PREPARATION PROCESS AND PURIFICATION PROCESS OF DIMERIC CYCLIC ESTER OF ALPHA-HYDROXYCARBOXYLIC ACID

摘要

The present invention provides a method for economically and efficiently producing a dimeric cyclic ester of the same α-hydroxycarboxylic acid oligomer by depolymerizing an α-hydroxycarboxylic acid oligomer, which method comprises (1) α-hydride. Heating a mixed liquid containing a oxycarboxylic acid oligomer and at least one high boiling polar organic solvent having a boiling point in the range of 230 to 450 ° C. at atmospheric pressure or reduced pressure to a temperature at which depolymerization of the oligomer occurs, (2 ) Dissolving the oligomer in the solvent until the residual ratio of the oligomer in the molten liquid phase is 0.5 or less, (3) further polymerizing the oligomer by heating at a temperature at which the depolymerization of the oligomer occurs, (4) high ratio Distilling the dimeric cyclic ester formed with an isopolar organic solvent, and (5) said dimer from said distillate And a step of recovering the cyclic ester. The method also provides a process for the purification of dimeric cyclic esters of crude α-hydroxycarboxylic acid.