Coating, and a gasket comprising it

Abstract

The invention pertains to a coating for application to a substrate, whereby the coating comprises at least one thermoplastic fluorine-containing polymer, and its hardness decreases from the first surface, which is destined for application to the substrate, in the direction of the second surface which is remote from the substrate. The hardness gradient can be achieved by adding filling or reinforcing agents or by addition of at least one thermoplastic polymer. The invention additionally pertains to a gasket that consists of the coating in accordance with the invention or that comprises it.

1 . A gasket comprising a substrate and a coating, said coating comprising a fluorocarbon polymer and being applied on a surface of the substrate, 
 wherein said coating has a first surface which is to contact the surface of the substrate and a second surface which is remote from the surface of the substrate, and    wherein the coating has a hardness which decreases in the direction from the first surface to the second surface.    
   
   
       2 . The gasket in accordance with  claim 1 , wherein the coating comprises at least one filling or reinforcing agent in addition to the at least one fluoro-carbon polymer, and wherein the concentration of the filling or reinforcing agent increases in the direction to the first surface.  
   
   
       3 . The gasket in accordance with  claim 2 , wherein the at least one filling or reinforcing agent is selected from the group consisting of graphite, carbon, carbon fibers, glass fibers, whiskers and molybdenum disulfide.  
   
   
       4 . The gasket in accordance with  claim 3 , wherein the at least one filling or reinforcing agent is selected from fibers and whiskers and wherein the fibers and/or whiskers of the reinforcing agent are aligned essentially in parallel to the first and second surfaces.  
   
   
       5 . The gasket in accordance with  claim 1 , further comprising at least one thermoplastic polycondensate with a hardness higher than the at least one fluorocarbon polymer, wherein the concentration of the thermoplastic poly-condensate increases in the direction to the first surface.  
   
   
       6 . The gasket in accordance with  claim 5 , wherein in the region of the first surface, the proportion of the at least one fluorocarbon polymer is 0 wt % and in the region of the second surface its proportion is 80-100 wt %.  
   
   
       7 . The gasket in accordance with  claim 6 , wherein the proportion of the at least one fluorocarbon polymer is in the region of the second surface is in the range of from 95 to 100 wt %.  
   
   
       8 . The gasket in accordance with  claim 5 , wherein said thermoplastic polycondensate incorporates at least one filling or reinforcing agent.  
   
   
       9 . The gasket in accordance with  claim 8 , wherein the at least one filling or reinforcing agent is selected from the group consisting of graphite, carbon, carbon fibers and glass fibers.  
   
   
       10 . The gasket in accordance with  claim 5 , wherein the thermoplastic polycondensate has an upper long-term usage temperature of at least 150° C.  
   
   
       11 . The gasket in accordance with  claim 5 , wherein the thermoplastic polycondensate has an upper long-term usage temperature of at least 180° C.  
   
   
       12 . The gasket in accordance with  claim 5 , wherein the thermoplastic polycondensate has an upper long-term usage temperature of at least 200° C.  
   
   
       13 . The gasket in accordance with  claim 5 , wherein the thermoplastic polycondensate has a dimensional stability under heat (ASTM D648; 1.8 N/mm 2 ) of at least 140° C.  
   
   
       14 . The gasket in accordance with  claim 13 , wherein the thermoplastic polycondensate has a dimensional stability under heat (ASTM D648; 1.8 N/mm 2 ) of at least 180° C.  
   
   
       15 . The gasket in accordance with  claim 14 , wherein the thermoplastic polycondensate has a dimensional stability under heat (ASTM D648; 1.8 N/mm 2 ) of at least 190° C.  
   
   
       16 . The gasket in accordance with  claim 5 , wherein the thermoplastic polycondensate is resistant to hydrolysis.  
   
   
       17 . The gasket in accordance with  claim 16 , wherein the thermoplastic polycondensate is resistant to hot steam up to at least 130° C.  
   
   
       18 . The gasket in accordance with  claim 5 , wherein the thermoplastic polycondensate is resistant to oil and grease.  
   
   
       19 . The gasket in accordance with  claim 18 , wherein the thermoplastic polycondensate is resistant to oil and grease up to a temperature of at least 150° C.  
   
   
       20 . The gasket in accordance with  claim 5 , wherein the thermoplastic polycondensate has a sliding friction coefficient μ of ≦0.7 at 40° C.  
   
   
       21 . The gasket in accordance with  claim 20 , wherein the thermoplastic polycondensate has a sliding friction coefficient μ of ≦0.55 at 40° C.  
   
   
       22 . The gasket in accordance with  claim 5 , wherein the thermoplastic polycondensate is selected from the group consisting of polysulfone (PSU), polyphenylene sulfide (PPS), polyphenylethersulfone (PPSU), polyethersulfone (PES), polyaryletherketone (PAEK), polyetherketone (PEK), polyetheretherketone (PEEK) and mixtures thereof.  
   
   
       23 . The gasket in accordance with  claim 22 , wherein the thermoplastic polycondensate is selected from the group consisting of filled and nonfilled PPS, PEK and PEEK and mixtures thereof.  
   
   
       24 . The gasket in accordance with  claim 1 , wherein the fluorocarbon polymer is selected from the group consisting of filled and nonfilled polytetrafluoroethylene (PTFE), as well as tetrafluoroethylene/hexafluoropropylene copolymer (FEP) and perfluoroalkoxy copolymer (PFA) and mixtures thereof.  
   
   
       25 . The gasket in accordance with  claim 1 , wherein said coating further comprises at least one adhesion-promoting agent and/or at least one adhesive in the region of the first surface.  
   
   
       26 . Process for the manufacture of a gasket in accordance with  claim 1 , wherein layers comprising a polymer of decreasing hardness are sequentially applied to a substrate and are sintered or partially melted by heating.  
   
   
       27 . Process in accordance with  claim 26 , wherein the sintering or heating is carried out at 350-400° C.