Process for the preparation of polyester polyols

摘要

Polyester polyols are prepared by the reaction of a polycarboxylic acid or anhydride with a polyhydric alcohol employing in an initial step a stoichiometric excess of polycarboxylic acid or anhydride, thereafter removing between 90 to 95% of the water of esterification, adjusting the stoichiometry of the reaction by addition of polyhydric alcohol, and continuing the esterification reaction until a polyester polyol having an acid number of less than two is obtained. The process allows for an increase in reactor capacity without equipment modification at the same cycle times and a decrease in side product formation.