Lubricating oil composition

Abstract

A lubricating oil composition having excellent cooling properties and insulating properties is found. The lubricating oil composition contains a base oil (A), solid particles (B) having an average primary particle diameter of 500 nm or less, and a dispersant (C), the content of the solid particles (B) being 0.1-30% by mass based on the total amount of the lubricating oil composition, and the content of the dispersant (C) being 0.1-20% by mass based on the total amount of the lubricating oil composition.

Description

Technical Field

[0001] The present invention relates to a lubricating oil composition, a method for using and a method for producing the lubricating oil composition, and a cooling device. Background Art

[0002] In recent years, from the perspective of global environmental protection, there is a strong demand for reducing CO2. Therefore, in the automotive field, efforts have been made to develop technologies for saving fuel consumption. As mainstream technologies for saving fuel consumption, there are hybrid vehicles and electric vehicles, which are expected to be rapidly popularized in the future. Hybrid vehicles and electric vehicles have electric motors and generators. When they are cooled by oil cooling, existing automatic transmission fluid (ATF) and continuously variable transmission fluid (CVTF) are mainly used as lubricating oil compositions.

[0003] These lubricating oil compositions are required to have excellent cooling properties and electrical insulation properties in order to maintain reliability of the insulation properties of electric motors over a long period of time. As such a lubricating oil composition, for example, Patent Document 1 discloses a coolant containing a base liquid and porous particles having a predetermined structure.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-113242 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Under such circumstances, a lubricating oil composition having excellent cooling properties and insulating properties is required.

[0009] Means for solving problems

[0010] The present inventors have conducted intensive studies and have found that a lubricating oil composition containing a specific amount of solid particles having an average primary particle size of 500 nm or less and a dispersant in a base oil can solve the above-mentioned problems, thereby completing the present invention.

[0011] That is, the present invention provides the following aspects [1] to

[15] .

[0012] [1] A lubricating oil composition comprising a base oil (A), solid particles (B) having an average primary particle size of 500 nm or less, and a dispersant (C), wherein the content of the solid particles (B) is 0.1 to 30% by mass based on the total amount of the lubricating oil composition, and the content of the dispersant (C) is 0.1 to 20% by mass based on the total amount of the lubricating oil composition.

[0013] [2] The lubricating oil composition according to [1], wherein the content ratio of the solid particles (B) to the dispersant (C) [(B) / (C)] is 0.05 or more and less than 3 in terms of mass ratio.

[0014] [3] The lubricating oil composition according to [1] or [2], wherein the average primary particle size of the solid particles (B) is 100 nm or less.

[0015] [4] The lubricating oil composition according to any one of claims 1 to 3, wherein the solid particles (B) are selected from SiO2, Al2O3, AlN, TiO2, ZrO2, Y2O3, WO3, Ta2O5, V2O5, Nb2O5, CeO2, B4C, Al2TiO5, BN, MoSi2, SiC, Si3N4, TiC, TiN, ZrB2, CaO, SrO, BaO, clay minerals and mixtures thereof, and thermally stable carbonates or sulfates thereof.

[0016] [5] The lubricating oil composition according to any one of [1] to [4], wherein the base oil (A) contains at least a mineral oil (A1).

[0017] [6] The lubricating oil composition according to any one of [1] to [5], wherein the base oil (A) has a kinematic viscosity of 10 mm at 40°C. 2 / s or less.

[0018] [7] The lubricating oil composition according to any one of [1] to [6], wherein the volume resistivity of the base oil (A) is 8.0×10 10 Ω·m or more.

[0019] [8] The lubricating oil composition according to any one of [1] to [7], which does not substantially contain water.

[0020] [9] The lubricating oil composition according to any one of [1] to [8], wherein the kinematic viscosity of the lubricating oil composition at 40°C is 20 mm 2 / s or less.

[0021]

[10] The lubricating oil composition according to any one of [1] to [9], wherein the volume resistivity of the lubricating oil composition is 1.0×10 8 Ω·m or more.

[0022]

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

[10] , which is used for cooling electric equipment.

[0023]

[12] The lubricating oil composition according to

[11] , wherein the electrical device is a motor, a battery, an inverter, or a generator.

[0024]

[13] A cooling device filled with the lubricating oil composition described in any one of [1] to

[12] , wherein the cooling device is used for cooling electrical equipment.

[0025]

[14] A method for using a lubricating oil composition, comprising applying the lubricating oil composition described in any one of [1] to

[12] to cool an electrical device.

[0026]

[15] A method for producing a lubricating oil composition, which is a method for producing the lubricating oil composition described in any one of [1] to

[12] , comprising the step of stirring at 10,000 rpm or more.

[0027] Effects of the Invention

[0028] The lubricating oil composition of one preferred embodiment of the present invention has excellent cooling properties and insulating properties. Therefore, the lubricating oil composition of one embodiment of the present invention can be suitably used for cooling electric equipment. DETAILED DESCRIPTION

[0029] Regarding the numerical range described in this specification, the upper limit and the lower limit can be arbitrarily combined. For example, when the numerical range is described as "preferably 30 to 100, more preferably 40 to 80", the range of "30 to 80" and the range of "40 to 100" are also included in the numerical range described in this specification. In addition, for example, 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 range of "30 to 80" and the range of "40 to 100" are also included in the numerical range described in this specification.

[0030] In addition, as a numerical range described in this specification, for example, the description of "60 to 100" means a range of "60 or more and 100 or less".

[0031] In the provisions of the upper limit and the lower limit described in the present specification, the numerical range from the lower limit to the upper limit can be defined by appropriately selecting and arbitrarily combining the various options.

[0032] Furthermore, various requirements described as preferred aspects described in this specification may be combined in plurality.

[0033] [Composition of lubricating oil composition]

[0034] One embodiment of the present invention is a lubricating oil composition comprising a base oil (A) (hereinafter also referred to as “component (A)”), solid particles (B) having an average primary particle size of 500 nm or less (hereinafter also referred to as “component (B)”), and a dispersant (C) (hereinafter also referred to as “component (C)”), wherein the content of the solid particles (B) is 0.1 to 30% by mass based on the total amount of the lubricating oil composition, and the content of the dispersant (C) is 0.1 to 20% by mass based on the total amount of the lubricating oil composition.

[0035] In the lubricating oil composition used for cooling electrical equipment, it is suitable to add a base oil (A) from the viewpoint of improving insulation. On the other hand, the lubricating oil composition formed by adding a base oil (A) is also required to improve cooling performance. The lubricating oil composition containing solid particles (B) can improve cooling performance, but a dispersant needs to be added in order to evenly disperse the solid particles (B). However, if the amount of dispersant added increases, there is a tendency for the viscosity of the lubricating oil composition to increase, and it is difficult to adjust the viscosity of the lubricating oil composition to an appropriate range while exerting excellent cooling performance.

[0036] In view of such problems, the present inventors have found that by adjusting the contents of component (B) and component (C) to predetermined ranges, a lubricating oil composition can be formed that can exhibit excellent cooling properties and insulating properties while maintaining the viscosity of the lubricating oil composition at a low level, thereby completing the present invention.

[0037] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity of 20 mm at 40°C. 2 / s or less, more preferably 19mm 2 / s or less, more preferably 18mm 2 / s or less, more preferably 17mm 2 / s or less, more preferably 16mm 2 / s or less, particularly preferably 15mm 2 / s or less.

[0038] The viscosity index of the lubricating oil composition according to one embodiment of the present invention is preferably 70 or more, more preferably 80 or more, even more preferably 90 or more, and even more preferably 100 or more.

[0039] The lubricating oil composition of one embodiment of the present invention contains substantially no water. "Contains substantially no water" means excluding lubricating oil compositions that are intentionally blended with water and mixed solvents containing water. However, the lubricating oil composition of one embodiment of the present invention does not exclude an embodiment that inevitably blends with water, and from the viewpoint of obtaining a lubricating oil composition having high insulating properties, the content of such water is preferably as small as possible.

[0040] Specifically, the content of inevitably mixed water is preferably less than 0.05 mass %, more preferably less than 0.03 mass %, further preferably less than 0.01 mass %, particularly preferably less than 0.001 mass %, based on the total amount (100 mass %) of the lubricating oil composition.

[0041] The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives in addition to the components (B) and (C).

[0042] In the lubricating oil composition of one embodiment of the present invention, the total content of components (A) and (B) is preferably 50 mass % or more, more preferably 60 mass % or more, more preferably 70 mass % or more, further preferably 80 mass % or more, particularly preferably 90 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition. It may be 100 mass % or less, 99.0 mass % or less, 98.0 mass % or less, 97.0 mass % or less, 96.0 mass % or less, or 95.0 mass % or less.

[0043] In the lubricating oil composition of one embodiment of the present invention, the total content of components (A) and (C) is preferably 50 mass % or more, more preferably 60 mass % or more, more preferably 70 mass % or more, further preferably 80 mass % or more, particularly preferably 90 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition. Alternatively, it may be 100 mass % or less, 99.5 mass % or less, or 99.0 mass % or less.

[0044] In the lubricating oil composition of one embodiment of the present invention, the total content of components (B) and (C) is preferably 0.2 mass % or more, more preferably 0.5 mass % or more, further preferably 1.0 mass % or more, even more preferably 3.0 mass % or more, even more preferably 5.0 mass % or more, even more preferably 8.0 mass % or more, and particularly preferably 10 mass % or more, and is preferably 50 mass % or less, more preferably 45 mass % or less, further preferably 40 mass % or less, further preferably 35 mass % or less, further preferably 30 mass % or less, further preferably 25 mass % or less, and particularly preferably 20 mass % or less.

[0045] Hereinafter, the details of each component contained in the lubricating oil composition according to one embodiment of the present invention will be described.

[0046] <Base oil (A)>

[0047] The base oil contained in the lubricating oil composition of one embodiment of the present invention may be a mineral oil or a synthetic oil, or a mixed oil of a mineral oil and a synthetic oil may be used.

[0048] Examples of the mineral oil include atmospheric residues obtained by subjecting crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil to atmospheric distillation; distillates obtained by subjecting these atmospheric residues to vacuum distillation; and refined oils obtained by subjecting the distillates to one or more of the refining treatments selected from solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrofining.

[0049] Examples of synthetic oils include poly-α-olefins such as α-olefins, homopolymers thereof, or α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; monoester oils such as phosphoric acid monoesters; ether oils such as polyphenylene 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)); synthetic 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.

[0050] The base oil used in one embodiment of the present invention preferably includes at least one selected from mineral oils and synthetic oils classified as Group 2 and Group 3 in the API (American Petroleum Institute) base oil category. In one embodiment of the present invention, these base oils may be used alone or in combination of two or more.

[0051] From the viewpoint of producing a lubricating oil composition having high insulating properties, the lubricating oil composition of one embodiment of the present invention preferably contains at least a mineral oil (A1). From the same viewpoint as above, the lubricating oil composition of another embodiment of the present invention preferably contains a mixed base oil of a mineral oil (A1) and one or more synthetic oils (A2) selected from naphthenic oils, polyα-olefins, aromatic oils, and ether oils, and the synthetic oil (A2) is more preferably a naphthenic oil and a polyα-olefin.

[0052] In the lubricating oil composition of another embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition having high insulating properties, it is preferred that the base oil (A) does not substantially contain a component having high polarity. Specifically, for example, it is preferred that it does not substantially contain alcohols (primary alcohols, secondary alcohols, tertiary alcohols, etc.) or ester compounds other than monoester compounds (diester compounds, triester compounds, etc.). “Does not substantially contain alcohols or ester compounds other than monoester compounds” means excluding lubricating oil compositions that intentionally contain these compounds, but does not exclude the embodiment in which they are inevitably contained. From the same viewpoint as above, the content of such alcohols or ester compounds other than monoester compounds is also preferably as small as possible.

[0053] Specifically, the content of the inevitably mixed alcohol or ester compound other than the monoester compound is preferably less than 0.05% by mass, more preferably less than 0.03% by mass, further preferably less than 0.01% by mass, and particularly preferably less than 0.001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0054] In addition, the lubricating oil composition of one embodiment of the present invention may contain a monoester compound as the base oil (A).

[0055] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition having high insulating properties, it is preferred that the base oil (A) contains substantially no vegetable oils such as soybean oil, palm oil, palm kernel oil, sunflower oil, and rapeseed oil. “Substantially containing no vegetable oil” means excluding lubricating oil compositions containing such oils intentionally, but does not exclude forms in which such oils are inevitably contained. From the same viewpoint as above, the content of such vegetable oils is preferably as small as possible.

[0056] Specifically, the content of the inevitably mixed vegetable oil is preferably less than 0.05 mass %, more preferably less than 0.03 mass %, further preferably less than 0.01 mass %, and particularly preferably less than 0.001 mass %, based on the total amount (100 mass %) of the lubricating oil composition.

[0057] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition having high insulating properties, the content of the alcohol or the ester compound other than the monoester compound is preferably 0 to 0.1 part by mass, more preferably 0 to 0.01 part by mass, and even more preferably 0 to 0.001 part by mass based on 100 parts by mass of the mineral oil (A1).

[0058] In the lubricating oil composition of another embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition having high insulating properties, the content of the alcohol or ester compound relative to 100 parts by mass of the mineral oil (A1) is preferably 0 to 0.1 parts by mass, more preferably 0 to 0.01 parts by mass, and even more preferably 0 to 0.001 parts by mass.

[0059] In the lubricating oil composition of another embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition having high insulating properties, the content of the vegetable oil relative to 100 parts by mass of the mineral oil (A1) is preferably 0 to 0.1 parts by mass, more preferably 0 to 0.01 parts by mass, and even more preferably 0 to 0.001 parts by mass.

[0060] The base oil (A) used in one embodiment of the present invention preferably has a kinematic viscosity of 10 mm at 40°C. 2 / s or less, more preferably 9.5 mm 2 / s or less, more preferably 9.0 mm 2 / s or less, particularly preferably 8.5 mm 2 / s or less, and preferably 1.0 mm 2 / s or more, more preferably 2.0 mm 2 / s or more, more preferably 2.5 mm 2 / s or more, more preferably 3.0 mm 2 / s or more. If the base oil has a kinematic viscosity of 10 mm at 40°C 2 / s or less, the viscosity of the lubricating oil composition can be kept low, and high cooling performance can be obtained, which is preferred. On the other hand, if the 40°C kinematic viscosity of the base oil is 1.0 mm 2 / s or more, the oil film is maintained, so it is preferred.

[0061] From the viewpoint of suppressing viscosity changes due to temperature changes and improving cooling properties, the viscosity index of the base oil (A) used in one embodiment of the present invention is preferably 70 or more, more preferably 80 or more, further preferably 90 or more, and further preferably 100 or more.

[0062] In this specification, kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000.

[0063] The volume resistivity of the base oil (A) used in one embodiment of the present invention is preferably 8.0×10 10 Ω·m or more, more preferably 1.0×10 11 Ω·m or more, more preferably 1.0×10 12 Ω·m or more, more preferably 5.0×10 12Ω·m or more, particularly preferably 15×10 12 Ω·m or more. If the volume resistivity of the base oil (A) is 8.0×10 10 If the volume resistivity is 0.0847 W·m or more, a lubricating oil composition with high insulating properties can be obtained. In this specification, the volume resistivity is measured under the conditions of a measurement temperature of 80° C. and an applied voltage of 250 V in accordance with JIS C2101.

[0064] In the lubricating oil composition of one embodiment of the present invention, the content of the base oil (A) is usually 55 mass % or more, preferably 60 mass % or more, more preferably 65 mass % or more, further preferably 70 mass % or more, further preferably 75 mass % or more, particularly preferably 80 mass % or more, and is preferably 99.9 mass % or less, more preferably 98 mass % or less, and further preferably 95 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

[0065] <Solid particles (B)>

[0066] The lubricating oil composition of one embodiment of the present invention contains solid particles (B) having an average primary particle size of 500 nm or less. By containing the solid particles (B), the cooling performance of the lubricating oil composition can be improved.

[0067] As solid particles (B), for example, silicon dioxide (SiO2), aluminum oxide (Al2O3), aluminum nitride (AlN), titanium oxide (TiO2), zirconium oxide (ZrO2), yttrium oxide (Y2O3), tungsten oxide (WO3), tantalum pentoxide (Ta2O5), vanadium pentoxide (V2O5), niobium pentoxide (Nb2O5), cerium oxide (CeO2), boron carbide (B4C), aluminum titanate (Al2TiO5), boron nitride (BN), molybdenum disilicide (MoSi2), silicon carbide (SiC), silicon nitride (Si3N4), titanium carbide (TiC), titanium nitride (TiN), zirconium boride (ZrB2), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO) and clay minerals can be mentioned. In addition, the solid particles (B) can be a mixture of the substances listed above, as well as a thermally stable carbonate or sulfate. Among them, as solid particles (B), silicon dioxide is particularly preferred.

[0068] In one embodiment of the present invention, these solid particles may be used alone or in combination of two or more.

[0069] The average primary particle size of the solid particles (B) used in one embodiment of the present invention is 500 nm or less, preferably 400 nm or less, more preferably 300 nm or less, further preferably 200 nm or less, particularly preferably 100 nm or less, and may be 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less, from the viewpoint of obtaining a lubricating oil composition having good dispersibility of the solid particles (B) and high cooling performance. The lower limit of the average primary particle size of the solid particles (B) is not particularly limited, and may be, for example, 1 nm or more, 3 nm or more, or 5 nm or more.

[0070] In this specification, the average primary particle size of the solid particles (B) refers to the value obtained by calculating the average of the equivalent circle diameters of 100 or more primary particles randomly selected using a scanning electron microscope (SEM). In addition, the solid particles (B) may or may not form secondary particles.

[0071] The solid particles (B) used in one embodiment of the present invention may be solid particles that have been surface treated with a surface treatment agent or may be solid particles that have not been surface treated. By using solid particles that have been surface treated, the dispersibility of the solid particles is further improved, and a lubricating oil composition with high cooling performance can be obtained. Examples of the surface treatment agent include silane coupling agents and silicone oils.

[0072] Examples of the silane coupling agent include vinyl trimethoxysilane, vinyl triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-glycidoxypropyl methyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyl diethoxysilane, 3-glycidoxypropyl triethoxysilane, p-phenylenediyl trimethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyl diethoxysilane, 3-methacryloxypropyl triethoxysilane, 3-acryloxypropyl Oxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and 3-trimethoxysilylpropylsuccinic anhydride.

[0073] Examples of the silicone oil include so-called straight silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane; and so-called modified silicone oils such as polyether-modified polysiloxane, amino-modified polysiloxane, epoxy-modified polysiloxane, polyether-modified polysiloxane, phenol-modified polysiloxane, carboxyl-modified polysiloxane, mercapto-modified polysiloxane, acrylic-modified polysiloxane, methacrylic-modified polysiloxane, and alkyl-modified polysiloxane.

[0074] The solid particles (B) used in one embodiment of the present invention may be porous solid particles having pores (porous) on the surface, or may be non-porous solid particles having no pores. From the viewpoint of producing a lubricating oil composition with high cooling performance, the lubricating oil composition of one embodiment of the present invention preferably uses non-porous solid particles (B).

[0075] In the lubricating oil composition of one embodiment of the present invention, the content of the solid particles (B) is 0.1 to 30% by mass based on the total amount (100% by mass) of the lubricating oil composition. From the viewpoint of obtaining a lubricating oil composition having high cooling performance, the content is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, further preferably 3.0% by mass or more, further preferably 5.0% by mass or more, and particularly preferably 10% by mass or more. From the viewpoint of improving the dispersibility of the solid particles (B), the content is preferably 25% by mass or less, more preferably 20% by mass or less, further preferably 18% by mass or less, and particularly preferably 15% by mass or less.

[0076] The content of the solid particles (B) refers to the content in terms of solid content. When surface-treated solid particles are used, the amount of the surface treatment agent is also included in the content of the solid particles (B).

[0077] <Dispersant (C)>

[0078] The lubricating oil composition of one embodiment of the present invention contains a dispersant (C). By containing the dispersant (C), the solid particles (B) can be uniformly dispersed in the lubricating oil composition, and the lubricating oil composition can be obtained with high cooling performance.

[0079] As the dispersant (C), for example, ashless dispersants such as succinimide dispersants, vinyl pyrrolidone (VP) / hexadecene copolymers, benzylamines, boron-containing benzylamines, succinates, mono- or di-carboxylic acid amides represented by fatty acids or succinic acid, etc. can be used. Among them, succinimide dispersants and VP / hexadecene copolymers are preferred.

[0080] The succinimide dispersant is preferably alkenyl succinimide, and may be a modified alkenyl succinimide obtained by reacting the alkenyl succinimide with one or more selected from boron compounds, alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, and organic acids.

[0081] In one embodiment of the present invention, these dispersants may be used alone or in combination of two or more.

[0082] In the lubricating oil composition of one embodiment of the present invention, the content of the dispersant (C) is 0.1 to 20% by mass based on the total amount (100% by mass) of the lubricating oil composition. From the viewpoint of improving the dispersibility of the solid particles, it is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, further preferably 1.5% by mass or more, and particularly preferably 2.0% by mass or more. From the viewpoint of maintaining the viscosity of the lubricating oil composition low, it is preferably 20% by mass or less, more preferably 15% by mass or less, further preferably 12% by mass or less, and further preferably 10% by mass or less.

[0083] In addition, the content of the dispersant (C) means the content calculated as solid content.

[0084] In the lubricating oil composition of one embodiment of the present invention, the content ratio [(B) / (C)] of the solid particles (B) to the dispersant (C) is 0.05 or more and less than 3 in terms of mass ratio. From the viewpoint of improving the dispersibility of the solid particles (B), it is preferably 0.06 or more, more preferably 0.07 or more, further preferably 0.08 or more, further preferably 0.09 or more, and particularly preferably 0.1 or more. From the viewpoint of improving the cooling performance and maintaining the viscosity of the lubricating oil composition low, it is preferably 3 or less, more preferably 2.5 or less, further preferably 2 or less, further preferably 1.5 or less, and particularly preferably 1 or less.

[0085] <Various additives>

[0086] The lubricating oil composition of one embodiment of the present invention may contain various additives as necessary within a range that does not impair the effects of the present invention.

[0087] Examples of such various additives include viscosity index improvers, pour point depressants, antioxidants, metal detergents, anti-wear agents, rust inhibitors, defoaming agents, extreme pressure additives, and the like.

[0088] These lubricating oil additives may be used alone or in combination of two or more.

[0089] The content of each of these various additives can be appropriately adjusted within a range that does not impair the effects of the present invention. The content of each additive independently is usually 0.001 to 15 mass %, preferably 0.005 to 10 mass %, and more preferably 0.01 to 5 mass %, based on the total amount (100 mass %) of the lubricating oil composition.

[0090] Furthermore, as the additive, a commercially available additive package containing a plurality of additives may be used.

[0091] In addition, a compound having multiple functions as the above-mentioned additives (for example, a compound having functions as an anti-wear agent and an extreme pressure additive) may also be used.

[0092] These lubricating oil additives may be used alone or in combination of two or more.

[0093] [Viscosity index improver]

[0094] The lubricating oil composition of one embodiment of the present invention may further contain a viscosity index improver. The viscosity index improver may be used alone or in combination of two or more.

[0095] Examples of the viscosity index improver used in one embodiment of the present invention include polymethacrylate, dispersed polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers), dispersed olefin copolymers, styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers), and the like.

[0096] [Pour point depressant]

[0097] The lubricating oil composition of one embodiment of the present invention may further contain a pour point depressant. The pour point depressants may be used alone or in combination of two or more.

[0098] Examples of the pour point depressant used in one embodiment of the present invention include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylates, and polyalkylstyrenes.

[0099] [Antioxidants]

[0100] The lubricating oil composition of one embodiment of the present invention may further contain an antioxidant. The antioxidant may be used alone or in combination of two or more.

[0101] As the antioxidant used in one embodiment of the present invention, for example, amine antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenol antioxidants such as 2,6-di-tert-butylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; sulfur antioxidants such as phenothiazine, dioctadecyl sulfide, 3,3'-dilauryl thiodipropionate, and 2-mercaptobenzimidazole.

[0102] [Metallic detergent]

[0103] The lubricating oil composition of one embodiment of the present invention may further contain a metallic detergent. The metallic detergent may be used alone or in combination of two or more.

[0104] As the metal detergent used in one embodiment of the present invention, metal salts such as metal sulfonates, metal salicylates and metal phenates can be cited. In addition, as the metal atom constituting the metal salt, it is preferably a metal atom selected from alkali metals and alkaline earth metals, more preferably sodium, calcium, magnesium or barium, and further preferably calcium.

[0105] [Anti-wear agent]

[0106] The lubricating oil composition of one embodiment of the present invention may further contain an anti-wear agent. The anti-wear agent may be used alone or in combination of two or more.

[0107] Examples of the anti-wear agent used in one embodiment of the present invention include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, molybdenum dithiocarbamate, molybdenum dithiophosphate, disulfides, sulfided olefins, sulfided oils and fats, sulfided esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphites, phosphates, phosphonates, and amine salts or metal salts thereof; and sulfur- and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphates, thiophosphonates, and amine salts or metal salts thereof.

[0108] [Rust inhibitor]

[0109] The lubricating oil composition of one embodiment of the present invention may further contain a rust inhibitor. The rust inhibitor may be used alone or in combination of two or more.

[0110] Examples of the rust inhibitor used in one embodiment of the present invention include fatty acids, alkenyl succinic acid half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, and alkyl polyoxyethylene ethers.

[0111] [Defoaming agent]

[0112] The composition of one embodiment of the present invention may further contain a defoaming agent. The defoaming agent may be used alone or in combination of two or more.

[0113] Examples of the defoaming agent used in one embodiment of the present invention include alkyl silicone-based defoaming agents, fluorosilicone-based defoaming agents, and fluoroalkyl ether-based defoaming agents.

[0114] [Extreme pressure additives]

[0115] The lubricating oil composition of one embodiment of the present invention may further contain an extreme pressure additive. The extreme pressure additive may be used alone or in combination of two or more.

[0116] As the extreme pressure additive used in one embodiment of the present invention, for example, there can be mentioned chlorine-based extreme pressure additives such as chlorinated paraffin, chlorinated fatty acids, and chlorinated fatty oils; sulfur-based extreme pressure additives such as sulfided olefins, sulfided lard, alkyl polysulfides, and sulfided fatty acids; phosphorus-based extreme pressure additives such as phosphates, phosphites, thiophosphates and their salts, phosphines, and tricresyl phosphate; and the like.

[0117] <Method for producing lubricating oil composition>

[0118] The method for producing a lubricating oil composition according to one embodiment of the present invention preferably includes a step of stirring a composition containing a base oil (A), solid particles (B) and a dispersant (C) at 10,000 rpm or more. This step allows the solid particles (B) to be uniformly dispersed in the lubricating oil composition. In this step, the stirring speed may be 12,000 rpm or more, 15,000 rpm or more, 17,000 rpm or more, or 20,000 rpm or more.

[0119] The method for producing a lubricating oil composition according to one embodiment of the present invention preferably further comprises the step of blending various other additives as required in addition to the above-mentioned components (A) to (C). The blending order of the components can be appropriately set.

[0120] [Properties of Lubricating Oil Composition]

[0121] The kinematic viscosity of the lubricating oil composition of one embodiment of the present invention at 100° C. is preferably 0.8 mm 2 / s or more, more preferably 1.0 mm 2 / s or more, more preferably 1.2 mm 2 / s or more, preferably 4.0 mm 2 / s or less, more preferably 3.5mm 2 / s or less, more preferably 3.0 mm 2 / s or less.

[0122] The volume resistivity of the lubricating oil composition of one embodiment of the present invention is preferably 1.0×10 8 Ω·m or more, more preferably 1.3×10 8 Ω·m or more, more preferably 1.5×10 8 Ω·m or more, more preferably 2.0×10 8 Ω·m or more, particularly preferably 2.1×10 8 Ω·m or more.

[0123] The cooling performance of the lubricating oil composition of one embodiment of the present invention is preferably 20.0°C / sec or more, more preferably 22.0°C / sec or more, further preferably 23.0°C / sec or more, and particularly preferably 25.0°C / sec or more. It should be noted that in this specification, the cooling performance refers to the value of the maximum cooling rate (°C / sec) during 12 seconds from the start of immersion when a silver bar heated to 200°C is immersed in oil controlled to 30°C in accordance with JIS K2242.

[0124] [Application of lubricating oil composition]

[0125] The lubricating oil composition of the present invention has excellent cooling and insulating properties. Therefore, the lubricating oil composition of the present invention can be suitably used for cooling electrical equipment. Examples of electrical equipment include electric motors, batteries, inverters, and engines.

[0126] Therefore, the present invention also provides the following cooling device [I] and the following method for using the lubricating oil composition [II].

[0127] [I] A cooling device filled with the lubricating oil composition according to one embodiment of the present invention, wherein the cooling device is used for cooling electric equipment.

[0128] [II] A method for using a lubricating oil composition, comprising applying the lubricating oil composition according to one embodiment of the present invention to cooling an electric device.

[0129] Example

[0130] Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. It should be noted that the various physical properties of the components used in the examples, comparative examples and reference examples and the obtained lubricating oil compositions were measured according to the following methods.

[0131] <Kinematic viscosity, viscosity index>

[0132] The measurement and calculation were performed in accordance with JIS K2283:2000.

[0133] <Cooling performance>

[0134] When a silver rod heated to 200° C. was immersed in oil controlled at 30° C., the maximum cooling rate (° C. / sec) during 12 seconds from the start of immersion was measured in accordance with JIS K2242.

[0135] <Volume resistivity>

[0136] The measurement was performed at a measurement temperature of 80° C. and an applied voltage of 250 V in accordance with JIS C2101.

[0137] Examples 1 to 5, Comparative Examples 1 to 3

[0138] Components (A) to (C) shown in Table 1 were added and mixed in the amounts shown in Table 1, and stirred at 20,000 rpm for 5 minutes using a homogenizer to prepare lubricating oil compositions. The prepared lubricating oil compositions contain substantially no water. Details of the components used in the preparation of the lubricating oil compositions are as follows.

[0139] <Base oil (A)>

[0140] Mineral oil: 40℃ kinematic viscosity = 8.2mm 2 / s, mineral oil classified as Group II in the API base oil category with a viscosity index of 103, and a volume resistivity of 18×10 12 Ω·m.

[0141] <Solid particles (B)>

[0142] SiO2: average primary particle size = 10 nm, silicon dioxide particles surface-treated with silicone oil.

[0143] <Dispersant (C)>

[0144] Succinimide (non-boron-modified alkenyl succinic acid bisimide, nitrogen atom content = 1.80 mass %)

[0145] ·Vinyl pyrrolidone (VP) / hexadecene copolymer

[0146] The various physical property values ​​of the lubricating oil compositions prepared in the examples and comparative examples were measured and calculated according to the above-mentioned measurement methods. The results are shown in Table 1. In Table 1, regarding "dispersibility", the presence or absence of precipitation after each prepared sample was left to stand for 1 week was visually confirmed, and the case where no precipitation was confirmed was evaluated as "A", and the case where precipitation was confirmed was evaluated as "F". In addition, the 40°C kinematic viscosity of the lubricating oil composition of the example measured and calculated according to the above-mentioned measurement method was 20 mm / s. 2 / s or less, and the viscosity index is 70 or more.

[0147]

Table 1

[0148]

[0149] As can be seen from Table 1, the lubricating oil compositions of Examples 1 to 5, which contain the base oil (A) and have the solid particles (B) and the dispersant (C) in the specified numerical ranges, have superior cooling properties and insulating properties compared to Comparative Examples 1 to 3, and also have good dispersibility of the solid particles (B).

Claims

1. A lubricating oil composition comprising a base oil (A), solid particles (B) having an average primary particle size of 500 nm or less, and a dispersant (C), wherein the content of the solid particles (B) is 0.1% to 30% by mass based on the total amount of the lubricating oil composition, and the content of the dispersant (C) is 0.1% to 20% by mass based on the total amount of the lubricating oil composition.

2. The lubricating oil composition according to claim 1, wherein The content ratio of the solid particles (B) to the dispersant (C), ie, (B) / (C), is 0.05 or more and less than 3 in terms of mass ratio.

3. The lubricating oil composition according to claim 1 or 2, wherein The average primary particle size of the solid particles (B) is 100 nm or less.

4. The lubricating oil composition according to any one of claims 1 to 3, wherein The solid particles (B) are selected from SiO2, Al2O3, AlN, TiO2, ZrO2, Y2O3, WO3, Ta2O5, V2O5, Nb2O5, CeO2, B4C, Al2TiO5, BN, MoSi2, SiC, Si3N4, TiC, TiN, ZrB2, CaO, SrO, BaO, clay minerals and mixtures thereof, and heat-stable carbonates or sulfates thereof.

5. The lubricating oil composition according to any one of claims 1 to 4, wherein The base oil (A) contains at least mineral oil (A1).

6. The lubricating oil composition according to any one of claims 1 to 5, wherein The kinematic viscosity of the base oil (A) at 40°C is 10 mm 2 / s or less.

7. The lubricating oil composition according to any one of claims 1 to 6, wherein The volume resistivity of base oil (A) is 8.0×10 10 Ω·m or more.

8. The lubricating oil composition according to any one of claims 1 to 7, which does not substantially contain water.

9. The lubricating oil composition according to any one of claims 1 to 8, wherein The kinematic viscosity of the lubricating oil composition at 40°C is 20 mm 2 / s or less.

10. The lubricating oil composition according to any one of claims 1 to 9, wherein The volume resistivity of the lubricating oil composition is 1.0×10 8 Ω·m or more. 11 . The lubricating oil composition according to claim 1 , which is used for cooling electric equipment.

12. The lubricating oil composition according to claim 11, wherein The electrical equipment is a motor, a battery, an inverter and a generator. 13 . A cooling device filled with the lubricating oil composition according to claim 1 , wherein the cooling device is used for cooling electric equipment.

14. A method for using a lubricating oil composition, wherein: The lubricating oil composition according to any one of claims 1 to 12 is used for cooling electric equipment. 15 . A method for producing a lubricating oil composition, comprising a step of stirring at 10,000 rpm or more.

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