Patent ID: 9624349
Date: 2017-04-18
CPC Classifications: B29C,B29D,B29K,B29L,C08J,C08L,H01M,Y02E

Claim:
1. A polyolefin microporous membrane produced by forming a gel-like molding using a polyolefin resin comprising 80% or more by mass of polyethylene composition based on 100% by mass of the total amount of the polyolefin and 0.5% or more but less than 5% by mass of polypropylene having a weight average molecular weight of more than 5×10 4 but less than 3×10 5 based on 100% by mass of the total amount of the polyolefin, wherein the polyethylene composition comprises polyethylene having a mass average molecular weight of from 2.5×10 5 to 5×10 5 and 18 to 50% by mass of ultra-high molecular weight polyethylene having a mass average molecular weight of 1×10 6 to 3×10 6 based on 100% by mass of polyethylene composition, and stretching the molding in at least one direction, followed by washing, the polyolefin microporous membrane having an injection of electrolyte of 20 seconds or less and a uniform polypropylene distribution in at least one plane perpendicular to the thickness direction.