JP2001214185A - Viscosity index improver and lubricating oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity index improver additive which is highly soluble in base oils and has excellent viscosity properties at low temperatures and a lubricating oil composition. SOLUTION: This viscosity index improver comprises (A) a polymer which contains as essential constitutional units (a) an alkyl (meth)acrylate and (b) the following monomer: a (meth)acrylate of (b5) a compound obtained by adding (b4) an alkylene oxide to (b3) a compound obtained by reacting (b1) a phenolic compound and (b2) a styrene compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a viscosity index improver. More specifically, the present invention relates to a viscosity index improver having excellent viscosity characteristics at low temperatures.

[0002]

2. Description of the Related Art In recent years, there has been an increasing tendency to protect the global environment, and there has been a further demand for more fuel-efficient automobiles. In order to improve the fuel efficiency of automobiles, there is a method of adding a viscosity index improver to engine oil to make it multi-grade. In Japan, nearly 30% of engine oils used in diesel engine vehicles are multi-grade oils to which a viscosity index improver is added. This multi-grade oil uses a viscosity index improver (hereinafter abbreviated as OCP-based viscosity index improver) composed of an ethylene / propylene copolymer. When further fuel economy is required, lower viscosity of the engine oil is required. In this case, the engine oil desirably has a high viscosity index and a low high-temperature high-shear viscosity (hereinafter abbreviated as TBS viscosity).
However, the OCP viscosity index improver has a low viscosity index,
It has the disadvantage of high TBS viscosity and does not contribute to further improvement in fuel economy. On the other hand, an engine oil using a viscosity index improver composed of an alkyl (meth) acrylate polymer (hereinafter abbreviated as a PMA-based viscosity index improver) is OC oil.
Since the viscosity index is higher and the TBS viscosity is lower than when a P-based viscosity index improver is used, more excellent fuel economy can be expected than engine oils using current OCP-based viscosity index improvers. A proposal has been made. For example, PMA-based viscosity index improvers containing a specific (meth) acrylate (Japanese Patent Application No. 9-92687) have been proposed. However, the low-temperature viscosity characteristics are not sufficient, and further improvement is required.

[0003]

As a result of intensive studies, the present inventors have found a PMA-based viscosity index improver excellent in low-temperature properties, and have reached the present invention. That is, the present invention is a viscosity index improver comprising a polymer (A) having an alkyl (meth) acrylate (a) and the following monomer (b) as essential constitutional units, and a lubricating oil composition. Monomer (b); phenols (b1) and styrenes (b)
(Meth) acrylic acid ester of compound (b5) obtained by adding alkylene oxide (b4) to compound (b3) obtained by reacting 2).

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION The alkyl (meth) acrylate (a1) used in the present invention is not particularly limited, but usually has a linear or branched alkyl group having 1 to 24 carbon atoms (meth). ) Acrylate (methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2
-Ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl petamethacrylate, hexadecyl methacrylate, octadecyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate , Tridecyl acrylate, tetradecyl acrylate, pentadecyl petaacrylate, hexadecyl acrylate, octadecyl acrylate, etc.). Among these various (meth) acrylates, an alkyl (meth) acrylate having an alkyl group having 18 or less carbon atoms is preferable from the viewpoint of reducing the amount of coking.

The monomer (b) used in the present invention comprises:
It is a (meth) acrylic acid ester of compound (b5) obtained by adding alkylene oxide (b4) to compound (b3) obtained by reacting styrenes (b2) with phenols (b1).

The phenols (b1) include phenol
And alkyl phenol, allyl phenol and aralkyl phenol. The alkyl group of the alkyl phenol generally has 1 to 20, preferably 1 to 12, carbon atoms. Specific examples of the alkyl phenol include cresol, butyl phenol, octyl phenol, and nonyl phenol. Examples of the allyl group of allylphenol include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group. Specific examples of the allylphenol include phenylphenol, biphenylphenol, and naphthylphenol. No. Examples of the aralkyl group of aralkylphenol include a benzyl group and a phenylethyl group. Specific examples of the aralkylphenol include benzylphenol and phenylethylphenol.

Of these, phenol, cresol, and phenol are preferred from the viewpoint of solubility in base oil and low-temperature characteristics.
Phenylphenol and a mixture of two or more thereof, and more preferably phenol.

The styrenes (b2) include styrene,
Examples thereof include α-methylstyrene, vinyltoluene, and a mixture of two or more thereof, and styrene is preferred from the viewpoint of low-temperature characteristics.

The synthesis of the compound (b3) is not particularly limited, and is generally obtained by a Friedel-Crafts reaction between the above-mentioned phenols (b1) and styrenes (b3). For example, it can be obtained by reacting 1 mol of phenols and 0.5 to 8 mol of styrenes at a temperature of 110 to 140 ° C. in the presence of an acidic catalyst such as a Lewis acid. In (c3), in addition to the styrenes added to the benzene nucleus of the phenols, those obtained by adding styrenes to the benzene nucleus of the styrenes once added, and only the styrenes are polymerized first, The polymer is pheno-
Benzene nuclei of benzenes or those added to benzene nuclei of styrenes once added. Phenols 1
The preferred number of moles of styrenes added per mole is 0.1.
It is 8 to 10 mol, and more preferably 1 to 7 mol.

As the alkylene oxide (b4),
For example, ethylene oxide, propylene oxide,
Isobutylene oxide, 1-butene oxide, 2-
Butene oxide, α-olefin oxide having 5 to 20 carbon atoms, trimethylethylene oxide, tetramethylethylene oxide, styrene oxide, α-methylstyrene oxide, 1,1-diphenylethylene oxide, cyclohexene oxide, oxetane, tetrahydrofuran, tetrahydropyran, Butadiene monoxide, epifluorhydrin, epichlorohydrin, epibromohydrin, glycidol, butyl glycidyl ether, hexyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, 2-
Chloroethyl glycidyl ether and methacryl chloride epoxide. Preferably, it has 2 to 1 carbon atoms.
And alkylene oxides having 2 to 4 carbon atoms. The addition reaction of (b4) is not particularly limited, and may be used alone or in combination of two or more. When two or more types are used together,
Random addition or block addition may be used.

As a method for the addition reaction of the alkylene oxide (b4), (b3) may be used, if necessary, in a suitable solvent (mineral oil, xylene, etc.) and a catalyst [anionic polymerization catalyst (for example, sodium hydroxide, potassium hydroxide). , Hydroxides of alkali metals such as cesium hydroxide; sodium methoxy,
Alkali metal alcoholate compounds such as butoxy sodium, methoxy potassium and butoxy potassium; alkyl amines such as tetrabutylamine; cationic polymerization catalysts (eg, chlorides such as aluminum, antimony, boron, phosphorus, iron, zinc, titanium, etc .; hydrochloric acid, odor) Acids, sulfuric acid, mineral acids such as perchloric acid), coordination anionic polymerization catalysts (for example, metal alkoxides such as triethoxy iron and alkaline earth metal compounds,
Acetylacetone or the like or a combination of an active hydrogen compound and a Lewis acid). From the viewpoints of economy and productivity, synthesis using an anionic polymerization catalyst is preferred. The anionic polymerization can be easily synthesized by adding the alkylene oxide (a1) while heating. The reaction temperature is 70 to 150 ° C., preferably 9 to 150 ° C.
0-130 ° C.

Particularly preferred as (b5) is a compound obtained by adding 1 to 4 moles of an alkylene oxide having 1 to 4 carbon atoms to a reaction product of 1 mole of phenol and 1 to 7 moles of styrene.

The monomer (b) is composed of the above (b5) and (meth)
Obtained by an esterification reaction with acrylic acid. As a method of esterification, a known method, for example, a method using a mineral acid such as sulfuric acid or hydrochloric acid, an organic acid such as aromatic sulfonic acid, or a Lewis acid catalyst such as boron fluoride ether; A method using an organic metal catalyst such as tin octylate; a method using an acidic ion exchange resin as a catalyst; a method using a drying agent such as anhydrous magnesium sulfate; a method using a dehydrating agent such as N, N′-dicyclohexylcarbodiimide; And combinations of the above methods.

The content of the monomer (a2) in the polymer (A) in the present invention is not particularly limited. However, from the viewpoint of low-temperature characteristics, the content of the monomer (a2) is preferably 0.1 to 0.1 based on the weight (A). 5
0.0 wt%, particularly preferably 0.2 to 35.0 wt% based on weight (A).

In the present invention, the copolymer (A) may contain other radically polymerizable monomers (c) as structural units in addition to (a) and (b). Examples thereof include unsaturated mono- and / or polycarboxylic acid esters having 1 to 30 carbon atoms in the alkyl group other than alkyl (meth) acrylate (butyl crotonate, octyl crotonate, dodecyl crotonate, dibutyl maleate, Dioctyl fumarate, dilauryl maleate, distearyl fumarate, dioctyl itaconate, dilauryl itaconate, etc .; vinyl aromatic compounds (styrene, vinyl toluene, etc.); vinyl esters (vinyl acetate, vinyl propionate, etc.); Alpha olefins (decene, dodecene, etc.); carboxylic compounds (maleic anhydride, methacrylic acid, crotonic acid, itaconic acid, etc.); acrolein; conjugated dienes (butadiene, isoprene, chloroprene, etc.); acetylene; substituted acetylene [Alkyl acetylene (propyne, 1-butyne, 1-pentyne, 1-hexyne, etc.), aryl acetylene (phenyl acetylene, p-methylphenyl acetylene, etc.)]; alkyl vinyl ether [usually, linear or branched having 1 to 18 carbon atoms] Alkyl vinyl ethers having an alkyl group (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, hexyl vinyl ether, heptyl vinyl ether, octyl vinyl ether, nonyl vinyl ether, decyl vinyl ether, dodecyl vinyl ether, tridecyl vinyl ether, tetradecyl vinyl ether, pentadecyl Vinyl ether, hexadecyl vinyl ether, octadecyl vinyl ether, etc.]; Alkyl ether having a linear or branched alkyl group having 1 to 18 carbon atoms (methyl allyl ether, ethyl allyl ether, propyl allyl ether, butyl allyl ether, amyl allyl ether, hexyl allyl ether, heptyl allyl ether, Octyl allyl ether, nonyl allyl ether, decyl allyl ether, dodecyl allyl ether, tridecyl allyl ether, tetradecyl allyl ether, pentadecyl allyl ether, hexadecyl allyl ether, octadecyl allyl ether, and the like. Among these, preferred are vinyl aromatic compounds and alkyl vinyl ethers, and particularly preferred are styrene and And alkyl vinyl ethers having 2 to 6 carbon atoms.

The content of the monomer (c) in the polymer (A) in the present invention is not particularly limited, but is usually the weight (A).
0 to 10% by weight based on the weight, preferably 0 to 5% by weight based on the weight body (A).

Further, in the present invention, the copolymer (A) is
If necessary, one or more monomers (d) having at least one atom selected from a nitrogen atom, an oxygen atom and a sulfur atom may be contained as a structural unit. In this case, the viscosity index improver is preferable because it can impart clean dispersibility, antioxidant property, and the like. Examples thereof include N-vinylpyrrolidone, N-vinylthiopyrrolidone, vinylpyridine, N, N-dialkylaminoalkyl (meth) acrylate (the alkyl group usually has 1 to 4 carbon atoms), N, N-dialkylaminoalkyl (Meth) acrylamide (the alkyl group usually has 1 to 4 carbon atoms), vinylimidazole, morpholinoalkylene (meth) acrylate, etc., aminophenothiazine, N-arylphenylenediamine, aminocarbazole, aminothiazole, aminoindole, amino Examples include pyrrole, aminoimidazoline, aminomercaptothiazole, and (meth) acrylate derivatives having an aminopiperidine residue. Of these, preferred are N-vinylpyrrolidone, N, N-dialkylaminoalkyl (meth) acrylate (the alkyl group usually has 1 to 4 carbon atoms), N, N-dialkylaminoalkyl (meth) acrylamide (alkyl group Are usually 1 to 4) and (meth) acrylate derivatives having an N-arylphenylenediamine residue.

The content of the monomer (d) in the polymer (A) in the present invention is not particularly limited, but is usually the weight (A).
0 to 5% by weight based on the weight, and preferably 0 to 3% by weight based on the weight body (A).

The number average molecular weight (Mn) of the polymer (A) is usually 1,000 to 700,000.
From the viewpoint of the thickening effect and the shear stability, preferably Mn
Is 3,000 to 500,000.

When used as a drive system lubricating oil (manual transmission oil, differential gear oil, automatic transmission oil, etc.), Mn is preferably 3,000 to 100,000, and hydraulic oil (hydraulic oil of construction machinery) is used. , Power steering oil, shock absorber oil, etc.)
When it is used in an engine oil (for gasoline, diesel, etc.), Mn is preferably in the range of 50,000 to 500,000.
It is preferable when it is within the range. In addition, this molecular weight is a molecular weight converted into polystyrene by gel permeation chromatography.

The endothermic peak temperature of the polymer (A) in the present invention measured by a differential scanning calorimeter is usually 50 ° C. or lower, preferably 30 ° C. or lower, from the viewpoint of low-temperature characteristics.
Incidentally, the endothermic peak temperature by the differential scanning calorimeter of the present invention,
Using UNIX DSC7 manufactured by PERKIN-ELMER, 5 mg of (meth) acrylate polymer was used as a sample,
It is an endothermic peak top temperature observed when cooling from 140 ° C. to −80 ° C. at an isothermal rate of 10 ° C./min.

The HLB value of the polymer (A) in the present invention is usually from 0.5 to 10.0, and preferably from 0.5 to 6.0 from the viewpoint of promoting the demulsifying property and the water-holding property. It is. The HLB value is a value calculated by the HLB of Griffin (“Introduction to New Surfactants”, P128, published by Sanyo Chemical Industries, Ltd.).

The solubility parameter of the polymer (A) in the present invention is not particularly limited and is usually from 8.5 to 12.0, and preferably from 8.5 to 10.0 in view of the solubility in the base oil.
It is. The solubility parameter is determined by the Fedors method [Poym. Eng. Sci. 14 (2) 152, (1
974)].

The polymer (A) in the present invention can be easily obtained by a usual method. For example, it can be obtained by radical polymerization of the above monomers in mineral oil or a solvent. In this case, an azo-based polymerization catalyst (for example,
Azobisisobutyronitrile, azobisvaleronitrile, etc.) and peroxides (eg, benzoyl peroxide, cumyl peroxide, lauryl peroxide, etc.)
Can be used.

The polymer (A) is obtained by polymerizing the monomers (c) and (d), if necessary, for the monomers (a) and (b). The obtained polymer can be further obtained by subjecting the monomer (d) to graft polymerization with a peroxide-based polymerization catalyst.

In the production of the polymer (A), a known chain transfer agent such as lauryl mercaptan or dibenzyl ether may be used if necessary.

The polymerization temperature in the production of the polymer (A) is usually from 40 to 180 ° C., and the method of polymerization may be either batch or continuous polymerization.

The viscosity index improver of the present invention preferably further contains a pour point depressant. As the pour point depressant, a conventionally known poly (meth) acrylate is used. For example, the alkyl group has 10 to 10 carbon atoms.
20 (meth) acrylates, or a combination of two or more (meth) acrylates having different compositions and molecular weights (for example, see
And those having a very high molecular weight (for example, those described in US Pat. No. 5,229,021). When a pour point depressant is contained as described above, the amount used is usually 30% by weight or less, preferably 1 to 20% by weight, based on the polymer (A).

The viscosity index improver of the present invention comprises other optional components such as detergents (sulfonate, salicylate, phenate, naphthenate, etc.), dispersants (isobutenyl succinimide, Mannich condensation). Substances), antioxidants (zinc dithiophosphate, amines, hindered phenols, etc.), oil agents (fatty acids,
Fatty acid ester type), friction and wear modifier (molybdenum dithiophosphate, molybdenum carbamate, etc.), and extreme pressure agent (sulfur phosphorus type, chlor type, etc.) may be included.

The viscosity index improver of the present invention comprising the polymer (A) as an essential component is useful for petroleum intermediate effluent oils (such as lubricating base oils). In particular, at least 18 to 40 carbon atoms
It is useful for lubricating base oils containing the above wax. The content of the viscosity index improver of the present invention in the lubricating oil is 0.05 to 2
0% by weight.

The base oil for lubricating oil in the lubricating oil composition of the present invention is not particularly limited as long as it is a mineral oil containing at least a wax having 18 to 40 carbon atoms.
A viscosity range of 0 to 300 neutral, for example, 50 to 30
Mineral oils having a viscosity range of 0 neutral, and high viscosity index treated base oils of mineral oils. As a high viscosity indexing method, a Dutch patent application No. 7613854
And JP-A-5-214349.

[0032]

EXAMPLES The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples. In the following, “part” indicates “part by weight” and “%” indicates “% by weight”. The meanings of the abbreviations of the raw materials used in the examples are as follows. ST; styrene C1MA; methyl methacrylate C12MA; decyl methacrylate C13MA; tridecyl methacrylate C14MA; tetradecyl methacrylate C15MA; pentadecyl methacrylate C16MA; hexadecyl methacrylate C18MA; octadecyl methacrylate PEP; , TRILENE CP-80)

(Production Example 1 of Monomer (b)) A flask equipped with a stirrer, a condenser, a thermometer and a dropping pump was charged with 34 parts of phenol and 3.5 parts of acid activated clay, and was heated to 110 ° C. After the temperature was raised, 66 parts of styrene was added dropwise over 3 hours, and the reaction was further carried out at 110 to 120 ° C. for 1 hour. The reaction product was filtered using diatomaceous earth to obtain styrenated phenol. The resulting styrenated phenol 8
2.8 parts were placed in an autoclave equipped with a stirrer and a thermometer, 0.2 parts of potassium hydroxide was added, the temperature was raised to 135 ° C., 23.1 parts of ethylene oxide were injected, and 135 parts of
The mixture was reacted at 160 ° C. for 3 hours to obtain an adduct of styrenated phenol ethylene oxide (1.75 mol). 91 parts of the obtained styrenated phenol ethylene oxide (1.75 mol) adduct is put in a 1 L Erlenmeyer flask, and 200 parts of chloroform and 51.5 parts of N, N'-dicyclohexylcarbodiimide are added and dissolved. After cooling to 2 ° C, 0.06 parts of dimethylaminopyridine was added, and
21.5 parts of methacrylic acid were gradually added dropwise while maintaining the temperature at 0 ° C., and after the completion of the addition, the reaction was maintained at the same temperature for 10 hours to complete the reaction. Then, by-product urea was filtered off and chloroform was distilled off to give a methacrylate (SE-2) of a styrenated phenol ethylene oxide (2 mol) adduct.
Got

(Production Example 2 of Monomer (b)) In a flask equipped with a stirrer, a condenser, a thermometer and a dropping pump, p
After charging 61.2 parts of -phenylphenol and 3.5 parts of acid-activated clay, the temperature was raised to 110 ° C, 85 parts of α-methylstyrene was added dropwise over 3 hours, and 110 to 120
The reaction was carried out at a temperature of 1 hour. The reaction product was filtered using diatomaceous earth to obtain α-methylstyrenated phenylphenol. The resulting α-methylstyrenated phenylphenol 1
01.5 parts were placed in an autoclave equipped with a stirrer and a thermometer, 0.2 parts of potassium hydroxide was added, the temperature was raised to 135 ° C., 19.3 parts of ethylene oxide was injected, and 135 parts were added.
The reaction was carried out at 160 ° C. for 3 hours to obtain an adduct of α-methylstyrenated phenylphenol ethylene oxide (1.75 mol). The obtained α-methylstyrenated phenylphenol ethylene oxide (1.75 mol) adduct 13
4.5 parts were placed in a 1 L Erlenmeyer flask, 200 parts of chloroform and 51.5 parts of N, N'-dicyclohexylcarbodiimide were added and dissolved, cooled to 2 ° C, and 0.06 parts of dimethylaminopyridine was added. While maintaining the temperature at 0 to 5 ° C, 21.5 parts of methacrylic acid was gradually added dropwise. After the completion of the dropwise addition, the liquid temperature was maintained at the same temperature for 10 hours to complete the reaction.
Then, the by-produced urea was separated by filtration and chloroform was distilled off, and methacrylic acid ester (A) of α-methylstyrenated phenylphenol ethylene oxide (3 mol) adduct was added.
SE-3) was obtained.

(Synthesis Example of Polymer) Synthesis Example 1 A reactor equipped with a stirrer, a heating device, a thermometer, and a nitrogen blowing tube was charged with 100 g of toluene, and a nitrogen atmosphere was prepared.
4 ° C. While stirring the reactor, monomer 1 shown in Table 1 was added.
000 g, and 2,2′-azobis- as an initiator
1.5 g of 2 ', 4-dimethylvaleronitrile was charged into the reactor at a constant rate over 8 hours, and a polymerization reaction was carried out at 80 ° C. for 8 hours from the end of the charging. After the completion of the reaction, toluene was removed under reduced pressure at 130 ° C. to obtain a polymer. Molecular weight, crystallization peak temperature by differential scanning calorimetry,
Table 2 shows the HLB values.

[0036]

[Table 1]

[0037]

[Table 2]

(Examples 1 to 6 and Comparative Examples 1 to 4) A viscosity index improver shown in Table 3 and 7.5% of a DI package for SJ grade gasoline engine oil were added to a solvent refined oil A.
In addition to (neutral oil having a viscosity index of 100) and solvent refined oil B (200 neutral oil having a viscosity index of 100), engine oils 1-21 and ratios 1-3 were prepared. At that time, the kinematic viscosity at 100 ° C. was set to 10.8 to 11.2 cSt,
And TBS viscosity (150 ° C, shear rate 10 ⁶ / sec)
Was adjusted to 3.1 mPa · s, and the blending amounts of the solvent refined oils A and B were adjusted. For these engine oils, CCS viscosity measurement at −25 ° C. was performed as an index for low-temperature viscosity evaluation.
Further, these engine oils were subjected to a panel coking test by the following method. Table 3 shows the results.
The viscosity index is also shown.

(Method of Panel Coking Test) The engine oil was prepared according to the panel coking test method Fed-791B.
A panel coking test was performed at a panel temperature of 285 ° C. and an engine oil temperature of 120 ° C. for 6 hours. After the test, the panel was washed with pentane, and the amount of coking was measured by a gravimetric method.

[0040]

[Table 3]

As can be seen from Table 3, the viscosity index improver of the present invention is a lubricating oil containing a conventional viscosity index improver comprising a (meth) acrylate polymer (Comparative Use Examples 1 to 4).
CCS viscosity can be kept low compared to Comparative Use Example 3). This is considered to be because phenols and styrenes are present in the (meth) acrylate side chain, so that they are easily aggregated at a low temperature and the viscosity increase due to the polymer is reduced. The amount of coking can be significantly reduced. This is considered to be because the (meth) acrylate side chain in the alkylene oxide has an ether bond, so that it is easily thermally decomposed and suppresses sludge formation caused by the polymer.

Further, as compared with the case where an OCP-based viscosity index improver was used (Comparative Use Example 4), the viscosity index was higher and the CCS
The viscosity is remarkably low, and the coking amount is equal or reduced.

[0043]

As is clear from the above examples, the engine oil using the viscosity index improver of the present invention can reduce the coking amount and the CCS viscosity as compared with the conventional engine oil using the viscosity index improver. Can be kept low,
In addition, since the viscosity index is high, it is possible to provide an excellent engine oil that can meet future demands for fuel economy of automobiles. Furthermore, the viscosity index improver of the present invention has particularly excellent shear stability in addition to the above characteristics, and is used as a viscosity number improver for lubricating oils other than engine oil (eg, gear oil, ATF, traction oil, and shock absorber oil). Are also very useful.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C10N 40:25 C10N 40:25 F term (reference) 4H104 CB08C DA02A EA01C EA03C LA01 LA03 LA04 PA02 PA03 PA05 PA41 4J002 AE032 AE051 BG043 BG053 BG063 BQ003 FD070 GT00 4J100 AL03P AL04P AL05P AL74Q BA08Q BC43Q CA04 DA01 DA24 DA38 JA28

Claims (7)

[Claims] 1. An alkyl (meth) acrylate (a)
And a viscosity index improver comprising a polymer (A) containing the following monomer (b) as an essential constituent unit. Monomer (b); phenols (b1) and styrenes (b)
(Meth) acrylic acid ester of compound (b5) obtained by adding alkylene oxide (b4) to compound (b3) obtained by reacting 2). 2. A method according to claim 1, wherein (b1) of the monomer (b) is phenol,
The viscosity index improver according to claim 1, wherein (b2) is styrene, and (b4) is an alkylene oxide having 2 to 4 carbon atoms. 3. The viscosity index improver according to claim 1, wherein the content of (b) in the polymer (A) is from 0.1% by weight to 50.0% by weight. 4. The polymer (A) has a number average molecular weight of 1,0.
The viscosity index improver according to any one of claims 1 to 3, wherein the viscosity index improver is from 00 to 700,000. 5. The viscosity index improver according to claim 1, wherein a crystallization peak temperature of the polymer (A) measured by a differential scanning calorimeter is 50 ° C. or less. 6. The polymer (A) having an HLB value of 0.5 to 1
The viscosity index improver according to any one of claims 1 to 5, which is 0.0. 7. A lubricating oil comprising a lubricating base oil containing at least a wax having 18 to 40 carbon atoms and 0.05 to 20% by weight of a viscosity index improver according to claim 1. Oil composition.