PROCESS FOR PREPARING POLYESTERS

摘要

A process for preparing a polyester which comprises reacting a di-lower alkyl ester of a difunctional carboxylic acid at least 90 mole % of which consists of terephthalic acid with a polymethylene glycol containing 2 to 10 carbon atoms at least 90 mole % of which consists of ethylene glycol in the presence of an ester-interchange reaction catalyst to form an esterinterchange reaction product, and then polycondensing it in the presence of a polycondensation catalyst, wherein a substantially uniform solution in ethylene glycol of (A) 20 to 150 millimole %, based on said di-lower alkyl ester of the difunctional carboxylic acid, of calcium acetate and (B) 2 to 25 millimole %, based on said di-lower alkyl ester, of cobalt acetate is used as the ester-interchange reaction catalyst. The fiber-forming polyester thus produced has enhanced whiteness over similar known polyesters which disadvantageously exhibit yellowness.