JP5283413B2 - Lubricating oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant oil composition which can keep excellent stability against shear stress to achieve a sufficient property for a low temperature. <P>SOLUTION: The lubricant oil composition comprises a lubricant base oil comprising a mineral oil and/or a synthetic oil, (A) a poly (meth)acrylate compound having a function as a viscosity index improver and a pour-point depressant, and (B) the ester between a carbonic acid including a hydroxy carbonic acid and an alcohol. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition suitable for an internal combustion engine.

  In recent years, lubricating oils used in internal combustion engines such as automobile engines have been required to have excellent low temperature characteristics in order to achieve fuel savings and achieve them.

  In recent years, lowering the viscosity of engine oils for automobiles has been studied for the purpose of improving fuel-saving characteristics. Recently, in order to improve the fuel efficiency of the engine oil when the engine is cold, the viscosity at the low temperature has been lowered and the improvement of the fluidity at the low temperature has been studied. As evaluation indexes for low temperature characteristics of lubricating base oils and lubricating oil compositions, pour point, cloud point, freezing point, etc. are common, and recently, lubricating base oils such as normal paraffin and isoparaffin contents are used. A technique for evaluating low-temperature viscosity characteristics based on this is known.

All of the conventional methods are methods for improving the low temperature fluidity by adding a polymer, and the low temperature fluidity is improved by the addition, but on the other hand, the addition of a polymer increases the shear stability of the composition. There is a concern that the lubricity deteriorates due to a decrease in viscosity. In addition, there are concerns that the effect of improving the low-temperature properties due to the polymer being cleaved, and that the cleaved polymer molecule adversely affects the oxidation stability. For this reason, the actual amount is that the amount of addition of the high molecular polymer is suppressed to achieve a compromise between the low temperature characteristics and the shear stability or the oxidation stability. Further, it has been pointed out that there is an optimum point even if the amount of addition of the polymer is increased, and that an easy increase may adversely affect the low temperature characteristics (see Patent Documents 1 to 4).
Japanese Patent Application Laid-Open No. 2002-167591 JP 2004-352946 A JP 2005-15780 A JP 2007-262245 A

  A typical example of the polymer additive is poly (meth) acrylate. Poly (meth) acrylate can be said to be an essential additive from the viewpoint of improving low-temperature characteristics in multi-grade type automobile engine oils. In addition, base oil for engine oil is shifting from Group I base oil, which is a conventional solvent refined oil, to Group III base oil that uses residual oil in fuel oil hydrocracking equipment as a raw material. Even if it has changed, poly (meth) acrylates adapted to that change have been developed and used.

  However, it is difficult to obtain sufficient low-temperature characteristics while maintaining excellent shear stability only by adding poly (meth) acrylate.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a lubricating oil composition capable of achieving sufficient low-temperature characteristics while maintaining excellent shear stability. .

In order to solve the above-mentioned problems, the present invention provides a lubricating base oil composed of mineral oil and / or synthetic oil, and (A) a poly (meth) acrylate compound having functions as a viscosity index improver and a pour point depressant. And (B) an ester of a carboxylic acid and an alcohol containing α-hydroxycarboxylic acid and / or ω-hydroxycarboxylic acid , and has a kinematic viscosity at 100 ° C. of 5 to 18 mm ² / s. A lubricating oil composition for an internal combustion engine is provided.

  According to the lubricating oil composition of the present invention, it is possible to achieve sufficient low-temperature characteristics while maintaining excellent shear stability.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  In the present invention, mineral oil and / or synthetic oil used for ordinary lubricating oil can be used as the lubricating base oil.

  Specifically, as mineral oil, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil can be desolvated, solvent extracted, hydrocracked, and solvent dewaxed. , Oils refined by one or more treatments such as hydrorefining, or lubricating oils produced by isomerizing wax isomerized mineral oil, GTL WAX (Gas Liquid Wax) produced by Fischer-Tropsch process, etc. A base oil can be illustrated.

  The total aromatic content of the mineral oil is not particularly limited, but is preferably 30% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less, and particularly preferably 5% by mass or less. When the total aromatic content of the mineral oil exceeds 30% by mass, the oxidation stability may be inferior.

  The sulfur content of the mineral oil is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and particularly preferably 0.005% by mass or less. By reducing the sulfur content of the mineral oil, a composition having better high-temperature cleanability can be obtained.

  Synthetic oils include polybutene or hydrides thereof; poly α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, Or a diester such as di-2-ethylhexyl sebacate; a polyol ester such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, or pentaerythritol pelargonate; a dicarboxylic such as dibutyl maleate Examples thereof include a copolymer of an acid and an α-olefin having 2 to 30 carbon atoms, an aromatic synthetic oil such as an alkylnaphthalene, an alkylbenzene, or an aromatic ester, or a mixture of two or more of these.

  As the lubricating base oil used in the present invention, mineral oil, synthetic oil, or any mixture of two or more lubricating base oils selected from these can be used. For example, 1 or more types of mineral oil, 1 or more types of synthetic oil, the mixed oil of 1 or more types of mineral oil and 1 or more types of synthetic oil is mentioned.

No particular limitation is imposed kinematic viscosity of the lubricating base oil used in the present invention, the kinematic viscosity at the 100 ° C. is, ^{1 mm} 2 / s or more, is preferably from ^{20mm 2 / s, 2mm 2 /} s or more, 10 mm ² / S or less is more preferable. When the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 20 mm ² / s, the low-temperature viscosity characteristics may be deteriorated. On the other hand, when the kinematic viscosity is less than 1 mm ² / s, Insufficient oil film formation may result in poor lubricity and may increase the evaporation loss of the lubricating base oil.

  The viscosity index of the lubricating base oil is not particularly limited, but the value is preferably 80 or more, more preferably 100 or more, and most preferably 120 or more so that excellent viscosity characteristics can be obtained from low temperature to high temperature. The upper limit of the viscosity index is not particularly limited, and is about 135 to 180 such as normal paraffin, slack wax, GTL wax and the like, or isoparaffin mineral oil obtained by isomerizing these, and 150 to about 150 to about complex ester base oil. A thing of about 250 can also be used. When the viscosity index of the lubricating base oil is less than 80, the low temperature viscosity characteristics may be deteriorated.

  The lubricating oil composition of the present invention has, as the component (A), a poly (meth) acrylate compound having a function as a viscosity index improver and a pour point depressant (hereinafter simply referred to as “poly (meth) acrylate compound”). .). The “poly (meth) acrylate” in the present invention is a general term for polyacrylate and polymethacrylate.

［式（１）中、Ｒ^１は水素又はメチル基を示し、Ｒ^２は炭素数１〜３０の直鎖状又は分枝状の炭化水素基を示す。］ The poly (meth) acrylate compound according to the present invention is preferably a polymer of a polymerizable monomer containing a (meth) acrylate monomer represented by the following general formula (1) (hereinafter referred to as “monomer M-1”). It is a coalescence.

[In formula (1), R ¹ represents hydrogen or a methyl group, R ² represents a linear or branched hydrocarbon group having 1 to 30 carbon atoms. ]

  The polymethacrylate obtained by copolymerization of one kind of the monomer represented by the general formula (1) or two or more kinds is a so-called non-dispersion type polymethacrylate. The compound includes a monomer represented by the general formula (1) and one or more monomers selected from the general formulas (2) and (3) (hereinafter referred to as “monomer M-2” and “monomer M-3”, respectively). And so-called dispersed polymethacrylates obtained by copolymerization of

［上記一般式（２）中、Ｒ^３は水素原子又はメチル基を示し、Ｒ^４は炭素数１〜１８のアルキレン基を示し、Ｅ^１は窒素原子を１〜２個、酸素原子を０〜２個含有するアミン残基又は複素環残基を示し、ａは０又は１を示す。］

[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 0 oxygen atoms. 2 represents an amine residue or heterocyclic residue, and a represents 0 or 1. ]

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

Specific examples of the group 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, an acetylamino group, a benzoylamino group, Examples thereof include a morpholino group, a pyrrolyl group, a pyrrolino group, a pyridyl group, a methylpyridyl group, a pyrrolidinyl group, a piperidinyl group, a quinonyl group, a pyrrolidonyl group, a pyrrolidono group, an imidazolino group, and a pyrazino group.

［上記一般式（３）中、Ｒ^５は水素原子又はメチル基を示し、Ｅ^２は窒素原子を１〜２個、酸素原子を０〜２個含有するアミン残基又は複素環残基を示す。］

[In the above 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 group 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, an acetylamino group, a benzoylamino group, and a morpholino group. Pyrrolyl group, pyrrolino group, pyridyl group, methylpyridyl group, pyrrolidinyl group, piperidinyl group, quinonyl group, pyrrolidonyl group, pyrrolidono group, imidazolino group, pyrazino group and the like.

  As preferable examples of the monomer M-2 and the monomer M-3, specifically, dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-methyl-5-vinylpyridine, morpholinomethyl methacrylate , Morpholinoethyl methacrylate, N-vinylpyrrolidone, and mixtures thereof.

  Although there is no restriction | limiting in particular about the copolymerization molar ratio of the copolymer of the monomer M-1 and the monomers M-2 to M-3, M-1: M-2 to M-3 = 10: 90-50: 50 The degree is preferable, more preferably 15:85 to 40:60, and still more preferably 20:80 to 30:70.

  The method for producing the poly (meth) acrylate compound according to the present invention is arbitrary. For example, in the presence of a polymerization initiator such as benzoyl peroxide, a mixture of monomer M-1 and monomers M-2 to M-3. Can be easily obtained by radical solution polymerization.

The weight average molecular weight (M _w ) of the poly (meth) acrylate compound according to the present invention is preferably 5,000 or more, more preferably 50,000 or more, and further preferably 100,000 or more. Particularly preferred is 200,000 or more, and most preferred is 300,000 or more. Moreover, it is preferable that it is 1,000,000 or less, More preferably, it is 700,000 or less, More preferably, it is 600,000 or less, Especially preferably, it is 500,000 or less. If the weight average molecular weight is less than 5,000, the effect of improving the viscosity index is small and not only fuel efficiency and low temperature viscosity characteristics are inferior, but also the cost may increase, and the weight average molecular weight exceeds 1,000,000. In some cases, shear stability, solubility in lubricating base oil, and storage stability may be deteriorated.

  The PSSI (Permanent Cystability Index) of the poly (meth) acrylate compound according to the present invention is preferably 40 or less, more preferably 5 to 40, still more preferably 10 to 35, still more preferably 15 to 30, particularly preferably. 20-25. When PSSI exceeds 40, shear stability may be deteriorated. Further, when PSSI is less than 5, the effect of improving the viscosity index is small, which is not only inferior in fuel economy and low-temperature viscosity characteristics, but also in cost.

  Note that “PSSI” here conforms to ASTM D 6022-01 (Standard Practication for Calculation of Permanent Shear Stable Stability Index), and ASTM D 6278-02 (Test Method for Stood For Shar. It means the permanent shear stability index of the polymer, calculated based on the data measured by Injector Apparatus.

  The content of the poly (meth) acrylate compound according to the present invention is desirably selected depending on whether the lubricating oil composition is a multigrade oil or a single grade oil, but preferably 0.01 to 15 % By mass, more preferably 0.05 to 10% by mass, still more preferably 0.08 to 8% by mass, and most preferably 0.1 to 6% by mass. If the addition amount is less than 0.01% by mass, sufficient low temperature characteristics may not be obtained, and if the addition amount exceeds 15% by mass, there is a risk of adversely affecting shear stability or oxidation stability. is there.

  The lubricating oil composition of the present invention contains an ester lanolin fatty acid ester of a carboxylic acid containing hydroxycarboxylic acid and an alcohol (hereinafter referred to as “ester compound (B)” for convenience) as the component (B). To do.

  Here, the “hydroxycarboxylic acid” (also referred to as “hydroxyacid”) in the present invention means a carboxylic acid further having a hydroxyl group in addition to the carboxylic acid group (—COOH). The number of carbon atoms of the hydroxycarboxylic acid is arbitrary, and usually a hydroxycarboxylic acid having 2 to 40 carbon atoms is used. From the viewpoint of low temperature characteristics, the number of carbon atoms of the hydroxycarboxylic acid is preferably 6 or more. More preferably, it is more preferably 10 or more. Moreover, from the viewpoint of precipitation prevention at low temperatures and solubility in a lubricating base oil, the number of carbon atoms of the hydroxycarboxylic acid is preferably 30 or less, and more preferably 24 or less.

  The hydroxycarboxylic acid may be a saturated carboxylic acid or an unsaturated carboxylic acid, but is preferably a saturated carboxylic acid from the viewpoint of stability. The hydroxycarboxylic acid may be a straight chain carboxylic acid or a branched carboxylic acid, but a straight chain carboxylic acid or a branched chain having 1 or 2 carbon atoms (more preferably 1 carbon atom) is represented by 1 to 3 A branched carboxylic acid having 1 (more preferably 1 to 2, particularly preferably 1) is preferable.

  Further, the number of carboxylic acid groups that the hydroxycarboxylic acid has is not particularly limited, and may be either the hydroxycarboxylic acid monobasic acid or the polybasic acid, but is preferably a monobasic acid.

  In addition, the number of hydroxyl groups that the hydroxycarboxylic acid has is not particularly limited, but is preferably 1 to 4, more preferably 1 to 3, more preferably 1 to 2 from the viewpoint of stability. Is more preferable and one is particularly preferable.

  Moreover, the bonding position of the hydroxyl group in the hydroxycarboxylic acid is arbitrary, but the α-hydroxycarboxylic acid in which the hydroxyl group is bonded to the bonding carbon atom of the carboxylic acid group (also referred to as “α-hydroxy acid”), or the bonding carbon of the carboxylic acid group It is preferably ω-hydroxycarboxylic acid (also referred to as “ω-hydroxy acid”) in which a hydroxyl group is bonded to a carbon atom at the other end of the main chain as viewed from the atom.

［式中、Ｒ^６は水素原子、炭素数１〜３８のアルキル基又は炭素数２〜３８のアルケニル基を示す。］

［式中、Ｒ^７は水素原子、炭素数１〜３８のアルキレン基又は炭素数２〜３８のアルケニレン基を示す。］ Specific preferred examples of the hydroxycarboxylic acid include α-hydroxycarboxylic acid represented by the following general formula (4) and ω-hydroxycarboxylic acid represented by the following general formula (5).

[Wherein, R ⁶ represents a hydrogen atom, an alkyl group having 1 to 38 carbon atoms, or an alkenyl group having 2 to 38 carbon atoms. ]

[Wherein, R ⁷ represents a hydrogen atom, an alkylene group having 1 to 38 carbon atoms, or an alkenylene group having 2 to 38 carbon atoms. ]

In the general formula (4), R ⁶ represents a hydrogen atom, an alkyl group having 1 to 38 carbon atoms, or an alkenyl group having 2 to 38 carbon atoms. Specific examples of the alkyl group and alkenyl group represented by R ⁶ include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and undecyl. , Dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, henicosyl group, docosyl group, tricosyl group, tetracosyl group, pentacosyl group, hexacosyl group, heptacosyl group, octacosyl Group, nonacosyl group, triacontyl group, hentriacontyl group, dotriacontyl group, tritriacontyl group, tetratriacontyl group, pentatriacontyl group, hexatriacontyl group, heptatriacontyl group, octatriacontyl group Alkyl etc. Group (including all isomers): ethenyl group (vinyl group), propenyl group (allyl group), butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group , Tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, nonadecenyl group, icocenyl group, henicosenyl group, dococenyl group, tricosenyl group, tetracocenyl group, pentacocenyl group, hexacocenyl group, heptacocenyl group, heptacocenyl group, heptacocenyl group, heptacocenyl group Group, triacontenyl group, hentriacontenyl group, dotriacontenyl group, tritriacontenyl group, tetratriacontenyl group, pentatriacontenyl group, hexatriacontenyl group, heptatri Konteniru group, (including all isomers) alkenyl groups such as octa thoria Conte sulfonyl group and the like.

In the general formula (5), R ⁷ represents a hydrogen atom, an alkylene group having 1 to 38 carbon atoms, or an alkenylene group having 2 to 38 carbon atoms. Specific examples of the alkylene group and alkenylene group represented by R ⁷ include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, and an undecylene group. , Dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group, nonadecylene group, icosylene group, heicosylene group, docosylene group, tricosylene group, tetracosylene group, pentacosylene group, hexacosylene group, heptacene group Group, octacosylene group, nonacosylene group, triacontylene group, hentriacontylene group, dotriacontylene group, tritriacontylene group, tetratriacontylene group, pentatriacontylene group, hexato Alkylene groups (including all isomers) such as rear contylene group, heptatria acetylene group, octatria contylene group; ethenylene group (vinylene group), propenyl group (arylene group), butenylene group, pentenylene group, hexenylene group, Heptenylene group, octenylene group, nonenylene group, decenylene group, undecenylene group, dodecenylene group, tridecenylene group, tetradecenylene group, pentadecenylene group, hexadecenylene group, heptadecenylene group, octadecenylene group, nonadecenylene group, icocenylene group, icocenylene group, Tetracosenylene group, Pentacosenylene group, Hexacosenylene group, Heptacosenylene group, Octacocenylene group, Nonacosenylene group, Triacontenylene group, Hentriaconte Alkenylene groups such as Len, Dotria Contenylene, Tritria Contenylene, Tetratria Contenylene, Pentatria Contenylene, Hexatria Contenylene, Heptatria Contenylene, Octatria Contenylene, etc. (all Isomers) and the like.

  As a raw material containing such a hydroxycarboxylic acid, a lanolin fatty acid obtained by purifying (hydrolyzing etc.) a waxy substance adhering to sheep wool can be preferably used.

  The constituent carboxylic acid of the ester compound (B) may be composed of only hydroxycarboxylic acid, but may further contain a carboxylic acid having no hydroxyl group.

  When the constituent carboxylic acid of the ester compound (B) contains both a hydroxycarboxylic acid and a carboxylic acid having no hydroxyl group, the content of the hydroxycarboxylic acid is preferably 3% by mass based on the total amount of the constituent carboxylic acid. Or more, more preferably 5% by mass or more, further preferably 10% by mass or more, particularly preferably 20% by mass or more, preferably 80% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass. % Or less, particularly preferably 40% by mass or less. If the content of hydroxycarboxylic acid is less than the lower limit, the effect of improving the low temperature characteristics tends to be insufficient. On the other hand, when the content of the hydroxycarboxylic acid exceeds the upper limit, the solubility in the lubricating base oil tends to be insufficient.

  The carboxylic acid having no hydroxyl group may be a saturated carboxylic acid or an unsaturated carboxylic acid, but a saturated carboxylic acid is preferable from the viewpoint of stability.

  The carboxylic acid having no hydroxyl group may be a linear carboxylic acid or a branched carboxylic acid, but may be a linear carboxylic acid or a component having 1 to 2 carbon atoms (more preferably 1 carbon atom). A branched carboxylic acid having 1 to 3 branch groups (more preferably 1 to 2, particularly preferably 1) is preferred. As for the branch of the branched carboxylic acid, methyl branch or ethyl branch is preferable, and methyl branch is particularly preferable.

  The carbon number of the carboxylic acid having no hydroxyl group is arbitrary, and usually a carboxylic acid having 2 to 40 carbon atoms is used. From the viewpoint of low temperature characteristics, the carbon number of the carboxylic acid is preferably 8 or more. More preferably, it is 10 or more. Further, from the viewpoint of solubility in a lubricating base oil and prevention of precipitation at low temperatures, the carbon number of the carboxylic acid is preferably 30 or less, and more preferably 24 or less.

  The number of carboxylic acid groups in the saturated carboxylic acid having no hydroxyl group is not particularly limited and may be either a monobasic acid or a polybasic acid, but is preferably a monobasic acid.

  Specific examples of the carboxylic acid having no hydroxyl group include linear or branched hexanoic acid, linear or branched heptanoic acid, linear or branched octanoic acid, linear Straight 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, linear or branched heicosanoic acid, linear or branched docosane Acid, linear or branched tricosanoic acid, linear or branched tetracosanoic acid, linear or branched Pentacosanoic acid, linear or branched hexacosanoic acid, linear or branched heptacosanoic acid, linear or branched octacosanoic acid, linear or branched nonacosanoic acid, linear Or a saturated fatty acid such as branched triacontanoic acid; linear or branched hexenoic acid, linear or branched heptenoic acid, linear or branched octenoic acid, linear or Branched nonenic acid, linear or branched decenoic acid, linear or branched undecenoic acid, linear or branched dodecenoic acid, linear or branched tridecenoic acid , Linear or branched tetradecenoic acid, linear or branched pentadecenoic acid, linear or branched hexadecenoic acid, linear or branched heptadecenoic acid, linear or branched Branched octadecenoic acid, linear or branched nonadecenoic acid, linear or branched ico Acid, linear or branched henicosenoic acid, linear or branched docosenoic acid, linear or branched tricosenoic acid, tetracosenoic acid, linear or branched pentacosenoic acid, Linear or branched hexacosenoic acid, linear or branched heptacenoic acid, linear or branched octacosenoic acid, linear or branched nonacosenic acid, linear or branched And unsaturated fatty acids such as triacontenoic acid, and mixtures of two or more thereof.

  When the constituent carboxylic acid of the ester compound (B) contains both a hydroxycarboxylic acid and a carboxylic acid having no hydroxyl group, the content of the carboxylic acid having no hydroxyl group is preferably based on the total amount of the constituent carboxylic acid. Is 97% by mass or less, more preferably 95% by mass or less, further preferably 90% by mass or less, particularly preferably 80% by mass or less, preferably 20% by mass or more, more preferably 40% by mass or more, Preferably it is 50 mass% or more, Most preferably, it is 60 mass% or more. When the content of the carboxylic acid having no hydroxyl group exceeds the upper limit, the effect of improving the low temperature characteristics tends to be insufficient. On the other hand, when the content of the carboxylic acid having no hydroxyl group is less than the lower limit, the solubility in the lubricating base oil tends to be insufficient.

  In the ester compound (B), the proportion of carboxylic acids having 24 or less carbon atoms in the constituent carboxylic acids (total of hydroxycarboxylic acids and carboxylic acids having no hydroxyl groups) is 75 on the basis of the total amount of the constituent carboxylic acids. Is preferably 100 to 100% by mass, more preferably 80 to 100% by mass, still more preferably 85 to 100% by mass, still more preferably 90 to 100% by mass, and 92 to 100% by mass. % Is particularly preferred. When the proportion of the carboxylic acid having 24 or less carbon atoms is less than the lower limit, the effect of improving the low temperature characteristics, the solubility in the lubricating base oil, and the precipitation preventing property at low temperatures tend to be insufficient. For the same reason, in the ester compound (B), the proportion of the carboxylic acid having 25 or more carbon atoms in the constituent carboxylic acid (total of hydroxycarboxylic acid and carboxylic acid having no hydroxyl group) is the total amount of the constituent carboxylic acid. Is preferably 0 to 25% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, and still more preferably 0 to 10% by mass. 0 to 8% by mass is particularly preferable.

  The alcohol constituting the ester compound (B) may be a monohydric alcohol or a polyhydric alcohol.

  The monohydric alcohol may be a linear alcohol or a branched alcohol, and may be either a saturated alcohol or an unsaturated alcohol. Moreover, although carbon number of monohydric alcohol is arbitrary, it is 1-36 normally, Preferably it is 1-24.

  Specific examples of the monohydric alcohol include methanol, ethanol, linear or branched propanol, linear or branched butanol, linear or branched pentanol, and linear. Or branched hexanol, linear or branched heptanol, linear or branched octanol, linear or branched nonanol, linear or branched decanol, linear Or branched undecanol, linear or branched dodecanol, linear or branched tridecanol, linear or branched tetradecanol, linear or branched pentadecanol , Linear or branched hexadecanol, linear or branched heptadecanol, linear or branched octadecanol, linear or branched nonadecanol, linear Or branched icosanol, straight chain Or branched Hen'ikosanoru, linear or branched Torikosanoru, such as straight-chain or branched tetracosanol, and mixtures thereof. Among these, a monohydric alcohol having 1 to 18 carbon atoms is preferable and a monohydric alcohol having 1 to 12 carbon atoms is more preferable from the viewpoint of solubility in a lubricating base oil.

  It is preferable to use a monohydric alcohol as the constituent alcohol of the ester compound (B) because the solubility in a lubricating base oil and the prevention of precipitation at low temperatures are further improved.

  Moreover, as a polyhydric alcohol used for an ester compound (B), 2-10 valence normally, Preferably a 2-6 valence alcohol is used. Specific examples of such polyhydric alcohols include ethylene glycol, diethylene glycol, polyethylene glycol (3 to 15 mer of ethylene glycol), propylene glycol, dipropylene glycol, and polypropylene glycol (3 to 15 amount of propylene glycol). Body), 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,2-propanediol, 2-methyl-1,3- Dihydric alcohols such as propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, neopentylglycol; glycerin, polyglycerin (2-8 of glycerin) Such as diglycerin, triglycer Phosphorus, tetraglycerin, etc.), trimethylolalkanes (trimethylolethane, trimethylolpropane, trimethylolbutane, 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 That.

  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-hexanetriol , 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 because they are more excellent in preventing cylinder noise.

  It is preferable to use a polyhydric alcohol as the constituent alcohol of the ester compound (B) because the low temperature characteristics are further improved. The ester compound (B) obtained using the polyhydric alcohol may be a complete ester in which all of the hydroxyl groups of the polyhydric alcohol are esterified, or a part of the hydroxyl groups remain unreacted. It may be a partial ester. Further, when the constituent carboxylic acid of the ester compound (B) is a polybasic acid, it may be a complete ester in which all of the carboxyl groups of the ester compound (B) are esterified, or a part of the carboxyl groups may be It may be a partial ester remaining unreacted. From the viewpoint of improving the low temperature characteristics, it is preferable to use a partial ester in which the hydroxyl group or carboxyl group remains unreacted.

  The preparation method of the ester compound (B) is arbitrary, but an ester obtained by reacting a fatty acid (lanolin fatty acid) obtained by saponifying and decomposing lanolin from sheep wool with an alcohol is particularly preferable.

  Specific examples of lanolin fatty acid esters include methyl ester, isobutyl ester, n-butyl ester, octyldodecanol ester, trimethylolpropane triester, trimethylolpropane diester, trimethylolpropane monoester, pentaerythritol tetraester of lanolin fatty acid ester, Examples include pentaerythritol triester and pentaerythritol diester. Specific examples of fatty acid esters using a mixture of acids other than lanolin fatty acid include pentaerythritol diester of a mixture of lanolin fatty acid and oleic acid, pentaerythritol triester of a mixture of lanolin fatty acid and oleic acid, and the like.

  The addition amount of the lanolin fatty acid ester is preferably 0.05 to 5% by mass, more preferably 0.1 to 4% by mass, further preferably 0.2 to 3% by mass, and most preferably 0.3 to 2% by mass. It is. If the addition amount is less than 0.05% by mass, sufficient low temperature characteristics may not be obtained, and if the addition amount exceeds 5% by mass, oxidation stability may be adversely affected.

  In addition, the lubricating oil composition of the present invention can contain various additives as necessary as long as the low temperature fluidity is not impaired. Such an additive is not particularly limited, and any additive conventionally used in the field of lubricating oils can be blended. Specific examples of such lubricating oil additives include metallic detergents, ashless dispersants, antioxidants, extreme pressure agents, antiwear agents, friction modifiers, viscosity index improvers other than the component (A), Pour point depressants other than the component (A), corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, antifoaming agents and the like can be mentioned. These additives may be used individually by 1 type, and may be used in combination of 2 or more type.

  The lubricating oil composition of the present invention may contain one or more selected from sulfonate detergents, salicylate detergents, and phenate detergents as metal detergents. As these metallic detergents, any of normal salts, basic normal salts, and overbased salts with alkali metals or alkaline earth metals can be blended.

  In the lubricating oil composition of the present invention, any ashless dispersant used in lubricating oils can be used as the ashless dispersant. For example, a linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms can be used. Mono- or bissuccinimide having at least one in the molecule, benzylamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or an alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule And polyamines having at least one of them, or modified products of these boron compounds, carboxylic acids, phosphoric acids and the like. In use, one kind or two or more kinds arbitrarily selected from these can be blended.

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

  Examples of the friction modifier include ashless friction modifiers such as fatty acid esters, aliphatic amines, and fatty acid amides, and metal friction modifiers such as molybdenum dithiocarbamate and molybdenum dithiophosphate.

  An extreme pressure agent that can be used in the lubricating oil composition of the present invention. As the antiwear agent, any extreme pressure agent / antiwear agent used in lubricating oils can be used. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, phosphites, thiophosphites, dithiophosphites, trithiophosphites Esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate, disulfide , Polysulfides, sulfurized olefins, sulfurized fats and oils, and the like.

  As the viscosity index improver, polymethacrylate viscosity index improver other than the component (A), olefin copolymer viscosity index improver, styrene-diene copolymer viscosity index improver, styrene-maleic anhydride copolymer Examples thereof include a systemic viscosity index improver or a polyalkylstyrene viscosity index improver. The weight average molecular weight of these viscosity index improvers is usually 800 to 1,000,000, preferably 100,000 to 900,000.

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

  Examples of the rust preventive 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, or 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 thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.
Examples of antifoaming agents include silicone oils having a kinematic viscosity at 25 ° C. of less than 0.1 to 100 mm ² / s, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long chain fatty acids, methyl salicylates and o. -Hydroxybenzyl alcohol etc. are mentioned.

  When these additives are contained in the lubricating oil composition of the present invention, the content thereof is 1 to 20% by mass based on the total amount of the composition.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is usually 4 to 24 mm ² / s, but the oil film thickness that suppresses seizure and wear is maintained, and the increase in stirring resistance is suppressed. From the viewpoint, it is preferably 5 to 18 mm ² / s, more preferably 6 to 15 mm ² / s, and further preferably 7 to 12 mm ² / s.

  The lubricating oil composition of the present invention having the above structure is excellent in low temperature viscosity characteristics, as well as in viscosity-temperature characteristics and thermal / oxidative stability, and is used for motorcycles, automobiles, power generation, marine use, etc. Not only as a lubricating oil for internal combustion engines such as gasoline engines and diesel engines, but also transmission oils such as automatic transmission oil and manual transmission oil, hydraulic oil for automobiles such as shock absorber oil and power steering oil, hydraulic hydraulic oil, turbine The effect is sufficiently exerted even in oil, compressor oil and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Examples 1-6, Comparative Examples 1-2]
In Examples 1 to 6 and Comparative Examples 1 and 2, various additives were blended into a mixture of the following three lubricant base oils to prepare a lubricant composition having the composition shown in Table 1. Table 2 shows the fatty acid composition of the lanolin fatty acid (I) used as the constituent carboxylic acid of the following additives B1 to B3.
(Lubricant base oil)
Base oil 1: paraffinic base oil (kinematic viscosity at 100 ° C .: 4.3 mm ² / s, viscosity index: 102, sulfur content: 0.25 mass%)
Base oil 2: paraffinic base oil (kinematic viscosity at 100 ° C .: 6.5 mm ² / s, viscosity index: 103, sulfur content: 0.31% by mass)
Base oil 3: highly paraffinic base oil (kinematic viscosity at 100 ° C .: 4.1 mm ² / s, viscosity index: 125, sulfur content: less than 0.1% by mass)
Base oil 4: highly refined paraffin base oil (kinematic viscosity at 100 ° C .: 6.3 mm ² / s, viscosity index: 135, sulfur content: 0.006% by mass)
(Pour point depressant 1)
A: Non-dispersed polymethacrylate (weight average molecular weight: 20000, PSSI: 50)
(Pour point depressant 2)
B1: Diester of lanolin fatty acid (I) and pentaerythritol
B2: Triester of lanolin fatty acid (I) and pentaerythritol
B3: Triester of lanolin fatty acid (I), oleic acid mixture and trimethylolpropane.
(Viscosity index improver)
C: Olefin copolymer (weight average molecular weight: 160,000)
(Ashless dispersant)
D: Performance additive (package containing metal detergent, ashless dispersant, zinc dialkyldithiophosphate)

  About the lubricating oil composition of Examples 1-6 and Comparative Examples 1-2, the MRV viscosity in -40 degreeC was measured based on the pour point based on JISK-2269, and JPI-5S-42-93. The obtained results are shown in Table 1.

As shown in Table 1, it was confirmed that the lubricating oil compositions of Examples 1 to 6 gave a very low −40 ° C. MRV viscosity as compared with Comparative Examples 1 and 2.

Claims (3)

A lubricating base oil composed of mineral oil and / or synthetic oil;
(A) a poly (meth) acrylate compound having a function as a viscosity index improver and a pour point depressant;
(B) an ester of a carboxylic acid and an alcohol containing α-hydroxycarboxylic acid and / or ω-hydroxycarboxylic acid ,
Containing lubricating oil composition for an internal combustion engine, wherein the kinematic viscosity at 100 ° C. is 5~18mm ² / s. The (A) poly (meth) acrylate compound having a function as a viscosity index improver and a pour point depressant is calculated based on data measured according to ASTM D 6278-02 in accordance with ASTM D 6022-01. 2. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the PSSI is 5 to 40. 3. The lubricating oil composition for internal combustion engines according to claim 1 or 2, further comprising 1 to 20% by mass of an olefin copolymer as a viscosity index improver based on the total amount of the composition.