Patent ID: 7060210

Claim:
A method of processing colloidal size polytetrafluoroethylene resin particles by plug flow in an unmelted state while in a hydrostatic coalescible condition to produce biaxially-planar oriented structures comprising the steps of: a. releasing said colloidal size polytetrafluoroethylene resin particles from coagulated dispersion aggregates at high shear in a solvent to create a mixture, wherein said particles are approximately 5 to 10 microns in size and said solvent is capable of wetting polytetrafluoroethylene surfaces; b. subjecting said mixture to high shear mixing; c. filtering said mixture to retain approximately 17 to 20 percent liquid to form a hydrostatic pressure coalescible filter cake; and d. processing said filter cake, said processing step comprising i) first uniaxially paste extruding said filter cake composition to produce a uniaxial planar oriented polytetrafluoroethylene structure having longitudinal stress containing approximately 17 to 20 percent lubricant; and ii) applying a means of re-orienting said uniaxially planar oriented polytetrafluoroethylene structure containing approximately 17 to 20 percent lubricant approximately 90 degrees to the initial uniaxial extrusion direction, wherein said means of re-orienting imparts a transverse stress to said structure, wherein said means of re-orienting comprises a single step of re-orientation for a sufficient period of time so that the transverse stress imparted by said re-orienting and the longitudinal stress imparted by said uniaxial paste extrusion are about equal.