Lubricating oil composition

Abstract

There has been a demand for a lubricating oil composition that can be suitably used for electric vehicles and that is superior in various performances such as cooling property and insulating property.　This lubricating oil composition contains a base oil (A), two or more surfactants (B) having an HLB different from each other, and less than 5.0 mass% of water (C) with respect to the total amount (100 mass%) of the lubricating oil composition. A weighted average of the HLBs of the surfactants (B) is more than 7.70 but not more than 9.70.

Description

lubricating oil composition

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

[0002] In recent years, there has been a strong demand for reducing carbon dioxide emissions from the perspective of protecting the global environment, and as a result, efforts have been made in the automotive field to develop fuel-saving technologies. Examples of fuel-saving automobiles include hybrid vehicles and electric vehicles, and these vehicles are expected to become increasingly popular in the future. Hybrid vehicles and electric vehicles are equipped with electric motors, generators, speed reducers, inverters, storage batteries, etc., and are driven by the power of the electric motor. Lubricating oil compositions that can be used in such electric vehicles are required to have both excellent cooling and insulating properties.

[0003] Furthermore, 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 dialkyldithiocarbamates (MoDTC), viscosity modifiers, and other lubricating oil additives in predetermined amounts, and have specific electrical conductivity and kinematic viscosity at 100°C.

[0004] Special table number 2019-529675 Special table number 2019-532151

[0005] Under these circumstances, there is a demand for lubricating oil compositions that are suitable for use in electric vehicles and that are excellent in various performances such as cooling properties and insulating properties.

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

[11] . [1] A lubricating oil composition comprising a base oil (A), two or more surfactants (B) having different HLBs, and less than 5.0 mass% of water (C), based on the total amount (100 mass%) of the lubricating oil composition, wherein the weighted average HLB of the surfactants (B) is greater than 7.70 and less than 9.70. [2] The lubricating oil composition according to [1], wherein the absolute value of X-Y is 5.00 or greater, where X is the product of the HLB of a surfactant (Bx) having an HLB equal to or greater than the weighted average and the total amount of surfactants (Bx), and Y is the product of the HLB of a surfactant (By) having an HLB less than the weighted average and the total amount of surfactants (By). [3] The lubricating oil composition according to [1] or [2], wherein the surfactant (B) comprises a nonionic surfactant. [4] The lubricating oil composition according to any one of [1] to [3], wherein the surfactant (B) comprises a surfactant (B1) having a high HLB and a surfactant (B2) having an HLB lower than that of the surfactant (B1), and wherein the HLB of the surfactant (B1) is greater than 7.0 and not greater than 20.0. [5] The lubricating oil composition according to [4], wherein the HLB of the surfactant (B2) is greater than 0 and not greater than 7.0. [6] The lubricating oil composition according to any one of [1] to [5], wherein the total content of the surfactants (B) is 0.1 to 10 mass%, based on the total amount (100 mass%) of the lubricating oil composition. [7] The lubricating oil composition according to any one of [1] to [6], wherein the content of water (C) is 3.0 mass% or less, based on the total amount (100 mass%) of the lubricating oil composition. [8] The lubricating oil composition according to any one of [1] to [7], wherein the lubricating oil composition is used for lubricating a mechanical device in which a motor and a reducer are integrated. [9] The lubricating oil composition according to [8], wherein the mechanical device is a hydraulic device, a fixed transmission, an automobile transmission, or a cooling device for a motor and a battery.

[10] A mechanical device in which a motor and a reduction gear are integrated, which is filled with the lubricating oil composition according to any one of [1] to [9].

[11] A method for using the lubricating oil composition, which comprises applying the lubricating oil composition according to any one of [1] to [9] to a mechanical device in which a motor and a reduction gear are integrated.

[0007] The lubricating oil composition of a preferred embodiment of the present invention has excellent cooling properties. The lubricating oil composition of a preferred embodiment of the present invention also has excellent insulating properties. The lubricating oil composition of a preferred embodiment of the present invention also has various other properties (e.g., water dispersibility) that are suitable for electric vehicles. Because the lubricating oil composition of a preferred embodiment of the present invention is excellent in various properties such as cooling properties and insulating properties, it can be suitably used for lubricating mechanical devices such as electric vehicle units in which a motor and a reducer are integrated.

[0008] Regarding the numerical ranges described herein, the upper and lower limits can be arbitrarily combined. For example, when a 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 herein. Furthermore, when a 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 herein. Furthermore, as a numerical range described herein, for example, "60 to 100" means a range of "60 or more (60 or more) and 100 or less (100 or less)." Furthermore, when specifying the upper and lower limits described herein, the numerical range from the lower limit to the upper limit can be specified by appropriately selecting from the respective options and combining them arbitrarily. In addition, multiple combinations of the various requirements described as preferred aspects of the present specification can be used.

[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)"), two or more surfactants (B) (hereinafter also referred to as "component (B)") having different HLBs, and less than 5.0 mass% of water (C) (hereinafter also referred to as "component (C)"), based on the total amount (100 mass%) of the lubricating oil composition, wherein the weighted average HLB of the surfactant (B) is greater than 7.70 and less than 9.70. As described above, lubricating oil compositions usable in electric vehicles are required to have both excellent cooling and insulating properties, and various studies have been conducted. In the present invention, water, which is not usually intentionally blended, is intentionally blended within a predetermined range to improve cooling properties. However, when water is blended into a lubricating oil composition mainly composed of a base oil, the water may not disperse in the lubricating oil composition, and excellent cooling properties may not be exhibited. For this reason, a surfactant is blended into the lubricating oil composition of the present invention, but the presence of the surfactant poses a problem of reduced insulating properties of the lubricating oil composition. In response to these problems, the present inventors have discovered that a lubricating oil composition containing a predetermined amount of water and two or more surfactants with different HLBs can provide a lubricating oil composition with excellent water dispersibility, cooling properties, and insulating properties in a well-balanced manner. The present invention was completed based on this finding. The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives besides component (B) 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 (C) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 98 mass% or more, and is preferably less than 100 mass%, more preferably 99.9 mass% or less, even more preferably 99.5 mass% or less.

[0011] Hereinafter, each component contained in the lubricating oil composition of one embodiment of the present invention will 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 residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and refined oils obtained by subjecting the distillates to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining.

[0013] Examples of synthetic oils include poly-α-olefins such as α-olefins, homopolymers thereof, and α-olefin copolymers (for example, α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester oils such as polyol esters, dibasic acid esters, monoesters, and phosphate esters; ether oils such as polyphenyl ethers; alkylbenzenes; alkylnaphthalenes; synthetic oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)); synthetic oils (CTL) obtained by isomerizing wax produced from coal by the Fischer-Tropsch process or the like (CTL wax (Coal To Liquids WAX)); and wax produced from biomass by the Fischer-Tropsch process or the like (BTL wax (Biomass To Liquids WAX)). Examples of suitable oils include synthetic oils (BTL) obtained by isomerizing waxes and waxes.

[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 kinematic viscosity at 100°C of the base oil (A) used in one embodiment of the present invention is 6.0 mmHg, from the viewpoint of providing a lubricating oil composition with improved cooling properties. ２ / s or less, 5.5mm２ / s or less, 5.0mm ２ / s or less, 4.5mm ２ / s or less, 4.0mm ２ / s or less, 3.5mm ２ / s or less, 3.0mm ２ / s or less, 2.5mm ２ / s or less, or 2.0 mm ２ On the other hand, from the viewpoint of obtaining a lubricating oil composition having good oil film retention and improved component protection by enhancing lubricating performance, the kinematic viscosity of the base oil (A) at 100°C is preferably 0.8 mm / s or less. ２ / s or more, 0.9 mm ２ / s or more, or 1.0 mm ２ The kinematic viscosity at 40°C of the base oil (A) used in one embodiment of the present invention is preferably 10 mm / s or more, from the viewpoint of providing a lubricating oil composition with improved cooling properties. ２ / s or less, 9.0mm ２ / s or less, 8.0mm ２ / s or less, 7.0mm ２ / s or less, 6.0mm ２ / s or less, 5.0mm ２ / s or less, 4.0mm ２ / s or less, 3.0mm ２ / s or less, or 2.5 mm ２ On the other hand, from the viewpoint of obtaining a lubricating oil composition having good oil film retention and improved component protection by enhancing lubricating performance, the kinematic viscosity of the base oil (A) at 40°C is preferably 1.4 mm / s or less. ２ / s or more, 1.6mm ２ / s or more, or 1.8 mm ２ / s or more is preferable.

[0016] The viscosity index of the base oil (A) used in one embodiment of the present invention is set appropriately 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 combining two or more base oils is used as component (A), the kinematic viscosity and viscosity index of the mixed oil are preferably within the above-mentioned ranges. Therefore, the mixed oil may be prepared by combining a low-viscosity base oil and a high-viscosity base oil so that the mixed oil has a kinematic viscosity and viscosity index within the above-mentioned ranges. The mixed oil may be a mixed oil combining two or more base oils whose kinematic viscosity and viscosity index at 100 ° C. fall within the above-mentioned ranges, or a mixed oil combining a base oil whose kinematic viscosity and viscosity index at 100 ° C. fall within the above-mentioned ranges with a base oil that does not fall within the above-mentioned ranges. It may also be a mixed oil adjusted to fall 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. do not fall 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) is preferably 80 mass % or more, more preferably 85 mass % or more, even more preferably 90 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 improved insulating properties, and is preferably 99.9 mass % or less, more preferably 99.0 mass % or less, even more preferably 98.0 mass % or less.

[0018] <Component (B): Surfactant> The lubricating oil composition of the present invention contains two or more surfactants (B) having different HLBs. This combination of surfactants allows for the addition of water, which is not typically used in lubricating oil compositions, while maintaining good water dispersibility and avoiding a decrease in insulating properties due to the addition of surfactants. In one embodiment of the present invention, the weighted average HLB of the surfactants (B) is greater than 7.70 and less than 9.70, from the viewpoint of obtaining a lubricating oil composition with improved water dispersibility and insulating properties. The weighted average may be 7.80 or more, 7.90 or more, 8.00 or more, 8.20 or more, 8.40 or more, or 8.60 or more, or may be 9.65 or less, or 9.60 or less. Here, the weighted average HLB of the surfactants (B) is the sum of the products of the HLB and the content (content ratio) of each surfactant divided by the total surfactant content (content ratio). For example, when a combination of x mass % of surfactant A having an HLB of a, y mass % of surfactant B having an HLB of b, and z mass % of surfactant C having an HLB of c is used, the weighted average of the HLBs of surfactant (B) is calculated as (a×x+b×y+c×z) / (x+y+z).

[0019] In one embodiment of the present invention, the surfactant (B) may include one or more surfactants (B1) having a high HLB and one or more surfactants (B2) having an HLB lower than that of the surfactant (B1). The HLB of the surfactant (B1) used in one embodiment of the present invention may be greater than 7.0, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.5 or more, or 10.0 or more, and may be 20.0 or less, 18.0 or less, 16.0 or less, 14.0 or less, or 13.0 or less. The HLB of the surfactant (B2) used in one embodiment of the present invention may be greater than 0, 1.0 or more, 1.5 or more, 2.0 or more, 2.5 or more, or 3.0 or more, and may be 7.0 or less, 6.8 or less, 6.4 or less, 6.2 or less, 6.0 or less, 5.5 or less, 5.0 or less, 4.5 or less, or 4.0 or less.

[0020] The total content of the surfactants (B1) used in one embodiment of the present invention may be 0.1 mass % or more, 0.5 mass % or more, 1.0 mass % or more, 1.5 mass % or more, or 2.0 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 improved water dispersibility; and may be 5.0 mass % or less, 4.0 mass % or less, or 3.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved insulating properties.

[0021] The total content of the surfactants (B2) used in one embodiment of the present invention may be 0.1 mass % or more, 0.5 mass % or more, 1.0 mass % or more, 1.5 mass % or more, or 2.0 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 improved water dispersibility; and may be 5.0 mass % or less, 4.0 mass % or less, or 3.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved insulating properties.

[0022] The total content of the surfactant (B1) and the surfactant (B2) used in one embodiment of the present invention may be 1.0 mass % or more, 1.5 mass % or more, 2.0 mass % or more, 2.5 mass % or more, or 3.0 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 improved water dispersibility; and may be 10.0 mass % or less, 7.0 mass % or less, or 5.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved insulating properties.

[0023] The total content of surfactant (B) used in one embodiment of the present invention may be 1.0 mass % or more, 1.5 mass % or more, 2.0 mass % or more, 2.5 mass % or more, or 3.0 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 improved water dispersibility; and may be 10.0 mass % or less, 7.0 mass % or less, or 5.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved insulating properties.

[0024] The content ratio (B1 / B2) of the surfactant (B1) to the surfactant (B2) used in one embodiment of the present invention may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 1.0 or more, 1.2 or more, 1.4 or more, 1.6 or more, 1.8 or more, 2.0 or more, 2.2 or more, 2.4 or more, 2.6 or more, 2.8 or more, 3.0 or more, 3.5 or more, 4.0 or more, 4.5 or more, or 5.0 or more, or may be 10 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, 4.0 or less, 3.5 or less, 3.0 or less, 2.8 or less, 2.6 or less, 2.4 or less, 2.2 or less, or 2.0 or less. Furthermore, the ratio may not be in the range of 1.0 to 1.5.

[0025] In one embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition with improved water dispersibility and insulating properties, a combination of two or more surfactants (B) far from the weighted average (i.e., a large difference in HLB) is preferred, rather than a combination of two or more surfactants (B) close to the weighted average (i.e., a small difference in HLB). In this case, surfactants (B) can be defined as surfactants (Bx) and (By) based on the weighted average of HLB. That is, surfactants (B1) and (B2) defined based on the absolute value of HLB as described above are distinguished from surfactants (Bx) and (By). For example, if the weighted average is 9.00, regardless of the numerical range of the HLB of surfactants (B1) and (B2), those with a value of 9.00 or greater are defined as surfactants (Bx), and those with a value of less than 9.00 are defined as surfactants (By).

[0026] In one embodiment of the present invention, when a surfactant having an HLB equal to or greater than the weighted average is defined as surfactant (Bx), and a surfactant having an HLB less than the weighted average is defined as surfactant (By), the product of the HLB of surfactant (Bx) and the total content of surfactant (Bx) is defined as X, and the product of the HLB of surfactant (By) and the total content of surfactant (By) is defined as Y, the absolute value of X-Y (|X-Y|) is preferably 5.00 or greater. From the viewpoint of obtaining a lubricating oil composition with improved water dispersibility and insulating properties, the absolute value of X-Y is more preferably 5.50 or greater, and even more preferably 6.00 or greater. The upper limit of the absolute value of X-Y is not particularly limited, but may be, for example, 30 or less, 25 or less, or 20 or less.

[0027] The total content of the surfactants (Bx) used in one embodiment of the present invention may be 0.1 mass % or more, 0.5 mass % or more, 1.0 mass % or more, 1.5 mass % or more, or 2.0 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 improved water dispersibility; and may be 5.0 mass % or less, 4.0 mass % or less, or 3.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved insulating properties.

[0028] The total content of the surfactants (By) used in one embodiment of the present invention may be 0.1 mass % or more, 0.5 mass % or more, 1.0 mass % or more, 1.5 mass % or more, or 2.0 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 improved water dispersibility; and may be 5.0 mass % or less, 4.0 mass % or less, or 3.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved insulating properties.

[0029] The total content of the surfactant (Bx) and the surfactant (By) used in one embodiment of the present invention may be 1.0 mass % or more, 1.5 mass % or more, 2.0 mass % or more, 2.5 mass % or more, or 3.0 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 improved water dispersibility; and may be 10.0 mass % or less, 7.0 mass % or less, or 5.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved insulating properties.

[0030] The surfactant (B) used in one embodiment of the present invention is not particularly limited and may be an ionic surfactant, a nonionic surfactant, or a combination thereof. Ionic surfactants include anionic surfactants and cationic surfactants. The surfactant (B) used in one embodiment of the present invention includes a nonionic surfactant.

[0031] Examples of anionic surfactants include polyoxyethylene alkyl ether carboxylic acids, polyoxyethylene alkyl ether phosphates, alkylbenzene sulfonic acids, α-olefin sulfonic acids, and salts thereof. Anionic surfactants may be used alone or in combination of two or more. Examples of cationic surfactants include quaternary ammonium salts such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, and alkyldimethylbenzylammonium salts. Cationic surfactants may be used alone or in combination of two or more.

[0032] Examples of nonionic surfactants include glycol, alkylene glycol, polyoxyalkylene glycol, polyoxyalkylene ether, polyoxyalkylene alkyl ether, polyoxyalkylene aryl ether, alkylphenol ethylene oxide adduct, higher alcohol ethylene oxide adduct, polyoxyalkylene fatty acid ester, glycerin, pentaerythritol or sorbitol fatty acid ester, sucrose fatty acid ester, fatty acid ester of polyoxyalkylene adduct of polyhydric alcohol, alkyl polyglycoside, fatty acid alkanolamide, etc. Nonionic surfactants may be used alone or in combination of two or more.

[0033] <Component (C): Water> The lubricating oil composition of the present invention contains less than 5.0 mass % of water (C) based on the total amount (100 mass %) of the lubricating oil composition. As mentioned above, lubricating oil compositions that can be used in electric vehicles are required to have excellent cooling properties. Therefore, in the present invention, water, which is not usually added to lubricating oil compositions, is intentionally added, and the water is dispersed in the lubricating oil composition with a surfactant (B), thereby achieving excellent cooling properties. In one embodiment of the present invention, the content of water (C) may be 0.001 mass % or more, 0.01 mass % or more, 0.05 mass % or more, 0.1 mass % or more, 0.5 mass % or more, or 1.0 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 improved cooling properties; and may be 4.5 mass % or less, 4.0 mass % or less, 3.5 mass % or less, 3.0 mass % or less, 2.5 mass % or less, or 2.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved insulating properties.

[0034] The water (C) used in one embodiment of the present invention is not particularly limited, and for example, tap water, distilled water, purified water, etc. can be used.

[0035] <Lubricating Oil Additives> The lubricating oil composition of one embodiment of the present invention may contain other lubricating oil additives besides component (B) as needed, as long as the effects of the present invention are not impaired. Examples of such lubricating oil additives include pour point depressants, viscosity index improvers, antioxidants, metal-based detergents, friction modifiers, anti-wear agents, metal deactivators, ashless dispersants, and anti-foaming agents. These lubricating oil additives may be used alone or in combination of two or more.

[0036] The content of each of the above lubricating oil additives can be adjusted as appropriate within a range that does not impair the effects of the present invention, but is typically 0.001 to 15 mass %, preferably 0.005 to 10 mass %, and more preferably 0.01 to 5 mass %, for each additive independently, based on the total amount (100 mass %) of the lubricating oil composition.

[0037] Furthermore, the lubricating oil composition of one embodiment of the present invention may have limited contents of the lubricating oil additives, and the content of each of the lubricating oil additives may be less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, less than 0.0001 mass%, or less than 0.00001 mass%, based on the total amount (100 mass%) of the lubricating oil composition. Furthermore, in the lubricating oil composition of one embodiment of the present invention, from the viewpoint of suppressing a decrease in the insulating properties of the lubricating oil composition, the content of an additive containing one or more selected from the group consisting of molybdenum atoms (Mo), zinc atoms (Zn), calcium atoms (Ca), sodium atoms (Na), and magnesium atoms (Mg) may be limited, and the content of the additive may be set to less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, less than 0.0001 mass%, or less than 0.00001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0038] [Pour Point Depressant] 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. 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.

[0039] The lubricating oil composition of one embodiment of the present invention may contain a viscosity index improver. The viscosity index improver may be used alone or in combination of two or more types. Examples of viscosity index improvers used in one embodiment of the present invention include polymers such as non-dispersant polymethacrylate, dispersant polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers), dispersant olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers).

[0040] [Antioxidant] 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. Examples of antioxidants 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.

[0041] [Metallic Detergent] The lubricating oil composition of one embodiment of the present invention may contain a metallic detergent. The metallic detergent may be used alone or in combination of two or more. Examples of the metallic detergent used in one embodiment of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. Furthermore, the metal atom constituting the metal salt is preferably a metal atom selected from alkali metals and alkaline earth metals, more preferably sodium, calcium, magnesium, or barium, and even more preferably calcium.

[0042] [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. Examples of the friction modifier and anti-wear agent 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 ester amine salts; 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.

[0043] [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. Examples of the metal deactivator used in one embodiment of the present invention include benzotriazole, triazole derivatives, benzotriazole derivatives, and thiadiazole derivatives.

[0044] [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 types. The ashless dispersant used in one embodiment of the present invention is preferably an alkenyl succinimide, and examples thereof include alkenyl succinic acid bisimide represented by the following general formula (f-1) and alkenyl succinic acid monoimide represented by the following general formula (f-2).

[0045]

[0046] 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 2500. ｆ１ , R ｆ２ and R ｆ３ Examples of the alkenyl group that can be selected as A include a polybutenyl group and a polyisobutenyl group. ｆ１ , A ｆ２ and A ｆ３ are each independently an alkylene group having 2 to 5 carbon atoms. x1 is an integer of 2 to 6. x2 is an integer of 2 to 6.

[0047] The compound represented by general formula (f-1) or (f-2) may be a modified alkenyl succinimide obtained by reacting it with one or more compounds selected from the group consisting of boron compounds, alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, and organic acids.

[0048] [Antifoaming Agent] The lubricating oil composition of one embodiment of the present invention may contain an antifoaming agent. The antifoaming agent may be used alone or in combination of two or more. Examples of the antifoaming agent used in one embodiment of the present invention include alkylsilicone-based antifoaming agents, fluorosilicone-based antifoaming agents, and fluoroalkyl ether-based antifoaming agents.

[0049] <Method for 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 that the method comprises a step of blending components (B) and (C) with component (A), and, as necessary, various additives. [Properties of lubricating oil composition] The kinematic viscosity at 100°C of the lubricating oil composition of one embodiment of the present invention is 6.0 mm ２ / s or less, 5.5mm ２ / s or less, 5.0mm ２ / s or less, 4.5mm ２ / s or less, 4.0mm ２ / s or less, 3.5mm ２ / s or less, 3.0mm ２ / s or less, 2.5mm ２ / s or less, or 2.0 mm ２ On the other hand, from the viewpoint of providing a lubricating oil composition that has good oil film retention and improves component protection by enhancing lubricating performance, the kinematic viscosity of the lubricating oil composition at 100°C is preferably 0.8 mm / s or less. ２ / s or more, 0.9 mm ２ / s or more, or 1.0 mm ２ / s or more is preferable.

[0050] The kinematic viscosity at 40°C of the lubricating oil composition of one embodiment of the present invention is 10 mm ２ / s or less, 9.0mm ２ / s or less, 8.0mm ２ / s or less, 7.0mm ２ / s or less, 6.0mm ２ / s or less, 5.0mm ２ / s or less, 4.0mm ２ / s or less, 3.0mm ２ / s or less, or 2.5 mm ２On the other hand, from the viewpoint of providing a lubricating oil composition that has good oil film retention and improves component protection by enhancing lubricating performance, the kinematic viscosity of the lubricating oil composition at 40°C is preferably 1.4 mm / s or less. ２ / s or more, 1.6mm ２ / s or more, or 1.8 mm ２ / s or more is preferable.

[0051] The viscosity index of the lubricating oil composition of one embodiment of the present invention is preferably 70 or greater, more preferably 80 or greater, even more preferably 90 or greater, and particularly preferably 100 or greater.

[0052] The volume resistivity of the lubricating oil composition of one embodiment of the present invention is preferably 1.0×10 ７ More than Ω cm, more preferably 5.0 × 10 ７ Ω cm or more, more preferably 1.0 × 10 ８ Ω cm or more, and even more preferably 2.0 × 10 ８ Ω cm or more, particularly preferably 3.0 × 10 ８ As will be described in the examples below, the volume resistivity is an index of the insulating properties of a lubricating oil composition.

[0053] [Characteristics and Uses of Lubricating Oil Composition] The present invention provides a lubricating oil composition that can achieve excellent water dispersibility, cooling properties, and insulating properties. Therefore, the lubricating oil composition of one embodiment of the present invention can be suitably used in mechanical devices in which a motor and a reduction gear are integrated, such as hydraulic devices, fixed transmissions, automotive transmissions, and motor / battery cooling devices. Therefore, the present invention also provides the following mechanical device [I] and the use of the lubricating oil composition [II]. [I] A mechanical device in which a motor and a reduction gear are integrated, which is filled with the lubricating oil composition of one embodiment of the present invention described above. [II] Use of the lubricating oil composition in which the lubricating oil composition of one embodiment of the present invention is applied to a mechanical device in which a motor and a reduction gear are integrated.

[0054] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The physical properties of the components used in the examples and comparative examples and the resulting lubricating oil compositions were measured according to the following methods.

[0055] (1) Kinematic viscosity and viscosity index: Measured and calculated in accordance with JIS K2283:2000. (2) HLB: Calculated by the Griffin method. (3) Volume resistivity: Measured in accordance with JIS C2101 under conditions of a measurement temperature of 80°C and an applied voltage of 250V. The volume resistivity is used as an index of insulating properties, and a volume resistivity of 1.0 x 10 ８ Those with a resistivity of Ω·cm or higher were judged to pass. (4) Cooling Ability According to JIS K2242, a silver rod heated to 200°C was immersed in oil controlled at 30°C, and the difference in the surface temperature of the silver rod was calculated between the start of immersion (0 seconds) and 12 seconds after the start of immersion. Those with a temperature difference of 90°C or higher were judged to pass. Note that the sample oils of Comparative Examples 1 to 11 did not meet the pass criteria for volume resistivity and water dispersibility, so cooling ability was not evaluated. (5) Water Dispersibility At room temperature, a maximum of 1 wt% of distilled water was dropped into the lubricating oil composition, stirred at approximately 100 rpm using a stirrer for 1 minute, and then allowed to stand for 5 minutes. After standing, the presence or absence of precipitation or cloudiness was visually confirmed, and those with no precipitation or cloudiness were rated "A," those with precipitation or cloudiness were rated "B," and those with water dispersibility of "A" were judged to pass.

[0056] Lubricating oil compositions were prepared by adding and mixing the components (A) to (C) and other additives shown in Tables 1 and 2 in the amounts shown in Tables 1 and 2. Details of the components used in preparing the lubricating oil compositions are as follows:

[0057] <Component (A): Base oil> - Base oil: 40°C kinematic viscosity = 2.3 mm ２ / s mineral oil (mineral oil that does not belong to any group in the API base oil category). <Component (B): Surfactant> - Surfactant (b1): glycol (nonionic surfactant having HLB = 11.1) - Surfactant (b2): polyoxyalkylene alkyl ether (nonionic surfactant having HLB = 11.7) - Surfactant (b3): ​​sorbitan sesquioleate (nonionic surfactant having HLB = 3.7) - Surfactant (b4): polyoxyethylene alkylamine (nonionic surfactant having HLB = 6.3) - Surfactant (b5): polyoxyethylene ether (nonionic surfactant having HLB = 8.8) - Surfactant (b6): polyoxyalkylene alkyl ether (nonionic surfactant having HLB = 12.7) <Component (C): Water> - Distilled water <Other Additives> - Additive mixture including metal deactivators, antiwear agents, friction modifiers, antioxidants, detergents, dispersants, and antifoaming agents.

[0058] For the lubricating oil compositions prepared in the Examples and Comparative Examples, various physical properties were measured and calculated according to the above-mentioned measurement methods. The results are shown in Table 1.

[0059] As can be seen from Table 1, the lubricating oil compositions of Examples 1 to 8, in which the weighted average HLB of the surfactant (B) was greater than 7.70 and not greater than 9.70, had excellent water dispersibility, and were also excellent in cooling and insulating properties, even when containing a certain amount of water. On the other hand, as can be seen from Table 2, the lubricating oil compositions of Comparative Examples 1 to 11, which contained 5.0 mass% or more of water (C) or in which the weighted average HLB of the surfactant (B) did not satisfy the numerical range of greater than 7.70 and not greater than 9.70, were inferior in insulating properties and water dispersibility to those of Examples 1 to 8.

Claims

1. A lubricating oil composition comprising a base oil (A), two or more surfactants (B) having different HLBs, and less than 5.0 mass% of water (C) based on the total amount (100 mass%) of the lubricating oil composition, wherein the weighted average HLB of the surfactants (B) is greater than 7.70 and not greater than 9.

70.

2. The lubricating oil composition according to claim 1, wherein X is the product of the HLB of a surfactant (Bx) having an HLB equal to or greater than the weighted average and the total content of surfactants (Bx), and Y is the product of the HLB of a surfactant (By) having an HLB less than the weighted average and the total content of surfactants (By), the absolute value of X-Y is 5.00 or greater.

3. The lubricating oil composition according to claim 1 or 2, wherein the surfactant (B) comprises a nonionic surfactant.

4. The lubricating oil composition according to any one of claims 1 to 3, wherein the surfactant (B) comprises a surfactant (B1) having a high HLB and a surfactant (B2) having an HLB lower than that of the surfactant (B1), and the HLB of the surfactant (B1) is greater than 7.0 and not greater than 20.

0.

5. The lubricating oil composition according to claim 4, wherein the HLB of the surfactant (B2) is greater than 0 and not greater than 7.

0.

6. The lubricating oil composition according to any one of claims 1 to 5, wherein the total content of the surfactant (B) is 0.1 to 10 mass % relative to the total amount (100 mass %) of the lubricating oil composition.

7. A lubricating oil composition according to any one of claims 1 to 6, wherein the content of water (C) is 3.0 mass% or less, based on the total amount (100 mass%) of the lubricating oil composition.

8. The lubricating oil composition according to any one of claims 1 to 7, which is used to lubricate a mechanical device in which a motor and a reducer are integrated.

9. The lubricating oil composition of claim 8, wherein the mechanical system is a hydraulic system, a stationary transmission, an automotive transmission, or a motor and battery cooling system.

10. A mechanical device incorporating a motor and a reducer, which is filled with the lubricating oil composition according to any one of claims 1 to 9.

11. A method for using the lubricating oil composition according to any one of claims 1 to 9, which comprises applying the lubricating oil composition to a mechanical device in which a motor and a reducer are integrated.

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