Lubricant composition

Abstract

To provide a lubricant composition capable of achieving reduction in low friction properties and copper elution to a higher degree.SOLUTION: A lubricant composition comprises: a base oil (A); an organomolybdenum compound (B); one or more sulfur-containing compounds (C) selected from zinc dithiophosphate (C1) and a sulfur-containing compound (C2) having a sulfur chain length of 2 or more and containing no metal atom in the molecule; and an overbased metal detergent (D) having a base number of 100 mgKOH / g or more. A content of the organomolybdenum compound (B) is more than 0.20 mass% and 1.45 mass% or less based on a total amount of the lubricant composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a lubricating oil composition, a mechanical device comprising said lubricating oil composition, and a method of using said lubricating oil composition. [Background technology]

[0002] In recent years, there has been a strong demand for reducing carbon dioxide emissions from the viewpoint of protecting the global environment, and therefore, in the field of automobiles, efforts have been focused on the development of fuel-saving technologies. Examples of fuel-saving automobiles include hybrid cars and electric cars, and these cars are expected to become widespread rapidly in the future. Hybrid cars and electric cars are equipped with electric motors, generators, reduction gears, inverters, storage batteries, etc., and run using the power of the electric motor. Lubricating oil compositions that can be used in such electric vehicles are required to have both excellent friction properties and material compatibility.

[0003] Also, various lubricating oil compositions that can be used in electric vehicles have been developed. For example, Patent Documents 1 and 2 disclose lubricating oils that contain lubricating base oils, metal detergents, dispersants, zinc dialkyldithiophosphate (ZDDP) antiwear agents, molybdenum dialkyldithiocarbamate (MoDTC), viscosity modifiers, and other lubricating oil additives in predetermined amounts, and have specific electrical conductivity and 100°C kinetic viscosity. The lubricating oil of Patent Document 2 does not essentially contain overbased metal detergents. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special table number 2019-529675 [Patent Document 2] Special table number 2019-532151 Summary of the Invention [Problem to be solved by the invention]

[0005] In light of this, there is a demand for lubricating oil compositions that have excellent friction characteristics and material compatibility and can achieve even higher levels of low friction and reduced copper elution. [Means for solving the problem]

[0006] The present invention provides the following aspects [1] to

[14] . [1] A lubricating oil composition comprising: a base oil (A); an organo-molybdenum compound (B); one or more sulfur-based compounds (C) selected from zinc dithiophosphate (C1) and a sulfur-containing compound (C2) which does not contain a metal atom in the molecule and has a sulfur chain length of two or more; and an overbased metal-based detergent (D) having a base number of 100 mgKOH / g or more, wherein the content of the organo-molybdenum compound (B) is more than 0.20 mass% and not more than 1.45 mass%, based on the total amount of the lubricating oil composition. [2] The lubricating oil composition according to [1], wherein the overbased metal detergent (D) comprises one or more selected from the group consisting of overbased calcium sulfonate (D1), overbased calcium salicylate (D2) and overbased calcium phenate (D3). [3] The lubricating oil composition according to [1] or [2], wherein the overbased metal detergent (D) comprises an overbased calcium sulfonate (D1). [4] The lubricating oil composition according to [3], wherein the content (d1) of the overbased calcium sulfonate (D1) in terms of calcium atoms is 50 ppm by mass or more, based on the total amount of the lubricating oil composition. [5] The lubricating oil composition according to any one of [1] to [4], having a sulfur content of 0.08 mass % or more based on the total amount of the lubricating oil composition. [6] The lubricating oil composition according to any one of [1] to [5], wherein the content ratio of the organic molybdenum compound (B) to the sulfur-based compound (C) [(B) / (C)] is, in mass ratio, 0.35 to 5.00. [7] The lubricating oil composition according to any one of [1] to [8], wherein the content ratio of the overbased metal detergent (D) to the sulfur-based compound (C) [(D) / (C)] is, in mass ratio, 0.01 to 10. [8] The lubricating oil composition according to any one of [1] to [7], wherein the sulfur-based compound (C) contains zinc dithiophosphate (C1), and the content ratio [(Mo) / (Zn)] of molybdenum (Mo) derived from the organomolybdenum compound (B) to zinc (Zn) derived from the zinc dithiophosphate (C1) is 0.35 to 2.70 in terms of mass ratio. [9] The sulfur-containing compound (C2) is R 2 COOR 1 -(S) x -R 1 COOR 2 (In the formula, R 1 and R 2 and each independently represent a hydrocarbon group having 1 to 30 carbon atoms, and x is an integer of 2 or more.

[10] The kinetic viscosity at 100°C is 4.0mm 2 The lubricating oil composition according to any one of [1] to [9], wherein the lubricating oil composition has a molecular weight of 1.0 to 1.5 μg / s or less.

[11] The lubricating oil composition according to any one of [1] to

[10] , which is used for lubricating a mechanical device in which a motor and a reducer are integrated.

[12] The lubricating oil composition according to

[11] , wherein the mechanical device is a hydraulic device, a fixed transmission, an automotive transmission, or a cooling device for a motor and a battery.

[13] A mechanical device incorporating a motor and a reducer, which is filled with the lubricating oil composition according to any one of [1] to

[10] .

[14] A method for using the lubricating oil composition according to any one of [1] to

[10] , comprising applying the lubricating oil composition to a mechanical device in which a motor and a reducer are integrated. Effect of the Invention

[0007] The lubricating oil composition according to a preferred embodiment of the present invention has excellent low friction properties and can reduce the amount of copper eluted, and therefore can be suitably used for lubricating mechanical devices such as electric vehicle units in which a motor and a reduction gear are integrated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The upper and lower limit values ​​of the numerical ranges described in this specification can be arbitrarily combined. For example, when the numerical range is described as "preferably 30 to 100, more preferably 40 to 80", the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described in this specification. In addition, when the numerical range is described as "preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less", the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described in this specification. In addition, as a numerical range described in this specification, for example, "60 to 100" means a range of "60 or more (60 or more) and 100 or less (100 or less)." Furthermore, in defining the upper and lower limits described in this specification, a numerical range from the lower limit to the upper limit can be defined by appropriately selecting from the respective options and combining them in any desired manner. In addition, various features described as preferred embodiments in this specification may be combined in multiple ways.

[0009] [Constitution of lubricating oil composition] One aspect of the present invention provides a lubricating oil composition comprising a base oil (A) (hereinafter also referred to as "component (A)"), an organomolybdenum compound (B) (hereinafter also referred to as "component (B)"), zinc dithiophosphate (C1), and one or more sulfur-based compounds (C) (hereinafter also referred to as "component (C1)", "component (C2)", or "component C") selected from a sulfur-containing compound (C2) that does not contain a metal atom in the molecule and has a sulfur chain length of 2 or more, and an overbased metal-based detergent (D) (hereinafter also referred to as "component (D)") having a base number of 100 mgKOH / g or more, wherein the content of the organomolybdenum compound (B) is more than 0.20 mass% and not more than 1.45 mass%, based on the total amount of the lubricating oil composition. Motors and reducers used in electric vehicle units such as hybrid cars and electric cars are required to have high efficiency and compatibility with copper parts. As a method for improving the efficiency of the reducer, for example, an organic molybdenum compound (B) is blended into a lubricating oil composition to improve low friction. That is, the organic molybdenum compound (B) is added to reduce the metal-to-metal friction coefficient, thereby reducing loss due to friction. However, there is a tendency that sufficient improvement in low friction is difficult to obtain by only adding the organic molybdenum compound (B). In response to this, the present inventors have found that low friction can be further improved by using a sulfur-based compound (C) in combination with the organic molybdenum compound (B). However, as a result of the investigation, it was found that the addition of the sulfur-based compound (C) causes a problem of deterioration in stability against oxidation and an increase in the amount of copper eluted. After further investigation to solve such a secondary problem, the present inventors found that a lubricating oil composition capable of reducing the amount of copper eluted while realizing a higher level of low friction can be obtained by adding an overbased metallic detergent (D) having a base number of 100 mgKOH / g or more. The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives other than components (B) to (D) as necessary, provided that the effects of the present invention are not impaired.

[0010] In the lubricating oil composition of one embodiment of the present invention, the total content of components (A) to (D) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably 80 mass% or more, more preferably 85 mass% or more, even more preferably 90 mass% or more, and still more preferably 95 mass% or more.

[0011] Each component contained in the lubricating oil composition according to one embodiment of the present invention will now be described in detail.

[0012] <Component (A): Base oil> The base oil contained in the lubricating oil composition of one embodiment of the present invention may be a mineral oil, a synthetic oil, or a mixture of a mineral oil and a synthetic oil. Examples of mineral oils include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil; distillate oils obtained by vacuum distillation of these atmospheric residual oils; refined oils obtained by subjecting the distillate oils to one or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; mineral oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)); mineral oils (CTL) obtained by isomerizing wax produced from coal by the Fischer-Tropsch process or the like (CTL wax (Coal To Liquids WAX)); mineral oils (BTL) obtained by isomerizing wax produced from biomass by the Fischer-Tropsch process or the like (BTL wax (Biomass To Liquids WAX)); and the like.

[0013] Examples of synthetic oils include poly-α-olefins such as α-olefins, homopolymers thereof, and α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffin; polyalkylene glycol; ester-based oils such as polyol esters, dibasic acid esters, monoesters, and phosphate esters; ether-based oils such as polyphenyl ether; alkylbenzenes; and alkylnaphthalenes.

[0014] Among these, the base oil used in one embodiment of the present invention preferably contains at least one selected from mineral oils classified into Group 2 and Group 3 of the API (American Petroleum Institute) base oil category and synthetic oils. In one embodiment of the present invention, these base oils may be used alone or in combination of two or more.

[0015] The base oil (A) used in one embodiment of the present invention has a kinetic viscosity at 100°C of 6.0 mmHg or less from the viewpoint of providing a lubricating oil composition with improved cooling properties. 2 / s or less, and more preferably 5.5 mm 2 / s or less, more preferably 5.0 mm 2 / s or less, and even more preferably 4.5 mm 2 / s or less, and even more preferably 4.0 mm 2 / s or less, and even more preferably 3.5 mm 2 / s or less, and particularly preferably 3.0 mm 2 / s or less. On the other hand, from the viewpoint of obtaining a lubricating oil composition having good oil film retention and improved part protection by improving lubricating performance, the kinematic viscosity of the base oil (A) at 100° C. is preferably 1.0 mm 2 / s or more, preferably 1.2 mm 2 / s or more, more preferably 1.4 mm 2 / s or more.

[0016] The viscosity index of the base oil (A) used in one embodiment of the present invention is appropriately set depending on the application of the lubricating oil composition, but is preferably 70 or more, more preferably 80 or more, even more preferably 90 or more, and particularly preferably 100 or more. In one embodiment of the present invention, when a mixed oil of two or more base oils is used as component (A), the mixed oil preferably has a kinematic viscosity and a viscosity index within the above ranges. Therefore, the mixed oil may be prepared by using a low-viscosity base oil and a high-viscosity base oil in combination so that the mixed oil has a kinematic viscosity and a viscosity index within the above ranges. The mixed oil may be a mixed oil obtained by combining two or more base oils whose kinematic viscosity and viscosity index at 100° C. are within the above-mentioned ranges, or a mixed oil obtained by combining a base oil whose kinematic viscosity and viscosity index at 100° C. are within the above-mentioned ranges with a base oil whose kinematic viscosity and viscosity index at 100° C. are not within the above-mentioned ranges. The mixed oil may also be a mixed oil adjusted to be within the above-mentioned ranges by combining a low-viscosity base oil and a high-viscosity base oil whose kinematic viscosity and viscosity index at 100° C. are not within the above-mentioned ranges. In this specification, the kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000.

[0017] In the lubricating oil composition of one embodiment of the present invention, the content of base oil (A), based on the total amount (100 mass%) of the lubricating oil composition, is usually 55 mass% or more, preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, particularly preferably 90 mass% or more, and is preferably 99.9 mass% or less, more preferably 99.0 mass% or less, and even more preferably 98.5 mass% or less.

[0018] <Component (B): Organic molybdenum compound> The lubricating oil composition of the present invention contains an organic molybdenum compound (B). By using the organic molybdenum compound (B) in combination with a sulfur-based compound (C) described below, it is possible to improve low friction properties. As the organic molybdenum compound (B), any organic compound having a molybdenum atom can be used, but it is preferable that the compound be represented by the following general formula (1). [ka]

[0019] In formula (1), R 1 ~R 4 are each independently a hydrocarbon group having 4 to 18 carbon atoms, and are preferably an alkyl group having 5 to 18 carbon atoms, an alkenyl group having 5 to 18 carbon atoms, a cycloalkyl group having 5 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, an alkylaryl group having 7 to 18 carbon atoms, or an arylalkyl group having 7 to 18 carbon atoms.

[0020] Examples of the alkyl group having 5 to 18 carbon atoms include a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group.

[0021] Examples of the alkenyl group having 5 to 18 carbon atoms include an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, and a pentadecenyl group.

[0022] Examples of the cycloalkyl group having 5 to 18 carbon atoms include a cyclohexyl group, a dimethylcyclohexyl group, an ethylcyclohexyl group, a methylcyclohexylmethyl group, a cyclohexylethyl group, a propylcyclohexyl group, a butylcyclohexyl group, and a heptylcyclohexyl group.

[0023] Examples of the aryl group having 6 to 18 carbon atoms include a phenyl group, a naphthyl group, an anthracenyl group, a biphenyl group, and a terphenyl group.

[0024] Examples of the alkylaryl group having 7 to 18 carbon atoms include a tolyl group, a dimethylphenyl group, a butylphenyl group, a nonylphenyl group, a methylbenzyl group, and a dimethylnaphthyl group.

[0025] Examples of the arylalkyl group having 7 to 18 carbon atoms include a phenylmethyl group, a phenylethyl group, and a diphenylmethyl group.

[0026] In formula (1), X 1 ~X 4 are each independently an oxygen atom or a sulfur atom. From the viewpoint of improving the solubility in the base oil (A), X 1 ~X 4 The molar ratio of sulfur atoms to oxygen atoms [S / O] therein is preferably from 1 / 3 to 3 / 1, and more preferably from 1.5 / 2.5 to 3 / 1.

[0027] In one embodiment of the present invention, the content of the organic molybdenum compound (B) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably more than 0.20 mass%, more preferably 0.25 mass% or more, even more preferably 0.30 mass% or more, and still more preferably 0.35 mass% or more, from the viewpoint of obtaining a lubricating oil composition that can improve low friction properties, and is preferably 1.45 mass% or less, more preferably 1.40 mass% or less, even more preferably 1.35 mass% or less, and still more preferably 1.30 mass% or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0028] In one embodiment of the present invention, the content of the organic molybdenum compound (B), calculated as molybdenum atoms, based on the total amount (100 mass%) of the lubricating oil composition is preferably 100 ppm by mass or more, more preferably 200 ppm by mass or more, and even more preferably 300 ppm by mass or more, from the viewpoint of obtaining a lubricating oil composition that can improve low friction properties, and is preferably 1400 ppm by mass or less, more preferably 1300 ppm by mass or less, and even more preferably 1200 ppm by mass or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0029] <Component (C): Sulfur-based compound> The lubricating oil composition of the present invention contains zinc dithiophosphate (C1) and one or more sulfur-based compounds (C) selected from sulfur-containing compounds (C2) that do not contain metal atoms in the molecule and have a sulfur chain length of at least 2. By containing the sulfur-based compound (C), it is possible to further improve the low friction properties achieved by adding the organic molybdenum compound (B).

[0030] The sulfur-based compound (C) used in one embodiment of the present invention is zinc dithiophosphate (C1) (ZnDTP). Examples of zinc dithiophosphate (C1) include zinc dithiophosphate having a primary alkyl group (c1), zinc dithiophosphate having a secondary alkyl group (c2), and zinc dithiophosphate having an aryl group (c3). The zinc dithiophosphate (C1) may be used alone or in combination of two or more. The number of carbon atoms in the alkyl group of the zinc dithiophosphate (C1) is not particularly limited and may be appropriately selected depending on the purpose, but for example, the number of carbon atoms is preferably 1 to 10, 2 to 9, or 3 to 8. Note that the zinc dithiophosphate (C1) having a secondary alkyl group or the like may contain an alkyl group having a different number of carbon atoms.

[0031] The sulfur-based compound (C) used in one embodiment of the present invention is a sulfur-containing compound (C2) that does not contain a metal atom in the molecule and has a sulfur chain length of 2 or more. The sulfur-containing compound (C2) in one embodiment is a compound represented by the following general formula (2). R 2 COOR 1 -(S) x -R 1 COOR 2 (2)

[0032] In the formula, R 1 and R 2 are each independently a hydrocarbon group having 1 to 30 carbon atoms. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, and a group formed by combining two or more of these. The number of carbon atoms in the hydrocarbon group is 1 to 30, but may be, for example, 2 to 26, 4 to 20, etc. In the formula, x is an integer of 2 or more. x may be 2 to 6, 2 to 4, 2 to 3, or 2.

[0033] Examples of the alkyl group include a methyl group, an ethyl group, a propyl group (n-propyl group, i-propyl group), a butyl group (n-butyl group, i-butyl group, s-butyl group, t-butyl group), a pentyl group (n-pentyl group, i-pentyl group, neopentyl group), a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, etc. The alkyl group may be a linear alkyl group or a branched alkyl group.

[0034] Examples of the alkenyl group include ethenyl group (vinyl group), propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, octadecenyl group (oleyl group), etc. The alkenyl group may be a linear alkenyl group or a branched alkenyl group.

[0035] Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and an adamantyl group.

[0036] Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a biphenyl group, and a terphenyl group.

[0037] In one embodiment of the present invention, the content of the sulfur-based compound (C) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and even more preferably 0.10 mass% or more, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction properties, and is preferably 1.00 mass% or less, more preferably 0.90 mass% or less, and even more preferably 0.80 mass% or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0038] In one embodiment of the present invention, the content of the sulfur-based compound (C), calculated as sulfur atoms, based on the total amount (100 mass%) of the lubricating oil composition is preferably 0.01 mass% or more, more preferably 0.02 mass% or more, and even more preferably 0.03 mass% or more, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction properties, and is preferably 0.30 mass% or less, more preferably 0.20 mass% or less, and even more preferably 0.15 mass% or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0039] When the sulfur-based compound (C) used in one embodiment of the present invention is zinc dithiophosphate (C1), the content of the sulfur-based compound (C), calculated as zinc atoms, based on the total amount (100 mass%) of the lubricating oil composition is preferably 10 ppm by mass or more, 50 ppm by mass or more, 100 ppm by mass or more, 300 ppm by mass or more, or 500 ppm by mass or more, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction properties, and is preferably 1000 ppm by mass or less, 900 ppm by mass or less, 800 ppm by mass or less, or 700 ppm by mass or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0040] In one embodiment of the present invention, the content ratio of the organic molybdenum compound (B) to the sulfur-based compound (C) [(B) / (C)], in terms of mass ratio, is preferably 0.35 or more, more preferably 0.50 or more, and even more preferably 0.70 or more, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction properties, and is preferably 5.00 or less, more preferably 3.00 or less, and even more preferably 2.30 or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0041] In one embodiment of the present invention, the ratio [Mo / S] of molybdenum atoms derived from the organic molybdenum compound (B) to sulfur atoms derived from the sulfur-based compound (C), in terms of mass ratio, is preferably 0.20 or more, more preferably 0.25 or more, and even more preferably 0.30 or more, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction properties, and is preferably 3.00 or less, more preferably 2.00 or less, and even more preferably 1.65 or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0042] When the sulfur-based compound (C) used in one embodiment of the present invention is zinc dithiophosphate (C1), the ratio [Mo / Zn] of molybdenum atoms derived from the organo molybdenum compound (B) to zinc atoms derived from the zinc dithiophosphate (C1), in terms of mass ratio, is preferably 0.35 or more, more preferably 0.50 or more, even more preferably 0.55 or more, and still more preferably 0.60 or more, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction, and is preferably 2.70 or less, more preferably 2.50 or less, even more preferably 2.30 or less, and still more preferably 2.20 or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0043] <Component (D): Overbased metal detergent> The lubricating oil composition of the present invention contains an overbased metallic detergent (D) having a base number of 100 mgKOH / g or more. By containing an overbased metallic detergent (D) having a base number of 100 mgKOH / g or more, it is possible to obtain a lubricating oil composition that can reduce the amount of copper elution while realizing a higher level of low friction. The overbased metal detergent (D) used in one embodiment of the present invention includes overbased metal sulfonates, overbased metal salicylates, overbased metal phenates, etc. In one embodiment, the metal of the overbased metal detergent (D) may be calcium (Ca), magnesium (Mg), sodium (Na), etc., and calcium (Ca) is more preferred.

[0044] The overbased metallic detergent (D) used in one embodiment of the present invention may be one or more overbased calcium detergents selected from overbased calcium sulfonates (D1), overbased calcium salicylates (D2) and overbased calcium phenates (D3). Among them, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, it is preferable to use overbased calcium sulfonates (D1) as the overbased metallic detergent (D).

[0045] In one embodiment of the present invention, the content of the overbased metallic detergent (D) is, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, preferably 0.01 mass % or more, 0.03 mass % or more, 0.05 mass % or more, 0.08 mass % or more, or 0.10 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition; and from the viewpoint of maintaining good wear resistance of the lubricating oil composition, preferably 1.5 mass % or less, 1.2 mass % or less, or 1.0 mass % or less.

[0046] <<Overbased Calcium Sulfonate (D1)>> An example of the overbased calcium sulfonate (D1) used in one embodiment of the present invention is a compound represented by the following general formula (d-1). [ka]

[0047] In the above general formula (d-1), R is each independently a hydrocarbon group having 8 to 30 carbon atoms. Examples of the hydrocarbon group that can be selected as R include alkyl groups having 8 to 30 carbon atoms.

[0048] In one embodiment of the present invention, the base number of the overbased calcium sulfonate (D1) may be 120 mgKOH / g or more, 150 mgKOH / g or more, 170 mgKOH / g or more, or 200 mgKOH / g or more, and may be 400 mgKOH / g or less, or 350 mgKOH / g or less. In this specification, the base number of the overbased calcium sulfonate (D1) means a value measured by the perchloric acid method in accordance with JIS K2501:2003.

[0049] In one embodiment of the present invention, the content of the overbased calcium sulfonate (D1) is preferably at least 0.01 mass%, at least 0.03 mass%, at least 0.05 mass%, at least 0.08 mass%, or at least 0.10 mass%, based on the total amount (100 mass%) of the lubricating oil composition from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, and is preferably at most 1.5 mass%, at most 1.2 mass%, or at most 1.0 mass%, from the viewpoint of maintaining good wear resistance of the lubricating oil composition.

[0050] In one embodiment of the present invention, the content (d1) of the overbased calcium sulfonate (D1), calculated as calcium atoms, is preferably at least 50 ppm by mass, at least 80 ppm by mass, at least 100 ppm by mass, or at least 120 ppm by mass, based on the total amount (100 mass%) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, and is preferably at most 1500 ppm by mass, at most 1300 ppm by mass, at most 1200 ppm by mass, or at most 1100 ppm by mass, from the viewpoint of maintaining good wear resistance of the lubricating oil composition.

[0051] <<Overbased Calcium Salicylate (D2)>> An example of the overbased calcium salicylate (D2) used in one embodiment of the present invention is a compound represented by the following general formula (d-2). [ka]

[0052] In the above general formula (d-2), R is each independently a hydrocarbon group having 8 to 30 carbon atoms. Examples of the hydrocarbon group that can be selected as R include alkyl groups having 8 to 30 carbon atoms.

[0053] In one embodiment of the present invention, the base number of the overbased calcium salicylate (D2) may be 120 mgKOH / g or more, 150 mgKOH / g or more, 170 mgKOH / g or more, or 200 mgKOH / g or more, and may be 400 mgKOH / g or less, or 350 mgKOH / g or less. In this specification, the base number of the overbased calcium salicylate (D2) means a value measured by the perchloric acid method in accordance with JIS K2501:2003.

[0054] In one embodiment of the present invention, the content of the overbased calcium salicylate (D2) is, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, preferably 0.01 mass % or more, 0.03 mass % or more, 0.05 mass % or more, 0.08 mass % or more, or 0.10 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition; and from the viewpoint of maintaining good wear resistance of the lubricating oil composition, preferably 1.5 mass % or less, 1.2 mass % or less, or 1.0 mass % or less.

[0055] In one embodiment of the present invention, the content (d2) of the overbased calcium salicylate (D2) calculated as calcium atoms is preferably 50 ppm by mass or more, 80 ppm by mass or more, 100 ppm by mass or more, or 120 ppm by mass or more based on the total amount (100 mass%) of the lubricating oil composition from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, and is preferably 1500 ppm by mass or less, 1300 ppm by mass or less, 1200 ppm by mass or less, or 1100 ppm by mass or less from the viewpoint of maintaining good wear resistance of the lubricating oil composition.

[0056] <<Overbased Calcium Phenate (D3)>> An example of the overbased calcium phenate (D3) used in one embodiment of the present invention is a compound represented by the following general formula (d-3). [ka]

[0057] In the above general formula (d-3), R is each independently a hydrocarbon group having 8 to 30 carbon atoms, and y is an integer of 0 or more. Examples of the hydrocarbon group that can be selected as R include alkyl groups having 8 to 30 carbon atoms.

[0058] In one embodiment of the present invention, the base number of the overbased calcium phenate (D3) may be 120 mgKOH / g or more, 150 mgKOH / g or more, 170 mgKOH / g or more, or 200 mgKOH / g or more, and may be 400 mgKOH / g or less, or 350 mgKOH / g or less. In this specification, the base number of the overbased calcium phenate (D3) means a value measured by the perchloric acid method in accordance with JIS K2501:2003.

[0059] In one embodiment of the present invention, the content of the overbased calcium phenate (D3) is, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, preferably 0.01 mass % or more, 0.03 mass % or more, 0.05 mass % or more, 0.08 mass % or more, or 0.10 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition; and from the viewpoint of maintaining good wear resistance of the lubricating oil composition, preferably 1.5 mass % or less, 1.2 mass % or less, or 1.0 mass % or less.

[0060] In one embodiment of the present invention, the content (d3) of the overbased calcium phenate (D3) in terms of calcium atoms is preferably 50 ppm by mass or more, 80 ppm by mass or more, 100 ppm by mass or more, or 120 ppm by mass or more based on the total amount (100 mass%) of the lubricating oil composition from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, and is preferably 1500 ppm by mass or less, 1300 ppm by mass or less, 1200 ppm by mass or less, or 1100 ppm by mass or less from the viewpoint of maintaining good wear resistance of the lubricating oil composition.

[0061] The lubricating oil composition of one embodiment of the present invention may contain a neutral metal detergent from the viewpoint of improving the detergency, or may not substantially contain a neutral metal detergent from the viewpoint of making the lubricating oil composition have a small amount of copper elution. Here, "substantially not containing a neutral metal detergent" means excluding lubricating oil compositions in which these are intentionally blended, and does not exclude even those in which these are inevitably blended, but when the neutral metal detergent is not contained, from the same viewpoint as above, it is preferable that the content of such a neutral metal detergent is as small as possible. Specifically, the content of the neutral metal-based detergent that is inevitably mixed in is preferably, for example, less than 0.05 mass%, less than 0.03 mass%, less than 0.01 mass%, or less than 0.001 mass%, based on the total amount (100 mass%) of the lubricating oil composition. On the other hand, when a neutral metal-based detergent is contained, from the same viewpoint as above, the content thereof is preferably, for example, 0.01 mass% or more, 0.03 mass% or more, 0.05 mass% or more, 0.08 mass% or more, or 0.10 mass% or more based on the total amount (100 mass%) of the lubricating oil composition, and is preferably 1.5 mass% or less, 1.2 mass% or less, or 1.0 mass% or less.

[0062] In one embodiment of the present invention, the content ratio of the overbased metallic detergent (D) to the sulfur-based compound (C) [(D) / (C)], in terms of mass ratio, is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, and is preferably 10 or less, more preferably 9.5 or less, and even more preferably 9.0 or less, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction properties.

[0063] In one embodiment of the present invention, the content ratio of the overbased calcium sulfonate (D1) to the sulfur-based compound (C) [(D1) / (C)], expressed by mass ratio, is preferably at least 0.01, more preferably at least 0.05, and even more preferably at least 0.10 from the viewpoint of providing a lubricating oil composition with a low amount of copper elution, and is preferably at most 10, more preferably at most 9.5, and even more preferably at most 9.0, from the viewpoint of providing a lubricating oil composition that can further improve low friction properties.

[0064] In one embodiment of the present invention, the ratio [Ca / S] of calcium atoms derived from the overbased calcium sulfonate (D1) to sulfur atoms derived from the sulfur-based compound (C), expressed by mass ratio, is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution, and is preferably 5.00 or less, more preferably 4.50 or less, and even more preferably 4.00 or less, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction properties.

[0065] When the sulfur-based compound (C) used in one embodiment of the present invention is zinc dithiophosphate (C1), the ratio of zinc atoms derived from the zinc dithiophosphate (C1) to calcium atoms derived from the overbased calcium sulfonate (D1) [Zn / Ca], in terms of mass ratio, is preferably 0.1 or more, 0.2 or more, 0.3 or more, or 0.4 or more from the viewpoint of obtaining a lubricating oil composition that can further improve low friction, and is preferably 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, or 0.6 or less from the viewpoint of obtaining a lubricating oil composition with low copper elution.

[0066] <Lubricant additives> The lubricating oil composition of one embodiment of the present invention may contain other lubricating oil additives other than the components (B) to (D) as necessary, provided that the effects of the present invention are not impaired. Examples of such lubricating oil additives include pour point depressants, antioxidants, friction modifiers, antiwear agents, metal deactivators, ashless dispersants, metal deactivators, and antifoaming agents. These lubricating oil additives may be used alone, or two or more of them may be used in combination.

[0067] [Pour point depressants] The lubricating oil composition of one embodiment of the present invention may contain a pour point depressant. The pour point depressants may be used alone or in combination of two or more kinds. Examples of pour point depressants used in one embodiment of the present invention include polymethacrylates, alkylated aromatic compounds, copolymers of fumarate and vinyl acetate, and copolymers of ethylene and vinyl acetate, and polymethacrylates having a weight average molecular weight of 40,000 to 200,000 are preferred.

[0068] [Antioxidants] The lubricating oil composition of one embodiment of the present invention may contain an antioxidant. The antioxidants may be used alone or in combination of two or more kinds. Examples of the antioxidant used in one embodiment of the present invention include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; and sulfur-based antioxidants such as phenothiazine, dioctadecyl sulfide, dilauryl-3,3'-thiodipropionate, and 2-mercaptobenzimidazole.

[0069] [Friction modifiers and anti-wear agents] The lubricating oil composition of one embodiment of the present invention may contain a friction modifier or an anti-wear agent. The friction modifier or anti-wear agent may be used alone or in combination of two or more kinds. Examples of friction modifiers and anti-wear agents used in one embodiment of the present invention include sulfur-based compounds such as sulfurized olefins, dialkyl polysulfides, diaryl alkyl polysulfides, and diaryl polysulfides; phosphorus-based compounds such as phosphate esters, thiophosphate esters, phosphites, alkyl hydrogen phosphites, phosphate ester amine salts, and phosphites amine salts; and ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, urea-based compounds, and hydrazide-based compounds.

[0070] [Metal deactivator] The lubricating oil composition of one embodiment of the present invention may contain a metal deactivator. The metal deactivators may be used alone or in combination of two or more kinds. Examples of the metal deactivator used in one embodiment of the present invention include benzotriazole, triazole derivatives, benzotriazole derivatives, and thiadiazole derivatives.

[0071] [Ashless dispersant] The lubricating oil composition of one embodiment of the present invention may contain an ashless dispersant from the viewpoint of improving dispersibility. The ashless dispersant may be used alone or in combination of two or more kinds. The ashless dispersant used in one embodiment of the present invention is preferably an alkenyl succinimide, and examples thereof include an alkenyl succinic acid bisimide represented by the following general formula (f-1) and an alkenyl succinic acid monoimide represented by the following general formula (f-2).

[0072] [ka]

[0073] In the above general formulas (f-1) and (f-2), R f1 , R f2 and R f3 are each independently an alkenyl group having a number average molecular weight (Mn) of 900 to 2,500. R f1 , R f2and R f3 Examples of the alkenyl group that can be selected as the alkyl group include a polybutenyl group and a polyisobutenyl group. A f1 , A f2 and A f3 each independently represents an alkylene group having 2 to 5 carbon atoms. x1 is an integer from 2 to 6. x2 is an integer from 2 to 6.

[0074] The compound represented by the general formula (f-1) or (f-2) may be a modified alkenyl succinimide reacted with one or more selected from a boron compound, an alcohol, an aldehyde, a ketone, an alkylphenol, a cyclic carbonate, an epoxy compound, and an organic acid.

[0075] [Antifoaming agent] The lubricating oil composition of one embodiment of the present invention may contain an antifoaming agent. The antifoaming agents may be used alone or in combination of two or more kinds. Examples of the defoaming agent used in one embodiment of the present invention include alkyl silicone defoaming agents, fluoro silicone defoaming agents, and fluoroalkyl ether defoaming agents.

[0076] <Method of producing lubricating oil composition> There are no particular limitations on the method for producing the lubricating oil composition of one embodiment of the present invention, but from the viewpoint of productivity, it is preferable for the method to be a method comprising a step of blending component (A) with components (B) to (D) and, as necessary, various additives.

[0077] [Properties of the lubricating oil composition] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 100°C of 1.0 mm 2 / s or more, preferably 1.2 mm 2 / s or more, more preferably 1.4 mm 2 From the viewpoint of providing a lubricating oil composition with excellent cooling properties, it is preferably 4.0 mm 2 / s or less, preferably 3.5 mm 2 / s or less, more preferably 3.0 mm 2 / s or less.

[0078] The lubricating oil composition according to one embodiment of the present invention preferably has a kinematic viscosity at 40°C of 20mm 2 / s or less, preferably 19 mm 2 / s or less, more preferably 18 mm 2 / s or less, and even more preferably 17 mm 2 / s or less, and even more preferably 16 mm 2 / s or less, particularly preferably 15 mm 2 / s or less.

[0079] The lubricating oil composition of one embodiment of the present invention preferably has a viscosity index of 70 or greater, more preferably 80 or greater, even more preferably 90 or greater, and particularly preferably 100 or greater.

[0080] The sulfur content of the lubricating oil composition of one embodiment of the present invention, based on the total amount (100 mass%) of the lubricating oil composition, is preferably 0.08 mass% or more, and more preferably 0.09 mass% or more, from the viewpoint of obtaining a lubricating oil composition that can further improve low friction properties, and is preferably less than 0.28 mass%, more preferably 0.27 mass% or less, and even more preferably 0.26 mass% or less, from the viewpoint of obtaining a lubricating oil composition with a low amount of copper elution.

[0081] [Characteristics and uses of lubricating oil composition] The present invention provides a lubricating oil composition that can achieve a higher level of low friction and reduced copper elution. A specific index for evaluating low friction is the metal-metal friction coefficient measured by the method described in the Examples below. The amount of copper elution can be evaluated by the method described in the Examples below.

[0082] The metal-to-metal friction coefficient measured using the lubricating oil composition of one embodiment of the present invention by the method described in the Examples below is preferably 0.059 or less, more preferably 0.058 or less, and even more preferably 0.057 or less. It can be said that the smaller the metal-to-metal friction coefficient, the more improved the low-friction properties of the lubricating oil composition. In the examples described later, those with a metal-to-metal friction coefficient of less than 0.060 were judged to pass.

[0083] The amount of copper eluted from the lubricating oil composition of one embodiment of the present invention, as measured by the method described in the Examples below, is preferably 70 ppm by mass or less, more preferably 65 ppm by mass or less, and even more preferably 60 ppm by mass or less. In the examples described later, samples with an amount of copper elution of 70 mass ppm or less were judged to pass.

[0084] Because the lubricating oil composition of one embodiment of the present invention has the above-mentioned properties, it can be suitably used in mechanical devices in which a motor and a reduction gear are integrated, such as hydraulic devices, fixed transmissions, automobile transmissions, and motor / battery cooling devices.

[0085] Therefore, the present invention also provides the use of the machinery and equipment described below in [I] and the lubricating oil composition described below in [II]. [I] A mechanical device incorporating a motor and a reducer, which is filled with the lubricating oil composition according to one embodiment of the present invention described above. [II] Use of the lubricating oil composition according to one embodiment of the present invention described above in a mechanical device in which a motor and a reducer are integrated. EXAMPLES

[0086] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. Various physical properties of the components used in the examples and comparative examples and the obtained lubricating oil compositions were measured according to the following methods.

[0087] (1)Kinematic viscosity, viscosity index Measurements and calculations were made in accordance with JIS K2283:2000. (2) Base number (perchloric acid method) Measurement was performed using the perchloric acid method in accordance with JIS K2501:2003 (perchloric acid method). (3) Calcium atom (Ca) content Measurements were performed in accordance with JPI-5S-38-92. (4) Molybdenum atom (Mo) content Measurements were performed in accordance with JPI-5S-38-92. (5) Zinc atom (Zn) content Measurements were performed in accordance with JPI-5S-38-92. (6) Sulfur atom (S) content Measurements were performed in accordance with JIS K2541-6:2013.

[0088] (7) Metal-to-metal friction coefficient The metal-metal friction coefficient was measured under the following conditions using MTM2 (Mini Traction Machine2, manufactured by PCS Instruments). Test temperature: 80℃ Test duration: 1 hour Load: 35N ·Average speed: 200mm / s - Sliding ratio: 50% Metal-to-metal friction coefficients of less than 0.060 were judged to pass. (8) Copper elution amount The ISOT test was carried out in accordance with JIS K2514. Specifically, the sample oil was degraded at 150°C for 120 hours using copper and iron pieces as catalysts. The amount of copper eluted from the degraded sample oil (unit: mass ppm) was measured by a method in accordance with JPI-5S-38. The smaller the value of the amount of copper elution, the higher the copper elution suppression effect of the lubricating oil composition. In this example, a lubricating oil composition with a copper elution amount of 70 mass ppm or less was judged to pass.

[0089] Examples 1 to 7, Comparative Examples 1 to 5 Lubricating oil compositions were prepared by adding and mixing the components (A) to (D) shown in Table 1 in the amounts shown in Table 1. Details of each component used in the preparation of the lubricating oil compositions are as follows.

[0090] <Base oil (A)> ·Mineral oil (A1): 100℃ kinematic viscosity = 2.2mm 2 / s, viscosity index = 109, 60N mineral oil classified in Group 2 of the API base oil category. ·Mineral oil (A2): 100℃ kinematic viscosity = 2.7mm 2 / s, viscosity index = 111, 70N mineral oil classified in Group 2 of the API base oil category. <Organomolybdenum Compounds (B)> Molybdenum dithiocarbamate (MoDTC) (R in formula (1) 1 ~R 4 are each independently 8 or 13 hydrocarbon groups; X 1 ~X 4 A compound in which the molybdenum atom content is 10.0 mass%, and the sulfur atom content is 11.5 mass%. <Sulfur compounds (C)> Sulfur-based compound (C1): Zinc dithiophosphate (ZnDTP) having a secondary alkyl group. Zinc atom content = 9.0 mass%, sulfur atom content = 17.1 mass%. Sulfur-based compound (C2): Dibutyl dithiodiglycolate (R 1 is an alkyl group having one carbon atom, and R 2 is an alkyl group having 4 carbon atoms, and x=2). Sulfur atom content: 20.7% by mass. <Overbased metallic detergents (D)> Overbased Ca sulfonate: Calcium sulfonate with base number (perchloric acid method) = 307 mg KOH / g, Ca content = 11.9 mass%. <Other additives> ·Additive blends including pour point depressants, antioxidants, dispersants, copper deactivators, and antifoam agents.

[0091] For the lubricating oil compositions prepared in the Examples and Comparative Examples, various physical properties were measured and calculated according to the above-mentioned measuring methods. The results are shown in Table 1. [Table 1]

[0092] As can be seen from Table 1, a lubricating oil composition comprising a base oil (A), an organo molybdenum compound (B), zinc dithiophosphate (C1), one or more sulfur-based compounds (C) selected from sulfur-containing compounds (C2) that do not contain metal atoms in the molecule and have a sulfur chain length of 2 or more, and an overbased metal-based detergent (D) having a base number of 100 mgKOH / g or more, and in which the content of the organo molybdenum compound (B) is more than 0.20 mass% and not more than 1.45 mass%, based on the total amount of the lubricating oil composition, had excellent low friction properties and a small amount of copper elution compared to Comparative Examples 1 to 5. Specifically, Comparative Examples 1 and 2 did not meet the pass criteria for the metal-to-metal friction coefficient because they did not contain the sulfur-based compound (C). Comparative Example 3 did not meet the pass criteria for the amount of copper elution because they did not contain the overbased metal-based detergent (D). Comparative Example 4 did not meet the pass criteria for the metal-to-metal friction coefficient because the content of the organic molybdenum compound (B) was low. Comparative Example 5 did not meet the pass criteria for the amount of copper elution because the content of the organic molybdenum compound (B) was high. In contrast to these Comparative Examples, the lubricating oil compositions of the Examples had both excellent low friction properties and reduced copper elution.

Claims

1. A lubricating oil composition comprising: a base oil (A); an organo-molybdenum compound (B); one or more sulfur-based compounds (C) selected from zinc dithiophosphate (C1) and sulfur-containing compounds (C2) that do not contain metal atoms in the molecule and have a sulfur chain length of 2 or more; and an overbased metal-based detergent (D) having a base number of 100 mgKOH / g or more, wherein the content of the organo-molybdenum compound (B) is more than 0.20 mass % and not more than 1.45 mass %, based on the total amount of the lubricating oil composition.

2. 2. The lubricating oil composition of claim 1, wherein the overbased metallic detergent (D) comprises one or more selected from overbased calcium sulfonates (D1), overbased calcium salicylates (D2), and overbased calcium phenates (D3).

3. 2. The lubricating oil composition of claim 1, wherein the overbased metallic detergent (D) comprises an overbased calcium sulfonate (D1).

4. 4. The lubricating oil composition according to claim 3, wherein the amount (d1) of the overbased calcium sulfonate (D1) calculated as calcium atoms is 50 ppm by mass or more based on the total amount of the lubricating oil composition.

5. 2. The lubricating oil composition according to claim 1, wherein the sulfur content is 0.08 mass % or more, based on the total amount of the lubricating oil composition.

6. 2. The lubricating oil composition according to claim 1, wherein the content ratio of the organic molybdenum compound (B) to the sulfur-based compound (C) [(B) / (C)] is, in mass ratio, 0.35 to 5.

00.

7. 2. The lubricating oil composition according to claim 1, wherein the content ratio of the overbased metal detergent (D) to the sulfur-based compound (C) [(D) / (C)] is 0.01 to 10 by mass.

8. 2. The lubricating oil composition according to claim 1, wherein the sulfur-based compound (C) comprises a zinc dithiophosphate (C1), and the content ratio [(Mo) / (Zn)] of the molybdenum (Mo) derived from the organomolybdenum compound (B) to the zinc (Zn) derived from the zinc dithiophosphate (C1) is 0.35 to 2.70 by mass.

9. The sulfur-containing compound (C2) is R ２ COOR １ - (S) ｘ -R １ COOR ２ (In the formula, R １ and R ２ and each independently represent a hydrocarbon group having 1 to 30 carbon atoms, and x is an integer of 2 or greater.

10. Kinematic viscosity at 100°C: 4.0 mm ２ 2. The lubricating oil composition of claim 1, wherein the viscosity of the lubricating oil composition is 100 ppm or less.

11. The lubricating oil composition according to any one of claims 1 to 10, which is used for lubricating a mechanical device in which a motor and a reducer are integrated.

12. 12. The lubricating oil composition of claim 11, wherein the mechanical system is a hydraulic system, a stationary transmission system, an automotive transmission system, or a motor and battery cooling system.

13. A mechanical device in which a motor and a reducer are integrated, which is filled with the lubricating oil composition according to any one of claims 1 to 10.

14. A method for using the lubricating oil composition according to any one of claims 1 to 10, which comprises applying the lubricating oil composition to a mechanical device in which a motor and a reducer are integrated.