U.S. patent application number 16/776778 was filed with the patent office on 2020-05-28 for lubricating oil compositions.
This patent application is currently assigned to Infineum International Limited. The applicant listed for this patent is Infineum International Limited. Invention is credited to Joseph P. Hartley, Anne W. Young.
Application Number | 20200165536 16/776778 |
Document ID | / |
Family ID | 58212974 |
Filed Date | 2020-05-28 |
United States Patent
Application |
20200165536 |
Kind Code |
A1 |
Hartley; Joseph P. ; et
al. |
May 28, 2020 |
Lubricating Oil Compositions
Abstract
A lubricating oil composition, a method of reducing low-speed
pre-ignition (LSPI) in a direct-injected spark-ignited internal
combustion engine, and a use of a lubricant composition to reduce
LSPI events in such an engine. Preferably, the composition
comprises a detergent package comprising a borated calcium
detergent, wherein the detergent package provides a calcium content
in the composition of at least 0.12 mass %, based on the total mass
of the composition, and wherein the borated calcium detergent
provides a boron content in the composition of at least 100 ppmm,
based on the total mass of the composition. Optionally, the
composition comprises a first detergent comprising a calcium
detergent, and a second detergent comprising a borated calcium
detergent.
Inventors: |
Hartley; Joseph P.; (Oxford,
GB) ; Young; Anne W.; (Brooklyn, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infineum International Limited |
Abingdon |
|
GB |
|
|
Assignee: |
Infineum International
Limited
Abingdon
GB
|
Family ID: |
58212974 |
Appl. No.: |
16/776778 |
Filed: |
January 30, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15907320 |
Feb 28, 2018 |
10584300 |
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16776778 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 159/00 20130101;
C10N 2030/04 20130101; C10M 2207/027 20130101; C10M 2215/28
20130101; C10M 2219/044 20130101; C10N 2060/14 20130101; C10M
139/00 20130101; C10M 2207/144 20130101; C10M 2207/262 20130101;
C10N 2040/255 20200501; C10M 2207/028 20130101; C10M 2207/144
20130101; C10M 2207/028 20130101; C10M 169/04 20130101; C10M
2207/028 20130101; C10M 2207/027 20130101; C10M 2219/044 20130101;
C10M 2219/046 20130101; C10M 2205/04 20130101; C10M 2219/044
20130101; C10M 141/12 20130101; C10M 2207/028 20130101; C10M 129/54
20130101; C10M 2207/262 20130101; C10M 2227/00 20130101; C10N
2040/10 20130101; C10M 2219/046 20130101; C10M 2219/046 20130101;
C10M 2207/144 20130101; C10M 2207/262 20130101; C10M 2219/044
20130101; C10M 2219/046 20130101; C10M 163/00 20130101; C10N
2010/04 20130101; C10M 2207/027 20130101; C10M 2209/062 20130101;
C10M 2207/027 20130101; C10M 169/044 20130101; C10M 2217/06
20130101; C10M 2205/04 20130101; C10M 2207/262 20130101; C10N
2010/04 20130101; C10N 2060/14 20130101; C10N 2010/04 20130101;
C10N 2010/04 20130101; C10M 2209/086 20130101; C10N 2010/04
20130101; C10N 2010/04 20130101; C10N 2010/04 20130101; C10N
2060/14 20130101; C10N 2010/04 20130101; C10N 2060/14 20130101;
C10N 2010/04 20130101; C10N 2010/04 20130101; C10N 2010/04
20130101; C10N 2060/14 20130101; C10N 2010/04 20130101; C10N
2010/04 20130101; C10N 2010/04 20130101; C10N 2060/14 20130101;
C10N 2060/14 20130101; C10M 2205/06 20130101; C10M 2205/06
20130101; C10N 2010/04 20130101; C10N 2010/04 20130101; C10N
2060/14 20130101; C10N 2060/02 20130101; C10N 2060/14 20130101;
C10N 2060/14 20130101; C10N 2010/04 20130101; C10N 2010/04
20130101; C10N 2010/04 20130101; C10N 2060/14 20130101; C10N
2010/04 20130101; C10N 2010/04 20130101; C10N 2010/04 20130101;
C10N 2010/04 20130101; C10N 2060/02 20130101 |
International
Class: |
C10M 141/12 20060101
C10M141/12; C10M 163/00 20060101 C10M163/00; C10M 159/00 20060101
C10M159/00; C10M 169/04 20060101 C10M169/04; C10M 139/00 20060101
C10M139/00; C10M 129/54 20060101 C10M129/54 |
Claims
1. A lubricating oil composition comprising a first detergent
comprising a calcium detergent and a second detergent comprising a
borated calcium detergent; wherein, the first and second detergents
together provide a calcium content, as measured by ASTM 4951, in
the lubricating oil composition of at least 0.12 mass %, based on
the total mass of the lubricating oil composition, and wherein the
second detergent provides a boron content, as measured by ASTM
D5185, in the lubricating oil composition of at least 100 ppmm,
based on the total mass of the lubricating oil composition.
2. A lubricating oil composition according to claim 1, wherein the
first detergent has a calcium content of from 2 mass % to 16 mass
%, based on the mass of the first detergent, andtor the second
detergent has a calcium content of from 4 mass % to 16 mass % ,
based on the mass of the second detergent.
3. A lubricating oil composition according to claim 1, wherein the
second detergent has a boron content of from 1 mass % to 10 mass %,
based on the mass of the second detergent.
4. A lubricating oil composition according to claim 1, wherein the
first and second detergents together provide a calcium content in
the lubricating oil composition of at least 0.14 mass, based on the
total mass of the lubricating oil composition.
5. A lubricating oil composition according to claim 1, wherein the
second detergent provides a boron content in the lubricating oil
composition of at least 150 ppmm, based on the total mass of the
lubricating oil composition.
6. A lubricating oil composition according to claim 1, wherein: the
first detergent comprises a calcium phenate, a calcium sulfonate
and/or a calcium salicylate; and the second detergent comprises a
borated calcium phenate, a borated calcium sulfonate and/or a
borated calcium salicylate.
7. A lubricating oil composition according to claim 1, wherein the
second detergent comprises a borated analogue of the calcium
detergent of the first detergent.
8. A lubricating oil composition according to claim 1, wherein the
second detergent comprises calcium and boron in a calcium mass % to
boron mass % ratio of 1:Z, based on the mass of the second
detergent, wherein Z is at least 0.1.
9. A lubricating oil composition according to claim 8, wherein Z is
from 0.1 to 4.
10. A lubricating oil composition according to claim 1, wherein the
first detergent and the second detergent are present in a ratio of
first detergent mass % to second detergent mass % of 1:X, based on
the total mass of the lubricating oil composition, wherein X is at
least 0.1.
11. A lubricating oil composition according to claim 10, wherein X
is from 0.1 to 10.
12. A lubricating oil composition according to claim 1, wherein at
least 50%, of the boron content of the lubricating oil composition
is provided by the second detergent.
13. A lubricating oil composition according to claim 12, wherein
100%, of the boron content of the lubricating oil composition is
provided by the second detergent.
Description
FIELD OF THE INVENTION
[0001] The present invention concerns lubricating compositions.
More particularly, but not exclusively, this invention concerns
lubricating compositions for reducing the occurrence of Low Speed
Pre-Ignition (LPSI) (or low speed pre-ignition events) in
spark-ignited internal combustion engines, in which a lubricating
oil composition having a defined detergent package is used to
lubricate the engine crankcase.
BACKGROUND OF THE INVENTION
[0002] Market demand, as well as governmental legislation, has led
automotive manufacturers to continuously improve fuel economy and
reduce CO2 emissions across engine families, while simultaneously
maintaining performance (horsepower). Using smaller engines
providing higher power densities, increasing boost pressure, by
using turbochargers or superchargers to increase specific output
and down-speeding the engine by using higher transmission gear
ratios allowed by higher torque generation at lower engine speeds
have allowed engine manufacturers to provide excellent performance
while reducing frictional and pumping losses. However, higher
torque at lower engine speeds has been found to cause random
pre-ignition in engines at low speeds, a phenomenon known as Low
Speed Pre-Ignition, or LSPI, resulting in extremely high cylinder
peak pressures, which can lead to catastrophic engine failure. The
possibility of LSPI prevents engine manufacturers from fully
optimizing engine torque at lower engine speed in such smaller,
high-output engines.
[0003] While not wishing to be bound by any specific theory, it is
believed that LSPI may be caused, at least in part, by
auto-ignition of droplets, e.g. comprising engine oil, or a mixture
of engine oil, fuel and/or deposits, that enter the engine
combustion chamber from the piston crevice (space between the
piston ring pack and cylinder liner) under high pressure, during
periods in which the engine is operating at low speeds, and
compression stroke time is longest (e.g., an engine having a 7.5
msec compression stroke at 4000 rpm may have a 24 msec compression
stroke when operating at 1250 rpm). Therefore, it would be
advantageous to identify and provide lubricating oil compositions
that are resistant to auto-ignition and therefore prevent or
ameliorate the occurrence of LSPI.
[0004] WO201542337 considers the use of ashless antioxidant
additives for reducing LSPI events. WO2015/42340 considers the use
of metal overbased detergents for reducing LSPI events.
WO2015/71980 relates to a method of reducing LSPI events by
providing a boron-containing compound comprising a borated
dispersant or a mixture of boron-containing compound and a
non-borated dispersant.
[0005] The prior art has also recognised that reducing the calcium
content of a lubricating oil formulation can lead to a reduction in
LSPI events, see for example, EP 2940110. However, detergents are
often considered to be necessary additives for maintaining basic
engine oils performance. Thus, recent efforts in providing
lubricating oil formulations that reduce LSPI events have focused
on replacing calcium detergents with alternative detergents.
Nevertheless, there remains a need for a lubricating oil
composition suitable for use in modern direct injection-spark
ignition engines that reduces occurrences of LSPI events.
SUMMARY OF THE INVENTION
[0006] The present inventors have surprisingly found that use of a
borated calcium detergent in a lubricating oil composition provides
an unexpectedly significant reduction in the occurrence of LSPI
events in direct injection-spark ignition internal combustion
engines when the crankcase of the engine is lubricated with said
lubricating oil composition, for example as compared to when the
crankcase is lubricated with a composition comprising only a
(non-borated) calcium detergent.
[0007] Thus, the present invention provides, according to a first
aspect, a lubricating oil composition comprising a calcium
detergent and a second detergent comprising a borated calcium
detergent, wherein, the first and second detergents together
provide a calcium content in the lubricating oil composition of at
least 0.12 mass % , based on the total mass of the lubricating oil
composition, and wherein the second detergent provides a boron
content in the lubricating oil composition of at least 100 ppmm,
such as at least 150 ppmm, based on the total mass of the
lubricating oil composition.
[0008] According to a second aspect, the present invention provides
a method of reducing low-speed pre-ignition (LSPI) events in a
direct-injection spark-ignition internal combustion engine
comprising lubricating the crankcase of the engine with a
lubricating oil composition, the composition comprising a detergent
package comprising a borated calcium detergent, wherein, the
detergent package provides a calcium content in the lubricating oil
composition of at least 0.12 mass %, based on the total mass of the
lubricating oil composition, and wherein the borated calcium
detergent provides a boron content in the lubricating oil
composition of at least 100 ppmm, such as at least 150 ppmm, based
on the total mass of the lubricating oil composition. Optionally,
the lubricating oil composition is the lubricating oil composition
of the first aspect of the invention.
[0009] According to a third aspect, the present invention provides
a use of a detergent package comprising a borated calcium detergent
in a lubricating oil composition to reduce LSP1 events when the
composition lubricates the crankcase of a direct injection-spark
ignition internal combustion engine, wherein, the detergent package
provides a calcium content in the lubricating oil composition of at
least 0.12 mass %, based on the total mass of the lubricating oil
composition, and wherein the borated calcium detergent provides a
boron content in the lubricating oil composition of at least 100
ppmm, such as at least 150 ppmm, based on the total mass of the
lubricating oil composition. Optionally, the lubricating oil
composition is the lubricating oil composition of the first aspect
of the invention.
[0010] In this specification, the following words and expressions,
if and when used, have the meanings ascribed below:
[0011] "active ingredients" or "(a.i.)" refers to additive material
that is not diluent or solvent;
[0012] "hydrocarbyl" means a chemical group of a compound that
normally contains only hydrogen and carbon atoms and that is bonded
to the remainder of the compound directly via a carbon atom but
that may contain hetero atoms provided that they do not detract
from the essentially hydrocarbyl nature of the group;
[0013] "oil-soluble" or "oil-dispersible", or cognate terms, do not
necessarily indicate that the compounds or additives are soluble,
dissolvable, miscible, or are capable of being suspended in the oil
in all proportions. These do mean, however, that they are, for
example, soluble or stably dispersible in oil to an extent
sufficient to exert their intended effect in the environment in
which the oil in employed. Moreover, the additional incorporation
of other additives may also permit incorporation of other additives
may also permit incorporation of higher levels of a particular
additive, if desired;
[0014] "major amount" mean in excess of 50 mass % of a
composition;
[0015] "minor amount" means less than or equal to 50 mass % of a
composition;
[0016] "TBN" means total base number as measured by ASTM D2896 in
units of mg KOHg.sup.-1;
[0017] "phosphorus content" is measured by ASTM D5185;
[0018] "metal content" of the lubricating oil composition or of an
additive component, for example molybdenum content or total metal
content of the lubricating oil composition (i.e. the sum of all
individual metal contents), is measured by ASTM D5185;
[0019] "boron content" is measured by ASTM D5185;
[0020] "calcium content" is as measured by ASTM 4951;
[0021] "sulphur content" is measured by ASTM D2622; and,
[0022] "sulphated ash content" is measured by ASTM D874.
[0023] Also, it will be understood that various components used,
essential as well as optimal and customary, may react under
conditions of formulation, storage or use and that the invention
also provides the product obtainable or obtained as a result of any
such reaction. Further, it is understood that any upper and lower
quantity, range and ratio limits set forth herein may be
independently combined. Furthermore, the constituents of this
invention may be isolated or be present within a mixture and remain
within the scope of the invention.
[0024] It will of course be appreciated that features described in
relation to one aspect of the present invention may be incorporated
into other aspects of the present invention. For example, the
method of the invention may incorporate any of the features
described with reference to the composition of the invention and
vice versa.
BRIEF DESCRIPTION OF THE FIGURES
[0025] FIG. 1 shows graphically the occurrence of LSPI events in an
engine, in accordance with the method of determining the occurrence
of LSPI events as used in the Examples of the present
Specification.
DETAILED DESCRIPTION
[0026] Several terms exist for various forms of abnormal combustion
in spark ignited internal combustion engines including knock,
extreme knock (sometimes referred to as super-knock or mega-knock),
surface ignition, and pre-ignition (ignition occurring prior to
spark ignition). Extreme knock occurs in the same manner as
traditional knock, but with increased knock amplitude, and can be
mitigated using traditional knock control methods. LSPI usually
occurs at low speeds and high loads. In LSPI, initial combustion is
relatively slow and similar to normal combustion, followed by a
sudden increase in combustion speed. LSPI is not a runaway
phenomenon, unlike some other types of abnormal combustion.
Occurrences of LSPI are difficult to predict, but are often
cyclical in nature.
[0027] LSPI is most likely to occur in direct-injected, boosted
(turbocharged or supercharged), spark-ignited (gasoline) internal
combustion engines that, in operation, generate a break mean
effective pressure level of greater than about 1,500 kPa (15 bar)
(peak torque), such as at least about 1,800 kPa (18 bar),
particularly at least about 2,000 kPa (20 bar) at engine speeds of
from about 1000 to about 2500 rotations per minute (rpm), such as
at engine speeds of from about 1000 to about 2000 rpm. As used
herein, break mean effective pressure (BMEP) is defined as the work
accomplished during an engine cycle, divided by the engine swept
volume; the engine torque normalized by engine displacement. The
word "brake" denotes the actual torque or power available at the
engine flywheel, as measured on a dynamometer. Thus, BMEP is a
measure of the useful power output of the engine.
[0028] WO2015/171978 and WO2015/171981 disclose that lubricating
oils comprising a zinc dialkyl dithiophosphate compound and a
borated dispersant are useful in the reduction of LSPI events.
Surprisingly, the present inventors have found that the
introduction of boron into a lubricating oil formulation via a
borated calcium detergent is unexpectedly more effective at
reducing the occurrence of LSPI events than the introduction of
boron via a borated dispersant. In other words, the present
inventors have found that, for a lubricating oil composition with a
given boron concentration, a formulation in which boron content is
provided by means of a borated calcium detergent may be more
effective at reducing the frequency of LSPI events than an
equivalent lubricating oil composition in which boron content is
provided principally by means of a borated dispersant.
[0029] It has now been found that the occurrence of LSPI in engines
can be reduced by lubricating the crankcase with lubricating oil
compositions comprising a detergent package comprising a borated
calcium detergent, for example a lubricating oil composition in
which the detergent package provides a calcium content in the
lubricating oil composition of at least 0.12 mass %, based on the
total mass of the lubricating oil composition, and wherein the
borated calcium detergent provides a boron content in the
lubricating oil composition of at least 100 ppmm, such as at least
150 ppmm, based on the total mass of the lubricating oil
composition. Without wishing to be bound the theory, the present
inventors believe that a borated calcium detergent is less
susceptible to LSPI than the corresponding (non-borated) calcium
detergent. Optionally, the detergent package comprises a borated
calcium detergent and a calcium detergent.
[0030] More particularly, it has now been found that LSPI events
can be reduced by using a lubricating oil composition comprising: a
first detergent comprising a calcium detergent and a second
detergent comprising a borated calcium detergent, wherein, the
first and second detergents together provide a calcium content in
the lubricating oil composition of at least 0.12 mass %, based on
the total mass of the lubricating oil composition, and wherein the
second detergent provides a boron content in the lubricating oil
composition of at least 100 ppmm, such as at least 150 ppmm, based
on the total mass of the lubricating oil composition.
[0031] Optionally, the first detergent comprises a calcium
detergent and has a calcium content of at least 2 mass %, based on
the mass of the first detergent. Optionally, the second detergent
comprises a borated calcium detergent and has a calcium content of
at least 4 mass %, and a boron content of at least 1 mass %, such
as at least 2 mass %, based on the mass of the second
detergent.
[0032] Optionally, the first and second detergents together provide
a calcium content in the lubricating oil composition of at least
0.14 mass %, preferably at least 0.15 mass %, for example at least
0.18 mass %, based on the total mass of the lubricating oil
composition. Optionally, the first and second detergents together
provide a calcium content in the lubricating oil composition of
from 0.12 mass % to 0.35 mass %, such as from 0.14 mass % to 030
mass %, preferably from 0.16 mass % to 0.25 mass %, for example
from 0.18 mass % to 0.20 wt mass %, based on the total mass of the
lubricating oil composition.
[0033] Optionally, the second detergent provides a boron content in
the lubricating oil composition of at least 150 ppmm, preferably at
least 200 ppmm, for example at least 220 ppmm, based on the total
mass of the lubricating oil composition. Optionally, the second
detergent provides a boron content in the lubricating oil
composition of from 100 ppmm to 800 ppmm, optionally from 150 ppmm
to 750 ppmm, such as from 180 ppmm to 700 ppmm, preferably from 220
ppmm to 650 ppmm, for example from 250 ppmm to 500 ppmm, based on
the weight of the lubricating oil composition.
[0034] It may be that the combination of a borated calcium
detergent and a (non-borated) calcium detergent is particularly
effective at providing a balance between detergent activity and
reduction of LSPI.
[0035] Optionally, the lubricating oil composition has calcium
content of at least 0.14 mass %, preferably at least 0.16 mass %,
for example at least 0.18 mass %, based on the weight of the
lubricating oil composition. Optionally, the lubricating oil
composition has a calcium content of from 0.12 mass % to 0.35 mass
%, such as from 0.14 mass % to 0.30 mass %, preferably from 0.16
mass % to 0.25 mass %, for example from 0.18 mass % to 0.20 mass %,
based on the total mass of the lubricating oil composition.
Optionally, the lubricating oil composition has a boron content of
at least 100 ppmm, such as at least 150 ppmm, preferably at least
200 ppmm, for example at least 250 ppmm, based on the total mass of
the lubricating oil composition. Optionally, the lubricating oil
composition has a boron content of from 100 ppmm to 800 ppmm,
optionally from 150 ppmm to 750 ppmm, such as from 180 ppmm to 700
ppmm, preferably from 220 ppmm to 650 ppmm, for example from 250
ppmm to 500 ppmm, based on the total mass of the lubricating oil
composition.
[0036] Lubricating oil compositions suitable for use as passenger
car motor oils conventionally comprise a major amount of oil of
lubricating viscosity and minor amounts of performance enhancing
additives, including detergents. Conveniently, boron is introduced
into the lubricating oil compositions used in all aspects of the
present invention by one or more borated calcium detergents. Any
borated calcium detergent would be a suitable source of boron.
Examples of suitable borated calcium detergents include, but are
not limited to, one or more borated calcium phenate detergent, one
or more borated calcium sulfonate detergent, one or more borated
calcium salicylate detergent, or a mixture thereof. Preferably,
such borated calcium detergents are overbased borated calcium
detergents.
[0037] The borated calcium detergents of all aspects of the
invention may be prepared by any conventional method. For example,
it may be that the borated calcium detergent is prepared by
treating a calcium detergent with boric acid. Methods of preparing
borated detergents are disclosed in U.S. Pat. Nos. 3,480,548,
3,679,584, 3,829,381, 3,909,691 and 4,965,004.
[0038] Optionally, the first detergent has a calcium content of
from 2 mass % to 16 mass %, such as from 4 mass % to 12 mass %, for
example from 6 rnass % to 10 mass %, based on the mass of the first
detergent. Optionally, the second detergent has a calcium content
of from 4 mass % to 16 mass %, preferably from 5 mass % to 12 mass
%, for example from 6 mass % to 10 mass %, based on the mass of the
second detergent. It may be that detergents having such calcium
contents are particularly useful as lubricating oil additives.
[0039] Optionally, the second detergent has a boron content of from
1 mass % to 10 mass %, preferably 2 mass % to 8 mass % , for
example 2 mass % to 6 mass %, based on the mass of the second
detergent. It may be that a calcium detergent having such boron
contents provides a particularly good balance between utility for
LSPI reduction and convenience of manufacture.
[0040] 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 have a total base number
or TBN (as can be measured by ASTM D2896) of from 0 to less than
150, such as 0 to about 80 or 100 mg KOH/g. 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 have a TBN of 150 mg KOH/g or
greater, and typically will have a TBN of from 200 to 450 mg KOH/g
or more.
[0041] Optionally, the first detergent comprises an overbased
borated calcium detergent, for examples having a Total Base Number
(TBN) of at least 150 mg KOH/g, preferably at least 200 mg KOH/g.
Optionally, the second detergent comprises a borated overbased
calcium detergent, for example having a TBN of at least 150 mg
KOH/g, preferably at least 200 mg KOH/g. Optionally, the overbased
borated calcium detergent and/or the borated overbased calcium
detergent has a TBN of from 200 to 450 mg KOH/g.
[0042] The first and second detergents are preferably used in an
amount together providing the lubricating oil composition with a
TBN of from about 4 to about 10 mg KOH/g, preferably from about 5
to about 8 mg KOH/g. Preferably, overbased detergents based on
metals other than calcium are present in amounts contributing no
greater than 60%, such as no greater than 50% or no greater than
40% of the TBN of the lubricating oil composition contributed by
overbased detergent. Preferably, lubricating oil compositions of
the present invention contain non-calcium-based overbased
ash-containing detergents in amounts providing no greater than
about 40% of the total TBN contributed to the lubricating oil
composition by overbased detergent. Combinations of overbased
calcium detergents may be used (e.g., comprising two or more of an
overbased calcium phenate, an overbased calcium salicylate and an
overbased calcium sulfonate; or comprising two or more calcium
detergents each having a different TBN of greater than 150 mg
KOH/g). Preferably, the first and/or second detergent will have, or
have on average, a TBN of at least about 200 mg KOH/g, such as from
about 200 to about 500 mg KOH/g; preferably at least about 250 mg
KOH, such as from about 250 to about 500 mg KOH/g; more preferably
at least about 300 mg KOH/g, such as from about 300 to about 450 mg
KOH/g.
[0043] Calcium detergents that may be used in all aspects of the
present invention include, oil-soluble neutral and overbased
sulfonates, phenates, sulfurized phenates, thiophosphonates,
salicylates, naphthenates and other oil-soluble carboxylates of
calcium, and mixtures thereof. It will be appreciated that suitable
calcium detergents may also comprise other metals, particularly
alkali or alkaline earth metals, e.g., barium, sodium, potassium,
lithium, calcium, and/or magnesium. The most commonly used
additional metals are magnesium and sodium, either of which or both
may be present in the calcium detergent and/or the borated calcium
detergent. The first and/or second detergents may comprise
combinations of detergents, whether overbased or neutral or
both.
[0044] 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
include those obtained by alkylating benzene, xylene, naphthalene,
diphenyl or their halogen derivatives such as chlorobenzene,
chlorotoluene and chloronaphthalene. The alkylation may be carried
out in the presence of a catalyst with alkylating agents having
from about 3 to more than 70 carbon atoms. The alkaryl sulfonates
usually contain from about 9 to about 80 or more carbon atoms,
preferably from about 16 to about 60 carbon atoms per alkyl
substituted aromatic moiety. In a preferred embodiment of the
present invention the sulfonate detergent is not obtained by
alkylation of toluene. Preferred sulfonate detergents are metal
salts of alkylbenzene sulfonates.
[0045] 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 mass % (preferably at least 125 mass %) of that
stoichiometrically required.
[0046] Metal salts of phenols and sulfurized 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. Sulfurized phenols may be prepared
by reacting a phenol with sulfur or a sulfur containing compound
such as hydrogen sulfide, sulfur monohalide or sulfur dihalide, to
form products which are generally mixtures of compounds in which 2
or more phenols are bridged by sulfur containing bridges.
[0047] 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
hetero-atoms, 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.
[0048] Preferred examples of aromatic carboxylic acids are
salicylic acids and sulfurized derivatives thereof, such as
hydrocarbyl substituted salicylic acid and derivatives thereof.
Processes for sulfurizing, for example a hydrocarbyl-substituted
salicylic acid, are known to those skilled in the art. Salicylic
acids are typically prepared by carboxylation, for example, by the
Kolbe-Schmitt process, of phenoxides, and in that case, will
generally be obtained, normally in a diluent, in admixture with
uncarboxylated phenol.
[0049] 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.
[0050] Detergents generally useful in the formulation of
lubricating oil compositions of the invention 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 U.S.
Pat. Nos. 6,153,565; 6,281,179; 6,429,178; and 6,429,178.
[0051] Optionally, the first detergent comprises a calcium phenate,
a calcium sulfonate and/or a calcium salicylate. In an embodiment,
the first detergent comprises a calcium salicylate. Optionally, the
second detergent comprises a borated calcium phenate, a borated
calcium sulfonate, a borated calcium salicylate, or mixtures
thereof. In an embodiment, the second detergent comprises a borated
calcium salicylate. Optionally, the second detergent comprises a
borated analogue of the calcium detergent of the first detergent.
For example, it may be that when the first detergent comprises a
calcium salicylate, the second detergent comprises a borated
calcium salicylate. It may be that, for example, the borated
calcium detergent of the second detergent is prepared by borating
the calcium detergent of the first detergent.
[0052] Optionally, the second detergent comprises calcium and boron
in a calcium mass % to boron mass % ratio of 1:Z, based on the
weight of the second detergent, wherein Z is at least 0.1,
preferably at least 0.2, for example at least 0.5. Optionally, Z is
from 0.1 to 4, preferably from 0.2 to 3, for example from 0.5 to 2.
It may be that such ratios provide a particularly good balance
between detergent activity and reduction in LSPI.
[0053] Optionally, the first detergent and the second detergent are
present in a ratio of first detergent mass % to second detergent
mass % of 1:X, based on the total mass of the lubricating oil
composition, wherein X is at least 0.1, preferably at least 0.2,
for example at least 0.3. Optionally, X is from 0.1 to 10,
preferably from 0.2 to 5, for example from 0.3 to 3.
[0054] Optionally, the first detergent comprises a plurality of
calcium detergents; and/or the second detergent comprises a
plurality of borated calcium detergents. Optionally, each calcium
detergent of the first detergent is independently a calcium
phenate, a calcium sulfonate or a calcium salicylate. Optionally,
each borated calcium detergent of the second detergent is
independently a borated calcium phenate, a borated calcium
sulfonate or a borated calcium salicylate. Preferably, the first
detergent is substantially free from any detergent that is not a
calcium detergent. Preferably, the second detergent is
substantially free from any detergent that is not a borated calcium
detergent. In other words, it may be that the first detergent
consists of one or more calcium detergents, and/or it may be that
the second detergent consists of one or more borated calcium
detergents. It will be appreciated that where a detergent is said
to be substantially free from anything other than a particular type
of detergent, or is said to consist of that particular type of
detergent, the detergent may nevertheless comprise trace amounts of
another material. For example, it may be that the detergent
comprises a trace amount of another material left over from the
preparation process used to make the detergent. It will be
appreciated that the first detergent is not a borated detergent (in
other words, the first detergent is a non-borated calcium
detergent), for example, it may be that the first detergent is
substantially free from boron.
[0055] Optionally, at least 75%, for example at least 90%, such as
at least 95%, or 100% of the calcium content of the lubricating oil
composition is provided by the first detergent and the second
detergent. Optionally, at least 50%, for example at least 75%, such
as at least 90%, of the boron content of the lubricating oil
composition is provided by the second detergent. It may be that
when the calcium and/or boron content of the lubricating
composition is provided principally by the first and second
detergents, the detergent and LSPI reduction characteristics of the
composition can be controlled particularly effectively.
[0056] Optionally, the composition additionally comprises a third
detergent. Preferably, the third detergent is substantially free of
calcium and/or boron. Optionally, the third detergent comprises one
or more phenate, sulfonate or salicylate detergents, or mixtures
thereof. The third detergent may be an overbased or neutral
detergent. Optionally, the third detergent comprises one or more
neutral metal-containing detergents (having a TBN of less than 150
mg KOH/g). These neutral metal-based detergents may be magnesium
salts or salts of other alkali or alkali earth metals, except
calcium. In all aspects of the invention, the first and second
detergents detergent may be the sole metal-containing detergents,
in which case 100% of the metal introduced into the lubricating oil
composition by detergent will originate from the first and second
detergents. Optionally, 100% of the metal introduced into the
lubricating oil composition by detergent is calcium.
[0057] The third detergent may also contain ashless (metal-free)
detergents such as oil-soluble hydrocarbyl phenol aldehyde
condensates described, for example, in US 2005/0277559 A1.
[0058] Preferably, detergent in total is used in an amount
providing the lubricating oil composition with from 0.2 to 2.0 mass
%, such as from 0.2 to 1.5 mass % or from 0.3 to 1.0 mass %, more
preferably from about 0.3 to about 0.8 mass % of sulfated ash
(SASH).
[0059] Optionally, the composition comprises one or more additional
additives from the list consisting of: dispersants, corrosion
inhibitors, antioxidants, pour point depressants, antifoaming
agents, supplemental anti-wear agents, friction modifiers, and
viscosity modifiers.
[0060] The oil of lubricating viscosity useful in the formulation
of lubricating oil compositions suitable for use 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 mm2/sec, most preferably from about 9 mm.sup.2/sec to
about 17 mm2/sec, measured at 100.degree. C.
[0061] 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.
[0062] 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 derivatives, analogs and
homologs thereof.
[0063] 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.
[0064] 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 include 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. Also useful are synthetic oils derived
from a gas to liquid process from Fischer-Tropsch synthesized
hydrocarbons, which are commonly referred to as gas to liquid, or
"GTL" base oils.
[0065] 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.
[0066] 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.
[0067] 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%. Preferably, the base stock or base stock
blend is a Group III or higher base stock or mixture thereof, or a
mixture of a Group II base stock and a Group III or higher base
stock or mixture thereof. Most preferably, the base stock, or base
stock blend, has a saturate content of greater than 90%.
Preferably, the oil or oil blend will have a sulfur content of less
than 1 mass %, preferably less than 0.6 mass %, most preferably
less than 0.4 mass %, such as less than 0.3 mass %.
[0068] Preferably the volatility of the oil or oil blend, as
measured by the Noack test (ASTM D5800), is less than or equal to
30 mass %, such as less than about 25 mass %, preferably less than
or equal to 20 mass %, more preferably less than or equal to 15
mass %, most preferably less than or equal 13 mass %. 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 200.
[0069] 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:
[0070] a) Group I base stocks contain less than 90 percent
saturates and/or greater than 0.03 percent sulfur and have a
viscosity index greater than or equal to 80 and less than 120 using
the test methods specified in Table 1;
[0071] b) Group II base stocks contain greater than or equal to 90
percent saturates and less than or equal to 0.03 percent sulfur and
have a viscosity index greater than or equal to 80 and less than
120 using the test methods specified in Table 1;
[0072] c) Group III base stocks contain greater than or equal to 90
percent saturates and less than or equal to 0.03 percent sulfur and
have a viscosity index greater than or equal to 120 using the test
methods specified in Table 1;
[0073] d) Group IV base stocks are polyalphaolefins (PAO); and,
[0074] e) Group V base stocks include all other base stocks not
included in Group I, II, III, or IV.
TABLE-US-00001 TABLE 1 Analytical Methods for Base Stock Property
Test Method Saturates ASTM D 2007 Viscosity ASTM D 2270 Index
Sulfur ASTM D 2622; ASTM D 4294; ASTM D 4927; ASTM D 3120
[0075] The lubricating oil compositions of all aspects of the
present invention may further comprise a phosphorus-containing
compound.
[0076] A suitable phosphorus-containing compound includes
dihydrocarbyl dithiophosphate metal salts, which are frequently
used as anti-wear and antioxidant agents. The metal may be an
alkali or alkaline earth metal, or aluminum, lead, tin, manganese,
nickel or copper. The zinc salts are most commonly used in
lubricating oil in amounts of 0.1 to 6 mass %, preferably 0.2 to 2
mass %, based upon the total mass 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 may be made by
reacting mixtures of primary and secondary alcohols. Alternatively,
multiple dithiophosphoric acids can be prepared where the
hydrocarbyl groups on one are entirely secondary in character and
the hydrocarbyl groups on the others are entirely primary in
character. To make the zinc salt, any basic or neutral zinc
compound could be used but the oxides, hydroxides and carbonates
are most generally employed. Commercial additives frequently
contain an excess of zinc due to the use of an excess of the basic
zinc compound in the neutralization reaction.
[0077] The preferred zinc dihydrocarbyl dithiophosphates are oil
soluble salts of dihydrocarbyl dithiophosphoric acids and may be
represented by the following formula:
##STR00001##
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 (ZDDP) can therefore comprise
zinc dialkyl dithiophosphates. Lubricating oil compositions useful
in the practice of the present invention will preferably contain
ZDDP or other zinc-phosphorus compounds, in an amount introducing
from 0.01 to 0.12mass % of phosphorus, such as from 0.03 to 0.10
mass % of phosphorus, preferably, from 0.04 to 0.08 mass % of
phosphorus, based on the total mass of the lubricating oil
composition.
[0078] Preferably, lubricating oil compositions of the present
invention suitably have a phosphorous content of no greater than
about 0.08 mass % (800 ppm).
[0079] Anti-oxidants are sometimes referred to as oxidation
inhibitors; they increase the resistance of the composition to
oxidation and may work by combining with and modifying peroxides to
render them harmless, by decomposing peroxides, or by rendering an
oxidation catalyst inert. Oxidative deterioration can be evidenced
by sludge in the lubricant, varnish-like deposits on the metal
surfaces, and by viscosity growth.
[0080] They may be classified as radical scavengers (e.g.
sterically hindered phenols, aromatic amines, particularly
secondary aromatic amines having at least two aromatic (e.g. phenyl
groups) groups attached directly to the nitrogen atom, and
organo-copper salts); hydroperoxide decomposers (e.g., organosulfur
and organophosphorus additives); and multifunctionals (e.g. zinc
dihydrocarbyl dithiophosphates, which may also function as
anti-wear additives).
[0081] The lubricating oil composition in all aspects of the
present invention may include an anti-oxidant, more preferably an
ashless anti-oxidant. Suitably, the anti-oxidant, when present, is
an ashless aromatic amine anti-oxidant, an ashless phenolic
anti-oxidant or a combination thereof. The lubricating oil
composition in all aspects of the present invention may include
both an aromatic amine and phenolic anti-oxidant.
[0082] Suitably, the total amount of anti-oxidant (e.g. aromatic
amine anti-oxidant, a phenolic anti-oxidant or a combination
thereof) which may be present in the lubricating oil composition is
greater than or equal to 0.05 mass %, preferably greater than or
equal to 0.1 mass % ), even more preferably greater than or equal
to 0.2 mass %, based on the total mass of the lubricating oil
composition. Suitably, the total amount of anti-oxidant which may
be present in the lubricating oil composition is less than or equal
to 5.0 mass %, preferably less than or equal to 3.0 mass %, even
more preferably less than or equal to 2.5 mass %, based on the
total mass of the lubricating oil composition
[0083] Dispersants maintain in suspension materials resulting from
oxidation during use that are insoluble in oil, thus preventing
sludge flocculation and precipitation, or deposition on metal
parts. The lubricating oil composition of the present invention
comprises at least one dispersant, and may comprise a plurality of
dispersants. The dispersant or dispersants are preferably
nitrogen-containing dispersants and preferably contribute, in
total, from 0.04 to 0.19 mass %, such as from 0.05 to 0.18 mass %,
most preferably from 0.06 to 0.16 mass % of nitrogen to the
lubricating oil composition.
[0084] Dispersants useful in the context of the present invention
include the range of nitrogen-containing, ashless (metal-free)
dispersants known to be effective to reduce formation of deposits
upon use in gasoline and diesel engines, when added to lubricating
oils and comprise an oil soluble polymeric long chain backbone
having functional groups capable of associating with particles to
be dispersed. Typically, such dispersants have amine, amine-alcohol
or amide polar moieties attached to the polymer backbone, often via
a bridging group. The ashless dispersant may be, for example,
selected from oil soluble salts, esters, amino-esters, amides,
imides and oxazolines of long chain hydrocarbon-substituted mono-
and poly-carboxylic acids or anhydrides thereof; thiocarboxylate
derivatives of long chain hydrocarbons; long chain aliphatic
hydrocarbons having polyamine moieties attached directly thereto;
and Mannich condensation products formed by condensing a long chain
substituted phenol with formaldehyde and polyalkylene
polyamine.
[0085] Generally, each mono- or di-carboxylic acid-producing moiety
will react with a nucleophilic group (amine or amide) and the
number of functional groups in the polyalkenyl-substituted
carboxylic acylating agent will determine the number of
nucleophilic groups in the finished dispersant.
[0086] The polyalkenyl moiety of the dispersant of the present
invention has a number average molecular weight of from 700 to
3000, preferably between 950 and 3000, such as between 950 and
2800, more preferably from about 950 to 2500, and most preferably
from 950 to 2400. In one embodiment of the invention, the
dispersant comprises a combination of a lower molecular weight
dispersant (e.g., having a number average molecular weight of from
700 to 1100) and a high molecular weight dispersant having a number
average molecular weight of from at least 1500, preferably between
1800 and 3000, such as between 2000 and 2800, more preferably from
2100 to 2500, and most preferably from 2150 to 2400. The molecular
weight of a dispersant is generally expressed in terms of the
molecular weight of the polyalkenyl moiety as the precise molecular
weight range of the dispersant depends on numerous parameters
including the type of polymer used to derive the dispersant, the
number of functional groups, and the type of nucleophilic group
employed.
[0087] The polyalkenyl moiety from which the high molecular weight
dispersants are derived preferably have a narrow molecular weight
distribution (MWD), also referred to as polydispersity, as
determined by the ratio of weight average molecular weight (Mw) to
number average molecular weight (Mn). Specifically, polymers from
which the dispersants of the present invention are derived have a
Mw Mn of from 1.5 to 2.0, preferably from 1.5 to 1.9, most
preferably from 1.6 to 1.8.
[0088] Suitable hydrocarbons or polymers employed in the formation
of the dispersants of the present invention include homopolymers,
interpolymers or lower molecular weight hydrocarbons. One family of
such polymers comprise polymers of ethylene and/or at least one
C.sub.3 to C.sub.28 alpha-olefin having the formula
H.sub.2C.dbd.CHR.sup.1 wherein R.sup.1 is straight or branched
chain alkyl radical comprising 1 to 26 carbon atoms and wherein the
polymer contains carbon-to-carbon unsaturation, preferably a high
degree of terminal ethenylidene unsaturation. Preferably, such
polymers comprise interpolymers of ethylene and at least one
alpha-olefin of the above formula, wherein R.sup.1 is alkyl of from
1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8
carbon atoms, and more preferably still of from 1 to 2 carbon
atoms. Therefore, useful alpha-olefin monomers and comonomers
include, for example, propylene, butene-1, hexene-1,
octene-1,4-methylpentene-1, decene-1, dodecene-1, tridecene-1,
tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1,
octadecene-1, nonadecene-1, and mixtures thereof (e.g., mixtures of
propylene and butene-1, and the like). Exemplary of such polymers
are propylene homopolymers, butene-1 homopolymers,
ethylene-propylene copolymers, ethylene-butene-1 copolymers,
propylene-butene copolymers and the like, wherein the polymer
contains at least some terminal and/or internal unsaturation.
Preferred polymers are unsaturated copolymers of ethylene and
propylene and ethylene and butene-1. The interpolymers of this
invention may contain a minor amount, e.g. 0.5 to 5 mol % of a
C.sub.4 to C.sub.18 non-conjugated diolefin comonomer. However, it
is preferred that the polymers of this invention comprise only
alpha-olefin homopolymers, interpolymers of alpha-olefin comonomers
and interpolymers of ethylene and alpha-olefin comonomers. The
molar ethylene content of the polymers employed in this invention
is preferably in the range of 0 to 80%, and more preferably 0 to
60%. When propylene and/or butene-1 are employed as comonomer(s)
with ethylene, the ethylene content of such copolymers is most
preferably between 15 and 50%, although higher or lower ethylene
contents may be present.
[0089] These polymers may be prepared by polymerizing alpha-olefin
monomer, or mixtures of alpha-olefin monomers, or mixtures
comprising ethylene and at least one C.sub.3 to C.sub.28
alpha-olefin monomer, in the presence of a catalyst system
comprising at least one metallocene (e.g., a
cyclopentadienyl-transition metal compound) and an alumoxane
compound. Using this process, a polymer in which 95% or more of the
polymer chains possess terminal ethenylidene-type unsaturation can
be provided. The percentage of polymer chains exhibiting terminal
ethenylidene unsaturation may be determined by FTIR spectroscopic
analysis, titration, or .sup.13C NMR. Interpolymers of this latter
type may be characterized by the formula
POLY-C(R.sup.1).dbd.CH.sub.2 wherein R.sup.1 is C.sub.1 to C.sub.26
alkyl, preferably C.sub.1 to C.sub.18 alkyl, more preferably
C.sub.1 to C.sub.8 alkyl, and most preferably C.sub.1 to C.sub.2
alkyl, (e.g., methyl or ethyl) and wherein POLY represents the
polymer chain. The chain length of the R.sup.1 alkyl group will
vary depending on the comonomer(s) selected for use in the
polymerization. A minor amount of the polymer chains can contain
terminal ethenyl, i.e., vinyl, unsaturation, i.e.,
POLY-CH.dbd.CH.sub.2, and a portion of the polymers can contain
internal mono-unsaturation, e.g POLY-CH.dbd.CH(R.sup.1), wherein
R.sup.1 is as defined above. These terminally unsaturated
interpolymers may be prepared by known metallocene chemistry and
may also be prepared as described in U.S. Pat. Nos. 5,498,809;
5,663,130; 5,705,577; 5,814,715; 6,022,929 and 6,030,930.
[0090] Another useful class of polymers is polymers prepared by
cationic polymerization of isobutene, styrene, and the like. Common
polymers from this class include polyisobutenes obtained by
polymerization of a C.sub.4 refinery stream having a butene content
of 35 to 75 mass %, and an isobutene content of 30 to 60 mass %, in
the presence of a Lewis acid catalyst, such as aluminum trichloride
or boron tritluoride. A preferred source of monomer for making
poly-n-butenes is petroleum feedstreams such as Raffinate II. These
feedstocks are disclosed in the art such as in U.S. Pat. No.
4,952,739. Polyisobutylene is a most preferred backbone of the
present invention because it is readily available by cationic
polymerization from butene streams (e.g., using AlCl.sub.3 or
BF-catalysts). Such polyisobutylenes generally contain residual
unsaturation in amounts of about one ethylenic double bond per
polymer chain, positioned along the chain. A preferred embodiment
utilizes polyisobutylene prepared from a pure isobutylene stream or
a Raffinate 1 stream to prepare reactive isobutylene polymers with
terminal vinylidene olefins. Preferably, these polymers, referred
to as highly reactive polyisobutylene (HR-PIB), have a terminal
vinylidene content of at least 65%, e.g., 70%, more preferably at
least 80%, most preferably, at least 85%. The preparation of such
polymers is described, for example, in U.S. Pat. No. 4,152,499.
HR-PIB is known and HR-PIB is commercially available under the
tradenames Glissopal.TM. (from BASF).
[0091] Polyisobutylene polymers that may be employed are generally
based on a hydrocarbon chain of from 700 to 3000. Methods for
making polyisobutylene are known. Polyisobutylene can be
functionalized by halogenation (e.g chlorination), the thermal
"ene" reaction, or by free radical grafting using a catalyst (e.g.
peroxide), as described below.
[0092] The hydrocarbon or polymer backbone can be functionalized,
e.g., with carboxylic acid producing moieties (preferably acid or
anhydride moieties) selectively at sites of carbon-to-carbon
unsaturation on the polymer or hydrocarbon chains, or randomly
along chains using any of the three processes mentioned above or
combinations thereof, in any sequence.
[0093] Processes for reacting polymeric hydrocarbons with
unsaturated carboxylic acids, anhydrides or esters and the
preparation of derivatives from such compounds are disclosed in
U.S. Pat. Nos. 3,087,936; 3,172,892; 3,215,707; 3,231,587;
3,272,746; 3,275,554; 3,381,022; 3,442,808; 3,565,804; 3,912,764;
4,110,349; 4,234,435; 5,777,025; 5,891,953; as well as EP 0 382 450
B1; CA-1,335,895 and GB-A-1,440,219. The polymer or hydrocarbon may
be functionalized, for example, with carboxylic acid producing
moieties (preferably acid or anhydride) by reacting the polymer or
hydrocarbon under conditions that result in the addition of
functional moieties or agents, i.e., acid, anhydride, ester
moieties, etc., onto the polymer or hydrocarbon chains primarily at
sites of carbon-to-carbon unsaturation (also referred to as
ethylenic or olefinic unsaturation) using the halogen assisted
functionalization (e.g. chlorination) process or the thermal "ene"
reaction.
[0094] Selective functionalization can be accomplished by
halogenating, e.g., chlorinating or brominating the unsaturated
.alpha.-olefin polymer to about 1 to 8 mass %, preferably 3 to 7
mass % chlorine, or bromine, based on the weight of polymer or
hydrocarbon, by passing the chlorine or bromine through the polymer
at a temperature of 60 to 250.degree. C., preferably 110 to
160.degree. C., e.g., 120 to 140.degree. C., for about 0.5 to 10,
preferably 1 to 7 hours. The halogenated polymer or hydrocarbon
(hereinafter backbone) is then reacted with sufficient
monounsaturated reactant capable of adding the required number of
functional moieties to the backbone, e.g., monounsaturated
carboxylic reactant, at 100 to 250.degree. C., usually about
180.degree. C. to 235.degree. C., for about 0.5 to 10, e.g., 3 to 8
hours, such that the product obtained will contain the desired
number of moles of the monounsaturated carboxylic reactant per mole
of the halogenated backbones. Alternatively, the backbone and the
monounsaturated carboxylic reactant are mixed and heated while
adding chlorine to the hot material.
[0095] While chlorination normally helps increase the reactivity of
starting olefin polymers with monounsaturated functionalizing
reactant, it is not necessary with some of the polymers or
hydrocarbons contemplated for use in the present invention,
particularly those preferred polymers or hydrocarbons which possess
a high terminal bond content and reactivity. Preferably, therefore,
the backbone and the monounsaturated functionality reactant, e.g.,
carboxylic reactant, are contacted at elevated temperature to cause
an initial thermal "ene" reaction to take place. Ene reactions are
known.
[0096] The hydrocarbon or polymer backbone can be functionalized by
random attachment of functional moieties along the polymer chains
by a variety of methods. For example, the polymer, in solution or
in solid form, may be grafted with the monounsaturated carboxylic
reactant, as described above, in the presence of a free-radical
initiator. When performed in solution, the grafting takes place at
an elevated temperature in the range of about 100 to 260.degree.
C., preferably 120 to 240.degree. C. Preferably, free-radical
initiated grafting would be accomplished in a mineral lubricating
oil solution containing, e.g., 1 to 50 mass %, preferably 5 to 30
mass % polymer based on the initial total oil solution.
[0097] The free-radical initiators that may be used are peroxides,
hydroperoxides, and azo compounds, preferably those that have a
boiling point greater than about 100.degree. C. and decompose
thermally within the grafting temperature range to provide
free-radicals. Representative of these free-radical initiators are
azobutyronitrile, 2,5-dimethylhex-3-ene-2,5-bis-tertiary-butyl
peroxide and dicumene peroxide. The initiator, when used, typically
is used in an amount of between 0.005% and 1% by weight based on
the weight of the reaction mixture solution. Typically, the
aforesaid monounsaturated carboxylic reactant material and
free-radical initiator are used in a weight ratio range of from
1.0:1 to 30:1, preferably 3:1 to 6:1. The grafting is preferably
carried out in an inert atmosphere, such as under nitrogen
blanketing. The resulting grafted polymer is characterized by
having carboxylic acid (or ester or anhydride) moieties randomly
attached along the polymer chains: it being understood, of course,
that some of the polymer chains remain un-grafted. The free radical
grafting described above can be used for the other polymers and
hydrocarbons of the present invention.
[0098] The preferred monounsaturated reactants that are used to
functionalize the backbone comprise mono- and di-carboxylic acid
material, i.e., acid, anhydride, or acid ester material, including
(i) monounsaturated C.sub.4 to C.sub.10 dicarboxylic acid wherein
(a) the carboxyl groups are vicinyl, (i.e., located on adjacent
carbon atoms) and (b) at least one, preferably both, of said
adjacent carbon atoms are part of said mono unsaturation; (ii)
derivatives of (i) such as anhydrides or C.sub.1 to C.sub.5 alcohol
derived mono- or diesters of (i); (iii) monounsaturated C.sub.3 to
C.sub.10 monocarboxylic acid wherein the carbon-carbon double bond
is conjugated with the carboxy group, i.e., of the structure
--C.dbd.C--CO--; and (iv) derivatives of (iii) such as C.sub.1 to
C.sub.5 alcohol derived mono- or diesters of (iii). Mixtures of
monounsaturated carboxylic materials (i)-(iv) also may be used.
Upon reaction with the backbone, the monounsaturation of the
monounsaturated carboxylic reactant becomes saturated. Thus, for
example, maleic anhydride becomes backbone-substituted succinic
anhydride, and acrylic acid becomes backbone-substituted propionic
acid. Exemplary of such monounsaturated carboxylic reactants are
fumaric acid, itaconic acid, maleic acid, maleic anhydride,
chloromaleic acid, chloromaleic anhydride, acrylic acid,
methacrylic acid, crotonic acid, cinnamic acid, and lower alkyl
(e.g., C.sub.1 to C.sub.4 alkyl) acid esters of the foregoing,
e.g., methyl maleate, ethyl fumarate, and methyl fumarate.
[0099] To provide the required functionality, the monounsaturated
carboxylic reactant, preferably maleic anhydride, typically will be
used in an amount ranging from equimolar amount to about 100 mass %
excess, preferably 5 to 50 mass % excess, based on the moles of
polymer or hydrocarbon. Unreacted excess monounsaturated carboxylic
reactant can be removed from the final dispersant product by, for
example, stripping, usually under vacuum, if required.
[0100] The functionalized oil-soluble polymeric hydrocarbon
backbone is then derivatized with a nitrogen-containing
nucleophilic reactant, such as an amine, aminoalcohol, amide, or
mixture thereof, to form a corresponding derivative. Amine
compounds are preferred. Useful amine compounds for derivatizing
functionalized polymers comprise at least one amine and can
comprise one or more additional amine or other reactive or polar
groups. These amines may be hydrocarbyl amines or may be
predominantly hydrocarbyl amines in which the hydrocarbyl group
includes other groups, e.g., hydroxy groups, alkoxy groups, amide
groups, nitriles, imidazoline groups, and the like. Particularly
useful amine compounds include mono- and polyamines, e.g.,
polyalkene and polyoxyalkylene polyamines of 2 to 60, such as 2 to
40 (e.g., 3 to 20) total carbon atoms having 1 to 12, such as 3 to
12, preferably 3 to 9, most preferably form 6 to about 7 nitrogen
atoms per molecule. Mixtures of amine compounds may advantageously
be used, such as those prepared by reaction of alkylene dihalide
with ammonia. Preferred amines are aliphatic saturated amines,
including, for example, 1,2-diaminoethane; 1,3-diaminopropane;
1,4-diaminobutane; 1,6-diaminohexane; polyethylene amines such as
diethylene triamine; triethylene tetramine; tetraethylene
pentamine; and polypropyleneamines such as 1,2-propylene diamine;
and di-(1,2-propylene)triamine. Such polyamine mixtures, known as
PAM, are commercially available. Particularly preferred polyamine
mixtures are mixtures derived by distilling the light ends from PAM
products. The resulting mixtures, known as "heavy" PAM, or HPAM,
are also commercially available. The properties and attributes of
both PAM and/or HPAM are described, for example, in U.S. Pat. Nos.
4,938,881; 4,927,551; 5,230,714; 5,241,003; 5,565,128; 5,756,431;
5,792,730; and 5,854,186.
[0101] Other useful amine compounds include: alicyclic diamines
such as 1,4-di(aminomethyl) cyclohexane and heterocyclic nitrogen
compounds such as imidazolines. Another useful class of amines is
the polyamido and related amido-amines as disclosed in U.S. Pat.
Nos. 4,857,217; 4,956,107; 4,963,275; and 5,229,022. Also usable is
tris(hydroxymethyl)amino methane (TAM) as described in U.S. Pat.
Nos. 4,102,798; 4,113,639; 4,116,876; and UK Patent No. 989,409.
Dendrimers, star-like amines, and comb-structured amines may also
be used. Similarly, one may use condensed amines, as described in
U.S. Pat. No. 5,053,152. The functionalized polymer is reacted with
the amine compound using conventional techniques as described, for
example, in U.S. Pat. Nos. 4,234,435 and 5,229,022, as well as in
EP-A-208,560.
[0102] A preferred dispersant composition is one comprising at
least one polyalkenyl succinimide, which is the reaction product of
a polyalkenyl substituted succinic anhydride (e.g., PIBSA) and a
polyamine (PAM) that has a coupling ratio of from 0.65 to 1.25,
preferably from 0.8 to 1.1, most preferably from 0.9 to 1. In the
context of this disclosure, "coupling ratio" may be defined as a
ratio of the number of succinyl groups in the PIBSA to the number
of primary amine groups in the polyamine reactant.
[0103] Another class of high molecular weight ashless dispersants
comprises Mannich base condensation products. Generally, these
products are prepared by condensing about one mole of a long chain
alkyl-substituted mono- or polyhydroxy benzene with about 1 to 2.5
moles of carbonyl compound(s) (e.g., formaldehyde and
paraformaldehyde) and about 0.5 to 2 moles of polyalkylene
polyamine, as disclosed, for example, in U.S. Pat. No. 3,442,808.
Such Mannich base condensation products may include a polymer
product of a metallocene catalyzed polymerization as a substituent
on the benzene group, or may be reacted with a compound containing
such a polymer substituted on a succinic anhydride in a manner
similar to that described in U.S. Pat. No. 3,442,808. Examples of
functionalized and/or derivatized olefin polymers synthesized using
metallocene catalyst systems are described in the publications
identified supra.
[0104] The dispersant(s) of the present invention are preferably
non-polymeric (e.g., are mono- or bis-succinimides).
[0105] The dispersant(s) of the present invention, particularly the
lower molecular weight dispersants, may optionally be borated. Such
dispersants can be borated by conventional means, as generally
taught in U.S. Pat. Nos. 3,087,936, 3,254,025 and 5,430,105.
Boration of the dispersant is readily accomplished by treating an
acyl nitrogen-containing dispersant with a boron compound such as
boron oxide, boron halide, boron acids, and esters of boron acids,
in an amount sufficient to provide from 0.1 to 20 atomic
proportions of boron for each mole of acylated nitrogen
composition. It will be appreciated that any boron provided in the
lubricating oil composition by the dispersant will be in addition
to the boron provided by the detergent. Preferably, no more than 50
mass %, such as no more than 25 mass %, for example no more than 10
mass %, of the boron in the lubricating oil composition is provided
by the dispersant.
[0106] Dispersants derived from highly reactive polyisobutylene
have been found to provide lubricating oil compositions with a wear
credit relative to a corresponding dispersant derived from
conventional polyisobutylene. This wear credit is of particular
importance in lubricants containing reduced levels of
ash-containing anti-wear agents, such as ZDDP. Thus, in one
preferred embodiment, at least one dispersant used in the
lubricating oil compositions of the present invention is derived
from highly reactive polyisobutylene.
[0107] 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
metal rust inhibitors, viscosity index improvers, corrosion
inhibitors, oxidation inhibitors, friction modifiers, anti-foaming
agents, anti-wear agents and pour point depressants. Some are
discussed in further detail below.
[0108] Friction modifiers and fuel economy agents that are
compatible with the other ingredients of the final oil may also be
included. Examples of such materials include glyceryl monoesters of
higher fatty acids, for example, glyceryl mono-oleate; esters of
long chain polycarboxylic acids with diols, for example, the butane
diol ester of a dimerized unsaturated fatty acid; oxazoline
compounds; and alkoxylated alkyl-substituted mono-amines, diamines
and alkyl ether amines, for example, ethoxylated tallow amine and
ethoxylated tallow ether amine.
[0109] The viscosity index of the base stock is increased, or
improved, by incorporating therein certain polymeric materials that
function as viscosity modifiers (VM) or viscosity index improvers
(VII). Generally, polymeric materials useful as viscosity modifiers
are those having number average molecular weights (Mn) of from
about 5,000 to about 250,000, preferably from about 15,000 to about
200,000, more preferably from about 20,000 to about 150,000. These
viscosity modifiers can be grafted with grafting materials such as,
for example, maleic anhydride, and the grafted material can be
reacted with, for example, amines, amides, nitrogen-containing
heterocyclic compounds or alcohol, to form multifunctional
viscosity modifiers (dispersant-viscosity modifiers). 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, "Modem 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).
[0110] One class of diblock copolymers useful as viscosity
modifiers has been found to provide a wear credit relative to, for
example, olefin copolymer viscosity modifiers. This wear credit is
of particular importance in lubricants containing reduced levels of
ash-containing anti-wear agents, such as ZDDP. Thus, in one
preferred embodiment, at least one viscosity modifier used in the
lubricating oil compositions of the present invention is a linear
diblock copolymer comprising one block derived primarily,
preferably predominantly, from vinyl aromatic hydrocarbon monomer,
and one block derived primarily, preferably predominantly, from
diene monomer. Useful vinyl aromatic hydrocarbon monomers include
those containing from 8 to about 16 carbon atoms such as
aryl-substituted styrenes, alkoxy-substituted styrenes, vinyl
naphthalene, alkyl-substituted vinyl naphthalenes and the like.
Dienes, or diolefins, contain two double bonds, commonly located in
conjugation in a 1,3 relationship. Olefins containing more than two
double bonds, sometimes referred to as polyenes, are also
considered within the definition of "diene" as used herein. Useful
dienes include those containing from 4 to about 12 carbon atoms,
preferably from 8 to about 16 carbon atoms, such as 1,3-butadiene,
isoprene, piperylene, methylpentadiene, phenylbutadiene,
3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene, with
1,3-butadiene and isoprene being preferred.
[0111] As used herein in connection with polymer block composition,
"predominantly" means that the specified monomer or monomer type
that is the principle component in that polymer block is present in
an amount of at least 85% by mass of the block.
[0112] Polymers prepared with diolefins will contain ethylenic
unsaturation, and such polymers are preferably hydrogenated. When
the polymer is hydrogenated, the hydrogenation may be accomplished
using any of the techniques known in the prior art. For example,
the hydrogenation may be accomplished such that both ethylenic and
aromatic unsaturation is converted (saturated) using methods such
as those taught, for example, in U.S. Pat. Nos. 3,113,986 and
3,700,633 or the hydrogenation may be accomplished selectively such
that a significant portion of the ethylenic unsaturation is
converted while little or no aromatic unsaturation is converted as
taught, for example, in U.S. Pat. Nos. 3,634,595; 3,670,054;
3,700,633 and U.S. Re 27,145. Any of these methods can also be used
to hydrogenate polymers containing only ethylenic unsaturation and
which are free of aromatic unsaturation.
[0113] The block copolymers may include mixtures of linear diblock
polymers as disclosed above, having different molecular weights
and/or different vinyl aromatic contents as well as mixtures of
linear block copolymers having different molecular weights and/or
different vinyl aromatic contents. The use of two or more different
polymers may be preferred to a single polymer depending on the
rheological properties the product is intended to impart when used
to produce formulated engine oil. Examples of commercially
available styrene/hydrogenated isoprene linear diblock copolymers
include Infineum SV140198 m, Infineum SV150.TM. and Infineum
SV160.TM., available from Infineum USA L.P. and Infineum UK Ltd.;
Lubrizol.RTM. 7318, available from The Lubrizol Corporation; and
Septon 1001.TM. and Septon 1020.TM., available from Septon Company
of America (Kuraray Group). Suitable styrene/1,3-butadiene
hydrogenated block copolymers are sold under the tradename
Glissoviscal.TM. by BASF.
[0114] Pour point depressants (PPD), otherwise known as lube oil
flow improvers (LOFIs) lower the temperature. Compared to VM, LOFIs
generally have a lower number average molecular weight. Like VM,
LOFIs can be grafted with grafting materials such as, for example,
maleic anhydride, and the grafted material can be reacted with, for
example, amines, amides, nitrogen-containing heterocyclic compounds
or alcohol, to form multifunctional additives.
[0115] In the present invention, it may be necessary to include an
additive which maintains the stability of the viscosity of the
blend. Thus, although polar group-containing additives achieve a
suitably low viscosity in the pre-blending stage it has been
observed that some compositions increase in viscosity when stored
for prolonged periods. Additives which are effective in controlling
this viscosity increase include the long chain hydrocarbons
functionalized by reaction with mono- or dicarboxylic acids or
anhydrides which are used in the preparation of the ashless
dispersants as hereinbefore disclosed. In another preferred
embodiment, the lubricating oil compositions of the present
invention contain an effective amount of a long chain hydrocarbons
functionalized by reaction with mono- or dicarboxylic acids or
anhydrides.
[0116] When lubricating compositions contain one or more of the
above-mentioned additives, each additive is typically blended into
the base oil in an amount that enables the additive to provide its
desired function. Representative effective amounts of such
additives, when used in crankcase lubricants, are listed below. All
the values listed (with the exception of detergent values) are
stated as mass percent active ingredient (A.I.). As used herein,
A.I. refers to additive material that is not diluent or
solvent.
TABLE-US-00002 MASS % MASS % ADDITIVE (Broad) (Preferred)
Dispersant 0.1-20 1-8 Metal Detergents 0.1-15 0.2-9 Corrosion
Inhibitor 0-5 0-1.5 Metal Dihydrocarbyl Dithiophosphate 0.1-6.sup.
0.1-4 Antioxidant 0-5 0.01-2.5 Pour Point Depressant 0.01-5
0.01-1.5 Antifoaming Agent 0-5 0.001-0.15 Supplemental Anti-wear
Agents .sup. 0-1.0 0-0.5 Friction Modifier 0-5 0-1.5 Viscosity
Modifier 0.01-10.sup. 0.25-3.sup. Base stock Balance Balance
[0117] Preferably, the Noack volatility of the fully formulated
lubricating oil composition (oil of lubricating viscosity plus all
additives) will be no greater than 20 mass %, such as no greater
than 15 mass %, preferably no greater than 13 mass %. Lubricating
oil compositions useful in the practice of the present invention
may have an overall sulfated ash content of from 0.3 to 1.2 mass %,
such as from 0.4 to 1.1 mass %, preferably from 0.5 to 1.0 mass
%.
[0118] 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.
[0119] The final composition may employ from 5 to 25 mass %,
preferably 5 to 22 mass %, typically 10 to 20 mass % of the
concentrate, the remainder being oil of lubricating viscosity.
[0120] Preferably, the engine of the method of the second aspect of
the invention, and/or the use of the third aspect of the invention,
is an engine that generates a break mean effective pressure level
of greater than 1,500 kPa, optionally greater than 2,000 kPa, at
engine speeds of from 1,000 to 2,500 rotations per minute (rpm),
optionally from 1,000 to 2,000 rpm.
[0121] Preferably, the lubricating oil composition in the method of
the second aspect of the invention, and/or the use of the third
aspect of the invention, has a calcium content of at least 0.12
mass % and a boron content of at least 100 ppmm, such as at least
150 ppmm, based on the total mass of the lubricating oil
composition.
[0122] Optionally, at least 50%, preferably at least 70%, such as
at least 90%, of the boron content of the lubricating oil
composition is provided by the detergent package, such as by the
berated calcium detergent. Optionally, the berated calcium
detergent has a calcium content of at least 4 mass %, such as from
4 mass % to 16 mass %, preferably from 5 mass % to 12 mass %, for
example from 6 mass % to 10 mass %, and/or a boron content of at
least 1 mass %, such as from 1 mass % to 10 mass %, preferably 2
mass % to 8 mass %, for example from 3 mass % to 8 mass %, based on
the weight of the berated calcium detergent. Optionally, the
berated calcium detergent comprises a berated overbased calcium
detergent and has a TBN of at least 150 mg KOH/g, preferably at
least 200 mg KOH/g, for example from 200 to 450 mg KOH/g.
[0123] Optionally, the borated calcium detergent comprises a
borated calcium phenate, a berated calcium sulfonate, a berated
calcium salicylate, or mixtures thereof. In an embodiment, the
berated calcium detergent comprises a berated calcium
salicylate.
[0124] Optionally, the berated calcium detergent comprises calcium
and boron in a calcium mass % to boron mass % ratio of 1:Z, based
on the mass of the berated calcium detergent, wherein Z is at least
0.2, preferably at least 0.5. Optionally, the lubricating
composition is the lubricating composition according to the first
aspect of the invention.
[0125] This invention will be further understood by reference to
the following examples, wherein all parts are parts by mass, unless
otherwise noted and which include preferred embodiments of the
invention.
DESCRIPTION OF THE EXAMPLES
[0126] Whilst the present invention has been described and
illustrated with reference to particular embodiments, it will be
appreciated by those of ordinary skill in the art that the
invention lends itself to many different variations not
specifically illustrated herein. By way of example only, certain
possible variations will now be described.
[0127] The borated calcium detergent used in the following examples
was a borated calcium salicylate made according to the following
method. A reactor flask equipped with Dean-Stark trap was charged
with 1 kg overbased calcium salicylate having a TBN of 225 mg KOH/g
and 1 kg of xylene. With stirring and under nitrogen, 124 g of
boric acid was added slowly at room temperature. The temperature
was then raised to 115.degree. C. over 2 hours, then held at
115.degree. C. for 1 hour after. The reaction mixture was then
heated to 140.degree. C. over 90 minutes followed by a 40 minute
hold at 140.degree. C. The reaction mixture was then cooled and the
mixture centrifuged before concentration in vacuo on a rotary
evaporator to afford approximately 1 kg of borated calcium
salicylate product. ICP analysis (measured according to ASTM D4951)
showed the product to have 3.09% boron and 6.77% calcium by mass.
The product had a TBN (measured according to ASTM D2896) of 186 mg
KOH/g.
[0128] In the following Examples, data regarding LSPI occurrences
was generated using turbocharged, direct injected, GM Ecotec 2.0
liter, 4 cylinder engines, the boost level of which was modified to
generate a break mean effective pressure level of about 2,300 kPa
(23 bar), at an engine speed of about 2000 rpm. For each cycle (a
cycle being 2 piston cycles (up/down, up/down), data was collected
at 0.5.degree. crank angle resolution. Post processing of the data
included calculation of combustion metrics, verification of
operating parameters being within target limits, and detection of
LSPI events (statistical procedure outlined below). From the above
data, outliers, which are potential occurrences of LSPI were
collected. For each LSPI cycle, data recorded included peak
pressure (PP), MFB02 (crank angle at 2% mass fraction burned), as
well as other mass fractions (10%, 50% and 90%), cycle number and
engine cylinder. A cycle was identified as having an LSPI event if
either or both of the crank angle corresponding to MFB02 of the
fuel and the cylinder PP are outliers. Outliers were determined
relative to the distribution of a particular cylinder and test
segment in which it occurs. Determination of "outliers" was an
iterative process involving calculation of the mean and standard
deviation of PP and MFB02 for each segment and cylinder; and cycles
with parameters that exceed n standard deviations from the mean.
The number of standard deviations n, used as a limit for
determining outliers, is a function of the number of cycles in the
test and was calculated using the Grubbs' test for outliers.
Outliers were identified in the severe tail of each distribution.
That is, if n is the number of standard deviations obtained from
Grubbs' test for outliers, an outlier for PP is identified as one
exceeding the mean plus n standard deviations of peak pressure.
Likewise, an outlier for MFB02 was identified as one being lower
than the mean less n standard deviations of MFB02. Data was further
examined to ensure that the outliers indicated an occurrence of
LSPI, rather than some other abnormal combustion event of an
electrical sensor error.
[0129] An LSPI "event" was taken as one in which there were three
"normal" cycles both before and after. An LSPI event may include
more than one LSPI cycle or outlier. While this method was used
here, it is not part of the present invention. Studies conducted by
others have counted each individual cycle, whether or not it is
part of a multiple cycle event. The present definition of an LSPI
event is shown in FIG. 1 wherein 1 represents a single LSPI event
comprising multiple LSPI cycles. This is considered to be a single
LSPI event because each single cycle was not preceded and followed
by three normal events; 2 represents more than three normal events,
and 3 represents a second LSPI event comprising only a single LSPI
cycle. The LSPI trigger level, represented by 4, is determined by
the engine used and relates to the normal function for that
engine.
[0130] A series of 5W-30 grade lubricating oil compositions
representing typical passenger car motor oils meeting the GF-4
specification were prepared. The formulation of these compositions
is shown in Table 2 below.
TABLE-US-00003 TABLE 2 Comparative Example and Example Formulations
Comparative Comparative Example 1 Example 2 Example 1 Qty Qty Qty
Constituent Description (mass %) (mass %) (mass %) Borated 0.54
1.92 0 (polyisobutylenesuccinimide- polyamine) dispersant
Non-Borated 5.2 (polyisobutyienesuccinimide- polvamine) dispersant
A Non-Borated 5.2 5.2 (polyisobutyienesuccinimide- polyamine)
dispersant B 225 TBN Ca-salicylate detergent 2.14 2.14 1.6 64 TBN
Ca-salicylate detergent 0.55 0.55 0.55 Borated Ca-salicylate.sup.1
detergent 0.65 Additive Package 3.87 3.87 3.87 Infineum V385 .TM.
0.2 0.2 0.2 Pour point Depressant Infineum SV261L .TM. 5.6 5.6 5.6
Viscosity modifier Base Oil Balance Balance Balance Ash % 0.78 0.81
0.81 B ppm 70 250 250 Ca % 0.184 0.184 0.184 N % 0.097 0.114 0.09 P
% 0.08 0.08 0.08 S % 0.194 0.196 0.196 .sup.1The borated Ca
salicylate detergent was made using the 225 TBN Ca salicylate
detergent, which was borated according to the description
above.
[0131] In Comparative Example 1, the formulation includes a
typical, low boron concentration of 70 ppmm. In Comparative Example
2, the formulation includes a higher boron concentration of 250
ppmm, provided by means of a borated dispersant. In Example 1, the
formulation includes the same boron concentration as Comparative
Example 2 (250 ppmm), but the boron is provided by means of a
borated detergent. This means the nitrogen content is closer to
that of Comparative Example 1.
[0132] The formulations were tested for LSPI event occurrence as
described above, the results being presented in Table 3.
TABLE-US-00004 TABLE 3 LSPI Test Results with Comparative Example
and Example Formulations. Run Engine Formulation Average LSPI Per
Test 1 1 Comparative Example 1 35 2 1 Comparative Example 1 30 3 2
Comparative Example 1 23 4 2 Comparative Example 1 22 5 1
Comparative Example 2 28 6 2 Example 1 12
[0133] Runs 1, 2 and 5 were carried out on Engine 1, and Runs 3, 4
and 6 were carried out on Engine 2. Run 5, using the formulation of
Comparative Example 2 in which additional boron was provided by the
dispersant, showed a small reduction in LSPI event frequency of 14%
as compared to the average LSPI event frequency of Runs 1 and 2,
using the formulation of Comparative Example 1 having a typical,
low boron concentration. Run 6, using the formulation of Example 1
in which additional boron was provided by the borated calcium
detergent, showed a substantial reduction in LSPI event frequency
of 47% as compared to the average LSPI event frequency of Runs 3
and 4, using the formulation of Comparative Example 1. Thus, the
results in Table 4 show an unexpectedly large reduction in LSPI
event frequency when boron is introduced into the lubricating oil
composition by means of a borated detergent as compared to a
borated dispersant.
[0134] Where in the foregoing description, integers or elements are
mentioned which have known, obvious or foreseeable equivalents,
then such equivalents are herein incorporated as if individually
set forth. Reference should be made to the claims for determining
the true scope of the present invention, which should be construed
so as to encompass any such equivalents. It will also be
appreciated by the reader that integers or features of the
invention that are described as preferable, advantageous,
convenient or the like are optional and do not limit the scope of
the independent claims. Moreover, it is to be understood that such
optional integers or features, whilst of possible benefit in some
embodiments of the invention, may not be desirable, and may
therefore be absent, in other embodiments.
* * * * *