U.S. patent application number 16/207553 was filed with the patent office on 2019-07-04 for lubrication of oxygenated diamond-like carbon surfaces.
The applicant listed for this patent is ExxonMobil Research and Engineering Company. Invention is credited to Aditya JAISHANKAR, Arben JUSUFI, Andrew R. KONICEK, Ko ONODERA, Alan M. SCHILOWITZ.
Application Number | 20190203144 16/207553 |
Document ID | / |
Family ID | 64902410 |
Filed Date | 2019-07-04 |
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United States Patent
Application |
20190203144 |
Kind Code |
A1 |
JUSUFI; Arben ; et
al. |
July 4, 2019 |
LUBRICATION OF OXYGENATED DIAMOND-LIKE CARBON SURFACES
Abstract
Methods are provided for lubricating oxygenated diamond-like
carbon surfaces to reduce friction while reducing or minimizing
wear on the surface. A diamond-like carbon surface layer having a
surface ratio of oxygen to carbon of 1:15 or more can be lubricated
using a lubricant oil that includes a molybdenum-based friction
modifier additive, a tungsten-based friction modifier additive, or
a combination thereof. The Mo-based friction modifier (and/or other
friction modifier based on a Group VI metal) can be selected based
on the Gibbs free energy of adsorption (.DELTA.G) for the friction
modifier on an oxygenated diamond-like carbon surface. Use of a
Group VI metal-based friction modifier having a .DELTA.G of
adsorption with a sufficiently large magnitude can reduce friction
at the surface of the oxygenated diamond-like carbon while causing
a reduced or minimized amount of wear during lubrication.
Inventors: |
JUSUFI; Arben; (Belle Mead,
NJ) ; SCHILOWITZ; Alan M.; (Highland Park, NJ)
; JAISHANKAR; Aditya; (Clinton, NJ) ; KONICEK;
Andrew R.; (Whitehouse Station, NJ) ; ONODERA;
Ko; (Yokohama, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Research and Engineering Company |
Annandale |
NJ |
US |
|
|
Family ID: |
64902410 |
Appl. No.: |
16/207553 |
Filed: |
December 3, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62611572 |
Dec 29, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2203/003 20130101;
C10N 2030/06 20130101; C10N 2020/06 20130101; C10M 135/18 20130101;
C10M 2223/045 20130101; C10N 2060/04 20130101; C10M 2227/066
20130101; C10N 2050/02 20130101; C10M 139/00 20130101; C10M 137/10
20130101; C10N 2030/56 20200501; C10M 169/04 20130101; C10N 2010/12
20130101; C10M 2219/068 20130101 |
International
Class: |
C10M 137/10 20060101
C10M137/10; C10M 135/18 20060101 C10M135/18; C10M 169/04 20060101
C10M169/04 |
Claims
1. A method for lubricating a machine surface comprising: supplying
a lubricant comprising a Group VI metal-containing friction
modifier to a surface layer comprising diamond-like carbon with a
surface oxygen to carbon ratio of 1:15 or more, the lubricant
comprising 0.05 wt % to 0.2 wt % of the Group VI metal-containing
friction modifier, the Group VI metal-containing friction modifier
comprising a .DELTA.G of adsorption on the diamond like carbon of
-25 kJ/mol or less.
2. The method of claim 1, wherein the surface oxygen to carbon
ratio is 1:10 or more.
3. The method of any of claim 1, wherein the surface oxygen to
carbon ratio comprises a top 0.7 nm at the surface of the
diamond-like carbon.
4. The method of claim 1, wherein the diamond-like carbon comprises
borated diamond-like carbon.
5. The method of claim 4, wherein the borated diamond-like carbon
comprises a ratio of boron to carbon of 0.5:100 or more.
6. The method of claim 1, wherein the surface oxygen to carbon
ratio is 1:10 or more.
7. The method of claim 1, wherein the diamond-like carbon comprises
15 mole % or more of hydrogen.
8. The method of claim 1, wherein the lubricant comprises 50 wppm
or more of Group VI metal.
9. The method of claim 1, wherein the Group VI metal-containing
friction modifier further comprises a polar site diameter of 7.0
Angstroms or more.
10. The method of claim 1, wherein the Group VI metal-containing
friction modifier comprises an Mo-containing friction modifier.
11. The method of claim 10, wherein the lubricant comprises 50 wppm
or more of Mo.
12. The method of claim 1, wherein the friction modifier comprises
MoDTP, [Mo.sub.3S.sub.4](dtc).sub.2, a trinuclear molybdenum
compound, or a combination thereof.
13. The method of claim 1, wherein the surface layer comprising
diamond-like carbon comprises a layer depth of 2.0 .mu.m or more of
diamond-like carbon.
14. The method of claim 1, wherein the lubricant further comprises
a friction coefficient of 0.06 or less.
15. The method of claim 1, wherein the lubricant is supplied to a
surface layer positioned in opposition to a steel surface
layer.
16. The method of any of claim 1, wherein a ratio of sp.sup.2 to
sp.sup.3 hybridized carbons in the diamond-like carbon is 0.5 to
2.5.
17. A method for lubricating a machine surface comprising,
supplying a lubricant comprising a Group VI metal-containing
friction modifier, to a surface layer comprising diamond-like
carbon with a surface oxygen to carbon ratio of 1:15 or more, the
lubricant comprising 0.05 wt % to 0.2 wt % of the Group VI
metal-containing friction modifier, the Group VI metal-containing
friction modifier comprising a polar site diameter of 5.0 Angstroms
or more and a .DELTA.G of adsorption of -25 kJ/mol or less.
18. The method of claim 17, wherein the Group VI metal-containing
friction modifier further comprises a polar site diameter of 7.0
Angstroms or more.
19. The method of claim 17, wherein the diamond-like carbon
comprises borated diamond-like carbon, or wherein the diamond-like
carbon comprises a surface oxygen to carbon ratio of 1:10 or more,
or a combination thereof.
20. The method of claim 17, wherein the Group VI metal-containing
friction modifier comprises an Mo-containing friction modifier, the
lubricant comprising 50 wppm or more of Mo.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/611,572, filed on Dec. 29, 2017, the entire
contents of which are incorporated herein by reference.
FIELD
[0002] This disclosure relates to methods for reducing friction
and/or wear during lubrication of diamond-like carbon surfaces.
BACKGROUND
[0003] Diamond-like carbon (DLC) and other new coating materials
are growing in importance. Thin layers of these advanced materials
are being used to enhance the friction and wear properties of
materials in engines and other operating equipment. For example,
DLC can provide a beneficial combination of a high hardness value
while also having a low friction coefficient. The ability to
lubricate these materials is an important factor for future
lubricants.
[0004] Unfortunately, providing a lubricant for lubrication of
diamond-like carbon surfaces can pose several challenges. Some
types of friction modifiers are not effective for reducing friction
at DLC surfaces. Other friction modifiers used in conventional
lubricant formulations can have a tendency to cause wear at
undesirable rates on DLC surfaces. In particular, it is
conventionally understood that molybdenum-based friction modifiers
are suitable for reducing friction at DLC surfaces, but that such
molybdenum-based friction modifiers also cause wear at a rate that
is not commercially desirable.
[0005] U.S. Pat. No. 8,846,590 describes methods for lubricating
DLC surfaces using a lubricating oil that contains an oil-soluble
organo-molybdenum compound selected from compounds that include a
variety of ligands. Various types of DLC surfaces are discussed,
including surfaces containing substantial amounts of hydrogen, but
oxygen is not mentioned as a potential element on the surface. The
reference describes that molybdenum friction reducers can be
effective for reducing friction at DLC surfaces, but no discussion
is provided regarding wear.
[0006] Various literature references describe the deleterious
effects of molybdenum friction modifiers on diamond like carbon
surfaces. Examples of such literature references include T.
Shinyoshi, Y. Fuwa and Y Ozaki, Wear analysis of DLC coating in oil
containing Mo-DTC, Japan Society of Automotive Engineers, 20077103,
(2007) pp. 956; and S. Kosarieh, A. Morina, E. Laine, J. Flemming
and A. Neville, The effect of molybdenum dithiocarbamate
(MoDTC)-type friction modifier on the wear performance of a
hydrogenated DLC coating, Wear, 302 (2013) pp. 890. Based on this
recognized difficulty of excessive wear when using Mo-containing
friction reducers on DLC surfaces, improved methods for lubricating
DLC surfaces while reducing or minimizing surface wear without the
use of other additives, such as zinc dialkyl dithiophosphate (ZDDP)
to mitigate DLC wear, are needed.
SUMMARY
[0007] In various aspects, a method for lubricating a machine
surface is provided. The method can include supplying a lubricant
comprising a Group VI metal-containing friction modifier to a
surface layer comprising diamond-like carbon with a surface oxygen
to carbon ratio of 1:15 or more. The lubricant can include 0.05 wt
% to 0.2 wt % of the Group VI metal-containing friction modifier.
The Group VI metal-containing friction modifier can have a .DELTA.G
of adsorption on the diamond-like carbon of -25 kJ/mol or less.
Examples of Group VI metal-containing friction modifiers can
include Mo-containing friction modifiers, such as molybdenum
dithiophosphate (MoDTP) and/or friction modifiers including a
trinuclear molybdenum core. The amount of Mo (or other Group VI
metal) in the lubricant can be 50 wppm or more. In some aspects,
the Group VI metal-containing friction modifier can have a polar
site diameter of 5.0 Angstroms or more, or 7.0 Angstroms or
more.
[0008] In some aspects, the diamond-like carbon can correspond to
borated diamond-like carbon where the ratio of boron to carbon is
0.5:100 or more. Additionally or alternately, the diamond-like
carbon can have a surface oxygen to carbon ratio of 1:10 or more.
The depth for determining the surface oxygen to carbon ratio can
correspond to the top 1.0 nm of the surface, or optionally the top
0.7 nm. In some aspects, the diamond-like carbon can have a ratio
of sp.sup.2 to sp.sup.3 hybridized carbons in the diamond-like
carbon of 0.5 to 2.5, or 0.7 to 1.5.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows X-ray photoelectron spectroscopy (XPS) data for
oxygen concentration relative to sputtering depth for a borated and
oxygenated diamond-like carbon surface.
[0010] FIG. 2 shows XPS data for carbon concentration relative to
sputtering depth for a borated and oxygenated diamond-like carbon
surface.
[0011] FIG. 3 shows adsorption isotherms for MoDTP on various
surfaces.
[0012] FIG. 4 shows adsorption isotherms for a trinuclear
molybdenum compound made up of an Mo.sub.3S.sub.7 core on various
surfaces.
[0013] FIG. 5 shows adsorption isotherms for MoDTC on various
surfaces.
[0014] FIG. 6 shows friction coefficient and wear depth for a base
formulated lubricant including various friction modifiers.
[0015] FIG. 7 shows the relationship of free energy of adsorption
versus friction coefficient and wear depth for a base formulated
lubricant including various friction modifiers.
[0016] FIG. 8 shows friction coefficient and wear depth relative to
Mo concentration for a base formulated lubricant including various
friction modifiers.
[0017] FIG. 9 shows adsorption isotherms for a trinuclear
molybdenum compound made up of an Mo.sub.3S.sub.4 core on various
surfaces.
DETAILED DESCRIPTION
[0018] All numerical values within the detailed description and the
claims herein are modified by "about" or "approximately" the
indicated value, and take into account experimental error and
variations that would be expected by a person having ordinary skill
in the art. The phrase "major amount" or "major component" as it
relates to components included within the lubricating oils of the
specification and the claims means greater than or equal to 50 wt.
%, or greater than or equal to 60 wt. %, or greater than or equal
to 70 wt. %, or greater than or equal to 80 wt. %, or greater than
or equal to 90 wt. % based on the total weight of the lubricating
oil. The phrase "minor amount" or "minor component" as it relates
to components included within the lubricating oils of the
specification and the claims means less than 50 wt. %, or less than
or equal to 40 wt. %, or less than or equal to 30 wt. %, or greater
than or equal to 20 wt. %, or less than or equal to 10 wt. %, or
less than or equal to 5 wt. %, or less than or equal to 2 wt. %, or
less than or equal to 1 wt. %, based on the total weight of the
lubricating oil. The phrase "essentially free" as it relates to
components included within the lubricating oils of the
specification and the claims means that the particular component is
at 0 weight % within the lubricating oil, or alternatively is at
impurity type levels within the lubricating oil (less than 100 ppm,
or less than 20 ppm, or less than 10 ppm, or less than 1 ppm). The
phrase "other lubricating oil additives" as used in the
specification and the claims means other lubricating oil additives
that are not specifically recited in the particular section of the
specification or the claims. For example, other lubricating oil
additives may include, but are not limited to, antioxidants,
detergents, dispersants, antiwear additives, corrosion inhibitors,
viscosity modifiers, metal passivators, pour point depressants,
seal compatibility agents, antifoam agents, extreme pressure
agents, friction modifiers and combinations thereof.
[0019] In various aspects, methods are provided for lubricating
oxygenated diamond-like carbon surfaces to reduce friction while
reducing or minimizing wear on the surface. A diamond-like carbon
surface layer having a surface ratio of oxygen to carbon of 1:15 or
more can be lubricated using a lubricant oil that includes a
molybdenum-based friction modifier additive, a tungsten-based
friction modifier additive, or a combination thereof. The Mo-based
friction modifier (and/or other friction modifier based on a Group
VI metal) can be selected based on the Gibbs free energy of
adsorption (.DELTA.G) for the friction modifier on an oxygenated
diamond-like carbon surface. Optionally, the Mo-based friction
modifier can further be selected based on a characteristic diameter
associated with the Mo-based compound, such as a molecular diameter
and/or a polar diameter. Use of a Mo-based friction modifier
(and/or other friction modifier based on a Group VI metal) having a
sufficiently low .DELTA.G of adsorption can reduce friction at the
surface of the oxygenated diamond-like carbon while causing a
reduced or minimized amount of wear during lubrication. In some
aspects, a sufficiently low .DELTA.G of adsorption value can
correspond to -25 kJ/mol or less, or -28 kJ/mol or less, or -30
kJ/mol or less.
[0020] Diamond-like carbon is a potentially valuable type of
coating for surfaces where having a high hardness, low friction
material is desirable. The friction coefficient of diamond-like
carbon without lubrication can be relatively low depending on
conditions, corresponding to about 0.16 or less. However,
attempting to further reduce this friction coefficient using a
lubricant can be challenging. Some challenges are due to
conventional friction modifiers that simply do not provide a
benefit on diamond-like carbon surfaces. For example, stearic acid
is a known organic friction modifier used in lubricating oils for
lubrication of steel surfaces and/or other surfaces. Unfortunately,
stearic acid provides little or no reduction of the friction
coefficient for diamond-like carbon. Without being bound by any
particular theory, this is believed to be due to the fact that
stearic acid has a low affinity for adsorption on a diamond-like
carbon surface. This was determined based on attempts to
characterize a Gibbs free energy of adsorption (.DELTA.G) of
stearic acid on to a diamond-like carbon surface. It was determined
that the the absolute value of .DELTA.G for stearic acid adsorbing
to the diamond-like carbon surface or the surface coverage was too
small to measure.
[0021] Other challenges can be related to increased wear of a
diamond-like carbon surface in the presence of certain friction
modifiers. In particular, it is conventionally understood that
Mo-based friction modifiers can cause wear on a diamond-like carbon
surface at an undesirable rate.
[0022] It has been discovered that the difficulties related to
increased wear for Mo-based friction modifiers (and/or other Group
VI metal-based friction modifiers) can be reduced or minimized for
diamond-like carbon surfaces that are oxygenated diamond-like
carbon surfaces. For such oxygenated diamond-like carbon surfaces,
Mo-based friction modifiers that have a sufficiently negative free
energy of adsorption (.DELTA.G) can be used to reduce the friction
coefficient of the surface while reducing or minimizing the amount
of wear. The free energy of adsorption (.DELTA.G) can represent an
amount of affinity of a compound for a surface. Adsorption of a
molecule to a surface corresponds to a loss of one or more degrees
of freedom of motion, and therefore it might be expected that
adsorption of a molecule to a surface corresponds to a loss of
entropy. In order to have a desirable .DELTA.G value for adsorption
to a given type of surface, the enthalpy of adsorption (.DELTA.H)
has to be sufficiently negative to overcome any decrease in entropy
(.DELTA.S) caused by the adsorption. It has been discovered that
Mo-based friction modifiers (or other friction modifiers based on a
Group VI metal) with a .DELTA.G value for adsorption of roughly -25
kJ/mol or lower, or -28 kJ/mol or lower, or -30 kJ/mol or lower,
can reduce the friction coefficient of a diamond-like carbon
surface without causing an undesirable level of surface wear.
[0023] The discovery that the free energy of adsorption is related
to reducing or minimizing wear on oxygenated DLC surfaces is
unexpected. The unexpected nature of this discovery is reinforced
because the Mo-containing friction modifiers that have a desirable
free energy of adsorption are different from the compounds that
would be expected to reduce or minimize wear based on other
factors. For example, without being bound by any particular theory,
one of skill in the art would conventionally expect that the
ability to reduce or minimize wear on a surface would be correlated
with the ability of a friction modifier to produce an increased
amount of surface coverage, such as covering an increased amount of
the surface with MoS.sub.2. It has been discovered that for
oxygenated diamond-like carbon surfaces, the MoS.sub.2 surface
coverage does not correlate with reducing or minimizing wear.
Instead, it has been unexpectedly discovered that friction
modifiers with a sufficiently negative free energy of adsorption
can result in reduced or minimized wear on a surface.
[0024] Additionally or alternately, suitable Group VI metal-based
friction modifiers for oxygenated diamond-like carbon surfaces can
also have a sufficiently large diameter. Without being bound by any
particular theory, it is believed that the adsorption of Group VI
metal-based friction modifiers to an oxygenated diamond-like carbon
surface is based in part on adsorption related to oxygen sites on
the surface. A friction modifier with a sufficiently large diameter
can have a sufficient size to bridge the distance between oxygen
sites on the surface. This can potentially correspond to a
sufficiently large molecular diameter and/or a sufficiently large
polar diameter.
Definitions
[0025] Free Energy of Adsorption (.DELTA.G)--In this discussion,
various Mo-based friction modifier additives (as well as other
friction modifier additives) were characterized based on adsorption
of the friction modifier to an oxygenated diamond-like carbon
surface. In various aspects, an adsorption isotherm can be
determined for a friction modifier on an oxygenated diamond-like
carbon surface. The oxygenated diamond-like carbon surface used for
determining the adsorption isotherm can have an oxygen to carbon
molar ratio of between 1:10 and 1:8.
[0026] Quartz Crystal Microbalance (QCM) experiments were performed
on a commercially-available instrument from Biolin Scientific
(QSense QCM-D, E4 flow cells). Hydrocarbon-resistant Kalrez o-rings
and seals were used in the flow cells. The injection flow-rate was
maintained at 150 uL/min using a peristaltic pump (Cole-Palmer).
Solvent-resistant PVC solva tubing (Cole Palmer) was chosen for the
peristaltic pump. Teflon inlet tubing and fittings were used as far
as possible. The quartz sensors (Biolin Scientific) were coated
with the material of interest. For example, diamond-like coatings
of various types and thicknesses can be applied in the normal
coating process used to apply them. Prior to experiments, the
sensors were thoroughly cleaned in ethanol, toluene and heptane,
and the flow modules were oxygen plasma cleaned for 30 seconds to
remove any residual organic matter. During measurements, the pure
solvent was first injected for 18-20 hours to allow the sensor to
stabilize and to determine the solvent contribution to the total
frequency shift. Subsequently, the additive blends were injected
and the total frequency shift measured, until adsorption
equilibrium was reached. The experiments were done in a flow-loop;
the volume of solution looped through the flow cells was ensured to
be large enough so that any additive lost from the blends arising
from surface adsorption made a negligible change in bulk
concentration. In this discussion and the claims, determination of
.DELTA.G values is performed using a QCM with a diamond-like
coating applied to the quartz sensor. The diamond-like coating
should be representative of how the material would be applied in
the corresponding target application for the diamond-like
carbon.
[0027] QCM measurements were performed at different additive bulk
concentrations to generate an adsorption isotherm. The
Braun-Emmett-Teller (BET) adsorption isotherm model was then
applied to the surface coverage vs. bulk concentration data to
determine the free energy of adsorption of the first adsorbed
layer, the free energy of adsorption of subsequent layers and the
maximum surface coverage. These quantities are fitting parameters
that can be obtained using a least squares fit of the model to the
data. For monolayer adsorption, the BET isotherm simplifies to the
Langmuir adsorption isotherm. In the case of multilayer adsorption,
the BET model provides two values of free energy of adsorption--one
corresponding to the first layer, and one corresponding to each
subsequent multilayer. It is the free energy corresponding to
adsorption of the first layer which is reported here and is used
for measuring friction efficacy on oxygenated diamond like carbon.
For most data the Langmuir and BET isotherms give similar results
for delta G.
[0028] Molecular Diameter is equal to two times the Molecular
Radius. In this discussion, molecular radius, R, is defined as the
average distance of all atoms in the molecule with respect to the
configurational center of the molecule (not mass weighted).
Molecular radius can be calculated by any convenient method, such
as based on published values or using commercial molecular modeling
tools.
[0029] Polar Site Diameter--The calculation for the polar site
diameter, 2R.sub.p, is similar to that of Molecular Diameter but
only accounts for the polar atoms within the friction modifier. For
determination of the polar diameter of a friction modifier, polar
atoms are defined as a) transition metals, b) phosphorus atoms, and
c) non-carbon and non-hydrogen atoms that have a bond to an atom
different from carbon and hydrogen. It is noted that the molecular
diameter of a minimized energy configuration for a molecule may be
different from the time-averaged value, and may also depend on
solvent effects. The polar site diameter is expected to have a
lower variation than molecular diameter with respect to such
factors. In some aspects, the polar site diameter of a
Mo-containing friction modifier can be 7.0 Angstroms or more, or
7.2 Angstroms or more.
[0030] Wear--In this discussion, the amount of wear at an
oxygenated diamond-like carbon surface can be determined by the
following method. Reciprocating sliding tests were conducted using
a High Frequency Reciprocating Rig (HFRR) (PCS Instruments)
ball-on-flat tribometer. Operating conditions were 50 Hz frequency,
100 g load, 50.degree. C. oil bath temperature, 2.0 mm stroke
length, and total test duration of 2 hours. The ball was held in a
fixed position by a set screw to prevent rolling. Lubricant
temperatures were equilibrated for 15 minutes before sliding began.
The ball and disk were standard 52100 bearing steel, with nominal
hardness values of 200 HV30 for the disk and 58-66 Rockwell C
hardness for the ball. In order to evaluate friction and wear on
diamond like carbon, disks were modified by depositing a coating of
diamond like carbon. In all cases the balls were used as supplied
without application of an additional surface coating.
[0031] Wear on the HFRR disk at end of test was quantified by
making linear height profiles across the width of the wear scar in
three different locations. Profiles were made using a stylus
profilometer (Veeco Dektak 150). The reported depth of the wear
scar was quantified by averaging the lowest point in the center of
the three line scans. In the claims, wear depth values correspond
to wear depth values measured using a stylus profilometer. Reported
friction is the average friction over the last 30 minutes of the
test.
[0032] In some examples described herein, friction and wear were
also measured with a Falex block on ring (LFW-1) machine with a
load of 294N (Hertzian contact pressure of about 300 MPa), a
sliding velocity of 0.3 m/s, an oil temperature of 80 C, and a
sliding duration of 30 min. The lowest friction coefficients during
test are reported. The ring was SAE4620 steel while the block was
steel coated with BDLC. In such examples, wear depth values were
determined using an optical profilometer. The wear depths were
measured at three points (center and two near edges) on the linear
wear scar with SURFTEST SV-3200 (manufactured by Mitsutoyo). The
three wear measurements are averaged. The optical values are
believed to be comparable to wear depth values that would be
obtained using a stylus profilometer.
[0033] Diamond-like carbon is an amorphous carbon material that can
provide some physical properties that are similar to diamond. The
physical properties can include providing a high hardness value,
such as a hardness value of 2 GPa or more, while also having a low
friction coefficient, such as a friction coefficient of 0.16 or
less prior to exposure to friction modifiers in a lubricating oil.
This combination of physical properties can potentially be
beneficial for use of diamond-like carbon layers in various machine
or tool applications. Without being bound by any particular theory,
it is believed that the beneficial combination of properties in
diamond-like carbon is due in part to combination of carbon atoms
that participate in both a diamond like tetrahedral bonding network
(sp.sup.3 type bonding) and a graphitic (sp.sup.2 type bonding)
network. In this discussion diamond-like carbon is defined as an
amorphous material that has a hardness value of 2 GPa or more and a
hydrogen content of 10 mole % or more. In some aspects, the
hydrogen content can be 15 mole % or more, or 20 mole % or more,
such as up to 40 mole % or possibly still higher. Such a material
can have 60 mole % or more (or 75% or more) of carbon atoms
relative to the total atoms in the amorphous material aside from
hydrogen. For such a material, the ratio of sp.sup.2 carbon atoms
to sp.sup.3 hybridized carbon atoms can be between 0.5 and 2.5, or
between 0.7 and 1.5. Such an amorphous material can be present, for
example, as a coating layer on another surface. Diamond-like carbon
can be in contrast to tetrahedral amorphous carbon, which has a
hydrogen content of 10 mole % or less. In some aspects, a
diamond-like carbon layer can have a layer depth of 2.0 .mu.m or
more.
[0034] Another type of element that can be included in diamond-like
carbon is oxygen. In various aspects, oxygenated diamond-like
carbon can correspond to diamond-like carbon that includes a
surface ratio of oxygen to carbon of 1:15 or more, such as 1:10 or
more, or 1:8 or more, such as up to 1:5 or possibly still higher.
Unless otherwise specified, this surface ratio can correspond to
the ratio of oxygen to carbon in the top 1.0 nm at the surface. In
some optional aspects, the surface ratio of 1:15 or more, or 1:10
or more, can correspond to the top 0.7 nm at the surface. Having a
surface ratio of oxygen to carbon of 1:15 or more can be beneficial
for providing adsorption locations for an Mo-based friction
modifier (or other Group VI metal-based friction modifier) to
adsorb to during adsorption. In some aspects, the ratio of oxygen
to carbon deeper in a diamond-like carbon layer, such as at 5 nm or
more, or 2 nm or more, can be lower than the surface ratio. In such
aspects, the ratio of oxygen to carbon deeper in the layer can be 1
20 or less, or 1:30 or less, or 1:40 or less.
[0035] In some aspects, an oxygenated diamond-like carbon can
correspond to a borated and oxygenated diamond-like carbon layer.
Without being bound by any particular theory, it is believed that
boron can be beneficial for allowing additional oxygen to be
incorporated into the surface of a diamond-like carbon layer. In
some aspects, the ratio of boron atoms to carbon atoms in a borated
diamond-like carbon layer can be 0.5:100 or more, or 1.0:100 or
more, such as up to 5.0:100 or possibly still higher.
Group VI Metal-Based Friction Reducing Additives
[0036] Molybdenum-based friction modifier additives are known to be
effective as friction reducing additives for diamond-like carbon
surfaces. However, the increased wear that is conventionally
believed to be caused by using Mo-based friction modifiers may make
it difficult to commercially implement such additives. It has been
unexpectedly discovered that using a Mo-based friction modifier
additive with a sufficiently negative free energy of adsorption
(.DELTA.G) can allow for use of a Mo-based friction modifier
additive while reducing or minimizing associated wear of an
oxygenated diamond-like carbon surface. More generally, it has been
unexpectedly discovered that Group VI metal-based friction
modifiers with a sufficiently negative free energy of adsorption
can be used, such as friction modifiers including Mo, W, or a
combination thereof.
[0037] The amount of Group VI metal-based friction modifier
included in a lubricant can correspond to 50 wppm or more of the
Group VI metal, or 100 wppm or more, or 200 wppm or more, or at
least 300 wppm, or at least 500 wppm, or at least 800 wppm, such as
up to 3000 wppm or possibly still higher. Suitable Group VI
metal-based friction modifiers can include commercially available
Mo-containing compounds as well as other Mo-containing compounds
known in the art, such as those described in U.S. Pat. No.
8,846,590.
[0038] One example of a class of suitable Mo-based friction
reducing additives can be additives corresponding to molybdenum
dithiophosphate (MoDTP), which is available commercially as Adeka
Sakura Lube 300. The carbon chain lengths in compounds referred to
as MoDTP can vary, but the specific carbon chain lengths are not
believed to be critical, so long as the MoDTP is soluble in the
lubricating oil. Examples of typical chain lengths for MoDTP can be
from 3 carbons to 30 carbons. By contrast, an example of a class of
Mo-based friction reducing additives that does not have a
sufficiently negative free energy of adsorption is molybdenum
dithiocarbamate (MoDTC) available commercially as Adeka Sakura Lube
515. MoDTC can also have a variety of carbon chain lengths, with
the chain length not being critical so long as the MoDTC is souble
in lubricating oil. On oxygenated borated diamond-like carbon, the
.DELTA.G of adsorption for MoDTC is about -24.6 kJ/mol, while the
.DELTA.G of adsorption for MoDTP is roughly -35 kJ/mol on
oxygenated borated diamond-like carbon.
[0039] Other examples of a Mo-based friction reducing additive with
a sufficiently negative free energy of adsorption on oxygenated
diamond-like carbon can correspond to compounds with a
molybdenum-sulfur core having a stoichiometry of Mo.sub.3S.sub.4.
These Mo.sub.3S.sub.4 compounds can include various ligands for
charge balance. An example of a suitable ligand can be
dithiocarbamate (dtc). An example of a friction modifier with a
Mo.sub.3S.sub.4 core can be
Mo.sub.3S.sub.4[(2-ethylhexyl).sub.2dtc]4. Still other examples of
an Mo-based friction reducing additive with a sufficiently low free
energy of adsorption on oxygenated diamond-like carbon can
correspond to compounds with a molybdenum-sulfur core having a
stoichiometry of Mo.sub.3S.sub.7. In this discussion, these types
of compounds that include a molybdenum-sulfur core containing three
molybdenum atoms are referred to as Mo-trimer compounds or
trinuclear molybdenum compounds. These Mo-trimer
compounds/trinuclear molybdenum compounds can include various
ligands for charge balance. An example of a suitable ligand can be
dithiocarbamate (dtc). An example of one such commercially
available Mo-trimer compound is Infineum C9455B.
[0040] Without being bound by any particular theory, it is
conventionally believed that Mo-containing friction modifiers are
chemically converted to molybdenum sulfide type compounds at a
surface that is being lubricated. One theory regarding the
mechanism of molybdenum and sulfur containing friction modifiers is
that, under lubricating conditions, the rubbing of the friction
modifier between two hard surfaces induces a reaction which
produces MoS.sub.2, a known solid lubricant. One of skill in the
art would therefore assume that performance would be greatest for a
friction modifier which most effectively covered the lubricated
surface with MoS.sub.2. In order to investigate this point the
following tests and analyses were conducted.
[0041] Three molybdenum containing compounds were blended into a
polyalphaolefin-based lubricant at a concentration corresponding to
700 ppm by weight molybdenum and tested in a HFRR test, as further
described herein. The three molybdenum-containing compounds
corresponded to MoDTC, MoDTP, and an Mo-trimer compound. After the
2 hour test the wear scar on the steel disk was analyzed using a
Raman Spectroscopy microscope to determine how much of the wear
scar track was covered by MoS.sub.2 produced by rubbing on the
friction modifier. Based on the Raman spectroscopy measurement, the
MoS.sub.2 coverage for the lubricant containing the Mo-trimer
corresponded to only 67% of the wear scar surface. The MoS.sub.2
coverage for the MoDTC-containing lubricant was roughly 78%, while
the coverage for the MoDTP-containing lubricant was roughly 79%.
Based on this one would predict that MoDTC would have equal
performance to MoDTP and both would perform better than the
Mo-trimer. In contrast to this conventionally expected result, it
has been discovered that wear performance is predicted by free
energy of adsorption and/or by the size of the polar core. Based on
free energy of adsorption, the MoDTC friction modifier results in
undesirable amounts of wear, while the Mo-trimer and MoDTP friction
modifiers can unexpectedly reduce or minimize wear on DLC
surfaces.
Lubricating Oil Base Stocks and Co-Base Stocks
[0042] A wide range of lubricating base oils is known in the art.
Lubricating base oils that are useful in the present disclosure are
natural oils, mineral oils and synthetic oils, and unconventional
oils (or mixtures thereof) can be used unrefined, refined, or
rerefined (the latter is also known as reclaimed or reprocessed
oil). Unrefined oils are those obtained directly from a natural or
synthetic source and used without added purification. These include
shale oil obtained directly from retorting operations, petroleum
oil obtained directly from primary distillation, and ester oil
obtained directly from an esterification process. Refined oils are
similar to the oils discussed for unrefined oils except refined
oils are subjected to one or more purification steps to improve at
least one lubricating oil property. One skilled in the art is
familiar with many purification processes. These processes include
solvent extraction, secondary distillation, acid extraction, base
extraction, filtration, and percolation. Rerefined oils are
obtained by processes analogous to refined oils but using an oil
that has been previously used as a feed stock.
[0043] Groups I, II, III, IV and V are broad base oil stock
categories developed and defined by the American Petroleum
Institute (API Publication 1509; www.API.org) to create guidelines
for lubricant base oils. Group I base stocks have a viscosity index
of between about 80 to 120 and contain greater than about 0.03%
sulfur and/or less than about 90% saturates. Group II base stocks
have a viscosity index of between about 80 to 120, and contain less
than or equal to about 0.03% sulfur and greater than or equal to
about 90% saturates. Group III stocks have a viscosity index
greater than about 120 and contain less than or equal to about
0.03% sulfur and greater than about 90% saturates. Group IV
includes polyalphaolefins (PAO). Group V base stock includes base
stocks not included in Groups I-IV. Table 1 below summarizes
properties of each of these five groups.
TABLE-US-00001 TABLE 1 Properties of Base Oil Groups Base Oil
Properties Saturates Sulfur Viscosity Index Group I <90 and/or
>0.03% and .gtoreq.80 and <120 Group II .gtoreq.90 and
.ltoreq.0.03% and .gtoreq.80 and <120 Group III .gtoreq.90 and
.ltoreq.0.03% and .gtoreq.120 Group IV polyalphaolefins (PAO) Group
V All other base oil stocks not included in Groups I, II, III or
IV
[0044] Natural oils include animal oils, vegetable oils (castor oil
and lard oil, for example), and mineral oils. Animal and vegetable
oils possessing favorable thermal oxidative stability can be used.
Of the natural oils, mineral oils are preferred. Mineral oils vary
widely as to their crude source, for example, as to whether they
are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils
derived from coal or shale are also useful. Natural oils vary also
as to the method used for their production and purification, for
example, their distillation range and whether they are straight run
or cracked, hydrorefined, or solvent extracted.
[0045] Group II and/or Group III hydroprocessed or hydrocracked
base stocks are also well known base stock oils.
[0046] Synthetic oils include hydrocarbon oil. Hydrocarbon oils
include oils such as polymerized and interpolymerized olefins
(polybutylenes, polypropylenes, propylene isobutylene copolymers,
ethylene-olefin copolymers, and ethylene-alphaolefin copolymers,
for example). Polyalphaolefin (PAO) oil base stocks are commonly
used synthetic hydrocarbon oil. By way of example, PAOs derived
from C.sub.8, C.sub.10, C.sub.12, C.sub.14 olefins or mixtures
thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064;
and 4,827,073.
[0047] The number average molecular weights of the PAOs, which are
known materials and generally available on a major commercial scale
from suppliers such as ExxonMobil Chemical Company, Chevron
Phillips Chemical Company, BP, and others, typically vary from
about 250 to about 3,000, although PAO's may be made in viscosities
up to about 150 cSt (100.degree. C.). The PAOs are typically
comprised of relatively low molecular weight hydrogenated polymers
or oligomers of alphaolefins which include, but are not limited to,
C.sub.2 to about C.sub.32 alphaolefins with the C.sub.8 to about
C.sub.16 alphaolefins, such as 1-octene, 1-decene, 1-dodecene and
the like, being preferred. The preferred polyalphaolefins are
poly-1-octene, poly-1-decene and poly-1-dodecene and mixtures
thereof and mixed olefin-derived polyolefins. However, the dimers
of higher olefins in the range of C.sub.12 to C.sub.18 may be used
to provide low viscosity base stocks of acceptably low volatility.
Depending on the viscosity grade and the starting oligomer, the
PAOs may be predominantly dimers, trimers and tetramers of the
starting olefins, with minor amounts of the lower and/or higher
oligomers, having a viscosity range of 1.5 cSt to 12 cSt. PAO
fluids of particular use may include 3 cSt, 3.4 cSt, and/or 3.6 cSt
and combinations thereof. Mixtures of PAO fluids having a viscosity
range of 1.5 cSt to approximately 150 cSt or more may be used if
desired. Unless indicated otherwise, all viscosities cited herein
are measured at 100.degree. C.
[0048] The PAO fluids may be conveniently made by the
polymerization of an alphaolefin in the presence of a
polymerization catalyst such as the Friedel-Crafts catalysts
including, for example, aluminum trichloride, boron trifluoride or
complexes of boron trifluoride with water, alcohols such as
ethanol, propanol or butanol, carboxylic acids or esters such as
ethyl acetate or ethyl propionate. For example the methods
disclosed by U.S. Pat. Nos. 4,149,178 or 3,382,291 may be
conveniently used herein. Other descriptions of PAO synthesis are
found in the following U.S. Pat. Nos. 3,742,082; 3,769,363;
3,876,720; 4,239,930; 4,367,352; 4,413,156; 4,434,408; 4,910,355;
4,956,122; and 5,068,487. The dimers of the C.sub.14 to C.sub.18
olefins are described in U.S. Pat. No. 4,218,330.
[0049] Other useful lubricant oil base stocks include wax isomerate
base stocks and base oils, comprising hydroisomerized waxy stocks
(e.g. waxy stocks such as gas oils, slack waxes, fuels hydrocracker
bottoms, etc.), hydroisomerized Fischer-Tropsch waxes,
Gas-to-Liquids (GTL) base stocks and base oils, and other wax
isomerate hydroisomerized base stocks and base oils, or mixtures
thereof. Fischer-Tropsch waxes, the high boiling point residues of
Fischer-Tropsch synthesis, are highly paraffinic hydrocarbons with
very low sulfur content. The hydroprocessing used for the
production of such base stocks may use an amorphous
hydrocracking/hydroisomerization catalyst, such as one of the
specialized lube hydrocracking (LHDC) catalysts or a crystalline
hydrocracking/hydroisomerization catalyst, preferably a zeolitic
catalyst. For example, one useful catalyst is ZSM-48 as described
in U.S. Pat. No. 5,075,269, the disclosure of which is incorporated
herein by reference in its entirety. Processes for making
hydrocracked/hydroisomerized distillates and
hydrocracked/hydroisomerized waxes are described, for example, in
U.S. Pat. Nos. 2,817,693; 4,975,177; 4,921,594 and 4,897,178 as
well as in British Patent Nos. 1,429,494; 1,350,257; 1,440,230 and
1,390,359. Each of the aforementioned patents is incorporated
herein in their entirety. Particularly favorable processes are
described in European Patent Application Nos. 464546 and 464547,
also incorporated herein by reference. Processes using
Fischer-Tropsch wax feeds are described in U.S. Pat. Nos. 4,594,172
and 4,943,672, the disclosures of which are incorporated herein by
reference in their entirety.
[0050] Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived
base oils, and other wax-derived hydroisomerized (wax isomerate)
base oils be advantageously used in the instant disclosure, and may
have useful kinematic viscosities at 100.degree. C. of about 2 cSt
to about 50 cSt, preferably about 2 cSt to about 30 cSt, more
preferably about 3 cSt to about 25 cSt, as exemplified by GTL 4
with kinematic viscosity of about 4.0 cSt at 100.degree. C. and a
viscosity index of about 141. These Gas-to-Liquids (GTL) base oils,
Fischer-Tropsch wax derived base oils, and other wax-derived
hydroisomerized base oils may have useful pour points of about
-20.degree. C. or lower, and under some conditions may have
advantageous pour points of about -25.degree. C. or lower, with
useful pour points of about -30.degree. C. to about -40.degree. C.
or lower. Useful compositions of Gas-to-Liquids (GTL) base oils,
Fischer-Tropsch wax derived base oils, and wax-derived
hydroisomerized base oils are recited in U.S. Pat. Nos. 6,080,301;
6,090,989, and 6,165,949 for example, and are incorporated herein
in their entirety by reference.
[0051] The hydrocarbyl aromatics can be used as a base oil or base
oil component and can be any hydrocarbyl molecule that contains at
least about 5% of its weight derived from an aromatic moiety such
as a benzenoid moiety or naphthenoid moiety, or their derivatives.
These hydrocarbyl aromatics include alkyl benzenes, alkyl
naphthalenes, alkyl biphenyls, alkyl diphenyl oxides, alkyl
naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A,
alkylated thiodiphenol, and the like. The aromatic can be
mono-alkylated, dialkylated, polyalkylated, and the like. The
aromatic can be mono- or poly-functionalized. The hydrocarbyl
groups can also be comprised of mixtures of alkyl groups, alkenyl
groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other
related hydrocarbyl groups. The hydrocarbyl groups can range from
about C.sub.6 up to about C.sub.60 with a range of about C.sub.8 to
about C.sub.20 often being preferred. A mixture of hydrocarbyl
groups is often preferred, and up to about three such substituents
may be present. The hydrocarbyl group can optionally contain
sulfur, oxygen, and/or nitrogen containing substituents. The
aromatic group can also be derived from natural (petroleum)
sources, provided at least about 5% of the molecule is comprised of
an above-type aromatic moiety. Viscosities at 100.degree. C. of
approximately 2 cSt to about 50 cSt are preferred, with viscosities
of approximately 3 cSt to about 20 cSt often being more preferred
for the hydrocarbyl aromatic component. In one embodiment, an alkyl
naphthalene where the alkyl group is primarily comprised of
1-hexadecene is used. Other alkylates of aromatics can be
advantageously used. Naphthalene or methyl naphthalene, for
example, can be alkylated with olefins such as octene, decene,
dodecene, tetradecene or higher, mixtures of similar olefins, and
the like. Alkylated naphthalene and analogues may also comprise
compositions with isomeric distribution of alkylating groups on the
alpha and beta carbon positions of the ring structure. Distribution
of groups on the alpha and beta positions of a naphthalene ring may
range from 100:1 to 1:100, more often 50:1 to 1:50 Useful
concentrations of hydrocarbyl aromatic in a lubricant oil
composition can be about 2% to about 25%, preferably about 4% to
about 20%, and more preferably about 4% to about 15%, depending on
the application.
[0052] Alkylated aromatics such as the hydrocarbyl aromatics of the
present disclosure may be produced by well-known Friedel-Crafts
alkylation of aromatic compounds. See Friedel-Crafts and Related
Reactions, Olah, G. A. (ed.), Inter-science Publishers, New York,
1963. For example, an aromatic compound, such as benzene or
naphthalene, is alkylated by an olefin, alkyl halide or alcohol in
the presence of a Friedel-Crafts catalyst. See Friedel-Crafts and
Related Reactions, Vol. 2, part 1, chapters 14, 17, and 18, See
Olah, G. A. (ed.), Inter-science Publishers, New York, 1964. Many
homogeneous or heterogeneous, solid catalysts are known to one
skilled in the art. The choice of catalyst depends on the
reactivity of the starting materials and product quality
requirements. For example, strong acids such as AlCl.sub.3,
BF.sub.3, or HF may be used. In some cases, milder catalysts such
as FeCl.sub.3 or SnCl.sub.4 are preferred. Newer alkylation
technology uses zeolites or solid super acids.
[0053] Esters comprise a useful base stock. Additive solvency and
seal compatibility characteristics may be secured by the use of
esters such as the esters of dibasic acids with monoalkanols and
the polyol esters of monocarboxylic acids. Esters of the former
type include, for example, the esters of dicarboxylic acids such as
phthalic acid, succinic acid, alkyl succinic acid, alkenyl succinic
acid, maleic acid, azelaic acid, suberic acid, sebacic acid,
fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl
malonic acid, alkenyl malonic acid, etc., with a variety of
alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol,
2-ethylhexyl alcohol, etc. Specific examples of these types of
esters include dibutyl adipate, di(2-ethylhexyl) sebacate,
di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate,
diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl
sebacate, etc.
[0054] Particularly useful synthetic esters are those which are
obtained by reacting one or more polyhydric alcohols, preferably
the hindered polyols (such as the neopentyl polyols, e.g.,
neopentyl glycol, trimethylol ethane,
2-methyl-2-propyl-1,3-propanediol, trimethylol propane,
pentaerythritol and dipentaerythritol) with alkanoic acids
containing at least about 4 carbon atoms, preferably C.sub.5 to
C.sub.30 acids such as saturated straight chain fatty acids
including caprylic acid, capric acid, lauric acid, myristic acid,
palmitic acid, stearic acid, arachic acid, and behenic acid, or the
corresponding branched chain fatty acids or unsaturated fatty acids
such as oleic acid, or mixtures of any of these materials.
[0055] Suitable synthetic ester components include the esters of
trimethylol propane, trimethylol butane, trimethylol ethane,
pentaerythritol and/or dipentaerythritol with one or more
monocarboxylic acids containing from about 5 to about 10 carbon
atoms. These esters are widely available commercially, for example,
the Mobil P-41 and P-51 esters of ExxonMobil Chemical Company.
[0056] Also useful are esters derived from renewable material such
as coconut, palm, rapeseed, soy, sunflower and the like. These
esters may be monoesters, di-esters, polyol esters, complex esters,
or mixtures thereof. These esters are widely available
commercially, for example, the Mobil P-51 ester of ExxonMobil
Chemical Company.
[0057] Turbine oil formulations containing renewable esters are
included in this disclosure. For such formulations, the renewable
content of the ester is typically greater than about 70 weight
percent, preferably more than about 80 weight percent and most
preferably more than about 90 weight percent.
[0058] Other useful fluids of lubricating viscosity include
non-conventional or unconventional base stocks that have been
processed, preferably catalytically, or synthesized to provide high
performance lubrication characteristics.
[0059] Non-conventional or unconventional base stocks/base oils
include one or more of a mixture of base stock(s) derived from one
or more Gas-to-Liquids (GTL) materials, as well as
isomerate/isodewaxate base stock(s) derived from natural wax or
waxy feeds, mineral and or non-mineral oil waxy feed stocks such as
slack waxes, natural waxes, and waxy stocks such as gas oils, waxy
fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal
crackates, or other mineral, mineral oil, or even non-petroleum oil
derived waxy materials such as waxy materials received from coal
liquefaction or shale oil, and mixtures of such base stocks.
[0060] GTL materials are materials that are derived via one or more
synthesis, combination, transformation, rearrangement, and/or
degradation/deconstructive processes from gaseous carbon-containing
compounds, hydrogen-containing compounds and/or elements as feed
stocks such as hydrogen, carbon dioxide, carbon monoxide, water,
methane, ethane, ethylene, acetylene, propane, propylene, propyne,
butane, butylenes, and butynes. GTL base stocks and/or base oils
are GTL materials of lubricating viscosity that are generally
derived from hydrocarbons; for example, waxy synthesized
hydrocarbons, that are themselves derived from simpler gaseous
carbon-containing compounds, hydrogen-containing compounds and/or
elements as feed stocks. GTL base stock(s) and/or base oil(s)
include oils boiling in the lube oil boiling range (1)
separated/fractionated from synthesized GTL materials such as, for
example, by distillation and subsequently subjected to a final wax
processing step which involves either or both of a catalytic
dewaxing process, or a solvent dewaxing process, to produce lube
oils of reduced/low pour point; (2) synthesized wax isomerates,
comprising, for example, hydrodewaxed or hydroisomerized cat and/or
solvent dewaxed synthesized wax or waxy hydrocarbons; (3)
hydrodewaxed or hydroisomerized cat and/or solvent dewaxed
Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy
hydrocarbons, waxes and possible analogous oxygenates); preferably
hydrodewaxed or hydroisomerized/followed by cat and/or solvent
dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or
hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T
waxes, or mixtures thereof.
[0061] GTL base stock(s) and/or base oil(s) derived from GTL
materials, especially, hydrodewaxed or hydroisomerized/followed by
cat and/or solvent dewaxed wax or waxy feed, preferably F-T
material derived base stock(s) and/or base oil(s), are
characterized typically as having kinematic viscosities at
100.degree. C. of from about 2 mm.sup.2/s to about 50 mm.sup.2/s
(ASTM D445). They are further characterized typically as having
pour points of -5.degree. C. to about -40.degree. C. or lower (ASTM
D97). They are also characterized typically as having viscosity
indices of about 80 to about 140 or greater (ASTM D2270).
[0062] In addition, the GTL base stock(s) and/or base oil(s) are
typically highly paraffinic (>90% saturates), and may contain
mixtures of monocycloparaffins and multicycloparaffins in
combination with non-cyclic isoparaffins. The ratio of the
naphthenic (i.e., cycloparaffin) content in such combinations
varies with the catalyst and temperature used. Further, GTL base
stock(s) and/or base oil(s) typically have very low sulfur and
nitrogen content, generally containing less than about 10 ppm, and
more typically less than about 5 ppm of each of these elements. The
sulfur and nitrogen content of GTL base stock(s) and/or base oil(s)
obtained from F-T material, especially F-T wax, is essentially nil.
In addition, the absence of phosphorus and aromatics make this
materially especially suitable for the formulation of low SAP
products.
[0063] The term GTL base stock and/or base oil and/or wax isomerate
base stock and/or base oil is to be understood as embracing
individual fractions of such materials of wide viscosity range as
recovered in the production process, mixtures of two or more of
such fractions, as well as mixtures of one or two or more low
viscosity fractions with one, two or more higher viscosity
fractions to produce a blend wherein the blend exhibits a target
kinematic viscosity.
[0064] The GTL material, from which the GTL base stock(s) and/or
base oil(s) is/are derived is preferably an F-T material (i.e.,
hydrocarbons, waxy hydrocarbons, wax).
[0065] Base oils for use in the formulated lubricating oils useful
in the present disclosure are any of the variety of oils
corresponding to API Group I, Group II, Group III, Group IV, and
Group V oils and mixtures thereof, preferably API Group II, Group
III, Group IV, and Group V oils and mixtures thereof, more
preferably the Group III to Group V base oils due to their
exceptional volatility, stability, viscometric and cleanliness
features. Minor quantities of Group I stock, such as the amount
used to dilute additives for blending into formulated lube oil
products, can be tolerated but should be kept to a minimum, i.e.
amounts only associated with their use as diluent/carrier oil for
additives used on an "as-received" basis. Even in regard to the
Group II stocks, it is preferred that the Group II stock be in the
higher quality range associated with that stock, i.e. a Group II
stock having a viscosity index in the range 100<VI<120.
[0066] The base oil constitutes the major component of the turbine
oil lubricant composition of the present disclosure and typically
is present in an amount ranging from about 80 to about 99.8 weight
percent, preferably from about 90 to about 99.5 weight percent, and
more preferably from about 95 to about 99 weight percent, based on
the total weight of the composition. The base oil may be selected
from any of the synthetic or natural oils typically used as
lubricating oils for industrial oils and turbomachines. The base
oil conveniently has a kinematic viscosity, according to ASTM
standards, of about 7 cSt to about 46 cSt (or mm.sup.2/s) at
40.degree. C. and preferably of about 10 cSt to about 32 cSt (or
mm.sup.2/s) at 40.degree. C., often more preferably from about 15
cSt to about 22 cSt. Mixtures of synthetic and natural base oils
may be used if desired. Bi-modal, tri-modal, and additional
combinations of mixtures of Group I, II, III, IV, and/or V base
stocks may be used if desired.
[0067] The co-base stock component is present in an amount
sufficient for providing solubility, compatibility and dispersancy
of polar additives in the lubricating oil. The co-base stock
component is present in the lubricating oils of this disclosure in
an amount from about 1 to about 99 weight percent, preferably from
about 5 to about 95 weight percent, and more preferably from about
10 to about 90 weight percent.
[0068] Table 2 below summarizes useful and preferred amounts of
illustrative lubricating base oils in accordance with this
disclosure.
TABLE-US-00002 TABLE 2 Useful and Preferred Amounts of Illustrative
Lubricating Base Oils Approximate Approximate wt % wt %
Illustrative Base Oils (Useful) (Preferred) Mineral Oil API Group
I, II/II+ 0-100 3-95 Naphthenic 0-100 3-95 API Group III/III+ = GTL
0-100 3-95 API Group IV PAO 0-100 3-95 API Group V (examples listed
below): 0-100 3-95 Ethylene-propylene copolymer (EPC) 0-100 3-95
Polyol Esters 0-100 3-95 Phosphate Esters 0-100 3-95 Phthalate
Esters 0-100 3-95 Dibasic Esters e.g. Adipate 0-100 3-95 Carbonate
Esters 0-100 3-95 Trimellitate Esters 0-100 3-95 Oil Soluble
Polyalkylene Glycols 0-100 3-95 Polyalkylene Glycols 0-100 3-95
Alkylated Naphthalenes 0-100 3-95 Viscobase Fluids 0-100 3-95
Olefin-esters (e.g. Ketjenlube) 0-100 3-95 Linear or Branched
Alkylbenzenes 0-100 3-95 TME-based esters 0-100 3-95 Polyethers
0-100 3-95 2 Ethylhexanoic acid ester 0-100 3-95 PMA/PAO
co-oligomers 0-100 3-95 Alkylated Diphenyl Oxide (ADPO) 0-100 3-95
Alkylated Sulfurized Diphenyl Oxide 0-100 3-95 (ASDPO) Bisphenol
Sulfide Ether (BPSE) 0-100 3-95 (C16,C20) 3-phenylpropionate 0-100
3-95 Hexyl 2-(decyloxy)benzoate 0-100 3-95 Diheptyl
N-octylsuccinate 0-100 3-95
Lubricating Oil Additives
[0069] The formulated lubricating oil useful in the present
disclosure may additionally contain one or more of the commonly
used lubricating oil performance additives including but not
limited to antiwear additives, dispersants, detergents, viscosity
modifiers, corrosion inhibitors, rust inhibitors, metal
deactivators, extreme pressure additives, anti-seizure agents, wax
modifiers, viscosity modifiers, fluid-loss additives, seal
compatibility agents, lubricity agents, anti-staining agents,
chromophoric agents, defoamants, demulsifiers, densifiers, wetting
agents, gelling agents, tackiness agents, colorants, and others.
For a review of many commonly used additives, see Klamann in
Lubricants and Related Products, Verlag Chemie, Deerfield Beach,
FL; ISBN 0-89573-177-0. Reference is also made to "Lubricant
Additives" by M. W. Ranney, published by Noyes Data Corporation of
Parkridge, N J (1973); see also U.S. Pat. No. 7,704,930, the
disclosure of which is incorporated herein in its entirety. These
additives are commonly delivered with varying amounts of diluent
oil, that may range from 5 weight percent to 50 weight percent.
[0070] The additives useful in this disclosure do not have to be
soluble in the lubricating oils. Insoluble additives in oil can be
dispersed in the lubricating oils of this disclosure.
[0071] The types and quantities of performance additives used in
combination with the instant disclosure in lubricant compositions
are not limited by the examples shown herein as illustrations.
Antiwear Additives
[0072] Alkyldithiophosphates, aryl phosphates and phosphites are
illustrative antiwear additives useful in the lubricating oils of
this disclosure. The illustrative antiwear additives may be
essentially free of metals, or they may contain metal salts.
[0073] A phosphate ester or salt may be a monohydrocarbyl,
dihydrocarbyl or a trihydrocarbyl phosphate, wherein each
hydrocarbyl group is saturated. In one embodiment, each hydrocarbyl
group independently contains from about 8 to about 30, or from
about 12 up to about 28, or from about 14 up to about 24, or from
about 14 up to about 18 carbons atoms. In an embodiment, the
hydrocarbyl groups are alkyl groups. Examples of hydrocarbyl groups
include tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl,
octadecyl groups and mixtures thereof.
[0074] A phosphate ester or salt is a phosphorus acid ester
prepared by reacting one or more phosphorus acid or anhydride with
a saturated alcohol. The phosphorus acid or anhydride is generally
an inorganic phosphorus reagent, such as phosphorus pentoxide,
phosphorus trioxide, phosphorus tetroxide, phosphorous acid,
phosphoric acid, phosphorus halide, lower phosphorus esters, or a
phosphorus sulfide, including phosphorus pentasulfide, and the
like. Lower phosphorus acid esters generally contain from 1 to
about 7 carbon atoms in each ester group. Alcohols used to prepare
the phosphorus acid esters or salts. Examples of commercially
available alcohols and alcohol mixtures include Alfol 1218 (a
mixture of synthetic, primary, straight-chain alcohols containing
12 to 18 carbon atoms); Alfol 20+ alcohols (mixtures of C18-C28
primary alcohols having mostly C20 alcohols as determined by GLC
(gas-liquid-chromatography)); and Alfo122+ alcohols (C18-C28
primary alcohols containing primarily C22 alcohols). Alfol alcohols
are available from Continental Oil Company. Another example of a
commercially available alcohol mixture is Adol 60 (about 75% by
weight of a straight chain C22 primary alcohol, about 15% of a C20
primary alcohol and about 8% of C18 and C24 alcohols). The Adol
alcohols are marketed by Ashland Chemical.
[0075] A variety of mixtures of monohydric fatty alcohols derived
from naturally occurring triglycerides and ranging in chain length
from C8 to C18 are available from Procter & Gamble Company.
These mixtures contain various amounts of fatty alcohols containing
12, 14, 16, or 18 carbon atoms. For example, CO-1214 is a fatty
alcohol mixture containing 0.5% of C10 alcohol, 66.0% of C12
alcohol, 26.0% of C14 alcohol and 6.5% of C16 alcohol.
[0076] Another group of commercially available alcohol mixtures
include the "Neodol" products available from Shell Chemical Co. For
example, Neodol 23 is a mixture of C12 and C13 alcohols; Neodol 25
is a mixture of C12 to C15 alcohols; and Neodol 45 is a mixture of
C14 to C15 linear alcohols. The phosphate contains from about 14 to
about 18 carbon atoms in each hydrocarbyl group. The hydrocarbyl
groups of the phosphate are generally derived from a mixture of
fatty alcohols having from about 14 up to about 18 carbon atoms.
The hydrocarbyl phosphate may also be derived from a fatty vicinal
diol. Fatty vicinal diols include those available from Ashland Oil
under the general trade designation Adol 114 and Adol 158. The
former is derived from a straight chain alpha olefin fraction of
C11-C14, and the latter is derived from a C15-C18 fraction.
[0077] The phosphate salts may be prepared by reacting an acidic
phosphate ester with an amine compound or a metallic base to form
an amine or a metal salt. The amines may be monoamines or
polyamines. Useful amines include those amines disclosed in U.S.
Pat. No. 4,234,435.
[0078] Illustrative monoamines generally contain a hydrocarbyl
group which contains from 1 to about 30 carbon atoms, or from 1 to
about 12, or from 1 to about 6. Examples of primary monoamines
useful in the present disclosure include methylamine, ethylamine,
propylamine, butylamine, cyclopentylamine, cyclohexylamine,
octylamine, dodecylamine, allylamine, cocoamine, stearylamine, and
laurylamine. Examples of secondary monoamines include
dimethylamine, diethylamine, dipropylamine, dibutylamine,
dicyclopentylamine, dicyclohexylamine, methylbutylamine,
ethylhexylamine, etc.
[0079] An amine is a fatty (C8-C30) amine which includes
n-octylamine, n-decylamine, n-dodecylamine, n-tetradecylamine,
n-hexadecylamine, n-octadecylamine, oleyamine, etc. Also useful
fatty amines include commercially available fatty amines such as
"Armeen" amines (products available from Akzo Chemicals, Chicago,
Ill.), such Armeen C, Armeen O, Armeen OL, Armeen T, Armeen HT,
Armeen S and Armeen SD, wherein the letter designation relates to
the fatty group, such as coco, oleyl, tallow, or stearyl
groups.
[0080] Other useful amines include primary ether amines, such as
those represented by the formula
R''(OR').times.NH2
wherein R' is a divalent alkylene group having about 2 to about 6
carbon atoms; x is a number from one to about 150, or from about
one to about five, or one; and R'' is a hydrocarbyl group of about
5 to about 150 carbon atoms. An example of an ether amine is
available under the name SURFAM.RTM. amines produced and marketed
by Mars Chemical Company, Atlanta, Ga. Preferred etheramines are
exemplified by those identified as SURFAM P14B
(decyloxypropylamine), SURFAM P16A (linear C16), SURFAM P17B
(tridecyloxypropylamine). The carbon chain lengths (i.e., C14,
etc.) of the SURFAMS described above and used hereinafter are
approximate and include the oxygen ether linkage.
[0081] An illustrative amine is a tertiary-aliphatic primary amine.
Generally, the aliphatic group, preferably an alkyl group, contains
from about 4 to about 30, or from about 6 to about 24, or from
about 8 to about 22 carbon atoms. Usually the tertiary alkyl
primary amines are monoamines the alkyl group is a hydrocarbyl
group containing from one to about 27 carbon atoms. Such amines are
illustrated by tert-butylamine, tert-hexylamine,
1-methyl-1-amino-cyclohexane, tert-octylamine, tert-decylamine,
tert-dodecylamine, tert-tetradecylamine, tert-hexadecylamine,
tert-octadecylamine, tert-tetracosanylamine, and
tert-octacosanylamine. Mixtures of tertiary aliphatic amines may
also be used in preparing the phosphate salt. Illustrative of amine
mixtures of this type are "Primene 81R" which is a mixture of
C11-C14 tertiary alkyl primary amines and "Primene JMT" which is a
similar mixture of C18-C22 tertiary alkyl primary amines (both are
available from Rohm and Haas Company). The tertiary aliphatic
primary amines and methods for their preparation are known to those
of ordinary skill in the art.
[0082] Another illustrative amine is a heterocyclic polyamine. The
heterocyclic polyamines include aziridines, azetidines, azolidines,
tetra- and dihydropyridines, pyrroles, indoles, piperidines,
imidazoles, di- and tetra-hydroimidazoles, piperazines, isoindoles,
purines, morpholines, thiomorpholines, N-aminoalkylmorpholines,
N-aminoalkylthiomorpholines, N-aminoalkyl-piperazines,
N,N'-diaminoalkylpiperazines, azepines, azocines, azonines,
azecines and tetra-, di- and perhydro derivatives of each of the
above and mixtures of two or more of these heterocyclic amines.
Preferred heterocyclic amines are the saturated 5- and 6-membered
heterocyclic amines containing only nitrogen, oxygen and/or sulfur
in the hetero ring, especially the piperidines, piperazines,
thiomorpholines, morpholines, pyrrolidines, and the like.
Piperidine, aminoalkyl substituted piperidines, piperazine,
aminoalkyl substituted piperazines, morpholine, aminoalkyl
substituted morpholines, pyrrolidine, and aminoalkyl-substituted
pyrrolidines, are especially preferred. Usually the aminoalkyl
substituents are substituted on a nitrogen atom forming part of the
hetero ring. Specific examples of such heterocyclic amines include
N-aminopropylmorpholine, N-aminoethylpiperazine, and
N,N'-diaminoethylpiperazine. Hydroxy heterocyclic polyamines are
also useful. Examples include N-(2-hydroxyethyl)cyclohexylamine,
3-hydroxycyclopentylamine, parahydroxyaniline,
N-hydroxyethylpiperazine, and the like.
[0083] The metal salts of the phosphorus acid esters are prepared
by the reaction of a metal base with the acidic phosphorus ester.
The metal base may be any metal compound capable of forming a metal
salt. Examples of metal bases include metal oxides, hydroxides,
carbonates, sulfates, borates, or the like. The metals of the metal
base include Group IA, IIA, IB through VIIB, and VIII metals (CAS
version of the Periodic Table of the Elements). These metals
include the alkali metals, alkaline earth metals and transition
metals. In one embodiment, the metal is a Group IIA metal, such as
calcium or magnesium, Group IIB metal, such as zinc, or a Group
VIIB metal, such as manganese. Preferably, the metal is magnesium,
calcium, manganese or zinc. Examples of metal compounds which may
be reacted with the phosphorus acid include zinc hydroxide, zinc
oxide, copper hydroxide, copper oxide, etc.
[0084] The lubricating oils of this disclosure also may include a
fatty imidazoline or a reaction product of a fatty carboxylic acid
and at least one polyamine. The fatty imidazoline has fatty
substituents containing from 8 to about 30, or from about 12 to
about 24 carbon atoms. The substituent may be saturated or
unsaturated, for example, heptadeceneyl derived olyel groups,
preferably saturated. In one aspect, the fatty imidazoline may be
prepared by reacting a fatty carboxylic acid with a
polyalkylenepolyamine. The fatty carboxylic acids are generally
mixtures of straight and branched chain fatty carboxylic acids
containing about 8 to about 30 carbon atoms, or from about 12 to
about 24, or from about 16 to about 18. Carboxylic acids include
the polycarboxylic acids or carboxylic acids or anhydrides having
from 2 to about 4 carbonyl groups, preferably 2. The polycarboxylic
acids include succinic acids and anhydrides and Diels-Alder
reaction products of unsaturated monocarboxylic acids with
unsaturated carboxylic acids (such as acrylic, methacrylic, maleic,
fumaric, crotonic and itaconic acids). Preferably, the fatty
carboxylic acids are fatty monocarboxylic acids, having from about
8 to about 30, preferably about 12 to about 24 carbon atoms, such
as octanoic, oleic, stearic, linoleic, dodecanoic, and tall oil
acids, preferably stearic acid. The fatty carboxylic acid is
reacted with at least one polyamine. The polyamines may be
aliphatic, cycloaliphatic, heterocyclic or aromatic. Examples of
the polyamines include alkylene polyamines and heterocyclic
polyamines.
[0085] The antiwear additive according to the disclosure has the
following advantges. It has very high effectiveness when used in
low concentrations and it is free of chlorine. For the
neutralization of the phosphoric esters, the latter are taken and
the corresponding amine slowly added with stirring. The resulting
heat of neutralization is removed by cooling. The antiwear additive
according to the disclosure can be incorporated into the respective
base liquid with the aid of fatty substances (e.g., tall oil fatty
acid, oleic acid, etc.) as solubilizers. The base liquids used are
napthenic or paraffinic base oils, synthetic oils (e.g.,
polyglycols, mixed polyglycols), polyolefins, carboxylic esters,
etc.
[0086] In an embodiment, the lubricating oils of this disclosure
can contain at least one phosphorus containing antiwear additive.
Examples of such additives are amine phosphate antiwear additives
such as that known under the trade name IRGALUBE 349 and/or
triphenyl phosphorothionate antiwear additives such as that known
under the trade name IRGALUBE TPPT. Such amine phosphates may be
present in an amount of from 0.01 to 2%, preferably 0.2 to 1.5% by
weight of the lubricant composition while such phosphorothionates
are suitably present in an amount of from 0.01 to 3%, preferably
0.5 to 1.5% by weight of the lubricant composition. A mixture of an
amine phosphate and phosphorothionate may be employed.
[0087] Neutral organic phosphates may be present in an amount from
zero to 4%, preferably 0.1 to 2.5% by weight of the composition.
The above amine phosphates can be mixed together to form a single
component capable of delievering antiwear performance. The neutral
organic phosphate is also a conventional ingredient of lubricating
oils.
[0088] Phosphates for use in the present disclosure include
phosphates, acid phosphates, phosphites and acid phosphites. The
phosphates include triaryl phosphates, trialkyl phosphates,
trialkylaryl phosphates, triarylalkyl phosphates and trialkenyl
phosphates. As specific examples of these, referred to are
triphenyl phosphate, tricresyl phosphate, benzyldiphenyl phosphate,
ethyldiphenyl phosphate, tributyl phosphate, ethyldibutyl
phosphate, cresyldiphenyl phosphate, dicresylphenyl phosphate,
ethylphenyldiphenyl phosphate, diethylphenylphenyl phosphate,
propylphenyldiphenyl phosphate, dipropylphenylphenyl phosphate,
triethylphenyl phosphate, tripropylphenyl phosphate,
butylphenyldiphenyl phosphate, dibutylphenylphenyl phosphate,
tributylphenyl phosphate, trihexyl phosphate, tri(2-ethylhexyl)
phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl
phosphate, tripalmityl phosphate, tristearyl phosphate, and
trioleyl phosphate.
[0089] The acid phosphates include, for example, 2-ethylhexyl acid
phosphate, ethyl acid phosphate, butyl acid phosphate, oleyl acid
phosphate, tetracosyl acid phosphate, isodecyl acid phosphate,
lauryl acid phosphate, tridecyl acid phosphate, stearyl acid
phosphate, and isostearyl acid phosphate.
[0090] The phosphites include, for example, triethyl phosphite,
tributyl phosphite, triphenyl phosphite, tricresyl phosphite,
tri(nonylphenyl) phosphite, tri(2-ethylhexyl) phosphite, tridecyl
phosphite, trilauryl phosphite, triisooctyl phosphite,
diphenylisodecyl phosphite, tristearyl phosphite, and trioleyl
phosphite.
[0091] The acid phosphites include, for example, dibutyl
hydrogenphosphite, dilauryl hydrogenphosphite, dioleyl
hydrogenphosphite, distearyl hydrogenphosphite, and diphenyl
hydrogenphosphite.
[0092] Amines that form amine salts with such phosphates include,
for example, mono-substituted amines, di-substituted amines and
tri-substituted amines. Examples of the mono-substituted amines
include butylamine, pentylamine, hexylamine, cyclohexylamine,
octylamine, laurylamine, stearylamine, oleylamine and benzylamine;
and those of the di-substituted amines include dibutylamine,
dipentylamine, dihexylamine, dicyclohexylamine, dioctylamine,
dilaurylamine, distearylamine, dioleylamine, dibenzylamine, stearyl
monoethanolamine, decyl monoethanolamine, hexyl monopropanolamine,
benzyl monoethanolamine, phenyl monoethanolamine, and tolyl
monopropanolamine. Examples of tri-substituted amines include
tributylamine, tripentylamine, trihexylamine, tricyclohexylamine,
trioctylamine, trilaurylamine, tristearylamine, trioleylamine,
tribenzylamine, dioleyl monoethanolamine, dilauryl
monopropanolamine, dioctyl monoethanolamine, dihexyl
monopropanolamine, dibutyl monopropanolamine, oleyl diethanolamine,
stearyl dipropanolamine, lauryl diethanolamine, octyl
dipropanolamine, butyl diethanolamine, benzyl diethanolamine,
phenyl diethanolamine, tolyl dipropanolamine, xylyl diethanolamine,
triethanolamine, and tripropanolamine. Phosphates or their amine
salts are added to the base oil in an amount from zero to 5% by
weight, preferably from 0.1 to 2% by weight, relative to the total
weight of the composition.
[0093] Illustrative carboxylic acids to be reacted with amines
include, for example, aliphatic carboxylic acids, dicarboxylic
acids (dibasic acids), and aromatic carboxylic acids. The aliphatic
carboxylic acids have from 8 to 30 carbon atoms, and may be
saturated or unsaturated, and linear or branched. Specific examples
of the aliphatic carboxylic acids include pelargonic acid, lauric
acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid,
isostearic acid, eicosanoic acid, behenic acid, triacontanoic acid,
caproleic acid, undecylenic acid, oleic acid, linolenic acid,
erucic acid, and linoleic acid. Specific examples of the
dicarboxylic acids include octadecylsuccinic acid,
octadecenylsuccinic acid, adipic acid, azelaic acid, and sebacic
acid. One example of the aromatic carboxylic acids is salicylic
acid. Illustrative amines to be reacted with carboxylic acids
include, for example, polyalkylene-polyamines such as
diethylenetriamine, triethylenetetramine, tetraethylenepentamine,
pentaethylenehexamine, hexaethyleneheptamine,
heptaethyleneoctamine, dipropylenetriamine,
tetrapropylenepentamine, and hexabutyleneheptamine; and
alkanolamines such as monoethanolamine and diethanolamine. Of
these, preferred are a combination of isostearic acid and
tetraethylenepentamine, and a combination of oleic acid and
diethanolamine. Reaction products of carboxylic acids and amines
may added to the base oil in an amount of from zero to 5% by
weight, preferably from 0.03 to 3% by weight, relative to the total
weight of the composition.
[0094] Other illustrative antiwear additives include phosphites,
thiophosphites, phosphates, and thiophosphates, including mixed
materials having, for instance, one or two sulfur atoms, i.e.,
monothio- or dithio compounds. As used herein, the term
"hydrocarbyl substituent" or "hydrocarbyl group" is used in its
ordinary sense, which is well-known to those skilled in the art.
Specifically, it refers to a group having a carbon atom directly
attached to the remainder of the molecule and having predominantly
hydrocarbon character.
[0095] Specific examples of some of the phosphites and
thiophosphites within the scope of the disclosure include
phosphorous acid, mono-, di-, or tri-thiophosphorous acid, mono-,
di-, or tri-propyl phosphite or mono-, di-, or tri-thiophosphite;
mono-, di-, or tri-butyl phosphite or mono-, di-, or
tri-thiophosphite; mono-, di-, or tri-amyl phosphite or mono-, di-,
or tri-thiophosphite; mono-, di-, or tri-hexyl phosphite or mono-,
di-, or tri-thiophosphite; mono-, di-, or tri-phenyl phosphite or
mono-, di-, or tri-thiophosphite; mono-, di-, or tri-tolyl
phosphite or mono-, di-, or tri-thiophosphite; mono-, di-, or
tri-cresyl phosphite or mono-, di-, or tri-thiophosphite; dibutyl
phenyl phosphite or mono-, di-, or tri-phosphite, amyl dicresyl
phosphite or mono-, di-, or tri-thiophosphite, and any of the above
with substituted groups, such as chlorophenyl or chlorobutyl.
[0096] Specific examples of the phosphates and thiophosphates
within the scope of the disclosure include phosphoric acid, mono-,
di-, or tri-thiophosphoric acid, mono-, di-, or tri-propyl
phosphate or mono-, di-, or tri-thiophosphate; mono-, di-, or
tri-butyl phosphate or mono-, di-, or tri-thiophosphate; mono-,
di-, or tri-amyl phosphate or mono-, di-, or tri-thiophosphate;
mono-, di-, or tri-hexyl phosphate or mono-, di-, or
tri-thiophosphate; mono-, di-, or tri-phenyl phosphate or mono-,
di-, or tri-thiophosphate; mono-, di-, or tritolyl phosphate or
mono-, di-, or trithiophosphate; mono-, di-, or tri-cresyl
phosphate or mono-, di-, or tri-thiophosphate; dibutyl phenyl
phosphate or mono-, di-, or tri-phosphate, amyl dicresyl phosphate
or mono-, di-, or tri-thiophosphate, and any of the above with
substituted groups, such as chlorophenyl or chlorobutyl.
[0097] These phosphorus compounds may be prepared by well known
reactions. One route the reaction of an alcohol or a phenol with
phosphorus trichloride or by a transesterification reaction.
Alcohols and phenols can be reacted with phosphorus pentoxide to
provide a mixture of an alkyl or aryl phosphoric acid and a dialkyl
or diaryl phosphoric acid. Alkyl phosphates can also be prepared by
the oxidation of the corresponding phosphites. Thiophosphates can
be prepared by the reaction of phosphites with elemental sulfur. In
any case, the reaction can be conducted with moderate heating.
Moreover, various phosphorus esters can be prepared by reaction
using other phosphorus esters as starting materials. Thus, medium
chain (C9 to C22) phosphorus esters have been prepared by reaction
of dimethylphosphite with a mixture of medium-chain alcohols by
means of a thermal transesterification or an acid- or
base-catalyzed transesterification. See, for example, U.S. Pat. No.
4,652,416. Most such materials are also commercially available; for
instance, triphenyl phosphite is available from Albright and Wilson
as Duraphos TPP.TM.; di-n-butyl hydrogen phosphite from Albright
and Wilson as Duraphos DBHP.TM.; and triphenylthiophosphate from
Ciba Specialty Chemicals as Irgalube TPPT.TM..
[0098] Examples of esters of the dialkylphosphorodithioic acids
include esters obtained by reaction of the dialkyl
phosphorodithioic acid with an alpha, beta-unsaturated carboxylic
acid (e.g., methyl acrylate) and, optionally an alkylene oxide such
as propylene oxide.
[0099] One or more of the above-identified metal dithiophosphates
may be used from about zero to about 2% by weight, and more
generally from about 0.1 to about 1% by weight, based on the weight
of the total composition.
[0100] The hydrocarbyl in the dithiophosphate may be alkyl,
cycloalkyl, aralkyl or alkaryl groups, or a substantially
hydrocarbon group of similar structure. Illustrative alkyl groups
include isopropyl, isobutyl, n-butyl, sec-butyl, the various amyl
groups, n-hexyl, methylisobutyl, heptyl, 2-ethylhexyl, diisobutyl,
isooctyl, nonyl, behenyl, decyl, dodecyl, tridecyl, etc.
Illustrative lower alkylphenyl groups include butylphenyl,
amylphenyl, heptylphenyl, etc. Cycloalkyl groups likewise are
useful and these include chiefly cyclohexyl and the lower
alkyl-cyclohexyl radicals. Many substituted hydrocarbon groups may
also be used, e.g., chloropentyl, dichlorophenyl, and
dichlorodecyl.
[0101] The phosphorodithioic acids from which the metal salts
useful in this disclosure are prepared are well known. Examples of
dihydrocarbylphosphorodithioic acids and metal salts, and processes
for preparing such acids and salts are found in, for example U.S.
Pat. Nos. 4,263,150; 4,289,635; 4,308,154; and 4,417,990. These
patents are hereby incorporated by reference.
[0102] The phosphorodithioic acids are prepared by the reaction of
a phosphorus sulfide with an alcohol or phenol or mixtures of
alcohols. A typical reaction involves four moles of the alcohol or
phenol and one mole of phosphorus pentasulfide, and may be carried
out within the temperature range from about 50.degree. C. to about
200.degree. C. Thus, the preparation of O,O-di-n-hexyl
phosphorodithioic acid involves the reaction of a mole of
phosphorus pentasulfide with four moles of n-hexyl alcohol at about
100.degree. C. for about two hours. Hydrogen sulfide is liberated
and the residue is the desired acid. The preparation of the metal
salts of these acids may be effected by reaction with metal
compounds as well known in the art.
[0103] The metal salts of dihydrocarbyldithiophosphates which are
useful in this disclosure include those salts containing Group I
metals, Group II metals, aluminum, lead, tin, molybdenum,
manganese, cobalt, and nickel. The Group II metals, aluminum, tin,
iron, cobalt, lead, molybdenum, manganese, nickel and copper are
among the preferred metals. Zinc and copper are especially useful
metals. Examples of metal compounds which may be reacted with the
acid include lithium oxide, lithium hydroxide, sodium hydroxide,
sodium carbonate, potassium hydroxide, potassium carbonate, silver
oxide, magnesium oxide, magnesium hydroxide, calcium oxide, zinc
hydroxide, strontium hydroxide, cadmium oxide, cadmium hydroxide,
barium oxide, aluminum oxide, iron carbonate, copper hydroxide,
lead hydroxide, tin butylate, cobalt hydroxide, nickel hydroxide,
nickel carbonate, and the like.
[0104] In some instances, the incorporation of certain ingredients
such as small amounts of the metal acetate or acetic acid in
conjunction with the metal reactant will facilitate the reaction
and result in an improved product. For example, the use of up to
about 5% of zinc acetate in combination with the required amount of
zinc oxide facilitates the formation of a zinc phosphorodithioate
with potentially improved performance properties.
[0105] Especially useful metal phosphorodithloates can be prepared
from phosphorodithloic acids which in turn are prepared by the
reaction of phosphorus pentasulfide with mixtures of alcohols. In
addition, the use of such mixtures enables the utilization of less
expensive alcohols which individually may not yield oil-soluble
phosphorodithioic acids. Thus a mixture of isopropyl and
hexylalcohols can be used to produce a very effective, oil-soluble
metal phosphorodithioate. For the same reason mixtures of
phosphorodithioic acids can be reacted with the metal compounds to
form less expensive, oil-soluble salts.
[0106] The mixtures of alcohols may be mixtures of different
primary alcohols, mixtures of different secondary alcohols or
mixtures of primary and secondary alcohols. Examples of useful
mixtures include: n-butanol and n-octanol; n-pentanol and
2-ethyl-1-hexanol; isobutanol and n-hexanol; isobutanol and isoamyl
alcohol; isopropanol and 2-methyl-4-pentanol; isopropanol and
sec-butyl alcohol; isopropanol and isooctyl alcohol; and the
like.
[0107] Organic triesters of phosphorus acids are also employed in
lubricants. Typical esters include triarylphosphates, trialkyl
phosphates, neutral alkylaryl phosphates, alkoxyalkyl phosphates,
triaryl phosphite, trialkylphosphite, neutral alkyl aryl
phosphites, neutral phosphonate esters and neutral phosphine oxide
esters. In one embodiment, the long chain dialkyl phosphonate
esters are used. More prferentially, the dimethyl-, diethyl-, and
dipropyl-oleyl phohphonates can be used. Neutral acids of
phosphorus acids are the triesters rather than an acid (HO-P) or a
salt of an acid.
[0108] Any C4 to C8 alkyl or higher phosphate ester may be employed
in the disclosure. For example, tributyl phosphate (TBP) and tri
isooctal phosphate (TOF) can be used. The specific triphosphate
ester or combination of esters can easily be selected by one
skilled in the art to adjust the density, viscosity etc. of the
formulated fluid. Mixed esters, such as dibutyl octyl phosphate or
the like may be employed rather than a mixture of two or more
trialkyl phosphates.
[0109] A trialkyl phosphate is often useful to adjust the specific
gravity of the formulation, but it is desirable that the specific
trialkyl phosphate be a liquid at low temperatures. Consequently, a
mixed ester containing at least one partially alkylated with a C3
to C4 alkyl group is very desirable, for example, 4-isopropylphenyl
diphenyl phosphate or 3-butylphenyl diphenyl phosphate. Even more
desirable is a triaryl phosphate produced by partially alkylating
phenol with butylene or propylene to form a mixed phenol which is
then reacted with phosphorus oxychloride as taught in U.S. Pat. No.
3,576,923.
[0110] Any mixed triaryl phosphate (TAP) esters may be used as
cresyl diphenyl phosphate, tricresyl phosphate, mixed xylyl cresyl
phosphates, lower alkylphenyl/phenyl phosphates, such as mixed
isopropylphenyl/phenyl phosphates, t-butylphenyl phenyl phosphates.
These esters are used extensively as plasticizers, functional
fluids, gasoline additives, flame-retardant additives and the
like.
[0111] A metal alkylthiophosphate and more particularly a metal
dialkyl dithio phosphate in which the metal constituent is zinc, or
zinc dialkyl dithio phosphate (ZDDP) can be a useful component of
the lubricating oils of this disclosure. ZDDP can be derived from
primary alcohols, secondary alcohols or mixtures thereof. ZDDP
compounds generally are of the formula
Zn[SP(S)(OR.sup.1)(OR.sup.2)].sub.2
where R.sup.1 and R.sup.2 are C1-C18 alkyl groups, preferably
C2-C12 alkyl groups. These alkyl groups may be straight chain or
branched. Alcohols used in the ZDDP can be propanol, 2-propanol,
butanol, secondary butanol, pentanols, hexanols such as
4-methyl-2-pentanol, n-hexanol, n-octanol, 2-ethyl hexanol,
alkylated phenols, and the like. Mixtures of secondary alcohols or
of primary and secondary alcohol can be preferred. Alkyl aryl
groups may also be used.
[0112] Preferable zinc dithiophosphates which are commercially
available include secondary zinc dithiophosphates such as those
available from for example, The Lubrizol Corporation under the
trade designations "LZ 677A", "LZ 1095" and "LZ 1371", from for
example Chevron Oronite under the trade designation "OLOA 262" and
from for example Afton Chemical under the trade designation "HITEC
7169".
[0113] Although their presence is not required to obtain the
benefit of this disclosure, ZDDP is typically used in amounts of
from about zero to about 3 weight percent, preferably from about
0.05 weight percent to about 2 weight percent, more preferably from
about 0.1 weight percent to about 1.5 weight percent, and even more
preferably from about 0.1 weight percent to about 1 weight percent,
based on the total weight of the lubricating oil, although more or
less can often be used advantageously. A secondary ZDDP may be
preferred and present in an amount of from zero to 1 weight percent
of the total weight of the lubricating oil.
Extreme Pressure, Anti-Scuffing, and Anti-Seize Agents
[0114] Extreme pressure agents and sulfur-based extreme pressure
agents, such as sulfides, sulfoxides, sulfones, thiophosphinates,
thiocarbonates, sulfurized fats and oils, sulfurized olefins and
the like; phosphorus-based extreme pressure agents, such as
phosphoric acid esters (e.g., tricresyl phosphate (TCP) and the
like), phosphorous acid esters, phosphoric acid ester amine salts,
phosphorous acid ester amine salts, and the like; halogen-based
extreme pressure agents, such as chlorinated hydrocarbons and the
like; organometallic extreme pressure agents, such as
thiophosphoric acid salts (e.g., zinc dithiophosphate (ZnDTP) and
the like) and thiocarbamic acid salts; and the like can be
used.
[0115] The phosphoric acid ester, thiophosphoric acid ester, and
amine salt thereof functions to enhance the lubricating
performances, and can be selected from known compounds
conventionally employed as extreme pressure agents. Generally
employed are phosphoric acid esters, a thiophosphoric acid ester,
or an amine salt thereof which has an alkyl group, an alkenyl
group, an alkylaryl group, or an aralkyl group, any of which
contains approximately 3 to 30 carbon atoms.
[0116] Examples of the phosphoric acid esters include aliphatic
phosphoric acid esters such as triisopropyl phosphate, tributyl
phosphate, ethyl dibutyl phosphate, trihexyl phosphate,
tri-2-ethylhexyl phosphate, trilauryl phosphate, tristearyl
phosphate, and trioleyl phosphate; and aromatic phosphoric acid
esters such as benzyl phenyl phosphate, allyl diphenyl phosphate,
triphenyl phosphate, tricresyl phosphate, ethyl diphenyl phosphate,
cresyl diphenyl phosphate, dicresyl phenyl phosphate, ethylphenyl
diphenyl phosphate, diethylphenyl phenyl phosphate, propylphenyl
diphenyl phosphate, dipropylphenyl phenyl phosphate, triethylphenyl
phosphate, tripropylphenyl phosphate, butylphenyl diphenyl
phosphate, dibutylphenyl phenyl phosphate, and tributylphenyl
phosphate. Preferably, the phosphoric acid ester is a
trialkylphenyl phosphate.
[0117] Examples of the thiophosphoric acid esters include aliphatic
thiophosphoric acid esters such as triisopropyl thiophosphate,
tributyl thiophosphate, ethyl dibutyl thiophosphate, trihexyl
thiophosphate, tri-2-ethylhexyl thiophosphate, trilauryl
thiophosphate, tristearyl thiophosphate, and trioleyl
thiophosphate; and aromatic thiophosphoric acid esters such as
benzyl phenyl thiophosphate, allyl diphenyl thiophosphate,
triphenyl thiophosphate, tricresyl thiophosphate, ethyl diphenyl
thiophosphate, cresyl diphenyl thiophosphate, dicresyl phenyl
thiophosphate, ethylphenyl diphenyl thiophosphate, diethylphenyl
phenyl thiophosphate, propylphenyl diphenyl thiophosphate,
dipropylphenyl phenyl thiophosphate, triethylphenyl thiophosphate,
tripropylphenyl thiophosphate, butylphenyl diphenyl thiophosphate,
dibutylphenyl phenyl thiophosphate, and tributylphenyl
thiophosphate. Preferably, the thiophosphoric acid ester is a
trialkylphenyl thiophosphate.
[0118] Also employable are amine salts of the above-mentioned
phosphates and thiophosphates. Amine salts of acidic alkyl or aryl
esters of the phosphoric acid and thiophosphoric acid are also
employable. Preferably, the amine salt is an amine salt of
trialkylphenyl phosphate or an amine salt of alkyl phosphate.
[0119] One or any combination of the compounds selected from the
group consisting of a phosphoric acid ester, a thiophosphoric acid
ester, and an amine salt thereof may be used.
[0120] The phosphorus acid ester and/or its amine salt function to
enhance the lubricating performances, and can be selected from
known compounds conventionally employed as extreme pressure agents.
Generally employed is a phosphorus acid ester or an amine salt
thereof which has an alkyl group, an alkenyl group, an alkylaryl
group, or an aralkyl group, any of which contains approximately 3
to 30 carbon atoms.
[0121] Examples of the phosphorus acid esters include aliphatic
phosphorus acid esters such as triisopropyl phosphite, tributyl
phosphite, ethyl dibutyl phosphite, trihexyl phosphite,
tri-2-ethylhexylphosphite, trilauryl phosphite, tristearyl
phosphite, and trioleyl phosphite; and aromatic phosphorus acid
esters such as benzyl phenyl phosphite, allyl diphenylphosphite,
triphenyl phosphite, tricresyl phosphite, ethyl diphenyl phosphite,
tributyl phosphite, ethyl dibutyl phosphite, cresyl diphenyl
phosphite, dicresyl phenyl phosphite, ethylphenyl diphenyl
phosphite, diethylphenyl phenyl phosphite, propylphenyl diphenyl
phosphite, dipropylphenyl phenyl phosphite, triethylphenyl
phosphite, tripropylphenyl phosphite, butylphenyl diphenyl
phosphite, dibutylphenyl phenyl phosphite, and tributylphenyl
phosphite. Also favorably employed are dilauryl phosphite, dioleyl
phosphite, dialkyl phosphites, and diphenyl phosphite. Preferably,
the phosphorus acid ester is a dialkyl phosphite or a trialkyl
phosphite.
[0122] The phosphate salt may be derived from a polyamine. The
polyamines include alkoxylated diamines, fatty polyamine diamines,
alkylenepolyamines, hydroxy containing polyamines, condensed
polyamines arylpolyamines, and heterocyclic polyamines. Examples of
these amines include Ethoduomeen T/13 and T/20 which are ethylene
oxide condensation products of N-tallowtrimethylenediamine
containing 3 and 10 moles of ethylene oxide per mole of diamine,
respectively.
[0123] In another embodiment, the polyamine is a fatty diamine. The
fatty diamines include mono- or dialkyl, symmetrical or
asymmetrical ethylene diamines, propane diamines (1,2 or 1,3), and
polyamine analogs of the above. Suitable commercial fatty
polyamines are Duomeen C (N-coco-1,3-diaminopropane), Duomeen S
(N-soya-1,3-diaminopropane), Duomeen T
(N-tallow-1,3-diaminopropane), and Duomeen O
(N-oleyl-1,3-diaminopropane). "Duomeens" are commercially available
from Armak Chemical Co., Chicago, Ill.
[0124] Such alkylenepolyamines include methylenepolyamines,
ethylenepolyamines, butylenepolyamines, propylenepolyamines,
pentylenepolyamines, etc. The higher homologs and related
heterocyclic amines such as piperazines and N-amino
alkyl-substituted piperazines are also included. Specific examples
of such polyamines are ethylenediamine, triethylenetetramine,
tris-(2-aminoethyl)amine, propylenediamine, trimethylenediamine,
tripropylenetetramine, tetraethylenepentamine,
hexaethyleneheptamine, pentaethylenehexamine, etc. Higher homologs
obtained by condensing two or more of the above-noted
alkyleneamines are similarly useful as are mixtures of two or more
of the aforedescribed polyamines.
[0125] In one embodiment the polyamine is an ethylenepolyamine.
Such polyamines are described in detail under the heading Ethylene
Amines in Kirk Othmer's "Encyclopedia of Chemical Technology", 2nd
Edition, Vol. 7, pages 22-37, Interscience Publishers, New York
(1965). Ethylenepolyamines are often a complex mixture of
polyalkylenepolyamines including cyclic condensation products.
[0126] Other useful types of polyamine mixtures are those resulting
from stripping of the above-described polyamine mixtures to leave,
as residue, what is often termed "polyamine bottoms". In general,
alkylenepolyamine bottoms can be characterized as having less than
2%, usually less than 1% (by weight) material boiling below about
200.degree. C. A typical sample of such ethylene polyamine bottoms
obtained from the Dow Chemical Company of Freeport, Tex. designated
"E-100". These alkylenepolyamine bottoms include cyclic
condensation products such as piperazine and higher analogs of
diethylenetriamine, triethylenetetramine and the like. These
alkylenepolyamine bottoms can be reacted solely with the acylating
agent or they can be used with other amines, polyamines, or
mixtures thereof. Another useful polyamine is a condensation
reaction between at least one hydroxy compound with at least one
polyamine reactant containing at least one primary or secondary
amino group. The hydroxy compounds are preferably polyhydric
alcohols and amines. The polyhydric alcohols are described below.
In one embodiment, the hydroxy compounds are polyhydric amines.
Polyhydric amines include any of the above-described monoamines
reacted with an alkylene oxide (e.g., ethylene oxide, propylene
oxide, butylene oxide, etc.) having from two to about 20 carbon
atoms, or from two to about four. Examples of polyhydric amines
include tri-(hydroxypropyl)amine, tris-(hydroxymethyl)amino
methane, 2-amino-2-methyl-1,3-propanediol,
N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, and
N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, preferably
tris(hydroxymethyl)aminomethane (THAM).
[0127] Polyamines which react with the polyhydric alcohol or amine
to form the condensation products or condensed amines, are
described above. Preferred polyamines include triethylenetetramine
(TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine
(PEHA), and mixtures of polyamines such as the above-described
"amine bottoms".
[0128] Examples of extreme pressure additives include sulphur-based
extreme pressure additives such as dialkyl sulphides, dibenzyl
sulphide, dialkyl polysulphides, dibenzyl disulphide, alkyl
mercaptans, dibenzothiophene and 2,2'-dithiobis(benzothiazole);
phosphorus-based extreme pressure additives such as trialkyl
phosphates, triaryl phosphates, trialkyl phosphonates, trialkyl
phosphites, triaryl phosphites and dialkylhydrozine phosphites, and
phosphorus- and sulphur-based extreme pressure additives such as
zinc dialkyldithiophosphates, dialkylthiophosphoric acid, trialkyl
thiophosphate esters, acidic thiophosphate esters and trialkyl
trithiophosphates. Extreme pressure additives can be used
individually or in the form of mixtures, conveniently in an amount
within the range from zero to 2% by weight of the lubricating oil
composition.
Dispersants
[0129] During machine operation, oil-insoluble oxidation byproducts
are produced. Dispersants help keep these byproducts in solution,
thus diminishing their deposition on metal surfaces. Dispersants
used in the formulation of the lubricating oil may be ashless or
ash-forming in nature. Preferably, the dispersant is ashless. So
called ashless dispersants are organic materials that form
substantially no ash upon combustion. For example,
non-metal-containing or borated metal-free dispersants are
considered ashless. In contrast, metal-containing detergents
discussed above form ash upon combustion.
[0130] Suitable dispersants typically contain a polar group
attached to a relatively high molecular weight hydrocarbon chain.
The polar group typically contains at least one element of
nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain
50 to 400 carbon atoms.
[0131] A particularly useful class of dispersants are the
(poly)alkenylsuccinic derivatives, typically produced by the
reaction of a long chain hydrocarbyl substituted succinic compound,
usually a hydrocarbyl substituted succinic anhydride, with a
polyhydroxy or polyamino compound. The long chain hydrocarbyl group
constituting the oleophilic portion of the molecule which confers
solubility in the oil, is normally a polyisobutylene group. Many
examples of this type of dispersant are well known commercially and
in the literature. Exemplary U.S. patents describing such
dispersants are U.S. Pat. Nos. 3,172,892; 3,2145,707; 3,219,666;
3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904;
3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are
described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025;
3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574;
3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250;
3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A
further description of dispersants may be found, for example, in
European Patent Application No. 471 071, to which reference is made
for this purpose.
[0132] Hydrocarbyl-substituted succinic acid and
hydrocarbyl-substituted succinic anhydride derivatives are useful
dispersants. In particular, succinimide, succinate esters, or
succinate ester amides prepared by the reaction of a
hydrocarbon-substituted succinic acid compound preferably having at
least 50 carbon atoms in the hydrocarbon substituent, with at least
one equivalent of an alkylene amine are particularly useful.
[0133] Succinimides are formed by the condensation reaction between
hydrocarbyl substituted succinic anhydrides and amines. Molar
ratios can vary depending on the polyamine. For example, the molar
ratio of hydrocarbyl substituted succinic anhydride to TEPA can
vary from about 1:1 to about 5:1. Representative examples are shown
in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746;
3,322,670; and 3,652,616, 3,948,800; and Canada Patent No.
1,094,044.
[0134] Succinate esters are formed by the condensation reaction
between hydrocarbyl substituted succinic anhydrides and alcohols or
polyols. Molar ratios can vary depending on the alcohol or polyol
used. For example, the condensation product of a hydrocarbyl
substituted succinic anhydride and pentaerythritol is a useful
dispersant.
[0135] Succinate ester amides are formed by condensation reaction
between hydrocarbyl substituted succinic anhydrides and alkanol
amines. For example, suitable alkanol amines include ethoxylated
polyalkylpolyamines, propoxylated polyalkylpolyamines and
polyalkenylpolyamines such as polyethylene polyamines. One example
is propoxylated hexamethylenediamine. Representative examples are
shown in U.S. Pat. No. 4,426,305.
[0136] The molecular weight of the hydrocarbyl substituted succinic
anhydrides used in the preceding paragraphs will typically range
between 800 and 2,500 or more. The above products can be
post-reacted with various reagents such as sulfur, oxygen,
formaldehyde, carboxylic acids such as oleic acid. The above
products can also be post reacted with boron compounds such as
boric acid, borate esters or highly borated dispersants, to form
borated dispersants generally having from about 0.1 to about 5
moles of boron per mole of dispersant reaction product.
[0137] Mannich base dispersants are made from the reaction of
alkylphenols, formaldehyde, and amines. See U.S. Pat. No.
4,767,551, which is incorporated herein by reference. Process aids
and catalysts, such as oleic acid and sulfonic acids, can also be
part of the reaction mixture. Molecular weights of the alkylphenols
range from 800 to 2,500. Representative examples are shown in U.S.
Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953;
3,798,165; and 3,803,039.
[0138] Typical high molecular weight aliphatic acid modified
Mannich condensation products useful in this disclosure can be
prepared from high molecular weight alkyl-substituted
hydroxyaromatics or HNR2 group-containing reactants.
[0139] Hydrocarbyl substituted amine ashless dispersant additives
are well known to one skilled in the art; see, for example, U.S.
Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209,
and 5,084,197.
[0140] Preferred dispersants include borated and non-borated
succinimides, including those derivatives from mono-succinimides,
bis-succinimides, and/or mixtures of mono- and bis-succinimides,
wherein the hydrocarbyl succinimide is derived from a
hydrocarbylene group such as polyisobutylene having a Mn of from
about 500 to about 5000, or from about 1000 to about 3000, or about
1000 to about 2000, or a mixture of such hydrocarbylene groups,
often with high terminal vinylic groups. Other preferred
dispersants include succinic acid-esters and amides,
alkylphenol-polyamine-coupled Mannich adducts, their capped
derivatives, and other related components.
[0141] Polymethacrylate or polyacrylate derivatives are another
class of dispersants. These dispersants are typically prepared by
reacting a nitrogen containing monomer and a methacrylic or acrylic
acid esters containing 5-25 carbon atoms in the ester group.
Representative examples are shown in U.S. Pat. Nos. 2,100,993, and
6,323,164. Polymethacrylate and polyacrylate dispersants are
normally used as multifunctional viscosity modifiers. The lower
molecular weight versions can be used as lubricant dispersants or
fuel detergents.
[0142] Illustrative preferred dispersants useful in this disclosure
include those derived from polyalkenyl-substituted mono- or
dicarboxylic acid, anhydride or ester, which dispersant has a
polyalkenyl moiety with a number average molecular weight of at
least 900 and from greater than 1.3 to 1.7, preferably from greater
than 1.3 to 1.6, most preferably from greater than 1.3 to 1.5,
functional groups (mono- or dicarboxylic acid producing moieties)
per polyalkenyl moiety (a medium functionality dispersant).
Functionality (F) can be determined according to the following
formula:
F=(SAP.times.M.sub.n)/((112,200.times.A.I.)-(SAP.times.98))
wherein SAP is the saponification number (i.e., the number of
milligrams of KOH consumed in the complete neutralization of the
acid groups in one gram of the succinic-containing reaction
product, as determined according to ASTM D94); M.sub.n is the
number average molecular weight of the starting olefin polymer; and
A.I. is the percent active ingredient of the succinic-containing
reaction product (the remainder being unreacted olefin polymer,
succinic anhydride and diluent).
[0143] The polyalkenyl moiety of the dispersant may have a number
average molecular weight of at least 900, suitably at least 1500,
preferably between 1800 and 3000, such as between 2000 and 2800,
more preferably from about 2100 to 2500, and most preferably from
about 2200 to about 2400. The molecular weight of a dispersant is
generally expressed in terms of the molecular weight of the
polyalkenyl moiety. This is because the precise molecular weight
range of the dispersant depends on numerous parameters including
the type of polymer used to derive the dispersant, the number of
functional groups, and the type of nucleophilic group employed.
[0144] Polymer molecular weight, specifically M.sub.n, can be
determined by various known techniques. One convenient method is
gel permeation chromatography (GPC), which additionally provides
molecular weight distribution information (see W. W. Yau, J. J.
Kirkland and D. D. Bly, "Modern Size Exclusion Liquid
Chromatography", John Wiley and Sons, New York, 1979). Another
useful method for determining molecular weight, particularly for
lower molecular weight polymers, is vapor pressure osmometry (e.g.,
ASTM D3592).
[0145] The polyalkenyl moiety in a dispersant preferably has a
narrow molecular weight distribution (MWD), also referred to as
polydispersity, as determined by the ratio of weight average
molecular weight (M.sub.w) to number average molecular weight
(M.sub.n). Polymers having a M.sub.w/M.sub.n of less than 2.2,
preferably less than 2.0, are most desirable. Suitable polymers
have a polydispersity of from about 1.5 to 2.1, preferably from
about 1.6 to about 1.8.
[0146] Suitable polyalkenes employed in the formation of the
dispersants include homopolymers, interpolymers or lower molecular
weight hydrocarbons. One family of such polymers comprise polymers
of ethylene and/or at least one C3 to C26 alpha-olefin having the
formula
H.sub.2C.dbd.CHR.sup.1
wherein R.sup.1 is a straight or branched chain alkyl radical
comprising 1 to 26 carbon atoms and wherein the polymer contains
carbon-to-carbon unsaturation, and a high degree of terminal
ethenylidene unsaturation. Preferably, such polymers comprise
interpolymers of ethylene and at least one alpha-olefin of the
above formula, wherein R.sup.1 is alkyl of from 1 to 18 carbon
atoms, and more preferably is alkyl of from 1 to 8 carbon atoms,
and more preferably still of from 1 to 2 carbon atoms.
[0147] Another useful class of polymers is polymers prepared by
cationic polymerization of monomers such as isobutene and styrene.
Common polymers from this class include polyisobutenes obtained by
polymerization of a C4 refinery stream having a butene content of
35 to 75% by wt., and an isobutene content of 30 to 60% by wt. A
preferred source of monomer for making poly-n-butenes is petroleum
feedstreams such as Raffinate II. These feedstocks are disclosed in
the art such as in U.S. Pat. No. 4,952,739. A preferred embodiment
utilizes polyisobutylene prepared from a pure isobutylene stream or
a Raffinate I stream to prepare reactive isobutylene polymers with
terminal vinylidene olefins. Polyisobutene polymers that may be
employed are generally based on a polymer chain of from 1500 to
3000.
[0148] The dispersant(s) are preferably non-polymeric (e.g., mono-
or bis-succinimides). Such dispersants can be prepared by
conventional processes such as disclosed in U.S. Patent Application
Publication No. 2008/0020950, the disclosure of which is
incorporated herein by reference.
[0149] The dispersant(s) can be borated by conventional means, as
generally disclosed in U.S. Pat. Nos. 3,087,936, 3,254,025 and
5,430,105.
[0150] Dispersants may be used in an amount of zero to 10 weight
percent or 0.01 to 8 weight percent, preferably about 0.1 to 5
weight percent, or more preferably 0.5 to 3 weight percent. Or such
dispersants may be used in an amount of zero to 8 weight percent,
preferably about 0.01 to 5 weight percent, or more preferably 0.1
to 3 weight percent. On an active ingredient basis, such additives
may be used in an amount of zero to 10 weight percent, preferably
about 0.3 to 3 weight percent. The hydrocarbon portion of the
dispersant atoms can range from C60 to C1000, or from C70 to C300,
or from C70 to C200. These dispersants may contain both neutral and
basic nitrogen, and mixtures of both. Dispersants can be end-capped
by borates and/or cyclic carbonates. Nitrogen content in the
finished oil can vary from about zero to about 2000 ppm by weight,
preferably from about 100 ppm by weight to about 1200 ppm by
weight. Basic nitrogen can vary from about zero to about 1000 ppm
by weight, preferably from about 100 ppm by weight to about 600 ppm
by weight.
[0151] Dispersants as described herein are beneficially useful with
the compositions of this disclosure. Further, in one embodiment,
preparation of the compositions of this disclosure using one or
more dispersants is achieved by combining ingredients of this
disclosure, plus optional base stocks and lubricant additives, in a
mixture at a temperature above the melting point of such
ingredients, particularly that of the one or more M-carboxylates
(M=H, metal, two or more metals, mixtures thereof).
[0152] As used herein, the dispersant concentrations are given on
an "as delivered" basis. Typically, the active dispersant is
delivered with a process oil. The "as delivered" dispersant
typically contains from about 20 weight percent to about 80 weight
percent, or from about 40 weight percent to about 60 weight
percent, of active dispersant in the "as delivered" dispersant
product.
Detergents
[0153] Illustrative detergents useful in this disclosure include,
for example, alkali metal detergents, alkaline earth metal
detergents, or mixtures of one or more alkali metal detergents and
one or more alkaline earth metal detergents. A typical detergent is
an anionic material that contains a long chain hydrophobic portion
of the molecule and a smaller anionic or oleophobic hydrophilic
portion of the molecule. The anionic portion of the detergent is
typically derived from an organic acid such as a sulfur-containing
acid, carboxylic acid (e.g., salicylic acid), phosphorus-containing
acid, phenol, or mixtures thereof. The counterion is typically an
alkaline earth or alkali metal. The detergent can be overbased as
described herein.
[0154] The detergent is preferably a metal salt of an organic or
inorganic acid, a metal salt of a phenol, or mixtures thereof. The
metal is preferably selected from an alkali metal, an alkaline
earth metal, and mixtures thereof. The organic or inorganic acid is
selected from an aliphatic organic or inorganic acid, a
cycloaliphatic organic or inorganic acid, an aromatic organic or
inorganic acid, and mixtures thereof.
[0155] The metal is preferably selected from an alkali metal, an
alkaline earth metal, and mixtures thereof. More preferably, the
metal is selected from calcium (Ca), magnesium (Mg), and mixtures
thereof.
[0156] The organic acid or inorganic acid is preferably selected
from a sulfur-containing acid, a carboxylic acid, a
phosphorus-containing acid, and mixtures thereof.
[0157] Preferably, the metal salt of an organic or inorganic acid
or the metal salt of a phenol comprises calcium phenate, calcium
sulfonate, calcium salicylate, magnesium phenate, magnesium
sulfonate, magnesium salicylate, an overbased detergent, and
mixtures thereof.
[0158] Salts that contain a substantially stochiometric amount of
the metal are described as neutral salts and have a total base
number (TBN, as measured by ASTM D2896) of from 0 to 80. Many
compositions are overbased, containing large amounts of a metal
base that is achieved by reacting an excess of a metal compound (a
metal hydroxide or oxide, for example) with an acidic gas (such as
carbon dioxide). Useful detergents can be neutral, mildly
overbased, or highly overbased. These detergents can be used in
mixtures of neutral, overbased, highly overbased calcium
salicylate, sulfonates, phenates and/or magnesium salicylate,
sulfonates, phenates. The TBN ranges can vary from low, medium to
high TBN products, including as low as 0 to as high as 600.
Preferably the TBN delivered by the detergent is between 1 and 20.
More preferably between 1 and 12. Mixtures of low, medium, high TBN
can be used, along with mixtures of calcium and magnesium metal
based detergents, and including sulfonates, phenates, salicylates,
and carboxylates. A detergent mixture with a metal ratio of 1, in
conjunction of a detergent with a metal ratio of 2, and as high as
a detergent with a metal ratio of 5, can be used. Borated
detergents can also be used.
[0159] Alkaline earth phenates are another useful class of
detergent. These detergents can be made by reacting alkaline earth
metal hydroxide or oxide (CaO, Ca(OH).sub.2, BaO, Ba(OH).sub.2,
MgO, Mg(OH).sub.2, for example) with an alkyl phenol or sulfurized
alkylphenol. Useful alkyl groups include straight chain or branched
C1-C30 alkyl groups, preferably, C4-C20 or mixtures thereof.
Examples of suitable phenols include isobutylphenol,
2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It
should be noted that starting alkylphenols may contain more than
one alkyl substituent that are each independently straight chain or
branched and can be used from 0.5 to 6 weight percent. When a
non-sulfurized alkylphenol is used, the sulfurized product may be
obtained by methods well known in the art. These methods include
heating a mixture of alkylphenol and sulfurizing agent (including
elemental sulfur, sulfur halides such as sulfur dichloride, and the
like) and then reacting the sulfurized phenol with an alkaline
earth metal base.
[0160] In accordance with this disclosure, metal salts of
carboxylic acids are preferred detergents. These carboxylic acid
detergents may be prepared by reacting a basic metal compound with
at least one carboxylic acid and removing free water from the
reaction product. These compounds may be overbased to produce the
desired TBN level. Detergents made from salicylic acid are one
preferred class of detergents derived from carboxylic acids. Useful
salicylates include long chain alkyl salicylates. One useful family
of compositions is of the formula
##STR00001##
where R is an alkyl group having 1 to about 30 carbon atoms, n is
an integer from 1 to 4, and M is an alkaline earth metal. Preferred
R groups are alkyl chains of at least C11, preferably C13 or
greater. R may be optionally substituted with substituents that do
not interfere with the detergent's function. M is preferably,
calcium, magnesium, barium, or mixtures thereof. More preferably, M
is calcium.
[0161] Hydrocarbyl-substituted salicylic acids may be prepared from
phenols by the Kolbe reaction (see U.S. Pat. No. 3,595,791). The
metal salts of the hydrocarbyl-substituted salicylic acids may be
prepared by double decomposition of a metal salt in a polar solvent
such as water or alcohol.
[0162] Alkaline earth metal phosphates are also used as detergents
and are known in the art.
[0163] Detergents may be simple detergents or what is known as
hybrid or complex detergents. The latter detergents can provide the
properties of two detergents without the need to blend separate
materials. See U.S. Pat. No. 6,034,039.
[0164] Preferred detergents include calcium sulfonates, magnesium
sulfonates, calcium salicylates, magnesium salicylates, calcium
phenates, magnesium phenates, and other related components
(including borated detergents), and mixtures thereof. Preferred
mixtures of detergents include magnesium sulfonate and calcium
salicylate, magnesium sulfonate and calcium sulfonate, magnesium
sulfonate and calcium phenate, calcium phenate and calcium
salicylate, calcium phenate and calcium sulfonate, calcium phenate
and magnesium salicylate, calcium phenate and magnesium phenate.
Overbased detergents are also preferred.
[0165] Although their presence is not required to obtain the
benefit of this disclosure, detergent concentration in the
lubricating oils of this disclosure can range from zero to about
6.0 weight percent, preferably zero to 5.0 weight percent, and more
preferably from about 0.01 weight percent to about 3.0 weight
percent, based on the total weight of the lubricating oil.
[0166] As used herein, the detergent concentrations are given on an
"as delivered" basis. Typically, the active detergent is delivered
with a process oil. The "as delivered" detergent typically contains
from about 20 weight percent to about 100 weight percent, or from
about 40 weight percent to about 60 weight percent, of active
detergent in the "as delivered" detergent product.
Viscosity Modifiers
[0167] Viscosity modifiers (also known as viscosity index improvers
(VI improvers), and viscosity improvers) can be included in the
lubricant compositions of this disclosure.
[0168] Viscosity modifiers provide lubricants with high and low
temperature operability. These additives impart shear stability at
elevated temperatures and acceptable viscosity at low
temperatures.
[0169] Suitable viscosity modifiers include high molecular weight
hydrocarbons, polyesters and viscosity modifier dispersants that
function as both a viscosity modifier and a dispersant. Typical
molecular weights of these polymers are between about 10,000 to
1,500,000, more typically about 20,000 to 1,200,000, and even more
typically between about 50,000 and 1,000,000.
[0170] Examples of suitable viscosity modifiers are linear or
star-shaped polymers and copolymers of methacrylate, butadiene,
olefins, or alkylated styrenes. Polyisobutylene is a commonly used
viscosity modifier. Another suitable viscosity modifier is
polymethacrylate (copolymers of various chain length alkyl
methacrylates, for example), some formulations of which also serve
as pour point depressants. Other suitable viscosity modifiers
include copolymers of ethylene and propylene, hydrogenated block
copolymers of styrene and isoprene, and polyacrylates (copolymers
of various chain length acrylates, for example). Specific examples
include styrene-isoprene or styrene-butadiene based polymers of
50,000 to 200,000 molecular weight.
[0171] Olefin copolymers are commercially available from Chevron
Oronite Company LLC under the trade designation "PARATONE.RTM."
(such as "PARATONE.RTM. 8921" and "PARATONE.RTM. 8941"); from Afton
Chemical Corporation under the trade designation "HiTEC.RTM." (such
as "HiTEC.RTM. 5850B"; and from The Lubrizol Corporation under the
trade designation "Lubrizol.RTM. 7067C". Hydrogenated polyisoprene
star polymers are commercially available from Infineum
International Limited, e.g., under the trade designation "SV200"
and "SV600". Hydrogenated diene-styrene block copolymers are
commercially available from Infineum International Limited, e.g.,
under the trade designation "SV 50".
[0172] The polymethacrylate or polyacrylate polymers can be linear
polymers which are available from Evnoik Industries under the trade
designation "Viscoplex.RTM." (e.g., Viscoplex 6-954) or star
polymers which are available from Lubrizol Corporation under the
trade designation Asteric.TM. (e.g., Lubrizol 87708 and Lubrizol
87725).
[0173] Illustrative vinyl aromatic-containing polymers useful in
this disclosure may be derived predominantly from vinyl aromatic
hydrocarbon monomer. Illustrative vinyl aromatic-containing
copolymers useful in this disclosure may be represented by the
following general formula:
A-B
wherein A is a polymeric block derived predominantly from vinyl
aromatic hydrocarbon monomer, and B is a polymeric block derived
predominantly from conjugated diene monomer.
[0174] Although their presence is not required to obtain the
benefit of this disclosure, viscosity modifiers may be used in an
amount of less than about 10 weight percent, preferably less than
about 7 weight percent, more preferably less than about 4 weight
percent, and in certain instances, may be used at less than 2
weight percent, preferably less than about 1 weight percent, and
more preferably less than about 0.5 weight percent, based on the
total weight of the lubricating oil composition. Viscosity
modifiers are typically added as concentrates, in large amounts of
diluent oil.
[0175] As used herein, the viscosity modifier concentrations are
given on an "as delivered" basis. Typically, the active polymer is
delivered with a diluent oil. The "as delivered" viscosity modifier
typically contains from 20 weight percent to 75 weight percent of
an active polymer for polymethacrylate or polyacrylate polymers, or
from 8 weight percent to 20 weight percent of an active polymer for
olefin copolymers, hydrogenated polyisoprene star polymers, or
hydrogenated diene-styrene block copolymers, in the "as delivered"
polymer concentrate.
Antioxidants
[0176] Antioxidants retard the oxidative degradation of base oils
during service. Such degradation may result in deposits on metal
surfaces, the presence of sludge, or a viscosity increase in the
lubricant. One skilled in the art knows a wide variety of oxidation
inhibitors that are useful in lubricating oil compositions. See,
Klamann in Lubricants and Related Products, op cite, and U.S. Pat.
Nos. 4,798,684 and 5,084,197, for example.
[0177] Two general types of oxidation inhibitors are those that
react with the initiators, peroxy radicals, and hydroperoxides to
form inactive compounds, and those that decompose these materials
to form less active compounds. Examples are hindered (alkylated)
phenols, e.g. 6-di(tert-butyl)-4-methylphenol
[2,6-di(tert-butyl)-p-cresol, DBPC], and aromatic amines, e.g.
N-phenyl-.alpha.-naphthalamine. These are used in turbine,
circulation, and hydraulic oils that are intended for extended
service.
[0178] Useful antioxidants include hindered phenols. These phenolic
antioxidants may be ashless (metal-free) phenolic compounds or
neutral or basic metal salts of certain phenolic compounds. Typical
phenolic antioxidant compounds are the hindered phenolics which are
the ones which contain a sterically hindered hydroxyl group, and
these include those derivatives of dihydroxy aryl compounds in
which the hydroxyl groups are in the o- or p-position to each
other. Typical phenolic antioxidants include the hindered phenols
substituted with C.sub.6+ alkyl groups and the alkylene coupled
derivatives of these hindered phenols. Examples of phenolic
materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl
phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol;
2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl
phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful
hindered mono-phenolic antioxidants may include for example
hindered 2,6-di-alkyl-phenolic proprionic ester derivatives.
Bis-phenolic antioxidants may also be advantageously used in
combination with the instant disclosure. Examples of ortho-coupled
phenols include: 2,2'-bis(4-heptyl-6-t-butyl-phenol);
2,2'-bis(4-octyl-6-t-butyl-phenol); and
2,2'-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenols
include for example 4,4'-bis(2,6-di-t-butyl phenol) and
4,4'-methylene-bis(2,6-di-t-butyl phenol).
[0179] Further examples of phenol-based antioxidants include
2-t-butylphenol, 2-t-butyl-4-methylphenol,
2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol,
2,4-dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol,
3-t-butyl-4-methoxyphenol, 2,5-di-t-butylhydroquinone (manufactured
by the Kawaguchi Kagaku Co. under trade designation "Antage DBH"),
2,6-di-t-butylphenol and 2,6-di-t-butyl-4-alkylphenols such as
2,6-di-t-butyl-4-methylphenol and 2,6-di-t-butyl-4-ethylphenol;
2,6-di-t-butyl-4-alkoxyphenols such as
2,6-di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol,
3,5-di-t-butyl-4-hydroxybenzylmercaptoocty-1 acetate,
alkyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionates such as
n-octyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (manufactured
by the Yoshitomi Seiyaku Co. under the trade designation "Yonox
SS"), n-dodecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and
2'-ethylhexyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate;
2,6-di-t-butyl-alpha-dimethylamino-p-cresol,
2,2'-methylenebis(4-alkyl-6-t-butylphenol) compounds such as
2,2'-methylenebis(4-methyl-6-t-butylphe-nol) (manufactured by the
Kawaguchi Kagaku Co. under the trade designation "Antage W-400")
and 2,2'-methylenebis(4-ethyl-6-t-butylphenol) (manufactured by the
Kawaguchi Kagaku Co. under the trade designation "Antage W-500");
bisphenols such as 4,4'-butylidenebis(3-methyl-6-t-butyl-phenol)
(manufactured by the Kawaguchi Kagaku Co. under the trade
designation "Antage W-300"), and
4,4'-methylenebis(2,6-di-t-butylphenol) (manufactured by Laporte
Performance Chemicals under the trade designation "Ionox
220AH").
[0180] Other examples of phenol-based antioxidants include
4,4'-bis(2,6-di-t-butylphenol), 2,2-(di-p-hydroxyphenyl)propane
(Bisphenol A), 2,2-bis(3,5-di-t-butyl-4-hydroxyphenyl)propane,
4,4'-cyclohexylidenebis(2,6-di-t-butylphenol), hexamethylene glycol
bis[3, (3,5-di-t-butyl-4-hydroxyphenyl)propionate] (manufactured by
the Ciba Speciality Chemicals Co. under the trade designation
"Irganox L109"), triethylene glycol
bis[3-(3-t-butyl-4-hydrox-y-5-methylphenyl)propionate]
(manufactured by the Yoshitomi Seiyaku Co. under the trade
designation "Tominox 917"),
2,2'-thio[diethyl-3-(3,5-di-t--butyl-4-hydroxyphenyl)propionate]
(manufactured by the Ciba Speciality Chemicals Co. under the trade
designation "Irganox L115"),
3,9-bis{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)-propionylo-
-xy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane (manufactured by the
Sumitomo Kagaku Co. under the trade designation "Sumilizer GA80")
and 4,4'-thiobis(3-methyl-6-t-butylphenol) (manufactured by the
Kawaguchi Kagaku Co. under the trade designation "Antage RC"),
2,2'-thiobis(4,6-di-t-butylresorcinol); polyphenols such as
tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionato]methane
(manufactured by the Ciba Speciality Chemicals Co. under the trade
designation "Irganox L101"),
1,1,3-tris(2-methyl-4-hydroxy-5-t-butylpheny-1)butane (manufactured
by the Yoshitomi Seiyaku Co. under the trade designation "Yoshinox
930"),
1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene
(manufactured by Ciba Speciality Chemicals under the trade
designation "Irganox 330"),
bis[3,3'-bis(4'-hydroxy-3'-t-butylpheny-1)butyric acid] glycol
ester,
2-(3',5'-di-t-butyl-4-hydroxyphenyl)-methyl-4-(2'',4''-di-t-butyl-3''-hyd-
roxyphenyl)methyl-6-t-butylphenol and
2,6-bis(2'-hydroxy-3'-t-butyl-5'-methylbenzyl)-4-methylphenol; and
phenol/aldehyde condensates such as the condensates of
p-t-butylphenol and formaldehyde and the condensates of
p-t-butylphenol and acetaldehyde.
[0181] The phenolic antioxidants include sulfurized and
non-sulfurized phenolic antioxidants. The terms "phenolic type" or
"phenolic antioxidant" used herein include compounds having one or
more than one hydroxyl group bound to an aromatic ring, which may
itself be mononuclear, e.g., benzyl, or poly-nuclear, e.g.,
naphthyl and spiro aromatic compounds. Thus "phenol type" includes
phenol per se, catechol, resorcinol, hydroquinone, naphthol, etc.,
as well as alkyl or alkenyl and sulfurized alkyl or alkenyl
derivatives thereof, and bisphenol type compounds including such
bi-phenol compounds linked by alkylene bridges sulfuric bridges or
oxygen bridges. Alkyl phenols include mono- and poly-alkyl or
alkenyl phenols, the alkyl or alkenyl group containing from 3-100
carbons, preferably 4 to 50 carbons and sulfurized derivatives
thereof, the number of alkyl or alkenyl groups present in the
aromatic ring ranging from 1 to up to the available unsatisfied
valences of the aromatic ring remaining after counting the number
of hydroxyl groups bound to the aromatic ring.
[0182] Generally, therefore, the phenolic antioxidant may be
represented by the general formula:
(R).sub.x--Ar--(OH).sub.y
where Ar is selected from the group consisting of:
##STR00002##
wherein R is a C3-C100 alkyl or alkenyl group, a sulfur substituted
alkyl or alkenyl group, preferably a C4-C50 alkyl or alkenyl group
or sulfur substituted alkyl or alkenyl group, more preferably
C3-C100 alkyl or sulfur substituted alkyl group, most preferably a
C4-C50 alkyl group, R.sup.G is a C1-C100 alkylene or sulfur
substituted alkylene group, preferably a C2-C50 alkylene or sulfur
substituted alkylene group, more preferably a C2-C20 alkylene or
sulfur substituted alkylene group, y is at least 1 to up to the
available valences of Ar, x ranges from 0 to up to the available
valances of Ar-y, z ranges from 1 to 10, n ranges from 0 to 20, and
m is 0 to 4 and p is 0 or 1, preferably y ranges from 1 to 3, x
ranges from 0 to 3, z ranges from 1 to 4 and n ranges from 0 to 5,
and p is 0.
[0183] Preferred phenolic antioxidant compounds are the hindered
phenolics and phenolic esters, which contain a sterically hindered
hydroxyl group, and these include those derivatives of dihydroxy
aryl compounds in which the hydroxyl groups are in the o- or
p-position to each other. Typical phenolic antioxidants include the
hindered phenols substituted with C1+ alkyl groups and the alkylene
coupled derivatives of these hindered phenols. Examples of phenolic
materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl
phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol;
2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl
phenol; 2-methyl-6-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4
methyl phenol; 2,6-di-t-butyl-4-ethyl phenol; and 2,6-di-t-butyl 4
alkoxy phenol; and
##STR00003##
[0184] Phenolic type antioxidants are well known in the lubricating
industry and commercial examples such as Ethanox.RTM. 4710,
Irganox.RTM. 1076, Irganox.RTM. L1035, Irganox.RTM. 1010,
Irganox.RTM. L109, Irganox.RTM. L118, Irganox.RTM. L135 and the
like are familiar to those skilled in the art. The above is
presented only by way of exemplification, not limitation on the
type of phenolic antioxidants which can be used.
[0185] Effective amounts of one or more catalytic antioxidants may
also be used. The catalytic antioxidants comprise an effective
amount of a) one or more oil soluble polymetal organic compounds;
and, effective amounts of b) one or more substituted
N,N'-diaryl-o-phenylenediamine compounds or c) one or more hindered
phenol compounds; or a combination of both b) and c). Catalytic
antioxidants are more fully described in U.S. Pat. No. 8,048,833,
herein incorporated by reference in its entirety.
[0186] Non-phenolic oxidation inhibitors which may be used include
aromatic amine antioxidants and these may be used either as such or
in combination with phenolics. Typical examples of non-phenolic
antioxidants include: alkylated and non-alkylated aromatic amines
such as aromatic monoamines of the formula
R.sup.8R.sup.9R.sup.10N
where R.sup.8 is an aliphatic, aromatic or substituted aromatic
group, R.sup.9 is an aromatic or a substituted aromatic group, and
R.sup.10 is H, alkyl, aryl or R.sup.11S(O)xR.sup.12 where R.sup.11
is an alkylene, alkenylene, or aralkylene group, R.sup.12 is a
higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is
0, 1 or 2. The aliphatic group R.sup.8 may contain from 1 to about
20 carbon atoms, and preferably contains from about 6 to 12 carbon
atoms. The aliphatic group is a saturated aliphatic group.
Preferably, both R.sup.8 and R.sup.9 are aromatic or substituted
aromatic groups, and the aromatic group may be a fused ring
aromatic group such as naphthyl. Aromatic groups R.sup.8 and
R.sup.9 may be joined together with other groups such as S.
[0187] Aromatic amine antioxidants include phenyl-.alpha.-naphthyl
amine, which is described by the following molecular structure:
##STR00004##
wherein R.sup.z is hydrogen or a C1-C14 linear or C3-C14 branched
alkyl group, preferably C1-C10 linear or C3-C10 branched alkyl
group, more preferably linear or branched C6-C8 and n is an integer
ranging from 1 to 5 preferably 1. A particular example is Irganox
L06.
[0188] Typical aromatic amines antioxidants have alkyl substituent
groups of at least about 6 carbon atoms. Examples of aliphatic
groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally,
the aliphatic groups will not contain more than about 14 carbon
atoms. The general types of amine antioxidants useful in the
present compositions include diphenylamines, phenyl naphthylamines,
phenothiazines, imidodibenzyls and diphenyl phenylene diamines.
Mixtures of two or more aromatic amines are also useful. Polymeric
amine antioxidants can also be used. Particular examples of
aromatic amine antioxidants useful in the present disclosure
include: p,p'-dioctyldiphenylamine;
t-octylphenyl-alpha-naphthylamine; phenyl-alphanaphthylamine; and
p-octylphenyl-alpha-naphthylamine.
[0189] Further examples of amine-based antioxidants include
dialkyldiphenylamines such as p,p'-dioctyldiphenylamine
(manufactured by the Seiko Kagaku Co. under the trade designation
"Nonflex OD-3"), p,p'-di-alpha-methylbenzyl-diphenylamine and
N-p-butylphenyl-N-p'-octylphenylamine; monoalkyldiphenylamines such
as mono-t-butyldiphenylamine, and monooctyldiphenylamine;
bis(dialkylphenyl)amines such as di(2,4-diethylphenyl)amine and
di(2-ethyl-4-nonylphenyl)amine; alkylphenyl-1-naphthylamines such
as octylphenyl-1-naphthylamine and
N-t-dodecylphenyl-1-naphthylamine; arylnaphthylamines such as
1-naphthylamine, phenyl-1-naphthylamine, phenyl-2-naphthylamine,
N-hexylphenyl-2-naphthylamine and N-octylphenyl-2-naphthylamine,
phenylenediamines such as N,N'-diisopropyl-p-phenylenediamine and
N,N'-diphenyl-p-phenylenediamine, and phenothiazines such as
phenothiazine (manufactured by the Hodogaya Kagaku Co.:
Phenothiazine) and 3,7-dioctylphenothiazine.
[0190] A sulfur-containing antioxidant may be any and every
antioxidant containing sulfur, for example, including dialkyl
thiodipropionates such as dilauryl thiodipropionate and distearyl
thiodipropionate, dialkyldithiocarbamic acid derivatives (excluding
metal salts), bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide,
mercaptobenzothiazole, reaction products of phosphorus pentoxide
and olefins, and dicetyl sulfide. Of these, preferred are dialkyl
thiodipropionates such as dilauryl thiodipropionate and distearyl
thiodipropionate.
[0191] Examples of sulphur-based antioxidants include
dialkylsulphides such as didodecylsulphide and dioctadecylsulphide;
thiodipropionic acid esters such as didodecyl thiodipropionate,
dioctadecyl thiodipropionate, dimyristyl thiodipropionate and
dodecyloctadecyl thiodipropionate, and 2-mercaptobenzimidazole.
Sulfurized alkyl phenols and alkali or alkaline earth metal salts
thereof also are useful antioxidants.
[0192] Other oxidation inhibitors that have proven useful in lube
compositions are chlorinated aliphatic hydrocarbons such as
chlorinated wax; organic sulfides and polysulfides such as benzyl
disulfide, bis(chlorobenzyl)disulfide, dibutyl tetrasulfide,
sulfurized methyl ester of oleic acid, sulfurized alkylphenol,
sulfurized dipentene, and sulfurized terpene; phosphosulfurized
hydrocarbons such as the reaction product of a phosphorus sulfide
with turpentine or methyl oleate, phosphorus esters including
principally dihydrocarbon and trihydrocarbon phosphites such as
dibutyl phosphite, diheptyl phosphite, dicyclohexyl phosphite,
pentylphenyl phosphite, dipentylphenyl phosphite, tridecyl
phosphite, distearyl phosphite, dimethyl naphthyl phosphite, oleyl
4-pentylphenyl phosphite, polypropylene (molecular weight
500)-substituted phenyl phosphite, diisobutyl-substituted phenyl
phosphite; metal thiocarbamates, such as zinc
dioctyldithiocarbamate, and barium heptylphenyl dithiocarbamate;
Group II metal phosphorodithioates such as zinc
dicyclohexylphosphorodithioate, zinc dioctylphosphorodithioate,
barium di(heptylphenyl)(phosphorodithioate, cadmium
dinonylphosphorodithioate, and the reaction of phosphorus
pentasulfide with an equimolar mixture of isopropyl alcohol,
4-methyl-2-pentanol, and n-hexyl alcohol.
[0193] Another class of antioxidants which may be used in the
lubricating oil compositions disclosed herein are oil-soluble
copper compounds. Any oil-soluble suitable copper compound may be
blended into the lubricating oil. Examples of suitable copper
antioxidants include copper dihydrocarbyl thio- or
dithio-phosphates and copper salts of carboxylic acid (naturally
occurring or synthetic). Other suitable copper salts include copper
dithiacarbamates, sulphonates, phenates, and acetylacetonates.
Basic, neutral, or acidic copper Cu(I) and or Cu(II) salts derived
from alkenyl succinic acids or anhydrides are known to be
particularly useful.
[0194] Preferred antioxidants include hindered phenols, arylamines.
These antioxidants may be used individually by type or in
combination with one another. Although their presence is not
required to obtain the benefit of this disclosure, antioxidant
additives may be used in an amount of about 0.01 to 5 weight
percent, preferably about 0.1 to 3 weight percent, more preferably
0.1 to 2 weight percent, more preferably 0.1 to 1.5 weight
percent.
Pour Point Depressants (PPDs)
[0195] Conventional pour point depressants (also known as lube oil
flow improvers) may be added to the compositions of the present
disclosure if desired. These pour point depressant may be added to
lubricating compositions of the present disclosure to lower the
minimum temperature at which the fluid will flow or can be poured.
Examples of suitable pour point depressants include
polymethacrylates, polyacrylates, polyarylamides, condensation
products of haloparaffin waxes and aromatic compounds, vinyl
carboxylate polymers, and terpolymers of dialkylfumarates, vinyl
esters of fatty acids and allyl vinyl ethers. U.S. Pat. Nos.
1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655, 479; 2,666,746;
2,721,877; 2,721,878; and 3,250,715 describe useful pour point
depressants and/or the preparation thereof. Although their presence
is not required to obtain the benefit of this disclosure, PPD
additives may be used in an amount of zero to 5 weight percent,
preferably about 0.01 to 1.5 weight percent.
Seal Compatibility Agents
[0196] Seal compatibility agents help to swell elastomeric seals by
causing a chemical reaction in the fluid or physical change in the
elastomer. Suitable seal compatibility agents for lubricating oils
include organic phosphates, aromatic esters, aromatic hydrocarbons,
esters (butylbenzyl phthalate, for example), polybutenyl succinic
anhydride and sulfolane-type seal swell agents such as Lubrizol
730-type seal swell additives. Although their presence is not
required to obtain the benefit of this disclosure, seal
combatibility additives may be used in an amount of zero to 3
weight percent, preferably about 0.01 to 2 weight percent.
Antifoam Agents
[0197] Antifoam agents may advantageously be added to lubricant
compositions. These agents retard the formation of stable foams.
Foam inhibitors include polymers of alkyl methacrylate especially
useful poly alkyl acrylate polymers where alkyl is generally
understood to be methyl, ethyl propyl, isopropyl, butyl, or iso
butyl and polymers of dimethylsilicone which form materials called
dimethylsiloxane polymers in the viscosity range of 100 cSt to
100,000 cSt. Other additives are defoamers, such as silicone
polymers which have been post reacted with various carbon
containing moieties, are the most widely used defoamers. Organic
polymers are sometimes used as defoamers although much higher
concentrations are required.
[0198] Antifoam agents are commercially available and may be used
in conventional minor amounts along with other additives such as
demulsifiers. Although their presence is not required to obtain the
benefit of this disclosure, usually the amount of these additives
combined is less than 1 weight percent and often less than 0.1
weight percent.
Demulsifiers
[0199] A demulsifier may advantageously be added to lubricant
compositions. The demulsifier is used to separate emulsions (e.g.,
water in oil). An illustrative demulsifying component is described
in EP-A-330,522. It is obtained by reacting an alkylene oxide with
an adduct obtained by reaction of a bis-epoxide with a polyhydric
alcohol. Demulsifiers are commercially available and may be used in
conventional minor amounts along with other additives such as
antifoam agents. Although their presence is not required to obtain
the benefit of this disclosure, usually the amount of these
additives combined is less than 1 weight percent and often less
than 0.1 weight percent.
[0200] Demulsifying agents include alkoxylated phenols and
phenol-formaldehyde resins and synthetic alkylaryl sulfonates such
as metallic dinonylnaphthalene sulfonates. A demulsifing agent is a
predominant amount of a water-soluble polyoxyalkylene glycol having
a pre-selected molecular weight of any value in the range of
between about 450 and 5000 or more. An especially preferred family
of water soluble polyoxyalkylene glycol useful in the compositions
of the present disclosure may also be one produced from
alkoxylation of n-butanol with a mixture of alkylene oxides to form
a random alkoxylated product.
[0201] Polyoxyalkylene glycols useful in the present disclosure may
be produced by a well-known process for preparing polyalkylene
oxide having hydroxyl end-groups by subjecting an alcohol or a
glycol ether and one or more alkylene oxide monomers such as
ethylene oxide, butylene oxide, or propylene oxide to form block
copolymers in addition polymerization while employing a strong base
such as potassium hydroxide as a catalyst. In such process, the
polymerization is commonly carried out under a catalytic
concentration of 0.3 to 1.0% by mole of potassium hydroxide to the
monomer(s) and at high temperature, as 100.degree. C. to
160.degree. C. It is well known fact that the potassium hydroxide
being a catalyst is for the most part bonded to the chain-end of
the produced polyalkylene oxide in a form of alkoxide in the
polymer solution so obtained.
[0202] An especially preferred family of soluble polyoxyalkylene
glycol useful in the compositions of the present disclosure may
also be one produced from alkoxylation of n-butanol with a mixture
of alkylene oxides to form a random alkoxylated product.
Inhibitors and Antirust Additives
[0203] Antirust additives (or corrosion inhibitors) are additives
that protect lubricated metal surfaces against chemical attack by
water, air or other contaminants. A wide variety of these are
commercially available.
[0204] One type of antirust additive is a polar compound that wets
the metal surface preferentially, protecting it with a film of oil.
Another type of antirust additive absorbs water by incorporating it
in a water-in-oil emulsion so that only the oil touches the metal
surface. Yet another type of antirust additive chemically adheres
to the metal to produce a non-reactive surface. Examples of
suitable additives include zinc dithiophosphates, metal phenolates,
basic metal sulfonates, fatty acids and amines. Although their
presence is not required to obtain the benefit of this disclosure,
inhibitors and antirust additives may be used in an amount from
zero to about 5 weight percent, preferably from 0.01 to about 1.5
weight percent.
[0205] Antirust additives include (short-chain) alkenyl succinic
acids, partial esters thereof and nitrogen-containing derivatives
thereof; and synthetic alkarylsulfonates, such as metal
dinonylnaphthalene sulfonates. Anti-rust agents include, for
example, monocarboxylic acids which have from 8 to 30 carbon atoms,
alkyl or alkenyl succinates or partial esters thereof,
hydroxy-fatty acids which have from 12 to 30 carbon atoms and
derivatives thereof, sarcosines which have from 8 to 24 carbon
atoms and derivatives thereof, amino acids and derivatives thereof,
naphthenic acid and derivatives thereof, lanolin fatty acid,
mercapto-fatty acids and paraffin oxides.
[0206] Examples of monocarboxylic acids (C8-C30), include, for
example, caprylic acid, pelargonic acid, decanoic acid, undecanoic
acid, lauric acid, myristic acid, palmitic acid, stearic acid,
arachic acid, behenic acid, cerotic acid, montanic acid, melissic
acid, oleic acid, docosanic acid, erucic acid, eicosenic acid, beef
tallow fatty acid, soy bean fatty acid, coconut oil fatty acid,
linolic acid, linoleic acid, tall oil fatty acid, 12-hydroxystearic
acid, laurylsarcosinic acid, myritsylsarcosinic acid,
palmitylsarcosinic acid, stearylsarcosinic acid, oleylsarcosinic
acid, alkylated (C8-C20) phenoxyacetic acids, lanolin fatty acid
and C8-C24 mercapto-fatty acids.
[0207] Examples of polybasic carboxylic acids include, for example,
the alkenyl (C10-C100) succinic acids indicated in CAS No.
27859-58-1 and ester derivatives thereof, dimer acid,
N-acyl-N-alkyloxyalkyl aspartic acid esters (U.S. Pat. No.
5,275,749).
[0208] Examples of the alkylamines which function as antirust
additives or as reaction products with the above carboxylates to
give amides and the like are represented by primary amines such as
laurylamine, coconut-amine, n-tridecylamine, myristylamine,
n-pentadecylamine, palmitylamine, n-heptadecylamine, stearylamine,
n-nonadecylamine, n-eicosylamine, n-heneicosylamine,
n-docosylamine, n-tricosylamine, n-pentacosylamine, oleylamine,
beef tallow-amine, hydrogenated beef tallow-amine and soy
bean-amine. Examples of the secondary amines include dilaurylamine,
di-coconut-amine, di-n-tridecylamine, dimyristylamine,
di-n-pentadecylamine, dipalmitylamine, di-n-pentadecylamine,
distearylamine, di-n-nonadecylamine, di-n-eicosylamine,
di-n-heneicosylamine, di-n-docosylamine, di-n-tricosylamine,
di-n-pentacosylamine, dioleylamine, di-beef tallow-amine,
di-hydrogenated beef tallow-amine and di-soy bean-amine.
[0209] Examples of the aforementioned N-alkylpolyalkyenediamines
include:ethylenediamines such as laurylethylenediamine, coconut
ethylenediamine, n-tridecylethylenediamine-, myri
stylethylenediamine, n-pentadecylethylenediamine,
palmitylethylenediamine, n-heptadecylethylenediamine,
stearylethylenediamine, n-nonadecylethylenediamine,
n-eicosylethylenediamine, n-heneicosylethylenediamine,
n-docosylethylendiamine, n-tricosylethylenediamine,
n-pentacosylethylenediamine, oleylethylenediamine, beef
tallow-ethylenediamine, hydrogenated beef tallow-ethylenediamine
and soy bean-ethylenediamine; propylenediamines such as
laurylpropylenediamine, coconut propylenediamine,
n-tridecylpropylenediamine, myristylpropylenediamine,
n-pentadecylpropylenediamine, palmitylpropylenediamine,
n-heptadecylpropylenediamine, stearylpropylenediamine,
n-nonadecylpropylenediamine, n-eicosylpropylenediamine,
n-heneicosylpropylenediamine, n-docosylpropylendiamine,
n-tricosylpropylenediamine, n-pentacosylpropylenediamine,
diethylene triamine (DETA) or triethylene tetramine (TETA),
oleylpropylenediamine, beef tallow-propylenediamine, hydrogenated
beef tallow-propylenediamine and soy bean-propylenediamine;
butylenediamines such as laurylbutylenediamine, coconut
butylenediamine, n-tridecylbutylenediamine-myristylbutylenediamine,
n-pentadecylbutylenediamine, stearylbutylenediamine,
n-eicosylbutylenediamine, n-heneicosylbutylenediamine,
n-docosylbutylendiamine, n-tricosylbutylenediamine,
n-pentacosylbutylenediamine, oleylbutylenediamine, beef
tallow-butylenediamine, hydrogenated beef tallow-butylenediamine
and soy bean butylenediamine; and pentylenediamines such as
laurylpentylenediamine, coconut pentylenediamine,
myristylpentylenediamine, palmitylpentylenediamine,
stearylpentylenediamine, oleyl-pentylenediamine, beef
tallow-pentylenediamine, hydrogenated beef tallow-pentylenediamine
and soy bean pentylenediamine.
Metal Passivators, Deactivators and Corrosion Inhibitors
[0210] This type of component includes
2,5-dimercapto-1,3,4-thiadiazoles and derivatives thereof,
mercaptobenzothiazoles, alkyltriazoles and benzotriazoles. Examples
of dibasic acids useful as anti-corrosion agents, other than
sebacic acids, which may be used in the present disclosure, are
adipic acid, azelaic acid, dodecanedioic acid, 3-methyladipic acid,
3-nitrophthalic acid, 1,10-decanedicarboxylic acid, and fumaric
acid. The anti-corrosion combination is a straight or
branch-chained, saturated or unsaturated monocarboxylic acid or
ester thereof which may optionally be sulphurised in an amount up
to 35% by weight. Preferably the acid is a C4 to C22 straight chain
unsaturated monocarboxylic acid. The monocarboxylic acid may be a
sulphurised oleic acid. However, other suitable materials are oleic
acid itself; valeric acid and erucic acid. A component of the
anti-corrosion combination is a triazole as previously defined. A
preferred triazole is tolylotriazole which may be included in the
compositions of the disclosure include triazoles, thiazoles and
certain diamine compounds which are useful as metal deactivators or
metal passivators. Examples include triazole, benzotriazole and
substituted benzotriazoles such as alkyl substituted derivatives.
The alkyl substituent generally contains up to 1.5 carbon atoms,
preferably up to 8 carbon atoms. The triazoles may contain other
substituents on the aromatic ring such as halogens, nitro, amino,
mercapto, etc. Examples of suitable compounds are benzotriazole and
the tolyltriazoles, ethylbenzotriazoles, hexylbenzotriazoles,
octylbenzotriazoles, chlorobenzotriazoles and nitrobenzotriazoles.
Benzotriazole and tolyltriazole are particularly preferred.
[0211] Illustrative substituents include, for example, alkyl that
is straight or branched chain, for example, methyl, ethyl,
n-propyl, iso-propyl, n-butyl, sec-butyl, n-pentyl, n-hexyl,
n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-dodecyl,
n-tetradecyl, n-hexadecyl, n-octadecyl or n-eicosyl; alkenyl that
is straight or branched chain, for example, prop-2-enyl,
but-2-enyl, 2-methyl-prop-2-enyl, pent-2-enyl, hexa-2,4-dienyl,
dec-10-enyl or eicos-2-enyl; cycloalkyl that is, for example,
cyclopentyl, cyclohexyl, cyclooctyl, cyclodecyl, adamantyl or
cyclododecyl; aralkyl that is, for example, benzyl, 2-phenylethyl,
benzhydryl or naphthylmethyl; aryl that is, for example, phenyl or
naphthyl; heterocyclic group that is, for example, a morpholine,
pyrrolidine, piperidine or a perhydroazepine ring; alkylene
moieties that include, for example, methylene, ethylene, 1:2- or
1:3-propylene, 1:4-butylene, 1:6-hexylene, 1:8-octylene,
1:10-decylene and 1:12-dodecylene.
[0212] Illustrative arylene moieties include, for example,
phenylene and naphthylene. 1-(or 4)-(dimethylaminomethyl) triazole,
1-(or 4)-(diethylaminomethyl) triazole, 1-(or
4)-(di-isopropylaminomethyl) triazole, 1-(or
4)-(di-n-butylaminomethyl) triazole, 1-(or
4)-(di-n-hexylaminomethyl) triazole, 1-(or
4)-(di-isooctylaminomethyl) triazole, 1-(or
4)-(di-(2-ethylhexyl)aminomethyl) triazole, 1-(or
4)-(di-n-decylaminomethyl) triazole, 1-(or
4)-(di-n-dodecylaminomethyl) triazole, 1-(or
4)-(di-n-octadecylaminomethyl) triazole, 1-(or
4)-(di-n-eicosylaminomethyl) triazole, 1-(or
4)-[di-(prop-2'-enyl)aminomethyl]triazole, 1-(or
4)-[di-(but-2'-enyl)aminomethyl]triazole, 1-(or
4)-[di-(eicos-2'-enyl)aminomethyl]triazole, 1-(or
4)-(di-cyclohexylaminomethyl) triazole, 1-(or
4)-(di-benzylaminomethyl) triazole, 1-(or 4)-(di-phenylaminomethyl)
triazole, 1-(or 4)-(4'-morpholinomethyl) triazole, 1-(or
4)-(1'-pyrrolidinomethyl) triazole, 1-(or 4)-(1'-piperidinomethyl)
triazole, 1-(or 4)-(1'-perhydoroazepinomethyl) triazole, 1-(or
4)-(2',2''-dihydroxyethyl)aminomethyl]triazole, 1-(or
4)-(dibutoxypropyl-aminomethyl) triazole, 1-(or
4)-(dibutylthiopropyl-aminomethyl) triazole, 1-(or
4)-(di-butylaminopropyl-aminomethyl) triazole,
1-(or-4)-(1-methanomine)-N,N-bis(2-ethylhexyl)-methyl
benzotriazole, N,N-bis-(1- or 4-triazolylmethyl) laurylamine,
N,N-bis-(1- or 4-triazolylmethyl) oleylamine, N,N-bis-(1- or
4-triazolylmethyl) ethanolamine and N,N,N',N'-tetra(1- or
4-triazolylmethyl) ethylene diamine.
[0213] The metal deactivating agents which can be used in the
lubricating oil include, for example, benzotriazole and the
4-alkylbenzotriazoles such as 4-methylbenzotriazole and
4-ethylbenzotriazole; 5-alkylbenzotriazoles such as
5-methylbenzotriazole, 5-ethylbenzotriazole; 1-alkylbenzotriazoles
such as 1-dioctylauainomethyl-2,3-benzotriazole; benzotriazole
derivatives such as the 1-alkyltolutriazoles, for example,
1-dioctylaminomethyl-2,3-t-olutriazole; benzimidazole and
benzimidazole derivatives such as 2-(alkyldithio)-benzimidazoles,
for example, such as 2-(octyldithio)-benzimidazole,
2-(decyldithio)benzimidazole and 2-(dodecyldithio)-benzimidazole;
2-(alkyldithio)-toluimidazoles such as
2-(octyldithio)-toluimidazole, 2-(decyldithio)-toluimidazole and
2-(dodecyldithio)-toluimidazole; indazole and indazole derivatives
of toluimidazoles such as 4-alkylindazole, 5-alkylindazole;
benzothiazole, 2-mercaptobenzothiazole derivatives (manufactured by
the Chiyoda Kagaku Co. under the trade designation "Thiolite
B-3100") and 2-(alkyldithio)benzothiazoles such as
2-(hexyldithio)benzothiazole and 2-(octyldithio)benzothiazole;
2-(alkyl-dithio)toluthiazoles such as 2-(benzyldithio)toluthiazole
and 2-(octyldithio)toluthiazole,
2-(N,N-dialkyldithiocarbamyl)benzothiazoles such as
2-(N,N-diethyldithiocarbamyl)benzothiazole,
2-(N,N-dibutyldithiocarbamyl)-benzotriazole and
2-N,N-dihexyl-dithiocarbamyl)benzotriazole; benzothiazole
derivatives of 2-(N,N-dialkyldithiocarbamyl)toluthiazoles such as
2-(N,N-diethyldithiocarbamyl)toluthiazole,
2-(N,N-dibutyldithiocarbamyl)toluthiazole,
2-(N,N-dihexyl-dithiocarbamyl)-toluthiazole;
2-(alkyldithio)benzoxazoles such as 2-(octyldithio)benzoxazo-le,
2-(decyldithio)-benzoxazole and 2-(dodecyldithio)benzoxazole;
benzoxazole derivatives of 2-(alkyldithio)toluoxazoles such as
2-(octyldithio)toluoxazole, 2-(decyldithio)toluoxazole,
2-(dodecyldithio)toluoxazole;
2,5-bis(alkyldithio)-1,3,4-thiadiazoles such as
2,5-bis(heptyldithio)-1,3,4-thiadiazole,
2,5-bis-(nonyldithio)-1-3,4-thiadiazole,
2,5-bis(dodecyldithio)-1,3,4-thiadiazole and
2,5-bis-(octadecyldithio)-1,3,4-thiadiazole;
2,5-bis(N,N-dialkyl-dithioca-rbamyl)-1,3,4-thiadiazoles such as
2,5-bis(N,N-diethyldithiocarbamyl)-1,3-4-thiadiazole,
2,5-bis(N,N-dibutyldithiocarbamyl)-1,3,4-thiadiazole and
2,5-bis(N,N-dioctyldithiocarbamyl) 1,3,4-thiadiazole; thiadiazole
derivatives of
2-N,N-dialkyldithiocarbamyl-5-mercapto-1,3,4-thiadiazoles such as
2-N,N-dibutyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole and
2-N,N-dioctyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole, and
triazole derivatives of 1-alkyl-2,4-triazoles such as
1-dioctylaminomethyl-2,4-triazole or concentrates and/or mixtures
thereof.
[0214] Although their presence is not required to obtain the
benefit of this disclosure, metal deactivators and corrosion
inhibitor additives may be present from zero to about 1% by weight,
preferably from 0.01% to about 0.5% of the total lubricating oil
composition.
Friction Modifiers
[0215] A friction modifier is any material or materials that can
alter the coefficient of friction of a surface lubricated by any
lubricant or fluid containing such material(s). Friction modifiers,
also known as friction reducers, or lubricity agents or oiliness
agents, and other such agents that change the ability of base oils,
formulated lubricant compositions, or functional fluids, to modify
the coefficient of friction of a lubricated surface may be
effectively used in combination with the base oils or lubricant
compositions of the present disclosure if desired. Friction
modifiers that lower the coefficient of friction are particularly
advantageous in combination with the base oils and lube
compositions of this disclosure.
[0216] In various aspects, at least one friction modifier in a
formulated lubricant can correspond to a friction modifier additive
including a metal salt of a Group VI metal, such as a
molybdenum-containing metal salt and/or tungsten-containing metal
salt. The friction modifier additive including the Group VI metal
can have a free energy of adsorption (.DELTA.G) on an oxygenated
diamond-like carbon surface of -25 kJ/mol or less, or -28 kJ/mol or
less, or -30 kJ/mol or less.
[0217] Some illustrative friction modifiers that include a Group VI
metal may include, for example, organometallic compounds or
materials, or mixtures thereof. Illustrative organometallic
friction modifiers useful in the lubricating oil formulations of
this disclosure include, for example, molybdenum amine, molybdenum
diamine, an organotungstenate, a molybdenum dithiocarbamate,
molybdenum dithiophosphates, molybdenum amine complexes, molybdenum
carboxylates, and the like, and mixtures thereof. Similar tungsten
based compounds may be preferable.
[0218] Other friction modifiers that include a Group VI metal can
include salts based on a cation including Group VI metal and
sulfur. Examples of the Group VI metal and sulfur-containing cation
can include, but are not limited to, Mo.sub.3S.sub.4 and
Mo.sub.3S.sub.7.
[0219] In addition to friction modifiers that include a Group VI
metal, a formulated lubricant may contain other friction modifiers.
Other illustrative friction modifiers can include, for example,
alkoxylated fatty acid esters, alkanolamides, polyol fatty acid
esters, borated glycerol fatty acid esters, fatty alcohol ethers,
and mixtures thereof.
[0220] Illustrative alkoxylated fatty acid esters include, for
example, polyoxyethylene stearate, fatty acid polyglycol ester, and
the like. These can include polyoxypropylene stearate,
polyoxybutylene stearate, polyoxyethylene isosterate,
polyoxypropylene isostearate, polyoxyethylene palmitate, and the
like.
[0221] Illustrative alkanolamides include, for example, lauric acid
diethylalkanolamide, palmic acid diethylalkanolamide, and the like.
These can include oleic acid diethyalkanolamide, stearic acid
diethylalkanolamide, oleic acid diethylalkanolamide,
polyethoxylated hydrocarbylamides, polypropoxylated
hydrocarbylamides, and the like.
[0222] Illustrative polyol fatty acid esters include, for example,
glycerol mono-oleate, saturated mono-, di-, and tri-glyceride
esters, glycerol mono-stearate, and the like. These can include
polyol esters, hydroxyl-containing polyol esters, and the like.
[0223] Illustrative borated glycerol fatty acid esters include, for
example, borated glycerol mono-oleate, borated saturated mono-,
di-, and tri-glyceride esters, borated glycerol mono-sterate, and
the like. In addition to glycerol polyols, these can include
trimethylolpropane, pentaerythritol, sorbitan, and the like. These
esters can be polyol monocarboxylate esters, polyol dicarboxylate
esters, and on occasion polyoltricarboxylate esters. Preferred can
be the glycerol mono-oleates, glycerol dioleates, glycerol
trioleates, glycerol monostearates, glycerol distearates, and
glycerol tristearates and the corresponding glycerol
monopalmitates, glycerol dipalmitates, and glycerol tripalmitates,
and the respective isostearates, linoleates, and the like. On
occasion the glycerol esters can be preferred as well as mixtures
containing any of these. Ethoxylated, propoxylated, butoxylated
fatty acid esters of polyols, especially using glycerol as
underlying polyol can be preferred.
[0224] Illustrative fatty alcohol ethers include, for example,
stearyl ether, myristyl ether, and the like. Alcohols, including
those that have carbon numbers from C3 to C50, can be ethoxylated,
propoxylated, or butoxylated to form the corresponding fatty alkyl
ethers. The underlying alcohol portion can preferably be stearyl,
myristyl, C11-C13 hydrocarbon, oleyl, isosteryl, and the like.
[0225] These other friction modifiers would be optionally in
addition to the fatty phosphites and fatty imidazolines. A useful
list of such other friction modifier additives is included in U.S.
Pat. No. 4,792,410. U.S. Pat. No. 5,110,488 discloses metal salts
of fatty acids and especially zinc salts, useful as friction
modifiers. Fatty acids are also useful friction modifiers. A list
of other friction modifiers suitable for disclosure includes: (i)
fatty phosphonates; (ii) fatty acid amides; (iii) fatty epoxides;
(iv) borated fatty epoxides; (v) fatty amines; (vi) glycerol
esters; (vii) borated glycerol esters; (viii) alkoxylated fatty
amines; (ix) borated alkoxylated fatty amines; (x) metal salts of
fatty acids; (xi) sulfurized olefins; (xii) condensation products
of carboxylic acids or equivalents and polyalkylene-polyamines;
(xiii) metal salts of alkyl salicylates; (xiv) amine salts of
alkylphosphoric acids; (xv) fatty esters; (xvi) condensation
products of carboxylic acids or equivalents with polyols and
mixtures thereof.
[0226] Representatives of each of these types of friction modifiers
are known and are commercially available. For instance, (i)
includes components generally of the formulas:
(RO).sub.2PHO,
(RO)(HO)PHO, and
P(OR)(OR)(OR),
wherein, in these structures, the term "R" is conventionally
referred to as an alkyl group but may also be hydrogen. It is, of
course, possible that the alkyl group is actually alkenyl and thus
the terms "alkyl" and "alkylated," as used herein, will embrace
other than saturated alkyl groups within the component. The
component should have sufficient hydrocarbyl groups to render it
substantially oleophilic. In some embodiments the hydrocarbyl
groups are substantially un-branched. Many suitable such components
are available commercially and may be synthesized as described in
U.S. Pat. No. 4,752,416. In some embodiments the component contains
8 to 24 carbon atoms in each of R groups. In other embodiments the
component may be a fatty phosphite containing 12 to 22 carbon atoms
in each of the fatty radicals, or 16 to 20 carbon atoms. In one
embodiment the fatty phosphite can be formed from oleyl groups,
thus having 18 carbon atoms in each fatty radical.
[0227] The (iv) borated fatty epoxides are known from Canadian
Patent No. 1,188,704. These oil-soluble boron-containing
compositions are prepared by reacting, at a temperature from
80.degree. C. to 250.degree. C., boric acid or boron trioxide with
at least one fatty epoxide having the formula:
##STR00005##
wherein each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is hydrogen
or an aliphatic radical, or any two thereof together with the epoxy
carbon atom or atoms to which they are attached, form a cyclic
radical. The fatty epoxide preferably contains at least 8 carbon
atoms.
[0228] The borated fatty epoxides can be characterized by the
method for their preparation which involves the reaction of two
materials. Reagent A can be boron trioxide or any of the various
forms of boric acid including metaboric acid (HBO.sub.2),
orthoboric acid (H.sub.3BO.sub.3) and tetraboric acid
(H.sub.2B.sub.4O.sub.7). Boric acid, and especially orthoboric
acid, is preferred. Reagent B can be at least one fatty epoxide
having the above formula. In the formula, each of the R groups is
most often hydrogen or an aliphatic radical with at least one being
a hydrocarbyl or aliphatic radical containing at least 6 carbon
atoms. The molar ratio of reagent A to reagent B is generally
1:0.25 to 1:4. Ratios of 1:1 to 1:3 are preferred, with about 1:2
being an especially preferred ratio. The borated fatty epoxides can
be prepared by merely blending the two reagents and heating them at
temperature of 80.degree. C. to 250.degree. C., preferably
100.degree. C. to 200.degree. C., for a period of time sufficient
for reaction to take place. If desired, the reaction may be
effected in the presence of a substantially inert, normally liquid
organic diluent. During the reaction, water is evolved and may be
removed by distillation.
[0229] The (iii) non-borated fatty epoxides, corresponding to
Reagent B above, are also useful as friction modifiers.
[0230] Borated amines are generally known from U.S. Pat. No.
4,622,158. Borated amine friction modifiers (including (ix) borated
alkoxylated fatty amines) are conveniently prepared by the reaction
of a boron compounds, as described above, with the corresponding
amines. The amine can be a simple fatty amine or hydroxy containing
tertiary amines. The borated amines can be prepared by adding the
boron reactant, as described above, to an amine reactant and
heating the resulting mixture at a 50.degree. C. to 300.degree. C.,
preferably 100.degree. C. to 250.degree. C. or 130.degree. C. to
180.degree. C., with stirring. The reaction is continued until
by-product water ceases to evolve from the reaction mixture
indicating completion of the reaction.
[0231] Among the amines useful in preparing the borated amines are
commercial alkoxylated fatty amines known by the trademark
"ETHOMEEN" and available from Akzo Nobel. Representative examples
of these ETHOMEEN.TM. materials is ETHOMEEN.TM. C/12
(bis[2-hydroxyethyl]-coco-amine); ETHOMEEN.TM. C/20
(polyoxyethylene[10]cocoamine); ETHOMEEN.TM. S/12
(bis[2-hydroxyethyl]soyamine); ETHOMEEN.TM. T/12
(bis[2-hydroxyethyl]-tallow-amine); ETHOMEEN.TM. T/15
(polyoxyethylene-[5]tallowamine); ETHOMEEN.TM. O/12
(bis[2-hydroxyethyl]oleyl-amine); ETHOMEEN.TM. 18/12
(bis[2-hydroxyethyl]octadecylamine); and ETHOMEEN.TM. 18/25
(polyoxyethylene[15]octadecylamine). Fatty amines and ethoxylated
fatty amines are also described in U.S. Pat. No. 4,741,848.
Dihydroxyethyl tallowamine (commercially sold as ENT-12.TM.) is
included in these types of amines.
[0232] The (viii) alkoxylated fatty amines, and (v) fatty amines
themselves (such as oleylamine and dihydroxyethyl tallowamine) are
generally useful as friction modifiers in this disclosure. Such
amines are commercially available.
[0233] Both borated and unborated fatty acid esters of glycerol can
be used as friction modifiers. The (vii) borated fatty acid esters
of glycerol are prepared by borating a fatty acid ester of glycerol
with boric acid with removal of the water of reaction. Preferably,
there is sufficient boron present such that each boron will react
with from 1.5 to 2.5 hydroxyl groups present in the reaction
mixture. The reaction may be carried out at a temperature in the
range of 60.degree. C. to 135.degree. C., in the absence or
presence of any suitable organic solvent such as methanol, benzene,
xylenes, toluene, or oil.
[0234] The (vi) fatty acid esters of glycerol themselves can be
prepared by a variety of methods well known in the art. Many of
these esters, such as glycerol monooleate and glycerol tallowate,
are manufactured on a commercial scale. The esters useful are
oil-soluble and are preferably prepared from C8 to C22 fatty acids
or mixtures thereof such as are found in natural products and as
are described in greater detail below. Fatty acid monoesters of
glycerol are preferred, although, mixtures of mono- and diesters
may be used. For example, commercial glycerol monooleate may
contain a mixture of 45% to 55% by weight monoester and 55% to 45%
diester.
[0235] Fatty acids can be used in preparing the above glycerol
esters; they can also be used in preparing their (x) metal salts,
(ii) amides, and (xii) imidazolines, any of which can also be used
as friction modifiers. Preferred fatty acids are those containing
10 to 24 carbon atoms, or 12 to 18. The acids can be branched or
straight-chain, saturated or unsaturated. In some embodiments the
acids are straight-chain acids. In other embodiments the acids are
branched. Suitable acids include decanoic, oleic, stearic,
isostearic, palmitic, myristic, palmitoleic, linoleic, lauric, and
linolenic acids, and the acids from the natural products tallow,
palm oil, olive oil, peanut oil, corn oil, coconut oil and Neat's
foot oil. A particularly preferred acid is oleic acid. Preferred
metal salts include zinc and calcium salts. Examples are overbased
calcium salts and basic oleic acid-zinc salt complexes, such as
zinc oleate, which can be represented by the general formula
Zn.sub.4Oleate.sub.6O.sub.1. Preferred amides are those prepared by
condensation with ammonia or with primary or secondary amines such
as ethylamine and diethanolamine. Fatty imidazolines are the cyclic
condensation product of an acid with a diamine or polyamine such as
a polyethylenepolyamine. The imidazolines are generally represented
by the structure:
##STR00006##
where R is an alkyl group and R' is hydrogen or a hydrocarbyl group
or a substituted hydrocarbyl group, including
--(CH.sub.2CH.sub.2NH)n- groups. In a preferred embodiment the
friction modifier is the condensation product of a C10 to C24 fatty
acid with a polyalkylene polyamine, and in particular, the product
of isostearic acid with tetraethylenepentamine.
[0236] The condensation products of carboxylic acids and
polyalkyleneamines (xiii) may generally be imidazolines or amides.
They may be derived from any of the carboxylic acids described
above and any of the polyamines described herein.
[0237] Sulfurized olefins (xi) are well known commercial materials
used as friction modifiers. A particularly preferred sulfurized
olefin is one which is prepared in accordance with the detailed
teachings of U.S. Pat. Nos. 4,957,651 and 4,959,168. Described
therein is a co-sulfurized mixture of 2 or more reactants selected
from the group consisting of (1) at least one fatty acid ester of a
polyhydric alcohol, (2) at least one fatty acid, (3) at least one
olefin, and (4) at least one fatty acid ester of a monohydric
alcohol. Reactant (3), the olefin component, comprises at least one
olefin. This olefin is preferably an aliphatic olefin, which
usually will contain 4 to 40 carbon atoms, preferably from 8 to 36
carbon atoms. Terminal olefins, or alpha-olefins, are preferred,
especially those having from 12 to 20 carbon atoms. Mixtures of
these olefins are commercially available, and such mixtures are
contemplated for use in this disclosure. The co-sulfurized mixture
of two or more of the reactants, is prepared by reacting the
mixture of appropriate reactants with a source of sulfur. The
mixture to be sulfurized can contain 10 to 90 parts of Reactant
(1), or 0.1 to 15 parts by weight of Reactant (2); or 10 to 90
parts, often 15 to 60 parts, more often 25 to 35 parts by weight of
Reactant (3), or 10 to 90 parts by weight of reactant (4). The
mixture, in the present disclosure, includes Reactant (3) and at
least one other member of the group of reactants identified as
reactants (1), (2) and (4). The sulfurization reaction generally is
effected at an elevated temperature with agitation and optionally
in an inert atmosphere and in the presence of an inert solvent. The
sulfurizing agents useful in the process of the present disclosure
include elemental sulfur, which is preferred, hydrogen sulfide,
sulfur halide plus sodium sulfide, and a mixture of hydrogen
sulfide and sulfur or sulfur dioxide. Typically often 0.5 to 3
moles of sulfur are employed per mole of olefinic bonds. Sulfurized
olefins may also include sulfurized oils such as vegetable oil,
lard oil, oleic acid and olefin mixtures.
[0238] Metal salts of alkyl salicylates (xiii) include calcium and
other salts of long chain (e.g. C12 to C16) alkyl-substituted
salicylic acids.
[0239] Amine salts of alkylphosphoric acids (xiv) include salts of
oleyl and other long chain esters of phosphoric acid, with amines
as described below. Useful amines in this regard are
tertiary-aliphatic primary amines, sold under the tradename
Primene.TM..
[0240] In some embodiments the friction modifier is a fatty acid or
fatty oil, a metal salt of a fatty acid, a fatty amide, a
sulfurized fatty oil or fatty acid, an alkyl phosphate, an alkyl
phosphate amine salt; a condensation product of a carboxylic acid
and a polyamine, a borated fatty epoxide, a fatty imidazoline, or
combinations thereof.
[0241] In other embodiments the friction modifier may be the
condensation product of isostearic acid and tetraethylene
pentamine, the condensation product of isostearic acid and
1-[tris(hydroxymethyl)]methylamine, borated polytetradecyloxirane,
zinc oleate, hydroxylethyl-2-heptadecenyl imidazoline, dioleyl
hydrogen phosphate, C14-C18 alkyl phosphate or the amine salt
thereof, sulfurized vegetable oil, sulfurized lard oil, sulfurized
oleic acid, sulfurized olefins, oleyl amide, glycerol monooleate,
soybean oil, or mixtures thereof.
[0242] In still other embodiments the friction modifier may be
glycerol monooleate, oleylamide, the reaction product of isostearic
acid and 2-amino-2-hydroxymethyl-1,3-propanediol, sorbitan
monooleate, 9-octadecenoic acid, isostearyl amide, isostearyl
monooleate or combinations thereof.
[0243] Friction modifiers may be used from 0.01 wt % to 2.0 wt %,
preferably 0.01 wt % to 1.5 wt % of the lubricating oil
composition. These ranges may apply to the amounts of individual
friction modifier present in the composition or to the total
friction modifier component in the compositions, which may include
a mixture of two or more friction modifiers.
[0244] Many friction modifiers tend to also act as emulsifiers.
This is often due to the fact that friction modifiers often have
non-polar fatty tails and polar head groups. Emulsibility, or
rather decreased demulsibility, is a result that is undesirable in
hydraulic fluids, where it is desirable for such compositions to
remain separate from and not entrain any water with which the fluid
may come into contact. The friction modifiers of the present
disclosure may be used to improve the antiwear performance of the
hydraulic fluid, however in some embodiments care must be taken to
avoid using the friction modifier at a level that would negatively
impact the demulsibility of the fluid.
[0245] The lubricating oils of this disclosure exhibit desired
properties, e.g., wear control, in the presence or absence of a
friction modifier.
Borated Ester Compounds
[0246] Illustrative boron-containing compounds useful in this
disclosure include, for example, 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, and
performs 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.
[0247] 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 disclosures 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
disclosures 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.
[0248] An illustrative borate ester utilized in this disclosure 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%.
The borated ester (Vanlube.TM. 289), which is marketed as an
antiwear/antiscuff additive and friction reducer, is a preferred
borate ester useful in this disclosure.
[0249] An illustrative borate ester useful in this disclosure is
the reaction product obtained by reacting about 1 mole fatty oil,
about 1.0 to 2.5 moles diethanolamine followed by subsequent
reaction with boric acid to yield about 0.1 to 3 percent boron by
mass. It is believed that the reaction products may include one or
both of the following two primary components, with the further
listed components being possible components when the reaction is
pushed toward full hydration:
##STR00007##
where R.sub.1=H or C.sub.xH.sub.y where x=1 to 60, and y=3 to
121
##STR00008##
wherein Y represents a fatty oil residue. The preferred fatty oils
are glyceryl esters of higher fatty acids containing at least 12
carbon atoms and may contain 22 carbon atoms and higher. Such
esters are commonly known as vegetable and animal oils. Vegetable
oils particularly useful are oils derived from coconut, corn,
cottonseed, linseed, peanut, soybean and sunflower seed. Similarly,
animal fatty oils such as tallow may be used.
[0250] The source of boron is boric acid or materials that afford
boron and are capable of reacting with the intermediate reaction
product of fatty oil and diethanolamine to form a borate ester
composition.
[0251] While the above organoborate ester composition is
specifically discussed above, it should be understood that other
organoborate ester compositions should also function with similar
effect in the present disclosure, such as those set forth in U.S.
Patent Application Publication No. 2003/0119682, which is
incorporated herein by reference. In addition, dispersions of
borate salts, such as potassium borate, may also be useful.
[0252] Other illustrative organoborate compositions useful in this
disclosure are disclosed, for example, in U.S. Patent Application
Publication No. 2008/0261838, which is incorporated herein by
reference.
[0253] In addition, other illustrative oranoborate compositions
useful in this disclosure are disclosed, for example, U.S. Pat.
Nos. 4,478,732, 4,406,802, 4,568,472 on borated mixed hydroxyl
esters, alkoxylated amides, and amines; U.S. Pat. No. 4,298,486 on
borated hydroxyethyl imidazolines; U.S. Pat. No. 4,328,113 on
borated alkyl amines and alkyl diamines; U.S. Pat. No. 4,370,248 on
borated hydroxyl-containing esters, including GMO; U.S. Pat. No.
4,374,032 on borated hydroxyl-containing hydrocarbyl oxazolines;
U.S. Pat. No. 4,376,712 on borated sorbitan esters; U.S. Pat. No.
4,382,006 on borated ethoxylated amines; U.S. Pat. No. 4,389,322 on
ethoxylated amides and their borates; U.S. Pat. No. 4,472,289 on
hydrocarbyl vicinal diols and alcohols and ester mixtures and their
borates; U.S. Pat. No. 4,522,734 on borates of hydrolyzed
hydrocarbyl epoxides; U.S. Pat. No. 4,537,692 on etherdiamine
borates; U.S. Pat. No. 4,541,941 on mixtures containing vicinal
diols and hydroxyl substituted esters and their borates; U.S. Pat.
No. 4,594,171 on borated mixtures of various hydroxyl and/or
nitrogen containing borates; and U.S. Pat. No. 4,692,257 on various
borated alcohols/diols, which are incorporated herein by
reference.
[0254] Although their presence is not required to obtain the
benefit of this disclosure, boron-containing compounds may be used
up from zero to 10.0% percent, more preferably from about 0.01% to
about 5%, and most preferably from about 0.1% to about 3.0%. 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.
[0255] When lubricating oil compositions contain one or more of the
additives discussed above, the additive(s) are blended into the
composition in an amount sufficient for it to perform its intended
function. Typical amounts of such additives useful in the present
disclosure are shown in Table 3 below.
[0256] It is noted that many of the additives are shipped from the
additive manufacturer as a concentrate, containing one or more
additives together, with a certain amount of base oil diluents.
Accordingly, the weight amounts in Table 3 below, as well as other
amounts mentioned herein, are directed to the amount of active
ingredient (that is the non-diluent portion of the ingredient). The
weight percent (wt %) indicated below is based on the total weight
of the lubricating oil composition.
TABLE-US-00003 TABLE 3 Typical Amounts of Lubricating Oil
Components Approximate Approximate wt % wt % Compound (Useful)
(Preferred) Dispersant 0-20 0-3 Detergent 0-20 0-3 Friction
Modifier .sup. 0-5 .sup. 0-1.5 Antioxidant 0.1-5 0.1-3.sup. Pour
Point Depressant (PPD) 0.0-5 0.01-1.5 Antifoam Agent 0.001-3
0.001-0.3 Demulsifier 0.001-3 0.001-0.15 Viscosity Modifier (solid
0.1-2 0.1-1.sup. polymer basis) Antiwear 0.2-3 0.5-1.5 Inhibitor
and Antirust 0.01-5 0.01-2
[0257] The foregoing additives are all commercially available
materials. These additives may be added independently but are
usually precombined in packages which can be obtained from
suppliers of lubricant oil additives. Additive packages with a
variety of ingredients, proportions and characteristics are
available and selection of the appropriate package will take the
requisite use of the ultimate composition into account.
EXAMPLES
Example 1--Variation in Oxygen Content with Depth for Oxygenated
Diamond-Like Carbon
[0258] A sample of borated diamond-like carbon was analyzed using
X-ray photoelectron spectroscopy (XPS) to determine elemental
composition. In order to see how composition varied with depth into
a sample, the surface of the sample was sputtered with an argon ion
(Ar+) beam. Based on the sputtering rate, each 6 seconds
corresponds to a drilling depth of 1 nm. At various depths the
sample was analyzed to generate plots of elemental concentration
versus depth into the sample.
[0259] FIG. 1 shows the relative concentration of oxygen plotted
against the sputtering time for the sample. FIG. 2 shows a similar
concentration profile versus sputtering time for carbon. As shown
in FIG. 1, the intensity of oxygen is highest at the initial
surface of the sample prior to any sputtering, but rapidly drops
off so that the oxygen concentration is substantially lower for the
measurement performed after the first six second time period. By
contrast, in FIG. 2 the carbon concentration increases modestly
after the initial sputtering time period and then generally remains
at the higher level. Based on the measured XPS intensities, an
initial oxygen to carbon ratio was calculated for the surface of
the borated diamond-like carbon sample prior to sputtering and
after the first six second time period. The oxygen to carbon ratio
prior to any sputtering was calculated as roughly 1:9. After
sputtering to remove the top 1 nm of the layer, the oxygen to
carbon ratio dropped to roughly 1:30. Although not shown in the
figures, the ratio of boron to carbon was also determined using XPS
on the sample at the various levels of sputtering. The boron to
carbon ratio in the borated sample remained relatively constant at
a value of roughly 1:14 or 1:15.
[0260] In a second set of experiments, a non-borated oxygenated
diamond-like carbon surface was characterized using XPS with argon
ion sputtering. Based on the XPS measurements, the surface of the
non-borated diamond-like carbon sample had an oxygen to carbon
ratio of roughly 1:13. This result may indicate that the presence
of boron in the diamond-like carbon layer facilitated incorporation
of additional oxygen at the surface of the layer. The
sp.sup.2/sp.sup.3 ratio of the DLC based on XPS analysis was
roughly 1:1.
[0261] In an effort to further characterize the nature of the
surface, molecular modeling was used to construct a borated and
oxygenated diamond-like carbon layer having a surface ratio of
oxygen to carbon that was similar to the measured ratio based on
the XPS analysis shown in FIGS. 1 and 2. The resulting molecular
model had a higher oxygen concentration of 1:7. Using the molecular
model, it was determined that a 1:7 ratio of surface oxygen to
carbon resulted in a distance between oxygen atoms on the surface
of roughly 0.6 nm. Without being bound by any particular theory,
this suggests that for an adsorbate to adsorb to oxygen and cover
the borated and oxygenated diamond-like carbon surface, the
adsorbate may need to span this distance of roughly 6 angstroms.
Molecules that are smaller than this distance to bridge between
oxygen sites may not form a complete layer on the BDLC surface, and
may not adequately protect the surface.
Example 2--Adsorption Isotherms for Mo-Containing Friction
Modifiers
[0262] Adsorption isotherms were determined according to the method
described herein for Mo-containing friction modifiers on various
surfaces. As explained above, this included using a quartz crystal
microbalance apparatus to determine mass adsorption for various
friction modifiers in lubricating oils at a series of
concentrations. In FIG. 3, adsorption values are shown
corresponding to amount of mass adsorbed relative to mole fraction
of Mo in a lubricant exposed to a surface for Adeka Sakura Lube
300--molybdenum dithiophosphate (MoDTP). The adsorption values
shown in FIG. 3 correspond to adsorption on an iron oxide surface,
a borated and oxygenated diamond-like carbon surface, and a
non-borated oxygenated diamond-like carbon surface. The iron oxide
surfaces in this and other examples corresponded to a surface of
Fe.sub.3O.sub.4 (magnetite). The DLC surfaces had a
sp.sup.2/sp.sup.3 ratio based on XPS analysis of roughly 1:1. FIG.
3 also shows curve fits representing adsorption isotherms for
adsorption on the iron oxide surface (curve 315) and the borated
and oxygenated diamond-like carbon surface (curve 325). Such a
curve fit can also be used to determine the free energy of
adsorption, as described above. FIG. 4 shows adsorption values for
an Infineum C9455B Mo-trimer compound on an iron oxide surface and
a borated and oxygenated diamond-like carbon surface. FIG. 4 also
shows a curve fit representing an adsorption isotherm for
adsorption on the borated and oxygenated diamond-like carbon
surface (curve 425). FIG. 5 shows adsorption values for Adeka
Sakura Lube 515 molybdenum dithiocarbamate (MoDTC) on an iron oxide
surface (data points 510), a borated and oxygenated diamond-like
carbon surface (data points 520), a non-borated oxygenated
diamond-like carbon surface (data points 530), and a
polytetrafluoroethylene surface (PTFE, data points 540). FIG. 5
also shows a curve fit representing an adsorption isotherm for
adsorption on the borated and oxygenated diamond-like carbon
surface (curve 525). FIG. 9 shows adsorption values for an
Mo.sub.3S.sub.4-based friction modifier (corresponding to
Mo.sub.3S.sub.4[(2-ethylhexyl).sub.2dtc]4) on an iron oxide surface
(data points 910) and a borated and oxygenated diamond-like carbon
surface (data points 920). FIG. 9 also shows curve fits
representing adsorption isotherms for the iron oxide surface (curve
915) and the borated and oxygenated diamond-like carbon surface
(curve 925).
[0263] Based on the data shown in FIG. 3, the MoDTP friction
modifier has a free energy of adsorption of less than -25 kJ/mol
for all of the surfaces investigated. The free energy of adsorption
(.DELTA.G) is somewhat lower on the diamond-like carbon surfaces.
In particular, the free energy of adsorption is -31 kJ/mol on the
iron oxide surface; is -35 kJ/mol on the non-borated DLC surface,
and -35 kJ/mol on the borated DLC surface. The data in FIG. 4 shows
similarly favorable adsorption values for the Mo-trimer
(Mo.sub.3S.sub.7) compound, with a free energy of adsorption of -32
kJ/mol on both the iron oxide and the borated DLC surfaces. The
data in FIG. 9 for the Mo.sub.3S.sub.4-based friction modifier also
resulted in a free energy of adsorption of -32 kJ/mol on the
borated DLC surface.
[0264] By contrast, FIG. 5 shows different adsorption behavior.
Based on the data in FIG. 5, the resulting free energy of
adsorption for MoDTC on both the borated and non-borated surfaces
was only -24.6 kJ/mol. The free energy of adsorption was still
higher on the iron oxide surface (-21.2 kJ/mol) and the PTFE
surface.
[0265] As an additional comparison, the procedures for determining
adsorption values were also used in an effort to determine
adsorption isotherms for stearic acid on the iron oxide and
diamond-like carbon surfaces (both borated and non-borated). A free
energy of adsorption of -22 kJ/mol was determined for stearic acid
on the iron oxide surface. However, the amount of adsorption on the
diamond-like carbon surfaces was sufficiently low that a free
energy of adsorption could not be determined for stearic acid on
those surfaces. This correlates with the observed lack of
significant friction reduction for stearic acid as a friction
modifier on diamond-like carbon surfaces.
[0266] The free energy of adsorption values described in this
example are summarized in Table 4. BDLC refers to the borated (and
oxygenated) diamond-like carbon surface, while n-BDLC refers to the
non-borated (but still oxygenated) surface. As noted above, the
free energy of adsorption could not be determined for stearic acid
on the diamond-like carbon surfaces. Table 4 also shows the final
surface coverage for the various friction modifiers at
saturation.
TABLE-US-00004 TABLE 4 .DELTA.G of Adsorption Values for Friction
Modifiers Delta G Values Final Surface [kJ/mol] Coverage [ng/cm2]
Additive Iron Oxide BDLC nBDLC Additive Iron Oxide BDLC nBDLC Mo
-32 -32 -- Mo >170 >170 -- trimer trimer (Mo.sub.3S.sub.7) Mo
DTC -21.2 -24.6 -24.6 Mo DTC >120 >120 >120 Mo DTP -31 -35
-35 Mo DTP 1550 2000 1800 Mo.sub.3S.sub.4 -27.6 -33 -- Mo3S4
>1400 >1000 --
Example 3--Wear Depth
[0267] Five friction modifiers were blended into an engine oil
formulation and tested in a block-on-ring test. The ring
corresponded to a stainless steel formulation while the block
corresponded to a test substrate with a surface layer of borated
and oxygenated diamond-like carbon. The surface layer of
diamond-like carbon had a depth of roughly 1.2 .mu.m. The ring and
block surfaces were exposed to each other during ring rotation for
30 minutes at a temperature of 80.degree. C., a speed of 0.3 m/s,
and a load of 300 MPa.
[0268] In the tests described in this example, an engine oil
formulation that did not include molybdenum was used as the base
lubricant. Friction modifiers were then added to this base
lubricant. The friction modifiers corresponded to MoDTC, MoDTP,
Mo.sub.3S.sub.4[(2-ethylhexyl).sub.2dtc]4, Infineum C9455B
(Mo-trimer), and a C.sub.18 thiol.
[0269] FIG. 6 shows the friction coefficient and wear depth
measured for each friction modifier at a concentration
corresponding with 700 wppm molybdenum, along with the friction
coefficient and wear depth for the engine oil without an added
friction modifier. As shown in FIG. 6, addition of MoDTC resulted
in a reduction in the friction coefficient at the diamond-like
carbon surface, but with an accompanying substantial increase in
wear depth on the diamond-like carbon surface relative to the
engine oil without an added friction modifier. The C.sub.18 thiol
did not result in increased wear, but also did not result in a
substantial reduction in the friction coefficient. The
Mo-containing friction modifiers with free energies of adsorption
on DLC of less than -25 kJ/mol all resulted in a substantial
reduction in friction coefficient while also unexpectedly reducing
the wear depth on the diamond-like carbon surface.
[0270] The results in FIG. 6 can be further illustrated by plotting
the friction coefficient and wear depth results versus the free
energy of adsorption for the various friction modifiers. FIG. 7
shows the results from FIG. 6, but replotted versus the .DELTA.G
value associated with each friction modifier on the borated and
oxygenated diamond-like carbon surface. As shown in FIG. 7, the
.DELTA.G value of the friction modifier does not appear to impact
the friction coefficient. However, the .DELTA.G value appears to be
correlated with the resulting wear depth associated with use of the
friction modifier. It is noted that the C.sub.18 thiol from FIG. 6
is not included in the plot shown in FIG. 7.
[0271] FIG. 8 provides an illustration of the relationship between
Mo content in a lubricant, friction coefficient, and wear depth. In
FIG. 8, results are shown from additional ring and block tests with
different concentrations of the Mo-containing friction modifiers in
the engine oil formulation.
[0272] As shown in FIG. 8, at relatively low concentrations of
MoDTC such as 100 wppm of Mo, it may be possible to use MoDTC to
provide a modest decrease in friction coefficient (friction
coefficient of roughly 0.08) while causing only a modest amount of
wear depth. However, at higher Mo concentrations of 300 wppm or
more, the wear depth in the ring and block test exceeded the 1.2 m
depth of the diamond-like carbon layer on the block.
[0273] For the Mo-trimer, Mo concentrations of up to 750 wppm or
possibly higher can be used while maintaining a wear depth that is
less than the sample depth of 1.2 .mu.m. As shown in FIG. 8, at Mo
concentrations of 100 wppm or more, the Mo-trimer provides a
substantially larger decrease in the friction coefficient (friction
coefficient of 0.05 or less) while also unexpectedly reducing or
minimizing the amount of wear depth.
[0274] For the MoDTP friction modifier, a substantial and
unexpected reduction in wear depth was achieved at all
concentrations investigated up to 1500 wppm. A friction coefficient
of 0.05 or less was achieved for Mo concentrations of 300 wppm or
greater.
Example 4--Molecular and Polar Site Diameter
[0275] The molecular diameter and polar site diameter for various
friction modifiers was calculated using a commercially available
molecular modeling tool. Table 5 shows the molecular weight,
molecular diameter, and polar diameter for the friction modifiers.
The molecular diameters were calculated based on twice the
molecular radius.
[0276] The molecular radius, R, is defined as the average distance
of all atoms in the molecule with respect to the configurational
center of the molecule (not mass weighted). The calculation for the
polar site diameter, 2R.sub.p, is similar, but only accounts for
the polar atoms within the friction modifier. It is noted that the
molecular diameter may be different from the time-averaged value,
and may also depend on solvent effects. The polar site diameter is
expected to have a lower variation with respect to such factors.
The configurations of the molecules were obtained from geometry
optimization calculations using Density Functional Theory (DFT).
Details of the DFT calculations are given in Section 2.4 of the
following publication on organo-metallic compounds: C.E.S.
Bernardes et al., J. Phys. Chem. A, 2013, 117, 11107-11113. It is
noted that the molecular diameter and polar site diameter for a
C.sub.18 thiol friction modifier is expected to be similar to the
values for stearic acid.
TABLE-US-00005 TABLE 5 Molecular Diameter and Polar Diameter for
Friction Modifiers Molecular Diameter, polar Friction Mol Wt
Diameter sites only Modifier (g/mol) (Angstroms) (Angstroms) MoDTC
921.27 15.5 6.8 MoDTP 995.17 16.1 8.0 Mo.sub.3S.sub.7(dtc).sub.2
1434.01 19.6 7.3 Mo-trimer 2227.48 20.8 7.3 Stearic Acid 284.48
13.8 2.3
[0277] Table 5 shows the molecular weight, the molecular diameter,
2R, and the polar diameter, 2R.sub.p, for different Mo-containing
friction modifiers. MoDTC and MoDTP both contain 2-ethylhexyl side
chains that are attached to the core structures; those structures
(MoDTC and MoDTP) were taken from the following publication: Y.
Yamamoto and S. Gondo, Tribology Transactions, 1989, 32, 251-257.
As shown in Table 5, MoDTC has a smaller polar site diameter than
the other Mo-containing friction modifiers in Table 5, even though
the molecular diameter of MoDTC is similar to the molecular
diameter for MoDTP. Without being bound by any particular theory,
the smaller polar site diameter of MoDTC may prevent MoDTC from
fully bridging between oxygen sites on an oxygenated diamond-like
carbon surface, which could reduce or minimize the likelihood of
forming a substantially complete layer of MoDTC on the surface.
PCT/EP Clauses and Additional Embodiments
Embodiment 1
[0278] A method for lubricating a machine surface comprising:
supplying a lubricant comprising a Group VI metal-containing
friction modifier to a surface layer comprising diamond-like carbon
with a surface oxygen to carbon ratio of 1:15 or more, the
lubricant comprising 0.05 wt % to 0.2 wt % of the Group VI
metal-containing friction modifier, the Group VI metal-containing
friction modifier comprising a .DELTA.G of adsorption on the
diamond-like carbon of -25 kJ/mol or less (or -28 kJ/mol or less,
or -30 kJ/mol or less).
Embodiment 2
[0279] The method of Embodiment 1, wherein the Group VI
metal-containing friction modifier comprises a polar site diameter
of 5.0 Angstroms or more (or 7.0 or more).
Embodiment 3
[0280] The method of any of the above embodiments, wherein the
diamond-like carbon comprises 15 mole % or more of hydrogen, or 20
mole % or more.
Embodiment 4
[0281] The method of any of the above embodiments, wherein the
Group VI metal-containing friction modifier comprises an
Mo-containing friction modifier.
Embodiment 5
[0282] The method of any of the above embodiments, wherein the
lubricant comprises 50 wppm or more of Group VI metal, or 200 wppm
or more, or 500 wppm or more, or 800 wppm or more; or wherein the
lubricant comprises 100 wppm or more of Mo, or 300 wppm or more, or
500 wppm or more, or 800 wppm or more.
Embodiment 6
[0283] The method of any of the above embodiments, wherein the
friction modifier comprises an Mo-containing friction modifier.
Embodiment 7
[0284] The method of any of the above embodiments, wherein the
friction modifier comprises MoDTP, [Mo.sub.3S.sub.4](dtc).sub.2, a
trinuclear molybdenum compound, or a combination thereof.
Embodiment 8
[0285] The method of any of the above embodiments, wherein the
surface layer comprising diamond-like carbon comprises a layer
depth of 2.0 m or more of diamond-like carbon.
Embodiment 9
[0286] The method of any of the above embodiments, wherein the
surface oxygen to carbon ratio is 1:10 or more.
Embodiment 10
[0287] The method of any of the above embodiments, wherein the
surface oxygen to carbon ratio comprises a top 1.0 nm at the
surface of the diamond-like carbon, or a top 0.7 nm.
Embodiment 11
[0288] The method of any of the above embodiments, wherein the
lubricant further comprises a friction coefficient of 0.06 or less,
or 0.05 or less.
Embodiment 12
[0289] The method of any of the above embodiments, wherein the
lubricant is supplied to a machine surface layer positioned in
opposition to a steel surface layer.
Embodiment 13
[0290] The method of any of the above embodiments, wherein the
diamond-like carbon comprises borated diamond-like carbon, the
borated diamond-like carbon optionally having a boron to carbon
ratio of 0.5:100 or more, or 1.0:100 or more.
Embodiment 14
[0291] The method of Embodiment 13, wherein the borated
diamond-like carbon comprises an oxygen to carbon ratio of 1:10 or
more in a surface portion having a depth of 1.0 nm, or in a surface
portion having a depth of 0.7 nm, or in a surface portion having a
depth of 0.5 nm.
Embodiment 15
[0292] The method of any of the above embodiments, wherein a ratio
of sp.sup.2 to sp.sup.3 hybridized carbons in the diamond-like
carbon is 0.5 to 2.5, or 0.7 to 1.5.
Additional Embodiment A
[0293] The method of any of the above embodiments, wherein the
Group VI metal-containing friction modifier comprises a molecular
diameter of 16.0 Angstroms or more.
[0294] While the present invention has been described and
illustrated by reference to particular embodiments, those of
ordinary skill in the art will appreciate that the invention lends
itself to variations not necessarily illustrated herein. For this
reason, then, reference should be made solely to the appended
claims for purposes of determining the true scope of the present
invention.
* * * * *
References