Process for producing lactide and process for producing polylactic acid from fermented lactic acid employed as starting material

摘要

A process for consistently producing lactide from ammonium lactate obtained by lactic acid fermentation; and a process for consistently producing polylactic acid from ammonium lactate obtained by lactic acid fermentation are provided. Namely, a process for producing lactide which comprises: (1) synthesizing a lactic acid ester from ammonium lactate obtained by lactic acid fermentation; (2) polycondensing this lactic acid ester in the presence of a catalyst other than monobutyl tin to synthesize polylactic acid (a lactic acid prepolymer) having a weight-average molecular weight less than 15,000; and (3) depolymerizing this polylactic acid to give lactide; and a process for producing polylactic acid which further involves (4) ring-opening polymerizing the lactide to give polylactic acid. A process for producing a lactic acid ester from ammonium lactate obtained by lactic acid fermentation.