JP2014513173A - Lubricant composition and method of using the lubricant composition - Google Patents

Abstract

A lubricant composition comprising 0.01 to 2.0% by weight of an oil soluble organomolybdenum friction modifier, and a fully formulated commercial lubricating oil comprising at least 0.1% by weight of active sulfur of a surface active sulfur donor component, Useful to inhibit the removal of the DLC coating while at the same time enabling a beneficial friction reducing effect from the molybdenum friction modifier.
[Selection] Figure 10

Description

  The present invention relates to lubricant compositions and methods of using such lubricant compositions.

  Diamond-like coating (DLC) is often used on metal surfaces to function as a low friction sliding material and to reduce wear. DLC coatings are used in internal combustion engines that are lubricated by oil. DLC coating provides lower friction compared to other wear resistant hard coating materials such as TiN and CrN. Friction modifiers are added to the lubricating oil to further reduce the friction characteristics of the DLC coated lubricated engine parts, and also to provide beneficial friction reducing characteristics for engine parts that have not received the DLC coating.

  One of the best classes of lubricant friction modifiers are organomolybdenum compounds such as molybdenum dithiocarbamate (MoDTC) and molybdenum dialkyldithiophosphate (MoDTP). However, although these friction modifiers are very effective in reducing the boundary friction in sliding contact between steels, they have been observed to remove DLC coating in sliding contact between steels and DLC. Yes.

  Thus, lubricants with MoDTC additives are incompatible with DLC processed parts where it is desired to minimize friction. Such incompatibility is particularly noticeable in demanding applications such as DLC-coated crankcase engines, where it may be particularly useful to use high concentrations of MoDTC friction modifiers.

  Current approaches to such incompatibility include (a) the use of lubricants without MoDTC friction modifiers; and (b) non-hydrogenated DLC coatings (more than for the heavy removal of DLC coatings by MoDTC friction modifiers). Use) which appears to be resistant. These require the use of non-hydrogenated DLC coatings that limit or inhibit the use of beneficial Mo friction modifiers or that can accelerate wear on opposing steel surfaces due to their extreme hardness. As such, neither “solution” is completely acceptable. In this regard, a softer hydrogenated DLC coating is preferred, which is the most common commercial coating type currently used in crankcase engine designs.

  The present invention provides lubricant formulations and methods of using such formulations to adapt lubricants containing MoDTC additives to DLC materials.

  The present invention is a lubricant composition and a method of using such a lubricant composition.

  In one aspect, the present invention provides a lubricant composition comprising a lubricating oil comprising 0.01 to 2.0% by weight of an oil soluble organomolybdenum friction modifier and at least 0.1% by weight of a surface active sulfur donor component. I will provide a.

  In another aspect, the present invention produces a lubricant composition comprising 0.01-2.0% by weight of an organomolybdenum friction modifier and at least 0.1% by weight of a surface active sulfur donor component; Lubricating an interface between one surface and a second surface with a lubricant, wherein at least one of the first and second surfaces has a diamond-like coating thereon; Less than 10% of the thickness of the diamond-like coating is removed after 3 hours of relative motion between the first and second surfaces under drag, a frequency of 20 Hz and a temperature of 130 ° C. A method is provided for improving the wear characteristics of a surface having a coating.

  In another aspect, the invention provides the aspects described above except that the lubricating oil is selected from the group consisting of synthetic oils, petroleum-derived oils, plant-derived oils, animal-derived oils, and combinations thereof. Further provided is a method for improving the wear properties of a surface having a lubricant composition and a diamond-like coating according to any of the above.

  In another aspect, the invention provides that the organomolybdenum friction modifier comprises an oil soluble organomolybdenum compound (eg, molybdenum dithiocarbamate or molybdenum dialkyldithiophosphate, and a surface active organosulfur compound (eg, aryl or alkyl sulfide, dimercapto). Improve wear of surfaces having a lubricant composition and a diamond-like coating according to any of the embodiments described above, except selected from the group consisting of thiodiazoles or metal dithiocarbamates), and combinations thereof Although surface active organosulfur compounds are most commonly classified as extreme pressure (or EP) additives, in this application, substantial properties are surface active and organomolybdenum friction modifiers. Is the ability to act as a sulfur donor for It not specifically limited to the specified compound as P additive.

  In another embodiment, the present invention provides the above-described embodiment except that the surface active sulfur donor is selected from the group consisting of sulfurized vegetable fatty oils, sulfurized olefins, thiophosphates, sulfurized hydrocarbons, and combinations thereof. A method for improving the wear properties of a surface having a lubricant composition and a diamond-like coating is provided.

  In another aspect, the present invention provides a method for improving the wear characteristics of a surface having a lubricant composition and a diamond-like coating according to any of the above aspects, except that the surface active sulfur donor is an EP additive. I will provide a.

  In another aspect, the present invention relates to the above described except that the surface active sulfur donor is selected from dialkyldithiophosphate esters, sulfurized isobutylene, sulfurized vegetable fatty oils and olefins, dialkylpentasulfides, and combinations thereof. According to any of the embodiments, there is provided a method for improving the wear properties of a surface having a lubricant composition and a diamond-like coating.

  In another aspect, the present invention relates to the wear of a surface having a lubricant composition and a diamond-like coating according to any of the above-described embodiments, except that no more than 10% of the thickness of the diamond-like coating is removed. Provide a way to improve.

  In another aspect, the present invention provides a wear property for a surface having a lubricant composition and a diamond-like coating according to any of the above-described embodiments, except that no more than 1% of the thickness of the diamond-like coating is removed. Provide a way to improve.

  In another aspect, the present invention provides a wear property of a surface having a lubricant composition and a diamond-like coating according to any of the above-described embodiments, except that the diamond-like coating comprises a hydrogen concentration of 0% to 35%. Provide a way to improve.

  In another aspect, the present invention further comprises one or more lubricant additive components selected from the group consisting of a detergent, a dispersant, an antiwear agent, and an antifoaming agent. A method is provided for improving the wear properties of a surface having a lubricant composition and a diamond-like coating, according to any of the embodiments described above.

  For the purpose of illustrating the invention, there are shown in the drawings exemplary forms. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a surface shape measurement scan showing removal of the DLC coating using the lubricant composition of Comparative Example 1. FIG. 2 is a surface profile measurement scan showing removal of the DLC coating using the lubricant composition of Example 1 of the present invention. FIG. 3 is a surface shape measurement scan showing the removal of the DLC coating using the lubricant composition of Example 2 of the present invention. FIG. 4 is a surface profile measurement scan showing removal of the DLC coating using the lubricant composition of Example 3 of the present invention. FIG. 5 is a surface profile measurement scan showing the removal of the DLC coating using the lubricant composition of Example 4 of the present invention. 6 is a surface shape measurement scan showing removal of the DLC coating using the lubricant composition of Comparative Example 2. FIG. FIG. 7 is a surface shape measurement scan showing removal of the DLC coating using the lubricant composition of Comparative Example 3. FIG. 8 is a surface shape measurement scan showing removal of the DLC coating using the lubricant composition of Comparative Example 4. FIG. 9 is a surface shape measurement scan showing removal of the DLC coating using the lubricant composition of Comparative Example 5. FIG. 10 shows surface shape measurement scans for Examples 5-6 and Comparative Examples 6-7 of the present invention. FIG. 11 shows surface shape measurement scans for Examples 7-8 and Comparative Example 8 of the present invention.

  The present invention provides a lubricant composition and a method of using such a lubricant composition to reduce or eliminate the removal of DLC material in the presence of a lubricating oil comprising an organomolybdenum compound.

  The lubricant composition according to the present invention comprises a lubricating oil comprising 0.01-2.0% by weight of an organomolybdenum friction modifier and at least 0.1% by weight of a surface active sulfur donor component.

  In another aspect of the invention, the organomolybdenum friction modifier is selected from the group consisting of molybdenum dithiocarbamate (MoDTC), molybdenum dialkyldithiophosphate (MoDTP), and combinations thereof. In a particular embodiment, the organomolybdenum friction modifier is MoDTC.

  In some embodiments, the lubricating oil is selected from the group consisting of synthetic oils, petroleum derived oils, plant derived oils, animal derived oils, and combinations thereof. In certain embodiments, the lubricating oil is a synthetic oil. Exemplary synthetic oils useful in the present invention include lubricants comprising poly alpha olefins (PAO) or Group III lubricant base stocks. Exemplary petroleum-derived oils useful in the present invention include lubricants containing Group I or II base stocks. Exemplary plant-derived oils useful in the present invention include lubricants derived from coconut, rapeseed, soy, or other plant-derived base stocks.

  The organomolybdenum friction modifier is present in the lubricating oil in an amount of 0.01 to 2.0% by weight. All individual values and subranges from 0.01 to 2.0% by weight are encompassed in the present invention and disclosed herein. For example, the amount of organic molybdenum in the lubricating oil is 0.05, 0.05, 0.1, 0.5, 1.0, 1.5, or 1.8% by weight from the lower limit. It may be up to an upper limit of 0.1, 0.5, 1.0, 1.5, 1.8, or 2.0% by weight. For example, the amount of organic molybdenum in the lubricating oil may range from 0.01 to 2.0% by weight, or in another aspect, the amount of organic molybdenum in the lubricating oil is 0.05 to 1.5. In another embodiment, the amount of organomolybdenum in the lubricating oil may be in the range of 0.01 to 1.0% by weight. When more than one type of surface organomolybdenum friction modifier is present in the lubricant composition of the present invention, the above range represents the combined amount of all organomolybdenum friction modifiers.

In some embodiments of the present invention, any organomolybdenum friction modifier that can form MoS _{2 in} the presence of surface active sulfur can be used. In one aspect, the organomolybdenum is selected from the group consisting of oil-soluble organomolybdenum compounds, and combinations thereof. In certain embodiments, the organomolybdenum friction modifier is selected from the group consisting of molybdenum dithiocarbamate, molybdenum dialkyldithiophosphate, and combinations thereof.

  In one embodiment of the lubricant composition of the present invention, the surface active sulfur donor is, for example, sulfurized vegetable fatty oil, sulfurized olefin, thiophosphate, sulfurized hydrocarbon, aryl sulfide, alkyl sulfide, dimercaptothiodiazole, metal dithiol. It is selected from the group consisting of surface active organosulfur compounds such as carbamates and combinations thereof. In certain embodiments, the surface active sulfur donor is selected from the group consisting of dialkyldithiophosphate esters, sulfurized isobutylene, sulfurized vegetable fatty oils and olefins, dialkylpentasulfides, and combinations thereof.

  In some embodiments, the surface active sulfur donor is an extreme pressure (EP) additive. Representative commercially available EP additives that are surface active sulfur donors and that can be used in some embodiments of the lubricant compositions of the present invention include IRGALUBE 353 (from BASF, Florham Park, NJ, USA). HiTEC 312 (available from Afton Chemical Corporation, Richmond, Virginia, USA), and ADDITIN RC 2515 and 2540 (both available from Rhein Chemie Rheinau GmbH, Mannheim, Germany).

  In the lubricant composition and method of the present invention, an effective amount of a surface active sulfur donor is used. As used herein, an “effective amount” is an amount that results in removal of 10% or less of the thickness of the DLC coating. The effective amount of surface active sulfur donor will vary with the specific sulfur donor. In general, effective amounts range from 0.04% to 1.0% by weight. However, the upper limit exceeds 1.0% by weight as shown below in Example 5 of the present invention, where 3.6% by weight of surface active sulfur was found to be an effective amount. Can be extended. When more than one surface active sulfur donor is present in the lubricant composition of the present invention, the above ranges indicate the combined amount of all surface active surface donors.

Test method:
Amount of surface active sulfur:
The amount of surface active sulfur was measured according to ASTM-D1662.

DLC coating wear test and removal:
The wear test was performed using Optimol SRV-4 (available from Optimol Instruments Pruftechnik GmbH Munich, Germany) which is a modular friction and wear test platform. A cylinder-on-flat structure using test pieces purchased from Optimol was used. The hardened steel cylinder was 11 × 15 mm (diameter × length). A custom sample pan holder was manufactured to fit a 6.9 × 22 mm Optimol hardened steel disc. The sample pan holds approximately 2 mL of typical oil, allowing long-term lubricant testing with full immersion in SRV-4. The disc piece was DLC coated steel. The steel cylinder was not DLC coated. Two specimens (eg cylinder and disk) were placed in the test chamber and pressed together using a normal force of 200 Newton (N). The top specimen was vibrated on the bottom specimen. The frequency was 20 Hz, the stroke was 3.0 mm, the test temperature was 130 ° C., and the test time was 180 minutes. The same DLC coating, specifically a diamond-like carbon coating available from Bekaert Corporation (Bekaert Diamond-Like Coatings, Karreweg 13, BE-9870 Zulte, Belgium) was used in all the inventive examples and comparative examples. It was. Wear was measured by surface profilometry using the Dektak 6M model from Bruker Instruments and recorded either during and / or after the test.

  The following examples illustrate the invention but are not intended to limit the scope of the invention.

Examples 1 to 4 and Comparative Examples 2 to 5 of the present invention:
Eight commercial EP additives exhibiting a range of chemical properties were obtained from various suppliers listed in Table 1. The commercial EP additive used in each of Examples 1 to 4 of the present invention was a surface active sulfur donor, while those used in Comparative Examples 2 to 5 were not surface active sulfur donors. The lubricating oil used in each example lubricant composition was a Pennzoil Platinum 5W30 formulation (API “SL”, but excluding friction modifiers). Each of Examples 1-4 and Comparative Examples 2-5 of the present invention includes 1 wt% organic molybdenum friction modifier, specifically a MoDTC additive manufactured by Adeka Corporation (Japan, SAKURA-LUBE S515). In addition).

Comparative Example 1:
The lubricant composition used in Comparative Example 1 contains 1.0 wt% MoDTC friction modifier, specifically Pennzoil Platinum 5W30 (API "SL" formulation) product top-treated with SAKURA-LUBE S515. It was out.

  1-9 are surface profile measurements of the DLC coated surface across the wear scar for each of the inventive lubricant compositions of Examples 1-4 and Comparative Examples 1-5 after completion of the SRV-4 friction test. Indicates a scan. The Bekaert DLC coating was about 1.5 microns (1500 nm) thick. Comparative Example 1 (which did not contain the EP additive) showed complete removal of the DLC film within the 3 hour test period. Abrasion tests using the lubricant compositions of Comparative Examples 2-5, each containing a non-surface active sulfur donor EP additive, showed complete or partial removal of the DLC film. There was no observed removal of the DLC coating when using the surface active sulfur donor EP additive in Examples 1-4 of the present invention in the abrasion test.

Examples 5-6 and Comparative Examples 6-7 of the present invention:
The surface active sulfur concentration was changed (3.6% by weight of surface active sulfur (1% by weight of ADDITIN RC2540) in Example 5 of the present invention (solid line in FIG. 10)), and Example 6 of the present invention ( In the embodiment of the present invention as described above with respect to Example 4 of the present invention, except for 1.8 wt.% Surface active sulfur (0.5 wt.% ADDITIN RC2540)). Five to six samples were produced.

  Samples of Comparative Examples 6 and 7 were prepared as in Example 4 of the present invention, except that lower levels of surface active sulfur were used. Specifically, the sample of Comparative Example 6 (bold dotted line in FIG. 10) contains 0.9% by weight of surface active sulfur (0.25% by weight of ADDITIN RC2540), and the sample of Comparative Example 7 (FIG. The dotted line at 10) contained 0.36 wt% surface active sulfur (0.1 wt% ADDITIN RC2540).

  FIG. 10 shows the surface shape measurement results after the wear test. As can be seen, an effective amount of ADDITIN RC2540 in a minimum amount of 0.5% by weight was found. In contrast, lower levels of ADDITIN RC2540 are not effective, meaning that more than 10% of the DLC coating thickness has been removed. However, not all DLC coating was removed even at the lowest level of ADDITIN RC2540.

Examples 7-8 and Comparative Example 8 of the present invention:
The surface active sulfur concentration was changed (in Example 7 of the present invention (solid line in FIG. 11), 0.4% by weight of surface active sulfur (1% by weight of ADDITIN RC2515), and Example 8 of the present invention ( In the broken line of FIG. 11, the embodiment of the present invention is as described above for Embodiment 3 of the present invention, except that 0.2 wt.% Surface active sulfur (0.5 wt.% ADDITIN RC2515)). Seven to eight samples were produced.

  Further, a sample of Comparative Example 8 was produced as in Example 3 of the present invention except that a lower level of surface active sulfur was used. Specifically, 0.04% by weight of surface active sulfur (0.1% by weight of ADDITIN RC2515) was included in the sample of Comparative Example 8 (dotted line in FIG. 11).

  FIG. 11 shows the surface shape measurement results after the wear test. As can be seen, an effective amount of ADDITIN RC2515 in a minimum amount of 0.5% by weight was found. In contrast, lower levels of ADDITIN RC2515, ie 0.1 wt%, were not effective. However, not all DLC coating was removed even at the lowest level of ADDITIN RC2515.

  The present invention may be embodied in other forms without departing from its spirit and essential characteristics, and thus the scope of the present invention should be referred to the appended claims rather than the foregoing specification. It is.

Claims (10)

Producing a lubricant composition comprising 0.01-2.0 wt% organomolybdenum friction modifier and at least 0.1 wt% surface active sulfur donor component;
Lubricating the interface between the first surface and the second surface with a lubricant, wherein at least one of the first and second surfaces has a diamond-like coating thereon;
Including that;
Less than 10% of the thickness of the diamond-like coating is removed after 3 hours of relative motion between the first and second surfaces under 200N normal drag, 20Hz frequency, 130 ° C temperature A method for improving the wear resistance of a surface having a diamond-like coating.   The method of claim 1 wherein 10% or less of the diamond-like coating thickness is removed.   The method of claim 1, wherein less than 1% of the thickness of the diamond-like coating is removed.   4. The method according to any one of claims 1 to 3, wherein the diamond-like coating has a hydrogen concentration of 0% to 35%.   Surface active sulfur donors from the group consisting of aryl sulfides, alkyl sulfides, dimercaptothiodiazoles, metal dithiocarbamates, dialkyl dithiophosphate esters, sulfurized isobutylene, sulfurized vegetable fatty oils and olefins, dialkyl pentasulfides, and combinations thereof The method according to any one of claims 1 to 4, wherein the method is selected.   A lubricant composition comprising 0.01 to 2.0% by weight of an oil soluble organomolybdenum friction modifier and a fully formulated commercial lubricating oil comprising active sulfur as a surface active sulfur donor component.   The lubricant composition according to claim 6, wherein the lubricating oil is selected from the group consisting of synthetic oil, petroleum-derived oil, plant-derived oil, animal-derived oil, and combinations thereof.   The lubricant composition according to any one of claims 6 to 7, wherein the organic molybdenum friction modifier is selected from the group consisting of molybdenum dithiocarbamate, molybdenum dialkyldithiophosphate, and combinations thereof.   Surface active sulfur donors from the group consisting of aryl sulfides, alkyl sulfides, dimercaptothiodiazoles, metal dithiocarbamates, dialkyl dithiophosphate esters, sulfurized isobutylene, sulfurized vegetable fatty oils and olefins, dialkyl pentasulfides, and combinations thereof The lubricant composition according to any one of claims 6 to 8, which is selected.   The lubricant composition according to any one of claims 6 to 9, wherein the surface active sulfur donor is an EP additive.