Lubricating oil base oil for power transmission

Abstract

To provide a lubricant base oil for power transmission that is high in traction coefficient and flash point and is superior in low temperature flowability.SOLUTION: The present invention relates to a lubricant base oil for power transmission that comprises a diester compound represented by the following general formula (1) [where R1 and R2 are the same or different to represent a C1-4 linear or branched alkyl group].SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a lubricating oil base oil for power transmission. Specifically, it relates to a lubricating oil base oil for traction drive.

Background Art

[0002] In recent years, with the progress of digital information socialization, the required accuracy for printers and copiers has been increasing. Particularly in the motor section where high-precision paper feeding is required, high rotational accuracy, low vibration, and low noise are demanded. When a gear system is adopted as the power transmission means for these rotating parts, vibration and noise are large, so traction drives with less of these are widely used.

[0003] In addition, the popularization of industrial robots has also advanced, and traction drives are also used in joint parts that require precise movement. In addition, the practical application of traction drives has progressed in fields such as continuously variable transmissions for industrial equipment, generators for aircraft, and rotor speed control for helicopters. In order to increase the power transmission amount, the study of increasing the size of traction drives has been underway, but the amount of heat generation tends to increase with the increase in the contact area.

[0004] The lubricating oil base oil for traction drive preferably has a high traction coefficient in order to enhance the power transmission ability, and alicyclic hydrocarbon compounds and the like have been proposed. For example, dicyclohexyl compounds represented by 2-methyl-2,4-dicyclohexylpentane, dimerized norbornanes, etc. can be mentioned (Patent Documents 1 and 2).

[0005] However, alicyclic hydrocarbon compounds represented by 2-methyl-2,4-dicyclohexylpentane tend to have a low flash point of 200°C or less, and are not always sufficient in fields where heat resistance and safety, which are important when large traction drives and the like are adopted.

[0006] In addition, ester compounds have been proposed as high flash point lubricating base oils for traction drives. For example, alicyclic diester compounds represented by di(cyclohexylmethyl) 1,2-cyclohexanedicarboxylate can be mentioned (Patent Document 3).

[0007] However, alicyclic diester compounds represented by di(cyclohexylmethyl) 1,2-cyclohexanedicarboxylate tend to have a high pour point of -20°C or higher, and are not always sufficient in fields where operability at low temperatures, such as in aircraft, helicopters, and automobiles, is highly regarded.

[0008] Patent Document 4 exemplifies diesters of neopentyl glycol and cyclohexanecarboxylic acid, diesters of neopentyl glycol and methylcyclohexanecarboxylic acid, and diesters of neopentyl glycol and a mixture of cyclohexanecarboxylic acid and methylcyclohexanecarboxylic acid (molar ratio of acids 1:1) as traction fluids, but there is no description or suggestion regarding low-temperature fluidity, flash point, and traction coefficient at high temperatures, so it is not always sufficient as a lubricating base oil for traction drives.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object of the present invention is to provide a base oil for a power transmission lubricating oil having a high traction coefficient, a high flash point, and good low-temperature fluidity (particularly, a base oil for a traction drive lubricating oil).

Means for Solving the Problems

[0011] The present inventors have found that a diester compound represented by the general formula (1) has a high traction coefficient and a high flash point, and also has good low-temperature fluidity, and is useful as a base oil for a power transmission lubricating oil (particularly, a base oil for a traction drive lubricating oil). The present invention has been completed by further study based on such findings.

[0012] That is, the present invention provides a base oil for a power transmission lubricating oil (particularly, a base oil for a traction drive lubricating oil) of the following items.

[0013] [Item 1] General formula (1)

Chemical formula

[0014] [Item 2] The base oil for a power transmission lubricating oil according to [Item 1], wherein R 1 and R 2 in the general formula (1) are the same or different and each is a methyl group, an ethyl group or an n-butyl group, respectively.

[0015] [Item 3] The base oil for a power transmission lubricating oil according to [Item 2], wherein R 1 and R 2 in the general formula (1) are each a methyl group.

[0016] [Item 4] The content of the diester compound represented by the general formula (1) is 70% by mass or more in the base oil for power transmission lubricating oil, the base oil for power transmission lubricating oil according to any one of [Item 1] to [Item 3].

[0017] [Item 5] The content of the diester compound represented by the general formula (1) is 90% by mass or more in the base oil for power transmission lubricating oil, the base oil for power transmission lubricating oil according to any one of [Item 1] to [Item 4].

[0018] [Item 6] The content of the diester compound represented by the general formula (1) is 98% by mass or more in the base oil for power transmission lubricating oil, the base oil for power transmission lubricating oil according to any one of [Item 1] to [Item 5].

[0019] [Item 7] The base oil for power transmission lubricating oil is a base oil for traction drive lubricating oil, the base oil for power transmission lubricating oil according to any one of [Item 1] to [Item 6].

[0020] [Item 8] A power transmission lubricating oil containing the base oil for power transmission lubricating oil according to any one of [Item 1] to [Item 7].

[0021] [Item 9] A power transmission lubricating oil containing the base oil for power transmission lubricating oil according to any one of [Item 1] to [Item 7] and an antioxidant.

[0022] [Item 10] The antioxidant is a phenolic antioxidant and / or an amine-based antioxidant, the power transmission lubricating oil according to [Item 9]. [Advantages of the Invention]

[0023] The diester compound of the present invention has characteristics of high traction coefficient (60 °C, 140 °C) and flash point, and good low-temperature fluidity, and thus can be suitably used as a base oil for power transmission lubricating oil (especially, a base oil for traction drive lubricating oil). [Brief Description of the Drawings]

[0024]

Figure 1

Figure 2

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] The lubricating base oil for power transmission of the present invention is represented by the general formula (1)

Chemical formula

[0026] In the general formula (1), R 1 and R 2 are the same or different and each represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group or a tert-butyl group, preferably a methyl group, an ethyl group or an n-butyl group, and particularly preferably a methyl group.

[0027] Specific examples of the diester compound represented by the general formula (1) include, for example, bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-methylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-n-propylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-isopropylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-methylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-methylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-methylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-methylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-n-propylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-isopropylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-ethylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-ethylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-ethylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-ethylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-propylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isopropyl-2-n-propylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-n-propylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-n-propylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-propylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-...3-(2-tert-butyl-2-n-propylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisopropylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-isopropylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-isopropylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-isopropylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-isopropylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-butylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-sec-butylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-sec-butylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-tert-butylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butylpropyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-tert-butylpropyl) may be mentioned. Among them, bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl) and bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-ethylpropyl) are preferable.,

[0028] The above diester compounds can be used alone or as a mixture of two or more as a base oil for power transmission lubricating oil.

[0029] The method for producing the diester compound represented by the general formula (1) is not particularly limited. For example, as shown in Reaction Scheme 1, the diester compound represented by the general formula (1) can be produced by reacting a carboxylic acid represented by the formula (2) or a derivative thereof with a diol represented by the general formula (3). Here, examples of the derivative of the carboxylic acid represented by the formula (2) include highly reactive derivatives such as acid halides (e.g., acid chlorides, etc.), mixed acid anhydrides, active esters, and lower (C1-C4) alkyl esters. [Chemical formula] [In the formula, R 1 and R 2 are the same as described above.] The diester compound represented by the general formula (1) can be produced, for example, by heating a carboxylic acid (3-methylcyclohexanecarboxylic acid) represented by the formula (2) and a diol represented by the general formula (3) in the presence of an acid catalyst (e.g., sulfuric acid, p-toluenesulfonic acid, etc.) and removing the by-produced water while performing dehydration condensation. Also, the acid catalyst can be changed to an inorganic metal catalyst (e.g., tin oxide, etc.) or an organic titanium catalyst (e.g., tetra-n-butoxytitanium, etc.), and the compound can be produced in the same manner. Further, the diester compound represented by the general formula (1) can also be produced by reacting a carboxylic acid represented by the formula (2) with a diol represented by the general formula (3) in the presence of a condensing agent (e.g., dicyclohexylcarbodiimide, carbonyldiimidazole, etc.). Also, the diester compound represented by the general formula (1) can be produced by converting the carboxylic acid represented by the formula (2) into a highly reactive derivative such as an acid halide (e.g., acid chloride, etc.), a mixed acid anhydride, or an active ester, and then reacting with a diol represented by the general formula (3) in the presence of a base (e.g., triethylamine, 4-(N,N-dimethylamino)pyridine, pyridine, etc.). In addition, the diester compound represented by the general formula (1) can also be produced by reacting a carboxylic acid represented by the formula (2) with a lower alcohol (having 1 to 4 carbon atoms, such as methanol, ethanol, etc.) (esterification) to form a lower alkyl ester, and then subjecting this to a transesterification reaction with a diol represented by the general formula (3). The reaction represented by the above Reaction Formula 1 can be carried out according to or in accordance with known reaction conditions depending on the type of the reaction.

[0030] Alternatively, as shown in Reaction Formula 2, the diester compound represented by the general formula (1) can be produced by reacting a compound (m-toluic acid) represented by the formula (4) or a derivative thereof with a diol represented by the general formula (3) (esterification or transesterification reaction) to obtain a compound represented by the general formula (5), and then subjecting the aromatic ring of the compound to nuclear hydrogenation (reduction). Here, examples of the derivative of m-toluic acid include highly reactive derivatives such as acid halides (e.g., acid chlorides, etc.), mixed acid anhydrides, active esters, and lower alkyl esters (having 1 to 4 carbon atoms). [Chemical formula] [In the formula, R 1 and R 2 are the same as above.] The reaction of reacting a compound (m-toluic acid) represented by the formula (4) or a derivative thereof with a diol represented by the general formula (3) to produce a compound represented by the general formula (5) can be carried out according to or in accordance with the reaction of reacting a carboxylic acid represented by the formula (2) or a derivative thereof in the above Reaction Formula 1 with a diol represented by the general formula (3) to produce a compound represented by the general formula (1). For the reaction of nuclear hydrogenation (reduction) of the compound represented by the general formula (5), a known method can be adopted. For example, in a hydrogen atmosphere (from room temperature to pressurized), in the presence of a reduction catalyst (transition metals such as platinum, palladium, nickel, rhodium, etc. or their oxides, Pd / C, etc.), by reducing the compound represented by the general formula (5), the compound represented by the general formula (1) can be produced.

[0031] From the viewpoints of simplicity and practicality, the method obtained by the esterification reaction of 3-methylcyclohexanecarboxylic acid and the diol represented by the general formula (3) is most preferable.

[0032] The acid value of the diester compound represented by the general formula (1) is preferably 0.1 mgKOH / g or less, more preferably 0.05 mgKOH / g or less. When the acid value is 0.1 mgKOH / g or less, the heat resistance of the diester compound represented by the general formula (1) itself tends to be further improved, and in such a preferable range, it also has a favorable effect on the improvement of the thermal oxidation stability of the base oil of the present invention. As a method for reducing the acid value, a method of sufficiently advancing the reaction, a method of neutralizing and washing with an alkaline component in the post-treatment step (for example, a method of washing (neutralizing) with an aqueous alkaline solution and washing with water), a method of adsorbing treatment with activated alumina, etc. are exemplified.

[0033] The hydroxyl value of the diester compound represented by the general formula (1) is preferably 2 mgKOH / g or less, more preferably 1 mgKOH / g or less. When the hydroxyl value is 2 mgKOH / g or less, the hygroscopicity of the diester compound represented by the general formula (1) itself becomes lower, and the heat resistance also tends to be further improved, and in such a preferable range, it also has a favorable effect on the improvement of the water resistance and thermal oxidation stability of the base oil of the present invention. As a method for reducing the hydroxyl value, a method of sufficiently advancing the reaction, a method of distilling off the raw material alcohol component under reduced pressure in the post-treatment step (for example, a method of distilling off excess raw material alcohol that can be distilled under reduced pressure or normal pressure), etc. are exemplified.

[0034] The present invention discloses a lubricating oil base oil for power transmission containing a diester compound represented by the general formula (1) (particularly, a lubricating oil base oil for traction drive).

[0035] The traction coefficient (60 °C) of the lubricating oil base oil for power transmission is usually 0.080 or more, preferably 0.090 or more. In the present specification and claims, the traction coefficient (60 °C) is a value measured by the method described in the examples below.

[0036] Also, the traction coefficient (at 140°C) is usually 0.075 or more, preferably 0.085 or more. In the present specification and claims, the traction coefficient (at 140°C) is the value measured by the method described in the examples below.

[0037] The low-temperature fluidity of the lubricating oil base oil for power transmission can be evaluated, for example, by the pour point. The pour point of the lubricating oil base oil is usually -30°C or lower, preferably -35°C or lower, from the viewpoint of low-temperature operability. In the present specification and claims, the pour point is the value measured by the method described in the examples below.

[0038] The flash point of the lubricating oil base oil for power transmission is usually 185°C or higher, preferably 200°C or higher, from the viewpoints of storage stability and handleability. If it is less than 185°C, there will be more restrictions on handling due to ignition. In the present specification and claims, the flash point is the value measured by the method described in the examples below.

[0039] As the lubricating base oil for power transmission, there are lubricating base oils for power transmission with a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.085 or more, a pour point of -30°C or less, and a flash point of 185°C or more; lubricating base oils for power transmission with a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.075 or more, a pour point of -35°C or less, and a flash point of 185°C or more; lubricating base oils for power transmission with a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.075 or more, a pour point of -30°C or less, and a flash point of 200°C or more; lubricating base oils for power transmission with a traction coefficient (60°C) of 0.080 or more, a traction coefficient (140°C) of 0.075 or more, a pour point of -35°C or less, and a flash point of 200°C or more. Further, lubricating base oils for power transmission with a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.085 or more, a pour point of -35°C or less, and a flash point of 185°C or more; lubricating base oils for power transmission with a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.085 or more, a pour point of -30°C or less, and a flash point of 200°C or more; lubricating base oils for power transmission with a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.075 or more, a pour point of -35°C or less, and a flash point of 200°C or more are preferred. In particular, a lubricating base oil for power transmission with a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.085 or more, a pour point of -35°C or less, and a flash point of 200°C or more is preferred.

[0040] Since the lubricating base oil for power transmission of the present invention has a high traction coefficient (60°C, 140°C) and flash point, and good low-temperature fluidity, it is preferably used as a lubricating base oil for power transmission, particularly as a lubricating base oil for traction drive.

[0041] The lubricating base oil for power transmission of the present invention can contain other base oils that can be used in combination (hereinafter referred to as "combined base oils"). That is, the lubricating base oil for power transmission of the present invention includes only the diester compound represented by the general formula (1) and a mixture of the diester compound represented by the general formula (1) and the combined base oil. Hereinafter, the lubricating base oil for power transmission may be referred to as "base oil".

[0042] Examples of the base oil to be used in combination include mineral oil (hydrocarbon oil obtained by refining petroleum), poly-α-olefin, polybutene, alkylbenzene, alkylnaphthalene, alicyclic hydrocarbon oil, animal and vegetable oils, organic acid esters (excluding diester compounds represented by the general formula (1)), polyalkylene glycol, polyvinyl ether, polyphenyl ether, alkylphenyl ether, silicone oil, and the like. At least one of these can be used in appropriate combination.

[0043] Examples of the mineral oil include solvent-refined mineral oil, hydrorefined mineral oil, and wax isomerized oil. Usually, those having a kinematic viscosity at 100 °C of 1 to 25 mm 2 / s, preferably 2 to 20 mm 2 / s are used.

[0044] Examples of the poly-α-olefin include polymers or copolymers of α-olefins having 2 to 16 carbon atoms (such as ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, etc.), which have a kinematic viscosity at 100 °C of 1 to 25 mm 2 / s and a viscosity index of 100 or more. In particular, those having a kinematic viscosity at 100 °C of 1.5 to 20 mm 2 / s and a viscosity index of 120 or more are preferred.

[0045] Examples of the polybutene include those obtained by polymerizing isobutylene and those obtained by copolymerizing isobutylene with normal butylene. Generally, those having a kinematic viscosity at 100 °C in a wide range of 2 to 40 mm 2 / s are included.

[0046] Examples of the alkylbenzene include monoalkylbenzene, dialkylbenzene, trialkylbenzene, tetraalkylbenzene, etc. having a molecular weight of 200 to 450 and substituted with a linear or branched alkyl group having 1 to 40 carbon atoms.

[0047] Examples of alkylnaphthalenes include monoalkylnaphthalenes and dialkylnaphthalenes substituted with linear or branched alkyl groups having 1 to 30 carbon atoms.

[0048] Examples of alicyclic hydrocarbon oils include naphthenic hydrocarbon oils, etc., and generally those having a kinematic viscosity at 100 °C in the wide range of 1 to 40 mm 2 / s are exemplified.

[0049] Examples of animal and vegetable oils include beef tallow, lard, palm oil, coconut oil, rapeseed oil, castor oil, sunflower oil, etc.

[0050] Examples of organic acid esters include fatty acid monoesters, aliphatic dibasic acid diesters, aliphatic dihydric alcohol diesters (excluding the diester compounds represented by the general formula (1)), polyol esters, and other esters.

[0051] Examples of fatty acid monoesters include esters of aliphatic linear or branched monocarboxylic acids having 5 to 22 carbon atoms and linear or branched saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

[0052] Examples of aliphatic dibasic acid diesters include diesters of aliphatic dibasic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonamethylenedicarboxylic acid, 1,10-decamethylenedicarboxylic acid, or their anhydrides and linear or branched saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

[0053] As the aliphatic dihydric alcohol diester (excluding the diester compound represented by the general formula (1)) and polyol ester, polyols having a neopentyl structure such as neopentyl glycol, 2,2 - diethylpropanediol, 2 - butyl - 2 - ethylpropanediol, trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, etc., 1,3 - propanediol, 1,4 - butanediol, 1,5 - pentanediol, 1,6 - hexanediol, 1,7 - heptanediol, 1,8 - octanediol, 1,9 - nonanediol, 1,10 - decanediol, 1,2 - propanediol, 2 - methyl - 1,3 - propanediol, 1,3 - butanediol, 2 - methyl - 1,4 - butanediol, 1,4 - pentanediol, 2 - methyl - 1,5 - pentanediol, 3 - methyl - 1,5 - pentanediol, 1,5 - hexanediol, 2 - methyl - 1,6 - hexanediol, 3 - methyl - 1,6 - hexanediol, 1,6 - heptanediol, 2 - methyl - 1,7 - heptanediol, 3 - methyl - 1,7 - heptanediol, 4 - methyl - 1,7 - heptanediol, 1,7 - octanediol, 2 - methyl - 1,8 - octanediol, 3 - methyl - 1,8 - octanediol, 4 - methyl - 1,8 - octanediol, 1,8 - nonanediol, 2 - methyl - 1,9 - nonanediol, 3 - methyl - 1,9 - nonanediol, 4 - methyl - 1,9 - nonanediol, 5 - methyl - 1,9 - nonanediol, 2 - ethyl - 1,3 - hexanediol, 2,4 - diethyl - 1,5 - pentanediol, glycerin, polyglycerin, sorbitol, etc., non - neopentyl - type polyols and full esters of linear and / or branched saturated or unsaturated fatty acids having 3 to 22 carbon atoms can be used.

[0054] As other esters, there may be mentioned esters of polymerized fatty acids such as dimer acid, hydrogenated dimer acid, or hydroxy fatty acids such as condensed castor oil fatty acid, hydrogenated condensed castor oil fatty acid, etc., and linear or branched saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

[0055] Examples of the polyalkylene glycol include a ring-opening polymer of an alcohol and a linear or branched alkylene oxide having 2 to 4 carbon atoms. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, and a polymer using one of these or a copolymer using a mixture of two or more of them can be used. Further, a compound in which the hydroxyl group portion at one or both ends is etherified can also be used. The kinematic viscosity of the polymer is preferably 5 to 1000 mm 2 / s (40 °C), more preferably 5 to 500 mm 2 / s (40 °C) is recommended.

[0056] The polyvinyl ether is a compound obtained by polymerization of a vinyl ether monomer. Examples of the monomer include methyl vinyl ether, ethyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, sec-butyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, 2-methoxyethyl vinyl ether, 2-ethoxyethyl vinyl ether, and the like. The kinematic viscosity of the polymer is preferably 5 to 1000 mm 2 / s (40 °C), more preferably 5 to 500 mm 2 / s (40 °C) is recommended.

[0057] Examples of the polyphenyl ether include a compound having a structure in which the meta positions of two or more aromatic rings are connected by an ether bond or a thioether bond. Specifically, bis(m-phenoxyphenyl) ether, m-bis(m-phenoxyphenoxy) benzene, and thioethers (commonly called C-ethers) in which one or more of their oxygens are replaced by sulfur are exemplified.

[0058] Examples of the alkylphenyl ether include a compound in which the polyphenyl ether is substituted with a linear or branched alkyl group having 6 to 18 carbon atoms, and an alkyldiphenyl ether substituted with one or more alkyl groups is particularly preferable.

[0059] Examples of silicone oils include dimethyl silicone, methylphenyl silicone, and modified silicones such as long-chain alkyl silicone and fluorosilicone.

[0060] The content of the diester compound represented by the general formula (1) in the lubricating oil base oil for power transmission of the present invention is usually 70% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0061] The content of the combined base oil in the lubricating oil base oil for power transmission of the present invention is usually 30% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

[0062] The present invention also provides a lubricating oil for power transmission containing the lubricating oil base oil for power transmission. In order to improve its performance, the lubricating oil for power transmission may be appropriately blended with at least one of additives such as antioxidants, metal detergents, ashless dispersants, oiliness agents, antiwear agents, extreme pressure agents, metal deactivators, rust preventives, viscosity index improvers, pour point depressants, antifoaming agents, hydrolysis inhibitors, thickeners, corrosion inhibitors, and hue stabilizers in the base oil. The blending amounts of these are not particularly limited as long as the effects of the present invention are achieved, and specific examples thereof are shown below.

[0063] Examples of the antioxidant include phenolic antioxidants, amine antioxidants, etc. Specifically, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-isopropylidenebisphenol, 2,4-dimethyl-6-tert-butylphenol, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 2,2'-dihydroxy-3,3'-di(α-methylcyclohexyl)-5,5'-dimethyl-diphenylmethane, 2,2'-isobutylidenebis(4,6-dimethylphenol), 2,6-bis(2'-hydroxy-3'-tert-butyl-5'-methylbenzyl)-4-methylphenol, 1,1'-bis(4-hydroxyphenyl)cyclohexane, 2,5-di-tert-amylhydroquinone, 2,5-di-tert-butylhydroquinone, 1,4-dihydroxyanthraquinone, 3-tert-butyl-4-hydroxyanisole, 2-tert-butyl-4-hydroxyanisole, 2,4-dibenzoylresorcinol, 4-tert-butylcatechol, 2,6-di-tert-butyl-4-ethylphenol, 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,4,5-trihydroxybenzophenone, α-tocopherol, bis[2-(2-hydroxy-5-methyl-3-tert-butylbenzyl)-4-methyl-6-tert-butylphenyl]terephthalate, triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], diphenylamine, monobutyl (including straight-chain and branched-chain) diphenylamine, monopentyl (including straight-chain and branched-chain) diphenylamine, monohexyl (including straight-chain and branched-chain) diphenylamine, monoheptyl (including straight-chain and branched-chain) diphenylamine, monooctyl (including straight-chain and branched-chain) diphenylamine and other monoalkyldiphenylamines, especially mono(C4-C9 alkyl) diphenylamine (that is, diphenylamine in which one of the two benzene rings of diphenylamine is mono-substituted with an alkyl group, especially a C4-C9 alkyl group), dibutyl (including straight-chain and branched-chain) diphenylamine, dipentyl (including straight-chain and branched-chain) diphenylamine, dihexyl (including straight-chain and branched-chain) diphenylamine, diheptyl (including straight-chain and branched-chain) diphenylamine, dioctyl (including straight-chain and branched-chain) diphenylamine, dinonyl (including straight-chain and branched-chain) diphenylamine and other di(alkylphenyl)amines, especially di(C4-C9 alkylphenyl)amine (that is, diphenylamine in which each of the two benzene rings of diphenylamine is mono-substituted with an alkyl group, especially a C4-C9 alkyl group, and the two alkyl groups are the same), di(mono C4-C9 alkylphenyl)amine in which the alkyl group on one benzene ring is different from the alkyl group on the other benzene ring, di(di-C4-C9 alkylphenyl)amine in which at least one of the four alkyl groups on the two benzene rings is different from the remaining alkyl groups, naphthylamines such as N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, 4-octylphenyl-1-naphthylamine, 4-octylphenyl-2-naphthylamine, phenylenediamines such as p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, etc. are exemplified.,

[0064] Among these, in particular, dioctyl (including linear and branched chains) diphenylamine, dinonyl (including linear and branched chains) diphenylamine, N-phenyl-1-naphthylamine, di(n-dodecyl) thiodipropionate, di(n-octadecyl) thiodipropionate and other thiodipropionate esters, sulfur compounds such as phenothiazine and the like are exemplified. These antioxidants can be used alone or in combination of two or more as appropriate. When using an antioxidant, it is usually desirable to add it in an amount of 0.01 to 5% by mass, preferably about 0.05 to 3% by mass, based on the base oil.

[0065] Here, in this specification and the claims, there may be cases where the range of the blending amount of an additive is defined using an expression such as "0.01 to 5% by mass based on the base oil". The "base oil" used in this case is used in either the meaning of a base oil consisting only of the diester compound represented by the general formula (1) or a base oil consisting of a mixture of the diester compound represented by the general formula (1) and a co-base oil. And also, for example, in the case of "0.01 to 5% by mass based on the base oil", it is synonymous with the meaning of 0.01 to 5 parts by mass with respect to 100 parts by mass of the base oil.

[0066] Examples of metal detergents include metal sulfonates such as Ca - petroleum sulfonate, overbased Ca - petroleum sulfonate, Ca - alkylbenzene sulfonate, overbased Ca - alkylbenzene sulfonate, Ba - alkylbenzene sulfonate, overbased Ba - alkylbenzene sulfonate, Mg - alkylbenzene sulfonate, overbased Mg - alkylbenzene sulfonate, Na - alkylbenzene sulfonate, overbased Na - alkylbenzene sulfonate, Ca - alkylnaphthalene sulfonate, overbased Ca - alkylnaphthalene sulfonate; metal phenates such as Ca - phenate, overbased Ca - phenate, Ba - phenate, overbased Ba - phenate; metal salicylates such as Ca - salicylate, overbased Ca - salicylate; metal phosphonates such as Ca - phosphonate, overbased Ca - phosphonate, Ba - phosphonate, overbased Ba - phosphonate; and overbased Ca - carboxylate etc. When using a metal detergent, it is usually desirable to add it in an amount of about 1 to 10% by mass, preferably about 2 to 7% by mass, based on the base oil.

[0067] Examples of ashless dispersants include polyalkenyl succinimide, polyalkenyl succinamide, polyalkenyl benzylamine, polyalkenyl succinate, etc. These ashless dispersants may be used alone or in combination. When using them, it is usually desirable to add them in an amount of 1 to 10% by mass, preferably about 2 to 7% by mass, based on the base oil.

[0068] Examples of the oily agent include aliphatic saturated and unsaturated monocarboxylic acids such as stearic acid and oleic acid, polymerized fatty acids such as dimer acid and hydrogenated dimer acid, hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid, aliphatic saturated and unsaturated monoalcohols such as lauryl alcohol and oleyl alcohol, aliphatic saturated and unsaturated monoamines such as stearylamine and oleylamine, aliphatic saturated and unsaturated monocarboxylic acid amides such as lauric acid amide and oleic acid amide, glycerin ethers such as batyl alcohol, chimyl alcohol, and ceralkyl alcohol, alkyl or alkenyl polyglyceryl ethers such as lauryl polyglycerin ether and oleyl polyglyceryl ether, poly(alkylene oxide) adducts of alkyl or alkenyl amines such as di(2-ethylhexyl) monoethanolamine and diisotridecyl monoethanolamine, etc. These oily agents may be used alone or in combination. When using these, usually, it is desirable to add them in an amount of 0.01 to 5% by mass, preferably about 0.1 to 3% by mass, based on the base oil.

[0069] Examples of the antiwear agent or extreme pressure agent include phosphate esters such as tricresyl phosphate, cresyl diphenyl phosphate, alkylphenyl phosphates, tributyl phosphate, and dibutyl phosphate, phosphite esters such as tributyl phosphite, dibutyl phosphite, and triisopropyl phosphite, and phosphorus-based compounds such as amine salts thereof, sulfurized oils and fats, sulfurized fatty acids such as sulfurized oleic acid, sulfur-based compounds such as dibenzyl disulfide, sulfurized olefin, and dialkyl disulfide, and organometallic compounds such as Zn-dialkyl dithiophosphate, Zn-dialkyl dithiophosphate, Mo-dialkyl dithiophosphate, and Mo-dialkyl dithiocarbamate. These antiwear agents may be used alone or in combination. When using these, usually, it is desirable to add them in an amount of 0.01 to 10% by mass, preferably about 0.1 to 5% by mass, based on the base oil.

[0070] Examples of metal deactivators include benzotriazole-based, thiadiazole-based, gallic acid ester-based compounds, etc. These metal deactivators may be used alone or in combination. When using them, usually, it is desirable to add 0.01 to 0.4% by mass, preferably about 0.01 to 0.2% by mass, based on the base oil.

[0071] Examples of rust inhibitors include alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic anhydride, dodecenyl succinamide, polyhydric alcohol partial esters such as sorbitan monooleate, glycerin monooleate, pentaerythritol monooleate, metal sulfonates such as Ca - petroleum sulfonate, Ca - alkylbenzene sulfonate, Ba - alkylbenzene sulfonate, Mg - alkylbenzene sulfonate, Na - alkylbenzene sulfonate, Zn - alkylbenzene sulfonate, Ca - alkylnaphthalene sulfonate, amines such as rosin amine, N - oleyl sarcosine, and dialkyl phosphite amine salts. These rust inhibitors may be used alone or in combination. When using them, usually, it is desirable to add 0.01 to 5% by mass, preferably about 0.05 to 2% by mass, based on the base oil.

[0072] Examples of viscosity index improvers include olefin copolymers such as polyalkyl methacrylate, polyalkyl styrene, polybutene, ethylene - propylene copolymer, styrene - diene copolymer, styrene - maleic anhydride ester copolymer. These viscosity index improvers may be used alone or in combination. When using them, usually, it is desirable to add 0.1 to 15% by mass, preferably about 0.5 to 7% by mass, based on the base oil.

[0073] Examples of pour point depressants include condensates of chlorinated paraffin and alkyl naphthalene, condensates of chlorinated paraffin and phenol, polyalkyl methacrylate which is the aforementioned viscosity index improver, polyalkyl styrene, polybutene, etc. These pour point depressants may be used alone or in combination. When using these, it is usually desirable to add them in an amount of 0.01 to 5% by mass, preferably about 0.1 to 3% by mass, based on the base oil.

[0074] As the antifoaming agent, liquid silicone is suitable. When using this, the addition amount is usually about 0.0005 to 0.01% by mass based on the base oil.

[0075] As the hydrolysis inhibitor, epoxy compounds such as alkyl glycidyl ethers, alkyl glycidyl esters, alkylene glycol glycidyl ethers, alicyclic epoxies, phenyl glycidyl ether, and carbodiimide compounds such as di-tert-butyl carbodiimide and 1,3-di-p-tolyl carbodiimide can be used, and usually, it is about 0.05 to 2% by mass based on the base oil.

[0076] By appropriately combining thickeners with the lubricating oil base oil for power transmission of the present invention, "grease" can be obtained.

[0077] Examples of thickeners include metal soap-based thickeners, composite metal soap-based thickeners, and non-soap-based thickeners.

[0078] Examples of metal soap-based thickeners include sodium soap, calcium soap, lithium soap, particularly lithium salts of aliphatic carboxylic acids having a hydroxyl group such as lithium-12-hydroxystearate, lithium salts of aliphatic carboxylic acids such as lithium stearate, or mixtures thereof.

[0079] Examples of the composite metal soap - based thickener include complexes of monovalent aliphatic carboxylic acid metal salts having a hydroxyl group and divalent aliphatic carboxylic acid metal salts. Specifically, composite lithium soap and composite aluminum soap are exemplified.

[0080] Examples of the non - soap - based thickener include bentonite, silica aerogel, sodium terephthalamate, polytetrafluoroethylene, boron nitride, urea compounds (including alicyclic, aromatic, aliphatic, diurea, triurea, tetraurea, urea - urethane compounds, etc.).

[0081] Among the above, from the viewpoints of heat resistance, water resistance, and shear stability, lithium soap, lithium complex soap, and urea compounds are suitable as thickeners, and in particular, urea compounds are preferred.

[0082] These thickeners can be used singly or in appropriate combinations of two or more. The addition amount is not particularly limited as long as the predetermined effect is achieved.

[0083] Examples of the corrosion inhibitor include sodium sulfonate and sorbitan ester, and it is usually added in an amount of about 0.1 - 3.0% by mass based on the base oil.

[0084] Examples of the hue stabilizer include substituted hydroquinone, furfuralazine, etc., and it is usually added in an amount of about 0.01 - 0.1% by mass based on the base oil.

[0085] As described above, the lubricating oil for power transmission of the present invention thus obtained contains a base oil having a high traction coefficient, flash point, and excellent low - temperature fluidity, and is therefore suitable as a lubricating oil for traction drive.

[0086] The lubricating oil base oil for power transmission of the present invention and the diester compound represented by the general formula (1) can improve the traction coefficient of the lubricating oil for power transmission (especially the lubricating oil for traction drive) by being added thereto. Therefore, it can be used as a traction coefficient improver.

[0087] The lubricating oil for power transmission of the present invention has high power transmission ability, generates little vibration and noise, and has a high flash point, so it can be used as a lubricating oil for a traction drive, that is, a power transmission device composed of two or more rotating bodies. Examples of the device adopting the traction drive include motors, speed changers, generators, speed reducers, etc. of automobiles, ships, airplanes, precision instruments, robots, etc.

Examples

[0088] Examples will be given below to explain the present invention in detail, but the present invention is not limited to these examples. In addition, the physical properties and chemical properties of the lubricating oil base oil and the lubricating oil composition in each example were evaluated by the following methods. Compounds not specifically mentioned used reagents.

[0089] <Compounds Used> ·Cyclohexanecarboxylic acid: manufactured by Sigma-Aldrich ·2-Methyl-cyclohexanecarboxylic acid: manufactured by Sigma-Aldrich ·3-Methyl-cyclohexanecarboxylic acid: manufactured by Sigma-Aldrich ·4-Methyl-cyclohexanecarboxylic acid: manufactured by Sigma-Aldrich ·2,2-Dimethyl-1,3-propanediol: manufactured by Tokyo Chemical Industry Co., Ltd. ·Diisodecyl adipate: manufactured by Shin Nippon Rika Co., Ltd., product name "Sun Sizer DIDA" ·Mineral oil Y: manufactured by NOF Corporation, product name "Polybutene 0N"

[0090] (a) Acid value (AV) Measured in accordance with JIS K2501 (2003). The detection limit is 0.01 mgKOH / g.

[0091] (b) Hydroxyl value (OHV) It was measured in accordance with JIS K0070 (1992). The detection limit is 0.1 mgKOH / g.

[0092] [Measurement of physical properties of lubricant base oil] (c) Coefficient of traction The maximum coefficient of traction when tested under the following apparatus and conditions was measured and taken as the coefficient of traction (60 °C, 140 °C). [Measurement conditions] Apparatus: Ball-on-ring type friction tester (manufactured by Phoenix Tribology, model TE54) Test piece shape: Upper test piece (sphere with a diameter of 25 mm), lower test piece (ring with a diameter of 50 mm) Test piece material: SUJ2 Sliding ratio: 5% Sample temperature: 60 °C, 140 °C Load: 150 N ><Evaluation of coefficient of traction (60 °C)> A: 0.090 or more B: 0.080 or more and less than 0.090 C: Less than 0.080 ><Evaluation of coefficient of traction (140 °C)> A: 0.085 or more B: 0.075 or more and less than 0.085 C: Less than 0.075

[0093] (d) Low-temperature fluidity test (pour point) The pour point was measured in accordance with JIS-K-2269 (1987). ><Evaluation of low-temperature fluidity> A: -35 °C or lower B: Exceeding -35 °C and -30 °C or lower C: Exceeding -30 °C

[0094] (e) Flash point It was measured in accordance with JIS K2265 (Cleveland open cup). ><Evaluation of flash point> A: 200 °C or higher B: Above 185°C and less than 200°C C: Less than 185°C

[0095] (f) Kinematic viscosity In accordance with JIS-K-2283 (2000), the kinematic viscosities at 40°C and 100°C were measured.

[0096] (g) Evaluation of lubricating oil base oil for power transmission As for the evaluation of the lubricating oil base oil for power transmission, in the results of the evaluation of the traction coefficient, the evaluation of the low-temperature fluidity, and the evaluation of the flash point, if there is 1 or more of C, it is unsuitable, if B is 2 or less (the other evaluations are A), it is good, and if B is 1 or less (the other evaluations are A), it is evaluated as particularly good.

[0097] <Infrared absorption spectrum (IR spectrum)> The IR spectrum of the obtained diester compound was measured by the ATR method (attenuated total reflection method) using an infrared spectroscopic analyzer (manufactured by PerkinElmer Japan Co., Ltd., Spectrum400).

[0098] <Proton nuclear magnetic resonance spectrum ( 1 H-NMR)> The 1 H-NMR of the obtained diester compound was measured by 1 H-NMR (500 MHz) after dissolving it in deuterated chloroform using a nuclear magnetic resonance apparatus (manufactured by Bruker, DRX-500).

[0099] [Example 1] A 1-liter four-necked flask equipped with a stirrer, a thermometer, and a water separator with a cooling tube was charged with 532.6 g (3.75 mol) of 3-methyl-cyclohexanecarboxylic acid, 177.2 g (1.70 mol) of 2,2-dimethyl-1,3-propanediol, 0.6 g of tin oxide, and 30 g of xylene as an entrainer. After purging the inside of the flask with nitrogen, the temperature was gradually raised to 230 °C. While adjusting the degree of vacuum so that xylene refluxed, the esterification reaction was carried out while removing the generated water distilled out with reference to the theoretically generated amount of water (30.7 g) using the water separator. After completion of the reaction, the remaining 3-methyl-cyclohexanecarboxylic acid and xylene were removed by distillation under reduced pressure to obtain a crude esterification product. Next, the obtained crude esterification product was neutralized with an aqueous sodium hydroxide solution at 1.5 times the equivalent of the acid value, and then washed with water repeatedly until it became neutral. Magnesium sulfate was added to the obtained crude esterification product for dehydration, and then magnesium sulfate was removed by filtration to obtain 487.8 g (1.38 mol) of bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl). The acid value of the obtained diester compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. Table 1 shows each physical property when the diester compound was evaluated as a lubricating base oil (A) for power transmission. Also, the IR spectrum of bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl), 1 the 1H-NMR spectrum was measured and shown in Figs. 1 to 2. Incidentally, 1 the peak around 7.27 ppm in the 1H-NMR spectrum is the peak of the residual proton of deuterated chloroform as the solvent.

[0100] IR (cm -1 ): 2927, 2857, 1731, 1475, 1457, 1379, 1303, 1275, 1255, 1216, 1173, 1134, 1088, 1045, 1024, 1006, 972, 936, 880, 853, 744, 701

[0101] [Comparative Example 1] Table 1 shows each physical property value when diisodecyl adipate was evaluated as a lubricating base oil (a) for power transmission.

[0102] [Comparative Example 2] Table 1 shows each physical property when mineral oil Y was evaluated as the lubricating oil base oil (b) for power transmission.

[0103] [Comparative Example 3] Except that 3-methyl-cyclohexanecarboxylic acid was changed to 521.6 g (4.07 mol) of cyclohexanecarboxylic acid, 514.2 g (1.58 mol) of bis(cyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl) was obtained in the same manner as in Example 1. The acid value of the obtained diester compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. Table 1 shows each physical property when the diester compound was evaluated as the lubricating oil base oil (c) for power transmission.

[0104] [Comparative Example 4] Except that 3-methyl-cyclohexanecarboxylic acid was changed to 532.6 g (3.75 mol) of 2-methyl-cyclohexanecarboxylic acid, 476.4 g (1.35 mol) of bis(2-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl) was obtained in the same manner as in Example 1. The acid value of the obtained diester compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. Table 1 shows each physical property when the diester compound was evaluated as the lubricating oil base oil (d) for power transmission.

[0105] [Comparative Example 5] Except that 3-methyl-cyclohexanecarboxylic acid was changed to 532.6 g (3.75 mol) of 4-methyl-cyclohexanecarboxylic acid, 497.4 g (1.41 mol) of bis(4-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl) was obtained in the same manner as in Example 1. The acid value of the obtained diester compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. Table 1 shows each physical property when the diester compound was evaluated as the lubricating oil base oil (e) for power transmission. In addition, since the values of the kinematic viscosity (at 40°C and 100°C) of this diester compound are in good agreement with those of the sample in Example A2 of Patent Document 4, the sample in Example A2 of Patent Document 4 is recognized to be bis(4-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl) of this Comparative Example 5.

[0106]

Table 1

[0107] From Table 1, it can be seen that the lubricating oil base oil for power transmission of the present invention described in Example 1 has a high traction coefficient (at 60°C) of 0.090 or more and a high traction coefficient (at 140°C) of 0.085 or more, a pour point of -30°C or lower, and a flash point of 200°C or higher.

Industrial Applicability

[0108] Since the lubricating oil base oil for power transmission of the present invention has a high traction coefficient, a high flash point, and good low-temperature fluidity, it can be suitably used as a lubricating oil base oil for power transmission (particularly, a lubricating oil base oil for traction drive) of automobiles, ships, aircraft, precision instruments, and the like.

Claims

1. General formula (1) 【Chemical 1】 [wherein, R1 and R2 are each a methyl group.] A base oil for a power transmission lubricating oil containing a diester compound represented by the formula.

2. The base oil for a power transmission lubricating oil according to Claim 1, wherein the content of the diester compound represented by the general formula (1) is 70% by mass or more in the base oil for a power transmission lubricating oil.

3. The base oil for a power transmission lubricating oil according to Claim 1 or 2, wherein the content of the diester compound represented by the general formula (1) is 90% by mass or more in the base oil for a power transmission lubricating oil.

4. The base oil for a power transmission lubricating oil according to any one of Claims 1 to 3, wherein the content of the diester compound represented by the general formula (1) is 98% by mass or more in the base oil for a power transmission lubricating oil.

5. The base oil for a power transmission lubricating oil according to any one of Claims 1 to 4, wherein the base oil for a power transmission lubricating oil is a base oil for a traction drive lubricating oil.

6. A power transmission lubricating oil containing the base oil for a power transmission lubricating oil according to any one of Claims 1 to 5.

7. A power transmission lubricating oil containing the base oil for a power transmission lubricating oil according to any one of Claims 1 to 5 and an antioxidant.

8. The power transmission lubricating oil according to Claim 7, wherein the antioxidant is a phenolic antioxidant and / or an amine-based antioxidant.

Images