U.S. patent application number 11/884851 was filed with the patent office on 2008-07-10 for lubricant.
Invention is credited to Miyuki Hashida, Tatsuya Hashimoto, Toshio Nitta, Wataru Sawaguchi, Akihiko Shimura, Jiro Yurimoto.
Application Number | 20080167208 11/884851 |
Document ID | / |
Family ID | 36927283 |
Filed Date | 2008-07-10 |
United States Patent
Application |
20080167208 |
Kind Code |
A1 |
Hashida; Miyuki ; et
al. |
July 10, 2008 |
Lubricant
Abstract
A lubricant in the form of lubricating oil or grease, for use in
contact with graphite or molybdenum disulfide or in contact with
aluminum materials, which comprises a perfluoropolyether oil free
from (CF.sub.2O).sub.n groups as a repeat unit of polymer and
having a kinetic viscosity at 40.degree. C. of 50-1,500
mm.sup.2/sec., as a base oil, where
F(CF.sub.2CF.sub.2CF.sub.2O).sub.mC.sub.2F.sub.5 or
RfO[CF(CF.sub.3)CF.sub.2O].sub.p(CF.sub.2CF.sub.2O).sub.qRf' s used
as the perfluoropolyether base oil. The lubricant undergoes no
considerable deterioration of high-temperature characteristics
(high-temperature durability), even if used in various uses as
mentioned above, and also has distinguished low-temperature
characteristics when the base oil has a kinetic viscosity of 50-250
mm.sup.2/sec.
Inventors: |
Hashida; Miyuki; (Ibaraki,
JP) ; Sawaguchi; Wataru; (Ibaraki, JP) ;
Nitta; Toshio; (Ibaraki, JP) ; Hashimoto;
Tatsuya; (Ibaraki, JP) ; Shimura; Akihiko;
(Ibaraki, JP) ; Yurimoto; Jiro; (Ibaraki,
JP) |
Correspondence
Address: |
BUTZEL LONG;IP DOCKETING DEPT
350 SOUTH MAIN STREET, SUITE 300
ANN ARBOR
MI
48104
US
|
Family ID: |
36927283 |
Appl. No.: |
11/884851 |
Filed: |
February 17, 2006 |
PCT Filed: |
February 17, 2006 |
PCT NO: |
PCT/JP2006/302801 |
371 Date: |
August 22, 2007 |
Current U.S.
Class: |
508/582 |
Current CPC
Class: |
C10M 2201/041 20130101;
C10M 2211/066 20130101; C10M 2213/0606 20130101; C10N 2030/02
20130101; C10N 2030/06 20130101; C10N 2020/02 20130101; C10N
2030/08 20130101; C10M 2201/066 20130101; C10N 2050/10 20130101;
C10M 107/38 20130101; C10N 2040/02 20130101; C10M 2211/063
20130101; C10M 2213/06 20130101 |
Class at
Publication: |
508/582 |
International
Class: |
C10M 107/38 20060101
C10M107/38 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2005 |
JP |
2005-044949 |
Claims
1. A lubricant for use in contact with graphite or molybdenum
disulfide or in contact with aluminum materials, which comprises a
perfluoropolyether oil free from (CF.sub.2O).sub.n groups as a
repeat unit of polymer and having a kinetic viscosity at 40.degree.
C. of 50-1,500 mm.sup.2/sec, as a base oil.
2. A lubricant according to claim 1, wherein the perfluoropolyether
base oil has a kinetic viscosity at 40.degree. C. of 50-250
mm.sup.2/sec.
3. A lubricant according to claim 1, wherein the perfluoropolyether
base oil is at least one of perfluoropolyether oil (A) represented
by the following general formula (A):
F(CF.sub.2CF.sub.2CF.sub.2O).sub.mC.sub.2F.sub.5 (where m is an
integer of 2-100), and perfluoropolyether oil (B) represented by
the following general formula:
RfO[CF(CF.sub.3)CF.sub.2O].sub.pCF.sub.2CF.sub.2O).sub.qRf' (where
Rf and Rf' are same or different perfluoroalkyl groups having 1-5
carbon atoms, p+q=2-200, q/p=0-2, and q can be zero, and
CF(CF.sub.3)CF.sub.2O groups and CF.sub.2CF.sub.2O groups are in
random combination in the main chain).
4. A lubricant according to claim 2, wherein the perfluoropolyether
base oil is at least one of perfluoropolyether oil (A), represented
by the following general formula:
F(CF.sub.2CF.sub.2CF.sub.2O).sub.mC.sub.2F.sub.5 (where m is an
integer of 2-100), and perfluoropolyether oil (B) represented by
the following general formula (B):
RfO[CF(CF.sub.3)CF.sub.2O].sub.p(CF.sub.2CF.sub.2O).sub.qRf' (where
Rf and Rf' are same or different perfluoroalkyl groups having 1-5
carbon atoms, p+q=2-200, q/p=0-2, and q can be zero, and
CF(CF.sub.3)CF.sub.2O groups and CF.sub.2CF.sub.2O groups are in
random combination in the main chain).
5. A lubricant according to claim 1, wherein the lubricant is a
lubricating oil.
6. A lubricant according to claim 2, wherein the lubricant is a
lubricating oil.
7. A lubricant according to claim 1, wherein a thickener is further
contained, and the lubricant is used as a grease.
8. A lubricant according to claim 7, wherein the thickener is
fluororesin powder.
9. A lubricant according to claim 2, wherein a thickener is further
contained, and the lubricant is used as a grease.
10. A lubricant according to claim 9, wherein the thickener is
fluororesin powder.
11. A lubricant according to claim 1, for use as impregnated in a
sintered, oil-impregnated bearing containing graphite or molybdenum
disulfide as a sintering component.
12. A lubricant according to claim 2, for use as impregnated in a
sintered, oil-impregnated bearing containing graphite or molybdenum
disulfide as a sintering component.
13. A lubricant according to claim 1, for use in contact with
metallic parts containing graphite or molybdenum disulfide.
14. A lubricant according to claim 2, for use in contact with
metallic parts containing graphite or molybdenum disulfide.
15. A lubricant according to claim 1, for use in atmospheres where
graphite or molybdenum disulfide prevails as scattered particles or
contaminants.
16. A lubricant according to claim 2, for use in atmospheres where
graphite or molybdenum disulfide prevails as scattered particles or
contaminants.
17. A lubricant according to claim 1, for use in contact with
aluminum materials as a sliding member.
18. A lubricant according to claim 2, for use in contact with
aluminum materials as a sliding member.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricant, and more
particularly to a lubricant comprising a lubricating oil or a
grease for use in contact with graphite or molybdenum disulfide
such as sintered, oil-impregnated bearings containing graphite or
molybdenum disulfide or for use in contact with aluminum materials
such as sliding members, etc., formed from aluminum materials.
BACKGROUND ART
[0002] Sintered, oil-impregnated bearings comprises porous bodies
made compression of several kinds of solid powder obtained by
adding solid lubricants such as graphite, molybdenum disulfide,
carbon black, etc. to metal powders such as iron, copper, tin,
zinc, etc. The sintered, oil-impregnated bearings can be used
without any addition of oil owing to the self-lubrication action of
a small amount of initially impregnated lubricant. Thus, it is
important for the life of bearings that the a sufficient amount of
lubricant can be retained in the bearings and can be stably used
for a long time.
[0003] Cheaper sintered, oil-impregnated bearings than the
ball-and-roller bearings have been increasingly used as automobile
bearings, and consequently the lubricant for use in such sintered,
oil-impregnated bearings have been inevitably exposed to such
situations more strict where the high-temperature durability and
low-temperature characteristics of lubricant are essentially
required. Lubricating oil compositions comprising a
perfluoropolyether oil as a base oil have been so far used in such
situations, and have been inevitably brought into and kept with
contact with some kinds of metals or solid lubricants having a very
large surface area, so even the perfluoropolyether oils fail to
maintain stable high-temperature characteristics, depending on
their structures.
[0004] Patent Literature 1: JP-B-2,595,583
[0005] Aluminum has a high specific strength in spite of its low
specific gravity, and can have a higher strength upon alloying or
processing and further has a corrosion resistance. Thus, the
aluminum has been used in various fields covering automobile parts,
airplane and marine vessel parts, domestic electric appliances,
electric tools, etc., of course, including sliding members,
contributing to lighter weight of the machinery, higher working
efficiency of high-speed revolution parts or sliding parts, or even
to energy consumption saving. It is required that lubricants for
use even in the parts of aluminum materials must be able to
maintain their distinguished performance stably for a long
time.
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0006] The present inventors have found that the high-temperature
characteristics of perfluoropolyether oil are drastically
deteriorated not only due to the structure of perfluoropolyether
oil, but also due to contact with graphite or molybdenum disulfide
used as one component of the sintered, oil-impregnated bearings,
and further have found that the perfluoropolyether oil also
undergoes drastic deterioration of the high-temperature
characteristics even by contact of aluminum materials.
[0007] An object of the present invention is to provide a lubricant
free from considerable deterioration of high-temperature
characteristics (high-temperature durability), when used in contact
with graphite or molybdenum disulfide such as sintered,
oil-impregnated bearings, etc. containing graphite or molybdenum
disulfide, or in contact with metallic parts such as ball bearings,
etc. containing graphite or molybdenum disulfide, or even used in
contact with aluminum materials including aluminum material as
sliding members.
Means for Solving the Problem
[0008] Such an object of the present invention can be attained by a
lubricant for use in contact with graphite or molybdenum disulfide,
or in contact with aluminum materials, which comprises a
perfluoropolyether oil free from (CF.sub.2O).sub.n groups as a
repeat unit of polymer and having a kinematic viscosity at
40.degree. C. of 50-1,500 mm.sup.2/sec., preferably 50-250
mm.sup.2/sec., more preferably 65-200 mm.sup.2/sec., as a base oil.
The lubricant may be in any form of lubricating oil or grease,
where perfluoropolyether oils represented by the following general
formulae can be used as a base oil:
F(CF.sub.2CF.sub.2CF.sub.2O).sub.mC.sub.2F.sub.5
RfO[CF(CF.sub.3)CF.sub.2O].sub.p(CF.sub.2CF.sub.2O).sub.qRf'
EFFECT OF THE INVENTION
[0009] Perfluoropolyether oils undergo dramatically deterioration
of the high-temperature characteristics (high-temperature
durability) not only due to the structure of perfluoropolyether
oils, but also due to contact with graphite or molybdenum disulfide
used as one component in the sintered, oil-impregnated bearings.
The present invention provides a lubricant free from considerable
deterioration of high-temperature characteristics when used in
contact with graphite or molybdenum disulfide such as the sintered,
oil-impregnated bearings, etc. containing graphite or molybdenum
disulfide, or in contact with metallic parts such as ball bearings,
etc. containing graphite or molybdenum disulfide. Cases of the
lubricant as used in contact with metallic parts include those used
in atmospheres where the graphite or molybdenum disulfide prevails
as scattered particles or as contaminants, for example, cases in
contact with graphite or molybdenum disulfide coming from motor
parts such as brushes, shafts, etc. The atmospheres where the
graphite or molybdenum disulfide prevails as scattered particles or
as contaminants are not to be restricted to the afore-mentioned
cases.
[0010] The perfluoropolyether oils having a kinematic viscosity at
40.degree. C. of 50-1,500 mm.sup.2/sec. can maintain the volatility
and stability for a long time, even if used at higher temperature
more than 150.degree. C. in the presence of a solid lubricant such
as graphite, molybdenum disulfide, etc., thereby attaining a longer
life of parts to be used. Particularly, perfluoropolyether oils
having a kinematic viscosity of 50-250 mm.sup.2/sec., preferably
65-200 mm.sup.2/sec., have distinguished low-temperature
characteristics as well.
[0011] The present lubricant can be used in any mode of sliding
including revolution, reciprocation, slipping, and oscillation, for
example, as sintered, oil-impregnated bearing or bushes containing
graphite or molybdenum disulfide in automobile uses fuel injectors
including units for controlling rates of idle revolution, units for
recycling an exhaust gas, units for electronic throttle
controlling, etc., and uses such as those requiring a heat
resistance, a low-temperature resistance and a load resistance,
typically hub units, traction motors, alternators, etc. or in those
requiring abrasion resistance or a low friction characteristics,
typically power transmission units, power wind motors, wipers,
etc.; in information system uses requiring a high speed, a low
friction coefficient, a low outgassing capacity, etc., typically
hard disc drives, flexible disc memory devices, compact disc
drives, photomagnetic disc drives, etc.; business machine uses,
typically LBP scanner motors, etc.; and motor uses such as domestic
electric appliances, sound equipment, etc., used in the
high-temperature circumstances, etc. The present lubricant can be
also effectively used in atmospheres where graphite or molybdenum
disulfide comes into contact with the lubricant directly or through
the contaminant prevailing there.
[0012] The high-temperature characteristics (high-temperature
durability) of perfluoropolyether oils are drastically lowered also
when used in contact with aluminum materials including aluminum
material as sliding members, but the present lubricant never
undergoes considerable deterioration of high-temperature
characteristics, even when used in such a case as above. That is,
the present lubricant can maintain the volatility or stability for
a long time and can show a lubricability in various sliding
operations, even if used in the presence of aluminum materials at
higher temperature more than 150.degree. C. or 200.degree. C.,
thereby attaining an extremely longer life of parts to be used.
[0013] Besides such various uses as mentioned above, the present
lubricant can be used also in bearings or bushes of heated rolls
used in plastics-processing machines, business machines, and
copiers, and those of chains, etc. used in construction machines,
machine tools, electrically driven tools, machines for printing,
book-binding and paper processing, or their parts, and also can be
used in lubrication of contacts between sliding members of
ball-and-roller bearings, plain bearings, sintered bearings, gears,
valves, cocks, oil seals, rolls, electric contacts, etc.
BRIEF DESCRIPTION OF DRAWING
[0014] [FIG. 1] A graph showing changes in percent weight loss with
time of various perfluoropolyether base oils in the presence of
graphite or molybdenum disulfide at 200.degree. C.
BEST MODES FOR CARRYING OUT THE INVENTION
[0015] Base oils for use in the present invention are those having
a kinetic viscosity at 40.degree. C. (according to JIS K2283,
corresponding to ASTM D445) of 50-1,500 mm.sup.2/sec., preferably
50-250 mm.sup.2/sec., more particularly 65-200 mm.sup.2/sec., and
free from (CF.sub.2O).sub.n groups as a repeat unit of polymer. As
shown in the following Example 1 and FIG. 1 graph, determination of
change with time (percent weight loss) of perfluoropolyether oils
allowed to stand in a thermostat tank at 200.degree. C. reveals
that changes with time of perfluoropolyol ether oil having
(CF.sub.2O).sub.n groups as a repeat unit of polymer are not
particularly considerable in the absence of graphite or molybdenum
disulfide, as compared with other perfluoropolyether oils, but are
very considerable in the presence of graphite or molybdenum
disulfide, whereas those free from (CF.sub.2O).sub.n groups as a
repeat unit of polymer have a slight change in such characteristic
tendency even in the presence of graphite or molybdenum disulfide,
and thus perfluoropolyether oils free from (CF.sub.2O).sub.n groups
as a repeat unit of polymer can be selected as a base oil for the
present invention.
[0016] As shown in the results of the following Example 2, percent
weight loss of the present lubricant at such a high temperature as
250.degree. C. even in the presence of aluminum materials is within
an allowable range, and have the similar tendency even at a the
kinetic viscosity at -40.degree. C.
[0017] Perfluoropolyether oils (base oil) free from
(CF.sub.2O).sub.n groups as a repeat unit of polymer includes the
following perfluoropolyether oils:
F(CF.sub.2CF.sub.2CF.sub.2O).sub.mC.sub.2F.sub.5 (A)
RfO[CF(CF.sub.3)CF.sub.2O].sub.p(CF.sub.2CF.sub.2O).sub.qRf'
(B)
[0018] Perfluoropolyether oil (A): obtainable by anionic
polymerization of 2,2,3,3-tetrafluorooxetane in the presence of a
cesium fluoride catalyst, followed by a fluorine gas treatment of
the resulting fluorine-containing polyether
(CH.sub.2CF.sub.2CF.sub.2O).sub.n under ultraviolet irradiation at
160.degree.-300.degree. C. The product oils having a kinetic
viscosity at 40.degree. C. of 5-2,000 mm.sup.2/sec. are available,
which can satisfy conditions of m=2-100 in the general formula for
perfluoropolyether oil (A).
[0019] Perfluoropolyether oil (B): obtainable by complete
fluorination of a precursor formed by photooxidation polymerization
of hexafluoropropylene or together with tetrafluoroethylene, or by
anionic polymerization of hexafluoropropylene oxide or together
with tetrafluoroethylene oxide in the presence of a cesium fluoride
catalyst, followed by a fluorine gas treatment of the resulting
acid fluoride compound having the terminal CF(CF.sub.3)COF groups.
The product oils having a kinetic viscosity at 40.degree. C. of
5-2,000 mm.sup.2/sec. are available, which can satisfy conditions
of p+q=2-200 and q/p=0-2:1 in the general formula for
perfluoropolyether oil (B).
[0020] When the kinetic viscosity is below 50 mm.sup.2/sec., the
percent evaporation loss (percent weight loss) will be larger, and
the oil film strength will be lowered, making the life shorter or
causing attrition or seizure, whereas when the kinetic viscosity is
above 1500 mm.sup.2/sec., the pour point will be much higher,
resulting in not only a failure to obtain satisfactory
low-temperature characteristics, but also the inconvenience of
increasing a viscous resistance, thereby increasing a power
consumption or a torque. So long as the base oil has a kinetic
viscosity at 40.degree. C. of 50-1,500 mm.sup.2/sec., a
satisfactory stability to heat resistance can be obtained.
Particularly when good low-temperature characteristics are required
at a low temperature, for example, at -40.degree. C.,
perfluoropolyether oil having a limited kinetic viscosity to 50-250
mm.sup.2/sec., preferably 65-200 mm.sup.2/sec., can be used. The
perfluoropolyether oil having such a limited kinetic viscosity can
not only satisfy the evaporation loss-resisting characteristics or
low-temperature characteristics fully, but can be also used stably
at high temperatures over 200.degree. C. A mixture of two or more
perfluoropolyether oils can be used, where the kinetic viscosity of
such a mixture of base oils must be within such a range as
mentioned above.
[0021] A thickener, preferably fluororesin, can be added to the
base oil. The fluororesin for use herein includes, for example,
polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropene
copolymer, perfluoroalkylene resin, etc. so far used as a
lubricant. Polytetrafluoroethylene for use herein is such one as
prepared by emulsion polymerization, suspension polymerization,
solution polymerization, etc. of tetrafluoroethylene, thereby
obtaining polytetrafluoroethylene having a number average molecular
weight Mn of about 1,000 to about 1,000,000, followed by heat
decomposition, electron beam-irradiated decomposition, physical
pulverization, etc. thereof, thereby reducing the number average
molecular weight Mn to about 1,000 to about 500,000.
Copolymerization of tetrafluoroethylene and hexafluoropropene, and
successive treatment to reduce the molecular weight to a lower one
can be carried out in the same manner as in the case of
polytetrafluoroethylene as mentioned above, and the resulting
copolymer having a number average molecular weight Mn of about
1,000 to about 600,000 can be used. Molecular weight can be also
controlled by using a chain transfer agent at the time of
copolymerization reaction. Powdery fluororesins thus obtained have
an average primary particle size of generally not more than about
500 .mu.m, preferably about 0.1 to about 30 .mu.m. Addition of
powdery fluororesin can give the lubricant an oil film formability,
anti-scattering and anti-leakage properties, and a rust
inhibitiveness, thereby making the lubricability and durability
much better.
[0022] Other thickeners for use herein than the fluororesins
include, for example, metal soaps such as Li soap, etc., urea
resin, minerals such as bentonite, etc., organic pigments,
polyethylene, polypropylene, polyamide, etc., but from the
viewpoint of heat resistance and lubricability it is preferable to
use aliphatic dicarboxylic acid metal salts, monoamide
mono-carboxylic acid metal salts, monoester carboxylic acid metal
salts, diurea, triurea, tetraurea, etc.
[0023] The thickener such as the powdery fluororesins, etc., can be
used as admixed in a proportion of 0.1-40% by weight, preferably
0.5-30% by weight, on the basis of total weight of composition
comprising a perfluoropolyether base oil and a thickener. When the
proportion is above 40% by weight, the composition will be too hard
to seal bearings, etc., whereas when the proportion is below 0.1%
by weight, the thickening capacity of fluororesin will not be
displayed, resulting in lowering of apparent viscosity and
deterioration of dispersibility into the base oil, and any
satisfactory increase in the oil film formability, anti-scattering
and anti-leakage property, and rust inhibitiveness cannot be
expected. When the thickener is used in a proportion from a little
less than about 10% by weight on the basis of total weight of the
thickener and the base oil, the composition takes a grease form.
When the thickener is used in a proportion of 5% by weight or less
on the same basis as above, the composition shows a fluidity in a
category of "liquid grease", as will be shown in the following
Examples and Comparative Examples, where the low-temperature
characteristics are evaluated as a low-temperature viscosity of
base oil mixtures, whereas in embodiments of using a thickener in a
proportion of 30% by weight, the composition shows a semi-solid
form in a category of grease, where the low-temperature
characteristics are evaluated as a low-temperature torque.
[0024] Within such a range as not to injure the object of the
invention, so far well known fluorine-based additives can be used,
if required, such as perfluoropolyether oils having terminals
substituted with alcohols, carboxylic acids or their esters,
amines, amides, phosphoric acids or their esters, phosphonic acid
or its ester, reaction products, formed from isocyanates and
alcohols or amines, etc.
[0025] The lubricant base oil can further contain additives so far
added to the conventional lubricants such as various
non-fluorine-based additives so far having had no compatibility
with perfluoropolyether oils, due to the addition of fluororesin, a
viscosity index-improver, a pour point depressant, an ashless
dispersant, a metal-based detergent, an antioxidant, a rust
inhibitor, a corrosion inhibitor, an antifoaming agent, an extreme
pressure agent, an oiliness agent, a friction-controlling agent, a
solid lubricant, etc., if required.
[0026] The antioxidant for use herein includes, for example, a
phenol-based antioxidant such as 2,6-di-t-butyl-4-methylphenol,
4,4-methylenebis (2,6-di-t-butylphenol), etc., and amine-based
antioxidants such as alkyldiphenylamine having an alkyl group of
4-20 carbon atoms, triphenylamine, phenyl-.alpha.-naphthylamine,
phenothiazine, alkylated .alpha.-naphthylamine, phenithiazine,
alkylated phenithiazine, etc.
[0027] The rust inhibitor for use herein includes, for example,
fatty acid, fatty acid amines, alkylsulfonic acid metal salts,
alkylsulfonic acid amine salts, oxidized paraffin, polyoxyethylene
alkyl ethers, etc., and the corrosion inhibitor includes, for
example, benzotriazole, benzoimidazole, thiadiazole, etc.
[0028] The extreme pressure agent includes, for example,
phosphorous-based compounds such as phosphoric acid esters,
phosphorous acid esters, phosphoric acid ester amine salts, etc.,
sulfur-based compounds such as sulfides, disulfides, etc.,
dialkyldithiophosphoric acid metal salts, dialkyldithiocarbamic
acid metal salts, etc.
[0029] The oiliness agent includes, for example, fatty acids or
their esters, higher alcohols, polyhydric alcohols or their esters,
aliphatic amines, fatty acid monoglycerides, etc.
[0030] The solid lubricant includes, for example, graphite,
molybdenum disulfide, boron nitride, silane nitride, etc. In the
case of using graphite or molybdenum disulfide as solid lubricant
lowering of changes in heat resistance with time of
perfluoropolyether base oil can effectively prevent.
[0031] A composition to be formed by adding a thickener to a
perfluoropolyether base oil can be prepared, for example, by any of
the following procedures:
[0032] (a) By mixing a perfluoropolyether base oil with a thickener
in a predetermined amounts, respectively, followed by thorough
kneading thereof through three rolls or a high pressure
homogenizer, (b) by adding a perfluoropolyether oil and an
aliphatic carboxylic acid to a heatable and stirrable reactor,
melting the content with heating, and then adding thereto a metal
hydroxide (and an amide compound or an alcohol compound) in
predetermined amounts, to conduct metal salting reaction (and
amidation reaction or esterification reaction), followed by cooling
and thorough kneading thereof through three rolls or a high
pressure homogenizer, and (c) by adding a perfluoropolyether oil
and an isocyanate to a heatable and stirrable reactor, heating the
content, adding a predetermined amount of an amine thereto,
followed the resulting reaction product by cooling and thorough
kneading thereof through three rolls or a high pressure
homogenizer.
EXAMPLES
[0033] The present invention will be described in detail below,
referring to Examples, but is not limited thereto.
Example 1
[0034] The following three kinds of perfluoropolyether base oils
were admixed with 10% by weight of graphite powder (flake graphite
powder CB-150, a product of Japan Graphite Co.; fixed carbon
content: 98.0% or more, and average particle size: 40 .mu.m), or
molybdenum disulfide (LM13-SM powder, a product of Daito Lubricant
Manufacturing Co.; average particle size: 0.4 .mu.m) on the basis
of the sample, and 0.6 g each of the samples was sampled into
individual glass dishes, 36 mm in diameter, smeared onto the dish
surfaces in a uniform thin film state, and left standing in a
thermostat tank at 200.degree. C. to determine changes in percent
oil weight loss with time.
[0035] The results are shown graphically in FIG. 1, where [0036] :
F(CF.sub.2CF.sub.2CF.sub.2O).sub.mC.sub.2F.sub.5 (kinetic viscosity
at 40.degree. C.: 100 mm.sup.2/sec.) [0037] .largecircle.:
+graphite [0038] .tangle-solidup.:
RfO[CF(CF.sub.3)CF.sub.2O].sub.p(CF.sub.2CF.sub.2O).sub.qRf'
(kinetic viscosity at 140.degree. C.: 180 mm.sup.2/sec.) [0039]
.DELTA.: +graphite [0040] .box-solid.:
RfO(CF.sub.2CF.sub.2O).sub.m(CF.sub.2O).sub.nRf' (kinetic viscosity
at 40.degree. C.: 160 mm.sup.2/sec.) [0041] : +graphite [0042]
.diamond-solid.: +molybdenum disulfide
[0043] It can be seen from the results that in the case of
perfluoropolyether base oils free from (CH.sub.2O).sub.n groups as
a repeat unit of polymer, the percent oil weight loss at
200.degree. C. is a substantially independent from the presence of
graphite, whereas in the case of perfluoropolyether oil having
(CH.sub.2O).sub.n groups as a repeat unit of polymer, substantially
all of the oil is evaporated and lost within a very short time by
the presence of graphite or molybdenum disulfide, particularly
graphite.
Example 2
[0044] The following perfluoropolyether base oils (A) or (B) having
various kinetic viscosities at 40.degree. C. were admixed with 10%
by weight of aluminum powder (a product of Wako Pure Chemical Co.,
purity: 99.5%, and particle sizes: 53-150 .mu.m) on the basis of
the sample, and 0.3 ml each of the samples was sampled into
individual glass dishes, 37 mm in diameter, smeared onto the dish
surfaces in a uniform thin film states and left standing in a
thermostat tank at 250.degree. C. to determine weights of entire
glass dishes after 100 hours, thereby calculating percent oil
weight losses.
[0045] Perfluoropolyether oil (A):
F(CF.sub.2CF.sub.2CF.sub.2O).sub.mC.sub.2F.sub.5 [0046] Kinetic
viscosity at 40.degree. C. (A-1) 65 mm.sup.2/sec. [0047] (A-2) 100
mm.sup.2/sec. [0048] (A-3) 200 mm.sup.2/sec. [0049] (A-4) 23
mm.sup.2/sec.
[0050] Perfluoropolyether oil (B):
RfO[CF(CF.sub.3)CF.sub.2O).sub.pRf' [0051] Kinetic viscosity at
40.degree. C. (B-1) 180 mm.sup.2/sec. [0052] (B-2) 400
mm.sup.2/sec. [0053] (B-3) 25 mm.sup.2/sec. [0054] (B-4) 1200
mm.sup.2/sec.
[0055] Perfluoropolyether oil (C):
RfO(CF.sub.2CF.sub.2O).sub.m(CF.sub.2O).sub.nRf' [0056] Kinetic
viscosity at 40.degree. C. 140 mm.sup.2/sec.
[0057] Emulsion-polymerized polytetrafluoroethylene powder (Mn:
about 50,000 to about 100,000; average primary particle size: 0.2
.mu.m) was used as fluororesin powder.
[0058] The results are shown in the following Table 1, together
with kinds and amounts (parts by weight) of base oils, amounts
(parts by weight) of fluororesin and additive, where the kinetic
viscosity at 40.degree. C. and pour point (according to JIS K2269,
corresponding to ASTM D97) of the base oil or base oil-fluororesin
mixture, and percent weight loss and low-temperature viscosity
(kinetic viscosity at -40.degree. C. according to JIS K2283,
corresponding to ASTM D445) are given as results of determination,
where Nos. 1-12 relate to Examples, whereas Nos. 13-15 relate to
Comparative Examples.
TABLE-US-00001 TABLE 1 Lubricating oil Items of determination
(composition) Kinetic Percent Low- Fluoro viscosity weight Pour
temperature Base oil resin at 40.degree. C. loss point viscosity
No. Kind Amount Amount (mm.sup.2/sec.) (%) (.degree. C.)
(mm.sup.2/sec.) 1 A-1 100 -- 65 41.3 <-60 8,800 2 A-2 100 1 100
27.7 <-60 15,500 3 A-3 100 -- 200 2.5 <-60 37,000 4 A-1 25 1
90 31.3 <-60 14,000 A-2 75 5 A-1 40 3 130 16.9 <-60 25,000
A-3 60 6 A-2 30 -- 162 10.7 <-60 30,000 A-3 70 7 A-1 70 -- 105
27.2 <-60 36,000 B-2 30 8 A-2 40 -- 140 31.2 -50.0 75,000 B-1 60
9 A-2 80 5 130 23.2 -55.0 45,000 B-2 20 10 A-3 50 3 190 29.8 -50.0
80,000 B-1 50 11 B-2 100 -- 400 34.2 -30 Impossible to determine 12
B-4 100 -- 1200 1.0 -15 >100,000 13 A-4 100 -- 23 94.4 <-60
30,000 14 B-3 100 3 25 98.3 -60.0 11,000 15 C 100 -- 140 93.0 -60.0
4,000
[0059] It can be seen from the results that the percent weight loss
at 250.degree. C. is considerably increased in the cases of using
base oils having a kinetic viscosity at 40.degree. C. of less than
50 mm.sup.2/sec. (Nos. 13 and 14), and the percent weight loss at
250.degree. C. is considerably increased after 100 hours in the
case of using a base oil having (CF.sub.2O).sub.n groups as a
repeat unit of polymer (No. 15), so the sample has been almost
lost, whereas the percent weight loss at such a high temperature as
250.degree. C. is within an acceptable range in the cases of using
base oil having a kinetic viscosity at 40.degree. C. in a range of
50-1,500 mm.sup.2/sec., and the base oils having a kinetic
viscosity at 40.degree. C. in a range of 50-250 mm.sup.2/sec. have
the similar tendency even at a kinetic viscosity at -40.degree. C.
(Nos. 1-10).
[0060] Furthermore, in addition above items, grease consisting of
70 parts by weight of A-1 and 30 parts by weight of fluororesin
(No. 21); 70 parts by weight of A-2 70 and 30 parts by weight of
fluororesin (No. 22); 70 parts by weight of B-2 and 30 parts by
weight of fluororesin (No. 23); and 70 parts by weight of B-3 and
30 parts by weight of fluororesin (No. 24) were subjected to a
low-temperature torque test (according to JIS K2220.5.14, torques
were measured at the start-up and in the stationary state;
corresponding to ASTM D1478). The results are shown in the
following Table 2. No. 24 relates to Comparative Example.
TABLE-US-00002 TABLE 2 Items of determination No. 21 No. 22 No. 23
No. 24 Kinetic viscosity at 40.degree. C. (mm.sup.2/sec.) 65 100
400 25 Percent weight loss (%) 29.1 20.3 15.8 69.4 Pour point
(.degree. C.) <-60 <-60 -30 -60.0 Low-temperature viscosity
(mm.sup.2/sec.) 8800 15500 X 11,000 Low-temperature torque At
start-up (N cm) 7.8 8.7 X 8.0 In stationary state (N cm) 3.8 4.5 X
4.1 Note) X: impossible to determine
* * * * *