| 摘要 |
A separator for a battery using an organic electrolytic solution, which comprises a microporous film comprising a matrix comprised of a polyethylene and a propylene polymer having a weight average molecular weight of from 10,000 to 1,000,000, the propylene polymer being present in a proportion of from 5 to 45% by weight, based on the total weight of the polyethylene and the propylene polymer, the polyethylene containing a fraction having a molecular weight of not smaller than 1,000,000 in a proportion of at least 10% by weight and a fraction having a molecular weight of not greater than 100,000 in a proportion of at least 5% by weight, and wherein the microporous film has a thickness of from 10 to 500 mu m, a porosity of from 40 to 85% and a maximum pore diameter of from 0.05 to 5 mu m.
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