Patent ID: 9623640
Date: 2017-04-18
CPC Classifications: B29D,B29K,B29L,B32B,Y10T

Claim:
1. A method of manufacturing a multilayer separator, the method comprising: manufacturing a precursor film by co-extruding and molding a polypropylene based resin melt having a melt index (2.16 kg, 230° C.) of 0.3 to 5 g/10 min and a polyethylene based resin melt having a melt index (2.16 kg, 190° C.) of 0.1 to 1.5 g/10 min so as to be alternately laminated; and heat-treating and stretching the manufactured film, wherein a melt index ratio (A/B) of the polypropylene based resin melt (A) and polyethylene based resin melt (B) is 2 to 10, and the manufacturing of the precursor film is performed in a range in which the draw down speed of the resin melt is 160 to 3,000 l/sec., wherein the draw down speed, DDS, is defined by the following equation: where, D is the die gap in mm; t is the thickness of film in μm; V d is the distance from an exit of a die to a frost line of the film in m; and DDR is the draw down ratio.