JP2627725B2 - Viscosity index improver and lubricating oil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a viscosity index improver and a lubricating oil. In particular, the present invention relates to a viscosity index improver excellent in viscosity index improving ability, low temperature viscosity property improving ability and oxidation resistance property, and a lubricating oil to which this is added.

[0002]

It is known to add viscosity index improvers consisting of polyalkyl (meth) acrylates to lubricating oils. For example, US Pat. No. 2,628,225 discloses adding a polyalkyl methacrylate to a lubricating oil as a viscosity index improver. Similarly, it is known to add to a lubricating oil a viscosity index improver consisting of an amorphous random copolymer of ethylene and an α-olefin, especially propylene. For example, published patent publications 48-278
No. 83 discloses a lubricating oil composition obtained by dissolving an ethylene / propylene copolymer having a propylene content of 20 to 70% in a lubricating oil. Polyalkyl (meth) acrylates are widely used because of their excellent viscosity index improving ability, low-temperature viscosity characteristics, and excellent pour point depressing ability, while ethylene / propylene copolymers have no pour point depressing ability and viscosity index Although it is inferior to polyalkyl (meth) acrylate in improving ability and low-temperature viscosity characteristics, it is used for various engine oil lubricating oils because it is economical because it has excellent thickening properties and generates little sludge. Published Patent Gazette Showa 4
JP-A-8-22962 discloses that an ethylene / unsaturated monobasic carboxylic acid ester copolymer or an ethylene / unsaturated polybasic carboxylic acid ester copolymer is used as a viscosity index improver. I have. However, its low temperature viscosity properties are not at a satisfactory performance level. In addition, Japanese Patent Application Laid-Open No. 4-100896 discloses adding a block copolymer composed of ethylene / acrylate to lubricating oil. However, it is hard to say that it has excellent viscosity index improving ability, low temperature viscosity property improving ability, and thickening property, and has excellent oxidation resistance and little sludge generation. JP-A 4-348107 discloses a lubricating oil in which an olefin copolymer portion composed of ethylene / propylene and the like and a block copolymer or a graft polymer composed of a polyalkyl (meth) acrylate portion are added to a lubricating oil. It is disclosed. However, it is hard to say that it has excellent viscosity index improving ability, low temperature viscosity property improving ability, and thickening property, and has excellent oxidation resistance and little sludge generation.

[0003]

In order to cope with the recent tightening of the CAFE regulations and the newly set lubricating oil standards in response to the tightening, there is a demand for lubricating oils for passenger cars, especially for low-temperature viscosity characteristics and oxidation resistance. Is getting stronger. However, conventional polyalkyl (meth) acrylates have problems in oxidation resistance, while ethylene / propylene copolymers have problems in low-temperature viscosity characteristics and the like, and can no longer respond to requests.

[0004]

Means for Solving the Problems As a result of intensive studies on these problems, the present inventors have found that ethylene, an α-olefin having 3 to 20 carbon atoms, alkyl (meth) acrylate, ( 1) selected from the group consisting of (meth) acrylalkylamides, alkylmaleates, alkylmaleamides, alkylmaleimides, maleic anhydrides, alkyl fumarates, and alkyl fmalamides
It has been found that a viscosity index improver comprising a copolymer containing at least one kind of compound has excellent viscosity index improving ability, low-temperature viscosity characteristics and excellent oxidation resistance.

That is, in the present invention, ethylene (a1) and α-olefin having 3 to 20 carbon atoms (a
2) and an alkyl (meth) acrylate (a3-1);
(Meth) acrylalkylamide (a3-2), alkylmaleate (a3-3), alkylmaleamide (a
3-4), 1 selected from the group consisting of alkyl maleimide (a3-5), maleic anhydride, alkyl fumarate (a3-6), alkyl fumalamide (a3-7)
A viscosity index improver comprising a copolymer (A) containing at least one compound (a3); and a lubricating oil comprising the viscosity index improver.

Α-olefin having 3 to 20 carbon atoms (a2)
Specific examples include propylene, 1-butene, 2-butene, isobutene, 1-propene, 1-hexene and the like. Among these, preferably propylene, 1-
Butene and isobutene are particularly preferred, and propylene is preferred.

The alkyl (meth) acrylate (a3-
Specific examples of 1) include methyl (meth) acrylate,
Ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, tetradecyl (meth) acrylate, octadecyl ( Alkyl (meth) acrylates such as (meth) acrylate and eicosyl (meth) acrylate. (Meth) acrylalkylamide (a3
Specific examples of -2) include (di) methyl (meth) acrylamide, (di) ethyl (meth) acrylamide,
(Di) butyl (meth) acrylamide, (di) hexyl (meth) acrylamide, (di) cyclohexyl (meth) acrylamide, (di) octyl (meth) acrylamide, (di) nonyl (meth) acrylamide, (di)
Decyl (meth) acrylamide, (di) tetradecyl (meth) acrylamide, (di) octadecyl (meth)
Examples of (di) alkyl (meth) acrylamides such as acrylamide and (di) eicosyl (meth) acrylamide [in the case of dialkyl (meth) acrylamide, the alkyl group may have the same or different carbon number] Can be Specific examples of the alkyl maleate (a3-3) include (di) methyl maleate, (di) ethyl maleate, (di) butyl maleate, (di) hexyl maleate, (di) cyclohexyl maleate, and ( Maleic esters such as di) octyl maleate, (di) decyl maleate, (di) octadecyl maleate, (di) eicosyl maleate [either monoester or diester may be used. The length of the alkyl group may be the same or different]. Specific examples of the alkylmaleamide (a3-4) include maleic amides such as methylmaleamide, ethylmaleamide, butylmaleamide, decylmaleamide, and octadecylmaleamide [monoamidic acid, diamide Any one may be, and may be any of a monoalkylamide and a dialkylamide,
And the alkyl group may have the same or different carbon number]. Alkyl maleimide (a
Specific examples of 3-5) include maleic imides such as methylmaleimide, ethylmaleimide, butylmaleimide, decylmaleimide, and octadecylmaleimide. Similarly, alkyl fumarate (a3-
Specific examples of 6) include (di) methyl fumarate,
(Di) ethyl fumarate, (di) butyl fumarate,
Fumaric acid esters such as (di) hexyl fumarate, (di) cyclohexyl fumarate, (di) octyl fumarate, (di) decyl fumarate, (di) octadecyl fumarate, and (di) eicosyl fumarate [monoester, And the length of each alkyl group may be the same or different in the case of a diester]. Specific examples of the alkyl fumalamides (a3-7) include fumaric acid amides such as methyl fumalamido, ethyl fumaramido, butyl fumaramido, decyl fumaramido, octadecyl fumaramido [monoamidic acid and diamide,
Further, any of monoalkylamide and dialkylamide may be used, and the alkyl group may have the same or different carbon number.]. Among them, (a3) is preferably at least one selected from alkyl (meth) acrylate (a3-1), alkyl maleate (a3-3), and alkyl fumarate (a3-6). Further, (a3-1), (a3-3) and (a
The carbon number of the alkyl group in each compound of 3-6) is 1 to 4.
0, preferably 4 to 18, and may be any one having a linear side chain. Particularly preferred is an alkyl (meth) acrylate having a straight chain and having 4 to 14 carbon atoms and having an average carbon number of 6 to 12.

The total molar ratio of (a1), (a2) and (a3) is preferably from 30:70 to 70:30,
Particularly preferably, it is 60:40 to 40:60. (A
When 1) is less than 30:70, the thickening is insufficient, and
If (a1) exceeds 70:30, problems may occur in the low-temperature viscosity characteristics. Further, the molar ratio between (a2) and (a3) is preferably from 90:10 to 10:90, particularly preferably 5:10.
0:50 to 20:80 is preferred. (A2) is 90: 1
If it exceeds 0, a problem may occur in thickening, and if it is less than 10:90, a problem may occur in low-temperature viscosity characteristics.

(A4) is a (meth) acrylate (a4-) having a (poly) oxyalkylene group having 2 to 4 carbon atoms per oxyalkylene repeating unit.
1) a maleic acid ester (a4-2) having a (poly) oxyalkylene group having 2 to 4 carbon atoms per oxyalkylene repeating unit, having 2 to 4 carbon atoms per oxyalkylene repeating unit Fumaric acid ester having a (poly) oxyalkylene group (a4-3),
One or more compounds selected from the group consisting of N-vinylpyrrolidone, N, N-dimethylaminoethyl (meth) acrylate, vinylpyridine, morpholinoethyl methacrylate, and vinylimidazole. Specific examples of (a4-1) include polyethylene glycol (meth) acryl such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having an average molecular weight of 500, polyethylene glycol having an average molecular weight of 2,000, and polyethylene glycol having an average molecular weight of 4,000. Acid esters, also (meth) acrylic acid esters of polypropylene oxide, and (meth) acrylic acid esters of polybutylene oxide. In addition, ethylene oxide, propylene oxide, butylene oxide of an aliphatic monoalcohol having 1 to 30 carbon atoms having an alkyl group, a fatty acid, and an alkylphenol having an alkyl group having 1 to 30 carbon atoms, and adducts of mixtures thereof ( (Meth) acrylic acid esters. Specific examples of (a4-2) include monoethylene glycol maleate such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having an average molecular weight of 500, polyethylene glycol having an average molecular weight of 2,000, and polyethylene glycol having an average molecular weight of 4000. Esters and diesters, maleic acid monoesters and diesters of polypropylene oxide, and maleic acid monoesters and diesters of polybutylene oxide also can be mentioned. In addition, an aliphatic monoalcohol having a C1-30 alkyl group, a fatty acid, and a C1-30
Ethylene oxide, propylene oxide, butylene oxide of an alkylphenol having an alkyl group,
Maleic esters of adducts of these and mixtures thereof,
Examples thereof include ethyl carboxylic acids having 1 to 30 carbon atoms and alkyl benzoic acids having 1 to 30 carbon atoms. Specific examples of (a4-3) include fumaric acid of fumaric acid, a polyethylene oxide such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having an average molecular weight of 500, polyethylene glycol having an average molecular weight of 2,000, and polyethylene glycol having an average molecular weight of 4,000. Esters and diesters, also fumaric acid monoesters and diesters of polypropylene oxide,
Similarly, fumaric acid monoester and diester of polybutylene oxide may be mentioned. In addition, carbon number 1
Examples include aliphatic monoalcohols having 30 alkyl groups, fatty acids, and fumaric acid esters of adducts of ethylene oxide, propylene oxide, butylene oxide of alkylphenols having an alkyl group having 1 to 30 carbon atoms, and mixtures thereof. Among (a4), from the viewpoint of clean dispersibility and solubility in mineral oil, carbon number 1 to 1
(Meth) acrylic acid ester of 1 to 10 mol ethylene oxide adduct of aliphatic monoalcohol having 30 alkyl groups and (meth) acrylic acid of 1 to 5 mol ethylene oxide adduct of carboxylic acid having 1 to 30 carbon atoms Esters, N-vinylpyrrolidone and N, N-dimethylaminoethyl (meth) acrylate are preferred, with N-vinylpyrrolidone being particularly preferred. The amount of (a4) is preferably 10% by weight or less of (A).

[0010] The polymer (A) in the present invention can be produced by a known method. For example, with or without a solvent, ethylene (a1) and α-
A blend of an olefin (a2) and an alkyl (meth) acrylate and / or a dialkyl maleate (a3) can be produced by polymerizing a mixture of a vanadium compound and an aluminum compound as a catalyst. As the solvent, aromatic solvents such as benzene and toluene, and hydrocarbon solvents such as hexane and heptane can be used. Further, after preparing a backbone polymer composed of (a1) and (a2) and, if necessary, (a3) using the same catalyst as described above, (a)
(A) is obtained by graft-polymerizing 3) and (a4) or (a4) using a peroxide catalyst. Further, (a1), (a2) and the lower alkyl (meth) acrylate are polymerized with the same catalyst and solvent system as described above, and then transesterification is performed with a higher alcohol having 8 to 30 carbon atoms. (A) can be prepared by performing an amidation reaction with an amine.

The weight average molecular weight of the polymer (A) in the present invention is usually from 10,000 to 900,000, preferably from 30,000 to 600,000. If the weight average molecular weight is less than 10,000, a sufficient thickening effect cannot be obtained. On the other hand, if it exceeds 900,000, the shear stability is poor, which may cause a problem in practical use. The weight average molecular weight is a value measured by GPC and obtained using polystyrene as a calibration curve.

The viscosity index improver of the present invention is usually a polymer (A) of a mineral oil, a high viscosity index mineral oil containing isomerized paraffin obtained by hydrocracking paraffin, a hydrocarbon synthetic lubricating oil, an ester synthetic lubricating oil. It is obtained as being diluted and dissolved in oils and oils selected from a mixture of two or more of these. The concentration of the polymer (A) in the viscosity index improver of the present invention is usually 5 to 80% by weight, preferably 10 to 7% by weight.
0% by weight. If the amount is less than 5% by weight, a sufficient thickening effect and the ability to improve the viscosity index may not be exhibited. If the amount exceeds 80% by weight, the viscosity of the additive becomes high and handling becomes difficult.

It is preferred that the viscosity index improver of the present invention further contains a pour point depressant (B). As the pour point depressant (B), a usual alkyl methacrylate pour point depressant (for example, a polymer mainly containing n-tetradecyl methacrylate), a chlorinated paraffin / naphthalene condensate, or the like can be used. The mixing ratio of the polymer (A) and the pour point depressant (B) is preferably from 80:20 to 99: 1.
(Weight ratio), particularly 90:10 to 95: 5. 80:
If the amount of the pour point depressant is larger than 20, the viscosity increase may be insufficient, or the polymer (A) and the pour point depressant may not be compatible with each other and may be separated from each other. Performance may be insufficient.

The viscosity index improver of the present invention is blended and dissolved in the lubricating base oil (C) so as to have a desired viscosity and used as the lubricating oil of the present invention. Among (C), the mineral oil has a viscosity range of ordinary 50 neutral oil to 500 neutral oil. As a specific example, ordinary mineral oil and paraffin are hydrogenated with a hydrogenation catalyst. High viscosity index mineral oil containing decomposed isomerized paraffin; hydrocarbon synthetic lubricating oil such as hydrocarbon synthetic lubricating oil composed of α-olefin oligomer; ester synthetic lubricating oil dioctyl adipate, fatty acid And an ester of trimethylolpropane. (C) may be a mixture of two or more of those exemplified above. In particular, an isomerized paraffin-containing high viscosity index oil having excellent low-temperature viscosity characteristics, excellent antioxidation properties, and excellent economic efficiency alone, or a mixture in which ordinary mineral oil is blended at 70% by weight or less is preferable. The viscosity index improver of the present invention is usually added to the lubricating base oil (C) in an amount of 0.5 to 30% by weight and used as the lubricating oil of the present invention. Preferred results are obtained when the lubricating oil of the present invention is added in an amount of 0.5 to 10% by weight when it is an engine oil, and in a case where it is 2 to 25% by weight when it is a gear oil or an automatic transmission oil.

[0015] The lubricating oil of the present invention may contain other known additives. These known additives include other viscosity index improvers, for example, known ones such as hydrogenated ethylene-propylene copolymer and styrene-isoprene copolymer, and further, these olefin-based viscosity index improvers. Known N-atom-containing clean dispersibility, known poly (meth) acrylate based viscosity index improver, etc., extreme pressure additives, detergents, dispersants, antioxidants, friction reduction Agents, pour point depressants and the like.

The intended uses of the lubricating oil of the present invention include gasoline engine oil, diesel engine oil, gear oil, automatic transmission oil, hydraulic oil, tractor oil, power steering oil, shock absorber oil, compressor oil and the like. .

[0017]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

EXAMPLE 1 100 ml of toluene, 0.06 mol of dodecyl methacrylate, and 50 mmol of diethylaluminum and 5 mmol of oxyvanadium trichloride were placed in toluene 1 in a pressure-resistant reaction vessel equipped with a stirrer, thermometer, nitrogen blowing tube and the like.
Dissolve and mix in 5 ml, put in a sealed ampoule, seal and cool to -78 ° C. 0.08 mol of ethylene,
After feeding 0.06 mol of propylene into the pressure-resistant reaction vessel, the temperature was raised to 25 ° C., the stirrer was moved, and the ampule was broken to cause polymerization. After the reaction for 5 hours, methyl alcohol is added to inactivate the catalyst and stop the reaction. The product was reprecipitated in 10% methanolic hydrochloric acid to remove the catalyst,
Further, the polymer was washed with methanol and dried to obtain a polymer. The obtained polymer had a weight average molecular weight of 150,000 by gel permeation chromatography using polystyrene as a standard substance, an ethylene content of 39 mol% measured by NMR, and a molar ratio of propylene to dodecyl methacrylate of 49 /. 51. 30 g of the obtained polymer was
It was dissolved in 70 g of 00 neutral at a concentration of 30% by weight to obtain a viscosity index improver (1).

Example 2 Polymerization was carried out in the same manner as in Example 1 except that the amount of dodecyl methacrylate was changed to 0.032 mol, the amount of ethylene was changed to 0.12 mol, and the amount of propylene was changed to 0.048 mol. A polymer having an ethylene content of 59 mol% and a molar ratio of propylene to dodecyl methacrylate of 59/41 was obtained. Further, a viscosity index improver (2) was obtained in the same manner as in Example 1.

Example 3 Polymerization was carried out in the same manner as in Example 1 except that dodecyl methacrylate was changed to ethyl acrylate. The weight average molecular weight was 145,000, the ethylene content was 39 mol%, and the molar ratio of propylene to dodecyl methacrylate was lower. A 49/51 polymer was obtained. 30 g of the obtained polymer was dissolved in xylene at a concentration of 50% by weight, and octyl alcohol 23.9 was obtained.
g, and 0.2 g of paratoluenesulfonic acid was added as a transesterification catalyst, and a transesterification reaction was performed under reflux of xylene under heating. The conversion was 95% based on octyl alcohol consumption. The xylene solvent was replaced with 100 neutral oil to obtain a viscosity index improver (3).

Example 4 In Example 3, octyl alcohol was changed to 23.8 g of octylamine, and xylene was subjected to amidation under reflux with heating. Reaction rate is 97 based on octylamine consumption
%Met. Similar to Example 3, the xylene solvent was replaced with 100 neutral oil to obtain a viscosity index improver (4).

Example 5 In Example 1, dodecyl methacrylate, ethylene and propylene were replaced with dodecyl acrylate 0.0
Weight average molecular weight: 145,000, ethylene content: 59 mol%, propylene by the same method except that 16 mol, 0.008 mol of didodecyl fumarate, 0.12 mol of ethylene, and 0.056 mol of 1-butene were used. The total molar ratio of dodecyl methacrylate and didodecyl fumarate is 48
/ 52 was obtained. Further, a viscosity index improver (5) was obtained in the same manner as in Example 1.

Example 6 The same method as in Example 1 was used except that 0.11 mol of ethylene, 0.045 mol of propylene, 0.0445 mol of dodecyl methacrylate, and 0.0005 mol of a methacrylic acid ester of a 2 mol adduct of propylene oxide with decanoic acid were used. Was copolymerized. The weight average molecular weight of the obtained polymer is 130,000,
The ethylene content was 54 mol%. This polymer is
It was dissolved in 0 neutral oil at a concentration of 30% by weight to obtain a viscosity index improver (6).

Example 7 9.5 g of the polymer obtained in Example 1 was hydrotreated.
T-solution was added to 9.5 g of neutral oil.
A solution obtained by dissolving 0.05 g of butyl perbenzoate and 0.5 g of N-vinylpyrrolidone in 5 g of hydrogenated and purified 100 neutral oil was stirred at a temperature of 130 ° C. for 30 days.
Minutes, and allowed to react for another 2 hours. After the reaction, 1
18.8 g of 00 neutral oil was added and diluted to 30% by weight to obtain a viscosity index improver (7). Example 8 100 parts of the viscosity index improver obtained in Examples 1 to 7 was used as an additive 1 as a polymethacrylate pour point depressant.
33 (manufactured by Sanyo Kasei Kogyo Co., Ltd.) were blended in 7 parts to obtain viscosity index improver compositions (8) to (14).

Comparative Example 1 100 ml of toluene, 0.08 mol of dodecyl methacrylate, and 50 mmol of diethylaluminum and 5 mmol of oxyvanadium trichloride were placed in a pressure-resistant reaction vessel equipped with a stirrer, a thermometer, a nitrogen blowing tube, and the like.
Dissolve and mix in 5 ml, put in a sealed ampoule, seal and cool to -78 ° C. After feeding 0.12 mol of ethylene into the pressure-resistant reaction vessel, the temperature was raised to 25 ° C., the stirrer was moved, and the ampule was broken to cause polymerization. After the reaction for 5 hours, methyl alcohol is added to inactivate the catalyst and stop the reaction. The product was reprecipitated in 10% hydrochloric acid methanol to remove the catalyst, and further washed with methanol.
After drying, a polymer was obtained. The weight average molecular weight of the obtained polymer determined by gel permeation chromatography using polystyrene as a standard substance was 145,000.
The ethylene content measured by the method was 59 mol%.
The polymer was dissolved in 100 neutral oil at a concentration of 30% by weight to prepare a viscosity index improver (ratio 1). further,
7 parts of a pour point depressant include 133 was added to 100 parts of the additive to obtain a viscosity index improver composition (ratio 2).

Comparative Example 2 100 ml of toluene and 50 mmol of diethylaluminum and 5 mmol of oxyvanadium trichloride were dissolved and mixed in 15 ml of toluene in a pressure-resistant reaction vessel equipped with a stirrer, a thermometer, a nitrogen blowing tube and the like. Put in the sealed one, seal and cool to -78 ° C. After feeding 0.12 mol of ethylene and 0.08 mol of propylene into the pressure-resistant reaction vessel, polymerization was carried out in the same manner as in Example 1,
A polymer having a molecular weight of 1490,000 and an ethylene content of 58 mol% was obtained. 30% by weight of this polymer in 100 neutral oil
And a viscosity index improver (ratio 3) was prepared. In addition, pour point depressant include 1 per 100 parts of additive
33 was mixed with 7 parts to obtain a viscosity index improver composition (ratio 4).

Comparative Example 3 9.5 g of the polymer prepared in Comparative Example 2 was hydropurified.
T-solution was added to 9.5 g of neutral oil.
A solution prepared by dissolving 0.05 g of butyl per-benzoate and 5.0 g of dodecyl methacrylate in 5 g of hydrogenated 100-neutral oil was stirred at 130.degree.
The mixture was added dropwise in 0 minutes, and the reaction was further performed for 2 hours. After the reaction,
100 neutral oil was added and diluted to 30% by weight to obtain a viscosity index improver (ratio 5). Further, 7 parts of a pour point depressant include 133 was added to 100 parts of the additive to obtain a viscosity index improver composition (ratio 6).

Test Example (Evaluation method of viscosity index) Viscosity index improver (1)-
(7) The viscosity index improver compositions (8) to (14) and (ratio 1) to (ratio 4) were uniformly dissolved in 10 parts each and 90 parts of 100 neutral mineral oil. And JIS-K2
According to 283, kinematic viscosities at 100 ° C. and 40 ° C. were measured and calculated by a standard method. (Method of low-temperature viscosity test) Viscosity index improver (1)-
(7) The viscosity index improver compositions (8) to (14) and (ratio 1) to (ratio 6) were uniformly dissolved in 10 parts each and 90 parts of 100 neutral mineral oil. The low temperature viscosity test method (JPI-5S-2) specified by the Japan Petroleum Institute
According to 6-85), the low-temperature viscosity was measured at -30 ° C.

(Method of Oxidation Resistance Test) A viscosity index improver (1) to (7) was added to 90 parts of 100 neutral mineral oil.
Viscosity index improver compositions (8) to (14), (ratio 1)
(Ratio 6) was uniformly dissolved in 10 parts of each, and JIS-K25
According to No. 14, an oxidation resistance test was conducted at 165.5 ° C. for 98 hours, and the amount of sludge generated by the B method was measured. Where B
The method is a method in which a sludge flocculant is added to the lubricating oil after the test and the amount of sludge settled by centrifugation is measured. The amount of sludge by the method B shows oxidation resistance.

[0030]

Table 1 Sample viscosity Viscosity index Viscosity at -30 ° C Sludge amount (addition (Agent) (100 ° C.) (cP) (%) −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− (1) 5 185 9500 0.47 (2) 15.9 179 11000 0.45 (3) 13.4 182 9800 0.50 (4) 13.3 184 9700 0.53 (5) 13.2 180 9400 0.51 (6) 13.6 184 9200 0.40 (7) 13.6 186 9600 0.34 (8) 13.3 185 5500 0.56 (9) 12.8 178 7100 0.44 (10) 13.2 183 5800 0.49 (11) 13.1 183 5800 0.53 (1 2) 13.0 181 5700 0.51 (13) 13.5 182 5400 0.40 (14) 13.4 184 5600 0.73 -------------------------- −−−−−−−−−−−−−−− (Comparative 1) 14.0 185 13,000 0.71 (Comparative 2) 13.9 184 10,100 0.73 (Comparative 3) 14.3 145 14,100 0.70 (ratio 4) 14.1 145 11,000 0.71 (ratio 5) 14.5 148 13,500 0.66 (ratio 6) 14.5 149 10,100 0.68 − −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0031]

EFFECTS OF THE INVENTION The viscosity index improver of the present invention comprises the excellent viscosity index improving ability and low temperature viscosity property improving ability of the conventional methacrylate polymer based viscosity index improver, and the excellent thickening and oxidation resistance properties of OCP VII. Has both. Therefore, the lubricating oil of the present invention using the additive of the present invention has a small amount of addition, is excellent in flow characteristics at low temperatures and oxidative stability at high temperatures, and can be used in a severe environment.

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Claims (6)

(57) [Claims] An ethylene (a1) as a structural unit,
Α-olefin (a2) having 3 to 20 carbon atoms, alkyl (meth) acrylate (a3-1), (meth) acrylalkylamide (a3-2), alkyl maleate (a
3-3), a group consisting of alkyl maleamide (a3-4), alkyl maleimide (a3-5), maleic anhydride, alkyl fumarate (a3-6), and alkyl fumalamide (a3-7) A viscosity index improver comprising a random copolymer (A) containing at least one compound (a3) selected from the group consisting of: 2. (meth) acrylic acid ester (a4-1) having a (poly) oxyalkylene group having 2 to 4 carbon atoms per one oxyalkylene repeating unit, and an oxyalkylene repeating unit as a structural unit. 1
Maleic ester (a4-2) having a (poly) oxyalkylene group having 2 to 4 carbon atoms per unit, having a (poly) oxyalkylene group having 2 to 4 carbon atoms per oxyalkylene repeating unit One or more compounds selected from the group consisting of fumaric acid esters (a4-3), N-vinylpyrrolidone, N, N-dimethylaminoethyl (meth) acrylate, vinylpyridine, morpholinoethyl (meth) acrylate, and vinylimidazole The viscosity index improver according to claim 1, comprising a polymer (A) containing (a4). 3. The polymer (A) comprises (a1) units, (a)
2) a backbone polymer comprising units and (a3) units;
The viscosity index improver according to claim 2, which is a polymer obtained by graft polymerization of 4. The viscosity index improver according to claim 1, further comprising a pour point depressant (B). 5. The viscosity index improver according to claim 1, which is used for gasoline engine oil and diesel engine oil. 6. A lubricating base oil (C) selected from a mineral oil, a high viscosity index mineral oil containing isomerized paraffin, a hydrocarbon-based synthetic lubricating oil, an ester-based synthetic lubricating oil, and a mixture of two or more thereof. A lubricating oil comprising the viscosity index improver according to claim 1.