Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic sulfur compound – wherein the sulfur is single bonded...
Reexamination Certificate
1999-07-14
2002-08-13
Johnson, Jerry D. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic sulfur compound, wherein the sulfur is single bonded...
C508S391000, C508S335000, C508S552000, C508S570000, C508S569000
Reexamination Certificate
active
06432889
ABSTRACT:
FIELD OF ART
This invention relates to a grease composition, particularly a grease composition suitable for a constant velocity joint.
BACKGROUND ART
A constant velocity joint is used in a system for transmitting driving force, e.g., transmitting the force from a transmission gearbox to tires on a car. The constant velocity joint includes fixed type joints such as a Birfield joint, a Rzeppa joint and an undercutting free joint, and slide type joints such as a double off-set joint, a tripod joint and a cross groove joint.
A conventional grease which has been mainly used for such constant velocity joints contains a base grease consisting of a lubricating base oil and a lithium soap and/or urea thickener, and additives such as molybdenum disulfide and a lead compound.
The grease for the constant velocity joint is required to exhibit performances such as anti-flaking, anti-seizure, abrasion resistance, and low friction. However, the performance of the conventional grease hardly catches up with the tendency to improved performance and quality of recent cars. Thus, particularly in order to prolong the lifetime of a constant velocity joint, improvement of a grease in the anti-flaking property is desired.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a grease composition for a constant velocity joint that exhibits superior anti-flaking performance.
According to the present invention, there is provided a grease composition comprising a lubricating base oil, and: (A) 2 to 30 wt % of a urea thickener, (B) 0.1 to 20 wt % of a sulfur-containing extreme pressure agent selected from the group consisting of dihydrocarbyl polysulfide, sulfurized oils and fats and mixtures thereof, and (C) 0.05 to 10 wt % of a sulfonate selected from the group consisting of an over-based zinc sulfonate, an over-based magnesium sulfonate and mixtures thereof having total base number of 100 to 500 mgKOH/g, each based on a total amount of said grease composition.
PREFERRED EMBODIMENTS OF THE INVENTION
The present grease composition contains a lubricating base oil. The lubricating base oil may be a mineral oil and/or a synthetic oil. The kinematic viscosity of the lubricating base oil may be 2 to 40 mm
2
/s, and preferably 3 to 20 mm
2
/s at 100° C. The viscosity index of the lubricating base oil may be not less than 90, and preferably not less than 100.
The mineral oil may be obtained by a conventional method commonly performed in a lubricating oil production process in oil refining industries. For example, the mineral oil may be obtained by preparing lubricant fractions of crude oil by distillation under atmospheric or reduced pressure, and then refining the lubricant fractions by at least one treatment selected from solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, contact dewaxing, hydrofining, washing with sulfuric acid, clay treatment, and the like.
Examples of the synthetic oil may include poly-&agr;-olefins such as polybutene, 1-octen oligomer and 1-decene oligomer, or hydrides of these poly-&agr;-olefins; diesters such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, or di-3-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethyl hexanoate, or pentaerythritol pelargonate; alkylnaphthalene; alkylbenzene; polyoxyalkylene glycol; polyphenyl ether; dialkyl diphenyl ether, silicone oil; and mixtures thereof.
The present grease composition contains (A) a specific content of a urea thickener. The component (A) may be a urea compound, a urea-urethane compound, a urethane compound or mixtures thereof.
Examples of the urea compound, urea-urethane compound and urethane compound may include a diurea compound, a triurea compound, a tetraurea compound, polyurea compounds other than diurea, triurea and tetraurea compounds, a urea-urethane compound, a diurethane compound and mixtures thereof. More specifically, any of compounds represented by the general formula (1) or mixtures thereof are preferable.
A—CONH—R
1
—NHCO—B (1)
In the formula (1), R
1
denotes a divalent hydrocarbon group. A and B are the same or different groups, and denote —NHR
2
, —NR
3
R, or —OR
5
. R
2
, R
3
, R
4
and R
5
are the same or different groups and denote a hydrocarbon residue having 6 to 20 carbon atoms.
Preferably, R
1
in the formula (1) is a divalent hydrocarbon residue having 6 to 20, more preferably 6 to 15 carbon atoms. The divalent hydrocarbon group may be a straight or branched alkylene group, a straight or branched alkenylene group, a cycloalkylene group or an aromatic group. Specific examples of R
1
may include an ethylene group, a 2,2-dimethyl-4-methylhexylene group and groups represented by the following formulae:
Among these, the following groups are particularly preferred.
R
2
, R
3
, R
4
and R
5
may be a straight or branched alkyl group, a straight or branched alkenyl group, a cycloalkyl group, an alkylcycloalkyl group, an aryl group, an alkylaryl group, or an arylalkyl group. Specific examples of R
2
, R
3
, R
4
and R
5
may include a straight or branched alkyl group such as a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, or an eicosyl group; a straight or branched alkenyl group such as a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, a nonadecenyl group or an eicosenyl group; a cyclohexyl group; an alkylcycloalkyl group such as a methylcyclohexyl group, a dimethylcyclohexyl group, an ethylcyclohexyl group, a diethylcyclohexyl group, a propylcyclohexyl group, an isopropylcyclohexyl group, a 1-methyl-3-propylcyclohexyl group, a butylcyclohexyl group, an amylcyclohexyl group, an amylmethylcyclohexyl group, a hexylcyclohexyl group, a heptylcyclohexyl group, an octylcyclohexyl group, a nonylcyclohexyl group, a decylcyclohexyl group, an undecylcyclohexyl group, a dodecylcyclohexyl group, a tridecylcyclohexyl group or a tetradecylcyclohexyl group; an aryl group such as a phenyl group or a naphthyl group; an alkylaryl group such as a toluyl group, an ethylphenyl group, a xylyl group, a propylphenyl group, a cumenyl group, a methylnaphthyl group, an ethylnaphthyl group, a dimethylnaphthyl group or a propylnaphthyl group; or an arylalkyl group such as a benzyl group, a methylbenzyl group or an ethylbenzyl group. Among these, a cyclohexyl group, a octadecyl group, and a toluyl group are particularly preferred.
The diurea compound, the urea-urethane compound, or the diurethane compound may be prepared by reacting diisocyanate represented by the formula OCN—R
1
—NCO with a compound represented by the formula R
2
NH
2
, R
3
R
4
NH or R
5
OH or mixtures thereof in the base oil at 10 to 200° C. In this case, R
1
, R
2
, R
3
, R
4
and R
5
are the same as those in the formula (1).
The lower limit of the content of the component (A) is 2 wt % and preferably 5 wt %; and the upper limit is 30 wt % and preferably 20 wt %, based on the total amount of the grease composition. If the content of the component (A) is less than 2 wt %, the component does not exhibit sufficient thickening effect, and the composition cannot thus be in a sufficiently greasy state. If the content of the component is more than 30 wt %, the composition becomes too hard as a grease to exhibit sufficient lubricating performance.
The present grease composition contains as component (B) a specific content of a sulfur-containing extreme pressure agent selected from the group consisting of dihydrocarbyl polysulfide, sulfurized oils and fats, and mixtures thereof.
The dihydrocarbyl polysulfide is a sulfur-containing compound which is generally called polysulfide or sulfurized olefin. Specifically
Kinoshita Hirotugu
Sakamoto Kiyomi
Darby & Darby
Nippon Mitsubishi Oil Corporation
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