Patent ID: 9446553
Filing Date: 2016-09-20
CPC Classification: A61F,A61L,B29C,B29K,B29L,Y10T

Claim Text:
1. A method of processing PTFE, comprising: extruding a compounded PTFE resin through an extruder in a machine direction to form a PTFE ribbon extrudate; calendering the PTFE ribbon extrudate in the machine direction to form a layer of PTFE having an upper surface, a lower surface and a longitudinal length in a machine direction of an extruder used to produce the layer of PTFE and having a width in a cross machine or transverse direction; applying a liquid stretching agent in an excess amount to at least a portion of the upper surface or the lower surface of the layer of PTFE; stretching the layer of PTFE in the transverse direction to the machine direction; and maintaining the excess amount of the liquid stretching agent on the at least portion of the upper or the lower surface of the layer of PTFE during at least part of the stretching to fully saturate the layer of PTFE throughout its thickness with the liquid stretching agent during the stretching to form a stretched layer of PTFE that has: (i) a closed cell microstructure with a plurality of interconnected high density regions of PTFE having no distinct fibrils interconnecting adjacent nodes when viewed at a magnification of 20,000 under a scanning electron microscope; and (ii) a thickness from 0.00005 inch to 0.005 inch; wherein the stretching is at a rate from 10 percent per second to 100 percent per second; wherein the stretching is performed at a stretch ratio from 2:1 to 20:1; and wherein stretching of the layer of PTFE is performed at a temperature of 80° F. to 100° F.