JPH07292379A - Viscosity index improver and lubricating oil - Google Patents

Abstract

PURPOSE:To obtain the subject improver having excellent viscosity index improving ability, low-temperature viscosity index improving ability, excellent thickening properties and oxidation resistance. CONSTITUTION:This viscosity index improver comprises a random copolymer containing ethylene, a 3-20C alpha-olefin and one or more compounds selected from the group consisting of an alkyl (meth)acrylate, a (meth)acrylalkylamide, an alkyl maleate, an alkyl maleamide, an acrylmaleimide, maleic anhydride, an alkyl fumarate and an alkylfumaramide.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to viscosity index improvers and lubricating oils. In particular, the present invention relates to a viscosity index improver excellent in viscosity index improving ability, low temperature viscosity characteristic improving ability and oxidation resistance, and a lubricating oil to which the agent 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 the addition of polyalkylmethacrylates to lubricating oils as viscosity index improvers. Similarly, it is known to add a viscosity index improver consisting of an amorphous random copolymer of ethylene and an α-olefin, especially propylene, to a lubricating oil. For example, Japanese Patent Publication No. 48-278
Japanese Patent Publication 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 combined pour point depressing ability. On the other hand, ethylene / propylene copolymers have no pour point depressing ability and thus have a low viscosity index. Although it is inferior to polyalkyl (meth) acrylates in improving ability and low temperature viscosity characteristics, it is used for various engine oil lubricating oils because of its excellent viscosity increasing, economical, and less sludge generation. Official Patent Gazette Sho 4
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. There is. However, its low temperature viscosity characteristics are not at a satisfactory performance level. Further, JP-A-4-100896 discloses that a block copolymer composed of ethylene / acrylic acid ester or the like is added to a lubricating oil. However, it is difficult to say that the viscosity index improving ability, the low temperature viscosity characteristic improving ability, and the thickening property are all excellent, and the oxidation resistance is excellent and the generation of sludge is small. Further, JP-A-4-348107 discloses that a block copolymer or graft polymer composed of an olefin copolymer part composed of ethylene / propylene and the like and a polyalkyl (meth) acrylate part is added to a lubricating oil. It is disclosed. However, it is difficult to say that the viscosity index improving ability, the low temperature viscosity characteristic improving ability, and the thickening property are all excellent, and the oxidation resistance is excellent and the generation of sludge is small.

[0003]

In order to comply with the recent tightening of CAFE regulations and the newly set lubricating oil standards in response to the regulations, passenger vehicle lubricating oils are required to have improved 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 it is becoming difficult to meet the demand.

[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, an alkyl (meth) acrylate, ( (Meth) acrylalkylamide, alkylmaleate, alkylmaleamide, alkylmaleimide, maleic anhydride, alkylfumarate, alkylfumaramide 1
It has been found that a viscosity index improver comprising a copolymer containing one or more compounds is excellent in viscosity index improving ability, low temperature viscosity characteristics, and oxidation resistance.

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

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

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 ( Examples thereof include alkyl (meth) acrylic acid esters such as (meth) acrylate and eicosyl (meth) acrylate. (Meth) acrylalkylamide (a3
As specific examples of -2), (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)
(Di) alkyl (meth) acrylamides such as acrylamide and (di) eicosyl (meth) acrylamide [in the case of dialkyl (meth) acrylamide, the alkyl groups may have the same or different carbon number] To 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, ( Maleates such as di) octyl maleate, (di) decyl maleate, (di) octadecyl maleate, (di) eicosyl maleate [either monoester or diester may be used. The lengths of the alkyl groups may be the same or different]. Specific examples of the alkylmaleamide (a3-4) include maleic amides such as methylmaleamide, ethylmaleamide, butylmaleamide, decylmaleamide, octadecylmaleamide [monoamic acid, diamide It may be any, and may be either a monoalkylamide or a dialkylamide,
Furthermore, the carbon numbers of the alkyl groups may be the same or different]. Alkyl maleimide (a
Specific examples of 3-5) include maleic imides such as methyl maleimide, ethyl maleimide, butyl maleimide, decyl maleimide, and octadecyl maleimide. Similarly, alkyl fumarate (a3-
Specific examples of 6) include (di) methyl fumarate,
(Di) ethyl fumarate, (di) butyl fumarate,
Fumarate esters such as (di) hexyl fumarate, (di) cyclohexyl fumarate, (di) octyl fumarate, (di) decyl fumarate, (di) octadecyl fumarate, and (di) eicosyl fumarate [monoester, It may be any diester, and in the case of diester, the alkyl groups may have the same length or different lengths]. Specific examples of the alkyl fumaramide (a3-7) include fumaric acid amides such as methyl fumaramide, ethyl fumaramide, butyl fumaramide, decyl fumaramide and octadecyl fumaramide [either monoamido acid or diamide may be used,
Further, it may be either monoalkylamide or dialkylamide, and the alkyl groups may have the same or different carbon numbers]. Among these, as (a3), one or more selected from alkyl (meth) acrylate (a3-1), alkyl maleate (a3-3) and alkyl fumarate (a3-6) is preferable. Further, (a3-1), (a3-3) and (a
The number of carbon atoms of the alkyl group of each compound of 3-6) is 1 to 4
It is 0, preferably 4 to 18, and may be a straight chain or one having a side chain. Particularly preferred is an alkyl (meth) acrylate having a straight chain and 4 to 14 carbon atoms and an average carbon number of 6 to 12.

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

(A4) is a (meth) acrylic ester (a4-) having a (poly) oxyalkylene group having 2 to 4 carbon atoms per oxyalkylene repeating unit.
1), a maleic ester (a4-2) having a (poly) oxyalkylene group having 2 to 4 carbon atoms per oxyalkylene repeating unit, and 2 to 4 carbon atoms per oxyalkylene repeating unit A fumaric acid ester (a4-3) having a (poly) oxyalkylene group,
It is one or more compounds selected from the group consisting of N-vinylpyrrolidone, N, N-dimethylaminoethyl (meth) acrylate, vinylpyridine, morpholinoethylmethacrylate, 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 2000, and polyethylene glycol having an average molecular weight of 4000. Examples thereof include acid esters, polypropylene oxide (meth) acrylic acid esters, and polybutylene oxide (meth) acrylic acid esters. In addition, aliphatic monoalcohols having 1 to 30 carbon atoms, fatty acids, and ethylene oxide, propylene oxide, butylene oxide of alkylphenols having 1 to 30 carbon atoms, and adducts of these mixtures ( (Meth) acrylic acid ester is mentioned. Specific examples of (a4-2) include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having an average molecular weight of 500, polyethylene glycol having an average molecular weight of 2000, and polyethylene oxide maleic acid such as polyethylene glycol having an average molecular weight of 4000. Examples thereof include esters and diesters, also maleic acid monoesters and diesters of polypropylene oxide, and maleic acid monoesters and diesters of polybutylene oxide. In addition, an aliphatic monoalcohol having 1 to 30 carbon atoms, a fatty acid, and 1 to 30 carbon atoms.
Alkylphenol-containing alkylphenol ethylene oxide, propylene oxide, butylene oxide,
And maleates of adducts of these mixtures,
Examples thereof include carboxylic acid having 1 to 30 carbon atoms and ethyl benzoic acid having 1 to 30 carbon atoms. Specific examples of (a4-3) include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having an average molecular weight of 500, polyethylene glycol having an average molecular weight of 2000, and polyethylene glycol fumaric acid such as polyethylene glycol having an average molecular weight of 4000. Ester and diester, also fumaric acid monoester and diester of polypropylene oxide,
Similarly, fumaric acid monoesters and diesters of polybutylene oxide may be mentioned. Also, the number of carbon atoms is 1
Examples thereof include fumaric acid esters of aliphatic monoalcohols having 30 alkyl groups, fatty acids, and adducts of ethylene oxide, propylene oxide, butylene oxide of alkylphenols having 1 to 30 carbon alkyl groups, and mixtures thereof. Among (a4), the number of carbon atoms is 1 to 1 because of its clean dispersibility and solubility in mineral oil.
(Meth) acrylic acid ester of an ethylene oxide 1 to 10 mol adduct of an aliphatic monoalcohol having 30 alkyl groups and (meth) acrylic acid of an ethylene oxide 1 to 5 mol adduct of a carboxylic acid of 1 to 30 carbon atoms Esters, N-vinylpyrrolidone and N, N dimethylaminoethyl (meth) acrylate are preferred, and N-vinylpyrrolidone is particularly preferred. The amount of (a4) is preferably 10% by weight or less of (A).

The polymer (A) in the present invention can be produced by a known method. For example, ethylene (a1) and α- having 3 to 20 carbon atoms may be used with or without a solvent.
A compound of olefin (a2) and alkyl (meth) acrylate and / or dialkyl maleate (a3) and the like can be produced by polymerizing 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. In addition, after preparing a trunk polymer composed of (a1) and (a2) and (a3) if necessary, using the same catalyst as described above,
(A) is obtained by graft-polymerizing 3) and (a4) or (a4) using a peroxide catalyst. Further, after polymerizing (a1), (a2) and lower alkyl (meth) acrylate with the same catalyst and solvent system as above, transesterification is carried out with a higher alcohol having 8 to 30 carbon atoms, or long chain alkyl An amidation reaction can be carried out with an amine to form (A).

The weight average molecular weight of the polymer (A) in the present invention is usually 10,000 to 900,000, preferably 30,000 to 600,000. If the weight average molecular weight is less than 10,000, a sufficient thickening effect cannot be obtained. Further, if it exceeds 900,000, the shear stability is poor and may be 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 mineral oil whose polymer (A) is a high viscosity index mineral oil containing isomerized paraffin obtained by hydrocracking paraffin, hydrocarbon synthetic lubricating oil, ester synthetic lubricating oil. It is obtained as a diluted solution in oils selected from oils and mixtures of two or more thereof. 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
It is 0% by weight. If it is less than 5% by weight, sufficient thickening effect and viscosity index improving ability may not be exhibited, and if it exceeds 80% by weight, the viscosity of the additive becomes high and handling becomes difficult.

It is preferable to add a pour point depressant (B) to the viscosity index improver of the present invention. As the pour point depressant (B), a usual alkylmethacrylate-based pour point depressant (for example, a polymer containing n-tetradecyl methacrylate as a main component) or a chlorinated paraffin / naphthalene condensate can be used. The compounding ratio of the polymer (A) and the pour point depressant (B) is preferably 80:20 to 99: 1.
(Weight ratio), particularly 90:10 to 95: 5. 80:
If the amount of the pour point depressant is more 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. If it is less than 99: 1, the pour point depressant may be decreased. There may be a lack of ability.

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. The mineral oil in (C) has a viscosity range of normal 50 neutral oil to 500 neutral oil, and specific examples include normal mineral oil and paraffin component hydrogenated by a hydrogenation catalyst. High-viscosity index mineral oil containing decomposed isomerized paraffin; hydrocarbon-based synthetic lubricating oil such as hydrocarbon-based synthetic lubricating oil consisting of α-olefin oligomer; ester-based synthetic lubricating oil such as dioctyl adipate, fatty acid And esters of trimethylolpropane and the like, respectively. (C) may be a mixture of two or more of those exemplified above. In particular, an isomerized paraffin-containing high-viscosity index oil, which has excellent low-temperature viscosity characteristics, excellent antioxidative properties, and excellent economical efficiency, is preferably used alone, or a mixture containing 70% by weight or less of ordinary mineral oil. 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. When the lubricating oil of the present invention is an engine oil, 0.5 to 10% by weight, and in the case of a gear oil or an automatic transmission oil, 2 to 25% by weight gives a preferable result.

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 products of ethylene / propylene copolymers and styrene / isoprene copolymers, and further these olefinic viscosity index improvers. Known N-atom-containing ones imparting known dispersibility, known poly (meth) acrylate viscosity index improvers, etc.}, extreme pressure additives, detergents, dispersants, antioxidants, friction reducing Agents, pour point depressants and the like.

The intended applications 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 the present invention is not 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 added to a toluene container of 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 the sealed one in an ampoule and seal, and cool to -78 ° C. Ethylene 0.08 mol,
After 0.06 mol of propylene was fed into the pressure resistant reactor, the temperature was raised to 25 ° C. and the stirrer was operated to break the ampoule to carry out polymerization. After reacting for 5 hours, methyl alcohol is added to inactivate the catalyst to stop the reaction. The product was reprecipitated in 10% hydrochloric acid methanol to remove the catalyst,
Further, it was washed with methanol and dried to obtain a polymer. The weight average molecular weight of the obtained polymer by gel permeation chromatography using polystyrene as a standard substance was 150,000, the ethylene content measured by the NMR method was 39 mol%, and the molar ratio of propylene and dodecyl methacrylate was 49 / It was 51. 30 g of the obtained polymer is 1
This 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 dodecyl methacrylate was changed to 0.032 mol, ethylene was changed to 0.12 mol, and propylene was changed to 0.048 mol. A polymer having an ethylene content of 59 mol% and a molar ratio of propylene and dodecyl methacrylate of 59/41 was obtained. Further, a viscosity index improver (2) was obtained by the same method as in Example 1.

Example 3 Polymerization was carried out in the same manner as in Example 1 except that ethyl acrylate was used instead of dodecyl methacrylate, and the weight average molecular weight was 145,000, the ethylene content was 39 mol%, and the molar ratio of propylene and dodecyl methacrylate was A polymer of 49/51 was obtained. 30 g of the obtained polymer was dissolved in xylene at a concentration of 50% by weight to give octyl alcohol 23.9.
g, and 0.2 g of paratoluenesulfonic acid as an ester exchange catalyst were added, and the transesterification reaction was carried out under a heating reflux of xylene. The reaction rate was 95% based on the consumption amount of octyl alcohol. 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 heating under reflux. The reaction rate is 97 based on the consumption of octylamine.
%Met. As in 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 mixed with dodecyl acrylate 0.0.
16 mol, didodecyl fumarate 0.008 mol, ethylene 0.12 mol, 1-butene 0.056 mol by the same method except that the weight average molecular weight 145,000, ethylene content 59 mol%, propylene, The total molar ratio of dodecyl methacrylate and didodecyl fumarate is 48.
A polymer of / 52 was obtained. Further, a viscosity index improver (5) was obtained by the same method as in Example 1.

EXAMPLE 6 0.11 mol of ethylene, 0.045 mol of propylene, 0.0445 mol of dodecyl methacrylate, and 0.0005 mol of methacrylic acid ester of a propylene oxide 2 mol adduct of decanoic acid were used in the same manner as in Example 1. Was copolymerized. The weight average molecular weight of the obtained polymer was 130,000,
The ethylene content was 54 mol%. 10 of this polymer
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 hydrorefined 1
To a solution dissolved in 9.5 g of 00 neutral oil, t-
A solution prepared by dissolving 0.05 g of butyl perbenzoate and 0.5 g of N-vinylpyrrolidone in 5 g of 100 hydrogenated and refined neutral oil was stirred at a temperature of 130 ° C. for 30 days.
The solution was added dropwise over 1 minute, and the reaction was continued for 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 improvers obtained in Examples 1 to 7 were added as a polymethacrylate-based pour point depressant, Include 1.
7 parts of 33 (manufactured by Sanyo Kasei Co., Ltd.) were blended 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 5 mmol were added to toluene 1 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 the sealed one in an ampoule and seal, and cool to -78 ° C. After feeding 0.12 mol of ethylene into the pressure resistant reactor, the temperature was raised to 25 ° C., the stirrer was operated, and the ampoule was broken to carry out polymerization. After reacting for 5 hours, methyl alcohol is added to inactivate the catalyst to stop the reaction. The product is reprecipitated in 10% hydrochloric acid methanol to remove the catalyst, and further washed with methanol,
A polymer was obtained by drying. The weight average molecular weight of the obtained polymer by gel permeation chromatography using polystyrene as a standard substance was 145,000.
The ethylene content measured by the method was 59 mol%.
This 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 Pour Point Depressant Aclue 133 was added to 100 parts of the additive to obtain a viscosity index improver composition (ratio 2).

Comparative Example 2 In a pressure resistant reaction vessel equipped with a stirrer, a thermometer, a nitrogen blowing tube, etc., 100 ml of toluene, and 50 mmol of diethylaluminum and 5 mmol of oxyvanadium trichloride were dissolved and mixed in 15 ml of toluene, and the mixture was placed in an ampoule. Add the sealed ones, seal and cool to -78 ° C. After feeding 0.12 mol of ethylene and 0.08 mol of propylene into a pressure resistant reactor, polymerization was carried out in the same manner as in Example 1,
A polymer having a molecular weight of 149000 and an ethylene content of 58 mol% was obtained. 30% by weight of this polymer in 100 neutral oil
Was dissolved at a concentration of to prepare a viscosity index improver (ratio 3). In addition, 1 part pour point depressant for 100 parts of additive
7 parts of 33 was blended to obtain a viscosity index improver composition (ratio 4).

Comparative Example 3 9.5 g of the polymer prepared in Comparative Example 2 was hydrorefined 1
To a solution dissolved in 9.5 g of 00 neutral oil, t-
A solution of 0.05 g of butyl per-benzoate and 5.0 g of dodecyl methacrylate dissolved in 5 g of 100 hydrogenated and refined neutral oil was stirred at a temperature of 130 ° C. for 3 days.
The solution was added dropwise over 0 minutes, and the reaction was continued 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 the 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), viscosity index improver compositions (8) to (14) and (ratio 1) to (ratio 4) were uniformly dissolved in 90 parts of mineral oil of 10 parts and 100 neutral, respectively. And JIS-K2
According to 283, the kinematic viscosity at 100 ° C. and 40 ° C. was 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 and 90 parts of 100 neutral mineral oil, respectively. Then, the low temperature viscosity test method (JPI-5S-2) defined by the Japan Petroleum Institute.
According to 6-85), the low temperature viscosity was measured at -30 ° C.

(Method of Oxidation Resistance Test) 90 parts of 100 neutral mineral oil, viscosity index improvers (1) to (7),
Viscosity index improver composition (8) to (14), (ratio 1) to
(Comparative 6) is uniformly dissolved in 10 parts each, and JIS-K25
14, the oxidation resistance test was performed 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 which is centrifuged and settled is measured. The sludge amount according to the B method shows oxidation resistance.

[0030]

[Table 1] ------------------------------------------------- Sample Viscosity Viscosity Index Viscosity at -30 ° C Sludge amount (Addition Agent) (100 ° C.) (cP) (%) ------------------------------------ (1) 13. 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) 13.2 180 940 400 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 −−−−−−−−−−−−−−−−−−− ------------------ (Ratio 1) 14.0 185 13,000 0.71 (Ratio 2) 13.9 184 10,100 0.73 (Ratio 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]

INDUSTRIAL APPLICABILITY The viscosity index improver of the present invention is excellent in viscosity index improving ability and low temperature viscosity characteristic improving ability of the conventional methacrylate polymer type viscosity index improving agent, and excellent viscosity increasing and oxidation resistance characteristics of OCP VII. Also has. Therefore, the lubricating oil of the present invention using the additive of the present invention has a small addition amount, is excellent in fluidity characteristics at low temperature and is excellent in oxidation stability at high temperature, and can be used even in a harsh environment.

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Claims (6)

[Claims] 1. Ethylene (a1) as a structural unit,
C3-C20 α-olefin (a2), alkyl (meth) acrylate (a3-1), (meth) acrylalkylamide (a3-2), alkyl maleate (a
3-3), alkylmaleamide (a3-4), alkylmaleimide (a3-5), maleic anhydride, alkylfumarate (a3-6), alkylfumaramide (a3-7) A viscosity index improver comprising a random copolymer (A) containing one or more compounds (a3) selected from 2. A (meth) acrylic acid ester (a4-1) having a (poly) oxyalkylene group having 2 to 4 carbon atoms per oxyalkylene repeating unit as a structural unit, an oxyalkylene repeating unit. 1
Maleic acid ester (a4-2) having a (poly) oxyalkylene group having 2 to 4 carbon atoms, and (poly) oxyalkylene group having 2 to 4 carbon atoms per one oxyalkylene repeating unit. One or more compounds selected from the group consisting of fumaric acid ester (a4-3), N-vinylpyrrolidone, N, N-dimethylaminoethyl (meth) acrylate, vinylpyridine, morpholinoethyl (meth) acrylate, and vinylimidazole. The viscosity index improver according to claim 1, comprising the polymer (A) containing (a4). 3. The polymer (A) is composed of (a1) units, (a)
2) units, a trunk polymer composed of (a3) units, (a4)
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 for gasoline engine oil and diesel engine oil. 6. A lubricating base oil (C) selected from mineral oil, high viscosity index mineral oil containing isomerized paraffin, hydrocarbon-based synthetic lubricating oil, ester-based synthetic lubricating oil and a mixture of two or more thereof. A lubricating oil obtained by adding the viscosity index improver according to any one of claims 1 to 5.