Patent ID: 8329857

Claim:
A method for producing a polyester resin, comprising carrying out a hot-water treatment and a heat treatment, in this order, of polyester prepolymer particles obtained by melt polycondensation of a dicarboxylic acid component and a diol component, wherein the hot-water treatment comprises bringing the polyester prepolymer particles with an intrinsic viscosity of from at least 0.10 dL/g to at most 1.0 dL/g and with a density of at most 1.36 g/cm 3 into contact with hot water having a temperature higher than the glass transition temperature of the polyester prepolymer particles and less than 100° C., under the condition satisfying the following formula (1): 40≦( T−Tg ) t≦ 6000 (1) wherein t is a hot-water treatment time (second), T is the temperature of the hot water (° C.) and Tg is the glass transition temperature (° C.) of the polyester prepolymer particles wherein the hot-water treatment time t (second) is from 30 to 80 seconds and wherein said polyester resin is a polyethylene terephthalate.