| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyolefin microporous film excellent not only in the balance between permeability and mechanical strength but also in dimensional stability. SOLUTION: A polyolefin containing polyethylene with a weight average molecular weight of 5×10<5> or more as an essential component and a liquid solvent are melted and kneaded to obtain a molten kneaded material which is, in turn, extruded from a die and cooled to obtain a gel-like molded article. This gel-like molded article is at least uniaxially stretched to obtain a stretched article which is, in turn, washed using a washing solvent (A) of which the surface tension at 25 deg.C is not more than 24 mN/m to remove the liquid solvent. The stretched article after washing is again stretched at least in a uniaxial direction at a temperature of the crystal dispersing temperature-melting point of the polyolefin and subsequently thermally fixed at the temperature of the crystal dispersing temperature-melting point of the polyolefin. |
