| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyolefin microporous film excellent in the balance among gas permeability, porosity, fine pore size, compression characteristics, mechanical strengths, dimensional stability, shut-down characteristics and melt- down characteristics, and its manufacturing method. SOLUTION: The polyolefin microporous film comprises a polyolefin composition (A) comprising as essential ingredients a polyolefin (A1) having a weight- average molecular weight of at least 5×105 and a polyolefin (A2) having a weight-average molecular weight of at least 1×104 and less than 5×105, where the polyolefin (A2) is a linear polyolefin having a weight-average molecular weight/number-average molecular weight ratio of at least 1 and less than 10.
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