Note: Descriptions are shown in the official language in which they were submitted.
CA 02615339 2007-12-18
LUBRICATING OIL WITH ENHANCED PISTON CLEANLINESS
CONTROL
The present invention relates to lubricating oil compositions. More
specifically, the present invention relates to lubricating oil compositions
that have
reduced levels of sulfated ash, phosphorus and sulfur (low "SAPS"), yet
provide
improved lubricant performance in internal combustion engines.
Environmental concerns have led to continued efforts to reduce the emissions
of carbon monoxide (CO), hydrocarbon and nitrogen oxide (NO) from compression-
ignited (diesel-fueled) and spark-ignited (gasoline-fueled) internal
combustion
engines. There have also been continued efforts to reduce the particulate
emissions
from compression-ignited internal combustion diesel engines. To meet the
contemporary emission standards for passenger cars and other vehicles,
original
equipment manufacturers (OEMs) have been applying exhaust gas after-treatment
devices. Such exhaust gas after-treatment devices include, but are not limited
to,
catalytic converters and/or particulate traps.
Catalytic converters typically contain one or more oxidation catalysts, NOx
storage catalysts, and/or NH3 reduction catalysts. The catalysts contained
therein
generally comprise a combination of catalytic metals such as platinum, and
metal
oxides. Catalytic converters are installed in the exhaust systems, for
example, the
exhaust pipes of automobiles, to convert the toxic gases to nontoxic gases.
The use of
catalytic converters is thought to be essential in bucking global warming
trends and
combating other environmental detriments. The catalysts, however, can be
poisoned
and rendered less effective, if not useless, as a result of exposure to
certain elements
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or compounds, especially phosphorus compounds. Among the many ways
phosphorus compounds may be introduced into the exhaust gas is the degradation
of
phosphorus-containing lubricating oil additives. Examples of phosphorus
lubricating
oil additives include zinc dialkyldithiophosphates and the like. Zinc
dialkyldithiophosphates are among the most effective and conventionally used
antioxidants and antiwear agents, from both a performance and cost-
effectiveness
standpoint, in lubricating oil compositions. While they are effective
antioxidants and
antiwear agents, the phosphorus, sulfur and ash they introduce into the engine
react
with the catalysts and may shorten the service life of the catalytic
converters.
Reduction catalysts are susceptible to damage by sulfur and sulfur compounds
in the
exhaust gas, which are introduced by the degradations of both the base oil
used to
blend the lubricants and sulfur-containing lubricant oil additives. Examples
of sulfur-
containing lubricant oil additives include, but are not limited to, magnesium
sulfonate
and other sulfated or sulfonated detergents.
Particulate traps are usually installed in the exhaust system, especially in
diesel engines, to prevent the carbon black particles or very fine condensate
particles
or agglomerates thereof (i.e., "diesel soot") from being released into the
environment.
Aside from polluting air, water, and other elements of the environment, diesel
soot is
a recognized carcinogen. These traps, however, can be blocked by metallic ash,
which is the degradation product of metal-containing lubricating oil additives
including common ash-producing detergent additives.
To insure a long service life for the after-treatment devices, it is desirable
to
identify lubricating oil additives that exert a minimum negative impact on
such
devices. To this end, OEMs often set various limits for maximum sulfur,
phosphorus,
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and/or sulfated ash levels for "new service fill" and "first fill" lubricants.
For
instance, when used in light-duty passenger-car internal combustion engines,
the
sulfur levels are typically required to be at or below 0.30 wt.%, the
phosphorus levels
at or below 0.08 wt%, and the sulfated ash contents at or below 0.8 wt%. The
maximum sulfur, phosphorus and/or sulfated ash levels may differ, however,
when
the lubricating compositions are used in heavy-duty internal combustion
engines. For
example, the maximum sulfated ash level may be as high as 1.0 wt.% in those
heavy-
duty engines. Such lubricating oil compositions are also referred to as "low
SAPS"
(low sulfated ash, phosphorus, sulfur) lubricating oil compositions for
gasoline
engines, and/or light duty diesel engines, and "low SAPS" or "LEDL" (low
emission
diesel lubricant) oil compositions for heavy duty diesel engines. Various
tests have
been established and standardized to measure the levels of SAPS in any
particular
lubricating oil compositions. For example, in Europe, a lubricant meeting the
ACEA
gasoline and diesel engine low SAPS specification must pass, inter alia, the
"CEC L-
78-1-99" test, which measures the cleanliness and extent of piston ring
sticking after
running a Volkswagen turbocharged direct injection automotive diesel engine
for an
extended time period, cycling alternatively between idle and full power.
Similar
specifications and testing standards of varied stingencies can also be found
in other
countries and regions, such as Japan, Canada, and the United States.
Meeting the low SAPS environmental standards does not eliminate the need to
provide adequate lubricant performance. Automobile spark ignition and diesel
engines have valve train systems, including valves, cams and rocker arms, all
of
which must be lubricated and protected from wear. Further, engine oils must
provide
sufficient detergency so as to insure engine cleanliness and suppress the
production of
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deposits, which are products of non-combustibles and incomplete combustibles
of
hydrocarbon fuels and deterioration of engine oils.
As discussed above, the need to preserve the integrity of catalytic converters
has led to the use of less phosphate and phosphoms-containing additives.
However,
the use of detergents, which are typically metal sulfonate detergents, is
often
inevitable because of the sustained needs to neutralize the oxidation-derived
acids and
suspend polar oxidation residues in the lubricant. These detergents, however,
contributes to the production of sulfated ash. Indeed, the amount of ash
permitted
under most of the current environmental standards can be exceeded by far less
metal
sulfonate detergent than is necessary to achieve adequate detergency
performance.
Reducing the levels of detergent overbasing may reduce the level of ash
produced, but
it also reduces the acid neutralizing capacity of the lubricant composition,
potentially
leading to acid corrosion of the engine pistons and other parts.
Therefore, it would be advantageous to identify low SAPS lubricating oil
compositions and additives that not only foster cleaner environment by
allowing the
catalyst converters and particulate traps to effectively reduce pollutants,
but also
improve fuel economy by, for instance, reducing friction within an engine. A
need is
thus apparent for compromises or new approaches through which both the
environmental standards and the engine lubrication needs can be satisfied.
Various low SAPS additives and lubricant compositions have been identified
as capable of providing piston cleanliness in internal combustion engines. For
example, U.S. Patent Application 11/217,674 (published as U.S. 2006/0052254)
disclosed a low SAPS lubricant composition that provided good piston
cleanliness in
an XUD-IIBTE (CEL-L-56-T-98) test. The lubricating oil composition of this
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application had a sulfur content of up to 0.3 wt.%, a phosphorus content of up
to 0.08
wt.%, a sulfated ash content of up to 0.80 wt.%, and contained less than 5
rnmoles of
salicylate soap per kilogram of lubricating oil composition. A companion
application,
U.S. 1atent Application 11/218,647 (published as U.S. 2006/0058200) disclosed
a
low SAPS lubricating oil composition with similar advantages. That composition
comprised (a) a major amount of an oil of lubricating viscosity; (b) at least
one
nitrogen-containing dispersant to provide a nitrogen content of at least 0.075
wt.%,
the dispersant having a polyalkenyl backbone of molecular weight of about 900
to
about 3000 Daltons; and (c) an oil-soluble or oil-dispersible source of boron
to
provide a wt.% ratio of nitrogen to boron of about 3:1 to about 5:1; (d) an
antioxidant;
and (e) a zinc dihydrocarbyldithiophosphate. In U.S. Patent Application
11/226,793
(published as U.S. 2006/0068999), yet another low SAPS lubricating oil
composition
comprising (1) a major amount of an oil of lubricating viscosity; (2) an
overbased
magnesium-containing lubricating oil detergent having a TBN of 200 to 500
present
in such an amount to provide a TBN of 5.3 to 7.3 to the finished composition;
and (3)
2.5 to 4 wt.% of an ashless dispersant, was said to provide enhanced piston
merits.
Low SAPS lubricating oil compositions have also been known to impart
certain other desirable properties. For example, an internal combustion engine
oil of
this kind was reported to retain high total base number (TBN) in U.S. Patent
Application 11/176,424 (published as U.S. 2006/0014653). The composition had a
sulfated ash content of not greater than 0.9 wt.%, and a phosphorus content
from 0.04
to 0.1 wt.%. The composition contained base oil; one or more detergents
selected
from phenate detergents, salicylate detergents, and sulphonate detergents,
wherein
said one or more detergents each, independently, had a TBN value of from 30 to
350
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mg KOH/g; and at least 3.5 wt.% of one or more antioxidants selected from the
group
of aminic antioxidants and phenolic antioxidants.
= In another example, U.S. Patent Application 11/288,600 (published as U.S.
2006/0116300) disclosed a low SAPS lubricating oil composition that provided
improved lubricant performance, and especially antiwear properties, in
compression-
ignited diesel engines according to a Mack T10 screener test. That low SAPS
lubricating oil composition comprised (1) a major amount of an oil of
lubricating
viscosity; (2) a minor amount of a calcium salicylate detergent; (3) a minor
amount of
an overbased magnesium detergent; and (4) a minor amount of a basic, low
molecular
weight nitrogen-containing dispersant derived from a polymer having a number
average molecular weight of no greater than 1100 Daltons.
It has now been found that reaction products of polyisobutylenes and
monounsaturated acylating agents, when accompanied by at least one ashless
dispersant, at least one metal-containing detergent, at least one antiwear
additive, and
at least one antioxidant, significantly enhance piston cleanliness control in
internal
combustion engines. The present invention therefore provides a low sulfated
ash, low
phosphorus and low sulfer lubricant composition, including an additive package
or a
concentrate, comprising such a reaction product of a polyisobutylene and a
monounsaturated acylating agent. The present invention also provides methods
of
using and making such a lubricating oil composition.
A reaction product of a polyisobutylene and a monounsaturated acylating
agent is typically prepared from its non-carboxylated polyisobutylene
precursor.
Polyisobutylenes (PIBs) are also known as polyisobutenes to persons skilled in
the
art. They have also been given the name "butyl rubber," as they are much used
in that
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capacity. In the lubricant and/or fuel additive field, PIBs have found wide
use as
dispersants, viscosity improvers, thickeners, and the like. The common uses
for PIBs
have been summarized, for example, in section 3.3 (page 846) of Speight,
CHEMISTRY
& TECHNOLOGY OF PETROLEUM CHEMICAL INDUSTRIES, v.76, 3d ed. (N.Y. Marcel
Dekker, Inc., 1999); and in section 4.1 of/mme/, ULMANN'S ENCYCLOPEDIA OF
INDUSTRIAL CHEMISTRY (Wiley-VCH Verlag GmbH & Co. KGaA, 2002). Useful
PIBs generally contain residual unsaturation in amounts of about one ethylene
double
bond per polymer chain, positioned anywhere along the chain. Preferably,
however,
the PIBs are prepared from a pure isobutylene steam or a Raffinate I stream,
resulting
in a reactive isobutylene polymer with terminal vinylidene olefins. These
particular
PIBs comprising t-iminal vinylidene olefins are often referred to as "highly
reactive
polyisobutylenes (HR-PIBs)" by those skilled in the art. Particularly
preferably, a
useful HR-PIB would have a terminal vinylidene content of at least about 50%,
for
example, at least about 55%, or at least about 65%, or at least about 70%, or
at least
about 80%, or more preferably, at least about 85%. Such HR-PIBs can be
prepared
according to various art-recognized techniques, such as, for example, those
described
in U.S. Patent Nos. 4,152,499 and 4,605,808. Certain HR-PIBs are commercially
available, for example, under the trade name of GLISSOPALTM (from BASED).
Reaction products of PIBs and monounsaturated acylating agents, especially
the succinic anhydride derivatives, namely, the polyisobutylene succcinic
anhydrides
(PIBSAs), have been used as precursors in manufacturing ashless dispersants.
Examples of such use can be found in U.S. Patent Nos. 5,827,806 and 6,245,725,
each
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disclosing, inter alia, the making of a preferred set of nitrogen-containing
ashless
dispersants from certain PIBSAs, polyethylene amines (e.g., tetraethylene
pentamine,
polyoxypropylene diamine), and aminoalcohols (e.g., triemethylolaminomethane).
PIBSAs have also been applied directly, i.e., without derivatization, as
dispersants. For example, U.S. Patent No. 6,632,781 disclosed using a
dispersant
mixture comprising a polyalkylene succunic dispersant selected from the group
consisting of: (1) a polyalkylene succinic anhydride, preferably a PIBSA; (2)
a non-
nitrogen containing derivative of the polyalkylene succinic anhydride; and (3)
mixtures of polyalkylene succinic anhydrides; (4) mixtures of non-nitrogen
containing
derivatives of the polyalkylene succinic anhydride; and (5) mixtures of one or
more
polyalkylene succinic anhydrides and one or more non-nitrogen containing
derivatives of polyalkylene succinic anhydrides. That dispersant was said to
impart
enhanced water tolerance and lubricant-oil compatibility for alkali metal
borates.
The present invention provides a low sulfated ash, low phosphorus and low
sulfur lubricant composition, including an additive package or a concentrate,
comprising at least one reaction product of a PIB and a monounsaturated
acylating
agent. The lubricant additive compositions of the invention provide superior
piston
cleanliness, but are also compatible for low SAPS applications. The present
invention
further provides methods of applying and making these compositions.
SUMMARY OF THE INVENTION
The present invention provides lubricating oil compositions that provide high
piston cleanliness, especially when the machines housing those compositions
operate
at elevated temperatures, but which introduce low levels of phosphorous, low
levels
of sulfur, and low levels of sulfated ash to the internal combustion engines.
The
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levels of phosphorous in the lubricating oil compositions of the present
invention are
typically at or below about 0.09 wt.%, and preferably at or below about 0.08
wt.%,
and more preferably at or below about 0.07 wt.%, and particularly preferably
at or
below about 0.05 wt.%. The levels of sulfur produced by the lubricating oil
compositions of the present invention are typically at or below about 0.30
wt.%, and
preferably at or below about 0.20 wt.%, and particularly preferably at or
below about
0.10 wt.%. The levels of sulfated ash produced by the lubricating oil
compositions of
the present invention are typically at or below about 1.60 wt.%, but
preferably at or
below about 1.00 wt.%, more preferably at or below about 0.80 wt.%, even more
preferably at or below about 0.50 wt.%, and particularly preferably at or
below about
0.45 wt.%. In one embodiment of the present invention, the level of sulfated
ash will
be from above about 0.50 to about 1.60 wt.%, preferably from above about 0.5
to
about 0.8 wt.%.
Therefore, the present lubricating compositions are more desirable from an
environmental standpoint than the conventional internal combustion engine
lubricating oils that contain higher phosphorous, sulfur and sulfated ash. The
compositions of the present invention facilitate longer service lives for the
catalytic
converters and the particulate traps, while providing the desired piston
cleanliness.
In a first aspect, the present lubricating oil composition comprises:
a major amount of a base oil of lubricating viscosity;
one or more detergents;
one or more dispersants; and
a piston-cleanliness-enhancing amount of at least one reaction product of a
polyisobutylene and a monounsaturated acylating agent, wherein the
polyisobutylene
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has a number average molecular weight of about 200 to about 5000 Daltons,
preferably from about 500 to about 4500 Daltons; wherein, based on the total
weight
of the lubricating composition, the phosphorus content is no more than about
0.09
wt.%; the sulfur content is no more than about 0.3 ,wt.%; and the sulfated ash
content
is no more than about 1.6 wt.%.
The reaction product of a polyisobutylene and a monounsaturated acylating
agent may be one represented by either Formula A or Formula B:
RI RI
R2 R2
[Formula A] [Formula B]
wherein R1 is a polyisobutylene chain of number average molecular
weight of about 200 to about 5000 Daltons, preferably from about 500 to about
4500
Daltons; and R2 is a carboxyl-containing group.
The lubricating oil composition of this aspect may optionally further comprise
one or more additives selected from: (1) antiwear agents; (2) friction
modifiers; (3)
antioxidants; (4) corrosion inhibitors; (5) anti-foam additives; (6) seal
fixes or seal
pacifiers; (7) pour point depressants; (8) viscosity index modifiers; and (9)
multifunctional additives.
In a second aspect, the invention provides an additive package composition or
a concentrate comprising at least one reaction product of a PIB and a
monounsaturated acylating agent in an organic diluent liquid, for example,
base oil.
The additive package composition or concentrate of this aspect preferably
further
comprises various other additives desired in lubricating oil, such as, for
example,
ashless dispersants, metal-containing detergents, antiwear additives,
antioxidants,
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friction modifiers, corrosion inhibitors, anti-foam additives, pour point
depressants,
viscosity index improvers, and seal fixes or seal pacifiers.
In a third aspect, the invention provides a method of operating an internal
combustion engine provided with one or more exhaust gas after-treatment
devices,
which method comprises lubricating said engine with a lubricating composition
of the
first aspect, or with an additive package composition or a concentrate of the
second
aspect.
In a fourth aspect, the invention provides a method of preparing a lubricating
oil composition of the first aspect or an additive package or a concentrate of
the
second aspect.
According to another aspect, there is provided a lubricant composition
suitable
for use in an internal combustion engine, which comprises an admixture of:
(a) a major amount of an oil of lubricating viscosity;
(b) one or more nitrogen-containing ashless dispersants;
(c) one or more metal-containing detergents; and
(d) a piston-cleanliness-enhancing amount of at least one
reaction product
of a polyisobutylene (PIB) and a monounsaturated acylating agent, wherein the
polyisobutylene has a number average molecular weight of about 200 to about
5000
Daltons; and wherein the piston-cleanliness-enhancing amount of the at least
one
reaction product of a PIB and a monounsaturated acylating agent is 0.01 to 5.0
wt.%,
based on the total weight of the lubricant composition;
wherein said lubricant composition has a sulfur content of at or below about
0.3 wt.%, a phosphorus content of at or below about 0.09 wt.%, and a sulfated
ash
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content of at or below about 1.6 wt.%, based on the total weight of said
lubricating oil composition.
Persons skilled in the art will understand other and further objects of
aspects,
advantages, and features of the present invention by reference to the
following
description.
DETAILED DESCRIPTION OF THE INVENTION
Various preferred features and embodiments are described below by way of
non-limiting illustrations.
The present invention provides lubricating oil compositions as described
above. The compositions have a total sulfur content of at or below about 0.30
wt.% in
typical embodiments, at or below about 0.20 wt.% in some other embodiments,
and at
or below about 0.10 wt.% in further embodiments. The major source of sulfur in
the
composition of the invention is often the base stocks and the additives. An
exemplary
lubricating oil composition of the present invention contains about 0.2 wt.%
of sulfur,
based on the total weight of the composition.
The lubricating oil compositions have a total phosphorus content of at or
below about 0.09 wt.% in typical embodiments, at or below about 0.08 wt.% in
some
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other embodiments, at or below about 0.07 wt.% in yet other embodiments, and
at or
below about 0.05 wt.% in further embodiments. An exemplary lubricating oil
composition of the present invention contains about 0.07 wt.% of phosphorus,
based
on the total weight of the composition.
The lubricating oil compositions have a total sulfated ash content of, as
determined by the ASTM D-874, at or below about 1.60 wt.% in typical
embodiments, at or below about 1.00 wt.% in some other embodiments, at or
below
about 0.80 wt.% in yet other embodiments, at or below about 0.50 wt.% in some
other
embodiments, and at or below about 0.45 wt.% in further embodiments. An
exemplary lubricating oil composition of the present invention has a sulfated
ash
content of about 0.6 wt.%, based on the weight of the lubricant compositions.
Another exemplary lubricating oil composition of the present invention has a
sulfated
ash content of about 0.8 wt.%, based on the weight of the lubricant
composition.
Oil of Lubricating Viscosity
The low-SAPS lubricating oil composition of the present invention is
comprised of one or more base oils, which are present in a major amount (i.e.,
an
amount greater than about 50 wt.%). Generally, the base oil is present in an
amount
greater than about 60 wt.%, or greater than about 70 wt.%, or greater than
about 80
wt.% of the lubricating oil composition. The base oil sulfur content is
typically less
than about 1.00 wt.%, preferably less than about 0.60 wt.%, more preferably
less than
about 0.40 wt.%, and particularly preferably less than about 0.30 wt.%.
The low-SAPS lubricating oil composition may have a viscosity at 100 C of
up to about 16.3 mm2/s, and in one embodiment of about 5 to about 16.3 mm2/s
(cSt),
and in one embodiment of about 6 to about 13 mm2/s (cSt). The low-SAPS
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lubricating oil composition may have a high-temperature/high-shear viscosity
at
150 C as measured by the procedure in ASTM D4683 of up to about 4 mm2/s (cSt),
and in one embodiment up to about 3.7 mm2/s (cSt), and in another embodiment
about
2 to about 4 mm2/s (cSt), and in yet another embodiment about 2.5 to about 3.7
mm2/s
(cSt), and in one further embodiment about 2.6 to about 3.5 mm2/s (cSt).
The base oil used in the lubricant compositions of the invention may be a
natural oil, a synthetic oil, or a mixture thereof, provided that the sulfur
content of
such an oil does not exceed the above-indicated sulfur concentration limit
required to
sustain the low SAPS lubricating oil compositions. The natural oils that are
suitable
include animal oils and vegetable oils (e.g., castor oil, lard oil). The
natural oils may
also include mineral lubricating oils such as liquid petroleum oils and
solvent-treated
or acid-treated mineral lubricating oils of the paraffinic, naphthenic or
mixed
paraffinic-naphthenic types. Oils derived from coal or shale are also useful.
Synthetic lubricating oils include hydrocarbon oils such as polymerized and
interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene
isobutylene
copolymers, etc.); poly(1-hexenes), poly-(1-octenes), poly(1-decenes), etc.
and
mixtures thereof; alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes,
dinonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g.,
biphenyls,
terphenyls, alkylated polyphenyls, etc.); alkylated diphenyl ethers and the
derivatives,
analogs and homologs thereof, and the like. Synthetic lubricating oils also
include
oils prepared by a known Fischer-Tropsch gas-to-liquid synthetic procedure.
Another class of known synthetic lubricating oils includes alkylene oxide
polymers and interpolymers and derivatives thereof where the terminal hydroxyl
groups have been modified by a process such as esterification or
etherification.
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Examples of these synthetic oils include polyoxyalkylene polymers prepared by
polymerization of ethylene oxide or propylene oxide, and the alkyl and aryl
ethers of
polyoxyalkylene polymers (e.g., methyl-polyiso-propylene glycol ether having a
molecular weight of 1000 Daltons or diphenyl ether of poly-ethylene glycol
having a
molecular weight of 1000 to 1500 Daltons); and mono- and polycarboxylic esters
thereof (e.g., acetic acid esters, mixed C3-C8 fatty acid esters, and C13 Oxo
acid diester
of tetraethylene glycol).
Another suitable class of synthetic lubricating oils are the esters of
dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids
and alkenyl
succinic acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric
acid,
adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acids, alkenyl
malonic
acids) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl
alcohol,
2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene
glycol). Specific examples of such esters includes 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, and 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.
Esters useful as synthetic oils also include those made from Cs to C12
monocarboxylic acids and polyols and polyol esters such as neopentyl glycol,
trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.
The synthetic oil can also be a poly-alpha-olefin (PAO). Typically, the PAOs
are derived from monomers having from 4 to 30, or from 4 to 20, or from 6 to
16
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carbon atoms. Examples of useful PAOs include those derived from octene,
decene,
mixtures thereof, and the like. These PAOs may have a viscosity from about 2
to
about 15, or from about 3 to about 12, or from about 4 to about 8 mm2/S (cSt)
at
100 c. Mixtures of mineral oil with one or more of the foregoing PAOs may be
used.
Unrefined, refined and rerefined oils, either natural or synthetic (as well as
mixtures of two or more) of the types of oils disclosed above can be used in
the
lubricating compositions of the present invention. Unrefined (or raw) oils are
those
obtained directly from a natural or synthetic source without further
purification
treatment. Refined oils are similar-to the unrefined oils except they have
been further
treated in one or more purification steps. Many such purification techniques
are
known to those skilled in the art such as solvent extraction, secondary
distillation,
acid or base extraction, filtration, percolation, and the like. Rerefined oils
are oils that
have been used in service but are subsequently treated so that they may be re-
applied
in service. Because the used oils almost always contain spent additives and
breakdown products, in addition to the standard oil refining steps, steps that
would
remove the spent additives and breakdown products must be taken. Such
rerefined
oils are also known as reclaimed or reprocessed oils.
Reaction Products of a PIB & a Monounsaturated Acylating Agent
It has been found that the incorporation of certain reaction products of
polyisobutylenes and monounsaturated acylating agents into base oils provides
low
SAPS lubricating oils that have the desired levels of piston cleanliness in
internal
combustion engines. The reaction products of polyisobutylenes and
monounsaturated
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acylating agents of the present invention may be represented by either Formula
A or
Formula B, as listed below:
RI RI
R2 R2
[Formula A] [Formula B]
wherein R1 is a polyisobutylene (PIB) chain; and R2 is a carboxyl-containing
group. This new approach allows for top tier engine performance with lower
than
conventional levels of detergents and wear inhibitors.
The R1 of Formula A and/or Formula B is a PIB chain. Suitable PIBs that
many constitute the chain may be any PIBs that have a number average weight of
about 200 to about 5000 Daltons, preferably from about 500 to about 4500
Daltons,
particularly preferably from about 1000 to about 3500 Daltons. An exemplary
lubricating oil composition of the present invention incorporates a PIB that
has a
number average molecular weight of about 2300 Daltons.
The R2 of Formula A and/or Formula B is a carboxyl-containing group derived
from a monocarboxylic acid, dicarboxylic acid, dicarboxylic acid anhydride,
anhydride-producing material, or derivatives thereof. Such materials may
include,
for example, acids, anhydrides, or acid esters. More specifically, such
materials may
include one or more selected from: (1) monounsaturated C4 to C20 dicarboxylic
acids,
wherein (a) the carboxyl groups are vicinyl (i.e., located on adjacent carbon
atoms),
and (b) at least one, preferably both, of said adjacent carbon atoms are part
of said
mono-unsaturation; (2) derivatives of (1) such as anhydrides and/or CI to Cio
alcohol-
derived monoesters or diesters of (1); (3) monounsaturated C3 to C20
monocarboxylic
acids wherein each of the carbon-carbon double bonds is conjugated with the
carboxyl
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CA 02615339 2007-12-18
group, i.e., is of the structure: -C=C-00-; and (4) derivatives of (3) such as
CI to Cio
alcohol-derived monoesters or diesters of (3). In certain embodiments, the R2
of
Formula A and/or Formula B can also be derived from a mixture comprising any
propo,rtions of 2 or more of materials (1) to (4). Such materials are also
termed
"monounsaturated acylating agents" herein. Upon reaction with the PIB
backbone,
the monounsaturation of each of the monocarboxylic acids, dicarboxylic acids,
anhydrides, or derivatives thereof becomes saturated. Thus, for example,
maleic
anhydride becomes backbone substituted succinic anhydride; acrylic acid
becomes
back-bone substituted propionic acid. Exemplary monounsaturated carboxylic
reactants include fumaric acid, itaconic acid, maleic acid, maleic anhydride,
chloromaleic acid, chloromaleic anhydride, acrylic acid, methacrylic acid,
crotonic
acid, cinnamic acid, and lower and intermediate alkyl (e.g., C1 to C10 alkyl)
acid esters
of the foregoing. Examples of suitable alkyl acid esters include methyl
maleate, ethyl
fumarate, methyl fumarate, and the like. A particularly preferred
monocarboxylic
acid-, dicarboxylic acid-, or anhydride-producing material is maleic
anhydride.
Accordingly, a preferred reaction product of a PIB and a monounsaturated
acylating
agent is a polyisobutylene succinic anhydride (PIBSA).
The reaction product of a PIB and a monounsaturated acylating agent of the
present invention can be prepared by known procedures. For example, an HR-PIB
precursor of Formula A and/or Formula B can be prepared by a cationic
polymerization process, at a temperature that is predetermined according to
the
desired molecular weight for the PIB oligomer. For example, a PIB that has an
average molecular weight of about 2300 Daltons can be prepared at a
temperature of
about 5 F. A catalyst such as BF3 is often used to advance the polymerization.
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CA 02615339 2014-05-27
Following the reaction, the catalyst is typically removed, for example, by
extracting
the catalyst dissolved in a hot distilled water phase. In another aspect of
the
polymerization process, the feed into the reactor may include materials such
as
hexanes and isopropanol. The unreacted residuals of reactive materials,
including the
unreacted isobutylene monomers, are often removed or purified from the PIB
oligomers according to known methods, such as, for example, by flashing in a
flash
drum and/or using an extraction column. Some HR-PIBs are also commercially
available, for example, under the trade name of GLISSOPALTM (by BASF ).
Reaction products of such HR-PIBs and monounsaturated acylating agents can
be prepared according to known methods. For example, The succinic anhydride
derivative of PIB (i.e., PIBSA) can be prepared in accordance with methods
described
in U.S. Patent Nos. 6,245,724, 6,933,351, 6,156,850, and others. Specifically,
a
PIBSA can be prepared using a catalyzed "thermal" or "ene" process, wherein
the
polyisobutylene is reacted with maleic anhydride at an elevated temperature in
the
presence of sulfonic acid or one or more other strong acid. This process is
capable of
producing PIBSAs with a range of apparent succinic ratios. Such ratios may be
adjusted to attain the desired apparent succinic ratios by modifying reaction
parameters such as, for example, the length of time it takes to inject the
sulfonic acid
or one or more strong acids into the reactor, the maleic anhydride:PIB charge
mole
ratio, and the reaction hold time. Persons skilled in the art would understand
that the
apparent succinic ratio is preferably in the range of between about 1 and
about 2,
preferably between about 1.2 to about 1.6, more
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CA 02615339 2007-12-18
preferably between about 1.3 and about 1.4. Various PIBSA products can also be
obtained from commercial vendors such as Chevron Oronite Company LLC.
Suitably, the reaction products of PIBs and monounsaturated acylating agents
may be present in the lubricating oil compositions of the present invention in
an
amount that is sufficient to provide substantially enhanced piston-cleanliness
and/or
maintain such cleanliness in internal combustion engines. By "substantially
enhanced," it is meant that the pistons are measurably cleaner when assessed
against
standards of various countries and regions, such as the ACEA standards in
Europe and
the JASO standards in Japan. Preferably, the amount of one or more reaction
products of PIBs and monounsaturated acylating agents is about 0.01 to about
5.00
wt.%, more preferably, about 0.50 to about 4.00 wt.%, particularly preferably,
about
1.00 wt.% to 2.50 wt.%. An exemplary lubricating oil composition of the
present
invention comprised about 2.00 wt.% of a PIBSA, wherein the PIB chain has a
number average molecular weight of about 2300 Daltons.
Metal-Containing Detergents
Metal-containing or ash-forming detergents function both as detergents to
reduce or remove deposits and as acid neutralizers or rust inhibitors, 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. The composition of 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
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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 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.
The acidic organic compounds useful in making the overbased compositions
of the present invention include carboxylic acids, sulfonic acids, phosphorus-
containing acids, phenols or mixtures thereof. Preferably, the acidic organic
compounds are carboxylic acids or sulfonic acids with sulfonic or thiosulfonic
groups
(such as hydrocarbyl-substituted benzenesulfonic acids), and hydrocarbyl-
substituted
salicylic acids.
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
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, fused or otherwise connected via
alkylene bridges. 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.
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In that case, salicylic acids are generally obtained in a diluent in admixture
with
uncarboxylated phenol.
Sulfonates can be prepared by using sulfonic acid in to sulfoniate alkyl-
substituted aromatic hydrocarbons such as those obtained from the
fractionation of
petroleum or those obtained from alkylation of aromatic hydrocarbons. Alkaryl
sulfonates usually contain from about 9 to about 80 or more carbon atoms,
preferably
from about 16 to about 60 carbon atoms per alkyl substituted aromatic moiety.
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.
The metal compounds useful in making the overbased salts are generally any
Group 1 or Group 2 metal compounds in the Periodic Table of the Elements. The
Group 1 metals of the metal compound include Group 1 a alkali metals (e.g.,
sodium,
potassium, lithium) as well as Group lb metals such as copper. The Group 1
metals
are preferably sodium, potassium, lithium and copper, more preferably sodium
or
potassium, and particularly preferably sodium. The Group 2 metals of the metal
base
include the Group 2a alkaline earth metals (e.g., magnesium, calcium,
strontium,
barium) as well as the Group 2b metals such as zinc or cadmium. Preferably the
Group 2 metals are magnesium, calcium, barium, or zinc, more preferably
magnesium
or calcium, particularly preferably calcium.
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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 with the lubricating oils of the
present
invention may be low overbased (i.e., Total Base Number (TBN) below about
100).
The TBN 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. The overbased
detergents
suitable for use with the lubricating oils of the present invention may
alternatively be
high overbased (i.e., TBN above about 100). The TBN of such a high-overbased
detergent may be from about 150 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
TBN of about 17, and a high-overbased calcium sulfurized phenate with a TBN of
about 260 are two exemplary overbased detergents in the lubricating oil
compositions
of the present invention. The lubricating oil compositions of the present
invention
may comprise more than one overbased detergents, which may be all low-TBN
detergents, all high-TBN detergents, or a mix of the those two types.
In the lubricant oil compositions of the present invention, the amount of the
overbased detergent(s), if present, may be about 0.05 to about 16 mM, or about
3 to
about 15 mM, or about 4 to about 14 mM. In an exemplary embodiment of the
present invention, about 4 mM of a low-TBN detergent plus about 10 mM of a
high-
TBN detergent are present in the lubricating oil composition.
Suitable detergents for the lubricating oil compositions of the present
invention also include "hybrid" detergents such as, for example,
phenate/salicylates,
sulfonate/phenates, sulfonate/salicylates, sulfonates/phenates/salicylates,
and the like.
Hybrid detergents have been described, for example, in U.S. Patent Nos.
6,153,565,
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CA 02615339 2014-05-27
6,281,179, 6,429,178, and 6,429,179.
Ashless Dispersants
Dispersants 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 TBN of a lubricating oil
composition to
which they are added, without introducing additional sulfated ash. 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.
Typical dispersants include, but are not limited to, amines, alcohols, amides,
or ester polar moieties attached to the polymer backbones via bridging groups.
The
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.
"Carboxylic dispersants" are reaction products of carboxylic acylating agents
(acids, anhydrides, esters, etc.) comprising at least 34 and preferably at
least 54
carbon atoms with nitrogen containing compounds (such as amines), organic
hydroxy
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CA 02615339 2007-12-18
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.
Succinimide dispersants are a type of carboxylic dispersants. 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.
Succinic-based dispersants have a wide variety of chemical structures, which
may be represented by the formula:
,0
// C -CH-R1
Ri-CH-C
N-IR2 -NH 1 -R2 -N
x
2-C hC-CH2
0 0
wherein each R1 is independently a hydrocarbyl group, such as a polyoiefin-
derived
group. Typically the hydrocarbyl group is an alkyl group, such as a
polyisobutyl
group. Alternatively expressed, the R1 groups can contain about 40 to about
500
carbon atoms, and these atoms may be present in aliphatic forms. R2 is an
alkylene
group, commonly an ethylene (C21-14) group. Succinimide dispersants have been
more
fully described in, for example, U.S. Patent Nos. 4,234,435, 3,172,892 and
6,165,235.
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CA 02615339 2014-05-27
The polyalkenes from which the substituent groups are derived are typically
homopolymers and interpolymers of polymerizable olefin monomers of 2 to 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.
Succinimide dispersants are referred to as such since they normally contains
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 normally liquid and substantially inert organic liquid
solvent/diluent.
The reaction temperature is generally in the range of about 80 C up to the
decomposition temperature of the mixture or the product, which typically falls
between about 100 C and about 300 C. Additional details and examples of the
procedures for preparing the succinimide dispersants of the present invention
have
been described in, for example, U.S. Patent Nos. 3,172,892, 3,219,666,
3,272,746,
4,234,435, 6,440,905 and 6,165,235.
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 thereof have been described, for
example, in U.S. Patent Nos. 3,275,554, 3,438,757, 3,454,555, 3,565,804, and
the
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CA 02615339 2014-05-27
like.
Suitable ashless dispersants may further include "Mannich dispersants," which
are reaction products of alkyl phenols in which the alkyl group contains at
least 30
carbon atoms with aldehydes (especially formaldehyde) and amines (especially
polyalkylene polyamines). These dispersants have been described, for example,
in
U.S. Patent Nos. 3,036,003, 3,586,629, 3,591,598, 3,980,569, and the like.
Suitable ashless dispersants may even include post-treated dispersants, which
are obtained by reacting carboxylic, amine or Mannich dispersants with
reagents such
as dimercaptothiazoles, urea, thiourea, carbon disulfide, aldehydes, ketones,
carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitrile
epoxides, boron
compounds and the like. Post-treated dispersants have been described, for
example,
in U.S. Patent Nos. 3,329,658, 3,449,250, 3,666,730, and the like.
Suitable ashless dispersants may 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. Polymeric
dispersants have been described, for example, in U.S. Patent Nos. 3,329,658,
3,449,250, 3,666,730, and the like.
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CA 02615339 2007-12-18
In an exemplary lubricating oil composition of the present invention, a
bissuccinimide treated with ethylene carbonate was used as the ashless
dispersant.
The dispersant(s) of the present invention are preferably non-polymeric (e.g.,
are
mono- or bissuccinimides).
The ashless dispersant is suitably present in an amount of about 0.5 to about
10.0 wt.%, preferably about 3.0 to about 7.0 wt.%. An exemplary lubricating
oil
composition of the present invention comprises an ethylene-carbonate treated
bissuccinimide dispersant derived from a PIBSA wherein the PIB chain has a
number
average molecular weight of about 2300 Daltons (PIBSA 2300) in an amount of
about
6.5 wt.%. Another lubricating oil composition of the present invention
comprises a
similar dispersant in an amount of about 6.0 wt.%, in combination with another
borated bissuccinimide derived from another PIBSA wherein the PIB chain has a
number average molecular weight of about 1300 Daltons (PIBSA 1300).
Preferably,
the lubricating oil composition comprises from about 0.01 to about 0.35 wt.%,
preferably from about 0.05 to about 0.25 wt.%, particularly preferably from
about
0.08 to about 0.12 wt.% of total nitrogen from dispersant.
Other Additives
The lubricating oil compositions of the present invention may optionally
comprise various other additives, including, but not limited to, antiwear
agents,
friction modifiers, antioxidants, corrosion inhibitors, viscosity index
improvers, and
other additives commonly used to lubricate internal combustion engines.
Antiwear Agents
Dihydrocarbyl dithiophosphate metal salts are frequently used as antiwear and
antioxidant agents. The metal may be an alkali or alkaline earth metal, or
aluminum,
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CA 02615339 2007-12-18
=
lead, tin, molybdenum, manganese, nickel or copper. The zinc salts are the
most
commonly used in lubricating oil in amounts of about 0.1 to about 10 wt.%,
preferably about 0.2 to about 2 wt.%, based upon the total weight of the
lubricating oil
comppsition. They may be prepared in accordance with known techniques by first
forming a dihydrocarbyl dithiophosphoric acid (DDPA), usually by reaction of
one or
more alcohol or a phenol with P2S5 and then neutralizing the formed DDPA with
a
zinc compound. For example, a dithiophosphoric acid may be made by reacting
mixtures of primary and secondary alcohols. Alternatively, multiple
dithiophosphoric
acids can be prepared where the hydrocarbyl groups on one are entirely
secondary in
character and the hydrocarbyl groups on the others are entirely primary in
character.
To make the zinc salt, any basic or neutral zinc compound could be used but
the
oxides, hydroxides and carbonates are most often employed. Commercial
additives
frequently contain an excess of zinc due to the use of an excess of the basic
zinc
compound in the neutralization reaction.
The preferred oil-soluble zinc dialkyldithiophosphates may be produced from
dialkykyldithiophosphoric acids of the formula:
RO As
Pc
SH
OR
The hydroxyl alkyl compounds from which the dialkyldithiophosphoric acids
are derived can be represented generically by the formula ROH or R'OH, wherein
R
or R' is alkyl or substituted alkyl, preferably branched or non-branched alkyl
containing 3 to 30 carbon atoms. More preferably, R or R' is a branched or non-
branched alkyl containing 3 to 8 carbon atoms.
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CA 02615339 2007-12-18
Mixtures of hydroxyl alkyl compounds may also be used. These hydroxyl
alkyl compounds need not be monohydroxy alkyl compounds. The
dialkyldithiophosphoric acids may thus be prepared from mono-, di-, tri-,
tetra-, and
other polyhydroxy alkyl compounds, or mixtures of two or more of the
foregoing.
Preferably, the zinc dialkyldithiophosphate derived from only primary alkyl
alcohols
is derived from a single primary alcohol. Preferably, that single primary
alcohol is 2-
ethylhexanol. Preferably, the zinc dialkyldithiophosphate derived from only
secondary alkyl alcohols. Preferably, that mixture of secondary alcohols is a
mixture
of 2-butanol and 4-methyl-2-pentanol.
The phosphorus pentasulfide reactant used in the dialkyldithiophosphoric acid
formation step may contain minor amounts of any one or more of P2S3, P4S3,
P4S7, or
P4S9. Compositions as such may also contain minor amounts of free sulfur.
Although the lubricating oil compositions of the present invention are capable
of providing excellent antiwear performance in the presence of amounts of zinc
dialkyldithiophosphate providing greater amounts of phosphorus, the improved
performance of the inventive lubricating oil compositions are particular
apparent in
low SAPS formulations which, by definition, have phosphorus levels of no
greater
than about 0.08 wt.%. Therefore, lubricating oil compositions of the present
invention contains less than about 0.08 wt.% of phosphorus, more preferably
from
about 0.03 to about 0.075 wt.% of phosphorus. An exemplary lubricating oil
composition of the present invention comprises about 11.5 mM zinc
dialkyldithiophosphate.
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Viscosity Index Modifiers
The viscosity index of the base stock is increased, or improved, by
incorporating therein certain polymeric materials that function as viscosity
modifiers
(VM), or viscosity index improvers (VII). Generally, polymeric materials
useful as
viscosity modifiers are those having number average molecular weights (Mn) of
from
about 5,000 to about 250,000, preferably from about 15,000 to about 200,000,
more
preferably from about 20,000 to 150,000 Daltons. These viscosity modifiers can
optionally be grafted with grafting materials such as, for example, maleic
anhydride,
and the grafted material can be reacted with, for example, amines, amides,
nitrogen-
containing heterocyclic compounds or alcohol, to form multifunctional
viscosity
modifiers (dispersant-viscosity modifiers).
Exemplary lubricating oil compositions of the present invention employ
various polyalkyl methacrylate copolymers, which may or may not be grafted by
maleic anhydride. The copolymers may be employed at an amount from about 0.1
to
about 10 wt.% of the lubricating oil composition.
Friction Modifiers
Lubricating oil compositions of the present invention further comprise a
sulfur-containing molybdenum compound. Certain sulfur-containing organo-
molybdenum compounds are known to function as friction modifiers in
lubricating oil
compositions, while also providing antioxidant and antiwear credits to a
lubricating
oil composition. Examples of such oil soluble organo-molybdenum compounds
include dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates,
thioxanthates, sulfides, and the like, and mixtures thereof.
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CA 02615339 2007-12-18
Oil-soluble or dispersible trinuclear molybdenum compounds can be prepared
by reacting in the appropriate liquid(s)/solvent(s) a molybdenum source such
as
(NH4)2Mo3Si3n(H20), where n varies between 0 and 2 and includes non-
stoichiometric values, with a suitable ligand source such as a
tetralkylthiuram
disulfide. Other oil-soluble or dispersible trinuclear molybdenum compounds
can be
formed during a reaction in the appropriate solvent(s) of a molybdenum source,
such
as of (NF14)2M03S13.n(H20), a ligand source such as tetralkylthiuram
disulfide,
dialkyldithiocarbamate, or dialkyldithiophosphate, and a sulfur-abstracting
agent such
as cyanide ions, sulfite ions, or substituted phosphines. Alternatively, a
trinuclear
molybdenum-sulfur halide salt such as [M']2[M03S7A6], where M' is a counter
ion,
and A is a halogen such as Cl, Br, or I, may be reacted with a ligand source
such as a
dialkyldithiocarbamate or dialkyldithiophosphate in the appropriate
liquid(s)/solvent(s) to form an oil-soluble or dispersible trinuclear
molybdenum
compound. The appropriate liquid/solvent may be, for example, aqueous or
organic.
The terms "oil-soluble" or "dispersible" used herein do not necessarily
indicate
that the compounds or additives are soluble, dissolvable, miscible, or capable
of being
suspended in the oil in all proportions. These do mean, however, that they
are, for
instance, soluble or stably dispersible in oil to an extent sufficient to
exert their
intended effect in the environment in which the oil is employed. Moreover, the
additional incorporation of other additives may also permit incorporation of
higher
levels of a particular additive, if desired.
An exemplary lubricating oil composition of the present invention employs a
molybdenum succinimide complex as friction modifier. Of the lubricating oil
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CA 02615339 2007-12-18
composition, the molybdenum complex may constitute from about 0.15 to about
0.55
wt.%, preferably from about 0.28 to about 0.45 wt.% .
Antioxidants
, Oxidation inhibitors or antioxidants reduce the tendency of mineral oils to
deteriorate in service. Such oxidation inhibitors include hindered phenols,
alkaline
earth metal salts of alkylphenolthioesters having preferably C5 to C12 alkyl
side
chains, calcium nonylphenol sulfide, oil soluble phenates and sulfurized
phenates,
phosphosulfurized or sulfurized hydrocarbons or esters, phosphorous esters,
metal
thiocarbamates, oil soluble copper compounds as described in, for example,
U.S.
Patent No. 4,867,890.
Aromatic amines having at least two aromatic groups attached directly to the
nitrogen constitute another class of compounds that is frequently used for
antioxidancy. Typical oil soluble aromatic amines having at least two aromatic
groups
attached directly to one amine nitrogen contain from 6 to 16 carbon atoms. The
amines may contain more than two aromatic groups. The aromatic rings are often
substituted by one or more substituents selected from, for example, alkyl,
cycloalkyl,
alkoxy, aryloxy, acyl, acylamino, hydroxy, and nitro groups.
Lubricating oil compositions in accordance with the present invention
preferably contain from about 0.05 to about 5.00 wt.%, more preferably from
about
0.10 to about 3.00 wt.%, and particularly preferably from about 0.20 to about
0.80
wt.% of phenolic antioxidant, aminic antioxidant, or a combination thereof,
based on
the total weight of the lubricating oil composition. An exemplary lubricating
oil
composition of the present invention comprises about 0.40 wt.% of an
antioxidant that
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CA 02615339 2007-12-18
is di-C8-diphenylamine. Another exemplary lubricating oil composition of the
present
invention comprises about 0.30 wt.% of a dinonyl diphenylamine as an
antioxidant.
Additional additives may be incorporated into the compositions of the
invention to satisfy the particular performance requirements associated with
low
SAPS applications in internal combustion engines. Examples of such other
additives
include, for example, rust inhibitors, anti-foaming agents, and seal fixes or
seal
pacifiers.
Rust inhibitor or anticorrosion agents may be a nonionic polyoxyethylene
surface active agent. Nonionic polyoxyethylene surface active agents include,
but are
not limited to, 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 mono-oleate, and polyethylene
glycol
monooleate. Rust inhibitors or anticorrosion agents may also be other
compounds,
which include, for example, 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 alcohols, and phosphoric esters. An
exemplary
lubricating oil composition of the present invention comprises a calcium
stearate salt.
Foam inhibitors typically include alkyl methacrylate polymers and dimethyl
silicone polymers. Exemplary compositions of the present invention contain
silicon-
based foam inhibitors in amounts ranging from about 5 to about 40 ppm,
preferably
from about 8 to about 35 ppm, more preferably from about 10 to about 25 ppm,
based
on the total weight of the composition.
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CA 02615339 2007-12-18
Seal fixes are also termed seal swelling agents or seal pacifiers. They are
often employed in lubricant or additive compositions to insure proper
elastomer
sealing, and prevent premature seal failures and leakages. Seal swell agents
may be,
for example, oil-soluble, saturated, aliphatic, or aromatic hydrocarbon esters
such as
di-2-ethylhexylphthalate, mineral oils with aliphatic alcohols such as
tridecyl alcohol,
triphosphite ester in combination with a hydrocarbonyl-substituted phenol, and
di-2-
ethylhexylsebacate.
Some of the above-mentioned additives can provide a multiplicity of effects;
thus for example, a single additive may act as a dispersant as well as an
oxidation
inhibitor. These multifunctional additives are well known.
When lubricating compositions contain one or more of the above-mentioned
additives, each additive is typically blended into the base oil in an amount
that enables
the additive to provide its desired function. It may be desirable, although
not
essential, to prepare one or more additive concentrates comprising additives
(concentrates sometimes being referred to as additive packages) whereby
several
additives can be added simultaneously to the oil to form the lubricating oil
composition. The final composition may employ from about 5 to about 30 wt.%,
preferably about 5 to about 25 wt.%, typically about 10 to about 20 wt.% of
the
concentrate, the remainder being the oil of lubricating viscosity. The
components can
be blended in any order and can be blended as combinations of components.
This invention will be further understood by reference to the following
examples, which are not to be considered as limitative of its scope.
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CA 02615339 2014-05-27
EXAMPLES
The following examples are provided to illustrate the present invention
without limiting it. While the present invention has been described with
reference to
specific embodiments, this application is intended to encompass those various
changes and substitutions that may be made by those skilled in the art without
departing from the scope of the appended claims.
Example 1:
Oil A was prepared and tested for piston cleanliness and tendency to piston
ring sticking according to the VolkswagenTM Turbocharged DI test, a European
passenger car diesel engine test (CEL-L-78-T-99), which is part of the ACEA B
specification promulgated by the European Automobile Manufacturers Association
in
2004. This test was used to simulate repeated cycles of high-speed operation
followed by idling. A VolkswagenTM 1.9 liter, inline, four-cylinder
turbocharged
direct injection automotive diesel engine (VW TDi) was mounted on an engine
dynamometer stand. A 54-hour, 2-phased procedure that cycles between 30
minutes
of 40 C oil sump at idle and 150 minutes of 145 C oil sump at full power (4150
rpm)
was carried out without interim oil top-ups. After the procedure, the pistons
were
rated for carbon and lacquer deposits, as well for groove carbon filling. The
piston
rings were evaluated for ring sticking. The piston cleanliness and ring
sticking of VW
TDi engine tests were also carried out with Comparative Example Oil B. The
results
are given in Table 1.
Oil A shows a distinct and surprising improvement over Comparative Oil B in
the VW TDi piston cleanliness and ring sticking test.
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CA 02615339 2007-12-18
Oil A: A lubricating oil composition was prepared comprising about 1.50
wt.% of a polyisobutylene succinic anhydride derived from a polyisobutylene
having
a number average molecular weight of about 2300 Daltons, an ethylene carbonate-
treated bissuccinimide dispersant, a low-overbased calcium sulfonate
detergent, an
overbased sulfurized and carbonated calcium phenate, a zinc dihydrocarbyl
dithiophosphate, a moly succinimide, a di-C8-diphenylamine antioxidant, a
silicon-
based foam inhibitor, an ethylene polymer, a rust inhibitor, and mineral oil
base
stocks. Oil A had a sulfated ash content of about 0.78 wt.%, nitrogen content
of about
0.092 wt.%, sulfur content of about 0.183 wt.%, and phosphorus content of
about
0.071 wt.%.
Comparative Example Oil B: the formulation of Oil A was duplicated except
that Oil B does not contain PIBSA 2300. Oil B had a sulfated ash content of
about
0.78 wt.%, nitrogen content of about 0.092 wt.%, sulfur content of 0.183 wt.%,
and
phosphorus content of 0.071 wt.%.
Table 1: Test type: VWTDI2 SAE: 5W30
Table 1: Test type: VWTDI2 SAE: 5W30
Components Oil A Oil B
=
PIBSA 2300 1.50 wt.% None
Bissuccinimide dispersant 6.50 wt.% 6.50 wt.%
Low-TBN calcium sulfonate 4 mM 4 mM
Calcium Stearate 35 mM 35 mM
High-TBN sulfurized & carbonated calcium phenate 10 mM 10 mM
Zinc dialkyldithiophosphate " 11.5 mM 11.5 mM
Moly succinimide 0.37 wt.% 0.37 wt.%
Di-C8-diphenylamine 0.40 wt.% 0.40 wt.%
Silicon-based foam inhibitor 25 ppm 25 ppm
Ethylene polymer 0.84 wt.% 0.82 wt.%
Diluent Oil 0.71 wt.% 0.71 wt.%
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CA 02615339 2007-12-18
Length of test 54 hours 54 hours
P-MER AVG:G1-3&L1&2 63 57
PCInRL206Avg 66 66
VW Lmt-PCLN Combnd AV 67 67
AvRStk (8R-4P) ASF (0-10) 0.62 0.93
MxRStk (1Rg) ASF (0-10) 2.5 5
Grvs. 1st RStk, AV, ASF 1.25 1.88
Grvs, 1st RStk, MX, ASF 2.5 5
Grvs. 2nd RStk, MX, ASF O 0
# of Rings with ASF >=2.5 2 3
Scoring (*) Pass ACEA B4 or Fail ACEA B4 & B5
B5
= The pass/fail score according to the ACEA standards B4 and B5 are listed
in the following Table 1.1:
Table 1.1
ACEA B4 limits ACEA B5 limits
P-MER Avg 63 (? RL206 - 3) 66 (?_. RL206)
# Rngs w/ASF > 2.5 < 1.2 < 1.2
Grvs. 1st RStk, MX. ASF < 2.5 < 2.5
Grvs. 2nd Rstk, MX. ASF < 0.0 < 0.0
Example 2
Oil C was prepared and tested for piston cleanliness and tendency to piston
ring sticking according to the Volkswagen Turbocharged DI test described
above.
The Piston cleanliness and ring sticking of VW TDi engine tests were also
carried out
with Comparative Example Oil D. The results are given in Table 3. The results
were
scored against the more stringent Japanese piston cleanliness standards (JAS
C2 test
standards), wherein the P-MER AVG has a minimum value of 65.
Oil C shows a distinct and surprising improvement over Comparative Oil D in
the VW TDi piston cleanliness and ring sticking test.
Oil C: A lubricating oil composition was prepared comprising about 2.00
wt.% of a succinic anhydride derivative of polyisobutylene having a number
average
molecular weight of about 2300, an ethylene carbonate-treated bissuccinimide
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CA 02615339 2007-12-18
=
dispersant that is a mixture of one derived from PIBSA 2300 and another
derived
from PIBSA 1300 (i.e., the polyisobutylene precursor had a number average
molecular weight of about 1300 Daltons), a low-overbased calcium sulfonate
detergent, an overbased sulfurized and carbonated calcium phenate, a mixture
of
primary and secondary zinc dihydrocarbyl dithiophosphate, a moly succinimide,
a
triborate wear inhibitor, a viscosity improver, a di-C8-diphenylamine
antioxidant, a
silicon-based foam inhibitor, and mineral oil base stocks. Oil C had a
sulfated ash
content of about 0.59 wt.%, nitrogen content of about 0.113 wt.%, sulfur
content of
about 0.213 wt.%, and phosphorus content of 0.074 wt.%.
Comparative Example Oil D: The formulation of Oil C was duplicated except
that Oil F did not contain PIBSA 2300. Oil D has a sulfated ash content of
about 0.59
wt.%, nitrogen content of about 0.113 wt.%, sulfur content of 0.213 wt.%, and
phosphorus content of 0.074 wt.%.
Table 3: Test: VWTDI2 SAE: 0W30
Components Oil C Oil D
PIBSA 2300 2.00 wt.% None
Bissuccinimide dispersant derived from PIBSA 2300 6.00 wt.% 6.00
wt.%
Bissuccinimide dispersant derived from PIBSA 1300 1.80 wt.% 1.80
wt.%
Low-TBN calcium sulfonate 7.5 mM 7.5 mM
High-TBN sulfurized and carbonated calcium phenate 17.5 mM = 17.5
mM
10 and 2 Zinc diallcyldithiophosphate mix 12.0 mM 12.0 mM
Moly succinimide 0.30 wt.% 0.30
wt.%
Dinonyl diphenylamine 0.30 wt.% 0.30
wt.%
Silicon-based foam inhibitor 10 ppm 10
ppm
Triborate wear/oxidation inhibitor 0.20 wt.% 0.20
wt.%
Viscosity improver polymer 5.80 wt.% 7.0
wt.%
Diluent Oil 0.71 wt.% 0.71
wt.%
Length of test 54 hours 54
hours
P-MER AVG:G1-3&L1&2 73 65
PCInRL148Avg , 62 62
PCInRL206Avg 65 65
VW Lmt-PCLN Combnd AV 66 66
AvRStk (8R-4P) ASF (0-10) 0 0
Grvs, 1st RStk, MX, ASF 0 0
Grvs. 2nd RStk, MX, ASF 0 0
# of Rings with ASF >=2.5 0 0
Scoring (**) Pass JASO C2
Borderline pass
JASO C2
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CA 02615339 2007-12-18
** The pass/fail scores were given according to the JASO piston cleanliness
standard C2
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