Patent ID: 7942275
Filing Date: 2011-05-17
Classification: B01D,B29C,B29K,C08J,Y10T

Abstract:
1. A method of making a porous membrane, said method comprising: mixing together about 60% to about 68% by weight of a first fine powder PTFE resin, about 15% to about 17% by weight of a second fine powder PTFE resin, and about 15% to about 25% by weight of the hydrocarbon lubricating aid, the weight percent based on the total weight of the PTFE resin mixture, to form a PTFE resin mixture, the first PTFE resin having a characteristic of forming more and longer fibrils than fibrils formed from the second PTFE resin, the second PTFE resin having a characteristic of forming thicker nodes than nodes formed from the first PTFE resin; forming a preform from the PTFE resin mixture; extruding the preform into a tape; passing the tape through a plurality of opposing calender rolls to form a calendered tape having a thickness of about 380 μm to about 1200 μm; and stretching the calendered tape in a transverse direction to form a porous membrane comprising a plurality of nodes and fibrils, the porous membrane having a thickness of about 100 μm to about 380 μm, and a machine direction peel strength of at least about 1.0 pounds-force per inch.