JP2017110196A - Viscosity index improver and lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity index improver excellent in shear stability of a lubricant composition, low in HTHS viscosity and high in viscosity index.SOLUTION: There is provided a viscosity index improver containing a (co)polymer (A) of a monomer (a) represented by the formula (1) as an essential component monomer and having a ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) of the (co)polymer (A), Mw/Mn of 1.6 or less and Mn of 1,000 or more. (1), where Ris H or a methyl group, Ris a polymer containing isobutylene and/or 1,2-butylene, Xis O, O(AO)or NH, A is a C2 to 4 alkylene group, m is an integer of 1 to 10 and p is 0 or 1.SELECTED DRAWING: None

Description

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

In recent years, in order to reduce CO ₂ emissions and protect petroleum resources, fuel consumption of automobiles has been further demanded. One way to save fuel is to reduce viscous resistance by reducing the viscosity of engine oil. However, when the viscosity is lowered, problems such as liquid leakage and seizure arise. In cold regions, low temperature startability is required. This problem is defined in the US SAE viscosity standard for engine oil (SAE J300). In the 0W-20 grade, 150 ° C. HTHS viscosity (ASTM D4683 or D5481) under high temperature and high shear is Min. . It is specified in 2.6. In addition, in order to guarantee startability in a cold region, the grade has a low-temperature viscosity at −40 ° C. of 60,000 mPa · s or less and no yield stress (ASTM D4684). For fuel saving, engine oil having a lower HTHS viscosity in an effective temperature range of 80 ° C. or 100 ° C. after satisfying the above standards is required, and various viscosity index improvers have been proposed. As such a viscosity index improver, methacrylic acid ester copolymers (Patent Documents 1 to 4), olefin copolymers (Patent Document 5), comb copolymers (Patent Documents 6 to 8) and the like are known. ing.
However, the above viscosity index improver is not yet sufficient for reducing the 80 ° C. HTHS viscosity when added to an engine oil composition, is susceptible to viscosity reduction due to shearing, and increases the viscosity at low temperatures. was there.

Japanese Patent No. 2732187 Japanese Patent No. 2754343 Japanese Patent No. 3831203 Japanese Patent No. 3999307 JP 2005-200454 A Japanese Patent No. 3474918 Special table 2008-546894 gazette Special table 2010-532805 gazette

  An object of the present invention is to provide a viscosity index improver that is excellent in shear stability of a lubricating oil composition, has a low HTHS viscosity in the effective temperature range of the lubricating oil composition, and has a high viscosity index of the lubricating oil composition. is there.

［Ｒ^１は水素原子又はメチル基；−Ｘ^１−は−Ｏ−、−Ｏ（ＡＯ）_ｍ−又は−ＮＨ−で表される基であって、Ａは炭素数２〜４の直鎖又は分岐アルキレン基、ｍは１〜１０の整数であり、ｍが２以上の場合のＡは同一でも異なっていてもよく、（ＡＯ）_ｍ部分はランダム結合でもブロック結合でもよい；Ｒ^２はイソブチレン及び／又は１，２−ブチレンを必須構成単量体とする炭化水素重合体の残基；ｐは０又は１の数；Ｍｎは１，０００以上］ As a result of intensive studies, the present inventors have arrived at the present invention. That is, the present invention is a viscosity index improver comprising a (co) polymer (A) having a monomer (a) represented by the following general formula (1) as an essential constituent monomer, It is a viscosity index improver in which the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the (co) polymer (A) is 1.6 or less.

[R ¹ is a hydrogen atom or a methyl group; —X ¹ — is a group represented by —O—, —O (AO) _m — or —NH—, and A is a straight chain having 2 to 4 carbon atoms or A branched alkylene group, m is an integer from 1 to 10, and when m is 2 or more, A's may be the same or different, and (AO) _m moiety may be a random bond or a block bond; R ² is isobutylene and Residue of hydrocarbon polymer having 1,2-butylene as essential monomer; p is 0 or 1; Mn is 1,000 or more]

  The lubricating oil composition containing the viscosity index improver of the present invention is excellent in shear stability, has a low HTHS viscosity in the effective temperature range, and is excellent in the viscosity index of the lubricating oil composition.

  The viscosity index improver of the present invention is a viscosity index improver containing a copolymer (A) having the monomer (a) represented by the general formula (1) as an essential constituent monomer, Lubricating oil composition comprising a viscosity index improver having a ratio Mw / Mn of 1.6 or less of the weight average molecular weight Mw and the number average molecular weight Mn of the coalescence (A), the viscosity index improver and a base oil It is.

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 the HTHS viscosity in the effective temperature range.

-X < ¹ >-in General formula (1) is group represented by -O-, -O (AO) _m-, or -NH-.
A is an alkylene group having 2 to 4 carbon atoms.
Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, a 1,2- or 1,3-propylene group, and a 1,2-, 1,3- or 1,4-butylene group.
m is an integer of 1 to 10, and preferably an integer of 1 to 4, more preferably an integer of 1 to 2, from the viewpoint of the HTHS viscosity in the effective temperature range.
When m is 2 or more, A may be the same or different, and (AO) _m part may be a random bond or a block bond.
Of the —X ¹ —, a group represented by —O— and —O (AO) _m — is preferable from the viewpoint of the HTHS viscosity in the effective temperature range, and more preferably —O— and —O ( CH ₂ CH ₂ O) —.

  p is a number of 0 or 1.

R ² in the general formula (1) represents one hydrogen atom from a hydrocarbon polymer having isobutylene and / or 1,2-butylene as an essential constituent monomer (hereinafter abbreviated as “hydrocarbon polymer”). Excluded residues.
Examples of the hydrocarbon polymer include polymers having the following (1) to (3) as constituent monomers in addition to isobutylene and / or 1,2-butylene. The hydrocarbon polymer may be a block polymer or a random polymer. When the hydrocarbon polymer has a double bond, a part or all of the double bond may be hydrogenated by hydrogenation.
(1) aliphatic unsaturated hydrocarbon [olefin having 2 to 36 carbon atoms (for example, ethylene, propylene, 2,3-butylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, triacocene, hexatriacocene, etc.) and C2-C36 dienes (for example, butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.)
(2) Alicyclic unsaturated hydrocarbon [for example, cyclohexene, (di) cyclopentadiene, pinene, limonene, indene, vinylcyclohexene, ethylidenebicycloheptene, etc.]
(3) Aromatic group-containing unsaturated hydrocarbon (for example, styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotyl) Benzene, vinyl naphthalene, divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene, etc.).

  From the viewpoint of the HTHS viscosity, viscosity index and shear stability, the total ratio of isobutylene and 1,2-butylene is preferably 30 mol% or more based on the total number of constituent monomers of the hydrocarbon polymer, and more preferably It is 40 mol% or more, particularly preferably 50 mol% or more, and most preferably 60 mol% or more.

Based on the total number of structural units of the hydrocarbon polymer, the total ratio of isobutylene and 1,2-butylene is calculated by analyzing the hydrocarbon polymer by 13C-nuclear magnetic resonance spectrum and using the following formula (1). Can be determined. In the 13C-nuclear magnetic resonance spectrum, the peak derived from the methyl group of isobutylene has an integrated value of 30-32 ppm (integrated value A), and a branched methylene group of 1,2-butylene (—CH ₂ —CH (CH ₂ CH ₃ )). A peak derived from-) appears in an integrated value (integrated value B) of 26-27 ppm. It can be determined from the integrated value of the peak and the integrated value (integrated value C) relating to the peak of all carbon in the hydrocarbon polymer.

  The monomer (a) represented by the general formula (1) is an ester of a hydroxyl group-containing (co) polymer (Y) having a hydroxyl group introduced at one end of a hydrocarbon polymer and (meth) acrylic acid. It can be obtained by a chemical reaction. Note that “(meth) acryl” means methacryl or acryl.

Specific examples of the one-terminal hydroxyl group-containing (co) polymer (Y) include the following.
Alkylene oxide adduct (Y1); (co) polymer obtained by polymerizing unsaturated hydrocarbon (x) in the presence of an ion polymerization catalyst (sodium catalyst, etc.) to alkylene oxide (ethylene oxide, propylene oxide, etc.) Obtained by adding.
Hydroboration product (Y2); (x) hydroboration reaction product of (co) polymer having a terminal double bond (for example, those described in US Pat. No. 4,316,973) and the like.
Maleic anhydride-ene-aminoalcohol adduct (Y3); imidation of a reaction product obtained by ene reaction of (co) polymer (x) having a terminal double bond and maleic anhydride with aminoalcohol And so on.
Hydroformyl-hydride (Y4); a product obtained by hydroformylating (co) polymer (x) having a terminal double bond and then hydrogenating (for example, those described in JP-A-63-175096) )etc.
Among (Y), (Y1), (Y2) and (Y3) are preferable, and (Y1) is more preferable.

The number average molecular weight (hereinafter abbreviated as Mn) of the monomer (a) is 1,000 or more, preferably from 1,000 to 25,000 from the viewpoint of shear stability and HTHS viscosity, more preferably 2,000 to 20,000, particularly preferably 2,000 to 15,000, and most preferably 2,500 to 10,000.
The Mn of the monomer (a) and the Mn and weight average molecular weight (hereinafter abbreviated as Mw) of the (co) polymer (A) described later can be measured by gel permeation chromatography under the following conditions. it can.
<Measurement conditions of Mn of monomer (a) 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: 0.5 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]

The crystallization temperature of (A) is preferably −40 ° C. or less, more preferably −50 ° C. or less, particularly preferably −55 ° C. or less, and most preferably −60 ° C. from the viewpoint of the low temperature viscosity of the lubricating oil composition. It is as follows.
The crystallization temperature of the (co) polymer (A) can be measured using a differential scanning calorimeter “Unix (registered trademark) DSC7” (manufactured by PERKIN-ELMER). This is the crystallization temperature observed when a sample is cooled from 100 ° C. to −80 ° C. at an isothermal rate of 10 ° C./min.

  Mw / Mn of the (co) polymer (A) is 1.6 or less, and when the (co) polymer has the same Mw and the same SP value, preferably from the viewpoint of the HTHS viscosity in the effective temperature range, It is 1.5 or less, More preferably, it is 1.4 or less, More preferably, it is 1.3 or less.

  The (co) polymer (A) in the present invention has a monomer (b) represented by the following general formula (2) and a linear alkyl group having 1 to 4 carbon atoms in addition to the monomer (a). From (meth) acrylic acid alkyl ester (c), (meth) acrylic acid alkyl ester (d) having a linear alkyl group having 12 to 36 carbon atoms and monomer (e) represented by general formula (3) From the viewpoint of the HTHS viscosity at the effective temperature, a copolymer that is a constituent monomer containing at least one monomer selected from the group consisting of

［Ｒ^３は水素原子又はメチル基；−Ｘ^２−は−Ｏ−又は−ＮＨ−で表される基；Ｒ^４は炭素数２〜４の直鎖又は分岐アルキレン基；Ｒ^５及びＲ^６はそれぞれ独立に炭素数８〜２４の直鎖アルキル基；ｑは０〜２０の整数であり、ｑが２以上の場合のＲ^４は同一でも異なっていてもよく、（Ｒ^４Ｏ）_ｑ部分はランダム結合でもブロック結合でもよい。］

[R ³ is a hydrogen atom or a methyl group; —X ² — is a group represented by —O— or —NH—; R ⁴ is a linear or branched alkylene group having 2 to ⁴ carbon atoms; R ⁵ and R ⁶ are Each independently a linear alkyl group having 8 to 24 carbon atoms; q is an integer of 0 to 20, and R ⁴ in the case where q is 2 or more may be the same or different, and the (R ⁴ O) _q moiety is Random coupling or block coupling may be used. ]

R ³ 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 < ² >-in General formula (2) is group represented by -O- or -NH-. Among these, the group represented by —O— is preferable from the viewpoint of the effect of improving the viscosity index.

R ⁴ 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, more preferably an integer of 0 to 2, from the viewpoint of the effect of improving the viscosity index.
When q is 2 or more, R ⁴ may be the same or different, and the (R ⁴ O) _q moiety may be a random bond or a block bond.

R ⁵ and R ⁶ in the general formula (2) are each independently a linear alkyl group having 8 to 24 carbon atoms. Specifically, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group, n-hexadecyl group, n-octadecyl group, n-eicosyl group and Examples include an n-tetracosyl group.
Of the linear alkyl groups having 8 to 24 carbon atoms, a linear alkyl group having 8 to 20 carbon atoms is more preferable from the viewpoint of viscosity index, and a linear alkyl group having 8 to 16 carbon atoms is more preferable.

Specific examples of the monomer (b) include 2-octyldecyl (meth) acrylate, an ester of ethylene glycol mono-2-octylpentadecyl ether and (meth) acrylic acid, and 2-octyl (meth) acrylate. Dodecyl, (meth) acrylic acid 2-decyltetradecyl, (meth) acrylic acid 2-dodecyl hexadecyl, (meth) acrylic acid 2-tetradecyl octadecyl, (meth) acrylic acid 2-dodecyl pentadecyl, (meth) acrylic 2-tetradecylheptadecyl acid, 2-hexadecylheptadecyl (meth) acrylate, 2-heptadecylicosyl (meth) acrylate, 2-hexadecyldocosyl (meth) acrylate, (meth) acrylic acid 2 -Eicosyl docosyl and (meth) acrylic acid 2-eicosyl tetracosyl etc. are mentioned.
Among the monomers (b), a (meth) acrylic acid alkyl ester having a branched alkyl group having 18 to 36 carbon atoms is preferred from the viewpoint of the viscosity index, and a branched one having 18 to 32 carbon atoms is more preferred. A (meth) acrylic acid alkyl ester having an alkyl group, particularly preferably a (meth) acrylic acid alkyl ester having a branched alkyl group having 18 to 28 carbon atoms.

As the (meth) acrylic acid alkyl ester (c) having an alkyl group having 1 to 4 carbon atoms, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate and butyl (meth) acrylate Etc.
Among (c), preferred are methyl (meth) acrylate and butyl (meth) acrylate, and particularly preferred is butyl (meth) acrylate.

As the (meth) acrylic acid alkyl ester (d) having a linear alkyl group having 12 to 36 carbon atoms, (meth) acrylic acid n-dodecyl, (meth) acrylic acid n-tridecyl, (meth) acrylic acid n- Tetradecyl, n-pentadecyl (meth) acrylate, n-hexadecyl (meth) acrylate, n-octadecyl (meth) acrylate, n-icosyl (meth) acrylate, n-tetracosyl (meth) acrylate, (meth) Examples include n-triacontyl acrylate and n-hexatriacontyl (meth) acrylate.
Of these, (d) is preferably a (meth) acrylic acid alkyl ester having a linear alkyl group having 12 to 32 carbon atoms, and more preferably (meth) having a linear alkyl group having 12 to 28 carbon atoms. Acrylic acid esters, particularly preferred are (meth) acrylic acid esters having a linear alkyl group having 12 to 22 carbon atoms.

［Ｒ^７は水素原子又はメチル基；−Ｘ^３−は−Ｏ−又は−ＮＨ−で表される基；Ｒ^８は炭素数２〜４の直鎖又は分岐アルキレン基；Ｒ^９は炭素数１〜８の直鎖アルキル基；ｒは１〜２０の整数であり、ｒが２以上の場合のＲ^８は同一でも異なっていてもよく、（Ｒ^８Ｏ）_ｒ部分はランダム結合でもブロック結合でもよい。］

[R ⁷ is a hydrogen atom or a methyl group; —X ³ — is a group represented by —O— or —NH—; R ⁸ is a linear or branched alkylene group having 2 to 4 carbon atoms; R ⁹ is a carbon number 1 A linear alkyl group of ˜8; r is an integer of 1-20, and when r is 2 or more, R ⁸ may be the same or different, and (R ⁸ O) _r moiety may be a random bond or a block bond Good. ]

R ⁷ in the general formula (3) is a hydrogen atom or a methyl group. Among these, a methyl group is preferable from the viewpoint of improving the viscosity index.

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

R ⁸ in the general formula (3) is a linear or branched alkylene group having 2 to 4 carbon atoms. Examples of the linear or branched 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.

In general formula (3), r is an integer of 1 to 20, preferably an integer of 1 to 5, more preferably an integer of 1 to 2, from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity.
A in the case where r is 2 or more may be the same or different, and the (R ⁸ O) _r portion may be a random bond or a block bond.

R ⁹ in the general formula (3) is a linear alkyl group having 1 to 8 carbon atoms. Specific examples include a methyl group, an ethyl group, n-propyl, n-butyl group, n-heptyl group, n-hexyl group, n-pentyl group and n-octyl group.
Of the linear alkyl groups having 1 to 8 carbon atoms, the linear alkyl group having 1 to 6 carbon atoms is preferable from the viewpoint of the viscosity index, and the linear alkyl group having 1 to 5 carbon atoms is particularly preferable. Preferred is a linear alkyl group having 1 to 4 carbon atoms, and most preferred is a linear alkyl group having 2 to 4 carbon atoms.

Specific examples of the monomer (e) include methoxypropyl (meth) acrylate, methoxybutyl (meth) acrylate, methoxyheptyl (meth) acrylate, methoxyhexyl (meth) acrylate, methoxypentyl (meth) acrylate, methoxyoctyl ( (Meth) acrylate, ethoxyethyl (meth) acrylate, ethoxypropyl (meth) acrylate, ethoxybutyl (meth) acrylate, ethoxyheptyl (meth) acrylate, ethoxyhexyl (meth) acrylate, ethoxypentyl (meth) acrylate, ethoxyoctyl (meth) ) Acrylate, proxymethyl (meth) acrylate, proxyethyl (meth) acrylate, proxypropyl (meth) acrylate, proxybutyl (meth) acrylate, Xyheptyl (meth) acrylate, proxyhexyl (meth) acrylate, proxypentyl (meth) acrylate, proxyoctyl (meth) acrylate, butoxymethyl (meth) acrylate, butoxyethyl (meth) acrylate, butoxypropyl (meth) acrylate, butoxybutyl (Meth) acrylate, butoxyheptyl (meth) acrylate, butoxyhexyl (meth) acrylate, butoxypentyl (meth) acrylate, butoxyoctyl (meth) acrylate, and an alkylene oxide having 2 to 4 carbon atoms in an alcohol having 1 to 8 carbon atoms Examples include (meth) acrylic acid esters of (meth) acrylic acid with addition of 2 to 20 mol of (ethylene oxide, propylene oxide, and butylene oxide). .
Among the monomers (e), ethoxyethyl (meth) acrylate and butoxyethyl (meth) acrylate are preferable from the viewpoint of the viscosity index.

In the present invention, the (co) polymer (A) contains, in addition to the monomers (a) to (e), a nitrogen atom-containing monomer (excluding (a), (b) and (e)) (f ), A hydroxyl group-containing monomer (g), and a phosphorus atom-containing monomer (h). It is preferable from the viewpoint of viscosity.
As the nitrogen atom-containing monomer (excluding (a), (b) and (e)) (f), the following monomers (f1) to (f4) may be mentioned.

Amide group-containing monomer (f1):
(Meth) acrylamide, monoalkyl (meth) acrylamide [one having an alkyl group having 1 to 4 carbon atoms bonded to a nitrogen atom; for example, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (Meth) acrylamide and Nn- or isobutyl (meth) acrylamide etc.], N- (N′-monoalkylaminoalkyl) (meth) acrylamide [one alkyl group having 1 to 4 carbon atoms bound to the nitrogen atom. Those having an aminoalkyl group (2 to 6 carbon atoms); for example, N- (N′-methylaminoethyl) (meth) acrylamide, N- (N′-ethylaminoethyl) (meth) acrylamide, N- (N ′ -Isopropylamino-n-butyl) (meth) acrylamide and N- (N'-n- or isobutylamino-n-butyl) ) (Meth) acrylamide etc.], dialkyl (meth) acrylamide [nitrogen atom having two C1-C4 alkyl groups bonded; for example, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meta ) Acrylamide, N, N-diisopropyl (meth) acrylamide and N, N-di-n-butyl (meth) acrylamide etc.], N- (N ′, N′-dialkylaminoalkyl) (meth) acrylamide [aminoalkyl group Having an aminoalkyl group (2 to 6 carbon atoms) in which two alkyl groups having 1 to 4 carbon atoms are bonded to the nitrogen atom of, for example, N- (N ′, N′-dimethylaminoethyl) (meth) acrylamide, N- (N ′, N′-diethylaminoethyl) (meth) acrylamide, N- (N ′, N′-dimethylaminopropyl) (meth) acrylic And N- (N ′, N′-di-n-butylaminobutyl) (meth) acrylamide etc.]; N-vinylcarboxylic acid amide [N-vinylformamide, N-vinylacetamide, N-vinyl-n- or Isopropionic acid amide, N-vinylhydroxyacetamide and the like] and the like.

Nitro group-containing monomer (f2):
4-nitrostyrene etc. are mentioned.

Monomer having a primary to tertiary amino group (f3):
Primary amino group-containing monomer {C3-C6 alkenylamine [(meth) allylamine, crotylamine, etc.], Aminoalkyl (C2-C6) (meth) acrylate [Aminoethyl (meth) acrylate, etc.}} Secondary amino group-containing monomer {monoalkylaminoalkyl (meth) acrylate [having an aminoalkyl group (2 to 6 carbon atoms) in which one alkyl group having 1 to 6 carbon atoms is bonded to a nitrogen atom; Nt-butylaminoethyl (meth) acrylate and N-methylaminoethyl (meth) acrylate, etc.], C6-C12 dialkenylamine [di (meth) allylamine, etc.]}; tertiary amino group-containing single amount Body {dialkylaminoalkyl (meth) acrylate [an aminoalkyl group in which two alkyl groups having 1 to 6 carbon atoms are bonded to a nitrogen atom (carbon Having 2 to 6); for example, N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate, etc.], alicyclic (meth) acrylate having a nitrogen atom [morpholinoethyl ( Meth) acrylates, etc.], aromatic monomers [N- (N ′, N′-diphenylaminoethyl) (meth) acrylamide, N, N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N -Vinyl pyrrole, N-vinyl pyrrolidone, N-vinyl thiopyrrolidone, etc.]} and their hydrochlorides, sulfates, phosphates or lower alkyl (C1-8) monocarboxylic acids (such as acetic acid and propionic acid) Examples include salts.

Nitrile group-containing monomer (f4):
Examples include (meth) acrylonitrile.

  Among (f), (f1) and (f3) are preferable, and N- (N ′, N′-diphenylaminoethyl) (meth) acrylamide, N- (N ′, N ′) are more preferable. -Dimethylaminoethyl) (meth) acrylamide, N- (N ', N'-diethylaminoethyl) (meth) acrylamide, N- (N', N'-dimethylaminopropyl) (meth) acrylamide, N, N-dimethyl Aminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate.

Hydroxyl-containing monomer (g):
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 bis-hydroxyalkyl (C1-C4) substituted (meth) acrylamide [N, N-bis (hydroxymethyl) (meth) acrylamide, N, N-bis (hydroxypropyl) (meth) acrylamide N, N-bis (2-hydroxybutyl) (meth) acrylamide etc.], vinyl alcohol, alkenol having 3 to 12 carbon atoms [(meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol and 1 -Undecenol and the like], an alkene monool having 4 to 12 carbon atoms, or Lucenediol [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)], 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 phosphorus atom-containing monomer (h) include the following monomers (h1) to (h2).

Phosphate group-containing monomer (h1):
(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 (h2):
(Meth) acryloyloxyalkyl (2 to 4 carbon atoms) phosphonic acid [(meth) acryloyloxyethyl phosphonic acid etc.] and alkenyl (2 to 12 carbon atoms) phosphonic acid [vinyl phosphonic acid, allyl phosphonic acid and octenyl Phosphonic acid, etc.].

  Among (h), (h1) is preferable, (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 (h), (A) is a copolymer having a monomer (i) having two or more unsaturated groups as a constituent monomer. From the viewpoint of HTHS viscosity in the region.

  Examples of the monomer (i) 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 and a glycol having an Mn of 500 or more and an ester of an unsaturated alcohol and a carboxylic acid described in International Publication WO01 / 009242.

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

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

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

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

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

Unsaturated polycarboxylic acid ester (p):
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 50% by weight, more preferably 5 to 40% by weight based on the weight of (A) from the viewpoint of the HTHS viscosity in the effective temperature range. %, Particularly preferably 8 to 40% by weight, most preferably 10 to 30% by weight.
The proportion of (b) constituting (A) is preferably 0 to 40% by weight based on the weight of (A) from the viewpoint of the HTHS viscosity in the effective temperature range and the low temperature viscosity of the lubricating oil composition. More preferably, it is 1 to 30% by weight, particularly preferably 1 to 25% by weight.
The proportion of (c) constituting (A) is preferably 1 to 80% by weight, more preferably 20 to 70% by weight, based on the weight of (A), from the viewpoint of HTHS viscosity in the effective temperature range. Particularly preferred is 30 to 65% by weight.
The proportion of (d) constituting (A) is preferably 1 to 40% by weight, more preferably 1 to 35% by weight based on the weight of (A) from the viewpoint of the HTHS viscosity in the effective temperature range. %, Particularly preferably 2 to 30% by weight.
The proportion of (e) constituting (A) is preferably 0 to 80% by weight, more preferably 5 to 60% by weight, based on the weight of (A), from the viewpoint of the HTHS viscosity in the effective temperature range. %, Particularly preferably 10 to 35% by weight, most preferably 10 to 30% by weight.
Each ratio of (f) to (h) constituting (A) is preferably 0 to 0 based on the weight of (A) from the viewpoint of the HTHS viscosity in the effective temperature range and the low temperature viscosity of the lubricating oil composition. It is 15% by weight, more preferably 1 to 12% by weight, and particularly preferably 2 to 10% by weight.
The proportion of (i) constituting (A) is preferably from 0.01 to 200 ppm, more preferably from 0.05 to 200 ppm, based on the weight of (A), from the viewpoint of the HTHS viscosity in the effective temperature range. 50 ppm, particularly preferably 0.1 to 20 ppm.
The proportions of (j) to (p) constituting (A) are 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, it is 1 to 7% by weight, particularly preferably 2 to 5% by weight.

The (co) polymer (A) preferably has a specific solubility parameter (hereinafter abbreviated as SP value) from the viewpoint of solubility in lubricating oil. The SP value of (A) is 7.3 to 9.5 (cal / cm ³ ) ^1/2 , and is preferably 8.5 to 8.5 from the viewpoint of improving the viscosity index and solubility in the lubricating oil composition. 9.5 (cal / cm ³ ) ^1/2 , more preferably 8.8 to 9.4 (cal / cm ³ ) ^1/2 , and particularly preferably 8.9 to 9.3 (cal / cm ³ ) ^{1 / 2} .
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 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).

Absolute value of the difference between the SP value and the base oil the SP value of (A), from the viewpoint of HTHS viscosity and low temperature viscosity of the effective temperature range, preferably ^{0.5~1.6 (cal / cm 3) 1} / ² , more preferably 0.6 to 1.4 (cal / cm ³ ) ^1/2 , and particularly preferably 0.7 to 1.1 (cal / cm ³ ) ^1/2 .

  Mw of (A) is preferably 5,000 to 2,000,000 from the viewpoint of HTHS viscosity and low temperature viscosity in the effective temperature range, and a more preferable range varies depending on the use of the lubricating oil composition. 1 is the range.

* ：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

  (A) can be obtained by a known atom transfer radical polymerization (ATRP) method, and is described, for example, in WO 05/087819. Specifically, the above-mentioned monomer forms a coordination compound with an atom transfer radical polymerization initiator, a reducing agent, a transition metal catalyst in an inactive state in at least one oxidation state in a solvent and / or base oil. And a method obtained by solution polymerization in the presence of a ligand capable of

  Examples of the solvent include toluene, xylene, alkylbenzene having 9 to 10 carbon atoms, and methyl ethyl ketone.

  The atom transfer radical polymerization initiator that can be used according to the present invention may be any compound having one or more atoms or atomic groups that can be transferred by radicals under polymerization conditions. The atoms or atomic groups that can be transferred by radicals are preferably halogen, more preferably Cl, Br and I. When there are more than two atoms or atomic groups that can be transmitted, star polymers can be obtained.

  Specific examples of the atom transfer radical polymerization initiator include propyl-2-bromopropionate, methyl-2-chloropropionate, ethyl-2-chloropropionate, methyl-2-bromopropionate, ethyl-2 -Bromoisobutyrate, methyl-2-bromoisobutyrate, ethylenebis (2-bromoisobutyrate), 1,1,1-tris (2-bromoisobutyloxymethyl) ethane and the like.

Initiator is generally 10 ^-5 mol / L～3 mol / L range, preferably from 10 ^-4 mol / L～10 range of ² mol / L and particularly preferably 5 - 10 ^-4 mol / • L ^ Used at concentrations in the range of 5 · 10 ⁻³ mol / L, but should not be limited thereby.

  To carry out the polymerization, a reducing agent and a transition metal catalyst that is in an inert state in at least one oxidation state are used. In this case, the reducing agent can reduce the transition metal catalyst in an inactive state in the oxidation state to a lower active oxidation state, and participate in the polymerization method and the transition metal catalyst in a lower active oxidation state. Forms the oxidation product of the reducing agent without The active oxidation state transition metal catalyst reacts with the atom transfer radical polymerization initiator to produce an inactive state transition metal catalyst in which a radical and a halide anion are coordinated. The generated radical may react with the monomer (growth reaction), react with each other (termination reaction), or react with the halide anion (deactivation reaction). The halogen-terminated polymer dormant species can be reactivated by reaction with an active oxidation state transition metal catalyst regenerated with a reducing agent.

In this case, advantageous transition metals include Cu, Fe, Co, Cr, Ne, Sm, Mn, Mo, Ag, Zn, Pd, Pt, Re, Rh, Ir, In, Yd and Ru. These metals can be used alone as well as as a mixture. These metals are envisaged to catalyze the redox cycle of the polymerization, for example the redox couple Cu ⁺ / Cu ²⁺ or Fe ²⁺ / Fe ³⁺ being effective. Correspondingly, the metal compound is added to the reaction mixture as a halide, such as chloride or bromide, or as an alkoxide. Preferred metal compounds are CuBr ₂ , CuCl ₂ , CuO, CrCl ₃ , Fe ₂ O ₃ and FeBr ₃ , and a particularly preferred metal compound is CuBr ₂ .

  The metal content of the transition metal catalyst used as the catalyst is less than 500 ppm, preferably less than 200 ppm, more preferably 100 ppm, based on the total weight of the constituent monomers constituting the (co) polymer (A). Is less than.

The reducing agent is ascorbic acid, ascorbic acid ester, organotin (II) compound, sodium sulfite, low oxidation state sulfur compound, sodium bisulfite, hydrazine hydrate, acetylacetonate, hydroxyacetone, reducing sugar, monosaccharide, Tetrahydrofuran, dihydroanthracene, silane, 2,3-dimethylbutadiene, amine, formamidinesulfinic acid, borane compound, aldehyde, and inorganic salt containing a metal selected from Fe ²⁺ , Cr ³⁺ , Al ³⁺ , Ti ³⁺ and Ti ⁴⁺ An inorganic compound or an organic compound selected from the group consisting of organic tin (II) compounds such as tin 2-ethylhexanoate.

  The polymerization is carried out in the presence of a ligand capable of forming a coordination compound with one or more transition metal catalysts. These ligands are particularly useful for improving the solubility of transition metal compounds. Another important function of the ligand is to avoid the formation of stable organometallic compounds. This is particularly important. This is because these stable compounds do not polymerize at the chosen reaction conditions. Furthermore, it is envisaged that the ligand facilitates the extraction of a transmissible atomic group.

  Known ligands can be used, and are described in, for example, WO97 / 18247 and WO98 / 40415.

  Preferred ligands include in particular triphenylphosphane, 2,2-bipyridine, alkyl-2,2-bipyridine, such as 4,4-di- (5-nonyl) -2,2-bipyridine, 4,4-dipyridine. -(5-heptyl) -2,2-bipyridine, tris (2-aminoethyl) amine (TREN), tris (2-pyridylmethyl) amine (TPMA), N, N, N ', N', N "- Pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine and / or tetramethylethylenediamine, but should not be limited by this, the ligands used alone or as a mixture be able to.

  These ligands can form a coordination compound with the metal compound in the reaction system, or can be first prepared as a coordination compound and subsequently added to the reaction mixture.

  The ratio of ligand to transition metal depends on the number of ligand conformations and the number of transition metal coordination. In general, the molar ratio is in the range from 100: 1 to 0.1: 1, preferably from 6: 1 to 0.1: 1, and particularly preferably from 3: 1 to 0.5: 1. Should not be limited.

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 any of a graft copolymer, a block copolymer, or a star 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 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.

  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.

Kinematic viscosity at 100 ° C. of the base oil (as measured by JIS-K2283) is preferably from the viewpoint of the HTHS viscosity at effective temperature is 1 to 15 mm ² / s, more preferably is 2 to 5 mm ² / s .
The viscosity index (measured according to JIS-K2283) of the base oil is preferably 110 or more from the viewpoint of the HTHS viscosity in the effective temperature range.

  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 reaction vessel equipped with a temperature control device, a vacuum stirring blade, a nitrogen inlet and an outlet, a terminal unsaturated group-containing polybutene (trade name: “NOF Polybutene 10N”, manufactured by NOF Corporation, Mn: 1,000 280 parts by weight, 400 parts by weight of tetrahydrofuran-boron-tetrahydrofuran 1 mol / L solution [manufactured by Wako Pure Chemical Industries, Ltd.] and 400 parts by weight of tetrahydrofuran were added, and hydroboration was performed for 4 hours at 25 ° C. Next, water 50 3 parts by weight, 3N-NaOH aqueous solution 50 parts by volume, 30% by weight hydrogen peroxide 50 parts by volume were oxidized and the supernatant was recovered with a separatory funnel, heated to 50 ° C., and reduced pressure at the same temperature. (0.027 to 0.040 MPa) Tetrahydrofuran was removed over 2 hours to obtain a one-terminal hydroxyl group-containing polymer (Y2-1).

<Production Example 2>
In a pressure-resistant reaction vessel made of SUS equipped with a temperature control device and a stirrer, polyunsene containing terminal unsaturated groups (trade name; “NOF Polybutene 200N”, manufactured by NOF Corporation, Mn: 2,650], 530 parts by weight, and 25 parts by weight of maleic anhydride [manufactured by Wako Pure Chemical Industries, Ltd.] was added, heated to 220 ° C. with stirring, and subjected to an ene reaction for 4 hours at the same temperature, then cooled to 25 ° C. and 2-aminoethanol 20 parts by weight was added, the temperature was raised to 130 ° C. with stirring, and an imidization reaction was carried out for 4 hours at the same temperature, and an unreacted anhydrous maleate under reduced pressure (0.027 to 0.040 MPa) at 120 to 130 ° C. The acid and 2-aminoalcohol were removed over 2 hours to obtain a one-terminal hydroxyl group-containing polymer (Y3-1).

<Examples 1-4, Comparative Example 1>
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) 500 parts by weight, 500 parts by weight of the monomer composition described in Table 2, 0.03 part by weight of CuBr ₂ and 0.04 part by weight of tris (2-pyridylmethyl) amine were added. After nitrogen substitution (gas phase oxygen concentration: 100 ppm), the temperature was raised to 70 ° C. with stirring in a sealed state. After the temperature increase, 0.35 g of an atom transfer radical polymerization initiator ethylene bis (2-bromoisobutyrate) and a reducing agent tin 2-ethylhexanoate (Neostan U-28, manufactured by Nitto Kasei) were added. The polymerization reaction was performed for 20 hours. After raising the temperature to 130 ° C., the unreacted monomer is removed under reduced pressure (0.03 MPa) at the same temperature over 2 hours, and the viscosity index containing the copolymers (A1) to (A4) and (H1) Improvement agents (R1) to (R4) and (S1) were obtained. The SP values of the obtained copolymers (A1) to (A4) and (H1) were calculated by the above method, and Mn and Mw 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 5 to 9, Comparative Example 2>
The method of Example 1 was repeated except that 0.19 part by weight of methyl-2-bromoisobutyrate was used instead of 0.35 part by weight of ethylenebis (2-bromoisobutyrate) as an atom transfer radical polymerization initiator. Thus, viscosity index improvers (R5) to (R9) and (S2) containing the copolymers (A5) to (A9) and (H2) were obtained. The SP values of the obtained copolymers (A5) to (A9) and (H2) were calculated by the above method, and Mn and Mw 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 10 to 12, Comparative Example 3>
Except for using 0.56 parts by weight of 1,1,1-tris (2-bromoisobutyloxymethyl) ethane instead of 0.35 parts by weight of ethylenebis (2-bromoisobutyrate) as an atom transfer radical polymerization initiator, In the same manner as in Example 1, viscosity index improvers (R10) to (R12) and (S3) containing the copolymers (A10) to (A12) and (H3) were obtained. The SP values of the obtained copolymers (A10) to (A12) and (H3) were calculated by the above method, and Mn and Mw 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.

<Comparative Examples 4-9>
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) 500 g, 500 parts by weight of the monomer blend described in Table 2, 2.50 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) and 2,2′- 1.50 parts by weight of azobis (2-methylbutyronitrile) was added, and after nitrogen substitution (gas phase oxygen concentration 100 ppm), the temperature was raised to 76 ° C. with stirring in a sealed state, and the same temperature was maintained for 4 hours. A polymerization reaction was performed. After raising the temperature to 130 ° C., the unreacted monomer is removed at the same temperature under reduced pressure (0.03 MPa) over 2 hours, and a viscosity index improver containing copolymers (H4) to (H9) (S4 ) To (S9) were obtained. The SP values of the obtained copolymers (H4) to (H9) were calculated by the above method, and Mn and Mw 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 (R12) and (S1) to (S9) 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 (a) to (h) described in Table 2 are as described below.
(Y1-1): Hydrogenated polybutadiene one-end hydroxyl group-containing polymer (trade name: KrasolHLBH-5000M, manufactured by Cray Valley, 1,2-butylene ratio: 65 mol%, hydroxyl value: 10.4 mgKOH / g, Mn: 6000)
(Y2-1): Hydroboration product of polybutene containing unsaturated group at one end of Production Example 1 (Mn: 1200)
(Y3-1): Maleic anhydride-ene-aminoalcohol adduct of polybutene containing unsaturated group at one end of Production Example 2 (Mn: 2700)
(A1-1): Methacrylate ester of (Y1-1) (a1-2): Methacrylate ester of (Y2-1) (a1-3): Methacrylate ester of (Y3-1) (b -1): 2-n-decyltetradecyl methacrylate (b-2): 2-n-dodecylhexadecyl methacrylate (c-1): methyl methacrylate (c-2): butyl methacrylate (d-1) ): N-dodecyl methacrylate (d-2): n-tetradecyl methacrylate (d-3): n-hexadecyl methacrylate (e-1): ethoxyethyl methacrylate (e-2): butoxyethyl methacrylate ( f-1): N, N-dimethylaminoethyl methacrylate (g-1): hydroxyethyl methacrylate (h-1): methacryloyloxyethyl phosphate

<Examples 13-24, Comparative Examples 10-18>
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 (R12) and (S1) to have an HTHS viscosity at 150 ° C. of 2.60 ± 0.05 (mm ² / s), respectively. (S9) was added to obtain lubricating oil compositions (V1) to (V12) and (W1) to (W9).
The shear stability, HTHS viscosity (100 ° C.), and viscosity index of the lubricating oil compositions (V1) to (V12) and (W1) to (W9) were measured by the following methods. The results are shown in Table 3.

<Measurement method and calculation method of shear stability of lubricating oil composition>
Measured by ASTM D 6278 method and calculated by ASTM D 6022 method.

<Method for Measuring HTHS Viscosity of Lubricating Oil Composition>
The measurement was performed at 100 ° C. by the method of ASTM D 5481.

<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.

  As is clear from the results in Table 3, the lubricating oil compositions (Examples 13 to 24) containing the viscosity index improver of the present invention are excellent in shear stability and have a low HTHS viscosity in the effective temperature range. It can be seen that the viscosity index is high and excellent. On the other hand, it can be seen that the lubricating oil compositions of Comparative Examples 10 to 18 are inferior in at least one of shear stability, HTHS viscosity in the effective temperature range, and viscosity index.

  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 viscosity index improver comprising a (co) polymer (A) having a monomer (a) represented by the following general formula (1) as an essential constituent monomer, wherein the (co) polymer ( A viscosity index improver having a ratio Mw / Mn of A) of weight average molecular weight (Mw) to number average molecular weight (Mn) of 1.6 or less.

[R ¹ is a hydrogen atom or a methyl group; —X ¹ — is a group represented by —O—, —O (AO) _m — or —NH—, and A is a straight chain having 2 to 4 carbon atoms or A branched alkylene group, m is an integer from 1 to 10, and when m is 2 or more, A's may be the same or different, and (AO) _m moiety may be a random bond or a block bond; R ² is isobutylene and / Or a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing 1,2-butylene as an essential constituent monomer; p is a number of 0 or 1; Mn is 1,000 or more] R ² in the general formula (1) is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having isobutylene and / or 1,2-butylene as an essential constituent monomer, and the hydrocarbon polymer 2. The residue according to claim 1, which is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer in which the total ratio of isobutylene and 1,2-butylene is 30 mol% or more based on the total number of constituent monomers. Viscosity index improver.   The viscosity index improvement according to claim 1 or 2, wherein (A) is a (co) polymer containing 1 to 50% by weight of (a) based on the weight of (A) as a constituent monomer. Agent. (A) is a monomer (b) represented by the following general formula (2) as a constituent monomer of (A), and a (meth) acrylic acid alkyl ester having a linear alkyl group having 1 to 4 carbon atoms. (C), 1 type chosen from the group which consists of the monomer (e) represented by the (meth) acrylic-acid alkylester (d) which has a C12-C36 linear alkyl group, and General formula (3) The viscosity index improver according to any one of claims 1 to 3, which is a copolymer containing the above monomer.

[R ³ is a hydrogen atom or a methyl group; —X ² — is a group represented by —O— or —NH—; R ⁴ is a linear or branched alkylene group having 2 to ⁴ carbon atoms; R ⁵ and R ⁶ are Each independently a linear alkyl group having 8 to 24 carbon atoms; q is an integer of 0 to 20, and R ⁴ in the case where q is 2 or more may be the same or different, and the (R ⁴ O) _q moiety is Random coupling or block coupling may be used. ]

[R ⁷ is a hydrogen atom or a methyl group; —X ³ — is a group represented by —O— or —NH—; R ⁸ is a linear or branched alkylene group having 2 to 4 carbon atoms; R ⁹ is a carbon number 1 A linear alkyl group of ˜8; r is an integer of 1-20, and when r is 2 or more, R ⁸ may be the same or different, and (R ⁸ O) _r moiety may be a random bond or a block bond Good. ]   (A) is a nitrogen atom-containing monomer (excluding (a), (b) and (e)) (f), a hydroxyl group-containing monomer (g) and a phosphorus atom-containing monomer (h). The viscosity index improver according to any one of claims 1 to 4, which is a copolymer having one or more monomers selected from the group consisting of constituent monomers as constituent monomers.   The viscosity index improver according to any one of claims 1 to 5, wherein (A) has a weight average molecular weight of 5,000 to 2,000,000.   A lubricating oil composition comprising the viscosity index improver according to any one of claims 1 to 6 and a base oil.   Furthermore, it contains one or more additives selected from the group consisting of detergents, dispersants, antioxidants, oiliness improvers, friction wear modifiers, extreme pressure agents, antifoaming agents, demulsifiers and corrosion inhibitors. The lubricating oil composition according to claim 7. The lubricating oil composition according to claim 7 or 8, 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 110 or more.   The manufacturing method of the viscosity index improver in any one of Claims 1-6 which used the atom transfer radical polymerization (ATRP) method.