JP2010280824A - Lubricant composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant composition which has a satisfactorily high viscosity index and is excellent in fuel saving properties and lubricity. <P>SOLUTION: The lubricant composition contains: a lubricant base oil which contains an ester-based base oil, that has 1-500 mm<SP>2</SP>/s kinetic viscosity at 100°C and is of 0.1-90 mass% based on the total mass of base oils, and has 1-20 mm<SP>2</SP>/s kinetic viscosity at 100°C; and a viscosity index improver which is of 0.1-50 mass% based on the total mass of the lubricant composition, and has ≥10,000 weight-average molecular weight, ≥0.8×10<SP>4</SP>ratio of the weight-average molecular weight to PSSI (the permanent shear stability index) and ≤2.0 ratio ΔHTHS100/ΔHTHS150 (wherein ΔHTHS100 is the increment of the HTHS viscosity at 100°C; ΔHTHS150 is the increment of the HTHS viscosity at 150°C). <P>COPYRIGHT: (C)2011,JPO&INPIT

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, in order to satisfy such required performance, conventional engine oils are blended with various additives such as antiwear agents, metallic detergents, ashless dispersants, antioxidants (for example, Patent Documents 1 to 3). ). In recent years, the fuel-saving performance required for lubricating oil has been increasing, and the application of a high viscosity index base oil and various friction modifiers has been studied (for example, Patent Document 4).

JP 2001-279287 A JP 2002-129182 A Japanese Patent Laid-Open No. 08-302378 Japanese Patent Laid-Open No. 06-306384

  However, conventional lubricating base oils and viscosity index improvers are not necessarily sufficient in terms of 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 the reduction in product viscosity and the reduction in base oil viscosity will reduce the lubrication performance under severe lubrication conditions such as high-temperature and high-shear conditions and cause problems such as wear, seizure, and fatigue failure. .

  Therefore, in order to prevent these problems and maintain durability, it is necessary to reduce the viscosity in the normal temperature range while maintaining the viscosity at a high temperature. That is, it is important to improve the viscosity index in order to provide further fuel saving while maintaining other practical performance.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a lubricating oil composition having a sufficiently high viscosity index and excellent fuel economy and lubricity.

In order to solve the above-mentioned problems, the present invention contains an ester base oil having a kinematic viscosity at 100 ° C. of 1 to 500 mm ² / s based on the total amount of the base oil, and a kinematic viscosity at 100 ° C. A lubricating base oil having a viscosity of 1 to ²⁰ mm ² / s and a weight average molecular weight of 10,000 to 50% by weight based on the total amount of the lubricating oil composition is 10,000 or more, and the ratio of the weight average molecular weight to PSSI is 0.8 × 10 ⁴ or more, and a ratio of an increase in HTHS viscosity at 100 ° C. ΔHTHS100 to a ratio of an increase in HTHS viscosity at 150 ° C. ΔHTHS150 ΔHTHS100 / ΔHTHS150 containing a viscosity index improver, A lubricating oil composition is provided.

  The HTHS viscosity at 100 ° C. referred to in the present invention indicates the high temperature and high shear viscosity at 100 ° C. as defined in ASTM D4683. Moreover, the HTHS viscosity at 150 ° C. indicates the high temperature and high shear viscosity at 150 ° C. defined in ASTM D4683. ΔHTHS100 means an increase in HTHS viscosity at 100 ° C. when 3.0% of a viscosity index improver is added to SK YUBASE4, and ΔHTHS150 is SKBASE YUBASE4 with a viscosity index improver of 3.0%. It means an increase in HTHS viscosity at 150 ° C. when added in%.

  The ester base oil is preferably one or a mixture of two or more selected from diesters and monoesters.

  According to the present invention, it is possible to provide a lubricating oil composition having a sufficiently high viscosity index and excellent fuel economy and lubricity.

  The lubricating oil composition of the present invention can also be suitably used for gasoline engines, diesel engines, gas engines, etc. for motorcycles, automobiles, power generation, cogeneration, etc. Not only can it be suitably used for these various engines using fuel of mass ppm or less, but it is also useful for various engines for ships and outboard motors.

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

In the lubricating oil composition of the present invention, as the lubricating base oil, an ester base oil having a kinematic viscosity at 100 ° C. of 1 to 500 mm ² / s (hereinafter sometimes referred to as base oil (A-1)) and A lubricating base oil (hereinafter sometimes referred to as base oil (A)) composed of other lubricating base oil (hereinafter sometimes referred to as base oil (A-2)) is used. Here, the kinematic viscosity at 100 ° C. means the kinematic viscosity at 100 ° C. as defined in ASTM D-445.

  The alcohol constituting the ester base oil (A-1) may be a monohydric alcohol or a polyhydric alcohol, and the acid constituting the ester base oil may be a monobasic acid or a polybasic acid. Moreover, if it is a base oil containing an ester bond, a complex ester compound may be used.

  As the monohydric alcohol, those having 1 to 24 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms are usually used. Such alcohols may be linear or branched, It may be saturated or unsaturated. Specific examples of the alcohol having 1 to 24 carbon atoms include methanol, ethanol, linear or branched propanol, linear or branched butanol, and linear or branched pentanol. , Linear or branched hexanol, linear or branched heptanol, linear or branched octanol, linear or branched nonanol, linear or branched decanol , Linear or branched undecanol, linear or branched dodecanol, linear or branched tridecanol, linear or branched tetradecanol, linear or branched Pentadecanol, linear or branched hexadecanol, linear or branched heptadecanol, linear or branched octadecanol, linear or branched nonade Nols, linear or branched icosanols, linear or branched heicosanols, linear or branched tricosanols, linear or branched tetracosanols, and mixtures thereof It is done.

  As the polyhydric alcohol, those having 2 to 10 valences, preferably 2 to 6 valences are usually used. Specific examples of the divalent to 10-valent polyhydric alcohol include, for example, ethylene glycol, diethylene glycol, polyethylene glycol (3 to 15 mer of ethylene glycol), propylene glycol, dipropylene glycol, and polypropylene glycol (3 to 3 of propylene glycol). 15-mer), 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,2-propanediol, 2-methyl-1, Dihydric alcohols such as 3-propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, neopentylglycol; glycerin, polyglycerin (glycerin 2 ~ Octamer, eg diglycerin, trig Serine, tetraglycerin, etc.), trimethylol alkanes (trimethylol ethane, trimethylol propane, trimethylol butane, etc.) and their 2-to 8-mer, pentaerythritol and their 2-to 4-mer, 1,2,4- Butanetriol, 1,3,5-pentanetriol, 1,2,6-hexanetriol, 1,2,3,4-butanetetrol, sorbitol, sorbitan, sorbitol glycerin condensate, adonitol, arabitol, xylitol, mannitol, etc. Polyhydric alcohols; sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, and mixtures thereof And the like.

  Among these polyhydric alcohols, ethylene glycol, diethylene glycol, polyethylene glycol (ethylene glycol 3-10 mer), propylene glycol, dipropylene glycol, polypropylene glycol (propylene glycol 3-10 mer), 1,3- Propanediol, 2-methyl-1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, glycerin, diglycerin, triglycerin, trimethylolalkane (trimethylolethane, trimethylolpropane, trimethylol Methylol butane and the like, and dimers and tetramers thereof, pentaerythritol, dipentaerythritol, 1,2,4-butanetriol, 1,3,5-pentanetriol, 1,2,6-hexanetrio Le, 1,2,3,4 butane tetrol, sorbitol, sorbitan, sorbitol glycerin condensate, adonitol, arabitol, xylitol, divalent to hexavalent polyhydric alcohols, and mixtures thereof, such as mannitol and the like are preferable. Furthermore, ethylene glycol, propylene glycol, neopentyl glycol, glycerin, trimethylol ethane, trimethylol propane, pentaerythritol, sorbitan, and a mixture thereof are more preferable. Among these, neopentyl glycol, trimethylol ethane, trimethylol propane, pentaerythritol, and a mixture thereof are most preferable because higher thermal / oxidative stability can be obtained.

  Of the acids constituting the ester used in the present invention, as the monobasic acid, a fatty acid having 2 to 24 carbon atoms is usually used, and the fatty acid may be linear or branched and saturated. Or unsaturated. Specifically, for example, acetic acid, propionic acid, linear or branched butanoic acid, linear or branched pentanoic acid, linear or branched hexanoic acid, linear or branched Branched heptanoic acid, linear or branched octanoic acid, linear or branched nonanoic acid, linear or branched decanoic acid, linear or branched undecanoic acid, Linear or branched dodecanoic acid, linear or branched tridecanoic acid, linear or branched tetradecanoic acid, linear or branched pentadecanoic acid, linear or branched Hexadecanoic acid, linear or branched heptadecanoic acid, linear or branched octadecanoic acid, linear or branched nonadecanoic acid, linear or branched icosanoic acid, straight Chain or branched henicosanoic acid, linear or branched docosa Acid, linear or branched tricosanoic acid, saturated fatty acid such as linear or branched tetracosanoic acid, acrylic acid, linear or branched butenoic acid, linear or branched Pentenoic acid, linear or branched hexenoic acid, linear or branched heptenoic acid, linear or branched octenoic acid, linear or branched nonenoic acid, linear Or branched decenoic acid, linear or branched undecenoic acid, linear or branched dodecenoic acid, linear or branched tridecenoic acid, linear or branched tetradecene Acid, linear or branched pentadecenoic acid, linear or branched hexadecenoic acid, linear or branched heptadecenoic acid, linear or branched octadecenoic acid, linear or Branched nonadecenoic acid, linear or branched icosenoic acid, Unsaturated fatty acids such as linear or branched heicosenoic acid, linear or branched docosenoic acid, linear or branched tricosenoic acid, linear or branched tetracosenoic acid, and the like And the like. Among these, from the point that lubricity and handleability are further improved, saturated fatty acids having 3 to 20 carbon atoms, unsaturated fatty acids having 3 to 22 carbon atoms and mixtures thereof are particularly preferable, and saturated fatty acids having 4 to 18 carbon atoms. More preferable are unsaturated fatty acids having 4 to 18 carbon atoms and mixtures thereof, and saturated fatty acids having 4 to 18 carbon atoms are most preferable from the viewpoint of oxidative stability.

  Examples of the polybasic acid include dibasic acids having 2 to 16 carbon atoms and trimellitic acid. The dibasic acid having 2 to 16 carbon atoms may be linear or branched, and may be saturated or unsaturated. Specifically, for example, ethanedioic acid, propanedioic acid, linear or branched butanedioic acid, linear or branched pentanedioic acid, linear or branched hexanedioic acid, Linear or branched heptanedioic acid, linear or branched octanedioic acid, linear or branched nonanedioic acid, linear or branched decanedioic acid, linear Linear or branched undecanedioic acid, linear or branched dodecanedioic acid, linear or branched tridecanedioic acid, linear or branched tetradecanedioic acid, linear or Branched heptadecanedioic acid, linear or branched hexadecanedioic acid, linear or branched hexenedioic acid, linear or branched heptenedioic acid, linear or branched Octenedioic acid, linear or branched nonene diacid, linear or branched decenedioic acid, linear Or branched undecenedioic acid, linear or branched dodecenedioic acid, linear or branched tridecenedioic acid, linear or branched tetradecenedioic acid, linear or branched Examples thereof include branched heptadecene diacid, linear or branched hexadecene diacid, and mixtures thereof.

The combination of the alcohol and the acid forming the ester is arbitrary and is not particularly limited. Examples of the ester that can be used in the present invention include the following esters. These esters may be used alone, or 2 You may combine seeds or more.
(A) ester of monohydric alcohol and monobasic acid (b) ester of polyhydric alcohol and monobasic acid (c) ester of monohydric alcohol and polybasic acid (d) polyhydric alcohol and polybasic acid Ester (e) monohydric alcohol, mixture of polyhydric alcohol and polybasic acid (f) mixed ester of polyhydric alcohol with monobasic acid, polybasic acid (g) monohydric alcohol , Mixtures of polyhydric alcohols with monobasic acids and polybasic acids

  As base oil (A-1), (a) ester of monohydric alcohol and monobasic acid, (b) ester of polyhydric alcohol and monobasic acid, (c) monohydric alcohol and polybasic acid An ester is preferably contained, and (b) an ester of a polyhydric alcohol and a monobasic acid is more preferably contained. Further, the ester form is preferably a diester or a monoester, more preferably a diester, and particularly preferably a glycol diester.

  In the present invention, the ester obtained when a polyhydric alcohol is used as the alcohol component may be a complete ester in which all the hydroxyl groups in the polyhydric alcohol are esterified. A partial ester may be used. The organic acid ester obtained when a polybasic acid is used as the acid component may be a complete ester in which all the carboxyl groups in the polybasic acid are esterified, or a part of the carboxyl groups is not esterified and carboxylated. It may be a partial ester remaining as a group.

  The base oil (A-1) preferably has 100 or less carbon atoms, more preferably 70 or less carbon atoms, and 50 or less carbon atoms in that the fluidity can be further improved. More preferably, the carbon number is particularly preferably 40 or less, and most preferably 30 or less.

  The ester base oil (A-1) used in the present invention may be composed of only one kind of the above-described ester compound, or may be composed of a mixture of two or more kinds. .

Kinematic viscosity at 100 ° C. of the base oil (A-1) is required to be 1 to 500 mm ² / s, preferably 10 mm ² / s or less, more preferably 5.0 mm ² / s or less, more preferably It is 4.0 mm ² / s or less, particularly preferably 3.5 mm ² / s or less, and most preferably 3.0 mm ² / s or less. When the kinematic viscosity at 100 ° C. of the base oil (A-1) is 500 mm ² / s or more, the viscosity temperature characteristic is deteriorated and the required fuel-saving property cannot be obtained, and the low temperature viscosity characteristic is insufficient. It tends to be. The kinematic viscosity at 100 ° C. of the base oil (A-1) is preferably ^{1 mm} 2 / s or more, more preferably 1.5 mm ² / s or higher, more preferably 2.0 mm ² / s or more, particularly preferably 2.5 mm ² / s or more. When the kinematic viscosity at 100 ° C. of the base oil (A-1) is less than 1 mm ² / s, oil film formation at the lubrication site tends to be insufficient and the lubricity tends to decrease. The amount of evaporation loss tends to increase.

As base oil (A-1), you may use together 1 type (s) or 2 or more types, as long as kinematic viscosity in 100 degreeC individually satisfy | fills less than 1-5 mm < ² > / s.

The kinematic viscosity at 40 ° C. of the base oil (A-1) is preferably 100 mm ² / s or less, more preferably 30 mm ² / s or less, still more preferably 20 mm ² / s or less, particularly preferably 15 mm ² / s or less, Most preferably, it is 10 mm ² / s or less. When the kinematic viscosity at 40 ° C. of the base oil (A-1) is 100 mm ² / s or more, the viscosity temperature characteristic is deteriorated and the required fuel-saving property cannot be obtained, and the low temperature viscosity characteristic is insufficient. There is a possibility. Moreover, kinematic viscosity at 40 ° C. of the base oil (A-1) is preferably ^{1 mm} 2 / s or more, more preferably ^{3 mm} 2 / s or higher, more preferably ^{5 mm} 2 / s or more, particularly preferably ^{6 mm} 2 / s That's it. When the kinematic viscosity at 40 ° C. of the base oil (A-1) is less than 1 mm ² / s, oil film formation at the lubrication site tends to be insufficient and the lubricity tends to decrease. The amount of evaporation loss tends to increase.

  The viscosity index of the base oil (A-1) is not particularly limited, but is preferably 40 or more, more preferably 100 or more, still more preferably 110 or more, particularly preferably 130 or more, and most preferably 150 or more. Further, it is preferably 250 or less, more preferably 220 or less, further preferably 200 or less, particularly preferably 190 or less. When the viscosity index is less than the lower limit, not only fuel economy and low-temperature viscosity characteristics are deteriorated, but heat / oxidation stability and volatilization prevention properties tend to be deteriorated. On the other hand, when the viscosity index exceeds the upper limit, fuel economy and low-temperature viscosity characteristics tend to deteriorate significantly. In addition, the viscosity index as used in the field of this invention means the viscosity index measured based on JISK2283-1993.

  The upper limit of the acid value of the base oil (A-1) is not particularly limited, but is preferably 5 mgKOH or less, more preferably 3 mgKOH or less, still more preferably 2 mgKOH or less, particularly preferably 1.5 mgKOH or less. Most preferably, it is 1.0 mgKOH or less. Moreover, although it may be 0.2 mgKOH or less as one aspect of the present invention, it is preferably 0.2 mgKOH or more, more preferably 0.5 mgKOH or more from the viewpoint of economy in production. In addition, the lubricating oil composition excellent in oxidation stability can be obtained by the acid value of the said (B) component being 5 mgKOH or less.

  The content of the base oil (A-1) needs to be 0.1 to 90% by mass based on the total amount of the base oil. Here, the base oil (A-1) is preferably 50% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and most preferably 10% by mass or less. Further, it is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, further preferably 2.0% by mass or more, and most preferably 4.0% by mass or more. When the mixing ratio of the base oil (A-1) exceeds 90% by mass, the oxidation stability, storage stability and fuel economy may be deteriorated, and the mixing ratio of the base oil (A-1) is 0.00. When the amount is less than 1% by mass, the viscosity temperature characteristic is deteriorated, and the required fuel economy may not be obtained.

It is preferred that the kinematic viscosity at 100 ° C. Other base oils (A-2) is 1 to 5 mm ² / s, the upper limit is more preferably 4.5 mm ² / s or less, more preferably 4.3 mm ² / It is s or less, particularly preferably 4.1 mm ² / s or less, and most preferably 4.0 mm ² / s or less. Further, the lower limit value of the kinematic viscosity at 100 ° C. of the base oil (A-2) is more preferably 1.5 mm ² / s or more, further preferably 2 mm ² / s or more, particularly preferably 3 mm ² / s or more, most preferably Preferably it is 3.5 mm < ² > / s or more. When the kinematic viscosity at 100 ° C. of the base oil (A-1) exceeds 5 mm ² / s, the viscosity-temperature characteristics tend to deteriorate and the low-temperature viscosity characteristics tend to be insufficient. When the kinematic viscosity at 100 ° C. of the base oil (A-2) is less than 1 mm ² / s, oil film formation at the lubrication site tends to be insufficient and the lubricity tends to decrease. The amount of evaporation loss tends to increase.

As a base oil (A-2), as long as the conditions of kinematic viscosity 1-100 mm < ² > / s in 100 degreeC are satisfy | filled individually, you may use together 1 type, or 2 or more types.

  The viscosity index of the base oil (A-2) is not particularly limited, but is preferably 100 or more, more preferably 120 or more, still more preferably 125 or more, particularly preferably 130 or more, and most preferably 135 or more. Further, it is preferably 180 or less, more preferably 170 or less, further preferably 160 or less, and particularly preferably 150 or less. When the viscosity index is less than the lower limit, not only fuel economy and low-temperature viscosity characteristics are deteriorated, but heat / oxidation stability and volatilization prevention properties tend to be deteriorated. On the other hand, when the viscosity index exceeds the upper limit, the low-temperature viscosity characteristics tend to deteriorate significantly. The viscosity index referred to in the present invention means a viscosity index measured according to JIS K 2283-1993.

The density (ρ ₁₅ ) of the base oil (A-2) at 15 ° C. is not particularly limited, but is preferably not more than the value of ρ represented by the formula (a), that is, ρ ₁₅ ≦ ρ.
ρ = 0.0025 × kv100 + 0.816 (a)
(Wherein, kv100 represents the kinematic viscosity of 100 ° C. of the base oil ^{(A) (mm 2 / s} ).)

When ρ ₁₅ > ρ, the viscosity-temperature characteristics and thermal / oxidation stability, as well as the volatilization prevention and low-temperature viscosity characteristics tend to be reduced, which may deteriorate the fuel economy. Moreover, when an additive is mix | blended with base oil (A), there exists a possibility that the effect of the said additive may fall.
The density (ρ ₁₅ ) of the base oil (A-2) at 15 ° C. is preferably 0.860 or less, more preferably 0.850 or less, still more preferably 0.840 or less, and particularly preferably 0.822 or less. . Here, the density at 15 ° C. means the density measured at 15 ° C. in accordance with JIS K 2249-1995.

  The pour point of the base oil (A-2) is not particularly limited, but is preferably -10 ° C or lower, more preferably -12.5 ° C or lower, further preferably -15 ° C or lower, particularly preferably -17.5 ° C. Hereinafter, it is most preferably −20 ° C. or lower. When the pour point exceeds the upper limit, the low temperature fluidity of the entire lubricating oil tends to be reduced. The pour point as used in the field of this invention means the pour point measured based on JISK2269-1987.

The aniline point (AP (° C.)) of the base oil (A-2) is not particularly limited, but is preferably not less than the value of A represented by the formula (b), that is, AP ≧ A.
A = 4.3 × kv100 + 100 (b)
(In the formula, kv100 represents the kinematic viscosity (mm ² / s) of the base oil (A) at 100 ° C.)

  When AP <A, viscosity-temperature characteristics and thermal / oxidation stability, volatilization prevention properties and low-temperature viscosity characteristics tend to decrease, and additives are added to the base oil (A-2). When this is done, the effectiveness of the additive tends to decrease.

  The iodine value of the base oil (A-2) is not particularly limited, but is preferably 7 or less, more preferably 5 or less, further preferably 3 or less, particularly preferably 1 or less, even more particularly preferably 0.5 or less, Preferably it is 0.2 or less. Moreover, although it may be less than 0.001, it is preferably 0.001 or more, more preferably 0.01 or more, and still more preferably 0.03 from the viewpoint of the small effect that can be met and economic efficiency. Above, especially preferably 0.05 or more. By making the iodine value of the base oil (A-2) smaller, the thermal and oxidation stability can be dramatically improved. The iodine value in the present invention means an iodine value measured by an indicator titration method according to JIS K 0070 “acid value, saponification value, iodine value, hydroxyl value and non-saponification value of a chemical product”.

  The NOACK evaporation amount of the base oil (A-2) is not particularly limited, but is preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less, and particularly preferably 9% by mass. Hereinafter, it is most preferably 8% by mass or less. When the NOACK evaporation amount is equal to or less than the above upper limit value, it is possible to achieve low evaporation and improve cleanliness. Moreover, it is preferable that NOACK evaporation is 1 mass% or more, More preferably, it is 3 mass% or more, More preferably, it is 5 mass% or more. If the NOACK evaporation amount is less than or equal to the above lower limit value, not only the required fuel economy can be obtained but also the low temperature viscosity characteristics may be deteriorated. The NOACK evaporation amount in the present invention means an evaporation loss amount (measurement condition: 250 ° C., 1 hour) measured in accordance with ASTM D 5800-95.

While% _{C P} is not particularly limited in the base oil (A-2), usually 70 or more, preferably 80 or more, more preferably 85 or more, more preferably 87 or more, particularly preferably 90 or more. Further, it is preferably 99 or less, more preferably 95 or less, still more preferably 94 or less, and particularly preferably 93 or less. If% C _P of base oil (A-2) is less than the above lower limit, the viscosity - temperature characteristic, heat and oxidation stability will tend to be reduced. In addition, when% C _P of base oil (A-2) exceeds the upper limit value, decrease the solubility of the additives tends to cleanliness may deteriorate.

While% C _A is not particularly limited in the base oil (A-2), preferably 5 or less, more preferably 2 or less, more preferably 1 or less, particularly preferably 0.5 or less. If the% C _A value of the base oil (A-2) exceeds the upper limit value, the viscosity - temperature characteristic, thermal and oxidation stability and frictional properties will tend to be reduced. Further, it may be a% C _A 0 of the base oil (A-2) is the% C _A by the above-described lower limit, it is possible to further improve the solubility of additives.

While% _{C N} is not particularly limited in the base oil (A-2), usually 30 or less, preferably 25 or less, more preferably 15 or less, more preferably 10 or less, particularly preferably 8 or less. Further, it is preferably 3 or more, more preferably 4 or more, further preferably 5 or more, and particularly preferably 6 or more. If the% C _N value of the base oil (A-2) exceeds the upper limit value, the viscosity - temperature characteristic, thermal and oxidation stability and frictional properties will tend to be reduced. Moreover, when% _CN is less than the said lower limit, the solubility of an additive falls and it exists in the tendency for cleanliness to deteriorate.

Incidentally, _say% C P in the present invention,% _C A _N and% _{C A,} obtained by a method in accordance with ASTM D 3238-85, respectively (n-d-M ring analysis), the total carbon number of the paraffin carbon number The percentage of the total number of naphthene carbons to the total number of carbons, and the percentage of aromatic carbons to the total number of carbons. That is, the preferable ranges of% C _P ,% C _N and% C _A described above are based on the values obtained by the above method. For example, even a base oil containing no naphthene is obtained by the above method. % _CN may show a value exceeding 0.

  The content of the saturated component in the base oil (A-2) is not particularly limited, but is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 99% by mass or more, based on the total amount of the base oil. In addition, the ratio of the cyclic saturated component in the saturated component is preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less, particularly preferably 25% by mass or less, and still more preferably. 21% by mass or less. When the content of the saturated component and the ratio of the cyclic saturated component in the saturated component satisfy the above conditions, the viscosity-temperature characteristics and the thermal / oxidation stability can be improved. The saturated content in the present invention means a saturated content measured by the method described in ASTM D 2007-93.

  In the method of separating saturated components, or in analyzing the composition of cyclic saturated components, non-cyclic saturated components, etc., a similar method can be used in which similar results can be obtained. For example, in addition to the above, the method described in ASTM D 2425-93, the method described in ASTM D 2549-91, the method by high performance liquid chromatography (HPLC), or a method obtained by improving these methods may be mentioned.

  Although the aromatic content in the base oil (A-2) is not particularly limited, it is preferably 5% by mass or less, more preferably 2% by mass or less, and still more preferably 1% by mass or less, based on the total amount of the base oil. Preferably it is 0.5 mass% or less, Most preferably, it is 0.3 mass% or less. Further, it is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, and particularly preferably 0.15% by mass or more. When the aromatic content exceeds the above upper limit, the viscosity-temperature characteristics, thermal / oxidative stability, friction characteristics, volatilization prevention characteristics and low-temperature viscosity characteristics tend to be reduced, and the base oil (A Although -2) may not contain an aromatic component, the solubility of the additive can be further increased by setting the content of the aromatic component to the above lower limit value or more. The aromatic content in the present invention means a value measured according to ASTM D 2007-93. In general, the aromatic component includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene, and alkylated products thereof, as well as compounds in which four or more benzene rings are condensed, pyridines, quinolines, phenols, naphthols, and the like. Aromatic compounds having atoms are included.

  The urea adduct value of the base oil (A-2) is preferably 5% by mass or less, more preferably 3% by mass from the viewpoint of improving the low temperature viscosity characteristic without impairing the viscosity-temperature characteristic and obtaining high thermal conductivity. % Or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. In addition, the urea adduct value of the base oil (A-2) may be 0% by mass, but it is possible to obtain a lubricating base oil with sufficient low-temperature viscosity characteristics and a higher viscosity index, and ease dewaxing conditions. In view of excellent economy, 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.

Here, the urea adduct value means a value measured by the following method.
100 g of weighed sample oil (base oil (A-2)) is put 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 measurement of urea adduct value, when urea adduct is used, isoparaffin which adversely affects low-temperature viscosity characteristics, component which deteriorates thermal conductivity, or normal paraffin remains in lubricating base oil This normal paraffin can be collected accurately and reliably, so that it is excellent as a low-temperature viscosity characteristic and thermal conductivity evaluation index of a 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.

  The content of the base oil (A-2) is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, and most preferably 70% by mass or more based on the total amount of the base oil. Further, it is preferably 99.9% by mass or less, more preferably 99% by mass or less, further preferably 98% by mass or less, particularly preferably 96% by mass or less, and most preferably 92% by mass or less. If the mixing ratio of the base oil (A-2) exceeds 99.9% by mass, the intended fuel economy may not be obtained, and the mixing ratio of the base oil (A-2) is less than 10% by mass. In such a case, the viscosity temperature characteristic is deteriorated and the desired fuel saving performance cannot be obtained, and the oxidation stability may be deteriorated.

  As the base oil (A-2), a mineral base oil and / or a synthetic base oil excluding an ester base can be used.

  Examples of the mineral oil base oil include a solvent oil removal, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrogen removal of a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and / or vacuum distillation. Paraffinic mineral oil, normal paraffinic base oil, or isoparaffinic base oil purified by combining one or more of purification treatments such as chemical purification, sulfuric acid washing, and clay treatment alone or in combination of two or more can be used.

  The synthetic base oil excluding the ester is preferably a hydrocarbon synthetic oil, and examples thereof include poly-α-olefin or a hydride thereof, isobutene oligomer or a hydride thereof, isoparaffin, alkylbenzene, and alkylnaphthalene. Of these, poly-α-olefins are preferred. The poly α-olefin is typically an oligomer or co-oligomer of α-olefin having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, such as 1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, and the like. Of the hydrides.

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

As a preferable example of the base oil constituting the base oil (A-2) according to the present invention, the following base oils (1) to (8) are used as raw materials, and are recovered from the raw oil and / or the raw oil. Examples of the base oil obtained by purifying the lubricating oil fraction by a predetermined refining method and collecting the lubricating oil fraction.
(1) Distilled oil obtained by atmospheric distillation of paraffin-based crude oil and / or mixed-base crude oil.
(2) Distilled oil (WVGO) by distillation under reduced pressure of atmospheric distillation residue of paraffin-based crude oil and / or mixed-base crude oil.
(3) Synthetic waxes such as Fischer-Tropsch wax and GTL wax obtained by a wax such as slack wax and / or a gas-to-liquid (GTL) process obtained by a lubricant dewaxing step.
(4) One or two or more mixed oils selected from base oils (1) to (3) and / or a mild hydrocracking treatment oil of the mixed oil.
(5) Two or more mixed oils selected from base oils (1) to (4).
(6) Base oil (1), (2), (3), (4) or (5) de-oiling oil (DAO).
(7) Mild hydrocracking treatment oil (MHC) of base oil (6).
(8) Two or more mixed oils selected from base oils (1) to (7).

  The above-mentioned predetermined purification methods include hydrorefining such as hydrocracking and hydrofinishing; solvent refining such as furfural solvent extraction; dewaxing such as solvent dewaxing and catalytic dewaxing; acid clay and activated clay White clay refining; chemical (acid or alkali) cleaning such as sulfuric acid cleaning and caustic soda cleaning are preferred. In the present invention, one of these purification methods may be performed alone, or two or more may be combined. Moreover, when combining 2 or more types of purification methods, the order in particular is not restrict | limited, It can select suitably.

As the base oil constituting the base oil (A-2) according to the present invention, a base oil selected from the base oils (1) to (8) or a lubricating oil fraction recovered from the base oil is subjected to a predetermined treatment. The following base oil (9) or (10) obtained by carrying out is particularly preferred.
(9) The base oil selected from the base oils (1) to (8) or the lubricating oil fraction recovered from the base oil is hydrocracked and recovered from the product or the product by distillation or the like. Hydrocracked mineral oil obtained by subjecting a lubricating oil fraction to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or distillation after the dewaxing treatment.
(10) A base oil selected from the base oils (1) to (8) or a lubricating oil fraction recovered from the base oil is hydroisomerized and recovered from the product or the product by distillation or the like. Hydroisomerized mineral oil obtained by subjecting the lubricating oil fraction to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or distillation after the dewaxing treatment.
Further, when obtaining the base oil of (9) or (10), a solvent refining treatment and / or a hydrofinishing treatment step may be further provided as necessary at a convenient step.

  The catalyst used in the hydrocracking / hydroisomerization is not particularly limited, but a composite oxide having cracking activity, for example, silica alumina, alumina boria, silica zirconia, or a combination of one or more of the composite oxides. A hydrocracking catalyst carrying one or more kinds of metals having hydrogenation ability, for example, metals of group VIa and VIII of the periodic table, or A hydroisomerization catalyst is preferably used in which a support containing zeolite, for example, ZSM-5, zeolite beta, and SAPO-11, is loaded with a metal having a hydrogenation ability including at least one of Group VIII metals. The The hydrocracking catalyst and the hydroisomerization catalyst may be used in combination by stacking or mixing.

The reaction conditions for hydrocracking / hydroisomerization are not particularly limited. For example, hydrogen partial pressure 0.1 to 20 MPa, average reaction temperature 150 to 450 ° C., LHSV 0.1 to 3.0 hr ⁻¹ , hydrogen / The oil ratio is preferably 50 to 20000 scf / bbl.

The kinematic viscosity at 100 ° C. of the base oil (A) according to the present invention is required to be 1 to ²⁰ mm ² / s, and the upper limit is preferably 6 mm ² / s or less, more preferably 5.5 mm ² / s. or less, more preferably 5.2 mm ² / s or less, particularly preferably 5.0 mm ² / s or less, and most preferably 4.8 mm ² / s or less, and most preferably not more than 4.5 mm ² / s. On the other hand, the lower limit value of the kinematic viscosity at 100 ° C. is preferably 1.5 mm ² / s or more, more preferably 2 mm ² / s or more, further preferably 2.5 mm ² / s or more, and particularly preferably 3 mm ² / s. That's it. When the 100 ° C. kinematic viscosity of the base oil (A) exceeds 20 mm ² / s, the low-temperature viscosity characteristics may deteriorate, and sufficient fuel economy may not be obtained. When the base oil is less than 1 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 kinematic viscosity at 40 ° C. of the base oil (A) is not particularly limited, but is preferably 80 mm ² / s or less, more preferably 50 mm ² / s or less, still more preferably 30 mm ² / s or less, particularly preferably 25 mm ² / s. s or less, most preferably 20 mm ² / s or less. On the other hand, the kinematic viscosity at 40 ° C. is preferably 6.0 mm ² / s or more, more preferably 8.0 mm ² / s or more, further preferably 12 mm ² / s or more, particularly preferably 14 mm ² / s or more, most preferably Preferably it is 15 mm < ² > / s or more. When the kinematic viscosity at 40 ° C. of the base oil (A) exceeds 80 mm ² / s, the low-temperature viscosity characteristics may be deteriorated, and sufficient fuel economy may not be obtained, and is less than 6.0 mm ² / s. In this case, the oil film formation at the lubrication site is insufficient, so that the lubricity is poor, and the evaporation loss of the lubricating oil composition may be increased.

  The viscosity index of the base oil (A) is not particularly limited, but is preferably 100 or more, more preferably 120 or more, still more preferably 125 or more, particularly preferably 130 or more, and most preferably 135 or more. Further, it is preferably 180 or less, more preferably 170 or less, further preferably 160 or less, and particularly preferably 150 or less. When the viscosity index is less than the lower limit, not only fuel economy and low-temperature viscosity characteristics are deteriorated, but heat / oxidation stability and volatilization prevention properties tend to be deteriorated. On the other hand, when the viscosity index exceeds the upper limit, the low-temperature viscosity characteristics tend to deteriorate significantly.

  The sulfur content in the base oil (A) depends on the sulfur content of the raw material. For example, when using a raw material that does not substantially contain sulfur such as a synthetic wax component obtained by a Fischer-Tropsch reaction or the like, a base oil (A) that does not substantially contain sulfur can be obtained. Moreover, when using raw materials containing sulfur such as slack wax obtained in the refining process of lubricating base oil and microwax obtained in the refining process, the sulfur content in the obtained base oil (A) is usually 100 mass. ppm or more.

  In the base oil (A), the content of sulfur is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, and more preferably 10 ppm by mass or less from the viewpoint of further improvement in thermal and oxidation stability and low sulfur content. Is more preferable, and 5 mass ppm or less is particularly preferable.

  The nitrogen content in the base oil (A) is not particularly limited, but is preferably 7 ppm by mass or less, more preferably 5 ppm by mass or less, and further preferably 3 ppm by mass or less. If the nitrogen content exceeds 7 ppm by mass, the thermal and oxidation stability tends to decrease. The nitrogen content in the present invention means a nitrogen content measured according to JIS K 2609-1990.

The lubricating oil composition of the present invention has a weight average molecular weight of 10,000 or more, a ratio of the weight average molecular weight to PSSI of 0.8 × 10 ⁴ or more, and an increase in HTHS viscosity at 100 ° C. ΔHTHS 100 and an HTHS viscosity at 150 ° C. A viscosity index improver (hereinafter referred to as a viscosity index improver (B)) having a ratio ΔHTHS100 / ΔHTHS150 of the increment ΔHTHS150 of 2.0 or less is contained.

  The compound used as the viscosity index improver (B) is not particularly limited as long as the weight average molecular weight, the ratio between the weight average molecular weight and PSSI, and the HTHS viscosity increase ratio satisfy the above conditions. Specifically, non-dispersed or dispersed poly (meth) acrylate, non-dispersed or dispersed ethylene-α-olefin copolymer or its hydride, polyisobutylene or its hydride, styrene-diene hydrogenated copolymer Examples thereof include a polymer, a styrene-maleic anhydride ester copolymer, and a polyalkylstyrene. The viscosity index improver (B) may be either non-dispersed or dispersed, but is more preferably dispersed.

Preferred examples of the viscosity index improver (B) include those containing 1 to 70 mol% of one or more (meth) acrylate structural units represented by the formula (1) (hereinafter, for convenience. "Polymethacrylate (B-1)"). In the formula (1), 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.
The polymethacrylate (B-1) may be either non-dispersed or dispersed, but is more preferably non-dispersed.

In the formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² is a linear or branched hydrocarbon group having 16 or more carbon atoms, preferably a linear or branched group having 18 or more carbon atoms. It is a branched hydrocarbon group, more preferably a linear or branched hydrocarbon group having 20 or more carbon atoms, and more preferably a branched hydrocarbon group having 20 or more carbon atoms. The upper limit of the carbon number of R ² is not particularly limited, but is usually 100 or less, preferably 50 or less, more preferably 30 or less, particularly preferably 25 or less.

  In the polymethacrylate (B-1), the proportion of the (meth) acrylate structural unit represented by the formula (1) in the polymer is preferably 1 to 70 mol%, more preferably 60 mol% or less, still more preferably 50. The mol% or less, more preferably 40 mol% or less, and particularly preferably 30 mol% or less. Further, it is preferably at least 3 mol%, more preferably at least 5 mol%, particularly preferably at least 10 mol%. If it exceeds 70 mol%, the effect of improving viscosity temperature characteristics, low-temperature viscosity characteristics and solubility in lubricating base oils may be inferior. If it is less than 0.5 mol%, the effect of improving viscosity temperature characteristics may be inferior. There is.

［式（２）中、Ｒ^１は水素原子またはメチル基を示し、Ｒ^２は炭素数１６以上の直鎖状または分枝状の炭化水素基を示す。］ Polymethacrylate (B-1) can contain a structural unit derived from an arbitrary (meth) acrylate structural unit or an arbitrary olefin in addition to the (meth) acrylate structural unit represented by the formula (1). As a preferable aspect of the polymethacrylate (B-1), one or more of the monomers represented by the formula (2) (hereinafter referred to as the monomer (M-1)) and other than the monomer (M-1) are used. Examples thereof include a copolymer obtained by copolymerizing with a monomer.

[In the 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. ]

［式（３）中、Ｒ^３は水素原子またはメチル基を示し、Ｒ^４は炭素数１〜１５の直鎖状または分枝状の炭化水素基を示す。］ Although the monomer combined with the monomer (M-1) is arbitrary, for example, a monomer represented by the 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.

[In 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. ]

［式（４）中、Ｒ^５は水素原子またはメチル基を示し、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または複素環残基を示し、ａは０または１を示す。式（５）中、Ｒ^７は水素原子またはメチル基を示し、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または複素環残基を示す。］ Other monomers to be combined with the monomer (M-1) include a monomer represented by the formula (4) (hereinafter referred to as monomer (M-3)) and a monomer represented by the formula (5) (hereinafter referred to as monomer ( One or more selected from M-4) are preferred. The copolymer of the monomer (M-1) and the monomer (M-3) and / or (M-4) is a so-called dispersed 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.

[In 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 2 oxygen atoms. An amine residue or a heterocyclic residue to be contained is shown, and a represents 0 or 1. In 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 alkylene group having 1 to 18 carbon atoms represented by R ⁶ in the formula (4) include ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, Nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, or octadecylene group (these alkylene groups may be linear or branched) can be exemplified.

As the group represented by E ¹ in the formula (4) or the group represented by E ² in the formula (5), a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, Anilino, toluidino, xylidino, acetylamino, benzoylamino, morpholino, pyrrolyl, pyrrolino, pyridyl, methylpyridyl, pyrrolidinyl, piperidinyl, quinonyl, pyrrolidonyl, pyrrolidono, imidazolino Or a pyrazino group.

  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 or a mixture 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: 95-50: 50, More preferably, it is 10: 90-40: 60.

  Although the manufacturing method of polymethacrylate (B-1) is arbitrary, for example, in the presence of a polymerization initiator such as benzoyl peroxide, monomer (M-1) and monomers (M-2) to (M-4) Can be easily obtained by radical solution polymerization.

  In the lubricating oil composition of the present invention, as the viscosity index improver (B), as long as the weight average molecular weight, the ratio of the weight average molecular weight to PSSI, and the viscosity increase ratio of the HTHS viscosity satisfy the above conditions, In addition to B-1), for example, the usual general non-dispersed or dispersed poly (meth) acrylate, non-dispersed or dispersed ethylene-α-olefin copolymer or hydride thereof, polyisobutylene or hydrogen thereof Viscosity index improvers such as fluoride, styrene-diene hydrogenated copolymer, styrene-maleic anhydride ester copolymer or polyalkylstyrene can be used.

  The PSSI of the viscosity index improver (B) is not particularly limited, but is preferably 40 or less, more preferably 35 or less, still more preferably 30 or less, and particularly preferably 25 or less. Further, it is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, and particularly preferably 20 or more. 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.

  Here, the PSSI, conforming to ASTM D 6022-01 (Standard Practice for Calculation of Permanent Shear Stability Index), by ASTM D 6278-02 (Test Method for Shear Stability of Polymer Containing Fluids Using a European Diesel Injector Apparatus) Means the permanent shear stability index of the polymer, calculated based on the measured data.

The weight average molecular weight (M _w ) of the viscosity index improver (B) needs to be 10,000 or more, more preferably 50,000 or more, further preferably 100,000 or more, particularly preferably 150,000 or more, most Preferably it is 200,000 or more. Moreover, it is preferable that it is 1 million 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 10,000, the effect of improving the viscosity index is small and not only the fuel efficiency and low temperature viscosity characteristics are inferior, but also the cost may increase. If the weight average molecular weight exceeds 1,000,000, shearing will occur. Stability, solubility in base oil, and storage stability may deteriorate.

Is not particularly limited weight ratio of the average molecular weight to number average molecular weight _(M W / M _n) is a viscosity index improver (B), preferably 0.5 to 5.0, more preferably 1.0 to 3.5 More preferably, it is 1.5-3, Most preferably, it is 1.7-2.5. When the ratio of the weight average molecular weight to the number average molecular weight is less than 0.5 or exceeds 5.0, 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 efficiency is improved. May get worse.

The weight average molecular weight and PSSI ratio of viscosity index improver _{(B) (M W / PSSI} ) is required to be 0.8 × 10 ⁴ or more, preferably 1.0 × 10 ⁴ or more, more preferably It is 2 × 10 ⁴ or more, more preferably 2.5 × 10 ⁴ or more. If M _W / PSSI is below 0.8 × 10 ^4, there is a possibility that the viscosity-temperature characteristic is deteriorated i.e. deteriorates fuel efficiency.

The kinematic viscosity thickening ratio ΔKV40 / ΔKV100 at 40 ° C. and 100 ° C. of the viscosity index improver (B) is preferably 4.0 or less, more preferably 3.5 or less, still more preferably 3.0 or less. Particularly preferred is 2.5 or less, and most preferred is 2.3 or less. Further, ΔKV40 / ΔKV100 is preferably 0.5 or more, more preferably 1.0 or more, still more preferably 1.5 or more, and particularly preferably 2.0 or more.
If ΔKV40 / ΔKV100 is less than 0.5, the effect of increasing viscosity and solubility may be small and the cost may increase. If it exceeds 4.0, the effect of improving viscosity temperature characteristics and low temperature viscosity characteristics may be obtained. May be inferior. ΔKV40 means an increase in kinematic viscosity at 40 ° C. when 3.0% of a viscosity index improver is added to SK YUBASE4, and ΔKV100 is 3.0% of SKBASE YUBASE4. It means an increase in kinematic viscosity at 100 ° C. when added in%.

  The viscosity increase ratio ΔHTHS100 / ΔHTHS150 of the viscosity index improver (B) at 100 ° C. and 150 ° C. needs to be 2.0 or less, more preferably 1.7 or less, still more preferably 1. 6 or less, particularly preferably 1.55 or less. ΔHTHS100 / ΔHTHS150 is preferably 0.5 or more, more preferably 1.0 or more, still more preferably 1.2 or more, and particularly preferably 1.4 or more. If it is less than 0.5, the effect of increasing the viscosity and the solubility are small and the cost may increase, and if it exceeds 2.0, the effect of improving the viscosity index, that is, fuel economy, is poor.

  In the lubricating oil composition of the present invention, the content ratio of the viscosity index improver (B) needs to be 0.1 to 50% by mass, preferably 0.5% by mass or more, based on the total amount of the composition. More preferably, it is 1% by mass or more, particularly preferably 2% by mass or more, and most preferably 5% by mass or more. Further, it is preferably 40% by mass or less, more preferably 30% by mass or less, and particularly preferably 20% by mass or less. If the content ratio of the viscosity index improver (B) 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. This will reduce the lubrication performance under severe lubrication conditions such as high-temperature high-shear conditions and wear. There is concern that it may cause defects such as seizure, seizure and fatigue failure.

  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 contained in order to further improve fuel economy performance.

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

  Other sulfur-containing organic molybdenum compounds include complexes of molybdenum compounds with sulfur-containing organic compounds or other organic compounds, or sulfur-containing molybdenum compounds such as molybdenum sulfide and sulfurized molybdenum acid, and alkenyl succinic acid. Examples include complexes with imides.

  Examples of the molybdenum compound include molybdenum oxide such as molybdenum dioxide and molybdenum trioxide; molybdic acid such as orthomolybdic acid, paramolybdic acid and (poly) sulfurized molybdic acid, and molybdic acid such as metal salts and ammonium salts of these molybdic acids. Examples thereof include molybdenum sulfides such as salts, molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, and polysulfide molybdenum, molybdenum sulfides, metal salts of molybdenum sulfides, amine salts, and molybdenum halides such as molybdenum chloride.

  Examples of the sulfur-containing organic compound include alkyl (thio) xanthate, thiadiazole, mercaptothiadiazole, thiocarbonate, tetrahydrocarbyl thiuram disulfide, bis (di (thio) hydrocarbyl dithiophosphonate) disulfide, organic (poly) sulfide, Examples include sulfurized esters.

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

  Examples of organic molybdenum compounds not containing sulfur include molybdenum-amine complexes, molybdenum-succinimide complexes, molybdenum salts of organic acids, molybdenum salts of alcohols, among others, molybdenum-amine complexes, molybdenum of organic acids. Salts 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, 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 50 carbon atoms, particularly 6 to 50 carbon atoms. Examples include amine compounds, amide compounds, imide compounds, and ester compounds having at least one linear alkyl group or linear alkenyl group in the molecule. Further examples include ashless friction modifiers such as fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, and urea friction modifiers.

  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 further 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 together, but the ashless friction modifier can be maintained for a longer period of time. It is more preferable to use

  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 normal salts such as alkali metal sulfonates or alkaline earth metal sulfonates, alkali metal phenates or alkaline earth metal phenates, alkali metal salicylates or alkaline earth metal salicylates, basic normal salts or overbased Salt. 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. 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 These are 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, as the phenol-based ashless antioxidant, for example, 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert- Examples of amine-based ashless antioxidants include 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, and sulfur-phosphorus extreme pressure agents can be used. Specifically, for example, phosphites, thiophosphites, dithiophosphites, trithiophosphites, phosphate esters, thiophosphates, dithiophosphates, trithiophosphorus Examples include acid esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate, disulfides, polysulfides, sulfurized olefins, and sulfurized fats and oils. 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, and imidazole compounds.

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

  As the pour point depressant, for example, a polymethacrylate-based 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, and 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. Dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, or 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.

  When these additives are contained in the lubricating oil composition of the present invention, the content thereof is preferably 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 preferably 1 to 100 mm ² / s, the upper limit is more preferably 12 mm ² / s or less, more preferably 9.3 mm ² / s or less, particularly preferably 9.0 mm ² / s or less, and most preferably 8.5 mm ² / s or less, and most preferably not more than 8.3 mm ² / s. The lower limit value of the kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is more preferably 4 mm ² / s or more, further preferably 5 mm ² / s or more, particularly preferably 6 mm ² / s or more, and most preferably 7 mm ² / s or more. When the kinematic viscosity at 100 ° C. is less than 1 mm ² / s, there is a risk of insufficient lubricity, and when it exceeds 100 mm ² / s, the necessary low temperature viscosity and sufficient fuel saving performance may not be obtained. is there.

Kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is not particularly limited, usually 4~80mm ² / s, preferably not more than 50 mm ² / s, more preferably 45 mm ² / s or less, more preferably 40 mm ² / S or less, particularly preferably 35 mm ² / s or less, and most preferably 33 mm ² / s or less. Further, it is preferably 10 mm ² / s or more, more preferably 20 mm ² / s or more, further preferably 25 mm ² / s or more, and particularly preferably 27 mm ² / s or more. 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 80 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 is not particularly limited, but is preferably in the range of 140 to 350, more preferably 190 or more, still more preferably 200 or more, still more preferably 220 or more, and particularly preferably 250. That's it. When the viscosity index is less than 140, it may be difficult to improve fuel economy while maintaining the HTHS viscosity, and it may be difficult to reduce the low temperature viscosity at -35 ° C. is there. On the other hand, when the viscosity index exceeds 350, low-temperature fluidity is deteriorated, and there is a possibility that problems due to insufficient solubility of the additive and compatibility with the sealing material may occur.

  The HTHS viscosity at 150 ° C. of the lubricating oil composition of the present invention is not particularly limited, but is preferably 3.5 mPa · s or less, more preferably 3.0 mPa · s or less, even more preferably 2.8 mPa · s or less, particularly The pressure is preferably 2.7 mPa · s or less. Further, it is preferably 2.0 mPa · s or more, more preferably 2.1 mPa · s or more, further preferably 2.2 mPa · s or more, particularly preferably 2.3 mPa · s or more, and most preferably 2.4 mPa · s or more. It is. When the HTHS viscosity at 150 ° C. is less than 2.0 mPa · s, there is a risk of insufficient lubricity, and when it exceeds 3.5 mPa · s, the necessary low temperature viscosity and sufficient fuel saving performance cannot be obtained. There is a fear.

  The lubricating oil composition of the present invention is excellent in fuel economy and lubricity, and has a significantly improved viscosity index that is effective for improving fuel efficiency while maintaining the HTHS viscosity at a certain level. The lubricating oil composition of the present invention having such excellent characteristics can be suitably used as fuel-saving engine oils such as fuel-saving gasoline engine oil and fuel-saving diesel engine oil.

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

[Examples 1-4, Comparative Examples 1-2]
In Examples 1-4 and Comparative Examples 1-2, lubricating oil compositions were prepared using the following base oils and additives. Table 1 shows the properties of the base oil A-2, and Table 2 shows the composition of the lubricating oil composition.
(Base oil)
Base oil A-1-1: oleic acid 2-ethylhexyl ester, 100 ° C. kinematic viscosity: 2.67 mm ² / s, 40 ° C. kinematic viscosity: 8.26 mm ² / s, viscosity index 183
Base oil A-1-2: Neopentyl glycol di-2-ethylhexyl ester, 100 ° C. kinematic viscosity: 2.05 mm ² / s, 40 ° C. kinematic viscosity: 7.47 mm ² / s, Viscosity index 52
Base oil A-1-3: Azelaic acid-di-2-ethylhexyl ester, 100 ° C. kinematic viscosity: 3.01 mm ² / s, 40 ° C. kinematic viscosity: 10.7 mm ² / s, viscosity index 146
Base oil A-1-4: trimethylolpropane ester, 100 ° C. kinematic viscosity: 4.41mm ² / s, 40 ℃ kinematic viscosity: 19.6mm ² / s, viscosity index 139
Base oil A-2: Mineral oil obtained by hydrocracking / hydroisomerizing n-paraffin-containing oil (additive)
B-1-1: Polymethacrylate (methyl methacrylate, dimethylaminoethyl methacrylate, and R ² in the above formula (2) is a total of 90 mol% of a methacrylate having an alkyl group having 12 to 20 carbon atoms. (2) Copolymer with 10 mol% of methacrylate in which R ² is a branched alkyl group having 22 carbon atoms), PSSI = 20, Mw = 400,000, Mw / Mn = 2.2, Mw / PSSI = 2 × 10 ⁴ , ΔKV40 / ΔKV100 = 2.2, ΔHTHS100 / ΔHTHS150 = 1.51
B-1-2: Distributed polymethacrylate (methyl methacrylate, methacrylate ^{R 4} is a linear alkyl group having 12 carbon atoms in the above formula (3), ^{R 4} is a carbon number in the formula (3) 13 linear alkyl groups and a methacrylate, methacrylate R ⁴ is a linear alkyl group having 14 carbon atoms in the formula (3), a linear alkyl group of R ⁴ is 15 carbon atoms in the formula (3) A copolymer of methacrylate and dimethylaminoethyl methacrylate), PSSI = 40, Mw = 300,000, Mw / Mn = 4.0, Mw / PSSI = 0.75 × 10 ⁴ , ΔKV40 / ΔKV100 = 3. 3. ΔHTHS100 / ΔHTHS150 = 1.79
C-1 (friction modifier 1): glycerin monooleate C-2 (friction modifier 2): molybdenum dithiocarbamate D-1 (other additives): metallic detergent, ashless dispersant, antioxidant, phosphorus Contains antiwear agents, pour point depressants, antifoaming agents, etc.

<Evaluation of lubricating oil composition>
About each lubricating oil composition of Examples 1-4 and Comparative Examples 1-2, kinematic viscosity in 40 degreeC and 100 degreeC, a viscosity index, and HTHS viscosity in 150 degreeC were measured. Each measurement was performed by the following evaluation methods. The results are shown in Table 2.
(1) Kinematic viscosity: ASTM D-445
(2) Viscosity index: JIS K 2283-1993
(3) HTHS viscosity: ASTM D4683

  From Table 2, the compositions of Examples 1 to 4 containing an ester base oil and adding a predetermined viscosity index improver have a low Mw / PSSI as well as the composition of Comparative Example 1 that does not contain an ester base oil. Compared to the composition of Comparative Example 2 using a viscosity index improver, the viscosity index is high and the kinematic viscosity at 40 ° C. is low, which indicates excellent fuel economy.

Claims (2)

Kinematic viscosity containing 0.1 to 90 wt% base oil the total amount of ester-based base oil is 1 to 500 mm ² / s at 100 ° C., lubricating oil kinematic viscosity at 100 ° C. is 1 to 20 mm ² / s Base oil,
0.1 to 50% by weight based on the total amount of the lubricating oil composition, the weight average molecular weight is 10,000 or more, the ratio of the weight average molecular weight to PSSI is 0.8 × 10 ⁴ or more, and the HTHS viscosity is increased at 100 ° C. A ratio ΔHTHS100 to an increase in HTHS viscosity at 150 ° C. ΔHTHS150 ratio ΔHTHS100 / ΔHTHS150 viscosity index improver of 2.0 or less;
A lubricating oil composition comprising:   The lubricating oil composition according to claim 1, wherein the ester base oil is one or a mixture of two or more selected from diesters and monoesters.