Note: Descriptions are shown in the official language in which they were submitted.
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LACQUER REDUCING LUBRICATING OIL
COMPOSITION AND METHOD OF USE OF SAME
FIELD OF INVENTION
[0001] This invention relates to lubricating oil compositions that have
surprisingly been shown to reduce the formation of lacquer deposits in
engines.
More specifically, this invention relates to a lubricating oil for natural gas
engines that reduces cylinder liner lacquer deposits.
BACKGROUND OF INVENTION
[0002] Over the last few years, natural gas fueled engines have become
increasingly popular as they generate energy efficiently and economically
while
limiting environmental pollution. These features have resulted in numerous
applications of natural gas fueled engines. For example, combined generation
of
heat and power, also known as co-generation, has achieved overall system
efficiencies of over 90 percent. Another well know application is the use of
these engines in natural gas compression and transmission. The engine is
connected to a compressor (either piston or rotary screw design) which takes
natural gas from an underground reserve and sends it through supply pipelines;
these engines typically either operate on the raw untreated gas, treated gas,
or
pipeline-quality gas.
[0003] Another effective use of natural gas fueled engines is the generation
of
electricity from landfill, bio, sewer or digester gas and other methane
generation
methods previously considered "waste" gasses. Instead of releasing the gas to
the atmosphere or flaring off, the gas is used to generate electricity in
natural gas
fueled engines. However, these gasses tend to be contaminated and costly
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methods of gas treatment (e.g. sweetening, filtration) are sometimes employed.
These contaminants can also necessitate more frequent engine maintenance.
[000~~] Although the contamination could be measured by directly determin-
ing the concentration of each contaminant within the gas, this would be a
costly
and lengthy process and would not provide useful information to the engine
operator in all cases. Natural gas engine manufacturers recognised quite early
that the heating value of natural gas not only varied by its natural
constituents
(percentage of methane, ethane, butane, etc.), but also its entrained
contaminants
(water, etc.). As such, they referred to the Higher Heating Value (HHV) and
Lower Heating Value (LHV) of a natural gas. The HHV is the amount of heat
generated by burning one unit of the gas to complete combustion. Unfortunately
this is not totally useful to an engine operator, as it does not account for
the
energy expended in changing the state of the entrained contaminants and of the
water produced from the combustion. The LHV is the HHV less the amount of
heat used to evaporate the water formed by combustion and other entrained
contaminants. More information and the calculation of LHV may be determined
from ANSI/ASME B.133.7M-1985, which is herein incorporated by reference.
[0005] The change in LHV has long been used to predict the combustion
efficiency of natural gas engines. An increase in LHV can lead to over
temperature operation which may cause hot spots in the combustion chamber. If
the gas engine is operated under this condition for a period of time, the
useful
life of its internal parts may be reduced. On the other hand if the LHV
decreases, the control system calls for an increase in fuel flow in order to
maintain the power output of the engine, which may cause incomplete
combustion and a drop in efficiency. In the case of very low LHV, the required
fuel flow for maximum power output may exceed the specification of the fuel
supply system and hence the desired power output may not be achieved.
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[0006] Plowever, the wide and often non-continuous variability of LIfV made
it difficult for natural gas angina operators to predict the proper air/fuel
ratio for
most efficient combustion. The more useful Wobbe Index was developed
allowing engine operators to maintain a steady air/fuel ratio for a given
Wobbe
Index. The Wobbe Index of a specific fuel stream directed to an engine is
determined by the equation:
WI = LFIV
Pier
where the LHV is determined as above, and the pai,. and peel are the density
of
the incoming air and fuel stream to the engine at standard conditions (101.3
kPa
and 273.15 °K). The standard metric units for the Wobbe Index (and the
LHV)
are MJoules/m3. Further determination of the Wobbe Index may be found in
SAE Technical Paper 861578, "Interchangeability of Gaseous Fuels - The
Importance of the Wobbe-Index", 1986, which is herein incorporated by
reference.
[0007] One concern in all engines, including natural gas fired engines is the
formation of deposits and lacquer and a resultant potential increase in Tube
oil
consumption. Lacquer is a deposit resulting from the oxidation and
polymerization of fuels and lubricants when exposed to high temperatures.
Noting that the term is often used interchangeably with varnish, the CRC
Deposit Rating Manual 20 defines lacquer as "a thin, hard, lustrous, oil-
insoluble
deposit, composed primarily of organic residue, and most readily definable by
color intensity. It is not easily removed by wiping with a clean, dry, soft,
lint-
free wiping material and is resistant to saturated solvents. Its color may
vary, but
it usually appears in gray, brown, or amber hues."
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[000] The problems associated with lacquer formation vary as to the
location of the lacquer. Lacquer is known to form both on pistons and on the
cylinder liners. While piston lacquer has often been discussed in the art, it
differs from cylinder liner lacquer. Piston lacquer appears to be a high
temperature phenomena, forming on the lands, grooves, skirt and undercrown of
the piston. ~ne current theory is that the formation of lacquer on these hot
locations is a function of the oxidative stability of the tube oil. Therefore,
a
lubricating oil employing a Group II base oil should produce less piston
lacquer
than one employing a Group I base oil.
[0009] The mechanism of cylinder liner lacquer formation differs from piston
lacquer as the cylinder liners generally operate at lower temperature.
Cylinder
liner lacquer is generally formed over the range of the top piston ring
travel, that
is, on the cylinder walls below the liner dead space (also known as the
"squish
area") and above the top compression ring at the bottom of piston travel. In
distillate or heavy fueled marine diesel engines, a partially clogged injector
may
lead to improper spray patterns. It is well known that irregular fuel
impingement
on the cylinder liner walls accelerates liner lacquer formation.
[0010] "Lean-burn" gas engines, as opposed to those that operate at
stoichiometric air/fuel ratios ("rich burn" engines) have shown increasing
problems due to the organic silicon compounds ("siloxanes") often contained in
the natural gas they employ. Engines that run on biogas, landfill gas or sewer
gas are particularly susceptible to this problem. Siloxanes have been shown to
increase the deposits on the cylinder heads, in areas of close tolerance or
small-
diameter passageways and increase lacquer on the cylinder liners. After as
little
as 1000 operating hours, lacquer buildup or other damage may occur that
necessitates the exchange of the cylinder liners.
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[0011] In extreme cases, the lacquer will fill in the cylinder liner cross
hatching grooves which are vital for providing a uniform, protective oil film.
Lube oil consumption, a major operating cost for these engines, can increase
dramatically. °This may result in bore polish, scuffing and scoring of
the cylinder
liners. Contrary to the theory of lacquer formation on hot surfaces, it is
theorized that the solubility characteristics of the base oil mixture are more
important than its oxidative stability for cylinder liner lacquer formation.
[0012] Many prior researchers had noticed some anti-varnish properties as a
secondary effect in various complex formulations. For example, Gatto (USP
6,147,035) noted anti-varnish effects in a molybdenum based formulation.
Bardasz (USP 5,595,964) teaches anti-varnishing characteristics when employ-
ing borated epoxides and hydrocarbylamine phosphate salts. Sougawa (USP
6,147,035) noted improvements in lacquer tests when employing a salicylate
based formulation. However, none of the prior art has suggested the efficacy
of
the formulation of the present invention, nor on its unexpected reduction of
cylinder liner lacquer or of lacquer deposits when used with non-Group I base
stocks.
[0013] As is well known in the art, there are many advantages of using Group
II, III and IV base stocks for lubricating oils. However, cylinder liner
lacquer
would be expected to become a more pronounced problem in modern lubricating
oils that employ more highly saturated Group II, Group III and Group IV base
oils, as their high paraffinicity also causes them to provide less solubility
for
modern additives and combustion produced contaminants. As such, lubricants
developed from Group II base stocks have traditionally required more
aggressive.
and carefully balanced additive systems to limit lacquering. Recent studies
have
shown that cylinder liner lacquer formation is further exacerbated in engines
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operated on landfill gas; current theory is that the increase is due to the
entrained
organic silicon compounds in the landfill gas.
[001] A lubricating oil composition that performs adequately in one engine
at given operating conditions does not necessarily perform adequately when
used
in a different engine or under different conditions. This is especially true
for
natural gas fueled engines. While theoretically, lubricants could be designed
for
each possible combination of engine and service condition, such a strategy
would be impractical because many different types of engines exist and the
engines are used under widely varying conditions. Accordingly, lubricants that
perform well in different types of engines and across a broad spectrum of
conditions (e.g., fuel type, operating load and temperature) are desired.
Design
of lubricating oil compositions is further complicated in that the
concentrated
mixture of chemicals added to lubricating oil base stocks to impart desirable
properties should perform well over a broad range of different quality base
stocks. Meeting these requirements has been very difficult because the
formulations are complicated, tests to ascertain whether a lubricant performs
well are very expensive and time consuming, and collecting field test data is
frequently difficult since variables cannot be fully controlled. While piston
deposit formation has often been controlled by mixtures of detergents and
dispersants, controlling lacquer formation, especially cylinder liner lacquer
formation, has been a more difficult objective to solve.
SUMMARY OF INVENTION
[0015] The present invention provides a method of reducing lacquer
formation in an internal combustion engine by using a lubricant comprising:
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(a) at least about 20 wt% of at least one base oil of lubricating viscosity
selected from the group consisting of Group II, Group III and Group
IV base stocks;
(b) a diarylamine, preferably an alkylated diphenyl amine;
(c) an alkaline earth metal phenate;
(d) an alkaline earth metal sulfonate;
(e) a borated aminated hydrocarbyl succinic derivative.
The present invention more specifically provides a method of reducing cylinder
liner lacquer in internal combustion engines employing the above formulation.
DETAILED DESCRIPTION OF INVENTION
[0016] It has been found that use of an aromatic antioxidant, an alkaline
earth
metal phenate sulfide detergent, a borated aminated hydrocarbyl succinic
deriva-
tive, and an alkaline earth metal sulfonate detergent as essential components
in a
specific combination and in particular proportions makes it possible to obtain
a
lubricating oil composition, especially a natural gas powered internal engine
lubricating oil composition, that reduces the formation of lacquer. More
specifically, it has been found that this composition is far superior to
others
when at least about 20 wt% of the final lubricant is made from a Group II base
stock.
[0017] In one aspect, the present invention relates to a lubricating oil
composition characterized in that the composition comprises a mixture of the
following components:
(a) at least about 20 wt% of at least one base oil of lubricating
viscosity selected from the group consisting of Group II, Group III
and Group IV base stocks;
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(b) about 0.05 to about 2 wt% of an alkylated Biphenyl amines;
(c) about 0.05 to about 5 wt% of at least one overbased alkaline earth
metal phenate;
(d) about 0.50 to about 5 wt% of a neutral or overbased alkaline earth
metal sulfonate; and
(e) about 1.0 to about 10 wt% of a borated aminated hydrocarbyl
succinic derivative.
[0018] In one aspect, the present invention relates to a lubricating oil
composition characterized in that the composition comprises a mixture of the
following components:
(a) at least about 20 wt% of at least one base oil of lubricating
viscosity selected from the group consisting of Group II, Group III
and Group IV base stocks;
(b) about 0.1 to about 1.0 wt% of an alkylated Biphenyl amines;
(c) about 0.75 to about 4.0 wt% of at least one overbased alkaline
earth metal phenate;
(d) about 0.5 to about 3.0 wt% of a neutral or overbased alkaline earth
metal sulfonate; and
(e) about 1:5 to about 6.0 wt% of a borated aminated polyalkenyl
succinic derivative.
[0019] In another embodiment, the present invention comprises a lubricating
oil composition that reduces lacquering in natural gas powered engines
characterized in that the composition comprises a lubricating base oil and a
mixture of the following components:
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(a) at least about 40 wt% of at least one base oil of lubricating
viscosity selected from the group consisting of Group II, Group III
and Group IV base stocks;
(b) about 0.20 to about 0.75 wt% of an alkylated Biphenyl amines;
(c) about 0.9 to about 2.7 wt% of at least one overbased calcium
phenate sulfide;
(d) about 0.50 to about 1.0 wt% of neutral calcium sulfonate; and
(e) about 1.75 to about 3.0 wt% of a borated aminated polybutenyl
succinic anhydride derivative;
[0020] One aspect of the present invention is an additive system for use in a
lubricating oil comprising at least about 20% of a Group II base stock, said
additive comprising portions (b) through (e) of the above formulations, alone
or
when in a diluent. In another aspect, the present invention provides a method
of
reducing cylinder liner lacquer using the formulations outlined above.
[0021] The base oil for the lubricant of the present invention may be a
mineral or synthetic oil ~or blends thereof, so long as about at least 20% is
a non-
Group I base stock as defined by API. A wide range of base stocks and base
oils are known in the art. Base stocks and base oils that may be used as co-
base
stocks or co-base oils in combination with the base stocks and base oils of
the
present invention are natural oils, mineral oils, and synthetic oils. These
lubricant base stocks and base oils may be used individually or in any combina-
tion of mixtures with the instant invention. Natural, mineral, and synthetic
oils
(or mixtures thereof] may 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, mineral, or synthetic source and used without added
purification. These include shale oil obtained directly from retorting
operations,
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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
for
example solvent extraction, distillation, secondary distillation, acid
extraction,
base extraction, filtration, percolation, dewaxing, hydroisomerization, hydro-
cracking, hydrofinishing, and others. Rerefined oils are obtained by processes
analogous to refined oils but using an oil that has been previously used.
[0022] Groups I,~ II, III, IV and V are broad categories of base oil stocks
developed and defined by the American Petroleum Institute (API Publication
1509; www.APLorg) to create guidelines for lubricant base stocks and base
oils.
Group I base stocks generally have a viscosity index of between about 80 to
120
and contains greater than about 0.03 wt% sulfur andlor less than about 90%
saturates. Group II base stocks generally have a viscosity index of between
about 80 to 120, and contain less than or equal to about 0.03 wt% sulfur and
greater than or equal to about 90% saturates. Group III stocks generally have
a
viscosity index greater than about 120 and contain less than about 0.03 wt%
sulfur and greater than or equal to about 90% saturates. Group IV includes
polyalphaolefins (PAO). Group V base stock includes base stocks not included
in Groups I-IV. The table below summarizes properties of each of these five
Groups.
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Table 1: API Classification of Base stocks and base oils
Saturates (wt%) Sulfur (wt%) Viscosity Index
(croup < 90 ~/or >_ 0.03% ~z >_ SO <_ 120
I
Group >_ 90 ~z < 0.03% ~ >_ SO ~ <_ 120
II
Group >_ 90 ~ < 0.03 % ~ > 120
III
Group Polyalphaolefins
IV (PAO)
Group All other base
V stocks and base
oils not included
in Groups I,
II, III, or IV
[0023] Base stocks and base oils may be derived from many sources. Natural
oils include animal oils, vegetable oils (castor oil and lard oil, for
example), and
mineral oils. In regard to animal and vegetable oils, those 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 in the present invention. 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.
[0024] Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oils
such as polymerized and interpolymerized olefins (polybutylenes, poly-
propylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and
ethylene-alphaolefin copolymers, polymers or copolymer of hydrocarbyl-
substituted olefins where hydrocarbyl optionally contains O, N, or S, for
example). Polyalphaolefin (PAO) oil base stocks are a commonly used synthetic
hydrocarbon oil. By way of example, PAOs derived from CS, C10, C12, C14
olefins or mixtures thereof may be utilized. See U.S. Patents 4,956,122;
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4,827,064; and 4,827,073, which are incorporated herein by reference in their
entirety.
[0025] 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. Patent No. 4,149178 or U.S. Patent
No. 3,382,291 may be conveniently used herein. Other descriptions of PAO
synthesis are found in the following U.S. Patent 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 C14 to C18 olefins are described in U.S.
4,218,330. All of the aforementioned patents are incorporated by reference
herein in their entirety.
[0026] Other synthetic base stocks and base oils include hydrocarbon oils that
are derived from the oligomerization or polymerization of low-molecular weight
compounds whose reactive group is not olefinic, into higher molecular weight
compounds, which may be optionally reacted further or chemically modified in
additional processes (e.g. isodewaxing, alkylation, esterification, hydro-
isomerization, dewaxing, etc.) to give a base oil of lubricating viscosity.
[0027] 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
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content. The hydroprocessing used for the production of such base stocks may
use an amorphous hydrocracking/hydroisomerization catalyst, such as one of the
specialized lobe hydrocracking (LII~C) catalysts or a crystalline
hydrocracking/hydroisomerization catalyst, preferably a zeolitic catalyst. For
example, one useful catalyst is ZSM-48 as described in U.S. Patent 5,075,269.
Processes for making hydrocracked/hydroisomerized distillates and
hydrocracked/hydroisomerized waxes are described, for example, in U.S. Patents
Nos. 2,817,693; 4,975,177; 4,921,594 and 4,897,178 as well as in Eritish
Patent
Nos. 1,429,494; 1,350,257; 1,440,230 and 1,390,359. Particularly favorable
processes are described in European Patent Application Nos. 464546 and
464547. Processes using Fischer-Tropsch wax feeds are described in US
4,594,172 and 4,943,672. Gas-to-Liquids (GTL) base stocks and base oils,
Fischer-Tropsch wax derived base stocks and base oils, and other wax isomerate
hydroisomerized (wax isomerate) base stocks and base oils be advantageously
used in the instant invention, and may have useful kinematic viscosities at
100°C
of about 3 cSt to about 50 cSt. These Gas-to-Liquids (GTL) base stocks and
base oils, Fischer-Tropsch wax derived base stocks and base oils, and other
wax
isomerate hydroisomerized base stocks and base oils may have useful pour
points of about -20°C or lower, and under some conditions may have
advantageous pour points of about -25°C or lower, with useful pour
points of
about -30°C to about -40°C or lower. Useful compositions of Gas-
to-Liquids
(GTL) base stocks and base oils, Fischer-Tropsch wax derived base stocks and
base oils, and wax isomerate hydroisomerized base stocks and base oils are
recited in U.S. Patent Nos. 6,080,301; 6,090,989, and 6,165,949 for example,
and are incorporated herein in their entirety by reference.
[0025] The diarylamines useful in this invention are well known antioxidants
and there is no particular restriction on the type of diarylamine that can be
used.
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Preferably, the diarylamine is a secondary diarylamine and has the general
formula:
R' ~ /R~
H
wherein I~1 and I~2 each independently represents a substituted or
unsubstituted
aryl group having from 6 to 30 carbon atoms. Illustrative of substituents for
the
aryl group include aliphatic hydrocarbon groups such as alkyl having from
about
1 to 30 carbon atoms, hydroxy groups, halogen radicals, carboxyl groups or
nitro
groups. The aryl is preferably substituted or unsubstituted phenyl or
naphthyl,
particularly wherein one or both of the aryl groups are substituted with at
least
one alkyl having from 4 to 30 carbon atoms, preferably from 4 to 18 carbon
atoms. It is further preferred that both aryl groups be substituted, e.g.,
alkyl
substituted phenyl.
[0029] The diarylamines used in this invention can be of a structure other
than that shown in the above formula that shows but one nitrogen atom in the
molecule. Thus, the diarylamine can be of a different structure provided that
at
least one nitrogen has 2 aryl groups attached thereto, e.g., as in the case of
various diamines having a secondary nitrogen atom as well as two aryls on one
of the nitrogens.
[0030] The diarylamines used in this invention should be soluble in the
formulated crankcase oil package. Examples of some diarylamines that may be
used in this invention include: diphenylamine; various alkylated
diphenylamines,
3-hydroxydiphenylamine; N-phenyl-1,2-phenylenediamine; N-phenyl-1,4-
phenylenediamine; dibutyldiphenylamine; dioctyldiphenylamine; dinonyldi-
phenylamine; phenyl-alpha-naphthylamine; phenyl-beta-naphthylamine;
diheptyldiphenylamine; and p-oriented styrenated diphenylamine, mixed
butyloctyldiphenylamine, and mixed octylstyryldiphenylamine.
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[0031] Examples of commercial diarylamines include, for example, Irganox~
L06 and Irganox~ L57 fronn Ciba Specialty Chemicals; l~Zaugalube~ AIDS,
hTaugalube~ 438, I~Taugalube~ 4388, Naugalube~ 438L, Naugalube~ 500,
Naugalube~ 640, Naugalube~ 680, and Naugard~ DANA from LTniroyal
Chemical Company; Vanlube~ DND, Vanlube~ NA, Vanlube~ PNA,
Vanlube~ SL, Vanlube~ SLHP, Vanlube~ SS, Vanlube~ 81, Vanlube~ 848,
and Vanlube~ 849 20 from R.T. Vanderbilt Company, Inc.
[0032] The concentration of the diarylamine in the lubricating composition
can vary depending upon the customer's requirements and applications. In a
preferred embodiment of the invention, a practical diarylamine use range in
the
lubricating composition is from about 500 parts per million to 20,000 parts
per
million (i.e., 0.05 to 2.0 wt%) based on the total weight of the lubricating
oil
composition, preferably the concentration is from 1,000 to 10,000 parts per
million (ppm) and more preferably from about 2,000 to 7,500 ppm by weight.
[0033] As used herein and in the claims the term "phenate" means the broad
class of metal phenates including salts of alkylphenols, alkylphenol sulfides,
and
the alkylphenol-aldehyde condensation products. Detergents formed from the
polar phenate substrate may be overbased. Normal phenate has the structural
formula:
O.~M~O
/\i / i
\ ~3 R4
whereas phenate sulfide has the formula:
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~.~M /~
Sx /~e
~3 ~q.
wherein H3 and H4 are individually alkyl groups preferably of eight or more
carbon atoms, M is a metallic element (e.g., Ca, Ba, Mg), and x may range from
1 to 3 depending on the particular metal involved. The calcium phenates is
preferred for use in the present invention.
[0034] Overbased alkaline-earth metal phenates are often referred to by the
amount of total basicity contained in the product. It is common to label a
detergent by its TBN (total base number), i.e., a 300 TBN synthetic sulfonate.
Base number is defined in terms of the equivalent amount of potassium
hydroxide contained in the material. A 300 TBN calcium sulfonate contains
base equivalent to 300 milligrams of potassium hydroxide per gram or, more
simply, 300 mg KOH/g.
(0035] The alkaline-earth metal phenates useful in the present invention
should have TBN's of from about 100 to 400, with 100 to 300 being more
preferred. TBN's may be determined using ASTM D 2896. The concentration
of the alkaline-earth metal phenates in the lubricating composition can vary
depending upon the customer's requirements and applications. In a preferred
embodiment of the invention, a practical alkaline-earth metal phenates use
range
in the lubricating composition is from about 500 parts per million to 50,000
parts
per million (i.e. 0.05 to 5.0 wt%) based on the total weight of the
lubricating oil
composition, preferably tlae concentration is from 7,500 to 40,000 parts per
million (ppm) and more preferably from about 9,000 to 27,000 ppm by weight.
[0036] Although the alkaline-earth metal phenates useful in the present
invention fall into the general class of additives known as detergents, the
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phenates are not interchangeable with other detergents, i.e., sulfonates, as
two
detergents having the same T~I~T, molecular weight, metal ratio and the like,
will
have widely different performance characteristics in the present invention.
[0037] The metal sulfonate useful in the present invention is represented,
e.g.,
by one of the general formulae
S~3
/ (R6)n
n(Rs)
\ \
\(R6)n
n(RS) S03 M S03
\R n
n(RS) ~ ~ S03 M S03 ( 6)
wherein, RS and R6 are each a hydrocarbon group, which may be the same or
different; and (n) is number of alkyl substituent(s) on the aromatic or
naphthalene ring, and an integer of 1 to 5 or 1 to 7, respectively, preferably
1 to
2. The hydrocarbon group is an alkyl or alkenyl group having a carbon number
of 8 to 28, preferably an alkyl group having a carbon number of 10 to 22. When
the carbon number is below 8, the metallic detergent may not be sufficiently
dissolved in the lubricant oil. When it exceeds 28, on the other hand, the
acid-
neutralizing function of the detergent may not increase as expected for its
content, and may conversely cause problems, such as oxidation of the alkyl
group in the metallic detergent, deteriorating the detergent itself into a
deposit.
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[003] T'he metal sulfonate of the present invention is preferably a calcium
sulfonate made from the salt of sulfonic acid having a hydrocarbon group
(e.g.,
petroleum-derived sulfonic acid, and sulfonic acid having a long-chain alkyl
benzene and alkyl naphthalene), and is not overbased.
[0039] The metal sulfonate for the lubricant oil composition of the present
invention is preferably a calcium sulfonate provided at 0.5 to 5.0 wt% as the
total content based on the whole composition, preferably at 0.5 to 3.0 wt% as
the
total content based on the whole composition, and more preferably at 0.5 to
1.0
wt% as the total content based on the whole composition. At a total content
below 0.5 wt%, the detergent may have an insufficient lacquer control. When it
exceeds 5.0 wt%, on the other hand, its acid-neutralizing function may not
increase as expected for its content, and may conversely cause problems, such
as
oxidation of the metallic detergent, deteriorating itself into a deposit.
[0040] Basic nitrogen-containing ashless dispersants useful in this invention
include hydrocarbyl succinimides; hydrocarbyl succinamides; mixed
ester/amides of hydrocarbyl-substituted succinic acids formed by reacting a
hydrocarbyl-substituted succinic acylating agent stepwise or with a mixture of
alcohols and amines, and/or with amino alcohols; Mannich condensation
products of hydrocarbyl-substituted phenols, formaldehyde and polyamines; and
amine dispersants formed by reacting high molecular weight aliphatic or
alicyclic halides with amines, such as polyalkylene polyamines. Mixtures of
such dispersants can also be used. As used herein, the terms "aminated
hydrocarbyl succinic derivatives" and "aminated polyalkenyl succinic
derivatives" include all items listed in this paragraph.
[004] Such basic nitrogen-containing ashless dispersants are well known
lubricating oil additives, and methods for their preparation are extensively
described in the patent literature. For example, hydrocarbyl-substituted
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succinimides and succinamides and methods for their preparation are described,
for example, in U.S. Pat. hTos. 3,018,247; 3,018,250; 3,018,291; 3,172,892;
3,185,704; 3,219,666; 3,272,746; 3,361,673; and 4,234,435. fixed ester-amides
of hydrocarbyl-substituted succinic acid are described, for exalTaple, in U.S.
Pat.
Nos. 3,576,743; 4,234,435 and 4,873,009. Mannish dispersants, which are
condensation products of hydrocarbyl-substituted phenols, formaldehyde and
polyamines are described, for example, in U.S. Pat. Nos. 3,368,972; 3,413,347;
3,539,633; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 3,798,247; 3,803,039;
3,985,802; 4,231,759 and 4,142,980. Amine dispersants and methods for their
production from high molecular weight aliphatic or alicyclic halides and
amines
are described, for example, in U.S. Pat. Nos. 3,275,554; 3,438,757; 3,454,555;
and 3,565,804.
[0042] In general amines containing basic nitrogen or basic nitrogen and
additionally one or more hydroxyl groups, including amines of the types
described in U.S. Pat. No. 4,235,435 can be used in the formation of the
ashless
dispersants. Usually, the amines are polyamines such as polyalkylene
polyamines, hydroxy-substituted polyamines and polyoxyalkylene polyamines.
Examples of polyalkylene polyamines include diethylene triamine, triethylene
tetramine, tetraethylene pentamine, pentaethylene hexamine, and dipropylene
triamine. While pure polyethylene polyamines can be used, it is generally
preferred to use mixtures of linear, branched and cyclic polyethylene
palyamines
having an average in the range of about 2.5 to about 7.5 nitrogen atoms per
molecule and more preferably an average in the range of about 3 to about 5
nitrogen atoms per molecule. Mixtures of this type are available as articles
of
commerce. I-Iydroxy-substituted amines include N-hydroxyalkyl-alkylene
polyamines such as N-(2-hydroxyethyl)ethylene diamine, N-(2-hydroxyethyl)
pipera~ine, and N-hydroxyalkylated alkylene diamines of the type described in
U.S. Pat. No. 4,873,009. Polyoxyalkylene polyamines typically include
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polyoxyethylene and polyoxypropylene diamines and triamines having average
molecular weights in the range of 200 to 2500.
[004] Borated polyalkenyl succinimides are described in LT.S. Pat. I~To.
4,63,624, which is herein incorporated by reference. Preferred borated
dispersants are boron derivatives derived from polyisobutylene substituted
with
succinic anhydride groups and reacted with polyethylene amines, polyoxy-
ethylene amines, and polyol amines (FIBSA/PAM) and are preferably added in
an amount from about 1.0 to 10.0 wt%, more preferably about 1.5-6.0 wt%, and
even more preferably in the amount of 1.75-3.0 wt% based on oil composition.
These reaction products are amides, imides or mixtures thereof. Borated
dispersants may provide benefits over non borated equivalents with respect to
corrosion, rust, seal swell and wear.
[0044] Other additives such as other antioxidants, pour point depressants,
viscosity index improvers, metal passivators, defoamants, friction modifiers,
thickeners, emulsifiers, demulsifiers, dyes, corrosion inhibitors, acid
sequestration agents, extreme pressure agents may be added without affecting
the lacquer reducing performance of the current invention.
[0045] Lacquer formation is generally not a problem in natural gas engines
running clean, dry methane of high Wobbe Index numbers. However, even in
that case, the present formulation would still be useful as it would reduce
lacquer
formation caused by the unusual circumstances of excessively high or low
engine temperatures combined with a non-optimized air/fuel rati~. In a
preferred
example, the present invention is employed in natural gas engines that use
less
pure forms of natural gas, such as bio, wellhead, sewer, landfill and digester
gas
and other gas engines where lacquer formation is more often found. In general,
the present invention is more useful when employing natural gas with a Wobbe
Index of less than 30 MJoules/m3
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EXAMPLES
(0046] A Caterpillar 63616 gas powered engine was operated on landfill gas
employing a commercially available lubricant that contained both Group I and
Group II base oils and a conventional additive set. After 16,24.9 hours of
operation, two of the power cylinders were overhauled. During this time, the
lubricant consumption had risen from the typical seven gallons per day to
approximately 10 gallons per day. The cylinder liners were removed and split.
Sections from the ring travel area (expected area of heavy lacquer formation)
and areas at the bottom of the liners (essentially no lacquer formation) were
removed and measured for surface roughness.
[0047] As expected, surface roughness was lower within the ring travel area
due to the lacquer formation. Since the cylinder liner honing procedure and
the
resulting surface roughness may vary from one liner to the next, the surface
roughness measurement at the bottom of each liner was used as a reference for
that liner. The surface roughness for the ring travel areas was measured and
the
difference between the two measurements was calculated to show the change of
surface roughness due to lacquering. With the commercially available
lubricant,
the average surface roughness delta was 0.73 micrometers.
[0048] The engine was placed back into operation, but now employing the
formulation of the current invention. Over the 7,778 hours of operation the
lubricant oil consumption remained at the typical 7 gallons/day. The cylinders
were then removed and the comparable surface roughness measurements were
taken. The formulation of the present invention produced a surface roughness
delta of 0.15 micrometers.
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[004] Caterpillar's standard to evaluate the performance of a new lubricating
oil formulation is to perform a 7,000 hour field test; the ~EI~1 has concluded
that
engine deposit levels, including cylinder liner lacquer, have achieved
equilibrium after that many hours of operation. ZJsing this standard, the
cylinder
lacquer formation employing the current invention was approximately one-fifth
that of the coml~nercially available lubricant. Even assuming that lacquer
formation is linear over time (as opposed to the current theory that it
reaches an
equilibrium point), the formulation of the current invention produced
approximately half the lacquer of the commercially available product.
