MICROPOROUS POLYOLEFIN MEMBRANE, PROCESS FOR PRODUCING THE SAME, SEPARATOR FOR CELL, AND CELL

摘要

A microporous polyolefin membrane which comprises a polyethylene resin and in which (a) the shutdown temperature is 135°C or lower which is the temperature at which the gas permeability as measured with heating at a heating rate of 5 °C/min reaches 1x10^5 sec/100 cm^3, (b) the maximum degree of melt shrinkage in the transverse direction in the temperature range of 135-145°C is 40% or lower as measured by thermomechanical analysis at a load of 2 gf and a heating rate of 5 °C/min, and (c) the meltdown temperature is 150°C or higher which is the temperature at which the gas permeability as measured with further continuous heating beyond the shutdown temperature reaches 1x10^5 sec/100 cm^3 again.