Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVEMENTS OF FUELS BY ADDING POLYMERIC
VISCOSITY INCREASING COMPONENTS
Field of the Invention
The present invention relates to influencing the
viscometric performance of a lubricant in an internal
combustion engine. In particular, though not exclusively,
the invention relates to counteracting a deterioration in
the viscometric performance of a lubricant associated
with the ingress of fuel into the lubricant.
Background of the Invention
In recent decades, the use of internal combustion
engines, powered by the ignition of hydrocarbon fuel, for
transportation and energy generation has become more and
more widespread.
For example, compression ignition engines, which
will be referred to further as "diesel" engines after
Rudolf Diesel (who invented the first compression
ignition engine in 1892) feature among the main type of
engines employed for passenger cars and heavy duty
applications, as well as for stationary power generation,
as a result of their high efficiency. In a diesel engine
a fuel/air mixture is ignited by being compressed until
it ignites due to the temperature increase due to
compression.
In spark ignition engines ("petrol") engines on the
other hand, which are another widespread form of internal
combustion engine, a separate source of ignition, such as
a spark plug, ignites the fuel.
Lubricant oils ("lubricants") are used in all
internal combustion engines to reduce friction between,
and hence wear on, moving parts. During use of an engine,
however, the properties (particularly the viscometric
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performance) of a lubricant can gradually deteriorate
over time, to a point where its performance is impaired
and it has to be replaced. Much of this lubricant
deterioration is due to contaminants that pass from the
combustion chamber into the crankcase and into the
lubricant. For example, a fraction of the fuel may enter
the lubricant.
The ingress of fuel into the lubricant generally
leads to a reduction of lubricant viscosity and/or
viscosity index, i.e. loss of viscometric performance,
and can thus result in increased engine wear. The
draining and replacement of an engine lubricant can be
costly and time consuming. It would, therefore, be
desirable to be able to reduce the rate of viscometric
performance loss, and hence to increase the interval
between lubricant changes (also known as "oil drain
interval").
A number of improved lubricant formulations have
been proposed over the years to reduce the rate of
lubricant performance loss and to increase the interval
between lubricant changes. Furthermore, engine designers
are conscious of the problem of fuel dilution and have
sought to minimise it by the incorporation of seals and
the like. However, nevertheless, the loss of viscometric
performance in lubricants remains a problem, especially
in diesel engines.
It is proposed in WO 2009/080673 to use a Fischer-
Tropsch (FT) derived oil, particularly a Fischer-Tropsch
extra heavy base oil, to mitigate loss of viscometric
performance of an engine oil. However significant
quantities of the FT oil are required to effect a
beneficial result, cf the Examples where 5 vol% of an FT
extra heavy base oil is used. It would be advantageous to
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achieve such a result without the need for such a high
amount of additive; it would be even more beneficial if
it would be possible to prevent lubricant deterioration
to a greater extent whilst utilising a lower additive
amount.
It is also known to use viscosity index improving
additives directly in lubricant formulations, where they
are used to maintain viscosity as constant as possible
particularly at high temperatures. In this use, also high
concentrations are utilised: typically between 1 and 20%
w/w of the additive.
Summary of the Invention
It has now been found that, surprisingly,
incorporating a polymeric viscosity index (VI) improving
additive into a fuel composition, and particularly a
diesel fuel composition, can advantageously influence the
viscometric performance of a lubricant in an internal
combustion engine running on said fuel composition, even
when used in the fuel composition at low concentrations.
The present invention is based on the appreciation
that fuel dilution, which is conventionally seen as a
cause of lubricant deterioration, can be made use of to
influence the viscometric performance of the lubricant,
by using viscosity index improving additives in the fuel.
In this manner, it is possible to counteract
deterioration of viscometric performance in the lubricant
(e.g. to achieve an increase in the interval between
lubricant changes) without the need to alter the engine
itself, and irrespective of the nature of the lubricant.
From a first aspect, the invention resides in the
use of a viscosity increasing component in a fuel
composition, for the purpose of influencing the
viscometric performance of a lubricant in an internal
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combustion engine into which the fuel composition is or
is intended to be introduced, wherein the viscosity
increasing component is a polymeric viscosity index (VI)
improving additive.
In the context of the present invention, "use" of a
viscosity increasing component in a fuel composition
means incorporating the component into the composition,
typically as a blend (i.e. a physical mixture) with one
or more fuel components (typically base fuels) and
optionally with one or more fuel additives.
The viscosity index improving additive may
preferably be incorporated into the fuel composition
before the composition is introduced into an engine that
is to be run on the composition.
Accordingly, the viscosity index improving additive
may be dosed directly into (e.g. blended with) one or
more components of the fuel composition or base fuel at
the refinery. For instance, it may be pre-diluted in a
suitable fuel component, which subsequently forms part of
the overall fuel composition.
Alternatively, it may be added to a fuel composition
downstream of the refinery. For example, it may be added
as part of an additive package containing one or more
other fuel additives. This can be particularly
advantageous because in some circumstances it can be
inconvenient or undesirable to modify the fuel
composition at the refinery. For example, the blending of
base fuel components may not be feasible at all
locations, whereas the introduction of fuel additives, at
relatively low concentrations, can more readily be
achieved at fuel depots or at other filling points such
as road tanker, barge or train filling points,
dispensers, customer tanks and vehicles.
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Accordingly, the "use" of the first aspect of the
invention may also encompass the supply of a polymeric
viscosity index improving additive together with
instructions for its use to achieve one of the benefits
of the present invention, e.g. counteracting performance
loss of a lubricant of an engine into which the fuel
composition is or is intended to be introduced. The
viscosity index improving additive may therefore be
supplied as a component of a formulation which is
suitable for and/or intended for use as a fuel additive,
without departing from the scope of the invention. By way
of example, the viscosity index improving additive may be
incorporated into an additive formulation or package
along with one or more other fuel additives. The one or
more fuel additives may be selected from any useful
additive, such as detergents, anti-corrosion additives,
esters, poly-alpha olefins, long chain organic acids,
components containing amine or amide active centres, and
mixtures thereof, as is known to the person of skill in
the art.
Instead, or in addition, the "use" of the first
aspect of the invention may involve running an engine on
the fuel composition containing the viscosity index
improving additive, typically by introducing the fuel
composition into a combustion chamber of the engine.
Accordingly, the "use" of the first aspect of the
invention may also encompass the supply of a fuel
composition comprising a polymeric viscosity index
improving additive together with instructions for its use
to achieve one of the benefits of the present invention,
e.g. influencing the viscometric performance of a
lubricant of an engine into which the fuel composition is
or is intended to be introduced.
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From a second aspect, the invention resides in the
use of a fuel composition comprising a polymeric
viscosity index improving additive in an internal
combustion engine for the purpose of influencing the
viscometric performance of a lubricant of the engine.
In the context of the invention, "influencing" the
viscometric performance of a lubricant embraces any
alteration of the viscometric performance compared to
viscometric performance in the absence of the viscosity
index improving additive in the fuel under otherwise
identical conditions.
Influence on viscometric performance may be
measured, for example, by comparing viscometric
performance in a lubricant when using the invention, with
viscometric performance when the same engine is run on an
otherwise identical fuel composition not including the
viscosity index improving additive. The difference in
viscometric performance represents the influence of using
the viscosity index improving additive (or the fuel
comprising said additive).
Preferably, influencing the viscometric performance
may comprise counteracting deterioration (or loss) of the
viscometric performance of the lubricant associated with
ingress of the fuel composition into the lubricant. It
may also comprise preserving and/or maintaining
viscometric performance.
In the context of the invention, the term
"counteracting deterioration" (e.g. of viscometric
performance) embraces mitigating, slowing down, reducing
or even stopping (i.e. reducing to zero) deterioration
(or the rate of loss). Counteracting deterioration of
lubricant performance also embrace mitigation, to at
least a degree, of an increase in deterioration due to
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another cause, e.g. the presence of other certain fuel
components. "Counteracting deterioration" according to
the invention is not restricted to any particular
mechanism of action.
Counteraction of deterioration of viscometric
performance may be measured by a comparison over a given
engine running time or engine running distance. For
example, counteraction of deterioration may be determined
by comparing deterioration of viscometric performance in
a lubricant when using the invention with the
deterioration when the same engine is run on an otherwise
identical fuel composition prior to adding a polymeric
viscosity index improving additive to it. The difference
(e.g. mitigation, slowing down, reduction or stopping) in
deterioration represents the counteraction.
The deterioration of viscometric performance may be
measured over a predetermined time period (i.e. engine
running time), in particular a period that begins at the
time of introduction of the (previously unused) lubricant
fluid into the engine. Deterioration may, for example, be
measured over a period of 100 hours or more of engine
running time, or 200 hours or more, or 250 hours or more,
for example 300 or 400 or 500 hours or more, following
the introduction of the lubricant fluid into the engine.
Alternatively deterioration may be measured over a
predetermined engine running distance, in particular
beginning at the time of introduction of the (previously
unused) lubricant fluid into the engine. Deterioration
may for example be measured over 5000 engine miles or
more, or 8000 engine miles or more, or 10000 engine miles
or more, or 13000 or 15000 engine miles or more,
following the introduction of the lubricant fluid into
the engine.
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Deterioration may accordingly be expressed as a
change per unit engine running time or as a change per
unit engine running distance.
The present invention may, for example, involve
adjusting the effects of the fuel composition on
viscometric performance of a lubricant, by means of the
viscosity index improving additive, in order to meet a
desired target.
In the context of the invention, "viscometric
performance" may preferably embrace all properties and
effects of the lubricant that vary in dependence on its
kinematic viscosity at 100 C (VK 100, as measured by EN
ISO 3104). References in this specification to viscosity
are, unless otherwise specified, intended to mean VK 100.
The viscometric performance (or properties) of the
lubricant may embrace one or more of: lubricant viscosity
at 40 C (VK 40) or 100 C (VK 100) or any other
temperature, lubricant SAE viscosity grade, lubricant
viscosity index (e.g. SAE scale), lubricant fluid changes
or oil drain interval, engine lubrification, lubricant
lifetime or lifespan, engine friction, and engine wear.
Since all expressions of viscometric performance
vary in dependence on VK 100, viscometric performance may
conveniently be measured based on VK 100, for instance
using the standard test method EN ISO 3104. From two or
more such measurements, the deterioration of viscometric
performance over a particular period of time or a
particular distance can be calculated, as described
above.
Other expressions of viscometric performance may
also provide an indication of viscometric performance,
based on relevant standard measurements, preferably EN
ISO, where available.
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Where the present invention is used to counteract
deterioration of viscometric performance, the
counteraction may advantageously lead to a reduction in
deterioration of VK 100 of at least 1 %, preferably of at
least 5 %, for example of at least 10 or 15 or 20 or 25%
or in cases even 30%, compared to the deterioration
observed when running the engine on the fuel composition
prior to incorporation of the viscosity index improving
additive, for example based on any of the time periods or
distances mentioned hereinabove.
The invention may be used for the purpose of
reducing the frequency of lubricant fluid changes, and/or
of increasing an interval between lubricant fluid changes
(oil drain interval). As described above, lubricant fluid
changes are necessary whenever the properties and/or
performance of the fluid deteriorate to such an extent as
to impair its performance, and/or to impede satisfactory
functioning of the engine which the fluid is used to
lubricate. In particular, the viscosity index improving
additive, or the fuel composition comprising it, may be
used to reduce the frequency of lubricant fluid changes
that are necessary due to changes in the viscosity or
viscosity index of the fluid. Where the present invention
is used to increase an interval between lubricant fluid
changes needed, the increase may be of at least 10 or 20
%, preferably of at least 50 or 60 or 70 or 80 %, in
cases of at least 90 or even 100 %, compared to the
intervals required when running the engine on a fuel
composition without the viscosity increasing component.
The point at which a lubricant change is deemed necessary
should be evaluated in each case using the same criteria,
which may preferably include the kinematic viscosity of
the fluid (e.g. at 100 C)
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A third aspect of the invention provides for the use
of a polymeric viscosity index improving additive in a
fuel composition, or the use of a fuel composition
comprising the polymeric viscosity index improving
additive, for the purpose of influencing, preferably
counteracting a deterioration of, one or more of:
viscosity; viscosity index; fluid change frequency or oil
drain interval; or lifetime or lifespan; of a lubricant
in an internal combustion engine into which the fuel
composition is or is intended to be introduced.
A fourth aspect of the invention provides for the
use of a polymeric viscosity index improving additive in
a fuel composition, or the use of a fuel composition
comprising the polymeric viscosity index improving
additive, for the purpose of influencing, preferably
counteracting a deterioration of, one or more of:
lubrification; lifetime; friction; or wear of or in an
internal combustion engine into which the fuel
composition is or is intended to be introduced.
A fifth aspect of the invention provides a method of
operating an internal combustion engine, and/or a system
(for example an automotive vehicle) which is powered by
such an engine, which method involves introducing into a
combustion chamber of the engine a fuel composition
containing a polymeric viscosity index improving additive
for one or more of the purposes defined in any one of the
first to the fourth aspects of the present invention. The
engine may preferably be a diesel engine. It may be of
the direct injection type, for example of the rotary
pump, in-line pump, unit pump, electronic unit injector
or common rail type, or of the indirect injection type.
A sixth aspect of the invention provides a method of
achieving a target viscometric performance associated
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with a lubricant of an internal combustion engine, the
method comprising powering the engine using a fuel
composition comprising a polymeric viscosity index
improving additive.
The VI improving additive used in the fuel
composition in accordance with the present invention is
polymeric in nature. The VI improving additive may, for
example, comprise a copolymer that contains one or more
olefin monomers (or monomer blocks), typically selected
from ethylene, propylene, butylene, butadiene, isoprene
and styrene monomers.
The VI improving additive may, for example, be
selected from: a) styrene-based copolymers, in particular
block copolymers, for example those available as
Kraton(TM) D or Kraton(TM) G additives (ex. Kraton) or as
SV(TM) additives (ex. Infineum, Multisol or others).
Particular examples include copolymers of styrenic and
ethylene/butylene monomers, for instance polystyrene-
polyisoprene copolymers and polystyrene-polybutadiene
copolymers. Such copolymers may be block copolymers, as
for instance SV(TM) 150 (a polystyrene-polyisoprene di-
block copolymer) or the Kraton(TM) additives (styrene-
butadiene-styrene tri-block copolymers or styrene-
ethylene-butylene block copolymers). They may be tapered
copolymers, for instance styrene-butadiene copolymers.
They may advantageously be stellate copolymers, as for
instance SV (TM) 260 (a styrene-polyisoprene star
copolymer) or SV (TM) 200 (a divinylbenzene-polyisoprene
star copolymer); b) other block copolymers based on
ethylene, butylene, butadiene, isoprene or other olefin
monomers, for example ethylene-propylene copolymers; c)
polyisobutylenes (PIBs); d) polymethacrylates (PMAs); e)
poly alpha olefins (PA0s); and f) mixtures thereof.
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Other examples of suitable viscosity index improvers
are disclosed in Japanese Patents Nos. 954077, 1031507,
1468752, 1764494 and 1751082. Yet further examples
include the dispersing-type VI improving additives, which
comprise copolymerised polar monomers containing nitrogen
and oxygen atoms alkyl aromatic-type VI improving
additives; and certain pour point depressants known for
use as VI improving additives.
Of the above, additives of type (a) and (b), or
mixtures thereof, are preferred, in particular additives
of type (a).
As aforesaid, the invention makes use of fuel
dilution to influence the viscometric performance of the
lubricant. Since fuel dilution typically occurs through
one or more pistons of the engine, i.e. in a high shear
environment, to enhance the efficiency with which the
viscosity improving component used in the fuel
composition is delivered to (and retained within) the
lubricant, the viscosity improving component, and in
particular the preferred VI improving additives, used
according to the invention may advantageously have a
stellate (i.e. star-like) structure and/or may form star-
like clusters (micelles). It is thought that a stellate
structure, and in particular the formation of star-like
clusters, enhances shear resistance, which means that a
greater proportion of such VI improving additives in fuel
is made available to influence the viscometric properties
of the lubricant.
The kinematic viscosity at 40 C (VK 40, as measured
by EN ISO 3104) of the VI improving additive may suitably
be 40 mm2/s or greater, preferably 100 mm2/s or greater,
more preferably 1000 mm2/s or greater. Its density at
15 C (EN ISO 3675) may suitably be 600 kg/m3 or greater,
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preferably 800 kg/m3 or greater. Its sulphur content (EN
ISO 20846) may suitably be 1000 mg/kg or lower,
preferably 350 mg/kg or lower, more preferably 10 mg/kg
or lower.
Suitably, the VI improving additive may be used at a
concentration in the range of from 0.01% w/w to 0.5% w/w
based on the total weight of the fuel composition. For
example, the VI improving additive may be used at a
concentration in the range of from: (i) 0.01% w/w to 1.0%
w/w; (ii) 0.05% w/w to 0.7% w/w; or (iii) 0.1% w/w to
0.5% w/w; based on the total weight of the fuel
composition.
The fuel compositions may contain any number of
additional useful additives known to the person of skill
in the art. In some embodiments, two or more viscosity
increasing components may be used, such as a VI improving
additive and a high viscosity fuel or oil component, e.g.
a refinery product, which has a higher kinematic
viscosity than the base fuel of the fuel composition. In
another embodiment there may be two or more VI improving
additives of the same or different structural class,
provided one is a polymeric VI improving additive. An
example of a VI improving additive of another class is an
inorganic compound, for example a zeolite.
In the present context, an internal combustion
engine may be, for example, a compression ignition
("diesel") engine or a spark ignition ("petrol") engine.
As aforesaid, all such engines suffer from fuel dilution,
i.e. ingress of fuel into the lubricant. Preferably, the
engine may permit a fuel dilution of at least 3%,
preferably 6%, most preferably 10% w/w fuel in the
lubricant in at least one operational mode and/or
operational span.
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The use according to the first aspect of the
invention is contemplated in (or may comprise the use of)
any fuel composition that is suitable for use in (i.e. to
power) the internal combustion engine into which it is or
is intended to be introduced. The fuel composition may,
for example, be an automotive fuel composition, for use
in powering an automotive vehicle.
The fuel composition may comprise petroleum derived
components ("distillate"), and/or synthetically derived,
e.g. Fischer-Tropsch derived, components. As used herein,
the term "Fischer-Tropsch derived" means that a material
is, or derives from, a synthesis product of a Fischer-
Tropsch condensation process. A Fischer-Tropsch derived
fuel component of use in the present invention may be
obtained directly from the refining or the Fischer-
Tropsch reaction, or indirectly for instance by
fractionation or hydrotreating of the refining or
synthesis product to give a fractionated or hydrotreated
product. A Fischer-Tropsch derived fuel or fuel component
will therefore be a hydrocarbon stream in which a
substantial portion, except for added hydrogen, is
derived directly or indirectly from a Fischer-Tropsch
condensation process. The Fischer-Tropsch process
converts carbon monoxide and hydrogen into longer chains,
which are usually paraffinic hydrocarbons. The carbon
monoxide and hydrogen may themselves be derived from
organic, inorganic, natural or synthetic sources, such as
from natural gas or from organically derived methane.
Fischer-Tropsch derived components may be obtained by
converting gas, biomass or coal to liquid (XtL),
specifically by gas to liquid conversion (GtL), or from
biomass to liquid conversion (BtL). Any form of Fischer-
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Tropsch derived fuel component may be used as a base
component in accordance with the invention.
The fuel composition may preferably contain no more
than 5000 ppmw (parts per million by weight) of sulphur,
typically from 2000 to 5000 ppmw, or from 1000 to 2000
ppmw, or alternatively up to 1000 ppmw. The composition
may, for example, be a low or ultra low sulphur fuel, or
a sulphur free fuel, for instance containing at most 500
ppmw, preferably no more than 350 ppmw, most preferably
no more than 100 or 50 or even 10 ppmw, of sulphur.
It has been found that fuel dilution is particularly
pronounced in compression ignition engines powered by
diesel fuel. Without wishing to be bound by theory, it is
thought that the relatively high boiling points of many
diesel fuel components (e.g. compared to gasoline fuel
components) make such components less likely to evaporate
and escape the lubricant following their ingress. This
can lead to a build-up of fuel components in the
lubricant, which, in the absence of viscosity increasing
components in the fuel, can in turn cause an increased
deterioration of the viscometric properties of the
lubricant.
Based on the appreciation that diesel fuel is
particularly likely to affect the viscometric properties
of the lubricant, the use according to the invention may
preferably be in (or comprise the use of) a diesel fuel
composition suitable and/or adapted and/or intended for
use in a compression ignition (diesel) engine. Such a
diesel fuel composition may comprise one or more diesel
fuel components of conventional type, typically
comprising liquid hydrocarbon middle distillate fuel
oil(s), for instance petroleum derived gas oils. In
general, such fuel components may be organically or
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synthetically derived, and are suitably obtained by
distillation of a desired range of fractions from a crude
oil. Such gas oils may be processed in a
hydrodesulphurisation (HDS) unit so as to reduce their
sulphur content to a level suitable for inclusion in a
diesel fuel composition. They will typically have boiling
points within the usual diesel range of 150 to 410 C or
170 to 370 C, depending on grade and use. In some cases,
the fuel composition will include one or more cracked
products obtained by splitting heavy hydrocarbons. Diesel
fuels contained in the a diesel composition will
typically have a density of from 750 to 900 kg/m3,
preferably from 800 to 860 kg/m8, at 15 C (ASTM 0-4052 or
EN ISO 3675) and/or a kinematic viscosity at 40 C (VK 40)
of from 1.5 to 6.0 centistokes (mm2/s) (ASTM D-445 or EN
ISO 3104).
The fuel composition may be a diesel fuel
composition that comprises a Fischer-Tropsch derived
diesel fuel component, typically a Fischer-Tropsch
derived gas oil.
In the context of reducing carbon emissions, it is
increasingly desirable for diesel fuel to contain one or
more so-called "biofuel" components, which may typically
be oxygenates. Thus, in beneficial embodiments of the
invention, the diesel fuel composition may consist of or
comprise a biofuel component or an oxygenate component,
such as a vegetable oil, hydrogenated vegetable oil or
vegetable oil derivative (e.g. a fatty acid ester, in
particular a fatty acid methyl ester, FAME), or another
oxygenate such as an acid, ketone or ester. The biofuel
or oxygenate may preferably be bio-derived, i.e. comprise
at least about 0.1 dpm/gC of carbon-14. It is known in
the art that carbon-14 (C-14), which has a half-life of
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about 5,700 years, is found in bio-derived materials but
not in fossil fuels.
It has been found that fuel dilution in internal
combustion engines particularly affects lubricant
performance when the fuel composition comprises a
biofuel, particularly an oxygenate. The ingress of diesel
fuel compositions comprising biofuel components,
especially esters of either a carboxylic acid or a
vegetable oil such as FAME, has been found to have a
particularly detrimental effect on lubricant performance.
Without wishing to be bound by theory, it is thought that
biofuels/oxygenates, in particular esters of either a
carboxylic acid or a vegetable oil, and most particularly
FAME, can accumulate relatively quickly in the lubricant
due to their relatively high boiling points. Furthermore,
biofuels/oxygenates, in particular esters of either a
carboxylic acid or a vegetable oil, and most particularly
FAME, have surprisingly been found to lower the viscosity
(i.e. viscometric performance) of lubricant beyond even
levels predicted by viscometric models.
Accordingly, to address such increased losses in
viscometric performance, the use according to the
invention is preferably contemplated in, or may
preferably comprise the use of, a fuel composition
(advantageously a diesel fuel composition), comprising an
oxygenate (advantageously an ester of either a carboxylic
acid or a vegetable oil, most advantageously FAME)
optionally having a high amount of polar components,
measurable for example with reference to unreacted acid
(Acid value greater than 0.5 mg/KOH/g) or, particularly
in the context of FAME, more than 0.8% w/w
monoglycerates.
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Where the fuel composition contains a biofuel
component or oxygenate, the biofuel or oxygenate
component may be present in quantities of between 1% and
99% w/w, for example. In one embodiment the fuel
comprises at least 2% w/w biofuel or oxygenate, such as
between 2% and 75% w/w. In some cases the biofuel or
oxygenate is present at between 2% and 45% w/w, such as
between 3% and 35% w/w, between 4% and 25% w/w, or
between 5% and 15% w/w. In one beneficial embodiment the
biofuel or oxygenate component is FAME. In a preferred
application FAME is present at 5% w/w to 15% w/w based on
the total weight of the fuel composition.
In diesel fuel compositions, the base fuel may
itself comprise a mixture of two or more diesel fuel
components of the types described above.
The fuel composition may also be a gasoline (petrol)
fuel composition. Such gasoline fuel compositions are
well known in the art.
It has been found that certain engine operating
cycles, such as diesel particulate filter (DPF)
regeneration and, in the case of automotive engines, city
driving, led to particularly high levels of fuel
dilution. Therefore, use according to the invention may
preferably be for the purpose of influencing the
viscometric performance of a lubricant (as described
anywhere herein) during a particulate filter regeneration
cycle and/or a city driving cycle of the internal
combustion engine.
In the context of the present invention, the
lubricant may be any lubricant fluid, typically an oil,
which is suitable and/or adapted and/or intended for use
in an internal combustion engine, in particular a diesel
engine. Typical lubricant fluids are composed primarily
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of one or more base oils, which may be selected from any
of the synthetic (lubricating) oils, mineral oils,
natural oils or mixtures thereof. Mineral oils include
liquid petroleum oils and solvent-treated or acid-treated
mineral lubricating oils of the paraffinic, naphthenic or
mixed paraffinic/naphthenic type, which may be further
refined by hydrofinishing processes and/or dewaxing.
Synthetic base oils include Fischer-Tropsch derived base
oils, as well as olefin oligomers (PA0s), dibasic acid
esters, polyol esters and dewaxed waxy raffinates.
For use in an internal combustion engine, a base oil
will suitably contain less than 1 %wt, preferably less
than 0.1 %wt, of sulphur, as determined, for instance, by
ASTM D-2622, D-4294, D-4927 or D-3120. It will suitably
have a viscosity index of more than 80, preferably of
more than 120, as measured according to ASTM D-2270. It
may conveniently have a VK 100 of from 3.8 to 26
centistokes (mm2/s) (ASTM 0-445).
A lubricant fluid for use in an internal combustion
engine might suitably have a VK 100 of from 2 to 80
centistokes (mm2/s), preferably from 3 to 70 centistokes
(mm2/s) or from 4 to 50 centistokes (mm2/s).
Natural oils suitable for use as base oils include
both animal and vegetable oils (e.g. castor or lard oil);
liquid petroleum oils; and hydrorefined, solvent-treated
or acid-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.
Alkylene oxide polymers and interpolymers and
derivatives thereof, in which the terminal hydroxyl
groups have been modified by esterification,
etherification, etc, constitute another class of known
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synthetic lubricating oils. These are exemplified by
polyoxyalkylene polymers prepared by polymerisation of
ethylene oxide or propylene oxide; the alkyl and aryl
ethers of these polyoxyalkylene polymers (e.g. methyl-
polyisopropylene glycol ether having an average molecular
weight of 1000, diphenyl ether of polyethylene glycol
having a molecular weight of 500-1000, diethyl ether of
polypropylene glycol having a molecular weight of 1000-
15001; and mono-and polycarboxylic esters thereof, for
example, the acetic acid esters, mixed 03-08 fatty acid
esters and the 013 oxo acid diester of tetraethylene
glycol. Another suitable class of synthetic lubricating
oils comprises the esters formed by reacting 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, adip+-c
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 05 to 012 monocarboxylic acids and polyols and
polyol ethers such as neopentyl glycol,
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trimethylolpropane, pentaerythritol, dipentaerythritol
and tripentaerythritol.
Silicon-based oils, such as the polyalkyl-,
polyaryl-, polyalkoxy, or polyaryloxysiloxane oils and
silicate oils, comprise another useful class of synthetic
lubricating oils; they include tetraethyl silicate,
tetraisopropyl silicate, tetra- (2-ethylhexyl) silicate,
tetra- (4-methyl-2-ethyl-hexyl) silicate, tetra- (p-
tertbutylphenyl) silicate, hexa- (4-methyl- 2-pentoxy)
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.
Lubricant fluids may typically contain additives as
known in the art, for example oxidation inhibitors
(antioxidants), dispersants, seal fix or seal
compatibility agents, and/or detergents. They may also
include other lubricant additives that perform specific
functions not provided by the main components. These
additional additives include, but are not limited to,
corrosion inhibitors, VI improving additives, pour point
depressants, zinc dialkyldithiophosphates, anti-wear
agents, anti-foam agents, and/or friction modifiers.
Suitable additives are described in US-A-5320765 and US-
B-652846l. Suitable oxidation inhibitors include, for
example, copper antioxidants, phenolic compounds and/or
aminic compounds. Suitable dispersants include, for
example, succinimides. Suitable detergents include, for
example, salicylate, phenate and sulphonate detergents.
Suitable anti-wear additives include zinc
dithiophosphates.
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Examples of lubricating base oils, and of additives
for use in lubricant fluids, are described at pages 15 to
23 of WO-A-2007/128740.
Throughout the description and claims of this
specification, the words "comprise" and "contain" and
variations of the words, for example "comprising" and
"comprises", mean "including but not limited to", and do
not exclude other moieties, additives, components,
integers or steps.
Throughout the description and claims of this
specification, the singular encompasses the plural unless
the context otherwise requires. In particular, where the
indefinite article is used, the specification is to be
understood as contemplating plurality as well as
singularity, unless the context requires otherwise.
Preferred features of each aspect of the present
invention may be as described in connection with any of
the other aspects. Other features of the present
invention will become apparent from the following
examples. Generally speaking the invention extends to any
novel one, or any novel combination, of the features
disclosed in this specification (including any
accompanying claims and drawings} . Thus, features,
integers, characteristics, compounds, chemical moieties
or groups described in conjunction with a particular
aspect, embodiment or example of the present invention
are to be understood to be applicable to any other
aspect, embodiment or example described herein unless
incompatible therewith. Moreover, unless stated
otherwise, any feature disclosed herein may be replaced
by an alternative feature serving the same or a similar
purpose.
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The following examples illustrate the use of
polymeric VI improving additives in fuel compositions, in
accordance with the present invention, and assess their
effects on¨the properties of lubricant oils in engines
running on the fuel compositions.
Example 1
The visoometric properties of a lubricant in a
compression ignition engine were observed whilst running
the engine on two different fuels.
One of the fuels, Fuel A, consisted of only base
fuel made up of regular mineral diesel including 5%v FAME
(without any performance additives). The properties of
Fuel A are summarised in Table 1:
Table 1
riuel Property ,Test method
Density @ 15 (g/ml) 838.6 DIN EN ISO 12185
Viscosity @ 40 C 3.1726 DIN EN ISO 3104
(mm2/s)
Distillation ( C) DIN EN ISO 3405
IBP 171.9
10% 226.0
30% 259.5
50% 283.6
70% 310.0
90% 341.5
95% 354.6
Final Boiling Point 363.8
The other fuel, Fuel B, consisted of Fuel A plus
0.5% w/w of a viscosity increasing component,
specifically viscosity index (VI) improving additive SV
(TM) 200, a divinylbenzene-polyisoprene star copolymer.
Table 2A illustrates the effect of the addition of the
viscosity increasing component.
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Table 2A
Fuel Properties Density @15 Viscosity @40
(kg/m3) 0m2.2/s)
Fuel A 838.2 3.779
Fuel B 838.5 4.910
Fuel A and Fuel B were successively used (in
respective "runs") to power a Mercedes Benz 0M646 common
rail diesel engine, having the properties shown in Table
2B under identical engine operating conditions for 10
hours.
Table 2B
Vehicle C 220 CDI, E 220, Construction
period CDI 2004-2007
Cylinder 4 DOHC
Displacement 2148 cm3
Power 110 kW @ 4200 lmin
Torque 340 Nm @ 2000 1/min
Compression 1 : 18
Engine management Bosch EDC
Emission standard EU 4
Injection-system Common Rail 3 - 1600 bar,Piezo-
Injector
Exhaust DPF, lambda probe, EGR
For each run, the engine was lubricated by
previously unused lubricant in the form of a mineral oil
based SAE 5W-30 low ash engine oil.
For both Fuel A and Fuel B, the engine operating
conditions were monitored at all times and kept as set
out in Table 3.
Table 3
Engine speed r/min 1500
Engine torque Nm 26
Start of Main Injection bTDC -10
(Crank Angle)
Start of Post Injection bTDC -38
(Crank Angle)
Quantity Post Injection MM3/stroke 10
(fuel)
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To shorten test duration, operating conditions were
chosen, for which the fuel dilution rate into the engine
oil is high, e.g. soot filter regeneration mode. The
engine was run continuously under-steady state conditions
with active post injection at low engine speed and engine
load, to simulate operating conditions for soot filter
regeneration (high exhaust gas temperature). For that
purpose the injection timings of the main and post
injections were delayed compared to normal operation. The
ratio of the injected fuel quantity between main and post
injection was 2/3.
During running of the engine with Fuel A and Fuel B,
every two hours oil samples were taken to analyse the
engine oil viscosity (at 100 C as per DIN EN 3104, VK
100). The results of the analysis are shown in Table 4.
For security reasons the engine was under idle conditions
when the oil samples were taken.
Table 4
Run Time (h) Fuel A OM 100) Fuel B 100)
(nm0s) (nme/s)
0 11.71 11.71
2 10.83 10.92
4 10.35 10.57
6 9.91 10.25
8 9.63 10.00
10 9.25 9.84
It was additionally noted that the amount of fuel in
the engine oil was substantially identical, greater than
10% w/w, after 10h in each run. This indicates that a
moderate level of fuel dilution occurred during both
runs.
The results of Table 4 show that, when using Fuel B
the viscosity of the lubricant is less affected by the
thinning effect of fuel dilution. The final viscosity,
after 10 hours testing differs from Fuel A by 0.58%.
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When using the base Fuel A, under the test
conditions the lubricant viscosity is so affected by fuel
dilution, that its end viscosity value is below 9.3
mm2/s, the defined limit between SAE 30 (the class in
which the oil belongs originally) and SAE 20. Being in an
SAE class lower, the oil is recommended to be changed. By
contrast, when using Fuel B which includes VI improving
additive, the lubricant remained within its initial SAE
viscosity range.
The use of VI improving additive therefore leads to
an increased oil drain interval (001). The use of the
viscosity increasing fuel component compensates the
dilution caused by fuel, and brings a longer ODI and a
better protection.
The presence of FAME (Fatty Acid Methyl Esters) in
diesel fuels tends to make the oil dilution effect even
worse, since FAME will be enriched in the lubricant;
Table 4 illustrates that this effect can be overcome
according to the invention.
Example 2
The viscometric properties of a lubricant in a
compression ignition engine powered vehicle were observed
whilst running the vehicle on two different fuels.
One of the fuels, Fuel A, consisted of only base
fuel made up of regular mineral sulphur free (<10 ppm)
winter diesel including 7%v FAME (with performance
additives).
The other fuel, Fuel B, consisted of Fuel A plus
0.2% w/w of a viscosity increasing component,
specifically viscosity index (VI) improving additive SV
(TM) 150, a polystyrene-polyisoprene di-block copolymer
having a tendency to form star-like clusters (micelles)
in solution.
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A pair of cars (VW-Golf 2.0 TDI from 2009) ran in
parallel for 25 000 km on the same routes and at the same
time. One car was fuelled with Fuel A and the other with
Fuel B to compare the impact on the lubricants (engine
oils), which were identical, previously unused mineral
oil based low ash SAE 5W-30.
The lubricant was regularly analysed for fuel
dilution and viscosity (at 100 C as per DIN EN 3104, VK
100).
After 25 000km, the car run on Fuel A is taken for a
further test (Transfer Test) in which it is powered by
Fuel B and driven for only about 2000 km. However, during
the Transfer Test, shortening test operating conditions
were chosen, for which the fuel dilution rate into the
engine oil is high, namely soot filter regeneration mode
(as in Example 1). 20 filter regenerations are triggered
followed by a short trip of driving on the road (100 km).
The engine oil was analysed for fuel dilution and
viscosity (at 100 C as per DIN EN 3104, VK 100). This
test represents a city driving cycle with short trips and
high load of the soot particle filter.
The viscosity and fuel dilution measurement results
are shown in Table 5.
Table 5
% Fuel VK 100 (rani2/s)-VK 100 (mm.2/s) VK 100
Dilution Golf without Golf with VI (mme/s) Golf
in VI improving improving from
lubricant additive additive Transfer
Test
0.5 11.82 11.82 11.91
3 10.82
3.4 10.7
4.3 10.72
4.5 10.26
5.4 10.47
5.5 10.04
5.8 9.69
6.4 9.68
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Table 5 (continued)
% Fuel 1VK 100 (=Os) VK 100 (mm2/s) VK 100
Dilution Golf without Golf with VI (mmOs) Golf
in va improving improving from
lubricant additive additive
Transfer
Test
6.6 9.31
8 9.15
7 9
7.5 9.12
7.9 9.75
8.4 9.56
9.6 9.33
13 8.50
As expected, the viscometrie performance of the
lubricant deteriorated in all three tests due to fuel
dilution. However, after running for 25 000 km in
comparable conditions, the impact of Fuel B on the
lubricant viscosity is 0.3 to 0.4 mm 2/s less than with
Fuel A. Thus Fuel B counteracts, more specifically
mitigages, the deterioration.
Furthermore, in the Transfer Test (which simulates a
city driving cycle or DPF regeneration), surprisingly,
Fuel B is able to counteract the deterioration in
viscometric performance even more effectively.
It is noted that if the Transfer Test had been
conducted over 25 000 km the influence (specifically the
counteracting effect) of Fuel B could be seen even more
clearly. With the same fuel dilution the viscosity of the
lubricant would decrease by about 2 mm2/s less and
clearly stay in the viscosity range of the SAE class.
In summary, Example 2 shows that low viscosity of
the lubricant and possible engine damage can be avoided
by the use of a viscosity increasing component,
(specifically a VI improving additive) in fuels. Such use
is particularly beneficial during a city driving cycle
and during DPF regeneration.
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Example 3
The viscometric properties of a lubricant in a
compression ignition engine were observed whilst running
the engine on three different fuels.
Fuel A consisted of a regular mineral diesel fuel
containing 5%v FAME; Fuel B consisted of Fuel A plus 5%v
of a Fischer-Tropsch derived extra heavy base oil, as
described in the Examples of NO 2009/080673; Fuel C
consisted of Fuel A plus 0.5% w/w of a viscosity
increasing component, specifically viscosity index (VI)
improving additive SV (TM) 200, a divinylbenzene-
polyisoprene star copolymer.
The three fuels were used in running an engine as
described in Example 1, wherein for each fuel the engine
operating conditions were kept as set out in Table 3 in
Example 1.
During running of the engine, every two hours engine
oil samples were taken to analyse the engine oil
viscosity VK100 (viscosity at 100 C as per DIN EN 3104).
The results of the analysis are shown in Table 6.
Table 6
Run Time (h) Fuel A CVK Fuel B Fuel C (fft
100) (mm2/s) 100) (mxn2/s) 100) (mm2/s)
0 11.71 11.71 11.71
2 10.83 10.95 10.92
4 10.35 10.53 10.57
6 9.91 10.14 10.25
8 9.63 9.77 10.00
10 9.25 9.44 9.84
It can be seen from the results of Table 6 that
while use of both fuels that incorporate a viscosity
increasing component reduces the deterioration of the
VK100 viscosity of the engine oil, Fuel C which
incorporates a far smaller amount of the polymeric VI
improving additive gives rise to a far reduced
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deterioration of viscosity than the significantly greater
amount of a Fischer-Tropsch heavy base oil viscosity
increasing component incorporated into Fuel B. It is
surprising that a smaller amount of polymer in Fuel C
provides a greater mitigating effect on the lubricating
oil viscosity deterioration.
