Abstract
A lubricant composition said composition comprising at least one base oil and from 1 to 70 wt % of at least one friction modifying additive, wherein the composition is such that the viscosity reversibly reduces at a pressure from 50 MPa to 3 GPa. A mechanical system comprising the lubricant composition; use of the lubricant composition and methods of reducing friction using the lubricant composition are also disclosed.
Claims
1. A lubricant composition, comprising: at least one base oil; and from 1 to 70 wt % of at least one friction modifying additives, wherein the composition is such that the viscosity reversibly reduces at a pressure from 50 MPa to 3 GPa.
2. The composition according to claim 1, wherein the friction modifying additive comprises at least one functional group capable of hydrogen bonding.
3. The composition according to claim 2, wherein the friction modifying additive comprises a hydrocarbon chain substituted with at least one functional group capable of hydrogen bonding, selected from alcohol, carboxylic acid and amine functional groups; optionally wherein the hydrocarbon chain length is from 8 to 30 carbon atoms, or from 10 to 20 carbon atoms.
4. The composition according to claim 1, wherein: a) the composition comprises at least 5 wt %, at least 10 wt %, at least 24 wt %, at least 30 wt %, at least 35 wt %, at least 40 wt % or at least 45 wt % of the at least one friction modifying additive; or b) the composition comprises from 30 to 60 wt % or from 40 to 50 wt % of the at least one friction modifying additive; or c) the at least one friction modifying additive is present in an amount up to 30 wt %, up to 20 wt %, up to 10 wt % or up to 5 wt %.
5-7. (canceled)
8. The composition according to claim 1, wherein the friction modifying additive comprises at least one alcohol functional group; and/or wherein the friction modifying additive comprises at least one amine functional group.
9. (canceled)
10. The composition according to claim 1, wherein the friction modifying additive comprises at least one alcohol having a carbon chain length of at least 8 carbon atoms, or a mixture thereof; or wherein the friction modifying additive comprises at least one alkylamine having a carbon chain length of at least 8 carbon atoms, or a mixture thereof.
11-12. (canceled)
13. The composition according to claim 10, wherein the alcohol is selected from the group consisting of lauryl alcohol, myristyl alcohol and stearyl alcohol, or mixtures thereof; and/or wherein the alkylamine is selected from dodecylamine or octadecylamine or mixtures thereof.
14. (canceled)
15. The composition according to claim 1, wherein the at least one base oil is selected from mineral oil, synthetic hydrocarbons, esters, polyglycols, natural oils, silicones, perfluoropolyethers and mixtures thereof.
16. A lubricant composition comprising at least one base oil and from 1 to 70 wt % of at least one friction modifying additive, wherein the friction modifying additive comprises at least one functional group capable of hydrogen bonding.
17-19. (canceled)
20. The composition according to claim 1, wherein the composition is a gear oil, an engine oil, a transmission fluid or a hydraulic oil, and wherein the composition additionally includes one or more lubricant additives selected from anti-wear additives, rust and corrosion inhibitors, detergents, surfactants, viscosity index improvers and modifiers, seal swell additives and agents, anti-foam additives, anti-oxidation compounds, cold flow improvers, high-temperature thickeners, gasket conditioners, pour point depressants and greases.
21. (canceled)
22. The composition according to claim 1, which has a viscosity of between 1 and 500 cP at 100° C.
23. A mechanical system comprising gears and/or bearings, wherein the system comprises a lubricant composition as defined in claim 1.
24. Apparatus comprising: a first component having a first interface surface; a second component movable relative to the first component, the second component having a second interface surface; wherein the first interface surface interfaces with the second interface surface; the apparatus further comprising a lubricant composition provided to lubricate movement of the second interface surface relative to the first interface surface, wherein the lubricant composition comprises an additive which reduces the viscosity of the lubricant composition when the lubricant composition is compressed between the first and second interface surfaces.
25-36. (canceled)
37. A method of reducing friction in mechanical apparatus comprising a first component having a first interface surface and a second component movable relative to the first component, the second component having a second interface surface, wherein the first interface surface interfaces with the second interface surface, the method comprising: providing a lubricant composition to lubricate movement of the second interface surface relative to the first interface surface, wherein the lubricant composition comprises an additive which reduces the viscosity of the lubricant composition when the lubricant composition is compressed between the first and second interface surfaces; and compressing the lubricant composition between the first and second interface surfaces.
38. A method according to claim 37, wherein: a) there is substantially sliding relative movement of the first and second interface surfaces and wherein providing the lubricant composition comprises providing a lubricant composition that is arranged to reduce contact between the first and second interface surfaces during the substantially sliding relative movement; or b) there is substantially rolling relative movement of the first and second interface surfaces and wherein providing the lubricant composition comprises providing a lubricant composition that is arranged to reduce contact between the first and second interface surfaces during the substantially rolling relative movement.
39. (canceled)
40. A method according to claim 37, wherein compressing the lubricant composition between the first and second interface surfaces comprises exerting a compressive stress on the lubricant composition by one of the first and second components acting on the respective other of the first and second components, and optionally wherein: a) the compressive stress has a vector component which is normal to the first and second interface surfaces; and/or b) exerting the compressive stress on the lubricant composition comprises exerting a compressive stress of at least 50 MPa, at least 100 MPa, at least 150 MPa, at least 200 MPa, at least 500 MPa or at least 1 GPa.
41-42. (canceled)
43. A method according to claim 37, wherein compressing the lubricant composition between the first and second interface surfaces comprises compressing the lubricant composition to cause elastohydrodynamic lubrication between the first and second interface surfaces.
44. A method according to claims 37, further comprising moving the first component relative to the second component to provide a full film of the lubricant composition between the first and second interface surfaces.
45. (canceled)
46. A method according to claim 37, wherein the lubricant composition is a composition according to claim 1.
47. A method of reducing friction in a mechanical system between a first part and a second part moving relative to one another, by providing a lubricant composition according to claim 1 between the first part and the second part.
48. (canceled)
49. Use of a lubricant composition according to claim 1 in reducing mechanical friction, wherein the use is as an engine oil, gear oil, transmission fluid, grease, turbine oil, compressor oil or hydraulic oil.
50. (canceled)
Description
BRIEF DESCRIPTION OF FIGURES
[0106] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which;
[0107] FIG. 1 is a schematic illustration of an oil film between two relatively moving parts;
[0108] FIG. 2 is a graph showing the coefficient of friction relative to the amount of sliding
[0109] FIG. 3a is a schematic illustration of an oil film between two relatively moving parts, along with the Ultra-Thin Film Interferometry equipment used to measure film thickness and friction under elastohydrodynamic conditions;
[0110] FIG. 3b is a graph showing the coefficient of friction relative to average surface speed;
[0111] FIG. 3c is a graph showing film thickness relative to average surface speed;
[0112] FIG. 4 is a graph showing the blend friction (full film) and viscosity for mixtures of dodecanol in hexadecane; and
[0113] FIG. 5 is a graph showing the friction coefficient relative to entrainment speed for mixtures of PAO and dodecanol.
[0114] FIG. 6 is a graph showing friction coefficient relative to entrainment speed for an elastohydrodynamic contact, showing the effect of dodecanol when added to a commercial engine oil. It is to be noted that for a lubricated contact “friction” and “traction” are interchangeable and these terms are used interchangeable herein.
[0115] FIG. 7 is a graph showing the coefficient of friction (i.e. the effective viscosity) for a blend and a range of liquids as a function of the average contact pressure in the contact.
[0116] FIG. 8 shows an infrared absorption spectroscopy measurement made of a sample of pure dodecanol.
[0117] FIG. 9 is a graph showing traction curves, plotting the coefficient of fiction relative to slide roll ratio, for hexadecane only and for blends of hexadecane with fatty alcohols of varying chain length.
[0118] FIG. 10 is a graph showing traction curves, plotting the coefficient of fiction relative to slide roll ratio for PAO only, a 50:50 mixture of PAO and hexyl-decanol and a 50:50 mixture of PAO and dodecanol.
[0119] FIG. 11 is a graph showing traction curves, plotting the coefficient of fiction relative to slide roll ratio for PAO only, a 75:25 mixture of PAO and 1-dodecanol and a 75:25 mixture of PAO and 2-dodecanol and a 75:25 mixture of PAO and 4-dodecanol. (Note: elsewhere in this document 1-dodecanol is referred to simply as “dodecanol”).
[0120] FIG. 12 is a flowchart of a method of reducing friction between two surfaces in mechanical apparatus.
DETAILED DESCRIPTION
[0121] FIG. 1 is a schematic illustration showing how a liquid film forms as oil is dragged through interfaces between sliding surfaces in a bearing or gear (hydrodynamic effect), and is subjected to ultra-high pressures. The viscosity at the low-pressure inlet is important since this causes the surfaces to be pushed apart by a film thickness, h, which prevents wear and seizure. The effective viscosity of the lubricant within the contact is important as it determines the energy loss due to frictional dissipation.
[0122] The first surface 1 in FIG. 1 is a surface of a first component 2. The second surface 3 in FIG. 1 is a surface of a second component 4. The second component 4 moves relative to the first component 2, meaning that the second surface 3 moves relative to the first surface 1 in the direction indicated by the arrow in FIG. 1. The first surface 1 interfaces with the second surface 3. A film 5 of lubricant composition is provided in between the first surface 1 and the second surface 3. The movement of the second surface 3 relative to the first surface 1 draws the lubricant composition through the interface between the first surface 1 and the second surface 2.
[0123] A first region 6 of the lubricant composition determines the thickness (indicated as ‘h’ in FIG. 1) of the film 5 of the lubricant composition. The first region 6 is an inlet region at relatively low pressure. The viscosity in the low pressure first region 6 determines the thickness h of the film 5 of lubricant composition.
[0124] A second region 7 of the lubricant composition determines the friction between the first surface 1 and the second surface 3. The friction between the first surface 1 and the second surface 3 is determined by the viscosity of the film 5 of the lubricant composition in the second region 7. The lubricant composition includes an additive which reduces the viscosity of the lubricant composition when the film 5 of lubricant composition is compressed between the first surface 1 and the second surface 3 (for example, in the form of a compressive stress exerted on the region 7 of the film 5 of lubricant composition by the second component 4 acting on the first component 2, or vice versa).
[0125] FIG. 2 is a graph showing the coefficient of friction for oil/additive blends, obtained using standard test equipment in which a ball (for example, the ball 8 shown in FIG. 3a) is rotated against a disc (for example, the disc 9 in FIG. 3a) to produce a contact similar to those found in bearings and gears (specifically, the equipment is a Mini-Traction-Machine (MTM), manufactured by PCS Instruments [LaFountain, A. R., Johnston, G. J., and Spikes, H. A. (2001), Tribology Transactions, 44, pp 648-656.]). The speed of rotation of both the ball and the disc can be varied to study lubricant behaviour. The results illustrated in FIGS. 2, 3b, 4, 5, 6, 7, 9, 10 were obtained using this test equipment for various lubricant compositions.
[0126] The results in FIGS. 2 and 3 use hexadecane as the model base oil.
[0127] FIG. 3a is a schematic illustration of an oil film between two relatively moving parts, observed using a microscope 10. The thickness of the film layer between the moving parts is shown as h. FIG. 3a also shows the test equipment referred to in relation to FIG. 2. The test equipment comprises a ball 8 which is rotated against a disc 9. A lubricant film is disposed between the ball 8 and the disc 9. The test equipment also comprises the microscope 10, which is used to observe the behaviour of the lubricant film between the ball 8 and the disc 9.
[0128] FIG. 3b is a graph showing the coefficient of friction relative to average surface speed (a Stribeck curve). As the average speed increases from zero and more liquid is entrained to separate the contacting surfaces, the coefficient of friction reduces. Therefore, in the left-hand region of the graph, friction arises from solid-solid contact where there is insufficient oil entrained to separate the surfaces. Conversely, on the right-hand side of the graph, friction arises due to shearing of the fluid as the surfaces are fully separated by oil. The graph shows the reduction in the coefficient of friction when using a lubricant composition of the invention. It is important to note that the friction is reducing in the full film region of the graph where the surfaces are completely separated by the oil.
[0129] FIG. 3c is a graph showing film thickness relative to average surface speed. Ordinarily, a reduction in viscous friction is accompanied by a decrease in film thickness. However, this is not the case for lubricant compositions of the invention. As shown, the lubricant compositions of the invention provide an increased film thickness as the average surface speed increases. FIG. 3c shows the film thickness relative to speed of movement of the parts (measured using an Ultra-Thin Film Interferometry, UTFI, rig from PCS Instruments). The addition of the additive to the oil unexpectedly reduces the friction while increasing the film thickness. In both cases the ball has a diameter of 19.05 mm; the applied load is 20 N and the contact is maintained at 40° C.
[0130] The results suggest that if this additive was blended with a car's engine and transmission oil at ratio of 1:10, the electrohydrodynamic friction (which accounts for ˜5.9% of the total fuel energy [Holmberg)) would be would be reduced by ˜30%.
[0131] FIG. 4 is a graph showing the blend friction (plot indicated by arrow pointing to “blend friction/hexadecane friction” axis) and viscosity (plot indicated by arrow pointing to “viscosity” axis) for mixtures of dodecanol in hexadecane. The blend friction plot shows the change in blend friction at high pressure (i.e. where the pressure is high enough to cause hydrogen bonding in the dodecanol) against the relative amount of dodecanol, whereas the viscosity plot shows the change in viscosity at atmospheric pressure against the relative amount of dodecanol. Hexadecane is used as a model for a base oil. Dodecanol (lauryl alcohol) is a preferred friction-modifying additive. As the relative amount of dodecanol increase, the blend friction generally decreases. As the amount of dodecanol increases so it becomes the major component of the blend, the blend friction begins to increase again. There is also a general trend of increasing viscosity at atmospheric pressure with increasing amounts of the friction-modifying additive.
[0132] FIG. 5 is a graph showing the traction (friction) coefficient relative to entrainment speed (Stribeck curves) for mixtures of a poly alpha olefin (PAO) and dodecanol. The PAO is used as a model for a base oil (in this case it is a PAO6, having a kinematic viscosity of 6 cSt at 100° C.). The graph shows the marked reduction in the traction coefficient with increasing entrainment speed for a mixture of the PAO and dodecanol relative to the PAO and dodecanol alone.
[0133] FIG. 6 is a graph showing the traction coefficient (friction) versus entrainment speed (Stribeck curve) for an elastohydrodynamic contact, showing the effect of dodecanol when added to a commercial engine oil. The graph below shows that the addition to dodecanol to a commercial engine oil (in this case a synthetic, fully formulated, 10W-30 oil) reduces the friction as least as well as when added to the pure hexadecane of PAO. This shows that the package of other lubricant additives present in the commercial engine oil do not interfere with the behaviour of the alcohol additive. This data was obtained on a Mini-Traction Machine (MTM) from PCS Instruments.
[0134] FIG. 7 is a graph showing the coefficient of friction (i.e. effective viscosity) of an EHL contact, versus the average contact pressure as a function of contact. As with FIGS. 3b, 4, 5 and 6, this has been obtained using a PCS Instruments MTM rig, which loads a ball against a disc to simulate a bearing contact. It can be seen here that the blend of dodecanol and PAO shows a coefficient of friction which reduces as the contact pressure increases. All other liquids show an increase in friction with pressure, which is classical behaviour.
[0135] FIG. 8 is a graph showing the infrared absorption spectra obtained for pure dodecanol at ambient pressure and at 1.5 GPa (produced using a diamond anvil cell). For this measurement, the sample is held in a diamond anvil cell, which can compress the lubricant up to very high pressures, enabling the measurements to be obtained at ambient conditions and at 1.5 GPa. In this type of spectroscopy measurement, infrared light is used to excite vibrational modes of the sample molecule, providing information on the type of molecular bonding present. Comparing these two spectra shows: a) additional CH.sub.2 and CH.sub.3 peaks appearing at 1.5 GPa, and b) a broadening of the O—H peak at 1.5 GPa. Both of these features suggest solidification due to hydrogen bonding (Vasileva, A., et al. “FTIR spectra of n-octanol in liquid and solid states.” Dataset Papers in Science 2014 (2014).).
[0136] FIG. 9 is a graph showing traction curves, plotting the coefficient of fiction relative to slide roll ratio for hexadecane (base oil) only and for blends of hexadecane with straight chain fatty alcohols of varying chain length (C10, C12, C14 and C18). A traction curve plots friction against slide roll ratio, which is the relative speed (i.e. sliding speed) of the two surfaces divided by the entrainment speed. Usually a traction curve is produced by keeping the entrainment speed contact (and sufficiently high to entrain fluid to completely separate the surfaces so that the contact is in the full film regime), while the sliding speed is varied (i.e. the average speed of the two surfaces is maintained constant while difference between the two surface speeds is increased—on surface speed is increased while the other is decreased). Going from left to right on the curve: friction is initially close to zero as the surfaces are not moving relative to one another and there is almost no friction. As the slide roll ratio increases, so does the amount of shearing the lubricant experiences and the friction increases. All blends tested showed a reduction in friction coefficient compared to that observed for base oil only.
[0137] FIG. 10 is a graph showing traction curves for PAO only, and for dodecanol/PAO and 2-hexyl-1-decanol/PAO blends. Both blends tested exhibited friction reduction compared to PAO (base oil) alone. Corresponding tests were also carried out for blends of PAO with octadecylamine and stearic acid, respectively. With just 0.1 wt % additive present in these blends, friction reduction was observed.
[0138] FIG. 11 is a graph showing traction curves for PAO only, and for 1-dodecanol/PAO and 2-dodecanol/PAO and 4-dodecanol/PAO blends. All three blends tested exhibited friction reduction compared to PAO (base oil) alone. (Note: elsewhere in this document 1-dodecanol is referred to simply as “dodecanol”).
[0139] FIG. 12 is a flowchart of a method 110 of reducing friction between two surfaces in mechanical apparatus. The method 110 reduces friction in mechanical apparatus comprising a first component having a first interface surface and a second component movable relative to the first component, wherein the second component has a second interface surface and the first interface surface interfaces with the second interface surface. For example, the method 110 reduces friction between the first surface 1 and the second surface 3 of the mechanical apparatus shown in FIG. 1.
[0140] At step 112, a lubricant composition is provided to lubricate movement of the second interface surface (e.g. the second surface 3 of the mechanical apparatus of FIG. 1) relative to the first interface surface (e.g. the first surface 1 of the mechanical apparatus of FIG. 1). The lubricant composition provided in step 112 comprises an additive which reduces the viscosity of the lubricant composition when the lubricant composition is compressed between the first and second interface surfaces.
[0141] At step 114, the lubricant composition is compressed between the first and second interface surfaces. Compression of the lubricant composition between the first and second interface surfaces causes the viscosity of the lubricant composition to be reduced, thereby reducing the friction between the first and second interface surfaces.
