WO2018021570A1

WO2018021570A1 - Lubricating oil composition

Info

Publication number: WO2018021570A1
Application number: PCT/JP2017/027565
Authority: WO
Inventors: 布治馬守; 植野　賢治; 光太郎平賀
Original assignee: エクソンモービルリサーチアンドエンジニアリングカンパニー; トヨタ自動車株式会社
Priority date: 2016-07-28
Filing date: 2017-07-28
Publication date: 2018-02-01
Also published as: EP3492565A4; JP6730122B2; JP2018016729A; SG11201900556SA; US20190177647A1; EP3492565A1

Abstract

The purpose of the present invention is to provide a lubricating oil composition that can suppress wear of bearings and the like and scoring of gear teeth surfaces and the like even at low viscosity. Provided is a lubricating oil composition that includes a lubricating oil base oil, a sulfur-based extreme pressure agent, and a phosphorus-based extreme pressure agent, wherein the lubricating oil composition is characterized in that: the quantity of active sulfur in the sulfur-based extreme pressure agent is 5-30% by mass; the sulfur-based extreme pressure agent is included in the composition at a quantity of 5-15% by mass relative to the mass of the entire lubricating oil composition; and the phosphorus-based extreme pressure agent is included in the composition at a quantity of 1.5-8% by mass relative to the mass of the entire lubricating oil composition.

Description

Lubricating oil composition

The present invention relates to a lubricating oil composition. In particular, the present invention relates to an automotive lubricating oil composition that can be applied to a differential gear and has a reduced viscosity.

Lubricating oil compositions are used in a wide variety of applications such as automobiles and machines. In recent years, lowering the viscosity of automotive lubricating oil compositions has been demanded from the viewpoint of fuel efficiency. However, lowering the viscosity of the lubricating oil composition affects the oil film forming ability. In particular, in the field of automotive gear oils, and more particularly in lubricating oils used for differential gears, reducing the viscosity of the lubricating oil causes problems such as the occurrence of wear on bearings and the occurrence of scoring on gear tooth surfaces. Therefore, it was difficult to cope with the low viscosity. Therefore, it is hoped to develop a gear oil composition for automobiles, particularly a differential gear oil composition, which can suppress wear on bearings and the like under conditions where oil film formation is difficult at high temperatures even with low viscosity oil. It is rare.

The inventors of the present invention can reduce the viscosity of a lubricating oil by using a low-viscosity base oil and a high-viscosity base oil in advance, and at the same time, can achieve bearing fatigue life characteristics and fuel economy that are particularly affected by oil film forming ability. And the invention described in Japanese Patent Application Laid-Open No. 2007-039480 (Patent Document 1) was made. However, the lubricating oil composition described in Patent Document 1 has room for improvement in wear resistance in bearings and the like and scoring prevention properties in gear tooth surfaces and the like.

Japanese Patent Application Laid-Open No. 2014-012855 (Patent Document 2) discloses specific acidic phosphoric acid alkyl esters, dialkylamines and / or trialkylamines, and a specific compound which does not contain a polysulfur bond of -SSSS or higher. A lubricating oil composition is disclosed consisting of a sulfur compound, and optionally certain thiophosphate trihydrocarbyl esters. However, the lubricating oil composition described in Patent Document 2 relates to a wind speed gearbox oil composition that requires seizure resistance and fatigue resistance, and there is no description regarding scoring.

Japanese Patent Laid-Open No. 2007-039480 JP 2014-012855 A

Therefore, the present invention has an object to provide a lubricating oil composition capable of suppressing the occurrence of wear on bearings and the like and scoring on gear tooth surfaces and the like even when the viscosity is lowered.

The present inventors have found that the above problem can be achieved by blending together a specific amount of an extreme pressure agent having a specific active sulfur amount and a specific amount of a phosphorus extreme pressure agent in the lubricating oil composition. Invented the invention.

That is, the present invention provides a lubricating oil composition comprising (A) a lubricating base oil, (B) a sulfur-based extreme pressure agent, and (C) a phosphorus-based extreme pressure agent, wherein (B) the sulfur-based electrode. The active sulfur amount of the pressure agent is 5 to 30% by mass, and the (B) sulfur-based extreme pressure agent is contained in the composition in an amount of 5 to 15% by mass with respect to the total mass of the lubricating oil composition, C) The lubricating oil composition is provided, wherein the phosphorus-based extreme pressure agent is contained in the composition in an amount of 1.5 to 8% by mass relative to the total mass of the lubricating oil composition.

Preferred embodiments of the present invention further have at least one of the following features (1) to (9).
(1) The sulfur-based extreme pressure agent (B) is a sulfurized olefin.
(2) The phosphorous extreme pressure agent (C) is phosphoric acid ester, acidic phosphoric acid ester, phosphorous acid ester, acidic phosphorous acid ester, thiophosphoric acid ester, acidic thiophosphoric acid ester, thiophosphorous acid ester, acidic It is at least one selected from a thiophosphite ester, an amine salt of an acidic phosphate ester, an amine salt of an acidic phosphite ester, an amine salt of an acidic thiophosphate ester, and an amine salt of an acidic thiophosphite ester.
(3) The (C) phosphorus extreme pressure agent is selected from an amine salt of an acidic phosphate, an amine salt of an acidic phosphite, an amine salt of an acidic thiophosphate, and an amine salt of an acidic thiophosphite At least one kind.
(4) The lubricating oil composition has a kinematic viscosity at 100 ° C. of 3 to 40 mm ² / s.
(5) At least one part of the (A) lubricating base oil is a GTL (Gas to Liquid) derived base oil.
(6) At least one part of the (A) lubricating base oil is a poly-α-olefin (PAO) base oil.
(7) The lubricating base oil (A) has a kinematic viscosity at 100 ° C. of 3 to 40 mm ² / s.
(8) The lubricating oil composition is a lubricating oil composition for a transmission.
(9) The lubricating oil composition is a differential gear lubricating oil composition.

The lubricating oil composition of the present invention can suppress the occurrence of wear on bearings and scoring on gear tooth surfaces even when the viscosity is lowered. The lubricating oil composition of the present invention can be suitably used as a lubricating oil for automobiles, and further suitable as a transmission gear oil and a differential gear oil.

Hereinafter, the present invention will be described in more detail.

(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 base oil include mineral base oils, synthetic base oils, and mixed base oils thereof.

The production method of the mineral base oil is not limited. Mineral oil base oils include highly refined paraffinic mineral oils (high viscosity index mineral oil base oils obtained by subjecting hydrorefined oil, catalytic isomerized oil, etc. to solvent dewaxing or hydrodewaxing, etc. ) Is preferred. Examples of mineral base oils other than the above include, for example, raffinates obtained by solvent refining using lube oil as an aromatic extraction solvent such as phenol and furfural, hydrogen such as cobalt and molybdenum using silica-alumina as a carrier. And hydrotreated oil obtained by hydrotreating using a hydrotreating catalyst. For example, 100 neutral oil, 150 neutral oil, 500 neutral oil, etc. can be mentioned.

Examples of synthetic base oils include base oils obtained by hydrocracking and hydroisomerization of raw materials such as wax obtained from natural gas such as methane by Fischer-Tropsch synthesis, etc. (so-called GTL-derived bases) Oil), PAO base oil, polybutene, alkylbenzene, polyol ester, polyglycol ester, dibasic acid ester, fatty acid ester, phosphate ester, and silicon oil. Of these, GTL-derived base oil and PAO base oil are preferable.

As long as the lubricating base oil is selected from the above mineral base oil, the above synthetic base oil, or a combination thereof, one kind may be used alone, or two or more kinds may be used in combination. When two or more kinds of lubricating base oils are used in combination, they may be mineral base oils, synthetic base oils, or a combination of mineral oil base oils and synthetic base oils, and the mode is not limited. In particular, a combination of a mineral base oil and a synthetic base oil is suitable.

When the mineral base oil and the synthetic base oil are used in combination, at least one selected from GTL-derived base oil and PAO base oil is preferably used as the synthetic base oil. The preferred mode of combined use is
(1) A combination of a mineral oil base oil and a GTL-derived base oil,
(2) Combination of mineral oil base oil and PAO base oil,
(3) A combination of a mineral oil base oil, a GTL-derived base oil, and a PAO base oil, or (4) A combination of a GTL-derived base oil and a PAO base oil.
Among them, the combination of (3) mineral oil base oil, GTL-derived base oil, and PAO base oil is particularly preferable.

The mineral oil base oil is not limited to those produced by the above production method, but preferably has a kinematic viscosity at 100 ° C. of 2 to 35 mm ² / s, more preferably 2 to 20 mm ² / s. More preferably, it is 3 to 10 mm ² / s.

The GTL-derived base oil is not particularly limited, but preferably has a kinematic viscosity of 2 to 40 mm ² / s at 100 ° C., more preferably 2 to 20 mm ² / s, and even more preferably 2 to 10 mm. ^It should be ² / s.

The PAO base oil is not particularly limited, and for example, 1-octene oligomer, 1-decene oligomer, ethylene-α-olefin oligomer, ethylene-propylene oligomer, isobutene oligomer and hydrides thereof can be used. The PAO base oil preferably has a kinematic viscosity at 100 ° C. of 2 to 200 mm ² / s, more preferably 2 to 150 mm ² / s, and even more preferably 4 to 50 mm ² / s.

The kinematic viscosity of the lubricating 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, the entire lubricating base oil preferably has a kinematic viscosity at 100 ° C. of 3 to 40 mm ² / s, more preferably 4 to 20 mm ² / s. Preferably it has 5 to 15 mm ² / s, particularly preferably 6 to 12 mm ² / s. If the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds the upper limit, it may be difficult to lower the viscosity of the lubricating oil composition, and it may be difficult to achieve fuel economy. Further, if the kinematic viscosity at 100 ° C. is less than the lower limit, fuel saving can be achieved, but it may be difficult to ensure wear prevention and scoring prevention.

(B) Sulfur-based extreme pressure agent The lubricating oil composition of the present invention contains a sulfur-based extreme pressure agent as an essential component. The sulfur-based extreme pressure agent used in the present invention is required to have an active sulfur amount of 5 to 30% by mass, preferably 5 to 20% by mass, more preferably 5 to 15% by mass, and particularly preferably 8%. ~ 12% by mass. If the amount of active sulfur exceeds the above upper limit, not only metal corrosion will occur, but it will be difficult to ensure wear resistance. On the other hand, if the amount of active sulfur is less than the lower limit, it is difficult to ensure scoring prevention.

Here, the amount of active sulfur is measured by the method prescribed in ASTM D1662. More specifically, the amount of active sulfur based on ASTM D1662 can be measured by the following procedure.
(1) Put 50 g of sample and 5 g of copper powder (purity 99% or more, particle size 75 μm or less) into a 200 ml beaker and heat to 150 ° C. while stirring with a stirrer (500 rpm).
(2) When the temperature reaches 150 ° C., 5 g of copper powder is further added and stirred for 30 minutes.
(3) Stop stirring and place a copper plate conforming to ASTM D130 into a beaker and immerse for 10 minutes. At this time, if discoloration is observed on the copper plate, 5 g of copper powder is further added and stirred for 30 minutes (this operation is continued until no discoloration of the copper plate is observed).
(4) When copper plate discoloration is no longer observed, the copper powder in the sample is filtered and the amount of sulfur contained in the filtrate is measured.
The amount of active sulfur (mass%) is “the amount of sulfur contained in the original sample (procedure 1) (mass%) − the amount of sulfur contained in the filtrate after the reaction with copper powder (procedure 4 above) %) ”.

The sulfur-based extreme pressure agent in the present invention is not particularly limited as long as it has the above-mentioned specific amount of active sulfur, and can be selected from known sulfur-based extreme pressure agents. Preferably, it is at least one selected from sulfide compounds typified by sulfurized olefins and sulfurized esters typified by sulfurized fats and oils, and sulfurized olefins are particularly preferable. In the present invention, the extreme pressure agent having sulfur and phosphorus, such as thiophosphate, is included in the (C) phosphorus extreme pressure agent described later, and therefore not included in the (B) sulfur extreme pressure agent. . Further, the sulfur-based extreme pressure agent of the present invention does not include zinc dithiophosphate.

The sulfur-based extreme pressure agent used in the present invention is represented by, for example, the following general formula (1).
R ¹ -(-S-) _x -R ² (1)
In the above formula (1), R ¹ and R ² are each independently a monovalent substituent, and contain at least one element of carbon, hydrogen, oxygen, and sulfur. Specifically, for example, a saturated or unsaturated hydrocarbon group having 1 to 40 carbon atoms and having a straight chain structure or a branched structure may be mentioned, and aliphatic, aromatic, or aliphatic carbon groups having an aromatic group It may be a hydrogen group. Further, it may contain oxygen and / or sulfur atoms. R ¹ and R ² may be bonded. When there is one bond, for example, it is represented by the following general formula (2).

In the above formulas (1) and (2), x is an integer of 1 or more, preferably an integer of 1 to 12. When x is small, the extreme pressure property is lowered, and when x is too large, the thermal oxidation stability tends to be lowered. In order to obtain both extreme pressure property and thermal oxidation stability, x is preferably an integer of 1 to 6, more preferably an integer of 2 to 5. The sulfur-based extreme pressure agents represented by the general formulas (1) and (2) are usually not a single x, but a mixture of various sulfur numbers, in which compounds having specific sulfur numbers are active. It is thought to function as sulfur.

Examples of sulfur-based extreme pressure agents are further described below.

Sulfurized olefins are obtained by sulfiding olefins, and are collectively referred to as sulfide compounds including those obtained by sulfiding hydrocarbon-based raw materials other than olefins. Examples of the sulfurized olefin include those obtained by sulfurizing olefins such as polyisobutenes and terpenes with sulfur or other sulfurizing agents.

Examples of sulfide compounds other than sulfurized olefins include diisobutyl polysulfide, dioctyl polysulfide, di-tert-butyl polysulfide, diisobutyl polysulfide, dihexyl polysulfide, di-tert-nonyl polysulfide, didecyl polysulfide, didodecyl polysulfide, diisobutene polysulfide, Examples thereof include octenyl polysulfide and dibenzyl polysulfide.

Sulfurized fats and oils are reaction products of fats and oils, and examples of fats and oils include animal and vegetable fats and oils such as lard, beef tallow, whale oil, palm oil, coconut oil and rapeseed oil. This reaction product is not a single substance species but a mixture of various substances, and the chemical structure itself is not necessarily clear.

In addition to the above sulfurized fats and oils, sulfurized esters are obtained by sulfurizing ester compounds obtained by reaction of various organic acids (saturated fatty acids, unsaturated fatty acids, dicarboxylic acids, aromatic carboxylic acids, etc.) with various alcohols with sulfur or other sulfurizing agents. Can be obtained. Like sulfurized fats and oils, the chemical structure itself is not always clear.

In the lubricating oil composition of the present invention, the content of the sulfur-based extreme pressure agent is 5% by mass to 15% by mass, preferably 6% by mass to 12% by mass, based on the total mass of the lubricating oil composition. It is also a feature of the present invention that the content of the sulfur-based extreme pressure agent is larger than that of the lubricating oil composition. The said sulfur type extreme pressure agent can also be used 1 type or in mixture of 2 or more types. If the content exceeds the above upper limit value, thermal oxidation stability is lowered and sludge is likely to be generated, and in addition, metal corrosion is likely to occur, which is not preferable. Moreover, when content is less than the said lower limit, since scoring prevention property falls, it is unpreferable.

(C) Phosphorus extreme pressure agent The lubricating oil composition of the present invention contains a phosphorus extreme pressure agent as an essential component. By containing the phosphorus-based extreme pressure agent in an amount within the range described later in combination with the sulfur-based extreme pressure agent, it is possible to achieve both anti-wear properties and anti-scoring properties in a well-balanced manner. In the present invention, the extreme pressure agent having sulfur and phosphorus, such as thiophosphate, is not included in the above-mentioned (B) sulfur extreme pressure agent, but is included in (C) phosphorus extreme pressure agent. Further, the phosphorus extreme pressure agent of the present invention does not include zinc dithiophosphate.

The phosphorus-based extreme pressure agent is not particularly limited and may be a conventionally known one. For example, phosphate ester, acid phosphate ester, phosphite ester, acid phosphite ester, thiophosphate ester, acid thiophosphate ester, thiophosphite ester, acid thiophosphite ester, amine of acid phosphate ester It may be at least one selected from among salts, amine salts of acidic phosphites, amine salts of acidic thiophosphates, and amine salts of acidic thiophosphites. Preferably, it is at least one selected from an amine salt of an acidic phosphate ester, an amine salt of an acidic phosphite ester, an amine salt of an acidic thiophosphate ester, and an amine salt of an acidic thiophosphite ester. Good.

The phosphoric acid ester and the acidic phosphoric acid ester are represented by (R ¹ O) _a P (═O) (OH) _3-a . a is 0, 1, 2, or 3; R ¹ is independently a monovalent hydrocarbon group having 1 to 30 carbon atoms. Here, the case where a = 3 is a phosphoric acid ester, the case where a = 1 or 2 is an acidic phosphoric acid ester, and the case where a = 0 is phosphoric acid.

The phosphite and acidic phosphite are represented by (R ² O) _b P (═O) (OH) _{2 -b} H. b is 0, 1 or 2; R ² is independently a monovalent hydrocarbon group having 1 to 30 carbon atoms. Here, when b = 2, phosphite is formed, when b = 1 is acidic phosphite, and when b = 0 is phosphorous.

The thiophosphate ester and the acidic thiophosphate ester are represented by (R ³ X ¹ ) (R ⁴ X ² ) (R ⁵ X ³ ) P (= X ⁴ ). R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 30 carbon atoms. Here, when one or two of R ³ , R ⁴ and R ⁵ are hydrogen atoms, it is an acidic thiophosphate, and when three are hydrogen atoms, it is thiophosphoric acid. X ¹ , X ² , X ³ and X ⁴ are each independently an oxygen atom or a sulfur atom. However, at least one of X ¹ , X ² , X ³ and X ⁴ is a sulfur atom.

The thiophosphite ester and the acidic thiophosphite ester are represented by (R ⁶ X ⁵ ) (R ⁷ X ⁶ ) P (= X ⁷ ) H. R ⁶ and R ⁷ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 30 carbon atoms. Here, when one of R ⁶ and R ⁷ is a hydrogen atom, it is an acidic thiophosphite, and when two are hydrogen atoms, it is a thiophosphorous acid. X ⁵ , X ⁶ and X ⁷ are each independently an oxygen atom or a sulfur atom. However, at least one of X ⁵ , X ⁶ and X ⁷ is a sulfur atom.

In the above, the monovalent hydrocarbon group having 1 to 30 carbon atoms specifically includes methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, dodecyl group. Tridecyl group, octadecyl group, eicosyl group, isobutyl group, isohexyl group, isodecyl group, isooctadecyl group, neopentyl group, 2-ethylhexyl group, and oleyl group. A monovalent hydrocarbon group having 4 to 20 carbon atoms is preferred.

The phosphoric acid ester and acidic phosphoric acid ester are preferably phosphoric acid monoalkyl ester, phosphoric acid dialkyl ester, and phosphoric acid trialkyl ester, but are not limited thereto.

The phosphite and acidic phosphite are preferably a monoalkyl phosphite and a dialkyl phosphite, but are not limited thereto.

The thiophosphate and acidic thiophosphate are preferably thiophosphate monoalkyl ester, thiophosphate dialkyl ester, and thiophosphate trialkyl ester, but are not limited thereto.

The thiophosphite and acidic thiophosphite are preferably a thiophosphite monoalkyl ester and a thiophosphite dialkyl ester, but are not limited thereto.

As phosphate ester, phosphite ester, thiophosphate ester, and thiophosphite ester, more specifically, monooctyl phosphate, dioctyl phosphate, trioctyl phosphate, monooctyl phosphite, dioctyl phosphite, Monooctyl thiophosphate, dioctyl thiophosphate, trioctyl thiophosphate, monooctyl thiophosphite, dioctyl thiophosphite, monododecyl phosphate, dododecyl phosphate, tridodecyl phosphate, monododecyl phosphite, didodecyl phosphite, Monododecyl thiophosphate, didodecyl thiophosphate, tridodecyl thiophosphate, monododecyl thiophosphite, didodecyl thiophosphite, monooctadecenyl phosphate, dioctadecenyl phosphate, trioctadecenyl phosphate, monophosphite phosphate Octadecenyl, dioctadetous phosphite Nyl, monooctadecenyl thiophosphate, dioctadecenyl thiophosphate, trioctadecenyl thiophosphate, monooctadecenyl thiophosphite, dioctadecenyl thiophosphite, etc. is not.

Furthermore, alkylamine salts and alkenylamine salts of the above compounds which are partial esters can also be suitably used. That is, an amine salt of the acidic phosphate ester, an amine salt of the acidic phosphite ester, an amine salt of the acidic thiophosphate ester, and an amine salt of the acidic thiophosphite ester can be used. It is not limited to.

More particularly, the amine salt of monooctyl phosphate, the amine salt of dioctyl phosphate, the amine salt of monooctyl phosphite, the amine salt of monooctyl thiophosphate, the amine salt of dioctyl thiophosphate, the monooctyl thiophosphite Amine salt, monododecyl phosphate amine salt, didodecyl phosphate amine salt, monododecyl phosphite amine salt, monothiodecyl thiophosphate amine salt, dodecyl thiophosphate amine salt, monooctadecenyl phosphate Amine salt of dioctadecenyl phosphate, amine salt of monooctadecenyl phosphite, amine salt of monooctadecenyl thiophosphate, amine salt of dioctadecenyl thiophosphate, and monooctadecene thiophosphite Nyl amine salt and the like.
The amine of the amine salt is represented by R ⁸ R ⁹ R ¹⁰ N. R ⁸ , R ⁹ and R ¹⁰ are independently of each other a hydrogen atom or a saturated or unsaturated aliphatic, aromatic, or araliphatic hydrocarbon group having a straight chain structure or a branched chain having 1 to 20 carbon atoms. It is. More specifically, a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, a nonyl group, a dodecyl group, a stearyl group, an oleyl group, and the like can be given.

The phosphorus extreme pressure agent can be used alone or in combination of two or more. In the case of combination, for example, the following embodiments are exemplified, but the invention is not limited thereto.
(1) Thiophosphate amine salt and phosphate ester amine salt In particular, a combination of a thiophosphate ester amine salt having an alkyl group and a phosphate ester amine salt having an alkyl group,
(2) Thiophosphate ester amine salt and phosphate ester In particular, a combination of a thiophosphate ester amine salt having an alkyl group and a phosphate ester having an alkyl group,
(3) Phosphate ester amine salt and thiophosphate ester In particular, a combination of a phosphate ester amine salt having an alkyl group and a thiophosphate ester having an alkyl group,
(4) Thiophosphate ester and phosphate ester In particular, a combination of a thiophosphate ester having an alkyl group and a phosphate ester having an alkyl group.

The amount of the phosphorus extreme pressure agent added is 1.5 to 8% by mass, 1.8 to 7% by mass, preferably 2 to 6% by mass, based on the total mass of the lubricating oil composition. If the amount of the phosphorus-based extreme pressure agent exceeds the above upper limit, the scoring prevention property on the tooth surface or the like may be deteriorated, which is not preferable. When the content is greater than or equal to the above lower limit with respect to the mass of the entire lubricating oil composition, the content further contributes to the improvement of wear prevention performance. If the amount of the phosphorous extreme pressure agent is less than the above lower limit value, the formation of the reaction coating is insufficient and the wear prevention performance deteriorates.

The lubricating oil composition of the present invention is characterized in that the (B) sulfur-based extreme pressure agent and the (C) phosphorus-based extreme pressure agent are used in combination in the specific amounts described above. When the amount of at least one of the component (B) and the component (C) is too small or too large, the wear prevention property or the scoring prevention property becomes insufficient. Preferably, the total content of (B) the sulfur-based extreme pressure agent and (C) the phosphorus-based extreme pressure agent is 7 to 20% by mass with respect to the total mass of the lubricating oil composition. The amount is preferably 8 to 18% by mass, more preferably 9 to 16% by mass. Further, the use ratio (mass ratio) of the (B) sulfur-based extreme pressure agent and the (C) phosphorus-based extreme pressure agent is preferably (B) / (C) = 1 to 10, more preferably 1 .1 to 8, more preferably 1.2 to 7, particularly preferably 1.4 to 5.

The lubricating oil composition of the present invention may further contain an extreme pressure agent other than the (B) sulfur-based extreme pressure agent and (C) the phosphorus-based extreme pressure agent in addition to the above-mentioned components (B) and (C). . For example, zinc dithiophosphate (ZnDTP) can be used. The content of ZnDTP is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and still more preferably 0.3 to 1% by mass with respect to the total mass of the lubricating oil composition.

(D) Ashless dispersant The lubricant composition of the present invention may further contain an ashless dispersant. A conventionally known ashless dispersant may be used and is not particularly limited. Examples thereof include nitrogen-containing compounds having 40 to 400 carbon atoms and having at least one alkyl group or alkenyl group having a straight chain structure or a branched structure in the molecule or derivatives thereof, or succinimides and modified products thereof. . Ashless dispersants may be used alone or in combination of two or more. A borated ashless dispersant can also be used. The boronated ashless dispersant is a borated version of any ashless dispersant used in lubricating oils. Boronation is generally performed by allowing boric acid to act on an imide compound to neutralize part or all of the remaining amino group and / or imino group.

The carbon number of the alkyl group or alkenyl group is preferably 40 to 400, more preferably 60 to 350. When the carbon number of the alkyl group and the alkenyl group is less than the lower limit, the solubility of the compound in the lubricating base oil tends to decrease. Moreover, when the carbon number of an alkyl group and an alkenyl group exceeds the said upper limit, it exists in the tendency for the low-temperature fluidity | liquidity of a lubricating oil composition to deteriorate. The alkyl group and alkenyl group may have a straight chain structure or a branched structure. Preferable embodiments include, for example, oligomers of olefins such as propylene, 1-butene and isobutene, branched alkyl groups or branched alkenyl groups derived from ethylene and propylene co-oligomers.

The succinimide is a reaction product of one end of a polyamine and succinic anhydride, a so-called monotype succinimide, and a reaction product of both ends of the polyamine and succinic anhydride. And succinimide. The lubricating oil composition of the present invention may contain one of monotype and bistype, or may contain both.

The modified product of succinimide is, for example, a product obtained by modifying succinimide with a boron compound (hereinafter sometimes referred to as boronated succinimide). Modifying with a boron compound means boronation. A boronated succinimide may be used individually by 1 type, or may use 2 or more types together. When used in combination, it may be a combination of two or more of boronated succinimides. Moreover, both a monotype and a bis type may be included, the combined use of monotypes, or the combined use of bistypes may be sufficient. A boronated succinimide and a non-borated succinimide may be used in combination.

For example, methods for producing a boronated succinimide are disclosed in JP-B-42-8013 and JP-A-42-8014, JP-A-51-52381, JP-A-51-130408, and the like. And the like. Specifically, for example, a boron compound such as boric acid, boric acid ester, or boric acid salt is added to polyamine and succinic anhydride (derivative) to organic solvents such as alcohols, hexane and xylene, light lubricating oil base oil, etc. It can be obtained by mixing and heat-treating under appropriate conditions. The boron content contained in the boronated succinimide thus obtained can usually be 0.1 to 4% by mass. In the present invention, a boron-modified compound of an alkenyl succinimide compound (boronated succinimide) is particularly preferable because of excellent heat resistance, antioxidant properties, and antiwear properties.

The boron content contained in the boronated ashless dispersant is not particularly limited. Usually, it is 0.1 to 3% by mass with respect to the mass of the ashless dispersant. As one aspect of the present invention, the boron content in the ashless dispersant is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and preferably 2.5% by mass or less. More preferably, it is 2.3 mass% or less, More preferably, it is 2.0 mass% or less. The boronated ashless dispersant is preferably a boronated succinimide, and particularly preferably a boronated bissuccinimide.

The borated ashless dispersant has a boron / nitrogen mass ratio (B / N ratio) of 0.1 or more, preferably 0.2 or more, preferably less than 1.0, more preferably 0.8 or less. What has is preferable.

The content of the ashless dispersant in the composition may be adjusted as appropriate. For example, it is preferably 0.01 to 20% by mass, more preferably 0.1 to the mass of the entire lubricating oil composition. ~ 10% by mass. If the content of the ashless dispersant is less than the above lower limit, the sludge dispersibility may be insufficient. Moreover, when content exceeds the said upper limit, there exists a possibility of deteriorating a specific rubber material or making low temperature fluidity worse.

(E) Other additives The lubricating oil composition of the present invention includes, as other additives other than the above components (A) to (D), a viscosity index improver, an antioxidant, a metallic detergent, and a friction modifier. , Corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, antifoaming agents, and pour point depressants. However, since the lubricating oil composition of the present invention is not grease, it does not contain a thickener. Examples of the thickener include metal soap and metal salt.

As the viscosity index improver, for example, a polymer or copolymer of one or more monomers selected from various methacrylic acid esters, or a hydride thereof, a so-called non-dispersed viscosity index improver, or So-called dispersible viscosity index improvers copolymerized with various methacrylic esters containing nitrogen compounds, non-dispersed or dispersed ethylene-α-olefin copolymers (for propylene, 1-butene, 1-pentene as α-olefins) Or a hydride thereof, polyisobutene or a hydride thereof, a hydride of a styrene-diene copolymer, a styrene-maleic anhydride ester copolymer, and a polyalkylstyrene.

It is necessary to select the molecular weight of the viscosity index improver in consideration of the shear stability of the lubricating oil composition. For example, the viscosity index improver has a weight average molecular weight of usually 5,000 to 1,000,000, preferably 100,000 to 900,000 in the case of dispersed and non-dispersed polymethacrylates. In the case of a hydride thereof, usually 800 to 5,000, preferably 1,000 to 4,000, and in the case of an ethylene-α-olefin copolymer or a hydride thereof, usually 800 to 500,000, preferably 3,000 to 200,000 are used.

Among the viscosity index improvers, when an ethylene-α-olefin copolymer or a hydride thereof is used, a lubricating oil composition having particularly excellent shear stability can be obtained. One or two or more compounds arbitrarily selected from the above viscosity index improvers can be contained in any amount.
The content of the viscosity index improver in the lubricating oil composition is 0.01 to 20% by mass, preferably 0.02 to 10% by mass, more preferably 0.05 to 5% by mass, based on the total amount of the composition. is there.

Antioxidants may be those commonly used in lubricating oils, for example, ashless antioxidants such as phenolic antioxidants and amine antioxidants and organometallic antioxidants. Can be mentioned. By adding an antioxidant, the oxidation stability of the lubricating oil composition can be further enhanced.

Examples of the metal detergent include those containing a compound selected from sulfonates such as calcium, magnesium and barium, phenates, salicylates, and carboxylates, such as overbased salts, basic salts, and neutral salts. Those having different base numbers can be arbitrarily selected and used. The metal detergent is usually blended in the lubricating oil composition at a metal amount of 0.01 to 1% by mass.

Examples of the friction modifier include organic molybdenum compounds, fatty acids, fatty acid esters, alcohols, amines, amides, and the like. The friction modifier is usually blended in the lubricating oil composition at 0.01 to 5% by mass.

Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds. The corrosion inhibitor is usually blended in the lubricating oil composition at 0.1 to 5% by mass.

Examples of the rust preventive include petroleum sulfonate, alkyl sulfonate, fatty acid, fatty acid soap, fatty acid amine, alkyl polyoxyalkylene, alkenyl succinic acid ester, and polyhydric alcohol fatty acid ester. The rust preventive is usually blended in the lubricating oil composition at 0.01 to 5% by mass.

Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether. The demulsifier is usually blended in the lubricating oil composition at 0.01 to 5% by mass.

Examples of the metal deactivator include pyrroles, imidazoles, pyrazoles, pyrazines, pyrimidines, pyridazines, triazines, triazoles, thiazoles, thiadiazoles and the like. The metal deactivator is usually blended in the lubricating oil composition at 0.01 to 3% by mass.

Examples of the antifoaming agent include dimethylpolysiloxanes and their fluorinated derivatives, polyacrylates and their fluorinated derivatives, and perfluoropolyethers. The antifoaming agent is usually blended in the lubricating oil composition at 0.001 to 1% by mass.

As the pour point depressant, for example, a polymethacrylate polymer compatible with the lubricating base oil to be used can be used. The pour point depressant is usually blended in the lubricating oil composition at 0.01 to 3% by mass.

Kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is preferably 20 ~ 120mm ² / s, more preferably 30 ~ 100mm ² / s. More preferably, it is 40 to 80 mm ² / s.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is preferably 3 to 40 mm ² / s, more preferably 4 to 20 mm ² / s, still more preferably 5 to 15 mm ² / s, and particularly preferably 6 to 12 mm ^2. / S.

Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated in detail, this invention is not restrict | limited by the following Example.

Each component used in the examples and comparative examples is as follows. Each component shown below was mixed with the composition shown in Table 1 to prepare a lubricating oil composition. In the following, KV40 means the kinematic viscosity at 40 ° C., KV100 means the kinematic viscosity at 100 ° C., and VI means the viscosity index.
(A) Lubricating base oil / mineral base oil 1: KV40 = 19 mm ² / s, KV100 = 4 mm ² / s
Synthetic base oil 1: GTL-derived base oil, KV100 = 8 mm ² / s
Synthetic base oil 2: ethylene-α-olefin base oil, KV100 = 40 mm ² / s

(B) Sulfur-based extreme pressure agent The amount of active sulfur in the following is a value measured by a method based on ASTM D1662, and is the amount of active sulfur in the sulfur-based extreme pressure agent.
・ Sulfur-based extreme pressure agent 1: Sulfurized olefin (active sulfur content = 11% by mass)
・ Sulfur-based extreme pressure agent 2: Sulfurized olefin (active sulfur content = 32 mass%)

(C) Phosphorus extreme pressure agent / phosphorus extreme pressure agent 1: Salt of acidic phosphate ester (having C4-C8 alkyl group) and amine (having C8-C18 alkyl group) / phosphorus extreme pressure agent 2: Salts of acidic thiophosphates (having C4-C8 alkyl groups) and amines (having C8-C18 alkyl groups)

(D) Ashless dispersant / borated polyisobutenyl succinimide (bisimide type)
Polybutenyl group molecular weight = 1,400, boron = 1.8 mass%, nitrogen = 2.4 mass%

(E) Other additives Antifoaming agent, pour point depressant, rust inhibitor

Various properties of each lubricating oil composition were measured according to the following method. The results are shown in Table 2.
(1) Kinematic viscosity at 40 ° C. (KV40)
Measured according to ASTM D445.
(2) Kinematic viscosity at 100 ° C. (KV100)
Measured according to ASTM D445.
(3) Viscosity index Measured according to ASTM D2270.
(4) Abrasion Evaluation Based on ASTM D2714, a test was conducted under the following conditions to evaluate the wear width formed on the block test piece after the test. Oil temperature: 120 ° C., load: 20 lbf, rotation speed: 1000 rpm, time: 1 h. A case where the wear width (mm) was 0.5 or less was regarded as acceptable.
(5) Evaluation of scoring property Using a four-ball wear tester defined by ASTM D4172, the 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 number of rotations (rpm) exceeded 1000 was regarded as acceptable.
(6) Oxidation stability The test was conducted under the following conditions in accordance with JIS K2514-1, and the pentane insoluble matter was measured for the sample oil after the test in accordance with ASTM D893 (Method B). Oil temperature: 135 ° C., time: 96 h. The case where the insoluble content of pentane (% by mass) was 2.4 or less was regarded as acceptable.

As shown in Table 2, the composition of Comparative Example 1 having a low content of sulfur-based extreme pressure agent does not have sufficient scoring prevention properties. The composition of Comparative Example 2 containing too much sulfur-based extreme pressure agent has poor oxidation stability. The composition of Comparative Example 3 using a sulfur-based extreme pressure agent having a high amount of active sulfur does not have sufficient wear resistance. Furthermore, the composition of Comparative Example 4 having a low content of phosphorus-based extreme pressure agent has a large wear width and poor wear resistance. The composition of Comparative Example 5 having a high phosphorus-based extreme pressure agent content does not have sufficient scoring prevention properties. On the other hand, the lubricating oil composition of the present invention is excellent in all of antiwear properties, antiscoring properties, and oxidation stability.

The lubricating oil composition of the present invention can suppress the occurrence of wear on bearings and scoring on gear tooth surfaces even when the viscosity is lowered. The lubricating oil composition of the present invention can be suitably used as an automotive lubricating oil, and is particularly suitable as a transmission gear oil and a differential gear oil.

Claims

In a lubricating oil composition containing (A) a lubricating base oil, (B) a sulfur-based extreme pressure agent, and (C) a phosphorus-based extreme pressure agent, the amount of active sulfur in the (B) extreme pressure agent is 5 to 30% by mass, and the (B) extreme pressure agent is contained in the composition in an amount of 5 to 15% by mass with respect to the total mass of the lubricating oil composition. The lubricating oil composition described above, wherein the lubricating oil composition is contained in the composition in an amount of 1.5 to 8% by mass relative to the total mass of the product.
The lubricating oil composition according to claim 1, wherein the sulfur-based extreme pressure agent is a sulfurized olefin.
(C) Phosphorus extreme pressure agent is phosphoric acid ester, acidic phosphoric acid ester, phosphorous acid ester, acidic phosphorous acid ester, thiophosphoric acid ester, acidic thiophosphoric acid ester, thiophosphorous acid ester, acidic thiophosphorous acid The acid ester, an amine salt of an acidic phosphate ester, an amine salt of an acidic phosphite ester, an amine salt of an acidic thiophosphate ester, and an amine salt of an acidic thiophosphite ester, Or the lubricating oil composition of Claim 2.
The (C) phosphorus-based extreme pressure agent is at least one selected from an amine salt of an acidic phosphate, an amine salt of an acidic phosphite, an amine salt of an acidic thiophosphate, and an amine salt of an acidic thiophosphite The lubricating oil composition of claim 3, which is a seed.
The lubricating oil composition according to claims 1 to 4, wherein the lubricating oil composition has a kinematic viscosity at 100 ° C of 3 to 40 mm 2 / s.
The lubricating oil composition according to any one of claims 1 to 5, wherein at least a part of the (A) lubricating base oil is a GTL (Gas to Liquid) derived base oil.
The lubricating oil composition according to any one of claims 1 to 6, wherein at least a part of the (A) lubricating base oil is a poly-α-olefin (PAO) base oil.
The lubricating oil composition according to any one of claims 1 to 7, wherein the (A) lubricating base oil has a kinematic viscosity at 100 ° C of 3 to 40 mm 2 / s.
The lubricating oil composition according to any one of claims 1 to 8, which is used for a transmission.
The lubricating oil composition according to any one of claims 1 to 8, which is used for a differential gear.