JP2022048706A - Lubricant composition - Google Patents

Abstract

To provide a lubricant composition excellent in low-temperature viscosity characteristics while maintaining low fuel consumption even when the viscosity is reduced and to provide a lubricant composition for an internal combustion engine as a preferable embodiment.SOLUTION: There is provided a lubricant composition which comprises (A) a lubricant base oil and (B) a metal friction modifier, wherein the lubricant base oil (A) has a kinematic viscosity at 100°C of 2.5 mm2/s or more and less than 6.5 mm2/s and contains 40 mass% or more and 97 mass% or less of at least one lubricant base oil (A1) selected from (A1-a) a GTL base oil having a viscosity index of 125 or more and (A1-b) a poly-α-olefin base oil based on the total mass of the lubricant composition, the amount of the metal friction modifier (B) is an amount so that the concentration as a metal element is 200 to 600 massppm based on the total mass of the lubricant composition and the lubricant composition has a kinematic viscosity at 100°C of 9.3 mm2/s or more and less than 12.5 mm2/s and a CCS viscosity at -35°C of 6200 mPa s or less.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.

Lubricating oil compositions are widely used in the automobile field such as for internal combustion engines, automatic transmissions, and gear oils. In recent years, it has been required to reduce the viscosity in order to improve fuel efficiency, but it is also required to have excellent low-temperature viscosity characteristics while maintaining fuel efficiency. 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 having a high viscosity index having a viscosity index improver having a specific star-shaped polymer structure. Further, Patent Document 2 discloses a lubricating oil composition comprising a base oil having a specific urea adduct value and a specific additive. Further, Patent Document 3 describes a lubricating oil composition using a metal detergent having a different base value.

Japanese Unexamined Patent Publication No. 2014-051572 JP-A-2015-180762 JP-A-2017-0437334

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 low temperature viscosity characteristics. Therefore, an object of the present invention is to provide a lubricating oil composition having excellent low-temperature viscosity characteristics while maintaining fuel efficiency even when the viscosity is lowered, and more preferably, a lubricating oil composition for an internal combustion engine. do.

As a result of diligent studies, the present inventors have highly blended a specific base oil having a kinematic viscosity of 2.5 to 6.5 mm or less than ² / s at 100 ° C. in the composition in an amount of 40% by mass or more, and metal friction. It has been found that the above object can be achieved by blending a specific amount of the modifier, and more preferably by combining the low-viscosity base oil and the high-viscosity base oil.

That is, the present invention relates to a lubricating oil composition containing (A) a lubricating oil base oil and (B) a metal friction modifier.
The (A) lubricating oil base oil has a kinematic viscosity of 2.5 mm ² / s or more and less than 6.5 mm ² / s at 100 ° C., and (A1-a) a GTL base oil having a viscosity index of 125 or more and (A1-a). A1-b) The lubricating oil base oil (A1), which is at least one selected from the poly α-olefin base oil, is contained in an amount of 40% by mass or more and 97% by mass or less based on the total mass of the lubricating oil composition. (B) The amount of the metal friction modifier is characterized in that the metal content with respect to the total mass of the lubricating oil composition is an amount of 200 to 600 mass ppm, and
The lubricating oil composition having a kinematic viscosity of 9.3 mm ² / s or more and less than 12.5 mm ² / s at 100 ° C. and a CCS viscosity of 6200 mPa · s or less at −35 ° C. offer.

As a preferred embodiment of the present invention, at least one requirement selected from the following (1) to (6) is satisfied.
(1) Lubricating oil base oil (A2) having a kinematic viscosity of 6.5 mm ² / s or more and 50 mm ² / s or less at 100 ° C. is 2% by mass or more and 20% by mass with respect to the total mass of the lubricating oil composition. Further contained below.
(2) The lubricating oil base oil (A2) is at least one selected from (A2-a) GTL base oil having a viscosity index of 125 or more and (A2-b) poly α-olefin base oil.
(3) The lubricating oil composition has a high-temperature high shear viscosity (HTHS viscosity) of 2.9 mPa · s or more and less than 3.7 mPa · s at 150 ° C.
(4) The amount of the (B) metal friction modifier is such that the concentration as a metal element with respect to the total mass of the lubricating oil composition is 250 to 550 mass ppm.
(5) The component (B) is a molybdenum-based friction modifier.
(6) A lubricating oil composition for an internal combustion engine.

Even if the viscosity of the lubricating oil composition of the present invention is reduced, the amount of NOACK evaporation can be reduced to maintain fuel efficiency, excellent low-temperature viscosity characteristics, and both friction reducing action and cleanliness are ensured. .. Therefore, the lubricating oil composition of the present invention is particularly suitable as a lubricating oil composition for an internal combustion engine.

(A) Lubricating oil base oil The lubricating oil base oil in the present invention has (A1) a kinematic viscosity of 2.5 to 6.5 mm less than ² / s at 100 ° C., and (A1-a) a viscosity index of 125 or more. Essentially contains a lubricating oil base oil, which is at least one selected from a certain GTL base oil and (A1-b) poly α-olefin base oil, and the component (A1) is 40 based on the total mass of the lubricating oil composition. It is characterized by containing in a mass% or more. The content of the (A1) lubricating oil base oil is 40% by mass or more and 97% by mass or less, preferably 40 to 85% by mass, and more preferably 45 to 80% by mass with respect to the total mass of the lubricating oil composition. It is preferably by mass, more preferably 50 to 80% by mass. By containing the above (A1) lubricating oil base oil in an amount of 40% by mass or more, fuel efficiency is ensured and low-temperature viscosity characteristics are improved. It is an essential requirement that the component (A1) has the above-mentioned kinematic viscosity and is at least one selected from the above-mentioned (A1-a) and (A1-b). Even if the lubricating oil base oil having a kinematic viscosity of 2.5 to 6.5 ^mm or less at 100 ° C. is contained, if neither of the above (A1-a) and (A1-b) is contained, the low-temperature viscosity is contained. It becomes difficult to improve the characteristics.

The component (A1-a) is a GTL base oil having a viscosity index of 125 or more, and the viscosity index is preferably 125 to 160, more preferably 127 to 150. The component (A1-b) is a poly α-olefin base oil, and examples thereof include 1-octene oligomer and 1-decene oligomer. The component (A1) may be either one of the components (A1-a) and the component (A1-b), or may be used in combination. In the case of combined use, the ratio is not particularly limited and the above-mentioned content may be satisfied. The kinematic viscosity of the component (A1) at 100 ° C. is preferably 2.7 to 6.5 mm ² / s, and more preferably 2.9 to 5.1 mm ² / s.

The lubricating oil composition of the present invention has a kinematic viscosity at 100 ° C. of less than 2.5 to 6.5 mm ² / s as long as the gist of the present invention is not impaired, and other than the above-mentioned (A1-a). Mineral oil and synthetic oils other than (A1-b) can be contained as (A) lubricating oil base oil. The lubricating oil base oil may be either mineral oil or synthetic oil, and these may be used alone or in combination. These contents are preferably 10% by mass or less, more preferably 7% by mass or less, still more preferably 5% by mass or less, based on the total amount of the lubricating oil composition. The lower limit is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.5% by mass or more.

As the mineral oil other than (A1-a), for example, the lubricating oil distillate obtained by distilling the atmospheric residual oil obtained by atmospheric distillation of crude oil under reduced pressure is removed from the solvent, extracted by solvent, and hydrolyzed. , Purified by one or more treatments such as solvent dewaxing and hydrorefining, or wax isomerized mineral oils, GTL (Gas to Liquid) base oils other than the above (A1-a), ATL ( Asphalt to Liquid) base oil, vegetable oil-based base oil, or a mixed base oil thereof can be mentioned.

Examples of synthetic oils other than (A1-b) include polybutene or a hydride thereof; monoesters such as 2-ethylhexyl laurate, 2-ethylhexyl palmitate, and 2-ethylhexyl stearate; ditridecylglutarate and di-2. -Diesters such as ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sevacate; neopentyl glycol di-2-ethylhexanoate, neopentyl glycol di-n-octanoate, neopentyl glycol di-n- Polyester esters such as decanoate, trimethylolpropane tri-n-octanoate, trimethylolpropane tri-n-decanoate, pentaerythritol tetra-n-pentanoate, pentaerythritol tetra-n-hexanoate, and pentaerythritol tetra-2-ethylhexanoate. Aromatic synthetic oils such as alkylnaphthalene, alkylbenzene, and aromatic esters, or mixtures thereof, can be exemplified.

The lubricating oil composition of the present invention preferably further contains (A2) a lubricating oil base oil having a kinematic viscosity of 6.5 to 50 mm ² / s or less at 100 ° C. in combination with the above component (A1). As a result, fuel efficiency is further ensured. The kinematic viscosity of the component (A2) at 100 ° C. is preferably 7 to 45 mm ² / s, more preferably 7.5 to 42 mm ² / s. The component (A2) is not particularly limited as long as it has the above kinematic viscosity, and may be appropriately selected from conventionally known mineral oils and synthetic oils.

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 removal, solvent extraction, hydrocracking, solvent removal, 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. The 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 and 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 sevacate; neopentyl glycol di-2-ethylhexanoate, neopentyl Glycoldi-n-octanoate, neopentyl glycol di-n-decanoate, trimethylolpropane tri-n-octanoate, trimethylolpropane tri-n-decanoate, pentaerythritol tetra-n-pentanoate, pentaerythritol tetra-n-hexanoate, Polyol esters such as pentaerythritol tetra-2-ethylhexanoate; aromatic synthetic oils such as alkylnaphthalene, alkylbenzene and aromatic esters, or mixtures thereof, can be exemplified. These may be used alone or in combination of two or more. The content of the component (A2) in the lubricating oil composition is not limited, but is preferably 2 to 20% by mass, more preferably 3 to 18% by mass, and 3 to 15% by mass. Is more preferable.

The component (A2) is preferably at least one selected from (A2-a) GTL base oil having a viscosity index of 125 or more and (A2-b) poly α-olefin base oil. By using these in combination with the above (A1), fuel efficiency is further ensured and low temperature viscosity characteristics are improved. The viscosity index of the (A2-a) GTL base oil is preferably 125 to 160, more preferably 128 to 150. The component (A2-b) is a poly α-olefin base oil, and examples thereof include 1-octene oligomer and 1-decene oligomer. These may be either (A2-a) or (A2-b) or may be used in combination. In the case of combined use, the ratio is not particularly limited and the above-mentioned content may be satisfied.

The lubricating oil base oil in the present invention is preferably a combination of the above (A1) component 40 to 97% by mass and the (A2) component 2 to 20% by mass. More preferably, a combination of (A1-a) GTL base oil and (A2-a) GTL base oil, a combination of (A1-a) GTL base oil and (A2-b) PAO, and (A1-b) PAO. It is preferably selected from the combination of (A2-a) GTL base oil and the combination of (A1-b) PAO and (A2-b) PAO.

In addition to the combination with the component (A1) and the component (A2), the above-mentioned (A1-a) or (A1-b) having a kinematic viscosity at 100 ° C. of less than 2.5 to 6.5 mm ² / s. ) May contain lubricating oil base oil. The content is as described above, preferably 10% by mass or less, more preferably 7% by mass or less, still more preferably 5% by mass or less. Within this content range, the predetermined effect of the present invention can be obtained without impairing the gist of the present invention.

(B) Metal Friction Modifier The lubricating oil composition of the present invention contains a metal friction modifier. In particular, it is preferable to contain a friction modifier having molybdenum (hereinafter referred to as a molybdenum-based friction modifier). The molybdenum-based friction modifier is not particularly limited, and conventionally known ones can be used. The molybdenum-based friction modifier is a compound having molybdenum, for example, a sulfur-containing organic molybdenum compound such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC), a molybdenum compound and a sulfur-containing organic compound, or other organic substances. Examples thereof include a complex with a compound and a complex between a sulfur-containing molybdenum compound such as molybdenum sulfide and molybdenum sulfide acid and an alkenyl succinate imide. Examples of the molybdenum compound include molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, molybdic acid such as orthomolybdic acid, paramolybdic acid and (poly) molybdate sulfide, and molybdates such as metal salts and ammonium salts of these molybdic acids. Examples thereof include molybdate sulfide such as molybdate, molybdate disulfide, molybdenum trisulfide, molybdenum pentasulfide and molybdenum polysulfide, molybdate sulfide, metal salt or amine salt of molybdate sulfide, molybdenum halide such as molybdenum chloride and the like. Examples of the sulfur-containing organic compound include alkyl (thio) xanthate, thiadiazole, thiadiazole, 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 preferred.

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 can be mentioned, and an alkyl group having 3 to 8 carbon atoms is 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.

As the friction modifier, a sulfur-free organic molybdenum compound can also be used. Examples of such a compound include a molybdenum-amine complex, a molybdenum-succinic acidimide complex, a molybdenum salt of an organic acid, and a molybdenum 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 has a concentration [Mo] of a metal (particularly molybdenum) as a mass ppm of 200 to 600 mass ppm, preferably 250 to 550 mass ppm, and more preferably 250 to 500 mass ppm with respect to the mass of the lubricating oil composition. It is added in an amount within the range of. By blending a metal friction modifier, particularly preferably a molybdenum-based friction modifier, in an amount within the range, it is possible to ensure both the friction reducing action and the cleanliness of the lubricating oil composition. If the amount of the friction modifier exceeds the above upper limit, the cleanliness may deteriorate, and if it is less than the above lower limit, the friction may not be sufficiently reduced or the cleanliness may deteriorate. ..

(C) Viscosity index improver In the present invention, a viscosity index improver can be used. Examples of the viscosity index improver include polymethacrylate, dispersed polymethacrylate, olefin copolymer (polyisobutylene, ethylene-propylene copolymer), dispersed olefin copolymer, polyalkylstyrene, styrene-butadiene hydrogenated copolymer, and the like. Examples thereof include those containing a styrene-maleic anhydride copolymer, stellate isoprene and the like. 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 be used, but is not limited.

The weight average molecular weight of the viscosity index improver is not particularly limited, but is preferably 10,000 to 2,000,000, more preferably 20,000 to 1,500,000, and 30,000 to 1, Million is even more preferred.

In the present invention, the weight average molecular weight of the viscosity index improver can be measured by gel permeation chromatography under the following conditions.
<Measurement conditions for Mw of polymethacrylate>
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 Solution injection amount: 30 μl
Detection device: Refractive index detector Reference material: Polystyrene (PS t Quick MP-M)

The content of the viscosity index improver is not limited, but is 0.5 to 10.0% by mass or less, preferably 0.8 to 8.0, based on the total mass of the lubricating oil composition. It is preferably by mass, more preferably 1.0 to 6.0% by mass, and even more preferably 1.2 to 6.0% by mass.

(D) Metal Purifying Agent A metal purifying agent can be used in the lubricating oil composition of the present invention. The metal cleaning agent 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.

As the metal cleaning agent, it is preferable to have 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, particularly Magnesium salicylate or magnesium sulfonate is preferred. 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, high-temperature cleaning property and rust preventive property required as a lubricating oil can be ensured. It can also reduce friction and thus torque. This is particularly advantageous in terms of fuel economy characteristics.

The magnesium-based detergent is not limited, but the concentration of magnesium with respect to the mass of the lubricating oil composition is preferably 200 to 1200 mass ppm, more preferably 300 to 1100 mass ppm, still more preferably 400 to 1000 mass ppm. It is added in an amount that is in the range. When the amount of the magnesium-based detergent exceeds the above upper limit, the wear becomes too large, and when it falls below the above lower limit, the effect of reducing friction is low.

Magnesium-based detergents are particularly preferably hyperbasic. This makes it possible to secure the acid neutralization property required for the lubricating oil. 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 detergent 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 detergents are mixed and used, it is preferable that the base value obtained by mixing is in the above range.

The magnesium content in the magnesium-based detergent 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.

As the metal cleaning agent, a cleaning agent having calcium (hereinafter referred to as a calcium-based cleaning agent) can be used. 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 detergent is a compound having sodium, and for example, sodium sulfonate, sodium phenate and sodium salicylate are preferable. These sodium-based detergents 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.

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 them may be mixed and used. May be good.

The calcium-based cleaning agent is preferably overbasic. This makes it possible to secure the acid neutralization property required for the lubricating oil. When a superbasic calcium-containing detergent is used, a neutral calcium-based detergent may be used in combination.

The total base value of the calcium-based detergent 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 can be ensured. When two or more kinds of metal detergents 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.
The calcium-based cleaning agent is not limited, but the concentration of calcium with respect to the mass of the lubricating oil composition is preferably 200 to 1500 mass ppm, more preferably 300 to 1300 mass ppm, still more preferably 400 to 1100 mass ppm. It is added in an amount that is in the range.

(E) Zinc Dialkyl Dithiophosphate The lubricating oil composition of the present invention can contain 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. Aryl groups, alkylaryl groups or arylalkyl groups of number 6-26; or hydrocarbon groups containing ester bonds, ether bonds, alcohol groups or carboxyl groups. Here ^, the primary alkyl group means that the carbon atom directly bonded to the oxygen atom in zinc dialkyldithiophosphate at the substituents ^R2 and R3 is a primary carbon atom. Similarly ^, the secondary alkyl group means that the carbon atom directly bonded to the oxygen atom in zinc dialkyldithiophosphate at the substituents ^R2 and R3 is a secondary carbon atom. ^R2 and R3 ^are preferably independent of each other, with 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. It 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, more preferably 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 each of them may be the same as or different from each other. Further, 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 ^R4 to R9 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, an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 24 carbon atoms is preferable, an alkyl group having 3 to 18 carbon atoms is more preferable, and an alkyl group having 4 to 15 carbon atoms is most preferable. Is.

Examples of the phosphorus compound represented by the general formulas (iii) and (iv) include a phosphoric acid monoester having one hydrocarbon group having 1 to 30 carbon atoms, (hydrocarbyl) subphosphonic acid, and phosphonic acid. Monoester, acidic phosphoric acid monoester; the above-mentioned phosphite diester having two hydrocarbon groups having 1 to 30 carbon atoms, monothio Subphosphate diester, phosphonic acid diester, acidic phosphoric acid diester and (hydrocarbyl) phosphonic acid monoester. Examples thereof include a phosphite triester having three hydrocarbon groups having 1 to 30 carbon atoms, a (hydrocarbyl) phosphonic acid diester; and a mixture thereof.

The metal salt or amine salt of the phosphorus compound represented by the general formulas (iii) and (iv) is the 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 hydrogen 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.

(F) Ash-free dispersant The lubricating oil composition of the present invention preferably has 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 or a derivative thereof having at least one alkyl group or alkenyl group having a linear structure or a branched structure in the molecule and having 40 to 400 carbon atoms, or a modified product of alkenyl succinimide. .. 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, it may be a borated version of the ashless dispersant as described above. 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, isobutylene, branched alkyl groups or branched alkenyl groups derived from ethylene and propylene co-oligomers, 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. The boron compound is boric acid, boric anhydride, boric acid ester, boron oxide, boron halide and the like. The boronized succinimide derivative may be used alone or in combination of two or more.

For example, as a method for producing a borated succinimide, it is disclosed in Japanese Patent Publication No. 42-8013, Japanese Patent Application Laid-Open No. 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 alcohols, hexane, and xylene, a polyamine in a light lubricating oil base oil, and a boron compound such as boric acid, boric acid ester, or borate in polyalkenylsuccinic acid (anhydride). 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, still more preferably 3000 or more, most preferably 5000 or more, and 15000 or less. 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, the viscosity is too high, the fluidity becomes insufficient, and there is a possibility that the deposit may increase.

When the ashless dispersant has boron, the boron content in the ashless dispersant is not limited, but it is preferably an ashless dispersant having 0.3% by mass to 5% by mass or less, preferably 0.5% by mass. It is more preferable that the ashless dispersant has% to 3% by mass or less. 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 nitrogen content of the ashless dispersant is not limited, but is preferably an ashless dispersant having 0.3% by mass to 5% by mass or less, and an ashless content having 0.5% by mass to 3% by mass or less. It is more preferably a powder, and further preferably an ashless dispersant having 0.8% by mass to 2% by mass or less.
The content of the 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 0 to 1 on the basis of the total amount of the composition. It is preferably 5% by mass, preferably 0.001 to 1.0% by mass, more preferably 0.01 to 0.75% by mass, and particularly preferably 0.1 to 0.5% by mass.

When the lubricating oil composition contains an ashless dispersant having boron, the boron content in the lubricating oil composition is not limited, but is preferably 50 to 500 mass ppm, preferably 100 to 400 mass ppm. More preferred. The nitrogen content derived from the ashless dispersant in the lubricating oil composition is not limited, but is preferably 50 to 3000 mass ppm, more preferably 100 to 2000 mass ppm.

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 the other additives, those generally used in the lubricating oil composition can be used, and for example, an antioxidant, a friction modifier other than the above (B), a corrosion inhibitor, a rust preventive, and a flow point. Additives such as depressants, anti-emulsifiers, metal inactivating agents and defoaming agents can be mentioned.

Examples of the antioxidant include ashless antioxidants such as phenol and amines, and metal-based antioxidants such as copper and molybdenum. For example, examples of the phenolic ashless antioxidant include 4,4'-methylenebis (2,6-di-tert-butylphenol), 4,4'-bis (2,6-di-tert-butylphenol), and isooctyl-. 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and the like, and examples of the amine-based antioxidant-free antioxidant 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.

Examples of the friction modifier other than the above (B) include organic friction modifiers. 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, an ether-based friction modifier, and an imide-based friction modifier. Particularly preferred are amine-based friction modifiers, ester-based friction modifiers, or imide-based friction modifiers, such as glycerin monooleate, glycerin monostearate, glycerin dioleate, glycerin distearate, oleylamine, oleic acid amide, and stearic acid. Examples thereof include acid amine and stearic acid amide. When the organic friction modifier is added, the content 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. It is 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. The pour point lowering agent is usually blended in the lubricating oil composition in an amount of 0.01 to 3% 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, β- (o-carboxybenzylthio) propionnitrile and the like. The metal deactivating 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 of 1000 to 100,000 mm ² / s at 25 ° C., 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 has a kinematic viscosity at 100 ° C. of less than 9.3 to 12.5 mm ² / s, preferably 9.5 to 12.0 mm ² / s.
The lubricating oil composition of the present invention has a high temperature and high shear viscosity (HTHS viscosity) at 150 ° C., preferably 2.9 mPa · s to less than 3.7 mPa · s, and more preferably 3.0 mPa · s to 3. It is less than 5 mPa · s.
The lubricating oil composition of the present invention has a CCS viscosity at −35 ° C. of 6200 mPa · s or less, preferably 6000 mPa · s or less.
By satisfying these physical property values, the requirements of 0W-30 of the SAE standard can be satisfied.
The NOACK evaporation amount of the lubricating oil composition is not limited, but is preferably less than 13.0% by mass, more preferably 12.0% by mass or less.
The lubricating oil composition of the present invention conforms to the SAE standard 0W-30, has excellent fuel saving properties, and has excellent low-temperature viscosity characteristics, and therefore can be particularly suitably used as a lubricating oil for internal combustion engines.

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 lubricating oil compositions described in Examples and Comparative Examples were measured by the following methods.
(1) Kinematic viscosity at 100 ° C (KV100)
Measured at 100 ° C. according to ASTM D445.
(2) Viscosity index (VI)
Calculated by a method according to ASTM D 2270.
(3) CCS viscosity at -35 ° C (CCS viscosity (@ -35 ° C))
Measured according to ASTM D5283.
(4) High temperature and high shear viscosity at 150 ° C (HTHS viscosity (@ 150 ° C))
Measured according to ASTM D4683.
(5) NOACK evaporation amount The NOACK evaporation amount was measured at 250 ° C. for 1 hour according to ASTM D 5800.

(6) Friction coefficient The friction coefficient was measured according to the following method.
A PCS Instrument standard test piece made of a plate test piece (material: AISI 52100 steel) and a PCS Instrument standard test piece made of a mating ball test piece (material: AISI 52100 steel) having a diameter of 0.75 inch. A ball-on-disc friction test was performed on each lubricating oil composition. A 2-hour ball-on-disk friction test was performed with a test load of 37 N, a slip rate of 50%, and an oil temperature of 60 ° C (constant), and the friction coefficient (late stage) after 2 hours was measured and used as the friction coefficient in this test. ..

(7) Hot tube test (evaluation of high temperature cleanliness) (hereinafter, may be referred to as "HTT")
Measured according to JPI 5S-55-99. The maximum score is 10 points and the minimum score is 0 points. The higher the score, the better the high temperature cleanliness.

The materials used in the examples and comparative examples are as follows.
(A) Lubricating oil base oil (A1-a-1) Low viscosity mineral oil 1 (GTL-derived base oil (GTL4), kinematic viscosity at 100 ° C. = 4.1 mm ² / s, VI = 129)
(A1-b-1) Low-viscosity synthetic oil 1 (poly α-olefin base oil (PAO4), kinematic viscosity at 100 ° C. = 4.1 mm ² / s)
(A1-a'-2) Low-viscosity mineral oil 2 (highly refined decomposition base oil, kinematic viscosity at 100 ° C. = 4.1 mm ² / s, VI = 134)
(A1-a'-3) Low-viscosity mineral oil 3 (highly refined decomposition base oil, kinematic viscosity at 100 ° C. = 4.2 mm ² / s, VI = 122)
(A1-a'-4) Low-viscosity mineral oil 4 (highly refined base oil, kinematic viscosity at 100 ° C. = 4.5 mm ² / s, VI = 116)
(A2-a-1) High-viscosity mineral oil 1 (GTL-derived base oil (GTL8), kinematic viscosity at 100 ° C. = 7.6 mm ² / s, VI = 140)
(A2-b-1) High-viscosity synthetic oil 1 (poly α-olefin base oil (PAO10), kinematic viscosity at 100 ° C. = 10.1 mm ² / s, VI = 136)
(A2-b-2) High-viscosity synthetic oil 2 (poly α-olefin base oil (PAO40), kinematic viscosity at 100 ° C. = 41.0 mm ² / s, VI = 152)

(B) Metal friction modifier (B1) Molybdenum dithiocarbamate (MODTC, molybdenum content 10% by mass)

Other additives Viscosity index improver (polymethacrylate, weight average molecular weight 200,000), metal detergent (containing calcium), zinc dialkyldithiophosphate, ashless dispersant, glycerin monooleate, antioxidant, pour point lowering agent Additive package consisting of

As shown in Table 2 above, both (A1-a) and (A1-b) above include highly refined cracked base oil having a kinematic viscosity of less than 2.5 to 6.5 mm ² / s at 100 ° C. Lubricating oil compositions not included (Comparative Examples 2-4, 6 and 7), in particular having a kinematic viscosity of 2.5 mm ² / s or more and less than 6.5 mm ² / s at 100 ° C. and a viscosity index of 125 or more. In the lubricating oil composition (Comparative Examples 2 to 4) containing the highly refined cracked base oil (A1-a'-2) in place of the (A1-a) GTL base oil, the NOACK evaporation amount is reduced. , CCS viscosity at −35 ° C. is high and low temperature viscosity characteristics are inferior. Further, in the lubricating oil composition (Comparative Examples 1 and 5) in which the amount of the base oil (A1) is less than 40% by mass with respect to the total mass of the lubricating oil composition, the NOACK evaporation amount is large and the fuel efficiency is inferior. ..
Further, (B) the composition of Comparative Example 8 containing no metal friction modifier has a large friction coefficient, and (B) the composition of Comparative Example 9 in which the amount of the metal friction modifier is too large is inferior in cleanliness.
On the other hand, as shown in Table 1, at least one of (A1-a) and (A1-b) having a kinematic viscosity of 2.5 to 6.5 mm ² / s at 100 ° C. is added to the total mass of the lubricating oil composition. On the other hand, the lubricating oil composition of the present invention, which contains 40% by mass or more and contains a predetermined amount of a metal friction modifier, reduces the amount of NOACK evaporation, has excellent low-temperature viscosity characteristics, and is even better. Friction reduction effect and cleanliness can be ensured.

Even if the viscosity of the lubricating oil composition of the present invention is reduced, the amount of NOACK evaporation can be reduced to maintain fuel efficiency, and the lubricating oil composition is excellent in low-temperature viscosity characteristics. Therefore, the lubricating oil composition of the present invention is particularly suitable as a lubricating oil composition for an internal combustion engine.

Claims (7)

In a lubricating oil composition containing (A) a lubricating oil base oil and (B) a metal friction modifier,
The (A) lubricating oil base oil has a kinematic viscosity of 2.5 mm ² / s or more and less than 6.5 mm ² / s at 100 ° C., and (A1-a) a GTL base oil having a viscosity index of 125 or more and (A1-a). A1-b) The lubricating oil base oil (A1), which is at least one selected from the poly α-olefin base oil, is contained in an amount of 40% by mass or more and 97% by mass or less based on the total mass of the lubricating oil composition. (B) The amount of the metal friction modifier is characterized in that the concentration as a metal element with respect to the total mass of the lubricating oil composition is 200 to 600 mass ppm, and
The lubricating oil composition having a kinematic viscosity of 9.3 mm ² / s or more and less than 12.5 mm ² / s at 100 ° C. and a CCS viscosity of 6200 mPa · s or less at −35 ° C. Lubricating oil base oil (A2) having a kinematic viscosity of 6.5 mm ² / s or more and 50 mm ² / s or less at 100 ° C. is further added at 2% by mass or more and 20% by mass or less with respect to the total mass of the lubricating oil composition. The lubricating oil composition according to claim 1, which is contained. The second aspect of claim 2, wherein the lubricating oil base oil (A2) is at least one selected from a GTL base oil having a viscosity index of 125 or more (A2-a) and a poly α-olefin base oil (A2-b). Lubricating oil composition. The one according to any one of claims 1 to 3, wherein the lubricating oil composition has a high-temperature high shear viscosity (HTHS viscosity) of 2.9 mPa · s or more and less than 3.7 mPa · s at 150 ° C. Lubricating oil composition. The one according to any one of claims 1 to 4, wherein the amount of the metal friction modifier (B) is such that the concentration as a metal element with respect to the total mass of the lubricating oil composition is 250 to 550 mass ppm. Lubricating oil composition. The lubricating oil composition according to claim 1 to 5, wherein the component (B) is a molybdenum-based friction modifier. The lubricating oil composition according to any one of claims 1 to 6, which is for an internal combustion engine.