JP2019123855A - Lubricant composition - Google Patents

Abstract

To provide a lubricant composition having excellent wear prevention properties while achieving reduced viscosity and reduced friction.SOLUTION: A lubricant composition contains (A) a lubricant base oil, (B) an acidic phosphate having one or two alkyl group, each of which has 4-10 carbon atoms, (C) a sulfur extreme pressure agent, and (D) a molybdenum friction modifier, where the lubricant composition does not contain a phosphite having at least one alkyl group having 9 or more carbon atoms.SELECTED DRAWING: None

Description

  The present invention relates to lubricating oil compositions, and in particular to lubricating oil compositions applicable for automotive applications. More particularly, the present invention relates to a lubricating oil composition suitable for use in an automotive transmission, a lubricating oil composition suitable for use in an automotive gear oil, and a lubricating oil composition suitable for use in a hybrid vehicle.

  Lubricating oil compositions are used in a wide variety of applications, such as automotive and mechanical applications. In recent years, the reduction of viscosity of automobile lubricating oil compositions has been demanded from the viewpoint of fuel saving. However, lowering the viscosity of the lubricating oil composition affects the ability to form an oil film. Although the reduction of viscosity is originally intended to realize the fuel saving, even if the viscosity of the one used as a conventional lubricating oil composition is reduced as it is, the oil film forming ability is inferior, so the friction is rather high. In some cases, fuel consumption can not be realized. In addition, when the oil film formation ability is lowered due to the lowering of viscosity, as a result of direct contact between metals, sufficient lubrication can not be performed, and as a result, the wear becomes intense, so the function as a lubricating oil composition I can not do enough.

  Patent Document 1 describes a lubricating oil composition suitably used as an automotive gear oil, and comprises a base oil, a viscosity index improver, a molybdenum-based friction modifier, a boron-containing dispersant, and a sulfur-based extreme pressure. A lubricating oil composition is described which comprises at least two extreme pressure agents selected from an agent, a phosphorus-based extreme pressure agent, and a sulfur-phosphorus-based extreme pressure agent, or a sulfur-phosphorus-based extreme pressure agent. Patent Document 1 describes that the lubricating oil composition achieves both fuel economy and extreme pressure, and further has shear stability, oxidation stability, and wear resistance.

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

JP, 2016-190897, A JP, 2017-132875, A

  In any of the above-mentioned patent documents, there is neither disclosure nor suggestion as a problem about further achieving both of low friction and low wear in addition to the fuel saving property accompanying the lowering of viscosity. An object of the present invention is to provide a lubricating oil composition having excellent antiwear properties while reducing viscosity and friction.

  The present inventors have intensively studied to solve the above-mentioned problems, and examined that the surface of the lubricating oil composition is smoothed to reduce the friction coefficient by specifying the additive. It has been found that lubricating oil compositions containing an acidic phosphate having a chain alkyl group and a molybdenum friction modifier have a low surface roughness and a low coefficient of friction. Furthermore, it discovered that the lubricating oil composition which has the outstanding abrasion resistance could be provided, and came to comprise this invention.

That is, the present invention relates to (A) lubricating oil base oil,
(B) An acidic phosphoric acid ester having one or two alkyl groups, each of which has 4 to 10 carbon atoms,
A lubricating oil composition comprising (C) a sulfur-based extreme pressure agent, and (D) a molybdenum friction modifier,
However, the lubricating oil composition does not contain a phosphite ester having at least one alkyl group having 9 or more carbon atoms.

Furthermore, the present invention provides a lubricating oil composition further having at least one feature of the following (1) to (9).
(1) Furthermore, it has at least one (C1) alkyl group having 11 to 30 carbon atoms which contains at least one selected from (F) the following component (F1), the following component (F2), and the following component (F3) And phosphorous acid ester (F3) phosphonic acid ester having 1 to 3 acidic phosphoric acid ester (F2) alkyl groups each having 4 to 8 carbon atoms.
(2) The lubricating oil base oil (A) has a kinematic viscosity at 100 ° C. of 1 to 15 mm ² / s.
(3) The (C) sulfur-based extreme pressure agent is at least one selected from sulfurized olefins, sulfurized oils and fats, and sulfurized esters.
(4) The (C) sulfur-based extreme pressure agent has an active sulfur content of 0.5 to 30% by mass.
(5) The (D) molybdenum friction modifier is at least one selected from molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate and a trinuclear molybdenum compound.
(6) Furthermore, (G) ashless dispersant is included.
(7) A lubricating oil composition for hybrid vehicles.
(8) A lubricating oil composition for a transmission.
(9) A lubricating oil composition for gear oil.

Furthermore, when the present inventors diligently studied for the purpose of providing a lubricating oil composition having more excellent scoring resistance under lower viscosity conditions in addition to the above-mentioned performance, the above (A) to (D) The lubricating oil composition containing the component has 1 to 3 (F2) alkyl groups as the component (F), and each of the alkyl groups is a phosphite having 4 to 8 carbon atoms and (F3) phosphonic acid By containing at least one selected from acid esters, the above-mentioned effect (small surface roughness, under the condition of a lower viscosity of ^{2 to} 10 mm ² / s at 100 ° C. of the lubricating oil composition) It has been found that, in addition to the low coefficient of friction and the excellent anti-wear properties), it is possible to provide excellent scoring resistance.

Therefore, as a more preferred embodiment of the present invention,
A lubricating oil composition as described above,
(F2) has one to three alkyl groups, and each alkyl group contains at least one selected from phosphites having 4 to 8 carbon atoms and (F3) phosphonates, and the lubricating oil composition The lubricating oil composition is provided, wherein the kinematic viscosity at 100 ° C. of the product is ² to 10 mm ² / s.
Also, the lubricating oil composition of the present invention is particularly free of amine salts of phosphoric acid esters.

As a further preferable embodiment, at least one of the following features (1) to (4) may be further included.
(1) It further contains (F4) thiophosphoric acid ester amine salt.
(2) The sulfur content in the lubricating oil composition is 0.3 to 5% by mass.
(3) The phosphorus content in the lubricating oil composition is 200 to 2000 ppm.
(4) The molybdenum content in the lubricating oil composition is 100 to 1,500 ppm.

  The lubricating oil composition of the present invention has low friction even when the viscosity is low, and can have the anti-abrasiveness required for gear oil. Furthermore, in the viscosity-reduced conditions, in addition to the above-mentioned effects, it is possible to provide a lubricating oil composition having excellent scoring resistance. The lubricating oil composition of the present invention can be suitably used particularly for hybrid vehicles, transmissions, and gear oils.

It is a schematic diagram which shows the aspect of a block on ring friction test.

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

  The process for producing the mineral base oil is not limited. As mineral oil base oil, highly refined paraffinic mineral oil (high viscosity index mineral oil base lubricating oil base oil obtained by subjecting hydrogenated refined oil, catalytic isomerized oil etc. to solvent dewaxing or hydrodewaxing etc. treatment) Is preferred. In addition, as mineral oil base oils other than the above, for example, raffinate obtained by solvent refining using an aromatic extraction solvent such as phenol and furfural as a lubricating oil raw material, hydrogen such as cobalt and molybdenum using silica-alumina as a carrier The hydrotreated oil etc. which are obtained by the hydrotreating using a hydrotreating catalyst are mentioned. For example, 100 neutral oil, 150 neutral oil, 500 neutral oil etc. can be mentioned.

  As a synthetic base oil, for example, a base oil obtained by hydrocracking treatment and hydroisomerization treatment of a raw material such as wax obtained by Fischer-Tropsch synthesis from natural gas such as methane (so-called Fischer-Tropsch derived Base oils), poly-α-olefin base oils, polybutenes, alkylbenzenes, polyol esters, polyglycol esters, dibasic acid esters, phosphoric acid esters, silicone oils and the like can be mentioned. The poly-α-olefin (PAO) base oil is not particularly limited, and for example, 1-octene oligomers, 1-decene oligomers, ethylene-propylene oligomers, isobutene oligomers and hydrogenated products thereof can be used.

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

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 whole lubricating oil base oil preferably has a kinematic viscosity of 1 to 15 mm ² / s at 100 ° C., more preferably 1 to 12 mm ² / s, Preferably, it has ² to 10 mm ² / s. If the kinematic viscosity of the lubricating base oil at 100 ° C. is above the upper limit value, it may be difficult to lower the viscosity of the lubricating oil composition, and it may be difficult to achieve fuel economy. If the kinematic viscosity at 100 ° C. is less than the lower limit, fuel economy can be achieved, but the wear characteristics may be adversely affected.

Particularly in the invention of a more preferred embodiment containing at least one of the (F2) component and the (F3) component described above, in order to obtain a lower viscosity lubricating oil composition, the entire lubricant base oil has a kinematic viscosity at 100 ° C. preferably has a 1~9mm ² / s, more preferably 1 to 8 mm ² / s, more preferably it may have a 2 to 6 mm ² / s.

(B) Acidic phosphoric acid ester having an alkyl group having 4 to 10 carbon atoms The lubricating oil composition of the present invention has one or two (B) alkyl groups, each of which has 4 to 10 carbon atoms It is characterized in that it contains an acidic phosphoric acid ester (hereinafter, simply referred to as an acidic phosphoric acid ester having an alkyl group having 4 to 10 carbon atoms) having 10, preferably 4 to 8. By containing the acidic phosphoric acid ester having the short chain alkyl group, the surface roughness of the lubricating oil composition can be reduced, and the friction coefficient can be reduced. If the carbon number of the alkyl group of the acidic phosphoric acid ester is longer than the above upper limit value, the surface of the lubricating oil composition may become rough.

From that of the acidic phosphoric acid ester represented by _{^{(R 1 O) a P (}} = O) (OH) 3-a. It can also be used as a mixture of compounds in which a = 1 or 2 and a is a different value. In the above formulas, R ^{1 's} are each independently an alkyl group having 4 to 10, preferably 4 to 8 carbon atoms. The alkyl group is, for example, a butyl group, a pentyl group, a hexyl group, and an octyl group, and may have a branch. The smaller the number of carbons in R ^1, the better. In particular, acidic phosphoric acid esters having an alkyl group having 4 carbon atoms are preferable because they are excellent in the reduction effect of the friction coefficient. The component (B) may be used alone or in combination of two or more of the above-mentioned acidic phosphoric acid esters having an alkyl group. Preferably, it is a combination of an acidic phosphoric acid ester having an alkyl group of 4 carbon atoms and an acidic phosphoric acid ester having an alkyl group of 5 to 8 carbon atoms, particularly 8 carbon atoms. When the component (B) is only one type of acidic phosphoric acid ester, particularly an acidic phosphoric acid ester having an alkyl group having 4 carbon atoms, it is preferable to further include (F) a phosphorus-based extreme pressure agent described later . By using these in combination as described above, it is possible to further ensure both the reduction of the friction coefficient and the wear resistance.

  The acidic phosphoric acid ester preferably includes acidic phosphoric acid (di) butyl ester, acidic phosphoric acid (di) pentyl ester, acidic phosphoric acid (di) hexyl ester, and acidic phosphoric acid (di) octyl ester . More preferably, it is acidic phosphoric acid (di) butyl ester or acidic phosphoric acid (di) hexyl ester, and most preferably acidic phosphoric acid (di) butyl ester.

  The amount of the acidic phosphoric acid ester contained in the lubricating oil composition of the present invention is not particularly limited, but it is preferably 100 to 1500 mass ppm as the phosphorus atom content with respect to the total mass of the lubricating oil composition 180 to 1200 mass ppm is more preferable, and 200 to 1000 mass ppm is more preferable. If the content exceeds the above upper limit, sludge may be generated, which is not preferable. When the content is less than the above lower limit value, the possibility of high friction is high, which may not contribute to fuel saving, which is not preferable. When using 2 or more types of acidic phosphoric acid ester together, it may mix | blend so that phosphorus atom content as a sum may satisfy the said range.

(C) 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 imparts seizure resistance and can function suitably as a lubricating oil composition for gear oil. Component (C) can be selected from known sulfur-based extreme pressure agents. Preferably, it is at least one selected from sulfurized olefins, sulfurized fats and oils, sulfurized esters, and polysulfides, and sulfurized olefins are particularly preferable. In the present invention, the component (C) does not include an extreme pressure agent having phosphorus.

The sulfurized olefin and polysulfide are represented by the following general formula (3). As described later, sulfurized olefins are obtained by sulfurizing olefins, and polysulfides are obtained by sulfurizing hydrocarbon raw materials other than olefins.
R ⁵ -S _x- (R ⁶ -S _x- ) _n -R ⁷ (3)

In the above formula (3), R ⁵ and R ⁷ are each independently a monovalent hydrocarbon group, and for example, a saturated or unsaturated aliphatic group having a linear structure or a branched chain having 2 to 20 carbon atoms A hydrocarbon group, a C2-C26 aromatic hydrocarbon group, etc. can be mentioned. More specifically, ethyl group, propyl group, butyl group, nonyl group, dodecyl group, propenyl group, butenyl group, benzyl group, phenyl group, tolyl group, hexylphenyl group and the like.

In the above formula (3), R ⁶ is a saturated or unsaturated aliphatic hydrocarbon group having a linear structure or branched chain having 2 to 20 carbon atoms, and an aromatic hydrocarbon group having 6 to 26 carbon atoms Etc. can be mentioned. More specifically, ethylene group, propylene group, butylene group, phenylene group and the like can be mentioned.

  In said formula (3), x is mutually independently an integer greater than or equal to 1, Preferably it is an integer of 1-8. If x is small, the extreme pressure property decreases, and if x is too large, thermal oxidation stability tends to decrease. In order to obtain both extreme pressure properties and thermal oxidation stability, x in the units shown in the parentheses is preferably an integer of 1 to 6, more preferably an integer of 2 to 4, and particularly preferably 2 or It is three.

  Examples of sulfurized olefins include those obtained by sulfurizing olefins such as polyisobutylene and terpenes with sulfur and other sulfurizing agents.

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

  Sulfurized oil and fat is a reaction product of oil and fat and sulfur, and it is obtained by using an animal or vegetable oil such as lard, beef tallow, soy sauce, palm oil, coconut oil, rapeseed oil and the like as a fat and oil, . The reaction product is not a single product but a mixture of various substances, and the chemical structure itself is not clear.

  The sulfurized ester is obtained by sulfurizing a fatty acid ester obtained by the reaction of the above-described oil and fat with various alcohols. Similar to sulfurized fats and oils, the chemical structure itself is not clear.

  The active sulfur content of the above-mentioned sulfur-based extreme pressure agent is not particularly limited, but it is preferably 30% by mass or less, preferably 15% by mass or less, based on the mass of the extreme pressure agent. It is characterized by having at 13 mass% or less more preferably. If the amount of active sulfur exceeds the above upper limit, not only metal corrosion occurs but also the occurrence of wear can not be suppressed. The lower limit of the amount of active sulfur is also not particularly limited, but for ensuring the extreme pressure property, it is preferably 0.5% by mass or more with respect to the mass of the extreme pressure agent, and more preferably 1% %, And more preferably 2% by mass or more.

Here, the amount of active sulfur is measured by the method defined in ASTM D1662. The amount of active sulfur based on ASTM D1662 can be measured in more detail by the following procedure.
1. Add 50 g of a sulfur-based additive (active sulfur-based extreme pressure agent) and 5 g of a copper powder in a beaker for 200 ml, and raise the temperature to 150 ° C. while stirring with a stirrer.
2. After reaching 150 ° C., add 5 g of copper powder and stir for 30 minutes.
3. After completion of the stirring, a copper plate conforming to ASTM D130 is put into a beaker and immersed. At this time, if discoloration is observed on the copper plate, 5 g of copper powder is further added and the mixture is stirred for 30 minutes (this operation is continued until no discoloration is observed).
4. When no color change is observed on the copper plate, the copper powder in the sulfur-based additive is removed by filtration, and the amount of sulfur contained in the additive is measured.
The amount of active sulfur is calculated as follows.
Active sulfur content (mass%) = sulfur content before reaction with copper powder (mass%)-sulfur content after reaction with copper powder (mass%)

  The content of the above-mentioned sulfur-based extreme pressure agent in the lubricating oil composition of the present invention is 0.1% by mass to 15% by mass, preferably 0.2% by mass to 12% by mass, with respect to the total mass of the lubricating oil composition More preferably, it is 0.3% by mass to 10% by mass. When the content exceeds the above upper limit, although occurrence of wear can be suppressed, sludge is generated, and in some cases, metal corrosion may be generated, which is not preferable.

  Although the sulfur content of the lubricating oil composition of the present invention is not limited, it is preferably 0.3 to 5% by mass, more preferably 0.4 to 4% by mass based on the total mass of the lubricating oil composition. %, More preferably 0.5 to 3% by mass. When the content exceeds the above upper limit, although occurrence of wear can be suppressed, sludge is generated, and in some cases, metal corrosion may be generated, which is not preferable.

(D) Molybdenum Friction Modifier As the component (D), known molybdenum friction modifiers can be used. For example, a sulfur-containing organic molybdenum compound such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC), a complex of a molybdenum compound and a sulfur-containing organic compound or another organic compound, or sulfurized molybdenum or sulfurized molybdic acid And complexes of sulfur-containing molybdenum compounds with alkenyl succinimides, and the like. Examples of the molybdenum compounds include molybdenum oxides such as molybdenum dioxide and molybdenum trioxide, orthomolybdic acids, paramolybdic acids, molybdic acids such as (poly) sulfurized molybdic acids, and metal salts of these molybdic acids and molybdenum salts such as ammonium salts. Acid salts, molybdenum disulfide such as molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, molybdenum polysulfide and the like, sulfurized molybdic acids, metal salts or amine salts of sulfurized molybdic acids, molybdenum halides such as molybdenum chloride, and the like.
Furthermore, trinuclear molybdenum compounds described in US Pat. No. 5,906,968 can also be used as a friction modifier in the present invention.

  Molybdenum dithiocarbamate (MoDTC) is a compound represented by the following formula [I], and molybdenum dithiophosphate (MoDTP) is a compound represented by the following [II].

In the above general formulas [I] and [II], R _{1 to} R ₈ may be the same or different from each other, and each is a hydrocarbon group having 1 to 30 carbon atoms. The hydrocarbon group may be linear or branched. As the hydrocarbon group, a linear or branched alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, a cycloalkyl group having 4 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, An alkylaryl group or an arylalkyl group etc. can be mentioned. In the arylalkyl group, the bonding position of the alkyl group is arbitrary. More specifically, as the alkyl group, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group And tetradecyl groups, pentadecyl groups, hexadecyl groups, heptadecyl groups, octadecyl groups, etc., and branched alkyl groups thereof. Particularly, alkyl groups having 3 to 8 carbon atoms are preferable. Also, X ₁ and X ₂ are an oxygen atom or a sulfur atom, and Y ₁ and Y ₂ are an oxygen atom or a sulfur atom.

  Sulfur-free organic molybdenum compounds can also be used as friction modifiers according to the invention. Examples of the organic molybdenum compound include molybdenum-amine complexes, molybdenum-succinimide complexes, molybdenum salts of organic acids, and molybdenum salts of alcohols. Among them, molybdenum-amine complexes, molybdenum salts of organic acids and molybdenum salts of alcohols are preferable.

The molybdenum - The molybdenum compounds constituting the amine complex, molybdenum trioxide or its hydrate _{(MoO 3 · nH 2 O)} , molybdic acid _(H 2 _MoO 4), molybdenum acid alkali metal salts _(M 2 _MoO 4; M represents an alkali metal), ammonium molybdate ((NH ₄ ) ₂ MoO ₄ or (NH ₄ ) ₆ [Mo ₇ O ₂₄ ] · 4H ₂ O), MoCl ₅ , MoOCl ₄ , MoO ₂ Cl ₂ , MoO ₂ Examples thereof include sulfur-free molybdenum compounds such as Br ₂ and Mo ₂ O ₃ Cl ₆ . Among these molybdenum compounds, hexavalent molybdenum compounds are preferable in terms of the yield of the molybdenum-amine complex. Further, among the hexavalent molybdenum compounds, molybdenum trioxide or its hydrate, molybdic acid, alkali metal molybdate and ammonium molybdate are preferable among the hexavalent molybdenum compounds from the viewpoint of availability.

  The amine compound constituting the above-mentioned molybdenum-amine complex is not particularly limited. For example, monoamines, diamines, polyamines and alkanolamines can be mentioned. More specifically, an alkylamine having an alkyl group having 1 to 30 carbon atoms (these alkyl groups may be linear or branched), and an alkenyl group having 2 to 30 carbon atoms (these alkenyl groups have a straight chain) An alkenylamine having a chain or branch), an alkanolamine having an alkanol group having 1 to 30 carbon atoms (these alkanol groups may be linear or branched), an alkylene having a carbon number of 1 to 30 Group-containing alkylene diamines, polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, the above monoamines, diamines, compounds having an alkyl group or alkenyl group having 8 to 20 carbon atoms in the polyamine, imidazoline and the like Heterocyclic compounds, and also the alkylene oxide of these compounds De adducts, and mixtures thereof and the like can be exemplified. Among these amine compounds, primary amines, secondary amines and alkanolamines are preferred.

  The carbon number of the hydrocarbon group contained in the amine compound constituting the molybdenum-amine complex is preferably 4 or more, more preferably 4 to 30, and particularly preferably 8 to 18. If the carbon number of the hydrocarbon group of the amine compound is less than 4, the solubility tends to deteriorate. Further, by setting the carbon number of the amine compound to 30 or less, the molybdenum content in the molybdenum-amine complex can be relatively increased, and the effect of the present invention can be further enhanced with a small amount of blending.

  As a molybdenum succinimide complex, the complex of the molybdenum compound which does not contain the sulfur illustrated in description of the said molybdenum-amine complex, and the succinimide which has a C4 or more alkyl group or an alkenyl group is mentioned. As succinimide, succinimide or derivatives thereof having at least one alkyl group having 40 to 400 carbon atoms or alkenyl group in the molecule described in the section of ashless dispersant to be described later, or 4 to 39 carbon atoms are preferable. The succinimide etc. which have a C8-C18 alkyl group or an alkenyl group are mentioned. If the carbon number of the alkyl group or the alkenyl group in succinimide is less than 4, the solubility tends to be deteriorated. In addition, although it is also possible to use a succinimide having an alkyl group or alkenyl group having a carbon number of more than 30 and 400 or less, by setting the carbon number of the alkyl group or alkenyl group to 30 or less The molybdenum content in the complex can be relatively increased, and the effect of the present invention can be further enhanced with a small amount of blending.

  Examples of the molybdenum salt of an organic acid include the salts of an organic acid with the molybdenum oxide exemplified in the description of the above-mentioned molybdenum-amine complex, or a molybdenum base such as molybdenum hydroxide, molybdenum carbonate or molybdenum chloride and the like. As an organic acid, a carboxylic acid is preferable. Moreover, as a carboxylic acid which comprises the molybdenum salt of carboxylic acid, any of a monobasic acid or a polybasic acid may be sufficient.

  As the monobasic acid, a fatty acid having 2 to 30, preferably 4 to 24 carbon atoms is used, and the fatty acid may be linear or branched, and may be saturated or unsaturated. Well, saturated fatty acids, mixtures thereof and the like can be mentioned. Further, as the monobasic acid, in addition to the above-mentioned fatty acid, a monocyclic or polycyclic carboxylic acid (which may have a hydroxyl group) may be used, and its carbon number is preferably 4 to 30, and more preferably 7 To 30. An aromatic carboxylic acid having 0 to 3, preferably 1 to 2 linear or branched alkyl group having 1 to 30, preferably 1 to 20 carbon atoms as a monocyclic or polycyclic carboxylic acid Or cycloalkyl carboxylic acid and the like.

  Examples of polybasic acids include dibasic acids, tribasic acids and tetrabasic acids. The polybasic acid may be either a linear polybasic acid or a cyclic polybasic acid. Moreover, in the case of a linear polybasic acid, it may be either linear or branched, and may be either saturated or unsaturated. As a chain | strand-shaped polybasic acid, a C2-C16 chain | strand-shaped dibasic acid is mentioned preferably.

  Examples of the molybdenum salt of alcohol include salts of alcohol and a sulfur-free molybdenum compound exemplified in the description of the above-mentioned molybdenum-amine complex, and the alcohol may be a monohydric alcohol, polyhydric alcohol, partial ester of polyhydric alcohol or a partial ester of polyhydric alcohol It may be any of partial ether compounds, nitrogen compounds having a hydroxyl group (alkanolamines and the like), and the like. Molybdic acid is a strong acid and forms an ester by reaction with an alcohol. The ester of molybdic acid and alcohol is also included in the molybdenum salt of alcohol as referred to in the present invention. Examples of nitrogen compounds having a hydroxyl group include alkanolamines exemplified in the description of the molybdenum-amine complex, and alkanolamides (diethanolamide etc.) in which the amino group of the alkanol is amidated, among which stearyldiethanolamine and polyethylene. Preferred are glycol stearyl amine, polyethylene glycol dioleyl amine, hydroxyethyl lauryl amine, oleic acid diethanolamide and the like.

  Molybdenum friction modifiers are not particularly limited as long as this is the case, but molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC) are particularly preferable.

  Although the content of the molybdenum friction modifier in the lubricating oil composition is not limited, it is preferably 50 to 1,500 mass ppm, preferably 100 to 1,500 mass ppm, and more preferably 100 to 1,200 mass ppm as a molybdenum atomic weight. Preferably, 300 to 1100 mass ppm is the most preferable. In particular, 250 to 1000 mass ppm is preferable.

(E) A phosphite ester having an alkyl group having 9 or more carbon atoms The lubricating oil composition of the present invention comprises a phosphite ester having at least one alkyl group having 9 or more carbon atoms, particularly 9 to 30 carbon atoms. It does not include phosphite esters having at least one alkyl group. This is because a lubricating oil composition containing an alkyl group-containing phosphite ester having 9 or more carbon atoms has a high coefficient of friction and does not contribute to fuel saving. In particular, it should not contain a phosphite ester having at least one alkyl group having 9 to 30 carbon atoms.

  Examples of phosphite esters having at least one alkyl group having 9 or more carbon atoms include, for example, turinolil phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, tritetradecyl phosphite, phosphorous Examples include, but are not limited to, tripentadecyl acid acid, trihexadecyl acid phosphite, triheptadecyl acid phosphite, trioctadecyl acid phosphite, torinadecyl acid phosphite, and trieicosyl phosphite.

(F) Specific Phosphorus Extreme Pressure Agent The lubricating oil composition of the present invention preferably further comprises (F) a specific phosphorus extreme pressure agent in addition to the component (B). The specific phosphorus-based extreme pressure agent is at least one selected from the following component (F1), the following component (F2), and the following component (F3).
(F1) Acidic phosphoric acid ester having at least one alkyl group having 11 to 30 carbon atoms (F2) having 1 to 3 alkyl groups, each of the alkyl groups having 4 to 8 carbon atoms, phosphorous Acid ester
(F3) Phosphonate ester.
As described above, by using the component (B) and the component (F) in combination, it is possible to more reliably obtain the excellent friction reduction effect and the wear resistance effect. The component (F) may be any one of the above (F1), (F2) and (F3), or two or more may be used in combination. In a more preferred embodiment, the component (F) is at least one of the components (F2) and (F3). In particular, the combined use of (F3) phosphonic acid ester and the above (B) component is preferable, and the coefficient of friction can be further lowered. Hereinafter, each of (F1) to (F3) will be described in more detail.

(F1) An acidic phosphoric acid ester having at least one alkyl group having 11 to 30 carbon atoms is represented by the following general formula, and (R ¹ O) _a P (= O) (OH) _3-a
It is a compound in which a is 1 or 2 and at least one of R ¹ is an alkyl group having 11 to 30 carbon atoms. When a is 2, the other R ¹ may be an alkyl group having 4 to 10 carbon atoms, but in particular, all of R ¹ are alkyl groups having 11 to 30 carbon atoms.

  Examples of (F1) include nonyl acid phosphate, decyl acid phosphate, undecyl acid phosphate, tridecyl acid phosphate, tridecyl acid phosphate, tetradecyl acid phosphate, pentadecyl acid phosphate, hexyldecyl acid phosphate, acidic Examples include, but are not limited to, pentyl decyl phosphate and octyl decyl acid phosphate. In particular, decyl acid phosphate, dodecyl acid phosphate, tetradecyl acid phosphate, hexyldecyl acid phosphate and octyldecyl acid phosphate are preferred.

(F2) The phosphite ester having an alkyl group having 4 to 8 carbon atoms is, for example, a compound represented by the following formula (1) or (2).
_{^{(R 2 O) b P (}} = O) (OH) 2-b H (1)
(R ³ O) ₃ P (2)
A b = 1 or 2 in formula (1), and ^{R 2,} independently of each other, an alkyl group having 4-8 carbon atoms. In said Formula (2), R < ³ > is mutually independently a C4-C8 alkyl group.

  Examples of the above phosphite ester include phosphite tributyl ester, phosphite dibutyl ester, phosphite monobutyl ester, phosphite tripentyl ester, phosphite dipentyl ester, phosphite monopentyl ester, phosphite Phosphoric acid trihexyl ester, phosphorous acid dihexyl ester, phosphorous acid monohexyl ester, phosphorous acid triheptyl ester, phosphorous acid diheptyl ester, phosphorous acid monoheptyl ester, phosphorous acid trioctyl ester, phosphorous acid Dioctyl ester and phosphite monooctyl ester can be mentioned. Among them, phosphite tributyl ester, phosphite tripentyl ester, phosphite trihexyl ester, phosphite triheptyl ester, and phosphite trioctyl ester are preferably used.

The component (F3) is a phosphonic acid ester and is represented by the following formula.
(R ⁴ O) (R ⁵ O) (R ⁶ ) P (= O) (3)

In formula (3), R ⁴ and R ⁵ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 30 carbon atoms, and at least one of R ⁴ and R ⁵ has 1 to 30 carbon atoms. R ⁶ is a monovalent hydrocarbon group having 1 to 30 carbon atoms.

In the above formula (3), R ⁴ and R ⁵ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 30 carbon atoms, at least one of which is a hydrocarbon group. That is, any one of R ⁴ and R ⁵ is an alkyl group having 1 to 30 carbon atoms, preferably an alkyl group having 2 to 20 carbon atoms, and more preferably an alkyl group having 4 to 18 carbon atoms. And an alkyl group having 8 to 18 carbon atoms is most preferable. As another preferred embodiment, ^{R 4} and ^{R 5} are both alkyl groups having 1 to 30 carbon atoms, more preferably ^{R 4} and ^{R 5} are both alkyl groups having 2 to 20 carbon atoms.

In the above formula (3), R ⁶ is a monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably an alkyl group, more preferably an alkyl group having 2 to 20 carbon atoms, and most preferably a carbon number It is an alkyl group of 4 to 18, particularly an alkyl group having 8 or 18 carbon atoms.

  Examples of phosphonic acid esters include dimethyl butyl phosphonate, diethyl butyl phosphonate, dipropyl butyl phosphonate, dibutyl phosphonate, dipentyl butyl phosphonate, dihexyl butyl phosphonate, diheptyl butyl phosphonate, dioctyl butyl phosphonate, hexyl phosphonate Diethyl hexylphosphonate, Dipropyl hexylphosphonate, Dibutylhexylphosphonate, Dipentyl hexylphosphonate, Dipentyl hexylphosphonate, Dihexyl hexylphosphonate, Diheptyl hexylphosphonate, Dioctyl hexylphosphonate, Dimethyl octylphosphonate, Diethyl octylphosphonate, Octylphosphonate Acid dipropyl, octyl phosphonate dibutyl, octyl phosphonate dipentyl, octyl phosphonate dihexyl, octo Diheptyl transphosphonate, Dioctyl octylphosphonate, Dimethyl decylphosphonate, Diethyl decylphosphonate, Dipropyl decylphosphonate, Dibutyl decylphosphonate, Dihexyl decylphosphonate, Dioctyl decylphosphonate, Didecyl decylphosphonate, Didecyl dodecylphosphonate, Dodecyl Diethyl phosphonate, Dipropyl dodecyl phosphonate, Dibutyl dodecyl phosphonate, Di hexyl dodecyl phosphonate, Dioctyl dodecyl phosphonate, Didecyl dodecyl phosphonate, Didecyl dodecyl phosphonate, Didodecyl dodecyl phosphonate, Dimethyl tetradecyl phosphonate, Diethyl tetradecyl phosphonate, Tetradecyl phosphonate Dipropyl, dibutyl tetradecylphosphonate, dihexyl tetradecylphosphonate, geotetradecylphosphonate Chilly, didecyl tetradecylphosphonate, didodecyl tetradecylphosphonate, ditetradecyl tetradecylphosphonate, dimethyl hexadecylphosphonate, diethyl hexadecylphosphonate, dipropyl hexadecylphosphonate, dibutyl hexadecylphosphonate, dihexyl hexadecylphosphonate, Dioctyl hexadecyl phosphonate, Didecyl hexadecyl phosphonate, Didodecyl hexadecyl phosphonate, Ditetradecyl hexadecyl phosphonate, Dimethyl octadecyl phosphonate, Diethyl octadecyl phosphonate, Dipropyl octadecyl phosphonate, Dibutyl octadecyl phosphonate, Dipentyl octadecyl phosphonate, Octadecyl Dihexyl phosphonate, diheptyl octadecylphosphonic acid, octadecylphosphonic acid Dioctyl, octadecyl phosphonic acid dioctadecyl etc. are mentioned.

  The content of the component (F) in the lubricating oil composition is not particularly limited, but it is preferably 100 to 1,500 mass ppm as phosphorus atom content, more preferably 200 to 1,200 mass ppm, and 300 to 1,000 mass ppm. Is more preferred. If the content exceeds the above upper limit, sludge may be generated, which is not preferable. When the content is less than the above lower limit value, the possibility of high friction is high, which may not contribute to fuel saving, which is not preferable. When using 2 or more types together, it may mix | blend so that phosphorus atom content as a sum may satisfy | fill the said range.

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

The carbon number of the above-mentioned alkyl group or alkenyl group is preferably 40 to 400, more preferably 60 to 350. When the carbon number of the alkyl group and the alkenyl group is less than the lower limit value, the solubility of the compound in a lubricating oil 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 be deteriorated. The alkyl group and the alkenyl group may have a linear structure or a branched structure. Preferred embodiments include, for example, oligomers of olefins such as propylene, 1-butene and isobutylene, branched alkyl groups or branched alkenyl groups derived from co-oligomers of ethylene and propylene, and the like.

  The succinimide includes so-called mono-type succinimide in which succinic anhydride is added to one end of a polyamine, and so-called bis-type succinimide in which succinic anhydride is added to both ends of a polyamine. The lubricating oil composition of the present invention may contain either one or both of mono type and bis type.

  The modified product of the alkenyl succinimide is, for example, one obtained by modifying a succinimide compound having an alkenyl with a boron compound (that is, a borated ashless dispersant). To modify with a boron compound means to perform boration (hereinafter referred to as borated succinimide). The borated succinimide may be used alone or in combination of two or more. When used in combination, the borated succinimide and the non-borated succinimide may be used in combination, or a combination of two or more of the borated succinimides may be used. Moreover, when using together, both a mono type and a bis type may be included, the combination of mono types may be used, or the combination of bis types may be used.

  For example, methods for producing borated succinimide are disclosed in JP-B-42-8013 and JP-B-42-8014, JP-A-51-52381 and JP-A-51-130408. Methods etc. can be mentioned. Specifically, for example, alcohols, organic solvents such as hexane and xylene, light lubricating oil base oils etc. polyamines and polyalkenylsuccinic acids (anhydrides) and boric compounds such as boric acid, boric acid esters or boric acid salts Can be obtained by mixing and heat-treating under appropriate conditions. The boron content in the borated succinimide obtained in this manner can be usually 0.1 to 4% by mass. In particular, a boron-modified compound of an alkenyl succinimide compound (borated succinimide) is preferable because it is excellent in heat resistance, antioxidant properties and antiwear properties.

  The content of boron contained in the borated ashless dispersant is not particularly limited. Usually, it is 0.1 to 3% by mass with respect to the mass of the ashless dispersant. In one embodiment 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% by mass or less, more preferably Is preferably 1.5% by mass or less, more preferably 1.0% by mass or less. The borated ashless dispersant is preferably a borated succinimide, and in particular a borated bissuccinimide is preferred. When a borated ashless dispersant is used, its boron content is 0.01% by mass or more, preferably 0.02% by mass or more, more preferably 0.025% by mass or more based on the mass of the entire composition. It is preferably at most 0.15 wt%, preferably at most 0.1 wt%, particularly preferably at most 0.05 wt%.

  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 0.5, more preferably 0.4 or less. It is preferable to have.

  The content of the ashless dispersant in the lubricating oil composition may be appropriately adjusted, but for example, it is preferably 0.01 to 20% by mass, more preferably 0 based on the total mass of the lubricating oil composition. And 1 to 10% by mass. If the content of the ashless dispersant is less than the above lower limit value, the effect of improving the cleanliness may be insufficient. When the content exceeds the above upper limit, sludge of the lubricating oil composition may be generated.

As a more preferable embodiment in the present invention, it has 1 to 3 of the above (F2) alkyl group, and each of the alkyl groups is selected from phosphite ester having 4 to 8 carbon atoms and (F3) phosphonate ester A lubricating oil composition comprising at least one as an essential component. Thereby, the above-described effects of the present invention (a small surface roughness, a low coefficient of friction, and a further excellent condition of the lubricating oil composition under the condition of a lower viscosity of ^{2 to} 10 mm ² / s at 100 ° C.) In addition to the above anti-abrasive properties, excellent scoring resistance can be provided.
That is, a more preferred embodiment is
(A) Lubricant base oil,
(B) An acidic phosphoric acid ester having one or two alkyl groups, each of which has 4 to 10 carbon atoms,
(F) At least one kind of (C) having one to three (F2) alkyl groups, each of which is selected from phosphites having 4 to 8 carbon atoms and (F3) phosphonates A lubricating oil composition comprising an extreme pressure agent and (D) a molybdenum friction modifier and having a kinematic viscosity at 100 ° C. of ^{2 to} 10 mm ² / s, provided that the alkyl has 9 or more carbon atoms. Said lubricating oil composition which does not contain the phosphite ester which has at least one group.
The components (A), (B), (F2), (F3), (C) and (D) are as described above. Particularly preferably in the lubricating oil composition, no amine salt of phosphoric acid ester is contained.

The lubricating oil composition of the present invention may further contain (F4) thiophosphoric acid ester amine salt. Thereby, the wear of the lubricating oil composition can be reduced.
The amine salt of the thiophosphoric acid ^ester, represented by _{(R 8 O) d P (} = X) (XH) 3-d · (NH e R 9 O 3-e) 3-d. In the above formulae, it can also be used as a mixture of compounds where d, e = 1 or 2 and d, e have different values. X is an oxygen atom or a sulfur atom, but at least one is an oxygen atom. In the above formulae, R ⁸ and R ⁹ are each independently an alkyl group having 4 to 30 carbon atoms. If it is a C4-C30 alkyl group, it may be linear or may have a branch. The component (F4) may be used alone or in combination of two or more kinds of amine salts of thiophosphate. The number of carbon atoms of R ⁸ and R ⁹ is not limited as long as it is in the range of 4 to 30, but the range of 4 to 20 carbon atoms is preferable, and the range of 4 to 16 carbon atoms is more preferable.

  The content of the components (B) and (F) in the lubricating oil composition is not particularly limited, but 200 to 2000 mass ppm is preferable as the phosphorus atom content in the lubricating oil composition, and 300 to 1900 mass. ppm is more preferable, and 600 to 1750 mass ppm is more preferable. If the content exceeds the above upper limit, sludge may be generated, which is not preferable. When the content is less than the above lower limit value, the possibility of high friction is high, which may not contribute to fuel saving, which is not preferable. When using 2 or more types together, it may mix | blend so that phosphorus atom content as a sum may satisfy | fill the said range.

(H) Other Additives The lubricating oil composition of the present invention contains the above-mentioned (B) component, (E) component and (F) component as other additives other than the above (A) to (G) components. Other phosphorus extreme pressure agents, metal detergents, viscosity index improvers, antiwear agents, antioxidants, corrosion inhibitors, antirust agents, anti-emulsifiers, metal deactivators, antifoam agents, friction control not applicable Agents (which do not correspond to the molybdenum friction modifier to be the above component (D)), pour point depressants, etc. can be contained.

  Phosphoric acid, phosphorous acid, phosphoric acid ester (except for acidic phosphoric acid ester), phosphorous acid ester as a phosphorus based extreme pressure agent which does not correspond to the above components (B), (E) and (F) Amine salts, amine salts of phosphoric acid esters, amine salts of acidic phosphoric acid esters, thiophosphoric acid esters, amine salts of thiophosphoric acid esters, thiophosphorous acid esters, zinc dithiophosphate can be mentioned.

  Other phosphates include didecyl phosphate, didodecyl phosphate, tridodecyl phosphate, tridodecyl thiophosphate, trihexadodecyl phosphate, trihexadodecyl thiophosphate, trioctadecenyl phosphate, and trioctathiophosphate And decenyl and the like.

  Examples of amine salts such as phosphoric acid esters include: monooctyl phosphate amine salt, dioctyl phosphate amine salt, trioctyl phosphate amine salt, dioctyl thiophosphate amine salt, trioctyl thiophosphate amine salt, didecyl phosphate Amine salt, amine salt of didodecyl phosphate, amine salt of tridodecyl phosphate, amine salt of tridodecyl thiophosphate, amine salt of trihexadodecyl phosphate, amine salt of trihexadodecyl thiophosphate, trioctadecenyl phosphate Amine salts and amine salts of trioctadecenyl thiophosphate and the like can be mentioned.

  The metal detergent is not particularly limited, but is preferably one or more metal detergents having an element selected from calcium and magnesium. As a metal detergent having calcium, calcium sulfonate, calcium phenate and calcium salicylate are preferable. One of these metal detergents may be used alone, or two or more thereof may be mixed and used. As the metal detergent having magnesium, magnesium sulfonate, magnesium phenate and magnesium salicylate are preferable. One of these metal detergents may be used alone, or two or more thereof may be mixed and used. The total base number of the metal detergent is not limited, but is preferably 50 to 600 (mg KOH / g), more preferably 100 to 500 (mg KOH / g), still more preferably 200 to 300 (mg KOH / g) is there.

  As a viscosity index improver, for example, a so-called non-dispersed viscosity index improver such as a polymer or copolymer of one or more monomers selected from various methacrylic acid esters, or a hydrogenated product thereof, or Further, so-called dispersed viscosity index improvers obtained by copolymerizing various methacrylic acid esters containing nitrogen compounds, non-dispersed or dispersed ethylene-α-olefin copolymers (propylene, 1-butene as α-olefin, 1 -Pentene etc. can be exemplified) or a hydride thereof, polyisobutylene or a hydrogenated product thereof, a hydride of a styrene-diene copolymer, a styrene-maleic anhydride ester copolymer, polyalkylstyrene and the like.

  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 generally 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 its hydride, it is usually 800 to 5,000, preferably 1,000 to 4,000, and in the case of ethylene-α-olefin copolymer or its hydride, usually 800 to 500,000, Preferably, 3,000 to 200,000 are used.

  Among the viscosity index improvers, when an ethylene-α-olefin copolymer or a hydride thereof is used, it is possible to obtain a lubricating oil composition excellent in shear stability. One or two or more compounds arbitrarily selected from the viscosity index improvers can be contained in any amount.

  The antioxidant may be any of those generally used in lubricating oils, and examples thereof include ashless antioxidants such as phenolic antioxidants and amine antioxidants, organometallic antioxidants, etc. It can be mentioned. The addition of an antioxidant further enhances the antioxidative properties of the lubricating oil composition and not only enhances the corrosion or corrosion and wear resistance performance of the lead-containing metal of the composition of the present invention, but also enhances the base number retention. Can.

  As a corrosion inhibitor, a benzotriazole type, a tolyltriazole type, a thiadiazole type, an imidazole type compound etc. are mentioned, for example.

  Examples of the antirust agent include petroleum sulfonate, alkyl benzene sulfonate, dinonyl naphthalene sulfonate, alkenyl succinic acid ester, polyhydric alcohol ester and the like.

  Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether.

  As a metal deactivator, for example, imidazoline, pyrimidine derivative, alkyl thiadiazole, mercaptobenzothiazole, benzotriazole or derivative thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis Examples include dialkyl dithiocarbamate, 2- (alkyl dithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

  As a friction modifier which does not correspond to (D) component, an organic friction modifier is mentioned. For example, amide-based friction modifiers, ester-based friction modifiers, and ether-based friction modifiers can be mentioned, and as a typical one, glycerin mono-oleate (GMO) can be mentioned.

As the antifoaming agent, for example, silicone oil having a kinematic viscosity of 1,000 to 100,000 mm ² / s at 25 ° C., alkenyl succinic acid derivative, ester of polyhydroxy aliphatic alcohol and long chain fatty acid, methyl salicylate and o- Hydroxybenzyl alcohol etc. are mentioned.

  As other additives, polydienes having functional groups at at least one end can be included. The polydiene having a functional group at at least one end is one in which at least one end of the polydiene molecular chain is modified by the introduction of a functional group (hereinafter sometimes referred to as a terminal-modified polydiene). The polydiene is obtained by (co) polymerizing a monomeric diene, and the saturated polydiene is a carbon-carbon double bond of the polydiene obtained as described above is saturated by hydrogenation. It is a hydride. The terminally modified polydiene may be a terminally modified unsaturated polydiene or a terminally modified saturated polydiene. From the viewpoint of solubility in a lubricating oil base oil, it is preferable to use a terminally modified saturated polydiene. The polydiene having a functional group is adsorbed on the sliding surface to partially increase the viscosity of the composition to increase the oil film thickness of the lubricating oil composition. Thereby, it is possible to suppress metal fatigue and wear of gear tooth flanks and bearings in a low viscosity lubricating oil composition, and to improve part protection performance. Here, the functional group is a functional group containing at least one hetero atom selected from the group consisting of oxygen, sulfur, nitrogen and phosphorus, and as a preferable functional group, a carboxyl group, an ester group, an anhydrous carboxyl group And hydroxyl groups, glycidyl groups, urethane groups and amino groups.

  The blending amount of the terminally modified polydiene is not particularly limited, but is 0.6 to 4.0% by mass, preferably 0.8 to 3.8% by mass with respect to the total mass of the lubricating oil composition. And more preferably 1.0 to 3.6% by mass.

The lubricating oil composition is obtained by mixing the components (A) to (D) and optional components (F), (G) and other additives. But it is not particularly limited kinematic viscosity of the lubricating oil composition, in order to ensure fuel economy, it is preferable that the kinematic viscosity of 100 ° C. is 1 to 25 mm ² / s, at 2 to 20 mm ² / s It is more preferable that

A further preferred embodiment is a lubricating oil composition essentially containing the above components (A) to (D) and (F2) and / or (F3) and having a kinematic viscosity at 100 ° C. of ² to 10 mm ² / s is preferably 2 to 8 mm ² / s, is preferably 3 to 8 mm ² / s. Thereby, the lubricating oil composition can secure further fuel efficiency.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples, but the present invention is not limited to the following examples.

Each component which comprises the lubricating oil composition of Examples 1-10 and Comparative Examples 1-7 is as follows.
(A) Lubricant base oil (A1) Highly refined hydrocracked base oil (Kinematic viscosity at 100 ° C. = 4.2 mm ² / s, viscosity index = 122,% cp = 72%,% Cn = 28%)
(B) Acidic phosphoric acid ester (B1) Acidic phosphoric acid ester having a C 4 alkyl group (a mixture of dibutyl acid phosphate and monobutyl acid phosphate)
(B2) Acidic phosphoric acid ester having an alkyl group having 8 carbon atoms (a mixture of dioctyl acid phosphate and monooctyl acid phosphate)
(C) Sulfur-based extreme pressure agent (C1) Sulfurized olefin (active sulfur content: 11% by mass)
(C2) Sulfurized ester (active sulfur content: 1.4% by mass)
(C3) Sulfurized oil and fat (active sulfur content: 4.1% by mass)
(D) Molybdenum friction modifier (D1) Molybdenum dithiocarbamate (MoDTC, molybdenum content 10% by mass)
(D2) Molybdenum dithiophosphate (MoDTP, molybdenum content 9% by mass)
(For comparison) Phosphorous ester having an alkyl group having 18 carbon atoms, represented by the following general formula: General formula (R ² O) P (= O) (OH) H, R ² is C ₁₈ H ₃₇ (octadecyl Basis)
(F) Phosphorus extreme pressure agents other than the above (B) (F1-1) Acidic phosphoric acid ester having an alkyl group having 18 carbon atoms (mixture of dioctadecyl acid phosphate and monooctadecyl acid phosphate)
(F2-1) A phosphorous acid ester having an alkyl group having 4 carbon atoms, represented by the following general formula (R ² O) P (= O) (OH) H, R ² is a C ₄ H ₉ (butyl group )
(F2-2) A phosphorous acid ester having an alkyl group having 8 carbon atoms, represented by the following general formula (R ² O) P (= O) (OH) H, R ² is a C ₈ H ₁₇ (octyl group )
(F3-1) Phosphonate ester (R ³ O) (R ⁴ O) (R ⁵ ) P (= O), R ³ , R ⁴ , having an alkyl group having 8 carbon atoms, represented by the following general formula And R ⁵ is C ₈ H ₁₇ (octyl group)
(F3-2) Phosphonate ester having an alkyl group having 18 carbon atoms (CH ₃ O) (CH ₃ O) (R ⁵ ) P (= O) represented by the following general formula, R ⁵ is C ₁₈ H ₃₇ (octadecyl group)
(G) Ashless dispersants Boron-modified polyisobutylene succinic acid bisimide (molecular weight of polyisobutylene; 2000, nitrogen content; 1.7% by mass, boron content; 0.3% by mass)

[Examples 1 to 10 and Comparative Examples 1 to 7]
The lubricating oil composition was prepared by mixing the components described above in the compositions and amounts described in Tables 1 to 3. The amounts of acid phosphate ester, phosphite ester, and phosphonate ester described in the table are mass ppm of phosphorus atom based on parts by mass of the lubricating oil composition as a whole. Molybdenum friction modifier is the mass ppm of molybdenum atoms based on parts by weight of the total lubricating oil composition. The amounts of the sulfur-based extreme pressure agent, the ashless dispersant and the other additives are% by mass based on the total mass of the lubricating oil composition.

The following tests were conducted on these lubricating oil compositions. The results are shown in Tables 1 to 3.
(1) Kinematic viscosity at 100 ° C (KV 100)
It conformed to ASTM D445.
(2) Measurement method of friction coefficient:
A ring test made of steel material having a sliding surface width of 6 mm (Standard test piece (hardness RC 58-63 made by FALEX made of steel material (SAE O1) made of steel material (SAE O1)) and 35 mm outside diameter and 9 mm width A block on ring friction test was performed using a piece (a standard test piece (hardness RC 58-63) manufactured by FALEX Co., Ltd. made of steel material (SAE 4620)). FIG. 1 is a schematic view showing the block on ring friction test. A block on ring friction test was conducted for 30 minutes with a test load of 294 N, a sliding speed of 0.3 m / s, and an oil temperature of 80 ° C. (constant), and the friction coefficient after 30 minutes was taken as the friction coefficient in this test.
(3) Measurement method of wear depth:
The surface roughness was measured using a surface roughness meter (SURFTEST SV-3200, manufactured by Mitutoyo Co., Ltd.) for each of the block test pieces before and after the block-on-ring friction test, and the amount of wear was calculated.

As shown in Table 3, the lubricating oil composition containing a phosphite having 18 carbon atoms and an acid phosphate having 4 carbon atoms has a large coefficient of friction (Comparative Example 1). The lubricating oil composition which does not contain the short chain alkyl group-containing acidic phosphoric acid ester is inferior in abrasion resistance or low in friction coefficient (Comparative Examples 2 and 3). The lubricating oil composition which does not contain the molybdenum friction modifier has a large friction coefficient and is inferior in abrasion resistance (Comparative Examples 4 to 6). The lubricating oil composition containing no sulfur-based extreme pressure agent has a large coefficient of friction (Comparative Example 7).
In contrast, as shown in Examples 1 to 10 of Tables 1 and 2, the lubricating oil composition of the present invention has a reduced coefficient of friction and has good wear resistance.

[Examples 11 to 16, Reference Example 1 and Comparative Examples 8 to 13]
Each component which comprises the lubricating oil composition of Examples 11-16, the reference example 1, and the comparative examples 8-13 is as follows.
(A) Lubricant base oil (A1) GTL base oil (hereinafter sometimes referred to as "GTL-4")
(Kinematic viscosity at 100 ° C. = 4.2 mm ² / s, viscosity index = 122,% cp = 100%,% Cn = 0%)
(A2) GTL base oil (hereinafter sometimes referred to as "GTL-8")
(Kinematic viscosity at 100 ° C. = 8.0 mm ² / s, viscosity index = 124,% cp = 100%,% Cn = 0%)
As a (B) component, the acidic phosphoric acid ester which has the same (B1) C4 alkyl group as the said Examples 1-10 was used.
For comparison, (B2) an acidic phosphoric acid ester having an alkyl group having 12 carbon atoms, and (B3) an acidic phosphoric acid ester having an alkyl group having 18 carbon atoms were used.
(F) As a phosphorus-based extreme pressure agent other than the above (B), the same (F2-1) phosphite ester having an alkyl group having 4 carbon atoms as in the above example and the same (F3-2) carbon as in the above example The phosphonic acid ester which has several 18 alkyl group was used. Moreover, the amine salt of the thiophosphoric acid ester which has a C4-C12 alkyl group as an arbitrary component was used.
The amine salt of phosphoric acid ester used in the comparative example has an alkyl group having 4 to 12 carbon atoms.
As the component (C), the same (C1) sulfurized olefin, (C2) sulfurized ester and (C3) sulfurized oil and fat as in the above example were used.
As the component (D), the same (D1) MoDTC and (D2) MoDTP as in the above example were used.
(E) Other Additives Oleic acid amide, polybutenyl succinimide, pour point depressant

  The lubricating oil composition was prepared by mixing each of the components described above in the composition and amount described in Table 4 or 5. The amount of each of the phosphorus-based extreme pressure agent components described in Tables 4 and 5 is the mass ppm of phosphorus atoms to the mass part of the entire lubricating oil composition. Molybdenum friction modifier is the mass ppm of molybdenum atoms based on parts by weight of the total lubricating oil composition. The amount of the sulfur-based extreme pressure agent and other additives is% by mass based on the mass of the entire lubricating oil composition.

The kinematic viscosity at 100 ° C., the coefficient of friction, and the wear mark diameter were measured for these lubricating oil compositions. The kinematic viscosity (KV100) at 100 ° C. conformed to ASTM D445. The measurement of the coefficient of friction and the wear scar diameter was performed according to the following method. Furthermore, scoring was evaluated according to the following method. The results are shown in Tables 4 and 5.

Coefficient of friction The measurement was carried out using a reciprocating dynamic friction tester under conditions of cylinder on plate, sliding speed 0.45 m / s, surface pressure 0.2 GPa, and oil temperature 160C. The cylinder and the plate were both of bearing steel SUJ-2. The friction coefficient is good if it is 0.045 or less, preferably 0.040 or less.

Wear scar diameter A test was conducted under the following conditions using a four-ball wear tester specified by ASTM D4172, and the wear scar diameter after the test was measured. Oil temperature 40 ° C, load 40 kgf, rotation speed: 100 rpm, time 60 minutes. If the wear scar diameter was less than 0.38 mm, it was regarded as a pass.

Scoring Evaluation A test was conducted under the following conditions using a four-ball abrasion tester specified by ASTM D4172, and the number of revolutions when seizure occurred was recorded. Oil temperature: room temperature, load: 100 kgf, rotation speed: increased by 100 rpm every 30 seconds. A case where the number of revolutions (rpm) exceeded 1000 was regarded as pass.

As shown in Examples 11 to 16 in Table 4, the lubricating oil composition, which is a more preferable embodiment of the present invention, contains at least one component selected from the (F2) component and the (F3) component. It has low friction and good wear resistance under low viscosity conditions of viscosity 10 mm ² / s or less. Furthermore, compared with the lubricating oil composition of Reference Example 1, it can have more excellent resistance to scoring.
In addition, as shown in Comparative Examples 8 to 10 and Comparative Example 13 in Table 5, amine salts of thiophosphates as the phosphorus-based extreme pressure agent which does not contain any of the components (B), (F2) and (F3) In the lubricating oil composition containing the amine salt of and phosphoric ester, the coefficient of friction is increased. As shown in Comparative Example 11, in the lubricating oil composition which does not contain the (B) component and the (F2) component, the friction coefficient becomes large. As shown in Comparative Example 12, in the lubricating oil composition which does not contain the (B) component and the (F3) component, the friction coefficient becomes large.

  The lubricating oil composition of the present invention has low friction even when the viscosity is lowered, and can have the anti-abrasiveness required for gear oil. Furthermore, another object of the present invention is to provide a lubricating oil composition having excellent scoring resistance under conditions of lower viscosity, in addition to the above-mentioned performance. The lubricating oil composition of the present invention can be suitably used particularly for hybrid vehicles, transmissions, and gear oils.

1 load 2 block test piece 3 ring test piece 4 lubricating oil composition

Claims (18)

(A) Lubricant base oil,
(B) An acidic phosphoric acid ester having one or two alkyl groups, each of which has 4 to 10 carbon atoms,
A lubricating oil composition comprising (C) a sulfur-based extreme pressure agent, and (D) a molybdenum friction modifier,
However, the lubricating oil composition does not contain a phosphite ester having at least one alkyl group having 9 or more carbon atoms. The lubricating oil composition (F1) according to claim 1, further comprising at least one selected from (F) the following component (F1), the following component (F2), and the following component (F3). A phosphorous acid ester (F3) phosphonic acid ester having 1 to 3 acidic phosphoric acid ester (F2) alkyl groups having at least one alkyl group, each of which has 4 to 8 carbon atoms. The lubricating oil composition according to claim 1, wherein the lubricating oil base oil (A) has a kinematic viscosity at 100 ° C. of 1 to 15 mm ² / s. The component (F) is at least one selected from the components (F2) and (F3), and has a kinematic viscosity at 100 ° C. of ^{2 to} 10 mm ² / s. The lubricating oil composition according to 2.   The lubricating oil composition of claim 4 which is free of amine salts of phosphoric acid esters.   The lubricating oil composition according to any one of claims 2 to 5, further comprising (F4) thiophosphoric acid ester amine salt.   The lubricating oil composition according to any one of claims 2 to 6, wherein the amount of the component (F) is 100 to 1500 mass ppm as the content of phosphorus atoms with respect to the total mass of the lubricating oil composition.   The lubricating oil composition according to any one of claims 1 to 7, wherein the sulfur content in the lubricating oil composition is 0.3 to 5% by mass.   The lubricating oil composition according to any one of claims 1 to 8, wherein the amount of the component (B) is 100 to 1500 mass ppm as the content of phosphorus atoms with respect to the total mass of the lubricating oil composition.   The lubricating oil composition according to any one of claims 1 to 9, wherein the phosphorus content in the lubricating oil composition is 200 to 2000 ppm.   The lubricating oil composition according to any one of the preceding claims, wherein the molybdenum content in the lubricating oil composition is 100-1500 ppm.   The lubricating oil composition according to any one of claims 1 to 11, wherein the (C) sulfur-based extreme pressure agent is at least one selected from sulfurized olefins, sulfurized oils and fats, and sulfurized esters.   The lubricating oil composition according to any one of claims 1 to 12, wherein the (C) sulfur-based extreme pressure agent has an active sulfur content of 0.5 to 30% by mass.   The lubricating oil composition according to any one of claims 1 to 13, wherein the (D) molybdenum friction modifier is at least one selected from molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate, and a trinuclear molybdenum compound. object.   The lubricating oil composition according to any one of claims 1 to 14, further comprising (G) an ashless dispersant.   The lubricating oil composition according to any one of claims 1 to 15, which is for hybrid vehicles.   The lubricating oil composition according to any one of claims 1 to 15, which is for a transmission.   The lubricating oil composition according to any one of claims 1 to 15, which is for gear oil.