Method of producing a polyester resin composition

A method of producing a polyethylene terephthalate resin composition, comprising:

• (A) reacting a dicarboxylic acid component and a diol component through an esterification reaction to obtain an esterification reaction product;
• (B) performing a polycondensation reaction of the esterification reaction product to obtain a condensation polymerization product;
• and
• adding a phosphorus compound selected from the group consisting of trimethyl phosphate and triethyl phosphate to the reaction mixture from step (A), before the esterification reaction in step (A) is terminated but after an organic chelate titanium complex comprising an acid selected from the group consisting of citric acid, lactic acid, trimellitic acid and malic acid and a compound containing at least one metal selected from the group consisting of an alkali metal, an alkaline earth metal, iron-group metal, manganese, tin, lead and zinc, are added to the reaction mixture from step (A), so as to satisfy the following formula (1) and formula (2):
• 0.10<Ti/P<0.20 (1)
• wherein Ti/P represents a mass content ratio of titanium element to phosphorus element in the polyethylene terephthalate resin composition;
• and
• 0.0172<ΔIV≦0.0185 (dL/g/hr) (2)
• wherein ΔIV represents an increase in an intrinsic viscosity of the polyethylene terephthalate resin composition per hour under conditions of 225° C. and 50 Pa;
• wherein the addition of the compound containing at least one metal to the reaction mixture from step (A) occurs after the organic chelate titanium complex has been added, and before the esterification reaction in step (A) is terminated.