Lubricant base oil

Abstract

Provided is a lubricant base oil for use in the cooling of equipment mounted in an electric vehicle, the lubricant base oil satisfying the following requirements (I) to (III): requirement (I): an average number of carbon atoms (Cav) measured using a gas chromatograph is 19.0 or less, requirement (II): a total integral intensity ratio of a CH group and a CH2 group (nonCH3) which is the ratio of integral intensity S1 of peaks derived from the CH group and the CH2 group to integral intensity S2 of a peak derived from a CH3 group [S1 / S2] is 1.75 or more in a 1H-NMR spectrum measured using an NMR apparatus, and requirement (III): a paraffin content calculated from the average number of carbon atoms (Cav), the total integral intensity ratio (nonCH3), and the average number of branches (avB) is 0.885 or more.

Description

Technical Field

[0001] The present invention relates to a lubricant base oil, and a lubricating oil composition containing the lubricant base oil.Background Art

[0002] In recent years, there has been a strong demand for carbon dioxide reduction from the viewpoint of global environment protection. For example, in the automobile field, a strong emphasis has been placed on the development of techniques for fuel efficiency, and hybrid vehicles or electric vehicles are prevailing which are automobiles excellent in fuel consumption and environmental performance. Such hybrid vehicles or electric vehicles have an electric motor, a generator, an inverter, a battery, and the like, and run through the use of the power of the electric motor.

[0003] Various pieces of equipment mounted in such electric vehicles need to be cooled because high temperatures incur reduction in efficiency or damages. Existing lubricating oil such as automatic transmission fluid (hereinafter, referred to as ATF) or continuous variable transmission fluid (hereinafter, referred to as CVTF) is typically used in the cooling of equipment, such as electric motors, generators, and batteries, mounted in electric vehicles. Since some hybrid vehicles or electric vehicles are in a format having a gear reducer, lubricating oil compositions for use in these vehicles need to have lubricity as well as cooling properties.

[0004] For example, Patent Literature 1 discloses a lubricating composition for cooling and / or insulating a cell or an electric motor in a kinetic energy recovery system (KERS) or a hybrid vehicle.Citation ListPatent Literature

[0005] Patent Literature 1: Japanese Translation of PCT International Application Publication No. 2013-522409Summary of InventionTechnical Problem

[0006] For example, lubricating oil compositions for cooling equipment mounted in electric vehicles are required to have not only cooling properties and insulation properties but various properties such as low-temperature fluidity, rubber compatibility, and handleability.

[0007] The present invention has been made in light of these circumstances, and an object of the present invention is to provide a lubricating oil composition having preferable physical properties for cooling equipment mounted in an electric vehicle.Solution to Problem

[0008] The present inventors have conducted diligent studies on lubricant base oils suitable for lubricating oil compositions for cooling equipment mounted in electric vehicles. As a result, the present inventors have gained the finding that a lubricant base oil adjusted so as to satisfy predetermined requirements is preferable for the preparation of a lubricating oil composition as described above. The present invention has been completed on the basis of the finding.

[0009] Specifically, an aspect of the present invention provides an invention described in [1] to

[17] below. [1] A lubricant base oil for use in the cooling of equipment mounted in an electric vehicle, the lubricant base oil satisfying the following requirements (I) to (III): requirement (I): an average number of carbon atoms (Cav) measured using a gas chromatograph is 19.0 or less, requirement (II): a total integral intensity ratio of a CH group and a CH 2 group (nonCH 3 ) which is the ratio of integral intensity S1 of peaks derived from the CH group and the CH 2 group to integral intensity S2 of a peak derived from a CH 3 group [S1 / S2] is 1.75 or more in a 1< H-NMR spectrum measured using an NMR apparatus, and requirement (III): a paraffin content calculated according to the following formula (i) is 0.885 or more: wherein nonCH 3 is the total integral intensity ratio of the CH group and the CH 2 group, Cav is the average number of carbon atoms, and avB represents an average number of branches and is a value calculated according to the following formula (ii) from a value of a ratio of total integral intensity (b) in a range of chemical shifts from 5.0 to 20.0 ppm and from 22.45 to 22.80 ppm derived from terminal CH 3 groups to total integral intensity (a) in a range of chemical shifts from 5.0 to 60.0 ppm [(b / (a)] in a 13< C-NMR spectrum measured using an NMR apparatus: avB = Cav × b / a − 2 . [2] The lubricant base oil according to [1] above, wherein avB in the formula (i) is 1.00 or more and 1.65 or less. [3] The lubricant base oil according to [1] or [2] above, wherein the total integral intensity ratio (nonCH 3 ) is less than 2.20. [4] The lubricant base oil according to any one of [1] to [3] above, wherein the lubricant base oil is a base oil obtained by a refining treatment of a raw oil (α) containing a bottom oil and a petroleum-derived wax. [5] The lubricant base oil according to [4] above, wherein the content ratio between the bottom oil and the wax [bottom oil / wax] in the raw oil (α) is a mass ratio of over 5 / 95 and less than 40 / 60. [6] The lubricant base oil according to [4] or [5] above, wherein the refining treatment includes at least hydroisomerization dewaxing treatment. [7] The lubricant base oil according to any one of [1] to [6] above, wherein the lubricant base oil has a kinematic viscosity at 40°C of 1.00 mm 2< / s or more and 5.00 mm 2< / s or less. [8] The lubricant base oil according to any one of [1] to [7] above, wherein the lubricant base oil has a density at 15°C of 0.750 g / cm 3< or more. [9] The lubricant base oil according to any one of [1] to [8] above, wherein the lubricant base oil has a flash point of 100°C or higher.

[10] The lubricant base oil according to any one of [1] to [9] above, wherein the lubricant base oil has a pour point of -50.0°C or lower.

[11] The lubricant base oil according to any one of [1] to

[10] , wherein the lubricant base oil has a volume resistivity of 1.0 TΩ·m or more measured under conditions of 80°C and 250 V / mm.

[12] The lubricant base oil according to any one of [1] to

[11] above, wherein the rubber swelling rate of an acrylic rubber for test, as measured by immersing the acrylic rubber for test in the lubricant base oil under conditions at 100°C for 100 hours by a rubber immersion test method in accordance with JIS K6258, is 9% or less.

[13] A lubricating oil composition for use in the cooling of equipment mounted in an electric vehicle, the lubricating oil composition comprising the lubricant base oil according to any one of [1] to

[12] above.

[14] The lubricating oil composition according to

[13] above, further comprising one or more additives for lubricating oil selected from a pour point depressant, a viscosity index improver, an antioxidant, an extreme pressure agent, a metallic detergent, an ashless dispersant, a metal deactivator, a corrosion inhibitor, a rust inhibitor, and a defoamer.

[15] The lubricating oil composition according to

[14] above, wherein the total content of the additives for lubricating oils is 5.0 mass% or less based on the total amount of the lubricating oil composition.

[16] A method for cooling equipment, comprising cooling equipment mounted in an electric vehicle using the lubricating oil composition according to any one of

[13] to

[15] above.

[17] The method for cooling equipment according to

[16] above, wherein the equipment is at least one selected from a motor, a battery, an inverter, and an engine. Advantageous Effects of Invention

[0010] The lubricant base oil according to a preferable aspect of the present invention has a low kinematic viscosity and high volume resistivity and is excellent in various properties such as low-temperature fluidity and rubber compatibility. The lubricant base oil according to a preferable aspect of the present invention therefore allows a lubricating oil composition with preferable physical properties for the cooling of equipment mounted in an electric vehicle to be prepared.Brief Description of Drawings

[0011] [Figure 1] Figure 1 shows a gas chromatogram of a lubricant base oil (1) measured on the basis of conditions described in the present examples. [Figure 2] Figure 2 shows a 1< H-NMR spectrum of the lubricant base oil (1) measured on the basis of conditions described in the present examples. [Figure 3] Figure 3 shows a 13< C-NMR spectrum of the lubricant base oil (1) measured on the basis of conditions described in the present examples. Description of Embodiments

[0012] For the numerical ranges described herein, any upper limit and lower limit can be combined. For example, in the case where "preferably 30 to 100, more preferably 40 to 80" is described as numerical ranges, the range of "30 to 80" and the range of "40 to 100" are also included in the numerical ranges disclosed in this description. Further, for example, in the case where "preferably 30 or more, more preferably 40 or more, further preferably 100 or less, more preferably 80 or less" is described as numerical ranges, the range of "30 to 80" and the range of "40 to 100" are also included in the numerical ranges disclosed in this description.

[0013] In addition, the description "60 to 100" as a numerical range disclosed in this description, for example, means the range of "60 or more (60 or over 60) and 100 or less (100 or less than 100)".[Configuration of lubricant base oil]

[0014] The lubricant base oil according to an aspect of the present invention is a lubricant base oil for use in the cooling of equipment mounted in an electric vehicle, the lubricant base oil satisfying the following requirements (I) to (III): requirement (I): an average number of carbon atoms (Cav) measured using a gas chromatograph (hereinafter, also referred to as "GC") is 19.0 or less, requirement (II): a total integral intensity ratio of a CH group and a CH 2 group (nonCH 3 ) which is the ratio of integral intensity S1 of peaks derived from the CH group and the CH 2 group to integral intensity S2 of a peak derived from a CH 3 group [S1 / S2] is 1.75 or more in a 1< H-NMR spectrum measured using an NMR apparatus, and requirement (III): a paraffin content calculated according to the following formula (i) is 0.885 or more: wherein nonCH 3 is the total integral intensity ratio of the CH group and the CH 2 group, Cav is the average number of carbon atoms, and avB represents an average number of branches and is a value calculated according to the following formula (ii) from a value of a ratio of total integral intensity (b) in a range of chemical shifts from 5.0 to 20.0 ppm and from 22.45 to 22.80 ppm derived from terminal CH 3 groups to total integral intensity (a) in a range of chemical shifts from 5.0 to 60.0 ppm [(b) / (a)] in a 13< C-NMR spectrum measured using an NMR apparatus: avB = Cav × b / a − 2 .

[0015] In this description, values of physical properties defined in the requirements (I) to (III) and values of physical properties necessary for calculating various values mean values measured and / or calculated in accordance with the methods described in Examples below.

[0016] Equipment, such as electric motors, generators, and batteries, mounted in electric vehicles need to be cooled because high temperatures incur reduction in efficiency or damages. Lubricating oil compositions for use in the cooling of various pieces of equipment mounted in such electric vehicles are required to have various properties such as cooling properties, insulation properties, low-temperature fluidity, rubber compatibility, and handleability.

[0017] The lubricant base oil according to an aspect of the present invention is preferable for cooling equipment mounted in an electric vehicle, and allows a lubricating oil composition with various properties as described above to be prepared.

[0018] More specifically, the lubricant base oil according to an aspect of the present invention improves fluidity by adjusting the average number of carbon atoms (Cav) so as to satisfy the requirement (I), and can thereby achieve a lubricant base oil that allows a lubricating oil composition with excellent cooling properties to be prepared.

[0019] The average number of carbon atoms (Cav) represents an average number of carbon atoms in components constituting the lubricant base oil. The lubricant base oil according to an aspect of the present invention achieves a lubricating oil composition with improved fluidity by adjusting the number of carbon atoms in the constituting components.

[0020] In the lubricant base oil according to an aspect of the present invention, the average number of carbon atoms (Cav) defined in the requirement (I) is 19.0 or less from the viewpoint above, but is preferably 18.5 or less, 18.0 or less, 17.5 or less, 17.0 or less, 16.8 or less, 16.6 or less, 16.5 or less, 16.4 or less, 16.2 or less, 16.0 or less, 15.8 or less, 15.6 or less, 15.5 or less, 15.4 or less, 15.2 or less, 15.0 or less, 14.9 or less, 14.8 or less, 14.7 or less, 14.6 or less, or 14.5 or less, and preferably 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.5 or more, 10.0 or more, 10.5 or more, 11.0 or more, 11.5 or more, 12.0 or more, 12.5 or more, 13.0 or more, 13.5 or more, or 14.0 or more, for more improving fluidity and achieving a lubricant base oil that allows a lubricating oil composition with much better cooling properties to be prepared, and furthermore, may be 14.2 or more, 14.4 or more, 14.6 or more, 14.8 or more, or 15.0 or more.

[0021] The lubricant base oil according to an aspect of the present invention can adjust a rubber swelling rate to a low value by adjusting the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group so as to satisfy the requirement (II), and can thereby achieve a lubricant base oil that allows a lubricating oil composition with excellent rubber compatibility to be prepared.

[0022] The total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group represents the ratio of the number of hydrogen atoms on chains except for the termini to the number of hydrogen atoms in terminal methyl groups, and is a parameter that indicates a structural state such as the number of branches or the length of a chain in components constituting the lubricant base oil.

[0023] In the lubricant base oil according to an aspect of the present invention, the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group defined in the requirement (II) is 1.75 or more from the viewpoint above, but is preferably 1.76 or more, 1.77 or more, 1.78 or more, 1.79 or more, or 1.80 or more, and furthermore, may be 1.85 or more, 1.90 or more, 1.95 or more, or 2.00 or more. The total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group is preferably 3.00 or less, 2.90 or less, 2.80 or less, 2.70 or less, 2.60 or less, 2.50 or less, 2.45 or less, 2.40 or less, 2.35 or less, 2.30 or less, 2.25 or less, 2.24 or less, 2.23 or less, 2.22 or less, 2.21 or less, less than 2.20, 2.19 or less, 2.18 or less, 2.17 or less, 2.16 or less, 2.14 or less, 2.13 or less, 2.12 or less, 2.11 or less, or 2.10 or less, for achieving a lubricant base oil that allows a lubricating oil composition with good fluidity and low-temperature fluidity to be prepared, and furthermore, may be 2.05 or less, 2.00 or less, 1.95 or less, 1.90 or less, 1.85 or less, or 1.80 or less.

[0024] The lubricant base oil according to an aspect of the present invention can adjust a pour point to a low value by adjusting the paraffin content so as to satisfy the requirement (III), and can thereby achieve a lubricant base oil that allows a lubricating oil composition with excellent low-temperature fluidity to be prepared.

[0025] The paraffin content is a value calculated according to the following formula (i):

[0026] The denominator of the right side in the formula (i) represents the total number of hydrogen atoms on the assumption that all components constituting the lubricant base oil are paraffin, and is a value calculated from the average number of carbon atoms (Cav) measured using GC.

[0027] The numerator of the right side in the formula (i) represents the number of hydrogen atoms in the components constituting the lubricant base oil, and is calculated from measurement values obtained in measurement by GC, 1< H-NMR, and 13< C-NMR. This value is obtained on the basis of the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group, the average number of carbon atoms (Cav), and an average number of branches (avB) calculated according to the formula (ii).

[0028] In short, the paraffin content represents the proportion of saturated aliphatic saturated hydrocarbons in all the components constituting the lubricant base oil. The term "paraffin" refers to a saturated aliphatic saturated hydrocarbon, and the saturated aliphatic saturated hydrocarbon is not limited by its number of carbon atoms.

[0029] In the lubricant base oil according to an aspect of the present invention, the paraffin content defined in the requirement (III) is 0.885 or more from the viewpoint above, but is preferably 0.887 or more, 0.890 or more, 0.892 or more, 0.885 or more, 0.897 or more, 0.900 or more, 0.902 or more, 0.904 or more, 0.905 or more, or 0.906 or more, for adjusting a pour point to a lower value and achieving a lubricant base oil that allows a lubricating oil composition with much better low-temperature fluidity to be prepared, and furthermore, may be 0.908 or more, 0.910 or more, 0.912 or more, 0.914 or more, 0.916 or more, 0.918 or more, 0.920 or more, 0.925 or more, or 0.930 or more. The paraffin content is preferably 0.999 or less, 0.995 or less, 0.990 or less, 0.985 or less, 0.980 or less, 0.975 or less, 0.970 or less, 0.965 or less, 0.960 or less, 0.955 or less, 0.950 or less, 0.945 or less, 0.940 or less, 0.935 or less, 0.930 or less, 0.925 or less, or 0.920 or less, for more improving fluidity and achieving a lubricant base oil that allows a lubricating oil composition with good cooling properties to be prepared, and furthermore, may be 0.918 or less, 0.916 or less, 0.914 or less, 0.912 or less, 0.910 or less, or 0.908 or less.

[0030] In the lubricant base oil according to an aspect of the present invention, the average number of branches (avB) calculated according to the formula (ii) is preferably 1.00 or more, 1.05 or more, 1.10 or more, 1.15 or more, 1.20 or more, 1.21 or more, 1.22 or more, 1.23 or more, 1.24 or more, 1.25 or more, 1.26 or more, 1.27 or more, or 1.28 or more, for adjusting a pour point to a lower value and achieving a lubricant base oil that allows a lubricating oil composition with much better low-temperature fluidity to be prepared, and furthermore, may be 1.29 or more or 1.30 or more. The average number of branches (avB) is preferably 1.65 or less, 1.60 or less, 1.55 or less, 1.50 or less, 1.45 or less, 1.42 or less, 1.40 or less, 1.38 or less, or 1.36 or less, for more improving fluidity and achieving a lubricant base oil that allows a lubricating oil composition with good cooling properties to be prepared, and furthermore, may be 1.34 or less, 1.32 or less, 1.30 or less, 1.29 or less, or 1.28 or less.[Raw oil for lubricant base oil]

[0031] The lubricant base oil according to an aspect of the present invention may be a mineral base oil composed of one or more mineral oils, may be a synthetic base oil composed of one or more synthetic oils, or may be a mixed base oil composed of one or more mineral oils and one or more synthetic oils.

[0032] Examples of the mineral oil constituting the lubricant base oil according to an aspect of the present invention include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil; distillate oils obtained by vacuum distillation of these atmospheric residual oils; and refined oils obtained by subjecting the distillate oils to one or more refining treatments such as Solvent De-Asphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining (hydrocracking).

[0033] Examples of the synthetic oils constituting the lubricant base oil according to an aspect of the present invention include poly α-olefins such as α-olefin homopolymers or α-olefin copolymers (α-olefin copolymers having 8 to 14 carbon atoms such as ethylene-α-olefin copolymer); isoparaffin; ester oils such as polyol ester, dibasic acid ester, and phosphoric acid ester; polyalkyleneglycol; ether oils such as polyphenyl ether; alkylbenzene; alkylnaphthalene; synthetic oils (GTL) obtained by hydroisomerization-dewaxing waxes (GTL waxes (Gas To Liquids WAXES)) produced from natural gas by the Fischer-Tropsch process or the like; and CTL (Coal to liquid) base oils (e.g., CTL base oils obtained by a direct liquefaction process of grinding coal, which is then mixed with a solvent, followed by direct reaction with hydrogen at a high temperature and a high pressure, and CTL base oils obtained by an indirect liquefaction process (the Fischer-Tropsch process or the like) of temporarily gasifying coal (coal gasification) and liquefying the generated gas through synthesis reaction with a separated or purified starting material).

[0034] The lubricant base oil according to an aspect of the present invention is preferably obtained by the purification of a raw oil.

[0035] Such a raw oil is preferably a raw oil containing a petroleum-derived wax, or a raw oil containing a bottom oil and a petroleum-derived wax, more preferably a raw oil containing a bottom oil and a petroleum-derived wax, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range. Alternatively, a solvent-dewaxed raw oil may be used.

[0036] The content ratios of the bottom oil and the petroleum-derived wax in the raw oil to be used in an aspect of the present invention are preferably 50 to 100 mass%, 60 to 100 mass%, 65 to 100 mass%, 70 to 100 mass%, 75 to 100 mass%, 80 to 100 mass%, 85 to 100 mass%, 90 to 100 mass%, 55 to 100 mass%, 98 to 100 mass%, or 99 to 100 mass%, based on the total amount (100 mass%) of the raw oil, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0037] In the case of using a raw oil containing a bottom oil and a petroleum-derived wax, the content ratio between the bottom oil and the wax [bottom oil / wax] in the raw oil is a mass ratio of preferably over 5 / 95, 6 / 94 or more, 7 / 93 or more, 8 / 92 or more, 9 / 91 or more, 10 / 90 or more, 12 / 88 or more, 14 / 86 or more, 15 / 85 or more, 16 / 84 or more, 18 / 82 or more, 20 / 80 or more, 22 / 78 or more, 24 / 76 or more, or 25 / 75 or more, for adjusting the lubricant base oil so as to satisfy, particularly, the requirement (I) as well as for adjusting avB in the formula (i) to the aforementioned range, and is a mass ratio of preferably less than 40 / 60, 38 / 62 or less, 36 / 64 or less, 34 / 66 or less, 32 / 68 or less, 30 / 70 or less, 28 / 72 or less, 26 / 74 or less, 25 / 75 or less, 24 / 76 or less, 22 / 78 or less, 20 / 80 or less, 19 / 81 or less, 18 / 82 or less, 17 / 83 or less, 16 / 84 or less, or 15 / 85 or less, for adjusting the lubricant base oil so as to satisfy, particularly, requirements (II) and (III).

[0038] Examples of the bottom oil to be used in an aspect of the present invention include bottom fractions that remain by hydrocracking oils containing heavy fuel oils obtained from a vacuum distillation apparatus, and separating and removing naphtha and kerosene and light oils therefrom, in usual fuel oil production processes with crude oils as starting materials.

[0039] Examples of the wax to be used in an aspect of the present invention include waxes separated by the solvent dewaxing of the aforementioned bottom fractions as well as waxes obtained by the solvent dewaxing of atmospheric residual oils that remain by atmospherically distilling crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil, and separating and removing naphtha and light oils therefrom; waxes obtained by the solvent dewaxing of distillate oils obtained by vacuum distillation of these atmospheric residual oils; and waxes obtained by the solvent dewaxing of these distillate oils subjected to Solvent De-Asphalting, solvent extraction, or hydrofinishing.

[0040] Examples of the solvent-dewaxed oil to be used in an aspect of the present invention include residual oils obtained by solvent-dewaxing the aforementioned bottom fractions and the like and separating and removing the aforementioned waxes therefrom. The solvent-dewaxed oil is different from the aforementioned bottom oil because of the refining treatment of solvent dewaxing applied thereto.

[0041] The method for obtaining the wax by solvent dewaxing is preferably, for example, a method of mixing a bottom fraction with a mixed solvent of methyl ethyl ketone and toluene and removing deposits with stirring in a low-temperature range.

[0042] A specific temperature in the low-temperature range in solvent dewaxing is preferably lower than the temperature of general solvent dewaxing and, specifically, is preferably -25°C or lower, more preferably -30°C or lower, for adjusting the lubricant base oil so as to satisfy, particularly, the requirements (II) and (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0043] The oil content of the raw oil is preferably 5 to 55 mass%, more preferably 7 to 45 mass%, further preferably 10 to 35 mass%, furthermore preferably 15 to 32 mass%, particularly preferably 21 to 30 mass%, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.[Preparation examples of lubricant base oil]

[0044] The lubricant base oil that satisfies the requirements (I) to (III) can be appropriately prepared in consideration of, for example, items below. The items below are given for illustrating one example of a preparation method, and the lubricant base oil may be prepared in consideration of other items.

[0045] For example, the aforementioned raw oil can be subjected to a refining treatment to prepare a lubricant base oil that satisfies the requirements (I) to (III).

[0046] The refining treatment preferably includes at least one of hydroisomerization dewaxing treatment and hydrogenation treatment, more preferably includes at least hydroisomerization dewaxing treatment, and further preferably includes both of hydroisomerization dewaxing treatment and hydrogenation reaction, for adjusting the lubricant base oil so as to satisfy, particularly, the requirement (II). It is preferable that the type and refining conditions of the refining treatment should be appropriately set depending on the type of the raw oil to be used.

[0047] More specifically, the refining treatment is preferably selected as described below depending on the type of the raw oil to be used, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0048] In the case of using a raw oil (α) containing a bottom oil and a petroleum-derived wax at the aforementioned content ratio, the raw oil (α) is preferably subjected to a refining treatment including at least hydroisomerization dewaxing treatment, and more preferably subjected to a refining treatment including both of hydroisomerization dewaxing treatment and hydrogenation treatment.

[0049] In the case of using a raw oil (β) containing a solvent-dewaxed oil, the raw oil (β) is preferably subjected to a refining treatment including hydrogenation treatment without being subjected to hydroisomerization dewaxing treatment.

[0050] The aforementioned raw oil (α), because of containing a bottom oil, tends to have large aromatic, sulfur, and nitrogen contents. The presence of aromatic series, sulfur, and nitrogen is responsible for deposits in the preparation of a lubricating oil composition and causes reduction in high-temperature washability of pistons.

[0051] The hydroisomerization dewaxing treatment can remove aromatic series, sulfur, and nitrogen and decrease their contents.

[0052] On the other hand, the aforementioned raw oil (β), which contains a wax, has a large content of branched paraffin because linear paraffin is deposited in a low-temperature environment by solvent dewaxing treatment and separated and removed. Use of the raw oil (β) therefore may adjust the content of branched paraffin so as to satisfy the requirement (II).(Hydroisomerization dewaxing treatment)

[0053] The hydroisomerization dewaxing treatment is a refining treatment that is performed for the purpose of isomerizing linear paraffin contained in the raw oil into branched isoparaffin, converting aromatic series into paraffin by ring opening, and removing impurities such as sulfur or nitrogen, for example. The hydroisomerization dewaxing treatment is capable of adjusting the lubricant base oil so as to satisfy the requirements (I) to (III), particularly, the requirements (II) and (III). The hydroisomerization dewaxing treatment is also preferably performed for adjusting avB in the formula (i) to the aforementioned range.

[0054] The hydroisomerization dewaxing treatment is preferably performed in the presence of a hydroisomerization dewaxing catalyst.

[0055] Examples of the hydroisomerization dewaxing catalyst include catalysts in which metal oxides such as nickel (Ni) / tungsten (W), nickel (Ni) / molybdenum (Mo), or cobalt (Co) / molybdenum (Mo), or noble metals such as platinum (Pt) or palladium (Pd) are supported on supports such as silica aluminophosphate (SAPO) or zeolite.

[0056] The hydrogen partial pressure in the hydroisomerization dewaxing treatment is preferably 2.0 to 220 MPa, more preferably 2.5 to 100 MPa, further preferably 3.0 to 50 MPa, furthermore preferably 3.5 to 25 MPa, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0057] The reaction temperature in the hydroisomerization dewaxing treatment is preferably set to be higher than the reaction temperature in general hydroisomerization dewaxing treatment and, specifically, is preferably 320 to 480°C, more preferably 325 to 420°C, further preferably 330 to 400°C, furthermore preferably 340 to 370°C, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0058] A high temperature as the reaction temperature can promote the isomerization of linear paraffin present in the raw oil into branched isoparaffin and facilitates preparing a lubricant base oil that satisfies the requirements (I) to (III), particularly, the requirements (II) and (III). Such a high temperature is also preferable for adjusting avB in the formula (i) to the aforementioned range.

[0059] The liquid hourly space velocity (LHSV) in the hydroisomerization dewaxing treatment is preferably 5.0 hr -1< or less, more preferably 2.0 hr -1< or less, further preferably 1.0 hr -1< or less, furthermore preferably 0.6 hr -1< or less, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0060] LHSV in the hydroisomerization dewaxing treatment is preferably 0.1 hr -1< or more, more preferably 0.2 hr -1< or more, for improving productivity.

[0061] The feed rate of hydrogen gas in the hydroisomerization dewaxing treatment is preferably 100 to 1000 Nm 3< , more preferably 200 to 800 Nm 3< , further preferably 250 to 650 Nm 3< , per kl of the raw oil to be supplied.(Hydrogenation treatment)

[0062] The hydrogenation treatment is a refining treatment that is performed for the purpose of completely saturating aromatic series contained in the raw oil, and removing impurities such as sulfur or nitrogen, for example. The hydrogenation treatment facilitates preparing a lubricant base oil that satisfies the requirements (I) to (III), particularly, the requirement (III).

[0063] The hydrogenation treatment is preferably performed in the presence of a hydrogenation catalyst.

[0064] Examples of the hydrogenation catalyst include catalysts in which metal oxides such as nickel (Ni) / tungsten (W), nickel (Ni) / molybdenum (Mo), or cobalt (Co) / molybdenum (Mo), or noble metals such as platinum (Pt) or palladium (Pd) are supported on amorphous supports such as silica / alumina or alumina, or crystalline supports such as zeolite.

[0065] The hydrogen partial pressure in the hydrogenation treatment is preferably set to be higher than the pressure in general hydrogenation treatment and, specifically, is preferably 16 MPa or higher, more preferably 17 MPa or higher, further preferably 20 MPa or higher, and preferably 30 MPa or lower, more preferably 22 MPa or lower, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III), particularly, the requirement (III).

[0066] The reaction temperature in the hydrogenation treatment is preferably 200 to 400°C, more preferably 250 to 350°C, further preferably 280 to 330°C, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III), particularly, the requirement (III).

[0067] The liquid hourly space velocity (LHSV) in the hydrogenation treatment is preferably 5.0 hr -1< or less, more preferably 2.0 hr -1< or less, further preferably 1.0 hr -1< or less, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III), particularly, the requirement (III), and is preferably 0.1 hr -1< or more, more preferably 0.2 hr -1< or more, further preferably 0.3 hr -1< or more, for productivity.

[0068] The feed rate of hydrogen gas in the hydrogenation treatment is preferably 100 to 1000 Nm 3< , more preferably 200 to 800 Nm 3< , further preferably 250 to 650 Nm 3< , per kl of the supplied oil to be treated.

[0069] The refined oil after the hydrogenation treatment can be vacuum-distilled under appropriately set conditions (pressure, temperature, time, etc.) to obtain a lubricant base oil that has a predetermined kinematic viscosity and satisfies the requirements (I) to (III), particularly, the requirement (I).[Properties of lubricant base oil]

[0070] The kinematic viscosity at 40°C of the lubricant base oil according to an aspect of the present invention is preferably such a low viscosity that a viscosity index is impossible to calculate, for achieving a lubricant base oil that allows a lubricating oil composition with good cooling properties to be prepared.

[0071] The kinematic viscosity at 40°C of the lubricant base oil according to an aspect of the present invention is preferably 5.00 mm 2< / s or less, 4.80 mm 2< / s or less, 4.60 mm 2< / s or less, 4.50 mm 2< / s or less, 4.40 mm 2< / s or less, 4.20 mm 2< / s or less, 4.00 mm 2< / s or less, 3.80 mm 2< / s or less, 3.60 mm 2< / s or less, 3.50 mm 2< / s or less, 3.40 mm 2< / s or less, 3.20 mm 2< / s or less, 3.00 mm 2< / s or less, 2.90 mm 2< / s or less, 2.80 mm 2< / s or less, 2.70 mm 2< / s or less, 2.65 mm 2< / s or less, 2.60 mm 2< / s or less, 2.55 mm 2< / s or less, 2.50 mm 2< / s or less, 2.45 mm 2< / s or less, 2.40 mm 2< / s or less, 2.35 mm 2< / s or less, 2.30 mm 2< / s or less, 2.25 mm 2< / s or less, 2.20 mm 2< / s or less, 2.15 mm 2< / s or less, or 2.10 mm 2< / s or less, for achieving a lubricant base oil that allows a lubricating oil composition with good cooling properties to be prepared, and furthermore, may be 2.05 mm 2< / s or less, 2.00 mm 2< / s or less, 1.95 mm 2< / s or less, 1.90 mm 2< / s or less, or 1.85 mm 2< / s or less. The kinematic viscosity is preferably 1.00 mm 2< / s or more, 1.10 mm 2< / s or more, 1.20 mm 2< / s or more, 1.30 mm 2< / s or more, 1.40 mm 2< / s or more, 1.50 mm 2< / s or more, 1.60 mm 2< / s or more, 1.65 mm 2< / s or more, 1.70 mm 2< / s or more, 1.75 mm 2< / s or more, 1.80 mm 2< / s or more, 1.85 mm 2< / s or more, 1.90 mm 2< / s or more, 1.95 mm 2< / s or more, or 2.00 mm 2< / s or more, for adjusting the lubricant base oil so as to have a high flash point, and furthermore, may be 2.10 mm 2< / s or more, 2.20 mm 2< / s or more, 2.30 mm 2< / s or more, 2.40 mm 2< / s or more, 2.50 mm 2< / s or more, or 2.60 mm 2< / s or more.

[0072] In this description, the kinematic viscosity and viscosity index means a value measured and calculated in accordance with JIS K2283: 2000.

[0073] The density at 15°C of the lubricant base oil according to an aspect of the present invention is preferably 0.750 g / cm 3< or more, 0.752 g / cm 3< or more, 0.754 g / cm 3< or more, 0.756 g / cm 3< or more, 0.758 g / cm 3< or more, 0.760 g / cm 3< or more, 0.762 g / cm 3< or more, 0.764 g / cm 3< or more, 0.766 g / cm 3< or more, 0.768 g / cm 3< or more, or 0.770 g / cm 3< or more, and preferably 1.10 g / cm 3< or less, 1.05 g / cm 3< or less, 1.00 g / cm 3< or less, 0.990 g / cm 3< or less, 0.970 g / cm 3< or less, 0.950 g / cm 3< or less, 0.920 g / cm 3< or less, 0.900 g / cm 3< or less, 0.890 g / cm 3< or less, 0.870 g / cm 3< or less, 0.850 g / cm 3< or less, 0.820 g / cm 3< or less, or 0.800 g / cm 3< or less, and furthermore, may be 0.790 g / cm 3< or less, 0.780 g / cm 3< or less, or 0.770 g / cm 3< or less.

[0074] In this description, the density means a value measured in accordance with JIS K2249.

[0075] The flash point of the lubricant base oil according to an aspect of the present invention is preferably 90°C or higher, 94°C or higher, 100°C or higher, 102°C or higher, 104°C or higher, 106°C or higher, 108°C or higher, 110°C or higher, 112°C or higher, 114°C or higher, 116°C or higher, or 118°C or higher, for achieving a lubricant base oil that allows a lubricating oil composition excellent in safety to be prepared, and may be 300°C or lower, 280°C or lower, 260°C or lower, 240°C or lower, 220°C or lower, or 200°C or lower.

[0076] In this description, the flash point means a value measured by the Pensky-Martens closed-cup process (PM process) in accordance with JIS K2265-3: 2007.

[0077] The pour point of the lubricant base oil according to an aspect of the present invention is preferably - 50.0°C or lower, -52.5°C or lower, -55.0°C or lower, - 57.5°C or lower, -60.0°C or lower, or lower than -60.0°C, for achieving a lubricant base oil that allows a lubricating oil composition with good low-temperature fluidity to be prepared.

[0078] In this description, the pour point means a value measured in accordance with JIS K2269: 1987 (testing methods for pour point and cloud point of crude oil and petroleum products).

[0079] The volume resistivity of the lubricant base oil according to an aspect of the present invention measured under conditions of 80°C and 250 V / mm is preferably 1.0 TΩ·m or more, 5.0 TΩ·m or more, 10.0 TΩ·m or more, 15.0 TΩ·m or more, 20.0 TΩ·m or more, 25.0 TΩ·m or more, 30.0 TΩ·m or more, 40.0 TΩ·m or more, 50.0 TΩ·m or more, 60.0 TΩ·m or more, 70.0 TΩ·m or more, 80.0 TΩ·m or more, 90.0 TΩ·m or more, or 100.0 TΩ·m or more, for achieving a lubricant base oil that allows a lubricating oil composition with high insulation properties to be prepared.

[0080] In this description, the volume resistivity means a value measured under conditions at a measurement temperature of 80°C and an applied voltage of 250 V in accordance with JIS C2101: 1999.

[0081] The rubber swelling rate of an acrylic rubber for test, as measured by immersing the acrylic rubber for test in the lubricant base oil according to an aspect of the present invention under conditions at 100°C for 100 hours by a rubber immersion test method in accordance with JIS K6258, is preferably 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less, for achieving a lubricant base oil that allows a lubricating oil composition with high rubber compatibility to be prepared.

[0082] In this description, the rubber swelling rate of the acrylic rubber for test is the volume change rate of the acrylic rubber between before and after immersion calculated according to the following formula, and specifically means a value measured by the method described in Examples. [Configuration of lubricating oil composition]

[0083] The lubricating oil composition according to an aspect of the present invention comprises the lubricant base oil according to an aspect of the present invention.

[0084] The lubricating oil composition according to an aspect of the present invention may further contain additives for lubricating oil. Specifically, it may or may not contain one or more additives for lubricating oil selected from a pour point depressant, a viscosity index improver, an antioxidant, an extreme pressure agent, a metallic detergent, an ashless dispersant, a metal deactivator, a corrosion inhibitor, a rust inhibitor, and a defoamer.

[0085] The lubricating oil composition according to an aspect of the present invention may or may not contain a friction modifier.

[0086] One of these additives for lubricating oil may be used alone, or two or more of them may be used in combination.

[0087] The content of such an additive for lubricating oil can be appropriately adjusted, as long as the effects of the present invention are not impaired, but the content of each additive may independently be 0.001 mass% or more, 0.005 mass% or more, 0.01 mass% or more, 0.05 mass% or more, 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, and may be less than 15.0 mass%, less than 10.0 mass%, less than 8.0 mass%, less than 6.0 mass%, less than 5.0 mass%, less than 4.0 mass%, less than 3.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.10 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0088] In the lubricating oil composition according to an aspect of the present invention, the content of the aforementioned lubricant base oil according to an aspect of the present invention is preferably 50.0 mass% or more, 60.0 mass% or more, 70.0 mass% or more, 80.0 mass% or more, 85.0 mass% or more, 90.0 mass% or more, 95.0 mass% or more, 96.0 mass% or more, 97.0 mass% or more, 98.0 mass% or more, or 99.0 mass% or more, based on the total amount (100 mass%) of the lubricating oil composition.<Pour point depressant>

[0089] Examples of the pour point depressant to be used in an aspect of the present invention include ethylene-vinyl acetate copolymer, a condensate of chlorinated paraffin and naphthalene, a condensate of chlorinated paraffin and phenol, polymethacrylate, and polyalkylstyrene.

[0090] One of these pour point depressants may be used alone, or two or more of them may be used in combination.<Viscosity index improver>

[0091] Examples of the viscosity index improver to be used in an aspect of the present invention include polymers such as non-dispersed polymethacrylates, dispersed polymethacrylates, olefin copolymers (e.g., ethylenepropylene copolymer), dispersed olefin copolymers, styrene copolymers (e.g., styrene-diene copolymer and styrene-isoprene copolymer).

[0092] One of these viscosity index improvers may be used alone, or two or more of them may be used in combination.

[0093] Further, the weight-average molecular weight (Mw) of the viscosity index improver to be used in an aspect of the present invention may be 5,000 or more, 7,000 or more, 10,000 or more, 15,000 or more, or 20,000 or more, and 1,000,000 or less, 700,000 or less, 500,000 or less, 300,000 or less, 200,000 or less, 100,000 or less, or 50,000 or less.<Antioxidant>

[0094] Examples of the antioxidant to be used in an aspect of the present invention include amine antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenolic 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.

[0095] One of these antioxidants may be used alone, or two or more of them may be used in combination.

[0096] In the lubricating oil composition according to an aspect of the present invention, an amine antioxidant and a phenolic antioxidant are preferably used as antioxidants in combination.<Extreme pressure agent (antiwear agent)>

[0097] Examples of the extreme pressure agent (antiwear agent) to be used in an aspect of the present invention include such as sulfur-containing compounds such as zinc dithiophosphate; phosphorus-containing compounds such as phosphorous acid esters, phosphoric acid esters, phosphonic acid esters, and amine salts or metal salts thereof; and sulfur- and phosphorus-containing compounds such as thiophosphorous acid esters, thiophosphoric acid esters, thiophosphonic acid esters, and amine salts or metal salts thereof.

[0098] One of these extreme pressure agents may be used alone, or two or more of them may be used in combination.

[0099] The lubricating oil composition according to an aspect of the present invention may be limited by the content of the extreme pressure agent (antiwear agent) and may substantially not contain the extreme pressure agent (antiwear agent).

[0100] In the lubricating oil composition according to this aspect, the content of the extreme pressure agent (antiwear agent) may be 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.

[0101] The lubricating oil composition according to an aspect of the present invention may be limited by the content of zinc dithiophosphate and may substantially not contain zinc dithiophosphate.

[0102] In the lubricating oil composition according to this aspect, the content on a zinc atom basis of zinc dithiophosphate may be less than 100 ppm by mass, less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 100 ppb by mass, less than 10 ppb by mass, less than 1.0 ppb by mass, or less than 0.1 ppb by mass, based on the total amount (100 mass%) of the lubricating oil composition.

[0103] In this description, the content of the zinc atom means a value measured in accordance with JPI-5S-38-92.<Fatty acid amide>

[0104] The lubricating oil composition according to an aspect of the present invention may contain an aliphatic amide for imparting friction reducing effect thereto, and may be limited by the content of fatty acid amide for suppressing reduction in insulation properties.

[0105] In the lubricating oil composition according to an aspect of the present invention, the content of the aliphatic amide may be less than 1.0 mass%, less than 0.5 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, for suppressing reduction in insulation properties.

[0106] Examples of the aliphatic amide include reaction products of aliphatic carboxylic acids and aliphatic amines.

[0107] Examples of the aliphatic carboxylic acids include palmitic acid, isopalmitic acid, stearic acid, isostearic acid, behenic acid, lignoceric acid, cetylonic acid, heptacanoic acid, montanic acid, melissic acid, lacceric acid, setoleic acid, and erucic acid.

[0108] Further, examples of the aliphatic amines include ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.<Metallic detergent>

[0109] Examples of the metallic detergent to be used in an aspect of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. Further, the metal atom constituting such a metal salt is preferably a metal atom selected from alkali metals and alkaline earth metals, more preferably sodium, calcium, magnesium, or barium, further preferably calcium.

[0110] One of these metallic detergents may be used alone, or two or more of them may be used in combination.

[0111] In the lubricating oil composition according to an aspect of the present invention, the metallic detergent preferably contains one or more selected from calcium sulfonate, calcium salicylate, and calcium phenate, more preferably calcium sulfonate.

[0112] The content ratio of calcium sulfonate is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, further preferably 70 to 100 mass%, furthermore preferably 80 to 100 mass%, based on the total amount (100 mass%) of the metallic detergent contained in the lubricating oil composition.

[0113] The base number of the metallic detergent is preferably 0 to 600 mgKOH / g.

[0114] However, in the lubricating oil composition according to an aspect of the present invention, the metallic detergent is preferably an overbased metallic detergent having a base number of 100 mgKOH / g or more.

[0115] The base number of the overbased metallic detergent is 100 mgKOH / g or more, preferably 150 to 500 mgKOH / g, more preferably 200 to 450 mgKOH / g.

[0116] As used herein, the "base number" means the base number measured by the perchloric acid method according to chapter 7 of "Petroleum products and lubricating oils-Neutralization value test method" of JIS K2501:2003.

[0117] The lubricating oil composition according to an aspect of the present invention may be limited by the content of the metallic detergent such as a calcium detergent, a magnesium detergent, and a sodium detergent, and may substantially not contain the metallic detergent.

[0118] In the lubricating oil composition according to this aspect, the content on an alkali metal atom or alkaline earth metal atom (e.g., calcium atom, magnesium atom, or sodium atom) basis of the metallic detergent may be less than 1000 ppm by mass, less than 700 ppm by mass, less than 500 ppm by mass, less than 300 ppm by mass, less than 200 ppm by mass, less than 100 ppm by mass, less than 70 ppm by mass, less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 100 ppb by mass, less than 10 ppb by mass, less than 1.0 ppb by mass, or less than 0.1 ppb by mass, based on the total amount (100 mass%) of the lubricating oil composition.

[0119] In this description, the content of the alkali metal atom or the alkaline earth metal atom, such as a calcium atom, a magnesium atom, or a sodium atom, means a value measured in accordance with JPI-5S-38-92.<Ashless dispersant>

[0120] Examples of the ashless dispersant to be used in an aspect of the present invention include boron-free succinimides such as boron-free alkenylsuccinimide, boron-containing succinimides such as boron-containing alkenylsuccinimide, benzylamines, boron-containing benzylamines, succinic acid esters, and monovalent or divalent carboxylic acid amides typified by fatty acids or succinic acid.

[0121] One of these ashless dispersants may be used alone, or two or more of them may be used in combination.<Metal deactivator>

[0122] Examples of the metal deactivator to be used in an aspect of the present invention include benzotriazole compounds, tolyltriazole compounds, imidazole compounds, thiadiazole compounds, and pyrimidine compounds.

[0123] One of these metal deactivators may be used alone, or two or more of them may be used in combination.<Corrosion inhibitor>

[0124] Examples of the corrosion inhibitor to be used in an aspect of the present invention include amine compounds, alkanolamine compounds, amide compounds, and carboxylic acid compounds.

[0125] One of these corrosion inhibitors may be used alone, or two or more of them may be used in combination.<Rust inhibitor>

[0126] Examples of the rust inhibitor to be used in an aspect of the present invention include fatty acids, alkenyl succinic acid half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohols fatty acid esters, fatty acid amines, oxidized paraffins, and alkyl polyoxyethylene ethers.

[0127] One of these rust inhibitors may be used alone, or two or more of them may be used in combination.<Defoamer>

[0128] Examples of the defoamer to be used in an aspect of the present invention include silicone oils, fluorosilicone oils, and fluoroalkyl ethers.

[0129] One of these defoamers may be used alone, or two or more of them may be used in combination.<Friction modifier>

[0130] The lubricating oil composition according to an aspect of the present invention may further contain a friction modifier. One of such friction modifiers may be used alone, or two or more of them may be used in combination.

[0131] Examples of the friction modifier to be used in an aspect of the present invention include molybdenum friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdic acid; ashless friction modifiers such as aliphatic amine, fatty acid ester, fatty acid amide, fatty acid, aliphatic alcohol, and aliphatic ether having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms in the molecule; and fats and oils, amine, amide, and sulfurized esters, and the like.

[0132] The lubricating oil composition according to an aspect of the present invention may be limited by the content of the aforementioned molybdenum compound and may substantially not contain the molybdenum compound.

[0133] In the lubricating oil composition according to this aspect, the content of a molybdenum atom derived from the molybdenum compound may be less than 100 ppm by mass, less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 100 ppb by mass, less than 10 ppb by mass, less than 1.0 ppb by mass, or less than 0.1 ppb by mass, based on the total amount (100 mass%) of the lubricating oil composition

[0134] In this description, the content of the molybdenum atom means a value measured in accordance with JPI-5S-38-92.[Properties of lubricating oil composition]

[0135] The kinematic viscosity at 40°C of the lubricating oil composition according to an aspect of the present invention is preferably less than 3.0 mm 2< / s, less than 2.9 mm 2< / s, less than 2.8 mm 2< / s, less than 2.7 mm 2< / s, less than 2.6 mm 2< / s, less than 2.5 mm 2< / s, less than 2.4 mm 2< / s, less than 2.3 mm 2< / s, less than 2.2 mm 2< / s, less than 2.1 mm 2< / s, or less than 2.0 mm 2< / s, for achieving a lubricating oil composition with good cooling properties, and may be 1.0 mm 2< / s or more, 1.1 mm 2< / s or more, 1.2 mm 2< / s or more, 1.3 mm 2< / s or more, 1.4 mm 2< / s or more, 1.5 mm 2< / s or more, or 1.6 mm 2< / s or more.

[0136] The flash point of the lubricating oil composition according to an aspect of the present invention is preferably 90°C or higher, 100°C or higher, 102°C or higher, 104°C or higher, 106°C or higher, 108°C or higher, 110°C or higher, 112°C or higher, 114°C or higher, 116°C or higher, or 118°C or higher, for handling safety.

[0137] The pour point of the lubricating oil composition according to an aspect of the present invention is preferably -50.0°C or lower, -52.5°C or lower, -55.0°C or lower, -57.5°C or lower, -60.0°C or lower, or lower than -60.0°C, for achieving a lubricating oil composition with good startability and excellent fuel efficiency because of good low-temperature fluidity.

[0138] The volume resistivity of the lubricating oil composition according to an aspect of the present invention measured under conditions of 80°C and 250 V / mm is preferably 1.0 TΩ·m or more, 5.0 TΩ·m or more, 10.0 TΩ·m or more, 15.0 TΩ·m or more, 20.0 TΩ·m or more, 25.0 TΩ·m or more, 30.0 TΩ·m or more, 40.0 TΩ·m or more, 50.0 TΩ·m or more, 60.0 TΩ·m or more, 70.0 TΩ·m or more, 80.0 TΩ·m or more, 90.0 TΩ·m or more, or 100.0 TΩ·m or more, for achieving a lubricating oil composition with high insulation properties.

[0139] The rubber swelling rate of an acrylic rubber for test, as measured by immersing the acrylic rubber for test in the lubricating oil composition according to an aspect of the present invention under conditions at 100°C for 100 hours by a rubber immersion test method in accordance with JIS K6258, is preferably 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less, for achieving a lubricating oil composition with high rubber compatibility.

[0140] The thermal conductivity of the lubricating oil composition according to an aspect of the present invention is preferably 0.130 W / mK or more, 0.132 W / mK or more, 0.134 W / mK or more, 0.136 W / mK or more, 0.138 W / mK or more, 0.140 W / mK or more, or 0.142 W / mK or more, and may be 0.200 W / mK or less, 0.180 W / mK or less, or 0.160 W / mK or less.

[0141] In this description, the thermal conductivity means a value measured in accordance with ASTM D7896-19.[Applications of lubricating oil composition]

[0142] The lubricant base oil according to an aspect of the present invention has a low kinematic viscosity and is excellent in various properties such as volume resistivity, low-temperature fluidity, and rubber compatibility. The lubricating oil composition comprising this lubricant base oil is therefore excellent in various properties such as cooling properties, insulation properties, low-temperature fluidity, and rubber compatibility and as such, has preferable physical properties for cooling equipment mounted in an electric vehicle.

[0143] In consideration of such properties, the lubricating oil composition according to an aspect of the present invention is suitable as a lubricating oil composition for cooling at least one piece of equipment mounted in an electric vehicle, selected from a motor, a battery, an inverter, and an engine.

[0144] Thus, an aspect of the present invention also provides the following invention. [1] A method for cooling equipment, comprising cooling equipment mounted in an electric vehicle using the lubricating oil composition according to an aspect of the present invention. [2] Equipment mounted in an electric vehicle, the equipment being filled with the lubricating oil composition according to an aspect of the present invention as a cooling fluid.

[0145] Examples of the electric vehicle described in [1] and [2] above include hybrid vehicles and electric vehicles.

[0146] Examples of the equipment mounted in an electric vehicle include at least one selected from motors, batteries, inverters, and engines.Examples

[0147] Next, the present invention will be described in more detail with reference to Examples; however, the present invention is not limited in any way by these Examples. The methods for measuring or calculating various properties are as follows.(1) Average number of carbon atoms (Cav)

[0148] The gas chromatogram of a measurement sample was obtained using a gas chromatograph under measurement conditions below. Measurement apparatus: 8890 Gas Chromatograph (GC) System (product name, available from Agilent Technologies, Inc.) Column: HP-5ms column (length: 30 mm, inside diameter: 0.25 mm, film thickness: 0.25 µm: available from Agilent Technologies, Inc.) Carrier gas: Helium (114 kPa) Measurement sample: 0.1 g of a sample was diluted with 1.0 mL of hexane and measured. Sample injection volume: 0.3 µL Split ratio: 10 Detector: Hydrogen flame ionization detector (FID) Detector temperature: 300°C Oven temperature: Held at 100°C for 1 minute, then elevated to 320°C at a temperature elevation rate of 5°C / min, and held for 10 minutes.

[0149] The gas chromatogram of a standard sample having each number of carbon atoms was obtained using the gas chromatograph under the aforementioned measurement conditions, and data on an elution time (min) of each number of carbon atoms was obtained in advance.

[0150] The numbers of carbon atoms at peaks in the gas chromatogram of the measurement sample were identified on the basis of the obtained data on the elution time of each number of carbon atoms. The content ratio of a component having each number of carbon atoms in the measurement sample was identified from the area ratio of the peak of each number of carbon atoms to the total area of all the peaks except for a solvent in the gas chromatogram. A weighted average value of the numbers of carbon atoms was regarded as the average number of carbon atoms (Cav) in the measurement sample.(2) Total integral intensity ratio of CH group and CH 2 group (nonCH 3 )

[0151] The 1< H-NMR spectrum of a measurement sample was obtained using an NMR apparatus under measurement conditions below. Measurement apparatus: JNM400RS3 (product name, available from JEOL Ltd.) Measurement sample: Solution obtained by diluting 1.0 mL of a lubricant base oil by the addition of 1.0 mL of deuterated chloroform Measurement temperature: 25°C Resonance frequency: 400 MHz Of two peaks detected in the range of chemical shifts from 0.0 to 2.0 ppm in the obtained 1< H-NMR spectrum of the measurement sample, a downfield peak was identified as a peak derived from a CH group or a CH 2 group, and the other upfield peak was identified as a peak derived from a CH 3 group. The ratio of integral intensity S1 of the peak derived from the CH group or the CH 2 group to integral intensity S2 of the peak derived from the CH 3 group [S1 / S2] was regarded as the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group. (3) Average number of branches (avB)

[0152] The 13< C-NMR spectrum of a measurement sample was obtained using an NMR apparatus under measurement conditions below. Measurement apparatus: JNM400RS3 (product name, available from JEOL Ltd.) Measurement sample: Solution obtained by diluting 1.0 mL of a lubricant base oil by the addition of 1.0 mL of deuterated chloroform Measurement temperature: 25°C Resonance frequency: 100 MHz Total integral intensity (a) in the range of chemical shifts from 5.0 to 60.0 ppm and total integral intensity (b) in the range of chemical shifts from 5.0 to 20.0 ppm and from 22.45 to 22.80 ppm derived from terminal CH 3 groups were calculated in the obtained 13< C-NMR spectrum of the measurement sample. The ratio of the total integral intensity (b) to the total integral intensity (a) [(b) / (a)] was calculated, and the average number of branches (avB) was calculated according to the following formula (ii) from the value of [(b) / (a)] and the average number of carbon atoms (Cav) determined in (1) above: avB = Cav × b / a − 2 (4) Paraffin content

[0153] The paraffin content was calculated according to the following formula (i) from the value of the average number of carbon atoms (Cav) determined in (1) above, the value of the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group determined in (2) above, and the value of the average number of branches (avB) determined in (3) above: Production Example 1 (production of bottom oil)

[0154] An oil containing a heavy fuel oil obtained from a vacuum distillation apparatus in a usual fuel oil production process using a paraffinic crude oil was hydrocracked, and naphtha and kerosene and light oils were separated and removed to isolate a remaining bottom fraction. The bottom fraction was used as a "bottom oil" in production below.Production Example 2 (production of solvent-dewaxed oil and slack wax)

[0155] The bottom oil thus obtained was treated by solvent dewaxing in a low-temperature range of -35°C to -30°C using a mixed solvent of methyl ethyl ketone and toluene, and a wax was separated to obtain a "solvent-dewaxed oil". The separated wax was used as a "slack wax".Example 1

[0156] A raw oil prepared by mixing 25 parts by mass of the bottom oil obtained in Production Example 1 with 75 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0157] Subsequently, the refined oil after hydroisomerization dewaxing was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0158] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 2.0 mm 2< / s was recovered to obtain a lubricant base oil (1).

[0159] Figure 1 shows the gas chromatogram of the lubricant base oil (1) measured on the basis of the aforementioned conditions. Figure 2 shows the 1< H-NMR spectrum of the lubricant base oil (1) measured on the basis of the aforementioned conditions. Figure 3 shows a 13< C-NMR spectrum of the lubricant base oil (1) measured on the basis of the aforementioned conditions.Example 2

[0160] A raw oil prepared by mixing 10 parts by mass of the bottom oil obtained in Production Example 1 with 90 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0161] Subsequently, the refined oil after hydroisomerization dewaxing treatment was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0162] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 1.8 mm 2< / s was recovered to obtain a lubricant base oil (2).Example 3

[0163] A raw oil prepared by mixing 20 parts by mass of the bottom oil obtained in Production Example 1 with 80 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0164] Subsequently, the refined oil after hydroisomerization dewaxing treatment was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0165] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 2.6 mm 2< / s was recovered to obtain a lubricant base oil (3).Comparative Example 1

[0166] A raw oil prepared by mixing 40 parts by mass of the bottom oil obtained in Production Example 1 with 60 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0167] Subsequently, the refined oil after hydroisomerization dewaxing treatment was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0168] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 2.4 mm 2< / s was recovered to obtain a lubricant base oil (4).Comparative Example 2

[0169] A lubricant base oil (5) was obtained in the same manner as in Comparative Example 1 except that the hydroisomerization dewaxing treatment was not performed.Comparative Example 3

[0170] A lubricant base oil (6) was obtained in the same manner as in Comparative Example 1 except that a bottom oil and a slack wax obtained from an intermediate base crude oil instead of the paraffinic crude oil was used; and a fraction with a kinematic viscosity at 40°C of around 8.4 mm 2< / s was recovered.Comparative Example 4

[0171] A raw oil prepared by mixing 5 parts by mass of the bottom oil obtained in Production Example 1 with 95 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0172] Subsequently, the refined oil after hydroisomerization dewaxing treatment was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0173] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 5.4 mm 2< / s was recovered to obtain a lubricant base oil (7).

[0174] The values of various physical properties were measured as to the produced lubricant base oils (1) to (7) by methods below. These results are shown in Table 1.[40°C kinematic viscosity]

[0175] It was measured in accordance with JIS K2283: 2000. [15°C density] It was measured at 15°C in accordance with JIS K2249. [Pour point]

[0176] It was measured in accordance with JIS K2269: 1987 (testing methods for pour point and cloud point of crude oil and petroleum products).[Flash point]

[0177] It was measured by the Pensky-Martens closed-cup process (PM process) in accordance with JIS K2265-3: 2007.[Rubber swelling rate]

[0178] A rubber immersion test in accordance with JIS K6258 was conducted.

[0179] Specifically, an acrylic rubber for test (product name: "T303", available from NOK CORPORATION) was immersed in each lubricant base oil as a measurement target under conditions at an immersion temperature of 100°C for an immersion time of 100 hours and measured. Then, the volume of the acrylic rubber for test was measured before and after the test, and the volume change rate was calculated from the following formula.

[0180] It can be said that the lower the value of the rubber swelling rate, the more excellent the rubber compatibility of the lubricant base oil. In this example, lubricant base oils with a rubber swelling rate of 9% or less were determined to have good rubber compatibility.[Volume resistivity]

[0181] It was measured under conditions at a measurement temperature of 80°C and an applied voltage of 250 V in accordance with JIS C2101: 1999.[Table 1]

[0182] Table 1CavnonCH3avBParaffin content40°C kinematic viscosity [mm 2< / s]15°C density [g / cm 3< ]Pour point [°C]Flash point [°C]Rubber swelling rate [%]Volume resistivity [TΩ·m]Example 114.31.801.300.9082.080.772-60.0>1065110Example 214.92.041.280.9411.830.766-60.094620Example 315.52.061.290.9142.610.777-60.0>119525Comparative Example 114.92.200.910.8802.370.775-27.5114546Comparative Example 214.11.690.350.6292.380.821-47.51061037Comparative Example 321.52.230.820.6078.230.831-32.5146427Comparative Example 419.92.681.700.9785.410.798-60.0>138430

[0183] From Table 1, the lubricant base oils (1) to (3) of Examples 1 to 3 are determined to have good cooling properties, low-temperature fluidity, rubber compatibility, and volume resistivity from the 40°C kinematic viscosity, pour point, rubber swelling rate, and volume resistivity values. By contrast, the lubricant base oils (4) to (7) of Comparative Examples 1 to 4 have a high pour point and are thus considered to be inferior in low-temperature fluidity. Also, the lubricant base oil (5) of Comparative Example 2 has a high rubber swelling rate and thus presents a problem associated with rubber compatibility. Furthermore, the lubricant base oils (6) and (7) of Comparative Examples 3 and 4 have a high 40°C kinematic viscosity and are thus determined to be inferior in cooling properties.

Examples

production example 1 (

Production Example 1 (production of bottom oil)

[0154]An oil containing a heavy fuel oil obtained from a vacuum distillation apparatus in a usual fuel oil production process using a paraffinic crude oil was hydrocracked, and naphtha and kerosene and light oils were separated and removed to isolate a remaining bottom fraction. The bottom fraction was used as a "bottom oil" in production below.

production example 2 (

Production Example 2 (production of solvent-dewaxed oil and slack wax)

[0155]The bottom oil thus obtained was treated by solvent dewaxing in a low-temperature range of -35°C to -30°C using a mixed solvent of methyl ethyl ketone and toluene, and a wax was separated to obtain a "solvent-dewaxed oil". The separated wax was used as a "slack wax".

example 1

[0156]A raw oil prepared by mixing 25 parts by mass of the bottom oil obtained in Production Example 1 with 75 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0157]Subsequently, the refined oil after hydroisomerization dewaxing was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0158]The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 2.0 mm 2< / s was recovered to obtain a lubricant base oil (1).

[0159]Figure 1 shows the gas chromatogram of the lubricant base oil (1) measured on the basis of the aforement...

Technical Field

[0001] The present invention relates to a lubricant base oil, and a lubricating oil composition containing the lubricant base oil.Background Art

[0002] In recent years, there has been a strong demand for carbon dioxide reduction from the viewpoint of global environment protection. For example, in the automobile field, a strong emphasis has been placed on the development of techniques for fuel efficiency, and hybrid vehicles or electric vehicles are prevailing which are automobiles excellent in fuel consumption and environmental performance. Such hybrid vehicles or electric vehicles have an electric motor, a generator, an inverter, a battery, and the like, and run through the use of the power of the electric motor.

[0003] Various pieces of equipment mounted in such electric vehicles need to be cooled because high temperatures incur reduction in efficiency or damages. Existing lubricating oil such as automatic transmission fluid (hereinafter, referred to as ATF) or continuous variable transmission fluid (hereinafter, referred to as CVTF) is typically used in the cooling of equipment, such as electric motors, generators, and batteries, mounted in electric vehicles. Since some hybrid vehicles or electric vehicles are in a format having a gear reducer, lubricating oil compositions for use in these vehicles need to have lubricity as well as cooling properties.

[0004] For example, Patent Literature 1 discloses a lubricating composition for cooling and / or insulating a cell or an electric motor in a kinetic energy recovery system (KERS) or a hybrid vehicle.Citation ListPatent Literature

[0005] Patent Literature 1: Japanese Translation of PCT International Application Publication No. 2013-522409Summary of InventionTechnical Problem

[0006] For example, lubricating oil compositions for cooling equipment mounted in electric vehicles are required to have not only cooling properties and insulation properties but various properties such as low-temperature fluidity, rubber compatibility, and handleability.

[0007] The present invention has been made in light of these circumstances, and an object of the present invention is to provide a lubricating oil composition having preferable physical properties for cooling equipment mounted in an electric vehicle.Solution to Problem

[0008] The present inventors have conducted diligent studies on lubricant base oils suitable for lubricating oil compositions for cooling equipment mounted in electric vehicles. As a result, the present inventors have gained the finding that a lubricant base oil adjusted so as to satisfy predetermined requirements is preferable for the preparation of a lubricating oil composition as described above. The present invention has been completed on the basis of the finding.

[0009] Specifically, an aspect of the present invention provides an invention described in [1] to

[17] below. [1] A lubricant base oil for use in the cooling of equipment mounted in an electric vehicle, the lubricant base oil satisfying the following requirements (I) to (III): requirement (I): an average number of carbon atoms (Cav) measured using a gas chromatograph is 19.0 or less, requirement (II): a total integral intensity ratio of a CH group and a CH 2 group (nonCH 3 ) which is the ratio of integral intensity S1 of peaks derived from the CH group and the CH 2 group to integral intensity S2 of a peak derived from a CH 3 group [S1 / S2] is 1.75 or more in a 1< H-NMR spectrum measured using an NMR apparatus, and requirement (III): a paraffin content calculated according to the following formula (i) is 0.885 or more: wherein nonCH 3 is the total integral intensity ratio of the CH group and the CH 2 group, Cav is the average number of carbon atoms, and avB represents an average number of branches and is a value calculated according to the following formula (ii) from a value of a ratio of total integral intensity (b) in a range of chemical shifts from 5.0 to 20.0 ppm and from 22.45 to 22.80 ppm derived from terminal CH 3 groups to total integral intensity (a) in a range of chemical shifts from 5.0 to 60.0 ppm [(b / (a)] in a 13< C-NMR spectrum measured using an NMR apparatus: avB = Cav × b / a − 2 . [2] The lubricant base oil according to [1] above, wherein avB in the formula (i) is 1.00 or more and 1.65 or less. [3] The lubricant base oil according to [1] or [2] above, wherein the total integral intensity ratio (nonCH 3 ) is less than 2.20. [4] The lubricant base oil according to any one of [1] to [3] above, wherein the lubricant base oil is a base oil obtained by a refining treatment of a raw oil (α) containing a bottom oil and a petroleum-derived wax. [5] The lubricant base oil according to [4] above, wherein the content ratio between the bottom oil and the wax [bottom oil / wax] in the raw oil (α) is a mass ratio of over 5 / 95 and less than 40 / 60. [6] The lubricant base oil according to [4] or [5] above, wherein the refining treatment includes at least hydroisomerization dewaxing treatment. [7] The lubricant base oil according to any one of [1] to [6] above, wherein the lubricant base oil has a kinematic viscosity at 40°C of 1.00 mm 2< / s or more and 5.00 mm 2< / s or less. [8] The lubricant base oil according to any one of [1] to [7] above, wherein the lubricant base oil has a density at 15°C of 0.750 g / cm 3< or more. [9] The lubricant base oil according to any one of [1] to [8] above, wherein the lubricant base oil has a flash point of 100°C or higher.

[10] The lubricant base oil according to any one of [1] to [9] above, wherein the lubricant base oil has a pour point of -50.0°C or lower.

[11] The lubricant base oil according to any one of [1] to

[10] , wherein the lubricant base oil has a volume resistivity of 1.0 TΩ·m or more measured under conditions of 80°C and 250 V / mm.

[12] The lubricant base oil according to any one of [1] to

[11] above, wherein the rubber swelling rate of an acrylic rubber for test, as measured by immersing the acrylic rubber for test in the lubricant base oil under conditions at 100°C for 100 hours by a rubber immersion test method in accordance with JIS K6258, is 9% or less.

[13] A lubricating oil composition for use in the cooling of equipment mounted in an electric vehicle, the lubricating oil composition comprising the lubricant base oil according to any one of [1] to

[12] above.

[14] The lubricating oil composition according to

[13] above, further comprising one or more additives for lubricating oil selected from a pour point depressant, a viscosity index improver, an antioxidant, an extreme pressure agent, a metallic detergent, an ashless dispersant, a metal deactivator, a corrosion inhibitor, a rust inhibitor, and a defoamer.

[15] The lubricating oil composition according to

[14] above, wherein the total content of the additives for lubricating oils is 5.0 mass% or less based on the total amount of the lubricating oil composition.

[16] A method for cooling equipment, comprising cooling equipment mounted in an electric vehicle using the lubricating oil composition according to any one of

[13] to

[15] above.

[17] The method for cooling equipment according to

[16] above, wherein the equipment is at least one selected from a motor, a battery, an inverter, and an engine. Advantageous Effects of Invention

[0010] The lubricant base oil according to a preferable aspect of the present invention has a low kinematic viscosity and high volume resistivity and is excellent in various properties such as low-temperature fluidity and rubber compatibility. The lubricant base oil according to a preferable aspect of the present invention therefore allows a lubricating oil composition with preferable physical properties for the cooling of equipment mounted in an electric vehicle to be prepared.Brief Description of Drawings

[0011] [Figure 1] Figure 1 shows a gas chromatogram of a lubricant base oil (1) measured on the basis of conditions described in the present examples. [Figure 2] Figure 2 shows a 1< H-NMR spectrum of the lubricant base oil (1) measured on the basis of conditions described in the present examples. [Figure 3] Figure 3 shows a 13< C-NMR spectrum of the lubricant base oil (1) measured on the basis of conditions described in the present examples. Description of Embodiments

[0012] For the numerical ranges described herein, any upper limit and lower limit can be combined. For example, in the case where "preferably 30 to 100, more preferably 40 to 80" is described as numerical ranges, the range of "30 to 80" and the range of "40 to 100" are also included in the numerical ranges disclosed in this description. Further, for example, in the case where "preferably 30 or more, more preferably 40 or more, further preferably 100 or less, more preferably 80 or less" is described as numerical ranges, the range of "30 to 80" and the range of "40 to 100" are also included in the numerical ranges disclosed in this description.

[0013] In addition, the description "60 to 100" as a numerical range disclosed in this description, for example, means the range of "60 or more (60 or over 60) and 100 or less (100 or less than 100)".[Configuration of lubricant base oil]

[0014] The lubricant base oil according to an aspect of the present invention is a lubricant base oil for use in the cooling of equipment mounted in an electric vehicle, the lubricant base oil satisfying the following requirements (I) to (III): requirement (I): an average number of carbon atoms (Cav) measured using a gas chromatograph (hereinafter, also referred to as "GC") is 19.0 or less, requirement (II): a total integral intensity ratio of a CH group and a CH 2 group (nonCH 3 ) which is the ratio of integral intensity S1 of peaks derived from the CH group and the CH 2 group to integral intensity S2 of a peak derived from a CH 3 group [S1 / S2] is 1.75 or more in a 1< H-NMR spectrum measured using an NMR apparatus, and requirement (III): a paraffin content calculated according to the following formula (i) is 0.885 or more: wherein nonCH 3 is the total integral intensity ratio of the CH group and the CH 2 group, Cav is the average number of carbon atoms, and avB represents an average number of branches and is a value calculated according to the following formula (ii) from a value of a ratio of total integral intensity (b) in a range of chemical shifts from 5.0 to 20.0 ppm and from 22.45 to 22.80 ppm derived from terminal CH 3 groups to total integral intensity (a) in a range of chemical shifts from 5.0 to 60.0 ppm [(b) / (a)] in a 13< C-NMR spectrum measured using an NMR apparatus: avB = Cav × b / a − 2 .

[0015] In this description, values of physical properties defined in the requirements (I) to (III) and values of physical properties necessary for calculating various values mean values measured and / or calculated in accordance with the methods described in Examples below.

[0016] Equipment, such as electric motors, generators, and batteries, mounted in electric vehicles need to be cooled because high temperatures incur reduction in efficiency or damages. Lubricating oil compositions for use in the cooling of various pieces of equipment mounted in such electric vehicles are required to have various properties such as cooling properties, insulation properties, low-temperature fluidity, rubber compatibility, and handleability.

[0017] The lubricant base oil according to an aspect of the present invention is preferable for cooling equipment mounted in an electric vehicle, and allows a lubricating oil composition with various properties as described above to be prepared.

[0018] More specifically, the lubricant base oil according to an aspect of the present invention improves fluidity by adjusting the average number of carbon atoms (Cav) so as to satisfy the requirement (I), and can thereby achieve a lubricant base oil that allows a lubricating oil composition with excellent cooling properties to be prepared.

[0019] The average number of carbon atoms (Cav) represents an average number of carbon atoms in components constituting the lubricant base oil. The lubricant base oil according to an aspect of the present invention achieves a lubricating oil composition with improved fluidity by adjusting the number of carbon atoms in the constituting components.

[0020] In the lubricant base oil according to an aspect of the present invention, the average number of carbon atoms (Cav) defined in the requirement (I) is 19.0 or less from the viewpoint above, but is preferably 18.5 or less, 18.0 or less, 17.5 or less, 17.0 or less, 16.8 or less, 16.6 or less, 16.5 or less, 16.4 or less, 16.2 or less, 16.0 or less, 15.8 or less, 15.6 or less, 15.5 or less, 15.4 or less, 15.2 or less, 15.0 or less, 14.9 or less, 14.8 or less, 14.7 or less, 14.6 or less, or 14.5 or less, and preferably 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.5 or more, 10.0 or more, 10.5 or more, 11.0 or more, 11.5 or more, 12.0 or more, 12.5 or more, 13.0 or more, 13.5 or more, or 14.0 or more, for more improving fluidity and achieving a lubricant base oil that allows a lubricating oil composition with much better cooling properties to be prepared, and furthermore, may be 14.2 or more, 14.4 or more, 14.6 or more, 14.8 or more, or 15.0 or more.

[0021] The lubricant base oil according to an aspect of the present invention can adjust a rubber swelling rate to a low value by adjusting the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group so as to satisfy the requirement (II), and can thereby achieve a lubricant base oil that allows a lubricating oil composition with excellent rubber compatibility to be prepared.

[0022] The total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group represents the ratio of the number of hydrogen atoms on chains except for the termini to the number of hydrogen atoms in terminal methyl groups, and is a parameter that indicates a structural state such as the number of branches or the length of a chain in components constituting the lubricant base oil.

[0023] In the lubricant base oil according to an aspect of the present invention, the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group defined in the requirement (II) is 1.75 or more from the viewpoint above, but is preferably 1.76 or more, 1.77 or more, 1.78 or more, 1.79 or more, or 1.80 or more, and furthermore, may be 1.85 or more, 1.90 or more, 1.95 or more, or 2.00 or more. The total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group is preferably 3.00 or less, 2.90 or less, 2.80 or less, 2.70 or less, 2.60 or less, 2.50 or less, 2.45 or less, 2.40 or less, 2.35 or less, 2.30 or less, 2.25 or less, 2.24 or less, 2.23 or less, 2.22 or less, 2.21 or less, less than 2.20, 2.19 or less, 2.18 or less, 2.17 or less, 2.16 or less, 2.14 or less, 2.13 or less, 2.12 or less, 2.11 or less, or 2.10 or less, for achieving a lubricant base oil that allows a lubricating oil composition with good fluidity and low-temperature fluidity to be prepared, and furthermore, may be 2.05 or less, 2.00 or less, 1.95 or less, 1.90 or less, 1.85 or less, or 1.80 or less.

[0024] The lubricant base oil according to an aspect of the present invention can adjust a pour point to a low value by adjusting the paraffin content so as to satisfy the requirement (III), and can thereby achieve a lubricant base oil that allows a lubricating oil composition with excellent low-temperature fluidity to be prepared.

[0025] The paraffin content is a value calculated according to the following formula (i):

[0026] The denominator of the right side in the formula (i) represents the total number of hydrogen atoms on the assumption that all components constituting the lubricant base oil are paraffin, and is a value calculated from the average number of carbon atoms (Cav) measured using GC.

[0027] The numerator of the right side in the formula (i) represents the number of hydrogen atoms in the components constituting the lubricant base oil, and is calculated from measurement values obtained in measurement by GC, 1< H-NMR, and 13< C-NMR. This value is obtained on the basis of the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group, the average number of carbon atoms (Cav), and an average number of branches (avB) calculated according to the formula (ii).

[0028] In short, the paraffin content represents the proportion of saturated aliphatic saturated hydrocarbons in all the components constituting the lubricant base oil. The term "paraffin" refers to a saturated aliphatic saturated hydrocarbon, and the saturated aliphatic saturated hydrocarbon is not limited by its number of carbon atoms.

[0029] In the lubricant base oil according to an aspect of the present invention, the paraffin content defined in the requirement (III) is 0.885 or more from the viewpoint above, but is preferably 0.887 or more, 0.890 or more, 0.892 or more, 0.885 or more, 0.897 or more, 0.900 or more, 0.902 or more, 0.904 or more, 0.905 or more, or 0.906 or more, for adjusting a pour point to a lower value and achieving a lubricant base oil that allows a lubricating oil composition with much better low-temperature fluidity to be prepared, and furthermore, may be 0.908 or more, 0.910 or more, 0.912 or more, 0.914 or more, 0.916 or more, 0.918 or more, 0.920 or more, 0.925 or more, or 0.930 or more. The paraffin content is preferably 0.999 or less, 0.995 or less, 0.990 or less, 0.985 or less, 0.980 or less, 0.975 or less, 0.970 or less, 0.965 or less, 0.960 or less, 0.955 or less, 0.950 or less, 0.945 or less, 0.940 or less, 0.935 or less, 0.930 or less, 0.925 or less, or 0.920 or less, for more improving fluidity and achieving a lubricant base oil that allows a lubricating oil composition with good cooling properties to be prepared, and furthermore, may be 0.918 or less, 0.916 or less, 0.914 or less, 0.912 or less, 0.910 or less, or 0.908 or less.

[0030] In the lubricant base oil according to an aspect of the present invention, the average number of branches (avB) calculated according to the formula (ii) is preferably 1.00 or more, 1.05 or more, 1.10 or more, 1.15 or more, 1.20 or more, 1.21 or more, 1.22 or more, 1.23 or more, 1.24 or more, 1.25 or more, 1.26 or more, 1.27 or more, or 1.28 or more, for adjusting a pour point to a lower value and achieving a lubricant base oil that allows a lubricating oil composition with much better low-temperature fluidity to be prepared, and furthermore, may be 1.29 or more or 1.30 or more. The average number of branches (avB) is preferably 1.65 or less, 1.60 or less, 1.55 or less, 1.50 or less, 1.45 or less, 1.42 or less, 1.40 or less, 1.38 or less, or 1.36 or less, for more improving fluidity and achieving a lubricant base oil that allows a lubricating oil composition with good cooling properties to be prepared, and furthermore, may be 1.34 or less, 1.32 or less, 1.30 or less, 1.29 or less, or 1.28 or less.[Raw oil for lubricant base oil]

[0031] The lubricant base oil according to an aspect of the present invention may be a mineral base oil composed of one or more mineral oils, may be a synthetic base oil composed of one or more synthetic oils, or may be a mixed base oil composed of one or more mineral oils and one or more synthetic oils.

[0032] Examples of the mineral oil constituting the lubricant base oil according to an aspect of the present invention include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil; distillate oils obtained by vacuum distillation of these atmospheric residual oils; and refined oils obtained by subjecting the distillate oils to one or more refining treatments such as Solvent De-Asphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining (hydrocracking).

[0033] Examples of the synthetic oils constituting the lubricant base oil according to an aspect of the present invention include poly α-olefins such as α-olefin homopolymers or α-olefin copolymers (α-olefin copolymers having 8 to 14 carbon atoms such as ethylene-α-olefin copolymer); isoparaffin; ester oils such as polyol ester, dibasic acid ester, and phosphoric acid ester; polyalkyleneglycol; ether oils such as polyphenyl ether; alkylbenzene; alkylnaphthalene; synthetic oils (GTL) obtained by hydroisomerization-dewaxing waxes (GTL waxes (Gas To Liquids WAXES)) produced from natural gas by the Fischer-Tropsch process or the like; and CTL (Coal to liquid) base oils (e.g., CTL base oils obtained by a direct liquefaction process of grinding coal, which is then mixed with a solvent, followed by direct reaction with hydrogen at a high temperature and a high pressure, and CTL base oils obtained by an indirect liquefaction process (the Fischer-Tropsch process or the like) of temporarily gasifying coal (coal gasification) and liquefying the generated gas through synthesis reaction with a separated or purified starting material).

[0034] The lubricant base oil according to an aspect of the present invention is preferably obtained by the purification of a raw oil.

[0035] Such a raw oil is preferably a raw oil containing a petroleum-derived wax, or a raw oil containing a bottom oil and a petroleum-derived wax, more preferably a raw oil containing a bottom oil and a petroleum-derived wax, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range. Alternatively, a solvent-dewaxed raw oil may be used.

[0036] The content ratios of the bottom oil and the petroleum-derived wax in the raw oil to be used in an aspect of the present invention are preferably 50 to 100 mass%, 60 to 100 mass%, 65 to 100 mass%, 70 to 100 mass%, 75 to 100 mass%, 80 to 100 mass%, 85 to 100 mass%, 90 to 100 mass%, 55 to 100 mass%, 98 to 100 mass%, or 99 to 100 mass%, based on the total amount (100 mass%) of the raw oil, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0037] In the case of using a raw oil containing a bottom oil and a petroleum-derived wax, the content ratio between the bottom oil and the wax [bottom oil / wax] in the raw oil is a mass ratio of preferably over 5 / 95, 6 / 94 or more, 7 / 93 or more, 8 / 92 or more, 9 / 91 or more, 10 / 90 or more, 12 / 88 or more, 14 / 86 or more, 15 / 85 or more, 16 / 84 or more, 18 / 82 or more, 20 / 80 or more, 22 / 78 or more, 24 / 76 or more, or 25 / 75 or more, for adjusting the lubricant base oil so as to satisfy, particularly, the requirement (I) as well as for adjusting avB in the formula (i) to the aforementioned range, and is a mass ratio of preferably less than 40 / 60, 38 / 62 or less, 36 / 64 or less, 34 / 66 or less, 32 / 68 or less, 30 / 70 or less, 28 / 72 or less, 26 / 74 or less, 25 / 75 or less, 24 / 76 or less, 22 / 78 or less, 20 / 80 or less, 19 / 81 or less, 18 / 82 or less, 17 / 83 or less, 16 / 84 or less, or 15 / 85 or less, for adjusting the lubricant base oil so as to satisfy, particularly, requirements (II) and (III).

[0038] Examples of the bottom oil to be used in an aspect of the present invention include bottom fractions that remain by hydrocracking oils containing heavy fuel oils obtained from a vacuum distillation apparatus, and separating and removing naphtha and kerosene and light oils therefrom, in usual fuel oil production processes with crude oils as starting materials.

[0039] Examples of the wax to be used in an aspect of the present invention include waxes separated by the solvent dewaxing of the aforementioned bottom fractions as well as waxes obtained by the solvent dewaxing of atmospheric residual oils that remain by atmospherically distilling crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil, and separating and removing naphtha and light oils therefrom; waxes obtained by the solvent dewaxing of distillate oils obtained by vacuum distillation of these atmospheric residual oils; and waxes obtained by the solvent dewaxing of these distillate oils subjected to Solvent De-Asphalting, solvent extraction, or hydrofinishing.

[0040] Examples of the solvent-dewaxed oil to be used in an aspect of the present invention include residual oils obtained by solvent-dewaxing the aforementioned bottom fractions and the like and separating and removing the aforementioned waxes therefrom. The solvent-dewaxed oil is different from the aforementioned bottom oil because of the refining treatment of solvent dewaxing applied thereto.

[0041] The method for obtaining the wax by solvent dewaxing is preferably, for example, a method of mixing a bottom fraction with a mixed solvent of methyl ethyl ketone and toluene and removing deposits with stirring in a low-temperature range.

[0042] A specific temperature in the low-temperature range in solvent dewaxing is preferably lower than the temperature of general solvent dewaxing and, specifically, is preferably -25°C or lower, more preferably -30°C or lower, for adjusting the lubricant base oil so as to satisfy, particularly, the requirements (II) and (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0043] The oil content of the raw oil is preferably 5 to 55 mass%, more preferably 7 to 45 mass%, further preferably 10 to 35 mass%, furthermore preferably 15 to 32 mass%, particularly preferably 21 to 30 mass%, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.[Preparation examples of lubricant base oil]

[0044] The lubricant base oil that satisfies the requirements (I) to (III) can be appropriately prepared in consideration of, for example, items below. The items below are given for illustrating one example of a preparation method, and the lubricant base oil may be prepared in consideration of other items.

[0045] For example, the aforementioned raw oil can be subjected to a refining treatment to prepare a lubricant base oil that satisfies the requirements (I) to (III).

[0046] The refining treatment preferably includes at least one of hydroisomerization dewaxing treatment and hydrogenation treatment, more preferably includes at least hydroisomerization dewaxing treatment, and further preferably includes both of hydroisomerization dewaxing treatment and hydrogenation reaction, for adjusting the lubricant base oil so as to satisfy, particularly, the requirement (II). It is preferable that the type and refining conditions of the refining treatment should be appropriately set depending on the type of the raw oil to be used.

[0047] More specifically, the refining treatment is preferably selected as described below depending on the type of the raw oil to be used, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0048] In the case of using a raw oil (α) containing a bottom oil and a petroleum-derived wax at the aforementioned content ratio, the raw oil (α) is preferably subjected to a refining treatment including at least hydroisomerization dewaxing treatment, and more preferably subjected to a refining treatment including both of hydroisomerization dewaxing treatment and hydrogenation treatment.

[0049] In the case of using a raw oil (β) containing a solvent-dewaxed oil, the raw oil (β) is preferably subjected to a refining treatment including hydrogenation treatment without being subjected to hydroisomerization dewaxing treatment.

[0050] The aforementioned raw oil (α), because of containing a bottom oil, tends to have large aromatic, sulfur, and nitrogen contents. The presence of aromatic series, sulfur, and nitrogen is responsible for deposits in the preparation of a lubricating oil composition and causes reduction in high-temperature washability of pistons.

[0051] The hydroisomerization dewaxing treatment can remove aromatic series, sulfur, and nitrogen and decrease their contents.

[0052] On the other hand, the aforementioned raw oil (β), which contains a wax, has a large content of branched paraffin because linear paraffin is deposited in a low-temperature environment by solvent dewaxing treatment and separated and removed. Use of the raw oil (β) therefore may adjust the content of branched paraffin so as to satisfy the requirement (II).(Hydroisomerization dewaxing treatment)

[0053] The hydroisomerization dewaxing treatment is a refining treatment that is performed for the purpose of isomerizing linear paraffin contained in the raw oil into branched isoparaffin, converting aromatic series into paraffin by ring opening, and removing impurities such as sulfur or nitrogen, for example. The hydroisomerization dewaxing treatment is capable of adjusting the lubricant base oil so as to satisfy the requirements (I) to (III), particularly, the requirements (II) and (III). The hydroisomerization dewaxing treatment is also preferably performed for adjusting avB in the formula (i) to the aforementioned range.

[0054] The hydroisomerization dewaxing treatment is preferably performed in the presence of a hydroisomerization dewaxing catalyst.

[0055] Examples of the hydroisomerization dewaxing catalyst include catalysts in which metal oxides such as nickel (Ni) / tungsten (W), nickel (Ni) / molybdenum (Mo), or cobalt (Co) / molybdenum (Mo), or noble metals such as platinum (Pt) or palladium (Pd) are supported on supports such as silica aluminophosphate (SAPO) or zeolite.

[0056] The hydrogen partial pressure in the hydroisomerization dewaxing treatment is preferably 2.0 to 220 MPa, more preferably 2.5 to 100 MPa, further preferably 3.0 to 50 MPa, furthermore preferably 3.5 to 25 MPa, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0057] The reaction temperature in the hydroisomerization dewaxing treatment is preferably set to be higher than the reaction temperature in general hydroisomerization dewaxing treatment and, specifically, is preferably 320 to 480°C, more preferably 325 to 420°C, further preferably 330 to 400°C, furthermore preferably 340 to 370°C, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0058] A high temperature as the reaction temperature can promote the isomerization of linear paraffin present in the raw oil into branched isoparaffin and facilitates preparing a lubricant base oil that satisfies the requirements (I) to (III), particularly, the requirements (II) and (III). Such a high temperature is also preferable for adjusting avB in the formula (i) to the aforementioned range.

[0059] The liquid hourly space velocity (LHSV) in the hydroisomerization dewaxing treatment is preferably 5.0 hr -1< or less, more preferably 2.0 hr -1< or less, further preferably 1.0 hr -1< or less, furthermore preferably 0.6 hr -1< or less, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III) as well as for adjusting avB in the formula (i) to the aforementioned range.

[0060] LHSV in the hydroisomerization dewaxing treatment is preferably 0.1 hr -1< or more, more preferably 0.2 hr -1< or more, for improving productivity.

[0061] The feed rate of hydrogen gas in the hydroisomerization dewaxing treatment is preferably 100 to 1000 Nm 3< , more preferably 200 to 800 Nm 3< , further preferably 250 to 650 Nm 3< , per kl of the raw oil to be supplied.(Hydrogenation treatment)

[0062] The hydrogenation treatment is a refining treatment that is performed for the purpose of completely saturating aromatic series contained in the raw oil, and removing impurities such as sulfur or nitrogen, for example. The hydrogenation treatment facilitates preparing a lubricant base oil that satisfies the requirements (I) to (III), particularly, the requirement (III).

[0063] The hydrogenation treatment is preferably performed in the presence of a hydrogenation catalyst.

[0064] Examples of the hydrogenation catalyst include catalysts in which metal oxides such as nickel (Ni) / tungsten (W), nickel (Ni) / molybdenum (Mo), or cobalt (Co) / molybdenum (Mo), or noble metals such as platinum (Pt) or palladium (Pd) are supported on amorphous supports such as silica / alumina or alumina, or crystalline supports such as zeolite.

[0065] The hydrogen partial pressure in the hydrogenation treatment is preferably set to be higher than the pressure in general hydrogenation treatment and, specifically, is preferably 16 MPa or higher, more preferably 17 MPa or higher, further preferably 20 MPa or higher, and preferably 30 MPa or lower, more preferably 22 MPa or lower, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III), particularly, the requirement (III).

[0066] The reaction temperature in the hydrogenation treatment is preferably 200 to 400°C, more preferably 250 to 350°C, further preferably 280 to 330°C, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III), particularly, the requirement (III).

[0067] The liquid hourly space velocity (LHSV) in the hydrogenation treatment is preferably 5.0 hr -1< or less, more preferably 2.0 hr -1< or less, further preferably 1.0 hr -1< or less, for adjusting the lubricant base oil so as to satisfy the requirements (I) to (III), particularly, the requirement (III), and is preferably 0.1 hr -1< or more, more preferably 0.2 hr -1< or more, further preferably 0.3 hr -1< or more, for productivity.

[0068] The feed rate of hydrogen gas in the hydrogenation treatment is preferably 100 to 1000 Nm 3< , more preferably 200 to 800 Nm 3< , further preferably 250 to 650 Nm 3< , per kl of the supplied oil to be treated.

[0069] The refined oil after the hydrogenation treatment can be vacuum-distilled under appropriately set conditions (pressure, temperature, time, etc.) to obtain a lubricant base oil that has a predetermined kinematic viscosity and satisfies the requirements (I) to (III), particularly, the requirement (I).[Properties of lubricant base oil]

[0070] The kinematic viscosity at 40°C of the lubricant base oil according to an aspect of the present invention is preferably such a low viscosity that a viscosity index is impossible to calculate, for achieving a lubricant base oil that allows a lubricating oil composition with good cooling properties to be prepared.

[0071] The kinematic viscosity at 40°C of the lubricant base oil according to an aspect of the present invention is preferably 5.00 mm 2< / s or less, 4.80 mm 2< / s or less, 4.60 mm 2< / s or less, 4.50 mm 2< / s or less, 4.40 mm 2< / s or less, 4.20 mm 2< / s or less, 4.00 mm 2< / s or less, 3.80 mm 2< / s or less, 3.60 mm 2< / s or less, 3.50 mm 2< / s or less, 3.40 mm 2< / s or less, 3.20 mm 2< / s or less, 3.00 mm 2< / s or less, 2.90 mm 2< / s or less, 2.80 mm 2< / s or less, 2.70 mm 2< / s or less, 2.65 mm 2< / s or less, 2.60 mm 2< / s or less, 2.55 mm 2< / s or less, 2.50 mm 2< / s or less, 2.45 mm 2< / s or less, 2.40 mm 2< / s or less, 2.35 mm 2< / s or less, 2.30 mm 2< / s or less, 2.25 mm 2< / s or less, 2.20 mm 2< / s or less, 2.15 mm 2< / s or less, or 2.10 mm 2< / s or less, for achieving a lubricant base oil that allows a lubricating oil composition with good cooling properties to be prepared, and furthermore, may be 2.05 mm 2< / s or less, 2.00 mm 2< / s or less, 1.95 mm 2< / s or less, 1.90 mm 2< / s or less, or 1.85 mm 2< / s or less. The kinematic viscosity is preferably 1.00 mm 2< / s or more, 1.10 mm 2< / s or more, 1.20 mm 2< / s or more, 1.30 mm 2< / s or more, 1.40 mm 2< / s or more, 1.50 mm 2< / s or more, 1.60 mm 2< / s or more, 1.65 mm 2< / s or more, 1.70 mm 2< / s or more, 1.75 mm 2< / s or more, 1.80 mm 2< / s or more, 1.85 mm 2< / s or more, 1.90 mm 2< / s or more, 1.95 mm 2< / s or more, or 2.00 mm 2< / s or more, for adjusting the lubricant base oil so as to have a high flash point, and furthermore, may be 2.10 mm 2< / s or more, 2.20 mm 2< / s or more, 2.30 mm 2< / s or more, 2.40 mm 2< / s or more, 2.50 mm 2< / s or more, or 2.60 mm 2< / s or more.

[0072] In this description, the kinematic viscosity and viscosity index means a value measured and calculated in accordance with JIS K2283: 2000.

[0073] The density at 15°C of the lubricant base oil according to an aspect of the present invention is preferably 0.750 g / cm 3< or more, 0.752 g / cm 3< or more, 0.754 g / cm 3< or more, 0.756 g / cm 3< or more, 0.758 g / cm 3< or more, 0.760 g / cm 3< or more, 0.762 g / cm 3< or more, 0.764 g / cm 3< or more, 0.766 g / cm 3< or more, 0.768 g / cm 3< or more, or 0.770 g / cm 3< or more, and preferably 1.10 g / cm 3< or less, 1.05 g / cm 3< or less, 1.00 g / cm 3< or less, 0.990 g / cm 3< or less, 0.970 g / cm 3< or less, 0.950 g / cm 3< or less, 0.920 g / cm 3< or less, 0.900 g / cm 3< or less, 0.890 g / cm 3< or less, 0.870 g / cm 3< or less, 0.850 g / cm 3< or less, 0.820 g / cm 3< or less, or 0.800 g / cm 3< or less, and furthermore, may be 0.790 g / cm 3< or less, 0.780 g / cm 3< or less, or 0.770 g / cm 3< or less.

[0074] In this description, the density means a value measured in accordance with JIS K2249.

[0075] The flash point of the lubricant base oil according to an aspect of the present invention is preferably 90°C or higher, 94°C or higher, 100°C or higher, 102°C or higher, 104°C or higher, 106°C or higher, 108°C or higher, 110°C or higher, 112°C or higher, 114°C or higher, 116°C or higher, or 118°C or higher, for achieving a lubricant base oil that allows a lubricating oil composition excellent in safety to be prepared, and may be 300°C or lower, 280°C or lower, 260°C or lower, 240°C or lower, 220°C or lower, or 200°C or lower.

[0076] In this description, the flash point means a value measured by the Pensky-Martens closed-cup process (PM process) in accordance with JIS K2265-3: 2007.

[0077] The pour point of the lubricant base oil according to an aspect of the present invention is preferably - 50.0°C or lower, -52.5°C or lower, -55.0°C or lower, - 57.5°C or lower, -60.0°C or lower, or lower than -60.0°C, for achieving a lubricant base oil that allows a lubricating oil composition with good low-temperature fluidity to be prepared.

[0078] In this description, the pour point means a value measured in accordance with JIS K2269: 1987 (testing methods for pour point and cloud point of crude oil and petroleum products).

[0079] The volume resistivity of the lubricant base oil according to an aspect of the present invention measured under conditions of 80°C and 250 V / mm is preferably 1.0 TΩ·m or more, 5.0 TΩ·m or more, 10.0 TΩ·m or more, 15.0 TΩ·m or more, 20.0 TΩ·m or more, 25.0 TΩ·m or more, 30.0 TΩ·m or more, 40.0 TΩ·m or more, 50.0 TΩ·m or more, 60.0 TΩ·m or more, 70.0 TΩ·m or more, 80.0 TΩ·m or more, 90.0 TΩ·m or more, or 100.0 TΩ·m or more, for achieving a lubricant base oil that allows a lubricating oil composition with high insulation properties to be prepared.

[0080] In this description, the volume resistivity means a value measured under conditions at a measurement temperature of 80°C and an applied voltage of 250 V in accordance with JIS C2101: 1999.

[0081] The rubber swelling rate of an acrylic rubber for test, as measured by immersing the acrylic rubber for test in the lubricant base oil according to an aspect of the present invention under conditions at 100°C for 100 hours by a rubber immersion test method in accordance with JIS K6258, is preferably 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less, for achieving a lubricant base oil that allows a lubricating oil composition with high rubber compatibility to be prepared.

[0082] In this description, the rubber swelling rate of the acrylic rubber for test is the volume change rate of the acrylic rubber between before and after immersion calculated according to the following formula, and specifically means a value measured by the method described in Examples. [Configuration of lubricating oil composition]

[0083] The lubricating oil composition according to an aspect of the present invention comprises the lubricant base oil according to an aspect of the present invention.

[0084] The lubricating oil composition according to an aspect of the present invention may further contain additives for lubricating oil. Specifically, it may or may not contain one or more additives for lubricating oil selected from a pour point depressant, a viscosity index improver, an antioxidant, an extreme pressure agent, a metallic detergent, an ashless dispersant, a metal deactivator, a corrosion inhibitor, a rust inhibitor, and a defoamer.

[0085] The lubricating oil composition according to an aspect of the present invention may or may not contain a friction modifier.

[0086] One of these additives for lubricating oil may be used alone, or two or more of them may be used in combination.

[0087] The content of such an additive for lubricating oil can be appropriately adjusted, as long as the effects of the present invention are not impaired, but the content of each additive may independently be 0.001 mass% or more, 0.005 mass% or more, 0.01 mass% or more, 0.05 mass% or more, 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, and may be less than 15.0 mass%, less than 10.0 mass%, less than 8.0 mass%, less than 6.0 mass%, less than 5.0 mass%, less than 4.0 mass%, less than 3.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.10 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0088] In the lubricating oil composition according to an aspect of the present invention, the content of the aforementioned lubricant base oil according to an aspect of the present invention is preferably 50.0 mass% or more, 60.0 mass% or more, 70.0 mass% or more, 80.0 mass% or more, 85.0 mass% or more, 90.0 mass% or more, 95.0 mass% or more, 96.0 mass% or more, 97.0 mass% or more, 98.0 mass% or more, or 99.0 mass% or more, based on the total amount (100 mass%) of the lubricating oil composition.<Pour point depressant>

[0089] Examples of the pour point depressant to be used in an aspect of the present invention include ethylene-vinyl acetate copolymer, a condensate of chlorinated paraffin and naphthalene, a condensate of chlorinated paraffin and phenol, polymethacrylate, and polyalkylstyrene.

[0090] One of these pour point depressants may be used alone, or two or more of them may be used in combination.<Viscosity index improver>

[0091] Examples of the viscosity index improver to be used in an aspect of the present invention include polymers such as non-dispersed polymethacrylates, dispersed polymethacrylates, olefin copolymers (e.g., ethylenepropylene copolymer), dispersed olefin copolymers, styrene copolymers (e.g., styrene-diene copolymer and styrene-isoprene copolymer).

[0092] One of these viscosity index improvers may be used alone, or two or more of them may be used in combination.

[0093] Further, the weight-average molecular weight (Mw) of the viscosity index improver to be used in an aspect of the present invention may be 5,000 or more, 7,000 or more, 10,000 or more, 15,000 or more, or 20,000 or more, and 1,000,000 or less, 700,000 or less, 500,000 or less, 300,000 or less, 200,000 or less, 100,000 or less, or 50,000 or less.<Antioxidant>

[0094] Examples of the antioxidant to be used in an aspect of the present invention include amine antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenolic 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.

[0095] One of these antioxidants may be used alone, or two or more of them may be used in combination.

[0096] In the lubricating oil composition according to an aspect of the present invention, an amine antioxidant and a phenolic antioxidant are preferably used as antioxidants in combination.<Extreme pressure agent (antiwear agent)>

[0097] Examples of the extreme pressure agent (antiwear agent) to be used in an aspect of the present invention include such as sulfur-containing compounds such as zinc dithiophosphate; phosphorus-containing compounds such as phosphorous acid esters, phosphoric acid esters, phosphonic acid esters, and amine salts or metal salts thereof; and sulfur- and phosphorus-containing compounds such as thiophosphorous acid esters, thiophosphoric acid esters, thiophosphonic acid esters, and amine salts or metal salts thereof.

[0098] One of these extreme pressure agents may be used alone, or two or more of them may be used in combination.

[0099] The lubricating oil composition according to an aspect of the present invention may be limited by the content of the extreme pressure agent (antiwear agent) and may substantially not contain the extreme pressure agent (antiwear agent).

[0100] In the lubricating oil composition according to this aspect, the content of the extreme pressure agent (antiwear agent) may be 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.

[0101] The lubricating oil composition according to an aspect of the present invention may be limited by the content of zinc dithiophosphate and may substantially not contain zinc dithiophosphate.

[0102] In the lubricating oil composition according to this aspect, the content on a zinc atom basis of zinc dithiophosphate may be less than 100 ppm by mass, less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 100 ppb by mass, less than 10 ppb by mass, less than 1.0 ppb by mass, or less than 0.1 ppb by mass, based on the total amount (100 mass%) of the lubricating oil composition.

[0103] In this description, the content of the zinc atom means a value measured in accordance with JPI-5S-38-92.<Fatty acid amide>

[0104] The lubricating oil composition according to an aspect of the present invention may contain an aliphatic amide for imparting friction reducing effect thereto, and may be limited by the content of fatty acid amide for suppressing reduction in insulation properties.

[0105] In the lubricating oil composition according to an aspect of the present invention, the content of the aliphatic amide may be less than 1.0 mass%, less than 0.5 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, for suppressing reduction in insulation properties.

[0106] Examples of the aliphatic amide include reaction products of aliphatic carboxylic acids and aliphatic amines.

[0107] Examples of the aliphatic carboxylic acids include palmitic acid, isopalmitic acid, stearic acid, isostearic acid, behenic acid, lignoceric acid, cetylonic acid, heptacanoic acid, montanic acid, melissic acid, lacceric acid, setoleic acid, and erucic acid.

[0108] Further, examples of the aliphatic amines include ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.<Metallic detergent>

[0109] Examples of the metallic detergent to be used in an aspect of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. Further, the metal atom constituting such a metal salt is preferably a metal atom selected from alkali metals and alkaline earth metals, more preferably sodium, calcium, magnesium, or barium, further preferably calcium.

[0110] One of these metallic detergents may be used alone, or two or more of them may be used in combination.

[0111] In the lubricating oil composition according to an aspect of the present invention, the metallic detergent preferably contains one or more selected from calcium sulfonate, calcium salicylate, and calcium phenate, more preferably calcium sulfonate.

[0112] The content ratio of calcium sulfonate is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, further preferably 70 to 100 mass%, furthermore preferably 80 to 100 mass%, based on the total amount (100 mass%) of the metallic detergent contained in the lubricating oil composition.

[0113] The base number of the metallic detergent is preferably 0 to 600 mgKOH / g.

[0114] However, in the lubricating oil composition according to an aspect of the present invention, the metallic detergent is preferably an overbased metallic detergent having a base number of 100 mgKOH / g or more.

[0115] The base number of the overbased metallic detergent is 100 mgKOH / g or more, preferably 150 to 500 mgKOH / g, more preferably 200 to 450 mgKOH / g.

[0116] As used herein, the "base number" means the base number measured by the perchloric acid method according to chapter 7 of "Petroleum products and lubricating oils-Neutralization value test method" of JIS K2501:2003.

[0117] The lubricating oil composition according to an aspect of the present invention may be limited by the content of the metallic detergent such as a calcium detergent, a magnesium detergent, and a sodium detergent, and may substantially not contain the metallic detergent.

[0118] In the lubricating oil composition according to this aspect, the content on an alkali metal atom or alkaline earth metal atom (e.g., calcium atom, magnesium atom, or sodium atom) basis of the metallic detergent may be less than 1000 ppm by mass, less than 700 ppm by mass, less than 500 ppm by mass, less than 300 ppm by mass, less than 200 ppm by mass, less than 100 ppm by mass, less than 70 ppm by mass, less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 100 ppb by mass, less than 10 ppb by mass, less than 1.0 ppb by mass, or less than 0.1 ppb by mass, based on the total amount (100 mass%) of the lubricating oil composition.

[0119] In this description, the content of the alkali metal atom or the alkaline earth metal atom, such as a calcium atom, a magnesium atom, or a sodium atom, means a value measured in accordance with JPI-5S-38-92.<Ashless dispersant>

[0120] Examples of the ashless dispersant to be used in an aspect of the present invention include boron-free succinimides such as boron-free alkenylsuccinimide, boron-containing succinimides such as boron-containing alkenylsuccinimide, benzylamines, boron-containing benzylamines, succinic acid esters, and monovalent or divalent carboxylic acid amides typified by fatty acids or succinic acid.

[0121] One of these ashless dispersants may be used alone, or two or more of them may be used in combination.<Metal deactivator>

[0122] Examples of the metal deactivator to be used in an aspect of the present invention include benzotriazole compounds, tolyltriazole compounds, imidazole compounds, thiadiazole compounds, and pyrimidine compounds.

[0123] One of these metal deactivators may be used alone, or two or more of them may be used in combination.<Corrosion inhibitor>

[0124] Examples of the corrosion inhibitor to be used in an aspect of the present invention include amine compounds, alkanolamine compounds, amide compounds, and carboxylic acid compounds.

[0125] One of these corrosion inhibitors may be used alone, or two or more of them may be used in combination.<Rust inhibitor>

[0126] Examples of the rust inhibitor to be used in an aspect of the present invention include fatty acids, alkenyl succinic acid half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohols fatty acid esters, fatty acid amines, oxidized paraffins, and alkyl polyoxyethylene ethers.

[0127] One of these rust inhibitors may be used alone, or two or more of them may be used in combination.<Defoamer>

[0128] Examples of the defoamer to be used in an aspect of the present invention include silicone oils, fluorosilicone oils, and fluoroalkyl ethers.

[0129] One of these defoamers may be used alone, or two or more of them may be used in combination.<Friction modifier>

[0130] The lubricating oil composition according to an aspect of the present invention may further contain a friction modifier. One of such friction modifiers may be used alone, or two or more of them may be used in combination.

[0131] Examples of the friction modifier to be used in an aspect of the present invention include molybdenum friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdic acid; ashless friction modifiers such as aliphatic amine, fatty acid ester, fatty acid amide, fatty acid, aliphatic alcohol, and aliphatic ether having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms in the molecule; and fats and oils, amine, amide, and sulfurized esters, and the like.

[0132] The lubricating oil composition according to an aspect of the present invention may be limited by the content of the aforementioned molybdenum compound and may substantially not contain the molybdenum compound.

[0133] In the lubricating oil composition according to this aspect, the content of a molybdenum atom derived from the molybdenum compound may be less than 100 ppm by mass, less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 100 ppb by mass, less than 10 ppb by mass, less than 1.0 ppb by mass, or less than 0.1 ppb by mass, based on the total amount (100 mass%) of the lubricating oil composition

[0134] In this description, the content of the molybdenum atom means a value measured in accordance with JPI-5S-38-92.[Properties of lubricating oil composition]

[0135] The kinematic viscosity at 40°C of the lubricating oil composition according to an aspect of the present invention is preferably less than 3.0 mm 2< / s, less than 2.9 mm 2< / s, less than 2.8 mm 2< / s, less than 2.7 mm 2< / s, less than 2.6 mm 2< / s, less than 2.5 mm 2< / s, less than 2.4 mm 2< / s, less than 2.3 mm 2< / s, less than 2.2 mm 2< / s, less than 2.1 mm 2< / s, or less than 2.0 mm 2< / s, for achieving a lubricating oil composition with good cooling properties, and may be 1.0 mm 2< / s or more, 1.1 mm 2< / s or more, 1.2 mm 2< / s or more, 1.3 mm 2< / s or more, 1.4 mm 2< / s or more, 1.5 mm 2< / s or more, or 1.6 mm 2< / s or more.

[0136] The flash point of the lubricating oil composition according to an aspect of the present invention is preferably 90°C or higher, 100°C or higher, 102°C or higher, 104°C or higher, 106°C or higher, 108°C or higher, 110°C or higher, 112°C or higher, 114°C or higher, 116°C or higher, or 118°C or higher, for handling safety.

[0137] The pour point of the lubricating oil composition according to an aspect of the present invention is preferably -50.0°C or lower, -52.5°C or lower, -55.0°C or lower, -57.5°C or lower, -60.0°C or lower, or lower than -60.0°C, for achieving a lubricating oil composition with good startability and excellent fuel efficiency because of good low-temperature fluidity.

[0138] The volume resistivity of the lubricating oil composition according to an aspect of the present invention measured under conditions of 80°C and 250 V / mm is preferably 1.0 TΩ·m or more, 5.0 TΩ·m or more, 10.0 TΩ·m or more, 15.0 TΩ·m or more, 20.0 TΩ·m or more, 25.0 TΩ·m or more, 30.0 TΩ·m or more, 40.0 TΩ·m or more, 50.0 TΩ·m or more, 60.0 TΩ·m or more, 70.0 TΩ·m or more, 80.0 TΩ·m or more, 90.0 TΩ·m or more, or 100.0 TΩ·m or more, for achieving a lubricating oil composition with high insulation properties.

[0139] The rubber swelling rate of an acrylic rubber for test, as measured by immersing the acrylic rubber for test in the lubricating oil composition according to an aspect of the present invention under conditions at 100°C for 100 hours by a rubber immersion test method in accordance with JIS K6258, is preferably 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less, for achieving a lubricating oil composition with high rubber compatibility.

[0140] The thermal conductivity of the lubricating oil composition according to an aspect of the present invention is preferably 0.130 W / mK or more, 0.132 W / mK or more, 0.134 W / mK or more, 0.136 W / mK or more, 0.138 W / mK or more, 0.140 W / mK or more, or 0.142 W / mK or more, and may be 0.200 W / mK or less, 0.180 W / mK or less, or 0.160 W / mK or less.

[0141] In this description, the thermal conductivity means a value measured in accordance with ASTM D7896-19.[Applications of lubricating oil composition]

[0142] The lubricant base oil according to an aspect of the present invention has a low kinematic viscosity and is excellent in various properties such as volume resistivity, low-temperature fluidity, and rubber compatibility. The lubricating oil composition comprising this lubricant base oil is therefore excellent in various properties such as cooling properties, insulation properties, low-temperature fluidity, and rubber compatibility and as such, has preferable physical properties for cooling equipment mounted in an electric vehicle.

[0143] In consideration of such properties, the lubricating oil composition according to an aspect of the present invention is suitable as a lubricating oil composition for cooling at least one piece of equipment mounted in an electric vehicle, selected from a motor, a battery, an inverter, and an engine.

[0144] Thus, an aspect of the present invention also provides the following invention. [1] A method for cooling equipment, comprising cooling equipment mounted in an electric vehicle using the lubricating oil composition according to an aspect of the present invention. [2] Equipment mounted in an electric vehicle, the equipment being filled with the lubricating oil composition according to an aspect of the present invention as a cooling fluid.

[0145] Examples of the electric vehicle described in [1] and [2] above include hybrid vehicles and electric vehicles.

[0146] Examples of the equipment mounted in an electric vehicle include at least one selected from motors, batteries, inverters, and engines.Examples

[0147] Next, the present invention will be described in more detail with reference to Examples; however, the present invention is not limited in any way by these Examples. The methods for measuring or calculating various properties are as follows.(1) Average number of carbon atoms (Cav)

[0148] The gas chromatogram of a measurement sample was obtained using a gas chromatograph under measurement conditions below. Measurement apparatus: 8890 Gas Chromatograph (GC) System (product name, available from Agilent Technologies, Inc.) Column: HP-5ms column (length: 30 mm, inside diameter: 0.25 mm, film thickness: 0.25 µm: available from Agilent Technologies, Inc.) Carrier gas: Helium (114 kPa) Measurement sample: 0.1 g of a sample was diluted with 1.0 mL of hexane and measured. Sample injection volume: 0.3 µL Split ratio: 10 Detector: Hydrogen flame ionization detector (FID) Detector temperature: 300°C Oven temperature: Held at 100°C for 1 minute, then elevated to 320°C at a temperature elevation rate of 5°C / min, and held for 10 minutes.

[0149] The gas chromatogram of a standard sample having each number of carbon atoms was obtained using the gas chromatograph under the aforementioned measurement conditions, and data on an elution time (min) of each number of carbon atoms was obtained in advance.

[0150] The numbers of carbon atoms at peaks in the gas chromatogram of the measurement sample were identified on the basis of the obtained data on the elution time of each number of carbon atoms. The content ratio of a component having each number of carbon atoms in the measurement sample was identified from the area ratio of the peak of each number of carbon atoms to the total area of all the peaks except for a solvent in the gas chromatogram. A weighted average value of the numbers of carbon atoms was regarded as the average number of carbon atoms (Cav) in the measurement sample.(2) Total integral intensity ratio of CH group and CH 2 group (nonCH 3 )

[0151] The 1< H-NMR spectrum of a measurement sample was obtained using an NMR apparatus under measurement conditions below. Measurement apparatus: JNM400RS3 (product name, available from JEOL Ltd.) Measurement sample: Solution obtained by diluting 1.0 mL of a lubricant base oil by the addition of 1.0 mL of deuterated chloroform Measurement temperature: 25°C Resonance frequency: 400 MHz Of two peaks detected in the range of chemical shifts from 0.0 to 2.0 ppm in the obtained 1< H-NMR spectrum of the measurement sample, a downfield peak was identified as a peak derived from a CH group or a CH 2 group, and the other upfield peak was identified as a peak derived from a CH 3 group. The ratio of integral intensity S1 of the peak derived from the CH group or the CH 2 group to integral intensity S2 of the peak derived from the CH 3 group [S1 / S2] was regarded as the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group. (3) Average number of branches (avB)

[0152] The 13< C-NMR spectrum of a measurement sample was obtained using an NMR apparatus under measurement conditions below. Measurement apparatus: JNM400RS3 (product name, available from JEOL Ltd.) Measurement sample: Solution obtained by diluting 1.0 mL of a lubricant base oil by the addition of 1.0 mL of deuterated chloroform Measurement temperature: 25°C Resonance frequency: 100 MHz Total integral intensity (a) in the range of chemical shifts from 5.0 to 60.0 ppm and total integral intensity (b) in the range of chemical shifts from 5.0 to 20.0 ppm and from 22.45 to 22.80 ppm derived from terminal CH 3 groups were calculated in the obtained 13< C-NMR spectrum of the measurement sample. The ratio of the total integral intensity (b) to the total integral intensity (a) [(b) / (a)] was calculated, and the average number of branches (avB) was calculated according to the following formula (ii) from the value of [(b) / (a)] and the average number of carbon atoms (Cav) determined in (1) above: avB = Cav × b / a − 2 (4) Paraffin content

[0153] The paraffin content was calculated according to the following formula (i) from the value of the average number of carbon atoms (Cav) determined in (1) above, the value of the total integral intensity ratio (nonCH 3 ) of the CH group and the CH 2 group determined in (2) above, and the value of the average number of branches (avB) determined in (3) above: Production Example 1 (production of bottom oil)

[0154] An oil containing a heavy fuel oil obtained from a vacuum distillation apparatus in a usual fuel oil production process using a paraffinic crude oil was hydrocracked, and naphtha and kerosene and light oils were separated and removed to isolate a remaining bottom fraction. The bottom fraction was used as a "bottom oil" in production below.Production Example 2 (production of solvent-dewaxed oil and slack wax)

[0155] The bottom oil thus obtained was treated by solvent dewaxing in a low-temperature range of -35°C to -30°C using a mixed solvent of methyl ethyl ketone and toluene, and a wax was separated to obtain a "solvent-dewaxed oil". The separated wax was used as a "slack wax".Example 1

[0156] A raw oil prepared by mixing 25 parts by mass of the bottom oil obtained in Production Example 1 with 75 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0157] Subsequently, the refined oil after hydroisomerization dewaxing was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0158] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 2.0 mm 2< / s was recovered to obtain a lubricant base oil (1).

[0159] Figure 1 shows the gas chromatogram of the lubricant base oil (1) measured on the basis of the aforementioned conditions. Figure 2 shows the 1< H-NMR spectrum of the lubricant base oil (1) measured on the basis of the aforementioned conditions. Figure 3 shows a 13< C-NMR spectrum of the lubricant base oil (1) measured on the basis of the aforementioned conditions.Example 2

[0160] A raw oil prepared by mixing 10 parts by mass of the bottom oil obtained in Production Example 1 with 90 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0161] Subsequently, the refined oil after hydroisomerization dewaxing treatment was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0162] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 1.8 mm 2< / s was recovered to obtain a lubricant base oil (2).Example 3

[0163] A raw oil prepared by mixing 20 parts by mass of the bottom oil obtained in Production Example 1 with 80 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0164] Subsequently, the refined oil after hydroisomerization dewaxing treatment was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0165] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 2.6 mm 2< / s was recovered to obtain a lubricant base oil (3).Comparative Example 1

[0166] A raw oil prepared by mixing 40 parts by mass of the bottom oil obtained in Production Example 1 with 60 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0167] Subsequently, the refined oil after hydroisomerization dewaxing treatment was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0168] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 2.4 mm 2< / s was recovered to obtain a lubricant base oil (4).Comparative Example 2

[0169] A lubricant base oil (5) was obtained in the same manner as in Comparative Example 1 except that the hydroisomerization dewaxing treatment was not performed.Comparative Example 3

[0170] A lubricant base oil (6) was obtained in the same manner as in Comparative Example 1 except that a bottom oil and a slack wax obtained from an intermediate base crude oil instead of the paraffinic crude oil was used; and a fraction with a kinematic viscosity at 40°C of around 8.4 mm 2< / s was recovered.Comparative Example 4

[0171] A raw oil prepared by mixing 5 parts by mass of the bottom oil obtained in Production Example 1 with 95 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0172] Subsequently, the refined oil after hydroisomerization dewaxing treatment was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0173] The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 5.4 mm 2< / s was recovered to obtain a lubricant base oil (7).

[0174] The values of various physical properties were measured as to the produced lubricant base oils (1) to (7) by methods below. These results are shown in Table 1.[40°C kinematic viscosity]

[0175] It was measured in accordance with JIS K2283: 2000. [15°C density] It was measured at 15°C in accordance with JIS K2249. [Pour point]

[0176] It was measured in accordance with JIS K2269: 1987 (testing methods for pour point and cloud point of crude oil and petroleum products).[Flash point]

[0177] It was measured by the Pensky-Martens closed-cup process (PM process) in accordance with JIS K2265-3: 2007.[Rubber swelling rate]

[0178] A rubber immersion test in accordance with JIS K6258 was conducted.

[0179] Specifically, an acrylic rubber for test (product name: "T303", available from NOK CORPORATION) was immersed in each lubricant base oil as a measurement target under conditions at an immersion temperature of 100°C for an immersion time of 100 hours and measured. Then, the volume of the acrylic rubber for test was measured before and after the test, and the volume change rate was calculated from the following formula.

[0180] It can be said that the lower the value of the rubber swelling rate, the more excellent the rubber compatibility of the lubricant base oil. In this example, lubricant base oils with a rubber swelling rate of 9% or less were determined to have good rubber compatibility.[Volume resistivity]

[0181] It was measured under conditions at a measurement temperature of 80°C and an applied voltage of 250 V in accordance with JIS C2101: 1999.[Table 1]

[0182] Table 1CavnonCH3avBParaffin content40°C kinematic viscosity [mm 2< / s]15°C density [g / cm 3< ]Pour point [°C]Flash point [°C]Rubber swelling rate [%]Volume resistivity [TΩ·m]Example 114.31.801.300.9082.080.772-60.0>1065110Example 214.92.041.280.9411.830.766-60.094620Example 315.52.061.290.9142.610.777-60.0>119525Comparative Example 114.92.200.910.8802.370.775-27.5114546Comparative Example 214.11.690.350.6292.380.821-47.51061037Comparative Example 321.52.230.820.6078.230.831-32.5146427Comparative Example 419.92.681.700.9785.410.798-60.0>138430

[0183] From Table 1, the lubricant base oils (1) to (3) of Examples 1 to 3 are determined to have good cooling properties, low-temperature fluidity, rubber compatibility, and volume resistivity from the 40°C kinematic viscosity, pour point, rubber swelling rate, and volume resistivity values. By contrast, the lubricant base oils (4) to (7) of Comparative Examples 1 to 4 have a high pour point and are thus considered to be inferior in low-temperature fluidity. Also, the lubricant base oil (5) of Comparative Example 2 has a high rubber swelling rate and thus presents a problem associated with rubber compatibility. Furthermore, the lubricant base oils (6) and (7) of Comparative Examples 3 and 4 have a high 40°C kinematic viscosity and are thus determined to be inferior in cooling properties.

Examples

production example 1 (

Production Example 1 (production of bottom oil)

[0154]An oil containing a heavy fuel oil obtained from a vacuum distillation apparatus in a usual fuel oil production process using a paraffinic crude oil was hydrocracked, and naphtha and kerosene and light oils were separated and removed to isolate a remaining bottom fraction. The bottom fraction was used as a "bottom oil" in production below.

production example 2 (

Production Example 2 (production of solvent-dewaxed oil and slack wax)

[0155]The bottom oil thus obtained was treated by solvent dewaxing in a low-temperature range of -35°C to -30°C using a mixed solvent of methyl ethyl ketone and toluene, and a wax was separated to obtain a "solvent-dewaxed oil". The separated wax was used as a "slack wax".

example 1

[0156]A raw oil prepared by mixing 25 parts by mass of the bottom oil obtained in Production Example 1 with 75 parts by mass of the slack wax obtained in Production Example 2 was subjected to hydroisomerization dewaxing treatment under conditions at a hydrogen partial pressure of 10 to 18 MPa, a reaction temperature of 200 to 250°C, and LHSV of 0.8 to 1.5 hr -1< using a hydroisomerization dewaxing catalyst.

[0157]Subsequently, the refined oil after hydroisomerization dewaxing was subjected to hydrogenation treatment under conditions at a hydrogen partial pressure of 15 to 18 MPa, a reaction temperature of 350 to 370°C, and LHSV of 1.0 to 2.0 hr -1< using a nickel-tungsten catalyst.

[0158]The refined oil after hydrogenation treatment was vacuum-distilled, and a fraction with a kinematic viscosity at 40°C of around 2.0 mm 2< / s was recovered to obtain a lubricant base oil (1).

[0159]Figure 1 shows the gas chromatogram of the lubricant base oil (1) measured on the basis of the aforement...

Claims

1. A lubricant base oil for use in the cooling of equipment mounted in an electric vehicle, the lubricant base oil satisfying the following requirements (I) to (III): requirement (I): an average number of carbon atoms (Cav) measured using a gas chromatograph is 19.0 or less, requirement (II): a total integral intensity ratio of a CH group and a CH2 group (nonCH3) which is the ratio of integral intensity S1 of peaks derived from the CH group and the CH2 group to integral intensity S2 of a peak derived from a CH3 group [S1 / S2] is 1.75 or more in a 1H-NMR spectrum measured using an NMR apparatus, and requirement (III): a paraffin content calculated according to the following formula (i) is 0.885 or more: wherein nonCH3 is the total integral intensity ratio of the CH group and the CH2 group, Cav is the average number of carbon atoms, and avB represents an average number of branches and is a value calculated according to the following formula (ii) from a value of a ratio of total integral intensity (b) in a range of chemical shifts from 5.0 to 20.0 ppm and from 22.45 to 22.80 ppm derived from terminal CH3 groups to total integral intensity (a) in a range of chemical shifts from 5.0 to 60.0 ppm [(b) / (a)] in a 13C-NMR spectrum measured using an NMR apparatus: avB = Cav × b / a − 2 .

2. The lubricant base oil according to claim 1, wherein avB in the formula (i) is 1.00 or more and 1.65 or less.

3. The lubricant base oil according to claim 1 or 2, wherein the total integral intensity ratio (nonCH3) is less than 2.20.

4. The lubricant base oil according to any one of claims 1 to 3, wherein the lubricant base oil is a base oil obtained by a refining treatment of a raw oil (α) containing a bottom oil and a petroleum-derived wax.

5. The lubricant base oil according to claim 4, wherein a content ratio between the bottom oil and the wax [bottom oil / wax] in the raw oil (α) is a mass ratio of over 5 / 95 and less than 40 / 60.

6. The lubricant base oil according to claim 4 or 5, wherein the refining treatment includes at least hydroisomerization dewaxing treatment.

7. The lubricant base oil according to any one of claims 1 to 6, wherein the lubricant base oil has a kinematic viscosity at 40°C of 1.00 mm2 / s or more and 5.00 mm2 / s or less.

8. The lubricant base oil according to any one of claims 1 to 7, wherein the lubricant base oil has a density at 15°C of 0.750 g / cm3 or more.

9. The lubricant base oil according to any one of claims 1 to 8, wherein the lubricant base oil has a flash point of 100°C or higher.

10. The lubricant base oil according to any one of claims 1 to 9, wherein the lubricant base oil has a pour point of -50.0°C or lower.

11. The lubricant base oil according to any one of claims 1 to 10, wherein the lubricant base oil has a volume resistivity of 1.0 TΩ·m or more measured under conditions of 80°C and 250 V / mm.

12. The lubricant base oil according to any one of claims 1 to 11, wherein a rubber swelling rate of an acrylic rubber for test, as measured by immersing the acrylic rubber for test in the lubricant base oil under conditions at 100°C for 100 hours by a rubber immersion test method in accordance with JIS K6258, is 9% or less.

13. A lubricating oil composition for use in the cooling of equipment mounted in an electric vehicle, the lubricating oil composition comprising the lubricant base oil according to any one of claims 1 to 12.

14. The lubricating oil composition according to claim 13, further comprising one or more additives for lubricating oils selected from a pour point depressant, a viscosity index improver, an antioxidant, an extreme pressure agent, a metallic detergent, an ashless dispersant, a metal deactivator, a corrosion inhibitor, a rust inhibitor, and a defoamer.

15. The lubricating oil composition according to claim 14, wherein a total content of the additives for lubricating oils is 5.0 mass% or less based on a total amount of the lubricating oil composition.

16. A method for cooling equipment, comprising cooling equipment mounted in an electric vehicle using the lubricating oil composition according to any one of claims 13 to 15.

17. The method for cooling equipment according to claim 16, wherein the equipment is at least one selected from a motor, a battery, an inverter, and an engine.

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