JP2016020498A - Lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition excellent in fuel efficiency and low temperature viscosity and capable of achieving fuel efficiency and low temperature viscosity at -35°C or less while maintaining high temperature high shear viscosity without using synthetic oil such as poly-α-olefin-based base oil and ester-based base oil, or a low viscosity mineral oil-based base oil.SOLUTION: There is provided a lubricant composition containing a lubricant base oil containing a lubricant base oil component having urea adduct value of 4 mass% or less, kinetic viscosity at 40°C of 25 mm/s or less and viscosity index of 120 or more in the amount of 10 to 100 mass% based on the total amount of the base oil, and a poly(meth)acrylate-based viscosity index improver having percentage of a structural unit represented by the formula (1) of 0.5 to 70 mol%, and having kinetic viscosity at 100°C of 4 to 12 mm/s and viscosity index of 140 to 300. In the formula (1), Ris H or a methyl group, Ris a C16 or more linear or branched hydrocarbon group.SELECTED DRAWING: None

Description

  The present invention relates to a lubricating oil composition.

  Conventionally, lubricating oil is used in an internal combustion engine, a transmission, and other mechanical devices in order to make the operation smooth. In particular, lubricating oil (engine oil) for internal combustion engines is required to have high performance as the performance of the internal combustion engine increases, the output increases, and the operating conditions become severe. Therefore, various additives such as antiwear agents, metallic detergents, ashless dispersants, and antioxidants are blended in conventional engine oils in order to satisfy these required performances.

  Recently, the fuel-saving performance required for lubricating oil has been increasing, and the application of high viscosity index base oil and various friction modifiers has been studied (for example, see Patent Document 1 below).

Japanese Patent Laid-Open No. 06-306384

  However, conventional lubricating oils still have room for improvement in terms of both fuel economy and low temperature viscosity characteristics.

  As a general method for reducing fuel consumption, there are known a method for reducing the kinematic viscosity of a product and a multi-gradation by combining a viscosity index improvement, that is, a base oil viscosity reduction and a viscosity index improver. However, there is a concern that reduction in product viscosity or reduction in base oil viscosity will reduce lubrication performance under severe lubrication conditions (high-temperature high-shear conditions) and cause problems such as wear, seizure, and fatigue failure. Therefore, in order to prevent such problems and maintain durability, it is necessary to maintain a high temperature and high shear viscosity (HTHS viscosity). In other words, in order to further improve fuel efficiency while maintaining practical performance, the HTHS viscosity at 150 ° C. is maintained, the kinematic viscosity at 40 ° C. and 100 ° C. and the HTHS viscosity at 100 ° C. are reduced, and the viscosity index is increased. It is important to improve.

  On the other hand, if only low-temperature performance such as CCS viscosity and MRV viscosity is to be improved, it is possible to reduce the kinematic viscosity at 40 ° C. and 100 ° C., and to make multi-grade by adding a viscosity index improver while reducing the base oil viscosity And so on. However, there is a concern that reduction in product viscosity or reduction in base oil viscosity may reduce lubrication performance under severe lubrication conditions (high temperature and high shear conditions) and cause problems such as wear, seizure, and fatigue failure. These problems can be solved to some extent by using a lubricating base oil having excellent low-temperature viscosity such as synthetic oil such as poly-α-olefin base oil and ester base oil and low viscosity mineral oil base oil. However, the synthetic oil is expensive, while the low-viscosity mineral base oil generally has a low viscosity index and a high NOACK evaporation amount. Therefore, when those lubricating base oils are blended, the manufacturing cost of the lubricating oil increases, or it becomes difficult to achieve a high viscosity index and low evaporation. In addition, when these conventional lubricating base oils are used, there is a limit to improving the fuel efficiency.

  The present invention has been made in view of such circumstances, and is excellent in fuel economy and low-temperature viscosity, and synthetic oils such as poly-α-olefin base oils and ester base oils, and low viscosity mineral oil base oils. Even without using, it is possible to achieve both fuel economy and low temperature viscosity at −35 ° C. or lower while maintaining a high temperature and high shear viscosity at 150 ° C. An object of the present invention is to provide a lubricating oil composition capable of reducing the HTHS viscosity at ° C, improving the viscosity index, and remarkably improving the CCS viscosity at -35 ° C.

［式（１）中、Ｒ^１は水素又はメチル基を示し、Ｒ^２は炭素数１６以上の直鎖状又は分枝状の炭化水素基を示す。］ In order to solve the above problems, the present invention provides a lubricating base oil component having a urea adduct value of 4% by mass or less, a kinematic viscosity at 40 ° C. of 25 mm ² / s or less, and a viscosity index of 120 or more. Poly (meth) acrylate viscosity in which the ratio of the lubricating base oil containing 10% by mass to 100% by mass based on the total amount of oil and the structural unit represented by the following general formula (1) is 0.5 to 70 mol% And an index improver, having a kinematic viscosity at 100 ° C. of 4 to 12 mm ² / s and a viscosity index of 140 to 300.

[In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents a linear or branched hydrocarbon group having 16 or more carbon atoms. ]

  Here, the “urea adduct value” in the present invention means a value measured by the following method. 100 g of weighed sample oil (lubricating base oil) is placed in a round bottom flask, 200 mg of urea, 360 ml of toluene and 40 ml of methanol are added and stirred at room temperature for 6 hours. As a result, white granular crystals are produced as urea adducts in the reaction solution. The reaction solution is filtered through a 1 micron filter to collect the produced white granular crystals, and the obtained crystals are washed 6 times with 50 ml of toluene. The recovered white crystals are put in a flask, 300 ml of pure water and 300 ml of toluene are added, and the mixture is stirred at 80 ° C. for 1 hour. The aqueous phase is separated and removed with a separatory funnel, and the toluene phase is washed three times with 300 ml of pure water. A desiccant (sodium sulfate) is added to the toluene phase for dehydration, and then toluene is distilled off. The ratio (mass percentage) of the urea adduct thus obtained to the sample oil is defined as the urea adduct value.

  In the measurement of the urea adduct value, as the urea adduct, normal paraffin remains in the isoparaffin component that adversely affects the low-temperature viscosity characteristics, the thermal conductivity deterioration component, or the lubricating base oil. In this case, the normal paraffin in the case can be collected accurately and reliably, so that it is excellent as a low temperature viscosity characteristic and thermal conductivity evaluation index of the lubricating base oil. The inventors of the present invention have analyzed by using GC and NMR that the main component of the urea adduct is a normal paraffin and an isoparaffin urea adduct having 6 or more carbon atoms from the end of the main chain to the branch position. Confirm that there is.

  Further, “poly (meth) acrylate” as used in the present invention is a general term for polyacrylate and polymethacrylate.

  In the lubricating oil composition of the present invention, the poly (meth) acrylate viscosity index improver is preferably a dispersion type poly (meth) acrylate viscosity index improver.

In the lubricating oil composition of the present invention, the PSSI of the poly (meth) acrylate viscosity index improver is 40 or less, and the ratio of the weight average molecular weight of the poly (meth) acrylate viscosity index improver to PSSI is 1. × 10 ⁴ or more is preferable.

  Here, “PSSI” in the present invention conforms to ASTM D 6022-01 (Standard Practicing for Calming of Permanent Shear Stability Index), and ASTM D 6278-02 (Test Method for Stood for Sto Permanent Shear Stability Index calculated based on data measured by European Diesel Injector Apparatus.

Further, as the poly (meth) acrylate viscosity index improver, those having a branched hydrocarbon group in which R ² in the general formula (1) has 20 or more carbon atoms are preferable.

  The lubricating oil composition of the present invention preferably further contains one or more friction modifiers selected from organic molybdenum compounds and ashless friction modifiers.

  The lubricating oil composition of the present invention is excellent in fuel economy and low-temperature viscosity characteristics, without using a synthetic oil such as a poly-α-olefin base oil or an ester base oil or a low viscosity mineral oil base oil. While maintaining the HTHS viscosity at 150 ° C., it is possible to achieve both fuel economy and low temperature viscosity at −35 ° C. or lower, especially reducing the kinematic viscosity at 40 ° C. and 100 ° C. and the HTHS viscosity at 100 ° C. The CCS viscosity at -35 ° C can be significantly improved.

  The lubricating oil composition of the present invention can also be suitably used for gasoline engines, diesel engines, gas engines for motorcycles, automobiles, power generation, cogeneration, etc., and further has a sulfur content of 50 mass. Not only can it be suitably used for these various engines using fuel of ppm or less, but it is also useful for various engines for ships and outboard motors. The lubricating oil composition of the present invention is particularly effective for improving the fuel consumption of an engine having a roller tappet type valve operating system in that it has excellent viscosity temperature characteristics.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

The lubricating oil composition of the present invention has a urea base adduct component having a urea adduct value of 4% by mass or less, a kinematic viscosity at 40 ° C. of 25 mm ² / s or less, and a viscosity index of 120 or more (hereinafter, for convenience). (Referred to as “the lubricating base oil according to the present invention” for convenience) (hereinafter referred to as “the lubricating base oil component according to the present invention”). Containing).

  The lubricating base oil component according to the present invention may be any of mineral base oil, synthetic base oil, or a mixture of both, provided that the urea adduct value, kinematic viscosity at 40 ° C. and viscosity index satisfy the above conditions. There may be.

  As the lubricating base oil component according to the present invention, it is possible to satisfy the requirements of viscosity-temperature characteristics, low temperature viscosity characteristics and thermal conductivity at a high level. A mineral base oil or a synthetic base oil obtained by hydrocracking / hydroisomerization, or a mixture of both is preferred so that the adduct value is 4% by mass or less and the viscosity index is 120 or more.

  The urea adduct value of the lubricating base oil component according to the present invention is 4% by mass or less as described above from the viewpoint of improving the low temperature viscosity characteristics without impairing the viscosity-temperature characteristics and obtaining high thermal conductivity. Is preferably 3.5% by mass or less, more preferably 3% by mass or less, and still more preferably 2.5% by mass or less. In addition, the urea adduct value of the lubricating base oil component may be 0% by mass, but a sufficient low temperature viscosity characteristic and a lubricating base oil having a higher viscosity index can be obtained, and the dewaxing conditions can be relaxed. In view of excellent economic efficiency, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 0.8% by mass or more.

Further, the 40 ° C. kinematic viscosity of the lubricating base oil component according to the present invention needs to be 25 mm ² / s or less, preferably 22 mm ² / s or less, more preferably 20 mm ² / s or less, and still more preferably. Is 18 or less, particularly preferably 16 or less. On the other hand, the 40 ° C. kinematic viscosity is preferably 8 mm ² / s or more, more preferably 10 mm ² / s or more, still more preferably 12 or more, and particularly preferably 14 or more. The kinematic viscosity at 40 ° C. here refers to the kinematic viscosity at 40 ° C. defined in ASTM D-445. If the 40 ° C. kinematic viscosity of the lubricating base oil component exceeds 25 mm 2 / ^s, the low temperature viscosity characteristics are deteriorated, and there may not be obtained sufficient fuel saving properties, the following cases 8 mm 2 / ^s Since the formation of an oil film at the lubrication site is insufficient, the lubricity is inferior, and the evaporation loss of the lubricating oil composition may increase.

The 100 ° C. kinematic viscosity of the lubricating base oil component according to the present invention is preferably 6.0 mm ² / s or less, more preferably 5.0 mm ² / s or less, and even more preferably 4.5 mm ² / s or less. Particularly preferably, it is 4.0 mm ² / s or less, and most preferably 3.9 mm ² / s or less. On the other hand, the 100 ° C. kinematic viscosity is preferably 2.5 mm ² / s or more, more preferably 3.0 mm ² / s or more, still more preferably 3.3 mm ² / s or more, and particularly preferably 3.5 mm. ² / s or more, most preferably 3.7 mm ² / s or more. The kinematic viscosity at 100 ° C. here refers to the kinematic viscosity at 100 ° C. as defined in ASTM D-445. When the 100 ° C. kinematic viscosity of the lubricating base oil component exceeds 6.0 mm ² / s, the low-temperature viscosity characteristics may be deteriorated, and sufficient fuel economy may not be obtained. 2.5 mm ² / s In the following cases, the formation of an oil film at the lubrication site is insufficient, resulting in poor lubricity, and the evaporation loss of the lubricating oil composition may be increased.

  The viscosity index of the lubricating base oil component according to the present invention should be 120 or more so that excellent viscosity characteristics can be obtained from low temperature to high temperature and in order to prevent evaporation even at low viscosity. Necessary, preferably 125 or more, more preferably 130 or more, still more preferably 135 or more, particularly preferably 140 or more. The upper limit of the viscosity index is not particularly limited, and is about 125 to 180, such as normal paraffin, slack wax, GTL wax, or isoparaffin mineral oil obtained by isomerizing these, complex ester base oil or HVI-PAO. The thing of about 150-250 like a base oil can also be used. However, for normal paraffin, slack wax, GTL wax and the like, or isoparaffin-based mineral oil obtained by isomerizing these, it is preferably 180 or less, more preferably 160 or less, in order to improve low-temperature viscosity characteristics. It is more preferably 150 or less, and particularly preferably 145 or less.

  The iodine value of the lubricating base oil component according to the present invention is preferably 1 or less, more preferably 0.5 or less, still more preferably 0.3 or less, and particularly preferably 0.15 or less. Preferably it is 0.1 or less. Further, it may be less than 0.01, but from the viewpoint of the small effect that is commensurate with it and the economy, it is preferably 0.001 or more, more preferably 0.01 or more, and still more preferably 0.03. Above, especially preferably 0.05 or more. By setting the iodine value of the lubricating base oil component to 0.5 or less, the thermal and oxidation stability can be dramatically improved. In addition, the iodine value as used in the field of this invention means the iodine value measured by the indicator titration method of JIS K0070 "the acid value of a chemical product, the saponification value, the iodine value, the hydroxyl value, and the unsaponification value."

  For the production of the lubricating base oil component according to the present invention, a raw oil containing normal paraffin can be used. The raw material oil may be either mineral oil or synthetic oil, or may be a mixture of two or more of these. Further, the content of normal paraffin in the raw material oil is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, more preferably 90% by mass, based on the total amount of the raw material oil. Especially preferably, it is 95 mass% or more, Most preferably, it is 97 mass% or more.

  Examples of the wax-containing raw material include oils derived from solvent refining methods such as raffinate, partial solvent dewaxed oil, dewaxed oil, distillate, reduced pressure gas oil, coker gas oil, slack wax, foots oil, and fisher Examples include Tropsch wax, and among these, slack wax and Fischer-Tropsch wax are preferable.

  Slack waxes are typically derived from hydrocarbon feedstocks by solvent or propane dewaxing. Slack wax may contain residual oil, which can be removed by deoiling. Foots oil corresponds to deoiled slack wax.

  Fischer-Tropsch wax is produced by a so-called Fischer-Tropsch synthesis method.

  Moreover, the raw material oil derived from solvent extraction is obtained by sending a high-boiling petroleum fraction from atmospheric distillation to a vacuum distillation apparatus and solvent-extracting the distillation fraction from this apparatus. The residue from the vacuum distillation may be denitrified. In the solvent extraction method, aromatic components are dissolved in the extraction phase while leaving more paraffinic components in the raffinate phase. Naphthene is partitioned into the extraction phase and the raffinate phase. As the solvent for solvent extraction, phenol, furfural, N-methylpyrrolidone and the like are preferably used. By controlling the solvent / oil ratio, the extraction temperature, the method of contacting the distillate to be extracted with the solvent, etc., the degree of separation between the extraction phase and the raffinate phase can be controlled. Furthermore, a bottom fraction obtained from a fuel oil hydrocracking apparatus may be used as a raw material by using a fuel oil hydrocracking apparatus having higher hydrogenation resolution.

The raw material oil is subjected to hydrocracking / hydroisomerization so that the urea adduct value of the material to be treated is 4% by mass or less and the viscosity index is 100 or more. Such a lubricating base oil component can be obtained. The hydrocracking / hydroisomerization step is not particularly limited as long as the urea adduct value and the viscosity index of the obtained workpiece satisfy the above conditions. The preferred hydrocracking / hydroisomerization step in the present invention is:
A first step of hydrotreating a raw oil containing normal paraffin using a hydrotreating catalyst;
A second step of hydrodewaxing the object to be treated obtained in the first step using a hydrodewaxing catalyst;
The to-be-processed object obtained by a 2nd process is equipped with the 3rd process of hydrotreating using a hydrotreating catalyst. About the to-be-processed object obtained after a 3rd process, you may separate and remove a predetermined component by distillation etc. as needed.

  In the lubricating base oil component according to the present invention obtained by the above production method, other properties are not particularly limited as long as the urea adduct value, the 40 ° C. viscosity, and the viscosity index satisfy the above-mentioned conditions. The lubricating base oil component preferably satisfies the following conditions.

  The content of the saturated component in the lubricant base oil component according to the present invention is preferably 90% by mass or more, more preferably 93% by mass or more, and still more preferably 95% by mass or more, based on the total amount of the lubricant base oil component. is there. Moreover, the ratio of the naphthene part to the said saturated part becomes like this. Preferably it is 0.1-40 mass%, More preferably, it is 1-30 mass%, More preferably, it is 5-20 mass%, Most preferably, it is 10-15 mass%. is there. By satisfying the above conditions for the content of the saturate and the proportion of the naphthene in the saturate, excellent viscosity-temperature characteristics, low-temperature viscosity characteristics and thermal / oxidation stability can be achieved. When an additive is blended in the lubricating base oil component, the additive function should be expressed at a higher level while the additive is sufficiently stably dissolved and retained in the lubricating base oil component. Can do. Furthermore, when the content of the saturate and the ratio of the naphthene to the saturate satisfy the above conditions, the friction characteristics of the lubricating base oil component itself can be improved, and as a result, the friction reduction effect is improved. As a result, energy saving can be improved. In addition, when content of a saturated part is less than 90 mass%, it exists in the tendency for a viscosity-temperature characteristic, thermal / oxidation stability, and a friction characteristic to become inadequate. Further, when the naphthene content in the saturated content is less than 0.1% by mass, when the additive is blended with the lubricating base oil component, the solubility of the additive becomes insufficient, and the lubricating oil base Since the effective amount of the additive dissolved and held in the oil component decreases, the function of the additive tends not to be obtained effectively. Furthermore, when the ratio of the cyclic saturated component in the saturated component exceeds 10% by mass, the effectiveness of the additive tends to be reduced when the additive is added to the lubricating base oil component.

  In the present invention, the ratio of the naphthene content in the saturated content of 0.1 to 40% by mass is equivalent to the paraffin content in the saturated content of 99.9 to 60% by mass. Here, the paraffin content includes both normal paraffin and isoparaffin. The ratio of normal paraffin and isoparaffin in the lubricating base oil component according to the present invention is not particularly limited as long as the urea adduct value satisfies the above conditions, but the isoparaffin ratio is preferably 60 based on the total amount of the lubricating base oil component. To 99.9% by mass, more preferably 70 to 99% by mass, still more preferably 80 to 95% by mass, and particularly preferably 85 to 90% by mass. When the ratio of isoparaffin in the lubricating base oil component satisfies the above conditions, viscosity-temperature characteristics and thermal / oxidative stability can be further improved, and an additive is added to the lubricating base oil component. In this case, the function of the additive can be expressed at a higher level while the additive is dissolved and held sufficiently stably.

  In addition, content of the saturated part said by this invention means the value (unit: mass%) measured based on ASTM D 2007-93.

  Moreover, the ratio of the naphthene content and the paraffin content in the saturated content referred to in the present invention is a naphthene content measured according to ASTM D 2786-91, respectively (measuring object: 1-ring to 6-ring naphthene, unit: mass%). ) And alkane content (unit: mass%).

  The content of the aromatic component in the lubricating base oil component according to the present invention is not particularly limited, but is preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less, particularly Preferably it is 0.5 mass% or less, Most preferably, it is 0.3 mass% or less. The total aromatic content may be 0% by mass, but it is preferably 0.01% by mass or more from the viewpoint of small effect corresponding to the total aromatics and economic efficiency and the solubility of the additive. The content is more preferably at least 05 mass%, further preferably at least 0.1 mass%. When the total aromatic content of the base oil exceeds 5% by mass, the oxidation stability is inferior, which is not preferable.

  In addition, the said total aromatic content means the aromatic fraction (aromatic fraction) content measured based on ASTMD2549. Usually, this aromatic fraction includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene, alkylated products thereof, compounds in which four or more benzene rings are condensed, and heterogeneous compounds such as pyridines, quinolines, phenols, and naphthols. Compounds having aromatics are included.

  Further, the sulfur content in the lubricating base oil component according to the present invention is not particularly limited, but is preferably 50 ppm by mass or less, more preferably 10 ppm by mass or less, still more preferably 5 ppm by mass or less, particularly preferably. Is 1 ppm by mass or less. By setting the sulfur content to 50 ppm by mass or less, excellent thermal and oxidation stability can be achieved.

  Further, the pour point of the lubricating base oil component according to the present invention is preferably −10 ° C. or lower, more preferably −12.5 ° C. or lower, still more preferably −15, although it depends on the viscosity grade of the lubricating base oil. ° C or lower, most preferably -17.5 ° C or lower, particularly preferably -20 ° C or lower. If the pour point exceeds the upper limit, the low temperature fluidity of the entire lubricating oil using the lubricating base oil component may be reduced. The pour point of the lubricating base oil component according to the present invention is preferably −50 ° C. or higher, more preferably −40 ° C. or higher, still more preferably −30 ° C. or higher, and particularly preferably −25 ° C. or higher. When the pour point is lower than the lower limit, the viscosity index of the entire lubricating oil using the lubricating base oil component is lowered, and there is a possibility that fuel economy is deteriorated. In addition, the pour point as used in the field of this invention means the pour point measured based on JISK2269-1987.

Further, the density (ρ ₁₅ ) at 15 ° C. of the lubricating base oil component according to the present invention depends on the viscosity grade of the lubricating base oil component, but is not more than the value of ρ represented by the following formula (A). That is, it is preferable that ρ ₁₅ ≦ ρ.
ρ = 0.0025 × kv100 + 0.816 (A)
[Wherein, kv100 represents the kinematic viscosity (mm ² / s) of the lubricating base oil component at 100 ° C. ]

When ρ ₁₅ > ρ, the viscosity-temperature characteristics and the heat / oxidation stability, as well as the volatilization prevention property and the low temperature viscosity characteristics tend to be lowered, and the fuel economy may be deteriorated. Moreover, when an additive is mix | blended with a lubricating base oil component, there exists a possibility that the effectiveness of the said additive may fall.

Specifically, the density (ρ ₁₅ ) at 15 ° C. of the lubricating base oil component according to the present invention is preferably 0.840 or less, more preferably 0.830 or less, still more preferably 0.825 or less, particularly preferably. Is 0.822 or less.

  In addition, the density in 15 degreeC said by this invention means the density measured in 15 degreeC based on JISK2249-1995.

  The amount of evaporation loss of the lubricating base oil component according to the present invention is preferably NOACK evaporation of 20% by mass or less, more preferably 16% by mass or less, and more preferably 10% by mass or less. Particularly preferred. When the NOACK evaporation amount of the lubricating base oil component exceeds 20% by mass, the evaporation loss of the lubricating oil is large, which causes an increase in viscosity and the like, which is not preferable. Here, the NOACK evaporation amount is a value obtained by measuring the evaporation amount of the lubricating oil measured in accordance with ASTM D 5800.

In the lubricating oil composition of the present invention, as a lubricating base oil component according to the present invention, a lubricating oil base that satisfies the requirements of a urea adduct value of 4% by mass or less, a 40 ° C. kinematic viscosity of 25 mm ² / s or less, and a viscosity index of 120 or more. One type of oil may be used alone, or two or more types may be used in combination.

  The content of the lubricating base oil component according to the present invention is 10 to 100% by mass, preferably 30 to 98% by mass, more preferably 50 to 95%, based on the total amount of the lubricating base oil according to the present invention. It is 70 mass%, More preferably, it is 70-93 mass%, Most preferably, it is 80-95 mass%. When the said content rate is less than 10 mass%, there exists a possibility that the required low temperature viscosity and fuel-saving performance may not be obtained.

  The lubricating base oil according to the present invention may be composed of only the lubricating base oil component according to the present invention, but a mineral base oil, a synthetic base oil other than the lubricating base oil component according to the present invention, or You may further contain the arbitrary mixtures of 2 or more types of lubricating oil chosen from these. However, when the lubricating base oil component according to the present invention and other lubricating base oil components are used in combination, the ratio of the other lubricating base oil components is based on the total amount of the lubricating base oil according to the present invention. It is necessary to set it to 90 mass% or less.

Although it does not restrict | limit especially as another lubricating base oil component used together with the lubricating base oil component which concerns on this invention, As a mineral oil type | system | group base oil, the solvent whose dynamic viscosity in 100 degreeC is 1-100 mm < ² > / s, for example Refined mineral oil, hydrocracked mineral oil, hydrorefined mineral oil, solvent dewaxing base oil and the like.

  Synthetic base oils include poly α-olefins or hydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridec Decyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycol, dialkyl Examples thereof include diphenyl ether and polyphenyl ether, and among them, poly α-olefin is preferable. As the poly α-olefin, typically, an oligomer or co-oligomer (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and those. Of the hydrides.

  The production method of the poly-α-olefin is not particularly limited. For example, Friedel-Crafts catalyst containing a complex of aluminum trichloride or boron trifluoride with water, alcohol (ethanol, propanol, butanol, etc.), carboxylic acid or ester. And a method of polymerizing α-olefin in the presence of a polymerization catalyst such as

［式（１）中、Ｒ^１は水素又はメチル基を示し、Ｒ^２は炭素数１６以上の直鎖状又は分枝状の炭化水素基を示す。］ In addition, the poly (meth) acrylate viscosity index improver contained in the lubricating oil composition of the present invention contains one or more (meth) acrylate structural units represented by the following general formula (1) as 0 0.5 to 70 mol% (hereinafter referred to as “viscosity index improver according to the present invention” for convenience). The (A) poly (meth) acrylate viscosity index improver used in the present invention may be either a non-dispersion type or a dispersion type, but is preferably a dispersion type.

[In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents a linear or branched hydrocarbon group having 16 or more carbon atoms. ]

R ² in the structural unit represented by the formula (1) is a linear or branched hydrocarbon group having 16 or more carbon atoms as described above, and preferably a linear or branched group having 18 or more carbon atoms. More preferably, it is a linear or branched hydrocarbon having 20 or more carbon atoms, more preferably a branched hydrocarbon group having 20 or more carbon atoms. The upper limit of the hydrocarbon group represented by R ² is not particularly limited, but is preferably a linear or branched hydrocarbon group having 100 or less carbon atoms. More preferably, it is a linear or branched hydrocarbon of 50 or less, more preferably a linear or branched hydrocarbon of 30 or less, particularly preferably a branched hydrocarbon of 30 or less. And most preferably 25 or less branched hydrocarbons.

  In the viscosity index improver according to the present invention, the proportion of the (meth) acrylate structural unit represented by the general formula (1) in the polymer is 0.5 to 70 mol% as described above, preferably It is 60 mol% or less, More preferably, it is 50 mol% or less, More preferably, it is 40 mol% or less, Most preferably, it is 30 mol% or less. Further, it is preferably 1 mol% or more, more preferably 3 mol% or more, further preferably 5 mol% or more, and particularly preferably 10 mol% or more. If it exceeds 70 mol%, the effect of improving viscosity temperature characteristics and low temperature viscosity characteristics may be inferior, and if it is less than 0.5 mol%, the effect of improving viscosity temperature characteristics may be inferior.

  The viscosity index improver according to the present invention may be a copolymer having any (meth) acrylate structural unit in addition to the (meth) acrylate structural unit represented by the general formula (1). Such a copolymer includes one or more monomers represented by the following general formula (2) (hereinafter referred to as “monomer (M-1)”) and monomers other than the monomer (M-1). Can be copolymerized.

［上記一般式（２）中、Ｒ^１は水素原子又はメチル基を示し、Ｒ^２は炭素数１６以上の直鎖状又は分枝状の炭化水素基を示す。］

[In the general formula (2), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a linear or branched hydrocarbon group having 16 or more carbon atoms. ]

  Although the monomer combined with the monomer (M-1) is arbitrary, for example, a monomer represented by the following general formula (3) (hereinafter referred to as “monomer (M-2)”) is preferable. The copolymer of the monomer (M-1) and the monomer (M-2) is a so-called non-dispersed poly (meth) acrylate viscosity index improver.

［上記一般式（３）中、Ｒ^３は水素原子又はメチル基を示し、Ｒ^４は炭素数１〜１５の直鎖状又は分枝状の炭化水素基を示す。］

[In the general formula (3), R ³ represents a hydrogen atom or a methyl group, and R ⁴ represents a linear or branched hydrocarbon group having 1 to 15 carbon atoms. ]

  Moreover, as another monomer combined with a monomer (M-1), it represents with the monomer (henceforth "monomer (M-3)") represented by the following general formula (4), and the following general formula (5). 1 type or 2 types or more chosen from the monomer (henceforth "monomer (M-4)") to be used is suitable. The copolymer of the monomer (M-1) and the monomer (M-3) and / or (M-4) is a so-called dispersion type poly (meth) acrylate viscosity index improver. The dispersed poly (meth) acrylate viscosity index improver may further contain a monomer (M-2) as a constituent monomer.

［上記一般式（４）中、Ｒ^５は水素原子又はメチル基を示し、Ｒ^６は炭素数１〜１８のアルキレン基を示し、Ｅ^１は窒素原子を１〜２個、酸素原子を０〜２個含有するアミン残基又は複素環残基を示し、ａは０又は１を示す。］

[In the general formula (4), R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents an alkylene group having 1 to 18 carbon atoms, E ¹ represents ¹ to 2 nitrogen atoms and 0 to 0 oxygen atoms. 2 represents an amine residue or heterocyclic residue, and a represents 0 or 1. ]

Specific examples of the alkylene group having 1 to 18 carbon atoms represented by R ⁶ include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, Examples include an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, and an octadecylene group (these alkylene groups may be linear or branched).

Specific examples of the group represented by E ¹ include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylidino group, an acetylamino group, a benzoylamino group, Examples thereof include a morpholino group, a pyrrolyl group, a pyrrolino group, a pyridyl group, a methylpyridyl group, a pyrrolidinyl group, a piperidinyl group, a quinonyl group, a pyrrolidonyl group, a pyrrolidono group, an imidazolino group, and a pyrazino group.

［上記一般式（５）中、Ｒ^７は水素原子又はメチル基を示し、Ｅ^２は窒素原子を１〜２個、酸素原子を０〜２個含有するアミン残基又は複素環残基を示す。］

[In the above general formula (5), R ⁷ represents a hydrogen atom or a methyl group, and E ² represents an amine residue or a heterocyclic residue containing 1 to 2 nitrogen atoms and 0 to 2 oxygen atoms. . ]

Specific examples of the group represented by E ² include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylidino group, an acetylamino group, a benzoylamino group, and a morpholino group. Pyrrolyl group, pyrrolino group, pyridyl group, methylpyridyl group, pyrrolidinyl group, piperidinyl group, quinonyl group, pyrrolidonyl group, pyrrolidono group, imidazolino group, pyrazino group and the like.

  As preferable examples of the monomers (M-3) and (M-4), specifically, dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-methyl-5-vinylpyridine, Examples thereof include morpholinomethyl methacrylate, morpholinoethyl methacrylate, N-vinylpyrrolidone, and mixtures thereof.

  Although there is no restriction | limiting in particular about the copolymerization molar ratio of the copolymer of a monomer (M-1) and monomer (M-2)-(M-4), Monomer (M-1): Monomer (M-2) -(M-4) = 0.5: 99.5-70: 30 is preferable, More preferably, it is 5: 90-50: 50, More preferably, it is 20: 80-40: 60.

  The method for producing the viscosity index improver according to the present invention is arbitrary, but for example, in the presence of a polymerization initiator such as benzoyl peroxide, the monomer (M-1) and the monomers (M-2) to (M-4) ) Can be easily obtained by radical solution polymerization.

  The PSSI (Permanent Cystability Index) of the viscosity index improver according to the present invention is preferably 40 or less, more preferably 5 to 40, still more preferably 10 to 35, still more preferably 15 to 30, particularly preferably 20 to 25. It is. When PSSI exceeds 40, shear stability may be deteriorated. Further, when PSSI is less than 5, the effect of improving the viscosity index is small, which is not only inferior in fuel economy and low-temperature viscosity characteristics, but also in cost.

  Note that “PSSI” here conforms to ASTM D 6022-01 (Standard Practication for Calculation of Permanent Shear Stable Stability Index), and ASTM D 6278-02 (Test Method for Stood For Shar. It means the permanent shear stability index of the polymer, calculated based on the data measured by Injector Apparatus.

The weight average molecular weight (M _w ) of the viscosity index improver according to the present invention is preferably 5,000 or more, more preferably 50,000 or more, still more preferably 100,000 or more, particularly preferably. Is 200,000 or more, most preferably 300,000 or more. Moreover, it is preferable that it is 1,000,000 or less, More preferably, it is 700,000 or less, More preferably, it is 600,000 or less, Especially preferably, it is 500,000 or less. If the weight average molecular weight is less than 5,000, the effect of improving the viscosity index is small and not only fuel efficiency and low temperature viscosity characteristics are inferior, but also the cost may increase, and the weight average molecular weight exceeds 1,000,000. In some cases, shear stability, solubility in base oil, and storage stability may be deteriorated.

The ratio of the weight average molecular weight to number average molecular weight of the viscosity index improver according to the present invention _(M W / M _n) is preferably from 0.5 to 5.0, more preferably 1.0 to 3. 5, more preferably 1.5 to 3, particularly preferably 1.7 to 2.5. When the ratio of the weight average molecular weight to the number average molecular weight is 0.5 or less or 5.0 or more, not only the solubility in the base oil and the storage stability are deteriorated, but also the viscosity-temperature characteristics are deteriorated, and the fuel economy is improved. May get worse.

The weight average molecular weight and PSSI ratio of viscosity index improver according to the present invention _(M W / PSSI) is at 1 × 10 ⁴ or more, preferably 1.5 × 10 ⁴ or more, more preferably 2 × 10 ⁴ or more, more preferably 2.5 × 10 ⁴ or more. If M _W / PSSI is below 1 × 10 ^4, there is a possibility that the viscosity-temperature characteristic is deteriorated i.e. deteriorates fuel efficiency.

  The content of the viscosity index improver according to the present invention is preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass, still more preferably 1 to 30% by mass, particularly based on the total amount of the composition. Preferably it is 5-20 mass%. When the content of the viscosity index improver is less than 0.1% by mass, the effect of improving the viscosity index and the effect of reducing the product viscosity are reduced, and thus there is a possibility that the fuel economy cannot be improved. Also, if it exceeds 50% by mass, the product cost will increase significantly and the viscosity of the base oil will need to be reduced. Therefore, the lubrication performance under severe lubrication conditions (high temperature and high shear conditions) will be reduced and wear will be reduced. There is a concern that defects such as burn-in, seizure and fatigue failure may be the cause.

  In addition, the lubricating oil composition of the present invention is not only the viscosity index improver according to the present invention described above, but also the usual general non-dispersed or dispersed poly (meth) acrylate, non-dispersed or dispersed ethylene-α. -An olefin copolymer or a hydrogenated product thereof, polyisobutylene or a hydrogenated product thereof, a styrene-diene hydrogenated copolymer, a styrene-maleic anhydride ester copolymer, a polyalkylstyrene, or the like may further be contained.

  In the lubricating oil composition of the present invention, a friction modifier selected from an organic molybdenum compound and an ashless friction modifier can be further added in order to improve fuel economy performance.

  Examples of the organic molybdenum compound used in the present invention include organic molybdenum compounds containing sulfur such as molybdenum dithiophosphate and molybdenum dithiocarbamate.

  Specific examples of preferred molybdenum dithiocarbamates include molybdenum sulfide diethyldithiocarbamate, molybdenum dipropyldithiocarbamate, molybdenum dibutyldithiocarbamate, molybdenum dipentyldithiocarbamate, molybdenum dihexyldithiocarbamate, molybdenum dihexyldithiocarbamate, molybdenum dioctyldithiocarbamate, and molybdenum disulfide. Decyl dithiocarbamate, sulfurized molybdenum didodecyl dithiocarbamate, molybdenum di (butylphenyl) dithiocarbamate, molybdenum di (nonylphenyl) dithiocarbamate, sulfurized oxymolybdenum diethyldithiocarbamate, sulfurized oxymolybdenum dipropyldithiocarbamate, sulfurized oxymolybdenum dibutyldithiocarbamate Oki Molybdenum dipentyldithiocarbamate, sulfurized oxymolybdenum dihexyldithiocarbamate, sulfurized oxymolybdenum dioctyldithiocarbamate, sulfurized oxymolybdenum didecyldithiocarbamate, sulfurized oxymolybdenum didodecyldithiocarbamate, sulfurized oxymolybdenum di (butylphenyl) dithiocarbamate, sulfurized oxymolybdenum di (nonylphenyl) Examples thereof include dithiocarbamate (the alkyl group may be linear or branched, and the bonding position of the alkyl group of the alkylphenyl group is arbitrary), and mixtures thereof. As these molybdenum dithiocarbamates, compounds having hydrocarbon groups having different carbon numbers and / or structures in one molecule can also be preferably used.

  Other organic molybdenum compounds containing sulfur include molybdenum compounds (for example, molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, orthomolybdic acid, paramolybdic acid, molybdic acid such as (poly) sulfurized molybdic acid, These metal salts of molybdate, molybdenum salts such as ammonium salts, molybdenum sulfides such as molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, and polysulfide molybdenum, molybdenum sulfides, metal salts or amine salts of molybdenum sulfides, chlorides Molybdenum halides such as molybdenum) and sulfur-containing organic compounds (eg, alkyl (thio) xanthates, thiadiazoles, mercaptothiadiazoles, thiocarbonates, tetrahydrocarbylthiuram disulfides, bis (di (thio) hydrocarbons). Bildithiophosphonate) disulfide, organic (poly) sulfide, sulfurized ester, etc.) or other organic compounds, etc., or a sulfur-containing molybdenum compound such as molybdenum sulfide or sulfurized molybdic acid, and an alkenyl succinimide complex, etc. Can be mentioned.

  As the organic molybdenum compound, an organic molybdenum compound containing no sulfur as a constituent element can be used.

  Specific examples of organic molybdenum compounds that do not contain sulfur as a constituent element include molybdenum-amine complexes, molybdenum-succinimide complexes, molybdenum salts of organic acids, and molybdenum salts of alcohols. Complexes, molybdenum salts of organic acids and molybdenum salts of alcohols are preferred.

  In the lubricating oil composition of the present invention, when an organic molybdenum compound is used, its content is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0, in terms of molybdenum element, based on the total amount of the composition. 0.005% by mass or more, more preferably 0.01% by mass or more, preferably 0.2% by mass or less, more preferably 0.1% by mass or less, still more preferably 0.05% by mass or less, particularly Preferably it is 0.03 mass% or less. When the content is less than 0.001% by mass, the thermal and oxidation stability of the lubricating oil composition becomes insufficient, and in particular, it tends to be impossible to maintain excellent cleanliness over a long period of time. On the other hand, when the content exceeds 0.2% by mass, an effect commensurate with the content cannot be obtained, and the storage stability of the lubricating oil composition tends to decrease.

  As the ashless friction modifier used in the present invention, any compound usually used as a friction modifier for lubricating oils can be used, for example, an alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly the number of carbon atoms. Ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, etc., having at least one 6-30 linear alkyl group or linear alkenyl group in the molecule. It is done. In addition, one or more compounds selected from the group consisting of nitrogen-containing compounds represented by the following general formulas (6) and (7) and acid-modified derivatives thereof, and various examples exemplified in International Publication No. 2005/037967 pamphlet Ashless friction modifiers may be mentioned.

In the general formula (6), R ⁸ has a hydrocarbon group having 1 to 30 carbon atoms or a hydrocarbon group having 1 to 30 carbon atoms, preferably a hydrocarbon group having 10 to 30 carbon atoms or a functionality. A hydrocarbon group having 10 to 30 carbon atoms, more preferably an alkyl group having 12 to 20 carbon atoms, an alkenyl group or a functional hydrocarbon group, particularly preferably an alkenyl group having 12 to 20 carbon atoms, R ⁹ and R ¹⁰ each independently has a hydrocarbon group having 1 to 30 carbon atoms, a hydrocarbon group having 1 to 30 carbon atoms or hydrogen having functionality, preferably a hydrocarbon group having 1 to 10 carbon atoms, or functionality. A hydrocarbon group or hydrogen having 1 to 10 carbon atoms, more preferably a hydrocarbon group or hydrogen having 1 to 4 carbon atoms, more preferably hydrogen, and X represents oxygen or sulfur, preferably oxygen.

In the general formula (7), R ¹¹ is a hydrocarbon group having 1 to 30 carbon atoms or a hydrocarbon group having 1 to 30 carbon atoms having functionality, preferably a hydrocarbon group or functionality having 10 to 30 carbon atoms. A hydrocarbon group having 10 to 30 carbon atoms, more preferably an alkyl group having 12 to 20 carbon atoms, an alkenyl group or a hydrocarbon group having functionality, particularly preferably an alkenyl group having 12 to 20 carbon atoms, and R ¹² _, R ¹³ and R ¹⁴ are each independently a hydrocarbon group having 1 to 30 carbon atoms, a hydrocarbon group having 1 to 30 carbon atoms or hydrogen having functionality, preferably a hydrocarbon group having 1 to 10 carbon atoms. , A functional hydrocarbon group having 1 to 10 carbon atoms or hydrogen, more preferably a hydrocarbon group having 1 to 4 carbon atoms or hydrogen, and more preferably hydrogen.

Specific examples of the nitrogen-containing compound represented by the general formula (7) include a hydrazide having 1 to 30 carbon atoms or a functional hydrocarbon group having 1 to 30 carbon atoms and derivatives thereof. is there. When R ¹¹ is a hydrocarbon group having 1 to 30 carbon atoms or a hydrocarbon group having 1 to 30 carbon atoms having functionality, and R ^{12 to} R ¹⁴ are hydrogen, the hydrocarbon group having 1 to 30 carbon atoms or the functionality Any of hydrazide having a hydrocarbon group having 1 to 30 carbon atoms, R ¹¹ and R ^{12 to} R ¹⁴ is a hydrocarbon group having 1 to 30 carbon atoms or a hydrocarbon group having 1 to 30 carbon atoms having functionality. When R ^{12 to} R ¹⁴ are hydrogen, N-hydrocarbyl hydrazide having a hydrocarbon group having 1 to 30 carbon atoms or a hydrocarbon group having 1 to 30 carbon atoms having functionality (hydrocarbyl is a hydrocarbon group) Etc.).

  When the ashless friction modifier is used in the lubricating oil composition of the present invention, the content of the ashless friction modifier is preferably 0.01% by mass or more, more preferably 0.1% by mass, based on the total amount of the composition. % Or more, more preferably 0.3% by mass or more, preferably 3% by mass or less, more preferably 2% by mass or less, and still more preferably 1% by mass or less. When the content of the ashless friction modifier is less than 0.01% by mass, the effect of reducing friction due to the addition tends to be insufficient, and when the content exceeds 3% by mass, the effect of an antiwear additive or the like. Tends to be inhibited, or the solubility of the additive tends to deteriorate.

  In the present invention, either one of the organic molybdenum compound or the ashless friction modifier may be used, or both may be used in combination, but it is more preferable to use the ashless friction modifier.

  In order to further improve the performance, the lubricating oil composition of the present invention may contain any additive generally used in lubricating oils depending on the purpose. Examples of such additives include metal detergents, ashless dispersants, antioxidants, antiwear agents (or extreme pressure agents), corrosion inhibitors, rust inhibitors, pour point depressants, demulsifiers, metals Examples thereof include additives such as an inactivating agent and an antifoaming agent.

  Examples of metal detergents include alkali metal sulfonates or alkaline earth metal sulfonates, alkali metal phenates or alkaline earth metal phenates, and alkali salts such as alkali metal salicylates or alkaline earth metal salicylates, basic positive salts, or overbased salts. Etc. In the present invention, one or more alkali metal or alkaline earth metal detergents selected from the group consisting of these, particularly alkaline earth metal detergents can be preferably used. In particular, a magnesium salt and / or a calcium salt is preferable, and a calcium salt is more preferably used.

  As the ashless dispersant, any ashless dispersant used in lubricating oils can be used. For example, a mono- or mono-chain having at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule or Bisuccinimide, benzylamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or these And modified products of boron compounds, carboxylic acids, phosphoric acids, and the like. In use, one kind or two or more kinds arbitrarily selected from these can be blended.

  Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants such as copper and molybdenum. Specifically, for example, as a phenol-based ashless antioxidant, 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert- Butylphenol) and the like are amine-based ashless antioxidants such as phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine.

  As the antiwear agent (or extreme pressure agent), any antiwear agent / extreme pressure agent used in lubricating oils can be used. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, phosphites, thiophosphites, dithiophosphites, trithiophosphites Esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate, disulfide , Polysulfides, sulfurized olefins, sulfurized fats and oils, and the like. Among these, addition of a sulfur-based extreme pressure agent is preferable, and sulfurized fats and oils are particularly preferable.

  Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, or imidazole compounds.

  Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.

  As the pour point depressant, for example, a polymethacrylate polymer compatible with the lubricating base oil to be used can be used.

  Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, or polyoxyethylene alkyl naphthyl ether.

  Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

Examples of antifoaming agents include silicone oils having a kinematic viscosity at 25 ° C. of less than 0.1 to 100 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.

  When these additives are contained in the lubricating oil composition of the present invention, the content thereof is 0.01 to 10% by mass based on the total amount of the composition.

Kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is required to be 4 to 12 mm ² / s, preferably 4.5~10mm ² / s, more preferably 5 to 9 mm ² / s, Most preferably, it is 6-8 mm < ² > / s. If the kinematic viscosity at 100 ° C. is less than 4 mm ² / s, there is a risk of insufficient lubricity, and if it exceeds 12 mm ² / s, the necessary low temperature viscosity and sufficient fuel saving performance may not be obtained. is there.

The kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is preferably 4 to 50 mm ² / s, preferably 10 to 40 mm ² / s, more preferably 20 to 35 mm ² / s, and particularly preferably 27. ~32mm is a ² / s. If the kinematic viscosity at 40 ° C. is less than 4 mm ² / s, there is a risk of insufficient lubricity, and if it exceeds 50 mm ² / s, the necessary low temperature viscosity and sufficient fuel saving performance may not be obtained. is there.

  The viscosity index of the lubricating oil composition of the present invention needs to be in the range of 140 to 300, preferably 190 or more, more preferably 200 or more, still more preferably 210 or more, and particularly preferably 220 or more. When the viscosity index of the lubricating oil composition of the present invention is less than 140, it may be difficult to improve fuel economy while maintaining the HTHS viscosity, and further reduce the low temperature viscosity at -35 ° C. May be difficult. In addition, when the viscosity index of the lubricating oil composition of the present invention is 300 or more, low temperature fluidity is deteriorated, and there is a risk of problems due to insufficient solubility of additives and compatibility with sealing materials. There is.

HTHS viscosity at 100 ° C. of the lubricating oil composition of the present invention is preferably 3.0~5.5mm ² / s, preferably 3.5~5.0mm ² / s, more preferably 4.0 ~4.9mm ² / s, particularly preferably 4.2~4.8mm ² / s, most preferably 4.3~4.7mm ² / s. Here, the HTHS viscosity at 100 ° C. indicates the high temperature and high shear viscosity at 100 ° C. defined in ASTM D4683. When the kinematic viscosity at 100 ° C. is less than 3.0 mm ² / s, there is a risk of insufficient lubricity, and when it exceeds 5.5 mm ² / s, the necessary low temperature viscosity and sufficient fuel saving performance are obtained. There is a risk of not being able to.

HTHS viscosity at 0.99 ° C. of the lubricating oil composition of the present invention is preferably 2.0~3.5mm ² / s, preferably 2.3~3.0mm ² / s, more preferably 2.4 ~2.8mm ² / s, particularly preferably 2.5~2.7mm ² / s. The HTHS viscosity at 150 ° C. here refers to the high temperature and high shear viscosity at 150 ° C. defined in ASTM ASTM D4683. When the kinematic viscosity at 150 ° C. is less than 2.0 mm ² / s, there is a risk of insufficient lubricity, and when it exceeds 3.5 mm ² / s, the necessary low temperature viscosity and sufficient fuel saving performance are obtained. There is a risk of not being able to.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

(Examples 1-2, Comparative Examples 1-4)
In Examples 1-2 and Comparative Examples 1-4, lubricating oil compositions having the compositions shown in Table 2 were prepared using the base oils shown below. Table 1 shows the properties of the base oils O-1 and O-2.
(Base oil)
O-1 (base oil 1): mineral oil obtained by hydrocracking / hydroisomerizing n-paraffin-containing oil O-2 (base oil 2): hydrocracked base oil (additive)
A-1 (viscosity index improver 1): Dispersed polymethacrylate (70% by mole of methyl methacrylate and dimethylaminoethyl methacrylate in total, R ² in the general formula (2) is an alkyl group having 16 carbon atoms. methacrylates of the general formula (2) R ² is the R ² of the methacrylate and the general formula (2) is an alkyl group of 18 carbon atoms and the sum of the methacrylate an alkyl group of 20 to 20 carbon atoms mol% in, and , A copolymer obtained by polymerizing 10 mol% of a methacrylate in which R ² in the general formula (2) is a branched alkyl group having 22 carbon atoms, MW = 400,000, Mw / Mn = 2. 2, PSSI = 20, Mw / PSSI ratio = 2 × 10 ⁴ )
A-2 (viscosity index improver 2): non-dispersed polymethacrylate (methyl methacrylate, methacrylate in which R ⁴ in general formula (3) is an alkyl group having 12 carbon atoms, and in general formula (3) and methacrylates R ⁴ is an alkyl group of 13 carbon atoms, the general formula (3) and methacrylate R ⁴ is an alkyl group of 14 carbon atoms in, R ⁴ carbon atoms in the general formula (3) 15) a copolymer obtained by polymerizing a methacrylate having an alkyl group of Mw = 80,000, Mw / Mn = 2.7, PSSI = 5, Mw / PSSI ratio = 2 × 10 ⁴ )
A-3 (viscosity index improver 3): Dispersed polymethacrylate (methyl methacrylate, methacrylate in which R ⁴ in general formula (3) is an alkyl group having 12 carbon atoms, and in general formula (3) and methacrylate R ⁴ is an alkyl group of 13 carbon atoms, the general formula (3) and methacrylate R ⁴ is an alkyl group of 14 carbon atoms in the general formula (3) R ⁴ is 15 carbon atoms in the (Mw = 300,000, Mw / Mn = 4.0, PSSI = 40, Mw / PSSI ratio = 7500)
B-1 (ashless friction modifier 1): glycerin monooleate B-2 (ashless friction modifier 2): oleyl urea C-1 (other additives): additive package (metal detergent, none Including ash dispersants, antioxidants, antiwear agents, pour point depressants, defoamers, etc.).

[Evaluation of lubricating oil composition]
About each lubricating oil composition of Examples 1-2 and Comparative Examples 1-4, kinematic viscosity at 40 ° C. or 100 ° C., viscosity index, HTHS viscosity at 40 ° C. or 100 ° C., and CCS viscosity at −35 ° C. were measured. . Each physical property value was measured by the following evaluation method. The obtained results are shown in Table 1.
(1) Kinematic viscosity: ASTM D-445
(2) HTHS viscosity: ASTM D4683
(3) CCS viscosity: ASTM D5293

  As shown in Table 2, the lubricating oil compositions of Examples 1 and 2 and Comparative Examples 1 to 4 have the same HTHS viscosity at 150 ° C., but in the lubricating oil compositions of Comparative Examples 1 to 4 In comparison, the lubricating oil compositions of Examples 1 and 2 had low 40 ° C. kinematic viscosity, 100 ° C. kinematic viscosity, 100 ° C. HTHS viscosity and CCS viscosity, and good low temperature viscosity and viscosity temperature characteristics. From this result, the lubricating oil composition of the present invention is excellent in fuel economy and low temperature viscosity, without using a synthetic oil such as a poly-α-olefin base oil or an ester base oil, or a low viscosity mineral oil base oil. , While maintaining the high shear viscosity at 150 ° C., it is possible to achieve both fuel saving and low temperature viscosity at −35 ° C. or lower, especially reducing the kinematic viscosity of lubricating oil at 40 ° C. and 100 ° C. It can be seen that the lubricating oil composition can significantly improve the CCS viscosity at -35 ° C.

Claims (5)

Contains 10% to 100% by mass of a lubricating base oil component having a urea adduct value of 4% by mass or less, a kinematic viscosity at 40 ° C. of 25 mm ² / s or less, and a viscosity index of 120 or more based on the total amount of the base oil. And a poly (meth) acrylate viscosity index improver in which the proportion of the structural unit represented by the following general formula (1) is 0.5 to 70 mol%,
And a kinematic viscosity at 100 ° C. of 4 to 12 mm ² / s and a viscosity index of 140 to 300.

[In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents a linear or branched hydrocarbon group having 16 or more carbon atoms. ]   The lubricating oil composition according to claim 1, wherein the poly (meth) acrylate viscosity index improver is a dispersion type poly (meth) acrylate viscosity index improver. The PS (SI) of the poly (meth) acrylate viscosity index improver is 40 or less, and the ratio of the weight average molecular weight of the poly (meth) acrylate viscosity index improver to PSSI is 1 × 10 ⁴ or more. The lubricating oil composition according to claim 1 or 2. The lubricating oil composition according to any one of claims 1 to 3, wherein R ² in the general formula (1) is a branched hydrocarbon group having 20 or more carbon atoms.   The lubricating oil composition according to any one of claims 1 to 4, further comprising one or more friction modifiers selected from organic molybdenum compounds and ashless friction modifiers.