Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2000-03-02
2001-07-24
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C508S465000, C508S496000, C508S539000
Reexamination Certificate
active
06265361
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a grease composition, and more particularly to a carbonate-based grease composition having such excellent characteristics that rotating torque is small, noise is small and life is long when the grease of the present invention is sealed in a bearing.
2. Description of the Related Art
Recently, earth environmental problem is particularly closed up, and an effort to reduce consumption of wasteful energy as less as possible is obligated to advanced countries. As one conclusion of energy saving problem, it is the current demand for using DC motor having good efficiency in place of AC motor. In particular, in fan motors of air conditioners for appliances, it has been approaching the age that DC motor having good efficiency is used in place of AC motor that has still the limitation even though a converter is provided to change an output.
In general, the performances required to a bearing grease composition used in a small-sized motor for use in appliances or the like are such that torque is small, acoustic performance is excellent, leakage (volatilization) is small and life is long.
A lithium soap-based grease using a mineral oil as a base oil, or a lithium soap-based grease using, as a base oil, a synthetic ester (diester oil, polyol ester oil or the like) that is a reaction product of an organic acid and an alcohol has conventionally been used as the bearing grease for motor, but it is the actual circumstances that further improvement is still required.
A lithium soap-based grease using a mineral oil as a base oil has been used as a general-purpose grease for many years, but has had the problems that for a small-sized motor, a thickening agent has poor dispersibility in a grease, acoustic and vibration properties at the rotation of bearing are not good, and temperature range of use is narrow.
Further, a lithium soap-based grease using, as a base oil, a synthetic ester (diester oil, polyol ester oil or the like) that is a reaction product of an organic acid and an alcohol has good dispersity of the lithium soap. Therefore, there is no problem on acoustic and vibration performances at the rotation of bearing, and the wide temperature range of use due to the use of a synthetic oil was preferable. However, this grease had the problem in low torque property that is the essential element inmotors for appliances in recent years.
SUMMARY OF THE INVENTION
The present invention has solved the problems associated with the prior art, and therefore has an object of the invention to provide a grease composition with stable low torque property, low noise property and low volatilization property that can be maintained when it is used as the grease for a bearing of a motor.
In the present invention, it has been found that by using a grease composition containing a carbonate represented by the general formula (I) and an ester-based synthetic oil, as a base oil, and a metallic soap, the characteristics particularly required in the bearing grease composition used in small-sized motor for appliances for home use or the like are satisfied.
Therefore, the grease composition of the present invention is characterized in that it contains: (A) an alkali metal salt and/or an alkaline earth metal salt synthesized from a hydroxide of an alkali metal or an alkaline earth metal, and a higher fatty acid having 10 or more carbon atoms or a higher hydroxyfatty acid having at least one hydroxyl group and 10 or more carbon atoms; (B) a carbonate compound represented by the general formula:
(R and R′ represent a branched alkyl group having 13-15 carbon atoms, and may be same or different); and (C) at least one kind of an ester-based synthetic oil selected from the group consisting of a diester-based synthetic oil represented by the general formula (i):
ROCO(CH
2
)
n
COOR′ (i)
(R and R′ represent an alkyl group having 3-18 carbon atoms, and may be the same or different, and n is 3-12);
a triester-based synthetic oil represented by the general formula (ii):
C
2
H
5
C(CH
2
OCOR)
3
(ii)
(R represents an alkyl group having 3-10 carbon atoms),
a tetraester-based synthetic oil represented by the following general formula (iii):
C(CH
2
OCOR)
4
(iii)
(R represents an alkyl group having 3-10 carbon atoms); and other neopentyl polyol ester-based synthetic oil.
The grease of the present invention is that the combination itself of components is novel, and any proportion can be used as the grease.
The blending ratio of each component is desirably that the alkali metal salt and/or alkaline earth metal salt of the component (a) is 5-30 parts by mass and the mixed base oil composed of the carbonate compound of the component (b) and the ester-based synthetic oil of the component (C) is 70-95 parts by mass.
More preferably, the alkali metal salt and/or alkaline earth metal salt of the component (a) is 10-25 parts by mass and the mixed base oil composed of the carbonate compound of the component (b) and the ester-based synthetic oil of the component (C) is 75-90 parts by mass.
If the alkali metal salt and/or alkaline earth metal salt of the component (a) is less than 5 parts by mass, the mixture consistency becomes soft and there is the possibility of leakage or scatter at the rotation of bearing, which requires attention. On the other hand, if it exceeds 30 parts by mass, the grease becomes too hard. As a result, fluidity of the grease inside the bearing lowers and there is the possibility to cause poor lubrication, which requires attention.
Next, the ratio of the carbonate compound (B) used as the base oil in the grease composition of the present invention and the ester-based synthetic oil is preferable that (B)/[(B)+(C)] is 0.1 or more and less than 0.95 by mass ratio.
More preferably, (B)/[(B)+(C)] is 0.2 or more and 0.8 or less by mass ratio. If (B)/[(B)+(C)] is less than 0.1, there is no effect of torque decrease, and if it is 0.95 or more, the volatility becomes too high.
Further, the grease composition of the present invention can contain various additives generally used in greases.
Examples of the additives are additives generally used in grease compositions, for example, oxidation inhibitors such as phenyl &agr;(&bgr;) naphthylamine, alkyl diphenylamine, phenothiazine or t-butylphenol, and rust preventives such as metal sulfonate, nonionic types or amine types.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Representative examples of the alkali metal salt and/or alkaline earth metal salt used as the component (A) in the present invention include lithium stearate and lithium 12 hydroxystearate.
The representative example of the carbonate compound used as the component (B) in the present invention is a compound represented by the following formula:
Further, examples of the ester-based synthetic oil used as the component (C) in the present invention include di-2-ethylhexyl sebacate, di-2-ethylhexyl azerate, di-2-ethylhexyl adipate, trimellitic acid ester, trimethylol propane ester, pentaerythritol ester and the like.
Preferred embodiment of the present invention is described below.
(1) A grease composition, characterized in that it contains:
(A) an alkali metal salt and/or an alkaline earth metal salt synthesized from a hydroxide of an alkali metal or an alkaline earth metal, and a higher fatty acid having 10 or more carbon atoms or a higher hydroxyfatty acid having at least one hydroxyl group and 10 or more carbon atoms; (B) a carbonate compound represented by the general formula:
(R and R′ represent a branched alkyl group having 13-15 carbon atoms, and may be same or different); and (C) at least one kind of an ester-based synthetic oil selected from at the group consisting of a diester-based synthetic oil represented by the general formula (i):
ROCO(CH
2
)
n
COOR′ (i)
(R and R′ represent an alkyl group having 3-18 carbon atoms, and may be the same or different, and n is 3-12);
a triester-based synthetic oil represent
Akiyama Motoharu
Miyamoto Yasuhiro
Okamura Seiji
McAvoy Ellen M.
Minebea Co. Ltd.
Oliff & Berridg,e PLC
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