JP2022022992A - Viscosity index improver and lubricating oil composition - Google Patents

Abstract

To provide a viscosity index improver which causes a lubricating oil composition with the viscosity index improver added therein to have a low kinematic viscosity at 40 to 80°C and a low HTHS viscosity at 60 to 100°C, and to provide the lubricating oil composition comprising the same.SOLUTION: A viscosity index improver comprises a copolymer (A) having as an essential constituent monomer: a monomer (a) represented by the following general formula (1), where R2 is a 2 to 3C alkyl group; a monomer (b) represented by the following general formula (1), where R2 is a 4C alkyl group; and a polyolefin monomer (c) represented by the following general formula (2). The copolymer (A) comprises 0.1 to 65 wt% of the monomer (a) on the basis of a weight of (A) as the constituent monomer. A weight ratio (a/b) of (a) and (b) is 0.17 to 65.SELECTED DRAWING: None

Description

The present invention relates to a viscosity index improver and a lubricating oil composition.

In recent years, in order to reduce CO ₂ emissions and protect petroleum resources, fuel efficiency of automobiles has been further demanded. One of the fuel efficiency reductions is to reduce the viscosity of engine oil. However, if the viscosity is too low, especially on the high temperature side, problems such as liquid leakage and seizure will occur. For this problem, the minimum guaranteed viscosity is set by the US SAE engine oil viscosity standard (SAE J300), and in the 0W-20 grade, the viscosity under high temperature and high shear (HTHS viscosity) is 150 ° C. The HTHS viscosity (ASTM D4683 or D5481) is specified to be 2.6 mPa · s or higher and 2.3 mPa · s or higher for the 0W-16 grade. In recent years, fuel efficiency has been reduced by hardware such as hybrid vehicles that combine electricity and gasoline and plug-in hybrid vehicles. Unlike conventional gasoline-powered vehicles, such hybrid vehicles have a low temperature of engine oil during driving. Specifically, gasoline-powered vehicles have a temperature of 80 to 100 ° C during normal driving, while hybrid vehicles have a temperature of 40 to 80 ° C. It becomes ℃. Therefore, engine oils used in hybrid vehicles and the like are further required to have a low viscosity in the range of 40 ° C to 80 ° C. Therefore, a method of adding a viscosity index improver to a lubricating oil to improve the temperature dependence of the viscosity is widely used. As the viscosity index improver, methacrylate ester copolymers (Patent Documents 1 to 3), comb-type copolymers (Patent Documents 4 to 6) and the like are known.
However, these viscosity index improvers have a problem that the kinematic viscosity at 40 to 80 ° C. and the effective viscosity (HTHS viscosity) under high shear are high. Therefore, there is a demand for a viscosity index improver capable of lowering the kinematic viscosity and the HTHS viscosity at 40 to 80 ° C. when the engine oil is used.

Japanese Patent No. 2732187 Japanese Patent No. 2754343 Japanese Patent No. 3831203 Japanese Patent No. 3474918 Japanese Patent Publication No. 2008-546894 Special Table 2010-532805 Gazette

An object of the present invention is a lubricating oil composition having a kinematic viscosity at 40 to 80 ° C. and a running viscosity under high shear (HTHS viscosity at 60 to 100 ° C.) to which a viscosity index improver is added. It is an object of the present invention to provide a viscosity index improver capable of obtaining the above-mentioned material and a lubricating oil composition containing the same.

［一般式（１）においてＲ^１は水素原子又はメチル基；－Ｘ^１－は－Ｏ－又は－ＮＨ－で表される基；Ｒ^２は炭素数２～４のアルキル基。］

[一般式（２）においてＲ³は水素原子又はメチル基；－Ｘ²－は－Ｏ－、－Ｏ（ＡＯ）_ｍ－又は－ＮＨ－で表される基であって、Ａは炭素数２～４のアルキレン基であり、ｍは１～１０の整数であり、ｍが２以上の場合のＡは同一でも異なっていてもよい；Ｒ⁴は１，２－ブチレン基を構成単位として含む炭化水素重合体から水素原子を１つ除いた残基；ｐは０又は１の数。］ The present inventors have arrived at the present invention as a result of studies for achieving the above object.
That is, the present invention is a monomer represented by the following general formula (1), wherein R ² is an alkyl group having 2 to 3 carbon atoms (a), and is represented by the following general formula (1). A monomer (b) which is a monomer and R ² is an alkyl group having 4 carbon atoms and a polyolefin-based monomer (c) represented by the following general formula (2) are used as essential constituent monomers. A viscosity index improver containing the polymer (A), wherein the copolymer (A) is a constituent monomer, and the monomer (a) is 0.1 to 65 based on the weight of the (A). A viscosity index improver containing% by weight and having a weight ratio (a / b) of (a) and (b) of 0.17 to 65; containing the viscosity index improver and the base oil (B). It is a lubricating oil composition.

[In the general formula (1), R ¹ is a hydrogen atom or a methyl group; -X ^1- is a group represented by -O- or -NH-; R ² is an alkyl group having 2 to 4 carbon atoms. ]

[In the general formula (2), R ³ is a hydrogen atom or a methyl group; -X ^2- is a group represented by -O-, -O (AO) _m- or -NH-, and A is a group having 2 carbon atoms. It is an alkylene group of -4, m is an integer of 1-10, and A when m is 2 or more may be the same or different; R ⁴ is a hydrocarbon containing a 1,2-butylene group as a constituent unit. A residue obtained by removing one hydrogen atom from a hydrogen polymer; p is a number of 0 or 1. ]

The viscosity index improver of the present invention has the effect of lowering the kinematic viscosity of the lubricating oil composition to which the viscosity index improver is added at 40 to 80 ° C. and the HTHS viscosity at 60 to 100 ° C.

［一般式（１）においてＲ^１は水素原子又はメチル基；－Ｘ^１－は－Ｏ－又は－ＮＨ－で表される基；Ｒ^２は炭素数２～４のアルキル基。］

[一般式（２）においてＲ³は水素原子又はメチル基；－Ｘ²－は－Ｏ－、－Ｏ（ＡＯ）_ｍ－又は－ＮＨ－で表される基であって、Ａは炭素数２～４のアルキレン基であり、ｍは１～１０の整数であり、ｍが２以上の場合のＡは同一でも異なっていてもよい；Ｒ⁴はブタジエンを必須構成単量体とする炭化水素重合体又はその炭化水素重合体の有する炭素－炭素二重結合の少なくとも一部が水素化された重合体から水素原子を１つ除いた残基；ｐは０又は１の数。］ The viscosity index improver of the present invention is a monomer represented by the following general formula (1), wherein R ² is an alkyl group having 2 or 3 carbon atoms (a), and the following general formula (1). A monomer (b) in which R ² is an alkyl group having 4 carbon atoms and a polyolefin-based monomer (c) represented by the following general formula (2) are essential constituent monomers. It is a viscosity index improver containing the copolymer (A), and the monomer (a) is 0. It is a viscosity index improver containing 1 to 65% by weight and having a weight ratio (a / b) of (a) and (b) of 0.17 to 65.

[In the general formula (1), R ¹ is a hydrogen atom or a methyl group; -X ^1- is a group represented by -O- or -NH-; R ² is an alkyl group having 2 to 4 carbon atoms. ]

[In the general formula (2), R ³ is a hydrogen atom or a methyl group; -X ^2- is a group represented by -O-, -O (AO) _m- or -NH-, and A is a group having 2 carbon atoms. It is an alkylene group of up to 4, m is an integer of 1 to 10, and when m is 2 or more, A may be the same or different; R ⁴ is a hydrocarbon weight containing butadiene as an essential constituent monomer. A residue obtained by removing one hydrogen atom from a polymer in which at least a part of a carbon-carbon double bond of a coalescence or a hydrocarbon polymer thereof is hydrogenated; p is a number of 0 or 1. ]

<Copolymer (A)>
The viscosity index improver of the present invention is a monomer represented by the above general formula (1), wherein R ² is an alkyl group having 2 or 3 carbon atoms (a), and the above general formula (1). A monomer (b) in which R ² is an alkyl group having 4 carbon atoms and a polyolefin-based monomer (c) represented by the above general formula (2) are essential constituent monomers. Contains the copolymer (A).
The structural unit derived from the monomer (c) has a low polarity because R ⁴ (residue obtained by removing one hydrogen atom from the hydrocarbon polymer) of (c) with respect to a polar group (ester group, etc.) is long. , The constituent units derived from the monomers (a) and (b) have a short alkyl group (2 to 4 carbon atoms) with respect to a polar group (ester group or the like), and thus have a high polarity. Conventionally, when a copolymer containing a monomer (c) and a monomer (b) as a constituent monomer is used, the behavior of the polymer chain in the base oil (high viscosity with respect to the base oil at low temperature). R ⁴ (hydrocarbon chain) aggregates so as to cover the structural unit derived from (b), and R ⁴ spreads at high temperature), and the temperature dependence becomes large, and it tends to be excellent as a viscosity index improver. Was known. In the present invention, the copolymer contains the monomer (a) as a constituent monomer in addition to the monomers (b) and (c), and further, the weight ratio (a /) of (a) and (b). By setting b) to a specific range of 0.17 to 65, the behavior of the polymer chain with respect to the temperature of the base oil of (A) is further excellent, the kinematic viscosity at 40 to 80 ° C. and the shearing at 60 to 100 ° C. It has been found that a lubricating oil composition having a low viscosity can be obtained.

In the general formula (1), R ¹ is a hydrogen atom or a methyl group, and a methyl group is preferable from the viewpoint of the effect of improving the viscosity index.

In the general formula (1), -X ^1- is a group represented by -O- or -NH-, and a group represented by -O- is preferable from the viewpoint of the effect of improving the viscosity index.

The monomer (a) is an alkyl group having R ² having 2 or 3 carbon atoms in the general formula (1).
Examples of the alkyl group having 2 or 3 carbon atoms include an ethyl group, an n-propyl group and an isopropyl group.
Specific examples of the monomer (a) include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, N-ethyl (meth) acrylamide and N-propyl (meth). Examples include acrylamide.
As the monomer (a), ethyl (meth) acrylate, n-propyl (meth) acrylate and isopropyl (meth) acrylate are preferable from the viewpoint of kinematic viscosity and HTHS viscosity lowering effect in a low temperature region. Ethyl (meth) acrylate is preferred.
In the present invention, "(meth) acrylic" means "acrylic and / or methacrylic".

The monomer (b) is an alkyl group having 4 carbon atoms in R ² in the general formula (1).
Examples of the alkyl group having 4 carbon atoms include an n-butyl group, an isobutyl group, an s-butyl group and a t-butyl group.
Specific examples of the monomer (b) include n-butyl (meth) acrylate, 1-methylpropyl (meth) acrylate, 2-methylpropyl (meth) acrylate, and 1,1 (meth) acrylate. -Dimethylethyl, N-butyl (meth) acrylamide and the like can be mentioned.
As the monomer (b), n-butyl (meth) acrylate and isobutyl (meth) acrylate are preferable, and n-butyl (meth) acrylate is more preferable, from the viewpoint of the effect of improving the viscosity index.

The polyolefin-based monomer (c) represented by the general formula (2) will be described.
R ³ in the general formula (2) is a hydrogen atom or a methyl group. Of these, a methyl group is preferable from the viewpoint of the viscosity index improving effect and the HTHS viscosity lowering effect.

-X ^2- in the general formula (2) is a group represented by -O-, -O (AO) _m- or -NH-.
A is an alkylene group having 2 to 4 carbon atoms, such as an ethylene group, a 1,2- or 1,3-propylene group and a 1,2-, 1,3-, 1,4- or 2,3-butylene group. Can be mentioned.
AO is an alkyleneoxy group having 2 to 4 carbon atoms, such as an ethyleneoxy group, a 1,2- or 1,3-propyleneoxy group, and a 1,2-, 1,3- or 1,4-butyleneoxy group. Can be mentioned.
m is the number of added moles of the alkylene oxide, which is an integer of 1 to 10, preferably an integer of 1 to 4, and more preferably an integer of 1 to 2 from the viewpoint of the effect of improving the viscosity index.
When m is 2 or more, A may be the same or different, and the binding form of the (AO) _m portion may be random or block.
Of -X ^2- , the groups represented by -O- and -O (AO) _m- are preferable from the viewpoint of the effect of improving the viscosity index, and more preferably -O- and -O (CH ₂ CH). ₂ O) It is a group represented by ₁ −.
p is a number of 0 or 1, and p is from the viewpoint that the behavior of the polymer chain in the base oil becomes large and the kinematic viscosity at 40 to 80 ° C. and the shear viscosity at 60 to 100 ° C. can be lowered. = 0 is preferable.

^R4 in the general formula (2) is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing 1-butane as an essential constituent monomer, or a butadiene (1,3-butadiene, etc.) as an essential constituent monomer. At least a part of the carbon-carbon double bond of the hydrocarbon polymer to be used is a residue obtained by removing one hydrogen atom from the hydride polymer. The hydrocarbon polymer preferably has 37 or more carbon atoms.

In the hydrocarbon polymer of the general formula (2), the ratio of 1,3-butadiene among all the monomers constituting the hydrocarbon polymer is 50% by weight from the viewpoint of the effect of improving the viscosity index and the effect of lowering the viscosity of HTHS. The above is preferable, more preferably 75% by weight or more, then further preferably 85% by weight or more, and particularly preferably 90% by weight or more.

In the hydrocarbon polymer according to the general formula (2), the ratio of 1,2-butylene groups in all the constituent units is dissolved in the base oil (hydrocarbon oil (B) in the present invention, the same shall apply hereinafter). From the viewpoint of sex, 1 to 80 mol% is preferable, and 20 to 75 mol% is more preferable.

For the structure derived from 1-butene and / or 1,3-butadiene of the hydrocarbon polymer in the general formula (2), the ratio of 1,2-butylene groups in all the structural units shall be measured by ¹³ C-NMR. Can be done. Specifically, for example, when only a monomer having 4 carbon atoms is used, the hydrocarbon polymer is analyzed by ¹³ C-NMR, and the following formula (1) is used to construct the hydrocarbon polymer. The mol% of 1,2-butylene groups can be calculated and determined based on the total number of moles of the unit. ¹³ In C-NMR, a peak appears at an integrated value of 26 to 27 ppm (integrated value B) derived from a tertiary carbon atom (-CH ₂ CH (CH ₂ CH ₃ )-) of a 1,2-butylene group. It can be obtained from the integral value of the above peak and the integral value (integral value C) relating to the peak of all carbon of the hydrocarbon polymer.
Ratio of 1,2-butylene groups (mol%) = {(integral value B) x 4} / (integral value C) x 100 (1)
In order to increase the ratio of 1,2-butylene groups, for example, in anionic polymerization using 1,3-butadiene, the reaction temperature should be set to the boiling point of 1,3-butadiene (-4.4 ° C) or lower. Moreover, the amount of the polymerization initiator added may be smaller than that of 1,3-butadiene, and in order to reduce the ratio of 1,2-butylene groups, the reaction temperature should be set to the boiling point of 1,3-butadiene or higher. The amount may be increased.

When the hydrocarbon polymer in R ⁴ contains butadiene, or butadiene and 1-butene as constituent monomers, butadiene, or butadiene and 1-butene constituting part or all of R ⁴ in the general formula (2). In the structure of origin, the molar ratio of 1,2-butylene group (1,2-added) to 1,4-butylene group (1,4-added) (1,2-added / 1,4-added) From the viewpoint of improving the viscosity index, HTHS viscosity, and solubility in base oil, the body) is preferably 1/99 to 55/45, more preferably 10/90 to 53/47, and particularly preferably 20/80 to. It is 50/50.
When the hydrocarbon polymer in R ⁴ contains butadiene or butadiene and 1-butene as constituent monomers, butadiene or butadiene and 1 constituting part or all of R ⁴ in the general formula (2). -The molar ratio of 1,2-added / 1,4-added in the structure derived from butene can be measured by ¹ H-NMR, ¹³ C-NMR, Raman spectroscopy or the like.

From the viewpoint of the effect of improving the viscosity index, ^R4 in the general formula (2) further contains an isobutylene group (-C (CH ₃ ) ₂ -CH _2- ) as a constituent unit in addition to the 1,2-butylene group. It is preferably a residue obtained by removing one hydrogen atom from the hydrogen polymer. Examples of the method for producing a hydrocarbon polymer containing an isobutylene group as a constituent unit include a method using isobutene as a constituent monomer (unsaturated hydrocarbon (x)).
The total ratio of the isobutylene group and the 1,2-butylene group in the hydrocarbon polymer is preferably 30 mol% or more, more preferably 30 mol% or more, based on the total number of constituent units of the hydrocarbon polymer, from the viewpoint of the effect of improving the viscosity index. Is 40 mol% or more, particularly preferably 50 mol% or more, and most preferably 60 mol% or more.

Based on the total number of building blocks of the hydrocarbon polymer, the total ratio of isobutylene groups and 1,2-butylene groups is determined by analyzing the hydrocarbon polymer with a ¹³ C-nuclear magnetic resonance spectrum and using the following formula (2). Can be calculated and determined. Specifically, in the ¹³ C-nuclear magnetic resonance spectrum, the peak derived from the methyl group of the isobutylene group is an integral value (integral value A) of 30 to 32 ppm, and a tertiary carbon atom of 1,2-butylene (-CH ₂ ). A peak derived from -CH (CH ₂ CH ₃ )-) appears in the integrated value (integrated value B) of 26 to 27 ppm. It can be obtained from the integral value of the above peak and the integral value (integral value C) relating to the peak of all carbon of the hydrocarbon polymer.
Total ratio of isobutylene group and 1,2-butylene group (mol%) = {(integral value A) x 2 + (integral value B) x 4} / (integral value C) x 100 (2)

In addition to the above-mentioned butadiene, 1-butene and isobutylene, the hydrocarbon polymer in the general formula (2) may contain the following (1) to (3) as the unsaturated hydrocarbon (x) as constituent monomers.
(1) aliphatic unsaturated hydrocarbons [olefins having 2 to 36 carbon atoms (for example, ethylene, propylene, 2-butene, isobutene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, triacocene, hexatriacocene, etc.) and Dienes having 4 to 36 carbon atoms (for example, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.)]
(2) Alicyclic unsaturated hydrocarbons [for example, cyclohexene, (di) cyclopentadiene, pinene, limonene, indene, vinylcyclohexene, etilidenbicycloheptene, etc.]
(3) Aromatic group-containing unsaturated hydrocarbons (eg, styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotyl) Benzene, vinylnaphthalene, divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene, etc.) and the like can be mentioned.
The hydrocarbon polymer composed of these may be a block polymer or a random polymer. When the hydrocarbon polymer has a double bond, a part or all of the double bond may be hydrogenated by hydrogenation. In one embodiment, the hydrocarbon polymer in ^R4 may be a hydrocarbon polymer using only a monomer having 4 carbon atoms as a constituent monomer, and the monomer having 4 carbon atoms is 1-butene. , 1,3-butadiene and isobutene may be at least one selected from the group.

The weight average molecular weight (hereinafter abbreviated as Mw) and the number average molecular weight (hereinafter abbreviated as Mn) of the monomer (c) can be measured by gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions. can.
<Measurement conditions for Mw and Mn of monomer (c)>
Equipment: "HLC-8320GPC" [manufactured by Tosoh Corporation]
Column: 2 "TSKgel GMHXL" [manufactured by Tosoh Corporation]
"TSKgel Multipole H _XL -M 1 measurement temperature: 40 ° C
Sample solution: 0.25 wt% tetrahydrofuran solution Injection volume: 10.0 μl
Detection device: Refractive index detector Reference material: Standard polystyrene (TS reference material: Standard polystyrene (TSKstandardPOLYSTYRENE)
12 points (molecular weight: 589, 1,050, 2,630, 9,100, 19,500, 37,900, 96,400, 190,000, 355,000, 1,090,000, 2,110,000 , 4,480,000) [manufactured by Tosoh Corporation]

The Mn of the monomer (c) is preferably 800 to 10,000, more preferably 1,000 to 9,500, and particularly preferably 1,200 to 9,500.
When the Mn of the monomer (c) is 800 or more, the temperature dependence of the behavior of the polymer chain in the base oil becomes high, and the effect of improving the viscosity index tends to be good, and when it is 10,000 or less. Shear stability during long-term use tends to be good.
The Mw of the monomer (c) is preferably 900 to 13,000, more preferably 1,200 to 12,000, and particularly preferably 1,500 to 11,000 from the viewpoint of the effect of improving the viscosity index. be.

The monomer (c) is an esterification reaction between a polymer (Y) containing a hydroxyl group at one end {a hydroxyl group introduced at one end of the above hydrocarbon polymer} and (meth) acrylic acid, or a weight. It can be obtained by a transesterification reaction between the combined (Y) and an alkyl (meth) acrylate (preferably, the alkyl group has 1 to 4 carbon atoms) such as methyl (meth) acrylate. Further, it can be obtained by an amidation reaction between a polymer having an amino group (-NH ₂ ) at one end and (meth) acrylic acid.

単量体（ｃ）に由来する構成単位のＳＰ値は、単量体（ｃ）に由来する構成単位の分子構造に基づいて、前記パラメータを用いて算出することができ、使用する単量体（不飽和炭化水素（ｘ））、重量分率を適宜調整することにより所望の範囲にすることができる。 The solubility parameter (hereinafter abbreviated as SP value) of the structural unit derived from the monomer (c) (the structure in which the vinyl of (c) reacts to form a single bond) is the solubility in lubricating oil. From the viewpoint, it is preferably 7.0 to 9.0 (cal / cm ³ ) ^1/2 , and more preferably 7.3 to 8.5 (cal / cm ³ ) ^1/2 .
For example, the SP value tends to be smaller when the degree of branching of ^R4 is large and the number of carbon atoms is large, and it tends to be large when the degree of branching is small and the number of carbon atoms is small.
The SP value in the present invention is the numerical value (atom or sensory) described on page 152 (Table. 5) of the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2 P. 147 to 154). It is a value calculated by the mathematical formula (28) (page 153) using the base (heat of vaporization at 25 ° C. and molar volume). Specifically, by applying the numerical values of Δe _i and Δv _i shown in Table 1 below, which are the parameters of the Fedors method, to the following mathematical formulas using the numerical values corresponding to the types of atoms and atomic groups in the molecular structure. Can be calculated.
SP value = (ΣΔe _i / ΣΔv _i ) ^1/2

The SP value of the structural unit derived from the monomer (c) can be calculated using the above parameters based on the molecular structure of the structural unit derived from the monomer (c), and the monomer used. (Unsaturated hydrocarbon (x)), the desired range can be obtained by appropriately adjusting the weight fraction.

Specific examples of the polymer (Y) containing a hydroxyl group at one end include the following (Y1) to (Y4).
An alkylene oxide adduct (Y1); an alkylene oxide (ethylene oxide, propylene oxide, etc.) is added to a polymer obtained by polymerizing an unsaturated hydrocarbon (x) in the presence of an ion polymerization catalyst (lithium catalyst, sodium catalyst, etc.). (In the general formula (2), -X ^2- is-(AO) _m- and p = 0).
Hydroboration product (Y2); hydroboration reaction product of a polymer of unsaturated hydrocarbon (x) having a double bond at one end (for example, as described in US Pat. No. 4,316,973) and the like. (In the general formula (2), -X ^2- is -O- and p = 0).
Maleic anhydride-ene-aminoalcohol adduct (Y3); Amino alcohol is a reaction product obtained by an ene reaction between a polymer of unsaturated hydrocarbon (x) having a double bond at one end and maleic anhydride. (In the general formula ( ² ), -X2- is -O- and p = 1) obtained by imidization with.
Hydroformyl-hydride (Y4); a polymer obtained by hydroformylating a polymer of unsaturated hydrocarbon (x) having a double bond at one end and then hydrogenating (for example, Japanese Patent Application Laid-Open No. 63-175096). (In the general formula ( ² ), -X2- is -O- and p = 0).
Among these polymers (Y) containing a hydroxyl group at one end, the alkylene oxide adduct (Y1) and the hydroboronized product (Y2) are preferable from the viewpoint of the HTHS viscosity lowering effect and the viscosity index improving effect. More preferred is the alkylene oxide adduct (Y1).

In the copolymer (A), the weight ratio of the monomer (a) to the constituent monomers of (A) is 0.1 to 65 based on the total weight of the monomers constituting (A). It is% by weight, preferably 0.5 to 55% by weight, and more preferably 1.0 to 50% by weight.
If the weight ratio of the monomer (a) is less than 0.1% by weight, it is difficult to reduce the kinematic viscosity and the HTHS viscosity at 40 to 80 ° C., and if it exceeds 65% by weight, the solubility in the base oil is difficult. Will be low.

In the copolymer (A), the weight ratio of the monomer (b) to the constituent monomers of (A) is based on the total weight of the monomers constituting (A), and has an effect of improving the viscosity index. From the viewpoint, it is preferably 1 to 80% by weight, more preferably 2 to 70% by weight.

In the copolymer (A), the weight ratio (a / b) of the weight of the monomer (a) to the weight of the monomer (b) among the constituent monomers of (A) is 0.17 to 65. It is preferably 0.18 to 30, and more preferably 0.20 to 10.
If the weight ratio (a / b) is less than 0.17, it is difficult to reduce the kinematic viscosity and the HTHS viscosity at 40 to 80 ° C., and if it exceeds 65, the solubility in the base oil becomes low.

In the copolymer (A), the total weight ratio of the monomers (a) and (b) among the constituent monomers of (A) is based on the total weight of the monomers constituting (A). From the viewpoint of the effect of improving the viscosity index and the solubility in the base oil, 98% by weight or less is preferable, and 35 to 70% by weight is more preferable.

In the copolymer (A), the weight ratio of the monomer (c) to the constituent monomers of (A) is based on the total weight of the monomers constituting (A), and has an effect of improving the viscosity index. From the viewpoint, it is preferably 1 to 30% by weight, more preferably 10 to 20% by weight.

In the copolymer (A), the total weight ratio of the monomers (a), (b) and (c) among the constituent monomers of (A) is the total weight of the monomers constituting (A). From the viewpoint of the effect of improving the viscosity index, 10% by weight or more is preferable, and 36 to 80% by weight is more preferable.

In the copolymer (A), the weight ratio (c / a) of the weight of the monomer (c) to the weight of the monomer (a) among the constituent monomers of (A) is in the low temperature region. From the viewpoint of kinematic viscosity and HTHS viscosity lowering effect, it is preferably 0.15 to 200, and more preferably 0.20 to 100.
In the copolymer (A), the weight ratio (c /) of the weight of the monomer (c) to the total weight of the monomers (a) and the monomers (b) among the constituent monomers of (A). (A + b)) is preferably 0.03 to 2, more preferably 0.12 to 1, from the viewpoint of the kinematic viscosity in the low temperature region and the effect of lowering the HTHS viscosity.

［一般式（３）においてＲ^５は水素原子又はメチル基；－Ｘ^３－は－Ｏ－又は－ＮＨ－で表される基；Ｒ^６は炭素数２～４のアルキレン基；ｑは１～２０の整数であり、ｑが２以上の場合のＲ^６は同一でも異なっていてもよい；Ｒ^７は炭素数１～４の直鎖又は分岐アルキル基。］ In the present invention, the copolymer (A) is a copolymer further containing the monomer (d) represented by the following general formula (3) as a constituent monomer from the viewpoint of the effect of improving the viscosity index. Is preferable.

[In the general formula (3), R ⁵ is a hydrogen atom or a methyl group; -X ^3- is a group represented by -O- or -NH-; R ⁶ is an alkylene group having 2 to 4 carbon atoms; q is 1 to 1 to An integer of 20 and where q is 2 or greater, R ⁶ may be the same or different; R ⁷ is a linear or branched alkyl group with 1 to 4 carbon atoms. ]

R5 in the general formula ( ³ ) is a hydrogen atom or a methyl group. Of these, a methyl group is preferable from the viewpoint of the effect of improving the viscosity index.

-X ^3- in the general formula (3) is a group represented by -O- or -NH-. Of these, from the viewpoint of the effect of improving the viscosity index, the group represented by —O— is preferable.

R ⁶ in the general formula (3) is an alkylene group having 2 to 4 carbon atoms.
Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, an isopropylene group, a 1,2- or 1,3-propylene group, an isobutylene group, and a 1,2-, 1,3- or 1,4-. Butylene group and the like can be mentioned.
R ⁶ O is an alkyleneoxy group having 2 to 4 carbon atoms, for example, an ethyleneoxy group, a 1,2- or 1,3-propyleneoxy group, and 1,2-, 1,3- or 1,4-. Butyleneoxy groups and the like can be mentioned.
Q in the general formula (3) is an integer of 1 to 20, preferably an integer of 1 to 5, and more preferably an integer of 1 to 2 from the viewpoint of the effect of improving the viscosity index.
When q is 2 or more, R ⁶ O may be the same or different, and the binding form of the (R ⁶ O) _q portion may be random or block.

R ⁷ in the general formula (3) is a linear or branched alkyl group having 1 to 4 carbon atoms. For example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group and the like can be mentioned.
Among the linear or branched alkyl groups having 1 to 4 carbon atoms, the linear alkyl group having 1 to 4 carbon atoms is preferable from the viewpoint of the effect of improving the viscosity index, and the linear alkyl group having 4 carbon atoms is more preferable. Group (n-butyl group).

Specifically, the monomer (d) includes methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, and ethoxypropyl (meth). Meta) acrylate, propoxypropyl (meth) acrylate, butoxypropyl (meth) acrylate, methoxybutyl (meth) acrylate, ethoxybutyl (meth) acrylate, propoxybutyl (meth) acrylate and butoxybutyl (meth) acrylate, and 1 carbon number. Examples thereof include an esterified product of (meth) acrylic acid and a product obtained by adding 2 to 20 mol of at least one selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide to the linear or branched alkyl alcohols of 4 to 4.
Among the monomers (d), ethoxyethyl (meth) acrylate and butoxyethyl (meth) acrylate are preferable from the viewpoint of the effect of improving the viscosity index, and n-butoxyethyl (meth) acrylate is more preferable.

In the copolymer (A), the weight ratio of the monomer (d) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 80% by weight or less, more preferably 1 to 50% by weight, and particularly preferably 5 to 15% by weight.

In the present invention, the copolymer (A) is a (meth) acryloyl monomer (e) having an alkyl group having 1 carbon atom in addition to the monomers (a) to (d) (hereinafter referred to as a monomer (hereinafter referred to as a monomer). It may be abbreviated as e)) and / or a (meth) acryloyl monomer (f) having a linear or branched alkyl group having 9 to 36 carbon atoms (hereinafter, abbreviated as monomer (f)). There may be a copolymer containing) as a constituent monomer. The monomer (e) has a high polarity because the number of carbon atoms of the alkyl group is short with respect to the polar group (ester group or the like), and the polarity of the copolymer (A) can be increased, and the monomer (f) is polar. Since the number of carbon atoms of the alkyl group with respect to the group (ester group or the like) is longer than (b) and shorter than (c), it has an intermediate polarity, and the polarity of the copolymer (A) can be adjusted.
In addition, one kind of monomer (e) and (f) may be used respectively, and two or more kinds may be used in combination.

Examples of the (meth) acryloyl monomer (e) having an alkyl group having 1 carbon atom include methyl (meth) acrylate and N-methyl (meth) acrylamide.
Among the monomers (e), methyl (meth) acrylate is preferable from the viewpoint of the effect of improving the viscosity index.

In the copolymer (A), the weight ratio of the monomer (e) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 1 to 80% by weight, more preferably 2 to 70% by weight.

［一般式（４）においてＲ^８は水素原子又はメチル基；－Ｘ^４－は－Ｏ－又は－ＮＨ－で表される基；Ｒ^９Ｏは炭素数２～４のアルキレンオキシ基；Ｒ^１０及びＲ^１１はそれぞれ独立に炭素数１～２４の直鎖アルキル基であり、Ｒ^１０及びＲ^１１の合計炭素数は７～３４；ｓは０～２０の整数であり、ｓが２以上の場合のＲ^９Ｏは同一でも異なっていてもよい。］ In the present invention, it is preferable that the copolymer (A) is a copolymer having the monomer (f) as a constituent monomer from the viewpoint of solubility in the base oil.
The monomer (f) is other than (c) and is represented by a (meth) acryloyl monomer (f1) having a linear alkyl group having 9 to 36 carbon atoms and the following general formula (4). A (meth) acryloyl monomer (f2) having a branched alkyl group having 9 to 36 carbon atoms is included.
In addition, 1 type may be used for the monomer (f), and 2 or more types may be used together.

[In the general formula (4), R ⁸ is a hydrogen atom or a methyl group; -X ^4- is a group represented by -O- or -NH-; R ⁹ O is an alkyleneoxy group having 2 to 4 carbon atoms; R ¹⁰ And R ¹¹ are independently linear alkyl groups having 1 to 24 carbon atoms, and the total carbon number of R ¹⁰ and R ¹¹ is 7 to 34; s is an integer of 0 to 20 and s is 2 or more. R ⁹ O may be the same or different. ]

Examples of the (meth) acrylic acid monomer (f1) having a linear alkyl group having 9 to 36 carbon atoms (hereinafter, may be abbreviated as monomer (f1)) include (meth) acrylic acid alkyl ester. {An esterified product of a linear alkyl alcohol having 9 to 36 carbon atoms and acrylic acid, for example, (meth) acrylic acid n-nonyl, (meth) acrylic acid n-decyl, (meth) acrylic acid n-undecyl, (Meta) n-dodecyl acrylate, (meth) n-tridecyl acrylate, (meth) n-tetradecyl acrylate, n-pentadecyl (meth) acrylate, n-hexadecyl (meth) acrylate, (meth) acrylate n-octadecyl, n-icosyl (meth) acrylate, n-docosyl (meth) acrylate, n-tetracosyl (meth) acrylate, n-triacontyl (meth) acrylate and n-hexatriacon (meth) acrylate. Chill, etc.}, esterified product of 1 to 20 mol of linear alkyl alcohol alkylene oxide (2 to 4 carbon atoms) with 9 to 36 carbon atoms and (meth) acrylic acid, and (meth) acrylic acid alkylamide { Amidates of linear alkylamines having 9 to 36 carbon atoms and acrylic acid} and the like can be mentioned.
Among the monomers (f1), from the viewpoint of the effect of improving the viscosity index, a (meth) acrylic acid alkyl ester having a linear alkyl group having 12 to 28 carbon atoms is preferable, and a (meth) acrylic acid alkyl ester having 12 to 28 carbon atoms is more preferable. A (meth) acrylic acid ester having 24 linear alkyl groups is particularly preferred, and a (meth) acrylic acid ester having a linear alkyl group having 12 to 20 carbon atoms is particularly preferable.
One type of monomer (f1) may be used, or two or more types may be used in combination.

In the monomer (f2), R8 ⁱⁿ the general formula (4) is a hydrogen atom or a methyl group. Of these, a methyl group is preferable from the viewpoint of the effect of improving the viscosity index.
-X 4- in the general formula ( ⁴ ) is a group represented by -O- or -NH-. Of these, from the viewpoint of the effect of improving the viscosity index, the group represented by —O— is preferable.
R ⁹ in the general formula (4) is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, an isopropylene group, a 1,2- or 1,3-propylene group, an isobutylene group and 1,2-, 1,3- or 1,4-butylene. The group is mentioned.
R ⁹ O is an alkyleneoxy group having 2 to 4 carbon atoms, for example, an ethyleneoxy group, a 1,2- or 1,3-propyleneoxy group, and 1,2-, 1,3- or 1,4-. Butyleneoxy groups and the like can be mentioned.
In the general formula (4), s is an integer of 0 to 20, preferably an integer of 0 to 5 from the viewpoint of the effect of improving the viscosity index, and more preferably an integer of 0 to 2.
When s is 2 or more, R ⁹ O may be the same or different, and the (R ⁹ O) _s portion may be a random bond or a block bond.
R ¹⁰ and R ¹¹ in the general formula (4) are independently linear alkyl groups having 1 to 24 carbon atoms. Specifically, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-heptyl group, an n-hexyl group, an n-pentyl group, an n-octyl group, an n-nonyl group and an n-decyl group. , N-Undecyl group, n-Dodecyl group, n-Tetradecyl group, n-Hexadecyl group, n-Octadecyl group, n-Eicosyl group, n-Tetracosyl group and the like. Among the linear alkyl groups having 1 to 24 carbon atoms, a linear alkyl group having 6 to 24 carbon atoms is preferable from the viewpoint of improving the viscosity index, and a linear alkyl group having 6 to 20 carbon atoms is more preferable. Groups, particularly preferred are linear alkyl groups having 8 to 16 carbon atoms.
The total number of carbon atoms of R ¹⁰ and R ¹¹ is 7 to 34, preferably 12 to 30 from the viewpoint of the effect of improving the viscosity index, and more preferably 14 to 26.

Specifically, as the monomer (f2), 2-octyldecyl (meth) acrylic acid, an esterified product of ethylene glycol mono-2-octylpentadecyl ether and (meth) acrylic acid, and 2-octyl (meth) acrylic acid. n-octyldodecyl, (meth) acrylate 2-n-decyltetradecyl, (meth) acrylate 2-n-dodecyl hexadecyl, (meth) acrylate 2-n-tetradecyl octadecyl, (meth) acrylate 2 -N-dodecylpentadecyl, (meth) acrylate 2-n-tetradecylheptadecyl, (meth) acrylate 2-n-hexadecylheptadecyl, (meth) acrylate 2-n-heptadecylicosyl, ( 2-n-Hexadecyldocosyl of (meth) acrylate, 2-n-eicosyldocosyl of (meth) acrylate, 2-n-tetracosylhexacosyl of (meth) acrylate and N-2-octyldecyl (meth) Meta) Acrylic acid and the like can be mentioned.
One type of monomer (f2) may be used, or two or more types may be used in combination.

Among the monomers (f2), a (meth) acryloyl monomer having a branched alkyl group having 12 to 32 carbon atoms is preferable from the viewpoint of solubility in a base oil and low temperature viscosity, and particularly preferable is a monomer (meth) acryloyl monomer. It is a (meth) acryloyl monomer having a branched alkyl group having 16 to 28 carbon atoms.

In the copolymer (A), the weight ratio of the monomer (f) among the constituent monomers of (A) is determined from the viewpoint of improving the viscosity index and making the copolymer (A) a preferable SP value. Based on the total weight of the monomers constituting A), it is preferably 1 to 64% by weight, more preferably 5 to 35% by weight.

When the copolymer (A) contains at least one selected from the group consisting of the monomer (d), the monomer (e) and the monomer (f) as a constituent monomer, of the (A). The total weight ratio of the monomer (d), the monomer (e) and the monomer (f) among the constituent monomers is a viewpoint of improving the viscosity index and making the copolymer (A) a preferable SP value. Therefore, it is preferably 90% by weight or less, more preferably 20 to 64% by weight, based on the total weight of the monomers constituting (A).

In addition to the above-mentioned monomers (a) to (f), the copolymer (A) in the present invention further comprises a phosphorus atom-containing monomer (g), an aromatic ring-containing vinyl monomer (h), and a monomer. Other monomers such as (i) to the monomer (m), the nitrogen atom-containing monomer (n), and the hydroxyl group-containing monomer (o) may be used as the constituent monomers.
One type of each of the monomers (g) to (o) may be used, or two or more types may be used in combination.

Examples of the phosphorus atom-containing monomer (g) include the following monomers (g1) to (g2).

Phosphoric acid ester group-containing monomer (g1):
(Meta) Acryloyloxyalkyl (2-4 carbon atoms) Phosphate Ester [(Meta) Acryloyloxyethyl Phosphate and (Meta) Acryloyloxyisopropyl Phosphate] and Phosphate Alkylester [Vinyl Phosphate, Allyl Phosphate, Propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, dodecenyl phosphate, etc.] and the like can be mentioned. In addition, "(meth) acryloyloxy" means acryloyloxy or methacryloyloxy.

Phosphono group-containing monomer (g2):
(Meta) acryloyloxyalkyl (2-4 carbon atoms) phosphonic acid [(meth) acryloyloxyethyl phosphonic acid, etc.] and alkenyl (2-12 carbon atoms) phosphonic acid [vinylphosphonic acid, allylphosphonic acid and octenyl Phosphonic acid, etc.] and the like.

Of the monomers (g), (g1) is preferable, (meth) acryloyloxyalkyl (2 to 4 carbon atoms) phosphate ester is more preferable, and (meth) acryloy is particularly preferable. Roxyethyl phosphate.

Aromatic ring-containing vinyl monomer (h):
Styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4-chrome Examples thereof include tylbenzene, inden and 2-vinylnaphthalene.

Of the monomers (h), styrene and α-methylstyrene are preferable, and styrene is more preferable.

The monomer (i) includes those having two or more unsaturated groups, for example, divinylbenzene, alkaziene having 4 to 12 carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene). And 1,7-octadien, etc.), (di) cyclopentadiene, vinylcyclohexene and etylidene bicycloheptene, limonene, ethylenedi (meth) acrylate, polyalkylene oxide glycol di (meth) acrylate, pentaerythritol triallyl ether, pentaerythritol tri. (Meta) Acrylate, Pentaerythritol Tetra (Meta) Acrylate, Trimethylol Propanetri (Meta) Acrylate, Esters and unsaturated carboxylic acids having Mn of 500 or more and unsaturated carboxylic acids described in WO01 / 009242. Examples include esters of alcohol and carboxylic acids.

Vinyl esters, vinyl ethers, vinyl ketones (j) (may be abbreviated as monomer (j)):
Vinyl esters of saturated fatty acids with 2 to 12 carbon atoms (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl octanoate, etc.), alkyl, aryl or alkoxyalkyl vinyl ethers with 1 to 12 carbon atoms (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, etc.) , Butyl vinyl ether, 2-ethylhexyl vinyl ether, phenyl vinyl ether, vinyl-2-methoxyethyl ether and vinyl-2-butoxyethyl ether, etc.) and alkyl or aryl vinyl ketones with 1 to 8 carbon atoms (methyl vinyl ketone, ethyl vinyl ketone and Phenylvinyl ketone, etc.) and the like.

Epoxy group-containing monomer (k) (may be abbreviated as monomer (k)):
Examples thereof include glycidyl (meth) acrylate and glycidyl (meth) allyl ether.

Halogen element-containing monomer (l) (may be abbreviated as monomer (l)):
Examples thereof include vinyl chloride, vinyl bromide, vinylidene chloride, allyl chloride (meth) and styrene halides (dichlorostyrene and the like).

Ester of unsaturated polycarboxylic acid (m) (may be abbreviated as monomer (m)):
Alkyl, cycloalkyl or aralkyl ester of unsaturated polycarboxylic acid [Alkyl diester (dimethylmaleate, dimethylfumarate, diethylmaleate) having 1 to 8 carbon atoms of unsaturated dicarboxylic acid (maleic acid, fumaric acid, itaconic acid, etc.) And dioctylmalate)] and the like.

Examples of the nitrogen atom-containing monomer (n) include the following monomers (n1) to (n4) excluding the monomers (a) to the monomers (f).
Amide group-containing monomer (n1):
(Meta) acrylamide, N- (N'-monoalkylaminoalkyl) (meth) acrylamide [Those having an aminoalkyl group (2 to 6 carbon atoms) in which one alkyl group having 1 to 4 carbon atoms is bonded to a nitrogen atom. For example, N- (N'-methylaminoethyl) (meth) acrylamide, N- (N'-ethylaminoethyl) (meth) acrylamide, N- (N'-isopropylamino-n-butyl) (meth) acrylamide and N- (N'-n- or isobutylamino-n-butyl) (meth) acrylamide, etc.], Dialkyl (meth) acrylamide [two alkyl groups having 1 to 4 carbon atoms bonded to a nitrogen atom; for example, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide and N, N-di-n-butyl (meth) acrylamide, etc.], N- (N', N'-dialkylaminoalkyl) (meth) acrylamide [those having an aminoalkyl group (2 to 6 carbon atoms) in which two alkyl groups having 1 to 4 carbon atoms are bonded to the nitrogen atom of the aminoalkyl group; for example, N-( N', N'-dimethylaminoethyl) (meth) acrylamide, N- (N', N'-diethylaminoethyl) (meth) acrylamide, N- (N', N'-dimethylaminopropyl) (meth) acrylamide and N- (N', N'-di-n-butylaminobutyl) (meth) acrylamide, etc.]; N-vinylcarboxylic acid amide [N-vinylformamide, N-vinylacetamide, N-vinyl-n- or isopropion Acid amide, N-vinyl hydroxyacetamide, etc.] and the like.

Nitro group-containing monomer (n2):
4-Nitrostyrene and the like can be mentioned.

1st to 3rd grade amino group-containing monomer (n3):
Primary amino group-containing monomer {alkenylamine with 3 to 6 carbon atoms [(meth) allylamine, crotylamine, etc.], aminoalkyl (2 to 6 carbon atoms) (meth) acrylate [aminoethyl (meth) acrylate, etc.]} Secondary amino group-containing monomer {monoalkylaminoalkyl (meth) acrylate [those having an aminoalkyl group (2 to 6 carbon atoms) in which one alkyl group having 1 to 6 carbon atoms is bonded to a nitrogen atom; for example. Nt-butylaminoethyl (meth) acrylate and N-methylaminoethyl (meth) acrylate, etc.], Dialkenylamine with 6 to 12 carbon atoms [di (meth) allylamine, etc.]}; Body {Dialkylaminoalkyl (meth) acrylate [Amine having an aminoalkyl group (2-6 carbon atoms) in which two alkyl groups having 1 to 6 carbon atoms are bonded to a nitrogen atom; for example, N, N-dimethylaminoethyl (meth). ) Acrylic and N, N-diethylaminoethyl (meth) acrylate, etc.], alicyclic (meth) acrylate having a nitrogen atom [morpholinoethyl (meth) acrylate, etc.], aromatic monomer [N- (N',) N'-diphenylaminoethyl) (meth) acrylamide, N, N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone, N-vinylthiopyrrolidone, etc.]}, and Examples thereof include these hydrochlorides, sulfates, phosphates, lower alkyl (1 to 8 carbon atoms) monocarboxylic acid (acetic acid, propionic acid, etc.) salts and the like.

Nitrile group-containing monomer (n4):
(Meta) Acrylonitrile and the like can be mentioned.

Of the monomers (n), (n1) and (n3) are preferable, and N- (N', N'-diphenylaminoethyl) (meth) acrylamide and N- (N') are more preferable. , N'-dimethylaminoethyl) (meth) acrylamide, N- (N', N'-diethylaminoethyl) (meth) acrylamide, N- (N', N'-dimethylaminopropyl) (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate.

Hydroxy group-containing monomer (o):
Hydroxyl-containing aromatic monomers (p-hydroxystyrene, etc.), hydroxyalkyl (2 to 6 carbon atoms) (meth) acrylates [2-hydroxyethyl (meth) acrylate, and 2- or 3-hydroxypropyl (meth) acrylate. Etc.], mono- or bis-hydroxyalkyl (1 to 4 carbon atoms) substituted (meth) acrylamide [N, N-bis (hydroxymethyl) (meth) acrylamide, N, N-bis (hydroxypropyl) (meth) acrylamide , N, N-bis (2-hydroxybutyl) (meth) acrylamide, etc.], vinyl alcohol, alkenol with 3 to 12 carbon atoms [(meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol and 1 -Undecenol, etc.], alkenemonool or alkenediol having 4 to 12 carbon atoms [1-buten-3-ol, 2-butene-1-ol, 2-butene-1,4-diol, etc.], hydroxyalkyl (carbon) Numbers 1 to 6) Alkenes (3 to 10 carbon atoms) ethers (2-hydroxyethylpropenyl ethers, etc.), polyhydric (3 to 8 valent) alcohols (glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, sugars, sugars, etc. ) Alkene (3 to 10 carbon atoms) ether or (meth) acrylate [sugar (meth) allyl ether, etc.];
Polyoxyalkylene glycol (alkylene group having 2 to 4 carbon atoms, degree of polymerization 2 to 50), polyoxyalkylene polyol [Polyoxyalkylene ether of the above 3 to 8 valent alcohol (alkylene group having 2 to 4 carbon atoms, degree of polymerization) 2 to 100)], mono (meth) acrylate of alkyl (carbon number 1 to 4) ether of polyoxyalkylene glycol or polyoxyalkylene polyol [polyethylene glycol (Mn: 100 to 300) mono (meth) acrylate, polypropylene glycol ( Mn: 130-500) Mono (meth) acrylate, methoxypolyethylene glycol (Mn: 110-310) (meth) acrylate, lauryl alcohol ethylene oxide adduct (2-30 mol) (meth) acrylate and mono (meth) acrylic acid Polyoxyethylene (Mn: 150-230) sorbitan, etc.] and the like;

In the copolymer (A), the weight ratio of the monomer (g) among the constituent monomers of (A) is a single amount constituting (A) from the viewpoint of the HTHS viscosity lowering effect and the viscosity index improving effect. Based on the total weight of the body, it is preferably 30% by weight or less, more preferably 1 to 20% by weight.
In the copolymer (A), the weight ratio of the monomer (h) among the constituent monomers of (A) is a single amount constituting (A) from the viewpoint of the HTHS viscosity lowering effect and the viscosity index improving effect. Based on the total weight of the body, it is preferably 20% by weight or less, more preferably 1 to 15% by weight.
In the copolymer (A), the weight ratio of the monomer (i) to the constituent monomers of (A) is preferably 10% by weight or less, more preferably 10% by weight, from the viewpoint of the effect of reducing the HTHS viscosity at the effective temperature. Is 1 to 5% by weight.
In the copolymer (A), the weight ratio of the monomer (j) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 5% by weight or less, more preferably 0.5 to 2% by weight.
In the copolymer (A), the weight ratio of the monomer (k) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 20% by weight or less, more preferably 1 to 10% by weight.
In the copolymer (A), the weight ratio of the monomer (l) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 5% by weight or less, more preferably 0.1 to 2% by weight.
In the copolymer (A), the weight ratio of the monomer (m) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 1% by weight or less, more preferably 0.01 to 0.5% by weight.
In the copolymer (A), the weight ratio of the monomer (n) among the constituent monomers of (A) is determined from the viewpoint of the effect of lowering the HTHS viscosity and the effect of improving the viscosity index at the execution temperature. Based on the total weight of the constituent monomers, it is preferably 50% by weight or less, more preferably 1 to 40% by weight.
In the copolymer (A), the weight ratio of the monomer (o) among the constituent monomers of (A) is a single amount constituting (A) from the viewpoint of the HTHS viscosity lowering effect and the viscosity index improving effect. Based on the total weight of the body, it is preferably 40% by weight or less, more preferably 1 to 30% by weight.

The Mw of the copolymer (A) is preferably 5,000 to 2,000,000. When the Mw of the copolymer (A) is 5,000 or more, the effect of improving the viscosity-temperature characteristics and the effect of improving the viscosity index tend to be good. In addition, the amount of the viscosity index improver added is not too large, which is advantageous in terms of cost. When it is 2,000,000 or less, the shear stability tends to be good.

The more preferable range of Mw of the copolymer (A) varies depending on the use of the viscosity index improver and the lubricating oil composition, and is the range shown in Table 2.

The Mn of the copolymer (A) is preferably 2,500 or more, more preferably 5,000 or more, particularly preferably 7,500 or more, and most preferably 15,000 or more. Further, it is preferably 1,000,000 or less, more preferably 850,000 or less, and particularly preferably 700,000 or less.
When Mn is 2,500 or more, the effect of improving the viscosity temperature characteristic and the effect of improving the viscosity index tend to be good. In addition, the amount of the viscosity index improver added is not too large, which is advantageous in terms of cost. When Mn is 1,000,000 or less, the shear stability tends to be good.
The molecular weight distribution (Mw / Mn) of the copolymer (A) is preferably 1.0 to 4.0, more preferably 1.5 to 3.5, from the viewpoint of shear stability.
The measurement conditions for the Mw, Mn and molecular weight distribution of the copolymer (A) are the same as the measurement conditions for the Mw and Mn of the monomer (c).

The copolymer (A) can be obtained by a known production method, and specific examples thereof include a method obtained by solution-polymerizing the above-mentioned monomer in a solvent in the presence of a polymerization catalyst.
Examples of the solvent include toluene, xylene, alkylbenzene having 9 to 10 carbon atoms, methylethylketone, hydrocarbon oil (mineral oil and the like), synthetic oil and the like, and mixtures thereof.
Examples of the polymerization catalyst include azo catalysts (2,2'-azobis (2-methylbutyronitrile) and 2,2'-azobis (2,4-dimethylvaleronitrile)) and peroxide catalysts (benzoyl peroxide). Oxides, cumyl peroxides, lauryl peroxides, etc.) and redox-based catalysts (mixtures of benzoyl peroxide and tertiary amines, etc.) can be mentioned. Further, if necessary for adjusting the molecular weight, a known chain transfer agent (alkyl mercaptan having 2 to 20 carbon atoms, etc.) can also be used.
The polymerization temperature is preferably 25 to 140 ° C, more preferably 50 to 120 ° C. In addition to the above solution polymerization, the copolymer (A) can be obtained by bulk polymerization, emulsion polymerization or suspension polymerization.
The polymerization form of the copolymer (A) may be either a random addition polymer or an alternate copolymer, and may be either a graft copolymer or a block copolymer.

The SP value of the copolymer (A) is preferably 9.0 to 10.0 (cal / cm ³ ) ^1/2 , more preferably 9.1 to 9.7 (cal / cm ³ ) ^1/2 . Yes, and particularly preferably 9.2 to 9.5 (cal / cm ³ ) ^1/2 .
When the SP value of the copolymer (A) is 9.0 (cal / cm ³ ) ^1/2 or more, the kinematic viscosity and viscosity index at 40 ° C. are good, and 10.0 (cal / cm ³ ) ^1/2 . If it is as follows, it tends to be easily dissolved in the base oil, although it depends on the SP value of the base oil.
The SP value of the copolymer (A) is the structural unit derived from each monomer constituting (A) (a structure in which a vinyl group becomes a single bond by a polymerization reaction) using the method for calculating the SP value. The SP value is calculated, and the additive average value is meant based on the weight fraction of each constituent monomer at the time of charging. For example, when the monomer is methyl methacrylate, the structural unit derived from methyl methacrylate is as an atomic group, since CH ₃ is 2, CH ₂ is 1, C is 1, and CO ₂ is 1. From the following formula, it can be seen that the SP value of the structural unit derived from methyl methacrylate is 9.933 (cal / cm ³ ) ^1/2 . By the same calculation, it can be seen that the SP value of the structural unit derived from ethyl methacrylate is 9.721 (cal / cm ³ ) ^1/2 .
ΣΔe _i = 1125 × 2 + 1180 + 350 + 4300 = 8080
ΣΔv _i = 33.5 × 2 + 16.1-19.2 + 18.0 = 81.9
δ = (8080 / 81.9) ^1/2 = 9.933 (cal / cm ³ ) ^1/2
When the copolymer is a polymer of 50% by weight of methyl methacrylate and 50% by weight of ethyl methacrylate, the SP value of the copolymer is the weight of the SP value of the constituent unit derived from each monomer as described below. It is calculated by adding and averaging based on the fraction.
SP value of copolymer = (9.933 × 50 + 9.721 × 50) / 100 = 9.827
The SP value of (A) can be set in a desired range by appropriately adjusting the monomer to be used and the weight fraction. Specifically, the SP value can be reduced by using a large number of monomers having a long carbon number of an alkyl group, and the SP value can be increased by using a large number of monomers having a short carbon number of an alkyl group. can do.

The shear stability index (SSI) of the copolymer (A) is preferably 10 or less, more preferably 5 or less, from the viewpoint of fuel efficiency.
In the present invention, the SSI of the copolymer (A) indicates the decrease in viscosity due to the shearing of the copolymer (A) as a percentage, and is a value measured according to ASTM D6278. More specifically, it is a value calculated by the following mathematical formula (3).
SSI = (Κν ₀ -Κν ₁ ) / (Κν ₀ -Κν _oil ) (3)
In the above formula (3), Κν ₀ is the value of the kinematic viscosity of the sample oil obtained by diluting the viscosity index improver containing the copolymer (A) with mineral oil at 100 ° C., and Κν ₁ is the copolymer. It is the value of the kinematic viscosity at 100 ° C. after passing the sample oil obtained by diluting the viscosity index improver containing (A) into mineral oil through a 30-cycle high shear Bosch diesel injector according to the procedure of ASTM D6278. Further, Κν _oil is a value of the kinematic viscosity of the mineral oil used when diluting the viscosity index improver at 100 ° C.

In addition to the above-mentioned copolymer (A), the viscosity index improver of the present invention may further contain a (meth) acrylic acid alkyl ester (co) polymer (C) other than the copolymer (A). , (Co) It is preferable to contain the polymer (C) from the viewpoint of low temperature viscosity.
The (co) polymer (C) includes a (co) polymer containing no monomer (c), for example, an alkyl (meth) acrylate having a linear or branched alkyl group having 9 to 36 carbon atoms. Examples thereof include a (co) polymer containing an ester (f) as an essential constituent monomer. Specifically, (meth) acrylic acid n-dodecyl, (meth) acrylic acid n-tetradecyl, (meth) acrylic acid n-hexadecyl and (meth) acrylic acid n-octadecyl copolymer, (meth) acrylic acid n. -Octadecyl / (meth) acrylate n-dodecyl (molar ratio 10 to 30/90 to 70) copolymer, (meth) acrylate n-tetradecyl / (meth) acrylate n-dodecyl (molar ratio 10 to 30 /) 90-70) Copolymer, n-hexadecyl (meth) acrylate / n-dodecyl (meth) acrylate / methyl (meth) acrylate (molar ratio 20-40 / 55-75 / 0-10) copolymer And n-dodecyl acrylate / n-dodecyl methacrylate (molar ratio 10 to 40/90 to 60) copolymers and the like, these may be used alone or in combination of two or more.

The content of the (co) polymer (C) is preferably 0.01 to 30% by weight, more preferably 0.01 to 10% by weight, based on the weight of the copolymer (A) from the viewpoint of low temperature viscosity. %.

The Mw of the (co) polymer (C) is preferably 5,000 to 100,000, more preferably 10,000 to 80,000 from the viewpoint of lowering the pour point temperature.
The SP value of the (co) polymer (C) is preferably 7.0 to 10, more preferably 8.0 to 9.5, from the viewpoint of solubility in the base oil.
The measurement conditions for Mw of the (co) polymer (C) are the same as the measurement conditions for Mw of the monomer (c). Further, the SP value of the (co) polymer (C) is a structural unit derived from each monomer constituting (C) using the method for calculating the SP value (vinyl group becomes a single bond by the polymerization reaction). The SP value of the structure) is calculated, and it means a value added to and averaged based on the weight fraction of each constituent monomer at the time of charging.

From the viewpoint of handleability, the viscosity index improver of the present invention preferably contains the copolymer (A) in an amount of 0.1 to 40% by weight based on the weight of the viscosity index improver.
In the viscosity index improver of the present invention, from the viewpoint of low temperature viscosity, it is preferable to contain the (co) polymer (C) in an amount of 0.01 to 10% by weight based on the weight of the viscosity index improver.

In the present invention, the viscosity index improver may contain a base oil (B). When the base oil (B) is contained, it is preferable because it is easy to further dilute it with the base oil or mix it with an additive described later when the lubricating oil composition is produced, and it is easy to produce the lubricating oil composition.
The base oil (B) is not particularly limited. Oils, etc.), synthetic lubricating oils [hydrogen-based synthetic lubricating oils (poly α-olefin-based synthetic lubricating oils, GTL base oils, etc.)], etc.}, non-hydrogenated synthetic oils (ester-based synthetic lubricating oils, ether-based synthetic lubricating oils, etc.) Oils, silicon-based synthetic lubricating oils, etc.) and mixtures thereof. Of these, hydrocarbon oils are preferable from the viewpoint of solubility, and mineral oils, polyα-olefin synthetic lubricating oils (PAO oils), and GTL base oils are more preferable.

The kinematic viscosity of the base oil (B) at 100 ° C. (measured by JIS-K2283) is preferably 1 to 15 mm ² / s, more preferably 1 to 15 mm 2 / s, from the viewpoint of the viscosity index and low temperature fluidity of the lubricating oil composition. It is 2 to 5 mm ² / s.
The viscosity index of the base oil (B) (measured by JIS-K2283) is preferably 100 or more from the viewpoint of the viscosity index of the lubricating oil composition and the low temperature fluidity.

The cloud point of the base oil (B) (measured by JIS-K2269) is preferably −5 ° C. or lower, more preferably −15 ° C. or lower. When the cloud point of the base oil is within this range, the low temperature viscosity of the lubricating oil composition tends to be good.

By using the viscosity index improver of the present invention, it is possible to obtain a lubricating oil composition having low kinematic viscosity and HTHS viscosity at 40 to 80 ° C. Therefore, the lubricating oil composition containing the viscosity index improver of the present invention can be obtained. Gear oil (differential oil, industrial gear oil, etc.), MTF, transmission oil [ATF, DCTF, belt-CVTF, etc.], traction oil (toroidal-CVTF, etc.), shock absorber oil, power steering oil, hydraulic oil (construction machinery) It can be suitably used for hydraulic oil, industrial hydraulic oil, etc.) and engine oil (for gasoline and diesel).

<Lubricating oil composition>
The lubricating oil composition of the present invention comprises the viscosity index improver of the present invention and the base oil (B). From the group consisting of detergents, dispersants, antioxidants, oiliness improvers, flow point lowering agents, friction and wear modifiers, extreme pressure agents, defoaming agents, anti-emulsifiers, metal deactivators and corrosion inhibitors, if necessary. It may contain at least one additive of choice.
The content of the copolymer (A) in the lubricating oil composition of the present invention is preferably 0.1 to 20% by weight based on the weight of the lubricating oil composition from the viewpoint of fuel efficiency.
The content of the (co) polymer (C) in the lubricating oil composition of the present invention is preferably 0.01 to 5% by weight based on the weight of the lubricating oil composition from the viewpoint of low temperature viscosity.
The content of the base oil (B) in the lubricating oil composition of the present invention is preferably 45% by weight or more, more preferably 50% by weight or more, and 99.8% by weight, based on the weight of the lubricating oil composition. % Or less, more preferably 99.79% by weight or less.

The SP value {(cal / cm ³ ) ^1/2 } of the base oil (B) in the lubricating oil composition is preferably 6 to 9, more preferably 7 to 9, from the viewpoint of the effect of improving the viscosity index. Particularly preferably, it is 8 to 9.
When a mixture of a plurality of hydrocarbon compounds such as mineral oil is used as the base oil (B), the approximate composition is obtained by measuring the molecular weight by GPC and analyzing the molecular structure by ¹ H-NMR and ¹³ C-NMR. The components and their molecular structure can be understood, and the SP value of the base oil (B) can be calculated by the additive average based on the mole fraction.
The absolute value {(cal / cm ³ ) ^1/2 } of the difference between the SP value of the copolymer (A) and the SP value of the base oil (B) in the lubricating oil composition is 0.5 to 1.5. Is preferable, and more preferably 0.6 to 1.2. When it is 1.5 or less, (A) tends to dissolve easily in (B), and when it is 0.5 or more, the temperature dependence of the behavior of the polymer chain of (A) in (B) becomes. It tends to be good, and the kinematic viscosity at 40 to 80 ° C. and the effective viscosity (HTHS viscosity) under high shear tend to be good.

When the lubricating oil composition is used as an engine oil, the copolymer (A) is added to the base oil (B) having a kinematic viscosity at 100 ° C. of 4 to 10 mm ² / s based on the weight of (B). Is preferably contained in an amount of 1 to 10% by weight.
When used as a gear oil, a base oil (B) having a kinematic viscosity at 100 ° C. of 2 to 10 mm ² / s is mixed with a copolymer (A) by 3 to 20 weight based on the weight of (B). % Is preferably contained.
When used as an automatic transmission fluid (ATF, belt-CVTF, etc.), the base oil (B) having a kinematic viscosity of 2 to 6 mm ² / s at 100 ° C. is copolymerized with respect to the weight of (B). Those containing 3 to 20% by weight of the coalescence (A) are preferable.
When used as a traction oil, a base oil (B) having a kinematic viscosity at 100 ° C. of 1 to 5 mm ² / s and a copolymer (A) of 0.5 to 0.5 based on the weight of (B). Those containing 10% by weight are preferable.

When the lubricating oil composition is used as an engine oil (0W-16), the viscosity index of the lubricating oil composition is preferably 190 or more, more preferably 195 to 249, from the viewpoint of fuel saving.
When the lubricating oil composition is used as an engine oil (0W-20), the viscosity index of the lubricating oil composition is preferably 230 or more, more preferably 235 to 295, from the viewpoint of fuel saving.

When the lubricating oil composition is used as an engine oil (0W-16), the 60 ° C. HTHS viscosity of the lubricating oil composition is preferably 8.5 to 9.2 (mPa · s) from the viewpoint of fuel efficiency. , More preferably 8.7 to 9.1 (mPa · s).
When the lubricating oil composition is used as an engine oil (0W-20), the 60 ° C. HTHS viscosity of the lubricating oil composition is preferably 9.0 to 10.2 (mPa · s) from the viewpoint of fuel efficiency. , More preferably 9.1 to 9.6 (mPa · s).

When the lubricating oil composition is used as an engine oil (0W-16), the HTHS viscosity ratio (60 ° C./100 ° C.) between the 100 ° C. HTHS viscosity and the 60 ° C. HTHS viscosity of the lubricating oil composition is fuel-saving. From the viewpoint, 2.0 to 2.3 is preferable, and 2.1 to 2.2 is more preferable.
When the lubricating oil composition is used as an engine oil (0W-20), the HTHS viscosity ratio (60 ° C./100 ° C.) between the 100 ° C. HTHS viscosity and the 60 ° C. HTHS viscosity of the lubricating oil composition is fuel-saving. From the viewpoint, it is preferably 1.9 to 2.2, more preferably 2.0 to 2.1.

When the lubricating oil composition is used as an engine oil (0W-16), the 40 ° C. kinematic viscosity of the lubricating oil composition is 23.0 to 26.1 (mm ² / s) from the viewpoint of fuel saving. It is preferable, more preferably 23.5 to 26.0 (mm ² / s).
When the lubricating oil composition is used as an engine oil (0W-20), the 40 ° C. kinematic viscosity of the lubricating oil composition is 25.0 to 28.0 (mm ² / s) from the viewpoint of fuel saving. It is preferable, more preferably 25.0 to 27.0 (mm ² / s).

When the lubricating oil composition is used as an engine oil (0W-16), the kinematic viscosity ratio (40 ° C./100 ° C.) of the 100 ° C. kinematic viscosity and the 40 ° C. kinematic viscosity of the lubricating oil composition is fuel-saving. From the viewpoint, 3.5 to 4.2 is preferable, and 3.7 to 4.2 is more preferable.
When the lubricating oil composition is used as an engine oil (0W-20), the kinematic viscosity ratio (40 ° C./100 ° C.) of the 100 ° C. kinematic viscosity and the 40 ° C. kinematic viscosity of the lubricating oil composition is fuel-saving. From the viewpoint, 3.0 to 3.85 is preferable, and 3.3 to 3.85 is more preferable.

Examples of the additive in the present invention include the following.
(1) Cleaner:
Basic, hyperbasic or neutral metal salts [superbasic or alkaline earth metal salts of sulfonates (petroleum sulfonates, alkylbenzene sulfonates, alkylnaphthalen sulphonates, etc.)], salicylates, phenates, naphthenates, etc. , Carbonates, Phosphonates and mixtures thereof;
(2) Dispersant:
Succinimides (bis- or mono-polybutenyl succinimides), Mannich condensates, borates, etc .;
(3) Antioxidant:
Hindered phenols and aromatic secondary amines, etc .;
(4) Oiliness improver:
Long-chain fatty acids and their esters (oleic acid and oleic acid esters, etc.), long-chain amines and their amides (oleylamine, oleylamide, etc.), etc.;
(5) Pour point lowering agent Polyalkyl methacrylate, ethylene-vinyl acetate copolymer, etc.;
(6) Friction wear adjuster:
Molybdenum-based and zinc-based compounds (molybdenum dithiophosphate, molybdenum dithiocarbamate, zinc dialkyldithiophosphate, etc.), etc.;
(7) Extreme pressure agent:
Sulfur-based compounds (mono or disulfide, sulfoxide and sulfur phosphide compounds), phosphide compounds and chlorinated compounds (chlorinated paraffin, etc.);
(8) Antifoaming agent:
Silicone oil, metal soap, fatty acid ester, phosphate compound, etc .;
(9) Anti-emulsifier:
Quaternary ammonium salts (tetraalkylammonium salts, etc.), sulfated oils and phosphates (polyoxyethylene-containing nonionic surfactants, phosphates, etc.), hydrocarbon solvents (toluene, xylene, ethylbenzene, etc.), etc.;
(10) Metal deactivator Nitrogen atom-containing compound (benzotriazole, etc.), nitrogen atom-containing chelate compound (N, N'-disalitidene-1,2-diaminopropane, etc.), nitrogen / sulfur atom-containing compound (2- (n) -Dodecylthio) benzimidazole, etc.);
(11) Corrosion inhibitor:
Nitrogen atom-containing compounds (benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate, etc.) and the like.

Only one of these additives may be added, or two or more of these additives may be added as required. Further, a compound containing these additives may be referred to as a performance additive or a package additive, and may be added.
The content of each of these additives is preferably 0.1 to 15% by weight based on the total amount of the lubricating oil composition. The total content of each additive is preferably 0.1 to 30% by weight, more preferably 0.3 to 20% by weight, based on the total amount of the lubricating oil composition.

The lubricating oil composition of the present invention includes gear oil (differential oil, industrial gear oil, etc.), MTF, transmission oil [ATF, DCTF, belt-CVTF, etc.], traction oil (toroidal-CVTF, etc.), shock absorber oil, and the like. It is suitably used for power steering oil, hydraulic oil (hydraulic hydraulic oil for construction machinery, industrial hydraulic oil, etc.) and engine oil (for gasoline and diesel).

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The ratio of 1,2-butylene groups in the constituent units of the hydrocarbon polymer was determined by analyzing the polymer by ¹³ C-NMR and using the above formula (1) by the above method, and the isobutylene groups and 1,2. The total ratio of -butylene groups was determined by analyzing the polymer by ¹³ C-NMR and using the above formula (2) by the above method.
The molar ratio of 1,2-adduct / 1,4-adduct in the hydrocarbon polymer (molar ratio in the structure derived from butadiene) was determined by analyzing the polymer by ¹³ C-NMR and using the above formula (1). From the value of the integrated value B and the value of the integrated value C used, it was obtained by the following mathematical formula (3).
1,2-Additive / 1,4-Adduct molar ratio = {100 x integrated value B x 2 / integrated value C} / {100- (100 x integrated value B x 2 / integrated value C)} (3 )

（１）の構造
ΣΔｅ_ｉ＝１１２５（ＣＨ_３）＋１１８０（ＣＨ_２）＋３５０（Ｃ）＋４３００（ＣＯ_２）＝６９５５
ΣΔｖ_ｉ＝３３．５（ＣＨ_３）＋１６．１（ＣＨ_２）－１９．２（Ｃ）＋１８．０（ＣＯ_２）＝４８．４
（２）の構造
ΣΔｅ_ｉ＝１１８０（ＣＨ_２）×２＋８００（Ｏ）＝３１６０
ΣΔｖ_ｉ＝１６．１（ＣＨ_２）×２＋３．８（Ｏ）＝３６
（３）の構造
ΣΔｅ_ｉ＝１１８０（ＣＨ_２）×２＋１１２５（ＣＨ_３）＋８２０（ＣＨ）＝４３０５
ΣΔｖ_ｉ＝１６．１（ＣＨ_２）×２＋３３．５（ＣＨ_３）－１．０（ＣＨ）＝６４．７
（４）の構造
ΣΔｅ_ｉ＝１１８０（ＣＨ_２）×４＝４７２０
ΣΔｖ_ｉ＝１６．１（ＣＨ_２）×４＝６４．４
ここで、１，２－ブチレン基及び１，４－ブチレン基の合計個数は下記である。
１，２－ブチレン基（３の構造）及び１，４－ブチレン基（４の構造）の合計個数＝（６８００（ｃ－１のＭｎ）－８５（（１）の構造）－４４（（２）の構造））／５６＝１１９．１２５
したがって、（ａ－１）に由来する構成単位のパラメータは下記である。
ΣΔｅ_ｉ＝６９５５＋３１６０＋４３０５×１１９．１２５×０．４５＋４７２０×１１９．１２５×０．５５＝５５０１３８．４
ΣΔｖ_ｉ＝４８．４＋３６＋６４．７×１１９．１２５×０．４５＋６４．４×１１９．１２５×０．５５＝７７７２．１３１９
ＳＰ値＝（ΣΔｅ_ｉ／ΣΔｖ_ｉ）^１／２＝（５５０１３８．４／７７７２．１３１９）^１／２＝８．４１３ <Manufacturing example 1>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 75 parts by weight of 1,3-butadiene, and 2 parts by weight of n-butyllithium were charged in a pressure resistant reaction vessel made of SUS equipped with a temperature controller and a stirrer. After that, the polymerization was carried out at a polymerization temperature of 70 ° C.
After the polymerization rate became almost 100%, 2 parts by weight of ethylene oxide was added, and the mixture was reacted at 50 ° C. for 3 hours. To stop the reaction, 50 parts by weight of water and 25 parts by weight of a 1N-hydrochloric acid aqueous solution were added, and the mixture was stirred at 80 ° C. for 1 hour. The organic phase of the reaction solution was recovered by a separating funnel, the temperature was raised to 70 ° C., and the solvent was removed under a reduced pressure of 0.027 to 0.040 MPa over 2 hours.
The obtained polybutadiene containing a hydroxyl group at one end was transferred to a reaction vessel equipped with a temperature controller, a stirrer, and a hydrogen introduction tube, and 150 parts by weight of tetrahydrofuran was added to uniformly dissolve the polybutadiene. After pouring a suspension in which 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran are mixed in advance, hydrogen is supplied to the liquid at a flow rate of 30 mL / min from a hydrogen introduction tube and reacted at room temperature for 8 hours. rice field. After that, palladium carbon is removed by filtration, the temperature of the obtained filtrate is raised to 70 ° C., and tetrahydrofuran is removed under a reduced pressure of 0.027 to 0.040 MPa, and a one-terminal hydroxyl group-containing polymer (Y1-) of hydrogenated polybutadiene is removed. 1) (Total ratio of isobutylene group and 1,2-butylene group; 45 mol%, 1,2-addition / 1,4-addition (molar ratio); 45/55, hydroxyl value; 8.0 mgKOH / g , Crystallization temperature; −60 ° C. or lower) was obtained.
245 parts by weight of a hydrogenated polybutadiene single-ended hydroxyl group-containing polymer (Y1-1), 245 parts by weight of methacrylic acid, and 98 parts by weight of a sulfonic acid group-supporting inorganic porous body (acid value 45 mgKOH / g, particle size 240 μm) were added. Esterification was performed at 120 ° C. Next, the sulfonic acid group-supported inorganic porous body was removed by filtration, and the reaction solution was subjected to removal of excess methacrylic acid under reduced pressure (0.027 to 0.040 MPa) to obtain a monomer (c-1). .. The obtained molecular weight of (c-1) was measured by GPC, and the ratio of 1,2-butylene groups was measured by ¹³ C-NMR. The results are Mw = 6,900, Mn = 6,800, 1,2-butylene group ratio = 45 mol%, -X ^2- is a group represented by -O (CH ₂ CH ₂ O) _1- , p. = 0. The SP value of (c-1) was calculated as follows.

Structure of (1) ΣΔe _i = 1125 (CH ₃ ) +1180 (CH ₂ ) +350 (C) +4300 (CO ₂ ) = 6955
ΣΔv _i = 33.5 (CH ₃ ) + 16.1 (CH ₂ ) -19.2 (C) + 18.0 (CO ₂ ) = 48.4
Structure of (2) ΣΔe _i = 1180 (CH ₂ ) × 2 + 800 (O) = 3160
ΣΔv _i = 16.1 (CH ₂ ) × 2 + 3.8 (O) = 36
Structure of (3) ΣΔe _i = 1180 (CH ₂ ) × 2 + 1225 (CH ₃ ) +820 (CH) = 4305
ΣΔv _i = 16.1 (CH ₂ ) × 2 + 33.5 (CH ₃ ) -1.0 (CH) = 64.7
Structure of (4) ΣΔe _i = 1180 (CH ₂ ) × 4 = 4720
ΣΔv _i = 16.1 (CH ₂ ) × 4 = 64.4
Here, the total number of 1,2-butylene groups and 1,4-butylene groups is as follows.
Total number of 1,2-butylene groups (3 structures) and 1,4-butylene groups (4 structures) = (6800 (mn of c-1) -85 (structure of (1))-44 ((2) ) Structure)) / 56 = 119.125
Therefore, the parameters of the structural unit derived from (a-1) are as follows.
ΣΔe _i = 6955 + 3160 + 4305 × 119.125 × 0.45 + 4720 × 119.125 × 0.55 = 550138.4
ΣΔv _i = 48.4 + 36 + 64.7 × 119.125 × 0.45 + 64.4 × 119.125 × 0.55 = 7772.1319
SP value = (ΣΔe _i / ΣΔv _i ) ^1/2 = (550138.4 / 7772.139) ^1/2 = 8.413

<Manufacturing example 2>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 122 parts by weight of 1,3-butadiene, and 2 parts by weight of n-butyllithium in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer. Was charged, and then polymerized at a polymerization temperature of 70 ° C. After that, the same procedure as in Production Example 1 was carried out, and the one-terminal hydroxyl group-containing polymer (Y1-2) of hydride polybutadiene (total ratio of isobutylene group and 1,2-butylene group; 45 mol%, 1,2-addition / adduct / A 1,4-addition (molar ratio); 45/55, hydroxyl value; 8.0 mgKOH / g, crystallization temperature; −60 ° C. or lower) was obtained. Further, esterification of (Y1-2) and methacrylic acid was carried out to obtain a monomer (c-2). The obtained molecular weight of (c-2) was measured by GPC, and the ratio of 1,2-butylene groups was measured by ¹³ C-NMR. The results are Mw = 9,300, Mn = 9,100, 1,2-butylene group ratio = 45 mol%, -X ^2- is a group represented by -O (CH ₂ CH ₂ O) _1- , p. = 0. Further, when calculated in the same manner as in (c-1), the SP value in (c-2) is 8.405.

<Manufacturing example 3>
400 parts by weight of degassed / dehydrated hexane, 1 part by weight of tetrahydrofuran, and 0.4 parts by weight of n-butyllithium were charged in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer, and then -40. Cooled to ° C. To this, 90 parts by weight of 1,3-butadiene liquefied at −40 ° C. was added, and the polymerization was carried out at a polymerization temperature of −40 ° C. After that, the same procedure as in Production Example 1 was carried out, and the one-terminal hydroxyl group-containing polymer (Y1-3) of hydride polybutadiene (total ratio of isobutylene group and 1,2-butylene group; 65 mol%, 1,2-addition / adduct / A 1,4-addition (molar ratio); 65/35, hydroxyl value; 13.1 mgKOH / g, crystallization temperature; −60 ° C. or lower) was obtained. Further, esterification of (Y1-3) and methacrylic acid was carried out to obtain a monomer (c-3). The obtained molecular weight of (c-3) was measured by GPC, and the ratio of 1,2-butylene groups was measured by ¹³ C-NMR. The results are Mw = 6,900, Mn = 6,800, ratio of 1,2-butylene groups = 65 mol%, -X ^2- is a group represented by -O (CH ₂ CH ₂ O) _1- , p. = 0. Further, when calculated in the same manner as in (c-1), the SP value in (c-3) is 8.334.

<Manufacturing example 4>
400 parts by weight of degassed / dehydrated hexane, 1 part by weight of tetrahydrofuran, and 0.4 parts by weight of n-butyllithium were charged in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer, and then -40. Cooled to ° C. To this, 90 parts by weight of 1,3-butadiene liquefied at −40 ° C. was added, and the polymerization was carried out at a polymerization temperature of −40 ° C. After that, the same procedure as in Production Example 1 was carried out, and the one-terminal hydroxyl group-containing polymer (Y1-4) of hydride polybutadiene (total ratio of isobutylene group and 1,2-butylene group; 65 mol%, 1,2-addition / adduct / A 1,4-addition (molar ratio); 65/35, hydroxyl value; 8.0 mgKOH / g, crystallization temperature; −60 ° C. or lower) was obtained. Further, esterification of (Y1-4) and methacrylic acid was carried out to obtain a monomer (c-4). The obtained molecular weight of (c-4) was measured by GPC, and the ratio of 1,2-butylene groups was measured by ¹³ C-NMR. The results are Mw = 9,300, Mn = 9,100, 1,2-butylene group ratio = 65 mol%, -X ^2- is a group represented by -O (CH ₂ CH ₂ O) _1- , p. = 0. Further, when calculated in the same manner as in (c-1), the SP value in (c-4) is 8.325.

<Production Example 5: Production of Copolymer (C)>
75 parts of base oil (kinematic viscosity at 100 ° C.: 4.2 mm ² / s, viscosity index: 128) was placed in a reaction vessel equipped with a stirrer, heating / cooling device, thermometer, dropping funnel, nitrogen blowing tube and depressurizing device. Into another glass beaker, 244 parts by weight of n-dodecyl methacrylate, 24 parts by weight of n-tetradecyl methacrylate, 41 parts by weight of n-hexadecyl methacrylate, 16 parts by weight of n-octadecyl methacrylate, as a chain transfer agent. Add 0.6 parts by weight of dodecyl mercaptan, 0.5 parts by weight of 2,2-azobis (2,4-dimethylvaleronitrile) and 0.2 parts by weight of 2,2-azobis (2-methylbutyronitrile). , Stirred at 20 ° C. and mixed to prepare a monomer solution, which was put into a dropping funnel.
After performing nitrogen substitution in the gas phase part of the reaction vessel (gas phase oxygen concentration: 100 ppm or less), the monomer solution was added dropwise over 2 hours while maintaining the temperature inside the closed system at 70 to 85 ° C. After aging at 85 ° C. for 2 hours from the end, the temperature was raised to 120 to 130 ° C., and the unreacted monomer was removed under reduced pressure (0.027 to 0.040 MPa) at the same temperature over 2 hours. A copolymer composition (C-1) containing 65% by weight of the copolymer (C) in oil was obtained. The Mw of the obtained copolymer (C) was 53,000, and the SP value was 9.0.

<Examples 1 to 11, 18 to 21, Comparative Examples 1 to 5>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer and a nitrogen introduction tube, 375 parts by weight of the base oil shown in Tables 3 to 5 and 125 parts by weight of the monomer formulation shown in Tables 3 to 5 are placed in a reaction vessel. , 2'-azobis (2,4-dimethylvaleronitrile) 0.2 part by weight and 2,2'-azobis (2-methylbutyronitrile) are added in the amounts shown in Tables 3 to 5, and nitrogen substitution (gas) is added. After the phase oxygen concentration (100 ppm) was carried out, the temperature was raised to 76 ° C. with stirring under sealing, and the polymerization reaction was carried out at the same temperature for 4 hours. After raising the temperature to 120 to 130 ° C., the unreacted monomer was removed under reduced pressure (0.027 to 0.040 MPa) over 2 hours at the same temperature, and the copolymers (A-2) to (A-11) were removed. , (A-18) to (A-21) and (A'-1) to (A'-5) obtained those having different Mw and molecular weight distributions by adjusting the catalytic amount shown in Tables 3 to 5. .. Viscosity index improvers (R-1) to (R-) containing 25% by weight of the obtained copolymers (A-1) to (A-11) and (A'-1) to (A'-5). 11), Polymers (A-1) to (A-11), (A-18) to (A) in (R-18) to (R-21) and (S-1) to (S-5). The SP values of -21) and (A'-1) to (A'-5) were calculated by the above method, and Mw and Mn were measured by the above method. The results of Mw and molecular weight distribution (Mw / Mn) are shown in Tables 3-5.

<Examples 12 to 17>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer and a nitrogen introduction tube, 370 parts by weight of the base oil shown in Table 4, 125 parts by weight of the monomer formulation shown in Table 4, 2,2'-. Add 0.2 parts by weight of azobis (2,4-dimethylvaleronitrile) and 2,2'-azobis (2-methylbutyronitrile) in the amounts shown in Table 4, and add nitrogen substitution (gas phase oxygen concentration 100 ppm). After that, the temperature was raised to 76 ° C. with stirring under sealing, and the polymerization reaction was carried out at the same temperature for 4 hours. After raising the temperature to 120 to 130 ° C., the unreacted monomer was removed under reduced pressure (0.027 to 0.040 MPa) over 2 hours at the same temperature, and the copolymers (A-12) to (A-17) were removed. Got The SP values of the obtained copolymers (A-12) to (A-17) were calculated by the above method, and Mw and Mn were measured by the above method. The results of Mw and molecular weight distribution (Mw / Mn) are shown in Table 4.
Further, 5 parts by weight of the copolymer composition (C-1) obtained in Production Example 5 was added, and 25% by weight of the copolymers (A-12) to (A-17) were added, respectively, and the copolymer (C) was added. ) In an amount of 0.81% by weight to obtain viscosity index improvers (R-12) to (R-17).

The compositions of the monomers (a) to (o) and the base oil shown in Tables 3 to 5 are as described below.
(A-1): Ethyl methacrylate (a-2): Propyl methacrylate (a-3): Isopropyl methacrylate (b-1): n-butyl methacrylate (b-2): Isobutyl methacrylate (c-) 1): Methacrylic acid esterified product of (Y1-1) [Mn: 6,800]
(C-2): Methacrylic acid esterified product of (Y1-2) [Mn: 9,100]
(C-3): Methacrylic acid esterified product of (Y1-3) [Mn: 6,800]
(C-4): Methacrylic acid esterified product of (Y1-4) [Mn: 9,100]
(D-1): ethoxyethyl methacrylate (d-2): n-butoxyethyl methacrylate (e-1): methyl methacrylate (f1-1): a linear and branched alkyl methacrylate mixture (SHELL) having 12 to 13 carbon atoms. Methacrylic acid esterified product of NEODOL23 (mixture of weight ratio = linear C12: branched C12: linear C13: branched C13 = 40:10:40:10))
(F1-2): Linear and branched alkyl methacrylate mixture having 14 to 15 carbon atoms (NEODOL45 manufactured by SHELL (weight ratio = linear C14: branched C14: linear C15: branched C15 = 40: 10: 40: 10). Methacrylic acid esterified product (f1-3): n-hexadecyl methacrylate (f1-4): n-octadecyl methacrylate (f2-1): 2-n-decyltetradecyl methacrylate (f2-2) : 2-n-Dodecylhexadecyl methacrylate (f2-3): 2-n-tetradecyl octadecyl methacrylate (g-1): Methacrylic acid oxyethyl phosphate (n-1): N, N-dimethylaminoethyl methacrylate (O-1): 2-Hydroxyethyl Methacrylic Mineral Oil 1: SK Lubricants, product name "Yubase 4" (kinematic viscosity at 100 ° C.: 4.24 mm ² / s, viscosity index: 122, SP value: 8.3 )
Mineral oil 2: Made by SK Lubricants, product name "Yubase 3" (kinematic viscosity at 100 ° C: 3.06 mm ² / s, viscosity index: 106, SP value: 8.3)
PAO oil 1: ExxonMobil, product name "Spectrasin PAO4" (100 ° C kinematic viscosity: 4.1 mm ² / s, viscosity index: 118, SP value: 8.4)
GTL oil 1: Made by Shell, product name "Shell Risella X 420", GTL4 (Fischer-Tropsch-derived base oil) (100 ° C. kinematic viscosity: 4.1 mm ² / s, viscosity index: 131, SP value: 8.3 )

Solubility of Copolymer (A) in Base Oil The appearances of the viscosity index improvers (R-1) to (R-21) and (S-1) to (S-5) were visually observed and described as follows. The base oil solubility was evaluated by the evaluation criteria.
[Evaluation criteria]
◯: Appearance is uniform and there is no insoluble material of the copolymer ×: Appearance is non-uniform and insoluble matter of the copolymer is recognized.

<Evaluation of Examples 22 to 42 and Comparative Examples 6 to 9: 0 W-20>
90 parts by weight of base oil A (hydrogenated oil, kinematic viscosity at 100 ° C.: 4.20 mm ² / s, viscosity index: 128, SP value: 8.3) and package additive in a stainless steel container equipped with a stirrer. (Infineum P5741) Add 10 parts by weight, and add a viscosity index improver (R-1) so that the HTHS viscosity at 150 ° C. of the obtained lubricating oil composition becomes 2.60 ± 0.05 (mPa · s). )-(R-21) or (S-1)-(S-3), (S-5), and the lubricating oil compositions (V-1)-(V-21) and (W-1). ~ (W-4) was obtained.
Shear stability (BOSCH SSI), HTHS viscosity (150 ° C, 100 ° C, 80 ° C, 60 ° C) of the lubricating oil compositions (V-1) to (V-21) and (W-1) to (W-4). ), The kinematic viscosity (100 ° C, 80 ° C, 60 ° C, 40 ° C), the viscosity index, and the low temperature viscosity (-40 ° C) were measured by the following methods. The results are shown in Table 6.
The viscosity index improver (S-4) was not evaluated because the copolymer (A'-4) had low solubility in the base oil.

<Evaluation of Examples 43 to 63 and Comparative Examples 10 to 13: 0W-16>
90 parts by weight of base oil A (hydrogenated oil, kinematic viscosity at 100 ° C.: 4.20 mm ² / s, viscosity index: 128, SP value: 8.3) and package additive in a stainless steel container equipped with a stirrer. (Infineum P5741) Add 10 parts by weight, and add a viscosity index improver (R-1) so that the HTHS viscosity at 150 ° C. of the obtained lubricating oil composition becomes 2.30 ± 0.05 (mPa · s). )-(R-21) or (S-1)-(S-3), (S-5), and the lubricating oil compositions (V-22)-(V-42) and (W-5). ~ (W-8) was obtained.
Shear stability (BOSCH SSI), HTHS viscosity (150 ° C, 100 ° C, 80 ° C, 60 ° C) of the lubricating oil compositions (V-22) to (V-42) and (W-5) to (W-8). ), The kinematic viscosity (100 ° C, 80 ° C, 60 ° C, 40 ° C), the viscosity index, and the low temperature viscosity (-40 ° C) were measured by the following methods. The results are shown in Table 7.
The viscosity index improver (S-4) was not evaluated because the copolymer (A'-4) had low solubility in the base oil.

<Measuring method of HTHS viscosity of lubricating oil composition>
Measured at 60 ° C, 80 ° C, 100 ° C and 150 ° C by the method of ASTM D 4683. The lower the HTHS viscosity at 100 ° C, 80 ° C and 60 ° C, the better.

<Method of measuring kinematic viscosity of lubricating oil composition and method of calculating viscosity index>
The kinematic viscosities of 40 ° C., 60 ° C., 80 ° C. and 100 ° C. were measured by the method of JIS-K2283 and calculated by the method of JIS-K2283. The lower the kinematic viscosity and the larger the value of the viscosity index, the higher the effect of improving the viscosity index.

<Measurement method and calculation method of shear stability (BOSCH SSI) of lubricating oil composition>
It was measured by the method of ASTM D 6278 and calculated by the method of ASTM D 6022. The smaller the value, the higher the shear stability.

<Method for measuring low temperature viscosity of lubricating oil composition>
The viscosity at −40 ° C. was measured by the method of JPI-5S-42-2004. The smaller the value, the lower the low temperature viscosity and the better.

From the results in Tables 6 and 7, the lubricating oil composition containing the viscosity index improver of the present invention has a kinematic viscosity at 40 to 80 ° C. and an HTHS viscosity at 60 to 100 ° C., a viscosity index, and shear stability. The low-temperature viscosity is also excellent, and it can be seen that it is excellent as a lubricating oil composition.
On the other hand, the lubricating oil compositions of Comparative Examples 6 and 10 containing the copolymer not containing the monomer (a) as the constituent monomer are substantially the same except that the monomer (a) is contained as the constituent monomer. It can be seen that the kinematic viscosity at 40 to 80 ° C. and the HTHS viscosity at 60 to 100 ° C. are higher, the viscosity index is lower, and the lubricating oil composition is inferior as compared with Example 22 or 43. Further, the lubricating oil compositions of Comparative Examples 7 and 11 containing the copolymer not containing the monomer (b) as the constituent monomer are the same except that the monomer (b) is contained as the constituent monomer. It can be seen that the kinematic viscosity at 40 to 80 ° C. and the HTHS viscosity at 60 to 100 ° C. are higher, the viscosity index is lower, and the lubricating oil composition is inferior as compared with Example 26 or 47. Further, the lubricating oil compositions of Comparative Examples 8 and 12 containing the copolymer not containing the monomer (c) as the constituent monomer are the same except that the monomer (c) is contained as the constituent monomer. Compared with Example 22 or 43, the kinematic viscosity at 40 to 80 ° C. and the HTHS viscosity at 60 to 100 ° C. are higher, the viscosity index is lower, the shear stability is higher, the low temperature viscosity is higher, and as a lubricating oil composition. It turns out to be inferior. Further, the lubricating oil compositions of Comparative Examples 9 and 13 in which the weight ratio (a / b) is outside the numerical range are 40 to 80 ° C. as compared with the same Example 27 or 48 except that they are within the numerical range. It can be seen that the kinematic viscosity and the HTHS viscosity at 60 to 100 ° C. are high, the viscosity index is low, and the viscosity is inferior.

By using the viscosity index improver of the present invention, it is possible to obtain a lubricating oil composition having a kinematic viscosity at 40 to 80 ° C. and an HTHS viscosity at 60 to 100 ° C. to which the viscosity index improver is added. Therefore, the lubricating oil composition containing the viscosity index improver of the present invention includes gear oil (differential oil, industrial gear oil, etc.), MTF, transmission oil [ATF, DCTF, belt-CVTF, etc.], traction oil (, etc.). It is suitably used for toroidal-CVTF, etc.), shock absorber oil, power steering oil, hydraulic oil (hydraulic hydraulic oil for construction machinery, industrial hydraulic oil, etc.) and engine oil (for gasoline and diesel).
Further, since the lubricating oil composition of the present invention has an excellent kinematic viscosity at 40 ° C. and a low gelation index at low temperatures, gear oils (differential oils, industrial gear oils, etc.), MTFs, transmission oils [ATF, DCTF, etc.) And belt-CVTF, etc.], traction oil (toroidal-CVTF, etc.), shock absorber oil, power steering oil, hydraulic oil (hydraulic hydraulic oil for construction machinery, industrial hydraulic oil, etc.) and engine oil (for gasoline and diesel) It is preferably used.

Claims (8)

A monomer represented by the following general formula (1), wherein R ² is an alkyl group having 2 to 3 carbon atoms (a), and a monomer represented by the following general formula (1). A copolymer (A) containing a monomer (b) in which R ² is an alkyl group having 4 carbon atoms and a polyolefin-based monomer (c) represented by the following general formula (2) as essential constituent monomers. A viscosity index improver contained, wherein the copolymer (A) contains 0.1 to 65% by weight of the monomer (a) as a constituent monomer based on the weight of the (A). A viscosity index improver having a weight ratio (a / b) of (a) and (b) of 0.17 to 65.

[In the general formula (1), R ¹ is a hydrogen atom or a methyl group; -X ^1- is a group represented by -O- or -NH-; R ² is an alkyl group having 2 to 4 carbon atoms. ]

[In the general formula (2), R ³ is a hydrogen atom or a methyl group; -X ^2- is a group represented by -O-, -O (AO) _m- or -NH-, and A is a group having 2 carbon atoms. It is an alkylene group of -4, m is an integer of 1-10, and A when m is 2 or more may be the same or different; R ⁴ is a hydrocarbon containing a 1,2-butylene group as a constituent unit. A residue obtained by removing one hydrogen atom from a hydrogen polymer; p is a number of 0 or 1. ] The viscosity index improver according to claim 1, wherein the copolymer (A) is a copolymer having a monomer (d) represented by the following general formula (3) as a constituent monomer.

[R ⁵ is a hydrogen atom or a methyl group; -X ^3- is a group represented by -O- or -NH-; R ⁶ is an alkylene group having 2 to 4 carbon atoms; q is an integer of 1 to 20. When q is 2 or more, R ² may be the same or different; R ⁷ is a linear or branched alkyl group having 1 to 4 carbon atoms. ] The viscosity index improver according to claim 1 or 2, wherein the solubility parameter of the copolymer (A) is 9.0 to 10.0 (cal / cm ³ ) ^1/2 . The copolymer (A) further has a (meth) acryloyl monomer (e) having an alkyl group having 1 carbon atom and / or a (meth) acryloyl monomer having a linear or branched alkyl group having 9 to 36 carbon atoms. The viscosity index improver according to any one of claims 1 to 3, which is a copolymer containing a weight (f) as a constituent monomer. The copolymer (A) is the monomer (a), the monomer (b), and the monomer (the monomer (b)) based on the total weight of the monomers constituting the constituent monomer (A). The total weight ratio of c) is 36 to 80% by weight, and the total weight ratio of the monomer (d), the monomer (e) and the monomer (f) is 20 to 64% by weight. The viscosity index improver according to claim 4. The viscosity index improver according to any one of claims 1 to 5, wherein the copolymer (A) has a weight average molecular weight of 5,000 to 2,000,000. Claims 1 to 6 containing 0.01 to 30% by weight of the (meth) acrylic acid alkyl ester (co) polymer (C) other than the copolymer (A) based on the weight of (A). The viscosity index improver according to any one of the above items. A lubricating oil composition comprising the viscosity index improver according to any one of claims 1 to 7 and the base oil (B).