Lubricant composition

Abstract

To provide an excellent lubricant composition that can suitably be used for electrically driven vehicles, and is excellent in various performances such as cooling property and insulation property.SOLUTION: The lubricant composition includes base oil (A), two or more kinds of surfactant (B) each having a different HLB, and water in an amount of less than 5.0 mass% relative to the total amount (100 mass%) of the lubricant, with the weighted average of the HLB of the surfactant (B) being in a range of higher than 7.70 and 9.70 or less.SELECTED DRAWING: None

Description

[Technical Field]

[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. [Background technology]

[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. [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] 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. [Means for solving the problem]

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

[11] . [1] The lubricating oil composition comprises a base oil (A), two or more surfactants (B) having different HLB values, and less than 5.0 mass% of water (C) relative to the total amount (100 mass%) of the lubricating oil composition, A lubricating oil composition, wherein the surfactant (B) has a weighted average HLB of more than 7.70 and not more than 9.70. [2] The product of the HLB of surfactants (Bx) whose HLB is equal to or greater than the weighted average and the total content of surfactants (Bx) is X, When the product of the HLB of the surfactant (By) whose HLB is less than the weighted average and the total content of the surfactant (By) is defined as Y, The lubricating oil composition according to [1], wherein the absolute value of XY is 5.00 or more. [3] 3. The lubricating oil composition of claim 1, 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 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 surfactant (B2) has an HLB of more than 0 and not more than 7.0. [6] The lubricating oil composition according to any one of [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] The lubricating oil composition according to any one of [1] to [6], wherein the content of water (C) is 3.0 mass % or less relative to the total amount (100 mass %) of the lubricating oil composition. [8] The lubricating oil composition according to any one of [1] to [7], which 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 or battery.

[10] 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 [1] to [9].

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

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

[0008] Regarding the numerical ranges described herein, the upper and lower limits can be combined in any combination. 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. 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) to 100 or less (100 or less)." Furthermore, in defining the upper and lower limits described in this specification, the numerical range from the lower limit to the upper limit can be defined by appropriately selecting from the respective options and combining them arbitrarily. In addition, the various features described as preferred embodiments in this specification can 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)"), 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 surfactants (B) is greater than 7.70 and not greater than 9.70. As mentioned above, lubricating oil compositions that can be used in electric vehicles are required to have both excellent cooling and insulating properties, and various studies have been conducted to address this. 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 be dispersed in the lubricating oil composition, and excellent cooling properties may not be exhibited. Therefore, a surfactant is blended into the lubricating oil composition of the present invention, but the presence of the surfactant causes a problem of a decrease in the 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 HLB values ​​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 other than component (B) as needed, 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 processes 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, their homopolymers, and α-olefin copolymers (e.g., 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 synthetic oils (BTL) obtained by isomerizing wax produced from biomass by the Fischer-Tropsch process or the like (BTL wax (Biomass to Liquids Wax)).

[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, 5.5mm 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 / s or less is preferable. 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 0.8mm 2 / s or more, 0.9 mm 2 / s or more, or 1.0 mm 2 / s or more is preferable. The kinematic viscosity at 40°C of the base oil (A) used in 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 2 / s or less is preferable. 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 1.4 mm 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 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 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 as to have a kinematic viscosity and 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 outside the above-mentioned ranges. The mixed oil may also be a mixed oil obtained by combining a low-viscosity base oil whose kinematic viscosity and viscosity index at 100° C. are outside the above-mentioned ranges with a high-viscosity base oil, so that the kinematic viscosity and viscosity index 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) with different HLB values. This combination of surfactants makes it possible to maintain good water dispersibility and avoid a decrease in insulating properties due to the addition of surfactants, even when water is added, which is not usually added to lubricating oil compositions. In one embodiment of the present invention, the weighted average HLB of the surfactant (B) is greater than 7.70 and not greater 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 greater, 7.90 or greater, 8.00 or greater, 8.20 or greater, 8.40 or greater, or 8.60 or greater, or may be 9.65 or less, or 9.60 or less. Here, the weighted average HLB of surfactant (B) is the value obtained by dividing the sum of the products of the HLB and the content (content ratio) of each surfactant by the total amount of the surfactant content (content ratio). For example, when a combination of x mass% of surfactant A with an HLB of a, y mass% of surfactant B with an HLB of b, and z mass% of surfactant C with an HLB of c is used, the weighted average HLB 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 surfactant (B1)(s) having a high HLB and surfactant (B2)(s) having a lower HLB than surfactant (B1). The HLB of 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 greater, 1.5 or greater, 2.0 or greater, 2.5 or greater, or 3.0 or greater, or 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 surfactant (B1) and 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 surfactant (B1) to 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 within 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, it is preferable to use a combination of two or more surfactants (B) that are far from the weighted average (i.e., have a large difference in HLB), rather than a combination of two or more surfactants (B) that are close to the weighted average (i.e., have a small difference in HLB). In this case, surfactant (B) can be defined as surfactant (Bx) and surfactant (By) based on the weighted average of HLB. That is, surfactant (B1) and surfactant (B2) defined based on the absolute value of HLB as described above are distinguished from surfactant (Bx) and surfactant (By). For example, if the weighted average is 9.00, regardless of the numerical range of the HLB of surfactant (B1) and surfactant (B2), those having a weighted average of 9.00 or more are defined as surfactant (Bx), and those having a weighted average of less than 9.00 are defined as surfactant (By).

[0026] In one embodiment of the present invention, when a surfactant having an HLB equal to or greater than the weighted average is designated as surfactant (Bx), and a surfactant having an HLB less than the weighted average is designated as surfactant (By), the product of the HLB of surfactant (Bx) and the total content of surfactant (Bx) is designated as X, and the product of the HLB of surfactant (By) and the total content of surfactant (By) is designated as Y, the absolute value of XY (|XY|) 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 XY is more preferably 5.50 or greater, and even more preferably 6.00 or greater. The upper limit of the absolute value of XY 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. The 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. The 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] <Ingredient (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 blended into lubricating oil compositions, is intentionally blended, 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% by mass or more, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved cooling properties; and may be 4.5% by mass or less, 4.0% by mass or less, 3.5% by mass or less, 3.0% by mass or less, 2.5% by mass or less, or 2.0% by mass or less, based on the total amount (100% by 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] <Lubricant additives> The lubricating oil composition of one embodiment of the present invention may contain other lubricating oil additives besides component (B) as needed, provided that the effects of the present invention are not impaired. Examples of such lubricating oil additives include pour point depressants, viscosity index improvers, antioxidants, metal 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 order to suppress a decrease in the insulating properties of the lubricating oil composition, the lubricating oil composition of one embodiment of the present invention may have a limited content of additives 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). The content of the 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.

[0038] [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. 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 kinds. 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] [Antioxidants] The lubricating oil composition of one embodiment of the present invention may contain an antioxidant. The antioxidant may be used alone or in combination of two or more kinds. 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 detergents] 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 kinds. Examples of the metal-based detergent used in one embodiment of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. 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 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 ester 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.

[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 to improve 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 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).

[0045] [ka]

[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. R f1 , R f2 and 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 are each independently 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.

[0047] The compound represented by the general formula (f-1) or (f-2) may be a modified alkenyl succinimide that is reacted 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 agents may be used alone or in combination of two or more. Examples of the defoaming agent used in one embodiment of the present invention include alkylsilicone-based defoaming agents, fluorosilicone-based defoaming agents, and fluoroalkyl ether-based defoaming agents.

[0049] <Method of manufacturing 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 component (A) with components (B) and (C), 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 mmHg, from the viewpoint of providing a lubricating oil composition with improved cooling properties. 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 / s or less is preferable. 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 0.8mm 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 2 / s or less is preferable. 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 40°C is 1.4 mm2 / 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, 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 the 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 reducer are integrated, such as hydraulic devices, fixed transmissions, automobile transmissions, and motor / battery cooling devices. Therefore, the present invention also provides the use of the following mechanical device [I] and the following lubricating oil composition [II]. [I] A mechanical device in which a motor and a reducer are integrated, which is filled with the lubricating oil composition according to one embodiment of the present invention. [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. [Example]

[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 various 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, viscosity index Measurements and calculations were made in accordance with JIS K2283:2000. (2) HLB Calculated using the Griffin method. (3) Volume resistivity Measurements were made in accordance with JIS C2101 at a temperature of 80°C and an applied voltage of 250 V. Volume resistivity was used as an index of insulation, and a volume resistivity of 1.0 × 10 8 Those with a resistance of Ω·cm or higher were judged to pass. (4) Cooling property According to JIS K2242, a silver rod heated to 200°C was immersed in oil controlled at 30°C, and the difference in surface temperature of the silver rod was calculated between the start of immersion (0 seconds) and 12 seconds after the start of immersion. Samples with a temperature difference of 90°C or more were judged to pass. Note that the sample oils of Comparative Examples 1 to 11 were not evaluated for cooling ability because their volume resistivity and water dispersibility did not meet the pass criteria. (5) Water dispersibility Distilled water was added dropwise at a maximum of 1% by weight to the lubricating oil composition at room temperature, stirred at approximately 100 rpm for 1 minute using a stirrer, and then allowed to stand for 5 minutes. After standing, the presence or absence of precipitation or cloudiness was visually confirmed, and samples showing no precipitation or cloudiness were rated "A," while samples showing precipitation or cloudiness were rated "B." Samples with a water dispersibility of "A" were judged to pass.

[0056] Examples 1 to 8, Comparative Examples 1 to 11 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 each component used in preparing the lubricating oil compositions are as follows:

[0057] <Component (A): Base oil> ·Base oil: 40℃ kinematic viscosity = 2.3mm 2 / s mineral oils (mineral oils that do not belong to any of the API base oil category groups). <Component (B): Surfactant> Surfactant (b1): Glycol (nonionic surfactant with HLB=11.1) Surfactant (b2): Polyoxyalkylene alkyl ether (nonionic surfactant with HLB=11.7) Surfactant (b3): ​​Sorbitan sesquioleate (nonionic surfactant with HLB=3.7) Surfactant (b4): Polyoxyethylene alkylamine (nonionic surfactant with HLB=6.3) Surfactant (b5): Polyoxyethylene ether (nonionic surfactant with HLB=8.8) Surfactant (b6): Polyoxyalkylene alkyl ether (nonionic surfactant with HLB=12.7) <Ingredient (C): Water> Distilled water <Other additives> Additive mixtures including metal deactivators, antiwear agents, friction modifiers, antioxidants, detergents, dispersants, and antifoam 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. [Table 1] [Table 2]

[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 even when containing a certain amount of water, and were also excellent in cooling and insulating properties. 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 more than 7.70 and not more than 9.70, were inferior in insulating property and water dispersibility to those of Examples 1 to 8.

Claims

1. The lubricating oil composition comprises a base oil (A), two or more surfactants (B) having different HLBs, and less than 5.0 mass % of water (C) relative to the total amount (100 mass %) of the lubricating oil composition, A lubricating oil composition, wherein the weighted average HLB of the surfactant (B) is greater than 7.70 and equal to or less than 9.

70.

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

3. 3. The lubricating oil composition of claim 1, 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 surfactant (B2) has an HLB of more than 0 and not more 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. The 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 for lubricating a mechanical device in which a motor and a reducer are integrated.

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

10. 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 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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