POLYOLEFIN MULTILAYER MICROPOROUS MEMBRANE AND BATTERY SEPARATOR

摘要

Disclosed is a polyolefin multilayer microporous membrane composed of at least three layers. This polyolefin multilayer microporous membrane comprises first porous layers respectively composed of a polyethylene resin and constituting at least both surface layers, and a second porous layer containing a polyethylene resin and polypropylene and constituting at least one layer interposed between the two surface layers. This polyolefin multilayer microporous membrane is characterized in that the heat of fusion ( H_m) of polypropylene as measured by a differential scanning calorimeter is not less than 90 J/g, and the polypropylene content is not more than 50% by mass when the total of the polyethylene resin and polypropylene in the second porous layer is taken as 100% by mass.