U.S. patent application number 16/142057 was filed with the patent office on 2019-03-28 for lubricating 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 Simon Crick, Carina Foster, Robert W. Shaw.
Application Number | 20190093041 16/142057 |
Document ID | / |
Family ID | 59974210 |
Filed Date | 2019-03-28 |
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United States Patent
Application |
20190093041 |
Kind Code |
A1 |
Shaw; Robert W. ; et
al. |
March 28, 2019 |
LUBRICATING COMPOSITIONS
Abstract
A method of reducing low-speed pre-ignition (LSPI) in a
direct-injected spark-ignited internal combustion engine comprising
lubricating the crankcase of the engine with a composition
comprising a combination of a molybdenum-containing additive and a
boron-containing additive. Preferably, the composition comprises a
calcium detergent providing a calcium content of at least 0.08 wt
%, based on the weight of the lubricating oil composition.
Inventors: |
Shaw; Robert W.; (Abingdon,
GB) ; Crick; Simon; (Wallingford, GB) ;
Foster; Carina; (Wantage, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infineum International Limited |
Abingdon |
|
GB |
|
|
Assignee: |
Infineum International
Limited
Abingdon
GB
|
Family ID: |
59974210 |
Appl. No.: |
16/142057 |
Filed: |
September 26, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 129/54 20130101;
C10M 2205/173 20130101; C10M 2219/062 20130101; C10M 2203/1025
20130101; C10N 2030/42 20200501; C10M 169/044 20130101; C10M
2219/044 20130101; C10N 2040/255 20200501; C10N 2030/04 20130101;
C10N 2030/40 20200501; C10M 2215/28 20130101; C10N 2040/10
20130101; C10N 2010/04 20130101; C10M 2219/068 20130101; C10M
2207/026 20130101; C10M 2219/046 20130101; C10N 2030/44 20200501;
C10M 2207/144 20130101; C10M 141/12 20130101; C10M 2201/066
20130101; C10M 2217/028 20130101; C10N 2030/52 20200501; C10M
141/10 20130101; C10M 155/04 20130101; C10M 2201/087 20130101; C10N
2030/43 20200501; C10M 137/10 20130101; C10M 2201/003 20130101;
C10M 2223/065 20130101; C10M 135/18 20130101; C10M 2215/064
20130101; C10M 2223/047 20130101; C10M 2227/061 20130101; C10M
135/10 20130101; C10M 2207/262 20130101; C10M 2223/045 20130101;
C10M 2229/00 20130101; C10M 2219/068 20130101; C10N 2010/12
20130101; C10M 2215/28 20130101; C10N 2060/14 20130101; C10M
2223/047 20130101; C10N 2010/12 20130101; C10M 2219/062 20130101;
C10N 2010/12 20130101; C10M 2223/065 20130101; C10N 2010/12
20130101; C10M 2207/262 20130101; C10N 2010/04 20130101; C10M
2223/045 20130101; C10N 2010/04 20130101; C10M 2203/1025 20130101;
C10N 2020/02 20130101; C10M 2219/046 20130101; C10N 2010/04
20130101; C10M 2219/068 20130101; C10N 2010/12 20130101; C10M
2223/047 20130101; C10N 2010/12 20130101; C10M 2219/062 20130101;
C10N 2010/12 20130101; C10M 2223/065 20130101; C10N 2010/12
20130101; C10M 2203/1025 20130101; C10N 2020/02 20130101; C10M
2207/262 20130101; C10N 2010/04 20130101; C10M 2223/045 20130101;
C10N 2010/04 20130101; C10M 2219/046 20130101; C10N 2010/04
20130101; C10M 2215/28 20130101; C10N 2060/14 20130101 |
International
Class: |
C10M 169/04 20060101
C10M169/04; C10M 155/04 20060101 C10M155/04; C10M 135/18 20060101
C10M135/18; C10M 135/10 20060101 C10M135/10; C10M 129/54 20060101
C10M129/54; C10M 137/10 20060101 C10M137/10; C10M 141/10 20060101
C10M141/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2017 |
EP |
17193419.3 |
Claims
1. 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 lubricating oil composition
comprising a boron-containing additive and a molybdenum-containing
additive, said lubricating oil composition having a molybdenum
content of at least 150 ppm by weight, based on the weight of the
lubricating oil composition, and having a boron content of at least
150 ppm by weight, based on the weight of the lubricating oil
composition.
2. A method according to claim 1, wherein, in operation, the engine
generates a brake mean effective pressure level of greater than
1,500 kPa, at engine speeds of from 1,000 to 2,500 rotations per
minute (rpm).
3. A method according to claim 1, wherein the lubricating oil
composition has a molybdenum content of from 150 ppm to 1500 ppm by
weight, based on the weight of the lubricating oil composition.
4. A method according to claim 2, wherein the lubricating oil
composition has a molybdenum content of from 150 ppm to 1500 ppm by
weight, based on the weight of the lubricating oil composition.
5. A method according to claim 1, wherein the lubricating oil
composition has a boron content of from 150 to 1500 ppm, based on
the weight of the lubricating oil composition.
6. A method according to claim 2, wherein the lubricating oil
composition has a boron content of from 150 to 1500 ppm, based on
the weight of the lubricating oil composition.
7. A method according to claim 3, wherein the lubricating oil
composition has a boron content of from 150 to 1500 ppm, based on
the weight of the lubricating oil composition.
8. A method according to claim 4, wherein the lubricating oil
composition has a boron content of from 150 to 1500 ppm, based on
the weight of the lubricating oil composition.
9. A method according to claim 1, wherein the lubricating oil
composition comprises a calcium detergent providing the lubricating
oil composition with a calcium content of from 0.08 to 0.5 wt. %,
based on the weight of the lubricating oil composition.
10. A method according to claim 7, wherein the lubricating oil
composition comprises a calcium detergent providing the lubricating
oil composition with a calcium content of from 0.08 to 0.5 wt. %,
based on the weight of the lubricating oil composition.
11. A method according to claim 1, wherein the lubricating oil
composition has a magnesium content of no more than 0.12 wt. %,
based on the weight of the lubricating oil composition.
12. A method according to claim 10, wherein the lubricating oil
composition has a magnesium content of no more than 0.12 wt. %,
based on the weight of the lubricating oil composition.
13. A method according to claim 11, wherein the lubricating oil
composition has a magnesium content of less than 0.05 wt. %, based
on the weight of the lubricating oil composition.
14. A method according to claim 12, wherein the lubricating oil
composition has a magnesium content of less than 0.05 wt. %, based
on the weight of the lubricating oil composition.
15. A method according to claim 1, wherein the boron-containing
additive Is one or more of: a borated dispersant, a borated
dispersant viscosity index improver, an alkali metal or an alkaline
earth metal borate, a borated overbased metal detergent, a borated
epoxide, a borate ester, a sulfurised borate ester, or a borate
amide; optionally wherein the boron-containing additive is one or
more of a borated dispersant, a borate ester or a borated overbased
metal detergent.
16. A method according to claim 1, wherein the
molybdenum-containing additive is an oil-soluble or oil-dispersible
organo-molybdenum compound, optionally wherein the
molybdenum-containing additive is one or more of a molybdenum
dithiocarbamate, a molybdenum dithiophosphate, a molybdenum
dithiophosphinate, a molybdenum xanthate, a molybdenum
thioxanthate, or a molybdenum sulfide.
17. A method according to claim 1, wherein the lubricating oil
composition has a phosphorus content of no more than 0.12 wt. %,
based on the weight of the lubricating oil composition.
18. A method according to claim 17, wherein the lubricating oil
composition has a phosphorus content of no more than 0.08 wt. %,
based on the weight of the lubricating oil composition.
19. A method according to claim 13, wherein the lubricating oil
composition has a phosphorus content of no more than 0.08 wt. %,
based on the weight of the lubricating oil composition.
20. A method according to claim 18, wherein the lubricating oil
composition has a phosphorus content of no more than 0.06 wt. %,
based on the weight of the lubricating oil composition,
21. A method according to claim 19, wherein the lubricating oil
composition has a phosphorus content of no more than 0.06 wt. %,
based on the weight of the lubricating oil composition.
Description
[0001] FIELD OF THE INVENTION
[0002] The present invention concerns a method of reducing
low-speed pre-ignition (LSPI) events in a direct-injection
spark-ignition combustion engine comprising lubricating the
crankcase of the engine with a lubricating composition comprising a
combination of a molybdenum-containing additive and a
boron-containing additive.
BACKGROUND OF THE INVENTION
[0003] Market demand, as well as governmental legislation, has fed
automotive manufacturers to continuously improve fuel economy and
reduce CO.sub.2 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.
[0004] 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.
[0005] Some attempts have been made in the an to address this
problem. For example, SAE 2013-01-2569 ("Investigation of Engine
Oil Effect on Abnormal Combustion in Turbocharged Direct
Injection-Spark Ignition Engines (Part 2)", Hirano et al.)
concludes that increasing calcium concentration leads to greater
LSPI frequency. It is also concluded that increasing zinc
dihydrocarbyl dithiophosphate (ZDDP) concentration can reduce LSPI
frequency. SAE 2014-01-2785 ("Engine Oil Development for Preventing
Pre-Ignition in Turbocharged Gasoline Engine", Fujimoto et al)
concludes that reducing the amount of calcium detergent in a
lubricating oil formulation is the most effective approach at
reducing LSPI events. It is also concluded that increasing the
amount of ZDDP can be effective in reducing LSPI frequency, SAE
2015-01-2027 ("Engine Oil Formulation Technology to Prevent
Pre-Ignition in Turbocharged Direct Injection Spark Ignition
Engines", Onodera et al.) concludes that (a) reducing calcium,
content together with increasing molybdenum content in engine oil
formulations, and (b) substitution of calcium with magnesium in
detergents for engine oil formulations, were both effective in
reducing the frequency of LSPI events. A method of reducing LSPI
frequency by using a lubricating oil having a reduced sodium
content and containing certain molybdenum-containing compounds is
disclosed in WO2017/011683. WO0015/171980 discloses a method of
reducing LSPI frequency by including in a lubricating oil
formulation at least one boron-containing compound, such as a
borated dispersant or a mixture of a boron-containing compound and
a dispersant. However, according to the examples disclosed in
WO2015/171980, it was necessary to replace a substantial amount, or
even ail of, the calcium detergent with a magnesium detergent in
order to obtain significant improvements in LSPI frequency.
[0006] The prior art has further recognised that reducing the
calcium content, and/or increasing the ZDDP content, of a
lubricating oil formulation can lead to a reduction in LSPI events.
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. However, alternative detergents capable of providing
appropriate detergent activity and adequate total base number (TBN)
can be challenging to develop. Furthermore, increased ZDDP contents
in lubricating oil formulations can lead to other, less desirable,
effects. In particular, increasing ZDDP concentration often leads
to an increase in ash formation and can lead to damage of catalysts
in engine exhaust systems. EP 3 101 095 discloses a lubricating oil
composition for reducing LSPI frequency, the composition comprising
a compound containing calcium and/or magnesium, a compound
containing molybdenum and/or phosphorus, and an ashless dispersion
containing nitrogen, According to the disclosure of EP 3 101 095,
LSPI event frequency can be reduced by controlling the relative
amounts of calcium, magnesium, molybdenum and phosphorus in the
lubricating oil composition.
[0007] Thus, 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
[0008] The present inventors have surprisingly found that the use
of both molybdenum-containing and boron-containing additives in a
lubricating oil composition significantly reduces in the frequency
of LSPI events in direct injection-spark ignition internal
combustion engines when the crankcase of the engine is lubricated
with said lubricating oil composition. More particularly, the
present inventors have surprisingly found a synergistic improvement
in LSPI reduction when using such a lubricating composition as
compared to using a lubricating oil composition comprising only
molybdenum-containing additives and not boron-containing additives,
and vice versa.
[0009] Thus, the present invention provides, according to a first
aspect, a method of reducing 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 boron-containing additive and a
molybdenum-containing additive, having a molybdenum content of at
least 150 ppm by weight, based on the weight of the lubricating oil
composition, and having a boron content of at least 150 ppm by
weight, based on the weight of the lubricating oil composition.
[0010] According to a second aspect, the present invention provides
the use of a combination of the composition a boron-containing
additive and a molybdenum-containing additive in a lubricating oil
composition to reduce LSPI events, when the composition lubricates
the crankcase of a direct injection-spark ignition internal
combustion engine, wherein, the molybdenum-containing additive
provides the lubricating oil composition with a molybdenum content
of at least 150 ppm by weight, based on the weight of the
lubricating oil composition, and the boron-containing additive
provides the lubricating oil composition with a boron content of at
least 150 ppm by weight, based on the weight of the lubricating oil
composition.
[0011] In this specification, the following words and expressions,
if and when used, have the meanings ascribed below:
[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 50 mass % or less of a composition;
[0016] "antifoam" is a chemical additive that reduces and hinders
the formation of foam in the lubricating oil composition, examples
of commonly used antifoams are polydimethylsiloxanes and other
silicones, certain alcohols, stearates and glycols;
[0017] "TBN" means total base number as measured by ASTM D2896 in
units of mg KOHg.sup.-1;
[0018] "phosphorus content" is measured by ASTM D5185;
[0019] "molybdenum content" is measured by ASTM D5185;
[0020] "boron content" is measured by ASTM D5185;
[0021] "sulfur 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
includes the use of 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 use
of the invention may incorporate any of the features described with
reference to the method of the invention and vice versa.
BRIEF DESCRIPTION OF THE FIGURES
[0025] FIG. 1 shows the LSPI test results of Example 3 in matrix
format.
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 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 brake 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, brake mean effective pressure (BMEP) is the mean effective
pressure calculated from measured brake torque. 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. BMEP is defined as the work
accomplished during an engine cycle, divided by the engine swept
volume; the engine torque normalized by engine displacement and can
be calculated using the following formula:
BMEP=2.pi.Tn.sub.c/V.sub.d
where T is torque (Nm), n.sub.c is the number of revolutions per
cycle, V.sub.d is displacement (m.sup.3). For a 4 stroke engine
n.sub.c is 2, for a 2 stroke engine n.sub.c is 1.
[0028] SAE 2014-01-2785 has concluded that LSPI event frequency is
strongly influenced by the calcium content of the lubricating oil
composition, and that it is preferable to avoid lubricating
composition calcium contents of greater than 0.11 wt. %, based on
the weight of the lubricating oil composition, in order to avoid
excessive LSPI event frequency.
[0029] Surprisingly, the present inventors have found that the
presence of a combination of molybdenum and boron in a lubricating
oil formulation is effective at reducing the occurrence of LSPI
events. Unexpectedly, it has been found that the combination of
both molybdenum and boron provides a synergistic improvement in
LSPI event reduction, the frequency reduction being greater than
expected from analysing the performance of lubricating oil
compositions comprising only molybdenum and compositions comprising
only boron. It has now been found that the occurrence of LSPI in
engines can be reduced by lubricating the crankcase with
lubricating oil compositions comprising at least 150 ppm by weight
molybdenum and at least 150 ppm by weight boron, based on fee
weight of the lubricating oil composition, compared to lubricating
the crankcase with lubricating oil compositions comprising less
than 150 ppm by weight molybdenum and less than 150 ppm by weight
boron. Surprisingly, the present inventors have found that the
method and use of the first and second aspects of the invention is
effective at reducing LSPI event frequency even when the
lubricating oil composition comprises a significant amount of
calcium, for example when the lubricating oil composition
additionally comprises at least 0.08 wt % calcium, based on the
weight of the lubricating oil composition.
[0030] Preferably, the engine of the method of the first aspect of
the invention, and/or the use of the second 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.
[0031] Optionally, the lubricating oil composition of all aspects
of the invention comprises at least 175 ppm molybdenum, preferably
at least 300 ppm molybdenum, optionally at least 350 ppm
molybdenum, such as at least 500 ppm molybdenum, for example at
least 700 ppm molybdenum, by weight, based on the weight of the
lubricating oil composition. Optionally, the lubricating oil
composition comprises no more than 1500 ppm molybdenum, preferably
no more than 1400 ppm molybdenum, such as no more than 1200 ppm
molybdenum, for example no more than 1100 ppm molybdenum,
optionally no more than 1000 ppm molybdenum, by weight, based on
the weight of the lubricating oil composition. Optionally, the
lubricating oil composition comprises from ISO to 1500 ppm
molybdenum, preferably from 175 to 1500 ppm molybdenum, optionally
from 300 to 1400 ppm molybdenum, such as from 350 to 1200 ppm
molybdenum, for example from 300 to 1100 ppm molybdenum, optionally
from 700 to 1000 ppm molybdenum, by weight, based on the weight of
the lubricating oil composition.
[0032] Optionally, the lubricating oil composition comprises at
least 200 ppm boron, preferably at least 300 ppm boron, such as at
least 400 ppm boron, by weight, based on the weight of the
lubricating oil composition. Optionally, the lubricating oil
composition comprises no more than 1500 ppm boron, preferably no
more than 1000 ppm boron, such as no more than 800 ppm boron, by
weight, based on the weight of the composition, Optionally, the
lubricating oil composition comprises from 150 to 1500 ppm boron,
preferably from 200 to 1000 ppm boron, optionally from 400 to 800
ppm boron, by weight, based on the weight of the lubricating oil
composition.
[0033] It will be understood that the boron-containing additive may
be any suitable oil-soluble compound or oil-dispersible compound.
Boron-containing additives may be prepared by reacting a boron
compound with an oil-soluble or oil-dispersible additive or
compound. Boron compounds include boron oxide, boron oxide hydrate,
boron trioxide, boron trifluoride, boron tribromide, boron
trichloride, boron acid such as boronic acid, boric acid,
tetraboric acid and rnetaboric acid, boron hydrides, boron amides
and various esters of boron acids, For example, the
boron-containing additive may be one or more of a borated
dispersant; a borated dispersant viscosity index improver; an
alkali metal or a mixed alkali metal or an alkaline earth metal
borate; a borated overbased metal detergent; a borated epoxide; a
borate ester; a sulfurised borate ester; and a borate amide.
Preferably, the boron-containing additive is one or more of a
borated dispersant, a borate ester or a borated overbased metal
detergent. Optionally, the borated overbased metal detergent, if
present, is a borated overbased metal detergent having a TBN of at
least 150, such as a borated overbased calcium detergent having a
TBN of at least 150.
[0034] Borated dispersants may be prepared by boration of
succinimide, succinic ester, benzylamine and their derivatives,
each of which has an alkyl or alkenyl group of molecular weight of
700 to 3000. Processes for manufacture of these additives are known
to those skilled in the art. A preferred amount of boron contained
in these dispersants is 0.1 to 5 mass % (especially 0.2 to 2 mass
%). A particularly preferable borated dispersant is a succinimide
derivative of boron, for example borated polyisobutenyl
succinimide. An example of a borated dispersant is a borated
polyisobutenyl succinimide wherein the average number molecular
weight (M.sub.n) of the polybutenyl backbone is in the range from
700 to 1250. Additionally or alternatively, borated dispersants are
made by borating the ashless dispersants described below, using
known borating means and techniques.
[0035] Ashless dispersants are non-metallic organic materials that
form substantially no ash on combustion, in contrast to
metal-containing, and hence ash-forming, materials. They comprise a
long chain hydrocarbon with a polar head, the polarity being
derived from inclusion of, e.g. an O, P or N atom. The hydrocarbon
is an oleophilic group that confers oil-solubility, having, for
example 40 to 500 carbon atoms. Thus, ashless dispersants may
comprise an oil-soluble polymeric hydrocarbon backbone having
functional groups that are capable of associating with particles to
be dispersed. Typically, dispersants comprise amine, alcohol,
amide, or ester polar moieties attached to the polymer backbone
often via a bridging group. Ashless dispersants may be, for
example, selected from oil-soluble salts, esters, ammo-esters,
amides, imides, and oxazolines of long chain
hydrocarbon-substituted mono- and dicarboxylic acids or their
anhydrides; thiocarboxylate derivatives of a long chain of
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
alkylene polyamine, such as described in U.S. Pat. No. 3,442,808.
The oil-soluble polymeric hydrocarbon backbone is typically an
olefin polymer or polyene, especially a polymer comprising a major
molar amount (i.e. greater than 50 mole %) of a C.sub.2 to C.sub.18
olefin (e.g. ethylene, propylene, butylenes, isobutylene, pentene,
octane-1, styrene), and typically a C.sub.2 to C.sub.5 olefin. The
oil-soluble polymeric hydrocarbon backbone may be homopolymeric
(e.g. comprising a copolymer of ethylene and an alpha-olefin such
as propylene or butylenes, or a copolymer of two different
alpha-olefins). A preferred class of olefin polymers comprises
polybutenes, specifically polyisobutenes (PIB) or poly-n-butenes,
such as may be prepared by polymerization of a C.sub.4 refinery
stream. Other classes of olefin polymers include ethylene
alpha-olefin (EAO) copolymers and alpha-olefin homo-and
copolymers.
[0036] Ashless dispersants include, for example, derivatives of
long chain hydrocarbon-substituted carboxylic acids, examples being
derivatives of high molecular weight hydrocarbyl-substituted
succinic acid. A noteworthy group of dispersants are
hydrocarbon-substituted succinimides, made, for example, by
reacting the above acids (or derivatives) with a
nitrogen-containing compound, advantageously a polyalkylene
polyamine, such as polyethylene polyamine. Particularly preferred
are the reaction products of polyalkylene polyamines with alkenyl
succinic anhydrides, such as described in U.S. Pat. No. 3,202,678;
3,154,560; 3,172,892; 3,024,195, 3,024,237; 3,219,666; and
3,216,936; and BE-A-66,875. Preferred dispersants are
polyalkene-substituted succinimides wherein the polyalkene group
has a number-average molecular weight in the range of 900 to 5,000.
The number-average molecular weight is measured by gel permeation
chromatography (GPC). The polyalkene group may comprise a major
molar amount (i.e. greater than 50 mole %) of a C.sub.2 to C.sub.18
alkene, e.g. ethene, propene, butene, iso butene, pentene, octane-1
and styrene. Preferably, the alkene is a C.sub.2 to C.sub.5 alkene;
more preferably it is butene or isobutene, such as may be prepared
by polymerisation of a C.sub.4 refinery stream. Most preferably,
the number average molecular weight of the polyalkene group is in
the range of 950 to 2,800.
[0037] The above ashless dispersants are post-treated with boron to
form a borated dispersant in ways known in the art, such as
described in U.S. Pat. Nos. 3,087,936, 3,254,025 and 5,430,105.
Boration may for example be accomplished by treating an acyl
nitrogen-containing dispersant with a boron compound selected from
boron oxide, boron halides, boron acids and esters of boron acids,
in an amount sufficient to provide from about 0.1 to about 20
atomic proportions of boron for each mole of ashless
dispersant.
[0038] Alkali metal and alkaline earth metal borates are generally
hydrated particulate metal borates, which are known in the art.
Alkali metal borates include mixed alkali and alkaline earth metal
borates. These metal borates are available commercially.
Representative patents describing suitable alkali metal and
alkaline earth metal borates and their methods of manufacture
include U.S. Pat. No. 3,997,454; 3,819,521; 3,853,772; 3,907,601;
3,997,454; and 4,089,790.
[0039] Borated amines may be prepared by reacting one or more of
the above boron compounds with one or more of fatty amines, e.g.,
an amine having from four to eighteen carbon atoms. They may be
prepared by reacting the amine with the boron compound at a
temperature in the range of from 50 to 300.degree. C., preferably
from 100 to 250.degree. C., and at a ratio from 3:1 to 1:3
equivalents of amine to equivalents of boron compound.
[0040] Borated epoxides are generally the reaction product of one
or more of the above boron compounds with at least one epoxide. The
epoxide is generally an aliphatic epoxide having from 8 to 30,
preferably from 10 to 24, more preferably from 12 to 20, carbon
atoms. Examples of useful aliphatic epoxides include heptyl epoxide
and octyl epoxide. Mixtures of epoxides may also be used, for
instance commercial mixtures of epoxides having from 14 to 16
carbon atoms and from 14 to 18 carbon atoms. The borated fatty
epoxides are generally known and are described in U.S. Pat. No.
4,584,115.
[0041] Borate esters may be prepared by reacting one or more of the
above boron compounds with one or more alcohols of suitable
oleophilicity. Typically, the alcohols contain from 6 to 30, or
from 8 to 24, carbon atoms. The methods of making such borate
esters are known in the art. The borate esters cars be borated
phospholipids. Such compounds, and processes for making such
compounds, are described in EP-A-0 684 298. Examples of sulfurised
borated esters are also known in the art: see EP-A-0 285 455 and
U.S. Pat. No. 6,028,210. Alternatively, it may be that a borate
ester is substantially absent in the lubricating oil compositions
of the method or use of the present invention.
[0042] Borated overbased metal detergents are known in the art
where the borate substitutes the carbonate in the core either in
part or in full. Borated detergents may be prepared by any
conventional method, for example, a borated detergent may be
prepared by treating a metal detergent with boric acid. Suitable
borated detergents and methods of preparing them are disclosed in
U.S. Pat. No. 3,480,548, 3,679,584, 3,829,381, 3,909,691 and 4,
965,004.
[0043] Preferably, at least a portion of the boron content of the
lubricating oil composition is provided by a boron-containing
dispersant additive, such as a major portion. In an embodiment of
the invention, 100 wt. % of the boron in the lubricating oil
composition, based on the weight of the boron in the lubricating
oil composition, is provided by one or more boron-containing
dispersant additives.
[0044] Alternatively or in addition, at least a portion of the
boron content of the lubricating oil composition is provided by a
borated detergent.
[0045] Additionally or alternatively, at least a portion of the
boron content of the lubricating oil composition is provided by a
borate ester.
[0046] In an embodiment of the invention, at least a portion of the
boron content of the lubricating oil composition is provided by a
boron-containing compound that is not a dispersant, such as a major
portion.
[0047] Optionally, 100 wt % of the boron in the lubricating oil
composition, based on the weight of the boron in the lubricating
oil composition is provided by one or more non-dispersant
boron-containing compounds, such as a borated detergent and/or a
borate ester. Optionally, from 20 wt. % to 100 wt. %, preferably
from 40 wt. % to 80 wt. %, such as from 50 wt. % to 70 wt. %, of
the boron in the lubricating oil composition, based on the weight
of the boron in die lubricating oil composition, is provided by one
or more borated detergent(s) and/or borate ester(s).
[0048] It will be understood that the molybdenum-containing
additive may be any suitable oil-soluble or oil-dispersible
organo-molybdenum compound. Preferably, 100 wt. % of the molybdenum
content of the lubricating oil composition is provided by an
organo-molybdenum compound, based on the weight of the lubricating
oil composition. Such molybdenum-containing additives generally
exhibit friction modifying properties when present in a lubricating
oil composition. Additionally or alternatively, such
molybdenum-containing additives may also provide antioxidant and
anti-wear credits to a lubricating oil composition.
[0049] To enable the molybdenum compound to be oil-soluble or
oil-dispersible, one or more ligands are typically bonded to a
molybdenum atom in the compound. The bonding of the ligands
includes bonding by electrostatic interaction as in the case of a
counter-ion and forms of bonding intermediate between covalent and
electrostatic bonding. Ligands within the same compound may be
differently bonded. For example, a ligand may be covalently bonded
and another ligand may be electrostatically bonded. Preferably, the
or each ligand is monoanionic and examples of such ligands are
dithiophosphates, dithiocarbamates, xanthates, carboxylates,
thioxanthates, phosphates and hydrocarbyl, preferably alkyl,
derivatives thereof.
[0050] The molybdenum-containing additive may be mono-, di-, tri-
or tetra-nuclear. Di-nuclear and tri-nuclear molybdenum compounds
are preferred. In the event that the compound is polynuclear, the
compound contains a molybdenum core consisting of non-metallic
atoms, such as sulfur, oxygen and selenium, preferably consisting
essentially of sulfur.
[0051] In a preferred embodiment, the molybdenum compound is a
molybdenum-sulfur compound. Preferably, the ratio of the number of
molybdenum atoms, for example, in the core in the event that the
molybdenum-sulfur compound is a poly-nuclear compound, to the
number of monoanionic ligands, which are capable of rendering the
compound oil-soluble or oil-dispersible, is greater than 1 to 1,
such as at least 3 to 2. The molybdenum-sulfur compound's
oil-solubility or oil-dispersibility may be influenced by the total
number of carbon atoms present among all of the compound's ligands.
The total number of carbon atoms present among all of the
hydrocarbyl groups of the compound's ligands typically will be at
least 21, e.g. 21 to 800, such as at least 25, at least 30 or at
least 35. For example, the number of carbon atoms in each alkyl
group will generally range between 1 to 100, preferably 1 to 40,
and more preferably between 3 and 20.
[0052] Examples of suitable organo-molybdenum compounds include
molybdenum dithiocarbamates, molybdenum dithiophosphates,
molybdenum dithiophosphinates, molybdenum xanthates, molybdenum
thioxanthates, molybdenum sulfides, and the like, and mixtures
thereof. Particularly preferred are molybdenum dithiocarbamates,
molybdenum dialkyldithiophosphates, molybdenum alkyl xanthates and
molybdenum alkylthioxanthates. An especially preferred
organo-molybdenum compound is a molybdenum dithiocarbamate. In an
embodiment of the present invention the oil-soluble or
oil-dispersible molybdenum compound consists of either a molybdenum
dithiocarbamate or a molybdenum dithiophosphate or a mixture
thereof, as the sole source of molybdenum atoms in the lubricating
oil composition. In an alternative embodiment of the present
invention the oil-soluble or oil-dispersible molybdenum compound
consists of a molybdenum dithiocarbamate, as the sole source of
molybdenum atoms in the lubricating oil composition.
[0053] Suitable dinuclear or dimeric molybdenum
dialkyldithiocarbamate are represented by the following
formula:
##STR00001##
[0054] R.sub.1 through R.sub.4 independently denote a straight
chain, branched chain or aromatic hydrocarbyl group having 1 to 24
carbon atoms; and X.sub.1 through X.sub.4independently denote an
oxygen atom or a sulfur atom. The four hydrocarbyl groups, R.sub.1
through R.sub.4, may be identical or different from one
another.
[0055] Other molybdenum-containing additives useful in the
compositions of this invention are organo-molybdenum compounds of
the formulae Mo(ROCS.sub.2).sub.4 and Mo(RSCS.sub.2).sub.4, wherein
R is an organo group selected from the group consisting of alkyl,
aryl, aralkyl and alkoxyalkyl, generally of from 1 to 30 carbon
atoms, and preferably 2 to 12 carbon atoms and most preferably
alkyl of 2 to 12 carbon atoms. Especially preferred are the
dialkyldithiocarbamates of molybdenum.
[0056] In a preferred embodiment, the molybdenum-containing
additive is an oil-soluble or oil-dispersible trinuclear
molybdenum-sulfur compound, Examples of trinuclear
molybdenum-sulfur compounds are disclosed in WO98/26030,
WO99/31113, WO99/66013, EP-A-1 138 752, EP-A-1 138 686 and European
patent application no. 02078011, each of which are incorporated
into the present description by reference, particularly with
respect to the characteristics of the molybdenum compound or
additive disclosed therein.
[0057] Suitable tri-nuclear organo-molybdenum compounds include
those of the formula Mo.sub.3S.sub.kL.sub.nQ.sub.z and mixtures
thereof wherein L are independently selected ligands having organo
groups with a sufficient number of carbon atoms to render the
compound soluble or dispersible in the oil n is from 1 to 4, k
varies from 4 through 7, Q is selected from the group of neutral
electron donating compounds such as water, amines, alcohols,
phosphines, and ethers, and z ranges from 0 to 5 and includes
non-stoichiometric values. At least 21 total carbon atoms should be
present among all the ligands' organo groups, such as at least 25,
at least 30, or at least 35 carbon atoms.
[0058] The ligands are independently selected from the group
of:
##STR00002##
[0059] and mixtures thereof, wherein X, X.sub.1, X.sub.2, and Y are
independently selected from the group of oxygen and sulfur, and
wherein R.sub.1, R.sub.2, and R are independently selected from
hydrogen and organo groups that may be the same or different.
Preferably, the organo groups are hydrocarbyl groups such as alkyl
(e.g., in which the carbon atom attached to the remainder of the
ligand is primary or secondary), aryl, substituted aryl and ether
groups. More preferably, each ligand has the same hydrocarbyl
group. Importantly, the organo groups of the ligands have a
sufficient number of carbon atoms to render the compound soluble or
dispersible in the oil. For example, the number of carbon atoms in
each group will generally range between about 1 to about 100,
preferably from about 1 to about 30, and more preferably between
about 4 to about 20. Preferred ligands include
dialkyldithiophosphate, alkylxanthate, and dialkyldithiocarbamate,
and of these dialkyldithiocarbamate is more preferred. Organic
ligands containing two or more of the above functionalities are
also capable of serving as ligands and binding to one or more of
the cores. Those skilled in the art will realize that formation of
the compounds of the lubricating oil composition of the present
invention requires selection of ligands having the appropriate
charge to balance the core's charge.
[0060] Particularly suitable molybdenum-containing additives
include compounds having the formula Mo.sub.3S.sub.kL.sub.nQ.sub.z,
having cationic cores surrounded by anionic ligands and being
represented by structures such as
##STR00003##
[0061] and having net charges of +4. Consequently, in order to
solubilize these cores the total charge among ail the ligands must
be -4. Four mono-anionic ligands are preferred. Without wishing to
be bound by any theory, it is believed that two or more tri-nuclear
cores may be bound or interconnected by means of one or more
ligands and the ligands may be multidentate. This includes the case
of a multidentate ligand having multiple connections to a single
core. It is believed that oxygen and/or selenium may be substituted
for sulfur in the core(s).
[0062] Additionally or alternatively, particularly suitable
trinuclear molybdenum-containing additives may be represented by
the formula Mo.sub.3S.sub.kE.sub.xL.sub.nA.sub.pQ.sub.z,
wherein:
[0063] k is an integer of at least 1;
[0064] E represents a non-metallic atom selected from oxygen and
selenium;
[0065] x can be 0 or an integer, and preferably k+x is at least 4,
more preferably in the range of 4 to 10, such as 4 to 7, most
preferably 4 or 7;
[0066] L represents a ligand that confers oil-solubility or
oil-dispersibility on the molybdenum-sulfur compound, preferably L
is a monoanionic ligand;
[0067] n is an integer in the range of 1 to 4;
[0068] A represents an anion other than L, if L is an anionic
ligand;
[0069] p can be 0 or an integer;
[0070] Q represents a neutral electron-donating compound; and
[0071] z is in the range of 0 to 5 and includes non-stoichiometric
values.
[0072] Those skilled in the art will realise that formation of the
trinuclear molybdenum-sulfur compound will require selection of
appropriate ligands (L) and other anions (A), depending on, for
example, fee number of sulfur and E atoms present in the core, i.e.
the total anionic charge contributed by sulfur atom(s), E atom(s),
if present, L and A, if present, must be -12. Examples of Q include
water, alcohol, amine, ether and phosphine. It is believed that the
electron-donating compound, Q, is merely present to fill any vacant
coordination sites on the trinuclear molybdenum-sulfur compound.
Examples of A can be of any valence, for example, monovalent and
divalent and include disulfide, hydroxide, alkoxide, amide and,
thiocyanate or derivative thereof; preferably A represents a
disulfide ion. Preferably, L is monoanionic ligand, such as
dithiophosphates, dithiocarbarnates, xanthates, carboxylases,
thioxanthates, phosphates and hydrocarbyl, preferably alkyl,
derivatives thereof. When n is 2 or more, the ligands can be the
same or different in an embodiment, independently of the other
embodiments, k is 4 or 7, n is either 1 or 2, L is a monoanionic
ligand, p is an integer to confer electrical neutrality on the
compound based on the anionic charge on A and each of x and z is
0.
[0073] In a further embodiment, independently of the other
embodiments, k is 4 or 7, L is a monoanionic ligand, n is 4 and
each of p, x and z is 0.
[0074] In another embodiment, the molybdenum-containing additive
comprises trinuclear molybdenum core and bonded thereto a ligand,
preferably a mono-aniomc ligand, such as a dithiocarbamate, capable
of rendering the core oil-soluble or oil-dispersible. For the
avoidance of doubt, the molybdenum-containing additive may also
comprise either negatively charged molybdenum species or positively
charged molybdenum species or both negatively and positively
charged molybdenum species.
[0075] The molybdenum-sulfur cores, for example, the structures
depicted in (I) and (II) above, may be interconnected by means of
one or more ligands that are multidentate, i.e. a ligand having
more than one functional group capable of binding to a molybdenum
atom, to form oligomers. Molybdenum-sulfur additives comprising
such oligomers are considered to fall within the scope of the
fabricating oil compositions of this invention.
[0076] Oil-soluble or oil-dispersible tri-nuclear
molybdenum-containing additives can be prepared by reacting in the
appropriate liquid(s)/solvent(s) a molybdenum source such as
(NH.sub.4).sub.2Mo.sub.3Si.sub.3.n(H.sub.2O), where n varies
between 0 and 2 and includes non-stoichiometric values, with a
suitable ligand source such as a tetralkylthiuram disulfide. Other
oil-soluble or dispersible tri-nuclear molybdenum-containing
additives can be formed during a reaction in the appropriate
solvent(s) of a molybdenum source such as of
(NH.sub.4).sub.2Mo.sub.3S.sub.13.n (H.sub.2O), a ligand source such
as tetralkylthiuram disulfide, dialkyldithiocarbamate, or
dialkyldithiophosphate, and a sulfur abstracting agent such as
cyanide ions, sulfite ions, or substituted phosphines.
Alternatively, a tri-nuclear molybdenum-sulfur halide salt such as
[M'].sub.2[Mo.sub.3S.sub.7A.sub.6], where M' is a counter ion, and
A is a halogen such as Cl, Br, or I, may be reacted with a ligand
source such as a dialkyldithiocarbamate or dialkyldithiophosphate
in the appropriate liquid(s)/solvent(s) to form an oil-soluble or
dispersible trinuclear molybdenum compound. The appropriate
liquid/solvent may be, for example, aqueous or organic,
[0077] A compound's oil solubility or dispersibility may be
influenced by the number of carbon atoms in the ligand's organo
groups. Preferably, at least 21 total carbon atoms should be
present among all the ligands' organo groups. Preferably, the
ligand source chosen has a sufficient number of carbon atoms in its
organo groups to render the compound soluble or dispersible in the
lubricating composition.
[0078] Other examples of molybdenum compounds include molybdenum
carboxylates and molybdenum nitrogen complexes, both of which may
be sulfurised.
[0079] Alternatively, the molybdenum-containing additive may be an
acidic molybdenum compound. These compounds will react with a basic
nitrogen compound as measured by ASTM test D-664 or D-2896
titration procedure and are typically hexavalent. Included are
molybdic acid, ammonium molybdate, sodium molybdate, potassium
molybdate, and other alkaline metal molybdates and other molybdenum
salts, e.g., hydrogen sodium molybdate, MoOCl.sub.4,
MoO.sub.2Br.sub.2, Mo.sub.2O.sub.3Cl.sub.6, molybdenum trioxide of
similar acidic molybdenum compounds.
[0080] Alternatively, the lubricating oil compositions of the
present invention can be provided with molybdenum by
molybdenum/sulfur complexes of basic nitrogen compounds as
described, for example, in U.S. Pat. Nos. 4,263,152; 4,285,822;
4,283,295; 4,272,387; 4,265,773; 4,261,843; 4,259,195 and
4,259,194; and WO 94/06897.
[0081] Optionally, the lubricating oil composition comprises one or
more molybdenum-containing compounds that is not a friction
modifier additive (for example that is not used as a friction
modifier additive). Optionally, at least a portion of the
molybdenum content of the lubricating oil composition is provided
by a molybdenum-containing compound that is not a friction
modifier, such as a major portion.
[0082] Optionally, the lubricating oil composition of all
embodiments of the present invention has a calcium content of at
least 0.08 wt %, based on the weight of the lubricating oil
composition. The lubricating oil composition of all aspects of the
invention may have a calcium content of at least 0.10 wt. %,
preferably at least 0.15 wt. %, for example at least 0.18 wt. %,
based on the weight of the lubricating oil composition. Optionally,
the lubricating oil composition of all aspects of the invention has
a calcium content of from 0.08 wt,% to 0.8 wt. %, preferably from
0.10 wt. % to 0,6 wt. %, for example from 0,15 wt. % to 0,5 wt. %,
such as from 0.18 wt. % to 0.3 wt. %, based on the weight of the
lubricating oil composition. It will be appreciated that it is
particularly advantageous to utilise LSPI-reducing additives in
lubricating oil compositions containing higher concentrations of
calcium.
[0083] Optionally, the lubricating oil composition has a magnesium
content of no more than 0.12 wt. %, such as no more than 0.6 wt. %,
for example no more than 0.03 wt. %, based on the weight of the
lubricating oil composition. Optionally, the lubricating oil
composition is substantially free from magnesium, for example
having a magnesium content of about 0.0 wt. %, based on the weight
of the lubricating oil composition.
[0084] Lubricating oil compositions suitable for use as passenger
ear motor oils conventionally comprise a major amount of oil of
lubricating viscosity and minor amounts of performance enhancing
additives, including detergents. 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. 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 or
greater, and typically will have a TBN of from 250 to 450 or
more.
[0085] Optionally, the lubricating oil composition comprises a
detergent, for example a calcium detergent. Optionally, the
detergent is a borated calcium detergent. Examples of suitable
borated calcium detergents include, but are not limited to, 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. Such borated calcium detergents 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. Suitable borated calcium detergents and methods of
preparing such borated calcium detergents are disclosed in U.S.
Pat. No. 3,480,548, 3,679,584, 3,829,381, 3,909,691 and 4,965,004.
Optionally, the detergent is an overbased calcium detergent, for
example having a Total Base Number (TBN) of at least 150,
preferably at least 200. Preferably, the overbased calcium
detergent has a TBN of from 200 to 450. It will be appreciated that
the composition optionally includes one or more additional
detergents, such as a detergent that is not an overbased calcium
detergent having a TBN of at least 150. For example, it may be that
the composition comprises a detergent package comprising the
overbased calcium detergent. The detergent is preferably used in an
amount 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 80%,
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). Preferably, the detergent will have, or
have on average, a TBN of at least about 200, such as front about
200 to about 500; preferably at least about 250, such as from about
250 to about 500; more preferably at least about 300, such as from
about 300 to about 450.
[0086] 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, and naphthenates and other oil-soluble carboxylates of
calcium. 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
detergent may optionally comprise combinations of detergents,
whether overbased or neutral or both.
[0087] 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, toluene, xylene,
naphthalene, diphenyl or their halogen derivatives such as
chlorobenzene, chlorotoluene and chloronaphthalene. The alkylation
may be carried out in the presence of a catalyst with alkylating
agents having from about 3 to more than 70 carbon atoms. The
alkaryl sulfonates usually contain from about 9 to about 80 or more
carbon atoms, preferably from about 16 to about 60 carbon atoms per
alkyl substituted aromatic moiety.
[0088] The oil soluble sulfonates or alkaryl sulfonic acids may be
neutralised with oxides, hydroxides, alkoxides, carbonates,
carboxylase, 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.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] 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.
[0093] 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.
[0094] Optionally, the detergent comprises a calcium phenate, a
calcium sulfonate and/or a calcium salicylate. Optionally, the
detergent comprises a borated calcium phenate, a borated calcium
sulfonate and/or a borated calcium salicylate, preferably a borated
calcium salicylate.
[0095] Optionally, the detergent comprises a plurality of calcium
detergents. Optionally, each calcium detergent is independently a
calcium phenate, a calcium sulfonate or a calcium salicylate.
Preferably, the detergent is substantially free from any detergent
that is not a calcium detergent. In other words, it may be that the
detergent consists of one or more 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.
[0096] Optionally, at least 75 %, for example at least 90 %, such
as at least 95 %, of the calcium content of the lubricating oil
composition is provided by the detergent. It may be that when the
calcium content of the lubricating composition is provided
principally by the detergent, the detergent and LSPI
characteristics of the composition can be controlled particularly
effectively.
[0097] Optionally, the composition additionally comprises a further
detergent. Preferably, the further detergent is substantially free
of calcium. Optionally, the farther detergent comprises one or more
phenate, sulfonate and/or salicylate detergents, The further
detergent may be an overbased or neutral detergent. Optionally, the
further detergent comprises one or more neutral metal-containing
detergents (having a TBN of less than 150). These neutral
metal-based detergents may be magnesium salts or salts of other
alkali or alkali earth metals, except calcium. Optionally, 100 % of
the metal introduced into the lubricating oil composition by
detergent is calcium. The further detergent may also contain
ashless (metal-free) detergents such as oil-soluble hydrocarbyl
phenol aldehyde condensates described, for example, in US
2005/0277559 A1.
[0098] 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 0.35 to 1.5 mass % or from 0.5 to 1.0 mass %, more
preferably from about 0.6 to about 0.8 mass % of sulfated ash
(SASH).
[0099] Optionally, the composition comprises one or more additives
from the list consisting of: dispersants, corrosion inhibitors,
antioxidants, pour point depressants, antifoaming agents,
supplemental anti-wear agents, friction modifiers, and viscosity
modifiers.
[0100] 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 mm.sup.2/sec, most preferably from about 9 mm.sup.2/sec to
about 17 mm.sup.2/sec, measured at 100.degree. C.
[0101] 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.
[0102] 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.
[0103] 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 alky) 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.
[0104] 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. 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.
[0105] 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, trimethylolpropaine,
pentaerythritol, dipentaerythritol and tripentaerythritol.
[0106] 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.
[0107] 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 %. In one
preferred embodiment, at least 30 mass %, preferably at least 50
mass more preferably at least 80 mass % of the oil of lubricating
viscosity used in lubricating oil compositions of the present
invention is Group III base stock, a Group IV base stock, or a
mixture of Group II and Group IV base stocks.
[0108] 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 140.
[0109] Definitions for the base stocks and base oils in the
lubricating oil compositions of 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:
[0110] a) Group I base stocks contain less than 30 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;
[0111] 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;
[0112] 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;
[0113] d) Group IV base stocks are polyalphaoleflns (PAO); and,
[0114] e) Group V base stocks include all other base stocks not
included in Group I, III, III, or IV.
TABLE-US-00001 TABLE 1 Analytical Methods for Base Stock Property
Test Method Saturates ASTM D 2007 Viscosity Index ASTM D 2270
Sulfur ASTM D 2622; ASTM D 4294; ASTM D 4927; ASTM D 3120
[0115] The lubricating oil compositions of all aspects of the
present invention may further comprise a phosphorus-containing
compound.
[0116] 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, molybdenum,
manganese, nickel or copper. The zinc salts are most commonly used
in lubricating oil in amounts of 0.1 to 10, preferably 0.2 to 2
mass %, 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 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.
[0117] The preferred zinc dihydrocarbyl dithiophosphates are oil
soluble salts of dihydrocarbyl dithiophosphoric acids and may be
represented by the following formula:
##STR00004##
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) preferably comprises zinc
dialkyl dithiophosphates.
[0118] Lubricating oil compositions useful in the practice of the
present invention will preferably contain a phosphorus-containing
compound, in an amount introducing from 0.01 to 0.12 wt. % of
phosphorus, such as from 0.04 to 0.10 wt. % of phosphorus,
preferably, from 0.05 to 0.08 wt. % of phosphorus, based on the
total mass of the lubricating oil composition into the lubricating
oil composition. Optionally, the lubricating oil composition has a
phosphorus content of no more than 0.1 wt. % (1000 ppm), for
example no more than 0.09 wt. % (900 ppm), preferably no more than
0.08 wt. % (800 ppm), based on the weight of the lubricating oil
composition. In a preferred embodiment of the present invention,
the lubricating oil composition has a phosphorous content of no
greater than 0.06 wt. % (600 ppm).
[0119] Oxidation inhibitors or antioxidants reduce the tendency of
mineral oils to deteriorate in service. Oxidative deterioration can
be evidenced by sludge in the lubricant, varnish-like deposits on
the metal surfaces, and by viscosity growth. Such oxidation
inhibitors include hindered phenols, alkaline earth metal salts of
alkylphenolthioesters having preferably C.sub.5 to C.sub.12 alkyl
side chains, calcium nonylphenol sulfide, oil soluble phenates and
sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons
or esters, phosphorous esters, metal thiocarbamates, oil soluble
copper compounds as described in U.S. Pat. No. 4,867,890, and
molybdenum-containing compounds.
[0120] Aromatic amines having at least two aromatic groups attached
directly to the nitrogen constitute another class of compounds that
is frequently used for antioxidancy. Typical oil soluble aromatic
amines having at least two aromatic groups attached directly to one
amine nitrogen contain from 6 to 16 carbon atoms. The amines may
contain more than two aromatic groups. Compounds having a total of
at least three aromatic groups in which two aromatic groups are
linked by a covalent bond or by an atom or group (e.g., an oxygen
or sulfur atom, or a --CO--, --SO.sub.2-- or alkylene group) and
two are directly attached to one amine nitrogen are also considered
aromatic amines having at least two aromatic groups attached
directly to the nitrogen. The aromatic rings are typically
substituted by one or more substituents selected from alkyl,
cycloalkyl, alkoxy, aryloxy, acyl, acylamino, hydroxy, and nitro
groups. The amount of any such oil soluble aromatic amines having
at least two aromatic groups attached directly to one amine
nitrogen should preferably not exceed 0.4 mass %.
[0121] 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. Optionally, the lubricating oil compositions used according
to the present invention comprise 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 0.05 to 0.19 mass %, such as from 0.08
to 0.18 mass %, most preferably from 0.07 to 0.16 mass % of
nitrogen to the lubricating oil composition.
[0122] 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.
[0123] Generally, each mono- or dl-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.
[0124] The polyalkenyl moiety of dispersants useful in 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 of the lubricating oil composition 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 polvalkenyl 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.
[0125] 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 dispersants useful in the practice 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.
[0126] Suitable hydrocarbons or polymers employed in the formation
of dispersants useful in the practice 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 may contain a minor amount, e.g. 0.5 to 5 mole % of a
C.sub.4 to C.sub.18 non-conjugated diolefin comonomer. However, it
is preferred that the polymers used in the practice of the present
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 copolymer's is most preferably between 15 and 50 %, although
higher or lower ethylene contents may be present.
[0127] 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.
[0128] 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
polymerisation 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, stick as aluminum
trichloride or boron trifluoride. A preferred source of monomer for
making poly-n-butenes is petroleum feedstreams such as Raffinate
II. These feedstocks are disclosed in the art such as in U.S. Pat.
No. 4,952,739. Polyisobutylene is a most preferred backbone of the
polymers useful in the practice of the present invention because it
is readily available by cationic polymerization from butene streams
(e.g., using AlCl.sub.3 or BF.sub.3 catalysts). Such
polyisobutylenes generally contain residual unsaturation in amounts
of about one ethylenic double bond per polymer chain, positioned
along the chain. A preferred embodiment utilizes polyisobutylene
prepared from a pure isobutylene stream or a Raffinate I stream to
prepare reactive isobutylene polymers with terminal vinylidene
olefins. Preferably, these polymers, referred to as highly reactive
polyisobutylene (HR-PIB), have a terminal vinylidene content of at
least 65%, e.g., 70%, more preferably at least 80%, most
preferably, at least 85%. The preparation of such polymers is
described, for example, in U.S. Pat. No. 4,152,499. HR-PIB is known
and HR-PIB is commercially available under the tradenames
Glissopal.TM. (from BASF).
[0129] 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.
[0130] 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.
[0131] 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.
[0132] 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.
[0133] 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.
[0134] 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.
[0135] 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 useful in the practice of the present invention.
[0136] 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
(s) 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, tnaleic 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.
[0137] 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. Unreached excess monounsaturated carboxylic
reactant can be removed from the final dispersant product by, for
example, stripping, usually under vacuum, if required.
[0138] 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, nitrites, 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-diammoethane; 1,3-diaminopropane;
1,4-diaminobutane; 1,6-diaminohexane; polyethylene amines such as
diethylene triamine; methylene 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.
[0139] Other useftil 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.
[0140] 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.
[0141] 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.
[0142] The dispersant(s) are preferably non-polymeric (e.g., are
mono- or bis-succinimides). The dispersants), 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.
[0143] 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.
[0144] Additional additives may be incorporated into the
lubricating oil composition 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, antifoaming
agents, anti-wear agents and pour point depressants. Some are
discussed in further detail below.
[0145] 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.
[0146] 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, "Modern Size Exclusion Liquid Chromatography", John Wiley and
Sons, New York, 1979). Another useful method for determining
molecular weight, particularly for lower molecular weight polymers,
is vapor pressure osmometry (see, e.g., ASTM D3592).
[0147] 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.
[0148] 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 weight of the block.
[0149] 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.
[0150] 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 SV140.TM., 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 due tradename
Glissoviscal.TM. by BASF.
[0151] Pour point depressants (PPD), otherwise known as lube oil
flow improvers (LOFls) 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.
[0152] In the lubricating oil compositions of 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.
[0153] 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
[0154] 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.
[0155] 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.
[0156] Preferably, the Noack volatility of the folly 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 %.
[0157] 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 %.
[0158] 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
[0159] 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.
[0160] The amounts of additives provided are additive amounts
including diluent oil, amounts unless otherwise indicated.
Example 1
[0161] Two SAE 0W-20 grade lubricating oil compositions
representing typical European mid-SAPS passenger car motor oils
were prepared. The formulation of these compositions is shown in
Table 2 below.
TABLE-US-00003 TABLE 2 Constituent Type Oil 1 Oil 2 Borated
Dispersant .sup.1 0.0057 0.0195 (B, mass %) Mg Salicylate Detergent
.sup.2 0.02 0.02 (Mg, mass %) Ca Salicylate Detergent .sup.3 0.15
0.15 (Ca, mass %) Molybdenum Compound .sup.4 0 0.0198 (Mo, mass %)
Additive Package .sup.5 8.053 8.053 (mass %) SN150 Diluent (mass %)
1.82 1.9 Pour Point Depressant.sup.6 0.3 0.3 (mass %) Viscosity 9.5
9.5 Modifier.sup.7(mass %) Base Stock.sup.8(mass %) 77.5 76 SASH,
mass % 0.73 0.75 P %, mass % 0.085 0.085 S %, mass % 0.2 0.2 .sup.1
The borated dispersant was a borated polyisobutenyl succinimide
dispersant available from Infineum UK Limited. .sup.2 The magnesium
detergent was a magnesium salicylate detergent having a total base
number of 342 available from Infineum UK Limited. .sup.3 The
calcium detergent was the same for each oil and comprised a mixture
of a calcium salicylate detergent having a total base number of 225
available from Infineum UK Limited and a calcium salicylate
detergent having a total base number of 64 available from Infineum
UK Limited. .sup.4 The molybdenum dithiocarbamate is a trimeric
molybdenum dithiocarbamate available from Infineum UK Limited.
.sup.5 The additive package was the same for each oil and included
non-borated dispersant, zinc dialkyldithiophosphate, aminic
antioxidant and silicon antifoam. .sup.6The pour point depressant
was Infineum V385 available from Infineum UK Ltd. .sup.7The
viscosity modifier was Infineum SV603 available from Infineum UK
Ltd. .sup.8The base stock comprised API Group III base oil.
[0162] Oil 1, being a comparative example, includes a typical dose
of a borated dispersant, the oil composition having a boron content
of 57 ppm, and no molybdenum-containing additive. Oil 2, being an
example of the invention, includes a higher dose of a borated
dispersant, the oil composition having a boron content of 195 ppm,
and a molybdenum containing compound providing the oil composition
with 198 ppm of molybdenum.
[0163] The oils were tested for LSPI event occurrence according to
the GM LSP1 test for approvals against Dexos.TM. specifications,
the results being presented in Table 3. The test limit for the
Dexos test for five runs is 0 0 0 2 2, meaning that a composition
achieving zero LSPI events in runs 1, 2 and 3 and two or fewer LSPI
events in runs 4 and 5, passes the test, whereas a composition with
more than zero LSPI events in runs 1, 2 and/or 3 and/or more than
two LSPI events in runs 4 and 5 fails the test.
TABLE-US-00004 TABLE 3 LSPI Events Per Run Run Oil 1 Oil 2 1 1 0 2
1 0 3 3 0 4 3 0 5 4 1
[0164] Across all five runs with each composition, Oil 2 showed a
lower LSPI event frequency, passing the Dexos.TM. test, whereas Oil
1 failed the Dexos.TM. test. These results indicate that a combined
increase in both boron and molybdenum contents provides a reduction
in LSPI event frequency.
Example 2
[0165] Two further SAE 0W-20 grade lubricating oil compositions
representing typical European mid-SAPS passenger car motor oils
with a phosphorous content of 0.09 mass % were prepared. The
formulation of these compositions is shown in Table 4 below.
TABLE-US-00005 TABLE 4 Constituent Type Amount Oil 3 Oil 4 Borated
Dispersant.sup.9 B, mass % 0.0037 0.0198 Ca Salicylate Detergent
.sup.10 Ca, mass % 0.18 0.18 Molybdenum compound .sup.11 Mo, mass %
0.0027 0.0330 Additive package .sup.12 mass % 8.254 8.254 APP150DIL
Diluent mass % 2.485 2.485 Pour Point Depressant.sup.13 mass %
0.300 0.300 Viscosity Modifier.sup.14 mass % 9.000 9.000 Base
Stock.sup.15 mass % 77.376 75.586 .sup.9The borated dispersant was
a borated polyisobutenyl succinimide dispersant available from
Infineum UK Limited. .sup.10 The calcium detergent comprised a
calcium salicylate detergent having a total base number of 225
available from Infineum UK Limited. .sup.11 The molybdenum
dithiocarbamate is a trimeric molybdernum dithiocarbamate available
from Infineum UK Limited. .sup.12 The additive package was the same
for each oil and included non-borated dispersant, zinc
dialkyldithiophosphate, aminic antioxidant, hindered phenol
antioxidant, ashless friction modifier and silicon antifoam.
.sup.13The pour point depressant was Infineum V385 available from
Infineum UK Ltd. .sup.14The viscosity modifier was Infineum SV603
available from Infineum UK Ltd. .sup.15The base stock comprised GTL
base oil.
[0166] It can be seen from Table 4 that Oil 3 has a lower boron
content and a lower molybdenum content than Oil 4 composition.
[0167] The compositions were tested for LSPI event occurrence
according to the ASTM (Ford) LSPI test for applications claiming
Gf-6/API SP, the results being presented in Table 6.
TABLE-US-00006 TABLE 5 LSPI Events Per Run Run Oil 3 Oil 4 1 7 4 2
17 2 3 12 4 4 10 4
[0168] Across all four runs with each composition, Oil 4 showed a
significantly lower LSPI event frequency than Oil 3, indicating
that an increase in both boron and molybdenum content provides a
reduction in LSPI event frequency.
Example 3
[0169] Five 5W-30 grade lubricating oil representing typical
European mid-SAPS passenger car motor oils were prepared. The
formulation of these compositions is shown in Table 6 below.
TABLE-US-00007 TABLE 6 Constituent Type Amount Oil 5 Oil 6 Oil 7
Oil 8 Oil 9 Borated B, mass % 0.000 0.000 0.040 0.040 0.020
Dispersant.sup.16 Non-Borated mass % 2.75 2.75 1.30 1.30 2.00
Dispersant.sup.17 Ca Sulfonate Ca, 0.151 0.151 0.151 0.151 0.151
Detergent.sup.18 mass % MgSulfonate Mg, 0.030 0.030 0.030 0.030
0.030 Detergent.sup.19 mass % Molybdenum Mo, 0.000 0.070 0.000
0.070 0.035 Compound.sup.20 mass % Additive mass % 3.103 3.103
3.103 3.103 3.103 Package.sup.21 Group II mass % 1.00 1.00 1.00
1.00 1.00 Diluent Pour Point mass % 0.30 0.30 0.30 0.30 0.30
Depressant.sup.22 Viscosity mass % 8.20 8.20 8.20 8.20 8.20
Modifier.sup.23 Base Stock.sup.24 mass % balance balance balance
balance balance SASH mass % 0.72 0.72 0.75 0.75 0.73 P % mass %
0.06 0.06 0.06 0.06 0.06 S % mass % 0.1 0.3 0.1 0.3 0.2 .sup.16The
borated dispersant was a borated polyisobutenyl succinimide
dispersant available from Infineum UK Limited. .sup.17The
non-borated dispersant was a polyisobutylene succinimide dispersant
available from Infineum UK Limited. The amount of non-borated
dispersant varies in order to balance the varied amount of borated
dispersant used to vary the amount of boron present in the oils.
.sup.18The calcium detergent comprised a calcium sulfonate
detergent having a total base number of 300 available from Infineum
UK Limited. .sup.19The magnesium detergent is a magnesium sulfonate
detergent having a total base number of 400 available from Infineum
UK Limited. .sup.20The molybdenum dithiocarbamate is a trimeric
molybdenum dithiocarbamate available from Infineum UK Limited.
.sup.21The additive package was the same for each oil and included
zinc dialkyldithiophosphate, aminic antioxidant, hindered phenol
antioxidant, ashless friction modifier, diluent oil and silicon
antifoam. .sup.22The pour point depressant was Infineum V387
available from Infineum UK Ltd. .sup.23The viscosity modifier was
Paralone 68530 available from Chevron Oronite. .sup.24The base
stock comprised an API Group II base stock.
[0170] Oils 5 and 6 include no boron (in order to maintain
equivalent dispersant functionality in the compositions, boron-free
dispersants are included in the compositions). Oils 5 and 7 contain
no molybdenum. Thus, Oil 5 contains neither boron nor molybdenum,
Oil 6 contains a relatively high molybdenum dose but no boron, and
Oil 7 contains a relatively high boron dose but no molybdenum. Oils
8 and 9 include boron and molybdenum. Oil 8 containing the same
relatively high boron dose and a relatively high molybdenum dose as
Oils 7 and 6, respectively, and Oil 9 including half the amount of
boron and molybdenum.
[0171] The compositions were tested for LSPI event occurrence
according to the ASTM (Ford) LSPI test for applications claiming
GF-6/API SP, the results being presented in Table 7. The tests were
run in a matrix fashion in a random order, with a reference oil run
every five tests.
TABLE-US-00008 TABLE 7 Average LSPI Event Occurance Oil 5 Oil 6 Oil
7 Oil 8 Oil 9 14 8 16 4 6
[0172] The LSPI test results set out in Table 7 are also shown in
matrix format in FIG. 1. The lest results indicate no reduction in
LSPI frequency through substantially increasing the boron content
of the composition from 0 ppm to 400 ppm in the absence of
molybdenum, and a modest reduction in LSPI frequency (43%
reduction) through substantially increasing molybdenum content of
the composition from 0 ppm to 700 ppm in the absence of boron. In
contrast, the test results show a significantly more substantial
reduction in LSPI frequency (57% reduction) through only moderately
increasing both the boron content and the molybdenum content from 0
ppm to 200 ppm and 350 ppm, respectively. Furthermore, the test
results show an even more significant reduction in LSPI frequency
(71% reduction) through substantially increasing both the boron
content and the molybdenum content from 0 ppm to 400 ppm and 700
ppm, respectively. Surprisingly, the test results of Example 3 show
a synergistic effect on LSPI frequency reduction resulting from the
combination of both boron and molybdenum in a lubricating oil
composition.
[0173] 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 drat 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.
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