Patent ID: 8143356

Claim:
A method for producing a polyester resin composition (C), the method comprising: melt-kneading a polyester resin (A) comprising phosphorus atoms and germanium atoms to satisfy the following formulae (1), (2) and (3), and a polyester resin (B) comprising titanium atoms to satisfy the following formula (4): P1≧10 (1) 0.1≦Ge1≦1.5 (2) 0.001≦Ge1/P1≦0.15 (3) 0≦P2/Ti1≦80 (4) wherein in the formulae (1), (2) and (3), P1 is a mole content of the phosphorus atoms and Ge1 is a mole content of the germanium atoms, per ton of the polyester resin (A), and in the formula (4), P2 is a mole content of the phosphorus atoms and Ti1 is a mole content of the titanium atoms, per ton of the polyester resin (B), so that the polyester resin composition (C) satisfies the following formula (6): (P3/Ti2)≧5 (6), wherein P3 is a mole content of phosphorus atoms and Ti2 is a mole content of titanium atoms, per ton of the composition (C), wherein the total amount of a phosphorus compound having the mole content P1 is added to the polyester resin (A) at the time of a polycondensation, at least 95 mol % of a diol component in both of the polyester resins (A) and (B) is ethylene glycol, wherein the phosphorus compound is at least one selected from the group consisting of orthophosphoric acid, polyphosphoric acid and ethyl acid phosphate, wherein in the polyester resin (A), only the germanium compound is used as a polycondensation catalyst, and the polyester resin (B) does not comprise a germanium compound, wherein the phosphorous atoms are from the phosphorus compound, wherein the germanium and titanium atoms are from germanium and titanium catalysts, respectively and wherein the germanium catalyst is at least one catalyst selected from the group consisting of germanium dioxide, germanium tetraoxide and germanium hydroxide.