JP2020070404A - Lubricant composition - Google Patents

Abstract

To provide the lubricant composition that can achieve both scoring prevention and wear prevention under conditions where the viscosity is lowered than that of conventional lubricant compositions (particularly, a kinematic viscosity at 100°C is 5 to 10 mm/s).SOLUTION: The lubricant composition comprising (A) a lubricant base oil, (B) a sulfur-based extreme pressure agent, and (C) a phosphorus-based extreme pressure agent contains at least (A-1) an ester compound of a polyol and a carboxylic acid as (A) the lubricant base oil, in an amount of 1 to 30 mass% based on a total mass of the lubricant composition, and (B) the sulfur-based extreme pressure agent has an active sulfur amount of 1 to 30 mass%.SELECTED DRAWING: None

Description

  The present invention relates to lubricating oil compositions. More particularly, it relates to a lubricating oil composition having a low viscosity and an excellent balance between anti-scoring properties and anti-wear properties.

  Lubricating oil compositions are used for various purposes such as automobiles and machines. In recent years, various lubricating oil compositions have been developed to achieve fuel efficiency. For example, in Patent Document 1, by using a low-viscosity base oil and a high-viscosity base oil in combination, it is possible to reduce the viscosity of the lubricating oil, and it is possible to simultaneously achieve the bearing fatigue life characteristics and the fuel efficiency, which are particularly affected by the oil film forming ability. Have been described. Patent Document 2 describes a gear oil composition having low viscosity but excellent in lubricity, oxidation stability and extreme pressure. Further, Patent Document 3 discloses a lubricating oil composition used for a transmission, particularly a differential gear, which can suppress wear in bearings and scoring on gear tooth surfaces even when the viscosity is reduced. It has been described.

  Further, Patent Document 4 describes a lubricating oil composition that can suppress wear in bearings and the like and scoring on gear tooth surfaces even when the viscosity is reduced. The lubricating oil composition is excellent in wear resistance, scoring resistance, and oxidation stability. Patent Document 4 describes that a combination of a mineral oil-based base oil, a GTL-derived base oil, and a PAO base oil is preferable as the base oil.

  In Patent Document 5, fuel economy can be realized while maintaining high seizure resistance and stability, which can be applied as gear oil for high-output automobiles and other high-output, high-rotation gear mechanisms. As a lubricating oil composition applicable to automotive gear oil, it contains GTL base oil, poly-α-olefin, and ester compound in a mixed state, SAE viscosity grade is 75W-85, API gear oil type The lubricating oil composition which satisfies GL-5 and has a viscosity index of 160 or more is described.

Japanese Patent Laid-Open No. 2007-039480 JP 2012-46683 A JP, 2017-132875, A JP, 2008-16729, A JP, 2017-115038, A

The lubricating oil compositions described in the examples of Patent Documents 3 to 5 all have kinematic viscosities at 100 ° C. of 11 to 12 mm ² / s, but with the increasing demand for fuel efficiency of automobiles, further reduction in viscosity is observed. Is required. When the lubricating oil composition has a low viscosity, direct contact between the sliding materials is likely to occur, and properties such as scoring prevention properties and wear prevention properties tend to deteriorate. For scoring prevention, the first step is to strengthen or increase the amount of sulfur-based extreme pressure agent, but the sulfur-based extreme pressure agent may adversely affect the wear prevention property, so scoring prevention And the wear resistance may be a trade-off. Particularly, the differential gear oil is required to have high anti-scoring property because it is necessary to apply it to a very severe part as a sliding condition of automobile parts.

In view of the above circumstances, the present invention has an anti-scoring property and an anti-wear property under conditions where the viscosity is lower than that of a conventional lubricating oil composition (particularly, a kinematic viscosity at 100 ° C. of 5 to 10 mm ² / s). An object of the present invention is to provide a lubricating oil composition that can satisfy both of the requirements.

  The inventors of the present invention have made diligent studies and found that by incorporating a polyol ester having a specific structure and a sulfur-based extreme pressure agent having a specific amount of active sulfur, conventional lubrication is performed even under conditions in which the viscosity is further lowered than in the past. It has been found that a lubricating oil composition (particularly preferably a differential gear oil) having anti-scoring properties and anti-wear properties comparable to those of the oil composition can be provided, and the present invention has been completed.

  That is, the present invention provides 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, wherein (A) the lubricating oil The base oil contains at least (A-1) an ester compound of a polyol and a carboxylic acid in an amount of 1 to 30% by mass based on the total mass of the lubricating oil composition, and the sulfur-based extreme pressure agent (B) has an amount of active sulfur. The lubricating oil composition is provided having 1 to 30% by mass.

A preferred embodiment of the present invention further has at least one of the following features (1) to (9).
(1) The lubricating oil composition has a kinematic viscosity at 100 ° C. of 5 to 10 mm ² / s.
(2) The lubricating base oil (A) has a kinematic viscosity at 100 ° C. of 3 to 10 mm ² / s.
(3) The amount of the (B) sulfur-based extreme pressure agent is 1 to 15 mass% with respect to the total weight of the lubricating oil composition, and the amount of the (C) phosphorus-based extreme pressure agent is the entire lubricating oil composition. It is 1.5-8 mass% with respect to the mass of.
(4) The sulfur-based extreme pressure agent (B) is a sulfurized olefin.
(5) The (C) phosphorus-based extreme pressure agent is selected from an amine salt of an acidic phosphoric acid ester, an amine salt of an acidic phosphorous acid ester, an amine salt of an acidic thiophosphoric acid ester, and an amine salt of an acidic thiophosphorous acid ester. It is at least one kind.
(6) Further, 30 to 70 mass% of (A-2) GTL (Gas to Liquid) -derived base oil is contained as the lubricating oil base oil (A) with respect to the total mass of the lubricating oil composition.
(7) Further, (A-3) poly-α-olefin (PAO) base oil is contained as the lubricating base oil (A) in an amount of 10 to 40% by mass based on the total mass of the lubricating oil composition.
(8) For a transmission.
(9) For differential gears.

The lubricating oil composition of the present invention has an anti-scoring property and an anti-wear property under the condition that the viscosity is further lowered than that of the conventional lubricating oil composition (in particular, the kinematic viscosity at 100 ° C. is 5 to 10 mm ² / s). It is compatible with both and has excellent reliability. The lubricating oil composition of the present invention can be suitably used as a lubricating oil for automobiles, and is also suitable as a gear oil for transmissions and a differential gear oil.

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

(A) Lubricating oil base oil The present invention uses (A-1) an ester compound of a polyol and a carboxylic acid as a lubricating oil base oil in an amount of 1 to 30% by mass, preferably 5 to 5% by mass based on the total mass of the lubricating oil composition. 27% by mass, and more preferably 8 to 22% by mass. This ensures the same scoring prevention property and wear prevention property as the conventional one under the condition that the viscosity is further increased than that of the conventional lubricating oil composition (in particular, the kinematic viscosity at 100 ° C. is 5 to 10 mm ² / s). You can do it.

  The polyol preferably has 2 to 6 hydroxyl groups, more preferably 2 to 4 hydroxyl groups. Further, it preferably has 1 to 30 carbon atoms, and more preferably a polyol having 2 to 24 carbon atoms. For example, ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, 3-methyl Examples thereof include diols such as -1,5-pentanediol and 1,6-hexanediol, trimethylolethane, trimethylolpropane, triols such as glycerin, pentaerythritol, sugar alcohols and the like. Of these, 3-methyl-1,5-pentanediol and trimethylolpropane are preferable. The carboxylic acid preferably has 1 to 30 carbon atoms, and is preferably an aliphatic monocarboxylic acid. An aliphatic monocarboxylic acid having 1 to 24 carbon atoms, and more preferably 1 to 18 carbon atoms is more preferable. Examples thereof include butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, octadecanoic acid, and oleic acid. An ester compound of trimethylolpropane and a monocarboxylic acid having 6 to 12 carbon atoms is preferable. The base oil may be a mixture of two or more polyol esters.

The ester compound can be represented by, for example, the following general formula.
In the above formula, R is a hydrogen atom or a monovalent hydrocarbon group having 1 to 29 carbon atoms, preferably 2 to 23 carbon atoms. n is an integer of 1 to 30, preferably 2 to 24, and may be branched. An ester compound of 3-methyl-1,5-pentanediol and nonanoic acid is preferable.

The ester compound used in the present invention preferably has a kinematic viscosity at 100 ° C. of 7 mm ² / s or less. It is more preferably 1.5 to ⁶ mm ² / s, still more preferably 1.8 to ⁵ mm ² / s, particularly preferably ² to 4.5 mm ² / s, and most preferably 2.5 to 4 mm. ² / s.

  The lubricating base oil in the present invention preferably further contains (A-2) GTL (Gas to Liquid) -derived base oil and / or (A-3) poly-α-olefin (PAO) base oil. The content of the (A-2) GTL (Gas to Liquid) -derived base oil is 30 to 70% by mass, preferably 35 to 67% by mass, and more preferably 40% by mass based on the mass of the entire lubricating oil composition. Is about 65% by mass. The content of the (A-3) poly-α-olefin (PAO) base oil is 10 to 40% by mass, preferably 12 to 28% by mass, preferably 15 to 25% by mass, based on the total mass of the lubricating oil composition. Is.

(A-2) GTL-derived base oil is a base oil obtained by hydrocracking and hydroisomerizing a raw material such as wax obtained by Fischer-Tropsch synthesis from natural gas such as methane. .. The kinematic viscosity at 100 ° C. is not particularly limited, but it is preferably 1 to ²⁰ mm ² / s, more preferably ² to 15 mm ² / s, and further preferably 3 to 10 mm ² / s. Is good.

The (A-3) PAO base oil is not particularly limited, and examples thereof include 1-octene oligomer, 1-decene oligomer, ethylene-α-olefin oligomer, ethylene-propylene oligomer, isobutene oligomer and hydrides thereof. Can be used. The kinematic viscosity at 100 ° C., preferably is 2~2,500mm ² / s, more preferably 2~200mm ² / s, more preferably 3~150mm ² / s, more preferably 4~50mm ² / s Good to have.

  The lubricating oil composition of the present invention may contain, in addition to the above synthetic base oil, one or more selected from other synthetic base oils and mineral oil base oils. These contents may be appropriately adjusted as long as the effects of the present invention are not impaired. Examples of other synthetic base oils include polybutene, alkylbenzene, fatty acid ester, phosphoric acid ester, and silicone oil. The lubricating oil composition of the present invention can also contain an aromatic dibasic acid ester in combination with the component (A-1).

Mineral oil base oils are highly refined paraffinic mineral oils (high viscosity index mineral oil base oils) obtained by subjecting hydrorefined oils, catalytic isomerized oils, etc. to solvent dewaxing or hydrodewaxing. ) Is mentioned. Alternatively, the lubricating oil raw material may be phenol, or raffinate obtained by solvent refining using an aromatic extraction solvent such as furfural, or silica-alumina may be obtained by hydrotreating using a hydrotreating catalyst such as cobalt or molybdenum. Examples include hydrotreated oil and the like. For example, 100 neutral oil, 150 neutral oil, 500 neutral oil, etc. can be mentioned. The mineral oil-based 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} 40 mm ² / s, more preferably ^{2 to 20} mm ² / s. And more preferably 3 to 10 mm ² / s.

The kinematic viscosity of the lubricating base oil is not limited as long as it does not impair the gist of the present invention. Particularly, in order to obtain a lubricating oil composition having a lower viscosity, it is preferable that the entire lubricating base oil has a kinematic viscosity at 100 ° C. of 3 to 10 mm ² / s, further preferably 4 to 9 mm ² / s, More preferably, it has 5-8 mm < ² > / s. When the kinematic viscosity of the lubricating base oil at 100 ° C. is within the above range, it is possible to reduce the viscosity of the lubricating oil composition and improve fuel economy. Further, the above-mentioned polyol ester can ensure abrasion resistance and scoring prevention even under such low viscosity conditions.

(B) Sulfur-based extreme pressure agent The lubricating oil composition of the present invention contains a sulfur-based extreme pressure agent. The sulfur-based extreme pressure agent has an active sulfur amount of 1 to 30% by mass, preferably 3 to 20% by mass, more preferably 5 to 15% by mass, and particularly preferably 8 to 12% by mass. Good to have. When the amount of active sulfur is within the above range, abrasion resistance and scoring prevention can be ensured.

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. In a 200 ml beaker, 50 g of a sample and 5 g of copper powder (purity 99% or more, particle size 75 μm or less) are put, and heated to 150 ° C. with stirring with a stirrer (500 rpm).
2. When the temperature reaches 150 ° C., 5 g of copper powder is added, and the mixture is stirred for 30 minutes.
3. The stirring is stopped, and a copper plate conforming to ASTM D130 is placed in a beaker and immersed 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 discoloration of the copper plate is no longer observed).
4. When the discoloration of the copper plate is no longer observed, the copper powder in the sample is filtered off and the amount of sulfur contained in the filtrate is measured.
The amount of active sulfur (mass%) is defined as “the amount of sulfur (mass%) contained in the original sample (step 1 above) -the amount of sulfur (mass step 4) after the reaction with the copper powder (step 4). %) ”.

  The sulfur-based extreme pressure agent in the present invention may be one having the above-mentioned specific amount of active sulfur, and can be selected from known sulfur-based extreme pressure agents. At least one selected from sulfide compounds represented by sulfurized olefins and sulfurized esters represented by sulfurized fats and oils is preferable, 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-based extreme pressure agent described later, and is not included in the (B) sulfur-based 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 substituents independent of each other and contain at least one element selected from carbon, hydrogen, oxygen and sulfur. Specifically, examples thereof include a saturated or unsaturated hydrocarbon group having a straight chain structure or a branched structure having 1 to 40 carbon atoms, and an aliphatic, aromatic, or aliphatic carbon group 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 to each other, and when there is one bond, they are represented by the following general formula (2).

In the above formulas (1) and (2), x is an integer of 1 or more, preferably 1 to 12. If x is small, extreme pressure property tends to decrease, and if x is too large, thermal oxidation stability tends to decrease. In order to obtain both extreme pressure properties and thermal oxidative 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 a compound having a specific sulfur number is active. It is considered to function as sulfur.

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

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

  Examples of the sulfide compound 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, and diobutyl polysulfide. Examples thereof include ctenyl 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 always clear.

  Sulfurized esters are sulfurized oils and fats, and sulfurized sulfur and other sulfurizing agents with ester compounds obtained by reacting various organic acids (saturated fatty acids, unsaturated fatty acids, dicarboxylic acids, aromatic carboxylic acids, etc.) with various alcohols. What can be obtained by doing. 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 1% by mass to 15% by mass, preferably 2% by mass to 12% by mass, and particularly preferably, the mass of the entire lubricating oil composition. It is 4 to 8 mass%. The above sulfur-based extreme pressure agents may be used alone or in combination of two or more. If the content exceeds the above upper limit, the thermal oxidative stability decreases, sludge is likely to be generated, and in addition, metal corrosion may be likely to occur. Further, if the content is less than the above lower limit, the scoring prevention property may decrease.

(C) Phosphorus Extreme Pressure Agent The lubricating oil composition of the present invention further contains a phosphorus extreme pressure agent. Containing the phosphorus-based extreme pressure agent together with the sulfur-based extreme pressure agent in an amount in the range described below is preferable because it is possible to achieve a well-balanced wear prevention property and scoring prevention property. In the present invention, the extreme pressure agent having sulfur and phosphorus, such as thiophosphate, is included in the (C) phosphorus extreme pressure agent, not the above-mentioned (B) sulfur type extreme pressure agent. The phosphorus-based extreme pressure agent of the present invention does not include zinc dithiophosphate.

  The phosphorus extreme pressure agent is not particularly limited and may be a conventionally known one. For example, phosphoric acid ester, acidic phosphoric acid ester, phosphorous acid ester, acidic phosphorous acid ester, phosphonic acid ester, thiophosphoric acid ester, acidic thiophosphoric acid ester, thiophosphorous acid ester, acidic thiophosphorous acid ester, acidic phosphoric acid ester At least one selected from an amine salt of an acid ester, an amine salt of an acidic phosphite ester, an amine salt of an acidic thiophosphoric acid ester, and an amine salt of an acidic thiophosphorous acid ester is preferable. Preferably, at least one selected from the amine salt of acidic phosphoric acid ester, the amine salt of acidic phosphorous acid ester, the amine salt of acidic thiophosphoric acid ester, and the amine salt of acidic thiophosphorous acid ester. Good.

Phosphoric acid esters and acidic phosphoric acid ester is represented by _{^{(R 1 O) a P (}} = O) (OH) 3-a. a is 0, 1, 2, or 3. R ^1's are each independently a monovalent hydrocarbon group having 1 to 30 carbon atoms. Here, when a = 3, it is a phosphoric acid ester, when a = 1 or 2, it is an acidic phosphoric acid ester, and when a = 0, it is phosphoric acid.

Phosphites and acid phosphites represented by _{^{(R 2 O) b P (}} = O) (OH) 2-b H. b is 0, 1, or 2. R ^2's are each independently a monovalent hydrocarbon group having 1 to 30 carbon atoms. Here, when b = 2, phosphorous acid ester, when b = 1, acidic phosphorous acid ester, and when b = 0, phosphorous acid.

Thiophosphate ester and an acidic thiophosphoric ester 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 thiophosphoric acid ester, and when three are hydrogen atoms, it is a thiophosphoric acid. X ¹ , X ² , X ³ and X ⁴ are, independently of each other, 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 becomes an acidic thiophosphorous acid ester, and when two are hydrogen atoms, it becomes a thiophosphorous acid. X ⁵ , X ⁶ and X ⁷ are, independently of each other, 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 is specifically, 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. It is preferably a monovalent hydrocarbon group having 4 to 20 carbon atoms.

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

  The phosphite ester and the acidic phosphite ester are preferably, but not limited to, monoalkyl phosphite ester and dialkyl phosphite ester.

  The thiophosphoric acid ester and the acidic thiophosphoric acid ester are preferably, but not limited to, thiophosphoric acid monoalkyl ester, thiophosphoric acid dialkyl ester, and thiophosphoric acid trialkyl ester.

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

  As a phosphoric acid ester, a phosphorous acid ester, a thiophosphoric acid ester, and a thiophosphorous acid ester, more specifically, monooctyl phosphate, dioctyl phosphate, trioctyl phosphate, monooctyl phosphate, dioctyl phosphite, Monooctyl thiophosphate, dioctyl thiophosphate, trioctyl thiophosphate, monooctyl thiophosphite, dioctyl thiophosphite, monododecyl phosphate, didodecyl phosphate, tridodecyl phosphate, monododecyl phosphite, didodecyl phosphite, Monododecyl thiophosphate, didodecyl thiophosphate, tridodecyl thiophosphate, monododecyl thiophosphite, didodecyl thiophosphite, monooctadecenyl phosphate, dioctadecenyl phosphate, trioctadecenyl phosphate, monophosphite Octadecenyl, dioctadecene phosphite And monooctadecenyl thiophosphate, dioctadecenyl thiophosphate, trioctadecenyl thiophosphate, monooctadecenyl thiophosphite, and dioctadecenyl thiophosphite, but are not limited to these. is not.

  Further, among the above compounds, alkylamine salts and alkenylamine salts of partial esters can be preferably used. That is, the amine salt of the acidic phosphoric acid ester, the amine salt of the acidic phosphorous acid ester, the amine salt of the acidic thiophosphoric acid ester, and the amine salt of the acidic thiophosphorous acid ester can be used. It is not limited to.

More specifically, amine salt of monooctyl phosphate, amine salt of dioctyl phosphate, amine salt of monooctyl phosphite, amine salt of monooctyl thiophosphate, amine salt of dioctyl thiophosphate, monooctyl thiophosphite Amine salt, monododecyl phosphate amine salt, didodecyl phosphate amine salt, monododecyl phosphite amine salt, monododecyl thiophosphate amine salt, didodecyl thiophosphate amine salt, monooctadecenyl phosphate Amine salt of dioctadecenyl phosphate, monooctadecenyl phosphite amine salt, monooctadecenyl thiophosphate amine salt, dioctadecenyl thiophosphate amine salt, and monooctadecenyl thiophosphite Examples thereof include amine salts of nil.
The amine of the amine salt is represented by R ⁸ R ⁹ R ¹⁰ N. R ⁸ , R ⁹ and R ¹⁰ are each independently 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. Is. More specifically, examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, a nonyl group, a dodecyl group, a stearyl group and an oleyl group.

The above phosphorus-based extreme pressure agents can be used alone or in combination of two or more kinds. In the case of combining, for example, the following modes can be mentioned, but the invention is not limited thereto.
(1) Thiophosphate ester 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) Phosphoric acid ester amine salt and thiophosphoric acid ester In particular, a combination of a phosphoric acid ester amine salt having an alkyl group and a thiophosphoric acid 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,
(5) At least one combination selected from an acidic phosphoric acid ester, a phosphorous acid ester, and a phosphonic acid ester having an alkyl group having 4 to 8 carbon atoms.

  The phosphorus-based extreme pressure agent is added in an amount of 1.5 to 8% by mass and 1.8 to 7% by mass, preferably 2 to 6% by mass, based on the total mass of the lubricating oil composition. It is preferable that the amount of the phosphorus-based extreme pressure agent is equal to or less than the above upper limit because the scoring prevention property on the tooth surface and the like can be excellently secured. Furthermore, when the content is at least the above lower limit value with respect to the total mass of the lubricating oil composition, it further contributes to the improvement of the wear prevention performance. If the amount of the phosphorus-based extreme pressure agent is less than the above lower limit value, the reaction coating may not be sufficiently formed and the antiwear performance may be deteriorated.

  In the lubricating oil composition of the present invention, the above-mentioned (B) sulfur-based extreme pressure agent and the (C) phosphorus-based extreme pressure agent are used in combination in the above-mentioned specific amounts, respectively, to obtain good wear resistance and Scoring prevention property can be secured. If the amount of at least one of the component (B) and the component (C) is too small or too large, the abrasion resistance or the scoring prevention property may be insufficient. More preferably, the total content of the sulfur-based extreme pressure agent (B) and the phosphorus-based extreme pressure agent (C) is 3 to 20 mass% with respect to the total mass of the lubricating oil composition, It is more preferably 4 to 15% by mass, and even more preferably 5 to 10% 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 5, more preferably 1 0.1 to 4, more preferably 1.2 to 3, and most preferably 1.3 to 2.

  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 the (C) phosphorus-based extreme pressure agent together with the (B) and (C) components. .. 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, based on the total mass of the lubricating oil composition.

(D) Ashless Dispersant The lubricant composition of the present invention may further contain an ashless dispersant. The ashless dispersant may be any conventionally known one, and is not particularly limited. For example, a nitrogen-containing compound having at least one alkyl group or alkenyl group having a linear or branched structure having 40 to 400 carbon atoms in the molecule or a derivative thereof, succinimide and a modified product thereof, and the like can be mentioned. .. The ashless dispersants may be used alone or in combination of two or more. It is also possible to use borated ashless dispersants. The borated ashless dispersant is a borated version of any ashless dispersant used in lubricating oils. Boration is generally carried out by reacting imide compounds with boric acid to neutralize some or all of the remaining amino groups and / or imino groups.

  The alkyl group or the alkenyl group has preferably 40 to 400 carbon atoms, and more preferably 60 to 350 carbon atoms. When the carbon number of the alkyl group and the alkenyl group is less than the lower limit value described above, the solubility of the compound in the lubricating base oil tends to decrease. When the carbon number of the alkyl group and the alkenyl group exceeds the above upper limit, the low temperature fluidity of the lubricating oil composition tends to deteriorate. The alkyl group and alkenyl group may have a linear structure or a branched structure. Preferred embodiments include, for example, olefin oligomers such as propylene, 1-butene and isobutene, and branched alkyl groups or branched alkenyl groups derived from ethylene and propylene cooligomers.

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

  The modified succinimide product is, for example, a product obtained by modifying succinimide with a boron compound (hereinafter sometimes referred to as borated succinimide). To be modified with a boron compound means to be boronized. The borated succinimide may be used alone or in combination of two or more. When used in combination, a combination of two or more borated succinimides may be used. Further, both monotypes and screw types may be included, or monotypes may be used together or screw types may be used together. Borated succinimide and non-borated succinimide may be used in combination.

  For example, a method for producing borated succinimide is disclosed in Japanese Examined Patent Publications Nos. 42-8013 and 42-8014, JP-A-51-52381, JP-A-51-130408, and the like. The method etc. are mentioned. Specifically, for example, organic solvents such as alcohols, hexane, and xylene; polyamines and succinic anhydrides (derivatives) in light lubricating base oils such as boric acid, boric acid esters, and boron compounds such as borate salts. It can be obtained by mixing and heat treatment under appropriate conditions. The boron content contained in the borated succinimide thus obtained can be usually 0.1 to 4% by mass. In the present invention, a boron-modified compound (boronated succinimide) of an alkenyl succinimide compound is particularly preferable because it is excellent in heat resistance, antioxidation property and antiwear property.

  The boron content contained in the borated ashless dispersant is not particularly limited. Usually, it is 0.1 to 3 mass% with respect to the mass of the ashless dispersant. As one aspect of the present invention, the content of boron 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, The amount is more preferably 2.3% by mass or less, and further preferably 2.0% by mass or less. The borated ashless dispersant is preferably borated succinimide, and particularly preferably borated 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 1.2, more preferably 1.0 or less. Those having are preferable.

  The content of the ashless dispersant in the composition may be appropriately adjusted, but is preferably 0.01 to 20% by mass, more preferably 0.1 to 20% by mass based on the total mass of the lubricating oil composition. 10 to 10% by mass. If the content of the ashless dispersant is less than the above lower limit, sludge dispersibility may be insufficient. On the other hand, if the content exceeds the above upper limit, there is a possibility that a specific rubber material is deteriorated or low temperature fluidity is deteriorated.

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

  As the viscosity index improver, for example, a so-called non-dispersion type viscosity index improver such as a polymer or copolymer of one or more monomers selected from various methacrylic acid esters, or a hydride thereof, or So-called dispersion type viscosity index improver obtained by copolymerizing various methacrylic acid ester containing nitrogen compound, non-dispersion type or dispersion type ethylene-α-olefin copolymer (as α-olefin, propylene, 1-butene, 1-pentene Etc.), or its hydride, polyisobutene or its hydride, a styrene-diene copolymer hydride, a styrene-maleic anhydride copolymer, and a polyalkylstyrene.

  The molecular weight of the viscosity index improver needs to be selected in consideration of the shear stability of the lubricating oil composition. For example, the weight average molecular weight of the viscosity index improver is usually 5,000 to 1,000,000, and preferably 100,000 to 900,000 in the case of dispersion type and non-dispersion type polymethacrylate. Or in the case of the hydride thereof, it is usually 800 to 5,000, preferably 1,000 to 4,000, and in the case of the ethylene-α-olefin copolymer or its hydride, it is usually 800 to 500,000, preferably 3,000 to 200,000 is used.

When the ethylene-α-olefin copolymer or its hydride is used among the viscosity index improvers, a lubricating oil composition having particularly excellent shear stability can be obtained. One kind or two or more kinds of 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, and more preferably 0.05 to 5% by mass, based on the total amount of the composition. is there.

  The antioxidant may be one commonly used in lubricating oils, and examples thereof include ashless antioxidants such as phenolic antioxidants and amine antioxidants, and organometallic antioxidants. Can be mentioned. Addition of an antioxidant can further enhance the oxidative stability of the lubricating oil composition.

  Examples of the metal-based 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 metallic detergent is usually added to the lubricating oil composition in an amount of 0.01 to 1% by mass as a metal amount.

  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 in an amount of 0.01 to 5% by mass.

  Examples of the corrosion inhibitor include benzotriazole-based, tolyltriazole-based, thiadiazole-based, and imidazole-based compounds. The corrosion inhibitor is usually added to the lubricating oil composition in an amount of 0.1 to 5% by mass.

  Examples of the rust preventive agent 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 added to the lubricating oil composition in an amount of 0.01 to 5% by mass.

  Examples of the demulsifier include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and polyoxyethylene alkylnaphthyl ether. The demulsifier is usually blended in the lubricating oil composition in an amount of 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 added to the lubricating oil composition in an amount of 0.01 to 3% by mass.

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

  As the pour point depressant, for example, a polymethacrylate-based polymer compatible with the lubricating base oil used can be used. The pour point depressant is usually added to the lubricating oil composition in an amount of 0.01 to 3% by mass.

The lubricating oil composition of the present invention preferably has a kinematic viscosity at 100 ° C. of 5 to 10 mm ² / s, more preferably 5.5 to 9.5 mm ² / s, still more preferably 6 to 9 mm ² / s, and particularly preferably It is 6.5-8 mm < ² > / s. Moreover, the viscosity index measured according to ASTM D2270 has 100 or more, preferably 120 or more, more preferably 130 or more, and more preferably 140 to 200.

  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 used in the examples and comparative examples are as follows. Lubricating oil compositions were prepared by mixing the components shown below with the composition shown in Table 1 or 2. In the following, KV100 means kinematic viscosity at 100 ° C.
(A) Lubricating base oil (A-1) Synthetic base oil 1 (GTL4) KV100 = 4.0 mm ² / s
(A-2) Synthetic base oil 2 (GTL8) KV100 = 8.0 mm ² / s
(A-3) Synthetic base oil 3 (PAO40) KV100 = 40 mm ² / s
(A-4) Synthetic base oil 4 (ester 1: 3-methyl-1,5-pentanediol-di (nonanoate)) KV100 = 2.8 mm ² / s
(A-5) Synthetic base oil 5 (ester 2: trimethylolpropane fatty acid ester C6-12) KV100 = 4.4 mm ² / s
(A-6) Synthetic base oil 6 (Comparative base oil 1: diisodecyl adipate (DIDA)) KV100 = 3.6 mm ² / s
(A-7) Synthetic base oil 7 (Comparative base oil 2: dibutyl adipate (DBA)) KV100 = 1.4 mm ² / s
(A-8) Synthetic base oil 8 (Comparative base oil 3: 2-ethylhexyl palmitate (2-EHP)) KV100 = 2.5 mm ² / s

(B) Sulfur-based extreme pressure agent The amount of active sulfur described below 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: olefin sulfide (active sulfur amount = 11 mass%)
・ Sulfur-based extreme pressure agent 2: Sulfurized olefin (active sulfur amount = 32% by mass)

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

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

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

Various properties of each lubricating base oil and the lubricating oil composition were measured according to the following methods. The results are shown in Tables 1 and 2.
(1) Kinematic viscosity at 100 ° C (KV100)
Measured according to ASTM D445.
(2) Viscosity index Measured according to ASTM D2270.
(3) Evaluation of Scoring Property A four-ball abrasion tester specified by ASTM D4172 was used to perform a test under the following conditions, and the number of revolutions when seizure occurred was recorded. Oil temperature: room temperature, load: 100 kgf, rotation speed: 100 rpm increments every 30 seconds. The case where the number of rotations (rpm) exceeded 1000 was regarded as a pass.
(4) Evaluation of wear prevention property Based on ASTM D2714, a test was performed under the following conditions, and the wear width formed on the block test piece after the test was evaluated. The case where the oil temperature: 120 ° C., the load: 20 lbf, the rotation speed: 1000 rpm, the time: 1 h, and the wear width (mm) was 0.45 or less was passed.

As shown in Table 1, in the lubricating oil compositions of Comparative Examples 1 to 4, at a low viscosity of KV100 of 7 mm ² / s, either the scoring prevention property or the wear prevention property is inferior, and these cannot be compatible. .. On the other hand, the lubricating oil composition of the present invention contains a specific polyol ester compound and a sulfur-based extreme pressure agent having a specific amount of active sulfur, so that KV100 has a low viscosity of 7 mm ² / s. Also, it can have the same scoring prevention property and wear prevention property as the conventional lubricating oil composition (Reference Example 1) having a KV100 of 11 mm ² / s.

Claims (10)

  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, at least as the (A) lubricating base oil, A-1) An ester compound of a polyol and a carboxylic acid is contained in an amount of 1 to 30% by mass with respect to the total mass of the lubricating oil composition, and the sulfur-based extreme pressure agent (B) is 1 to 30% by mass of active sulfur The lubricating oil composition, comprising: The lubricating oil composition according to claim 1, wherein the lubricating oil composition has a kinematic viscosity at 100 ° C. of 5 to 10 mm ² / s. The lubricating oil composition according to claim 1, wherein the lubricating base oil (A) has a kinematic viscosity at 100 ° C. of 3 to 10 mm ² / s. The amount of the (B) sulfur-based extreme pressure agent is 1 to 15 mass% with respect to the total weight of the lubricating oil composition, and the amount of the (C) phosphorus-based extreme pressure agent is based on the total weight of the lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 3, which is from 1.5 to 8 mass%. The lubricating oil composition according to any one of claims 1 to 4, wherein the (B) sulfur-based extreme pressure agent is a sulfurized olefin.   The (C) phosphorus-based extreme pressure agent is at least one selected from amine salts of acidic phosphoric acid esters, amine salts of acidic phosphorous acid esters, amine salts of acidic thiophosphoric acid esters, and amine salts of acidic thiophosphorous acid esters. The lubricating oil composition according to any one of claims 1 to 5, which is a seed. Further, as the lubricating base oil (A), (A-2) GTL (Gas to Liquid) -derived base oil is contained in an amount of 30 to 70% by mass based on the total mass of the lubricating oil composition. The lubricating oil composition according to item 1. Further, as (A) lubricating base oil, (A-3) poly-α-olefin (PAO) base oil is contained in an amount of 10 to 40% by mass based on the total mass of the lubricating oil composition. The lubricating oil composition according to item 1. The lubricating oil composition according to any one of claims 1 to 8, which is for a transmission. The lubricating oil composition according to any one of claims 1 to 8, which is for a differential gear.