U.S. patent application number 12/378678 was filed with the patent office on 2010-08-19 for method for preventing exhaust valve seat recession.
This patent application is currently assigned to Chevron Oronite Company LLC. Invention is credited to Melanie F. Tobias, Jon F. Von Staden.
Application Number | 20100206260 12/378678 |
Document ID | / |
Family ID | 42558798 |
Filed Date | 2010-08-19 |
United States Patent
Application |
20100206260 |
Kind Code |
A1 |
Tobias; Melanie F. ; et
al. |
August 19, 2010 |
Method for preventing exhaust valve seat recession
Abstract
A method for preventing or inhibiting exhaust valve seat
recession in a natural gas fueled internal combustion engine is
disclosed. The method involves lubricating the engine with a
lubricating oil composition comprising (a) a major amount of an oil
of lubricating viscosity, and (b) a minor amount of a natural gas
engine oil additive package, wherein the lubricating oil
composition is substantially free of each of any zinc compounds and
alkaline earth metal salts of a condensation product of an alkylene
polyamine, an aldehyde and a substituted phenol.
Inventors: |
Tobias; Melanie F.;
(Pleasant Hill, CA) ; Von Staden; Jon F.; (San
Antonio, TX) |
Correspondence
Address: |
M. CARMEN & ASSOCIATES, PLLC
1201 RXR Plaza
Uniondale
NY
11556
US
|
Assignee: |
Chevron Oronite Company LLC
San Ramon
CA
|
Family ID: |
42558798 |
Appl. No.: |
12/378678 |
Filed: |
February 18, 2009 |
Current U.S.
Class: |
123/188.9 |
Current CPC
Class: |
F01L 1/16 20130101; C10N
2030/06 20130101; C10N 2030/40 20200501; C10N 2030/45 20200501;
C10M 163/00 20130101; F01L 1/46 20130101; F01L 2810/02 20130101;
F01L 3/24 20130101; F01L 3/22 20130101; C10M 2203/1025 20130101;
C10M 2207/028 20130101; C10M 141/08 20130101; C10M 2215/28
20130101; C10M 2219/046 20130101; C10N 2030/42 20200501; F01M 9/02
20130101; C10N 2030/52 20200501; C10M 2207/026 20130101; C10N
2040/25 20130101 |
Class at
Publication: |
123/188.9 |
International
Class: |
F01L 1/00 20060101
F01L001/00 |
Claims
1. A method for preventing or inhibiting exhaust valve seat
recession in a natural gas fueled engine, the method comprising
lubricating the engine with a lubricating oil composition
comprising (a) a major amount of an oil of lubricating viscosity;
and (b) a minor amount of a natural gas engine oil additive
package, wherein the lubricating oil composition is substantially
free of each of any zinc compounds and alkaline earth metal salts
of a condensation product of an alkylene polyamine, an aldehyde and
a substituted phenol.
2. The method of claim 1, wherein the oil of lubricating viscosity
is a natural gas engine lubricating oil.
3. The method of claim 1, wherein the natural gas engine oil
additive package includes (i) one or more ashless dispersants, (ii)
one or more metal-containing detergents, and (iii) one or more
antioxidants.
4. The method of claim 3, wherein the one or more ashless
dispersants is a bissuccinimide.
5. The method of claim 4, wherein the bissuccinimide ashless
dispersant is derived from one or more polyalkylene succinic
anhydrides.
6. The method of claim 5, wherein the polyalkylene group is a
polyisobutenyl group having an average molecular weight of from
about 700 to about 2300.
7. The method of claim 3, wherein the one or more ashless
dispersants is present in an amount of about 1 wt. % to about 8 wt.
%, based on the total weight of the lubricating oil
composition.
8. The method of claim 3, wherein the one or more metal-containing
detergents is an overbased alkaline earth metal salt detergent
having a base number (BN) of about 10 to about 450.
9. The method of claim 3, wherein the one or more metal-containing
detergents comprises two metal-containing detergents.
10. The method of claim 9, wherein the two metal-containing
detergents comprise a first metal-containing detergent which is an
overbased alkaline earth metal phenate detergent having a BN of
about 100 to about 450 and a second metal-containing detergent
which is an overbased alkaline earth metal sulfonate detergent
having a BN of about 10 to about 50.
11. The method of claim 3, wherein the one or more metal-containing
detergents is present in an amount of about 0.5 wt. % to about 8.5
wt. %, based on the total weight of the lubricating oil
composition.
12. The method of claim 10, wherein the first metal-containing
detergent is present in an amount of about 0.5 wt. % to about 5 wt.
% and the second metal-containing detergent is present in an amount
of about 0.1 wt. % to about 1 wt. %, based on the total weight of
the lubricating oil composition.
13. The method of claim 3, wherein the one or more antioxidants is
a hindered phenol compound.
14. The method of claim 3, wherein the one or more antioxidants is
present in an amount of about 0.1 wt. % to about 3 wt. %, based on
the total weight of the lubricating oil composition.
15. The method of claim 1, wherein the lubricating oil composition
has a sulfated ash content of about 0.1 wt. % to about 1.5 wt. % as
determined by ASTM D 874.
16. The method of claim 1, wherein the lubricating oil composition
has a sulfated ash content of about 0.15 to about 0.5 wt. % as
determined by ASTM D 874.
17. The method of claim 1, wherein the lubricating oil composition
comprises: about 1 wt. % to about 8 wt. % of one or more ashless
dispersants, about 0.5 wt. % to about 8.5 wt. % of one or more
metal-containing detergents, and about 0.1 wt. % to about 3 wt. %
of one or more antioxidants, based on the total weight of the
lubricating oil composition.
18. A natural gas engine lubricating oil composition comprising (a)
a major amount of an oil of lubricating viscosity, (b) one or more
ashless dispersants, (c) one or more metal-containing detergents,
and (d) one or more antioxidants, wherein the lubricating oil
composition is substantially free of each of any zinc compounds and
alkaline earth metal salts of a condensation product of an alkylene
polyamine, an aldehyde and a substituted phenol.
19. The natural gas engine lubricating oil composition of claim 18,
wherein the oil of lubricating viscosity is a natural gas engine
lubricating oil.
20. The natural gas engine lubricating oil composition of claim 18,
wherein the one or more ashless dispersants is a
bissuccinimide.
21. The natural gas engine lubricating oil composition of claim 20,
wherein the bissuccinimide ashless dispersant is derived from one
or more polyalkylene succinic anhydrides.
22. The natural gas engine lubricating oil composition of claim 21,
wherein the polyalkylene group is a polyisobutenyl group having an
average molecular weight of from about 700 to about 2300.
23. The natural gas engine lubricating oil composition of claim 18,
wherein the one or more metal-containing detergents is an overbased
alkaline earth metal salt detergent having a BN of about 10 to
about 450.
24. The natural gas engine lubricating oil composition of claim 23,
wherein the one or more metal-containing detergents comprises two
metal-containing detergents.
25. The natural gas engine lubricating oil composition of claim 24,
wherein the two metal-containing detergents comprise a first
metal-containing detergent which is an overbased alkaline earth
metal phenate detergent having a BN of about 100 to about 450 and a
second metal-containing detergent which is an overbased alkaline
earth metal sulfonate detergent having a BN of about 10 to about
50.
26. The natural gas engine lubricating oil composition of claim 18,
wherein the one or more antioxidants is a hindered phenol
compound.
27. The natural gas engine lubricating oil composition of claim 18,
having a sulfated ash content of about 0.1 wt. % to about 1.5 wt. %
as determined by ASTM D 874.
28. The natural gas engine lubricating oil composition of claim 18,
having a sulfated ash content of about 0.15 to about 0.5 wt. % as
determined by ASTM D 874.
29. The natural gas engine lubricating oil composition of claim 18,
comprising: about 1 wt. % to about 8 wt. % of one or more ashless
dispersants, about 0.5 wt. % to about 8.5 wt. % of one or more
metal-containing detergents, and about 0.1 wt. % to about 3 wt. %
of one or more antioxidants, based on the total weight of the
lubricating oil composition.
30. The natural gas engine lubricating oil composition of claim 18,
which has an exhaust valve seat recession reducing property greater
than that of a corresponding natural gas engine lubricating oil
composition in which a zinc compound is present therein.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention generally relates to a method for
preventing or inhibiting exhaust valve seat recession in natural
gas fueled internal combustion engines.
[0003] 2. Description of the Related Art
[0004] Natural gas fueled engines are engines that use natural gas
as a fuel source. Lubricating oils with high resistance to
oxidation, nitration and viscosity increase are generally preferred
for lubricating oils used in natural gas engines because of the
conditions related to this type of engine.
[0005] Natural gas has a higher specific heat content than liquid
hydrocarbon fuels and therefore it will burn hotter than liquid
hydrocarbon fuels under typical conditions. In addition, since it
is already a gas, natural gas does not cool the intake air by
evaporation as compared to liquid hydrocarbon fuel droplets.
Furthermore, many natural gas fueled engines are run either at or
near stoichiometric conditions, where less excess air is available
to dilute and cool combustion gases. As a result, natural gas
fueled engines generate higher combustion gas temperatures than
engines burning liquid hydrocarbon fuels. In most cases, natural
gas fueled engines are used continuously at 70 to 100% load,
whereas an engine operating in vehicular service may only spend 50%
of its time at full load.
[0006] This condition of running continuously near full load places
severe demands on the lubricant. For example, by subjecting the
lubricating to a sustained high temperature environment, the life
of the lubricant is often limited by oil oxidation processes. Also,
since the rate of formation of nitrogen (NOx), increases
exponentially with temperature, natural gas fueled engines may
generate NO.sub.x concentrations high enough to cause severe
nitration of lubricating oil.
[0007] Good valve wear control is also important for keeping engine
operating costs down and may be achieved by providing the proper
amount and composition of ash. In addition, minimizing combustion
chamber deposits and spark plug fouling are considerations in
setting the ash content in these oils. Lubricating oil ash levels
are limited, so detergents must be carefully selected to minimize
piston deposits and ring sticking.
[0008] Valve wear resistance is important to the durability of
natural gas fueled engines. In general, exhaust valve recession is
wear which occurs at the valve and valve seat interface and is the
most pronounced form of valve wear in natural gas fueled engines.
When the valve is prevented from seating properly, it can cause
engine roughness, poor fuel economy and excessive emissions. In
order to correct excessive valve wear, a cylinder head overhaul is
usually required. Although natural gas fueled engines typically use
very hard corrosion-resistant material for the valve face and seat
mating surface to give extended cylinder head life, it does not
completely eliminate valve recession.
[0009] There is a difference in the lubricating oil requirements
for natural gas fueled engines and engines that are fueled by
liquid hydrocarbon fuels. The combustion of liquid hydrocarbon
fuels such as diesel fuel often results in a small amount of
incomplete combustion (e.g., exhaust particulates). In a liquid
hydrocarbon fueled engine, these incombustibles provide a small but
critical degree of lubrication to the exhaust valve/seat interface,
thereby ensuring the durability of both cylinder heads and
valves.
[0010] Natural gas fueled engines burn fuel that is introduced to
the combustion chamber in the gaseous phase. The combustion of
natural gas fuel is often very complete, with virtually no
incombustible materials. This has a significant affect on the
intake and exhaust valves because there is no fuel-derived
lubricant such as liquid droplets or soot to aid in lubrication to
the exhaust valve/seat interface in a natural gas fueled engine.
Therefore, the durability of the cylinder head and valve is
controlled by the ash content and other properties of the
lubricating oil and its consumption rate to provide lubricant
between the hot valve face and its mating seat. Too little ash or
the wrong type can accelerate valve and seat wear, while too much
ash may lead to valve guttering and subsequent valve torching. Too
much ash can also lead to loss of compression or detonation from
combustion chamber deposits. Consequently, gas engine builders
frequently specify a narrow ash range that they have learned
provides the optimum performance. Since most gas is low in sulfur,
excess ash is generally not needed to address alkalinity
requirements, and ash levels are largely optimized around the needs
of the valves. There may be exceptions to this in cases where sour
gas or landfill gas is used.
[0011] Zinc dialkyldithiophosphates are a very effective additive
used in natural gas engine oil additive packages for anti-wear and
oxidation protection and, for example, has been shown to contribute
to the ash formed on the exhaust valve. However, it is believed
that zinc dialkyldithiophosphates may actually chemically react
with the surface or form a compound with the other sources of ash
that can be easily removed from the valve surface.
[0012] In addition, a problem associated with the use of zinc
dialkyldithiophosphate is that their phosphorus and sulfur
derivatives poison the catalyst components of the catalytic
converters. This is a major concern as effective catalytic
converters are needed to reduce pollution and to meet governmental
regulation designed to reduce toxic gases such as, for example,
hydrocarbons, carbon monoxide and nitrogen oxides, in the internal
combustion engine exhaust emissions. Such catalytic converters
generally use a combination of catalytic metals, e.g., platinum and
metal oxides, and are installed in the exhaust streams, e.g., the
exhaust pipes of automobiles, to convert the toxic gases to
nontoxic gases. Accordingly, it would be desirable to eliminate the
amount of zinc dialkyldithiophosphate in lubricating oils, thus
reducing catalyst deactivation and hence increasing the life and
effectiveness of catalytic converters while also meeting future
industry standard proposed phosphorus and sulfur contents in the
engine oil. However, simply decreasing the amount of zinc
dialkyldithiophosphate presents problems because this necessarily
lowers the antiwear properties and oxidation inhibition properties
of the lubricating oil. Therefore, it is necessary to find a way to
retain the antiwear and oxidation properties of the engine
oils.
[0013] U.S. Pat. No. 3,798,163 ("the '163 patent") discloses a
method for controlling or inhibiting exhaust valve recession in
natural gas fueled internal combustion engines by maintaining a
lubricating amount of a lubricating oil composition on the engine
components of the internal combustion engine. The '163 patent
further discloses that the lubricating oil composition contains (a)
a major amount of an oil of lubricating viscosity, (b) at least one
alkaline earth metal sulfonate in an amount sufficient to improve
the detergency of the composition, and (c) at least one alkaline
earth metal salt of a condensation product of (i) an alkylene
polyamine, (ii) an aldehyde, and (iii) a substituted phenol,
wherein the alkaline earth metal salt of the condensation product
is present in an amount sufficient to inhibit the recession of the
engine's exhaust valves into the engine cylinder head.
[0014] U.S. Pat. No. 5,726,133 ("the '133 patent") discloses a low
ash gas engine oil comprising a major amount of a base oil of
lubricating viscosity and a minor amount sufficient to contribute a
sulfated ash content of about 0.1 to 0.6% ash by ASTM D 874 of an
additive mixture comprising a mixture of detergents comprising at
least one first alkali or alkaline earth metal salt or mixture
thereof of low Total Base Number (TBN) of about 250 and less and at
least one second alkali or alkaline earth metal salt or mixture
thereof which is more neutral than the first low TBN salt. The '133
patent further discloses that the fully formulated gas engine oil
can also typically contain other standard additives known to those
skilled in the art, including antiwear additives such as zinc
dithiophosphates, dispersants, phenolic or aminic antioxidants,
metal deactivators, pour point depressants, antifoaming agents, and
viscosity index improvers.
[0015] U.S. Pat. No. 6,174,842 ("the '842 patent") discloses a
lubricating composition containing (a) a major amount of
lubricating oil, (b) an oil-soluble molybdenum compound
substantially free of reactive sulfur, (c) an oil-soluble
diarylamine and (d) an alkaline earth metal phenate. The '842
patent further discloses that the composition can further include a
zinc dihydrocarbyl dithiophosphate as an antiwear agent. In
addition, Oil Blend 18 disclosed in Example 2 of the '842 patent
contained an antiwear agent and was evaluated for exhaust valve
recession in a Cummins Natural Gas Engine test.
[0016] It is desirable to develop improved methods for preventing
or inhibiting exhaust valve recession in natural gas fueled
internal combustion engines employing a lubricating oil composition
free of at least any zinc compound and which utilizes a minimum
number of components.
SUMMARY OF THE INVENTION
[0017] In accordance with one embodiment of the present invention,
there is provided a method for preventing or inhibiting exhaust
valve seat recession in a natural gas fueled engine, the method
comprising lubricating the engine with a lubricating oil
composition comprising (a) a major amount of an oil of lubricating
viscosity, and (b) a minor amount of a natural gas engine oil
additive package, wherein the lubricating oil composition is
substantially free of each of any zinc compounds and alkaline earth
metal salts of a condensation product of an alkylene polyamine, an
aldehyde and a substituted phenol.
[0018] In accordance with a second embodiment of the present
invention, there is provided a method for enhancing the life of an
exhaust valve in a natural gas fueled engine as evidenced by
protection or inhibition in exhaust valve seat recession in the
natural gas fueled engine, the method comprising lubricating the
engine with a lubricating oil composition comprising (a) a major
amount of an oil of lubricating viscosity, and (b) a minor amount
of a natural gas engine oil additive package, wherein the
lubricating oil composition is substantially free of each of any
zinc compounds and alkaline earth metal salts of a condensation
product of an alkylene polyamine, an aldehyde and a substituted
phenol.
[0019] In accordance with a third embodiment of the present
invention, the use of a lubricating oil composition comprising (a)
a major amount of an oil of lubricating viscosity, and (b) a minor
amount of a natural gas engine oil additive package, wherein the
lubricating oil composition is substantially free of each of any
zinc compounds and alkaline earth metal salts of a condensation
product of an alkylene polyamine, an aldehyde and a substituted
phenol for the purpose of preventing or inhibiting exhaust valve
seat recession in a natural gas fueled engine is provided.
[0020] In accordance with a fourth embodiment of the present
invention, a natural gas engine lubricating oil composition is
provided comprising (a) a major amount of an oil of lubricating
viscosity, (b) one or more ashless dispersants, (c) one or more
metal-containing detergents, and (d) one or more antioxidants,
wherein the lubricating oil composition is substantially free of
each of any zinc compounds and alkaline earth metal salts of a
condensation product of an alkylene polyamine, an aldehyde and a
substituted phenol.
[0021] In accordance with a fifth embodiment of the present
invention, a natural gas engine lubricating oil composition is
provided comprising (a) a major amount of an oil of lubricating
viscosity, (b) one or more ashless dispersants, (c) one or more
metal-containing detergents, and (d) one or more antioxidants,
wherein the lubricating oil composition is substantially free of
each of any zinc compounds and alkaline earth metal salts of a
condensation product of an alkylene polyamine, an aldehyde and a
substituted phenol, and further wherein the lubricating oil
composition has an exhaust valve seat recession reducing property
greater than that of a corresponding lubricating oil composition in
which a zinc compound is present therein.
[0022] In accordance with a sixth embodiment of the present
invention, a natural gas engine lubricating oil composition is
provided consisting essentially of (a) a major amount of an oil of
lubricating viscosity, (b) one or more ashless dispersants, (c) one
or more metal-containing detergents, and (d) one or more
antioxidants, wherein the lubricating oil composition is
substantially free of any zinc compounds.
[0023] In accordance with a seventh embodiment of the present
invention, there is provided a natural gas fueled internal
combustion engine lubricated with a lubricating oil composition
comprising (a) a major amount of an oil of lubricating viscosity,
and (b) a minor amount of a natural gas engine oil additive
package, wherein the lubricating oil composition is substantially
free of each of any zinc compounds and alkaline earth metal salts
of a condensation product of an alkylene polyamine, an aldehyde and
a substituted phenol.
[0024] By lubricating a natural gas fueled internal combustion
engine with a lubricating oil composition comprising (a) a major
amount of an oil of lubricating viscosity, and (b) a minor amount
of a natural gas engine oil additive package, wherein the
lubricating oil composition is substantially free of each of any
zinc compounds and alkaline earth metal salts of a condensation
product of an alkylene polyamine, an aldehyde and a substituted
phenol, exhaust valve seat recession in the natural gas fueled
engine is advantageously prevented or inhibited as compared to a
corresponding lubricating oil composition in which a zinc compound
such as a zinc dihydrocarbyl dithiophosphate compound is present
therein. This is unexpected as zinc dihydrocarbyl dithiophosphate
is a known antiwear agent which contributes to the ash formed on
the exhaust valve and typically used in a natural gas engine
lubricating oil composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] The present invention is directed to methods for preventing
or inhibiting exhaust valve seat recession in a natural gas fueled
engine. Generally, the methods involve lubricating a natural gas
fueled engine with a lubricating oil composition containing at
least (a) a major amount of an oil of lubricating viscosity, and
(b) a minor amount of a natural gas engine oil additive package,
wherein the lubricating oil composition is substantially free of
each of any zinc compounds and alkaline earth metal salts of a
condensation product of an alkylene polyamine, an aldehyde and a
substituted phenol. The term "substantially free" as used herein
shall be understood to mean only trace amounts, typically below
0.001 wt. %, based on the total weight of the lubricating oil
composition, if any, of each of the zinc compounds and alkaline
earth metal salts of the condensation product in the lubricating
oil compositions.
[0026] The lubricating oil compositions according to the present
invention for use in natural gas fueled engines will have a
sulfated ash content of no more than about 1.5 wt. % as determined
by ASTM D 874, preferably a sulfated ash content of no more than
about 0.95 wt. % as determined by ASTM D 874 and most preferably a
sulfated ash content of no more than about 0.5 wt. % as determined
by ASTM D 874. In one embodiment, a lubricating oil composition
according to the present invention for use in natural gas fueled
engines has a sulfated ash content of about 0.1 wt. % to about 1.5
wt. % as determined by ASTM D 874, preferably about 0.12 wt. % to
about 0.95 wt. % as determined by ASTM D 874 and most preferably
about 0.15 wt. % to about 0.5 wt. % as determined by ASTM D 874.
The lubricant ash advantageously acts as a solid lubricant to
protect the valve/seat interface in place of naturally occurring
exhaust particles in a hydrocarbon fueled engine.
[0027] In one embodiment, the lubricating oil composition of the
present invention is substantially free of any phosphorus, e.g., a
phosphorus content not exceeding 0.08 wt. % and more preferably not
exceeding 0.05 wt. %. In another embodiment, the lubricating oil
composition of the present invention contains relatively low levels
of sulfur, i.e., not exceeding 0.7 wt. %, preferably not exceeding
0.5 wt. % and more preferably not exceeding 0.3 wt. %.
[0028] The internal combustion engines to which the present
invention is applicable may be characterized as those operated on,
i.e., fueled by, natural gas and include internal combustion
engines. Examples of such engines include four cycle engines and
the like. In a preferred embodiment, the internal combustion engine
is a stationary engine used in, for example, well-head gas
gathering, compression, and other gas pipeline services; electrical
power generation (including co-generation); and irrigation.
[0029] The oil of lubricating viscosity for use in the lubricating
oil compositions of this invention, also referred to as a base oil,
is typically present in a major amount, e.g., an amount of greater
than 50 wt. %, preferably greater than about 70 wt. %, more
preferably from about 80 to about 99.5 wt. % and most preferably
from about 85 to about 98 wt. %, based on the total weight of the
composition. The expression "base oil" as used herein shall be
understood to mean a base stock or blend of base stocks which is a
lubricant component that is produced by a single manufacturer to
the same specifications (independent of feed source or
manufacturer's location); that meets the same manufacturer's
specification; and that is identified by a unique formula, product
identification number, or both. The base oil for use herein can be
any presently known or later-discovered oil of lubricating
viscosity used in formulating lubricating oil compositions for any
and all such applications, e.g., engine oils, marine cylinder oils,
functional fluids such as hydraulic oils, gear oils, transmission
fluids, etc. Additionally, the base oils for use herein can
optionally contain viscosity index improvers, e.g., polymeric
alkylmethacrylates; olefinic copolymers, e.g., an
ethylene-propylene copolymer or a styrene-butadiene copolymer; and
the like and mixtures thereof.
[0030] As one skilled in the art would readily appreciate, the
viscosity of the base oil is dependent upon the application.
Accordingly, the viscosity of a base oil for use herein will
ordinarily range from about 2 to about 2000 centistokes (cSt) at
100.degree. Centigrade (C). Generally, individually the base oils
used as engine oils will have a kinematic viscosity range at
100.degree. C. of about 2 cSt to about 30 cSt, preferably about 3
cSt to about 16 cSt, and most preferably about 4 cSt to about 12
cSt and will be selected or blended depending on the desired end
use and the additives in the finished oil to give the desired grade
of engine oil, e.g., a lubricating oil composition having an SAE
Viscosity Grade of 0W, 0W-20, 0W-30, 0W-40, 0W-50, 0W-60, 5W,
5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40,
10W-50, 15W, 15W-20, 15W-30,15W-40, 30, 40 and the like.
[0031] Base stocks may be manufactured using a variety of different
processes including, but not limited to, distillation, solvent
refining, hydrogen processing, oligomerization, esterification, and
rerefining. Rerefined stock shall be substantially free from
materials introduced through manufacturing, contamination, or
previous use. The base oil of the lubricating oil compositions of
this invention may be any natural or synthetic lubricating base
oil. Suitable hydrocarbon synthetic oils include, but are not
limited to, oils prepared from the polymerization of ethylene or
from the polymerization of 1-olefins to provide polymers such as
polyalphaolefin or PAO oils, or from hydrocarbon synthesis
procedures using carbon monoxide and hydrogen gases such as in a
Fischer-Tropsch process. For example, a suitable base oil is one
that comprises little, if any, heavy fraction; e.g., little, if
any, lube oil fraction of viscosity 20 cSt or higher at 100.degree.
C.
[0032] The base oil may be derived from natural lubricating oils,
synthetic lubricating oils or mixtures thereof. Suitable base oil
includes base stocks obtained by isomerization of synthetic wax and
slack wax, as well as hydrocracked base stocks produced by
hydrocracking (rather than solvent extracting) the aromatic and
polar components of the crude. Suitable base oils include those in
all API categories I, II, III, IV and V as defined in API
Publication 1509, 14th Edition, Addendum I, December 1998. Group IV
base oils are polyalphaolefins (PAO). Group V base oils include all
other base oils not included in Group I, II, III, or IV. Although
Group II, III and IV base oils are preferred for use in this
invention, these base oils may be prepared by combining one or more
of Group I, II, III, IV and V base stocks or base oils.
[0033] Useful natural oils include mineral lubricating oils such
as, for example, liquid petroleum oils, solvent-treated or
acid-treated mineral lubricating oils of the paraffinic, naphthenic
or mixed paraffinic-naphthenic types, oils derived from coal or
shale, animal oils, vegetable oils (e.g., rapeseed oils, castor
oils and lard oil), and the like.
[0034] Useful synthetic lubricating oils include, but are not
limited to, hydrocarbon oils and halo-substituted hydrocarbon oils
such as polymerized and interpolymerized olefins, e.g.,
polybutylenes, polypropylenes, propylene-isobutylene copolymers,
chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes),
poly(1-decenes), and the like and mixtures thereof; alkylbenzenes
such as dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes,
di(2-ethylhexyl)-benzenes, and the like; polyphenyls such as
biphenyls, terphenyls, alkylated polyphenyls, and the like;
alkylated diphenyl ethers and alkylated diphenyl sulfides and the
derivative, analogs and homologs thereof and the like.
[0035] Other useful synthetic lubricating oils include, but are not
limited to, oils made by polymerizing olefins of less than 5 carbon
atoms such as ethylene, propylene, butylenes, isobutene, pentene,
and mixtures thereof. Methods of preparing such polymer oils are
well known to those skilled in the art.
[0036] Additional useful synthetic hydrocarbon oils include liquid
polymers of alpha olefins having the proper viscosity. Especially
useful synthetic hydrocarbon oils are the hydrogenated liquid
oligomers of C.sub.6 to C.sub.12 alpha olefins such as, for
example, 1-decene trimer.
[0037] Another class of useful synthetic lubricating oils include,
but are not limited to, alkylene oxide polymers, i.e.,
homopolymers, interpolymers, and derivatives thereof where the
terminal hydroxyl groups have been modified by, for example,
esterification or etherification. These oils are exemplified by the
oils prepared through polymerization of ethylene oxide or propylene
oxide, the alkyl and phenyl ethers of these polyoxyalkylene
polymers (e.g., methyl poly propylene glycol ether having an
average molecular weight of 1,000, diphenyl ether of polyethylene
glycol having a molecular weight of 500-1000, diethyl ether of
polypropylene glycol having a molecular weight of 1,000-1,500,
etc.) or mono- and polycarboxylic esters thereof such as, for
example, the acetic esters, mixed C.sub.3-C.sub.8 fatty acid
esters, or the C.sub.13 oxo acid diester of tetraethylene
glycol.
[0038] Yet another class of useful synthetic lubricating oils
include, but are not limited to, the esters of dicarboxylic acids
e.g., phthalic acid, succinic acid, alkyl succinic acids, alkenyl
succinic acids, maleic acid, azelaic acid, suberic acid, sebacic
acid, fumaric acid, adipic acid, linoleic acid dimer, malonic
acids, alkyl malonic acids, alkenyl malonic acids, etc., with a
variety of alcohols, e.g., butyl alcohol, hexyl alcohol, dodecyl
alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol
monoether, propylene glycol, etc. Specific examples of these esters
include dibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl
fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate,
dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the
2-ethylhexyl diester of linoleic acid dimer, the complex ester
formed by reacting one mole of sebacic acid with two moles of
tetraethylene glycol and two moles of 2-ethylhexanoic acid and the
like.
[0039] Esters useful as synthetic oils also include, but are not
limited to, those made from carboxylic acids having from about 5 to
about 12 carbon atoms with alcohols, e.g., methanol, ethanol, etc.,
polyols and polyol ethers such as neopentyl glycol, trimethylol
propane, pentaerythritol, dipentaerythritol, tripentaerythritol,
and the like.
[0040] Silicon-based oils such as, for example, polyalkyl-,
polyaryl-, polyalkoxy- or polyaryloxy-siloxane oils and silicate
oils, comprise another useful class of synthetic lubricating oils.
Specific examples of these include, but are not limited to,
tetraethyl silicate, tetra-isopropyl silicate,
tetra-(2-ethylhexyl)silicate, tetra-(4-methyl-hexyl)silicate,
tetra-(p-tert-butylphenyl)silicate,
hexyl-(4-methyl-2-pentoxy)disiloxane, poly(methyl)siloxanes,
poly(methylphenyl)siloxanes, and the like. Still yet other useful
synthetic lubricating oils include, but are not limited to, liquid
esters of phosphorous containing acids, e.g., tricresyl phosphate,
trioctyl phosphate, diethyl ester of decane phosphionic acid, etc.,
polymeric tetrahydrofurans and the like.
[0041] The lubricating oil may be derived from unrefined, refined
and rerefined oils, either natural, synthetic or mixtures of two or
more of any of these of the type disclosed hereinabove. Unrefined
oils are those obtained directly from a natural or synthetic source
(e.g., coal, shale, or tar sands bitumen) without further
purification or treatment. Examples of unrefined oils include, but
are not limited to, a shale oil obtained directly from retorting
operations, 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 they have been further treated
in one or more purification steps to improve one or more
properties. These purification techniques are known to those of
skill in the art and include, for example, solvent extractions,
secondary distillation, acid or base extraction, filtration,
percolation, hydrotreating, dewaxing, etc. Rerefined oils are
obtained by treating used oils in processes similar to those used
to obtain refined oils. Such rerefined oils are also known as
reclaimed or reprocessed oils and often are additionally processed
by techniques directed to removal of spent additives and oil
breakdown products.
[0042] Lubricating oil base stocks derived from the
hydroisomerization of wax may also be used, either alone or in
combination with the aforesaid natural and/or synthetic base
stocks. Such wax isomerate oil is produced by the
hydroisomerization of natural or synthetic waxes or mixtures
thereof over a hydroisomerization catalyst.
[0043] Natural waxes are typically the slack waxes recovered by the
solvent dewaxing of mineral oils; synthetic waxes are typically the
wax produced by the Fischer-Tropsch process. Examples of useful
oils of lubricating viscosity include HVI and XHVI basestocks, such
isomerized wax base oils and UCBO (Unconventional Base Oils) base
oils.
[0044] The lubricating oil compositions for use in the method of
the present invention will also contain a minor amount of a natural
gas engine oil additive package. Typically, an additive package
will contain one or more additive components, optionally with one
or more diluent oils to make them easy to handle during shipping
and storage. Suitable diluents for the additive package include any
inert diluent, preferably an oil of lubricating viscosity, so that
the additive package may be readily mixed with lubricating oils to
prepare lubricating oil compositions. Suitable lubricating oils
that may be used as diluents can have a viscosity in the range from
about 35 to about 500 Saybolt Universal Seconds (SUS) at
100.degree. F. (38.degree. C.), although any oil of lubricating
viscosity may be used. If present, the one or more diluent oils
will be present in an amount of about 10 wt. % to about 90 wt. %,
based on the total weight of the additive package. The additive
package advantageously provides excellent prevention or inhibition
of exhaust valve seat recession in a natural gas fueled engine when
incorporated into a lubricating oil composition.
[0045] Generally, the additive package is present in the
lubricating oil composition from about 5 wt. % to about 15 wt. %,
and preferably from about 6 wt. % to about 9 wt. %, based on the
total weight of the lubricating oil composition. In one embodiment,
the additive package contains at least (i) one or more ashless
dispersants, (ii) one or more metal-containing detergents, and
(iii) one or more antioxidants, wherein the lubricating oil
composition is substantially free of each of any zinc compounds,
e.g., zinc dialkyl dithiophosphate compound, and alkaline earth
metal salts of a condensation product of an alkylene polyamine, an
aldehyde and a substituted phenol.
[0046] The one or more ashless dispersant compounds employed in the
lubricating oil composition of the present invention are generally
used to maintain in suspension insoluble materials resulting from
oxidation during use, thus preventing sludge flocculation and
precipitation or deposition on metal parts. Nitrogen-containing
ashless (metal-free) dispersants are basic, and contribute to the
base number or BN (as can be measured by ASTM D 2896) of a
lubricating oil composition to which they are added, without
introducing additional sulfated ash. The term "Base Number" or "BN"
as used herein refers to the amount of base equivalent to
milligrams of KOH in one gram of sample. Thus, higher BN numbers
reflect more alkaline products, and therefore a greater alkalinity.
BN was determined using ASTM D 2896 test. An ashless dispersant
generally comprises an oil soluble polymeric hydrocarbon backbone
having functional groups that are capable of associating with
particles to be dispersed. Many types of ashless dispersants are
known in the art.
[0047] Representative examples of ashless dispersants include, but
are not limited to, amines, alcohols, amides, or ester polar
moieties attached to the polymer backbones via bridging groups. An
ashless dispersant of the present invention may be, for example,
selected from oil soluble salts, esters, amino-esters, amides,
imides, and oxazolines of long chain hydrocarbon substituted mono
and dicarboxylic acids or their anhydrides; thiocarboxylate
derivatives of long chain hydrocarbons, long chain aliphatic
hydrocarbons having a polyamine attached directly thereto; and
Mannich condensation products formed by condensing a long chain
substituted phenol with formaldehyde and polyalkylene
polyamine.
[0048] Carboxylic dispersants are reaction products of carboxylic
acylating agents (acids, anhydrides, esters, etc.) comprising at
least about 34 and preferably at least about 54 carbon atoms with
nitrogen containing compounds (such as amines), organic hydroxy
compounds (such as aliphatic compounds including monohydric and
polyhydric alcohols, or aromatic compounds including phenols and
naphthols), and/or basic inorganic materials. These reaction
products include imides, amides, and esters.
[0049] Succinimide dispersants are a type of carboxylic dispersant.
They are produced by reacting hydrocarbyl-substituted succinic
acylating agent with organic hydroxy compounds, or with amines
comprising at least one hydrogen atom attached to a nitrogen atom,
or with a mixture of the hydroxy compounds and amines. The term
"succinic acylating agent" refers to a hydrocarbon-substituted
succinic acid or a succinic acid-producing compound, the latter
encompasses the acid itself. Such materials typically include
hydrocarbyl-substituted succinic acids, anhydrides, esters
(including half esters) and halides.
[0050] Succinic-based dispersants have a wide variety of chemical
structures. One class of succinic-based dispersants may be
represented by the formula:
##STR00001##
wherein each R.sup.1 is independently a hydrocarbyl group, such as
a polyolefin-derived group. Typically the hydrocarbyl group is an
alkyl group, such as a polyisobutyl group. Alternatively expressed,
the R.sup.1 groups can contain about 40 to about 500 carbon atoms,
and these atoms may be present in aliphatic forms. R.sup.2 is an
alkylene group, commonly an ethylene (C.sub.2H.sub.4) group.
Examples of succinimide dispersants include those described in, for
example, U.S. Pat. Nos. 3,172,892, 4,234,435 and 6,165,235.
[0051] The polyalkenes from which the substituent groups are
derived are typically homopolymers and interpolymers of
polymerizable olefin monomers of 2 to about 16 carbon atoms, and
usually 2 to 6 carbon atoms. The amines which are reacted with the
succinic acylating agents to form the carboxylic dispersant
composition can be monoamines or polyamines.
[0052] Succinimide dispersants are referred to as such since they
normally contain nitrogen largely in the form of imide
functionality, although the amide functionality may be in the form
of amine salts, amides, imidazolines as well as mixtures thereof.
To prepare a succinimide dispersant, one or more succinic
acid-producing compounds and one or more amines are heated and
typically water is removed, optionally in the presence of a
substantially inert organic liquid solvent/diluent. The reaction
temperature can range from about 80.degree. C. up to the
decomposition temperature of the mixture or the product, which
typically falls between about 100.degree. C. to about 300.degree.
C. Additional details and examples of procedures for preparing the
succinimide dispersants of the present invention include those
described in, for example, U.S. Pat. Nos. 3,172,892, 3,219,666,
3,272,746, 4,234,435, 6,165,235 and 6,440,905.
[0053] Suitable ashless dispersants may also include amine
dispersants, which are reaction products of relatively high
molecular weight aliphatic halides and amines, preferably
polyalkylene polyamines. Examples of such amine dispersants include
those described in, for example, U.S. Pat. Nos. 3,275,554,
3,438,757, 3,454,555 and 3,565,804.
[0054] Suitable ashless dispersants may further include "Mannich
dispersants," which are reaction products of alkyl phenols in which
the alkyl group contains at least about 30 carbon atoms with
aldehydes (especially formaldehyde) and amines (especially
polyalkylene polyamines). Examples of such dispersants include
those described in, for example, U.S. Pat. Nos. 3,036,003,
3,586,629. 3,591,598 and 3,980.569.
[0055] Suitable ashless dispersants may also be post-treated
ashless dispersants such as post-treated succinimides, e.g.,
post-treatment processes involving borate or ethylene carbonate as
disclosed in, for example, U.S. Pat. Nos. 4,612,132 and 4,746,446;
and the like as well as other post-treatment processes. The
carbonate-treated alkenyl succinimide is a polybutene succinimide
derived from polybutenes having a molecular weight of about 450 to
about 3000, preferably from about 900 to about 2500, more
preferably from about 1300 to about 2400, and most preferably from
about 2000 to about 2400, as well as mixtures of these molecular
weights. Preferably, it is prepared by reacting, under reactive
conditions, a mixture of a polybutene succinic acid derivative, an
unsaturated acidic reagent copolymer of an unsaturated acidic
reagent and an olefin, and a polyamine, such as disclosed in U.S.
Pat. No. 5,716,912, the contents of which are incorporated herein
by reference.
[0056] Suitable ashless dispersants may also be polymeric, which
are interpolymers of oil-solubilizing monomers such as decyl
methacrylate, vinyl decyl ether and high molecular weight olefins
with monomers containing polar substitutes. Examples of polymeric
dispersants include those described in, for example, U.S. Pat. Nos.
3,329,658; 3,449,250 and 3,666,730.
[0057] In a preferred embodiment of the present invention, an
ashless dispersant for use in the lubricating oil composition is a
bis-succinimide derived from a polyisobutenyl group having a number
average molecular weight of about 700 to about 2300. The
dispersant(s) for use in the lubricating oil compositions of the
present invention are preferably non-polymeric (e g., are mono- or
bis-succinimides).
[0058] Generally, the one or more ashless dispersants are present
in the lubricating oil composition in an amount ranging from about
1 to about 8 wt. %, and preferably from about 1.5 to about 6 wt. %,
based on the total weight of the lubricating oil composition.
[0059] The one or more metal-containing detergent compounds
employed in the lubricating oil composition of the present
invention functions both as a detergent to reduce or remove
deposits and as an acid neutralizer or rust inhibitor, thereby
reducing wear and corrosion and extending engine life. Detergents
generally comprise a polar head with long hydrophobic tail, with
the polar head comprising a metal salt of an acid organic
compound.
[0060] The lubricating oil composition according to the present
invention may contain one or more detergents, which are normally
salts, and especially overbased salts. Overbased salts, or
overbased materials, are single phase, homogeneous Newtonian
systems characterized by a metal content in excess of that which
would be present according to the stoichiometry of the metal and
the particular acidic organic compound reacted with the metal. The
overbased materials are prepared by reacting an acidic material
(typically an inorganic acid or lower carboxylic acid such as
carbon dioxide) with a mixture comprising an acidic organic
compound, in a reaction medium comprising at least one inert,
organic solvent (such as mineral oil, naphtha, toluene, xylene) in
the presence of a stoichiometric excess of a metal base and a
promoter.
[0061] Useful acidic organic compounds for making the overbased
compositions include carboxylic acids, sulfonic acids,
phosphorus-containing acids, phenols and mixtures thereof.
Preferably, the acidic organic compounds are carboxylic acids or
sulfonic acids and hydrocarbyl-substituted salicylic acids.
[0062] Carboxylate detergents, e.g., salicylates, can be prepared
by reacting an aromatic carboxylic acid with an appropriate metal
compound such as an oxide or hydroxide. Neutral or overbased
products may then be obtained by methods well known in the art. The
aromatic moiety of the aromatic carboxylic acid can contain one or
more heteroatoms such as nitrogen and oxygen. Preferably, the
moiety contains only carbon atoms. More preferably, the moiety
contains six or more carbon atoms, such as a benzene moiety. The
aromatic carboxylic acid may contain one or more aromatic moieties,
such as one or more benzene rings, optionally fused together or
otherwise connected via alkylene bridges. Representative examples
of aromatic carboxylic acids include salicylic acids and sulfurized
derivatives thereof such as hydrocarbyl substituted salicylic acid
and derivatives thereof. Processes for sulfurizing, for example, a
hydrocarbyl-substituted salicylic acid, are known to those skilled
in the art. Salicylic acids are typically prepared by
carboxylation, for example, by the Kolbe-Schmitt process, of
phenoxides. In that case, salicylic acids are generally obtained in
a diluent in admixture with an uncarboxylated phenol.
[0063] Metal salts of phenols and sulfurized phenols are prepared
by reaction with an appropriate metal compound such as an oxide or
hydroxide. Neutral or overbased products may be obtained by methods
well known in the art. For example, sulfurized phenols may be
prepared by reacting a phenol with sulfur or a sulfur-containing
compound such as hydrogen sulfide, sulfur monohalide or sulfur
dihalide, to form products that are mixtures of compounds in which
2 or more phenols are bridged by sulfur-containing bridges.
[0064] The metal compounds useful in making the overbased salts are
generally any Group I or Group II metal compounds in the Periodic
Table of the Elements. Preferably, the metal compounds are Group II
metals and include Group IIa alkaline earth metals (e.g.,
magnesium, calcium, strontium, barium) as well as Group IIb metals
such as zinc or cadmium. Preferably, the Group II metals are
magnesium, calcium, barium, or zinc, more preferably magnesium or
calcium, and most preferably calcium.
[0065] Examples of the overbased detergents include, but are not
limited to, calcium sulfonates, calcium phenates, calcium
salicylates, calcium stearates and mixtures thereof. Overbased
detergents suitable for use in the lubricating oil compositions of
the present invention may be low overbased, e.g., an overbased
detergent having a BN below about 100. The BN of such a
low-overbased detergent may be from about 5 to about 50, or from
about 10 to about 30, or from about 15 to about 20. Alternatively,
the overbased detergents suitable for use in the lubricating oil
compositions of the present invention may be high overbased (e.g.,
an overbased detergent having a BN above about 100). The BN of such
a high-overbased detergent may be from about 100 to about 450, or
from about 200 to about 350, or from about 250 to about 280. A
low-overbased calcium sulfonate detergent with a BN of about 17 and
a high-overbased sulfurized calcium phenate with a BN of about 120
are two exemplary overbased detergents for use in the lubricating
oil compositions of the present invention.
[0066] The lubricating oil compositions according to the present
invention may contain more than one overbased detergent, which may
be all low-BN detergents, all high-BN detergents, or a mixture
thereof. For example, the lubricating oil compositions of the
present invention may contain a first metal-containing detergent
which is an overbased alkaline earth metal sulfonate or phenate
detergent having a BN of about 100 to about 450 and a second
metal-containing detergent which is an overbased alkaline earth
metal sulfonate or phenate detergent having a BN of about 10 to
about 50.
[0067] Suitable detergents for use in the lubricating oil
compositions also include "hybrid" detergents such as, for example,
phenate/salicylates, sulfonate/phenates, sulfonate/salicylates,
sulfonates/phenates/salicylates, and the like. Examples of hybrid
detergents include those described in, for example, U.S. Pat. Nos.
6,153,565, 6,281,179, 6,429,178, and 6,429,179.
[0068] Generally, the one or more metal-containing detergents are
present in the lubricating oil composition in an amount ranging
from about 0.5 to about 8.5 wt. %, and preferably from about 1 to
about 6 wt. %, based on the total weight of the lubricating oil
composition. Where two metal-containing detergents are employed,
the first metal-containing detergent is present in the lubricating
oil composition in an amount ranging from about 0.5 to about 5 wt.
%, and preferably from about 1 to about 3 wt. %, and the second
metal-containing detergent is present in the lubricating oil
composition in an amount ranging from about 0.1 to about 1.0 wt. %,
and preferably from about 0.2 to about 0.5 wt. %, based on the
total weight of the lubricating oil composition.
[0069] The one or more antioxidant compounds employed in the
lubricating oil composition of the present invention reduce the
tendency of base stocks to deteriorate in service, which
deterioration can be evidenced by the products of oxidation such as
sludge and varnish-like deposits on the metal surfaces and by
viscosity growth. Such oxidation inhibitors include hindered
phenols, ashless oil soluble phenates and sulfurized phenates,
diphenylamines, alkyl-substituted phenyl and naphthylamines and the
like and mixtures thereof. Diphenyamine-type oxidation inhibitors
include, but are not limited to, alkylated diphenylamine,
phenyl-.alpha.-naphthylamine, and
alkylated-.alpha.-naphthylmine.
[0070] Generally, the one or more antioxidant compounds are present
in the lubricating oil composition in an amount ranging from about
0.1 to about 3 wt. %, and preferably from about 0.2 to about 2.5
wt. %, based on the total weight of the lubricating oil
composition.
[0071] The lubricating oil compositions of the present invention
can be conveniently prepared by simply blending or mixing the
additive package, optionally with other additives, with the oil of
lubricating viscosity. The additive package may also be preblended
as a concentrate in the appropriate ratios to facilitate blending
of a lubricating composition containing the desired concentration
of additives. The additive package is blended with the base oil
using a concentration at which they are both soluble in the oil and
compatible with other additives in the desired finished lubricating
oil. Compatibility in this instance generally means that the
present compounds as well as being oil soluble in the applicable
treat rate also do not cause other additives to precipitate under
normal conditions. Suitable oil solubility/compatibility ranges for
a given compound of lubricating oil formulation can be determined
by those having ordinary skill in the art using routine solubility
testing procedures. For example, precipitation from a formulated
lubricating oil composition at ambient conditions (about 20.degree.
C. to 25.degree. C.) can be measured by either actual precipitation
from the oil composition or the formulation of a "cloudy" solution
which evidences formation of insoluble wax particles.
[0072] As previously stated, the lubricating oil compositions
described herein are substantially free of any zinc compounds and
alkaline earth metal salts of a condensation product of an alkylene
polyamine, an aldehyde and a substituted phenol. In one embodiment,
the lubricating oil compositions are also substantially free of any
molybdenum-containing compounds. The alkylene polyamines of the
condensation product can the following structure
NH.sub.2[R(R)--NH].sub.nH wherein R is an alkylene radical
containing from about 2 about 6 carbon atoms, and n is an integer
from 1 to about 10. Typical alkylene polyamines include
diethylenetriamine, triethylenetetramine, tetraethylenepentamine
and the like. The aldehydes are generally aliphatic aldehydes which
contain from one to about 3 carbon atoms per molecule. The
substituted phenols are the alkylated monohydric phenols having at
least one alkyl group of sufficient length to impart oil-solubility
to the condensation products. Representative alkyl phenols are
those in which the alkyl group contains from about 4 to about 24
carbon atoms, and preferably those having from about 8 to about 24
carbon atoms, such as, for example, n-amyl phenol, diamylphenol,
octyl phenol, nonyl phenol, p-ter-octyl phenol, a mixture of
phenols, wax alkylated phenols and the like.
[0073] The lubricating oil compositions for use in the method of
the present invention may also contain other conventional additives
for imparting auxiliary functions to give a finished lubricating
oil composition in which these additives are dispersed or
dissolved. For example, the lubricating oil compositions may be
blended with antiwear agents other than zinc-containing antiwear
agents such as zinc dialkyl dithiophosphate, rust inhibitors,
dehazing agents, demulsifying agents, metal deactivating agents,
friction modifiers, pour point depressants, antifoaming agents,
co-solvents, package compatibilisers, corrosion-inhibitors, dyes,
extreme pressure agents and the like and mixtures thereof. A
variety of the additives are known and commercially available.
These additives, or their analogous compounds, can be employed for
the preparation of the lubricating oil compositions of the
invention by the usual blending procedures.
[0074] Examples of rust inhibitors include, but are not limited to,
nonionic polyoxyalkylene agents, e.g., polyoxyethylene lauryl
ether, polyoxyethylene higher alcohol ether, polyoxyethylene
nonylphenyl ether, polyoxyethylene octylphenyl ether,
polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether,
polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol
monooleate, and polyethylene glycol monooleate; stearic acid and
other fatty acids; dicarboxylic acids; metal soaps; fatty acid
amine salts; metal salts of heavy sulfonic acid; partial carboxylic
acid ester of polyhydric alcohol; phosphoric esters; (short-chain)
alkenyl succinic acids; partial esters thereof and
nitrogen-containing derivatives thereof; synthetic
alkarylsulfonates, e.g., metal dinonylnaphthalene sulfonates; and
the like and mixtures thereof.
[0075] Examples of friction modifiers include, but are not limited
to, alkoxylated fatty amines; borated fatty epoxides; fatty
phosphites, fatty epoxides, fatty amines, borated alkoxylated fatty
amines, metal salts of fatty acids, fatty acid amides, glycerol
esters, borated glycerol esters; and fatty imidazolines as
disclosed in U.S. Pat. No. 6,372,696, the contents of which are
incorporated by reference herein; friction modifiers obtained from
a reaction product of a C.sub.4 to C.sub.75, preferably a C.sub.6
to C.sub.24, and most preferably a C.sub.6 to C.sub.20, fatty acid
ester and a nitrogen-containing compound selected from the group
consisting of ammonia, and an alkanolamine and the like and
mixtures thereof.
[0076] Examples of antifoaming agents include, but are not limited
to, polymers of alkyl methacrylate; polymers of dimethylsilicone
and the like and mixtures thereof.
[0077] Each of the foregoing additives, when used, is used at a
functionally effective amount to impart the desired properties to
the lubricant. Thus, for example, if an additive is a friction
modifier, a functionally effective amount of this friction modifier
would be an amount sufficient to impart the desired friction
modifying characteristics to the lubricant. Generally, the
concentration of each of these additives, when used, ranges from
about 0.001% to about 20% by weight, and in one embodiment about
0.01% to about 10% by weight based on the total weight of the
lubricating oil composition.
[0078] The following non-limiting examples are illustrative of the
present invention.
EXAMPLE 1
[0079] A lubricating oil composition was formed containing 3.3 wt.
% of a bis-succinimide (derived from a 1300 MW polyisobutenyl
succinic anhydride (PIBSA)) and a mixture of heavy polyamine and
diethylenetriamine, 0.43 wt. % of a calcium sulfonate (17 BN), 3.0
wt. % of a sulfurized calcium phenate (114 BN), 0.9 wt. % of a
hindered phenol antioxidant, 5 ppm of a foam inhibitor and the
balance being a Group II base oil. The lubricating oil composition
had a sulfated ash content of 0.46 wt. % as determined by ASTM D
874.
COMPARATIVE EXAMPLE A
[0080] A lubricating oil composition was prepared by top-treating
the lubricating oil composition of Example 1 with 0.38 wt. % of a
zinc dialkyldithiophosphate derived from a primary alcohol. The
lubricating oil composition had a sulfated ash content of 0.50 wt.
% as determined by ASTM D 874.
Testing
[0081] The lubricating oil compositions of Example 1 and
Comparative Example A were evaluated for exhaust valve seat
recession prevention efficacy in a Waukesha F11 GSID engine. In
this test, a 6-cylinder 250 BHP Waukesha F11 GSID engine was
instrumented in order to obtain dynamic voltage measurements (e.g.,
as described in U.S. Pat. No. 4,672,843) from the 12 valves--6
intake and 6 exhaust valves. Each test was run for 400 hours at
1800 rpm operated at 90% load. Stoichiometric conditions were
maintained during the tests with intake air temperatures ranging
between 110 to 150.degree. Fahrenheit. The average valve recession
wear rates of the lubricating compositions of Example 1 and
Comparative Example A were calculated by a linear fit based on the
last 300 hours of data from each test and reported on a wear rate
per 1000 hours. The exhaust valve recession results are presented
in Table 1. In this Table, the lower valve wear recession rate
represents greater exhaust valve seat recession prevention
efficacy.
TABLE-US-00001 TABLE 1 Waukesha F11 Exhaust Valve Recession Results
Average Exhaust Valve Wear Sulfated Ash Recession Rate Ex./Comp.
Ex. (wt. %) (in/1000 hr) 1 0.46 -0.00052 A 0.50 0.00071
[0082] As the data show, the lubricating oil composition of Example
1 exhibited superior prevention of exhaust valve wear recession
over the lubricating oil composition of Comparative Example A
containing a zinc dialkyldithiophosphate wear inhibitor.
[0083] It will be understood that various modifications may be made
to the embodiments disclosed herein. Therefore the above
description should not be construed as limiting, but merely as
exemplifications of preferred embodiments. For example, the
functions described above and implemented as the best mode for
operating the present invention are for illustration purposes only.
Other arrangements and methods may be implemented by those skilled
in the art without departing from the scope and spirit of this
invention. Moreover, those skilled in the art will envision other
modifications within the scope and spirit of the claims appended
hereto.
* * * * *