U.S. patent application number 11/803715 was filed with the patent office on 2010-01-28 for high temperature shear stable nanographite dispersion lubricants with enhanced thermal conductivity and method for making.
Invention is credited to Frances E. Lockwood, Stephanie M. McCoy, Thomas R. Smith, Gefei Wu, Zhiqiang Zhang.
Application Number | 20100022422 11/803715 |
Document ID | / |
Family ID | 41569170 |
Filed Date | 2010-01-28 |
United States Patent
Application |
20100022422 |
Kind Code |
A1 |
Wu; Gefei ; et al. |
January 28, 2010 |
High temperature shear stable nanographite dispersion lubricants
with enhanced thermal conductivity and method for making
Abstract
A process for producing a nanographite dispersion in a fluid
wherein the thermal conductivity of the dispersion is enhanced from
the base fluid by more than 10% for a 1% graphite dispersion. A
high purity graphite with high crystallinity and reduced surface
damage and oxidation is selected as the starting material. The
starting material is subjected to a process of wet media milling in
the presence of dispersant and solvent fluid. The mill temperature
is controlled to control and reduce surface damage to yield a
nanographite with flake shape and controlled aspect ratio until a
particle size average of 300 nm diameter and 50 nm is obtained. The
process recycles a portion of the milled material to increase the
ratio of small particle distribution to large particles in an
intermediate product with small and large particle bi-modal
distribution. The large particle distribution is removed by a
separation process such as centrifugation or filtration.
Inventors: |
Wu; Gefei; (Lexington,
KY) ; Zhang; Zhiqiang; (Lexington, KY) ;
Lockwood; Frances E.; (Georgetown, KY) ; McCoy;
Stephanie M.; (Lexington, KY) ; Smith; Thomas R.;
(Lexington, KY) |
Correspondence
Address: |
WOOD, HERRON & EVANS, LLP
2700 CAREW TOWER, 441 VINE STREET
CINCINNATI
OH
45202
US
|
Family ID: |
41569170 |
Appl. No.: |
11/803715 |
Filed: |
May 15, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11796708 |
Apr 27, 2007 |
|
|
|
11803715 |
|
|
|
|
10730762 |
Dec 8, 2003 |
7348298 |
|
|
11796708 |
|
|
|
|
PCT/US02/16888 |
May 30, 2002 |
|
|
|
10730762 |
|
|
|
|
60795814 |
Apr 27, 2006 |
|
|
|
Current U.S.
Class: |
508/118 ;
508/113; 508/122; 508/128; 508/130; 508/131; 977/775 |
Current CPC
Class: |
C10M 2209/104 20130101;
C10M 2205/0285 20130101; C10N 2030/68 20200501; C10M 141/06
20130101; C10M 2209/084 20130101; C10M 171/06 20130101; C10M
2215/26 20130101; C10M 2219/046 20130101; C10M 2201/041 20130101;
C10N 2030/74 20200501; C10M 2207/34 20130101; C10N 2040/25
20130101; C10N 2020/06 20130101; B82Y 30/00 20130101; C10M 163/00
20130101; C10M 2203/1006 20130101; C10M 2223/02 20130101; C10N
2030/00 20130101; C10M 2217/024 20130101; C10M 2205/02 20130101;
C10M 2215/28 20130101; C10M 2217/028 20130101; C10M 141/10
20130101; C10M 2217/043 20130101; C10M 2217/022 20130101; C10M
2209/104 20130101; C10M 2209/084 20130101; C10M 2217/022 20130101;
C10M 2209/084 20130101; C10M 2217/028 20130101; C10M 2209/084
20130101; C10M 2219/046 20130101; C10N 2010/04 20130101; C10M
2219/046 20130101; C10N 2010/04 20130101 |
Class at
Publication: |
508/118 ;
508/113; 508/122; 508/128; 508/130; 508/131; 977/775 |
International
Class: |
C10M 125/02 20060101
C10M125/02; C10M 129/26 20060101 C10M129/26; C10M 133/00 20060101
C10M133/00; C10M 129/00 20060101 C10M129/00; C10M 145/14 20060101
C10M145/14 |
Claims
1. A product made from a process for producing a nanographite
dispersion in a fluid having the thermal conductivity of the
dispersion enhanced from the base fluid by more than 10% for a 1%
graphite dispersion, comprising the steps of: selecting a high
purity graphite with high crystallinity, reduced surface damage,
and reduced oxidation as the starting material; wet media milling
said starting material in the presence of a dispersant and a
solvent; controlling a mill temperature and atmosphere to control
and reduce surface damage to said starting material; milling until
a desired nanographite with flake shape and controlled aspect ratio
is achieved; milling until a particle size average of 300 nm
diameter and 50 nm thick is or smaller is obtained; recycling a
portion of the milled material to increase the ration of small
particle distribution to large particle in an intermediate product
with small and large particle bi-modal distribution; removing the
large particle distribution from the finished product by
centrifugation or filtration, and adding said intermediate product
to a lubricant.
2. The product by process of claim 1, wherein said mill is selected
from a dry ball mill, a wet ball mill, and a jet mill.
3. The product by process of claim 1, wherein the dispersant is an
ashless dispersant.
4. The product by process of claim 1, wherein the dispersant is
selected from the group consisting of a lipophilic hydrocarbon
group and a polar functional hydrophilic group wherein the polar
functional group comprises a carboxylate, ester, amine, amide,
imine, imide, hydroxyl, ether, epoxide, phosphorus, ester carboxyl,
anhydride, and nitrile, and the lipophilic group comprises an
oligomeric or polymeric compound from 70 to 200 carbon atoms to
ensure oil solubility and hydrocarbon polymers treated with various
reagents to introduce polar functions including products prepared
by treating polyolefins such as polyisobutene first with maleic
anhydride, or phosphorus sulfide or chloride, or by thermal
treatment, and then with reagents such as polyamine, amine, and
ethylene oxide.
5. The process of claim 1, wherein the dispersant is selected from
the group consisting of a N-substituted polyisobutenyl succinimides
and succinates, alkyl methacrylate-vinyl pyrrolidinone copolymers,
alkyl methacrylate-dialkylaminoethyl methacrylate copolymers, alkyl
methacrylate-polyethylene glycol methacrylate copolymers, and
polystearamides. Preferred oil-based dispersants that are include
dispersants from the chemical classes of alkylsuccinimide,
succinate esters, high molecular weight amines, MANNICH base and
phosphoric acid derivatives. Some specific examples are
polyisobutenyl succinimide-polyethylenepolyamine, polyisobutenyl
succinic ester, polyisobutenyl hydroxybenzyl-polyethylenepolyamine,
bis-hydroxypropyl phosphorate, LUBRIZOL 890 (an ashless PIB
succinimide), LUBRIZOL 6420 (a high molecular weight PIB
succinimide), ETHYL HITEC 646 (a non-boronated PIB succinimide), a
PIB Succinimide, and a dispersant VI improver ETHYL 5777.
6. The product by process of claim 1 wherein said starting material
comprises a pasty liquid of particles with mean size less than 500
nanometers in diameter and having a range of from 100 to 500 nm in
diameter and from 20 to 80 nm in thickness.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Application Ser. No. 60/800,557 filed on May 15, 2006 and U.S.
application Ser. No. 11/796,708 filed on Apr. 27, 2007 claiming
priority from Provisional Application Ser. No. 60/795,814 filed on
Apr. 27, 2006 and claims priority from 11/370,118 filed on Mar. 7,
2006 claiming priority from PCT/US06/001675 filed on Jan. 17, 2006
claiming priority from Provisional Application Ser. No. 60/644,042
filed on Jan. 14, 2005 all of which are incorporated by reference
herein in their entirety. Reference to documents made in the
specification is intended to result in such patents or literature
cited are expressly incorporated herein by reference, including any
patents or other literature references cited within such documents
as if fully set forth in this specification.
TECHNICAL FIELD
[0002] The technical field of this invention is a process for
making nanographite dispersions.
BACKGROUND OF THE INVENTION
[0003] Thermally conductive nano-sized graphite particles can only
be produced under specific processing conditions. Heretofore the
common processing for making graphite particles (larger than the
particles disclosed herein, typically with average particle size
0.8 microns and above) has included dry milling and other milling
processes that render the final particles low in thermal
conductivity. For example, the commercially available samples from
Acheson, Inc. have a thermal conductivity for 1% graphite in oil
dispersions insignificantly greater than the oils without graphite
(typically 0.13 to 0.14 W/mK) By the methods of this invention,
flake, or more specifically, plate shaped nanographites are
produced that have significantly higher thermal conductivity, and
when dispersed in oil at 1 percent by weight, have an increased
thermal conductivity of up to 10 to 15 percent as measured in W/mK,
resulting in experimental values of typically from 0.165 to 0.17
WmK or more as compared to the 0.13 to 0.14 values for oil without
the graphite particles control sample of the instant invention.
DESCRIPTION OF THE PRIOR ART
[0004] The starting material for making nanographites can be any
high thermal conductivity graphite either in fibers. Previously,
naturally formed "nano-graphites" have not been available in the
marketplace at all. Recently, Hyperion Catalysis International,
Inc. commercialized carbon nanotubes or so-called carbon fibrils,
which have a graphitic content as set forth in U.S. Pat. No.
5,165,909 by Tennent et al. which issued in Nov. 24, 1992 and is
hereby incorporated by reference. Carbon nanotubes are typically
hollow graphite-like tubules having a diameter of generally several
to several tens nanometers. They exist in the form either as
discrete fibers or aggregate particles of nanofibers. The thermal
conductivity of the Hyperion Catalysis International, Inc. material
is not stated in their product literature; however, the potential
of carbon nanotubes to convey thermal conductivity in a material is
discussed in U.S. Pat. No. 5,165,909. Actual measurement of the
thermal conductivity of the carbon fibrils they produced was not
given in the patent, so the inference of thermal conductivity is
general and somewhat speculative, based on graphitic structure.
[0005] Bulk graphite with high thermal conductivity is available
from Poco Graphite as a graphite foam, with thermal conductivity
higher than 100 W/mK, and is also available from the
Carbide/Graphite Group, Inc. Graphite powders can be obtained from
UCAR Carbon Company Inc., with thermal conductivity 10-500 W/mK,
and typically >80 W/mK, and from Cytec Carbon Fibers LLC, with
thermal conductivity 400-700 W/mK.
[0006] For many applications carbon nanotubes would be a preferable
substitute, however, for stability in a high shear fluid flow, the
nano graphites are stable whereas carbon nanotubes break up. The
present invention provides a process to mill graphite into plate
shape and the subsequently dispersions have a higher thermal
conductivity and are shear stable at a high temperature of as much
as 430.degree. C. Typically, engine lubricant applications are
subjected to temperatures in the 200 to 300.degree. F. range.
SUMMARY OF THE INVENTION
[0007] The compositions, methods, or embodiments discussed are
intended to be only illustrative of the invention disclosed by this
specification. Variation on these particle nanomaterial,
compositions, methods, or embodiments are readily apparent to a
person of skill in the art based upon the teachings of this
specification and are therefore intended to be included as part of
the inventions disclosed herein.
[0008] Graphite materials having a controlled aspect ratio and high
thermal conductivity are produced by the milling process of the
present invention. The aspect ration must not be too high so as to
be brittle in shear fields, but high enough to have enhanced
thermal conductivity.
[0009] The bulk graphite from Poco Graphite is a graphite foam with
a high thermal conductivity and can be obtained in bulk quantities
and reduced to a nanometer-sized powder by the methods of this
invention.
[0010] The use of bulk graphite foam or graphite powders as an
inexpensive sources of nanomaterials for further processing into
controlled aspect ratio and high thermal conductivity products has
not been used before. The instant invention provides a method of
reducing the graphite to produce an inexpensive nanomaterial having
a particle size suitable for long term dispersion in various
fluids, polymers, composites, gels, greases, plastics etc. and the
method of dispersing same.
[0011] However, only certain processes will produce these
nanographites with high thermal conductivity and the thermal
conductivity can either be drastically reduced (to impart no
benefit) or increased by the subsequent processing. Dry milling
imparts too much change in surface characteristics and reduces
thermal conductivity. It is critical to have the graphite powder
further milled in a horizontal mill with liquid media (e.g. base
oil or solvent) and to use dispersants during wet milling in order
to prevent paste formation.
[0012] It is an object of the present invention to provide a
process for producing a nanographite dispersion in a fluid wherein
the thermal conductivity of the dispersion is enhanced from the
base fluid by more than 10% for a 1% graphite dispersion.
[0013] It is an object of the present invention to provide a
process wherein a high purity graphite with high crystallinity and
reduced surface damage and oxidation is selected as the starting
material.
[0014] It is an object of the present invention to provide a
process of wet media milling the starting material in the presence
of dispersant and solvent (fluid).
[0015] It is an object of the present invention to provide a
process of controlling mill temperature to adjust the viscosity of
the milling mixture to achieve high milling efficiency.
[0016] It is an object of the present invention to provide a
process of milling until a nanographite with flake shape and
controlled aspect ratio is achieved.
[0017] It is an object of the present invention to provide a
process of milling until a particle size average of 300 nm diameter
and 50 nm thick is reached or smaller.
[0018] It is an object of the present invention to provide a
process of recycling the milled material throughly to increase the
ration of small particle distribution to large particle in an
intermediate product with small and large particle bi-modal
distribution.
[0019] It is an object of the present invention to provide a
process of removing the large particle distribution from the
finished product by centrifugation or filtration.
[0020] It is an object of the present invention to provide a method
of preparing a stable dispersion of the carbon nanomaterials in a
liquid medium with the combined use of dispersants/surfactants and
physical agitation for use in a lubricant.
[0021] It is an object of the present invention to provide a method
in which the carbon nanomaterials are made from cost-effective
high-thermal-conductivity graphite (with thermal conductivity
higher than 80 W/mK).
[0022] It is an object of the present invention to provide a method
of developing a method of forming carbon nanomaterials from
inexpensive bulk graphite.
[0023] It is an object of the present invention to provide a method
of utilizing carbon nanotube, graphite flakes, carbon fibrils,
carbon particles and combinations thereof.
[0024] It is an object of the present invention to provide a method
of using carbon nanotubes which are either single-walled, or
multi-walled, with typical aspect ratio of 500-5000.
[0025] It is an object of the present invention whereby the carbon
nanomaterial can optionally be surface treated to be hydrophilic at
surface for ease of dispersing into the aqueous medium.
[0026] It is an object of the present invention to provide a method
wherein the said dispersants/surfactants are soluble or highly
dispersible in the said liquid medium.
[0027] Other objects, features, and advantages of the invention
will be apparent with the following detailed description taken in
conjunction with the accompanying drawings showing a preferred
embodiment of the invention and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] A better understanding of the present invention will be had
upon reference to the following description in conjunction with the
accompanying drawings in which like numerals refer to like parts
throughout the several views and wherein:
[0029] FIG. 1 is a scanning electron microscope microphotograph of
the graphitic raw material obtained from UCAR GS4-E showing the
material shaped as chunks;
[0030] FIG. 2 is a scanning electron microscope microphotograph
showing the graphitic material of FIG. 1 after solvent milling
illustrating the graphite nanoparticles shown as plate-like
structure.
[0031] FIG. 3 is a graph showing rheological measurement of
graphite dispersion;
[0032] FIG. 4 is a graph showing rheological measurement of
graphite dispersion;
[0033] FIG. 5 is an enlarged section taken from the microphotograph
of FIG. 1;
[0034] FIG. 6 is an enlarged section taken from a microphotograph
after further processing of the nanographite material of FIG.
1;
[0035] FIG. 7 is an enlarged section taken from the microphotograph
of FIG. 2 resulting from additional processing of the nanographite
material shown in FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] The following examples of the process is illustrated with
nanographites dispersed in lubricant formulations.
[0037] The term dispersant in the instant invention refers to a
surfactant added to a medium to promote uniform suspension of
extremely fine solid particles, often of colloidal size. In the
examples provided the dispersant is generally a long chain oil
soluble or dispersible compound that attaches to the particles and
disperses them. The term surfactant in the instant invention refers
to any chemical compound that reduces surface tension of a liquid
when dissolved into it, or reduces interfacial tension between two
liquids or between a liquid and a solid. It is usually, but not
exclusively, a long chain molecule comprised of two moieties; a
hydrophilic moiety and a lipophilic moiety. The hydrophilic and
lipophilic moieties refer to the segment in the molecule with
affinity for water, and that with affinity for oil, respectively.
These two terms, dispersant and surfactant, are mostly used
interchangeably in the instant invention for often a surfactant has
dispersing characteristics and many dispersants have the ability to
reduce interfacial tensions.
[0038] The ashless dispersants used in the examples contain a
lipophilic hydrocarbon group and a polar functional hydrophilic
group. The polar functional group can be of the class of
carboxylate, ester, amine, amide, imine, imide, hydroxyl, ether,
epoxide, phosphorus, ester carboxyl, anhydride, or nitrile. The
lipophilic group can be oligomeric or polymeric in nature, usually
from 70 to 200 carbon atoms to ensure oil solubility. Hydrocarbon
polymers treated with various reagents to introduce polar functions
include products prepared by treating polyolefins such as
polyisobutene first with maleic anhydride, or phosphorus sulfide or
chloride, or by thermal treatment, and then with reagents such as
polyamine, amine, and ethylene oxide.
[0039] Of these ashless dispersants the ones typically used include
N-substituted polyisobutenyl succinimides and succinates, alkyl
methacrylate-vinyl pyrrolidinone copolymers, alkyl
methacrylate-dialkylaminoethyl methacrylate copolymers, alkyl
methacrylate-polyethylene glycol methacrylate copolymers, and
polystearamides. Preferred oil-based dispersants include
dispersants from the chemical classes of alkylsuccinimide,
succinate esters, high molecular weight amines, MANNICH base and
phosphoric acid derivatives. Some specific examples are
polyisobutenyl succinimide-polyethylenepolyamine, polyisobutenyl
succinic ester, polyisobutenyl hydroxybenzyl-polyethylenepolyamine,
bis-hydroxypropyl phosphorate. Commercial dispersants suitable
include LUBRIZOL 890 (an ashless PIB succinimide), LUBRIZOL 6420 (a
high molecular weight PIB succinimide), and ETHYL HITEC 646 (a
non-boronated PIB succinimide), and ORONITE OLOA 12002
(succinimide). Preferred dispersants include PIB Succinimide and a
dispersant VI improver olefin copolymer such as ORONITE OLOA
19075.
[0040] Furthermore, the carbon nanomaterial dispersion can be
pre-sheared in a turbulent flow such as a nozzle, a high pressure
fuel injector, an ultrasonic device, or a mill in order to achieve
a stable viscosity. This may be especially desirable in the case
where carbon nanotubes with high aspect ratio are used as the
graphite source, since they, even more than spherical particles,
will thicken the fluid but loose viscosity when exposed in
turbulent flows. Pre-shearing, for example by milling, sonicating,
or passing through a small orifice, such as in a fuel injector, is
a particularly effective way to disperse the particles and to bring
them to a stable size so that their viscosity increasing effect
will not change upon further use.
[0041] The milling process itself, or other pre-shearing process,
can have a rather dramatic effect on the long term dispersion
stability.
[0042] A novel method has been developed whereby graphite particles
are milled to form a thick pasty liquid of particles with mean size
less than 500 nanometers in diameter and typically 300 nm plus or
minus 200 nm in diameter and 50 nm plus or minus 30 nm in
thickness. It is expected that there are many ways of process that
would produce similar particle sizes but destroy the thermal
conductivity of the particles because the energy input causes
surface damage such that the particle structure becomes less
crystalline, more amorphous and also has a chunk-like shape instead
of a platelet shape. For example, if one takes high thermal
conductivity powders produced in a jet mill and further dry mills
these powders, a material of low thermal conductivity would be
expected to result due to high surface temperatures produced in the
dry milling process.
Oil Base Stocks
[0043] The petroleum liquid medium can be any petroleum distillates
or synthetic petroleum oils, greases, gels, or oil-soluble polymer
composition. More typically, it is the mineral base stocks or
synthetic base stocks used in the lube industry, e.g., Group I
(solvent refined mineral oils), Group II (hydrocracked mineral
oils), Group III (severely hydrocracked oils, sometimes described
as synthetic or semi-synthetic oils), Group IV (polyalphaolefins),
and Group VI (esters, naphthenes, and others). One preferred group
includes the polyalphaolefins, synthetic esters, and
polyalkylglycols.
[0044] Synthetic lubricating oils include hydrocarbon oils and
halo-substituted hydrocarbon oils such as polymerized and
interpolymerized olefins (e.g., polybutylenes, polypropylenes,
propylene-isobutylene copolymers, chlorinated polybutylenes,
poly(1-octenes), poly(1-decenes), etc., and mixtures thereof;
alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes,
dinonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls
(e.g., biphenyls, terphenyls, alkylated polyphenyls, etc.),
alkylated diphenyl, ethers and alkylated diphenyl sulfides and the
derivatives, analogs and homologs thereof and the like.
[0045] Alkylene oxide polymers and interpolymers and derivatives
thereof where the terminal hydroxyl groups have been modified by
esterification, etherification, etc. constitute another class of
known synthetic oils.
[0046] Another suitable class of synthetic oils comprises the
esters of dicarboxylic acids (e.g., phtalic acid, succinic acid,
alkyl succinic acids and alkenyl succinic acids, maleic acid,
azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic
acid, alkenyl malonic acids, etc.) with a variety of alcohols
(e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene glycol diethylene glycol monoether, propylene
glycol, etc.). Specific examples of these esters include dibutyl
adipate, di(2-ethylhexyl) sebacate, di-hexyl fumarate, dioctyl
sebacate, diisooctyl azelate, diisodecyl azealate, dioctyl
phthalate, didecyl phthalate, dicicosyl sebacate, the 2-ethylhexyl
diester of linoleic acid dimer, the complex ester formed by
reacting one mole of sebacic acid with two moles of tetraethylene
glycol and two moles of 2-ethylhexanoic acid, and the like.
[0047] Esters useful as synthetic oils also include those made from
C (5) to C (12) monocarboxylic acids and polyols and polyol ethers
such as neopentyl glycol, trimethylolpropane, pentaerythritol,
dipentaerythritol, tripentaerythritol, etc. Other synthetic oils
include liquid esters of phosphorus-containing acids (e.g.,
tricresyl phosphate, trioctyl phosphate, diethyl ester of
decylphosphonic acid, etc.), polymeric tetrahydrofurans and the
like.
[0048] Polyalphaolefins (PAO), useful in the present invention
include those sold by BP Amoco Corporation as DURASYN fluids, those
sold by Exxon-Mobil Chemical Company, (formerly Mobil Chemical
Company) as SHF fluids, and those sold by Ethyl Corporation under
the name ETHYLFLO, or ALBERMARLE. PAO's include the ETHYL-FLOW
series by Ethyl Corporation, Albermarle Corporation, including
ETHYL-FLOW 162, 164, 166, 168, and 174, having varying viscosity
from about 2 to about 460 centistokes.
[0049] MOBIL SHF-42 from Exxon-Mobil Chemical Company, EMERY 3004
and 3006, and Quantum Chemical Company provide additional
polyalphaolefins base stocks. For instance, EMERY 3004
polyalphaolefin has a viscosity of 3.86 centistokes (cSt) at
212.degree. F. (100.degree. C.) and 16.75 cSt at 104.degree. F.
(40.degree. C.). It has a viscosity index of 125 and a pour point
of -98.degree. F. and it also has a flash point of about
432.degree. F. and a fire point of about 478[deg] F. Moreover,
EMERY 3006 polyalphaolefin has a viscosity of 5.88 cSt at
+212.degree. F. and 31.22 cSt at +104.degree. F. It has a viscosity
index of 135 and a pour point of -87.degree. F.
[0050] Additional satisfactory polyalphaolefins are those sold by
Uniroyal Inc. under the brand SYNTON PAO-40, which is a 40
centistoke polyalphaolefin.
[0051] It is contemplated that Gulf Synfluid 4 cSt PAO,
commercially available from Gulf Oil Chemicals Company, a
subsidiary of Chevron-Texaco Corporation, which is similar in many
respects to EMERY 3004 may also be utilized herein. MOBIL SHF-41
PAO, commercially available from Mobil Chemical Corporation, is
also similar in many respects to EMERY 3004.
[0052] Especially useful are the polyalphaolefins will have a
viscosity in the range of up to 100 centistoke at 100[deg] C., with
viscosity of 2 and 10 centistoke being more preferred.
[0053] The most preferred synthetic based oil ester additives are
polyolesters and diesters such as di-aliphatic diesters of alkyl
carboxylic acids such as di-2-ethylhexylazelate,
di-isodecyladipate, and di-tridecyladipate, commercially available
under the brand name EMERY 2960 by Emery Chemicals, described in
U.S. Pat. No. 4,859,352 to Waynick. Other suitable polyolesters are
manufactured by Mobil Oil. MOBIL polyolester P-43, NP343 containing
two alcohols, and Hatco Corp. 2939 are particularly preferred.
[0054] Diesters and other synthetic oils have been used as
replacements of mineral oil in fluid lubricants. Diesters have
outstanding extreme low temperature flow properties and good
residence to oxidative breakdown.
[0055] The diester oil may include an aliphatic diester of a
dicarboxylic acid, or the diester oil can comprise a dialkyl
aliphatic diester of an alkyl dicarboxylic acid, such as di-2-ethyl
hexyl azelate, di-isodecyl azelate, di-tridecyl azelate,
di-isodecyl adipate, di-tridecyl adipate. For instance,
Di-2-ethylhexyl azelate is commercially available under the brand
name of EMERY 2958 by Emery Chemicals.
[0056] Also useful are polyol esters such as EMERY 2935, 2936, and
2939 from Emery Group of Henkel Corporation and HATCO 2352, 2962,
2925, 2938, 2939, 2970, 3178, and 4322 polyol esters from Hatco
Corporation, described in U.S. Pat. No. 5,344,579 to Ohtani et al.
and MOBIL ESTER P 24 from Exxon-Mobil Chemical Company. Esters made
by reacting dicarboxylic acids, glycols, and either monobasic acids
or monohydric alcohols like EMERY 2936 synthetic-lubricant base
stocks from Quantum Chemical Corporation and MOBIL P 24 from
Exxon-Mobil Chemical Company can be used. Polyol esters have good
oxidation and hydrolytic stability. The polyol ester for use herein
preferably has a pour point of about -100.degree. C. or lower to
40.degree. C. and a viscosity of about 2 to 100 centistoke at
100.degree. C.
[0057] A hydrogenated oil is a mineral oil subjected to
hydrogennation or hydrocracking under special conditions to remove
undesirable chemical compositions and impurities resulting in a
base oil having synthetic oil component and properties. Typically
the hydrogenated oil is defined by the American Petroleum Institute
as a Group III base oil with a sulfur level less than 0.03 with
saturates greater than or equal to 90 and a viscosity index of
greater than or equal to 120. Most useful are hydrogenated oils
having a viscosity of from 2 to 60 CST at 100 degrees centigrade.
The hydrogenated oil typically provides superior performance to
conventional motor oils with no other synthetic oil base. The
hydrogenated oil may be used as the sole base oil component of the
instant invention providing superior performance to conventional
mineral oil bases oils or used as a blend with mineral oil and/or
synthetic oil. An example of such an oil is YUBASE-4.
[0058] When used in combination with another conventional synthetic
oil such as those containing polyalphaolefins or esters, or when
used in combination with a mineral oil, the hydrogenated oil may be
utilized as the oil base stock in an amount of up to 100 percent by
volume, more preferably from about 10 to 80 percent by volume, more
preferably from 20 to 60 percent by volume and most preferably from
10 to 30 percent by volume of the base oil composition.
[0059] A Group I or II mineral oil basestock may be incorporated in
the present invention as a portion of the concentrate or a
basestock to which the concentrate may be added. Preferred as
mineral oil base stocks are the ASHLAND 325 Neutral defined as a
solvent refined neutral having a SABOLT UNIVERSAL viscosity of 325
SUS @ 100.degree. F. and ASHLAND 100 Neutral defined as a solvent
refined neutral having a SABOLT UNIVERSAL viscosity of 100 SUS @
100.degree. F., manufactured by the Marathon Petroleum
corporation.
[0060] Other acceptable petroleum-base fluid compositions include
white mineral, paraffinic and MVI naphthenic oils having the
viscosity range of about 20-400 centistokes. Preferred white
mineral oils include those available from Witco Corporation, Arco
Chemical Company, PSI and Penreco. Preferred paraffinic oils
include API Group I and II oils available from Exxon-Mobil Chemical
Company, HVI neutral oils available from Shell Chemical Company,
and Group II oils available from Arco Chemical Company. Preferred
MVI naphthenic oils include solvent extracted oils available from
Equilon Enterprises and San Joaquin Refining, hydrotreated oils
available from Equilon Enterprises and Ergon Refining, and
naphthenic oils sold under the names HYDROCAL and CALSOL by
Calumet, and described in U.S. Pat. No. 5,348,668 to Oldiges.
Dispersants
[0061] The ashless dispersants commonly used in the automotive
industry contain an lipophilic hydrocarbon group and a polar
functional hydrophilic group. The polar functional group can be of
the class of carboxylate, ester, amine, amide, imine, imide,
hydroxyl, ether, epoxide, phosphorus, ester carboxyl, anhydride, or
nitrile. The lipophilic group can be oligomeric or polymeric in
nature, usually from 70 to 200 carbon atoms to ensure oil
solubility. Hydrocarbon polymers treated with various reagents to
introduce polar functions include products prepared by treating
polyolefins such as polyisobutene first with maleic anhydride, or
phosphorus sulfide or chloride, or by thermal treatment, and then
with reagents such as polyamine, amine, ethylene oxide, etc.
[0062] Of these ashless dispersants the ones typically used in the
petroleum industry include N-substituted polyisobutenyl
succinimides and succinates, allyl methacrylate-vinyl pyrrolidinone
copolymers, alkyl methacrylate-dialkylaminoethyl methacrylate
copolymers, alkylmethacrylate-polyethylene glycol methacrylate
copolymers, and polystearamides. Preferred oil-based dispersants
that are most important in the instant application include
dispersants from the chemical classes of alkylsuccinimide,
succinate esters, high molecular weight amines, Mannich base and
phosphoric acid derivatives. Some specific examples are
polyisobutenyl succinimide-polyethylenepolyamine, polyisobutenyl
succinic ester, polyisobutenyl hydroxybenzyl-polyethylenepolyamine,
bis-hydroxypropyl phosphorate. For instance, bis-succinimide is a
dispersant based on polybutene and an amine which is suitable for
oil based dispersions and is commercially available under the
tradenames of INFINEUM C9231, INFINEUM C9232, and INFINEUM C9235
which is sold by Infineum, USA, L.P. The C9231 is borated while the
C9232 and C9235 are not; however, all are bis-succinimides which
differ due to their amine to polymer ratio.
[0063] The dispersant may be combined with other additives used in
the lubricant industry to form a dispersant-detergent (DD additive
package, e.g., LUBRIZOL[R] 9802A and/or the concentrated package
(LUBRIZOL[R] 9802AC), which are mixed Dispersants having a high
molecular weight succinimide and ester-type dispersant as the
active ingredient, and which also contains from about to 9.9
percent by weight of zinc alkyldithiophosphate, from 1 to 4.9
percent by weight of a substituted phenol, from 1 to 4.9 percent of
a calcium sulfonate, and from 0.1 to 0.9 percent by weight of a
diphenylamine; wherein the whole DI package can be used as
dispersing agent for the carbon nanomaterial dispersion.
[0064] Another preferred dispersant package is LUBRIZOL OS#154250
which contains from about 20 to 29.9 percent by weight of a
polyolefin amide alkeneamine, from 0.5 to 1.5 percent by weight of
an alkylphosphite, about 1.1 percent by weight of a phosphoric
acid, and from 0.1 to 0.9 percent by weight of a diphenylamine,
with primary active ingredient believed to be polyisobutenyl
succinimides and succinates. Another preferred dispersant package
is a high molecular weight succinimide DI package for diesel
engines LUBRIZOL[R] 4999 which also contains from about 5 to 9.9
percent zinc alkyldithiophosphate by weight.
Other Types of Dispersants
[0065] Alternatively a surfactant or a mixture of surfactants with
low HLB value (typically less than or equal to 8), preferably
nonionic, or a mixture of nonionics and ionics, may be used in the
instant invention.
[0066] The dispersant for the water based carbon nanomaterial
dispersion, more specifically carbon nanotube dispersion, should be
of high HLB value (typically less than or equal to 10), preferable
nonylphenoxypoly(ethyleneoxy)ethanol-type surfactants are
utilized.
[0067] The dispersant can be in a range of up from 0.001 to 30
percent, more preferably in a range of from between 0.5 percent to
20 percent, more preferably in a range of from between 1.0 to 8.0
percent, and most preferably in a range of from between 2 to 6
weight percent.
[0068] The carbon nanotube or graphite nanoparticles can be of any
desired weight percentage in a range of from 0.0001 up to 50
percent by weight providing for an effective amount to obtain the
desired thermal enhancement of the selected fluid media. For
practical application an effective amount of carbon nanomaterials
is usually in a range of from between 0.01 percent to 20 percent,
and more preferably in a range of from 0.02 to 10 percent, and most
preferably in a range of from between 0.05 percent to 5 percent.
The remainder of the formula is the selected medium comprising oil,
water, or combinations thereof together with any chemical additives
deemed necessary to provide lubricity, corrosion protection,
viscosity, or the like.
[0069] It is believed that in the instant invention the dispersant
functions by adsorbing onto the surface of the nanoparticle
material.
Other Chemical Compounds
[0070] This dispersion may also contain a large amount of one or
more other chemical compounds, preferably polymers, not for the
purpose of dispersing, but to achieve thickening or other desired
fluid characteristics.
[0071] The viscosity improvers used in the lubricant industry can
be used in the instant invention for the oil medium, which include
olefin copolymers (OCP), polymethacrylates (PMA), hydrogenated
styrene-diene (STD), and styrene-polyester (STPE) polymers. Olefin
copolymers are rubber-like materials prepared from ethylene and
propylene mixtures through vanadium-based Ziegler-Natta catalysis.
Styrene-diene polymers are produced by anionic polymerization of
styrene and butadiene or isoprene. Polymethacrylates are produced
by free radical polymerization of alkyl methacrylates.
Styrene-polyester polymers are prepared by first co-polymerizing
styrene and maleic anhydride and then esterifying the intermediate
using a mixture of alcohols.
[0072] Other compounds which can be used in the instant invention
in either the aqueous medium or the oil medium include: acrylic
polymers such as polyacrylic acid and sodium polyacrylate,
high-molecular-weight polymers of ethylene oxide such as Polyox[R]
WSR from Union Carbide, cellulose compounds such as
carboxymethylcellulose, polyvinyl alcohol (PVA), polyvinyl
pyrrolidone (PVP), xanthan gums and guar gums, polysaccharides,
alkanolamides, amine salts of polyamide such as DISPARLON AQ series
from King Industries, hydrophobically modified ethylene oxide
urethane (e.g., ACRYSOL series from Rohmax), silicates, and fillers
such as mica, silicas, cellulose, wood flour, clays (including
organoclays) and nanoclays, and resin polymers such as polyvinyl
butyral resins, polyurethane resins, acrylic resins and epoxy
resins.
[0073] Other chemical additives used in lubricants such as pour
point depressant can also be used in the instant invention. Most
pour point depressants are organic polymers, although some
nonpolymeric substances have been shown to be effective. Commercial
pour point depressants include alkylnaphthalenes,
polymethacrylates, polyfumarates, styrene esters, oligomerized
alkylphenols, phthalic acid esters, ethylenevinyl acetate
copolymers, and other mixed hydrocarbon polymers. The treatment
level of these additives is usually low. In nearly all cases, there
is an optimum concentration above and below which pour point
depressants become less effective.
[0074] Acrylic copolymers such as manufactured by Supeleo Inc. in
Bellefonte, Pa. as ACRYLOID 3008 is a pour point depressant useful
in the present invention.
[0075] Still other chemical additives used in lubricants, such as
rust and oxidation inhibitors, demulsifiers, foam inhibitors, and
seal-swelling agents can also be used in the instant invention.
Physical Agitation.
[0076] The following trade names correspond to the chemical
definition as follows:
TABLE-US-00001 Additive Description Yubase 4 Group III base oil
Yubase 6 Group III base oil PAO 4 Group IV base oil LZ 21303
Passenger car detergent-inhibitor package LZ 8676 Antioxidant
mixture LZ 8650 Organic friction modifier Afton 5777 dispersant
viscosity modifier LZ 7749B PMA pour point depressant T503-209-2
Nano graphite concentrate Star 4 Group II base oil Star 8 Group II
base oil LZ 20010 Passenger car detergent-inhibitor package LZ 6473
Calcium sulfonate detergent LZ 7075F OCP viscosity modifier A-11
Nano graphite concentrate
[0077] Milling Procedure:
[0078] Graphite particles were obtained by pulverizing big graphite
chunks from the Carbide/Graphite Group, and size-selected through a
mesh filter to be less than 75 .mu.m. Thirty (30) grams of the
above graphite particles and 270 grams of DURASYN 162 (a commercial
2 centistokes polyalphaolefin, abbreviated hereafter as 2 cSt PAO
or preferably 4 csT PAO), were added into the EIGER Mini Mill
(Model: M250-VSE-EXP). The milling speed was gradually increased to
4000 rpm. In about 4 hours the above mixture turned into thick
paste. Sixty grams of this paste was discharged and labeled as
Paste A. For the rest of the mixture in the mill, 48 grams of a
dispersant was added and an additional dispersant inhibitor package
(DI package) from Lubrizol, LUBRIZOL 9677MX was added into the mill
and the paste became very thin, and successful recirculation was
restored. The mill was stopped after another 4 hours of milling and
the discharged paste was labeled as Paste B. Paste C was obtained
by milling a mixture of 30 grams of graphite with diameter less
than 75 .mu.m, 60 grams of LUBRIZOL 9677MX, and 270 grams of DRASYN
162 at 4000 rpm for 8 hours. Note here the dispersing agent
LUBRIZOL 9677MX was added into the mill at the very beginning.
Three fluids A through C were formulated using the above three
pastes as concentrates whereby their final composition were exactly
the same: 2% graphite, 4% LUBRIZOL 9677 MX, 18% DURASYN 162, 76%
DURASYN 166 (a commercial 6 centistokes polyalphaolefin,
abbreviated hereafter as 6 cSt PAO) (all percentage by weight).
Example 3 illustrates the 100.degree. C. viscosity and thermal
conductivity increase of the fluids.
[0079] It was also found that the graphite particle size before
milling was very critical on the viscosity modification effect as
well. For example, starting with graphite smaller than 10 (obtained
as graphite powder from UCAR Carbon Company Inc.) and following the
same procedure as Paste B, a thin Paste D was obtained. A fluid D
was formulated with the same composition as fluid A and the result
is listed in Example 3 as well. The particle size is measured by
atomic force microscopy (AFM), and FIG. 2 illustrates an AFM
picture of Fluid B. The graphite nanoparticles are plate-like
structure, with average diameter is around 50 nm and thickness
around 5 nm (as described earlier, nanodisks or nanoplates).
TABLE-US-00002 TABLE 1 Fluids and viscosity data from Example 1
Fluid A B C D From Concentrate Paste A Paste B Paste C Paste D
Kinematic viscosity at 100.degree. C., cSt 7.55 19.68 10.83 7.48
Kinematic viscosity at 40.degree. C., cSt 28.44 29.32 28.77 27.85
Thermal Conductivity W/mK 0.18 0.19
[0080] It is important to note that without added dispersant the
mixture of graphite and base oil turns into paste in hours and thus
sufficient milling can not be accomplished. With good dispersant
the milling can be extended to as long as desirable without paste
formation. It is also important to adjust the temperature to
maintain the right viscosity during the milling process so that the
efficient milling is achieved.
[0081] To illustrate the importance of the milling process, and in
minimizing the heating that occurs in dry milling we compared the
thermal conductivity increase achieved using two dry processes and
the wet process described in this invention. Sample "V 174-01" is
obtained by milling "UCAR GS4-E" in PAO 2 with a
polyisobutenylsuccinimide dispersant for 11 hours at 120.degree. F.
The UCAR GS4-E starting material has high bulk thermal
conductivity, but due to its shape and size does not give the
desired benefit in increasing fluid thermal conductivity. Thus the
wet milling creates the particle shape that improves thermal
conductivity and also avoids surface damage that can decrease
thermal conductivity. The thermal conductivity (k) percent increase
reported is compared to the base fluid (PAO) alone. The data are
shown in Table 2 below:
TABLE-US-00003 TABLE 2 Thermal Conductivity Percent Increase
Compared to Base Fluid Alone Graphite Source Way of Milling peak 1
peak 2 k increase @2%(%) Acheson SLA1275 dry(ball) 124 nm(33%) 497
nm(67%) 8.59 V 174-01 wet(horizontal) 117 nm(69%) 2413 nm(31% 29.27
UCAR GS4-E dry(jet) 3304 nm(100% 3.4
[0082] It is evident that both the particle size and the way of
milling are important to thermal conductivity increase.
[0083] Results from the table show that the commercial Acheson
sample generally has smaller particles than the sample V174-01 of
graphitic material obtained from the instant process, however, the
V174-01 sample has a much higher thermal conductivity boost. This
surprising result is contrary to the expected relationship of
increasing thermal conductivity with decreasing particle size, but
it indicates the importance of the invention milling process in
increasing thermal conductivity.
[0084] It is believed that in the dry ball milling process, local
high temperature exists which could cause graphite surface fracture
or surface defects, including oxidation which reduces thermal
conductivity. For example, in U.S. Pat. No. 4,434,064 which issued
in February of 1984 by Chao et al., a graphite dispersion was made
(with larger graphite particles as compared to the instant
invention) and surface oxidation caused by dry grinding in oxygen
atmosphere is preferred because it aids in dispersion. In the
instant invention, the wet milling process this effect is very much
controlled and minimized. It is also important to begin with
graphites developed in a process that preserves purity and
crystalline structure.
[0085] One preferred starting material is jet-milled graphite. Jet
mills have higher efficiency in producing ultra fine grade
particles and they are claimed to be contamination free. The basic
premise of the jet mill is to utilize the energy of compressed gas
to perform the grinding. The gas accelerates the material, causing
high-speed particle-on-particle collisions. As a result, the
material grinds against itself, ensuring product quality. With the
expansion of the compressed gas, a cooling effect takes place
allowing heat-sensitive materials to be processed without
degradation. However, without further milling in the solvents, the
thermal conductivity boost is still very limited due to size and
shape. For example, a 2% dispersion of jet-milled graphite has only
3.4% increase in thermal conductivity.
[0086] Scanning electron microscope pictures demonstrate this
important shape change which occurs to the graphite particle shape
with solvent milling. The raw material, UCAR GS4-E, is composed in
the shape of chunks as best illustrated in FIG. 1. After the
solvent milling, the chunks are processed and appear as a
plate-like shape as shown in FIG. 2.
[0087] Carbon nanotubes, double wall, multi-wall or single wall
having a controlled aspect ratio, are another preferred type of
nanomaterial or particles. The nanotubes have a typical nanoscale
diameter of 1-200 nanometers. More typically the diameter is around
10-30 nanometers. The length of the tube can be in submicron and
micron scale, usually from 50 nanometers to 100 microns. More
typical length is 500 nanometers to 50 microns. The aspect ratio of
the tube (which is defined by the average length of the tubes
divided by the average diameter) can be from hundreds to thousands,
more typical 100 to 2000. The surface of the nanotube can be
treated chemically to achieve certain level of hydrophilicity, or
left as is from the production.
[0088] The nanoplates and nanotubes can be mixed to obtain desired
viscosity/shear and thermal conductivity behavior. Other high
thermal conductivity carbon materials are also acceptable as long
as they meet the thermal conductivity and size criteria set forth
heretofore.
[0089] To confer long-term stability, an effective amount of one or
more chemical dispersants or surfactants is preferred, although the
special milling procedure in base oil described heretofore will
also confer long term stability. The thermal conductivity
enhancement, compared to the fluid without graphite, is
proportional to the amount of nanomaterials added, their thermal
conductivity, and their size and method of dispersion. The
particles of the instant invention will impart a thermal
conductivity in fluid higher than the neat fluid, wherein the term
`neat` is defined as the fluid before the particles are added.
[0090] The concentration, size and shape of the graphite
nanoparticles or nanotubes, along with the dispersant/surfactant
type and concentration, is adjusted to provide the desired
contribution to the overall fluid characteristics as for example
the .viscosity and shear stability. Similar adjustments can be
envisioned for producing composite resins or polymer melts to
produce plastics.
[0091] It is observed that a bimodal distribution of particles is
found in the finished sample. To reduce the large particle
distribution recycling of the dispersion in the mill is necessary.
A selected recycle ratio of to is desirable. Furthermore the large
particles in the final material can be removed by a filtration or
centrifugation step.
[0092] High-Temperature Shear Stable Graphite Dispersion.
[0093] According to the Albert Einstein equation regarding the
viscosity of dispersions, a good dispersion just has slight
viscosity increase while a bad dispersion has a big viscosity
increase. The viscosity ranges of many fluids are very critical. So
it is very important to not cause viscosity change while
integrating nano particles into many fluids. The particles can be
dispersed in oil by choosing the right dispersants, typically
fairly low molecular weight materials (<2500 m. w.) such as
polysuccinimides, and somewhat higher molecular weight viscosity
index improvers, with dispersant functionality. To determine good
or bad dispersions rheometer are used instead of viscosity tubes.
The rheometer measures viscosities under varying shear stress. For
a Newtonian fluid the viscosity is a constant regardless of shear
rate. Many fluids are non-Newtonian fluids, but at low shear rates
the viscosity is also a constant. For bad dispersions the viscosity
shows shear-thinning with a increase in shear rate and builds up at
high temperature as time pass by. As set forth in FIG. 3,
repeatable almost flat lines in the rheometer plots of viscosity
are comparable against the shear rate for well dispersed graphite
oils shown in FIG. 4.
[0094] The viscosity ranges of many fluids are very critical. So it
can be very important to not cause viscosity change while
integrating nano particles into many fluids. By choosing the right
viscosity improver, "VI", (polymers known to the lubricants
industry as viscosity index improvers), dispersions can be
improved. The VI improvers we used are dispersant VI improvers.
[0095] To determine good or bad dispersions a rheometer is used
instead of viscosity tubes. Rheometer measures viscosities under
shear stress which is variable. For a Newtonian fluid the viscosity
is a constant regardless of shear rate. Motor oils are
non-Newtonian fluids, but at low shear rates the viscosity is also
a constant. For bad dispersions the viscosity shows shear-thinning
with a increase in shear rate and builds up at high temperature as
time passes by as exhibited in FIG. 3. Repeatable, almost flat
lines in the rheometer plots of viscosity against the shear rate
for well dispersed graphite oils as shown in FIG. 4.
[0096] Table 3 shows how increasing the percentage of carbon
nanotubes in oil results in a much greater increase in viscosity as
compared with increasing the percentage of carbon nanographite
particles of the instant invention due to the particle shape which
is changed during the milling process.
TABLE-US-00004 TABLE 3 Viscosity Increase with Weight Percentage of
nanotube and Nanographite % Carbon Viscosity 100.degree. % Milled
Viscosity 100.degree. Nanotube C./cST Nanographite C./cST 0 3.92 0
3.92 0.005 4 0.01 5.36 0.05 8.59 0.1 16.75 0.1 4.04 0.2 65 0.2
4.19
[0097] The following examples provide formulations of compositions
in accordance with the present invention and provide examples of
the range of ingredient percentages by weight providing an
effective amount of the particular ingredients deemed necessary to
obtain the desired results in single application.
Example 1
Synthetic Lubricant Composition Containing Nanographite
Particles
TABLE-US-00005 [0098] Synthetic SAE 5W-30 Yubase 4 39.43 Yubase 6
25.00 PAO 4 10.00 LZ 21303C 11.00 LZ 8676 1.00 LZ 8650 3.40 Afton
5777 3.60 LZ 7749B 0.40 T503-209-2 (Cut 2) 9.17 V100 Before V100
After 9.88 Delta V CCS@-30 C. 5361 NOACK, % Loss 12.08 MRV @ -35 C.
YS <35 Viscosity 17022 HTHS
Example 2
Conventional Lubricant Composition Containing Nanographite
Particles
TABLE-US-00006 [0099] Conventional SAE 5W-30 Yubase 4 50.00 Star 4
8.59 Star 8 20.50 LZ 20010 10.85 LZ 8650 0.30 LZ 8676 0.30 LZ 6473
0.50 Afton 5777 1.00 LZ 7075F 4.60 LZ 7749B 0.40 A-11 2.96 100.00
KV (100 C.)bfr KV (100 C.) aftr CCS (-30 C.) NOACK After Bosch
Example 3
Semi Synthetic Lubricant Composition Containing Nanographite
Particles
TABLE-US-00007 [0100] Ingredients Percentage range Graphite 0.1-2
Group III and IV base oils 80.0-85.0 LZ DI package 7.0-15.0 LZ
additives 0.1-2.0 Viscosity improver 1.0-7.5 Viscosity at
100.degree. C. 7.5-15.0
[0101] Table 4 shows that adding nanomaterials into a lubricant can
significantly increase the thermal conductivity of the formulation,
which implies better thermal management for the system.
[0102] For example in Table 4, a semi-synthetic blended motor oil
such as DURABLEND which is sold by Valvoline Inc., a division of
ASHLAND INC. is compared as DB (a conventional 5W-30 motor oil),
NF-1 (a 5W-30 motor oil containing graphite nanoplates), and NF-2
(a 5W-30 motor oil containing graphite nanoplates and carbon
nanotubes) showing the effect on viscosity index and thermal
conductivity K(w/mK).
TABLE-US-00008 Code DB NF-1 NF-2 Product Conventional DuraBlend
DuraBlend 5W-30 with DuraBlend 5W-30 with graphite description
5W-30 graphite nanoplate nanoplate and carbon nanotubes Percent by
wt. 0 1.0, graphite nanoplate* 1.0, graphite nanoplate*
Nanomaterial 0.1, carbon nanotubes** Vis 100.degree. C. 10.66 10.9
10.9 Vis at 4.degree. C. 61.14 57.1 54.34 Viscosity Index 166 186
197 k (w/m K) 0.1423 0.1591 0.1768 *Graphite is obtained as carbon
fibers from Union Carbide and further processed through in-house
method into graphite nanoplate. **Multiwalled carbon nanotubes are
obtained from University of Kentucky.
[0103] The foregoing detailed description is given primarily for
clearness of understanding and no unnecessary limitations are to be
understood therefrom, for modification will become obvious to those
skilled in the art upon reading this disclosure and may be made
upon departing from the spirit of the invention and scope of the
appended claims. Accordingly, this invention is not intended to be
limited by the specific exemplifications presented herein above.
Rather, what is intended to be covered is within the spirit and
scope of the appended claims.
* * * * *