JP2023004934A - Viscosity index improver and lubricating oil composition - Google Patents

Abstract

To provide a viscosity index improver which, for a purpose of reduction in fuel economy, can decrease a kinematic viscosity at 40 to 80°C and an HTHS viscosity at 100°C of a lubricating oil composition, can decrease a storage elastic modulus at a low temperature (-20°C) of the lubricating oil composition, and has a high viscosity index improving effect.SOLUTION: A viscosity index improver includes a copolymer (A) including as a constituent monomer: a polyolefin monomer (a); a monomer (b) represented by the general formula (2), where R4 is a 2 to 4C alkyl group; and a monomer (c) where R4 is a 12 to 16C alkyl group. The copolymer (A) has a weight average molecular weight of 48,0000 to 60,0000. The copolymer (A) has a solubility parameter of 9.23 to 9.25 (cal/cm3)1/2. A weight ratio (b/a) between the monomers (a) and (b) constituting the copolymer (A) is 3.5 to 4.9. A weight ratio (b/c) between the monomers (b) and (c) constituting the copolymer (A) is 4.1 or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to viscosity index improvers and lubricating oil compositions.

In recent years, in order to reduce CO ₂ emissions and conserve petroleum resources, there has been an increasing demand for fuel-saving automobiles. One way to save fuel 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 US SAE engine oil viscosity standard (SAE J300) stipulates the minimum guaranteed viscosity, and in the 0W-20 grade, the viscosity under high temperature and high shear (HTHS viscosity) is 150 ° C. HTHS viscosity (ASTM D4683 or D5481) is specified as 2.6 mPa·s or greater and 0W-16 grade as 2.3 mPa·s or greater. Moreover, in recent years, efforts have been made to reduce fuel consumption through the use of hardware such as hybrid vehicles that combine electricity and gasoline, plug-in hybrid vehicles, and the like. Unlike a conventional gasoline vehicle, such a hybrid vehicle has a low engine oil temperature during running. ℃. Therefore, engine oil used in hybrid vehicles and the like is required to have a lower viscosity in the range of 40 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 practiced. As viscosity index improvers, methacrylic acid ester copolymers (Patent Documents 1 to 3), comb-shaped copolymers (Patent Documents 4 to 6), and the like are known.
However, these viscosity index improvers have the problem of high kinematic viscosity at 40 to 80° C. and high effective viscosity under high shear (HTHS viscosity). Therefore, there is a demand for a viscosity index improver that reduces the kinematic viscosity and HTHS viscosity at 40 to 80° C. when used as engine oil.
On the other hand, conventional lubricating oil compositions have the problem of increased elasticity at low temperatures and poor startability in cold climates. It has been difficult to obtain a lubricating oil with reduced low-temperature elasticity and good startability in cold climates.

Japanese Patent No. 2732187 Japanese Patent No. 2754343 Japanese Patent No. 3831203 Japanese Patent No. 3474918 Japanese Patent Publication No. 2008-546894 Japanese translation of PCT publication No. 2010-532805

An object of the present invention is to reduce fuel consumption, and can reduce the kinematic viscosity at 40 to 80 ° C. and the HTHS viscosity at 100 ° C. of the lubricating oil composition, and the storage elasticity at low temperature (-20 ° C.). To provide a viscosity index improver capable of lowering the viscosity index and having a high viscosity index improving effect.

［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－、－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；Ｒ^２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の数である。］

［一般式（２）においてＲ^３は水素原子又はメチル基；－Ｘ^２－は－Ｏ－又は－ＮＨ－で表される基；Ｒ^４は炭素数２～４又は１２～１６のアルキル基。］ The present inventors arrived at the present invention as a result of earnest studies.
That is, the present invention provides a polyolefin monomer (a) represented by the following general formula (1) and a monomer represented by the following general formula (2) in which R ⁴ is an alkyl having 2 to 4 carbon atoms and a monomer (c) represented by the following general formula (2) in which R ⁴ is an alkyl group having 12 to 16 carbon atoms. A viscosity index improver containing a copolymer (A) as a monomer, wherein the weight average molecular weight of the copolymer (A) is 480,000 to 600,000, and the copolymer (A) has a solubility parameter of 9.23 to 9.25 (cal/cm ³ ) ^1/2 , and the weight ratio of the monomers (a) and (b) constituting the copolymer (A) ( a viscosity index improver having a b/a) of 3.5 to 4.9 and a weight ratio (b/c) of the monomers (b) and (c) of 4.1 or more; improvers and the group consisting of detergents, dispersants, antioxidants, oiliness improvers, pour point depressants, friction and wear modifiers, extreme pressure agents, defoamers, demulsifiers, metal deactivators and corrosion inhibitors and at least one additive selected from the lubricating oil composition.

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

[In general formula (2), R ³ is a hydrogen atom or a methyl group; -X ² - is a group represented by -O- or -NH-; R ⁴ is an alkyl group having 2 to 4 or 12 to 16 carbon atoms. ]

The viscosity index improver of the present invention can lower the kinematic viscosity at 40 to 80 ° C. and the HTHS viscosity at 100 ° C. of the lubricating oil composition, and lower the storage modulus at low temperature (-20 ° C.). It is possible to achieve the effect that the effect of improving the viscosity index is high.

Kinematic viscosity at 60 ° C. (horizontal axis) and storage elastic modulus (horizontal axis) and storage elastic modulus ( vertical axis). Kinematic viscosity at 60 ° C. (horizontal axis) and storage elastic modulus (horizontal axis) and storage elastic modulus ( vertical axis).

［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－、－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；Ｒ^２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の数である。］

［一般式（２）においてＲ^３は水素原子又はメチル基；－Ｘ^２－は－Ｏ－又は－ＮＨ－で表される基；Ｒ^４は炭素数２～４又は１２～１６のアルキル基。］ The viscosity index improver of the present invention comprises a polyolefin monomer (a) represented by the following general formula (1) and a monomer represented by the following general formula (2) in which R ⁴ has 2 carbon atoms. A monomer (b) that is an alkyl group of 1 to 4 and a monomer (c) that is a monomer represented by the following general formula (2) in which R ⁴ is an alkyl group having 12 to 16 carbon atoms A viscosity index improver containing a copolymer (A) containing as a constituent monomer, wherein the copolymer (A) has a weight average molecular weight of 480,000 to 600,000, and the copolymer The solubility parameter of the coalescence (A) is 9.23 to 9.25 (cal/cm ³ ) ^1/2 , and the monomers (a) and (b) constituting the copolymer (A) is 3.5 to 4.9, and the weight ratio (b/c) of the monomers (b) and (c) is 4.1 or more. is.

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

[In general formula (2), R ³ is a hydrogen atom or a methyl group; -X ² - is a group represented by -O- or -NH-; R ⁴ is an alkyl group having 2 to 4 or 12 to 16 carbon atoms. ]

In the present invention, the copolymer (A) has a highly polar group (ester group, amide group, etc.) near the main skeleton by using the monomer (a) as a constituent monomer, and has a polar side chain. At low temperatures, the polymer chain of the copolymer ( ^A ) is centered around the main chain with respect to the base oil (hydrocarbon oil (C)) with low polarity It is presumed that there is a tendency for the long side chains of the copolymer (A) to be small (aggregate) and spread at high temperatures. Here, the weight ratio (b/a) of the monomer (b) having a short alkyl group with 2 to 4 carbon atoms and the monomer (a) having a long hydrocarbon polymer is within the above specific range, The weight ratio (b/c) between the monomer (b) and the monomer (c) having a medium carbon number (12 to 16 carbon atoms) is set within the above specific range, and the copolymer ( By setting the solubility parameter (SP value) of A) to the above specific range and the Mw of the copolymer (A) to the above specific range, the storage elastic modulus is lowered at low temperatures (eg, −20° C.). It can be suppressed. It is presumed that this is because the aggregation of the polymer chains of the copolymer (A) becomes moderate in the base oil at low temperature. In addition, the aggregation of polymer chains becomes moderate even at 40 to 100°C, the kinematic viscosity at 40 to 80°C and the HTHS viscosity at 100°C can be lowered, and the effect of improving the viscosity index can be high. guessed.

<Copolymer (A)>
In the present invention, the copolymer (A) is a polyolefin monomer (a) represented by the general formula (1) and a monomer represented by the general formula (2), wherein R ⁴ is carbon A monomer (b) which is an alkyl group having a number of 2 to 4, and a monomer represented by the general formula (2) in which R ⁴ is an alkyl group having 12 to 16 carbon atoms ( c) as constituent monomers.
Monomers (a), (b) and (c) may be used alone or in combination of two or more.

In the present invention, R ¹ in the general formula (1) representing the monomer (a) is a hydrogen atom or a methyl group, preferably a methyl group from the viewpoint of improving the viscosity index.

-X ¹ - in general formula (1) is a group represented by -O-, -O(AO) _m - or -NH-.
A 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, a 1,2- or 1,3-propylene group, and a 1,2-, 1,3- or 1,4-butylene group.
m is an integer of 1 to 10, preferably an integer of 1 to 4, more preferably an integer of 1 to 2 from the viewpoint of solubility in the hydrocarbon oil (C).
When m is 2 or more, A may be the same or different, and the (AO) _m portion may be a random bond or a block bond.
-X ¹ - is preferably a group represented by -O- or -O(AO) _m -, more preferably -O- or -O(CH ₂ CH ₂ O), from the viewpoint of improving the viscosity index. It is a group represented by _m- .

p in the general formula (1) is the number of 0 or 1, preferably 0 from the viewpoint of solubility in the hydrocarbon oil (C).

R ² in general formula (1) is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a structural unit. From the viewpoint of improving the viscosity index, it preferably has 50 to 1,000 carbon atoms.
The 1,2-butylene group is a group represented by -CH ₂ CH(CH ₂ CH ₃ )- or -CH(CH ₂ CH ₃ )CH ₂ -.
Hydrocarbon polymers having 1,2-butylene groups as constituent units include polymers using 1-butene as constituent monomers (unsaturated hydrocarbon (x)), and 1 obtained by polymerizing 1,3-butadiene. , a polymer obtained by hydrogenating the double bond of a 2-adduct.
In addition to 1-butene and 1,3-butadiene, the hydrocarbon polymer may contain one or more of the following (1) to (3) as unsaturated hydrocarbons (x) as constituent monomers.
(1) aliphatic unsaturated hydrocarbons [olefins having 2 to 36 carbon atoms (e.g., ethylene, propylene, isobutene, 2-butene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, triacosene, hexatriacosene, etc.) and dienes having 4 to 36 carbon atoms (e.g., isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.), etc.]
(2) alicyclic unsaturated hydrocarbons [e.g. cyclohexene, (di)cyclopentadiene, pinene, limonene, indene, vinylcyclohexene and ethylidenebicycloheptene, etc.]
(3) aromatic group-containing unsaturated hydrocarbons (e.g. styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotyl benzene, vinylnaphthalene, divinylbenzene, divinyltoluene, divinylxylene and trivinylbenzene, etc.)
The hydrocarbon polymer composed of these may be a block polymer or a random polymer. Further, when the hydrocarbon polymer has double bonds, it may be obtained by hydrogenating part or all of the double bonds by hydrogenation. In one embodiment, the hydrocarbon polymer for R ² 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 and 1,3-butadiene.

The number average molecular weight (hereinafter abbreviated as Mn) of the monomer (a) is preferably 800 to 10,000, more preferably 1,000 to 9,000, still more preferably 1,200 to 8, 500, particularly preferably 2,000 to 8,000. When the Mn of the monomer (a) is 800 or more, the solubility in the hydrocarbon oil (C) tends to be good, and when it is 10,000 or less, copolymerization with other monomers is difficult. tend to be good.

In the present invention, the weight average molecular weight (hereinafter abbreviated as Mw) and Mn can be measured by gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions.
<Mw and Mn measurement conditions>
Apparatus: "HLC-8320GPC" [manufactured by Tosoh Corporation]
Column: 2 "TSKgel GMHXL" [manufactured by Tosoh Corporation]
"TSKgel Multipore H _XL -M 1 measurement temperature: 40 ° C
Sample solution: 0.25% by weight tetrahydrofuran solution Injection amount: 10.0 μl
Detection device: Refractive index detector Standard substance: Standard polystyrene (TS Standard substance: Standard polystyrene (TSKstandard POLYSTYRENE)
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 monomer (a) is an esterification reaction between a polymer (Y) containing a hydroxyl group at one end obtained by introducing a hydroxyl group at one end of a hydrocarbon polymer and (meth)acrylic acid, or It can be obtained by transesterification with an alkyl (meth)acrylate (preferably having 1 to 4 carbon atoms) such as methyl (meth)acrylate. In addition, "(meth)acryl" means "acryl and/or methacryl".

Specific examples of the polymer (Y) containing a hydroxyl group at one end include the following (Y1) to (Y4).
Alkylene oxide adduct (Y1): A hydrocarbon polymer obtained by polymerizing an unsaturated hydrocarbon (x) in the presence of an ionic polymerization catalyst (such as a sodium catalyst) is added with an alkylene oxide (such as ethylene oxide and propylene oxide). Those obtained by addition (in this case, the monomer (a) is a compound in which -X ¹ - is -(AO) _m - and p=0 in general formula (1)).
Hydroboride (Y2); a hydroboration reaction product of a hydrocarbon polymer of an unsaturated hydrocarbon (x) having a double bond at one end (for example, those described in U.S. Pat. No. 4,316,973) ) and the like (in this case, the monomer (a) is a compound in which -X ¹ - is -O- and p=0 in the general formula (1)).
Maleic anhydride-ene-aminoalcohol adduct (Y3); a reactant obtained by an ene reaction between a hydrocarbon polymer of an unsaturated hydrocarbon (x) having a double bond at one end and maleic anhydride, Those obtained by imidization with an amino alcohol (in this case, the monomer (a) is a compound in which -X ¹ - is -O- and p is 1 in general formula (1)).
Hydroformyl hydride (Y4); obtained by hydroformylating a hydrocarbon polymer of unsaturated hydrocarbon (x) having a double bond at one end and then hydrogenating it (for example, JP-A-63-175096 (In this case, the monomer (a) is a compound in which —X ¹ — is —O— and p=0 in general formula (1)).
Among these polymers (Y) containing a hydroxyl group at one end, from the viewpoint of improving the viscosity index, preferred are alkylene oxide adducts (Y1) and hydroborides (Y2), and more preferred are alkylene Oxide adduct (Y1).

Ratio of butadiene among all monomers constituting R ² in general formula (1) (in a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit, 1,3- The weight percentage of butadiene) is preferably 50% by weight or more, more preferably 75% by weight or more, still more preferably 85% by weight or more, and particularly preferably 90% by weight or more, from the viewpoint of improving the viscosity index.

The hydrocarbon polymer containing a 1,2-butylene group in general formula (1) as a structural unit may have an isobutylene group from the viewpoint of improving the viscosity index.
The total amount of the isobutylene group and the 1,2-butylene group is preferably 30 mol% or more based on the total number of moles of the constituent monomers of the hydrocarbon polymer, from the viewpoint of improving the viscosity index. It is more preferably 40 mol % or more, still more preferably 50 mol % or more.
As a method for increasing the ratio of the total amount of isobutylene groups and 1,2-butylene groups in the hydrocarbon polymer, for example, the following method can be employed. In the case of the above alkylene oxide adduct (Y1), for example, in anionic polymerization using 1,3-butadiene, the reaction temperature is set low {for example, below the boiling point of 1,3-butadiene (-4.4°C)}, In addition, by reducing the amount of the polymerization initiator charged relative to 1,3-butadiene, the ratio of the total amount of isobutylene groups and 1,2-butylene groups in the hydrocarbon polymer can be increased. In the case of the above hydroboride (Y2), maleic anhydride-ene-aminoalcohol adduct (Y3) and hydroformyl-hydride (Y4), the degree of polymerization of the hydrocarbon polymer having a double bond at one end is increased. By doing so, the above ratio can be increased.

For the structure derived from 1-butene and/or 1,3-butadiene of the hydrocarbon polymer in general formula (1), a 1,2-butylene group based on the total number of moles of the constituent monomers of the hydrocarbon polymer The ratio (number of moles of 1,2-butylene group / total number of moles of constituent monomers × 100) is 30 mol% or more from the viewpoint of the effect of improving the viscosity index and copolymerization with other monomers. It is preferably 30 to 70 mol %, more preferably 30 to 70 mol %.
The proportion of 1,2-butylene groups can be measured by ¹³ C-NMR. Specifically, for example, when only a monomer having 4 carbon atoms is used, the hydrocarbon polymer is analyzed by ¹³ C-NMR, and the structure of the hydrocarbon polymer is determined using the following formula (1). The mole percent of 1,2-butylene groups based on the total number of moles of units can be calculated and determined. In ¹³ C-NMR, a peak derived from the tertiary carbon atom (--CH ₂ CH(CH ₂ CH ₃ )--) of the 1,2-butylene group appears at the integral value (integral value B) of 26 to 27 ppm. It can be obtained from the integrated value of the above peak and the integrated value (integrated value C) of the total carbon peak of the hydrocarbon polymer.
Ratio of 1,2-butylene groups (mol%) = {(integral value B) × 4}/(integral value C) × 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 below the boiling point of 1,3-butadiene (−4.4° C.), In addition, the amount of the polymerization initiator to be added may be reduced with respect to 1,3-butadiene. The dosage should be increased.

The total amount of isobutylene groups and 1,2-butylene groups in the hydrocarbon polymer containing 1,2-butylene groups as structural units in general formula (1) can be measured by ¹³ C-NMR. Specifically, for example, when only a monomer having 4 carbon atoms is used, the hydrocarbon polymer is analyzed by ¹³ C-NMR and calculated using the following formula (2). It is possible to determine the total mole % of the isobutylene group and the 1,2-butylene group based on the total number of moles of the constitutional units. In ¹³ C-NMR, the peak derived from the methyl group of the isobutylene group is the integrated value (integral value A) of 30 to 32 ppm, the branched methylene group of the 1,2-butylene group (-CH ₂ CH (CH ₂ CH ₃ )- Alternatively, a peak derived from —CH(CH ₂ CH ₃ )CH ₂ —) appears at an integral value (integral value B) of 26 to 27 ppm. The total mol % of the isobutylene group and the 1,2-butylene group based on the total number of moles of the structural units of the hydrocarbon polymer is the integrated value of the above peak and the integrated value of the total carbon peak of the hydrocarbon polymer ( It can be obtained from the integrated value C).
Total amount of isobutylene group and 1,2-butylene group (mol%) = 100 x {(integral value A) x 2 + (integral value B) x 4}/(integral value C) (2)

When the hydrocarbon polymer in R ² contains butadiene, or butadiene and ¹ -butene as constituent monomers, butadiene or butadiene and 1 -In the butene-derived structure, the molar ratio of the 1,2-adduct and the 1,4-adduct (1,2-adduct/1,4-adduct) is effective in improving the viscosity index and with other monomers. From the viewpoint of copolymerizability, it is preferably from 5/95 to 95/5, more preferably from 20/80 to 80/20, still more preferably from 30/70 to 70/30.

When the hydrocarbon polymer for R ² contains 1,3-butadiene, or 1,3-butadiene and 1-butene as constituent monomers, it constitutes part or all of R ² in general formula (1) The molar ratio of 1,2-adducts/1,4-adducts in structures derived from 1,3-butadiene or 1,3-butadiene and 1-butene is ¹ H-NMR, ¹³ C-NMR, Raman It can be measured by spectroscopy or the like.

The solubility parameter (hereinafter abbreviated as the SP value) of the structural unit derived from the monomer (a) (the structure in which the vinyl of (a) reacts to form a single bond) is the weight fraction of (A) From the viewpoint of moderate SP value calculated based on and solubility in hydrocarbon oil (C), it is preferably 7.0 to 9.0 (cal/cm ³ ) ^1/2 , 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 R ² is high and the number of carbon atoms is large, and tends to be large when the degree of branching is low and the number of carbon atoms is small.
The SP value in the present invention is the numerical value (atom or functional group (heat of vaporization at 25°C and molar volume of Specifically, from the numerical values of Δe _i and v _i described in Table 1 below, which are parameters of the Fedors method, numerical values corresponding to the types of atoms and atomic groups in the molecular structure are used and applied to the following formula. can be calculated.
SP value = (ΣΔe _i /Σv _i ) ^1/2

The SP value of the structural unit derived from the monomer (a) can be calculated using the parameters based on the molecular structure of the structural unit derived from the monomer (a). A desired range can be obtained by appropriately adjusting the weight fractions of (unsaturated hydrocarbon (x)) and monomer (unsaturated hydrocarbon (x)).
Further, when the copolymer (A) uses two or more types of monomers (a) in combination, the SP value of each of the plurality of structural units constituting (a) is calculated by the above method, and each The SP value of the structural unit derived from the monomer (a) of the SP of the structural unit derived from the monomer (a) is the arithmetic mean value based on the weight fraction of the constituent monomer unit It is preferable to fill a range of values.

R ³ in the general formula (2) representing the monomer (b) or (c) in the present invention is a hydrogen atom or a methyl group, preferably a methyl group from the viewpoint of improving the viscosity index.
-X ² - in the general formula (2) representing the monomer (b) or (c) is a group represented by -O- or -NH-, and from the viewpoint of improving the viscosity index, -O- The groups represented are preferred.

In the monomer (b), R ⁴ in general formula (2) is an alkyl group having 2 to 4 carbon atoms, such as ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s -butyl group, t-butyl group and the like.
Specific examples of the monomer (b) include ethyl (meth)acrylate, n-propyl (meth)acrylate, isobutyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylic acid. 1-methylpropyl, 2-methylpropyl (meth)acrylate, 1,1-dimethylethyl (meth)acrylate, N-butyl(meth)acrylamide and the like.
From the viewpoint of improving the viscosity index, the monomer (b) is preferably ethyl (meth)acrylate, n-butyl (meth)acrylate and isobutyl (meth)acrylate, more preferably (meth)acrylic acid. Ethyl and n-butyl (meth)acrylate, particularly preferably n-butyl (meth)acrylate.

In monomer (c), R ⁴ in general formula (2) is an alkyl group having 12 to 16 carbon atoms, such as a linear alkyl group (e.g., n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, etc.), branched alkyl groups (e.g., 2-methylundecyl group, isododecyl group, 2-methyldodecyl group, isotridecyl group, 2-methyltridecyl group, isotetradecyl group , 2-methyltetradecyl group, isopentadecyl group, 2-methylpentadecyl group, isohexadecyl group, etc.).
Specific examples of the monomer (c) include linear alkyl (meth)acrylates (e.g., n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, etc.), linear alkyl (meth)acrylamide (e.g., N-dodecyl (meth)acrylamide, N-tridecyl (meth)acrylamide, N-tetradecyl ( meth)acrylamide, N-pentadecyl(meth)acrylamide, N-hexadecyl(meth)acrylamide, etc.), branched alkyl (meth)acrylates (e.g., 2-methylundecyl (meth)acrylate, isododecyl (meth)acrylate, ( 2-methyldodecyl meth)acrylate, isotridecyl (meth)acrylate, 2-methyltridecyl (meth)acrylate, isotetradecyl (meth)acrylate, 2-methyltetradecyl (meth)acrylate, (meth)acrylate isopentadecyl acrylate, 2-methylpentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, etc.), branched alkyl (meth)acrylamide (e.g., N-2-methylundecyl (meth)acrylamide, N -isododecyl (meth)acrylamide, N-2-methyldodecyl (meth)acrylamide, N-isotridecyl (meth)acrylamide, N-2-methyltridecyl (meth)acrylamide, N-isotetradecyl (meth)acrylamide, N- 2-methyltetradecyl(meth)acrylamide, N-isopentadecyl(meth)acrylamide, N-2-methylpentadecyl(meth)acrylamide, N-isohexadecyl(meth)acrylamide, etc.).
As the monomer (c), linear alkyl (meth)acrylates and branched alkyl (meth)acrylates are preferable from the viewpoint of improving the viscosity index.
Examples of the monomer (c) include Neodol (registered trademark) 23 (a mixture of linear and branched alkyl alcohols having 12 to 13 carbon atoms, manufactured by SHELL) and Neodol (registered trademark) 45 (a straight chain having 14 to 15 carbon atoms). (Meth)acrylic acid esters of mixtures of alkyl alcohols such as mixtures of chained and branched alkyl alcohols (SHELL) may also be used.

In the present invention, the weight ratio (b/a) of the monomers (a) and (b) constituting the copolymer (A) is 3.5-4.9, and the weight ratio (b/a) is 3.5-4.9. From the viewpoint of viscosity reduction, it is preferably 3.8 to 4.5, more preferably 4.0 to 4.4. If it is less than 3.5 or more than 4.9, the molecular behavior of (A) with respect to temperature tends to decrease, and when the HTHS viscosity at 150°C is kept constant, the kinematic viscosity tends to increase at 40 to 80°C. There is a tendency for the storage modulus at low temperatures to be high.

In the present invention, the weight ratio (b/c) of the monomers (b) and (c) constituting the copolymer (A) is 4.1 or more, and the kinematic viscosity is reduced at 40 to 80 ° C., From the viewpoint of reducing the storage modulus at low temperatures and improving the viscosity index, it is preferably 4.5 to 10.0, more preferably 5.0 to 9.0. If it is less than 4.1, the molecular behavior of (A) with respect to temperature tends to be small, the viscosity index tends to be low, and the kinematic viscosity at 40 to 80 ° C. when the HTHS viscosity at 150 ° C. is constant. tends to be high, and the storage modulus at low temperatures tends to be high.

In the present invention, the weight ratio {b/(a+c)} of (b) to the total weight of the monomers (a) and (c) constituting the copolymer (A) is the kinematic viscosity at 40 to 80 ° C. 2.0 to 3.5 is preferable from the viewpoint of reduction, low-temperature storage modulus reduction, and viscosity index improvement effect.

In the copolymer (A), the weight ratio of the monomer (a) among the constituent monomers of (A) is such that the kinematic viscosity is reduced at 40 to 80 ° C., the storage modulus is reduced at low temperatures, and the viscosity index is improved. From the viewpoint of effect, it is preferably 1 to 22% by weight, more preferably 10 to 21% by weight, and particularly preferably 12 to 20% by weight, based on the total weight of the monomers constituting (A). .

In the copolymer (A), the weight ratio of the monomer (b) among the constituent monomers of (A) is such that the kinematic viscosity is reduced at 40 to 80 ° C., the storage modulus is reduced at low temperatures, and the viscosity index is improved. From the viewpoint of effect, it is preferably 4.1 to 77% by weight, more preferably 35 to 75% by weight, and particularly preferably 42 to 75% by weight, based on the total weight of the monomers constituting (A). is.

In the copolymer (A), the weight ratio of the monomer (c) among the constituent monomers of (A) reduces the kinematic viscosity at 40 to 80 ° C., reduces the storage modulus at low temperatures, and improves the viscosity index. From the viewpoint of effect, it is preferably 1 to 17% by weight, more preferably 3 to 15% by weight, and particularly preferably 8 to 13% by weight, based on the total weight of the monomers constituting (A). .

In the copolymer (A), the total weight ratio of the monomer (a), the monomer (b) and the monomer (c) among the constituent monomers of (A) is 40 to 80 ° C. From the viewpoint of kinematic viscosity reduction, low-temperature storage modulus reduction and viscosity index improvement effect, based on the total weight of the monomers constituting (A), it is preferably 70% by weight or more, more preferably 70 to 97% by weight. %, particularly preferably 78 to 95% by weight.

［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) includes, in addition to the monomers (a) to (c), a monomer (d) represented by the following general formula (3), and a monomer (d) represented by the general formula (2). A monomer (e) in which R ⁴ is an alkyl group having 1 carbon atom and a (meth)acryloyl monomer (f) having a linear or branched alkyl group having 17 to 36 carbon atoms (hereinafter sometimes abbreviated as monomer (f)) may be a copolymer containing at least one selected from the group consisting of monomers. From the viewpoint of reducing the HTHS viscosity at 100°C, it is preferably a copolymer containing the monomer (d) as a constituent monomer. Further, the monomer (e) has a high polarity due to the short carbon number of the alkyl group with respect to the polar group (ester group, etc.), and the polarity of the copolymer (A) can be increased. has an intermediate degree of polarity because the carbon number of the alkyl group for the polar group (ester group, etc.) is longer than (b) and (c) and shorter than (a), and the polarity of the copolymer (A) can be adjusted. can be done.

[In 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; It is an integer of 20, and when q is 2 or more, R ⁶ may be the same or different; R ⁷ is a linear or branched alkyl group having 1 to 4 carbon atoms. ]

R5 in general formula ( ³ ) is a hydrogen atom or a methyl group. Among these, the methyl group is preferable from the viewpoint of reducing the HTHS viscosity at 100°C.

—X ³ — in general formula (3) is a group represented by —O— or —NH—. Among these, from the viewpoint of reducing the HTHS viscosity at 100° C., the group represented by —O— is preferred.

R ⁶ in general formula (3) is an alkylene group having 2 to 4 carbon atoms.
Examples of alkylene groups having 2 to 4 carbon atoms include ethylene group, isopropylene group, 1,2- or 1,3-propylene group, isobutylene group, and 1,2-, 1,3- or 1,4- A butylene group etc. are mentioned.
R ⁶ O is an alkyleneoxy group having 2 to 4 carbon atoms, such as ethyleneoxy group, 1,2- or 1,3-propyleneoxy group, and 1,2-, 1,3- or 1,4- butyleneoxy group and the like.
q in the general formula (3) is an integer of 1 to 20, preferably an integer of 1 to 5, more preferably an integer of 1 to 2, from the viewpoint of reducing the HTHS viscosity at 100°C.
When q is 2 or more, R ⁶ O may be the same or different, and the bonding form of (R ⁶ O) _q moieties may be random or block.

R ⁷ in general formula (3) is a linear or branched alkyl group having 1 to 4 carbon atoms. Examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group and t-butyl group.
Among straight or branched alkyl groups having 1 to 4 carbon atoms, straight chain alkyl groups having 1 to 4 carbon atoms are preferable from the viewpoint of reducing HTHS viscosity at 100° C., and more preferably straight chain alkyl groups having 1 to 4 carbon atoms. It is a straight chain alkyl group (n-butyl group).

Specific examples of the monomer (d) include methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, ethoxypropyl ( meth)acrylate, propoxypropyl (meth)acrylate, butoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, propoxybutyl (meth)acrylate and butoxybutyl (meth)acrylate, and 1 carbon atom Esterified products obtained by adding 2 to 20 moles of at least one selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide to linear or branched alkyl alcohols of 1 to 4 and (meth)acrylic acid.
Of the monomers (d), ethoxyethyl (meth)acrylate and butoxyethyl (meth)acrylate are preferred from the viewpoint of reducing HTHS viscosity at 100°C, and n-butoxyethyl (meth)acrylate is more preferred. is.

In the copolymer (A), the weight ratio of the monomer (d) among the constituent monomers of (A) is, from the viewpoint of HTHS viscosity reduction at 100° C., the ratio of the monomers constituting (A) to Based on the total weight, 25% by weight or less is preferred, 1 to 20% by weight is more preferred, and 5 to 15% by weight is particularly preferred.

In the monomer (e), R ³ in general formula (2) is a hydrogen atom or a methyl group, preferably a methyl group from the viewpoint of improving the viscosity index.
—X ² — in the general formula (2) is a group represented by —O— or —NH—, and from the viewpoint of improving the viscosity index, a group represented by —O— is preferable.
R ⁴ in the general formula (2) is a C 1 alkyl group, such as a methyl group.
Specific examples of the monomer (e) include methyl (meth)acrylate, N-methyl(meth)acrylamide, etc. Among the monomers (e), from the viewpoint of improving the viscosity index, preferred It is methyl (meth)acrylate.

In the copolymer (A), the weight ratio of the monomer (e) among the constituent monomers of (A) is reduced kinematic viscosity at 40 to 80 ° C., reduced storage modulus at low temperatures, and improved viscosity index. From the viewpoint of effect, it is preferably less than 0.2% by weight, more preferably 0.1% by weight or less, based on the total weight of the monomers constituting (A).

［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１５～３４；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。］ As the monomer (f), other than (a), a (meth)acryloyl monomer (f1) having a linear alkyl group having 17 to 36 carbon atoms and represented by the following general formula (4) and a (meth)acryloyl monomer (f2) having a branched alkyl group having 17 to 36 carbon atoms.
In addition, monomer (f) may use 1 type, and may use 2 or more types together.

[In 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 ^; and R ¹¹ are each independently a linear alkyl group having 1 to 24 carbon atoms, the total number of carbon atoms of R ¹⁰ and R ¹¹ is 15 to 34; s is an integer of 0 to 20, and s is 2 or more; of R ⁹ O may be the same or different. ]

Examples of the (meth)acryloyl monomer (f1) having a linear alkyl group having 17 to 36 carbon atoms (hereinafter sometimes abbreviated as the monomer (f1)) include (meth)acrylic acid alkyl esters {Esterification product of linear alkyl alcohol having 17 to 36 carbon atoms and acrylic acid, for example, n-heptadecyl (meth)acrylate, n-octadecyl (meth)acrylate, n-icosyl (meth)acrylate, n-docosyl (meth)acrylate, n-tetracosyl (meth)acrylate, n-triacontyl (meth)acrylate and n-hexatriacontyl (meth)acrylate}, linear alkyls having 17 to 36 carbon atoms Esterified products of alcohol alkylene oxide (C2-C4) 1-20 mol adducts with (meth)acrylic acid, and (meth)acrylic acid alkylamides {straight-chain alkylamines having 17-36 carbon atoms and acrylic acid Amidated products with and the like} and the like.
Of the monomers (f1), from the viewpoint of improving the viscosity index, preferred are (meth)acrylic acid alkyl esters having a linear alkyl group having 17 to 28 carbon atoms, and more preferred are those having 17 to 28 carbon atoms. (Meth)acrylic acid esters having 24 straight-chain alkyl groups, particularly preferred are (meth)acrylic acid esters having a straight-chain alkyl group having 17 to 20 carbon atoms.
One type of the monomer (f1) may be used, or two or more types may be used in combination.

In the monomer (f2), R8 ⁱⁿ general formula (4) is a hydrogen atom or a methyl group. Among these, the methyl group is preferable from the viewpoint of the effect of improving the viscosity index.
—X ⁴ — in general formula (4) is a group represented by —O— or —NH—. Among these, the group represented by —O— is preferable from the viewpoint of improving the viscosity index.
R ⁹ in general formula (4) is an alkylene group having 2 to 4 carbon atoms. Examples of alkylene groups having 2 to 4 carbon atoms include ethylene, isopropylene, 1,2- or 1,3-propylene, isobutylene and 1,2-, 1,3- or 1,4-butylene. groups.
R ⁹ O is an alkyleneoxy group having 2 to 4 carbon atoms, such as ethyleneoxy group, 1,2- or 1,3-propyleneoxy group, and 1,2-, 1,3- or 1,4- butyleneoxy group and the like.
s in the general formula (4) is an integer of 0 to 20, preferably an integer of 0 to 5, more preferably an integer of 0 to 2, from the viewpoint of improving the viscosity index.
R ⁹ O when s is 2 or more 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 general formula (4) are each independently a linear alkyl group having 1 to 24 carbon atoms. Specifically, methyl group, ethyl group, n-propyl group, n-butyl group, n-heptyl group, n-hexyl group, n-pentyl group, n-octyl group, n-nonyl group, n-decyl group , n-undecyl group, n-dodecyl group, n-tetradecyl group, n-hexadecyl group, n-octadecyl group, n-eicosyl group and n-tetracosyl group. Of the straight-chain alkyl groups having 1 to 24 carbon atoms, one of them is preferably a straight-chain alkyl group having 6 to 24 carbon atoms from the viewpoint of the effect of improving the viscosity index. One of them is a straight-chain alkyl group having 6 to 20 carbon atoms, and it is particularly preferable that one of them is a straight-chain alkyl group having 8 to 16 carbon atoms.
The total carbon number of R ¹⁰ and R ¹¹ is 15 to 34, preferably 15 to 30, more preferably 15 to 26 from the viewpoint of improving the viscosity index.

Specific examples of the monomer (f2) include 2-octyldecyl (meth)acrylate, esters of ethylene glycol mono-2-octylpentadecyl ether and (meth)acrylic acid, (meth)acrylic acid 2- n-octyldodecyl, 2-n-decyltetradecyl (meth)acrylate, 2-n-dodecylhexadecyl (meth)acrylate, 2-n-tetradecyloctadecyl (meth)acrylate, (meth)acrylic acid 2 -n-dodecylpentadecyl, 2-n-tetradecylheptadecyl (meth)acrylate, 2-n-hexadecylheptadecyl (meth)acrylate, 2-n-heptadecylicosyl (meth)acrylate, ( 2-n-hexadecyl docosyl meth)acrylate, 2-n-eicosyl docosyl (meth) acrylate, 2-n-tetracosylhexacosyl (meth) acrylate and N-2-octyldecyl ( meth) acrylamide and the like.
One type of the monomer (f2) may be used, or two or more types may be used in combination.

Among the monomers (f2), preferred from the viewpoint of solubility in the hydrocarbon oil (C) and low-temperature viscosity reduction are (meth)acryloyl monomers having a branched alkyl group having 17 to 32 carbon atoms. A (meth)acryloyl monomer having a branched alkyl group having 17 to 28 carbon atoms is particularly preferred.

In the copolymer (A), the weight ratio of the monomer (f) among the constituent monomers of (A) is SP calculated based on the effect of improving the viscosity index and the weight fraction of the copolymer (A) From the viewpoint of value, it is preferably 5% by weight or less based on the total weight of the monomers constituting (A).

When the copolymer (A) contains as a constituent monomer at least one selected from the group consisting of the monomer (d), the monomer (e) and the monomer (f), the Among the constituent monomers, the total weight ratio of monomer (d), monomer (e) and monomer (f) is kinematic viscosity at 40 to 80 ° C., storage modulus at low temperature, viscosity index From the viewpoint of the improvement effect and the SP value calculated based on the weight fraction of the copolymer (A), it is preferably 3 to 30% by weight, more preferably 3 to 30% by weight, based on the total weight of the monomers constituting (A). is 5 to 22% by weight.

The copolymer (A) in the present invention includes, in addition to the above monomers (a) to (f), a phosphorus atom-containing monomer (g), an aromatic ring-containing vinyl monomer (h), a monomer Other monomers such as (i) to monomer (m), nitrogen atom-containing monomer (n) and hydroxyl group-containing monomer (o) may be used as constituent monomers.
Each of the monomers (g) to (o) may be used alone, or two or more thereof may be used in combination.

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

Phosphate ester group-containing monomer (g1):
(Meth)acryloyloxyalkyl (C2-C4) phosphate [(meth)acryloyloxyethyl phosphate and (meth)acryloyloxyisopropyl phosphate] and alkenyl phosphate [vinyl phosphate, allyl phosphate, propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, dodecenyl phosphate, etc.] and the like. In addition, "(meth)acryloyloxy" means acryloyloxy or methacryloyloxy.

Phosphono group-containing monomer (g2):
(Meth)acryloyloxyalkyl (2-4 carbon atoms) phosphonic acid [(meth)acryloyloxyethylphosphonic 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), preferred is (g1), more preferred is (meth)acryloyloxyalkyl (C2-4) phosphate ester, and particularly preferred is (meth)acryloyl It is oxyethyl 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-chloro Thylbenzene, indene, 2-vinylnaphthalene, and the like.

Among monomers (h), preferred are styrene and α-methylstyrene, and more preferred is styrene.

Examples of monomer (i) include those having two or more unsaturated groups, such as divinylbenzene, alkadiene having 4 to 12 carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene and 1,7-octadiene, etc.), (di)cyclopentadiene, vinylcyclohexene and ethylidenebicycloheptene, limonene, ethylene di(meth)acrylate, polyalkylene oxide glycol di(meth)acrylate, pentaerythritol triallyl ether, pentaerythritol tri (meth)acrylates, pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, esters of unsaturated carboxylic acids with a Mn of 500 or more and glycols and unsaturated esters described in WO01/009242 Examples include esters of alcohols and carboxylic acids.

Vinyl esters, vinyl ethers, vinyl ketones (j) (sometimes 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) , 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 having 1 to 8 carbon atoms (methyl vinyl ketone, ethyl vinyl ketone and phenyl vinyl ketone, etc.).

Epoxy group-containing monomer (k) (sometimes abbreviated as monomer (k)):
glycidyl (meth)acrylate, glycidyl (meth)allyl ether, and the like.

Halogen element-containing monomer (l) (sometimes abbreviated as monomer (l)):
Examples include vinyl chloride, vinyl bromide, vinylidene chloride, (meth)allyl chloride, and halogenated styrene (dichlorostyrene, etc.).

Ester (m) of unsaturated polycarboxylic acid (sometimes abbreviated as monomer (m)):
Alkyl, cycloalkyl or aralkyl esters of unsaturated polycarboxylic acids [alkyl diesters with 1 to 8 carbon atoms of unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, etc.) (dimethyl maleate, dimethyl fumarate, diethyl maleate and dioctyl maleate)] and the like.

Examples of the nitrogen atom-containing monomer (n) include the following monomers (n1) to (n4), excluding the monomers (a) to (f).
Amido group-containing monomer (n1):
(Meth)acrylamide, N-(N'-monoalkylaminoalkyl)(meth)acrylamide [having an aminoalkyl group (2 to 6 carbon atoms) in which one alkyl group having 1 to 4 carbon atoms is bonded to the 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 [one in which two alkyl groups having 1 to 4 carbon atoms are bonded to the nitrogen atom; N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide and N,N-di-n-butyl(meth)acrylamide], N-(N', N'-dialkylaminoalkyl)(meth)acrylamide [having an aminoalkyl group (having 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; 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-vinylhydroxyacetamide, etc.] and the like.

Nitro group-containing monomer (n2):
4-nitrostyrene and the like.

Primary to tertiary amino group-containing monomer (n3):
Primary amino group-containing monomers {alkenylamines having 3 to 6 carbon atoms [(meth)allylamine, crotylamine, etc.], aminoalkyl (carbon atoms 2 to 6) (meth)acrylates [aminoethyl (meth)acrylate, etc.]} ; Secondary amino group-containing monomer {monoalkylaminoalkyl (meth)acrylate [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; Nt-butylaminoethyl (meth)acrylate and N-methylaminoethyl (meth)acrylate, etc.], dialkenylamine having 6 to 12 carbon atoms [di(meth)allylamine, etc.]}; tertiary amino group-containing monomer body {dialkylaminoalkyl (meth)acrylate [having an aminoalkyl group (2 to 6 carbon atoms) in which two alkyl groups having 1 to 6 carbon atoms are bonded to a nitrogen atom; ) acrylates and N,N-diethylaminoethyl (meth)acrylate, etc.], alicyclic (meth)acrylates having a nitrogen atom [morpholinoethyl (meth)acrylate, etc.], aromatic monomers [N-(N', N′-diphenylaminoethyl)(meth)acrylamide, N,N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone and N-vinylthiopyrrolidone, etc.]}, and Hydrochlorides, sulfates, phosphates, or lower alkyl (C1-8) monocarboxylic acid (acetic acid, propionic acid, etc.) salts of these are included.

Nitrile group-containing monomer (n4):
(Meth)acrylonitrile and the like.

Among the monomers (n), preferred are (n1) and (n3), more preferred are N-(N',N'-diphenylaminoethyl)(meth)acrylamide, N-(N' , 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.

Hydroxyl group-containing monomer (o):
Hydroxyl group-containing aromatic monomer (p-hydroxystyrene, etc.), hydroxyalkyl (C2-C6) (meth)acrylate [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, alkenols having 3 to 12 carbon atoms [(meth)allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol and 1 -undecenol, etc.], alkene monools or alkenediols having 4 to 12 carbon atoms [1-butene-3-ol, 2-buten-1-ol and 2-butene-1,4-diol, etc.], hydroxyalkyls (carbon Numbers 1-6) Alkenyl (C 3-10) ethers (2-hydroxyethyl propenyl ether, etc.), polyhydric (tri- to octahydric) alcohols (glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, sugars and sucrose, etc.) ) alkenyl (3 to 10 carbon atoms) ether or (meth) acrylate [sucrose (meth) allyl ether, etc.], etc.;
Polyoxyalkylene glycol (alkylene group having 2 to 4 carbon atoms, degree of polymerization 2 to 50), polyoxyalkylene polyol [polyoxyalkylene ether of the above tri- to octahydric alcohol (alkylene group having 2 to 4 carbon atoms, degree of polymerization 2 to 100)], mono (meth) acrylate of polyoxyalkylene glycol or alkyl (carbon number 1 to 4) ether of 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 to 230) sorbitan, etc.] and the like;

In the copolymer (A), the weight ratio of the monomer (g) among the constituent monomers of (A) is, from the viewpoint of improving the viscosity index, the total weight of the monomers constituting (A). 5% by weight or less, more preferably 1% by weight or less.
In the copolymer (A), the weight ratio of the monomer (h) among the constituent monomers of (A) is, from the viewpoint of improving the viscosity index, the total weight of the monomers constituting (A). Based on this, it is preferably 5% by weight or less, more preferably 1% by weight or less, and particularly preferably 0.1% by weight or less.
In the copolymer (A), the weight ratio of the monomer (i) among the constituent monomers of (A) is preferably 5% by weight or less from the viewpoint of the HTHS viscosity lowering effect at the effective temperature.
In the copolymer (A), the weight ratio of the monomer (j) among the constituent monomers of (A) is, from the viewpoint of improving the viscosity index, the total weight of the monomers constituting (A). Based on this, 5% by weight or less is preferable.
In the copolymer (A), the weight ratio of the monomer (k) among the constituent monomers of (A) is, from the viewpoint of improving the viscosity index, the total weight of the monomers constituting (A). Based on this, 5% by weight or less is preferred.
In the copolymer (A), the weight ratio of the monomer (l) among the constituent monomers of (A) is, from the viewpoint of improving the viscosity index, the total weight of the monomers constituting (A). Based on this, 5% by weight or less is preferred.
In the copolymer (A), the weight ratio of the monomer (m) among the constituent monomers of (A) is, from the viewpoint of improving the viscosity index, the total weight of the monomers constituting (A). 1% by weight or less is preferred.
In the copolymer (A), the weight ratio of the monomer (n) among the constituent monomers of (A) is set to (A) from the viewpoint of the HTHS viscosity lowering effect and the viscosity index improving effect at the execution temperature. It is preferably 5% by weight or less, more preferably 3% by weight or less, and particularly preferably 1% by weight or less, based on the total weight of the constituent monomers.
In the copolymer (A), the weight ratio of the monomer (o) among the constituent monomers of (A) is, from the viewpoint of the HTHS viscosity lowering effect and the viscosity index improving effect, Preferably 5% or less, more preferably 1% or less, by weight based on total body weight.

Mw of the copolymer (A) is 480,000 to 600,000. When the Mw of the copolymer (A) is less than 480,000, the molecular behavior of (A) with respect to temperature tends to be small, and the HTHS viscosity (100°C) when the HTHS viscosity (150°C) is adjusted to be constant increases, the kinematic viscosity at 40 to 80 ° C. tends to increase, and the storage elastic modulus at low temperatures tends to increase. The kinematic viscosity at ~80°C tends to increase, and the storage modulus at low temperatures tends to increase.

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 conditions for measuring Mw and molecular weight distribution (Mw/Mn) of copolymer (A) are the same as those for measuring Mw and Mn of monomer (a).

The copolymer (A) can be obtained by a known production method, specifically a method of solution polymerization of the above monomers in a solvent in the presence of a polymerization catalyst.
Examples of the solvent include toluene, xylene, alkylbenzene having 9 to 10 carbon atoms, methyl ethyl ketone, hydrocarbon oils (mineral oil, GTL oil, etc.), synthetic oils and mixtures thereof.
Polymerization catalysts include azo catalysts (2,2′-azobis(2-methylbutyronitrile) and 2,2′-azobis(2,4-dimethylvaleronitrile), etc.), peroxide catalysts (benzoyl peroxide oxide, cumyl peroxide, lauryl peroxide, etc.) and redox catalysts (mixtures of benzoyl peroxide and tertiary amines, etc.). Further, a known chain transfer agent (alkylmercaptan having 2 to 20 carbon atoms, etc.) may be used if necessary for molecular weight adjustment.
The polymerization temperature is preferably 25-140°C, more preferably 50-120°C. In addition to the solution polymerization described above, 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 alternating copolymer, and may be either a graft copolymer or a block copolymer.

The SP value calculated based on the weight fraction of copolymer (A) is 9.23 to 9.25 (cal/cm ³ ) ^1/2 .
When the SP value calculated based on the weight fraction of the copolymer (A) is less than 9.23 (cal/cm ³ ) ^1/2 , the molecular behavior of (A) with respect to temperature tends to decrease, The kinematic viscosity tends to be high at 40 to 80° C., a high viscosity index cannot be obtained, and the storage modulus at low temperatures tends to be high. If it exceeds 9.25 (cal/cm ³ ) ^1/2 , it may become insoluble in hydrocarbon oil (C) (especially base oil including GTL base oil), and may not be used as a viscosity index improver. be.
The SP value calculated based on the weight fraction of the copolymer (A) is a structural unit derived from each monomer constituting (A) using the above SP value calculation method (a vinyl group is It means the value obtained by calculating the SP value of the single bond structure) and taking the arithmetic mean based on the weight fraction of each constituent monomer at the time of preparation. For example, when the monomer is methyl methacrylate, the constitutional unit derived from methyl methacrylate has 2 _CH3 , 1 _CH2 , 1 C, and 1 _CO2 as atomic groups. 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 . A similar calculation reveals 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
Σv _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 structural unit derived from each monomer as follows. Calculated by arithmetic averaging based on fractions.
SP value of the copolymer = (9.933 × 50 + 9.721 × 50) / 100 = 9.827
Also, the SP value calculated based on the weight fraction of (A) can be set within a desired range by appropriately adjusting the monomers and weight fraction used. Specifically, the SP value can be decreased by using a large amount of a monomer with a long alkyl group, and the SP value can be increased by using a large amount of a monomer with a short alkyl group. can do.

<(Co)polymer (B)>
The viscosity index improver of the present invention may contain, in addition to the copolymer (A), a (meth)acrylic acid alkyl ester (co)polymer (B) other than the copolymer (A). , (co)polymer (B) is preferably contained from the viewpoint of low-temperature viscosity reduction.
The (co)polymer (B) includes a (co)polymer that does not contain the monomer (a), for example, an alkyl (meth)acrylate having a linear or branched alkyl group having 9 to 36 carbon atoms Examples thereof include (co)polymers having an ester (f) as an essential constituent monomer. Specifically, n-dodecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate and n-octadecyl (meth)acrylate copolymer, n-(meth)acrylate -octadecyl/n-dodecyl (meth)acrylate (molar ratio 10 to 30/90 to 70) copolymer, n-tetradecyl (meth)acrylate/n-dodecyl (meth)acrylate (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, and these may be used alone or in combination of two or more.

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

Mw of the (co)polymer (B) 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 calculated based on the weight fraction of the (co)polymer (B) is preferably from 7.0 to 10, more preferably from 8.0 to 8.0, from the viewpoint of solubility in the hydrocarbon oil (C). 9.5.
The conditions for measuring the Mw of the (co)polymer (B) are the same as the conditions for measuring the Mw of the monomer (a).

The viscosity index improver of the present invention preferably contains 0.1 to 40% by weight of the copolymer (A) based on the weight of the viscosity index improver, from the viewpoint of handleability.
From the viewpoint of low-temperature viscosity reduction, the viscosity index improver of the present invention preferably contains the (co)polymer (B) in an amount of 0.01 to 10% by weight based on the weight of the viscosity index improver. .

<Hydrocarbon oil (C)>
In the present invention, the viscosity index improver may contain hydrocarbon oil (C). When the hydrocarbon oil (C) is contained, when producing the lubricating oil composition, it is easy to further dilute with the hydrocarbon oil (C) or mix with additives described later, etc., making it easy to produce the lubricating oil composition. Therefore, it is preferable.
The hydrocarbon oil (C) is not particularly limited, but for example, mineral oil (solvent refined oil, paraffin oil, high viscosity index oil containing isoparaffin, high viscosity index oil obtained by hydrocracking isoparaffin, naphthenic oil, etc.) , synthetic lubricating oils [hydrocarbon synthetic lubricating oils (poly-α-olefin synthetic lubricating oils, GTL (Gas to Liquid) base oils, etc.)], and mixtures thereof. Of these, (A) mineral oils, poly-α-olefin synthetic lubricating oils (PAO oils), and GTL base oils are preferable from the viewpoint of solubility.

The kinematic viscosity (measured according to JIS-K2283) of the hydrocarbon oil (C) at 100° C. is preferably 1 to 15 mm ² /s, more preferably from the viewpoint of the viscosity index and low-temperature fluidity of the lubricating oil composition. is 2 to 5 mm ² /s, particularly preferably 2.0 to 4.5 mm ² /s, most preferably 2.4 to 4.3 mm ² /s.
The viscosity index (measured according to JIS-K2283) of the hydrocarbon oil (C) is preferably 100 or more from the viewpoint of the viscosity index and low-temperature fluidity of the lubricating oil composition.

The cloud point (as measured by JIS-K2269) of the hydrocarbon oil (C) is preferably -5°C or lower, more preferably -15°C or lower. When the cloud point of the hydrocarbon oil (C) 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, the effect of improving the viscosity index is high, the kinematic viscosity of the lubricating oil composition at 40 to 80 ° C. and the HTHS viscosity at 100 ° C. can be lowered, and the low temperature (-20 ° C. ), the lubricating oil composition containing the viscosity index improver of the present invention can be used as a gear oil (differential oil, industrial gear oil, etc.), MTF, transmission oil [ATF, DCTF and belt-CVTF, etc.], traction oil (toroidal-CVTF, etc.), shock absorber oil, power steering oil, hydraulic oil (construction machine hydraulic oil and industrial hydraulic oil, etc.) and engine oil (gasoline and diesel) It can be suitably used, particularly as a lubricating oil composition for internal combustion engines, particularly as a lubricating oil composition for hybrid vehicles.

<Lubricating oil composition>
The lubricating oil composition of the present invention comprises the viscosity index improver of the present invention, a detergent, a dispersant, an antioxidant, an oiliness improver, a pour point depressant, a friction and wear modifier, an extreme pressure agent, an antifoaming agent, It contains at least one additive selected from the group consisting of demulsifiers, metal deactivators and corrosion inhibitors.
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 economy.
The content of the (co)polymer (B) 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 reduction.
The content of the hydrocarbon oil (C) in the lubricating oil composition of the present invention is preferably 45% by weight or more, more preferably 50% by weight or more, based on the weight of the lubricating oil composition. It is preferably 99.79% by weight or less, more preferably 99.79% by weight or less.

The SP value {(cal/cm ³ ) ^1/2 } of the hydrocarbon oil (C) in the lubricating oil composition is preferably 6 to 9, more preferably 7 to 9, from the viewpoint of improving the viscosity index. , particularly preferably 8-9.
When a mixture of a plurality of hydrocarbon compounds such as mineral oil is used as the hydrocarbon oil ^{( C} ), measurement of the molecular weight by GPC, analysis of the molecular structure by The constituent components and their molecular structures are known, and the SP value of the hydrocarbon oil (C) can be calculated by arithmetic mean based on the mole fractions.

The hydrocarbon oil (C) in the lubricating oil composition is not particularly limited. oils, naphthenic oils, etc.), synthetic lubricating oils [hydrocarbon synthetic lubricating oils (poly-α-olefin synthetic lubricating oils, GTL base oils, etc.)], and mixtures thereof.
The lubricating oil composition preferably contains a GTL base oil from the viewpoint of the effect of improving the viscosity index and the storage modulus at low temperature (−20° C.). GTL base oils are base oils synthesized by the Fischer-Tropsch process that converts natural gas into liquid fuels. Although the reason is not clear, when the GTL base oil is contained, the behavior of the polymer chains of the copolymer (A) tends to be better, and the effect of improving the viscosity index and the storage modulus at low temperatures tend to be better.

The content of the GTL base oil in the lubricating oil composition is based on the weight of the hydrocarbon oil (C) in the lubricating oil composition, the effect of improving the viscosity index and the storage elastic modulus at low temperature (-20 ° C.) Therefore, it is preferably 50 to 95% by weight, more preferably 70 to 93% by weight.
The content of the GTL base oil in the lubricating oil composition is preferably 60 to 94% by weight, more preferably 70 to 90% by weight, based on the weight of the lubricating oil composition, from the viewpoint of fuel consumption reduction and cost. , particularly preferably 70 to 85% by weight.
The content of the hydrocarbon base oil other than the GTL base oil in the lubricating oil composition is preferably 2 to 20% by weight, more preferably 5% by weight, based on the weight of the lubricating oil composition, from the viewpoint of fuel consumption reduction and cost. to 18% by weight, particularly preferably 8 to 17% by weight.

The kinematic viscosity of the GTL base oil at 100° C. (measured according to JIS-K2283) (unit: mm ² /s, abbreviated hereinafter) is preferably 2.0 to 4.5, more preferably 2.0 to 4.5, from the viewpoint of reducing fuel consumption. is between 2.0 and 3.5.
The lubricating oil composition contains 80% by weight or more of a GTL base oil having a kinematic viscosity at 100° C. in the above range based on the weight of the GTL base oil (B) contained in the lubricating oil composition. preferably 90% by weight or more, particularly preferably 95% by weight or more.
When two types of GTL base oils are used in combination, from the viewpoint of reducing fuel consumption and moderate NOACK transpiration amount, a GTL base oil having a kinematic viscosity at 100 ° C. of 2.00 to 3.50 mm ² / s and a kinematic viscosity at 100 ° C. is preferably 3.51 to 5.00 mm ² /s, more preferably a GTL base oil having a kinematic viscosity at 100 ° C. of 2.50 to 3.00 mm ² / s and at 100 ° C. It is used in combination with a GTL base oil having a kinematic viscosity of 3.80 to 4.50 mm ² /s.
The kinematic viscosity of the GTL base oil at 40° C. (measured according to JIS-K2283) (unit: mm ² /s, abbreviated hereinafter) is preferably 5.0 to 20.0, more preferably 5.0 to 20.0, from the viewpoint of reducing fuel consumption. is between 8.0 and 19.0.

^When the lubricating oil composition is used as an engine oil, the copolymer (A ) is preferably contained in an amount of 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, particularly preferably 0.5 to 5% by weight.
When used as a gear oil, a hydrocarbon oil (C) having a kinematic viscosity at 100° C. of 2 to 10 mm ² /s is added with a copolymer (A) of 3 to 20% based on the weight of (C). % by weight is preferred.
When used as an automatic transmission oil (ATF, belt-CVTF, etc.), a hydrocarbon oil (C) with a kinematic viscosity at 100 ° C. of 2 to 6 mm ² / s, based on the weight of (C), Those containing 3 to 20% by weight of the polymer (A) are preferred.
When used as a traction oil, a hydrocarbon oil (C) having a kinematic viscosity at 100° C. of 1 to 5 mm ² /s is added with 0.5 of the copolymer (A) based on the weight of (C). A content of up to 10% by weight is preferred.

Examples of additives in the present invention include the following.
(1) Detergency:
Basic, overbased or neutral metal salts [such as overbased or alkaline earth metal salts of sulfonates (petroleum sulfonates, alkylbenzene sulfonates and alkylnaphthalene sulfonates, etc.)], salicylates, phenates, naphthenates , carbonates, phosphonates and mixtures thereof;
(2) Dispersant:
succinimides (bis- or mono-polybutenyl succinimides), Mannich condensates and borates, etc.;
(3) Antioxidants:
hindered phenols and aromatic secondary amines;
(4) Oiliness improver:
Long-chain fatty acids and their esters (oleic acid and oleic acid esters, etc.), long-chain amines and their amides (oleylamine and oleylamide, etc.), etc.;
(5) Pour point depressant polyalkyl methacrylate, ethylene-vinyl acetate copolymer, etc.;
(6) Friction and wear modifier:
molybdenum-based and zinc-based compounds (molybdenum dithiophosphate, molybdenum dithiocarbamate and zinc dialkyldithiophosphate, etc.);
(7) extreme pressure agent:
sulfur compounds (mono- or disulfides, sulfoxides and sulfur phosphide compounds), phosphide compounds and chlorine compounds (chlorinated paraffins, etc.);
(8) Defoamer:
Silicon oil, metallic soap, fatty acid ester and phosphate compound, etc.;
(9) Demulsifier:
Quaternary ammonium salts (tetraalkylammonium salts, etc.), sulfated oils and phosphates (polyoxyethylene-containing nonionic surfactant phosphates, etc.), hydrocarbon solvents (toluene, xylene, ethylbenzene), etc.;
(10) metal deactivator nitrogen atom-containing compounds (benzotriazole, etc.), nitrogen atom-containing chelate compounds (N,N'-disalitidene-1,2-diaminopropane, etc.), nitrogen/sulfur atom-containing compounds (2-(n - dodecylthio) benzimidazole, etc.);
(11) Corrosion inhibitor:
nitrogen atom-containing compounds (benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate, etc.);

One of these additives may be added, or two or more additives may be added as necessary. A mixture of these additives is sometimes called 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. Further, the total content of each additive is preferably 0.1 to 30% by weight, more preferably 0.3 to 20% by weight, and further preferably 3 to 10% by weight based on the total amount of the lubricating oil composition. %.

When the lubricating oil composition is used as an engine oil (0W-16), the viscosity index of the lubricating oil composition (measured according to JIS-K2283) is preferably 250 to 290 from the viewpoint of fuel economy, and further Preferably it is 260-280.
When the lubricating oil composition is used as an engine oil (0W-20), the viscosity index of the lubricating oil composition (measured according to JIS-K2283) is preferably 300 to 330 from the viewpoint of fuel economy, and further Preferably it is 310-325.

When the lubricating oil composition is used as an engine oil (0W-16), the HTHS viscosity (100° C.) (according to ASTM D4683) of the lubricating oil composition is 3.50 to 4.0 from the viewpoint of fuel saving. 10 mPa·s is preferable, and 3.60 to 4.00 mPa·s is more preferable.
When the lubricating oil composition is used as an engine oil (0W-20), the HTHS viscosity (100° C.) (according to ASTM D4683) of the lubricating oil composition is 4.00 to 4.00 from the viewpoint of fuel economy. 40 mPa·s is preferable, and 4.10 to 4.30 mPa·s is more preferable.

When the lubricating oil composition is used as an engine oil (0W-16), the kinematic viscosity (100 ° C.) of the lubricating oil composition (measured according to JIS-K2283) is 6.00 from the viewpoint of fuel economy. It is preferably up to 6.70 mm ² /s, more preferably 6.10 to 6.60 mm ² /s.
When the lubricating oil composition is used as an engine oil (0W-20), the kinematic viscosity (100 ° C.) of the lubricating oil composition (measured according to JIS-K2283) is 7.40 from the viewpoint of fuel economy. It is preferably up to 7.80 mm ² /s, more preferably 7.50 to 7.70 mm ² /s.

When the lubricating oil composition is used as an engine oil (0W-16), the kinematic viscosity (80 ° C.) of the lubricating oil composition (measured according to JIS-K2283) is 7.75 from the viewpoint of fuel economy. 8.30 mm ² /s is preferable, and 7.85 to 8.20 mm ² /s is more preferable.
When the lubricating oil composition is used as an engine oil (0W-20), the kinematic viscosity (80 ° C.) of the lubricating oil composition (measured according to JIS-K2283) is 8.70 from the viewpoint of fuel economy. It is preferably up to 9.60 mm ² /s, more preferably 8.90 to 9.50 mm ² /s.

When the lubricating oil composition is used as an engine oil (0W-16), the kinematic viscosity (60 ° C.) of the lubricating oil composition (measured according to JIS-K2283) is 11.5 from the viewpoint of fuel economy. It is preferably up to 13.0 mm ² /s, more preferably 12.0 to 12.5 mm ² /s.
When the lubricating oil composition is used as an engine oil (0W-20), the kinematic viscosity (60 ° C.) of the lubricating oil composition (measured according to JIS-K2283) is 12.5 from the viewpoint of fuel economy. It is preferably up to 14.5 mm ² /s, more preferably 13.0 to 14.0 mm ² /s.

When the lubricating oil composition is used as an engine oil (0W-16), the kinematic viscosity (40 ° C.) of the lubricating oil composition (measured according to JIS-K2283) is 21.0 from the viewpoint of fuel economy. It is preferably up to 22.5 mm ² /s, more preferably 21.5 to 22.0 mm ² /s.
When the lubricating oil composition is used as an engine oil (0W-20), the kinematic viscosity (40 ° C.) of the lubricating oil composition (measured according to JIS-K2283) is 22.5 to 22.5 from the viewpoint of fuel saving. 25.0 mm ² /s is preferable, and 23.0 to 24.5 mm ² /s is more preferable.

When the lubricating oil composition is used as an engine oil (0W-16), the ratio of the kinematic viscosity at 60 ° C. and the kinematic viscosity at 80 ° C. of the lubricating oil composition (60 ° C. kinematic viscosity / 80 ° C. kinematic viscosity) is From the viewpoint of reducing fuel consumption, it is preferably 1.3 to 1.7, more preferably 1.35 to 1.6.
When the lubricating oil composition is used as an engine oil (0W-16), the ratio of the kinematic viscosity at 40 ° C. and the kinematic viscosity at 100 ° C. of the lubricating oil composition (40 ° C. kinematic viscosity / 100 ° C. kinematic viscosity) is From the viewpoint of reducing fuel consumption, it is preferably 3.0 to 4.0, more preferably 3.1 to 3.7.
When the lubricating oil composition is used as an engine oil (0W-16), the ratio of the kinematic viscosity at 60 ° C. and the kinematic viscosity at 100 ° C. of the lubricating oil composition (60 ° C. kinematic viscosity / 100 ° C. kinematic viscosity) is From the viewpoint of reducing fuel consumption, it is preferably 1.8 to 2.1, more preferably 1.8 to 2.0.
When the lubricating oil composition is used as an engine oil (0W-20), the ratio of the kinematic viscosity at 60 ° C. and the kinematic viscosity at 80 ° C. of the lubricating oil composition (60 ° C. kinematic viscosity / 80 ° C. kinematic viscosity) is From the viewpoint of reducing fuel consumption, it is preferably 1.3 to 1.7, more preferably 1.35 to 1.6.
When the lubricating oil composition is used as an engine oil (0W-20), the ratio of the kinematic viscosity at 40 ° C. and the kinematic viscosity at 100 ° C. of the lubricating oil composition (40 ° C. kinematic viscosity / 100 ° C. kinematic viscosity) is From the viewpoint of reducing fuel consumption, it is preferably 3.0 to 3.5, more preferably 3.1 to 3.3.
When the lubricating oil composition is used as an engine oil (0W-20), the ratio of the kinematic viscosity at 60 ° C. and the kinematic viscosity at 100 ° C. of the lubricating oil composition (60 ° C. kinematic viscosity / 100 ° C. kinematic viscosity) is From the viewpoint of reducing fuel consumption, it is preferably 1.8 to 2.0, more preferably 1.8 to 1.9.

The storage elastic modulus G' of the lubricating oil composition (measurement temperature -20 ° C., measurement conditions below) is preferably 125 Pa or less in the case of engine oil (0W-16) from the viewpoint of reducing fuel consumption. More preferably, it is 120 Pa or less. As a lower limit, 90 Pa or more is preferable.
The storage elastic modulus G' of the lubricating oil composition (measurement temperature -20 ° C., measurement conditions below) is preferably 169 Pa or less in the case of engine oil (0W-20) from the viewpoint of reducing fuel consumption. More preferably, it is 165 Pa or less. As a lower limit, 90 Pa or more is preferable.

The lubricating oil composition of the present invention includes gear oils (differential oils, industrial gear oils, etc.), MTF, transmission oils [ATF, DCTF, belt-CVTF, etc.], traction oils (toroidal-CVTF, etc.), shock absorber oils, It is suitably used for power steering fluids, hydraulic fluids (construction machinery hydraulic fluids, industrial hydraulic fluids, etc.) and engine oils (for gasoline and diesel), especially lubricating oil compositions for internal combustion engines, especially for hybrid vehicles. It can be suitably used as a lubricating oil composition.

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples, but the present invention is not limited to these.

The ratio of 1,2-butylene groups in the constituent units of the hydrocarbon polymer was obtained by analyzing the polymer by ¹³ C-NMR and using the above formula (1) in 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) is obtained by analyzing the polymer by ¹³ C-NMR and using the above formula (1). From the value of the integral value B and the value of the integral value C used, it was obtained by the following formula (3).
1,2-adduct/1,4-adduct molar ratio={100×integral value B×4/integral value C}/{100−(100×integral value B×4/integral value C)} (3 )

<Production Example 1>
400 parts by weight of degassed and dehydrated hexane, 0.5 parts by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, and 0 part of n-butyllithium were placed in a 1 L SUS pressure-resistant reaction vessel equipped with a temperature controller and a stirrer. After charging 9 parts by weight, polymerization was carried out at a polymerization temperature of 50°C.
After the polymerization rate reached approximately 100%, 2 parts by weight of ethylene oxide was added, and the mixture was reacted at 50° C. for additional 3 hours. In order to stop the reaction, 50 parts by weight of water and 25 parts by weight of 1N-hydrochloric acid aqueous solution were added and stirred at 80° C. for 1 hour. The organic phase of the reaction solution was collected with a separating funnel, heated to 70° C., and the solvent was removed under 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 control device, 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 prepared by mixing 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran in advance, the mixture was reacted at room temperature for 8 hours while supplying hydrogen into the liquid at a flow rate of 30 mL/min from the hydrogen introduction pipe. rice field. After that, palladium carbon is removed by filtration, and the resulting filtrate is heated to 70° C. and tetrahydrofuran is removed under reduced pressure of 0.027 to 0.040 MPa to remove hydrogenated polybutadiene one-end hydroxyl group-containing polymer (Y1). got
The molecular weight of the obtained (Y1) was measured by GPC, and the ratio of 1,2-butylene groups was measured by ¹³ C-NMR. As a result, Mw = 7,000, Mn = 6,500, the ratio of 1,2-butylene groups = 45 mol%, and the molar ratio (1,2-adduct/1,4-adduct) = 45/55. rice field.

<Production Example 2>
400 parts by weight of degassed and dehydrated hexane, 2 parts by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, and 0.9 of n-butyllithium were placed in a 1 L SUS pressure-resistant reaction vessel equipped with a temperature controller and a stirrer. After charging the weight part, polymerization was carried out at a polymerization temperature of -0°C.
After the polymerization rate reached approximately 100%, 2 parts by weight of ethylene oxide was added and reacted at 50° C. for 3 hours. In order to stop the reaction, 50 parts by weight of water and 25 parts by weight of 1N-hydrochloric acid aqueous solution were added and stirred at 80° C. for 1 hour. The organic phase of the reaction solution was collected with a separating funnel, heated to 70° C., and the solvent was removed under 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 control device, 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 prepared by mixing 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran in advance, the mixture was reacted at room temperature for 8 hours while supplying hydrogen into the liquid at a flow rate of 30 mL/min from the hydrogen introduction pipe. rice field. After that, palladium carbon is removed by filtration, and the obtained filtrate is heated to 70° C. and tetrahydrofuran is removed under reduced pressure of 0.027 to 0.040 MPa to remove hydrogenated polybutadiene having one terminal hydroxyl group (Y2). got
The molecular weight of the obtained (Y2) was measured by GPC, and the ratio of 1,2-butylene groups was measured by ¹³ C-NMR. As a result, Mw = 7,000, Mn = 6,500, the ratio of 1,2-butylene groups = 65 mol%, and the molar ratio (1,2-adduct/1,4-adduct) = 65/35. rice field.

<Examples 1 to 26 and Comparative Examples 1 to 14>
<Preparation of viscosity index improvers containing copolymers (A-1) to (A-12) and (A'-1) to (A'-7)>
In a reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer and a nitrogen inlet tube, 400 parts of the hydrocarbon oil 1 described below and a total of 100 parts by weight of the monomer blends described in Tables 2 to 5 are added. 2,2-azobis (2,4-dimethylvaleronitrile), 2,2-azobis (2-methylbutyronitrile), t-butylperoxy-2-ethylhexyl monocarbonate as catalysts Table 2- 5, and after nitrogen substitution (gas phase oxygen concentration: 100 ppm), the temperature was raised to 76° C. while stirring in a sealed state, and polymerization reaction was carried out at the same temperature for 4 hours. After raising the temperature to 120 to 130° C., unreacted monomers were removed over 2 hours under reduced pressure (0.027 to 0.040 MPa) at the same temperature, and the copolymer (A) and hydrocarbon oil 1 were contained. A viscosity index improver was obtained. The SP value calculated based on the weight fraction of the obtained copolymer (A) (SP value of (A)) was calculated by the above method, and Mw was measured by the above method.

<Adjustment of lubricating oil composition>
A lubricating oil composition was obtained by blending the viscosity index improver obtained in the above preparation, other additives, and a base oil in amounts shown in Tables 2 to 5. The content of the copolymer (A) in the table is the pure content (% by weight) of the copolymer (A) contained in the lubricating oil composition when the total amount of the lubricating oil composition is 100% by weight. is. In addition, Examples 1 to 13 and Comparative Examples 1 to 7 are evaluations in the case of 0W-16 grade (HTHS viscosity: 2.3 mPa s or more), and Examples 14 to 26 and Comparative Examples 8 to 14 are 0W. -20 grade (HTHS viscosity: 2.6 mPa·s or more).

The compositions of monomers (a) to (d) listed in Tables 2 to 5 are as described below.
(a-1): methacrylic acid ester of hydrogenated polybutadiene polymer containing hydroxyl group at one end obtained in Production Example 1 (ratio of 1,2-butylene = 45 mol%) (Y1) [Mn: 6,600, general p=0 in formula (1), -X ¹ -=-O(CH ₂ CH ₂ O) ₁ -]
(a-2): methacrylic acid ester of hydrogenated polybutadiene polymer containing hydroxyl group at one end obtained in Production Example 2 (ratio of 1,2-butylene = 65 mol%) (Y2) [Mn: 6,600, general p=0 in formula (1), -X ¹ -=-O(CH ₂ CH ₂ O) ₁ -]
(a-3): One-end hydroxyl group-containing hydrogenated polybutadiene manufactured by CrayValley (Paris, France) [trade name; Krasol HLBH-5000M, 1,2-butylene ratio = 65 mol%, molar ratio isomer/1,4-adduct)=65/35, crystallization temperature of −60° C. or less] and esterified product of methacrylic acid [Mn: 4,800, p=0 in general formula (1), −X ¹ − =-O-]
(b-1): n-butyl methacrylate (b-2): ethyl methacrylate (c-1): Neodol 23 (manufactured by Shell Chemicals, linear or branched alkyl alcohol having 12 to 13 carbon atoms (weight ratio = linear Chain C12: branched C12: straight chain C13: branched C13 = 40:10:40:10)) methacrylic acid ester (c-2): Neodol 45 (manufactured by Shell Chemicals, straight chain with 14 to 15 carbon atoms or a mixture of branched alkyl alcohol (weight ratio = linear C14: branched C14: linear C15: branched C15 = 40:10:40:10) methacrylic acid ester (d-1): ethoxyethyl methacrylate (d- 2): Butoxyethyl methacrylate

The base oils and DI packages listed in Tables 2-5 are as follows.
Hydrocarbon oil 1: SK Lubricants, product name “Yubase4”, Group III (SP value: 8.3, kinematic viscosity at 100°C: 4.2 mm ² /s, kinematic viscosity at 40°C: 19.6 mm ² /s )
GTL base oil 1: Group III (SP value: 8.3, kinematic viscosity at 100°C: 4.1 mm ² /s, kinematic viscosity at 40°C: 18 mm ² /s)
GTL base oil 2: Group III (SP value: 8.3, kinematic viscosity at 100°C: 2.7 mm ² /s, kinematic viscosity at 40°C: 9.9 mm ² /s)
P5741: Infinium Co., Ltd. DI package, package additive containing detergent, dispersant, antioxidant, etc. PV1510: Lubrizol Co., Ltd. DI package, package additive containing detergent, dispersant, antioxidant, etc. agent

（１）の構造
ΣΔｅ_ｉ＝１１２５（ＣＨ_３）＋１１８０（ＣＨ_２）＋３５０（Ｃ）＋４３００（ＣＯ_２）＝６９５５
Σｖ_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
Σｖ_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
Σｖ_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
Σｖ_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＝（６６００－８６（（１）の構造）－４４（（２）の構造））／５６＝１１５．５５
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＋４３０５×１１５．５５×０．４５＋４７２０×１１５．５５×０．５５＝５３３９４８．２
Σｖ_ｉ＝４８．４＋３６＋６４．７×１１５．５５×０．４５＋６４．４×１１５．５５×０．５５＝７５４１．６４９７
ＳＰ値＝（ΣΔｅ_ｉ／Σｖ_ｉ）^１／２＝（５３３９４８．２／７５４１．６４９７）^１／２＝８．４１４ The SP value of a structural unit (structure in which a carbon-carbon double bond reacts to form a single bond) derived from each monomer was calculated based on the following formula.
Structural unit derived from (a-1)

Structure of (1) ΣΔe _i =1125( _CH3 )+1180( _CH2 )+350(C)+4300( _CO2 )=6955
Σv _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
Σv _i =16.1(CH ₂ )×2+3.8(O)=36
Structure of (3) ΣΔe _i =1180(CH ₂ )×2+1125(CH ₃ )+820(CH)=4305
Σv _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
Σv _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 (structure (3)) and 1,4-butylene groups (structure (4)) = (6600-86 (structure (1)) - 44 (structure (2) ))/56=115.55
Therefore, the parameters of the structural unit derived from (a-1) are as follows.
ΣΔe _i =6955+3160+4305×115.55×0.45+4720×115.55×0.55=533948.2
Σv _i =48.4+36+64.7×115.55×0.45+64.4×115.55×0.55=7541.6497
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(533948.2/7541.6497) ^1/2 =8.414

１，２－ブチレン基及び１，４－ブチレン基の合計個数＝（６６００－８５－４４）／５６＝１１５．５５
ΣΔｅ_ｉ＝６９５５＋３１６０＋４３０５×１１５．５５×０．６５＋４７２０×１１５．５５×０．３５＝５２４３５７．３
Σｖ_ｉ＝４８．４＋３６＋６４．７×１１５．５５×０．６５＋６４．４×１１５．５５×０．３５＝７５４８．５８３
ＳＰ値＝（ΣΔｅ_ｉ／Σｖ_ｉ）^１／２＝（５２４３５７．３／７５４８．５８３）^１／２＝８．３３５ Structural unit derived from (a-2)

Total number of 1,2-butylene groups and 1,4-butylene groups = (6600-85-44)/56 = 115.55
ΣΔe _i =6955+3160+4305×115.55×0.65+4720×115.55×0.35=524357.3
Σv _i =48.4+36+64.7×115.55×0.65+64.4×115.55×0.35=7548.583
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(524357.3/7548.583) ^1/2 =8.335

１，２－ブチレン基及び１，４－ブチレン基の合計個数＝（４８００－８５）／５６＝８４．２０
ΣΔｅ_ｉ＝６９５５＋４３０５×８４．２０×０．６５＋４７２０×８４．２０×０．３５＝３８１６５０．２
Σｖ_ｉ＝４８．４＋６４．７×８４．２０×０．６５＋６４．４×８４．２０×０．３５＝５４８７．０６８
ＳＰ値＝（ΣΔｅ_ｉ／Σｖ_ｉ）^１／２＝（３８１６５０．２／５４８７．０６８）^１／２＝８．３４０ Structural unit derived from (a-3)

Total number of 1,2-butylene groups and 1,4-butylene groups = (4800-85)/56 = 84.20
ΣΔe _i =6955+4305×84.20×0.65+4720×84.20×0.35=381650.2
Σv _i =48.4+64.7×84.20×0.65+64.4×84.20×0.35=5487.068
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(381650.2/5487.068) ^1/2 =8.340

Structural unit ΣΔe _i derived from (b-1) = 6955 + 1180 × 3 + 1125 = 11620
Σv _i =48.4+16.1×3+33.5=130.2
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(11620/130.2) ^1/2 =9.447
Structural unit ΣΔe _i derived from (b-2) = 6955 + 1180 + 1125 = 9260
Σv _i =48.4+16.1+33.5=98
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(9260/98) ^1/2 =9.721

Structural unit straight chain C12 derived from (c-1)
ΣΔe _i =6955+1180×11+1125=21060
Σv _i =48.4+16.1×11+33.5=259
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(21060/259) ^1/2 =9.017
Branch C12
ΣΔe _i =6955+1180×9+1125×2+820=20645
Σv _i =48.4+16.1×9+33.5×2−1.0=259.3
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(20645/259.3) ^1/2 =8.923
Linear C13
ΣΔe _i =6955+1180×12+1125=22240
Σv _i =48.4+16.1×12+33.5=275.1
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(22240/275.1) ^1/2 =8.991
Branch C13
ΣΔe _i =6955+1180×10+1125×2+820=21825
Σv _i =48.4+16.1×10+33.5×2−1.0=275.4
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(21825/275.4) ^1/2 =8.902
SP value of structural unit derived from (c-1) = (9.017 × 40 + 8.923 × 10 + 8.991 × 40 + 8.902 × 10) / 100 = 8.986

Structural unit straight chain C14 derived from (c-2)
ΣΔe _i =6955+1180×13+1125=23420
Σv _i =48.4+16.1×13+33.5=291.2
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(23420/291.2) ^1/2 =8.968
Branch C14
ΣΔe _i =6955+1180×11+1125×2+820=23005
Σv _i =48.4+16.1×11+33.5×2−1.0=291.5
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(23005/291.5) ^1/2 =8.884
Linear C15
ΣΔe _i =6955+1180×14+1125=24600
Σv _i =48.4+16.1×14+33.5=307.3
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(24600/307.3) ^1/2 =8.947
Branch C15
ΣΔe _i =6955+1180×12+1125×2+820=24185
Σv _i =48.4+16.1×12+33.5×2−1.0=307.6
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(24185/307.6) ^1/2 =8.867
SP value of structural unit derived from (c-2) = (8.968 × 40 + 8.884 × 10 + 8.947 × 40 + 8.867 × 10) / 100 = 8.941

Structural unit ΣΔe _i derived from (d−1) = 6955 + 3160 + 1180 + 1125 = 12420
Σv _i =48.4+36+16.1+33.5=134
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(12420/134) ^1/2 =9.627
Structural unit ΣΔe _i derived from (d-2) = 6955 + 3160 + 1180 × 3 + 1125 = 14780
Σv _i =48.4+36+16.1×3+33.5=166.2
SP value=(ΣΔe _i /Σv _i ) ^1/2 =(14780/166.2) ^1/2 =9.430

<Method for measuring NOACK evaporation amount of lubricating oil composition>
It was measured according to the method of ASTM D 5800 (measurement conditions: 250°C, 1 hour).

<Method for measuring HTHS viscosity of lubricating oil composition>
Measured at 100°C and 150°C according to the method of ASTM D 4683.

<Method for measuring dynamic viscosity of lubricating oil composition and method for calculating viscosity index>
The kinematic viscosities at 40°C, 60°C, 80°C and 100°C were measured by the method of JIS-2283, and the viscosity index was calculated by the method of JIS-2283. It means that the larger the value of the viscosity index, the higher the effect of improving the viscosity index.

<Method for measuring storage modulus (−20° C.) of lubricating oil composition-rheometer>
It was measured by the following procedure using a rheometer "Physica MCR302" manufactured by Anton paar. First, the target sample oil was inserted into a cone plate (50 mm diameter, 1° inclination angle) and held at −20° C. for 10 minutes. At this time, care was taken not to distort the inserted solution. Then, the storage modulus G' was measured at −20° C. with a frequency of 1 Hz and a shear strain of 0.00996 to 100% in vibration mode. In the above measurement, the value of the storage elastic modulus G' (Pa) at a shear strain amount of 0.0096% is shown in the table.

From the results in Tables 2 to 5, the lubricating oil compositions containing the viscosity index improvers of Examples 1 to 26 of the present invention have low kinematic viscosities at 40 to 80 ° C. and HTHS viscosities at 100 ° C. It can be seen that the storage modulus is low and the effect of improving the viscosity index is high. In particular, when comparing the 0W-16 grade examples with a small amount of viscosity index improver added and the comparative examples, the examples of the present invention have extremely low kinematic viscosities at 40 to 80 ° C. and at -20 ° C. It can be seen that the storage elastic modulus is low and the fuel consumption reduction effect is high. Also, when comparing the 0W-20 grade examples with a large amount of viscosity index improver added and the comparative examples, the examples of the present invention show the effect of reducing the kinematic viscosity at 40 to 80 ° C. and the effect at -20 ° C. In addition to the storage elastic modulus reduction effect, the 100° C. HTHS viscosity tends to be low, indicating that the fuel consumption reduction effect is extremely high.

The viscosity index improver of the present invention has a high viscosity index improving effect, and the lubricating oil composition containing the viscosity index improver of the present invention has a low kinematic viscosity at 40 to 80 ° C. and a low HTHS viscosity at 100 ° C. Since the storage modulus at (-20 ° C) is low, it is expected to reduce fuel consumption, so gear oils (differential oils, industrial gear oils, etc.), MTF, transmission oils [ATF, DCTF, belt-CVTF, etc.] , traction oil (toroidal-CVTF, etc.), shock absorber oil, power steering oil, hydraulic oil (construction machine hydraulic oil, industrial hydraulic oil, etc.) and engine oil (for gasoline and diesel), especially It can be suitably used as a lubricating oil composition for internal combustion engines, particularly as a lubricating oil composition for hybrid vehicles.

Claims (7)

A polyolefin monomer (a) represented by the following general formula (1) and a monomer represented by the following general formula (2) in which R ⁴ is an alkyl group having 2 to 4 carbon atoms (b) and a monomer (c), which is a monomer represented by the following general formula (2) and wherein R ⁴ is an alkyl group having 12 to 16 carbon atoms, as constituent monomers: A viscosity index improver containing a polymer (A), wherein the weight average molecular weight of the copolymer (A) is 480,000 to 600,000, and the weight fraction of the copolymer (A) is The solubility parameter calculated based on the above is 9.23 to 9.25 (cal/cm ³ ) ^1/2 , and the monomers (a) and (b) constituting the copolymer (A) A viscosity index improver having a weight ratio (b/a) of 3.5 to 4.9 and a weight ratio (b/c) of the monomers (b) and (c) of 4.1 or more.

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

[In general formula (2), R ³ is a hydrogen atom or a methyl group; -X ² - is a group represented by -O- or -NH-; R ⁴ is an alkyl group having 2 to 4 or 12 to 16 carbon atoms. ] The viscosity index improver according to Claim 1, further comprising a hydrocarbon oil (C). R ² in the general formula (1) is hydrogen from a hydrocarbon polymer in which the ratio of 1,2-butylene groups is 30 mol% or more based on the total number of moles of the monomers constituting the hydrocarbon polymer. The viscosity index improver according to claim 1 or 2, which is a residue with one atom removed. The copolymer (A) contains 1 to 22% by weight of the monomer (a) based on the total weight of the monomers constituting (A) as constituent monomers, and the monomer (c) The viscosity index improver according to claim 1 or 2, which is a copolymer containing 1 to 17% by weight of The total weight ratio of the monomer (a), the monomer (b) and the monomer (c) based on the total weight of the monomers constituting the copolymer (A) is 70% by weight or more The viscosity index improver according to claim 1 or 2. Claim 1 or 2, containing 0.01 to 30% by weight of the (meth)acrylic acid alkyl ester (co)polymer (B) other than the copolymer (A), based on the weight of (A). Viscosity index improver according to. The viscosity index improver according to claim 1 or 2, a detergent, a dispersant, an antioxidant, an oiliness improver, a pour point depressant, a friction and wear modifier, an extreme pressure agent, an antifoaming agent, a demulsifier, and a metal. A lubricating oil composition containing at least one additive selected from the group consisting of inert agents and corrosion inhibitors.

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