| 摘要 |
PURPOSE: To simply and economically obtain a high-purity lactide by polycondensing lactic acid and then thermally decomposing the resultant polylactic acid under specific conditions. CONSTITUTION: Purified lactic acid or crude lactic acid obtained in a fermenting step, etc., or containing inorganic salts is vacuum distilled and dehydrated, preferably at 60-100 deg.C to provide a concentrated lactic acid, which is then usually polycondensed at 100-200 deg.C (preferably 100-180 deg.C) under <=30mmHg (preferably <=10mmHg) for 5-20hr to afford polylactic acid having 2000-20000 weight- average molecular weight. Ferrous oxide as a catalyst in an amount of <=5wt.% is then added to the resultant polymer and catalytic thermal decomposition of the polymer is usually carried out at 200-300 deg.C (preferably 230-300 deg.C) under 1-30mmHg (preferably 1-15mmHg) for 1-3hr. Thereby, the objective lactide is obtained. |
