PRODUCTION OF MODIFIED POLYALKYLENE TEREPHTHALATES

摘要

A process for the production of a modified polyalkylene terephthalate from the radical of terephthalic acid and the radical of a glycol of two to six carbon atoms in which from 1 to 50 mole % of the terephthalic acid radical has been replaced by an aliphatic dicarboxylic acid radical of four to twelve carbon atoms. The aliphatic dicarboxylic acid is esterified by heating with the glycol in a molar ratio of from 1:1.2 to 1:1.8 at a temperature of from about 5 to 20.degree.C below the boiling point of the glycol until the degree of esterification is from 90 to 95 mole % based on the aliphatic dicarboxylic acid; a dialkyl terephthalate is transesterified with the glycol in a molar ratio of from 1:1.2 to 1:2 in the presence of a catalyst in an amount of from 0.01 to 0.2% by weight base on dialkyl-terephthalate by heating to a temperature of from 130.degree. to 240.degree.C at atmospheric pressure until at least 95% of the alkoxy groups present have been eliminated. The esterification product is mixed with the transesterification product and polycondensation is carried out at a temperature of from 240.degree. to 290.degree.C and a pressure of from 0.1 to 760 mm, in the presence of a catalyst in an amount of from 0.01 to 0.2% by weight based on the polyester. The polyester obtained is suitable for example for mouldings or as an adhesive.