PROCESS FOR PRODUCING POLYESTER RESIN

摘要

A process for polyester resin production in which a high rate of solid-phase polycondensation is attained. The process for polyester resin production comprises condensation-polymerizing a dicarboxylic acid ingredient consisting mainly of terephthalic acid or an ester-forming derivative thereof with a diol ingredient consisting mainly of ethylene glycol via esterification or transesterification to produce a molten polymer and subjecting the polymer to solid-phase polycondensation, and is characterized in that the molten polymer obtained has a content of comonomer units other than terephthalic acid units and ethylene glycol units of 5.5 or lower, an intrinsic viscosity of 0.08 to 0.50 dl/g, and an apparent crystallite size smaller than 9 nm and the molten polymer is subjected to solid-phase polycondensation at a temperature which is higher by at least 140°C than the glass transition temperature of the polymer and is not higher than the melting point thereof to obtain the polyester resin having an apparent crystallite size smaller than 9 nm.