Bearing material and method of producing the same
An object of the present invention is to provide a method of producing a bearing material having excellent wear-resistance and oxidation resistance. The method of producing a bearing material 10 according to the present invention comprises molding a substrate 12 containing a radical scavenger and a polymer material; washing at least a part 16 of the substrate 12 with a washing liquid; and grafting a polymer chain having a phosphorylcholine group from at least the part 16 of the surface after washing so as to form a polymer film 30 on at least the part of the surface.
1. A method of producing a bearing material comprising:
molding a substrate comprising 0.1% vitamin E by weight based on ultrahigh molecular weight polyethylene (UHMWPE);
washing at least a part of a surface of the substrate by immersing the substrate in a washing liquid at 40° C. to 80° C. for 6 hours or more; and
fixing a polymer chain having a phosphorylcholine group at at least the part of the surface by a graft bond after washing so as to form a non-defective polymer film on at least the part of the surface.
2. The method according to claim 1 , wherein the washing liquid is an aqueous solution containing a surfactant.
3. The method according to claim 2 , wherein the surfactant is a nonionic surfactant.
4. The method according to claim 1 , wherein in the washing step, at least a part of the surface is washed at 70° C. to 80° C. for 12 hours or more.
5. The method according to claim 1 further comprising preparing a substrate material, before the step of molding the substrate,
wherein the step of preparing the substrate material comprises mixing a powder of the UHMWPE with the vitamin E, and subjecting the obtained the mixed powder to compression molding to obtain the substrate material comprising the 0.1% vitamin E by weight based on UHMWPE.
6. The method according to claim 1 , wherein the step of forming the non-defective polymer film comprises irradiating at least the part of the surface with the ultraviolet-ray of an intensity of 0.5 mW/cm 2 or more while the part of the surface is in contact with a polymerizable monomer having the phosphorylcholine group.
7. The method according to claim 6 , wherein the intensity of the ultraviolet-ray is from 1.0 mW/cm 2 to 13 mW/cm 2 .
8. The method according to claim 6 , wherein total energy of the irradiated the ultraviolet-ray is from 6,000 mJ/cm 2 to 70,000 mJ/cm 2 .
9. The method according to claim 6 , wherein the irradiation time of the ultraviolet-ray is from 0.5 hours to 24 hours.
10. The method according to claim 1 , wherein the step of forming the non-defective polymer film comprises irradiating at least the part of the surface of the substrate with the ultraviolet-ray while at least the part of the surface is immersed in an aqueous solution containing a polymerizable monomer having the phosphorylcholine group, and
the concentration of the polymerizable monomer in the aqueous solution is 0.15 mol/L to 1.0 mol/L.
11. The method according to claim 10 , wherein the concentration of the polymerizable monomer in the aqueous solution is 0.27 mol/L to 1.0 mol/L.
12. The method according to claim 6 , wherein the step of forming the non-defective polymer film further comprises applying a photoinduced polymerization initiator to at least the part of the surface before irradiating with the ultraviolet-ray, and
the photoinduced polymerization initiator is excited by the irradiated ultraviolet-ray.
13. The method according to claim 1 , wherein the UHMWPE has a molecular weight of 3×10 6 g/mol or more.
14. The method according to claim 13 , further comprising crosslinking the UHMWPE before the step of washing.