| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous film which shows high strength and a high percentage of vacancies and further, reliable thickness stability. SOLUTION: In the method for manufacturing a porous film by which a mixture of a polyolefin composition and a solvent is melt-kneaded and the melt mixture thus obtained is extruded into a sheetlike form, which is, in turn, cooled and the obtained sheetlike molding is rolled, the characteristics are that the molding is rolled at a rolling ratio of 5 or more times and in the machine axial and the width direction, using a double belt press with its feed rate/line velocity during rolling adjusted to 0.2-1.
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