JP2023003249A - Viscosity index improver and lubricant composition - Google Patents

Abstract

[Problem] To provide a viscosity index improver having excellent shear stability, low HTHS viscosity in the effective temperature range, and high viscosity index, and a lubricating oil composition containing the same. A copolymer (A) comprising a monomer (a) represented by the general formula (1) and a monomer (b) represented by a specific formula as essential constituent monomers. viscosity index improver. TIFF2023003249000017.tif41134 [R1 is a hydrogen atom or a methyl group; -X1- is a group represented by -O-, -O(AO)m- or -NH-, and A is an alkylene group having 2 to 4 carbon atoms and m is an integer of 0 to 10, and when m is 2 or more, A may be the same or different, the (AO) m portion may be a random bond or a block bond; R2 is an isobutylene group and / or a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having a 1,2-butylene group as an essential structural unit; p is 0 or 1; ] [Selection] None

Description

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

In recent years, in order to reduce CO ₂ emissions and conserve petroleum resources, there has been an increasing demand for fuel-saving automobiles. One way to save fuel is to reduce viscous resistance by lowering the viscosity of engine oil. However, when the viscosity is lowered, problems such as liquid leakage and seizure arise. Also, low-temperature startability is required in cold regions. This problem is stipulated in the US SAE engine oil viscosity standard (SAE J300), and in the 0W-20 grade, 150 ° C. HTHS viscosity (ASTM D4683 or D5481) under high temperature and high shear is Min. . 2.6. In addition, the same grade is stipulated to have a low-temperature viscosity of 60,000 mPa·s or less at −40° C. and no yield stress (ASTM D4684) in order to guarantee startability in cold regions. For fuel saving, there is a demand for an engine oil that satisfies the above standards and has a lower HTHS viscosity in the effective temperature range of 80°C or 100°C, and various viscosity index improvers have been proposed. As such viscosity index improvers, methacrylic acid ester copolymers (Patent Documents 1 to 4), olefin copolymers (Patent Document 5), comb copolymers (Patent Documents 6 to 8), etc. are known. ing.

However, the viscosity index improver described above is still insufficient to reduce the HTHS viscosity at 100° C. when added to an engine oil composition, and there is a problem that the viscosity is easily reduced by shearing.

Japanese Patent No. 2732187 Japanese Patent No. 2754343 Japanese Patent No. 3831203 Japanese Patent No. 3999307 JP 2005-200454 A Japanese Patent No. 3474918 WO 2007/003238 Pamphlet WO 2009/007147 pamphlet

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

［Ｒ^１は水素原子又はメチル基；－Ｘ^１－は－Ｏ－、－Ｏ（ＡＯ）_ｍ－又は－ＮＨ－で表される基であって、Ａは炭素数２～４のアルキレン基であり、ｍは０～１０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はイソブチレン基及び／又は１，２－ブチレン基を必須構成単位とする炭化水素重合体から水素原子を１つ除いた残基；ｐは０又は１の数。］

［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のアルキレン基；Ｒ^５は炭素数３～８の分岐アルキル基；ｑは１～２０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。］ The present inventors arrived at the present invention as a result of earnest studies.
That is, the present invention provides a copolymer ( A) a viscosity index improver comprising: the viscosity index improver, as well as detergents, dispersants, antioxidants, oiliness improvers, friction and wear modifiers, extreme pressure agents, defoamers, demulsifiers and A lubricating oil composition comprising one or more additives selected from the group consisting of corrosion inhibitors.

[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 an alkylene group having 2 to 4 carbon atoms; where m is an integer of 0 to 10, and when m is 2 or more, A may be the same or different; (AO) _m portion may be a random bond or a block bond; R ² is an isobutylene group and/or or a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having a 1,2-butylene group as an essential structural unit; ]

[R ³ is a hydrogen atom or a methyl group; -X ² - is a group represented by -O- or -NH-; R ⁴ is an alkylene group having 2 to 4 carbon atoms; R ⁵ is a branched group having 3 to 8 carbon atoms alkyl group; q is an integer of 1 to 20, R ⁴ when q is 2 or more may be the same or different, and the (R ⁴ O) _q portion may be a random bond or a block bond. ]

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

［Ｒ^１は水素原子又はメチル基；－Ｘ^１－は－Ｏ－、－Ｏ（ＡＯ）_ｍ－又は－ＮＨ－で表される基であって、Ａは炭素数２～４のアルキレン基であり、ｍは０～１０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はイソブチレン基及び／又は１，２－ブチレン基を必須構成単位とする炭化水素重合体から水素原子を１つ除いた残基；ｐは０又は１の数。］

［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のアルキレン基；Ｒ^５は炭素数３～８の分岐アルキル基；ｑは１～２０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。］ The viscosity index improver of the present invention comprises a polyolefin monomer (a) represented by the following general formula (1) and a monomer (b) represented by the following general formula (2) as essential constituent monomers. A viscosity index improver containing a copolymer (A).

[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 an alkylene group having 2 to 4 carbon atoms; where m is an integer of 0 to 10, and when m is 2 or more, A may be the same or different; (AO) _m portion may be a random bond or a block bond; R ² is an isobutylene group and/or or a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having a 1,2-butylene group as an essential structural unit; ]

[R ³ is a hydrogen atom or a methyl group; -X ² - is a group represented by -O- or -NH-; R ⁴ is an alkylene group having 2 to 4 carbon atoms; R ⁵ is a branched group having 3 to 8 carbon atoms alkyl group; q is an integer of 1 to 20, R ⁴ when q is 2 or more may be the same or different, and the (R ⁴ O) _q portion may be a random bond or a block bond. ]

<Copolymer (A)>
The copolymer (A) in the present invention comprises the polyolefin monomer (a) represented by the general formula (1) and the monomer (b) represented by the general formula (2) as essential constituent monomers It is a copolymer with
The polyolefin-based monomer (a) in the present invention is a monomer obtained by modifying a hydrocarbon polymer described later and reacting it with (meth)acrylic acid. In addition, "(meth)acryl" means methacryl or acryl.

R ¹ in general formula (1) is a hydrogen atom or a methyl group. Among these, the methyl group is preferable from the viewpoint of the HTHS viscosity in the effective temperature range.

-X ¹ - in general formula (1) is a group represented by -O-, -O(AO) _m - or -NH-.
A is an alkylene group having 2 to 4 carbon atoms.
The alkylene group having 2 to 4 carbon atoms includes 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 0 to 10, preferably an integer of 0 to 4, more preferably an integer of 0 to 2 from the viewpoint of HTHS viscosity in the effective temperature range.
When m is 2 or more, A may be the same or different, and the (AO) _m portion may be a random bond or a block bond.
Among -X ¹ -, groups represented by -O- and -O(AO) _m - are preferable from the viewpoint of HTHS viscosity in the effective temperature range, and more preferably -O- and -O( It is a group represented by CH ₂ CH ₂ O)—.

p is a number of 0 or 1;

R ² in the general formula (1) is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having an isobutylene group and/or a 1,2-butylene group as an essential structural unit.
Hydrocarbon polymers having isobutylene and/or 1,2-butylene as constituent units include polymers having isobutene, 1-butene and 2-butene as constituent monomers, and 1 obtained by polymerizing 1,3-butadiene. , and a polymer obtained by hydrogenating the terminal double bond of a 2-adduct.
The hydrocarbon polymer may be a block polymer or a random polymer.
The hydrocarbon polymer containing isobutylene and/or 1,2-butylene as an essential structural unit may be a hydrocarbon polymer further containing structural units other than isobutylene and/or 1,2-butylene. Constituent monomers include (1) aliphatic unsaturated hydrocarbons, (2) alicyclic unsaturated hydrocarbons and (3) aromatic group-containing unsaturated hydrocarbons, excluding isobutene, 1-butene and 2-butene. Hydrogen etc. are mentioned. When the hydrocarbon polymer has double bonds, it may be obtained by hydrogenating part or all of the double bonds by hydrogenation.

(1) Aliphatic unsaturated hydrocarbons [olefins having 2 to 36 carbon atoms (e.g., ethylene, propylene, isobutene, 1-butene, 2-butene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, triacocene and hexadecene triacosene, etc.), dienes having 2 to 36 carbon atoms (e.g., 1,2-butadiene, 1,3-butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.)]
(2) alicyclic unsaturated hydrocarbons [e.g. cyclohexene, (di)cyclopentadiene, pinene, limonene, indene, vinylcyclohexene and ethylidenebicycloheptene, etc.]
(3) aromatic group-containing unsaturated hydrocarbons (e.g. styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotyl benzene, vinylnaphthalene, divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene, etc.).
Among these monomers, from the viewpoint of HTHS viscosity and viscosity index, aliphatic unsaturated hydrocarbons are preferable, and olefins having 2 to 36 carbon atoms and dienes having 2 to 36 carbon atoms are more preferable. Olefins having 2 to 16 carbon atoms and dienes having 2 to 10 carbon atoms are preferred, and isobutene, 1-butene, 2-butene and 1,3-butadiene are particularly preferred.

Based on the total number of structural units of the hydrocarbon polymer, the total of isobutylene and/or 1,2-butylene is preferably 30 mol% or more, more preferably 40, from the viewpoint of HTHS viscosity, viscosity index and shear stability. mol % or more, particularly preferably 50 mol % or more, most preferably 60 mol % or more.

Based on the total number of structural units of the hydrocarbon polymer, the total of isobutylene and 1,2-butylene is calculated by analyzing the hydrocarbon polymer by ¹³ C-nuclear magnetic resonance spectroscopy and using the following formula (1). can decide. In the ¹³ C-nuclear magnetic resonance spectrum, the peak derived from the methyl group of isobutylene is the integrated value (integral value A) of 30 to 32 ppm, the branched methylene group of 1,2-butylene (—CH ₂ —CH(CH ₂ CH ₃ )-) appears at the integral value (integral value B) of 26 to 27 ppm. It can be obtained from the integrated value of the above peak and the integrated value (integrated value C) of the total carbon peak of the hydrocarbon polymer.

The monomer (a) represented by the general formula (1) is a hydroxyl group-containing (co)polymer obtained by introducing a hydroxyl group into a hydrocarbon polymer or an amino group-containing (co)polymer obtained by introducing an amino group into a hydrocarbon polymer. It can be obtained by coalescence and an esterification reaction or amidation reaction with (meth)acrylic acid.

Specific examples of hydroxyl group-containing (co)polymers and amino group-containing (co)polymers (Y) include the following hydroxyl group-containing (co)polymers (Y1) to (Y4) and amino group-containing (co)polymers (Y5) can be mentioned.
Alkylene oxide adduct (Y1); the above (1) aliphatic unsaturated hydrocarbon, (2) alicyclic unsaturated hydrocarbon and (3) aromatic group-containing unsaturated hydrocarbon (for example, olefin having 2 to 36 carbon atoms etc.) in the presence of an ionic polymerization catalyst (sodium catalyst, etc.), to which alkylene oxide (ethylene oxide, propylene oxide, etc.) is added.
Hydroboronates (Y2); hydroboration reaction products of hydrocarbon polymers (eg those described in US Pat. No. 4,316,973) and the like.
Maleic anhydride-ene-aminoalcohol adduct (Y3): product obtained by imidizing the reaction product obtained by the ene reaction between a hydrocarbon polymer having a double bond and maleic anhydride with an aminoalcohol, etc. .
Hydroformyl hydride (Y4); a product obtained by hydroformylating a hydrocarbon polymer having a double bond followed by hydrogenation (for example, those described in JP-A-63-175096), and the like.
Maleic anhydride-ene-ethylenediamine adduct (Y5): one obtained by imidizing the reaction product obtained by the ene reaction between a hydrocarbon polymer having a double bond and maleic anhydride with ethylenediamine.
Among (Y), preferred from the viewpoint of HTHS viscosity and viscosity index are (Y1), (Y2) and (Y3), and more preferred is (Y1).

The number average molecular weight of the hydroxyl group-containing (co)polymer and amino group-containing (co)polymer (Y) is preferably 1,000 to 25,000, more preferably 2, from the viewpoint of shear stability and HTHS viscosity. ,000 to 20,000, particularly preferably 3,000 to 15,000, most preferably 4,000 to 10,000.

The crystallization temperature of (Y) is preferably −40° C. or less, more preferably −50° C. or less, particularly preferably −55° C. or less, from the viewpoint of the viscosity index improver and the low-temperature viscosity of the lubricating oil composition. It is preferably -60°C or lower.
The crystallization temperature of (Y) and the copolymer (A) described later can be measured using a differential scanning calorimeter "UNIX (registered trademark) DSC7" (manufactured by PERKIN-ELMER). Y), (A) Crystallization temperature observed when 5 mg of a sample is cooled from 100° C. to −80° C. at an isothermal rate of 10° C./min.

The number average molecular weight (hereinafter abbreviated as Mn) of the polyolefin monomer (a) is preferably 1,000 to 25,000, more preferably 1,500 to 20, from the viewpoint of shear stability and HTHS viscosity. ,000, particularly preferably 2,000 to 15,000, most preferably 2,500 to 10,000.
The Mn of the polyolefin monomer (a) and the weight average molecular weight (hereinafter abbreviated as Mw) of the copolymer (A) described below can be measured by gel permeation chromatography under the following conditions.
<Conditions for measuring Mn of polyolefin monomer (a) and Mw of (A)>
Apparatus: "HLC-802A" [manufactured by Tosoh Corporation]
Column: 2 "TSK gel GMH6" [manufactured by Tosoh Corporation] Measurement temperature: 40 ° C.
Sample solution: 0.5% by weight tetrahydrofuran solution Solution injection volume: 200 μl
Detection device: refractive index detector Reference material: 12 standard polystyrene (TSK standard POLYSTYRENE) (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]

［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のアルキレン基；Ｒ^５は炭素数３～８の分岐アルキル基；ｑは１～２０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。］ The copolymer (A) in the present invention is a copolymer having a monomer (b) represented by the following general formula (2) as a constituent monomer.

[R ³ is a hydrogen atom or a methyl group; -X ² - is a group represented by -O- or -NH-; R ⁴ is an alkylene group having 2 to 4 carbon atoms; R ⁵ is a branched group having 3 to 8 carbon atoms alkyl group; q is an integer of 1 to 20, R ⁴ when q is 2 or more may be the same or different, and the (R ⁴ O) _q portion may be a random bond or a block bond. ]

R ³ in general formula (2) is a hydrogen atom or a methyl group. Among these, the methyl group is preferable from the viewpoint of the viscosity index.

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

R ⁴ in general formula (2) is an alkylene group having 2 to 4 carbon atoms. Examples of alkylene groups having 2 to 4 carbon atoms include ethylene group, isopropylene group, 1,2- or 1,3-propylene group, isobutylene group, and 1,2-, 1,3- or 1,4-butylene group. is mentioned.

q in the general formula (2) 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 viscosity index and low-temperature viscosity.
When q is 2 or more, A may be the same or different, and the (R ⁴ O) _q moiety may be random bond or block bond.

R ⁵ in general formula (2) is a branched alkyl group having 3 to 8 carbon atoms. Specifically, isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, sec-pentyl group, tert-pentyl group, 1-ethylpropyl group, 1,2-dimethylpropyl group, 2, 2-dimethylpropyl group, isohexyl group, sec-hexyl group, tert-hexyl group, 2-methylhexyl group, 1-ethylbutyl group, 2-ethylbutyl group, 1,2-dimethylbutyl group, 1-ethyl-2-methyl propyl group, sec-octyl group and the like.
Among branched alkyl groups having 3 to 8 carbon atoms, from the viewpoint of viscosity index, branched alkyl groups having 3 to 6 carbon atoms are preferable, branched alkyl groups having 3 to 5 carbon atoms are more preferable, and branched alkyl groups having 3 to 5 carbon atoms are further preferable. A branched alkyl group of number 4 (isobutyl group, sec-butyl group, tert-butyl group), particularly preferably sec-butyl group.

Specific examples of the monomer (b) include isopropoxymethyl (meth) acrylate, isopropoxyethyl (meth) acrylate, isopropoxypropyl (meth) acrylate, isopropoxybutyl (meth) acrylate, isopropoxyheptyl (meth) acrylates, isopropoxyhexyl (meth)acrylate, isopropoxypentyl (meth)acrylate, isopropoxyoctyl (meth)acrylate, isobutoxymethyl (meth)acrylate, isobutoxyethyl (meth)acrylate, isobutoxypropyl (meth)acrylate, isobutoxybutyl (meth)acrylate, isobutoxyheptyl (meth)acrylate, isobutoxyhexyl (meth)acrylate, isobutoxypentyl (meth)acrylate, isobutoxyoctyl (meth)acrylate, tert-butoxymethyl (meth)acrylate, tert -butoxyethyl (meth) acrylate, tert-butoxypropyl (meth) acrylate, tert-butoxybutyl (meth) acrylate, tert-butoxyheptyl (meth) acrylate, tert-butoxyhexyl (meth) acrylate, tert-butoxypentyl (meth) ) acrylate, tert-butoxyoctyl (meth)acrylate, sec-butoxymethyl (meth)acrylate, sec-butoxyethyl (meth)acrylate, sec-butoxypropyl (meth)acrylate, sec-butoxybutyl (meth)acrylate, sec- butoxyheptyl (meth)acrylate, sec-butoxyhexyl (meth)acrylate, sec-butoxypentyl (meth)acrylate, sec-butoxyoctyl (meth)acrylate, isopentyloxymethyl (meth)acrylate, isopentyloxyethyl (meth)acrylate Acrylate, isopentyloxypropyl (meth)acrylate, isopentyloxybutyl (meth)acrylate, isopentyloxyheptyl (meth)acrylate, isopentyloxyhexyl (meth)acrylate, isopentyloxypentyl (meth)acrylate, isopentyloxy Octyl (meth)acrylate, tert-pentyloxymethyl (meth)acrylate, tert-pentyloxyethyl (meth)acrylate, tert-pentyloxypropyl (meth)acrylate, tert-pentyl Oxybutyl (meth)acrylate, tert-pentyloxyheptyl (meth)acrylate, tert-pentyloxyhexyl (meth)acrylate, tert-pentyloxypentyl (meth)acrylate, tert-pentyloxyoctyl (meth)acrylate, sec-pentyloxy methyl (meth)acrylate, sec-pentyloxyethyl (meth)acrylate, sec-pentyloxypropyl (meth)acrylate, sec-pentyloxybutyl (meth)acrylate, sec-pentyloxyheptyl (meth)acrylate, sec-pentyloxy Hexyl (meth)acrylate, sec-pentyloxypentyl (meth)acrylate, sec-pentyloxyoctyl (meth)acrylate, sec-hexyloxyethyl (meth)acrylate, sec-octyloxyethyl (meth)acrylate, etc. and 3 carbon atoms 2 to 20 moles of at least one selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide added to an alcohol having 8 to 8 branched alkyl groups, and esters of (meth)acrylic acid.
Among the monomers (b), sec-butoxyethyl (meth)acrylate is preferred from the viewpoint of viscosity index.

The copolymer (A) in the present invention includes, in addition to the monomers (a) and (b), a (meth)acrylic acid alkyl ester (c) having an alkyl group having 1 to 4 carbon atoms and/or 12 carbon atoms. From the viewpoint of the HTHS viscosity at the effective temperature, it is preferable to use a copolymer having the (meth)acrylic acid alkyl ester (d) having a linear alkyl group of up to 36 as a constituent monomer.

Examples of alkyl groups having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group and tert-butyl group.
The (meth)acrylic acid alkyl ester (c) having an alkyl group having 1 to 4 carbon atoms includes methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate and butyl (meth)acrylate. etc.
Among (c), methyl (meth)acrylate and butyl (meth)acrylate are preferable from the viewpoint of HTHS viscosity and viscosity index, and butyl (meth)acrylate is more preferable.

Examples of the (meth)acrylic acid alkyl ester (d) having a linear alkyl group having 12 to 36 carbon atoms include n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, and n-(meth)acrylate. Tetradecyl, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, n-icosyl (meth)acrylate, n-tetracosyl (meth)acrylate, (meth)acrylate Examples include n-triacontyl acrylate and n-hexatriacontyl (meth)acrylate.
Among (d), from the viewpoint of HTHS viscosity and viscosity index, preferred are (meth)acrylic acid alkyl esters having a straight-chain alkyl group with 12 to 32 carbon atoms, and more preferred are straight-chain alkyl esters with 12 to 28 carbon atoms. A (meth)acrylic acid ester having a chain alkyl group, particularly preferably a (meth)acrylic acid ester having a linear alkyl group having 12 to 22 carbon atoms.

The copolymer (A) in the present invention can use a monomer (e) represented by the following general formula (3) as a constituent monomer.

［Ｒ^６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^７は炭素数２～４のアルキレン基；Ｒ^８、Ｒ^９はそれぞれ独立に炭素数４～２４の直鎖アルキル基；ｒは０～２０の整数であり、ｒが２以上の場合のＲ^７は同一でも異なっていてもよく、（Ｒ^７Ｏ）_ｒ部分はランダム結合でもブロック結合でもよい。］

[R ⁶ is a hydrogen atom or a methyl group; -X ³ - is a group represented by -O- or -NH-; R ⁷ is an alkylene group having ² to ⁴ carbon atoms; a linear alkyl group having a number of 4 to 24; r is an integer of 0 to 20, and when _r is ² or more, R ⁷ may be the same or different; May be combined. ]

R6 in general formula ( ³ ) is a hydrogen atom or a methyl group. Among these, the methyl group is preferable from the viewpoint of the viscosity index.

—X ³ — in 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 viscosity index.

R ⁷ in general formula (3) is an alkylene group having 2 to 4 carbon atoms. Examples of alkylene groups having 2 to 4 carbon atoms include ethylene group, isopropylene group, 1,2- or 1,3-propylene group, isobutylene group, and 1,2-, 1,3- or 1,4-butylene group. is mentioned.

r in the general formula (3) is an integer of 0 to 20, preferably an integer of 0 to 5, more preferably an integer of 0 to 2, from the viewpoint of viscosity index.
R ⁷ when r is 2 or more may be the same or different, and the (R ⁷ O) _r moiety may be a random bond or a block bond.

R ⁸ and R ⁹ in general formula (3) are each independently a linear alkyl group having 4 to 24 carbon atoms. Specifically, n-butyl group, n-heptyl group, n-hexyl group, n-pentyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, Examples include n-tetradecyl group, n-hexadecyl group, n-octadecyl group, n-eicosyl group and n-tetracosyl group.
Among straight or branched alkyl groups having 4 to 24 carbon atoms, straight chain alkyl groups having 6 to 24 carbon atoms are preferable from the viewpoint of viscosity index, and straight or branched alkyl groups having 6 to 20 carbon atoms are more preferable. A branched alkyl group, particularly preferably a straight-chain or branched alkyl group having 8 to 16 carbon atoms.

Specific examples of the monomer (e) include 2-octyldecyl (meth)acrylate, an ester of ethylene glycol mono-2-octylpentadecyl ether and (meth)acrylic acid, and 2-octyl (meth)acrylate. dodecyl, 2-n-decyltetradecyl (meth)acrylate, 2-n-dodecylhexadecyl (meth)acrylate, 2-tetradecyloctadecyl (meth)acrylate, 2-dodecylpentadecyl (meth)acrylate, 2-tetradecylheptadecyl (meth) acrylate, 2-hexadecylheptadecyl (meth) acrylate, 2-heptadecyl icosyl (meth) acrylate, 2-hexadecyl docosyl (meth) acrylate, (meth) ) 2-eicosyldocosyl acrylate, 2-tetracosylhexacosyl (meth)acrylate and N-2-octyldecyl (meth)acrylamide.
Of the monomers (e), preferred from the viewpoint of viscosity index are (meth)acrylic acid alkyl esters having a branched alkyl group and having a carbon number of 12 to 36, and more preferably having a branched alkyl group and having a carbon number (Meth)acrylic acid alkyl esters having 14 to 32 carbon atoms, particularly preferred are (meth)acrylic acid alkyl esters having a branched alkyl group and having 16 to 28 carbon atoms.

The above-mentioned monomers (b) to (e) are monomers obtained by reacting the terminal hydroxy group or amino group of the hydrocarbon group-containing compound with (meth)acrylic acid, but the hydrocarbon polymer Since it is not modified, it does not correspond to polyolefin monomers. In (b), alcohol having a branched alkyl group having 3 to 8 carbon atoms is added with 2 to 20 moles of at least one selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide, and in (e), carbon The addition of 1 to 20 moles of at least one selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide to an alcohol having 10 to 50 branched alkyl groups is not a modified hydrocarbon polymer. , does not correspond to polyolefin monomers.

The copolymer (A) in the present invention comprises one or more selected from the group consisting of a nitrogen atom-containing monomer (f), a hydroxyl group-containing monomer (g) and a phosphorus atom-containing monomer (h). From the viewpoint of HTHS viscosity in the effective temperature range, it is preferable to use a copolymer as a monomer.
Examples of the nitrogen atom-containing monomer (f) include monomers (f1) to (f4) below, excluding monomers (a), (b) and (e).

Amido group-containing monomer (f1):
(Meth)acrylamide, monoalkyl (meth)acrylamide [one alkyl group having 1 to 4 carbon atoms bonded to the 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 is attached 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], dialkyl(meth)acrylamide [nitrogen atom has 1 to 4 carbon atoms two alkyl groups of; (Meth)acrylamide, etc.], N-(N',N'-dialkylaminoalkyl)(meth)acrylamide [aminoalkyl group in which two alkyl groups having 1 to 4 carbon atoms are bonded to the nitrogen atom of an aminoalkyl group (carbon numbers 2 to 6); for example, N-(N',N'-dimethylaminoethyl) (meth)acrylamide, N-(N',N'-diethylaminoethyl)(meth)acrylamide, N-(N' , N'-dimethylaminopropyl) (meth)acrylamide and N-(N',N'-di-n-butylaminobutyl) (meth)acrylamide, etc.]; N-vinylcarboxylic acid amide [N-vinylformamide, N -vinylacetamide, N-vinyl-n- or isopropionic acid amide and N-vinylhydroxyacetamide, etc.] and the like.

Nitro group-containing monomer (f2):
4-nitrostyrene and the like.

Primary to tertiary amino group-containing monomer (f3):
Primary amino group-containing monomers {alkenylamines having 3 to 6 carbon atoms [(meth)allylamine, crotylamine, etc.], aminoalkyl (carbon atoms 2 to 6) (meth)acrylates [aminoethyl (meth)acrylate, etc.]} ; Secondary amino group-containing monomer {monoalkylaminoalkyl (meth)acrylate [having an aminoalkyl group (2 to 6 carbon atoms) in which one alkyl group having 1 to 6 carbon atoms is bonded to a nitrogen atom; Nt-butylaminoethyl (meth)acrylate and N-methylaminoethyl (meth)acrylate, etc.], dialkenylamine having 6 to 12 carbon atoms [di(meth)allylamine, etc.]}; tertiary amino group-containing monomer body {dialkylaminoalkyl (meth)acrylate [those having an aminoalkyl group (2 to 6 carbon atoms) in which two alkyl groups having 1 to 6 carbon atoms are bonded to a nitrogen atom; ) acrylates and N,N-diethylaminoethyl (meth)acrylate, etc.], alicyclic (meth)acrylates having a nitrogen atom [morpholinoethyl (meth)acrylate, etc.], aromatic monomers [N-(N', N′-diphenylaminoethyl)(meth)acrylamide, N,N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone and N-vinylthiopyrrolidone, etc.]}, and Hydrochlorides, sulfates, phosphates, or lower alkyl (C1-8) monocarboxylic acid (acetic acid, propionic acid, etc.) salts thereof are included.

Nitrile group-containing monomer (f4):
(Meth)acrylonitrile and the like.

Among (f), preferred from the viewpoint of sludge dispersibility are (f1) and (f3), and more preferred are N-(N',N'-diphenylaminoethyl) (meth)acrylamide, N- (N',N'-dimethylaminoethyl)(meth)acrylamide, N-(N',N'-diethylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminopropyl)(meth)acrylamide , N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate.

Hydroxyl group-containing monomer (g):
Hydroxyl group-containing aromatic monomer (p-hydroxystyrene, etc.), hydroxyalkyl (C2-C6) (meth)acrylate [2-hydroxyethyl (meth)acrylate, and 2- or 3-hydroxypropyl (meth)acrylate etc.], mono- or bis-hydroxyalkyl (1 to 4 carbon atoms) substituted (meth)acrylamide [N,N-bis(hydroxymethyl)(meth)acrylamide, N,N-bis(hydroxypropyl)(meth)acrylamide , N,N-bis(2-hydroxybutyl) (meth)acrylamide, etc.], vinyl alcohol, alkenols having 3 to 12 carbon atoms [(meth)allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol and 1 -undecenol, etc.], alkene monools or alkenediols having 4 to 12 carbon atoms [1-butene-3-ol, 2-buten-1-ol and 2-butene-1,4-diol, etc.], hydroxyalkyls (carbon Numbers 1-6) Alkenyl (C 3-10) ethers (2-hydroxyethyl propenyl ether, etc.), polyhydric (tri- to octahydric) alcohols (glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, sugars and sucrose, etc.) ) alkenyl (3 to 10 carbon atoms) ether or (meth) acrylate [sucrose (meth) allyl ether, etc.], etc.;
Polyoxyalkylene glycol (alkylene group having 2 to 4 carbon atoms, degree of polymerization 2 to 50), polyoxyalkylene polyol [polyoxyalkylene ether of the above tri- to octahydric alcohol (alkylene group having 2 to 4 carbon atoms, degree of polymerization 2 to 100)], mono (meth) acrylate of polyoxyalkylene glycol or alkyl (carbon number 1 to 4) ether of polyoxyalkylene polyol [polyethylene glycol (Mn: 100 to 300) mono (meth) acrylate, polypropylene glycol ( Mn: 130-500) mono(meth)acrylate, methoxypolyethylene glycol (Mn: 110-310) (meth)acrylate, lauryl alcohol ethylene oxide adduct (2-30 mol) (meth)acrylate and mono(meth)acrylic acid polyoxyethylene (Mn: 150 to 230) sorbitan, etc.] and the like;

Examples of the phosphorus atom-containing monomer (h) include the following monomers (h1) to (h2).

Phosphate ester group-containing monomer (h1):
(Meth)acryloyloxy alkyl (C2-4) phosphate [(meth)acryloyloxyethyl phosphate and (meth)acryloyloxyisopropyl phosphate] and alkenyl phosphate [vinyl phosphate, allyl phosphate, propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, dodecenyl phosphate, etc.] and the like. In addition, "(meth)acryloyloxy" means acryloyloxy or methacryloyloxy.

Phosphono group-containing monomer (h2):
(Meth) acryloyloxy alkyl (2-4 carbon atoms) phosphonic acid [(meth) acryloyloxyethyl phosphonic acid, etc.] and alkenyl (2-12 carbon atoms) phosphonic acid [vinyl phosphonic acid, allyl phosphonic acid and octenyl phosphonic acid, etc.] and the like.

Among (h), (h1) is preferable from the viewpoint of the coefficient of friction with the metal surface, and (meth)acryloyloxyalkyl (having 2 to 4 carbon atoms) phosphate esters are more preferable, and particularly preferable. is (meth)acryloyloxyethyl phosphate.

(A) is, in addition to the monomers (a) to (h), a copolymer whose constituent monomers are a monomer (i) having two or more unsaturated groups; It is preferable from the viewpoint of HTHS viscosity in the range.

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 esters of glycols and unsaturated carboxylic acids having an Mn of 500 or more, and esters of unsaturated alcohols and carboxylic acids, which are described in International Publication WO01/009242.

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

Aliphatic hydrocarbon monomer (j):
Examples thereof include alkenes having 2 to 20 carbon atoms (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.).

Alicyclic hydrocarbon-based monomer (k):
cyclopentene, cyclohexene, cycloheptene, cyclooctene, pinene and the like.

Aromatic hydrocarbon-based monomer (l):
Styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4-chloro Thylbenzene, indene, 2-vinylnaphthalene, and the like.

Vinyl esters, vinyl ethers, vinyl ketones (m):
Vinyl esters of saturated fatty acids with 2 to 12 carbon atoms (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl octanoate, etc.), alkyl, aryl or alkoxyalkyl vinyl ethers with 1 to 12 carbon atoms (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether) , butyl vinyl ether, 2-ethylhexyl vinyl ether, phenyl vinyl ether, vinyl-2-methoxyethyl ether and vinyl-2-butoxyethyl ether) 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):
glycidyl (meth)acrylate, glycidyl (meth)allyl ether, and the like.

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

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

The ratio 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 HTHS viscosity in the effective temperature range. %, particularly preferably 8-40% by weight, most preferably 10-30% by weight.
The ratio of (b) constituting (A) is preferably 1 to 80% by weight, more preferably 1 to 60% by weight, based on the weight of (A), from the viewpoint of HTHS viscosity in the effective temperature range. %, particularly preferably 10-35% by weight, most preferably 10-30% by weight.
The total ratio of (a) and (b) constituting (A) is preferably 10% by weight or more based on the weight of (A) from the viewpoint of the HTHS viscosity in the effective temperature range, and further Preferably 15 to 90% by weight, particularly preferably 20 to 80% by weight, most preferably 20 to 50% by weight.
The ratio 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 preferably 30 to 65% by weight.
The ratio 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 HTHS viscosity in the effective temperature range. %, particularly preferably 2 to 30% by weight.
The ratio of (e) constituting (A) is preferably 0 to 40% by weight, more preferably 1, based on the weight of (A), from the viewpoint of HTHS viscosity and low-temperature viscosity in the effective temperature range. to 30% by weight, particularly preferably 1 to 25% by weight.
The ratio of each of (f) to (h) constituting (A) is preferably 0 to 15% by weight based on the weight of (A) from the viewpoint of HTHS viscosity and low temperature viscosity in the effective temperature range. , more preferably 1 to 12% by weight, particularly preferably 2 to 10% by weight.
The ratio of (i) constituting (A) is preferably 0.01 to 200 ppm, more preferably 0.05 to 200 ppm, based on the weight of (A), from the viewpoint of HTHS viscosity in the effective temperature range. 50 ppm, particularly preferably 0.1 to 20 ppm.
The ratio of each of (j) to (p) constituting (A) is preferably 0 to 10% by weight, more preferably 1, based on the weight of (A), from the viewpoint of viscosity index and low-temperature viscosity. to 7% by weight, particularly preferably 2 to 5% by weight.

The solubility parameter (hereinafter abbreviated as SP value) of (A) is preferably 9.1 to 10.3 (cal/cm ³ ) ^1/2 from the viewpoint of viscosity index and solubility in base oil. more preferably 9.1 to 9.7 (cal/cm ³ ) ^1/2 , particularly preferably 9.1 to 9.5 (cal/cm ³ ) ^1/2 , most preferably 9.1 to 9 .3 (cal/cm ³ ) ^1/2 .
The SP values of (A) and the base oil described later are described on page 152 (Table.5) of the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2 P. 147-154). (heat of vaporization and molar volume of an atom or functional group at 25° C.) are calculated by the formula (28) (page 153).
The SP value of (A) is calculated by the method described above for each structural unit (a structure in which a carbon-carbon double bond reacts to form a single bond) derived from a monomer that constitutes (A). and the SP value of each structural unit is arithmetically averaged based on the weight fraction of the structural monomer unit. Specifically, the SP value of a structural unit derived from a monomer is determined from the values of _Δei and _vi described in Table 1 below, which are parameters of the Fedors method, depending on the types of atoms and atomic groups in the molecular structure. It can be calculated by applying the following formula using the corresponding numerical values.
SP value = (ΣΔe _i /Σv _i ) ^1/2

原子団として、ＣＨ_３が２個、ＣＨ_２が１個、Ｃが１個、ＣＯ_２が１個なので、下記数式により、メタクリル酸メチルに由来する構成単位のＳＰ値は９．９３（ｃａｌ／ｃｍ^３）^１／２であることが分かる。
ΣΔｅ_ｉ＝１１２５×２＋１１８０＋３５０＋４３００＝８０８０
Σｖ_ｉ＝３３．５×２＋１６．１－１９．２＋１８．０＝８１．９
δ＝（８０８０／８１．９）^１／２＝９．９３（ｃａｌ／ｃｍ^３）^１／２ For example, when the monomer is methyl methacrylate, the structural unit is represented by the following chemical formula.

As atomic groups, there are two _CH3 , one _CH2 , one C, and one _CO2 . Therefore, according to the following formula, the SP value of the structural unit derived from methyl methacrylate is 9.93 (cal/ cm ³ ) ^1/2 .
ΣΔe _i =1125×2+1180+350+4300=8080
Σv _i =33.5×2+16.1−19.2+18.0=81.9
δ=(8080/81.9) ^1/2 =9.93 (cal/cm ³ ) ^1/2

The SP value of (A) can be calculated by arithmetically averaging the SP values of the structural units derived from the monomers used and the weight ratio of the monomers based on the weight fractions. Moreover, the SP value of (A) can be adjusted by appropriately adjusting the amount of the monomer used. Specifically, the SP value tends to decrease if a large number of alkyl groups with a large number of carbon atoms or an alkyl group with a large degree of branching is used, and the SP value tends to decrease if a large amount of polar groups (ether groups, etc.) are used. tends to increase.

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 is a viscosity index improver and a lubricating oil composition. The range shown in Table 2 varies depending on the application.

＊ ：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, particularly preferably −50° C. or less, from the viewpoint of the viscosity index improver and the low-temperature viscosity of the lubricating oil composition. It is preferably -60°C or lower.

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

In addition to (A) and the base oil, the viscosity index improver of the present invention may use an alkyl (meth)acrylic acid ester (co)polymer (B) other than (A) in combination.
(B) is not particularly limited as long as it is an alkyl (meth)acrylic acid ester (co)polymer other than (A), but an alkyl (meth)acrylic acid ester having a linear alkyl group having 1 to 18 carbon atoms (Co)polymers and the like.
Specific examples of (B) include n-octadecyl methacrylate/n-dodecyl methacrylate (molar ratio 10 to 30/90 to 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 10-40/90-60) copolymers, etc., 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 40% by weight, more preferably 0% by weight, 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 type of base oil constituting the lubricating oil composition of the present invention is not particularly limited, but for example, mineral oil (solvent refined oil, paraffin oil, high viscosity index oil containing isoparaffin, high viscosity index oil by hydrocracking isoparaffin) viscosity index oils, naphthenic oils, etc.), synthetic lubricating oils [hydrocarbon synthetic lubricating oils (poly-α-olefin synthetic lubricating oils, etc.) and ester synthetic lubricating oils, etc.] and mixtures thereof. Among these, mineral oil is preferable from the viewpoint of oxidation stability.

The SP value of the base oil is preferably 7.8 to 9.5 (cal/cm ³ ) ^1/2 . When the SP value of the base oil is 7.8 (cal/cm ³ ) ^1/2 or more, the HTHS viscosity and viscosity index tend to be good, and 9.5 (cal/cm ³ ) ^1/2 or less. (A) tends to be easily dissolved in the base oil.
When a mixture of ^a plurality of ^hydrocarbon compounds such as mineral oil is used as the base oil, the approximate constituents and their The molecular structure is known, and the SP value of the base oil (B) can be calculated by arithmetic averaging based on the mole fractions measured by NMR.
The SP value of the base oil is more preferably 7.9 to 9.0 (cal/cm ³ ) ^1/2 , still more preferably 8.0 to 8.5 (cal/cm ³ ) ^1/2 , and particularly preferably 8.0 to 8.3 (cal/cm ³ ) ^1/2 , most preferably 8.3 (cal/cm ³ ) ^1/2 .

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

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

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

Since the viscosity index improver of the present invention contains a base oil, the viscosity index improver of the present invention itself functions as a lubricating oil composition depending on the mixing ratio of the copolymer (A) and the base oil. However, it is described as a viscosity index improver to distinguish it from those containing one or more of the other additives described below.

The lubricating oil composition of the present invention contains one or more of various additives shown below in addition to the viscosity index improver of the present invention. Additives include the following.
(1) Detergency:
Basic, overbased or neutral metal salts [such as overbased or alkaline earth metal salts of sulfonates (petroleum sulfonates, alkylbenzene sulfonates and alkylnaphthalene sulfonates, etc.)], salicylates, phenates, naphthenates , carbonates, phosphonates and mixtures thereof;
(2) Dispersant:
succinimides (bis- or mono-polybutenyl succinimides), Mannich condensates and borates, etc.;
(3) Antioxidants:
hindered phenols and aromatic secondary amines;
(4) Oiliness improver:
Long-chain fatty acids and their esters (oleic acid and oleic acid esters, etc.), long-chain amines and their amides (oleylamine and oleylamide, etc.), etc.;
(5) Friction and wear modifier:
molybdenum-based and zinc-based compounds (molybdenum dithiophosphate, molybdenum dithiocarbamate and zinc dialkyldithiophosphate, etc.);
(6) extreme pressure agent:
sulfur compounds (mono- or disulfides, sulfoxides and sulfur phosphide compounds), phosphide compounds and chlorine compounds (chlorinated paraffins, etc.);
(7) Defoamer:
Silicon oil, metallic 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.), etc.;
(9) Corrosion inhibitor:
nitrogen atom-containing compounds (benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate, etc.);
Each additive is called a component additive, and a mixture of two or more component additives is sometimes called a package additive.

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

<Production Example 1>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 75 parts by weight of 1,3-butadiene, and 2 parts by weight of n-butyllithium were charged into a SUS pressure-resistant reaction vessel equipped with a temperature controller and a stirrer. After that, polymerization was carried out at a polymerization temperature of 70°C.
After the polymerization rate reached approximately 100%, 2 parts by weight of ethylene oxide was added and reacted at 50° C. for 3 hours. In order to stop the reaction, 50 parts by weight of water and 25 parts by weight of 1N-hydrochloric acid aqueous solution were added and stirred at 80° C. for 1 hour. The organic phase of the reaction solution was collected with a separating funnel, heated to 70° C., and the solvent was removed under reduced pressure of 0.027 to 0.040 MPa over 2 hours.
The obtained polybutadiene containing a hydroxyl group at one end was transferred to a reaction vessel equipped with a temperature control device, a stirrer and a hydrogen introduction tube, and 150 parts by weight of tetrahydrofuran was added to uniformly dissolve the polybutadiene. After pouring a suspension prepared by mixing 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran in advance, the mixture was reacted at room temperature for 8 hours while supplying hydrogen into the liquid at a flow rate of 30 mL/min from the hydrogen introduction pipe. rice field. After that, palladium carbon is removed by filtration, and the obtained filtrate is heated to 70 ° C. and tetrahydrofuran is removed under a reduced pressure of 0.027 to 0.040 MPa to remove hydrogenated polybutadiene one-end hydroxyl group-containing polymer (Y1- 1) (Total ratio of isobutylene group and 1,2-butylene group: 45 mol%, 1,2-adduct/1,4-adduct (molar ratio): 45/55, hydroxyl value: 8.0 mgKOH/g , crystallization temperature: −60° C. or lower).
245 parts by weight of a hydrogenated polybutadiene hydroxyl-containing polymer (Y1-1), 245 parts by weight of methacrylic acid, and 98 parts by weight of an inorganic porous material carrying a sulfonic acid group (acid value: 45 mgKOH/g, particle size: 240 μm) were added, Esterification was carried out at 120°C. Next, the sulfonic acid group-carrying inorganic porous material was removed by filtration, and excess methacrylic acid was removed from the reaction solution under reduced pressure (0.027 to 0.040 MPa) to obtain a monomer (a-1). . The molecular weight of the obtained (a-1) was measured by GPC, and the ratio of 1,2-butylene groups was measured by ¹³ C-NMR. As a result, Mw = 6,900, Mn = 6,800, the ratio of 1,2-butylene groups in general formula (1) = 45 mol%, -X ¹ - is -O(CH ₂ CH ₂ O) ₁ - The group represented, p=0.

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

<Examples 1 to 17, Comparative Example 1>
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) 233.33 parts by weight, 100 parts by weight of the monomer formulation shown in Table 3 were charged, and after nitrogen replacement (gas phase oxygen concentration: 100 ppm), stirring was performed while sealing. After heating to 76 ° C., 2,2′-azobis (2-methylbutyronitrile), 2,2-azobis (2,4-dimethylvaleronitrile), t-butylperoxy in the amounts shown in Table 3 -2-Ethylhexyl monocarbonate was added and the polymerization reaction was carried out at the same temperature for 4 hours. After raising the temperature to 120-130° C., unreacted monomers were removed over 2 hours under reduced pressure (0.027-0.040 MPa) at the same temperature. 166.67 parts by weight of base oil A was added thereto, and a viscosity index improver (R-1) containing copolymers (A-1) to (A-17) or (A'-1) and base oil was added. ~ (R-17), (S-1) were obtained. The SP values of the obtained copolymers (A-1) to (A-17) and (A'-1) were calculated by the above method, and Mw was measured by the above method. Also, the base oil solubility of the copolymer was evaluated by the following method. Table 3 shows the results.

<Evaluation method for base oil solubility of copolymer>
The appearance of the viscosity index improvers (R1) to (R17) and (S1) was visually observed, and the base oil solubility was evaluated according to the following evaluation criteria.
[Evaluation criteria]
○: Appearance is uniform, no insoluble matter ×: Appearance is uneven, insoluble matter is observed

The compositions of monomers (a) to (h) listed in Table 3 are as described below.
(a-1): methacrylic acid ester of (Y1-1) [Mn: 6800]
(a-2): Methacrylate of (Y1-2) [Mn: 6800]
(b-1): isopropoxyethyl methacrylate (b-2): sec-butoxyethyl methacrylate (b-3): isopentyloxyethyl methacrylate (b-4): sec-hexyloxyethyl methacrylate (b-5): sec-octyloxyethyl methacrylate (b′-1): n-butoxyethyl methacrylate (c-1): methyl methacrylate (c-2): ethyl methacrylate (c-3): n-butyl methacrylate (d- 1): n-dodecyl methacrylate (d-2): a mixture of linear and branched alkyl methacrylates having 12 to 15 carbon atoms (methacrylic acid ester of NEODOL23 manufactured by SHELL)
(d-3): A mixture of linear and branched alkyl methacrylates having 14 to 16 carbon atoms (methacrylic acid ester of NEODOL45 manufactured by SHELL) (d-4): n-hexadecyl methacrylate (d-5): n-methacrylate Octadecyl (e-1): 2-n-decyltetradecyl methacrylate (e-2): 2-n-dodecylhexadecyl methacrylate (e-3): 2-n-tetradecyloctadecyl methacrylate (f-1 ): N,N-dimethylaminoethyl methacrylate (g-1): 2-hydroxyethyl methacrylate (h-1): methacryloyloxyethyl phosphate

<Examples 18 to 34, Comparative Example 2: 0W-20 evaluation>
90 weight of 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) was added to a stainless steel container equipped with a stirrer. and 10 parts by weight of a package additive (Infineum P5741) are added, and the viscosity index is improved so that the 150 ° C. HTHS viscosity of the resulting lubricating oil composition is 2.60 ± 0.05 (mPa s) Agents (R-1) to (R-17) or (S-1) were added to obtain lubricating oil compositions (V-1) to (V-17) and (W-1).
Shear stability of lubricating oil compositions (V-1) to (V-17), (W-1), HTHS viscosity (100 ° C.), kinematic viscosity (40 ° C., 100 ° C.), viscosity index, additive-containing group Solubility in oil was measured by the following method. Table 4 shows the results.

<Examples 35 to 51, Comparative Example 3: 0W-16 evaluation>
90 weight of 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) was added to a stainless steel container equipped with a stirrer. and 10 parts by weight of a package additive (Infineum P5741) are added, and the viscosity index is improved so that the HTHS viscosity at 150 ° C. of the resulting lubricating oil composition is 2.30 ± 0.05 (mPa s). Agents (R-1) to (R-17) or (S-1) were added to obtain lubricating oil compositions (V-18) to (V-34) and (W-2).
Shear stability of lubricating oil compositions (V-18) to (V-34), (W-2), HTHS viscosity (100 ° C.), kinematic viscosity (40 ° C., 100 ° C.), viscosity index, additive-containing group Solubility in oil was measured by the following method. Table 5 shows the results.

<Method for measuring and calculating 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>
It was measured at 80°C and 100°C according to the method of ASTM D 5481.

<Method for calculating the viscosity index of the lubricating oil composition>
The kinematic viscosity at 40°C and 100°C was measured by the method of ASTM D 445 and calculated by the method of ASTM D2270.

<Method for evaluating solubility of copolymer in additive-containing base oil>
The appearance of the lubricating oil compositions (V1) to (V34) and (W1) to (W2) was visually observed, and the base oil solubility was evaluated according to the following evaluation criteria.
[Evaluation criteria]
○: Appearance is uniform, no insoluble matter ×: Appearance is uneven, insoluble matter is observed

As is clear from the results in Tables 4 and 5, the lubricating oil composition containing the viscosity index improver of the present invention has excellent shear stability, a low HTHS viscosity in the effective temperature range, and a viscosity index of It can be seen that it is highly superior.

The viscosity index improver of the present invention and the lubricating oil composition containing the same include drive system lubricating oil (MTF, differential gear oil, ATF and belt-CVTF, etc.), hydraulic oil (mechanical hydraulic oil, power steering oil and shock absorber oils, etc.), engine oils (for gasoline and diesel, etc.) and traction oils.

Claims (12)

A copolymer (A) containing a polyolefin monomer (a) represented by the following general formula (1) and a monomer (b) represented by the following general formula (2) as essential constituent monomers viscosity index improver.

[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 an alkylene group having 2 to 4 carbon atoms; where m is an integer of 0 to 10, and when m is 2 or more, A may be the same or different; (AO) _m portion may be a random bond or a block bond; R ² is an isobutylene group and/or or a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having a 1,2-butylene group as an essential structural unit; ]

[R ³ is a hydrogen atom or a methyl group; -X ² - is a group represented by -O- or -NH-; R ⁴ is an alkylene group having 2 to 4 carbon atoms; R ⁵ is a branched group having 3 to 8 carbon atoms alkyl group; q is an integer of 1 to 20, R ⁴ when q is 2 or more may be the same or different, and the (R ⁴ O) _q portion may be a random bond or a block bond. ] The copolymer (A) contains 1 to 50% by weight of (a), 1 to 80% by weight of (b), and (a) and (b) as constituent monomers based on the weight of (A). 2. The viscosity index improver according to claim 1, which is a copolymer containing 10% by weight or more of the total of A hydrocarbon polymer having an isobutylene group and/or a 1,2-butylene group as an essential structural unit in the general formula (1), based on the total number of structural units, the total of the isobutylene group and the 1,2-butylene group is The viscosity index improver according to claim 1 or 2, which is a polymer having a content of 30 mol% or more. The copolymer (A) further comprises a (meth)acrylic acid alkyl ester (c) having an alkyl group having 1 to 4 carbon atoms as a constituent monomer of (A) and/or a linear chain having 12 to 36 carbon atoms. The viscosity index improver according to any one of claims 1 to 3, which is a copolymer containing a (meth)acrylic acid alkyl ester (d) having an alkyl group. 5. The viscosity index improver according to claim 4, wherein the copolymer (A) further comprises a monomer (e) represented by the following general formula (3) as a constituent monomer.

[R ⁶ is a hydrogen atom or a methyl group; -X ³ - is a group represented by -O- or -NH-; R ⁷ is an alkylene group having ² to ⁴ carbon atoms; a linear alkyl group having a number of 4 to 24; r is an integer of 0 to 20, and when _r is ² or more, R ⁷ may be the same or different; May be combined. ] The copolymer (A) contains 5 to 40% by weight of (a), 1 to 60% by weight of (b), and 1 to 80% by weight of (c) based on the weight of (A) as constituent monomers. %, 1 to 40% by weight of (d) and 1 to 30% by weight of (e). The copolymer (A) further comprises one or more selected from the group consisting of a nitrogen atom-containing monomer (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 6, which is a copolymer as a monomer. The viscosity index improver according to any one of claims 1 to 7, wherein the copolymer (A) has a weight average molecular weight of 5,000 to 2,000,000. 9. The composition according to any one of claims 1 to 8, further comprising a (co)polymer (B) other than the copolymer (A) in an amount of 0.01 to 40% by weight based on the weight of (A). viscosity index improver. The viscosity index improver according to any one of claims 1 to 9, further comprising a base oil, wherein the base oil has a solubility parameter of 7.8 to 9.5 (cal/cm ³ ) ^1/2 . . 11. The viscosity index improver according to claim 10, wherein the base oil has a kinematic viscosity at 100° C. of 1 to 15 mm ² /s and a viscosity index of 100 or more. A viscosity index improver according to any one of claims 1 to 11, together with detergents, dispersants, antioxidants, oiliness improvers, friction and wear modifiers, extreme pressure agents, defoamers, demulsifiers and corrosion inhibitors. A lubricating oil composition containing one or more additives selected from the group consisting of agents.