Lubricating oil composition

Abstract

The present invention provides a lubricating oil composition comprising a base oil, molybdenum dithiocarbamate and a metal-based detergent, wherein the amount of molybdenum dithiocarbamate in terms of molybdenum atoms (C Mo ) is greater than 200 ppm and 2,000 ppm or less relative to the total amount of the lubricating oil composition, and the amount of sulfated ash is less than 0.85% by mass relative to the total amount of the lubricating oil composition.

Description

Technical Field

[0001] The present invention relates to a lubricating oil composition having excellent wear resistance. Background Art

[0002] From the viewpoints of depletion of petroleum resources and environmental protection, automobiles are required to have higher fuel efficiency. In particular, with the trend of automobiles becoming lighter, improvements in the energy efficiency of engines, and improvements in the power transmission of drivelines, a lubricating oil composition having excellent performance is needed.

[0003] For example, "Type and Performance of Additives (1): Antiwear Agent / Extreme Pressure Agent" (R.J. Hartley et al., Tribologist, Vol. 40, No. 4, p. 326, 1995) noted the improvement in the wear resistance of iron materials in internal combustion engines when antiwear agents such as zinc dialkyldithiophosphate were added to lubricating oils for internal combustion engines.

[0004] When used for aluminum and / or aluminum alloys, which are the main materials in engines, the wear resistance of conventional lubricating oil compositions has not been fully studied. In particular, with the recent reduction in engine size, the material constituting the friction bearing surface has a very large impact on wear resistance, and it has been found that even when the wear resistance for iron-based materials is high, excellent wear resistance is not always obtained for aluminum and / or aluminum alloys.

[0005] Therefore, an object of the present invention is to provide a novel lubricating oil composition having excellent wear resistance even when used for aluminum and / or aluminum alloys.

[0006] As a result of extensive research, the present inventors have found that a lubricating oil composition containing a specific amount of a specific component can achieve this object. Specifically, the present invention is as follows. Summary of the Invention

[0007] The present invention is a lubricating oil composition comprising a base oil, molybdenum dithiocarbamate, and a metal-based detergent, wherein the content C of molybdenum dithiocarbamate in terms of molybdenum atoms Mo is greater than 200 ppm and 2,000 ppm or less relative to the total amount of the lubricating oil composition, and the amount of sulfated ash is less than 0.85 mass% relative to the total amount of the lubricating oil composition.

[0008] The metal-based detergent preferably includes a calcium-based detergent and a magnesium-based detergent. The content C of the calcium-based detergent in terms of calcium atoms Ca may be 100 ppm to 2,000 ppm relative to the total amount of the lubricating oil composition.

[0009] The content C of the magnesium-based detergent in terms of magnesium atoms MgIt may be 50 ppm to 1,000 ppm relative to the total amount of the lubricating oil composition. (C Mg +C Mo / 2) / C Ca It may be 0.4 to 1.2.

[0010] The lubricating oil composition may further contain zinc dialkyldithiophosphate.

[0011] The lubricating oil composition can be used to lubricate sliding surfaces containing aluminum and / or aluminum alloys. Detailed Description

[0012] The present invention can provide a novel lubricating oil composition that has excellent wear resistance even when used for aluminum and / or aluminum alloys.

[0013] The following is a description of the components, amounts of components, physical properties and performance, production methods, and applications of the lubricating oil composition of the present invention.

[0014] When upper and lower limit values are mentioned for a certain numerical range, all combinations of numerical ranges including these values are included therein. Additionally, "from numerical value A to numerical value B" means "equal to or greater than numerical value A and equal to or less than numerical value B". Here, "equal to or greater than" and "equal to or less than" can be understood as "greater than" and "less than", respectively.

[0015] The kinematic viscosity in the present invention is the value measured according to JIS K2283:2000.

[0016] The lubricating oil composition contains a base oil, a metal-based detergent, and molybdenum dithiocarbamate. The lubricating oil composition preferably contains zinc dialkyldithiophosphate. The lubricating oil composition may also contain other components.

[0017] There is no specific limitation on the base oil, and any mineral oil, synthetic oil, animal oil, or vegetable oil, or a combination thereof, commonly used in lubricating oil compositions can be selected. Specific examples include base oils belonging to API (American Petroleum Institute) base oil categories 1, 2, 3, and 4, which can be used alone or as a mixture.

[0018] Group 1 base oils include paraffinic mineral oils obtained by an appropriate combination of refining methods (such as solvent refining, hydrorefining, and dewaxing) for lubricating oil fractions obtained from the atmospheric distillation of crude oil.

[0019] Group 2 base oils include paraffinic mineral oils obtained by an appropriate combination of refining methods (such as hydrorefining and dewaxing) for lubricating oil fractions obtained from the atmospheric distillation of crude oil.

[0020] Group III base oils and Group II base oils include paraffinic mineral oils prepared by highly hydrorefining lubricating oil fractions obtained from the atmospheric distillation of crude oil, base oils refined using the Isodewax process, which dewaxes the wax prepared by a dewaxing process and replaces it with isoparaffins, and gas-to-liquid (GTL) oils synthesized using the Fischer-Tropsch method that converts natural gas into liquid fuels. These base oils are preferably used. Compared with mineral oil base oils refined from crude oil, GTL base oils have a very low sulfur content and aromatic content and a very high paraffin ratio. Therefore, they have excellent oxidation stability and undergo extremely low evaporation losses. They are particularly preferably used as base oils.

[0021] Examples of synthetic oils include polyolefins, dibasic acid diesters, trimellitic acid triesters, polyol esters, alkylbenzenes, alkylnaphthalenes, polyoxyalkylene glycols, polyoxyalkylene glycol esters, polyoxyalkylene glycol ethers, polyphenylene ethers, dialkyl diphenyl ethers, fluorine-containing compounds (perfluoropolyethers, fluorinated polyolefins, etc.), and silicones. Polyolefins include polymers of various olefins or their hydrides. Any polyolefin can be used, and examples include ethylene, propylene, butene, and α-olefins having five or more carbon atoms. In the preparation of polyolefins, one type of olefin or a combination of two or more types of olefins can be used. Particularly preferred are polyolefins called poly-α-olefins (PAO), which are Group IV base oils.

[0022] Any component commonly used in the art can be used as a metal-based detergent. Examples of metal-based detergents include alkali metal-based detergents (alkali metal sulfonates, alkali metal phenates, and alkali metal salicylates) and alkaline earth metal-based detergents (alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates). These metal-based detergents can be used alone or in combination of two or more.

[0023] The metal-based detergent preferably includes a calcium-based detergent and / or a magnesium-based detergent. The calcium-based detergent is preferably calcium salicylate. The magnesium-based detergent is preferably magnesium sulfonate.

[0024] Calcium salicylate and magnesium sulfonate are preferred forms of metal-based detergents. These metal-based detergents will be described in detail, but the metal-based detergents are not limited to these examples.

[0025] Any calcium salicylate commonly used in the art can be used. An example is the compound represented by the following formula (1).

[0026]

[0027] In this formula, R can be a hydrocarbon group having 4 to 30 carbon atoms, but is preferably a straight-chain or branched alkyl group having 6 to 18 carbon atoms.

[0028] Any magnesium sulfonate commonly used in the art can be used. An example is the compound represented by the following formula (2).

[0029]

[0030] In this formula, R may be a hydrocarbon group having 4 to 30 carbon atoms, but is preferably a linear or branched alkyl group having 6 to 18 carbon atoms.

[0031] Any molybdenum dithiocarbamate (MoDTC) commonly used in the art can be used. An example is the compound represented by the following formula (3).

[0032]

[0033] In this formula, R1 to R4 represent alkyl groups, and X1 to X4 represent oxygen atoms or sulfur atoms. More specifically, in this formula, the alkyl groups R1, R2, R3, and R4 are each independently a lipophilic group having 2 to 30 carbon atoms.

[0034] Here, the molybdenum dithiocarbamate is preferably the compound represented by the following formula (4).

[0035]

[0036] In this formula, R1 to R4 represent alkyl groups. More specifically, the alkyl groups R1, R2, R3, and R4 are each independently a lipophilic group having 2 to 30 carbon atoms.

[0037] Any zinc dialkyldithiophosphate commonly used in the art can be used. It is typically the compound represented by the following formula (5).

[0038]

[0039] In this formula, R a , R b , R c and R d each independently represent a hydrocarbon group having 3 to 24 carbon atoms. Preferred examples of the hydrocarbon group include a linear or branched alkyl group having 3 to 24 carbon atoms, a linear or branched alkenyl group having 3 to 24 carbon atoms, a cycloalkyl group having 5 to 13 carbon atoms or a linear or branched alkylcycloalkyl group, an aryl group having 6 to 18 carbon atoms or a linear or branched alkylaryl group, and an aralkyl group having 7 to 19 carbon atoms. These alkyl groups and alkenyl groups can be primary, secondary, or tertiary groups.

[0040] Specific examples of zinc dialkyldithiophosphates include zinc diisopropyldithiophosphate, zinc diisobutyldithiophosphate, zinc di-sec-butyldithiophosphate, zinc di-sec-pentyldithiophosphate, zinc di-n-hexyldithiophosphate, zinc di-sec-hexyldithiophosphate, zinc dioctyldithiophosphate, zinc di-2-ethylhexyldithiophosphate, zinc di-n-decyldithiophosphate, zinc di-n-dodecyldithiophosphate, zinc diisotridecyldithiophosphate, and any combination and mixture thereof. These antiwear agents can be used alone or in combination of two or more.

[0041] Depending on the intended application, in addition to those described above, the lubricating oil composition may further contain other components commonly used in the art. Examples of these other components include additives such as dispersants, antifoaming agents, pour point depressants, metal deactivators, antioxidants, and viscosity index improvers. In addition to the above components, the lubricating oil composition may further contain detergents or antiwear agents.

[0042] The base oil content is preferably 50% to 95% by mass, more preferably 60% to 90% by mass, even more preferably 70% to 85% by mass, based on the total amount of the lubricating oil composition.

[0043] The content of the metal-based detergent can be determined based on the metal atoms and is, for example, preferably 0.05% to 0.5% by mass, more preferably 0.1% to 0.4% by mass, even more preferably 0.13% to 0.25% by mass, based on the total amount of the lubricating oil composition.

[0044] Preferred embodiments of the metal-based detergents are calcium salicylate and magnesium sulfonate, and the specific contents of these metal-based detergents will now be explained.

[0045] The content C of calcium salicylate in terms of calcium atoms Ca is preferably 100 ppm to 2,000 ppm, more preferably 500 ppm to 1,800 ppm, even more preferably 700 ppm to 1,500 ppm, and still more preferably 900 ppm to 1,400 ppm, based on the total amount of the lubricating oil composition.

[0046] The content C of magnesium sulfonate in terms of magnesium atoms Mg is preferably 50 ppm to 1,000 ppm, more preferably 200 ppm to 800 ppm, even more preferably 300 ppm to 600 ppm, based on the total amount of the lubricating oil composition.

[0047] The content C of molybdenum dithiocarbamate in terms of molybdenum atoms MoPreferably, it is greater than 200 ppm and 2,000 ppm or less, more preferably 250 ppm to 1,700 ppm, even more preferably 300 ppm to 1,500 ppm, and still more preferably 400 ppm to 1,200 ppm, relative to the total amount of the lubricating oil composition. When the amount of molybdenum dithiocarbamate is within this range, the abrasion resistance of aluminum and aluminum alloys can be improved while maintaining excellent fuel economy.

[0048] Ratio (C Mg + C Mo / 2) / C Ca is preferably 0.4 to 1.2 (i.e., 0.35 or more and less than 1.25), more preferably 0.4 to 0.9 (i.e., 0.35 or more and less than 0.95).

[0049] C Ca 、C Mg and C Mo The total amount of (C Ca + C Mg + C Mo ) is preferably 1,000 ppm to 4,000 ppm, more preferably 1,500 ppm to 3,000 ppm, even more preferably 1,700 ppm to 3,000 ppm, and still more preferably 1,800 ppm to 2,750 ppm.

[0050] The content C of zinc dialkyldithiophosphate in terms of phosphorus atoms Zn is preferably 200 ppm to 2,000 ppm, more preferably 300 ppm to 1,500 ppm, and even more preferably 500 ppm to 1,000 ppm, relative to the total amount of the lubricating oil composition.

[0051] The balance can be other components. The amount of other components can be 1% by mass or more, 3% by mass or more, or 5% by mass or more, and 25% by mass or less, 20% by mass or less, or 15% by mass or less, relative to the total amount of the lubricating oil composition.

[0052] The amount of sulfated ash is preferably less than 0.85% by mass or 0.84% by mass or less, relative to the total amount of the lubricating oil composition. When the amount of sulfated ash is within this range, the effects of the present invention increase and the engine complies with emission regulations. There is no particular limitation on the lower limit value, and it can be 0.1% by mass, 0.3% by mass, or 0.5% by mass.

[0053] The sulfated ash content can be measured by the method specified in JIS K 2272. The sulfated ash content can be adjusted by changing, for example, the amount of metal-based detergent used.

[0054] A ring made of alloy steel (AISI 4620) and an aluminum alloy block (AC8A-T6) were used, and the wear resistance was evaluated using a Falex block-on-ring tribometer (LFW-1). The test conditions included: ring rotation speed of 1,000 rpm, load of 200 N, oil temperature of 80 °C, and operation time of 15 minutes after applying a 200 N load. The width (mm) of the wear on the block was measured after the test.

[0055] From the viewpoint of wear resistance, the wear width of the block after the test is preferably 5 mm or less, and particularly preferably 4.5 mm or less. When the wear resistance is within this range, the downsized engine has sufficient durability.

[0056] The lubricating oil composition can be produced by any method commonly used in the art. The respective components can be appropriately mixed together, and there is no particular limitation on the order in which the components are mixed together. The additives can be added in the form of an additive package of a mixture containing different additives.

[0057] The lubricating oil composition of the present invention can improve the balance among cleanliness, fuel economy, and wear resistance (particularly the wear resistance of aluminum and / or aluminum alloys). The lubricating oil composition of the present invention is suitable for gasoline engines with exhaust gas regulation measures (equipped with GPF or gasoline particulate filter), and gasoline engines compatible with low-sulfated ash engine oils equivalent to European ACEA C2, C3, and C5 Mid SAPS categories (low-sulfated ash engine oil standards for gasoline engine vehicles and diesel engine vehicles compatible with catalyst and GPF / DPF devices). The lubricating oil composition of the present invention is a low-viscosity engine oil with SAE viscosity grades of 0W-20, 0W-16, and 0W-8, which is suitable for engines with high fuel efficiency.

[0058] There is no particular limitation on the application of these lubricating oil compositions, and they can be used as lubricating oils in various machines. For example, they can be used to lubricate rotating parts and sliding parts in vehicles and production machines. These lubricating oil compositions are preferably used as lubricating oils for the sliding surfaces of parts containing aluminum and / or aluminum alloys (or internal combustion engines containing these metal materials in their parts).

[0059] Examples

[0060] The following components were mixed together in the amounts (mass %) shown in the table to produce the lubricating oil compositions in the examples and comparative examples. The SAE viscosity grade of each example was 0W-20.

[0061] · Base oil - GTL base oil

[0062] · Viscosity index improver - polymethacrylate

[0063] · Metal-based detergent A - Calcium-based detergent: Overbased calcium salicylate

[0064] · Metal-based detergent B - Magnesium-based detergent: Overbased magnesium sulfonate

[0065] · Antiwear agent - Zinc dialkyldithiophosphate

[0066] · Friction modifier - Molybdenum dithiocarbamate

[0067] · Ashless dispersant - Boron-free dispersant: Olefin succinimide; Boron-containing dispersant: Olefin succinimide

[0068] · Antioxidant - Mixture of amine-based antioxidant and phenol-based antioxidant

[0069] · Antifoaming agent - Kerosene solution containing 3% by mass of dimethylpolysiloxane (DCF)

[0070] In each lubricating oil composition, the amounts of the metal-based detergent and the friction modifier are expressed as the amounts (mass ppm) of calcium, magnesium, or molybdenum in the metal components of these reagents relative to the total mass of the lubricating oil composition.

[0071] For other additives, it refers to the general amount added, which, relative to the total mass of the lubricating oil composition, is 500 ppm to 1,500 ppm of nitrogen equivalent (0 ppm to 200 ppm of boron equivalent) in the case of the ashless dispersant, 500 ppm to 1,200 ppm of zinc equivalent in the case of the antiwear agent, and 3 ppm to 20 ppm of silicon equivalent in the case of the antifoaming agent. The amount of the viscosity index improver is 20% by mass or less, and the amount of the antioxidant is 5% by mass or less.

[0072] The equivalent amount of each component is measured according to well-known methods. For example, JPI-5S-38 is used for calcium, magnesium, and molybdenum, and JIS K 2609 is used for nitrogen.

[0073] Sulfated ash is used in each lubricating oil composition shown in the table.

[0074] The abrasion resistance test is conducted using the above method. The wear width (mm) of each block after the test is shown in the table. Regarding the evaluation criteria, when the wear width is 4.5 mm or less, the specified evaluation is When the wear width is 5.0 mm or less, the specified evaluation is i. When the wear width is greater than 5.0 mm, the specified evaluation is x.

[0075] Table 1

[0076]

[0077] Table 2

[0078]

Claims

1. Use of a lubricating oil composition for lubricating sliding surfaces containing aluminum and / or aluminum alloys, wherein the lubricating oil composition comprises a base oil, molybdenum dithiocarbamate and a metal-based detergent, wherein the content C of the molybdenum dithiocarbamate in terms of molybdenum atoms Mo is greater than 200 ppm and 2,000 ppm or less relative to the total amount of the lubricating oil composition, and the amount of sulfated ash is less than 0.85% by mass relative to the total amount of the lubricating oil composition, and wherein the metal-based detergent comprises a calcium-based detergent and a magnesium-based detergent.

2. Use according to claim 1, wherein the content C of the calcium-based detergent in terms of calcium atoms Ca is 100 ppm to 2,000 ppm relative to the total amount of the lubricating oil composition, and the content C of the magnesium-based detergent in terms of magnesium atoms Mg is 50 ppm to 1,000 ppm relative to the total amount of the lubricating oil composition, and (C Mg +C Mo / 2) / C Ca is from 0.4 to 1.

2.

3. Use according to any one of claims 1 to 2, wherein the lubricating oil composition further comprises zinc dialkyldithiophosphate.

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