| 摘要 |
<p>A separator for battery which exhibits a low electrical resistivity at normal time, good SD characteristics and a high mechanical strength is disclosed. A high molecular weight polypropylene having a weight average molecular weight of 500,000 or more and a polyethylene having a melting point of from 100 to 140 DEG C are extruded through a T-die film-forming machine to prepare a laminate film comprising a laminate of the high molecular polypropylene layer and the polyethylene layer. The laminate film is stretched at a temperature as low as from -20 DEG C to 80 DEG C by 10% to 100% based on the length of the original film, stretched at a temperature as high as 80 DEG C to 130 DEG C by 60% to 300% based on the length of the unstretched film, and then shrunk at the same temperature by 5% to 30% based on the length of the stretched film to render the film porous. Thus, a porous laminate film having a Gurley value of from 200 to 1,500 is prepared as a separator for battery. <IMAGE></p> |
