| 摘要 |
PROBLEM TO BE SOLVED: To provide a process for producing lactic acid by regenerating a by-product produced in a production process of a lactic acid-based composition and, at the same time, producing a lactide and a polylactic acid having arbitrary optical purity using the regenerated lactic acid. SOLUTION: An essentially optically inactive lactic acid component is produced from a lactic acid component in a condensed water, a still residue, process washing liquid, vacuum pump waste liquid in a direct synthesis of a lactic acid prepolymer or a polylactic acid, still residue, process washing liquid, waste liquid discharged from a vacuum pump, etc., in a depolymerziation of the lactic acid prepolymer to obtain lactide, a waste liquid of a lactide purification process such as process washing liquid and a vacuum pump waste liquid, a loss generated in the molding of a polylactic acid such as a waste polymer produced in the polymerization of a lactide to form a polylactic acid, a waste polymer generated in the market, etc., by racemizing the above raw materials in the presence or absence of a catalyst. An optically inactive lactide or polylactic acid is produced from the optically inactive lactic acid component and the produced lactide or polylactic acid is mixed with a lactide or a polylactic acid having an optical purity of 90-100%e.e. at an arbitrary ratio to obtain a lactide or polylactic acid having arbitrary optical purity. |
