Patent ID: 6653440
Filing Date: 2003-11-25
Classification: C08G

Abstract:
A process for producing a copolyester resin comprising a dicarboxylic acid constituting unit derived from a dicarboxylic acid and/or an ester-forming derivative thereof and a diol constituting unit derived from a sublimable diol and a non-sublimable diol, and containing a constituting unit derived from the sublimable diol in an amount of 5 to 60 mol % based on the diol constituting unit, the process comprising:a step 1 for producing an oligomer by the reaction of the dicarboxylic acid and/or the ester-forming derivative thereof with the sublimable diol and the non-sublimable diol in the presence of the non-sublimable diol in excess of the amount of the non-sublimable diol for constituting the copolyester resin, while distilling off water and/or alcohol generated from the ester-forming derivative from the reaction system until a conversion of the dicarboxylic acid and/or the ester-forming derivative reaches 85 mol % or more; a step 2 for subjecting the oligomer to transesterification reaction while distilling off mainly the non-sublimable diol at 150 to 250Â° C. under a pressure not higher than a vapor pressure of the non-sublimable diol but not lower than a vapor pressure of sublimable diol until an amount of the sublimable diol remaining in an oligomer solution is reduced to 10% by weight or less based on the sublimable diol added to the reaction system; and a step 3 for increasing the molecular weight of the oligomer under further reduced pressure.