Patent ID: 9492965
Filing Date: 2016-11-15
CPC Classification: B29C,B29K,B32B,H01M,Y02E

Claim Text:
1. A method for producing a multi-layer, microporous polyolefin membrane comprising a microporous polypropylene layer and a microporous polyethylene resin layer, comprising the steps of simultaneously extruding a melt blend of 20 to 55% by mass of polypropylene and 45 to 80% by mass of a membrane-forming solvent and a melt blend of 20 to 55% by mass of a polyethylene resin and 45 to 80% by mass of a membrane-forming solvent through a die to form a laminar extrudate, cooling the laminar extrudate to provide a gel-like laminate sheet, first stretching the gel-like laminate sheet biaxially at a temperature of −20° C. or higher and lower than +90° C., conducting re-stretching biaxially at a temperature of 90 to 135° C., and removing the membrane-forming solvent from the stretched gel-like laminate sheet, wherein said polyethylene resin is a composition of ultra-high molecular weight polyethylene having molecular weight of 5×10 5 or higher and another polyethylene having molecular weight of 1×10 4 or more and less than 5×10 5 , and wherein the content of said ultra-high molecular weight polyethylene is 10 to 80% by mass based on 100% by mass of said polyethylene composition.