JP2021116339A - Lubricant composition - Google Patents

Abstract

To provide a lubricant composition that maintains an appropriate high-temperature shear viscosity even when viscosity is lowered, has excellent fuel economy and low temperature viscosity characteristics, is preferably a lubricant composition for an internal combustion engine, and is more preferably a lubricant composition for a diesel engine.SOLUTION: The lubricant composition comprises: (A) a lubricating oil base oil, (B-1) polymethacrylate, and (B-2) an α-olefin copolymer, wherein (A) the lubricating oil base oil has a kinematic viscosity of 2.0 to 10.0 mm2/s at 100°C, (B-1) the polymethacrylate has a weight average molecular weight of 100,000 to 400,000, the content of the polymethacrylate is 0.5 to 5.0 mass% with respect to the total mass of the lubricant composition, (B-2) the α-olefin copolymer has an SSI (shear stability index) of 20 to 30, an amount of the olefin copolymer is 0.5 to 8.0 mass% with respect to the total mass of the lubricant composition, the lubricant composition has a kinematic viscosity of 6.9 or more to less than 9.3 mm2/s at 100°C, and has a CCS viscosity of 6.2 Pa s or less at -35°C, and the lubricant composition has a high temperature and high shear viscosity (HTHS viscosity) of 2.6 mPa s or more at 150°C.SELECTED DRAWING: None

Description

The present invention relates to a lubricating oil composition. More specifically, the present invention relates to a lubricating oil composition for an internal combustion engine, particularly a lubricating oil composition for a diesel engine.

Lubricating oil compositions are widely used in the automobile field such as for internal combustion engines, automatic transmissions, and gear oils. In recent years, low viscosity has been required to improve fuel efficiency, but excellent low temperature viscosity characteristics are also required while maintaining high temperature and high shear viscosity. In order to achieve the above object, a lubricating oil composition in which a base oil is selected and a specific additive is combined is known. For example, Patent Document 1 discloses a lubricating oil composition comprising a base oil having a specific urea adduct value and polymethacrylate having a specific structure. Further, Patent Document 2 describes a lubricating oil composition using a polymethacrylate-based viscosity index improver whose structure is further specified.

Japanese Unexamined Patent Publication No. 2009-155639 JP-A-2015-13693

However, the lubricating oil composition as described in the above patent document still has room for improvement in terms of achieving both fuel efficiency and high-temperature shear viscosity. Therefore, according to the present invention, a lubricating oil composition excellent in fuel efficiency and low-temperature viscosity characteristics while maintaining an appropriate high-temperature shear viscosity even when the viscosity is lowered, preferably a lubricating oil composition for an internal combustion engine. More preferably, it is an object of the present invention to provide a lubricating oil composition for a diesel engine.

As a result of diligent studies, the present inventors have achieved the above object by adding a polymethacrylate having a specific molecular weight and an α-olefin copolymer having a specific shear stability index to a specific lubricating oil base oil. Found to be done.

That is, the present invention
In a lubricating oil composition containing (A) lubricating oil base oil, (B-1) polymethacrylate and (B-2) α-olefin copolymer,
The (A) lubricating oil base oil has a kinematic viscosity of 2.0 to 10.0 mm ² / s at 100 ° C., and the (B-1) polymethacrylate has a weight average molecular weight of 100,000 to 400,000. The content of polymethacrylate is 0.5 to 5.0% by mass with respect to the total mass of the lubricating oil composition, and the (B-2) α-olefin copolymer has an SSI (shear stability index) of 20 to 20 to. It is characterized by having 30 and the amount of the olefin copolymer is 0.5 to 8.0% by mass with respect to the total mass of the lubricating oil composition.
The lubricating oil composition has a kinematic viscosity of 6.9 or more and ^{less than 9.3 mm 2} / s at 100 ° C., a CCS viscosity of 6.2 Pa · s or less at −35 ° C., and a high temperature of 150 ° C. The lubricating oil composition having a shear viscosity (HTHS viscosity) of 2.6 mPa · s or more.

A preferred embodiment of the present invention satisfies at least one of the following requirements (1) to (5).
(1) The (A) lubricating oil base oil contains mineral oil.
(2) The (A) lubricating oil base oil contains GTL.
(3) The HTHS viscosity of the lubricating oil composition at 150 ° C. is 2.9 mPa · s or less.
(4) The lubricating oil composition is for an internal combustion engine.
(5) The lubricating oil composition is for a diesel engine.

The lubricating oil composition of the present invention is a lubricating oil composition excellent in fuel efficiency and low temperature viscosity characteristics while maintaining high temperature shear viscosity. In particular, it is suitable as a lubricating oil composition for an internal combustion engine and further as a lubricating oil composition for a diesel engine.

(A) Lubricating oil base oil The lubricating oil base oil in the present invention is not particularly limited. It may be either mineral oil or synthetic oil, and these can be used alone or in combination.

As the mineral oil, for example, the lubricating oil distillate obtained by distilling the atmospheric residual oil obtained by atmospheric distillation of crude oil under reduced pressure is subjected to solvent desorption, solvent extraction, hydrocracking, solvent dewaxing, and hydrogen. Purified by one or more treatments such as chemical refining, or wax isomerized mineral oil, GTL (Gas to Liquid) base oil, ATL (Asphalt to Liquid) base oil, vegetable oil-based base oil, or a mixture thereof. Base oil can be mentioned.

Examples of the synthetic oil include polybutene or a hydride thereof; a poly-α-olefin such as 1-octene oligomer or 1-decene oligomer or a hydride thereof; 2-ethylhexyl laurate, 2-ethylhexyl palmitate, 2-stearate. Monoesters such as ethylhexyl; diesters such as ditridecylglutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; neopentyl glycol di-2-ethylhexanoate, neopentyl Glycoldi-n-octanoate, neopentyl glycol di-n-decanoate, trimethylpropanthritol-n-octanoate, trimethylolpropanthry-n-decanoate, pentaerythritol tetra-n-pentanoate, pentaerythritol tetra-n-hexanoate, Polypolyesters such as pentaerythritol tetra-2-ethylhexanoate; aromatic synthetic oils such as alkylnaphthalene, alkylbenzenes and aromatic esters, or mixtures thereof, can be exemplified.

Kinematic viscosity at 100 ° C. of the lubricating base oil ^(mm 2 / s) is 2.0~10.0mm ² / s, preferably 2.5~9.5mm ² / s, more preferably 3. It is 0 to 9.0 mm ² / s, most preferably 3.5 to 8.0 mm ² / s. As a result, it is possible to obtain a lubricating oil composition having a low viscosity, excellent lubricity, and a small evaporation loss.

The viscosity index (VI) of the lubricating oil base oil is not particularly limited, but is preferably 100 or more, more preferably 120 or more, and most preferably 130 or more. As a result, the viscosity at low temperature can be reduced while ensuring the oil film at high temperature.

The lubricating oil base oil preferably contains at least one mineral oil, and more preferably at least one GTL. It is more preferable to contain at least one mineral oil and at least one GTL, and particularly preferably to contain at least one GTL. Most preferably it does not contain synthetic oils.

The lubricating oil base oil of the present invention preferably has a kinematic viscosity (mm ² / s) of 2.0 to 5.8 ^{mm 2 / s at 100 ° C., preferably 2.5 to 5.5 mm 2} / s, and more preferably. 3.0 to 5.0 mm ² / s, and most preferably a base oil having 3.5~4.5mm ² / s (A1), kinematic viscosity at ^{100 ℃ (mm 2 /s)5.8mm 2 /} s Ultra to 12.0 mm ² / s, preferably 6.5 to 10.0 mm ² / s, more preferably 7.0 to 9.0 mm ² / s, most preferably 7.5 to 8.5 mm ² / s. It is preferable to use it in combination with the base oil (A2) to have. The mass ratio of the base oil (A1) to the base oil (A2) is preferably 99: 1 to 80:20 (mass ratio) for (A1) :( A2), more preferably 98: 2 to 85:15, and further. It is preferably 97: 3 to 90:10, particularly preferably 96: 4 to 92: 8.

(B) Viscosity Index Improver The lubricating oil composition of the present invention is characterized by essentially containing (B-1) polymethacrylate and (B-2) α-olefin copolymer as a viscosity index improver. .. (B-1) The polymethacrylate has a weight average molecular weight of 100,000 to 400,000, preferably 150,000 to 350,000, and more preferably 200,000 to 300,000. The amount of polymethacrylate is 0.5 to 5.0% by mass or less, preferably 0.8 to 3.0% by mass, and more preferably 1.0 to 2% by mass with respect to the total mass of the lubricating oil composition. It is preferably .0% by mass, more preferably 1.2 to 1.8% by mass. The polymethacrylate may be either dispersed or non-dispersed. (B-2) The α-olefin copolymer has an SSI (shear stability index) of 20 to 30, preferably 21 to 28, and more preferably 23 to 27. The weight average molecular weight of the (B-2) α-olefin copolymer may be 50,000 to 300,000, preferably 80,000 to 250,000, and more preferably 100,000 to 200,000. Anything is fine. The amount of the (B-2) α-olefin copolymer is 0.5 to 8.0% by mass, preferably 1.0 to 7.0% by mass, based on the total mass of the lubricating oil composition. It is more preferably 2.0 to 5.0% by mass, further preferably 2.5 to 4.5% by mass, and particularly preferably 3.0 to 4.0% by mass. Examples of the α-olefin copolymer include olefin copolymers (polyisobutylene and ethylene-propylene copolymers) and dispersed olefin copolymers. In the present invention, the weight average molecular weight of the polymethacrylate and α-olefin copolymer can be measured by, for example, gel permeation chromatography under the following conditions.
<Measurement conditions for Mw of α-olefin copolymer>
Equipment: "HLC-8320" [manufactured by Tosoh Corporation]
Column: 3 "TSK gel SuperMultipore HZ-M" Measurement temperature: 40 ° C
Sample solution: 0.2 (w / v)% tetrahydrofuran solution Injection amount: 30 μl
Detector: Refractive index detector Reference material: Polystyrene (PS t Quick MP-M)

In addition, other viscosity index improvers may be contained in combination with the polymethacrylate and α-olefin copolymers. Those containing polyalkylstyrene, styrene-butadiene hydrogenated copolymer, styrene-maleic anhydride copolymer, stellate isoprene and the like may be added. Further, a comb-shaped polymer containing at least a repeating unit based on a polyolefin macromer and a repeating unit based on an alkyl (meth) acrylate having an alkyl group having 1 to 30 carbon atoms in the main chain can also be used. The amount of the viscosity index improver other than the polymethacrylate and α-olefin copolymer in the lubricating oil composition may be 0.5 to 5% by mass, preferably 0.5 to 5% by mass, based on the total mass of the lubricating oil composition. May be 0.8 to 3.0% by mass, more preferably 1.0 to 2.0% by mass.

(C) Metal Cleaner The lubricating oil composition of the present invention preferably contains a metal cleanser. The metal cleaning agent is generally known and is not limited, but is preferably a cleaning agent having an alkali metal or an alkaline earth metal. Examples of the metal cleaning agent include calcium salicylate, calcium sulfonate, calcium phenate, magnesium salicylate, magnesium sulfonate, magnesium phenate and the like.

Among them, it is preferable to require a cleaning agent having magnesium (hereinafter referred to as magnesium-based cleaning agent), and the above-mentioned magnesium sulfonate, magnesium phenate, magnesium salicylate and the like can be used, and among these, magnesium salicylate in particular. Alternatively, magnesium sulfonate is preferable. As the magnesium-based cleaning agent, one type may be used alone, or two or more types may be mixed and used.

By containing a magnesium-based cleaning agent, the high-temperature cleaning property and rust preventive property required as a lubricating oil can be ensured. It can also reduce friction and therefore torque. This is particularly advantageous in terms of fuel economy characteristics.

The magnesium-based cleaning agent has a concentration [Mg] of magnesium in terms of mass ppm of magnesium with respect to the mass of the lubricating oil composition in the range of 100 to 1000 mass ppm, preferably 200 to 800 mass ppm, and more preferably 300 to 500 mass ppm. Is added in such an amount. If the amount of the magnesium-based cleaning agent exceeds the above upper limit, the wear becomes too large, and if it falls below the above lower limit, the effect of reducing friction is low.

Magnesium-based detergents are particularly preferably hyperbasic. As a result, the acid neutralization property required for the lubricating oil can be ensured. When a superbasic magnesium-based cleaning agent is used, a neutral magnesium-based cleaning agent or a calcium-based cleaning agent may be mixed.

The total base value of the magnesium-based cleaning agent is not limited, but is preferably 20 to 600 mgKOH / g, more preferably 50 to 500 mgKOH / g, and most preferably 100 to 450 mgKOH / g. As a result, the acid neutralization property, high temperature cleanliness property and rust preventive property required for the lubricating oil can be ensured. When two or more kinds of metal cleaning agents are mixed and used, the base value obtained by mixing is preferably in the above range.

The magnesium content in the magnesium-based cleaning agent is preferably 0.5 to 20% by mass, more preferably 1 to 16% by mass, and most preferably 2 to 14% by mass, but in the lubricating oil composition. It may be added so as to contain the amount of magnesium in the above range.

The lubricating oil composition of the present invention may contain other metal-based cleaning agents in addition to the magnesium-based cleaning agents. As other additives, a preferable one is a cleaning agent having calcium (hereinafter, referred to as a calcium-based cleaning agent). When the lubricating oil composition further contains a calcium-based cleaning agent, the high-temperature cleaning property and rust preventive property required for the lubricating oil can be further ensured. Further, a sodium-based cleaning agent may be contained as a metal-based cleaning agent other than the above as long as the effect of the present invention is not impaired. The sodium-based cleaning agent is a compound having sodium, and for example, sodium sulfonate, sodium phenate and sodium salicylate are preferable. These sodium-based cleaning agents may be used alone or in combination of two or more. By containing a sodium-based cleaning agent, the high-temperature cleaning property and rust preventive property required as a lubricating oil can be ensured. The sodium-based cleaning agent can be used in combination with the magnesium-based cleaning agent described above and any calcium-based cleaning agent. However, the amount of the calcium-based cleaning agent and the sodium-based cleaning agent added may be limited depending on the amount of the magnesium-based cleaning agent.

Examples of the calcium-based cleaning agent include the above-mentioned calcium sulfonate, calcium phenate and calcium salicylate, and one of these calcium-based cleaning agents may be used, or two or more of these calcium-based cleaning agents may be used in combination. May be good.

The content of the calcium-based cleaning agent is not particularly limited, but an amount satisfying the following formula (i) is preferable.
{[Mg] / ([Mg] + [Ca])} × 100 ≧ 5 (i)
Here, [Ca] indicates the concentration of calcium in terms of mass ppm with respect to the mass of the lubricating oil composition.
The value of {[Mg] / ([Mg] + [Ca])} × 100 is more preferably 10 or more, still more preferably 15 or more, and particularly preferably 20 or more. If the value is less than the above lower limit, the effect of reducing friction is small. The upper limit of {[Mg] / ([Mg] + [Ca])} × 100 is preferably 100, more preferably 80, still more preferably 60, and most preferably 40.

The calcium-based cleaning agent is preferably hyperbasic. As a result, the acid neutralization property required for the lubricating oil can be ensured. When a superbasic calcium-containing cleaning agent is used, a neutral calcium-based cleaning agent may be used in combination.

The total base value of the calcium-based cleaning agent is not limited, but is preferably 20 to 500 mgKOH / g, more preferably 50 to 400 mgKOH / g, and most preferably 100 to 350 mgKOH / g. As a result, the acid neutralization property, high temperature cleanliness property and rust preventive property required for the lubricating oil composition can be ensured. When two or more kinds of metal cleaning agents are mixed and used, it is preferable that the base value obtained by mixing is within the above range.

The calcium content in the calcium-based cleaning agent is preferably 0.5 to 20% by mass, more preferably 1 to 16% by mass, and most preferably 2 to 14% by mass.

(D) Zinc Dialkyl Dithiophosphate The lubricating oil composition of the present invention preferably further contains zinc dialkyl dithiophosphate (ZnDTP (also referred to as ZDDP)). The compound functions as an anti-wear agent and is represented by the following formula (ii).

上記式（ｉｉ）において、Ｒ^２及びＲ^３は、各々、互いに同一であっても異なっていてもよく、水素原子または炭素数１〜２６の一価炭化水素基である。一価炭化水素基としては、炭素数１〜２６の第１級（プライマリー）または第２級（セカンダリー）アルキル基；炭素数２〜２６のアルケニル基；炭素数６〜２６のシクロアルキル基；炭素数６〜２６のアリール基、アルキルアリール基またはアリールアルキル基；またはエステル結合、エーテル結合、アルコール基またはカルボキシル基を含む炭化水素基である。ここで、１級アルキル基とは、置換基Ｒ^２及びＲ^３において、ジアルキルジチオリン酸亜鉛中の酸素原子に直接結合する炭素原子が１級炭素原子であるという意味である。同様に２級アルキル基とは、置換基Ｒ^２、Ｒ^３において、ジアルキルジチオリン酸亜鉛中の酸素原子に直接結合する炭素原子が２級炭素原子であるという意味である。Ｒ^２及びＲ^３は、好ましくは、互いに独立に、炭素数３〜１２の、第１級または第２級アルキル基、炭素数８〜１８のシクロアルキル基、又は炭素数８〜１８のアルキルアリール基である。ただし、本発明において、Ｒ^２及びＲ^３の少なくとも１は、第１級または第２級アルキル基である。第１級アルキル基は、炭素数３〜１２を有することが好ましく、より好ましくは炭素数４〜１０を有する。例えば、プロピル基、ブチル基、ペンチル基、ヘキシル基、オクチル基、ノニル基、デシル基、ドデシル基、２−エチル−ヘキシル基、及び２，５−ジメチルヘキシル基等が挙げられる。第２級アルキル基は、炭素数３〜１２を有することが好ましく、より好ましくは炭素数３〜１０を有する。例えば、イソプロピル基、セカンダリーブチル基、イソペンチル基、及びイソヘキシル基等が挙げられる。

In the above formula (ii), R ² and R ³ may be the same or different from each other, and are hydrogen atoms or monovalent hydrocarbon groups having 1 to 26 carbon atoms. The monovalent hydrocarbon group includes a primary (primary) or secondary (secondary) alkyl group having 1 to 26 carbon atoms; an alkenyl group having 2 to 26 carbon atoms; a cycloalkyl group having 6 to 26 carbon atoms; carbon. An aryl group, an alkylaryl group or an arylalkyl group of number 6 to 26; or a hydrocarbon group containing an ester bond, an ether bond, an alcohol group or a carboxyl group. Here, the primary alkyl group, in the substituents R ² and R ^3, which means that the carbon atom directly attached to the oxygen atom in the zinc dialkyldithiophosphate is a primary carbon atom. Similarly, the secondary alkyl group, the substituents R ^2, R ^3, it is meant that the carbon atom directly attached to the oxygen atom in the zinc dialkyldithiophosphate is a secondary carbon atom. R ² and R ³ are preferably independent of each other, a primary or secondary alkyl group having 3 to 12 carbon atoms, a cycloalkyl group having 8 to 18 carbon atoms, or an alkylaryl having 8 to 18 carbon atoms. Is the basis. However, in the present invention, ^{at least 1 of R 2} and R ³ is a primary or secondary alkyl group. The primary alkyl group preferably has 3 to 12 carbon atoms, more preferably 4 to 10 carbon atoms. For example, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, a 2-ethyl-hexyl group, a 2,5-dimethylhexyl group and the like can be mentioned. The secondary alkyl group preferably has 3 to 12 carbon atoms, and more preferably has 3 to 10 carbon atoms. For example, an isopropyl group, a secondary butyl group, an isopentyl group, an isohexyl group and the like can be mentioned.

The content of zinc dialkyldithiophosphate in the lubricating oil composition is an amount of 300 to 1000 mass ppm as the concentration [P] of zinc dialkyldithiophosphate in mass ppm with respect to the total mass of the lubricating oil composition. It is preferably 400 to 1,000 mass ppm, more preferably 500 to 1,000 mass ppm, and particularly preferably 600 to 900 mass ppm.

The lubricating oil composition of the present invention may further contain an anti-wear agent other than zinc dialkyldithiophosphate. For example, a compound represented by the above formula, in which R ² and R ³ are independently of each other, a hydrogen atom or a monovalent hydrocarbon group having 1 to 26 carbon atoms and not an alkyl group can be mentioned. The monovalent hydrocarbon group includes an alkenyl group having 2 to 26 carbon atoms; a cycloalkyl group having 6 to 26 carbon atoms; an aryl group having 6 to 26 carbon atoms, an alkylaryl group or an arylalkyl group; or an ester bond or an ether. A hydrocarbon group containing a bond, alcohol group or carboxyl group. R ² and R ³ are preferably a cycloalkyl group having 8 to 18 carbon atoms and an alkylaryl group having 8 to 18 carbon atoms, and may be the same or different from each other. Moreover, zinc dithiocarbamate (ZnDTC) may be used in combination.

Further, at least one compound selected from phosphates represented by the following formulas (iii) and (iv), phosphite-based phosphorus compounds, and metal salts and amine salts thereof can also be used in combination.

上記一般式（ｉｉｉ）中、Ｒ^６は炭素数１〜３０の一価炭化水素基であり、Ｒ^４及びＲ^５は互いに独立に、水素原子又は炭素数１〜３０の一価炭化水素基であり、ｋは０又は１である。

上記一般式（ｉｖ）中、Ｒ^９は炭素数１〜３０の一価炭化水素基であり、Ｒ^７及びＲ^８は互いに独立に水素原子又は炭素数１〜３０の一価炭化水素基であり、ｔは０又は１である。

In the above general formula (iii), R ⁶ is a monovalent hydrocarbon group having 1 to 30 carbon atoms, and R ⁴ and R ⁵ are independent hydrogen atoms or monovalent hydrocarbon groups having 1 to 30 carbon atoms. Yes, k is 0 or 1.

In the above general formula (iv), R ⁹ is a monovalent hydrocarbon group having 1 to 30 carbon atoms, and R ⁷ and R ⁸ are hydrogen atoms or monovalent hydrocarbon groups having 1 to 30 carbon atoms independently of each other. , T is 0 or 1.

In the above general formulas (iii) and (iv) ^{, examples of the monovalent hydrocarbon group having 1 to 30 carbon atoms represented by R 4 to} R ⁹ include an alkyl group, a cycloalkyl group, an alkenyl group, and an alkyl-substituted cyclo. Alkyl groups, aryl groups, alkyl-substituted aryl groups, and arylalkyl groups can be mentioned. In particular, it is preferably an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 24 carbon atoms, more preferably an alkyl group having 3 to 18 carbon atoms, and most preferably an alkyl group having 4 to 15 carbon atoms. Is.

Examples of the phosphorus compounds represented by the general formulas (iii) and (iv) include the above-mentioned phosphorous acid monoester having one hydrocarbon group having 1 to 30 carbon atoms, (hydrocarbyl) phosphonic acid, and phosphonic acid. Monoester, acidic phosphorous acid monoester; the above-mentioned phosphorous acid diester having two hydrocarbon groups having 1 to 30 carbon atoms, monothiophosphorous acid diester, phosphonic acid diester, acidic phosphorous acid diester and (hydrocarbyl) phosphonic acid monoester. Esters: Phosphorous acid triesters having three hydrocarbon groups having 1 to 30 carbon atoms, and (hydrocarbyl) phosphonic acid diesters; and mixtures thereof.

The metal salt or amine salt of the phosphorus compound represented by the general formulas (iii) and (iv) is a phosphorus compound represented by the general formula (iii) or (iv), and a metal oxide, a metal hydroxide, or the like. A metal base such as a metal carbonate or a metal chloride, ammonia, a nitrogen compound such as an amine compound having only a hydrocarbon group having 1 to 30 carbon atoms or a hydroxyl group-containing hydrocarbon group in the molecule, and the like remain. It can be obtained by neutralizing part or all of the acidic hydrogen. Examples of the metal in the above metal base include alkali metals such as lithium, sodium, potassium and cesium, alkaline earth metals such as calcium, magnesium and barium, and heavy metals such as zinc, copper, iron, lead, nickel, silver and manganese. (However, molybdenum is excluded) and the like. Among these, alkaline earth metals such as calcium and magnesium and zinc are preferable, and zinc is particularly preferable.

(E) Ash-free dispersant The lubricating oil composition of the present invention preferably further contains an ash-free dispersant. The ashless dispersant is not particularly limited, and conventionally known ones may be used. Examples thereof include a nitrogen-containing compound having at least one alkyl group or alkenyl group having a linear structure or a branched structure in the molecule or a derivative thereof, or a modified product of alkenyl succinimide having 40 to 400 carbon atoms. .. One type of ashless dispersant may be used alone, or two or more types may be used in combination. When a borated ashless dispersant is used, the ashless dispersant as described above may be boronized. Borylation is generally carried out by allowing boric acid to act on the nitrogen-containing compound to neutralize some or all of the remaining amino and / or imino groups.

The alkyl group or alkenyl group preferably has 40 to 400 carbon atoms, more preferably 60 to 350 carbon atoms. When the number of carbon atoms of the alkyl group and the alkenyl group is less than the above lower limit value, the solubility of the compound in the lubricating oil base oil tends to decrease. Further, when the carbon number of the alkyl group and the alkenyl group exceeds the above upper limit value, the low temperature fluidity of the lubricating oil composition tends to deteriorate. The alkyl group and the alkenyl group may have a linear structure or a branched structure. Preferred embodiments include, for example, olefin oligomers such as propylene, 1-butene and isobutylene, branched alkyl groups derived from ethylene and propylene co-oligomers, branched alkenyl groups and the like.

The succinimide includes a so-called monotype 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. The lubricating oil composition of the present invention may contain either monotype or bistype, or may contain both.

The monotype succinimide derivative can be represented by, for example, the following formula (a). The bis-type succinimide derivative can be represented by, for example, the following formula (b).

In the above formula, R ¹ is an alkyl group or an alkenyl group having 40 to 400 carbon atoms independently of each other, m is an integer of 1 to 20, and n is an integer of 0 to 20. In particular, a bis-type succinimide compound is preferable. The succinimide derivative may be a combination of monotype and bistype, a combination of two or more monotypes, and a combination of two or more bistypes.
By reacting the above-mentioned succinimide derivative with a boron compound, a boronized succinimide derivative can be obtained. Boron compounds include boric acid, boric anhydride, boric acid ester, boron oxide, and boron halide. The boronized succinimide derivative may be used alone or in combination of two or more.

For example, as a method for producing an imide boronated succinimide, it is disclosed in Japanese Patent Application Laid-Open No. 42-8013 and 42-8014, Japanese Patent Application Laid-Open No. 51-52381, Japanese Patent Application Laid-Open No. 51-130408, and the like. The method used is mentioned. More specifically, an organic solvent such as alcohol, hexane, or xylene, a polyamine as a base oil for a light lubricating oil, and a boron compound such as boric acid, boric acid ester, or borate as polyalkenyl succinic acid (anhydrous) are used. It can be obtained by mixing and heat-treating under appropriate conditions. The boron content of the boronized succinimide thus obtained can be usually 0.1 to 4% by mass. In particular, a boron-modified compound (borated succinimide) of an alkenyl succinimide compound is preferable because it is excellent in heat resistance, antioxidant property and wear resistance.

The number average molecular weight (Mn) of the ashless dispersant is preferably 2000 or more, more preferably 2500 or more, even more preferably 3000 or more, most preferably 5000 or more, and 15000 or less, although not limited. Is preferable. If the number average molecular weight of the ashless dispersant is less than the above lower limit, the dispersibility may not be sufficient. On the other hand, if the number average molecular weight of the ashless dispersant exceeds the above upper limit value, the viscosity becomes too high, the fluidity becomes insufficient, and the deposit may increase.

The content of boron derived from the ashless dispersant with respect to the total mass of the lubricating oil composition is preferably 250 mass ppm or less, more preferably 200 mass ppm or less, and further preferably 150 mass ppm or less. When the ashless dispersant has boron, it is preferably an ashless dispersant having 1.0% by mass or less of boron, and more preferably an ashless dispersant having 0.8% by mass or less of boron. As the ashless dispersant, both a ashless dispersant containing boron and an ashless dispersant containing no boron can be used, and can be used in combination. The content of the boron-containing ashless dispersant in the lubricating oil composition depends on the boron content in the boron-containing ashless dispersant, but in particular, the blending amount of the boron-containing ashless dispersant is based on the total amount of the composition. It is preferably 0 to 5.0% by weight, preferably 0.1 to 4.0% by mass, more preferably 0.5 to 3.0% by mass, and particularly preferably 1.0 to 2.0% by mass. .. The blending amount of the ashless dispersant containing no boron is 0.1 to 10% by mass, preferably 0.5 to 9.0% by mass, and more preferably 1.0 to 8.0% by mass based on the total amount of the composition. Particularly preferably, it is 2.5 to 7.0% by mass, and most preferably 4.0 to 6.0% by mass.

(F) Friction modifier The lubricating oil composition of the present invention may further contain a friction modifier. The friction modifier is not particularly limited, and conventionally known ones can be used. Friction modifiers include, for example, sulfur-containing organic molybdenum compounds such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC), complexes of molybdenum compounds with sulfur-containing organic compounds or other organic compounds, and molybdenum sulfide and Examples thereof include a complex of a sulfur-containing molybdenum compound such as molybdenum sulfide and an alkenyl succinate imide. Examples of the molybdenum compound include molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, molybdenum acid such as orthomolybdenum acid, paramolybdenum acid and (poly) molybdenum sulfide acid, and molybdenum such as metal salts and ammonium salts of these molybdenum acid acids. Examples thereof include molybdate sulfides such as acid salts, molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide and polymolybdenum polysulfide, molybdenum sulfide acid, metal salts or amine salts of molybdenum sulfide acid, and molybdenum halides such as molybdenum chloride. Examples of the sulfur-containing organic compound include alkyl (thio) xanthate, thiadiazole, mercaptothiadiazole, thiocarbonate, tetrahydrocarbylthiuram disulfide, bis (di (thio) hydrocarbyldithiophosphonate) disulfide, and organic (poly) sulfide. And sulfide ester and the like. In particular, organic molybdenum compounds such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC) are preferable.

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

In the above general formulas [I] and [II], R _{1 to} R ₈ may be the same or different from each other, and are monovalent hydrocarbon groups having 1 to 30 carbon atoms. The hydrocarbon group may be linear or branched. The monovalent hydrocarbon group includes a linear or branched alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; a cycloalkyl group having 4 to 30 carbon atoms; an aryl having 6 to 30 carbon atoms. Groups, alkylaryl groups, arylalkyl groups and the like can be mentioned. In the arylalkyl group, the bonding position of the alkyl group is arbitrary. More specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group and a tridecyl group. , Tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and the like, and branched alkyl groups thereof, and alkyl groups having 3 to 8 carbon atoms are particularly preferable. Further, X ₁ and X ₂ are oxygen atoms or sulfur atoms, and Y ₁ and Y ₂ are oxygen atoms or sulfur atoms.

A sulfur-free organic molybdenum compound can also be used as the friction modifier. Examples of such a compound include a molybdenum-amine complex, a molybdenum-succinimide complex, a molybdate salt of an organic acid, and a molybdate salt of an alcohol.

Further, as the friction modifier in the present invention, the trinuclear molybdenum compound described in US Pat. No. 5,906,968 can also be used.

The friction modifier is added in an amount such that the concentration [Mo] of molybdenum as mass ppm of molybdenum with respect to the mass of the lubricating oil composition is 0 to 100 mass ppm, preferably 0 to 50 mass ppm, and more preferably 0 to 10 mass ppm. It is particularly preferably 0% by mass. If the amount of the friction modifier exceeds the above upper limit, the cleanliness may deteriorate, and if it is blended within the above range, good cleanliness can be obtained and a sufficient friction reducing effect can be secured.

Other Additives The lubricating oil composition of the present invention may further contain other additives depending on the purpose in order to improve its performance. As other additives, those generally used in lubricating oil compositions can be used. For example, antioxidants, friction modifiers other than the above, corrosion inhibitors, rust inhibitors, flow point lowering agents, etc. Additives such as anti-emulsifiers, metal inactivating agents and antifoaming agents can be mentioned.

Examples of the antioxidant include ashless antioxidants such as phenol-based and amine-based, and metal-based antioxidants such as copper-based and molybdenum-based. For example, examples of phenolic antioxidants include 4,4'-methylenebis (2,6-di-tert-butylphenol), 4,4'-bis (2,6-di-tert-butylphenol), and isooctyl-. Examples of 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and amine-based antioxidants include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, dialkyldiphenylamine and the like. Be done. The antioxidant is usually compounded in the lubricating oil composition in an amount of 0.1 to 5% by mass.

The lubricating oil composition of the present invention may contain an organic friction modifier as a friction modifier other than the above. The organic friction modifier means a friction modifier having no metal. For example, it is composed of an organic compound such as an amine-based friction modifier, an amide-based friction modifier, an ester-based friction modifier, and an ether-based friction modifier. Particularly preferably, it is an ester-based friction modifier, and functions suitably as a phosphorus scavenger. If the organic friction modifier is not included, it becomes difficult to secure excellent wear resistance and seizure resistance. The content of the organic friction modifier in the lubricating oil composition is preferably 0.1 to 2% by mass, more preferably 0.2 to 1.5% by mass, and further preferably 0.2 to 1% by mass. %. The organic friction modifier may be used alone or in combination of two or more.

Examples of the corrosion inhibitor include benzotriazole-based, tolyltriazole-based, thiadiazole-based, and imidazole-based compounds. Examples of the rust preventive agent include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, polyhydric alcohol ester and the like. The corrosion inhibitor and the rust inhibitor are usually blended in the lubricating oil composition in an amount of 0.01 to 5% by mass, respectively.

As the pour point lowering agent, for example, a polymethacrylate-based polymer compatible with the lubricating oil base oil to be used can be used. As the polymethacrylate, for example, a polymethacrylate-based polymer having a weight average molecular weight of less than 100,000, preferably 10,000 to 90,000, more preferably 20,000 to 80,000, still more preferably 30,000 to 70,000. It has a weight average molecular weight different from that of the polymethacrylate used as the viscosity index improver described above. The pour point depressant is usually added in a lubricating oil composition in an amount of 0.01 to 3% by mass.

Examples of the anti-emulsifier include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether. The anti-emulsifier is usually blended in the lubricating oil composition in an amount of 0.01 to 5% by mass.

Examples of the metal inactivating agent include imidazoline, pyrimidine derivative, alkylthiadiazole, mercaptobenzothiazole, benzotriazole or its derivative, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazole-2,5-. Examples thereof include bisdialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propionnitrile. The metal inactivating agent is usually blended in the lubricating oil composition in an amount of 0.01 to 3% by mass.

Examples of the defoaming agent include silicone oil having a kinematic viscosity at 25 ° C. of 10 to 100,000 mm ² / s, an alkenyl succinic acid derivative, an ester of a polyhydroxy fatty alcohol and a long-chain fatty acid, methyl salicylate and o. -Hydroxybenzyl alcohol and the like can be mentioned. The defoaming agent is usually blended in the lubricating oil composition in an amount of 0.001 to 1% by mass.

Lubricating oil composition The lubricating oil composition of the present invention requires that the kinematic viscosity at 100 ° C. in the range of less than 6.9 mm ² / s or more 9.3 mm ² / s. It is preferably 7.2 or more and ^{less than 9.0 mm 2} / s, and more preferably 7.5 or more and ^{less than 8.7 mm 2} / s. As a result, the viscosity of the lubricating oil composition can be reduced. This meets the requirements of SAE0W-20. The kinematic viscosity (KV100) at 100 ° C. was measured at 100 ° C. in accordance with ASTM D445.

The CCS viscosity of the lubricating oil composition of the present invention at −35 ° C. is 6.2 Pa · s or less, preferably 5.5 Pa · s or less, more preferably 5.0 Pa · s or less, and most preferably. Is 4.5 Pa · s or less. The CCS viscosity (CCS viscosity) at −35 ° C. was measured according to ASTMD5283.

The high-temperature high shear viscosity (HTHS viscosity) of the lubricating oil composition of the present invention at 150 ° C. is 2.6 mPa · s or more, preferably 2.7 mPa · s or more. The upper limit is preferably 2.9 mPa · s or less. The high temperature and high shear viscosity (HTHS150) at 150 ° C. was measured according to ASTMD4683.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

The components used in the examples and comparative examples are as follows.
(A) Lubricating oil base oil (A1-1) GTL-derived base oil (kinematic viscosity at 100 ° C. = 4.1 mm ² / s, VI = 129)
(A1-2) Mineral oil (kinematic viscosity at 100 ° C. = 4.1 mm ² / s, VI = 134)
(A2-1) GTL-derived base oil (kinematic viscosity at 100 ° C. = 7.6 mm ² / s, VI = 140)
(A2-2) Mineral oil (kinematic viscosity at 100 ° C. = 7.2 mm ² / s, VI = 125)
(A2-3) Poly-α-olefin (PAO) (kinematic viscosity at 100 ° C. = 5.9 mm ² / s, VI = 132)
(B) Viscosity index improver (B1-1) Non-dispersive polymethacrylate (Mw = 200,000)
(B1-2) Non-dispersive polymethacrylate (Mw = 240,000)
(B1-3) Non-dispersive polymethacrylate (Mw = 400,000)
(B1-4) Non-dispersive polymethacrylate (Mw = 50,000)
(B1-5) Non-dispersive polymethacrylate (Mw = 500,000)
(B2-1) α-olefin copolymer (SSI = 24, Mw = 150,000)

[Other additives]
Metal cleaners (calcium sulfonate, magnesium sulfonate), anti-wear agents (ZnDTP), ashless dispersants (polyisobutenyl succinimide, or boronized polyisobutenyl succinimide), friction modifiers (esters), Antioxidant (phenolic), antifoaming agent (dimethyl silicone), flow point lowering agent (PMA with Mw less than 100,000)

Examples and Comparative Examples A lubricating oil composition was prepared by mixing a lubricating oil base oil, a viscosity index improver, and other components in the amounts shown in Tables 1 and 2 below. The parts by mass shown in the table are parts by mass with respect to the total amount (100 parts by mass) of the lubricating oil composition. For the obtained composition, the CCS viscosity at −35 ° C., the high temperature high shear viscosity at 150 ° C. (HTHS150), and the kinematic viscosity at 100 ° C. (KV100) were measured. Each measuring method is as described above. The results are shown in Tables 1 and 2.

As shown in Table 2 above, the lubricating oil composition of Comparative Example has a kinematic viscosity of 9.3 mm ² / s or more at 100 ° C. (Comparative Examples 4, 5, 8 and 9), and a CCS viscosity at −35 ° C. 6. More than 2 Pa · s (Comparative Examples 4 and 5), high temperature and high shear viscosity at 150 ° C. (HTHS viscosity) less than 2.6 mPa · s (Comparative Examples 1, 2, 3, 6 and 7). On the other hand, the lubricating oil composition of the present invention shown in Table 1 has low-temperature viscosity characteristics (CCS viscosity at −35 ° C.) and high-temperature viscosity characteristics (high-temperature high-shear viscosity at 150 ° C. (HTHS viscosity) even when the viscosity is lowered. ) Is excellent in balance.

Claims (6)

In a lubricating oil composition containing (A) lubricating oil base oil, (B-1) polymethacrylate and (B-2) α-olefin copolymer,
The (A) lubricating oil base oil has a kinematic viscosity of 2.0 to 10.0 mm ² / s at 100 ° C., and the (B-1) polymethacrylate has a weight average molecular weight of 100,000 to 400,000. The content of polymethacrylate is 0.5 to 5.0% by mass with respect to the total mass of the lubricating oil composition, and the (B-2) α-olefin copolymer has an SSI (shear stability index) of 20 to 20 to. 30 and the amount of the olefin copolymer is 0.5 to 8.0% by mass with respect to the total mass of the lubricating oil composition.
The lubricating oil composition has a kinematic viscosity of 6.9 or more and ^{less than 9.3 mm 2} / s at 100 ° C., a CCS viscosity of 6.2 Pa · s or less at −35 ° C., and a high temperature of 150 ° C. The lubricating oil composition, which has a high shear viscosity (HTHS viscosity) of 2.6 mPa · s or more. The lubricating oil composition according to claim 1, wherein the lubricating oil base oil (A) contains mineral oil. The lubricating oil composition according to claim 1 or 2, wherein the lubricating oil base oil (A) contains GTL. The lubricating oil composition according to any one of claims 1 to 3, wherein the lubricating oil composition has an HTHS viscosity of 2.9 mPa · s or less at 150 ° C. The lubricating oil composition according to any one of claims 1 to 4, which is used for an internal combustion engine. The lubricating oil composition according to claim 5, which is for a diesel engine.