GB656138A - Improvements in or relating to high molecular weight polyesters - Google Patents

Abstract

A dihydric alcohol and an alpha beta unsaturated dicarboxylic acid are reacted until a resin having a low acid number not exceeding 50 is produced, about 0.5 to 2.0 per cent of an acid, an hydroxy acid or an alcohol with a total of at least 3 hydroxyl and carboxyl groups and no CH2=C= groups is added and the reaction continued until a polyester of high molecular weight is obtained. It may be copolymerized with a compatible polymerizable substance having a CH2=C group, a boiling-point of at least 60 DEG C., and no conjugated double bonds. The dihydric alcohols are preferably those containing only primary hydroxyl groups, e.g. the glycols. The alpha beta unsaturated acids include maleic, fumaric, itaconic, citraconic, mesaconic, halogenated maleic and may in part be substituted by acrylic, beta-benzoyl acrylic, methacrylic, cinnamic, and crotonic acids. The compound with at least 3 carboxyl and hydroxyl groups may be any such alcohol, acid or hydroxy acid as pentaerythritol, glycerol, pentaglycerol, sorbitol, mannitol, trimethylol benzene; citric, malic, dihydroxystearic, tartaric, trihydroxyglutaric, methylol phthalic, or benzene tricarboxylic, fumaric or maleic acid or adducts of higher fatty acids with a conjugated double bond such as linseed fatty acids. The compatible polymerizable substance may be styrene or a styrene derivative, an isopropenyl toluene or benzene, styrene with nuclear-substituted fluorine, bromine or chlorine, vinyl-naphthalene, -mesitylene, -diphenyl, -carbazole, -phenol, or -furane, dialkyl esters of maleic, fumaric and itaconic acid, diallyl esters of high boiling-point various specified allyl esters and compounds, acrylic and methacrylic acids, methyl methacrylate, methyl acrylate and ether esters. Polymerization catalysts such as various specified peroxides may be employed in the copolymerization and polymerization inhibitors may be used during the preparation of the preliminary alkyd resin or during copolymerization. An inert solvent such as xylol or toluene may be included in the reaction mixture to remove water of esterification and thus reduce esterification temperature. Eight examples are given in seven of which a saturated aliphatic dibasic acid and in the other phthalic anhydride, is included in the reacting mixture in higher molecular proportion than the unsaturated acid. Samples have been furnished under Sect. 2 (5) of polyesters in which the reacting mixture (1) does not include such a saturated acid; (2) includes phthalic anhydride in lesser molecular proportion.