▎ 摘　　要

NOVELTY - Preparing modified polylactic acid non-woven fabric involves mixing modified nanocellulose and lactic acid in water to obtain mixed dispersion. The modified nanocellulose has sulfonic acid group and hydroxyl group. The mixed dispersion is heated and stirred until solid content of mixed dispersion is 80-95%, and in-situ catalytic melt condensation is carried out for 1-12 hours under conditions of 140-180degrees Celsius and pressure of 2-6 kilopascal. The separated moisture is removed from reaction system to obtain nanocellulose polylactic acid prepolymer composite material. The nanocellulose polylactic acid prepolymer composite material is pulverized to obtain powder. The powder is kept at 70-120degrees Celsius for 0.1-5 hours, and subjected to solid-phase condensation polymerization for 0.1-20 hours at 120-160degrees Celsius and pressure of less than or equal to 2 kilopascal to prepare multi-arm star structured polylactic acid material. USE - Method for preparing modified polylactic acid non-woven fabric. ADVANTAGE - The method enables to have large free volume, plays role in plasticization, improves effect of toughening, melt strength, melt fluidity, spinning process, spinning efficiency and quality, and increases bonding between fibers. DETAILED DESCRIPTION - Preparing modified polylactic acid non-woven fabric involves mixing modified nanocellulose and lactic acid in water to obtain mixed dispersion. The modified nanocellulose has sulfonic acid group and hydroxyl group. The mixed dispersion is heated and stirred until solid content of mixed dispersion is 80-95%, and in-situ catalytic melt condensation is carried out for 1-12 hours under conditions of 140-180degrees Celsius and pressure of 2-6 kilopascal. The separated moisture is removed from reaction system to obtain nanocellulose polylactic acid prepolymer composite material. The nanocellulose polylactic acid prepolymer composite material is pulverized to obtain powder. The powder is kept at 70-120degrees Celsius for 0.1-5 hours, and subjected to solid-phase condensation polymerization for 0.1-20 hours at 120-160degrees Celsius and pressure of less than or equal to 2 kilopascal to prepare multi-arm star structured polylactic acid material. The polylactic acid material with multi-arm star structure is used as modifier of polylactic acid, mixed polylactic acid with polylactic acid material with multi-arm star structure to prepare polylactic acid composite material. The polylactic acid composite material is subjected to solution spinning treatment or melt spinning treatment to prepare modified polylactic acid fibers, and modified polylactic acid fibers are subjected to non-woven fabric forming treatment. INDEPENDENT CLAIMS are also included for: 1. a multi-layer laminated modified polylactic acid non-woven fabric, which is obtained by multi-layer lamination treatment of modified poly lactic acid non-woven fabric; and 2. an air filter product, which comprises modified polylactic acid non-woven fabric or multi-layered modified polylactic acid non-woven fabric.