JP2011195734A - Lubricating oil composition for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricating oil composition for internal combustion engines that has low viscosity and nevertheless reduces noise while running, suppresses fatigue damage such as gear pitting, reduces oil consumption, and has good fuel efficiency.SOLUTION: The lubricating oil composition for internal combustion engines is obtained by blending, based on the total amount of the composition, 0.1-10 mass% of (A) a 2-20C olefin polymer having a mass-average molecular weight of 500-10,000 and/or (B) a polymer compound having a mass-average molecular weight of 10,000 or more and less than 100,000 with base oil having a viscosity index of 125 or more and Noack evaporation loss (250°C×1h) of 15 mass% or less, wherein (C) the blending amount of a polymer compound having a mass-average molecular weight of 100,000 or more is less than 1.0 mass%.

Description

  The present invention relates to a lubricating oil composition for an internal combustion engine, and more specifically, a four-cycle for a motorcycle that has reduced noise during running, increased fatigue life, reduced oil consumption, and good fuel economy. The present invention relates to an internal combustion engine lubricating oil composition that is also useful as an engine lubricating oil.

Due to demands for energy saving, carbon dioxide (CO ₂ ) reduction, etc., fuel efficiency is strongly demanded as a necessary performance even in lubricating oil for internal combustion engines (engine oil).
Conventionally, with respect to engine oil used in four-wheeled vehicles, reducing the viscosity of engine oil has been performed as a means for improving fuel economy.
However, even with the same engine oil, reducing the viscosity of the engine oil in order to improve the fuel efficiency of the engine oil used in motorcycles causes various problems due to the difference in mechanical structure between the four-wheeled vehicle and the two-wheeled vehicle. appear.
In other words, since it is necessary to downsize the engine and other devices, the two-wheeled vehicle usually has a structure in which the transmission for transmission as well as the engine is lubricated with the same engine oil.
When engine oil having a low viscosity is used as an engine oil used for a motorcycle having such a structure in order to improve fuel efficiency, fatigue damage such as gear pitching occurs in the transmission for transmission. Further, in a motorcycle, since the engine is exposed, the engine noise becomes large, which causes a noise problem. Furthermore, since the two-wheeled vehicle has a small engine, the oil is hotter than the four-wheeled vehicle, and the oil consumption due to the evaporation of the oil increases.
Therefore, it is necessary to solve these problems when attempting to improve fuel economy by reducing the viscosity of engine oil used in motorcycles.

Conventionally, as a means for lowering the viscosity in the actual use temperature range, a viscosity index is improved by combining a base oil with a viscosity index improver that is a polymer compound (see, for example, Patent Document 1). However, a lubricating oil containing a viscosity index improver causes a decrease in viscosity due to the orientation of the polymer under high shear such as engine bearings and gear tooth surfaces. For this reason, conventional multi-grade engine oils (lubricants containing polymer compounds) tend to have low metal fatigue resistance due to insufficient high-temperature and high-shear viscosity, and lower the engine oil used for motorcycles. It is an obstacle on the top.
Therefore, the present situation is that it is not possible to solve this type of problem when attempting to improve fuel economy by reducing the viscosity of engine oil used in motorcycles.

JP 2000-087070 A

  Under such circumstances, the present invention reduces noise during running even at low viscosity, suppresses fatigue damage such as gear pitching, reduces oil consumption, and has good fuel economy. An object of the present invention is to provide a lubricating oil composition for an internal combustion engine.

  As a result of extensive research, the present inventors can achieve the object by blending a specific base oil with a polymer having a specific structure and molecular weight and / or a polymer compound with a specific molecular weight. I found. The present invention has been completed based on such findings. That is, the present invention

[1] To a base oil having a viscosity index of 125 or more and a Noack evaporation (250 ° C. × 1 h) of 15% by mass or less, based on the total amount of the composition, (A) a mass average molecular weight of 500 to 10,000 Containing 0.1 to 10% by mass of a C 2-20 olefin polymer and / or (B) a polymer compound having a mass average molecular weight of 10,000 or more and less than 100,000, and (C) a mass average molecular weight of 100. A lubricating oil composition for an internal combustion engine, wherein the blending amount of the polymer compound of 1,000 or more is less than 1.0% by mass,
[2] The internal combustion according to [1], wherein the polymer compound is one or two or more polymer compounds selected from polymethacrylate, olefin copolymer, styrene copolymer, and polyisobutylene. Lubricating oil composition for engine,
[3] The lubricating oil composition for internal combustion engines according to the above [1] or [2], further comprising a molybdenum friction modifier or an ashless friction modifier,
[4] The lubricating oil for internal combustion engines according to any one of [1] to [3], wherein the Noack evaporation amount (250 ° C. × 1 h) is 10.0% by mass or less and the viscosity index is 140 or more. Composition,
[5] The lubricating oil composition for internal combustion engines according to any one of the above [1] to [4], which is a lubricating oil for a four-cycle engine for a motorcycle.
Is to provide.

  According to the present invention, a lubricating oil for an internal combustion engine that reduces noise during traveling, suppresses fatigue damage such as gear pitching, reduces oil consumption, and has good fuel economy even with low viscosity. A composition can be provided.

  The lubricating oil composition for internal combustion engines of the present invention (hereinafter also referred to as “the present composition”) is a base oil having a viscosity index of 125 or more and a Noack evaporation (250 ° C. × 1 h) of 15 mass% or less. Based on the total amount of the composition, (A) an olefin polymer having 2 to 20 carbon atoms having a mass average molecular weight of 500 to 10,000, and / or (B) having a mass average molecular weight of 10,000 to less than 100,000. For internal combustion engines, comprising 0.1 to 10% by mass of a polymer compound, and (C) the compounding amount of a polymer compound having a mass average molecular weight of 100,000 or more is less than 1.0% by mass. It is a lubricating oil composition. Hereinafter, the composition will be described in detail.

1. Base oil The base oil used in the present invention is a lubricating base oil composed of mineral oil, synthetic oil, or a mixture thereof, and the viscosity index is required to be 125 or more. The higher the viscosity index of the base oil, the lower the viscosity of the lubricating oil composition for internal combustion engines at high temperatures, and the lower the wear resistance and fatigue life. The viscosity index is more preferably 130 or more.
The viscosity index is a value measured according to JIS K 2283.
The base oil used in the present invention is required to have a Noack evaporation (250 ° C. × 1 h) of 15% by mass or less. When the Noack evaporation amount (250 ° C. × 1 h) exceeds 15% by mass, oil consumption due to evaporation loss of the composition increases. The Noack evaporation is preferably 10% by mass or less.
The Noack evaporation amount is a value measured by a method defined in CEC-L-40-A-93 and ASTM D5800.

As the base oil, in% by ring analysis C _A of 3.0 or less, the sulfur content is include: 100 ppm by mass is preferably used.
Here, the% C _A by ring analysis shows a proportion of aromatic content calculated by ring analysis n-d-M method (percentage). The sulfur content is a value measured according to JIS K2541.
_A base oil having a% CA of 3.0 or less and a sulfur content of 100 mass ppm or less provides a lubricating oil composition having good oxidation stability and capable of suppressing an increase in acid value and sludge formation. be able to. More preferable% C _A is 1.0 or less, and further 0.5 or less.

The base oil used in the composition preferably has a kinematic viscosity of ^{2 to 20} mm ² / s at 100 ° C., more preferably a kinematic viscosity in the range of 3 to 15 mm ² / s, and even more preferable kinematic viscosity. Is in the range of 3.5 to 10 mm ² / s. When the kinematic viscosity of the base oil is too high, the stirring resistance is increased when the composition is used, and the coefficient of friction in the fluid lubrication region is increased, so that the fuel saving characteristics are deteriorated. On the other hand, if the kinematic viscosity is too low, wear increases in sliding parts such as valve systems, pistons, rings and bearings of internal combustion engines.

  As the mineral oil, for example, a lubricating oil fraction obtained by atmospheric distillation of a crude oil or a lubricating oil fraction obtained by vacuum distillation of an atmospheric residual oil, solvent removal, solvent extraction, solvent dewaxing, By isomerizing a wax refined by one or more treatments such as catalytic dewaxing, hydrorefining, hydrocracking, or a wax produced by a mineral oil-based wax or a Fischer-Tropsch process (GTL wax) Examples include manufactured mineral oils.

In particular, a base oil having a viscosity index of 125 or more in the present invention is preferably produced by solvent dewaxing or hydrodewaxing a product oil obtained by hydrocracking a lubricating oil fraction or hydroisomerizing a wax. can do.
In hydrocracking, the above-mentioned lubricating oil fraction is usually separated from a hydrocracking catalyst such as one or more group 8 metals such as nickel and cobalt on a silica-alumina carrier, and a group 6A metal such as molybdenum and tungsten. In the presence of hydrogen having a hydrogen partial pressure of 7 to 14 MPa and a temperature of 350 to 450 ° C. and an LHSV (liquid space velocity) of 0.1 to 2 hr ⁻¹ .
Also, the hydroisomerization of the wax may be performed by, for example, converting a slack wax obtained in a solvent dewaxing process of a mineral oil or a wax obtained by Fischer-Tropsch synthesis into a hydroisomerization catalyst such as alumina or silica-alumina. A catalyst in which one or more of group 8 metals such as nickel and cobalt and a group 6A metal such as molybdenum and tungsten are supported on a support, a zeolite catalyst or a catalyst in which platinum or the like is supported on a zeolite-containing support; In the presence of 14 MPa hydrogen, the contact is performed at a temperature of 300 to 450 ° C. and an LHSV (liquid space velocity) of 0.1 to 2 hr ⁻¹ .

The hydrocracked product oil and hydroisomerized product oil obtained by the above method are usually obtained by distilling off the light fraction to obtain a lubricating oil fraction, which is further dewaxed to remove the wax content, A lubricating base oil having a low pour point (eg, −10 ° C. or lower) can be obtained.
The lubricating oil fraction obtained by the above method may be further subjected to solvent purification or hydrorefining as desired.

On the other hand, various known oils can be used as the synthetic oil. For example, poly-α-olefin, polybutene, polyol ester, dibasic acid ester, aromatic ester, phosphoric acid ester, polyphenyl ether, alkylbenzene. , Alkyl naphthalene, polyoxyalkylene glycol, neopentyl glycol, silicone oil, trimethylolpropane, pentaerythritol, and hindered ester can be used. Especially, poly-α-olefin has a relatively high viscosity index. And since it is a composition close to mineral oil, it is preferable at the point which can use the additive currently used with the conventional mineral oil as it is.
The base oil used in the present invention may be two or more kinds of mineral oils, a mixture of two or more kinds of synthetic oils, or a mixture of mineral oil and synthetic oil as long as the above properties are satisfied. The mixing ratio of more than one type of base oil can be arbitrarily selected.

2. Olefin polymer and polymer compound The lubricating oil composition for an internal combustion engine of the present invention is (A) an olefin polymer having 2 to 20 carbon atoms having a mass average molecular weight of 500 to 10,000, And / or (B) 0.1 to 10% by mass, preferably 0.3 to 7% by mass, more preferably 0.5 to 5% by mass of the polymer compound having a mass average molecular weight of 10,000 or more and less than 100,000. %, And the amount of the polymer compound having a mass average molecular weight of 100,000 or more is less than 1.0% by mass.
By blending a olefin polymer having 2 to 20 carbon atoms having a mass average molecular weight of 500 to 10,000 and a polymer compound having a mass average molecular weight of 10,000 to less than 100,000, only the viscosity index of the composition is increased. In other words, the generation of noise can be suppressed.
The reason why the mass average molecular weight of the polymer compound (B) blended with the base oil is less than 100,000 is that the viscosity index improves as the molecular weight of the polymer compound blended with the base oil increases. Although the effect is large, the molecular chain of the polymer compound is oriented by shearing, which may cause a temporary decrease in viscosity and may not be able to maintain the required high temperature and high shear viscosity. This is because the chain may be cleaved to reduce the molecular weight and reduce the viscosity.
Therefore, it is desirable not to add the above-mentioned (C) polymer compound having a mass average molecular weight of 100,000 or more (more preferably 70,000 or more, more preferably 50,000 or more), but the viscosity index is improved. Therefore, it may be unavoidably added. However, even in that case, the lubricating oil composition for an internal combustion engine of the present invention can be obtained by making the amount less than 1.0% by mass, preferably less than 0.1% by mass, and more preferably less than 0.01% by mass. Obtainable.
In addition, it is preferable that the mass mean molecular weight of the said (B) polymer compound is 70,000 or less, and it is more preferable that it is 50,000 or less.

As the olefin polymer (A), one or more selected from homopolymers and copolymers of olefins having 2 to 20, preferably 2 to 16, and more preferably 2 to 14 carbon atoms are used. Typical examples of the olefin polymer having 2 to 20 carbon atoms include an ethylene-α-olefin copolymer and an α-olefin homopolymer and copolymer. Among these, as an ethylene-alpha-olefin copolymer, the copolymer of 15-80 mol% ethylene and C3-C20 alpha olefins, such as propylene, 1-butene, and 1-decene, is mentioned. It may be a random body or a block body. The copolymer is non-dispersed with respect to lubricating oil, but is a dispersion type in which an ethylene-α-olefin copolymer is grafted with maleic acid, N-vinylpyrrolidone, N-vinylimidazole, glycidyl acrylate, etc. Can also be used. The α-olefin homopolymers and copolymers are preferably 4-20 carbon atoms, more preferably 6-16 carbon atoms, and even more preferably 6-14 carbon atoms α-olefin homopolymers and copolymers. The polymer may be a random body or a block body.
These olefin polymers can be produced by any method. For example, it can be produced by a non-catalytic thermal reaction, and an organic peroxide catalyst such as benzoyl peroxide; aluminum chloride, aluminum chloride-polyhydric alcohol, aluminum chloride-titanium tetrachloride, aluminum chloride-alkyltin Friedel-Crafts type catalysts such as halides 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 The catalyst can be produced by homopolymerizing or copolymerizing the above olefin using a known catalyst system such as Lewis acid complex catalyst such as aluminum chloride-base system or boron fluoride-base system. Although the above-mentioned olefin polymer can be used, since the olefin polymer usually has a double bond, considering the thermal and oxidation stability, the double bond in the olefin polymer is hydrogenated. It is preferable to use a hydrogenated olefin polymer.
The mass average molecular weight of the olefin polymer is preferably 2,000 to 9,000, and more preferably 3,000 to 8,000.

The polymer compound is at least one selected from polymethacrylate (PMA), olefin copolymer (olefin copolymer), styrene copolymer (for example, styrene-diene hydrogenated copolymer) and polyisobutylene. One type is preferred. The polymethacrylate can be used in either a dispersion type or a non-dispersion type. A typical olefin copolymer is an ethylene-α-olefin copolymer.
One of these can be used alone or in combination of two or more. More preferably, a polymethacrylate (PMA) and an olefin copolymer (olefin copolymer) are used.

3. Friction modifier In addition, in the lubricating oil composition for an internal combustion engine of the present invention, it is preferable to blend a molybdenum friction modifier or an ashless friction modifier in order to improve fuel saving characteristics. More preferably, a molybdenum friction modifier and an ashless friction modifier are used in combination.
As the molybdenum friction modifier, at least one selected from molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (hereinafter also referred to as MoDTP), and an amine salt of molybdic acid (hereinafter also referred to as Mo amine salt) is preferably used. . Among molybdenum-based friction modifiers, MoDTC is preferable in terms of effects. These can be used singly or in combination of two or more, and the preferred blending amount is preferably in the range of 10 to 1000 ppm by mass, more preferably 100 to 800 ppm by mass as the amount of molybdenum based on the total amount of the composition. . If the amount of molybdenum is less than 10 ppm by mass, sufficient low friction cannot be obtained, and if it exceeds 1000 ppm by weight, the effect of improving the friction characteristics is not seen for that amount.
MoDTC is represented by the following general formula (I).

In general formula (I), R < ¹ > -R < ⁴ > is a C5-C16 hydrocarbon group, and may be the same or different altogether. X is S (sulfur atom) or O (oxygen atom). Examples of the hydrocarbon group represented by R ^{1 to} R ⁴ include an alkyl group having 5 to 16 carbon atoms, an alkenyl group having 5 to 16 carbon atoms, a cycloalkyl group having 5 to 16 carbon atoms, and 5 to 16 carbon atoms. And an arylalkyl group having 5 to 16 carbon atoms. Specific examples of the hydrocarbon having 5 to 16 carbon atoms include various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various undecyl groups, various dodecyl groups, various tridecyl groups, Various tetradecyl groups, various pentadecyl groups, various hexadecyl groups, various octenyl groups, various nonenyl groups, various decenyl groups, various undecenyl groups, various dodecenyl groups, various tridecenyl groups, various tetradecenyl groups, various pentadecenyl groups, cyclohexyl groups, dimethylcyclohexyl groups , Ethylcyclohexyl group, methylcyclohexylmethyl group, cyclohexylethyl group, propylcyclohexyl group, butylcyclohexyl group, heptylcyclohexyl group, phenyl group, tolyl group, dimethylphenyl group, butylphenyl group, nonylphenol Group, can be exemplified a methyl benzyl group, phenylethyl group, a naphthyl group, dimethyl naphthyl group and the like.
MoDTP is represented by the following general formula (II).

In general formula (II), R < ⁵ > -R < ⁸ > is a C5-C16 hydrocarbon group, and may be same or different altogether. Y is S (sulfur atom) or O (oxygen atom). Examples of the hydrocarbon group represented by R ⁵ to R ^8, for example, an alkyl group having 5 to 16 carbon atoms, an alkenyl group having 5 to 16 carbon atoms, a cycloalkyl group having 5 to 16 carbon atoms, carbon atoms 5-16 And an arylalkyl group having 5 to 16 carbon atoms. Specific examples of the hydrocarbon having 5 to 16 carbon atoms include various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various undecyl groups, various dodecyl groups, various tridecyl groups, Various tetradecyl groups, various pentadecyl groups, various hexadecyl groups, various octenyl groups, various nonenyl groups, various decenyl groups, various undecenyl groups, various dodecenyl groups, various tridecenyl groups, various tetradecenyl groups, various pentadecenyl groups, cyclohexyl groups, dimethylcyclohexyl groups , Ethylcyclohexyl group, methylcyclohexylmethyl group, cyclohexylethyl group, propylcyclohexyl group, butylcyclohexyl group, heptylcyclohexyl group, phenyl group, tolyl group, dimethylphenyl group, butylphenyl group, nonylphenol Group, can be exemplified a methyl benzyl group, phenylethyl group, a naphthyl group, dimethyl naphthyl group and the like.
The Mo amine salt is a secondary amine salt of molybdic acid represented by the following general formula (III).

  In the general formula (III), R is a hydrocarbon group having 5 to 18 carbon atoms, and the four hydrocarbon groups may be the same or different. Examples of the hydrocarbon group having 5 to 18 carbon atoms include an alkyl group having 5 to 18 carbon atoms, an alkenyl group having 5 to 18 carbon atoms, a cycloalkyl group having 5 to 18 carbon atoms, and an alkylaryl having 5 to 18 carbon atoms. And arylalkyl groups having 5 to 18 carbon atoms. Specific examples of the hydrocarbon having 5 to 18 carbon atoms include various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various undecyl groups, various dodecyl groups, various tridecyl groups, Various tetradecyl groups, various pentadecyl groups, various hexadecyl groups, various heptadecyl groups, various octadecyl groups, various octenyl groups, various nonenyl groups, various decenyl groups, various undecenyl groups, various dodecenyl groups, various tridecenyl groups, various tetradecenyl groups, various pentadecenyl groups Group, cyclohexyl group, dimethylcyclohexyl group, ethylcyclohexyl group, methylcyclohexylmethyl group, cyclohexylethyl group, propylcyclohexyl group, butylcyclohexyl group, heptylcyclohexyl group, phenyl group, tolyl group, dimethyl group Eniru group, butylphenyl group, nonylphenyl group, a methyl benzyl group, phenylethyl group, a naphthyl group, dimethyl naphthyl group and the like.

  Examples of the ashless friction modifier include fatty acids, higher alcohols, fatty acid esters, fats and oils, amines, amides, and sulfurized esters. These friction modifiers can be contained alone or in any combination of a plurality of types, but the compounding amount is usually in the range of 0.01 to 10% by mass based on the total amount of the composition.

4). Lubricating oil composition for internal combustion engine The lubricating oil composition for internal combustion engine of the present invention comprises a viscosity index of base oil, Noack evaporation (250 ° C. × 1 h), olefin polymer, mass average molecular weight of polymer compound and polymer compound It can obtain by making the compounding quantity of the above-mentioned specified range. Such a blend provides a fuel-saving internal combustion engine lubricating oil composition having a viscosity index of 135 or 140, low noise, and excellent effects of suppressing fatigue damage such as gear pitching.

Moreover, it is preferable that this composition is 3.0% or less with respect to the viscosity at the time of low shear in the viscosity decreasing rate at the time of high shear at 150 degreeC. This is because a lubricating oil for internal combustion engines having a viscosity reduction rate of more than 3.0% during high shear needs to set a high low shear viscosity in anticipation of the viscosity reduction and deteriorates fuel economy.
Furthermore, the lubricating oil composition preferably has a kinematic viscosity at 100 ° C. of less than 11.0 mm ² / s. This is because if it is 11.0 mm ² / s or more, the kinematic viscosity in the actual operating temperature range (80 ° C. to 100 ° C.) of the lubricating oil for internal combustion engines is high, so that it is not possible to save fuel.
In particular, the lubricating oil composition preferably has a kinematic viscosity at 100 ° C. of less than 9.0 mm ² / s when the high shear viscosity at 150 ° C. is 2.9 mPa · s or more equivalent to 30 in the SAE viscosity grade. When the high shear viscosity at 150 ° C. is 2.6 mPa · s or more corresponding to 20 in the SAE viscosity grade, the kinematic viscosity at 100 ° C. is preferably less than 7.5 mm ² / s. If these 100 ° C. kinematic viscosities are exceeded, the viscosity of the lubricating oil for internal combustion engines in the actual operating temperature range (80 ° C. to 100 ° C.) becomes too high, and it is not possible to save fuel consumption compared to conventional oils. Because.

5. Other Additives Furthermore, in the lubricating oil composition for internal combustion engines of the present invention, an ashless dispersant, a metallic detergent, an extreme pressure agent, and a metal deactivator within a range that does not impair the object of the present invention. Various additives typified by rust preventives, antifoaming agents, demulsifiers and colorants may be used alone or in combination.
Ashless dispersants include polybutenyl succinimide having a polybutenyl group having a weight average molecular weight of 900 to 3,500, polybutenylbenzylamine, polybutenylamine, and derivatives thereof such as boric acid-modified products Etc. These ashless dispersants can be contained alone or in any combination of two or more kinds, but the compounding amount is usually in the range of 0.01 to 10% by mass based on the total amount of the composition.

  Examples of metal 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. What is necessary is just to select suitably the total base number and compounding quantity of these metal type detergents according to the performance of the required lubricating oil. The total base number is usually from 0 to 500 mgKOH / g, desirably from 10 to 400 mgKOH / g by the perchloric acid method. Moreover, the compounding quantity is the range of 0.1-10 mass% normally on the composition whole quantity basis.

  Examples of extreme pressure agents include sulfur compounds such as sulfurized olefins, dialkyl polysulfides, diarylalkyl polysulfides, diaryl polysulfides, phosphate esters, thiophosphate esters, phosphite esters, alkyl hydrogen phosphites, phosphate ester amine salts, Examples thereof include phosphorus compounds such as phosphite amine salts, and the compounding amount is usually in the range of 0.01 to 10% by mass based on the total amount of the composition.

Examples of the metal deactivator include benzotriazole, triazole derivatives, benzotriazole derivatives, thiadiazole derivatives, and the like. Usually, the blending amount is in the range of 0.01 to 3% by mass based on the total amount of the composition.
Examples of the rust inhibitor include sulfonates, phenates of fatty acids, alkenyl succinic acid half esters, fatty acid soaps, alkyl sulfonates, 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 and the like can be mentioned, and the compounding amount is usually in the range of 0.01 to 5% by mass based on the total amount of the composition.
As the antifoaming agent, liquid silicone is suitable, and for example, methyl silicone, fluorosilicone, polyacrylate, and the like can be used. A preferable blending amount of these antifoaming agents is 0.0005 to 0.1% by mass based on the total amount of the composition.
As demulsifiers, ethylene propylene block polymers, sulfonates of alkaline earth metals (calcium (Ca), magnesium (Mg), etc.), phenates, salicylates, naphthenates, etc. can be used. % By mass.
As the colorant, dyes, pigments, and the like can be used. Usually, the blending amount is 0.001 to 1% by mass based on the total amount of the composition.

  The lubricating oil composition for an internal combustion engine of the present invention thus prepared is blended as described above, so it has a low viscosity but a low evaporation loss, a high viscosity index, and a high temperature and high shear. It has the effect that the viscosity reduction rate at the time is low. In particular, in addition to having such properties, it has an effect of reducing noise, an effect of suppressing fatigue damage, and fuel efficiency. Therefore, it can be suitably used as a lubricating oil composition for an internal combustion engine that is useful as a lubricating oil for an internal combustion engine, particularly a four-cycle engine lubricating oil for a motorcycle.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by the following examples.
The properties of the lubricating oil composition (sample oil) in each example were determined by the following method.
(1) Kinematic viscosity (40 ° C., 100 ° C.) and viscosity index It was measured by the method of JIS K 2283.
(2) HTHS viscosity (150 ° C)
It was measured by the method of ASTM D4683 using a TBS high temperature viscometer (Tapered Bearing Simulator). Test conditions are shown below.
・ Shear rate: 10 ⁶ sec ^-1
・ Rotation speed (motor): 3000rpm
・ Spacing (rotor / stator): 2 to 3 μm
-Sample volume: 20-50ml
・ Measurement time: Calibration 4-6 hours
: Test 15 minutes (3) Low temperature viscosity (CCS viscosity)
Based on JIS K2606, the viscosity at -25 ° C and -30 ° C was measured.
(4) Noack evaporation amount The evaporation amount was measured by the method prescribed in CEC-L-40-A-93 and ASTM D5800 / A. The test conditions are 1 hour at 250 ° C.

(5) Noise evaluation The noise generated under the following engine motoring device and operating conditions was measured by the following method.
[Engine motoring device and operating conditions]
Engine: Water-cooled 600CC for motorcycles, 4-cylinder engine Drive motor: 7.5kw
Valve type: DOHC (Direct stroke)
Engine speed: 3000rpm
Oil pan oil temperature: 100 ° C
[Noise measurement method]
Using a sound level meter (LA5560 manufactured by Ono Sokki Co., Ltd.), a power spectrum (dB) having a frequency of 6300 Hz was measured with a frequency analyzer (Repolizer XN-8100 manufactured by Ono Sokki).
(6) Evaluation of fuel efficiency The engine with the following specifications was filled with engine oil and a motoring torque test was performed to measure the torque (dB) at a predetermined rotational speed. Test conditions are shown below.
・ Engine motoring device and operating conditions ・ Engine: Water-cooled 600CC 4-cylinder engine for motorcycles ・ Valve type: DOHC
・ Engine speed: 5000rpm
・ Oil pan oil temperature: 100 ℃
・ Drive motor: 7.5kw
(7) Fatigue life Fatigue life was measured in the following manner using a four-ball rolling fatigue tester.
(bearing)
Material: Bearing steel Test piece: Φ60 x Heat 5mm
Test steel ball dimensions: φ3 / 8 inch (Test conditions)
Load: 147N
Rotational speed: 2200 rpm
Oil temperature: 120 ° C
(Evaluation methods)
The time until flaking occurred on the test piece was defined as the fatigue life, the results of six tests were subjected to Weibull statistical processing, and L50 (minutes) was calculated.
(8) Viscosity reduction rate From the kinematic viscosity at 100 ° C. and the viscosity index, to the value obtained from kinematic viscosity at 150 ° C. From the density at 15 ° C. and the density at 80 ° C. measured according to JIS K 2249, the density at 150 ° C. Was multiplied by the value obtained by extrapolating to obtain a viscosity at 150 ° C. at low shear. From this value and the HTHS viscosity (150 ° C.), the viscosity reduction rate was calculated.

[Examples 1-5, Comparative Examples 1-7]
A lubricating oil composition (sample oil) for an internal combustion engine was prepared according to the composition shown in Table 1 using various base oils, various copolymers, polymer compounds, and additives shown below.
The prepared sample oil was evaluated for each property by the method described above, and the results are shown in Table 1.
(Base oil)
・ Base oil-1 Mineral oil hydrocracked base oil (API classification GIII) 100N, 100 ° C. Kinematic viscosity 4.175 mm ² / s, Viscosity index 131, Sulfur content 0.01 mass% or less,% C _A 0, Noack Evaporation 14% by mass
Base oil-2 Mineral oil hydrocracked base oil (API classification GIII), 150 N, 100 ° C. kinematic viscosity 6.274 mm ² / s, viscosity index 129, sulfur content 0.01 mass% or less,% C _A 0, Noack evaporation 6 mass%
Base oil-3 Mineral oil hydrorefined base oil (API classification GII), 150 N, 100 ° C. kinematic viscosity 5.284 mm ² / s, viscosity index 104, sulfur content 0.01 mass% or less,% C _A 0, Noack evaporation 14% by mass
Base oil-4 Mineral oil hydrorefined base oil (API classification GII), 500 N, 100 ° C. kinematic viscosity 10.89 mm ² / s, viscosity index 107, sulfur content 0.01 mass% or less,% C _A 0, Noack evaporation 4% by mass
Base oil-5 Mineral oil hydrorefined base oil (API classification GII), Brightstock, API classification GII), 100 ° C. kinematic viscosity 30.86 mm ² / s, viscosity index 107, sulfur content 0.01 mass% or less ,% C _A 0, Noack evaporation 2 mass% or less

(Olefin polymer)
-Copolymer-1 Ethylene-α-olefin copolymer Mass average molecular weight 4,700 (Lucant HC600 manufactured by Mitsui Chemicals)
-Copolymer-2 Ethylene-α-olefin copolymer Mass average molecular weight 7,000 (Mitsui Chemicals, Lucant HC2000)
(Polymer compound)
-High molecular compound-1 polymethacrylate (PMA), mass average molecular weight 45,000 (manufactured by Sanyo Chemical Industries, Inc. C-728)
-High molecular compound-2 olefin copolymer (OCP), mass average molecular weight 100,000 (Paratone 8057, manufactured by Chevron)
(Pour point depressant)
PMA, mass average molecular weight 690,000, (PLEXOL-162 manufactured by Degussa)
(Friction modifier)
Molybdenum friction modifier: Molybdenum dialkyldithiocarbamate was used as the molybdenum friction modifier. The molybdenum content is 4.5 wt%.
(DI agent)
Package additive, ZnDTP (1.1), metallic detergent (4), boron-modified succinimide A (1), boron-modified succinimide B (1), polybutenyl succinimide (2.1) , A mixture of amine antioxidant (0.8) and diluent oil (remainder). Figures in parentheses indicate mass%.

From the results in Table 1, the following can be understood.
(1) The lubricating oil composition for an internal combustion engine of the present invention has good low noise properties, fatigue life resistance, fuel economy, evaporation resistance, and low viscosity lowering properties (Examples 1 to 5). ). In contrast, compositions that do not meet any of the requirements of the present invention do not meet one or more of these capabilities.
(2) Specifically, the following is clear.
(I) The compositions of Example 1, Example 2 and Example 5 have a viscosity grade of 5W-20 oil, but the viscosity grade is 10W-30 and a higher viscosity (kinematic viscosity) Comparative Example 3 It has low noise properties, fatigue life resistance, and evaporation resistance that are equal to or better than the above composition.
(Ii) The composition of Example 3 has a viscosity grade of 10W-20 oil, but the viscosity grade is 40, which is equivalent to or better than the composition of Comparative Example 7 having a higher viscosity (kinematic viscosity). Low noise and fatigue life.
(Iii) The composition of Example 4 has a viscosity grade of 10W-30 oil, but the viscosity grade is 10W-40 and is equal to or higher than the composition of Comparative Example 4 having a higher viscosity (kinematic viscosity). Have good low noise, fatigue life and evaporation resistance.

  The lubricating oil composition for an internal combustion engine of the present invention reduces running noise even when the viscosity is low, suppresses fatigue damage such as gear pitching, reduces oil consumption, and provides good fuel economy. The lubricating oil composition for internal combustion engines can be provided. Therefore, it can be suitably used as a lubricating oil composition for an internal combustion engine that can be effectively used as a lubricating oil for a four-cycle engine for a motorcycle.

Claims (5)

  A base oil having a viscosity index of 125 or more and a Noack evaporation (250 ° C. × 1 h) of 15% by mass or less, based on the total amount of the composition, (A) a carbon number having a mass average molecular weight of 500 to 10,000 2 to 20 olefin polymers and / or (B) 0.1 to 10% by mass of a polymer compound having a mass average molecular weight of 10,000 or more and less than 100,000, and (C) a mass average molecular weight of 100,000 or more. A lubricating oil composition for internal combustion engines, wherein the amount of the polymer compound is less than 1.0% by mass.   The lubricating oil composition for an internal combustion engine according to claim 1, wherein the polymer compound is one or two or more polymer compounds selected from polymethacrylate, olefin copolymer, styrene copolymer, and polyisobutylene. object.   The lubricating oil composition for internal combustion engines according to claim 1 or 2, further comprising a molybdenum friction modifier or an ashless friction modifier.   The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 3, wherein a Noack evaporation amount (250 ° C x 1h) is 10.0% by mass or less and a viscosity index is 140 or more.   The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 4, which is a lubricating oil for a four-cycle engine for a motorcycle.