| 摘要 |
The process enables an easy recycling of impurities and avoids chemical and thermal deterioration of the lactide during purification. The lactide is sufficiently pure for synthesis of a polylactide(PLA). The process of purification of the cyclic dimeric ester of lactic acid from a crude lactide product containing impurities is effected in the following stages: (a) extraction and controlled crystallisation of the crude in an aqueous medium; in controlling the geometry of the formed crystals and inducing a separation of phases between the lactide(solid phase) and impurities (liquid phase), aqueous extraction of the impurities is favored; (b) separation of the suspension of crystals obtained in (A) into a liquid phase depleted in lactide and containing impurities and a moist cake rich in lactide crystals; (c) drying of the moist cake obtained in (b); (d) recrystallization in a melt medium of the impure dried lactide and recovery of the purified product. |
