Cooling oil composition and cooling system

Abstract

Provided is a cooling oil composition. The cooling oil composition contains: a base oil containing a compound represented by formula (1); and an antioxidant containing an amine-based antioxidant.　[In formula (1), m represents an integer between 2 and 8.　R1 represents a hydrogen atom or a C1-8 alkyl group.　R2 represents a C1-6 alkylene group. The plurality of R2 moieties that are present may be the same as or different from each other.　R3 represents a hydrogen atom or a C1-8 alkyl group.]

Description

Cooling oil composition and cooling system

[0001] The present invention relates to cooling oil compositions and cooling systems.

[0002] In recent years, in the field of automobiles, efforts have been made to develop fuel-saving technologies, and hybrid vehicles and electric vehicles (hereinafter sometimes referred to as "electric vehicles"), which are vehicles with excellent fuel efficiency and environmental performance, are becoming more and more popular. Electric vehicle equipment equipped in electric vehicles requires cooling oil with excellent cooling performance.

[0003] Known examples of such cooling oils include lubricating oil compositions (cooling oil compositions) containing one or more synthetic oils selected from the group consisting of polyalkylene glycols having predetermined structural units and polyvinyl ethers having predetermined structural units (see, for example, Patent Document 1).

[0004] International Publication No. 2022 / 045050

[0005] However, conventional cooling oil compositions tend to deteriorate over time, and the cooling performance may also decrease significantly (for example, the FOM value, which will be described later, may decrease significantly).

[0006] Therefore, a main object of the present invention is to provide a cooling oil composition that can sufficiently suppress the deterioration of cooling performance.

[0007] The present inventors conducted extensive research to solve the above problems and discovered that by combining a specific base oil with a specific oxidation stabilizer, it is possible to sufficiently suppress the deterioration of the cooling performance of a cooling oil composition, which led to the completion of the present invention.

[0008] The present invention provides refrigerant oil compositions according to [1] to [3] and a refrigeration system according to [4]. [1] The refrigerant oil composition contains a base oil containing a compound represented by the following formula (1) and an antioxidant containing an amine-based antioxidant: [In formula (1), m represents an integer of 2 to 8. R １ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ２ represents an alkylene group having 1 to 6 carbon atoms. ２may be the same or different. ３ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.] [2] The cooling oil composition according to [1], wherein the antioxidant further contains a sulfur-based antioxidant. [3] The cooling oil composition according to [1] or [2], which is used for cooling equipment for electric vehicles. [4] A cooling system for cooling equipment for electric vehicles, comprising the cooling oil composition according to [1] or [2].

[0009] The present invention may also relate to the use (application) of the composition as a cooling oil or for producing a cooling oil, wherein the composition contains a compound represented by formula (1) and an amine-based antioxidant. Here, the cooling oil may be a cooling oil for electric vehicle equipment.

[0010] According to the present invention, a cooling oil composition capable of sufficiently suppressing a decrease in cooling performance is provided. Some forms of the cooling oil composition are also excellent in suppressing a decrease in volume resistivity. Furthermore, according to the present invention, a cooling system using such a cooling oil composition is provided.

[0011] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0012] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0013] In this specification, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more within the range that meets the conditions. When multiple substances corresponding to each component are present, the content of each component means the total amount of the multiple substances unless otherwise specified.

[0014] In this specification, a cooling oil composition after an ISOT test (test temperature 90°C and test time 150 hours) in accordance with JIS K2514-1:2013 may be referred to as an "aged oil." Correspondingly, a cooling oil composition before being subjected to an ISOT test (test temperature 90°C and test time 150 hours) may be referred to as a "new oil."

[0015] [Cooling oil composition] <Base oil> (Compound represented by formula (1)) A cooling oil composition of one embodiment contains a base oil containing a compound represented by formula (1). The cooling oil composition can also be referred to as a lubricating oil composition.

[0016]

[0017] In formula (1), m represents an integer of 2 to 8. １ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ２ represents an alkylene group having 1 to 6 carbon atoms. ２ may be the same or different. ３ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

[0018] R １ and R ３ When both R and R are hydrogen atoms, the compound represented by formula (1) can be called a "polyalkylene glycol." １ and R ３ When one of R is a hydrogen atom and the other is an alkyl group having 1 to 8 carbon atoms, the compound represented by formula (1) can be called a "polyalkylene glycol monoalkyl ether." １ and R ３ and (iii) are alkyl groups having 1 to 8 carbon atoms, the compound represented by formula (1) can be called a "polyalkylene glycol dialkyl ether." The compound represented by formula (1) is preferably a polyalkylene glycol dialkyl ether.

[0019] m is preferably 2 to 6, more preferably 2 to 4, and even more preferably 3, as this provides better cooling performance.

[0020] R１ The alkyl group represented by the formula (I) may be a linear alkyl group, a branched alkyl group, or a cyclic alkyl group. The number of carbon atoms in the alkyl group is preferably 1 to 4, more preferably 1 or 2, and even more preferably 1, in order to provide better cooling performance.

[0021] Examples of the alkyl group include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-hexyl, and n-octyl; branched alkyl groups such as isopropyl, isobutyl, sec-butyl, tert-butyl, and 2-ethylhexyl; and cyclic alkyl groups such as cyclopentyl and cyclohexyl. Among these, the alkyl group is preferably a methyl group, an ethyl group, or an isopropyl group, more preferably a methyl group, because these groups have better cooling performance.

[0022] R ２ The alkylene group represented by the formula (I) may be either a linear alkylene group or a branched alkylene group. The number of carbon atoms in the alkylene group is preferably 2 to 4, more preferably 2 or 3, and even more preferably 2, in order to provide better cooling performance.

[0023] Examples of the alkylene group include a methylene group, an ethylene group, a linear or branched propylene group, a linear or branched butylene group, a linear or branched pentylene group, and a linear or branched hexylene group. Among these, the alkylene group is preferably an ethylene group or a propylene group, more preferably an ethylene group, because it has better cooling performance.

[0024] R ３ The alkyl group represented by R １ Examples of the alkyl group include those similar to those represented by the following alkyl groups: ３ The alkyl group represented by the formula (I) is preferably a methyl group, an ethyl group, or an isopropyl group, more preferably a methyl group, since these groups have better cooling performance.

[0025] The molecular weight of the compound represented by formula (1) is preferably 120 or more, more preferably 140 or more, and even more preferably 160 or more, from the viewpoint of superior safety, and is preferably 400 or less, more preferably 300 or less, and even more preferably 250 or less, from the viewpoint of superior cooling properties. When the molecular weight of the compound represented by formula (1) is 120 or more, the flash point becomes sufficiently high and safety tends to be superior. When the molecular weight of the compound represented by formula (1) is 400 or less, excessive viscosity can be prevented, and cooling performance tends to be superior.

[0026] Specific examples of polyalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, and hexapropylene glycol.

[0027] Examples of polyalkylene glycol monoalkyl ethers include diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopentyl ether, dipropylene glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, triethylene glycol monopentyl ether, triethylene glycol monohexyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monopropyl ether, tetraethylene glycol monobutyl ether, tetraethylene glycol monopentyl ether, and tetraethylene glycol monohexyl ether.

[0028] Specific examples of polyalkylene glycol dialkyl ethers include diethylene glycol dimethyl ether (diglyme), diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, diethylene glycol dipentyl ether, diethylene glycol dihexyl ether, dipropylene glycol dimethyl ether, dipropylene glycol dipropyl ether, dipropylene glycol dibutyl ether, dipropylene glycol dipentyl ether, dipropylene glycol dihexyl ether, triethylene glycol dimethyl ether (triglyme), tetraethylene glycol dimethyl ether (tetraglyme), tetraethylene glycol dipropyl ether, tetraethylene glycol dibutyl ether, tetraethylene glycol dipentyl ether, and tetraethylene glycol dihexyl ether.

[0029] The polyalkylene glycol, polyalkylene glycol monoalkyl ether, and polyalkylene glycol dialkyl ether may be, for example, commercially available products.

[0030] The content of the compound represented by formula (1) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the total amount of the base oil. The content of the compound represented by formula (1) may be 100% by mass or less, based on the total amount of the base oil. The content of the compound represented by formula (1) may be 100% by mass, based on the total amount of the base oil. That is, the base oil may consist of the compound represented by formula (1).

[0031] (Base oil other than the compound represented by formula (1)) The base oil may contain a base oil other than the compound represented by formula (1) (hereinafter, may be referred to as "other base oil"). Examples of other base oils include mineral oils and synthetic oils.

[0032] Examples of mineral oils include paraffinic base oils and naphthenic base oils obtained by subjecting lubricating oil fractions obtained by atmospheric or vacuum distillation of crude oil to one or more suitable combinations of refining methods, such as solvent deasphalting, solvent extraction, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment. Mineral oils classified as Group II and Group III of the API base oil classification are usually produced via a hydrorefining process. Other examples of mineral oils include wax isomerized base oils and base oils produced by isomerizing GTL wax (gas-to-liquid wax).

[0033] Examples of synthetic oils include poly-α-olefins, various esters, various ethers, alkylbenzenes, alkylnaphthalenes, fluorine-containing compounds, silicone oils, and derivatives thereof.

[0034] The content of the other base oil is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the total amount of base oil. The content of the other base oil may be 0% by mass or more, based on the total amount of base oil. The content of the other base oil may be 0% by mass, based on the total amount of base oil.

[0035] From the viewpoint of safety, the flash point of the base oil (or the compound represented by formula (1)) is preferably 85°C or higher, more preferably 90°C or higher, even more preferably 95°C or higher, and particularly preferably 100°C or higher. The flash point of the base oil may be, for example, 200°C or lower. In this specification, the flash points of the base oil and the cooling oil composition refer to values ​​measured by the Cleveland Open Chamber method (COC method) in accordance with JIS K 2265-4:2007.

[0036] The kinematic viscosity of the base oil (or the compound represented by formula (1)) at 25°C is preferably 10.00 mm because it provides better cooling performance. ２ / s or less, more preferably 8.00 mm ２ / s or less, more preferably 6.00 mm ２ / s or less, particularly preferably 5.00 mm ２ / s or less, most preferably 4.00 mm ２ The kinematic viscosity of the base oil at 25°C is, for example, 1.00 mm ２ / s or more or 1.50 mm ２ In this specification, the kinematic viscosity at 25°C of the base oil and the cooling oil composition refers to a value measured in accordance with JIS K2283:2000.

[0037] The kinematic viscosity of the base oil (or the compound represented by formula (1)) at 40°C is preferably 4.00 mmHg, as this provides better cooling performance. ２ / s or less, more preferably 3.50 mm ２ / s or less, more preferably 3.00 mm ２ / s or less, particularly preferably 2.50 mm ２ / s or less, most preferably 2.00 mm ２ The kinematic viscosity of the base oil at 40°C is, for example, 1.00 mm ２ / s or more or 1.20 mm ２ In this specification, the kinematic viscosity at 40°C of the base oil and the cooling oil composition refers to a value measured in accordance with JIS K2283:2000.

[0038] The absolute viscosity of the base oil (or the compound represented by formula (1)) at 25°C is preferably 4.00 mPa·s or less, more preferably 3.50 mPa·s or less, even more preferably 3.00 mPa·s or less, particularly preferably 2.50 mPa·s or less, and most preferably 2.00 mPa·s or less, because this provides better cooling performance. The absolute viscosity of the base oil at 25°C may be, for example, 1.00 mPa·s or more or 1.20 mPa·s or more. In this specification, the absolute viscosity of the base oil and the cooling oil composition at 25°C is referred to as the kinematic viscosity (mm ２ / s) and density at 25°C (g / cm ３ ) and the value calculated by multiplying it by 1.

[0039] The thermal conductivity of the base oil (or the compound represented by formula (1)) at 25 ° C. is preferably 0.135 W / (m K) or more, more preferably 0.140 W / (m K) or more, even more preferably 0.145 W / (m K) or more, particularly preferably 0.150 W / (m K) or more, and most preferably 0.155 W / (m K) or more, since this provides better cooling performance. The thermal conductivity of the base oil at 25 ° C. may be, for example, 0.190 W / (m K) or less. In this specification, the thermal conductivity of the base oil and the cooling oil composition at 25 ° C. refers to the value measured in accordance with ASTM D 7984 using an electrical conductivity meter (for example, TRIDENT (manufactured by C-THERM Technology)).

[0040] The density of the base oil (or the compound represented by formula (1)) at 25°C is preferably 0.85 g / cm3 because this provides better cooling performance. ３ More preferably, 0.87 g / cm ３ More preferably, 0.90 g / cm ３ More preferably, 0.92 g / cm ３ or more, most preferably 0.95 g / cm ３ The density of the base oil at 25°C is, for example, 1.20 g / cm ３ In this specification, the densities of the base oil and the cooling oil composition at 25°C refer to values ​​measured in accordance with JIS K 2249-1:2011.

[0041] The specific heat at 25 ° C. of the base oil (or the compound represented by formula (1)) is preferably 1.60 J / (g K) or more, more preferably 1.70 J / (g K) or more, even more preferably 1.75 J / (g K) or more, particularly preferably 1.80 J / (g K) or more, and most preferably 1.85 J / (g K) or more, because the cooling performance is better. The specific heat at 25 ° C. of the base oil may be, for example, 2.20 J / (g K) or less. In this specification, the specific heat at 25 ° C. of the base oil and cooling oil composition means the value calculated according to the following formula using the measured values ​​of thermal conductivity and thermal effusivity measured by an electrical conductivity meter (for example, TRIDENT (manufactured by C-THERM Technology)), as well as the measured values ​​of the density. (Specific heat at 25°C [J / (g K)]) = (Thermal effusivity at 25°C [J / (m ２ ・s １／２ ・K)]) ２ / {(thermal conductivity at 25°C [W / (m·K)]) × (density at 25°C [g / cm ３ ])

[0042] The volume resistivity at 25°C of the base oil (or the compound represented by formula (1)) is preferably 1.0 x 10 because it provides better electrical insulation. ５ Ω·m or more, more preferably 1.0×10 ６ Ω·m or more, more preferably 1.0×10 ７ Ω·m or more, particularly preferably 1.0×10 ８ The volume resistivity of the base oil at 25°C is, for example, 1.0 × 10 １０ In this specification, the volume resistivity at 25°C of the base oil and the cooling oil composition refers to a value measured in accordance with JIS C2101:1999 at a measurement temperature of 25°C and an applied voltage of 250V.

[0043] The pour point of the base oil (or the compound represented by formula (1)) is preferably −20° C. or lower, more preferably −30° C. or lower, even more preferably −40° C. or lower, and particularly preferably −45° C. or lower, because this provides better handleability at low temperatures. In this specification, the pour points of the base oil and the cooling oil composition refer to values ​​measured in accordance with JIS K 2269:1987.

[0044] The FOM (Figure of Merit) of the base oil (or the compound represented by formula (1)) is preferably 0.010 or more, more preferably 0.020 or more, even more preferably 0.030 or more, particularly preferably 0.035 or more, and most preferably 0.040 or more, because this provides better cooling performance. In this specification, the FOM of the base oil and the cooling oil composition refers to a value calculated according to the following formula based on Annual Review of Heat Transfer 2012, 15, 93-129: FOM={(density at 25°C [g / cm ３ ]) ２ × (thermal conductivity at 25 ° C [W / (m K)]) １．８ × (specific heat at 25 ° C [J / (g K)]) １．６} / (Absolute viscosity at 25°C [mPa s]) １．４

[0045] The content of the base oil is preferably 90 mass % or more, more preferably 95 mass % or more, even more preferably 98 mass % or more, and particularly preferably 99 mass % or more, based on the total amount of the cooling oil composition.

[0046] <Antioxidant> (Amine-based antioxidant) The cooling oil composition of one embodiment contains an antioxidant including an amine-based antioxidant. By combining such an oxidation stabilizer with the base oil, it is possible to sufficiently suppress a decrease in the cooling performance of the cooling oil composition.

[0047] The amine-based antioxidant is not particularly limited, and additives commonly used in the field of lubricating oils can be used. Examples of the amine-based antioxidant include diphenylamine compounds (e.g., alkylated diphenylamines), naphthylamine compounds (e.g., alkylated phenyl-α-naphthylamines), and the like.

[0048] Other examples of amine-based antioxidants include hindered amine-based compounds known as hindered amine light stabilizers (HALS).

[0049] The amine-based antioxidant is preferably a diphenylamine-based compound because it has superior cooling performance.

[0050] The content of the amine-based antioxidant is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on the total amount of the antioxidants. The content of the amine-based antioxidant may be 100% by mass or less, based on the total amount of the antioxidants.

[0051] (Antioxidants other than amine-based antioxidants) The antioxidant may contain antioxidants other than amine-based antioxidants (hereinafter, may be referred to as "other antioxidants"). Examples of other antioxidants include phenol-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0052] Examples of phenolic antioxidants include monophenolic antioxidants such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol (DBPC), 2,6-di-tert-butyl-4-ethylphenol, isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; and diphenolic antioxidants such as 4,4'-methylenebis(2,6-di-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol).

[0053] Examples of sulfur-based antioxidants include sulfurized esters. Sulfurized esters are a group of compounds obtained by crosslinking, with sulfur atoms, alkyl esters of 1 to 4 carbon atoms of unsaturated fatty acids (e.g., oleic acid, linoleic acid, etc.) having 14 to 20 carbon atoms and at least one unsaturated bond in the molecule. Examples of alkyl esters of unsaturated fatty acids include methyl oleate, ethyl oleate, propyl oleate, methyl linoleate, ethyl linoleate, and propyl linoleate. That is, examples of sulfurized esters include sulfurized methyl oleate, sulfurized ethyl oleate, sulfurized propyl oleate, sulfurized methyl linoleate, sulfurized ethyl linoleate, and sulfurized propyl linoleate. The sulfurized ester is preferably sulfurized methyl oleate.

[0054] Other examples of sulfur-based antioxidants include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, pentaerythrityl tetrakis(3-laurylthiopropionate), and the like.

[0055] By combining an amine-based antioxidant and a sulfur-based antioxidant, the volume resistivity tends to be improved and electrical insulation properties tend to be more excellent.

[0056] Examples of phosphorus-based antioxidants include trioctyl phosphite, trilauryl phosphite, tridecyl phosphite, tris(nonylphenyl)phosphite, distearyl pentaerythritol diphosphite, and tetra(tridecyl)-1,1,3-tris(2-methyl-5-tert-butyl-4-hydroxyphenyl)butane diphosphite.

[0057] The content of the other antioxidants is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less, based on the total amount of the antioxidants. The content of the other antioxidants may be 0% by mass or more, based on the total amount of the antioxidants.

[0058] The content of the antioxidant is preferably 0.01 mass% or more, more preferably 0.03 mass% or more, and even more preferably 0.05 mass% or more, based on the total amount of the cooling oil composition, and is preferably 3 mass% or less, more preferably 1 mass% or less, and even more preferably 0.5 mass% or less.

[0059] <Additives> The cooling oil composition of this embodiment may further contain additives other than the antioxidant, such as antiwear agents, viscosity modifiers, rust inhibitors, metal deactivators, antifoaming agents, dispersants, friction modifiers, etc., as necessary, to the extent that the effects of the present invention are not impaired. The content of the additives is preferably 0 to 20 mass%, more preferably 0 to 15 mass%, even more preferably 0 to 10 mass%, and particularly preferably 0 to 5 mass%, based on the total amount of the cooling oil composition.

[0060] Examples of the anti-wear agent include known phosphorus-based, sulfur-based, or phosphorus-sulfur-based anti-wear agents such as phosphites, thiophosphites, dithiophosphites, trithiophosphites, phosphate esters, thiophosphates, dithiophosphates, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, thiadiazole compounds, sulfurized oils and fats, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl (poly)sulfides, alkylthiocarbamoyl compounds, thiocarbamate compounds, thioterpene compounds, dialkylthiodipropionate compounds, sulfurized mineral oil, and zinc dithiocarbamate.

[0061] Examples of viscosity modifiers include polymethacrylate, dispersion-type polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers), dispersion-type olefin copolymers, and styrene copolymers (e.g., styrene-butadiene copolymers, styrene-isoprene copolymers).

[0062] Examples of the rust inhibitor include fatty acids, alkenyl succinic acid half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amides, oxidized paraffins, and alkyl polyoxyethylene ethers.

[0063] Examples of metal deactivators include benzotriazole, triazole derivatives, benzotriazole derivatives, and thiadiazole derivatives.

[0064] Examples of the antifoaming agent include silicone compounds such as dimethylpolysiloxane, and polyacrylates.

[0065] Examples of dispersants include succinimide compounds, boron-based imide compounds, and acid amide compounds.

[0066] Examples of friction modifiers include ashless friction modifiers such as ester-based, amine-based, amide-based and glycol-based friction modifiers, and metal-based friction modifiers such as molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP).

[0067] <Cooling Oil Composition> The cooling oil composition can be obtained by mixing a base oil containing the compound represented by formula (1), an antioxidant containing an amine-based antioxidant, and additives that are added as needed.

[0068] The kinematic viscosity of the cooling oil composition (new oil) at 25°C is preferably 10.00 mmHg, as this provides better cooling performance. ２ / s or less, more preferably 8.00 mm ２ / s or less, more preferably 6.00 mm ２ / s or less, particularly preferably 5.00 mm ２ / s or less, most preferably 4.00 mm ２ The kinematic viscosity of the cooling oil composition (new oil) at 25°C is, for example, 1.00 mm ２ / s or more or 1.50 mm ２ / s or more.

[0069] The kinematic viscosity of the cooling oil composition (new oil) at 40°C is preferably 4.00 mmHg, as this provides better cooling performance. ２ / s or less, more preferably 3.50 mm ２ / s or less, more preferably 3.00 mm ２ / s or less, particularly preferably 2.50 mm ２ / s or less, most preferably 2.00 mm ２The kinematic viscosity of the cooling oil composition (new oil) at 40°C is, for example, 1.00 mm ２ / s or more or 1.20 mm ２ / s or more.

[0070] The density of the cooling oil composition (new oil) at 25°C is preferably 0.85 g / cm3 because this provides better cooling performance. ３ More preferably, 0.87 g / cm ３ More preferably, 0.90 g / cm ３ More preferably, 0.92 g / cm ３ or more, most preferably 0.95 g / cm ３ The density of the cooling oil composition (new oil) at 25°C is, for example, 1.20 g / cm ３ It may be the following:

[0071] The acid value of the refrigerant oil composition (new oil) is preferably 0.20 mgKOH / g or less, more preferably 0.10 mgKOH / g or less, and even more preferably 0.05 mgKOH / g or less. The acid value of the refrigerant oil composition (new oil) may be, for example, 0.001 mgKOH / g or more. In this specification, the acid value of the refrigerant oil composition means the value measured in accordance with JIS K2501:2003 (indicator method).

[0072] The acid value of the cooling oil composition (degraded oil) after an ISOT test (test temperature 90°C, test time 150 hours) in accordance with JIS K2514-1:2013 is preferably 3.00 mgKOH / g or less, more preferably 2.00 mgKOH / g or less, and even more preferably 1.00 mgKOH / g or less. The acid value of the cooling oil composition (degraded oil) may be, for example, 0.001 mgKOH / g or more.

[0073] The water concentration of the cooling oil composition (new oil) is preferably 15,000 ppm or less, more preferably 10,000 ppm or less, and even more preferably 5,000 ppm or less. The water concentration of the cooling oil composition (new oil) may be, for example, 100 ppm or more. In this specification, the water concentration of the cooling oil composition means the value measured in accordance with JIS K2275-3:2015 (Karl Fischer coulometric titration method).

[0074] The volume resistivity of the cooling oil composition (new oil) at 25°C is preferably 1.0 x 10 because it has better electrical insulation properties. ５ Ω·m or more, more preferably 1.0×10 ６ Ω·m or more, more preferably 1.0×10 ７ The volume resistivity of the base oil at 25°C is, for example, 1.0 × 10 １０ It may be Ω·m or less.

[0075] The volume resistivity at 25°C of the cooling oil composition (deteriorated oil) after the ISOT test (test temperature 90°C and test time 150 hours) in accordance with JIS K2514-1:2013 is preferably 1.0 × 10 because it has better electrical insulation properties. ５ Ω·m or more, more preferably 4.0×10 ５ Ω·m or more, more preferably 7.0×10 ５ Ω·m or more, particularly preferably 1.0×10 ６ Ω·m or more, most preferably 2.0×10 ６ The volume resistivity of the cooling oil composition (deteriorated oil) at 25°C is, for example, 1.0 × 10 ７ It may be Ω·m or less.

[0076] The thermal conductivity of the cooling oil composition (new oil) at 25°C is preferably 0.135 W / (m·K) or more, more preferably 0.140 W / (m·K) or more, even more preferably 0.145 W / (m·K) or more, particularly preferably 0.150 W / (m·K) or more, and most preferably 0.155 W / (m·K) or more, because this provides better cooling performance. The thermal conductivity of the cooling oil composition (new oil) at 25°C may, for example, be 0.190 W / (m·K) or less.

[0077] The specific heat of the cooling oil composition (new oil) at 25°C is preferably 1.60 J / (g·K) or more, more preferably 1.70 J / (g·K) or more, even more preferably 1.75 J / (g·K) or more, particularly preferably 1.80 J / (g·K) or more, and most preferably 1.85 J / (g·K) or more, because this provides better cooling performance. The specific heat of the cooling oil composition (new oil) at 25°C may be, for example, 2.20 J / (g·K) or less.

[0078] The absolute viscosity of the cooling oil composition (new oil) at 25°C is preferably 4.00 mPa s or less, more preferably 3.50 mPa s or less, even more preferably 3.00 mPa s or less, particularly preferably 2.50 mPa s or less, and most preferably 2.30 mPa s or less, because this provides better cooling performance. The absolute viscosity of the cooling oil composition (new oil) at 25°C may be, for example, 1.00 mPa s or more or 1.20 mPa s or more.

[0079] The FOM of the cooling oil composition (new oil) is preferably 0.010 or more, more preferably 0.020 or more, even more preferably 0.030 or more, particularly preferably 0.035 or more, and most preferably 0.040 or more, since this provides better cooling performance.

[0080] The FOM of the cooling oil composition (degraded oil) after an ISOT test (test temperature 90°C and test time 150 hours) in accordance with JIS K2514-1:2013 is preferably 0.010 or more, more preferably 0.020 or more, even more preferably 0.030 or more, particularly preferably 0.035 or more, and most preferably 0.040 or more, because this provides better cooling performance.

[0081] The absolute value of the difference between the FOM of the refrigerant oil composition (new oil) and the FOM of the refrigerant oil composition (degraded oil) ([FOM of refrigerant oil composition (new oil)] - [FOM of refrigerant oil composition (degraded oil)]) is preferably within 0.005, more preferably within 0.004, even more preferably within 0.003, particularly preferably within 0.002 or more, and most preferably within 0.001, in order to achieve better cooling performance.

[0082] The cooling oil composition (lubricating oil composition) may be used to cool electric vehicle equipment. For example, by circulating the cooling oil composition through the electric vehicle equipment, the cooling oil composition can cool the electric vehicle equipment while lubricating the electric vehicle equipment. Here, examples of electric vehicle equipment include motors, generators, capacitors, converters, inverters, engines, and transmissions. The electric vehicle equipment is preferably at least one selected from the group consisting of motors, generators, capacitors, converters, inverters, engines, and transmissions.

[0083] The refrigerant oil composition can be obtained, for example, by a production method including a step of mixing a base oil containing the compound represented by formula (1) with an antioxidant including an amine-based antioxidant. When the refrigerant oil composition further contains additives other than the antioxidant, the production method of the refrigerant oil composition may include a step of mixing the additives. The additives may be blended by any method, and the order and method of blending are not limited.

[0084] [Cooling System] A cooling system in one embodiment is for cooling electric vehicle equipment, computers, other electronic devices, etc., and comprises the cooling oil composition described above. The electric vehicle equipment is preferably at least one selected from the group consisting of a motor, a generator, a capacitor, a converter, an inverter, an engine, and a transmission.

[0085] The cooling system includes a circulation unit through which the cooling oil composition circulates, and a cooling target unit. The cooling target unit is an electric vehicle device. The cooling method for the cooling target unit may be either a direct cooling method or an indirect cooling method, and is appropriately set depending on the cooling method required for the electric vehicle device. The cooling system may further include a supply unit that supplies the cooling oil composition to the cooling target unit via the circulation unit. The cooling system may also include a sensor unit that detects the temperature of the cooling target unit, and a control unit that controls the operation of the supply unit in accordance with the temperature detected by the sensor unit.

[0086] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0087] Examples 1 to 5 and Comparative Examples 1 to 5 [Preparation of Cooling Oil Compositions] (Preparation of Blending Components) Component (A): Base oil (A-1) Triethylene glycol dimethyl ether (triglyme) (Tokyo Chemical Industry Co., Ltd.) Component (B): Antioxidant (B-1) Amine-based antioxidant (diphenylamine-based compound, molecular weight: 320.6) (B-2) Amine-based antioxidant (naphthylamine-based compound, molecular weight: 388.6) (B-3) Amine-based antioxidant (hindered amine-based compound, molecular weight: 509.0) (B-4) Phenol-based antioxidant (2,4,6-alkylphenol, molecular weight: 220.4) (B-5) Phenol-based antioxidant (2,4,6-alkylphenol, molecular weight: 374.6) (B-6) Sulfur-based antioxidant (sulfurized methyl oleate (mixture))

[0088] (Properties of base oil) The properties of component (A) were measured as follows. The results are shown in Table 1. (1) Flash point The flash point was measured by the Cleveland Open Cylinder (COC) method in accordance with JIS K 2265-4:2007. (2) Kinematic viscosity at 25°C The kinematic viscosity at 25°C was measured in accordance with JIS K2283:2000. (3) Kinematic viscosity at 40°C The kinematic viscosity at 40°C was measured in accordance with JIS K2283:2000. (4) Absolute viscosity at 25°C The absolute viscosity at 25°C is the kinematic viscosity (mm ２ / s) and density at 25°C (g / cm ３) and calculated by the product of (5) Thermal Conductivity at 25°C The thermal conductivity at 25°C was measured in accordance with ASTM D 7984 using an electric conductivity meter (TRIDENT (manufactured by C-THERM Technology)). (6) Density at 25°C The density at 25°C was measured in accordance with JIS K 2249-1:2011. (7) Specific Heat at 25°C The specific heat at 25°C was measured using a differential scanning calorimeter in accordance with JIS K 7123:2012. (8) Volume Resistivity at 25°C The volume resistivity at 25°C was measured in accordance with JIS C2101:1999 under conditions of a measurement temperature of 25°C and an applied voltage of 250V. (9) Pour Point The pour point was measured in accordance with JIS K 2269:1987. (10) Figure of Merit (FOM) The FOM was calculated according to the following formula based on Annual Review of Heat Transfer 2012, 15, 93-129: FOM = {(density at 25°C [g / cm ３ ]) ２ × (thermal conductivity at 25 ° C [W / (m K)]) １．８ × (specific heat at 25 ° C [J / (g K)]) １．６} / (Absolute viscosity at 25°C [mPa s]) １．４

[0089]

[0090] (Preparation of Cooling Oil Compositions) Cooling oil compositions (fresh oils) of Examples 1 to 5 and Comparative Examples 1 to 5 were prepared by mixing the components shown in Table 2 in the amounts (% by mass based on the total amount of the cooling oil composition) shown in Table 2. The remainder in component (A) refers to the value (% by mass) obtained by subtracting the amount (% by mass) of component (B) from 100% by mass.

[0091] [Evaluation of Coolant Oil Composition (New Oil)] The properties of the coolant oil composition (new oil) were measured as follows. The results are shown in Table 2. (1) Viscosity at 25°C The kinematic viscosity at 25°C was measured in accordance with JIS K2283:2000. (2) Kinematic Viscosity at 40°C The kinematic viscosity at 40°C was measured in accordance with JIS K2283:2000. (3) Density at 25°C The density at 25°C was measured in accordance with JIS K 2249-1:2011. (4) Acid Number The acid number was measured in accordance with JIS K2501:2003 (indicator method). (5) Base Number The base number was measured in accordance with JIS K2501:2003 (hydrochloric acid method and perchloric acid method). (6) Water Concentration The water concentration was measured in accordance with JIS K2275-3:2015 (Karl Fischer coulometric titration method). (7) Volume Resistivity at 25°C The volume resistivity at 25°C was measured in accordance with JIS C2101:1999 under conditions of a measurement temperature of 25°C and an applied voltage of 250V. (8) Thermal Conductivity at 25°C The thermal conductivity at 25°C was measured in accordance with ASTM D 7984 using an electrical conductivity meter (TRIDENT (manufactured by C-THERM Technology)). (9) Specific Heat at 25°C The specific heat at 25°C was measured in accordance with JIS K 7123:2012 using a differential scanning calorimeter. (10) Absolute Viscosity at 25°C The absolute viscosity at 25°C is the kinematic viscosity (mm ２ / s) and density at 25°C (g / cm ３ (11) FOM (Figure of Merit) The FOM was calculated according to the following formula based on Annual Review of Heat Transfer 2012, 15, 93-129: FOM = {(density at 25°C [g / cm ３ ]) ２ × (thermal conductivity at 25 ° C [W / (m K)]) １．８ × (specific heat at 25 ° C [J / (g K)]) １．６} / (Absolute viscosity at 25°C [mPa s]) １．４

[0092] [Preparation of Cooling Oil Compositions (Deteriorated Oils)] Using the cooling oil compositions (new oils) of Examples 1 to 5 and Comparative Examples 1 to 5, an ISOT test in accordance with JIS K2514-1:2013 was carried out at a test temperature of 90°C for a test time of 150 hours, to obtain cooling oil compositions (deteriorated oils) of Examples 1 to 5 and Comparative Examples 1 to 5.

[0093] [Evaluation of Cooling Oil Compositions (Degraded Oil)] The same properties as those of the cooling oil compositions (fresh oil) were measured for the cooling oil compositions (degraded oil). Note that instead of "(6) Water Concentration", the following "(6') Water Concentration" was evaluated. In addition, the cooling oil compositions (degraded oil) were also evaluated for "(12) Pentane Insolubles" below. The results are shown in Table 2.

[0094] (6') Water Concentration The water concentration was measured by the Karl Fischer vaporization method as follows. The degraded oil was heated to 120-130°C, and the vaporized water was introduced into an electrolytic cell using nitrogen and reacted with the Karl Fischer reagent (KF reagent). Since the water in the sample reacts quantitatively with the iodine produced by the electrolysis of iodide ions in the KF reagent, the amount of water was calculated from the amount of electricity required to generate the iodine consumed until the end of the reaction, and the water concentration was determined. (12) Pentane Insolubles The pentane insolubles represent the proportion of components in the degraded oil that are not soluble in pentane (unit: mass%) and were measured in accordance with ASTM D893-12 as follows. The degraded oil, pentane, n-butylethanolamine, and 2-propanol were added to a centrifuge test tube, mixed, and the insolubles were separated using a centrifuge. The supernatant was removed. This procedure was repeated three times. Next, the test tube was dried and then weighed. The mass (g) of the insoluble matter was determined from the mass of the test tube before and after the treatment, and the proportion of the component that was insoluble in pentane was calculated.

[0095]

[0096] As shown in Table 2, the refrigerant oil compositions of Examples 1 to 5 had a smaller absolute value of the difference between the FOM of fresh oil and the FOM of degraded oil than the refrigerant oil compositions of Comparative Examples 1 to 5. Furthermore, the refrigerant oil composition of Example 2, which combined an amine-based antioxidant and a sulfur-based antioxidant, had a higher volume resistivity of degraded oil than the other refrigerant oil compositions, demonstrating that it was possible to suppress a decrease in volume resistivity. These results confirmed that the refrigerant oil composition of the present invention is capable of sufficiently suppressing a decrease in cooling performance.

Claims

1. A cooling oil composition comprising: a base oil containing a compound represented by the following formula (1); and an antioxidant containing an amine-based antioxidant: [In formula (1), m represents an integer of 2 to 8. R １ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ２ represents an alkylene group having 1 to 6 carbon atoms. ２ may be the same or different. ３ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

2. The cooling oil composition of claim 1, wherein the antioxidant further comprises a sulfur-based antioxidant.

3. The cooling oil composition according to claim 1 or 2, which is used to cool equipment for electric vehicles.

4. A cooling system for cooling an electric vehicle device, comprising the cooling oil composition according to claim 1 or 2.

Images