Method for producing polyolefin porous film, and laminated porous film

Abstract

Provided is a method for reproducibly and efficiently producing a polyolefin porous film having a porous structure suitable for a separator for a battery without requiring a special apparatus. The method according to the present invention is a method for producing a polyolefin porous film, the method including conveying a raw material polyolefin sheet having pores into a furnace of a tenter type stretching machine, and tenter-stretching the sheet in a plurality of stretching regions in the furnace to produce a polyolefin porous film, wherein the plurality of stretching regions include at least two stretching regions having different film widening speeds, and the temperature of a stretching region having a high film widening speed is lower than that of a stretching region having a low film widening speed in the at least two stretching regions, and a stretching region having the highest film widening speed is situated in the front stage with respect to a stretching region having the lowest film widening speed.

Dependencies are inferred from the claim text.