| 摘要 |
According to the present invention, disclosed is a method for producing polylactic acid through ring-opening polymerization by using lactide as a main ingredient. Production process simplicity, efficiency, and mass-production properties are ensured, and polylactic acid having high molecular weight and high purity is produced. In particular, non-reacted residual lactide may be effectively removed in a short time. The method for producing polylactic acid through ring-opening polymerization by using lactide as a main ingredient comprises the steps of: (a) sequentially dissolving, mixing, and polymerizing the lactide; cooling polymerized polylactic acid and making the same into pellets; and (c) removing residual lactide from the pellets of polylactic acid at a temperature which is lower than a polymerization temperature of step (a). Step (c) comprises a step of simultaneously removing the residual lactide while a temperature is increased and pressure is decreased. |
