| abstract |
Provided is a microporous polyolefin multilayer film which is used as a separator for a battery, and a preparing method thereof. The microporous polyolefin multilayer film is a 3 layer mi¬ croporous film which is prepared by a wet process to have both surface layers containing polyethylene of 95 wt% or more having a melting temperature of 1250C or higher, and an inner layer containing polypropylene of 50-90 wt% having a melting temperature of 16O0C or higher and polyethylene of 10-50 wt% having a melting temperature of 1250C or higher, wherein a thickness of the film is 9-50/M, a puncture strength is 0.15N//M or more, a permeability is 1.5X105 Darcy or more, a multiplication of the puncture strength and the permeability is 0.4X10 - 5 DarcyN/μm or more, a shrinkage in a transverse direction at 12O0C for 1 hour is 15% or less, and a melt fracture temperature of 16O0C or higher. |