mainly for the production of polyethylene terephthalate) [1]. 

In the case of the esterification of the diacid, the reaction is self-catalyzed as the terephthalic acid acts as its own acid catalyst. The reverse reaction, the formation of TPA and EG from BHET is catalytic with regard to the usual metal oxides used to make PET, but is enhanced by either the presence of hydroxyl groups or protons. In the case of transesterification of dimethyl terephthalate with ethylene glycol, the reaction is catalytic, with a metal oxide needed to bring the reaction rate to commercial potential. The catalysts used to produce BHET are the same as those needed to depolymerize both the polymer to BHET and BHET to its simpler esters. Typically, titanium, manganese and zinc oxides are used for catalysts. 

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