WO2017122721A1

WO2017122721A1 - Lubricant composition

Info

Publication number: WO2017122721A1
Application number: PCT/JP2017/000815
Authority: WO
Inventors: 一生田川; 成小山; 彰高木
Original assignee: Ｊｘエネルギー株式会社
Priority date: 2016-01-12
Filing date: 2017-01-12
Publication date: 2017-07-20
Also published as: JP6862359B2; JPWO2017122721A1

Abstract

Provided is a lubricant composition including a lubricant base oil and (A) a (meth)acrylate polymer including a structural unit represented by general formula (1) and having a value of parameter a represented by formula (2) of 0.12 or less. (In formula (1), R^[ represents a hydrogen or a methyl group, R² represents a C10-36 alkyl group.) ａ＝Ｌｏｇ（Ｍ_ｈ（ｔ_１／２））－Ｌｏｇ（Ｍ（ｔ）） …（２） (In formula (2), M(t) represents the peak top molecular weight in the differential molecular weight distribution curve of the polystyrene-equivalent molecular weight obtained by GPC measurement of the (meth)acrylate polymer; M_h(t_1/2) represents the polystyrene-equivalent molecular weight of the high molecular weight side that gives an intensity of 1/2 the intensity at the molecular weight M(t) in the differential molecular weight distribution curve.)

Description

Lubricating oil composition

The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition for an internal combustion engine.

Generally, lubricating oil prevents the sliding surfaces from coming into direct contact with each other by forming an oil film between the sliding surfaces (fluid lubrication). In the fluid lubrication condition, friction and wear are greatly reduced as compared with the lubrication condition (boundary lubrication) in which the oil film is not maintained between the sliding surfaces. The higher the viscosity of the lubricating oil, the easier it is to maintain the oil film, but at the same time the sliding resistance increases, which is disadvantageous in terms of energy saving.

For example, a lubricating oil composition (lubricating oil composition for an internal combustion engine) used for lubricating an internal combustion engine such as an automobile engine is used in order to improve fuel economy, while using a low-viscosity base oil. It has been proposed to compensate for the base oil viscosity drop at high temperatures by the addition of viscosity index improvers such as acrylates.

Japanese Patent Laying-Open No. 2015-013957 Japanese Patent Laying-Open No. 2015-013962 Japanese Patent Laying-Open No. 2015-013963 Japanese Patent Laying-Open No. 2015-013964 Special table 2003-515630 International Publication No. 2014/017554 Pamphlet Special table 2008-518051 gazette Special table 2007-512413 gazette JP 2007-084658 A Japanese Patent Publication No. 7-25859 JP 11-335432 A JP-A-6-93060 Japanese Patent No. 4681187

When a lubricating oil with insufficient heat resistance is used at a high temperature, a product (carbonaceous material) altered by heat tends to precipitate as an insoluble matter. For this reason, for example, lubricating oil that lubricates high-temperature machine elements, such as lubricating oil for internal combustion engines, is also required to have coking resistance.

An object of the present invention is to provide a lubricating oil composition containing a poly (meth) acrylate viscosity index improver and having improved coking resistance.

One embodiment of the present invention includes a lubricating base oil and (A) a structural unit represented by the following general formula (1), and the value of parameter a represented by the following formula (2) is 0.12. A lubricating oil composition comprising the following (meth) acrylate polymer.

(In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents an alkyl group having 10 to 36 carbon atoms.)

a = Log (M _h (t _1/2 )) − Log (M (t)) (2)
(In Formula (2), M (t) represents the peak top molecular weight in the differential molecular weight distribution curve of the polystyrene conversion molecular weight obtained by the gel permeation chromatography measurement of the said (meth) acrylate type polymer; M _h (t _{1 / 2} ) represents the molecular weight in terms of polystyrene on the high molecular weight side giving half the strength of the molecular weight M (t) in the differential molecular weight distribution curve.)

In this specification, “(meth) acryl” means a generic name of “methacryl” and “acryl”, and “(meth) acrylate” means a generic name of “methacrylate” and “acrylate”. Log means a common logarithm (base 10 logarithm).

In one preferred embodiment, the (meth) acrylate polymer is a polymer obtained by polymerizing a raw material containing one or more (meth) acrylate polymerizable monomers by living anionic polymerization, Content of the compound which has a hydroxyl group in a raw material is 0.2 mass part or less with respect to 100 mass parts of 1 or more types of (meth) acrylate type | system | group polymerizable monomer in this raw material.

According to the present invention, it is possible to provide a lubricating oil composition containing a poly (meth) acrylate-based viscosity index improver and having improved coking resistance.

M (t), M _h (t _1/2 ), M _l (t _1/2 ), a value, and full width at half maximum (b value) in a polystyrene-equivalent differential molecular weight curve obtained by GPC measurement of the polymer FIG.

Hereinafter, the present invention will be described in detail. Unless otherwise specified, the notation “A to B” for the numerical values A and B means “A to B”. In this notation, when a unit is attached to only the numerical value B, the unit is also applied to the numerical value A. Further, the terms “or” and “or” mean logical sums unless otherwise specified.

<Lubricant base oil>
The lubricating base oil is not particularly limited, and a lubricating base oil used for ordinary lubricating oil can be used. Specifically, a mineral base oil, a synthetic base oil, or a mixed base oil obtained by mixing two or more kinds of lubricating base oils selected from these at any ratio 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. Examples thereof include paraffinic mineral oil refined by one or more treatments selected from purification treatments such as chemical purification, sulfuric acid washing, and clay treatment, normal paraffin base oils, isoparaffin base oils, and mixtures thereof.

Preferable examples of the mineral oil base oil include the following base oils (1) to (8) as raw materials, and the raw oil and / or the lubricating oil fraction recovered from the raw oil is obtained by a predetermined refining method. The base oil obtained by refine | purifying 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 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 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.

Furthermore, as the mineral oil base oil, the following base oil obtained by subjecting a base oil selected from the above base oils (1) to (8) or a lubricating oil fraction recovered from the base oil to a predetermined treatment ( 9) or (10) is particularly preferred.
(9) The base oil selected from the above 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 subjecting the lubricating oil fraction to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or distillation after the dewaxing treatment, and 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. As the dewaxing step, a base oil produced through a contact dewaxing step is preferable.

In addition, when obtaining the lubricating base oil of (9) or (10) above, a solvent refining treatment and / or a hydrofinishing treatment step may be further performed at an appropriate stage, if necessary.

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) A hydroisomerization catalyst in which a catalyst or a support containing zeolite (eg, ZSM-5, zeolite beta, SAPO-11, etc.) is loaded with a metal having a hydrogenation ability containing at least one of the 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 and 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 , the hydrogen / oil ratio. 50 to 20000 scf / b is preferable.

Synthetic base oils include, for example, polybutene or hydrides thereof; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate Diesters such as ditridecyl adipate, di-2-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate; alkylnaphthalene, Aromatic synthetic oils such as alkylbenzene, and mixtures thereof can be exemplified.

The kinematic viscosity of the lubricating base oil at 100 ° C. is preferably 2.0 to 8.0 mm ² / s. Further, more preferably not more than ^{5 mm} 2 / s, more preferably 4.5 mm ² / s or less, particularly preferably 4.4 mm ² / s or less, and most preferably not more than 4.3 mm ² / s. On the other hand, the kinematic viscosity at 100 ° C. is more preferably 2.0 mm ² / s or more, more preferably 2.5 mm ² / s or more, particularly preferably 3.0 mm ² / s or more, most preferably 3 .3 mm ² / s or more. When the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 8.0 mm ² / s, the low-temperature viscosity characteristics of the lubricating oil composition may deteriorate, and sufficient fuel economy may not be obtained. If it is less than 0.0 mm ² / s, the formation of an oil film at the lubrication site is insufficient, resulting in poor lubricity, and the evaporation loss of the lubricating oil composition may be increased. In this specification, “kinematic viscosity at 100 ° C.” means the kinematic viscosity at 100 ° C. as defined in ASTM D-445.

The kinematic viscosity at 40 ° C. of the lubricating base oil 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, particularly preferably 22 mm ² / s or less, and 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 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 of the lubricating oil composition may be deteriorated, and sufficient fuel economy may not be obtained. If it is less than ² / s, the oil film formation at the lubrication site is insufficient, so that the lubricity is inferior, and the evaporation loss of the lubricating oil composition may increase. In this specification, “kinematic viscosity at 40 ° C.” means the kinematic viscosity at 40 ° C. as defined in ASTM D-445.

The viscosity index of the lubricating base oil is preferably 100 or more. More preferably, it is 110 or more, More preferably, it is 115 or more, Especially preferably, it is 120 or more, Most preferably, it is 125 or more. When the viscosity index is less than 100, not only the viscosity-temperature characteristics, thermal / oxidative stability and volatilization prevention properties of the lubricating oil composition deteriorate, but also the friction coefficient tends to increase, and the wear prevention property It tends to decrease. In the present specification, the viscosity index means a viscosity index measured according to JIS K 2283-1993.

The density (ρ ₁₅ ) of the lubricating base oil 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 0.835 or less. In this specification, the density at 15 ° C. means the density measured at 15 ° C. in accordance with JIS K 2249-1995.

The pour point of the lubricating base oil is preferably −10 ° C. or lower, more preferably −12.5 ° C. or lower, still more preferably −15 ° C. or lower, and most preferably −17.5 ° C. or lower. When the pour point exceeds the above upper limit, the low temperature fluidity of the entire lubricating oil composition tends to be lowered. In this specification, the pour point means a pour point measured according to JIS K 2269-1987.

The sulfur content in the lubricating base oil 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, the sulfur content is preferably 100 mass ppm or less, more preferably 50 mass ppm or less, from the viewpoint of further improvement in thermal and oxidation stability and low sulfur content. It is more preferably 10 ppm by mass or less, and particularly preferably 5 ppm by mass or less.

The content of nitrogen in the lubricating base oil is preferably 10 ppm by mass or less, more preferably 5 ppm by mass or less, and even more preferably 3 ppm by mass or less. When the content of nitrogen exceeds 10 ppm by mass, the heat / oxidation stability tends to decrease. In the present specification, the nitrogen content means a nitrogen content measured in accordance with JIS K 2609-1990.

% _{C P} of the lubricating base oil is preferably 70 or more, more preferably 80 or more, more preferably 85 or more, and usually 99 or less, preferably 95 or less, more preferably 94 or less. When% C _P of lubricating base oil is less than the above lower limit value, viscosity-temperature characteristics, thermal / oxidative stability and friction characteristics tend to decrease, and when additives are added to 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.

% C _A of the lubricating base oil 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.

% C _N of the lubricating base oil is preferably 30 or less, more preferably 25 or less, more preferably 20 or less, particularly preferably 15 or less. The% C _N of the lubricating base oil is preferably 1 or more, more preferably 4 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.

In the present specification,% C _P ,% C _N and% C _A are the percentages of the number of paraffin carbons to the total number of carbons determined by a method (ndM ring analysis) based on ASTM D 3238-85, respectively. Mean the percentage of naphthene carbons to total carbons, and the percentage of aromatic carbons to total 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. The% _{CN that} is obtained can exhibit values greater than zero.

The content of the saturated component in the lubricant base oil is preferably 90% by mass or more, preferably 95% by mass or more, more preferably 99% by mass or more, based on the total amount of the lubricant base oil. The proportion 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, and more preferably 25% by mass or less. More preferably, it is 21% by mass or less. 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 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, 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. In the present specification, the saturated content means a value measured in accordance with ASTM D 2007-93.

In addition, a similar method that can obtain the same result can be used for 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 method described in ASTM D 2007-93, 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 these methods may be used. The improved method etc. can be mentioned.

The aromatic content in the lubricating base oil is preferably 10% by weight or less, more preferably 5% by weight or less, still more preferably 1% by weight or less, particularly preferably 0.2%, based on the total amount of the lubricating base oil. A base oil that is not more than mass% and does not substantially contain an aromatic component can also be preferably used. In the present specification, the phrase “base oil does not substantially contain an aromatic component” means that the aromatic component content is 0 to 1000 ppm by mass based on the total amount of the base oil. If 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 decrease. When an additive is blended with the additive, the effectiveness of the additive tends to decrease.

In the present specification, the aromatic content means a value measured according to ASTM D 2007-93. The aromatic component usually includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene and alkylated products thereof, and compounds having four or more condensed benzene rings, pyridines, quinolines, phenols, naphthols, etc. An aromatic compound having a hetero atom is included.

<(A) (Meth) acrylate polymer>
The lubricating oil composition of the present invention comprises (A) a structural unit represented by the following general formula (1), and the value of parameter a represented by the following formula (2) is 0.12 or less (meta ) An acrylate polymer (hereinafter sometimes referred to as “component (A)” or “(meth) acrylate polymer (A)”).

It is important that the (meth) acrylate polymer (A) not only has a narrow molecular weight distribution but also has a narrow molecular weight distribution on the high molecular weight side from the viewpoint of enhancing the coking resistance of the lubricating oil composition. As a method for evaluating the molecular weight distribution on the high molecular weight side, the following method is used.

A chromatogram obtained by gel permeation chromatography (GPC) measurement is replaced with a differential molecular weight distribution curve having a molecular weight in terms of polystyrene using a calibration curve indicating the relationship between the elution time and the molecular weight of standard polystyrene. At that time, the measured intensity at the peak top molecular weight (molecular weight having the highest measured intensity) M (t) in terms of polystyrene of the (meth) acrylate polymer is defined as I (t). In the differential molecular weight distribution curve, the molecular weight in terms of polystyrene on the high molecular weight side at the point where the strength is 0.5I (t) is defined as M _h (t _1/2 ). In the (meth) acrylate polymer (A), the value of the parameter a represented by the above formula (2) is 0. 0 with respect to M (t) and M _h (t _1/2 ) determined in this way. It must be 12 or less (see FIG. 1). The (meth) acrylate polymer (A) having a parameter a value of 0.12 or less is a polymer having a small molecular weight distribution on the high molecular weight side.

From the viewpoint of further improving the coking resistance of the lubricating oil composition and obtaining a (meth) acrylate polymer having good shear viscosity stability, the a value is preferably 0.11 or less, and 0.10. The following is more preferable, and 0.095 or less is more preferable. In the above formula (2), Log means a common logarithm (base 10 logarithm). The a value is usually 0.05 or more.

In the (meth) acrylate polymer (A), the value of parameter b represented by the following formula (3) is preferably 0.3 or less.
b = Log (M _h (t _1/2 )) − Log (M _l (t _1/2 )) (3)
(In formula (3), M _h (t _1/2 ) is as defined above, and M _l (t _1/2 ) is _½ of the intensity at molecular weight M (t) in the differential molecular weight distribution curve. Represents the polystyrene equivalent molecular weight on the low molecular weight side that gives strength.)

The value of parameter b represents the full width at half maximum. When the half-value width is 0.3 or less, the molecular weight distribution on the low molecular weight side is narrow, that is, the amount of the polymer having a molecular weight smaller than the peak top molecular weight M (t) is small. The ratio is reduced, and therefore the amount of component (A) added can be reduced. From the same viewpoint, the b value is more preferably 0.25 or less. The b value is usually 0.1 or more.

Furthermore, it is preferable that the ratio a / b between the half width half width a and the full width half maximum b is 0.46 or less. When the ratio a / b is 0.46 or less, the molecular weight distribution on the high molecular weight side is narrow, and there are few high molecular weight polymer molecules that are easily cut when subjected to shearing force. Shear viscosity stability can be further improved. From the same viewpoint, the a / b ratio is more preferably 0.44 or less, further preferably 0.43 or less, and most preferably 0.42 or less. The a / b ratio is usually 0.1 or more.

The content of the structural unit represented by the general formula (1) in the (meth) acrylate polymer (A) is 40 based on the total amount of the (meth) acrylate polymer (A) (100% by mass). It is preferably ˜80% by mass.

The (meth) acrylate polymer (A) preferably includes a structural unit represented by the following general formula (4) and a structural unit represented by the following general formula (5).

(In the formula (4) and (5), ^{R 3} and ^{R 5} each independently represent a hydrogen or a methyl group; ^{R 4} represents a group represented by the following general formula (6); ^{R 6} is a linear or Represents an alkyl group having 1 to 36 carbon atoms having a branch having 5 or less carbon atoms.)

(In formula (6), m and n are integers satisfying m ≧ 5, n ≧ 4, and m + n ≦ 31.)

In addition, regarding R ⁶ , “straight chain or alkyl group having 1 to 36 carbon atoms having a branch having 5 or less carbon atoms” means “straight chain alkyl group having 1 to 36 carbon atoms or a side chain having 5 or less carbon atoms”. It has the same meaning as the “branched alkyl group having 3 to 36 carbon atoms”.

Each of R ³ and R ⁵ may be either hydrogen or a methyl group, but is preferably a methyl group.

R ⁴ is preferably a group in which m is 5 to 16 and n is 4 to 15, more preferably a group in which m is 6 to 15 and n is 6 to 10, and m is 7 from the viewpoint of reducing viscosity. More preferred is a group having ˜10 and n is 6˜9. When the structural unit represented by the general formula (4) contained in the (meth) acrylate polymer (A) is two or more, R ³ and R ⁴ may be the same or different among the structural units.

The (meth) acrylate polymer (A) is the total amount of the structural units contained in the (meth) acrylate polymer (A) from the viewpoint of reducing the viscosity. Is preferably 20 to 80% by mass, more preferably 20 to 70% by mass, and still more preferably 20 to 50% by mass. In addition, the (meth) acrylate polymer (A) is a structural unit contained in the (meth) acrylate polymer (A) from the viewpoint of fuel economy, the structural unit represented by the general formula (5). 20 to 80% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 80% by mass, based on the total amount. The total content of the structural unit represented by the general formula (4) and the structural unit represented by the general formula (5) in the (meth) acrylate polymer (A) is (meta ) Based on the total amount of structural units contained in the acrylate polymer (A), it is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. 100 mass%.

When the (meth) acrylate polymer (A) contains two or more structural units represented by the general formula (5), R ⁵ and R ⁶ may be the same or different among the structural units. From the viewpoint of fuel economy, the (meth) acrylate polymer (A) contains the structural unit of the above general formula (5) in which R ⁶ is a methyl group in the (meth) acrylate polymer (A). Based on the total amount of structural units to be produced, it is preferably contained in an amount of 20% by mass or more, more preferably 30% by mass or more, and further preferably 35% by mass or more. From the viewpoint of low-temperature fluidity, the (meth) acrylate polymer (A) has a structural unit of the above general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms. The content is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more, based on the total amount of structural units contained in the polymer (A). The content in the (meth) acrylate polymer (A) of the structural unit of the above general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is the (meth) acrylate polymer (A). Is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less, based on the total amount of structural units contained in. Further, from the viewpoint of solubility of the (meth) acrylate polymer (A), the content of the structural unit of the above general formula (5) in which R ⁶ is a methyl group in the (meth) acrylate polymer (A) Is preferably 50% by mass or less, more preferably 45% by mass or less, based on the total amount of structural units contained in the (meth) acrylate polymer (A); and R ⁶ is an alkyl group having 18 or more carbon atoms. The content of the structural unit of the general formula (5) in the (meth) acrylate polymer (A) is preferably based on the total amount of the structural unit contained in the (meth) acrylate polymer (A). Is 35% by mass or less. From the viewpoint of solubility of the (meth) acrylate polymer (A), the content of the structural unit of the general formula (4) in the (meth) acrylate polymer (A) is such that the (meth) acrylate weight More preferably, it is 25% by mass or more based on the total amount of structural units contained in the coalescence (A).
In the (meth) acrylate polymer (A), the structural unit represented by the general formula (4), the structural unit of the general formula (5) in which R ⁶ is a methyl group, and R ⁶ are carbon. The total content of the structural unit of the general formula (5) which is an alkyl group of several 18 or more is less than 100% by mass based on the total amount of the structural unit contained in the (meth) acrylate polymer (A). In some cases, it is preferable that the (meth) acrylate polymer (A) further includes a structural unit of the above general formula (5) in which R ⁶ is an alkyl group having 2 to 18 carbon atoms.
From the viewpoint of further improving fuel economy, R ⁶ is a methyl group based on the total amount of structural units contained in the (meth) acrylate polymer (A) in the (meth) acrylate polymer (A). The content of the structural unit of the general formula (5) is preferably 35% by mass or more, more preferably 40% by mass or more, and R ⁶ is an alkyl group having 18 or more carbon atoms. The content of the structural unit is preferably 25% by mass or more.

The (meth) acrylate polymer (A) may contain only the structural unit represented by the general formula (4) and the structural unit represented by the general formula (5), or other than these. A structural unit may be further included. The polymer chain end of the (meth) acrylate polymer (A) is not particularly limited. Among such polymer chains, the polymer chain contains only the structural unit represented by the general formula (4) and the structural unit represented by the general formula (5), and the terminal is a hydrogen atom. The polymer chain represented by the general formula (7) is preferable.

In formula (7), R ⁷ represents hydrogen or a methyl group, and R ⁸ represents a group represented by the above general formula (6), a linear alkyl group having 1 to 36 carbon atoms, or a side having 5 or less carbon atoms. A branched alkyl group having 3 to 36 carbon atoms having a chain is shown, and p is an integer selected so that Mw and Mw / Mn are within a desired range. p is an integer of 400 to 2000, for example.

The weight average molecular weight Mw of the (meth) acrylate polymer (A) is preferably 50,000 or more, more preferably 100,000 or more, further preferably 150,000 or more, particularly preferably from the viewpoint of fuel saving performance. 190,000 or more, preferably 500,000 or less, more preferably 400,000 or less, and further preferably 300,000 or less.

The ratio of the weight average molecular weight Mw and the number average molecular weight Mn of the (meth) acrylate polymer (A) (Mw / Mn; hereinafter referred to as “molecular weight distribution”) is the shear viscosity stability and fuel economy. In view of the above, it is preferably 1.6 or less, more preferably 1.5 or less, and preferably 1.01 or more, more preferably 1.05 or more. Mw and Mn are, for example, the amount of a compound having a hydroxyl group or a polymerization inhibitor in a raw material containing a (meth) acrylate-based polymerizable monomer used in the production of the (meth) acrylate-based polymer (A). Depends on. Mw and Mn are values of molecular weight in terms of polystyrene determined from the above-described measurement by GPC.

The number average molecular weight Mn of the (meth) acrylate polymer (A) can be appropriately selected so that Mw / Mn satisfies the above conditions. From the viewpoint of fuel saving performance, Mn is preferably 75,000 or more, more preferably 94,000 or more, and further preferably 110,000 or more. The upper limit of Mn is not particularly limited, but Mn is, for example, 400,000 or less.

The shear viscosity stability is evaluated by, for example, the viscosity reduction rate. The viscosity reduction rate is preferably 3.0% or less, more preferably 2.0% or less, and still more preferably 1.5% or less. When the viscosity reduction rate is less than or equal to the above upper limit, fuel economy is excellent. In this specification, the shear viscosity reduction rate means the viscosity reduction rate in the ultrasonic shear test, and specifically, according to JASO M347-95 (automatic transmission oil shear stability test method), sample volume This means the rate of decrease in thickening due to the viscosity index improver when evaluated under only increased conditions.

More specifically, after adjusting the output with the standard oil A defined in the ASTM test method (ASTM D6022-06 (2012)), the amplitude is 28 μm, the vibration frequency is 10 KHz, the irradiation time is 10 minutes, and the sample volume is 50 mL. This means a permanent shear stability index PSSI (Permanent Shear Stability） Index) calculated based on the measured kinematic viscosity. PSSI is a viscosity increase (V1) per 100 ° C. viscosity index improver measured before the shear test and a viscosity increase per 100 ° C. viscosity index improver measured after the shear test (V1). V2) and ((V1−V2) / V1 × 100) (%).

The content of the (meth) acrylate polymer (A) in the lubricating oil composition is usually 0.1 to 30% by mass, preferably 0.5% by mass or more, more preferably based on the total amount of the composition. 1 mass% or more, More preferably, it is 2 mass% or more, Preferably it is 20 mass% or less, More preferably, it is 15 mass% or less. When the content is less than 0.1% by mass, the fuel efficiency is deteriorated and the low temperature characteristics may be insufficient. When the content exceeds 30% by mass, the fuel efficiency of the composition is decreased. May deteriorate and shear stability may deteriorate.

The (meth) acrylate polymer (A) is a polymerized (meth) acrylate polymerizable monomer containing, for example, a (meth) acrylic acid alkyl ester that gives the structural unit represented by the general formula (1). Can be obtained.

((Meth) acrylate polymerizable monomer)
Examples of the (meth) acrylic acid alkyl ester giving the structural unit represented by the general formula (1) include n-decyl (meth) acrylate, n-undecyl (meth) acrylate, and n- (meth) acrylic acid. Dodecyl, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, n-pentadecyl (meth) acrylate, n-hexadecyl (meth) acrylate, n-heptadecyl (meth) acrylate, (meth) N-octadecyl acrylate, n-nonadecyl (meth) acrylate, n-eicosyl (meth) acrylate, n-henecosyl (meth) acrylate, n-docosyl (meth) acrylate, n-tricosyl (meth) acrylate , N-tetracosyl (meth) acrylate, n-pentacosyl (meth) acrylate, n (meth) acrylic acid Hexacosyl, n-heptacosyl (meth) acrylate, n-octacosyl (meth) acrylate, n-nonacosyl (meth) acrylate, n-triacontyl (meth) acrylate, n-hentriacontyl (meth) acrylate, ( (Meth) acrylic acid n-detriacontyl, (meth) acrylic acid n-tritriacontyl, (meth) acrylic acid n-tetratriacontyl, (meth) acrylic acid n-pentatriacontyl, (meth) acrylic acid n- Straight chain alkyl group-containing (meth) acrylic acid alkyl ester such as hexatriacontyl; isodecyl (meth) acrylate, 2,4,6-trimethylheptyl (meth) acrylate, 2-butyloctyl (meth) acrylate, (Meth) acrylic acid 2-ethyl-n-dodecyl, (meth) acrylic acid 2-methyl-n Tetradecyl, isohexadecyl (meth) acrylate, 2-n-octyl-n-nonyl (meth) acrylate, isooctadecyl (meth) acrylate, (meth) 1-n-hexyl-n-tridecyl acrylate, 2-ethyl-n-heptadecyl (meth) acrylate, isoicosyl (meth) acrylate, 1-n-octyl-n-pentadecyl (meth) acrylate, 2-n-decyl-n-tetradecyl (meth) acrylate, ( 2-n-dodecyl-n-pentadecyl methacrylate), isotriacontyl (meth) acrylate, 2-n-tetradecyl-n-heptadecyl (meth) acrylate, 2-n-hexadecyl (meth) acrylate n-heptadecyl, 2-n-hexadecyl-n-icosyl (meth) acrylate and 2-n-te (meth) acrylate Branched alkyl group containing such Radeshiru -n- docosyl (meth) acrylic acid alkyl ester; and the like. The (meth) acrylic acid alkyl ester having an alkyl group having 10 to 36 carbon atoms is preferably a (meth) acrylic acid alkyl ester having a branched alkyl group having 10 to 36 carbon atoms from the viewpoint of the effect of improving the viscosity index. .

Among the above (meth) acrylic acid alkyl esters having an alkyl group having 10 to 36 carbon atoms, (meth) acrylic acid alkyl esters having an alkyl group having 14 to 30 carbon atoms from the viewpoint of improving viscosity index and shear stability (Meth) acrylic acid alkyl ester having an alkyl group having 16 to 28 carbon atoms is more preferable, and (meth) acrylic acid alkyl ester having an alkyl group having 16 to 24 carbon atoms is particularly preferable. The said (meth) acrylic acid ester may be used independently, and 2 or more types may be mixed and used for it.

The (meth) acrylate polymerizable monomer contains other (meth) acrylate polymerizable monomers other than the (meth) acrylic acid alkyl ester having an alkyl group having 10 to 36 carbon atoms. May be. Examples of such other (meth) acrylate-based polymerizable monomers include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and tricyclododecyl (meth) acrylate. (Meth) acrylic acid ester having a formula alkyl group; (meth) aromatic hydrocarbon such as phenyl (meth) acrylate, benzyl (meth) acrylate, naphthyl (meth) acrylate, biphenyl (meth) acrylate Acrylic acid ester; methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-ethoxy (meth) acrylate Propyl, (meth) acrylic acid methoxypolyethylene glycol, (meth) (Meth) acrylic acid ester having an ether bond such as methoxypolypropylene glycolate; (meth) N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide N, N-dialkyl (meth) acrylamide such as N, N-di-n-butyl (meth) acrylamide; (meth) acrylic acid ester having an epoxy group such as glycidyl (meth) acrylate; 1,3-propane Diol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (Meth) acrylate, 1,10-decanediol di (meth) a Relate, neopentyl glycol di (meth) acrylate, polyalkylene glycol di (meth) acrylate, bisphenol A di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerin tri Polyfunctional (meth) acrylic acid esters such as (meth) acrylate and pentaerythritol tetra (meth) acrylate are exemplified.

Further, as the other (meth) acrylate polymerizable monomer, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 9 carbon atoms may be contained. Examples of such (meth) acrylic acid alkyl ester having an alkyl group having 1 to 9 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and (meth) acrylic. N-butyl acid, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, etc. (Meth) acrylic acid alkyl ester having a linear alkyl group having 1 to 9 carbon atoms; isopropyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isoamyl (meth) acrylate , T-amyl (meth) acrylate, isohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) (Meth) acrylic acid alkyl ester having a branched alkyl group having a carbon number of 3-9, such as acrylic acid isononyl and the like.

From the viewpoint of improving the viscosity index, the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 9 carbon atoms is preferably a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms. ) Methyl acrylate is more preferred. The other (meth) acrylate polymerizable monomers may be used alone or in combination of two or more.

From the viewpoint of the effect of improving the viscosity index and the shear stability, the (meth) acrylate polymerizable monomer may be a (meth) acrylic acid alkyl ester having a linear alkyl group having 1 to 4 carbon atoms, a carbon number of 10 to A mixture containing (meth) acrylic acid alkyl ester having 36 linear alkyl groups and (meth) acrylic acid alkyl ester having a branched alkyl group having 10 to 36 carbon atoms is preferred, methyl (meth) acrylate, carbon A mixture containing a (meth) acrylic acid alkyl ester having a linear alkyl group of 12 to 20 and a (meth) acrylic acid alkyl ester having a branched alkyl group of 16 to 28 carbon atoms is more preferred.

The (meth) acrylate polymerizable monomer is not particularly limited as long as it contains a (meth) acrylic acid alkyl ester having an alkyl group having 10 to 36 carbon atoms, but from the viewpoint of an effect of improving the viscosity index. The (meth) acrylate polymerizable monomer has a linear alkyl group having 1 to 4 carbon atoms based on the total amount of the (meth) acrylate polymerizable monomer (100% by mass) ( (Meth) acrylic acid ester 5 to 90% by mass, (meth) acrylic acid alkyl ester 5 to 60% by mass having a linear alkyl group having 10 to 36 carbon atoms, and a branched alkyl group having 10 to 36 carbon atoms (meta) ) Preferably a mixture containing 5 to 60% by weight of an alkyl acrylate ester, 10 to 60% by weight of methyl (meth) acrylate, 12 to 20 carbon atoms It is a mixture containing 10 to 60% by mass of a (meth) acrylic acid alkyl ester having a chain alkyl group and 10 to 60% by mass of a (meth) acrylic acid alkyl ester having a branched alkyl group having 16 to 28 carbon atoms. More preferred.

(Compound having a hydroxyl group in a raw material containing a (meth) acrylate polymerizable monomer)
In order to obtain the (meth) acrylate polymer (A) having the above characteristics, it is preferable to control the concentration of the compound containing a hydroxyl group in the raw material containing the (meth) acrylate polymerizable monomer. The compound containing a hydroxyl group contained in the raw material is not particularly limited, and examples thereof include water, a compound having a phenolic hydroxyl group, and a compound having an alcoholic hydroxyl group (for example, alcohol).

The compound having a phenolic hydroxyl group is used as, for example, a polymerization inhibitor that ensures the storage stability of the (meth) acrylate polymerizable monomer. Examples of the compound having a phenolic hydroxyl group include hydroquinone, methoxyphenol, p-tert-butylcatechol, 2,4-dimethyl-6-tert-butylphenol, 2,6-tert-butyl-4-methylphenol, and the like. It is done. As the polymerization inhibitor, hydroquinone, methoxyphenol, and 2,6-tert-butyl-4-methylphenol, which have a high polymerization inhibition effect, are preferably used.

Examples of the compound having an alcoholic hydroxyl group contained in the raw material include alcohols corresponding to the (meth) acrylic acid alkyl ester contained in the (meth) acrylate polymerizable monomer. In particular, an alkyl alcohol having an alkyl group having 10 to 36 carbon atoms corresponding to an alkyl (meth) acrylate having an alkyl group having 10 to 36 carbon atoms has a high boiling point, and when the alkyl alcohol is contained in the raw material, It is difficult to completely remove the alkyl alcohol without affecting the (meth) acrylic acid alkyl ester.

The content of the compound having a hydroxyl group in the raw material is preferably 0.2 parts by mass or less, more preferably 0.1 parts by mass or less, with respect to 100 parts by mass of the (meth) acrylate polymerizable monomer. is there. The content of water in the raw material is preferably 0.002 parts by mass or less with respect to 100 parts by mass of the (meth) acrylate polymerizable monomer, and the content of the compound having a phenolic hydroxyl group in the raw material is It is preferable that it is 0.005 mass part or less, and it is preferable that content of the compound which has the alcoholic hydroxyl group in a raw material is 0.2 mass part or less.

The content of water in the raw material is preferably 0.00001 parts by mass or more with respect to 100 parts by mass of the (meth) acrylate-based polymerizable monomer, and the content of the compound having a phenolic hydroxyl group in the raw material The amount is preferably 0.00001 part by mass or more, and the content of the compound having an alcoholic hydroxyl group in the raw material is preferably 0.0001 part by mass or more.
It is difficult to reduce the content of water and the compound having an alcoholic hydroxyl group in the raw material to less than the above lower limit from the viewpoint of removal efficiency and economy. In particular, a (meth) acrylic acid alkyl ester having an alkyl group having 10 to 36 carbon atoms contained in the raw material of the (meth) acrylate polymer (A) has a high boiling point. In the raw material containing ester, there is a tendency that many compounds having a hydroxyl group remain. Moreover, when the content of the compound having a phenolic hydroxyl group in the raw material is not less than the above lower limit, it becomes easy to ensure the storage stability of the (meth) acrylate polymerizable monomer contained in the raw material. .

The content of the compound having a hydroxyl group in the raw material of the (meth) acrylate polymer (A) can be determined by, for example, an internal standard method or an absolute calibration curve method using gas chromatography or liquid chromatography.

There is no limitation on the method for reducing the content of the compound having a hydroxyl group contained in the raw material of the (meth) acrylate polymer (A). For example, distillation, recrystallization, etc. from a mixture containing a (meth) acrylate monomer A method of reducing the content of a compound having a hydroxyl group by a method, a method of reducing a compound having a hydroxyl group by an adsorption treatment using an adsorbent from a mixture containing a (meth) acrylate monomer, and (meth) A method of suppressing the remaining amount by consuming raw material alcohol during the production of the acrylate monomer is also included. Especially, the method of reducing the compound which has a hydroxyl group by adsorption | suction processing from a viewpoint of the recovery rate of the raw material containing a (meth) acrylate type | system | group polymerizable monomer, and the ease of operation is preferable.

As the adsorbent, an adsorbent capable of adsorbing and removing a compound having a hydroxyl group can be used without particular limitation. From the high adsorption efficiency, activated alumina, silica, activated clay, acidic clay, activated carbon, ion exchange are used. Resins, zeolites, and molecular sieves are preferred. Of these, activated alumina, zeolite, and molecular sieves are more preferable.

As a method for the adsorption treatment, a mixture containing a (meth) acrylate monomer and an adsorbent are mixed in a batch system, and then stirred or left standing, or (meth) acrylate is packed in a packed tower filled with an adsorbent. And a method of continuously introducing a mixture containing a monomer.

The adsorption treatment may be performed after diluting a mixture containing a (meth) acrylate monomer in a solvent. As the solvent used in the adsorption treatment, a solvent that does not adversely affect the adsorption treatment can be used without particular limitation. For example, aliphatic hydrocarbons such as pentane, n-hexane, octane, etc .; cyclopentane, methylcyclopentane, cyclohexane, And alicyclic hydrocarbons such as methylcyclohexane and ethylcyclohexane; aromatic hydrocarbons such as benzene, toluene, ethylbenzene and xylene; ethers such as diethyl ether, tetrahydrofuran, 1,4-dioxane, anisole and diphenyl ether; Among these, aromatic hydrocarbons are preferable and toluene and xylene are more preferable from the viewpoints that they can be used in the subsequent polymerization reaction as they are and that the solvent can be easily recovered and purified. These solvents may be used alone or in combination of two or more.

(Method for producing a mixture containing a methacrylate polymerizable monomer)
The manufacturing method of the mixture containing the (meth) acrylate-based polymerizable monomer that is the raw material of the (meth) acrylate-based polymer (A) is not particularly limited, and for example, a known or known method can be employed. For example, a (meth) acrylic acid ester having a short chain alkyl group such as methyl (meth) acrylate and an alkyl alcohol are heated in the presence of a Bronsted acid or a Lewis acid catalyst to distill off the generated short chain alcohol. A transesterification reaction, a condensation reaction carried out by heating (meth) acrylic acid and alkyl alcohol in the presence of sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid or a solid acid catalyst, (meth) acrylic acid chloride Alternatively, a method of reacting (meth) acrylic anhydride and alkyl alcohol in the presence of a base such as triethylamine or pyridine can be exemplified.

In obtaining a mixture containing a (meth) acrylate polymerizable monomer from the reaction solution, known methods such as extraction and recrystallization can be used without particular limitation. For example, acquisition of the mixture containing the (meth) acrylate polymerizable monomer from the reaction solution obtained by the reaction of (meth) acrylic acid and alkyl alcohol is, for example, (meth) acrylic acid and alkyl alcohol, Heat in an organic solvent such as toluene or hexane in the presence of an acid catalyst such as sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid or solid acid, and perform the reaction while removing the water generated by azeotropic dehydration out of the system. After obtaining the reaction solution, it can be carried out by neutralizing and extracting the acid catalyst by adding an alkaline aqueous solution such as sodium hydroxide to the reaction solution, and then distilling off the solvent in the organic layer.

In the production of the mixture containing the above (meth) acrylate polymerizable monomer, it is preferable to use a polymerization inhibitor. Examples of the polymerization inhibitor include quinones such as hydroquinone, methylhydroquinone, and benzoquinone; methoxyphenol, p-tert-butylcatechol, 2,4-dimethyl-6-tert-butylphenol, and 2,6-tert-butyl- A compound having at least one phenolic hydroxyl group selected from 4-methylphenol; and cuperone and phenothiazine. As the polymerization inhibitor, hydroquinone, methoxyphenol, p-tert-butylcatechol, and 2,6-tert-butyl-4-methylphenol having a high polymerization inhibition effect are preferably used.

From the viewpoint of preventing polymerization of (meth) acrylic acid and (meth) acrylic acid ester, the amount of the polymerization inhibitor used in the production of the mixture containing the (meth) acrylate polymerizable monomer is (meth) acrylic acid (meth) acrylate. ) It is preferably 0.001 part by mass or more, more preferably 0.005 part by mass or more, and further preferably 0.01 part by mass or more with respect to 100 parts by mass of acrylic acid or (meth) acrylic acid short chain alkyl ester . Moreover, the said usage-amount is from a useful viewpoint of a product, Preferably it is 10 mass parts or less, More preferably, it is 1 mass part or less, More preferably, it is 0.5 mass part or less.

The content of the polymerization inhibitor in the mixture containing the (meth) acrylate polymerizable monomer is preferably from 100 parts by mass of the (meth) acrylate monomer from the viewpoint of preventing polymerization during storage. It is 0.00001 mass part or more, More preferably, it is 0.0001 mass part or more, More preferably, it is 0.0005 mass part or more. Further, the content is preferably 0.5 parts by mass or less, more preferably 0.2 parts by mass or less, and further preferably 0.1 parts by mass or less, from the viewpoint of easy removal before use in polymerization.

(Method for producing (meth) acrylate polymer (A))
The production method of the (meth) acrylate polymer (A) is not particularly limited, but in order to make the a value within a desired range, the production method is atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer. Polymerization (RAFT), nitroxide-mediated polymerization (NMP), iodine transfer polymerization, polymerization using high-cycle heteroelements (such as organic tellurium, antimony, bismuth, etc.), boron-mediated polymerization, catalyst transfer polymerization (CCT), and cobalt, titanium, etc. Precise radical polymerization such as a polymerization system (OMRP) using a metal and a carbon bond as a dormant species, and living anion polymerization are preferable. Especially, since a (meth) acrylate type polymer (A) with high heat stability is obtained, living anion polymerization is more preferable. As such living anionic polymerization method, for example, an anionic polymerization in the presence of a mineral salt such as an alkali metal or alkaline earth metal salt using an organic alkali metal compound as a polymerization initiator (see Japanese Patent Publication No. 7-25859). ), Anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organic aluminum compound (see JP-A-11-335432), anionic polymerization using an organic rare earth metal complex or a metallocene metal complex as a polymerization initiator And the like (see JP-A-6-93060). Among them, since a polymer having a smaller Mw / Mn is obtained, the shear stability is improved, and since a polymer having a high syndiotacticity is obtained, the effect of improving the viscosity index is increased. A method of anionic polymerization using a metal compound as a polymerization initiator in the presence of an organoaluminum compound is preferred.

Anionic polymerization in the presence of an organoaluminum compound using an organoalkali metal compound as a polymerization initiator is, for example, an organolithium compound and the following general formula (8) or (9):
AlR ⁹ R ¹⁰ R ¹¹ (8)
(In General Formula (8), R ⁹ , R ¹⁰ and R ¹¹ each independently have an alkyl group that may have a substituent, a cycloalkyl group that may have a substituent, or a substituent. Represents an aryl group which may have a substituent, an aralkyl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent, or an N, N-disubstituted amino group .)
AlR ⁹ R ¹² (9)
(In general formula (9), R ⁹ is as defined above, and R ¹² represents an aryleneoxy group which may have a substituent.)
In the presence of the organoaluminum compound represented by the formula, an ether such as dimethyl ether, dimethoxyethane, diethoxyethane, 12-crown-4; or triethylamine, N, N, N ′ if necessary in the reaction system. , N′-tetramethylethylenediamine, N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, pyridine, 2,2 This is carried out by polymerizing the alkyl (meth) acrylate in the presence of a nitrogen-containing compound such as' -dipyridyl.

Examples of the organic lithium compound used in the anionic polymerization include methyl lithium, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, isobutyl lithium, tert-butyl lithium, and n-pentyl lithium. Alkyllithium and alkyldilithium such as n-hexyllithium, tetramethylenedilithium, pentamethylenedilithium and hexamethylenedilithium; phenyllithium, m-tolyllithium, p-tolyllithium, xylyllithium, lithium naphthalene, etc. Aryllithium and aryldilithium; benzyllithium, diphenylmethyllithium, trityllithium, 1,1-diphenyl-3-methylpentyllithium, α-methylstyrene Aralkyllithium and aralkyldilithium such as dilithium produced by the reaction of rillithium, diisopropenylbenzene and butyllithium; lithium amides such as lithium dimethylamide, lithium diethylamide and lithium diisopropylamide; , Isopropoxylithium, n-butoxylithium, sec-butoxylithium, tert-butoxylithium, pentyloxylithium, hexyloxylithium, heptyloxylithium, octyloxylithium, phenoxylithium, 4-methylphenoxylithium, benzyloxylithium, 4 -Lithium alkoxides such as methylbenzyloxylithium can be used alone or in combination. .

Examples of the organoaluminum compound represented by the general formula (8) or (9) include trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, and tri-n-octylaluminum; dimethyl (2,6 -Di-tert-butyl-4-methylphenoxy) aluminum, dimethyl (2,6-di-tert-butylphenoxy) aluminum, diethyl (2,6-di-tert-butyl-4-methylphenoxy) aluminum, diethyl ( Dialkylphenols such as 2,6-di-tert-butylphenoxy) aluminum, diisobutyl (2,6-di-tert-butyl-4-methylphenoxy) aluminum, diisobutyl (2,6-di-tert-butylphenoxy) aluminum Noxyaluminum; methylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, methylbis (2,6-di-tert-butylphenoxy) aluminum, ethyl [2,2′-methylenebis (4-methyl) -6-tert-butylphenoxy)] aluminum, ethylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, ethylbis (2,6-di-tert-butylphenoxy) aluminum, ethyl [2,2 '-Methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum, isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, isobutylbis (2,6-di-tert-butyl) Phenoxy) aluminum, isobutyl [2,2'- Alkyldiphenoxyaluminum such as methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum; methoxybis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, methoxybis (2,6-di-tert) -Butylphenoxy) aluminum, methoxy [2,2'-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum, ethoxybis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, ethoxybis ( 2,6-di-tert-butylphenoxy) aluminum, ethoxy [2,2'-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum, isopropoxybis (2,6-di-tert-butyl- 4-methylphenoxy Alkoxydiphenoxyaluminum such as aluminum, isopropoxybis (2,6-di-tert-butylphenoxy) aluminum, isopropoxy [2,2'-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum; Triphenoxyaluminum such as (2,6-di-tert-butyl-4-methylphenoxy) aluminum and tris (2,6-diphenylphenoxy) aluminum can be used alone or in combination. Among them, isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, isobutylbis (2,6-di-tert-butylphenoxy) aluminum, isobutyl [2,2′-methylenebis (4-methyl) -6-tert-butylphenoxy)] aluminum and the like are particularly preferably used because they are easy to handle and can progress polymerization of (meth) acrylic acid esters without deactivation under relatively mild temperature conditions. It is done.

The anionic polymerization is preferably performed in a solvent. As the solvent, a solvent that does not adversely influence the reaction can be used without particular limitation. For example, aliphatic hydrocarbons such as pentane, n-hexane, and octane; cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane And alicyclic hydrocarbons such as: aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene; ethers such as diethyl ether, tetrahydrofuran, 1,4-dioxane, anisole, and diphenyl ether. Among them, aromatic hydrocarbons are preferable from the viewpoints of high solubility of the polymer or copolymer to be produced, difficulty in mixing in wastewater, easy recovery and purification of the solvent, and toluene and xylene. More preferred. These solvents may be used alone or in combination of two or more. The solvent is preferably purified in advance by degassing and dehydrating from the viewpoint of allowing the polymerization reaction to proceed smoothly.

Further, the polymerization reaction for producing the (meth) acrylate polymer (A) is preferably performed in an atmosphere of an inert gas such as nitrogen, argon or helium.

The polymerization temperature for producing the (meth) acrylate polymer (A) may be appropriately selected according to the type of (meth) acrylic acid ester used, the concentration in the polymerization reaction solution, and the like. In the case of producing by a method of anionic polymerization in the presence of an organoaluminum compound using a metal compound as a polymerization initiator, the polymerization time can be shortened, and since there are few deactivation reactions during the polymerization, it is usually −20 A temperature in the range of ~ 80 ° C is preferred. This is an extremely mild temperature condition compared with the conventional anionic polymerization conditions of (meth) acrylic acid ester. Therefore, when industrially carrying out the method of the present invention, the cooling equipment is compared with the conventional method. The cost can be greatly reduced.

As a polymerization method for producing the (meth) acrylate polymer (A), for example, a batch polymerization method, a continuous polymerization method, or the like can be used.

The (meth) acrylate polymer (A) can be obtained, for example, by stopping the polymerization reaction by adding a polymerization terminator to the polymerization reaction solution that continuously flows out from the final reactor to be produced. . Examples of the polymerization terminator include protic compounds such as water, methanol, acetic acid and hydrochloric acid. The amount of the polymerization terminator to be used is not particularly limited, but is usually in the range of 1 to 100 times mol with respect to the polymerization initiator to be used.

When aluminum derived from the used organoaluminum compound remains in the (meth) acrylate polymer (A) obtained separately from the polymerization reaction liquid after the polymerization is stopped, the (meth) acrylate polymer (A) In addition, since the physical properties of the material using the same may be deteriorated, it is preferable to remove aluminum derived from the organoaluminum compound after completion of the polymerization. Examples of the method for removing aluminum include a method in which a polymerization reaction liquid after adding a polymerization terminator is subjected to a washing treatment using an acidic aqueous solution, a method in which an adsorption treatment using an adsorbent such as an ion exchange resin is performed, and the like. It is valid.

The method for separating and obtaining the (meth) acrylate polymer (A) from the polymerization reaction solution after stopping the polymerization and performing the aluminum removal treatment operation is not particularly limited, and a known method can be appropriately employed. For example, a method in which a polymerization reaction solution is poured into a poor solvent of a (meth) acrylate polymer (A) to precipitate the (meth) acrylate polymer (A); a solvent is distilled off from the soot polymerization reaction solution under reduced pressure And a method for obtaining the (meth) acrylate polymer (A). First, after removing most of the solvent and low-boiling components from the polymerization reaction solution using a thin-film evaporator, etc., the obtained residue is continuously supplied to the melt extruder, and in the melt extruder, It is also possible to recover the (meth) acrylate polymer (A) as a strand, pellet or cage-like block by distilling off the solvent under reduced pressure. Alternatively, it may be taken out as a polymerization reaction solution, or it may be taken out as a solution dissolved in another solvent used in the polymerization by adding a solvent having a boiling point higher than the solvent used and removing the solvent.

The (meth) acrylate polymer (A) may be a homopolymer produced from a single monomer or a copolymer produced from a plurality of monomers. The homopolymer may be linear or star-shaped. The copolymer may be a random copolymer, a block copolymer, a graft copolymer, or a star copolymer.

<Other additives>
In order to further improve the performance, the lubricating oil composition of the present invention can contain other additives generally used in lubricating oils depending on the purpose. Examples of such additives include viscosity index improvers other than the above component (A), ashless dispersant, friction modifier, antiwear or extreme pressure agent, antioxidant, corrosion inhibitor, and metal deactivation. Agents, rust inhibitors, demulsifiers, and antifoaming agents.

As a viscosity index improver other than the component (A), a poly (meth) acrylate viscosity index improver other than the (meth) acrylate polymer (A), as long as it does not adversely affect the caulking resistance, Examples thereof include polyisobutene-based viscosity index improvers, ethylene-propylene copolymer-based viscosity index improvers, and styrene-butadiene hydrogenated copolymer-based viscosity index improvers. The lubricating oil composition may or may not contain a viscosity index improver other than the component (A). The content of the viscosity index improver other than the component (A) in the lubricating oil composition is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass based on the total amount of the lubricating oil composition. % Or less, particularly preferably 1% by mass or less, and may be 0% by mass. Furthermore, the content of the viscosity index improver other than the component (A) in the lubricating oil composition is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, with respect to 100 parts by mass of the component (A). More preferably, it is 20 mass parts or less, Most preferably, it is 10 mass parts or less, and may be 0 mass part.

Metal detergents include alkali metal sulfonates or alkaline earth metal sulfonates, alkali metal phenates or alkaline earth metal phenates, and normal salts, basic salts or overbased salts such as alkali metal salicylates or alkaline earth metal salicylates. Etc. In the present invention, one or more alkali metal or alkaline earth metal detergents selected from the group consisting of these, particularly alkaline earth metal detergents can be preferably used. In particular, a magnesium salt and / or a calcium salt is preferable, and a calcium salt is more preferably used. When the lubricating oil composition contains a metallic detergent, the content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, based on the total amount of the lubricating oil composition, as a metal amount. More preferably, it is 0.1% by mass or more, particularly preferably 0.15% by mass or more, preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and further preferably 0.5% by mass. Hereinafter, it is particularly preferably 0.3% by mass or less. If the content of the metal detergent is less than 0.01% by mass in terms of metal element, there is a risk that sufficient cleanliness cannot be exhibited, and if it exceeds 1.5% by mass, the sulfated ash content May increase the exhaust gas aftertreatment device.

As the ashless dispersant, an ashless dispersant used for lubricating oil can be used without any particular limitation. Examples of the ashless dispersant that can be used in the present invention include mono- or bissuccinimide having at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, and 40 to 40 carbon atoms. Benzylamine having at least one alkyl or alkenyl group of 400 in the molecule, polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a boron compound, carboxylic acid, or Examples of such modified products include phosphoric acid, and one or more selected from these can be blended. When the ashless dispersant is contained in the lubricating oil composition, the content thereof is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, based on the total amount of the lubricating oil composition. . When the content of the ashless dispersant is less than 0.01% by mass, the effect of improving the clean dispersibility may be insufficient. On the other hand, when the content exceeds 20% by mass, the low-temperature fluidity of the lubricating oil composition is low. There is a risk of significant deterioration.

As the friction modifier, known friction modifiers can be used without particular limitation, and organic molybdenum compounds and / or ashless friction modifiers can be preferably used.

Examples of the organic molybdenum compound include organic molybdenum compounds containing sulfur such as molybdenum dithiophosphate and molybdenum dithiocarbamate (MoDTC); molybdenum compounds (eg, molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, orthomolybdic acid, para-molybdenum) Acids, molybdic acids such as (poly) sulfurized molybdic acid, metal salts of these molybdates, molybdates such as ammonium salts, molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, molybdenum sulfide such as polysulfide molybdenum, molybdenum sulfide Acid, metal salts of sulfur molybdate or amine salts, molybdenum halides such as molybdenum chloride, etc.) and sulfur-containing organic compounds (eg, alkyl (thio) xanthate, thiadiazole, mercaptothiadiazo , Thiocarbonate, tetrahydrocarbyl thiuram disulfide, bis (di (thio) hydrocarbyl dithiophosphonate) disulfide, organic (poly) sulfide, sulfide ester, etc.) or other organic compounds, etc .; and above An organic molybdenum compound containing sulfur such as a complex of a sulfur-containing molybdenum compound such as molybdenum sulfide or sulfurized molybdenum acid and an alkenyl succinimide can be given.

Also, as the organic molybdenum compound, an organic molybdenum compound that does not contain 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, when an organomolybdenum compound is used as a friction modifier, the content thereof can be, for example, 0.1 to 1.0% by mass based on the total amount of the composition. The content of the organic molybdenum compound in terms of molybdenum element is preferably 10 mass ppm or more, more preferably 50 mass ppm or more, still more preferably 100 mass ppm or more, particularly preferably 200, based on the total amount of the lubricating oil composition. It is mass ppm or more. On the other hand, from the viewpoints of solubility in lubricating base oil, storage stability and oxidation stability, and economic efficiency, it is preferably 400 ppm by mass or less, more preferably 300 ppm by mass or less, and particularly preferably 250 ppm by mass or less. is there. In addition, when the content of the organic molybdenum compound in terms of molybdenum element exceeds 400 ppm by mass, the stability of the lubricating oil composition at high temperatures is particularly hindered, and the formation of deposits is promoted, which is not preferable. It is not preferable from the viewpoint of sex.

As the ashless friction modifier, a compound usually used as a friction modifier for lubricating oil can be used without any particular limitation. Examples of the ashless friction modifier that can be used in the lubricating oil composition of the present invention include, for example, one having at least one heteroelement selected from an oxygen atom, a nitrogen atom, and a sulfur atom in the molecule and having 6 to 50 carbon atoms. The compound of this is mentioned. More specifically, 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. Examples thereof include ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, urea compounds, hydrazide compounds, and the like.

The content of the ashless friction modifier in the lubricating oil composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.3% by mass, based on the total amount of the lubricating oil composition. % Or more, preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.8% by mass or less. If 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 if it exceeds 2% by mass, the solubility of the additive deteriorates. In addition, the effects of anti-wear additives may be hindered.

Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants such as copper and molybdenum. Specifically, for example, phenol-based ashless antioxidants include 4,4′-methylenebis (2,6-di-tert-butylphenol) and 4,4′-bis (2,6-di-tert-butylphenol). Examples of amine-based ashless antioxidants include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine. When the antioxidant is contained in the lubricating oil composition, the content is usually 5.0% by mass or less, preferably 3.0% by mass or less, and preferably based on the total amount of the lubricating oil composition. It is 0.1 mass% or more, More preferably, it is 0.5 mass% or more.

As the antiwear agent or extreme pressure agent, the antiwear agent / extreme pressure agent used in the lubricating oil can be used without particular limitation. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, phosphites, thiophosphites, dithiophosphites, trithiophosphites Esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, zinc dithiophosphate, dithiocarbamate, zinc dithiocarbamate, disulfide , Polysulfides, sulfurized olefins, sulfurized fats and oils, and the like. When the lubricating oil composition contains an antiwear agent or extreme pressure agent, the content is based on the total amount of the lubricating oil composition, and the content is based on the total amount of the lubricating oil composition, for example 0.05-2. It can be 0% by mass, and from the viewpoint of improving wear resistance or load resistance, it is preferably 0.01 to 10% by mass.

Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds. When a corrosion inhibitor is contained in the lubricating oil composition, the content thereof is preferably 0.005 to 5% by mass based on the total amount of the lubricating oil composition.

Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinate, and polyhydric alcohol ester. When the lubricating oil composition contains a rust inhibitor, its content is preferably 0.005 to 5% by mass based on the total amount of the lubricating oil composition.

Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether. When the anti-emulsifier is contained in the lubricating oil composition, the content thereof is preferably 0.005 to 5% by mass based on the total amount of the lubricating oil composition.

Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile. When these metal deactivators are contained in the lubricating oil composition, the content thereof is preferably 0.005 to 1% by mass based on the total amount of the lubricating oil composition.

Examples of antifoaming agents include silicone oils having a kinematic viscosity at 25 ° C. of 1000 to 100,000 mm ² / s, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long chain fatty acids, methyl salicylates, and O-hydroxybenzyl alcohol and the like, and silicone oil can be particularly preferably used. When these antifoaming agents are contained in the lubricating oil composition, the content thereof is preferably 0.0001 to 0.1% by mass based on the total amount of the lubricating oil composition.

<Lubricating oil composition>
Kinematic viscosity at 100 ° C. of the lubricating oil composition is preferably 3.0 mm ² / s or more, more preferably 3.5 mm ² / s or more, more preferably 4.0 mm ² / s or more, and preferably 16 .3mm ² / s or less, more preferably 12.5 mm ² / s, more preferably not more than 9.3 mm ² / s. When the kinematic viscosity at 100 ° C. is not less than the above lower limit value, it becomes easy to ensure lubricity, while when the kinematic viscosity at 100 ° C. is not more than the above upper limit value, fuel economy is further improved.

The viscosity index of the lubricating oil composition is preferably 150 or more, more preferably 160 or more, still more preferably 170 or more, and preferably 300 or less, more preferably 280 or less, and even more preferably 260 or less. When the viscosity index is equal to or higher than the lower limit, fuel economy can be further improved while maintaining the HTHS viscosity, and the low temperature viscosity is easily lowered. On the other hand, when the viscosity index is less than or equal to the above upper limit, low temperature fluidity, solubility of additives, and compatibility with sealing materials can be ensured.

The HTHS viscosity at 150 ° C. of the lubricating oil composition is preferably 1.7 mPa · s or more, more preferably 2.0 mPa · s or more, still more preferably 2.3 mPa · s or more, and most preferably 2.6 mPa · s or more. In addition, it is preferably 4.0 mPa · s or less, more preferably 3.0 mPa · s or less. When the HTHS viscosity at 150 ° C. is equal to or higher than the lower limit, evaporation of the lubricating oil composition can be suppressed, and lubricity can be ensured. Further, when the HTHS viscosity at 150 ° C. is not more than the above upper limit value, fuel economy can be improved.

The HTHS viscosity at 100 ° C. of the lubricating oil composition is preferably 5.2 mPa · s or less, more preferably 5.1 mPa · s or less, still more preferably 5.0 mPa · s or less, and preferably 3.0 mPa · s or less. s or more, more preferably 3.5 mPa · s or more, and still more preferably 4.0 mPa · s or more. When the HTHS viscosity at 100 ° C. is not more than the above upper limit value, higher fuel economy can be obtained. Moreover, lubricity can be ensured when the HTHS viscosity at 100 ° C. is equal to or higher than the lower limit.
In the present specification, the HTHS viscosity at 150 ° C. or 100 ° C. means the high temperature and high shear viscosity at 150 ° C. or 100 ° C. as defined in ASTM D-4683.

The MRV viscosity of the lubricating oil composition at −40 ° C. is preferably 60,000 mPa · s or less, more preferably 40,000 mPa · s or less, and still more preferably 30,000 mPa · s or less. When the MRV viscosity at −40 ° C. is not more than the above upper limit value, the pumping characteristics at low temperature are excellent. In the present specification, the MRV viscosity at −40 ° C. means the MRV viscosity at −40 ° C. defined by ASTM D-4684.

The evaporation loss amount of the lubricating oil composition is preferably 20% by mass or less, more preferably 16% by mass or less, and particularly preferably 15% by mass or less as the NOACK evaporation amount at 250 ° C. When the NOACK evaporation amount of the lubricating base oil component exceeds 20% by mass, the evaporation loss of the lubricating oil is large, which causes an increase in viscosity and the like, which is not preferable. In the present specification, the NOACK evaporation amount is a value obtained by measuring the evaporation amount of the lubricating oil measured according to ASTM D 5800. The lower limit of the NOACK evaporation amount at 250 ° C. of the lubricating oil composition is not particularly limited, but is usually 5% by mass or more.

As described above, the present invention includes at least the following aspects [1] to [44].
[1] A lubricating base oil and (A) a structural unit represented by the following general formula (1), wherein the value of parameter a represented by the following formula (2) is 0.12 or less (meta And) an acrylate polymer.

(In the formula (1), R ¹ represents hydrogen or a methyl group, and R ² represents an alkyl group having 10 to 36 carbon atoms.)
a = Log (M _h (t _1/2 )) − Log (M (t)) (2)
(In Formula (2), M (t) represents the peak top molecular weight in the differential molecular weight distribution curve of the polystyrene conversion molecular weight obtained by the gel permeation chromatography measurement of the said (meth) acrylate type polymer; M _h (t _{1 / 2} ) represents the molecular weight in terms of polystyrene on the high molecular weight side giving half the strength of the molecular weight M (t) in the differential molecular weight distribution curve.)

[2] The lubricating oil composition according to [1], wherein the value of parameter b represented by the following formula (3) is 0.3 or less.
b = Log (M _h (t _1/2 )) − Log (M _l (t _1/2 )) (3)
(In Formula (3), M _l (t _1/2 ) represents a molecular weight in terms of polystyrene on the low molecular weight side that gives half the strength of the molecular weight M (t) in the differential molecular weight distribution curve.)
[3] The content of the structural unit represented by the general formula (1) in the (meth) acrylate polymer is 40 to 80% by mass based on the total amount of the (meth) acrylate polymer. The lubricating oil composition according to [1] or [2].
[4] The lubricating oil composition according to any one of [1] to [3], wherein the (meth) acrylate polymer has a weight average molecular weight Mw of 50,000 to 500,000.
[5] The lubricating oil according to any one of [1] to [4], wherein the ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the (meth) acrylate polymer is 1.6 or less. Composition.
[6] The (meth) acrylate polymer includes any one of [1] to [5] including a structural unit represented by the following general formula (4) and a structural unit represented by the following general formula (5): A lubricating oil composition according to claim 1.

[7] The lubricating oil composition according to [6], wherein m is 5 to 16 and n is 4 to 15 in the formula (6).
[8] The lubricating oil composition according to [6], wherein m is 6 to 15 and n is 6 to 10 in the formula (6).
[9] The lubricating oil composition according to [6], wherein m is 7 to 10 and n is 6 to 9 in the formula (6).

[10] The content of the structural unit represented by the general formula (4) in the (meth) acrylate polymer is 20 based on the total amount of the structural units contained in the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [9], which is 80% by mass.
[11] The content of the structural unit represented by the general formula (4) in the (meth) acrylate polymer is 25 masses based on the total amount of the structural units contained in the (meth) acrylate polymer. % Of the lubricating oil composition according to [10].
[12] The content of the structural unit represented by the general formula (4) in the (meth) acrylate polymer is 70 masses based on the total amount of the structural units contained in the (meth) acrylate polymer. % Of the lubricating oil composition according to [10] or [11].
[13] The content of the structural unit represented by the general formula (4) in the (meth) acrylate polymer is 50 masses based on the total amount of the structural units contained in the (meth) acrylate polymer. % Of the lubricating oil composition according to any one of [10] to [12].

[14] The content of the structural unit represented by the general formula (5) in the (meth) acrylate polymer is 20 to 20 based on the total amount of the structural units contained in the (meth) acrylate polymer. The lubricating oil composition according to any one of [10] to [13], which is 80% by mass.
[15] The content of the structural unit represented by the general formula (5) in the (meth) acrylate polymer is 30 masses based on the total amount of the structural units contained in the (meth) acrylate polymer. % Of the lubricating oil composition according to [14].
[16] The content of the structural unit represented by the general formula (5) in the (meth) acrylate polymer is 50 masses based on the total amount of the structural units contained in the (meth) acrylate polymer. % Of the lubricating oil composition according to [14].

[17] The total content of the structural unit represented by the general formula (4) and the structural unit represented by the general formula (5) in the (meth) acrylate-based polymer is ) The lubricating oil composition according to any one of [6] to [16], which is 70% by mass or more based on the total amount of structural units contained in the acrylate polymer.
[18] The total content of the structural unit represented by the general formula (4) and the structural unit represented by the general formula (5) in the (meth) acrylate polymer is the above (meta ) The lubricating oil composition according to any one of [6] to [16], which is 80% by mass or more based on the total amount of structural units contained in the acrylate polymer.
[19] The total content of the structural unit represented by the general formula (4) and the structural unit represented by the general formula (5) in the (meth) acrylate polymer is ) The lubricating oil composition according to any one of [6] to [16], which is 90% by mass or more based on the total amount of structural units contained in the acrylate polymer.
[20] The total content of the structural unit represented by the general formula (4) and the structural unit represented by the general formula (5) in the (meth) acrylate-based polymer is ) The lubricating oil composition according to any one of [6] to [16], which is 100% by mass based on the total amount of structural units contained in the acrylate polymer.

[21] A structure in which the content of the structural unit represented by the general formula (5) in which R ⁶ is a methyl group in the (meth) acrylate polymer is included in the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [20], which is 20% by mass or more based on the total amount of units.
[22] A structure in which the content of the structural unit represented by the general formula (5) in which R ⁶ is a methyl group in the (meth) acrylate polymer is included in the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [20], which is 30% by mass or more based on the total amount of units.
[23] A structure in which the content of the structural unit represented by the general formula (5) in which R ⁶ is a methyl group in the (meth) acrylate polymer is included in the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [20], which is 35% by mass or more based on the total amount of units.
[24] A structure in which the content of the structural unit represented by the general formula (5) in which R ⁶ is a methyl group in the (meth) acrylate polymer is included in the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [20], which is 40% by mass or more based on the total amount of units.

[25] A structure in which the content of the structural unit represented by the general formula (5) in which R ⁶ is a methyl group in the (meth) acrylate polymer is included in the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [24], which is 50% by mass or less based on the total amount of units.
[26] A structure in which the content of the structural unit represented by the general formula (5) in which R ⁶ is a methyl group in the (meth) acrylate polymer is included in the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [24], which is 45% by mass or less based on the total amount of units.

[27] In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is the above (meth) acrylate-based polymer. The lubricating oil composition according to any one of [6] to [26], which is 5% by mass or more based on the total amount of structural units contained in the coalescence.
[28] In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is the above (meth) acrylate polymer weight. The lubricating oil composition according to any one of [6] to [26], which is 10% by mass or more based on the total amount of structural units contained in the coalescence.
[29] In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is the above (meth) acrylate-based polymer. The lubricating oil composition according to any one of [6] to [26], which is 20% by mass or more based on the total amount of structural units contained in the coalescence.
[30] In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is greater than the weight of the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [26], which is 25% by mass or more based on the total amount of structural units contained in the coalescence.

[31] In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is greater than the weight of the (meth) acrylate polymer. The lubricating oil composition according to any one of [6] to [30], which is 50% by mass or less based on the total amount of structural units contained in the coalescence.
[32] In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is the above (meth) acrylate-based polymer. The lubricating oil composition according to any one of [6] to [30], which is 45% by mass or less based on the total amount of structural units contained in the coalescence.
[33] In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is the above (meth) acrylate-based polymer. The lubricating oil composition according to any one of [6] to [30], which is 40% by mass or less based on the total amount of structural units contained in the coalescence.
[34] In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 18 or more carbon atoms is the above (meth) acrylate-based polymer. The lubricating oil composition according to any one of [6] to [30], which is 35% by mass or less based on the total amount of structural units contained in the coalescence.

[35] In the (meth) acrylate polymer, the structural unit represented by the general formula (4), the structural unit represented by the general formula (5) in which R ⁶ is a methyl group, and R The total content of the structural unit represented by the general formula (5) in which ⁶ is an alkyl group having 18 or more carbon atoms is 100 based on the total amount of the structural units contained in the (meth) acrylate polymer. When the content is less than mass%, the (meth) acrylate polymer further includes a structural unit represented by the general formula (5) in which R ⁶ is an alkyl group having 2 to 18 carbon atoms. [6] The lubricating oil composition according to any one of [34].

[36] The lubricating oil composition according to any one of [6] to [35], wherein the content of the (meth) acrylate polymer is 0.1 to 30% by mass based on the total amount of the lubricating oil composition. .
[37] The lubricating oil composition according to [36], wherein the content of the (meth) acrylate polymer is 0.5% by mass or more based on the total amount of the lubricating oil composition.
[38] The lubricating oil composition according to [36], wherein the content of the (meth) acrylate polymer is 1% by mass or more based on the total amount of the lubricating oil composition.
[39] The lubricating oil composition according to [36], wherein the content of the (meth) acrylate polymer is 2% by mass or more based on the total amount of the lubricating oil composition.
[40] The lubricating oil composition according to any one of [36] to [39], wherein the content of the (meth) acrylate polymer is 20% by mass or less based on the total amount of the lubricating oil composition.
[41] The lubricating oil composition according to any one of [36] to [39], wherein the content of the (meth) acrylate polymer is 15% by mass or less based on the total amount of the lubricating oil composition.

[42] The (meth) acrylate polymer is a polymer obtained by polymerizing a raw material containing one or more (meth) acrylate polymerizable monomers by living anion polymerization; [1] to [41], wherein the content of the compound having a hydroxyl group is 0.2 parts by mass or less with respect to 100 parts by mass of the one or more (meth) acrylate polymerizable monomers in the raw material. The lubricating oil composition according to any one of the above.
[43] Metal-based detergent, ashless dispersant, friction modifier, antiwear agent, antioxidant, corrosion inhibitor, metal deactivator, viscosity index improver other than component (A), pour point depressant The lubricating oil composition according to any one of [1] to [42], further comprising one or more additives selected from the group consisting of a rust inhibitor, a demulsifier, and an antifoaming agent.
[44] The lubricating oil composition according to any one of [1] to [43], which is used for lubricating an internal combustion engine.

Hereinafter, the present invention will be described in more detail based on examples and comparative examples. However, the present invention is not limited to these examples.

(Content of (meth) acrylate polymerizable monomer, content of compound having phenolic hydroxyl group, content of compound having alcoholic hydroxyl group)
Injection gas temperature was measured using a gas chromatograph GC-2014 manufactured by Shimadzu Corporation and connected to InertCap 1 (df = 0.4 μm, 0.25 mm ID × 60 m) manufactured by GL Sciences Inc. as a column. Measurement was performed under the conditions of 240 ° C., detector temperature 300 ° C., column temperature increased from 180 ° C. to 280 ° C. at a heating rate of 10 ° C./min, and held for 10 minutes. The purity of the (meth) acrylate polymerizable monomer was calculated from the simple area of the peak in the chart obtained by gas chromatography measurement. The content of the compound having a phenolic hydroxyl group and the compound having an alcoholic hydroxyl group was calculated as a mass ratio with respect to 100 parts by mass of the monomer by an absolute calibration curve method.

(Moisture content in raw material)
Using a Coulometric titration Karl Fischer moisture meter CA-200 manufactured by Mitsubishi Chemical Analytic Co., Ltd., the moisture content in the monomer was measured and calculated as a ratio to 100 parts by mass of the monomer.

(Weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw / Mn))
Gel permeation chromatography (GPC) measurement was performed under the following conditions, and the values of Mw, Mn, and Mw / Mn converted to the molecular weight of standard polystyrene were calculated from the obtained chromatogram. The baseline is that the slope of the peak on the high molecular weight side of the GPC chart changes from zero to plus when viewed from the earlier retention time, and the slope of the peak on the low molecular weight side is minus when viewed from the earlier retention time. A line connecting the points that change from zero to zero.
GPC device: manufactured by Tosoh Corporation, HLC-8320
Detector: Differential refractive index detector Column: Two TSKgel SuperMultipore HZMMs manufactured by Tosoh Corporation and Super HZ4000 connected in series from the upstream side in the above order were used.
Eluent: Tetrahydrofuran eluent Flow rate: 0.35 ml / min Column temperature: 40 ° C
Calibration curve: Created using 10 standard polystyrene data

(Monomer composition in polymer)
Using a nuclear magnetic resonance apparatus (Bruker ULTRA SHIELD 400 PLUS), ¹ H-NMR spectrum was measured for 10 mg of resin under the conditions of 1 mL of deuterated chloroform, room temperature, and 64 integrations. Of these, the area values of signals derived from methylene, methine, and methyl groups adjacent to the oxygen atom of the ester group appearing at 3.3 to 4.2 ppm when the chemical shift of the peak of TMS (tetramethylsilane) is 0 ppm (integrated) Value), the composition of the structural unit derived from the monomer in the (meth) acrylate polymer (A) was calculated.

(Raw material production example 1)
A methacrylic acid 2-synthesized by esterification of 2-octyldodecanol and methacrylic acid in a 500 mL three-necked flask equipped with a thermometer, a distillation column (inner diameter 2 cm, length 25 cm) packed with glass Raschig rings, and a glass capillary Mixture containing octyldodecyl ((meth) acrylate monomer) (2-octyldodecyl methacrylate 98.67% by mass; as content with respect to 100 parts by mass of 2-octyldodecyl methacrylate, 0.0101 parts by mass of methoxyphenol, 0.25 g of 2-octyldodecanol in an amount of 0.2533 parts by mass and 0.0203 parts by mass of water) and 0.46 g of Adekastab AO-60 (a compound having a phenolic hydroxyl group: manufactured by Adeka Co., Ltd.) as a polymerization inhibitor Bubbling air from a glass capillary While, pressure 0.1 kPa, an inner temperature of 214 ~ 234 ° C., over a period of 18 hours at a column top temperature of 185 ~ 191 ° C., distillation was carried out while dividing the fraction of about 70 g. Of these, 82.1 g (recovery rate 18.0%) of raw material (1) was obtained using a fraction having a low content of 2-octyldodecanol and methoxyphenol as the raw material of the (meth) acrylate polymer (A). . As a result of measurement by gas chromatography and Karl Fischer moisture meter, the content of 2-octyldodecyl methacrylate in the raw material (1) of the (meth) acrylate polymer (A) was 99.54% by mass, The content of water is 0.0007 parts by mass, the content of 2-octyldodecanol is 0.017 parts by mass with respect to 100 parts by mass of the (meth) acrylate monomer, and methoxyphenol and Adeka Stab AO-60 Was not detected.

(Raw material production example 2)
A mixture containing n-stearyl methacrylate ((meth) acrylate monomer) synthesized by esterification of n-stearyl alcohol and methacrylic acid in a 1 L three-necked flask equipped with a thermometer and a mechanical stirrer (n-methacrylic acid n- Stearyl 99.26% by mass; including 250 parts by mass of methoxyphenol 0.0252 parts by mass, n-stearyl alcohol 0.3425 parts by mass and water 0.0181 parts by mass as a content with respect to 100 parts by mass of n-stearyl methacrylate By adding 583 g of isopropanol and stirring at 25 ° C., n-stearyl methacrylate was dissolved. The solution was then cooled to −20 ° C. over 4 hours. The precipitated crystals were filtered and dried to obtain 243.3 g (recovery rate 97.3%) of the raw material (2) of the crystalline (meth) acrylate polymer (A). As a result of measurement by gas chromatography and a Karl Fischer moisture meter, the content of n-stearyl methacrylate in the raw material (2) of the (meth) acrylate polymer (A) was 99.67% by mass ( The water content was 0.001 parts by mass and the n-stearyl alcohol content was 0.006 parts by mass with respect to 100 parts by mass of the (meth) acrylate monomer, and no methoxyphenol was detected.

(Raw material production example 3)
A mixture containing 2-octyldodecyl methacrylate ((meth) acrylate monomer) synthesized by esterification of 2-octyldodecanol and methacrylic acid in a 500 mL three-necked flask containing a magnetic stir bar (2-methacrylic acid 2-methacrylate) Octyldecyl 98.67% by mass; as a content with respect to 100 parts by mass of 2-octyldodecyl methacrylate, 0.0101 parts by mass of methoxyphenol, 0.2533 parts by mass of 2-octyldodecanol, and 0.0203 parts by mass of water ), 210 g of toluene, and 30 g of activated alumina GP-20 manufactured by Mizusawa Chemical as an adsorbent were added and stirred at 25 ° C. for 4 hours. Thereafter, activated alumina is removed by filtration, and toluene is distilled off at a liquid temperature of 35 ° C. or lower using an evaporator, thereby obtaining 86.1 g of a liquid (meth) acrylate polymer (A) raw material (3). It was. As a result of measurement by gas chromatography and a Karl Fischer moisture meter, the content of 2-octyldodecyl methacrylate in the raw material (3) of the (meth) acrylate polymer (A) was 98.88% by mass, The content of water was 0.0006 parts by mass and the content of 2-octyldodecanol was 0.14 parts by mass with respect to 100 parts by mass of the (meth) acrylate monomer, and no methoxyphenol was detected. .

(Raw material production example 4)
A mixture (n-stearyl methacrylate 99) containing n-stearyl methacrylate ((meth) acrylate monomer) synthesized by esterification of n-stearyl alcohol and methacrylic acid in a 500 mL three-necked flask containing a magnetic stir bar .26 mass%; as a content with respect to 100 mass parts of n-stearyl methacrylate, 90 g of toluene (including 0.0252 mass parts of methoxyphenol, 0.3425 mass parts of n-stearyl alcohol, and 0.0181 mass parts of water) 210 g and 30 g of activated alumina GP-20 made by Mizusawa Chemical as an adsorbent were added and stirred at 25 ° C. for 4 hours. Thereafter, activated alumina is removed by filtration, and toluene is distilled off at a liquid temperature of 35 ° C. or lower using an evaporator, thereby obtaining 87.2 g of a liquid (meth) acrylate polymer (A) raw material (4). It was. As a result of measurement by gas chromatography and a Karl Fischer moisture meter, the content of n-stearyl methacrylate in the raw material (4) of the (meth) acrylate polymer (A) is 99.20% by mass ( The content of water was 0.0007 parts by mass and the content of 2-stearyl alcohol was 0.11 parts by mass with respect to 100 parts by mass of the (meth) acrylate monomer, and methoxyphenol was not detected.

(Raw material production example 5)
In the raw material (3) containing 2-octyldodecyl methacrylate obtained by the raw material production example 3, p-methoxyphenol is contained in an amount of 0.0005 parts by mass with respect to 100 parts by mass of the (meth) acrylate monomer. The raw material (5) of the (meth) acrylate polymer (A) was prepared by adding the mixture so that

(Raw material production example 6)
In the raw material (4) containing n-stearyl methacrylate obtained by the raw material production example 4, p-methoxyphenol is contained in an amount of 0.0005 parts by mass with respect to 100 parts by mass of the (meth) acrylate monomer. By adding so that the raw material (6) of the (meth) acrylate polymer (A) was produced.

(Raw material production example 7)
2-Octyldodecanol was added to the raw material (3) containing 2-octyldodecyl methacrylate obtained in Raw Material Production Example 3, and its content was 0.32 mass per 100 mass parts of the (meth) acrylate monomer. By adding so that it might become a part, the raw material (7) of the (meth) acrylate type polymer (A) was produced.

(Raw material production example 8)
N-stearyl alcohol was added to the raw material (4) containing n-stearyl methacrylate obtained in Raw Material Production Example 4, and the content thereof was 0.36 parts by mass with respect to 100 parts by mass of the (meth) acrylate monomer. By adding so that the raw material (8) of the (meth) acrylate polymer (A) was produced.

<Production Example 1>
A (meth) acrylate polymer was produced by the following procedure. A three-way cock was attached to a well-dried 2 L three-necked flask and the inside was replaced with nitrogen. At room temperature, 480 g of toluene, 24 g of 1,2-dimethoxyethane, isobutyl bis (2,6-di-t-butyl- 10 g of a 0.45 M toluene solution of 4-methylphenoxy) aluminum was added, and 0.62 g of a mixed solution of cyclohexane and n-hexane containing 1.0 mmol of sec-butyllithium was further added. Subsequently, 30% by mass of the raw material (1) obtained in Raw Material Production Example 1 containing 2-octyldodecyl methacrylate, which is a (meth) acrylate polymerizable monomer, and methacryl which is a (meth) acrylate polymerizable monomer 30% by mass of raw material (2) obtained in Raw Material Production Example 2 containing acid stearyl, and methyl methacrylate raw material (manufactured by Kuraray Co., Ltd .: content of methyl methacrylate of 99.9% by mass or more; In contrast, the water content is 0.0003 parts by mass, the methanol content is 0.0002 parts by mass or less, and the content of the polymerization inhibitor 2,4-dimethyl-6-tert-butylphenol is 0.0001 parts by mass). The mixture containing the mass% of the raw material (the content of the alcohol: 0.0070 parts by mass with respect to 100 parts by mass of the (meth) acrylate monomer), the content of water: 0.0. 006 parts by weight, the content of the compound having a phenolic hydroxyl group: In addition 85g as the detection limit or less), and stirred at room temperature for 12 hours. The reaction solution was initially colored yellow, but became colorless after stirring for 12 hours. Thereafter, 1.0 g of methanol was added to stop the polymerization reaction. The obtained reaction solution was poured into 6.0 kg of methanol to precipitate a white precipitate. Thereafter, the white precipitate was collected by filtration and dried to obtain 80 g of a methacrylate polymer.

As a result of ¹ H-NMR measurement and GPC measurement of the obtained methacrylate polymer, the polymer was a random copolymer, the weight average molecular weight (Mw) of the polymer was 81800, and the number average molecular weight (Mn). Was 75600, and the molecular weight distribution (Mw / Mn) was 1.08.
Further, the mass ratio of the structure derived from each monomer in the obtained methacrylate polymer was 40% by mass of the structure derived from methyl methacrylate, 30% by mass of the structure derived from stearyl methacrylate, and methacrylic acid. It was found that the structure derived from the acid 2-octyldodecyl was 30% by mass. The results are shown in Table 1.

<Production Example 2>
Other than changing 0.62 g of a mixed solution of cyclohexane and n-hexane containing 1.0 mmol of sec-butyllithium to 0.39 g of a mixed solution of cyclohexane and n-hexane containing 0.64 mmol of sec-butyllithium. Was similar to Production Example 1 to obtain 80 g of a methacrylate polymer. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Production Example 3>
Other than changing 0.62 g of a mixed solution of cyclohexane and n-hexane containing 1.0 mmol of sec-butyllithium to 0.33 g of a mixed solution of cyclohexane and n-hexane containing 0.55 mmol of sec-butyllithium. Was similar to Production Example 1 to obtain 80 g of a methacrylate polymer. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Production Example 4>
Other than changing 0.62 g of a mixed solution of cyclohexane and n-hexane containing 1.0 mmol of sec-butyllithium to 0.27 g of a mixed solution of cyclohexane and n-hexane containing 0.44 mmol of sec-butyllithium. Was similar to Production Example 1 to obtain 80 g of a methacrylate polymer. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Production Example 5>
Other than changing 0.62 g of a mixed solution of cyclohexane and n-hexane containing 1.0 mmol of sec-butyllithium to 0.25 g of a mixed solution of cyclohexane and n-hexane containing 0.41 mmol of sec-butyllithium. Was similar to Production Example 1 to obtain 80 g of a methacrylate polymer. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Production Example 6>
In place of the raw material used in Production Example 3, the raw material (3) obtained in Raw Material Production Example 3 containing 2-octyldodecyl methacrylate, which is a (meth) acrylate polymerizable monomer, 30% by mass, (meth) acrylate 30% by mass of raw material (4) obtained in raw material production example 4 containing stearyl methacrylate, which is a system polymerizable monomer, and methyl methacrylate raw material (manufactured by Kuraray Co., Ltd .: content of methyl methacrylate 99.9% by mass) Or more; with respect to 100 parts by weight of methyl methacrylate, the water content is 0.0003 parts by weight, the methanol content is 0.0002 parts by weight or less, and the polymerization inhibitor 2,4-dimethyl-6-tert-butylphenol Content of alcohol: 0.075 with respect to 100 parts by mass of raw material ((meth) acrylate monomer) Parts by weight water content: 0.0005 part by weight, the content of the compound having a phenolic hydroxyl group: except adding 85g as the detection limit or less) in the same manner as in Preparation Example 3, to obtain a methacrylate polymer 80 g. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Production Example 7>
In place of the raw material used in the raw material production example 3, the raw material (5) obtained in the raw material production example 5 containing 2-octyldodecyl methacrylate, which is a (meth) acrylate-based polymerizable monomer, 30% by mass, (meth) 30% by mass of raw material (6) obtained in Raw Material Production Example 6 containing stearyl methacrylate, which is an acrylate polymerizable monomer, and methyl methacrylate raw material (manufactured by Kuraray Co., Ltd .: content of methyl methacrylate 99.9% by mass) % Of water: 0.0003 parts by mass of water, 0.0002 parts by mass or less of methanol with respect to 100 parts by mass of methyl methacrylate, 2,4-dimethyl-6-tert-butylphenol which is a polymerization inhibitor Content of 0.0001 parts by mass) A mixture containing 40% by mass of the raw material (100 parts by mass of the (meth) acrylate monomer), alcohol content: 0.0 51 parts by mass, water content: 0.0005 parts by mass, content of compound having a phenolic hydroxyl group: 0.0003 parts by mass), and a methacrylate polymer in the same manner as in Production Example 3 except that 85 g was added. 80 g was obtained. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Comparative Production Example 1>
Instead of the raw material used in Production Example 5, a mixture containing 2-octyldodecyl methacrylate synthesized by esterification of 2-octyldodecanol and methacrylic acid (content of 2-octyldodecyl methacrylate 98.67% by mass; As a content with respect to 100 parts by mass of 2-octyldodecyl methacrylate, 35% by mass of n-stearyl (including 0.0101 parts by mass of methoxyphenol, 0.2533 parts by mass of 2-octyldodecanol and 0.0203 parts by mass of water) Mixture containing n-stearyl methacrylate synthesized by esterification of alcohol and methacrylic acid (content of n-stearyl methacrylate 99.26% by mass; content relative to 100 parts by mass of n-stearyl methacrylate; 0252 parts by mass, n-stearyl al 0.3425 parts by mass of water and 0.0181 parts by mass of water) 35% by mass, and methyl methacrylate raw material (manufactured by Kuraray Co., Ltd .: content of methyl methacrylate 99.9% by mass or more; methyl methacrylate 100 The content of water is 0.0003 parts by mass, the content of methanol is 0.0002 parts by mass or less, and the content of 2,4-dimethyl-6-tert-butylphenol as a polymerization inhibitor is 0.0001 parts by mass. Part) A mixture containing 30% by mass of raw material (100 parts by mass of (meth) acrylate monomer), alcohol content: 0.2066 parts by mass, water content: 0.0134 parts by mass, phenolic 80 g of a methacrylate polymer was obtained in the same manner as in Production Example 5 except that 85 g was added as a compound having a hydroxyl group (content: 0.0123 parts by mass). The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Comparative Production Example 2>
Instead of the raw material used in Production Example 3, the raw material obtained in Raw Material Production Example 7 containing 2-octyldodecyl methacrylate, which is a (meth) acrylate-based polymerizable monomer, (7) 30% by mass, (meth) acrylate 30% by mass of raw material (8) obtained in Raw Material Production Example 8 containing stearyl methacrylate, which is a polymerizable monomer, and methyl methacrylate raw material (manufactured by Kuraray Co., Ltd .: content of methyl methacrylate 99.9% by mass) Or more; with respect to 100 parts by weight of methyl methacrylate, the water content is 0.0003 parts by weight, the methanol content is 0.0002 parts by weight or less, and the polymerization inhibitor 2,4-dimethyl-6-tert-butylphenol Content of alcohol: 0.204 with respect to 100 parts by mass of raw material ((meth) acrylate monomer) 80 parts by weight of a methacrylate polymer was obtained in the same manner as in Production Example 3 except that 85 g was added as a part by weight, a content of water: 0.0005 parts by weight, and a content of a compound having a phenolic hydroxyl group: below the detection limit. It was. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Comparative Production Example 3>
A methacrylate polymer was produced by the following procedure. A 2 W three-neck flask that was sufficiently dried was equipped with a stirring blade, a Dimroth cooler, and a three-way cock. After the inside was replaced with nitrogen, the (meth) acrylate polymerizable monomer obtained in Raw Material Production Example 3 at room temperature. 30% by mass of raw material (3) containing 2-octadodecyl methacrylate as a raw material (4) containing 30% by mass of stearyl methacrylate (meth) acrylate polymerizable monomer obtained in Raw Material Production Example 4; And methyl methacrylate raw material (manufactured by Kuraray Co., Ltd .: content of methyl methacrylate is 99.9% by mass or more; with respect to 100 parts by mass of methyl methacrylate, water content is 0.0003 parts by mass, methanol content is 0.00. A mixture containing 40% by mass of 0002 parts by mass or less and a content of 0.0001 parts by mass of 2,4-dimethyl-6-tert-butylphenol as a polymerization inhibitor) (Based on 100 parts by weight of the (meth) acrylate monomer): alcohol content: 0.07508 parts by weight, water content: 0.0051 parts by weight, content of compounds having phenolic hydroxyl groups: detection 500 g as the lower limit), 500 g of highly refined mineral oil, and 0.53 g of cumyldithiobenzoic acid (CDTBA) were added to obtain a homogeneous solution under stirring. The 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, after introducing 0.0083 g of azobisisobutyronitrile (AIBN) as a radical initiator from the sample introduction port under a nitrogen flow, polymerization was carried out at a solution temperature of 90 ° C. for 12 hours under a nitrogen atmosphere, A solution containing the polymer was obtained. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Comparative Production Example 4>
A methacrylate polymer was produced by the following procedure. A 2 W three-neck flask that was sufficiently dried was equipped with a stirring blade, a Dimroth cooler, and a three-way cock. After the inside was replaced with nitrogen, the (meth) acrylate polymerizable monomer obtained in Raw Material Production Example 3 was obtained at room temperature. 30% by mass of raw material (3) containing 2-octadodecyl methacrylate as a raw material (4) containing 30% by mass of stearyl methacrylate (meth) acrylate polymerizable monomer obtained in Raw Material Production Example 4; And methyl methacrylate raw material (manufactured by Kuraray Co., Ltd .: content of methyl methacrylate is 99.9% by mass or more; with respect to 100 parts by mass of methyl methacrylate, water content is 0.0003 parts by mass, methanol content is 0.00. A mixture containing 40% by mass of 0002 parts by mass or less and a content of 0.0001 parts by mass of 2,4-dimethyl-6-tert-butylphenol as a polymerization inhibitor) (Based on 100 parts by weight of (meth) acrylate monomer) 0.07508 parts by weight of alcohol, 0.0051 parts by weight of water, content of compounds having phenolic hydroxyl groups: below detection limit ) And 500 g of highly refined mineral oil were added, and the atmosphere was inerted by nitrogen continuity. Subsequently, 0.18 g of CuBr and 0.22 g of a ligand (pentamethyldiethylenetriamine (PMDETA)) were added as catalysts. After heating to 90 ° C., 0.45 g of initiator (ethyl-2-bromoisobutyrate) was added. The temperature in the three-neck flask was raised to 100 ° C., and polymerization was carried out for 20 hours to obtain a solution containing a methacrylate polymer. The evaluation results of the obtained methacrylate polymer are shown in Table 1.

<Examples 1 to 7, Comparative Examples 1 to 4>
Using the base oils and performance additives shown below, and the (meth) acrylate polymers obtained in Production Examples 1 to 7 and Comparative Production Examples 1 to 4, the lubricating oil composition of the present invention (Examples) 1 to 7) and a comparative lubricating oil composition (Comparative Examples 1 to 4) were prepared. In the table, “mass%” represents mass% based on the total amount of the composition.

Base oil: Group III base oil, kinematic viscosity (100 ° C.) 4.2 mm ² / s, viscosity index 125
Performance additive: Additive package containing calcium sulfonate metal detergent, succinimide ashless dispersant, molybdenum friction modifier, and ZnDTP antiwear agent

(Evaluation of lubricating oil composition)
The lubricating oil compositions of Examples 1 to 7 and Comparative Examples 1 to 4 were measured for kinematic viscosity at 100 ° C., viscosity index, and HTHS viscosity at 100 ° C. and 150 ° C. The coking resistance was evaluated by a panel coking test. The results are also shown in Table 1.
(1) Kinematic viscosity: measured according to ASTM D-445.
(2) Viscosity index: measured in accordance with JIS K 2283-1993.
(3) HTHS viscosity: measured in accordance with ASTM D-4683.
(4) Panel coking test: Fed. A panel coking test was conducted according to Test Method 791-3462. Table 1 shows the weight increase (unit: mg) of the panel before and after the test. It can be said that the smaller the weight increase of the panel, the better the coking resistance.

<Example 8, Comparative Examples 5 to 7>
Lubricating oil composition of the present invention (Example 8) and a comparative lubricating oil composition containing a (meth) acrylate polymer having the same monomer composition as in Example 8 (Comparative Examples 5 to 7) ) Was prepared. The base oil and performance additives used are the same as those in Examples 1 to 7 and Comparative Examples 1 to 4. Table 2 shows the properties of the (meth) acrylate polymer together with the evaluation results of the panel coking test.

<Examples 9 to 17>
Lubricating oil compositions (Examples 9 to 17) of the present invention were prepared. The base oil and performance additives used are the same as in Examples 1-8 and Comparative Examples 1-7. The properties of the (meth) acrylate polymer are shown in Table 3 together with the evaluation results of the lubricating oil composition. In Table 3, in the item of “solubility”, “transparent” means that no insoluble matter was observed when the lubricating oil composition was visually observed, and “turbidity” means that the lubricating oil composition was suspended. Means that. In Table 3, in the item “Structural unit in polymer”, “A1”, “A2” and “A3” mean the structural unit represented by the general formula (4), respectively, and the values of m and n Means the values of m and n in the general formula (6).

Since the lubricating oil composition of the present invention has improved coking resistance, it can be preferably used as a lubricating oil for lubricating high temperature machine elements such as a lubricating oil for internal combustion engines, a gas engine oil and a high temperature bearing oil.

Claims

Lubricating base oil,
(A) a (meth) acrylate polymer containing a structural unit represented by the following general formula (1) and having a parameter a value represented by the following formula (2) of 0.12 or less. A lubricating oil composition characterized by the above.

(In the formula (1), R 1 represents hydrogen or a methyl group, and R 2 represents an alkyl group having 10 to 36 carbon atoms.)
a = Log (M h (t 1/2 )) − Log (M (t)) (2)
(In Formula (2), M (t) represents the peak top molecular weight in the differential molecular weight distribution curve of the polystyrene conversion molecular weight obtained by the gel permeation chromatography measurement of the said (meth) acrylate type polymer; M h (t 1 / 2 ) represents the molecular weight in terms of polystyrene on the high molecular weight side giving half the strength at the molecular weight M (t) in the differential molecular weight distribution curve.)
The value of the parameter b represented by the following formula (3) is 0.3 or less,
The lubricating oil composition according to claim 1.
b = Log (M h (t 1/2 )) − Log (M l (t 1/2 )) (3)
(In Formula (3), M l (t 1/2 ) represents a molecular weight in terms of polystyrene on the low molecular weight side giving half the strength of the molecular weight M (t) in the differential molecular weight distribution curve.)
In the (meth) acrylate polymer, the content of the structural unit represented by the general formula (1) is 40 to 80% by mass based on the total amount of the (meth) acrylate polymer.
The lubricating oil composition according to claim 1 or 2.
The (meth) acrylate polymer has a weight average molecular weight Mw of 50,000 to 500,000.
The lubricating oil composition according to any one of claims 1 to 3.
The ratio Mw / Mn of the weight average molecular weight Mw and the number average molecular weight Mn of the (meth) acrylate polymer is 1.6 or less.
The lubricating oil composition according to any one of claims 1 to 4.
The (meth) acrylate polymer includes a structural unit represented by the following general formula (4) and a structural unit represented by the following general formula (5).
The lubricating oil composition according to any one of claims 1 to 5.

(In the formula (4) and (5), R 3 and R 5 each independently represent a hydrogen or a methyl group; R 4 represents a group represented by the following general formula (6); R 6 is a linear or Represents an alkyl group having 1 to 36 carbon atoms having a branch having 5 or less carbon atoms.)

(In formula (6), m and n are integers satisfying m ≧ 5, n ≧ 4, and m + n ≦ 31.)
The (meth) acrylate polymer is a polymer obtained by polymerizing a raw material containing at least one (meth) acrylate polymerizable monomer by living anion polymerization,
The content of the compound having a hydroxyl group in the raw material is 0.2 parts by mass or less with respect to 100 parts by mass of the one or more (meth) acrylate polymerizable monomers in the raw material.
The lubricating oil composition according to any one of claims 1 to 6.
Metal detergents, ashless dispersants, friction modifiers, antiwear agents, antioxidants, corrosion inhibitors, metal deactivators, viscosity index improvers other than the above component (A), pour point depressants, rust prevention Further comprising one or more additives selected from the group consisting of an agent, a demulsifier, and an antifoaming agent,
The lubricating oil composition according to any one of claims 1 to 7.
The lubricating oil composition according to any one of claims 1 to 8, which is used for lubricating an internal combustion engine.