Lubricating oil composition, lubricating method and transmission

Abstract

Provided are: a lubricating oil composition containing a base oil (A), a sulfur-based extreme pressure agent (B) and a phosphorus-based extreme pressure agent (C), the sulfur-based extreme pressure agent (B) being a thiadiazole having a branched organic group having 3-24 carbon atoms, and the phosphorus-based extreme pressure agent (C) being a phosphorus-based extreme pressure agent (C); the phosphorus-based extreme pressure agent (C) is a phosphoric acid ester having an organic group having 6-24 carbon atoms and containing a ring structure.

Description

Technical Field

[0001] The present invention relates to a lubricating oil composition, a lubricating method using the lubricating oil composition, and a transmission equipped with the lubricating oil composition. Background Art

[0002] In recent years, the lubricating oil composition used in vehicles equipped with automatic transmissions has been required to have a lower viscosity in order to improve fuel efficiency. In addition to reducing the viscosity of the lubricating oil composition, fuel efficiency can also be achieved by miniaturizing the automatic transmission. However, by miniaturizing the automatic transmission, the diameter of the gears used is reduced, and the tooth width is also reduced. As a result, the force applied to the tooth surface increases, and therefore, the lubricating oil used in the transmission has a higher requirement for gear protection.

[0003] In addition, in electric vehicles, the integration of the motor and the transmission has increased the demand for the dual use of the motor cooling oil and the transmission lubricating oil. In such dual use, there is also a strong demand for lower viscosity in order to improve fuel efficiency and motor cooling performance.

[0004] In order to meet these requirements, for example, lubricating oil compositions to which sulfur-based extreme pressure agents and phosphorus-based extreme pressure agents are added have been studied (Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-80429 Summary of the invention

[0008] Problems to be solved by the invention

[0009] If the viscosity of the lubricating oil composition is reduced, fuel saving and cooling performance can be improved, but the fluidity increases, so it is difficult to form an oil film of the lubricating oil composition on the surface of the tooth surface. In addition, due to the low viscosity of the lubricating oil composition, when the tooth surface becomes locally overheated, the layer thickness of the oil film of the lubricating oil composition may sometimes decrease or break. If the layer thickness of the oil film on the surface of the tooth surface is reduced or broken in this way, it is easy to cause damage such as scuffing (Japanese: scuffing, English: scuffing) on ​​the gears of the transmission. In this way, the low viscosity of the lubricating oil composition becomes the main cause of gear damage. That is, it can be said that the low viscosity of the lubricating oil composition and the gear protection of the lubricating oil composition, including the property of inhibiting scuffing, are in a trade-off relationship.

[0010] In the above-mentioned Patent Document 1, in order to improve the scoring property (which has the same meaning as the galling resistance in the present application), the combined use of a sulfur-based extreme pressure agent and a phosphorus-based extreme pressure agent is studied. However, the lubricating oil composition of Patent Document 1 has a large kinematic viscosity at 100° C., which cannot meet the requirement of lowering the viscosity, and it cannot be said that the improvement of the scoring property is sufficient.

[0011] Although not studied in Patent Document 1, if the extreme pressure agent is added to a lubricating oil composition, the copper corrosion resistance and oxidation stability of the lubricating oil composition tend to decrease due to the influence of the extreme pressure agent and decomposition products derived from the extreme pressure agent.

[0012] An object of the present invention is to provide a lubricating oil composition that achieves both low viscosity and gear protection at a high level and also achieves superior copper corrosion resistance and oxidation stability, a lubrication method using the lubricating oil composition, and a transmission including the lubricating oil composition.

[0013] Means for solving problems

[0014] In order to solve the above-mentioned problems, the present inventors provide the following [1] to

[15] .

[0015] [1] A lubricating oil composition comprising a base oil (A), a sulfur-based extreme pressure agent (B) and a phosphorus-based extreme pressure agent (C),

[0016] The sulfur-based extreme pressure agent (B) is a thiadiazole having a branched organic group having 3 or more and 24 or less carbon atoms.

[0017] The phosphorus-based extreme pressure agent (C) is a phosphoric acid ester having an organic group having 6 to 24 carbon atoms and a ring structure.

[0018] [2] The lubricating oil composition according to [1], wherein the base oil (A) has a kinematic viscosity of 6.000 mm / s at 100°C. 2 / s or less.

[0019] [3] The lubricating oil composition according to [1] or [2], wherein the base oil (A) contains a mineral oil, and the content of the mineral oil is 70.00% by mass or more based on the total amount of the base oil (A) (100% by mass).

[0020] [4] The lubricating oil composition according to any one of [1] to [3], wherein the thiadiazole is a compound selected from the group consisting of compounds represented by general formulas (B1) to (B3).

[0021] [Chemical formula 1]

[0022]

[0023] (In general formulas (B1) to (B3), R B11 ~R B32 Each independently represents a branched organic group having 3 to 24 carbon atoms, and nB11 to nB32 each independently represent an integer of 1 to 4.

[0024] [5] The lubricating oil composition according to any one of [1] to [4], wherein the organic group having a carbon number of 6 to 24, including a ring structure, of the phosphoric acid ester is an aromatic group which may have a substituent.

[0025] [6] The lubricating oil composition according to any one of [1] to [5], wherein the phosphate ester is not an amine salt.

[0026] [7] The lubricating oil composition according to any one of [1] to [6], wherein the phosphate ester is a neutral phosphate ester.

[0027] [8] The lubricating oil composition according to [7], wherein the neutral phosphate ester is a compound represented by the general formula (C1).

[0028] [Chemical formula 2]

[0029]

[0030] (In general formula (C1), R C11 ~R C13 Each independently represents a hydrocarbon group having 1 to 24 carbon atoms, wherein -CH2- in the hydrocarbon group may be substituted by -O-, -S-, -CO- or -CS-, and nC11 to nC13 each independently represent an integer from 0 to 5. There may be multiple R in the same molecule. C11 ~R C13 In the case of C11 ~X C13 Each independently represents -O- or -S-, X C14 Indicates =O or =S. )

[0031] [9] The lubricating oil composition according to any one of [1] to [8], wherein the content of sulfur atoms in the lubricating oil composition is 0.01 mass % or more and 0.20 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

[0032]

[10] The lubricating oil composition according to any one of [1] to [9], wherein the content of phosphorus atoms in the lubricating oil composition is 0.005 mass % or more and 0.100 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

[0033]

[11] The lubricating oil composition according to any one of [1] to

[10] , wherein the mass ratio of sulfur atoms to phosphorus atoms (S / P ratio) contained in the lubricating oil composition is 1.00 or more and 7.00 or less.

[0034]

[12] The lubricating oil composition according to any one of [1] to

[11] , wherein the kinematic viscosity of the lubricating oil composition at 100° C. is 6.000 mm 2 / s or less.

[0035]

[13] The lubricating oil composition according to any one of [1] to

[12] , which is used in a transmission.

[0036]

[14] A lubrication method using the lubricating oil composition described in any one of [1] to

[13] .

[0037]

[15] A transmission comprising the lubricating oil composition described in any one of [1] to

[13] .

[0038] Effects of the Invention

[0039] According to the present invention, there can be provided a lubricating oil composition that achieves both low viscosity and gear protection at a high level and also achieves superior copper corrosion resistance and oxidation stability, a lubrication method using the lubricating oil composition, and a transmission including the lubricating oil composition. DETAILED DESCRIPTION

[0040] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") is described. It should be noted that in this specification, the upper and lower limit values ​​involved in the numerical range of "above", "below", and "to" are values ​​that can be combined arbitrarily, and the values ​​of the examples can also be used as the upper and lower limit values.

[0041] The lubricating oil composition of the present embodiment, the lubrication method using the lubricating oil composition, and the transmission including the lubricating oil composition are merely one embodiment of the present invention, and the present invention is not limited thereto.

[0042] [Lubricating oil composition]

[0043] The lubricating oil composition of the present embodiment needs to contain a base oil (A), a sulfur-based extreme pressure agent (B) and a phosphorus-based extreme pressure agent (C), wherein the sulfur-based extreme pressure agent (B) is a thiadiazole having a branched organic group having 3 to 24 carbon atoms, and the phosphorus-based extreme pressure agent (C) is a phosphate ester having an organic group having 6 to 24 carbon atoms including a ring structure.

[0044] The lubricating oil composition of the present embodiment contains a sulfur-based extreme pressure agent (B) having a specific structure and a phosphorus-based extreme pressure agent (C) having a specific structure in addition to the above-mentioned base oil (A), thereby achieving both low viscosity and gear protection at a high level, and also achieving better copper corrosion resistance and oxidation stability. By using the sulfur-based extreme pressure agent (B) having a specific structure and the phosphorus-based extreme pressure agent (C) having a specific structure in this way, in addition to the effect as an extreme pressure agent, even a lubricating oil composition with low viscosity can exhibit high gear protection, and can also achieve copper corrosion resistance and oxidation stability.

[0045] In this specification, "lowering viscosity" means reducing the kinematic viscosity of the lubricating oil composition at 100°C, and specifically, preferably reducing the kinematic viscosity to 6.000 mm / s. 2 The kinematic viscosity at 100° C. can be determined by the method described in Examples.

[0046] As described above, the lubricating oil composition of Patent Document 1 has a large kinematic viscosity at 100° C. In order to confirm that this is improved in the lubricating oil composition of the present embodiment, attention was paid to the kinematic viscosity at 100° C.

[0047] Gears are subject to galling (scratching), spalling (Japanese: スポーリング, English: spalling), pitting (Japanese: ピッチング, English: pitting) and wear when in use. "Gear protection" includes galling resistance, which refers to the property of not causing or suppressing damage to gears contained in the gears. "Gear resistance" refers to the property of reducing local surface damage (galling) caused by solid phase welding generated on the sliding contact surfaces such as the tooth surfaces of the gears. As described above, low viscosity and gear protection are in a trade-off relationship. In the present embodiment, by using a sulfur-based extreme pressure agent (B) with a specific structure and a phosphorus-based extreme pressure agent (C) with a specific structure together with the base oil (A), these properties can be taken into account at a high level. The reason for this is not clear, but it is believed that the reason is that by using these sulfur-based extreme pressure agents (B) and phosphorus-based extreme pressure agents (C), the surface of the metal of the transmission as the lubricated object, especially the metal having fine irregularities on the surface, can be coated, thereby improving the property of the lubricating oil composition to form an oil film and the ability to form an oil film (hereinafter also referred to as "oil film forming property"). It is believed that if the oil film forming property is high, the oil film can suppress the impact and solid phase welding between metals, so that high gear protection can be obtained. In addition, it is believed that excellent copper corrosion resistance and oxidation stability are exhibited by the sulfur-based extreme pressure agent (B) having a specific structure and the phosphorus-based extreme pressure agent (C) having a specific structure.

[0048] "Gear protection" is a property of reducing local surface damage caused by solid phase welding, for example, on the tooth surface of the gear, and can be evaluated, for example, by observing the wear scars produced by the Shell four-ball wear test according to ASTM D4172-18 described in the Examples and the diameter of the wear scars. The occurrence of surface damage can be confirmed by observing the wear scars, and the extent of the damage can be confirmed by the size of the wear scar diameter. When the wear scar diameter is small, it can be evaluated that the "gear protection" is high.

[0049] In addition, "copper corrosion resistance" and "oxidation stability" are indicators for evaluating whether the lubricating oil composition has a chemical effect on the lubricated object or whether the lubricating oil composition is chemically affected by the lubricated object. As described above, by adding sulfur-based extreme pressure agents and phosphorus-based extreme pressure agents, high gear protection can be obtained, but for example, the copper surface of the lubricated object is corroded, or the metal on the surface of the lubricated object acts as a catalyst to decompose the sulfur-based extreme pressure agent and the phosphorus-based extreme pressure agent. If metal is eluted in the lubricating oil composition or its constituent components are degraded, the performance of the lubricating oil composition originally possessed will be reduced, so it is not preferred. The lubricating oil composition of this embodiment can suppress the performance reduction of the lubricating oil composition by combining the above-mentioned components. "Copper corrosion resistance" can be evaluated, for example, by the amount of copper dissolved as described in the examples, and "oxidation stability" can be evaluated, for example, by the internal combustion engine lubrication oxidation stability test (ISOT test) described in the examples and the increase in acid value before and after the ISOT test.

[0050] In the lubricating oil composition of the present embodiment, the total content of the base oil (A), the sulfur-based extreme pressure agent (B), and the phosphorus-based extreme pressure agent (C) is preferably 60.00% by mass or more, more preferably 70.00% by mass or more, further preferably 80.00% by mass or more, further preferably 85.00% by mass or more, further preferably 88.00% by mass or more, and further preferably 89.00% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, in order to improve low viscosity and gear protection. In addition, in order to exhibit excellent copper corrosion resistance and oxidation stability, the upper limit is preferably 100% by mass or less, more preferably 99.00% by mass or less, further preferably 97.00% by mass or less, further preferably 95.00% by mass or less, and further preferably 92.00% by mass or less.

[0051] If the content of sulfur atoms in the lubricating oil composition is 0.01% by mass or more and 0.20% by mass or less based on the total amount (100% by mass) of the lubricating oil composition, it is preferred because excellent copper corrosion resistance and oxidation stability can be achieved while improving gear protection. As a lower limit, it is more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more. As an upper limit, it is more preferably 0.15% by mass or less, even more preferably 0.10% by mass or less, and even more preferably 0.09% by mass or less.

[0052] If the phosphorus atom content in the lubricating oil composition is 0.005 mass % or more and 0.100 mass % or less based on the total amount (100 mass %) of the lubricating oil composition, excellent copper corrosion resistance and oxidation stability can be achieved while improving gear protection, which is preferred. As a lower limit, it is more preferably 0.010 mass % or more, and even more preferably 0.013 mass % or more. As an upper limit, it is more preferably 0.080 mass % or less, even more preferably 0.050 mass % or less, and even more preferably 0.035 mass % or less.

[0053] If the mass ratio of sulfur atoms to phosphorus atoms (S / P ratio) contained in the lubricating oil composition is 1.00 or more and 7.00 or less, it is possible to improve the gear protection and copper corrosion resistance, in particular, and therefore it is preferred. It is more preferred that the content of sulfur atoms and the content of phosphorus atoms are within the above ranges, and the S / P ratio is within the above ranges. As the lower limit of the S / P ratio, it is more preferred to be 1.10 or more, and even more preferred to be 1.15 or more. As the upper limit, it is more preferred to be 6.50 or less, even more preferred to be 6.00 or less, and even more preferred to be 5.40 or less.

[0054] The content of sulfur atoms in the lubricating oil composition can be appropriately adjusted mainly by the content of the sulfur-based extreme pressure agent (B), and the content of phosphorus atoms in the lubricating oil composition can be appropriately adjusted mainly by the content of the phosphorus-based extreme pressure agent (C). Therefore, the S / P ratio can also be appropriately adjusted by the contents of the sulfur-based extreme pressure agent (B) and the phosphorus-based extreme pressure agent (C).

[0055] In order to achieve excellent fuel efficiency and oil film forming properties, the kinematic viscosity of the lubricating oil composition at 100° C. is preferably 6.000 mm / s as an upper limit. 2 / s or less, more preferably 5.000mm 2 / s or less, more preferably 4.800mm 2 / s or less, more preferably 4.500mm 2 / s or less, and more preferably 4.100mm 2 / s or less, the lower limit is not particularly limited, but is preferably 2.000 mm 2 / s or more, more preferably 3.000mm 2 / s or more, more preferably 3.300mm 2 / s or more, more preferably 3.600mm 2 / s or more, and more preferably 3.800mm 2 / s or more.

[0056] The kinematic viscosity of the lubricating oil composition at 40° C. is preferably set to an upper limit of 20.00 mm / s in order to achieve excellent fuel efficiency and oil film forming properties. 2 / s or less, more preferably 18.00 mm 2 / s or less, more preferably 16.50mm 2 / s or less, more preferably 16.00mm 2 / s or less, and more preferably 15.90mm 2 / s or less, the lower limit is not particularly limited, but is preferably 12.00 mm 2 / s or more, more preferably 13.00 mm 2 / s or more, more preferably 14.00mm 2 / s or more, more preferably 15.00mm 2 / s or more, and more preferably 15.50mm 2 / s or more.

[0057] Regarding the viscosity index of the lubricating oil composition, in order to achieve excellent fuel saving and oil film forming properties, the upper limit is preferably 180 or less, more preferably 175 or less, further preferably 170 or less, and further preferably 167 or less. The lower limit is not particularly limited, but is preferably 130 or more, more preferably 140 or more, further preferably 145 or more, further preferably 150 or more, and further preferably 155 or more.

[0058] As described above, the gear protection is evaluated based on the observation of the wear scar produced by the Shell four-ball wear test and the wear scar diameter. The upper limit of the wear scar diameter is preferably 0.65 mm or less, more preferably 0.63 mm or less, further preferably 0.60 mm or less, further preferably 0.58 mm or less, and further preferably 0.55 mm or less. The lower limit is not particularly limited, but is usually about 0.30 mm.

[0059] As described above, the oxidation stability is evaluated by measuring the increase in acid value before and after the ISOT test under the conditions of the test, and the upper limit of the acid value increase is preferably 0.20 or less, more preferably 0.15 or less, further preferably 0.12 or less, and further preferably 0.10 or less. The lower limit is not particularly limited, and generally, there is no problem in actual use as long as it is about 0.01.

[0060] Regarding the above copper corrosion resistance, the upper limit of the copper dissolution amount is preferably 50 mass ppm or less, more preferably 45 mass ppm or less, further preferably 40 mass ppm or less, and further preferably 38 mass ppm or less. The lower limit is not particularly limited, and usually there is no problem in actual use as long as it is about 5 mass ppm or more.

[0061] <Base oil (A)>

[0062] The base oil (A) used in the present embodiment may be a mineral oil or a synthetic oil, or a mixed oil of a mineral oil and a synthetic oil may be used.

[0063] Examples of the mineral oil include atmospheric residues obtained by subjecting crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil to atmospheric distillation; distillates obtained by subjecting these atmospheric residues to reduced pressure distillation; and mineral oils obtained by subjecting the distillates to one or more of the refining treatments selected from solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrofining.

[0064] In addition, as the above-mentioned mineral oil, from the viewpoint of achieving a low friction coefficient and improving copper corrosion resistance, it is preferred to use a mineral oil corresponding to either Group II or Group III in the base oil classification of API (American Petroleum Institute), and it is more preferred to use mineral oils corresponding to both Group II and Group III.

[0065] Examples of the synthetic oil include poly-α-olefins such as polybutene, ethylene-α-olefin copolymers, and α-olefin homopolymers or copolymers; various ester oils such as polyol esters, dibasic acid esters, and phosphate esters; various ethers such as polyphenylene ether; polyethylene glycol; alkylbenzenes; alkylnaphthalenes; and GTL base oils obtained by isomerizing wax (GTL wax (Gas to Liquids WAX)) produced from natural gas using the Fischer-Tropsch process or the like.

[0066] The base oil (A) may be any one of the mineral oils and synthetic oils described above, or may be a combination of a plurality of mineral oils, a combination of a plurality of synthetic oils, or a combination of a mineral oil and a synthetic oil.

[0067] The base oil (A) contains the mineral oil, and the lower limit of the content of the mineral oil based on the total amount of the base oil (A) (100% by mass) is preferably 70.00% by mass or more, more preferably 80.00% by mass or more, further preferably 90.00% by mass or more, further preferably 95.00% by mass or more, further preferably 98.00% by mass or more, and further preferably it is substantially only the mineral oil.

[0068] The viscosity of the base oil (A) is not particularly limited, but the lower limit of the kinematic viscosity at 40° C. is preferably 8.000 mm 2 / s or more, more preferably 10.000mm 2 / s or more, more preferably 13.000mm 2 / s or more, and the upper limit is preferably 20.000 mm 2 / s or less, more preferably 17.500mm 2 / s or less, more preferably 14.500mm 2 / s or less.

[0069] The upper limit of the kinematic viscosity of the base oil (A) at 100° C. is preferably 6.000 mm 2 / s or less, more preferably 5.500mm 2 / s or less, more preferably 5.000mm 2 / s or less, and the lower limit is preferably 2.000 mm 2 / s or more, more preferably 2.500mm 2 / s or more, more preferably 3.000mm 2 / s or more.

[0070] The lower limit of the content of the base oil (A) based on the total amount (100% by mass) of the lubricating oil composition is preferably 70.00% by mass or more, more preferably 80.00% by mass or more, and even more preferably 85.00% by mass or more, and the upper limit is preferably 99.00% by mass or less, more preferably 95.00% by mass or less, and even more preferably 92.00% by mass or less. If the content of the base oil (A) is within the above range, it is preferred because it is possible to achieve both low viscosity and gear protection at a high level together with the sulfur-based extreme pressure agent (B) and the phosphorus-based extreme pressure agent (C) described later, and it is easy to improve better copper corrosion resistance and oxidation stability.

[0071] <Sulfur-based extreme pressure agent (B)>

[0072] The sulfur-based extreme pressure agent (B) used in the present embodiment needs to be a thiadiazole having a branched organic group having 3 to 24 carbon atoms. This is preferred because it can achieve both low viscosity and gear protection at a high level and can easily improve copper corrosion resistance and oxidation stability.

[0073] It is believed that thiadiazole having a branched organic group with a carbon number of 3 or more and 24 or less has a substituent that is crowded in space compared to thiadiazole having a straight-chain organic group, so that a metal having a catalytic effect is less likely to approach the reaction site, and therefore thiadiazole is less likely to be affected and has excellent copper corrosion resistance and oxidation stability.

[0074] In order to show the above characteristics, the branched organic group may have a branched portion, preferably a branched alkyl group, a branched alkenyl group or a branched alkynyl group, and the branched alkyl group, the branched alkenyl group or the branched alkynyl group may have -O-, -CO-, -COO-, -OCO-, -S-, -S2-, -S3-, -S4-, -CS-, -C(=S)O-, -C(=O)S-, -SC(=S)-, -NH-, -NHCO- or -C(=O)NH-. The branched organic group is preferably a branched alkyl group or a branched alkenyl group, and more preferably a branched alkyl group. The branched organic group preferably has 5 to 20 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 7 to 15 carbon atoms, further preferably 8 to 13 carbon atoms, and further preferably 9 to 12 carbon atoms.

[0075] As the branched organic group, a substituent represented by the general formula (B0) is preferred. It should be noted that the branch in the branched alkyl group simply means that the "alkyl group" has a branch.

[0076] [Chemical formula 3]

[0077]

[0078] (In general formula (B0), R B01 and R B02 Each independently represents an alkyl group having 1 to 22 carbon atoms, and R B03 represents a hydrogen atom or an alkyl group having 1 to 21 carbon atoms, and nB01 represents an integer from 0 to 20.

[0079] R B01 It is preferably a straight-chain alkyl group having 1 to 22 carbon atoms, more preferably a straight-chain alkyl group having 1 to 8 carbon atoms, further preferably a methyl group, an ethyl group or an n-propyl group, further preferably a methyl group or an ethyl group, and still further preferably a methyl group.

[0080] R B02The straight-chain alkyl group is preferably a straight-chain alkyl group having 1 to 22 carbon atoms, more preferably a straight-chain alkyl group having 3 to 12 carbon atoms, further preferably a straight-chain alkyl group having 6 to 10 carbon atoms, and still further preferably a straight-chain alkyl group having 6 to 9 carbon atoms.

[0081] R B03 It is preferably a hydrogen atom or a straight-chain alkyl group having 1 to 22 carbon atoms, more preferably a hydrogen atom or a straight-chain alkyl group having 1 to 8 carbon atoms, further preferably a methyl group, an ethyl group or an n-propyl group, further preferably a methyl group or an ethyl group, and still further preferably a methyl group.

[0082] nB01 is preferably an integer of 0 to 8, more preferably an integer of 0 to 4, further preferably an integer of 0 to 2, further preferably 0 or 1, and further preferably 0.

[0083] The sulfur-based extreme pressure agent (B) is a compound selected from the compounds represented by the general formulae (B1) to (B3). It is easy to achieve both low viscosity and gear protection at a high level and to improve copper corrosion resistance and oxidation stability. Therefore, the compound represented by the general formula (B1) is preferred, and more preferred.

[0084] [Chemical formula 4]

[0085]

[0086] (In general formulas (B1) to (B3), R B11 ~R B32 Each independently represents a branched organic group having 3 to 24 carbon atoms, and nB11 to nB32 each independently represent an integer of 1 to 4.

[0087] R present in the same molecule B11 ~R B32 They may be the same branched organic groups or different branched organic groups, but are preferably the same branched organic groups in terms of availability. B11 ~R B32 It is sufficient to have a branched portion, preferably a branched alkyl group, a branched alkenyl group or a branched alkynyl group, and the branched alkyl group, the branched alkenyl group or the branched alkynyl group may have -O-, -CO-, -COO-, -OCO-, -S-, -S2-, -S3-, -S4-, -CS-, -C(=S)O-, -C(=O)S-, -SC(=S)-, -NH-, -NHCO- or -C(=O)NH-. The branched organic group is preferably a branched alkyl group or a branched alkenyl group, and more preferably a branched alkyl group. The branched organic group preferably has 5 to 20 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 7 to 15 carbon atoms, further preferably 8 to 13 carbon atoms, and further preferably 9 to 12 carbon atoms. The branched organic group is preferably a substituent represented by the above-mentioned general formula (B0).

[0088] Each of nB11 to nB32 is independently preferably an integer of 1 to 3, more preferably 1 or 2, and further preferably 2.

[0089] In order to obtain better gear protection, the lower limit of the content of sulfur atoms in the above-mentioned sulfur-based extreme pressure agent (B) is preferably 10.00 mass % or more, more preferably 20.00 mass % or more, and further preferably 30.00 mass % or more, and the upper limit is preferably 50.00 mass % or less, more preferably 40.00 mass % or less, and further preferably 36.00 mass % or less.

[0090] In order to improve the gear protection, the lower limit of the content of the sulfur-based extreme pressure agent (B) is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, further preferably 0.05% by mass or more, and further preferably 0.08% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition. In addition, in order to exhibit excellent copper corrosion resistance and oxidation stability, the upper limit is preferably 5.00% by mass or less, more preferably 3.00% by mass or less, further preferably 2.00% by mass or less, further preferably 1.00% by mass or less, further preferably 0.50% by mass or less, and further preferably 0.30% by mass or less.

[0091] If the content of sulfur atoms derived from the sulfur-based extreme pressure agent (B) is 0.01% by mass or more and 0.20% by mass or less based on the total amount (100% by mass) of the lubricating oil composition, it is preferred because excellent copper corrosion resistance and oxidation stability can be achieved while improving gear protection. As a lower limit, it is more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more. As an upper limit, it is more preferably 0.15% by mass or less, even more preferably 0.10% by mass or less, and even more preferably 0.09% by mass or less.

[0092] <Phosphorus-based extreme pressure agent (C)>

[0093] The phosphorus-based extreme pressure agent (C) used in the present embodiment needs to be a phosphate ester having an organic group including a ring structure having 6 to 24 carbon atoms. This is preferred because it can achieve both low viscosity and gear protection at a high level and can easily improve copper corrosion resistance and oxidation stability.

[0094] Preferred examples of the phosphate ester include neutral phosphate ester, acidic phosphate ester, phosphite ester, hydrogen phosphite ester and the like, and amine salts of the phosphate ester. In order to achieve both low viscosity and gear protection at a high level and to achieve better copper corrosion resistance and oxidation stability, the phosphate ester is more preferably not an amine salt, and is further preferably a neutral phosphate ester.

[0095] It is believed that the above-mentioned phosphate ester having an organic group with a carbon number of 6 to 24 including a ring structure has a substituent that is crowded in space compared to the phosphate ester with a carbon number of 6 to 24 without a ring structure, so the metal with a catalytic effect is not easy to approach the reaction site, so the phosphate ester is hardly affected and has excellent copper corrosion resistance and oxidation stability.

[0096] The carbon number of the organic group containing a ring structure is preferably 6 to 20, more preferably 6 to 16, further preferably 6 to 14, further preferably 6 to 11, further preferably 6 to 10, particularly preferably 9.

[0097] In order to exhibit the above characteristics, the organic group having a carbon number of 6 or more and 24 or less, including a ring structure, of the above phosphate ester is preferably an aryl group which may have a substituent. It is believed that the aryl group contributes to steric hindrance, and the chemical stability of the aryl group itself is also high, thus exhibiting excellent copper corrosion resistance and oxidation stability.

[0098] As the aryl group, phenyl, naphthalene-1-yl or naphthalene-2-yl is preferred, and phenyl is more preferred. The aryl group may be unsubstituted or may have a substituent. As the substituent, an organic group having 1 to 18 carbon atoms is preferred, a hydrocarbon group having 1 to 18 carbon atoms is more preferred, an alkyl group having 1 to 18 carbon atoms is further preferred, an alkyl group having 1 to 8 carbon atoms is further preferred, an alkyl group having 1 to 6 carbon atoms is further preferred, and an alkyl group having 1 to 4 carbon atoms is further preferred.

[0099] The neutral phosphate ester is preferably a compound represented by the general formula (C1).

[0100] [Chemical formula 5]

[0101]

[0102] (In general formula (C1), R C11 ~R C13 Each independently represents a hydrocarbon group having 1 to 24 carbon atoms, the -CH2- in the above alkyl group may be substituted by -O-, -S-, -CO- or -CS-, nC11 to nC13 each independently represent an integer from 0 to 5, and multiple R may exist in the same molecule. C11 ~R C13 In the case of C11 ~X C13 Each independently represents -O- or -S-, X C14 Indicates =O or =S. )

[0103] R C11 ~R C13 Each independently represents a hydrocarbon group having 1 to 24 carbon atoms, and as the hydrocarbon group, an alkyl group having 1 to 8 carbon atoms is more preferred, an alkyl group having 1 to 6 carbon atoms is further preferred, and an alkyl group having 1 to 4 carbon atoms is further preferred.

[0104] Each of nC11 to nC13 is independently preferably an integer of 0 to 3, preferably an integer of 0 to 2, and preferably 0 or 1. C11 ~X C13 Preferred is -O-.

[0105] In order to obtain better gear protection, the phosphorus content in the above-mentioned phosphorus-based extreme pressure agent (C) is preferably 1.00 mass% or more, more preferably 3.00 mass% or more, and further preferably 6.00 mass% or more, and the upper limit is preferably 15.00 mass% or less, more preferably 13.00 mass% or less, and further preferably 10.00 mass% or less.

[0106] In order to improve the gear protection, the lower limit of the content of the phosphorus-based extreme pressure agent (C) is preferably 0.01% by mass, more preferably 0.03% by mass, further preferably 0.05% by mass, and further preferably 0.10% by mass, based on the total amount (100% by mass) of the lubricating oil composition. In addition, in order to exhibit excellent copper corrosion resistance and oxidation stability, the upper limit is preferably 3.00% by mass, more preferably 2.00% by mass, further preferably 1.00% by mass, further preferably 0.70% by mass, and further preferably 0.50% by mass.

[0107] If the content of phosphorus atoms derived from the phosphorus-based extreme pressure agent (C) is 100 mass ppm or more and 500 mass ppm or less based on the total amount (100 mass %) of the lubricating oil composition, it is preferred because excellent copper corrosion resistance and oxidation stability can be achieved while improving gear protection. As a lower limit, it is more preferably 120 mass ppm or more, and even more preferably 140 mass ppm or more. As an upper limit, it is more preferably 450 mass ppm or less, even more preferably 400 mass ppm or less, and even more preferably 350 mass ppm or less.

[0108] In order to improve the gear protection, the lower limit of the total content of the sulfur-based extreme pressure agent (B) and the phosphorus-based extreme pressure agent (C) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, further preferably 0.10% by mass or more, and further preferably 0.20% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition. In order to exhibit excellent copper corrosion resistance and oxidation stability, the upper limit is preferably 3.00% by mass or less, more preferably 2.00% by mass or less, further preferably 1.00% by mass or less, further preferably 0.80% by mass or less, and further preferably 0.60% by mass or less.

[0109] In order to achieve both low viscosity and gear protection at a high level and to achieve even better copper corrosion resistance and oxidation stability, the lower limit of the value obtained by multiplying the value obtained by dividing the total content of the sulfur-based extreme pressure agent (B) and the phosphorus-based extreme pressure agent (C) by the content of the base oil (A) by 100 times is preferably 0.10 or more, more preferably 0.20 or more, and even more preferably 0.30 or more. In order to achieve excellent copper corrosion resistance and oxidation stability, the upper limit is preferably 1.00 or less, more preferably 0.80 or less, more preferably 0.70 or less, and even more preferably 0.60 or less.

[0110] The lubricating oil composition may contain only the base oil (A), the sulfur-based extreme pressure agent (B) and the phosphorus-based extreme pressure agent (C), or may contain other additives described below, or may contain only the base oil (A), the sulfur-based extreme pressure agent (B), the phosphorus-based extreme pressure agent (C) and other additives described below.

[0111] <Other additives>

[0112] The lubricating oil composition of the present embodiment may further contain at least one selected from other sulfur-based extreme pressure agents, other phosphorus-based extreme pressure agents, viscosity index improvers, antioxidants, pour point depressants, detergents, friction modifiers, defoamers, and dispersants as other additives that can improve the quality of the product.

[0113] In order to achieve both low viscosity and gear protection at a high level and to achieve better copper corrosion resistance and oxidation stability, the lower limit of the content of the other additive mixture is preferably 0.10% by mass or more, more preferably 1.00% by mass or more, further preferably 3.00% by mass or more, further preferably 5.00% by mass or more, and further preferably 8.00% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition. The upper limit is preferably 40.00% by mass or less, more preferably 30.00% by mass or less, further preferably 20.00% by mass or less, further preferably 15.00% by mass or less, further preferably 12.00% by mass or less, and further preferably 11.00% by mass or less.

[0114] In this specification, "other additive mixture" refers not only to the addition of other additives to the lubricating oil composition in the form of a mixture of other additives, but also includes the case where only one other additive is used. When each other additive added to the lubricating oil composition is made into a mixture, it means the content based on the total amount of the above-mentioned lubricating oil composition.

[0115] (Other sulfur-based extreme pressure agents)

[0116] The lubricating oil composition of the present embodiment may further contain another sulfur-based extreme pressure agent different from the sulfur-based extreme pressure agent (B). However, from the viewpoint of easily exhibiting the effects of the present invention, the content of the other sulfur-based extreme pressure agent is preferably small.

[0117] The content of the other sulfur-based extreme pressure agent is preferably less than 0.10% by mass, more preferably less than 0.05% by mass, even more preferably less than 0.01% by mass, based on the total amount (100% by mass) of the lubricating oil composition. It is even more preferred that the other sulfur-based extreme pressure agent is not contained.

[0118] Examples of the other sulfur-based extreme pressure agents include the following compounds: thiadiazoles having no branched organic group having 3 or more and 24 or less carbon atoms in their structure and having a linear organic group, wherein among the compounds represented by the general formulae (B1) to (B3), R B11 ~R B32 Each independently represents a linear organic group having 1 to 24 carbon atoms, and nB11 to nB32 each independently represent an integer of 1 to 4.

[0119] (Other phosphorus-based extreme pressure agents)

[0120] The lubricating oil composition of the present embodiment may further contain other phosphorus-based extreme pressure agents other than the phosphorus-based extreme pressure agent (C). However, from the viewpoint of easily exhibiting the effects of the present invention, the content of the other phosphorus-based extreme pressure agent is preferably small.

[0121] The content of the other phosphorus-based extreme pressure agent is preferably less than 0.47% by mass, more preferably less than 0.20% by mass, further preferably less than 0.10% by mass, further preferably less than 0.01% by mass, based on the total amount (100% by mass) of the lubricating oil composition. It is further preferred that no other phosphorus-based extreme pressure agent is contained.

[0122] The above-mentioned other phosphorus-based extreme pressure agents are phosphates that do not have a ring structure in their structure, specifically, phosphates that do not have a ring structure in their structure and have a carbon number of more than 6 and less than 24. More specifically, phosphate compounds such as neutral phosphates, acidic phosphates, phosphites, and hydrogen phosphites that do not have a ring structure in their structure, and amine salts of the phosphate compounds, etc. can be cited. Among them, it is preferred that the content of the acidic phosphate or its amine salt that does not have a ring structure in its structure is small. The specific content of the acidic phosphate or its amine salt that does not have a ring structure in its structure is the same as the specific content of the above-mentioned other phosphorus-based extreme pressure agents. It should be noted that the above-mentioned other phosphorus-based extreme pressure agents can be used alone, or a variety of them can be used in combination.

[0123] Examples of the phosphoric acid ester having no ring structure in the above structure include tributyl phosphate, ethyl dibutyl phosphate, trihexyl phosphate, tri(2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, and trioleyl phosphate.

[0124] Examples of the acidic phosphate ester having no ring structure in the above structure include mono(di)ethyl acid phosphate, mono(di)n-propyl acid phosphate, mono(di)2-ethylhexyl acid phosphate, mono(di)butyl acid phosphate, mono(di)oleyl acid phosphate, mono(di)isodecyl acid phosphate, mono(di)lauryl acid phosphate, mono(di)stearyl acid phosphate, and mono(di)isostearyl acid phosphate.

[0125] Examples of the phosphite having no ring structure in the above structure include triethyl phosphite, tributyl phosphite, tri(2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, triisooctyl phosphite, tristearyl phosphite, and trioleyl phosphite.

[0126] Examples of the hydrogen phosphite having no ring structure in the above structure include mono(di)ethyl hydrogen phosphite, mono(di)n-propyl hydrogen phosphite, mono(di)n-butyl hydrogen phosphite, mono(di)-2-ethylhexyl hydrogen phosphite, mono(di)lauryl hydrogen phosphite, mono(di)oleyl hydrogen phosphite, and mono(di)stearyl hydrogen phosphite.

[0127] In addition, as the amine salt of the phosphate compound such as the phosphate ester having no ring structure in the above structure, the acidic phosphate ester, the phosphite ester, the hydrogen phosphite ester, etc., preferably, an amine salt formed from these phosphate compounds and an amine can be mentioned. Here, as the amine used in the formation of the amine salt, primary amines, secondary amines, tertiary amines, polyalkyleneamines, etc. can be mentioned, and as the primary amine, secondary amine, tertiary amine, for example, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexethyleneheptamine, heptaethyleneoctamine, tetrapropylenepentamine, hexamethyleneheptamine, etc. can be mentioned.

[0128] (Viscosity index improver)

[0129] The lubricating oil composition of this embodiment preferably further contains a viscosity index improver. The viscosity index improver is preferably contained because even if the kinematic viscosity of the lubricating oil composition is reduced, a decrease in oil film formation at high temperatures can be suppressed, and a decrease in gear protection at high temperatures is less likely to occur.

[0130] Examples of the viscosity index improver include polymers such as non-dispersed polymethacrylate, dispersed polymethacrylate, and styrene-based copolymers (for example, styrene-diene copolymers and styrene-isoprene copolymers).

[0131] The mass average molecular weight (Mw) of the viscosity index improver is appropriately set depending on the type thereof, and is preferably 500 to 1,000,000, more preferably 5,000 to 800,000, and even more preferably 10,000 to 600,000, from the viewpoint of viscosity characteristics.

[0132] In the case of non-dispersed and dispersed polymethacrylates, Mw is preferably 5,000 to 300,000, more preferably 10,000 to 100,000, and even more preferably 20,000 to 50,000.

[0133] Mw can be measured, for example, by GPC (gel permeation chromatography) in terms of standard polystyrene.

[0134] (Antioxidant)

[0135] The lubricating oil composition of the present embodiment preferably further contains the above-mentioned antioxidant. By containing the antioxidant, excellent copper corrosion resistance and oxidation stability can be achieved.

[0136] As the antioxidant, amine antioxidants and phenolic antioxidants are preferred.

[0137] Examples of the amine antioxidant include dioctyldiphenylamine, phenyl-α-naphthylamine, diphenylamine, dinonyldiphenylamine, monobutylphenylmonoctylphenylamine, p-tert-octylphenyl-1-naphthylamine, and 4,4′-bis(α,α-dimethylbenzyl)diphenylamine.

[0138] The phenolic antioxidant preferably has a hindered phenol structure, and examples thereof include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-tert-butyl-4-hydroxymethylphenol, 2,6-di-tert-butylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-isopropylbis(2,6-di-tert-butylphenol), (2,6-di-tert-butylphenol), 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate tridecyl ester, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octyl ester, 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl ester, and 3-(3-methyl-5-tert-butyl-4-hydroxyphenyl) propionate octyl ester, etc.

[0139] (Pour Point Depressant)

[0140] The lubricating oil composition of the present embodiment preferably further contains the above-mentioned pour point depressant. Examples of the above-mentioned pour point depressant include polymers such as ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylate (PMA), and polyalkylstyrene, and polymethacrylate is preferred. The weight average molecular weight (Mw) of these polymers is preferably 50,000 or more and 150,000 or less.

[0141] Mw can be measured, for example, by GPC (gel permeation chromatography) in terms of standard polystyrene.

[0142] (Detergent)

[0143] The lubricating oil composition of the present embodiment preferably further contains the above-mentioned detergent. Examples of the above-mentioned detergent include metal-based detergents such as salicylates of sodium, calcium, magnesium, etc., sulfonates, and phenates, and calcium sulfonate is more preferred.

[0144] These may be used alone or in combination of two or more.

[0145] (Friction Modifier)

[0146] The lubricating oil composition of the present embodiment preferably further contains the above-mentioned friction modifier. As the above-mentioned friction modifier, an ashless friction modifier is preferred. As ashless compounds, for example, amine friction modifiers, ester friction modifiers, amide friction modifiers, fatty acid friction modifiers, alcohol friction modifiers, ether friction modifiers, urea friction modifiers, hydrazide friction modifiers, etc. are mentioned, preferably containing at least one selected from amine friction modifiers, ester friction modifiers and amide friction modifiers, and more preferably amine friction modifiers. As the amine friction modifier, an amine friction modifier commonly used in the field of the above-mentioned lubricating oil composition can be used, and secondary amines are more preferred.

[0147] (Defoaming agent)

[0148] The lubricating oil composition of the present embodiment preferably further contains the above-mentioned defoaming agent. Examples of the above-mentioned defoaming agent include silicone-based defoaming agents, fluorine-based defoaming agents such as fluorosilicone oil and fluoroalkyl ether, and polyacrylate-based defoaming agents, and silicone-based defoaming agents are preferred.

[0149] (Dispersant)

[0150] The lubricating oil composition of the present embodiment preferably further contains the above-mentioned dispersant. Examples of the above-mentioned dispersant include ashless dispersants such as boron-free succinimides, boron-containing succinimides, benzylamines, boron-containing benzylamines, succinates, monovalent or divalent carboxylic acid amides represented by fatty acids or succinic acid, etc., and boron-free succinimides or boron-containing succinimides are more preferred, polyalkenyl succinimides or boron-containing polyalkenyl succinimides are further preferred, and polybutenyl succinimides or boron-containing polybutenyl succinimides are further preferred. The weight average molecular weight (Mw) of the polyalkenyl succinimides or boron-containing polyalkenyl succinimides is preferably 500 or more and 2000 or less, more preferably 750 or more and 1500 or less, and further preferably 800 or more and 1200 or less. In addition, the carbon number of the above-mentioned alkenyl group is preferably 2 or more and 8 or less, and preferably 3 or more and 5 or less.

[0151] Mw can be measured, for example, by GPC (gel permeation chromatography) in terms of standard polystyrene.

[0152] These may be used alone or in combination of two or more.

[0153] [Lubrication method and transmission]

[0154] The lubricating oil composition of the present embodiment can achieve both low viscosity and gear protection at a high level, and can also achieve more excellent copper corrosion resistance and oxidation stability. Therefore, the lubricating oil composition of the present embodiment can be used as a lubricating oil composition for drive system equipment such as a shock absorber, a transmission, and a power steering device, especially for a transmission, especially for a transmission of a gasoline vehicle, a hybrid vehicle, an electric vehicle, etc., and can be particularly suitably used as a lubricating oil composition for a transmission of a hybrid vehicle or an electric vehicle.

[0155] The lubrication method of the present embodiment is a lubrication method using the lubricating oil composition, and the transmission of the present embodiment is a transmission including the lubricating oil composition. The lubrication method using the lubricating oil composition of the present embodiment and the transmission including the lubricating oil composition of the present embodiment as a constituent component achieve both low viscosity and gear protection at a high level, and also achieve more excellent copper corrosion resistance and oxidation stability.

[0156] In addition, other uses of the lubricating oil composition that can be applied to the present embodiment include, for example, internal combustion engine oil, hydraulic oil, turbine oil, compressor oil, lubricating oil for machine tools, cutting oil, gear oil, fluid bearing oil composition, rolling bearing oil, etc.

[0157] Furthermore, according to the present embodiment, use of the lubricating oil composition as a lubricating oil for a transmission is provided.

[0158] Example

[0159] Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples at all.

[0160] Examples 1 to 6, Comparative Examples 1 to 5

[0161] Lubricating oil compositions were prepared with the blending amounts (mass %) shown in Tables 1 and 2. The obtained lubricating oil compositions were subjected to various tests by the following methods to evaluate their physical properties. The evaluation results are shown in Tables 3 and 4.

[0162] The properties of the lubricating oil composition were measured by the following methods.

[0163] (1) Kinematic viscosity at 40°C (40°C kinematic viscosity), kinematic viscosity at 100°C (100°C kinematic viscosity) and viscosity index

[0164] The kinematic viscosity at 40°C and 100°C was measured in accordance with JIS K2283:2000, and the viscosity index was calculated.

[0165] (2) Viscosity index (VI)

[0166] Calculated according to ASTM D2270.

[0167] (3) Acid value

[0168] The measurement is carried out by the indicator photometric titration method (see Appendix 1 of the above JIS standard) in accordance with JIS K2501. The acid value of the lubricating oil composition before and after the ISOT test for evaluating the amount of copper elution described later is measured, and the difference is taken as the acid value increase. The smaller the acid value increase, the better the oxidation stability.

[0169] (4) Sulfur atom content

[0170] The measurement was conducted in accordance with JIS K2541-6.

[0171] (5) Phosphorus atomic content

[0172] The measurement was carried out according to ASTM D4951.

[0173] (6) Shell four-ball wear test (Shell wear)

[0174] The wear scar diameter (mm) was measured by testing in accordance with ASTM D4172-18 at 80°C, 1200 rpm, 392 N, and 30 minutes.

[0175] Wear scars are observed under a microscope to confirm the occurrence of surface damage, and the extent of the damage is further confirmed by the size of the wear scar diameter. The smaller the wear scar diameter, the better the gear protection (wear resistance).

[0176] (7) Copper dissolution (Cu dissolution)

[0177] The ISOT test is conducted in accordance with JIS K-2514-1 (2013) "Lubricating Oil - Oxidation Stability Test". That is, an iron-copper plate is placed in oil, stirred at 150°C, and the amount of copper eluted (mass ppm) after 72 hours is measured by ASTM D4951. The less the amount of copper eluted, the better the copper corrosion resistance.

[0178] [Table 1]

[0179]

[0180] [Table 2]

[0181]

[0182] In Tables 1 and 2, (A), (B), and (C) represent the contents of the base oil (A), the sulfur-based extreme pressure agent (B), and the phosphorus-based extreme pressure agent (C) based on the total amount (100% by mass) of the lubricating oil composition. A blank column indicates that the component is not contained. In Tables 3 and 4, S / P represents the mass ratio of sulfur atoms to phosphorus atoms contained in the lubricating oil composition.

[0183] [Table 3]

[0184]

[0185] [Table 4]

[0186]

[0187] In Tables 3 and 4, the acid value, acid value increase, and copper elution amount described below after ISOT are values ​​after the ISOT test.

[0188] [Table 5]

[0189]

[0190] Thiadiazole (branched): a compound represented by formula (B-1) (having a branched organic group having 12 carbon atoms.)

[0191] [Chemical formula 6]

[0192]

[0193] Thiadiazole (straight chain): a mixture of compounds represented by the general formula (B-2)

[0194] [Chemical formula 7]

[0195]

[0196] (Where R b21 ~R b22 Each independently represents a linear alkyl group having 6 to 10 carbon atoms, and mb21 to mb22 each independently represent an integer of 1 to 4.

[0197] Benzotriazole: a mixture of compounds represented by the general formula (BT)

[0198] [Chemical formula 8]

[0199]

[0200] (Where R BT1 represents a straight-chain alkyl group having 1 to 4 carbon atoms or a hydrogen atom, and R BT2 ~R BT3 Each independently represents a straight-chain alkyl group having 1 to 20 carbon atoms or a hydrogen atom.

[0201] Phosphorus compound (1): a compound represented by formula (C-1) (having an organic group having a ring structure and having 6 or 10 carbon atoms)

[0202] Phosphorus compound (2): a compound represented by formula (C-2) (having an organic group containing a ring structure having 9 carbon atoms)

[0203] Phosphorus compound (3): a compound represented by formula (C-3) (having an organic group containing a ring structure having 7 carbon atoms)

[0204] Phosphorus compound (4): a compound represented by formula (C-4) (having an organic group containing a ring structure having 6 carbon atoms)

[0205] [Chemical formula 9]

[0206]

[0207] Acidic phosphoric acid extreme pressure agent: dilauryl acid phosphate

[0208] Other additive mixtures: viscosity index improvers, antioxidants, pour point depressants, detergents, friction modifiers, defoamers, dispersants, etc.

[0209] The results in Table 3 show that the lubricating oil compositions of Examples 1 to 6 achieve both low viscosity and gear protection at a high level, and also have more excellent copper corrosion resistance and oxidation stability.

[0210] In contrast, as shown in Tables 1 to 4, in Comparative Example 1 in which the sulfur-based extreme pressure agent (B) of Example 3 was replaced by thiadiazole (straight chain), Comparative Example 2 in which the sulfur-based extreme pressure agent (B) of Example 4 was replaced by thiadiazole (straight chain), and Comparative Example 3 in which the sulfur-based extreme pressure agent (B) of Example 5 was replaced by thiadiazole (straight chain), it was confirmed that the gear protection was reduced, and the copper corrosion resistance and oxidation stability were also reduced.

[0211] In Comparative Example 4 in which the sulfur-based extreme pressure agent (B) of Example 3 was replaced with benzotriazole, it was confirmed that the gear protection performance was significantly deteriorated, although the copper corrosion resistance and oxidation stability were not reduced.

[0212] In Comparative Example 5 in which the phosphorus-based extreme pressure agent (C) was replaced with an acidic phosphoric acid extreme pressure agent, a uniform lubricating oil composition was formed, but precipitation occurred thereafter and the composition became non-uniform. Therefore, the physical property values ​​could not be measured and a practical lubricating oil composition could not be formed.

Claims

1. A lubricating oil composition comprising a base oil (A), a sulfur-based extreme pressure agent (B) and a phosphorus-based extreme pressure agent (C), The sulfur-based extreme pressure agent (B) is a thiadiazole having a branched organic group having 3 or more and 24 or less carbon atoms. The phosphorus-based extreme pressure agent (C) is a phosphoric acid ester having an organic group having 6 to 24 carbon atoms and a ring structure.

2. The lubricating oil composition according to claim 1, wherein The kinematic viscosity of the base oil (A) at 100°C is 6.000 mm 2 / s or less.

3. The lubricating oil composition according to claim 1 or 2, wherein The base oil (A) contains a mineral oil, and the content of the mineral oil is 70.00% by mass or more based on 100% by mass, which is the total amount of the base oil (A).

4. The lubricating oil composition according to any one of claims 1 to 3, wherein The thiadiazole is a compound selected from the compounds represented by general formulas (B1) to (B3), In the general formulas (B1) to (B3), R B11 ~R B32 Each independently represents a branched organic group having 3 to 24 carbon atoms, and nB11 to nB32 each independently represent an integer of 1 to 4.

5. The lubricating oil composition according to any one of claims 1 to 4, wherein The organic group having 6 to 24 carbon atoms including a ring structure contained in the phosphoric acid ester is an aryl group which may have a substituent.

6. The lubricating oil composition according to any one of claims 1 to 5, wherein The phosphate esters are not amine salts.

7. The lubricating oil composition according to any one of claims 1 to 6, wherein The phosphate ester is a neutral phosphate ester.

8. The lubricating oil composition according to claim 7, wherein The neutral phosphate ester is a compound represented by the general formula (C1), In the general formula (C1), R C11 ~R C13 Each independently represents a hydrocarbon group having 1 to 24 carbon atoms, wherein -CH2- in the hydrocarbon group is independently optionally substituted by -O-, -S-, -CO- or -CS-, and nC11 to nC13 each independently represent an integer from 0 to 5. There are multiple R in the same molecule. C11 ~R C13 In the case of C11 ~X C13 Each independently represents -O- or -S-, X C14 Indicates =O or =S.

9. The lubricating oil composition according to any one of claims 1 to 8, wherein The content of sulfur atoms in the lubricating oil composition is 0.01% by mass or more and 0.20% by mass or less, based on 100% by mass of the total amount of the lubricating oil composition.

10. The lubricating oil composition according to any one of claims 1 to 9, wherein The content of phosphorus atoms in the lubricating oil composition is 0.005 mass % or more and 0.100 mass % or less, based on 100 mass % of the total amount of the lubricating oil composition.

11. The lubricating oil composition according to any one of claims 1 to 10, wherein The mass ratio of sulfur atoms to phosphorus atoms contained in the lubricating oil composition, that is, S / P ratio, is 1.00 or more and 7.00 or less.

12. The lubricating oil composition according to any one of claims 1 to 11, wherein The kinematic viscosity of the lubricating oil composition at 100°C is 6.000 mm 2 / s or less. 13 . The lubricating oil composition according to claim 1 , which is used for a transmission. 14 . A lubrication method using the lubricating oil composition according to claim 1 . 15 . A transmission comprising the lubricating oil composition according to claim 1 .

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