Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
ENGINE LUBRICANTS FOR SILOXANE DEPOSIT CONTROL
BACKGROUND OF THE INVENTION
[0001] The disclosed technology relates to a lubricant for a sump-
lubricated
internal combustion engine, especially such an engine that is fueled by
natural
gas, and more particularly, engines fueled by natural gasses containing high
levels
of siloxanes and other silicon containing compounds, such as are commonly
found in landfill gases.
[0002] Internal combustion engines may be fueled by a variety of liquid
or
gaseous fuels, including natural gas. While liquefied natural gas or
compressed
natural gas may sometimes be used to fuel small engines on vehicles, more
typically natural gas is used to power large compression ignited or spark
ignited
"stationary gas" engines that may be fueled by natural gas supplied directly
from
a gas wellhead. One common application for stationary gas engines is at
landfills,
where the engines may be fueled by gas emanating from decomposition of refuse
at the landfill.
[0003] Landfill gasses tend not to be very clean and often have
elevated levels
of silicon containing compounds and other corrosive materials. In an engine
combusting landfill gas, the silicon containing compounds in the landfill gas
will
form siloxane macromolecules which will deposit on the engine component
surfaces leading to increased wear in the cylinders, valve areas and bearings.
Over time, this wear reduces engine performance, may cause valve seat
recession,
may increase oil consumption, and may ultimately necessitate refurbishment of
the engine. Typically, lubricants are replaced once the silicon concentration
in
the lubricant approaches 120 to 125 parts per million (ppm).
[0004] To prevent siloxane deposit buildup in engines operating on
landfill
gases (or other natural gas feedstocks containing high concentrations of
silicon
compounds), one existing method involves scrubbing the gas feedstock through
various filters and other media before using it as a fuel stock for the
engine.
1
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Scrubbing silicon compounds from landfill gases requires additional equipment
that must be maintained and generally complicates the feed stream.
Alternatively,
lubricant formulations containing detergents and anti-wear agents have been
introduced specifically for natural gas and landfill gas engines. These
lubricants
are directed to cleaning the engine surface from siloxane deposits and/or
providing a sacrificial wear layer, but their efficacy is limited as
detergency loses
effectiveness and particularly once the siloxane macromolecules have formed.
Accordingly, these lubricant formulations require frequent
replenishment/replacement leading to increased lubricant consumption and
engine
downtime.
[0005] The present invention is directed to lubricant compositions
which are
formulated, according to the theory of the invention, to chemically cleave
siloxane macromolecules into smaller compounds that can be more readily
dispersed, thus reducing the formation of deposits and rendering the silicon
less
detrimental in deposit formation even at lubricant silicon concentrations of
125
ppm and higher. The subject lubricating formulations may be effectively used
in
siloxane deposit control for longer periods of time at elevated silicon
concentrations, thereby facilitating the use of unscrubbed natural and
landfill
gases and extending the oil change intervals, leading to less engine downtime.
[0006] Improved siloxane deposit control and extended cleanliness and
performance benefits may be provided by the lubricant of the disclosed
technology.
SUMMARY OF THE INVENTION
[0007] The disclosed technology provides a method for lubricating a
sump-
lubricated stationary gas engine, comprising supplying to the engine a
substantially zinc-free lubricant comprising:
(a) an oil of lubricating viscosity;
(b) 0.03 to about 3.0 weigh percent with respect to the lubricant
composition (or 0.05 to 2.8 wt. % or 0.05 to 2.5 wt. %) of a phosphite
compound;
(c) a metal containing detergent;
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(d) at least a first dispersant, wherein the first dispersant is a
polyisobutylene succinimide dispersant derived from an ethylene
polyamine and having a carbonyl to nitrogen ratio equal or greater
than 1 or 1:1 to 4:3 or 1.1:1 to 4:3;
(e) at least one other dispersant selected from the group consisting of a
succinimide dispersant having a carbonyl to nitrogen ratio less than
1, a Mannich dispersant, and a polyisobutylene succinic acid ester
dispersant;
(f) boron containing compound in amount to provide at least 25 ppm
boron to the lubricant composition;
wherein the lubricant composition is substantially free of zinc, and
wherein the lubricant composition has a sulfated ash content of less than
about 1.0 wt. % (or 0.7 wt. %).
The disclosed technology further provides the lubricant as thus described,
and also provides a lubricant comprising:
(g) an oil of lubricating viscosity;
(b) 0.03 to about 3.0 weigh percent with respect to the lubricant composition
(or
0.05 to 2.8 wt. % or 0.05 to 2.5 wt. %) of a phosphite compound;
à an metal containing detergent;
(d) at least a first dispersant, wherein the first dispersant is a
polyisobutylene
succinimide dispersant derived from an ethylene polyamine and having a
carbonyl
to nitrogen ratio equal or greater than 1 or 1:1 to 4:3 or 1.1:1 to 4:3;
à at least one other dispersant selected from the group consisting of a
succinimide dispersant having a carbonyl to nitrogen ratio less than 1, a
Mannich
dispersant, and a polyisobutylene succinic acid ester dispersant;
(f) a boron containing compound in amount to provide at least 25 ppm
boron to the lubricant composition;
wherein the lubricant composition is substantially free of zinc, and
wherein the lubricant composition has a sulfated ash content of less than
about 1.0 wt. %.
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DETAILED DESCRIPTION OF THE INVENTION
[0008] Various preferred features and embodiments will be described
below
by way of non-limiting illustration.
[0009] The amount of each chemical component described is presented
exclusive of any solvent or diluent oil, which may be customarily present in
the
commercial material, that is, on an active chemical basis, unless otherwise
indicated. However, unless otherwise indicated, each chemical or composition
referred to herein should be interpreted as being a commercial grade material
which may contain the isomers, by-products, derivatives, and other such
materials
that are normally understood to be present in the commercial grade.
[0010] Fuels
[0011] In the methods of the present invention, it is contemplated that
the
lubricant formulations will be employed in engines that are fueled with
natural
gas and in some preferred embodiments, landfill gas. Landfill gas refers
primarily to the source of the gas, namely, gas created by the action of
microorganisms within a landfill. Such landfill gas may comprise only about 30
to 80 percent methane. In a particularly useful embodiment, the method of
operating the engine comprises operating the engine using as its primary or
only
fuel natural gas having a concentration of silicon that is in excess of 10
mg/m3
or 15 mg/m3 or 20 mg/m3 or 25 mg/m3 or 30 mg/m3 as measured by gas
chromatography mass spectrometry.
[0012] Base Oils
[0013] One element of the lubricating compositions of the present
technology
is an oil of lubricating viscosity. Such oils include natural and synthetic
oils, oil
derived from hydrocracking, hydrogenation, and hydrofinishing, unrefined,
refined, re-refined oils or mixtures thereof. A more detailed description of
unrefined, refined and re-refined oils is provided in International
Publication
W02008/147704, paragraphs [0054] to [0056]. A more detailed description of
natural and synthetic lubricating oils is provided in paragraphs [0058] to
[0059]
respectively of W02008/147704. Synthetic oils may also be produced by
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Fischer-Tropsch reactions and typically may be hydroisomerized Fischer-Tropsch
hydrocarbons or waxes. In one embodiment oils may be prepared by a Fischer-
Tropsch gas-to-liquid synthetic procedure as well as other gas-to-liquid oils.
[0014] Oils of lubricating viscosity may also be selected from any of
the base
5 oils in Groups I-V as specified in the American Petroleum Institute (API)
Base
Oil Interchangeability Guidelines. The five base oil groups are as follows:
Group
I: >0.03% sulfur and/or <90% saturates and viscosity index 80 to 120; Group
II:
<0.03 % S and >90% saturates and VI 80 to 120; Group III: <0.03 % S and >90
% saturates and VI >120; Group IV: all polyalphaolefins; Group V: all others.
Groups I, II and III are mineral oil base stocks.
[0015] The amount of the oil of lubricating viscosity present is
typically the
balance remaining after subtracting from 100 wt % the sum of the amount of the
compound of the invention and the other performance additives.
[0016] The lubricating composition may be in the form of a concentrate
and/or
a fully formulated lubricant. If the lubricating composition of the invention
(comprising the additives disclosed hereinabove) is in the form of a
concentrate
which may be combined with additional oil to form, in whole or in part, a
finished
lubricant), the ratio of the of these additives to the oil of lubricating
viscosity
and/or to diluent oil include the ranges of 1:99 to 99:1 by weight, or 80:20
to
10:90 by weight.
[0017] Phosphite Antiwear Compounds
[0018] The lubricant compositions of the present invention will
comprise at
least one phosphite compound. In some embodiments, the phosphite compound
will include at least one phosphite ester, and more usefully in some
embodiments,
at least one phosphite diester or triester compound. In one embodiment, the
phosphite compound may comprise phosphorous acid (H3P03).
[0019] It will be understood that the term phosphite includes the
tautomer(s).
Similarly it will be understood that phosphite esters may be referred to
generally as
alkyl phosphites or alkyl hydrogen phosphites and these terms may be used
interchangeably.
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[0020] Examples of suitable phosphite compounds may include compounds
having the general Formula I
(R10)3P
FORMULA I
[0021] In the above formula, each le independently may be hydrogen or a
hydrocarbyl group having 1 to 36, or 1 to 24, or 1 to 18 or 2 to 30 or 2 to 24
or 2 to
carbon atoms or 12 to 36 or 12 to 30 or 12 to 20 carbon atoms. The hydrocarbyl
10 group may be a linear or branched, may be a substituted or
unsubstituted, may be
aromatic or aliphatic or alicylic or heterocyclic or may be saturated or
unsaturated
and each le may be the same or different.
[0022] Exemplary phosphite monoesters may include phosphite monesters
comprising Ci to C30 hydrocarbyl groups.
[0023] Exemplary phosphite diesters may include dimethyl hydrogen
phosphite,
diethyl hydrogen phosphite, dipropyl hydrogen phosphite, dibutyl hydrogen
phosphite, diethylhexyl hydrogen phosphite, didecyl hydrogen phosphite,
didodecyl
hydrogen phosphite (dilauryl hydrogen phosphite), dioctadecyl hydrogen
phosphite
(distearyl hydrogen phosphite), di-9-octadecenyl hydrogen phosphite (dioleyl
hydrogen phosphite), diphenyl hydrogen phosphite and the like.
[0024] Examples of the phosphite triesters include, for example,
triphenyl
phosphite, triethyl phosphite, tributyl phosphite, tripropyl phosphite,
trioctyl
phosphite, tri-iso-octyl phosphite, tris 2-ethylhexyl phosphite, tri-isodecyl
phosphite,
tris tridecyl phosphite, trioleyl phosphite, etc. and the like.
[0025] In one embodiment, the phosphite ester may comprise a
polyphosphite ester, which may be produced as the reaction product, e.g.,
condensation product, of a monomeric phosphorous acid or an ester thereof with
at least two alkylene diols. Exemplary polyphosphite esters are more fully
described in International Publication W02016/089565.
[0026] In some embodiments, the phosphite compound may comprise a mixture
of two or more phosphite compounds. In a particularly useful embodiment, the
phosphite compound may comprise a first alkyl phosphite ester having C2 to C10
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hydrocarbyl groups and a second alkyl phosphite ester having C12 to C30
hydrocarbyl groups. In one embodiment, the phosphite may comprise a mixture of
two or more phosphite diesters, wherein one diester has C2 to C10 hydrocarbyl
groups and a second diester has C12 to C30 hydrocarbyl groups. In such an
embodiment, the ratio of the C2 to C10 diester to the C12 to C30 diester may
be from
20:80 to 80:20 or 40:60 to 60:40 or 60:40 to 90:10. In still another
embodiment, the
phosphite may comprise dibutyl phosphite.
[0027] The phosphite compound may be present in the lubricating
composition
(on an oil free basis) in an amount from about 0.03 to about 3.0 weight
percent with
respect to the lubricant composition (or 0.05 to 2.8 wt. % or 0.05 to 2.5 wt.
% or 0.1
to 2.5 wt. % or 0.5 to 2.5 wt. % or 1.0 to 2.5 wt. %).
[0028] In some embodiments, the phosphite compounds may be present in
an
amount to provide 0.001 wt. % to 0.05 wt. % phosphorus (or 10 to 500 ppm
phosphorus), or 0.005 to 0.04 wt. % phosphorus, or 0.005 to about 0.03 wt. %
.. phosphorus to the lubricant composition. In still other embodiments, the
phosphite
may contribute greater than 80 % or 90% or 95% of the total phosphorous in the
lubricant composition. In still another embodiment, the phosphite compound may
constitute the only phosphorous containing antiwear additive in the
lubricating
composition. The lubricant composition may be free of or substantially free of
other
phosphorus containing antiwear compounds or other phosphorous containing
compounds. In some embodiments, the total amount of phosphorus in the
lubricant
composition may be less than about 0.03 wt. %
Dispersants
[0029] Another component in the lubricant compositions is a dispersant.
Dispersants are well known in the field of lubricants and include what are
known
as ashless-type dispersants and polymeric dispersants. Suitable dispersants
may
be chosen from a succinimide dispersant, a Mannich dispersant, a succinamide
dispersant, a polyolefin (typically isobutylene) succinic acid ester, ester-
amide,
or mixtures thereof. The dispersant may be present as a single dispersant;
however, a mixture of more than one type of dispersant is particularly useful.
Metal containing (ash containing) dispersants may be used, but in some
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embodiments, the dispersant is free of or substantially free of ash containing
dispersants.
[0030] Ashless type dispersants are characterized by a polar group
attached to
a relatively high molecular weight hydrocarbon chain. Typical ashless
dispersants include nitrogen-containing dispersants such as N-substituted long
chain alkenyl succinimides, also known as succinimide dispersants.
[0031] The succinimide dispersant may be derived from an aliphatic
amine,
aliphatic polyamine, or mixtures thereof. The aliphatic polyamine may include
such compounds as ethylenepolyamine, a propylenepolyamine, a
butylenepolyamine, or mixtures thereof. In one embodiment the aliphatic
polyamine may be ethylenepolyamine. In one embodiment the aliphatic
polyamine may be chosen from ethylenediamine, diethylenetriamine,
triethylenetetramine, tetraethyl enepentamine, pentaethylenehexamine,
polyamine
still bottoms, and mixtures thereof. Succinimide dispersants are more fully
described in U.S. Patents 4,234,435 and 3,172,892.
[0032] In one embodiment, the dispersant may comprise the condensation
product of a hydrocarbyl-substituted succinic anhydride or reactive equivalent
thereof with an alkylene polyamine, wherein the alkylene polyamine is a
condensed amine. Such dispersants derived from condensed amines are more
fully described in US Pat. Pub. 2009/0018040.
[0033] In one embodiment the succinimide dispersant may be a derivative
of
an aromatic amine, an aromatic polyamine, or mixtures thereof. The aromatic
amine may be 4-aminodiphenylamine (ADPA) (also known as N-
phenylphenylenediamine), derivatives of ADPA, a nitroaniline, an
.. aminocarbazole, an amino-indazolinone, an aminopyrimidine, 4-(4-
nitrophenylazo)aniline, or combinations thereof. In one embodiment, the
dispersant may comprise a derivative of an aromatic amine wherein the aromatic
amine has at least three non-continuous aromatic rings.
[0034] The succinimide dispersant may be a derivative of a polyether
amine or
.. polyether polyamine. Typical polyether amine compounds contain at least one
ether unit and will be chain terminated with at least one amine moiety. The
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polyetherpolyamines can be based on polymers derived from C2-C6 epoxides
such as ethylene oxide, propylene oxide, and butylene oxide. Examples of
polyether polyamines are sold under the Jeffamineg brand and are commercially
available from Huntsman Corporation located in Houston, Texas.
[0035] Another class of ashless dispersant is high molecular weight esters,
prepared by reaction of a hydrocarbyl acylating agent, such as a succinic
anhydride or alkylated (typically polyisobutylene) succinic anhydride or their
reactive equivalents, and a polyhydric aliphatic alcohol such as ethylene
glycol,
propylene glycol, butylene glycol, pentaerythritol, mannitol, sorbitol,
glycerol,
diglycerol, triglycerol, tetraglycerol, erythritol, 2-hydroxymethy1-2-methy1-
1,3
propanediol (trimethylolethane), 2-ethy1-2-(hydroxymethyl)-1,3 propanediol
(trimethylolpropane), 1,3,4-hexane triol and mixtures thereof. Such materials
are
described in more detail in U.S. Patent 3,381,022.
[0036] A polyolefin succinic acid ester-amide may be a polyisobutylene
succinic acid reacted with an alcohol (such as pentaerythritol) and an amine
(such as a diamine, typically diethyleneamine).
[0037] Another class of ashless dispersant is Mannich bases. These are
materials which are formed by the condensation of a higher molecular weight,
alkyl substituted phenol, an alkylene polyamine, and an aldehyde such as
formaldehyde and are described in more detail in U.S. Patent 3,634,515. Other
dispersants include polymeric dispersant additives, which are generally
hydrocarbon-based polymers which contain polar functionality to impart
dispersancy characteristics to the polymer.
[0038] Where the dispersants described above are derived from
a polyisobutylene succinic acid or anhydride, the polyisobutylene may have a
number average molecular weight of 350 to 5000, or 750 to 2500 or 500 to 1500
or 750 to 1250.
[0039] A succinimide dispersant may be obtained/obtainable from a
chlorine-
assisted process, often involving Diels-Alder chemistry, leading to formation
of
carbocyclic linkages from the hydrocarbon chain to the succinic moiety. The
process is known to a person skilled in the art. The chlorine-assisted process
may
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produce a dispersant that is a polyisobutylene succinimide having a
carbocyclic
ring present on 50 mole % or more, or 60 to 100 mole % of the non-borated
dispersant molecules. Both the thermal and chlorine-assisted processes are
described in greater detail in U.S. Patent 7,615,521, columns 4-5 and
preparative
5 examples A and B.
[0040] Alternatively, a succinimide dispersant may be prepared/
obtained/
obtainable from reaction of succinic anhydride by an "ene" or "thermal"
reaction,
by what is referred to as a "direct alkylation process." The "ene" reaction
mechanism and general reaction conditions are summarized in "Maleic
10 Anhydride", pages, 147-149, Edited by B.C. Trivedi and B.C. Culbertson
and
Published by Plenum Press in 1982. The dispersant prepared by a process that
includes an "ene" reaction may be a polyisobutylene succinimide having a
carbocyclic ring present of less than 50 mole %, or 0 to less than 30 mole %,
or 0
to less than 20 mole %, or 0 mole % of the non-borated dispersant molecules.
The "ene" reaction may have a reaction temperature of 180 C to less than 300
C,
or 200 C to 250 C, or 200 C to 220 C. The polyisobutene particularly useful in
preparing an "ene" type succinimide dispersant may desirably have at least 50
percent terminal vinylidene groups, such as at least 60, or 70, or 80 percent.
[0041] In certain embodiments, the succinimide dispersant prepared by
the
"thermal" or "ene" route may be particularly useful.
[0042] The dispersants may also be post-treated by conventional methods
by
a reaction with any of a variety of agents. Among these are boron compounds
(such as boric acid), urea, thiourea, dimercaptothiadiazoles, carbon
disulphide,
aldehydes, ketones, carboxylic acids such as terephthalic acid, hydrocarbon-
substituted succinic anhydrides, maleic anhydride, nitriles, epoxides, and
phosphorus compounds. In one embodiment the post-treated dispersant may be
borated. In one embodiment the post-treated dispersant may be reacted with
dimercaptothiadiazoles. In one embodiment the post-treated dispersant may be
reacted with phosphoric or phosphorous acid. In one embodiment the post-
treated dispersant may be reacted with terephthalic acid and boric acid (as
described in US Patent Application U52009/0054278.
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[0043] In one embodiment, the ashless dispersant may be boron-
containing,
i.e., has incorporated boron and delivers said boron to the lubricant
composition.
The boron- containing dispersant may be present in an amount to deliver at
least
25 ppm boron, or at least 50 ppm boron, or at least 100 ppm or at least 200
ppm
or 300ppm or 500 ppm or 200 to 500 ppm or 300 to 500 ppm boron to the
lubricant composition. In one embodiment, the lubricant composition may be
free of a boron- containing dispersant, i.e. the boron containing dispersant
delivers no more than 10 ppm boron to the final formulation.
[0044] The lubricant compositions of the present invention include at
least
one polyisobutylene succinimide dispersant derived from an ethylene polyamine
and having a carbonyl to nitrogen ratio equal to or greater than 1:1 or
between
about 1:1 to 4:3 or about 1.1:1 to 4:3 or about 1:1 to about 6:5 or about
1.1:1 to
about 6:5. This dispersant (on an oil free basis) may be present in an amount
of
0.1 wt % to 2 wt % (or 0.1 to 1.5 wt %, or 0.2 wt % to 2 wt %, or 0.3 wt % to
1
wt %) of the lubricant composition.
[0045] The dispersant may typically comprise a dispersant package of
two or
more dispersants. In one embodiment, the dispersant package comprises at least
one polyisobutylene succinimide dispersant derived from an ethylene polyamine
and having a carbonyl to nitrogen ratio equal to or greater than 1:1 or
between
about 1:1 to 4:3 or about 1.1:1 to 4:3 or about 1:1 to about 6:5 or about
1.1:1 to
about 6:5 and a second dispersant selected from dispersants having a carbonyl
to
nitrogen ratio less than 1:1 and succinic acid ester dispersants. In one
embodiment, the second dispersant may be a conventional polyisobutylene
succinimide dispersant. In another embodiment, the second dispersant may be a
polyisobutylene succinic acid ester dispersant. The second dispersant may by a
Mannich dispersant. The second dispersant may be a borated dispersant.
[0046] In still a further embodiment, the dispersant package may
comprise
three or more dispersants, including at least one polyisobutylene succinimide
dispersant derived from an ethylene polyamine and having a carbonyl to
nitrogen
ratio equal to or greater than 1:1 or between about 1:1 to 4:3 or about 1.1:1
to 4:3
or about 1:1 to about 6:5 or about 1.1:1 to about 6:5, a second dispersant
which
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is a polyisobutylene succinimide dispersant having a carbonyl to nitrogen
ratio
less than 1:1 and a third dispersant which is an alkenyl (typically
polyisobutylene) succinic acid ester dispersant or a borated dispersant or a
Mannich dispersant or mixtures thereof.
[0047] In a dispersant package comprising two or more dispersants, the
polyisobutylene succinimide dispersant derived from an ethylene polyamine and
having a carbonyl to nitrogen ratio equal to or greater than 1:1 or between
about
1:1 to 4:3 or about 1.1:1 to 4:3 or about 1:1 to about 6:5 or about 1.1:1 to
about
6:5 will typically comprise from about 5 to 80 wt. % or 10 to 60 wt. %, 15 to
50
wt. % and 15 to 30 wt. % of the total dispersant package.
[0048] The total dispersant or dispersant package (on an oil free
basis) may be
present it the lubricant composition in an amount of 1.0 wt % to 6.0 wt. % or
1.5 wt.
% to 5.0 wt. %, 2.0 to 4.0 wt. %.
Detergents
[0049] The disclosed lubricant may include one or more alkaline or alkali
earth metal-containing detergent. The metal-containing detergent which may be
present as an additive component in the lubricant is, in one embodiment, an
overbased detergent. It may, alternatively, be a neutral detergent. Overbased
materials, otherwise referred to as overbased or superbased salts, are
generally
homogeneous Newtonian systems characterized by a metal content in excess of
that which would be present for neutralization 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, preferably carbon dioxide) with a
mixture
comprising an acidic organic compound (in this instance, a hydrocarbyl-
substituted salicylic acid), a reaction medium comprising at least one inert,
organic solvent (e.g., mineral oil, naphtha, toluene, xylene) for said acidic
organic
material, a stoichiometric excess of a metal base, and a promoter such as a
phenol
or alcohol and optionally ammonia. The acidic organic material will normally
have a sufficient number of carbon atoms, for instance, as a hydrocarbyl
sub stituent, to provide a reasonable degree of solubility in oil. The amount
of
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excess metal is commonly expressed in terms of metal ratio. The term "metal
ratio" is the ratio of the total equivalents of the metal to the equivalents
of the
acidic organic compound. A neutral metal salt has a metal ratio of one. A salt
having 4.5 times as much metal as present in a normal salt will have metal
excess
of 3.5 equivalents, or a ratio of 4.5.
[0050] Overbased detergents are often characterized by Total Base
Number
(TBN). TBN is the amount of strong acid needed to neutralize all of the
overbased material's basicity, expressed as potassium hydroxide equivalents
(mg
KOH per gram of sample). Since overbased detergents are commonly provided in
a form which contains a certain amount of diluent oil, for example, 40-50%
oil,
the actual TBN value for such a detergent will depend on the amount of such
diluent oil present, irrespective of the "inherent" basicity of the overbased
material. For the purposes of the present invention, the TBN of an overbased
detergent is to be recalculated to an oil-free basis. Detergents which are
useful in
the present invention typically have a TBN (oil-free basis) of 100 to 800, and
in
one embodiment 150 to 750, and in another, 400 to 700. If multiple detergents
are
employed, the overall TBN of the detergent component (that is, an average of
all
the specific detergents together) will typically be in the above ranges.
[0051] The metal compounds useful in making the basic metal salts are
gener-
ally any Group 1 or Group 2 metal compounds (CAS version of the Periodic
Table of the Elements). The Group 1 metals of the metal compound include
Group la alkali metals such as sodium, potassium, and lithium, as well as
Group
lb metals such as copper. The Group 1 metals can be sodium, potassium, lithium
and copper, and in one embodiment sodium or potassium, and in another
embodiment, sodium. The Group 2 metals of the metal base include the Group 2a
alkaline earth metals such as magnesium, calcium, and barium, as well as the
Group 2b metals such as zinc or cadmium. In one embodiment the Group 2
metals are magnesium, calcium, barium, or zinc, and in another embodiments
magnesium or calcium. In certain embodiments the metal is magnesium, calcium
or sodium or a mixture of calcium and magnesium. In some embodiments of the
present invention, the lubricant is zinc free or substantially zinc free and
thus will
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not include zinc containing detergents. Generally the metal compounds are
delivered as metal salts. The anionic portion of the salt can be hydroxide,
oxide,
carbonate, borate, or nitrate.
[0052] In one embodiment the lubricants may contain an overbased
sulfonate
detergent. Oil-soluble sulfonates can be represented by one of the following
formulas: R2-T-(S03), and R3-(S03-)b, where T is a cyclic nucleus such as
typically benzene; R2 is an aliphatic group such as alkyl, alkenyl, alkoxy, or
alkoxyalkyl; (R2)-T typically contains a total of at least 15 carbon atoms;
and R3
is an aliphatic hydrocarbyl group typically containing at least 15 carbon
atoms.
.. Examples of R3 are alkyl, alkenyl, alkoxyalkyl, and carboalkoxyalkyl
groups. In
one embodiment the sulfonate detergent may be a predominantly linear
alkylbenzenesulfonate detergent having a metal ratio of at least 8 as
described in
paragraphs [0026] to [0037] of US Patent Application 2005-065045.
[0053] Another overbased material which can be present is an overbased
.. phenate detergent. The phenols useful in making phenate detergents can be
represented by the formula (R4)a-Ar-(OH)b, wherein R5 is an aliphatic
hydrocarbyl group of 4 to 400 carbon atoms, or 6 to 80 or 6 to 30 or 8 to 25
or 8
to 15 carbon atoms; Ar is an aromatic group (which can be a benzene group or
another aromatic group such as naphthalene); a and b are independently numbers
.. of at least one, the sum of a and b being in the range of two up to the
number of
displaceable hydrogens on the aromatic nucleus or nuclei of Ar. In one
embodiment, a and b are independently numbers in the range of 1 to 4, or 1 to
2.
R4 and a are typically such that there is an average of at least 8 aliphatic
carbon
atoms provided by the R4 groups for each phenol compound. Phenate detergents
are also sometimes provided as sulfur-bridged species. In some embodiments,
the
phenate detergent contains less than 20% or less than 10% or less than 5% or
less
than 2% or less than 1%, e.g., 0 or 0.05% to 0.5% of monomeric para-
dodecylphenol or sulfurized monomer thereof or salt thereof, based on the
active
chemical amount of the phenate detergent. Methods for preparing phenolic
.. dispersants of this type are disclosed in numerous applications or
publications,
including PCT/US2012/060839, PCT/U52013/024877, and U.S. Patent 7,435,709.
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[0054] In one embodiment, detergent may comprise a salicylate detergent
such
as an overbased calcium hydrocarbyl-substituted salicylate detergent. The
presence of a salicylate detergent may be beneficial in providing oxidation
resistance to the lubricant. In one embodiment the salicylate detergent has a
Total
5 Base Number of about 200 to about 700 or 250 to 500 or 250 to 400 or 300
to 700
or 450 to 700 or greater than about 400 on an oil free basis, that is,
factoring out
the effect of diluent oil. Salicylate detergents are known; see, for instance,
U.S.
Pat. Nos. 5,688,751 or 4,627,928. In a particularly useful embodiment, the
detergent may comprise an overbased calcium salicylate detergent and in
another
10 .. embodiment, an overbased magnesium salicylate detergent and in still
another
embodiment a mixture of calcium and magnesium salicylate detergents.
[0055] In one embodiment, the overbased material is an overbased
saligenin
detergent. Overbased saligenin detergents are commonly overbased magnesium
salts which are based on saligenin derivatives. Saligenin detergents are
disclosed
15 in greater detail in U.S. Patent 6,310,009, with special reference to
their methods
of synthesis (Column 8 and Example 1) and suitable amounts of the various
species of X and Y (Column 6).
[0056] Salixarate detergents may also be present. Salixarates and
methods of
their preparation are described in greater detail in U.S. patent number
6,200,936
and PCT Publication WO 01/56968. It is believed that the salixarate
derivatives
have a predominantly linear, rather than macrocyclic, structure, although both
structures are intended to be encompassed by the term "salixarate."
[0057] Patents describing techniques for making basic salts of sulfonic
acids,
carboxylic acids, (hydrocarbyl-substituted) phenols, phosphonic acids, and
mixtures of any two or more of these include U.S. Patents 2,501,731;
2,616,905;
2,616,911; 2,616,925; 2,777,874; 3,256,186; 3,384,585; 3,365,396; 3,320,162;
3,318,809; 3,488,284; and 3,629,109.
[0058] Other overbased detergents can include overbased detergents
having a
Mannich base structure, as disclosed in U.S. Patent 6,569,818.
[0059] Either a single detergent or multiple additional detergents can be
present. The amount of the detergent or detergents (individually or in total)
in the
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lubricants of the present technology may be 0.5 to 5 percent by weight, or 1
to 3
percent. The amount in a concentrate will be correspondingly higher. The total
amount of detergents present in the lubricants of the disclosed technology may
be
an amount suitable to provide 1 to 5 TBN, or 2 to 4, or 2.5 to 3 TBN to the
lubricant.
Boron compound
[0060] The lubricant compositions of the present invention may comprise
a
boron containing compound or mixture of boron containing compounds in an
amount to provide the lubricant composition with 25 ppm boron, or at least 50
ppm boron, or at least 100 ppm or at least 200 ppm or 300 ppm or 500 ppm or
200 to 500 ppm or 300 to 500 ppm boron to the lubricant composition. Useful
boron containing compounds may include boric acid (including metaboric acid,
HB02, orthoboric acid, H3B03, and a tetraboric acid, H2B407) and borate
esters,
which may be prepared by the reaction of boric acid, a boric oxide, a boron
trioxide or an alkyl borate and at least one compound selected from epoxy
compounds, halohydrin compounds, epihalohydrin compounds, alcohols and
mixtures thereof. Typically the alcohols include monohydric alcohols, dihydric
alcohols, trihydric alcohols or higher alcohols. Borate esters may also be
prepared from boron halides.
[0061] The borated ester may contains at least one hydrocarbyl group often
containing about 4 to about 30, or 8 to about 30 carbon atoms.
[0062] In one embodiment, the boron containing compound may comprise a
borate ester comprising at least one C8 to C30 hydrocarbyl group. The boron
containing compound may comprise one or more borated dispersants discussed
above. In one embodiment, it the boron containing compound may comprise a
mixture of a borate ester and a boron containing dispersant.
Other Performance Additives
[0063] The lubricant of the disclosed technology may also contain 3 to
80
ppm (or 5 to 70, or 10 to 60, or 20 to 50 ppm) of one or more silicon-
containing
antifoam agents. At least a small amount of such an antifoam agent is
desirable to
minimize foaming while the lubricant is lubricating the engine. However, an
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excessive amount may be deleterious to the anti-emulsion performance of the
lubricant as it may be used for the lubrication of a compressor.
[0064] Silicon antifoam agents may be fluorinated molecules, or
molecules
without fluorine, or mixtures of such molecules. Such materials are
commercially
available and includes such species as polydimethylsiloxane and trimethyl,
trifluoropropylmethyl siloxane. These materials may be provided commercially
as oil-diluted compositions; the amounts reported herein are an oil-free
basis.
[0065] In certain embodiments, the disclosed lubricant may also contain
a
silicon-free polymeric antifoam agent. The amount of this agent, if it is
present,
may be up to 200 parts per million by weight, e.g., 10 to 200, or 20 to 100,
or 25
to 80, or 30 to 70 ppm. The silicon-free polymeric antifoam agent may comprise
an alkyl acrylate polymer, such as a copolymer of ethyl acrylate and 2-
ethylhexyl
acrylate. Such an antifoam agent may aid in improving anti-emulsion
performance of the lubricant.
[0066] Another component that may be included in the lubricant is a
corrosion
inhibitor (which may also function as a rust inhibitor or a metal
deactivator).
Corrosion inhibitors typically may include nitrogen-containing materials such
as
triazoles and thiadiazoles and derivatives thereof. Suitable triazoles include
aromatic triazoles such as benzotriazole or alkylbenzotriazoles such as
tolutriazole.
z %N
NH
H3C
(methyl-l-H-benzo [d][1,2,3]triazole or tolutriazole)
Thiadiazoles include dimercaptothiadiazoles and mono- or di-alkyl derivatives
of
dimercaptothiadiazoles.
R-S
S-R
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(including species with multiple S atoms in a chain). The amount of the
corrosion inhibitor (such as the amount of the aromatic triazole) may be 0.001
to
0.1 wt. %, or 0.003 to 0.03 wt. %, or 0.005 to 0.1 wt. %.
[0067] Additional conventional components may be used in preparing a
lubricant according to the present technology, for instance, those additives
typically employed in a crankcase lubricant. Crankcase lubricants may
typically
contain any or all of the following components hereinafter described.
[0068] One component is an antioxidant, sometimes referred to an
ashless
antioxidant if it is desired to distinguish metal-containing materials from
metal-
free (ashless) compounds. Antioxidants encompass phenolic antioxidants, which
may comprise a butyl substituted phenol containing 2 or 3 t-butyl groups. The
para position may also be occupied by a hydrocarbyl group or a group bridging
two aromatic rings. They may also contain an ester group at the para position,
for
example, an antioxidant of the formula
t-alkyl
HO CH2CH2COR3
t-alkyl
wherein R3 is a hydrocarbyl group such as an alkyl group containing, e.g., 1
to 18
or 2 to 12 or 2 to 8 or 2 to 6 carbon atoms; and t-alkyl can be t-butyl. Such
antioxidants are described in greater detail in U.S. Patent 6,559,105.
Antioxidants also include aromatic amines, such as nonylated diphenylamines.
Other antioxidants include sulfurized olefins, titanium compounds, and
molybdenum compounds. U.S. Pat. No. 4,285,822, for instance, discloses
lubricating oil compositions containing a molybdenum and sulfur containing
composition. Typical amounts of antioxidants will, of course, depend on the
specific antioxidant and its individual effectiveness, but illustrative total
amounts
can be 0.01 to 5 wt. % or 0.15 to 4.5 wt. % or 0.2 to 4 wt. %. Additionally,
more
than one antioxidant may be present, and certain combinations of these can be
synergistic in their combined overall effect.
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[0069] Viscosity improvers (also sometimes referred to as viscosity
index
improvers or viscosity modifiers) may be included in the disclosed
compositions.
Viscosity improvers are usually polymers, including polyisobutenes,
polymethacrylic acid esters, diene polymers, polyalkylstyrenes, esterified
styrene-
maleic anhydride copolymers, alkenylarene-conjugated diene copolymers and
polyolefins. Multifunctional viscosity improvers, which also have dispersant
and/or antioxidancy properties are known and may optionally be used. Viscosity
improvers may be used at, e.g., 0.1 to 0.8 wt. % or 0.3 to 0.6 wt. %.
[0070] The lubricant compositions of the present invention may include
one or
.. more antiwear agents other than the phosphite compounds disclosed above.
Examples of other anti-wear agents may include phosphorus-containing
antiwear/extreme pressure agents such as metal thiophosphates, phosphoric acid
esters and salts thereof, and phosphorus-containing carboxylic acids, esters,
ethers, and amides. The present technology is particularly useful for
formulations
in which the total amount of phosphorus as delivered by various components
including the antiwear agent, does not exceed 0.075% or 0.07% or 0.06%.
Suitable amounts may include 0.005 to about 0.055 percent by weight or 0.01 to
0.05 percent or 0.02 to 0.05 percent. Non-phosphorus-containing anti-wear
agents, which may also be used, include borate esters (including borated
epoxides), dithiocarbamate compounds, molybdenum-containing compounds, and
sulfurized olefins.
[0071] Other additives that may optionally be used in lubricating oils
include
pour point depressing agents, extreme pressure agents, and color stabilizers.
[0072] The present technology is particularly useful also when the
total
sulfated ash of a lubricant is relatively low, for instance, less than 1 % or
less than
0.8%, e.g., 0.01 to 0.8, or 0.1 to 0.75, or 0.2 to 0.7 %.
[0073] In a particularly useful embodiment a lubricant formulation may
be
free or substantially free of any zinc containing compounds, such as the
antiwear
agent zinc dialkyldithiophosphate (ZDDP). In other embodiments, the lubricant
may be free of or substantially free of any metal thiophosphates.
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[0074] The lubricant formulations of the present invention are intended
to
effectively inhibit siloxane deposit formation and associated engine wear in
engines fueled using natural or landfill gas having high concentrations of
silicon,
while also maintaining or improving seals performance and corrosion
inhibition.
5 Thus, in come embodiments of the method of the present invention, the
lubricant
composition may comprise greater than 120 ppm or 125 ppm or 130 ppm or 140
or 160 or 175 or 200 or 250 or 300 ppm of silicon. This silicon may be derived
from contamination from silicon compounds in the fuel source or byproducts of
combustion of the fuel source.
10 [0075] It is known that some of the materials described above may
interact in
the final formulation, so that the components of the final formulation may be
different from those that are initially added. For instance, metal ions (of,
e.g., a
detergent) can migrate to other acidic or anionic sites of other molecules.
The
products formed thereby, including the products formed upon employing the
15 composition of the present invention in its intended use, may not be
susceptible of
easy description. Nevertheless, all such modifications and reaction products
are
included within the scope of the present technology; the present technology
encompasses the composition prepared by admixing the components described
above.
20 EXAMPLES
[0076] Reference Example 1 (RE1). A low-ash stationary-gas engine
lubricant may be prepared comprising an oil of lubricating viscosity, 2.54 wt.
%
of a succinimide dispersant (chlorine-route); 0.74 wt. % of overbased Ca
sulfonate detergent(s); 0.97 wt. % overbased Ca phenate detergent(s), 0.27 wt.
%
zinc dialkylthiophosphate(s); 2.85 wt. % antioxidants (phenolic, aminic,
and/or
sulfurized olefin); 0.35 wt. % of a borate ester, and 0.007 percent by weight
of
polydimethylsiloxane antifoam agent (commercial material, about 10% in oil,
corresponding to 7 ppm antifoam agent on an active chemical basis).
[0077] Preparative Example 1 (PE1). A low-ash stationary-gas engine
lubricant may be prepared comprising an oil of lubricating viscosity, 0.24 wt.
%
of a phosphite compound(s), 1.8 wt. % of a succinimide dispersant (chlorine-
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route); 0.6 wt. % of a polyisobutylene succinimide dispersant with a carbonyl
to
nitrogen ratio of 4:3, 0.34 wt.% of a borated succinimide dispersant, 0.28 wt.
%
succinic acid ester dispersant, 0.1 wt. % of a polypropylene oxide, 1.2 wt. %
of
overbased Ca salicylate detergent; 2.95 wt. % antioxidants (phenolic, aminic,
and/or sulfurized olefin); 0.35 wt. % of a borate ester, 0.01 wt. % of a
corrosion
inhibitor, 0.05 wt. % of a titanium alkylate and 0.007 percent by weight of
polydimethylsiloxane antifoam agent (commercial material, about 10% in oil,
corresponding to 7 ppm antifoam agent on an active chemical basis).
[0078] Each of the documents referred to above is incorporated herein
by
reference. The mention of any document is not an admission that such document
qualifies as prior art or constitutes the general knowledge of the skilled
person in
any jurisdiction. Except in the Examples, or where otherwise explicitly
indicated,
all numerical quantities in this description specifying amounts of materials,
reac-
tion conditions, molecular weights, number of carbon atoms, and the like, are
to
be understood as modified by the word "about." It is to be understood that the
upper and lower amount, range, and ratio limits set forth herein may be
independently combined. Similarly, the ranges and amounts for each element of
the invention can be used together with ranges or amounts for any of the other
elements. As used herein, the expression "consisting essentially of" permits
the
inclusion of substances that do not materially affect the basic and novel
charac-
teristics of the composition under consideration.
[0079] As used herein, the term "substantially free of' means that the
material in question is only present in amounts consistent with contamination
and/or by-products present in commercial grades of desired components.
[0080] As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl
group" is used in its ordinary sense, which is well-known to those skilled in
the
art. Specifically, it refers to a group having a carbon atom directly attached
to the
remainder of the molecule and having predominantly hydrocarbon character.
Examples of hydrocarbyl groups include hydrocarbon substituents, including
aliphatic, alicyclic, and aromatic substituents; substituted hydrocarbon
substituents, that is, substituents containing non-hydrocarbon groups which,
in the
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context of this invention, do not alter the predominantly hydrocarbon nature
of
the substituent; and hetero substituents, that is, substituents which
similarly have
a predominantly hydrocarbon character but contain other than carbon in a ring
or
chain. A more detailed definition of the term "hydrocarbyl substituent" or
"hydrocarbyl group," including permissible amounts of other atoms, is found in
paragraphs [0118] to [0119] of International Publication W02008147704 as well
as paragraphs [0137] to [0141] of published application US 2010-0197536.
