JP2014132054A - Viscosity index improver and lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity index improver which is highly fuel-efficient and hardly increases low-temperature viscosity of a lubricant composition.SOLUTION: The viscosity index improver contains a (co)polymer (A) comprising a monomer (a) represented by the general formula (1) as an essential constituent monomer. [Ris a hydrogen atom or a methyl group; Ris a C2-C4 alkylene group; Rand Rare each independently a hydrogen atom or a C1-C36 alkyl group, where the total number of carbon atoms in Rand Ris 3 or more; Ris a hydrogen atom or a C1-C16 alkyl group; Rand Rare each independently a hydrogen atom or a C8-C36 alkyl group, where the total number of carbon atoms in Rand Ris 8 or more; and X, X, and Xare each independently a group represented by -O-, -NH- or -S-.]

Description

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

Lubricating oils and hydraulic oils used in automobiles and the like have a lower viscosity as the temperature increases, but in practice, it is desirable that the viscosity does not change as much as possible over a wide range from a low temperature to a high temperature. 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 Documents 1 to 3), an olefin copolymer (Patent Document 4) and the like are known.
However, the above-described viscosity index improver is not yet sufficiently effective in improving the viscosity index, and when added to the lubricating oil composition, there is a problem that the viscosity at a low temperature of the lubricating oil composition increases.

Japanese Patent No. 2732187 JP-A-8-53683 JP 2004-307551 A JP 2005-200454 A

  An object of the present invention is to provide a viscosity index improver that has a high effect of improving the viscosity index and hardly increases the low temperature viscosity of the lubricating oil composition.

  As a result of intensive studies, the present inventors have arrived at the present invention. That is, the present invention provides a viscosity index improver containing a (co) polymer (A) having the monomer (a) represented by the following general formula (1) as an essential constituent monomer; A lubricating oil composition comprising a base oil.

［Ｒ^１は水素原子又はメチル基；Ｒ^２は炭素数２〜４のアルキレン基；Ｒ^３、Ｒ^４は、それぞれ独立に水素原子又は炭素数１〜３６のアルキル基であって、Ｒ^３とＲ^４の炭素数の合計は３以上である。；Ｒ^５は水素原子又は炭素数１〜１６のアルキル基；Ｒ^６、Ｒ^７は、それぞれ独立に水素原子又は炭素数８〜３６のアルキル基であって、Ｒ^６とＲ^７の炭素数の合計は８以上である。；Ｘ^１、Ｘ^２、Ｘ^３は、それぞれ独立に−Ｏ−、−ＮＨ−又は−Ｓ−で表される基；ｍは０〜２０の数であり、ｍが２以上の場合のＲ^２は同一でも異なっていてもよく、（Ｘ^１Ｒ^２）_ｍ部分はランダム結合でもブロック結合でもよい。；ｎは０〜２０の数］

^{[R 1} is a hydrogen atom or a methyl group; an alkylene group of ^{R 2} is ^C2-4; R 3, ^{R 4} are each independently a hydrogen atom or an alkyl group having a carbon number of 1 to 36, and ^{R 3} The total number of carbon atoms of R ⁴ is 3 or more. R ⁵ is a hydrogen atom or an alkyl group having 1 to 16 carbon atoms; R ⁶ and R ⁷ are each independently a hydrogen atom or an alkyl group having 8 to 36 carbon atoms, and each having R ⁶ and R ⁷ carbon atoms; The total is 8 or more. X ¹ , X ² and X ³ are each independently a group represented by —O—, —NH— or —S—; m is a number from 0 to 20, and R ² when m is 2 or more; May be the same or different, and the (X ¹ R ² ) _m moiety may be a random bond or a block bond. N is a number from 0 to 20]

  The lubricating oil composition containing the viscosity index improver of the present invention has a high viscosity index improving effect and exhibits an effect that it is difficult to increase the low temperature viscosity of the lubricating oil composition.

  The viscosity index improver of the present invention is a viscosity index improver containing a (co) polymer (A) having the monomer (a) represented by the general formula (1) as an essential constituent monomer. “(Co) polymerization” means polymerization or copolymerization.

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.

R ² in the general formula (1) is an alkylene group having 2 to 4 carbon atoms. Among these, an ethylene group having 2 carbon atoms is preferred from the viewpoint of the effect of improving the viscosity index.

M in the general formula (1) is a number of 0 to 20, and preferably 0 to 10 from the viewpoint of improving the viscosity index. When m is 2 or more, R ² may be the same or different, and the (X ¹ R ² ) _m moiety may be a random bond or a block bond.

R ³ and R ⁴ in the general formula (1) are each independently a hydrogen atom or an alkyl group having 1 to 36 carbon atoms, and the total number of carbon atoms of R ³ and R ⁴ is 3 or more. Among these, the alkyl group having 4 to 30 carbon atoms is preferable from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity, the alkyl group having 6 to 24 carbon atoms is more preferable, and the carbon group having 8 to 8 carbon atoms is particularly preferable. 20 alkyl groups, most preferred are 10-18 alkyl groups.

R ⁵ in the general formula (1) is a hydrogen atom or an alkyl group having 1 to 16 carbon atoms. Among these, a hydrogen atom is preferable from the viewpoint of the effect of improving the viscosity index.

R ⁶ and R ⁷ in the general formula (1) are each independently a hydrogen atom or an alkyl group having a carbon number, and the total number of carbon atoms of R ⁶ and R ⁷ is 8 or more.
Examples of the alkyl group having 8 to 36 carbon atoms include a linear alkyl group having 8 to 36 carbon atoms and a branched alkyl group having 8 to 36 carbon atoms.
Examples of the linear alkyl group having 8 to 36 carbon atoms include n-octyl group, n-nonyl group, n-decyl, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, and n-hexadecyl group. Group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosyl group, n-docosyl group, n-tetracosyl group, n-hexacosyl group and the like.
Examples of the branched alkyl group having 8 to 36 carbon atoms include 2-ethylhexyl group, isooctyl group, isononyl group, isodecyl group, isododecyl group, 2-hexyldecyl group, 2-octadodecyl group, 2-decyltetradecyl group, 2- A dodecyl hexadecyl group, 2-tetradecyl octadecyl, 2-hexadecyl eicosyl group, etc. are mentioned. Among these, a linear alkyl group having 8 to 16 carbon atoms and a branched alkyl group having 8 to 32 carbon atoms are preferable from the viewpoint of the effect of improving the viscosity index.

X ¹ , X ² and X ³ in the general formula (1) are each independently a group represented by —O—, —NH— or —S—. Among these, a group represented by -O- is preferable from the viewpoint of the effect of improving the viscosity index.

  N in the general formula (1) is a number from 0 to 20, preferably from 0 to 5, and more preferably from 0 to 2 from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity.

  The production method of (a) is not particularly limited. For example, [1] a reaction between a heterocyclic compound (p1) having 5 to 38 carbon atoms and an active hydrogen-containing compound (q) having one or more active hydrogen groups. A method obtained by esterifying the active hydrogen group-containing reaction product (X1) and (meth) acrylic acid obtained by the reaction, [2] (X1) and a heterocyclic compound having 2 to 4 carbon atoms (p2) A method obtained by an esterification reaction of an active hydrogen group-containing reaction product (X2) obtained by reaction with (meth) acrylic acid, [3] (X1) having an alkyl group having 1 to 4 carbon atoms (meta ) Acrylic acid ester [methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, etc.] obtained by transesterification, [4] (X2) And C 1-4 alkyl How obtained having a group and a (meth) acrylic acid ester by transesterification reaction, and the like. “(Meth) acryl” means acryl and / or methacryl.

As a C5-C38 heterocyclic compound (p1), C5-C36 cyclic ether, cyclic amine, or cyclic thioether is mentioned.
Examples of the cyclic ether having 3 to 36 carbon atoms include 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1,2-epoxynonane, 1,2- Epoxydecane, 1,2-epoxydodecane, 1,2-epoxytetradecane, 1,2-epoxyhexadecane, 1,2-epoxyoctadecane, 1,2-epoxyeicosane, 1,2-epoxydocosan, 1,2- Examples thereof include epoxy tetracosane, 1,2-epoxy hexacosane, and 1,2-epoxy octacosane.
As the cyclic amine or cyclic thioether having 3 to 36 carbon atoms, the group represented by —O— of the compound exemplified as the cyclic ether having an alkyl group having 3 to 36 carbon atoms is substituted with —NH— or —S—. Compounds.
Among these, a cyclic ether having 5 to 36 carbon atoms is preferable from the viewpoint of the effect of improving the viscosity index, and a 1,2-epoxyalkane having 10 to 36 carbon atoms is more preferable.

As a C2-C4 heterocyclic compound (p2), C2-C4 cyclic ether, cyclic amine, or cyclic thioether is mentioned.
Examples of the cyclic ether having 2 to 4 carbon atoms include ethylene oxide, 1,2- or 1,3-propylene oxide, and 1,2-, 1,3- or 1,4-butylene oxide.
Examples of the cyclic amine or cyclic thioether having 2 to 4 carbon atoms include compounds in which the group represented by -O- of the compound exemplified as the cyclic ether having 2 to 4 carbon atoms is substituted with -NH- or -S-. It is done.
Among these, ethylene oxide is preferable from the viewpoint of the effect of improving the viscosity index.

Examples of the one or more active hydrogen-containing compounds (q) include saturated aliphatic alcohols having 10 to 60 carbon atoms, saturated aliphatic amines, and saturated aliphatic thiols.
Examples of the saturated aliphatic alcohol having 10 to 60 carbon atoms include linear saturated aliphatic alcohol having 10 to 30 carbon atoms and branched saturated aliphatic alcohol having 10 to 60 carbon atoms.
Examples of the linear saturated aliphatic alcohol having 10 to 30 carbon atoms include n-decyl alcohol, n-dodecyl alcohol, n-tetradecyl alcohol, n-hexadecyl alcohol, n-octadecyl alcohol and n-icosyl alcohol. .
Examples of the branched saturated aliphatic alcohol having 10 to 60 carbon atoms include gerbet alcohol (2-hexyldecyl alcohol, 2-octyldodecyl alcohol, 2-decyltetradecyl alcohol, 2-dodecylhexadecyl alcohol and 2-tetradecyloctadecyl alcohol). Etc.), and reduced alcohols of branched fatty acids (such as isotetradecyl alcohol, isohexadecyl alcohol and isooctadecyl alcohol).

The active hydrogen group-containing reaction product (X1) is a compound obtained by subjecting (p1) and (q) to an addition reaction in the presence of an acid catalyst or a base catalyst.
The reaction temperature for the addition reaction of (p1) and (q) is preferably 80 to 180 ° C, more preferably 100 to 150 ° C from the viewpoint of the reaction time. The reaction pressure is preferably 0.1 to 2.5 MPa. The reaction time is preferably 2 to 20 hours, more preferably 3 to 10 hours.
As the acid catalyst, known ones can be used. Specifically, mineral acids (such as sulfuric acid and hydrochloric acid), organic acids (such as paratoluenesulfonic acid and trifluoromethanesulfonic acid), and Lewis acids [Al ( Oi-Pr) ₃ etc.].
A well-known thing can be used as a base catalyst, Specifically, potassium t-butoxide, potassium ethoxide, etc. are mentioned.

The active hydrogen group-containing reaction product (X2) is a compound obtained by subjecting (X1) and (p2) to an addition reaction in the presence of an acid catalyst or a base catalyst.
The reaction conditions for the addition reaction of (X1) and (p2), the acid catalyst, and the base catalyst are the reaction conditions for the above addition reaction of (p1) and (q) in the presence of an acid catalyst or a base catalyst. Are the same.

(X1) and (meth) acrylic acid are esterified to obtain (a), (X2) and (meth) acrylic acid are esterified to obtain (a), (X1) and carbon number A method of obtaining (a) by transesterification with a (meth) acrylic acid ester having 1 to 4 alkyl groups, (X2) and a (meth) acrylic acid ester having an alkyl group having 1 to 4 carbon atoms. The reaction temperature in the method of obtaining (a) by transesterification is preferably 80 to 150 ° C., more preferably 90 to 130 ° C., from the viewpoint of reaction time and prevention of polymerization of (meth) acrylic acid. .
In the esterification reaction and the transesterification reaction, the reaction pressure may be reduced for the purpose of removing generated water or an alcohol having 1 to 4 carbon atoms. A preferable reaction pressure is preferably 0.007 to 0.095 MPa, more preferably 0.01 to 0.092 MPa, from the viewpoint of reaction time and prevention of polymerization of (meth) acrylic acid.
The reaction time for the esterification reaction and the transesterification reaction is preferably 2 to 24 hours, and more preferably 3 to 10 hours. The esterification reaction is desirably performed in the presence of a catalyst.
The catalyst may be a known catalyst that is usually used, and examples thereof include sulfuric acid and p-toluenesulfonic acid. A solvent may be used for the esterification reaction, and examples of the solvent include water-insoluble solvents having a boiling point of 150 ° C. or lower, such as cyclohexane and toluene.

  In addition to the monomer (a), the (co) polymer (A) in the present invention has a (meth) acrylic acid alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms and / or 8 carbon atoms. It is preferable from a viewpoint of a viscosity index improvement effect that it is a copolymer which uses the (meth) acrylic-acid alkylester (c) which has -36 linear alkyl group as a structural monomer.

Examples of the (meth) acrylic acid alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and ( (Meth) acrylic acid n-butyl etc. are mentioned.
Of these, (b) is preferably a (meth) acrylic acid ester having a linear alkyl group having 1 to 3 carbon atoms, more preferably methyl (meth) acrylate and ethyl (meth) acrylate, Particularly preferred is methyl (meth) acrylate.

Examples of the (meth) acrylic acid alkyl ester (c) having a linear alkyl group having 8 to 36 carbon atoms include n-octyl (meth) acrylate, n-nonyl (meth) acrylate, and n- (meth) acrylate. Decyl, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, n-pentadecyl (meth) acrylate, n-hexadecyl (meth) acrylate, (meth) Examples include n-octadecyl acrylate, n-icosyl (meth) acrylate, n-tetracosyl (meth) acrylate, n-triacontyl (meth) acrylate, n-hexatriacontyl (meth) acrylate, and the like.
Among (c), (meth) acrylic acid alkyl ester having a linear alkyl group having 12 to 32 carbon atoms is preferred, and (meth) having a linear alkyl group having 16 to 30 carbon atoms is more preferred. Acrylic acid esters, particularly preferred are (meth) acrylic acid esters having a linear alkyl group having 18 to 28 carbon atoms.

  The (co) polymer (A) in the present invention is a copolymer having a monomer (d) represented by the following general formula (2) as a constituent monomer in addition to (a). It is preferable from the viewpoint of the effect of improving the viscosity index.

［Ｒ^８は水素原子又はメチル基；Ｒ^９は炭素数２〜４のアルキレン基；Ｒ^１０は炭素数１６〜６０の分岐アルキル基；Ｘ^４は−Ｏ−又は−ＮＨ−で表される基；ｐは０〜２０の数であり、ｐが２以上の場合のＲ^９は同一でも異なっていてもよく、（Ｒ^９Ｏ）_ｐ部分はランダム結合でもブロック結合でもよい。］

[R ⁸ is a hydrogen atom or a methyl group; R ⁹ is an alkylene group having 2 to 4 carbon atoms; R ¹⁰ is a branched alkyl group having 16 to 60 carbon atoms; X ⁴ is a group represented by —O— or —NH—. P is a number from 0 to 20, and when p is 2 or more, R ^{9 s} may be the same or different, and the (R ⁹ O) _p moiety may be a random bond or a block bond. ]

R ⁸ in the general formula (2) is a hydrogen atom or a methyl group. Among these, a methyl group is preferable from the viewpoint of improving the viscosity index.

X ⁴ in the general formula (2) is a group represented by —O—, —NH— or —S—. Among these, the group represented by —O— is preferable from the viewpoint of the effect of improving the viscosity index.

R ⁹ 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 an ethylene group, 1,2- or 1,3-propylene group, and 1,2-, 1,3- or 1,4-butylene group. Among these, the ethylene group and the 1,2-propylene group are preferable from the viewpoint of the effect of improving the viscosity index.

P in the general formula (2) is a number from 0 to 20, preferably from 0 to 5, more preferably from 0 to 2 from the viewpoint of the effect of improving the viscosity index and low temperature viscosity.
R ⁹ when p is 2 or more may be the same or different, and the (R ⁹ O) _p moiety may be a random bond or a block bond.

R ¹⁰ in the general formula (2) is a branched alkyl group having 16 to 60 carbon atoms.
Examples of the branched alkyl group having 16 to 60 carbon atoms include isohexadecyl group, 2-octylnonyl group, 2-hexylundecyl group, 2-ethylpentadecyl group, 2- (3-methylhexyl) -7-methyl- Nonyl group, isooctadecyl group, 1-hexyltridecyl group, 2-ethylheptadecyl group, 2-octylundecyl group, isoicosyl group, 1-undecyldodecyl group, 1-octylpentadecyl group, 2-decyltridecyl group, 2-decyltetradecyl group, 2- (1,4,4-trimethylbutyl) -5,7,7-trimethyl-heptyl group, 2-dodecylpentadecyl group, isotricontyl group, 2-tetradecylheptadecyl group, 2 -Hexadecyl heptadecyl group, 1-heptyltricontyl group, 2-heptadecylicosyl group, 1-octadecylico Group, 2-hexadecyl docosyl group, 2- (1,4,4-trimethylbutyl) -5,7,7-trimethyl-tricontyl group, 2-icosyl docosyl group, 1-icosyl tetracosyl group, 2 -Ethyl-4-butyl-tetracontyl group, 2-tetracosylhexacosyl group, 2-methylpentacontyl group, 2-tetradecyltetracontyl group, 2-dodecylhexatetracontyl group, 2- (3- Methylhexyl) -7-ethyl-pentacontyl group, 1-octacosyltricontyl group, 1-icosyltetracontyl group, 2-decylpentacontyl group and olefin [for example, propylene oligomer (13 to 20-mer), ethylene / Propylene oligomer (18-28 mer, molar ratio 16/1 to 1/11) and isobutene oligomer (10-15 mer), etc.] Residue excluding hydroxyl group, and the like from oxo alcohols obtained al.
Of the branched alkyl groups having 16 to 60 carbon atoms, preferred are branched alkyl groups having 16 to 50 carbon atoms, and more preferred are branched alkyl groups having 16 to 44 carbon atoms, particularly from the viewpoint of improving the viscosity index. A branched alkyl group having 20 to 40 carbon atoms is preferred.

  Specific examples of the monomer (d) include isohexadecyl (meth) acrylate, 2-octylnonyl (meth) acrylate, an ester of ethylene glycol mono-2-ethylpentadecyl ether and (meth) acrylic acid. , Isooctadecyl (meth) acrylate, 1-hexyltridecyl (meth) acrylate, 2-ethylheptadecyl (meth) acrylate, isoicosyl (meth) acrylate, 1-octylpentadecyl (meth) acrylate, ( (Meth) acrylic acid 2-decyltetradecyl, (meth) acrylic acid 2-dodecylpentadecyl, (meth) acrylic acid isotricontyl, (meth) acrylic acid 2-tetradecylheptadecyl, (meth) acrylic acid 2-hexadecylhepta Decyl, 2-heptadecyl icosyl (meth) acrylate, (meth) acrylic 2-hexadecyl docosyl, (meth) acrylic acid 2-eicosyl docosyl, (meth) acrylic acid 2-tetracosyl hexacosyl, (meth) acrylic acid 2-methylpentacontyl, (meth) acrylic acid 2 An oxo alcohol obtained from tetradecyltetracontyl, 2-dodecylhexatetracontyl (meth) acrylate, 1-octacosyltricontyl (meth) acrylate, and propylene oligomer (13 to 20-mer) ( And esters with (meth) acrylic acid.

(A) is a copolymer further comprising a nitrogen atom-containing monomer (e), a hydroxyl group-containing monomer (f) and / or a phosphate group-containing monomer (g) as a constituent monomer. Is preferable from the viewpoint of the effect of improving the viscosity index.
Examples of the nitrogen atom-containing monomer (e) include the following monomers (e1) to (e4).

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

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

Hydroxyl group-containing monomer (f):
Hydroxyl group-containing aromatic monomer (p-hydroxystyrene and the like), hydroxyalkyl (2 to 6 carbon atoms) (meth) acrylate [2-hydroxyethyl (meth) acrylate, and 2- or 3-hydroxypropyl (meth) acrylate 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 monools or alkene diols [ -Buten-3-ol, 2-buten-1-ol, 2-butene-1,4-diol and the like], hydroxyalkyl (C1-6) alkenyl (C3-10) ether (2-hydroxyethyl) Propenyl ether, etc.), polyhydric (3-8 valent) alcohols (glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, saccharides, sucrose, etc.) alkenyl (3 to 10 carbon atoms) ether or (meth) acrylate [sucrose ( Meta) allyl ether 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)], mono (meth) acrylates of polyoxyalkylene glycol or polyoxyalkylene polyol alkyl (carbon number 1-4) ether [polyethylene glycol (Mn: 100-300) 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) acryl Polyoxyethylene (Mn: 150 to 230), sorbitan, etc.] or the like; and the like.

  Examples of the phosphate group-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.]. “(Meth) acryloyloxy” means acryloyloxy or methacryloyloxy.

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 (g), (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) may use the following monomers (h) to (n) as constituent monomers.

Aliphatic hydrocarbon monomer (h):
Alkenes having 2 to 20 carbon atoms (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.) and alkadienes having 4 to 12 carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1 , 6-heptadiene and 1,7-octadiene).

Alicyclic hydrocarbon monomer (i):
Examples include cyclohexene, (di) cyclopentadiene, pinene, limonene, vinylcyclohexene, and ethylidenebicycloheptene.

Aromatic hydrocarbon monomer (j):
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 (k):
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 (l):
Examples thereof include glycidyl (meth) acrylate and glycidyl (meth) allyl ether.

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

Unsaturated polycarboxylic acid ester (n):
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 80% by weight, more preferably, based on the weight of (A), from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. Is 5 to 65% by weight, particularly preferably 10 to 50% by weight.
The proportion of (b) constituting (A) is preferably 5 to 70% by weight, more preferably, based on the weight of (A), from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. Is 10 to 65% by weight, particularly preferably 20 to 60% by weight.
The proportion of (c) constituting (A) is preferably 0 to 70% by weight, more preferably, based on the weight of (A), from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. Is 10 to 60% by weight, particularly preferably 20 to 50% by weight.
The proportion of (d) constituting (A) is preferably 0 to 50% by weight, more preferably, based on the weight of (A), from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. Is 5 to 45% by weight, particularly preferably 10 to 40% by weight.
The ratio of (e) to (g) constituting (A) is preferably 0 to 15% by weight, based on the weight of (A), from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. More preferably 1 to 12% by weight, particularly preferably 2 to 10% by weight.
The proportion of (h) to (n) constituting (A) is preferably 0 to 10% by weight based on the weight of (A) from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. More preferably 1 to 7% by weight, particularly preferably 2 to 5% by weight.

The solubility parameter (hereinafter abbreviated as SP value) of (A) is 7.3 to 9.7 (cal / cm ³ ) ^1/2 , and the viewpoint of improving the viscosity index and the low temperature viscosity of the lubricating oil composition Therefore, it is preferably 9.0 to 9.6 (cal / cm ³ ) ^1/2 , and more preferably 9.1 to 9.5 (cal / cm ³ ) ^1/2 .
The SP value of (A) is a value obtained by calculating the SP value of each monomer constituting (A) and averaging the SP value of each monomer based on the mole fraction of the constituent monomer units. It is.
The SP value of (A) can be adjusted to 7.3 to 9.5 (cal / cm ³ ) ^1/2 by appropriately adjusting the SP value and molar fraction of the monomer used.
The SP value in the present invention 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).

The absolute value of the difference between the SP value of (A) and the SP value of the base oil is preferably 0.5 to 1.8 (cal / cm ³ ) from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. It is ^1/2 , More preferably, it is 0.7-1.7 (cal / cm < ³ >) < ^1/2 >.

The weight average molecular weight (hereinafter abbreviated as Mw) of (A) is preferably 5,000 to 2,000,000 from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition, and a more preferable range is Depends on the use of the lubricating oil composition, and is in the range shown in Table 1.
Mw of (A) can be measured under the following conditions by gel permeation chromatography (GPC).
<GPC measurement conditions>
Apparatus: “HLC-802A” [manufactured by Tosoh Corporation]
Column: Two “TSK gel GMH6” [manufactured by Tosoh Corporation] Measurement temperature: 40 ° C.
Sample solution: 0.5 wt% tetrahydrofuran solution Solution injection amount: 200 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]

* ：オートマチックトランスミッション油
** ：ベルト−コンティニュアスリーバリュアブルトランスミッション油
*** ：マニュアルトランスミッション油

*: Automatic transmission oil
**: Belt-Continuously variable transmission oil
***: Manual transmission oil

The crystallization temperature of (A) is preferably −30 ° C. or less, more preferably −40 ° C. or less, and particularly preferably −50 ° C. or less from the viewpoint of the low temperature viscosity of the lubricating oil composition.
The crystallization temperature of (A) was determined by using a differential scanning calorimeter “UNIX (registered trademark) DSC7” (manufactured by PERKIN-ELMER), using 5 mg of a viscosity index improver as a sample, and an isothermal rate of 10 ° C./min. Is the crystallization temperature observed when cooled from 100 ° C. to −70 ° 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, alkylbenzene having 9 to 10 carbon atoms, methyl ethyl ketone, and mineral oil.
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 a tertiary amine and the like. 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 140 ° C, more preferably 50 to 120 ° 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 of the present invention may be used in combination with (A) and an alkyl (meth) acrylate (co) polymer (B) other than (A).
(B) 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 (B) 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 (B) are used in combination, the amount of (B) used is preferably 0.01 to 30% by weight based on the weight of (A) from the viewpoint of the low temperature viscosity of the lubricating oil composition. More preferably, the content is 0.01 to 20% by weight, and particularly preferably 0.01 to 10% by weight.

  The lubricating oil composition of the present invention comprises the viscosity index improver of the present invention and a base oil. Base oils include mineral oils (solvent refined oils, paraffin oils, high viscosity index oils containing isoparaffins, high viscosity index oils obtained by hydrocracking isoparaffins, naphthenic oils, etc.), synthetic lubricating oils (hydrocarbon synthetic lubricating oils) (Poly α-olefin-based synthetic lubricating oil, etc.) and ester-based synthetic lubricating oil, etc.] and mixtures thereof. Of these, mineral oil is preferred.

(Measured by JIS-K2283) kinematic viscosity at 100 ° C. of the base oil is preferably from the viewpoint of the viscosity index improving effect is 1 to 15 mm ² / s, more preferably from 2 to 5 mm ² / s.
The viscosity index (measured according to JIS-K2283) of the base oil is preferably 90 or more, more preferably 100 or more, from the viewpoint of the effect of improving the viscosity index.

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

The content of the viscosity index improver in the lubricating oil composition of the present invention is preferably 1 to 30% by weight in terms of the weight of (A) in the viscosity index improver based on the weight of the base oil. .
When the lubricating oil composition is used as an engine oil, a base oil having a kinematic viscosity at 100 ° C. of 4 to 10 mm ² / s and containing 2 to 10% by weight of (A) is preferable.
When the lubricating oil composition is used as a gear oil, a base oil having a kinematic viscosity at 100 ° C. of ² to 10 mm ² / s and containing 3 to 30% by weight of (A) is preferable.
When the lubricating oil composition is used as an automatic transmission oil (such as ATF and belt-CVTF), a base oil having a kinematic viscosity at 100 ° C. of ² to 6 mm ² / s and 3 to 25% by weight of (A) What is contained is preferable.
When the lubricating oil composition is used as a traction oil, a base oil having a kinematic viscosity at 100 ° C. of 1 to 5 mm ² / s and containing (A) of 0.5 to 10% by weight is preferable. .

The lubricating oil composition of the present invention may contain various additives. The following are mentioned as an additive.
(1) Detergent:
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;
(2) Dispersant:
Succinimides (bis- or mono-polybutenyl succinimides), Mannich condensation products, borates and the like;
(3) Antioxidant:
Hindered phenols and aromatic secondary amines, etc .;
(4) Oiliness improver:
Long chain fatty acids and their esters (such as oleic acid and oleic acid esters), long chain amines and their amides (such as oleylamine and oleylamide), etc .;
(5) Friction and wear modifier:
Molybdenum and zinc compounds (such as molybdenum dithiophosphate, molybdenum dithiocarbamate and zinc dialkyldithiophosphate);
(6) Extreme pressure agent:
Sulfur compounds (mono or disulfides, sulfoxides and sulfur phosphide compounds), phosphide compounds and chlorinated compounds (chlorinated paraffins, etc.);
(7) Antifoaming agent:
Silicon oil, metal soap, fatty acid ester and phosphate compound, etc .;
(8) Demulsifier:
Quaternary ammonium salts (tetraalkylammonium salts, etc.), sulfated oils and phosphates (polyoxyethylene-containing nonionic surfactant phosphates, etc.);
(9) Corrosion inhibitor:
Nitrogen atom-containing compounds (such as benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate) and the like.

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

<Production Example 1>
In a glass reaction vessel equipped with a stirrer, a heating / cooling device, and a thermometer, 1,000 parts by weight of xylene, 37,5 parts by weight of 1,2-epoxyoctadecane [manufactured by ARKEMA], 2-decyltetradecyl alcohol [Shin Nihon Rika Co., Ltd.] 600 parts by weight and t-butoxypotassium [Wako Pure Chemical Industries, Ltd.] 10 parts by weight were added, and the temperature was raised to 120 ° C. with stirring, followed by polymerization at the same temperature for 8 hours. After raising the temperature to 130 ° C., xylene was removed at the same temperature under reduced pressure (0.027 to 0.040 MPa) over 2 hours, and then the catalyst was removed with an adsorbent. Next, 200 parts by weight of methacrylic acid and 1 part by weight of paratoluenesulfonic acid were added, the temperature was raised to 130 ° C. with stirring, an esterification reaction was carried out at the same temperature for 4 hours, and distillate water was separated. Further cooled to 25 ° ^C., it was confirmed esterification reaction product in 1 H-NMR (98 mol% yield). 300 parts by weight of a 10% by weight aqueous sodium hydrogen carbonate solution was added and stirred to sufficiently neutralize paratoluenesulfonic acid. The supernatant is collected with a separatory funnel, heated to 120 to 130 ° C., and unreacted monomer is removed under reduced pressure (0.027 to 0.040 MPa) at the same temperature over 2 hours. The body (a-1) 1,150 weight part was obtained. SP value of (a-1): 8.7 (cal / cm ³ ) ^1/2 , melting point: −25 ° C. In (a-1), R ¹ in the general formula (1) is a methyl group, X ² and X ³ are groups represented by —O—, R ³ is a hexadecyl group, R ⁴ and R ⁵ are hydrogen atoms, R ⁶ is a monomer represented by a decyl group, R ⁷ is a dodecyl group, m is 0, and n is 1.

<Production Example 2>
In a glass reaction vessel equipped with a stirrer, a heating / cooling device and a thermometer, 1,000 parts by weight of xylene, 430 parts by weight of 1,2-epoxyoctadecane [manufactured by ARKEMA], isooctadecyl alcohol [manufactured by Higher Alcohol Industry Co., Ltd. 520 parts by weight and 10 parts by weight of t-butoxy potassium [manufactured by Wako Pure Chemical Industries, Ltd.] were added, the temperature was raised to 120 ° C. with stirring, and a polymerization reaction was performed at the same temperature for 8 hours. After raising the temperature to 130 ° C., xylene was removed at the same temperature under reduced pressure (0.027 to 0.040 MPa) over 2 hours, and then the catalyst was removed with an adsorbent. Next, 200 parts by weight of methacrylic acid and 1 part by weight of paratoluenesulfonic acid were added, the temperature was raised to 130 ° C. with stirring, an esterification reaction was carried out at the same temperature for 4 hours, and distillate water was separated. Further cooled to 25 ° ^C., it was confirmed esterification reaction product in 1 H-NMR (98 mol% yield). 300 parts by weight of a 10% by weight aqueous sodium hydrogen carbonate solution was added and stirred to sufficiently neutralize paratoluenesulfonic acid. The supernatant is collected with a separatory funnel, heated to 120 to 130 ° C., and unreacted monomer is removed under reduced pressure (0.027 to 0.040 MPa) at the same temperature over 2 hours. The body (a-2) 1,100 weight part was obtained. SP value of (a-2): 8.7 (cal / cm ³ ) ^1/2 , melting point: −35 ° C. (A-2) is a group in which R ¹ in the general formula (1) is a methyl group, X ² and X ³ are represented by —O—, R ³ is a hexadecyl group, R ⁴ , R ⁵ and R ⁶ are hydrogen. An atom, R ⁷ is an isoheptadecyl group, m is 0, and n is 0.

<Production Example 3>
In a glass reaction vessel equipped with a stirrer, a heating / cooling device, and a thermometer, 1,000 parts by weight of xylene, 326 parts by weight of 1,2-epoxyhexadecane [manufactured by ARKEMA], 2-dodecylhexadecyl alcohol [Shin Nippon Rika ( 492 parts by weight and 10 parts by weight of t-butoxy potassium [manufactured by Wako Pure Chemical Industries, Ltd.] were added, the temperature was raised to 120 ° C. with stirring, and a polymerization reaction was performed at the same temperature for 8 hours. After raising the temperature to 130 ° C., xylene was removed at the same temperature under reduced pressure (0.027 to 0.040 MPa) over 2 hours, and then the catalyst was removed with an adsorbent. Next, 200 parts by weight of methacrylic acid and 1 part by weight of paratoluenesulfonic acid were added, the temperature was raised to 130 ° C. with stirring, an esterification reaction was carried out at the same temperature for 4 hours, and distillate water was separated. Furthermore, it cooled to 25 degreeC and confirmed the esterification reaction material by 1H-NMR (yield 98 mol%). 300 parts by weight of a 10% by weight aqueous sodium hydrogen carbonate solution was added and stirred to sufficiently neutralize paratoluenesulfonic acid. The supernatant is collected with a separatory funnel, heated to 120 to 130 ° C., and unreacted monomer is removed under reduced pressure (0.027 to 0.040 MPa) at the same temperature over 2 hours. The body (a-3) 1,150 weight part was obtained. SP value of (a-3): 9.7 (cal / cm ³ ) ^1/2 , melting point: −45 ° C. In (a-3), R ¹ in the general formula (1) is a methyl group, X ² and X ³ are groups represented by —O—, R ³ is a tetradecyl group, R ⁴ and R ⁵ are hydrogen atoms, R ⁶ is a monomer represented by a dodecyl group, R ⁷ is a tetradecyl group, m is 0, and n is 1.

<Examples 1-6, Comparative Examples 1-4>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a nitrogen introducing tube, base oil A (SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C .: 4.2 mm ² / S, viscosity index: 128) 400 parts by weight, 100 parts by weight of the monomer blend described in Table 2, 0.5 parts by weight of 2,2-azobis (2,4-dimethylvaleronitrile) and 2,2- After 0.2 part by weight of azobis (2-methylbutyronitrile) was added and nitrogen substitution (gas phase oxygen concentration 100 ppm) was performed, the temperature was raised to 76 ° C. with stirring and hermetically sealed for 4 hours at the same temperature. A polymerization reaction was performed. 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 (A6), (H1 ) To (H4) viscosity index improvers (R1) to (R6) and (S1) to (S4) were obtained. The SP values of the obtained copolymers (A1) to (A6) and (H1) to (H4) were calculated by the above method, and Mw and the crystallization temperature were measured by the above method. Moreover, the base oil solubility of the copolymer was evaluated by the following method. The results are shown in Table 2.

<Examples 7-8, Comparative Examples 5-6>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a nitrogen introduction tube and a decompression device, base oil B [SP value: 8.3 (cal / cm ³ ) ^1/2 , 100 ° C. Viscosity: 2.4 mm ² / s, Viscosity index: 96] 100 parts by weight were charged, and in another glass beaker, 100 parts by weight of the monomers listed in Table 2 and 1.0 part by weight of dodecyl mercaptan as a chain transfer agent Part, 0.5 part by weight of 2,2-azobis (2,4-dimethylvaleronitrile) and 0.2 part by weight of 2,2-azobis (2-methylbutyronitrile) are added and stirred and mixed at 20 ° C. A monomer solution was prepared and charged into 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 (A7) to (A8) Viscosity index improvers (R7) to (R8) and (S5) to (S6) comprising (H5) to (H6). The SP values of the obtained copolymers (A7) to (A8) and (H5) to (H6) were calculated by the above method, and Mw and crystallization temperature were measured by the above method. Moreover, the base oil solubility of the copolymer was evaluated by the following method. The results are shown in Table 2.

<Evaluation method of base oil solubility of copolymer>
The appearance of the viscosity index improvers (R1) to (R8) and (S1) to (S6) was visually observed, and the base oil solubility 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 (b) to (g) described in Table 2 are as described below.
(B-1): methyl methacrylate (c-1): n-tetradecyl methacrylate (c-2): n-hexadecyl methacrylate (c-3): n-octadecyl methacrylate (d-1): methacrylic acid 2-n-decyl-n-tetradecyl (e-1): N, N-dimethylaminoethyl methacrylate (f-1): hydroxyethyl methacrylate (g-1): methacryloyloxyethyl phosphate

<Examples 9-14, Comparative Examples 7-10 (Evaluation of Lubricating Oil Composition for Engine Oil)>
Base oil A (SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C .: 4.2 mm ² / s, viscosity index: 128) is put into a stainless steel container equipped with a stirrer. Viscosity index improvers (R1) to (R6) and (S1) to respectively have an HTHS viscosity at 150 ° C. of 2.60 ± 0.05 (mm ² / s). (S4) was added to obtain lubricating oil compositions (V1) to (V6) and (W1) to (W4).
The viscosity index, HTHS viscosity (80 ° C.), and low temperature viscosity (−40 ° C.) of the lubricating oil compositions (V1) to (V6) and (W1) to (W4) were measured by the following methods. The results are shown in Table 3.

<Examples 15-16, Comparative Examples 11-12 (Evaluation of Lubricating Oil Composition for Gear Oil)>
Base oil B (SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C .: 2.4 mm ² / s, viscosity index: 96) is put into a stainless steel container equipped with a stirrer. Viscosity index improvers (R7) to (R8) and (S5) to (S5) so that the resulting lubricant composition has a kinematic viscosity at 100 ° C. of 4.50 ± 0.02 (mm ² / s). S6) was added to obtain lubricating oil compositions (V7) to (V8) and (W5) to (W6).
The viscosity index, kinematic viscosity at 40 ° C., HTHS viscosity and low temperature viscosity (−40 ° C.) of the lubricating oil compositions (V7) to (V8) and (W5) to (W6) were measured by the following methods. The results are shown in Table 4.

<Measuring method of viscosity index of lubricating oil composition and kinematic viscosity at 40 ° C.>
It measured by the method of JIS-K2283.

<Method for Measuring HTHS Viscosity of Lubricating Oil Composition>
The measurement was performed at 80 ° C. by the method of ASTM D 5481.

<Method for measuring low temperature viscosity of lubricating oil composition>
The viscosity at −40 ° C. was measured by the method of JPI-5S-26-85.

  As apparent from the results of Tables 3 and 4, the lubricating oil compositions (Examples 9 to 16) containing the viscosity index improver of the present invention were compared with the lubricating oil compositions of Comparative Examples 7 to 12. Thus, the viscosity index improving effect is high and the low temperature viscosity is low.

  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 (12)

A viscosity index improver containing a (co) polymer (A) having a monomer (a) represented by the following general formula (1) as an essential constituent monomer.

^{[R 1} is a hydrogen atom or a methyl group; an alkylene group of ^{R 2} is ^C2-4; R 3, ^{R 4} are each independently a hydrogen atom or an alkyl group having a carbon number of 1 to 36, and ^{R 3} The total number of carbon atoms of R ⁴ is 3 or more. R ⁵ is a hydrogen atom or an alkyl group having 1 to 16 carbon atoms; R ⁶ and R ⁷ are each independently a hydrogen atom or an alkyl group having 8 to 36 carbon atoms, and the total number of carbon atoms of R ⁶ and R ⁷ Is 8 or more. X ¹ , X ² and X ³ are each independently a group represented by —O—, —NH— or —S—; m is a number from 0 to 20, and R ² when m is 2 or more; May be the same or different, and the (X ¹ R ² ) _m moiety may be a random bond or a block bond. N is a number from 0 to 20]   The viscosity index improver according to claim 1, wherein the absolute value of the difference between the solubility parameter of (A) and the solubility parameter of the base oil is 0.5 to 1.8. The viscosity index improver according to claim 1 or 2, wherein X ² in the general formula (1) is a group represented by -O-. The viscosity index improver according to any one of claims 1 to 3, wherein X ³ in the general formula (1) is a group represented by -O-.   (A) is a (meth) acrylic acid alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms and / or a linear alkyl group having 8 to 36 carbon atoms as a constituent monomer of (A). The viscosity index improver according to any one of claims 1 to 4, which is a copolymer comprising (meth) acrylic acid alkyl ester (c). 6. (A) is a copolymer having the monomer (d) represented by the general formula (2) as a constituent monomer as the constituent monomer of (A). The viscosity index improver described in 1.

[R ⁸ is a hydrogen atom or a methyl group; R ⁹ is an alkylene group having 2 to 4 carbon atoms; R ¹⁰ is a branched alkyl group having 16 to 60 carbon atoms; X ⁴ is a group represented by —O— or —NH—. P is a number from 0 to 20, and when p is 2 or more, R ^{9 s} may be the same or different, and the (R ⁹ O) _p moiety may be a random bond or a block bond. ]   (A) further comprises a nitrogen atom-containing monomer (e), a hydroxyl group-containing monomer (f), and / or a phosphate group-containing monomer (g) as a constituent monomer of (A). The viscosity index improver according to any one of claims 1 to 6, which is a copolymer obtained by polymerization.   The viscosity index improver according to any one of claims 1 to 7, wherein (A) has a weight average molecular weight of 5,000 to 2,000,000.   Furthermore, the (co) polymer (B) other than (A) is contained in an amount of 0.01 to 30% by weight based on the weight of (A), improving the viscosity index according to any one of claims 1 to 8. Agent.   A lubricating oil composition comprising the viscosity index improver according to claim 1 and a base oil.   The lubricating oil composition according to claim 10, further comprising at least one additive selected from the group consisting of a dispersant, a detergent, an antioxidant, an oiliness improver, a friction wear modifier, and an extreme pressure agent. . The lubricating oil composition according to claim 10 or 11, wherein the base oil has a kinematic viscosity at 100 ° C of 1 to 15 mm ² / s, and the base oil has a viscosity index of 90 or more.