JP2017078138A - Lubricating oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition suitable for an automatic transmission which secures a clutch-torque capacity while significantly reducing a friction coefficient between metals at a low temperature for improving efficiency, has excellent extreme pressure property and is excellent in fuel consumption saving and durability.SOLUTION: There is provided a lubricant composition which comprises (A) a lubricant base oil, (B) 20-1000 mass ppm of a molybdenum compound in terms of molybdenum element based on the total amount of the composition, (C) 5-500 mass ppm of a thiophosphate having a carboxyl group represented by the following formula (1) in terms of phosphorus element based on the total amount of the composition and (D) 10-1000 mass ppm of an alkali metal- and/or an alkaline earth metal-based cleaner in terms of metal element based on the total amount of the composition. (where Rrepresents a hydrogen atom or a hydrocarbyl group having 1-20 carbon atoms; Rrepresents a hydrocarbyl group having 1-20 carbon atoms; Rrepresents a divalent hydrocarbyl group having 1-8 carbon atoms.)SELECTED DRAWING: None

Description

  The present invention relates to a lubricating oil composition, particularly a lubricating oil composition suitable for an automatic transmission.

  A technology that is often applied in recent years as a fuel-saving technology for drive system oil is to reduce the stirring loss by lowering the product viscosity. However, it is a well-known fact that by reducing the product viscosity to save fuel, the oil film thickness decreases and extreme pressure properties and wear resistance decrease.

Japanese Patent Application Laid-Open No. 2004-262979 JP 2006-117853 A

  In view of the circumstances as described above, the present invention is a lubricating oil composition that ensures clutch torque capacity and is excellent in extreme pressure properties while greatly reducing the coefficient of friction between metals in a wide temperature range in order to improve fuel economy. The purpose is to provide.

  As a result of intensive studies on the above problems, the present inventors have found that a lubricating oil composition comprising a predetermined base oil in combination with a predetermined molybdenum compound, a thiophosphate having a carboxy group, and a metal detergent in a predetermined ratio. Has been found to solve the problem, and the present invention has been completed.

（式（１）中、Ｒ_１は水素原子もしくは炭素数１〜２０のヒドロカルビル基、Ｒ_２は炭素数１〜２０のヒドロカルビル基、Ｒ_３は炭素数１〜８の２価のヒドロカルビル基を示す。） That is, the present invention has (A) a lubricating base oil, (B) a molybdenum compound in terms of molybdenum element, 20 to 1000 ppm by mass based on the total amount of the composition, and (C) a carboxy group represented by the following formula (1). Contains thiophosphoric acid ester in terms of phosphorus, 5 to 500 mass ppm based on total composition, (D) alkali metal and / or alkaline earth metal detergent in terms of metal elements, based on 10 to 1000 mass ppm based on total composition It is a lubricating oil composition characterized by the above.

(In Formula (1), R ₁ represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, R ₂ represents a hydrocarbyl group having 1 to 20 carbon atoms, and R ₃ represents a divalent hydrocarbyl group having 1 to 8 carbon atoms. .)

  The present invention also provides the lubricating oil composition as described above, wherein the component (D) is calcium sulfonate.

Further, the present invention is, (A) a lubricating base oil,% _{C P} is 60 or more,% _{C N} is less than 40,% _{C A} is in the lubricating oil composition of the wherein a is 3 or less is there.

The present invention also provides the lubricating oil composition as described above, wherein (A) the lubricating base oil has a kinematic viscosity at 100 ° C. of 2.0 to 4.3 mm ² / s.

Further, in the present invention, the lubricating oil composition has a kinematic viscosity at 40 ° C. of 4 to 25 mm ² / s and a kinematic viscosity at 100 ° C. of 2.0 to 5.4 mm ² / s. It is a lubricating oil composition.

  The present invention is the above-described lubricating oil composition, further comprising (E) a pour point depressant.

  Furthermore, the present invention is the lubricating oil composition described above, which is used in an automatic transmission.

  The lubricating oil composition of the present invention is an automatic transmission that greatly reduces the coefficient of friction between metals at low temperatures to ensure efficiency while ensuring clutch torque capacity, excellent extreme pressure, fuel saving and durability. It is a lubricating oil composition suitable for machine use.

  Hereinafter, the present invention will be described in detail.

  The lubricating oil composition of the present invention contains a lubricating base oil as component (A).

  As the lubricating base oil, a base oil usually used as a lubricating base oil can be used. Examples thereof include mineral oil base oils, synthetic base oils, and mixtures thereof.

  As a mineral oil base oil, a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and vacuum distillation is subjected to solvent removal, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining. In addition, paraffinic and naphthenic mineral oil base oils, normal paraffins, isoparaffins, and the like, which are refined by appropriately combining purification treatments such as sulfuric acid washing and clay treatment, and the like. These base oils may be used alone or in combination of two or more at any ratio.

Preferred mineral oil base oils include the following base oils.
[1] Distilled oil obtained by atmospheric distillation of paraffin-based crude oil and / or mixed-base crude oil;
[2] Vacuum distillation distillate (WVGO) of paraffin base crude oil and / or mixed base crude oil at atmospheric distillation residue;
[3] A wax obtained by a lubricant dewaxing step and / or a Fischer-Tropsch wax produced by a GTL process or the like;
[4] Mild hydrocracking treatment oil (MHC) of one or two or more mixed oils selected from [1] to [3];
[5] A mixed oil of two or more oils selected from [1] to [4];
[6] Degassed oil (DAO) of [1], [2], [3], [4] or [5];
[7] Mild hydrocracking treatment oil (MHC) of [6];
[8] A mixed oil of two or more kinds of oils selected from [1] to [7] is used as a feedstock oil, and this feedstock oil and / or a lubricating oil fraction recovered from this feedstock oil is used as a normal oil fraction. Lubricating oil obtained by refining by the refining method and collecting the lubricating oil fraction

  The normal refining method here is not particularly limited, and a refining method used in the production of the lubricating base oil can be arbitrarily employed. Examples of conventional purification methods include (a) hydrorefining such as hydrocracking and hydrofinishing, (b) solvent purification such as furfural solvent extraction, and (c) dewaxing such as solvent dewaxing and catalytic dewaxing. And (d) white clay refining with acid clay and activated clay, and (e) chemical (acid or alkali) purification such as sulfuric acid washing and caustic soda washing. In the present invention, one or more of these can be used in any combination and in any order.

As the mineral oil base oil used in the present invention, a base oil obtained by further subjecting the base oil selected from the above [1] to [8] to the following treatment is particularly preferable.
That is, the base oil selected from the above [1] to [8] is used as it is, or the lubricating oil fraction recovered from this base oil is hydrocracked or wax-isomerized, and the product is used as it is or from this. After the fraction is collected and then subjected to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, and then subjected to solvent purification and / or hydrorefining treatment, or after solvent purification treatment and / or hydrorefining treatment Hydrocracked mineral oil and / or wax isomerized isoparaffin base oil produced by performing a dewaxing process such as solvent dewaxing or catalytic dewaxing is preferably used. The hydrocracked mineral oil and / or wax isomerized isoparaffin base oil is preferably used in an amount of 30% by mass or more, more preferably 50% by mass or more, and particularly preferably 70% by mass or more based on the total amount of the base oil.

  Synthetic lubricating base oils include, for example, poly α-olefins (ethylene-propylene copolymers, polybutenes, 1-octene oligomers, 1-decene oligomers, and hydrides thereof), fragrances such as alkylbenzenes and alkylnaphthalenes. Group base oil, monoester (butyl stearate, octyl laurate), diester (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sepacate, etc.), polyester ( Such as trimellitic acid esters), polyol esters (such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate) Ether base oils such as tellurium base oils, polyoxyalkylene glycols, polyphenyl ethers, dialkyldiphenyl ethers, phosphate esters (tricresyl phosphate, etc.), fluorine-containing compounds (perfluoropolyethers, fluorinated polyolefins, etc.), silicones High performance hydrocarbon base oil obtained by isomerizing and hydrogenating oil, synthetic wax such as FT reaction and / or wax obtained from petroleum refining process (preferably slack wax obtained in solvent dewaxing process), terpene Examples thereof include hydrocarbon base oils obtained by hydrogenating such naturally derived unsaturated hydrocarbons.

  Preferable synthetic lubricating base oils include poly α-olefins. The poly α-olefin is typically an α-olefin oligomer or co-oligomer having 2 to 32 carbon atoms, preferably 6 to 16 (eg, 1-octene oligomer, 1-decene oligomer, ethylene-propylene co-oligomer). And hydrides thereof.

  The lubricating base oil may be a mixture of two or more mineral base oils or a mixture of two or more synthetic base oils, and is a mixture of a mineral base oil and a synthetic base oil. There is no problem. And the mixing ratio of 2 or more types of base oil in the said mixture can be chosen arbitrarily. In the present invention, the lubricating base oil is preferably a hydrocarbon base oil, and more preferably a hydrocracked mineral oil excellent in viscosity-temperature characteristics, more preferably a wax isomerized base oil, from the viewpoint of fuel economy. .

% C _P of the lubricating base oil is not particularly limited but is preferably 60 or more, more preferably 65 or more, more preferably 70 or more.
% C _N of the lubricating base oil is not particularly limited but is preferably 40 or less, more preferably 35 or less, more preferably 30 or less.
% C _A of the lubricating base oil is not particularly limited, preferably 3 or less, more preferably 2 or less, more preferably 1 or less.

Kinematic viscosity at 100 ° C. of the lubricating base oil is not particularly limited, preferably not more than 4.3 mm ² / s, more preferably less 4.2 mm ² / s, more preferably not more than 4.0 mm ² / s. By setting the kinematic viscosity at 100 ° C. to 4.3 mm ² / s or less, it is possible to obtain a lubricating oil composition having a lower frictional resistance at a lubricating point because the fluid resistance becomes smaller.
On the other hand, the kinematic viscosity at 100 ° C. of the lubricating base oil is preferably at least 2.0 mm ² / s, more preferably at least 2.2 mm ² / s, still more preferably at least 2.4 mm ² / s. By setting it to 2.0 mm ² / s or more, it becomes possible to obtain a lubricating oil composition in which oil film formation is sufficient, lubricity is excellent, and evaporation loss of the base oil is small under high temperature conditions.

  The viscosity index of the lubricating base oil is not particularly limited, but is preferably 80 or more, more preferably 90 or more, and particularly preferably 100 or more. By setting the viscosity index to 80 or more, it is possible to obtain a composition that is more excellent in fatigue life, extreme pressure after initial use and long-term use.

  Although there is no restriction | limiting in particular in sulfur content of lubricating base oil, 100 mass ppm or less is preferable, 50 mass ppm or less is more preferable, 10 mass ppm or less is more preferable, 1 mass ppm or less is especially preferable.

  In addition, when lubricating base oil is a mixture, the said property is judged as the said mixture, and it does not depend on the property of each base oil which comprises a mixture.

  The lubricating oil composition of the present invention contains a molybdenum compound as component (B).

  Examples of the molybdenum compound used in the present invention include various organic molybdenum compounds such as (B1) an organic molybdenum compound containing sulfur or (B2) an organic molybdenum compound containing no sulfur as a constituent element.

  First, (B1) organic molybdenum compounds containing sulfur include molybdenum dithiophosphate, molybdenum dithiocarbamate, and the like.

  As molybdenum dithiophosphate, the compound represented by following General formula (2) is mentioned, for example.

In the general formula (2), R ^{1 to} R ⁴ are each independently an alkyl group having 2 to 30 carbon atoms, preferably 5 to 18 carbon atoms, more preferably 5 to 12 carbon atoms, or 6 to 18 carbon atoms. , Preferably a hydrocarbon group such as an (alkyl) aryl group having 10 to 15 carbon atoms. Y ^{1 to} Y ⁴ each independently represent a sulfur atom or an oxygen atom.

  As a molybdenum dithiocarbamate, the compound represented by following General formula (3) can be mentioned, for example.

In the general formula (3), R ^{5 to} R ⁸ are each independently an alkyl group having 2 to 24 carbon atoms, preferably 4 to 13 carbon atoms, or 6 to 24 carbon atoms, preferably 10 to 15 carbon atoms. A hydrocarbon group such as an (alkyl) aryl group is shown. Y ⁵ , Y ⁶ , Y ⁷ and Y ⁸ each independently represent a sulfur atom or an oxygen atom.

  In addition, organic molybdenum compounds containing sulfur other than these include molybdenum compounds (for example, molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, orthomolybdic acid, paramolybdic acid, molybdic acid such as (poly) sulfurized molybdic acid, Molybdenum salts such as metal salts of molybdic acid, ammonium salts, molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, polysulfide molybdenum, etc. Molybdenum halides such as molybdenum) and sulfur-containing organic compounds (eg, alkyl (thio) xanthates, thiadiazoles, mercaptothiadiazoles, thiocarbonates, tetrahydrocarbylthiuram disulfides, bis (di (thio) hydrocarbons). Bildithiophosphonate) disulfide, organic (poly) sulfide, sulfurized ester, etc.) or complexes with other organic compounds, or sulfur-containing molybdenum compounds such as molybdenum sulfide and sulfurized molybdic acid, and sulfur as a constituent element to be described later Amine compounds, succinimides, organic acids, complexes with alcohols, etc., or elemental sulfur, hydrogen sulfide, phosphorus pentasulfide, sulfur oxide, inorganic sulfide, hydrocarbyl (poly ) Constituent elements described in the section of sulfur sources such as sulfide, sulfurized olefin, sulfurized ester, sulfurized wax, sulfurized carboxylic acid, sulfurized alkylphenol, thioacetamide, thiourea, and organic molybdenum compounds that do not contain sulfur As sulfur-free molybdenum A sulfur-containing organic molybdenum obtained by reacting a compound with an organic compound not containing sulfur, such as an amine compound, a succinimide, an organic acid, or an alcohol, described in the section of an organic molybdenum compound containing no sulfur as a constituent element described later Various compounds such as compounds can be mentioned. Specifically, organic molybdenum compounds such as those described in JP-A-56-10591 and US Pat. No. 4,263,152 can be exemplified.

  (B2) Specific examples of the organic molybdenum compound not containing sulfur as a constituent element include molybdenum-amine complexes, molybdenum-succinimide complexes, organic acid molybdenum salts, alcohol molybdenum salts, and the like. Preference is given to molybdenum-amine complexes, molybdenum salts of organic acids and molybdenum salts of alcohols.

  As the organomolybdenum compound according to the present invention, a sulfur-containing organomolybdenum compound is preferable and molybdenum dithiocarbamate is particularly preferably used from the viewpoint of excellent friction reduction effect.

In the lubricating oil composition used in the present invention, the content of the (B) organomolybdenum compound is preferably 20 mass ppm or more, more preferably 60 mass ppm or more, and more preferably 100 mass ppm as the molybdenum element equivalent on the basis of the total composition. More preferred is ppm or more, and particularly preferred is 150 mass ppm or more. When the content is less than 20 ppm by mass, a fuel saving effect cannot be expected.
On the other hand, 1000 mass ppm or less is preferable, 800 mass ppm or less is more preferable, and 600 mass ppm or less is more preferable. When the content exceeds 1000 mass ppm, the stability of the lubricating oil composition, particularly at high temperatures, tends to decrease, such being undesirable.

The lubricating oil composition of the present invention contains, as the component (C), a thiophosphate having a carboxy group at the terminal shown in the following formula (1).

In formula (1), R ₁ represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, R ₂ represents a hydrocarbyl group having 1 to 20 carbon atoms, and R ₃ represents a divalent hydrocarbyl group having 1 to 8 carbon atoms.

The number of carbon atoms of the hydrocarbyl group R ₁ and _{R 2} are 1 to 20, preferably 1-12, more preferably 1-8.

Examples of the hydrocarbyl group for R ₁ and R ₂ include an alkyl group, a cycloalkyl group, an alkylcycloalkyl group, an aryl group, and an alkylaryl group. More specifically, n-butyl group, isobutyl group, tert-butyl group, cyclopentyl group, cyclohexyl group, methylcyclopentyl group, phenyl group, benzyl group, tolyl group (cresyl group), xylenyl group and the like can be mentioned. The hydrocarbyl group may be saturated or unsaturated, and may be linear or branched.

  Among these, a saturated hydrocarbon group is preferable and an alkyl group is particularly preferable.

The carbon number of the divalent hydrocarbyl group of R ₃ is 1-8, preferably 2-6, more preferably 2-4.

Examples of the hydrocarbyl group for R ₃ include an alkylene group, a cycloalkylene group, and an alkylcycloalkylene group. More specific examples include a methylene group and an ethylene group. The hydrocarbyl group may be saturated or unsaturated, and may be linear or branched.

  Among these, a saturated hydrocarbon group is preferable, and an alkylene group is particularly preferable.

The content of the thiophosphate ester having a carboxy group at the end shown in Formula (1) is 5 mass ppm or more, more preferably 25 mass ppm or more, and more preferably 50 mass ppm or more, in terms of phosphorus element, based on the total amount of the composition. More preferred is 100 mass ppm or more. If the content is less than 5 ppm by mass, the effect of improving wear resistance and friction characteristics tends to be insufficient.
On the other hand, the content is 500 mass ppm or less, preferably 400 mass ppm or less, and more preferably 300 mass ppm or less. Even if it exceeds 500 ppm by mass, a further improvement effect of wear resistance corresponding to the content cannot be obtained, and oxidation stability and sludge suppression tend to decrease.

  The lubricating oil composition of the present invention contains an alkali metal and / or alkaline earth metal detergent as component (D).

  Specific examples of the alkali metal and / or alkaline earth metal detergents include, for example, alkali metal and / or alkaline earth metal sulfonates, phenates and salicylates, and one or two selected from these. More than one type of metallic detergent can be used.

  More specifically, examples of the sulfonate include a metal salt of an alkyl aromatic sulfonic acid obtained by sulfonating an alkyl aromatic compound having a molecular weight of 100 to 1500, preferably 200 to 700. Specific examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid.

  More specifically, the phenate is an alkylphenol having at least one linear or branched alkyl group having 4 to 30 carbon atoms, preferably 6 to 18 carbon atoms, and an alkylphenol obtained by reacting the alkylphenol with sulfur. Mention may be made of a metal salt of sulfide or a Mannich reaction product of alkylphenol obtained by reacting this alkylphenol with formaldehyde.

  More specifically, examples of the salicylate include metal salts of alkyl salicylic acid having at least one linear or branched alkyl group having 4 to 30 carbon atoms, preferably 6 to 18 carbon atoms.

  The sulfonate, phenate and salicylate include not only neutral salts (normal salts) but also neutral salts (normal salts) and excess alkali metal and / or alkaline earth metal salts and alkali metals and / or alkaline earths. A basic salt obtained by heating an alkali metal base (an alkali metal and / or alkaline earth metal hydroxide or oxide) in the presence of water, or a neutral salt (a normal salt in the presence of carbon dioxide) Also included are overbased salts (superbasic salts) obtained by reacting) with an alkali metal and / or alkaline earth metal base.

  Examples of the alkali metal and / or alkaline earth metal include sodium, potassium, magnesium, calcium, etc. Among them, magnesium and calcium are preferable, and calcium is particularly preferable.

  As the alkali metal and / or alkaline earth metal detergent, calcium sulfonate is most preferable.

  The base number of the alkali metal and / or alkaline earth metal detergent is not particularly limited, but is preferably 100 to 600 mgKOH / g, more preferably 150 to 500 mgKOH / g, and 200 to 400 mgKOH from the viewpoint of ensuring oxidation stability. / G is more preferable.

The content of the alkali metal and / or alkaline earth metal detergent is preferably 10 ppm by mass or more, more preferably 40 ppm by mass or more, and further preferably 70 ppm by mass or more based on the total amount of the metal element.
On the other hand, from the viewpoint of preventing the reduction of the friction coefficient due to clogging of the friction material of the clutch plate, 1000 ppm by mass or less is preferable, 600 ppm by mass or less is more preferable, 400 ppm by mass or less is more preferable, and 200 ppm by mass or less is particularly preferable. preferable.

The lubricating oil composition of the present invention preferably contains a pour point depressant as the component (E) as necessary. It is preferable to contain a pour point depressant because the low temperature fluidity of the lubricating oil composition can be improved.
A known pour point depressant can be arbitrarily selected as the pour point depressant, but a polymethacrylate pour point depressant is particularly preferred. The weight average molecular weight of the pour point depressant is preferably 10,000 or more, and more preferably 50,000 or more. Moreover, it is preferable that it is 300,000 or less, 200,000 or less is more preferable, and 150,000 or less is still more preferable. When the weight average molecular weight exceeds 300,000, the shear stability of the composition is lowered, which is not preferable. When the weight average molecular weight is less than 10,000, the effect as a pour point effect agent is small. The content of the pour point depressant is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, based on the total amount of the lubricating oil composition. 5 mass% or less is further more preferable, 2 mass% or less is especially preferable, and 1 mass% or less is the most preferable. If the addition amount exceeds 20% by mass, the shear stability of the composition is lowered, which is not preferable. If it is less than 0.01% by mass, the effect as a pour point effect agent is small.
When a synthetic base oil is used as the lubricating base oil, the pour point depressant is not necessarily contained. However, when a mineral base oil is used as the lubricating base oil, the pour point depressant is used. It is preferable to contain.

  The lubricating oil composition of the present invention has a known lubricating oil additive such as an ashless dispersant, an antiwear agent, an antioxidant, a friction modifier, a metal deactivator, and corrosion prevention for the purpose of further enhancing the performance. Various additives represented by agents, antifoaming agents, colorants and the like can be blended alone or in combination.

  As the ashless dispersant, any compound usually used as an ashless dispersant for lubricating oils can be used. For example, succinimide having an alkyl group or alkenyl group having 40 to 400 carbon atoms, benzylamine, polyamine, and the like Examples thereof include derivatives modified with boron compounds, phosphorus compounds, sulfur compounds, oxygen-containing organic compounds, and the like.

  As the antiwear agent, any compound usually used as an antiwear agent for lubricating oils can be used, and examples thereof include phosphorus and / or sulfur containing antiwear agents.

  Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants such as copper and molybdenum.

  As the friction modifier, any compound usually used as a friction modifier for lubricating oils can be used. For example, molybdenum friction modifier, amine compound, imide compound, fatty acid ester, fatty acid amide, fatty acid, aliphatic Examples include ashless friction modifiers such as alcohol and aliphatic ether.

  Metal deactivators include imidazolines, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfides, 1,3,4-thiadiazolyl-2,5-bisdialkyldithio Examples thereof include carbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

  As the corrosion inhibitor, any compound usually used as a corrosion inhibitor for lubricating oils can be used, and examples thereof include benzotriazole, tolyltriazole, and imidazole compounds.

  As the antifoaming agent, any compound usually used as an antifoaming agent for lubricating oil can be used. For example, silicones such as dimethyl silicone and fluorosilicone, alkenyl succinic acid derivatives, polyhydroxy aliphatic alcohols and Examples include esters of chain fatty acids, methyl salicylate and o-hydroxybenzyl alcohol.

  The blending ratio in the case of blending the above various additives is not particularly limited, and usually within the range of 0.001 to 10% by mass on the basis of the total amount of the lubricating oil composition, taking into account each purpose and effect. Can be determined as appropriate.

The lubricating oil composition of the present invention may contain a viscosity index improver, but it is more preferable not to contain it.
Examples of the viscosity index improver include known dispersion index improvers that are non-dispersed or dispersed. Examples of the non-dispersed viscosity index improver include olefin polymers such as polymethacrylate, ethylene-propylene copolymer, styrene-diene copolymer, polyisobutylene, and polystyrene. Examples of the dispersion type viscosity index improver include a polymer obtained by copolymerizing a monomer that forms the non-dispersion type viscosity index improver and a nitrogen-containing monomer.
The content ratio of the viscosity index improver in the lubricating oil composition of the present invention is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, and 0 to 3% by mass based on the total amount of the lubricating oil composition. More preferably, it is most preferable not to contain substantially.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is preferably 2.0 mm ² / s or more, and more preferably 2.2 mm ² / s or more. Sufficient lubricity is securable by setting it as 2.0 mm < ² > / s or more.
Meanwhile, the kinematic viscosity at 100 ° C., preferably not more than 5.4 mm ² / s, more preferably at most 5.0 mm ² / s. By setting it to 5.4 mm ² / s or less, a lubricating oil composition having excellent low-temperature viscosity characteristics can be obtained.

Kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is preferably not more than 25.0 mm ² / s, more preferably not more than 22.5 mm ² / s, more preferably not more than 20.0 mm ² / s. By setting the kinematic viscosity at 40 ° C. to 25.0 mm ² / s or less, it is possible to obtain a lubricating oil composition having a smaller frictional resistance because the fluid resistance becomes smaller.
On the other hand, the kinematic viscosity at 40 ° C. of the lubricating oil composition is preferably 4.0 mm ² / s or more, more preferably 6.0 mm ² / s or more, and even more preferably 8.0 mm ² / s or more. By setting it to 4.0 mm ² / s or more, it becomes possible to obtain a lubricating oil composition in which oil film formation is sufficient, lubricity is excellent, and base oil evaporation loss is low under high temperature conditions.

  The use of the lubricating oil composition of the present invention is not particularly limited and can be used for any application, but by containing a specific amount of a thiophosphate having a carboxy group at the terminal shown in Formula (1) as the component (C), The clutch torque capacity and extreme pressure characteristics are excellent while reducing the coefficient of friction between metals at low temperatures, so that it can be suitably used particularly for an automatic transmission.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Examples 1-6 and Comparative Examples 1-8)
Lubricating oil compositions having the compositions shown in Table 1 were prepared. The addition amount (mass% or mass ppm) of each additive is based on the total amount of the composition. The properties of each lubricating oil composition were evaluated and listed in Table 1.

Claims (7)

(A) Lubricating base oil, (B) Molybdenum compound in terms of molybdenum element, 20 to 1000 ppm by mass based on the total amount of the composition, (C) Thiophosphate ester having a carboxy group represented by the following formula (1) is elemental phosphorus 5 to 500 ppm by mass on the basis of the total amount of the composition, (D) 10 to 1000 ppm by mass of the alkali metal and / or alkaline earth metal detergent based on the total amount of the composition in terms of the metal element Lubricating oil composition.

(In Formula (1), R ₁ represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, R ₂ represents a hydrocarbyl group having 1 to 20 carbon atoms, and R ₃ represents a divalent hydrocarbyl group having 1 to 8 carbon atoms. .)   The lubricating oil composition according to claim 1, wherein the component (D) is calcium sulfonate. (A) a lubricating base oil,% _{C P} is 60 or more,% _{C N} is less than 40,% _{C A} lubricating oil composition according to claim 1 or 2, characterized in that is 3 or less. (A) Kinematic viscosity in 100 degreeC of lubricating base oil is 2.0-4.3mm < ² > / s, The lubricating oil composition in any one of Claims 1-3 characterized by the above-mentioned. 5. The kinematic viscosity at 40 ° C. of the lubricating oil composition is 4 to 25 mm ² / s, and the kinematic viscosity at 100 ° C. is 2.0 to 5.4 mm ² / s. The lubricating oil composition described.   Furthermore, (E) Pour point depressant is contained, The lubricating oil composition in any one of Claims 1-5 characterized by the above-mentioned.   The lubricating oil composition according to claim 1, wherein the lubricating oil composition is used in an automatic transmission.