METHOD FOR PURIFYING HYDROXYCARBOXYLIC ACID, METHOD FOR PRODUCING CYCLIC ESTER, AND METHOD FOR PRODUCING POLYHYDROXYCARBOXYLIC ACID

摘要

PROBLEM TO BE SOLVED: To provide a method for purifying a hydroxycarboxylic acid suitable as a raw material for producing a polyhydroxycarboxylic acid, a method for producing a cyclic ester containing the hydroxycarboxylic acid, and a method for producing the polyhydroxycarboxylic acid. SOLUTION: The method for purifying a hydroxycarboxylic acid, by distillation, is characterized by that an aqueous hydroxycarboxylic acid solution containing a high-boiling-point hydroxy compound consisting of at least one alcohol or phenol having a boiling point higher than that of the hydroxycarboxylic acid is distilled. The purified hydroxycarboxylic acid is polycondensed to form an oligomer of the dihydroxycarboxylic acid; the oligomer is depolymerized to form a cyclic ester consisting of a dimer of the hydroxycarboxylic acid; and the cyclic ester is subjected to ring-opening polymerization to form the polyhydroxycarboxylic acid. COPYRIGHT: (C)2008,JPO&INPIT