| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a separator for a battery having a high mechanical strength, an excellent SD characteristic and a low electrical resistance when ordinary usage is practiced. SOLUTION: A T-die film making machine performs the extrusion molding of macromolecular polypropylene having a weight average molecular weight of 500,000 or more and polyethylene having a melting point ranging from 100 to 140 deg.C, and a laminated film is produced by laminating the macromolecular polypropylene layer 1 and the polyethylene layer 2. This laminated film is extended so that the length thereof increases 10 to 100% of the original film length at a low temperature ranging from -20 to 80 deg.C and then increases 60 to 300% of the unextencied film length at a high temperature ranging from 80 to 130 deg.C. The laminated film is shortened so that the length thereof decreases 5 to 30% of the extended film length at the high temperature, and the porosity of the laminated film is heightened, and a porous laminated film having Gurley's number of seconds, 20 to 1,500 at a temperature of 25 deg.C is produced to be used as a battery separator.</p> |
