Patent ID: 7744792

Claim:
A process for making staple length micro-fibers in a multi-directional planar oriented isotropic polytetrafluoroethylene (PTFE) resin structure, said method comprising the steps of: (a) preparing a wetting liquid slurry of 20 parts of wetting liquid to 1 part polytetrafluoroethylene resin at a temperature of about 125° C. comprising: (i) polytetrafluoroethylene resin primary dispersion particles ranging in size from 0.05 to 5.0 microns in diameter contained within an aggregate particle of a coagulated dispersion resin having an average aggregate size of about 500 microns; and (ii) a wetting liquid having a contact angle near zero and that will spread on PTFE polymer surfaces, wherein said wetting liquid has a surface tension of about 30 dynes/cm or less; (b) applying to said slurry a liquid shearing force provided by a high shear stirrer operating at a tip speed of 2000 feet/minute or higher to produce a an isotropic micro-fibered polytetrafluoroethylene resin slurry; (c) after step (b) diluting said micro-fiber slurry with 35 volumes of a wetting liquid at ambient temperature to terminate fiber formation and provide a free flowing mixture of diluted micro-fibers; (d) uniformly depositing said diluted micro-fiber slurry onto a porous surface to form a homogeneous uniform thickness mat of micro-fibers wherein said wetting liquid is removed such that 16 to 20 percent of said wetting liquid is retained with said micro-fiber mat; (e) drying said micro-fiber mat composition at a temperature not exceeding the melt transition temperature of said polytetrafluoroethylene resin micro-fibers; (f) compressing said micro-fiber mat; and (g) sintering said compressed dried micro-fiber mat at a temperature of between 327° C. to 400° C., whereby a multi-directional planar oriented isotropic PTFE resin structure is produced.