JP2006045277A - Viscosity index improver and lubricating oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viscosity index improver excellent not only in viscosity index improving effect but also in shear stability, compared with the conventional polymethacrylate viscosity index improver. <P>SOLUTION: The viscosity index improver comprises a polymer (A) which has a Z average mol. wt. of 10,000-1,000,000, measured by gel permeation chromatography and which uses as an essential constituting monomer an alkyl (meth)acrylate (a) having a 1-30C alkyl group. The lubricating oil composition contains the above viscosity index improver and a base oil. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a viscosity index improver and a lubricating oil composition containing the same. Specifically, the present invention relates to a poly (meth) acrylate viscosity index improver having a specific Z average molecular weight and a lubricating oil composition containing the same.

In recent years, the trend of protecting the global environment has been increasing, and the fuel efficiency of automobiles has been further demanded. One means for reducing fuel consumption is reducing friction loss by reducing the viscosity of the lubricating oil. However, simply reducing the viscosity causes problems such as liquid leakage and image sticking. In order to solve this problem, it is generally necessary to increase the viscosity index, and various viscosity index improvers have been conventionally proposed (for example, see Patent Document 1).
JP 7-48421 A

  However, the conventional polymethacrylate viscosity index improvers have a problem that they are insufficient in the effect of improving the viscosity index and in the shear stability.

As a result of intensive studies, the present inventors have found that a polymer having a specific Z average molecular weight and composed of a specific monomer is excellent in shear stability and ability to improve viscosity index. It came to.
That is, the present invention is a (meth) acrylic acid alkyl ester (a) having a Z average molecular weight of 10,000 to 1,000,000 and having an alkyl group having 1 to 30 carbon atoms as measured by gel permeation chromatography. ) As an essential constituent monomer, a viscosity index improver comprising the polymer (A); an additive composition for lubricating oil comprising the viscosity index improver and a diluent and / or other additives; A lubricating oil composition comprising an agent and a base oil; and a lubricating oil composition comprising the lubricating oil additive composition and a base oil.

  The lubricating oil composition using the viscosity index improver of the present invention can improve the viscosity index as compared with the lubricating oil composition using the conventional PMA viscosity index improver, and is excellent in shear stability and low temperature viscosity. Therefore, it is possible to meet future fuel efficiency requirements of automobiles.

  In the present invention, the lower limit of the Z average molecular weight (hereinafter abbreviated as Mz) is usually 10,000, preferably 15,000, more preferably 20,000, and the upper limit is usually 1,000,000, preferably 400,000. More preferably, it is 250,000, and particularly preferably 150,000. If Mz is less than 10,000, the viscosity index improving ability is poor. If it exceeds 1,000,000, the shear stability will be poor. In addition, Mz is measured by gel permeation chromatography and is calculated in terms of polystyrene.

Examples of the (meth) acrylic acid alkyl ester (a) having an alkyl group having 1 to 30 carbon atoms, which is an essential constituent monomer of the polymer (A), include the following (a1) to (a4).
(A1) (meth) acrylic acid alkyl ester having a C 1-4 alkyl group: for example, methyl (meth) acrylate, ethyl (meth) acrylate, n- or iso-propyl (meth) acrylate, ( Examples thereof include n-, iso- and sec-butyl (meth) acrylates, and methyl methacrylate and n-butyl methacrylate are preferred.
(A2) (meth) acrylic acid alkyl ester having a linear and / or branched alkyl group having 8 to 15 carbon atoms:
For example, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-decyl (meth) acrylate, n-isodecyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) N-dodecyl acrylate, 2-methylundecyl (meth) acrylate, n-tridecyl (meth) acrylate, 2-methyldodecyl (meth) acrylate, n-tetradecyl (meth) acrylate, (meth) acrylic acid 2-methyltridecyl, n-pentadecyl (meth) acrylate, 2-methyltetradecyl (meth) acrylate, alcohol produced by oxo synthesis [e.g., trade name "DOBANOL 23" (manufactured by Mitsubishi Chemical Corporation), "TRIDECanol ”(Manufactured by Kyowa Hakko),“ Oxocol 1213 ”(manufactured by Nissan Chemical),“ Dovanol 45 ”(manufactured by Mitsubishi Chemical), (Meth) acrylic acid ester with “Oxocol 1415” (manufactured by Nissan Chemical Co., Ltd.) and the like (hereinafter, methacrylic acid ester with “Dovanol 23” is abbreviated as D23, and methacrylic acid ester with “Dovanol 45” is abbreviated as D45) . Among these, (meth) acrylic acid alkyl esters having a linear and / or branched alkyl group having 12 to 15 carbon atoms are preferred.
(A3) (Meth) acrylic acid alkyl ester having a linear and / or branched alkyl group having 16 to 24 carbon atoms:
For example, n-hexadecyl acrylate, n-hexadecyl methacrylate (hereinafter abbreviated as HMA), n-octadecyl acrylate, n-octadecyl methacrylate (hereinafter abbreviated as OMA), n-eicosyl (meth) acrylate, (meth) acrylic N-docosyl acid, 2-methylpentadecyl (meth) acrylate, 2-hexyldecyl (meth) acrylate, 2-methylhexadecyl (meth) acrylate, 2-octyldecyl (meth) acrylate, (meth) 2-hexyldecyl acrylate, 2-methylheptadecyl (meth) acrylate, 2-methyloctadecyl (meth) acrylate, 2-octyldodecyl (meth) acrylate, 2-decyltetradecyl (meth) acrylate, etc. Of these, preferred are straight chain alkyl groups having 16 to 18 carbon atoms. (Meth) acrylic acid alkyl ester and (meth) acrylate, 2-decyl tetradecyl.
(A4) (meth) acrylic acid alkyl ester having a linear and / or branched alkyl group having 5 to 7 carbon atoms:
(Meth) acrylic acid n-, iso-, sec- and neopentyl (meth) acrylic acid, hexyl, heptyl (meth) acrylate, etc.
Preferred among (a) are (a1) to (a3).

  In the polymer (A), the following monomers (d) to (n) may be mentioned as monomers for copolymerization with (a).

(D) a nitrogen atom-containing monomer;
(D1) Nitro group-containing monomer:
For example, 4-nitrostyrene
(D2) A primary to tertiary amino group-containing vinyl monomer:
Primary amino group-containing vinyl monomer, for example, alkenylamine having 3 to 6 carbon atoms [(meth) allylamine, crotylamine, etc.], aminoalkyl (2 to 6 carbon atoms) (meth) acrylate [aminoethyl (meth) acrylate Etc.] Secondary amino group-containing vinyl monomer, for example, alkyl (C1-6) aminoalkyl (C2-6) (meth) acrylate [t-butylaminoethyl methacrylate, methylaminoethyl (meth) Acrylate etc.], diphenylamine (meth) acrylamide [4-diphenylamine (meth) acrylamide, 2-diphenylamine (meth) acrylamide etc.], C6-C12 dialkenylamine [di (meth) allylamine etc.], tertiary amino group Containing vinyl monomer, for example, dialkyl (1 to 4 carbon atoms) Aminoalkyl (2 to 6 carbon atoms) (meth) acrylate [dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, etc., dialkyl (1 to 4 carbon atoms) aminoalkyl (2 to 6 carbon atoms) (meth) Acrylamide [dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, etc.], tertiary amino group-containing aromatic vinyl monomer [N, N-dimethylaminostyrene, etc.] , Nitrogen-containing heterocyclic ring-containing vinyl monomers [morpholinoethyl (meth) acrylate, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone, N-vinylthiopyrrolidone, etc.]
(D3) Quaternary ammonium base-containing vinyl monomer:
For example, the above-mentioned tertiary amino group-containing vinyl monomer is quaternized with a quaternizing agent (alkyl chloride having 1 to 12 carbon atoms, dialkyl sulfuric acid, dialkyl carbonate, benzyl chloride, etc.). Can be mentioned. Specifically, examples of the alkyl (meth) acrylate quaternary ammonium salt include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyltriethylammonium chloride, and (meth) acryloyloxyethyldimethylbenzylammonium. Chloride, (meth) acryloyloxyethylmethylmorpholino ammonium chloride and the like; alkyl (meth) acrylamide quaternary ammonium salts include, for example, (meth) acryloylaminoethyltrimethylammonium chloride, (meth) acryloylaminoethyltriethylammonium chloride, (Meth) acryloylaminoethyldimethylbenzylammonium chloride, etc .; other quaternary ammonium salts The containing vinyl monomers, for example, dimethyl diallyl ammonium methyl sulfate, etc. trimethyl vinylphenyl ammonium chloride,
(D4) Amphoteric vinyl monomer:
N- (meth) acryloyloxy (or amino) alkyl (C1-10) N, N-dialkyl (C1-5) ammonium-N-alkyl (C1-5) carboxylate (or sulfate), For example, N- (meth) acryloyloxyethyl N, N-dimethylammonium N-methylcarboxylate, N- (meth) acryloylaminopropyl N, N-dimethylammonium N-methylcarboxylate, and N- (meth) acryloyloxy Ethyl N, N-dimethylammonium propyl sulfate, etc.
(D5) Nitrile group-containing monomer:
(Meth) acrylonitrile, etc.

(E) Aliphatic hydrocarbon vinyl monomer:
For example, alkenes having 2 to 20 carbon atoms [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.] and alkadienes having 4 to 12 carbon atoms [butadiene, isoprene, 1,4- Pentadiene, 1,6-heptadiene, 1,7-octadiene, etc.]

(F) Alicyclic hydrocarbon vinyl monomer:
For example, cyclohexene, (di) cyclopentadiene, pinene, limonene, indene, vinylcyclohexene, and ethylidenebicycloheptene, etc.

(G) Aromatic hydrocarbon vinyl monomer:
For example, styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4 -Crotylbenzene, 2-vinylnaphthalene, etc.

(H) Vinyl esters, vinyl ethers, vinyl ketones:
For example, vinyl esters of saturated fatty acids having 2 to 12 carbon atoms [vinyl acetate, vinyl propionate, vinyl butyrate, vinyl octoate, etc.], alkyl ethers having 1 to 12 carbon atoms, aryl or alkoxyalkyl vinyl ethers [methyl vinyl ether, ethyl vinyl ether , Propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, phenyl vinyl ether, vinyl 2-methoxyethyl ether, vinyl 2-butoxyethyl ether, etc.], and alkyl or aryl vinyl ketones having 1 to 8 carbon atoms [methyl vinyl ketone, ethyl vinyl] Ketone, phenyl vinyl ketone, etc.],

(I) an epoxy group-containing vinyl monomer;
For example, glycidyl (meth) acrylate glycidyl (meth) allyl ether, etc.

(J) a halogen element-containing vinyl monomer;
For example, vinyl chloride, vinyl bromide, vinylidene chloride, (meth) allyl chloride, halogenated styrene (dichlorostyrene and the like) and the like can be mentioned.

(K) an ester of an unsaturated polycarboxylic acid;
Examples thereof include alkyl, cycloalkyl or aralkyl esters of unsaturated polycarboxylic acids, and among them, alkyl diesters having 1 to 8 carbon atoms of unsaturated dicarboxylic acids [maleic acid, fumaric acid, itaconic acid, etc.] [dimethyl maleate, Dimethyl fumarate, diethyl maleate, dioctyl maleate]

(L) a hydroxyl group-containing vinyl monomer;
For example, hydroxyl group-containing aromatic vinyl monomer [p-hydroxystyrene etc.], hydroxyalkyl (2 to 6 carbon atoms) (meth) acrylate [2-hydroxyethyl (meth) acrylate, 2 or 3-hydroxypropyl (meta) ) Acrylates, etc.], mono- or di-hydroxyalkyl (1 to 4 carbon atoms) substituted (meth) acrylamide [N, N-dihydroxymethyl (meth) acrylamide, N, N-dihydroxypropyl (meth) acrylamide, N, N -Di-2-hydroxybutyl (meth) acrylamide etc.], vinyl alcohol (formed by hydrolysis of vinyl acetate unit), C3-C12 alkenol [(meth) allyl alcohol, crotyl alcohol, isocrotyl Alcohol, 1-octenol, 1-undece Etc.], C 4-12 alkene diol [1-buten-3-ol, 2-buten-1-ol, 2-butene-1,4-diol etc.], hydroxyalkyl (C 1-6 ) Alkenyl (3 to 10 carbon atoms) ether [2-hydroxyethylpropenyl ether and the like], polyhydric (3 to 8 valent) alcohol (alkane polyol, intramolecular or intermolecular dehydrated product, saccharide such as glycerin, pentaerythritol, Alkitol (3 to 10 carbon atoms) ether or (meth) acrylate [sucrose (meth) allyl ether] of sorbitol, sorbitan, diglycerin, sucrose,

(M) a polyoxyalkylene chain-containing vinyl monomer;
For example, polyoxyalkylene glycol (alkylene group having 2 to 4 carbon atoms, degree of polymerization 2 to 50), or polyoxyalkylene polyol [polyoxyalkylene ether of 3 to 8 valent alcohol (alkyl group having 2 to 4 carbon atoms) , Degree of polymerization 2-100)], or mono (meth) acrylates thereof (polyethylene glycol (molecular weight 100-300) mono (meth) acrylate, polypropylene glycol (molecular weight 130-500) Mono (meth) acrylate, methoxypolyethylene glycol (molecular weight 110-310) (meth) acrylate, lauryl alcohol ethylene oxide adduct (2-30 mol) (meth) acrylate, mono (meth) acrylic acid polyoxyethylene (molecular weight 150-230 Sorbitan], etc.,

(N) a carboxyl group-containing vinyl monomer;
Monocarboxyl group-containing vinyl monomers such as unsaturated monocarboxylic acids [(meth) acrylic acid, α-methyl (meth) acrylic acid, crotonic acid, cinnamic acid, etc.], monoalkyls of unsaturated dicarboxylic acids (carbon number) 1-8) Esters [maleic acid monoalkyl esters, fumaric acid monoalkyl esters, itaconic acid monoalkyl esters, etc.]; vinyl monomers containing two or more carboxyl groups, such as maleic acid, fumaric acid, itaconic acid Citraconic acid, etc.

  Among these monomers (d) to (n), preferred are (d), (l) and a combination thereof.

  Among (d), preferred are (d2), and more preferred are dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate (hereinafter abbreviated as DAE), diethylaminoethyl (meth) acrylate, and morpholinoethyl (meth) acrylate.

  The lower limit of the proportion of (a1) in the monomer constituting (A) is usually 0% from the viewpoint of viscosity index and solubility (hereinafter, unless otherwise specified,% represents% by mass), preferably Is 5%, more preferably 10%, and the upper limit is preferably 45%, more preferably 40%, particularly preferably 35%, particularly preferably 25%, most preferably 22%.

  The proportion of (a2) in the monomer constituting (A) is preferably 0.1%, more preferably 20%, particularly preferably 30%, particularly preferably from the viewpoint of viscosity index and solubility. Is 40%, most preferably 50%, and the upper limit is usually 100%, preferably 95%.

  The proportion of (a3) in the monomer constituting (A) is usually 0%, preferably 5%, and the upper limit is preferably 75%, more preferably 65, from the viewpoint of viscosity index and low temperature viscosity. %, Particularly preferably 50%, particularly preferably 20%.

From the viewpoint of sludge dispersibility, the ratio of (d) in the monomer constituting (A) is preferably 0.1%, more preferably 1%, particularly preferably 2%, and the upper limit is preferably Is 10%, more preferably 7%, particularly preferably 5%.

A preferred combination of (a1), (a2), and (a3) mass% in (A) is (a1) 0 to 45%, (a2) 0.1 to 100%, and (a3) 0. More preferable combinations are (a1) 5 to 40%, (a2) 20 to 95% and (a3) 0 to 65%.

  The means for adjusting Mz in (A) in the present invention can be adjusted by, for example, the temperature during polymerization, the monomer concentration (solvent concentration), the catalyst amount, the chain transfer agent amount, and the like.

  (A) in the present invention can be obtained by a known production method. For example, it can be obtained by radical polymerization of the above monomer in a solvent in the presence of a polymerization catalyst.

  Examples of the solvent include toluene, xylene, alkylbenzene having 9 to 10 carbon atoms, methyl ethyl ketone, and mineral oil. Examples of the polymerization catalyst include azo catalysts (for example, 2,2′-azobisisobutyronitrile, 2,2 '-Azobis (2-methylbutyronitrile) (hereinafter abbreviated as AMBN), 2,2'-azobis (2,4-dimethylvaleronitrile) (hereinafter abbreviated as ADVN), dimethyl 2,2-azobisisobutyrate Etc.) and peroxides (for example, t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneoheptanoate, t-butyl peroxyneodecanoate, t-butyl peroxy Oxy 2-ethyl hexanoate, t-butyl peroxy isobutyrate, t-amyl peroxy 2-ethyl hexanoate 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, dibutylperoxytrimethyladipate, benzoyl peroxide, cumyl peroxide, lauryl peroxide, benzoyl peroxide, cumyl peroxide, lauryl peroxide, etc. ) Can be used. Furthermore, if necessary, a chain transfer agent may be used in combination. Examples of such compounds include thiocarboxylic acids (n-lauryl mercaptan (hereinafter abbreviated as DM), mercaptoethanol, mercaptopropanol, etc.), thiolic acids (thioglycolic acid). , Thiomalic acid, etc.), amines (dibutylamine, etc.) and the like. The amount of the chain transfer agent is preferably 0.001 to 5%, more preferably 0.05 with respect to the mass of the monomer. ~ 3%. The reaction temperature is 50 to 140 ° C, preferably 70 to 120 ° C. In addition to the above solution polymerization, it can also be obtained by bulk polymerization, emulsion polymerization or suspension polymerization. Furthermore, the polymerization mode when (A) is a copolymer may be either random addition polymerization or alternating copolymerization, and may be either graft copolymerization or block copolymerization.

The viscosity index improver of the present invention can be used as an additive composition for lubricating oil obtained by polymerizing a monomer in the presence of a solvent and diluted with a solvent, or It can also be diluted with a diluent such as a solvent after polymerization and used as an additive composition for lubricating oil. Dilution with a diluent in advance is preferable in that it can be easily dissolved when added to a lubricating oil.
Diluents include aliphatic solvents [aliphatic hydrocarbons having 6 to 18 carbon atoms (hexane, heptane, cyclohexane, octane, decalin, kerosene, etc.)]; aromatic solvents {aromatic solvents having 7 to 15 carbon atoms [toluene] , Xylene, ethylbenzene, aromatic mixed solvent having 9 carbon atoms (mixture of trimethylbenzene, ethyltoluene, etc.), aromatic mixed solvent having 10 to 11 carbon atoms, etc.], mineral oil [for example, solvent refined oil, paraffin oil, isoparaffin And / or hydrocracking high viscosity index oils, naphthenic oils], synthetic lubricating oils [hydrocarbon-compatible lubricating oils (poly-α-olefin based synthetic lubricating oils), ester based synthetic lubricating oils], etc. Of these, mineral oil is preferred.
When the lubricating oil additive composition of the present invention contains a diluent, the lower limit of the ratio of the diluent is preferably 10%, more preferably 30%, particularly preferably based on the mass of the viscosity index improver of the present invention. The upper limit is preferably 40%, and the upper limit is preferably 900%, more preferably 800%, and particularly preferably 600% based on the mass of the viscosity index improver of the present invention.
A higher ratio of diluent is preferred in that it dissolves easily in the base oil, but too much is not economical.

  Furthermore, the additive composition for lubricating oil of the present invention may contain two or more different types (A). A preferred combination is (A1) composed of (a1) to (a3) and (A2) composed of (a2) and (a3), and from the viewpoint of low temperature viscosity, a preferred mass ratio is (A1) / (A2). = (99 to 85) / (1 to 15).

The mass ratio of the monomers constituting (A1) is preferably (a1) / [(a2) + (a3) = (5-30) / (95-70), more preferably (10-22) / ( 90-78).
The preferable constituent ratio of the monomer in (A2) includes at least one monomer having 12 to 18 carbon atoms and an average carbon number of 12 to 16.
As a specific example of (A) in the case of containing two or more types (A),
(A1); For example, methyl methacrylate / methacrylic acid ester having an alkyl group having 12 to 15 carbon atoms / methacrylic acid ester having an alkyl group having 16 to 20 carbon atoms (0 to 22% / 20 to 90% / 0 to 20) %) Copolymer, etc.
(A2); for example, dodecyl methacrylate / hexadecyl methacrylate (10-50% / 50-90%) copolymer [average carbon number: 12.3-15.6], dodecyl methacrylate / tetradecyl methacrylate (90- 70% / 10-30%) copolymer [average carbon number: 12.2-12.6], and D23 / HMA / OMA (30-70% / 5-50% / 3-20%) copolymer [Average carbon number: 13.7 to 15.4].

  The above (A1) or (A2) is not in the form of the additive composition for lubricating oil, but may be added to the base oil alone, or each diluted alone to be added to the diluent. Also good. For example, the lubricating oil additive composition comprising (A1) and a diluent and the lubricating oil additive composition comprising (A2) and a diluent can be separately added to the base oil.

Is not particularly restricted but includes base oil viscosity index improver of the present invention is added, kinematic viscosity at 100 ° C. is 1 to 15 mm ² / s, preferably 2 to 5 mm ² / s, the viscosity index is usually 80 As mentioned above, Preferably it is 100 or more, More preferably, it is 105-180. A lubricating oil composition in which the viscosity index improver of the present invention is blended with such a base oil has a higher viscosity index and better fuel economy.

  Further, the cloud point (JIS K2269-1993) of the base oil to which the viscosity index improver of the present invention is added is preferably −5 ° C. or lower. More preferably, it is −15 ° C. to −60 ° C. When the cloud point of the base oil is within this range, the amount of wax precipitated is small and the low-temperature viscosity is good. Base oils include solvent refined oils, high viscosity index oils containing isoparaffins and / or hydrocracking, hydrocarbon synthetic lubricating oils (polyalphaolefin synthetic lubricating oils), ester synthetic lubricating oils, naphthenic oils, etc. Can be mentioned. Of these, high viscosity index oils containing isoparaffins and / or hydrocracking are preferred.

  The lubricating oil composition of the present invention is preferably produced by adding 0.5 to 30% of a viscosity index improver in terms of (A) with respect to the base oil.

When the lubricating oil composition is engine oil, it is preferable that 0.5 to 15% is added as (A) to a base oil having a kinematic viscosity at 100 ° C. of 3 to 10 mm ² / s.
In the case of gear oil, 3 to 30% is preferably added to a base oil having a kinematic viscosity at 100 ° C. of 3 to 10 mm ² / s.
In the case of an automatic transmission oil (ATF, belt CVT oil), 2 to 25% is preferably added to a base oil having a kinematic viscosity at 100 ° C. of ² to 6 mm ² / s.
In the case of traction oil, 0.5 to 15% is preferably added to a base oil having a kinematic viscosity at 100 ° C. of 1 to 5 mm ² / s.
In the case of hydraulic oil, 0.5 to 25% is preferably added to a base oil having a kinematic viscosity at 100 ° C. of 1 to 10 mm ² / s.

  The additive composition for lubricating oil of the present invention is based on the mass of (A) with other additives such as detergents (sulfate, salicylate, phenate, naphthenate and other Ca and Mg salts, calcium carbonate). 0 to 20%, preferably 0.1 to 10%, and 0 to 20%, preferably 0.2 to 10%, of a dispersant (succinimide type; histyp, monotype, borate type, Mannich condensate system, etc.) %, Antioxidant (zinc dithiophosphate, amine type; diphenylamine, hindered phenol type, zinc thiophosphate, trialkylphenol, etc.) 0-5%, preferably 0.1-3%, oiliness improver (long chain fatty acid) System: oleic acid, long chain fatty acid ester; oleic acid ester, long chain amine system: oleylamine, etc., long chain amide; 0.1 to 1%, friction and wear modifier (molybdenum dithiophosphate, molybdenum carbamate, zinc dialkyldithiophosphate, etc.) 0 to 5%, preferably 0.1 to 3%, extreme pressure agent (sulfur phosphorus, Sulfur type, phosphorus type, chloro type, etc.) 0-20%, preferably 0.1-10%, antifoaming agents (silicone oil, metal soap, fatty acid ester, phosphate ester, etc.) 2-1000 ppm, preferably 10 ~ 700ppm, Demulsifier (quaternary ammonium salt, sulfated oil, phosphate ester) 0-3%, preferably 0-1%, corrosion inhibitor (nitrogen compounds such as benzotriazole, 1,3,4-thiodiazolyl Sulfur and nitrogen-containing compounds such as -2,5-bisdialkyldithiocarbamate) may be contained in an amount of 0 to 3%, preferably 0 to 2%.

  The lubricating oil composition of the present invention is used for engine oil, gear oil, automatic transmission oil (ATF, CVT oil), traction oil, shock absorber oil, power steering oil, etc. for transportation equipment and various machine tools.

<Example>
The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In addition,% and part in an Example and a comparative example represent the mass% and a mass part.
(Measurement method of Z average molecular weight by GPC)
Apparatus: HLC-802A manufactured by Toyo Soda
Column: TSK gel GMH6 2 Measurement temperature: 40 ° C
Sample solution: 0.5 wt% THF solution Injection amount: 200 μl
Detector: Refractive index detector Standard: Polystyrene

(Test method for low temperature viscosity)
The viscosity at −40 ° C. was measured by the method of JPI-5S-26-85.

(Test method for viscosity index)
It was carried out by the method of JIS-K-2283.

(Shear stability test method)
The kinematic viscosity reduction rate at 100 ° C. was determined by the method of JASO M347-95.

Examples 1-6 and Comparative Example 1;
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, and a nitrogen blowing tube, 25 parts of mineral oil was charged, and a total of 100 parts of the monomers listed in Table 1 were placed in another glass beaker. , Dodecyl mercaptan (abbreviated as DM) as the chain transfer agent in the amounts shown in Table 1, and 2,2′-azobis (2,4-dimethylvaleronitrile: abbreviated as ADVN), 2,2 ′ as the radical polymerization initiator -Azobis (2-methylbutyronitrile: abbreviated as AMBN) is charged in the amount shown in Table 1, stirred and mixed at 20 ° C to prepare a monomer solution, and charged into a dropping funnel. After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was dropped over 4 hours at 85 ° C. in a sealed state, and after aging at 85 ° C. for 2 hours from the end of dropping, the obtained polymer was cooled to 130 ° C. Low boiling components were removed under reduced pressure for 3 hours to obtain copolymers (A-1) to (A-6) and (X-1), which were used as viscosity index improvers. Table 2 shows the Z-average molecular weight of the obtained copolymer.

Examples 7-12, Comparative Example 2
75 parts of each of the copolymers (A-1) to (A-6) and (X-1) are mixed and dissolved in 25 parts of mineral oil (solvent refined oil: 100 ° C. kinematic viscosity 2.4 mm ² / s). Thus, lubricating oil additive compositions were prepared, and the lubricating oil additive compositions of Examples 7 to 12 and Comparative Example 2 were used.

Examples 13-18, Comparative Example 3
Using a stainless steel container equipped with a stirring and mixing device, the lubricating oil additive composition containing (A-1) to (A-6) and (X-1) was added to the base oil (100 Kinematic viscosity at 0 ° C .: 3.0 mm ² / s, viscosity index: 117) were dissolved to prepare lubricating oil compositions of the present invention and comparative lubricating oil compositions. Table 3 shows the measurement results of the viscosity index, shear stability, and -40 ° C viscosity of the obtained lubricating oil composition.

  The lubricating oil composition using the viscosity index improver of the present invention can improve the viscosity index as compared with the lubricating oil composition using the conventional PMA viscosity index improver, and is excellent in shear stability and low temperature viscosity. Therefore, it is possible to meet future fuel efficiency requirements of automobiles. Therefore, drive system lubricating oil (manual transmission oil, differential gear oil, automatic transmission oil, belt CVT oil, etc.), hydraulic oil (machine hydraulic oil, power steering oil, shock absorber oil, etc.), engine oil (for gasoline, diesel) And the like, and can be suitably used for traction oil.

Claims (9)

  A Z-average molecular weight measured by gel permeation chromatography is 10,000 to 1,000,000, and a (meth) acrylic acid alkyl ester (a) having an alkyl group having 1 to 30 carbon atoms is essential. A viscosity index improver comprising the polymer (A) as a polymer.   Polymer (A) (meth) acrylic acid alkyl ester (a1) having an alkyl group having 1 to 4 carbon atoms, (meth) acrylic acid alkyl ester (a2) having an alkyl group having 8 to 15 carbon atoms and carbon number A (meth) acrylic acid alkyl ester (a3) having 16 to 24 alkyl groups is used as a constituent monomer, and (a1) is 0 to 45% by mass and (a2) is 0.00 based on the total mass of the monomers. The viscosity index improver according to claim 1, wherein 1 to 100% by mass and (a3) is 0 to 75% by mass.   3. (A) further comprises a nitrogen atom-containing vinyl monomer (d) as a constituent monomer, and (d) is 0.1 to 10% by mass based on the mass of all monomers. The viscosity index improver described.   The additive composition for lubricating oil which consists of a viscosity index improver in any one of Claims 1-3, a diluent, and / or another additive.   The additive composition for lubricating oil according to claim 4, wherein the diluent is 10 to 900% by mass based on the mass of the viscosity index improver.   The additive composition for lubricating oil according to claim 4 or 5, comprising two or more different types (A).   A lubricating oil composition comprising the viscosity index improver according to any one of claims 1 to 3 and a base oil.   A lubricating oil composition comprising the lubricating oil additive composition according to any one of claims 4 to 6 and a base oil. 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 100 or more.