JP2016028138A - Viscosity index improver and lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity index improver which realizes a lubricant composition with high metal friction reducibility, excellent shear stability and low HTHS viscosity, and hardly increases low-temperature viscosity.SOLUTION: A viscosity index improver comprises a copolymer (A) comprising a monomer (a) represented by the general formula (1) as an essential constituent monomer. [Ris H or a methyl group; Xis O or NH; Rare C2-4 linear or branched alkylene groups; p is an integer from 0 to 20; when p is 2 or more, Rmay be identical or different, and (RO)moiety may have random bonds or block bonds; Y is a C1-5 linear or branched alkylene group; and Rare each independently a C1-8 alkyl group.]SELECTED DRAWING: None

Description

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

In recent years, in order to reduce CO ₂ emissions and protect petroleum resources, fuel consumption of automobiles has been further demanded. One way to save fuel is to reduce viscous resistance by reducing the viscosity of engine oil. However, when the viscosity is lowered, problems such as seizure due to metal contact on the piston / cylinder surface and the like arise. For this problem, it is common to use additives that are adsorbed or oriented on the metal surface, such as friction reducers and extreme pressure agents. It is desired. On the other hand, a viscosity index improver provided with a functional group having metal adsorption ability has been proposed. Examples of such a viscosity index improver include a hydroxyl group-containing viscosity index improver (Patent Document 1), a phosphate group-containing viscosity index improver (Patent Document 2), and a polysiloxane moiety-containing viscosity index improver (Patent Document 3). Etc. are known.
However, the above viscosity index improver, when added to an engine oil composition, does not have sufficient metal frictional ability, is still not sufficient for reducing the 100 ° C. HTHS viscosity, and is susceptible to viscosity reduction due to shearing, There was a problem that the viscosity at low temperature increased.

Japanese Patent No. 2732187 Japanese Patent No. 5122875 JP 2013-209553 A

  The object of the present invention is that the lubricating oil composition has a high metal friction reducing ability, the lubricating oil composition has excellent shear stability, the lubricating oil composition has a low HTHS viscosity, and the lubricating oil composition does not easily increase the low-temperature viscosity. It is to provide a viscosity index improver.

As a result of intensive studies, the present inventors have arrived at the present invention. That is, the present invention provides a viscosity index improver containing a (co) polymer (A) having the monomer (a) represented by the following general formula (1) as an essential constituent monomer, and 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— or —NH—, R ² is a linear or branched alkylene group having 2 to 4 carbon atoms, p Is an integer of 0 to 20, and when p is 2 or more, R ² may be the same or different, and the (R ² O) _p moiety may be a random bond or a block bond; To 5 linear or branched alkylene groups; each R ³ is independently an alkyl group having 1 to 8 carbon atoms]

  The lubricating oil composition containing the viscosity index improver of the present invention has the effect that the lubricating oil composition has a low HTHS viscosity, is excellent in fuel economy, and is difficult to increase the low temperature viscosity of the lubricating oil composition.

  The (co) polymer (A) in the present invention has the monomer (a) represented by the general formula (1) as an essential constituent monomer. “(Co) polymerization” means homopolymerization or copolymerization.

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

-X ¹ in the general formula (1) - is a group represented by -O- or -NH-. Of these, —O— is preferable from the viewpoint of solubility in base oil.

R ² in the general formula (1) is a linear or branched alkylene group having 2 to 4 carbon atoms, and examples thereof include an ethylene group, a propylene group, and a butylene group. Examples of propylene groups include 1,2- or 1,3-propylene groups.
Examples of the butylene group include 1,2-, 1,3- or 1,4-butylene groups. Among these, preferred are an ethylene group and a propylene group, which are linear or branched alkylene groups having 2 to 3 carbon atoms, from the viewpoint of the effect of improving the viscosity index.

P in the general formula (1) is an integer of 0 to 20, and preferably an integer of 0 to 10 from the viewpoint of solubility in base oil and low temperature viscosity of the lubricating oil composition. More preferably, it is an integer of 0-5. R ² when p is 2 or more may be the same or different, and when they are different, they may be random bonds or block bonds. From the viewpoint of the low temperature viscosity of the lubricating oil composition, a random bond is preferred.

  Y in General formula (1) is a C1-C5 linear or branched alkylene group, and a methylene group, ethylene group, a propylene group, a butylene group, etc. are mentioned. Examples of propylene groups include 1,2- or 1,3-propylene groups. Examples of the butylene group include 1,2-, 1,3- or 1,4-butylene groups. Among these, a linear or branched alkylene group having 1 to 3 carbon atoms is preferable from the viewpoint of the effect of improving the viscosity index.

R < ³ > in General formula (1) is a C1-C8 alkyl group each independently, and a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group etc. are mentioned. Among these, a methyl group, an ethyl group, a propyl group, and a butyl group are preferable from the viewpoint of friction reduction ability and solubility in a base oil, and a methyl group that is an alkyl group having 1 to 2 carbon atoms is more preferable. , An ethyl group.

The solubility parameter (SP value) of (A) is 7.3 to 9.8 (cal / cm ³ ) ^1/2 , preferably from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. It is 9.0-9.5 (cal / cm < ³ >) < ^1/2 >, More preferably, it is 9.1-9.3 (cal / cm < ³ >) < ^1/2 >.
The SP value of (A) is calculated based on the SP value of each monomer constituting (A) by the above method, and the SP value of each monomer is based on the mole fraction of the constituent monomer units. The average value.
The SP value of (A) can be adjusted to 7.3 to 9.8 (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 1.6 (cal / cm ³ ) ¹ from the viewpoint of the effect of improving the viscosity index and the solubility in the lubricating oil. ^{/ 2} , more preferably 0.6 to 1.2 (cal / cm ³ ) ^1/2 , and particularly preferably 0.7 to 1.0 (cal / cm ³ ) ^1/2 .

  (A) is a (meth) acrylic acid alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms in addition to the monomer (a), a straight chain having 12 to 36 carbon atoms in the alkyl group. A copolymer having a (meth) acrylic acid alkyl ester (c) having a chain alkyl group as a constituent monomer is preferred from the viewpoint of the effect of improving the viscosity index and the fuel efficiency.

  Examples of (meth) acrylic acid alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms of the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, and n-propyl (meth) acrylate. And n-butyl (meth) acrylate. Among (b), preferred are methyl (meth) acrylate and n-butyl (meth) acrylate, more preferred are methyl (meth) acrylate, and particularly preferred is methyl methacrylate.

Examples of the (meth) acrylic acid alkyl ester (c) having a linear alkyl group having 12 to 36 carbon atoms of the alkyl group include (meth) acrylic acid n-dodecyl, (meth) acrylic acid n-tetradecyl, and (meth) acrylic. N-pentadecyl acid, n-hexadecyl (meth) acrylate, n-octadecyl (meth) acrylate, n-icosyl (meth) acrylate, n-tetracosyl (meth) acrylate, n-triacontyl (meth) acrylate, Examples include (meth) acrylic acid n-hexatriacontyl.
Among (c), a (meth) acrylic acid alkyl ester having a linear alkyl group having 12 to 30 carbon atoms in the alkyl group is preferable, and a linear alkyl having 14 to 24 carbon atoms in the alkyl group is more preferable. A (meth) acrylic acid ester having a straight chain alkyl having 16 to 22 carbon atoms in the alkyl group is particularly preferred.

(A) is preferably a copolymer having the monomer (d) represented by the general formula (2) as a constituent monomer, from the viewpoint of the effect of improving the viscosity index.
[R ⁴ is a hydrogen atom or a methyl group; —X ² — is a group represented by —O—, —O (AO) _m — or —NH—, and A is a straight chain having 2 to 4 carbon atoms or a branched alkylene group, m is an integer of 0 to 20, a when m is 2 or more may be the same or different, (AO) _m moiety may be block also coupled with a random bond; is R ⁵ A residue obtained by removing one hydrogen atom from a hydrocarbon polymer having isobutylene and / or 1,2-butylene as an essential constituent unit; q is a number of 0 or 1]

R ⁴ in the general formula (2) is a hydrogen atom or a methyl group.

In the general formula (2), —X ² — is a group represented by —O—, —O (AO) _m —, or —NH—, and A is a linear or branched alkylene group having 2 to 4 carbon atoms. Yes, an ethylene group, a propylene group, and a butylene group are mentioned. Examples of propylene groups include 1,2- or 1,3-propylene groups.
Examples of the butylene group include 1,2-, 1,3- or 1,4-butylene groups. Among these, a propylene group and a butylene group are preferable from the viewpoint of solubility in a base oil. m is an integer of 0 to 20, and when m is 2 or more, A may be the same or different, and the (AO) _m moiety may be a random bond or a block bond. Of these, —O— is preferable from the viewpoint of solubility in base oil.

R ⁵ in the general formula (2) is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having isobutylene and / or 1,2-butylene as an essential constituent unit, and q is a number of 0 or 1. .

(A) is preferably a copolymer having the monomer (e) represented by the general formula (3) as a constituent monomer, from the viewpoint of the effect of improving the viscosity index.
[R ⁶ is a hydrogen atom or a methyl group; —X ³ — is a group represented by —O— or —NH—; R ⁷ is a linear or branched alkylene group having 2 to 4 carbon atoms; R ⁸ is 1 carbon atom] A linear alkyl group of ˜8; r is an integer of 1-20, and R ^{7 in} the case where 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 Good. ]

R ⁶ in the general formula (3) is a hydrogen atom or a methyl group.

In formula (3), —X ³ — is a group represented by —O— or —NH—, and among these, —O— is preferable from the viewpoint of solubility in a base oil.

R ⁷ in the general formula (3) is a linear or branched alkylene group having 2 to 4 carbon atoms. Examples of R ⁷ include an ethylene group, a propylene group, and a butylene group. Examples of propylene groups include 1,2- or 1,3-propylene groups.
Examples of the butylene group include 1,2-, 1,3- or 1,4-butylene groups. Of these, ethylene is preferred from the viewpoint of the effect of improving the viscosity index.
In the formula, r is an integer of 1 to 20, and when R is 2 or more, R ⁷ may be the same or different, and the (R ⁷ O) _r moiety may be a random bond or a block bond.

R ⁸ in the general formula (3) is a linear alkyl group having 1 to ⁸ carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-butyl group, an n-hexyl group, and an n-octyl group. From the viewpoint of the effect of improving the viscosity index and the solubility in base oil, a methyl group and an n-butyl group are preferable.

(A) is preferably a copolymer having the monomer (f) represented by the general formula (4) as a constituent monomer, from the viewpoint of the effect of improving the viscosity index.
[R ⁹ is a hydrogen atom or a methyl group; —X ⁴ — is a group represented by —O— or —NH—; R ¹⁰ is a linear or branched alkylene group having 2 to 4 carbon atoms; R ¹¹ and R ¹² are Each independently a linear alkyl group having 4 to 24 carbon atoms; s is an integer of 0 to 20, and when s is 2 or more, R ¹⁰ may be the same or different, and the (R ¹⁰ O) _s moiety is Random coupling or block coupling may be used. ]

R ⁹ in the general formula (4) is a hydrogen atom or a methyl group.

—X ⁴ — in the general formula (4) is a group represented by —O— or —NH—, and among these, —O— is preferable from the viewpoint of solubility in a base oil.

R ¹⁰ in the general formula (4) is a linear or branched alkylene group having 2 to 4 carbon atoms. Examples of R ⁷ include an ethylene group, a propylene group, and a butylene group. Examples of propylene groups include 1,2- or 1,3-propylene groups.
Examples of the butylene group include 1,2-, 1,3- or 1,4-butylene groups. Of these, ethylene is preferred from the viewpoint of the effect of improving the viscosity index.
In the formula, s is an integer of 0 to 20, and when s is 2 or more, R ¹⁰ may be the same or different, and the (R ¹⁰ O) _s moiety may be a random bond or a block bond.

R ¹¹ and R ¹² in the general formula (4) are each independently a linear alkyl group having 4 to 24 carbon atoms, and are an n-butyl group, an n-hexyl group, an n-octyl group, an n-decyl group, an n- A dodecyl group, n-tetradecyl group, n-hexadecyl group, n-octadecyl group, n-undecyl group, n-undodecyl group, n-untetradecyl group, etc. are mentioned. Among these, a combination of linear alkyl groups having a total carbon number of R ¹¹ and R ¹² of ¹² to 40 is more preferable, and a linear alkyl group having a total carbon number of R ¹¹ and R ¹² of 14 to 36 is more preferable. The combination, particularly preferred is a combination of linear alkyl groups having a total carbon number of R ¹¹ and R ¹² of 18 to 32.

In order to improve the viscosity index, (A) further includes a nitrogen atom-containing monomer (excluding (a) and (d) to (f)) (g), a hydroxyl group-containing vinyl monomer (h), And a copolymer having at least one selected from the group consisting of a phosphorus atom-containing vinyl monomer (i) as a constituent monomer.
Examples of the nitrogen atom-containing vinyl monomer (g) include the following monomers (g1) to (g4) other than (a) and (d) to (f).

Amide group-containing vinyl monomer (g1):
(Meth) acrylamide, monoalkylamino (meth) acrylamide [nitrogen atom having one alkyl group having 1 to 4 carbon atoms bonded thereto; for example, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N- Isopropyl (meth) acrylamide and Nn- or isobutyl (meth) acrylamide, etc.], monoalkylaminoalkyl (meth) acrylamide [aminoalkyl group in which one alkyl group having 1 to 4 carbon atoms is bonded to the nitrogen atom (carbon number 2-6); for example N-methylaminoethyl (meth) acrylamide, N-ethylaminoethyl (meth) acrylamide, N-isopropylamino-n-butyl (meth) acrylamide and Nn- or isobutylamino- n-butyl (meth) acrylamide etc.], dialkyl Mino (meth) acrylamide [nitrogen atom having two alkyl groups having 1 to 4 carbon atoms bonded; for example, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-diisopropyl (Meth) acrylamide and N, N-di-n-butyl (meth) acrylamide, etc.], dialkylaminoalkyl (meth) acrylamide [aminoalkyl group in which two alkyl groups having 1 to 4 carbon atoms are bonded to a nitrogen atom (carbon Having 2 to 6); for example, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide and N, N-di -N-butylaminobutyl (meth) acrylamide etc.], N-vinylcarboxylic acid amide [ - vinyl formamide, N- vinyl acetamide, include those having a N- vinyl -n- or isopropionyl and N- vinyl-hydroxyacetamide etc.] amide groups only on the nitrogen atom and the like.

Nitro group-containing monomer (g2):
4-nitrostyrene etc. are mentioned.

Primary to tertiary amino group-containing vinyl monomer (g3):
Primary amino group-containing vinyl monomer {alkenylamine having 3 to 6 carbon atoms [(meth) allylamine, crotylamine, etc.], aminoalkyl (2 to 6 carbon atoms) (meth) acrylate [aminoethyl (meth) acrylate, etc.] }; Secondary amino group-containing vinyl monomer {monoalkylaminoalkyl (meth) acrylate [having an aminoalkyl group (2 to 6 carbon atoms) in which one alkyl group having 1 to 6 carbon atoms is bonded to a nitrogen atom] For example, t-butylaminoethyl (meth) acrylate and methylaminoethyl (meth) acrylate, etc.], C 6-12 dialkenylamine [di (meth) allylamine, etc.}}; tertiary amino group-containing vinyl monomer {Dialkylaminoalkyl (meth) acrylate [Aminoalkyl having two alkyl groups having 1 to 6 carbon atoms bonded to a nitrogen atom] Having a sulfur group (2 to 6 carbon atoms); for example, dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate, etc.], alicyclic (meth) acrylate having a nitrogen atom [morpholinoethyl (meth) acrylate, etc. ], Aromatic vinyl monomers [N, N-diphenylaminoethyl (meth) acrylamide, N, N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone and N-vinylthiopyrrolidone etc.], and their hydrochlorides, sulfates, phosphates or lower alkyl (C 1-8) monocarboxylic acids (such as acetic acid and propionic acid) salts.

Nitrile group-containing vinyl monomer (g4):
Examples include (meth) acrylonitrile.

  (G) is preferably (g1) and (g3), more preferably N, N-diphenylaminoethyl (meth) acrylamide, dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide. Dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.

Hydroxyl-containing vinyl monomer (h):
Hydroxyl group-containing aromatic vinyl monomer (p-hydroxystyrene and the like), hydroxyalkyl (2 to 6 carbon atoms) (meth) acrylate [2-hydroxyethyl (meth) acrylate, and 2- or 3-hydroxypropyl (meth) 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, C3-C12 alkenol [(meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol and 1-undecenol etc.], carbon Number 4 to 12 alkene monool or alkenegio [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 (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, 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)], poly (oxyalkylene glycol) or poly (oxyalkylene polyol) alkyl (carbon number 1-4) ether mono (meth) acrylate [polyethylene glycol (number average molecular weight, hereinafter abbreviated as Mn: 100-300) mono (Meth) acrylate, polypropylene glycol (Mn: 130 to 500) mono (meth) acrylate, methoxypolyethylene glycol (Mn: 110 to 310) (meth) acrylate, and the like.

  Examples of the phosphorus atom-containing monomer (i) include the following monomers (i1) to (i2).

Phosphoric ester group-containing monomer (i1):
(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.].

Phosphono group-containing monomer (i2):
(Meth) acryloyloxyalkyl (2 to 4 carbon atoms) phosphonic acid [(meth) acryloyloxyethylphosphonic acid etc.] and alkenyl (2 to 12 carbon atoms) phosphonic acid [vinyl phosphonic acid, allyl phosphonic acid and octenyl phosphonic acid Etc.].

  Of (i), (i1) is preferred, (meth) acryloyloxyalkyl (2 to 4 carbon atoms) phosphate is more preferred, and (meth) acryloyloxyethyl phosphate is particularly preferred. It is.

The proportion of (a) constituting (A) is preferably 1 to 60% by weight, more preferably, based on the weight of (A), from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. Is 5 to 50% by weight, particularly preferably 10 to 30% by weight.
The proportion of (b) constituting (A) is preferably 0 to 70% by weight, based on the weight of (A), from the viewpoint of improving the viscosity index and solubility in the lubricating base oil. Preferably it is 5 to 60 weight%, Most preferably, it is 20 to 55 weight%.
The proportion of (c) constituting (A) is preferably 1 to 80% by weight based on the weight of (A) from the viewpoint of solubility in a lubricating base oil and low temperature viscosity of the lubricating oil composition. More preferably 10 to 70% by weight, particularly preferably 15 to 60% by weight.
The proportion of (d) constituting (A) is preferably 1 to 40% by weight, more preferably, based on the weight of (A), from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. Is 5 to 30% by weight, particularly preferably 10 to 25% by weight.
The proportion of (e) constituting (A) is preferably 1 to 30% by weight, more preferably, based on the weight of (A), from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. Is 5 to 25% by weight, particularly preferably 10 to 20% by weight.
The proportion of (f) constituting (A) is preferably 0 to 50% by weight, more preferably, based on the weight of (A), from the viewpoint of the viscosity index improving effect and the low temperature viscosity of the lubricating oil composition. Is 5 to 40% by weight, particularly preferably 10 to 30% by weight.
The proportion of (g) to (i) constituting (A) is preferably 0 to 15% by weight based on the weight of (A), from the viewpoint of the effect of improving the viscosity index and the low temperature viscosity of the lubricating oil composition. More preferably 1 to 10% by weight, particularly preferably 2 to 8% 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. Mw of (A) can be measured by gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions.
<Measurement conditions of Mw of (A)>
Apparatus: “HLC-802A” [manufactured by Tosoh Corporation]
Column: Two “TSK gel GMH6” [manufactured by Tosoh Corporation] Measurement temperature: 40 ° C.
Sample solution: 0.25 wt% tetrahydrofuran solution Solution injection amount: 100 μl
Detection device: Refractive index detector Reference material: Standard polystyrene (TSK standard POLYSTYRENE) 12 points (molecular weight: 500, 1,050, 2,800, 5,970, 9,100, 18,100, 37,900, 96,400) , 190,000, 355,000, 1,090,000, 2,890,000) [manufactured by Tosoh Corporation]

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

The crystallization temperature of (A) is preferably −20 ° C. or less, more preferably −30 ° C. or less, particularly preferably −40 ° C. or less, and most preferably −50 ° C. from the viewpoint of the low temperature viscosity of the lubricating oil composition. It is as follows.
The crystallization temperature of (A) was determined by using a differential scanning calorimeter “Unix (registered trademark) DSC7” (manufactured by PERKIN-ELMER), (A) using 5 mg as a sample at an isothermal rate of 10 ° C./min. It is the crystallization temperature observed when cooling 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 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, ethyl acetate, mineral oil, ester oil and the like.
Polymerization catalysts include azo catalysts (azobisisobutyronitrile, azobisvaleronitrile, etc.), peroxide catalysts (benzoyl peroxide, cumyl peroxide, lauryl peroxide, etc.) and redox catalysts (benzoyl peroxide). And a mixture of a tertiary amine and the like. Furthermore, if necessary, a known chain transfer agent (such as an alkyl mercaptan having 2 to 20 carbon atoms) can also be used.
The polymerization temperature is preferably 25 to 150 ° C, more preferably 50 to 130 ° C. In addition to the above solution polymerization, (A) can be obtained by bulk polymerization, emulsion polymerization or suspension polymerization.
When (A) is a copolymer, the polymerization form may be either a random addition polymer or an alternating copolymer, and may be either a graft copolymer or a block copolymer.

The viscosity index improver of the present invention may be used in combination with (A) and an alkyl (meth) acrylate (co) polymer (B) other than (A).
(B) is not particularly limited as long as it is an alkyl (meth) acrylic acid ester (co) polymer other than (A), but a (meth) acrylic acid alkyl ester having a linear alkyl group having 1 to 18 carbon atoms. Examples include (co) polymers.
Specific examples of (B) include n-octadecyl methacrylate / n-dodecyl methacrylate (molar ratio 10-30 / 90-70) copolymer, n-tetradecyl methacrylate / n-dodecyl methacrylate (molar ratio 10). -30 / 90-70) Copolymer, n-hexadecyl methacrylate / n-dodecyl methacrylate / methyl methacrylate (molar ratio 20-40 / 55-75 / 0-10) copolymer and n-dodecyl acrylate / N-dodecyl methacrylate (molar ratio 10 to 40/90 to 60) copolymer and the like, and these may be used alone or in combination of two or more.

  When (A) and (B) are used in combination, the amount of (B) used is preferably 0.01 to 30% by weight based on the weight of (A) from the viewpoint of the low temperature viscosity of the lubricating oil composition. More preferably, it is 0.1 to 20% by weight, particularly preferably 0.3 to 10% by weight.

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

(Measured by JIS-K2283) kinematic viscosity at 100 ° C. of the base oil is preferably from the viewpoint of the viscosity index improving effect is 1 to 15 mm ² / s, more preferably from 2 to 5 mm ² / s.
The viscosity index (measured according to JIS-K2283) of the base oil is preferably 90 or more, more preferably 100 or more, particularly preferably 110 or more, and most preferably 120 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 (A) in the viscosity index improver in the lubricating oil composition of the present invention is preferably 1 to 30% by weight 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, MTF, belt-CVTF, etc.), a base oil having a kinematic viscosity at 100 ° C. of ² to 6 mm ² / s is used. Those containing by weight are preferred.

  The lubricating oil composition of the present invention includes gear oil (differential oil and industrial gear oil, etc.), MTF, transmission oil [ATF and belt-CVTF etc.], traction oil (toroidal-CVTF etc.), shock absorber oil, power steering It is suitably used for oil, hydraulic oil (such as construction machine hydraulic oil and industrial hydraulic oil) and engine oil. Of these, gear oil, MTF, transmission oil, traction oil and engine oil are preferable, and differential oil, MTF, ATF, belt-CVTF and engine oil are more preferable, and MTF and ATF are particularly preferable. , Belt-CVTF and engine oil.

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

  These additives may be used alone, or two or more additives may be used as necessary.

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

<Production Example 1>
In a pressure-resistant reaction vessel made of SUS equipped with a temperature control device and a stirrer, polyunsene containing terminal unsaturated groups (trade name; “NOF Polybutene 200N”, manufactured by NOF Corporation, Mn: 2,650], 530 parts by weight, and 25 parts by weight of maleic anhydride [manufactured by Wako Pure Chemical Industries, Ltd.] was added, and the inside of the container was purged with nitrogen, heated to 220 ° C. with stirring, and subjected to an ene reaction at the same temperature for 4 hours. 0.027 to 0.040 MPa) Unreacted maleic anhydride was removed over 2 hours, followed by cooling to 25 ° C., adding 20 parts by weight of 2-aminoethanol, and raising the temperature to 130 ° C. with stirring. The imidation reaction was carried out at the same temperature for 4 hours, and unreacted 2-aminoalcohol was removed over 5 hours under reduced pressure (0.027 to 0.040 MPa) at 120 to 130 ° C. (M-1) was obtained.

<Examples 1-9, Comparative Examples 1-5>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a nitrogen introduction tube, base oil [SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C .: 4.2 mm ² / s, viscosity index: 128] 200 parts by weight, 100 parts by weight of the monomer blend described in Table 2, 0.5 part by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) and 2,2 ′ -After 0.2 parts by weight of azobis (2-methylbutyronitrile) was added and nitrogen substitution (gas phase oxygen concentration 100 ppm) was performed, the temperature was raised to 76 ° C. with stirring and sealed, and the temperature was 6 at the same temperature. A time polymerization reaction was carried out. After raising the temperature to 120 to 130 ° C., unreacted monomers are removed under reduced pressure (0.027 to 0.040 MPa) at the same temperature over 2 hours, and copolymers (A1) to (A9), (H1 ) To (H5) to obtain viscosity index improvers (R1) to (R9) and (S1) to (S5). The SP values of the obtained copolymers (A1) to (A9) and (H1) to (H5) were calculated by the above method, and Mw was measured using the above GPC. Moreover, the base oil solubility of the viscosity index improvers (R1) to (R9) and (S1) to (S5) was evaluated by the following method. The results are shown in Table 2.

<Evaluation method of base oil solubility of viscosity index improver>
The appearance of the viscosity index improvers (R1) to (R9) and (S1) to (S5) was visually observed, and the base oil solubility was evaluated according to the following evaluation criteria.
[Evaluation criteria]
○: Appearance is uniform and there is no insoluble matter in the copolymer ×: Appearance is inhomogeneous and insoluble matter in the copolymer is observed

The monomers listed in Table 2 are as described below.
(M-2): One-end hydroxyl group-containing polymer of hydrogenated polybutadiene (trade name: Krasol HLBH-5000M, manufactured by Cray Valley, 1,2-butylene ratio: 65 mol%, hydroxyl value: 10.4 mg KOH / g, Mn: 5,000, SP value: 8.3)
(A-1): 3-Methacryloxypropyltrimethoxysilane (trade name: KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.)
(A-2): 3-methacryloxypropyltriethoxysilane (trade name: KBE-503, manufactured by Shin-Etsu Chemical Co., Ltd.)
(A-3): 3-acryloxypropyltrimethoxysilane (trade name: KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd.)
(A-4): 3-methacryloxymethyltriethoxysilane (trade name; SIM6482.0, manufactured by Amax Co., Ltd.)
(B-1): methyl methacrylate (b-2): n-butyl methacrylate (c-1): n-dodecyl methacrylate (c-2): n-tetradecyl methacrylate (c-3): methacrylic acid n-hexadecyl (c-4): n-octadecyl methacrylate (c-5): n-behenyl methacrylate (d-1): methacrylic ester of (M-1) (d-2): (M- 2) Methacrylic ester (e-1): n-butoxyethyl methacrylate (f-1): 2-n-decyl-n-tetradecyl methacrylate (h-1): 2-methacryloyloxyethyl phosphate (trade name) ; Light ester P1-M, manufactured by Kyoeisha Chemical Co., Ltd.)
(I-1): Hydroxyethyl methacrylate

<Examples 10 to 18 and Comparative Examples 6 to 10>
A base oil [SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C .: 4.2 mm ² / s, viscosity index: 128] is put into a stainless steel container equipped with a stirrer. The viscosity index improvers (R1) to (R9) and (S1) to (S5) are added so that the HTHS viscosity at 150 ° C. of the obtained lubricating oil composition is 2.6 (mm ² / s). Thus, lubricating oil compositions (X1) to (X9) and (Y1) to (Y5) were obtained.
Kinematic viscosity (40 ° C., 100 ° C.), viscosity index, HTHS viscosity (100 ° C.), shear stability, low temperature viscosity (−40 ° C.) of lubricating oil compositions (X1) to (X9), (Y1) to (Y5) ), The friction coefficient and the wear scar diameter were measured by the following methods. The results are shown in Table 3.

<Method for Measuring HTHS Viscosity of Lubricating Oil Composition>
HTHS viscosities at 150 ° C and 100 ° C were measured by the method of ASTM D 4683.

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

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

<Method for measuring low temperature viscosity of lubricating oil composition>
Viscosity and yield stress at −40 ° C. were measured by the method of ASTM D 4684. Here, the yield stress of 35 Pa or less indicates that there is no yield stress.

<Measuring method of friction coefficient and wear scar diameter of lubricating oil composition>
High-Frequency-Reciprocating-Rig (manufactured by HFRR PCS Instruments Co., Ltd.), the material of the test steel ball was SUJ2, the diameter of the test steel ball was 6 mm, and the material of the test disk was SUJ2. The test was performed at a load of 7.84 N (800 g), a stroke of 1000 μm, a frequency of 20 Hz, a test time of 60 min, and a temperature of 100 ° C., and the friction coefficient was measured. Moreover, the wear scar diameter was measured after completion | finish of a test.

  As is apparent from the results in Table 3, the lubricating oil compositions (Examples 10 to 18) containing the viscosity index improver of the present invention were compared with the lubricating oil compositions of Comparative Examples 6 to 10, The metal friction reducing ability is high, the shear stability is excellent, the HTHS viscosity of the lubricating oil composition is low, and the low temperature viscosity of the lubricating oil composition is hardly increased.

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 (15)

A viscosity index improver containing a (co) polymer (A) having a monomer (a) represented by the following general formula (1) as an essential constituent monomer.
[R ¹ is a hydrogen atom or a methyl group; —X ¹ — is a group represented by —O— or —NH—, R ² is a linear or branched alkylene group having 2 to 4 carbon atoms, p Is an integer of 0 to 20, and when p is 2 or more, R ² may be the same or different, and the (R ² O) _p moiety may be a random bond or a block bond; To 5 linear or branched alkylene groups; each R ³ is independently an alkyl group having 1 to 8 carbon atoms]   The viscosity index improver according to claim 1, wherein the absolute value of the difference between the solubility parameter of (A) and the solubility parameter of the base oil is 0.5 to 1.6.   The viscosity index improver according to claim 1 or 2, wherein (A) is a copolymer containing 1 to 60% by weight of (a) based on the weight of (A) as a structural unit. In the monomer (a), R ² is a linear or branched alkylene group having 2 to 3 carbon atoms, and R ³ is each independently an alkyl group having 1 to 2 carbon atoms. The viscosity index improver described in 1.   (A) is a (meth) acrylic acid alkyl ester (b) having a linear alkyl group having 1 to 4 carbon atoms as the constituent monomer of (A) and / or an alkyl group having 12 to 12 carbon atoms. The viscosity index improver according to any one of claims 1 to 4, which is a copolymer comprising (meth) acrylic acid alkyl ester (c) having 36 linear alkyl groups.   (A) contains 5 to 50% by weight of (a), 5 to 60% by weight of (b), and 1 to 80% by weight of (c) based on the weight of (A) as a constituent monomer. The viscosity index improver according to claim 5, which is a polymer. The viscosity index improver according to any one of claims 1 to 6, wherein (A) is a copolymer having the monomer (d) represented by the general formula (2) as a constituent monomer.
[R ⁴ is a hydrogen atom or a methyl group; —X ² — is a group represented by —O—, —O (AO) _m — or —NH—, and A is a straight chain having 2 to 4 carbon atoms or a branched alkylene group, m is an integer of 0 to 20, a when m is 2 or more may be the same or different, (AO) _m moiety may be block also coupled with a random bond; is R ⁵ A residue obtained by removing one hydrogen atom from a hydrocarbon polymer having isobutylene and / or 1,2-butylene as an essential constituent unit; q is a number of 0 or 1] The viscosity index improver according to any one of claims 1 to 7, wherein (A) is a copolymer having the monomer (e) represented by the 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 a linear or branched alkylene group having 2 to 4 carbon atoms; R ⁸ is 1 carbon atom] A linear alkyl group of ˜8; r is an integer of 1-20, and R ^{7 in} the case where 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 Good. ] The viscosity index improver according to any one of claims 1 to 8, wherein (A) is a copolymer having the monomer (f) represented by the general formula (4) as a constituent monomer.
[R ⁹ is a hydrogen atom or a methyl group; —X ⁴ — is a group represented by —O— or —NH—; R ¹⁰ is a linear or branched alkylene group having 2 to 4 carbon atoms; R ¹¹ and R ¹² are Each independently a linear alkyl group having 4 to 24 carbon atoms; s is an integer of 0 to 20, and when s is 2 or more, R ¹⁰ may be the same or different, and the (R ¹⁰ O) _s moiety is Random coupling or block coupling may be used. ]   (A) is a nitrogen atom-containing monomer (excluding (a) and (d) to (f)) (g), a hydroxyl group-containing monomer (h), and a phosphorus atom-containing monomer ( The viscosity index improver according to any one of claims 1 to 9, which is a copolymer having at least one selected from the group consisting of i) as a constituent monomer. The weight index molecular weight of (A) is 5,000-2,000,000, The viscosity index improver in any one of Claims 1-10.   Furthermore, the (co) polymer (B) other than (A) is contained in an amount of 0.01 to 30% by weight based on the weight of (A), improving the viscosity index according to any one of claims 1 to 11. Agent.   A lubricating oil composition comprising the viscosity index improver according to any one of claims 1 to 12 and a base oil.   Furthermore, it contains at least one additive selected from the group consisting of detergents, dispersants, antioxidants, oiliness improvers, friction wear modifiers, extreme pressure agents, antifoaming agents, demulsifiers and corrosion inhibitors. The lubricating oil composition according to claim 13. The lubricating oil composition according to claim 13 or 14, wherein the base oil has a kinematic viscosity at 100 ° C of 1 to 15 mm ² / s, and the base oil has a viscosity index of 110 or more.