METHOD FOR PRODUCING POLYOLEFIN MICROPOROUS FILM AND MICROPOROUS FILM

摘要

Disclosed is a polyolefin microporous film which is obtained by a process (a) wherein a gel molding material containing a polyolefin and a solvent for film formation is stretched at least uniaxially at a temperature from the crystalline dispersion temperature of the polyolefin + 15°C to the crystalline dispersion temperature of the polyolefin + 40°C, the solvent for film formation is removed, and then the resulting material is again stretched 1.1-2.5 times at least uniaxially, or by a process (b) wherein the gel molding material is stretched at least uniaxially, the thus-stretched film is brought into contact with a hot solvent before and/or after removing the solvent for film formation, and then the resulting material is again stretched 1.1-2.5 times at least uniaxially. This polyolefin microporous film has large pore sizes while being excellent in air permeability, mechanical strength and compression resistance.