| 摘要 |
PROBLEM TO BE SOLVED: To provide a microporous film excellent in resistance to film-breakdown, having high film-breakdown temperature; and a battery separator using the film. SOLUTION: This microporous film comprises a polypropylene resin composition having 500,000-750,000 weight-average molecular weight, and has air permeability of 10 to 5,000 sec/100 cc and elongation viscosity of 30,000 to 60,000 Pa s. The method of production includes a cold-stretch step of stretching the film comprising the polypropylene resin composition at a temperature not lower than -20°C and lower than 90°C; and a hot-stretch step of stretching the resultant film at a temperature not lower than 90°C and lower than 150°C. COPYRIGHT: (C)2011,JPO&INPIT
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