Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02491823 2005-O1-10
LUBRICANT COMPOSITIONS FOR PROVIDING ANTI-SHUDDER
PERFORMANCE AND ELASTOMERIC COMPONENT COMPATIBILITY
FIELD
The present disclosure relates to lubricant compositions and methods utilizing
the
lubricant compositions to provide andlor improve anti-shudder capabilities of
automotive
transmission fluids. The present disclosure also provides lubricant
compositions that provide
and/or improve compatibility with elastomeric components.
BACKGROUND
New and advanced transmission systems are being developed by the automotive
industry. These new systems often involve high energy requirements. Therefore,
friction
materials technology must be developed to meet the increasing energy
requirements of these
advanced fluid systems.
The high speeds generated during engagement and disengagement of some of the
newer transmission systems mean that a friction system must be able to
maintain a relatively
constant friction throughout the engagement. It is important that the
frictional engagement be
relatively constant over a wide range of speeds and temperatures in order to
minimize
"shuddering" of materials during transmission power shift from one gear to
another.
In particular, new high energy type friction materials are being developed and
used.
The new high energy friction materials are able to withstand high speeds
wherein internal
transmission plate surface speeds are up to about 65 m/second. It is also
important that the
friction material be useful under limited lubrication conditions. One such
material being
developed for automatic transmission applications is a carbon fiber containing
material.
In view of new materials and greater demands on transmissions, automotive
power
transmission fluids are called upon to provide specific frictional properties
under very
demanding conditions of speed, temperature, and pressure. Changes in a fluid's
frictional
properties as a function of relative sliding speed, temperature, or pressure
may cause
performance degradation immediately noticeable to the vehicle operator. Such
effects may
CA 02491823 2005-O1-10
include unacceptably long or short gear shifts, vehicle shudder or vibration,
noise, and/or
harsh shifts ("gear change shock"). Thus, there is a need for transmission
fluids that exhibit
improved characteristics such as shear and friction stability at high
temperatures and
pressures. Such fluids would reduce equipment and performance problems while
improving
the interval between fluid changes. By enabling smooth engagement of torque
converter and
shifting clutches, these fluids may reduce shudder, vibration, and/or noise,
and in some cases
improve fuel economy, over a longer fluid lifetime.
Friction modifiers are used in transmission fluids to control friction between
surfaces
(e.g., the members of a torque converter clutch or a shifting clutch) at low
sliding speeds. The
result is a fi-iction vs. velocity (u-v) curve that has a positive slope,
which in turn leads to
smooth clutch engagements and minimizes "stick-slip" behavior (e.g., shudder,
noise, and
harsh shifts). Many conventional friction modifiers, however, are thermally
unstable. Upon
prolonged exposure to heat, these additives decompose, and the benefits they
confer on clutch
performance may be lost.
In addition, deterioration of structural elastomeric elements or components
such as
seals, belts, gaskets, bushings, filters, and/or hoses in engines,
transmissions, gears, and/or
axles may occur. Such deterioration may be attributed to interactions between
the elastomeric
material of said elements and the reactive or deteriorative components of a
lubricant
composition or fluid. Further, a lubricating fluid should provide appropriate
swelling of seals,
gaskets, and the like. It is additionally an object of the compositions and
methods of the
present invention to reduce the deterioration of, improve the compatibility
with, and promote
proper swell of such seals, hoses, and like elements and components.
SUMMARY OF EMBODIMENTS
In an embodiment, a power transmitting fluid for use in a power transmitting
device
may comprising a major amount of a base oil and a minor amount of an additive
composition.
The additive composition may comprise at least one non-dispersant viscosity
index improver,
wherein the power transmitting fluid provides anti-shudder performance to the
power
transmitting device.
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CA 02491823 2005-O1-10
In another embodiment, a lubricating fluid having compatibility with an
elastomeric
component may comprise a major amount of a base oil and a minor amount of an
additive
composition having at least one non-dispersant viscosity index improver.
In another embodiment, a method of improving the anti-shudder capabilities of
a
power transmission fluid may comprise lubricating a power transmission with a
power
transmission fluid comprising a major amount of a base oil and a minor amount
of an additive
composition comprising at least one non-dispersant viscosity index improver.
In another embodiment, a method of improving the torque performance of a power
transmission fluid may comprise lubricating a power transmission with a power
transmission
fluid comprising a major amount of a base oil and a minor amount of an
additive composition
comprising at least one non-dispersant viscosity index improver.
In another embodiment, a method of improving the compatibility of a
lubricating fluid
with an elastomeric component may comprise lubricating an elastomeric
component with a
fluid comprising a major amount of a base oil and a minor amount of an
additive composition
comprising at least one non-dispersant viscosity index improver.
In another embodiment, a method of promoting seal swell of an elastomeric seal
may
comprise lubricating the elastomeric seal with a lubricating fluid comprising
a major amount
of a base oil and a minor amount of an additive composition comprising at
least one non-
dispersant viscosity index improver.
In another embodiment, a method of making a power transmitting fluid having
anti-
shudder capabilities may comprise adding to a major amount of a base oil a
minor amount of
an additive composition having a non-dispersant viscosity index improver.
In another embodiment, a method of making a lubricating fluid having improved
compatibility with an elasotmeric component may comprise adding to a major
amount of a
base oil a minor amount of an additive composition having a non-dispersant
viscosity index
improver.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates torque performance of a fluid according to an embodiment as
measured using a ZF GK test rig.
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FIG. 2 illustrates torque performance of a comparative fluid measured using a
ZF GK
test rig.
DETAILED DESCRIPTION OF EMBODIMENTS
As power transmission fluids operate under increasingly severe conditions, the
oils
used to lubricate those transmissions should be formulated to endure higher
temperatures and
pressures. To reduce equipment problems and increase the interval between
transmission oil
changes, the oil should be formulated so that important oil properties change
as little as
possible in the face of these stresses. In particular, the shear stability
properties of the oil,
which depend in great measure on the additive package, should stay relatively
constant over a
wide range of temperatures and operating speeds. This ensures smooth
engagement of torque
converter and shifting clutches and minimized shudder, vibration and noise,
and improved
fuel economy as constant viscosity allows good hydraulic control.
The present disclosure describes compositions and methods that provide and/or
improve anti-shudder performance of power transmission fluids, and also
methods for
providing and/or improving the compatibility of lubricating fluids with
elastomeric
components, for example, seals, gaskets, belts, and/or hoses. Non-dispersant
viscosity index
improvers are known to improve rheological properties, such as viscosity
index, of power
transmission fluids and/or lubricating fluids. Thus, the compositions of the
present disclosure
provide a single solution to multiple problems, and thus an inherent cost
benefit.
In an embodiment, a power transmission fluid may include a base oil and an
additive
composition. The additive composition may include a non-dispersant viscosity
index
improver. Non-dispersant viscosity index improvers differ from dispersant
viscosity index
improvers by the absence of dispersant functional groups. A non-dispersant
viscosity index
improver suitable for use in at least one of the present embodiments may
comprise a
polymethacrylate, an olefin copolymer, a polystyrene, a metallocene polymer, a
polymer of a
hydrogenated dime and/or a copolymer thereof with a vinyl amine, a homopolymer
of a
hydrogenated conjugated diene or a copolymer thereof with a vinyl aromatic
hydrocarbon,
and the like. A wide range of molecular weight polymers of the latter type can
be utilized as
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CA 02491823 2005-O1-10
the base polymer of the non-dispersant viscosity index improver, and such
polymers may
include linear, branched, or star-shaped configurations.
The presence of a non-dispersant viscosity index improver in the compositions
and
methods of the present embodiments eliminate and/or reduce the need for
conventionally
utilized friction-modifying agents or other agents for providing anti-shudder
performance.
Further, inclusion of a non-dispersant viscosity index improver may improve
the anti-shudder
properties of a fluid relative to a fluid including a dispersant viscosity
index improver.
Embodiments may include an amount of a non-dispersant viscosity index improver
sufficient
to provide and/or improve the anti-shudder characteristics of a power
transmission fluid. For
example, an additive composition may comprise from about 0.01 wt% to about 50
wt% of
non-dispersant viscosity index improver. As a further example, an additive
composition may
comprise from about 1.0 wt% to about 25 wt% of non-dispersant viscosity index
improver.
As an even further example, an additive composition may comprise from about 3
wt% to
about 15 wt% of non-dispersant viscosity index improver.
In addition, some embodiments provide and/or improve compatibility of
elastomeric
components found within an automotive transmission, including an automatic and
manual
transmission, a gear component, and/or an axle component. Such elastomeric
components
may comprise seals, hoses, gaskets, belts, and the like. Further, these
components may be
composed of elastomeric materials such as nitrile rubber, polyacrylate,
silicone,
fluoroelastomers, and/or chlorinated polyethylene. Elastomeric components may
deteriorate,
shrink, or fail to swell properly because of contact with certain chemicals
contained in
lubricating fluids. Further, some chemicals, such as seal swell agents, may
improve the
tolerance of seals and hoses to lubricating fluids. Embodiments disclosed
herein have been
found to positively interact with seals and hoses to improve tensile strength
and/or elongation.
Both of these factors are indicative of proper seal swell and resistance or
tolerance to
deterioration. Such embodiments include a lubricating fluid comprising a non-
dispersant
viscosity index improver.
The presence of a non-dispersant viscosity index improver in the compositions
and
methods of the present embodiments eliminate and/or reduce the need for
conventionally
utilized seal swell agents or other agents. For example, inclusion of a non-
dispersant
viscosity index improver in a lubricating fluid may improve the compatibility
of the
CA 02491823 2005-O1-10
lubricating fluid with elastomeric components. In particular, this improvement
may be
compared to fluids including dispersant viscosity index improvers and/or
fluids including a
conventional seal swell agent.
Embodiments may include a suitable amount of a non-dispersant viscosity index
improver sufficient to provide the desired swelling and/or provide or improve
the
compatibility between a lubricating fluid and elastomeric components. For
example, an
additive composition may comprise from about 0.01 wt% to about 50 wt% of non-
dispersant
viscosity index improver. As a further example, an additive composition may
comprise from
about 1.0 wt% to about 25 wt% of non-dispersant viscosity index improver. As
an even
further example, an additive composition may comprise from about 3 wt% to
about 15 wt% of
non-dispersant viscosity index improver.
Base Oil
Base oils suitable for use in formulating transmission fluid compositions may
be
selected from any of the synthetic or natural oils or mixtures thereof.
Natural oils include
animal oils and vegetable oils (e.g., castor oil, lard oil) as well as mineral
lubricating oils such
as liquid petroleum oils and solvent treated or acid-treated mineral
lubricating oils of the
paraffmic, naphthenic or mixed paraffinic-naphthenic types. Oils derived from
coal or shale
are also suitable. T'he base oil typically has a viscosity of about 2 to about
15 cSt or, as a
further example, about 2 to about 10 cSt at 100° C. Further, gas-to-
liquid stocks are also
suitable.
The synthetic base oils include alkyl esters of dicarboxylic acids,
polyglycols; and
alcohols, poly-alpha-olefins, including polybutenes, alkyl benzenes, organic
esters of
phosphoric acids, and polysilicone oils. Synthetic oils include hydrocarbon
oils such as
polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes,
propylene
isobutylene copolymers, etc.); poly(1-hexenes), poly-(1-octenes), poly(1-
decenes), etc. and
mixtures thereof; alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, di-
nonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g., biphenyls,
terphenyl,
alkylated polyphenyls, etc.); alkylated diphenyl ethers and alkylated diphenyl
sulfides and the
derivatives, analogs and homologs thereof and the like.
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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 that may be used. Such oils 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., methyl-polyisopropylene glycol ether
having an
average molecular weight of about 1000, diphenyl ether of polyethylene glycol
having a
molecular weight of about 500-1000, diethyl ether of polypropylene glycol
having a
molecular weight of about 1000-1500, etc.) or mono- and polycarboxylic esters
thereof, for
example, the acetic acid esters, mixed C3_8 fatty acid esters, or the Ci3 Oxo
acid diester of
tetraethylene glycol.
Another class of synthetic oils that may be used includes the esters of
dicarboxylic
acids (e.g., phthalic acid, succinic acid, alkyl succinic acids, alkenyl
succinic acids, malefic
acid, azelaic acid, suberic acid, sebacic acid, fiunaric acid, adipic acid,
linoleic acid dimer,
malonic acid, alkyl malonic acids, 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-n-hexyl fumarate,
dioctyl sebacate,
diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate,
dieicosyl 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.
Esters useful as synthetic oils also include those made from CS to C,2
monocarboxylic
acids and polyols and polyol ethers such as neopentyl glycol, trimethylol
propane,
pentaerythritoI, dipentaerythritol, tripentaerythritol, etc.
Hence, the base oil used which may be used to make the transmission fluid
compositions as described herein may be selected from any of the base oils in
Groups I-V as
specified in the American Petroleum Institute (API) Base Oil
Interchangeability Guidelines.
Such base oil groups are as follows:
ase Oil Group ulfur (wt%) Saturates (wt%) Viscosity Index
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roup I 0.03 d/or 90 0 to 120
roup II 0.03 d 90 0 to I20
roup III 0.03 d 90 120
roup IV 11 polyalphaolefins
(PAOs)
roup V 1 others
not included
in Groups
I-IV
' Groups I-III are mineral oil base stocks.
As set forth above, the base oil may be a poly-alpha-olefin (PAO). Typically,
the
poly-alpha-olefins are derived from monomers having from about 4 to about 30,
or from
about 4 to about 20, or from about 6 to about 16 carbon atoms. Examples of
useful PAOs
include those derived from octene, decene, mixtures thereof, and the like.
PAOs may have a
viscosity of from about 2 to about 1 S, or from about 3 to about 12, or from
about 4 to about 8
cSt at 100° C. Examples of PAOs include 4 cSt at 100° C poly-
alpha-olefins, 6 cSt at 100° C
poly-alpha-olefins, and mixtures thereof. Mixtures of mineral oil with the
foregoing poly-
alpha-olefins may be used.
The base oil may be an oil derived from Fischer-Tropsch synthesized
hydrocarbons.
Fischer-Tropsch synthesized hydrocarbons are made from synthesis gas
containing H2 and
CO using a Fischer-Tropsch catalyst. Such hydrocarbons typically require
further processing
in order to be useful as the base oil. For example, the hydrocarbons may be
hydroisomerized
using processes disclosed in U.S. Pat. Nos. 6,103,099 or 6,180,575;
hydrocracked and
hydroisomerized using processes disclosed in U.S. Pat. Nos. 4,943,672 or
6,096,940;
dewaxed using processes disclosed in U.S. Pat. No. 5,882,505; or
hydroisomerized and
dewaxed using processes disclosed in U.S. Pat. Nos. 6,013,171; 6,480,301; or
6,165,949.
Unrefined, refined and rerefmed oils, either natural or synthetic (as well as
mixtures of
two or more of any of these) of the type disclosed hereinabove can be used in
the base oils.
Unrefined oils are those obtained directly from a natural or synthetic source
without further
purification treatment. For example, a shale oil obtained directly from
retorting operations, a
petroleum oil obtained directly from primary distillation or ester oil
obtained directly from an
esterification process and used without further treatment would be an
unrefined oil. Refined
oils are similar to the unrefined oils except they have been further treated
in one or more
purification steps to improve one or more properties. Many such purification
techniques are
CA 02491823 2005-O1-10
known to those skilled in the art such as solvent extraction, secondary
distillation, acid or base
extraction, filtration, percolation, etc. Rerefined oils are obtained by
processes similar to
those used to obtain refined oils applied to refined oils which have been
already used in
service. Such rerefined oils are also known as reclaimed or reprocessed oils
and often are
additionally processed by techniques directed to removal of spent additives,
contaminants,
and oil breakdown products.
The base oil may be combined with an additive composition as disclosed in
embodiments herein to provide a power transmission fluid. The base oil may be
present in the
power transmission fluid in an amount from about 50 wt% to about 95 wt %.
Other Optional Components
The power transmission fluid may also include conventional additives of the
type used
in automatic transmission fluid formulations in addition to the components
described above.
Such additives include, but are not limited to, ashless dispersants, friction
modifiers,
antioxidants, extreme pressure additives, corrosion inhibitors, antiwear
additives, antirust
additives, metal deactivators, antifoamants, pour point depressants, air
entrainment additives,
metallic detergents, and/or additional seal swell agents.
Additives used in formulating the compositions described herein can be blended
into
the base oil individually or in various sub-combinations. However, it is
suitable to blend all
of the components concurrently using an additive concentrate (i.e., additives
plus a diluent,
such as a hydrocarbon solvent). The use of an additive concentrate takes
advantage of the
mutual compatibility afforded by the combination of ingredients when in the
form of an
additive concentrate simulates actual plant blending conditions. Also, the use
of a concentrate
reduces blending time and lessens the possibility of blending errors.
The power transmission fluids disclosed herein may include fluids suitable for
any
power transmitting application, such as a step automatic transmission, having
from about 3 to
about 7 speeds, or a manual transmission. Further, the power transmission
fluids of the
present disclosure are suitable for use in transmissions with a slipping
torque converter, a
lock-up torque converter, a starting clutch, and/or one or more shifting
clutches. Such
transmissions include three-, four-, five-, six-, and seven-speed
transmissions, and
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continuously variable transmissions (chain, belt, or disk type). They may also
be used in
manual transmissions, including automated manual and dual-clutch
transmissions.
EXAMPLES
Fluids tested in the following examples included the following components
prepared
in the proportions disclosed below. Components that were varied are discussed
with respect
to each example below. Unless otherwise specified tested samples were
identical except for
varied components.
Example 2 Example 2
Component type Proportion in Proportion in
Finished Finished
FIuid, wt% Fluid, wt%
Antioxidants 0.1- 2.5 0.2 - 0.5
Rust lrihibitors 0 - 0.2 0 - 0.06
Thiadiazole 0 - 2.0 0.01 - 0.6
Antifoam agents 0 -1.5 0.05 - 0.20
Friction Modifiers 0 - 5.0 0.005 - 0.25
Dispersant 0 -10 1 - 5%
Seal Swell Agents 0 - 20 0 -10
Polymethacrylate viscosity
0.5-30 3-25
index improver
Basestock 60 - 90 60 - 90
Diluent Oil 0 - 20 2 - S
EXAMPLE 1
Two transmission fluid formulations were tested and evaluated for
effectiveness in
reducing shudder. Each fluid had identical concentrations of supplemental
additives and
differed only in the types of viscosity index improver.
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A polymethacrylate non-dispersant viscosity index improver was used in Formula
A at
a concentration of 5.13 wt%, and a viscosity index improver with dispersant
functionality was
used in Formula B at a concentration of 5.13 wt%.
As shown in Figures 1 and 2, the two automatic transmission fluids were
subjected to
shudder testing by evaluating friction characteristics using the ZF GK rig.
This test was
developed by ZF to measure a slip-controlled clutch's opening and closing
performance. An
interchangeable intermediate shaft allows the measurement of frictional
vibration that is the
basis for evaluation of "green" or initial shudder characteristics of the test
fluid. The Green
Shudder portion of the "GVRK-Kurztest CFT23" consists of a torque controlled
continuous
slip module, containing three 20-minute sections. The entire sequence
encompasses 60
minutes of test time. During each 20-minute section, force is proportional to
both slip speed
and output torque. The result is a 0.345 m/s (50.0 rpm) constant clutch speed,
with variable
force to control 100Nm of output torque, which is also constant. Each 20-
minute section is
analyzed for torque variation. Due to the 1000 Hz speed data acquisition,
shudder can be
depicted. A 1-minute stabilization period takes place between each continuous
slip section.
Test fluid temperature is controlled at 120°C.
Measurements in Figures 1 and 2 are displayed as torque over the function of
time.
The variation in torque measurements is indicative of shudder. Fluids without
shudder will
display constant torque over time. Fluids with shudder will display varying
torque over time.
Shudder tests were run with a polymethacrylate non-dispersant viscosity index
improver fluid (Formula A) in Figure 1 and a dispersant viscosity index
improver (Formula
B) in Figure 2. The green shudder characteristics of Formula A in Figure 1
show a reduction
in green shudder associated with the incorporation of a non-dispersant
viscosity index
improver. The results using Formula A demonstrate no green shudder, as
evidenced by
constant torque over time. The results using Formula B demonstrate varying
torque over time
which is indicative of green shudder.
EXAMPLE 2
The incorporation of a non-dispersant viscosity index improver in a
lubricating fluid
was tested for compatibility by representative elastomeric component. The
component tested
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was a hose composed of a chlorinated polyethylene. Table 1 demonstrates the
results
obtained from the testing of several power transmission fluid with the
chlorinated
polyethylene hose. The performance was determined by the tensile strength and
the
elongation of the hose at the end of the test, with a more positive number
indicating better
performance. Sample 1 did not contain any of non-dispersant viscosity index
improver,
dispersant viscosity index improver, or seal swell agent. Sample 2 contained
an equal amount
of a non-dispersant viscosity index improver and a dispersant viscosity index
improver.
Sample 3 contained an equal amount of a non-dispersant viscosity index
improver and a
dispersant viscosity index improver and additionally a seal swell agent.
Sample 4 contained a
non-dispersant viscosity index improver and a seal swell agent. All other
components in the
fluids tested were identical.
Table 1.
Sample 1 Sample Sample 3 Sample
2 4
Non-dispersant
viscosity index 0.00 5.80 5.80 10.80
improver, wt%
Dispersant viscosity
indez improver, 0.00 5.80 5.80 0.00
wt%
Seal Swell Agent,
0.00 0.00 0.40 0.60
wt%
Tensile Strength,-55.07 -52.22 -51.89 -41.89
%
Elongation, % -74 -77.74 -73.19 -68.48
The results shown in Table I show that Sample 4, which contained non-
dispersant
viscosity index improver, demonstrated superior tensile strength compared to
samples having
less or no non-dispersant viscosity index improver. Furthermore, the
incorporation of a seal
swell agent to Samples 3 and 4 did not provide a significant benefit. Notably,
the benefit
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achieved through the use of solely the non-dispersant viscosity index improver
greatly
exceeded that achieved by the mixed formulation with or without the seal swell
agent.
At numerous places throughout this specification, reference has been made to a
number of U.S. Patents. All such cited documents are expressly incorporated in
full into this
disclosure as if fully set forth herein.
Other embodiments will be apparent to those skilled in the art from
consideration of
the specification and practice of the invention disclosed herein. As used
throughout the
specification and claims, "a" and/or "an" may refer to one or more than one.
Unless
otherwise indicated, all numbers expressing quantities of ingredients,
properties such as
molecular weight, percent, ratio, reaction conditions, and so forth used in
the specification and
claims are to be understood as being modified in all instances by the term
"about."
Accordingly, unless indicated to the contrary, the numerical parameters set
forth in the
specification and claims are approximations that may vary depending upon the
desired
properties sought to be obtained by the present invention. At the very least,
and not as an
attempt to limit the application of the doctrine of equivalents to the scope
of the claims, each
numerical parameter should at least be construed in light of the number of
reported significant
digits and by applying ordinary rounding techniques. Notwithstanding that the
numerical
ranges and parameters setting forth the broad scope of the invention are
approximations, the
numerical values set forth in the specific examples are reported as precisely
as possible. Any
numerical value, however, inherently contains certain errors necessarily
resulting from the
standard deviation found in their respective testing measurements. It is
intended that the
specification and examples be considered as exemplary only, with a true scope
and spirit of
the invention being indicated by the following claims.
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