PROCESS FOR REDUCING THE PROCESSING TIME IN THE PRODUCTION OF POLYESTERS

摘要

PROCESS FOR REDUCING THE PROCESSING TIME IN THE PRODUCTION OF POLYESTERS 75T32 of the Invention Polyesters obtained by reacting isophthalic acid or terephthalic acid with a polyol with or without a catalyst in a first stage to form a half-ester mixture which is reacted in a second stage with an aliphatic polycarboxylic acid are produced at reduced processing times. In the first stage a portion of the total polyol to be reacted is contacted with substantially all of the isophthalic acid or terephthalic acid. Then, this mixture is heated to a temperature of at least 190.degree.C. and the remaining portion of the polyol is added to the heated mixture in such a manner that the temperature remains at or above the 190.degree.C. This temperature is maintained until the reaction to form a half-ester mixture is completed. This reaction may be conducted in the presence of an esterification catalyst, The polyester-monomer mixture is reacted in a second stage with an aliphatic polycarboxylic acid to produce the polyester.