JP5398218B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition, and in particular, has a low traction coefficient, excellent energy saving, and high efficiency, and suitable for automotive manual transmission, automatic transmission, continuously variable transmission, or industrial gear system. It relates to an oil composition.

  In recent years, there has been an urgent need to save energy in automobiles, construction machinery, agricultural machinery, etc., that is, to save fuel, in response to environmental issues such as reducing carbon dioxide emissions. Engines, transmissions, final reduction gears, compression Devices such as machines and hydraulic devices are strongly required to contribute to energy saving. Therefore, the lubricating oil used for these is required to reduce the stirring resistance and frictional resistance as compared with the conventional one.

  As one of the fuel saving means of the transmission and the final reduction gear, there is a reduction in viscosity of the lubricating oil. For example, among automatic transmissions, automatic transmissions for automobiles and continuously variable transmissions have torque converters, wet clutches, gear bearing mechanisms, oil pumps, hydraulic control mechanisms, etc., and manual transmissions and final reduction gears have gear bearings. By reducing the viscosity of the lubricating oil used in these mechanisms, the stirring resistance and friction resistance of torque converters, wet clutches, gear bearing mechanisms, oil pumps, etc. are reduced, and power transmission efficiency As a result, the fuel efficiency of the automobile can be improved.

  However, when the viscosity of the lubricating oil used in these is reduced, the fatigue life is significantly reduced, and seizure or the like may occur, resulting in problems with the transmission or the like. In particular, when a phosphorus-based extreme pressure agent is blended in order to improve the extreme pressure property of a low-viscosity oil, it is generally difficult to reduce the viscosity because the fatigue life is remarkably deteriorated. In addition, the sulfur-based extreme pressure agent can improve the fatigue life of the lubricating oil, but the oxidation stability deteriorates, and a large amount of antioxidant is required.

Since there is a limit to reducing the viscosity in this way, it is effective to reduce the friction of parts in elastic fluid lubrication conditions such as gear tooth surfaces as an alternative to or in addition to energy saving and high efficiency. It is. In general, since the contact pressure of the gear tooth surface may be 1 GPa or more, it is known that the condition is usually in elastohydrodynamic lubrication conditions. Under such conditions, a lubricating oil composition having a low traction coefficient is used. This is known to reduce friction and contribute to energy saving.
Japanese Patent Application No. 10-213552 Japanese Patent Application No. 9-68161

  The present invention has been made in view of such circumstances, and manual gear shifting for an automobile that can reduce friction in a portion in an elastic fluid lubrication condition such as a gear tooth surface and achieve energy saving and high efficiency. An object of the present invention is to provide a lubricating oil composition having a low traction coefficient suitable for a machine, an automatic transmission, a continuously variable transmission, or an industrial gear system.

  As a result of intensive studies to solve the above problems, the present inventors have solved the above problems by using a lubricating oil composition containing (A) a base oil containing a polyhydric alcohol and a partial ester of a carboxylic acid. The inventors have found what can be done and have completed the present invention.

That is, the present invention provides (A) a polyhydric alcohol, a linear or branched saturated or unsaturated monobasic acid having 2 to 24 carbon atoms, a linear or branched chain having 2 to 16 carbon atoms. 0.1 to 80% by weight of a partial ester of at least one carboxylic acid selected from the group consisting of a saturated or unsaturated dibasic acid, and trimellitic acid, and 2-ethylhexyl oleate, ditridecyl glutarate, di- A kinematic viscosity at 100 ° C. of 1 to 15 mm ² / s, comprising ²⁰ to 99.9% by mass of at least one ester selected from 2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, and di-2-ethylhexyl sebacate A traction coefficient characterized by having a kinematic viscosity at 100 ° C. of 1 to 20 mm ² / s. It is a low lubricating oil composition for automobile manual transmissions, automatic transmissions, continuously variable transmissions, or industrial gear systems.

  The present invention also provides the lubricating oil composition as described above, wherein (A) the partial ester of polyhydric alcohol and carboxylic acid is a partial ester of trimethylolpropane and monovalent carboxylic acid.

（一般式（Ｉ）において、Ｒ_１は水素又はメチル基、Ｒ_２は炭素数１〜３０の炭化水素基を示す。） The present invention also includes (B) 0.01 to 20% by mass of a poly (meth) acrylate compound comprising a structural unit represented by the following general formula (I): It is a composition.

(In general formula (I), R ₁ represents hydrogen or a methyl group, and R ₂ represents a hydrocarbon group having 1 to 30 carbon atoms.)

  The present invention also provides the lubricating oil composition described above, wherein the traction coefficient is 0.013 or less.

Further, the present invention provides the lubricating oil composition as described above, wherein the ratio of the traction coefficient to the kinematic viscosity at 100 ° C. (mm ² / s) in the lubricating oil composition is 1.2E-03 or less. is there.

  The present invention also provides the lubricating oil composition as described above, wherein the viscosity of Brukfield at −40 ° C. is 40,000 mPa · s or less.

  Since the lubricating oil composition of the present invention has a low traction coefficient, it maintains the characteristics required as gear oil when applied to a manual transmission, an automatic transmission, a continuously variable transmission or an industrial gear system for automobiles. However, energy saving and high efficiency can be achieved.

Hereinafter, the lubricating oil composition of the present invention will be described.
The lubricating oil composition of the present invention contains (A) an ester base oil composed of a partial ester of a polyhydric alcohol and a carboxylic acid as a base oil.
The alcohol constituting the ester base oil is a polyhydric alcohol, and the carboxylic acid constituting the ester base oil may be a monobasic acid or a polybasic acid. It is necessary that the hydroxyl group of the monohydric alcohol is a partial ester that remains without being esterified.

  As the polyhydric alcohol, those having 2 to 10 valences, preferably 2 to 6 valences are usually used. Specific examples of the divalent to 10-valent polyhydric alcohol include, for example, ethylene glycol, diethylene glycol, polyethylene glycol (3 to 15 mer of ethylene glycol), propylene glycol, dipropylene glycol, and polypropylene glycol (3 to 3 of propylene glycol). 15-mer), 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,2-propanediol, 2-methyl-1, Dihydric alcohols such as 3-propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, neopentylglycol; glycerin, polyglycerin (glycerin 2 ~ Octamer, eg diglycerin, trig Serine, tetraglycerin, etc.), trimethylol alkanes (trimethylol ethane, trimethylol propane, trimethylol butane, etc.) and their 2-to 8-mer, pentaerythritol and their 2-to 4-mer, 1,2,4- Butanetriol, 1,3,5-pentanetriol, 1,2,6-hexanetriol, 1,2,3,4-butanetetrol, sorbitol, sorbitan, sorbitol glycerin condensate, adonitol, arabitol, xylitol, mannitol, etc. Polyhydric alcohols; sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, and mixtures thereof And the like.

  Among these polyhydric alcohols, ethylene glycol, diethylene glycol, polyethylene glycol (ethylene glycol 3-10 mer), propylene glycol, dipropylene glycol, polypropylene glycol (propylene glycol 3-10 mer), 1,3- Propanediol, 2-methyl-1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, glycerin, diglycerin, triglycerin, trimethylolalkane (trimethylolethane, trimethylolpropane, trimethylol Methylol butane and the like, and dimers and tetramers thereof, pentaerythritol, dipentaerythritol, 1,2,4-butanetriol, 1,3,5-pentanetriol, 1,2,6-hexanetrio Le, 1,2,3,4 butane tetrol, sorbitol, sorbitan, sorbitol glycerin condensate, adonitol, arabitol, xylitol, divalent to hexavalent polyhydric alcohols, and mixtures thereof, such as mannitol and the like are preferable. Furthermore, ethylene glycol, propylene glycol, neopentyl glycol, glycerin, trimethylol ethane, trimethylol propane, pentaerythritol, sorbitan, and a mixture thereof are more preferable. Among these, neopentyl glycol, trimethylol ethane, trimethylol propane, pentaerythritol, and a mixture thereof are particularly preferable, and trimethylol propane is most preferable because higher thermal and oxidative stability can be obtained.

  Of the acids constituting the ester base oil used in the present invention, as the monobasic acid, a fatty acid having 2 to 24 carbon atoms is usually used, and the fatty acid may be linear or branched, It may be saturated or unsaturated. Specifically, for example, acetic acid, propionic acid, linear or branched butanoic acid, linear or branched pentanoic acid, linear or branched hexanoic acid, linear or branched Branched heptanoic acid, linear or branched octanoic acid, linear or branched nonanoic acid, linear or branched decanoic acid, linear or branched undecanoic acid, Linear or branched dodecanoic acid, linear or branched tridecanoic acid, linear or branched tetradecanoic acid, linear or branched pentadecanoic acid, linear or branched Hexadecanoic acid, linear or branched heptadecanoic acid, linear or branched octadecanoic acid, linear or branched nonadecanoic acid, linear or branched icosanoic acid, straight Chain or branched henicosanoic acid, linear or branched docosa Acid, linear or branched tricosanoic acid, saturated fatty acid such as linear or branched tetracosanoic acid, acrylic acid, linear or branched butenoic acid, linear or branched Pentenoic acid, linear or branched hexenoic acid, linear or branched heptenoic acid, linear or branched octenoic acid, linear or branched nonenoic acid, linear Or branched decenoic acid, linear or branched undecenoic acid, linear or branched dodecenoic acid, linear or branched tridecenoic acid, linear or branched tetradecene Acid, linear or branched pentadecenoic acid, linear or branched hexadecenoic acid, linear or branched heptadecenoic acid, linear or branched octadecenoic acid, linear or Branched nonadecenoic acid, linear or branched icosenoic acid, Unsaturated fatty acids such as linear or branched heicosenoic acid, linear or branched docosenoic acid, linear or branched tricosenoic acid, linear or branched tetracosenoic acid, and the like And the like. Among these, from the point that lubricity and handleability are further improved, saturated fatty acids having 3 to 20 carbon atoms, unsaturated fatty acids having 3 to 22 carbon atoms and mixtures thereof are particularly preferable, and saturated fatty acids having 4 to 18 carbon atoms. More preferable are unsaturated fatty acids having 4 to 18 carbon atoms and mixtures thereof, and saturated fatty acids having 4 to 18 carbon atoms are most preferable from the viewpoint of oxidative stability.

  Examples of the polybasic acid include dibasic acids having 2 to 16 carbon atoms and trimellitic acid. The dibasic acid having 2 to 16 carbon atoms may be linear or branched, and may be saturated or unsaturated. Specifically, for example, ethanedioic acid, propanedioic acid, linear or branched butanedioic acid, linear or branched pentanedioic acid, linear or branched hexanedioic acid, Linear or branched heptanedioic acid, linear or branched octanedioic acid, linear or branched nonanedioic acid, linear or branched decanedioic acid, linear Linear or branched undecanedioic acid, linear or branched dodecanedioic acid, linear or branched tridecanedioic acid, linear or branched tetradecanedioic acid, linear or Branched heptadecanedioic acid, linear or branched hexadecanedioic acid, linear or branched hexenedioic acid, linear or branched heptenedioic acid, linear or branched Octenedioic acid, linear or branched nonene diacid, linear or branched decenedioic acid, linear Or branched undecenedioic acid, linear or branched dodecenedioic acid, linear or branched tridecenedioic acid, linear or branched tetradecenedioic acid, linear or branched Examples thereof include branched heptadecene diacid, linear or branched hexadecene diacid, and mixtures thereof.

The combination of the alcohol and the acid forming the ester is arbitrary and is not particularly limited. Examples of the ester that can be used in the present invention include the following esters. These esters may be used alone, or 2 You may combine seeds or more.
(A) Partial ester of polyhydric alcohol and monobasic acid (b) Partial ester of polyhydric alcohol and polybasic acid (c) Mixed partial ester of a mixture of polyhydric alcohol with monobasic acid and polybasic acid

  Of the hydroxyl groups in the polyhydric alcohol, the proportion of hydroxyl groups remaining unesterified is preferably 3 to 80%, more preferably 5 to 70%, still more preferably 10 to 60%, and most preferably. Is 15-50%. When the ratio of residual hydroxyl groups is less than 3%, there is a risk that a sufficient reduction in traction coefficient may not be obtained. When the ratio of residual hydroxyl groups exceeds 80%, friction increases due to increased viscosity and oxidation stability deteriorates. There is a fear.

  Among these, since it is excellent in a traction coefficient, (a) a partial ester of a polyhydric alcohol and a monobasic acid is preferable, and a diester of trimethylolpropane and a monobasic acid having 12 to 18 carbon atoms is more preferable. The diester of trimethylolpropane and oleic acid is most preferred.

  The partial ester of polyhydric alcohol and carboxylic acid needs to be contained in an amount of 0.1 to 80% by mass based on the total amount of the base oil, preferably 5 to 75% by mass, more preferably 10 to 70% by mass, and still more preferably. Is 15 to 65% by mass, most preferably 20 to 60% by mass. If the content is less than 0.1% by mass, the traction coefficient requirement may not be satisfied. If the content exceeds 80% by mass, the friction may increase due to an increase in viscosity or the oxidation stability may deteriorate.

As base oil components other than the partial ester of polyhydric alcohol and carboxylic acid, as long as the kinematic viscosity at 100 ° C. of the mixed base oil satisfies 1 to 15 mm ² / s, any one or more mineral oil base oils, 1 More than one type of synthetic base oil and mixtures thereof can be used.

  Specifically, as the mineral base oil, the lubricating oil fraction obtained by subjecting the crude oil to atmospheric distillation obtained under reduced pressure is subjected to solvent removal, solvent extraction, hydrocracking, Refined by performing one or more treatments such as hydroisomerization, solvent dewaxing, hydrorefining, etc., or base oil produced by isomerizing wax isomerized mineral oil, GTL WAX (gas-trimmed wax), etc. Can be illustrated.

  Specific examples of synthetic base oils include polybutene or hydrides thereof; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; complete esters of polyhydric alcohols and carboxylic acids as described above Or monoesters such as 2-ethylhexyl oleate, ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, and diesters such as di-2-ethylhexyl sebacate, etc. (A) polyhydric alcohol And esters other than partial esters of carboxylic acids; aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes, and aromatic esters, or mixtures thereof.

Kinematic viscosity at 100 ° C. of the lubricating base oil used in the present invention is required to be 1 to 15 mm ² / s, preferably 2~14mm ² / s, more preferably 3~13mm ² / s, further Preferably it is 4-12 mm < ² > / s, Most preferably, it is 5-11 mm < ² > / s. When the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 15 mm ² / s, the low-temperature viscosity characteristic deteriorates. On the other hand, when the kinematic viscosity is less than 1 mm ² / s, an oil film is formed at the lubrication point. Insufficient lubrication results in poor lubricity and increases the evaporation loss of the lubricating base oil, which is not preferable.

  Further, the lubricating base oil in the present invention is not particularly limited in its viscosity index, but the viscosity index is preferably 80 or more, more preferably 90 or more, and particularly preferably 110 or more. By setting the viscosity index to 80 or more, it is possible to obtain a composition exhibiting good viscosity characteristics from a low temperature to a high temperature.

The lubricating oil composition of the present invention preferably contains (B) a poly (meth) acrylate compound having a structural unit represented by the following general formula (I).
This poly (meth) acrylate compound has a function as a viscosity index improver and / or a pour point depressant. In addition, the “poly (meth) acrylate compound” in this specification is a general term for a polyacrylate compound and a polymethacrylate compound.

（一般式（Ｉ）において、Ｒ_１は水素又はメチル基、Ｒ_２は炭素数１〜３０の炭化水素基を示す。）

(In general formula (I), R ₁ represents hydrogen or a methyl group, and R ₂ represents a hydrocarbon group having 1 to 30 carbon atoms.)

  (B) A poly (meth) acrylate compound is a polymer of a polymerizable monomer containing a (meth) acrylate monomer (hereinafter referred to as “monomer M-1”) represented by the following general formula (1).

In the general formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents a linear or branched hydrocarbon group having 1 to 30 carbon atoms.
Specific examples of the linear or branched hydrocarbon group having 1 to 30 carbon atoms represented by R ² include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, Alkyl groups such as heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group (these alkyl groups may be linear or branched); butenyl group, pentenyl Group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tetradecenyl group, hexadecenyl group, octadecenyl group and the like alkenyl groups (these alkenyl groups may be linear or branched, The position of the double bond is also arbitrary).

  A typical poly (meth) acrylate-based compound is a so-called non-dispersed poly (meth) acrylate obtained by homopolymerization of the monomer M-1 or copolymerization of two or more monomers M-1.

  The poly (meth) acrylate-based compound is composed of the monomer M-1, a (meth) acrylate monomer represented by the following general formula (2) (hereinafter referred to as “monomer M-2”), and the following general formula (3). Or a so-called dispersed poly (meth) acrylate obtained by copolymerization with one or more monomers selected from the group consisting of monomers represented by the formula (hereinafter referred to as “monomer M-3”).

In the general formula (2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkylene group having 1 to 18 carbon atoms, E ¹ represents ¹ to 2 nitrogen atoms, and 0 to 2 oxygen atoms. Each represents an amine residue or a heterocyclic residue, and a represents 0 or 1.

Specific examples of the alkylene group having 1 to 18 carbon atoms represented by R ⁴ include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, and a decylene group. And an undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, and octadecylene group (these alkylene groups may be linear or branched).

Specific examples of the amine residue or heterocyclic residue represented by E ¹ include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylidino group, and an acetylamino group. Examples thereof include a group, benzoylamino group, morpholino group, pyrrolyl group, pyrrolino group, pyridyl group, methylpyridyl group, pyrrolidinyl group, piperidinyl group, quinonyl group, pyrrolidonyl group, pyrrolidono group, imidazolino group and pyrazino group.

In the general formula (3), R ⁵ represents a hydrogen atom or a methyl group, and E ² represents an amine residue or a heterocyclic residue containing 1 to 2 nitrogen atoms and 0 to 2 oxygen atoms.
Specific examples of the amine residue or heterocyclic residue represented by E ² include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylidino group, and an acetylamino group. Examples thereof include a group, benzoylamino group, morpholino group, pyrrolyl group, pyrrolino group, pyridyl group, methylpyridyl group, pyrrolidinyl group, piperidinyl group, quinonyl group, pyrrolidonyl group, pyrrolidono group, imidazolino group and pyrazino group.

  The amine residue in the general formulas (2) and (3) refers to a monovalent group obtained by removing the hydrogen of the amino group from the amine, and the heterocyclic residue constitutes a heterocyclic ring from a molecule having a heterocyclic structure. A monovalent group excluding hydrogen bonded to carbon.

  Preferred specific examples of monomer M-2 and monomer M-3 include dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-methyl-5-vinylpyridine, morpholinomethyl methacrylate, morpholinoethyl methacrylate. , N-vinylpyrrolidone, and mixtures thereof.

  There is no particular limitation on the copolymerization molar ratio of the copolymer of monomer M-1 and monomers M-2 and M-3, but M-1: M-2 and M-3 are preferably 99: 1 to 1. 80:20, more preferably 98: 2-85: 15, still more preferably 95: 5-90: 10.

  (B) The manufacturing method of a poly (meth) acrylate type compound is arbitrary, for example, in the presence of a polymerization initiator such as benzoyl peroxide, monomer M-1 alone, or monomer M-1 and monomer M-2 to It can be easily obtained by radical solution polymerization of a mixture of M-3.

(B) The weight average molecular weight (M _w ) of the poly (meth) acrylate-based compound is preferably 5,000 or more, more preferably 10,000 or more, and further preferably 20,000 or more. It is particularly preferably 30,000 or more, and most preferably 40,000 or more. On the other hand, the weight average molecular weight _{(M W)} is preferably 400,000 or less, more preferably 300,000 or less, further preferably 200,000 or less, 100,000 or less Is particularly preferred.
When the weight average molecular weight is less than 5,000, a sufficient viscosity index improvement effect cannot be obtained, and the cost of the composition may increase. On the other hand, when the weight average molecular weight exceeds 400,000, the shear stability and storage stability of the lubricating oil composition may be impaired.

  The PSSI (Permanent Cystability Index) of the poly (meth) acrylate compound is preferably 40 or less, more preferably 5 to 40, still more preferably 10 to 35, particularly preferably 15 to 30, and most preferably 20 to 25. is there. When PSSI exceeds 40, there exists a possibility that shear stability may be impaired. On the other hand, when PSSI is less than 5, a sufficient viscosity index improving effect cannot be obtained and the cost of the composition may be increased.

  In this specification, “PSSI” is based on ASTM D 6022-01 (Standard Practice for Calculation of Permanent Shear Stability Index), and ASTM D 6278-02 (Test Metohd for Shear Stability of Polymer Containing Fluids Using a European Means the permanent shear stability index of the polymer, calculated based on the data measured by the Diesel Injector Apparatus.

  The content of the (B) poly (meth) acrylate compound in the lubricating oil composition of the present invention is preferably 0.01 to 20% by mass, more preferably 0.03 to 10% by mass, based on the total amount of the lubricating oil composition. %, More preferably 0.06 to 5% by mass, particularly preferably 0.1 to 3% by mass. When the content is less than 0.01% by mass, the predetermined viscosity index improvement effect may not be obtained, and when the content exceeds 20% by mass, the shear stability of the composition may be deteriorated.

  For the purpose of further improving the performance of the lubricating oil composition of the present invention or for imparting the required performance, an extreme pressure agent, an ashless dispersant, a metallic detergent, a friction modifier, as necessary. , Antioxidants, corrosion inhibitors, viscosity index improvers other than component (B), rust inhibitors, demulsifiers, metal deactivators, pour point depressants, seal swelling agents, antifoaming agents, colorants, etc. You may mix | blend various additives individually or in combination of several types.

  Examples of extreme pressure agents include phosphorous acid, phosphorous acid monoesters, phosphorous acid diesters, phosphorous acid triesters, and salts thereof, and at least one phosphorus-based extreme pressure agent, sulfurized fats and oils , Sulfurized olefins, dihydrocarbyl polysulfides, dithiocarbamates, thiadiazoles, and benzothiazoles, and / or thiophosphorous acid, thiophosphorous acid monoesters Thiophosphite diesters, thiophosphite triesters, dithiophosphite, dithiophosphite monoesters, dithiophosphite diesters, dithiophosphite triesters, trithiophosphite, trithio Selected from phosphorous acid monoesters, trithiophosphite diesters, trithiophosphite triesters, and salts thereof Preferably blended the extreme pressure agent comprising a sulfur-based extreme pressure agent - at least one phosphorus that.

  As the ashless dispersant, an ashless dispersant such as succinimide, benzylamine, polyamine, and / or a boron compound derivative thereof having a hydrocarbon group having 40 to 400 carbon atoms can be blended. The content of the ashless dispersant is usually 0.01 to 15% by mass based on the total amount of the composition.

  Examples of the metal detergent include metal detergents such as alkaline earth metal sulfonate, alkaline earth metal phenate, and alkaline earth metal salicylate. The content of the metal detergent is generally 0.01 to 10% by mass, preferably 0.1 to 5% by mass, based on the total amount of the composition.

  As the friction modifier, any compound usually used as a friction modifier for lubricating oils can be used, but an alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly a linear alkyl group having 6 to 30 carbon atoms. Alternatively, amine compounds, imide compounds, fatty acid esters, fatty acid amides, fatty acid metal salts, and the like having at least one linear alkenyl group in the molecule are preferably used. An organic molybdenum compound such as molybdenum dithiophosphate or molybdenum dithiocarbamate can also be used. The content of the friction modifier is usually 0.01 to 5.0% by mass based on the total amount of the composition.

  As the antioxidant, any phenolic compound or amine compound that is generally used in lubricating oils can be used. Specifically, alkylphenols such as 2,6-di-tert-butyl-4-methylphenol and bisphenols such as methylene-4,4-bisphenol (2,6-di-tert-butyl-4-methylphenol) , Naphthylamines such as phenyl-α-naphthylamine, dialkyldiphenylamines, zinc dialkyldithiophosphates such as zinc di-2-ethylhexyldithiophosphate, (3,5-di-tert-butyl-4-hydroxyphenyl) fatty acid ( Propionic acid etc.) or (3-methyl-5-tertbutyl-4-hydroxyphenyl) fatty acid (propionic acid etc.) and mono- or polyhydric alcohols such as methanol, octanol, octadecanol, 1,6-hexadiol, Neopentyl glycol, thiodiethylene glycol Triethylene glycol, esters of pentaerythritol and the like. The content of the antioxidant is usually 0.01 to 5% by mass based on the total amount of the lubricating oil composition.

  Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds.

  As the viscosity index improver other than the component (B), a non-dispersed or dispersed ethylene-α-olefin copolymer or a hydride thereof, polyisobutylene or a hydride thereof, a styrene-diene hydrogenated copolymer, a styrene- Examples thereof include maleic anhydride ester copolymers and polyalkylstyrene.

  Examples of the rust inhibitor include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.

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

  Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

  As the pour point depressant, a known pour point depressant can be arbitrarily selected according to the lubricating base oil, but polymethacrylate having a weight average molecular weight of 80,000 to 200,000 is preferable.

  As the antifoaming agent, any compound usually used as an antifoaming agent for lubricating oil can be used, and examples thereof include silicones such as dimethyl silicone and fluorosilicone.

  As the seal swelling agent, any compound usually used as a seal swelling agent for lubricating oil can be used, and examples thereof include ester-based, sulfur-based and aromatic-based seal swelling agents.

  As the colorant, any compound that is usually used can be used, and any amount can be blended.

  When these additives are contained in the lubricating oil composition of the present invention, the content thereof is usually 0.0005 to 5% by mass based on the total amount of the composition unless otherwise specified.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is required to be 1 to ²⁰ mm ² / s, preferably ² to 15 mm ² / s, more preferably 3 to 13 mm ² / s, still more preferably. It is desirable to adjust to 4 to 12 mm ² / s, particularly preferably 5 to 11 mm ² / s. When the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 20 mm ² / s, the low-temperature viscosity characteristic deteriorates. On the other hand, when the kinematic viscosity is less than 1 mm ² / s, an oil film is formed at the lubrication site. Since it is inadequate, it is inferior to lubricity, and since evaporation loss becomes large, it is unpreferable, respectively.

  The traction coefficient of the lubricating oil composition of the present invention is preferably 0.013 or less, more preferably 0.010 or less, still more preferably 0.008 or less, and particularly preferably 0.006 or less. When the traction coefficient exceeds 0.013, there is a possibility that the energy-saving property cannot be exhibited because the friction is large.

In the lubricating oil composition of the present invention, the ratio between the traction coefficient and the kinematic viscosity (mm ² / s) at 100 ° C. is preferably 1.2E-03 or less, more preferably 1.1E-03 or less, still more preferably. Is 1.0E-03 or less, particularly preferably 9.5E-04 or less. When the ratio between the traction coefficient and the kinematic viscosity (mm ² / s) at 100 ° C. exceeds 1.2E-03, there is a possibility that the energy saving property cannot be exhibited because the friction is large.

There is no particular limitation on the kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is preferably from 10 to 100 mm ² / s, more preferably 15~90mm ² / s, more preferably 20 to 80 mm ² / S, particularly preferably adjusted to 25 to 70 mm ² / s. When the kinematic viscosity at 40 ° C. of the lubricating oil composition exceeds 100 mm ² / s, the low-temperature viscosity characteristics deteriorate, whereas when the kinematic viscosity is less than 10 mm ² / s, the formation of an oil film at the lubrication site Since it is inadequate, it is inferior to lubricity, and since evaporation loss becomes large, it is unpreferable, respectively.

  Although there is no restriction | limiting in particular in the Brookfield viscosity (BF viscosity) in -40 degreeC of the lubricating oil composition of this invention, It is preferable that it is 40,000 mPa * s or less, More preferably, it is 35,000 mPa * s or less, More preferably Is 30,000 mPa · s or less, particularly preferably 25,000 mPa · s or less. When the BF viscosity at −40 ° C. exceeds 40,000 mPa · s, the low-temperature viscosity characteristics are deteriorated, which may adversely affect energy saving. In addition, BF viscosity here means the viscosity measured based on the "low temperature viscosity test method of gear oil" prescribed | regulated to JPI-5S-26-85.

  Further, the viscosity index of the lubricating oil composition of the present invention is not particularly limited, but the viscosity index is preferably 120 or more, more preferably 140 or more, and particularly preferably 160 or more. By setting the viscosity index to 120 or more, it is possible to obtain a composition exhibiting good viscosity characteristics from a low temperature to a high temperature.

  Further, the evaporation loss amount of the lubricating oil composition of the present invention is not particularly limited, but the NOACK evaporation amount is preferably 10 to 50% by mass, more preferably 20 to 40% by mass, and particularly preferably 22 to 35% by mass. It is. By using the lubricating oil composition in which the NOACK evaporation amount is adjusted to the above range, both low temperature characteristics and evaporability can be achieved. The NOACK evaporation amount here means an evaporation amount measured in accordance with CEC L-40-T-87.

  Since the lubricating oil composition of the present invention is excellent in energy saving and high efficiency, it is used, for example, for a manual transmission for an automobile, an automatic transmission, a continuously variable transmission, or an industrial gear system. As a result, it becomes possible to contribute to improving the fuel efficiency of automobiles or saving energy in factories.

  Hereinafter, the content of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.

(Examples 1-2, Comparative Examples 1-5)
According to the composition shown in Table 1, lubricating oil compositions (Examples 1 and 2) according to the present invention were prepared. The traction coefficient was measured for these compositions, and the results are also shown in Table 1.
Moreover, according to the composition shown in Table 1, lubricating oil compositions for comparison (Comparative Examples 1 to 5) were prepared, and the traction coefficient was similarly measured for these compositions. The results are also shown in Table 1. .

[Measurement of traction coefficient]
Using a thin film EHL tester ^* , the traction coefficient was measured under the following conditions.
(*) As described in R. Kapadia et al .; Tribology International (March 2007).
(Test conditions)
Test piece: SUJ2
Oil temperature: 100 ° C
Surface pressure: 0.514 GPa
Slip rate: 100%

  As shown in Table 1, compositions (Examples 1 and 2) using polyhydric alcohols and partial esters of carboxylic acids were trimerized when complete esters of polyhydric alcohols were used (Comparative Examples 1 to 3). It is clear that the traction coefficient is lower than when acid esters are used (Comparative Example 4) or when PAO is used (Comparative Example 5).

Claims (6)

(A) a polyhydric alcohol, a C2-C24 linear or branched saturated or unsaturated monobasic acid, a C2-C16 linear or branched saturated or unsaturated 0.1 to 80% by mass of a partial ester of at least one carboxylic acid selected from the group consisting of dibasic acid and trimellitic acid and 2-ethylhexyl oleate, ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl Base oil based on a lubricating oil having a kinematic viscosity at 100 ° C. of 1 to 15 mm ² / s, comprising ²⁰ to 99.9% by mass of at least one ester selected from adipate, ditridecyl adipate and di-2-ethylhexyl sebacate And a manual for an automobile with a low traction coefficient characterized by a kinematic viscosity at 100 ° C. of 1 to 20 mm ² / s Lubricating oil composition for transmission, automatic transmission, continuously variable transmission or industrial gear system.   The lubricating oil composition according to claim 1, wherein the partial ester of a polyhydric alcohol and a carboxylic acid is a partial ester of trimethylolpropane and a monovalent carboxylic acid. (B) 0.01 to 20% by mass of a poly (meth) acrylate compound composed of a structural unit represented by the following general formula (I): The lubricating oil composition according to claim 1 or 2, object.

(In general formula (I), R ₁ represents hydrogen or a methyl group, and R ₂ represents a hydrocarbon group having 1 to 30 carbon atoms.)   4. The lubricating oil composition according to claim 1, wherein a traction coefficient is 0.013 or less. In the lubricating oil composition, the lubricating oil composition according to any one of claims 1 to 4 ratio of the kinematic viscosity at traction coefficient and 100 ℃ (mm 2 / ^s) is equal to or less than 1.2E-03 object.   The lubricating oil composition according to any one of claims 1 to 5, wherein a Bruckfield viscosity at -40 ° C is 40,000 mPa · s or less.