METHOD FOR PRODUCING POROUS FILM

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a porous film suitable for a battery separator. SOLUTION: A primary film is manufactured from a resin composition comprising a thermoplastic resin and 15-85 pts.vol. of a filler 1μm or below in average particle size per 100 pts.vol. of the thermoplastic resin and stretched at least in one direction at a distortion speed of 1-300%/s. By stretching the primary film under the above conditions, a porous film suitable for a battery separator can be obtained.