U.S. patent application number 10/727941 was filed with the patent office on 2005-06-09 for lubricating oil compositions.
Invention is credited to Emert, Jacob, Gutierrez, Antonio, Minotti, Michael, Ritchie, Andrew J. D..
Application Number | 20050124509 10/727941 |
Document ID | / |
Family ID | 34465775 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050124509 |
Kind Code |
A1 |
Gutierrez, Antonio ; et
al. |
June 9, 2005 |
Lubricating oil compositions
Abstract
Soot induced kinematic viscosity increase of lubricating oil
compositions for diesel engines can be ameliorated by combined use
of derivatized high molecular weight olefin copolymers and high
molecular weight nitrogen-containing dispersant.
Inventors: |
Gutierrez, Antonio;
(Mercerville, NJ) ; Emert, Jacob; (Brooklyn,
NY) ; Ritchie, Andrew J. D.; (Chatham, NJ) ;
Minotti, Michael; (Summit, NJ) |
Correspondence
Address: |
Infineum USA L.P.
Law Department
1900 East Linden Avenue
P.O. Box 710
Linden
NJ
07036-0710
US
|
Family ID: |
34465775 |
Appl. No.: |
10/727941 |
Filed: |
December 4, 2003 |
Current U.S.
Class: |
508/291 |
Current CPC
Class: |
C10N 2030/44 20200501;
C10M 2207/026 20130101; C10M 2203/1006 20130101; C10N 2010/04
20130101; C10N 2040/252 20200501; C10M 2205/024 20130101; C10N
2030/41 20200501; C10N 2020/01 20200501; C10M 2217/06 20130101;
C10N 2020/04 20130101; C10M 2203/1065 20130101; C10M 2207/028
20130101; C10N 2030/42 20200501; C10N 2030/45 20200501; C10M
2223/045 20130101; C10M 169/048 20130101; C10N 2030/04 20130101;
C10N 2030/43 20200501; C10M 169/044 20130101; C10M 2207/289
20130101; C10N 2030/041 20200501; C10M 2205/022 20130101; C10M
2215/28 20130101; C10N 2060/09 20200501; C10M 161/00 20130101; C10M
2203/1025 20130101; C10N 2030/02 20130101; C10M 2205/024 20130101;
C10M 2205/022 20130101; C10M 2205/024 20130101; C10M 2205/022
20130101; C10N 2060/09 20200501; C10M 2205/024 20130101; C10M
2205/022 20130101; C10N 2060/09 20200501 |
Class at
Publication: |
508/291 |
International
Class: |
C10M 133/46 |
Claims
What is claimed is:
1. A lubricating oil composition comprising a major amount of at
least one of a Group I, Group II Group III mineral oil of
lubricating viscosity, or a mixture thereof; a minor amount of one
or more high molecular weight polymers comprising olefin copolymers
containing at least one moiety selected from alkyl amine, alkyl
amide, aryl amine or aryl amide groups, nitrogen-containing
heterocyclic groups or ester linkages; and a minor amount of
dispersant comprising one or more nitrogen-containing dispersants
that are the reaction product of a polyalkenyl-substituted mono- or
dicarboxylic acid, anhydride or ester and a polyamine; at least one
of the nitrogen-containing dispersants having a polyalkenyl moiety
with a number average molecular weight of at least about 1800, and
from about 1.3 to 1.7 mono- or dicarboxylic acid producing moieties
per polyalkenyl moiety; dispersant contributing at least about 0.08
wt. % of nitrogen to the lubricating oil composition.
2. A lubricating oil composition of claim 1, wherein said
polyalkenyl moiety with a number average molecular weight of from
about 1800 to about 3000.
3. A lubricating oil composition of claim 1, wherein the high
molecular weight olefin copolymer comprises an ethylene-propylene
copolymer grafted with maleic anhydride and derivatized with an
aryl amine.
4. A lubricating oil composition of claim 2, wherein the total
amount of diaryl amine moieties in the lubricating oil composition
is from about 0.5 to 5 mmols/kg, and greater than about 50% of said
diaryl amine moieties are derived from molecules having a number
average molecular weight of greater than about 5000.
5. A lubricating oil composition of claim 1, further comprises from
about 6 to about 50 mmols of phenate surfactant per kilogram of
finished lubricating oil.
6. A lubricating oil composition of claim 5, wherein said
dispersant comprises from about 1.3 to about 1.6 mono- or
di-carboxylic acid producing moieties per polyalkenyl moiety, and
has a boron content of less than about 20 ppm.
7. A lubricating oil composition of claim 1, having a sulfated ash
content of less than about 0.5 wt. %.
8. A lubricating oil composition comprising a major amount of at
least one of a Group I, Group II and/or Group III mineral oil of
lubricating viscosity, or a mixture thereof; a minor amount of one
or more high molecular weight polymers comprising olefin copolymers
containing at least one moiety selected from alkyl amine, alkyl
amide, aryl amine or aryl amide groups, nitrogen-containing
heterocyclic groups or ester linkages; and a minor amount of
dispersant comprising one or more nitrogen-containing dispersants
that are the reaction product of a polyalkenyl-substituted mono- or
dicarboxylic acid, anhydride or ester and a polyamine; at least one
of the nitrogen-containing dispersants having a polyalkenyl moiety
with a number average molecular weight of at least about 1800, and
is derived from a polyalkene moiety having a molecular weight
distribution (M.sub.w/M.sub.n) of from about 1.5 to about 2; said
dispersant being essentially chlorine-free.
9. A lubricating oil composition of claim 8, wherein said
polyalkenyl moiety with a number average molecular weight of from
about 1800 to about 3000.
10. A lubricating oil composition of claim 8, wherein said
dispersant contributes at least about 0.08 wt. % of nitrogen to the
lubricating oil composition.
11. A lubricating oil composition of claim 8, wherein the high
molecular weight olefin copolymer comprises an ethylene-propylene
copolymer grafted with maleic anhydride and derivatized with an
aryl amine.
12. A lubricating oil composition of claim 11, wherein the total
amount of diaryl amine moieties in the lubricating oil composition
is from about 0.5 to 5 mmols/kg, and greater than about 50% of said
diaryl amine moieties are derived from molecules having a number
average molecular weight of greater than about 5000.
13. A lubricating oil composition of claim 8, further comprises
from about 6 to about 50 mmols of phenate surfactant per kilogram
of finished lubricating oil.
14. A lubricating oil composition of claim 8, wherein said
dispersant comprises from about 1.3 to about 1.6 mono- or
di-carboxylic acid producing moieties per polyalkenyl moiety, and
has a boron content of less than about 20 ppm.
15. A lubricating oil composition of claim 8, having a sulfated ash
content of less than about 0.5 wt. %.
16. A lubricating oil composition of claim 8, having a sulfur
content less than about 0.3 wt. %, a sulfated ash content of less
than about 0.5 wt. %, and a chlorine content of less than about 50
ppm.
17. A lubricating oil composition of claim 8, wherein the
functionalized, high molecular weight olefin molecule is derived
from an amorphous ethylene-propylene copolymer, or a blend of an
amorphous and a semi-crystalline ethylene-propylene copolymer with
an SSI of from about 5 to about 30, produced by simultaneously
shearing and functionalizing higher molecular weight
ethylene-propylene copolymers, with maleic anhydride, in an
extruder.
18. A lubricating oil composition of claim 17, wherein said
semi-crystalline ethylene-propylene copolymer has a tapered
stricture and is produced in a tubular reactor.
19. A method of operating a diesel engine, which method comprises
the step of lubricating said engine with a lubricating oil
composition of claim 1.
20. The method of claim 19, wherein said diesel engine is provided
with an exhaust gas recirculation system.
21. A method of operating a diesel engine, which method comprises
the step of lubricating said engine with a lubricating oil
composition of claim 8.
22. The method of claim 21, wherein said diesel engine is provided
with an exhaust gas recirculation system.
Description
[0001] The present invention relates to lubricating oil
compositions. More specifically, the present invention is directed
to lubricating oil compositions that provide improved lubricant
performance in highly sooted environments, such as those present in
heavy duty diesel (HDD) engines provided with exhaust gas
recirculation (EGR) systems.
BACKGROUND OF THE INVENTION
[0002] Environmental concerns have led to continued efforts to
reduce the NO.sub.x emissions of compression ignited (diesel)
internal combustion engines. The latest technology being used to
reduce the NO.sub.x emissions of diesel engines is known as exhaust
gas recirculation or EGR. EGR reduces NO.sub.x emissions by
introducing non-combustible components (exhaust gas) into the
incoming air-fuel charge introduced into the engine combustion
chamber. This reduces peak flame temperature and NO.sub.x
generation. In addition to the simple dilution effect of the EGR,
an even greater reduction in NO.sub.x emission is achieved by
cooling the exhaust gas before it is returned to the engine. The
cooler intake charge allows better filling of the cylinder, and
thus, improved power generation. In addition, because the EGR
components have higher specific heat values than the incoming air
and fuel mixture, the EGR gas further cools the combustion mixture
leading to greater power generation and better fuel economy at a
fixed NO.sub.x generation level.
[0003] Diesel fuel contains sulfur. Even "low-sulfur" diesel fuel
contains 300 to 400 ppm of sulfur. When the fuel is burned in the
engine, this sulfur is converted to SO.sub.x. In addition, one of
the major by-products of the combustion of a hydrocarbon fuel is
water vapor. Therefore, the exhaust stream contains some level of
NO.sub.x, SO.sub.x and water vapor. In the past, the presence of
these substances has not been problematic because the exhaust gases
remained extremely hot, and these components were exhausted in a
disassociated, gaseous state. However, when the engine is equipped
with an EGR, and particularly when the exhaust gas is mixed with
cooler intake air and recirculated through the engine, the water
vapor can condense and react with the NO.sub.x and SO.sub.x
components to form a mist of nitric and sulfuric acids in the EGR
stream. This phenomenon is further exacerbated when the EGR stream
is cooled before it is returned to the engine.
[0004] In the presence of these acids, it has been found that soot
levels in lubricating oil compositions build rapidly, and that
under said conditions, the kinematic viscosity (kv) of lubricating
oil compositions increase to unacceptable levels, even in the
presence of relatively small levels of soot (e.g., 3 wt. % soot).
Because increased lubricant viscosity adversely affects
performance, and can even cause engine failure, the use of an EGR
system requires more frequent lubricant replacement. It has been
found that the simple addition of an additional amount of
dispersant does not adequately address the problem.
[0005] Therefore, it would be advantageous to identify lubricating
oil compositions that better perform in HDD engines, particularly
those equipped with EGR systems. Surprisingly, it has been found
that by using, in combination, selected nitrogen-containing
dispersants and high molecular weight functionalized olefinic
polymers or copolymers, rapid increases in lubricant viscosity
associated with high soot levels can be ameliorated.
SUMMARY OF THE INVENTION
[0006] In accordance with a first aspect of the invention, there is
provided a lubricating oil composition comprising a major amount of
at least one of a Group I, Group II and/or Group III mineral oil of
lubricating viscosity; a minor amount of one or more high molecular
weight polymers comprising olefin copolymers containing alkyl or
aryl amine or amide groups, nitrogen-containing heterocyclic groups
or ester linkages; and a minor amount of dispersant comprising one
or more nitrogen-containing dispersants that are the reaction
product of a polyalkenyl-substituted mono- or dicarboxylic acid,
anhydride or ester and a polyamine; at least one the
nitrogen-containing dispersants having a polyalkenyl moiety with a
number average molecular weight of at least about 1800, and from
about 1.3 to 1.7 mono- or dicarboxylic acid producing moieties per
polyalkenyl moiety; the one or more nitrogen-containing dispersants
contributing at least 0.08 wt. % of nitrogen to the lubricating oil
composition.
[0007] In accordance with a second aspect of the invention, there
is provided a lubricating oil composition, as described in the
first aspect, wherein the high molecular weight olefin copolymer
comprises an ethylene-propylene copolymer grafted with maleic
anhydride and derivatized with an aryl amine.
[0008] In accordance with a third aspect of the invention, there is
provided a lubricating oil composition, as described in the first
or second aspect, wherein the total amount of diaryl amine moieties
in the lubricating oil composition is from about 0.5 to 5 mmols/kg,
with greater than 50% of said diaryl amine moieties being
introduced via molecules having a molecular weight of greater than
about 5000.
[0009] In accordance with a fourth aspect of the invention, there
is provided a lubricating oil composition, as described in the
first, second or third aspect, wherein the lubricating oil
composition further comprises from about 6 to about 50 mmols of
phenate surfactant per kilogram of finished lubricating oil.
[0010] In accordance with a fifth aspect of the invention, there is
provided a lubricating oil composition, as described in the first,
second, third or fourth aspect, wherein said dispersant comprises
from about 1.3 to about 1.6 mono- or di-carboxylic acid producing
moieties per polyalkenyl moiety, and a boron content of less than
about 20 ppm.
[0011] In accordance with a sixth aspect of the invention, there is
provided a lubricating oil composition, as described in any of the
first to fifth aspect, having a sulfated ash content of less than
about 0.5 wt. %.
[0012] In accordance with a seventh aspect of the invention, there
is provided a lubricating oil composition comprising a major amount
of at least one of a Group I, Group II and/or Group III mineral oil
of lubricating viscosity; a minor amount of one or more high
molecular weight polymers comprising olefin copolymers containing
alkyl or aryl amine or amide groups, nitrogen-containing
heterocyclic groups or ester linkages; and a minor amount of
dispersant comprising one or more nitrogen-containing dispersants
that are the reaction product of a polyalkenyl-substituted mono- or
dicarboxylic acid, anhydride or ester and a polyamine; at least one
the nitrogen-containing dispersants having a polyalkenyl moiety
with a number average molecular weight of at least about 1800, and
is derived from a polyalkene moiety having a molecular weight
distribution (M.sub.w/M.sub.n) of from about 1.5 to about 2; said
dispersants being chlorine-free.
[0013] In accordance with an eighth aspect of the invention, there
is provided a lubricating oil composition, as in the seventh
aspect, wherein said dispersant comprises from about 1.3 to about
1.6 mono- or di-carboxylic acid producing moieties per polyalkenyl
moiety, and has a boron content of less than 20 ppm.
[0014] In accordance with a ninth aspect of the invention, there is
provided a lubricating oil composition, as in the seventh or eighth
aspect, having a sulfur content less than about 0.3 wt. %, a
sulfated ash content of less than about 0.5 wt. %, and a chlorine
content of less than about 50 ppm.
[0015] In accordance with a tenth aspect of the invention, there is
provided a lubricating oil composition, as in any of the first to
ninth aspect, wherein the functionalized, high molecular weight
olefin molecule is derived from an amorphous ethylene-propylene
copolymer, or a blend of an amorphous and a semi-crystalline
ethylene-propylene copolymer with an SSI of from about 5 to about
30, produced by simultaneously shearing and functionalizing higher
molecular weight ethylene-propylene copolymers, with maleic
anhydride, in an extruder.
[0016] In accordance with an eleventh aspect of the invention,
there is provided a method of operating a diesel engine provided
with an exhaust gas recirculation system, which method comprises
lubricating said engine with a lubricating oil composition of any
of the first to tenth aspect.
[0017] Other and further objects, advantages and features of the
present invention will be understood by reference to the following
specification.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The oils of lubricating viscosity useful in the practice of
the invention may range in viscosity from light distillate mineral
oils to heavy lubricating oils such as gasoline engine oils,
mineral lubricating oils and heavy duty diesel oils. Generally, the
viscosity of the oil ranges from about 2 mm.sup.2/sec (centistokes)
to about 40 mm.sup.2/sec, especially from about 3 mm.sup.2/sec to
about 20 mm.sup.2/sec, most preferably from about 4 mm.sup.2/sec to
about 10 mm.sup.2/sec, as measured at 100.degree. C.
[0019] Natural oils include animal oils and vegetable oils (e.g.,
castor oil, lard oil); liquid petroleum oils and hydrorefined,
solvent-treated or acid-treated mineral oils of the paraffinic,
naphthenic and mixed paraffinic-naphthenic types. Oils of
lubricating viscosity derived from coal or shale also serve as
useful base oils.
[0020] The oil of lubricating viscosity may comprise a Group I,
Group II or Group III, base stock or base oil blends of the
aforementioned base stocks. Preferably, the oil of lubricating
viscosity is a Group II or Group III base stock, or a mixture
thereof, or a mixture of a Group I base stock and one or more a
Group II and Group III. The base stock, or base stock blend
preferably has a saturate content of at least 65%, more preferably
at least 75%, such as at least 85%. Most preferably, the base
stock, or base stock blend, has a saturate content of greater than
90%. Preferably, the oil or oil blend will have a sulfur content of
less than 1%, preferably less than 0.6%, most preferably less than
0.3%, by weight.
[0021] Preferably the volatility of the oil or oil blend, as
measured by the NOACK test (ASTM D5880), is less than or equal to
30%, preferably less than or equal to 25%, more preferably less
than or equal to 20%, most preferably less than or equal 16%.
Preferably, the viscosity index (VI) of the oil or oil blend is at
least 85, preferably at least 100, most preferably from about 105
to 140.
[0022] Definitions for the base stocks and base oils in this
invention are the same as those found in the American Petroleum
Institute (API) publication "Engine Oil Licensing and Certification
System", Industry Services Department, Fourteenth Edition, December
1996, Addendum 1, December 1998. Said publication categorizes base
stocks as follows:
[0023] a) Group I base stocks contain less than 90 percent
saturates and/or greater than 0.03 percent sulfur and have a
viscosity index greater than or equal to 80 and less than 120 using
the test methods specified in Table 1.
[0024] b) Group II base stocks contain greater than or equal to 90
percent saturates and less than or equal to 0.03 percent sulfur and
have a viscosity index greater than or equal to 80 and less than
120 using the test methods specified in Table 1.
[0025] c) Group III base stocks contain greater than or equal to 90
percent saturates and less than or equal to 0.03 percent sulfur and
have a viscosity index greater than or equal to 120 using the test
methods specified in Table 1.
[0026] d) Group IV base stocks are polyalphaolefins (PAO).
[0027] e) Group V base stocks include all other base stocks not
included in Group I, II, III, or IV.
1TABLE 1 Analytical Methods for Base Stock Property Test Method
Saturates ASTM D 2007 Viscosity Index ASTM D 2270 Sulfur ASTM D
2622 ASTM D 4294 ASTM D 4927 ASTM D 3120
[0028] High molecular weight polymers useful in the practice of the
present invention are olefin copolymers (OCPs) containing
dispersing groups such as alkyl or aryl amine, or amide groups,
nitrogen-containing heterocyclic groups or ester linkages. The
olefin copolymers can comprise any combination of olefin monomers,
but are most commonly ethylene and at least one other
.alpha.-olefin. The at least one other .alpha.-olefin monomer is
conventionally an .alpha.-olefin having 3 to 18 carbon atoms, and
is most preferably propylene. As is well known, copolymers of
ethylene and higher .alpha.-olefins, such as propylene, often
include other polymerizable monomers. Typical of these other
monomers are non-conjugated dienes such as the following,
non-limiting examples:
[0029] a. straight chain dienes such as 1,4-hexadiene and
1,6-octadiene;
[0030] b. branched chain acyclic dienes such as
5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene;
3,7-dimethyl-1,7-octadiene and mixed isomers of dihydro-mycene and
dihydroocinene;
[0031] c. single ring alicyclic dienes such as 1,4-cyclohexadiene;
1,5-cyclooctadiene; and 1,5-cyclododecadiene;
[0032] d. multi-ring alicyclic fused and bridged ring dienes such
as tetrahydroindene; methyltetrahydroindene; dicyclopentadiene;
bicyclo-(2,2,1)-hepta-2,5-diene; alkenyl, alkylidene, cycloalkenyl
and cycloalkylidene norbornenes such as 5-methylene-2-norbornene
(MNB), 5-ethylidene-2-norbornene (ENB), 5-propylene-2-norbornene,
5-isoproylidene-2-norbornene, 5-(4-cyclopentyenyl)-2-norbornene;
5-cyclohexylidene-2-norbornene.
[0033] Of the non-conjugated dienes typically used, dienes
containing at least one of the double bonds in a strained ring are
preferred. The most preferred diene is 5-ethylidene-2-norbornene
(ENB). The amount of diene (wt. basis) in the copolymer can be from
0% to about 20%, with 0% to about 15% being preferred, and 0% to
about 10% being most preferred. As already noted, the most
preferred olefin copolymer is ethylene-propylene. The average
ethylene content of the copolymer can be as low as 20% on a weight
basis. The preferred minimum ethylene content is about 25%. A more
preferred minimum is 30%. The maximum ethylene content can be as
high as 90% on a weight basis; preferably the maximum ethylene
content is 85%, most preferably about 80%. Preferably, the olefin
copolymers contain from about 35 to 75 wt. % ethylene, more
preferably from about 40 to about 70 wt. % of ethylene.
Ethylene-propylene copolymers having an ethylene content of up to
about 55 wt. % are considered amorphous; such copolymers having
higher ethylene contents are referred to as semi-crystalline.
Ethylene content of ethylene-propylene can generally be measured
using the procedure of ASTM-D3900.
[0034] The molecular weight (number average) of the olefin
copolymer can be as low as 2000, but the preferred minimum is
10,000. The more preferred minimum is 15,000, with the most
preferred minimum number average molecular weight being 20,000. It
is believed that the maximum number average molecular weight can be
as high as 12,000,000. The preferred maximum is about 1,000,000,
with the most preferred maximum being about 750,000. An especially
preferred range of number average molecular weight for the olefin
copolymers of the present invention is from about 50,000 to about
500,000.
[0035] Polymer molecular weight, specifically, {overscore
(M)}.sub.n can be determined by various known techniques. One
convenient method is gel permeation chromatography (GPC), which
additionally provides molecular weight distribution information
(see W. W. Yau, J. J. Kirkland and D. D. Bly, "Modern Size
Exclusion Liquid Chromatography", John Wiley and Sons, New York,
1979). Another useful method for determining molecular weight,
particularly for lower molecular weight polymers, is vapor pressure
osmometry (see, e.g., ASTM D3592).
[0036] Olefin copolymers can be rendered multifunctional by
attaching a nitrogen-containing polar moiety (e.g., amine,
amine-alcohol or amide) to the polymer backbone. The
nitrogen-containing moieties are conventionally of the formula
R--N--R'R", wherein R, R' and R" are independently alkyl, aryl of
H. Also suitable are aromatic amines of the formula
R--R'--NH--R"--R, wherein R' and R" are aromatic groups and each
are is alkyl. The most common method for forming a multifunctional
OCP viscosity modifier involves the free radical addition of the
nitrogen-containing polar moiety to the polymer backbone. The
nitrogen-containing polar moiety can be attached to the polymer
using a double bond within the polymer (i.e., the double bond of
the diene portion of an EPDM polymer, or by reacting the polymer
with a compound providing a bridging group containing a double bond
(e.g., maleic anhydride as described, for example, in U.S. Pat.
Nos. 3,316,177; 3,326,804; and carboxylic acids and ketones as
described, for example, in U.S. Pat. No. 4,068,056), and
subsequently derivatizing the functionalized polymer with the
nitrogen-containing polar moiety. A more complete list of
nitrogen-containing compounds that can be reacted with the
functionalized OCP is described infra, in the discussion of
dispersants. Multifunctionalized OCPs and methods for forming such
materials are known in the art and are available commercially
(e.g., HITEC 5777 available from Ethyl Corporation and PA 1160, a
product of Dutch Staaten Minen).
[0037] Preferred are low ethylene olefin copolymers containing
about 50 wt. % ethylene (amorphous) and having a number average
molecular weight between 10,000 and 20,000 functionalized by
grafting with maleic anhydride and aminated with arylphenyldiamine
or other diaryl amine. In one preferred embodiment, the
functionalized high molecular weight olefin polymer is derived from
an amorphous ethylene-propylene copolymer or a blend of an
amorphous and semi-crystalline ethylene-propylene copolymer having,
or having on average, a Shear Stability Index, or "SSI" of from
about 5 to about 30 (as determined according to ASTM D6278-98)
produced via simultaneous shearing and functionalizing higher
molecular weight ethylene-propylene copolymers with maleic
anhydride in an extruder. Such methods are known and described, for
example, in U.S. Pat. No. 5,075,383. In a further preferred
embodiment, the semi-crystalline ethylene-propylene copolymer is
produced in a tubular reactor to have a tapered structure
(ethylene-propylene distribution).
[0038] Lubricating oil compositions useful in the practice of the
present invention contain the high molecular weight olefin
copolymers (OCPs) containing dispersing groups in an amount of from
about 0.10 to about 2 wt. %, based on polymer weight; more
preferably from about 0.2 to about 1 wt. %, most preferably from
about 0.3 to about 0.8 wt. %. Alternatively said components are
present in an amount providing from about 0.0001 to about 0.02 wt.
%, preferably from about 0.0002 to about 0.01 wt. %, most
preferably from about 0.0003 to about 0.008 wt. % of nitrogen to
the lubricating oil composition. Preferably, the total amount of
diaryl amine moieties in the lubricating oil composition is from
about 0.5 to 5 mmols/kg, with greater than 50% of the diaryl amine
moieties being introduced into the lubricating oil composition via
molecules having a number average molecular weight of greater than
about 5000.
[0039] Dispersants useful in the context of the present invention
include the range of nitrogen-containing, ashless (metal-free)
dispersants known to be effective to reduce formation of deposits
upon use in gasoline and diesel engines, when added to lubricating
oils. The ashless, dispersants of the present invention comprise an
oil soluble polymeric long chain backbone having functional groups
capable of associating with particles to be dispersed. Typically,
such dispersants have amine, amine-alcohol or amide polar moieties
attached to the polymer backbone, often via a bridging group. The
ashless dispersant may be, for example, selected from oil soluble
salts, esters, amino-esters, amides, imides and oxazolines of long
chain hydrocarbon-substituted mono- and polycarboxylic acids or
anhydrides thereof; thiocarboxylate derivatives of long chain
hydrocarbons; long chain aliphatic hydrocarbons having polyamine
moieties attached directly thereto; and Mannich condensation
products formed by condensing a long chain substituted phenyl with
formaldehyde and polyalkylene polyamine.
[0040] The dispersant compositions of the present invention
comprise at least one dispersant that is derived from
polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or
ester, which dispersant has a polyalkenyl moiety with a number
average molecular weight of at least about 1800 and from greater
than about 1.3 to about 1.7, preferably from greater than about 1.3
to about 1.6, most preferably from greater than about 1.3 to about
1.5 functional groups (mono- or dicarboxylic acid producing
moieties) per polyalkenyl moiety (a medium functionality
dispersant). Functionality (F) can be determined according to the
following formula:
F=(SAP.times.M.sub.n)/((112,200.times.A.I.)-(SAP.times.98)) (1)
[0041] wherein SAP is the saponification number (i.e., the number
of milligrams of KOH consumed in the complete neutralization of the
acid groups in one gram of the succinic-containing reaction
product, as determined according to ASTM D94); M.sub.n is the
number average molecular weight of the starting olefin polymer; and
A.I. is the percent active ingredient of the succinic-containing
reaction product (the remainder being unreacted olefin polymer,
succinic anhydride and diluent).
[0042] Generally, each mono- or dicarboxylic acid-producing moiety
will react with a nucleophilic group (amine, alcohol, amide or
ester polar moieties) and the number of functional groups in the
polyalkenyl-substituted carboxylic acylating agent will determine
the number of nucleophilic groups in the finished dispersant.
[0043] The polyalkenyl moiety of the dispersant of the present
invention has a number average molecular weight of at least 1800,
preferably between 1800 and 3000, such as between 2000 and 2800,
more preferably from about 2100 to 2500, and most preferably from
about 2200 to about 2400. The molecular weight of a dispersant is
generally expressed in terms of the molecular weight of the
polyalkenyl moiety as the precise molecular weight range of the
dispersant depends on numerous parameters including the type of
polymer used to derive the dispersant, the number of functional
groups, and the type of nucleophilic group employed.
[0044] The polyalkenyl moiety suitable for forming the dispersant
used in the dispersant composition of the present invention
preferably has a narrow molecular weight distribution (MWD), also
referred to as polydispersity, as determined by the ratio of weight
average molecular weight (Mw) to number average molecular weight
(M.sub.n). Polymers having a M.sub.w/M.sub.n of less than 2.2,
preferably less than 2.0, are most desirable. Suitable polymers
have a polydispersity of from about 1.5 to 2.0, preferably from
about 1.6 to about 1.8.
[0045] Suitable hydrocarbons or polymers employed in the formation
of the dispersants of the present invention include homopolymers,
interpolymers or lower molecular weight hydrocarbons. One family of
such polymers comprise polymers of ethylene and/or at least one
C.sub.3 to C.sub.28 alpha-olefin having the formula
H.sub.2C.dbd.CHR.sup.1 wherein R.sup.1 is straight or branched
chain alkyl radical comprising 1 to 26 carbon atoms and wherein the
polymer contains carbon-to-carbon unsaturation, preferably a high
degree of terminal ethenylidene unsaturation. Preferably, such
polymers comprise interpolymers of ethylene and at least one
alpha-olefin of the above formula, wherein R.sup.1 is alkyl of from
1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8
carbon atoms, and more preferably still of from 1 to 2 carbon
atoms. Therefore, useful alpha-olefin monomers and comonomers
include, for example, propylene, butene-1, hexene-1,
octene-1,4-methylpentene-1, decene-1, dodecene-1, tridecene-1,
tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1,
octadecene-1, nonadecene-1, and mixtures thereof (e.g., mixtures of
propylene and butene-1, and the like). Exemplary of such polymers
are propylene homopolymers, butene-1 homopolymers,
ethylene-propylene copolymers, ethylene-butene-1 copolymers,
propylene-butene copolymers and the like, wherein the polymer
contains at least some terminal and/or internal unsaturation.
Preferred polymers are unsaturated copolymers of ethylene and
propylene and ethylene and butene-1. The interpolymers of this
invention may contain a minor amount, e.g. 0.5 to 5 mole % of a
C.sub.4 to C.sub.18 non-conjugated diolefin comonomer. However, it
is preferred that the polymers of this invention comprise only
alpha-olefin homopolymers, interpolymers of alpha-olefin comonomers
and interpolymers of ethylene and alpha-olefin comonomers. The
molar ethylene content of the polymers employed in this invention
is preferably in the range of 0 to 80%, and more preferably 0 to
60%. When propylene and/or butene-1 are employed as comonomer(s)
with ethylene, the ethylene content of such copolymers is most
preferably between 15 and 50%, although higher or lower ethylene
contents may be present.
[0046] These polymers may be prepared by polymerizing alpha-olefin
monomer, or mixtures of alpha-olefin monomers, or mixtures
comprising ethylene and at least one C.sub.3 to C.sub.28
alpha-olefin monomer, in the presence of a catalyst system
comprising at least one metallocene (e.g., a
cyclopentadienyl-transition metal compound) and an alumoxane
compound. Using this process, a polymer in which 95% or more of the
polymer chains possess terminal ethenylidene-type unsaturation can
be provided. The percentage of polymer chains exhibiting terminal
ethenylidene unsaturation may be determined by FTIR spectroscopic
analysis, titration, or C.sup.13 NMR. Interpolymers of this latter
type may be characterized by the formula
POLY-C(R.sup.1).dbd.CH.sub.2 wherein R.sup.1 is C.sub.1 to C.sub.26
alkyl, preferably C.sub.1 to C.sub.18 alkyl, more preferably
C.sub.1 to C.sub.8 alkyl, and most preferably C.sub.1 to C.sub.2
alkyl, (e.g., methyl or ethyl) and wherein POLY represents the
polymer chain. The chain length of the R.sup.1 alkyl group will
vary depending on the comonomer(s) selected for use in the
polymerization. A minor amount of the polymer chains can contain
terminal ethenyl, i.e., vinyl, unsaturation, i.e.
POLY-CH.dbd.CH.sub.2, and a portion of the polymers can contain
internal monounsaturation, e.g. POLY-CH.dbd.CH(R.sup.1), wherein
R.sup.1 is as defined above. These terminally unsaturated
interpolymers may be prepared by known metallocene chemistry and
may also be prepared as described in U.S. Pat. Nos. 5,498,809;
5,663,130; 5,705,577; 5,814,715; 6,022,929 and 6,030,930.
[0047] Another useful class of polymers is polymers prepared by
cationic polymerization of isobutene, styrene, and the like. Common
polymers from this class include polyisobutenes obtained by
polymerization of a C.sub.4 refinery stream having a butene content
of about 35 to about 75% by wt., and an isobutene content of about
30 to about 60% by wt., in the presence of a Lewis acid catalyst,
such as aluminum trichloride or boron trifluoride. A preferred
source of monomer for making poly-n-butenes is petroleum
feedstreams such as Raffinate II. These feedstocks are disclosed in
the art such as in U.S. Pat. No. 4,952,739. Polyisobutylene is a
most preferred backbone of the present invention because it is
readily available by cationic polymerization from butene streams
(e.g., using AlC1.sub.3 or BF.sub.3 catalysts). Such
polyisobutylenes generally contain residual unsaturation in amounts
of about one ethylenic double bond per polymer chain, positioned
along the chain. A preferred embodiment utilizes polyisobutylene
prepared from a pure isobutylene stream or a Raffinate I stream to
prepare reactive isobutylene polymers with terminal vinylidene
olefins. Preferably, these polymers, referred to as highly reactive
polyisobutylene (HR-PIB), have a terminal vinylidene content of at
least 65%, e.g., 70%, more preferably at least 80%, most
preferably, at least 85%. The preparation of such polymers is
described, for example, in U.S. Pat. No. 4,152,499. HR-PIB is known
and HR-PIB is commercially available under the tradenames
Glissopal.TM. (from BASF) and Ultravis.TM. (from BP-Amoco).
[0048] Polyisobutylene polymers that may be employed are generally
based on a hydrocarbon chain of from about 1800 to 3000. Methods
for making polyisobutylene are known. Polyisobutylene can be
functionalized by halogenation (e.g. chlorination), the thermal
"ene" reaction, or by free radical grafting using a catalyst (e.g.
peroxide), as described below.
[0049] The hydrocarbon or polymer backbone can be functionalized,
e.g., with carboxylic acid producing moieties (preferably acid or
anhydride moieties) selectively at sites of carbon-to-carbon
unsaturation on the polymer or hydrocarbon chains, or randomly
along chains using any of the three processes mentioned above or
combinations thereof, in any sequence.
[0050] Processes for reacting polymeric hydrocarbons with
unsaturated carboxylic acids, anhydrides or esters and the
preparation of derivatives from such compounds are disclosed in
U.S. Pat. Nos. 3,087,936; 3,172,892; 3,215,707; 3,231,587;
3,272,746; 3,275,554; 3,381,022; 3,442,808; 3,565,804; 3,912,764;
4,110,349; 4,234,435; 5,777,025; 5,891,953; as well as EP 0 382 450
B1; CA-1,335,895 and GB-A-1,440,219. The polymer or hydrocarbon may
be functionalized, for example, with carboxylic acid producing
moieties (preferably acid or anhydride) by reacting the polymer or
hydrocarbon under conditions that result in the addition of
functional moieties or agents, i.e., acid, anhydride, ester
moieties, etc., onto the polymer or hydrocarbon chains primarily at
sites of carbon-to-carbon unsaturation (also referred to as
ethylenic or olefinic unsaturation) using the halogen assisted
functionalization (e.g. chlorination) process or the thermal "ene"
reaction.
[0051] Selective functionalization can be accomplished by
halogenating, e.g., chlorinating or brominating the unsaturated
.alpha.-olefin polymer to about 1 to 8 wt. %, preferably 3 to 7 wt.
% chlorine, or bromine, based on the weight of polymer or
hydrocarbon, by passing the chlorine or bromine through the polymer
at a temperature of 60 to 250.degree. C., preferably 110 to
160.degree. C., e.g., 120 to 140.degree. C., for about 0.5 to 10,
preferably 1 to 7 hours. The halogenated polymer or hydrocarbon
(hereinafter backbone) is then reacted with sufficient
monounsaturated reactant capable of adding the required number of
functional moieties to the backbone, e.g., monounsaturated
carboxylic reactant, at 100 to 250.degree. C., usually about
180.degree. C. to 235.degree. C., for about 0.5 to 10, e.g., 3 to 8
hours, such that the product obtained will contain the desired
number of moles of the monounsaturated carboxylic reactant per mole
of the halogenated backbones. Alternatively, the backbone and the
monounsaturated carboxylic reactant are mixed and heated while
adding chlorine to the hot material.
[0052] While chlorination normally helps increase the reactivity of
starting olefin polymers with monounsaturated functionalizing
reactant, it is not necessary with some of the polymers or
hydrocarbons contemplated for use in the present invention,
particularly those preferred polymers or hydrocarbons which possess
a high terminal bond content and reactivity. It is advantageous to
reduce the chlorine content of lubricating oil compositions to as
low a level as possible. Preferably, lubricating oil compositions
of the present invention have a chlorine content of less than 50
ppm. Preferably, therefore, the backbone and the monounsaturated
functionality reactant used to form the dispersant(s), e.g.,
carboxylic reactant, are contacted at elevated temperature to cause
an initial thermal "ene" reaction to take place. Ene reactions are
known.
[0053] The hydrocarbon or polymer backbone can be functionalized by
random attachment of functional moieties along the polymer chains
by a variety of methods. For example, the polymer, in solution or
in solid form, may be grafted with the monounsaturated carboxylic
reactant, as described above, in the presence of a free-radical
initiator. When performed in solution, the grafting takes place at
an elevated temperature in the range of about 100 to 260.degree.
C., preferably 120 to 240.degree. C. Preferably, free-radical
initiated grafting would be accomplished in a mineral lubricating
oil solution containing, e.g., 1 to 50 wt. %, preferably 5 to 30
wt. % polymer based on the initial total oil solution.
[0054] The free-radical initiators that may be used are peroxides,
hydroperoxides, and azo compounds, preferably those that have a
boiling point greater than about 100.degree. C. and decompose
thermally within the grafting temperature range to provide
free-radicals. Representative of these free-radical initiators are
azobutyronitrile, 2,5-dimethylhex-3-ene-2,5-bis-tertiary-butyl
peroxide and dicumene peroxide. The initiator, when used, typically
is used in an amount of between 0.005% and 1% by weight based on
the weight of the reaction mixture solution. Typically, the
aforesaid monounsaturated carboxylic reactant material and
free-radical initiator are used in a weight ratio range of from
about 1.0:1 to 30:1, preferably 3:1 to 6:1. The grafting is
preferably carried out in an inert atmosphere, such as under
nitrogen blanketing. The resulting grafted polymer is characterized
by having carboxylic acid (or ester or anhydride) moieties randomly
attached along the polymer chains: it being understood, of course,
that some of the polymer chains remain ungrafted. The free radical
grafting described above can be used for the other polymers and
hydrocarbons of the present invention.
[0055] The preferred monounsaturated reactants that are used to
functionalize the backbone comprise mono- and dicarboxylic acid
material, i.e., acid, anhydride, or acid ester material, including
(i) monounsaturated C.sub.4 to C.sub.10 dicarboxylic acid 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; (ii)
derivatives of (i) such as anhydrides or C.sub.1 to C.sub.5 alcohol
derived mono- or diesters of (i); (iii) monounsaturated C.sub.3 to
C.sub.10 monocarboxylic acid wherein the carbon-carbon double bond
is conjugated with the carboxy group, i.e., of the structure
--C.dbd.C--CO--; and (iv) derivatives of (iii) such as C.sub.1 to
C.sub.5 alcohol derived mono- or diesters of (iii). Mixtures of
monounsaturated carboxylic materials (i)-(iv) also may be used.
Upon reaction with the backbone, the monounsaturation of the
monounsaturated carboxylic reactant becomes saturated. Thus, for
example, maleic anhydride becomes backbone-substituted succinic
anhydride, and acrylic acid becomes backbone-substituted propionic
acid. Exemplary of such monounsaturated carboxylic reactants are
fumaric acid, itaconic acid, maleic acid, maleic anhydride,
chloromaleic acid, chloromaleic anhydride, acrylic acid,
methacrylic acid, crotonic acid, cinnamic acid, and lower alkyl
(e.g., C.sub.1 to C.sub.4 alkyl) acid esters of the foregoing,
e.g., methyl maleate, ethyl fumarate, and methyl fumarate.
[0056] To provide the required functionality, the monounsaturated
carboxylic reactant, preferably maleic anhydride, typically will be
used in an amount ranging from about equimolar amount to about 100
wt. % excess, preferably 5 to 50 wt. % excess, based on the moles
of polymer or hydrocarbon. Unreacted excess monounsaturated
carboxylic reactant can be removed from the final dispersant
product by, for example, stripping, usually under vacuum, if
required.
[0057] The functionalized oil-soluble polymeric hydrocarbon
backbone is then derivatized with a nucleophilic reactant, such as
an amine, amino-alcohol, alcohol, metal compound, or mixture
thereof, to form a corresponding derivative. Useful amine compounds
for derivatizing functionalized polymers comprise at least one
amine and can comprise one or more additional amine or other
reactive or polar groups. These amines may be hydrocarbyl amines or
may be predominantly hydrocarbyl amines in which the hydrocarbyl
group includes other groups, e.g., hydroxy groups, alkoxy groups,
amide groups, nitriles, imidazoline groups, and the like.
Particularly useful amine compounds include mono- and polyamines,
e.g., polyalkene and polyoxyalkylene polyamines of about 2 to 60,
such as 2 to 40 (e.g., 3 to 20) total carbon atoms having about 1
to 12, such as 3 to 12, preferably 3 to 9, most preferably form
about 6 to about 7 nitrogen atoms per molecule. Mixtures of amine
compounds may advantageously be used, such as those prepared by
reaction of alkylene dihalide with ammonia. Preferred amines are
aliphatic saturated amines, including, for example,
1,2-diaminoethane; 1,3-diaminopropane; 1,4-diaminobutane;
1,6-diaminohexane; polyethylene amines such as diethylene triamine;
triethylene tetramine; tetraethylene pentamine; and
polypropyleneamines such as 1,2-propylene diamine; and
di-(1,2-propylene)triamine. Such polyamine mixtures, known as PAM,
are commercially available. Particularly preferred polyamine
mixtures are mixtures derived by distilling the light ends from PAM
products. The resulting mixtures, known as "heavy" PAM, or HPAM,
are also commercially available. The properties and attributes of
both PAM and/or HPAM are described, for example, in U.S. Pat. Nos.
4,938,881; 4,927,551; 5,230,714; 5,241,003; 5,565,128; 5,756,431;
5,792,730; and 5,854,186.
[0058] Other useful amine compounds include: alicyclic diamines
such as 1,4-di(aminomethyl)cyclohexane and heterocyclic nitrogen
compounds such as imidazolines. Another useful class of amines is
the polyamido and related amido-amines as disclosed in U.S. Pat.
Nos. 4,857,217; 4,956,107; 4,963,275; and 5,229,022. Also usable is
tris(hydroxymethyl)amino methane (TAM) as described in U.S. Pat.
Nos. 4,102,798; 4,113,639; 4,116,876; and UK 989,409. Dendrimers,
star-like amines, and comb-structured amines may also be used.
Similarly, one may use condensed amines, as described in U.S. Pat.
No. 5,053,152. The functionalized polymer is reacted with the amine
compound using conventional techniques as described, for example,
in U.S. Pat. Nos. 4,234,435 and 5,229,022, as well as in
EP-A-208,560.
[0059] A preferred dispersant composition is one comprising at
least one polyalkenyl succinimide, which is the reaction product of
a polyalkenyl substituted succinic anhydride (e.g., PIBSA) and a
polyamine (PAM) that has a coupling ratio of from about 0.65 to
about 1.25, preferably from about 0.8 to about 1.1, most preferably
from about 0.9 to about 1. In the context of this disclosure,
"coupling ratio" may be defined as a ratio of succinyl groups in
the PIBSA to primary amine groups in the polyamine reactant.
[0060] The functionalized, oil-soluble polymeric hydrocarbon
backbones may also be derivatized with hydroxy compounds such as
monohydric and polyhydric alcohols, or with aromatic compounds such
as phenyls and naphthols. Preferred polyhydric alcohols include
alkylene glycols in which the alkylene radical contains from 2 to 8
carbon atoms. Other useful polyhydric alcohols include glycerol,
mono-oleate of glycerol, monostearate of glycerol, monomethyl ether
of glycerol, pentaerythritol, dipentaerythritol, and mixtures
thereof. An ester dispersant may also be derived from unsaturated
alcohols, such as allyl alcohol, cinnamyl alcohol, propargyl
alcohol, 1-cyclohexane-3-ol, and oleyl alcohol. Still other classes
of alcohols capable of yielding ashless dispersants comprise
ether-alcohols, including oxy-alkylene and oxy-arylene. Such
ether-alcohols are exemplified by ether-alcohols having up to 150
oxy-alkylene radicals in which the alkylene radical contains from 1
to 8 carbon atoms. The ester dispersants may be di-esters of
succinic acids or acid-esters, i.e., partially esterified succinic
acids, as well as partially esterified polyhydric alcohols or
phenyls, i.e., esters having free alcohols or phenolic hydroxy
radicals. An ester dispersant may be prepared by any one of several
known methods as described, for example, in U.S. Pat. No.
3,381,022.
[0061] Another class of high molecular weight ashless dispersants
comprises Mannich base condensation products. Generally, these
products are prepared by condensing about one mole of a long chain
alkyl-substituted mono- or polyhydroxy benzene with about 1 to 2.5
moles of carbonyl compound(s) (e.g., formaldehyde and
paraformaldehyde) and about 0.5 to 2 moles of polyalkylene
polyamine, as disclosed, for example, in U.S. Pat. No. 3,442,808.
Such Mannich base condensation products may include a polymer
product of a metallocene catalyzed polymerization as a substituent
on the benzene group, or may be reacted with a compound containing
such a polymer substituted on a succinic anhydride in a manner
similar to that described in U.S. Pat. No. 3,442,808. Examples of
functionalized and/or derivatized olefin polymers synthesized using
metallocene catalyst systems are described in the publications
identified supra.
[0062] The dispersant(s) of the invention are preferably
non-polymeric (e.g., are mono- or bis-succinimides). The
dispersant(s) of the present invention can be borated by
conventional means, as generally taught in U.S. Pat. Nos.
3,087,936, 3,254,025 and 5,430,105. Boration of the dispersant is
readily accomplished by treating an acyl nitrogen-containing
dispersant with a boron compound such as boron oxide, boron halide
boron acids, and esters of boron acids. Preferably, dispersants of
the present invention are non-borated, or have a boron content of
less than 20 ppm.
[0063] The dispersant or dispersants can be present in an amount
sufficient to contribute at least 0.08 wt. % of nitrogen,
preferably from about 0.10 to about 0.18 wt. %, more preferably
from about 0.115 to about 0.16 wt. %, and most preferably from
about 0.12 to about 0.14 wt. % of nitrogen to the lubricating oil
composition.
[0064] Additional additives may be incorporated into the
compositions of the invention to enable particular performance
requirements to be met. Examples of additives which may be included
in the lubricating oil compositions of the present invention are
detergents, metal rust inhibitors, viscosity index improvers
corrosion inhibitors, oxidation inhibitors, friction modifiers,
anti-foaming agents, anti-wear agents and pour point depressants.
Some are discussed in further detail below.
[0065] Metal-containing or ash-forming detergents function as both
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 a long
hydrophobic tail. The polar head comprises a metal salt of an
acidic organic compound. The salts may contain a substantially
stoichiometric amount of the metal in which case they are usually
described as normal or neutral salts, and would typically have a
total base number or TBN (as can be measured by ASTM D2896) of from
0 to 80. A large amount of a metal base may be incorporated by
reacting excess metal compound (e.g., an oxide or hydroxide) with
an acidic gas (e.g., carbon dioxide). The resulting overbased
detergent comprises neutralized detergent as the outer layer of a
metal base (e.g. carbonate) micelle. Such overbased detergents may
have a TBN of 150 or greater, and typically will have a TBN of from
250 to 450 or more.
[0066] Detergents that may be used include oil-soluble neutral and
overbased sulfonates, phenates, sulfurized phenates,
thiophosphonates, salicylates, and naphthenates and other
oil-soluble carboxylates of a metal, particularly the alkali or
alkaline earth metals, e.g., barium, sodium, potassium, lithium,
calcium, and magnesium. The most commonly used metals are calcium
and magnesium, which may both be present in detergents used in a
lubricant, and mixtures of calcium and/or magnesium with sodium.
Particularly convenient metal detergents are neutral and overbased
calcium sulfonates having TBN of from 20 to 450, neutral and
overbased calcium phenates and sulfurized phenates having TBN of
from 50 to 450 and neutral and overbased magnesium or calcium
salicylates having a TBN of from 20 to 450. Combinations of
detergents, whether overbased or neutral or both, may be used.
[0067] Sulfonates may be prepared from sulfonic acids which are
typically obtained by the sulfonation of alkyl substituted aromatic
hydrocarbons such as those obtained from the fractionation of
petroleum or by the alkylation of aromatic hydrocarbons. Examples
included those obtained by alkylating benzene, toluene, xylene,
naphthalene, diphenyl or their halogen derivatives such as
chlorobenzene, chlorotoluene and chloronaphthalene. The alkylation
may be carried out in the presence of a catalyst with alkylating
agents having from about 3 to more than 70 carbon atoms. The
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.
[0068] The oil soluble sulfonates or alkaryl sulfonic acids may be
neutralized with oxides, hydroxides, alkoxides, carbonates,
carboxylate, sulfides, hydrosulfides, nitrates, borates and ethers
of the metal. The amount of metal compound is chosen having regard
to the desired TBN of the final product but typically ranges from
about 100 to 220 wt. % (preferably at least 125 wt. %) of that
stoichiometrically required.
[0069] Metal salts of phenyls and sulfurized phenyls are prepared
by reaction with an appropriate metal compound such as an oxide or
hydroxide and neutral or overbased products may be obtained by
methods well known in the art. Sulfurized phenyls may be prepared
by reacting a phenyl with sulfur or a sulfur containing compound
such as hydrogen sulfide, sulfur monohalide or sulfur dihalide, to
form products which are generally mixtures of compounds in which 2
or more phenyls are bridged by sulfur containing bridges.
[0070] 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 and neutral or overbased
products may 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; for example benzene is a preferred moiety.
The aromatic carboxylic acid may contain one or more aromatic
moieties, such as one or more benzene rings, either fused or
connected via alkylene bridges. The carboxylic moiety may be
attached directly or indirectly to the aromatic moiety. Preferably
the carboxylic acid group is attached directly to a carbon atom on
the aromatic moiety, such as a carbon atom on the benzene ring.
More preferably, the aromatic moiety also contains a second
functional group, such as a hydroxy group or a sulfonate group,
which can be attached directly or indirectly to a carbon atom on
the aromatic moiety.
[0071] Preferred examples of aromatic carboxylic acids are
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, and in that case, will
generally be obtained, normally in a diluent, in admixture with
uncarboxylated phenyl.
[0072] Preferred substituents in oil-soluble salicylic acids are
alkyl substituents. In alkyl-substituted salicylic acids, the alkyl
groups advantageously contain 5 to 100, preferably 9 to 30,
especially 14 to 20, carbon atoms. Where there is more than one
alkyl group, the average number of carbon atoms in all of the alkyl
groups is preferably at least 9 to ensure adequate oil
solubility.
[0073] Detergents generally useful in the formulation of
lubricating oil compositions also include "hybrid" detergents
formed with mixed surfactant systems, e.g., phenate/salicylates,
sulfonate/phenates, sulfonate/salicylates,
sulfonates/phenates/salicylates, as described, for example, in
pending U.S. patent application Ser. Nos. 09/180,435 and 09/180,436
and U.S. Pat. Nos. 6,153,565 and 6,281,179.
[0074] Preferably, the detergent used will be a detergent system in
which from about 60% to 100% of the total amount of detergent
surfactant is phenate and/or salicylate. Phenate neutral and
overbased detergents are preferred. Preferably, lubricating oil
compositions useful in the present invention will contain no more
than about 30 wt. %, preferably no more than about 20 wt. %, more
preferably no more than 5 wt. % sulfonate detergent, based on the
total weight of detergent. More preferably, the detergent system
will provide the lubricating oil composition with from about 6 to
about 50 mmols, more preferably from about 9 to about 40 mmols,
most preferably from about 12 to about 30 mmols of neutral or
overbased phenate detergent surfactant, and less than 1 mmol of
salicylate detergent surfactant per kilogram of finished lubricant.
Further preferably, the detergent system comprises sulfur-free
detergent, particularly sulfur-free phenate detergent.
[0075] It is not unusual to add a detergent or other additive, to a
lubricating oil, or additive concentrate, in a diluent, such that
only a portion of the added weight represents an active ingredient
(A.I.). For example, detergent may be added together with an equal
weight of diluent in which case the "additive" is 50% A.I.
detergent. As used herein, the term weight percent (wt. %), when
applied to a detergent or other additive refers to the weight of
active ingredient. Detergents conventionally comprise from about
0.5 to about 5 wt. %, preferably from about 0.8 to about 3.8 wt. %,
most preferably from about 1.2 to about 3 wt. % of a lubricating
oil composition formulated for use in a heavy duty diesel
engine.
[0076] Dihydrocarbyl dithiophosphate metal salts are frequently
used as antiwear and antioxidant agents. The metal may be an alkali
or alkaline earth metal, or aluminum, lead, tin, molybdenum,
manganese, nickel or copper. The zinc salts are most commonly used
in lubricating oil in amounts of 0.1 to 10, preferably 0.2 to 2 wt.
%, based upon the total weight of the lubricating oil composition.
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 phenyl with P.sub.2S.sub.5 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 generally 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.
[0077] The preferred zinc dihydrocarbyl dithiophosphates are oil
soluble salts of dihydrocarbyl dithiophosphoric acids and may be
represented by the following formula: 1
[0078] wherein R and R' may be the same or different hydrocarbyl
radicals containing from 1 to 18, preferably 2 to 12, carbon atoms
and including radicals such as alkyl, alkenyl, aryl, arylalkyl,
alkaryl and cycloaliphatic radicals. Particularly preferred as R
and R' groups are alkyl groups of 2 to 8 carbon atoms. Thus, the
radicals may, for example, be ethyl, n-propyl, i-propyl, n-butyl,
i-butyl, sec-butyl, amyl, n-hexyl, i-hexyl, n-octyl, decyl,
dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl,
methylcyclopentyl, propenyl, butenyl. In order to obtain oil
solubility, the total number of carbon atoms (i.e. R and R') in the
dithiophosphoric acid will generally be about 5 or greater. The
zinc dihydrocarbyl dithiophosphate can therefore comprise zinc
dialkyl dithiophosphates. The present invention may be particularly
useful when used with lubricant compositions containing phosphorus
levels of from about 0.02 to about 0.12 wt. %, preferably from
about 0.03 to about 0.10 wt. %. More preferably, the phosphorous
level of the lubricating oil composition will be less than about
0.08 wt. %, such as from about 0.05 to about 0.08 wt. %.
[0079] Oxidation inhibitors or antioxidants reduce the tendency of
mineral oils to deteriorate in service. Oxidative deterioration can
be evidenced by sludge in the lubricant, varnish-like deposits on
the metal surfaces, and by viscosity growth. Such oxidation
inhibitors include hindered phenyls, alkaline earth metal salts of
alkylphenylthioesters having preferably C.sub.5 to C.sub.12 alkyl
side chains, calcium nonylphenyl sulfide, oil soluble phenates and
sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons
or esters, phosphorous esters, metal thiocarbamates, oil soluble
copper compounds as described in U.S. Pat. No. 4,867,890, and
molybdenum-containing compounds.
[0080] Aromatic amines having at least two aromatic groups attached
directly to the nitrogen constitute another class of compounds that
is frequently used for antioxidancy. While these materials may be
used in small amounts, preferred embodiments of the present
invention are free of these compounds. They are preferably used in
only small amounts, i.e., up to 0.4 wt. %, or more preferably
avoided altogether other than such amount as may result as an
impurity from another component of the composition.
[0081] 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. Compounds having a total of at least three
aromatic groups in which two aromatic groups are linked by a
covalent bond or by an atom or group (e.g., an oxygen or sulfur
atom, or a --CO--, --SO.sub.2-- or alkylene group) and two are
directly attached to one amine nitrogen also considered aromatic
amines having at least two aromatic groups attached directly to the
nitrogen. The aromatic rings are typically substituted by one or
more substituents selected from alkyl, cycloalkyl, alkoxy, aryloxy,
acyl, acylamino, hydroxy, and nitro groups. The amount of any such
oil soluble aromatic amines having at least two aromatic groups
attached directly to one amine nitrogen should preferably not
exceed 0.4 wt. % active ingredient.
[0082] Preferably, lubricating oil compositions in accordance with
the present invention contain from about 0.05 to about 5 wt. %,
preferably from about 0.10 to about 3 wt. %, most preferably from
about 0.20 to about 1.5 wt. % of phenylic antioxidant, based on the
total weight of the lubricating oil composition. Even more
preferably, lubricating oil compositions in accordance with the
present invention contain phenylic antioxidant in the amount set
forth above, and comprise less than 0.1 wt. %, based on the total
weight of the lubricating oil composition, aromatic amine
antioxidant.
[0083] Friction modifiers and fuel economy agents that are
compatible with the other ingredients of the final oil may also be
included. Examples of such materials include glyceryl monoesters of
higher fatty acids, for example, glyceryl mono-oleate; esters of
long chain polycarboxylic acids with diols, for example, the butane
diol ester of a dimerized unsaturated fatty acid; oxazoline
compounds; and alkoxylated alkyl-substituted mono-amines, diamines
and alkyl ether amines, for example, ethoxylated tallow amine and
ethoxylated tallow ether amine. A preferred lubricating oil
composition contains a dispersant composition of the present
invention, base oil, and a nitrogen-containing friction
modifier.
[0084] Other known friction modifiers comprise oil-soluble
organo-molybdenum compounds. Such organo-molybdenum friction
modifiers also provide 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. Particularly
preferred are molybdenum dithiocarbamates, dialkyldithiophosphates,
alkyl xanthates and alkylthioxanthates.
[0085] Additionally, the molybdenum compound may be an acidic
molybdenum compound. These compounds will react with a basic
nitrogen compound as measured by ASTM test D-664 or D-2896
titration procedure and are typically hexavalent. Included are
molybdic acid, ammonium molybdate, sodium molybdate, potassium
molybdate, and other alkaline metal molybdates and other molybdenum
salts, e.g., hydrogen sodium molybdate, MoOCl.sub.4,
MoO.sub.2Br.sub.2, Mo.sub.2O.sub.3Cl.sub.6, molybdenum trioxide or
similar acidic molybdenum compounds.
[0086] Among the molybdenum compounds useful in the compositions of
this invention are organo-molybdenum compounds of the formula
Mo(ROCS.sub.2).sub.4 and
Mo(RSCS.sub.2).sub.4
[0087] wherein R is an organo group selected from the group
consisting of alkyl, aryl, aralkyl and alkoxyalkyl, generally of
from 1 to 30 carbon atoms, and preferably 2 to 12 carbon atoms and
most preferably alkyl of 2 to 12 carbon atoms. Especially preferred
are the dialkyldithiocarbamates of molybdenum.
[0088] Another group of organo-molybdenum compounds useful in the
lubricating compositions of this invention are trinuclear
molybdenum compounds, especially those of the formula
Mo.sub.3S.sub.kL.sub.nQ.sub.z and mixtures thereof wherein the L
are independently selected ligands having organo groups with a
sufficient number of carbon atoms to render the compound soluble or
dispersible in the oil, n is from 1 to 4, k varies from 4 through
7, Q is selected from the group of neutral electron donating
compounds such as water, amines, alcohols, phosphines, and ethers,
and z ranges from 0 to 5 and includes non-stoichiometric values. At
least 21 total carbon atoms should be present among all the
ligands' organo groups, such as at least 25, at least 30, or at
least 35 carbon atoms.
[0089] The ligands are independently selected from the group of
2
[0090] and mixtures thereof, wherein X, X.sub.1, X.sub.2, and Y are
independently selected from the group of oxygen and sulfur, and
wherein R.sub.1, R.sub.2, and R are independently selected from
hydrogen and organo groups that may be the same or different.
Preferably, the organo groups are gydrocarbyl groups such as alkyl
(e.g., in which the carbon atom attached to the remainder of the
ligand is primary or secondary), aryl, substituted aryl and ether
groups. More preferably, each ligand has the same hydrocarbyl
group.
[0091] The term "hydrocarbyl" denotes a substituent having carbon
atoms directly attached to the remainder of the ligand and is
predominantly hydrocarbyl in character within the context of this
invention. Such substituents include the following:
[0092] 1. Hydrocarbon substituents, that is, aliphatic (for example
alkyl or alkenyl), alicyclic (for example cycloalkyl or
cycloalkenyl) substituents, aromatic-, aliphatic- and
alicyclic-substituted aromatic nuclei and the like, as well as
cyclic substituents wherein the ring is completed through another
portion of the ligand (that is, any two indicated substituents may
together form an alicyclic group).
[0093] 2. Substituted hydrocarbon substituents, that is, those
containing non-hydrocarbon groups which, in the context of this
invention, do not alter the predominantly hydrocarbyl character of
the substituent. Those skilled in the art will be aware of suitable
groups (e.g., halo, especially chloro and fluoro, amino, alkoxyl,
mercapto, alkylmercapto, nitro, nitroso, sulfoxy, etc.).
[0094] 3. Hetero substituents, that is, substituents which, while
predominantly hydrocarbon in character within the context of this
invention, contain atoms other than carbon present in a chain or
ring otherwise composed of carbon atoms.
[0095] Importantly, the organo groups of the ligands have a
sufficient number of carbon atoms to render the compound soluble or
dispersible in the oil. For example, the number of carbon atoms in
each group will generally range between about 1 to about 100,
preferably from about 1 to about 30, and more preferably between
about 4 to about 20. Preferred ligands include
dialkyldithiophosphate, alkylxanthate, and dialkyldithiocarbamate,
and of these dialkyldithiocarbamate is more preferred. Organic
ligands containing two or more of the above functionalities are
also capable of serving as ligands and binding to one or more of
the cores. Those skilled in the art will realize that formation of
the compounds of the present invention requires selection of
ligands having the appropriate charge to balance the core's
charge.
[0096] Compounds having the formula Mo.sub.3S.sub.kL.sub.nQ.sub.z
have cationic cores surrounded by anionic ligands and are
represented by structures such as 3
[0097] and have net charges of +4. Consequently, in order to
solubilize these cores the total charge among all the ligands must
be -4. Four monoanionic ligands are preferred. Without wishing to
be bound by any theory, it is believed that two or more trinuclear
cores may be bound or interconnected by means of one or more
ligands and the ligands may be multidentate. Such structures fall
within the scope of this invention. This includes the case of a
multidentate ligand having multiple connections to a single core.
It is believed that oxygen and/or selenium may be substituted for
sulfur in the core(s).
[0098] Oil-soluble or dispersible trinuclear molybdenum compounds
can be prepared by reacting in the appropriate liquid(s)/solvent(s)
a molybdenum source such as
(NH.sub.4).sub.2Mo.sub.3S.sub.13.n(H.sub.2O), 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
(NH.sub.4).sub.2Mo.sub.3S.sub.13.n(H.sub.2O), a ligand source such
as tetralkylthiuram disulfide, dialkyldithiocarbamate, or
dialkyldithiophosphate, and a sulfur abstracting agent such cyanide
ions, sulfite ions, or substituted phosphines. Alternatively, a
trinuclear molybdenum-sulfur halide salt such as
[M'].sub.2[Mo.sub.3S.sub.7A.sub.6], 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.
[0099] A compound's oil solubility or dispersibility may be
influenced by the number of carbon atoms in the ligand's organo
groups. In the compounds of the present invention, at least 21
total carbon atoms should be present among all the ligand's organo
groups. Preferably, the ligand source chosen has a sufficient
number of carbon atoms in its organo groups to render the compound
soluble or dispersible in the lubricating composition.
[0100] 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.
[0101] The molybdenum compound is preferably an organo-molybdenum
compound. Moreover, the molybdenum compound is preferably selected
from the group consisting of a molybdenum dithiocarbamate (MoDTC),
molybdenum dithiophosphate, molybdenum dithiophosphinate,
molybdenum xanthate, molybdenum thioxanthate, molybdenum sulfide
and mixtures thereof. Most preferably, the molybdenum compound is
present as molybdenum dithiocarbamate. The molybdenum compound may
also be a trinuclear molybdenum compound.
[0102] 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 about 150,000. These
viscosity modifiers can 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). Certain of
the high molecular weight olefin copolymers (OCPs) containing
dispersing groups useful in the practice of the invention can be
classified as dispersant-viscosity modifiers. In this instance, the
high molecular weight olefin copolymers (OCPs) containing
dispersing groups need not comprise the sole VM in the lubricating
oil composition, and other VM, such as a hydrogenated
styrene-isoprene block copolymer, or non-functionalized olefin
copolymer VM may be used in combination therewith.
[0103] Representative examples of suitable viscosity modifiers
other than the high molecular weight olefin copolymers (OCPs)
containing dispersing groups of the invention are polyisobutylene,
copolymers of ethylene and propylene, polymethacrylates,
methacrylate copolymers, copolymers of an unsaturated dicarboxylic
acid and a vinyl compound, interpolymers of styrene and acrylic
esters, and partially hydrogenated copolymers of styrene/isoprene,
styrene/butadiene, and isoprene/butadiene, as well as the partially
hydrogenated homopolymers of butadiene and isoprene.
[0104] Pour point depressants (PPD), otherwise known as lube oil
flow improvers (LOFIs) lower the temperature. Compared to VM, LOFIs
generally have a lower number average molecular weight. Such
additives are well known. Typical additives that improve the low
temperature fluidity of the fluid are C.sub.8 to C.sub.18 dialkyl
fumarate/vinyl acetate copolymers, and polymethacrylates. Like VM,
LOFIs can 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 additives.
[0105] Foam control can be provided by an antifoamant of the
polysiloxane type, for example, silicone oil or polydimethyl
siloxane.
[0106] Some of the above-mentioned additives can provide a
multiplicity of effects; thus for example, a single additive may
act as a dispersant-oxidation inhibitor. This approach is well
known and need not be further elaborated herein.
[0107] In the present invention it may be necessary to include an
additive which maintains the stability of the viscosity of the
blend. Thus, although polar group-containing additives achieve a
suitably low viscosity in the pre-blending stage it has been
observed that some compositions increase in viscosity when stored
for prolonged periods. Additives which are effective in controlling
this viscosity increase include the long chain hydrocarbons
functionalized by reaction with mono- or dicarboxylic acids or
anhydrides which are used in the preparation of the ashless
dispersants as hereinbefore disclosed.
[0108] 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. Representative effective amounts of such
additives, when used in crankcase lubricants, are listed below. All
the values listed are stated as mass percent active ingredient.
2 MASS % MASS % ADDITIVE (Broad) (Preferred) Metal Detergents
0.1-15 0.2-9 Corrosion Inhibitor 0-5 0-1.5 Metal Dihydrocarbyl
Dithiophosphate 0.1-6 0.1-4 Antioxidant 0-5 0.01-2 Pour Point
Depressant 0.01-5 0.01-1.5 Antifoaming Agent 0-5 0.001-0.15
Supplemental Antiwear Agents 0-1.0 0-0.5 Friction Modifier 0-5
0-1.5 Viscosity Modifier 0.01-10 0.25-3 Basestock Balance
Balance
[0109] Fully formulated lubricating oil compositions of the present
invention preferably have a sulfur content of less than about 0.3
wt. %, preferably less than about 0.25 wt. % more preferably less
than about 0.20 wt. %, most preferably less than about 0.15 wt. %.
Preferably, the Noack volatility of the fully formulated
lubricating oil composition (oil of lubricating viscosity plus all
additives) will be no greater than 12, such as no greater than 10,
preferably no greater than 8. Fully formulated lubricating oil
compositions of the present invention preferably have a sulfated
ash (SASH) content of less than about 0.5 wt. %.
[0110] 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.
[0111] The final composition may employ from 5 to 25 mass %,
preferably 5 to 18 mass %, typically 10 to 15 mass % of the
concentrate, the remainder being oil of lubricating viscosity.
[0112] This invention will be further understood by reference to
the following examples, wherein all parts are parts by weight,
unless otherwise noted and which include preferred embodiments of
the invention.
EXAMPLES
[0113] The most recent and stringent industry standard test for
evaluating the ability of diesel engine oils to control
soot-induced viscosity increase, is conducted in a T-11,
EGR-equipped diesel engine, and is commonly referred to as the
"Mack T-11" test (ASTM designation number not yet assigned). The
Mack T-11 test determines the used oil soot load at which the
difference between used oil KV-100 (kinematic viscosity at
100.degree. C., reported in cSt.) and KV-100 of a sheared fresh oil
sample exceeds 12. To pass, a lubricating oil composition must
score at least 6 (6% soot load). Higher numbers indicate better
results (more soot handling capability).
[0114] To demonstrate the advantages of the present invention, a
comparison was made between the T-11 performance of lubricating oil
compositions formulated with Group II base oil, a base DI
(detergent-inhibitor) package and modified versions thereof. The
base DI package was a commercial heavy duty diesel (HDD) package
containing dispersant, a detergent blend, a hindered phenyl (HP)
antioxidant (AO), antiwear agent (ZDDP) and an olefin copolymer
viscosity modifier. The dispersant employed ("Disp. 1") was a high
molecular weight PIBSA-PAM-type dispersant (about 2200 M.sub.n PIB)
having a functionality of about 1.4 and a nitrogen content of about
1.2 wt. %. This "base lubricant" provided a calculated (based on
bench test results) Mack T-11 score of 3.6.
[0115] "Disp. 2" is a commercial low molecular weight
PIBSA-PAM-type dispersant (about 1000 M.sub.n PIB) and a nitrogen
content of about 1.6 wt. %. HITEC 5777 (H5777), a commercial
product available from Ethyl Corporation, is a multifunctional
dispersant viscosity modifier (DVM), which is prepared by
functionalizing a high molecular weight ethylene-propylene
copolymer with maleic anhydride, and derivatizing the resulting
functionalized copolymer with arylphenylamine. "DPA", or
dialkyl-diphenylamine, is a low molecular weight compound
conventionally used in lubricating oil compositions as an
antioxidant (AO). Using the above-components, lubricating oil
compositions representing variations of the base lubricant were
prepared as shown and subjected to Mack T-11 testing. Both
calculated and actual Mack T-11 test results are provided.
3TABLE 1 Disp. N DVM N AO N Total N Mack T-11 Mack T-11 Ex. Disp.
(wt. %) (ppm) DVM/Amount (ppm) AO (ppm) (ppm) (Predicted)
(Measured) Base Disp. 1 876 -- -- HP -- 876 3.6 -- Comp. 1 Disp. 1
1679 -- -- HP -- 1679 5.1 5.2 Comp. 2 Disp. 2 1420 -- -- HP -- 1420
2.6 2.6 Comp. 3 Disp. 1 876 -- -- DPA 140 1016 3.1 -- Inv. 1 Disp.
1 876 H5777/0.9 38 DPA 140 1054 6.9 6.8
[0116] A comparison between the results achieved with the base
lubricant and Comp. 1 demonstrates that increased nitrogen content
improves Mack T-11 performance to a certain extent. Testing of
Comp. 2 shows that the use of a low molecular weight dispersant, at
higher nitrogen content, causes a debit in Mack T-11 performance,
as does the introduction of low molecular weight DPA (Comp. 3). As
shown by the results achieved with Inv. 1, the combination of a
high molecular weight dispersant and a small amount of an aminated,
high molecular weight olefin copolymer provides an improvement in
soot handling performance far greater than would be forecast based
on compositional nitrogen content. The Mack T-11 results
demonstrate that compositions of the invention achieve Mack T-11
results exceeding those of compositions containing approximately
double the amount of dispersant nitrogen (Comp 1), even in the
presence the performance debit-causing low molecular weight DPA
antioxidant.
[0117] As a bench test, a Haake Rheometer can used to simulate the
soot viscosity performance in the Mack T-11 test using carbon black
as a soot surrogate. This test method uses a rheometer in a
controlled shear rate mode of operation to determine the rotational
viscosity of heavy duty diesel oils at 100.degree. C. at different
levels of carbon black. A fresh oil sample is heated at 90.degree.
C. for 30 minutes and then added slowly to the corresponding amount
of carbon black (e.g., 99.00 g of fresh oil plus 1.00 gram carbon
black for a 1% carbon black test). The mixture is heated at
90.degree. C. and blended overnight (16 hours). The blend is then
heated to 100.degree. C. and blended for 30 minutes before
testing.
[0118] Lubricating oil samples, prepared with a Group I base oil
and a base DI package identical but for the dispersant employed,
were tested in a Haake Rheometer according to the above procedure,
at a carbon black level of 4.76 wt. % and a shear rate of 0.45
sec.sup.-1. The samples all contained PIBSA-PAM-type dispersants of
varying functionalities and molecular weight distributions; the
amount of dispersant in each sample was adjusted to provide
comparable dispersant nitrogen levels. Dispersants having a MWD of
1.8 were based on HR-PIB while those having a MWD of 2.1 were
derived from conventional PIB. The measured rotational viscosities
of the samples are set forth in Table 2:
4TABLE 2 Polymer Dispersant Sample Nitrogen Rot. Viscosity Sample
MWD Functionality Content (gN/100 g) (Pa.multidot. s) A 1.8 1.4
0.050 2.476 B 1.8 1.4 0.025 5.546 C 2.1 1 0.050 3.470 D 2.1 1 0.025
6.105
[0119] The data of Table 2 demonstrate that, when used at
comparable nitrogen levels, dispersants having a higher level of
functionality and narrow molecular weight distribution provide an
improved ability to maintain soot dispersal in the oil.
[0120] Using the above-described procedure, samples containing
borated dispersants were then compared to otherwise identical
samples containing non-borated dispersants. All dispersants were
PIBSA-PAM-type dispersants having a polymer number average
molecular weight of about 2200 and a functionality of 1.4.
Dispersants based on both HR-PIB (MWD of 1.8) and conventional PIB
(MWD of 2.1) were tested. The results are provided in Table 3:
5TABLE 3 Rot. Polymer Sample Nitrogen Dispersant Boron Viscosity
Sample MWD Content (gN/100 g) Content (wt. %) (Pa.multidot. s) E
1.8 0.050 0.00 5.02 F 1.8 0.050 0.27 7.35 G 2.1 0.050 0.00 4.00 H
2.1 0.050 0.13 6.30 I 1.8 0.025 0.00 6.06 J 1.8 0.025 0.27 7.19 K
2.1 0.025 0.00 7.42 L 2.1 0.025 0.13 9.02
[0121] The above data demonstrate that the presence of significant
amounts of boron adversely affect the resulting performance of the
dispersant. A comparison between the samples containing the
HR-PIB-based dispersant and the corresponding samples containing
the dispersant produced from conventional PIB further illustrates
the advantages of using a dispersant based on a polymer having a
narrow molecular weight distribution.
[0122] The disclosures of all patents, articles and other materials
described herein are hereby incorporated, in their entirety, into
this specification by reference. All amounts are expressed on an
active ingredient (AI) basis, unless otherwise indicated.
Compositions described as "comprising" a plurality of defined
components are to be construed as including compositions formed by
mixing the defined plurality of defined components. Principles,
preferred embodiments and modes of operation of the present
invention have been described in the foregoing specification. What
applicants submit is their invention, however, is not to be
construed as limited to the particular embodiments disclosed, since
the disclosed embodiments are regarded as illustrative rather than
limiting. Changes may be made by those skilled in the art without
departing from the spirit of the invention.
* * * * *