PURPOSE: To obtain a polyester having a high softening point and improved color, by polycondensation of a glycol ester of a bifunctional aromatic carboxylic acid, using the reation product of a titanium compound with an aromatic multivalent carboxylic acid and a phosphorus compound as a catalyst.
CONSTITUTION: A glycol ester of a bifunctional aromatic carboxylic acid, e.g. terephthalic acid, etc. and/or its low polymer is subjected to polycondensation with the reaction product of a titanium compound expressed by the formula Ti(OR)4 (R is alkyl group) with an aromatic multivalent corboxylic acid expressed by formulaI: (n is an integer 2W4) or its anhydride in the presence of a phosphorus compound of formula II: (R1, R2, and R3 are H or alkyl groups; at least one of the R1, R2, and R3 is alkyl group) as a catalyst. Tetrapropyl titanate, tetrabutyl titanate, etc. may be cited as the titanium compound.
KUNO TADASHI
MORIMATSU YASUO
