METHOD FOR PRODUCING PROPYLENE-BASED RESIN MICROPOROUS FILM AND PROPYLENE-BASED RESIN MICROPOROUS FILM

摘要

Provided is a method for producing a propylene-based resin microporous film whereby a high-performance lithium ion battery can be configured. A method for producing a propylene-based resin microporous film, the method comprising: an extrusion step of obtaining a propylene-based resin film by melt-kneading and extruding a propylene-based resin with an extruder; a first stretching step of uniaxially stretching the propylene-based resin film at a surface temperature of -20°C to 100°C; a second stretching step in which a stretching foundation step of uniaxially stretching the propylene-based resin film after the first stretching step at a surface temperature 10°C to 100°C lower than the melting point of the propylene-based resin is repeated a plurality of times, where, between stretching foundation steps continuous with each other, the stretching ratio of the earlier stretching foundation step is adjusted so as to be lower than the stretching ratio of the later stretching foundation step; and an annealing step of annealing the propylene-based resin film after the second stretching step.