| 摘要 |
PROBLEM TO BE SOLVED: To obtain the practical and safe subject film having specific physical properties, excellent in shutdown characteristics, and capable of forming a thin film by forming a composition containing a low molecular weight polyethylene and a high melting point polymer. SOLUTION: This film has η5 Ω.cm<2> membrane resistance measured in an organic electrolyte liquid at room temperature and >=100 Ω.cm<2> membrane resistance measured in the organic electrolyte at room temperature after sealing the film for one sec under a substantial seal pressure of 5 kg/cm<2> within the temperature range of 100-130 deg.C. Preferably, the air permeability of the film is <=400 sec/100 cc. Preferably, this film is obtained by forming a film composed of a composition comprising (A) 10-80 wt.% low molecular weight polyethylene having >=50% crystallinity and 500-10,000 weight average molecular weight, and (B) 90-20 wt.% polymer having a melting point >=5 deg.C higher than that of the component A (a high melting point polymer), and subjecting the film to orientation to form the film into the porous one. |
