| 摘要 |
PROBLEM TO BE SOLVED: To provide polyester having excellent hydrolysis resistance, and little increase in terminal carboxyl group amount when melted and molded into a film or the like.SOLUTION: Upon carrying out melt polymerization of polyester which is composed of aromatic dicarboxylic acid as a main acid component and alkyleneglycol having 2 to 4 carbon atoms as a glycol component, oxalic acid glycol ester and/or its low polymerization degree oligomer which is represented by the following formula (1), having 1-8 of average polymerization degree, and having 2% or more ratio of those having alkyl group on at least one terminal, is added at a ratio of 0.1-5.0 mol% of an oxalic acid component based on the total acid components of polyester at a stage when inherent viscosity becomes 0.2dl/g or more, and polymerization reaction is further continued. XO-[C(O)C(O)ORO]-C(O)C(O)OX(1)(wherein R is alkylene group having 2-4 atoms, Xand Xare respectively alkyl group having 4 or less carbon atoms or -ROH group, and n represents 0 or more integer (provided that, n is 1 or more if X, Xare both alkyl group)). |
