| 摘要 |
<p>A process for the preparation of cyclic lactic acid oligomers, which comprises (i) the first heating step of condensing lactic acid through dehydration by heating under such conditions of pressure and temperature that by-product water can be distilled away while avoiding the distillation-off of lactide, and (ii) the second heating step of lowering the pressure of the resulting reaction system to 100mmHg or below at a temperature higher than that of the first step under such conditions of pressure and temperature that by-product water can be distilled away while avoiding the distillation-off of lactide, and further continuing the reaction under the resulting lowered pressure by heating to form a condensate of lactic acid; and cyclic lactic acid oligomers prepared by the process.</p> |
