JP2021080339A - Lubricating oil composition - Google Patents

Abstract

To provide a lubricating oil composition that has low abrasion, seizure resistance of a differential part and scoring resistance.SOLUTION: A lubricating oil composition includes (A) a lubricating base oil, (B) a sulfur-based extreme pressure agent, (C) a phosphorus-based extreme pressure agent and (D) an ashless dispersant. The lubricating oil composition is characterized in that the sulfur-based extreme pressure agent (B) includes a thiadiazole having two or more sulfur atoms and that the lubricating oil composition includes, as the phosphorus-based extreme pressure agent (C), at least one kind selected from (C1) a phosphonate ester oligomer represented by formula (1) as given below and (C2) a phosphonate ester, and has a kinematic viscosity at 100°C of 2 to 10 mm2/s. (In formula (1), R's are each independently a 1-20C monovalent hydrocarbon group; and n is an integer of 2 to 10).SELECTED DRAWING: None

Description

The present invention relates to lubricating oil compositions, in particular, lubricating oil compositions applicable for automobiles. More specifically, the present invention relates to a lubricating oil composition suitable for an automobile transmission, a lubricating oil composition suitable for an automobile gear oil, and further a lubricating oil composition suitable for a hybrid automobile.

Lubricating oil compositions are used in a wide variety of applications such as automobiles and machinery. In recent years, it has been required to reduce the viscosity of the lubricating oil composition for automobiles from the viewpoint of fuel efficiency. However, lowering the viscosity of the lubricating oil composition affects the oil film forming ability. The low viscosity is originally intended to realize fuel saving, but even if the viscosity of the conventional lubricating oil composition is lowered as it is, the oil film forming ability is inferior, so that the friction is rather high. Depending on the situation, it may not be possible to achieve fuel efficiency. Further, when the oil film forming ability is lowered due to the low viscosity, direct contact between the metals occurs, and as a result, sufficient lubrication is not performed, and as a result, wear becomes severe, so that the function as a lubricating oil composition can be obtained. It will not be fully fulfilled.

Patent Document 1 describes a lubricating oil composition preferably used as a gear oil for automobiles, and includes a base oil, a viscosity index improver, a molybdenum-based friction modifier, a boron-containing dispersant, and a sulfur-based extreme pressure. Lubricating oil compositions containing at least two extreme pressure agents selected from agents, phosphorus-based extreme pressure agents, and sulfur-phosphorus-based extreme pressure agents, or sulfur-phosphorus-based extreme pressure agents are described. Patent Document 1 describes that the lubricating oil composition has both fuel efficiency and extreme pressure, and further has shear stability, oxidation stability, and wear resistance.

Further, Patent Document 2 describes a lubricating oil composition suitable as a gear oil for automobiles, particularly a differential gear oil. It is described that a lubricating oil composition containing a specific sulfur-based extreme pressure agent can suppress the occurrence of bearing wear and scoring on the gear tooth surface even if the viscosity is lowered.

Japanese Unexamined Patent Publication No. 2016-190897 Japanese Unexamined Patent Publication No. 2017-132875

None of the above patent documents is disclosed or suggested as a problem to further achieve both low wear and seizure resistance of the differential portion in addition to fuel saving due to low viscosity. It is an object of the present inventors to provide a lubricating oil composition having low wear, seizure resistance to differential portions, and scoring resistance.

The present inventors diligently studied in order to solve the above problems, and examined to achieve both low wear, seizure resistance of the differential portion, and scoring resistance by specifying the additive. A lubricating oil composition containing at least one of a phosphonate ester oligomer and a phosphonate ester, which uses thiadiazol as a sulfur-based extreme pressure agent, has low wear, seizure resistance and scoring resistance in a differential portion. It was found that it became lower, and the present invention was made.

（式（１）中、Ｒは、互いに独立に、炭素数１〜２０の一価炭化水素基であり、ｎは２〜１０の整数である）。 That is, the present invention
(A) Lubricating oil base oil,
(B) Sulfur-based extreme pressure agent,
A lubricating oil composition containing (C) a phosphorus-based extreme pressure agent and (D) an ashless dispersant.
The (B) sulfur-based extreme pressure agent contains (B1) thiadiazole, the thiadiazole has two or more sulfur atoms, and the (C) phosphorus-based extreme pressure agent (C1) has the following formula (1). It is characterized by containing at least one selected from the phosphonate ester oligomer represented by (C2) phosphonic acid ester.
Provided is the lubricating oil composition having a kinematic viscosity of ^{2 to 10 mm 2 / s at 100 ° C.}

(In the formula (1), R is a monovalent hydrocarbon group having 1 to 20 carbon atoms independently of each other, and n is an integer of 2 to 10).

Preferred embodiments of the present invention are as follows.
(1) The (A) lubricating oil base oil contains at least one selected from diesters and triesters.
(2) As thiadiazole containing 2 or more sulfur atoms in (B1), 2,5-bis (hydrocarbyldithio) -1,3,4-thiadiazole and 2,5-bis (hydrocarbylthio) -1,3,4 Includes at least one selected from -thiadiazole, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazole or 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazole.
(3) The (B) sulfur-based extreme pressure agent further contains at least one selected from (B2) sulfide olefin, (B3) sulfide fat and oil, and (B4) sulfide ester.
(4) The sulfur-based extreme pressure agent (B) has an active sulfur amount of 0.1 to 40% by mass.
(5) As the (C) phosphorus-based extreme pressure agent, at least one selected from (C3) phosphite ester is further contained.
(6) The (C) phosphorus-based extreme pressure agent further contains at least one selected from (C4) an amine salt of a phosphoric acid ester and (C5) an amine salt of a thiophosphate ester.
(7) The ashless dispersant (D) is polyalkylene succinimide.
(8) The sulfur content is 0.3 to 5% by mass with respect to the total mass of the lubricating oil composition.
(9) The phosphorus content is 1000 to 2500 mass ppm with respect to the total mass of the lubricating oil composition.
(10) The boron content is 60 to 400 ppm with respect to the total mass of the lubricating oil composition.
(11) Lubricating oil composition for hybrid vehicles.
(12) Lubricating oil composition for transmission oil.
(13) Lubricating oil composition for gear oil.

The lubricating oil composition of the present invention can have low friction even when the viscosity is low, and can have the anti-wear property required for gear oil. Further, under the condition of lower viscosity, it is possible to provide a lubricating oil composition having excellent scoring resistance and seizure resistance of the differential portion in addition to the above effects. The lubricating oil composition of the present invention can be suitably used particularly for hybrid vehicles, transmissions, and gear oils.

It is a schematic diagram which shows the mode of the block-on-ring friction test which measures the seizure resistance of a differential part.

(A) Lubricating oil base oil The lubricating oil base oil in the present invention is not particularly limited, and conventionally known lubricating oil base oils can be used. Examples of the lubricating oil base oil include mineral oil-based base oils, synthetic base oils, and mixed base oils thereof.

The method for producing mineral oil-based base oil is not limited. Mineral oil-based base oils are highly refined paraffin-based mineral oils (high viscosity index mineral oil-based lubricating oil base oils) that have been subjected to solvent dewaxing or hydrodewaxing treatments such as hydrorefined oils and catalytic isomerized oils. ) Is preferable. Examples of mineral oil-based base oils other than the above include raffinate obtained by solvent refining using an aromatic extraction solvent such as phenol and furfural as a lubricating oil raw material, and hydrogen such as cobalt and molybdenum using silica-alumina as a carrier. Examples thereof include hydrogenated oil obtained by hydrogenation treatment using a hydrogenation treatment catalyst. For example, 100 neutral oil, 150 neutral oil, 500 neutral oil and the like can be mentioned.

As the synthetic base oil, for example, a base oil (derived from so-called Fischer-Tropsch) obtained by hydrocracking and hydrogenating isomerizing a raw material such as wax obtained by Fischer-Tropsch synthesis from a natural gas such as methane. Base oil), poly-α-olefin base oil, polybutene, alkylbenzene, polyol ester, polyglycol ester, ester, phosphoric acid ester, silicon oil and the like. The poly-α-olefin (PAO) base oil is not particularly limited, and for example, 1-octene oligomer, 1-decene oligomer, ethylene-propylene oligomer, isobutene oligomer, and hydrides thereof can be used. Preferably, the (A) lubricating oil base oil of the present invention preferably contains at least one ester. Scoring resistance can be improved by containing an ester.

Examples of the ester include monoesters, diesters, and polyol esters, and among them, diesters and triesters are preferable. Examples of the diester include a dibasic acid ester, preferably a dibasic acid ester having 2 to 30 carbon atoms, for example, dioctyl adipate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl ceva. Kate and ditridecylglutarate can be mentioned, and in particular, dioctyl adipate, di-2-ethylhexyl adipate, diisodecyl adipate, and ditridecyl adipate are preferable, and a mixture thereof can also be used. As the polyol ester, a polyol ester having 6 to 30 carbon atoms is preferable, and for example, trimethylolpropane caprilate, trimethylolpropane pelargonate, trimethylolpropane oleate, pentaerythritol 2-ethylhexanoate, and pentaerythritol pelargonate are used. Can be mentioned. These may be a mixture of two or more. Preferably, the lubricating oil base oil (A) of the present invention contains at least one selected from diesters and triesters.

The lubricating oil base oil may be used alone or in combination of two or more. When two or more kinds of lubricating oil base oils are used in combination, they may be mineral oil-based base oils, synthetic base oils, or a combination of mineral oil-based base oils and synthetic base oils, and the mode thereof is not limited.

The kinematic viscosity of the lubricating oil base oil is not limited as long as the gist of the present invention is not impaired. In particular, in order to obtain a low-viscosity lubricating oil composition, ^{it is preferable that the entire lubricating oil base oil has a kinematic viscosity of 1 to 9 mm 2} / s at 100 ° C., and more preferably 1 to 8 mm ² / s. It preferably has ² to 6 mm 2 / s. If the kinematic viscosity of the lubricating oil base oil at 100 ° C. exceeds the above upper limit value, it may be difficult to reduce the viscosity of the lubricating oil composition, and it may be difficult to achieve fuel efficiency. If the kinematic viscosity at 100 ° C. is less than the lower limit, fuel efficiency can be achieved, but the wear characteristics may be adversely affected.

上記式（２）〜（４）中、Ｒ^１〜Ｒ^６は、互いに独立に、水素原子、又は炭素数１〜３０を有し、酸素原子、窒素原子若しくは硫黄原子を含むことができる、一価炭化水素基であり、ａ、ｂ、ｃ、ｄ、ｅ及びｆはそれぞれ０〜８の整数であるが、ａ及びｂのいずれかは１〜８の整数であり、ｃ及びｄのいずれかは１〜８の整数であり、ｅ及びｆのいずれかは１〜８の整数である。 (B) Sulfur-based extreme pressure agent The lubricating oil composition of the present invention is characterized in that (B) the sulfur-based extreme pressure agent contains (B1) thiadiazole having two or more sulfur atoms. The component (B1) has high adsorptivity, and by including the highly adsorptive thiadiazole in combination with a specific phosphorus-based extreme pressure agent described later, the lubricating oil composition obtained has abrasion resistance, scoring resistance, and The seizure resistance of the differential portion can be improved. If thiadiazole having two or more sulfur atoms is not contained, the improvement of the seizure resistance of the differential portion becomes insufficient, which is not preferable. The thiadiazole having two or more sulfur atoms (B1) is not particularly limited as long as it is thiadiazole containing two or more sulfur atoms, but for example, 1, 3 represented by the following general formula (2). Examples thereof include a 4-thiadiazole compound, a 1,2,4-thiadiazole compound represented by the following general formula (3), and a 1,4,5-thiadiazole compound represented by the general formula (4). In the present invention, the component (B) does not include a sulfur-based extreme pressure agent having phosphorus.

In the above formulas (2) to (4), R ^{1 to} R ⁶ have hydrogen atoms or carbon atoms 1 to 30 independently of each other and can contain oxygen atoms, nitrogen atoms or sulfur atoms. It is a valent hydrocarbon group, and a, b, c, d, e and f are integers of 0 to 8, respectively, but any of a and b is an integer of 1 to 8, and any of c and d. Is an integer of 1 to 8, and any of e and f is an integer of 1 to 8.

Examples of the monovalent hydrocarbon group having 1 to 30 carbon atoms include an alkyl group, a cycloalkyl group, an alkylcycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, and an arylalkyl group.

As the component (B1), among the above, the 1,3,4-thiadiazole compound represented by the general formula (2) is particularly preferable, and in particular, 2,5-bis (hydrocarbyldithio) -1,3,4-thiadiazole , 2,5-bis (hydrocarbylthio) -1,3,4-thiadiazole, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazole or 2-mercapto-5-hydrocarbylthio-1,3,4 -Preferably selected from thiadiazole.

More specifically, 2,5-bis (dioctyldithio) -1,3,4-thiadiazole, 2,5-bis (di (2'-ethylhexyl) dithio) -1,3,4-thiadiazole, 2,5 -Bis (t-norylthio) -1,3,4-thiadiazole, 2,5-bis (dimethylhexylthio) -1,3,4-thiadiazole, 2,5-bis (octadecenylthio) -1,3 , 4-Thiadiazole, 2,5-bis (methylhexadecenylthio) -1,3,4-thiadiazole, 2,5-bis (2-hydroxyoctadecylthio) -1,3,4-thiadiazole, 2,5 -Bis (n-octoxycarbonylmethylthio) -1,3,4-thiadiazole, 2-mercapto-5- (2-ethylhexylthio) -1,3,4-thiadiazole, 2-mercapto-5- (t-nolylthio) ) -1,3,4-Thiadiazole, 2,5-bis (t-nolyldithio) -1,3,4-thiadiazole, 2,5-bis (dimethylhexyldithio) -1,3,4-thiadiazole, 2, 5-bis (octadecenyldithio) -1,3,4-thiadiazole, 2,5-bis (methylhexadecenyldithio) -1,3,4-thiadiazole, 2,5-bis (2-hydroxy) Octadecyldithio) -1,3,4-thiadiazole, 2,5-bis (n-octoxycarbonylmethyldithio) -1,3,4-thiadiazole, 2-mercapto-5- (2-ethylhexyldithio) -1, Examples thereof include 3,4-thiadiazole and 2-mercapto-5- (t-nolyldithio) -1,3,4-thiadiazole. Of these, 2,5-bis (dioctyldithio) -1,3,4-thiadiazole and 2,5-bis (di (2'-ethylhexyl) dithio) -1,3,4-thiadiazole are preferable.

The lubricating oil composition of the present invention can further contain at least one selected from (B2) olefin sulfide, (B3) sulfide oil and fat, and (B4) sulfide ester as the (B) sulfur-based extreme pressure agent.

The olefin sulfide and polysulfide are represented by the following general formula (5). As will be described later, olefin sulfide is obtained by sulfurizing olefins, and polysulfide is obtained by sulfurizing a hydrocarbon raw material other than olefins.
R ^11- S _x- (R ^12- S _x- ) _n- R ¹³ (5)

In the above formula (5), R ¹¹ and R ¹³ are monovalent hydrocarbon groups independently of each other, and are saturated or unsaturated aliphatic groups having a linear structure or a branched chain having, for example, 2 to 20 carbon atoms. Examples thereof include a hydrocarbon group and an aromatic hydrocarbon group having 2 to 26 carbon atoms. More specifically, there are ethyl group, propyl group, butyl group, nonyl group, dodecyl group, propenyl group, butenyl group, benzyl group, phenyl group, tolyl group, hexylphenyl group and the like.

In the above formula (5), R ¹² is a saturated or unsaturated aliphatic hydrocarbon group having a linear structure or a branched chain having 2 to 20 carbon atoms, and an aromatic hydrocarbon group having 6 to 26 carbon atoms. And so on. More specifically, ethylene group, propylene group, butylene group, phenylene group and the like can be mentioned.

In the above equation (5), x is an integer of 1 or more, preferably an integer of 1 to 8, independently of each other. When x is small, the extreme pressure property tends to be small, and when x is too large, the thermal oxidation stability tends to decrease. In order to obtain both extreme pressure and thermal oxidation stability, x in the unit shown in parentheses is preferably an integer of 1 to 6, more preferably an integer of 2 to 4, and particularly preferably 2 or. It is 3.

Examples of the sulfide olefin include those obtained by sulphurizing olefins such as polyisobutylene and terpenes with sulfur or other sulfide agents.

Examples of the polysulfide compound include diisobutyldisulfide, dioctylpolysulfide, di-tert-butylpolysulfide, and di-tert-benzylpolysulfide.

Sulfurized fats and oils are reaction products of fats and oils and sulfur, and are obtained by using animal and vegetable fats and oils such as lard, beef tallow, whale oil, palm oil, coconut oil, and rapeseed oil as fats and oils and sulphurizing them. .. This reaction product is not a single product, but a mixture of various substances, and the chemical structure itself is not clear.

The sulfurized ester is obtained by sulfurizing a fatty acid ester obtained by reacting the above fats and oils with various alcohols. Like sulfide fats and oils, the chemical structure itself is not clear.

In the present invention, the sulfur-based extreme pressure agent has active sulfur in an amount of 40% by mass or less, preferably 35% by mass or less, and more preferably 33% by mass or less with respect to the mass of the extreme pressure agent. preferable. If the amount of active sulfur exceeds the above upper limit, not only metal corrosion occurs, but also wear cannot be suppressed. The lower limit of the amount of active sulfur is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, based on the mass of the extreme pressure agent, in order to ensure extreme pressure. More preferably, it is 1% by mass or more.

Here, the amount of active sulfur is measured by the method specified in ASTM D1662. The amount of active sulfur based on ASTM D1662 can be measured in more detail by the following procedure.
1. Put 50 g of a sulfur-based additive (active sulfur-based extreme pressure agent) and 5 g of copper powder in a 200 ml beaker, and raise the temperature to 150 ° C. while stirring with a stirrer.
2. When the temperature reaches 150 ° C., add 5 g of copper powder and stir for 30 minutes.
3. 3. After the stirring is completed, an ASTM D130 compliant copper plate is placed in a beaker and immersed. At this time, if discoloration is observed on the copper plate, add 5 g of copper powder and stir for 30 minutes (continue this operation until discoloration is no longer observed).
4. When the discoloration of the copper plate is no longer observed, the copper powder in the sulfur-based additive is removed by filtration, and the amount of sulfur contained in the additive is measured.
The amount of active sulfur is calculated as follows.
Amount of active sulfur (% by mass) = Amount of sulfur before reaction with copper powder (% by mass) -Amount of sulfur after reaction with copper powder (% by mass)

The content of the sulfur-based extreme pressure agent (B) in the lubricating oil composition of the present invention is not limited, but is preferably 0.1% by mass to 15% by mass with respect to the total mass of the lubricating oil composition. , More preferably 0.2% by mass to 12% by mass, still more preferably 0.3% by mass to 10% by mass. If the content exceeds the above upper limit, wear can be suppressed, but sludge will be generated, which may cause metal corrosion, which is not preferable. The (B) sulfur-based extreme pressure agent may be a combination of the component (B1) and another sulfur-based extreme pressure agent, and particularly preferably the above-mentioned (B2) sulfide olefin, (B3) sulfide fat and oil, and (B4). It is a combination with at least one selected from sulfurized esters. (B1) The amount of thiadiazole having two or more sulfur atoms is 0.05% by mass to 2% by mass, more preferably 0.1% by mass to 1% by mass, still more preferably, with respect to the total mass of the lubricating oil composition. It is preferably 0.12% by mass to 0.5% by mass.

In the lubricating oil composition of the present invention, the sulfur content is not limited, but is preferably 0.3 to 5% by mass, more preferably 0.4 to 4% by mass, based on the total mass of the lubricating oil composition. %, More preferably 0.5 to 3% by mass. If the content exceeds the above upper limit, wear can be suppressed, but sludge will be generated, which may cause metal corrosion, which is not preferable.

（式（１）中、Ｒは、互いに独立に、炭素数１〜２０の一価炭化水素基であり、ｎは２〜１０の整数である）。 (C) Phosphorus-based extreme pressure agent The lubricating oil composition of the present invention is at least selected from (C1) a phosphonate ester oligomer represented by the following formula (1) and (C2) a phosphonic acid ester as a phosphorus-based extreme pressure agent. It is characterized in that one kind is contained together with the above-mentioned component (B1).

(In the formula (1), R is a monovalent hydrocarbon group having 1 to 20 carbon atoms independently of each other, and n is an integer of 2 to 10).

In the above formula (1), R is a monovalent hydrocarbon group having 1 to 20 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 12 carbon atoms, and more preferably 1 carbon number, independently of each other. It is preferably a monovalent hydrocarbon group of 10 to 10, and examples thereof include an alkyl group, a cycloalkyl group, an alkylcycloalkyl group, an alkenyl group, and an aryl group, and more preferably an alkyl group. n is an integer of 2 to 10, preferably an integer of 3 to 6.

The (C2) phosphonic acid ester can be represented by, for example, the following formula (6).
(R ⁸ O) (R ⁹ O) (R ¹⁰ ) P (= O) (6)
In formula (6), R ⁸ and R ⁹ are independent hydrogen atoms or monovalent hydrocarbon groups, ^{at least one of R 8} and R ⁹ is a monovalent hydrocarbon group, and R ¹⁰ is monovalent. It is a hydrocarbon group. R ⁸ and R ⁹ are independent of each other, preferably a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 12 carbon atoms, and further. It is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms. Particularly preferably, it is an alkyl group. R ¹⁰ is preferably a monovalent hydrocarbon group having 1 to 30 carbon atoms, more preferably an alkyl group, still more preferably an alkyl group having 2 to 20 carbon atoms, and most preferably 4 to 18 carbon atoms. It is an alkyl group of, particularly an alkyl group having 8 or 18 carbon atoms.

Examples of the phosphonic acid ester include dimethyl butylphosphonate, diethyl butylphosphonate, dipropyl butylphosphonate, dibutyl butylphosphonate, dipentyl butylphosphonate, dihexyl butylphosphonate, diheptyl butylphosphonate, dioctyl butylphosphonate, and hexylphosphone. Dimethyl oxyate, diethyl hexyl phosphonate, dipropyl hexyl phosphonate, dibutyl hexyl phosphonate, dipentyl hexyl phosphonate, dihexyl hexyl phosphonate, diheptyl hexyl phosphonate, dioctyl hexyl phosphonate, dimethyl octyl phosphonate, diethyl octyl phosphonate, octyl phosphone Dipropyl acid, dibutyl octylphosphonate, dipentyl octylphosphonate, dihexyl octylphosphonate, diheptyl octylphosphonate, dioctyl octylphosphonate, dimethyl decylphosphonate, diethyl decylphosphonate, dipropyl decylphosphonate, dibutyl decylphosphonate, decylphosphone Dihexyl acid, dioctyl decylphosphonate, didecyl decylphosphonate, dimethyl dodecylphosphonate, diethyl dodecylphosphonate, dipropyl dodecylphosphonate, dibutyl dodecylphosphonate, dihexyl dodecylphosphonate, dioctyl dodecylphosphonate, didecyl dodecylphosphonate, dodecylphosphone Didodecyl acid, dimethyl tetradecylphosphonate, diethyl tetradecylphosphonate, dipropyl tetradecylphosphonate, dibutyl tetradecylphosphonate, dihexyl tetradecylphosphonate, dioctyl tetradecylphosphonate, dodecyl tetradecylphosphonate, diddecyl tetradecylphosphonate , Tetetradecyl tetradecylphosphonate, dimethyl hexadecylphosphonate, diethyl hexadecylphosphonate, dipropyl hexadecylphosphonate, dibutyl hexadecylphosphonate, dihexyl hexadecylphosphonate, dioctyl hexadecylphosphonate, didecyl hexadecylphosphonate, hexa Didecyl decylphosphonate, ditetradecyl hexadecylphosphonate, dimethyl octadecylphosphonate, diethyl octadecylphosphonate, dipropyl octadecylphosphonate, dibutyl octadecylphosphonate, dipentyl octadecylphosphonate, dihexyl octadecylphosphonate, diheptyl octadecylphosphonate, octadecylphosphonic acid Dioctyl, dioctadecyl octadecylphosphonate and the like can be mentioned.

The amounts of the (C1) phosphonate ester oligomer and the (C2) phosphonate ester are not particularly limited, but the phosphorus atom content is preferably 100 to 2000 mass ppm with respect to the total mass of the lubricating oil composition. , 180 to 1800 mass ppm is more preferable, and 200 to 1700 mass ppm is further preferable. If the content exceeds the above upper limit, sludge may be generated, which is not preferable. If the content is less than the above lower limit, wear is likely to be high, which is not preferable.

The lubricating oil composition of the present invention can further contain at least one (C3) phosphite ester as a phosphorus-based extreme pressure agent.

The (C3) phosphite ester is, for example, a compound represented by the following formula (7) or (8).
(R ⁶ O) _b P (= O) (OH) _2-b H (7)
(R ⁷ O) ₃ P (8)
In the above formula (7), b = 1 or 2, and R ⁶ is a hydrocarbon group independently of each other. In the above formula (8), R ⁷ is a hydrocarbon group independently of each other. The number of carbon atoms of ^{R 6} and R ^{7 is not particularly limited.}

In the above formula (7), R ⁶ is preferably an alkyl group having 4 to 30 carbon atoms, more preferably an alkyl group having 4 to 20 carbon atoms, still more preferably an alkyl group having 4 to 12 carbon atoms, most preferably. Is preferably an alkyl group having 4 to 8 carbon atoms. In the above formula (8), R ⁷ is preferably an alkyl group having 4 to 30 carbon atoms, more preferably an alkyl group having 4 to 20 carbon atoms, still more preferably an alkyl group having 4 to 12 carbon atoms, and most preferably. It is an alkyl group having 4 to 8 carbon atoms.

Examples of the phosphite ester include phosphite tributyl ester, phosphite dibutyl ester, phosphite monobutyl ester, phosphite tripentyl ester, phosphite dipentyl ester, phosphite monopentyl ester, and sub. Trihexyl phosphate, dihexyl phosphite, monohexyl phosphite, triheptyl phosphite, diheptyl phosphite, monoheptyl phosphite, trioctyl phosphite, phosphite Examples include dioctyl ester and monooctyl phosphite ester. Of these, phosphorous acid tributyl ester, phosphorous acid tripentyl ester, phosphorous acid trihexyl ester, phosphorous acid triheptyl ester, and phosphorous acid trioctyl ester are preferable.
The content of the (C3) phosphite ester is not particularly limited, but the phosphorus atom content is preferably 50 to 1000 mass ppm, preferably 100 to 800 mass ppm, with respect to the total mass of the lubricating oil composition. Is more preferable, and 200 to 800 mass ppm is further preferable. If the content exceeds the above upper limit, sludge may be generated, which is not preferable. If the content is less than the above lower limit, wear is likely to be high, which is not preferable.

The lubricating oil composition of the present invention can further contain at least one selected from the amine salt of (C4) phosphate ester and the amine salt of (C5) thiophosphate ester.

What is the amine salt of (C4) phosphate ester? (R ¹ O) _b P (= O) (OH) _3-b · (NH _c R ² O _3-c ) _3-b , especially acidic phosphorus The amine salt of the acid ester is used. In the above formula, b, c = 1 or 2, and b, c may be a mixture of compounds having different values. In the above formula, R ¹ and R ² are monovalent hydrocarbon groups having 4 to 30 carbon atoms independently of each other, and may be linear or have branches. As the monovalent hydrocarbon group, an alkyl group having 4 to 30 carbon atoms is preferable. It is preferably an alkyl group having 4 to 20 carbon atoms, and more preferably an alkyl group having 4 to 16 carbon atoms. The component (C4) may be used alone or in combination of two or more.

The amount of the amine salt of the (C4) phosphoric acid ester is not particularly limited, but the phosphorus atom content is preferably 100 to 1500 mass ppm, and 180 to 1200 mass, based on the total mass of the lubricating oil composition. ppm is more preferred, and 200-1000 mass ppm is even more preferred. If the content exceeds the above upper limit, sludge may be generated, which is not preferable. If the content is less than the above lower limit, wear is likely to be high, which is not preferable. When two or more kinds of amine salts of phosphoric acid esters are used in combination, they may be blended so that the total phosphorus atom content satisfies the above range.

The amine salt of the (C5) thiophosphate ester is represented by (R ³ O) _d P (= X) (XH) _3-d · (NH _e R ⁴ O _3-e ) _3-d . In the above formula, it may be a mixture of compounds in which d, e = 1 or 2 and d, e have different values. X is an oxygen atom or a sulfur atom, but at least one is an oxygen atom. In the above formula, R ³ and R ⁴ are alkyl groups having 4 to 30 carbon atoms independently of each other, and may be linear or have a branch. It is preferably an alkyl group having 4 to 20 carbon atoms, and more preferably an alkyl group having 4 to 16 carbon atoms. The component (C5) may be used alone or in combination of two or more.

The amount of the amine salt of the (C5) thiophosphate ester is not particularly limited, but the phosphorus atom content is preferably 100 to 1500 mass ppm, and 180 to 1200 mass, based on the total mass of the lubricating oil composition. ppm is more preferred, and 200-1000 mass ppm is even more preferred. If the content exceeds the above upper limit, sludge may be generated, which is not preferable. If the content is less than the above lower limit, wear is likely to be high, which is not preferable. When two or more kinds of amine salts of thiophosphates are used in combination, they may be blended so that the total phosphorus atom content satisfies the above range.

The amount of the (C) phosphorus-based extreme pressure agent in the lubricating oil composition is not particularly limited, but the phosphorus atom content with respect to the total mass of the lubricating oil composition is preferably 1000 to 2500 mass ppm, preferably 1100 to 2300 mass. ppm is more preferred, and 1300 to 2200 mass ppm is even more preferred. If the content exceeds the above upper limit, sludge may be generated, which is not preferable. If the content is less than the above lower limit, friction is likely to increase, which may not contribute to fuel efficiency, which is not preferable. When two or more kinds are used in combination, they may be blended so that the total phosphorus atom content satisfies the above range.

(D) Ash-free dispersant In the present invention, the (D) ash-free dispersant may be any conventionally known one, and is not particularly limited, but is preferably polyalkylene succinimide or a boronized product thereof.

The ashless dispersant may or may not have boron. Examples thereof include a nitrogen-containing compound having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule or a derivative thereof, which has a linear structure or a branched structure, or a modified product of alkenyl succinimide. .. One type of ashless dispersant may be used alone, or two or more types may be used in combination. It is also possible to use a borated ashless dispersant. Borylated ashless dispersant is a boronized version of any ashless dispersant used in lubricating oils. Borylation is generally carried out by allowing boric acid to act on the nitrogen-containing compound to neutralize some or all of the remaining amino and / or imino groups.

The alkyl group or alkenyl group preferably has 40 to 400 carbon atoms, and more preferably 60 to 350 carbon atoms. When the number of carbon atoms of the alkyl group and the alkenyl group is less than the above lower limit value, the solubility of the compound in the lubricating oil base oil tends to decrease. Further, when the carbon number of the alkyl group and the alkenyl group exceeds the above upper limit value, the low temperature fluidity of the lubricating oil composition tends to deteriorate. The alkyl group and the alkenyl group may have a linear structure or a branched structure. Preferred embodiments include, for example, olefin oligomers such as propylene, 1-butene and isobutylene, branched alkyl groups derived from ethylene and propylene co-oligomers, branched alkenyl groups and the like.
The succinimide includes a so-called monotype succinimide in which succinic anhydride is added to one end of the polyamine, and a so-called bis-type succinimide in which succinic anhydride is added to both ends of the polyamine. The lubricating oil composition of the present invention may contain either monotype or bistype, or may contain both.

For example, as a method for producing an imide boronated succinimide, it is disclosed in Japanese Patent Application Laid-Open No. 42-8013 and 42-8014, Japanese Patent Application Laid-Open No. 51-52381, Japanese Patent Application Laid-Open No. 51-130408, and the like. The method used is mentioned. Specifically, for example, organic solvents such as alcohols, hexane, and xylene, polyamines in light lubricating oil base oils, and boron compounds such as boric acid, borate ester, and borate in polyalkenylsuccinic acid (anhydrous). Can be obtained by mixing and heat-treating under appropriate conditions. The boron content of the boronized succinimide thus obtained can be usually 0.1 to 4% by mass. In particular, a boron-modified compound (borated succinimide) of an alkenyl succinimide compound is preferable because it is excellent in heat resistance, antioxidant property and wear resistance.

The boron content contained in the boronized ashless dispersant is not particularly limited, but is preferably 0.01% by mass to 7% by mass, and more preferably 0.1 to 5% by mass. The boronized ashless dispersant is preferably an imide borated succinimide, and particularly preferably an imide borated bisuccinate. The boronized ashless dispersant is not particularly limited in the boron / nitrogen mass ratio (B / N ratio), but has a boron / nitrogen mass ratio (B / N ratio) of 0.1 or more, preferably 0.2 or more, preferably less than 0.5, more preferably. Is preferably 0.4 or less.

The component (D) preferably has 0.1 to 3% by mass, more preferably 0.1 to 2% by mass, and most preferably 0.2 to 1% by mass in the lubricating oil composition.
When the boronized polyalkylene succinimide is used, the boron content contained in the lubricating oil composition is not particularly limited, but is preferably 60 to 400 ppm, preferably 100 to 380 ppm. Is more preferable.

Other Additives The lubricating oil composition of the present invention may contain other known additives in addition to the above components (A) to (D). Examples include friction modifiers, anti-wear agents, metal cleaners, antioxidants, metal inactivating agents, viscosity index improvers, defoamers, pour point lowering agents, anti-emulsifiers, and rust inhibitors. it can. These additives may be used alone or in combination of two or more.

As the friction modifier, either a molybdenum-containing friction modifier or an organic friction modifier can be used, and the molybdenum-containing friction modifier includes molybdenum dithiophosphate (MoDTP), molybdenum dithiocarbamate (MoDTC), and the like. Organic molybdenum compounds and the trinuclear molybdenum compounds described in US Pat. No. 5,906,968 can be used, and examples of the organic friction modifier include esters, amines, amides, and sulfide esters. .. The above-mentioned friction modifier having molybdenum can be blended in the lubricating oil composition as a molybdenum content of 30 to 800 mass ppm, and when the above-mentioned organic friction modifier is used, the lubricating oil composition is usually used. It is blended in 0.01 to 3% by mass.

As the anti-wear agent, conventionally known ones can be used. Among them, a wear inhibitor having phosphorus is preferable, and zinc dithiophosphate (ZnDTP (also referred to as ZDDP)) represented by the following formula is particularly preferable.

In the above formula, R ¹ and R ² may be the same or different from each other, and are a hydrogen atom or a monovalent hydrocarbon group having 1 to 26 carbon atoms. The monovalent hydrocarbon group includes a primary (primary) or secondary (secondary) alkyl group having 1 to 26 carbon atoms; an alkenyl group having 2 to 26 carbon atoms; a cycloalkyl group having 6 to 26 carbon atoms; carbon. An aryl group, an alkylaryl group or an arylalkyl group of number 6 to 26; or a hydrocarbon group containing an ester bond, an ether bond, an alcohol group or a carboxyl group. R ¹ and R ² are preferably a primary or secondary alkyl group having 2 to 12 carbon atoms, a cycloalkyl group having 8 to 18 carbon atoms, and an alkylaryl group having 8 to 18 carbon atoms, respectively. They may be the same or different from each other. In particular, zinc dialkyldithiophosphate is preferable, and the primary alkyl group preferably has 3 to 12 carbon atoms, and more preferably 4 to 10 carbon atoms. The secondary alkyl group preferably has 3 to 12 carbon atoms, and more preferably 3 to 10 carbon atoms. The above zinc dithiophosphate may be used alone or in combination of two or more. Moreover, zinc dithiocarbamate (ZnDTC) may be used in combination.

When an anti-wear agent is used, it is usually blended in the lubricating oil composition in an amount of 0.1 to 5.0% by mass, preferably 0.2 to 3.0% by mass. The amount of phosphorus in the lubricating oil composition is not limited, but is preferably 100 to 1500 ppm, more preferably 200 to 1400 ppm, and most preferably 300 to 1300 ppm.

As the metal cleaning agent, known ones can be used. For example, a cleaning agent having an alkali metal or an alkaline earth metal can be used. As the alkali metal or alkaline earth metal, it is preferable to use sodium, calcium, magnesium, and barium.

Examples of metal detergents include sodium salicylate, sodium sulfonate, sodium phenate, sodium carboxylate, calcium salicylate, calcium sulfonate, calcium phenate, calcium carboxylate, magnesium salicylate, magnesium sulfonate, magnesium phenylate, and magnesium carboxylate. Can be mentioned. Of these, calcium salicylate, calcium sulfonate, calcium phenate, calcium carboxylate, magnesium salicylate, magnesium sulfonate, magnesium phenate, and magnesium carboxylate are preferable, and calcium salicylate, calcium sulfonate, magnesium salicylate, and magnesium sulfonate are more preferable. .. These metal cleaning agents may be used alone or in combination of two or more. When two or more kinds are used in combination, the same kind (for example, calcium salicylate) having different base values can be used. In addition, when used in combination, even if the calcium purifying agent and the magnesium purifying agent are used in combination, one kind selected from calcium salicylate and calcium sulfonate and one kind selected from magnesium salicylate and magnesium sulfonate are mixed. Good.

The base value of the metal cleaning agent is preferably 5 to 450 mg / KOH · g, more preferably 70 to 400 mg / KOH · g, and most preferably 100 to 400 mg / KOH · g.

As the metal inactivating agent, known substances can be used. For example, benzotriazole, 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate and the like can be mentioned. The metal inactivating agent is not particularly limited, but is preferably blended in the lubricating oil composition in an amount of 0.01 to 5% by mass.

A known viscosity index improver can be used. Examples of the viscosity index improver include polymethacrylate, dispersed polymethacrylate, olefin copolymer (polyisobutylene, ethylene-propylene copolymer), dispersed olefin copolymer, polyalkylstyrene, styrene-butadiene hydrogenated copolymer, and the like. Examples thereof include those containing a styrene-maleic anhydride copolymer, stellate isoprene and the like. Further, a comb-shaped polymer containing at least a repeating unit based on polyolefin macromer and a repeating unit based on an alkyl (meth) acrylate having an alkyl group having 1 to 30 carbon atoms in the main chain can also be used.

The viscosity index improver usually consists of the above polymer and a diluent oil. When it is not necessary to reduce the viscosity, the addition is not particularly limited, but it is preferably 0.001 to 20% by mass, more preferably 0.1 to 20% by mass, and 1 to 15% by mass. It is preferable to do so. However, in order to reduce the viscosity, it is preferable not to add it, and even if it is added, it is preferably 0.001 to 1% by mass in the lubricating oil composition, and 0.001 to 0.5. More preferably, it is by mass.

Examples of the defoaming agent include silicone oil having a kinematic viscosity at 25 ° C. of 10 to 100,000 mm ² / s, an alkenyl succinic acid derivative, an ester of a polyhydroxy fatty alcohol and a long-chain fatty acid, methyl salicylate and o-. Hydroxybenzyl alcohol and the like can be mentioned. The content of the defoaming agent is not limited, but is blended in the lubricating oil composition in an amount of 0.001 to 1% by mass.

As the pour point lowering agent, for example, a polymethacrylate-based polymer compatible with the lubricating oil base oil used can be used. The content of the pour point lowering agent is not limited, but is preferably blended in the lubricating oil composition in an amount of 0.01 to 3% by mass.

Examples of the anti-emulsifier include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether. The content of the anti-emulsifier is not limited, but is preferably blended in the lubricating oil composition in an amount of 0.01 to 5% by mass.

Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, polyhydric alcohol ester and the like. The content of the rust preventive is not limited, but it is preferably blended in the lubricating oil composition in an amount of 0.01 to 5% by mass.

In order to ensure fuel efficiency, the lubricating oil composition of the present invention has a kinematic viscosity at 100 ° C. of ^{2 to 10 mm 2 / s, preferably 2 to} 8 mm 2 / s, and preferably 3 to ^{8 mm 2} / s. Is preferable.

The sulfur content in the lubricating oil composition is preferably 0.3 to 5% by mass, more preferably 0.4 to 4% by mass, and even more preferably 0.5 to 3% by mass.

The phosphorus content in the lubricating oil composition is preferably 1000 to 2500 ppm, more preferably 1100 to 2300 mass ppm, still more preferably 1300 to 2200 mass ppm.

The boron content in the lubricating oil composition is preferably 60 to 400 ppm, more preferably 100 to 380 ppm.

The lubricating oil composition of the present invention is not particularly limited, but can be suitably used as a lubricating oil for automobiles, particularly a lubricating oil for hybrid automobiles. Further, the lubricating oil composition of the present invention can be suitably used as a lubricating oil for a transmission oil and a lubricating oil for a gear oil.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
The components constituting the lubricating oil compositions of Examples and Comparative Examples are as follows.

(A) Lubricating oil base oil (A-1) Mineral oil (kinematic viscosity at 100 ° C. = 5 mm ² / s) (hereinafter referred to as mineral oil-1)
(A-2) Mineral oil (kinematic viscosity at 100 ° C. = 12 mm ² / s) (hereinafter referred to as mineral oil-2)
(A-3) Diester (diisodecyl adipate) (hereinafter referred to as ester-1)
(A-4) Triester (trimethylolpropane isostearate) (hereinafter referred to as ester-2)
(A-5) GTL base oil (kinematic viscosity at 100 ° C. = 4 mm ² / s) (hereinafter referred to as GTL-1)
(A-6) GTL base oil (kinematic viscosity at 100 ° C. = 8 mm ² / s) (hereinafter referred to as GTL-2)

(B) Sulfur-based extreme pressure agent (B-1) 2,5-bis (dioctyldithio) -1,3,4-thiadiazole (hereinafter referred to as high sulfur thiadiazole-1)
(B-2) 2,5-bis (di2'-ethylhexyl) dithio) -1,3,4-thiadiazole (hereinafter referred to as high sulfur thiadiazole-2)
(B-4) Sulfide olefin (active sulfur amount 11% by mass) (hereinafter referred to as sulfide olefin-1)
(B-5) Olefin sulfide (32% by mass of active sulfur) (hereinafter referred to as olefin-2 sulfide)
(B-6) Sulfide fats and oils (active sulfur amount 4.1% by mass)
(B-7) Sulfate ester (active sulfur amount 1.4% by mass)

(B') Comparative sulfur-based extreme pressure agent (B-3) 2,5-dimethyl-1,3,4-thiadiazole represented by the following formula (hereinafter referred to as low-sulfur thiadiazole)

(C) Phosphorus-based extreme pressure agent (C-1) Phosphonate ester oligomer:
In the above-mentioned general formula (1), a mixture of compounds in which R is an alkyl group having 1 to 4 carbon atoms and n is 3 to 6 (hereinafter, referred to as phosphonate ester oligomer A).
(C-2) Phosphonate ester oligomer:
In the above-mentioned general formula (1), a mixture of compounds in which R is an alkyl group having 2 to 5 carbon atoms and n is 2 to 10 (hereinafter, referred to as phosphonate ester oligomer B).
(C-3) Phosphonate ester having an alkyl group having 18 carbon atoms (C-4) Phosphite ester having an alkyl group having 4 carbon atoms (C-5) Thiophosphate ester amine salt (with 4 to 12 carbon atoms) Mixtures of those with alkyl groups)
(C-6) Phosphate ester amine salt (mixture of those having an alkyl group having 4 to 12 carbon atoms)
(C-7) Acidic phosphate ester having an alkyl group having 4 carbon atoms

(D) Ash-free dispersant (D-1) Boron-modified polyisobutenyl succinimide (bisimide type, polybutenyl group molecular weight 2,000, nitrogen 1.7% by mass, boron 1.9% by mass)

(E) Molybdenum friction modifier (E-1) Molybdenum dithiocarbamate (MoDTC, molybdenum content 10% by mass)
(F) Other additives Oleic acid amide, pour point lowering agent

Examples 1-12 and Comparative Examples 1-5
Lubricating oil compositions were prepared by mixing the amounts of each component shown in Tables 1 and 2.
The amount of the sulfur-based extreme pressure agent is a part by mass, and the value described in parentheses is the mass% of sulfur with respect to the mass of the entire lubricating oil composition.
The amount of the phosphorus-based extreme pressure agent is a part by mass, and the value described in parentheses is the mass% of phosphorus with respect to the mass of the entire lubricating oil composition.
The amount of the molybdenum friction-soluble material is a part by mass, and the value described in parentheses is the mass% of molybdenum with respect to the mass of the entire lubricating oil composition.
The amount of ashless dispersant and other additives is by weight. The amount of the base oil is 100 parts by mass and the balance of the entire lubricating oil composition.

The following tests were carried out on the obtained composition. The results are shown in Tables 2 and 4.
(1) Bearing side wear:
Using a four-ball wear tester defined by ASTM D4172, a test was conducted under the following conditions, and the average value of the wear scar diameters of the three lower balls was calculated. Oil temperature: 40 ° C, load: 40 kgf, rotation speed: 100 rpm, time: 60 minutes. The case where the wear mark diameter was 0.45 mm or less was regarded as acceptable.
(2) Scoring resistance Using a four-ball wear tester specified by ASTM D4172, a test was conducted under the following conditions, and the number of revolutions when seizure occurred was recorded. Oil temperature: room temperature, load: 100 kgf, rotation speed: increase by 100 rpm every 30 seconds. The case where the rotation speed (rpm) was 800 or more was regarded as a pass.
(3) Seizure resistance of differential part A block test piece with a sliding surface width of 6 mm (FALEX standard test piece made of steel (SAE O1) (hardness RC58-63)) and a mating outer diameter of 35 mm and width. A block-on-ring seizure test was performed using a ring test piece having a diameter of 9 mm and made of a steel material (FALEX standard test piece (hardness RC58-63) made of a steel material (SAE4620)). With a rotation speed of 1000 rpm, an oil amount of 10 μL, and an oil temperature of room temperature, the load was increased by 44.5 N, and the surface pressure (GPa) when seizure occurred was calculated. A seizure-generating surface pressure of 0.31 (GPa) or higher was considered acceptable.

As shown in Table 4, when the ^{viscosity of the conventional lubricating oil composition is reduced to KV100 = 7 mm 2} / s as shown in Comparative Example 1, the oil film forming ability is low and the wear is large, and the scoring resistance and differential are increased. Partial seizure resistance is inferior. On the other hand, as shown in Tables 3 and 4 above, the lubricating oil composition of the present invention contains (B1) high-sulfur thiadiazol and a specific phosphorus-based extreme pressure agent (C1) or (C2). Even if the viscosity of KV100 is ^{reduced to KV100 = 7 mm 2} / s, it is possible to have excellent wear prevention property, excellent scoring resistance and seizure resistance of the differential portion (Examples 1 to 12). Although the phosphorus-based extreme pressure agent (C2) of the present invention is contained, the composition of Comparative Example 5 containing low-sulfur thiadiazole is inferior in scoring resistance, and contains high-sulfur thiadiazole but contains a phosphorus-based extreme pressure agent (C1). The composition of Comparative Example 4 containing neither (C2) nor (C2) is inferior in abrasion resistance.

The lubricating oil composition of the present invention can be suitably used particularly for hybrid vehicles, transmissions, and gear oils.

1 Load 2 Block test piece 3 Ring test piece 4 Lubricating oil composition

Claims (14)

(A) Lubricating oil base oil,
(B) Sulfur-based extreme pressure agent,
A lubricating oil composition containing (C) a phosphorus-based extreme pressure agent and (D) an ashless dispersant.
The (B) sulfur-based extreme pressure agent contains (B1) thiadiazole, the thiadiazole has two or more sulfur atoms, and (C1) the following formula (1) as the (C) phosphorus-based extreme pressure agent. It is characterized by containing at least one selected from the phosphonate ester oligomer represented by (C2) and the (C2) phosphonate ester.
The lubricating oil composition having a kinematic viscosity of ^{2 to 10 mm 2 / s at 100 ° C.}

(In the formula (1), R is a monovalent hydrocarbon group having 1 to 20 carbon atoms independently of each other, and n is an integer of 2 to 10). The lubricating oil composition according to claim 1, wherein the lubricating oil base oil (A) contains at least one selected from a diester and a triester. The thiadiazole having two or more (B1) sulfur atoms is 2,5-bis (hydrocarbyldithio) -1,3,4-thiadiazole, 2,5-bis (hydrocarbylthio) -1,3,4-thiadiazole, The invention according to claim 1 or 2, which comprises at least one selected from 2-mercapto-5-hydrocarbyldithio-1,3-4-thiadiazole and 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazole. Lubricating oil composition. The one according to any one of claims 1 to 3, wherein the (B) sulfur-based extreme pressure agent contains at least one selected from (B2) sulfide olefin, (B3) sulfide oil and fat, and (B4) sulfide ester. Lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 4, wherein the sulfur-based extreme pressure agent (B) has an active sulfur amount of 0.1 to 40% by mass. The lubricating oil composition according to any one of claims 1 to 5, wherein the (C) phosphorus-based extreme pressure agent further contains at least one (C3) phosphite ester. The invention according to any one of claims 1 to 6, wherein the (C) phosphorus-based extreme pressure agent further comprises at least one selected from (C4) an amine salt of a phosphoric acid ester and (C5) an amine salt of a thiophosphate ester. Lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 7, wherein the (D) ashless dispersant is an imide polyalkylene succinimide. The lubricating oil composition according to any one of claims 1 to 8, wherein the sulfur content is 0.3 to 5% by mass with respect to the total mass of the lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 9, wherein the phosphorus content is 1000 to 2500 mass ppm with respect to the total mass of the lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 10, wherein the boron content is 60 to 400 mass ppm with respect to the total mass of the lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 11, which is used for a hybrid vehicle. The lubricating oil composition according to any one of claims 1 to 12, which is used for transmission oil. The lubricating oil composition according to any one of claims 1 to 12, which is used for gear oil.

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