BEARING MATERIAL, BEARING AND METHOD

Abstract

A bearing material may include a polyamide/imide plastics polymer material having an amine content including a fluorinated diamine and a non-fluorinated diamine.

Claims

1. A bearing material comprising a polyamide/imide plastics polymer material, wherein an amine content of the polyamide/imide plastics polymer material includes a fluorinated diamine and a non-fluorinated diamine.

2. A bearing material according to claim 1, wherein the fluorinated diamine is an aromatic fluorinated diamine.

3. A bearing material according to claim 1, wherein the fluorinated diamine is a fluorinated dianiline.

4. A bearing material according to claim 1, wherein the fluorinated diamine comprises at least one of: 4,4-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline; 2,5-Diaminobenzotrifluoride; 3,5-Diaminobenzotrifluoride; 1,3-Diamino-2,4,5,6-tetrafluorobenzene; 2,2-Bis (trifluoromethyl) benzidine; 3,3-Bis (trifluoromethyl) benzidine; 2,2-Bis [4-(4-aminophenoxy phenyl)] hexafluoropropane; 2,2-Bis (4-aminophenyl) hexafluoropropane; 2,2-Bis (3-amino-4-hydroxyphenyl)-hexafluoropropane; 2,2-Bis (3-amino-4-methylphenyl)-hexafluoropropane; 3,5-Difluorobenzene-1,2-diamine; 4,5-Difluorobenzene-1,2-diamine; 2-(Trifluoromethyl)benzene-1,4-diamine; 3,5-Diaminobenzotrifluoride; 2,4,5,6-Tetrafluorobenzene-1,3-diamine; 3,3,3-Trifluoropropane-1,2-diamine hydrochloride; 3,3-Bis(trifluoromethyl)-[1,1-biphenyl]-4,4-diamine; 6-[(2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxy]-1,3,5-triazine-2,4-diamine; 4-(1,1,2,2-tetrafluoroethoxy)benzene-1,3-diamine; 2-(Trifluoromethyl)pyrimidine-4,6-diamine; 2,4-Diaminobenzotrifluoride; 1,4-Diamino-2,6-difluorobenzene; 2,5-Difluorobenzene-1,4-diamine; Perfluorobenzene-1,4-diamine; and 6-[4-(Trifluoromethyl)phenyl]-1,3,5-triazine-2,4-diamine.

5. A bearing material according to claim 1, wherein the fluorinated diamine is aromatic and is one of meta- or para-substituted.

6. A bearing material according to claim 1, wherein the fluorinated diamine comprises two aromatic rings, the two aromatic rings being fluorinated.

7. A bearing material according to claim 1, wherein a molar ratio of the fluorinated diamine and the non-fluorinated amine is between 0.4 and 0.05.

8. A bearing element having a bearing-surface layer, the bearing-surface layer including a bearing material comprising a polyamide/imide plastics polymer material, and wherein an amine content of the polyamide/imide plastics polymer material includes a fluorinated diamine and a non-fluorinated diamine.

9. A bearing element according to claim 8, wherein the bearing-surface layer comprises a plurality of particles of at least one other material within a matrix of the bearing material.

10. A method for making a bearing material comprising: copolymerising an anhydride monomer, a fluorinated diamine and a non-fluorinated diamine to form a bearing material comprising a polyamide/imide plastics polymer material.

11. A method for making a bearing material according to claim 10, wherein the fluorinated diamine is an aromatic fluorinated diamine.

12. A method for making a bearing material according to claim 10, wherein the fluorinated diamine is a fluorinated dianiline.

13. A method for making a bearing material according to claim 10, wherein the fluorinated diamine comprises at least one of: 4,4-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline; 2,5-Diaminobenzotrifluoride; 3,5-Diaminobenzotrifluoride; 1,3-Diamino-2,4,5,6-tetrafluorobenzene; 2,2-Bis (trifluoromethyl) benzidine; 3,3-Bis (trifluoromethyl) benzidine; 2,2-Bis [4-(4-aminophenoxy phenyl)] hexafluoropropane; 2,2-Bis (4-aminophenyl) hexafluoropropane; 2,2-Bis (3-amino-4-hydroxyphenyl)-hexafluoropropane; 2,2-Bis (3-amino-4-methylphenyl)-hexafluoropropane; 3,5-Difluorobenzene-1,2-diamine; 4,5-Difluorobenzene-1,2-diamine; 2-(Trifluoromethyl)benzene-1,4-diamine; 3,5-Diaminobenzotrifluoride; 2,4,5,6-Tetrafluorobenzene-1,3-diamine; 3,3,3-Trifluoropropane-1,2-diamine hydrochloride; 3,3-Bis(trifluoromethyl)-[1,1-biphenyl]-4,4-diamine; 6-[(2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxy]-1,3,5-triazine-2,4-diamine; 4-(1,1,2,2-tetrafluoroethoxy)benzene-1,3-diamine; 2-(Trifluoromethyl)pyrimidine-4,6-diamine; 2,4-Diaminobenzotrifluoride; 1,4-Diamino-2,6-difluorobenzene; 2,5-Difluorobenzene-1,4-diamine; Perfluorobenzene-1,4-diamine; and 6-[4-(Trifluoromethyl)phenyl]-1,3,5-triazine-2,4-diamine.

14. A method for making a bearing material according to claim 10, wherein the fluorinated diamine is aromatic and is one of meta- or para-substituted.

15. A method for making a bearing material according to claim 10, wherein a molar ratio of the fluorinated diamine and the non-fluorinated amine is between 0.4 and 0.05.

16. A bearing material according to claim 5, wherein the fluorinated diamine is aromatic and is para-substituted.

17. A bearing material according to claim 1, wherein a molar ratio of the fluorinated diamine and the non-fluorinated amine is between 0.25 and 0.1.

18. A method for making a bearing material according to claim 10, wherein the fluorinated diamine is aromatic and is para-substituted.

19. A method for making a bearing material according to claim 10, wherein a molar ratio of the fluorinated diamine and the non-fluorinated amine is between 0.25 and 0.1.

20. A bearing element according to claim 8, further comprising at least one shell comprising a backing of steel, a bearing lining layer comprising a layer of a copper-based alloy or an aluminium-based alloy bonded to one of the backing of steel and a nickel diffusion barrier or an interlayer, and wherein the bearing-surface layer is bonded to the bearing liner layer.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0036] Specific embodiments of the invention will now be described by way of example, with reference to the accompanying drawing, in which;

[0037] FIG. 1 is a schematic diagram of a half-shell of a plain bearing.

DETAILED DESCRIPTION

[0038] FIG. 1 shows a half shell 2 of a cylindrical sliding bearing comprising a strong backing 4 of steel, a bearing lining layer 6, comprising a layer 8 of a copper-based alloy or an aluminium-based alloy bonded to the backing and a nickel diffusion barrier, or interlayer, 10, and a plastics, polymer-based overlay layer 12 embodying the present invention bonded to the lining layer. In other embodiments of the invention the overlay may be bonded directly to the backing, and the lining layer omitted, depending on the compatibility of the materials used and the intended use of the bearing.

[0039] The overlay layer, or sliding layer, comprises a modified PAI resin matrix embodying the invention and fabricated as described below. The PAI matrix may incorporate filler materials as follows.

[0040] As in prior-art polymer bearings, the sliding layer material may optionally include at least one solid lubricant. Suitable solid lubricants include: metal sulphides with layered structures; graphite; hexagonal boron nitride (h-BN); molybdenum disulfide (MoS.sub.2); tungsten disulphide (WS.sub.2); PTFE; or a combination of any of these materials. Other suitable materials are envisaged and will be readily apparent to the skilled person.

[0041] Also as in prior-art polymer bearings, the sliding layer material may also include harder particles in powdered and/or flaked form. This may provide improved wear resistance. The harder particles may include, in any suitable combination, one or more different types of hard particle. Some suitable hard particles include nitrides, carbides, borides, oxides, and metal powders. Other suitable materials are envisaged and will be readily apparent to the skilled person.

[0042] The total thickness of the sliding layer material is between about 3 m, or 6 m, and about 14 m. A preferred thickness of the sliding layer material for bearing elements embodying the present invention is between about 8 m and about 12 m, or particularly preferably in the range 9 m to 11 m.

[0043] A conventional PAI polymer for a bearing material is formed by the copolymerisation of polyamide imide monomers such as trimellitic anhydride and methylene diamine. These monomers are mixed in known manner, in combination with suitable solvents and catalytic materials, to allow the monomers to copolymerise. An initial polymerisation step produces a polymer which may be applied to the surface of a bearing element, for example by spraying, and cured to form a thermoset PAI bearing layer. This process is described in the prior art, such as in patent publications WO 2004/113749 and GB 2521004A.

[0044] In a preferred embodiment of the present invention, this prior art process is modified by substituting a fluorinated diamine monomer for at least a portion of the monomer that is to form the amide portion of the copolymer. The bearing material may thus be formed by the copolymerisation of three monomers, such as trimellitic anhydride and methylene diamine as used to make a conventional PAI material), and a fluorinated amine monomer. In the embodiments described below, the fluorinated amine monomer is 4,4-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline. This mixture is then copolymerised using a conventional condensation polymerisation suitable for the synthesis of polyamide imides.

[0045] Two examples will now be described. In both examples, the overall molar ratio of amine monomers to anhydride monomers was 0.93. As is known in the conventional copolymerisation of PAI, this ratio can be varied from about 0.9 to less than 1, the excess of amine monomers being used to control the molecular weight of the resulting polymer. In the first example, in the amine fraction of the monomer mixture, the molar ratio of fluorinated monomer to non-fluorinated monomer was 0.1. In the second example, the ratio was 0.2.

[0046] In principle, the fluorinated monomer could be used as the whole contribution of the amine monomer, omitting the non-fluorinated amine monomer. The monomer mixture could then incorporate fluorinated monomer and anhydride monomer in a ratio of between 0.9 and less than 1, depending on the desired molecular weight of the polymer, but this may disadvantageously increase costs as the fluorinated monomer is more expensive than the non-fluorinated monomer, without providing benefits in bearing performance.

[0047] The quantites and molar ratios of the synthesis constituents in each example are set out below.

EXAMPLE 1

5% Fluorination

[0048]

TABLE-US-00001 Mass (g) Moles Molar ratios Trimellitic anhydride 10 0.052048 1 4,4'-(hexafluoroisopropylidene) 2.5093 0.00484 0.092991 bis(p-phenyleneoxy)dianiline methylene diamine 8.636206 0.04356 0.836918

EXAMPLE 2

10% Fluorination

[0049]

TABLE-US-00002 10% Fluoro Mass (g) Moles Molar ratios Trimellitic anhydride 10 0.052048 1 4,4'-(hexafluoroisopropylidene) 5.0193 0.00968 0.186007 bis(p-phenyleneoxy)dianiline methylene diamine 7.677361 0.038724 0.743998

[0050] Monomer mixtures having these compositions were prepared and copolymerisation reactions performed using conventional conditions for forming known PAI polymers, and samples of the polymers sprayed onto plain bearing shells to form sliding layers of thickness 10%. Corresponding conventional PAI polymers were also prepared, using the same 0.93 ratio of amine monomers to anhydride monomers, and sprayed onto bearing shells in the same way, for comparative testing.

[0051] Comparative wear tests were carried out, which demonstrated that the 5% fluorinated material of Example 1 lost material through wear at an average rate about 7% lower than the conventional material (in terms of volume of material lost, with wear tests carried out on a number of different samples), and the 10% fluorinated material of Example 2 lost material through wear at an average rate about 13% lower than the conventional material. These are significant reductions in wear rate, demonstrating that the modified PAI material of the invention maintains good integrity and strength, providing advantageously low wear rates.

[0052] Stribeck curves, plotting friction coefficient against sliding speed, for several samples of each type of bearing material were then prepared. In each case, the lubricated sliding of a steel journal against each bearing material was tested, and particular attention was paid to the running in phase of sliding and the steady state phase, which was reached after about 250 sliding cycles (rotations).

[0053] For the 5% fluoro-PAI copolymer formulation in Example 1, the measured initial friction coefficient was similar to the that of the conventional PAI polymer but the results varied less from sample to sample. This indicates that the run-in phase of the bearing material of Example 1 is similar that for the conventional bearing material, but that the behaviour of the bearing material of Example 1 is advantageously more predictable, or reliable, than that of the conventional material.

[0054] Friction measurements after the run-in period, after 250 cycles, demonstrated that the fluorinated coating has a lower coefficient of friction than the conventional material after the run in period. In conclusion, therefore, the 5% fluorinated material of Example 1 possesses similar frictional properties to a conventional PAI material on start up, but an advantageously lower coefficient of friction after the run in period, for example making it more suitable for start stop internal combustion engine applications.

[0055] For the 10% fluoro-PAI copolymer formulation in Example 2, the same tests were carried out. Again, the measured initial friction coefficient was similar to the that of the conventional PAI polymer in the test emulating engine start-up. In the same way as for the 5% fluoro-PAI material of Example 1, the measure initial friction was within the band of friction measurements for the conventional PAI polymer but the results were advantageously less varied, providing more reliable performance.

[0056] Friction measurements after the run-in period, after 250 cycles, for 10% fluoro-PAI copolymer formualtion demonstrated that the fluorinated coating has a lower coefficient of friction after run-in, again making it more suitable than the conventional PAI material for stop-start applications.

[0057] Interestingly, the measured coefficient of friction for the polymer of Example 2 was not significantly lower than for the polymer of Example 1. Therefore, the increase of fluorination from 5% to 10% reduced wear rates, as described above, but did not significantly further reduce friction coefficient.

[0058] Other fluorinated monomers that could be used instead of 4,4-(hexafluoroisopropylidene) bis(p-phenyleneoxy)dianiline in the Examples include: [0059] 2,5-Diaminobenzotrifluoride [0060] 3,5-Diaminobenzotrifluoride [0061] 1,3-Diamino-2,4,5,6-tetrafluorobenzene [0062] 2,2-Bis (trifluoromethyl) benzidine [0063] 3,3-Bis (trifluoromethyl) benzidine [0064] 2,2-Bis [4-(4-aminophenoxy phenyl)] hexafluoropropane [0065] 2,2-Bis (4-aminophenyl) hexafluoropropane [0066] 2,2-Bis (3-amino-4-hydroxyphenyl)-hexafluoropropane [0067] 2,2-Bis (3-amino-4-methylphenyl)-hexafluoropropane [0068] 3,5-Difluorobenzene-1,2-diamine [0069] 4,5-Difluorobenzene-1,2-diamine [0070] 2-(Trifluoromethyl)benzene-1,4-diamine [0071] 3,5-Diaminobenzotrifluoride [0072] 2,4,5,6-Tetrafluorobenzene-1,3-diamine [0073] 3,3,3-Trifluoropropane-1,2-diamine hydrochloride [0074] 3,3-Bis(trifluoromethyl)-[1,1-biphenyl]-4,4-diamine [0075] 6-[(2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxy]-1,3,5-triazine-2,4-diamine [0076] 4-(1,1,2,2-tetrafluoroethoxy)benzene-1,3-diamine [0077] 2-(Trifluoromethyl)pyrimidine-4,6-diamine [0078] 2,4-Diaminobenzotrifluoride [0079] 1,4-Diamino-2,6-difluorobenzene [0080] 2,5-Difluorobenzene-1,4-diamine [0081] Perfluorobenzene-1,4-diamine [0082] 6-[4-(Trifluoromethyl)phenyl]-1,3,5-triazine-2,4-diamine [0083] 4-(Trifluoromethoxy)benzene-1,3-diamine [0084] 2,2,3,3,4,4,5,5-Octafluoro-1,6-hexamethylenediamine

[0085] Other conventional PAI monomers could also be used in place of the trimellitic anhydride and the methylene diamine used in the Examples.