| 摘要 |
PROBLEM TO BE SOLVED: To provide a porous film which has a microfine porous structure and an appropriate porosity and are high in membrane strength an air permeability (Gurley value) and prevents short circuit between the positive and negative electrodes at a high temperature, and a process for producing the same. SOLUTION: The porous film is composed of 30-85 wt.% polyolefin containing an ultra-high-molecular-weight polyolefin having a weight average molecular weight of nor smaller than 1×106 and 15-70 wt.% inorganic powder and/or inorganic fibers, and the inorganic powder and/or inorganic fibers comprise as inorganic material having a plate structure. A process for producing porous films comprises the steps of kneading a resin composition composed of 5-25 wt.% polyolefin and inorganic powder and/or inorganic fibers containing an inorganic material having a plate structure in total and 75-95 wt.% solvent, molding the composition into the form of a sheet and effecting stretching and desolvation treatment.
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