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

摘要

A process for purification of a hydroxycarboxylic acid by distillation, comprising: distilling a hydroxycarboxylic acid solution containing a high-boiling point hydroxy compound comprising at least one species selected from the group consisting of alcohols and phenols having a higher boiling point than the hydroxycarboxylic acid. As a result, a hydroxycarboxylic acid suitable as a starting material for production of a polyhydroxycarboxylic acid can be obtained. The purified hydroxycarboxylic acid is further polycondensed to provide a hydroxycarboxylic acid oligomer, which is de-polymerized to provide a cyclic ester comprising a dimer of the hydroxycarboxylic acid, and the cyclic ester is converted into a polyhydroxycarboxylic acid by ring-opening polymerization thereof.