METHOD OF PRODUCING POLYESTER

摘要

PROBLEM TO BE SOLVED: To provide a polyester that gives molded products having excellent transparency and showing good crystallinity at the mouth cock part without including any foreign material. SOLUTION: Dicarboxylic acids mainly include aromatic dicarboxylic acids or their ester-forming derivatives and glycols or their ester-forming derivatives are subjected to the polycondensation reaction by using a solution including germanium dioxide and a compound that can form a complex together with the dioxide as a polycondensation catalyst to produce a melt-polycondensate polyester. The polyester is chipped as it is cooled down with the water containing sodium (content: N), magnesium (content: M), silicon (content: S) and calcium (content: C) so that they may satisfy the following formulas (1)-(4): (1) N<=1.0 (ppm); (2) M<=0.5 (ppm); (3) S<=2.0 (ppm); and (4) C<=1.0 (ppm).