Paste extruded insulator with air channels

Abstract

The invention provides an insulated wire having a conductor and an insulator of paste extruded PTFE fine powder around the conductor. The paste extruded insulator has at least one closed continuous longitudinal air channel spaced apart from the conductor. The invention further provides a process for forming an insulator around a conductor by paste extruding lubricated PTFE fine powder in an extrusion device comprising a die, mandrel, and at least one channel-forming member. The die and mandrel form a converging chamber leading to an extrusion orifice and the channel-forming member is positioned in the orifice. The mandrel has a central bore for supplying the conductor. Lubricated PTFE fine powder is forced through the chamber and out of the exit of the orifice as a lubricated green extrudate around the conductor forming an insulator with at least one closed longitudinal air channel spaced apart from the conductor.

What is claimed is : 
     
         1 . An insulated wire comprising a conductor and an insulator of paste extruded PTFE fine powder pressure coalesced around said conductor, wherein said insulator has at least one closed continuous longitudinal air channel spaced apart from said conductor. 
     
     
         2 . The insulated wire of  claim 1  wherein said insulator has multiple closed continuous longitudinal air channels spaced from each other. 
     
     
         3 . The insulated wire of  claim 2  wherein said longitudinal air channels are disposed symmetrically about the conductor. 
     
     
         4 . The insulated wire of  claim 1  wherein said insulator has been sintered. 
     
     
         5 . A coaxial cable comprising the insulated wire of  claim 1 . 
     
     
         6 . The insulated wire of  claim 1  wherein said insulator has a diameter of greater than about 8 mm. 
     
     
         7 . The insulated wire of  claim 1  wherein said insulator has a diameter greater than about 10 mm. 
     
     
         8 . A lubricated green extrudate of paste extruded PTFE fine powder pressure coalesced around a conductor, said lubricated green extrudate comprising organic lubricant, wherein said lubricated green extrudate has at least one closed continuous longitudinal air channel spaced apart from said conductor.