Power transmission lubricant base oil

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 is a C1-4 linear or branched alkyl group, and R2 and R3 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 base oil for power transmission, and more particularly to a lubricating base oil for traction drives. [Background technology]

[0002] In recent years, with the advancement of digital information society, the demands for precision in printers and copiers have been increasing. In particular, high rotational precision, low vibration, and low noise are required for motors, which are required for highly accurate paper feeding. Since gear systems are used as the power transmission means for these rotating parts, which generate large amounts of vibration and noise, traction drives, which have fewer of these problems, are often used.

[0003] Furthermore, with the increasing popularity of industrial robots, traction drives are now being used in joints that require precise movement. Other applications of traction drives include continuously variable transmissions for industrial equipment, aircraft generators, and helicopter rotor speed control. Research has been conducted into enlarging the size of traction drives to increase the amount of power transmitted, but the increase in contact area tends to increase the amount of heat generated.

[0004] Lubricating base oils for traction drives preferably have a high traction coefficient to enhance power transmission performance, and alicyclic hydrocarbon compounds have been proposed, such as dicyclohexyl compounds typified by 2-methyl-2,4-dicyclohexylpentane and dimerized norbornanes (Patent Documents 1 and 2).

[0005] However, alicyclic hydrocarbon compounds such as 2-methyl-2,4-dicyclohexylpentane tend to have low flash points of 200°C or less, which is not necessarily sufficient for use in fields where heat resistance and safety are important, such as those using large traction drives.

[0006] Ester compounds have also been proposed as lubricating base oils for traction drives with high flash points, such as alicyclic diester compounds typified by di(cyclohexylmethyl) 1,2-cyclohexanedicarboxylate (Patent Document 3).

[0007] However, alicyclic diester compounds, such as 1,2-cyclohexanedicarboxylic acid di(cyclohexylmethyl), tend to have high pour points of -20°C or higher, which is not necessarily sufficient for use in aircraft, helicopters, automobiles, and other fields where low-temperature operability is important.

[0008] Patent Document 4 exemplifies, as traction fluids, a diester of neopentyl glycol and cyclohexanecarboxylic acid, a diester of neopentyl glycol and methylcyclohexanecarboxylic acid, and a diester of neopentyl glycol and a mixture of cyclohexanecarboxylic acid and methylcyclohexanecarboxylic acid (molar ratio of acids: 1:1). However, there is no description or suggestion regarding low-temperature fluidity, flash point, or high-temperature traction coefficient, and therefore these are not necessarily sufficient as lubricating base oils for traction drives. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 47-7664 [Patent Document 2] Japanese Patent Application Publication No. 3-95295 [Patent Document 3] International Publication No. 2018 / 008667 [Patent Document 4] Japanese Patent Publication No. 62-153393 (Patent Publication No. 6-31365) Summary of the Invention [Problem to be solved by the invention]

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

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

[0012] That is, the present invention provides a lubricating base oil for power transmission (particularly, a lubricating base oil for traction drives) that meets the following requirements:

[0013] [Section 1] General formula (1) [ka] [In the formula, R 1 represents a linear or branched alkyl group having 1 to 4 carbon atoms, and R 2 and R 3 are the same or different and each represents a linear or branched alkyl group having 1 to 4 carbon atoms.] A power transmission lubricating base oil containing a diester compound represented by the formula:

[0014] [Section 2] R in general formula (1) 1 [Item 1] The power transmission lubricating base oil according to [Item 1], wherein

[0015] [Section 3] R in general formula (1) 2 and R 3 are the same or different and are each a methyl group, an ethyl group, or an n-butyl group.

[0016] [Section 4] R in general formula (1) 2 and R 3 and each of the groups is a methyl group.

[0017] [Section 5] The power transmission lubricating base oil according to any one of [Item 1] to [Item 4], wherein the content of the diester compound represented by general formula (1) in the power transmission lubricating base oil is 70 mass % or more.

[0018] [Section 6] Item 5. A power transmission lubricating base oil according to any one of [Item 1] to [Item 5], wherein the content of the diester compound represented by general formula (1) in the power transmission lubricating base oil is 90 mass % or more.

[0019] [Section 7] Item 1. A power transmission lubricating base oil according to any one of items 1 to 6, wherein the content of the diester compound represented by general formula (1) in the power transmission lubricating base oil is 98 mass % or more.

[0020] [Section 8] The power transmission lubricant base oil according to any one of [Item 1] to [Item 7], wherein the power transmission lubricant base oil is a traction drive lubricant base oil.

[0021] [Section 9] A power transmission lubricating oil containing the power transmission lubricating base oil according to any one of [Item 1] to [Item 8].

[0022] [Section 10] A lubricating oil for power transmission, comprising the lubricating base oil for power transmission according to any one of [Item 1] to [Item 8] and an antioxidant.

[0023] [Section 11] Item 10. The lubricating oil for power transmission according to item 10, wherein the antioxidant is a phenolic antioxidant and / or an amine antioxidant.

[0024] [Section 12] General formula (1) [ka] [In the formula, R 1 represents an isopropyl group, and R 2 and R 3 Each represents a methyl group. A diester compound represented by the formula: [Effects of the Invention]

[0025] The diester compound of the present invention has the characteristics of having a high traction coefficient (60°C, 140°C), a high flash point, and good low-temperature fluidity, and therefore can be suitably used as a lubricating base oil for power transmission (particularly, a lubricating base oil for traction drives). [Brief explanation of the drawings]

[0026] [Figure 1] 1 is an IR spectrum of 1,3-(2,2,4-trimethylpentyl bis(3-methylcyclohexanecarboxylic acid) obtained in Example 1. [Figure 2] 1 is a H-NMR spectrum of bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2,4-trimethylpentyl) obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0027] The lubricating base oil for power transmission of the present invention is a compound represented by the general formula (1) [ka] [In the formula, R 1 represents a linear or branched alkyl group having 1 to 4 carbon atoms, and R 2 and R 3 are the same or different and each represents a linear or branched alkyl group having 1 to 4 carbon atoms.] The present invention is characterized in that it contains a diester compound represented by the following formula:

[0028] R according to general formula (1)1 Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group. Of these, a methyl group, an ethyl group, an isopropyl group, and a tert-butyl group are preferred, and an isopropyl group is particularly preferred.

[0029] Also, R 2 and R 3 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, and is preferably a methyl group, an ethyl group, or an n-butyl group, and particularly preferably a methyl group.

[0030] Specific examples of the diester compound represented by general formula (1) include bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-methylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-n-propylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isopropyl-2-methylbutyl), and bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl). -2-methylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-sec-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-methylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-tert-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-n-propylbutyl), bis(3-methyl Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-isopropylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-n-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-sec-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-isobutylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-tert-butylbutyl), bis(3-methylcyclohexanecarboxylic acid) Acid)-1,3-(2,2-di-n-propylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-propyl-2-isopropylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-n-propylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-n-propylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-propylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-n-propylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisopropylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-isopropylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-isopropylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-isopropylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-te tert-butyl-2-isopropylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-isobutylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-sec-butylbutyl) butyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-sec-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-tert-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butylbutyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-tert-butylbutyl), Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl -2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n- propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isopropyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-t ert-butyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)- 1,3-(2,2-di-sec-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-sec-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-tert-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1 ,3-(2,2-di-tert-butylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2,4-trimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,4-dimethyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,4-dimethyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,4-dimethyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2 -n-butyl-2,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-4-methyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-isopropyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-ethyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-ethyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-ethyl-4-methylpentyl), bis(3 -methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-ethyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-propyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isopropyl-2-n-propyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-4-methyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-se c-butyl-4-methyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-4-methyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-4-methyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisopropyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-4-methyl-2-isopropylpentyl), Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-4-methyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-4-methyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-4-methyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-isobutyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-sec-butyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-sec-butyl-4-methylpentyl), bi, Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-tert-butyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-tert-butyl-4-methylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2, 2,4,4-tetramethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2,4,4-trimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-propyl-2,4,4-trimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isopropyl-2,4,4-trimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2,4,4-trimethylpentyl), bis(3-methylcyclohexanecarboxylic acid) -1,3-(2-sec-butyl-2,4,4-trimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2,4,4-trimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2,4,4-trimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(4,4-dimethyl-2-ethyl-2-n-propylpentyl), Bis(3-methylcyclohexanecarboxylic acid)-1,3-(4,4-dimethyl-2-ethyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-4,4-dimethyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-4,4-dimethyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-4,4-dimethyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-4,4-dimethyl-2-ethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(4,4-dimethyl-2,2-di-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(4,4-dimethyl-2-isopropyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-4,4-dimethyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-4,4 -dimethyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-4,4-dimethyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-4,4-dimethyl-2-n-propylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisopropyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-4,4-dimethyl-2-isopropylpentyl) ethyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-4,4-dimethyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-4,4-dimethyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-4,4-dimethyl-2-isopropylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)- Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-sec-butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-sec-butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-tert-butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-tert -butyl-4,4-dimethylpentyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-methylhexyl), bis( 3-Methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid) carboxylic acid)-1,3-(2-ethyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-ethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-ethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-ethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-ethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isopropyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2- tert-butyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2 -tert-butyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-( 2,2-di-sec-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-sec-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-tert-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-tert-butylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2,4-trimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2,4-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,4-dimethyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,4-dimethyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n- butyl-2,4-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2,4-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2,4-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2,4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1, 3-(2-ethyl-4-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-4-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-ethyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-ethyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-ethyl-4-methylhexyl), Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-ethyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(4-methyl-2,2-di-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(4-methyl-2-isopropyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-4-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-4-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-4-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-4-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(4-methyl-2,2-diisopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl, bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-4-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-4-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-4-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butyl-4-methylhexyl), bis(3-methyl Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-butyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-sec-butyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-s ec-butyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-tert-butyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butyl-4-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-tert-butyl-4-methylhexyl), bis(3-methylcyclohexa Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2,5-trimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,5-dimethyl-2-ethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,5-dimethyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,5-dimethyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2,5-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2,5-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2,5-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2,5-dimethylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-5-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid) Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-5-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-ethyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-ethyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-ethyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl- 2-ethyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-propyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(5-methyl-2-n-propyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-5-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-5-methyl-2-n-propylhexyl), bis( 3-Methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-5-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-5-methyl-2-n-propylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisopropyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-5-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-5-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-5-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-5-methyl-2-isopropylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butyl-5-methyl hexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-isobutyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-sec-butyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-isobutyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)- 1,3-(2-sec-butyl-2-tert-butyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-tert-butyl-5-methylhexyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylheptyl), bis(3-methylcyclohexanecarboxylic acid) Bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-methylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-n-propylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-methyl-2-isopropylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-methylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-methylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-methylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-methylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diethylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-n-propylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-ethyl-2-isopropylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl- 2-ethylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-ethylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-ethylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-ethylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-propylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isopropyl-2-n-propyl) bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-n-propylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-n-propylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-propylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-n-propylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutyl-2-n-propylheptyl), isopropylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-isopropylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-isopropylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-isopropylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-tert-butyl-2-isopropylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-n-butylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-sec-butylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-n-butylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-n-butyl-2-tert-butylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-sec-butylheptyl), bis(3-methylcyclohexanecarboxylic acid) )-1,3-(2-isobutyl-2-sec-butylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-sec-butyl-2-tert-butylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-diisobutylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2-isobutyl-2-tert-butylheptyl), bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2-di-tert-butylheptyl). Among these, bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2,4-trimethylpentyl) is preferred.

[0031] The above diester compounds can be used alone or in admixture of two or more types as the lubricating base oil for power transmission.

[0032] The method for producing the diester compound represented by general formula (1) is not particularly limited. For example, the diester compound represented by general formula (1) can be produced by reacting a carboxylic acid represented by formula (2) or a derivative thereof with a diol represented by general formula (3), as shown in reaction formula 1. Here, examples of the derivative of the carboxylic acid represented by formula (2) include highly reactive derivatives such as acid halides (e.g., acid chlorides), mixed acid anhydrides, activated esters, and lower (1 to 4 carbon atoms) alkyl esters. [ka] [In the formula, R 1 , R 2 , and R 3is the same as above.] The diester compound represented by general formula (1) can be produced, for example, by dehydration condensation of a carboxylic acid represented by formula (2) (3-methylcyclohexanecarboxylic acid) and a diol represented by general formula (3) in the presence of an acid catalyst (e.g., sulfuric acid, p-toluenesulfonic acid, etc.) while heating and removing the by-product water. Alternatively, the diester compound can be produced by a similar method by changing the acid catalyst to an inorganic metal catalyst (e.g., tin oxide, etc.) or an organic titanium catalyst (e.g., tetra-n-butoxytitanium, etc.). The diester compound represented by general formula (1) can also be produced by reacting a carboxylic acid represented by formula (2) with a diol represented by general formula (3) in the presence of a condensing agent (e.g., dicyclohexylcarbodiimide, carbonyldiimidazole, etc.). Alternatively, the diester compound represented by general formula (1) can be produced by converting the carboxylic acid represented by formula (2) into a highly reactive derivative such as an acid halide (e.g., acid chloride), a mixed acid anhydride, or an activated ester, and then reacting the resulting derivative with a diol represented by general formula (3) in the presence of a base (e.g., triethylamine, 4-(N,N-dimethylamino)pyridine, pyridine, etc.). Alternatively, the diester compound represented by general formula (1) can be produced by reacting (esterifying) the carboxylic acid represented by formula (2) with a lower (carbon number 1 to 4) alcohol (e.g., methanol, ethanol, etc.) to form a lower alkyl ester, and then subjecting this to a transesterification reaction with a diol represented by general formula (3). The reaction shown in the above reaction formula 1 can be carried out according to or in accordance with known reaction conditions depending on the type of reaction.

[0033] Alternatively, the diester compound represented by general formula (1) can also be produced by reacting (esterification or transesterification) a compound represented by formula (4) (m-toluic acid) or a derivative thereof with a diol represented by general formula (3) to obtain a compound represented by general formula (5), and then hydrogenating (reducing) the aromatic ring of the compound, as shown in reaction formula 2. Here, examples of derivatives of m-toluic acid include highly reactive derivatives such as acid halides (e.g., acid chlorides), mixed acid anhydrides, and activated esters, as well as lower (1 to 4 carbon atoms) alkyl esters. [ka] [In the formula, R 1 , R 2 , and R 3 is the same as above.] The reaction of reacting the compound represented by formula (4) (m-toluic acid) or a derivative thereof with the diol represented by general formula (3) to produce the compound represented by general formula (5) can be carried out in accordance with or in accordance with the reaction of reacting the carboxylic acid represented by formula (2) or a derivative thereof with the diol represented by general formula (3) in the above reaction scheme 1 to produce the compound represented by general formula (1). The reaction of hydrogenating (reducing) the compound represented by general formula (5) can be carried out by a known method. For example, the compound represented by general formula (1) can be produced by reducing the compound represented by general formula (5) in a hydrogen atmosphere (from room temperature to pressurized) in the presence of a reduction catalyst (a transition metal such as platinum, palladium, nickel, or rhodium, or an oxide thereof, palladium / C, etc.).

[0034] From the viewpoint of practicality such as simplicity, the method of obtaining the compound by esterification reaction of 3-methylcyclohexanecarboxylic acid with a diol represented by general formula (3) is most preferred.

[0035] The acid value of the diester compound represented by 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 general formula (1) itself tends to be further improved, and such a preferable range also has a favorable effect on improving the thermal oxidation stability of the base oil of the present invention. Examples of methods for reducing the acid value include a method of allowing the reaction to proceed sufficiently, a method of neutralizing with an alkaline component and washing with water in a post-treatment step (for example, a method of washing (neutralizing) with an alkaline aqueous solution and washing with water), and a method of adsorption treatment on activated alumina.

[0036] The hydroxyl value of the diester compound represented by 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 general formula (1) itself tends to be lower and the heat resistance tends to be improved. This preferred range also has a favorable effect on improving the water resistance and thermal oxidation stability of the base oil of the present invention. Examples of methods for reducing the hydroxyl value include a method of allowing the reaction to proceed sufficiently and a method of distilling off the raw material alcohol component under reduced pressure in a post-treatment step (for example, a method of distilling off excess distillable raw material alcohol under reduced pressure or normal pressure).

[0037] The present invention discloses a lubricating base oil for power transmission (particularly, a lubricating base oil for traction drives) containing a diester compound represented by general formula (1). The traction coefficient (60°C) of the power transmission lubricating base oil is usually 0.080 or more, preferably 0.090 or more. In this specification and claims, the traction coefficient (60°C) is a value measured by the method described in the Examples below.

[0038] The traction coefficient (140°C) is usually 0.075 or more, and preferably 0.085 or more. In this specification and claims, the traction coefficient (140°C) is a value measured by the method described in the Examples below.

[0039] The low-temperature fluidity of a power transmission lubricating base oil can be evaluated, for example, by its pour point. From the viewpoint of low-temperature operability, the pour point of the lubricating base oil is usually −30° C. or lower, preferably −35° C. or lower. In this specification and claims, the pour point is a value measured by the method described in the Examples below.

[0040] From the viewpoint of storage stability and ease of handling, the flash point of a power transmission lubricating base oil is usually 185°C or higher, preferably 200°C or higher. If it is lower than 185°C, there are many restrictions on handling due to ignition. In this specification and claims, the flash point is a value measured by the method described in the Examples below.

[0041] Examples of lubricating base oils for power transmission include: 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; and 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 preferred are lubricating base oils for power transmission having 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 having 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; and lubricating base oils for power transmission having 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, and particularly preferred are lubricating base oils for power transmission having 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.

[0042] 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, and is therefore suitable for use as a lubricating base oil for power transmission, particularly as a lubricating base oil for traction drives.

[0043] The power transmission lubricating base oil of the present invention can contain other base oils that can be used in combination (hereinafter referred to as "combination base oils"). In other words, the power transmission lubricating base oil of the present invention includes only the diester compound represented by general formula (1) and a mixture of the diester compound represented by general formula (1) and the combination base oil. Hereinafter, the power transmission lubricating base oil may be referred to as "base oil".

[0044] Examples of base oils that can be used in combination include mineral oils (hydrocarbon oils obtained by refining petroleum), poly-α-olefins, polybutenes, alkylbenzenes, alkylnaphthalenes, alicyclic hydrocarbon oils, animal and vegetable oils, organic acid esters (excluding diester compounds represented by general formula (1)), polyalkylene glycols, polyvinyl ethers, polyphenyl ethers, alkylphenyl ethers, silicone oils, etc. At least one of these can be used in combination as appropriate.

[0045] Examples of mineral oils include solvent refined mineral oils, hydrorefined mineral oils, and wax isomerized oils. Generally, the kinematic viscosity at 100°C is 1 to 25 mm. 2 / s, preferably 2 to 20 mm 2 The range of / s is used.

[0046] The poly-α-olefin is a polymer or copolymer of an α-olefin having 2 to 16 carbon atoms (e.g., ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, etc.), and has a kinematic viscosity at 100°C of 1 to 25 mm 2 / s, and viscosity index of 100 or more are exemplified, particularly those with a kinematic viscosity of 1.5 to 20 mm at 100°C. 2 / s and a viscosity index of 120 or more is preferred.

[0047] Polybutene includes those polymerized with isobutylene and those copolymerized with normal butylene, and generally has a kinematic viscosity at 100°C of 2 to 40 mm 2 A wide range of / s can be mentioned.

[0048] Examples of alkylbenzenes include monoalkylbenzenes, dialkylbenzenes, trialkylbenzenes, tetraalkylbenzenes, etc., which are substituted with a linear or branched alkyl group having 1 to 40 carbon atoms and have a molecular weight of 200 to 450.

[0049] Examples of alkylnaphthalene include monoalkylnaphthalene and dialkylnaphthalene substituted with a linear or branched alkyl group having 1 to 30 carbon atoms.

[0050] Alicyclic hydrocarbon oils include naphthenic hydrocarbon oils, and generally have a kinematic viscosity at 100°C of 1 to 40 mm 2 Examples include a wide range of / s.

[0051] Examples of animal and vegetable oils include beef tallow, lard, palm oil, coconut oil, rapeseed oil, castor oil, and sunflower oil.

[0052] Examples of organic acid esters include fatty acid monoesters, aliphatic dibasic acid diesters, aliphatic dihydric alcohol diesters (excluding the diester compounds represented by general formula (1)), polyol esters, and other esters.

[0053] 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.

[0054] 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, and 1,10-decamethylenedicarboxylic acid, or anhydrides thereof, with linear or branched, saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

[0055] Aliphatic dihydric alcohol diesters (excluding the diester compounds represented by the general formula (1)), polyol esters such as neopentyl-type polyols such as neopentyl glycol, 2,2-diethylpropanediol, 2-butyl-2-ethylpropanediol, trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane, and dipentaerythritol, 1,3-propanediol, and 1,4-butanediol, Diol, 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 Sandiol, 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 It is possible to use full esters of polyols having a non-neopentyl structure, such as 2-ethyl-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, and sorbitol, with linear and / or branched, saturated or unsaturated fatty acids having 3 to 22 carbon atoms.

[0056] Other esters include esters of polymerized fatty acids such as dimer acids and hydrogenated dimer acids, or hydroxy fatty acids such as condensed castor oil fatty acids and hydrogenated condensed castor oil fatty acids, with linear or branched saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

[0057] Examples of polyalkylene glycols include ring-opening polymers of alcohols and linear or branched alkylene oxides having 2 to 4 carbon atoms. Examples of alkylene oxides include ethylene oxide, propylene oxide, and butylene oxide, and polymers using one of these or copolymers using a mixture of two or more of these can be used. Compounds in which the hydroxyl groups at one or both ends are 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℃) is recommended.

[0058] Polyvinyl ether is a compound obtained by polymerization of vinyl ether monomers, and examples of the monomers 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, etc. 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℃) is recommended.

[0059] Examples of polyphenyl ethers include compounds having a structure in which the meta positions of two or more aromatic rings are linked by an ether bond or a thioether bond. Specific examples include bis(m-phenoxyphenyl) ether, m-bis(m-phenoxyphenoxy)benzene, and thioethers in which one or more oxygen atoms of these ethers have been substituted with sulfur (commonly known as C-ethers).

[0060] Examples of alkyl phenyl ethers include compounds in which polyphenyl ethers are substituted with linear or branched alkyl groups having 6 to 18 carbon atoms, and alkyl diphenyl ethers substituted with one or more alkyl groups are particularly preferred.

[0061] Examples of silicone oils include dimethyl silicone, methylphenyl silicone, and modified silicones such as long-chain alkyl silicone and fluorosilicone.

[0062] The content of the diester compound represented by general formula (1) in the power transmission lubricating base oil of the present invention is usually 70 mass% or more, preferably 90 mass% or more, more preferably 95 mass% or more, and particularly preferably 98 mass% or more.

[0063] The content of the combined base oil in the power transmission lubricating base oil of the present invention is usually 30 mass % or less, preferably 10 mass % or less, more preferably 5 mass % or less, and particularly preferably 2 mass % or less.

[0064] The present invention also provides a power transmission lubricating oil containing the power transmission lubricating oil base oil. To improve the performance of the power transmission lubricating oil, the base oil may contain at least one additive, such as an antioxidant, metal detergent, ashless dispersant, oiliness agent, antiwear agent, extreme pressure agent, metal deactivator, rust inhibitor, viscosity index improver, pour point depressant, antifoaming agent, hydrolysis inhibitor, thickener, corrosion inhibitor, or color stabilizer. The amounts of these additives are not particularly limited as long as the effects of the present invention are achieved, and specific examples are shown below.

[0065] Examples of the antioxidant include phenol-based antioxidants and amine-based antioxidants, and specific examples thereof include 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'-isopropylidenebispheno 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, in particular mono(C4-C9 alkyl)diphenylamines (i.e., diphenylamines in which one of the two benzene rings of the diphenylamine is mono-substituted with an alkyl group, particularly 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, etc. Examples include di(C4-C9 alkylphenyl)amines, particularly di(C4-C9 alkylphenyl)amines (i.e., diphenylamines in which each of the two benzene rings of the diphenylamine is mono-substituted with an alkyl group, particularly a C4-C9 alkyl group, and the two alkyl groups are the same), di(monoC4-C9 alkylphenyl)amines 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)amines 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, and 4-octylphenyl-2-naphthylamine, and phenylenediamines such as p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, etc.

[0066] Among these, particular examples include dioctyl diphenylamine (including straight-chain and branched-chain) diphenylamine, dinonyl diphenylamine (including straight-chain and branched-chain) diphenylamine, N-phenyl-1-naphthylamine, thiodipropionic acid esters such as di(n-dodecyl) thiodipropionate and di(n-octadecyl) thiodipropionate, and sulfur-based compounds such as phenothiazine. These antioxidants can be used alone or in combination of two or more. When an antioxidant is used, it is generally added in an amount of 0.01 to 5 mass %, preferably 0.05 to 3 mass %, based on the base oil.

[0067] Here, in the present specification and claims, the range of the amount of additive blended may be specified using the expression "based on the base oil," such as "0.01 to 5 mass% based on the base oil." In this case, "base oil" refers to either a base oil consisting solely of a diester compound represented by general formula (1) or a base oil consisting of a mixture of a diester compound represented by general formula (1) and a combined base oil. Furthermore, the phrase "0.01 to 5 mass% based on the base oil" is synonymous with 0.01 to 5 parts by mass based on 100 parts by mass of the base oil.

[0068] Metal detergents include calcium petroleum sulfonates, overbased calcium petroleum sulfonates, calcium alkylbenzene sulfonates, overbased calcium alkylbenzene sulfonates, barium alkylbenzene sulfonates, overbased bamboo alkylbenzene sulfonates, magnesium alkylbenzene sulfonates, overbased magnesium alkylbenzene sulfonates, sodium alkylbenzene sulfonates, overbased sodium alkylbenzene sulfonates, and calcium alkylnaphthalenes. Metal sulfonates such as overbased Ca-alkylnaphthalene sulfonates, metal phenates such as Ca-phenate, overbased Ca-phenate, Ba-phenate, and overbased Ba-phenate, metal salicylates such as Ca-salicylate and overbased Ca-salicylate, metal phosphonates such as Ca-phosphonate, overbased Ca-phosphonate, Ba-phosphonate, and overbased Ba-phosphonate, and overbased Ca-carboxylate, etc. When a metal detergent is used, it is generally desirable to add it in an amount of about 1 to 10 mass %, preferably about 2 to 7 mass %, based on the base oil.

[0069] Examples of ashless dispersants include polyalkenyl succinimides, polyalkenyl succinamides, polyalkenyl benzylamines, polyalkenyl succinate esters, etc. These ashless dispersants may be used alone or in combination, and when used, they are typically added in an amount of 1 to 10 mass %, preferably 2 to 7 mass %, relative to the base oil.

[0070] Examples of oiliness agents include saturated and unsaturated aliphatic 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, saturated and unsaturated aliphatic monoalcohols such as lauryl alcohol and oleyl alcohol, saturated and unsaturated aliphatic monoamines such as stearylamine and oleylamine, saturated and unsaturated aliphatic monocarboxylic acid amides such as lauric acid amide and oleic acid amide, glycerin ethers such as batyl alcohol, chimyl alcohol, and selachyl alcohol, alkyl or alkenyl polyglyceryl ethers such as lauryl polyglycerin ether and oleyl polyglyceryl ether, and poly(alkylene oxide) adducts of alkyl or alkenyl amines such as di(2-ethylhexyl)monoethanolamine and diisotridecylmonoethanolamine. These oiliness agents may be used alone or in combination, and when used, they are typically added in an amount of 0.01 to 5 mass % of the base oil, preferably about 0.1 to 3 mass %.

[0071] Examples of antiwear agents or extreme pressure agents include phosphorus-based agents such as tricresyl phosphate, cresyl diphenyl phosphate, alkylphenyl phosphates, phosphate esters such as tributyl phosphate and dibutyl phosphate, phosphites such as tributyl phosphite, dibutyl phosphite and triisopropyl phosphite, and their amine salts, sulfur-based agents such as sulfurized oils and fats, sulfurized fatty acids such as sulfurized oleic acid, dibenzyl disulfide, sulfurized olefins and dialkyl disulfides, and organometallic compounds such as Zn-dialkyldithiophosphate, Zn-dialkyldithiophosphate, Mo-dialkyldithiophosphate and Mo-dialkyldithiocarbamate. These antiwear agents may be used alone or in combination, and when used, they are typically added in an amount of 0.01 to 10 mass %, preferably 0.1 to 5 mass %, based on the base oil.

[0072] Examples of metal deactivators include benzotriazole-based, thiadiazole-based, and gallic acid ester-based compounds. These metal deactivators may be used alone or in combination, and when used, they are typically added in an amount of about 0.01 to 0.4% by mass, and preferably about 0.01 to 0.2% by mass, based on the base oil.

[0073] Examples of rust inhibitors include alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic anhydride, and dodecenyl succinamide; polyhydric alcohol partial esters such as sorbitan monooleate, glycerin monooleate, and pentaerythritol monooleate; metal sulfonates such as Ca-petroleum sulfonate, Ca-alkylbenzene sulfonate, Ba-alkylbenzene sulfonate, Mg-alkylbenzene sulfonate, Na-alkylbenzene sulfonate, Zn-alkylbenzene sulfonate, and Ca-alkylnaphthalene sulfonate; amines such as rosin amine and N-oleyl sarcosine; and dialkyl phosphite amine salts. These rust inhibitors may be used alone or in combination, and when used, they are typically added in an amount of 0.01 to 5 mass %, preferably 0.05 to 2 mass %, based on the base oil.

[0074] Examples of viscosity index improvers include olefin copolymers such as polyalkyl methacrylate, polyalkylstyrene, polybutene, ethylene-propylene copolymer, styrene-diene copolymer, styrene-maleic anhydride copolymer, etc. These viscosity index improvers may be used alone or in combination, and when used, they are typically added in an amount of about 0.1 to 15 mass %, preferably about 0.5 to 7 mass %, based on the base oil.

[0075] Examples of pour point depressants include condensates of chlorinated paraffin and alkylnaphthalene, condensates of chlorinated paraffin and phenol, and the aforementioned viscosity index improvers such as polyalkyl methacrylate, polyalkylstyrene, polybutene, etc. These pour point depressants may be used alone or in combination, and when used, they are generally added in an amount of about 0.01 to 5 mass %, preferably about 0.1 to 3 mass %, based on the base oil.

[0076] Liquid silicone is suitable as the antifoaming agent, and when used, the amount added is usually about 0.0005 to 0.01% by mass relative to the base oil.

[0077] As the hydrolysis inhibitor, epoxy compounds such as alkyl glycidyl ethers, alkyl glycidyl esters, alkylene glycol glycidyl ethers, alicyclic epoxies, and phenyl glycidyl ether, and carbodiimide compounds such as di-tert-butylcarbodiimide and 1,3-di-p-tolylcarbodiimide can be used, and the amount used is usually about 0.05 to 2 mass% based on the base oil.

[0078] By appropriately combining the power transmission lubricating base oil of the present invention with a thickener, it is possible to produce a "grease."

[0079] Examples of thickeners include metal soap-based thickeners, complex metal soap-based thickeners, and non-soap-based thickeners.

[0080] Examples of metal soap-based thickeners include sodium soaps, calcium soaps, lithium soaps, and in particular, 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, and mixtures thereof.

[0081] Examples of complex metal soap thickeners include complexes of a monovalent metal salt of an aliphatic carboxylic acid having a hydroxyl group and a divalent metal salt of an aliphatic carboxylic acid, and specific examples include lithium complex soaps and aluminum complex soaps.

[0082] Examples of non-soap thickeners include bentonite, silica aerogel, sodium terephthalamate, polytetrafluoroethylene, boron nitride, and urea compounds (including alicyclic, aromatic, aliphatic, diurea, triurea, tetraurea, and urea-urethane compounds).

[0083] Among the above, lithium soaps, lithium complex soaps and urea compounds are suitable as thickeners from the viewpoints of heat resistance, water resistance and shear stability, and urea compounds are particularly preferred.

[0084] These thickeners can be used alone or in combination of two or more kinds, and the amount added is not particularly limited as long as the desired effect is achieved.

[0085] Examples of corrosion inhibitors include sodium sulfonate and sorbitan ester, which are usually added in an amount of about 0.1 to 3.0% by mass to the base oil.

[0086] Examples of color stabilizers include substituted hydroquinone and furfural azine, and they are usually added in an amount of about 0.01 to 0.1% by mass to the base oil.

[0087] The thus obtained lubricating oil for power transmission of the present invention contains a base oil having a high traction coefficient and flash point and excellent low-temperature fluidity, as described above, and is therefore suitable as a lubricating oil for traction drives.

[0088] The power transmission lubricating base oil and the diester compound represented by general formula (1) of the present invention can be added to a power transmission lubricating oil (particularly a traction drive lubricating oil) to improve the traction coefficient of the power transmission lubricating oil, and therefore can be used as a traction coefficient improver.

[0089] The lubricating oil for power transmission of the present invention has high power transmission performance, low vibration and noise generation, and a high flash point, and therefore can be used as a lubricating oil for traction drives, i.e., power transmission devices consisting of two or more rotating bodies. Devices that employ such traction drives include motors, transmissions, generators, reducers, etc. in automobiles, ships, aircraft, precision instruments, robots, etc. [Example]

[0090] The present invention will be described in detail below with reference to examples, but is not limited to these examples. The physical and chemical properties of the lubricating base oils and lubricating oil compositions in each example were evaluated by the following methods. Reagents were used for compounds not specifically mentioned.

[0091] <Compound used> Cyclohexanecarboxylic acid: Sigma-Aldrich 2-Methyl-cyclohexanecarboxylic acid: Sigma-Aldrich 3-Methyl-cyclohexanecarboxylic acid: Sigma-Aldrich 4-Methyl-cyclohexanecarboxylic acid: Sigma-Aldrich 2,2-Dimethyl-1,3-propanediol: Tokyo Chemical Industry Co., Ltd. 2,2,4-trimethyl-1,3-pentanediol: manufactured by Tokyo Chemical Industry Co., Ltd. Diisodecyl adipate: Product name: Sanso Cizer DIDA, manufactured by New Japan Chemical Co., Ltd. Mineral oil Y: NOF Corporation, product name "Polybutene 0N"

[0092] (a) Acid value (AV) Measurements were performed in accordance with JIS K2501 (2003), with a detection limit of 0.01 mg KOH / g.

[0093] (b) Hydroxyl value (OHV) Measurements were made in accordance with JIS K0070 (1992), with a detection limit of 0.1 mg KOH / g.

[0094] [Measurement of physical properties of lubricant base oil] (c) Traction coefficient The maximum traction coefficient was measured when the test was carried out using the following equipment and conditions, and this was taken as the traction coefficient (60°C, 140°C). [Measurement conditions] Equipment: Ball-on-ring type friction tester (Phoenix Tribology TE54 model) Test piece shape: Upper test piece (25 mm diameter sphere), lower test piece (50 mm diameter ring) Test piece material: SUJ2 Slip rate: 5% Sample temperature: 60℃, 140℃ Load: 150N <Traction coefficient (60℃) evaluation> A: 0.090 or more B: 0.080 or more and less than 0.090 C: Less than 0.080 <Traction coefficient (140℃) evaluation> A: 0.085 or more B: 0.075 or more and less than 0.085 C: Less than 0.075

[0095] (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℃ or less B: Over -35℃ and below -30℃ C: Above -30°C

[0096] (e) Flash point Measurements were made in accordance with JIS K2265 (Cleveland open type). <Flash point evaluation> A: 200℃ or higher B: 185℃ or higher and less than 200℃ C: Less than 185°C

[0097] (f) Kinematic viscosity The kinematic viscosity was measured at 40°C and 100°C in accordance with JIS-K-2283 (2000).

[0098] (g) Evaluation of power transmission lubricant base oils In the evaluation of power transmission lubricant base oils, the traction coefficient, low-temperature fluidity, and flash point are evaluated as follows: if C is 1 or higher, it is considered unsuitable; if B is 2 or lower (other evaluations are A), it is considered good; and if B is 1 or lower (other evaluations are A), it is considered particularly good.

[0099] <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 spectrometer (Spectrum 400 manufactured by PerkinElmer Japan Co., Ltd.).

[0100] <Proton nuclear magnetic resonance spectrum ( 1 H-NMR) The resulting diester compound 1 H-NMR was performed using a nuclear magnetic resonance spectrometer (Bruker DRX-500) after dissolving the compound in deuterated chloroform. 1 H-NMR (500 MHz) measurement was performed.

[0101] [Example 1] A 1-liter four-neck flask equipped with a stirrer, thermometer, and condenser-equipped water fractional distillation receiver was charged with 532.6 g (3.75 mol) of 3-methylcyclohexanecarboxylic acid, 222.3 g (1.52 mol) of 2,2,4-trimethyl-1,3-pentanediol, 0.6 g of tin oxide, and 30 g of xylene as an entrainer. The flask was then purged with nitrogen and gradually heated to 230 °C. The esterification reaction was carried out while adjusting the vacuum level to reflux the xylene and removing the distilled water in the water fractional distillation receiver until the theoretical amount of water (30.7 g) was reached. After the reaction was completed, the remaining 3-methylcyclohexanecarboxylic acid and xylene were removed by distillation under reduced pressure to obtain a crude esterified product. The crude esterified product was then neutralized with 1.5 equivalents of aqueous caustic soda based on the acid value of the resulting product, and repeatedly washed with water until neutral. Magnesium sulfate was added to the obtained crude esterified product for dehydration, and the magnesium sulfate was then removed by filtration to obtain 439.2 g (1.11 mol) of 1,3-(2,2,4-trimethylpentyl)bis(3-methylcyclohexanecarboxylate). 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. The diester compound was evaluated as a power transmission lubricating base oil (A), and the physical properties thereof are shown in Table 1. The IR spectrum of bis(3-methylcyclohexanecarboxylic acid)-1,3-(2,2,4-trimethylpentyl) 1 The H-NMR spectrum was measured and is shown in Figures 1 and 2. 1 The peak at around 7.27 ppm in the H-NMR spectrum is the peak of the residual protons of the solvent, deuterated chloroform.

[0102] IR(cm -1 ):2927,2857,1730,1457,1371,1303,1276,1253,1216,1173,1135,1109,1088,1044,994,969,946,917,902,881,845,743,702

[0103] [Comparative Example 1] Table 1 shows the physical properties of diisodecyl adipate when it was evaluated as a power transmission lubricating base oil (a).

[0104] Comparative Example 2 Table 1 shows the physical properties of mineral oil Y when it was evaluated as a lubricating base oil (b) for power transmission.

[0105] Comparative Example 3 The same method as in Example 1 was used, except that 521.6 g (4.07 mol) of cyclohexanecarboxylic acid was used instead of 3-methyl-cyclohexanecarboxylic acid, and 177.2 g (1.70 mol) of 2,2-dimethyl-1,3-propanediol was used instead of 2,2,4-trimethyl-1,3-pentanediol, to obtain 514.2 g (1.58 mol) of bis(cyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl). The acid value of the obtained compound was 0.01 mg KOH / g or less, and the hydroxyl value was 1 mg KOH / g or less. The physical properties of this compound when evaluated as a power transmission lubricating base oil (c) are shown in Table 1.

[0106] Comparative Example 4 The same method as in Example 1 was used except that 532.6 g (3.75 mol) of 2-methyl-cyclohexanecarboxylic acid was used instead of 3-methyl-cyclohexanecarboxylic acid, and 177.2 g (1.70 mol) of 2,2-dimethyl-1,3-propanediol was used instead of 2,2,4-trimethyl-1,3-pentanediol. 476.4 g (1.35 mol) of bis(2-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl) was obtained. The acid value of the obtained compound was 0.01 mg KOH / g or less, and the hydroxyl value was 1 mg KOH / g or less. The physical properties of this compound when evaluated as a power transmission lubricating base oil (d) are shown in Table 1.

[0107] Comparative Example 5 The same method as in Example 1 was used except that 532.6 g (3.75 mol) of 4-methyl-cyclohexanecarboxylic acid was used instead of 3-methyl-cyclohexanecarboxylic acid, and 177.2 g (1.70 mol) of 2,2-dimethyl-1,3-propanediol was used instead of 2,2,4-trimethyl-1,3-pentanediol. 497.4 g (1.41 mol) of bis(4-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl) was obtained. The acid value of the obtained compound was 0.01 mg KOH / g or less, and the hydroxyl value was 1 mg KOH / g or less. The physical properties of this compound when evaluated as a power transmission lubricating base oil (e) are shown in Table 1. The kinematic viscosity (40°C and 100°C) of this diester compound is in good agreement with that of the sample of Example A2 of Patent Document 4, and therefore the sample of Example A2 of Patent Document 4 is recognized to be bis(4-methylcyclohexanecarboxylic acid)-1,3-(2,2-dimethylpropyl) of Comparative Example 5.

[0108] [Table 1]

[0109] From Table 1, it can be seen that the power transmission lubricating base oil of the present invention described in Example 1 has a high traction coefficient (60°C) of 0.090 or more and a high traction coefficient (140°C) of 0.085 or more, a pour point of -30°C or less, and a high flash point of 200°C or more. [Industrial Applicability]

[0110] The power transmission lubricating base oil of the present invention has a high traction coefficient, a high flash point, and good low-temperature fluidity, and can therefore be suitably used as a power transmission lubricating base oil (particularly a traction drive lubricating base oil) for automobiles, ships, aircraft, precision instruments, etc.

Claims

1. General formula (1) 【Chemistry 1】 [In the formula, R １ represents a linear or branched alkyl group having 1 to 4 carbon atoms; R ２ and R ３ are the same or different and each represents a linear or branched alkyl group having 1 to 4 carbon atoms. A power transmission lubricating base oil containing a diester compound represented by the formula:

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

3. The power transmission lubricating base oil according to claim 1 or 2, wherein the power transmission lubricating base oil is a traction drive lubricating base oil.

4. A power transmission lubricating oil containing the power transmission lubricating base oil according to any one of claims 1 to 3.

5. General formula (1) 【Chemistry 2】 [In the formula, R １ represents an isopropyl group, and R ２ and R ３ Each represents a methyl group. A diester compound represented by the formula:

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