JP6235549B2 - Lubricating oil composition - Google Patents

Description

The present invention relates to a lubricating oil composition, and in particular, to a lubricating oil composition for an internal combustion engine, particularly a lubricating oil composition for a gasoline engine.

Lubricating oil compositions are widely used in the automotive field such as for internal combustion engines, automatic transmissions, and gear oils. In recent years, a reduction in viscosity has been demanded in order to improve fuel efficiency, but the oil film becomes thinner due to the reduction in viscosity, and friction cannot be reduced sufficiently. Therefore, molybdenum dithiocarbamate (MoDTC) that can reduce friction by generating molybdenum disulfide under boundary lubrication conditions has been conventionally used. Under the present circumstances, it is normal to use a calcium type detergent in combination (for example, patent document 1). However, with this combination, there is a limit to the reduction of friction, and the fuel consumption cannot be sufficiently improved.

It is also known to use a magnesium-based detergent as the detergent (for example, Patent Documents 2 and 3). The use of magnesium-based detergents can reduce friction more than calcium-based detergents, but there is a problem that wear tends to occur.

JP 2013-199594 A JP 2011-184666 A JP 2006-328265 A

An object of the present invention is to provide a lubricating oil composition capable of reducing friction while ensuring wear resistance even when the viscosity is lowered.

As a result of intensive studies, the present inventors have found that the above object can be achieved by adding a specific amount of a magnesium-based detergent and a specific amount of a molybdenum-based friction modifier to a lubricating base oil.

That is, the present invention provides a lubricating oil composition comprising a lubricating base oil, (A) a magnesium-based detergent, and (B) a molybdenum-based friction modifier, wherein the amount of the (A) component is the lubricating oil. Magnesium in mass ppm [Mg] with respect to the total amount of the composition is in the range of 200 to 1200 ppm by mass, and the amount of component (B) is 500 to 1500 in terms of mass ppm [Mo] of molybdenum with respect to the total amount of the lubricating oil composition. A lubricating oil composition characterized by being in a mass ppm range.
In particular lubricant composition of the present invention, that does not contain a calcium-based detergent.

In a preferred embodiment of the present invention, the lubricating oil composition further has at least one of the following features (1) to (7).
(1) The amount of the component (A) is in the range of 300 to 800 ppm by mass as the amount of magnesium in the lubricating oil composition.
(2) The quantity of (B) component is the range of 600-1200 mass ppm as molybdenum quantity in a lubricating oil composition.
(3) [Mg] / [Mo] ≦ 2.4 is satisfied.
(4) A calcium-based detergent (A ′) is further included, and ([Mg] + [Ca]) / [Mo] <3.0 ([Ca] is the concentration in terms of ppm by mass of calcium in the lubricating oil composition) Meet).
(5) The CCS viscosity at −35 ° C. is 6.2 Pa · s or less.
(6) The high temperature high shear viscosity (HTHS viscosity) at 150 ° C. is 1.7 to 2.9 mPa · s.
(7) The kinematic viscosity at 100 ° C. is less than 9.3 mm ² / s.
(8) For internal combustion engines.
Furthermore, the present invention relates to a method for reducing friction while maintaining low wear by using the lubricating oil composition or the lubricating oil composition of the above embodiments (1) to (8).

The lubricating oil composition of the present invention can reduce friction while ensuring wear resistance even when the viscosity is lowered, and can be suitably used particularly as a lubricating oil composition for an internal combustion engine.

Lubricating base oil The lubricating base oil in the present invention is not particularly limited. Either a mineral oil or a synthetic oil may be used, and these can be used alone or in combination.

As mineral oil, for example, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil is subjected to solvent removal, solvent extraction, hydrocracking, solvent dewaxing, and hydrogen removal. Refined by one or more treatments such as hydrorefining, wax isomerized mineral oil, GTL (Gas to Liquid) base oil, ATL (Asphalt to Liquid) base oil, vegetable oil base oil or a mixture thereof Mention may be made of base oils.

Synthetic oils include, for example, polybutene or hydrides thereof; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; 2-ethylhexyl laurate, 2-ethylhexyl palmitate, stearic acid 2- Monoesters such as ethylhexyl; diesters such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; neopentyl glycol di-2-ethylhexanoate, neopentyl Glycol di-n-octanoate, neopentyl glycol di-n-decanoate, trimethylolpropane tri-n-octanoate, trimethylolpropane tri-n-decanoate, pentaerythritol tetra Examples include polyol esters such as n-pentanoate, pentaerythritol tetra-n-hexanoate, and pentaerythritol tetra-2-ethylhexanoate; aromatic synthetic oils such as alkylnaphthalene, alkylbenzene, and aromatic esters, or mixtures thereof. .

The kinematic viscosity (mm ² / s) at 100 ° C. of the lubricating base oil is not particularly limited, but is preferably ² to 15 mm ² / s, more preferably 3 to 10 mm ² / s, and still more preferably 3 to 3 mm ² / s. 8 mm ² / s, most preferably 3 to 6 mm ² / s. As a result, it is possible to obtain a lubricating oil composition that has sufficient oil film formation, excellent lubricity, and low evaporation loss.

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

(A) Magnesium-based detergent The magnesium-based detergent is not particularly limited, and conventional ones can be used. Examples include magnesium sulfonate, magnesium phenate, and magnesium salicylate. Among these, magnesium salicylate or magnesium sulfonate is particularly preferable. A magnesium type detergent may be used individually by 1 type, and may mix and use 2 or more types.

By containing the component (A), it is possible to ensure high-temperature cleanliness and rust prevention necessary as a lubricating oil. Also, friction can be reduced and thus torque can be reduced. This is particularly advantageous in terms of fuel consumption characteristics.

In the component (A), the concentration [Mg] of magnesium in the lubricating oil composition in terms of mass ppm is in the range of 200 to 1200 mass ppm, preferably 250 to 1000 mass ppm, more preferably 300 to 800 mass ppm. In small amounts. When the amount of the component (A) exceeds the upper limit, wear becomes excessive, and when the amount is lower than the lower limit, the friction reducing effect is low.

The amount of component (A) is preferably the following formula (1):
[Mg] / [Mo] ≦ 2.4 (1)
([Mo] indicates the concentration by mass ppm of molybdenum in the lubricating oil composition). The value of [Mg] / [Mo] is more preferably 2.0 or less, still more preferably 1.8 or less, and even more preferably 1.5 or less. If the value is greater than 2.4, wear may be excessive. The lower limit of [Mg] / [Mo] is preferably 0.1, more preferably 0.2, and still more preferably 0.3.

The lubricating oil composition of the present invention may contain a calcium-based detergent (A ′) described later as a metal detergent other than the magnesium-based detergent (A). By containing a calcium-based detergent, it is possible to further ensure high-temperature cleanliness and rust prevention necessary as a lubricating oil.

The component (A ′) is preferably added in an amount that satisfies the following formula (2).
([Mg] + [Ca]) / [Mo] <3.0 (2)
Here, [Ca] indicates the concentration by mass ppm of calcium in the lubricating oil composition. The value of ([Mg] + [Ca]) / [Mo] is more preferably less than 2.8, even more preferably less than 2.6, and particularly preferably less than 2.5. If the value exceeds the upper limit, the torque reduction effect may be low. The lower limit of ([Mg] + [Ca]) / [Mo] is preferably 0.2 or more, more preferably 0.5, and even more preferably 1.0.

The magnesium-based detergent (A) is particularly preferably an overbased magnesium-based detergent. Thereby, the acid neutralization property required for lubricating oil is securable. When an overbased magnesium detergent is used, a neutral magnesium or calcium detergent may be mixed.

The total base number of the magnesium-based detergent (A) 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. Thereby, the acid neutralization property, high temperature cleanliness, and rust prevention property which are required for lubricating oil are securable. In addition, when using it, mixing 2 or more types of metal detergents, it is preferable that the base number obtained by mixing becomes said range.

The magnesium content in the magnesium-based detergent (A) is preferably 0.5 to 20% by mass, more preferably 1 to 16% by mass, and most preferably 2 to 14% by mass. What is necessary is just to add so that magnesium of the quantity of the said range may be contained in a thing.

A calcium type detergent (A ') is not specifically limited, A conventional thing can be used. Examples include calcium sulfonate, calcium phenate, and calcium salicylate. These calcium-based detergents may be used alone or in combination of two or more.

The calcium-based detergent (A ′) is preferably an overbased calcium-based detergent. Thereby, the acid neutralization property required for lubricating oil is securable. When using an overbased calcium detergent, a neutral calcium detergent may be used in combination.

The total base number of the calcium detergent (A ′) 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. Thereby, the acid neutralization property, high temperature cleanliness, and rust prevention property which are required for lubricating oil are securable. In addition, when mixing and using 2 or more types of metal detergents, it is preferable that the base number obtained by mixing becomes in the said range.

The calcium content in the calcium detergent (A ′) is preferably 0.5 to 20% by mass, more preferably 1 to 16% by mass, and most preferably 2 to 14% by mass.

The amount of magnesium and calcium in the lubricating oil composition of the present invention preferably satisfies the following formula (3).
{[Mg] / ([Mg] + [Ca])} * 100 ≧ 5 (3)
The value of {[Mg] / ([Mg] + [Ca])} * 100 is more preferably 10 or more, and even more preferably 15 or more. If the value is less than the 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 still more preferably 50.

The lubricating oil composition of the present invention may contain a sodium-based detergent as a metal detergent other than those described above as long as the effects of the present invention are not impaired. As the sodium-based detergent, sodium sulfonate, sodium phenate and sodium salicylate are preferable. One of these sodium-based detergents may be used alone, or two or more thereof may be mixed and used. By including a sodium-based detergent, it is possible to ensure the high-temperature cleanability and rust prevention necessary as a lubricating oil. Sodium-based detergents can be used in admixture with the magnesium-based detergents described above and optional calcium-based detergents.

The total amount of the metal detergent in the lubricating oil composition of the present invention may be an amount such that the amount of magnesium contained in the composition satisfies the specific range described above. Accordingly, the amount of calcium detergent added can be limited.

(B) Molybdenum friction modifier The molybdenum friction modifier is not particularly limited, and conventionally known ones can be used. 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 sulfides and sulfurized molybdenum acids. And a complex of a sulfur-containing molybdenum compound and an alkenyl succinimide. Examples of the molybdenum compounds include molybdenum oxides such as molybdenum dioxide and molybdenum trioxide, molybdenum acids such as orthomolybdic acid, paramolybdic acid and (poly) sulfurized molybdic acid, and molybdenum such as metal salts and ammonium salts of these molybdic acids. Examples thereof include molybdenum sulfides such as acid salts, molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide and polysulfide molybdenum, molybdenum sulfides, metal salts or amine salts of molybdenum sulfides, and molybdenum halides such as molybdenum chloride. Examples of the sulfur-containing organic compound include alkyl (thio) xanthate, thiadiazole, mercaptothiadiazole, thiocarbonate, tetrahydrocarbyl thiuram disulfide, bis (di (thio) hydrocarbyl dithiophosphonate) disulfide, and organic (poly) sulfide. And sulfurized esters. 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 general formulas [I] and [II], R _{1 to} R ₈ may be the same as or different from each other, and are monovalent hydrocarbon groups having 1 to 30 carbon atoms. The hydrocarbon group may be linear or branched. Examples of the monovalent hydrocarbon group include 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; and an aryl having 6 to 30 carbon atoms. A group, an alkylaryl group or an arylalkyl group. 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. A tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, and the like, and branched alkyl groups thereof. Particularly, an alkyl group having 3 to 8 carbon atoms is preferable. 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 component (B), an organic molybdenum compound containing no sulfur can also be used. Examples of such compounds include molybdenum-amine complexes, molybdenum-succinimide complexes, molybdenum salts of organic acids, and molybdenum salts of alcohols.

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

The component (B) is added in such an amount that the concentration [Mo] of molybdenum in the lubricating oil composition as ppm is in the range of 500 to 1500 mass ppm, preferably 600 to 1200 mass ppm. When the amount of the component (B) exceeds the above upper limit, the cleanliness may be deteriorated, and when it is less than the above lower limit, the friction may not be sufficiently reduced or the cleanliness may be deteriorated. is there.

As described above for the component (A), the amount of the component (B) is preferably the following formula (1):
[Mg] / [Mo] ≦ 2.4 (1)
Meet. The value of [Mg] / [Mo] is more preferably 2.0 or less, still more preferably 1.8 or less, and even more preferably 1.5 or less. The lower limit of [Mg] / [Mo] is preferably 0.1, more preferably 0.2, and still more preferably 0.3.

The lubricating oil composition of the present invention comprises the above-mentioned lubricating base oil, component (A) and component (B) as essential components. As optional components, conventionally known antiwear agents, ashless dispersants and viscosity index improvers are used. May be included.

A conventionally well-known thing can be used as said abrasion inhibitor. Among these, a wear inhibitor having phosphorus is preferable, and zinc dithiophosphate (ZnDTP (also referred to as ZDDP)) represented by the following formula is particularly preferable.

上記式において、Ｒ^１及びＲ^２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。Ｒ^１及びＲ^２は、好ましくは炭素数２〜１２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、炭素数８〜１８のアルキルアリール基であり、各々、互いに同一であっても異なっていてもよい。特にはジアルキルジチオリン酸亜鉛が好ましく、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である。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である。上記ジチオリン酸亜鉛は１種を単独で使用してもよく、２種以上を混合して使用してもよい。また、ジチオカルバミン酸亜鉛（ＺｎＤＴＣ）を組合せて使用してもよい。

In the above formula, R ¹ and R ² may be the same as or different from each other, and are each a hydrogen atom or a monovalent hydrocarbon group 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 A hydrocarbon group containing an aryl group, an alkylaryl group or an arylalkyl group of formula 6 to 26; or an ester bond, an ether bond, an alcohol group or a carboxyl group. R ¹ and R ² are preferably a primary or secondary alkyl group having 2 to 12 carbon atoms, a cycloalkyl group having 8 to 18 carbon atoms, and an alkylaryl group having 8 to 18 carbon atoms, They may be the same or different. In particular, zinc dialkyldithiophosphate is preferable, and the primary alkyl group preferably has 3 to 12 carbon atoms, more preferably 4 to 10 carbon atoms. The secondary alkyl group preferably has 3 to 12 carbon atoms, more preferably 3 to 10 carbon atoms. The said zinc dithiophosphate may be used individually by 1 type, and may mix and use 2 or more types. Further, zinc dithiocarbamate (ZnDTC) may be used in combination.

Also, at least one compound selected from phosphates represented by the following formulas (4) and (5), phosphite-based phosphorus compounds, and metal salts and amine salts thereof can be used.

上記一般式（４）中、Ｒ^３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、ｍは０又は１である。

In the general formula (4), R ³ is a monovalent hydrocarbon group having 1 to 30 carbon atoms, and R ⁴ and R ⁵ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 30 carbon atoms. And m is 0 or 1.

上記一般式（５）中、Ｒ^６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、ｎは０又は１である。

In the general formula (5), R ⁶ is a monovalent hydrocarbon group having 1 to 30 carbon atoms, and R ⁷ and R ⁸ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 30 carbon atoms. , N is 0 or 1.

In the general formulas (4) and (5), examples of the monovalent hydrocarbon group having 1 to 30 carbon atoms represented by R ^{3 to} R ⁸ include an alkyl group, a cycloalkyl group, an alkenyl group, and an alkyl-substituted cyclo Mention may be made of alkyl groups, aryl groups, alkyl-substituted aryl groups, and arylalkyl groups. In particular, an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 24 carbon atoms is preferable, more preferably an alkyl group having 3 to 18 carbon atoms, and most preferably an alkyl group having 4 to 15 carbon atoms. It is.

Examples of the phosphorus compound represented by the general formula (4) include phosphorous acid monoester and (hydrocarbyl) phosphonous acid having one hydrocarbon group having 1 to 30 carbon atoms; A phosphite diester having two hydrocarbon groups, a monothiophosphite diester, and a (hydrocarbyl) phosphonous monoester; a phosphite triester having three hydrocarbon groups having 1 to 30 carbon atoms, and (Hydrocarbyl) phosphonous acid diesters; and mixtures thereof.

The metal salt or amine salt of the phosphorus compound represented by the general formula (4) or (5) is a metal oxide, metal hydroxide, phosphorus compound represented by the general formula (4) or (5), Remains after acting with metal base such as metal carbonate, metal chloride, ammonia, nitrogen compound such as amine compound having only 1-30 hydrocarbon group or hydroxyl group-containing hydrocarbon group in the molecule. It can be obtained by neutralizing part or all of the acidic hydrogen. Examples of the metal in the 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, excluding molybdenum). Among these, alkaline earth metals such as calcium and magnesium and zinc are preferable, and zinc is particularly preferable.

The antiwear agent is usually blended in the lubricating oil composition at 0.1 to 5.0 mass%, preferably 0.2 to 3.0 mass%.

Examples of the ashless dispersant include nitrogen-containing compounds having at least one linear or branched alkyl group or alkenyl group having 40 to 500 carbon atoms, preferably 60 to 350, or derivatives thereof, and Mannich dispersants. Or a mono- or bissuccinimide (for example, alkenyl succinimide), an alkyl group having 40 to 500 carbon atoms or a benzylamine having at least one alkenyl group in the molecule, or an alkyl group or alkenyl group having 40 to 400 carbon atoms And polyamines having at least one in the molecule, or modified products of these compounds with boron compounds, carboxylic acids, phosphoric acids, and the like. One type or two or more types arbitrarily selected from these can be blended. In particular, alkenyl succinimide is preferably contained.

The method for producing the succinimide is not particularly limited. For example, an alkyl succinic acid or alkenyl succinic acid obtained by reacting a compound having an alkyl group or alkenyl group having 40 to 500 carbon atoms with maleic anhydride at 100 to 200 ° C. It is obtained by reacting an acid with a polyamine. Here, examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. Examples of the derivative of the nitrogen-containing compound exemplified as the above ashless dispersant include, for example, monocarboxylic acids such as fatty acids, oxalic acid, phthalic acid, trimellitic acid, pyromellitic to the above-mentioned nitrogen-containing compound having 1 to 30 carbon atoms. C2-30 polycarboxylic acids such as acids or their anhydrides, or ester compounds, alkylene oxides having 2-6 carbon atoms, hydroxy (poly) oxyalkylene carbonate, and the remaining amino group and / or Modified compounds by so-called oxygen-containing organic compounds, in which some or all of the imino groups are neutralized or amidated; one of the remaining amino groups and / or imino groups by reacting boric acid with the nitrogen-containing compounds described above A so-called boron-modified compound obtained by neutralizing a part or the whole or amidated; A so-called phosphoric acid-modified compound obtained by neutralizing or amidating part or all of the amino group and / or imino group; a sulfur-modified compound obtained by allowing a sulfur compound to act on the nitrogen-containing compound described above; and the nitrogen-containing compound described above And modified compounds in which two or more kinds of modifications selected from modification with oxygen-containing organic compounds, boron modification, phosphoric acid modification, and sulfur modification are combined. Among these derivatives, a boric acid-modified compound of alkenyl succinimide, particularly a boric acid-modified compound of bis-type alkenyl succinimide, can further improve heat resistance when used in combination with the above base oil.

The amount of the ashless dispersant is 20% by mass or less, preferably 15% by mass or less, more preferably 5% by mass or less, based on the total amount of the composition. Further, as an ashless dispersant, a boron-containing ashless dispersant may be used by mixing with an ashless dispersant not containing boron. In addition, when using a boron-containing ashless dispersant, the content ratio is not particularly limited, but the amount of boron contained in the composition is preferably 0.001 to 0.2% by mass based on the total amount of the composition, More preferably, it is 0.003-0.1 mass%, Most preferably, it is 0.005-0.05 mass%.

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 preferably 15000 or less. . If the number average molecular weight of the ashless dispersant is less than the above lower limit, dispersibility may not be sufficient. On the other hand, when the number average molecular weight of the ashless dispersant exceeds the above upper limit, the viscosity is too high, the fluidity becomes insufficient, and the deposit increases.

Examples of the viscosity index improver include polymethacrylate, dispersed polymethacrylate, olefin copolymer (polyisobutylene, ethylene-propylene copolymer), dispersed olefin copolymer, polyalkylstyrene, styrene-butadiene hydrogenated copolymer. Styrene-maleic anhydride copolymer, star-like isoprene, and the like. Further, a comb 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 may be used.

Viscosity index improvers usually consist of the polymer and diluent oil. The content of the viscosity index improver is preferably 0.01 to 20% by mass, more preferably 0.02 to 10% by mass, most preferably 0.05 to 5% by mass as a polymer amount based on the total amount of the composition. %. If the content of the viscosity index improver is less than the lower limit, the viscosity temperature characteristics and the low temperature viscosity characteristics may be deteriorated. On the other hand, if it exceeds the upper limit, the viscosity temperature characteristics and the low temperature viscosity characteristics may be deteriorated, and the product cost will be significantly increased.

The lubricating oil composition of the present invention can 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 component (B), corrosion inhibitors, rust inhibitors, flow Examples thereof include additives such as point depressants, demulsifiers, metal deactivators and antifoaming agents.

Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants such as copper and molybdenum. For example, as the phenol-based ashless antioxidant, 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert-butylphenol), isooctyl- 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and the like, and amine-based ashless antioxidants include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, dialkyldiphenylamine and the like. It is done. Antioxidant is normally mix | blended with a lubricating oil composition at 0.1-5 mass%.

Examples of the friction modifier other than the component (B) include esters, amines, amides, and sulfurized esters. The said friction modifier is normally mix | blended with a lubricating oil composition at 0.01-3 mass%.

Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds. Examples of the rust inhibitor include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester. A corrosion inhibitor is normally mix | blended with a lubricating oil composition at 0.01-5 mass%.

As the pour point depressant, for example, a polymethacrylate polymer compatible with the lubricating base oil to be used can be used. The pour point depressant is usually placed in the lubricating oil composition at 0.01 to 3% by weight.

Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl naphthyl ether, and the like. A demulsifier is normally mix | blended with a lubricating oil composition at 0.01-5 mass%.

Examples of the metal deactivator include imidazoline, pyrimidine derivatives, alkylthiadiazole, mercaptobenzothiazole, benzotriazole or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5- Examples thereof include bisdialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, β- (o-carboxybenzylthio) propiononitrile. A metal deactivator is normally mix | blended with a lubricating oil composition at 0.01-3 mass%.

Examples of the antifoaming agent include silicone oils having a kinematic viscosity at 25 ° C. of 1000 to 100,000 mm ² / s, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long chain fatty acids, methyl salicylates and o. -Hydroxybenzyl alcohol etc. are mentioned. An antifoamer is normally mix | blended with a lubricating oil composition at 0.001-1 mass%.

As other additives, alkali borate additives can be added. An alkali borate-based additive contains an alkali metal borate hydrate and can be represented by the following general formula.
M ₂ O · xB ₂ O ₃ · yH ₂ O
In the above formula, M is an alkali metal, x is 2.5 to 4.5, and y is 1.0 to 4.8.
Specific examples include lithium borate hydrate, sodium borate hydrate, potassium borate hydrate, rubidium borate hydrate, cesium borate hydrate, and the like. Hydrates and sodium borate hydrate are preferable, and potassium borate hydrate is particularly preferable. The average particle size of the alkali metal borate hydrate particles is generally 1 micron (μ) or less. In the alkali metal borate hydrate used in the present invention, the ratio of boron to alkali metal is preferably in the range of about 2.5: 1 to 4.5: 1. The addition amount of the alkali borate-based additive is 0.002 to 0.05% by mass as a boron amount based on the total amount of the lubricating oil composition.

The CCS viscosity at −35 ° C. of the lubricating oil composition of the present invention is not limited, but is preferably 6.2 Pa. s or less, more preferably 5.0 Pa.s. s or less, more preferably 4.0 Pa.s. s or less, most preferably 3.5 Pa.s. s or less.

In the lubricating oil composition of the present invention, the amount of molybdenum contained in the lubricating oil composition and the CCS viscosity at −35 ° C. preferably satisfy the following formula (6).
[CCS viscosity] / [Mo] ≦ 0.01 (6)
([CCS viscosity] indicates the value (Pa · s) of the CCS viscosity at −35 ° C. of the lubricating oil composition, and [Mo] indicates the concentration in terms of ppm by mass of molybdenum in the lubricating oil composition.)
The value of [CCS viscosity] / [Mo] is more preferably 0.008 or less, and still more preferably 0.005 or less. If the above value exceeds 0.01, the torque reduction rate may be reduced or the cleanliness may be deteriorated. The lower limit value of [CCS viscosity] / [Mo] is not limited, but is preferably 0.002 and more preferably 0.003.

The high temperature high shear viscosity (HTHS viscosity) at 150 ° C. of the lubricating oil composition of the present invention is not limited, but is preferably 1.7 to 2.9 mPa.s, more preferably 2.0 to 2.6 mPa.s. is there.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is not limited, but is preferably less than 9.3 mm ² / s, more preferably less than 8.2 mm ² / s.

The lubricating oil composition of the present invention has sufficient frictional characteristics and wear characteristics even when the viscosity is low, and has an effect of obtaining a high torque reduction rate, and can be suitably used for an internal combustion engine. .

EXAMPLES Hereinafter, although this invention is shown in detail by an Example and a comparative example, this invention is not limited to the following Example.

The materials used in Examples and Comparative Examples are as follows.
Lubricating oil base oil Lubricating oil base oil: Fischer-Tropsch derived base oil, kinematic viscosity at 100 ° C. = 4.1 mm ² / s, VI = 127

Magnesium detergent (A)
Magnesium-based detergent 1: Magnesium salicylate (total base number 340 mgKOH / g, magnesium content 7.5% by mass)
Magnesium detergent 2: Magnesium sulfonate (total base number 400 mgKOH / g, magnesium content 9.0% by mass)

Calcium detergent (A ')
Calcium detergent 1: Calcium salicylate (total base number 350 mgKOH / g, calcium content 12.0% by mass)
Calcium-based detergent 2: calcium salicylate (total base number 220 mgKOH / g, calcium content 8.0% by mass)

Molybdenum friction modifier (B)
Molybdenum friction modifier: MoDTC (molybdenum content 10% by mass)

Antiwear agent Antiwear agent 1: pri-ZnDTP (primary alkyl type)
Antiwear agent 2: sec-ZnDTP (secondary alkyl type)

Other additives <br/> Antioxidant: Phenolic antioxidant Ashless dispersant: Succinimide viscosity index improver: Polymethacrylate antifoaming agent: Dimethyl silicone

Examples 1-8 and Comparative Examples 1-6
Lubricating oil compositions were prepared by mixing the components in the amounts shown in Table 1. The amounts of magnesium-based detergent, calcium-based detergent and molybdenum-based friction modifier are shown in ppm by mass with respect to the total amount of the lubricating oil composition converted to the contents of magnesium, calcium and molybdenum, respectively, and wear inhibitors and other additives are added. The amount of the agent is represented by parts by mass relative to the total amount (100 parts by mass) of the lubricating oil composition. In addition, the amount of magnesium-based detergent and calcium-based detergent was such that the total molar amount of magnesium and calcium contained in these detergents was as identical as possible in all examples and comparative examples. The following test was done about the obtained composition. The results are shown in Table 1. Examples 1 to 5, 7 and 8 are reference examples.

(1) High temperature high shear viscosity at 150 ° C. (HTHS150)
Measured according to ASTM D4683.

(2) CCS viscosity at -35 ° C (CCS viscosity)
Measured according to ASTM D5293.

(3) Kinematic viscosity at 100 ° C (KV100)
Measurement was performed at 100 ° C. in accordance with ASTM D445.

(4) Torque reduction rate Torque was measured in a motoring test using a gasoline engine using the lubricating oil compositions obtained in the examples and comparative examples as test compositions. The engine was a Toyota 2ZR-FE1.8L inline 4-cylinder engine, a torque meter was installed between the motor and the engine, and the torque at an oil temperature of 80 ° C. and an engine speed of 700 RPM was measured. Torque was measured in the same manner using a commercially available GF-50O-20 oil as a standard oil. The torque (T) of the test composition was compared with the torque (T ₀ ) of the standard oil, and the reduction rate ({(T ₀ −T) / T ₀ } × 100) (%) from the torque of the standard oil was calculated. It shows that fuel consumption is so favorable that a reduction rate is large. A reduction rate of 5.5% or more was accepted.

(5) Measured according to the shell four-ball test (ASTM D 4172) except that the shell wear scar diameter rotation speed was 1800 rpm, the load was 40 kgf, the test temperature was 90 ° C., and the test time was 30 minutes. Those having a wear scar diameter of 0.7 mm or less were regarded as acceptable.

(6) Hot tube test (evaluation of high temperature cleanliness)
The lubricating oil composition was continuously supplied at a rate of 0.3 ml / hour, air at 10 ml / second, and the temperature of the glass tube at 270 ° C. for 16 hours in a glass tube having an inner diameter of 2 mm. The lacquer adhering in the glass tube was compared with the color sample, and the score was given as 10 points for transparent and 0 points for black. The higher the score, the better the high temperature cleanliness. A score of 5.0 or higher was accepted.

As is apparent from Table 1, the lubricating oil composition of the present invention has low wear, high torque reduction rate and high temperature cleanliness despite the low kinematic viscosity at 100 ° C.

On the other hand, the compositions of Comparative Examples 1 to 3 not containing the magnesium-based detergent (A) have a low torque reduction rate, and the composition of Comparative Example 6 has a larger amount of magnesium-based detergent (A) than the upper limit of the present invention. Wear is great. Further, the compositions of Comparative Examples 4 and 5 in which the amount of the molybdenum friction modifier (B) is less than the lower limit of the present invention has a low torque reduction rate and is inferior in high temperature cleanliness.

Claims (6)

A lubricating oil composition comprising a lubricating base oil, (A) a magnesium-based detergent, and (B) a molybdenum-based friction modifier, wherein the amount of component (A) is magnesium relative to the total amount of the lubricating oil composition The mass ppm [Mg] is 200 to 1200 mass ppm, and the amount of the component (B) is 500 to 1500 mass ppm in terms of molybdenum mass ppm [Mo] with respect to the total amount of the lubricating oil composition. , lubricant compositions are free of calcium-based detergent, the lubricating oil composition. Following formula (1):
[Mg] / [Mo] ≦ 2.4 (1)
The lubricating oil composition according to claim 1, wherein: The lubricating oil composition according to claim 1, wherein the CCS viscosity at −35 ° C. is 6.2 Pa · s or less. The lubricating oil composition according to any one of claims 1 to 3 , wherein a high-temperature high-shear viscosity (HTHS viscosity) at 150 ° C is 1.7 to 2.9 mPa · s. Kinematic viscosity at 100 ° C. is less than 9.3 mm ² / s, the lubricating oil composition of any one of claims 1-4. The lubricating oil composition according to any one of claims 1 to 5 , which is used for an internal combustion engine.