POROUS FILM AND SEPARATOR FOR NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To obtain a porous film for a low-temperature shutdown when used as a separator for a battery and a temperature is above an ordinary use temperature. SOLUTION: The porous film is formed from a polyolefin-based resin comprising an ethylene-α-olefin copolymer composed of an ethylene-derived constituent unit and a constituent unit derived from one or more kinds of monomers selected from 4-10Cα-olefins and has a shutdown temperature of≤125°C. The porous film has a piercing strength of≥250 gf. The porous film has the intrinsic viscosity [η] of the ethylene-α-olefin copolymer of≥9.1 dl/g and≤15.0 dl/g and the number of the short chain branches (SCB)≥4.8 and≤20.0 based on 1,000 carbon atoms in the copolymer. COPYRIGHT: (C)2008,JPO&INPIT