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

摘要

A microporous polyolefin membrane comprising a polyethylene resin, and having (a) a shutdown temperature of 135°C or lower, at which the air permeability measured while heating at a temperature-elevating speed of 5°C/minute reaches 1 x 10 5 sec/100 cm 3 , (b) a maximum melting shrinkage ratio of 40% or less in a transverse direction in a temperature range of 135 to 145°C, which is measured by thermomechanical analysis under a load of 2 gf and at a temperature-elevating speed of 5°C/minute, and (c) a meltdown temperature, at which the air permeability measured while further heating after reaching the above shutdown temperature becomes 1 x 10 5 sec/100 cm 3 again, being 150°C or higher.