Compositions for compounding, extrusion and melt processing of foamable and cellular fluoropolymers

Abstract

The present invention relates generally to the use of talc as a chemical foaming agent in perfluoropolymers to form foamable and foamed compositions. For example, in one aspect, a foamable composition is disclosed, which comprises (i) one or more base perfluoropolymers comprising at least 50 percent by weight of the composition, and (ii) talc blended with the one or more base perfluoropolymers, where the talc comprises 3 percent to about 15 percent by weight of the composition. Each of the perfluoropolymers is selected from the group consisting of tetrafluoroethylene/perfluoromethylvinyl ether copolymer (MFA), hexafluoropropylene/tetrafluoroethylene copolymer (FEP) and perfluoroalkoxy (PFA) and any blend thereof, where hydrogen-containing fluoropolymers are absent from the composition. The one or more base perfluoropolymers are melt-processable at one or more elevated processing temperatures of at least about 600° F. at which the talc functions as a chemical foaming agent for extrusion or mold processing of the composition into a foamed article having uniform cell structures.

What is claimed is: 
     
         1 - 20 . (canceled) 
     
     
         21 . A method for manufacturing a foamed article comprising:
 heating a composition comprising a melt-processable perfluoropolymer and talc to a processing temperature of at least 600° F. at which said talc functions as a chemical foaming agent, thereby causing the foaming of said composition at a foaming rate in a range from 20% to 50% so as to form a foamed article;   wherein said melt-processable perfluoroploymer is selected from the group consisting of tetrafluoroethylene/perfluoromethylvinyl ether copolymer (MFA), hexafluoropropylene/tetrafluoroethylene copolymer (FEP), perfluoroalkoxy (PFA) and any blend thereof, and   wherein said talc is the only foaming agent in said composition and wherein said foaming is achieved without gas injection.   
     
     
         22 . The method of  claim 21 , wherein said processing temperature is in a range of about 600° F. to about 660° F. 
     
     
         23 . The method of  claim 21 , wherein said processing temperature is in a range of about 630° F. to about 660° F. 
     
     
         24 . The method of  claim 21 , wherein said processing temperature is in a range of about 640° F. to about 660° F. 
     
     
         25 . The method of  claim 21 , wherein said talc comprises recycled talc. 
     
     
         26 . The method of  claim 21 , wherein said perfluoropolymer comprises recycled perfluoropolymer. 
     
     
         27 . The method of  claim 21 , wherein said foamed article comprises any of a separator, wire insulation or cable jacketing. 
     
     
         28 . The method of  claim 21 , further comprising extruding said foaming composition to form said foamed article. 
     
     
         29 . The method of  claim 21 , further comprising mold processing said foaming composition to form said foamed article. 
     
     
         30 . The method of  claim 21 , wherein said perfluoropolymer comprises at least 50 percent by weight of the composition.