U.S. patent application number 12/206297 was filed with the patent office on 2008-12-25 for grease composition and bearing.
Invention is credited to Yuji Onuki, Osamu SAITA.
Application Number | 20080318819 12/206297 |
Document ID | / |
Family ID | 38474708 |
Filed Date | 2008-12-25 |
United States Patent
Application |
20080318819 |
Kind Code |
A1 |
SAITA; Osamu ; et
al. |
December 25, 2008 |
GREASE COMPOSITION AND BEARING
Abstract
A grease composition which is suitable for a ball bearing
exposed to high temperatures and exhibits stable lubricity for a
prolonged period of time, and a bearing which encapsulates the
grease composition are provided. A grease composition comprising
(a) a base oil, (b) a thickener, (c) a compound having
alkylthiocarbamoyl group of the general formula (1), and an
amine-ketone condensate-based antioxidant. A grease composition
further comprising (e) a metal inactivator. ##STR00001## (wherein
R.sub.1, R.sub.2, R.sub.3, R.sub.4 are independently
C.sub.1-C.sub.20 alkyl, and X is S, S--S, S--CH.sub.2--S,
S--CH.sub.2CH.sub.2--S, or S--CH.sub.2CH.sub.2CH.sub.2--S)
Inventors: |
SAITA; Osamu; (Fujisawa-shi,
JP) ; Onuki; Yuji; (Fujisawa-shi, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
38474708 |
Appl. No.: |
12/206297 |
Filed: |
September 8, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2006/325056 |
Dec 15, 2006 |
|
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12206297 |
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Current U.S.
Class: |
508/463 ;
508/555 |
Current CPC
Class: |
C10M 169/06 20130101;
F16C 2300/54 20130101; C10M 2207/1285 20130101; C10N 2040/02
20130101; C10N 2050/10 20130101; C10M 2219/066 20130101; C10M
2207/1276 20130101; C10M 2215/18 20130101; C10M 2207/026 20130101;
C10N 2010/02 20130101; C10M 2215/223 20130101; C10M 2207/0406
20130101; C10N 2030/10 20130101; C10M 2215/221 20130101; F16C
33/6633 20130101; C10M 2215/065 20130101; C10M 2207/289 20130101;
C10N 2030/08 20130101; C10M 2207/2835 20130101; C10M 2207/289
20130101; C10M 2207/026 20130101 |
Class at
Publication: |
508/463 ;
508/555 |
International
Class: |
C10M 105/34 20060101
C10M105/34; C10M 133/06 20060101 C10M133/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 2006 |
JP |
2006-062664 |
Claims
1. A grease composition comprising (a) a base oil, (b) a thickener,
(c) a compound having alkylthiocarbamoyl group of the general
formula (1), and an amine-ketone condensate-based antioxidant.
##STR00008## (wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 are
independently C.sub.1-C.sub.20 alkyl, and X is S, S--S,
S--CH.sub.2--S, S--CH.sub.2CH.sub.2--S, or
S--CH.sub.2CH.sub.2CH.sub.2--S)
2. The grease composition according to claim 1, wherein said
thickener is at least one selected from the group consisting of
lithium soaps and lithium complex soaps.
3. The grease composition according to claim 1, further comprising
(e) a metal inactivator.
4. The grease composition according to claim 2, further comprising
(e) a metal inactivator.
5. The grease composition according to claim 1, which comprises (a)
50 or more percent by mass of said base oil, (b) 1-30 percent by
mass of said thickener, (c) 0.1-10 percent by mass of said compound
having alkylthiocarbamoyl group of the general formula (1), and (d)
0.1-10 percent by mass of said amine-ketone condensate-based
antioxidant based on the entire grease composition.
6. The grease composition according to claim 2, which comprises (a)
50 or more percent by mass of said base oil, (b) 1-30 percent by
mass of said thickener, (c) 0.1-10 percent by mass of said compound
having alkylthiocarbamoyl group of the general formula (1), and (d)
0.1-10 percent by mass of said amine-ketone condensate-based
antioxidant based on the entire grease composition.
7. The grease composition according to claim 5, comprising (e)
0.1-10 percent by mass of said metal inactivator.
8. The grease composition according to claim 6, comprising (e)
0.1-10 percent by mass of said metal inactivator.
9. A bearing comprising said grease composition according to claim
1 encapsulated therein.
Description
TECHNICAL FIELD
[0001] The present invention relates to a grease composition
comprising a base oil, a thickener, and a specific antioxidant.
Particularly, the present invention relates to a grease composition
which is suitable for use in a ball bearing exposed to high
temperatures and of which lubricant life is improved; and a bearing
which encapsulates the grease composition therein.
BACKGROUND ART
[0002] The properties required for a grease composition to improve
lubricant life thereof are thermo-oxidative stability and the like,
and various proposals for improving the properties of the grease
composition have hitherto been made.
[0003] Improved lubricants in fatigue life have been proposed, in
which a compound having alkylthiocarbamoyl group and a molybdenum
compound are added to a lubricant base material, or an ester
compound is further added thereto, thereby improving fatigue life
(see, for example, Patent Document 1). An abrasive resistant
extreme pressure composition with improved antioxidative property,
which composition comprises (a)
methylenebis(di-n-butyldithiocarbamate) and (b) a diphenylamine
derivative of tolutriazol or benzotriazol, wherein the ratio
(a):(b) in percent by mass is in the range of about 4:1 to about
50:1; and a lubricant comprising the extreme pressure composition
have been proposed (see, for example, Patent Document 2).
Additionally, a lithium grease composition which comprises (a) a
lubricating oil, (b) at least one compound selected from the group
consisting of a lithium salt of C.sub.12-C.sub.24 aliphatic
monocarboxylic acid comprising at least one hydroxyl group, a
dilithium salt of C.sub.2-C.sub.12 aliphatic dicarboxylic acid, and
a lithium salt of C.sub.12-C.sub.24 aliphatic monocarboxylic acid,
and (c) at least one compound selected from the group consisting of
3-(N-salicyloyl)amino-1,2,4-triazol and decamethylene-dicarboxylic
acid-disalicyloylhydrazide, has been proposed (see, for example,
Patent Document 3).
[0004] However, even if the grease composition using these
additives is employed in a roll bearing exposed to high
temperatures, thermo-oxidative stability and lubricant life are
insufficient, and a grease composition satisfying users has not
been obtained at present.
[0005] Patent Document 1: JP-B-03-31760
[0006] Patent Document 2: JP-T-2005-509732
[0007] Patent Document 3: Japanese Patent No. 2936084
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0008] An object of the present invention is to provide a grease
composition which is suitable for a ball bearing exposed to high
temperatures and exhibits stable lubricity for a prolonged period
of time. That is, the object of the present invention is to provide
a grease composition which is excellent in thermo-oxidative
stability and lubricant life.
[0009] Another object of the present invention is to provide a
bearing which encapsulates the grease composition.
Means for Solving the Problems
[0010] The present inventors intensively studied in order to attain
the above-described object to improve thermo-oxidative stability
and lubricant life by using a base oil, a thickener, and a specific
antioxidant; and preferably by further using a metal inactivator,
thereby completing the grease composition which is suitable for a
ball bearing exposed to high temperatures and exhibits stable
lubricity for a prolonged period of time.
[0011] The present invention provides the following grease
composition and a bearing.
1. A grease composition comprising (a) a base oil, (b) a thickener,
(c) a compound having alkylthiocarbamoyl group of the general
formula (1), and an amine-ketone condensate-based antioxidant.
##STR00002##
(wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 are independently
C.sub.1-C.sub.20 alkyl, and X is S, S--S, S--CH.sub.2--S,
S--CH.sub.2CH.sub.2--S, or S--CH.sub.2CH.sub.2CH.sub.2--S) 2. The
grease composition according to the above-item 1, wherein the
thickener is at least one selected from the group consisting of
lithium soaps and lithium complex soaps. 3. The grease composition
according to the above-item 1 or 2, further comprising (e) a metal
inactivator. 4. The grease composition according to any one of the
above-items 1 to 3, which comprises (a) 50 or more percent by mass
of the base oil, (b) 1-30 percent by mass of the thickener, (c)
0.1-10 percent by mass of the compound having alkylthiocarbamoyl
group of the general formula (1), and (d) 0.1-10 percent by mass of
the amine-ketone condensate-based antioxidant based on the entire
grease composition. 5. The grease composition according to any one
of the above-items 2 to 4, comprising (e) 0.1-10 percent by mass of
the metal inactivator. 6. A bearing which encapsulates the grease
composition according to any one of the above-items 1 to 5.
EFFECTS OF THE INVENTION
[0012] The grease composition of the present invention is very
useful in that it shows improved thermo-oxidative stability and
lubricant life, and is suitable for use in a ball bearing exposed
to high temperatures and exhibits stable lubricity for a prolonged
period of time.
[0013] A satisfactory proposal has not been made on a grease
composition of which thermo-oxidative stability and lubricant life
are improved, which is suitable for use in a ball bearing exposed
to high temperatures and which exhibits stable lubricity for a
prolonged period of time by using a specific antioxidant and a
metal inactivator, which grease composition is encapsulated in the
bearing together with a base oil. Thus, the present invention is
very useful.
[0014] The present invention was made based on the discovery that
thermo-oxidative stability and lubricant life are drastically
improved by using a specific antioxidant, or by further using a
specific metal inactivator, more preferably by specifying the
mixing ratio of these.
[0015] The reason why the grease composition of the present
invention is excellent in lubricant life under the condition of
high temperature is thought as follows. That is, the function of
each component is well exhibited by using the antioxidant
particularly selected or by further using a metal inactivator in
the grease composition comprising a base oil and a thickener, and
excellent thermo-oxidative stability, lubricity and lubricant life
are given to the grease composition exposed to high temperatures
also by virtue of the proper formulation of the grease
composition.
BEST MODE FOR CARRYING OUT THE INVENTION
[0016] The present invention will be explained in detail below.
[0017] The base oil used for the grease composition of the present
invention is preferably one comprising at least one of the groups
of mineral oils and/or synthetic oils. Examples of the synthetic
oil include ester synthetic oils typified by esters and polyol
esters; synthetic hydrocarbon oils typified by poly(.alpha.-olefin)
and polybutene; ether synthetic oils typified by alkyl diphenyl
ethers and polypropyleneglycol; and silicone oils, fluorinated
oils, and the like. The synthetic oil is not restricted as long as
it can be used in a lubricating oil and a grease composition.
[0018] The thickener used in the grease composition of the present
invention is at least one selected from the group consisting of
metal soap thickeners; urea thickeners typified by diurea;
inorganic thickeners typified by organic clay and silica; organic
thickeners typified by polytetrafluoroethylene and melamine
cyanurate. Preferred examples of the thickener are those selected
from the group consisting of lithium soaps and lithium complex
soaps, and most preferably lithium soaps, for example lithium
stearate and lithium 12-hydroxystearate.
[0019] The antioxidant used in the grease composition of the
present invention is (c) the compound (ATC) having the
alkylthiocarbamoyl group of the general formula (1); and (d) the
amine-ketone condensate-based antioxidant.
[0020] Specific examples of the compound (ATC) having an
alkylthiocarbamoyl group of the general formula (1) include
methylenebis(di-n-butyldithiocarbamate),
bis(dimethylcarbamoyl)monosulfide, bis(dimethylcarbamoyl)disulfide,
bis(dibutylcarbamoyl)disulfide, bis(diamylcarbamoyl)disulfide,
bis(dioctylcarbamoyl)disulfide, and the like.
[0021] Examples of (d) the amine-ketone condensate-based
antioxidant include TMDQ (2,2,4-trimethyl-1,2-dihydroquinoline
polymer) of the formula (2) designated by JIS K6220-3 code, ETMDQ
(6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline) of the formula (3),
ADPAL (the reaction mixture of diphenylamine and acetone), and the
like.
TMDQ; 2,2,4-trimethyl-1,2-dihydroquinoline polymer
##STR00003##
wherein n is an integer of 1 to 10, preferably 1 to 6, most
preferably 2 to 3. ETMDQ;
6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline
##STR00004##
[0022] The grease composition of the present invention preferably
comprises a metal inactivator. Examples of the metal inactivator
include oxalic acid derivatives, salicylic acid derivatives,
hydrazine derivatives and the like. Especially, examples thereof
include 3-(N-salicyloyl)amino-1,2,4-triazol of the formula (4),
decamethylenecarboxylic acid disalicyloylhydrazide (MCSH) of the
formula (5),
N,N-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine of
the formula (6), isophthalic acid bis(2-phenoxypropionylhydrazide),
N-formyl-N'-salicyloylhydrazine,
2,2-oxamidebis-[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],
oxalyl-bis-benzylidene-hydrazide and the like. [0023]
3-(N-salicyloyl)amino-1,2,4-triazol
##STR00005##
[0023] MCSH; decamethylenecarboxylic acid disalicyloylhydrazide
##STR00006## [0024]
N,N-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine
##STR00007##
[0025] The grease composition of the present invention comprises
(a) 50 or more percent by mass, preferably 60 or more percent by
mass of the base oil, (b) 1-30 percent by mass, preferably 5-20
percent by mass of the thickener, (c) 0.1-10 percent by mass,
preferably 0.5-5 percent by mass of the compound having
alkylthiocarbamoyl group of the general formula (1), and (d) 0.1-10
percent by mass, preferably 0.5-5 percent by mass of the
amine-ketone condensate-based antioxidant based on the entire
grease composition. To the mixture of (a)-(d), 0.1-10 percent by
mass, preferably 0.5-5 percent by mass of the metal inactivator may
be added.
[0026] The present invention also provides a bearing which
encapsulates the above-described grease composition.
[0027] The present invention will be further described in detail
below by way of Examples, however, the present invention is not
restricted to the following Examples. Any modification without
departing from the spirit of the invention is within the scope of
the present invention.
EXAMPLES
1. Test Greases
[0028] The grease compositions of Examples 1 to 8 and Comparative
Examples 1 to 5 were prepared according to the formulation shown in
Tables 1 and 2. The amount of each component is based on percent by
mass.
2. Method for Preparing Grease
[0029] Into 467.5 g of the base oil, 82.5 g of 12-hydroxystearic
acid was added, and the resulting mixture was heated to the
temperature (80-90.degree. C.) at which the mixture became a clear
liquid. To this mixture, a solution prepared by adding 11.9 g of
lithium hydroxide monohydrate to 60 g of water and heating the
obtained mixture to dissolve the solute, was added. The
saponification of 12-hydroxystearic acid was carried out under
vigorous stirring to obtain lithium 12-hydroxystearate. To the
obtained mixture, 26 g of azelaic acid was then added, and stirring
was continued until the mixture became a uniform solution. To this
mixture, a solution prepared by adding 11.9 g of lithium hydroxide
monohydrate to 60 g of water and heating the obtained mixture to
dissolve the solute, was added. The saponification of azelaic acid
was carried out under vigorous stirring. The saponification was
terminated after confirming that the absorption of the unreacted
fatty acid was not found by infrared spectroscopic analysis at
about 60 minutes after the start of the reaction. In the subsequent
heating step, the contents were slowly heated to 200.degree. C.
When the temperature of the contents reached 200.degree. C., 400.2
g of the residual base oil was added the contents, followed by
cooling them to room temperature. Lithium complex grease was
obtained by mixing the contents using a three-roll mill twice. The
amount of the final product was 1000 g.
[0030] The ether oil (alkyl diphenyl ether: kinematic viscosity
40.degree. C. 100 mm.sup.2/s, 100.degree. C. 12.5 mm.sup.2/s), the
ester oil (pentaerythritol ester: kinematic viscosity 40.degree. C.
102 mm.sup.2/s, 100.degree. C. 12.9 mm.sup.2/S), and 1:1 mixture
thereof were used as the base oil.
3. Analytical Method and Evaluation Test Method
Bearing-Lubrication Life Test
[0031] The test was carried out according to the method based on
ASTM D 3336. The test was conducted at 150.degree. C., and
lubricant life is expressed in terms of hour (h).
Thin Film Test at High Temperature
[0032] An SPCC steel plate sizing 60.times.80.times.1 mm is coated
with a grease having a thickness of 2 mm, and the total acid value
is measured after the prescribed time (500 h) passed at the
prescribed temperature (160.degree. C.).
4. Results of Evaluation Test
[0033] The test results of the grease compositions of Examples 1 to
6 and Comparative Examples 1 to 5 are shown in Tables 1 and 2.
TABLE-US-00001 TABLE 1 Example Example Example Example Example
Example Example Example 1 2 3 4 5 6 7 8 (a)ether oil 41.75 41.5
40.25 40.0 39.5 38.5 83.5 -- (a)ester oil 41.75 41.5 40.25 40.0
39.5 38.5 -- 83.5 (b)thickener 13.0 13.0 13.0 13.0 13.0 13.0 13.0
13.0 (c)ATC*.sup.1 0.5 0.5 0.5 1.0 1.0 2.0 0.5 0.5 (d)TMDQ 2.0 2.0
4.0 4.0 4.0 5.0 2.0 2.0 (e)MCSH -- 0.5 1.0 -- 1.0 2.0 -- -- Amine
-- -- -- -- -- -- -- -- antioxidant*.sup.2 Phenol 1.0 1.0 1.0 2.0
2.0 1.0 1.0 1.0 antioxidant*.sup.3 Bearing- 1310 2750 1530 1780
2370 2260 1220 1190 lubrication life (150.degree. C.)h Evaluation
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle. results
Total acid 0.04 0.05 0.05 0.04 0.07 0.06 0.06 0.05 value before
thin film test at high temperature (mgKOH/g) Total acid .019 0.15
0.18 0.16 0.12 0.15 0.17 0.18 value after thin film test at high
temperature (mgKOH/g) Change in 0.15 0.10 0.13 0.12 0.05 0.09 0.11
0.13 acid value (mgKOH/g) Evaluation .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. results on change in acid value Total
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle. evaluation
*.sup.1ATC: methylenebis(di-n-butyldithiocarbamate) *.sup.2Amine
antioxidant: N-phenyl-1,1,3,3-tetramethylbutylnaphthalene-1-amine
*.sup.3Phenol antioxidant: pentaerythritol
tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate
TABLE-US-00002 TABLE 2 Comparative Comparative Comparative
Comparative Comparative Example 1 Example 2 Example 3 Example 4
Example 5 (a)ether oil 41.75 -- 84.0 42.75 42.0 (a)ester oil 41.75
84.0 -- 42.75 42.0 (b)thickener 13.0 13.0 13.0 13.0 13.0
(c)ATC*.sup.1 -- -- -- 0.5 -- (d)TMDQ -- -- -- -- 2.0 (e)MCSH 0.5
-- -- -- -- Amine 2.0 2.0 2.0 antioxidant*.sup.2 Phenol 1.0 1.0 1.0
1.0 1.0 antioxidant*.sup.3 Bearing- 860 590 410 630 780 lubrication
life (150.degree. C.) h Evaluation x x x x x results Total acid
0.05 0.06 0.06 0.06 0.05 value before thin film test at high
temperature (mgKOH/g) Total acid 1.90 2.20 10.6 1.26 0.68 value
after thin film test at high temperature (mgKOH/g) Change in acid
1.85 2.14 10.54 1.20 0.63 value (mgKOH/g) Evaluation x x x x x
results on change in acid value Total x x x x x evaluation
Evaluation Criteria
[0034] Change in acid value (mgKOH/g) o: 0.02 or less, x; over 0.20
Bearing-lubrication life o: pass, over 1000 h, x: fail, 1000 or
less
Total Evaluation
[0035] o: Both of change in acid value and bearing-lubrication life
passed the criteria (O).
[0036] x: Change in Acid Value and/or bearing-lubrication life
failed(x).
Test Results
[0037] The grease compositions of Examples 1, 4, 7 and 8 comprising
components (a)-(d), and Examples 2, 3, 5 and 6 comprising
components (a)-(e) showed smaller changes in acid value, and were
excellent in thermo-oxidative stability. All the grease
compositions attained criteria of bearing-lubrication life, and
passed the criteria of the total evaluation.
[0038] On the other hand, in Comparative Example 4 having the same
composition as in Example 1 except that the component (d) was not
contained, the change in acid value was larger, thermo-oxidative
stability was poorer, and bearing-lubrication life was shorter.
[0039] In Comparative Example 5 having the same composition as in
Example 1 except that the component (c) was not contained, the
change in acid value was larger, thermo-oxidative stability was
poorer, and bearing-lubrication life was shorter.
[0040] In Comparative Example 1 having the same composition as in
Example 2 except that the conventional amine antioxidant was
contained instead of components (c) and (d), the change in acid
value was larger, thermo-oxidative stability was poorer, and
bearing-lubrication life was shorter.
[0041] In Comparative Example 2 in which the ester oil was used as
the base oil and the conventional amine antioxidant was contained
instead of components (c)-(e), the change in acid value was larger,
thermo-oxidative stability was poorer, and bearing-lubrication life
was shorter.
[0042] In Comparative Example 3 in which the ether oil was used as
the base oil and the conventional amine antioxidant was contained
instead of components (c)-(e), the change in acid value was larger,
thermo-oxidative stability was poorer, and bearing-lubrication life
was shortest.
* * * * *