U.S. patent application number 10/649572 was filed with the patent office on 2004-07-01 for combination of a low ash lubricating oil composition and low sulfur fuel.
Invention is credited to Arrowsmith, Stephen, Brown, Alisdair J..
Application Number | 20040127371 10/649572 |
Document ID | / |
Family ID | 32050093 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040127371 |
Kind Code |
A1 |
Arrowsmith, Stephen ; et
al. |
July 1, 2004 |
Combination of a low ash lubricating oil composition and low sulfur
fuel
Abstract
A lubricating oil composition for use in an internal combustion
engine operated with a fuel having a sulphur content of less than
50 ppm, that contains a minor amount of at least one
metal-containing detergent, which lubricating oil composition, when
formulated for use in a diesel engine has a total ash content of
less than 1.0 wt. %, and when formulated for use in a gasoline
engine has a total ash content of less than 0.7 wt. %.
Inventors: |
Arrowsmith, Stephen;
(Didcot, GB) ; Brown, Alisdair J.; (Abingdon,
GB) |
Correspondence
Address: |
Infineum USA L.P.
Law Department
1900 East Linden Avenue
P. O. Box 710
Linden
NJ
07036-0710
US
|
Family ID: |
32050093 |
Appl. No.: |
10/649572 |
Filed: |
August 27, 2003 |
Current U.S.
Class: |
508/518 |
Current CPC
Class: |
C10N 2030/52 20200501;
C10M 171/00 20130101; C10N 2070/02 20200501; C10N 2030/45 20200501;
C10N 2010/02 20130101; C10N 2040/25 20130101; C10N 2030/06
20130101; C10N 2010/04 20130101; C10M 2207/144 20130101; C10M
2219/044 20130101; C10M 2223/045 20130101; C10N 2030/43 20200501;
C10M 2207/103 20130101; C10M 2207/023 20130101; C10M 129/54
20130101; C10N 2030/50 20200501; C10N 2040/253 20200501; C10N
2040/255 20200501 |
Class at
Publication: |
508/518 |
International
Class: |
C10M 129/54 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2002 |
EP |
02256354.8 |
Claims
What is claimed is:
1. A lubricating oil composition used in, or for use in, a
compression ignited (diesel) internal combustion engine operated
with diesel fuel having a sulphur content of less than 50 ppm, said
lubricating oil composition comprising a major amount of oil of
lubricating viscosity, and a minor amount of at least one
metal-containing detergent, wherein said lubricating oil
composition has a total ash content of less than 1.0 wt. %, based
on the total weight of the lubricating oil composition.
2. The lubricating oil composition as claimed in claim 1, wherein
the total amount of ash contributed to said lubricating oil
composition by said at least one metal-containing detergent is from
0 to less than 0.9 wt. %, based on the total weight of the
lubricating oil composition.
3. A lubricating oil composition used in, or for use in, a spark
ignited (gasoline) internal combustion engine operated with
gasoline having a sulphur content of less than 50 ppm, said
lubricating oil composition comprising a major amount of oil of
lubricating viscosity, and a minor amount of at least one
metal-containing detergent, wherein said lubricating oil
composition has a total ash content of less than 0.7 wt. %, based
on the total weight of the lubricating oil composition.
4. The lubricating oil composition as claimed in claim 3, wherein
the total amount of ash contributed to said lubricating oil
composition by said at least one metal-containing detergent is from
0 to less than 0.6 wt. %, based on the total weight of the
lubricating oil composition.
5. The lubricating oil composition as claimed in claim 1 wherein
said at least one metal-containing detergent comprises at least one
salicylate detergent.
6. The lubricating oil composition as claimed in claim 5 wherein
said at least one metal-containing detergent consists essentially
of at least one salicylate detergent.
7. The lubricating oil composition as claimed in claim 3 wherein
said at least one metal-containing detergent comprises at least one
salicylate detergent.
8. The lubricating oil composition as claimed in claim 7 wherein
said at least one metal-containing detergent consists essentially
of at least one salicylate detergent.
9. A compression ignited (diesel) internal combustion engine
operated with diesel fuel having a sulphur content of less than 50
ppm, and lubricated with a lubricating oil composition as claimed
in claim 1.
10. The internal combustion engine as claimed in claim 9, wherein
said engine is a heavy duty diesel engine.
11. A spark ignited (gasoline) internal combustion engine operated
with gasoline having a sulphur content of less than 50 ppm, and
lubricated with a lubricating oil composition as claimed in claim
3.
12. The internal combustion engine as claimed in claim 9, wherein
said engine is equipped with a particulate trap.
13. The internal combustion engine as claimed in claim 11, wherein
said engine is equipped with a particulate trap.
14. The internal combustion engine as claimed in claim 9, wherein
said engine is equipped with an exhaust gas recirculation
system.
15. The internal combustion engine as claimed in claim 11, wherein
said engine is equipped with an exhaust gas recirculation
system.
16. The internal combustion engine as claimed in claim 14, wherein
exhaust gases and/or combustion air is cooled prior to introduction
into the engine combustion chamber.
17. The internal combustion engine as claimed in claim 15, wherein
exhaust gases and/or combustion air is cooled prior to introduction
into the engine combustion chamber.
18. A method of operating a compression ignited (diesel) internal
combustion engine, which method comprises operating said engine
with a fuel having a sulphur content of less than 50 ppm, and
lubricating said engine with a lubricating oil composition as
claimed in claim 1.
19. A method of operating a spark ignited (gasoline) internal
combustion engine, which method comprises operating said engine
with a fuel having a sulphur content of less than 50 ppm, and
lubricating said engine with a lubricating oil composition as
claimed in claim 3.
Description
[0001] The present invention relates to low-ash lubricating oil
compositions for use in, or used in, engines operated by
low-sulphur fuels, which oil compositions provide improved
lubricant properties, particularly improved lead corrosion
protection and improved compatibility with engines equipped with
particulate traps.
BACKGROUND OF THE INVENTION
[0002] Environmental concerns have led to continued efforts to
reduce the particulate emissions of vehicular internal combustion
engines, particularly compression ignited (diesel) internal
combustion engines. One technology being used to reduce particulate
emissions of diesel engines is the particulate trap, which is to be
incorporated into all passenger car and heavy duty diesel vehicles
designed to comply with the requirements of Euro IV emissions
legislation. When lubricant is consumed during use in the engine,
ash derived from metal-containing additives in the lubricant,
primarily from metal-containing detergents and antiwear agents,
accumulate in the particulate trap. This ash cannot be purged
without removing the trap from the engine and cleaning either via
washing or blowing the ash from the particulate trap with
compressed air. Ash allowed to accumulate in the particulate trap
may cause an increase in pressure behind the trap (back pressure).
If this back pressure becomes severe, internal exhaust gas
recirculation may occur with a resulting loss of fuel economy and
eventual engine failure. Because lubricants require acid
neutralization (provided by detergents), and wear protection
(provided by ZDDP), metal-containing additives that form ash upon
use in engines cannot simply be removed.
[0003] Concurrently, to provide compatibility with exhaust catalyst
systems, there has been a move to fuels containing lower sulphur
contents. While fuels used in the United States presently may
contain up to 400 ppm or more of sulphur, reduced sulphur fuels
containing no more than 50 ppm are now in use in Europe, and the
trend toward even lower sulphur fuels (>15 ppm) continues.
Further, for both environmental reasons, and to ensure proper
functioning of catalytic converters and certain aftertreatment
devices such as exhaust gas recirculation (EGR) systems,
particularly in heavy duty diesel applications, future lubricating
oil specifications (ACEA E6 in Europe, PC-10 in the United States)
will most likely require lubricating oil compositions to contain
reduced amounts of phosphorus and sulphur.
[0004] The use of reduced amounts of ZDDP, in combination with low
sulphur fuels is described in WO 02/18521. In WO 02/18521, it is
noted that in spite of the reduced lubricity of low-sulphur fuels,
the amount of metal-containing antiwear agent, particularly ZDDP
can be reduced while maintaining adequate wear performance. While
reducing the amount of added ZDDP will reduce the ash content of
the lubricant, WO 02/18521 does not suggest the use of lubricants
in which ash content is minimized by reducing the amount of other
metal-containing additives, particularly metal-containing
detergents.
[0005] Therefore, it would be advantageous to identify other means
for reducing the amount of metal-containing additives, and thus,
the ash content of lubricating oil compositions used in combination
with low sulphur fuels, such that said lubricating oil compositions
are more suitable for use in engines provided with particulate
traps.
[0006] Engine combustion generates nitrogen oxide gases (NO.sub.x).
Further, when sulphur-containing fuel is burned in the engine, the
sulphur is converted to sulphur oxide gases (SO.sub.x). In
addition, one of the major by-products of the combustion of a
hydrocarbon fuel is water vapor. When the NO.sub.x and SO.sub.x
gases react with the water vapor mineral acids are formed. A
portion of the mineral acids becomes introduced into the lubricants
via blow-by causing engine corrosion. These problems are
exacerbated in engines in which emissions are reduced by means of
exhaust gas recirculation (EGR) systems, particularly EGR systems
in which exhaust gases and/or combustion air is cooled prior to
introduction into the engine combustion chamber. Acids, including
mineral acids, are neutralized by the action of detergents in the
lubricant.
[0007] It was previously believed that NO.sub.x gases were the
major contributor to acids that cause corrosion in the engine
because of the greater proportion of NO.sub.x gases compared to
other mineral acid forming gases (see FIG. 1). The amount of
SO.sub.x gases was considered a lesser concern since many typical
fuels contain only about 400 ppm of sulphur, and reducing the
sulphur content to, for example 50 ppm, does not result in a
significant reduction in the overall amount of acid in the
lubricant. Therefore, it was believed that a reduction in the
amount of sulphur in the fuel would not have a significant impact
in the amount of detergent needed to neutralize acid in the
lubricant. Surprisingly, it has now been found that acids derived
from fuel sulphur are a major contributor to engine corrosion and
the amount of sulphur in the fuel has a greater than expected
impact on engine corrosion. Therefore, unexpectedly, the amount of
detergent needed to neutralize mineral acids generated during
combustion and ameliorate engine corrosion can be reduced
dramatically in engines operated by low sulphur fuels. The use of
reduced levels of metal-containing detergents allows for the
formulation of low ash content lubricants that are more compatible
with engines equipped with particulate traps.
SUMMARY OF THE INVENTION
[0008] Therefore, in accordance with a first aspect of the
invention, there is provided a lubricating oil composition used in,
or for use in, a compression ignited (diesel) internal combustion
engine operated with diesel fuel having a sulphur content of less
than 50 ppm, preferably less than 30 ppm, more preferably less than
15 ppm, such as less than 10 ppm, said lubricating oil composition
comprising a major amount of oil of lubricating viscosity, and a
minor amount of at least one metal-containing detergent, wherein
said lubricating oil composition has a total ash content of less
than 1.0 wt. %, preferably less than 0.8 wt. %, such as less than
0.7 wt. %, more preferably less than 0.6 wt. %, based on the total
weight of the lubricating oil composition.
[0009] In an embodiment of the first aspect, the total amount of
ash contributed to said lubricating oil composition by said at
least one metal-containing detergent is from 0 to less than 0.9 wt.
%, preferably less than 0.8 wt. %, more preferably less than 0.7
wt. %, such as less than 0.6 wt. %, based on the total weight of
the lubricating oil composition.
[0010] In accordance with a second aspect of the invention, there
is provided a lubricating oil composition used in, or for use in, a
spark ignited (gasoline) internal combustion engine operated with
gasoline having a sulphur content of less than 50 ppm, preferably
less than 30 ppm, more preferably less than 15 ppm, such as less
than 10 ppm, said lubricating oil composition comprising a major
amount of oil of lubricating viscosity, and a minor amount of at
least one metal-containing detergent, wherein said lubricating oil
composition has a total ash content of less than 0.7 or less than
0.65%, preferably less than 0.6 wt. %, more preferably less than
0.5 wt. %, such as less 0.4 wt. %, based on the total weight of the
lubricating oil composition.
[0011] In an embodiment of the second aspect, the total amount of
ash contributed to said lubricating oil composition by said at
least one metal-containing detergent is from 0 to less than 0.6 or
less than 0.55 wt. %, preferably less than 0.5 wt. %, more
preferably less than 0.4 wt. %, such as less than 0.3 wt. %, based
on the total weight of the lubricating oil composition.
[0012] In an embodiment, independently of other embodiments, of
either the first or second aspect, said at least one
metal-containing detergent comprises, and preferably consists
essentially of, at least one salicylate detergent.
[0013] In accordance with a third aspect of the invention, there is
provided a compression ignited (diesel) internal combustion engine
operated with diesel fuel having a sulphur content of less than 50
ppm, preferably less than 30 ppm, more preferably less than 15 ppm,
such as less than 10 ppm and lubricated with a lubricating oil
composition as defined in the first aspect.
[0014] In accordance with a fourth aspect of the invention, there
is provided a spark ignited (gasoline) internal combustion engine
operated with gasoline having a sulphur content of less than 50
ppm, preferably less than 30 ppm, more preferably less than 15 ppm,
such as less than 10 ppm and lubricated with a lubricating oil
composition as defined in the second aspect.
[0015] In accordance with a fifth aspect of the invention, there is
provided a method of operating a compression ignited (diesel)
internal combustion engine, which method comprises operating said
engine with a fuel having a sulphur content of less than 50 ppm,
preferably less than 30 ppm, more preferably less than 15 ppm, such
as less than 10 ppm, and lubricating said engine with a lubricating
oil composition as defined in the first aspect.
[0016] In accordance with a sixth aspect of the invention, there is
provided a method of operating a spark ignited (gasoline) internal
combustion engine, which method comprises operating said engine
with a fuel having a sulphur content of less than 50 ppm,
preferably less than 30 ppm, more preferably less than 15 ppm, such
as less than 10 ppm, and lubricating said engine with a lubricating
oil composition as defined in the second aspect.
[0017] In accordance with a seventh aspect of the invention, there
is provided a use of a lubricating oil composition as defined in
either the first or second aspect to reduce the amount of
particulate ash generated by consumption of metal-containing
lubricant additives during operation of a lubricated internal
combustion engine operated with a fuel having a sulphur content of
less than 50 ppm, preferably less than 30 ppm, more preferably less
than 15 ppm, such as less than 10 ppm.
[0018] In accordance with an eighth aspect of the invention, there
is provided the use of a lubricating oil composition as defined in
either the first or second aspect to reduce corrosion in an
internal combustion engine operated with a fuel having less than 50
ppm of sulphur, preferably less than 30 ppm, more preferably less
than 15 ppm, such as less than 10 ppm.
[0019] In accordance with another aspect of the invention, there is
provided a combination of (i) a fuel having less than 50 ppm of
sulphur, preferably less than 30 ppm, more preferably less than 15
ppm, such as less than 10 ppm, and (ii) a lubricating oil
composition as defined in the first or second aspect, in an
internal combustion engine, such as a compression- or spark-ignited
engine.
[0020] The features of the invention will now be discussed in more
detail.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows graphically the amount of NO.sub.x and SO.sub.x
gas in the exhaust gas, as measured during the Mack T10 engine test
with and without an exhaust gas recirculation device, which engine
was fuelled with 400 ppm of sulfur fuel.
[0022] FIG. 2 shows graphically a comparison between TBN depletion
and TAN increase for low ash lubricating oil compositions in
engines operated with high and low sulphur content fuels.
[0023] FIG. 3 compares graphically the lead corrosion profile of
lubricating oil compositions containing phenate/sulfonate
detergents and salicylate detergents.
[0024] FIG. 4 compares graphically TBN depletion and TAN increase
profiles for lubricating oil compositions containing
phenate/sulfonate detergents and salicylate detergents.
DETAILED DESCRIPTION OF THE INVENTION
[0025] As described in the above aspects, the invention is
applicable to all internal combustion engines including both
spark-ignited (gasoline fueled) and compression-ignited (diesel
fueled) internal combustion engines.
[0026] In an embodiment, the present invention is particularly
applicable to internal combustion engines provided with a
particulate trap or an exhaust gas recirculation (EGR) system or
both particulate trap and an exhaust gas recirculation (EGR)
system. In the event that the engine is provided with an EGR system
the exhaust gases and/or combustion air is/are preferably cooled
prior to introduction into the engine combustion chamber.
[0027] Preferably, the internal combustion engine is a passenger
car diesel engine (PCD) or heavy duty diesel (HDD) engine, more
particularly a PCD or HDD engine provided with a particulate
trap.
[0028] Fuels, whether gasoline or diesel fuel, useful in the
practice of the invention have a sulphur content below 50 ppm,
preferably below 30 ppm, more preferably below 15 ppm, such as
below 10 ppm. In an embodiment, the sulphur content of the fuel is
at least 5 ppm. The level of sulphur may be determined using
various methods including X-ray (ASTM D2622-1) or UV (ASTM
D5453-93). Such fuels may comprise saturated, olefinic and aromatic
hydrocarbons or mixtures thereof. Such fuels can be derived from
straight run streams, thermally or catalytically cracked
hydrocarbon feedstocks, hydrocracked petroleum fractions,
catalytically reformed hydrocarbons or synthetically produced
hydrocarbon mixtures, such as those derived from methane. The
sulphur content of fuels containing sulphur can be reduced by known
methods, such as, for example, catalytic hydrodesulphurization.
[0029] 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.
[0030] 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.
[0031] Synthetic lubricating oils include hydrocarbon oils and
halo-substituted hydrocarbon oils such as polymerized and
interpolymerized olefins (e.g. polybutylenes, polypropylenes,
propylene-isobutylene copolymers, chlorinated polybutylenes,
poly(1-hexenes), poly(1-octenes), poly(1-decenes)); alkylbenzenes
(e.g. dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes,
di(2-ethylhexyl)benzenes); polyphenyls (e.g. biphenyls, terphenyls,
alkylated polyphenols); and alkylated diphenyl ethers and alkylated
diphenyl sulfides and derivative, analogs and homologs thereof.
[0032] Alkylene oxide polymers and interpolymers and derivatives
thereof where the terminal hydroxyl groups have been modified by
esterification, etherification, etc., constitute another class of
known synthetic lubricating oils. These are exemplified by
polyoxyalkylene polymers prepared by polymerization of ethylene
oxide or propylene oxide, and the alkyl and aryl ethers of
polyoxyalkylene polymers (e.g. methyl-polyiso-propylene glycol
ether having a molecular weight of 1000 or diphenyl ether of
poly-ethylene glycol having a molecular weight of 1000 to 1500);
and mono- and polycarboxylic esters thereof, for example, the
acetic acid esters, mixed C.sub.3-C.sub.8 fatty acid esters and
C.sub.13 Oxo acid diester of tetraethylene glycol.
[0033] Another suitable class of synthetic lubricating oils
comprises the esters of dicarboxylic acids (e.g. phthalic acid,
succinic acid, alkyl succinic acids and alkenyl succinic acids,
maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric
acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic
acids, alkenyl malonic acids) with a variety of alcohols (e.g.
butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoether, propylene
glycol). Specific examples of such esters includes dibutyl adipate,
di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate,
diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl
phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic
acid dimer, and the complex ester formed by reacting one mole of
sebacic acid with two moles of tetraethylene glycol and two moles
of 2-ethylhexanoic acid.
[0034] Esters useful as synthetic oils also include those made from
C.sub.5 to C.sub.12 monocarboxylic acids and polyols and polyol
esters such as neopentyl glycol, trimethylolpropane,
pentaerythritol, dipentaerythritol and tripentaerythritol.
[0035] Silicon-based oils such as the polyalkyl-, polyaryl-,
polyalkoxy- or polyaryloxysilicone oils and silicate oils comprise
another useful class of synthetic lubricants; such oils include
tetraethyl silicate, tetraisopropyl silicate,
tetra-(2-ethylhexyl)silicate,
tetra-(4-methyl-2-ethylhexyl)silicate, tetra-(p-tert-butyl-phenyl)
silicate, hexa-(4-methyl-2-ethylhexyl)disiloxane,
poly(methyl)siloxanes and poly(methylphenyl)siloxanes. Other
synthetic lubricating oils include liquid esters of
phosphorous-containing acids (e.g. tricresyl phosphate, trioctyl
phosphate, diethyl ester of decylphosphonic acid) and polymeric
tetrahydrofurans.
[0036] Unrefined, refined and re-refined oils can be used in
lubricants of the present invention. Unrefined oils are those
obtained directly from a natural or synthetic source without
further purification treatment. For example, a shale oil obtained
directly from retorting operations; petroleum oil obtained directly
from distillation; or ester oil obtained directly from an
esterification and used without further treatment would be an
unrefined oil. Refined oils are similar to unrefined oils except
that the oil is further treated in one or more purification steps
to improve one or more properties. Many such purification
techniques, such as distillation, solvent extraction, acid or base
extraction, filtration and percolation are known to those skilled
in the art. Re-refined oils are obtained by processes similar to
those used to provide refined oils but begin with oil that has
already been used in service. Such re-refined oils are also known
as reclaimed or reprocessed oils and are often subjected to
additionally processing using techniques for removing spent
additives and oil breakdown products.
[0037] The oil of lubricating viscosity may comprise a Group I,
Group II, Group III, Group IV or Group V base stocks or base oil
blends of the aforementioned base stocks. Preferably, the oil of
lubricating viscosity is a Group II, Group III, Group IV or Group V
base stock, or a mixture thereof, or a mixture of a Group I base
stock and one or more a Group II, Group III, Group IV or Group V
base stock. 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 itself will have a sulphur content
of less than 0.5%, preferably less than 0.05%, more preferably less
than 0.03%, by weight. The sulphur content of oil or oil blend is
preferably zero, more preferably at least 0.005 weight %.
[0038] 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%.
[0039] 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.
[0040] 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:
[0041] a) Group I base stocks contain less than 90 percent
saturates and/or greater than 0.03 percent sulphur and have a
viscosity index between 80 and 120;
[0042] b) Group II base stocks contain at least 90 percent
saturates and no more than 0.03% sulphur and have a viscosity index
between 80 and 120;
[0043] c) Group III base stocks contain at least 90 percent
saturates no more than 0.03% sulphur and have a viscosity index
between 80 and 120;
[0044] d) Group IV base stocks are polyalphaolefins (PAO).
[0045] 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 Sulphur ASTM D
2622 ASTM D 4294 ASTM D 4927 ASTM D 3120
[0046] 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.
[0047] Detergents that may be used include oil-soluble neutral and
overbased sulfonates, phenates, sulphurized 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 sulphurized 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.
[0048] 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
alkylaryl 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.
[0049] 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.
[0050] Metal salts of phenols and sulphurized phenols 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. Sulphurized phenols may be prepared
by reacting a phenol with sulphur or a sulphur containing compound
such as hydrogen sulfide, sulphur monohalide or sulphur dihalide,
to form products which are generally mixtures of compounds in which
2 or more phenols are bridged by sulphur containing bridges.
Alkylene bridged phenols are also suitable for use as metal
phenates.
[0051] 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.
[0052] Preferred examples of aromatic carboxylic acids are
salicylic acids and sulphurized derivatives thereof, such as
hydrocarbyl substituted salicylic acid and derivatives thereof.
Processes for sulphurizing, 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 phenol.
[0053] 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.
[0054] 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 and EP 0 750 659.
[0055] Preferably, the metal-containing detergent, present in the
lubricating oil compositions of the invention, comprises,
preferably consists essentially of, at least one salicylate
detergent. It is preferred that the detergent consists essentially
of a calcium salicylate having a TBN of less than 80 and another
calcium salicylate having a TBN greater than 150.
[0056] Surprisingly, it has been found that, in engines operated by
low-sulphur (less than 50 ppm) fuels, the amount of detergent
needed to provide detergency and acid neutralization can be reduced
from conventional amounts. Specifically, it has been found that in
diesel engines operated by low-sulphur (less than 50 ppm) fuels, an
amount of detergent contributing from 0 to less than 0.9 wt. %,
preferably less than 0.8 wt. %, more preferably less than 0.7 wt.
%, such as less than 0.6 wt % of ash to the lubricating oil
composition is preferably sufficient to provide detergency and acid
neutralization; in an embodiment the amount is zero ash, i.e. no
metal-containing detergents, preferably at least 0.1 wt % of ash is
derived from the metal containing detergent(s).
[0057] In gasoline engines operated by low-sulphur (less than 50
ppm) fuels, it has been found that an amount of detergent
contributing from 0 to less than 0.6 or less than 0.55 wt. %,
preferably less than 0.5 wt. %, more preferably less than 0.4 wt.
%, such as less than 0.3 wt %, of ash to the lubricating oil
composition is preferably sufficient to provide detergency and acid
neutralization; in an embodiment the amount is zero ash, i.e. no
metal-containing detergents, preferably at least 0.1 wt % of ash is
derived from the metal containing detergent(s).
[0058] This is in contrast to conventional lubricating oil
compositions for engines operated by high sulphur fuels, which
generally require amounts of detergent contributing more than 1.0
wt. % of ash for diesel engine lubricating oil compositions and
more than 0.6 wt. % of ash for gasoline engine lubricating oil
compositions. Ash content expressed as "sulfated ash" or "SASH" can
be determined by the methods of ASTM D874.
[0059] 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.
[0060] The use of reduced amounts of metal-containing detergents
allows for the formulation of lower ash content lubricating oil
compositions. Preferably, the total ash content of the lubricating
oil composition of the present invention is less than 0.9 wt. %,
preferably less than 0.8 wt. %, such as less than 0.7 wt. %, more
preferably less than 0.6 wt. %, such as less than 0.5 wt. % for
lubricating oil formulated for diesel engines. In an embodiment,
the lubricating oil formulated for diesel engines has zero ash,
i.e. no metal-containing additives, more preferably at least 0.1
weight t %, based on the weight of the lubricating oil
composition.
[0061] For gasoline engines, the total ash content of the
lubricating oil composition of the present invention is preferably
less than 0.65 wt. %, preferably less than 0.6 wt. %, such as less
than 0.5 wt. %, such as less than 0.4 wt. %, based on the total
weight of the lubricating oil composition. In an embodiment, the
lubricating oil formulated for gasoline engines has zero ash, i.e.
no metal-containing additives, more preferably at least 0.1 weight
t %, based on the weight of the lubricating oil composition.
[0062] Major sources of additive ash other than metal-containing
detergents, include metal-containing antioxidant and/or antiwear
agents, such as dihydrocarbyl dithiophosphate metal salts. The
metal may be an alkali or alkaline earth metal, or aluminum, lead,
tin, molybdenum, manganese, nickel or copper. The zinc salts are
conventionally 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 phenol with P.sub.2S.sub.5 and then neutralizing the
formed DDPA with a zinc compound. For example, a dithiophosphoric
acid can be made by reacting a mixture 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.
[0063] The preferred zinc dihydrocarbyl dithiophosphates are oil
soluble salts of dihydrocarbyl dithiophosphoric acids and may be
represented by the following formula: 1
[0064] 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. Preferably, the amount of dihydrocarbyl
dithiophosphate metal salt is reduced concurrent with the amount of
metal-containing detergent such that the dihydrocarbyl
dithiophosphate metal salt and other metal-containing additives
introduces no more than 0.1 wt. % to about 0.15 wt. % of ash into
the lubricating oil composition. The present invention may be
particularly useful when the lubricant phosphorus level is from 0
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. %, as determined by the method of ASTM
D5185.
[0065] As noted above, environmental concerns and expected future
oil specification requirements have also dictated that the overall
sulphur level of the lubricant be reduced. Preferably, lubricating
oil compositions of the present invention contain no more than 0.5
wt. %, preferably no more than 0.3 wt. %, most preferably no more
than 0.2 wt. % of sulphur, based on the total weight of the
lubricating oil composition. In an embodiment, the lubricating oil
composition contains at least 0.05, such as at least 0.1, wt % of
sulphur, as determined by the method of ASTM D5185.
[0066] Sulphur is contributed both by the base oil and certain
lubricant additives. Thus, to provide the preferred sulphur levels,
in addition to selecting low sulphur base oils (or sulphur-free
base oils), the use of sulphur-containing additives should be
minimized or avoided where possible. A reduction in the amount of
ZDDP to reduce phosphorus content will also reduce the sulphur
content of the lubricating oil composition. In addition, reduced
sulphur requirements favors the use of salicylate detergents, which
are sulphur-free, over phenate and sulfonate detergents.
2TABLE 2 Additive Contribution to Formulation Sulphur Approx % of
sulphur contribution Component to oil composition ZDDP (0.12% P)
0.24-0.28 ZDDP (0.05% P) 0.10-0.12 Detergent (PC-9) Salicylate 0.00
Phenate/Sulphonate 0.07-0.09 Diluent Oils VM/Components
0.04-0.06
[0067] 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
ashless dispersants, metal rust inhibitors, viscosity index
improvers, corrosion inhibitors, oxidation inhibitors, ashless
friction modifiers, anti-foaming agents, ashless anti-wear agents
and pour point depressants, some of which are described below.
These additives, where ashless (metal-free) do not bear on the
present invention. Where other metal-containing additives are used,
e.g. organo-molybdenum antioxidant/antiwear agents, it is
preferable to control the amount thereof and use, where possible,
alternate, metal-free additives.
[0068] The ashless dispersant 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 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.
[0069] Rust inhibitors selected from the group consisting of
nonionic polyoxyalkylene polyols and esters thereof,
polyoxyalkylene phenols, and anionic alkyl sulfonic acids may be
used.
[0070] Copper and lead bearing corrosion inhibitors may be used,
but are typically not required with the formulation of the present
invention. Typically such compounds are the thiadiazole
polysulfides containing from 5 to 50 carbon atoms, their
derivatives and polymers thereof. Derivatives of 1,3,4 thiadiazoles
such as those described in U.S. Pat. Nos. 2,719,125; 2,719,126; and
3,087,932; are typical. Other similar materials are described in
U.S. Pat. Nos. 3,821,236; 3,904,537; 4,097,387; 4,107,059;
4,136,043; 4,188,299; and 4,193,882. Other additives are the thio
and polythio sulfenamides of thiadiazoles such as those described
in UK Patent Specification No. 1,560,830. Benzotriazoles
derivatives also fall within this class of additives. When these
compounds are included in the lubricating composition, they are
preferably present in an amount not exceeding 0.2 wt. % active
ingredient.
[0071] Oxidation inhibitors or 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. Such oxidation inhibitors include hindered phenols,
alkaline earth metal salts of alkylphenolthioesters having
preferably C.sub.5 to C.sub.12 alkyl side chains, calcium
nonylphenol sulfide, ashless oil soluble phenates and sulphurized
phenates, phosphosulphurized or sulphurized hydrocarbons, alkyl
substituted diphenylamine, alkyl substituted phenyl and
naphthylamines, phosphorus esters, metal thiocarbamates, ashless
thiocarbamates and oil soluble copper compounds as described in
U.S. Pat. No. 4,867,890. Most preferred are the alkyl-substituted
diphenylamines.
[0072] 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
additives that improve the low temperature fluidity of the fluid
are C.sub.8 to C.sub.18 dialkyl fumarate/vinyl acetate copolymers,
polyalkylmethacrylates and the like.
[0073] Foam control can be provided by many compounds including an
antifoamant of the polysiloxane type, for example, silicone oil or
polydimethyl siloxane.
[0074] A small amount of a demulsifying component may be used. A
particularly suitable demulsifying component is described in EP
330,522. It is obtained by reacting an alkylene oxide with an
adduct obtained by reacting a bis-epoxide with a polyhydric
alcohol. The demulsifier should be used at a level not exceeding
0.1 mass % active ingredient. A treat rate of 0.001 to 0.05 mass %
active ingredient is conventional.
[0075] The viscosity modifier (VM) functions to impart high and low
temperature operability to lubricating oil. Suitable viscosity
modifiers are polyisobutylene, 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.
[0076] 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. Multifunctional viscosity
modifiers that also function as dispersants are also known. The use
of multifunctional additives is well known and does not require
further elaboration.
[0077] 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 (excluding metal detergents and metal dihydrocarbyl
dithiophates, which are discussed above), when used in crankcase
lubricants, are listed below. All the values listed are stated as
mass percent active ingredient.
3 MASS % MASS % ADDITIVE (Broad) (Preferred) Dispersant 1-10 1-7
Corrosion Inhibitor 0-5 0-1.5 Antioxidant 0-5 0.01-3 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
[0078] Preferably, the Noack volatility of the fully formulated
lubricating oil composition (oil of lubricating viscosity plus all
additives) will be no greater than 15, such as no greater than 13,
preferably no greater than 10, such as no greater than 8 wt. %, as
measured by ASTM 5880.
[0079] In a preferred embodiment, the lubricating oil composition
of the present invention is a multigrade lubricating oil
composition in the form of an SAE 15W-X, SAE 10W-X, SAE 5W-X or
0W-X composition, wherein X represents any one of 20, 30 and 40.
Preferably, the oil composition is in the form of an SAE 5W-X or
0W-X when used in a gasoline engine, and the oil composition is in
the form of an SAE 15W-X or 10W-X when used in a diesel engine.
Advantageously, X represents either 30 or 40, especially 30. The
properties of multigrades are defined in the Society of Automotive
Engineers document SAE J300.
[0080] 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.
[0081] The final composition may employ 5 to 25 mass %, preferably
5 to 18 mass %, typically 10 to 15 mass % of the concentrate (based
on active ingredient), the remainder being oil of lubricating
viscosity.
[0082] In this specification:
[0083] The term "hydrocarbyl" as used means that the group
concerned is primarily composed of hydrogen and carbon atoms and is
bonded to the remainder of the molecule via a carbon atom, but does
not exclude the presence of other atoms or groups in a proportion
insufficient to detract from the substantially hydrocarbon
characteristics of the group.
[0084] The term "comprising" or "comprises" means the presence of
stated features, integers, steps or components, but does not
preclude the presence or addition of one or more other features,
integers, steps, components or groups thereof. In the instance the
term "comprising" or "comprises" is used herein, the term
"consisting essentially of" and its cognate are within its scope
and are a preferred embodiment of it, and consequently the term
"consisting of" and its cognate are within the scope of "consisting
essentially of" and are a preferred embodiment of it.
[0085] The term "oil-soluble" or "oil-dispersible" does not mean
that the compounds are soluble, dissolvable, miscible or capable of
being suspended in the oil in all proportions. They do mean,
however, that the compounds are, for instance, soluble or stable
dispersible in the oil to an extent sufficient to exert their
intended effect in the environment in which the composition is
employed. Moreover, the additional incorporation of other additives
such as those described above may affect the solubility or
dispersibility of the compounds.
[0086] The term "major amount" means in excess of 50 mass % of the
composition.
[0087] The term "minor amount" means less than 50 mass % of the
composition.
[0088] 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
[0089] Lubricant comprising conventional additives,
metal-containing detergents and a ZDDP component were prepared by
methods known in the art. Table 3 provides the characteristics of
the lubricants used in the Mack T10 engine test. The lubricants in
Table 3 were blended to SAE 15W-40 viscometric grade.
[0090] The Mack T10 engine test developed for the API CI-4 category
was used to examine the bearing lead corrosion, ring and liner wear
performance of reduced ash lubricants also containing reduced
levels of phosphorus and sulphur. The standard Mack T10 test method
incorporating EGR was used, however the tests were run on a
non-automated stand. The fuel sulphur level was varied during the
experiments from 400 ppm to 15 ppm. All rated parameters were
reported in the normal manner with the exception that an overall
merit was not established.
[0091] A summary of the results obtained is given in Table 4. It is
clear from the data of Table 4 that a reduction in both phosphorus
and more particularly the ash content of the lubricant is possible
when using low sulphur fuel. Passing lead corrosion performance was
achieved at ash levels as low as 0.6% in combination with a
phosphorus content of 0.06% when using 15 ppm sulphur fuel. Testing
has demonstrated that fuel sulphur, even at the relatively low
concentration of 400 ppm, is a major contributor to mineral acid
formation, TBN (total base number) depletion, and hence lubricant
ash requirement. This was surprising as it was considered that the
nitric and nitrous acids formed via NO.sub.x gas hydrolysis would
have played a far more dominant role in terms of TBN depletion. The
introduction of low sulphur fuel for after-treatment durability is
also consistent with the formulation of reduced ash lubricants to
meet diesel particulate filter (DPF) requirements.
[0092] It is likely that testing using the Mack T10 in the presence
of EGR represents a worst case scenario in terms of ash
requirement, TBN depletion and lead corrosion for meeting the
expected requirements of the PC-10 specification. The use of
NO.sub.x reduction after-treatment devices to meet US Tier III
legislation could result in the removal of EGR from the engine
design or more likely the use EGR systems operated at lower
recirculation rates. The incorporation of particulate traps into US
Tier III emission solutions and their requirement for reduced ash
formulations, would appear feasible with the introduction of a 15
ppm sulphur limit in 2006.
4TABLE 3 Characteristics of the Lubricants Typical Units PC-9 Oil
Oil A Oil B Oil C Oil D Oil E Phosphorus wt. % 0.12 0.06 0.06 0.06
0.06 0.06 Sulphur wt. % 0.6 0.2 0.2 0.19 0.13 0.14 Lubricant wt. %
1.2 1.0 1.0 0.75 0.75 0.6 ash Ash wt. % 0.95 0.95 0.95 0.67 0.64
0.38 contributed by detergent(s) TBN mgKOH/g 10.0 9.1 9.1 7.2 7.3
5.9 (D2896)
[0093]
5TABLE 4 Mack T10 Lead Corrosion Performance Results Typical CI-4
PC-9 Limit Oil Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Lubricant used -- -- A
B C D E Fuel sulphur, -- 400 400 15 15 15 15 ppm EOT Pb*, ppm 35 25
10** 19 24 15 27 .DELTA.Pb 14 10 -- 9 9 6 9 250-300 hrs, ppm *End
Of Test lead **Test terminated at 220 hours owing to a mechanical
fault
[0094] The effect of fuel sulphur level on TBN depletion is
illustrated graphically in FIG. 2. The TBN depletion and TAN (total
acid number) increase profiles for oils A and B are given. Oils A
and B are in fact back-to-back runs of the same lubricant tested
using high (400 ppm) and low (15 ppm) sulphur fuel, respectively.
The TBN depletion profile when testing with 400 ppm sulphur fuel is
typical of a PC-9 oil. TBN and TAN commonly cross between 150-200
hours. Approximately fifty to seventy five hours after the
cross-over point, lead corrosion begins to increase significantly.
In contrast, when 15 ppm sulphur fuel is used, TBN and TAN do not
cross for the entirety of the 300 hour test.
[0095] Oils C and D compare the performance of phenate/sulphonate
detergents with salicylate based detergents in typical PC-9
lubricating oil formulations. The oils were matched for ZDDP, TBN
and soap content. The sulphur content of the salicylate formulation
(Oil D) is lower than that of the phenate/sulphonate formulation
(Oil C) as the salicylate detergent is sulphur free. Both chemistry
types provide passing performance, however, the data suggest that
lead corrosion performance is superior for the salicylate
chemistry. FIG. 3 illustrates the lead corrosion profile with test
duration for the two test oils. The technical justification for
this performance difference can be found by comparing the TBN
depletion and TAN increase profiles of the two lubricants. Such a
comparison is made in FIG. 4. The TBN depletion for the salicylate
oil is markedly reduced in comparison to that of the
phenate/sulphonate oil. A possible explanation for this reduced TBN
depletion is that the salicylate oil neutralises acid present less
effectively. However, if this were the case, a more rapid increase
in TAN would be expected together with inferior corrosion
performance. In contrast, the TAN increase for the salicylate oil
is comparable to that of the phenate/sulphonate oil. The superior
performance of salicylate detergent allows for the formulation of
lower ash lubricating oil compositions.
[0096] The performance of the detergent in the low ash lubricating
oil compositions of the present invention was determined in
passenger car diesel engines operated with both high (400 and 3000
ppm) and low (10 ppm) sulphur fuels using an OM 602A engine test
(CEC L-051-A-9A).
[0097] The piston cleanliness performance of lubricating oil
compositions of the present invention was evaluated in passenger
car diesel engines operated with low (10 ppm) and high (400 ppm and
3000 ppm) sulphur diesel fuels. All the tested compositions (Oils F
to G) were SAE 5W-30 grade and contained comparable additives
including identical salicylate detergents. The characteristics of
the lubricating oil compositions and fuels used, and the results
obtained, are set forth in Table 5.
6TABLE 5 Characteristics of the lubricating oil compositions and
fuel, and OM602A engine test results Lower Limit Ex. 6 Ex. 7 Ex. 8
For Passing Lubricant F G H -- Phosphorus, wt. % 0.06 0.05 0.05 --
Lubricant ash, wt. % 0.56 0.50 0.50 -- Ash contributed by 0.35 0.39
0.38 -- detergent (s), wt. % Fuel sulphur, ppm 10 400 3000 --
Piston Merit (avg.) 32.1 26.0 22.8 24
[0098] The above-data demonstrate the ability of lubricating oil
compositions formulated with amounts of detergent contributing
reduced amounts of ash to maintain piston cleanliness at acceptable
levels in engines operated with low sulphur fuels.
[0099] The disclosures of all patents, articles and other materials
described herein are hereby incorporated, in their entirety, into
this specification by reference.
[0100] Compositions described as "comprising" a plurality of
defined components are to be construed as including compositions
formed by admixing the defined plurality of defined components The
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.
* * * * *