JPWO2014017556A1 - Lubricating oil composition - Google Patents

Abstract

The proportion of the lubricating base oil having a kinematic viscosity at 100 ° C. of 1 to 10 mm 2 / s and the structural unit represented by the following general formula (1) is 30 to 90 mol%, and the degree of branching is 0.1 to 8 A lubricating oil composition comprising a branched poly (meth) acrylate viscosity index improver that is 0.0. [In the formula (1), R 1 represents hydrogen or a methyl group, and R 2 represents a linear or branched hydrocarbon group having 6 or less carbon atoms. ] [Chemical formula 1]

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, metal detergents, ashless dispersants, and antioxidants (for example, Patent Documents 1 to 1 below). 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, see Patent Document 4 below). .

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 oils are not always sufficient in terms of fuel economy.

  For example, as a general method for reducing fuel consumption, it is known to reduce the kinematic viscosity of lubricants and improve viscosity index (multigrade by combining low viscosity base oil and viscosity index improver) and blend friction reducer. ing. When the viscosity is reduced, the lubrication performance under severe lubrication conditions (high temperature and high shear conditions) deteriorates due to a decrease in the viscosity of the lubricating oil or the base oil that composes it, resulting in wear, seizure, and fatigue failure. There are concerns about the occurrence of such problems. As for the blending of the friction reducing agent, ashless or molybdenum based friction modifiers are known. However, fuel-saving oils that exceed those of these general friction reducing agent blended oils are required.

In order to prevent the problem of low viscosity and maintain fuel durability while providing fuel economy, the HTHS viscosity at 150 ° C. (“HTHS viscosity” is also called “high temperature high shear viscosity”) is high. On the other hand, it is effective to lower the kinematic viscosity at 40 ° C., the kinematic viscosity at 100 ° C., and the HTHS viscosity at 100 ° C., but it has been very difficult to satisfy all these requirements with conventional lubricating oils.
Furthermore, in order to maintain durability while improving fuel economy, it is important to reduce the viscosity drop due to use while reducing the kinematic viscosity at the time of new oil and the HTHS viscosity at 100 ° C. It is also important to reduce the friction coefficient in the boundary lubrication region while reducing the kinematic viscosity as much as possible.

  The present invention has been made in view of such circumstances, and the kinematic viscosity at 40 ° C. and the kinematic viscosity at 100 ° C. can be lowered over a long period from the initial stage to after use, and the viscosity after shearing. An object of the present invention is to provide a lubricating oil composition excellent in durability and fuel-saving properties capable of suppressing the decrease.

［式（１）中、Ｒ^１は水素またはメチル基を示し、Ｒ^２は炭素数６以下の直鎖状また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 having a kinematic viscosity at 100 ° C. of 1 to 10 mm ² / s, and (A) one type of structural unit represented by the following general formula (1) Alternatively, a lubricating oil composition comprising a branched poly (meth) acrylate viscosity index improver having a ratio of two or more of 30 to 90 mol% and a degree of branching of 0.1 to 8.0. Offer things.

[In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents a linear or branched hydrocarbon group having 6 or less carbon atoms. ]

The (A) viscosity index improver is preferably a viscosity index improver having a PSSI of 5 or less and a ratio of molecular weight to PSSI (Mw / PSSI) of 2 × 10 ⁴ or more.

  The lubricating oil composition preferably further contains (B) a friction modifier.

  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.

  As described above, according to the present invention, while maintaining the HTHS viscosity at 150 ° C., the kinematic viscosity at 40 ° C. and the kinematic viscosity at 100 ° C. can be sufficiently lowered over a long period from the beginning to after use. It is possible to provide a lubricating oil composition that can sufficiently suppress a decrease in viscosity after shearing and is excellent in durability and fuel saving.

  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 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.

［式（１）中、Ｒ^１は水素またはメチル基を示し、Ｒ^２は炭素数６以下の直鎖状または分枝状の炭化水素基を示す。］The lubricating oil composition according to this embodiment includes a lubricating base oil having a kinematic viscosity at 100 ° C. of 1 to 10 mm ² / s and (A) one of structural units represented by the following general formula (1): A branched poly (meth) acrylate viscosity index improver having a ratio of two or more of 30 to 90 mol% and a degree of branching of 0.1 to 8.0 is contained.

[In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents a linear or branched hydrocarbon group having 6 or less carbon atoms. ]

In the lubricating oil composition according to the present embodiment, a lubricating base oil (hereinafter referred to as “the lubricating base oil according to the present embodiment”) having a kinematic viscosity at 100 ° C. of 1 to 10 mm ² / s is used. .

As the lubricating base oil according to the present embodiment, for example, a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and / or vacuum distillation is subjected to solvent removal, solvent extraction, hydrocracking, solvent dewaxing, Paraffinic mineral oil, or normal paraffinic base oil, isoparaffinic base oil, etc., refined by combining one or more of refining treatments such as catalytic dewaxing, hydrorefining, sulfuric acid washing, clay treatment, etc. Among them, those having a kinematic viscosity at 100 ° C. of 1 to 5 mm ² / s can be mentioned.

As a preferable example of the lubricating base oil according to the present embodiment, the following base oils (1) to (8) are used as raw materials, and the raw oil and / or the lubricating oil fraction recovered from the raw oil is The base oil obtained by refine | purifying with a predetermined refinement | purification method and collect | recovering lubricating oil fractions can be mentioned.
(1) Distilled oil by atmospheric distillation of paraffinic crude oil and / or mixed base crude oil (2) Distilled oil by vacuum distillation of atmospheric distillation residue of paraffinic crude oil and / or mixed base crude oil ( WVGO)
(3) Wax (slack wax, etc.) obtained by the lubricant dewaxing process and / or synthetic wax (Fischer-Tropsch wax, GTL wax, etc.) obtained by the gas-to-liquid (GTL) process, etc.
(4) One or two or more mixed oils selected from base oils (1) to (3) and / or mild hydrocracked oils of the mixed oils (5) selected from base oils (1) to (4) 2 or more kinds of mixed oils (6) Base oil (1), (2), (3), (4) or (5) debris 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 this embodiment, 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.

Furthermore, as the lubricating base oil according to the present embodiment, a base oil selected from the above base oils (1) to (8) or a lubricating oil fraction recovered from the base oil is obtained by performing a predetermined treatment. The following base oil (9) or (10) 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. Hydrocracking base oil (10) obtained by performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the lubricating oil fraction, or distillation after the dewaxing treatment (10) The above base oils (1) to ( The base oil selected from 8) or the lubricating oil fraction recovered from the base oil is hydroisomerized, and the product or the lubricating oil fraction recovered from the product by distillation or the like is subjected to solvent dewaxing or catalytic desorption. Hydroisomerized base oil obtained by performing dewaxing treatment such as wax or by distillation after the dewaxing treatment.

  Moreover, when obtaining the lubricating base oil of (9) or (10) above, a solvent refining treatment and / or a hydrofinishing treatment step may be further provided as necessary at an advantageous step.

  The catalyst used for the hydrocracking / hydroisomerization is not particularly limited, but a composite oxide having cracking activity (for example, silica alumina, alumina boria, silica zirconia, etc.) or one kind of the composite oxide. Hydrogenolysis with a combination of the above combined with a binder and supporting a metal having hydrogenation ability (for example, one or more metals such as Group VIa metal or Group VIII metal in the periodic table) Hydroisomerization catalyst in which a catalyst or a support containing zeolite (for example, ZSM-5, zeolite beta, SAPO-11, etc.) is loaded with a metal having a hydrogenation ability containing at least one of Group VIII metals Are preferably used. The hydrocracking catalyst and the hydroisomerization catalyst may be used in combination by stacking or mixing.

  The reaction conditions in the hydrocracking / hydroisomerization are not particularly limited, but the hydrogen partial pressure is 0.1 to 20 MPa, the average reaction temperature is 150 to 450 ° C., the LHSV is 0.1 to 3.0 hr-1, and the hydrogen / oil ratio. It is preferable to set it as 50-20000 scf / b.

The kinematic viscosity at 100 ° C. of the lubricating base oil according to this embodiment needs to be 10 mm ² / s or less, preferably 4.5 mm ² / s or less, more preferably 4 mm ² / s or less, preferably 3.8 mm ² / s or less, particularly preferably 3.7 mm ² / s or less, and most preferably not more than 3.6 mm ² / s. On the other hand, the kinematic viscosity at 100 ° C. needs to be 1 mm ² / s or more, preferably 1.5 mm ² / s or more, more preferably 2 mm ² / s or more, and still more preferably 2. It is 5 mm ² / s or more, particularly preferably 3 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 kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 10 mm 2 / ^s, the worse the low temperature viscosity characteristics, also there is a risk that can not be obtained sufficient fuel saving properties, the following cases 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.

Moreover, the kinematic viscosity at 40 ° C. of the lubricating base oil according to the present embodiment is preferably 40 mm ² / s or less, more preferably 30 mm ² / s or less, still more preferably 25 mm ² / s or less, and particularly preferably 20 mm ^2. / S or less, and most preferably 17 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 10 mm ² / s or more, particularly preferably 12 mm ² / s or more, most preferably Preferably it is 14 mm < ² > / s or more. When the kinematic viscosity at 40 ° C. of the lubricating base oil exceeds 40 mm 2 / ^s, the low temperature viscosity characteristics are deteriorated, and there may not be obtained sufficient fuel economy, less 6.0 mm 2 / ^s In such a 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 lubricating base oil according to this embodiment is preferably 100 or more. More preferably, it is 105 or more, More preferably, it is 110 or more, Especially preferably, it is 115 or more, Most preferably, it is 120 or more. When the viscosity index is less than 100, not only the viscosity-temperature characteristics, thermal / oxidative stability, and volatilization prevention properties deteriorate, but also the friction coefficient tends to increase, and the wear prevention properties tend to decrease. .

  In addition, the viscosity index as used in the field of this invention means the viscosity index measured based on JISK2283-1993.

The lubricating base oil used in the lubricating oil composition according to the present embodiment has a first lubricating base oil component having a kinematic viscosity at 100 ° C. of 3.5 mm ² / s or more and a viscosity index of 120 or more, and 100 A mixture of the second lubricating base oil component having a kinematic viscosity at less than 3.5 mm ² / s is preferred. By using a mixture of the first lubricating base oil component and the second lubricating base oil component, it is possible to impart excellent viscosity temperature characteristics and further improve fuel economy.

The density (ρ ₁₅ ) at 15 ° C. of the first lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably 0.860 or less, more preferably 0.850 or less, and still more preferably 0.00. It is 840 or less, particularly preferably 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 pour point of the first lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably −10 ° C. or lower, more preferably −12.5 ° C. or lower, even more preferably −15 ° C. or lower, particularly Preferably it is -20 degrees C or less. When the pour point exceeds the upper limit, the low temperature fluidity of the entire lubricating oil using the lubricating base oil tends to decrease. In addition, the pour point as used in the field of this invention means the pour point measured based on JISK2269-1987.

The kinematic viscosity at 100 ° C. of the first lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably 5 mm ² / s or less, more preferably 4.5 mm ² / s or less, and further Preferably it is 4.0 mm < ² > / s or less, Most preferably, it is 3.9 mm < ² > / s or less. On the other hand, the kinematic viscosity at 100 ° C. is preferably 3.5 mm ² / s or more, more preferably 3.6 mm ² / s or more, still more preferably 3.7 mm ² / s or more, and particularly preferably 3. 8 mm ² / s or more. When the kinematic viscosity at 100 ° C. is more than 5 mm 2 / ^s, the low temperature viscosity characteristics are deteriorated, and there may not be obtained sufficient fuel economy, in the case of less than 3.5 mm 2 / ^s at lubricating sites Insufficient oil film formation may result in poor lubricity and increase in evaporation loss of the lubricating oil composition.

The kinematic viscosity at 40 ° C. of the first lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably 40 mm ² / s or less, more preferably 30 mm ² / s or less, and even more preferably 25 mm ² / s. s or less, particularly preferably 20 mm ² / s or less, and most preferably 17 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 10 mm ² / s or more, particularly preferably 12 mm ² / s or more, most preferably Preferably it is 14 mm < ² > / s or more. When the kinematic viscosity at 40 ° C. is more than 40 mm 2 / ^s, the low temperature viscosity characteristics are deteriorated, and there may not be obtained sufficient fuel saving properties, the following cases 6.0 mm 2 / ^s at lubricating sites Insufficient oil film formation may result in poor lubricity and increase in evaporation loss of the lubricating oil composition.

  The viscosity index of the first lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably 100 or more. More preferably, it is 110 or more, More preferably, it is 120 or more, Especially preferably, it is 130 or more, Most preferably, it is 140 or more. Further, it is preferably 170 or less, more preferably 160 or less, further preferably 155 or less, and particularly preferably 150 or less. When the viscosity index is less than 100, not only the viscosity-temperature characteristics, thermal / oxidative stability, and volatilization prevention properties deteriorate, but also the friction coefficient tends to increase, and the wear prevention properties tend to decrease. . On the other hand, when the viscosity index exceeds 170, the low-temperature viscosity increases, and the fuel efficiency at low oil temperature tends to deteriorate, and the startability tends to deteriorate.

The density (ρ ₁₅ ) at 15 ° C. of the second lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably 0.860 or less, more preferably 0.850 or less, and even more preferably 0.8. It is 840 or less, particularly preferably 0.835 or less.

  The pour point of the second lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably −10 ° C. or lower, more preferably −12.5 ° C. or lower, even more preferably −15 ° C. or lower, particularly Preferably it is -20 degrees C or less. When the pour point exceeds the upper limit, the low temperature fluidity of the entire lubricating oil using the lubricating base oil tends to decrease.

The kinematic viscosity at 100 ° C. of the second lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably less than 3.5 mm ² / s, more preferably 3.4 mm ² / s or less. More preferably, it is 3.3 mm ² / s or less. On the other hand, the kinematic viscosity at the 100 ° C. is preferably ^{2 mm} 2 / s or more, more preferably 2.5 mm ² / s or more, further preferably 3.0 mm ² / s or more. When the kinematic viscosity at 100 ° C. is more than 3.5 mm 2 / ^s, the low temperature viscosity characteristics are deteriorated, and there may not be obtained sufficient fuel economy, in the case of less than 2 mm 2 / ^s at lubricating sites Insufficient oil film formation may result in poor lubricity and increase in evaporation loss of the lubricating oil composition.

The kinematic viscosity at 40 ° C. of the second lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably 20 mm ² / s or less, more preferably 18 mm ² / s or less, and even more preferably 16 mm ² / s. s or less, particularly preferably 14 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 10 mm ² / s or more, particularly preferably 12 mm ² / s or more, most preferably Preferably, it is 13 mm ² / s or more. When the kinematic viscosity at 40 ° C. is more than 20 mm 2 / ^s, the low temperature viscosity characteristics are deteriorated, and there may not be obtained sufficient fuel saving properties, the following cases 6.0 mm 2 / ^s at lubricating sites Insufficient oil film formation may result in poor lubricity and increase in evaporation loss of the lubricating oil composition.

  The viscosity index of the second lubricating base oil component used in the lubricating oil composition according to this embodiment is preferably 100 or more. More preferably, it is 105 or more, More preferably, it is 110 or more. Further, it is preferably 160 or less, more preferably 150 or less, further preferably 140 or less, and particularly preferably 135 or less. When the viscosity index is less than 100, not only the viscosity-temperature characteristics, thermal / oxidative stability, and volatilization prevention properties deteriorate, but also the friction coefficient tends to increase, and the wear prevention properties tend to decrease. . On the other hand, when the viscosity index exceeds 160, the low-temperature viscosity increases, and the fuel economy at low oil temperature tends to deteriorate, and the startability tends to deteriorate.

  Further, the sulfur content in the lubricating base oil used in the present embodiment depends on the sulfur content of the raw material. For example, when a raw material that does not substantially contain sulfur such as a synthetic wax component obtained by a Fischer-Tropsch reaction or the like is used, a lubricating base oil that does not substantially contain sulfur can be obtained. In addition, when using raw materials containing sulfur such as slack wax obtained in the refining process of the lubricating base oil and microwax obtained in the refining process, the sulfur content in the obtained lubricating base oil is usually 100 mass ppm. That's it. In the lubricating base oil according to the present embodiment, the content of sulfur is preferably 100 ppm by mass or less, and 50 ppm by mass or less, from the viewpoint of further improvement in thermal and oxidation stability and low sulfur content. More preferably, it is more preferably 10 ppm by mass or less, and particularly preferably 5 ppm by mass or less.

  Further, the content of nitrogen in the lubricating base oil used in the present embodiment 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 5 ppm by mass, the thermal and oxidation stability tends to decrease. In addition, the nitrogen content as used in the field of this invention means the nitrogen content measured based on JISK2609-1990.

The% C _p of the lubricating base oil used in the present embodiment is preferably 70 or more, preferably 80 or more, more preferably 85 or more, still more preferably 87 or more, and particularly preferably 90 or more. . Further, it is preferably 99.9 or less, more preferably 98 or less, still more preferably 96 or less, and particularly preferably 94 or less. When% C _p of the lubricating base oil is less than the above lower limit, viscosity-temperature characteristics, thermal / oxidative stability, and friction characteristics tend to decrease, and further, when additives are blended in the lubricating base oil In addition, the effectiveness of the additive tends to decrease. Further, when the% C _p value of the lubricating base oil exceeds the upper limit value, the additive solubility will tend to be lower.

Moreover,% C _A of the lubricating base oil used in the present embodiment is preferably 2 or less, more preferably 1 or less, more preferably 0.8 or less, particularly preferably 0.5 or less. When% C _A of the lubricating base oil exceeds the upper limit value, the viscosity - temperature characteristic, thermal and oxidation stability and fuel efficiency tends to decrease.

Moreover,% C _N of the lubricating base oil used in the present embodiment is preferably 30 or less, preferably 25 or less, more preferably 20 or less, more preferably 15 or less, particularly preferably 10 or less . Further, it is preferably 1 or more, more preferably 3 or more, further preferably 5 or more, and particularly preferably 6 or more. If the% C _N value of the lubricating base oil 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, it exists in the tendency for the solubility of an additive to fall.

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. In other words, the preferred ranges of% C _P ,% C _N and% C _A described above are based on the values obtained by the above method. For example, even for a lubricating base oil containing no naphthene, it can be obtained by the above method. is% C _N may indicate a value greater than zero.

  Further, the content of the saturated component in the lubricating base oil used in the present embodiment is preferably 90% by mass or more, preferably 95% by mass or more, more preferably 99% by mass based on the total amount of the lubricating oil base oil. The ratio of the cyclic saturated component in the saturated component is preferably 40% by mass or less, preferably 35% by mass or less, preferably 30% by mass or less, more preferably 25%. It is at most 21% by mass, more preferably at most 21% by mass. Moreover, the ratio of the cyclic | annular saturated part which occupies for the said saturated part becomes like this. Preferably it is 5 mass% or more, More preferably, it is 10 mass% or more. 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 / oxidative stability can be improved. When the additive is blended, the function of the additive can be expressed at a higher level while the additive is sufficiently stably dissolved and held in the lubricating base oil. Furthermore, according to the present embodiment, it is possible to improve the friction characteristics of the lubricating base oil itself, and as a result, it is possible to achieve an improvement in friction reduction effect and an improvement in energy saving.

  The saturated content in the present invention is measured by the method described in the ASTM D 2007-93.

  In addition, a similar method that can obtain the same result can be used in the separation method of the saturated component or the composition analysis of the cyclic saturated component and the non-cyclic saturated component. For example, in addition to the above, a method described in ASTM D 2425-93, a method described in ASTM D 2549-91, a method using high performance liquid chromatography (HPLC), a method obtained by improving these methods, and the like can be given.

  The aromatic content in the lubricating base oil used in the present embodiment is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 2% by mass or less, based on the total amount of the lubricating oil base oil. Especially preferably, it is 1 mass% or less, Preferably it is 0.1 mass% or more, More preferably, it is 0.2 mass% or more. If the aromatic content exceeds the above upper limit, the viscosity-temperature characteristics, thermal / oxidative stability, friction characteristics, volatilization prevention properties, and low-temperature viscosity characteristics tend to decrease. When an additive is blended with the additive, the effectiveness of the additive tends to decrease. Further, the lubricating base oil according to the present embodiment may not contain an aromatic component, but the solubility of the additive is further increased by setting the aromatic content to be equal to or higher than the above lower limit value. be able to.

  In addition, the aromatic component as used in the field of this invention means the value measured based on 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 and naphthols. Aromatic compounds having atoms are included.

A synthetic base oil may be used as the lubricating base oil according to the present embodiment. Synthetic base oils include poly α-olefins or hydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecylglutarate) having a kinematic viscosity at 100 ° C. of 1 to 10 mm ² / s. Rate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, Pentaerythritol pelargonate), polyoxyalkylene glycols, dialkyl diphenyl ethers, polyphenyl ethers, etc., among which poly α-olefins are preferred. Arbitrariness. As the poly α-olefin, typically, an α-olefin oligomer or co-oligomer having 1 to 32 carbon atoms, preferably 6 to 16 (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) and the like. Of the hydrides.

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

  In the lubricating oil composition according to the present embodiment, the lubricating base oil according to the present embodiment may be used alone, and the lubricating base oil according to the present embodiment may be one of other base oils or You may use together with 2 or more types. In addition, when using together the lubricating base oil which concerns on this embodiment, and another base oil, the ratio of the lubricating base oil which concerns on this embodiment in those mixed base oils is 30 mass% or more Is more preferable, it is more preferable that it is 50 mass% or more, and it is still more preferable that it is 70 mass% or more.

Other base oil used in combination with the lubricating base oil of the present embodiment is not particularly limited, examples of mineral base oils, for example, a kinematic viscosity at 100 ° C. is 10 mm 2 / ^s, greater 1000 mm 2 / ^s or less Solvent refined mineral oil, hydrocracked mineral oil, hydrorefined mineral oil, solvent dewaxing base oil, and the like.

Moreover, as another synthetic base oil used together with the lubricating base oil according to this embodiment, the above-described synthetic base oil whose kinematic viscosity at 100 ° C. is out of the range of 1 to 10 mm ² / s is mentioned. It is done.

［式（１）中、Ｒ^１は水素またはメチル基を示し、Ｒ^２は炭素数６以下の直鎖状または分枝状の炭化水素基を示す。］In the lubricating oil composition according to this embodiment, (A) the proportion of one or more structural units represented by the following general formula (1) is 30 to 90 mol%, and the degree of branching is 0.00. 1 to 8.0 of a branched poly (meth) acrylate viscosity index improver (hereinafter referred to as “viscosity index improver according to the present embodiment” for convenience). Thereby, compared with the case where it does not have this structure, fuel-saving property, maintainability of fuel-saving property, and durability can be improved. Moreover, the ratio of the structural unit represented by following General formula (1) is 30-90 mol%, and it is called the branched poly (meth) acrylate type viscosity index improver whose branching degree is 0.1-8.0. As long as the conditions are satisfied, the form of the compound is arbitrary. Specific examples of the compound include a non-dispersed or dispersed poly (meth) acrylate viscosity index improver, a (meth) acrylate-olefin copolymer, or a mixture thereof.

[In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents a linear or branched hydrocarbon group having 6 or less carbon atoms. ]

R ² in the structural unit represented by the formula (1) is a linear or branched hydrocarbon group having 6 or less carbon atoms as described above, and may be one kind or a mixture of two or more kinds. Preferably, it is a linear or branched hydrocarbon having 4 or less carbon atoms, more preferably a linear or branched hydrocarbon having 3 or less carbon atoms, more preferably a carbon having 2 or less carbon atoms. It is a hydrogen group.

  In the viscosity index improver according to this embodiment, the proportion of the (meth) acrylate structural unit represented by the general formula (1) in the polymer is 30 to 90 mol% as described above, and preferably 85. The mol% or less, more preferably 80 mol% or less, still more preferably 75 mol% or less, and particularly preferably 70 mol% or less. Moreover, it is 30 mol% or more preferably, More preferably, it is 35 mol% or more, More preferably, it is 40 mol% or more. If it exceeds 90 mol%, the solubility in base oil and the effect of improving viscosity temperature characteristics and low temperature viscosity characteristics may be inferior, and if it is less than 30 mol%, the effect of improving viscosity temperature characteristics may be inferior.

［式（２）中、Ｒ^３は水素またはメチル基を示し、Ｒ^４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。］In the viscosity index improver according to this embodiment, (A) the proportion of one or more structural units represented by the following general formula (2) is preferably 0.1 to 50 mol%. .

[In the formula (2), R ³ represents hydrogen or a methyl group, and R ⁴ represents a linear or branched hydrocarbon group having 16 or more carbon atoms. ]

As described above, R ⁴ in the structural unit represented by the formula (2) is preferably one or a mixture of two or more linear or branched hydrocarbon groups having 16 or more carbon atoms. A linear or branched hydrocarbon group having 17 or more carbon atoms is more preferable, and a linear or branched hydrocarbon group having 18 or more carbon atoms is more preferable.

  In the viscosity index improver according to this embodiment, the proportion of the (meth) acrylate structural unit represented by the general formula (2) in the polymer is preferably 0.1 to 50 mol% as described above. More preferably, it is 45 mol% or less, More preferably, it is 40 mol% or less, Especially preferably, it is 35 mol% or less, Most preferably, it is 30 mol% or less. Further, it is preferably 0.2 mol% or more, more preferably 1 mol% or more, further preferably 5 mol% or more, particularly preferably 10 mol% or more, and most preferably 20 mol% or more. . If it exceeds 50 mol%, the effect of improving viscosity temperature characteristics may be inferior, and if it is less than 0.1 mol%, it may be inferior in solubility in base oil, low-temperature viscosity characteristics, or even the effect of improving viscosity temperature characteristics. There is.

  The viscosity index improver according to this embodiment may be a copolymer having an arbitrary (meth) acrylate structural unit in addition to the (meth) acrylate structural unit represented by the general formulas (1) and (2). . Such a copolymer is represented by one or more monomers represented by the following general formula (3) (hereinafter referred to as “monomer (M-1)”) and the following general formula (4). Obtained by copolymerizing one or more monomers (hereinafter referred to as “monomer (M-2)”) with monomers other than the monomer (M-1) and the monomer (M-2). Can do.

［上記一般式（３）中、Ｒ^１は水素原子またはメチル基を示し、Ｒ^２は炭素数６以下の直鎖状または分枝状の炭化水素基を示す。］

[In the general formula (3), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a linear or branched hydrocarbon group having 6 or less carbon atoms. ]

［上記一般式（４）中、Ｒ^３は水素原子またはメチル基を示し、Ｒ^４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。］

[In the general formula (4), R ³ represents a hydrogen atom or a methyl group, and R ⁴ represents a linear or branched hydrocarbon group having 16 or more carbon atoms. ]

  Although the monomer combined with the monomer (M-1) and the monomer (M-2) is arbitrary, for example, a monomer represented by the following general formula (5) (hereinafter referred to as “monomer (M-3)”) is preferable. It is. The monomer (M-1) and the copolymer of the monomer (M-2) and the monomer (M-3) are so-called non-dispersed poly (meth) acrylate viscosity index improvers.

［上記一般式（５）中、Ｒ^５は水素原子またはメチル基を示し、Ｒ^６は炭素数７以上、１５以下の直鎖状または分枝状の炭化水素基を示す。］

[In the general formula (5), R ⁵ represents a hydrogen atom or a methyl group, and R ⁶ represents a linear or branched hydrocarbon group having 7 to 15 carbon atoms. ]

R ⁶ in the structural unit represented by the formula (5) is a linear or branched hydrocarbon group having 7 to 15 carbon atoms, preferably a linear or branched group having 10 or more carbon atoms. More preferably, it is a linear or branched hydrocarbon having 11 or more carbon atoms, and more preferably a branched hydrocarbon group having 12 or more carbon atoms.

  Further, in the viscosity index improver according to the present embodiment, the (meth) acrylate structural unit represented by the general formula (5) in the polymer may be one type or a mixture of two or more types, but the ratio is 60 mol% or less, more preferably 50 mol% or less, still more preferably 45 mol% or less, particularly preferably 40 mol% or less, and most preferably 30 mol% or less. . If it exceeds 60 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.

  Moreover, as another monomer combined with monomer (M-1) and (M-2), the monomer (henceforth "monomer (M-4)") represented by the following general formula (6), and the following general One or more selected from monomers represented by the formula (7) (hereinafter referred to as “monomer (M-5)”) are preferable. The copolymer of the monomers (M-1) and (M-2) and the monomers (M-4) and / or (M-5) 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-3) as a constituent monomer.

［上記一般式（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。］

[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 a 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 morpholino group, pyrrolyl group, pyrrolino group, pyridyl group, methylpyridyl group, pyrrolidinyl group, piperidinyl group, quinonyl group, pyrrolidonyl group, pyrrolidono group, imidazolino group, and pyrazino group.

［一般式（７）中、Ｒ^７は水素原子または炭化水素基を示し、Ｅ^２は炭化水素基または窒素原子を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。］

[In General Formula (7), R ⁷ represents a hydrogen atom or a hydrocarbon group, E ² represents an amine residue or a heterocyclic ring containing 1 to 2 hydrocarbon groups or nitrogen atoms and 0 to 2 oxygen atoms. Indicates residue. ]

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-4) and (M-5), specifically, dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-methyl-5-vinylpyridine, Examples thereof include morpholinomethyl methacrylate, morpholinoethyl methacrylate, N-vinylpyrrolidone and a mixture thereof.

  Although there is no particular limitation on the copolymerization molar ratio of the monomers (M-1) and (M-2) and the monomers (M-3) to (M-5), the monomer (M-1), (M-2): Monomers (M-2) to (M-4) are preferably about 20:80 to 90:10, more preferably 30:70 to 80:20, and still more preferably 40:60 to 70: 30.

  The method for producing the viscosity index improver according to the present embodiment is not particularly limited. For example, by using a controlled radical polymerization process, an alkyl methacrylate that forms an arm part (polymer chain of alkyl methacrylate) is polymerized, and then, Examples include a method of reacting a polyalkyl methacrylate with a polyfunctional compound having two or more ethylenically unsaturated double bonds.

Controlled radical polymerization processes include atom transfer radical polymerization (ATRP) processes, reversible addition-fragmentation chain transfer (RAFT) processes, or nitrogen oxide mediated polymerization processes.
A discussion of the polymer mechanism of ATRP polymerization is given by Matyjaszewski et al., Reaction Scheme 11.1 on page 524, Reaction Scheme 11.1 on page 564, Reaction Scheme 11.4 on page 571, Reaction Scheme 11 on page 571, Reaction Schemes 11.8 and 575 on page 572. The reaction scheme on page 11.9 is shown.
A discussion of the polymer mechanism of RAFT polymerization is given in Matjazezewski et al., Section 12.4.4, pages 664-665.
A detailed description of nitrogen oxide mediated polymerization (Chapter 10, pages 463-522), ATRP (Chapter 11, pages 523-628) and RAFT (Chapter 12, pages 629-690) can be found in “Handbookof Radical Polymerization” (Krzysztof Mattyzzewski). and by Thomas P. Davis, Copyright 2002, published by John Wiley and Sons Inc. (hereinafter referred to as “Matyjazewski et al.”).

  Also, the above synthesis can be performed as a batch operation, semi-batch operation, continuous process, feed process or bulk process. The synthesis can also be made in an emulsion, solution or suspension.

  In the above synthesis, the average molecular weight of the resulting polymethacrylate or viscosity index improver is adjusted by changing the amount of initiator and polyfunctional compound having two or more ethylenically unsaturated double bonds. can do.

  The reaction rate to the viscosity index improver using the synthesized arm portion is 70% or more, preferably 80% or more, more preferably 85% or more, based on the amount of the polymer reacted with the viscosity index improver. is there. If the reaction rate is low, the arm portion remains and the molecular weight cannot be increased.

  The PSSI (Permanent Cystability Index) in the diesel injector method of the viscosity index improver according to this embodiment is preferably 20 or less, more preferably 15 or less, still more preferably 10 or less, particularly preferably 5 or less, and most preferably 3 It is as follows. When PSSI exceeds 20, the shear stability is poor, and the kinematic viscosity and HTHS viscosity after use are kept at a certain level or more, so that the initial fuel economy may be deteriorated.

  The “PSSI in the Diesel Injector Method” referred to here conforms to ASTM D 6022-01 (Standard Practice for Calculation of Permanent Shear Stability Index), and ASTM D 6278-02 (Test Metal Stoford Metal Test Stood. Means the permanent shear stability index of the polymer, calculated based on data measured by the Usaing a European Diesel Inspector Apparatus.

The weight average molecular weight (M _w ) of the viscosity index improver according to this embodiment is preferably 100,000 or more, more preferably 200,000 or more, still more preferably 300,000 or more, particularly Preferably it is 400,000 or more. Moreover, it is preferable that it is 1,000,000 or less, More preferably, it is 900,000 or less, More preferably, it is 700,000 or less, Especially preferably, it is 600,000 or less. When the weight average molecular weight is less than 100,000, the effect of improving the viscosity index when dissolved in a lubricating base oil is small, and the fuel economy and low temperature viscosity characteristics are inferior, and the cost may increase. In addition, when the weight average molecular weight exceeds 1,000,000, the effect of increasing the viscosity becomes too large, and not only the fuel saving property and the low temperature viscosity property are inferior, but also shear stability and solubility in lubricating base oil. , Storage stability becomes worse.

PSSI ratio of the weight average molecular weight and diesel injectors method of viscosity index improver according to the present embodiment _(M W / PSSI) is preferably 1.0 × 10 ⁴ or more, more preferably 2.0 × 10 ⁴ or more, more preferably 5.0 × 10 ⁴ or more, and particularly preferably 8.0 × 10 ⁴ or more. If M W _/ PSSI is below 1.0 × 10 ^4, there is a possibility that fuel saving properties and low-temperature startability i.e. viscosity temperature characteristics and low temperature viscosity characteristics are deteriorated.

The ratio (M _W / M _N ) between the weight average molecular weight (M _W ) and the number average molecular weight (M _N ) of the viscosity index improver according to this embodiment is preferably 5.0 or less, more preferably 4. It is 0 or less, more preferably 3.5 or less, particularly preferably 3.0 or less, and most preferably 2.0 or less. _Further, it is preferred that the M W / _{M N} is 1.0 or more, more preferably 1.1 or more, more preferably 1.2 or more. When M _W / M _N is 4.0 or more or 1.0 or less, there is a possibility that sufficient storage stability and fuel economy cannot be maintained due to deterioration of solubility and viscosity temperature characteristics. .

  The degree of branching of the viscosity index improver according to this embodiment is 0.1 to 8.0, more preferably 6.0 or less, more preferably 4.0 or less, even more preferably 3.0 or less, particularly Preferably it is 2.5 or less, Most preferably, it is 2.0 or less. Moreover, Preferably it is 0.2 or more, More preferably, it is 0.5 or more, More preferably, it is 1.0 or more. When the degree of branching exceeds 8.0, the viscosity temperature characteristic and the fuel efficiency are deteriorated. On the other hand, when the degree of branching is less than 0.1, the viscosity-temperature characteristics and fuel economy are deteriorated, and the shear stability and durability may be deteriorated.

  The “branch degree” as used in the present invention is the ratio of the number of carbon atoms derived from the monomer constituting the main chain which is the longest atomic chain in the molecule and the number of carbon atoms derived from the monomer constituting the arm branched therefrom. (Number of carbon atoms in the arm portion / number of carbon atoms constituting the main chain).

  For example, in the case of star-shaped polymethacrylate, the number of carbon atoms derived from the monomer constituting the main chain, which is the longest atomic chain in the molecule, refers to the number of carbon atoms in the two longest arm parts, and constitutes a branched arm part The number of carbon atoms derived from the monomer to be used refers to the number of carbon atoms in the other arm portion. The degree of branching is a value calculated based on the number of carbon atoms in the arm part, and does not include the number of carbon atoms in the core part.

The following formula schematically shows an example of a star polymer. This star-shaped polymer has six arm parts connected to the core part, and the carbon number of the longest arm part is A, and the carbon number of the second longest arm part is B. The degree of branching in this case is (C + D + E + F) / (A + B).

  The content of the viscosity index improver according to the present embodiment is preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass, still more preferably 1 to 30% by mass, based on the total amount of the composition. Especially 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.

  The lubricating oil composition according to the present embodiment is not only the viscosity index improver according to the present embodiment described above, but also a normal general non-dispersion type or dispersion type poly (meth) acrylate, non-dispersion type or dispersion type. An ethylene-α-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 Good.

  The content of the viscosity index improver in the lubricating oil composition according to the present embodiment is preferably 0.1 to 50% by mass, preferably 0.5 to 20% by mass, based on the total amount of the composition. Preferably it is 1.0-15 mass%, More preferably, it is 1.5-12 mass%. If the content is less than 0.1% by mass, the low temperature characteristics may be insufficient, and if the content exceeds 50% by mass, the shear stability of the composition may be deteriorated.

  The lubricating oil composition according to this embodiment preferably contains (B) a friction modifier. Thereby, compared with the case where it does not have this structure, a fuel-saving performance can be improved. (B) As a friction modifier, 1 or more types of friction modifiers chosen from an organic molybdenum compound and an ashless friction modifier are mentioned.

  Examples of the organic molybdenum compound used in the present embodiment include sulfur-containing organic molybdenum compounds such as molybdenum dithiophosphate and molybdenum dithiocarbamate (MoDTC), molybdenum compounds (for example, molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, and orthomolybdic acid. , Molybdate such as paramolybdic acid, (poly) sulfurized molybdate, metal salts of these molybdates, molybdate such as ammonium salt, molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, molybdenum sulfide such as polysulfide molybdenum , Sulfurized molybdic acid, metal salts or amine salts of sulfurized molybdic acid, molybdenum halides such as molybdenum chloride, etc.) and sulfur-containing organic compounds (eg, alkyl (thio) xanthate, thiadiazole, mercaptothiadi) Sol, thiocarbonate, tetrahydrocarbyl thiuram disulfide, bis (di (thio) hydrocarbyl dithiophosphonate) disulfide, organic (poly) sulfide, sulfide ester, etc.) or other organic compounds, or the above sulfides A complex of a sulfur-containing molybdenum compound such as molybdenum or sulfurized molybdic acid and an alkenyl succinimide can be given.

  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 according to the present embodiment, when an organic molybdenum compound is used, its content is not particularly limited, but based on the total amount of the lubricating oil composition, preferably in terms of molybdenum element, preferably 0.001% by mass or more, More preferably 0.005% by mass or more, further preferably 0.01% by mass or more, particularly preferably 0.03% by mass or more, and preferably 0.2% by mass or less, more preferably 0.1% by mass. % Or less, more preferably 0.08 mass% or less, and particularly preferably 0.06 mass% or less. When the content is less than 0.001% by mass, the friction reduction effect due to the addition tends to be insufficient, and the fuel economy and thermal / oxidation stability of the lubricating oil composition tend to be insufficient. . 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.

  Further, as the ashless friction modifier, any compound usually used as a friction modifier for lubricating oil can be used. For example, one or two selected from oxygen atom, nitrogen atom, sulfur atom in the molecule Examples thereof include compounds having 6 to 50 carbon atoms and containing at least a hetero element. More specifically, it has at least one alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly a straight chain alkyl group, straight chain alkenyl group, branched alkyl group or branched alkenyl group having 6 to 30 carbon atoms in the molecule. Ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, aliphatic ethers, urea compounds, hydrazide compounds, and the like.

  The content of the ashless friction modifier in the lubricating oil composition according to this embodiment is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably, based on the total amount of the lubricating oil composition. Is 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 embodiment, (B) the friction modifier is preferably an organic molybdenum friction modifier, more preferably an organic molybdenum compound containing sulfur, and even more preferably molybdenum dithiocarbamate.

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

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

Kinematic viscosity at 100 ° C. of the lubricating oil composition according to the present embodiment is preferably 4 to 12 mm ² / s, preferably not more than 9.0 mm ² / s, more preferably 8.0 mm ² / s or less, More preferably, it is 7.0 mm < ² > / s or less, Most preferably, it is 6.8 mm < ² > / s or less. Further, the kinematic viscosity at 100 ° C. of the lubricating oil composition according to the present embodiment is preferably 4.5 mm ² / s or more, more preferably 5.0 mm ² / s or more, and further preferably 5.5 mm ² / s or more. Particularly preferably, it is 6.0 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. 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 according to this embodiment is preferably 4 to 50 mm ² / s, preferably 40 mm ² / s or less, more preferably 35 mm ² / s or less, and particularly preferably 30 mm. ² / s or less, most preferably 28 mm ² / s or less. Further, the kinematic viscosity at 40 ° C. of the lubricating oil composition according to the present embodiment is preferably 15 mm ² / s or more, more preferably 18 mm ² / s or more, further preferably 20 mm ² / s or more, and particularly preferably 22 mm ^2. / S or more, most preferably 25 mm ² / s or more. The kinematic viscosity at 40 ° C. here refers to the kinematic viscosity at 40 ° C. defined in ASTM D-445. 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 according to this embodiment is preferably in the range of 140 to 400, preferably 180 or more, more preferably 190 or more, still more preferably 200 or more, particularly preferably 210 or more, and most preferably. Is 215 or more. When the viscosity index of the lubricating oil composition according to the present embodiment is less than 140, it may be difficult to improve fuel economy while maintaining the HTHS viscosity of 150 ° C., and further at −35 ° C. It may be difficult to reduce the low temperature viscosity. In addition, when the viscosity index of the lubricating oil composition according to the present embodiment is 400 or more, there is a possibility that the evaporability may be deteriorated, and further, a problem due to insufficient solubility of the additive and compatibility with the sealing material. May occur.

  The HTHS viscosity at 100 ° C. of the lubricating oil composition according to this embodiment is preferably 5.5 mPa · s or less, more preferably 5.0 mPa · s or less, even more preferably 4.7 mPa · s or less, particularly Preferably it is 4.5 mPa * s or less, Most preferably, it is 4.4 mPa * s or less. Further, it is preferably 3.0 mPa · s or more, more preferably 3.5 mPa · s or more, particularly preferably 4.0 mPa · s or more, and most preferably 4.1 mPa · s or more. The HTHS viscosity at 100 ° C. referred to in the present embodiment refers to the high temperature and high shear viscosity at 100 ° C. defined in ASTM D4683. When the HTHS viscosity at 100 ° C. is less than 3.0 mPa · s, there is a risk of insufficient lubricity, and when it exceeds 5.5 mPa · s, the necessary low temperature viscosity and sufficient fuel saving performance cannot be obtained. There is a fear.

  The HTHS viscosity at 150 ° C. of the lubricating oil composition according to the present embodiment is preferably less than 4.0 mPa · s, more preferably 2.7 mPa · s or less, further preferably 2.5 mPa · s or less, Particularly preferably, it is 2.4 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, and particularly preferably 2.3 mPa · s or more. The HTHS viscosity at 150 ° C. here refers to the high temperature and high shear viscosity at 150 ° C. defined in ASTM D4683. If the HTHS viscosity at 150 ° C. is less than 2.0 mPa · s, the lubricity may be insufficient, and if it exceeds 4.0 mPa · s, sufficient fuel saving performance may not be obtained.

  In addition, the ratio of the HTHS viscosity at 150 ° C. to the HTHS viscosity at 100 ° C. (HTHS viscosity at 150 ° C./HTHS viscosity at 100 ° C.) of the lubricating oil composition according to the present embodiment is preferably 0.50 or more. More preferably, it is 0.52 or more, More preferably, it is 0.53, Most preferably, it is 0.54 or more. If the ratio is less than 0.50, the necessary low temperature viscosity and sufficient fuel saving performance may not be obtained.

  The lubricating oil composition according to the present embodiment sufficiently reduces the kinematic viscosity at 40 ° C., the kinematic viscosity at 100 ° C., and the HTHS viscosity at 100 ° C. in an engine oil having an HTHS viscosity at 150 ° C. of less than 2.6 mPa · s. In addition, the increase in the friction coefficient in the boundary lubrication region can be sufficiently suppressed, and the fuel efficiency is excellent. The lubricating oil composition according to this embodiment having such excellent characteristics can be suitably used as a fuel-saving engine oil such as a fuel-saving gasoline engine oil and a fuel-saving diesel engine oil.

  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.

(Synthesis Example 1: Synthesis of non-dispersed PMA viscosity index improver A-1)
<Synthesis of arm molecules>
A 300 ml five-neck separable flask equipped with a vertical metal stirring blade (with a vacuum seal), a Dimroth cooler, a three-way cock for introducing nitrogen, and a sample inlet is equipped with 25.2 parts by mass of methyl methacrylate, general formula (3 ) In which R ⁴ is an alkyl group having 18 carbon atoms, 36.5 parts by mass of a methacrylate, and 120 parts by mass of a hydrocarbon solvent (SAE10) as a solvent were added to obtain a homogeneous solution. This solution was cooled to 0 ° C. in an ice bath, and vacuum degassing / nitrogen purging of the reaction system was performed 5 times using a diaphragm pump. Furthermore, 0.27 parts by mass of azobisisobutyronitrile (AIBN), 0.013 parts by mass of 1,4-cyclohexadiene and 0.11 parts by mass of iodine were introduced as radical initiators from the sample introduction port under a nitrogen flow. Thereafter, polymerization was carried out in a nitrogen atmosphere at a solution temperature of 80 ° C. for 12 hours to obtain an arm molecule solution.
As a result of GPC analysis (standard substance: polystyrene), the obtained arm molecule had a weight average molecular weight of 87400, a number average molecular weight (Mn) of 62000, and a dispersity (Mw / Mn) of 1.41.
<Synthesis of star polymer>
After adding 0.07 parts by mass of azobisisobutyronitrile (AIBN) and 2.14 parts by mass of ethylene glycol dimethacrylate to the above arm solution, polymerization reaction was carried out at a solution temperature of 80 ° C. for 12 hours in a nitrogen atmosphere. As a result, a target star-shaped polymer (hereinafter referred to as “non-dispersed PMA viscosity index improver A-1”) solution was obtained.
As a result of GPC analysis (standard material: polystyrene), the obtained non-dispersed PMA viscosity index improver A-1 has a weight average molecular weight (Mw) of 570,000, a number average molecular weight (Mn) of 470,000, and a dispersion degree ( Mw / Mn) was 1.23, PSSI was 3.8, and Mw / PSSI was 1.5 × 10 ⁵ . Moreover, the arm conversion rate of the non-dispersed PMA viscosity index improver A-1 was 64% by mass, the average number of arms was 8, and the degree of branching was 3.0.
Here, the arm conversion rate and the average number of arms are values calculated based on the following equations, respectively.
Arm conversion rate = GPC area of star polymer / (GPC area of star polymer + GPC area of remaining arm molecule) × 100
Average number of arms = Mn of star polymer / Mn of arm molecule (rounded to the nearest decimal place)
The weight average molecular weight and number average molecular weight were determined by using three TSKgel SuperMultiPore HZ-M columns (4.6 mm ID × 15 cm) manufactured by Tosoh Corporation in series with an HLC-8220 GPC apparatus manufactured by Tosoh Corporation. Tetrahydrofuran was used as the solvent. , Temperature 40 ° C., flow rate 0.35 mL / min, sample concentration 1 mass%, sample injection amount 5 μL, weight average molecular weight and number average molecular weight in terms of polystyrene measured with a detector differential refractometer (RI).

(Synthesis Example 2: Synthesis of non-dispersed PMA viscosity index improver A-2)
Instead of the arm molecule solution of Synthesis Example 1, 70 mol% of methyl methacrylate and 30 mol% of the methacrylate molecule in which R4 in the general formula (4) is an alkyl group having 18 carbon atoms (weight average molecular weight 54000, number average molecular weight) (Mn) 42000, dispersity (Mw / Mn) 1.29) except that an arm molecule solution was used, and a star-shaped polymer (hereinafter referred to as “non-dispersed PMA system”) in the same manner as in Synthesis Example 1. Viscosity index improver A-2 ") was synthesized.
The obtained non-dispersed PMA viscosity index improver A-2 has Mw of 490,000, Mn of 410,000, Mw / Mn of 1.19, PSSI of 2.2, and Mw / PSSI of 2.2 × 10 ^5. The degree of branching was 3.9.

(Synthesis Example 3: Synthesis of non-dispersed PMA viscosity index improver A-3)
Instead of the arm molecule solution of Synthesis Example 1, 70 mol% of methyl methacrylate and 30 mol% of the methacrylate molecule in which R4 in the general formula (4) is an alkyl group having 18 carbon atoms (weight average molecular weight 85000, number average molecular weight) (Mn) 60000, dispersity (Mw / Mn) 1.42) Except that an arm molecule solution was used, a star-shaped polymer (hereinafter referred to as “non-dispersed PMA system” was used in the same manner as in Synthesis Example 1. Viscosity index improver A-3 ") was synthesized.
The obtained non-dispersed PMA viscosity index improver A-3 had Mw of 450,000, Mn of 380,000, Mw / Mn of 1.19, PSSI of 3.0, and Mw / PSSI of 1.5 × 10 ^5. The degree of branching was 2.0.

(Examples 1-5, Comparative Examples 1-4)
In Examples 1 to 5 and Comparative Examples 1 to 4, lubricating oil compositions having the compositions shown in Table 2 were prepared using the base oils and additives shown below. Table 1 shows the properties of the base oils O-1, O-2, and O-3.
(Base oil)
O-1 (base oil 1): hydrocracked / hydroisomerized mineral oil O-2 (base oil 2): hydrocracked mineral oil O-3 (base oil 3): hydrocracked n-paraffin-containing oil Mineral oil (additive)
A-1: Non-dispersed PMA viscosity index improver (70 mol% methyl methacrylate, 30 mol% methacrylate in which R ² in the general formula (3) is an alkyl group having 18 carbon atoms, and a small amount of polymerization Copolymer obtained by reacting an initiator and glycol dimethacrylate, Mw = 570,000, Mn = 470,000, Mw / Mn = 1.23, PSSI = 3.8, Mw / PSSI = 1.5 × 10 ⁵ , Branching degree = 3.0)
A-2: Non-dispersed PMA viscosity index improver (70 mol% methyl methacrylate, 30 mol% methacrylate in which R ² in the general formula (3) is an alkyl group having 18 carbon atoms, and a small amount of polymerization Copolymer obtained by reacting an initiator and glycol dimethacrylate, Mw = 490,000, Mn = 410,000, Mw / Mn = 1.19, PSSI = 2.2, Mw / PSSI = 2.2 × 10 ⁵ , Branching degree = 3.9)
A-3: Non-dispersive PMA based viscosity index improver (a methyl methacrylate 70 mol%, and methacrylate 30 mol% of R ² in general formula (3) is an alkyl group of 18 carbon atoms, a small amount of polymerization Copolymer obtained by reacting an initiator and glycol dimethacrylate, Mw = 450,000, Mn = 380,000, Mw / Mn = 1.19, PSSI = 3.0, Mw / PSSI = 1.5 × 10 ⁵ , Degree of branching = 2.0)
a-1: non-dispersion type PMA based viscosity index improver (a methyl methacrylate 70 mol%, and methacrylate 30 mol% of R ² in general formula (3) is an alkyl group of 18 carbon atoms, a small amount of polymerization Copolymer obtained by reacting an initiator and glycol dimethacrylate, Mw = 620,000, Mn = 440,000, Mw / Mn = 1.41, PSSI = 5.7, Mw / PSSI = 1.1 × 10 ⁵ , Degree of branching = 9.0)
a-2: Dispersion type PMA viscosity index improver (methyl methacrylate 20 mol%, R ² in the general formula (3) is 80 mol% of a methacrylate having 12 to 15 carbon atoms, a small amount A copolymer obtained by reacting a dispersing group and a polymerization initiator, Mw = 300,000, Mn = 70,000, Mw / Mn = 4.0, PSSI = 40, Mw / PSSI = 7.5 × 10 ³ , branched Degree = 0)
a-3: Dispersion-type PMA viscosity index improver (methyl methacrylate 20 mol%, R ² in the general formula (3) is 80 mol% of a methacrylate having 12 to 15 carbon atoms, and a small amount A copolymer obtained by reacting a dispersing group and a polymerization initiator, Mw = 80,000, Mn = 30,000, Mw / Mn = 2.7, PSSI = 10, Mw / PSSI = 8.0 × 10 ³ , branched Degree = 0)
B-1: MoDTC (alkyl group chain length C8 / C13, Mo content 10 mass%, sulfur content 11 mass%)
B-2: Glycerol monooleate C-1: Other additives (succinimide dispersant, ZnDTP, antioxidant, antiwear agent, pour point depressant, antifoaming agent, etc.)

[Evaluation of lubricating oil composition]
About each lubricating oil composition of Examples 1-4 and Comparative Examples 1-3, kinematic viscosity at 40 ° C. or 100 ° C., viscosity index, HTHS viscosity at 100 ° C. or 150 ° C., viscosity reduction rate after ultrasonic shear test It was measured.
(1) Kinematic viscosity: ASTM D-445
(2) Viscosity index: JIS K 2283-1993
(3) HTHS viscosity: ASTM D-4683
(4) Ultrasonic shear test: After adjusting the output with standard oil A defined in ASTM test method in accordance with JASO M347-95, amplitude 28 μm, frequency 10 KHz, irradiation time 10 minutes, sample A shear test was performed with a volume of 60 mL, a kinematic viscosity at 100 ° C. was measured, and a viscosity reduction rate was calculated.

As shown in Table 2, the lubricating oil compositions of Examples 1 to 4 containing the component (A) have a low kinematic viscosity and a HTHS viscosity at 100 ° C., and a small viscosity reduction rate after the ultrasonic shear test. The lubricating oil composition of Comparative Example 1 containing a viscosity index improver having a degree of branching of greater than 8.0, or the lubricating oil composition of Comparative Examples 2 to 3 having a low C6 or lower methacrylate content ratio and a degree of branching of 0 Compared to, it shows excellent fuel economy and durability after use.

Claims (3)

A lubricating base oil having a kinematic viscosity at 100 ° C. of 1 to 10 mm ² / s;
A branched poly (meth) acrylate viscosity index improver having a proportion of structural units represented by the following general formula (1) of 30 to 90 mol% and a degree of branching of 0.1 to 8.0;
A lubricating oil composition containing

[In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents a linear or branched hydrocarbon group having 6 or less carbon atoms. ] The lubricating oil according to claim 1, wherein the viscosity index improver is a viscosity index improver having a PSSI of 5 or less and a ratio of molecular weight to PSSI (Mw / PSSI) of 2 x 10 ⁴ or more. Composition.   The lubricating oil composition according to claim 1, further comprising a friction modifier.