Griffin, Butler, Whisenhunt & Szipl
Gasket for sanitary piping and method of manufacturing the same
 A gasket for use in sealing sanitary piping comprises an annular plate of porous polytetrafluoroethylene, the inner surface layer of the gasket being heat treated to form a pore-free fused solidified layer for directly contacting a fluid to be sealed. The fused solidified layer prevents osmotic leakage of sealed fluid. Since the solidified layer is formed only in the surface layer the intrinsic properties of porous polytetrafluoroethylene, such as flexibility and affinity, are retained. The gasket is made by inserting a tubular member with an internal heater into a porous polytetrafluoroethylene gasket so that the tubular member directly contacts the inner surface layer of the gasket. The tubular member is operated at a temperature of 420.degree. to 460.degree. C. and contacts a gasket for 10 to 30 seconds to form the fused and pore-free layer. 
Nippon Pillar Packing Co., Ltd.
F F C
F16J F16L C09K
inventional inventional inventional
Takeshi Katsuo Makoto Tetsuya Tosiyasu
Miyoshi Wada Abe Akai Tanimura