| 摘要 |
PROBLEM TO BE SOLVED: To provide a porous membrane having a low shutdown(SD)-initiating temperature and a large SD rate and useful as a separator for a battery. SOLUTION: This porous membrane is formed from a mixture of a polyolefin with a substance which has a lower melting point than that of the polyolefin and is incompatible with the polyolefin. The substance comprises at least one of a resin having a viscosity-average mol.wt. of 100-10,000 and an aliphatic compound having 9-22 carbon atoms in the aliphatic chain. When the ion transmission-interrupting temperature of the porous membrane is set to a range of 105-130 deg.C, and when the electric resistance of the porous membrane is measured on the basis of JIS C 2313, the electric resistance value of the porous membrane after a thermal treatment at 130 deg.C for 0.6 sec is set to >=20 times an electric resistance before the treatment. Polypropylene and highly dense polyethylene wax may be used as the polyolefin and the substance, respectively. |
