Poly(ethylene/alkylene) terephthalates which crystallize rapidly

Claim 1

A process for the production of thermoplastic terephthalic acid copolyesters which crystallize more rapidly than polyethylene terephthalate homopolymer comprising (1) esterifying or transesterifying an acid component consisting of (a) at least 90 mol % of terephthalic acid and dimethyl terephthalic acid ester, and (b) up to 10 mol % of other aliphatic and aromatic dicarboxylic acids and acid esters with (2) 1.05 to 2.04 equivalents of a diol component consisting of (a) 90 to 99.5 mol % of ethylene glycol, and (b) 10 to 0.5 mol % of 2,2-diethylpropane-1,3-diol at (3) a temperature of between 150° and 250° C in the presence of esterification or transesterification catalysts, and (4) polycondensing the initial reaction products at a temperature between 200 and 300° under reduced pressure in the presence of an esterification catalyst, wherein the 2,2-diethylpropane-1,3-diol is added to the reaction mixture after substantially all of the acid component has been reacted to di(2-hydroxyethyl)ester.