JP2017057378A - Viscosity index improver composition and lubricating oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity index improver excellent in viscosity index improvement effect, a lubricating oil composition having little viscosity reduction caused by long-term use and excellent in low temperature viscosity and a production method therefor.SOLUTION: There is provided the viscosity index improver composition containing: a copolymer (A) having a monomer (a) represented by formula (1) and (meth)acrylic acid linear alkyl ester (b) having a C1 to 4 linear alkyl group as essential constitutional monomers; and an ester oil base oil having a kinetic viscosity at 100°C of 1.0 to 2.5 mm/s. (1), where Ris H or a methyl group, Xis O or NH, Ris each independently a C2 to 4 linear/branched alkylene group, p is an integer of 0 to 20, a (RO)part may be a random bond or a block bond and Ris a C32 to 44 branched alkyl group.SELECTED DRAWING: None

Description

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

Lubricants such as ATF, CVTF, and MTF used in automobile transmissions decrease in viscosity as the temperature increases, but in practice, the viscosity does not change as much as possible over a wide range from low temperature to high temperature, that is, the viscosity index is high. Is desirable. In recent years, as a means for improving fuel economy, reducing the viscosity resistance by reducing the viscosity of a lubricating oil has been performed. However, when the viscosity of the lubricating oil is lowered, various problems such as oil leakage and seizure may occur.
Thus, as a means for improving fuel economy, there is a method using a viscosity index improver. If the viscosity index is high, the viscosity resistance of the lubricating oil at low temperatures is lowered, leading to improved fuel economy. Therefore, a method for improving the temperature dependence of viscosity by adding a viscosity index improver to lubricating oil is widely used. As such a viscosity index improver, a methacrylic acid ester copolymer (Patent Literatures 1 to 4), an olefin copolymer (Patent Literature 5), a macromonomer copolymer (Patent Literature 6) and the like are known. Yes.
However, the above-mentioned lubricating oil composition has a problem that the effect of improving the viscosity index is not yet sufficient, and the shear stability after long-time operation and the low-temperature characteristics at start-up are not yet sufficient in practical use.

Japanese Patent No. 2732187 Japanese Patent No. 2941392 JP-A-7-62372 JP 2004-307551 A JP 2005-200454 A JP 2008-546894 A

  An object of the present invention is to provide a viscosity index improver excellent in a viscosity index improving effect, a viscosity index improver composition and a lubricating oil composition excellent in low temperature viscosity with little decrease in viscosity due to long-term use.

As a result of intensive studies, the present inventors have arrived at the present invention. That is, the present invention comprises a monomer (a) represented by the following general formula (1) and a (meth) acrylic acid linear alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms. A viscosity index improver composition comprising a copolymer (A) as a monomer and an ester oil base oil having a kinematic viscosity at 100 ° C. of 1.0 to 2.5 mm ² / s, A) contains 80 to 95 mol% of (b) based on the number of moles of the constituent monomer of (A) as the constituent monomer, and the molar ratio (a / b) of (a) and (b) ) Is a viscosity index improver composition that is a copolymer of 0.010 to 0.200.

[In General Formula (1), R ¹ is a hydrogen atom or a methyl group; —X ¹ — is a group represented by —O— or —NH—, and R ² is a straight chain having 2 to 4 carbon atoms or A branched alkylene group, p is an integer of 0 to 20, and R ² when p is 2 or more may be the same or different, and the (R ² O) _p moiety may be a random bond or a block bond; R ³ is a branched alkyl group having 32 to 44 carbon atoms. ]

  The viscosity index improver composition of the present invention has an effect that the viscosity index is high, there is little decrease in viscosity due to long-term shearing, and it is difficult to increase the viscosity at low temperatures.

  The viscosity index improver composition of the present invention is a (meth) acrylic acid linear alkyl ester (b) having a monomer (a) represented by the general formula (1) and a linear alkyl group having 1 to 4 carbon atoms. Containing a copolymer (A) having an essential constituent monomer. In addition, (meth) acrylic acid means acrylic acid or methacrylic acid.

The copolymer (A) in the present invention has (a) represented by the general formula (1) as an essential constituent monomer. R ¹ in the general formula (1) is a hydrogen atom or a methyl group. Among these, a methyl group is preferable from the viewpoint of improving the viscosity index.

-X ¹ in the general formula (1) - is a group represented by -O- or -NH-. Of these, —O— is preferable from the viewpoint of the effect of improving the viscosity index.

R ² in the general formula (1) is a linear or branched alkylene group having 2 to 4 carbon atoms, and examples thereof include an ethylene group, a propylene group, and a butylene group. Examples of propylene groups include 1,2- or 1,3-propylene groups. Examples of the butylene group include 1,2-, 1,3- or 1,4-butylene groups. Among these, preferred are an ethylene group and a propylene group, which are linear or branched alkylene groups having 2 to 3 carbon atoms, from the viewpoint of the effect of improving the viscosity index.

R ³ in the general formula (1) is a branched alkyl group having 32 to 44 carbon atoms. Examples of the branched alkyl group having 32 to 44 carbon atoms include 2-tetradecyloctadecyl group (carbon number 32), 2-tetradecylicosyl group (carbon number 34), 2-hexadecyloctadecyl group (carbon number 34), 2 -Hexadecylicosyl group (36 carbon atoms), 2-isohexadecylisoicosyl group (36 carbon atoms), 2-octadecyl docosyl group (40 carbon atoms), 2-icosyltetracosyl group (carbon number) 44), olefins [for example, propylene oligomer (11 to 15 mer), ethylene / propylene oligomer (11 to 21 mer, molar ratio 20/1 to 1/10) and isobutene oligomer (8 to 11 mer, etc.)]. Examples thereof include a residue obtained by removing a hydroxyl group from the obtained oxo alcohol.
Of the branched alkyl groups having 32 to 44 carbon atoms, a branched alkyl group having 32 to 40 carbon atoms is preferred from the viewpoint of solubility of the viscosity index improver in an ester oil base oil, and more preferred is a carbon number. A branched alkyl group having 32 to 36 carbon atoms, particularly preferred is a branched alkyl group having 32 to 36 carbon atoms branched at the 2-position of the alkyl group.

P in the general formula (1) is an integer of 0 to 20, and is preferably an integer of 0 to 5 from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity. More preferably, it is an integer of 0-2. When p is 2 or more, R ² may be the same or different, and when the (R ² O) _p moiety is different, it may be a random bond or a block bond. Random bonds are preferred from the viewpoint of low temperature viscosity.

Specific examples of the monomer (a) include 2-tetradecyloctadecyl (meth) acrylate, 2-tetradecylicosyl (meth) acrylate, ethylene glycol mono-2-tetradecylicosyl group and (meth) Esters with acrylic acid, 2-hexadecyloctadecyl (meth) acrylate, 2-hexadecylicosyl (meth) acrylate, 2-isohexadecylisoicosyl (meth) acrylate, 2- (meth) acrylic acid 2- Examples include octadecyl docosyl, 2-methosyl tetracosyl (meth) acrylate, and (meth) acrylic acid (propylene oligomer).
Among the monomers (a), from the viewpoint of viscosity index and low temperature viscosity, 2-tetradecyloctadecyl (meth) acrylate, 2-tetradecylicosyl (meth) acrylate, (meth) acrylic acid 2 are preferable. -Hexadecyloctadecyl, particularly preferred is 2-tetradecyloctadecyl (meth) acrylate, 2-tetradecylicosyl (meth) acrylate, and most preferred is 2-tetradecyloctadecyl (meth) acrylate.

  The copolymer (A) in the present invention further comprises (meth) acrylic acid linear alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms as an essential constituent monomer.

As the (meth) acrylic acid linear alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, An example is n-butyl (meth) acrylate.
Of these, (b) is preferably a (meth) acrylic acid linear alkyl ester having a linear alkyl group having 1 to 3 carbon atoms, and more preferably methyl (meth) acrylate and ethyl (meth) acrylate. Particularly preferred is methyl (meth) acrylate.

  (A) has a monomer (c) represented by general formula (2) and a linear alkyl group having 12 to 36 carbon atoms in addition to (a) and (b) as constituent monomers (meta) ) It is preferable from a viewpoint of the low-temperature viscosity of a lubricating oil composition to contain 1 or more types chosen from the group which consists of acrylic acid alkylester (d).

[In General Formula (2), R ⁴ is a hydrogen atom or a methyl group; —X ² — is a group represented by —O— or —NH—, and R ⁵ is a straight chain having 2 to 4 carbon atoms or A branched alkylene group, q is an integer from 0 to 20, and R ⁵ when q is 2 or more may be the same or different, and the (R ⁵ O) _q moiety may be a random bond or a block bond; R ⁶ is each independently a linear or branched alkyl group having 6 to 14 carbon atoms.

R ⁴ in the general formula (2) is a hydrogen atom or a methyl group. Among these, a methyl group is preferable from the viewpoint of the viscosity index.

-X < ² >-in General formula (2) is group represented by -O- or -NH-. Among these, a group represented by —O— is preferable from the viewpoint of the viscosity index.

R ⁵ in the general formula (2) is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group 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-butylene group. Is mentioned.

  Q in the general formula (2) is an integer of 0 to 20, and preferably an integer of 0 to 5 from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity. More preferably, it is an integer of 0-2. When p is 2 or more, A may be the same or different, and when they are different, they may be random bonds or block bonds. Random bonds are preferred from the viewpoint of low temperature viscosity.

^{R 6} in the general formula (3) are each independently a linear or branched alkyl group having 6 to 14 carbon atoms. Specifically, linear alkyl such as n-hexyl group, n-pentyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group, etc. In addition, branched alkyl groups such as isohexyl group, isooctyl group, isodecyl group, isododecyl group, isotetradecyl group and the like can be mentioned.
Of the straight chain or branched alkyl groups having 6 to 14 carbon atoms, the straight chain or branched alkyl groups having 7 to 13 carbon atoms are preferred from the viewpoint of viscosity index and low temperature viscosity, and more preferred are 8 to 8 carbon atoms. 12 straight-chain or branched alkyl groups, particularly preferred are straight-chain or branched alkyl groups having 8 to 10 carbon atoms.

Specific examples of the monomer (c) include 2-hexyloctyl (meth) acrylate, 2-octyldecyl (meth) acrylate, ethylene glycol mono-2-octylpentadecyl ether and (meth) acrylic acid. Ester, 2-methydecyl (meth) acrylate, 2-isooctyl isododecyl (meth) acrylate, 2-decyl tetradecyl (meth) acrylate, 2-isodecyl isotetradecyl (meth) acrylate, (meta ) 2-dodecylhexadecyl acrylate, 2-dodecylpentadecyl (meth) acrylate, N-2-octyldecyl (meth) acrylamide, and the like.
Among the monomers (c), from the viewpoint of the viscosity index and the low temperature viscosity, 2-octyldodecyl (meth) acrylate, 2-isooctylisododecyl (meth) acrylate, (meth) acrylic acid 2- Decyltetradecyl, 2-isodecylisotetradecyl (meth) acrylate, 2-dodecylhexadecyl (meth) acrylate, particularly preferably 2-octyldodecyl (meth) acrylate, 2-iso (meth) acrylate Octylisododecyl, 2-decyltetradecyl (meth) acrylate, 2-isodecylisotetradecyl (meth) acrylate, most preferred 2-octyldodecyl (meth) acrylate, 2-decyl (meth) acrylate Tetradecyl.

Specific examples of the (meth) acrylic acid linear alkyl ester (d) having a linear alkyl group having 12 to 36 carbon atoms include (meth) acrylic acid n-dodecyl, (meth) acrylic acid n-tridecyl, (meta ) N-tetradecyl acrylate, n-pentadecyl (meth) acrylate, n-hexadecyl (meth) acrylate, n-octadecyl (meth) acrylate, n-icosyl (meth) acrylate, n- (meth) acrylate Examples include docosyl, n-tetracosyl (meth) acrylate, n-triacontyl (meth) acrylate, and n-hexatriacontyl (meth) acrylate.
Of these, (meth) acrylic acid linear alkyl ester having a linear alkyl group having 12 to 20 carbon atoms is preferred from the viewpoint of viscosity index and low temperature viscosity, and more preferred is 12 to 18 carbon atoms. (Meth) acrylic acid linear alkyl ester having a straight chain alkyl group, and (meth) acrylic acid linear alkyl ester having a linear alkyl group having 14 to 18 carbon atoms is particularly preferred.

The solubility parameter (hereinafter abbreviated as SP value) of (A) is preferably 9.0 to 10.0 (cal / cm ³ ) ¹ from the viewpoint of improving the viscosity index and solubility in ester oil base oil. ^{/ 2,} more preferably ^{9.1~9.7 (cal / cm 3) 1/2} , more preferably from 9.2~9.6cal ^/ cm ^{3) 1/2.}
In addition, SP value of (A) and ester oil base oil is a value calculated by the method described in the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2 P. 147 to 154). is there.
The SP value of (A) is calculated based on the SP value of each monomer constituting (A) by the above method, and the SP value of each monomer is based on the mole fraction of the constituent monomer units. The average value.
The SP value of (A) can be set to a predetermined value by appropriately adjusting the SP value and the mole fraction of the monomer used.

Furthermore, the degree of dispersion of the SP value of (A) is preferably 0.10 to 1.00, more preferably 0.00 from the viewpoint of the effect of improving the viscosity index and the solubility in the lubricating base oil ester oil base oil. It is 10 to 0.80, more preferably 0.10 to 0.70, particularly preferably 0.15 to 0.60, and most preferably 0.15 to 0.50.
Note that the degree of dispersion of the SP value in (A) can be calculated and determined using the following formula (1). The degree of dispersion of the SP value of (A) can be set to a predetermined value by appropriately adjusting the molar fraction of the constituent monomers.

(Dispersity of SP value of (A)) = Σ [(Mole fraction of constituent monomer) × {(SP value of homopolymer of constituent monomer) − (SP value of (A))} ² ] (1)

(A) further comprises a nitrogen atom-containing monomer (excluding (a) and (c)) (e), a hydroxyl group-containing monomer (f), and a phosphorus atom-containing monomer (g). The copolymer which uses 1 or more types chosen from a group as a structural monomer may be sufficient.
Examples of the nitrogen atom-containing monomer (e) include the following monomers (e1) to (e4) other than (a) and (c).

Amide group-containing vinyl monomer (e1):
(Meth) acrylamide, monoalkylamino (meth) acrylamide [nitrogen atom having one alkyl group having 1 to 4 carbon atoms bonded thereto; for example, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N- Isopropyl (meth) acrylamide and Nn- or isobutyl (meth) acrylamide, etc.], monoalkylaminoalkyl (meth) acrylamide [aminoalkyl group in which one alkyl group having 1 to 4 carbon atoms is bonded to the nitrogen atom (carbon number 2-6); for example N-methylaminoethyl (meth) acrylamide, N-ethylaminoethyl (meth) acrylamide, N-isopropylamino-n-butyl (meth) acrylamide and Nn- or isobutylamino- n-butyl (meth) acrylamide etc.], dialkyl Mino (meth) acrylamide [nitrogen atom having two alkyl groups having 1 to 4 carbon atoms bonded; for example, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-diisopropyl (Meth) acrylamide and N, N-di-n-butyl (meth) acrylamide, etc.], dialkylaminoalkyl (meth) acrylamide [aminoalkyl group in which two alkyl groups having 1 to 4 carbon atoms are bonded to a nitrogen atom (carbon Having 2 to 6); for example, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide and N, N-di -N-butylaminobutyl (meth) acrylamide etc.], N-vinylcarboxylic acid amide [ - vinyl formamide, N- vinyl acetamide, include those having a N- vinyl -n- or isopropionyl and N- vinyl-hydroxyacetamide etc.] amide groups only on the nitrogen atom and the like.

Nitro group-containing monomer (e2):
4-nitrostyrene etc. are mentioned.

Primary to tertiary amino group-containing vinyl monomer (e3):
Primary amino group-containing vinyl monomer {alkenylamine having 3 to 6 carbon atoms [(meth) allylamine, crotylamine, etc.], aminoalkyl (2 to 6 carbon atoms) (meth) acrylate [aminoethyl (meth) acrylate, etc.] }; Secondary amino group-containing vinyl 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] For example, t-butylaminoethyl (meth) acrylate and methylaminoethyl (meth) acrylate, etc.], C 6-12 dialkenylamine [di (meth) allylamine, etc.}}; tertiary amino group-containing vinyl monomer {Dialkylaminoalkyl (meth) acrylate [Aminoalkyl having two alkyl groups having 1 to 6 carbon atoms bonded to a nitrogen atom] Having a sulfur group (2 to 6 carbon atoms); for example, dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate, etc.], alicyclic (meth) acrylate having a nitrogen atom [morpholinoethyl (meth) acrylate, etc. ], Aromatic vinyl monomers [N, N-diphenylaminoethyl (meth) acrylamide, N, N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone and N-vinylthiopyrrolidone etc.], and their hydrochlorides, sulfates, phosphates or lower alkyl (C 1-8) monocarboxylic acids (such as acetic acid and propionic acid) salts.

Nitrile group-containing vinyl monomer (e4):
Examples include (meth) acrylonitrile.

  Among (d), (e1) and (e3) are preferable, and N, N-diphenylaminoethyl (meth) acrylamide, dimethylaminoethyl (meth) acrylamide, and diethylaminoethyl (meth) acrylamide are more preferable. Dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, and diethylaminoethyl (meth) acrylate, and particularly preferred are dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.

Hydroxyl group-containing monomer (f):
Hydroxyl group-containing aromatic vinyl monomer (p-hydroxystyrene and the like), hydroxyalkyl (2 to 6 carbon atoms) (meth) acrylate [2-hydroxyethyl (meth) acrylate, and 2- or 3-hydroxypropyl (meth) Acrylates, etc.], mono- or di-hydroxyalkyl (1 to 4 carbon atoms) substituted (meth) acrylamide [N, N-dihydroxymethyl (meth) acrylamide, N, N-dihydroxypropyl (meth) acrylamide, N, N- Di-2-hydroxybutyl (meth) acrylamide etc.], vinyl alcohol, C3-C12 alkenol [(meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol and 1-undecenol etc.], carbon Number 4 to 12 alkene monool or alkenegio [1-buten-3-ol, 2-buten-1-ol, 2-butene-1,4-diol, etc.], hydroxyalkyl (C1-6) alkenyl (C3-10) ether (2 -Hydroxyethylpropenyl ether, etc.), polyvalent (3-8 valent) alcohols (glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, saccharides, sucrose, etc.) alkenyl (carbon number 3-10) ether or (meth) acrylate [Sucrose (meth) allyl ether etc.] etc .;
Polyoxyalkylene glycol (alkylene group having 2 to 4 carbon atoms, polymerization degree 2 to 50), polyoxyalkylene polyol [polyoxyalkylene ether of 3 to 8 valent alcohol (alkylene group having 2 to 4 carbon atoms, polymerization degree) 2-100)], poly (oxyalkylene glycol) or poly (oxyalkylene polyol) alkyl (carbon number 1-4) ether mono (meth) acrylate [polyethylene glycol (number average molecular weight, hereinafter abbreviated as Mn: 100-300) mono (Meth) acrylate, polypropylene glycol (Mn: 130 to 500) mono (meth) acrylate, methoxypolyethylene glycol (Mn: 110 to 310) (meth) acrylate, and the like.

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

Phosphoric ester group-containing monomer (g1):
(Meth) acryloyloxyalkyl (2 to 4 carbon atoms) phosphoric acid ester [(meth) acryloyloxyethyl phosphate and (meth) acryloyloxyisopropyl phosphate] and phosphoric acid alkenyl ester [vinyl phosphate, allyl phosphate, Propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, dodecenyl phosphate, etc.].

Phosphono group-containing monomer (g2):
(Meth) acryloyloxyalkyl (2 to 4 carbon atoms) phosphonic acid [(meth) acryloyloxyethylphosphonic acid etc.] and alkenyl (2 to 12 carbon atoms) phosphonic acid [vinyl phosphonic acid, allyl phosphonic acid and octenyl phosphonic acid Etc.].

  Of these, (g1) is preferable among (i), (meth) acryloyloxyalkyl (2 to 4 carbon atoms) phosphate is more preferable, and (meth) acryloyloxyethyl phosphate is particularly preferable. It is.

  In addition to the monomers (a) to (g), (A) is a copolymer having a monomer (h) having two or more unsaturated groups as a constituent monomer. It is preferable from the viewpoint of the improvement effect and the low temperature viscosity of the lubricating oil composition.

  Examples of the monomer (h) having two or more unsaturated groups include 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, trimethylolpropane tri (meth) acrylate And an ester of an unsaturated carboxylic acid having an Mn of 500 or more and an glycol and an ester of an unsaturated alcohol and a carboxylic acid described in International Publication WO01 / 009242.

  In addition to the monomers (a) to (h), (A) may use the following monomers (i) to (o) as constituent monomers.

Aliphatic hydrocarbon monomer (i):
C2-C20 alkene (Ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.) etc. are mentioned.

Alicyclic hydrocarbon monomer (j):
Examples include cyclopentene, cyclohexene, cycloheptene, cyclooctene, and pinene.

Aromatic hydrocarbon monomer (k):
Styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4-chloro Examples include tilbenzene, indene, and 2-vinylnaphthalene.

Vinyl esters, vinyl ethers, vinyl ketones (l):
Vinyl esters of saturated fatty acids having 2 to 12 carbon atoms (such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl octoate), alkyl, aryl or alkoxyalkyl vinyl ethers having 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) 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 (m):
Examples thereof include glycidyl (meth) acrylate and glycidyl (meth) allyl ether.

Halogen element-containing monomer (n):
Examples thereof include vinyl chloride, vinyl bromide, vinylidene chloride, (meth) allyl chloride and halogenated styrene (dichlorostyrene and the like).

Unsaturated polycarboxylic acid esters (o):
Alkyl, cycloalkyl or aralkyl ester of unsaturated polycarboxylic acid [alkyl diester having 1 to 8 carbon atoms of unsaturated dicarboxylic acid (such as maleic acid, fumaric acid and itaconic acid) (dimethyl maleate, dimethyl fumarate, diethyl maleate) And dioctyl maleate)] and the like.

The proportion of (a) constituting (A) is preferably 1 to 20 based on the total number of moles of monomers constituting (A) from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. The mol% is more preferably 2 to 16 mol%, particularly preferably 3 to 13 mol%, and most preferably 5 to 10 mol%.
The proportion of (b) constituting (A) is 80 to 95 mol% based on the total number of moles of the monomers constituting (A), and the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition From the viewpoint, it is preferably 81 to 95 mol%, more preferably 82 to 95 mol%, and particularly preferably 84 to 94 mol%.
The proportions of (c) and (d) constituting (A) are based on the total number of moles of monomers constituting (A) from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. Preferably it is 0-10 mol%, More preferably, it is 0.5-8 mol%, Most preferably, it is 1.5-6 mol%.
The total ratio of (c) and (d) constituting (A) is based on the total number of moles of monomers constituting (A) from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. Preferably, it is 0-15 mol%, More preferably, it is 0.5-10 mol%, Most preferably, it is 2-6 mol%.
Each ratio of (e) to (g) constituting (A) is based on the total number of moles of the monomers constituting (A) from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. Preferably it is 0-15 mol%, More preferably, it is 0.5-10 mol%, Most preferably, it is 2-6 mol%.
The proportions of (h) to (i) constituting (A) are based on the total number of moles of monomers constituting (A) from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. Preferably it is 0-15 mol%, More preferably, it is 0.5-10 mol%, Most preferably, it is 2-6 mol%.
The proportion of (j) constituting (A) is preferably 0.01 based on the total number of moles of monomers constituting (A) from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. It is -0.1 mol%, More preferably, it is 0.02-0.07 mol%, Most preferably, it is 0.03-0.06 mol%.
The proportions of (k) to (o) constituting (A) are based on the total number of moles of monomers constituting (A) from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. Preferably it is 0-10 mol%, More preferably, it is 0.5-8 mol%, Most preferably, it is 1.5-6 mol%.

  The molar ratio (a / b) between (a) and (b) constituting (A) is from 0.010 to 0.200, preferably from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. Is 0.030 to 0.195, more preferably 0.035 to 0.190, particularly preferably 0.040 to 0.185, and most preferably 0.045 to 0.180.

The weight average molecular weight (hereinafter abbreviated as Mw) of (A) is preferably 5,000 to 200,000, more preferably 10, from the viewpoint of the effect of improving the viscosity index and the shear stability of the lubricating oil composition. 000 to 120,000, particularly preferably 12,000 to 80,000, most preferably 15,000 to 65,000.
If the Mw is less than 5,000, the effect of improving the viscosity temperature characteristic and the effect of improving the viscosity index are small and the cost may increase. If the Mw exceeds 200,000, the shear stability and the ester oil base oil will be increased. There is a possibility that the solubility and storage stability of the resin may deteriorate.

  The number average molecular weight (hereinafter abbreviated as Mn) of (A) is preferably 2,500 or more, more preferably 5,000 or more, particularly preferably 10,000 or more, and most preferably 15,000. That's it. Further, it is preferably 200,000 or less, more preferably 80,000 or less, particularly preferably 60,000 or less, and most preferably 40,000 or less. When Mn is less than 2,500, the effect of improving viscosity temperature characteristics and the effect of improving the viscosity index are small, and the cost may increase. When Mn exceeds 200,000, shear stability and ester oil base oil are improved. There is a possibility that the solubility and storage stability of the resin may deteriorate.

The ratio (Mw / PSSI) of Mw and PSSI in (A) is preferably 0.8 × 10 ⁴ or more, more preferably 1.0 × 10 ⁴ or more, further preferably from the viewpoint of viscosity temperature characteristics, that is, fuel economy. Is 1.5 × 10 ⁴ or more, particularly preferably 1.8 × 10 ⁴ or more, and most preferably 2.0 × 10 ⁴ or more. Mn and Mw in (A) can be measured by gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions.
<Measurement conditions of Mn and Mw of (A)>
Apparatus: “HLC-802A” [manufactured by Tosoh Corporation]
Column: Two “TSK gel GMH6” [manufactured by Tosoh Corporation] Measurement temperature: 40 ° C.
Sample solution: 0.25 wt% tetrahydrofuran solution Solution injection amount: 100 μl
Detection device: Refractive index detector Reference material: Standard polystyrene (TSK standard POLYSTYRENE) 12 points (molecular weight: 500, 1,050, 2,800, 5,970, 9,100, 18,100, 37,900, 96,400) , 190,000, 355,000, 1,090,000, 2,890,000) [manufactured by Tosoh Corporation]

The crystallization temperature of (A) is preferably −20 ° C. or less, more preferably −30 ° C. or less, particularly preferably −40 ° C. or less, and most preferably −50 ° C. from the viewpoint of the low temperature viscosity of the lubricating oil composition. It is as follows.
The crystallization temperature of (A) was determined by using a differential scanning calorimeter “Unix (registered trademark) DSC7” (manufactured by PERKIN-ELMER), (A) using 5 mg as a sample at an isothermal rate of 10 ° C./min. It is the crystallization temperature observed when cooling from 100 ° C to -60 ° C.

(A) can be obtained by a known production method, and specifically includes a method obtained by solution polymerization of the above monomer in a solvent in the presence of a polymerization catalyst.
Examples of the solvent include toluene, xylene, methyl ethyl ketone, ethyl acetate, ester oil and the like.
Polymerization catalysts include azo catalysts (azobisisobutyronitrile, azobisvaleronitrile, etc.), peroxide catalysts (benzoyl peroxide, cumyl peroxide, lauryl peroxide, etc.) and redox catalysts (benzoyl peroxide). And a mixture of tertiary amines). Furthermore, if necessary, a known chain transfer agent (such as an alkyl mercaptan having 2 to 20 carbon atoms) can also be used.
The polymerization temperature is preferably 25 to 150 ° C, more preferably 50 to 130 ° C. In addition to the above solution polymerization, (A) can be obtained by bulk polymerization, emulsion polymerization or suspension polymerization.
When (A) is a copolymer, the polymerization form may be either a random addition polymer or an alternating copolymer, and may be either a graft copolymer or a block copolymer.

The viscosity index improver composition of the present invention comprises, in addition to (A), a (co) polymer (B) having a macromonomer (r) as a constituent monomer. It is preferable from the viewpoint of the effect of improving the viscosity index.
As the (co) polymer (B), in addition to the macromonomer (r), as a constituent monomer other than the macromonomer (r), the above monomers (a) to (d) from the viewpoint of the effect of improving the viscosity index Any one or more of these are preferably used as constituent monomers.

The macromonomer (r) is a macromonomer based on a hydrocarbon polymer. Specifically, the alkene having 2 to 10 carbon atoms [for example, ethylene, propylene, normal butene, isobutene, etc.] and 2 to 10 carbon atoms. A hydroxyl group-containing (co) polymer in which a hydroxyl group is introduced only at one end of a hydrocarbon polymer comprising one or more monomers selected from the group consisting of alkadienes [for example, butadiene, isoprene, etc.] or Esterification reaction or amidation reaction of an amino group-containing (co) polymer in which an amino group is introduced only at one end into a hydrocarbon polymer and (meth) acrylic acid, or transesterification with methyl (meth) acrylate, etc. It is a macromonomer that can be obtained by:
When the hydrocarbon polymer has a double bond, a part or all of the double bond may be hydrogenated by hydrogenation.

The Mn of the hydrocarbon polymer is preferably 700 to 50,000 from the viewpoint of improving the viscosity index.
Mn in (r) is preferably 700 to 50,000, more preferably 1,500 to 5,000 from the viewpoint of the effect of improving the viscosity index.

  The proportion of (r) constituting (B) is preferably 2 to 60% by weight, more preferably, based on the weight of (B), from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. Is 5 to 55% by weight, particularly preferably 10 to 50% by weight, and most preferably 15 to 45% by weight.

  The Mw of (B) is preferably 100,000 to 1,000,000. The lower limit is more preferably 150,000 or more, further preferably 200,000 or more, particularly preferably 250,000 or more, and most preferably 300,000 or more. The upper limit is more preferably 800,000 or less, still more preferably 700,000 or less, particularly preferably 600,000 or less, and most preferably 550,000 or less. If the Mw is less than 150,000, the effect of improving the viscosity temperature characteristics and the effect of improving the viscosity index may be small and the cost may increase. If the Mw exceeds 1,000,000, the shear stability and ester oil base may be increased. There is a possibility that solubility in oil and storage stability may deteriorate.

  Mn of (B) is preferably 50,000 or more, more preferably 80,000 or more, particularly preferably 100,000 or more, and most preferably 120,000 or more. Further, it is preferably 500,000 or less, more preferably 300,000 or less, particularly preferably 250,000 or less, and most preferably 200,000 or less. When Mn is less than 50,000, the effect of improving the viscosity temperature characteristic and the effect of improving the viscosity index are small, and the cost may increase. When Mn exceeds 500,000, the shear stability and the ester oil base oil are increased. There is a possibility that the solubility and storage stability of the resin may deteriorate.

The ratio (Mw / PSSI) of Mw and PSSI in (B) is preferably 0.8 × 10 ⁴ or more, more preferably 1.0 × 10 ⁴ or more, and further preferably from the viewpoint of temperature characteristics, that is, fuel economy. Is 1.5 × 10 ⁴ or more, particularly preferably 1.8 × 10 ⁴ or more, and most preferably 2.0 × 10 ⁴ or more. In addition, Mn and Mw of (B) can be measured on the same conditions as Mn and Mw of (A).

  The ratio (Mw / Mn) of Mw and Mn in (B) is preferably 0.5 or more, preferably 1.0 or more, more preferably 1.5 or more, still more preferably 2.0 or more, particularly Preferably it is 2.1 or more. Further, Mw / Mn is preferably 6.0 or less, more preferably 4.0 or less, still more preferably 3.5 or less, and particularly preferably 3.0 or less. When Mw / Mn is less than 0.5 or exceeds 6.0, the viscosity temperature characteristic may be deteriorated, that is, the fuel economy may be deteriorated.

  (B) can be obtained by a known production method as in (A).

  When (A) and (B) are used in combination, the amount of (B) used is preferably 0.01 to 30% by weight and more preferably 0 based on the weight of (A) from the viewpoint of low temperature viscosity. 0.01 to 20% by weight, particularly preferably 0.01 to 10% by weight.

  In addition to (A) and (B), the viscosity index improver composition of the present invention may be used in combination with an alkyl (meth) acrylate (co) polymer (C) other than (A).

(C) is not particularly limited as long as it is an alkyl (meth) acrylic acid ester (co) polymer other than (A), but a (meth) acrylic acid alkyl ester having a linear alkyl group having 1 to 18 carbon atoms. Examples include (co) polymers.
Specific examples of (C) include n-octadecyl methacrylate / n-dodecyl methacrylate (molar ratio 10-30 / 90-70) copolymer, n-tetradecyl methacrylate / n-dodecyl methacrylate (molar ratio 10). -30 / 90-70) Copolymer, n-hexadecyl methacrylate / n-dodecyl methacrylate / methyl methacrylate (molar ratio 20-40 / 55-75 / 0-10) copolymer and n-dodecyl acrylate / N-dodecyl methacrylate (molar ratio 10 to 40/90 to 60) copolymer and the like, and these may be used alone or in combination of two or more.

  When (A) and (C) are used in combination, the amount of (C) used is preferably 0.01 to 30% by weight, more preferably 0, based on the weight of (A), from the viewpoint of low temperature viscosity. 0.01 to 20% by weight, particularly preferably 0.01 to 10% by weight.

(A) is preferably dissolved in an API group V lubricant base oil having a kinematic viscosity at 100 ° C. of 1.0 to ^2.5 mm ² / s. Here, dissolution means that 100 parts by weight of (A) is dissolved in 100 parts by weight of ester oil base oil, the appearance is uniform, and there is no insoluble matter of (A).

  (A) is a spectrum obtained by nuclear magnetic resonance analysis (13C-NMR), wherein the peak total area M1 between the chemical shift 29-31 ppm relative to the total area of all peaks and the peak between the chemical shift 67-73 ppm. The ratio M1 / M2 of the total area M2 is 1.0 or more.

  M1 / M2 needs to be 1.0 or more, preferably 2.0 or more, more preferably 3.0 or more, particularly preferably 4.0 or more, and most preferably 5.0 or more. M1 / M2 is preferably 35 or less, more preferably 32 or less, particularly preferably 30 or less, and most preferably 27 or less. When M1 / M2 is less than 1.0, the required fuel economy cannot be obtained, and the low-temperature viscosity characteristics may be deteriorated. Moreover, when M1 / M2 exceeds 27, there exists a possibility that the required fuel-saving property may not be acquired, and there exists a possibility that solubility and storage stability may deteriorate.

  (A) is a spectrum obtained by nuclear magnetic resonance analysis (13C-NMR), wherein the peak total area M3 between the chemical shift 10-20 ppm relative to the total area of all peaks and the peak between the chemical shift 25-35 ppm. The ratio M3 / M4 of the total area M4 is 0.20 or more.

  M3 / M4 needs to be 0.20 or more, preferably 0.3 or more, more preferably 0.4 or more, particularly preferably 0.5 or more, and most preferably 0.6 or more. M3 / M4 is preferably 5.0 or less, more preferably 3.0 or less, particularly preferably 2.0 or less, and most preferably 1.5 or less. When M3 / M4 is less than 0.20, not only the required fuel saving performance is not obtained, but also the low-temperature viscosity characteristics may be deteriorated. Moreover, when M3 / M4 exceeds 5.0, there exists a possibility that the required fuel-saving property may not be acquired, and there exists a possibility that solubility and storage stability may deteriorate.

  (A) is a spectrum obtained by nuclear magnetic resonance analysis (13C-NMR), wherein the peak total area M5 between the chemical shift 44-46 ppm relative to the total area of all peaks and the peak between the chemical shift 63-72 ppm. The ratio M5 / M6 of the total area M6 is 0.20 or more.

  M5 / M6 needs to be 0.20 or more, preferably 0.3 or more, more preferably 0.4 or more, particularly preferably 0.5 or more, and most preferably 0.6 or more. M5 / M6 is preferably 3.0 or less, more preferably 2.0 or less, particularly preferably 1.0 or less, and most preferably 0.8 or less. When M5 / M6 is less than 0.20, not only the required fuel economy is not obtained, but also the low-temperature viscosity characteristics may be deteriorated. Moreover, when M5 / M6 exceeds 3.0, there exists a possibility that the required fuel-saving property may not be acquired, and there exists a possibility that solubility and storage stability may deteriorate.

  The nuclear magnetic resonance analysis (13C-NMR) spectrum is obtained from a polymer obtained by separating the diluent oil by rubber membrane dialysis or the like when the diluent oil is contained in (A).

In addition, the total area (M1) of the peak between the chemical shifts 29-31 ppm with respect to the total area of all the peaks is the side chain of the poly (meth) acrylate with respect to the total integrated intensity of all the carbons measured by 13C-NMR. It means the proportion of integrated intensity derived from a specific ethylene structure. The total area (M2) of the peak between chemical shifts 67-73 ppm relative to the total area of all peaks is the specific ether of the poly (meth) acrylate side chain relative to the total integrated intensity of all carbons, as measured by 13C-NMR. It means the ratio of integral intensity derived from the structure.
The total peak area (M3) between 10-20 ppm chemical shift relative to the total area of all peaks is the specific methyl of the poly (meth) acrylate side chain relative to the total integrated intensity of all carbons, as measured by 13C-NMR. It means the ratio of integral intensity derived from the structure.
The total peak area (M4) between 25-35 ppm chemical shift relative to the total area of all peaks is the specific methylene of the poly (meth) acrylate side chain relative to the total integrated carbon total intensity, as measured by 13C-NMR. It means the ratio of integral intensity derived from the structure.
The total peak area (M5) between 44-46 ppm chemical shift relative to the total area of all peaks is the specific methine of the poly (meth) acrylate side chain relative to the total integrated carbon total intensity as measured by 13C-NMR. It means the ratio of integral intensity derived from the structure.
The total area of the peak (M5) between chemical shifts 63-72 ppm relative to the total area of all peaks is the oxygen atom of the poly (meth) acrylate side chain relative to the total integrated intensity of all carbons, as measured by 13C-NMR. It means the ratio of integrated intensity derived from adjacent carbon atoms.

  M1 / M2 means the ratio of the specific methylene structure and the specific ether structure of the poly (meth) acrylate side chain, but other methods may be used as long as equivalent results are obtained. In the 13C-NMR measurement, 0.1 g of a sample diluted with 2 ml of deuterated chloroform was used as a sample, the measurement temperature was room temperature, the resonance frequency was 100 MHz, and the measurement method was a decoupling method with a reverse gate. It was used.

From the above analysis,
(A) Sum of integral intensities with chemical shifts of about 10-74 ppm (sum of integral intensities due to total carbon of hydrocarbons), and (b) Sum of integral intensities with chemical shifts of 29-31 ppm (for specific β-branch structures) Sum of integral intensities resulting from), and (c) sum of integral intensities of chemical shifts 67-73 ppm (sum of integral intensities due to specific linear structures)
(D) Sum of integral intensities with chemical shift of 10-20 ppm (sum of integral intensities resulting from specific β-branch structure), and (e) Sum of integral intensities of chemical shifts of 29-31 ppm (with particular linear structure) Sum of integral intensities)
(F) Sum of integral intensities with chemical shifts 44-46 ppm (sum of integral intensities due to specific β-branch structure), and (g) Sum of integral intensities with chemical shifts of 63-72 ppm (because of specific linear structure) Sum of integral intensities)
Were measured, and the ratio (%) of (b) when (a) was set to 100% was calculated as M1. Similarly, the ratio (%) of (c), (d), (e), (f), and (g) when (a) is set to 100% is calculated, and M2, M3, M4, M5, M6.

  The shear stability index (hereinafter abbreviated as PSSI) of (A) is preferably 20 or less, more preferably 15 or less, still more preferably 10 or less, and particularly preferably 8 or less. Moreover, it is preferable that it is 0.1 or more, More preferably, it is 0.5 or more, More preferably, it is 1 or more, Especially preferably, it is 2 or more. If the shear stability index is less than 0.1, the effect of improving the viscosity index may be small and the cost may increase. If the shear stability index exceeds 20, the shear stability and storage stability may be deteriorated. is there.

  The ratio (Mw / Mn) of Mw and Mn in (A) is preferably 1.0 or more, preferably 1.2 or more, more preferably 1.3 or more, still more preferably 1.5 or more, particularly Preferably it is 1.6 or more. Moreover, it is preferable that Mw / Mn is 6.0 or less, More preferably, it is 4.0 or less, More preferably, it is 3.0 or less, Most preferably, it is 2.0 or less. When Mw / Mn is less than 1.0 or exceeds 6.0, the viscosity temperature characteristic may be deteriorated, that is, the fuel economy may be deteriorated.

  The content of (A) in the lubricating oil composition of the present invention is preferably 0.01 to 37% by weight, more preferably 0.2 to 35% by weight, and still more preferably based on the total amount of the lubricating oil composition. It is 0.5 to 33% by weight, particularly preferably 1 to 30% by weight. If the content of (A) is less than 0.01% by weight, the effect of improving the viscosity index and the effect of reducing the product viscosity are diminished, and thus there is a possibility that the fuel economy cannot be improved.

The ester oil base oil of the present invention has a kinematic viscosity at 100 ° C. of 1.0 to 2.5 mm ² / s.

  The ester oil base oil according to the present invention is not particularly limited as long as the above conditions are satisfied. Specifically, ester oil base oils that satisfy the above conditions can be used among monoester lubricant base oils, diester lubricant base oils, polyester lubricant base oils, and the like.

The upper limit of 100 ° C. kinematic viscosity of the ester base oil of the invention must be less than or equal 2.5 mm ² / s, preferably 2.25 mm ² / s or less, more preferably 2.00 mm ² / s or less, more preferably 1.75 mm ² / s or less, particularly preferably 1.50 mm ² / s or less, and most preferably not more than 1.35 mm ² / s. On the other hand, the lower limit of the 100 ° C. kinematic viscosity needs to be 1.0 mm ² / s or more, preferably 1.02 mm ² / s or more, more preferably 1.05 mm ² / s or more, more preferably 1.07 mm ² / s or more, particularly preferably 1.1 mm ² / s or more. The kinematic viscosity at 100 ° C. here refers to the kinematic viscosity at 100 ° C. as defined in ASTM D-445. If the 100 ° C. kinematic viscosity of the ester base oil component exceeds 2.5 mm ² / s, the low temperature viscosity characteristics are deteriorated and no sufficient fuel savings are obtained in the case of less than 1.0 mm ² / s Is inferior in lubricity due to insufficient oil film formation at the lubrication site, and the evaporation loss of the lubricating oil composition increases.

The upper limit of the kinematic viscosity at 40 ° C. of the ester base oil of the present invention is preferably 7.0 mm ² / s or less, more preferably 6.50 mm ² / s or less, more preferably 6.0 mm ² / s or less, particularly preferably 5.50 mm ² / s or less, and most preferably not more than 5.0 mm ² / s. On the other hand, the lower limit of the 40 ° C. kinematic viscosity is preferably 2.5 mm ² / s or more, more preferably 2.55 mm ² / s or higher, more preferably 2.6 mm ² / s or more, particularly preferably 2.65 mm ² / S or more, most preferably 2.7 mm ² / s or more. When the 40 ° C. kinematic viscosity of the ester oil base oil component exceeds 4.0 mm ² / s, the low-temperature viscosity characteristics may deteriorate, and sufficient fuel economy may not be obtained. 2.5 mm ² / s If it is less than 1, the formation of an oil film at the lubrication site is insufficient, resulting in poor lubricity, and the evaporation loss of the lubricating oil composition may increase.

The SP value of the ester oil base oil is preferably 8.0 to 9.5 (cal / cm ³ ) ^1/2 and more preferably 8.2 to 9.4 (cal from the viewpoint of the effect of improving the viscosity index. / Cm ³ ) ^1/2 , more preferably 8.4 to 9.3 (cal / cm ³ ) ^1/2 .

Further, the density (ρ15) at 15 ° C. of the ester oil base oil according to the present invention depends on the viscosity grade of the lubricating base oil component, but is not more than the value of ρ represented by the following formula (A), that is, ρ15. It is preferable that ≦ ρ.
ρ = 0.0025 × kv100 + 0.816 (A)
[Wherein, kv100 represents the kinematic viscosity (mm ² / s) of the lubricating base oil component at 100 ° C. ]

  When ρ15> ρ, the viscosity-temperature characteristics and thermal / oxidation stability, as well as the volatilization prevention property and the low-temperature viscosity characteristics tend to be lowered, and the fuel economy may be deteriorated.

Specifically, the density (ρ15) at 15 ° C. of the ester base oil according to the present invention is preferably 0.880 g / cm ³ or less, more preferably 0.875 g / cm ³ or less, and even more preferably 0.870 g. / Cm ³ or less, particularly preferably 0.860 g / cm ³ or less.

  In addition, the density in 15 degreeC said by this invention means the density measured in 15 degreeC based on JISK2249-1: 2011.

  Further, the pour point of the ester oil base oil according to the present invention is preferably −10 ° C. or lower, more preferably −12.5 ° C. or lower, and further preferably −15 ° C. or lower. When the pour point exceeds the upper limit, the low temperature fluidity of the entire lubricating oil tends to be reduced. In addition, the pour point as used in the field of this invention means the pour point measured based on JISK2269: 1987.

  The viscosity index of the lubricating oil composition of the present invention is preferably 400 to 800, more preferably 450 to 750, still more preferably 470 to 720, particularly preferably 500 to 700, and most preferably 520 to 680. When the viscosity index of the lubricating oil composition of the present invention is less than 400, it may be difficult to improve fuel economy, and it may be difficult to reduce the low temperature viscosity at −40 ° C. is there. Moreover, when the viscosity index of the lubricating oil composition of the present invention exceeds 800, the low-temperature fluidity is deteriorated, and there is a possibility that problems due to poor solubility of the additive may occur.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is preferably 4.2 to 5.7 mm ² / s from the viewpoint of low temperature viscosity. The 100 limit ℃ kinematic viscosity is more preferably 5.6 mm ² / s or less, more preferably 5.5 mm ² / s or less, particularly preferably 5.4 mm ² / s or less, and most preferably 5.3 mm ² / s It is as follows. On the other hand, in view of the lower limit of the viscosity index improving effect and evaporation properties of the 100 ° C. kinematic viscosity, more preferably 4.3 mm ² / s or higher, more preferably 4.4 mm ² / s or more, particularly preferably 4.5 mm ² / S or more. If the kinematic viscosity is less than 4.2 mm 2 / ^s is at 40 ° C., there is insufficient lubricity may give low temperature viscosity and sufficient fuel efficiency performance required in the case of more than 5.7 mm 2 / ^s There is a risk of not being able to.

The kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is preferably 4 to 25 mm ² / s. The upper limit of the 40 ° C. kinematic viscosity is more preferably 22 mm ² / s or less, further preferably 20 mm ² / s or less, particularly preferably 18 mm ² / s or less, still more preferably 16 mm ² / s or less, and most preferably 14 mm ^2. / S or less. On the other hand, the lower limit of the 40 ° C. kinematic viscosity is more preferably 5 mm ² / s or more, still more preferably 6 mm ² / s or more, particularly preferably 7 mm ² / s or more, and still more preferably 8 mm ² / s or more. When the kinematic viscosity at 40 ° C. is less than 4 mm ² / s, there is a risk of insufficient lubricity, and when it exceeds 25 mm ² / s, the necessary low temperature viscosity and sufficient fuel saving performance may not be obtained. is there.

  The upper limit of the HTHS viscosity at 100 ° C. of the lubricating oil composition of the present invention is preferably 6.0 mPa · s or less, more preferably 5.5 mPa · s or less, and even more preferably 5.3 mPa · s or less. Yes, particularly preferably 5.0 mPa · s or less, and most preferably 4.5 mPa · s or less. Further, the lower limit of the HTHS viscosity at 100 ° C. is preferably 3.0 mPa · s or more, more preferably 3.5 mPa · s or more, still more preferably 3.8 mPa · s or more, particularly preferably 4.0 mPa · s. s or more, most preferably 4.2 mPa · s or more. The HTHS viscosity at 100 ° C. here refers to the high temperature and high shear viscosity at 100 ° C. defined in ASTM D4683. When the HTHS viscosity at 100 ° C. is less than 3.0 mPa · s, there is a risk of high evaporation and insufficient lubricity. When it exceeds 6.0 mPa · s, the necessary low temperature viscosity and sufficient fuel saving Performance may not be obtained.

  The upper limit of the HTHS viscosity at 150 ° C. of the lubricating oil composition of the present invention is preferably 3.5 mPa · s or less, more preferably 3.0 mPa · s or less, and even more preferably 2.8 mPa · s or less. Yes, particularly preferably 2.7 mPa · s or less. The lower limit of the HTHS viscosity at 150 ° C. is preferably 2.0 mPa · s or more, more preferably 2.3 mPa · s or more, still more preferably 2.4 mPa · s or more, and particularly preferably 2.5 mPa · s or more. Most preferably, it is 2.6 mPa · s or more. Here, the HTHS viscosity at 150 ° C. indicates a high-temperature high-shear viscosity at 150 ° C. as defined in ASTM ASTM D4683. When the HTHS viscosity at 150 ° C. is less than 2.0 mPa · s, there is a risk of high vaporization and insufficient lubricity. When it exceeds 3.5 mPa · s, the necessary low temperature viscosity and sufficient fuel saving Performance may not be obtained.

In the lubricating oil composition of the present invention, it is preferable that the ratio of the HTHS viscosity at 100 ° C. to the HTHS viscosity at 150 ° C. satisfies the condition represented by the following formula (C).
HTHS (100 ° C.) / HTHS (150 ° C.) ≦ 2.04 (C)
[Wherein, HTHS (100 ° C.) represents the HTHS viscosity at 100 ° C., and HTHS (150 ° C.) represents the HTHS viscosity at 150 ° C. ]

  The upper limit of HTHS (100 ° C.) / HTHS (150 ° C.) is preferably 2.04 or less, more preferably 2.00 or less, still more preferably 1.98 or less, and particularly preferably 1.80 or less. Preferably it is 1.70 or less. If HTHS (100 ° C.) / HTHS (150 ° C.) exceeds 2.04, sufficient fuel saving performance and low temperature characteristics may not be obtained. Further, the lower limit of HTHS (100 ° C.) / HTHS (150 ° C.) is preferably 0.50 or more, more preferably 0.70 or more, still more preferably 1.00 or more, and particularly preferably 1.30 or more. When HTHS (100 ° C.) / HTHS (150 ° C.) is less than 0.50, there is a possibility that the cost of the substrate is significantly increased and the solubility of the additive cannot be obtained.

The content of the viscosity index improver in the lubricating oil composition of the present invention is preferably 1 to 70% by weight in terms of the weight of (A) in the viscosity index improver based on the weight of the ester oil base oil. It is.
When the lubricating oil composition is used as an engine oil, it preferably contains 2 to 30% by weight of (A).
When the lubricating oil composition is used as a gear oil, it preferably contains 10 to 70% by weight of (A).
When the lubricating oil composition is used as an automatic transmission oil (such as ATF and belt-CVTF), it preferably contains 10 to 70% by weight of (A).
When the lubricating oil composition is used as a traction oil, it preferably contains 0.5 to 20% by weight of (A).

  The upper limit of the shear stability (hereinafter abbreviated as SS) of the lubricating oil composition of the present invention is preferably 10% or less, and more preferably 9% or less from the viewpoint of reducing friction and preventing wear after running for a long time. More preferably, it is 8% or less, particularly preferably 7% or less, and most preferably 6% or less. On the other hand, from the viewpoint of reducing the use amount of the viscosity index improver, the lower limit of SS is more preferably 0.5% or more, further preferably 1% or more, and particularly preferably 1.5% or more. When SS exceeds 10%, there is a possibility that inter-wear and seizure and sufficient fuel saving performance cannot be obtained.

  The low temperature viscosity at −40 ° C. of the lubricating oil composition of the present invention is preferably 5,000 mPa · s or less from the viewpoint of the initial startability of the engine. More preferably, it is 4,500 mPa * s or less, More preferably, it is 4,000 mPa * s or less.

  The lubricating oil composition of the present invention includes gear oil (differential oil and industrial gear oil, etc.), MTF, transmission oil [ATF and belt-CVTF, etc.], traction oil (toroidal-CVTF, etc.), shock absorber oil, power steering It is suitably used for oil, hydraulic oil (such as construction machine hydraulic oil and industrial hydraulic oil). Of these, gear oil, MTF, transmission oil, and traction oil are preferred, more preferred are differential oil, MTF, ATF, and belt-CVTF, and particularly preferred are MTF, ATF, and belt-CVTF. .

  The lubricating oil composition of the present invention may contain various additives. Additives include additives such as dispersants, detergents, antioxidants, oiliness improvers, pour point depressants, friction wear modifiers, extreme pressure agents, antifoaming agents, demulsifiers and corrosion inhibitors. It is done. These additives can be used individually by 1 type or in combination of 2 or more types.

  Examples of the dispersant include succinimides (bis- or mono-polybutenyl succinimides), Mannich condensation products, borates, and the like.

  Detergents include basic, overbased or neutral metal salts [overbased or alkaline earth metal salts of sulfonates (such as petroleum sulfonates, alkylbenzene sulfonates and alkylnaphthalene sulfonates)], salicylates Phenates, naphthenates, carbonates, phosphonates, and mixtures thereof.

  Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants such as zinc, copper, and molybdenum.

  Examples of phenolic antioxidants include 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert-butylphenol), 4,4 ′. -Bis (2-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4,4′-isopropylidenebis (2,6-di-tert-butylphenol), 2,2′-methylenebis (4-methyl-6) -Nonylphenol), 2,2'-isobutylidenebis (4,6-dimethylphenol), 2,2'-methylenebis (4-methyl) 6-cyclohexylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2, 6-di-tert-α-dimethylamino-p-cresol, 2,6-di-tert-butyl-4- (N, N-dimethylaminomethylphenol), 4,4′-thiobis (2-methyl-6) -Tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,2'-thiobis (4-methyl-6-tert-butylphenol), bis (3-methyl-4- Hydroxy-5-tert-butylbenzyl) sulfide, bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide 2,2′-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tridecyl-3- (3,5-di-tert-butyl-4-hydroxy Phenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) ) Propionate, stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octyl-3- (3-methyl-5-di-tert-butyl-4-hydroxyphenyl) propionate It is done. You may use these in mixture of 2 or more types.

  Examples of oiliness improvers include long chain fatty acids and their esters (such as oleic acid and oleic acid ester), long chain amines and their amides (such as oleylamine and oleylamide), and the like.

  Examples of the pour point depressant include a copolymer of a long-chain alkyl methacrylate (alkyl group having 12 to 18 carbon atoms).

  Examples of the friction and wear adjusting agent include molybdenum-based and zinc-based compounds (such as molybdenum dithiophosphate, molybdenum dithiocarbamate, and zinc dialkyldithiophosphate).

  Examples of extreme pressure agents include sulfur compounds (mono or disulfides, sulfoxides and sulfur phosphide compounds), phosphide compounds and chlorinated compounds (chlorinated paraffin, etc.).

  Examples of the antifoaming agent include silicon oil, metal soap, fatty acid ester, and phosphate compound.

  Examples of the demulsifier include quaternary ammonium salts (such as tetraalkylammonium salts), sulfated oils and phosphates (such as phosphates of polyoxyethylene-containing nonionic surfactants).

  Examples of the corrosion inhibitor include nitrogen atom-containing compounds (such as benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate).

  These additives may be used alone, or two or more additives may be used as necessary. A blend of these additives may be called a performance additive.

  The method for producing a lubricating oil composition in the present application is a method for producing a lubricating oil composition including a step of mixing a viscosity index improver and a lubricating oil base oil. Moreover, the process of mixing various additives etc. may be included.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

<Examples 1 to 10, Comparative Examples 1 to 4>
Into a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a nitrogen introduction tube and a decompression device, 100 parts by weight of the base oil described in Table 1 was charged, and another glass beaker described in Table 1 was added. Monomer, dodecyl mercaptan as chain transfer agent, 0.5 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) and 0.22′-azobis (2-methylbutyronitrile) 0.2 A part by weight was added and stirred and mixed at 20 ° C. to prepare a monomer solution, which was then added to a dropping funnel. After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was dropped over 2 hours while maintaining the temperature in the system under sealed at 70 to 85 ° C., and ripened at 85 ° C. for 2 hours from the end of dropping. Then, after raising the temperature to 120 to 130 ° C., the unreacted monomer is removed under reduced pressure (0.027 to 0.040 MPa) at the same temperature over 2 hours, and the copolymers (A1) to (A10) Viscosity index improver compositions (R1) to (R10) containing comparative copolymers (H1) to (H4) and comparative viscosity index improvers (S1) to (S4). The SP values and the dispersion values of the SP values of the obtained copolymers (A1) to (A10) and (H1) to (H4) were calculated by the above method, and Mw was measured by the above method. Moreover, the low-temperature storage stability of the viscosity index improver compositions (R1) to (R10) and (S1) to (S4) was evaluated by the following method. The results are shown in Table 1.

<Evaluation method of low temperature storage stability of viscosity index improver composition>
Viscosity index improver compositions (R1) to (R10) and (S1) to (S4) were added to 10% by weight based on the weight of the base oil to homogenize, and the appearance after storage at -25 ° C for 24 hours was visually observed. The low-temperature storage stability was evaluated according to the following evaluation criteria.
[Evaluation criteria]
○: Appearance is uniform and there is no insoluble matter in the copolymer ×: Appearance is inhomogeneous and insoluble matter in the copolymer is observed

The compositions of the monomers (a) to (g) described in Tables 1 and 2 are as described below.
(A-1): 2-tetradecyloctadecyl methacrylate (Isolol produced by Sasol and esterified product of methacrylic acid) (32 carbon atoms)
(A-2): 2-tetradecylicosyl methacrylate (carbon number 34)
(A-3): 2-hexadecylicosyl methacrylate (C36)
(B-1): Methyl methacrylate (C1)
(B-2): n-butyl methacrylate (carbon number 4)
(C-1): 2-octyldodecyl methacrylate (carbon number 20)
(C-2): 2-n-decyltetradecyl methacrylate (carbon number 24)
(C-1): 2-dodecyl hexadecyl methacrylate (C28)
(D-1): n-dodecyl methacrylate (12 carbon atoms)
(D-2): n-tetradecyl methacrylate (carbon number 14)
(D-3): n-hexadecyl methacrylate (16 carbon atoms)
(D-4): n-octadecyl methacrylate (carbon number 18)
(E-1): N, N-dimethylaminoethyl methacrylate (f-1): hydroxyethyl methacrylate (g-1): methacryloyloxyethyl phosphate

<Production Example 1>
Production of diester oil base oil (base oil E5) A reaction vessel equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a water fractionator with a cooling tube was charged with 255.0 parts of neopentyl glycol and 776.9 octanoic acid. Part and xylene 48 parts were charged and heated to 200 ° C. in a nitrogen atmosphere. The esterification reaction was carried out for about 10 hours while removing the produced water distilled off with the moisture fraction receiver with the theoretical amount of produced water (88 g) as the target. After completion of the reaction, excess acid and xylene were removed by distillation to obtain an esterified crude product. Next, the obtained esterified crude product was transferred to an eggplant type flask equipped with a Vigreux fractionation tube, and distilled at 220 ° C. under reduced pressure. The middle distillate was collected by removing 15% by volume of the first fraction and the latter fraction by vacuum distillation. The middle distillate was diester (base oil E5): neopentyl glycol di n-octanoate (molecular weight 356), and the total acid value of (base oil E5) was 0.01 mgKOH / g.

<Production Example 2>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a nitrogen introduction tube, 4400 parts by weight of base oil E1 as an ester oil base oil, 20 parts of hydrogenated polybutadiene methacrylate (Mn: 7,000), monomer (B-2) 65 parts, monomer (d-1) 10 parts, monomer (d-2) 5 parts 100 parts by weight, 2,2′-azobis (2-methylbutyronitrile) After adding 0.15 part by weight and carrying out nitrogen substitution (gas phase oxygen concentration 100 ppm), the temperature was raised to 76 ° C. with stirring in a sealed state, and a polymerization reaction was carried out at the same temperature for 4 hours. After raising the temperature to 120 to 130 ° C., the unreacted monomer is removed over 2 hours under reduced pressure (0.027 to 0.040 MPa) at the same temperature, and the viscosity index improver containing the copolymer (B1) A composition (T1) (Mw: 450,000) was obtained.

<Examples 11-20, Comparative Examples 5-8 (Evaluation of Lubricating Oil Composition)>
In a stainless steel container equipped with a stirrer, the performance additive [metal] as shown in Table 3 so that the resulting lubricant composition has a kinematic viscosity at 100 ° C. of 4.50 ± 0.02 (mm ² / s). -Based (TBN 300mgKOH / g calcium sulfonate) detergent, ashless residue (succinimide), friction modifier (oleylamide), antiwear agent (phosphoric acid), antioxidant (diphenylamine), metal deactivation Agent (thiadiazole) and sulfur-based additive (sulfurized ester)], viscosity index improver compositions (R1) to (R10), (S1) to (S4), (T1), base oil, and Were mixed to obtain lubricating oil compositions (V1) to (V10) and (W1) to (W4).
The viscosity index, kinematic viscosity at 40 ° C., viscosity index, and low temperature viscosity (−40 ° C.) of the lubricating oil compositions (V1) to (V10) and (W1) to (W4) were measured by the following methods. The results are shown in Table 3.

<Examples 20-30, Comparative Examples 9-12 (Evaluation of Lubricating Oil Composition)>
In a stainless steel container equipped with a stirrer, the performance additive and the performance additive as described in Table 4 are used so that the resulting lubricant composition has a kinematic viscosity at 100 ° C. of 5.50 ± 0.02 (mm ² / s). Viscosity index improver compositions (R1) to (R10), (S1) to (S4), and (T1) are mixed with base oil, and lubricating oil compositions (V11) to (V20) and (W5) are mixed. ) To (W8) were obtained.
The viscosity index, kinematic viscosity at 40 ° C., viscosity index, HTHS viscosity and low temperature viscosity (−40 ° C.) of the lubricating oil compositions (V11) to (V20) and (W5) to (W8) were measured by the following methods. The results are shown in Table 4.

The physical properties of the base oils listed in Tables 1 to 4 are as described below.
(Base oil E1): Monoester oil base oil (M fine ester EHO-100 manufactured by Miyoshi Oil & Fats, 100 ° C. kinematic viscosity 1.1 mm ² / s, 40 ° C. kinematic viscosity: 2.7 mm ² / s, viscosity index: not calculable SP value 8.45)
(Base oil E2): Monoester oil base oil (M fine ester CO-108 manufactured by Miyoshi Oil & Fats, 100 ° C. kinematic viscosity 1.1 mm ² / s, 40 ° C. kinematic viscosity: 2.9 mm ² / s, viscosity index: not calculable SP value 8.54)
(Base oil E3): Diester oil base oil (DBA manufactured by Daihachi Chemical Industry Co., Ltd., 100 ° C. kinematic viscosity: 1.41 mm ² / s, 40 ° C. kinematic viscosity: 3.58 mm ² / s, viscosity index: not calculable, SP value 9.26)
(Base oil E4): Diester oil base oil (DBS manufactured by Daihachi Chemical Industry Co., Ltd., 100 ° C. kinematic viscosity: 2.04 mm ² / s, 40 ° C. kinematic viscosity: 5.72 mm ² / s, viscosity index: 182, SP value 9 .19)
(Base oil E5): Diester oil base oil (Production Example 1, 100 ° C. kinematic viscosity: 2.22 mm ² / s, 40 ° C. kinematic viscosity: 7.00 mm ² / s, viscosity index: 132, SP value 8.93)
(Base oil K): Highly refined mineral base oil (SK-based YUBASE-2, 100 ° C. kinematic viscosity 2.2 mm ² / s, 40 ° C. kinematic viscosity: 7.4 mm ² / s, viscosity index: 99, SP value 8 .30)

<Calculation method of viscosity index of lubricating oil composition>
The kinematic viscosities at 40 ° C. and 100 ° C. were measured by the method of ASTM D 445 and calculated by the method of ASTM D 2270.

<Measurement method and calculation method of shear stability of lubricating oil composition>
According to the same procedure as the method of JASO M347-2007, the test time was changed from 1 hour to 10 hours and measured. The shear stability was calculated by the method of JASO M347-2007.

<Method of measuring low temperature viscosity (−40 ° C.) of lubricating oil composition>
The measurement was made at -40 ° C by the method of ASTM D 2983.

  As is apparent from the results in Table 3, the lubricating oil compositions (Examples 11 to 20) containing the viscosity index improver of the present invention have the effect that the viscosity index improvement effect is high and the low-temperature viscosity is low. Although both are satisfied, the lubricating oil compositions of Comparative Examples 5 to 8 are inferior in at least one of the effects. Further, as is clear from the results in Table 4, the lubricating oil compositions (Examples 21 to 30) containing the viscosity index improver of the present invention are similarly highly effective in improving the viscosity index and have a low temperature viscosity. Although both low effects are satisfied, the lubricating oil compositions of Comparative Examples 5 to 8 are inferior in at least one of the effects.

  The lubricating oil composition containing the viscosity index improver of the present invention includes a drive system lubricating oil (MTF, differential gear oil, ATF, belt-CVTF, etc.), hydraulic oil (mechanical hydraulic oil, power steering oil, and shock). Absorber oil etc.), engine oil (gasoline and diesel etc.) and traction oil are suitable.

Claims (10)

A copolymer comprising the monomer (a) represented by the following general formula (1) and a (meth) acrylic acid linear alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms as essential constituent monomers. A viscosity index improver composition comprising a polymer (A) and an ester oil base oil having a kinematic viscosity at 100 ° C. of 1.0 to 2.5 mm ² / s, wherein (A) comprises Based on the number of moles of the constituent monomer (A) as a monomer, 80 to 95 mol% of (b) is contained, and the molar ratio (a / b) between (a) and (b) is 0.010. A viscosity index improver composition that is a copolymer of ˜0.200.
[In General Formula (1), R ¹ is a hydrogen atom or a methyl group; —X ¹ — is a group represented by —O— or —NH—, and R ² is a straight chain having 2 to 4 carbon atoms or A branched alkylene group, p is an integer of 0 to 20, and R ² when p is 2 or more may be the same or different, and the (R ² O) _p moiety may be a random bond or a block bond; R ³ is a branched alkyl group having 32 to 44 carbon atoms. ] The kinematic viscosity at 40 ° C. of the ester oil base oil is 2.5 to 7.0 mm ² / s or the solubility parameter of the ester oil base oil is 8.0 to 9.5 (cal / cm ³ ) ^1/2 The viscosity index improver composition according to claim 1. The viscosity index improver composition according to claim 1 or 2, wherein the solubility parameter of (A) is 9.0 to 10.0 (cal / cm ³ ) ^1/2 . (A) is a monomer (c) represented by the following general formula (2) as a constituent monomer and a (meth) acrylic acid linear alkyl ester having a linear alkyl group having 12 to 36 carbon atoms ( The viscosity index improver composition according to any one of claims 1 to 3, which is a copolymer containing one or more selected from the group consisting of d).
[In General Formula (2), R ⁴ is a hydrogen atom or a methyl group; —X ² — is a group represented by —O— or —NH—, and R ⁵ is a straight chain having 2 to 4 carbon atoms or A branched alkylene group, q is an integer from 0 to 20, and R ⁵ when q is 2 or more may be the same or different, and the (R ⁵ O) _q moiety may be a random bond or a block bond; R ⁶ is each independently a linear or branched alkyl group having 6 to 14 carbon atoms.   The dispersity of the solubility parameter of (A) is 0.10 to 1.00. The viscosity index improver composition according to any one of claims 1 to 4.   (A) is based on the total number of moles of the monomers constituting (A), (a) 2-16 mol%, (b) 82-95 mol%, and (c) and (d) The viscosity index improver composition according to claim 4 or 5, which is a copolymer containing a total of 0.5 to 10 mol%.   (A) is a nitrogen atom-containing monomer (excluding (a) and (c)) (e), a hydroxyl group-containing monomer (f) and a phosphorus atom-containing monomer (g The viscosity index improver composition according to any one of claims 1 to 6, which is a copolymer comprising at least one selected from the group consisting of:   The viscosity index improver composition according to any one of claims 1 to 7, wherein (A) has a weight average molecular weight of 5,000 to 200,000.   The viscosity index improver composition according to any one of claims 1 to 8, which is a viscosity index improver composition comprising a (co) polymer (B) having a macromonomer (r) as a constituent monomer. object.   One or more additives selected from the group consisting of dispersants, detergents, antioxidants, oiliness improvers, pour point depressants, friction and wear modifiers, extreme pressure agents, antifoaming agents, demulsifiers and corrosion inhibitors And a lubricating oil composition comprising the viscosity index improver composition according to claim 1.