JP2019151804A - Lubricant oil composition - Google Patents

Abstract

To provide a lubricant oil composition which has a lower viscosity than a conventional one, has good wear resistance and good seizure resistance (gear fatigue characteristic, bearing characteristics), and is appropriately used as a lubricant oil composition for a driving oil.SOLUTION: A lubricate oil composition of the present invention comprises: (A) a lubricant base oil; (B) a sulfur-based extreme-pressure agent; (C) a phosphorus-based extreme-pressure agent. The (A) lubricant base oil has a kinematic viscosity at 100°C of 2 mm/s or larger and less than 3 mm/s. As the component of the (A), the lubricate oil composition comprises: 80 mass% or larger of (A-1) a mineral oil-based base oil which has a kinematic viscosity at 100°C of 2 mm/s or larger and less than 3 mm/s based on the total mass of the lubricant oil composition; 10 mass% or less of at least one selected from (A-2) GTL(Gas to Liquid) derived base oil which has a kinematic viscosity at 100°C of 3 mm/s or larger and 5 mm/s or less and (A-3) poly-α-olefin (PAO) base oil which has a kinematic viscosity at 100°C of 3 mm/s or larger and 5 mm/s or less based on the total mass of the lubricant oil composition. The (B) sulfur-based extreme-pressure agent comprises active sulfur in an amount of 5-30 mass%. The lubricate oil composition comprises 5-15 mass% of the component (B) based on the total mass of the lubricant oil composition. The lubricant oil composition also comprises 1.5-8 mass% of the component (C) based on the total mass of the lubricant oil composition.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 room for improvement in wear resistance in bearings and the like and scoring prevention properties in 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.

Patent Document 3 describes a lubricating oil composition containing an extreme pressure agent having a specific amount of active sulfur, and the lubricating oil composition has a kinematic viscosity at 100 ° C. of 5 to 15 mm ² / s. Is described.

JP 2007-039480 A JP 2014-012855 A JP 2017-132875 A

  The present invention is a lubricating oil composition having a lower viscosity than the lubricating oil composition described in Patent Document 3, and has good wear resistance and seizure resistance (gear fatigue characteristics, bearing characteristics). Another object of the present invention is to provide a lubricating oil composition that can be suitably used as a lubricating oil composition for driving oil.

The present inventors have specific amount of a specific lubricant base oil component, and a lubricating base oil kinematic viscosity of 100 ° C. has a less than 2.0 mm ² / s or more 3.0 mm ² / s, the specific activity It has been found that a lubricating oil composition containing a specific amount of an extreme pressure agent having a sulfur amount and a specific amount of a phosphorus-based extreme pressure agent can achieve the above-mentioned problems, and has led to the present invention.

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.
The (A) lubricating base oil has a kinematic viscosity at 100 ° C. of 2 mm ² / s or more and less than 3 mm ² / s, and as the component (A), (A-1) a kinematic viscosity at 100 ° C. of 2 mm ² / s s or more and less than 3 mm ² / s of a mineral base oil containing 80% by mass or more based on the total amount of the lubricating oil composition, and (A-2) a kinematic viscosity at 100 ° C. of 3 mm ² / s or more and 5 mm ² / GTL (Gas to Liquid) -derived base oil having s or less and (A-3) a poly-α-olefin (PAO) base oil having a kinematic viscosity at 100 ° C. of 3 mm ² / s to 5 mm ² / s at least 1 type is contained in 10 mass% or less with respect to the mass of the whole lubricating oil composition,
The amount of active sulfur of the (B) extreme pressure agent is 5 to 30% by mass, the component (B) is contained in an amount of 5 to 15% by mass with respect to the mass of the entire lubricating oil composition, and
The component (C) is contained in an amount of 1.5 to 8% by mass with respect to the mass of the entire lubricant composition, and the lubricant composition is provided.

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 (B) is a sulfurized olefin.
(2) The phosphorous extreme pressure agent (C) is a thiophosphate ester, an amine salt of a thiophosphate ester, an acidic thiophosphate ester, an amine salt of an acidic thiophosphate ester, an acidic phosphate ester, an amine salt of an acidic phosphate ester, It is at least one selected from acidic thiophosphites and amine salts of acidic thiophosphites.
(3) The (A) lubricating oil composition has a kinematic viscosity at 40 ° C. of less than 10.5 mm ² / s.
(4) The (A) lubricating oil composition has a kinematic viscosity at 100 ° C. of 2.0 or more and less than 3.5 mm ² / s.
(5) A lubricating oil composition for a transmission.
(6) A lubricating oil composition for a differential gear.
(7) A lubricating oil composition for electric vehicles.

  Although the lubricating oil composition of the present invention has a low viscosity, it can suppress the occurrence of wear on bearings and the like and scoring on gear tooth surfaces and the like. The lubricating oil composition of the present invention can be suitably used as an automotive lubricating oil, and is further suitable as a transmission gear oil, a differential gear oil, and an electric vehicle gear oil.

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

(A) Lubricating base oil The present invention is characterized in that the lubricating base oil has a kinematic viscosity at 100 ° C. of 2.0 mm ² / s or more and less than 3.0 mm ² / s. Most preferably, it is 2.3-2.7 mm < ² > / s. When the kinematic viscosity at 100 ° C. of the lubricating base oil is within the above range, the viscosity can be further reduced as compared with the conventional lubricating oil composition, and fuel efficiency can be further ensured. Furthermore, the lubricating base oil in the present invention is a combination of a mineral base oil and a synthetic base oil. The synthetic base oil is preferably at least one selected from a GTL-derived base oil and a poly-α-olefin (PAO) base oil. Therefore, the lubricating base oil of the present invention is
(1) A combination of (A-1) mineral oil base oil and (A-2) GTL-derived base oil,
(2) A combination of (A-1) mineral oil base oil and (A-3) PAO base oil, or (3) (A-1) mineral oil base oil, and (A-2) GTL-derived base oil (A-3) Combination with PAO base oil.

More specifically, the lubricating base oil of the present invention comprises (A-1) a mineral oil base oil having a kinematic viscosity of less than 2 to 3 mm ² / s at 100 ° C. of 80% by mass or more based on the total amount of the lubricating oil composition. , Preferably 80 to 90% by mass, more preferably 82 to 88% by mass. The lubricating base oil of the present invention further comprises (A-2) a GTL (Gas to Liquid) -derived base oil having a kinematic viscosity of 3 to 5 mm ² / s at 100 ° C., and (A-3) a kinematic viscosity at 100 ° C. At least one selected from poly-α-olefin (PAO) base oils having 3 to 5 mm ² / s or less is 10% by mass or less, preferably 1 to 10% by mass, based on the total mass of the lubricating oil composition. More preferably 3 to 8% by mass is contained. Among them, a combination of (A-1) mineral oil base oil and (A-2) GTL-derived base oil or a combination of (A-1) mineral oil base oil and (A-3) PAO base oil is particularly preferable. . However, as described above, (A) the kinematic viscosity at 100 ° C. of the entire lubricating base oil is 2 mm ² / s or more and less than 3 mm ² / s. Hereinafter, each base oil will be described in more detail.

(A-1) mineral base oil than the kinematic viscosity 2 to 3 mm ² / s at 100 ° C., particularly preferably from 2.3~2.7mm ² / s. The production method of the mineral oil base oil is not limited, and highly refined paraffinic mineral oil (highly refined oil obtained by subjecting hydrorefined oil, catalytic isomerized oil, etc., to solvent dewaxing or hydrodewaxing, etc. Viscosity index mineral oil-based lubricating base oil) 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.

(A-2) GTL-derived base oil has a kinematic viscosity of 3 to 5 mm ² / s or less at 100 ° C., preferably 3.5 to 4.5 mm ² / s, more preferably 3.8 to 4.3 mm ^2. / S. The GTL-derived base oil is a base oil obtained by hydrocracking and hydroisomerizing a raw material such as wax obtained from natural gas such as methane by Fischer-Tropsch synthesis or the like.

(A-3) PAO base oil has a kinematic viscosity at 100 ° C. of 3 to 5 mm ² / s or less, preferably 3.5 to 4.5 mm ² / s, more preferably 3.8 to 4.3 mm 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.

In addition, in the range where the kinematic viscosity at 100 ° C. of the lubricating base oil is 2.0 mm ² / s or more and less than 3.0 mm ² / s, as synthetic base oils other than the above, for example, polybutene, alkylbenzene, polyol ester, Polyglycol esters, dibasic acid esters, fatty acid esters, phosphate esters, silicone oils, and the like can also be used in combination.

(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. 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 (mass%) is “the amount of sulfur (mass%) contained in the original sample (procedure 1) —the amount of sulfur (mass mass) contained in the filtrate after the reaction with copper powder (procedure 4 above). %) ”.

  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. 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. In detail, for example, a saturated or unsaturated hydrocarbon group having 1 to 40 carbon atoms and having a straight chain structure or a branched structure can be mentioned, and aliphatic, aromatic, or aliphatic carbonization 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 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 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 sulfur, 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 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, a thiophosphate ester, an amine salt of a thiophosphate ester, an acidic phosphate ester, an amine salt of an acidic phosphate ester, an acidic thiophosphate ester, an amine salt of an acidic thiophosphate ester, an acidic thiophosphite ester, and an acidic thioester It is good to be at least one selected from amine salts of phosphites.

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 phosphate ester, the case where a = 1 or 2 is an acidic phosphate ester, and the case where a = 0 is phosphoric acid.

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 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 a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, and a dodecyl group. Tridecyl group, octadecyl group, eicosyl group, isobutyl group, isohexyl group, isodecyl group, isooctadecyl group, neopentyl group, 2-ethylhexyl group, and oleyl group. Preferably it is a C4-C20 monovalent hydrocarbon group.

  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 ester and acidic thiophosphite ester are preferably thiophosphite monoalkyl ester and 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, 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 the thiophosphate ester, 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 Although it can be used, it is not limited to these.

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 monooctadece 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 each independently a hydrogen atom or a saturated or unsaturated aliphatic, aromatic or araliphatic hydrocarbon group having a straight chain structure or 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 addition amount of the phosphorus extreme pressure agent is 1.5 to 8% by mass, 1.8 to 7% by mass, preferably 2 to 6% by mass, based on the mass of the entire 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 (B) the sulfur-based extreme pressure agent and (C) the 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 the (B) sulfur-based extreme pressure agent and the (C) phosphorus-based extreme pressure agent is 7 to 20% by mass with respect to the total mass of the lubricating oil composition, and more Preferably it is 8-18 mass%, More preferably, it is 9-16 mass%. Furthermore, 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, and 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 the (C) phosphorus-based extreme pressure agent in addition to the 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 mass of the entire lubricating oil composition.

(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, or a succinimide and a modified product thereof can be used. . 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 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 the succinimide is, for example, a product obtained by modifying 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, 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 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.

  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, polyisobutene 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. Or, 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 3,000-200,000 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, 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 corrosion inhibitor 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.

The kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention should be less than 10.5 mm ² / s, more preferably 9.0 to 10.4 mm ² / s, and even more preferably 9.5. 10.3 mm ² / s.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention should be 2.0 or more and less than 3.5 mm ² / s, more preferably 2.3 to 3.2 mm ² / s, and still more preferably. 2.5-3.0 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 (mass%) shown in Table 1 or 2 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) the lubricating base oil (A1) mineral base oil ^{1: KV40 = 9.4mm 2 /s,KV100=2.6mm 2} / s
(A2) Synthetic base oil 1: GTL-derived base oil, KV100 = 4.1 mm ² / s
(A3) Synthetic base oil 2: ethylene-α-olefin base oil, KV100 = 4.1 mm ² / s
(A4) (comparison) mineral base oil ^{2: KV40 = 36mm 2 /s,KV100=6.4mm 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.
(B1) Sulfurized olefin 1 (active sulfur content = 11% by mass)
(B2) (For comparison) Sulfurized olefin 2 (active sulfur content = 32 mass%)

(C) Phosphorus extreme pressure agent (C1) Phosphorus extreme pressure agent 1: Salt of acidic phosphate ester (having C4 to C8 alkyl group) and amine (having C8 to C18 alkyl group) (C2) Phosphorus system Extreme pressure agent 2: Salt of acidic thiophosphate ester (having C4-C8 alkyl group) and amine (having C8-C18 alkyl group)

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

(E) Other additives
Antioxidants, metal deactivators, antifoaming agents

Various properties of each lubricating oil composition were measured according to the following method. The results are shown in Tables 1 and 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) Wearability evaluation Based on ASTM D2714, the test was performed under the following conditions, and the wear width formed on the block test piece after the test was evaluated. Oil temperature: 120 ° C., load: 20 lbf, rotation speed: 1000 rpm, time: 1 h. The case where the wear width (mm) was 0.55 mm or less was regarded as acceptable.
(4) Seizure resistance Based on ASTM D2783, a load (non-seizure load, N) up to seizure at room temperature and 1760 rpm was measured. More than 700N was considered acceptable.

  The lubricating oil composition of the present invention has a low viscosity and can suppress the occurrence of wear on bearings and the like and scoring on gear tooth surfaces and the like. The lubricating oil composition of the present invention can be suitably used as a lubricating oil for automobiles, and is particularly suitable for gear oils for transmissions, differential gear oils, and electric vehicles.

Claims (8)

In 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,
The (A) lubricating base oil has a kinematic viscosity at 100 ° C. of 2 mm ² / s or more and less than 3 mm ² / s, and as the component (A), (A-1) a kinematic viscosity at 100 ° C. of 2 mm ² / s s or more and less than 3 mm ² / s of a mineral base oil containing 80% by mass or more based on the total amount of the lubricating oil composition, and (A-2) a kinematic viscosity at 100 ° C. of 3 mm ² / s or more and 5 mm ² / GTL (Gas to Liquid) -derived base oil having s or less and (A-3) a poly-α-olefin (PAO) base oil having a kinematic viscosity at 100 ° C. of 3 mm ² / s to 5 mm ² / s at least 1 type is contained in 10 mass% or less with respect to the mass of the whole lubricating oil composition,
The amount of active sulfur of the (B) extreme pressure agent is 5 to 30% by mass, the component (B) is contained in an amount of 5 to 15% by mass with respect to the mass of the entire lubricating oil composition, and
The said lubricating oil composition characterized by containing the said (C) component in the quantity of 1.5-8 mass% with respect to the mass of the whole lubricating oil composition. The lubricating oil composition according to claim 1, wherein the sulfur-based extreme pressure agent is a sulfurized olefin.   The (C) phosphorus-based extreme pressure agent is a thiophosphate, an amine salt of a thiophosphate, an acidic thiophosphate, an amine salt of an acidic thiophosphate, an acidic phosphate, an amine salt of an acidic phosphate, The lubricating oil composition according to claim 1 or 2, wherein the lubricating oil composition is at least one selected from an amine salt of a phosphate ester and an acidic thiophosphite ester. The lubricating oil composition according to claim 1, wherein the (A) lubricating oil composition has a kinematic viscosity at 40 ° C. of less than 10.5 mm ² / s. The lubricating oil composition according to any one of claims 1 to 4, wherein the (A) lubricating oil composition has a kinematic viscosity at 100 ° C of 2.0 mm ² / s or more and less than 3.5 mm ² / s. The lubricating oil composition according to any one of claims 1 to 5, which is used for a transmission. The lubricating oil composition according to any one of claims 1 to 5, which is used for a differential gear. The lubricating oil composition according to any one of claims 1 to 5, which is used for an electric vehicle.