GB852886A - A process for the manufacture of unsaturated polyesters and copolymers thereof - Google Patents

Abstract

Unsaturated polyesters, copolymerizable with vinyl monomers to give resins of improved heat-resistance, bending strength, impact strength and shatter-proofness, are made by re-esterifying an alkyl ester of terephthalic acid or a substituted terephthalic acid (e.g. 2 : 5-dichloroterephthalic acid) with an aliphatic glycol to an extent of about 65-85% and at a temperature of about 120 DEG -200 DEG C., and thereafter adding an unsaturated dicarboxylic acid or anhydride and esterifying the remaining hydroxyl groups of the glycol at a higher temperature. The glycol may be ethylene glycol, diethylene glycol, 1 : 3-butylene glycol, 1 : 2 butylene glycol, 1 : 3-propanediol or 1 : 4-butenediol. Specified unsaturated dicarboxylic acids are fumaric, maleic, mesaconic, citraconic, itaconic and moconic acids. As additional polyester forming reactants, there may be used saturated acids (e.g. adipic or phthalic acids) and tri- or higher poly-hydric alcohols (e.g. glycerol or pentaerythritol). Reesterification may be effected in the presence of sodium methylate and the final esterification may be effected in the presence of xylene. Specified vinyl monomers are styrene, vinyl acetate, vinyl crotonate and acrylonitrile. In examples unsaturated polyesters were made from (1)-(4) Dimethyl terephthalate, ethylene glycol, diethylene glycol and fumaric acid or maleic anhydride; (5) Dimethyl terephthalate, 1 : 3- butylene glycol, diethylene glycol and maleic anhydride; (6) Dimethyl terephthalate, diethylene glycol, glycerol and maleic anhydride. All of these polyesters were copolymerized with styrene in the presence of a peroxide catalyst and an accelerator. The styrene was stabilized with hydroquinone or t-butyl pyrocatechol.