Thermoplastic polyesters of high viscosity - by melt polycondensn. in presence of small amt. of unsatd. diol or dicarboxylic acid

摘要

Thermoplastic polyesters having a melt viscosity at 250 degrees C 6000 beta and a relative viscosity 1.6 when measured at 25 degrees C in a 2:1 mixt. of phenol/o-chlorophenol are prepd. by melt polycondensn., at least partly at a temp. above 220 degrees C (pref. above 230 degrees C), of a mixt. of aliphatic and/or cycloaliphatic diols and dicarboxylic acids and/or esters contg. 0.1-10 mol. % of an aliphatic diol having at least one olefinic double bond and/or an aliphatic dicarboxylic acid or ester having at least one olefinic double bond immediately adjacent to the COOH or ester gps. Thermoplastic polyesters of relative viscosity as high as 1.6 were previously very difficult to prepare and required a 2nd condensn. stage which led to operating troubles and prods. of poor quality. The process of the invention enables such prods. to be prepd. very easily by a single stage melt condens.