Unsaturated dibasic acids

Unsaturated Polyesters. Unsaturated polyesters are produced by reaction between two types of dibasic acids, one of which is unsaturated, and an alcohol to produce an ester. Double bonds in the body of the unsaturated dibasic acid are obtained by using maleic anhydride or fumaric acid. 

Other by-products formed are relatively easy to separate, including esters of higher unsaturated monobasic acids (alkyl 3-pentenoate and 3,5-heptadienoate) (5) and esters of multiply-unsaturated dibasic acids, eg, suberates. 

Esters. Neopentyl glycol diesters are usually Hquids or low melting soflds. Polyesters of neopentyl glycol, and in particular unsaturated polyesters, are prepared by reaction with polybasic acids at atmospheric pressure. High molecular weight linear polyesters (qv) are prepared by the reaction of neopentyl glycol and the ester (usually the methyl ester) of a dibasic acid through transesterification (37—38). The reaction is usually performed at elevated temperatures, in vacuo, in the presence of a metallic catalyst. 

Uses. About 35% of the isophthahc acid is used to prepare unsaturated polyester resins. These are condensation products of isophthahc acid, an unsaturated dibasic acid, most likely maleic anhydride, and a glycol such as propylene glycol. The polymer is dissolved in an inhibited vinyl monomer, usually styrene with a quinone inhibitor. When this viscous hquid is treated with a catalyst, heat or free-radical initiation causes cross-linking and sohdification. A range of properties is possible depending on the reactants used and their ratios (97). 

The properties of polymers formed by the step growth esterification (1) of glycols and dibasic acids can be manipulated widely by the choice of coreactant raw materials (Table 1) (2). The reactivity fundamental to the majority of commercial resins is derived from maleic anhydride [108-31-6] (MAN) as the unsaturated component in the polymer, and styrene as the coreactant monomer. Propylene glycol [57-55-6] (PG) is the principal glycol used in most compositions, and (i9f2v (9)-phthahc anhydride (PA) is the principal dibasic acid incorporated to moderate the reactivity and performance of the final resins. 

Glycol Dibasic acid or anhydride Unsaturated acid or anhydride Unsaturated monomer... 

Polyester Resins. Reinforced polyester resins are thermosets based on unsaturated polyesters from glycols and dibasic acids, either or both of which contain reactive double bonds. The ratio of saturated to unsaturated components controls the degree of cross-linking and thus the rigidity of the product (see Polyesters, unsaturated). Typically, the glycols and acids are esterified until a viscous Hquid results, to which an inhibitor is added to prevent premature gelation. Addition of the monomer, usually styrene, reduces the viscosity to an easily workable level. 

As can be deduced from plant purchases, the PRC is still at the formative stage where emphasis is on producing only the most basic petrochemicals. No plants were purchased for producing dibasic acids (phthalic and maleic anhydrides, etc.) and fluro-carbon or tetrafluoro ethylene or some of the advanced engineering plastics like ABS polyacetals, polycarbonates, polyimides or any other unsaturated polyesters. Another important area of low Chinese activity is thermoplastics for space and defense applications. ... 

The liquid phases of polar columns are usually the heat-stable polymers of ethyleneglycol and the dibasic acids, succinic or adipic (Table 12.13). Fatty acids are separated on the basis of both chain length and the degree of unsaturation and some columns are capable of resolving fatty acids with the same chain length but different numbers of double bonds (0-6). The saturated fatty acids show the shortest retention times followed by the monoenoic, dienoic, etc. (Figure 12.19). 

Glycolysis is also conducted to create polyols for unsaturated polyester usage. The PET can be dissolved in DEG to create polyols with ether linkages [30], The reaction can be carried out with propylene glycol [31] or by reacting with an unsaturated dibasic acid [32] and needed additives and catalysts [33],... 

Uses. About 60% of the MA produced is used to make unsaturated polyester and aikyd resins, which are formed by reaction of MA with glycols. Polyester resins are used in the fabrication of glass fiber reinforced parts. Applications include boat hulls, automobile body parts, patio furniture, shower stalls, and pipe. Aikyd resins are mostly used in coatings (paint, varnish, lacquers, and enamels). MA also is widely used as a chemical intermediate in the manufacture of plasticizers and dibasic acids (fumaric, maleic, and succinic). About 15% of MA production goes into the manufacture of viscosity index improvers and dispersants used as additives in lube oils. Several agricultural chemicals are based on maleic anhydride, the best known being Malathion. 

Polyesterification between a diol and dibasic acid is usually done by (i) a 1-step process, (ii) a 2-step process and (iii) a 3-step process [163]. The commercially available unsaturated polyesters are generally manufactured by 1-step polyesterification process and as a result, possess poor flexibility and inferior heat resistance. 

In the manufacture of unsaturated polyester resins the polyester is synthesized and then diluted with a vinyl reactive monomer such as styrene (see POLYESTERS, UNSATURATED). A portion of the dibasic acid of the polyester is maleic or some other vinyl reactive diacid that can be polymerized with the styrene to yield a highly cross-linked, high performance polymer system. Other esters made with propylene glycol, dipropylene glycol, and tripropylene glycol are used as emulsifiers in foods, as plasticizers in polymer systems, and as part of acrylate resin systems. 

The structure of the methyl ester m.p. 174° C. (XL) was proven (5) mainly by the fact that the corresponding dibasic acid (XLI R = H) and its dimethyl ester (XLI R = Me) are oxidized with periodate and that the dimethyl ester is oxidized by manganese dioxide to a trisubstituted a,/ -unsaturated ketone (XLII) which regenerates (XLII R = Me) with sodium borohydride. 

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