Lubricant composition

Abstract

To provide a lubricant composition which has excellent heat stability at high temperature and can be suitably used for lubrication of a traction drive.SOLUTION: A lubricant composition used in lubrication of a traction drive includes a base oil (A) including a synthetic oil (A1) having a bicyclo[2.2.1]heptane dimer structure, a phenolic antioxidant (B), and an aromatic amine-based antioxidant (C) and satisfies the following requirement (I). The requirement (I): a kinematic viscosity ratio at 40°C, calculated by the following formula (i), before and after a CEC oxidation test in accordance to CEC L-48-A-00, under a measurement condition of 130°C and 96 hours, is under 1.20. The formula: [kinematic viscosity ratio at 40°C]=[kinematic viscosity of the lubricant composition after the CEC oxidation test at 40°C ((mm2 / s)] / [kinematic viscosity of the lubricant composition before the CEC oxidation test at 40°C (mm2 / s)].SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to lubricating oil compositions and methods for lubricating traction drives. [Background technology]

[0002] Traction drive transmissions are mechanisms that transmit power via a film of lubricating oil. Compared to power transmission by gears, they do not generate noise or vibration caused by meshing of gears, making them suitable for high-speed rotation. Planetary roller type transmissions and toroidal type continuously variable transmissions are in practical use in industrial machinery, automobiles, aircraft, and other fields. A traction drive transmission is required to have a high traction coefficient in order to ensure torque transmission capacity. Patent Document 1, for example, discloses a traction drive fluid containing a bicyclo[2.2.1]heptane derivative as a traction drive fluid that exhibits excellent traction performance even at high temperatures. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-17280 A Summary of the Invention [Problem to be solved by the invention]

[0004] Under such circumstances, in the usage environment of traction drives, the temperature of the lubricating oil rises due to heat transfer from the power source and shear heating caused by rotation, so there is a demand for a lubricating oil composition that has excellent thermal stability at high temperatures and can be suitably used for power transmission and lubrication of traction drives. [Means for solving the problem]

[0005] One aspect of the present invention provides a lubricating oil composition for use in lubricating traction drives, which comprises a base oil containing a synthetic oil having a bicyclo[2.2.1]heptane dimer structure, a phenolic antioxidant, and an aromatic amine antioxidant, and which reduces the amount of increase in acid value to a predetermined value or less. More specifically, one embodiment of the present invention provides the following [1] to [9]. [1] A lubricating oil composition for use in the lubrication of traction drives, comprising a base oil (A) containing a synthetic oil (A1) having a bicyclo[2.2.1]heptane dimer structure, a phenolic antioxidant (B), and an aromatic amine antioxidant (C), and satisfying the following requirement (I): Requirement (I): The kinematic viscosity ratio at 40°C calculated from the following formula (i) before and after a CEC oxidation test in accordance with CEC L-48-A-00 at 130°C for 96 hours is less than 1.20. Formula (i): [Kinematic viscosity ratio at 40°C] = [Kinematic viscosity (mm 2 / s)] / [Kinematic viscosity of the lubricating oil composition at 40°C before the CEC oxidation test (mm 2 / s)] [2] The lubricating oil composition according to the above [1], further satisfying the following requirement (II): Requirement (II): The increase in acid value calculated from the following formula (ii) before and after a CEC oxidation test at 130°C for 96 hours in accordance with CEC L-48-A-00 is 1.40 mgKOH / g or less. Equation (ii): [Acid number increase (mg KOH / g)]=[Acid number of the lubricating oil composition after the CEC oxidation test (mg KOH / g)]−[Acid number of the lubricating oil composition before the CEC oxidation test (mg KOH / g)] [3] The lubricating oil composition according to the above [1] or [2], wherein component (B) comprises an ester group-containing phenolic antioxidant (B1). [4] The lubricating oil composition according to the above [3], wherein the content of component (B1) in component (B) is 80 to 100 mass % based on the total amount of component (B). [5] The lubricating oil composition according to any one of the above [1] to [4], wherein the content of the ester group-free phenolic antioxidant in component (B) is 0 to 10 mass % based on the total amount of component (B). [6] The lubricating oil composition according to any one of the above [1] to [5], wherein component (A) contains only component (A1). [7] The lubricating oil composition according to any one of the above [1] to [5], wherein component (A) further comprises, in addition to component (A1), component (A2) having a longifolene structure. [8] The lubricating oil composition according to any one of the above [1] to [7], wherein the content ratio of component (B) to component (C) [(B) / (C)] is, in mass ratio, 10 / 90 to 90 / 10. [9] A method for lubricating a traction drive, comprising applying the lubricating oil composition according to any one of the above [1] to [8] to lubricate the traction drive. Effect of the Invention

[0006] The lubricating oil composition of one embodiment of the present invention has excellent thermal stability even in high temperature environments of, for example, 130° C. or higher, and can be suitably used for lubricating traction drives. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The upper and lower limit values ​​of the numerical ranges described in this specification can be arbitrarily combined. For example, when the numerical range is described as "preferably 30 to 100, more preferably 40 to 80", the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described in this specification. In addition, when the numerical range is described as "preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less", the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described in this specification. In addition, as a numerical range described in this specification, for example, "60 to 100" means a range of "60 or more (60 or more) and 100 or less (100 or less)."

[0008] In this specification, the kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000. In this specification, the acid value refers to a value measured in accordance with JIS K2501:2003 (potential difference method).

[0009] [Constitution of lubricating oil composition] A lubricating oil composition according to one embodiment of the present invention is a lubricating oil composition used for lubricating traction drives, which contains a base oil (A) (hereinafter also referred to as "component (A)") containing a synthetic oil (A1) (hereinafter also referred to as "component (A1)") having a bicyclo[2.2.1]heptane dimer structure, a phenol-based antioxidant (B) (hereinafter also referred to as "component (B)"), and an aromatic amine-based antioxidant (C) (hereinafter also referred to as "component (C)"), and which satisfies the following requirement (I): Requirement (I): The kinematic viscosity ratio at 40°C calculated from the following formula (i) before and after a CEC oxidation test in accordance with CEC L-48-A-00 at 130°C for 96 hours is less than 1.20. Formula (i): [Kinematic viscosity ratio at 40°C] = [Kinematic viscosity (mm 2 / s)] / [Kinematic viscosity of the lubricating oil composition at 40°C before the CEC oxidation test (mm 2 / s)]

[0010] Generally, lubricating oil compositions used in traction drives are required to exhibit stable performance over a wide temperature range from low to high. In particular, it has been found that even lubricating oil compositions that can maintain good thermal stability in an environment of about 120°C exhibit reduced thermal stability in a high-temperature environment of 130°C or higher. In order to address these problems, the lubricating oil composition of one embodiment of the present invention contains component (A1) as a base oil and uses components (B) and (C) in combination as antioxidants, and is adjusted to satisfy requirement (I). This provides excellent thermal stability even in high-temperature environments of 130°C or higher, thereby resolving the above issues.

[0011] The above requirement (I) specifies the kinematic viscosity ratio at 40° C. before and after a CEC oxidation test in a high-temperature environment at 130° C. for 96 hours. The lubricating oil composition of one embodiment of the present invention is adjusted to satisfy requirement (I), and therefore has excellent thermal stability even in a high-temperature environment of 130° C. or higher. In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition with improved thermal stability when used in a high temperature environment of 130°C or higher, the kinematic viscosity ratio at 40°C specified in requirement (I) is preferably less than 1.20, 1.90 or less, 1.80 or less, 1.70 or less, 1.60 or less, 1.50 or less, 1.40 or less, 1.30 or less, 1.20 or less, 1.10 or less, 1.09 or less, 1.08 or less, 1.07 or less, 1.06 or less, 1.05 or less, 1.04 or less, 1.03 or less, or 1.02 or less.

[0012] Furthermore, the lubricating oil composition of one embodiment of the present invention preferably satisfies the following requirement (II). Requirement (II): The increase in acid value calculated from the following formula (ii) before and after a CEC oxidation test at 130°C for 96 hours in accordance with CEC L-48-A-00 is 1.40 mgKOH / g or less. Equation (ii): [Acid number increase (mg KOH / g)]=[Acid number of the lubricating oil composition after the CEC oxidation test (mg KOH / g)]−[Acid number of the lubricating oil composition before the CEC oxidation test (mg KOH / g)]

[0013] The lubricating oil composition of this embodiment contains component (A1) as a base oil, and components (B) and (C) are used in combination as antioxidants, and is adjusted to satisfy requirement (II), thereby making it possible to obtain a lubricating oil composition having excellent thermal stability even in high-temperature environments of 130°C or higher. In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition with improved thermal stability when used in a high temperature environment of 130°C or higher, the acid number increase specified in requirement (II) is 1.40 mgKOH / g or less, 1.30 mgKOH / g or less, 1.20 mgKOH / g or less, 1.10 mgKOH / g or less, 1.00 mgKOH / g or less, 0.90 mgKOH / g or less, 0.80 mgKOH / g or less, 0.70 mgKOH / g or less. It is preferable that the KOH / g or less, 0.60 mgKOH / g or less, 0.50 mgKOH / g or less, 0.40 mgKOH / g or less, 0.30 mgKOH / g or less, 0.20 mgKOH / g or less, 0.90 mgKOH / g or less, 0.17 mgKOH / g or less, 0.15 mgKOH / g or less, 0.12 mgKOH / g or less, 0.10 mgKOH / g or less, 0.07 mgKOH / g or less, or 0.05 mgKOH / g or less.

[0014] Furthermore, the lubricating oil composition of one embodiment of the present invention preferably satisfies the following requirement (III). Requirement (III): The kinematic viscosity ratio at 100°C calculated from the following formula (iii) before and after a CEC oxidation test in accordance with CEC L-48-A-00 at 130°C for 96 hours is less than 1.10. Formula (iii): [Kinematic viscosity ratio at 100°C] = [Kinematic viscosity (mm 2 / s)] / [Kinematic viscosity of the lubricating oil composition at 100°C before the CEC oxidation test (mm 2 / s)]

[0015] The lubricating oil composition of this embodiment contains component (A1) as a base oil, and components (B) and (C) are used in combination as antioxidants, and is adjusted to satisfy requirement (III), thereby making it possible to obtain a lubricating oil composition having excellent thermal stability even in high-temperature environments of 130°C or higher. In one embodiment of the lubricating oil composition of the present invention, from the viewpoint of providing a lubricating oil composition with improved thermal stability when used in a high temperature environment of 130°C or higher, the kinematic viscosity ratio at 100°C specified in requirement (III) is preferably less than 1.10, 1.09 or less, 1.08 or less, 1.07 or less, 1.06 or less, 1.05 or less, 1.04 or less, 1.03 or less, 1.02 or less, or 1.01 or less.

[0016] In the lubricating oil composition of one embodiment of the present invention, for example, the types, contents, and ratios of the base oil (A) containing component (A1), and the components (B) and (C), the contents of other additives, and the like can be appropriately set while taking into consideration the description of each component and examples below, so as to adjust the composition to satisfy the above requirements (I) and (II).

[0017] The lubricating oil composition of one embodiment of the present invention may further contain additives other than components (A) to (C) to the extent that the effects of the present invention are not impaired. In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition with improved thermal stability when used in a high-temperature environment of 130°C or higher, the total content of components (A), (B) and (C) is preferably 70 mass% or more, 75 mass% or more, 80 mass% or more, 85 mass% or more, 90 mass% or more, 95 mass% or more, 97 mass% or more, 98 mass% or more, or 99 mass% or more based on the total amount (100 mass%) of the lubricating oil composition. Each component contained in the lubricating oil composition according to one embodiment of the present invention will be described in detail below.

[0018] <Component (A): Base oil> The base oil (A) used in one embodiment of the present invention includes a synthetic oil (A1) having a bicyclo[2.2.1]heptane dimer structure. By using a lubricating oil composition containing component (A1) as a base oil, it is possible to obtain a lubricating oil composition having good viscosity characteristics over a wide temperature range and good thermal stability in high temperature environments.

[0019] In view of the above, the content of component (A1) in component (A) used in one embodiment of the present invention may be 40 mass% or more, 50 mass% or more, 60 mass% or more, 65 mass% or more, 70 mass% or more, or 75 mass% or more, based on the total amount (100 mass%) of component (A) contained in the lubricating oil composition, and may be 100 mass% or less, 99 mass% or less, 95 mass% or less, or 93 mass% or less.

[0020] Component (A1) used in one embodiment of the present invention may be any synthetic oil having a bicyclo[2.2.1]heptane dimer structure. From the viewpoint of providing a lubricating oil composition with good viscosity characteristics over a wide temperature range and good thermal stability in high temperature environments, it is preferable that the component (A1) is a synthetic oil containing one or more compounds represented by the following general formula (a-1). [ka]

[0021] In the general formula (a-1), p and q each independently represent an integer of 0 to 12, preferably an integer of 1 to 8, and more preferably an integer of 1 to 5.

[0022] Examples of the compound represented by the general formula (a-1) include endo-2-methyl-exo-3-methyl-exo-2-[(exo-3-methylbicyclo[2.2.1]hept-exo-2-yl)methyl]bicyclo[2.2.1]heptane and endo-2-methyl-exo-3-methyl-exo-2-[(endo-3-methylbicyclo[2.2.1]hept-endo-2-yl)methyl]bicyclo[2.2.1]heptane.

[0023] Component (A) used in one embodiment of the present invention may consist of only component (A1), or may contain component (A1) and also component (A2) having a longifolene structure (hereinafter also referred to as "component (A2)").

[0024] Component (A2) used in one embodiment of the present invention is a synthetic oil containing one or more compounds having a longifolene structure represented by the following formula (a-2): The compound constituting component (A2) may be a compound in which at least one hydrogen atom of the longifolene structure represented by the following formula (a-2) has been substituted with a substituent. [ka]

[0025] Component (A2) used in one embodiment of the present invention may be a refined oil extracted from pine, cypress, or the like, and refined to a purity of 60% or more (preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more). In addition, in the refined oil, the content of β-caryophyllene ((1R,4E,9S)-4,11,11-trimethyl-8-methylene-bicyclo[7.2.0]undec-4-ene), which can be a factor in reducing oxidation stability, is preferably as low as possible. In the lubricating oil composition of one embodiment of the present invention, the content of β-caryophyllene is preferably less than 1.0 mass%, more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably less than 0.001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0026] By preparing a lubricating oil composition containing component (A2) together with component (A1), it is possible to obtain a lubricating oil composition which has good viscosity characteristics over a wide temperature range, good thermal stability in high-temperature environments, and further has an increased traction coefficient at high temperatures, and is capable of maintaining an oil film at high temperatures. In the lubricating oil composition of one embodiment of the present invention, the content of component (A2) relative to 100 parts by mass of the total amount of component (A1) is preferably 100 parts by mass or less, 85 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 55 parts by mass or less, 50 parts by mass or less, 45 parts by mass or less, 40 parts by mass or less, 35 parts by mass or less, 30 parts by mass or less, or 27 parts by mass or less, from the viewpoint of obtaining a lubricating oil composition having good viscosity characteristics over a wide temperature range and good thermal stability in high temperature environments; and preferably 0 parts by mass or more, 0.1 parts by mass or more, 1.0 parts by mass or more, 3.0 parts by mass or more, 5.0 parts by mass or more, 7.0 parts by mass or more, 9.0 parts by mass or more, 12 parts by mass or more, or 15 parts by mass or more, from the viewpoint of obtaining a lubricating oil composition having a high traction coefficient at high temperatures and capable of maintaining an oil film at high temperatures.

[0027] The component (A) used in one embodiment of the present invention may contain a base oil other than the components (A1) and (A2). The other base oils include one or more selected from mineral oils and synthetic oils other than components (A1) and (A2). Examples of mineral oils include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffin-based crude oil, intermediate-based crude oil, and naphthene-based crude oil; distillate oils obtained by vacuum distillation of these atmospheric residual oils; and refined oils obtained by subjecting the distillate oils to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. Examples of synthetic oils other than components (A1) and (A2) include poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (for example, α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester oils such as polyol esters, dibasic acid esters, and phosphate esters; ether oils such as polyphenyl ether; alkylbenzenes; alkylnaphthalenes; and synthetic oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)).

[0028] In one embodiment of the lubricating oil composition of the present invention, from the viewpoint of providing a lubricating oil composition having good viscosity characteristics over a wide temperature range and good thermal stability in high-temperature environments, the total content of components (A1) and (A2) in component (A) is preferably 70 to 100 mass%, more preferably 80 to 100 mass%, even more preferably 90 to 100 mass%, still more preferably 95 to 100 mass%, and particularly preferably 98 to 100 mass%, based on the total amount (100 mass%) of component (A) contained in the lubricating oil composition.

[0029] Furthermore, in the lubricating oil composition of one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition having good viscosity characteristics over a wide temperature range and good thermal stability in high-temperature environments, the respective contents of mineral oil, poly-α-olefin, isoparaffin, polyalkylene glycol, ester-based oil, ether-based oil, alkylbenzene, alkylnaphthalene, and GTL in component (A) are preferably less than 30 mass%, less than 20 mass%, less than 10 mass%, less than 5.0 mass%, less than 3.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, or less than 0.001 mass%, based on the total amount (100 mass%) of component (A) contained in the lubricating oil composition.

[0030] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition having good viscosity characteristics over a wide temperature range and good thermal stability in high-temperature environments, the content of component (A) is preferably 60 mass% or more, 65 mass% or more, 70 mass% or more, 75 mass% or more, 80 mass% or more, 85 mass% or more, 90 mass% or more, 93 mass% or more, 95 mass% or more, 96 mass% or more, 97 mass% or more, or 98 mass% or more based on the total amount (100 mass%) of the lubricating oil composition, and is preferably 99.99 mass% or less, 99.90 mass% or less, 99.50 mass% or less, or 99.00 mass% or less.

[0031] <Component (B): Phenolic antioxidant> The phenol-based antioxidant (B) used in one embodiment of the present invention includes compounds having antioxidant properties and containing a phenol structure. The component (B) may be used alone or in combination of two or more kinds.

[0032] However, the component (B) used in one embodiment of the present invention preferably contains an ester group-containing phenolic antioxidant (B1) (hereinafter also referred to as "component (B1)"). By containing component (B1) as a phenolic antioxidant, it is possible to prepare a lubricating oil composition that satisfies the above requirements (I) and (II) and has good thermal stability in a high-temperature environment.

[0033] From the above viewpoints, in the lubricating oil composition of one embodiment of the present invention, the content of component (B1) in component (B) is preferably 80 to 100 mass%, more preferably 85 to 100 mass%, even more preferably 90 to 100 mass%, still more preferably 95 to 100 mass%, and particularly preferably 98 to 100 mass%, based on the total amount (100 mass%) of component (B) contained in the lubricating oil composition.

[0034] From the viewpoint of preparing a lubricating oil composition that satisfies the above requirements (I) and (II) and has good thermal stability in a high-temperature environment, component (B1) used in one embodiment of the present invention is preferably a compound that has antioxidant properties and contains at least one structure represented by the following general formula (b-1): [ka]

[0035] In the above general formula (b-1), m is an integer of 0 to 5, preferably an integer of 1 to 5, and more preferably an integer of 1 to 3. R 1 ~R 5 are each independently a hydrogen atom, a hydroxyl group, or an alkyl group having 1 to 10 carbon atoms; R 1 ~R 5 At least one of them is a branched alkyl group having 3 to 10 carbon atoms.

[0036] From the viewpoint of preparing a lubricating oil composition that satisfies the above requirements (I) and (II) and has good thermal stability in a high-temperature environment, the component (B) used in one embodiment of the present invention preferably contains an ester group-containing hindered phenol-based antioxidant (B11) as component (B1). Component (B11) is preferably a compound having antioxidant properties and containing at least one structure represented by the following general formula (b-11). [ka] In the above general formula (b-11), m is an integer of 0 to 5, preferably an integer of 1 to 5, and more preferably an integer of 1 to 3.

[0037] Component (B) used in one embodiment of the present invention may contain a phenolic antioxidant not containing an ester group other than component (B1) to the extent that the effects of the present invention are not impaired. Examples of phenol-based antioxidants not containing an ester group include monophenol-based antioxidants such as 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and benzenepropanoic acid-3,5-bis(1,1-dimethylethyl)-4-hydroxyalkyl ester; and diphenol-based antioxidants such as 4,4'-methylenebis(2,6-di-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), and thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate].

[0038] However, from the viewpoint of preparing a lubricating oil composition that satisfies the above requirements (I) and (II) and has good thermal stability in high-temperature environments, the content of the ester group-free phenolic antioxidant is preferably as small as possible. From the above viewpoints, in the lubricating oil composition of one embodiment of the present invention, the content of the ester group-free phenolic antioxidant in component (B) is preferably 0 to 10 mass%, 0 to 5.0 mass%, 0 to 2.0 mass%, 0 to 1.0 mass%, 0 to 0.1 mass%, 0 to 0.01 mass%, or 0 to 0.001 mass%, based on the total amount (100 mass%) of component (B) contained in the lubricating oil composition.

[0039] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of preparing a lubricating oil composition which satisfies the above requirements (I) and (II) and has good thermal stability in a high-temperature environment, the content of component (B) is preferably 0.01 mass% or more, 0.05 mass% or more, 0.10 mass% or more, 0.20 mass% or more, 0.30 mass% or more, 0.40 mass% or more, or 0.50 mass% or more, based on the total amount (100 mass%) of the lubricating oil composition, and is preferably 5.0 mass% or less, 4.0 mass% or less, 3.0 mass% or less, 2.0 mass% or less, 1.5 mass% or less, 1.2 mass% or less, or 1.0 mass% or less.

[0040] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of preparing a lubricating oil composition which satisfies the above requirements (I) and (II) and has good thermal stability in a high-temperature environment, the content of component (B1) is preferably 0.01 mass% or more, 0.05 mass% or more, 0.10 mass% or more, 0.20 mass% or more, 0.30 mass% or more, 0.40 mass% or more, or 0.50 mass% or more, based on the total amount (100 mass%) of the lubricating oil composition, and is preferably 5.0 mass% or less, 4.0 mass% or less, 3.0 mass% or less, 2.0 mass% or less, 1.5 mass% or less, 1.2 mass% or less, or 1.0 mass% or less.

[0041] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of preparing a lubricating oil composition which satisfies the above requirements (I) and (II) and has good thermal stability in a high-temperature environment, the content ratio of component (B1) to component (A1) [(B1) / (A1)] is preferably 0.0001 or more, 0.0005 or more, 0.0010 or more, 0.0020 or more, 0.0030 or more, 0.0035 or more, 0.0040 or more, 0.0045 or more, or 0.0050 or more, and is preferably 0.0500 or less, 0.0400 or less, 0.0300 or less, 0.0200 or less, 0.0150 or less, 0.0100 or less, 0.0090 or less, 0.0080 or less, 0.0075 or less, 0.0070 or less, or 0.0065 or less.

[0042] When the lubricating oil composition of one embodiment of the present invention contains component (A2), from the viewpoint of preparing a lubricating oil composition with good thermal stability in high temperature environments, the content ratio of component (B1) to component (A2) [(B1) / (A2)] is preferably 0.001 or more, 0.005 or more, 0.010 or more, 0.015 or more, 0.020 or more, or 0.025 or more, and is preferably 0.500 or less, 0.400 or less, 0.300 or less, 0.200 or less, 0.150 or less, 0.100 or less, 0.090 or less, 0.080 or less, 0.075 or less, 0.070 or less, or 0.065 or less.

[0043] <Component (C): Aromatic amine antioxidant> The aromatic amine-based antioxidant (C) used in one embodiment of the present invention includes a compound having an antioxidant ability and containing an aromatic amine structure. The component (C) may be used alone or in combination of two or more kinds. By preparing a lubricating oil composition that contains component (A1) as a base oil and also contains components (B) and (C) as antioxidants, it is possible to prepare a lubricating oil composition that satisfies the above requirements (I) and (II) and has good thermal stability in high-temperature environments.

[0044] Examples of component (C) used in one embodiment of the present invention include aromatic amine-based antioxidants represented by any one of the following general formulas (c-1) to (c-3). From the viewpoint of preparing a lubricating oil composition that satisfies the above requirements (I) and (II) and has good thermal stability in a high-temperature environment, it is preferable for the component (C) to contain an aromatic amine-based antioxidant having antioxidant performance and represented by the following general formula (c-2). [ka]

[0045] In the above general formulas (c-1) to (c-3), R A and R B are each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. R is an alkyl group having 1 to 20 carbon atoms. R A , R B and examples of the alkyl group that may be selected as R include a methyl group, an ethyl group, a propyl group (n-propyl group, isopropyl group), a butyl group (n-butyl group, s-butyl group, t-butyl group, isobutyl group), a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a 1-methylheptyl group, a nonyl group, a 1-methyloctyl group, a 1,1-dimethylheptyl group, a decyl group, a 1-methylheptyl group, an undecyl group, a 1-methyl ... Examples of the alkyl group include straight-chain alkyl groups or branched-chain alkyl groups such as ethyl, dodecyl, 1-methylundecyl, tridecyl, 1-methyldodecyl, tetradecyl, 1-methyltridecyl, pentadecyl, 1-methyltetradecyl, hexadecyl, 1-methylpentadecyl, 2-hexyldecyl, heptadecyl, 1-methylhexadecyl, octadecyl, 1-methylheptadecyl, nonadecyl, and 1-methyloctadecyl. R A , R B The alkyl group that may be selected as R preferably has 1 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, even more preferably 3 to 12 carbon atoms, and even more preferably 4 to 8 carbon atoms.

[0046] In the above general formulas (c-1) to (c-3), a, b and c each independently represent an integer of 0 to 5. However, in the above general formula (c-1), a is preferably an integer of 1 to 5, and more preferably an integer of 1 to 2. In addition, in the above general formula (c-2), a+b is preferably 1 or more, more preferably a is an integer of 1 to 5 and b is an integer of 1 to 5, and even more preferably a is an integer of 1 to 2 and b is an integer of 1 to 2. Furthermore, in the above general formula (c-3), a+b+c is preferably 1 or more, and it is more preferable that a is an integer from 1 to 5, b is an integer from 1 to 5, and c is an integer from 1 to 5, and it is even more preferable that a is an integer from 1 to 2, b is an integer from 1 to 2, and c is an integer from 1 to 2.

[0047] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of preparing a lubricating oil composition which satisfies the above requirements (I) and (II) and has good thermal stability in high-temperature environments, the content of component (C) is preferably 0.01 mass% or more, 0.05 mass% or more, 0.10 mass% or more, 0.20 mass% or more, 0.30 mass% or more, 0.40 mass% or more, or 0.50 mass% or more, based on the total amount (100 mass%) of the lubricating oil composition, and is preferably 5.0 mass% or less, 4.0 mass% or less, 3.0 mass% or less, 2.0 mass% or less, 1.5 mass% or less, 1.2 mass% or less, or 1.0 mass% or less.

[0048] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of preparing a lubricating oil composition which satisfies the above requirements (I) and (II) and has good thermal stability in high temperature environments, the content ratio of components (B) to (C) [(B) / (C)], in mass ratio, is preferably 10 / 90 or more, 15 / 85 or more, 20 / 80 or more, 25 / 75 or more, 30 / 70 or more, 35 / 65 or more, or 40 / 60 or more, and is preferably 90 / 10 or less, 85 / 15 or less, 80 / 20 or less, 75 / 25 or less, 70 / 30 or less, 65 / 35 or less, or 60 / 40 or less.

[0049] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of preparing a lubricating oil composition which satisfies the above requirements (I) and (II) and has good thermal stability in a high temperature environment, the content ratio of component (C) to component (A1) [(C) / (A1)] is preferably 0.0001 or more, 0.0005 or more, 0.0010 or more, 0.0020 or more, 0.0030 or more, 0.0035 or more, 0.0040 or more, 0.0045 or more, or 0.0050 or more, and is preferably 0.0500 or less, 0.0400 or less, 0.0300 or less, 0.0200 or less, 0.0150 or less, 0.0100 or less, 0.0090 or less, 0.0080 or less, 0.0075 or less, 0.0070 or less, or 0.0065 or less.

[0050] When the lubricating oil composition of one embodiment of the present invention contains component (A2), from the viewpoint of preparing a lubricating oil composition with good thermal stability in high temperature environments, the content ratio of component (C) to component (A2) [(C) / (A2)] is preferably 0.001 or more, 0.005 or more, 0.010 or more, 0.015 or more, 0.020 or more, or 0.025 or more, and is preferably 0.500 or less, 0.400 or less, 0.300 or less, 0.200 or less, 0.150 or less, 0.100 or less, 0.090 or less, 0.080 or less, 0.075 or less, 0.070 or less, or 0.065 or less.

[0051] <Other antioxidants> The lubricating oil composition of one embodiment of the present invention may contain antioxidants other than components (B) and (C) to the extent that the effects of the present invention are not impaired. However, from the viewpoint of preparing a lubricating oil composition that satisfies the above requirements (I) and (II) and has good thermal stability in high-temperature environments, the content of antioxidants other than components (B) and (C) is preferably as small as possible. In the lubricating oil composition of one embodiment of the present invention, the content of other antioxidants may be less than 30 parts by mass, less than 20 parts by mass, less than 10 parts by mass, less than 5.0 parts by mass, less than 2.0 parts by mass, less than 1.0 part by mass, less than 0.1 part by mass, less than 0.01 part by mass, less than 0.001 part by mass, or less than 0.0001 part by mass, per 100 parts by mass of the total amount of components (B) and (C) contained in the lubricating oil composition.

[0052] <Various additives> The lubricating oil composition according to one embodiment of the present invention may contain various additives as required. Examples of such additives include viscosity index improvers, metal detergents, ashless dispersants, extreme pressure agents, metal deactivators, oiliness agents, rust inhibitors, and antifoaming agents. These lubricating oil additives may be used alone, or two or more of them may be used in combination.

[0053] Examples of viscosity index improvers used in one embodiment of the present invention include polymethacrylates having a weight average molecular weight (Mw) of 500 to 1,000,000, such as non-dispersant polymethacrylate and dispersant polymethacrylate; olefin-based copolymers having a mass average molecular weight (Mw) of 800 to 300,000, such as ethylene-propylene copolymers; styrene-based copolymers such as styrene-diene copolymers and styrene-isoprene copolymers; and the like. In the lubricating oil composition of one embodiment of the present invention, the content of the viscosity index improver may be, based on the total amount (100 mass%) of the lubricating oil composition, 0.1 mass% or more, 0.5 mass% or more, or 1.0 mass% or more, and may be less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, or less than 0.001 mass%.

[0054] Examples of metal detergents used in one embodiment of the present invention include metal sulfonates, metal salicylates, and metal phenates. In the lubricating oil composition of one embodiment of the present invention, the content of the metal detergent, based on the total amount (100 mass%) of the lubricating oil composition, may be 0.1 mass% or more, 0.5 mass% or more, or 1.0 mass% or more, or may be less than 10.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, or less than 0.001 mass%.

[0055] Examples of ashless dispersants used in one embodiment of the present invention include boron-free succinimides, boron-containing succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, fatty acids, and mono- or di-carboxylic acid amides represented by succinic acid. In the lubricating oil composition of one embodiment of the present invention, the content of the ashless dispersant may be, based on the total amount (100 mass%) of the lubricating oil composition, 0.01 mass% or more, 0.1 mass% or more, or 0.5 mass% or more, and may be less than 10.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, or less than 0.001 mass%. Furthermore, the lubricating oil composition of one embodiment of the present invention may or may not contain a boron-containing succinimide. The content of the boron-containing succinimide in this embodiment may be, based on the total amount (100 mass%) of the lubricating oil composition, 0.01 mass% or more, 0.1 mass% or more, or 0.5 mass% or more, or may be less than 10.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.2 mass%, or less than 0.1 mass%.

[0056] Examples of the extreme pressure agent used in one embodiment of the present invention include sulfur-based extreme pressure agents such as sulfurized oils and fats, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiadiazole compounds, alkylthiocarbamoyl compounds, and thiocarbamate compounds; sulfur-nitrogen-based extreme pressure agents such as zinc dialkylthiocarbamate (Zn-DTC) and molybdenum dialkylthiocarbamate (Mo-DTC); and sulfur-phosphorus-based extreme pressure agents such as molybdenum dialkyldithiophosphate (Mo-DTP). In the lubricating oil composition of one embodiment of the present invention, the content of the extreme pressure agent may be, based on the total amount (100 mass%) of the lubricating oil composition, 0.01 mass% or more, 0.1 mass% or more, or 1.0 mass% or more, and may be less than 20.0 mass%, less than 10.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, or less than 0.001 mass%.

[0057] Examples of the metal deactivator used in one embodiment of the present invention include benzotriazole-based compounds, tolyltriazole-based compounds, thiadiazole-based compounds, and imidazole-based compounds. In the lubricating oil composition of one embodiment of the present invention, the content of the metal deactivator may be, based on the total amount (100 mass%) of the lubricating oil composition, 0.01 mass% or more, 0.1 mass% or more, or 0.5 mass% or more, and may be less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, or less than 0.001 mass%.

[0058] Examples of oily agents used in one embodiment of the present invention include fatty alcohols; fatty acid compounds such as fatty acids and fatty acid metal salts; ester compounds such as polyol esters, sorbitan esters, and glycerides; and amine compounds such as aliphatic amines. In the lubricating oil composition of one embodiment of the present invention, the content of the oiliness agent may be, based on the total amount (100 mass%) of the lubricating oil composition, 0.01 mass% or more, 0.1 mass% or more, or 0.5 mass% or more, and may be less than 20.0 mass%, less than 10.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, or less than 0.001 mass%.

[0059] Examples of the rust inhibitor used in one embodiment of the present invention include succinic acid esters; alkylamines; alkanolamines such as monoisopropanolamine; and the like. In the lubricating oil composition of one embodiment of the present invention, the content of the rust inhibitor may be, based on the total amount (100 mass%) of the lubricating oil composition, 0.01 mass% or more, 0.1 mass% or more, or 0.5 mass% or more, and may be less than 10.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, or less than 0.001 mass%.

[0060] Examples of the defoaming agent used in one embodiment of the present invention include silicone-based defoaming agents such as fluorosilicone oil; ether-based defoaming agents such as fluoroalkyl ether; and the like. In the lubricating oil composition of one embodiment of the present invention, the content of the antifoaming agent may be, based on the total amount (100 mass%) of the lubricating oil composition, 0.001 mass% or more, 0.005 mass% or more, or 0.01 mass% or more, and may be less than 2.0 mass%, less than 1.0 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%.

[0061] [Properties of the lubricating oil composition] The lubricating oil composition of one embodiment of the present invention has a kinematic viscosity at 40°C of 4.0 mm 2 / s or more, 6.0mm 2 / s or more, 8.0mm 2 / s or more, 10.0mm 2 / s or more, 12.0mm 2 / s or more, 14.0mm 2 / s or more, 16.0mm 2 / s or more, or 18.0 mm 2 / s or more, and 80 mm 2 / s or less, 70mm 2 / s or less, 60mm 2 / s or less, 50mm 2 / s or less, 40mm 2 / s or less, 35mm 2 / s or less, or 30 mm 2 / s or less may be used.

[0062] The lubricating oil composition of one embodiment of the present invention has a kinematic viscosity at 100°C of 2.0 mm 2 / s or more, 2.3mm 2 / s or more, 2.5mm 2 / s or more, 2.7mm 2 / s or more, 3.0mm 2 / s or more, 3.3mm 2 / s or more, 3.5mm 2 / s or more, or 3.7 mm 2 / s or more, and 20.0 mm 2 / s or less, 15.0mm 2 / s or less, 10.0mm 2 / s or less, 8.0mm 2 / s or less, 6.0mm 2 / s or less, 5.5mm 2 / s or less, or 5.0 mm 2 / s or less may be used.

[0063] The viscosity index of the lubricating oil composition of one embodiment of the present invention may be 50 or more, 55 or more, 60 or more, 65 or more, or 70 or more; and may be 150 or less, 130 or less, 120 or less, 110 or less, or 100 or less.

[0064] The acid value of the lubricating oil composition of one embodiment of the present invention may be 1.00 mgKOH / g or less, 0.70 mgKOH / g or less, 0.50 mgKOH / g or less, 0.30 mgKOH / g or less, 0.10 mgKOH / g or less, 0.07 mgKOH / g or less, 0.05 mgKOH / g or less, 0.04 mgKOH / g or less, or 0.03 mgKOH / g or less, or may be 0.00 mgKOH / g or more, more than 0.00 mgKOH / g, or 0.01 mgKOH / g or more.

[0065] [Uses of the lubricating oil composition] The lubricating oil composition of one embodiment of the present invention has excellent thermal stability even in high-temperature environments of, for example, 130° C. or higher, and therefore can be suitably used for lubricating traction drives. As a traction drive type power transmission device, for example, it can be suitably used in a continuously variable transmission, a planetary roller type transmission, and a traction drive in an automobile and an aircraft engine generator. Also included are power transmission devices equipped with a friction drive system, drive parts of machine tools, construction machinery and agricultural machinery, and power transmission devices for industrial use such as speed increasers for wind power generation.

[0066] In consideration of the above-mentioned characteristics of the lubricating oil composition of one embodiment of the present invention, the present invention can also provide the following [1] and [2]. [1] A traction drive using the lubricating oil composition according to one embodiment of the present invention. [2] A method for lubricating a traction drive, comprising applying the lubricating oil composition according to one embodiment of the present invention to lubricate a traction drive. The traction drive type power transmission device is as described above. EXAMPLES

[0067] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The methods for measuring or evaluating various physical properties are as follows.

[0068] (1)Kinematic viscosity, viscosity index Measurements and calculations were made in accordance with JIS K2283:2000. (2) Density Measurements were performed in accordance with JIS K2249-1:2011. (3) Acid value Measurements were performed in accordance with JIS K2501:2003 (potential difference method).

[0069] Examples 1 to 4, Comparative Examples 1 to 24 The types of base oils and various additives shown in Tables 1 to 4 were added and mixed in the amounts shown in each table to prepare respective lubricating oil compositions. The details of each component used in preparing the lubricating oil composition are as follows:

[0070] "Synthetic oil (a1)": A hydrogenated product of an addition compound of 2-methyl-3-methylenenorbornane and 2,3-dimethyl-2-norbornene, a synthetic oil containing one or more compounds represented by the general formula (a-1) above, which falls under component (A1). - "Longifolene (a2)": Refined oil of longifolene with a purity of 90% or more, which corresponds to component (A2). "Ester group-containing phenolic antioxidant (b1)": Pentaerythritol tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), a compound containing four structures in which m=2 in the general formula (b-11), which corresponds to component (B11). "Aromatic ring-containing amine-based antioxidant (c1)": Dialkylphenylamine, R in the general formula (c-2) A is a hydrogen atom, R is an octyl group or a t-butyl group, and a=b=1; this corresponds to component (C). "Non-ester group-containing phenolic antioxidant": 2,6-di-t-butyl-p-cresol

[0071] The kinematic viscosity, viscosity index, density, and acid number of the prepared lubricating oil compositions were measured or calculated. Then, a CEC oxidation test was performed at 130°C for 96 hours in accordance with CEC L-48-A-00, and these physical property values ​​were also measured after the test. The kinematic viscosity ratios at 40° C. and 100° C. and the increase in acid value before and after the CEC oxidation test were calculated from the following formulas (i) to (iii). These results are shown in Tables 1 to 4. Formula (i): [Kinematic viscosity ratio at 40°C] = [Kinematic viscosity of the lubricating oil composition at 40°C after the CEC oxidation test (mm 2 / s)] / [Kinematic viscosity of the lubricating oil composition at 40°C before the CEC oxidation test (mm 2 / s)] Equation (ii): [Acid number increase (mg KOH / g)]=[Acid number of the lubricating oil composition after the CEC oxidation test (mg KOH / g)]−[Acid number of the lubricating oil composition before the CEC oxidation test (mg KOH / g)] Formula (iii): [Kinematic viscosity ratio at 100°C] = [Kinematic viscosity of the lubricating oil composition at 100°C after the CEC oxidation test (mm 2 / s)] / [Kinematic viscosity of the lubricating oil composition at 100°C before the CEC oxidation test (mm 2 / s)]

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] [Table 4]

[0076] As can be seen from Tables 1 to 4, the lubricating oil compositions prepared in Examples 1 to 4 have suppressed kinematic viscosity ratios before and after the CEC oxidation test under measurement conditions of 130°C and 96 hours compared to the lubricating oil compositions of Comparative Examples 1 to 24. Therefore, the lubricating oil compositions of Examples 1 to 4 have excellent thermal stability even in high-temperature environments of 130°C or higher, and can be suitably used for lubricating traction drives.

Claims

1. A lubricating oil composition for use in lubricating a traction drive, comprising a base oil (A) containing a synthetic oil (A1) having a bicyclo[2.2.1]heptane dimer structure, a phenolic antioxidant (B), and an aromatic amine antioxidant (C), and satisfying the following requirement (I). Requirement (I): The kinematic viscosity ratio at 40°C, calculated from formula (i) below, before and after a CEC oxidation test conducted under measurement conditions of 130°C for 96 hours in accordance with CEC L-48-A-00, is less than 1.

20. Formula (i): [Kinematic viscosity ratio at 40°C] = [Kinematic viscosity of the lubricating oil composition at 40°C after the CEC oxidation test (mm²)] ２ / s)] / [The kinematic viscosity (mm) of the lubricating oil composition at 40°C before the CEC oxidation test. ２ / s)]

2. Furthermore, the lubricating oil composition according to claim 1 satisfies the following requirement (II). Requirement (II): The increase in acid value calculated from the following formula (ii) before and after the CEC oxidation test under measurement conditions of 130°C for 96 hours, in accordance with CEC L-48-A-00, is 1.40 mg KOH / g or less. Formula (ii): [Increase in acid value (mgKOH / g)] = [Acid value of the lubricating oil composition after the CEC oxidation test (mgKOH / g)] - [Acid value of the lubricating oil composition before the CEC oxidation test (mgKOH / g)]

3. The lubricating oil composition according to claim 1 or 2, wherein component (B) comprises an ester group-containing phenolic antioxidant (B1).

4. The lubricating oil composition according to claim 3, wherein the content ratio of component (B1) in component (B) is 80 to 100% by mass relative to the total amount of component (B).

5. The lubricating oil composition according to claim 1 or 2, wherein the content of the ester-free phenolic antioxidant in component (B) is 0 to 10% by mass relative to the total amount of component (B).

6. The lubricating oil composition according to claim 1 or 2, wherein component (A) comprises only component (A1).

7. The lubricating oil composition according to claim 1 or 2, wherein component (A) further comprises component (A1) and component (A2) having a longifolene structure.

8. The lubricating oil composition according to claim 1 or 2, wherein the content ratio of component (B) to component (C) [(B) / (C)] is 10 / 90 to 90 / 10 by mass ratio.

9. A method for lubricating a traction drive, comprising applying the lubricating oil composition described in claim 1 or 2 to the lubrication of the traction drive.