▎ 摘　　要

NOVELTY - An antibacterial direct heat-sealing bidirectional stretched polylactic acid film comprises an upper surface layer, a core layer, and a bottom layer. The raw material of the upper surface layer is heat-sealed polylactic acid chip including 80-90 wt.% crystalline polylactic acid and 10-20 wt.% amorphous polylactic acid. The raw material of the core layer is crystalline polylactic acid chips. The raw materials of the bottom layer include 80-90 wt.% crystalline polylactic acid chips and 10-20 wt.% inorganic antibacterial masterbatch including graphene-loaded silver and crystalline polylactic acid. USE - The antibacterial direct heat-sealing bidirectional stretched polylactic acid film is useful in food packaging industry. ADVANTAGE - The antibacterial direct heat-sealing bidirectional stretched polylactic acid film can increase the storage time of food. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of the antibacterial direct heat-sealing bidirectional stretched polylactic acid film, which involves: (S1) drying the raw materials of the core layer, adding to a main extruder to heat and melt, filtering the core layer melt using a filter, separating the raw materials of the upper surface layer, heating and melting the raw materials of the bottom layer in two co-extruders, carrying out vacuum treatment to obtain an upper surface layer melt and a bottom surface layer melt, and introducing the core layer melt, the upper surface layer melt and the bottom surface layer melt into a three-layer co-extrusion die, mixing and extruding to obtain a film; (S2) attaching the film to a chill roller using electrostatic adsorption, and cooling to form a cast sheet; (S3) preheating the cast sheet, longitudinally stretching, then cooling and shaping to obtain a sheet; and (S4) preheating the sheet, transversely stretching, shaping and crystallizing.