| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing an isophthalate-based polyester which is practical in the aspects of cost and productivity, contains oligomers in controlled amounts, has a high quality and has a polymerization degree sufficient as a molding material. SOLUTION: This method for producing an isophthalate-based polyester by thermally polycondensing a bis(2-hydroxyalkyl)isophthalate and/or the oligomers thereof, characterized by adding a bis-2-hydroxyalkyl oxalate of formula (1): HO-R-O-C(O)-C(O)-O-R-OH (R is the same alkylene group as an alkylene group constituting the diol component of the polyester) in an amount of 1 to 50 mol.% based on the isophthalate structural units, subjecting the mixture to a polycondensation reaction, further adding an oxalic acid-based active ester compound represented by formula (2): Ar-O-C(O)-C(O)-O-Ar' (Ar and Ar' are each the same or different monovalent aromatic hydrocarbon group whose nucleus may be substituted) in an amount of 0.1 to 10 mol.% based on the polymerization mixture at a substantially polycondensation reaction-finished step, and subjecting the mixture to a chain-extending reaction. Thereby, the polymer having a sufficient polymerization degree is efficiently produced.
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