Self-lubricating bearings and other machine elements and a process for their manufacture

Abstract

Self-lubricating bearings and other machine elements are prepared by admixing perfluoroalkylene polymers such as polytetrafluoroethylene with defined inorganic solid lubricants and epoxy resins followed by a cold molding technique and heating cycle which allows the economical production of large numbers of self-lubricating parts with excellent precision and low dimensional change.

That which is claimed is: 
     
       1. Cold molded self-lubricating bearing consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalents weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH) 2 , CaF 2 , Na 3  AlF 6  and FeF 2 , and   (c) 2-30 percent by weight of solid polytetrafluoroethylene having a molecular weight of 35,000 to 150,000 grams/mole and an average particle size of less than 0.075 mm. the percentages of (a), (b) and (c) being based on the total weight of the three components.   
     
     
       2. The bearing as in claim 1, consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a solid thermosetting condensate of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)propane cross-linked with 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH) 2 , CaF 2 , Na 3  AlF 6  and FeF 2 , and   (c)  .[.2-3.]. .Iadd.2-30 .Iaddend.percent by weight of  a solid polytetrafluoroethylene having a molecular weight of 35,000 to 150,000 grams/mole and a particle size of less than 0.075 mm.   
     
     
       3. Cold molded self-lubricating bearing consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH) 2 , CaF 2 , Na 3  AlF 6  and FeF 2 , and   (c) 2-30 percent by weight of a solid tetrafluoroethylene-perfluoropropylene copolymer with an average particle size of less than 0.075 mm. and a molecular weight of 35,000 to 150,000 grams/mole, the percentages of (a), (b) and (c) being based on the total weight of the three components.   
     
     
       4. The bearing as in claim 3 consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a solid thermosetting condensate of epichlorohydrin and 2,2-bis(4-hydrophenyl)-propane cross-linked with 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH).sub. 2, CaF 2 , Na 3  AlF 6  and FeF 2 , and   (c) 2-30 percent by weight of a solid tetrafluoroethylene-perfluoropropylene copolymer with an average particle size of less than 0.075 mm. and a molecular weight of 35,000 to 150,000 grams/mole, the percentages of (a), (b) and (c) being based on the total weight of the three components.   
     
     
       5. The bearing as in claim 1 consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles of equal weights of MoS 2  and ZnS and,   (c) 2-30 percent by weight of solid polytetrafluoroethylene with a molecular weight of 35,000 to 150,000 grams/mole and a particle size of less than 0.075.   
     
     
       6. The bearing as in claim 3 consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy  resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles of equal weights of MoS 2  and ZnS, and   (c) 2-30 percent by weight of a solid tetrafluoroethylene-perfluoropropylene copolymer with an average particle size of less than 0.075 mm. and a molecular weight of 35,000 to 150,000 grams/mole, the percentages of (a), (b) and (c) being based on the total weight of the three components.   
     
     
       7. A composition for producing a cold molded self-lubricating bearing consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH) 2 , CaF 2 , Na.sub. 3 AlF 6  and FeF 2 , and   (c) 2-30 percent by weight of solid polytetrafluoroethylene having a molecular weight of 35,000 to 150,000 grams/mole and an average particle size of less than 0.075 mm. the percentages of (a), (b) and (c) being based on the total weight of the three components.   
     
     
       8. The composition as claimed in claim 7 consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a solid thermosetting condensate of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)propane cross-linked with 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH) 2 , CaF 2 , Na 3  AlF 6  and FeF 2 , and   (c) 2-30 percent by weight of solid polytetrafluoroethylene with a molecular weight of 35,000 to 150,000 grams/mole and a particle size of less than 0.075 mm.   
     
     
       9. A composition for producing a cold molded self-lubricating bearing consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH).sub. 2, CaF 2 , Na 3  AlF 6  and FeF 2 , and   (c) 2-30 percent by weight of a solid tetrafluoroethylene-perfluoropropylene copolymer with an average particle size of less than 0.075 mm. and a molecular weight of 35,000 to 150,000 grams/mole, the percentages of (a), (b) and (c) being based on the total weight of the three components.   
     
     
       10. The composition as claimed in claim 9 consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a solid thermosetting condensate of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane cross-linked with 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO Ca(OH) 2 , CaF 2 , Na 3  AlF.sub. 6 and FeF 2 , and   (c) 2-30 percent by weight of a solid tetrafluoroethylene-perfluoropropylene copolymer with an average particle size of less than 0.075 mm. and a molecular weight of 35,000 to 150,000 grams/mole, the percentages of (a), (b) and (c) being based on the total weight of the three components.   
     
     
       11. The composition as claimed in claim 7 consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles of equal weights of MoS 2  and ZnS and,   (c) 2-30 percent by weight of solid polytetrafluoroethylene with a molecular weight of 35,000 to 150,000 grams/mole and a particle size of less than 0.075 mm.   
     
     
       12. The composition as claimed in claim 9 consisting essentially of (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane or condensates of epichlorohydrin and cycloaliphatic epoxy resins with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH) 2 , CaF 2 , Na 3  AlF 6  and FeF 2 , and   (c) 2-30 percent by weight of a solid tetrafluoroethylene-perfluoropropylene copolymer with an average particle size of less than 0.075 mm. and a molecular weight of 35,000 to 150,000 grams/mole, the percentages of (a), (b) and (c) being based on the total weight of the three components.   
     
     
       13. A process for manufacturing cold molded self-lubricating bearings wherein the components (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH) 2 , CaF 2 , Na 3  AlF 6  and FeF 2 , are (1) mixed and made into a powder;   (2) plasticized and homogenized at a temperature above the softening temperature of Component (a);   (3) repowdered and sieved to obtain a fraction with a particle size distribution consisting of at least 80 percent particles with a particle size of less than 0.315 mm. which are then intimately mixed with 2-30 weight percent of solid polyperfluoroalkylene selected from a group consisting of polytetrafluoroethylene or tetrafluoroethylene-perfluoropropylene copolymer or mixtures thereof having a molecular weight of 35,000 to 150,000 grams/mole and a particle size of less than 0.075 mm., and   (4) molded in a steel multi-cavity die with a predetermined molding pressure of 15-50 kp./mm. 3  at room temperature based on the amount of polyperfluoroalkylene added to the mixture, and   (5) heating in an oven at increasing temperatures for specific time periods of 2 hours at 170° C., 2 hours at 200° C. and 4 hours at 230° C. to obtain the final molded product.     
     
     
       14. A process for manufacturing cold molded self-lubricating bearings wherein the components (a) 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a curing, solid thermosetting epoxy resin consisting of condensates of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane with epoxy equivalent weights of 200 to 1,000,   (b) 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight of solid particles with an average particle size of less than 0.075 mm. which are inorganic solids selected from a group consisting of graphite, boron nitride, barium sulphate, glass fibers, asbestos, MoS 2 , WS 2 , ZnS, ZnO, PbO, Ca(OH) 2 , CaF 2 , Na 3  AlF 6  and FeF 2 , are (1) mixed and made into a powder;   (2) plasticized and homogenized at a temperature above the softening temperature of component (a);   (3) repowdered and sieved to obtain a fraction with a particle size distribution consisting of at least 80 weight percent particles with a particle size of less than 0.315 mm. which are then intimately mixed with 2-30 weight percent of polytetrafluoroethylene-polyperfluoropropylene copolymer having a molecular weight of 35,000 to 150,000 grams/mole and a particle size of less than 0.075 mm., and   (4) molded in a steel multi-cavity die with a predetermined molding pressure of 15-50 kp./mm. 2  at room temperature based on the amount of polyperfluoroalkylene added to the mixture, and   (5) heating in an oven at increasing temperature for specific time periods of 2 hours at 170° C., 2 hours at 200° C. and 4 hours at 230° C. to obtain the final molded product.     
     
     
       15. A process as in claim 13 wherein component (c) is 2-30 percent by weight of solid polytetrafluoroethylene having a molecular weight of 35,000 to 150,000 gram/mole and particle size of less than 0.075 mm. 
     
     
       16. A process as in claim 13 wherein component (b) is present in 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight and consists essentially of a 50/50 equal weight mixture of MoS 2  and ZnS. 
     
     
       17. A process as in claim 14 wherein the component (a) is 10-25 .[.percent.]. .Iadd.parts .Iaddend.by weight of a solid thermosetting condensate of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)propane cross-linked with 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride. 
     
     
       18. A process as in claim 14 wherein component (b) is present in 90-75 .[.percent.]. .Iadd.parts .Iaddend.by weight and consists essentially of a 50/50 equal weight mixture of MoS 2  and ZnS. 
     
     
       19. A process as claimed in claim 13 wherein component (c) is a mixture of polytetrafluoroethylene and polytetrafluoroethylene-perfluoropropylene copolymer.