JPH11323370A - Gear oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear oil compsn. which can maintain a constant viscosity at a high temp., has low viscosity at a very low temp., and possesses excellent shear stability, extreme pressure properties, abrasion resistance, stability against oxidation and other properties. SOLUTION: This gear oil compsn. comprises: a base oil having a kinematic viscosity at 100 deg.C of 1.5 to 50 mm<2> /sec, a pour point of -25 deg.C or below, and a viscosity index of not less than 80; and, based on the total amt. of the compsn., 1.0 to 20 wt.% ethylene-α-olefin copolymer having an no. average mol.wt. of 2,000 to 8,000, 0.2 to 2.0 wt.% zinc dialkyldithiophosphate, 0.1 to 2.0 wt.% sulfurized fat and oil, and 0.2 to 3.0 wt.% calcium sulfonate having a total base value of not less than 200 mg KOH/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear oil composition, and more particularly, to a gear oil composition which maintains a constant viscosity at a high temperature, has a low viscosity even at a very low temperature, and has shear stability, extreme pressure resistance, abrasion resistance and oxidation resistance. The present invention relates to a gear oil composition having excellent stability and the like.

[0002]

2. Description of the Related Art Gear oil is a lubricating oil for gear units. It is used for high-speed gears of automobiles and other high-speed gears, relatively light-weight gears of general machinery, and relatively high-load gears of general machinery. It is used to prevent bearing damage and seizure. In general, such gear oils are required to maintain a constant viscosity at high temperatures, have a low viscosity even at extremely low temperatures, and have excellent shear stability, extreme pressure properties, abrasion resistance, oxidation stability and the like. . Conventionally, in order to improve the temperature characteristics of gear oil, a large amount of a polymer compound having a viscosity index improving effect and a pour point lowering effect has been blended. However, a lubricating oil composition containing a large amount of the above-mentioned polymer compound has a problem in that it lacks shear stability, easily suffers from a decrease in viscosity due to mechanical shearing, and does not satisfy the initial lubricating performance. As a lubricating oil composition having improved temperature characteristics, there is disclosed a lubricating oil composition obtained by adding an extreme pressure agent or the like to an ethylene-α-olefin copolymer to a purified oil having a high viscosity index (Japanese Patent Application Laid-Open No. 280796), which has a problem that the oxidation stability is not always sufficiently satisfactory.

[0003]

Under these circumstances, the present inventors have maintained a constant viscosity at high temperature,
It is an object of the present invention to provide a gear oil composition having a low viscosity even at an extremely low temperature and having excellent shear stability, extreme pressure properties, abrasion resistance and oxidation stability.

[0004]

The present inventors have conducted intensive studies to develop a gear oil composition having the above-mentioned preferable properties. As a result, the base oil having a specific property has a molecular weight within a certain range. It has been found that the object can be achieved by blending the ethylene-α-olefin copolymer, zinc dialkyldithiophosphate, sulfurized oil and fat, and calcium sulfonate having a total base number within a certain range, respectively, in a predetermined ratio. . The present invention has been completed based on such findings. That is, according to the present invention, (A) the kinematic viscosity at 100 ° C. is 1.5 to 50 mm ² / sec, and the pour point is −2.
(B) 1.0 to 20% by weight of an ethylene-α-olefin copolymer having a number average molecular weight of 2,000 to 8,000, based on the base oil having a temperature of 5 ° C. or less and a viscosity index of 80 or more,
(C) 0.2 to 2.0% by weight of zinc dialkyldithiophosphate;
(D) 0.1 to 2.0% by weight of sulfurized oil and fat and (E) total base number 2
Calcium sulfonate 0.2 mg or more of KOH / g
To 3.0% by weight of a gear oil composition.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the gear oil composition of the present invention, the kinematic viscosity at 100 ° C. is in the range of 1.5 to 50 mm ² / sec and the pour point is −
Those having a temperature of 25 ° C. or less and a viscosity index of 80 or more are used. Here, the kinematic viscosity at 100 ° C. is 1.5 mm ² / s
If it is less than ec, there is a disadvantage that the evaporation loss is large, and if it exceeds 50 mm ² / sec, power loss due to viscous resistance increases. Considering the evaporation loss and the viscous resistance, the preferable range of the kinematic viscosity at 100 ° C. is 2 to
30 mm ² / sec. On the other hand, if the pour point exceeds −25 ° C., the low-temperature characteristics deteriorate. From the viewpoint of low-temperature characteristics, the pour point is particularly preferably −30 ° C. or lower. Further, when the viscosity index is less than 80, the temperature dependency of the viscosity is large, and a gear oil composition having excellent target temperature characteristics cannot be obtained. From the viewpoint of temperature dependence of viscosity, the viscosity index is particularly preferably 85 or more. The base oil of the component (A) is not particularly limited as long as it has the above properties, and any of various known mineral oils and synthetic oils conventionally used for gear oils can be used. It can be appropriately selected and used.

As a specific example of the mineral oil which can be used as the base oil of the component (A), a paraffin-based crude oil or an intermediate-based crude oil is subjected to atmospheric distillation or a residual oil obtained by atmospheric distillation is subjected to reduced-pressure distillation. Examples include refined oil obtained by purifying the obtained distillate according to a conventional method, and deep-dewaxed oil obtained by further deep-waxing treatment after purification. The purification method at this time is not particularly limited, and various methods can be considered. Usually, (a) hydrotreating,
(B) dewaxing treatment (solvent dewaxing or hydrogenation dewaxing),
(C) solvent extraction, (d) alkali distillation or sulfuric acid washing, and (e) clay treatment are performed alone or in an appropriate combination. It is also effective to repeat the same process in a plurality of stages. For example, hydrogenated distillate or hydrogenated, followed by alkali distillation or sulfuric acid washing, hydrogenated distillate, dewaxing, distillate oil solvent After the extraction treatment, a method of hydrogenation treatment, a two-stage or three-stage hydrogenation treatment of the distillate, or a method of alkali distillation or sulfuric acid washing treatment thereafter, and after the treatment as described above, again, There is a method of dewaxing to give deeply dewaxed oil. In any method, the properties of the obtained base oil (gear oil base oil) may be adjusted so as to have the above-mentioned viscosity, pour point and viscosity index.

On the other hand, examples of the synthetic oil include α-olefin oligomer, diester dihydrochloride, polyol ester, polyglycol ester, alkylbenzene, alkylnaphthalene and the like. In the present invention,
As the base oil of the component (A), one kind of the above-mentioned mineral oils and synthetic oils may be used, or two or more kinds thereof may be used in combination, but a mineral oil obtained by deep dewaxing treatment is particularly preferable. This deep dewaxing treatment is performed by a solvent dewaxing method under severe conditions, a contact hydrodewaxing method using a zeolite catalyst, or the like. Next, in the gear oil composition of the present invention, the component (B) has a number average molecular weight of 2,000 to 80.
An ethylene-α-olefin copolymer in the range of 00 is used. Here, if the number average molecular weight is less than 2,000, the effect of improving the viscosity index is not sufficient, and
If it exceeds 00, the shear stability is reduced. Considering the effect of improving the viscosity index and shear stability, the preferred number average molecular weight of the ethylene-α-olefin copolymer is in the range of 2500 to 5000.

[0008] The α-olefin used in the ethylene-α-olefin copolymer is preferably a compound having 3 to 3 carbon atoms.
20 alpha-olefins are preferred, e.g. propylene,
Preferred examples include 1-butene and 1-decene. The ratio of ethylene to α-olefin is 1: 9 to
A range of 9: 1 (weight ratio) is preferred. In the composition of the present invention, the ethylene-α-olefin copolymer of the component (B) may be used alone or in combination of two or more, and the content is based on the total amount of the composition. , 1.
It is selected in the range of 0 to 20% by weight. This amount is 1.0% by weight
If it is less than 3, the effect of improving the viscosity index is not sufficient.
If it exceeds 0% by weight, the viscosity at low temperature becomes high, and the practicality becomes poor. From the viewpoint of improving the viscosity index and balancing the viscosity at low temperatures, the preferred content of the component (B) is in the range of 2.0 to 10% by weight. In the gear oil composition of the present invention, zinc dialkyldithiophosphate is used as the component (C). As the zinc dialkyldithiophosphate, for example, a compound represented by the general formula (I)

[0009]

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(Wherein, R ¹ and R ² each represent a primary alkyl group having 1 to 18 carbon atoms or a secondary alkyl group having 3 to 18 carbon atoms, and they may be the same or different. May be preferably exemplified.

In the general formula (I), examples of the primary alkyl group having 1 to 18 carbon atoms among R ¹ and R ² include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, and Various primary pentyl groups, various hexyl groups, various octyl groups, various decyl groups, various dodecyl groups,
Examples include various tetradecyl groups, various hexadecyl groups, various octadecyl groups, and the like. As examples of 3 to 18 carbon atoms secondary alkyl groups of R ¹ and R ^2, an isopropyl group, sec- butyl group and secondary of various pentyl groups, various hexyl groups, various octyl groups, various Examples include decyl, various dodecyl, various tetradecyl, various hexadecyl, various octadecyl, cyclopentyl, cyclohexyl, and cyclooctyl groups.
As R ¹ and R ² , a primary alkyl group is preferred from the viewpoint of performance, and a primary alkyl group having 3 to 8 carbon atoms is particularly preferred.

In the present invention, the zinc dialkyldithiophosphate of the component (C) may be used alone or in combination of two or more, and the content thereof is 0.1% based on the total amount of the composition. It is selected in the range of 2 to 2.0% by weight.
If this amount is less than 0.2% by weight, the abrasion resistance and oxidation stability may not be sufficiently exhibited, and if it exceeds 2.0% by weight, no improvement in the effect is recognized for the amount. Economically disadvantageous. In consideration of abrasion resistance, oxidation stability, economy and the like, the preferred content of the component (C) is in the range of 0.5 to 1.5% by weight. Further, it is preferred that the composition contains about 0.05 to 0.2% by weight of a zinc atom in the composition from the viewpoint of maintaining abrasion resistance. In the gear oil composition of the present invention, a sulfurized oil or fat is used as the component (D). The sulfided oil is not particularly limited, and may be any of conventionally known ones, such as sulfided rice bran oil, sulfided rapeseed oil, sulfided lard, sulfided farm oil, and sulfided soybean oil.
Any one can be selected and used.

In the present invention, the sulfurized fat or oil of the component (D) may be used alone or in combination of two or more, and its content is 0.1 to 2.2% based on the total amount of the composition.
It is selected in the range of 0% by weight. If the amount is less than 0.1% by weight, extreme pressure resistance and wear resistance may be insufficient.
When the content exceeds 2.0% by weight, no improvement in the effect is recognized for the amount, and it is rather economically disadvantageous and the oxidation stability tends to decrease. Considering extreme pressure resistance, abrasion resistance, oxidation stability, economy and the like, the preferred content of the component (D) is in the range of 0.5 to 1.5% by weight. Further, as the sulfur atom in the sulfurized fat or oil, 0.05 to 0.05
The content of about 0.5% by weight is preferable in terms of achieving both extreme pressure properties and oxidation stability.

Further, in the gear oil composition of the present invention, the component (E) has a total base number of 200 mgKOH /
g or more of the calcium sulfonate is used. This calcium sulfonate has a total base number of 200 mg KOH /
If it is less than g, the oxidation stability is insufficient, and the object of the present invention cannot be achieved. From the viewpoint of oxidation stability, a preferable total base number of the component (E) is 300 mgKOH / g or more, and the upper limit is not particularly limited, but is practically 500 mgKOH / g.
It is about KOH / g. In the composition of the present invention, the calcium sulfonate of the component (E) may be used alone or in combination of two or more, and the content thereof is 0.2 to 3 based on the total amount of the composition. It is selected in the range of 0.0% by weight. If the amount is less than 0.2% by weight, the cleaning effect is insufficient and a gear oil composition having desired performance cannot be obtained. On the other hand, if the content exceeds 3.0% by weight, the effect is not improved in spite of the amount, which is rather economically disadvantageous, increases ash content, and deteriorates solubility in base oil. Considering the effects, solubility in base oil, ash content and economics,
The preferred content of the component (E) is 0.5 to 2.5% by weight.
Range. The gear oil composition of the present invention may further contain other additives such as an antioxidant, an ashless dispersant, a viscosity index improver, and a pour point depressant as long as the object of the present invention is not impaired. , Rust inhibitor, metal corrosion inhibitor, defoamer,
A copper deactivator, a surfactant, a coloring agent, and the like can be appropriately added.

Here, as the antioxidant, hindered phenol-based or amine-based antioxidants are preferably used. Hindered phenolic antioxidants include, for example, 4,4′-methylenebis (2,6-di-t-butylphenol); 4,4′-bis (2,6-di-t-butylphenol); '-Bis (2-methyl-6-t-
2,2′-methylenebis (4-ethyl-6-t-butylphenol); 2,2′-methylenebis (4-methyl-6-t-butylphenol);
4,4'-butylidenebis (3-methyl-6-t-butylphenol); 4,4'-isopropylidenebis (
2,6-di-t-butylphenol); 2,2′-methylenebis (4-methyl-6-nonylphenol);
2'-isobutylidenebis (4,6-dimethylphenol); 2,2'-methylenebis (4-methyl-6-cyclohexylphenol); 2,6-di-t-butyl-4
2,6-di-tert-butyl-4-ethylphenol; 2,4-dimethyl-6-tert-butylphenol; 2,6-di-tert-amyl-p-cresol;
2,6-di-t-butyl-4- (N, N'-dimethylaminomethylphenol);4,4'-thiobis(2-methyl-6-t-butylphenol);4,4'-thiobis (3 -Methyl-6-t-butylphenol); 2,
2'-thiobis (4-methyl-6-tert-butylphenol); bis (3-methyl-4-hydroxy-5-tert-butylbenzyl) sulfide; bis (3,5-di-tert-butyl-4-hydroxy) Benzyl) sulfide; n-octadecyl-3- (4-hydroxy-3,5-di-t-butylphenyl) propionate; 2,2′-thio [diethyl-bis-3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate].
Of these, bisphenols and ester group-containing phenols are particularly preferred.

The amine antioxidants include, for example, monooctyldiphenylamine; monoalkyldiphenylamine such as monononyldiphenylamine,
4,4'-dipentyldiphenylamine;4,4'-dihexyldiphenylamine;4,4'-diheptyldiphenylamine; 4,
4'-dioctyldiphenylamine; dialkyldiphenylamines such as 4,4'-dinonyldiphenylamine;tetrabutyldiphenylamine;tetrahexyldiphenylamine;tetraoctyldiphenylamine; polyalkyldiphenylamines such as tetranonyldiphenylamine; and naphthylamines, specifically Phenyl-α-naphthylamine; butylphenyl-α-naphthylamine; pentylphenyl-α-naphthylamine; hexylphenyl-α-naphthylamine; heptylphenyl-α-naphthylamine; octylphenyl-α-naphthylamine;
Examples include alkyl-substituted phenyl-α-naphthylamine such as nonylphenyl-α-naphthylamine. Of these, dialkyldiphenylamine-based and naphthylamine-based ones are preferred.

Examples of the ashless dispersant include succinimides, boron-containing succinimides, benzylamines, boron-containing benzylamines, succinates, fatty acids and succinic acids. And amides of divalent or divalent carboxylic acids. Examples of the viscosity index improver include polymethacrylate, dispersion-type polymethacrylate, and styrene-based copolymer (for example,
Styrene-diene hydrogenated copolymer, etc.) and pour point depressants include, for example, polymethacrylate.

As rust preventives, for example, alkenyl succinic acid and its partial ester are used. As metal corrosion inhibitors, for example, benzotriazole, benzimidazole, benzothiazole, thiadiazole and the like are used.
Examples of the antifoaming agent include dimethylpolysiloxane and polyacrylate, and examples of the surfactant include:
For example, polyoxyethylene alkyl phenyl ether is used.

[0019]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1 and 2 and Comparative Examples 1 to 3 Using the following components, gear oil compositions shown in Table 1 were prepared. Highly refined mineral oil: Hydrorefined base oil, kinematic viscosity at 100 ° C 5.6 mm
² / sec, viscosity index 90, pour point -40 ° C Ethylene-α-olefin copolymer: number average molecular weight 36
00 ethylene-propylene copolymer ZnDTP: zinc di-primary n-hexyldithiophosphate,
Zn content 9.8% by weight Sulfurized oil and fat: sulfurized lard, S content 10% by weight Ca sulfonate 300TBN: Total base number 300mgK
OH / g calcium sulfonate Ca sulfonate 100TBN: total base number 100mgK
OH / g calcium sulfonate polymethacrylate: number average molecular weight 2100

Next, the gear oil composition was subjected to an actual machine durability test and an oxidation deterioration test by the following method, and the total acid value was measured. In addition, temperature 100 ℃
Was measured. Table 1 shows the results. (1) Endurance test of actual machine Mission: 5-speed commercial mission Engine: 4-cycle, 3-cylinder, 660 cc Revolution: 8350 rpm (5th) Engine revolution: 7000 rpm (WOT) Durability: 300 hr. Mission oil temperature: 105 ° C. A real machine durability test was performed under the above conditions, and a change in viscosity was measured. (2) Total acid value An oxidation deterioration test was performed by a method in accordance with JIS K2514-4 Lubricating oil oxidation stability test for internal combustion engines, and JIS K250
The total acid value was measured by the method according to 1. The oxidation deterioration conditions were a temperature of 166.5 ° C. and a time of 72 hours.

[0021]

[Table 1]

[0022]

The gear oil composition of the present invention maintains a constant viscosity at a high temperature, has a low viscosity even at a very low temperature, and has excellent shear stability, extreme pressure properties, abrasion resistance and oxidation stability. I have.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10M 137: 10 135: 06 159: 24) C10N 10:04 20:02 20:04 30:04 30:06 30:08 30:10 40: 04

Claims (2)

[Claims] (A) a kinematic viscosity at 100 ° C. of 1.5 to 1.5;
(B) an ethylene-α-olefin copolymer having a number average molecular weight of 2,000 to 8,000 based on 50 mm ² / sec, a base oil having a pour point of −25 ° C. or less and a viscosity index of 80 or more, and the total amount of the composition; 20% by weight, (C) 0.2 to 2.0% by weight of zinc dialkyldithiophosphate, (D) sulfurated oil and fat 0.1 to 0.1%
A gear oil composition comprising 2.0% by weight and (E) 0.2 to 3.0% by weight of a calcium sulfonate having a total base number of 200 mgKOH / g or more. 2. The gear oil composition according to claim 1, wherein the zinc dialkyldithiophosphate of the component (C) has a primary alkyl group.