JP7709014B2 - Power transmission lubricant base oil - Google Patents

Description

The present invention relates to a lubricant base oil for power transmission. Specifically, the present invention relates to a lubricant base oil for traction drives.

In recent years, with the advancement of the digital information society, the demands for precision from printers and copiers are increasing. In particular, high rotational precision, low vibration and low noise are required for the motor section, which is required for highly accurate paper feeding. When gear systems are used as the power transmission method for these rotating parts, large vibrations and noise are generated, so traction drives, which have fewer vibrations and noise, are widely used.

In addition, with the widespread use of industrial robots, traction drives are now used in joints that require precise movement. Other applications of traction drives include continuously variable transmissions for industrial equipment, aircraft generators, and rotor speed control for helicopters. In order to increase the amount of power transmitted, efforts have been made to enlarge the traction drives, but there is a tendency for the amount of heat generated to increase as the contact area increases.

In order to improve power transmission performance, it is preferable for the lubricant base oil to have a high traction coefficient, and alicyclic hydrocarbon compounds have been proposed. Examples include dicyclohexyl compounds such as 2-methyl-2,4-dicyclohexylpentane, and dimerized norbornanes (Patent Documents 1 and 2).

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 in fields where heat resistance and safety are important, such as large traction drives.

Ester compounds have also been proposed as base oils for power transmission lubricants with high flash points. For example, alicyclic diester compounds such as 1,2-cyclohexanedicarboxylate di(cyclohexylmethyl) are listed (Patent Document 3).

However, alicyclic diester compounds, such as 1,2-cyclohexanedicarboxylate di(cyclohexylmethyl), tend to have high pour points of -20°C or higher, which is not necessarily sufficient for use in areas where low-temperature operation is important, such as aircraft, helicopters, and automobiles.

Japanese Unexamined Patent Publication No. 47-7664 Japanese Patent Application Publication No. 3-95295 International Publication No. WO2018/008667

The present invention aims to provide a lubricant base oil for power transmission (particularly a lubricant base oil for traction drives) that has a high traction coefficient and flash point and good low-temperature fluidity.

The inventors have discovered that certain ester compounds have a high traction coefficient and flash point, and also have good low-temperature fluidity. The present invention was completed through further investigation based on this knowledge.

That is, the present invention provides a power transmission lubricant base oil (particularly a traction drive lubricant base oil) that meets the following criteria:

[Section 1]
General formula (1)
[In the formula, 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 a 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):
represents.]
The present invention relates to a power transmission lubricating base oil containing an ester compound represented by the formula:

[Section 2]
The power transmission lubricant base oil according to [Item 1], wherein R ¹ in the general formula (1) has 7 to 10 carbon atoms.

[Section 3]
The power transmission lubricant base oil according to [Item 1] or [Item 2], wherein R ¹ in the general formula (1) has 8 carbon atoms.

[Section 4]
The power transmission lubricant base oil according to any one of [Item 1] to [Item 3], wherein the ester compound is an ester compound represented by the following general formula (2) or general formula (3):

[Section 5]
The content of the ester compound represented by the general formula (1) in the power transmission lubricant base oil is 70 mass% or more in the power transmission lubricant base oil.

[Section 6]
The content of the ester compound represented by the general formula (1) in the power transmission lubricant base oil is 90 mass% or more in the power transmission lubricant base oil.

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

[Section 8]
A power transmission lubricant containing the power transmission lubricant base oil according to any one of [Item 1] to [Item 7].

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

[Section 10]
Item 10. The lubricating oil for power transmission according to item 9, wherein the antioxidant is a phenol-based antioxidant and/or an amine-based antioxidant.

The specific ester compound of the present invention has the characteristics of a high traction coefficient and flash point, and good low-temperature fluidity, and can therefore be suitably used as a lubricant base oil for power transmission (particularly, a lubricant base oil for traction drives).

The power transmission lubricating base oil of the present invention is represented by the general formula (1)
[In the formula, 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 a 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):
represents.]
The present invention is characterized in that it contains a specific ester compound represented by the formula:

R ¹ in the general formula (1) is a branched alkyl group having 4 to 12 carbon atoms (the branched alkyl group is composed of a linear alkyl group as a 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.

Furthermore, branched alkyl groups consisting of a linear alkyl group as the main chain and two or more methyl groups (branched) bonded to it are preferred.

Specific examples of R ¹ include a 1,1-dimethylethyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, a 1,1,2-trimethylpropyl group, a 1,2,2-trimethylpropyl group, a 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, a 3,3-dimethylbutyl group, a 1,1,2-trimethylbutyl group, a 1,1,3-trimethylbutyl group, a 1,2,2-trimethylbutyl group, a methylbutyl 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, Methylpentyl 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, 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-dimethyl hexyl 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, Methylheptyl 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 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 octyl 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-trimethyl Octyl 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, 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, Methylnonyl 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 nonyl 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 a 5,8,8-trimethylnonyl group, a 6,8,8-trimethylnonyl group, a 7,8,8-trimethylnonyl group, a 1,2,3-trimethylnonyl group, a 1,2,4-trimethylnonyl group, a 1,2,5-trimethylnonyl group, a 1,2,6-trimethylnonyl group, a 1,2,7-trimethylnonyl group, a 1,2,8-trimethylnonyl group, a 1,3,4-trimethylnonyl group, a 1,3,5-trimethylnonyl group, a 1,3,6-trimethylnonyl group, a 1,3,7-trimethylnonyl group, a 1,3,8-trimethylnonyl group, Tyrnonyl 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 dimethyldecyl 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, 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, Examples of the dimethyldecyl group include dimethyldecyl, 4,9-dimethyldecyl, 5,5-dimethyldecyl, 5,6-dimethyldecyl, 5,7-dimethyldecyl, 5,8-dimethyldecyl, 5,9-dimethyldecyl, 6,6-dimethyldecyl, 6,7-dimethyldecyl, 6,8-dimethyldecyl, 6,9-dimethyldecyl, 7,7-dimethyldecyl, 7,8-dimethyldecyl, 7,9-dimethyldecyl, 8,8-dimethyldecyl, 8,9-dimethyldecyl, and 9,9-dimethyldecyl groups. Among these, 2,2-dimethylpropyl and 2,4,4-trimethylpentyl groups are preferred, and 2,4,4-trimethylpentyl is particularly preferred.

Specific examples of the ester compound represented by the general formula (1) include 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-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoate, -trimethyl-1-octanoic acid 2,2-dimethylbutyl, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid 2,3-dimethylbutyl, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid 3,3-dimethylbutyl, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid 3,3-dimethyl-2-butyl, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid 4-methyl-2-pentyl, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid 1,2,2-trimethylpropyl, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid 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-(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-methyl-3-octyl, 2-(1,3,3-trimethylbutyl)-5,7,7-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,
2,6,8-trimethyl-4-nonyl is exemplified, 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.

The above ester compounds can also be used as a mixture of two or more types as a lubricant base oil for power transmission.

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

For example, there is an esterification reaction between 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyloctanol and the corresponding branched aliphatic monocarboxylic acid, and an esterification reaction between 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyloctanoic acid and the corresponding branched aliphatic alcohol.

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 improved, and such a preferred range also has a positive 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 and washing with an alkaline component in a post-treatment process (a process of washing (neutralization) with an alkaline aqueous solution and washing with water), and a method of adsorption treatment with activated alumina.

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 ester compound itself tends to have lower hygroscopicity and improved heat resistance, and such a 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 in the post-treatment process under reduced pressure (a process of distilling off excess distillable raw materials under reduced pressure or normal pressure).

The traction coefficient (60°C) of the power transmission lubricant base oil is usually 0.080 or more, and 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.

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

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

As the lubricating oil base oil for power transmission, a lubricating oil base oil for power transmission having a traction coefficient (60°C) of 0.090 or more, a pour point of -30°C or less, and a flash point of 185°C or more, a lubricating oil base oil for power transmission having a traction coefficient (60°C) of 0.080 or more, a pour point of -40°C or less, and a flash point of 185°C or more, a lubricating oil base oil for power transmission having a traction coefficient (60°C) of 0.090 or more, a pour point of -30°C or less, and a flash point of 200°C or more is preferred, and particularly preferred are a lubricating oil base oil for power transmission having a traction coefficient (60°C) of 0.090 or more, a pour point of -30°C or less, and a flash point of 200°C or more. Power transmission lubricant base oils with a dynamic point of -40°C or less and a flash point of 185°C or more, power transmission lubricant base oils with a traction coefficient (60°C) of 0.090 or more, a pour point of -30°C or less and a flash point of 200°C or more, and power transmission lubricant base oils with a traction coefficient (60°C) of 0.090 or more, a pour point of -40°C or less and a flash point of 185°C or more are more preferred, and power transmission lubricant base oils with a traction coefficient (60°C) of 0.090 or more, a pour point of -40°C or less and a flash point of 200°C or more are particularly preferred.

The power transmission lubricant base oil of the present invention has a high traction coefficient and flash point, and good low-temperature fluidity, and is therefore suitable for use as a power transmission lubricant base oil, particularly as a traction drive lubricant base oil.

The power transmission lubricant base oil of the present invention may contain other base oils that can be used in combination (hereinafter referred to as "combination base oils"). In other words, the power transmission lubricant base oil of the present invention includes only ester compounds, and mixtures of the ester compounds and combination base oils. Hereinafter, the power transmission lubricant base oil may be referred to as "base oil".

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

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

Examples of poly-α-olefins include polymers or copolymers of α-olefins 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.) having a kinetic viscosity of 1 to 25 mm ² /s at 100°C and a viscosity index of 100 or more, and particularly preferred are those having a kinetic viscosity of 1.5 to 20 mm ² /s at 100°C and a viscosity index of 120 or more.

Polybutene includes those obtained by polymerizing isobutylene and those obtained by copolymerizing isobutylene with normal butylene, and generally includes those having a kinetic viscosity at 100° C. in a wide range of 2 to 40 mm ² /s.

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

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

Alicyclic hydrocarbon oils include naphthenic hydrocarbon oils and the like, and generally include those having a kinetic viscosity at 100° C. in a wide range of 1 to 40 mm ² /s.

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

Examples of organic acid esters 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.

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. However, this does not include the ester compounds of the present invention.

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 their anhydrides, with linear or branched, saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

Aliphatic dihydric alcohol diesters and polyol esters include neopentyl-type polyols such as neopentyl glycol, 2,2-diethylpropanediol, 2-butyl-2-ethylpropanediol, trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane, and dipentaerythritol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 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, It is possible to use full esters of polyols with non-neopentyl structure such as hexanediol, 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.

Other esters include 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 with linear or branched, saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

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 recommended kinetic viscosity of the polymer is preferably 5 to 1000 mm ² /s (40°C), more preferably 5 to 500 mm ² /s (40°C).

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 kinetic viscosity of the polymer is preferably 5 to 1000 mm ² /s (40°C), more preferably 5 to 500 mm ² /s (40°C).

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

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.

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

The content of the ester compound in the power transmission lubricant base oil of the present invention is usually 70% by mass or more, and preferably 90% by mass or more.

The content of the combined base oil in the power transmission lubricant base oil of the present invention is usually 30 mass% or less, preferably 10 mass% or less.

The present invention also provides a power transmission lubricant containing the power transmission lubricant base oil. In order to improve the performance of the power transmission lubricant, at least one of additives such as antioxidants, metal detergents, ashless dispersants, oiliness agents, antiwear agents, extreme pressure agents, metal deactivators, rust inhibitors, viscosity index improvers, pour point depressants, antifoam agents, hydrolysis inhibitors, thickeners, corrosion inhibitors, and color stabilizers may be appropriately blended into the base oil. 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.

Antioxidants 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'-isopropylidenebisphenol, 2,4-dimethyl-6-tert-butylphenol, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methyl benzene, 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-t 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-butyl monoalkyldiphenylamines such as mono(C 111) diphenylamine, monobutyl (including linear and branched chain) diphenylamine, monopentyl (including linear and branched chain) diphenylamine, monohexyl (including linear and branched chain) diphenylamine, monoheptyl (including linear and branched chain) diphenylamine, and monooctyl (including linear and branched chain) diphenylamine, in particular mono(C 111) diphenylamine, ... _di ( _alkylphenyl )amines such as 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, in particular di(C ₄ -C ₉ alkylphenyl)amines (i.e. diphenylamines in which each of the two benzene rings of the diphenylamine is monosubstituted with an alkyl group, in particular a C _{4 -C 9} alkyl group, the two alkyl groups being the same), di(mono C ₄ -C ₉ alkylphenyl)amines in which the alkyl group on one benzene ring is different from the alkyl group on the other benzene ring, di(di-C ₄ -C _9- 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.

Among these, in particular, 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 are exemplified. These antioxidants can be used alone or in combination of two or more kinds as appropriate. When an antioxidant is used, it is usually desirable to add about 0.01 to 5 mass %, preferably about 0.05 to 3 mass %, based on the base oil.

Here, in the present specification and claims, the range of the amount of additives to be blended may be specified using the expression "with respect to the base oil," such as "0.01 to 5 mass% with respect to the base oil." In this case, "base oil" is used to mean either a base oil consisting of only 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 combined base oil. In addition, in the example of "0.01 to 5 mass% with respect to the base oil," this is synonymous with 0.01 to 5 mass parts with respect to 100 mass parts of base oil.

Metal detergents include 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 Metal sulfonates such as overbased Ca-alkylnaphthalene sulfonates, metal phenates such as Ca-phenates, overbased Ca-phenates, Ba-phenates, and overbased Ba-phenates, metal salicylates such as Ca-salicylate and overbased Ca-salicylate, metal phosphonates such as Ca-phosphonates, overbased Ca-phosphonates, Ba-phosphonates, and overbased Ba-phosphonates, and overbased Ca-carboxylates can be used. When using a metal detergent, it is usually desirable to add about 1 to 10 mass % of the base oil, preferably about 2 to 7 mass %.

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, it is usually desirable to add about 1 to 10 mass % of the base oil, preferably about 2 to 7 mass %.

Examples of oiliness agents 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 selachyl alcohol, alkyl or alkenyl polyglyceryl ethers such as lauryl polyglycerin ether and oleyl polyglyceryl ether, poly(alkylene oxide) adducts of alkyl or alkenyl amines such as di(2-ethylhexyl)monoethanolamine and diisotridecylmonoethanolamine, etc. These oiliness agents may be used alone or in combination, and when used, it is usually desirable to add about 0.01 to 5 mass %, preferably about 0.1 to 3 mass %, to the base oil.

Examples of anti-wear agents and extreme pressure agents include phosphorus-based agents such as tricresyl phosphate, cresyl diphenyl phosphate, alkyl phenyl phosphates, phosphoric acid esters such as tributyl phosphate and dibutyl phosphate, phosphorous acid esters 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-dialkyl dithiophosphate, Zn-dialkyl dithiophosphate, Mo-dialkyl dithiophosphate and Mo-dialkyl dithiocarbamate. These anti-wear agents may be used alone or in combination, and when used, they are usually added in an amount of 0.01 to 10 mass %, preferably 0.1 to 5 mass %, based on the base oil.

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 usually added in an amount of 0.01 to 0.4% by mass, preferably 0.01 to 0.2% by mass, relative to the base oil.

Examples of rust inhibitors include alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic acid anhydride, and dodecenyl succinic acid amide; 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. When used, they are usually added in an amount of 0.01 to 5 mass %, preferably 0.05 to 2 mass %, based on the base oil.

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

Examples of pour point depressants include condensates of chlorinated paraffins and alkylnaphthalenes, condensates of chlorinated paraffins and phenols, and the viscosity index improvers already mentioned, such as polyalkyl methacrylates, polyalkylstyrenes, and polybutenes. These pour point depressants may be used alone or in combination, and when used, they are usually added in an amount of 0.01 to 5 mass %, preferably 0.1 to 3 mass %, relative to the base oil.

Liquid silicone is a suitable defoaming agent, and when used, the amount added is usually about 0.0005 to 0.01% by mass relative to the base oil.

Hydrolysis inhibitors that can be used include 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, and are usually used in amounts of about 0.05 to 2% by mass based on the base oil.

By appropriately combining the power transmission lubricant base oil of the present invention with a thickener, it can be made into a "grease."

Thickeners include metal soap-based thickeners, complex metal soap-based thickeners, and non-soap-based thickeners.

Examples of metal soap-based thickeners include sodium soap, calcium soap, lithium soap, and in particular lithium salts of aliphatic carboxylates having hydroxyl groups such as lithium-12-hydroxystearate, lithium salts of aliphatic carboxylates such as lithium stearate, or mixtures thereof.

Examples of complex metal soap thickeners include complexes of a monovalent metal salt of an aliphatic carboxylate having a hydroxyl group and a divalent metal salt of an aliphatic carboxylate, and specific examples include complex lithium soap and complex aluminum soap.

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).

Of the above, from the viewpoints of heat resistance, water resistance, and shear stability, lithium soaps, lithium complex soaps, and urea compounds are suitable as thickeners, with urea compounds being particularly preferred.

These thickeners can be used alone or in combination of two or more, and there are no particular limitations on the amount added as long as the desired effect is achieved.

Examples of corrosion inhibitors include sodium sulfonate and sorbitan ester, which are usually added at about 0.1 to 3.0 mass% to the base oil.

Examples of color stabilizers include substituted hydroquinone and furfural azine, and are usually added at about 0.01 to 0.1% by mass to the base oil.

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

The power transmission lubricant base oil of the present invention and the ester compound represented by general formula (1) can be added to a power transmission lubricant (particularly a traction drive lubricant) to improve the traction coefficient of the power transmission lubricant. Therefore, it can be used as a traction coefficient improver.

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, that is, power transmission devices consisting of two or more rotating bodies. Devices that employ such traction drives include, for example, motors, transmissions, generators, reducers, etc. in automobiles, ships, aircraft, precision instruments, robots, etc.

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

<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: Nissan Chemical Co., Ltd., product name "Fine Oxocol 180"
3,5,5-trimethyl-1-hexanoic acid: KH Neochem Co., Ltd., product name "Kyowanoic-N"
3,5,5-Trimethyl-1-hexanol: Product name "Nonanol" manufactured by KH Neochem Co., Ltd.
1-Nonanoic acid: product name "Nonanoic Acid" manufactured by Tokyo Chemical Industry Co., Ltd.
2-Hexyl-1-decanol: Product name "2-Hexyl-1-decanol" 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"

(a) Acid Value (AV)
Measurements were performed in accordance with JIS K2501 (2003) with a detection limit of 0.01 KOHmg/g.

(b) Hydroxyl Value (OHV)
The measurement was performed in accordance with JIS K0070 (1992) with a detection limit of 0.1 KOHmg/g.

[Measurement of physical properties of lubricant base oil]
(c) Traction Coefficient The maximum traction coefficient was measured when testing was performed using the following device and conditions, and this was taken as the traction coefficient (60° 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°C
Load: 150N
<Traction coefficient evaluation>
A: 0.090 or more B: 0.080 or more but less than 0.090 C: Less than 0.080

(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℃ or lower B: -40℃ to -30℃ or lower C: Above -30℃

(e) Flash point: Measured in accordance with JIS K2265 (Cleveland open cup).
<Flash point evaluation>
A: 200°C or higher B: 185°C or higher but less than 200°C C: Less than 185°C (f) Evaluation of Lubricant Base Oils for Power Transmission In evaluating the traction coefficient, low temperature fluidity and flash point of a lubricant base oil for power transmission, if C is 1 or higher it is rated as unsuitable, if B is 2 or lower (other evaluations are A), it is rated as good, and if B is 1 or lower (other evaluations are A), it is rated as particularly good.

[Example 1]
A 1-liter four-neck flask equipped with a stirrer, a thermometer, and a water fractional distillation receiver with a condenser was charged with 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, and the flask was substituted with nitrogen, and then the temperature was gradually raised to 230 ° C. While adjusting the degree of vacuum so that xylene refluxed, the generated water was removed in the water fractional distillation receiver with the theoretical amount of generated water (28.8 g) as a target, and an esterification reaction was performed. After the reaction was completed, the remaining 3,5,5-trimethyl-1-hexanoic acid and xylene were removed by distillation under reduced pressure to obtain a crude esterified product. Next, the obtained esterified crude product was neutralized with 1.5 times the equivalent of an aqueous solution of caustic soda relative to the acid value, and then repeatedly washed with water until it became neutral. Magnesium sulfate was added to the obtained esterified crude product, and the product was dehydrated, and the 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 mg KOH/g or less, and the hydroxyl value was 1 mg KOH/g or less. The physical properties of the compound evaluated as a power transmission lubricant base oil (A) are shown in Table 1.

[Example 2]
An esterification reaction was carried out in the same manner as in Example 1, except that 3,5,5-trimethyl-1-hexanoic acid was replaced with 455.2 g (1.60 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanoic acid, and 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1- octanol was replaced with 277.0 g (1.92 mol) of 3,5,5-trimethyl-1-hexanol. After completion of the reaction, the remaining 3,5,5-trimethyl-1-hexanol and xylene were removed by distillation under reduced pressure to obtain an esterified crude product. Next, the resulting esterified crude product was neutralized with an aqueous caustic soda solution in an amount 1.5 times the acid value of the esterified crude product, and then repeatedly washed with water until it became neutral. Magnesium sulfate was added to the obtained esterified crude product, followed by dehydration, and the 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 mg KOH/g or less, and the hydroxyl value was 1 mg KOH/g or less. The physical properties of the compound evaluated as a power transmission lubricant base oil (B) are shown in Table 1.

[Comparative Example 1]
Table 2 shows the physical properties of diisodecyl adipate when it was evaluated as a power transmission lubricating base oil (a).

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

[Comparative Example 3]
552.0 g (1.34 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 1-nonanoate was obtained in the same manner as in Example 1, except that 278.5 g (1.76 mol) of 1-nonanoic acid was used instead of 3,5,5-trimethyl-1-hexanoic acid. 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 the compound evaluated as a power transmission lubricant base oil (c) are shown in Table 2.

[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 2-hexyl-1-decanol 417.0 g (1.72 mol) in the same manner as in Example 1, to obtain 566.0 g (1.48 mol) of 2-hexyl-1-decyl 3,5,5-trimethyl-1-hexanoate. 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 the compound evaluated as a power transmission lubricant base oil (d) are shown in Table 2.

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

The power transmission lubricant 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 lubricant base oil (particularly a traction drive lubricant base oil) for automobiles, ships, aircraft, precision instruments, etc.

Claims (4)

General formula (1)
[In the formula, 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 a 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):
represents.]
The present invention contains an ester compound represented by the formula:
A power transmission lubricant base oil, wherein the content of the ester compound represented by the general formula (1) in the power transmission lubricant base oil is 70 mass% or more . The power transmission lubricant base oil according to claim 1, wherein the ester compound is an ester compound represented by the following general formula (2) or general formula (3):
The power transmission lubricant base oil according to claim 1 or 2 , wherein the power transmission lubricant base oil is a traction drive lubricant base oil. A power transmission lubricating oil comprising the power transmission lubricating base oil according to any one of claims 1 to 3 .