Note: Descriptions are shown in the official language in which they were submitted.
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FUEL COMPOSITIONS COMPRISING ESTER-COMPRISING POLYMERS
The present invention relates to fuel compositions which
comprise renewable raw materials, to the use of ester-
comprising polymers in fuel compositions, and to the processes
for operating diesel engines with fuel compositions of the
present invention.
Fuels are nowadays generally obtained from fossil sources.
However, these resources are limited, so that replacements are
being sought. Therefore, interest is rising in renewable raw
materials which can be used to produce fuels. A very
interesting replacement is in particular biodiesel fuels.
The term biodiesel is in many cases understood to mean a
mixture of fatty acid esters, usually fatty acid methyl esters
(FAMEs), with chain lengths of the fatty acid fraction of 14 to
24 carbon atoms with 0 to 3 double bonds. The higher the carbon
number and the fewer double bonds are present, the higher is
the melting point of the FAME. Typical raw materials are
vegetable oils (i.e. glycerides) such as rapeseed oils,
sunflower oils, soya oils, palm oils, coconut oils and, in
isolated cases, even used vegetable oils. These are converted
to the corresponding FAMEs by transesterification, usually with
methanol under basic catalysis.
In contrast to rapeseed oil methyl ester (RME), which is
frequently used in Europe and typically contains approx. 5%
C16:0+C18:0-FAME, palm oil methyl ester (PME) contains approx.
50% C16:0+C18.0-FAME. A similar high C16:0+C18:0 FAME content
is also possessed by the analogous derivatives of animal
tallows, for example beef tallow. Such a high wax content can
barely be influenced by polymeric flow improvers, which are
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typically added with an addition rate of up to 2%. In
comparison to rapeseed oil, palm oil can be obtained
with more than three times as high a crop yield per
hectare. This gives rise to immense economic
advantages. However, a disadvantage is the high pour
point of PME, which is about +12 C.
The use of pure biodiesel is an important aim from an
ecological point of view. However, these fuel oils
differ from conventional diesel fuel in important
properties. For instance, it is found that many seal
materials are attacked by biodiesel. Failure of the
seal materials leads inevitably to engine damage.
Moreover, in the case of direct-injection diesel
engines, fuel can get into the motor oil, which, owing
to the low chemical stability of vegetable oil esters,
can lead to deposits in the engine. Moreover, biodiesel
fuels exhibit different combustion owing to viscosity
differences compared to mineral diesel fuels, which
lead to different atomization behaviour. In the case of
modern diesel engines whose engine electronics are
adjusted specifically to fossil diesel fuel, problems
can therefore occur as a result of altered combustion
characteristics. In particular, the development of
economical and high-performance diesel engines which
are optimized for the use of fossil fuels has thus to
date been a hindrance for the use of pure biodiesel
fuel.
In addition to the utilization of 100% biodiesel
(usually RME) in Europe, mixtures of fossil diesel,
i.e. the middle distillate of crude oil distillation,
and biodiesel are therefore also of interest owing to
improved low-temperature properties and the better
combustion properties. Even as a blend, tax advantages
for the renewable raw material can be passed through to
the end user. In addition to these economic advantages,
the advantageous ecological balance for the renewable
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raw material biodiesel should of course also be
mentioned. For instance, 5% blends of biodiesel
(usually RME) with fossil diesel are being discussed in
Europe, and in Asia (South Korea, India, Indonesia,
Malaysia, Thailand, Philippines) and Australia even 20%
or higher blends (usually PME). In the case of the 20%
PME blend, moreover, significantly more wax-like chains
are present with approx. 10% C16:0+C18:0-FAME in the
fuel mixture than in the RME (approx. 5%). There is
also a comprehensive review on this subject in H.
Vogel, A. Bertola: Palmolmethylester - eine neue
vorteilhafte Biokomoponente fir Dieselkraftstoffe [Palm
Oil Methyl Ester - A New Advantageous Biological
Component for Diesel Fuels] Mineraloltechnik 50 (2005),
1.
Polyalkyl (meth)acrylates PA(M)As as pour point
improvers for mineral oils, both without M(M)A (for
example US 3 869 396 to Shell Oil Company) and with
M(M)A (for example US 5 312 884 to Rohm & Haas
Company), or else as pour point improvers for vegetable
oils (US 5 696 066 to Rohm & Haas Company), have been
established and described for some time. Use of these
polymers in fuel compositions which comprise at least
one diesel fuel of mineral origin and at least one
biodiesel fuel is, however, not described.
Moreover, the publication WO 01/40334 (RohMax Additives
GmbH) describes polyalkyl (meth)acrylates which can be
used in biodiesel fuels. This publication relates to
the particular preparation which imparts exceptional
properties to these polymers. However, there is a lack
of examples herein which relate to biodiesel fuels. In
addition, the advantageousness of polymers which have a
high content of certain ester-comprising repeat units
is not detailed. Furthermore, the low-temperature
properties achievable in lubricant oil by adding
additives are not necessarily applicable to mineral
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diesel fuels, since their boiling behaviour, their
viscosity and hence their composition of hydrocarbons
is different. Mixtures which comprise mineral diesel
fuel and biodiesel are not described in WO 01/40334.
Furthermore, hydroxy-functional PAMAs are known as flow
improvers for biodiesel in the literature (EP 1 032 620
to RohMax Additives GmbH). In the general part of the
publication EP 1 032 620, mixtures of fossil fuels with
biodiesel fuels are described, but no examples which
use such a mixture are adduced. In this context, it can
be taken from the document that a biodiesel fuel,
especially based on RME, which has particularly good
low-temperature properties should be provided. In the
case of use of mixtures with a high content of diesel
fuels of mineral origin, it is found that the
effectiveness of the polymers detailed in general terms
in EP 1 032 620 can be improved.
Flow improvers based on oil-soluble polymers for
mixtures of fossil diesel and biodiesel are also known
(WO 94/10267, Exxon Chemical Patents Inc.). However, in
the examples, only ethylene-vinyl acetate copolymers
(EVA) and copolymers which contain C12/CI4-alkyl
fumarate and vinyl acetate units are described. There
is no comprehensive and unambiguous description of
particular ester-comprising polymers in WO 94/10267.
In addition, a series of optimized EVA copolymers for
diesel-biodiesel mixtures have also become known (EP
1 541 662 to 664). For instance, EP 1 541 663 details
mixtures comprising 75% by volume of diesel fuel of
mineral origin and 25% by volume of biodiesel, which
comprise 150 ppm of poly(dodecyl methacrylate) and from
100 to 200 ppm of ethylene-vinyl acetate copolymer
(EVA). However, the use of EVA is described herein as
obligatory. EVA is, however, quite an expensive
additive. Accordingly, alternatives in which the use of
EVA can be dispensed with are desirable. There is no
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indication in EP 1 541 663 to the advantageousness of
particular ester-comprising polymers.
In view of the prior art, it is thus an object of the present
invention to provide fuel compositions which, with a property
profile which corresponds essentially to that of mineral
diesel fuel, comprise a maximum proportion of renewable raw
materials. At the same time, the fuel should in particular
have very good low-temperature properties. In addition, the
combustion behaviour, especially the behaviour of the fuel in
relation to the engine control characteristics, should as far
as possible correspond to the behaviour of mineral diesel
fuel. Furthermore, it was an object of the present invention
to provide a fuel which has a high stability towards
oxidation. In addition, the fuel should have a maximum cetane
number. At the same time, the novel fuels should be simple
and inexpensive to produce. Furthermore, it was an object of
the present invention to provide the processes for operating
diesel engines which have high environmental compatibility.
This object and further objects which are not stated
explicitly but are immediately derivable or discernible from
the connections discussed herein by way of introduction, are
achieved by a fuel composition comprising:
20.0 to 97.95% by weight of at least one diesel fuel of
mineral origin,
2.0 to 79.95% by weight of at least one biodiesel fuel, and
0.05 to 5% by weight of at least one ester-comprising polymer
wherein the ester-comprising polymer comprises units of the
following polymerized monomers
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0.1 to 30% by weight of one or more ethylenically unsaturated
ester compounds of the formula (I):
R3\
(1),
R2 0
in which R is hydrogen or methyl, Rl is a linear or branched
alkyl radical having 1 to 6 carbon atoms, R2 and R2 are each
independently hydrogen or a group of the formula -COOR' in
which R' is hydrogen or an alkyl group having 1 to 6 carbon
atoms,
to 98% by weight of one or more ethylenically unsaturated
ester compounds of the formula (II):
R6OR4
R5 0
in which R is hydrogen or methyl, R4 is a linear or branched
alkyl radical having 7 to 15 carbon atoms, R6 and R6 are each
independently hydrogen or a group of the formula -COOR" in
which R" is hydrogen or an alkyl group having 7 to 15 carbon
atoms, and
0.1 to 80% by weight of one or more ethylenically unsaturated
ester compounds of the formula (III):
R9 OR7
(III),
R8 0
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in which R is hydrogen or methyl, R7 is a linear or branched
alkyl radical having 16 to 40 carbon atoms, R8 and R9 are
each independently hydrogen or a group of the formula -
COOR"' in which R'" is hydrogen or an alkyl group having 16
to 40 carbon atoms.
Also disclosed is a process for operating a diesel engine and
the use of ester-comprising polymers as flow improvers.
By virtue of a fuel composition containing 20% by weight of
diesel fuel of mineral origin and from 0.05 to 5% by weight
of at least one ester-comprising polymer which comprises
repeat units which are derived from ester monomers having 16
to 40 carbon atoms in the
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alcohol radical, and repeat units which are derived
from ester monomers having 7 to 15 carbon atoms in the
alcohol radical, it is surprisingly possible to provide
a fuel composition which comprises at least one diesel
fuel of mineral origin and at least one biodiesel fuel,
which, with a property profile which is very similar to
that of mineral diesel fuel, comprises a very high
proportion of renewable raw materials.
At the same time, the inventive fuel compositions can
achieve a series of further advantages. These include:
The inventive fuel compositions can be used in
conventional diesel engines without the seal materials
used customarily being attacked.
Furthermore, modern diesel engines can be operated with
the fuel of the present invention without the engine
control having to be altered.
Preferred fuel compositions of the present invention
have a particularly high cetane number which can be
improved in particular by the use of biodiesel fuels
having a high proportion of long-chain saturated fatty
acids.
In addition, the present invention is aimed at the use
of very oxidation-stable biodiesel fuels. This allows
reduction of the formation of deposits in the engine,
which can lead to a low overall performance of the
engine.
Moreover, very high fractions of palm oil alkyl esters
can be used in the fuels. For ecological and economic
reasons, palm oil is preferred over the customarily
used rapeseed oil. For instance, the crop yield in the
production of palm oil is significantly higher than
that of rapeseed oil. Moreover, to obtain rape, very
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large amounts of ecologically controversial chemicals,
especially fertilizers and crop protection
compositions, are used. At the same time, rape is not
self-compatible in production and has to be cultivated
in a crop rotation system, in which case cultivation of
rape in the same field is possible only every 3 to 5
years. For this reason, a further increase in rape
production is difficult.
However, palm oil alkyl esters have a significantly
higher cloud point (approx. +13 C in the case of the
methyl ester) in comparison to rapeseed oil alkyl
esters; the cloud point of rapeseed oil alkyl ester is
significantly lower (approx. -7 C in the case of the
methyl ester). In a particular aspect, the present
invention thus enables the use of particularly high
proportions of palm oil alkyl esters for producing fuel
compositions without the low-temperature properties
assuming impermissible values.
The fuel composition of the present invention comprises
diesel fuel of mineral origin, i.e. diesel, gas oil or
diesel oil. Mineral diesel fuel is widely known per se
and is commercially available. This is understood to
mean a mixture of different hydrocarbons which is
suitable as a fuel for a diesel engine. Diesel can be
obtained as a middle distillate, in particular by
distillation of crude oil. The main constituents of the
diesel fuel preferably include alkanes, cycloalkanes
and aromatic hydrocarbons having about 10 to 22 carbon
atoms per molecule.
Preferred diesel fuels of mineral origin boil in the
range of 120 to 450 C, more preferably 170 and 390 C.
Preference is given to using those middle distillates
which contain 0.05% by weight of sulphur and less, more
preferably less than 350 ppm of sulphur, in particular
less than 200 ppm of sulphur and in special cases less
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than 50 ppm of sulphur, for example less than 10 ppm of
sulphur. They are preferably those middle distillates
which have been subjected to refining under
hydrogenating conditions, and which therefore contain
only small proportions of polyaromatic and polar
compounds. They are preferably those middle distillates
which have 95% distillation points below 370 C, in
particular below 350 C and in special cases below
330 C. Synthetic fuels, as obtainable, for example, by
the Fischer-Tropsch process, are also suitable as
diesel fuels of mineral origin.
The kinematic viscosity of diesel fuels of mineral
origin to be used with preference is in the range of
0.5 to 8 mm2/s, more preferably 1 to 5 mm2/s and
especially preferably 1.5 to 3 mm2/s, measured at 40 C
to ASTM D 445.
The fuel compositions of the present invention comprise
at least 20% by weight, in particular at least 30% by
weight, preferably at least 50% by weight, more
preferably at least 70% by weight and most preferably
at least 80% by weight of diesel fuels of mineral
origin.
In addition, the present fuel composition comprises at
least one biodiesel fuel component. Biodiesel fuel is a
substance, especially an oil, which is obtained from
vegetable or animal material or both, or a derivative
thereof which can be used in principle as a replacement
for mineral diesel fuel.
In a preferred embodiment, the biodiesel fuel, which is
frequently also referred to as "biodiesel" or "biofuel"
comprises fatty acid alkyl esters formed from fatty
acids having preferably 6 to 30, more preferably 12 to
24 carbon atoms, and monohydric alcohols having 1 to 4
carbon atoms. In many cases, some of the fatty acids
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may contain one, two or three double bonds. The
monohydric alcohols include in particular methanol,
ethanol, propanol and butanol, methanol being
preferred.
Examples of oils which derive from animal or vegetable
material and which can be used in accordance with the
invention are palm oil, rapeseed oil, coriander oil,
soya oil, cottonseed oil, sunflower oil, castor oil,
olive oil, groundnut oil, corn oil, almond oil, palm
kernel oil, coconut oil, mustardseed oil, oils which
are derived from animal tallow, especially beef tallow,
bone oil, fish oils and used cooking oils. Further
examples include oils which derive from cereal, wheat,
jute, sesame, rice husks, jatropha, arachis oil and
linseed oil. The fatty acid alkyl esters to be used
with preference may be obtained from these oils by
processes known in the prior art.
Preference is given in accordance with the invention to
highly C16:0/C18:0-glyceride-containing oils, such as
palm oils and oils which are derived from animal
tallow, and also derivatives thereof, especially the
palm oil alkyl esters which are derived from monohydric
alcohols. Palm oil (also: palm fat) is obtained from
the fruit flesh of the palm fruits. The fruits are
sterilized and pressed. Owing to their high carotene
content, fruits and oils have an orange-red colour
which is removed in the refining. The oil may contain
up to 80% C18:0-glyceride.
Particularly suitable biodiesel fuels are lower alkyl
esters of fatty acids. Useful examples here are
commercial mixtures of the ethyl, propyl, butyl and
especially methyl esters of fatty acids having 6 to 30,
preferably 12 to 24, more preferably 14 to 22 carbon
atoms, for example of caprylic acid, capric acid,
lauric acid, myristic acid, palmitic acid, margaric
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acid, stearic acid, arachic acid, behenic acid,
lignoceric acid, cerotic acid, palmitoleic acid,
stearic acid, oleic acid, elaidic acid, petroselic
acid, ricinoleic acid, elaeostearic acid, linoleic
acid, linolenic acid, eicosanoic acid, gadoleic acid,
docosanoic acid or erucic acid.
In a particular aspect of the present invention, a
biodiesel fuel is used which comprises preferably at
least 30% by weight, more preferably at least 35% by
weight and most preferably at least 40% by weight of
saturated fatty acid esters which have at least 16
carbon atoms in the fatty acid radical. These include
in particular the esters of palmitic acid and stearic
acid.
For reasons of cost, these fatty acid esters are
generally used as a mixture. Biodiesel fuels usable in
accordance with the invention preferably have an iodine
number of at most 150, in particular at most 125, more
preferably at most 70 and most preferably at most 60.
The iodine number is a measure known per se for the
content in a fat or oil of unsaturated compounds, which
can be determined to DIN 53241-1. As a result of this,
the fuel compositions of the present invention form a
particularly low level of deposits in the diesel
engines. Moreover, these fuel compositions have
particularly high cetane numbers.
In general, the fuel compositions of the present
invention may comprise at least 0.5% by weight, in
particular at least 3% by weight, preferably at least
5% by weight and more preferably at least 15% by weight
of biodiesel fuel.
In addition, the fuel composition of the present
invention comprises 0.05 to 5% by weight, preferably
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0.08 to 3% by weight and more preferably 0.1 to 1.0% by
weight of at least one ester-comprising polymer.
In the present context, ester-comprising polymers are
understood to mean polymers which are obtainable by
polymerizing monomer compositions which comprise
ethylenically unsaturated compounds having at least one
ester group, which are referred to hereinafter as ester
monomers. Accordingly, these polymers contain ester
groups as part of the side chain. These polymers
include in particular polyalkyl (meth)acrylates
(PAMAs), polyalkyl fumarates and/or polyalkyl maleates.
Ester monomers are known per se. These include in
particular (meth)acrylates, maleates and fumarates
which may have different alcohol radicals. The term
(meth)acrylates encompasses methacrylates and
acrylates, and also mixtures of the two. These monomers
are widely known. In this context the alkyl radical may
be linear, cyclic or branched. Moreover, the alkyl
radical may have known substituents.
The ester-comprising polymers contain repeat units
which are derived from ester monomers having 16 to 40
carbon atoms in the alcohol radical, and repeat units
which are derived from ester monomers having 7 to 15
carbon atoms in the alcohol radical.
The term "repeat unit" is widely known in the technical
field. The present ester-comprising polymers may
preferably be obtained via free-radical polymerization
of monomers, the ATRP, RAFT and NMP processes which
will be detailed later being included in the free-
radical processes in the context of the invention,
without any intention that this should impose a
restriction. In the polymerization, double bonds are
opened up to form covalent bonds. Accordingly, the
repeat unit is formed from the monomers used.
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The ester-comprising polymer may contain 5 to 99.9% by
weight, in particular 20 to 98% by weight, preferably
30 to 95% by weight and most preferably 70 to 92% by
weight of repeat units which are derived from ester
monomers having 7 to 15 carbon atoms in the alcohol
radical.
In a particular aspect, the ester-comprising polymer
may contain 0.1 to 80% by weight, preferably 0.5 to
60% by weight, more preferably 2 to 50% by weight and
most preferably 5 to 20% by weight of repeat units
which are derived from ester monomers having 16 to 40
carbon atoms in the alcohol radical.
In addition, the ester-comprising polymer may contain
0.1 to 30% by weight, preferably 0.5 to 20% by weight,
of repeat units which are derived from ester monomers
having 1 to 6 carbon atoms in the alcohol radical.
The ester-comprising polymer comprises preferably at
least 40% by weight, more preferably at least 60% by
weight, especially preferably at least 80% by weight
and most preferably at least 95% by weight of repeat
units which are derived from ester monomers.
Mixtures from which the inventive ester-comprising
polymers are obtainable may contain 0 to 40% by weight,
preferably 0.1 to 30% by weight, in particular 0.5 to
20% by weight, of one or more ethylenically unsaturated
ester compounds of the formula (I)
R3oR 1
R2 0 (I)
in which R is hydrogen or methyl, Rl is a linear or
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branched alkyl radical having 1 to 6 carbon atoms, R2
and R2 are each independently hydrogen or a group of
the formula -COOR' in which R' is hydrogen or an alkyl
group having 1 to 6 carbon atoms.
Examples of component (I) include
(meth)acrylates, fumarates and maleates which derive
from saturated alcohols, such as methyl (meth)acrylate,
ethyl (meth)acrylate, n-propyl
(meth)acrylate,
isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-
butyl (meth)acrylate and pentyl (meth)acrylate, hexyl
(meth)acrylate;
cycloalkyl (meth)acrylates such as cyclopentyl
(meth)acrylate, cyclohexyl (meth)acrylate;
(meth)acrylates which derive from unsaturated alcohols,
such as 2-propynyl (meth)acrylate, allyl (meth)acrylate
and vinyl (meth)acrylate.
The compositions to be polymerized preferably contain
10 to 98% by weight, in particular 20 to 95% by weight,
of one or more ethylenically unsaturated ester
compounds of the formula (II)
R6 (II)
R5 0
in which R is hydrogen or methyl, R4 is a linear or
branched alkyl radical having 7 to 15 carbon atoms, R5
and R6 are each independently hydrogen or a group of
the formula -COOP)' in which R" is hydrogen or an alkyl
group having 7 to 15 carbon atoms.
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Examples of component (II) include:
(meth)acrylates, fumarates and maleates which derive
from saturated alcohols, such as 2-ethylhexyl
(meth)acrylate, heptyl (meth)acrylate, 2-
tert-
butylheptyl(meth)acrylate, octyl (meth)acrylate, 3-iso-
propylheptyl (meth)acrylate, nonyl (meth)acrylate,
decyl (meth)acrylate, undecyl (meth)acrylate, 5-methyl-
undecyl (meth)acrylate, dodecyl
(meth)acrylate,
2-methyldodecyl (meth)acrylate, tridecyl
(meth)-
acrylate, 5-methyltridecyl (meth)acrylate, tetradecyl
(meth)acrylate, pentadecyl (meth)acrylate;
(meth)acrylates which derive from unsaturated alcohols,
for example oleyl (meth)acrylate;
cycloalkyl (meth)acrylates such as 3-vinylcyclohexyl
(meth)acrylate, bornyl (meth)acrylate; and the
corresponding fumarates and maleates.
In addition, preferred monomer compositions contain 0.1
to 80% by weight, preferably 0.5 to 60% by weight, more
preferably 2 to 50% by weight and most preferably 5 to
20% by weight of one or more ethylenically unsaturated
ester compounds of the formula (III)
R9 ro7
R8 0
in which R is hydrogen or methyl, R7 is a linear or
branched alkyl radical having 16 to 40, preferably 16
to 30, carbon atoms, R8 and R9 are each independently
hydrogen or a group of the formula -COOP!'' in which
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R"' is hydrogen or an alkyl group having 16 to 40,
preferably 16 to 30, carbon atoms.
Examples of component (III) include (meth)acrylates
which derive from saturated alcohols, such as hexadecyl
(meth)acrylate, 2-methylhexadecyl
(meth)acrylate,
heptadecyl (meth)acrylate, 5-
isopropylheptadecyl
(meth)acrylate, 4-tert-butyloctadecyl (meth)acrylate,
5-ethyloctadecyl (meth)acrylate, 3-isopropyloctadecyl
(meth)acrylate, octadecyl (meth)acrylate, nonadecyl
(meth)acrylate, eicosyl (meth)acrylate, cetyleicosyl
(meth)acrylate, stearyleicosyl (meth)acrylate, docosyl
(meth)acrylate and/or eicosyltetratriacontyl (meth)-
acrylate;
cycloalkyl (meth)acrylates such as 2,4,5-tri-t-buty1-
3-vinylcyclohexyl (meth)acrylate, 2,3,4,5-
tetra-
t-butylcyclohexyl (meth)acrylate;
and the corresponding fumarates and maleates.
The ester compounds having a long-chain alcohol
radical, especially the components (II) and (III), can
be obtained, for example, by reacting (meth)acrylates,
fumarates, maleates and/or the corresponding acids with
long-chain fatty alcohols, which generally gives a
mixture of esters, for example (meth)acrylates with
various long-chain alcohol radicals. These fatty
alcohols include Oxo Alcohol 7911 and Oxo Alcohol
7900, Oxo Alcohol 1100; Alfol 610, Alfol 810, Lial
125 and Nafol types (Sasol); Alphanol 79 (ICI);
Epal 610 and Epal0 810 (Afton); Linevol 79, Linevol0
911 and Neodol0 25E (Shell AG); DehydadO, Hydrenol
and Lorol types (Cognis); Acropol0 35 and Exxal 10
(Exxon Chemicals); Kalcol 2465 (Kao Chemicals).
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Among the ethylenically unsaturated ester compounds,
particular preference is given to the (meth)acrylates
over the maleates and fumarates, i.e. R2, R3, R5, R6,
R8 and R9 of the formulae (I), (II) and (III) are each
hydrogen in particularly preferred embodiments.
The weight ratio of ester monomers of the formula (II)
to the ester monomers of the formula (III) may be
within a wide range. The ratio of ester compounds of
the formula (II) which contain 7 to 15 carbon atoms in
the alcohol radical to the ester compounds of the
formula (III) which contain 16 to 40 carbon atoms in
the alcohol radical is preferably in the range of 50:1
to 1:30, more preferably in the range of 10:1 to 1:3,
especially preferably 5:1 to 1:1.
Component (IV) comprises in particular ethylenically
unsaturated monomers which can be copolymerized with
the ethylenically unsaturated ester compounds of the
formulae (I), (II) and/or (III).
However, particularly suitable comonomers for
polymerization according to the present invention are
those which correspond to the formula:
R1*
R2*
R3* R4*
(IV)
in which RI* and le* are each independently selected
from the group consisting of hydrogen, halogens, CN,
linear or branched alkyl groups having 1 to 20,
preferably 1 to 6 and more preferably 1 to 4, carbon
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atoms which may be substituted by 1 to (2n+1) halogen
atoms, where n is the number of carbon atoms of the
alkyl group (for example CF2), a,-unsaturated linear
or branched alkenyl or alkynyl groups having 2 to 10,
preferably 2 to 6 and more preferably 2 to 4, carbon
atoms which may be substituted by 1 to (2n-1) halogen
atoms, preferably chlorine, where n is the number of
carbon atoms of the alkyl group, for example CH2=CC1-,
cycloalkyl groups having 3 to 8 carbon atoms which may
be substituted by 1 to (2n-1) halogen atoms, preferably
chlorine, where n is the number of carbon atoms of the
cycloalkyl group; C(=Y*)R", C(=Y*)NR6*R7*, Y*C(=Y*)R5*,
SOR5*, SO2R5*, OSO2R5*, NR8*S02R5*, PR5*2, P(=Y*)R5*2, Y*PR5*2,
Y*P(=Y*)R5*2, NR"2 which may be quaternized with an
additional R", aryl or heterocyclyl group, where Y* may
be NR", S or 0, preferably 0; R" is an alkyl group
having from 1 to 20 carbon atoms, an alkylthio having 1
to 20 carbon atoms, OR15 (1215 is hydrogen or an alkali
metal), alkoxy of 1 to 20 carbon atoms, aryloxy or
heterocyclyloxy; R6* and R" are each independently
hydrogen or an alkyl group having 1 to 20 carbon atoms,
or R" and R" together may form an alkylene group
having 2 to 7, preferably 2 to 5 carbon atoms, in which
case they form a 3- to 8-membered, preferably 3- to 6-
membered, ring, and R" is hydrogen, linear or branched
alkyl or aryl groups having 1 to 20 carbon atoms;
R" and 124* are independently selected from the group
consisting of hydrogen, halogen (preferably fluorine or
chlorine), alkyl groups having 1 to 6 carbon atoms and
COORS* in which R" is hydrogen, an alkali metal or an
alkyl group having 1 to 40 carbon atoms, or R" and R4*
together may form a group of the formula (CH2)n, which
may be substituted by 1 to 2n' halogen atoms or C1 to C4
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alkyl groups, or form the formula C(=0)-Y*-C(=0) where
n' is 2 to 6, preferably 3 or 4, and Y* is as defined
above; and where at least 2 of the RI*, R.2*, R3* and Fe*
radicals are hydrogen or halogen.
The preferred comonomers (IV) include hydroxyalkyl
(meth)acrylates such as 3-hydroxypropyl methacrylate,
3,4-dihydroxybutyl methacrylate, 2-
hydroxyethyl
methacrylate, 2-hydroxypropyl methacrylate, 2,5-
dimethy1-1,6-hexanediol (meth)acrylate,1,10-decanediol
(meth)acrylate; aminoalkyl (meth)acrylates such as N-
(3-dimethylaminopropyl)methacrylamide, 3-diethylamino-
pentyl methacrylate, 3-
dibutylaminohexadecyl
(meth)acrylate; nitriles of (meth)acrylic acid and
other nitrogen-containing methacrylates, such as N-
(methacryloyloxyethyl)diisobutyl ketimine, N-
(methacryloyloxyethyl)dihexadecyl ketimine,
meth-
cryloylamidoacetonitrile,2-methacryloyloxyethylmethyl-
cyanamide, cyanomethyl methacrylate;
aryl
(meth)acrylates such as benzyl methacrylate or phenyl
methacrylate in which the aryl radicals may each be
unsubstituted or up to tetrasubstituted; carbonyl-
containing methacrylates such as 2-carboxyethyl
methacrylate, carboxymethyl
methacrylate,
oxazolidinylethyl methacrylate, N-(methacryloyloxy)-
formamide, acetonyl methacrylate, N-
methacryl-
oylmorpholine, N-methacryloy1-2-pyrrolidinone, N-(2-
methacryloyloxyethyl)-2-pyrrolidinone, N-(3-methacryl-
oyloxypropy1)-2-pyrrolidinone, N-(2-
methacryl-
oyloxypentadecy1)-2-pyrrolidinone, N-(3-
methacryl-
oyloxyheptadecy1)-2-pyrrolidinone; glycol
dimeth-
acrylates such as 1,4-butanediol methacrylate, 2-
butoxyethyl methacrylate, 2-
ethoxyethoxymethyl
methacrylate, 2-ethoxyethyl methacrylate; methacrylates
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of ether alcohols, such as tetrahydrofurfuryl
methacrylate, vinyloxyethoxyethyl
methacrylate,
methoxyethoxyethyl methacrylate, 1-
butoxypropyl
methacrylate, 1-methyl-(2-vinyloxy)ethyl methacrylate,
cyclohexyloxymethyl methacrylate, methoxymethoxyethyl
methacrylate, benzyloxymethyl methacrylate, furfuryl
methacrylate, 2-butoxyethyl methacrylate, 2-
ethoxyethoxymethyl methacrylate, 2-
ethoxyethyl
methacrylate, allyloxymethyl
methacrylate, 1-
ethoxybutyl methacrylate, methoxymethyl methacrylate,
1-ethoxyethyl methacrylate, ethoxymethyl methacrylate;
methacrylates of halogenated alcohols, such as 2,3-
dibromopropyl methacrylate, 4-bromophenyl methacrylate,
1,3-dichloro-2-propyl methacrylate, 2-
bromoethyl
methacrylate, 2-iodoethyl methacrylate, chloromethyl
methacrylate; oxiranyl methacrylates such as
2,3-epoxybutyl methacrylate, 3,4-
epoxybutyl
methacrylate, 10,11-epoxyundecyl methacrylate, 10,11-
epoxyhexadecyl methacrylate, 2,3-
epoxycyclohexyl
methacrylate; glycidyl methacrylate;
phosphorus-, boron- and/or silicon-containing meth-
acrylates such as
2-(dimethylphosphato)propyl methacrylate,
2-(ethylenephosphito)propyl methacrylate,
dimethylphosphinomethyl methacrylate,
dimethylphosphonoethyl methacrylate,
diethylmethacryloyl phosphonate,
dipropylmethacryloyl phosphate, 2-(dibutylphosphono)-
ethyl methacrylate,
2,3-butylenemethacryloylethyl borate,
methyldiethoxymethacryloylethoxysilane,
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diethylphosphatoethyl methacrylate;
vinyl halides, for example vinyl chloride, vinyl
fluoride, vinylidene chloride and vinylidene fluoride;
heterocyclic (meth)acrylates, such as 2-(1-
imidazolyl)ethyl (meth)acrylate, 2-(4-morpholinyl)ethyl
(meth)acrylate and 1-(2-
methacryloxyethyl)-2-
pyrrolidinone;
vinyl esters such as vinyl acetate;
styrene, substituted styrenes having an alkyl
substituent in the side chain, for example a-methyl-
styrene and a-ethylstyrene, substituted styrenes having
an alkyl substituent on the ring, such as vinyltoluene
and p-methylstyrene, halogenated styrenes, for example
monochlorostyrenes, dichlorostyrenes, tribromostyrenes
and tetrabromostyrenes;
heterocyclic vinyl compounds such as 2-vinylpyridine,
3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-
4-vinylpyridine, 2,3-dimethy1-5-vinylpyridine, vinyl-
pyrimidine, vinylpiperidine, 9-vinylcarbazole, 3-vinyl-
carbazole, 4-vinylcarbazole, 1-
vinylimidazole,
2-methyl-1-vinylimidazole, N-vinylpyrrolidone, 2-vinyl-
pyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine,
N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane,
vinylfuran, vinylthiophene, vinylthiolane, vinyl-
thiazoles and hydrogenated vinylthiazoles, vinyl-
oxazoles and hydrogenated vinyloxazoles;
vinyl and isoprenyl ethers;
maleic acid and maleic acid derivatives different from
those mentioned under (I), (II) and (III), for example
maleic anhydride, methylmaleic anhydride, maleimide,
methylmaleimide;
fumaric acid and fumaric acid derivatives different
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from those mentioned under (I), (II) and (III).
The proportion of comonomers (IV) can be varied
depending on the use and property profile of the
polymer. In general, this proportion may be in the
range from 0 to 60% by weight, preferably from 0.01 to
20% by weight and more preferably from 0.1 to 10% by
weight. Owing to the combustion properties and for
ecological reasons, the proportion of the monomers
which comprise aromatic groups, heteroaromatic groups,
nitrogen-containing groups,
phosphorus-containing
groups and sulphur-containing groups should be
minimized. The proportion of these monomers can
therefore be restricted to 1% by weight, in particular
0.5% by weight and preferably 0.01% by weight.
The comonomers (IV) and the ester monomers of the
formulae (I), (II) and (III) can each be used
individually or as mixtures.
Surprisingly, ester-comprising polymers have a better
activity in mixtures of mineral diesel fuel and
biodiesel fuel which comprise merely a small
proportion, if any, of units which are derived from
hydroxyl-containing monomers. This is especially true
of biodiesel fuels which have a high proportion of
saturated fatty acids which have at least 16 carbon
atoms in the acid radical. Accordingly, ester-
comprising polymers to be used with preference in the
inventive fuel mixtures preferably contain at most 5%
by weight, preferably at most 3% by weight, more
preferably at most 1% by weight and most preferably at
most 0.1% by weight of units which are derived from
hydroxyl-containing monomers. These
include
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hydroxyalkyl (meth)acrylates and vinyl alcohols. These
monomers have been detailed above.
Similarly, ester-comprising polymers have a better
activity in mixtures of mineral diesel fuel and
biodiesel fuel which comprise only a small proportion,
if any, of repeat units which derive from monomers
having oxygen-containing alcohol radicals of the
formula
(IV'
R12 OR10
(1V),
R11 6
where
R is hydrogen or methyl, RI is an alkyl radical which
is substituted by an OH group and has 2 to 20 carbon
atoms, or an alkoxylated radical of the formula (V)
R13 R14
-E CH - CH-0+ R'5 (V),
in which 122-3 and RI4 are each independently hydrogen or
methyl, RI5 is hydrogen or an alkyl radical having 1 to
20 carbon atoms, and n is an integer of 1 to 30,
Ril and RI2 are each independently hydrogen or a group
of the formula -COOR"" in which R'"' is hydrogen or
an alkyl radical which is substituted by an OH group
and has 2 to 20 carbon atoms, or an alkoxylated radical
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of the formula (V)
R13 R14
-4 CH - CH-0-1- R15 (V),
in which R13 and R14 are each independently hydrogen or
methyl, R15 is hydrogen or an alkyl radical having 1 to
20 carbon atoms, and n is an integer of 1 to 30.
Ester-comprising polymers to be used with preference
have a thickening efficiency TE100 in the range of 4.0
to 50 mm2/s, preferably 7.5 to 29 mm2/s. The thickening
efficiency (TE100) is determined at 100 C in a 150N
reference oil (KV100 = 5.42 mm2/s, KV40 = 31.68 mm2/s
and VI = 103), using 5% by weight of polymer. The
designations KV100 and KV40 describe the kinematic
viscosity of the oil at 100 C and 40 C respectively to
ASTM D445, the abbreviation VI the viscosity index
determined to ASTM D 2270.
The ester-comprising polymers to be used in accordance
with the invention may generally have a molecular
weight in the range of 1000 to 1 000 000 g/mol,
preferably in the range of 25 000 to 700 000 g/mol and
more preferably in the range of 40 000 to 600 000 g/mol
and most preferably in the range of 60 000 to 300
000 g/mol, without any intention that this should
impose a restriction. These values are based on the
weight-average molecular weight M, of the polydisperse
polymers in the composition. This parameter can be
determined by GPC.
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The preferred copolymers which can be obtained by
polymerizing unsaturated ester compounds preferably
have a polydispersity Mw/Mn in the range of 1 to 10,
more preferably 1.05 to 6.0 and most preferably 1.2 to
5Ø This parameter can be determined by GPC.
The architecture of the ester-comprising polymers is
not critical for many applications and properties.
Accordingly, the ester-comprising polymers may be
random copolymers, gradient copolymers, block
copolymers and/or graft copolymers.
Block copolymers and gradient copolymers can be
obtained, for example, by altering the monomer
composition discontinuously during the chain growth.
The blocks derived from ester compounds of the formulae
(I), (II) and/or (III) preferably have at least 30
monomer units.
The preparation of the polyalkyl esters from the above-
described compositions is known per se. Thus, these
polymers can be obtained in particular by free-radical
polymerization and related processes, for example ATRP
(= Atom Transfer Radical Polymerization) or RAFT (=
Reversible Addition Fragmentation Chain Transfer).
Customary free-radical polymerization is described,
inter alia, in Ullmann's Encyclopedia of Industrial
Chemistry, Sixth Edition. In general, a polymerization
initiator and a chain transferrer are used for this
purpose. The usable initiators include the azo
initiators widely known in the technical field, such as
AIBN and 1,1-azobiscyclohexanecarbonitrile, and also
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peroxy compounds such as methyl ethyl ketone peroxide,
acetylacetone peroxide, dilauryl peroxide, tert-butyl
per-2-ethylhexanoate, ketone peroxide, tert-butyl
peroctoate, methyl isobutyl ketone peroxide,
cyclohexanone peroxide, dibenzoyl peroxide, tert-butyl
peroxybenzoate, tert-butyl peroxyisopropylcarbonate,
2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane,
tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-
3,5,5-trimethylhexanoate, dicumyl peroxide, 1,1-
bis(tert-butylperoxy)cyclohexane, 1,1-bis(tert-
butylperoxy)-3,3,5-trimethylcyclohexane, cumyl
hydroperoxide, tert-butyl hydroperoxide, bis(4-tert-
butylcyclohexyl) peroxydicarbonate, mixtures of two or
more of the aforementioned compounds with one another,
and mixtures of the aforementioned compounds with
compounds which have not been mentioned but can
likewise form free radicals. Suitable chain
transferrers are in particular oil-soluble mercaptans,
for example dodecyl mercaptan or 2-mercaptoethanol, or
else chain transferrers from the class of the terpenes,
for example terpineols.
The ATRP process is known per se. It is assumed that it
is a "living" free-radical polymerization, without any
intention that this should restrict the description of
the mechanism. In these processes, a transition metal
compound is reacted with a compound which has a
transferable atom group. This transfers the
transferable atom group to the transition metal
compound, which oxidizes the metal. This reaction forms
a radical which adds onto ethylenic groups. However,
the transfer of the atom group to the transition metal
compound is reversible, so that the atom group is
transferred back to the growing polymer chain, which
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forms a controlled polymerization system. The structure
of the polymer, the molecular weight and the molecular
weight distribution can be controlled correspondingly.
This reaction is described, for example, by J S. Wang,
et al., J. Am. Chem. Soc., vol. 117, p. 5614-5615
(1995), by Matyjaszewski, Macromolecules, vol. 28, p.
7901-7910 (1995). In addition, the patent applications
WO 96/30421, WO 97/47661, WO 97/18247, WO 98/40415 and
WO 99/10387 disclose variants of the ATRP explained
above.
In addition, the inventive polymers may be obtained,
for example, also via RAFT methods. This process is
presented in detail, for example, in WO 98/01478 and WO
2004/083169, to which reference is made explicitly for
the purposes of disclosure.
In addition, the inventive polymers are also obtainable
by NMP processes (nitroxide-mediated polymerization),
which is described, inter alia, in US 4581429.
These methods are described comprehensively, in
particular with further references, inter alia, in K.
Matyjazewski, T.P. Davis, Handbook of Radical
Polymerization, Wiley Interscience, Hoboken 2002, to
which reference is made explicitly for the purposes of
disclosure.
The polymerization may be carried out at standard
pressure, reduced pressure or elevated pressure. The
polymerization temperature too is uncritical. However,
it is generally in the range of -20 - 200 C,
preferably 0 - 130 C and more preferably 60 - 120 C.
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The polymerization may be carried out with or without
solvent. The term solvent is to be understood here in a
broad sense.
The polymerization is preferably carried out in a
nonpolar solvent. These include hydrocarbon solvents,
for example aromatic solvents such as toluene, benzene
and xylene, saturated hydrocarbons, for example
cyclohexane, heptane, octane, nonane, decane, dodecane,
which may also be present in branched form. These
solvents may be used individually and as a mixture.
Particularly preferred solvents are mineral oils,
diesel fuels of mineral origin, natural vegetable and
animal oils, biodiesel fuels and synthetic oils (e.g.
ester oils such as dinonyl adipate), and also mixtures
thereof. Among these, very particular preference is
given to mineral oils and mineral diesel fuels.
The inventive fuel composition may comprise further
additives in order to achieve specific solutions to
problems. These additives include dispersants, for
example wax dispersants and dispersants for polar
substances, demulsifiers, defoamers,
lubricity
additives, antioxidants, cetane number improvers,
detergents, dyes, corrosion inhibitors and/or
odourants.
For example, the inventive fuel composition may
comprise ethylene copolymers which are described, for
example, in EP-A-1 541 663. These ethylene copolymers
may contain 8 to 21 mol% of one or more vinyl and/or
(meth)acrylic esters and 79 to 92% by weight of
ethylene. Particular preference is given to ethylene
copolymers containing 10 to 18 mol% and especially 12
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to 16 mol% of at least one vinyl ester. Suitable vinyl
esters derive from fatty acids having linear or
branched alkyl groups having 1 to 30 carbon atoms.
Examples include vinyl acetate, vinyl propionate, vinyl
butyrate, vinyl hexanoate, vinyl heptanoate, vinyl
octanoate, vinyl laurate and vinyl stearate, and also
esters of vinyl alcohol based on branched fatty acids,
such as vinyl isobutyrate, vinyl pivalate, vinyl 2-
ethylhexanoate, vinyl isononanoate, vinyl neononanoate,
vinyl neodecanoate and vinyl neoundecanoate. Comonomers
which are likewise suitable are esters of acrylic acid
and methacrylic acid having 1 to 20 carbon atoms in the
alkyl radical, such as methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, n- and isobutyl
(meth)acrylate, hexyl (meth)acrylate, octyl
(meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl
(meth)acrylate, dodecyl (meth)acrylate, tetradecyl
(meth)acrylate, hexadecyl (meth)acrylate, octadecyl
(meth)acrylate, and also mixtures of two, three or four
or else more of these comonomers.
Particularly preferred terpolymers of vinyl 2-
ethylhexanoate, of vinyl neononanoate and of vinyl
neodecanoate contain, apart from ethylene, preferably
3.5 to 20 mol%, in particular 8 to 15 mol%, of vinyl
acetate and 0.1 to 12 mol%, in particular 0.2 to 5
mol%, of the particular long-chain vinyl ester, the
total comonomer content being between 8 and 21 mol%,
preferably between 12 and 18 mol%. Further preferred
copolymers contain, in addition to ethylene and 8 to 18
mol% of vinyl esters, also 0.5 to 10 mol% of olefins
such as propene, butene, isobutylene, hexene, 4-
methylpentene, octene, diisobutylene and/or norbornene.
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The ethylene copolymers preferably have molecular
weights which correspond to melt viscosities at 140 C
of from 20 to 10 000 mPas, in particular 30 to
5000 mPas and especially 50 to 1000 mPas. The degrees
of branching determined by means of IH NMR spectroscopy
are preferably between 1 and 9 CH3/100 CH2 groups, in
particular between 2 and 6 CH3/100 CH2 groups, for
example 2.5 to 5 CH3/100 CH2 groups, which do not stem
from the comonomers.
Such ethylene copolymers are described in detail, inter
alia, in DE-A-34 43 475, EP-B-0 203 554, EP-B-0 254
284, EP-B-0 405 270, EP-B-0 463 518, EP-B-0 493 769,
EP-0 778 875, DE-A-196 20 118, DE-A-196 20 119 and EP-
A-0 926 168.
Preference is given in this context to ethylene-vinyl
acetate copolymers and terpolymers which, in addition
to ethylene and vinyl acetate repeat units, also have
repeat (meth)acrylic ester units. These polymers may be
structured, for example, as random copolymers, as block
copolymers or as graft copolymers.
In a preferred embodiment, the inventive fuel
composition may comprise 0.0005 to 2% by weight,
preferably 0.01 to 0.5% by weight, of ethylene
copolymers.
For reasons of cost, however, a proportion of the
above-described ethylene copolymers can be dispensed
with in a further embodiment, in which case these fuel
compositions without a significant proportion of
ethylene copolymers have outstanding properties. In
this specific embodiment, the proportion of ethylene
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copolymers may preferably be at most 0.05% by weight,
more preferably at most 0.001% by weight and most
preferably at most 0.0001% by weight.
Preferred fuel compositions consist of
20.0 to 97.95% by weight, in particular 70 to 94.95% by
weight, of mineral diesel fuel,
2.0 to 79.95% by weight, in particular 5.0 to 29.95% by
weight, of biodiesel fuel,
0.05 to 5% by weight, in particular 0.1 to 1% by
weight, of ester-comprising polymer
and
0 to 60% by weight, in particular 0.1 to 10% by weight,
of additives.
The inventive fuel compositions preferably have an
iodine number of at most 30, more preferably at most 20
and most preferably at most 10.
In addition, the inventive fuel compositions have
outstanding low-temperature properties. In particular,
the pour point (PP) to ASTM D97 preferably has values
of less than or equal to 0 C, preferably less than or
equal to -5 C and more preferably less than or equal to
-10 C. The limit of filterability (cold filter plugging
point, CFPP) measured to DIN EN 116 is preferably at
most 0 C, more preferably at most -50C and more
preferably at most -10 C. Moreover, the cloud point
(CP) to ASTM D2500 of preferred fuel compositions may
assume values of less than or equal to 0 C, preferably
less than or equal to -5 C and more preferably less
than or equal to -10 C.
The cetane number to DIN 51773 of inventive fuel
compositions is preferably at least 50, more preferably
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at least 53, in particular at least 55 and most
preferably at least 58.
The viscosity of the present fuel compositions may be
within a wide range, and this can be adjusted to the
intended use. This adjustment can be effected, for
example, by selecting the biodiesel fuels or the
mineral diesel fuels. In addition, the viscosity can be
varied by the amount and the molecular weight of the
ester-comprising polymers used. The kinematic viscosity
of preferred fuel compositions of the present invention
is in the range of 1 to 10 mm2/s, more preferably 2 to
5 mm2/s and especially preferably 2.5 to 4 mm2/s,
measured at 40 C to ASTM D445.
The use of ester-comprising polymers which comprise
repeat units derived from unsaturated esters having 7
to 15 carbon atoms in the alcohol radical and repeat
units derived from unsaturated esters having 16 to 40
carbon atoms in the alcohol radical in a concentration
of 0.05 to 5% by weight as a flow improver in fuel
compositions which comprise at least one diesel fuel of
mineral origin and at least one biodiesel fuel
accordingly provides fuel compositions with exceptional
properties, as a result of which known diesel engines
can be operated in a simple and inexpensive manner.
The invention will be illustrated in detail hereinafter
with reference to examples and a comparative example,
without any intention that this should impose a
restriction.
Examples and Comparative Examples
General method for the preparation of the polymers
600 g of monomer composition according to the
composition detailed in each case in Table 1 and n-
dodecyl mercaptan (20 g to 2 g depending on the desired
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molecular weight) are mixed. 44.4 g of this monomer/
regulator mixture are charged together with 400 g of
carrier oil (e.g. 100N mineral oil, synthetic dinonyl
adipate or vegetable oil) into the 2 1 reaction flask
of an apparatus with sabre stirrer, condenser,
thermometer, feed pump and N2 feed line. The apparatus
is inertized and heated to 100 C with the aid of an oil
bath. The remaining amount of 555.6 g of monomer/
regulator mixture is admixed with 1.4 g of tert-butyl
peroctoate. When the mixture in the reaction flask has
attained a temperature of 100 C, 0.25 g of tert-butyl
peroctoate is added, and the feed of the monomer/
regulator/initiator mixture by means of a pump is
started simultaneously. The addition is effected
uniformly over a period of 210 min at 100 C. 2 h after
the end of feeding, another 1.2 g of tert-butyl
peroctoate are added and the mixture is stirred at
100 C for a further 2 h. A 60% clear concentrate is
obtained.
The mass-average molecular weight M, and the
polydispersity index PDI of the polymers were
determined by GPC. The measurements were effected in
tetrahydrofuran at 35 C against a polymethyl
methacrylate calibration curve composed of a set of ._25
standards (Polymer Standards Service or Polymer
Laboratories), whose Mpeak was distributed in a
logarithmically uniform manner over the range of 5x106
to 2x102 g/mol. A combination of six columns (Polymer
Standards SDV 100A / 2xSDV LXL / 2xSDV 100A / Shodex
KF-800D) was used. To record the signal, an RI detector
(Agilent 1100 Series) was used.
Table 1: Properties of the polymers used
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Polymer Monomer Mw PDI TE 100
composition [g/mol] (Mw/Mn)
(weight ratio)
Example I DPMA-SMA-MMA 130 000 2.3 10.8
75.4-14.6-10
Example 2 DPMA-SMA 490 000 3.5 24.6
70-30
Example 3 DPMA-SMA-MMA 60 000 2.2 8.65
Comparative DPMA-MMA 60 000 2.2 8.54
Example 1 99-1
DPMA: alkyl methacrylate which has 12 to 15 carbon
atoms in the alkyl radical
SMA: alkyl methacrylate which has 16 to 18 carbon
atoms in the alkyl radical
MMA: methyl methacrylate
Subsequently, the polymers thus obtained were
investigated in an 80/20 mixture of mineral diesel/
biodiesel. The amount of polymer used is shown in Table
2. The mineral diesel used was a summer diesel of
Australian origin with a pour point of -9 C. A palm oil
methyl ester (PME) (source of palm oil raw material:
Malaysia) having a pour point of +12 C was used as the
biodiesel. An 80/20 mixture of mineral diesel/biodiesel
exhibited a pour point of 0 C.
To investigate the low-temperature properties, the pour
point (PP) to ASTM D97 of the mixtures and of the
mineral diesel fuel was determined. The results
obtained are shown in Table 2.
Table 2: Properties of mineral diesel fuels and of the
mixtures comprising approx. 80% by weight of mineral
diesel and approx. 20% by weight of biodiesel, each of
which contain ester-comprising polymers.
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Polymer used Proportion of Pour point to Pour point to
the polymer ASTM D97 of ASTM D97 of
in the the 80/20 the mineral
mixture mixture diesel [0C]
[96 by wt.] [ C]
unadditized -9
Example 1 0.280 -6
Example 1 0.350 -12 -12
Example 1 0.420 -9
Example 1 0.490 -9
Example 1 0.700 -9 -12
Example 1 1.400 -6 -12
Example 2 0.350 -6 -9
Example 3 0.350 -6 -9
Comparative 0.350 -3 -9
Example 1
The examples detailed above show that ester-comprising
polymers containing repeat units which are derived from
ester monomers having 16 to 40 carbon atoms in the
alcohol radical lead to significantly better low-
temperature properties of mixtures which comprise
biodiesel, especially palm oil esters, and mineral
diesel.
Particularly surprisingly, preferred mixtures which
comprise certain ester-comprising polymers have an
improved pour point compared to the pure mineral diesel
fuel without additive, this improved pour point also
being retained in the case of addition of biodiesel.
