Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02735498 2011-03-30
=
- 1 -
LUBRICATING OIL COMPOSITION
The present invention relates to lubricating oil compositions. More
particularly, the present invention relates to lubricating oil compositions
for use in
engines comprising emission control systems.
BACKGROUND OF THE INVENTION
Environmental concerns have led to continued efforts to reduce the CO,
hydrocarbon and nitrogen oxide (NOõ) emissions of compression ignited (diesel-
fueled) and spark ignited (gasoline-fueled) light duty internal combustion
engines.
Further, there have been continued efforts to reduce the particulate emissions
of
compression ignited light duty internal combustion engines. To meet the
current and
upcoming emission standards for vehicles, original equipment manufacturers
(OEMs) rely on the use of exhaust gas after-treatment devices. Such exhaust
gas
after-treatment devices may include exhaust gas recirculation arrangements and
cooled exhaust gas recirculation arrangements, catalytic converters, which can
contain one or more oxidation catalysts, NO, storage catalysts, and/or NH3
reduction
catalysts and/or a particulate trap. OEM's are also looking at using selective
catalytic reduction (SCR) systems to further reduce NO emissions.
Oxidation catalysts can become poisoned and rendered less effective by
exposure to certain elements/compounds present in engine exhaust gasses,
particularly by exposure to phosphorus and phosphorus compounds introduced
into
the exhaust gas by the degradation of phosphorus-containing lubricating oil
additives. Reduction catalysts are sensitive to sulfur and sulfur compounds in
the
engine exhaust gas introduced by the degradation of both the base oil used to
blend
the lubricant, and sulfur-containing lubricating oil additives. Particulate
traps can
become blocked by metallic ash, which is a product of degraded metal-
containing
lubricating oil additives. Thus in addition to designing engines to include a
variety
of emission control systems, OEM's also require lubricating oil compositions
to be
CA 02735498 2011-03-30
4
- 2 -
formulated to reduce the presence of detrimental materials in the exhaust gas
stream.
At the same time, the selected lubricating oil composition must provide
adequate
lubricant performance, including adequate wear protection and detergency.
European patent application 1 167 497 A2 discloses a lubricating oil
composition having restricted sulfur, phosphorous and sulfated ash content
comprising an ashless dispersant with a certain nitrogen content, a metal-
containing
detergent containing an organic acid metal salt selected from the group
comprising
an alkali or alkaline earth metal salt of an alkyl salicylic acid and an
alkali or
alkaline earth metal salt of an alkylphenol derivative having a marmich base
structure providing a certain sulphated ash content, a zinc
dialkyldithiophosphate
providing a specified phosphorus amount and an oxidiation inhibitor.
Lubricating
oils formulated in accordance with this patent application are stated to
exhibit good
high temperature detergency despite the lower sulfur, phosphorus and sulphated
ash
levels of the compositions.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the present invention there is provided a
lubricating oil composition having a phosphorus content of up to 0.12 wt%, a
sulfated ash content of up to 1.2 wt% comprising, (a) a major amount of an oil
of
lubricating viscosity; (b) an alkali metal or alkaline earth metal alkyl
salicylate
lubricating oil detergent providing from 7-15 mmol of salicylate soap per
kilogram
of lubricating oil composition; (c) one or more dispersants providing the
lubricating
oil composition with from at least 0.12 wt% to 0.20 wt% atomic nitrogen, based
on
the weight of the lubricating oil composition, and (d) a dispersant-viscosity
modifier.
In accordance with a second aspect of the present invention there is provided
a method of lubricating a vehicle engine comprising an exhaust gas
recirculation
(EGR) system comprising use in that engine of a lubricating oil composition
according to the first aspect of the invention.
CA 02735498 2011-03-30
- 3 -
In accordance with a third aspect of the present invention there is provided a
method according to the second aspect, wherein the engine further comprises a
selective catalytic reduction (SCR) system.
Unless otherwise stated, all amounts of additives are reported in wt. % on an
active ingredient ("a.i.") basis, i.e., independent of the diluent or carrier
oil.
Oil of Lubricating Viscosity
The oil of lubricating viscosity may be selected from Group I, II, III, W or V
base stocks, synthetic ester base stocks or mixtures thereof. The base stock
groups
are defined in the American Petroleum Institute (API) publication "Engine Oil
Licensing and Certification System", Industry Services Department, Fourteenth
Edition, December 1996, Addendum 1, December 1998. The base stock will have a
viscosity preferably of 3-12, more preferably 4-10, most preferably 4.5-8
mm2/s
(cSt.) at 100 C.
(a) Group I mineral oil base stocks contain less than 90% saturates and/or
greater than 0.03% sulfur and have a viscosity index greater than or
equal to 80 and less than 120 using the test methods specified in
Table A below.
(b) Group II mineral oil base stocks contain greater than or equal to 90%
saturates and less than or equal to 0.03% sulfur and have a viscosity
index greater than or equal to 80 and less than 120 using the test
methods specified in Table A below.
(c) Group III mineral oil base stocks contain greater than or equal to 90%
saturates and less than or equal to 0.03% sulfur and have a viscosity
index greater than or equal to 120 using the test methods specified in
Table A below.
CA 02735498 2011-03-30
- 4 -
(d) Group IV base stocks are polyalphaolefins (PAO).
(e) Suitable ester base stocks that can be used comprise the esters of
dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic
acids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid,
sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic
acid, alkyl malonic acids, alkenyl malonic acids, etc.) with a variety
of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol 2-
ethylhexyl alcohol, ethylene glycol, diethylenc glycol monoether,
propylene glycol, etc.) Specific examples of these esters include
dibutyl adipate, di(e-ethylhexyl) sebacate, din-n-hexyl fumarate,
dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl
phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl
diester of linoleic acid dimer, the complex ester formed by reacting
one mole of sebacic acid with two moles of tetraethylene glycol and
two moles of 2-ethylhexanoic acid and the like.
Esters useful as synthetic base stock oils also include those made from C5 to
C12 monocarboxylic acids and polyols and polyol ethers such as neopentyl
glycol,
trimethylol propane, pentaerythritol, dipentaerythritol, tripentaerythritol,
etc.
In one embodiment of the present invention, the oil of lubricating viscosity
comprises less than 50 wt% of a Fischer-Tropsch base oil, suitably less than
30 wt%,
preferably less than 10 wt% and most preferably substantially no Fischer-
Tropsch
base oil; wherein substantially no Fischer-Tropsch base oil means no more than
an
impurity amount.
Table A - Analytical Methods for Testing Base Stocks
Property Test Method
Saturates ASTM D2007
Viscosity Index ASTM D2270
CA 02735498 2011-03-30
- 5 -
Sulfur ASTM D2622, D4294,
D4927, or D3120
Metal Salicvlate Detergent
The present invention requires the presence of at least one alkali metal or
alkaline earth lubricating oil salicylate detergent.
The metal salicylate detergent may be C8-C30 alkyl salicylates or mixtures
thereof, with C10-C20 alkyl salicylates being particularly preferred.
Preferably, the
salicylate detergent will be a calcium and/or magnesium salicylate and will
have a
Total Base Number at 100% active mass (TBN) between 10 and 1000, more
preferably between 20 and 850. The most preferred detergent for use in this
invention is one or a mixture of overbased calcium alkyl salicylate detergents
having
a TBN between 300 and 600. In one embodiment, the metal salicylate detergent
comprises substantially no magnesium alkyl salicylate detergent.
In the present invention, the amount of metal salicylate detergent used can
vary broadly, but typically will be from about 0.1 to about 5 wt.%, preferably
0.5 to
1.5 wt.% based on the total weight of the composition, so as to provide from 7-
15
mmoles of metal salicylate detergent per kilogram of the finished oil
composition.
Suitably, the amount of metal salicylate detergent used in the present
invention
provides the composition with at least 8 mmol soap per kilogram of the
finished oil
composition. Suitably, the amount of metal salicylate detergent used in the
present
invention provides the composition with no more than 11 mmol soap per kilogram
of the finished oil composition.
Suitably, the metal salicylate detergent provides greater than 0.3 mass%,
preferably at least 0.4 mass% metal as sulphated ash to the lubricating oil
composition.
CA 02735498 2011-03-30
- 6 -
The metal salicylate may be the sole metal lubricating oil detergent present
in
the lubricating oil compositions of the invention. Alternatively, other metal-
containing detergents, such as metal sulfonates or phenates, may be present in
the
lubricating composition. Advantageously, where the lubricating oil composition
comprises a mixture of detergent types, the lubricating oil composition
suitably
comprises a mixture of metal salicylate and metal sulphonate detergents. The
additional detergents may be either calcium or magnesium metal salts. In one
embodiment of the present invention the additional detergents are calcium
metal
salts and the lubricating oil composition comprises substantially no magnesium
metal salts. Preferably, the salicylate detergent provides the majority of the
detergent additive in the lubricating oil composition.
By substantially no magnesium metal salt detergent and substantially no
magnesium alkyl salicylate detergent it is meant no more than an impurity
amount,
such as an amount providing less than 50 ppm magnesium preferably less than 30
ppm magnesium and most preferably less than 10 ppm magnesium.
Metal salts of organic acids typically used as lubricating oil detergents are
present as stable colloidal dispersions of salt in oil. The components are
generally
made by neutralizing the organic acid with a strong metal base in the presence
of
process aids. When the component is overbased, the organic acid is neutralized
with
a strong metal base in the presence of an acidic gas (often carbon dioxide).
In
consequence both the organic acid and the acidic gas are converted to the
metal salt
and the component contains metal in an amount in excess of that required to
neutralize the organic acid.
Manufacture of these components is extremely complex and the final
composition of the colloidal dispersion is not known with accuracy. For
example
sulfurized metal phenates are generally described as bis-thiophenates with
sulfur
linkages of varying lengths. In fact the number of phenolic groups actually
linked
together is not known with certainty. Similarly, the amount of phenol assumed
to
CA 02735498 2011-03-30
- 7 -
convert to a metal salt is often assumed to be 100%. In fact the degree of the
neutralization depends on the acidity of the phenol and the acidity of the
neutralizing
base. Further the equilibria established when the component is made shift
whenever
the component is blended with other materials containing strong bases. For
these
reasons, the amounts of carbonate, sulfonate, and phenolic hydroxide present
in a
lubricant are inferred from the amounts present in the individual components
that are
blended to make the finished lubricant. And those amounts are in turn inferred
from
the charge ratios of raw materials used to make the detergents or by resort to
analytical methods that can determine detectable moieties allowing inference
of the
remaining moieties.
Thus the moles of metal salt of an organic acid present can be determined
directly in some cases and in others must be derived. When the salt is a
calcium
sulfonate, direct analysis is possible using the liquid chromatography method
described in ASTM 3712. For other organic acids, the moles of salt must be
derived. When this is required tittimetry including two phase titrimetric
methods,
total acid number (TAN) as determined using ASTM D664, dialysis and other well
known analytical techniques allow determination of the organic salt content.
Thus
for phenates and carboxylates (including salicylates) the total amount of
metal must
be determined and allocated between organic and inorganic acids using a metal
ratio.
The total amount of metal present is conveniently determined by inductively
coupled
plasma atomic emission spectrometry--ASTM D4951. Metal ratio is defined as the
total amount of metal present divided by the amount of metal in excess of that
required to neutralize any organic acid present, i.e., the amount of metal
neutralizing
inorganic acids. Metal ratios are quoted by manufacturers of commercial
detergents
and can be determined by a manufacturer having knowledge of the total amount
of
salts present and the average molecular weight of the organic acid. The amount
of
metal salt present in a detergent may be determined by dialyzing the detergent
and
quantifying the amount of the residue. If the average molecular weight of the
organic salts is not known, the residue from the dialyzed detergent can be
treated
with strong acid to convert the salt to its acid form, analyzed by
chromatographic
CA 02735498 2011-03-30
op
- 8 -
methods, proton NMR, and mass spectroscopy and correlated to acids of known
properties. More particularly, the detergent is dialysed and then residue is
treated
with strong acid to convert any salts to their respective acid form. The
hydroxide
number of the mixture can then be measured by the method described in ASTM
D1957. If the detergent contains non-phenolic hydroxyl groups on the phenolic
compound (e.g., alcoholic derivatives of ethylene glycol used in manufacture
of
commercial phenates or carboxylic acid groups on salicylic acid), separate
analyses
must be conducted to quantify the amounts of those hydroxyl groups so that the
hydroxide number determined by ASTM D1957 can be corrected. Suitable
techniques to determine the quantity of non-phenolic hydroxyl groups include
analyses by mass spectroscopy, liquid chromatography, and proton NMR and
correlation to compounds having known properties.
A second method for deriving the number of moles of metal salt of an
organic acid present assumes that all of the organic acid charged to make the
component is in fact converted to the salt. In practice the two methods can
give
slightly different results, but both are believed to be sufficiently precise
to allow
determination of the amount of salt present to the precision required to
practice the
present invention.
In addition to being constrained by the amount of soap present in the finished
oil composition, the total amount of detergent present is limited by the
maximum 1.2
wt% sulfated ash content of the finished oil composition.
The total soap content of the lubricating oil is suitably no more than 1.5
wt%,
preferably no more than 1.2wt% and more preferably no more than 1.0 wt%. The
total
soap content of the lubricating oil composition is suitably at least 0.7 wt%,
preferably
at least 0.75 wt%.
CA 02735498 2011-03-30
- 9 -
Ashless Dispersant
An ashless dispersant generally comprises an oil soluble polymeric
hydrocarbon backbone having functional groups that are capable of associating
with
particles to be dispersed. Typically, the dispersants comprise amine, alcohol,
amide, or
ester polar moieties attached to the polymer backbone often via a bridging
group. 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. The most common dispersant in use is the well known
succinimide dispersant, which is a condensation product of hydrocarbyl-
substituted
succinic anhydride and a poly(alkyleneamine). Both mono-succinimide and bis-
succinimide dispersants (and mixtures thereof) are well known.
Preferred groups of dispersant include polyamine-derivatized poly a-olefin,
dispersants, particularly ethylene/butene alpha-olefin and polyisobutylene-
based
dispersants. Particularly
preferred are ashless dispersants derived from
polyisobutylene substituted with succinic anhydride groups and reacted with
polyethylene amines, e.g., polyethylene diamine, tetraethylene pentamine; or a
polyoxyalkylene polyamine, e.g., polyoxypropylene diamine,
trimethylolaminomethane; a hydroxy compound, e.g., pentaerythritol; and
combinations thereof. One particularly preferred dispersant combination is a
combination of (A) polyisobutylene substituted with succinic anhydride groups
and
reacted with (B) a hydroxy compound, e.g., pentaerythritol; (C) a
polyoxyalkylene
polyamine, e.g., polyoxypropylene diamine, or (D) a polyalkylene diamine,
e.g.,
polyethylene diamine and tetraethylene pentamine using about 0.3 to about 2
moles
of (B), (C) and/or (D) per mole of (A). Another preferred dispersant
combination
comprises a combination of (A) polyisobutenyl succinic anhydride with (B) a
CA 02735498 2011-03-30
- 10 -
polyalkylene polyamine, e.g., tetraethylene pentamine, and (C) a polyhydric
alcohol
or polyhydroxy-substituted aliphatic primary amine, e.g., pentaerythritol or
trismethylolaminomethane, as described in U.S. Patent No. 3,632,511.
Another class of ashless dispersants comprises Mannich base condensation
products. Generally, these products are prepared by condensing about one mole
of
an 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. Patent 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. Patent No.
3,442,808. Examples of
functionalized and/or derivatized olefin polymers
synthesized using metallocene catalyst systems are described in the
publications
identified supra.
The dispersant can be further post treated by a variety of conventional post
treatments such as boration, as generally taught in U.S. Patent Nos. 3,087,936
and
3,254,025. 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, in an amount sufficient to
provide from
about 0.1 to about 20 atomic proportions of boron for each mole of acylated
nitrogen
composition. Useful dispersants contain from about 0.05 to about 2.0 mass %,
e.g.,
from about 0.05 to about 0.7 mass % boron. The boron, which appears in the
product as dehydrated boric acid polymers (primarily (HB02)3), is believed to
attach
to the dispersant imides and diimides as amine salts, e.g., the metaborate
salt of the
diimide. Boration can be carried out by adding from about 0.5 to 4 mass %,
e.g.,
from about 1 to about 3 mass % (based on the mass of acyl nitrogen compound)
of a
boron compound, preferably boric acid, usually as a slurry, to the acyl
nitrogen
compound and heating with stirring at from about 135 C to about 190 C, e.g.,
140 C
CA 02735498 2011-03-30
- 11 -
to 170 C, for from about 1 to about 5 hours, followed by nitrogen stripping.
Alternatively, the boron treatment can be conducted by adding boric acid to a
hot
reaction mixture of the dicarboxylic acid material and amine, while removing
water.
Other post reaction processes commonly known in the art can also be applied.
The dispersant may also be further post treated by reaction with a so-called
"capping agent". Conventionally, nitrogen-containing dispersants have been
"capped" to reduce the adverse effect such dispersants have on the
fluoroelastomer
engine seals. Numerous capping agents and methods are known. Of the known
"capping agents", those that convert basic dispersant amino groups to non-
basic
moieties (e.g., amido or imido groups) are most suitable. The reaction of a
nitrogen-
containing dispersant and alkyl acetoacetate (e.g., ethyl acetoacetate (EAA))
is
described, for example, in U.S. Patent Nos. 4,839,071; 4,839,072 and
4,579,675.
The reaction of a nitrogen-containing dispersant and formic acid is described,
for
example, in U.S. Patent No. 3,185,704. The reaction product of a nitrogen-
containing dispersant and other suitable capping agents are described in U.S.
Patent
Nos. 4,663,064 (glycolic acid); 4,612,132; 5,334,321; 5,356,552; 5,716,912;
5,849,676; 5,861,363 (alkyl and alkylene carbonates, e.g., ethylene
carbonate);
5,328,622 (mono-epoxide); 5,026,495; 5,085,788; 5,259,906; 5,407,591 (poly
(e.g.,
bis)-epoxides) and 4,686,054 (maleic anhydride or succinic anhydride). The
foregoing list is not exhaustive and other methods of capping nitrogen-
containing
dispersants are known to those skilled in the art.
Preferably, the dispersant is a thermally maleated dispersant formed by
reacting
a polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester; and
a
polyamine, having from greater than about 1.3 to less than about 1.7 mono- or
di-
carboxylic acid producing moieties per polyalkenyl moiety and wherein said
polyalkenyl moiety has a molecular weight distribution (Mw/Mr,) of from 1.5 to
2.0
and a number average molecular weight (Ma) of from about 1800 to about 3000.
Such preferred dispersants are described, for example, in U.S. Patent Nos.
6,734,148
and 6,743,757.
- 12 -
The ashless dispersant is suitably present in an amount of from 4 to 10 wt.%,
preferably about 5 to 8 wt.% on a 100% active matter basis. The dispersant
should provide
the lubricating oil composition with at least 0.12 wt % of atomic nitrogen.
The dispersant
suitably provides the lubricating oil composition with no more than 0.2 wt %
atomic nitrogen.
Preferably, the dispersant provides the lubricating oil composition with from
0.12 to 0.17 wt%
atomic nitrogen.
The nitrogen content provided to the lubricating oil composition by the
dispersant can
be determined in accordance with the procedures of ASTM D5762
Preferred dispersants are borated or non-borated polyisobutenyl succinimide
dispersants wherein the polyisobutenyl has a number average molecular weight
(Mn) of about
400 to 3,000, preferably about 900 to 2,500.
An embodiment of the present invention utilizes polyisobutenyl succinimide
dispersants prepared using 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.
Patent No. 4,152,499. HR-PIB is known and HR-PIB is commercially available
under the
tradenames GlissopalTM (from BASFTM) and UltravisTM (from BP-AmocoTm).
The dispersant may comprise one dispersant or a combination of dispersants. If
the
dispersant comprises a combination of dispersants, the mixture suitable
comprises a low
molecular weight dispersant and a high molecular weight dispersant. A low
molecular weight
dispersant is a dispersant with a polymeric hydrocarbon backbone having a
number average
molecular weight (Mn) of about 500 to 1750. A high molecular weight dispersant
is a
dispersant with a polymeric hydrocarbon backbone having a number average
molecular
weight (Mn) of about 1800 to 3000. In
CA 2735498 2017-09-21
CA 02735498 2011-03-30
- 13 -
one embodiment, the total dispersant present in the lubricating oil
composition
comprises less than 40 mass%, less than 35 mass% or less than 30 mass% of low
molecular weight dispersants.
Polymer molecular weight, specifically Mn, 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).
Viscosity Modifier
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. Suitable
viscosity modifiers are
polyisobutylene, olefin copolymers, such as copolymers of ethylene and
propylene and
higher alpha-olefins, polymethacrylates, polyalkylmethacrylates, methacrylate
copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl
compound,
inter polymers 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 and
isoprene/divinylbenzene.
Dispersant-viscosity Modifier
Dispersant-viscosity modifiers are produced from grafting viscosity
modifiers, such as those described above, with grafting materials such as, for
- 14 -
example, maleic anhydride, and then reacting the grafted material with, for
example,
amines, amides, nitrogen-containing heterocyclic compounds or alcohol.
Examples of dispersant - viscosity modifiers include amine, derivatized
hydrocarbyl-
substituted mono-or di-carboxylic acids in which the hydrocarbyl substituent
comprises a
chain of sufficient length to impart viscosity index improving properties to
the compounds. In
general, the dispersant-viscosity modifier may be made from, for example, a
polymer of a C4
to C24 unsaturated ester of vinyl alcohol or a C3 to Ci0 unsaturated mono-
carboxylic acid or a
C4 to C10 di-carboxylic acid derivatized with an unsaturated nitrogen-
containing monomer
having 4 to 20 carbon atoms; a polymer of a C2 to C20 olefin with an
unsaturated C3 to C10
mono- or di-carboxylic acid derivatized with an amine, hydroxyl amine or an
alcohol; or a
polymer of ethylene with a C3 to C20 olefin further reacted either by grafting
a C4 to C20
unsaturated nitrogen-containing monomer thereon or by grafting an unsaturated
acid onto the
polymer backbone and then reacting carboxylic acid groups of the grafted acid
with an amine,
hydroxy amine or alcohol.
Preferred dispersant-viscosity modifiers comprise an aromatic amine
derivatized,
maleic anhydride grafted polymer. A preferred aromatic amine is N-phenyl -1,4
¨
phenylenediamine. Suitably the polymer is an ethylene-propylene copolymer. The
polymer
preferably has a number average molecular weight Mn of at least 5,000,
preferably at least
8,000 and suitably at least 10,000. The polymer may have an Mn as high as
100,000, but is
suitably no more than 60,000 and preferably around 40,000.
Suitable commercially available dispersant-viscosity modifiers include, but
are not
limited to, HiTecTm 5777, available from Afton ChemicalsTM, or multifunctional
polymethacrylate viscosity modifiers such as the Viscoplex TM or AcryloidTM
range of
products available from Rohmax GmbHTM
CA 2735498 2017-09-21
CA 02735498 2011-03-30
- 15 -
The present invention comprises a dispersant-viscosity modifier. It may be
present in amounts of from 0.05 to 5 wt. %, preferably about 0.5 to 3 wt.% on
an active
matter basis.
A lubricating oil composition according to the present invention may
additionally comprise one or more standard crankcase lubricating oil
additives;
examples or which are discussed below.
Antioxidants
Antioxidants reduce the tendency of base stocks to deteriorate in service
which
deterioration can be evidenced by the products of oxidation such as sludge and
varnish-like deposits on the metal surfaces and by viscosity growth. In the
present
invention they are suitably present in amount of from 0.1 to 5.0 wt.%.
Suitable
oxidation inhibitors include hindered phenols, alkaline earth metal salts of
alkylphenolthioesters having preferably C5 to C12 alkyl side chains, calcium
nonylphenol sulfide, ashless oil soluble phenates and sulfurized phenates,
phosphosulfurized or sulfurized hydrocarbons, alkyl substituted diphenylamine,
alkyl
substituted phenyl and napthylamines, phosphorous esters, metal
thiocarbamates,
ashless thiocarbamates and oil soluble copper compounds as described in U.S.
4,867,890. Most preferred are the dialkyl substituted diphenylamines, wherein
the
alkyl is C4-C20, such as dinonyl diphenylamine and the hindered phenols, such
as
isoocty1-3,5-di-tert-butyl-4-hydroxycinnamate and mixtures of same.
Zinc Dihydrocarbyldithi ophosphates
Zinc dihydrocarbyl dithiophosphates are oil soluble salts of dihydrocarbyl
dithiophosphoric acids and may be represented by the following formula:
CA 02735498 2011-03-30
-16-
-
RO
\
P ¨ S Zn
RIO
¨2
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,
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 (ZDDP)
can
therefore comprise zinc dialkyl dithiophosphates. ZDDP is the most commonly
used
antioxidantiantiwear agent in lubricating oil compositions for internal
combustion
engines, and in conventional passenger car diesel engines formulated to meet
present
European ACEA specifications. The lubricating oil compositions of the present
invention suitably contain an amount of ZDDP (or other dihydrocarbyl
dithiophosphate metal salt) that introduces about 0.02 to 0.12 wt.%,
preferably 0.02
to 0.1 wt.%, more preferably 0.05 to 0.08 wt.% of phosphorus into the
lubricating oil
composition. The phosphorus content of the lubricating oil compositions is
determined in accordance with the procedures of ASTM D5185.
Molybdenum Compound
For the lubricating oil compositions of this invention, any suitable oil
soluble
organo-molybdenum compound may be employed. The molybdenum compound is
thought to function both as an antiwear and antioxidant additive. Preferably,
dimeric
CA 02735498 2011-03-30
- 17 -
and trimeric molybdenum compounds are used. Examples of such oil soluble
organo-molybdenum compounds are the
dialkyldithiocarbamates,
dialkyldithiophosphates, dialkyldithiophosphinates, xanthates, thioxanthates,
carboxylates and the like, and mixtures thereof. Particularly preferred are
molybdenum dialkylthiocarbamates.
Suitable molybdenum dialkyldithiocarbamates include dimeric molybdenum
dialkyldithiocarbamates such as those having the following formula:
SX1
Ri I X I
/\/ 2 X4\11 /S R
\ /3
N¨ C Mo Mo :C ¨N
R2
X3 R4
R1 through R4 independently denote a straight chain, branched chain or
aromatic
hydrocarbyl group; and X1 through X4 independently denote an oxygen atom or a
sulfur atom. The four hydrocarbyl groups, R1 through R4, may be identical or
different from one another.
Another group of organo-molybdenum compounds useful in the lubricating
compositions of this invention are trinuclear (trimeric) molybdenum compounds,
especially those of the formula Mo3SkLõQz 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 in the oil, n is from 1 to 4, k
varies
from 4 to 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.
CA 02735498 2011-03-30
- 18 -
The ligands are selected from the group consisting of
¨X¨ R 1,
X1\
¨ ¨ R 2,
X2
x1 \ z R
3,
X2
x1 \ z
4,
X2
R2
and
X1 \ /0 ¨R1
5,
-y2 )/ \O -R2
-
and mixtures thereof, wherein X, Xi, X2, and Y are independently selected from
the
group of oxygen and sulfur, and wherein RI, R2, and R are independently
selected from
hydrogen and organo groups that may be the same or different. Preferably, the
organo
groups are hydrocarbyl 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.
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:
CA 02735498 2011-03-30
- 19 -
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).
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,
allcoxyl,
mercapto, alkylmercapto, nitro, nitroso, sulfoxy, etc.).
Importantly, the organo groups of the ligands should have a sufficient number
of carbon atoms to render the compound soluble 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 410
about 20.
Preferred ligands include dialkyldithiophosphate, alkylxanthate, carboxylates,
dialkyldithiocarbamate, and mixtures thereof Most preferred
are the
dialkyldithiocarbamates. Those skilled in the art will realize that formation
of the
compounds requires selection of ligands having the appropriate charge to
balance the
core's charge (as discussed below).
Compounds having the formula Mo3SkLQ, have cationic cores surrounded by
anionic ligands, wherein the cationic cores are represented by structures such
as
s ,11077\11.71
8
mo or- >01/
Mo t'440
6, and 7,
CA 02735498 2011-03-30
- 20 -
which 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, i.e., having multiple connections to one or more cores.
It is
believed that oxygen and/or selenium may be substituted for sulfur in the
core(s).
Oil-soluble trinuclear molybdenum compounds are preferred and can be
prepared by reacting in the appropriate liquid(s)/solvent(s) a molybdenum
source such
as (NH4)2Mo3S13-n(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 trinuclear molybdenum compounds can be formed
during
a reaction in the appropriate solvent(s) of a molybdenum source such as
(NI-14)21\403S13.n(H20), a ligand source such as tetralkylthiuram disulfide,
dialkyldithiocarbamate, or dialkyldithiophosphate, and a sulfur abstracting
agent such
cyanide ions, sulfite ions, or substituted phosphincs. 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 trinuclear molybdenum compound. The appropriate
liquid/solvent may be, for example, aqueous or organic.
The ligand chosen must have a sufficient number of carbon atoms to render the
compound soluble in the lubricating composition. The term "oil-soluble" as
used
herein does not necessarily indicate that the compounds or additives are
soluble in the
oil in all proportions. It does mean that they are soluble in use,
transportation, and
storage.
A sulfurized molybdenum containing composition prepared by (i) reacting an
acidic molybdenum compound and a basic nitrogen compound selected from the
group
consisting of succinimide, a carboxylic acid amide, a hydrocarbyl monoamine, a
CA 02735498 2011-03-30
- 21 -
phosphoramide, a thiophosphoramide, a Mannich base, a dispersant-viscosity
index
improver, or a mixture thereof, in the presence of a polar promoter, to form a
molybdenum complex (ii) reacting the molybdenum complex with a sulfur
containing
compound, to thereby form a sulfur and molybdenum containing composition is
useful
within the context of this invention. The sulfurized molybdenum containing
compositions may be generally characterized as a molybdenum/sulfur complex of
a
basic nitrogen compound. The precise molecular formula of these molybdenum
compositions is not known with certainty. However, they are believed to be
compounds in which molybdenum, whose valences are satisfied with atoms of
oxygen
or sulfur, is either complexed by, or the salt of one or more nitrogen atoms
of the basic
nitrogen containing compound used in the preparation of these compositions.
The lubricating compositions of the present invention may contain a minor
amount of an oil soluble molybdenum compound. If present an amount of at least
10
ppm up to about 600 ppm of molybdenum from a molybdenum compound may be
present in the lubricating oil composition. Preferably, about 10 ppm to 300
ppm of
molybdenum from a molybdenum compound is used. More preferably, no more than
100 ppm of molybdenum from a molybdenum compound is used. These values are
based upon the weight of the lubricating composition.
Friction Modifiers
The lubricating oil composition may contain an organic oil-soluble friction
modifier. Typically, the friction modifier may make up about 0.02 to 2.0 wt.%
of the
lubricating oil composition.
Friction modifiers include such compounds as aliphatic amines or ethoxylated
aliphatic amines, aliphatic fatty acid amides, aliphatic carboxylic acids,
aliphatic
carboxylic esters of polyols such as glycerol esters of fatty acids as
exemplified by
glycerol oleate, which is preferred, aliphatic carboxylic ester-amides,
aliphatic
phosphonates, aliphatic thiophosphates, etc., wherein the aliphatic group
usually
CA 02735498 2011-03-30
- 22 -
contains above about eight carbon atoms so as to render the compound suitably
oil
soluble. Also suitable are aliphatic substituted succinimides formed by
reacting one or
more aliphatic succinic acids or anhydrides with ammonia.
Pour point depressants, otherwise known as lube oil flow improvers, lower the
minimum temperature at which the fluid will flow or can be poured. Such
additives
are well known. Typical of those additives which improve the low temperature
fluidity of the fluid are Cg to C18 dialkyl fumarate/vinyl acetate copolymers,
polyalkylmethacrylates and the like. These may be used in amounts of from 0.01
to
5.0 wt.%, preferably about 0.1 to 3.0 wt.%. They are preferably used when
mineral oil
base stocks are employed but are not generally required when the base stock is
a PAO
or synthetic ester.
Foam control can be provided by many compounds including an antifoamant
of the polysiloxane type, for example, silicone oil or polydimethyl siloxane.
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 does not require further elaboration.
The individual additives may be incorporated into a base stock in any
convenient way. Thus, each of the components can be added directly to the base
stock
or base oil blend by dispersing or dissolving it in the base stock or base oil
blend at the
desired level of concentration. Such blending may occur at ambient temperature
or at
an elevated temperature. The invention comprising the product results from the
admixture of the additive components to form a lubricating oil composition.
Preferably, the additives are blended together to form a concentrate or
additive
package that is subsequently blended into base stock to make the finished
lubricant.
The concentrate or additive package may contain the viscosity modifier, or the
viscosity modifier may be added separately from the concentrate or additive
package to
-23 -
form the lubricating oil composition. The concentrate will typically be
formulated to
contain the additive(s) in proper amounts to provide the desired concentration
in the final
formulation when the concentrate is combined with a predetermined amount of a
base
lubricant.
The final crankcase lubricating oil formulation may employ from 10 to
50 mass %, preferably 15 to 40 mass% of the concentrate or additive package,
with the
remainder being base stock.
The present invention will now be further described with references to the
following illustrative examples; in which all quantities are given on a 100%
active matter
basis (i.e. excluding any diluent oil).
Example 1
Lubricating oil composition Oil A, was prepared by mixing an additive package
comprising 4.8 mass% of a polyisobutenyl succinimide dispersant made from a
polyisobutenyl with a number average molecular weight (Mn) of 2225, 1.08 mass%
of
polyisobutenyl succinimide dispersants made from a polyisobutenyl with a
number average
molecular weight (Mn) of 950, 0.74 mass% of a 321 TBN ovcrbascd calcium
salicylate
detergent and 0.34 mass% of a 565 TBN overbased calcium salicylate detergent,
0.43 mass%
of 709 TBN overbased magnesium sulfonate detergent, 0.84 mass% of HiTecTm 5777
dispersant-viscosity modifier, and additional zinc dialkyl dithiophosphate,
organic
molybdenum dithiocarbamate and antioxidant into a base stock comprising a
mixture of
Group I and Group III base oils. Oil A comprised 0.96 wt% sulphated ash, 0.08
wt%
phosphorous, 0.21 wt% sulfur, 130 ppm of atomic boron, 50 ppm molybdenum,
0.153 mass
% calcium and 0.069 mass% magnesium. The salicylate soap content of Oil A was
8.8mmol
and the total soap content of the Oil was 0.85 mass% soap. The calcium
salicylate detergents
provide the lubricating oil composition with 0.5 mass% calcium as sulphated
ash. The
dispersants provide the lubricating oil composition with 0.135 mass% nitrogen,
with 0.096
mass% N being
CA 2735498 2017-09-21
CA 02735498 2011-03-30
- 24 -
provided by the high molecular weigh dispersant and 0.039 mass% being provided
by
low molecular weight dispersant.
Oil A was then run in the ASTM D7422 engine test, more commonly known as
the Mack T-12. The Mack T-12 test is designed to evaluate the ability of an
oil to
minimize wear in an engine equipped with an EGR system. The Mack T-12 engine
test is part of the API CJ-4 and ACEA E6 performance categories.
The engine used is a modified Mack E7 E-Tech 460 rated at 460 bhp and 1,800
rpm, with EGR system. The test runs over 300 hours and at the end of the test
piston
ring wear, cylinder liner wear, lead bearing corrosion, oil consumption and
oxidation
are evaluated.
The pass fail limits and the results for Oil A are set out in Table 1 below:
Table 1
Criteria Pass/Fail Limit Oil A
Top ring weight loss <105 73
Cylinder wear <21 5.9
Lead corrosion <30
23
Oil Consumption <80
56.8
Merits 1000 1342
Oil A clearly passed the Mack T-12 test at the required API CJ-4 and ACEA
E6 performance levels.
Example 2
Lubricating oil composition Oil B, was prepared by mixing an additive
package comprising 4.8 mass% of a polyisobutenyl succinimide dispersant made
from
CA 02735498 2011-03-30
- 25 -
a polyisobutenyl with a number average molecular weight (Mn) of 2225, 1.08
mass%
of polyisobutenyl succinimide dispersants made from a polyisobutenyl with a
number
average molecular weight (Mn) of 950, 0.84 mass% of a 321 TBN overbased
calcium
salicylate detergent and 0.34 mass% of a 565 TBN overbased calcium salicylate
detergent, 0.43 mass% a 709 TBN of overbased magnesium sulfonate detergent,
0.84
mass% of HiTec 5777 dispersant-viscosity modifier, and zinc dialkyl
dithiophosphate,
molybdenum dithiocarbamate and antioxidant, into a base stock comprising a
mixture
of Group I and Group III base oils. Oil B comprised 1.0 wt% sulphated ash,
0.08 wt%
phosphorous, 0.21 wt% sulfur, 130 ppm of atomic boron 50 ppm molybdenum, 0.165
mass% calcium and 0.069 mass% magnesium. The salicylate soap content of Oil B
was 9.8mmol and the total soap content of the Oil was 0.92mass% soap. The
calcium
salicylate detergents providing the lubricating oil composition with 0.54
mass%
calcium as sulphated ash. The dispersants provide the lubricating oil
composition with
0.135 mass% nitrogen, with 0.096 mass% nitrogen being provided by high
molecular
weight dispersant and 0.039 mass% being provided by low molecular weight
dispersant.
Oil B was then run in the Mercedes-Benz 0M646 LA (CEC L-99-08) engine
test, which is part of the ACEA and Daimler specifications. This 300-hour test
uses
the 2.2L common rail diesel 0M646 DE 22 LA engine to evaluate engine lubricant
performance with respect to engine wear and overall cleanliness, as well as
piston
cleanliness and ring sticking.
The pass fail limits and the results for Oil B are set out in Table 2 below:
Table 2
Criteria Pass/Fail Limit (ACEA Oil B
E6)
Cam outlet wear <140
87.3
CA 02735498 2011-03-30
- 26 -
It can be seen from the results in Table 2 that Oil B passes the 0M646LA
engine test at the required performance level for ACEA E6. The test also
achieves
all of the necessary parameters for the more stringent MB 228.51 specification
level.
