Mitsubishi Chemical Corporation

Kyosuke Watanabe

Keishin Handa

Toshio Fujii

A porous film or sheet including a resin composition mainly of an ultra-high molecular weight polyethylene having a viscosity-average molecular weight of not less than 500,000, and having a thickness of 10 to 100 .mu.m, an air permeability of 20 to 2,000 sec/100 cc, a porosity of 15 to 80%, a pin puncture strength (per 25 .mu.m of film thickness) of not less than 120 g, a thermal-shut down temperature of 90.degree. to 150.degree. C. and a heat puncture temperature of not less than 160.degree. C., and a process for producing the same.

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Kurashiki, Japan

Kyosuke Watanabe