Patent ID: 8779082

Claim:
A method for producing a polyester comprising adding a phosphorus compound represented by the following formula (1) and at least one compound selected from the group consisting of a magnesium compound, a manganese compound, a calcium compound and a cobalt compound to a reaction system, in a method for obtaining a polyethylene terephthalate which comprises esterification or transesterification-reacting terephthalic acid or an ester-forming derivative thereof, and ethylene glycol or an ester-forming derivative thereof, and polycondensing this in the presence of a titanium-based polycondensation catalyst: wherein, R 1 , R 2 , R 3 , and R 4 are each a linear alkyl group, the carbon number of which is 8 to 16; a mole ratio (Mg+Mn+Ca+Co)/P of a sum of metal atoms in the magnesium compound, the manganese compound, the calcium compound and the cobalt compound, to a phosphorus atom in the phosphorus compound represented by the formula (1) is 0.1 to 10, an amount of the titanium-based polycondensation catalyst relative to a weight of the polyester is 3 to 15 ppm in terms of titanium atom, an amount in atom terms of magnesium relative to the polyester is 5 to 25 ppm, and a mole ratio of a sum of mole amounts of titanium, magnesium and phosphorus is 0.3≦(Ti+Mg)/P≦18 and the phosphorous compound and titanium-based polycondensation catalyst are added to the reaction system before initiation of the polycondensation reaction.