JP2003055680A - Propeller shaft grease - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a propeller shaft grease composition which excels in seizing resistance, oxidative stability, oil separating properties and the like and can maintain high lubricity performance for a long period of time in the sealed environment susceptible to a high temperature and a high-speed centrifugal force. SOLUTION: The propeller shaft grease composition comprises a base oil, a thickening agent having a dropping point of >=240 deg.C, and a viscosity index improver, and furthermore (a) 0.1-5 wt.% nickel dithiocarbamate, (b) 0.2-30 wt.% zinc dithiocarbamate, and (c) 0.2-10 wt.% phosphoric acid based additive as the lubricity improvers.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a grease composition for a propeller shaft. More specifically, the present invention provides
In a sealed environment that receives high temperature and high speed centrifugal force,
Excellent in seizure resistance, oxidation stability and oil separation resistance,
In particular, the present invention relates to a propeller shaft grease composition suitable as a lubricant for a universal joint mounted on a propeller shaft of an automobile for transmitting a driving force from an engine to an axle.

[0002]

2. Description of the Related Art Propeller shafts used in FW vehicles and 4WD vehicles are shafts that connect a transmission side and a differential gear side, and a universal joint is appropriately provided on the way. Conventionally, many greases for wheel bearings and general-purpose greases (multipurpose greases) have been used as lubricants for this universal joint. However, with the recent technological progress, there is a demand for a grease that can be used for a long period of time even in a severe environment such as sealing, high temperature, high speed, high torque, and high angle. As a lubricating grease for a universal joint, for example, one disclosed in Japanese Patent Laid-Open No. 6-17075 is known, but this lubricating grease is not always satisfactory under the harsh environment. Of course, there has been a demand for the development of a lubricating grease for universal joints that exhibits excellent performance even in the severe environment.

[0003]

Under the circumstances, the present invention is excellent in seizure resistance, oxidation stability, oil separation property, etc. in a sealed environment subjected to high temperature and high speed centrifugal force. An object of the present invention is to provide a grease composition for a propeller shaft, which can maintain lubrication performance for a long period of time and is particularly suitable as a lubricant for a universal joint attached to a propeller shaft of an automobile for transmitting a driving force from an engine to an axle. It is what

[0004]

Means for Solving the Problems As a result of intensive studies to develop the above-mentioned grease composition having excellent performance, the present inventors have found that a base oil, a thickener, and a viscosity index improver are included. As a lubricity improver, they have found that a grease composition containing three kinds of compounds in a specific ratio can meet the purpose. The present invention has been completed based on such findings. That is, the present invention uses a base oil and a dropping point 2
A thickener having a temperature of 40 ° C. or higher and a viscosity index improver are included, and as a lubricity improver, (a) nickel dithiocarbamate 0.1 to 5% by weight, and (b) zinc dithiocarbamate 0.2 to 30% by weight. And (c) phosphorus-based additive 0.2 to
The present invention provides a grease composition for a propeller shaft, which comprises 10% by weight.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As the base oil in the grease composition of the present invention, a mineral oil or a synthetic oil conventionally used as a base oil for grease is used, but a base oil excellent in oxidation stability is preferable. As the mineral oil, highly refined paraffinic mineral oil obtained by solvent refining or hydrorefining is suitable, and as the synthetic oil, poly α-olefin oligomer, polyol ester, polyglycol ester, dibasic acid ester, phosphoric acid ester. And ester-based oils such as, alkylbenzenes, alkylaryl compounds such as alkylnaphthalene, ether-based oils such as phenyl ether and perfluoropolyalkyl ethers, and silicone oils. These base oils may be used alone or in combination of two or more. It is also possible to use a mixture of mineral oil and synthetic oil. The viscosity of this base oil is not particularly limited, but is usually 5 to 500 mm at 40 ° C.
² / s, preferably 20 to 400 mm ² / s is appropriately selected from the range.

In the grease composition of the present invention, a thickening agent having a dropping point of 240 ° C. or higher is used.
If the dropping point is less than 240 ° C, the heat resistance is insufficient,
There is concern that the grease composition may leak due to softening. The preferred dropping point is 260 ° C or higher, especially 280 ° C.
The above is preferable. The thickener is not particularly limited as long as it has the above-mentioned dropping point, and can be appropriately selected and used from those conventionally used as thickeners in conventional greases. Specifically, lithium complex-based, calcium complex-based, aluminum complex-based, monourea, diurea, triurea, tetraurea, polyurea and other urea-based,
Calcium sulfonate, silica, benton, etc. are used. These may be used singly or in combination of two or more, and may be used at 150 to 200 ° C.
Lithium complex thickeners that are less likely to be thermally cured at the above temperature are suitable.

In the grease composition of the present invention, the content of the thickener is usually selected in the range of 2 to 40% by weight. If the content is less than 2% by weight, the desired consistency may not be obtained, and if it exceeds 40% by weight, lubricating performance may be deteriorated. From the viewpoint of the balance of consistency and lubricating performance, the content of the thickener is preferably 5 to 30% by weight, and particularly preferably 10 to 23% by weight. The viscosity index improver used in the grease composition of the present invention is a conventionally known one, for example, polymethacrylate (PMA) type, ethylene-propylene copolymer (OCP) type, polyisobutylene type, styrene-butadiene hydrogenation type. Examples include polymer systems. These may be used alone or in combination of two or more.

The content of the viscosity index improver in the grease composition is usually within the range of 0.5 to 30% by weight, and is appropriately selected according to the type. For example, when the viscosity index improver is a polymethacrylate type and an ethylene-propylene copolymer type, its content is in the range of 1 to 20% by weight, and in the case of a polyisobutylene type and a low molecular weight ethylene-propylene copolymer type, it is 5 to 30%. In the case of a styrene-butadiene hydrogenation copolymer system, it is preferable to select in the range of 0.5 to 10% by weight. If the content of each viscosity index improver is less than the above range, the effect of including it may not be sufficiently exhibited, and a grease composition having desired properties may not be obtained, and if it is more than the above range. The performance balance as a grease may deteriorate.

In the grease composition of the present invention, (a) nickel dithiocarbamate (NiDTC) and (b) zinc dithiocarbamate (Zn) are used as lubricity improvers.
A combination of DTC) and (c) phosphorus-based additives is used. Examples of the NiDTC of the component (a) include those represented by the general formula (I)

[0010]

[Chemical 1]

(In the formula, R ¹ and R ² each represent an alkyl group or an alkenyl group having 3 to 20 carbon atoms, which may be the same or different from each other.) Nickel dialkyldithiocarbamate Can be mentioned. In the general formula (I), the alkyl group or alkenyl group having 3 to 20 carbon atoms may be linear, branched or cyclic. A typical example of this NiDTC is nickel dibutyldithiocarbamate.

The NiDTC as the component (a) may be used alone or in combination of two or more kinds. The content of the grease composition is selected in the range of 0.1 to 5% by weight. If this content is less than 0.1% by weight, the effect of improving the lubricating performance is not sufficiently exerted, and a grease composition having desired characteristics cannot be obtained, and the content is 5% by weight.
If it exceeds, the effect is not improved for the amount, and it is rather economically disadvantageous. The preferable content of this NiDTC is in the range of 0.3 to 3.0% by weight, and particularly 0.5 to 1.
A range of 5% by weight is preferred. In addition, the component (b) ZnD
Examples of TC include general formula (II)

[0013]

[Chemical 2]

(In the formula, R ³ and R ⁴ each represent an alkyl group or an alkenyl group having 3 to 20 carbon atoms, and they may be the same or different from each other.) Zinc dialkyldithiocarbamate Can be mentioned. In the general formula (II), the alkyl group or alkenyl group having 3 to 20 carbon atoms may be linear, branched or cyclic. A typical example of this ZnDTC is zinc dibutyldithiocarbamate. The ZnDTC as the component (b) may be used alone or in combination of two or more. Further, the content in the grease composition is 0.2 to 30% by weight.
It is selected in the range of. If the content is less than 0.2% by weight, the effect of improving the lubricating performance is not sufficiently exerted, and a grease composition having desired properties cannot be obtained, and if it exceeds 30% by weight, the effect is relatively small. No improvement is recognized and it is rather economically disadvantageous. The preferable content of ZnDTC is in the range of 0.5 to 10% by weight, and particularly preferably in the range of 1 to 6% by weight. Further, examples of the phosphorus-based additive of the component (c) include compounds represented by the general formula (III)

[0015]

[Chemical 3]

(In the formula, R ⁵ , R ⁶ and R ⁷ are each a hydrogen atom or a hydrocarbon group having 3 to 20 carbon atoms, and they may be the same or different from each other. At least one of which is a hydrocarbon group having 3 to 20 carbon atoms) or a general formula (IV)

[0017]

[Chemical 4]

(In the formula, R ⁸ , R ⁹ and R ¹⁰ are each a hydrogen atom or a hydrocarbon group having 3 to 20 carbon atoms, and they may be the same or different from each other. At least one of them is a hydrocarbon group having 3 to 20 carbon atoms). In the above general formula (III) and general formula (IV), R ⁵
As the hydrocarbon group having 3 to 20 carbon atoms in R ¹⁰ to R ¹⁰ ,
A linear, branched or cyclic alkyl or alkenyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms,
Alkylaryl group having 7 to 20 carbon atoms, 7 to 20 carbon atoms
And an arylalkyl group thereof. Specific examples of such groups include a propyl group, a butyl group,
Examples thereof include a pentyl group, a hexyl group, a cyclohexyl group, an octyl group, a decyl group, a lauryl group, a myristyl group, a palmityl group, a stearyl group, an oleyl group, an eicosyl group, a phenyl group, a xylyl group, a benzyl group and a phenethyl group.

The phosphorus-based additive as the component (c) may be used alone or in combination of two or more. The content in the grease composition is 0.2 to 1
It is selected in the range of 0% by weight. If the content is less than 0.2% by weight, the effect of improving the lubrication performance is not sufficiently exerted, and a grease composition having desired characteristics cannot be obtained.
If it exceeds the weight%, the effect is not improved for the amount, and it is rather economically disadvantageous. The preferable content of this phosphorus-based additive is in the range of 0.4 to 5% by weight, and particularly in the range of 0.6 to 3% by weight.

In the grease composition of the present invention, if necessary, other additives conventionally used in grease, for example, a lubricity improver such as zinc dithiophosphate (ZnDTP) and sulfurized oxymolybdenum dithiocarbamate (MoDTC) are added. An ashless detergent dispersant, an antioxidant, a metal detergent, an anticorrosive agent, a corrosion inhibitor, a coloring agent and the like can be appropriately added. Examples of ashless detergent dispersants include succinimide-based, succinamide-based, benzylamine-based, and ester-based ones, and antioxidants include, for example, alkylated diphenylamine, phenyl-α-naphthylamine, Examples include amine-based antioxidants such as alkylphenyl-α-naphthylamine, and phenol-based antioxidants such as 2,6-ditertiary butylphenol and 4,4′-methylenebis- (2,6-ditertiarybutylphenol). it can.

Examples of the metal detergent include Ca-sulfonate, Mg-sulfonate, Ba-sulfonate,
There are Ca-salicylate, Mg-salicylate, Ca-phenate, Ba-phenate and the like. Examples of the rust preventive agent include alkenyl succinic acid or its partial ester. The method for preparing the grease composition of the present invention is not particularly limited, and a method conventionally used for preparing grease can be used. For example, a base oil is mixed with a thickener and a viscosity index improver in a predetermined ratio, heated to a suitable temperature for homogenization and then cooled, and then three types of lubricity improvers and other optional additives are used. The grease composition of the present invention can be obtained by blending the additives in predetermined proportions.

[0022]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The various properties of the grease composition obtained in each example were determined according to the following points. (1) Miscibility, Immiscibility and Drop Point The miscibility, immiscibility and drop point were measured according to JIS K2220. (2) Seizure load A SRV test was conducted in accordance with ASTM D5706.
That is, a steel ball is placed on a disk coated with the grease composition, and a vertical load and a horizontal amplitude are applied to the steel ball to measure the friction coefficient μ. The load was increased stepwise, and the load at which the friction coefficient sharply increased was taken as the seizure load, and the seizure resistance was evaluated.

(3) Sealing heating test Using a grease oxidation stability tester of JIS K2220, a grease composition is filled in the same manner as JIS K2220, and air at atmospheric pressure is filled and sealed in a cylinder, and then 140 ° C.
And allowed to stand for 240 hours to prepare a deteriorated grease composition. With respect to this deteriorated grease composition, changes in impermeability, changes in miscibility, and changes in seizure load were determined. (4) Centrifuge test Ultracentrifuge "Himac CP7" manufactured by Hitachi Koki Co., Ltd.
0G ”was used to fill the grease composition into the container, and the grease composition-filled portion was separated from the grease composition when an acceleration of 1.8 × 10 ⁵ m ² / s was applied at 40 ° C. for 10 hours. The oil content was expressed as a weight ratio.

Examples 1 and 2 and Comparative Examples 1 to 11 Consistency grade No. 1 having the composition shown in Table 1. The grease composition of No. 2 was prepared and various properties were evaluated. The results are shown in Table 1.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3] (Note) Mineral oil: paraffinic mineral oil, kinematic viscosity at 40 ° C 140 mm ² / s
,% C _A 0.1%, sulfur content 3 ppm Li Complex: dropping point 300 ° C. or higher viscosity index improvers: styrenic polymer NiDTC: Ni dibutyldithiocarbamate carbide ZnDTC: Zn di Ami dithio carbide MoDTC: Mo dioctyldithiophosphoric carbide Ashless DTC: Vanlu manufactured by Vanderbilt
be7723 ZnDTP: Zn dioctyldithiophosphate antioxidant: dinonyldiphenylamine rust inhibitor: Ca sulfonate The amount of the thickener is indicated by the sum of carboxylic acid and lithium hydroxide (monohydrate).

Examples 3 to 8 and Comparative Example 12 Consistency grade No. 3 having the composition shown in Table 2. The grease composition of No. 2 was prepared and various properties were evaluated. The results are shown in Table 2. For reference, a commercially available grease A
The characteristics of B and B are also shown in Table 2.

[0029]

[Table 4]

[0030]

[Table 5] (Note) Mineral oil, viscosity index improver, NiDTC, ZnDT
C, the antioxidant and the rust preventive are the same as the footnotes in Table 1. Synthetic oil: Ester oil (Kinematic viscosity at 40 ° C: 100 mm ² / s
) Urea system: Drop point 286 ° C Ca complex system: Drop point 254 ° C Li complex system: Drop point 300 ° C or more

Examples 9 to 16 and Comparative Examples 13 to 15 Consistency grade No. 3 having the composition shown in Table 3. The grease composition of No. 2 was prepared and various properties were evaluated. The results are shown in Table 3.

[0032]

[Table 6]

[0033]

[Table 7]

[0034]

[Table 8] (Note) Mineral oil, NiDTC, ZnDTC, antioxidant and rust preventive are the same as the footnote in Table 1. Li complex system: Drop point 300 ° C or higher Ca complex system: Drop point 254 ° C Urea system: Drop point 281 ° C PMA: Polymethacrylate system OCP: Ethylene-propylene copolymer system Styrene polymer: Styrene-butadiene hydrogenation copolymer system

[0035]

INDUSTRIAL APPLICABILITY The grease composition of the present invention is excellent in seizure resistance, oxidation stability and oil separation property in a sealed environment subjected to high temperature and high speed centrifugal force, and can maintain high lubrication performance for a long period of time. It has characteristics such as the above, and is particularly suitable as a lubricant for a universal joint mounted on a propeller shaft of an automobile for transmitting a driving force from an engine to an axle.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C10N 10:02 C10N 10:02 10:04 10:04 10:16 10:16 20:00 20: 00 Z 30:02 30:02 30:06 30:06 30:08 30:08 30:10 30:10 40:02 40:02 50:10 50:10 (72) Inventor Koji Saito Toyota City, Aichi Prefecture Toyota Town 1 Toyota Motor Co., Ltd. (72) Inventor Hideyuki Suzuki Toyota City, Aichi Prefecture Toyota Town 1 Toyota Motor Co., Ltd. F Term (reference) 4H104 BB16B BG10C BH02C BH03C DA02A EA01B EB02 FA01 FA02 FA08 LA01 LA03 LA04 LA05 PA01 QA18

Claims (4)

[Claims] 1. A base oil, a thickener having a dropping point of 240 ° C. or higher, and a viscosity index improver, and (a) 0.1-5% by weight of nickel dithiocarbamate, (b) as a lubricity improver. ) Zinc dithiocarbamate 0.2-30% by weight
And (c) 0.2 to 10% by weight of a phosphorus-based additive, a grease composition for a propeller shaft. 2. The grease composition for a propeller shaft according to claim 1, wherein the thickener having a dropping point of 240 ° C. or higher is a lithium complex type thickener. 3. The grease composition for a propeller shaft according to claim 1, wherein the content of the thickener having a dropping point of 240 ° C. or higher is 2 to 40% by weight. 4. The content of the viscosity index improver is 0.5 to 3.
The grease composition for propeller shafts according to claim 1, 2 or 3, which is 0% by weight.