JPH10168477A - Lubricating oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a power steering fluid composition which can prevent the deteriorating of a rubber hose exposed to high temperature and high pressure and the seizure of a hydraulic pump that rotates at high speed and which is excellent in lubricvity to aluminum alloys and in anticorrosiveness to copper alloys by blending a lube base oil with a zinc-base antioxidant, a branched monobasic fatty acid or cyclic mono- or dibasic fatty acid, a thiadiazole derivative and a benzotriazole derivative each in a specified amount. SOLUTION: This composition is obtained by blending a lube base oil with a zinc-base antioxidant (A), a component (B) comprising a branched monobasic fatty acid or a cyclic mono- or dibasic fatty acid, and an least one compound (C) selected from thiadiazole derivatives represented by formula I (R<1> and R<2> are each a 1-12C linear or branched alkyl) and benzotriazole derivatives represented by formula II [wherein R<3> is H or methyl; and X is H or -CH2 NR<4> (R<5> ) R<4> and R<5> are each an 8-18C linear or branched alkyl)], the amounts of components A, B and C respectively being 0.1-3wt.%, 0.01-1wt.% and 0.01-0.5wt.% based on the total composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition suitable for a power steering fluid of an automobile.

[0002]

2. Description of the Related Art In recent years, the attachment of power steering to passenger cars has become commonplace. On the other hand, due to demands for higher performance and lighter weight of passenger cars, power steering fluid (hereinafter sometimes abbreviated as PSF) is used at a maximum pressure of 140 kg / cm ² and a maximum oil temperature of 150 ° C. Often used. Hydraulic pumps have been reduced in size and increased in speed due to the demand for weight reduction, and aluminum alloys have begun to be used.In addition to steel and copper alloys that have been used as metal materials, lubricating properties are required for aluminum alloys. It has come to be. Until now, PSF
Is an automatic transmission fluid (A
Abbreviated as TF. ), But ATF is required to maintain appropriate friction characteristics of the wet friction agent, maintain gear characteristics for the speed reducer, and to be compatible with the rubber sealant, mainly to reduce shock during shifting. You. In contrast, recent PSFs use rubber hoses as part of the high-temperature, high-pressure power steering circuit, as well as oxidation stability at high temperatures, so that they have even better rubber compatibility and compact, high-speed pumps. With the demand for high-speed seizure resistance at high speeds, lubricity against aluminum alloys, metal corrosion prevention, and the like, a PSF-specific oil has been demanded.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents deterioration of a rubber hose exposed to high temperature and high pressure, prevents seizure of a small, high-speed rotating hydraulic pump, and It is an object of the present invention to provide a lubricating oil composition which is excellent in lubricating properties for aluminum alloys and further excellent in corrosion inhibiting properties for copper alloys and is suitable for power steering fluids.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above object of the present invention can be effectively achieved by using a specific fatty acid as an additive in combination. The invention has been completed. That is, the present invention relates to a lubricant base oil comprising (A) 0.1 to 3% by weight of a zinc-based antioxidant, (B) a branched monovalent fatty acid or a cyclic monovalent or divalent fatty acid, based on the total amount of the composition. 0.01 to 1% by weight of a polyvalent fatty acid and (C) the following general formula (I)

[0005]

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(Wherein, R ¹ and R ² each represent a linear or branched alkyl group having 1 to 12 carbon atoms, which may be the same or different). Thiadiazole derivative and the following general formula (II)

[0007]

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[Wherein, R ³ represents hydrogen or a methyl group;
X represents hydrogen or —CH ₂ NR ⁴ (R ⁵ ), wherein R ⁴ and R ⁵ each represent a linear or branched alkyl group having 8 to 18 carbon atoms, and they are the same. But they may be different. At least one selected from benzotriazole derivatives represented by the formula: 0.01 to 0.5% by weight
And a lubricating oil composition further comprising (D) 0.1 to 10% by weight of a metallic detergent based on the total amount of the composition.

[0009]

Embodiments of the present invention will be described below. In the lubricating oil composition of the present invention, mineral oil and / or synthetic oil is used as the lubricating base oil. This mineral oil or synthetic oil is not particularly limited as long as it is generally used as a base oil for a lubricating oil, but is not limited in terms of wear resistance and efficiency of a power steering gear portion, or fluidity at a low temperature. Kinematic viscosity at 100 ° C is 1 to 30m
m ² / s, preferably ^{2 to 10} mm ²
/ S is more preferable. The pour point, which is an index of the low-temperature fluidity of the base oil, is not particularly limited, but is preferably −10 ° C. or lower.

[0010] There are various types of such mineral oils and synthetic oils, and they may be appropriately selected depending on the use and the like. As the mineral oil, for example, a distillate obtained by distilling a paraffinic-base crude oil, an intermediate-base crude oil or a naphthenic-base crude oil under normal pressure, or a residual oil obtained by normal-pressure distillation under reduced pressure, or a distillate obtained by a conventional method Accordingly, refined oils obtained by refining, for example, solvent refined oils, hydrogenated refined oils, dewaxed oils, and clay treated oils can be exemplified.

On the other hand, synthetic oils include, for example, poly α-olefin, α-olefin copolymer, polybutene, alkylbenzene, polyol ester, dibasic acid ester, polyoxyalkylene glycol, polyoxyalkylene glycol ester, polyoxyalkylene glycol ether, Examples include silicone oil. These base oils can be used alone or in combination of two or more, and mineral oil and synthetic oil may be used in combination.

Next, (A), which is blended with the lubricating base oil,
The components (B), (C) and (D) will be described. The (A) component zinc-based antioxidant is not particularly limited as long as it contains zinc and has an antioxidant ability. Primary type zinc dithiophosphate having a primary alkyl group has antioxidant properties at high temperatures and rubber aging. It is preferable from the viewpoint of prevention. In the present invention, the above-mentioned component (A) may be used alone or in combination of two or more. The compounding amount is usually 0.1 to 3 based on the total amount of the composition.
In the range of wt%, the range of 0.1 to 1 wt% is more preferable, and the range of 0.2 to 0.8 wt% is particularly preferable. If it exceeds 3% by weight, rubber aging characteristics may be adversely affected, and if it is less than 0.1% by weight, a sufficient effect cannot be obtained.

(B) Component The branched monovalent fatty acid is a saturated or unsaturated fatty acid having 8 to 30 carbon atoms, and islauric acid, isomyristic acid, isopalmitic acid, isostearic acid, isoarachinic acid,
Isobehenic acid, isocaproleic acid, isolindelic acid,
Examples include isomiristoleic acid, isosomalic acid, isooleic acid, and isoerucic acid, and preferred are isopalmitic acid, isostearic acid, and isooleic acid.

The cyclic monovalent or divalent fatty acid is a saturated or unsaturated fatty acid having 8 to 30 carbon atoms, for example, 9,10-methylene-9-octadecenoic acid; areprilic acid, alepic acid, gorlic acid, α-cyclopentyl Acid, α-cyclohexyl acid, α-cyclopentylethyl acid, α-cyclohexylmethyl acid, ω-cyclohexyl acid; 5 (6) -carboxy-4-hexyl-2-cyclohexene-1-octanoic acid, etc. Things. Above all, 5
(6) -Carboxy-4-hexyl-2-cyclohexene-1-
Octanoic acid; 9,10-methylene-9-octadecenoic acid;

In the present invention, the above component (B) may be used alone or in combination of two or more.
The compounding amount is usually 0.01% based on the total amount of the composition.
In the range of 1 to 1% by weight, the range of 0.03 to 0.5% by weight is more preferable. If the amount exceeds 1% by weight, the effect may be saturated and disadvantages such as precipitation may occur. If the amount is less than 0.01% by weight, a sufficient effect cannot be obtained. Component (C) The following general formula (I)

[0016]

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(Wherein R ¹ and R ² are the same as described above), or the following general formula (II)

[0018]

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(Wherein, R ³ , X, R ⁴ and R ⁵ are the same as described above). Specific examples of the alkyl group of R ¹ and R ^{2 in} the general formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, various butyl groups, various pentyl groups,
Examples include various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various undecyl groups, and various dodecyl groups. A preferred alkyl group has 1 to 8 carbon atoms.

Specific examples of the alkyl group of R ⁴ and R ^{5 in} the general formula (II) include various octyl groups, various nonyl groups, various decyl groups, various undecyl groups, various dodecyl groups, various tridecyl groups, various tetradecyl groups, and the like. Groups, various pentadecyl groups, various hexadecyl groups, various heptadecyl groups, and various octadecyl groups. Preferred alkyl groups have 10 to 16 carbon atoms.

In the present invention, the above component (C) may be used alone or in combination of two or more.
The compounding amount is usually 0.01% based on the total amount of the composition.
In the range of 0.5 to 0.5% by weight, the range of 0.05 to 0.3% by weight is more preferable. If it exceeds 0.5% by weight, the effect is saturated, and if it is less than 0.01% by weight, a sufficient effect cannot be obtained.

Component (D) In the present invention, in addition to the components (A), (B) and (C), a metal-based detergent of the component (D) can be blended if necessary for the purpose of preventing sludge formation. . The metal-based detergent is preferably one kind selected from sulfonates, phenates and salicylates of overbased alkaline earth metals. Preferred total base number is 20-600 mgKOH / g
(JIS K-2501: perchloric acid method). If the total base number is too low, neutralization of acidic substances generated by oxidation may be insufficient. If the total base number is too high, the ash content in the lubricating oil increases, and there is a risk that a large amount of deposits may be generated over a long period of use, which is not preferable.

The overbased alkaline earth metal sulfonate is an alkaline earth metal salt of various sulfonic acids, and is usually obtained by a method of carbonating an alkaline earth metal salt of various sulfonic acids. Examples of the sulfonic acid include aromatic petroleum sulfonic acid, alkyl sulfonic acid, aryl sulfonic acid, and alkylaryl sulfonic acid, and specifically, dodecylbenzene sulfonic acid, dilauryl cetyl benzene sulfonic acid, and paraffin wax-substituted benzene sulfonic acid. And polyolefin-substituted benzenesulfonic acid, polyisobutylene-substituted benzenesulfonic acid, and naphthalenesulfonic acid.

The overbased alkaline earth metal phenate is an alkaline earth metal salt of an alkylphenol or a sulfurized alkylphenol, and is usually obtained by a method of carbonating an alkaline earth metal salt of an alkylphenol or a sulfurized alkylphenol. Salicylate of an overbased alkaline earth metal is an alkali metal salt of alkyl salicylic acid, usually alkylating phenol with an α-olefin having 8 to 18 carbon atoms, then introducing a carboxyl group by a Kolbeschmidt reaction, followed by metathesis. And carbonation. Specific examples of the alkyl salicylic acid include dodecyl salicylic acid, dodecyl methyl salicylic acid, tetradecyl salicylic acid, hexadecyl salicylic acid, octadecyl salicylic acid, and dioctyl salicylic acid.

Examples of the alkaline earth metals of the above sulfonates, phenates and salicylates include calcium, barium and magnesium, but calcium is preferred in view of the effect. In the present invention, one type of the component (D) may be used, or two or more types may be used. The compounding amount is in the range of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the total amount of the composition. If the content is less than 0.1% by weight, a sufficient effect cannot be obtained, and
Even if it exceeds 0% by weight, no improvement in the effect corresponding to the blending amount is observed.

The composition of the present invention can be obtained by blending the above components (A) to (C) or the components (A) to (D) with a lubricating base oil. In order to maintain the basic performance as a fluid, a viscosity index improver as long as the object of the present invention is not impaired,
Ashless friction modifier, Ashless antioxidant, Ashless dispersant,
An antifoaming agent or the like can be appropriately compounded.

Examples of the viscosity index improver include polymethacrylate, polyisobutylene, ethylene-propylene copolymer and the like. The compounding amount is usually 0.5 to 20% by weight based on the total amount of the composition. Examples of the ashless friction modifier include a fatty acid amide compound, a reaction product of a fatty acid and diethanolamine, a succinic acid ester derivative, N-oleyl sarcosine, a fatty acid glyceride, an acid phosphate ester amine salt, a phosphite, and the like. The compounding amount is usually 0.05 to 3% by weight based on the total amount of the composition.

Examples of the ashless antioxidants include phenolic compounds, amine compounds, carbamate compounds and the like, and the compounding amount is usually 0.1% based on the total amount of the composition.
~ 2% by weight. Examples of the ashless dispersant include alkenyl succinimide, benzylamine, polyoxyalkylene amide and the like, and the compounding amount is usually 0.1 to 3% by weight based on the total amount of the composition. Examples of the antifoaming agent include dimethylpolysiloxane, polyacrylate and the like.
0.005% by weight.

[0029]

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 to 5 and Comparative Examples 1 to 4 Power steering fluid compositions of the present invention were prepared at the ratios shown in Table 1. The compositions of these Examples and Comparative Examples were subjected to a rubber compatibility test, a corrosion test of a copper alloy, a seizure resistance test between steel and steel, and a lubricity test between steel and aluminum alloy in the following manner. Table 1 shows the results.

[Rubber compatibility test] The following method was used. Test method: JIS Z-6301 (rubber swelling test) Rubber agent used: HNBR (hydrogenated NBR) Test temperature: 150 ° C Test time: 144 hours Evaluation items: strength change rate, elongation change rate (%)

[Corrosion test of copper alloy] The test was performed by the following method. Test method: JIS K-2513 (copper plate corrosion test) Test temperature: 100 ° C Test time: 3 hours

[Steel-to-Steel Seizure Resistance Test] The test was carried out by the following method. Test method: ASTM D-3704 Ring material: S10 material Block material: H60 material Rotation speed: 3000 rpm Test temperature: 100 ° C Test item: Seizure load (Lb)

[Lubricity test between steel and aluminum alloy]
The procedure was as follows. In the friction test between steel and aluminum alloy, the soft aluminum alloy is easily worn, and the seizure load may not be clearly detected.
It was evaluated by the coefficient of friction. Test method: ASTM D-3704 Ring material: JIS H-5202-AC5A Material Block material: H60 Material Rotation speed: 3000 rpm Test temperature: 100 ° C Test item: Coefficient of friction at a load of 20 Lb

[0034]

[Table 1]

(Note) * 1: Kinematic viscosity of paraffinic mineral oil at 100 ° C.
2 mm ² / s * 2: pri. Zinc hexyl dithiophosphate * 3: sec. Zinc hexyl dithiophosphate * 4: 2-heptylundecanoic acid * 5: 2-hexyldecanoic acid * 6: 5 (6) -carboxy-4-hexyl-2-cyclohexene-1-octanoic acid * 7: 2,5 bis (1 , 1,3,3-tetramethylbutanedithio)
1,3,4-thiadiazole * 8: Total base number 150 mgKOH / g * 9: Total base number 250 mgKOH / g * 10: Total base number 150 mgKOH / g * 11: Viscosity index improver, dispersant, ashless friction adjustment Agent and defoamer.

[0036]

[Table 2]

(Note) * 1 to * 11: Same as Table 1

[0038]

Industrial Applicability The lubricating oil composition of the present invention prevents deterioration of a rubber hose exposed to high temperature and high pressure, prevents seizure of a small, high-speed rotating hydraulic pump, and has excellent lubricating properties for aluminum alloys. In addition, it can be used for a long period of time with the latest power steering system, which has excellent corrosion protection against copper alloys.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10M 129: 42 133: 44) (C10M 141/08 125: 24 129: 40 129: 42 135: 36) C10N 10:04 30: 04 30:08 30:10 30:12 40:04

Claims (2)

[Claims] Claims 1. A lubricating base oil comprising (A)
0.1 to 3% by weight of a zinc-based antioxidant, (B) 0.01 of a branched monovalent fatty acid or a cyclic monovalent or divalent fatty acid
To 1% by weight and (C) the following general formula (I): (Wherein, R ¹ and R ² each represent a linear or branched alkyl group having 1 to 12 carbon atoms, which may be the same or different from each other.) And the following general formula (II): [Wherein, R ³ represents hydrogen or a methyl group, X represents hydrogen or —CH ₂ NR ⁴ (R ⁵ ), wherein R ⁴ and R ⁵ are each a linear or It represents a branched alkyl group, which may be the same or different. ] A lubricating oil composition comprising 0.01 to 0.5% by weight of at least one selected from the benzotriazole derivatives represented by the formula: 2. A lubricating oil composition comprising the composition according to claim 1 and 0.1 to 10% by weight of a metal detergent (D) based on the total amount of the composition.