JP2017132875A - Lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition used for a speed change gear, especially differential gear even when made to have low viscosity and capable of suppressing generation of abrasion due to bearing or the like and scoring on a gear tooth flank or the like.SOLUTION: There is provided a lubricant composition containing a lubricant base oil and a sulfur extreme pressure agent, where active sulfur amount of the extreme pressure agent is 5 to 30 mass% and the extreme pressure agent is contained at the amount of 5 to 15 mass% based on mass of whole lubricant composition. The sulfur extreme pressure agent is olefin sulfide, the lubricant composition has kinetic viscosity of 5 to 15 mm/s at 100°C and the lubricant base oil preferably has kinetic viscosity of 5 to 15 mm/s at 100°C.SELECTED DRAWING: None

Description

  The present invention relates to a lubricating oil composition. In particular, the present invention relates to a lubricating oil composition for automobiles having a reduced viscosity that can be applied to a differential gear.

  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. The invention described in Patent Document 1 was made. However, the lubricating oil composition described in Patent Document 1 has insufficient wear prevention properties for bearings and the like and scoring properties for gear tooth surfaces and the like.

  Patent Document 2 discloses specific acidic phosphoric acid alkyl esters, dialkylamines and / or trialkylamines, specific sulfur compounds containing no -S-S-S- or higher polysulfur bond, and optionally A lubricating oil composition comprising thiophosphoric acid trihydrocarbyl esters is disclosed. 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.

JP 2007-039480 A JP 2014-012855 A

  Accordingly, the present invention has an object to provide a lubricating oil composition that can suppress 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 problems can be achieved by blending a specific amount of an extreme pressure agent having a specific active sulfur amount into the lubricating oil composition, and have achieved the present invention.

  That is, the present invention provides a lubricating oil composition containing a lubricating base oil and a sulfur-based extreme pressure agent, wherein the active sulfur amount of the extreme pressure agent is 5 to 30% by mass, and the extreme pressure agent is a lubricating oil. The lubricating oil composition is provided, wherein the lubricating oil composition is contained in the composition in an amount of 5 to 15% by mass based on the total mass of the composition.

Preferred embodiments of the present invention further have at least one of the following features (1) to (7).
(1) The sulfur-based extreme pressure agent is a sulfurized olefin.
(2) The lubricating oil composition has a kinematic viscosity at 100 ° C. of 5 to 15 mm ² / s.
(3) At least one part of the lubricating base oil is a Fischer-Tropsch derived base oil.
(4) At least one part of the lubricating base oil is a poly-α-olefin (PAO) base oil.
(5) The lubricating base oil has a kinematic viscosity at 100 ° C. of 5 to 15 mm ² / s.
(6) The lubricating oil composition is a lubricating oil composition for a transmission.
(7) 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 the like 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 method for producing the mineral oil 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 those described 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 from hydrocracking and hydroisomerization of raw materials such as waxes obtained from Fischer-Tropsch synthesis from natural gas such as methane (so-called Fischer-Tropsch derived) Base oil), poly-α-olefin base oil (PAO), polybutene, alkylbenzene, polyol ester, polyglycol ester, dibasic acid ester, phosphate ester, and silicon oil. Of these, Fischer-Tropsch derived base oil and poly-α-olefin (PAO) base oil are preferred.

  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 a mineral base oil and a synthetic base oil are used in combination, at least one selected from a Fischer-Tropsch derived base oil and a poly-α-olefin (PAO) base oil is used as the synthetic base oil. Good. The preferred mode of combined use is
(1) A combination of mineral oil base oil and Fischer-Tropsch derived base oil,
(2) A combination of a mineral oil base oil and a poly-α-olefin (PAO) base oil,
(3) A combination of mineral oil base oil, Fischer-Tropsch derived base oil, and poly-α-olefin (PAO) base oil, or (4) Fischer-Tropsch derived base oil, and poly-α-olefin (PAO). ) Combination with base oil.
Among them, a combination of (3) mineral oil base oil, Fischer-Tropsch derived base oil, and poly-α-olefin (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 of ^{2 to} 35 mm ² / s at 100 ° C., more preferably ^{2 to 20} mm ² / s. More preferably, the thickness is 3 to 10 mm ² / s.

The Fischer-Tropsch 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 It may be 10 mm ² / s.

The poly-α-olefin (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 hydrogen thereof. Can be used. The poly-α-olefin (PAO) base oil preferably has a kinematic viscosity at 100 ° C. of ^{2 to} 100 mm ² / s, more preferably ² to 50 mm ² / s, and even more preferably 10 to 50 mm ² / s. There should be.

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 5 to 15 mm ² / s, particularly preferably may have a 8 to 15 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 18% by mass, and still more preferably 5%. -15% by mass, 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 prevention and scoring prevention. The lower limit of the amount of active sulfur is not particularly limited, but the above lower limit is preferable for ensuring extreme pressure.

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. In a 200 ml beaker, put 50 g of a sample and 5 g of copper powder (purity 99% or more, particle size 75 μm or less), and heat to 150 ° C. while stirring with a stirrer (500 rpm).
2. When the temperature reaches 150 ° C., add 5 g of copper powder and stir for 30 minutes.
3. Stirring is stopped, and an ASTM D130-compliant copper plate 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 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 is calculated as follows.
Active sulfur content (mass%) = copper powder and sulfur content before reaction (mass%)-copper powder and sulfur content after reaction (mass%)

  The sulfur type extreme pressure agent in this invention should just have the specific active sulfur amount mentioned above, and can be selected from a well-known sulfur type extreme pressure agent. 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.

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. Specific examples include saturated or unsaturated hydrocarbon groups having a linear or branched structure having 1 to 40 carbon atoms, and may be aliphatic, aromatic, or araliphatic. 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 said formula (1) and (2), x is an integer greater than or equal to 1, Preferably it is an integer of 1-12. 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 properties and thermal oxidation stability, x is preferably an integer of 1 to 10, more preferably an integer of 1 to 8, and particularly 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 polyisobutylenes and terpenes with sulfur or other sulfurizing agents.

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

  Sulfurized fats and oils are reaction products of fats and sulfur, and are obtained by sulfidizing animal and vegetable fats and oils such as lard, beef tallow, whale oil, palm oil, coconut oil and rapeseed oil as fats and oils. . 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. 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, sulfur-containing phosphorous extreme pressure agent The lubricating oil composition of the present invention may further contain a phosphorous extreme pressure agent and / or a sulfur-containing phosphorous extreme pressure agent as optional components. it can. The sulfur element contained in the sulfur-containing phosphorus-based extreme pressure agent here is not sulfur (active sulfur) measured by ASTM D1662, and the extreme-pressure agent is distinguished from the above-described sulfur-based extreme pressure agent. It is.

  The phosphorus extreme pressure agent and the sulfur-containing phosphorus extreme pressure agent are not particularly limited and may be conventionally known ones. 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 And at least one selected from a salt, an amine salt of acidic phosphite, an amine salt of acidic thiophosphite, and an amine salt of acidic thiophosphite, phosphoric acid, and phosphorous acid .

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 4 to 30 carbon atoms. Here, the case where a = 0 is phosphoric acid, and the case where a = 1 or 2 is an acidic phosphate ester.

The phosphite ester and the acid phosphite ester 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 4 to 30 carbon atoms. Here, the case of b = 0 is phosphorous acid, and the case of b = 1 is acidic phosphite.

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 a hydrogen atom or a monovalent hydrocarbon group having 4 to 30 carbon atoms. Here, when one or two of R ³ , R ⁴ and R ⁵ are hydrogen atoms, an acidic thiophosphate is formed. 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 is 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 4 to 30 carbon atoms. Here, when one of R ⁶ and R ⁷ is a hydrogen atom, it is an acidic thiophosphate. 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.

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

  The thiophosphite is preferably a thiophosphite monoalkyl ester and a thiophosphite dialkyl ester, but is 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, dioctadece phosphite , Monooctadecenyl thiophosphate, dioctadecenyl thiophosphate, trioctadecenyl thiophosphate, monooctadecenyl thiophosphite, dioctadecenyl thiophosphite, etc. is not.

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

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, and R ⁸ , R ⁹ and R ¹⁰ are each independently hydrogen or a linear or branched chain having 1 to 20 carbon atoms, saturated or unsaturated. A saturated aliphatic hydrocarbon group, and more specifically, a methyl group, an ethyl group, a propyl group, a butyl group, a nonyl group, a dodecyl group, a propenyl group, a butenyl group, an oleyl group, and the like.

The phosphorus extreme pressure agent and sulfur-containing 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 addition amounts of the phosphorus-based extreme pressure agent and the sulfur-containing phosphorus-based extreme pressure agent are not limited and may be adjusted as appropriate. For example, 10 mass% or less is preferable with respect to the mass of the whole lubricating oil composition, More preferably, it is 1-8 mass%, More preferably, it is 2-6 mass%. If the content exceeds the above upper limit value, scoring prevention property on the tooth surface or the like may be deteriorated, which is not preferable. When the content is equal to or more than the lower limit value relative to the mass of the entire lubricating oil composition, it further contributes to wear prevention performance.

(D) Ashless Dispersant The lubricant composition of the present invention can further contain an ashless dispersant. A conventionally known ashless dispersant may be used and is not particularly limited. For example, a nitrogen-containing compound or derivative thereof having at least one alkyl group or alkenyl group having a straight chain structure or a branched structure having 40 to 400 carbon atoms in the molecule, or a modified product of alkenyl succinimide can be mentioned. . 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.

Carbon number of the said alkyl group or alkenyl group becomes like this. Preferably it is 40-400, More preferably, it is 60-350. 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 isobutylene, branched alkyl groups or branched alkenyl groups derived from ethylene and propylene co-oligomers.

  The alkenyl 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, so-called bis-type. 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 the alkenyl succinimide is, for example, a product obtained by modifying an alkenyl succinimide with a boron compound (hereinafter sometimes referred to as a 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, organic compounds such as alcohols, hexane, xylene, etc., light lubricating oil base oil, polyamine and polyalkenyl succinic acid (anhydride), boric acid, boric acid ester, or boron compounds such as borate 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 borated ashless dispersant is not particularly limited. Usually, it is 0.1 to 3% by mass relative 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 appropriately adjusted. For example, the content of the ashless dispersant is preferably 0.01 to 20% by mass, more preferably 0.1%, based on the mass of the entire lubricating oil composition. -10 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 is a viscosity index improver, an antioxidant, a metal detergent, and a friction modifier as additives other than the above components (A) to (D). , 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 dispersion type viscosity index improver copolymerized with various methacrylic acid esters containing nitrogen compounds, non-dispersion type or dispersion type ethylene-α-olefin copolymer (as α-olefin, propylene, 1-butene, 1-pentene Or a hydride thereof, polyisobutylene or a hydride thereof, a hydride of a styrene-diene copolymer, a styrene-maleic anhydride ester 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, preferably 100,000 to 900,000 in the case of dispersed and non-dispersed polymethacrylates. In the case of isobutylene or 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 is used.

Among the viscosity index improvers, when an ethylene-α-olefin copolymer or a hydride thereof is used, a lubricating oil composition particularly excellent in 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. A metallic detergent is normally mix | blended with 0.01-1 mass% as a metal amount in a lubricating oil composition.

  Examples of the friction modifier include organic molybdenum compounds, fatty acids, fatty acid esters, fats and oils, alcohols, amines, amides, and the like. A friction modifier is normally mix | blended with a lubricating oil composition at 0.01-5 mass%.

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

Examples of the rust inhibitor include petroleum sulfonates, alkyl sulfonates, fatty acids, fatty acid soaps, fatty acid amines, alkyl polyoxyalkylenes, alkenyl succinic acid esters, and polyhydric alcohol fatty acid esters. A rust preventive agent is normally mix | blended with a lubricating oil composition at 0.01-5 mass%.

Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether. A demulsifier is normally mix | blended with a lubricating oil composition at 0.01-5 mass%.

Examples of the metal deactivator include pyrroles, imidazoles, pyrazoles, pyrazines, pyrimidines, pyridazines, triazines, triazoles, thiazoles, thiadiazoles and the like. A metal deactivator is normally mix | blended with a lubricating oil composition at 0.01-3 mass%.

Examples of antifoaming agents include dimethylpolysiloxanes and their fluorinated derivatives, polyacrylates and their fluorinated derivatives, and perfluoropolyethers. An antifoamer is normally mix | blended with 0.001-1 mass% in lubricating oil composition.

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, 40~100mm 2 /} s is more preferable. More preferably, it is 50-80 mm < ² > / s.

Kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is preferably 3~40mm ² / s, more preferably 4 to 20 mm ² / s, more preferably 5 to 15 mm ² / s, particularly preferably 8 to 15 mm ² / S.

  EXAMPLES 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 oil base oil 1: KV40 = 19.0 mm ² / s, KV100 = 4 mm ² / s
Synthetic base oil 1: Fischer-Tropsch 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,
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: Acid phosphate ester amine salt (C8-C18 alkyl)
Phosphorus extreme pressure agent 2: acidic thiophosphate ester amine salt (C8-C18 alkyl)

(D) Ashless dispersant, boronated polybutenyl succinimide (bisimide type)
Polybutenyl group molecular weight = 1,400, boron = 1.8% by mass, nitrogen = 2.4% by 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. A case where the rotational speed (rpm) exceeded 1000 was regarded as acceptable.
(6) Oxidation stability Based on JIS K2514-1, it tested on the following conditions, The pentane insoluble content was measured about the sample oil after a test based on ASTM D893 (B method). Oil temperature: 135 ° C., time: 96 h. The case where the pentane insoluble matter (% by mass) was 2.0 or less was regarded as acceptable.

As is apparent from Table 2, it can be seen that the lubricating oil composition of the present invention is excellent in wear prevention, scoring prevention and oxidation stability.
On the other hand, Comparative Example 1 with a low content of sulfur-based extreme pressure agent has insufficient scoring prevention properties, and Comparative Example 2 with a too high content of sulfur-based extreme pressure agent has poor oxidation stability. In Comparative Example 3 using a sulfur-based extreme pressure agent having a high amount of active sulfur, the wear resistance is not sufficient.

  The lubricating oil composition of the present invention can suppress the occurrence of wear on bearings and the like 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 (8)

  In a lubricating oil composition containing a lubricating base oil and a sulfur-based extreme pressure agent, the amount of active sulfur in the extreme pressure agent is 5 to 30% by mass, and the extreme pressure agent is in the mass of the entire lubricating oil composition. The lubricating oil composition, wherein the lubricating oil composition is contained in the composition in an amount of 5 to 15% by mass.   The lubricating oil composition according to claim 1, wherein the sulfur-based extreme pressure agent is a sulfurized olefin. The lubricating oil composition according to claim 1, wherein the lubricating oil composition has a kinematic viscosity at 100 ° C. of 5 to 15 mm ² / s.   The lubricating oil composition according to any one of claims 1 to 3, wherein at least a part of the lubricating base oil is a Fischer-Tropsch derived base oil.   The lubricating oil composition according to any one of claims 1 to 4, wherein at least a part of the lubricating base oil is a poly-α-olefin (PAO) base oil. The lubricating oil composition according to claim 1, wherein the lubricating base oil has a kinematic viscosity at 100 ° C. of 5 to 15 mm ² / s.   The lubricating oil composition according to any one of claims 1 to 6, which is used for a transmission.   The lubricating oil composition according to any one of claims 1 to 6, which is used for a differential gear.