Dynamic seal using vulcanization of fluorocarbon elastomers

Abstract

A dynamic seal assembly for installation between first and second relatively rotating members, comprising a ring for fixed engagement with said first member and an annular seal extending radially from said ring and configured to slidably engage said second member, wherein said radial seal has a thickness, and a length that is from about 1 to about 15 times greater than said thickness. In various embodiments, the seal is formed of a rubber composition comprising a vulcanized fluorocarbon elastomer dispersed in a matrix of a thermoplastic polymeric material. In various embodiments, the matrix forms a continuous phase and the vulcanized elastomeric material is in the form of particles forming a non-continuous phase. The compositions may be made by combining a curative, an uncured fluorocarbon elastomer, and a thermoplastic material, and heating the mixture to effect vulcanization of the elastomeric material, while applying mechanical energy.

1 . A dynamic seal assembly for installation between first and second relatively rotating members, said assembly comprising: 
 a ring for fixed engagement with said first member and an annular seal extending radially from said ring and configured to slidably engage said second member, wherein said radial seal has a thickness, and a length that is from about 1 to about 15 times greater than said thickness.    
   
   
       2 . A dynamic seal assembly according to  claim 1 , wherein said length is from about 5 to about 15 times greater than said thickness.  
   
   
       3 . A dynamic seal assembly according to  claim 2 , wherein said length is from about 5 to about 12 times greater than said thickness.  
   
   
       4 . A dynamic seal according to  claim 1 , wherein said radial seal is comprises a cured fluorocarbon elastomer dispersed in a matrix comprising a thermoplastic material.  
   
   
       5 . A dynamic seal according to  claim 4 , wherein said cured fluorocarbon elastomer is present as a discrete phase or a phase co-continuous with said matrix, and wherein said radial seal has a tan-delta of less than 1.0.  
   
   
       6 . A dynamic seal according to  claim 4 , wherein the radial seal is made by a process comprising the step of dynamically vulcanizing a fluorocarbon elastomer in the presence of a thermoplastic material.  
   
   
       7 . A dynamic seal according to  claim 4 , wherein the hardness of said annular seal is Shore A 50 or greater, the tensile strength of the seal is 4 MPa or greater, the modulus at 100% of the article is at least about 4 MPa, and the elongation at break of the article is 10% or greater.  
   
   
       8 . A dynamic seal according to  claim 4 , wherein said cured fluorocarbon elastomer is present at a level of at least about 35% by weight based on the total weight of said cured fluorocarbon elastomer and said thermoplastic polymer.  
   
   
       9 . A dynamic seal according to  claim 8 , wherein said cured fluorocarbon elastomer is present at a level of at least about 50% by weight based on said total weight.  
   
   
       10 . A dynamic seal according to  claim 4 , wherein said thermoplastic material is a thermoplastic elastomeric material comprising an amorphous polymer having a glass transition temperature of at least about −40° C.  
   
   
       11 . A dynamic seal according to  claim 4 , wherein said thermoplastic material is a reactive oligomer material which comprises a semi-crystalline polymer having a melting point of at least about 80° C.  
   
   
       12 . A dynamic seal according to  claim 4 , wherein said fluorocarbon elastomer is selected from the group consisting of VDF/HFP, VDF/HFP/TFE, VDF/PFVE/TFE, TFE/Pr, TFE/Pr/VDF, TFE/Et/PFVE/VDF, TFE/Et:PFVE, TFE/PFVE; and mixtures thereof.  
   
   
       13 . A dynamic seal according to  claim 1 , wherein said radial seal is made by a process comprising the steps of: 
 (a) combining an uncured or partially cured fluorocarbon elastomer, a curative agent capable of reacting with the fluorocarbon elastomer to effect cure, and a thermoplastic material;    (b) mixing the combination;    (c) applying heat to the combination during the mixing step; and    (d) forming the seal by subjecting the composition to one of blow molding, compressive molding, injection molding, or extrusion.    
   
   
       14 . A dynamic seal according to  claim 1  wherein the radial seal is made by a process comprising made by a process comprising the steps of: 
 (a) mixing the elastomer and thermoplastic components in the presence of the curative agent;    (b) heating during mixing to effect cure of the elastomeric components; and    (c) injection molding the composition.    
   
   
       15 . A dynamic seal according to  claim 1 , wherein said first member is a housing, and said second member is a rotating shaft.  
   
   
       16 . A method for making a dynamic seal comprising: 
 (a) forming a mixture by combining a curative, an uncured or partially cured elastomeric material, and a thermoplastic material; and    (b) heating the mixture at a temperature and for a time sufficient to effect vulcanization of the elastomeric material, wherein mechanical energy is applied to mix the mixture during the heating step; wherein the elastomeric material comprises a fluorocarbon elastomer; and wherein the thermoplastic material comprises a non-fluorine-containing polymeric material; and    (c) injection molding the mixture.    
   
   
       17 . A method according to  claim 16 , wherein said fluorocarbon elastomer is selected from the group consisting of: VDF/HFP, VDF/HFP/TFE, VDF/PFVE/TFE, TFE/Pr, TFE/Pr/VDF, TFE/Et/PFVE/VDF, TFE/Et:PFVE, TFE/PFVE; and mixtures thereof.  
   
   
       18 . A dynamic seal assembly for installation between an inner rotating shaft and an outer housing comprising: 
 an annular radial seal extending from said non-rotating housing into sliding contact with said shaft, said annular radial seal being configured to slidably engage said shaft, said radial seal having a thickness, and a length which is from about 1 to about 15 times greater than said thickness, said annular radial seal further comprising a flat bearing surface which contacts the rotating shaft.    
   
   
       19 . A dynamic seal assembly according to  claim 18 , wherein said length is from about 5 to about 15 times greater than said thickness.  
   
   
       20 . A dynamic seal assembly according to  claim 19 , wherein said length is from about 5 to about 12 times greater than said thickness.  
   
   
       21 . A dynamic seal according to  claim 18  wherein said flat bearing surface comprises a variegated surface.  
   
   
       22 . A dynamic seal according to  claim 21 , wherein said variegated surface is a helical spiral groove.  
   
   
       23 . A dynamic seal according to  claim 18 , wherein said annular seal comprises a reinforcing bead.  
   
   
       24 . A dynamic seal according to  claim 18 , wherein said annular seal comprises a pair of suspension flanges and a spring disposed between the suspension flanges.  
   
   
       25 . A dynamic seal according to  claim 18 , wherein the annular seal is formed of a material having a tangent delta of less than about 1.0.  
   
   
       26 . A dynamic seal according to  claim 18 , wherein said annular seal is formed of a material having a ratio of loss modulus to storage modulus which is less than about 0.1.