JP6729866B2 - Lubricating oil composition - Google Patents

Description

The present invention relates to a lubricating oil composition having excellent fuel economy, fatigue resistance and excellent low temperature viscosity characteristics, and more specifically, an internal combustion engine capable of lubricating gears and bearings as engine oil for two wheels, transmission oil, etc. The present invention relates to a lubricating oil composition.

Due to the demand for energy saving and reduction of carbon dioxide, fuel economy is also required for lubricating oil for internal combustion engines (engine oil). Regarding engine oils used in four-wheeled vehicles, it has heretofore been attempted to reduce the viscosity and improve the viscosity index as a means for improving fuel economy. Proposals have also been made (for example, see Patent Documents 1 to 8). However, in the case of using a low-viscosity engine oil in, for example, a two-wheeled vehicle from the viewpoint of fuel economy, various problems may occur due to the difference in mechanical structure between the four-wheeled vehicle and the two-wheeled vehicle (for example, Patent Document 9). reference).

JP, 10-114895, A Japanese Patent No. 3955573 Patent No. 4359807 Japanese Patent No. 4283120 JP, 2008-208221, A JP, 2009-221382, A JP, 2010-280821, A Japanese Patent No. 5319996 JP, 2011-195734, A

That is, the two-wheeled vehicle usually has a structure in which the transmission for transmission is lubricated with the same engine oil as well as the lubrication of the engine. Therefore, for example, when engine oil having a low viscosity (for example, 10W-30 viscosity grade) is used in a two-wheeled vehicle, fatigue damage such as pitching occurs in the gears and bearings of the transmission for shifting (especially radial needle bearings in the crankshaft). The possibility increases.

Thus, for example, in a two-wheel engine oil, the gears and bearings of a transmission for transmission are also lubricated, so that in addition to lowering the viscosity of the engine oil, improving fatigue life, that is, improving fatigue resistance, is a problem. Therefore, when it is attempted to improve the fuel efficiency by lowering the viscosity of the engine oil used in the motorcycle, it is necessary to solve these problems.
An object of the present invention is to provide a lubricating oil composition that achieves both low viscosity for fuel economy and fatigue resistance for improving fatigue life, and that is excellent in low temperature viscosity characteristics.

As a result of intensive studies in view of the above problems, the present inventors have found that a low viscosity lubricating oil having a kinematic viscosity at 100° C. and a high temperature high shear viscosity (HTHS viscosity) at 150° C. in a specific range has a specific low molecular weight polymer. It was found that the above-mentioned problems of the present invention can be solved by containing the above, and the present invention has been completed.
That is, the present invention is as follows.
[1] (1) Base oil containing base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less, (2) mass average molecular weight of 40,000 or less one or more selected from acrylate-based polymers and olefinic polymers, and (3) containing an additive containing a sulfur-based extreme pressure agent, a kinematic viscosity at 100 ° C. is 9.3 mm ² / s ultra 12.5 mm ² / and a high temperature high shear viscosity at 150° C. of 2.9 mPa·s or more.
[2] The lubricating oil composition according to [1], which has a CCS viscosity at -25°C of 7,000 mPa·s or less and a viscosity index of 135 or more.

[3] The acrylate-based polymer and/or olefin-based polymer having a mass average molecular weight of 40,000 or less is obtained from at least one selected from α-olefins having 8 or more and 12 or less carbon atoms, and has a kinematic viscosity at 100° C. of 100 mm ^2. /S or more and 2,000 mm< ² >/s or less, The lubricating oil composition as described in said [1] or [2] which is a poly alpha olefin.
[4] The lubrication according to any one of the above [1] to [3], wherein a central oil film thickness in an elastohydrodynamic lubrication (EHL) oil film thickness measurement is 50 nm or more at a rolling speed of 1.6 m/s. Oil composition.
[5] The lubricating oil composition according to any one of the above [1] to [4], which has a 50% failure probability (L50) of 3.0×10 ⁶ times or more in fatigue life evaluation of radial rolling bearings.
[6] The lubricating oil composition according to any one of [1] to [5], wherein the base oil further contains a base oil having a viscosity index of more than 120.

[7] The lubricating oil composition according to any one of [1] to [6], which has a kinematic viscosity after a shear test at 100° C. of 9 mm ² /s or more.
[8] The lubricating oil composition according to any one of [1] to [7], which is for an internal combustion engine.
[9] The lubricating oil composition according to any one of [1] to [8], which is for a two-wheel internal combustion engine.

[10] (1) In a base oil containing a base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less, (2) a mass average molecular weight of 40,000. A kinematic viscosity at 100° C. is more than 9.3 mm ² /s by blending one or more selected from the following acrylate-based polymers and olefin-based polymers and (3) a lubricating oil additive containing a sulfur-based extreme pressure agent. The manufacturing method of the lubricating oil composition which manufactures the lubricating oil composition which is 0.5 mm< ² >/s or less and whose high temperature high shear viscosity in 150 degreeC is 2.9 mPa*s or more.
[11] (1) Base oil containing base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less, (2) mass average molecular weight of 40,000 or less Containing at least one selected from the acrylate-based polymers and olefin-based polymers described above, and (3) a lubricating oil additive containing a sulfur-based extreme pressure agent, and having a kinematic viscosity at 100° C. of more than 9.3 mm ² /s 12.5 mm. ^An internal combustion engine using a lubricating oil composition having a high-temperature high-shear viscosity at 150° C. of 2.9 mPa·s or more at ² /s or less.
[12] (1) A base oil containing a base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less, (2) a mass average molecular weight of 40,000 or less. Containing at least one selected from the acrylate-based polymers and olefin-based polymers described above, and (3) a lubricating oil additive containing a sulfur-based extreme pressure agent, and having a kinematic viscosity at 100° C. of more than 9.3 mm ² /s 12.5 mm. A lubricating method for an internal combustion engine lubricated using a lubricating oil composition having a high-temperature high-shear viscosity at 150° C. of ² /s or less and 2.9 mPa·s or more.

According to the present invention, it is possible to provide a lubricating oil composition having both low viscosity for fuel economy and fatigue resistance for improving fatigue life, and excellent low temperature viscosity characteristics.
Further, according to the present invention, as a lubricating oil composition for a two-wheel internal combustion engine, it is possible to provide a lubricating oil composition capable of lubricating both an engine and a transmission for shifting.

Hereinafter, the present invention will be described in more detail.
The lubricating oil composition of the present invention comprises (1) a base oil containing a base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less, and a viscosity index of 120 or less; Contains at least one selected from acrylate polymers and olefin polymers having a molecular weight of 40,000 or less, and (3) an additive containing a sulfur extreme pressure agent, and has a kinematic viscosity at 100° C. of more than 9.3 mm ² /s. It is 12.5 mm ² /s or less, and the high temperature high shear viscosity at 150° C. (hereinafter referred to as “HTHS viscosity”) is 2.9 mPa·s or more.

[(1) Base oil]
The base oil used in the lubricating oil composition of the present invention contains base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less. As the base oil that can be used in the low-viscosity lubricating oil, a high-quality one having a high viscosity index has hitherto been used, but in the present invention, a relatively low-quality base oil having a low viscosity index is also used. Can be used. That is, as the base oil A, those having a kinematic viscosity at 100° C. of 3 mm ² /s or more and 6 mm ² /s or less and a viscosity index of 110 or less can be preferably used from the viewpoint of lowering the viscosity and reducing the cost. Specifically, mineral base oils belonging to Group I and Group II in the API (American Petroleum Institute) base oil category can also be used.
The viscosity index of the base oil and the kinematic viscosity at 100°C can be measured according to JIS K 2283 (ASTM D445).

From the above viewpoints, the base oil in the lubricating oil composition of the present invention preferably contains 70% by mass or more, more preferably 80% by mass or more, and further preferably 100% by mass of the base oil A.
Further, it is optional to use other base oil in addition to the base oil A in the base oil of the present invention. The base oil that can be used is not particularly limited, but a base oil having a viscosity index of more than 120 can be used from the viewpoint of low-temperature viscosity characteristics as long as the effect of the present invention is not impaired. Specifically, mineral oils or synthetic base oils belonging to Group III in the API base oil category can be used, and such base oils are preferably contained in the base oil of the present invention in an amount of less than 30% by mass.
The properties of the base oil containing the base oil A, which is the base oil in the lubricating oil composition of the present invention, are not particularly limited as long as they satisfy the properties specified for the resulting lubricating oil composition.

In the present invention, as the mineral oil-based base oil, for example, crude oil is subjected to atmospheric distillation, or atmospheric residual oil obtained by atmospheric distillation is subjected to solvent distillation to obtain a lubricating oil fraction obtained by vacuum distillation. Refining, solvent extraction, hydrocracking, solvent dewaxing, hydrorefining, and other refinements, or mineral oil wax or wax produced by the Fischer-Tropish process (gas liquid wax) Examples include base oils produced by isomerizing
On the other hand, examples of the synthetic oil include poly-α-olefin, polybutene, polyol ester, dibasic acid ester, aromatic ester, phosphoric acid ester, polyphenyl ether, alkylbenzene, alkylnaphthalene, polyoxyalkylene glycol, neopentyl glycol. , Silicone oil, trimethylolpropane, pentaerythritol, hindered ester and the like can be used.

[(2) Acrylate-based polymer and olefin-based polymer]
The lubricating oil composition of the present invention is one or more kinds selected from acrylate-based polymers and olefin-based polymers having a weight average molecular weight of 40,000 or less, from the viewpoint of improving fatigue resistance, especially in radial needle fatigue life, to extend the life. Contains.
Examples of the acrylate-based polymer having a mass average molecular weight of 40,000 or less include polymethacrylate (PMA), and the polymethacrylate can be used in either a dispersion type or a non-dispersion type. Specifically, so-called non-dispersed polymethacrylates such as copolymers and hydrides thereof relating to various methacrylic acid esters or any combination thereof, and various methacrylic acid esters containing a nitrogen compound are copolymerized, so-called Dispersion type polymethacrylate etc. can be illustrated. These polymethacrylates may be used alone or in combination of two or more.

Examples of the olefin-based polymer having a mass average molecular weight of 40,000 or less include α-olefin homopolymers or copolymers, ethylene-α-olefin copolymers, and polybutene. Among them, the α-olefin homopolymers and copolymers preferably have 2 to 30 carbon atoms, more preferably 4 to 22 carbon atoms, still more preferably 6 to 16 carbon atoms, and even more preferably 6 to 6 carbon atoms. 14, particularly preferably 8 to 12 α-olefin homopolymers and copolymers, which may be random or block.

Examples of the α-olefin that can be used include ethylene, propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-undecene, 1-dodecene. , 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene and the like, and α-olefins having 2 to 30 carbon atoms.
Further, the ethylene-α-olefin copolymer includes a copolymer of ethylene and α-olefin, and the α-olefin used in propylene or the homopolymer and copolymer of the α-olefin. The same ones are used. The ethylene-α-olefin copolymer may be random.
These olefin polymers may be used alone or in combination of two or more.

These olefin-based polymers can be produced by any method. For example, it can be produced by thermal reaction without a catalyst, and an organic peroxide catalyst such as benzoyl peroxide; aluminum chloride, aluminum chloride-polyhydric alcohol system, aluminum chloride-titanium tetrachloride system, aluminum chloride-alkyltin. Friedel-Crafts type catalysts such as halide type and boron fluoride; Ziegler type catalysts such as organic aluminum chloride-titanium tetrachloride type, organic aluminum-titanium tetrachloride type; metallocenes such as aluminoxane-zirconocene type, ionic compound-zirconocene type Type catalyst: It can be produced by homopolymerizing or copolymerizing an olefin using a known catalyst system such as a Lewis acid complex type catalyst such as aluminum chloride-base system or boron fluoride-base system. In the present invention, the above-mentioned olefin-based polymer can be used, but in consideration of its thermal and oxidation stability, a hydride of the olefin-based polymer obtained by hydrogenating the double bond in the olefin-based polymer may also be used. it can.

Among the above (2) acrylate-based polymers and olefin-based polymers, in the present invention, from the viewpoint of fatigue resistance, olefin-based polymers are preferably used, and lower viscosity and improved fatigue resistance, and low viscosity characteristics From the viewpoint of improvement, a poly α-olefin obtained from at least one selected from α-olefins having 8 to 12 carbon atoms and having a kinematic viscosity at 100° C. of 100 mm ² /s or more and 2,000 mm ² /s or less. (Hereinafter referred to as “high viscosity PAO”) is used.

The carbon number of α-olefin, which is a raw material monomer for high-viscosity PAO, is preferably 8 or more and 12 or less, more preferably 9 or more and 11 or less, from the viewpoint of improvement in fatigue resistance, workability, adaptability to lubricating oil, and the like. And more preferably 10. Specifically, among the α-olefins, those having 8 to 12 carbon atoms are used. Further, the kinematic viscosity of the high-viscosity PAO at 100° C. is preferably 100 mm ² /s or more and 1800 mm ² /s or less from the viewpoint of excellent viscosity index improving ability, good fluidity and excellent fatigue resistance. , More preferably 100 mm ² /s or more and 1,500 mm ² /s or less, and further preferably 200 mm ² /s or more and 1,000 mm ² /s or less.
The kinematic viscosity of high viscosity PAO at 100°C can be measured according to JIS K 2283 (ASTM D445).

In the present invention, as the high-viscosity PAO, those having at least one of the following composition (I) and properties (II) from the viewpoint of lowering viscosity, fatigue resistance, and low-temperature viscosity characteristics, and/or the following production The product obtained by the method (III) can be more preferably used.
(I) In the high viscosity PAO, the proportion of the dimer and trimer components is preferably less than 2% by mass, more preferably less than 1.5% by mass, and less than 1.0% by mass. Is more preferable. As a result, the high-viscosity PAO has a small molecular weight distribution, a more uniform composition, and a polymer having a desired viscosity range can be obtained. In addition, since it has almost no performance-reducing component, it is useful as a lubricating oil component. The proportions of the dimer and trimer components can be controlled by the polymerization conditions, and can be determined using gas chromatography.

(II) The high-viscosity PAO preferably has at least one of the following four properties from the viewpoints of lowering viscosity, fatigue resistance, and low-temperature viscosity property.
(II-1) Amorphous, (II-2) Viscosity index is 150 or more, (II-3) Pour point is -15°C or less, (II-4) Average carbon number is 4 or more. It is 15 or less.
The higher the viscosity index, the smaller the temperature dependence and the better the low-temperature characteristics. Therefore, the viscosity index of high-viscosity PAO is more preferably 170 or more. Further, the lower the low temperature pour point, the better the low temperature characteristics. Therefore, the pour point of the high viscosity PAO is more preferably -20°C or lower, and further preferably -30°C or lower. Furthermore, it is more preferable that the high-viscosity PAO has an average carbon number of 8 or more and 12 or less.
The term "amorphous" as used herein is generally amorphous because it has no melting point but only a glass transition temperature, has transparency, and has little change in volume upon cooling and solidification. It is meant to have the characteristics that appear in some cases. The viscosity index of high viscosity PAO can be measured according to JIS K 2283 (ASTM D445), the pour point can be measured according to JIS K 2269, and the average carbon number can be measured by NMR measurement.

(III) The high-viscosity PAO described above is preferably produced, for example, according to the method described in International Publication WO2012/035710.
That is, specifically, the high-viscosity PAO is a compound capable of reacting with the meso-type transition metal compound (A) and the (B-1) transition metal compound (A) or a derivative thereof to form an ionic complex. , And (B-2) at least one compound (B) of the aluminoxane and an organoaluminum compound (C) are used for the polymerization, and one of the α-olefins is used alone, or two or more of them are used. It can be obtained by polymerizing a mixture of

For the meso-type transition metal compound (A), refer to paragraphs [0036] to [0063] of International Publication WO2012/035710, and for the compound (B), refer to paragraphs [0065] to [0075] of the pamphlet. The organoaluminum compound (C) is described in paragraphs [0077] and [0078] of the pamphlet, and the obtained polymerization catalyst is described in paragraphs [0076] and [0079] to [0089] of the pamphlet. Each one can be used.

Specifically, the polymerization catalyst is preferably (1,1′-ethylene)(2,2′-tetramethyldisilirene)-bis(indenyl)zirconium dichloride, (1,1′-tetramethylenediene). Silylene)(2,2'-ethylene)-bis(indenyl)zirconium dichloride, (1,1'-tetramethylethylene)(2,2'-tetramethyldisilylene)-bis(indenyl)zirconium dichloride, (1, 1'-tetramethylene disilylene)(2,2'-tetramethylethylene)-bis(indenyl)zirconium dichloride, (1,1'-dimethylethylsilylene methylene)(2,2'-ethylene)-bis(3- Methylindenyl)zirconium dichloride, (1,1′-ethylene)(2,2′-dimethylylylenemethylene)-bis(3-methylindenyl)zirconium dichloride, (1,1′-ethylene)(2,2 '-Tetramethyldigermylene)-bis(indenyl)zirconium dichloride, (1,1'-Tetramethyldigermylene)(2,2'-ethylene)-bis(indenyl)zirconium dichloride,

(1,1′-Ethylene)(2,2′-tetramethyldisilylene)-bis(3-methylindenyl)zirconium dichloride, (1,1′-Tetramethyldisilylene)(2,2′-ethylene) -Bis(3-methylindenyl)zirconium dichloride, (1,1'-tetramethylethylene)(2,2'-tetramethyldisilylene)-bis(3-methylindenyl)zirconium dichloride, (1,1'-Tetramethydisilylene)(2,2'-tetramethylethylene)-bis(3-methylindenyl)zirconium dichloride, (1,1'-Dimethylysilylenemethylene)(2,2'-ethylene)-bis( 3-Methylindenyl)zirconium dichloride, (1,1′-ethylene)(2,2′-dimethylylsilylenemethylene)-bis(3-methylindenyl)zirconium dichloride, (1,1′-ethylene)(2 ,2'-Tetramethyldigermylene)-bis(3-methylindenyl)zirconium dichloride, (1,1'-Tetramethyldigermylene)(2,2'-ethylene)-bis(3-methylindenyl) ) Zirconium dichloride and the like, and those obtained by substituting zirconium in these compounds with titanium or hafnium can be mentioned. Further, it may be a compound similar to a metal element of another group or a lanthanoid series.
The polymerization method is not particularly limited, but the polymerization can be performed according to the method described in paragraphs [0090] to [0095] of the pamphlet.

The molecular weight of the above (2) acrylate-based polymer and olefin-based polymer is 40,000 or less in terms of mass average molecular weight from the viewpoint of fatigue resistance for improving fatigue life, but from the same viewpoint, preferably 35, 000 or less, more preferably 30,000 or less, further preferably 25,000 or less, and particularly preferably 20,000 or less. Although the lower limit value is not particularly limited, it is preferably 5,000 or more from the viewpoints of fatigue resistance and low temperature viscosity characteristics. The mass average molecular weight can be measured by gel permeation chromatography (GPC) method and can be determined from a calibration curve prepared using polystyrene. For example, the mass average molecular weight of each polymer can be calculated as a polystyrene conversion value by the following GPC method.
<GPC measuring device>
・Column: TOSO GMHHR-H(S)HT
・Detector: RI detector for liquid chromatogram WATERS 150C
<Measurement conditions, etc.>
-Solvent: 1,2,4-trichlorobenzene-Measuring temperature: 145°C
-Flow rate: 1.0 ml/min-Sample concentration: 2.2 mg/ml-Injection amount: 160 microliters-Calibration curve: Universal Calibration
・Analysis program: HT-GPC (Ver, 1.0)

In addition, the kinematic viscosity of the above (2) acrylate-based polymer and olefin-based polymer at 100° C. is preferably 5 mm ² /s or more and 15,000 mm ² /s or less from the viewpoint of low viscosity, fatigue resistance and low temperature viscosity characteristics. , More preferably 50 mm ² /s or more and 10,000 mm ² /s or less, further preferably 100 mm ² /s or more and 10,000 mm ² /s or less, particularly preferably 100 mm ² /s or more and 5,000 mm ² /s or less. ..
Further, the viscosity index of the (2) acrylate-based polymer and olefin-based polymer is preferably 120 or more, and more preferably 150 or more. On the other hand, the viscosity index is preferably 350 or less, and more preferably 250 or less.

The above (2) acrylate-based polymer and/or olefin-based polymer is preferably contained in the lubricating oil composition of the present invention in the range of 0.1% by mass or more and less than 20% by mass based on the total amount of the composition. .. When the amount is within the above range, the obtained lubricating oil composition achieves low viscosity and improvement in fatigue resistance, and also has good low temperature viscosity characteristics. From the above viewpoint, the content of the acrylate-based polymer and/or the olefin-based polymer is more preferably 0.5% by mass or more and 20% by mass or less, and further preferably 1% by mass or more and 15% by mass, based on the total amount of the composition. It is as follows.

[(3) Lubricating oil additive containing sulfur-based extreme pressure agent]
The lubricating oil composition of the present invention contains a lubricating oil additive containing a sulfur-based extreme pressure agent together with the polymer.
Examples of the sulfur-based extreme pressure agents include zinc dithiophosphate (ZnDTP), sulfurized olefins, dialkyl polysulfides, diaryl polysulfides, zinc dithiocarbamate, disulfides, sulfurized fats and oils, sulfurized esters, thiocarbonates, and thiocarbamates. Further, thiophosphorous acid esters, thiophosphoric acid esters, thiophosphonic acid esters and the like, amine salts thereof, metal salts thereof and the like can be mentioned. The above-mentioned sulfur-based extreme pressure agents may be used alone or in combination of two or more. The content thereof is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less based on the total amount of the composition. By using the above sulfur-based extreme pressure agent, for example, in a two-wheel engine using a wet clutch, etc., it is possible to reduce friction and improve lubricity by reacting with a metal surface to form a film having a small friction coefficient. preferable.

In the lubricating oil composition of the present invention, as the other additive, any of the additives usually used as the lubricating oil additive can be used, and preferably the additive used as the lubricating oil additive for two wheels is used. Used. Specifically, extreme pressure agents other than sulfur, friction modifiers, ashless dispersants, metal detergents, antioxidants, metal deactivators, rust inhibitors, defoamers, demulsifiers and colorings. Lubricating oil additives represented by agents and the like can be used.
Examples of the extreme pressure agent other than the sulfur-based agent include phosphite esters, phosphate esters, phosphonate esters, alkyl hydrogen phosphite and amine salts thereof, or phosphorus-containing extreme pressure agents such as metal salts thereof. Can be mentioned.

In addition, the lubricating oil composition of the present invention may contain a metal-based friction modifier or an ashless friction modifier in order to improve fuel economy characteristics. Specific examples of the friction modifier include organic molybdenum compounds, fatty acids, higher alcohols, oils and fats, amides, sulfurized esters, phosphoric acid esters, phosphorous acid esters, and phosphoric acid ester amine salts. These friction modifiers can be used alone or in combination of two or more kinds, and the content thereof is usually 0.01% by mass or more and 10% by mass or less based on the total amount of the composition.

Examples of the ashless dispersant include polybutenyl succinimide having a polybutenyl group having a mass average molecular weight of 900 or more and 3500 or less, polybutenylbenzylamine, polybutenylamine, and their boric acid modified products. Examples thereof include derivatives. These ashless dispersants may be contained alone or in any combination of two or more kinds, and the content thereof is usually 0.01% by mass or more and 10% by mass or less based on the total amount of the composition.

Examples of the metal-based detergents include sulfonates, phenates, salicylates and naphthenates of alkali metals (sodium (Na), potassium (K), etc.) or alkaline earth metals (calcium (Ca), magnesium (Mg), etc.). Can be mentioned. These can be used alone or in combination of two or more kinds. The total base number and content of these metal-based detergents may be appropriately selected according to the required performance of the lubricating oil. The total base number is usually 0 mgKOH/g or more and 500 mgKOH/g or less, preferably 10 mgKOH/g or more and 400 mgKOH/g or less by the perchloric acid method. Moreover, the content thereof is usually in the range of 0.1% by mass or more and 10% by mass or less based on the total amount of the composition.

As the antioxidant, any of known antioxidants conventionally used as antioxidants for engine oils can be appropriately selected and used. Phenol-based antioxidants, amine-based antioxidants Agents, molybdenum-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants and the like can all be used. Specifically, amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine and alkylated phenyl-α-naphthylamine; 2,6-di-tert-butylphenol, 4,4′-methylenebis(2,6 -Di-tert-butylphenol), isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) Examples thereof include phenolic antioxidants such as propionate; sulfur antioxidants such as dilauryl-3,3′-thiodipropionate; phosphorus antioxidants such as phosphite; and molybdenum antioxidants. These antioxidants may be used alone or in combination of two or more. The blending amount is in the range of 0.01% by mass or more and 10% by mass or less based on the total amount of the lubricating oil composition.

Examples of the metal deactivator include benzotriazole, triazole derivatives, benzotriazole derivatives, thiadiazole derivatives, and the content thereof is usually 0.01% by mass or more and 3% by mass or less based on the total amount of the composition. is there.
Examples of the rust preventive agent include fatty acids; alkenyl succinic acid half esters; fatty acid soaps; alkyl sulfonates; sulfonates and phenates of alkaline earth metals (calcium (Ca), magnesium (Mg), barium (Ba), etc.). Salicylates and naphthenates; polyhydric alcohol fatty acid esters; fatty acid amines; oxidized paraffins; alkyl polyoxyethylene ethers, etc., and the content thereof is usually 0.01% by mass or more and 5% by mass or less based on the total amount of the composition. Is.

As the defoaming agent, liquid silicone is suitable, and for example, methyl silicone, fluorosilicone, polyacrylate and the like can be used. The preferable content of these defoaming agents is 0.0005 mass% or more and 0.1 mass% or less based on the total amount of the composition.
As the demulsifier, ethylene propylene block polymer, alkaline earth metal (calcium (Ca), magnesium (Mg), etc.) sulfonates, phenates, salicylates and naphthenates can be used, and the content thereof is usually based on the total amount of the composition. It is 0.0005 mass% or more and 1 mass% or less.
As the colorant, dyes and pigments can be used, and the content thereof is usually 0.001% by mass or more and 1% by mass or less based on the total amount of the composition.

As described above, a sulfur-based extreme pressure agent, and further, if necessary, a non-sulfur-based extreme pressure agent, a friction modifier, an antioxidant, a metal-based detergent, an ashless dispersant, and a metal inert agent. Lubricating oil compositions comprising various additives selected from agents, rust preventives, defoaming agents, demulsifiers, colorants, etc., usually contain the compounded ingredients, In some cases, at least a part of the added additives may react with each other to form another compound.

[Lubricant composition]
The lubricating oil composition of the present invention comprises: (1) a base oil containing a base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less; ) A weight-average molecular weight of 40,000 or less, an acrylate-based polymer and/or an olefin-based polymer, and a lubricating oil additive containing the above (3) sulfur-based extreme pressure agent. in is the kinematic viscosity of 9.3 mm ² / s or less ultrasonic 12.5 mm ² / s, and by the 0.99 ° C. 2.9 mPa · s or more HTHS viscosity at, fatigue and low viscosity for fuel economy It is possible to obtain a lubricating oil composition that has both fatigue resistance for improving the life and excellent low temperature viscosity characteristics.

As described above, in the lubricating oil composition of the present invention, kinematic viscosity at 100 ° C. is not more than 9.3 mm ² / s Ultra 12.5 mm ² / s, and HTHS viscosity of 2.9 mPa · s or more. The HTHS viscosity is a viscosity in a lowered state under high temperature and high shear conditions. By setting the kinematic viscosity at 100° C. and the HTHS viscosity at 150° C. in the above ranges, a 10W-30 viscosity grade low viscosity two-wheel engine oil is obtained. It is possible to use it, maintain lubricity, realize low viscosity, and contribute to fuel economy. From this point of view, the kinematic viscosity at 100 ° C. of the lubricating oil composition is preferably not more than 9.3 mm ² / s Ultra 11.0 mm ² / s, HTHS viscosity at 0.99 ° C. is a 3.0 mPa · s or more It is preferable. Here, the upper limit of the HTHS viscosity at 150° C. is not particularly limited, but is usually about 3.7 mPa·s.

The HTHS viscosity at 150° C. in the lubricating oil composition can be adjusted by selecting the viscosity of the base oil, the type, molecular weight, content, etc. of the acrylate-based polymer or olefin-based polymer or other viscosity index improver. The kinematic viscosity of the lubricating oil composition at 100°C can be measured according to JIS K 2283 (ASTM D445), and the HTHS viscosity at 150°C can be measured according to JPI-5S-36-03 (ASTM D 4683). Can be measured.

The lubricating oil composition of the present invention preferably has a low temperature viscosity (CCS viscosity at −25° C.) of 7,000 mPa·s or less and a viscosity index of 135 or more. By setting either the CCS viscosity at -25°C or the viscosity index within the above range, the lubricity can be maintained and the viscosity can be reduced, and good low temperature viscosity characteristics can be obtained, which contributes to fuel economy. You can From this viewpoint, the CCS viscosity of the lubricating oil composition at −25° C. is more preferably 6,000 mPa·s or less, further preferably 5,500 mPa·s or less, and the viscosity index is more preferably 137 or more, further It is preferably 140 or more.
The CCS viscosity at -25°C can be adjusted by selecting the viscosity of the base oil, the type, molecular weight, content, etc. of the acrylate-based polymer or olefin-based polymer or other viscosity index improver. Further, the CCS viscosity at −25° C. in the lubricating oil composition can be measured according to JIS K 2010 (ASTM D 2602), and the viscosity index can be measured according to JIS K 2283 (ASTM D 445). ..

Further, the lubricating oil composition of the present invention preferably has a kinematic viscosity after shearing at 100° C. of 9 mm ² /s or more. If the kinematic viscosity after the shear test at 100° C. is less than 9 mm ² /s, the lubricity is insufficient due to the viscosity decrease at high temperature. In view of the above, the kinematic viscosity at 100 ° C. after shearing of the lubricating oil composition of the present invention is preferably, 9.3 mm ² / s or more 11.0 mm ² / s or less.
The “viscosity after a shear test at 100° C.” in the present invention means, for example, controlling the viscosity and the like of the base oil by the molecular weight and content of the acrylate polymer or the olefin polymer and other viscosity index improvers. Can be adjusted by. The shearing method is based on JPI-5S-29 (ASTM D3945).

The lubricating oil composition of the present invention has a low viscosity for fuel economy, and from the viewpoint of providing a lubricating oil composition having excellent low temperature viscosity characteristics, a central oil film thickness in elastohydrodynamic lubrication (EHL) oil film thickness measurement. At a rolling speed of 1.6 m/s, it is preferably 50 nm or more, more preferably 55 nm or more, still more preferably 66 nm or more.
The oil film thickness is measured using an EHL ultra-thin film measurement system manufactured by PCS under the conditions of load: 20 N, temperature: 120° C., rolling speed: 0.05 to 1.6 m/s, and oil film thickness: 1 to 250 nm. be able to.

Further, from the viewpoint of providing a lubricating oil composition having excellent fatigue resistance for improving the fatigue life, the lubricating oil composition of the present invention has a 50% failure probability as a pitching life in the fatigue life of a radial rolling bearing ( L50) is preferably 3.0×10 ⁶ times or more, more preferably 4.0×10 ⁶ times or more, further preferably 5.0×10 ⁶ times or more, and particularly 6.0×10 ⁶ times or more. Is preferred.
The fatigue life evaluation can be performed using a radial type needle bearing fatigue evaluation tester manufactured by A&D Co., as a load: 3000 N, temperature: 120° C., rotation speed: 2000 rpm, bearing: radial bearing (solid needle bearing, NSK LM1710). it can.

[Internal combustion engine]
Since the lubricating oil composition of the present invention has the above-mentioned constitution and effects, it can be preferably used as a lubricating oil composition for an internal combustion engine, and in particular, it has a low viscosity for fuel saving and an improvement in fatigue life. It is suitable for lubrication of each member of the engine because it has both excellent fatigue resistance for low temperature and excellent low temperature viscosity characteristics, and for a two-wheeled vehicle having a structure in which a transmission for transmission is also lubricated with the same engine oil, that is, It can be suitably used for lubrication of a two-wheel internal combustion engine.

[Method for producing lubricating oil composition]
The present invention also provides (1) a base oil containing a base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less, (2) a mass average molecular weight of 40, 000 following acrylate polymer and / or an olefin-based polymer, and (3) by blending a lubricating oil additive containing a sulfur-based extreme pressure agent, a kinematic viscosity at 100 ° C. is 9.3 mm ² / s ultra 12.5 mm ² /S or less and an HTHS viscosity at 150° C. of 2.9 mPa·s or more, to a method for producing a lubricating oil composition.
The base oil (1), the acrylate polymer and/or the olefin polymer (2) having a mass average molecular weight of 40,000 or less, a lubricating oil additive (3) containing a sulfur extreme pressure agent, and a lubrication having the specific properties obtained. The oil composition is as described above. Regarding the method of blending the polymer (2) and the lubricating oil additive (3) with the base oil (1), as long as each component is blended so as to have a kinematic viscosity of 100° C. and an HTHS viscosity of 150° C. within the specified ranges, There is no limitation, and there is no particular limitation on the compounding order and compounding conditions.

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
[Evaluation items and methods]
Each property of the lubricating oil composition was measured by the following methods.
(1) Kinematic viscosity (40° C., 100° C.): Measured according to JIS K 2283 (ASTM D 445).
(2) Viscosity index (VI): Measured in accordance with JIS K 2283 (ASTM D 445).
(3) CCS viscosity (Cold Cracking Simulator): The viscosity at -25°C was measured according to JIS K 2010 (ASTM D 2602).

(4) HTHS viscosity (High Temperature High Shear): Measured under the following conditions in accordance with JPI-5S-36-03 (ASTM D4683).
・Apparatus: TBS high temperature viscometer (Tapered Bearing Simulator)
・Shear rate: 10 ⁶ sec ^-1
・Rotation speed (motor): 3000 rpm
・Spacing (rotor/stator): 2-3 μm
・Sample volume: 20-50 ml
・Measurement time: calibration 4-6 hours, test 15 minutes

(5) Shear test: conducted in accordance with JPI-5S-29 (ASTM D3945).
(6) Melting point: Measured with a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer Co., Ltd.).
(7) Pour point: measured according to JIS K 2269.
(8) Amount of dimer and trimer components: Measured by gas chromatography (GC).
(9) Average carbon number: Obtained from peak areas of 0.9 ppm and 1.2 ppm by NMR measurement.
(10) Fatigue life evaluation: It measured on the following conditions using the following apparatus.
-Apparatus: A&D radial needle bearing fatigue evaluation tester-Load: 3000N, temperature: 120°C, rotation speed: 2000 rpm
・Bearing: Radial bearing (solid needle bearing, NSK LM1710)
-Test conditions: 6 devices are filled with test oil, and start simultaneously under the above conditions. The time when each device exceeded the vibration limiter was recorded as the life. Weibull plot of the six data, and 10% damage probability L10 (times) and 50% damage probability L50 (times) were calculated from the approximate straight lines.
(11) Measurement of oil film thickness: Measured under the following conditions using the following device.
・Equipment: PCS EHL ultra-thin film measurement system (EHD2)
・Load: 20 N, temperature: 120° C., rolling speed: 0.2 m/s, 1.6 m/s

Examples 1 to 7 and Comparative Examples 1 and 2
As shown in Table 1, after preparing various lubricating oil compositions by adding various additives to the base oils shown in the same table, kinematic viscosities (40°C, 100°C) of each of the obtained lubricating oil compositions, Various properties such as viscosity index, HTHS viscosity at 150° C., CCS viscosity at −25° C. and viscosity after shear test (100° C.) were measured. Further, the fatigue life and the oil film thickness of these lubricating oil compositions were evaluated. In addition, the compounding quantity of each polymer in Table 1 shows the compounding quantity (mass %) as a resin component.
The results are shown in Table 1.

The base oil and each additive used are as follows.
(1) Base oil 150N: 100° C. kinematic viscosity; 5.28 mm ² /s, viscosity index; 104
(2) PMA-1: polymethacrylate, mass average molecular weight; about 35,000
(3) High viscosity PAO-1: mass average molecular weight; about 24,000, 100° C. kinematic viscosity; 710 mm ² /s, amorphous, pour point; −30 to −40° C., dimer and trimer components Amount: 1 mass% or less, raw material monomer; 1-decene (4) high viscosity PAO-2: mass average molecular weight; about 12,300, 100° C. kinematic viscosity; 230 mm ² /s, amorphous, pour point; -30 -40°C, dimer and trimer component amount; 1% by mass or less, raw material monomer; 1-decene (5) high viscosity PAO-3: mass average molecular weight; about 8,000, 100°C kinematic viscosity; 130 mm ² /s, amorphous, pour point; −30 to −40° C., dimer and trimer component amount; 1% by mass or less, raw material monomer; 1-decene

(6) PAO-a: ethylene/propylene copolymer, mass average molecular weight; about 14,000, kinematic viscosity at 100° C.; 2,000 mm ² /s, viscosity index; 300
(7) PAO-b: SPECTRASYN 100 (poly α-olefin (polymer of α-olefin having 4 to 22 carbon atoms), manufactured by Exxon Mobil Corp., mass average molecular weight; about 16,000, movement at 100° C. Viscosity: 100 mm ² /s, viscosity index: 170
(8) Polybutene: mass average molecular weight; about 1,300
(9) OCP: olefin copolymer (ethylene/propylene copolymer), mass average molecular weight; about 90,000
(10) PMA-2: polymethacrylate, mass average molecular weight; about 400,000
(11) Package additive: Sulfur-based extreme pressure agent: Zinc dithiophosphate (10), Ashless dispersant: Polybutenyl succinimide (20), Metal-based detergent: Ca phenate (12.2), Ca Sulfonate (5.6), Antioxidant: Amine Antioxidant (8.9), Phenolic Antioxidant (4.4), Others: Friction Modifier, Antirust Agent, Metal Deactivator (5 .6), diluent oil: (33.3). The value in parentheses indicates the mass% based on the total amount of package additives.

The compositions of Examples 1 to 7, which are lubricating oil compositions of the present invention, were prepared by blending a base oil with an acrylate-based polymer or olefin-based polymer having a molecular weight within the specified range of the present invention, and various lubricating oil additives. The viscosity (100° C.) and the HTHS viscosity (150° C.) were adjusted within the ranges specified by the present invention, and both the radial fatigue life and the central oil film thickness were excellent.
On the other hand, in Comparative Examples 1 and 2 in which an acrylate-based polymer and an olefin-based polymer having a molecular weight outside the range of the present invention are blended, both kinematic viscosity (100° C.) and HTHS viscosity (150° C.) are within the range of the present invention. Even if adjusted, it was inferior to both the radial fatigue life and the central oil film thickness.

The lubricating oil composition of the present invention has both low viscosity for fuel economy and fatigue resistance for improving fatigue life, and is excellent in low temperature viscosity characteristics. In particular, since it can lubricate both the engine and the speed change transmission, it can be preferably used as a lubricating oil composition for a two-wheel internal combustion engine.

Claims (11)

(1) A base oil containing a base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less, (2) a mass average molecular weight of 8,000 or more and 40,000 or more. At least one selected from the following acrylate-based polymers and olefin-based polymers, and (3) a lubricating oil additive containing a sulfur-based extreme pressure agent are contained, and the kinematic viscosity at 100° C. exceeds 9.3 mm ² /s. A lubricating oil composition for a two-wheel internal combustion engine , which has a high-temperature high-shear viscosity at 150° C. of 5 mm ² /s or less and 2.9 mPa·s or more. The lubricating oil composition for a two-wheel internal combustion engine according to claim 1, which has a CCS viscosity at -25°C of 7,000 mPa·s or less and a viscosity index of 135 or more. The lubricating oil composition for a two-wheel internal combustion engine according to claim 1, wherein the acrylate-based polymer and the olefin-based polymer are an acrylate-based polymer and an olefin-based polymer having a mass average molecular weight of 12,300 or more and 40,000 or less. The acrylate-based polymer and the olefin-based polymer are obtained from at least one selected from α-olefins having 8 to 12 carbon atoms, and have a kinematic viscosity at 100° C. of 100 mm ² /s to 2,000 mm ² /s. The lubricating oil composition for a two-wheel internal combustion engine according to any one of claims 1 to 3, which is an α-olefin. The two-wheel internal combustion engine according to any one of claims 1 to 4, wherein a central oil film thickness in an oil film thickness measurement in an elastohydrodynamic lubrication state (EHL) is 50 nm or more at a rolling speed of 1.6 m/s. Lubricating oil composition. The lubricating oil composition for a two-wheel internal combustion engine according to any one of claims 1 to 5, which has a 50% failure probability (L50) of 3.0×10 ⁶ times or more in fatigue life evaluation of radial rolling bearings. .. The lubricating oil composition for a two-wheel internal combustion engine according to any one of claims 1 to 6, wherein the base oil further contains a base oil having a viscosity index of more than 120. The lubricating oil composition for a two-wheeled internal combustion engine according to any one of claims 1 to 7, which has a kinematic viscosity of 9 mm ² /s or more after a shear test at 100°C. The lubricating oil composition for a two-wheel internal combustion engine according to any one of claims 1 to 8, which is for an internal combustion engine . (1) A base oil containing a base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less, (2) a mass average molecular weight of 8,000 or more, 40, Kinematic viscosity at 100° C. exceeds 9.3 mm ² /s by blending one or more kinds selected from acrylate-based polymers and olefin-based polymers of 000 or less, and (3) a lubricating oil additive containing a sulfur-based extreme pressure agent. production of 12.5 mm ² / s or less, and the lubricating oil composition for two-wheeled internal combustion engine high-temperature high-shear viscosity at 0.99 ° C. to produce a lubricating oil composition for two-wheeled engine is 2.9 mPa · s or more Method. (1) A base oil containing a base oil A having a kinematic viscosity at 100° C. of 2 mm ² /s or more and 7 mm ² /s or less and a viscosity index of 120 or less, (2) a mass average molecular weight of 8,000 or more, 40, Kinematic viscosity at 100° C. exceeds 9.3 mm ² /s by blending one or more kinds selected from acrylate-based polymers and olefin-based polymers of 000 or less, and (3) a lubricating oil additive containing a sulfur-based extreme pressure agent. A two-wheel internal combustion engine in which a lubricating oil composition having a high-temperature high-shear viscosity at 150° C. of 12.5 mm ² /s or less and 2.9 mPa·s or more is used.