Note: Descriptions are shown in the official language in which they were submitted.
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LUBRICATING OIL CONTAINING AN ADDITIVE COMPRISING THE
REACTION PRODUCT OF MOLYBDENUM DITHIOCARBAMATE AND
METAL DIHYDROCARBYL DITHIOPHOSPHATE
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to lubricating oils containing additives which
impart low friction and antiwear characteristics.
DESCRIPTION OF THE RELATED ART
The reduction in fiiction and improved antiwear performance in lubricants
has been pursued in the industry for a number of years.
U.S. Patent 4,178,258 teaches a lubricating oil for use in spark ignition and
compression ignition engines which exhibits enhanced antiwear and friction
characteristics by containing an antiwear amount of a molybdenum bis(dialkyl
dithiocarbamate). The lubricant is described as being especially effective in
reducing wear and friction if the lubricant also contains a zinc
dialkyldithiophosphate (ZDDP}.
U.S. Patent 4,395,434 teaches an antioxidant additive combination for lube
oils prepared by combining (1) a sulfur containing molybdenum compound
prepared by reacting an acidic molybdenum compound, a basic nitrogen
compound and carbon disulfide with (2) an organic sulfur compound. The
organic sulfur compound is described as including metal dialkyl-
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dithiophosphates, and metal dithiocarbamates, among other organic sulfur
compounds.
U.S. Patent 4,529,526 teaches a lubricating oil composition comprising a
base oil and a sulfurized oxymetal organic phosphorodithioate and/or a
sulfurized oxymetal-dithiocarbamate and at least one zinc alkylcarbyl
dithiophosphate, along with a calcium alkybenzene or calcium petroleum
sulfonate and an alkenylsuccinic acid imide.
U.S. Patent 4,786,423 teaches an improved lubricant which contains a
mineral or synthetic base stock oil and two heavy metal compounds as well as a
metal and sulfur free phosphorous compound. The heavy metal compounds can
be molybdenum dithiocarbamate in combination with zinc
dialkyldithiophosphate. The other phosphorous compound can be trialkyl or
triaryl phosphate. The lubricant is prepared by, for example, heating the base
stock to between room temperature and about 100°C for two hours, then
adding
the subsequent components to the heated oil approximately 20 minutes apart
under the referenced elevated temperature.
WO 95/19411 (PCT/US95/00424) is directed to additives for lubricants
which are combinations and reaction products of metallic dithiocarbamates and
metallic dithiophosphates. The preblended combinations and reaction products
are described as showing good stability and compatibility when used in the
presence of other commonly used additives in grease or lubricant compositions.
The metals of the metal dithiophosphates and metal dithiocarbamates may be
selected from nickel, antimony, molybdenum, copper, cobalt, iron, cadmium,
zinc, manganese, sodium, magnesium, calcium and lead. The combination and
reaction products are described as providing enhanced friction reducing and
anti-
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wear properties at extreme pressure. Additional anti- oxidation, cleanliness,
anti-fatigue, high temperature stabilizing and anti-corrosion properties are
also
described as potentially present. The metallic dithiocarbamate and metallic
dithiophosphate are mixed, generally at any suitable conditions with
temperatures varying from -20°C to 250°C, preferably between
50°C and 150°C.
Reaction rather than blending will usually occur if the temperature is between
70°C and 100°C. The metallic dithiocarbamates and the metallic
dithiophosphates may be combined in any ratio from 1:9 to 9:1. In the
Examples, reaction temperatures of only 80°C to 100°C were
employed.
U.S. Patent 4,812,246 teaches a lubricating composition comprising a
particular base oil and additives comprising a phenol based antioxidant and/or
organomolybdenum compounds such as molybdenum dithiocarbamate. The
lubricating composition can also contain other common additives such as zinc
dialkyl dithiophosphates, etc.
It is well known in the art that in formulating engine oils, there is a
delicate
balance between friction and wear performance. According to the literature
[Kubo et al, Toraiborojisuto, 34(3), 185 (1989)], organomolybdenum
compounds compete with ZDDP for the metal surface. The structure and
friction coeff cient of the film depends on the surface affinity of the two
compounds. ZDDP adsorbs onto the metal surface first to form a film, on top of
which adsorbs MoDTC to form a shearable film rich in molybdenum and sulfur
[M. Muraki and H. Wads, Toraiborojisuto, 38(10), 919 (1993)].
The amount of ZDDP that can be added is limited by industry concerns.
Apparently, the phosphorous contained m some additive compounds may affect
the catalytic converters in modern vehicles. It is anticipated that future
engine
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oil specifications will have lower limits on phosphorous concentrations, and
there are additional concerns on whether such a reduction would affect the
antiwear performance of engine oils.
It would be desirable to have an engine oil with improved friction
performance, wear protection, and low phosphorous concentration to meet the
increasing performance demands placed on modem oils.
SUMMARY OF TIDE INVENTION
This invention is a method for forming a lubricating composition comprising
adding to a major amount of an oil of lubricating viscosity a minor amount of
metal dihydrocarbyl dithiophosphate and molybdenum dithiocarbamate, and
heating the admixture in air to a temperature ranging from above about
135°C to
about 200°C thereby forming a lubricating composition.
In another embodiment, the invention is a lubricating composition
formed by adding to a major amount of an oil of lubricating viscosity a minor
amount of the reaction product formed upon heating the admixture of metal
dihydrocarbyl dithiophosphate and molybdenum dithiocarbamate in air to a
termperature ranging from above about 135°C to about 200°C.
In still another embodiment, the invention is a method for enhancing the
friction reducing and wear reducing properties of a lubricating composition
having a major amount of an oil of lubricating viscosity, comprising a minor
of
the reaction product formed upon heating the admixture of metal dihydrocarbyl
dithiophosphate and molybdenum dithiocarbamate in air to a temperature
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ranging from above about 135°C to about 200°C in the presence of
air, zinc
dialkyldithiocarbamate, and molybdenum dithiocarbamate.
DESCRIPTION OF THE FIGURES
Figure 1 is the phosphorous x:ANES spectra of (A) fresh, unreacted 1%
w/w mixed primary/secondary ZDDP in S 150N Tube basestock; (B) 1% w/w
mixed primary/secondary ZDDP in S 150N tube basestock heated at 150 °C
for
16 hours with an air spurge of 55 cc/min; (C) reaction product of 1% w/w mixed
primaiy/secondary ZDDP combined with 1% Molybdenum Dithiocarbamate
(MoDTC) in S 150N Tube basestock, heated at 150 °C for 16 hours with an
air
spurge of 55 cc/min. Descriptions of the ZDDP and MoDTC compounds and the
reaction and separation procedures are given in Example 1.
Figure 2 is the sulfur XANES spectra of (A) fresh, unreacted 1% w/w
mixed primary/secondary ZDDP combined with 1% MoDTC in S 150N tube
basestock; (B) linear combination of the x;ANES spectra of the starting
materials, i.e., mixed primary/secondary ZDDP and Molybdenum
Dithiocarbamate (MoDTC) individually heated at 1% w/w in S150N Tube
basestock at 150 °C for 16 hours with an air spurge of 55 cc/min; (C)
reaction
product of 1% w/w mixed primary/secondary ZDDP combined with 1% MoDTC
in S 150N lube basestock, heated at 150 °C for 16 hours with an air
spurge of 55
cc/min. Descriptions of the ZDDP and MoDTC compounds and the reaction and
separation procedures are given in Example 1.
Figure 3 is a radial distribution function, centered on the molybdenum
atom, derived from the molybdenum EXAFS spectra of (A) fresh, unreacted 1
w/w MoDTC in S 150N Tube basestock, (B) 1% w/w MoDTC in S 150N tube
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basestock heated at 150 ° C for 16 hours with an air spurge of 55
cc/min, and (C)
reaction product of 1% w/w mixed primary/secondary ZDDP combined with 1%
w/w MoDTC in S 150N lube basestock, heated at 150 ° C for 16 hours with
an
air spurge of 55 cc/min. Descriptions of the ZDDP and MoDTC compounds and
the reaction and separation procedures are given in Example 1.
Figure 4 is the sulfur X:ANES spectra of (A) fresh, unreacted 1% w/w
mixed primary/secondary ZDDP combined with 1% MoDTC in S150N lube
basestock (B) reaction product of 1 % w/w mixed primary/secondary ZDDP
combined with 1% w/w MoDTC in S 150N lube basestock, heated at I35 °C
for
16 hours with an air spurge of 55 cc/min, and {C) reaction product of 1% w/w
mixed primary/secondary ZDDP combined with 1% w/w MoDTC in S 150N Tube
basestock, heated at 150 °C for 16 hours with an air spurge of 55
cc/min.
Descriptions of the ZDDP and MoDTC compounds and the reaction and
separation procedures are given in Example 1.
Figure 5 is a radial distribution function, centered on the molybdenum atom,
derived from the molybdenum EXAFS spectra of (A) fresh, unreacted 1 % w/w
MoDTC in S 150N Tube basestock, (B) 1% w/w MoDTC in S 150N lube
basestock heated at 150 °C for 16 hours with an air spurge of 55
cc/min, (C)
reaction product of 1% w/w primary ZDDP combined with 1% w/w MoDTC in
S 150N lube basestock heated at 150 ° C for 16 hours with an air
spurge of SS
cc/min as described in Example 2, and (D) reaction product of 1% w/w
secondary ZDDP combined with 1% w/w MoDTC in S 150N Tube basestock,
heated at 150 °C for 16 hours with an air spurge of 55 cc/min as
described in
Example 3.
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DESCRIPTION OF THE INVENTION
The present invention is directed to a multifunctional lube additive formed as
the reaction product of a metal dihydrocarbyl dithiophosphate and molybdenum
dithiocarbamate in air at a temperature above 135°C, preferably about
150 °C.
The invention also relates to a lubricant formulation additive that imparts
improved antiwear and reduced friction characteristics to the lubricant in
which
it is employed at a lower phosphorous content as compared to the metal
dihydrocarbyl dithiophosphate starting material.
The product is prepared by reacting the metal dihydrocarbyl dithiophosphate
aad the molybdenum dithiocarbamate in solution (typically and preferably
lubricating oil base stock) at a temperature above about 135 °C to
about 200°C,
preferably at about 150°C at times sufficient for reaction to occur,
preferably for
about 8 to 16 hours, with an air spurge sufficient to saturate the mixture
with air.
Reactant concentrations of 0.1% w/w or greater of each are typically employed.
Any metal dithiophosphate in which the solubilizing ligands are C3-C 16
primary, secondary, mixed primary-secondary alkyl ligands, and combinations
thereof are usable as starting materials in production of the composition of
the
present invention. While alkyl ligands are preferred, the invention can also
be
practiced with ligands having organo groups selected from aryl, substituted
aryl,
and ether groups. Preferably, the solubilizing ligands are C3-C 12 P~~'Y
secondary, mixed primary-secondary alkyl ligands, and combinations thereof.
The metallic moiety may be copper, lead, molybdenum, magnesium, calcium,
iron, and zinc. Of these zinc, copper, and molybdenum are preferred; zinc is
most preferred.
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_g_
The molybdenum dithiocarbamates (MoDTC) usable as starting materials in
production of the composition of the present invention are of the structural
formula shown below:
2
R~N-C-S-Mo~ Mo-S-C-N\
S
where R1-R4 are independently selected C3-C16 primary, secondary, mixed
primary-secondary alkyl ligands, and mixtures thereof. X1 and X2 are each,
either O or S. While alkyl ligands are preferred, the invention can also be
practiced with aryl and alkyl aryl ligands.
In practicing the present invention, the list of usable starting materials is
quite broad, being generally defined as metallic dihydrocarbyl
dithiophosphates
and molybdenum dithiocarbamates, combined in just about any ratio. So long as
both starting materials are present, some quantity of the desired reaction
products
will be formed if the reaction is run in air at a temperature above 135
°C,
preferably at about 150 °C.
The ratio and extent of reaction, and the time required to complete the
reaction will depend on the nature of the starting materials within the range
of
the materials described. Similarly, the solubility of the final product will
also
depend on the ligand structure of the starting molecules. Because the starting
materials must first be put into solution before reaction occurs, materials
with
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chains which are too short will not dissolve sufficiently to facilitate
production
of the desired reaction product. Thus, the ligands on the metallic
dihydrocarbyl
dithiophosphate and molybdenum dithiocarbamate are independently selected
primary, secondary or mixtures of primary and secondary C3-C 16 alkyl ligands,
provided that the total number of carbon atoms present among the ligand's
organo groups is sufficient to render the starting material and reaction
product oil
soluble.
The starting materials are mixed together in a solvent which may be any
material in which both reactants are at least somewhat soluble, which does not
compete with or otherwise react with one or the other of the starting
materials
and which remains chemically and physically stable at the reaction temperature
of above about 135°C, preferably about 150 °C and higher.
Preferred solvent is
the lubricating oil base stock of the type in which the final reaction product
is
intended for use.
Following reaction, at temperatures of above about 135°C,
preferably about
i50 °C and higher at times sufficient for reaction to occur, preferably
about 8-16
hours at temperatures of about 150 °C with air sparge sufficient to
saturate the
reaction mixture with air, the soluble product is purified by separation of
insoluble materials from the soluble products by methods known to those
skilled
in the art. The reaction product in the recovered liquid phase will be used in
the
formulated oil in an amount su~icier<t to attain the desired molybdenum
concentration in the formulated oil.
Alternatively, purified reaction product may be added to a suitable
oleagenous carrier in order to form a concentrate for blending with
lubricating
oils. The amount of purified reaction product ranges from about 1 to about 90%
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wt.% based on the weight of the carrier and reaction product. Suitable
oleagenous carriers include base stock, animal oils, vegetable oils, mineral
oil,
synthetic oils, and mixtures thereof.
The amount of reaction product per se, measured as a function of
molybdenum wt % active ingredient, in the final formulated oil will range from
0.004 wt % to 0.4 wt %, and preferably from 0.005 wt % to 0.2 wt %.
The lubricating composition according to the invention requires a major
amount of lubricating oil basestock. In general, the lubricating oil basestock
will
have a kinematic viscosity ranging from about 2 to about 1,000 cSt at
40°C. The
lubricating oil basestock can be derived from natural lubricating oils,
synthetic
lubricating oils, or mixtures thereof. Suitable lubricating oil basestocks
include
basestocks obtained by isomerization of synthetic wax and slack wax, as well
as
hydrocrackate basestocks produced by hydrocracking (rather than solvent
extracting) the aromatic and polar components of the crude.
Natural lubricating oils include animal oils, vegetable oils (e.g., castor
oils
and lard oil), petroleum oils, mineral oils, and oils derived from coal or
shale,
and mixtures thereof.
Synthetic oils include hydrocarbon oils and halo-substituted hydrocarbon
oils such as polymerized and interpolymerized olefins, alkylbenzenes,
polyphenyls, allcylated Biphenyl ethers, alkylated Biphenyl ethers, alkylated
Biphenyl sulfides, as well as their derivatives, analogs, and homologs
thereof,
and the like. Synthetic lubricating oils also include alkylene oxide polymers,
interpolymers, copolymers and derivatives thereof wherein the terminal
hydroxyl
groups have been modified by esterification, etherification, etc. Another
suitable
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class of synthetic lubricating oils comprises the esters of dicarboxylic acids
with
a variety of alcohols. Esters useful as synthetic oils also include those made
from CS to C 12 monocarboxylic aids and polyols and polyol ethers.
Silicon-based oils (such as the polyalkyl-, polyaryl-, polyalkoxy-, or
polyaryloxy-siloxane oils and silicate oils) comprise another useful class of
synthetic lubricating oils. Other synthetic lubricating oils include liquid
esters of
phosphorus-containing acids, polymeric tetrahydrofurans, polyalphaolefins, and
the like.
The lubricating oil may be derived from unrefined, refined, rerefined oils, or
mixtures thereof, Unrefined oils are obtained directly from a natural source
or
synthetic source (e.g., coal, shale, or tar sands bitumen) without further
purification or treatment. Examples of unrefined oils include a shale oil
obtained
directly from a retorting operation, a petroleum oil obtained directly from
distillation, or an ester oil obtained directly from an esterification
process, each
of which is then used without further treatment. Refined oils are similar to
the
unrefined oils except that refined oils have been treated in one or more
purification steps to improve one or more properties. Suitable purification
techniques include distillation, hydrotreating, dewaxing, solvent extraction,
acid
or base extracrion, filtration, and percolation, all of which are known to
those
skilled in the art. Rerefined oils are obtained by treating refined oils in
processes
similar to those used to obtain the refined oils. These rerefined oils are
also
known as reclaimed or reprocessed oils and often are additionally processed by
techniques for removal of spent additives and oil breakdown products.
The lubricating oil formulation containing the reaction product is compatible
with and may also contain one or more of the following classes of additives:
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viscosity index improvers, antioxidants, friction modifiers, antifoamants,
anti-
wear agents, corrosion inhibitors, hydrolytic stabilizers, metal deactivator,
detergents, dispersants, pour point depressants, extreme pressure additives,
etc.
Lubricating oil additives are described generally in "Lubricants and Related
Products" by Dieter Klamann, Verlag Chemie, Deerfield, Florida, 1984, and also
in "Lubricant Additives" by C. V. Smalheer and R. Kennedy Smith, 1967, pages
1-11, the disclosures of which are incorporated herein by reference.
This invention may be further understood by reference to, but not limited by,
the following examples which include preferred embodiments.
EXAMPLE 1
I. Synthesis and Chemical Analysis of the Reaction Product
In the first example, we start with a commercial mixed primary-secondary
zinc dialkyl dithiophosphate (ECA 6654 available from Exxon Chemical
Company) and a commercial molybdenum dithiocarbamate (Sakura Lube 155
available from Asahi Denka Kogyo). Each additive is present at concentration
1% w/w in S 150N mineral Tube base stock. The compounds, individually at 1%
w/w and in combination at 1% w/w each are subjected to reaction conditions of
150 °C for 16 hours with an air spurge of 55 cc/min. The oil soluble
reaction
product is separated and the liquid phase is decanted. The spectra in Figures
1
through 4 and the performance data in Tables 1 and 2 were obtained with the
above described liquid product.
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XANJES (X-Ray Absorption Near Edge Spectroscopy) and EXAFS
(Extended X-Ray Absorption Fine Structure) spectroscopy data were acquired
from the starting materials and the reaction products. The spectra reported
here
were obtained using standard practices as described in "X Ray Absorption:
Principles, Applications Tech»iques of EXAFS, SEXAFS a»d XANES", D. C.
Koningsberger & R. Prins Editors, John Wiley & Sons (1988). The sulfur
intensities have been normalized to equivalent sulfur concentrations.
Figures 1, 2 and 4 respectively compare the phosphorous (Figure 1), sulfur
(Figure 2 and 4) XANES spectra, and the molybdenum radial distribution
function based on EXAFS spectra (Figure 3) of the initial reactants in their
unreacted fresh condition, the individual reactants after heating to 150
°C for 16
hours with an air spurge, and the reaction product of this invention.
Figure 1 shows that no change occurs in the chemical structure of the soluble
phosphorous on heating the zincdihydrocarbyl dithiophosphate alone to 150
°C
in air for 16 hours. See spectra A and B. In contrast heating the zinc
dihydrocarbyl dithiophosphate in the presence of the molybdenum
dithiocarbamate at 150 °C in air for 16 hours results in the formation
of the
reaction product. See spectrum C. Comparing samples 7 and 8 in Table 1 shows
that the reaction product improves the friction and wear performance in a
lubricating composition in the presence of only half the phosphorous present
in
the unreacted mixture of lubricating oils and starting materials (see the
discussion of the performance data in the following section).
Figure 2 illustrates the chemical changes which occur to the sulfur moieties
in the starting materials during the formation of the reaction product of this
invention. As can be seen from figure 2, heating the metal dihydrocarbyl
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dithiophosphate in the presence of the molybdenum dithiocarbamate at
150°C in
air for 16 hours results in the conversion of the sulfur to a new chemical
form.
The sulfur spectrum of the reaction product formed in this invention (spectrum
C) is not the same as that of the fresh mixed ZDDP and MoDTC combination
(spectrum A) and it is different from the spectrum obtained by a linear
superposition of the spectra of the starting materials heated individually at
1%
w/w concentration in S 150N base stock at 150 °C in air (spectrum B).
The
existence of a reaction product of this invention is shown by the change in
the
sulfur XANES spectra of figure 2 (spectrum C).
Figure 3 illustrates the changes in the radial distribution function (RDF)
centered on the molybdenum EXAFS contained in the product and starting
materials of this invention. Comparing the molybdenum RDF of the
molybdenum dithiocarbamate starting material (A) and the product of oxidizing
the molybdenum dithiocarbamate alone at 150 °C for 16 hours in air (B)
shows
that no substantial change in the chemical coordination of the molybdenum has
occurred. In contrast, when the molybdenum dithiocarbamate starting material
is
heated in the presence of the zinc dithiocarbyl dithiophosphate of Example 1,
the
RDF is radically changed indicating a change in the chemical coordination of
the
molybdenum atoms (C). The existence of a reaction product is shown by the
molybdenum RDF in spectrum C of Figure 3.
The reaction product of the present invention is not formed in-situ in engines
run using formulated lubricating oils containing, e.g., zinc dialkyldithio
phosphates (ZDDP) and molybdenum dithiocarbamates (MoDTC). The sump
temperatures in engines are usually below 135 °C, which was shown to be
a
threshold temperature below which the reaction will not occur. This is
illustrated in figure 4, which shows that no change to the sulfur moeitfes
occurs
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upon heating the metal dihydrocarbyl dithiophosphate in the presence of
molybdenum dithiocarbamate at 135 °C in air for 16 hours (see spectrum
B). In
contrast, heating the two compounds at 150 °C, results in the formation
of new
products (spectrum C in figure 4). Furthermore, the presence of blowby gases
in
the crankcase oil and NOx in particular are known to degrade ZDDP and
MoDTC, which in turn will slow down or eliminate the formation of the reaction
product. As shown by Johnston et al (M.D. Johnson, S. Korcek and M.J.
Rokosz, Lubrication Science, 6-3, 247 ( 1994)), NOx initiated oxidation
processes and direct interactions between N02 and ZDDP derived intermediates
accelerate the consumption of ZDDP. Arai, et al (K. Arai, M. Yamada, S.
Asano, S. Yoshizawa, H. Ohira, I. Hoshino, F. Ueda, I. Akiyama, SAE 952533
(1995)) also reported deterioration of MoDTC and ZDDP in the presence of
N02 which was reflected in an increase in the friction coefficient. The
presence
of other additives in fully formulated engine oils are also expected to affect
the
reaction. For example, ashless dispersants are known to interact with ZDDP and
would be expected to inhibit formation of the reaction product of the present
invention.
II. Performance Data
The compounds, mixtures, and reaction products studied in example 1 were
evaluated for friction and wear performance using a Falex block-on-ring
tribometer. Average friction coefficients were measured during the
experimental runs under 670N load applied on the block for 2.0 hours at
100°C.
Wear scars on the block at the end of the experiment were measured by
profilometry. .
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In Tables 1 and 2, samples 8 and 14 show results for tube oils containing the
reaction product additive of the present invention. As in the case of the
spectroscopy data, the reaction product's properties are compared with those
of
MoDTC and ZDDP in Solvent 150 neutral (S 150I~ base stock. Two different
concentrations of 1% w/w of each additive (1% w/w MoDTC and 1% w/w
ZDDP) and 0.5% w/w of each additive (0.5% w/w MoDTC and 0.5% w/w
ZDDP) are chosen, as demonstrated in Tables 1 and 2, respectively.
The data in Tables 1 and 2 indicate that the new class of compounds
(samples 8 and 14) provide an excellent combination of low friction and low
wear performance. Furthermore, the new class of compounds, samples 8 and 14,
have lower phosphorous concentrations compared with the unreacted compounds
samples 7 and 13, respectively. As measured by Inductively Coupled Plasma
Atomic Emission Spectroscopy, the phosphorous concentration in sample 8 is
393 wppm compared with 813 wppm in sample 7. Similarly, the phosphorous
concentration in sample 14 is 310 wppm compared with 418 wppm in sample 13.
As explained in the introduction, low phosphorous levels are desirable for the
longevity of catalytic converters in modern vehicles.
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TABLE 1
Average Friction Coefficient Wear Scar Volume x 100 (mm3)
Sample 1 0.101 1.87
Sample 2 0.102 1.88
Sample 3 0.117 0.27
Sample 4 0.117 0.25
Sample 5 0.046 1.33
Sample 6 0.058 1.98
Sample 7 0.057(average of 2 runs) 0.70 (average of 2 runs)
Sample 8 0.053 (average of 2 runs) 0.62 (average of 2 runs)
Sample 1: S 150N base stock
Sample 2: S 150N base stock heated in air for 16 hours at 150 °C
Sample 3: 2% w/w mixed ZDDP in S 150N
Sample 4: 2% w/w mixed ZDDP in S 150N heated in air for 16 hours at 150
°C
Sample 5: 2% w/w MoDTC in S 150N
Sample 6: 2% w/w MoDTC in S 150N heated in air for 16 hours at 150
°C
Sample 7: 1% w/w mixed ZDDP combined with 1% w/w MoDTC in S150N
Sample 8: Reaction product of 1% w/w mixed ZDDP combined with 1% w/w
MoDTC in S 150N heated in air for 16 hours at 150 °C
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TABLE 2
Average Friction Coe~cient Wear Scar Volume x 100 (mm3)
Sample 9 0.116 (average of 4 runs) 0.47 (average of 4 runs)
Sample 10 0.111 (average of 6 runs) 1.06 (average of 6 runs)
Sample 11 0.052 2.14
Sample 12 0.069 2.69
Sample 13 0.063 0.60
Sample 14 0.047 0.54
Sample 9: 1% w/w mixed ZDDP in S150N
Sample 10: 1% w/w mixed ZDDP in S 150N heated in air for 16 hours at 150
°C
Sample 11: 1% w/w MoDTC in S 150N
Sample 12: 1% w/w MoDTC in S 150N heated in air for 16 hours at 150
°C
Sample 13: 0.5% w/w mixed ZDDP combined with 0.5% w/w MoDTC in
S 150N
Sample 14: Reaction product of 0.5% w/w mixed ZDDP combined with 0.5%
w/w MoDTC in S 150N heated in air for 16 hours at 150 °C
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EXAMPLE 2
I. Synthesis and Chemical Analysis of the Reaction Product
In the second example, we start with a commercial primary zinc dialkyl
dithiophosphate (Additin RC3180 available from Rhein Chemie) and a
commercial molybdenum dithiocarbamate (Sakvra Lube 155 available from
Asahi Denka Kogyo). Each additive is present at concentration 1% w/w in
S150N mineral lube base stock. The compounds, individually at 1% w/w and in
combination at 1% w/w are subjected to reaction conditions of 150 °C
for 16
hours with an air spurge of 55 cc/min. The crude product is dialysis filtered
through a latex membrane using pentane as the carrier. Following dialysis
filtration, the pentane solvent is removed by distillation. The product of
this
invention is recovered as the oil soluble product that passes through the
membrane. The EXAFS spectrum (C) in Figure 5 and the performance data in
Table 3 were obtained with the above described liquid product.
In Figure 5, the radial distribution function centered on the molybdenum
atom derived from the molybdenum EXAFS of the reaction product of this
invention (spectrum C) is compared with the spectra of the "fresh" 1% w/w
MoDTC in S150N base stock (spectrum A) and the heated 1% w/w MoDTC
solution at 150 °C for 16 hours (spectrum B). The reaction product of
this
invention is distinctly different from the heated MoDTC sample and is
characterized by a change in the coordination of Mo.
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II. Performance Data
The frictional and anti-wear characteristics of the compounds under study in
Example 2 were evaluated using a Falex block-on-ring tribometer; the test
conditions were the same as described in Example 1.
Table 3, summarizes the average friction coefficients and wear scar volumes
on the block of the Falex tribometer at the end of the experiment. Sample 16
represents the reaction product of this invention, as described in Example 2.
Its
performance is compared with the performance of the "fresh", unreacted mixture
of primary ZDDP and MoDTC utilized in Example 2. The data in Table 3 show
that the reaction product of this invention, Sample 16, has improved friction
and
wear performance. Furthermore, the product of this invention has lower
phosphorous concentration. As measured by Inductively Coupled Plasma
Atomic Emission Spectroscopy, the phosphorous concentration in Sample 16 of
Table 3 is 680 wppm compared with 780 wppm in Sample 15.
TABLE 3
Average Fiction Coeffcient Wear Scar Volume x 100 (mm3)
Sample 15 0.043 2.34
Sample 16 0.042 0.73
Sample 15: 1% w/w primary ZDDP mixed with 1% w/w MoDTC in S150N
Sample 16: Reaction product of 1% w/w primary ZDDP mixed with 1% w/w
MoDTC in S 150N heated as described in Example 2
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EXAMPLE 3
I. Synthesis and Chemical Analysis of the Reaction Product
In the third example, we start with a commercial secondary zinc dialkyl
dithiophosphate (Parabar 9419 available from Exxon Chemical Company) and a
commercial molybdenum dithiocarbamate (Sakura Lube 155 available from
Asahi Denka Kogyo). Each additive is present at concentration 1% w/w in
S 150N mineral tube base stock. The compounds, individually at 1% w/w and in
combination at 1% w/w are subjected to reaction conditions of 150 °C
for 16
hours with an air sparge of 55 cc/min. The crude product is dialysis filtered
through a latex membrane using pentane as the carrier. Following dialysis
filtration, the pentane solvent is removed by distillation. The product of
this
invention is recovered as the oil soluble product that passes through the
membrane. The EXAFS spectrum (D) in Figure 5 and the performance data in
Table 4 were obtained with the above described liquid product.
In Figure 5, the radial distribution function centered on the molybdenum
atom derived from the molybdenum EXAFS (spectrum D) of the reaction
product of this invention is compared with the spectra of the "fresh" 1% w/w
MoDTC in S150N base stock (spectrum A) and the heated 1% w/w MoDTC
solution at 150 C for 16 hours (spectrum B). The reaction product of this
invention is distinctly different and is characterized by a change in the
coordination of Mo.
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II. Performance Data
The frictional and anti-wear characteristics of the compounds under study in
Example 3 were evaluated using the Falex block-on-ring tribometer; the test
conditions were the same as described in Example 1.
Table 4, summarizes the average friction coefficients and wear scar volumes
on the block of Falex tribometer at the end of the experiments. Sample 18
represents the reaction product of this invention, as described in Example 3.
Its
performance is compared with the performance of the "fresh", unreacted mixture
of secondary ZDDP and MoDTC utilized in Example 3. The data in Table 4
show that the reaction product of this invention, Sample 18, has improved wear
performance. Furthermore, the product of this invention has lower phosphorous
concentration compared with the starting materials. As measured by Inductively
Coupled Plasma Atomic Emission Spectroscopy, the phosphorous concentration
in Sample 18 of Table 4 is below 160 wppm (detection limit for phosphorous)
compared with 770 wppm in Sample 17.
TABLE 4
Average Fiction Coefficient Wear Scar Volume x 100 (mm3)
Sample 17 0.053 p.g7
Sample 18 0.053 ~ 0.67
Sample 17: 1% w/w secondary ZDDP mixed with 1% w/w MoDTC in S 150N
Sample 18: Reaction product of 1% w/w secondary ZDDP with 1% w/w
MoDTC in S 150N heated, as described in Example 3.
