Lubricating oil base oil for power transmission

Abstract

To provide a lubricant base oil for power transmission that has a high traction coefficient and a high flash point, and excellent low-temperature fluidity.SOLUTION: Specifically for example, ester compounds such as 3,5,5-trimethyl-1-hexanoic acid 2-(1,3,3-trimethyl butyl)-5,7,7-trimethyl-1-octyl, and 2-(1,3,3-trimethyl butyl)-5,7,7-trimethyl-1-octanoic acid 3,5,5-trimethyl 1-hexyl, are used as a lubricant base oil for power transmission.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 drives.

Background Art

[0002] In recent years, with the progress of digital information socialization, the required precision 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, the vibration and noise are large. Therefore, traction drives with less of these problems are widely used.

[0003] In addition, the popularization of industrial robots has also advanced, and traction drives are used in joint parts that require precise movement. In addition, the practical application of traction drives has been progressing 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] Lubricating oil base oils for power transmission preferably have 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, are emphasized.

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

[0007] However, alicyclic diester compounds typified 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 is important, such as aircraft, helicopters, and automobiles.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a base oil for power transmission lubricants (particularly, a base oil for traction drive lubricants) having a high traction coefficient, a high flash point, and good low-temperature fluidity.

Means for Solving the Problems

[0010] The present inventors have found that a specific ester compound has a high traction coefficient and a high flash point, and has good low-temperature fluidity. The present invention has been completed by further study based on such findings.

[0011] That is, the present invention provides a base oil for power transmission lubricants (particularly, a base oil for traction drive lubricants) of the following items.

[0012] [Item 1] General formula (1) [Chemical formula] [In the formula, R 1 represents a branched alkyl group having 4 to 12 carbon atoms (the branched alkyl group consists of a linear alkyl group as the main chain and two or more alkyl groups (branches) having 1 to 3 carbon atoms bonded thereto), and X represents the following (a) or (b) [Chemical formula] [Chemical formula] [represents.] A base oil for a power transmission lubricant containing an ester compound represented by the formula.

[0013] [Item 2] R as described in general formula (1) 1 having 7 to 10 carbon atoms, the base oil for a power transmission lubricant according to [Item 1].

[0014] [Item 3] R as described in general formula (1) 1 having 8 carbon atoms, the base oil for a power transmission lubricant according to [Item 1] or [Item 2].

[0015] [Item 4] The ester compound is an ester compound represented by the following general formula (2) or general formula (3), and the base oil for a power transmission lubricant according to any one of [Item 1] to [Item 3]. [Chemical formula] [Chemical formula]

[0016] [Item 5] The content of the ester compound represented by the general formula (1) is 70% by mass or more in the lubricating base oil for power transmission, the lubricating base oil for power transmission according to any one of [Item 1] to [Item 4].

[0017] [Item 6] The content of the ester compound represented by the general formula (1) is 90% by mass or more in the lubricating base oil for power transmission, the lubricating base oil for power transmission according to any one of [Item 1] to [Item 5].

[0018] [Item 7] The lubricating base oil for power transmission according to any one of [Item 1] to [Item 6], wherein the lubricating base oil for power transmission is a lubricating base oil for traction drive.

[0019] [Item 8] A lubricating oil for power transmission containing the lubricating base oil for power transmission according to any one of [Item 1] to [Item 7].

[0020] [Item 9] A lubricating oil for power transmission, characterized by containing the lubricating base oil for power transmission according to any one of [Item 1] to [Item 7] and an antioxidant.

[0021] [Item 10] The lubricating oil for power transmission according to [Item 9], wherein the antioxidant is a phenolic antioxidant and / or an amine antioxidant. [Advantages of the Invention]

[0022] The specific ester compound of the present invention has the characteristics of high traction coefficient and flash point, and good low-temperature fluidity, so it can be preferably used as a lubricating base oil for power transmission (especially a lubricating base oil for traction drive). [Embodiments for Carrying Out the Invention]

[0023] The lubricating base oil for power transmission of the present invention has the general formula (1) [Chemical Formula] [In the formula, R 1 represents a branched alkyl group having 4 to 12 carbon atoms (the branched alkyl group consists of a linear alkyl group as the main chain and two or more alkyl groups (branches) having 1 to 3 carbon atoms bonded thereto), and X represents the following (a) or (b)

Chemical formula

Chemical formula

[0024] R described in the general formula (1) 1 is a branched alkyl group having 4 to 12 carbon atoms (the branched alkyl group consists of a linear alkyl group as the main chain and two or more alkyl groups (branches) having 1 to 3 carbon atoms bonded thereto), and preferably a branched alkyl group having 7 to 10 carbon atoms is preferred.

[0025] Also, a branched alkyl group consisting of a linear alkyl group as the main chain and two or more methyl groups (branches) bonded thereto is preferred.

[0026] R 1Specific examples thereof include 1,1-dimethylethyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1,1,2-trimethylbutyl group, 1,1,3-trimethylbutyl group, 1,2,2-trimethylbutyl group, 2,2,3-trimethylbutyl group, 1,3,3-trimethylbutyl group, 2,3,3-trimethylbutyl group, 1,2,3-trimethylbutyl group, 1,1-dimethylpentyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3-dimethylpentyl group, 3,4-dimethylpentyl group, 4,4-dimethylpentyl group, 1,1,2-trimethylpentyl group, 1,1,3-trimethylpentyl group, 1,1,4-trimethylpentyl group, 1,2,2-trimethylpentyl group, 2,2,3-trimethylpentyl group, 2,2,4-trimethylpentyl group, 1,3,3-trimethylpentyl group, 2,3,3-trimethylpentyl group, 3,3,4-trimethylpentyl group, 1,4,4-trimethylpentyl group, 2,4,4-trimethylpentyl group, 3,4,4-trimethylpentyl group, 1,2,3-trimethylpentyl group, 1,2,4-trimethylpentyl group, 1,3,4-trimethylpentyl group, 2,3,4-trimethylpentyl group, 1,1-dimethylhexyl group, 1,2-dimethylhexyl group, 1,3-dimethylhexyl group, 1,4-dimethylhexyl group, 1,5-dimethylhexyl group, 2,2-dimethylhexyl group, 2,3-dimethylhexyl group, 2,4-dimethylhexyl group, 2,5-dimethylhexyl group, 3,3-dimethylhexyl group, 3,4-dimethylhexyl group, 3,5-dimethylhexyl group, 4,4-dimethylhexyl group, 4,5-dimethylhexyl group, 5,5-dimethylhexyl group, 1,1,2-trimethylhexyl group, 1,1,3-trimethylhexyl group, 1,1,4-trimethylhexyl group, 1,1,5-trimethylhexyl group, 1,2,2-trimethylhexyl group, 2,2,3-trimethylhexyl group, 2,2,4-trimethylhexyl group, 2,2,5-trimethylhexyl group, 1,3,3-trimethylhexyl group, 2,3,3-trimethylhexyl group, 3,3,4-trimethylhexyl group, 3,3,5-trimethylhexyl group, 1,4,4-trimethylhexyl group, 2,4,4-trimethylhexyl group, 3,4,4-trimethylhexyl group, 4,4,5-trimethylhexyl group, 1,5,5-trimethylhexyl group, 2,5,5-trimethylhexyl group, 3,5,5-trimethylhexyl group, 4,5,5-trimethylhexyl group, 1,2,3-trimethylhexyl group, 1,2,4-trimethylhexyl group, 1,2,5-trimethylhexyl group, 1,3,4-trimethylhexyl group, 1,3,5-trimethylhexyl group, 1,4,5-trimethylhexyl group, 2,3,4-trimethylhexyl group, 2,3,5-trimethylhexyl group, 2,4,5-trimethylhexyl group, 3,4,5-trimethylhexyl group, 1,1-dimethylheptyl group, 1,2-dimethylheptyl group, 1,3-dimethylheptyl group, 1,4-dimethylheptyl group, 1,5-dimethylheptyl group, 1,6-dimethylheptyl group, 2,2-dimethylheptyl group, 2,3-dimethylheptyl group, 2,4-dimethylheptyl group, 2,5-dimethylheptyl group, 2,6-dimethylheptyl group, 3,3-dimethylheptyl group, 3,4-dimethylheptyl group, 3,5-dimethylheptyl group, 3,6-dimethylheptyl group, 4,4-dimethylheptyl group, 4,5-dimethylheptyl group, 4,6-dimethylheptyl group, 5,5-dimethylheptyl group, 5,6-dimethylheptyl group, 6,6-dimethylheptyl group, 1,1,2-trimethylheptyl group, 1,1,3-trimethylheptyl group, 1,1,4-trimethylheptyl group, 1,1,5-trimethylheptyl group, 1,1,6-trimethylheptyl group, 1,2,2-trimethylheptyl group, 2,2,3-trimethylheptyl group, 2,2,4-trimethylheptyl group, 2,2,5-trimethylheptyl group, 2,2,6-trimethylheptyl group, 1,3,3-trimethylheptyl group, 2,3,3-trimethylheptyl group, 3,3,4-trimethylheptyl group, 3,3,5-trimethylheptyl group, 3,3,6-trimethylheptyl group, 1,4,4-trimethylheptyl group, 2,4,4-trimethylheptyl group, 3,4,4-trimethylheptyl group, 4,4,5-trimethylheptyl group, 4,4,6-trimethylheptyl group, 1,5,5-trimethylheptyl group, 2,5,5-trimethylheptyl group, 3,5,5-trimethylheptyl group, 4,5,5-trimethylheptyl group, 5,5,6-trimethylheptyl group, 1,6,6-trimethylheptyl group, 2,6,6-trimethylheptyl group, 3,6,6-trimethylheptyl group, 4,6,6-trimethylheptyl group, 5,6,6-trimethylheptyl group, 1,2,3-trimethylheptyl group, 1,2,4-trimethylheptyl group, 1,2,5-trimethylheptyl group, 1,2,6-trimethylheptyl group, 1,3,4-trimethylheptyl group, 1,3,5-trimethylheptyl group, 1,3,6-trimethylheptyl group, 1,4,5-trimethylheptyl group, 1,4,6-trimethylheptyl group, 2,3,4-trimethylheptyl group, 2,3,5-trimethylheptyl group, 2,3,6-trimethylheptyl group, 3,4,5-trimethylheptyl group, 3,4,6-trimethylheptyl group, 4,5,6-trimethylheptyl group, 1,1-dimethyloctyl group, 1,2-dimethyloctyl group, 1,3-dimethyloctyl group, 1,4-dimethyloctyl group, 1,5-dimethyloctyl group, 1,6-dimethyloctyl group, 1,7-dimethyloctyl group, 2,2-dimethyloctyl group, 2,3-dimethyloctyl group, 2,4-dimethyloctyl group, 2,5-dimethyloctyl group, 2,6-dimethyloctyl group, 2,7-dimethyloctyl group, 3,3-dimethyloctyl group, 3,4-dimethyloctyl group, 3,5-dimethyloctyl group, 3,6-dimethyloctyl group, 3,7-dimethyloctyl group, 4,4-dimethyloctyl group, 4,5-dimethyloctyl group, 4,6-dimethyloctyl group, 4,7-dimethyloctyl group, 5,5-dimethyloctyl group, 5,6-dimethyloctyl group, 5,7-dimethyloctyl group, 6,6-dimethyloctyl group, 6,7-dimethyloctyl group, 7,7-dimethyloctyl group, 1,1,2-trimethyloctyl group, 1,1,3-trimethyloctyl group, 1,1,4-trimethyloctyl group, 1,1,5-trimethyloctyl group, 1,1,6-trimethyloctyl group, 1,1,7-trimethyloctyl group, 1,2,2-trimethyloctyl group, 2,2,3-trimethyloctyl group, 2,2,4-trimethyloctyl group, 2,2,5-trimethyloctyl group, 2,2,6-trimethyloctyl group, 2,2,7-trimethyloctyl group, 1,3,3-trimethyloctyl group, 2,3,3-trimethyloctyl group, 3,3,4-trimethyloctyl group, 3,3,5-trimethyloctyl group, 3,3,6-trimethyloctyl group, 3,3,7-trimethyloctyl group, 1,4,4-trimethyloctyl group, 2,4,4-trimethyloctyl group, 3,4,4-trimethyloctyl group, 4,4,5-trimethyloctyl group, 4,4,6-trimethyloctyl group, 4,4,7-trimethyloctyl group, 1,5,5-trimethyloctyl group, 2,5,5-trimethyloctyl group, 3,5,5-trimethyloctyl group, 4,5,5-trimethyloctyl group, 5,5,6-trimethyloctyl group, 5,5,7-trimethyloctyl group, 1,6,6-trimethyloctyl group, 2,6,6-trimethyloctyl group, 3,6,6-trimethyloctyl group, 4,6,6-trimethyloctyl group, 5,6,6-trimethyloctyl group, 6,6,7-trimethyloctyl group, 1,7,7-trimethyloctyl group, 2,7,7-trimethyloctyl group, 3,7,7-trimethyloctyl group, 4,7,7-trimethyloctyl group, 5,7,7-trimethyloctyl group, 6,7,7-trimethyloctyl group, 1,2,3-trimethyloctyl group, 1,2,4-trimethyloctyl group, 1,2,5-trimethyloctyl group, 1,2,6-trimethyloctyl group, 1,2,7-trimethyloctyl group, 1,3,4-trimethyloctyl group, 1,3,5-trimethyloctyl group, 1,3,6-trimethyloctyl group, 1,3,7-trimethyloctyl group, 1,4,5-trimethyloctyl group, 1,4,6-trimethyloctyl group, 1,4,7-trimethyloctyl group, 1,5,6-trimethyloctyl group, 1,5,7-trimethyloctyl group, 1,6,7-trimethyloctyl group, 2,3,4-trimethyloctyl group, 2,3,5-trimethyloctyl group, 2,3,6-trimethyloctyl group, 2,3,7-trimethyloctyl group, 2,4,5-trimethyloctyl group, 2,4,6-trimethyloctyl group, 2,4,7-trimethyloctyl group, 2,5,6-trimethyloctyl group, 2,5,7-trimethyloctyl group, 2,6,7-trimethyloctyl group, 3,4,5-trimethyloctyl group, 3,4,6-trimethyloctyl group, 3,4,7-trimethyloctyl group, 3,5,6-trimethyloctyl group, 3,5,7-trimethyloctyl group, 3,6,7-trimethyloctyl group, 4,5,6-trimethyloctyl group, 4,5,7-trimethyloctyl group, 4,6,7-trimethyloctyl group, 5,6,7-trimethyloctyl group, 1,1-dimethylnonyl group, 1,2-dimethylnonyl group, 1,3-dimethylnonyl group, 1,4-dimethylnonyl group, 1,5-dimethylnonyl group, 1,6-dimethylnonyl group, 1,7-dimethylnonyl group, 1,8-dimethylnonyl group, 2,2-dimethylnonyl group, 2,3-dimethylnonyl group, 2,4-dimethylnonyl group, 2,5-dimethylnonyl group, 2,6-dimethylnonyl group, 2,7-dimethylnonyl group, 2,8-dimethylnonyl group, 3,3-dimethylnonyl group, 3,4-dimethylnonyl group, 3,5-dimethylnonyl group, 3,6-dimethylnonyl group, 3,7-dimethylnonyl group, 3,8-dimethylnonyl group, 4,4-dimethylnonyl group, 4,5-dimethylnonyl group, 4,6-dimethylnonyl group, 4,7-dimethylnonyl group, 4,8-dimethylnonyl group, 5,5-dimethylnonyl group, 5,6-dimethylnonyl group, 5,7-dimethylnonyl group, 5,8-dimethylnonyl group, 6,6-dimethylnonyl group, 6,7-dimethylnonyl group, 6,8-dimethylnonyl group, 7,7-dimethylnonyl group, 7,8-dimethylnonyl group, 8,8-dimethylnonyl group, 1,1,2-trimethylnonyl group, 1,1,3-trimethylnonyl group, 1,1,4-trimethylnonyl group, 1,1,5-trimethylnonyl group, 1,1,6-trimethylnonyl group, 1,1,7-trimethylnonyl group, 1,1,8-trimethylnonyl group, 1,2,2-trimethylnonyl group, 2,2,3-trimethylnonyl group, 2,2,4-trimethylnonyl group, 2,2,5-trimethylnonyl group, 2,2,6-trimethylnonyl group, 2,2,7-trimethylnonyl group, 2,2,8-trimethylnonyl group, 1,3,3-trimethylnonyl group, 2,3,3-trimethylnonyl group, 3,3,4-trimethylnonyl group, 3,3,5-trimethylnonyl group, 3,3,6-trimethylnonyl group, 3,3,7-trimethylnonyl group, 3,3,8-trimethylnonyl group, 1,4,4-trimethylnonyl group, 2,4,4-trimethylnonyl group, 3,4,4-trimethylnonyl group, 4,4,5-trimethylnonyl group, 4,4,6-trimethylnonyl group, 4,4,7-trimethylnonyl group, 4,4,8-trimethylnonyl group, 1,5,5-trimethylnonyl group, , 2,5,5-trimethylnonyl group, 3,5,5-trimethylnonyl group, 4,5,5-trimethylnonyl group, 5,5,6-trimethylnonyl group, 5,5,7-trimethylnonyl group, 5,5,8-trimethylnonyl group, 1,6,6-trimethylnonyl group, 2,6,6-trimethylnonyl group, 3,6,6-trimethylnonyl group, 4,6,6-trimethylnonyl group, 5,6,6-trimethylnonyl group, 6,6,7-trimethylnonyl group, 6,6,8-trimethylnonyl group, 1,7,7-trimethylnonyl group, 2,7,7-trimethylnonyl group, 3,7,7-trimethylnonyl group, 4,7,7-trimethylnonyl group, 5,7,7-trimethylnonyl group, 6,7,7-trimethylnonyl group, 7,7,8-trimethylnonyl group, 1,8,8-trimethylnonyl group, 2,8,8-trimethylnonyl group, 3,8,8-trimethylnonyl group, 4,8,8-trimethylnonyl group, 5,8,8-trimethylnonyl group, 6,8,8-trimethylnonyl group, 7,8,8-trimethylnonyl group, 1,2,3-trimethylnonyl group, 1,2,4-trimethylnonyl group, 1,2,5-trimethylnonyl group, 1,2,6-trimethylnonyl group, 1,2,7-trimethylnonyl group, 1,2,8-trimethylnonyl group, 1,3,4-trimethylnonyl group, 1,3,5-trimethylnonyl group, 1,3,6-trimethylnonyl group, 1,3,7-trimethylnonyl group, 1,3,8-trimethylnonyl group, 1,4,5-trimethylnonyl group, 1,4,6-trimethylnonyl group, 1,4,7-trimethylnonyl group, 1,4,8-trimethylnonyl group, 1,5,6-trimethylnonyl group, 1,5,7-trimethylnonyl group, 1,5,8-trimethylnonyl group, 1,6,7-trimethylnonyl group, 1,6,8-trimethylnonyl group, 1,7,8-trimethylnonyl group, 2,3,4-trimethylnonyl group, 2,3,5-trimethylnonyl group, 2,3,6-trimethylnonyl group, 2,3,7-trimethylnonyl group, 2,3,8-trimethylnonyl group, 2,4,5-trimethylnonyl group, 2,4,6-trimethylnonyl group, 2,4,7-trimethylnonyl group, 2,4,8-trimethylnonyl group, 2,5,6-trimethylnonyl group, 2,5,7-trimethylnonyl group, 2,5,8-trimethylnonyl group, 2,6,7-trimethylnonyl group, 2,6,8-trimethylnonyl group, 2,7,8-trimethylnonyl group, 3,4,5-trimethylnonyl group, 3,4,6-trimethylnonyl group, 3,4,7-trimethylnonyl group, 3,4,8-trimethylnonyl group, 3,5,6-trimethylnonyl group, 3,5,7-trimethylnonyl group, 3,5,8-trimethylnonyl group, 3,6,7-trimethylnonyl group, 3,6,8-trimethylnonyl group, 3,7,8-trimethylnonyl group, 4,5,6-trimethylnonyl group, 4,5,7-trimethylnonyl group, 4,5,8-trimethylnonyl group, 4,6,7-trimethylnonyl group, 4,6,8-trimethylnonyl group, 4,7,8-trimethylnonyl group, 5,6,7-trimethylnonyl group, 5,6,8-trimethylnonyl group, 5,7,8-trimethylnonyl group, 6,7,8-trimethylnonyl group, 1,1-dimethyldecyl group, 1,2-dimethyldecyl group, 1,3-dimethyldecyl group, 1,4-dimethyldecyl group, 1,5-dimethyldecyl group, 1,6-dimethyldecyl group, 1,7-dimethyldecyl group, 1,8-dimethyldecyl group, 1,9-dimethyldecyl group, 2,2-dimethyldecyl group, 2,3-dimethyldecyl group, 2,4-dimethyldecyl group, 2,5-dimethyldecyl group, 2,6-dimethyldecyl group, 2,7-dimethyldecyl group, 2,8-dimethyldecyl group, 2,9-dimethyldecyl group, 3,3-dimethyldecyl group, 3,4-dimethyldecyl group, 3,5-dimethyldecyl group, 3,6-dimethyldecyl group, 3,7-dimethyldecyl group, 3,8-dimethyldecyl group, 3,9-dimethyldecyl group, 4,4-dimethyldecyl group, 4,5-dimethyldecyl group, 4,6-dimethyldecyl group, 4,7-dimethyldecyl group, 4,8-dimethyldecyl group, 4,9-dimethyldecyl group, 5,5-dimethyldecyl group, 5,6-dimethyldecyl group, 5,7-dimethyldecyl group, 5,8-dimethyldecyl group, 5,9-dimethyldecyl group, 6,6-dimethyldecyl group, 6,7-dimethyldecyl group, 6,8-dimethyldecyl group, 6,9-dimethyldecyl group, 7,7-dimethyldecyl group, 7,8-dimethyldecyl group, 7,9-dimethyldecyl group, 8,8-dimethyldecyl group, 8,9-dimethyldecyl group, 9,9-dimethyldecyl group, etc. are mentioned. Among them, 2,2-dimethylpropyl group and 2,4,4-trimethylpentyl group are preferable, and particularly 2,4,4-trimethylpentyl group is preferable.,

[0027] Specific examples of the ester compound represented by the general formula (1) include, for example, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl pivalate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,3-dimethylbutanoate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5,5-trimethylhexanoate, 1,2-dimethylpropyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2,2-dimethylpropyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2,2-dimethylbutyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2,3-dimethylbutyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 3,3-dimethylbutyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 3,3-dimethyl-2-butyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 4-methyl-2-pentyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 1,2,2-trimethylpropyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 4,4-dimethyl-2-pentyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2,4-dimethyl-3-pentyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2-methyl-3-hexyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 5-methyl-3-heptyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 6-methyl-3-heptyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2,2-dimethyl-3-hexyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2,5-dimethyl-3-hexyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl2-Methyl-3-octyl 7-trimethyl-1-octanoate, 2,4-dimethyl-4-heptyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2,6-dimethyl-4-heptyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 3,5,5-trimethylhexyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 3,7-dimethyloctyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, Examples include 2,6,8-trimethyl-4-nonyl, and particularly preferred are 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5,5-trimethylhexanoate and 3,5,5-trimethylhexyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate.

[0028] The above ester compounds can also be used as a base oil for power transmission lubricants as a mixture of two or more.

[0029] The method for producing the ester compound is not particularly limited as long as the compound can be obtained.

[0030] Examples include an esterification reaction between 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyloctanol and the corresponding branched-chain aliphatic monocarboxylic acid, and an esterification reaction between 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyloctanoic acid and the corresponding branched-chain aliphatic alcohol.

[0031] The acid value of the ester compound 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 ester compound itself tends to be further improved, and within such a preferable range, it also has a favorable effect on improving the heat-resistant 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 and washing with an alkaline component in a post-treatment step (a step of performing washing (neutralization) with an aqueous alkaline solution and washing with water), and a method of performing an adsorption treatment with activated alumina.

[0032] The hydroxyl value of the ester compound 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 ester compound itself becomes lower, and the heat resistance also tends to be further improved. Within such a preferable range, it also has a favorable effect on improving the water resistance and heat-resistant 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 (a step of distilling off excess raw materials that can be distilled under reduced pressure or normal pressure).

[0033] 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.

[0034] The low-temperature fluidity of the lubricating oil base oil for power transmission can be evaluated, for example, by the pour point. From the viewpoint of low-temperature operability, the pour point of the lubricating oil base oil is usually -30°C or lower, preferably -40°C or lower. In the present specification and claims, the pour point is a value measured by the method described in the examples below.

[0035] From the viewpoints of storage stability and handleability, the flash point of the base oil for power transmission lubricants is usually 185°C or higher, preferably 200°C or higher. If it is less than 185°C, there will be more restrictions in handling due to ignition. In this specification and the claims, the flash point is the value measured by the method described in the examples below.

[0036] As the base oil for power transmission lubricants, a base oil for power transmission lubricants having a traction coefficient (60°C) of 0.090 or more, a pour point of -30°C or lower, and a flash point of 185°C or higher, a base oil for power transmission lubricants having a traction coefficient (60°C) of 0.080 or more, a pour point of -40°C or lower, and a flash point of 185°C or higher, and a base oil for power transmission lubricants having a traction coefficient (60°C) of 0.090 or more, a pour point of -30°C or lower, and a flash point of 200°C or higher are preferred. In particular, a base oil for power transmission lubricants having a traction coefficient (60°C) of 0.090 or more, a pour point of -40°C or lower, and a flash point of 185°C or higher, a base oil for power transmission lubricants having a traction coefficient (60°C) of 0.090 or more, a pour point of -30°C or lower, and a flash point of 200°C or higher, and a base oil for power transmission lubricants having a traction coefficient (60°C) of 0.090 or more, a pour point of -40°C or lower, and a flash point of 185°C or higher are more preferred. In particular, a base oil for power transmission lubricants having a traction coefficient (60°C) of 0.090 or more, a pour point of -40°C or lower, and a flash point of 200°C or higher is preferred.

[0037] Since the base oil for power transmission lubricants of the present invention has a high traction coefficient and flash point, and good low-temperature fluidity, it is suitably used as a base oil for power transmission lubricants, particularly as a base oil for traction drive lubricants.

[0038] The base oil for power transmission lubricants of the present invention can contain other base oils (hereinafter referred to as "combined base oils") that can be used in combination. That is, the base oil for power transmission lubricants of the present invention includes only ester compounds and mixtures of the ester compounds and combined base oils. Hereinafter, the base oil for power transmission lubricants may be referred to as "base oil" in some cases.

[0039] Examples of the base oils 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 the ester compounds according to the present invention), polyalkylene glycols, polyvinyl ethers, polyphenyl ethers, alkylphenyl ethers, silicone oils, and the like. At least one of these can be used in combination as appropriate.

[0040] Examples of mineral oils include solvent-refined mineral oils, hydrorefined mineral oils, and wax isomerized oils. Usually, those having a kinematic viscosity at 100 °C in the range of 1 to 25 mm 2 / s, preferably 2 to 20 mm 2 / s are used.

[0041] Examples of poly-α-olefins 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 in the range 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.

[0042] Examples of polybutenes 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.

[0043] Examples of alkylbenzenes include monoalkylbenzenes, dialkylbenzenes, trialkylbenzenes, tetraalkylbenzenes, etc. having a molecular weight of 200 to 450 and substituted with a linear or branched alkyl group having 1 to 40 carbon atoms.

[0044] Examples of the alkylnaphthalene include monoalkylnaphthalene, dialkylnaphthalene, etc. which are substituted with a linear or branched alkyl group having 1 to 30 carbon atoms.

[0045] Examples of the alicyclic hydrocarbon oil include naphthenic hydrocarbon oil, etc., and generally those having a kinematic viscosity at 100 °C in a wide range of 1 to 40 mm 2 / s are exemplified.

[0046] Examples of the animal and vegetable oils include beef tallow, lard, palm oil, coconut oil, rapeseed oil, castor oil, sunflower oil, etc.

[0047] Examples of the organic acid ester include fatty acid monoesters (excluding the ester compounds according to the present invention), aliphatic dibasic acid diesters, aliphatic dihydric alcohol diesters, polyol esters and other esters.

[0048] Examples of the fatty acid monoesters include esters of an aliphatic linear or branched monocarboxylic acid having 5 to 22 carbon atoms and a linear or branched saturated or unsaturated aliphatic alcohol having 3 to 22 carbon atoms. However, the ester compounds according to the present invention are excluded.

[0049] Examples of the 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.

[0050] As the aliphatic dihydric alcohol diester and polyol ester, full esters of polyols with a neopentyl-type structure such as neopentyl glycol, 2,2-diethylpropanediol, 2-butyl-2-ethylpropanediol, trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, etc., polyols with a non-neopentyl-type structure such as 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., and linear and / or branched saturated or unsaturated fatty acids having 3 to 22 carbon atoms can be used.

[0051] As other esters, there may be mentioned esters of polymerized fatty acids such as dimer acid and hydrogenated dimer acid, or hydroxy fatty acids such as condensed castor oil fatty acid and hydrogenated condensed castor oil fatty acid, and linear or branched saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

[0052] Examples of the polyalkylene glycol include ring-opening polymers 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.

[0053] The polyvinyl ether is a compound obtained by polymerization of a vinyl ether monomer, and 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.

[0054] Examples of the polyphenyl ether include compounds having a structure in which the meta positions of two or more aromatic rings are connected by an ether bond or a thioether bond, and 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 substituted with sulfur, and the like.

[0055] Examples of the alkylphenyl ether include compounds in which the polyphenyl ether is substituted with a linear or branched alkyl group having 6 to 18 carbon atoms, and alkyl diphenyl ethers substituted with one or more alkyl groups are particularly preferred.

[0056] Examples of silicone oils include dimethyl silicone, methylphenyl silicone, and modified silicones such as long-chain alkyl silicone and fluorosilicone.

[0057] In the base oil for lubricating oil for power transmission of the present invention, the content of the ester compound is usually 70% by mass or more, preferably 90% by mass or more.

[0058] In the base oil for lubricating oil for power transmission of the present invention, the content of the combined base oil is usually 30% by mass or less, preferably 10% by mass or less.

[0059] The present invention also provides a lubricating oil for power transmission containing the base oil for lubricating oil for power transmission. In order to improve its performance, the lubricating oil for power transmission may be appropriately blended with at least one additive such as an antioxidant, a metal detergent, an ashless dispersant, an oiliness agent, an antiwear agent, an extreme pressure agent, a metal deactivator, a rust inhibitor, a viscosity index improver, a pour point depressant, an antifoaming agent, a hydrolysis inhibitor, a thickener, a corrosion inhibitor, and a hue stabilizer 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.

[0060] As antioxidants, 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 (i.e., 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 (i.e., 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.,

[0061] 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-based compounds such as phenothiazine, etc. 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.

[0062] Here, in this specification and the claims, there are 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 ester compound represented by the general formula (1) according to the present invention or a base oil consisting of a mixture of the ester 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 0.01 to 5 parts by mass with respect to 100 parts by mass of the base oil.

[0063] 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 about 1 - 10% by mass, preferably about 2 - 7% by mass, based on the base oil.

[0064] 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 about 1 - 10% by mass, preferably about 2 - 7% by mass, based on the base oil.

[0065] Examples of the oiliness 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 polyglyceryl 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 oiliness 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.

[0066] Examples of the antiwear agent and 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-dialkyldithiophosphate, Zn-dialkyldithiophosphate, Mo-dialkyldithiophosphate, and Mo-dialkyldithiocarbamate. 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.

[0067] Examples of the metal deactivator 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.

[0068] Examples of the rust inhibitor 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; dialkyl phosphite amine salts, etc. 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.

[0069] Examples of the viscosity index improver 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.

[0070] Examples of pour point depressants include condensates of chlorinated paraffin and alkyl naphthalene, condensates of chlorinated paraffin and phenol, polyalkyl methacrylate, polyalkyl styrene, polybutene, etc., which are the aforementioned viscosity index improvers. These pour point depressants may be used alone or in combination. When using them, it is usually desirable to add about 0.01 to 5% by mass, preferably about 0.1 to 3% by mass, based on the base oil.

[0071] As the antifoaming agent, liquid silicone is suitable. When using it, the addition amount is usually about 0.0005 to 0.01% by mass based on the base oil.

[0072] As hydrolysis inhibitors, 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-butylcarbodiimide and 1,3-di-p-tolylcarbodiimide can be used, and usually, it is about 0.05 to 2% by mass based on the base oil.

[0073] By appropriately combining thickeners with the lubricating oil base oil for power transmission of the present invention, "grease" can be obtained.

[0074] Examples of thickeners include metal soap-based thickeners, composite metal soap-based thickeners, and non-soap-based thickeners.

[0075] 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.

[0076] Examples of the complex metal soap - based thickeners include complexes of monovalent aliphatic carboxylic acid metal salts having a hydroxyl group and divalent aliphatic carboxylic acid metal salts. Specifically, complex lithium soap and complex aluminum soap are exemplified.

[0077] Examples of the non - soap - based thickeners include bentonite, silica aerogel, sodium terephthalamate, polytetrafluoroethylene, boron nitride, urea compounds (including alicyclic, aromatic, aliphatic, diurea, triurea, tetraurea, urea - urethane compounds, etc.).

[0078] 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.

[0079] These thickeners can be used alone or in combination of two or more as appropriate, and the addition amount is not particularly limited as long as the predetermined effect is achieved.

[0080] Examples of the corrosion inhibitors include sodium sulfonate and sorbitan ester, and they are usually added in an amount of about 0.1 - 3.0% by mass based on the base oil.

[0081] Examples of the hue stabilizers include substituted hydroquinone, furfuralazine, etc., and they are usually added in an amount of about 0.01 - 0.1% by mass based on the base oil.

[0082] 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.

[0083] The lubricating oil base oil for power transmission of the present invention and the ester compound represented by the general formula (1) can improve the traction coefficient of the lubricating oil for power transmission (particularly, the lubricating oil for traction drive) when added thereto. Therefore, it can be used as a traction coefficient improver.

[0084] 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, transmissions, generators, speed reducers, etc. of automobiles, ships, airplanes, precision instruments, robots, etc.

Examples

[0085] The present invention will be described in detail with reference to the following examples, 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.

[0086] <Compounds Used> 2-(1,3,3-Trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid: "Product Name 'Isostearic Acid'" manufactured by Tokyo Chemical Industry Co., Ltd. 2-(1,3,3-Trimethylbutyl)-5,7,7-trimethyl-1-octanol: "Product Name 'Fine Oxocol 180'" manufactured by Nissan Chemical Industries, Ltd. 3,5,5-Trimethyl-1-hexanoic acid: "Product Name 'Kyowa Noic-N'" manufactured by KH Neochem Co., Ltd. 3,5,5-Trimethyl-1-hexanol: "Product Name 'Nonanol'" manufactured by KH Neochem Co., Ltd. 1-Nonanoic acid: "Trade Name 'Nonanoic Acid'" manufactured by Tokyo Chemical Industry Co., Ltd. 2-Hexyl-1-decanol: "Trade Name '2-Hexyl-1-decanol'" 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 ON"

[0087] (a) Acid value (AV) Measured in accordance with JIS K2501 (2003). The detection limit is 0.01 KOHmg / g.

[0088] (b) Hydroxyl value (OHV) Measured in accordance with JIS K0070 (1992). The detection limit is 0.1 KOHmg / g.

[0089] [Measurement of physical properties of lubricating 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). [Measurement conditions] Apparatus: Ball-on-ring type friction tester (TE54 type manufactured by Phoenix Tribology) 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 Load: 150 N >[Evaluation of coefficient of traction] A: 0.090 or more B: 0.080 or more and less than 0.090 C: Less than 0.080

[0090] (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: -40 °C or lower B: Exceeding -40 °C and -30 °C or lower C: Exceeding -30 °C

[0091] (e) Flash point Measured in accordance with JIS K2265 (Cleveland open cup). <Evaluation of flash point> A: 200 °C or higher B: 185 °C or higher and less than 200 °C C: Less than 185 °C (f) Evaluation of base oil for power transmission lubricant As for the evaluation of the base oil for power transmission lubricant, 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 judged as unsuitable, if B is 2 or less (the other evaluations are A), it is judged as good, and if B is 1 or less (the other evaluations are A), it is judged as particularly good.

[0092] [Example 1] Into a 1-liter four-necked flask equipped with a stirrer, a thermometer, and a water separation receiver with a condenser tube, 278.5 g (1.76 mol) of 3,5,5-trimethyl-1-hexanoic acid as a carboxylic acid, 432.8 g (1.60 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanol as an alcohol, 0.7 g of tin oxide as an esterification catalyst, and 30 g of xylene as an entrainer were charged. After replacing 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 theoretical amount of generated water (28.8 g) using the water separation receiver. After completion of the reaction, the remaining 3,5,5-trimethyl-1-hexanoic acid and xylene were removed by distillation under reduced pressure to obtain a crude esterification product. Next, after neutralizing the obtained crude esterification product with an aqueous sodium hydroxide solution in an amount 1.5 times the equivalent of the acid value, washing with water was repeated until neutral. Magnesium sulfate was added to the obtained crude esterification product for dehydration, and then magnesium sulfate was removed by filtration to obtain 545.4 g (1.33 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5,5-trimethyl-1-hexanoate. The acid value of the obtained compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. The physical properties of each when the obtained compound was evaluated as a base oil (A) for power transmission lubricant are shown in Table 1.

[0093] [Example 2] In the same manner as in Example 1, except that 3,5,5-trimethyl-1-hexanoic acid was changed to 277.0 g (1.92 mol) of 3,5,5-trimethyl-1-hexanol and 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid was changed to 455.2 g (1.60 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanol An esterification reaction was carried out. After completion of the reaction, the remaining 3,5,5-trimethyl-1-hexanol and xylene were removed by distillation under reduced pressure to obtain a crude esterification product. Next, the obtained crude esterified 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 esterified product for dehydration, and then magnesium sulfate was removed by filtration to obtain 558.6 g (1.36 mol) of 3,5,5-trimethyl-1-hexyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate. The acid value of the obtained 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 obtained compound was evaluated as a lubricating base oil (B) for power transmission.

[0094] [Comparative Example 1] Table 2 shows each physical property value when diisodecyl adipate was evaluated as a lubricating base oil (a) for power transmission.

[0095] [Comparative Example 2] Table 2 shows each physical property when mineral oil Y was evaluated as a lubricating base oil (b) for power transmission.

[0096] [Comparative Example 3] In the same manner as in Example 1, except that 3,5,5-trimethyl-1-hexanoic acid was changed to 278.5 g (1.76 mol) of 1-nonanoic acid, 552.0 g (1.34 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 1-nonanoate was obtained. The acid value of the obtained compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. Table 2 shows each physical property when the obtained compound was evaluated as a lubricating base oil (c) for power transmission.

[0097] [Comparative Example 4] The amount of 3,5,5-trimethyl-1-hexanoic acid charged was changed to 299.4 g (1.89 mol), and 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanol was changed to 417.0 g (1.72 mol) of 2-hexyl-1-decanol. In the same manner as in Example 1, 566.0 g (1.48 mol) of 2-hexyl-1-decyl 3,5,5-trimethyl-1-hexanoate was obtained. The acid value of the obtained compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. Table 2 shows the physical properties of the compound when evaluated as a lubricating base oil (d) for power transmission.

[0098]

Table 1

[0099]

Table 2

[0100] From Table 1, it can be seen that the lubricating base oils for power transmission of the present invention described in Example 1 and Example 2 have a high traction coefficient of 0.090 or more, a pour point of -40°C or less, and a flash point of 185°C or more.

Industrial Applicability

[0101] Since the lubricating 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 base oil for power transmission (particularly, a lubricating base oil for traction drive) for automobiles, ships, aircraft, precision instruments, etc.

Claims

1. General formula (1) 【Chemical Formula 1】 [wherein, R １ represents a branched alkyl group having 4 to 12 carbon atoms (the branched alkyl group is composed of a linear alkyl group as the main chain and two or more alkyl groups (branches) having 1 to 3 carbon atoms bonded thereto), and X is the following (a) or (b) 【Chemical 2】 [Chemical Formula 3] represents.] containing an ester compound represented by a base oil for a power transmission lubricant, wherein the content of the ester compound represented by the general formula (1) is 70% by mass or more in the base oil for a power transmission lubricant.

2. The base oil for a power transmission lubricant according to claim 1, wherein the ester compound is an ester compound represented by the following general formula (2) or general formula (3). 【Chemical Formula 4】 [Chemical Formula 5]

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

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

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