The unit which was formed from

摘要

PROBLEM TO BE SOLVED: To obtain a target resin by improving the reaction conversion of a sublimable diol in conducting the polycondensation step in producing a copolyester resin using the sublimable diol as the raw material and to provide a method for stably producing the resin without clogging the reduced-pressure portions of piping and the like in the production apparatus due to the sublimation of the sublimable diol.;SOLUTION: The method produces a copolyester resin comprising a dicarboxylic acid constituting unit and a diol constituting unit and, simultaneously, a unit formed from a sublimable diol in the diol constituting unit by (1) a step of distilling off water and/or an alcohol to produce an oligomer, (2) a step of mainly distilling off a nonsublimable diol to perform transesterification until the amount of the sublimable diol comes to ≤10 wt.% based on its added amount, and (3) a step of allowing the oligomer to have a high molecular weight under reduced pressure.;COPYRIGHT: (C)2003,JPO