JP2017171882A - Viscosity index improver and lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity index improver and a lubricant composition having high viscosity-index improvement effect and being excellent in shear stability of a lubricant composition.SOLUTION: A viscosity index improver comprises copolymer (A) that comprises monomer (a) represented by general formula (1), specific monomer (b), and (meth)acrylic acid alkyl ester (c) with an alkyl group having 1-4 carbon atoms as essential constituent monomers. The total weight of (b) and (c) is 30-70 wt.% as constituent monomers relative to the (A) weight. [Ris a hydrogen atom or a methyl group; Xis a group represented by -O-, -O(AO)-, -NH- or -NH(AO)-; A is an alkylene group having 2-4 carbon atoms; n is an integer of 1-20, where if n is 2 or more, A may be the same or different; Ris a branched-chain alkyl group having 32-44 carbon atoms].SELECTED DRAWING: None

Description

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

Lubricating oils and hydraulic oils used in automobiles and the like have a lower viscosity as the temperature increases, but in practice, it is desirable that the viscosity does not change as much as possible over a wide range from a low temperature to a high temperature. Therefore, a method for improving the temperature dependence of viscosity by adding a viscosity index improver to lubricating oil is widely used. As such viscosity index improvers, methacrylic acid ester copolymers (Patent Documents 1 to 4), olefin copolymers (Patent Document 5), macromonomer copolymers (Patent Document 6) and the like are known. .
However, the above-mentioned viscosity index improver is still insufficient in the effect of improving the viscosity index, and has a problem that the shear stability after long-time operation is not yet sufficient in practical use.

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

  An object of the present invention is to provide a viscosity index improver that has a high viscosity index improving effect and is excellent in the shear stability of a lubricating oil composition.

［Ｒ^１は水素原子又はメチル基；Ｘ¹は−Ｏ−、−Ｏ（ＡＯ）_ｎ−、−ＮＨ−又は−ＮＨ（ＡＯ）_ｎ−で表される基；Ａは炭素数２〜４のアルキレン基；ｎは１〜２０の整数であり、ｎが２以上の場合のＡは同一でも異なっていてもよい；Ｒ^２は炭素数３２〜４４の分岐アルキル基である。］

［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１〜８のアルキル基；ｐは１〜２０の整数であり、ｐが２以上の場合のＲ^４は同一でも異なっていてもよい。］ As a result of intensive studies, the present inventors have arrived at the present invention. That is, the present invention provides (a) represented by the following general formula (1), (b) represented by the general formula (2), and a (meth) acryl having a linear alkyl group having 1 to 4 carbon atoms. A viscosity index improver comprising a copolymer (A) having an acid alkyl ester (c) as an essential constituent monomer, wherein the solubility parameter of (A) is 8.5 to 9.6 (cal / Cm ³ ) ^1/2 , and a viscosity index improver in which the total of (b) and (c) is 30 to 65% by weight based on the total number of constituent monomers in (A), the viscosity index improvement A lubricating oil composition comprising an agent and a base oil.

[R ¹ is a hydrogen atom or a methyl group; X ¹ is a group represented by —O—, —O (AO) _n —, —NH— or —NH (AO) _n —; An alkylene group; n is an integer of 1 to 20, and when n is 2 or more, A may be the same or different; R ² is a branched alkyl group having 32 to 44 carbon atoms. ]

[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 an alkyl having 1 to 8 carbon atoms; Group; p is an integer of 1 to 20, and R ⁴ when p is 2 or more may be the same or different. ]

  The lubricating oil composition containing the viscosity index improver of the present invention has a high viscosity index improving effect and an effect of being excellent in shear stability.

  The viscosity index improver of the present invention has (a) represented by the general formula (1), (b) represented by the general formula (2), and a linear alkyl group having 1 to 4 carbon atoms ( It comprises a copolymer (A) having a (meth) acrylic acid alkyl ester (c) as an essential constituent monomer. In addition, (meth) acrylic acid means acrylic acid or methacrylic acid.

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

X ¹ in the general formula (1) is a group represented by —O—, —O (AO) _n —, —NH—, or —NH (AO) _n —. Among these, groups represented by —O— and —O (AO) _n — are preferable from the viewpoint of the effect of improving the viscosity index.

A ¹ in the general formula (1) is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, 1,2- or 1,3-propylene group, and 1,2-, 1,3- or 1,4-butylene group. Among these, the ethylene group and the 1,2-propylene group are preferable from the viewpoint of the effect of improving the viscosity index.

In the general formula (1), n is an integer of 1 to 20 in the case of 1 or more, preferably an integer of 1 to 5, more preferably 1 to 2, from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity. It is an integer.
When n is 2 or more, A may be the same or different, and (AO) _n part may be a random bond or a block bond.

R ² in the general formula (1) is a branched alkyl group having 32 to 44 carbon atoms.
Examples of the branched alkyl group having 32 to 44 carbon atoms include 2-tetradecyloctadecyl group, 2-tetradecylicosyl group, 2-hexadecyloctadecyl group, 2-hexadecylicosyl group, and 2-isohexadecylisoicosyl. Group, 2-octadecyl docosyl, 2-icosyl tetracosyl, olefin [for example, propylene oligomer (11 to 14 mer), ethylene / propylene oligomer (14 to 20 mer, molar ratio 20/1 to 1/14) And a residue obtained by removing a hydroxyl group from an oxo alcohol obtained from an isobutene oligomer (8 to 11-mer).
Of the branched alkyl groups having 32 to 44 carbon atoms, preferred from the viewpoint of the effect of improving the viscosity index is
A branched alkyl group having 32 to 40 carbon atoms, more preferred is a branched alkyl group having 32 to 36 carbon atoms, and particularly preferred is a branched alkyl group having 32 to 36 carbon atoms branched at the 2-position of the alkyl group. .

  The proportion of (a) constituting (A) is preferably 30 to 70% by weight based on the weight of (A), from the viewpoint of the effect of improving the viscosity index and the shear stability of the lubricating oil composition. From the viewpoint of the effect of improving the index and the shear stability of the lubricating oil composition, it is preferably 33 to 68% by weight, more preferably 34 to 66% by weight, and particularly preferably 35 to 64% by weight.

The copolymer (A) in the present invention has (b) represented by the general formula (2) as an essential constituent monomer. R ³ in the general formula (2) is a hydrogen atom or a methyl group. Among these, a methyl group is preferable from the viewpoint of improving the viscosity index.

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

P 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 the effect of improving the viscosity index and the low temperature viscosity.
When p is 2 or more, A may be the same or different, and the (R ⁴ O) _p moiety may be a random bond or a block bond.

R ⁵ in the general formula (2) is an alkyl group having 1 to 8 carbon atoms. Specifically, methyl group, ethyl group, n-propyl, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-heptyl group, isoheptyl group, n-hexyl group, 2-ethylhexyl group, n -A pentyl group and n-octyl group are mentioned.
Among the alkyl groups having 1 to 8 carbon atoms, the alkyl group having 1 to 6 carbon atoms is preferable from the viewpoint of the viscosity index, the alkyl group having 1 to 5 carbon atoms is more preferable, and the alkyl group having 1 to 5 carbon atoms is particularly preferable. 4 alkyl groups.

Specific examples of the monomer (b) include methoxyethyl methacrylate, methoxypropyl methacrylate, methoxybutyl methacrylate, methoxypentyl methacrylate, methoxyhexyl methacrylate, methoxyheptyl methacrylate, methoxyoctyl methacrylate, ethoxy methacrylate. Ethyl, ethoxypropyl methacrylate, ethoxybutyl methacrylate, ethoxyheptyl methacrylate, ethoxyhexyl methacrylate, ethoxypentyl methacrylate, ethoxyoctyl methacrylate, proxy methyl methacrylate, proxy ethyl methacrylate, proxy propyl methacrylate, proxy butyl methacrylate , Proxy heptyl methacrylate, Proxy hexyl methacrylate, Proxy pentyl methacrylate, Proxy methacrylate Cutyl, butoxymethyl methacrylate, butoxyethyl methacrylate, butoxypropyl methacrylate, butoxybutyl methacrylate, butoxyheptyl methacrylate, butoxyhexyl methacrylate, butoxypentyl methacrylate, butoxyoctyl methacrylate, and alcohols having 1 to 8 carbon atoms Examples include those obtained by adding 2 to 20 moles of ethylene oxide to butylene oxide and (meth) acrylic acid esters.
Among the monomers (b), methoxyethyl methacrylate, ethoxyethyl methacrylate, and butoxyethyl methacrylate are preferable from the viewpoint of the viscosity index.

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

Examples of the (meth) acrylic acid alkyl ester (c) having a linear alkyl group having 1 to 4 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and (meth) ) N-butyl acrylate.
Among (c), preferred are (meth) acrylic acid esters having a linear alkyl group having 1 to 3 carbon atoms, and more preferred are methyl (meth) acrylate and ethyl (meth) acrylate, Particularly preferred is methyl (meth) acrylate.

The total of (b) and (c) constituting (A) is 30 to 70% by weight based on the weight of (A), from the viewpoint of the effect of improving the viscosity index and the shear stability of the lubricating oil composition. , Preferably 32 to 67% by weight, more preferably 34 to 66% by weight, particularly preferably 36 to 65% by weight.
The weight ratio (b / c) of (b) and (c) constituting (A) is preferably 1/99 to 99/1 from the viewpoint of the effect of improving the viscosity index and the shear stability of the lubricating oil composition. More preferably 10/90 to 90/10, and particularly preferably 20/80 to 80/20.

  (A) further includes monomers (a), (b) and (c), and (meth) acrylic acid alkyl ester (d) having a branched alkyl group having 16 to 28 carbon atoms as a constituent monomer. From the viewpoint of viscosity index improvement effect and shear stability, the copolymer is preferably used.

Examples of the (meth) acrylic acid alkyl ester (d) having a branched alkyl group having 16 to 28 carbon atoms include isohexadecyl group, 2-octylnonyl group, 2-hexylundecyl group, 2-ethylpentadecyl group, 2 -(3-methylhexyl) -7-methyl-nonyl group, isooctadecyl group, 1-hexyltridecyl group, 2-ethylheptadecyl group, 2-octylundecyl group, isoicosyl group, 1-undecyldodecyl group, Examples include 1-octylpentadecyl group, 2-decyltridecyl group, 2-decyltetradecyl group, 2-dodecylpentadecyl group, and the like.
Of these, (d) is preferably a (meth) acrylic acid alkyl ester having a branched alkyl group having 18 to 28 carbon atoms, and more preferably a (meth) acrylic acid having a branched alkyl group having 20 to 28 carbon atoms. Esters, particularly preferred are (meth) acrylic acid esters having a branched alkyl group having 24 to 28 carbon atoms.

  The proportion of (d) constituting (A) is preferably 0.01 to 40% by weight based on the weight of (A), from the viewpoint of viscosity index effect and shear stability, when (d) is used. More preferably, it is 5 to 35% by weight, particularly preferably 10 to 30% by weight.

(A) is a nitrogen atom-containing monomer (e) excluding monomers (a) and (b), a hydroxyl group-containing monomer (f), and a phosphorus atom-containing monomer (g). A copolymer having at least one selected monomer as a constituent monomer is preferable from the viewpoint of the effect of improving the viscosity index.
Examples of the nitrogen atom-containing monomer (e) include the following monomers (e1) to (e4) excluding the monomers (a) and (b).

Amide group-containing monomer (e1):
(Meth) acrylamide, monoalkyl (meth) acrylamide [one having an alkyl group having 1 to 4 carbon atoms bonded to a nitrogen atom; for example, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (Meth) acrylamide and Nn- or isobutyl (meth) acrylamide etc.], N- (N′-monoalkylaminoalkyl) (meth) acrylamide [one alkyl group having 1 to 4 carbon atoms bound to the nitrogen atom. Those having an aminoalkyl group (2 to 6 carbon atoms); for example, N- (N′-methylaminoethyl) (meth) acrylamide, N- (N′-ethylaminoethyl) (meth) acrylamide, N- (N ′ -Isopropylamino-n-butyl) (meth) acrylamide and N- (N'-n- or isobutylamino-n-butyl) ) (Meth) acrylamide etc.], dialkyl (meth) acrylamide [nitrogen atom having two C1-C4 alkyl groups bonded; for example, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meta ) Acrylamide, N, N-diisopropyl (meth) acrylamide and N, N-di-n-butyl (meth) acrylamide etc.], N- (N ′, N′-dialkylaminoalkyl) (meth) acrylamide [aminoalkyl group Having an aminoalkyl group (2 to 6 carbon atoms) in which two alkyl groups having 1 to 4 carbon atoms are bonded to the nitrogen atom of, for example, N- (N ′, N′-dimethylaminoethyl) (meth) acrylamide, N- (N ′, N′-diethylaminoethyl) (meth) acrylamide, N- (N ′, N′-dimethylaminopropyl) (meth) acrylic And N- (N ′, N′-di-n-butylaminobutyl) (meth) acrylamide etc.]; N-vinylcarboxylic acid amide [N-vinylformamide, N-vinylacetamide, N-vinyl-n- or Isopropionic acid amide, N-vinylhydroxyacetamide and the like] and the like.

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

Primary to tertiary amino group-containing monomer (e3):
Primary amino group-containing monomer {C3-C6 alkenylamine [(meth) allylamine, crotylamine, etc.], Aminoalkyl (C2-C6) (meth) acrylate [Aminoethyl (meth) acrylate, etc.}} Secondary amino group-containing monomer {monoalkylaminoalkyl (meth) acrylate [having an aminoalkyl group (2 to 6 carbon atoms) in which one alkyl group having 1 to 6 carbon atoms is bonded to a nitrogen atom; Nt-butylaminoethyl (meth) acrylate and N-methylaminoethyl (meth) acrylate, etc.], C6-C12 dialkenylamine [di (meth) allylamine, etc.]}; tertiary amino group-containing single amount Body {dialkylaminoalkyl (meth) acrylate [an aminoalkyl group in which two alkyl groups having 1 to 6 carbon atoms are bonded to a nitrogen atom (carbon Having 2 to 6); for example, N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate, etc.], alicyclic (meth) acrylate having a nitrogen atom [morpholinoethyl ( Meth) acrylates, etc.], aromatic monomers [N- (N ′, N′-diphenylaminoethyl) (meth) acrylamide, N, N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N -Vinyl pyrrole, N-vinyl pyrrolidone, N-vinyl thiopyrrolidone, etc.]} and their hydrochlorides, sulfates, phosphates or lower alkyl (C1-8) monocarboxylic acids (such as acetic acid and propionic acid) Examples include salts.

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

  Of these, (e) is preferably (e1) and (e3), more preferably N- (N ′, N′-diphenylaminoethyl) (meth) acrylamide, N- (N ′, N′-dimethyl). Aminoethyl) (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 (f):
Hydroxyl group-containing aromatic monomer (p-hydroxystyrene and the like), hydroxyalkyl (2 to 6 carbon atoms) (meth) acrylate [2-hydroxyethyl (meth) acrylate, and 2- or 3-hydroxypropyl (meth) acrylate Etc.], mono- or bis-hydroxyalkyl (C1-C4) substituted (meth) acrylamide [N, N-bis (hydroxymethyl) (meth) acrylamide, N, N-bis (hydroxypropyl) (meth) acrylamide N, N-bis (2-hydroxybutyl) (meth) acrylamide etc.], vinyl alcohol, alkenol having 3 to 12 carbon atoms [(meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol and 1 -Undecenol and the like], an alkene monool having 4 to 12 carbon atoms, or Lucenediol [1-buten-3-ol, 2-buten-1-ol, 2-butene-1,4-diol, etc.], hydroxyalkyl (C1-6) alkenyl (C3-10) ether (2 -Hydroxyethylpropenyl ether, etc.), polyvalent (3-8 valent) alcohols (glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, saccharides, sucrose, etc.) alkenyl (carbon number 3-10) ether or (meth) acrylate [Sucrose (meth) allyl ether etc.] etc .;
Polyoxyalkylene glycol (alkylene group having 2 to 4 carbon atoms, polymerization degree 2 to 50), polyoxyalkylene polyol [polyoxyalkylene ether of 3 to 8 valent alcohol (alkylene group having 2 to 4 carbon atoms, polymerization degree) 2-100)], mono (meth) acrylates of polyoxyalkylene glycol or polyoxyalkylene polyol alkyl (carbon number 1-4) ether [polyethylene glycol (Mn: 100-300) mono (meth) acrylate, polypropylene glycol ( Mn: 130-500) mono (meth) acrylate, methoxypolyethylene glycol (Mn: 110-310) (meth) acrylate, lauryl alcohol ethylene oxide adduct (2-30 mol) (meth) acrylate and mono (meth) acryl Polyoxyethylene (Mn: 150 to 230), sorbitan, etc.] or the like; and the like.

  Preferred among (f) are 2-hydroxyethyl (meth) acrylate, 2- or 3-hydroxypropyl (meth) acrylate, and N, N-bis (hydroxypropyl) (meth) acrylamide.

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

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

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

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

  (A) may use the following monomers (h) to (o) as constituent monomers in addition to the monomers (a) to (g).

(Meth) acrylic acid alkyl ester having linear alkyl group having 8 to 18 carbon atoms (h)
N-octyl (meth) acrylate, n-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-undecyl (meth) acrylate, n-dodecyl (meth) acrylate, (meth) acrylic acid Examples include n-tridecyl, n-tetradecyl (meth) acrylate, n-pentadecyl (meth) acrylate, n-hexadecyl (meth) acrylate, and n-octadecyl (meth) acrylate.

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

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

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

Vinyl esters, vinyl ethers, vinyl ketones (l):
Vinyl esters of saturated fatty acids having 2 to 12 carbon atoms (such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl octoate), alkyl, aryl or alkoxyalkyl vinyl ethers having 1 to 12 carbon atoms (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether) Butyl vinyl ether, 2-ethylhexyl vinyl ether, phenyl vinyl ether, vinyl-2-methoxyethyl ether and vinyl-2-butoxyethyl ether) and alkyl or aryl vinyl ketones having 1 to 8 carbon atoms (methyl vinyl ketone, ethyl vinyl ketone and Phenyl vinyl ketone, etc.).

Epoxy group-containing monomer (m):
Examples thereof include glycidyl (meth) acrylate and glycidyl (meth) allyl ether.

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

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

  The ratio of (e) to (o) constituting (A) is preferably independently selected based on the weight of (A) from the viewpoint of the effect of improving the viscosity index when using (e) to (o). Is 0.01 to 10% by weight, more preferably 1 to 7% by weight, and particularly preferably 2 to 5% by weight.

  The weight average molecular weight (hereinafter abbreviated as Mw) of (A) is preferably 5,000 to 2,000,000 from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition, and a more preferable range is Depends on the use of the lubricating oil composition, and is in the range shown in Table 1.

* ：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-continuous variable transmission oil
***: Manual transmission oil

In addition, Mw of (A) can be measured on condition of the following by gel permeation chromatography.
<Measurement conditions of Mw>
Apparatus: “HLC-802A” [manufactured by Tosoh Corporation]
Column: 2 “TSK gel GMH6” Measurement temperature: 40 ° C.
Sample solution: 0.5 wt% tetrahydrofuran solution Solution injection amount: 200 μl
Detector: Refractive index detector Standard: Polystyrene

The solubility parameter (hereinafter abbreviated as SP value) of (A) is preferably 8.5 to 9.6 (cal / cm ³ ) ¹ from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. ^{/ 2} , more preferably 9.0 to 9.5 (cal / cm ³ ) ^1/2 , and particularly preferably 9.1 to 9.4 (cal / cm ³ ) ^1/2 .
The SP value of (A) is a value calculated by the method described in the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2 P. 147 to 154).
The SP value of (A) is calculated based on the SP value of each monomer constituting (A) by the above method, and the SP value of each monomer is based on the mole fraction of the constituent monomer units. The average value.
The SP value of (A) can be adjusted to 8.5 to 9.6 (cal / cm ³ ) ^1/2 by appropriately adjusting the SP value and molar fraction of the monomer used.

  The absolute value of the difference between the SP value of (A) and the SP value of the base oil is preferably 0.5 to 1.5, more preferably from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. It is 0.6 to 1.1, particularly preferably 0.7 to 1.0.

The crystallization temperature of (A) is preferably 0 ° C. or lower, more preferably −10 ° C. or lower, particularly preferably −20 ° C. or lower.
The crystallization temperature of (A) was determined by using a differential scanning calorimeter “UNIX (registered trademark) DSC7” (manufactured by PERKIN-ELMER), using 5 mg of a viscosity index improver as a sample, and an isothermal rate of 10 ° C./min. Is the crystallization temperature observed when cooled from 100 ° C. to −60 ° C.

(A) can be obtained by a known production method, and specifically includes a method obtained by solution polymerization of the 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.
As radical polymerization initiators, known azo initiators (such as 2,2-azobis (2-methylbutyronitrile) and 2,2-azobis (2,4-dimethylvaleronitrile)), peroxide initiators Agents (benzoyl peroxide, cumyl peroxide, lauryl peroxide, etc.) and redox initiators (a mixture of benzoyl peroxide and tertiary amine, etc.). Furthermore, if necessary, a known chain transfer agent (such as an alkyl mercaptan having 2 to 20 carbon atoms) can also be used.
The polymerization temperature is preferably 25 to 140 ° C, more preferably 50 to 120 ° C. In addition to the above solution polymerization, (A) can be obtained by bulk polymerization, emulsion polymerization or suspension polymerization.
The polymerization form of (A) may be either a random addition polymer or an alternating copolymer, and may be either a graft copolymer or a block copolymer.

The viscosity index improver of the present invention may be used in combination with (A) and an alkyl (meth) acrylic acid ester (co) polymer (B) other than (A).
(B) is not particularly limited as long as it is an alkyl (meth) acrylate polymer other than (A), but (meth) acrylic acid alkyl ester having a linear alkyl group having 1 to 15 carbon atoms, etc. Can be mentioned.
Specific examples of (B) include n-octadecyl methacrylate / n-dodecyl methacrylate (molar ratio 10-30 / 90-70) copolymer, n-tetradecyl methacrylate / n-dodecyl methacrylate (molar ratio 10). -30 / 90-70) Copolymer, n-hexadecyl methacrylate / n-dodecyl methacrylate / methyl methacrylate (molar ratio 20-40 / 55-75 / 0-10) copolymer and n-dodecyl acrylate / N-dodecyl methacrylate (molar ratio 10 to 40/90 to 60) copolymer and the like, and these may be used alone or in combination of two or more.

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

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

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

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

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

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

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

<Examples 1-12, Comparative Examples 1-8>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a nitrogen blowing tube and a decompression device, base oil A (SP value: 8.3, kinematic viscosity at 100 ° C .: 2.2 mm ² / s, Viscosity index: 105) 100 parts were charged, and in another glass beaker, 100 parts by weight of the monomers listed in Table 2, 0.6 part by weight of dodecyl mercaptan as a chain transfer agent, 2,2-azobis (2, 4-dimethylvaleronitrile) 0.5 part by weight and 2,2-azobis (2-methylbutyronitrile) 0.2 part by weight are added, and stirred and mixed at 20 ° C. to prepare a monomer solution. It was put into a dropping funnel. After performing nitrogen substitution (gas phase oxygen concentration: 100 ppm or less) in the gas phase part of the reaction vessel, the monomer solution was dropped over 2 hours while maintaining the internal temperature of the system in a sealed state at 70 to 85 ° C. After aging at 85 ° C. for 2 hours after completion, the temperature was raised to 120 to 130 ° C., and unreacted monomers were removed at the same temperature under reduced pressure (0.027 to 0.040 MPa) over 2 hours. Viscosity index improvers (R1) to (R12) and (S1) to (S8) comprising the polymers (A1) to (A12) and (H1) to (H8) were obtained. The SP values of the obtained copolymers (A1) to (A12) and (H1) to (H8) were calculated by the above method, and Mw was measured by the above method. Moreover, the base oil solubility of the viscosity index improver was evaluated by the following method. The results are shown in Tables 2 and 3.

<Evaluation method of base oil solubility of viscosity index improver>
10 parts by weight of viscosity index improvers (R1) to (R12) and (S1) to (S8) are added to the base oil A, the appearance at room temperature is visually observed, and the base oil solubility is evaluated according to the following evaluation criteria. did.
[Evaluation criteria]
○: Appearance is uniform and there is no insoluble matter in the copolymer ×: Appearance is inhomogeneous and insoluble matter in the copolymer is observed

The compositions of the monomers (a) to (h) described in Table 2 are as described below.
(A-1): 2-tetradecyloctadecyl methacrylate (a-2): 2-hexadecylicosyl methacrylate (a-3): 2-icosyltetracosyl methacrylate (b-1): methacrylic acid Methoxyethyl (b-2): Ethoxyethyl methacrylate (b-3): Butoxyethyl methacrylate (b-4): Hexoxyethyl methacrylate (c-1): Methyl methacrylate (c-1): Ethyl methacrylate ( d-1): 2-decyltetradecyl methacrylate (d-2): 2-dodecylhexadecyl methacrylate (e-1): N, N-dimethylaminoethyl methacrylate (f-1): 2-hydroxyethyl methacrylate (G-1): Methacryloyloxyethyl phosphate (h-1): Hexadecyl methacrylate (h-2): Meta Lil octadecyl

<Examples 13-24, Comparative Examples 9-13>
A base oil A (SP value: 8.3, kinematic viscosity at 100 ° C .: 2.2 mm ² / s, viscosity index: 105) is put into a stainless steel container equipped with a stirrer, and the resulting lubricating oil composition is obtained. Viscosity index improvers (R1) to (R12), (S1), (S2) to (S6), (S8) so that the 100 ° C. kinematic viscosity is 5.00 ± 0.02 (mm ² / s). ) Were added to obtain lubricating oil compositions (V1) to (V12), (W1), (W2) to (W6), and (W8). The viscosity index improvers (S3), (S4), and (S7) were not evaluated because there were insolubles.
Lubricating oil compositions (V1) to (V12), (W1), (W2) to (W6), (W8) viscosity index, 40 ° C. kinematic viscosity, shear stability and low temperature viscosity (−40 ° C.) Measured by the method. The results are shown in Table 3.

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

<Method for measuring low temperature viscosity of lubricating oil composition>
The viscosity at −40 ° C. was measured by the method of ASTM D 2983.
<Measurement Method of Shear Stability (SS) of Lubricating Oil Composition>
Lubricating oil composition for gear oil: Measured by the method of ASTM D 2603.

  As is clear from the results in Table 3, the lubricating oil compositions (Examples 13 to 24) containing the viscosity index improver of the present invention were compared with the lubricating oil compositions of Comparative Examples 8 to 13, The effect of improving the viscosity index is high, the shear stability is low, and the low-temperature viscosity is low.

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

Claims (8)

The monomer (a) represented by the following general formula (1), the monomer (b) represented by the following general formula (2), and the alkyl group having 1 to 4 carbon atoms (meth) A viscosity index improver comprising a copolymer (A) having an alkyl acrylate ester (c) as an essential constituent monomer, wherein (b) is a constituent monomer based on the weight of (A). ) And (c) is a viscosity index improver of 30 to 70% by weight.

[R ¹ is a hydrogen atom or a methyl group; X ¹ is a group represented by —O—, —O (AO) _n —, —NH— or —NH (AO) _n —; An alkylene group; n is an integer of 1 to 20, and when n is 2 or more, A may be the same or different; R ² is a branched alkyl group having 32 to 44 carbon atoms. ]

[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 an alkyl having 1 to 8 carbon atoms; Group; p is an integer of 1 to 20, and R ⁴ when p is 2 or more may be the same or different. ] Viscosity index improver according to claim 1 solubility parameter is 8.5~9.6 (cal ^/ cm ^{3) 1/2} of (A).   The viscosity index improver according to claim 1 or 2, wherein (A) has a weight average molecular weight of 5,000 to 2,000,000.   The copolymer (A) is a copolymer having (meth) acrylic acid alkyl ester (d) having 16 to 28 carbon atoms in the branched alkyl group as a constituent monomer. Viscosity index improver.   (A) is further from the group consisting of a nitrogen atom-containing monomer (e), a hydroxyl group-containing monomer (f) and a phosphorus atom-containing monomer (g) excluding the monomers (a) and (b). The viscosity index improver according to any one of claims 1 to 4, which is a copolymer having one or more selected constituent monomers as constituent monomers.   A lubricating oil composition comprising the viscosity index improver according to any one of claims 1 to 5 and a base oil.   The lubricating oil composition according to claim 6, wherein the absolute value of the difference between the solubility parameter of (A) and the solubility parameter of the base oil is 0.5 to 1.5.   Furthermore, it contains one or more additives selected from the group consisting of detergents, dispersants, antioxidants, oiliness improvers, friction wear modifiers, extreme pressure agents, antifoaming agents, anti-emulsifiers and corrosion inhibitors. The lubricating oil composition according to claim 7.