Highly chemically resistant thermoplastic vulcanizates based on fluorocarbon polymers and seal-gasket products made with same

Abstract

Disclosed are new fluid resistant, in particular resistant to chemically basic compounds, and exceptional processing fluorine containing thermoplastic vulcanizate compositions comprising a continuous phase of at least one melt-formable thermoplastic fluorocarbon resin and a disperse phase consisting of a blend of at least two vulcanizable fluorine containing elastomers with at least one of the fluoroelastomers being a terpolymer of vinylidene fluoride/tetrafluoroethylene/propylene. The vinylidene fluoride/tetrafluoroethylene/propylene fluoroelastomer comprises between 5 and 95 weight percent of the total dispersed elastomer phase, which the total disperse elastomer phase comprises from between 40 and 90 weight percent based on the total amount of the continuous phase and the disperse phase combined.

What is claimed:  
     
         1 . A fluorine containing thermoplastic vulcanizate composition comprising a continuous phase of at least one uncured melt formable thermoplastic resin and a blend of at least two cured fluorine containing elastomers forming a dispersed elastomer phase where one of the elastomers is a vinylidene fluoride/tetrafluoroethylene/propylene terpolymer; 
 wherein the vinylidene fluoride/tetrafluoroethylene/propylene terpolymer comprises between 5 and 95 weight percent of the total dispersed elastomer phase, and the total dispersed elastomer phase comprises from between 40 and 90 weight percent based on the total amount of the continuous phase and the disperse phase combined.    
     
     
         2 . The composition of  claim 1  wherein the thermoplastic fluorocarbon resin has a fluorine content of at least 35 weight percent.  
     
     
         3 . The composition of  claim 1  wherein the vinylidene fluoride/tetrafluorethylene/propylene terpolymer comprises between about 23 and about 75 weight percent of the total dispersed elastomer phase.  
     
     
         4 . The composition of  claim 1  wherein the total dispersed elastomer phase comprises between about 56 and about 67 weight percent of the total amount of the continuous phase and the disperse phase combined.  
     
     
         5 . The composition of  claim 1  wherein the thermoplastic resin is a terpolymer of tetrafluoroethylene/vinylidene fluoride/hexafluoropropylene.  
     
     
         6 . The composition of  claim 1  wherein the thermoplastic resin is a copolymer of tetrafluoroethylene/ethylene.  
     
     
         7 . The composition of  claim 1  wherein the thermoplastic resin is a copolymer of tetrafluorethylene/hexafluoropropylene.  
     
     
         8 . An article formed from the composition of  claim 1 .  
     
     
         9 . An article formed from the composition of  claim 5 .  
     
     
         10 . An article formed from the composition of  claim 6 .  
     
     
         11 . An article formed from the composition of  claim 7 .  
     
     
         12 . A process for producing a fluorine containing thermoplastic vulcanizate composition comprising the steps of: 
 melt blending at least one uncured melt formable thermoplastic fluorocarbon resin with a blend of fluorine containing elastomers, where at least one of the elastomeric components is a vinylidene fluoride/tetrafluoroethylene/propylene terpolymer, and where the elastomers and thermoplastic is melt blended at a temperature higher than the melting temperature of the thermoplastic; and    vulcanizing the fluorine containing elastomers while maintaining the shear mixing forces on the blend thereby forming a dual phase composition comprising a cured dispersed particle phase of the fluorine containing elastomers suspended in an uncured melt formable continuous phase of the fluorocarbon resin.    
     
     
         13 . The process according to  claim 12  wherein at least one member selected from the group consisting of vulcanizing agents and vulcanization accelerators is added after the melt blending step and before the vulcanizing step.  
     
     
         14 . A product formed according to the process of  claim 12 .  
     
     
         15 . The process of  claim 12  further comprising the step of forcing the composition through an extrusion die.  
     
     
         16 . The process of  claim 12  further comprising the step of injecting the composition into a mold cavity.  
     
     
         17 . A product formed according to a process comprising the steps of: 
 melt blending at least one uncured melt formable thermoplastic fluorocarbon resin and a blend of fluorine containing elastomers, where at least one of the components of the blend of elastomers is a vinylidene fluoride/tetrafluoroethylene/propylene terpolymer, and where the blend of elastomers and thermoplastic is melt blended at a temperature higher than the melting temperature of the thermoplastic; and    partitioning the mixture into a dual phase composition by vulcanizing the fluorine containing elastomers while maintaining shear mixing forces, thereby forming an uncured continuous phase of the thermoplastic fluorocarbon resin and a cured dispersed phase of the fluorine containing elastomers.    
     
     
         18 . The product of  claim 17  wherein the thermoplastic resin is a terpolymer of tetrafluoroethylene/vinylidene fluoride/hexafluoropropylene.  
     
     
         19 . The product of  claim 17  wherein the thermoplastic resin is a copolymer of tetrafluoroethylene/ethylene.  
     
     
         20 . The product of  claim 17  wherein the thermoplastic resin is a copolymer of tetrafluoroethylene/hexafluoropropylene.  
     
     
         21 . The product of  claim 17  wherein the thermoplastic resin is a copolymer of tetrafluoroethylene/perfluoropropylvinyl ether.  
     
     
         22 . The product of  claim 17  wherein the thermoplastic resin is a copolymer of trifluoroethylene chloride/ethylene.  
     
     
         23 . The product of  claim 17  wherein the thermoplastic resin is a vinylidene fluoride polymer.  
     
     
         24 . The product of  claim 17  wherein the process further comprises the step of extruding the product.  
     
     
         25 . The product of  claim 17  wherein the process further comprises the step of injection molding the product.  
     
     
         26 . A fluorine containing thermoplastic vulcanizate composition comprising a continuous phase of at least one uncured melt formable thermoplastic resin and a blend of at least two cured fluorine containing elastomers forming a dispersed elastomer phase where one of the elastomers is a vinylidene fluoride/tetrafluoroethylene/propylene terpolymer; 
 wherein the vinylidene fluoride/tetrafluoroethylene/propylene terpolymer comprises between about 23 and about 75 weight percent of the total dispersed elastomer phase, and the total dispersed elastomer phase comprises from between about 56 and about 67 weight percent based on the total amount of the continuous phase and the disperse phase combined.