PRODUCTION METHOD FOR PREPARING POLYLACTIC ACID BY MEANS OF RING-OPENING POLYMERIZATION METHOD, AND PREPOLYMER MIXTURE AND POLYLACTIC ACID

The present invention relates to the technical field of the production of polylactic acid, and in particular to a production method for preparing polylactic acid by means of a ring-opening polymerization method, and a prepolymer mixture and the polylactic acid. The production method comprises: (1) enabling an initiator, a catalyst and a monomer I to be in contact in a production device to undergo a ring-opening polymerization reaction, so as to generate a prepolymer mixture containing a polylactic acid prepolymer; and (2) enabling the prepolymer mixture and a monomer II to be in contact with one another to undergo a reaction, so as to generate a high molecular weight polylactic acid. The monomer I and the monomer II are the same or are different, and each independently comprises lactide. The production method provided by the present invention can reduce the fluctuation in the feeding quality of the initiator and the catalyst, and can improve the production stability during the production process.