U.S. patent application number 10/915251 was filed with the patent office on 2005-06-09 for lubricant and additive formulation.
This patent application is currently assigned to ASHLAND INC.. Invention is credited to Baumgart, Richard J., Dituro, Michael A., Lockwood, Frances E., Smith, Thomas R., Wu, Gefei, Zhang, Zhigiang.
Application Number | 20050124504 10/915251 |
Document ID | / |
Family ID | 34632618 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050124504 |
Kind Code |
A1 |
Zhang, Zhigiang ; et
al. |
June 9, 2005 |
Lubricant and additive formulation
Abstract
A lubricant composition for use as a concentrate and motor oil
having an enhanced thermal conductivity. One preferred composition
contains a lubricant composition, nanomaterial, and a dispersing
agent or surfactant for the purpose of stabilizing the
nanomaterial. One preferred nanomaterial is a high thermal
conductivity graphite, exceeding 80 W/m in thermal conductivity.
Carbon nano material or nanostructures such as nanotubes,
nanofibrils, and nanoparticles formed by grounding and/or milling
graphite to obtain a mean particle size less than 500 nm in
diameter, and preferably less than 100 nm, and most preferably less
than 50 nm. Other high thermal conductivity carbon materials are
also acceptable. To confer long-term stability, the use of one or
more chemical dispersants or surfactants is useful. The graphite
nanomaterials contribute to the overall fluid viscosity and
providing a very high viscosity index. Particle size and dispersing
chemistry is controlled to get the desired combination of viscosity
and thermal conductivity increase from the lubricant. The resulting
fluids have unique properties due to the high thermal conductivity
and high viscosity index of the suspended particles, as well as
their small size.
Inventors: |
Zhang, Zhigiang; (Lexington,
KY) ; Smith, Thomas R.; (Lexington, KY) ; Wu,
Gefei; (Lexington, KY) ; Lockwood, Frances E.;
(Georgetown, KY) ; Baumgart, Richard J.; (Paris,
KY) ; Dituro, Michael A.; (Huntington, WV) |
Correspondence
Address: |
David W. Carrithers
CARRITHERS LAW OFFICE, PLLC
One Paragon Center
6060 Dutchman's Lane, Suite 140
Louisville
KY
40205
US
|
Assignee: |
ASHLAND INC.
|
Family ID: |
34632618 |
Appl. No.: |
10/915251 |
Filed: |
August 10, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10915251 |
Aug 10, 2004 |
|
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10206852 |
Jul 26, 2002 |
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6774091 |
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Current U.S.
Class: |
508/128 ;
508/113; 508/116; 508/118; 508/185 |
Current CPC
Class: |
B82Y 30/00 20130101;
C10N 2040/25 20130101; C10M 161/00 20130101; C10M 125/02 20130101;
C10N 2030/02 20130101; C10M 169/044 20130101; C10N 2010/12
20130101; C10M 2227/061 20130101; C10N 2020/06 20130101; C10M
2215/064 20130101; C10M 2201/041 20130101; C10M 2223/045
20130101 |
Class at
Publication: |
508/128 ;
508/185; 508/113; 508/118; 508/116 |
International
Class: |
C10M 125/02 |
Claims
1. An engine oil lubricant concentrate used in combination with a
crankcase lubricant for dilution with a mineral oil, a synthetic
oil, a semi-synthetic severely hydro cracked oil, and combinations
thereof, said lubricant concentrate comprising: from 0.05 weight
percent to 5.0 weight percent of an oil soluble molybdenum
additive; from 10.0 volume percent to 95 volume percent of a base
oil comprising selected from the group consisting of a synthetic
base oil, a mineral oil, a severely hydro cracked oil, alone and in
combination one with another; from 0.5 volume percent to 35.0
volume percent of a dispersant inhibitor containing zinc
dithiophosphate; from 0.5 weight percent to 25.0 weight percent of
a viscosity index improver; an effective amount of nano structures;
and an effective amount of a boron compound containing an effective
amount of less than 1000 ppm of an elemental boron.
2. An engine oil lubricant concentrate used in combination with a
conventional crankcase lubricant comprising a mineral oil, a
synthetic oil, a semi-synthetic severely hydro cracked oil, and
combinations thereof, said lubricant concentrate comprising: from
0.05 weight percent to 5.0 weight percent of an oil soluble
molybdenum additive; from 10.0 volume percent to 95 volume percent
of a synthetic base oil, a mineral oil, a severely hydro cracked
oil, and combinations thereof; from 0.5 volume percent to 35.0
volume percent of a dispersant inhibitor; from 0.5 weight percent
to 25.0 weight percent of a viscosity index improver; and an
effective amount of a nanostructure.
3. The lubricant concentrate according to claim 2, wherein said
synthetic base oil comprises from 10.0 volume percent to 95 volume
percent of an ester.
4. The lubricant concentrate according to claim 2, wherein said
synthetic base comprises from 10.0 volume percent to 95 volume
percent of a diester.
5. The lubricant concentrate according to claim 2, wherein said
synthetic base stock comprises from 10.0 volume percent to 95
volume percent of a polyalphaolefin.
6. The lubricant concentrate according to claim 2, wherein said
synthetic oil comprises from 10.0 volume percent to 95 volume
percent of a polyalphaolefin in combination with an ester.
7. The lubricant concentrate according to claim 2, comprising from
1.0 to 3.0 weight percent of said oil soluble molybdenum
additive.
8. The lubricant concentrate according to claim 2 wherein said
synthetic base stock comprises at least 10% polyalphaolefins.
9. The lubricant concentrate according to claim 2, said dispersant
inhibitor containing zinc dithiophosphate.
10. The lubricant concentrate according to claim 2, wherein said
viscosity index improver is selected from the group consisting of
polyisobutenes, polymethacrylate acid esters, polyacrylate acid
esters, diene polymers, polyalkyl styrenes, alkenyl aryl conjugated
diene copolymers, polyolefins, and combinations thereof.
11. The lubricant concentrate of claim 2, wherein said diester is a
di-aliphatic diesters of alkyl carboxylic acid.
12. The lubricant concentrate of claim 11, wherein said
di-aliphatic diesters of alkyl carboxylic acid is selected from the
group consisting of di-2-ethylhexylazelate, di-isodecyladipate, and
di-tridecyladipate.
13. The lubricant concentrate of claim 3, wherein said ester has a
pour point of less than -100.degree. C. and a viscosity of from 2
to 460 centistoke at 100.degree. C.
14. The lubricant of concentrate of claim 2, wherein said base oil
is a combination of a mineral oil and a severely hydro cracked
oil.
15. The lubricant concentrate of claim 2, wherein said base oil is
a synthetic oil.
16. The lubricant concentrate of claim 5, wherein said
polyalphaolefin is has a viscosity of from 2 to 460 centistoke.
17. The lubricant concentrate of claim 5, wherein said
polyalphaolefin has a viscosity of from 2 to 10 centistoke at
200.degree. C.
18. The lubricant concentrate of claim 5, wherein said
polyalphaolefin has a viscosity of from 4 to 6 centistoke at
200.degree. C.
19. The lubricant concentrate of claim 2, wherein said synthetic
base stock comprises from 25 to 90 percent by volume.
20. The lubricant concentrate of claim 2, wherein said synthetic
base stock comprises from 60 to 85 percent by volume.
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Description
BACKGROUND OF THE INVENTION
[0001] This application is a Continuation-In-Part of copending U.S.
application Ser. No. 10/206,852 filed on Jul. 26, 2002 which claims
priority from Ser. No. 09/520,738 filed on Mar. 7, 2000; which
claims priority from U.S. Pat. No. 6,034,038 which issued on Mar.
7, 2000; which claims priority from U.S. Pat. No. 5,962,377 issued
on Oct. 5, 1999; which claims priority from U.S. Pat. No. 5,763,369
which issued on Jun. 9, 1998 and U.S. Pat. No. 5,641,731 which
issued on Jun. 24, 1997; and U.S. application Ser. No. 10/737,731
filed on Dec. 16, 2003; Ser. No. 10/730,762 filed on Dec. 8, 2003
which claims priority from PCT/US02/16888 filed on May 30, 2002 and
from 10/021,767 filed on Dec. 12, 2001 which claims priority from
U.S. Provisional Application Ser. No. 60/254,959 filed on Dec. 12,
2000 all of which are incorporated by reference herein.
TECHNICAL FIELD
[0002] The invention relates to the general field of additives to
improve the performance of lubricating oils and function as an
engine treatment oil additive and/or complete motor oil lubricants
containing nanomaterial dispersed within engine oil, oil additive
packages, and oil treatment concentrates which exhibit enhanced
thermal conductivity as compared to conventional fluids without the
nanomaterial dispersions.
DESCRIPTION OF THE PRIOR ART
[0003] Lubrication involves the process of friction reduction,
accomplished by maintaining a film of a lubricant between surfaces
which are moving with respect to each other. The lubricant prevents
contact of the moving surfaces, thus greatly lowering the
coefficient of friction. In addition to this function, the
lubricant also can be called upon to perform heat removal,
containment of contaminants, and other important functions.
Additives have been developed to establish or enhance various
properties of lubricants. Various additives which are used include
viscosity improvers, detergents, dispersants, antioxidants, extreme
pressure additives, and corrosion inhibitors.
[0004] Anti-wear agents, many of which function by a process of
interactions with the surfaces, provide a chemical film which
prevents metal-to-metal contact under high load conditions. Wear
inhibitors which are useful under extremely high load conditions
are frequently called "extreme pressure agents". Certain of these
materials, however, must be used judiciously in certain
applications due to their property of accelerating corrosion of
metal parts, such as bearings. The instant invention utilizes the
synergy between several chemical constituents to provide an
additive formula which enhance the performance of conventional
engine oil and inhibits the undesirable side effects which may be
attributable to use of one of more of the chemical constituents
when used at particular concentrations.
[0005] Several references teach the use of individual chemical
components to enhance the performance of conventional engine oil.
For instance, U.S. Pat. No. 4,879,045 by Eggerichs adds lithium
soap to a synthetic base oil comprising diester oil and
polyalphaolefins which can comprise an aliphatic diester of a
carboxylic acid such as di-2-ethylhexylazelate, di-isodecyladipate,
or ditridecyl-adipate, as set forth in the Encyclopedia of Chemical
Technology, 34th addition, volume 14, pp 477-526, which describes
lubricant additives including detergent-dispersant, viscosity index
(VI) improvers, foam inhibitors, and the like.
[0006] The thermal conductivity of oils, e.g., mineral oil,
polyalphaolefin, ester synthetic oil, ethylene oxide/propylene
oxide synthetic oil, polyalkylene glycol synthetic oil, etc. is
typically 0.12 to 0.16 W/m at room temperature, and thus they are
inferior as heat transfer agents to water, since water has a much
higher thermal conductivity, 0.61 W/m as set forth in Table 1.
Usually these oils have many other important functions, and they
are carefully formulated to perform to exacting specifications for
example for friction and wear performance, low temperature
performance, fuel efficiency performance etc. Often designers will
desire a fluid with higher thermal conductivity than the
conventional oil, but are restricted to oil due to the many other
parameters the fluid must meet.
1TABLE 1 Thermal conductivity of various materials (at room
temperature) Material Thermal Conductivity (W/m) Mineral oil 0.13
Typical fully-formulated 0.12-0.16 engine oil Ethylene glycol 0.253
Water 0.613 Commercial antifreeze 0.40 Graphite 80-700
[0007] The use of graphite in fluids such as lubricants is well
known. The graphite is added as a friction reducing agent, which
also carries some of the load imposed on the working fluid, and
therefore helps to reduce surface damage to working parts. In order
to be low friction, it is well known that the graphite layered
structure must contain some water or other material to create the
interlayer spacing and thereby lamellar structure. There are
various commercially available graphite suspensions, e.g., from
Acheson Colloid Co., which are specifically intended for use in
lubricants. The size of the particles is varied for different
dispersions, but the minimum average size for commercially
available products is in the submicron range, typically mean as
500-800 nm (nanometers). The thermal advantage of the graphite is
nor mentioned in the sales literature, nor is the product sold or
promoted for its thermal conductivity property.
[0008] While there have been various patents filed on lubricants
containing graphite, e.g. U.S. Pat. No. 6,169,059, there are none
which specifically rely on graphite to improve the thermal
conductivity of the fluid formulated for specific applications.
[0009] Furthermore, there are none which teach specifically the use
of nanometer-sized graphite with mean particle size much
significantly less than 1000 nm in order to increase thermal
conductivity and that reducing particle size improves thermal
conductivity. While graphite-containing automotive engine oil was
once commercialized (Arco graphite), the potential to use graphite
as a heat transfer improving material in this oil was not realized.
The particle size of graphite used was larger (mean greater than
one micron) than for the instant invention. As a result, the
graphite had some settling tendency in the fluid. Graphite of this
size also significantly affects the friction and wear properties of
the fluid, and heretofore has been used to reduce friction and
improve wear performance of the fluid, e.g. in metalworking fluids.
On the other hand, the use of graphite in lubricants for
recirculating systems was made unpopular, partly due to evidence
that micron size graphite could "pile up" in restricted flow areas
in concentrated contacts, thereby leading to lubricant starvation.
No recognition of effect of graphite particle size on this
phenomena was made.
[0010] 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, e.g., U.S. Pat. No.
5,165,909. 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 mentioned
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.
[0011] Automotive engine oils have stringent requirements for
viscosity, stability to oxidation, temperature and shear, low
temperature fluidity, and static and dynamic coefficient of
friction. Additionally, the heat transfer requirements are
significant. It is generally necessary to use some form of cooling.
Because of the relatively large particle size of conventional
graphite dispersions, the use of graphite in these fluids is not
known.
SUMMARY OF THE INVENTION
[0012] The present invention comprises various formulations of
lubricant additive concentrates for addition to conventional engine
oil or as motor oil lubricants incorporating said additives therein
as complete formulas for improving the lubricating properties of
the engine oil, enhance the performance of the engine, and reduce
engine wear and possibly reduce the consumption of the oil.
[0013] One preferred embodiment of the engine treatment oil
additive comprises a blend of chemical constituents including an
oil soluble molybdenum additive, a dispersant inhibitor containing
zinc dithiophosphate, and a viscosity index improvers in a
synthetic base stock such as a polyalphaolefin. A selected
synthetic constituent comprising a ester such as a diester, and/or
a polyolester, provides optimal performance characteristics to the
composition. The composition may include a mineral oil or a Group
III hydrogenated oil as an additive to the base formula.
[0014] In this invention, fluids of enhanced thermal conductivity
are prepared by dispersing nanometer-sized carbon nanomaterials of
thermal conductivity higher than 80 W/m into the fluid. The term
carbon nanomaterials used in this invention refers to graphite
nanoparticles, carbon nanotubes or fibrils, and other nanoparticles
of carbon with graphitic structure. Stable dispersion is achieved
by physical and chemical treatments.
[0015] A metal containing a high pressure antiwear agent such as a
borate compound and preferably a borate ester may be added
optionally as a corrosion inhibitor for yellow metals.
[0016] A nonaqueous polytetrafluoroethylene compound may be added
to further improve the lubricity of the composition.
[0017] The constituents may be combined to give particularly
performance properties for formulating various embodiments of the
lubricant additive concentrate for use with conventional crankcase
engine oil or the formulation of a complete engine oil
incorporating the additive concentrate package.
[0018] A preferred embodiment of the present invention comprises
effective amounts of a combination of chemical constituents
including an oil soluble molybdenum additive, base oil (synthetic,
mineral, and/or Group III semi-synthetics), a dispersant inhibitor
containing zinc dithiophosphate, and viscosity index improvers.
Addition of selected synthetics such as polyalphaolefin and/or
esters such as a diester or polyolester, and/or a nonaqueous
polytetrafluoroethylene compound, and/or a antiwear/extreme
pressure agent such as a metal containing borate compound such as a
borate ester, may be used to formulate one or more embodiments of
the additive in combination with a conventional crankcase lubricant
containing mineral oil, synthetic oil, semi-synthetic, or
combinations thereof up to 50 volume percent and more preferably
from about 10 to 40 volume percent, more preferably from about 15
to 30 percent and most preferably from about 20 to about a 25%
volume/percent after dilution with motor oil, wherein typically 1
quart is blended with 4 or 5 quarts of motor oil. The various
constituents are preblended and/or sold as a complete motor oil
formulation.
[0019] The additive is used in combination with a conventional
crankcase lubricant containing mineral oil, synthetic oil or
combinations thereof up to about 50 percent by volume, more
preferably from about 10 to 40 percent by volume, more preferably
from 15 to 30 percent by volume, and most preferably from about 20
to about a 25% volume/percent.
[0020] One preferred nanomaterial is a high thermal conductivity
graphite, exceeding 80 W/m in thermal conductivity, and ground,
milled, or naturally prepared with mean particle size less than 500
nm in diameter, and preferably less than 100 nm, and most
preferably less than 50 nm. The graphite is dispersed in the fluid
by one or more of various methods, including ultrasonication,
milling, and chemical dispersion. It is contemplated that
nanoparticles can be selected from any metal from the Group IV
elements, such as carbon materials (carbon nanotubes, fullerenes,
graphite, amorphous carbon, carbon particles, carbon fibrils and
combinations thereof, etc.), silicone carbide, and clay materials,
metal (including transition metals) particles (such as silver,
copper, aluminum, etc.), metal oxides, alloy particles, and
combinations thereof may be applicable to the instant
invention.
[0021] Carbon nanotubes with a graphitic structure are another
preferred type of nanomaterial or particles. Other high thermal
conductivity carbon materials are also acceptable as long as they
meet the thermal conductivity and size criteria set forth
heretofore.
[0022] To confer long-term stability, an effective amount of one or
more chemical dispersants or surfactants is preferred, although a
special grinding procedure in base oil will also confer long term
stability. The thermal conductivity enhancement, compared to the
fluid without graphite, is proportional to the amount of
nanomaterials added. The graphite nanoparticles or nanotubes
contribute to the overall fluid viscosity, partly or completely
eliminating the need for viscosity index improvers and providing a
very high viscosity index. Particle size and dispersing chemistry
is controlled to get the desired combination of viscosity and
thermal conductivity increase from the base oil while controlling
the amount of temporary viscosity loss in shear fields. The
resulting fluids have unique properties due to the high thermal
conductivity and high viscosity index of the suspended particles,
as well as their small size.
[0023] The particle-containing fluid of the instant invention will
have a thermal conductivity higher than the neat fluid, wherein the
term `neat` is defined as the fluid before the particles are
added.
[0024] The fluid can have other chemical agents or other type
particles added to it as well to impart other desired properties,
e.g. friction reducing agents, antiwear or anticorrosion agents,
detergents, antioxidants, dispersants to define a lubricant
composition suitable for use in vehicle applications or the like.
Furthermore, the term fluid in the instant invention is broadly
defined to include pastes, gels, greases, and liquid crystalline
phases in either organic or aqueous media, emulsions and
microemulsions.
[0025] As set forth above, the preferred carbon nanomaterials are
selected from graphitic carbon structures with bulk thermal
conductivity exceeding 80 W/m. A preferred form of carbon
nanomaterials is carbon nanotubes. Another preferred form of carbon
nanomaterials is high thermal conductivity graphite. A preferred
form of the high thermal conductivity graphite is Poco Foam from
Poco Graphite. Another preferred form of high thermal conductivity
graphite is graphite powders from UCAR Carbon Company Inc. Still
another preferred form of high thermal conductivity graphite is
graphite powders from Cytec Carbon Fibers LLC. Still another
preferred form of graphite is bulk graphite from The
Carbide/Graphite Group, Inc.
[0026] Of course, one of the major drawbacks concerning commercial
use of the carbon nanotubes and other prepared carbon structures is
the cost of preparation and availability of same for commercial
applications. The instant invention has resulted in the development
of a method of reducing very inexpensive graphite to a nanomaterial
comprising particles, fabrils and flakes suitable for use and long
term dispersion in lubricant compositions.
[0027] The carbon nanomaterial containing dispersion may also
contain a large amount of one or more other chemical compounds,
such as polymers, antiwear agents, friction reducing agents,
anti-corrosion agents, detergents, metal passivating agents,
antioxidants, antifoaming agents, corrosion inhibitors, pour point
depressants, and viscosity index improvers that are not for the
purpose of dispersing, but to achieve thickening or other desired
fluid characteristics.
[0028] Another preferred embodiment of the engine treatment oil
additive comprises a blend of chemical constituents including an
oil soluble molybdenum additive, a synthetic, mineral, or Group III
semi-synthetic base oil. Moreover, a dispersant inhibitor
containing zinc dithiophosphate, polytetrafluoroethylene, and
viscosity index improvers are blended together and added thereto.
An extreme pressure antiwear agent such as a borate compound may
also be utilized in the present composition.
[0029] One preferred composition contains an effective amount of at
least one base oil such as mineral oil, hydrocracked mineral oil
with high viscosity index, vegetable derived oils,
polyalphaolefins, poly-internal-olefins, polyalkylglycols,
polycyclopentadienes, propylene oxide or ethylene oxide based
synthetics, silicone oils, phosphate esters or other synthetic
esters, or any suitable base oil; an effective amount of at least
one type of nanomaterial, preferably graphite nanoparticle or
carbon nanotubes, and an effective amount of at least one
dispersing agents or surfactants for the purpose of stabilizing the
nanoparticles.
[0030] The improved performance of the engine additive in
comparison with conventional crankcase lubricants is attributable
to optimizing the design parameters for each of the individual
chemical constituents and combining the chemical constituents to
obtain surprisingly good results including improved: wear,
oxidation resistance, viscosity stability, engine cleanliness, fuel
economy, cold starting, reduced oil consumption, and inhibition of
acid formation. The novel engine additive formulation comprises a
combination of compounds, ingredients, or components, each of which
alone is insufficient to give the desired properties, but when used
in concert give outstanding lubricating properties. Additional
components may be added to the engine additive formulation to
enhance specific properties for special applications. Moreover, the
formulation is compatible with engine warranty requirements, i.e.,
service classification API SH and SJ.
[0031] Moreover, viscosity index is defined as the relationship of
viscosity to the temperature of a fluid. It is determined by
measuring the kinematic viscosities of the oil at 40.degree. C. and
100.degree. C. and using the tables or formulas included in ASTM
D2270. It is important to note that the smaller particles give the
best thermal conductivity increase, and higher viscosity index of
fluid, but also contribute to higher temporary viscosity loss in
shear fields. A fluid made with heat transfer improvement of 20% at
100.degree. C. may have an improvement of 60% or more when compared
to a conventional fluid at 40.degree. C. Therefore the heat
transfer improvement due to the particles may be twofold, due to
the higher thermal conductivity of the particles, and also due to
the exceptional viscosity index of the particle-containing
fluid.
[0032] The lubricating and oil-based functional fluid compositions
of the present invention are based on natural and synthetic
lubricating oils and mixtures thereof in combination with the
additives.
[0033] The individual components can be separately blended into the
base fluid or can be blended therein in various subcombinations.
Moreover, the components can be blended in the form of separate
solutions in a diluent. Blending the components used in the form of
an oil additive concentrate simplifies the blending operations,
reduces the likelihood of blending errors, and takes advantage of
the compatibility and solubility characteristics afforded by the
overall concentrate. Of course, the preblended complete motor oil
is convenient to use and is often preferable for adding to an
engine one quart or less at a time such as for routine maintenance
of older cars having engine wear and requiring additional motor oil
lubricant between oil changes. The complete motor oil does not
require the consumer to determine the amount of additive required
for optional performance when blending with a conventional motor
oil in small quantifies between oil changes.
[0034] The combination of chemical constituents of the present
invention are not disclosed by any known prior art references. The
incorporation of molybdenum compounds, extreme antiwear compounds
such as boric acid agents and/or a PFTE lubricant provide improved
performance to motor oil and greases. Moreover, the incorporation
of semi-synthetic oils defined by the American Petroleum Institute
(API) as severely hydro cracked oils) provide an means to reduce
the cost of lubricating oils while maintaining many of the
desirable characteristics of synthetic oil.
[0035] These lubricating compositions are effective in a variety of
applications including crankcase lubricating oils for spark-ignited
and compression-ignited internal combustion engines, two-cycle
engines, aviation piston engines, marine and low-load diesel
engines, and the like. The invention will find use in a wide
variety of lubricants, including motor oils, greases, sucker-rod
lubricants, cutting fluids, and even spray-tube lubricants. The
invention has the multiple advantages of saving energy, reducing
engine or other hardware maintenance and wear, and therefore,
provides an economical solution to many lubricating problems
commonly encountered in industry or consumer markets. It is also
contemplated that the formulation may be applicable to transaxle
lubricants, gear lubricants, hydraulic fluids, and other
lubricating oil compositions which can benefit from the
incorporation of the compositions of the instant invention.
[0036] More particularly, one preferred concentrate for addition to
conventional motor oil for improving the lubricating properties of
the motor oil and enhancing the performance of the engine comprises
the following chemical constituents: an oil soluble molybdenum
additive, a ("synthetic base") such as polyalphaolefin (PAO), a
synthetic polyolester, and/or a synthetic diester, a Dispersant
Inhibitor (DI) package containing zinc dithiophosphate (ZDP) and
which may also contain a detergent and/or corrosion inhibitor, such
as CHEMALOY D-036; a Mineral Oil Base Stock; and a Viscosity Index
Improver, such as for example, (SHELLVIS 90-SBR); and an extreme
anti-wear agent (borate ester). The addition of a nonaqueous
polytetrafluoroethylene, ("PTFE") provides additional protection
and increased performance characteristics.
[0037] Bulk graphite with high thermal conductivity is available
from Poco Graphite as a graphite foam, with thermal conductivity
higher than 100 W/m, 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/m, and
typically >80 W/m, and from Cytec Carbon Fibers LLC, with
thermal conductivity 400-700 W/m. These bulk materials must be
reduced to a nanometer-sized powder by various methods for use in
the instant invention.
[0038] Utilization of these inexpensive sources of nanomaterials
have not been released in lubrication formulations before and a
point of novelty in the instant invention is the ability to reduce
the graphite to produce an inexpensive nanomaterial having a
particle size suitable for long term dispersion in lubricating
compositions and the method of dispersing same.
[0039] As set forth above, the preferred carbon nanomaterials are
selected from graphitic carbon structures with bulk thermal
conductivity exceeding 80 W/m. A preferred form of carbon
nanomaterials is carbon nanotubes. Another preferred form of carbon
nanomaterials is high thermal conductivity graphite. A preferred
form of the high thermal conductivity graphite is Poco Foam from
Poco Graphite. Another preferred form of high thermal conductivity
graphite is graphite powders from UCAR Carbon Company Inc. Still
another preferred form of high thermal conductivity graphite is
graphite powders from Cytec Carbon Fibers LLC. Still another
preferred form of graphite is bulk graphite from The
Carbide/Graphite Group, Inc.
[0040] Of course, one of the major drawbacks concerning commercial
use of the carbon nanotubes and other prepared carbon structures is
the cost of preparation and availability of same for commercial
applications. The instant invention has resulted in the development
of a method of reducing very inexpensive graphite to a nanomaterial
comprising particles, fabrils and flakes suitable for use and long
term dispersion in lubricant compositions.
[0041] Furthermore, the carbon nanomaterial dispersion can be
pre-sheared, in a turbulent flow, such as a nozzle, or high
pressure fuel injector, ultrasonic device, or 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 such as the flow regime in engines. Pre-shearing,
e.g. 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.
[0042] The milling process itself, or other pre-shearing process,
can have a rather dramatic effect on the long term dispersion
stability.
[0043] 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. The pasty liquid is then used
as concentrate to prepare lubricants of various viscosity grades,
and can be easily diluted to make a fluid with suitable viscosity
for an engine oil. A very effective paste can be made by mixing
particles in a viscous base fluid in a loading of 5% to 20' by
weight and milling for a period of several hours. The base fluid
preferably contains from 20% up to 100% of the
dispersant/surfactant mixture with the remainder being natural,
synthetic, or mineral base oil. Once the thermally conductive
concentrate prepared by milling is diluted to liquid consistency
with base oil and other fluid components, the entire fluid can
(optionally) be passed through a small orifice to further increase
the uniformity and decrease the size of dispersed particles.
[0044] 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
lubricant industry the term dispersant is generally accepted to
describe the long chain oil soluble or dispersible compounds which
function to disperse the "cold sludge" formed in engines. 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.
[0045] Finally, a preferred composition of the instant invention
provides improved lubricating properties and comprises a lubricant
concentrate for dilution with conventional, synthetic blend, and/or
fully synthetic motor oil. A lubricating composition comprising a
major amount of an oil of lubricating viscosity and a minor amount
of the concentrate aforementioned concentrate additive provides a
complete motor oil with improved lubricating properties.
[0046] It is an object of the present invention to provide a method
of preparing a lubricant as a stable dispersion of the carbon
nanomaterials in a liquid medium with the combined use of
dispersants/surfactants and physical agitation.
[0047] It is an object of the present invention to provide a in
which the carbon nanomaterials are made from cost-effective
high-thermal-conductivi- ty graphite (with thermal conductivity
higher than 80 W/m).
[0048] It is an object of the present invention to provide a method
of developing a method of forming carbon nanomaterials from
inexpensive bulk graphite.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] It is an object of the present invention to provide a
process for preparing a lubricant composition containing
nanomaterial by a) dissolving the said dispersants/surfactants or
dispersant additive package into the base fluid; b) adding a high
concentration (5-20% by weight) of the said carbon nanomaterials
into the above mixture while being strongly agitated by high impact
milling, and/or ultrasonication, to form a pasty liquid; and c) the
pasty liquid obtained in b) is further diluted with base oil and
additives as needed to make the final lubricant.
[0053] It is an object of the present invention to provide a method
of using a liquid medium selected from a natural oil (vegetable or
animal oil), or a synthetic oil, or a mineral oil or a combination
thereof.
[0054] It is an object of the present invention to provide a method
of defining an appropriate dispersants/surfactants for a liquid
medium of the type used in the lubricant industry, whereby it is a
surfactant or a mixture of surfactants with low HLB value (<8),
preferably nonionic or mixture of nonionic and ionic
surfactants.
[0055] It is an object of the present invention to provide that the
dispersants can be the ashless polymeric dispersants used in the
lubricant industry.
[0056] It is an object of the present invention to provide a
uniform dispersion in the form of a gel or paste with designed
viscosity of carbon nanomaterials in base oil medium.
[0057] It is an object of the present invention to provide a
uniform dispersion in a form as a gel or paste of high thermal
conductivity graphite nanoparticle in petroleum, natural, or
synthetic liquid medium.
[0058] It is an object of the present invention to provide a
uniform and stable dispersion in a form containing dissolved
non-dispersing, other functional compounds in the liquid
medium.
[0059] It is an object of the present invention to provide a
uniform and stable dispersion in a form without polymeric viscosity
index improvers, where all viscosity index improvement comes from
the carbon nanomaterials.
[0060] It is an object of the present invention to provide a
uniform and stable dispersion where due to the absence of polymeric
materials the dispersion exhibits no permanent, only temporary loss
in viscosity due to shear fields and turbulence.
[0061] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0062] 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:
[0063] FIG. 1 is a bar chart of ASTM D4172 four-ball wear results
versus lube compositions;
[0064] FIG. 2 is a multiple parameter graph of base oil compared to
adiditized oil showing viscosity increase and acid number increase
versus time in ASTM Sequence IIIE tests wherein the additive
defined in Example 1 contains PTFE, but not a boron agent;
[0065] FIG. 3 graphs ASTM Sequence VE test results of average (and
maximum) cam wear for oil including the additive of the present
invention defined in Example 1 containing PTFE, but not a boron
agent, versus conventional motor oil;
[0066] FIG. 4 graphs the substantial improvement in engine
cleanliness in the Sequence VE test for the oil including the
additive defined in Example 1 of the present invention containing
PTFE, but not a borate agent, versus conventional motor oil;
[0067] FIG. 5 graphs ASTM Sequence VI fuel economy and shows 17%1
improvement when using the additive defined by Example 1 of the
present invention containing PTFE, but not a boron agent; and
[0068] FIG. 6 graphs CRC L-38 Crankcase Oxidation Test and shows a
36.7% improvement from using the additive defined by Example 1 of
the present invention including a boron agent.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0069] Each of the preferred ingredients of the engine treatment
oil additive formulation, whether mandatory or optional, is
discussed below:
Oil Base Stocks
[0070] The complete motor oil formula and/or the concentrated
additive contains preferably up to 95 percent by volume, more
preferably from about 10 to about 95 percent by volume, more
preferably from about 25 to about 90 percent by volume, more
preferably from about 40 to about 85% by volume, and most
preferably from about 55 to 75 percent by volume of a base stock
composed of a mineral oil base stock, a severely hydrocracked oil
base stock, and/or a synthetic base alone or blended together,
and/or the following base stocks defined as Group I (solvent
refined mineral oils), Group II (hydro cracked mineral oils), Group
III (severely hydro cracked oil); Group IV (polyolefins), and Group
V (esters, and napthenes). Typically the base oils from Groups III,
IV and V together with additives are deemed synthetic oils. As used
in the instant application, oils from Group III are deemed severly
hydro cracked (semi-synthetic) base oils.
Synthetic Base Stock
[0071] 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.
[0072] 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. These are exemplified by the oils prepared
through polymerization of ethylene oxide or propylene oxide, the
alkyl and aryl ethers of these polyoxyalkylene polymers (e.g.,
methylpolyisopropylene glycol either having an average molecular
weight of 1000, diphenyl either of polyethylene glycol have a
molecular weight of 500-1000, diethyl ether of polypropylene glycol
having a molecular weight of 1000-1500, etc.) or mono- and
polycarboxylic esters thereof, for example, the acetic acid esters,
mixed C.sub.3-C-.sub.8 fatty acid esters, esters, or the
C.sub.130.times.0 acid diester of tetraethylene glycol.
[0073] Another suitable class of synthetic oils comprises the
esters of dicarboxylic acids (e.g., phthalic 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.
[0074] Esters useful as synthetic oils also include those made from
C.sub.5 to C.sub.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.
[0075] The concentrate additive and/or complete motor oil contains
preferably up to 95 percent by volume, more preferably from about
10 to about 95 percent by volume, more preferably from about 25 to
about 90 percent by volume, more preferably from about 40 to about
85% by volume, and most preferably from about 55 to 75 percent by
volume of a synthetic, Group III severely hydro cracked
(semi-synthetic), and/or mineral oil base stock used alone or
blended together as a base stock.
[0076] One preferred synthetic base stock comprises at least a
significant portion of a polyalphaolefin.
Polyalphaolefin (PAO)
[0077] Although not essential, the preferred synthetic base stock
comprises at least a significant portion of a polyalphaolefin.
Polyalphaolefin, ("PAO"), is a synthetic fluid effective at high
temperatures, such as occurs during operation of internal
combustion engines. It is also very effective at low temperatures.
It is especially effective in the presence of diesters.
Polyalphaolefin provides superior oxidation and hydrolytic
stability and high film strength. Polyalphaolefin also has a high
molecular weight, higher flash point, higher fire point, lower
volatility, higher viscosity index, and lower pour point than
mineral oil. U.S. Pat. No. 4,859,352 hereby incorporated by
reference provides additional polyalphaolefin derivatives.
[0078] Preferred polyalphaolefins, ("PAO"), include those sold by
EXXON-MOBIL USA 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
viscosities from about 2 to about 460 centistoke. Also useful are
blends of about 56% of the 460 centistoke product and about 44% of
the 45 centistoke product as set forth in U.S. Pat. No. 5,348,668
hereby incorporated by reference.
[0079] MOBIL SHF-42 from EXXON-MOBIL USA, EMERY 3004 and 3006,
Equilon, 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 C.) and 16.75 cSt at +104 F. (40 C.). It has a
viscosity index of 125 and a pour point of -98 F and it also has a
flash point of +432 F. and a fire point of +478 F. Moreover, EMERY
3006 polyalphaolefin has a viscosity of 5.88 cSt at +212 F. and
31.22 cSt at +104 F. It has a viscosity index of 135 and a pour
point of -87 F. It also has a flash point of +464 F. and a fire
point of +514 F.
[0080] Additional satisfactory polyalphaolefins are those sold by
Uniroyal Inc. under the brand SYNTON PAO-40, which is a 40
centistoke polyalphaolefin. Also useful are the ORONITE brand
polyalphaolefins manufactured by CHEVRON-TEXACO Chemical
Company.
[0081] 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 EXXON-MOBIL Chemical Corporation,
is also similar in many respects to EMERY 3004.
[0082] Preferably the polyalphaolefins will have a viscosity of up
to 100 centistoke and more typically in the range of about 2-10
centistoke at 100.degree. C. with viscosities of 4 and 6 centistoke
being particularly preferred.
[0083] Moreover, a preferred embodiment may incorporate up to 95
percent by volume, more preferably from 10 to 90 percent by volume,
and more preferably from about 40 to 85 percent by volume of
polyalphaolefins having a viscosity of about 4cSt at 100.degree. C.
such as is available from Ethyl Corporation under the trademark
name of DURASYN 164.
[0084] A preferred concentrate embodiment may incorporate up to 85
percent by volume, more preferably from 5 to 85 percent by volume,
more preferably from about 10 to 60 percent by volume, and most
preferably from 10 to 30 percent by volume of polyalphaolefins
having a viscosity of about 6cSt at 100.degree. C. such as is
available from Ethyl Corporation under the trademark name of
DURASYN 166.
[0085] Moreover, an even more preferred embodiment of the present
invention further providing even more enhanced performance
characteristics utilizes synthetics which include a specific
portion comprising esters, polyesters, or combinations thereof. One
preferred embodiment utilizes polyolefins as the synthetic base
stock together with at least a portion comprising esters and/or
polyesters.
Esters
[0086] 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 EXXON-MOBIL Oil. Exxon-Mobil polyolester P-43,
NP343 containing two alcohols, and Hatco Corp. 2939 are
particularly preferred.
[0087] 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.
[0088] 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-ethyl
hexyl azelate is commercially available under the brand name of
EMERY 2958 by Emery Chemicals.
[0089] 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 USA. EXXON-MOBIL esters such
as 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 USA 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 2-460 centistoke
at 100.degree. C.
[0090] Although not essential, a preferred additive concentrate
and/or motor oil comprises at least a portion of a ester. The
concentrate additive and/or complete motor oil contains preferably
up to 25 percent by volume, more preferably from about 5 to about
20 percent by volume, more preferably from about 5 to about 15
percent by volume, of a polyester or diester such as obtained from
EMERY under the trademark 2960.
Severely Hydro Cracked Oils
[0091] A hydrogenated oil is a mineral oil subjected to
hydrogenation or hydrocracking under special conditions to remove
undesirable chemical compositions and impurities resulting in a
base oil having synthetic oil components and properties. Typically
the hydrogenated oil is defined by the American Petroleum Institute
(API) as a Group III petroleum based stock 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 may optionally be
utilized in amounts up to 95 percent by volume, more preferably
from 5.0 to 50 percent by volume and more preferably from 20 to 40
percent by volume when used alone or in combination with a
synthetic or mineral oil.
[0092] The hydrogenated oil may be used as the sole base oil
component of the instant invention providing superior performance
to conventional motor oils with no other synthetic oil base or
mineral oil base or used as a blend with mineral oil and/or
synthetic oil. An example of such an oil is YUBASE-4. Other
suppliers include CHEVRON-TEXACO Company. A complete motor oil or
an additive concentrate embodiment may incorporate up to 95 percent
by volume, more preferably from 5 to 85 percent by volume of the
semi-synthetic as the oil base stock. When used in combination with
another conventional synthetic oil such as those containing
polyolefins or esters, or when used in combination with a mineral
oil, the hydrogenated oil may be present in an amount of up to 95
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.
[0093] More particularly, the hydrogenated oil is a base oil for a
lubricating oil consisting of a mineral oil and/or a synthetic oil,
having a viscosity index of at least 120, and having a viscosity of
from 2 to 3,000 CST at 100 degrees C. Hydrogenated oils can be
obtained by subjecting raw materials for lubricating oils to
hydrogenation treatment, using a hydrogenation catalyst such as
cobalt or molybdenum with a silica-alumina carrier, and lubricating
oil factions which can be obtained by the isomerization of waxes.
The hydro cracked or wax-isomerized oils contain 90 percent by
weight or greater of saturates and 300 ppm or less of sulfur.
Mineral Oil Base Stock
[0094] Although not essential, a mineral oil base stock may be
incorporated in the present invention as a portion of the
concentrate or a base stock to which the concentrate may be added
to produce a motor oil. Particularly preferred as mineral oil base
stocks are the ASHLAND 325 Neutral defined as a solvent refined
neutral having a SABOLT UNIVERSAL of 325 SUS @ 100.degree. F. and
ASHLAND 100 Neutral defined as a solvent refined neutral having a
SABOLT UNIVERSAL of 100 SUS @ 100.degree. F., manufactured by
MARATHON ASHLAND PETROLEUM and by others.
[0095] Other acceptable petroleum-base fluid compositions include
white mineral, paraffinic and MVI naphthenic oils having the
viscosity range of about 20-400 Centistoke. Preferred white mineral
oils include those available from WITCO Corporation, ARCO BP
Chemical Company, PSI and PENRECO. Preferred paraffinic oils
include API Group I and Group II oils available from EXXON MOBIL
USA, Group II oils available from MOTIVA ENTERPRISES, LLC., and
Group II oils available from CHEVRON EXXON Corp. Preferred MVI
naphthenic oils include solvent extracted oils available from
EQUILON ENTERPRISES and SAN JOAQUIN REFINING, hydro treated oils
available form EQUILON ENTERPRISES, and naphthenic oils sold under
the names HYDROCAL and CALSOL by CALUMET, and naphthenic oils such
as are described in U.S. Pat. No. 5,348,668 to Oldiges.
[0096] Mineral oil base stock can comprise the entire base oil
typically up to 95% by volume, more preferably 5-85 percent by
volume, more preferably 50-80 percent by volume and most preferably
70-80 percent by volume in the complete motor oil, but is not
narrowly critical. More particularly, the mineral oil base stock
can be used up to about 95 percent in the concentrate and up to 50
percent and preferably up to about 35 percent by volume of the
motor engine oil upon dilution. Typically one unit of the
concentrate is diluted with about 4 or 5 units of the motor oil
which may be a fully synthetic, mineral oil, or blend.
[0097] Finally, vegetable oils may also be utilizes as the liquid
medium in the instant invention. Soybean or rapeseed oil,
particularly of the high oleic or mid oleic genetically engineered
type, commercially available from Archer Daniels Midland Company,
are good examples of these oils. Soybean oil is of interest because
it has a high thermal conductivity itself.
Dispersants Used in Lubricant Industry
[0098] Dispersants used in the lubricant industry are typically
used to disperse the "cold sludge" formed in gasoline and diesel
engines, which can be either "ashless dispersants", or containing
metal atoms. They can be used in the instant invention since they
are found to be an excellent dispersing agent for nanoparticles
with graphitic structure of this invention. They are also needed to
disperse wear debris and products of lubricant degradation within
the engine.
[0099] 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.
[0100] Of these ashless dispersants the ones typically used in the
petroleum industry include N-substituted polyisobutenyl
succinimides and succinates, alkyl 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-polyethylencpolyamine, polyisobutenyl
succinic ester, polyisobutenyl hydroxybenzyl-polyethylcncpolyamine,
bis-hydroxypropyl phosphorate. Commercial dispersants suitable for
lubricating fluids are for example, Lubrizol 890 (an ashless PIB
succinimide), Lubrizol 6420 (a high molecular weight PIB
succinimide), ETHYL HITEC 646 (a non-boronated PIB succinimide).
The dispersant may be combined with other additives used in the
lubricant industry to form a ispersant-detergent (DI) additive
package for lubricating fluids, e.g., LUBRIZOL 9677MX, and the
whole DI package can be used as dispersing agent for the
nanoparticle dispersions.
Other Types of Dispersants
[0101] 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.
[0102] The dispersants selected should be soluble or dispersible in
the liquid medium. The dispersant can be in a range of up from 0.01
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
to 15 percent, and most preferably in a range of from between 2 to
13 percent. The carbon nanomaterials can be of any desired weight
percentage in a range of from 0.001 up to 10 percent. For practical
application it is usually in a range of from between 0.01 percent
to 10 percent, and most preferably in a range of from between 0.1
percent to 5 percent. The remainder of the formula is the selected
medium.
[0103] It is believed that in the instant invention the dispersant
functions by adsorbing onto the surface of the carbon
nanomaterials.
[0104] Though not narrowly critical, the Dispersant Inhibitor
("DI"), is exemplified by those which contain alkyl zinc
dithiophosphates, succinimides, esters, or Mannich dispersant,
calcium, magnesium, sodium sulfonates, phenates, phenylic and amine
antioxidants, plus various friction modifiers such as sulfurized
fatty acids. Dispersant inhibitors are readily available from
Lubrizol, Ethyl, Oronite, a division of CHEVRON-TEXACO Chemical,
and INFINEUM.
[0105] Generally acceptable are those commercial detergent
inhibitor packages used in formulated engine oils meeting the API
SH CD or higher performance specifications. Particularly preferred
are dispersants such as LUBRIZOL 8955 having chemical and physical
properties such as those described in U.S. Pat. No. 5,490,945 of
the Lubrizol Corporation which is hereby incorporated by reference,
ETHYL HITEC 1111 and 1131, and similar formulations available from
INFINEUM, or Oronite, a division of CHEVRON-TEXACO Chemical.
[0106] An effective amount of an additive package which
incorporates a dispersion inhibitor such as the one listed
heretofore may also be utilized and include a conventional
detergent and/or a corrosion inhibitor. Such an additive package
may be utilized with or in substitution of a selected dispersion
inhibitor or combinations thereof with each other and/or other
dispersion inhibitors commercially available in an effective amount
of up to 35 percent by volume, more preferably from about 0.5 to 25
percent by volume and more preferably from about 1 to 15 percent by
volume of the complete motor oil formula and up to 6.times. that
amount in the concentrate. The DI concentration is generally up to
15% by volume of the total formulation of the complete engine oil
and more particularly from 5.0 to 15% by volume. Concentrations
produced for dilution will generally be in these ranges.
[0107] Zinc dithiophosphate is a multi-function additive in that it
functions as a corrosion inhibitor, antiwear agent, and
antioxidants added to organic materials to retard oxidation.
[0108] Other metal dithiophosphates such as zinc isopropyl,
methylamyl dithiophosphate, zinc isopropyl isooctyl
dithiophosphate, barium di(nonyl) dithiophosphate, zinc
di(cyclohexyl) dithiophosphate, copper di(isobutyl)
dithio-phosphate, calcium di(hexyl) dithiophosphate, zinc isobutyl
isoamyl dithiophosphate, and zinc isopropyl secondary-butyl
dithiophosphate may be applicable. These metal salts of phosphorus
acid esters are typically prepared by reacting the metal base with
the phosphorus acid ester such as set forth in U.S. Pat. No.
5,354,485 hereby incorporated by reference. Moreover, a preferred
dispersion inhibitor is described in U.S. Pat. No. 5,490,945 hereby
incorporated by reference which describes a compound containing at
least one carboxylic derivative composition produced by reacting at
least one substituted succinic acylating agent containing at least
about 50 carbon atoms in the substituent with at least one amine
compound containing at least one HN<group.
Pour Point Depressant
[0109] A pour point depressant in an effective amount of up to 10.0
volume percent of the complete engine oil formula and more
preferably about 0.01 to 5.0 percent by weight and most preferably
from about 0.1 to 1.0 percent by weight is not essential but can be
utilized an embodiment of the formulation. Of course, a sufficient
amount of the viscosity improver may also be incorporated in the
base oils or motor oil to be treated. Also the pour point
depressant is typically not concentrated 4.times. or 5.times. in
the additive package. An example of a suitable pour point
depressant is polymethacyrlate, alkylated bicyclic aromatics,
styrene esters, polyfumerates, oligomerized alky phenyls, dialkyl
esters of phthalate acid, ethylene vinyl acetate copolymers, and
other mixed hydrocarbon polymers from LUBRIZOL, the ETHYL
Corporation, or ROHMAX, a Division of Degussa. A commercially
available pour point depressant is sold under the brand name of
ACRYLOID 3008 which is a polymethyrlate formula.
Additive Packages
[0110] Additive packages which incorporate a dispersion inhibitor
with a conventional detergent and/or a corrosion inhibitor may also
be utilized with or in substitution of the dispersion inhibitor.
For instance as set forth heretofore, such an additive package may
comprise Lubrizol's LZ8955 and/or LZ9802 or combinations thereof
with each other and/or other dispersion inhibitors in an effective
amount of up to 35 percent by volume, more preferably from about
0.5 to 25 percent by volume and more preferably from about 1 to 10
percent by volume of the concentrate.
[0111] Because the base oils typically contain an effective amount
of a pour point depressant and/or the motor oil to which the
additive is added typically contain an effective amount of a pour
point depressant, it would not typically be concentrated 4.times.
or 5.times. in the additive package.
Viscosity Index Imrover (VI)
[0112] Viscosity improvers, ("VI"), include, but are not limited
to, polyisobutenes, polymethacrylate acid esters, polyacrylate acid
esters, diene polymers, polyalkyl styrenes, alkenyl aryl conjugated
diene copolymers, polyolefins and multifunctional viscosity
improvers and SHELLVIS 90, a linear styrene isoprene rubber in
mineral oil base or SHELLVIS 260 a cyclic styrene isoprene
compound.
[0113] The lubricant additive contain up to 15 percent by volume of
a viscosity improver, more preferably from about 0.005-10 percent
by volume, more preferably 0.05 to 8 and more preferably from 0.1
to 1.0 percent by volume. Of course, a sufficient amount of the
viscosity improver may also be incorporated in the base oils or
motor oil to be treated.
Molybdenum Additive
[0114] The most preferred molybdenum additive is an oil-soluble
decomposable organo molybdenum compound, such as MOLYVAN 855 which
is an oil soluble secondary diarylamine defined as substantially
free of active phosphorus and active sulfur. The MOLYVAN 855 is
described in Vanderbilt's Material Data and Safety Sheet as a
organomolybdenum compound having a density of 1.04 and viscosity at
100 EC of 47.12 cSt. In general, the organo molybdenum compounds
are preferred because of their superior solubility and
effectiveness.
[0115] A less effective alternative molybdenum additive is MOLYVAN
L is sulfonated oxymolybdenum dialkyldithiophosphate described in
U.S. Pat. No. 5,055,174 by Howell hereby incorporated by
reference.
[0116] MOLYVAN A made by R.T. Vanderbilt company, Inc., New York,
N.Y., USA, is also an alternative additive which contains about
28.8 wt. % Mo, 31.6 wt. % C, 5.4 wt. % H., and 25.9 wt. % S. Also
useful are MOLYVAN 855, 822, 856, and 807 in decreasing order of
preference.
[0117] Also useful is SAKURA LUBE-500, which is more soluble Mo
dithiocarbamate containing lubricant additive obtained from Asahi
Denki Corporation and comprised of about 20.2 wt. % MO, 43.8 wt. %
C, 7.4 wt. % H, and 22.4 wt. % S.
[0118] Also useful is MOLYVAN 807, a mixture of about 50 wt. %
molybdenum ditridecyldithyocarbonate, and about 50 wt. % of an
aromatic oil having a specific gravity of about 38.4 SUS and
containing about 4.6 wt. molybdenum, also manufactured by R.T.
Vanderbilt and marketed as an antioxidant and antiwear
additive.
[0119] Other sources are molybdenum Mo(Co).sub.6, and Molybdenum
octoate, Mo(C.sub.7H.sub.15CO.sub.2).sub.2 containing about 8 wt-%
Mo marketed by Aldrich Chemical Company, Milwaukee, Wis. and
molybdenum naphthenethioctoate marketed by Shephard Chemical
Company, Cincinnati, Ohio.
[0120] Inorganic molybdenum compounds such as molybdenum sulfide
and molybdenum oxide are substantially less preferred than the
organic compounds as described in 855, 822, 856, and 807.
[0121] Whereas 1% is equal to 10,000 parts per million (ppm), the
preferred dosage in the molybdenum additive is up to 5.0 percent by
mass. More preferably the preferred dosage is up to 3,000 ppm by
mass, more preferably from about 100 ppm to about 2,000 ppm by
mass, more preferably from about 300 to about 1,500 ppm by mass,
more preferably from 300 to about 1000 ppm by mass of
molybdenum.
Nanomaterials
[0122] One preferred type of graphitic particles are carbon
nanotubes, the nanotubes can be either single-walled, or
multi-walled, having 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 500 nanometers to 500 microns. More typical length is
1 micron to 100 microns. The aspect ratio of the tube can be from
hundreds to thousands, more typical 500 to 5000. The surface of the
nanotube can be treated chemically to achieve certain level of
hydrophilicity, or left as is from the production. Unfortunately,
the commercial availability of the prepared nanotubes is limited
making them too expensive for incorporation into commodity type
lubricants at this time.
[0123] Therefor, a novel method has been developed to form
nanomaterials suitable for use with commodity type lubricants at a
low cost and capable of being produced in a large quantity using
readily available equipment. Other acceptable form of graphite is a
high-thermal-conductivity graphite commercially available, e.g.
POCO FOAM, available from Poco Graphite, Inc., and graphite powders
available from UCAR Carbon Company Inc. POCO FOAM is a high thermal
conductivity foamed graphite, thermal conductivity typically in the
range 100 to 150 W/m. A readily commercially available graphite is
graphite powders from UCAR Carbon Company Inc., thermal
conductivity of 10 to 500 W/m, and typically >80 W/m. Still
another acceptable form of graphite is the
high-thermal-conductivity graphite, Part#875G, from The
Carbide/Graphite Group, Inc.
[0124] These graphite are prepared for the instant invention by
pulverizing to a fine powder, dispersing chemically and physically
in a fluid of choice, and then ball milled or otherwise size
reduced until particle, flake, fibril or combinations thereof
produce nanomaterial of a size of less than 500 nm mean size is
attained. The preferred method is to disperse the graphite by ball
milling in a viscous fluid of most additives (detergents,
dispersants, etc.) and then diluting the obtained concentrate with
base oil and other additives as needed to attain the final
viscosity and performance characteristics. The finer the particle
size attained upon milling, the better the thermal conductivity
increase but also the more viscosity thickening effect of the pasty
concentrate on the final blend. These effects must be balanced to
attain a suitable lubricating film thickness at the maximum shear
rate and temperature of fluid use. In general, any high thermal
conductivity graphite can be used, provided that pulverization,
milling and other described chemical and physical methods can be
used to reduce the size of the final graphite dispersion to below a
mean particle size of 500 nm or less.
[0125] In the process of making lubricating fluid such as the
engine oil or engine treatment concentrate additive with the
nanomaterial, the mechanical process and sequence of adding the
components are important in order to fully take advantage of the
high viscosity index of the nanoparticles and to make the final
fluid product with exceptionally high viscosity index. High impact
mixing is necessary to achieve a homogeneous dispersion. Ball mill
is one of the examples of a high impact mixer. In the instant
invention, an Eiger Mini Mill (Model: M250-VSE-EXP) is used as the
high impact ball mill. It utilizes high wear resistant zirconia
beads as the grinding media and circulates the dispersion
constantly during milling.
[0126] To achieve the best milling effect and therefore the best
viscosity index improvement, the proper milling procedure has been
developed. Firstly a 5% to 20% by weight of graphite powders, and
more preferably 10% by weight of graphite powders, in base oil
dispersion is milled into a paste state. Usually this step takes
about 3 to 4 hours. Then add the appropriate effective amount of at
least one dispersing agent(s), usually 1 to 2 times of the weight
of graphite, into the mill. With the addition of dispersing
agent(s) the paste changes from paste into liquid almost instantly,
and extended milling becomes possible. For most cases the extended
milling period is 4 hours. It should be pointed out that if the
mixture in the mill turns into a paste, the recirculation of it
becomes very difficult and thus a poor milling is resulted. It is
also found that if the dispersing agent(s) is(are) added into the
mill at the very beginning, the viscosity index of the final
nanofluids made from the milling process is not as high.
[0127] Graphite nanomaterials are obtained by pulverizing big
graphite chunks weight several pounds or kilograms obtained from
The Carbide/Graphite Group. The resulting pulverized material is
size-selected through a mesh filter to be less than 75 .mu.m.
Thirty (30) grams of the above pulverized graphite particles and
270 grams of a base oil, DURASYN 162 (a commercial 2 centistokes
polyalphaolefin) 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.
About 60 grams of this paste was discharged and labeled Paste `A`.
Forty-eight (48) grams of a dispersant package from Lubrizol,
LUBRIZOL 9677MX, was added to the rest of the mixture in the mill.
The paste became very thin, and successful recirculation was
restored. Stopped the mill after another 4 hours of milling and
labeled the discharged paste 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 DURASYN 162
at 4000 rpm for 8 hours. Note here the dispersing agent LUBRIZOL
9677MX was added into the mill at the very beginning. Then engine
oil concentrates can be formulated using the above three pastes as
concentrates respectively. The final compositions were exactly the
same by weight and ingredients except for the graphite material: 2%
graphite, 4% LUBRIZOL 9677 MX, 18% DURASYN 162, 76% DURASYN 166 (a
commercial 6 centistokes polyalphaolefin base oil) (all percentage
by weight). Example 1 illustrates the 100.degree. C. viscosity and
viscosity index (VI) of the fluids. It was also found that the
graphite particle size before milling was an important variable to
control 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. The particle size is measured
by atomic force microscopy (AFM), and the graphite nanoparticles
appear to be flakes or a plate-like structure, with average
diameter of around 50 nm and thickness around 5 nm.
[0128] The present invention provides at a minimum, a fluid of
lubricant containing less than 10% by weight graphite
nanoparticles. Preferably, however, a minimum of one or more
chemical dispersing agents and/or surfactants is also added to
achieve long term stability.
Polytetrafluoroethylene Additive
[0129] Polytetrafluoroethylene sold commercially under the
trademark of TEFLON by the DUPONT Corporation. It is a solid
lubricant which can be defined as an oil soluble functional
additive. The term "oil soluble" water-insoluble functional
additive refers to a functional additive which is not soluble in
water above a level of about 1 gram per 100 ml of water at 25 EC.,
but is soluble in mineral oil to the extent of at least 1 gram per
liter at 25 EC.
[0130] These functional additives can also include frictional
polymer formers, which are polymer forming materials which are
dispersed in a liquid carrier at low concentration and which
polymerize at rubbing or contacting surfaces to form protective
polymeric films on the surfaces. The polymerization are believed to
result from the heat generated by the friction and, possibly, from
catalytic and/or chemical action of the freshly exposed
surface.
[0131] It is theorized that polytetrafluoroethylene, ("PTFE"),
containing lubricants provide enhanced lubrication by virtue of the
fact that the PTFE particles somehow become attached to the
surfaces of the engine thus lubricated, thereby creating a
renewable coating of PTFE. The composition may contain a mixture of
a carrier lubricant medium, such as mineral oil, a quantity of
fluoropolymer particles, such as ground and sintered particles of
polytetrafluoroethylene which are well dispersed in the carrier
lubricant. It is important that these particles are well dispersed
in the carrier lubricant in order to prevent coagulation,
agglomeration, and/or settling.
[0132] The size of the PTFE particles is selected based on the
consideration that the PTFE particles may actually become attached
within the pores of the surface thus coated. The frictional forces
applied by the moving parts of the engine wipe after the
composition is applied to it removing excess lubricant and working
the lubricant into the surface by the exertion of heat and pressure
to the surface to enhance penetration of the lubricant into the
surface. Thus, it is thought that the PTFE may become attached to
the surface, and particularly within the pores of the surface.
[0133] It is thought that the other additives in the additive
package aid in bonding of the PTFE particles to the surface
lowering the coefficient of friction of the surface and reducing
fluid drag on the surface.
[0134] The PTFE for use with selected embodiments of the present
invention are preferably a nonaqueous dispersion of fine particles
in colloidal form. A preferred average particle size would be in
the range of from about 0.05-3.0 micrometers (microns) and can be
in any convenient nonaqueous media; e.g., synthetic or mineral base
oil, compatible with the remainder of the formulation. Commercial
PTFE dispersions which are suitable for the invention include
ACHINSON SLA 1612 manufactured by Acheson Colloids Company,
Michigan.
[0135] The preferred dosage of PTFE in the selected concentrate
additive is up to 10.0 percent by weight, preferably from about
0.01 to about 10 weight percent, more preferably from about 0.05 to
about 5 weight percent, and most preferably from about 0.01-3
weight percent PTFE.
Anti-Wear Extreme Pressure Agents
[0136] The preferred anti-wear extreme pressure agent is a boron
antiwear/extreme pressure agent, preferably a borate ester, a boric
acid, other boron compounds such as a boron oxide. The boron
compound is hydrolytically stable and is utilized for improved
antiwear, antiweld, extreme pressure and/or friction properties,
and perform as a rust and corrosion inhibitor for copper bearings
and other metal engine components. The borated ester compound acts
as an inhibitor for corrosion of metal to prevent corrosion of
either ferrous or non-ferrous metals (e.g. copper, bronze, brass,
titanium, aluminum and the like) or both, present in concentrations
in which they are effective in inhibiting corrosion.
[0137] Patents describing techniques for making basic salts of
sulfonic, carboxylic acids and mixtures thereof include U.S. Pat.
Nos. 5,354,485; 2,501,731; 2,616,911; 2,777,874; 3,384,585;
3,320,162; 3,488,284; and 3,629,109. The disclosure of these
patents are hereby incorporated by reference. Methods of preparing
borated overbased compositions are found in U.S. Pat. Nos.
4,744,920; 4,792,410; and PCT publication WO 88/03144. The
disclosure of these references are hereby incorporated by
reference. The oil-soluble neutral or basic salts of alkali or
alkaline earth metals salts may also be reacted with a boron
compound.
[0138] The borate ester utilized in the preferred embodiment is
manufactured by EXXON-MOBIL USA under the product designation of
("MCP 1286") and MOBIL ADC700. Test data show the viscosity at
100.degree. C. using the D-445 method is 2.9 cSt; the viscosity at
40.degree. C. using the D-445 method is 11.9; the flash point using
the D-93 method is 146; the pour point using the D-97 method is
-69; and the percent boron as determined by the ICP method is
5.3%.
[0139] The preferred dosage of boron compound in the total
crankcase lubricant is up to 10.0 volume percent, more preferably
from about 0.01 to about 10.0 volume %, more preferably from about
0.01 to about 5 volume %, and most preferably from about 0.1-3.0
volume %. An effective elemental boron range of up to 1000 ppm or
less than 1% elemental boron. Thus, a preferred concentration of
elemental boron is from 100 to 1000 ppm and more preferably from
100 to 300 ppm and most preferably in one preferred embodiment as
set forth in Table 3 about 166 ppm.
[0140] As demonstrated in FIG. 6, the engine treatment oil additive
formulation was found to comply with all requirements of engine
additives specification CRC L-38 for a Crankcase Oxidation Test
showing the Total Adjusted Bearing Weight Loss comparing the blend
of Components comprising the engine treatment oil additive with an
API SG 5w-30 Motor Oil. The surprisingly good results show the
total adjusted bearing weight loss was reduced from 30.9 mg for the
Motor Oil without the engine treatment oil additive to 22.6 mg. for
the motor oil used in combination with the engine treatment oil
additive.
[0141] Other corrosion resisting compounds which may be used
together with boron or independently may be selected from the group
comprising dimercapto, thiediapoles, and benzotriazoles,
benzotriazole derivatives, benzothiazole, benzothiazole
derivatives, triazole, triazole derivatives, benzoimidazole, and
benzoiidazole derivitives in levels of to 1% by weight.
Other Additives
[0142] The invention also contemplates the use of an effective
amount of other additives in the lubricating and functional fluid
compositions of this invention. Such additives include, for
example, detergents and dispersants of the ash-producing or ashless
type, corrosion and oxidation-inhibiting agents, pour point
depressing agents, auxiliary extreme pressure and/or antiwear
agents, color stabilizers and anti-foam agents.
Physical Agitation
[0143] The physical mixing includes high shear mixing, such as with
a high speed mixer, homogenizers, microfluidizers, a Kady mill, a
colloid mill, etc., high impact mixing, such as attritor, ball and
pebble mill, etc., and ultrasonication methods or passing through a
small orifice such as a fuel injector. Turbulent flows of any type
will assist mixing.
[0144] Ball milling is the most preferred physical method in the
instant invention since it is effective at rapidly reducing the
graphite particles to very small size while simultaneously
dispersing them into a concentrated paste as previously described.
The concentrate can then be diluted with base oil and other
additives to hit a final target viscosity, depending on the maximum
temperature and shear conditions anticipated in the lubricant
application. For further size reduction and reducing particle
maximum size the diluted oil can be passed through a small orifice
such as a fuel injector. The raw material mixture may be pulverized
by any suitable known dry or wet grinding method. One grinding
method includes pulverizing the raw material mixture in the fluid
mixture of the instant invention to obtain the concentrate, and the
pulverized product may then be dispersed further in a liquid medium
with the aid of the dispersants described above. However,
pulverization or milling reduces the carbon nanotube average aspect
ratio. A detailed description has been given in an earlier section
of the instant invention.
[0145] Ultrasonication is another physical method in the instant
invention since it is less destructive to the carbon nanomaterial
structure than the other methods described. Ultrasonication can be
done either in the bath-type ultrasonicator, or by the horn-type
ultrasonicator. More typically, horn-type ultrasonication is
applied for higher energy output. Sonication at the medium-high
instrumental intensity for up to 30 minutes, and usually in a range
of from 10 to 20 minutes is desired to achieve better
homogeneity.
[0146] The instant method of forming a stable dispersion of carbon
nanomaterials in a solution consist of three steps. First select
the appropriate concentrate of dispersant or mixture of dispersing
and other additives for the carbon nanomaterials, and the medium,
and dissolve the dispersant into the liquid medium to form a
concentrate solution (keeping in mind the final additive
concentrations desired following dilution); secondly add a high
concentration of the carbon nanomaterials into the
dispersant-containing solution, initiate strongly agitating, ball
milling, or ultrasonicating, or any combination of physical methods
named; following an agitation time of several hours, the resulting
paste will be extremely stable and easily dilutable into more base
oil and additives to give the final desired concentrations of
additives and the desired final viscosity.
EXPERIMENTAL RESULTS
[0147] The novel engine treatment oil additive comprises a
combination of chemical constituents including an oil soluble
molybdenum additive, polyalphaolefin, ester such as a polyolester
or diester, dispersant inhibitor containing zinc dithiophosphate,
and viscosity index improvers. A polytetrafluoroethylene compound
increases the effect of the other chemical constituents
considerably. A borate ester may also be incorporated in the blend
with or without the polytetrafluoroethylene additive providing an
even greater improvement in the oxidation inhibition capabilities
thereof. The blend is typically used in combination with a
conventional crankcase lubricant such as a mineral oil, synthetic,
or mineral/oil synthetic blend at about a 20 to about a 25%
volume/percent. The improved performance of the engine additive in
comparison with conventional mineral oil crankcase lubricants is
attributable to optimizing the design parameters for each of the
individual chemical constituents and combining the chemical
constituents according to the present invention to obtain
surprisingly good results including improved: wear, oxidation
resistance, viscosity stability, engine cleanliness, fuel economy,
cold starting, and inhibition of acid formation. The novel engine
additive formulation comprises a combination of compounds,
ingredients, or components, each of which alone is insufficient to
give the desired properties, but when used in concert give
outstanding lubricating properties.
[0148] It is theorized that the combination of chemical
constituents comprising the instant invention result in a reduction
of friction between the moving parts of the engine so that in
operation an extremely fine film of the chemical constituents is
formed on the metal surfaces. At the high temperature and high
pressure within the engine, the surface active ingredients react
with the film continuously forming an extremely thin lubricating
layer thereon having an extremely low coefficient of friction and
wear even under extreme temperature and pressure providing superior
lubrication during the start-up and running phase of the
engine.
EXPERIMENTAL EVALUATION
[0149] The following Examples provide the results of tests
performed comparing the combination of formula components of the
present invention with conventional API SG motor oil. The Examples
exemplify the technology previously described. The combination of
the formula components in the Examples provide excellent
performance at high temperatures while also maintaining excellent
performance at moderately elevated temperatures and normal
temperatures, as well as provide resistance to ferrous and copper
corrosion, improved wear, oxidation resistance, viscosity
stability, engine cleanliness, fuel economy, cold starting,
inhibition of acid formation, and other desirable high performance
properties greater than exhibited by the individual components.
Example 1
The Invention Using Mo. Synthetic, PTFE, DI and VI Additive
[0150] The additive package is designed for addition to
conventional motor oil in the crankcase of an internal combustion
engine is prepared in a 2000 gallon jacketed, stirred vessel heated
to approximately 40 EC. First there is added 600 gallons of
polyalphaolefins (PAO 4 cSt) obtained from Ethyl Corporation under
the trademark DURASYN 164; 43 gallons of PAO 6 centistoke DURASYM
166 obtained from the same source and 93 gallons of diester
obtained under the brand name EMERY 2960. Stirring continues during
the addition of all the ingredients. The above mixture is termed
"synthetic" and is a synthetic base stock. To the synthetic is
added 123 gallons of dispersant inhibitor (DI) package obtained
under the brand name LUBRIZOL 8955, Lubrizol Corporation; 5 gallons
of an 8% concentrate of SHELL VIS 1990 viscosity index improver, 25
gallons of MOLYVAN 855 obtained from R. T. Vanderbilt and Company,
and 52 gallons of SLA 1612 obtained from Acheson Colloids, a 20%
concentration of colloidal DUPONT TEFLON.RTM. brand PTFE. The
resulting mixture is stirred for an additional 30 minutes, sampled
and tested for viscosity, metal concentration, and other quality
control checks.
[0151] The resulting concentrate is bottled into one quart
containers and a single container is added to the four quarts of
conventional motor oil in a five quart crank case of an
automobile.
[0152] The result is improved wear (FIGS. 1 and 3), oxidation
resistance (FIG. 2), viscosity stability (FIG. 2), engine
cleanliness (FIG. 4), fuel economy (FIG. 5), cold starting (Table
2, and inhibited acid formation (FIG. 2).
Example 2
The Invention of Example 1 Under Standard Tests
[0153] When one of the one quart formulations prepared in Example 1
is tested under conventional lubricant test procedures, results are
as given in Tables 1 and 2, and FIGS. 1-5. Note that the Shell
four-ball wear test ASTM D4172 of FIG. 1 and Table 1 is a bench
test indicative of wear performance of a lubricant.
[0154] When the same ingredients of Example 1 are formulated while
omitting one or more of the ingredients, the comparative results
are as shown in Table 1 and FIG. 1.
2TABLE 1 ASTM 4172 Shell Four Ball AC + AC + AC + AC + SYN + AC +
AC + AC + SYN + SYN + MOLY + MOLY + TEST AC SYN SYN TEF MOLY TEF
MOLY TEF VI + DI* Shell 0.405 0.360 0.373 0.422 0.330 0.375 0.332
0.335 0.308 Four- Ball Wear, mm MO Motor Oils, VALVOLINE 10W30
All-Climate SYN VALVOLINE 5W30 Synthetic, includes DI and VI AC +
SYN 10W30 AC + (20%) 5W30 Synthetic MOLY Molybdenum TEF TEFLON
.RTM. ADDITIVE Invention of Example 1
[0155]
3TABLE 2 ASTM 4742 - 88 Oxidation RFOUT TFOUT CCS@20NC TP1@20NF
Sample (min)** (min)* Ruler*** cP cP A 180 138 211 3,030 12,540 C
370 279 322 2,160 9,360 Note: A 10W30 All Climate (Motor Oil
Control) *C 80% Control plus 20% Additive **Thin Film Oxygen Uptake
***Modified test of ASTM 4742 Remaining useful Life Evaluation
Routine
[0156] As can be seen from Tables 1 and 2, and FIGS. 1 through 5,
the results using this additive show a remarkable improvement when
compared to a conventional motor oil tested without the additive of
the invention.
Example 3
[0157] A grease composition according to the invention of Example 1
can be conventionally mixed with a lithium soap of a fatty acid to
thicken the composition and to result in an improved grease.
Example 4
[0158] A boron containing compound, more particularly a borate
ester was added to the additive produced in Example 1. As
demonstrated in FIG. 6, the engine treatment oil additive
formulation was found to comply with all requirements of engine
additives specification CRC L-38 for a Crankcase Oxidation Test
showing the Total Adjusted Bearing weight Loss comparing the blend
of Components comprising the engine treatment oil additive with an
API SG 5w-30 Motor Oil. The surprisingly good results show the
total adjusted bearing weight loss was reduced from 30.9 mg for the
Motor Oil without the engine treatment oil additive to 22.6 mg. for
the motor oil used in combination with the engine treatment oil
additive.
[0159] As set forth herebelow, Table 3 shows various additive
combinations and the preferred formulas by weight and/or volume
percent.
4TABLE 3 ADDITIVE COMPOSITIONS Target More Most Formulation
Parameter Units Preferred Preferred Preferred Vol. % Base Stock
Vol. % Up to 95 25-90 60-85 74 Polyolefins Vol. % 15-85 25-80 50-75
65 Diesters Vol % 1-25 3-20 5-15 9.5 Viscosity Wt. % 0.05-5 0.07-3
0.1-2 6.5 Improver 100% Molybdenum (Mo) Wt. % 0.05-5 0.07-3 0.1-2
2.5 PTFE Wt. % 0.01-10 0.0005-5 0.1-3 20 Dispersant Vol. % 0 . . .
5-35 1-25 5-20 12.3 (12.3% vol.) Dilution Before Vol. 0.25 0.5-15
1-10 4-5 Use: Lubr. Vol. Addit Borate Esters Vol. % 0.01-1.0
0.05-.7 0.1-.5 1 10-1000 50-700 10-500 1000 ppm ppm ppm ppm
Modifications
[0160] Specific compositions, methods, or embodiments discussed are
intended to be only illustrative of the invention disclosed by this
specification. Variation on these 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.
[0161] 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.
[0162] 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 hereinabove.
Rather, what is intended to be covered is within the spirit and
scope of the appended claims.
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