Patent ID: 6967235

Claim:
A process of producing polybutylene terephthalate (PBT) from butanediol (BDO) and terephthalic acid (TPA), in which a mixture of BDO and TPA is subjected to an esterification in the presence of a catalyst solution containing alkyl titanate at temperatures in the range from 130 to 260° C. and the product of the esterification is subjected to a polycondensation, wherein the catalyst solution contains 0.05 to 10 wt-% alkyl titanate, 85 to 99 wt-% BDO, 50 to 50,000 ppm dicarboxylic acid and/or hydroxycarboxylic acid and/or monohydroxyalkyl dicarboxylic acid and not more than 0.5 wt-% water.