Patent ID: 6471687
Filing Date: 2002-10-29
Classification: A61F,A61K,A61L,A61N

Abstract:
A method of making a polytetrafluoroethylene laminate comprising:forming a first polytetrafluoroethylene material by providing a coagulated dispersion of fine powder polytetrafluoroethylene; lubricating said coagulated dispersion with a hydrocarbon extrusion aid; extruding said lubricated dispersion into a shaped article having an original width; stretching said extruded article transversely to 1.5 to 5 times the original width of the shaped article; drying said transversely stretched article to remove said extrusion aid; expanding said dry transversely stretched article longitudinally in a heated space at a temperature below 327 degrees centigrade; expanding said longitudinally and transversely stretched article transversely at a temperature less than 327 degrees centigrade to at least 1.5 times the original width, while restraining the article from longitudinal contraction; heating said restrained article above 327 degrees centigrade to sinter said article; forming a second polytetrafluoroethylene material by providing a coagulated dispersion of fine powder polytetrafluoroethylene; lubricating said coagulated dispersion with a hydrocarbon extrusion aid; extruding said lubricated dispersion into a shaped article having an original width; stretching said extruded shaped article in at least one direction to form nodes and fibrils therein; drying said longitudinally stretched article to remove said extrusion aid; sintering said nodes and fibrils; laminating said first polytetrafluoroethylene material to said second polytetrafluoroethylene material by holding said first and second polytetrafluoroethylene materials together in a combination; expanding said combination longitudinally between banks of rolls at a temperature below 327Â° C.; expanding said combination transversely at a temperature less than 327Â° C. to at least 1.5 times the original width of said first polytetrafluoroethylene material while restraining said combination from longitudinal and transverse contraction; and heating said combination under constraint to a temperature above 327Â° C.