JPH09272885A - Lubricating oil composition for wet clutch - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: By changing the base oil composition itself of an automatic transmission oil for automobiles and a lubricating oil for wet clutches of construction machinery and agricultural machinery, it has a high friction coefficient and excellent thermal oxidation stability. A lubricating oil composition is provided. A lubricating oil composition for a wet clutch, which contains, as all or part of a base oil, polybutene in an amount of 10.0 to 95.0 mass% of the total amount of the composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lubricating oil composition used for a wet clutch of an automatic transmission for automobiles, construction machinery, agricultural machinery and the like. More specifically, it relates to a lubricating oil composition for a wet clutch, which has a high coefficient of friction and is excellent in thermal oxidation stability.

[0002]

2. Description of the Related Art It is important for automatic transmission oils for automobiles and lubricating oils for wet clutches of construction machinery and agricultural machinery that they have excellent properties such as friction characteristics against wet clutches, thermal oxidation stability, and wear resistance. is there. As a standard, GM company DEXR
There are ONIII standard and Ford MERCON standard.

Conventionally, as automatic transmission oils for automobiles and lubricating oils for wet clutches of construction machinery and agricultural machinery that meet these standards, various additives (antioxidants, detergent dispersants, antiwear agents, etc.) have been conventionally added to base oils. A rust preventive agent, a metal deactivator, a friction coefficient adjusting agent, a defoaming agent, a coloring agent, a seal swelling agent, a viscosity index improving agent, etc.) are blended. As the base oil, mineral oils such as general mineral oils, mineral oils having improved low-temperature fluidity excluding wax content, mineral oils having improved viscosity index, and poly α
-Synthetic oils such as olefins are used alone or in combination.

[0004]

In the automatic transmission oil for automobiles of recent years, in order to increase the transmission torque capacity in response to the weight reduction of the automatic transmission and the high output of the engine, a wet multi-plate clutch is used. It is required to increase the friction coefficient. Further, since the heat load increases with the reduction in weight and size, improvement in thermal oxidation stability is required.
The same applies to the lubricating oil for wet clutches of construction machines and agricultural machines.

A friction material in which a cellulose resin is impregnated with a phenol resin is widely used for a wet clutch of an automatic transmission for automobiles and construction machinery / agricultural machinery. Since this paper friction material is porous with elasticity, the friction characteristics of the wet clutch using it are as follows: friction material (fiber or resin material, cellulose fiber diameter, pore diameter, porosity, etc.), lubricating oil (Viscosity, additives), surface temperature, pressing load, sliding speed, etc. affect intricately, making their control and prediction difficult.

In the conventional art, in order to increase the dynamic friction coefficient of the wet clutch, the present situation is to deal with it by selecting a lubricating oil additive and adjusting the blending ratio. For example, metallic detergent dispersants such as sulfonate and phenate are used as friction coefficient adjusters. However, the addition of these metallic detergent dispersants tends to significantly increase the total oxidation of the lubricating oil. This is because the sulfonate and phenate contain a sulfur atom in the molecule, so that they are thermally decomposed in the process of use to generate an acidic component such as H ₂ SO ₄ .

According to the present invention, by changing the base oil composition itself of the lubricating oil for wet clutches, it has a friction adjusting function equivalent to that of the lubricating oil for wet clutches to which sulfonate or phenate is added, and moreover, the thermal oxidation stability is improved. An object is to provide an excellent lubricating oil composition for wet clutches.

[0008]

Means for Solving the Problems The present inventors conducted experiments and studies based on the idea of changing the base oil composition itself, rather than dealing with the additive formulation as in the prior art. It was possible to complete the lubricating oil composition for wet clutches of the present invention, which has an excellent friction coefficient and thermal oxidation stability. The present invention is characterized by containing 10.0 to 95.0 mass% of polybutene with respect to the total amount of the composition as the whole or a part of the base oil.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized in that polybutene, which is a hydrocarbon-based synthetic oil, is used as all or part of a base oil. When polybutene is used as the base oil of the lubricating oil for wet clutches, it has the effects of increasing the friction coefficient and improving the thermal oxidation stability. Polybutene is generally used for automobile engine oils, traction drive oils, etc., but it has not been used as a base oil for automobile automatic transmission oils and other wet clutch lubricating oils. The polybutene used in the present invention is not particularly limited, and its production method does not matter. From the viewpoint of easy availability, polyisobutylene represented by the following formula is preferable.

[0010]

Embedded image (In the formula, n is an integer of 5 to 60.)

The blending ratio of polybutene is 10.0 to 95.0% by mass with respect to the total amount of the composition. Preferably,
It is 45.0-91.0 mass%. If it is less than 10.0% by mass, the effect of increasing the friction coefficient and the effect of improving the thermal oxidation stability are insufficient. If it exceeds 95.0% by mass, there is no effect in proportion to the increase in the amount, and since the compounding ratio of the additive decreases, the required performance may be adversely affected.

In the present invention, mineral oil or synthetic oil can be used as the base oil composition other than polybutene. As the mineral oil, in addition to general mineral oil, solvent refining or hydrorefining is performed to further remove the wax content to improve low-temperature fluidity, and mineral oil with improved viscosity index by various manufacturing methods (high viscosity index base oil) Etc. can be used. Examples of synthetic oils include poly-α-olefin oligomers, diesters, and polyol esters. Considering the solubility of additives and the like, it is preferable to use a mixture of mineral oil and a synthetic oil, rather than using them alone.

The kinematic viscosity of the base oil containing polybutene at 100 ° C. is
Considering the appropriate viscosity for gears and the fluidity at low temperature, it is preferably 2.5 to 10.0 mm ² / s. If necessary, various viscosity index improvers having a thickening effect are used.

The viscosity of the composition of the present invention has a kinematic viscosity of 2.0 to 30.0 mm ² / s at 100 ° C. from the viewpoints of abrasion resistance, seizure resistance, fluidity at low temperature and the like.
Is preferred. It is more preferably 5.0 to 15.0 mm ² / s. As an automatic transmission oil for automobiles, even more preferably, the kinematic viscosity at 100 ° C. is 6.0 to 8.0 mm ² / s,
The kinematic viscosity at -40 ° C is 20,000 cP or less.

In order to maintain the basic performance as a lubricating oil for wet clutches, the composition of the present invention is an antioxidant, an antiwear agent, a detergent dispersant, and a metal within the scope of achieving the object of the present invention. Deactivating agent, friction coefficient adjusting agent, defoaming agent,
An appropriate amount of a viscosity index improver or the like can be added.

Examples of the antioxidant include phenol compounds (2,6-di-t-butyl-P-cresol,
2,6-di-t-butylphenol, 2,6'-di-t
-Butyl-α-dimethylamino-P-cresol, 4,
4'-thiobis- (6-di-t-butyl-o-cresol), 4,4'-methylenebis- (2,6-di-t-butylphenol), etc., amine compounds (diphenylamine, 4,4'- Tetramethyl-diaminodiphenyl-
Methane, phenyl-α-naphthylamine, alkylphenyl-β-naphthylamine, phenothiazine, etc.), sulfur compounds (olefin sulfides, terpene sulfides, dialkyl sulfides, dialkyl disulfides, etc.), zinc dithiophosphate compounds (Zn-dialkyldithiophosphite) , Zn-dialkylallyldithiophosphate, Zn-dialkyldithiocarbamate, etc.) and others.

Examples of the antiwear agent include, for example, acidic phosphoric acid esters (tricresyl phosphate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, 2-ethylhexyl acid phosphate, isohydrate). Decyl acid phosphate, lauryl acid phosphate, tridecyl acid phosphate, stearyl acid phosphate, isostearyl acid phosphate, oleyl acid phosphate, di-2-ethylhexyl phosphate, etc.), phosphites (triphenyl) Phosphite, tri (p-cresyl) phosphite, tris (nonylphenyl) phosphite, triisooctylphosphite, diphenylisodecylphosphite, phenyl Diisodecyl phosphite, tri-isodecyl phosphite, tristearyl phosphite,
Trioleyl phosphite, trilauryl trithiophosphite, di-2-ethylhexyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, etc.), amine salt compounds of phosphoric acid ester (trialkylthiophosphate, Di (2-ethylhexyl) dithiophosphoric acid, 2-methylhexyl hydroxymethylphosphonate, triethyl-3-
Phosphonopropionate, etc.) and others.

Examples of the detergent dispersant include alkaline earth metal sulfonates, alkaline earth metal phenates,
Examples thereof include alkaline earth metal salicylates, succinimides, and benzylamine.

Examples of the metal deactivator include benzotriazole and thiadiazole.

Examples of the friction coefficient adjusting agent include higher fatty acids (oleic acid, stearic acid, palmitic acid, etc.), higher alcohols (lauryl alcohol, oleyl alcohol, cetyl alcohol, etc.), esters (ethyl oleate, sorbitan, etc.). Monostearate, oleic acid monoglyceride, etc.), amine compounds (cetylamine, octadecylamine, etc.) and the like.

Examples of the defoaming agent include silicone compounds (dimethylsiloxane, phenylmethylsiloxane, cyclic organosiloxane, etc.), ester compounds (sorbitan monolaurate, alkenylsuccinic acid derivative, etc.) and the like.

Examples of the viscosity index improver include PMA.
(Polymethacrylate), EPC (ethylene / propylene copolymer), SDC (styrene / diester copolymer), OCP (olefin copolymer) and the like.

[0023]

EXAMPLES Examples and comparative examples of the present invention will be described below. Note that the present invention is not limited to the embodiments.

1. Composition Table 1 shows compositions of Examples and Comparative Examples. Mineral oil is 10
The one having a kinematic viscosity at 0 ° C. of 4.0 mm ² / s was used.
The polybutene used was polyisobutylene represented by the formula (average value of n = 6) and having an average molecular weight of 350.
The kinematic viscosity of the base oil at 100 ° C. is 4.0 mm ² / s in both Examples and Comparative Examples. As the package additive for ATF (automatic transmission oil for automobiles), one manufactured by Ethyl Co. was used. This is a mixture of an antioxidant, a detergent dispersant, an antiwear agent, a metal deactivator, a friction coefficient modifier, a defoaming agent, a viscosity index improver, and a pour point depressant.

[0025]

[Table 1]

2. Test method The friction characteristics of the examples and the comparative examples are SA by Automax.
ENo. The thermal oxidation stability was evaluated by a 2 friction tester and a lubricating oil oxidation stability test for internal combustion engines (JIS K2514). The respective test conditions are shown in Tables 2 and 3.

[0027]

[Table 2]

[0028]

[Table 3]

3. Test results Test results are shown in Tables 4 and 5. In addition, in Table 4 and Table 5,
μ1800 is a dynamic friction coefficient at 1800 rpm, and μs is a static friction coefficient.

[0030]

[Table 4]

[0031]

[Table 5]

4. Evaluation The target standard value for having a high friction coefficient is μ1800.
(Dynamic friction coefficient) 0.140 or more, μs (Static friction coefficient)
It was set to 0.110 or more. The target standard value for making the thermal oxidation stability favorable was a total oxidation increase of 1.0 mgKOH / g or less.

(1) Examples 1 to 5 All of the examples have a high friction coefficient and excellent thermal oxidation stability. In addition, Example 2 in which polybutene is 50% of the base oil has better friction coefficient and thermal oxidation stability than Example 1 (polybutene is 11% of the base oil). Example 4 in which the amount of polybutene was increased (polybutene was 100% of the base oil and 90.5 wt% of the total composition) showed the best value in the overall evaluation of the friction coefficient and thermooxidative stability. Further, in Example 5 in which the amount of polybutene was increased (polybutene was 100% of the base oil and 95% by weight of the entire composition), the thermal oxidation stability was better, but the friction coefficient was not increased, as compared with Example 4. showed that. In addition, 50% of the mineral oil in Example 2 is poly-α-
In Example 3 in which the olefin was substituted, the thermal oxidation stability was remarkably improved, but the friction coefficient was not changed, as compared with Example 2.

(2) Comparative Examples 1 and 2 Comparative Example 1 in which no polybutene was added to the base oil (the base oil was mineral oil 1
00%) is inferior in both friction coefficient and thermal oxidation stability. Comparative Example 2 (base oil is 100% poly-α-olefin) has good thermal oxidation stability, but has a poor friction coefficient.

(3) Comparative Example 3 Comparative Example 3 (polybutene is 9.0 wt% of the entire composition)
Both the friction coefficient and the thermal oxidation stability are below the target standard values. From Example 1 and Comparative Example 3, the lower limit of the blending ratio of polybutene in the present invention is 1 with respect to the entire composition.
It can be seen that the content is 0.0% by mass.

(4) Comparative Example 4 Comparative Example 4 (polybutene is 96 wt% of the entire composition)
The coefficient of friction is less than or equal to the target standard value. Example 5 and Comparative Example 4
From the above, it is understood that the upper limit of the blending ratio of polybutene in the present invention is 95.0 mass% with respect to the entire composition. The amount of polybutene increased above this upper limit is A
To reduce the amount of TF package additive compounded,
May adversely affect performance.

[0037]

The lubricating oil composition for wet clutches of the present invention is constructed based on the technical idea of using polybutene as all or part of the "base oil". This is completely different from the conventional technical idea in which polybutene is used as an “additive” such as a viscosity index improver in the field of lubricating oil for wet clutches. The present invention can maintain a high coefficient of friction while exhibiting excellent thermo-oxidative stability. Therefore, by using the lubricating oil for a wet clutch prepared by the composition of the present invention, it is possible to further reduce the weight and the output of a construction machine / agricultural machine equipped with an automatic transmission for automobiles and a wet clutch.

[Procedure amendment]

[Submission date] April 16, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

In the conventional art, in order to increase the dynamic friction coefficient of the wet clutch, the present situation is to deal with it by selecting a lubricating oil additive and adjusting the blending ratio. For example, metallic detergent dispersants such as sulfonate and phenate are used as friction coefficient adjusters. However, the addition of these metallic detergent-dispersant, a tendency that the total acid number of the lubricating oil is increased considerably. This is because the sulfonate or phenate contains a sulfur atom in the molecule, so that it undergoes thermal decomposition in the process of use and produces an acidic component such as H ₂ SO ₄ .

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

[0030]

[Table 4]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

[0031]

[Table 5]

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction contents]

4. Evaluation The target standard value for having a high friction coefficient is μ1800.
(Dynamic friction coefficient) 0.140 or more, μs (Static friction coefficient)
It was set to 0.110 or more. Target reference value thermal oxidation stability is good was less total acid number increase 1.0 mgKOH / g.

Claims (1)

[Claims] 1. A lubricating oil composition for a wet clutch, which comprises, as a whole or a part of a base oil, 10.0 to 95.0% by mass of polybutene based on the total amount of the composition.