Patent ID: 7538176

Claim:
A method of producing a polyester polymer from a dicarboxylic acid compound and a dihydroxy compound, said dicarboxylic acid compound comprising dicarboxylic acid or its ester-forming derivative, wherein the method comprises: the first step of transesterification or direct esterification of the dicarboxylic acid compound and the dihydroxy compound, the sulfur content in the dicarboxylic acid compound as raw material being 50 ppm or less, the dicarboxylic acid compound comprising an alicyclic dicarboxylic acid and/or its ester-forming derivative, the sulfur content in the dihydroxy compound being 20 ppm or less, the dihydroxy compound comprising ethylene glycol and a compound of the general formula (1): wherein R 1 represents an alkylene group having 2 to 4 carbon atoms; R 2 , R 3 , R 4 , and R 5 are the same or different and each represents a hydrogen atom, an alkyl having 1 to 4 carbon atoms, an aryl or an aralkyl group; and the second step of condensation polymerization under a reduced pressure; and wherein the polyester polymer has a content of diethylene glycol of 6 mol % or lower and a sulfur content of 70 ppm or less.