JP2015183058A - engine oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine oil composition having excellent fuel saving performance and having excellent wear resistance.SOLUTION: This invention provides an engine oil composition in which a lubricant base oil having specific properties contains, as viscosity index improvers, a star polymer and a polymer having a nitrogen-containing group, and as a friction modifier, an amide compound, an imide compound, or a mixture of both compounds.

Description

  The present invention relates to an engine oil composition having excellent fuel economy performance.

In recent years, as a response to environmental problems such as global warming, an effect of reducing fuel consumption has been demanded for engine oil. The fuel-saving improvement technology by engine oil includes friction reduction in the fluid lubrication region by lowering the viscosity and friction reduction technology in the boundary lubrication region by adding a friction reducing agent.
However, excessively low viscosity has a problem of adverse effects on engine durability and increased friction in the boundary lubrication region due to insufficient oil film strength. This is a problem common to both gasoline and diesel engines, but particularly in diesel engines, the adverse effect of lowering the viscosity of engine oil is significant.

  In Patent Documents 1 to 3, a specific viscosity index improver is added to a lubricating base oil having a viscosity index of 120 or more as an engine oil having a constant viscosity under high temperature and high shear and good fuel economy performance. Engine oil is disclosed.

JP 2010-095662 A JP 2010-095663 A JP 2010-095664 A

Although the engine oils according to Patent Documents 1 to 3 described above have a certain fuel consumption reduction effect, they are still not satisfactory.
Then, the subject of this invention is providing the engine oil composition which was excellent in the fuel-saving performance, and was excellent in abrasion resistance.

  As a result of diligent research on the above problems, the inventors of the present invention have a lubricant base oil having a specific property, a polymer having a star polymer and a nitrogen-containing group as a viscosity index improver, and an amide compound, an imide compound as a friction modifier, Alternatively, it has been found that by containing a mixture of both compounds, excellent wear resistance and fuel saving effect can be expressed, and the present invention has been completed.

That is, according to the present invention, a lubricating base oil having a saturated content of 70% by mass or more and a viscosity index of 90 or more and 160 or less, (A) (A-1) a star polymer and (A-2) weight average There is provided an engine oil composition comprising a polymer having a nitrogen-containing group having a molecular weight of 200,000 or more and 400,000 or less and (B) an amide compound, an imide compound, or a mixture of both compounds.
Moreover, it is preferable that the said star polymer is a polymer which has a core part of a polyalkenyl compound, and 4-15 arm parts couple | bonded with this core part.

  Since the engine oil composition of the present invention contains a specific polymer containing a star polymer in a lubricating base oil having specific properties, it can exhibit excellent fuel consumption performance and extremely good wear resistance. it can.

Hereinafter, the present invention will be described in detail.
The base oil of the engine oil composition of the present invention is a lubricating base oil having a saturated content of 70% by mass or more and a viscosity index of 90 or more and 160 or less (hereinafter sometimes simply referred to as a base oil).

The saturated content of the base oil is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. In particular, it is most preferable that almost all is saturated, specifically 99% by mass or more. When the saturated content is less than 70% by mass, the oxidation stability is not sufficient for use under high temperature and high shear lubrication conditions, and the performance of the present invention cannot be realized due to poor viscosity-temperature characteristics.
In addition, content of the saturated part said by this invention means the value (unit: mass%) measured based on ASTMD2007-11.

The base oil of the present invention preferably has a% Cp of 60 or more, more preferably 70 or more. Moreover, it is preferable that it is 100 or less, and it is more preferable that it is 95 or less. In addition,% Cp as used in the field of this invention means the percentage (%) with respect to the total carbon number of the carbon which comprises the paraffin in a base oil, and is measured based on ASTM D3238.
In addition, the base oil of the present invention preferably has a% _CN of 40 or less, more preferably 30 or less. Moreover, it is preferably 1 or more, and more preferably 3 or more. Note that the means% C _N in the present invention means a percentage (%) to the total number of carbon atoms of the carbon atoms constituting the naphthene ring in the base oil, measured according to ASTM D3238.
Further, the base oil of the present invention,% C _A is preferably 10 or less, more preferably 2 or less. Moreover, it is preferable that it is 0 or more. Note that says% C _A in the present invention means a percentage (%) to the total number of carbon atoms of the carbon atoms constituting the aromatic ring in the base oil, measured according to ASTM D3238.

Further, the viscosity index of the base oil is preferably 110 or more, more preferably 120 or more, and further preferably 125 or more. On the other hand, it is preferably 160 or less. When the viscosity index is less than 90, not only the viscosity-temperature characteristics, thermal / oxidative stability, and volatilization prevention properties deteriorate, but also the friction coefficient tends to increase, and the wear prevention properties tend to decrease. . On the other hand, when the viscosity index exceeds 160, the low-temperature viscosity characteristics tend to deteriorate.
In addition, the viscosity index as used in the field of this invention means the viscosity index measured based on JISK2283-1993.

  In addition, as a base oil of this invention, a mineral oil type base oil or a synthetic oil type base oil is mentioned. These may be used alone or in combination of two or more.

Mineral oil base oils include, for example, a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and vacuum distillation, and solvent removal, solvent extraction, hydrocracking, hydroisomerization, solvent dewaxing, catalytic dewaxing. Examples thereof include paraffinic mineral oils, or normal paraffinic mineral oils, isoparaffinic mineral oils, etc., which are refined by combining one or more of purification processes such as wax, hydrorefining, sulfuric acid washing, and clay treatment alone.
In particular, hydrocracking lube oil fractions recovered from atmospheric distillation bottom oil and vacuum distillation equipment, and solvent dewaxing and catalytic desorption of the product or lube oil fractions recovered from the product by distillation or the like. Hydrocracked mineral oil obtained by performing a dewaxing treatment such as wax or by distillation after the dewaxing treatment is particularly preferred. Among these, those subjected to contact dewaxing treatment are more preferable.

  The pour point of the mineral base oil of the present invention is preferably −12.5 ° C. or lower, more preferably −15 ° C. or lower. Moreover, it is preferable that it is higher than -35 degreeC, -30 degreeC or more is more preferable, -25 degreeC or more is further more preferable, and -20 degreeC or more is especially preferable. This is because if the pour point is higher than -12.5 ° C, the characteristics at low temperatures deteriorate, and if it is -35 ° C or lower, a sufficient viscosity index cannot be obtained. In addition, the pour point as used in the field of this invention means the pour point measured based on JISK2269-1987.

  Furthermore, the NOACK value (NOACK evaporation) in the mineral oil base oil is preferably 15% by weight or less. The NOACK value means the amount of evaporation loss (% by weight) measured according to ASTM D 5800-95.

  The sulfur content of the mineral oil base oil is not particularly limited, but the sulfur content in the base oil is 100 mass ppm or less from the viewpoint of further improving thermal and oxidation stability and reducing sulfur content. It is preferably 50 ppm by mass or less, more preferably 10 ppm by mass or less, and particularly preferably 5 ppm by mass or less. In addition, the sulfur content here is a value measured by JIS 5S-38-2003.

The aromatic content of the mineral base oil is not particularly limited, but the content of the aromatic content in the base oil is 30% by mass from the viewpoint of further improving thermal and oxidation stability and reducing sulfur content. Is preferably 10% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% by mass or less.
If it exceeds 30% by mass, the oxidation stability is not sufficient for use under high temperature and high shear lubrication conditions, and the viscosity-temperature characteristics may be poor and the effects of the present invention may not be exhibited.

  On the other hand, synthetic base oils include poly α-olefins or hydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridec Decyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycol, Examples include dialkyl diphenyl ether and polyphenyl ether, and among them, poly α-olefin is preferable. As the poly α-olefin, typically, an oligomer or co-oligomer (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and those. Of the hydrides.

Mineral, either synthetic, kinematic viscosity is preferably at least 1 mm ² / s at 100 ° C. of the base oil, more preferably at least 2 mm ² / s, more preferably at least ^{3mm 2 / s, 3.5mm 2 /} s or more Is particularly preferred. On the other hand, it is preferably 10 mm ² / s or less, more preferably 5 mm ² / s or less, and particularly preferably 4.5 mm ² / s or less. If the 100 ° C. kinematic viscosity exceeds 10 mm ² / s, the low-temperature viscosity characteristics may deteriorate, and sufficient fuel economy may not be obtained. If it is less than 1 mm ² / s, an oil film is formed at the lubrication point. Is insufficient because the lubricity is poor and the evaporation loss of the engine oil composition may increase.
Here, the kinematic viscosity at 100 ° C. refers to the kinematic viscosity at 100 ° C. defined in ASTM D-445.

Furthermore, mineral, either synthetic, kinematic viscosity is preferably at least 8 mm ² / s at 40 ° C. of the base oil, more preferably at least 10 mm ² / s, still more preferably at least 12 mm ² / s. On the other hand, it is preferably 45 mm ² / s or less, more preferably 40 mm ² / s or less, and still more preferably 36 mm ² / s or less. Kinematic viscosity poor lubricity because its insufficient oil film formation at lubricating sites and less than 8 mm ² / s at 40 ° C., also not preferred because it may evaporation loss of the engine oil composition is increased, 45 mm ² If it exceeds / s, the low-temperature viscosity characteristics deteriorate and sufficient fuel economy cannot be obtained.
Here, the kinematic viscosity at 40 ° C. refers to the kinematic viscosity at 40 ° C. defined in ASTM D-445.

  The engine oil composition of the present invention comprises (A-1) a star polymer as component (A) as a viscosity index improver and (A-2) a nitrogen-containing group having a weight average molecular weight of 200,000 or more and 400,000 or less. Containing a polymer having

The engine oil composition of the present invention preferably contains (A-1) a star polymer at least 4% by mass or more based on the total amount of the engine oil composition. In the present invention, the star polymer is also referred to as a star-shaped (or star-shaped) polymer or a star-shaped (or star-shaped) polymer. A polymer (polymer) having a shape in which the arm portion extends outward to form is meant.
Examples of the production of the star polymer used in the present invention include, for example, U.S. Pat. Nos. 4,116,917, 4,141,847, 4,346,193, 4,409,120, or Japanese Patent Application Laid-Open No. 2013-129835. The method shown in the above can be applied.

The star polymer of the present invention is preferably a polymer having a core part of a polyalkenyl compound and four or more arm parts bonded to the core part. More preferably, it has 5 or more arm parts, and more preferably 6 or more. Moreover, it is preferable that an arm part is 20 or less, and it is more preferable that it is 15 or less.
If the number of arms is less than 4, the shear stability is not sufficient, the viscosity decreases with the passage of time of use, and the inherently required viscosity may not be ensured. On the other hand, when the number of arms exceeds 20, there is a risk that the viscosity reduction at high shear is not sufficient, and the fuel saving performance that is the object of the present invention cannot be secured.

This will be described in more detail below. The star polymer includes a monomer having two or more double bonds (core portion forming monomer) such as divinylbenzene and polyvinyl aliphatic compound, and an aliphatic diene having two double bonds (arm portion forming monomer). It is preferable to have a polymer structure composed of a core part and an arm part, which is obtained by a copolymerization reaction of the monomer composition it has. The polydiene of the arm part (diene polymer) has a polymer chain extending from the double bond part in the polyalkenyl compound that is a polymer of the core part forming monomer, and the double chain in the polymer chain The bond is hydrogenated after the copolymerization reaction.
As the structure of the arm portion, a structure in which an aromatic monomer such as styrene or alkene or an aliphatic monomer is bonded to the terminal of the polydiene of the hydrogenated arm portion by block polymerization is preferable. More preferably, a structure in which a polystyrene part is present at the end of the arm part is preferable. More preferred is a structure in which a polystyrene part is present at the end of every arm part in the star polymer.
Further, it is preferable that almost all of the double bond portion of the polydiene in the arm portion is hydrogenated.
Hereinafter, the polymer part of the arm part may be referred to as hydrogenated polydiene including the terminal polystyrene part.

The polyalkenyl compound that forms the core (core part) of the star polymer is preferably divinylbenzene or a polyvinyl aliphatic compound, particularly preferably divinylbenzene. The diene that makes up the hydrogenated polydiene in the arm is preferably butadiene, isoprene or the like. Moreover, since it is preferable to have a polystyrene structure in the terminal part of an arm part as mentioned above, it is desirable to use styrene as a raw material as a polymerization monomer of an arm part.
The styrene content is preferably 2 mol% or more, more preferably 3 mol% or more, based on the total amount of the star polymer. Moreover, 10 mol% or less is preferable, Furthermore, 7 mol% or less is more preferable. If the styrene content is 2 mol% or less, a sufficient decrease in high-temperature shear viscosity cannot be obtained, and if it is more than 10 mol%, sufficient solubility in the base oil cannot be obtained.

  The weight average molecular weight of the arm part in a star polymer is 5,000-600,000, More preferably, it is 10,000-500,000, More preferably, it is 10,000-300,000. This is because the shear stability is good and the wear resistance is excellent.

Specifically, the molecular weight of the star polymer is preferably a weight average molecular weight of 10,000 to 1,000,000, more preferably 100,000 to 800,000, and still more preferably 300,000 to 600,000. 000. This is because the shear stability is good.
The weight average molecular weight can be measured under the following conditions for both (A-1) and (A-2).
Measuring equipment Waters Alliance 2695
Column Tosoh GMH6 × 2 (book)
Solvent tetrahydrofuran detector RI
Standard material Polystyrene Measurement conditions Flow rate 1 mL / min, sample concentration 2.0% by mass, implantation amount 100 μL

The method for producing the (A-1) star polymer of the present invention is not particularly limited. For example, after the formation of divinylbenzene or the like for forming the core part by radical polymerization, the double polymer existing in the formed core part is formed. The diene can be similarly radically polymerized starting from the bond, and then the terminal polystyrene part can be formed and hydrogenated. In addition, either the polystyrene part formation of the arm part terminal or hydrogenation may be performed first.
Alternatively, after forming an arm part polymer having a reaction starting point at the end, it is reacted with a core part forming monomer to simultaneously form the core part and bond the arm part, or after forming the core part and the arm part polymer, respectively. A method of reacting the reaction starting points can be employed.
More specifically, it can be produced by the method described in the above US patent or Japanese patent.

  The star polymer preferably has a PSSI (Permanent Shear Stability Index) of 45 or less, more preferably 40 or less. When PSSI exceeds 45, the shear stability is deteriorated, so that it is necessary to increase the initial kinematic viscosity, which may deteriorate the fuel economy. In addition, when PSSI is less than 1, the viscosity index improvement effect when dissolved in a lubricating base oil is small, and it is not only inferior in fuel efficiency and low-temperature viscosity characteristics, but also may increase costs. Is preferably 1 or more.

Here, “PSSI” in the present invention refers to ASTM D 6022-01 (Stand
ard Practice for Calculation of Permanen
t Shear Stability Index) and ASTM D 6278
-02 (Test Method for Shear Stability of P
Polymer Containing Fluids Using a Europe
n Permanent Shear Index of polymers calculated based on data measured by n Diesel Injector Apparatus
Means Stability Index).

The content ratio of the star polymer in the engine oil composition of the present invention is preferably at least 4% by mass, more preferably 5% by mass or more, based on the total amount of the engine oil composition. On the other hand, it is preferable that it is 20 mass% or less, More preferably, it is 15 mass% or less, More preferably, it is 10 mass% or less. When the content is less than 4% by mass, at 100 ° C. and 10 ⁷ / s, while maintaining a high temperature and high shear viscosity (HTHS viscosity) at 100 ° C. and 10 ⁶ / s, which is a source of fuel saving effect, If the content exceeds 20% by mass, the shear stability may be deteriorated.

The polymer having a nitrogen-containing group (A-2), which is another viscosity index improver in the present invention, is a polymer obtained by copolymerizing a monomer containing nitrogen and another monomer described below, and (A-2 ) Contains 0.01% by weight or more of nitrogen.
The polymer having a nitrogen-containing group preferably has a weight average molecular weight of 200,000 or more and 400,000 or less, and a PSSI of 60 or less. When the weight average molecular weight is within this range, the fuel saving performance can be enhanced, and when the PSSI satisfies 60 or less, the fuel saving performance can be further enhanced.

(A-2) Specific examples of the polymer having a nitrogen-containing group include the following. Here, all of the following copolymers have the nitrogen-containing monomer-derived part in the polymer by copolymerizing a nitrogen-containing monomer represented by the formula (2) or (3) described later as a copolymerization monomer. . In addition, the example of (A-2) is shown below, without specifically showing the name of the said nitrogen-containing monomer origin part for convenience.
Poly (meth) acrylates, hydrides of styrene-diene copolymers, ethylene-α-olefin copolymers or hydrides thereof, polyisobutylene or hydrides thereof, styrene-maleic anhydride ester copolymers, polyalkylstyrenes, and (meth) Examples include acrylate-olefin copolymers.

The viscosity index improver in the engine-derived composition of the present invention is essentially composed of the two types of polymers (A-1) star polymer and (A-2) nitrogen-containing group polymer (A) described above. Although included, other viscosity index improvers may be included as long as the effects of the present invention are not impaired. In view of maximizing the effects of the present invention, the viscosity index improver is preferably only the component (A).
Examples of the other viscosity index improvers include, for example, ester group-containing viscosity index improvers and polymers corresponding to the above-exemplified polymer (A-2) that do not copolymerize nitrogen-containing monomers. . Poly (meth) acrylate is preferable.

(A-2) As an example of a polymer having a nitrogen-containing group, poly (meth) acrylate will be further described. Here, poly (meth) acrylate means a general term such as polyacrylate, polymethacrylate, a copolymer of acrylate and methacrylate, and a mixture thereof, and any of these may be used.
When (A-2) is this poly (meth) acrylate, the following configurations can be exemplified. That is, a (meth) acrylate monomer represented by the following formula (1) (hereinafter referred to as “monomer M-1”) and one or more monomers selected from formulas (2) and (3) (hereinafter, respectively). It is a poly (meth) acrylate having a nitrogen-containing group in the molecule, copolymerized with “monomer M-2” and “monomer M-3”.

［式（１）中、Ｒ¹は水素又はメチル基を示し、Ｒ²は炭素数１〜１８の直鎖状又は分岐状の炭化水素基を示す。］

[In Formula (1), R < ¹ > shows hydrogen or a methyl group, R < ² > shows a C1-C18 linear or branched hydrocarbon group. ]

［式（２）中、Ｒ³は水素原子又はメチル基を示し、Ｒ⁴は炭素数１〜１８のアルキレン基を示し、Ｅ¹は窒素を１〜２個、酸素を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 Formula (2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkylene group having 1 to 18 carbon atoms, and E ¹ contains ¹ to 2 nitrogen atoms and 0 to 2 oxygen atoms. An amine residue or a heterocyclic residue is represented, and a represents 0 or 1. ]

［式（３）中、Ｒ⁵は水素又はメチル基を示し、Ｅ²は窒素を１〜２個、酸素を０〜２個含有するアミン残基又は複素環残基を示す。］

[In Formula (3), R ⁵ represents hydrogen 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 ¹ and 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, and a benzoylamino group. 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.

  Specific examples of monomer M-2 and monomer M-3 include dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-methyl-5-vinylpyridine, and morpholino. Examples thereof include methyl methacrylate, morpholinoethyl methacrylate, N-vinyl pyrrolidone and a mixture thereof.

  There is no particular limitation on the copolymerization molar ratio of the monomer M-1 and the copolymer of “monomer M-2 or M-3, or both (hereinafter referred to as M-2 to M-3”). M-1: M-2 to M-3 = 99: 1 to 80:20 is preferable, 98: 2 to 85:15 is more preferable, and 95: 5 to 90:10 is more preferable.

  (A-2) As another example of a polymer having a nitrogen-containing group, a hydride of a styrene-diene copolymer can be mentioned, and the copolymer is also used as a comonomer in addition to styrene and diene. 3 was copolymerized. Specifically, as the diene, butadiene, isoprene and the like are preferable, and isoprene is particularly preferable. Hydrogenation is carried out after copolymerization.

  Another example of (A-2) is an ethylene-α-olefin copolymer, and the copolymer is also used as a comonomer by using the above M-2 to M-3 in addition to ethylene and α-olefin. Copolymerized. Specific examples of the α-olefin include propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene and 1-dodecene.

  It is preferable that the nitrogen content in the polymer having these (A-2) nitrogen-containing groups is 0.01 to 1.0% by mass on the basis of the total amount of (A-2) for all polymers. 0.05 mass% or more is more preferable, and 0.1 mass% or more is particularly preferable. Moreover, 0.5 mass% or less is especially preferable. If it is less than 0.01% by weight, the wear resistance that is the object of the present invention cannot be achieved, and if it exceeds 1.0% by weight, there is a concern about oxidation stability.

The weight average molecular weight (M _W ) of (A-2) is 200,000 or more, preferably 250,000 or more for any of the above types of polymers. Moreover, it is 400,000 or less, Preferably it is 380,000 or less, More preferably, it is 360,000 or less. When the weight average molecular weight is less than 200,000, there is a possibility that sufficient wear prevention performance cannot be obtained. In addition, when the weight average molecular weight exceeds 400,000, the effect of increasing the viscosity becomes too large, which may be inferior in fuel saving and low temperature viscosity characteristics, and further, shear stability and solubility in lubricating base oil. , Storage stability may be deteriorated.

The PSSI of (A-2) is preferably 60 or less, more preferably 55 or less, and still more preferably 50 or less. If PSSI is 60 or less, the shear stability is better and the fuel economy is further improved.
Further, PSSI is preferably 1 or more. This is because the effect of improving the viscosity index when dissolved in the lubricating base oil is sufficiently exhibited, and the fuel economy and low temperature viscosity characteristics are improved.

The ratio (M _w / M _n : polydispersity) of the weight average molecular weight (M _w ) and the number average molecular weight (M _n ) of the component (A) is 5 for both (A-1) and (A-2). It is preferably 0.0 or less, more preferably 4.0 or less, still more preferably 3.5 or less, and particularly preferably 3.0 or less. Further, M _w / M _n is preferably 1.0 or more, more preferably 2.0 or more, further preferably 2.5 or more, and particularly preferably 2.6 or more. When M _w / M _n exceeds 5.0 or less than 1.0, there is a concern that the effect of improving the solubility and viscosity temperature characteristics may be reduced, and sufficient storage stability and fuel efficiency cannot be maintained. There is a fear.

The content of the (A) component [(A-1) + (A-2)], which is a viscosity index improver, is preferably 0.1 to 50% by mass, preferably based on the total amount of the engine oil composition. Is 0.5 to 20% by mass, more preferably 1.0 to 15% by mass, and still more preferably 1.5 to 12% by mass. When the content is less than 0.1% by mass, the low temperature characteristics may be insufficient, and when the content exceeds 50% by mass, the shear stability of the composition may be deteriorated.
When the viscosity index improver other than the component (A) is included, the content of the other viscosity index improver is preferably 10% by mass or less based on the total amount of the engine oil composition. Preferably it is 5 mass% or less, More preferably, it is 3 mass% or less.

Ratio of high temperature high shear viscosity (b) at a shear rate of 1 × 10 ⁷ / s and 100 ° C. to high temperature high shear viscosity (a) at a shear rate of 1 × 10 ⁶ / s and an engine oil composition It is preferable that (b / a) be 0.85 or less. If it exceeds 0.85, fuel economy may be reduced.

  The engine oil composition of the present invention contains the component (B) as a friction modifier. Specifically, an amide compound is preferable, and a fatty acid amide is more preferable. An imide compound or a mixture of both compounds may be contained, and the imide compound is preferably a fatty acid imide. Moreover, the thing derived from a linear fatty acid is more preferable.

  Specific examples of the fatty acid amide include fatty acid amides having at least one alkyl group or alkenyl group having 10 to 30 carbon atoms and containing one nitrogen atom. The fatty acid amide is, for example, a fatty acid having an alkyl group or alkenyl group having 10 to 30 carbon atoms or an acid chloride thereof, only ammonia, a hydrocarbon group having 1 to 30 carbon atoms or a hydroxyl group-containing hydrocarbon group in the molecule. It can be obtained by reacting the amine compound contained therein. Particularly preferred is a fatty acid amide having an amide group at the molecular end obtained by reacting ammonia with a fatty acid having an alkyl group or alkenyl group having 12 to 24 carbon atoms.

  Specific examples of fatty acid amides include lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, coconut oil fatty acid amide, synthetic mixed fatty acid amides having 12 to 13 carbon atoms, and mixtures thereof. Can be mentioned. These fatty acid amides are particularly preferable because they are excellent in wear prevention effect in addition to friction reduction effect.

  Examples of other amide compounds include hydrazide (oleic acid hydrazide and the like), semicarbazide (oleyl semicarbazide and the like), urea (oleyl urea and the like), ureido (oleylureido and the like), allophanic acid amide (exemplified in International Publication No. 2005037967. Oleyl allophanoic acid amide etc.) and derivatives thereof.

In addition, carbon atoms such as dodecyl urea, tridecyl urea, tetradecyl urea, pentadecyl urea, hexadecyl urea, heptadecyl urea, octadecyl urea, oleyl urea (C ₁₈ H ₃₅ —NH—C (═O) —NH ₂ ), etc. And urea compounds having 24 alkyl groups or alkenyl groups, and acid-modified derivatives thereof (boric acid-modified derivatives and the like).
In addition, dodecanoic acid hydrazide, tridecanoic acid hydrazide, tetradecanoic acid hydrazide, pentadecanoic acid hydrazide, hexadecanoic acid hydrazide, heptadecanoic acid hydrazide, octadecanoic acid hydrazide, oleic acid hydrazide (C ₁₇ H ₃₃ —C (═O) —NH—NH ₂ ) Hydrazide compounds having an alkyl or alkenyl group having 12 to 24 carbon atoms, such as erucic acid hydrazide (C ₂₁ H ₄₁ —C (═O) —NH—NH ₂ ), and acid-modified derivatives thereof (boric acid-modified derivatives) Etc.).

Furthermore, as another form of the amide compound, an amide compound having a hydroxyl group, a carboxylic acid group, or both functional groups in the same molecule can be given. Examples thereof include a hydroxyl group-containing fatty acid amide obtained by reacting a fatty acid having an alkyl group or alkenyl group having 10 to 30 carbon atoms or an acid chloride thereof with an amine compound having 1 to 30 carbon atoms having a hydroxyl group.
Among these, a compound represented by the following formula (4) is preferable.

In the formula (4), R ⁶ is a hydrocarbon group having 1 to 30 carbon atoms, preferably a hydrocarbon group having 10 to 30 carbon atoms, more preferably an alkyl group or alkenyl group having 12 to 24 carbon atoms, particularly preferably. Is an alkenyl group having 12 to 20 carbon atoms. R ⁷ is a hydrocarbon group having 1 to 30 carbon atoms or hydrogen. In the case of a hydrocarbon group, R ⁷ is preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms. Among them, hydrogen is particularly preferable. R ⁸ is a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms, still more preferably a hydrocarbon group having 1 to 2 carbon atoms, most preferably 1 carbon atom.

The compound represented by the formula (4) can be synthesized by, for example, a reaction between a hydroxy acid and an aliphatic amine. Of the hydroxy acids, aliphatic hydroxy acids are preferred, and linear aliphatic α-hydroxy acids are more preferred. In particular, glycolic acid is preferable among α-hydroxy acids.
Other preferred specific examples include N-oleoyl sarcosine and the like.

  As the imide compound as the component (B), mono- and / or bissuccinimide having one or two linear or branched, preferably branched hydrocarbon groups, boric acid or Examples thereof include succinimide-modified compounds obtained by reacting one or more selected from phosphoric acid, carboxylic acids having 1 to 20 carbon atoms, and sulfur-containing compounds.

Specific examples of the succinimide include compounds represented by the following formulas (5) and (6).

In the formulas (5) and (6), R ⁹ and R ¹⁰ each independently represent an alkyl group or alkenyl group having 8 to 30 carbon atoms, preferably 12 to 24 carbon atoms, and R ¹¹ and R ¹² are Each independently represents an alkylene group having 1 to 4 carbon atoms, preferably 2 to 3 carbon atoms, and R ¹³ represents a hydrogen atom or an alkyl group or alkenyl group having 1 to 30 carbon atoms, preferably 8 to 30 carbon atoms. , N represents an integer of 1 to 7, preferably an integer of 1 to 3.

  Content of (B) component which is a friction modifier is 0.01-10 mass% on the basis of engine oil composition whole quantity, Preferably it is 0.1 mass% or more, More preferably, it is 0.3 mass% or more Moreover, it is preferably 3% by mass or less, more preferably 2% by mass or less, and further preferably 1% by mass or less. When the content of the component (B) is less than 0.01% by mass, the effect of reducing friction due to the addition tends to be insufficient, and when it exceeds 10% by mass, effects such as an anti-wear additive are obtained. It tends to be inhibited or the solubility of the additive tends to deteriorate.

  Nitrogen in the component (B) is preferably 0.0005 to 0.4% by mass, more preferably 0.001 to 0.3% by mass, and particularly preferably as the content relative to the total amount of the engine oil composition. Is 0.005-0.25 mass%. If it is less than 0.0005% by mass, sufficient anti-wear properties may not be obtained, and if it exceeds 0.4% by mass, the solubility in the engine oil composition will be reduced, resulting in precipitation and turbidity. There is a fear.

The engine oil composition of the present invention can contain a metallic detergent.
As metal-based detergents, alkali salts / basic salts such as alkali metal / alkaline earth metal sulfonate, alkali metal / alkaline earth metal phenate, alkali metal / alkaline earth metal salicylate, and alkali metal / alkaline earth metal salicylate Mention may be made of salts. Examples of the alkali metal include sodium and potassium, and examples of the alkaline earth metal include magnesium, calcium and barium. Magnesium or calcium is preferable, and calcium is more preferable.
These metal detergents may be arbitrarily combined and blended in the engine oil composition.

More specifically, the alkali metal / alkaline earth metal sulfonate is an alkali metal / alkyl aromatic sulfonic acid obtained by sulfonating an alkyl aromatic compound having a molecular weight of 100 to 1500, preferably 200 to 700. Mention may be made of alkaline earth metal salts. Specific examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid.
In the present invention, it is preferable to use an overbased sulfonate and / or a low basic sulfonate.

In the case of an overbased sulfonate, the base number is 150 mgKOH / g or more, preferably 200 mgKOH / g or more, more preferably 250 mgKOH / g or more, most preferably 300 mgKOH / g or more, and 350 mgKOH / g or less. preferable.
With respect to the overbased sulfonate, the base number of the engine oil composition is 2 mgKOH / g or more, preferably 3 mgKOH / g or more, preferably 10 mgKOH / g or less, more preferably based on the total amount of the engine oil composition. Is preferably 7 mgKOH / g or less, more preferably 5 mgKOH / g or less. If the base number is less than 2 mgKOH / g, the oxidation stability required for the engine oil composition of the present invention may be insufficient, and if it exceeds 10 mgKOH / g, the amount of ash is excessive and the combustion chamber deposits. May increase.

In the case of a low basic sulfonate, the base number is 50 mgKOH / g or less, preferably 30 mgKOH / g or less, more preferably 20 mgKOH / g or less, and 5 mgKOH / g or more, preferably 10 mgKOH / g or more. .
The base number of the engine oil composition is 0.01 mgKOH / g or more, preferably 0.02 mgKOH / g or more, preferably 2 mgKOH / g, based on the total amount of the engine oil composition. In the following, it is preferably contained so as to be 1 mgKOH / g or less, more preferably 0.5 mgKOH / g or less. If the base number is less than 0.01 mgKOH / g, the cleanability of the crankcase required for the engine oil composition may be insufficient, and if it exceeds 2 mgKOH / g, the effect does not increase and 2 mgKOH / g There is no advantage of containing in excess of g.
The base number referred to here is 7. JIS K2501 “Petroleum products and lubricating oils-Neutralization number test method”. Means the base number measured by the perchloric acid method according to the above.

More specifically, the alkali metal / alkaline earth metal 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, the alkylphenol and sulfur. Or an alkali metal / alkaline earth metal salt of a Mannich reaction product of an alkylphenol obtained by reacting the alkylphenol with formaldehyde.
The alkali metal / alkaline earth metal phenate has a base number of 150 mgKOH / g or more, preferably 200 mgKOH / g or more, more preferably 250 mgKOH / g or more, and preferably 350 mgKOH / g or less.
The base number of the engine oil composition is 0.3 mgKOH / g or more, preferably 0.7 mgKOH / g or more, more preferably 1 mgKOH, based on the total amount of the engine oil composition. / G or more, preferably 5 mgKOH / g or less, more preferably 3 mgKOH / g or less, still more preferably 2 mgKOH / g or less. If the base number is less than 0.3 mg KOH / g, the oxidation stability required for the engine oil composition of the present invention may be insufficient, and if it exceeds 5 mg KOH / g, the effect does not increase and 5 mg KOH / g. There is no advantage of containing in excess of g.

More specifically, the alkali metal / alkaline earth metal salicylate is an alkali metal / alkyl salicylic acid having at least one linear or branched alkyl group having 4 to 30 carbon atoms, preferably 6 to 18 carbon atoms. Mention may be made of alkaline earth metal salts.
The alkali metal / alkaline earth metal salicylate has a base number of 150 mgKOH / g or more, preferably 200 mgKOH / g or more, more preferably 250 mgKOH / g or more, particularly preferably 300 mgKOH / g or more, and 350 mgKOH / g. The following is preferred.
The alkali metal / alkaline earth metal salicylate has a base number of 2 mgKOH / g or more, preferably 3 mgKOH / g or more, preferably 10 mgKOH / g or less, based on the total amount of the engine oil composition. More preferably, it is contained so as to be 7 mgKOH / g or less, and more preferably 5 mgKOH / g or less. If the base number is less than 2 mgKOH / g, the oxidation stability required for the engine oil composition of the present invention may be insufficient, and if it exceeds 10 mgKOH / g, the amount of ash is too much, and the combustion chamber deposit is too high. May increase.

The alkali metal / alkaline earth metal sulfonate, alkali metal / alkaline earth metal phenate and alkali metal / alkaline earth metal salicylate are not only neutral salts (normal salts) but also basic salts and overbased salts (super A basic salt) or a mixture thereof.
It is preferable to use a combination of an overbased sulfonate, a low basic sulfonate, an overbased phenate, and an overbased salicylate having a base number in the above range. Most preferably, a combination of the three types of metal detergents, based on the total amount of the engine oil composition, the base number of the engine oil composition is 2 mgKOH / g or more, preferably 3 mgKOH / g or more, The content is preferably 10 mg KOH / g or less, more preferably 7 mg KOH / g or less, and still more preferably 5 mg KOH / g or less. This makes it possible to achieve a balance between cleanliness required for engine oil and fuel efficiency.

  When the metal detergent is contained in the engine oil composition of the present invention, the content thereof is preferably 500 mass ppm or more, more preferably 800 mass in terms of metal element, based on the total amount of the engine oil composition. ppm or more, more preferably 1000 mass ppm or more. Further, it is preferably 3500 mass ppm or less, more preferably 3000 mass ppm or less, and further preferably 2600 mass ppm or less. If it is less than 500 ppm by mass, sufficient base number maintenance and high-temperature cleanability may not be exhibited. On the other hand, if it exceeds 3500 ppm by mass, the amount of sulfated ash generated by use increases. There is concern about accelerating filter clogging.

Further, the engine oil composition of the present invention can contain an ashless dispersant.
Examples of the ashless dispersant include nitrogen-containing compounds having at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or derivatives thereof. Specific examples include succinimide, alkenyl succinimide, and modified products thereof. One type or two or more types arbitrarily selected from these can be blended.

  The carbon number of the alkyl group or alkenyl group of the ashless dispersant is preferably 40 to 400, more preferably 60 to 350. When the carbon number of the alkyl group or alkenyl group is less than 40, the solubility of the compound in the lubricating base oil tends to decrease, whereas when the carbon number of the alkyl group or alkenyl group exceeds 400, the engine oil composition The low-temperature fluidity of the product tends to deteriorate. The alkyl group or alkenyl group may be linear or branched, and specifically, preferred are derived from olefin oligomers such as propylene, 1-butene and isobutylene and ethylene / propylene co-oligomers. And branched alkyl groups and branched alkenyl groups.

  Preferred examples of the succinimide include a so-called mono-type succinimide in which succinic anhydride is added to one end of the polyamine, and a so-called bis-type succinimide in which succinic anhydride is added to both ends of the polyamine. In addition, either one of monotype and bis type succinimide may be contained, or both may be contained.

Benzylamine can also be used as another ashless dispersant. Preferable examples of benzylamine include compounds represented by the following formula (7).
_{^{R 14 -Ph-CH 2 NH- (}} CH 2 CH 2 NH) p -H (7)
In the formula (7), R ¹⁴ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably an alkyl group or alkenyl group having 60 to 350 carbon atoms, Ph represents a phenylene group, and p represents 1 to 5 , Preferably an integer of 2-4.

Furthermore, a polyamine can also be used as another ashless dispersant. Specific examples of polyamines include compounds represented by the following formula (8).
^{_{R 15 -NH- (CH 2 CH 2}} NH) q -H (8)
In the formula (8), R ¹⁵ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably an alkyl group or alkenyl group having 60 to 350, and q is an integer of 1 to 5, preferably 2 to 4. Show.

  Specific examples of derivatives of the above nitrogen-containing compounds that can be used as ashless dispersants include monocarboxylic acids having 1 to 30 carbon atoms (fatty acids, etc.), oxalic acid, phthalic acid, trimellitic acid, pyromellitic compounds. An amide obtained by reacting an oxygen-containing compound such as a polycarboxylic acid having 2 to 30 carbon atoms such as an acid or a hydroxy (poly) alkylene carbonate to neutralize part or all of the remaining amino group and / or imino group And a modified compound with a modified organic acid or the like, or a sulfur-modified compound obtained by allowing a sulfur compound to act on the aforementioned nitrogen-containing compound. Furthermore, the thing modified | denatured with the boron compound is also mentioned.

The boronated ashless dispersant is a borated version of any ashless dispersant used in lubricating oils. Boronation is generally performed by allowing boric acid or the like to act on the nitrogen-containing compound described above to neutralize part or all of the remaining amino group and / or imino group.
For example, methods for producing a boronated succinimide are disclosed in JP-B-42-8013 and JP-A-42-8014, JP-A-51-52381, JP-A-51-130408, and the like. And the like. Specifically, for example, organic compounds such as alcohols, hexane, xylene, etc., light lubricating oil base oil, polyamine and polyalkenyl succinic acid (anhydride), boric acid, boric acid ester, or boron compounds such as borate Can be obtained by mixing and heat-treating under appropriate conditions. In addition, the boron content in the boronated succinimide thus obtained can be usually 0.1 to 4.0% by mass.

  When the engine oil composition of the present invention contains an ashless dispersant, the content of the ashless dispersant is preferably 0.1 to 20% by mass, more preferably 1 to 10%, based on the total amount of the engine oil composition. % By mass. Furthermore, it is more preferably 2.5% by mass or more, and most preferably 5% by mass or more. When the content of the ashless dispersant is less than 0.1% by mass, the effect of improving friction reduction may be insufficient. On the other hand, when the content exceeds 20% by mass, the low-temperature fluidity of the engine oil composition is low. There is a risk of significant deterioration.

When a boronated ashless dispersant such as the boronated succinimide is used, the boron content in the engine oil composition is 0.01% by mass or more, preferably 0.02% based on the total amount of the engine oil composition. It is at least mass%, more preferably at least 0.025 mass%, and it is at most 0.15 mass%, preferably at most 0.1 mass%, particularly preferably at most 0.05 mass%.
In the present invention, it is preferable to contain both a boronated succinimide and a non-borated succinimide as an ashless dispersant. The ratio of the boronated succinimide to the non-borated succinimide is preferably 0.1 or more, more preferably 0.2 or more, and further preferably 0.3 or more. Moreover, 0.6 or less is preferable, 0.5 or less is more preferable, and 0.4 or less is still more preferable. If it is less than 0.1, the heat resistance and wear resistance of the boronated succinimide are not sufficient, and if it exceeds 0.6, the cleanliness is insufficient.

Furthermore, the engine oil composition of the present invention can contain an antioxidant.
Antioxidants can be used as long as they are commonly used in lubricating oils, such as ashless antioxidants such as phenolic antioxidants and amine antioxidants, and organometallic antioxidants. It is. By adding an antioxidant, the antioxidant property of the engine oil composition can be further enhanced, and not only the corrosion or corrosion wear prevention performance of the lead-containing metal of the composition of the present invention is enhanced, but also the base number maintenance property is further enhanced. be able to.

  Examples of phenolic antioxidants include 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert-butylphenol), 4,4 ′. -Bis (2-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4,4′-isopropylidenebis (2,6-di-tert-butylphenol), 2,2′-methylenebis (4-methyl-6) -Nonylphenol), 2,2'-isobutylidenebis (4,6-dimethylphenol), 2,2'-methylenebis (4-methyl-6-cyclohexene) Xylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6- Di-tert-α-dimethylamino-p-cresol, 2,6-di-tert-butyl-4 (N, N′-dimethylaminomethylphenol), 4,4′-thiobis (2-methyl-6-tert) -Butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,2'-thiobis (4-methyl-6-tert-butylphenol), bis (3-methyl-4-hydroxy-) 5-tert-butylbenzyl) sulfide, bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, 2,2′-thio-di Ethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tridecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythrityl- Tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octadecyl-3- ( Preferred examples include 3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3-methyl-5-tert-butyl-4-hydroxyphenyl substituted fatty acid esters, and the like. You may use these in mixture of 2 or more types.

  Examples of the amine antioxidant include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine which are aromatic amine antioxidants. You may use these in mixture of 2 or more types.

  Although the said phenolic antioxidant and amine antioxidant can be used independently, it is preferable to mix | blend in combination. As a blending ratio, the amine antioxidant is preferably 10% by mass or more, more preferably 20% by mass or more, and more preferably 40% by mass or more with respect to the total amount of the phenolic antioxidant and the amine antioxidant. Is more preferable. Moreover, 80 mass% or less is preferable, and 60 mass% or less is more preferable.

  In the engine oil composition of the present invention, for the purpose of further improving the performance, if necessary, in addition to the additive, other friction modifiers other than the component (B), and further an antiwear agent (or Extreme pressure agents, corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, pour point depressants, rubber swelling agents, antifoaming agents, colorants, and other various additives alone or in combination You may do it.

Examples of other friction modifiers include friction modifiers selected from organic molybdenum compounds and ashless friction modifiers.
Organic molybdenum compounds include sulfur-containing organic molybdenum compounds such as molybdenum dithiophosphate and molybdenum dithiocarbamate, complexes of molybdenum compounds with sulfur-containing organic compounds or other organic compounds, molybdenum sulfide, sulfurized molybdenum acid, etc. And a complex of a sulfur-containing molybdenum compound and an alkenyl succinimide.

  When the organic molybdenum compound is used, the content is not particularly limited, but is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, particularly preferably 0.01% by mass or more, in terms of molybdenum element, based on the total amount of the engine oil composition. Preferably it is 0.03 mass% or more, Preferably it is 0.2 mass% or less, More preferably, it is 0.1 mass% or less, More preferably, it is 0.08 mass% or less. When the content is less than 0.005% by mass, the heat / oxidation stability of the engine oil composition becomes insufficient, and in particular, it tends to be impossible to maintain excellent cleanliness over a long period of time. On the other hand, when content exceeds 0.2 mass%, the effect corresponding to content will not be acquired and it exists in the tendency for the storage stability of an engine oil composition to fall.

  As the ashless friction modifier, any compound usually used as a friction modifier for lubricating oils can be used. For example, an alkyl group or an alkenyl group having 6 to 30 carbon atoms, particularly 6 to 30 carbon atoms. And ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols and aliphatic ethers having at least one linear alkyl group or linear alkenyl group in the molecule. Moreover, 1 or more types of compounds chosen from the group which consists of a nitrogen-containing compound and its acid modification derivative, and the various ashless friction modifiers illustrated by the international publication 2005/037967 pamphlet are mentioned.

  When using an ashless friction modifier, the content thereof is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.3% by mass, based on the total amount of the engine oil composition. Further, it is preferably 3% by mass or less, more preferably 2% by mass or less, and further preferably 1% by mass or less. When the content of the ashless friction modifier is less than 0.01% by mass, the effect of reducing friction due to the addition tends to be insufficient, and when the content exceeds 3% by mass, the effect of an antiwear additive or the like. Tends to be inhibited, or the solubility of the additive tends to deteriorate.

As the antiwear agent (or extreme pressure agent), any antiwear agent / extreme pressure agent used for lubricating oil can be used. For example, sulfur-based, phosphorus-based, sulfur-phosphorus-based extreme pressure agents and the like can be used.
In the present invention, zinc alkyldithiophosphate is effective. Alkyl groups having 3 to 12 carbon atoms are usually used. In the present invention, it is preferable to use a zinc alkyldithiophosphate having a primary alkyl group and a secondary alkyl group, respectively, in order to balance extreme pressure and oxidation stability. The ratio of primary to secondary is preferably 0.3 or more, more preferably 0.5 or more, and most preferably 0.55 or more. Moreover, 0.8 or less is preferable and 0.7 or less is more preferable. If it is less than 0.3, the oxidation stability may be insufficient, and if it exceeds 0.8, the extreme pressure property may be insufficient. In addition, the combined use of primary and secondary alkyl groups may be within the same zinc alkyldithiophosphate, or may be a mixture of different zinc alkyldithiophosphates.

  When zinc alkyldithiophosphate is used, its content is preferably 0.02 mass% or more, more preferably 0.05 mass%, more preferably 0.08 mass% in terms of phosphorus element, based on the total amount of the engine oil composition. % Or more is more preferable. Moreover, 0.2 mass% or less is preferable, 0.15 mass% or less is more preferable, and 0.1 mass% or less is further more preferable. If it is less than 0.02% by mass, sufficient extreme pressure cannot be obtained, and if it exceeds 0.2% by mass, there is a concern that the exhaust gas aftertreatment device may be adversely affected.

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

  As the pour point depressant, for example, a polymethacrylate polymer compatible with the lubricating base oil to be used can be used. The weight average molecular weight is preferably 150,000 or less, more preferably 100,000 or less, and still more preferably 80,000 or less. Moreover, 20,000 or more are preferable and 40,000 or more are more preferable. If it exceeds 150,000, there is a concern that the product viscosity will deviate from the target, and if it is less than 20,000, the function as a pour point depressant may be insufficient. When the pour point depressant is contained in the lubricating oil composition of the present invention, the content thereof is usually selected from the range of 0.005 to 5% by mass based on the total amount of the composition.

Examples of antifoaming agents include silicone oils having a kinematic viscosity at 25 ° C. of 1,000 to 100,000 mm ² / s, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long chain fatty acids, methyl salicylates, o-Hydroxybenzyl alcohol and the like can be mentioned.

  When these additives are contained in the engine oil composition of the present invention, the content of the antifoaming agent is 0.0001 to 0.01% by mass based on the total amount of the engine oil composition. It is preferable that it is 01-10 mass%.

  The viscosity index of the engine oil composition of the present invention is preferably 140 or more, more preferably 150 or more, and further preferably 160 or more. When the viscosity index is less than 140, there is a possibility that sufficient fuel saving performance cannot be exhibited at low temperatures. In addition, there is no restriction | limiting in particular about the upper limit of a viscosity index, About 135-180 things, such as normal paraffin, slack wax, GTL wax, etc., or isoparaffin type mineral oil which hydrocracked / isomerized these, or complex ester type | system | group group About 150 to 250 such as oil or HVI-PAO base oil can be used.

Kinematic viscosity at 100 ° C. of the engine oil composition of the present invention is preferably 5.6 mm ² / s or more, more preferably 9.3 mm ² / s or more. Also it is preferably 12.5 mm ² / s or less, and more preferably less 11.5 mm ² / s. When the kinematic viscosity at 100 ° C. exceeds 12.5 mm ² / s, the fuel saving effect may be reduced. When the kinematic viscosity is less than 5.6 mm ² / s, the engine oil pressure does not reach the predetermined pressure, and the engine oil composition There is a risk of seizure due to insufficient supply of goods.

  The engine oil composition of the present invention can be applied to various engine engines and is not particularly limited, but is preferably used for diesel engine engines.

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

High temperature and high shear viscosity and abrasion resistance were measured and evaluated as shown below as indicators of fuel economy.
1. High temperature high shear viscosity (HTHS viscosity) of engine oil composition
High temperature and high shear viscosity at shear rates of 1 × 10 ⁶ / s and 1 × 10 ⁷ / s, which affect fuel economy, were measured as follows. The high temperature high shear viscosity at a shear rate of 1 × 10 ⁶ / s was measured according to ASTM D4683-10, and the high temperature high shear viscosity at a shear rate of 1 × 10 ⁷ / s was measured by USV manufactured by PCS Instruments. It measured using the viscometer. The measurement temperature is 100 ° C. for all.
In addition, good fuel economy can be exhibited by keeping the viscosity at a shear rate of 1 × 10 ⁶ / s constant and reducing the viscosity at 1 × 10 ⁷ / s. Specifically, it is preferable that the former is 6.0 mPa · s or more and the latter is 5.5 mPa · s or less.

2. Engine oil composition wear resistance The wear resistance of the engine oil composition was evaluated using a shell four ball tester. The test method conformed to ASTM D2266. However, the test conditions are a rotation speed of 1800 rpm, a load of 492 N, an oil temperature of 120 ° C., and a test time of 1 minute.

Example 1
Using the components shown below, an engine oil composition according to Example 1 having a formulation composition (parts by mass) shown in Table 1 was prepared. About the engine oil composition of Example 1, the above 1. 1. high temperature high shear viscosity, and Abrasion resistance was evaluated. The evaluation results are shown in Table 1.
(1) Lubricating base oil: Base oil A; hydrocracking, catalytic dewaxing base oil. Details are shown in the margin of Table 1.
(2-1) (A-1): VM-A; SV261 (manufactured by Infinium); Mw 430,000, PSSI 25
(2-2) (A-2): VM-B; polymethacrylate having a nitrogen-containing group, Mw 260,000, PSSI 50, nitrogen content 0.1% by mass
(3-1) (B): Oleylamide (4) Metal-based detergent and antioxidant: A composition having the components shown in Table 2 (hereinafter referred to as a package additive). In addition, content of each component shown in Table 2 is a mass part when the engine oil composition whole quantity of (1) is 100 mass parts.

(Examples 2 to 5)
The base oil and each additive were mix | blended with the compounding quantity shown in Table 1 and Table 2, and the engine oil composition of each Example was prepared. Each engine oil composition is the same as in Example 1 above. 1. high temperature high shear viscosity, and Abrasion resistance was evaluated. The evaluation results are shown in Table 1.
Here, components other than the above-described components are as follows.
(1) Lubricating base oil: Base oil B; hydrocracking, catalytic dewaxing base oil. Details are shown in the margin of Table 1.
(5) Pour point depressant (PPD): polymethacrylate, weight average molecular weight 55,800

(Comparative Examples 1-9)
The base oil and each additive were mix | blended with the compounding quantity shown in Table 1 and Table 2, and the engine oil composition of each comparative example was prepared. Each engine oil composition is the same as in Example 1 above. 1. high temperature high shear viscosity, and Abrasion resistance was evaluated. The evaluation results are shown in Table 1.
In Comparative Examples 1 to 8, priority is given to fuel saving, and high temperature and high shear viscosity is set, and the high temperature and high shear viscosity characteristics are almost the same as those of the examples. On the other hand, Comparative Example 9 is set with priority on wear resistance, and has a higher high-temperature and high-shear viscosity than the Examples and other Comparative Examples, and the viscosity at 1 × 10 ⁷ / s is particularly 5. It greatly exceeds 5 mPa · s.
Here, components other than the above-described components are as follows.
(2-3) Viscosity index improvers other than component (A):
VM-C: polymethacrylate having a nitrogen-containing group, Mw 100,000, PSSI 5, nitrogen content 0.2% by mass
VM-D; polymethacrylate, Mw 430,000, PSSI 5
VM-E; polymethacrylate, Mw 450,000, PSSI 5
VM-F; polymethacrylate, Mw 380,000, PSSI 25
(3-2) Friction modifier other than the component (B): oleylamine or glycerin monooleate (Adeka Cruve FM210 manufactured by Asahi Denka Kogyo Co., Ltd.) was used.

As is clear from Table 1, (A-1) a star polymer, (A-2) a polymer having a nitrogen-containing group, and (B) an amide compound, an imide compound, or a mixture of both compounds. The engine oil achieves a balance between fuel efficiency and wear resistance, which is significantly superior to the engine oils of Comparative Examples 1 to 9.
That is, the engine oil composition of each example has a low high-temperature high-shear viscosity characteristic equivalent to that of Comparative Examples 1 to 8 and exhibits performance excellent in fuel saving performance, while being significantly better than Comparative Examples 1 to 8. It also has excellent wear resistance. The wear resistance of each of the examples is equivalent to that of Comparative Example 9 having high high temperature and high shear viscosity characteristics in which fuel saving performance cannot be expected. Therefore, both fuel saving performance and wear resistance are highly compatible. You can see that

Claims (5)

A lubricating base oil having a saturated content of 70% by mass or more and a viscosity index of 90 or more and 160 or less,
(A) (A-1) a star polymer and (A-2) a polymer having a nitrogen-containing group having a weight average molecular weight of 200,000 or more and 400,000 or less,
(B) an amide compound, an imide compound, or a mixture of both compounds,
Engine oil composition. The star polymer is a polymer having a core part of a polyalkenyl compound and 4 to 15 arm parts bonded to the core part.
The engine oil composition according to claim 1. The lubricating base oil has a 100 ° C. kinematic viscosity of 3.5 to 5.0 mm ² / s,
The engine oil composition according to claim 1 or 2. The engine oil composition has a kinematic viscosity at 100 ° C. of 5.6 mm ² / s or more and less than 12.5 mm ² / s, a shear rate of 1 × 10 ⁶ / s, and a high temperature high shear viscosity at 150 ° C. of 2.6 mPa.・ S or more,
The engine oil composition according to any one of claims 1 to 3. It is for diesel engine,
The engine oil composition according to any one of claims 1 to 4.