Note: Descriptions are shown in the official language in which they were submitted.
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A LUBRICATING OIL COMPOSITION
FIELD OF THE INVENTION
The present invention relates to automotive lubricating oil compositions
having low levels
of sulphated ash which are suitable for extended drain interval applications.
More
specifically, the present invention relates to such automotive lubricating oil
compositions
for use in gasoline (spark-ignited) and diesel (compression-ignited) internal
combustion
engines, especially diesel engines, crankcase lubrication, such compositions
being referred
to as crankcase lubricants; and to the use of additives in such compositions
for extending
the drain interval of the lubricating oil composition.
In particular, although not exclusively, the present invention relates to
automotive
lubricating oil compositions, especially automotive lubricating oil
compositions for use in
heavy duty diesel (HDD) engines, having low levels of sulphated ash, and
preferably low
levels of phosphorus and also low levels of sulfur, which, in use, exhibit an
extended time
to reach the TBN/TAN cross-over point for the lubricant, thereby extending the
drain
interval of the lubricant.
BACKGROUND OF THE INVENTION
A crankcase lubricant is an oil used for general lubrication in an internal
combustion engine
where an oil sump is situated generally below the crankshaft of the engine and
to which
circulated oil returns. It is well known to include additives in crankcase
lubricants for
several purposes.
With an increasing emphasis on oil conservation and the desire for more
maintenance free
vehicles, there is a trend towards extending the drain interval of a crankcase
lubricant
without detriment to engine durability and performance. Typically, a crankcase
lubricant
when new has a relatively high total base number (TBN) and a relatively low
total acid
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number (TAN). The TBN of a lubricant represents a measure of the quantity of
basic
components in the lubricant and provides an indication of the capacity of the
lubricant to
neutralize the acidic species produced in the lubricant and the acidic
products of
combustion which contaminate the lubricant, during use. The TAN of a lubricant
represents a measure of the quantity of acidic species present in the
lubricant.
More specifically, the TBN of a lubricant is the quantity of acid, expressed
in terms of the
equivalent number of milligrams of potassium hydroxide, that is required to
neutralize the
basic components present in 1 gram of the lubricant and it is expressed as mg
KOH per
gram of lubricant (mg/g KOH). Typically, a lubricant having a relatively high
TBN has a
greater capacity to neutralize the acidic species produced in the lubricant
and the acidic
products of combustion which contaminate the lubricant, during use, than a
lubricant
having a lower TBN. Usually, metal-containing or ash-forming detergents which
are
present in a lubricant contribute the majority of the TBN to the lubricant;
the metal-
containing detergents function as both detergents to reduce and remove
deposits and as acid
neutralizers, thereby reducing wear and corrosion and extending engine life.
The TAN of a lubricant is the number of milligrams of potassium hydroxide that
are
required to neutralize the acidic species present in 1 gram of the lubricant
and it is
expressed as mg KOH per gram of lubricant (mg/g KOH). A lubricant having a
relatively
high TAN is indicative of the presence of more acidic species than a lubricant
having a
lower TAN.
When new, the TBN of a lubricant is relatively high and its TAN is relatively
low. In use,
acidic species are produced in the lubricant and the lubricant becomes
contaminated with
acidic species of combustion. Such acidic species are neutralized by the basic
components
(e.g. the metal-containing detergent) in the lubricant, thereby depleting the
TBN of the
lubricant. The longer the lubricant is used the general trend is a decrease in
TBN and an
increase in TAN. The time taken, in use, to reach a point where the TBN and
the TAN of
the lubricant are equivalent (referred to herein as the "TBN/TAN cross-over
point")
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represents one measure for determining the useful oil change interval for the
lubricant, as
the lubricant no longer has the ability to neutralize acidic species produced
in or which may
contaminate the lubricant. Indeed, studies have shown that when TAN exceeds
TBN,
engine wear and/or corrosion may accelerate at abnormally high rates.
Accordingly, in
order to extend the drain interval of a lubricant it is desirable to extend,
in use, the time
taken to reach the TBN/TAN cross-over point.
Concurrent with the desire to extend the drain interval of a lubricant, there
has been a
continued effort to reduce the content of sulphated ash, phosphorus and
sulphur in the
lubricant due to both environmental concerns and to insure compatibility with
pollution
control devices (e.g. three-way catalytic converters and particulate traps).
In Europe, a
lubricant meeting the ACEA E6 SAPS (sulphated ash, phosphorus and sulphur)
limitation
and, in the USA, a lubricant meeting the API CJ-4 SAPS limitation, the amount
of ash
contributed by the detergent(s), combined with the ash contributed by the ash-
containing
anti-wear agents in the formulation, must be less than or equal to 1.0 mass %.
The need to
meet this stringent limitation on ash level and still provide adequate
detergency
performance typically led formulators to reduce the level of detergent
overbasing.
However, a reduction in the amount of overbasing typically reduces the acid
neutralization
capacity of the lubricant which may, in use, reduce the time taken to reach
the TBN/TAN
cross-over point thereby shortening the maximum drain interval of the
lubricant.
Accordingly, there is a need to identify a lubricating oil composition which
meets the ash
constraints of the ACEA E6 and API CJ-4 specifications (i.e. a sulphated ash
level of less
than or equal to 1.0 mass % as determined by ASTM D874) and, in use, extends
the time
taken to reach the TBN/TAN cross-over point for the lubricant, thereby
extending the drain
interval of the lubricant.
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SUMMARY OF THE INVENTION
Surprisingly, it has been found that by using a combination of an overbased
magnesium
salicylate detergent and an ashless alkylene bis(dihydrocarbyldithiocarbamate)
additive
component in a lubricating oil composition it is possible to formulate a
lubricating oil
composition having a low sulphated ash level of less than or equal to 1.0 mass
% as
determined by ASTM D874 which, in use, substantially extends the time taken to
reach the
TBN/TAN cross-over point for the lubricant, thereby extending the drain
interval of the
lubricant.
Thus, in accordance with a first aspect, the present invention provides a
lubricating oil
composition having a sulphated ash content of less than or equal to 1.0 mass %
as
determined by ASTM D874, the composition comprising or made by admixing:
(A) an oil of lubricating viscosity in a major amount;
(B) one or more oil-soluble or oil-dispersible overbased magnesium
salicylate
detergent(s) having a TBN of greater than or equal to 220 mg/g KOH as
determined
by ASTM D2896, as an additive in an effective minor amount; and,
(C) an oil-soluble or oil-
dispersible ashless alkylene
bis(dihydrocarbyldithiocarbamate), as an additive in an effective minor
amount.
Preferably, the lubricating oil composition according to the present invention
is a crankcase
lubricant. Even more preferably, the lubricating composition according to the
present
invention is suitable for use in a heavy duty diesel engine.
According to a second aspect, the present invention provides a method of
lubricating a
spark-ignited or compression-ignited internal combustion engine comprising
lubricating the
engine with a lubricating oil composition as defined in accordance with the
first aspect of
the present invention.
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According to a third aspect, the present invention provides a method of
extending the time
taken to reach the TBN/TAN cross-over point (i.e. extending the drain
interval) of a
lubricating oil composition comprising an oil of lubricating viscosity in a
major amount, the
method comprising admixing with the lubricating oil composition one or more
oil-soluble
or oil-dispersible overbased magnesium salicylate detergent(s) (B) as defined
in accordance
with the first aspect of the present invention, as an additive in an effective
minor amount,
and an oil-soluble or oil-dispersible ashless alkylene
bis(dihydrocarbyldithiocarbamate) (C)
as defined in accordance with the first aspect of the present invention, as an
additive in an
effective minor amount, and lubricating a spark-ignited or compression ignited
internal
combustion engine with the lubricating oil composition.
According to a fourth aspect, the present invention provides the use, in the
lubrication of a
spark-ignited or compression ignited internal combustion engine, of one or
more oil-soluble
or oil-dispersible overbased magnesium salicylate detergent(s) (B) as defined
in accordance
with the first aspect of the present invention, as an additive in an effective
minor amount, in
combination with an oil-soluble or oil-dispersible ashless alkylene
bis(dihydrocarbyldithiocarbamate) (C) as defined in accordance with the first
aspect of the
present invention, as an additive in an effective minor amount, in a
lubricating oil
composition comprising an oil of lubricating viscosity in a major amount, to
extend the
drain interval of the lubricating oil composition during operation of the
engine.
According to a fifth aspect, the present invention provides the use, in the
lubrication of a
spark-ignited or compression ignited internal combustion engine, of one or
more oil-soluble
or oil-dispersible overbased magnesium salicylate detergent(s) (B) as defined
in accordance
with the first aspect of the present invention, as an additive in an effective
minor amount, in
combination with an oil-soluble or oil-dispersible ashless alkylene
bis(dihydrocarbyldithiocarbamate) (C) as defined in accordance with the first
aspect of the
present invention, as an additive in an effective minor amount, in a
lubricating oil
composition comprising an oil of lubricating viscosity in a major amount, to
extend the
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time taken to reach the TBN/TAN cross-over point of the lubricating oil
composition
during operation of the engine.
Suitably, the time taken to reach the TBN/TAN cross-over point of a
lubricating oil
composition as defined in the third and fifth aspects of the present invention
and the drain
interval of a lubricating oil composition as defined in the fourth aspect of
the present
invention is measured by employing the extended Mack T-12 engine test
procedure (ASTM
D7422) and running the test until the TBN/TAN cross-over point is at least
reached, as
described herein, and represents the time elapsed to reach the earliest
specific 25 hour
sampling point at which the TBN is equivalent to TAN or, if the TBN/TAN cross-
over
point is not met exactly at a specific 25 hour sampling point, the time
elapsed to reach the
first 25 hour sampling point where the TBN has fallen below TAN.
Preferably, the time taken to reach the TBN/TAN cross-over point of a
lubricating oil
composition as defined in the third and fifth aspects of the present invention
is greater than
400, more preferably greater than or equal to 425, most preferably greater
than or equal to
450 hours as determined by employing the Mack T-12 engine test procedure (ASTM
D7422) and running the test until the TBN/TAN cross-over point is reached, as
described
herein.
Preferably, the drain interval of a lubricating oil composition as defined in
the fourth aspect
of the present invention is greater than 400, more preferably greater than or
equal to 425,
most preferably greater than or equal to 450 hours as determined by employing
the Mack
T-12 engine test procedure (ASTM D7422) and running the test until the TBN/TAN
cross-
over point is reached, as described herein.
Preferably, the engine as defined in the second, third, fourth and fifth
aspects of the present
invention is a compression-ignited internal combustion engine (i.e. a diesel
engine), more
preferably a heavy duty diesel engine.
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Preferably, the one or more overbased salicylate detergent(s) in the
lubricating oil
composition of the first aspect of the present invention and as defined in the
second, third,
fourth and fifth aspects of the present invention are the sole metal
containing detergent(s)
which are present in the lubricating oil composition (i.e. the only metal
containing
detergents which are present in the lubricating oil composition are the one or
more
overbased metal salicylate detergents). More preferably, the only metal
containing
detergents which are present in the lubricating oil composition are the one or
more
overbased magnesium salicylate detergents.
Preferably, the lubricating oil composition of the first aspect of the present
invention and as
defined in the second, third, fourth and fifth aspects of the present
invention further
includes an anti-oxidant, as an additive in an effective minor amount. More
preferably, the
anti-oxidant comprises an aminic antioxidant, preferably an aromatic amine
anti-oxidant, a
phenolic anti-oxidant or a combination thereof, especially an aromatic amine
anti-oxidant.
In a highly preferred lubricating oil composition of the first aspect of the
present invention
and as defined in the second, third, fourth and fifth aspects of the present
invention the
lubricating oil composition includes both an aromatic amine and phenolic anti-
oxidant.
Suitably, the anti-oxidant(s) are ashless anti-oxidant(s).
Preferably, the lubricating oil composition of the first aspect of the present
invention and as
defined in the second, third, fourth and fifth aspects of the present
invention further
includes an oil-soluble or oil-dispersible organo-molybdenum compound, as an
additive in
an effective minor amount. Suitably, when present, the organo-molybdenum
compound
provides the lubricating oil composition with at least 10 ppm of molybdenum
(ASTM
D5185), based on the total mass of the lubricating oil composition.
Preferably, the lubricating oil composition of the first aspect of the present
invention and as
defined in the second, third, fourth and fifth aspects of the present
invention further
includes a dihydrocarbyl dithiophosphate metal salt, as an additive component
in an
effective minor amount.
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Preferably, the lubricating oil composition of the first aspect of the present
invention and as
defined in the second, third, fourth and fifth aspects of the present
invention further
includes one or more co-additives in an effective minor amount (e.g. 5 to 25,
preferably 5
to 18, more preferably 7 to 15, mass % of the one or more co-additives), other
than additive
components (B) and (C), selected from ashless dispersants, metal detergents,
corrosion
inhibitors, antioxidants, pour point depressants, antiwear agents, friction
modifiers,
demulsifiers, antifoam agents and viscosity modifiers.
Preferably, the lubricating oil composition of the present invention has a
sulphated ash
content of less than or equal to 0.95 mass % as determined by ASTM D874.
Preferably, the lubricating oil composition of the present invention contains
low levels of
phosphorus. Suitably, the lubricating oil composition contains phosphorus in
an amount of
less than or equal to 0.12 mass %, preferably up to 0.11 mass %, more
preferably less than
or equal to 0.10 mass %, even more preferably less than or equal to 0.09 mass
%, even
more preferably less than or equal to 0.08 mass %, most preferably less than
or equal to
0.06, mass % of phosphorus (ASTM D5185) based on the total mass of the
composition.
Suitably, the lubricating oil composition contains phosphorus in an amount of
greater than
or equal to 0.02, preferably greater than or equal to 0.03, mass % of
phosphorus (ASTM
D5185) based on the total mass of the composition.
Typically, the lubricating oil composition may contain low levels of sulfur.
Preferably, the
lubricating oil composition contains sulphur in an amount of up to 0.4, more
preferably up
to 0.3, mass % sulphur (ASTM D2622) based on the total mass of the
composition.
Suitably, the lubricating oil composition may have a total base number (TBN),
as measured
in accordance with ASTM D2896, of 4 to 15, preferably 5 to 15.
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In this specification, the following words and expressions, if and when used,
have the
meanings given below:
"active ingredients" or "(a.i.)" refers to additive material that is not
diluent or
solvent;
"comprising" or any cognate word specifies the presence of stated features,
steps, or
integers or components, but does not preclude the presence or addition of one
or
more other features, steps, integers, components or groups thereof. The
expressions
"consists of' or "consists essentially of' or cognates may be embraced within
"comprises" or cognates, wherein "consists essentially of' permits inclusion
of
substances not materially affecting the characteristics of the composition to
which it
applies;
"hydrocarbyl" means a chemical group of a compound that contains hydrogen and
carbon atoms and that is bonded to the remainder of the compound directly via
a
carbon atom. The group may contain one or more atoms other than carbon and
hydrogen provided they do not affect the essentially hydrocarbyl nature of the
group.
Those skilled in the art will be aware of suitable groups (e.g., halo,
especially chloro
and fluoro, amino, alkoxyl, mercapto, alkylmercapto, nitro, nitroso, sulfoxy,
etc.).
Preferably, the group consists essentially of, more preferably consists only
of,
hydrogen and carbon atoms, unless specified otherwise. Preferably, the
hydrocarbyl
group comprises an aliphatic hydrocarbyl group. The term "hydrocarbyl"
includes
"alkyl", "alkenyl", "alkynyl" and "aryl" as defined herein;
"alkyl" means a C1 to C30, preferably a CI to C12, group which is bonded to
the
remainder of the compound directly via a single carbon atom. Unless otherwise
specified, alkyl groups may, when there are a sufficient number of carbon
atoms, be
linear (i.e. unbranched) or branched, be cyclic, acyclic or part
cyclic/acyclic.
Preferably, the alkyl group comprises a linear or branched acyclic alkyl
group.
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Representative examples of alkyl groups include, but are not limited to,
methyl,
ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-
pentyl, iso-
pentyl, neo-pentyl, hexyl, heptyl, octyl, dimethyl hexyl, nonyl, decyl,
undecyl,
dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,
nonadecyl, icosyl and triacontyl;
"alkenyl" means a C2 to C30, preferably a C2 to C12, group which includes at
least
one carbon to carbon double bond and is bonded to the remainder of the
compound
directly via a single carbon atom, and is otherwise defined as "alkyl";
"alkynyl" means a C2 to C30, preferably a C2 to C12, group which includes at
least
one carbon to carbon triple bond and is bonded to the remainder of the
compound
directly via a single carbon atom, and is otherwise defined as "alkyl";
"aryl" means a C6 to C18, preferably C6 to C10, aromatic group, optionally
substituted
by one or more alkyl groups, halo, hydroxyl, alkoxy and amino groups, which is
bonded to the remainder of the compound directly via a single carbon atom.
Preferred aryl groups include phenyl and naphthyl groups and substituted
derivatives thereof, especially phenyl and alkyl substituted derivatives
thereof;
"alkylene" means a C1 to C20, preferably a CI to C10, bivalent saturated
aliphatic
radical which may be linear or branched. Representative examples of alkylene
include methylene, ethylene, propylene, butylene, pentylene, hexylene,
heptylene,
octylene, nonylene, decylene, 1-methyl ethylene, 1-ethyl ethylene, 1-ethy1-2-
methyl
ethylene, 1,1-dimethyl ethylene and 1-ethyl propylene;
"halo" or "halogen" includes fluoro, chloro, bromo and iodo;
"oil-soluble" or "oil-dispersible", or cognate terms, used herein do not
necessarily
indicate that the compounds or additives are soluble, dissolvable, miscible,
or are
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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 is
employed.
Moreover, the additional incorporation of other additives may also permit
incorporation of higher levels of a particular additive, if desired;
"ashless" in relation to an additive means the additive does not include a
metal;
"ash-containing" in relation to an additive means the additive includes a
metal;
"TBN/TAN cross-over point" in relation to a lubricating oil composition means
when the TBN (ASTM D4739) and TAN (ASTM D664) of the lubricating oil
composition are equivalent;
"drain interval" in relation to a lubricating oil composition as used herein
represents
the time taken, in use, to reach the TBN/TAN cross-over point;
"to extend the drain interval" and "extend the time taken to reach the TBN/TAN
cross-over point" in relation to a lubricating oil composition means extending
the
time taken, in use, to reach the TBN/TAN cross-over point of a lubricating oil
composition by employing a combination of one or more oil-soluble or oil-
dispersible overbased magnesium salicylate detergent(s) (B) as defined in
accordance with the first aspect of the present invention, as an additive in
an
effective minor amount, in combination with an oil-soluble or oil-dispersible
ashless
alkylene bis(dihydrocarbyldithiocarbamate) (C) as defined in accordance with
the
first aspect of the present invention, as an additive in an effective minor
amount, in
comparison with a comparable lubricating oil composition which does not
include
the oil-soluble or oil-dispersible ashless alkylene
bis(dihydrocarbyldithiocarbamate)
(C);
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"major amount" means in excess of 50 mass % of a composition;
"minor amount" means less than 50 mass % of a composition, expressed in
respect
of the stated additive and in respect of the total mass of all the additives
present in
the composition, reckoned as active ingredient of the additive or additives;
"effective minor amount" in respect of an additive means an amount of such an
additive of less than 50 mass % of the lubricating oil composition so that the
additive provides the desired technical effect;
"ppm" means parts per million by mass, based on the total mass of the
lubricating
oil composition;
"metal content" of the lubricating oil composition or of an additive
component, for
example magnesium content, molybdenum content or total metal content (i.e. the
sum of all individual metal contents), is measured by ASTM D5185;
"TBN" in relation to an additive component or of a fresh lubricating oil
composition of the present invention (i.e. unused lubricating oil
composition), with
the exception of measuring the TBN of a lubricating oil composition when
determining the TBN/TAN cross-over point of the lubricating oil composition,
means total base number as measured by ASTM D2896;
"TBN" of a lubricating oil composition when determining the TBN/TAN cross-over
point of the lubricating oil composition means total base number as measured
by
ASTM D4739;
"TAN" means total acid number as measured by ASTM D664;
"phosphorus content" is measured by ASTM D5185;
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"sulfur content" is measured by ASTM D2622; and,
"sulfated ash content" is measured by ASTM D874.
All percentages reported are mass % on an active ingredient basis, i.e.
without regard to
carrier or diluent oil, unless otherwise stated.
Also, it will be understood that various components used, essential as well as
optimal and
customary, may react under conditions of formulation, storage or use and that
the invention
also provides the product obtainable or obtained as a result of any such
reaction.
Further, it is understood that any upper and lower quantity, range and ratio
limits set forth
herein may be independently combined.
Also, it will be understood that the preferred features of each aspect of the
present invention
are regarded as preferred features of every other aspect of the present
invention.
Accordingly, preferred and more preferred features of one aspect of the
present invention
may be independently combined with other preferred and/or more preferred
features of the
same aspect or different aspects of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The features of the invention relating, where appropriate, to each and all
aspects of the
invention, will now be described in more detail as follows:
OIL OF LUBRICATING VISCOSITY (A)
The oil of lubricating viscosity (sometimes referred to as "base stock" or
"base oil") is the
primary liquid constituent of a lubricant, into which additives and possibly
other oils are
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blended, for example to produce a final lubricant (or lubricant composition).
A base oil is
useful for making concentrates as well as for making lubricating oil
compositions therefrom,
and may be selected from natural (vegetable, animal or mineral) and synthetic
lubricating
oils and mixtures thereof
The base stock groups are defined in the American Petroleum Institute (API)
publication
"Engine Oil Licensing and Certification System", Industry Services Department,
Fourteenth Edition, December 1996, Addendum 1, December 1998. Typically, the
base
stock will have a viscosity preferably of 3-12, more preferably 4-10, most
preferably 4.5-8,
mm2/S (cSt) at 100 C.
Definitions for the base stocks and base oils in this invention are the same
as those found in
the American Petroleum Institute (API) publication "Engine Oil Licensing and
Certification
System", Industry Services Department, Fourteenth Edition, December 1996,
Addendum 1,
December 1998. Said publication categorizes base stocks as follows:
a) Group I base stocks contain less than 90 percent saturates and/or greater
than
0.03 percent sulphur and have a viscosity index greater than or equal to 80
and less
than 120 using the test methods specified in Table E-1.
b) Group II base stocks contain greater than or equal to 90 percent saturates
and less
than or equal to 0.03 percent sulphur and have a viscosity index greater than
or
equal to 80 and less than 120 using the test methods specified in Table E-1.
c) Group III base stocks contain greater than or equal to 90 percent saturates
and
less than or equal to 0.03 percent sulphur and have a viscosity index greater
than or
equal to 120 using the test methods specified in Table E-1.
d) Group IV base stocks are polyalphaolefins (PAO).
e) Group V base stocks include all other base stocks not included in Group I,
II, III,
or IV.
Table E-1: Analytical Methods for Base Stock
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Property Test Method
Saturates ASTM D 2007
Viscosity Index ASTM D 2270
Sulphur ASTM D 2622
ASTM D 4294
ASTM D 4927
ASTM D 3120
Preferably, the oil of lubricating viscosity comprises greater than or equal
to 10 mass %,
more preferably greater than or equal to 20 mass %, even more preferably
greater than or
equal to 25 mass %, even more preferably greater than or equal to 30 mass %,
even more
preferably greater than or equal to 40 mass %, even more preferably greater
than or equal to
45 mass % of a Group II or Group III base stock, based on the total mass of
the oil of
lubricating viscosity. Even more preferably, the oil of lubricating viscosity
comprises
greater than 50 mass %, preferably greater than or equal to 60 mass %, more
preferably
greater than or equal to 70 mass %, even more preferably greater than or equal
to 80
mass %, even more preferably greater than or equal to 90 mass % of a Group IT
or Group
III base stock, based on the total mass of the oil of lubricating viscosity.
Most preferably,
the oil of lubricating viscosity consists essentially of a Group II or Group
III base stock. In
some embodiments the oil of lubricating viscosity consists solely of Group II
or Group III
base stock. In the latter case it is acknowledged that additives included in
the lubricating
oil composition may comprise a carrier oil which is not a Group II or Group
III base stock.
Other oils of lubricating viscosity which may be included in the lubricating
oil composition
are detailed as follows:
Natural oils include animal and vegetable oils (e.g. castor and lard oil),
liquid petroleum
oils and hydrorefined, solvent-treated mineral lubricating oils of the
paraffinic, naphthenic
and mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived
from coal or
shale are also useful base oils.
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Synthetic lubricating oils include 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); polyphenols (e.g. biphenyls, terphenyls, alkylated
polyphenols);
and alkylated diphenyl ethers and alkylated diphenyl sulfides and the
derivatives, analogues
and homologues thereof
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 these
esters include
dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl
sebacate, diisooctyl
azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl
sebacate, the 2-
ethylhexyl diester of linoleic acid dimer, and the complex ester formed by
reacting one
mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-
ethylhexanoic acid.
Esters useful as synthetic oils also include those made from C5 to C12
monocarboxylic acids
and polyols, and polyol ethers such as neopentyl glycol, trimethylolpropane,
pentaerythritol,
dipentaerythritol and tripentaerythritol.
Unrefined, refined and re-refined oils can be used in the compositions of the
present
invention. Unrefined oils are those obtained directly from a natural or
synthetic source
without further purification treatment. For example, a shale oil obtained
directly from
retorting operations, a petroleum oil obtained directly from distillation or
ester oil obtained
directly from an esterification process and used without further treatment
would be
CA 02883416 2015-02-26
17
unrefined oil. Refined oils are similar to the unrefined oils except they have
been further
treated in one or more purification steps to improve one or more properties.
Many such
purification techniques, such as distillation, solvent extraction, acid or
base extraction,
filtration and percolation are known to those skilled in the art. Re-refined
oils are obtained
by processes similar to those used to obtain refined oils applied to refined
oils which have
been already used in service. Such re-refined oils are also known as reclaimed
or
reprocessed oils and often are additionally processed by techniques for
approval of spent
additive and oil breakdown products.
Other examples of base oil are gas-to-liquid ("GTL") base oils, i.e. the base
oil may be an
oil derived from Fischer-Tropsch synthesised hydrocarbons made from synthesis
gas
containing 112 and CO using a Fischer-Tropsch catalyst. These hydrocarbons
typically
require further processing in order to be useful as a base oil. For example,
they may, by
methods known in the art, be hydroisomerized; hydrocracked and
hydroisomerized;
dewaxed; or hydroisomerized and dewaxed.
The oil of lubricating viscosity may also comprise a Group I, Group IV or
Group V base
stocks or base oil blends of the aforementioned base stocks.
Preferably, the volatility of the oil of lubricating viscosity or oil blend,
as measured by the
NOACK test (ASTM D5880), is less than or equal to 16%, preferably less than or
equal to
13.5%, preferably less than or equal to 12%, more preferably less than or
equal to 10%,
most preferably less than or equal to 8%. Preferably, the viscosity index (VI)
of the oil of
lubricating viscosity is at least 95, preferably at least 110, more preferably
at least 120,
even more preferably at least 125, most preferably from about 130 to 140.
The oil of lubricating viscosity is provided in a major amount, in combination
with a minor
amount of additive components (B) and (C), as defined herein and, if
necessary, one or
more co-additives, such as described hereinafter, constituting a lubricating
oil composition.
This preparation may be accomplished by adding the additives directly to the
oil or by
CA 02883416 2015-02-26
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adding them in the form of a concentrate thereof to disperse or dissolve the
additive.
Additives may be added to the oil by any method known to those skilled in the
art, either
before, at the same time as, or after addition of other additives.
Preferably, the oil of lubricating viscosity is present in an amount of
greater than 55
mass %, more preferably greater than 60 mass %, even more preferably greater
than 65
mass %, based on the total mass of the lubricating oil composition.
Preferably, the oil of
lubricating viscosity is present in an amount of less than 98 mass %, more
preferably less
than 95 mass %, even more preferably less than 90 mass %, based on the total
mass of the
lubricating oil composition.
When concentrates are used to make the lubricating oil compositions, they may
for example
be diluted with 3 to 100, e.g. 5 to 40, parts by mass of oil of lubricating
viscosity per part
by mass of the concentrate.
Preferably, the lubricating oil composition is a multigrade oil identified by
the viscometric
descriptor SAE 20WX, SAE 15WX, SAE 1 OWX, SAE 5WX or SAE OWX, where X
represents any one of 20, 30, 40 and 50; the characteristics of the different
viscometric
grades can be found in the SAE J300 classification. In an embodiment of each
aspect of the
invention, independently of the other embodiments, the lubricating oil
composition is in the
form of an SAE 15 WX, SAE lOWX, SAE 5WX or SAE OWX, wherein X represents any
one of 20, 30, 40 and 50. Preferably X is 20, 30 or 40.
OVERBASED MAGNESIUM SALICYLATE DETERGENT (B)
The lubricating oil composition of the present invention requires the presence
of at least
one overbased magnesium salicylate detergent having a TBN of greater than or
equal to
220 mg/g KOH, as measured in accordance with ASTM D2896.
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19
A detergent is an additive that reduces formation of piston deposits, for
example high-
temperature varnish and lacquer deposits, in engines; it normally has acid-
neutralising
properties and is capable of keeping finely-divided solids in suspension. Most
detergents
are based on metal "soaps", that is metal salts of acidic organic compounds.
Accordingly,
the lubricating oil composition includes a magnesium salt of salicylic acid as
the metal soap.
Detergents generally comprise a polar head with a long hydrophobic tail, the
polar head
comprising a metal salt of an acidic organic compound. The salts may contain a
substantially stoichiometric amount of the metal when they are usually
described as normal
or neutral salts and would typically have a total base number or TBN (as may
be measured
by ASTM D2896) of from 0 to 80. Large amounts of a metal base can be included
by
reaction of an excess of a metal compound, such as an oxide or hydroxide, with
an acidic
gas such as carbon dioxide. The resulting overbased detergent comprises
neutralised
detergent as an outer layer of a metal base (e.g. carbonate) micelle. Such
overbased
detergents may have a TBN of 150 or greater, and typically of from 200 to 500
or more.
The overbased magnesium salicylate detergent is preferably a C8 to C30 alkyl
salicylate and
mixtures thereof, with C10 to C20 alkyl salicylates, particularly C14 to C18
alkyl salicylates
and mixtures thereof being particularly preferred. The alkyl group(s) may be
linear or
branched and examples of suitable alkyl groups include: octyl; nonyl; decyl;
dodecyl;
pentadecyl; octadecyl; eicosyl; docosyl; tricosyl; hexacosyl; and, triacontyl.
The overbased
magnesium salicylate detergent, as defined herein, may also include sulfurized
derivatives
thereof.
The overbased magnesium salicylate may be prepared by methods well known to
those
skilled in the art, for example, by reacting the appropriate salicylic acid(s)
with an excess of
magnesium oxide or hydroxide and an acidic gas such as carbon dioxide. The
salicylic
acid(s) are typically prepared by carboxylation, for example by the Kolbe-
Schmitt process,
of phenoxides. Processes for sulfurizing the salicylic acid(s) are known to
those skilled in
the art.
CA 02883416 2015-02-26
Preferably, the overbased magnesium salicylate detergent has a TBN of at least
250, more
preferably at least 300, most preferably at least 320, mg/g KOH as determined
by ASTM
D2896. Preferably, the overbased magnesium salicylate detergent has a TBN of
less than
500, most preferably less than 450, mg/g KOH as determined by ASTM D2896.
Preferably, the overbased magnesium salicylate detergent provides the
lubricating oil
composition with greater than or equal to 0.05, more preferably greater than
or equal to
0.06, more preferably greater than or equal to 0.07, most preferably greater
than or equal to
0.10 mass % of magnesium as measured by ASTM D5185, based on the total mass of
the
lubricating oil composition. Preferably, the overbased magnesium salicylate
detergent
provides the lubricating oil composition with less than or equal to 0.50, even
more
preferably less than or equal to 0.40, most preferably less than or equal to
0.30, mass % of
magnesium as measured by ASTM D5185, based on the total mass of the
lubricating oil
composition.
It will be appreciated that the overbased magnesium salicylate detergent is
included in the
lubricating oil composition in an amount such that total amount of sulfated
ash contributed
by the detergent component to the lubricant, and any other metal containing
component
which may be present (e.g. ZDDP), is less than or equal to 1.0, preferably
less than or equal
to 0.95, mass % as determined by ASTM D874. Preferably, the overbased
magnesium
salicylate detergent is included in the lubricating oil composition in an
amount such that
total amount of sulfated ash contributed by the detergent component to the
lubricant, and
any other metal containing component which may be present, is greater than or
equal to
0.30, preferably greater than or equal to 0.40, mass % as determined by ASTM
D874.
Preferably, the amount of overbased magnesium detergent provides the
lubricating oil
composition with greater than or equal to 5, preferably greater than or equal
to 7, mmoles
of magnesium salicylate soap per kilogram of the lubricating oil composition.
Preferably,
the amount of overbased magnesium detergent provides the lubricating oil
composition
CA 02883416 2015-02-26
21
with less than or equal to 20, preferably less than or equal to 15, mmoles of
magnesium
salicylate soap per kilogram of the lubricating oil composition. By the term
"magnesium
salicylate soap" we mean the amount of magnesium salicylate contributed by the
overbased
magnesium salicylate detergent exclusive of any overbasing material.
Preferably, the overbased magnesium salicylate detergent is present in an
amount of greater
than or equal to 0.1, more preferably greater than or equal to 0.2, most
preferably greater
than or equal to 0.5, mass % based on the total mass of the lubricating oil
composition.
Preferably, the overbased magnesium salicylate detergent is present in an
amount of less
than or equal to 15, more preferably less than or equal to 9, most preferably
less than or
equal to 5, mass % based on the total mass of the lubricating oil composition.
Other metal containing detergents may be present in the lubricating oil
composition and
include oil-soluble salts of neutral and overbased sulfonates, phenates,
sulfurized phenates,
thiophosphonates and naphthenates of a metal, particularly the alkali or
alkaline earth
metals, e.g. sodium, potassium, lithium, calcium and magnesium. The most
commonly
used metals are calcium and magnesium, which may both be present in detergents
used in a
lubricant, and mixtures of calcium and/or magnesium with sodium. Detergents
may be
used in various combinations.
According to a highly preferred aspect of the present invention, the one or
more overbased
magnesium salicylate detergent(s) represent the sole metal containing
detergents in the
lubricating oil composition.
ALKYLENE BIS(DIHYDROCARBYLDITHIOCARBAMATE) (C)
The lubricating oil composition of the present invention requires the presence
of an ashless
alkylene bis(dihydrocarbyldithiocarbamate).
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22
Preferably, the ashless alkylene bis(dihydrocarbyldithiocarbamate) is a
compound of
formula (I):
S S
R1 N/ R3
N S¨(X)¨S
I 1
R2 R4
(I)
wherein:
RI, R2, R3 and R4 each independently represent, at each occurrence when used
herein, a C1 to C30 hydrocarbyl group; and,
X represents a CI to C20 alkylene group.
Preferably, RI, R2, R3 and R4 each independently represent, at each occurrence
when used
herein, a C1 to C20 hydrocarbyl group. More preferably, RI, R2, R3 and R4 each
independently represent, at each occurrence when used herein, a branched or
linear (i.e.
unbranched) C1 to C16 alkyl group or a substituted or unsubstituted aryl
group. Even more
preferably, RI, R2, R3 and R4 each independently represent, at each occurrence
when used
herein, a branched or linear C1 to C16 alkyl group, a CI to C16 alkyl
substituted aryl group or
an unsubstituted aryl group. Even more preferably, RI, R2, R3 and R4 each
independently
represent, at each occurrence when used herein, a branched or linear C1 to C16
alkyl group,
a C1 to C16 alkyl substituted phenyl group or an unsubstituted phenyl group.
It will be appreciated that when RI, R2, R3 and R4 each independently
represent a
substituted or unsubstituted aryl group as defined herein, then the
appropriate nitrogen atom
of a compound of formula I is bonded to a carbon atom of the aryl ring of the
appropriate
substituted or unsubstituted aryl group by a nitrogen to carbon single bond.
In a highly preferred compound of formula I, RI, R2, R3 and R4 each
independently
represent a branched or linear C1 to C16 alkyl group, especially a branched or
linear C1 to
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23
Ci0 alkyl group. Preferably, in such a compound of formula I each of RI, R2,
R3 and R4 are
identical.
In an alternative highly preferred compound of formula I, RI, R2, R3 and R4
each
independently represent a CI to C16 alkyl substituted aryl group or an
unsubstituted aryl
group, more preferably a C1 to C16 alkyl substituted phenyl group or an
unsubstituted
phenyl group, even more preferably a C3 to C16 alkyl substituted phenyl group.
Preferably,
in such a compound of formula Teach of RI, R2, R3 and R4 are identical.
In a still further alternative highly preferred compound of formula I:
RI and R3 each independently represent a branched or linear C1 to C16 alkyl
group,
especially a branched or linear C1 to Ci0 alkyl group; and,
R2 and R4 each independently represent a C1 to C16 alkyl substituted aryl
group or
an unsubstituted aryl group, more preferably a C1 to C16 alkyl substituted
phenyl
group or an unsubstituted phenyl group, even more preferably an unsubstituted
phenyl group.
Preferably, in such a compound of formula I, RI and R3 are identical, and R2
and R4 are
identical.
Preferably, X in a compound of formula I, as defined herein, represents a C1
to C10 alkylene
group. More preferably, X in a compound of formula I represents (CH2)n where n
is an
integer from 1 to 20, preferably an integer from 1 to 10, more preferably an
integer from 1
to 5, especially 1 (i.e. X represents methylene when n is 1).
Highly preferred compounds of formula I include: methylene bis(N-n-octyl-N-
phenyldithiocarbamate); methylene bis(di(nonylphenyl)dithiocarbamate) ¨
wherein each
nitrogen atom of the dithiocarbamate is bonded to two phenyl rings, each of
said rings are
substituted with a C9 alkyl group; and, methylene bis(dibutyldithiocarbamate).
An
especially preferred compound of formula I is methylene
bis(dibutyldithiocarbamate).
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24
The ashless alkylene bis(dihyrocarbyldithiocarbamates) may be prepared by
methods well
known to those skilled in the art. For example, an appropriate amine may be
reacted with
sodium hydride, the resulting product reacted with carbon disulphide, and the
resulting
product reacted with a dihaloalkane, e.g. iodomethane. Suitably, methylene
bis(N-n-octyl-
N-phenyldithiocarbamate) and methylene bis(di(nonylphenyl)dithiocarbamate) may
be
prepared as described in European patent application EP 2,692,840A and
methylene
bis(dibutyldithiocarbamate) is commercially available and sold under the trade
name of
Vanlube 7723 by Vanderbilt Chemicals LLC, USA.
Preferably, the ashless alkylene bis(dihydrocarbyldithiocarbamate) is present
in an amount
of greater than or equal to 0.1, more preferably greater than or equal to 0.2,
mass %, based
on the total mass of the lubricating oil composition. Preferably, the ashless
alkylene
bis(dihydrocarbyldithiocarbamate) is present in an amount of less than or
equal to 5.0, more
preferably less than or equal to 3.0, even more preferably less than or equal
to 2.0, most
preferably less than or equal to 1.0, mass %, based on the total mass of the
lubricating oil
composition.
ENGINES
The lubricating oil compositions of the invention may be used to lubricate
mechanical
engine components, particularly in internal combustion engines, e.g. spark-
ignited or
compression-ignited internal combustion engines, particularly spark-ignited or
compression-ignited two- or four- stroke reciprocating engines, by adding the
composition
thereto. The engines may be conventional gasoline or diesel engines designed
to be
powered by gasoline or petroleum diesel, respectively; alternatively, the
engines may be
specifically modified to be powered by an alcohol based fuel or biodiesel
fuel. Most
preferably, the engine comprises a compression-ignited internal combustion
engine,
especially a heavy duty diesel engine. Preferably, the lubricating oil
compositions are
crankcase lubricants.
CA 02883416 2015-02-26
CO-ADDITIVES
Co-additives, with representative effective amounts, that may also be present,
different
from additive components (B) and (C), are listed below. All the values listed
are stated as
mass percent active ingredient in a fully formulated lubricant.
Additive Mass % Mass %
(Broad) (Preferred)
Ashless Dispersant 0.1 ¨20 1 ¨ 8
Metal Detergents 0.1 ¨ 15 0.2 ¨ 9
Friction modifier 0 ¨ 5 0 ¨ 1.5
Corrosion Inhibitor 0 ¨ 5 0 ¨ 1.5
Metal Dihydrocarbyl Dithiophosphate 0 ¨ 10 0 ¨ 4
Anti-Oxidants 0 ¨ 5 0.01 ¨ 3
Pour Point Depressant 0.01 ¨ 5 0.01 ¨ 1.5
Anti-Foaming Agent 0 ¨ 5 0.001 ¨ 0.15
Supplement Anti-Wear Agents 0 ¨ 5 0 ¨ 2
Viscosity Modifier (1) 0 ¨ 6 0.01 ¨ 4
Mineral or Synthetic Base Oil Balance Balance
(1) Viscosity modifiers are used only in multi-graded oils.
The final lubricating oil composition, typically made by blending the or each
additive into
the base oil, may contain from 5 to 25, preferably 5 to 18, typically 7 to 15,
mass % of the
co-additives, the remainder being oil of lubricating viscosity.
Suitably, the lubricating oil composition includes one or more co-additives in
a minor
amount, other than additive components (B) and (C), selected from ashless
dispersants,
metal detergents, corrosion inhibitors, antioxidants, pour point depressants,
antiwear agents,
friction modifiers, demulsifiers, antifoam agents and viscosity modifiers.
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26
The above mentioned co-additives are discussed in further detail as follows;
as is known in
the art, some additives can provide a multiplicity of effects, for example, a
single additive
may act as a dispersant and as an oxidation inhibitor.
A dispersant is an additive whose primary function is to hold solid and liquid
contaminations in suspension, thereby passivating them and reducing engine
deposits at the
same time as reducing sludge depositions. For example, a dispersant maintains
in
suspension oil-insoluble substances that result from oxidation during use of
the lubricant,
thus preventing sludge flocculation and precipitation or deposition on metal
parts of the
engine.
Dispersants are usually "ashless", being 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 hydrocarbon chain with a polar head, the
polarity being
derived from inclusion of e.g. an 0, 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 backbone.
A preferred class of olefin polymers is constituted by polybutenes,
specifically
polyisobutenes (PIB) or poly-n-butenes, such as may be prepared by
polymerization of a C4
refinery stream.
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 is constituted by
hydrocarbon-substituted succinimides, made, for example, by reacting the above
acids (or
derivatives) with a nitrogen-containing compound, advantageously a
polyalkylene
polyamine, such as a polyethylene polyamine. Particularly preferred are the
reaction
products of polyalkylene polyamines with alkenyl succinic anhydrides, such as
described in
US-A-3,202,678; US-A-3,154,560; US-A-3,172,892; US-A-3,024,195; US-A-
3,024,237,
CA 02883416 2015-02-26
27
US-A-3,219,666; and US-A-3,216,936, that may be post-treated to improve their
properties,
such as borated (as described in US-A-3,087,936 and US-A-3,254,025)
fluorinated and
oxylated. For example, boration may 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.
Friction modifiers 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.
Other known friction modifiers comprise oil-soluble or oil-dispersible organo-
molybdenum
compounds. Such organo-molybdenum friction modifiers also provide antioxidant
and
antiwear credits to a lubricating oil composition. Suitable oil-soluble or oil-
dispersible
organo-molybdenum compounds have a molybdenum-sulfur core. As examples there
may be
mentioned dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates,
thioxanthates,
sulfides, and mixtures thereof Particularly preferred are molybdenum
dithiocarbamates,
dialkyldithiophosphates, alkyl xanthates and alkylthioxanthates. The
molybdenum compound
is dinuclear or trinuclear.
One class of preferred oil-soluble or oil-dispersible organo-molybdenum
compounds useful in
all aspects of the present invention is tri-nuclear molybdenum compounds of
the formula
Mo3SkL,,Qz and mixtures thereof wherein L are independently selected ligands
having organo
groups with a sufficient number of carbon atoms to render the compounds
soluble or
dispersible in the oil, n is from 1 to 4, k varies from 4 through to 7, Q is
selected from the
group of neutral electron donating compounds such as water, amines, alcohols,
phosphines,
and ethers, and z ranges from 0 to 5 and includes non-stoichiometric values.
At least 21 total
CA 02883416 2015-02-26
28
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.
Suitably, the oil-soluble or oil-dispersible organo-molybdenum compounds may
be present in
the lubricating oil composition in an amount of greater than or equal to 0.02,
preferably greater
than or equal to 0.05, mass % based on the total mass of the lubricating oil
composition.
Suitably, the oil-soluble or oil-dispersible organo-molybdenum compounds may
be present in
the lubricating oil composition in an amount of less than or equal to 2.0,
preferably less than or
equal to 1.0, even more preferably less than or equal to 0.5, mass % based on
the total mass of
the lubricating oil composition.
Suitably, the oil-soluble or oil-dispersible organo-molybdenum compound
provides the
lubricant with greater than or equal to 10, preferably greater than or equal
to 20, more
preferably greater than or equal to 30, ppm of molybdenum (ASTM D5185) based
on the total
mass of the lubricating oil composition. Suitably, oil-soluble or oil-
dispersible organo-
molybdenum compound provides the lubricant with less than or equal to 1500,
preferably less
than or equal to 1000, more preferably less than or equal to 700, ppm of
molybdenum (ASTM
D5185) based on the total mass of the lubricating oil composition.
Anti-oxidants are sometimes referred to as oxidation inhibitors; they increase
the resistance
of the composition to oxidation and may work by combining with and modifying
peroxides
to render them harmless, by decomposing peroxides, or by rendering an
oxidation catalyst
inert. Oxidative deterioration can be evidenced by sludge in the lubricant,
varnish-like
deposits on the metal surfaces, and by viscosity growth.
They may be classified as radical scavengers (e.g. sterically hindered
phenols, aromatic
amines, particularly secondary aromatic amines having at least two aromatic
(e.g. phenyl
groups) groups attached directly to the nitrogen atom, and organo-copper
salts);
hydroperoxide decomposers (e.g., organosulfur and organophosphorus additives);
and
multifunctionals (e.g. zinc dihydrocarbyl dithiophosphates, which may also
function as
CA 02883416 2015-02-26
29
anti-wear additives, and organo-molybdenum compounds, which may also function
as
friction modifiers and anti-wear additives).
Preferably, the lubricating oil composition in all aspects of the present
invention includes
an anti-oxidant, more preferably an ashless anti-oxidant. More preferably, the
anti-oxidant,
when present, is an aromatic amine anti-oxidant, a phenolic anti-oxidant or a
combination
thereof, especially an aromatic amine anti-oxidant. Even more preferably, the
lubricating
oil composition in all aspects of the present invention includes both an
aromatic amine and
phenolic anti-oxidant. Accordingly, the aromatic amine and/or phenolic anti-
oxidants,
when present, are ashless anti-oxidants.
Suitably, the total amount of anti-oxidant (e.g. aromatic amine anti-oxidant,
a phenolic anti-
oxidant or a combination thereof) which may be present in the lubricating oil
composition
is greater than or equal to 0.05, preferably greater than or equal to 0.1,
even more
preferably greater than or equal to 0.2, mass % based on the total mass of the
lubricating oil
composition. Suitably, the total amount of anti-oxidant which may be present
in the
lubricating oil composition is less than or equal to 5.0, preferably less than
or equal to 3.0,
even more preferably less than or equal to 2.5, mass % based on the total mass
of the
lubricating oil composition
Anti-wear agents reduce friction and excessive wear and are usually based on
compounds
containing sulfur or phosphorous or both, for example that are capable of
depositing
polysulfide films on the surfaces involved. Noteworthy are dihydrocarbyl
dithiophosphate
metal salts wherein the metal may be an alkali or alkaline earth metal, or
aluminium, lead,
tin, molybdenum, manganese, nickel, copper, or preferably, zinc.
Dihydrocarbyl dithiophosphate metal salts may be prepared in accordance with
known
techniques by first forming a dihydrocarbyl dithiophosphoric acid (DDPA),
usually by
reaction of one or more alcohols or a phenol with P2S5 and then neutralizing
the formed
DDPA with a metal compound. For example, a dithiophosphoric acid may be made
by
CA 02883416 2015-02-26
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 metal salt, any basic or neutral metal compound could
be used but
the oxides, hydroxides and carbonates are most generally employed. Commercial
additives
frequently contain an excess of metal due to the use of an excess of the basic
metal
compound in the neutralization reaction.
The preferred dihydrocarbyl dithiophosphate metal salts are zinc dihydrocarbyl
dithiophosphates (ZDDPs) which are oil-soluble salts of dihydrocarbyl
dithiophosphoric
acids and may be represented by the following formula:
S
R1C\ II
P¨S Zn
R20/
_ ¨ 2
wherein RI and R2 may be the same or different hydrocarbyl radicals containing
from 1 to
18, preferably 2 to 12, carbon atoms and include radicals such as alkyl,
alkenyl, aryl,
arylalkyl, alkaryl and cycloaliphatic radicals. Particularly preferred as RI
and R2 groups are
alkyl groups of 2 to 8 carbon atoms, especially primary alkyl groups (i.e. RI
and R2 are
derived from predominantly primary alcohols). Thus, the radicals may, for
example, be
ethyl, n-propyl, i-propyl, n-butyl, iso-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.
R1 and R2) in the dithiophosphoric acid will generally be about 5 or greater.
Preferably, the
zinc dihydrocarbyl dithiophosphate comprises a zinc dialkyl dithiophosphate.
Preferably, the lubricating oil composition contains an amount of
dihydrocarbyl
dithiophosphate metal salt that introduces 0.02 to 0.12, more preferably 0.02
to 0.11, even
more preferably 0.02 to 0.10, even more preferably 0.02 to 0.09, even more
preferably 0.02
CA 02883416 2015-02-26
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to 0.08 mass %, most preferably 0.02 to 0.06, mass % of phosphorus as measured
in
accordance with ASTM D5185, based on the total mass of the composition.
To limit the amount of phosphorus introduced into the lubricating oil
composition to no
more than 0.12 mass %, the dihydrocarbyl dithiophosphate metal salt should
preferably be
added to the lubricating oil compositions in amounts no greater than 1.5 mass
% (a.i.),
based upon the total mass of the lubricating oil composition.
Examples of ashless anti-wear agents include 1,2,3-triazoles, benzotriazoles
and sulfurised
fatty acid esters.
Rust and corrosion inhibitors serve to protect surfaces against rust and/or
corrosion. As rust
inhibitors there may be mentioned non-ionic polyoxyalkylene polyols and esters
thereof,
polyoxyalkylene phenols, thiadiazoles and anionic alkyl sulfonic acids.
Pour point depressants, otherwise known as lube oil flow improvers, lower the
minimum
temperature at which the oil will flow or can be poured. Such additives are
well known.
Typical of these additive are C8 to C18 dialkyl fumarate/vinyl acetate
copolymers and
polyalkylmethacrylates.
Additives of the polysiloxane type, for example silicone oil or polydimethyl
siloxane, can
provide foam control.
A small amount of a demulsifying component may be used. A preferred
demulsifying
component is described in EP-A-330,522. It is obtained by reacting an alkylene
oxide with
an adduct obtained by reaction of a bis-epoxide with a polyhydric alcohol. The
demulsifier
should be used at a level not exceeding 0.1 mass % active ingredient. A treat
rate of 0.001
to 0.05 mass % active ingredient is convenient.
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Viscosity modifiers (or viscosity index improvers) impart high and low
temperature
operability to a lubricating oil. Viscosity modifiers that also function as
dispersants are
also known and may be prepared as described above for ashless dispersants. In
general,
these dispersant viscosity modifiers are functionalised polymers (e.g.
interpolymers of
ethylene-propylene post grafted with an active monomer such as maleic
anhydride) which
are then derivatised with, for example, an alcohol or amine.
The lubricant may be formulated with or without a conventional viscosity
modifier and
with or without a dispersant viscosity modifier. Suitable compounds for use as
viscosity
modifiers are generally high molecular weight hydrocarbon polymers, including
polyesters.
Oil-soluble viscosity modifying polymers generally have weight average
molecular weights
of from 10,000 to 1,000,000, preferably 20,000 to 500,000, which may be
determined by
gel permeation chromatography or by light scattering.
The additives may be incorporated into an oil of lubricating viscosity (also
known as a base
oil) in any convenient way. Thus, each additive can be added directly to the
oil by
dispersing or dissolving it in the oil at the desired level of concentration.
Such blending
may occur at ambient temperature or at an elevated temperature. Typically an
additive is
available as an admixture with a base oil so that the handling thereof is
easier.
When a plurality of additives are employed it may be desirable, although not
essential, to
prepare one or more additive packages (also known as additive compositions or
concentrates) comprising additives and a diluent, which can be a base oil,
whereby the
additives, with the exception of viscosity modifiers, multifuntional viscosity
modifiers and
pour point depressants, can be added simultaneously to the base oil to form
the lubricating
oil composition. Dissolution of the additive package(s) into the oil of
lubricating viscosity
may be facilitated by diluent or solvents and by mixing accompanied with mild
heating, but
this is not essential. The additive package(s) will typically be formulated to
contain the
additive(s) in proper amounts to provide the desired concentration in the
final formulation
when the additive package(s) is/are combined with a predetermined amount of
oil of
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lubricating viscosity. Thus, one or more detergents may be added to small
amounts of base
oil or other compatible solvents (such as a carrier oil or diluent oil)
together with other
desirable additives to form additive packages containing from 2.5 to 90,
preferably from 5
to 75, most preferably from 8 to 60, mass %, based on the mass of the additive
package, of
additives on an active ingredient basis in the appropriate proportions. The
final
formulations may typically contain 5 to 40 mass % of the additive package(s),
the
remainder being oil of lubricating viscosity.
EXAMPLES
The invention will now be particularly described in the following examples
which are not
intended to limit the scope of the claims hereof.
TBN/TAN Cross-Over: The Extended Mack T-12 Test
The TBN/TAN cross-over point of a lubricant is evaluated using an extended
Mack T-12
engine test procedure as described in ASTM D7422; this test method is commonly
referred
to as the Mack T-12.
The Mack T-12 engine test procedure is a standard engine-dynamometer test for
evaluating
the ability of a diesel engine lubricant to control lead corrosion, oil
consumption, and wear
of piston rings and cylinder liners in an engine equipped with Exhaust Gas
Recirculation
(EGR) and running on ultra-low sulphur diesel (ULSD). The Mack T-12 test
employs a
Mack E-TECH V-MAC III diesel engine equipped with exhaust gas recirculation
(EGR).
The diesel engine is an in-line, six cylinder, four-stroke, turbocharged
engine with 12 litre
displacement. The standard Mack T-12 procedure is a two phase test lasting 300-
hours
where the engine in each phase is run at constant speed and load. The first
100-hour phase
has retarded injection timing to produce soot in the oil. The second 200-hour
phase is run
at heavy load to promote piston ring and cylinder liner wear. The steady-state
operating
parameters for the two phases are set out in Table 1 of ASTM D7422. In the
Mack T-12
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test the engine initially includes 32.7 kg of lubricant and after the 100 hour
point, i.e. after
completion of Phase 1, 2.27 kg of fresh lubricant is added at every 50-hour
interval. If
necessary, used lubricant is removed first so that the lubricant mass is below
the full mark
by 2.27kg. When determining the TBN/TAN cross-over point of a lubricant, the
test
procedure is run for an extended time. In the extended Mack T-12 test used
herein for
evaluating the TBN/TAN cross-over point of a lubricant the engine is continued
to run
under the Phase 2 conditions until the TBN/TAN cross-over point is at least
reached, more
preferably for 50-hours afterwards, up to a maximum test length of 600-hours.
The initial TBN and TAN of a lubricant are measured in accordance with ASTM
D4739
and D664, respectively, prior to the Mack T-12 test. During the Mack T-12 test
for each
lubricant, a sample of the lubricant (120 ml) is removed from the engine at 25-
hours
intervals throughout the test for physical and chemical analysis. The TBN
(ASTM D4739)
and the TAN (ASTM D664) of the lubricant sample is measured and recorded. The
TBN/TAN cross-over point represents the earliest specific 25 hour sampling
point at which
the TBN is equivalent to TAN or, if the TBN/TAN cross-over point is not met
exactly at a
specific 25 hour sampling point, the first 25 hour sampling point where the
TBN has fallen
below TAN.
TBN/TAN Cross-Over Point Results
A series of 15W/40 multigrade lubricating oil compositions of essentially
equal sulfated ash
(ASTM D874) were prepared by admixing a Group II base stock with known
additives, as
detailed herein. Each of the Comparative lubricating oil compositions and the
Inventive
lubricating oil compositions included identical amounts of the following
additives which
are available from Infineum UK Ltd: a dispersant (4.75 mass %); a tri-nuclear
organo
molybdenum compound; an anti-foam; a pour point depressant; and, a viscosity
modifier.
Further details of the composition of each lubricant is set out below, where
Lubricants A to
C are comparative lubricants and lubricants 1 and 2 represent lubricants of
the present
invention:
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Lubricant A: Overbased calcium sulphonate detergent (TBN 300 mg/g KOH);
overbased
magnesium sulphonate detergent (TBN 400 mg/g KOH); overbased calcium
phenate detergent (TBN 140 mg/g KOH); ZDDP; aromatic amine anti-
oxidant (0.50 mass %). Sulphated Ash 0.95 mass % (ASTM D874);
phosphorus 0.12 mass % (ASTM D5185); sulphur 0.3 mass % (ASTM
D2622).
Lubricant B: Overbased magnesium salicylate detergent (TBN 342 mg/g KOH);
ZDDP;
aromatic amine anti-oxidant (0.50 mass %). Sulphated Ash 0.92 mass %
(ASTM D874); phosphorus 0.12 mass % (ASTM D5185); sulphur 0.3
mass % (ASTM D2622).
Lubricant C: Overbased magnesium salicylate detergent (TBN 342 mg/g KOH);
ZDDP;
aromatic amine anti-oxidant (1.50 mass %); phenolic anti-oxidant (1.0
mass %). Sulphated Ash 0.93 mass % (ASTM D874); phosphorus 0.12
mass % (ASTM D5185); sulphur 0.3 mass % (ASTM D2622).
Lubricant 1: Overbased magnesium salicylate detergent (TBN 342 mg/g KOH);
ZDDP;
aromatic amine anti-oxidant (0.50 mass %); methylene
bis(dibutyldithiocarbamate) (0.40 mass %). Sulphated Ash 0.93 mass %
(ASTM D874); phosphorus 0.06 mass % (ASTM D5185); sulphur 0.3
mass % (ASTM D2622); TBN 9.9 mg/g KOH (D4739) or 12.7 mg/g KOH
(D2896); magnesium salicylate soap (12 mmoles); magnesium (0.2 mass %).
Lubricant 2: Overbased magnesium salicylate detergent (TBN 342 mg/g KOH);
ZDDP;
aromatic amine anti-oxidant (1.50 mass %); phenolic anti-oxidant (1.0
mass %); methylene bis(dibutyldithiocarbamate) (0.40 mass %). Sulphated
Ash 0.93 mass % (ASTM D874); phosphorus 0.06 mass % (ASTM D5185);
sulphur 0.3 mass % (ASTM D2622); TBN 9.9 mg/g KOH (D4739) or 13.9
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mg/g KOH (D2896); magnesium salicylate soap (12 mmoles); magnesium
(0.2 mass %).
Each of the aforementioned additives as used in Lubricants A to C and
Lubricants 1 and 2,
with the exception of methylene bis(dibutylditiocarbamate), are available from
Infineum
UK Ltd; methylene bis(dibutylditiocarbamate) is sold under the trade name of
Vanlube
7723 and is available fromVanderbilt Chemicals LLC, USA.
The TBN/TAN cross-over point of each of the aforementioned lubricants was
determined
using the extended Mack T-12 test procedure and the results are set out in
Table 1 below.
The results demonstrate that at equivalent sulphated ash levels a lubricant
which includes
an overbased magnesium salicylate detergent has an extended TBN/TAN cross-over
point
compared with a lubricant which includes a mixture of overbased sulphonate and
phenate
detergents; compare Lubricant B which has a TBN/TAN cross-over point of 375
hours with
Lubricant A which has a TBN/TAN cross-over point of 225 hours.
Moreover, the results clearly demonstrate that, at equivalent sulphated ash
levels, the
combination of an overbased magnesium salicylate detergent and an alkylene
bis(dihydrocarbyldithiocarbamate) additive in a lubricant further
significantly extends the
TBN/TAN cross-over point for a lubricant; compare Lubricant 2 of the present
invention
which has a TBN/TAN cross-over point of 500 hours with Lubricant C which has a
TBN/TAN cross-over point of 400 hours. Accordingly, the lubricants of the
present
invention are suitable for extended drain intervals.
Table 1
TBN/TAN Cross-Over Point (hours)
Lubricant A 225
Lubricant B 375
Lubricant C 400
Lubricant 1
Lubricant 2 500
