Microporous polyolefin multilayer film possessing good mechanical properties and thermal stability

摘要

Provided is a microporous polyolefin multilayer film which may be used as a separator for a battery, and a method for preparing the same. At least one layer of the microporous polyolefin multilayer film contains 90-100 wt% of polyethylene having a melting temperature of 130ˆ¼140 °C and at least the other layer has 20 wt% or more of a heat resistant resin and 80 wt% or less of a filler selected from the group consisting of an organic filler, an inorganic filler and a mixture thereof. The heat resistant resin is preferably a semi crystalline polymer or an amorphous polymer. Preferably, the semi crystalline polymer has a degree of crystallinity of 10ˆ¼45% or a heat of fusion for melting of 20-90 J/g and has a melting temperature of 145ˆ¼250 °C and a glass transition temperature of -100ˆ¼90 °C . Also, preferably, the amorphous polymer has no crystal and has a glass transition temperature of 90ˆ¼120 °C.