U.S. patent application number 13/143660 was filed with the patent office on 2011-12-08 for fuel compositions having improved cloud point and improved storage properties.
This patent application is currently assigned to EVONIK ROHMAX ADDITIVES GMBH. Invention is credited to Yann D'Herve, Brian Hess, Phil Hutchinson, Rene Koschabek, Sandra Kuenzel.
Application Number | 20110296743 13/143660 |
Document ID | / |
Family ID | 41723119 |
Filed Date | 2011-12-08 |
United States Patent
Application |
20110296743 |
Kind Code |
A1 |
Koschabek; Rene ; et
al. |
December 8, 2011 |
FUEL COMPOSITIONS HAVING IMPROVED CLOUD POINT AND IMPROVED STORAGE
PROPERTIES
Abstract
The present invention relates to a fuel composition comprising
at least one biodiesel fuel and comprising 0.05 to 5% by weight of
at least one polymer comprising ester groups, which comprises
repeat units derived from ester monomers having 16 to 40 carbon
atoms in the alcohol radical, and repeat units derived from ester
monomers having 7 to 15 carbon atoms in the alcohol radical, and
the polymer comprising ester groups has a weight-average molecular
weight in the range from 5000 to 100 000 g/mol. The present
invention further describes the use of polymers comprising ester
groups as flow improvers in fuel compositions which comprise at
least one biodiesel fuel. Surprising advantages can be achieved
especially with regard to the improvement of the cloud point and
the low-temperature storability.
Inventors: |
Koschabek; Rene; (Weinheim,
DE) ; D'Herve; Yann; (Merion Station, PA) ;
Hutchinson; Phil; (Whitehaven, GB) ; Hess; Brian;
(Willow Grove, PA) ; Kuenzel; Sandra; (Otzberg,
DE) |
Assignee: |
EVONIK ROHMAX ADDITIVES
GMBH
DARMSTADT
DE
|
Family ID: |
41723119 |
Appl. No.: |
13/143660 |
Filed: |
December 29, 2009 |
PCT Filed: |
December 29, 2009 |
PCT NO: |
PCT/EP09/67983 |
371 Date: |
July 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61144258 |
Jan 13, 2009 |
|
|
|
Current U.S.
Class: |
44/307 ;
44/397 |
Current CPC
Class: |
C10L 1/026 20130101;
Y02E 50/10 20130101; Y02E 50/13 20130101; C10L 1/1963 20130101;
C10L 1/1966 20130101; C10L 10/14 20130101; C10L 1/143 20130101 |
Class at
Publication: |
44/307 ;
44/397 |
International
Class: |
C10L 1/19 20060101
C10L001/19; C10L 1/00 20060101 C10L001/00 |
Claims
1. A fuel composition comprising at least one biodiesel fuel,
wherein the fuel composition further comprises 0.05 to 5% by weight
of at least one polymer comprising ester groups, which comprises
repeat units derived from ester monomers having 16 to 40 carbon
atoms in the alcohol radical, and repeat units derived from ester
monomers having 7 to 15 carbon atoms in the alcohol radical, and
the polymer comprising ester groups has a weight-average molecular
weight in the range from 5000 to 100 000 g/mol.
2. The fuel composition according to claim 1, wherein the fuel
composition comprises at least 80% by weight of biodiesel fuel.
3. The fuel composition according to claim 1, wherein the polymer
comprising ester groups is selected from the group consisting of a
polyalkyl (meth)acrylate (PAMA), a polyalkyl fumarate and a
polyalkyl maleate.
4. The fuel composition according to claim 2, wherein the polymer
comprising ester groups comprises 40 to 70% by weight of units
derived from ester monomers having 16 to 40 carbon atoms in the
alcohol radical.
5. The fuel composition according to claim 2, wherein the polymer
comprising ester groups comprises 30 to 60% by weight of units
derived from ester monomers having 7 to 15 carbon atoms in the
alcohol radical.
6. The fuel composition according to t claim 2, wherein the polymer
comprising ester groups is obtainable by polymerizing a monomer
mixture which comprises 0 to 40% by weight of one or more
ethylenically unsaturated ester compounds of the formula (I)
##STR00008## in which R is hydrogen or methyl, R.sup.1 is a linear
or branched alkyl radical having 1 to 6 carbon atoms, R.sup.2 and
R.sup.3 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, 10 to 98% by weight of one or more ethylenically
unsaturated ester compounds of the formula (II) ##STR00009## in
which R is hydrogen or methyl, R.sup.4 is a linear or branched
alkyl radical having 7 to 15 carbon atoms, R.sup.5 and R.sup.6 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) ##STR00010## in
which R is hydrogen or methyl, R.sup.7 is a linear or branched
alkyl radical having 16 to 40 carbon atoms, R.sup.8 and R.sup.9 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.
7. The fuel composition according to claim 6, wherein the weight
ratio of repeat units derived from ester monomers having 7 to 15
carbon atoms in the alcohol radical to repeat units derived from
ester monomers having 16 to 40 carbon atoms in the alcohol radical
is in the range from 1:1 to 1:3.
8. The fuel composition according to claim 2, wherein the biodiesel
fuel comprises fatty acid esters derived from monohydric alcohols
having 1 to 4 carbon atoms.
9. The fuel composition according to claim 8, wherein the monoester
is a methyl ester.
10. The fuel composition according to claim 9, wherein the fuel
comprises at least 6% by weight of palmitic acid methyl ester
and/or stearic acid methyl ester.
11. The fuel composition according to claim 2, wherein the
biodiesel fuel comprises at least 35% by weight of saturated fatty
acid esters which have at least 16 carbon atoms in the fatty acid
radical.
12. The fuel composition according to claim 2, wherein the
biodiesel fuel is derived from palm oil, soya oil, jatropha oil or
animal tallow.
13. The fuel composition according to claim 2, wherein the fuel
composition comprises at least one additive.
14. The fuel composition according to claim 12, wherein at least
one additive is selected from the group consisting of a dispersant,
a demulsifier, a defoamer, a lubricity additive, an antioxidant, a
cetane number improver, a detergent, a dye, a corrosion inhibitor
and an odorant.
15. The fuel composition according to claim 2, wherein the fuel
composition comprises 0.1 to 1% by weight of at least one polymer
comprising ester groups.
16. The fuel composition according to claim 2, wherein the fuel
composition comprises at most 0.05% by weight of ethylene
copolymer.
17. (canceled)
18. The fuel composition which comprises at least one biodiesel
fuel according to claim 1 wherein the cloud point of the fuel
composition decreases from a value less than or equal to 12.degree.
C. by at least 1.degree. C.
19. (canceled)
20. The fuel composition which comprises at least one biodiesel
fuel according to claim 1 wherein the fuel composition may be
stored at temperatures below the cloud point without significant
separation of the fuel or formation of precipitate.
21. The fuel composition according to claim 12, wherein the animal
tallow is selected from a group consisting of beef fat, chicken
fat, and pork fat.
22. The fuel composition according to claim 1, wherein the fuel
composition has a pour point having a value less than or equal to
12.degree. C.
Description
[0001] The present invention relates to fuel compositions which
comprise renewable raw materials, and to the use of polymers
comprising ester groups in fuel compositions for improving the
cloud point and the storage properties of fuels based on biodiesel
at low temperatures.
[0002] Decreasing global mineral oil reserves and discussions
regarding CO.sub.2 imbalances resulting from the use of fossil
fuels are leading to an increasing interest in alternatives based
on renewable raw materials.
[0003] For instance, bioethanol is increasingly being added to
commercial petroleum. In the case of diesel fuels, so-called
biodiesel is used. This can either be added to diesel of fossil
origin in different contents or be used in pure form. The advantage
of biodiesel is the minor influence on the global CO.sub.2 balance.
For instance, the combustion of these fuels can release only as
much carbon dioxide as the biomass from which it has been produced
had stored. Neglecting the greenhouse gases obtained through the
production of these biofuels, they do not influence CO.sub.2
balance.
[0004] Biodiesel has the advantage that it can be obtained from a
multitude of raw materials. Typical raw materials are vegetable
oils (i.e. triglycerides), such as rapeseed oil, sunflower oil,
soya oil, palm oil, coconut oil, coriander oil, cottonseed oil,
castor oil, olive oil, peanut oil, jatropha oil, Pongamia pinnata
(karanji) oil, nahar oil (Mesua ferrea L.), corn oil, almond oil,
mustardseed oil, algae oil, and used vegetable oils. Further
examples include oils which derive from wheat, jute, sesame, shea
tree nut, arachis oil and linseed oil. It is also possible to use
oils and fats of animal origin. Examples thereof are bovine tallow,
pork fat, chicken fat, bone and fish oil, and further fats and oils
which can be obtained in the slaughter of wild and farm
animals.
[0005] The term "biodiesel" is understood in many cases to mean a
mixture of fatty acid esters, usually fatty acid methyl esters
(FAMEs), with chain lengths of the fatty acid component of 14 to 24
carbon atoms with 0 to 3 double bonds. The higher the number of
carbon atoms 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 FAME by
transesterification, usually with methanol under basic
catalysis.
[0006] In contrast to rapeseed oil methyl ester (RME), which is
widely used in Europe and typically comprises approx. 5%,
occasionally even more than 6%, of C16:0+C18:0-FAME, palm oil
methyl ester (PME) contains approx. 50% C16:0+C18:0-FAME. A
similarly high C16:0+C18:0-FAME content is also possessed by the
analogous derivatives from animal tallows, for example bovine
tallow. Such a high wax content can barely be influenced by
polymeric flow improvers, which are typically added at an addition
rate of up to 2%. Compared to rapeseed oil, palm oil can be
produced with more than three times the yield per hectare. This
gives rise to immense economic advantages. However, a disadvantage
is the high pour point of PME, which is about +12.degree. C.
[0007] Polyalkyl (meth)acrylates, PA(M)As, as pour point improvers
for mineral oils, either without M(M)A (e.g. U.S. Pat. No.
3,869,396 to Shell Oil Company) or with M(M)A (e.g. U.S. Pat. No.
5,312,884 to Rohm & Haas Company), or else as pour point
improvers for ester-based lubricants (U.S. Pat. No. 5,696,066 to
Rohm & Haas Company) have been established and described for
quite a long time. Use of these polymers in fuel compositions which
comprise at least one biodiesel fuel is, however, not
described.
[0008] In addition, the publication WO 01/40334 (RohMax Additives
GmbH) describes polyalkyl (meth)acrylates which can be used in
biodiesel fuels. This publication provides a particular preparation
which imparts exceptional properties to these polymers. However,
there is a lack therein of examples relating to biodiesel fuels.
Furthermore, the advantage of polymers which have a high proportion
of particular repeat units comprising ester groups is not
described.
[0009] 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, the examples describe only
ethylene-vinyl acetate copolymers (EVAs) and copolymers which have
C.sub.12/C.sub.14-alkyl fumarate and vinyl acetate units. There is
no comprehensive and clear description of particular polymers
comprising ester groups in WO 94/10267.
[0010] In addition, a series of optimized EVA copolymers for
diesel/biodiesel mixtures have also become known (EP 1 541 662 to
664; WO 2008/113735 and DE 103 57 877). For instance, EP 1 541 663
describes 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 100 to 200 ppm of
ethylene-vinyl acetate copolymer (EVA). However, the use of EVA is
described herein as necessary. EVA is, though, quite an expensive
additive. Accordingly, alternatives are desirable, in which the use
of EVA can be dispensed with. There is no reference to the
advantage of particular polymers comprising ester groups in EP 1
541 663.
[0011] In addition, additives for fuel mixtures which comprise
mineral diesel and biodiesel are described in WO 2007/113035. In
addition, the low-temperature properties achievable in
diesel/biodiesel mixtures through addition of additives are not
necessarily applicable to pure biodiesel fuels, since their boiling
behaviour, their viscosity and hence their composition of
hydrocarbons is different.
[0012] In view of the prior art, it is thus an object of the
present invention to provide fuel compositions which, given 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 more particularly have
very good low-temperature properties. It was a further object of
the present invention to provide a fuel which possesses a high
stability to oxidation. In addition, the fuel should have a maximum
cetane number. At the same time, the novel fuels should be
producible simply and inexpensively.
[0013] It was a further object of the present invention to provide
additives which are capable of lowering the cloud point of
biodiesel. It was a further object of the present invention to
provide fuels which, when stored below the cloud point, exhibit
only minor precipitation. At the same time, this formation of
precipitate should be delayed for as long as possible.
[0014] These objects and further objects which are not stated
explicitly but which are immediately derivable or discernible from
the connections discussed herein by way of introduction are
achieved by a fuel composition having all features of claim 1.
Appropriate modifications of the inventive fuel composition are
protected in the dependent claims referring back to Claim 1. With
regard to the use of polymers comprising ester groups as flow
improvers for improving the cloud point and the low-temperature
storability, Claims 17, 18 and 20 constitute a solution to the
problem.
[0015] The present invention accordingly provides a fuel
composition comprising at least one biodiesel fuel, characterized
in that the fuel composition comprises 0.05 to 5% by weight of at
least one polymer comprising ester groups, which comprises repeat
units derived from ester monomers having 16 to 40 carbon atoms in
the alcohol radical, and repeat units derived from ester monomers
having 7 to 15 carbon atoms in the alcohol radical, and the polymer
comprising ester groups has a weight-average molecular weight in
the range from 5000 to 100 000 g/mol.
[0016] This makes it possible, in an unforeseeable manner, to
provide a fuel composition which comprises at least one biodiesel
fuel and which includes an excellent profile of properties. For
instance, the present fuel compositions especially have a
surprisingly low cloud point, a very good low-temperature
storability and excellent flow properties at low temperatures.
[0017] In addition, very high proportions of palm oil alkyl esters
can be used in the fuels. For ecological and economic reasons, palm
oil is preferred over the typically used rapeseed oil. For
instance, the yield in the production of palm oil is significantly
higher than that of rapeseed oil. In addition, production of rape
uses very large amounts of chemicals, especially fertilizers and
crop protection compositions, which are ecologically harmful. At
the same time, rape is self-incompatible in production and has to
be cultured in a crop rotation system, cultivation of rape in the
same field being possible only every 3 to 5 years. For this reason,
a further increase in rape production is difficult.
[0018] However, palm oil alkyl esters exhibit a significantly
higher cloud point (approx. +13.degree. C. in the case of the
methyl ester) compared to rapeseed oil alkyl esters; the cloud
point of rapeseed oil alkyl ester is significantly lower (approx.
-7.degree. 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
unacceptable values.
[0019] Similar advantages can also be identified with regard to
other biodiesel fuels with a high proportion of saturated fatty
acids. It is especially also possible to use fats of animal origin
as a fuel source, which are obtainable very inexpensively.
[0020] The fuel composition of the present invention 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 in principle
be used as a replacement for mineral diesel fuel.
[0021] In a preferred embodiment, the biodiesel fuel, which is
frequently also referred to as "biodiesel" or "biofuel", comprises
fatty acid alkyl esters of fatty acids having preferably 6 to 30
and more preferably 12 to 24 carbon atoms, and monohydric alcohols
having 1 to 4 carbon atoms. In many cases, some of the fatty acids
may contain one, two or three double bonds. The monohydric alcohols
include especially methanol, ethanol, propanol and butanol,
preference being given to methanol.
[0022] 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, peanut oil, corn oil, almond
oil, palm kernel oil, coconut oil, mustardseed oil, oils derived
from animal tallow, especially bovine tallow, bone oil, fish oils
and used cooking oils. Further examples include oils which derive
from cereals, wheat, jute, sesame, rice husks, jatropha, arachis
oil and linseed oil. Surprising advantages can be achieved
especially in the case of use of palm oil, soya oil, jatropha oil
or animal tallow, especially beef fat, chicken fat or pork fat, as
a reactant for preparing biodiesel. The fatty acid alkyl esters for
use with preference can be obtained from these oils by methods
known in the prior art.
[0023] Preference is given in accordance with the invention to oils
with a high C16:0/C18:0-glyceride content, such as palm oils and
oils derived from animal tallow, and derivatives thereof,
especially the palm oil alkyl esters which are derived from
monohydric alcohols. Palm oil (also: palm fat) is obtained from the
flesh of the palm fruits. The fruits are sterilized and pressed.
Owing to their high carotene content, fruits and oil have an
orange-red colour which is removed in the refining step. The oil
may contain up to 80% C18:0-glyceride.
[0024] Particularly suitable biodiesel fuels are lower alkyl esters
of fatty acids. Examples here include commercial mixtures of the
ethyl, propyl, butyl and especially methyl esters of fatty acids
having 6 to 30, preferably 12 to 24 and more preferably 14 to 22
carbon atoms, for example of caprylic acid, capric acid, lauric
acid, myristic acid, palmitic acid, margaric 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, gadoleinic acid, docosanoic acid or erucasic acid.
[0025] In a particular aspect of the present invention, a biodiesel
fuel 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 is used. This includes
especially the esters of palmitic acid and stearic acid. Advantages
which were unforeseeable for the person skilled in the art can
especially be achieved with fuels which comprise at least 6% by
weight, more preferably at least 10% by weight and most preferably
at least 40% by weight of palmitic acid methyl ester and/or stearic
acid methyl ester.
[0026] 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,
especially 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, the fuel compositions of
the present invention form a particularly low level of deposits in
the diesel engines. In addition, these fuel compositions exhibit
particularly high cetane numbers.
[0027] In general, the fuel compositions of the present invention
may comprise at least 40% by weight, especially at least 60% by
weight, preferably at least 80% by weight and more preferably at
least 95% by weight of biodiesel fuel.
[0028] The fuel composition of the present invention further
comprises 0.05 to 5% by weight, preferably 0.08 to 3% by weight and
more preferably 0.1 to 1.0% by weight of at least one polymer
comprising ester groups.
[0029] Polymers comprising ester groups are understood in the
present context 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 especially polyalkyl (meth)acrylates (PAMAs),
polyalkyl fumarates and/or polyalkyl maleates.
[0030] Ester monomers are known per se. They include especially
(meth)acrylates, maleates and fumarates, which may have different
alcohol radicals. The expression "(meth)acrylates" includes
methacrylates and acrylates, and mixtures of the two. These
monomers are widely known. In this context, the alkyl radical may
be linear, cyclic or branched. The alkyl radical may also have
known substituents.
[0031] The polymers comprising ester groups contain repeat units
derived from ester monomers having 16 to 40 carbon atoms in the
alcohol radical, and repeat units derived from ester monomers
having 7 to 15 carbon atoms in the alcohol radical.
[0032] The term "repeat unit" is widely known in the technical
field. The present polymers comprising ester groups can preferably
be obtained by means of free-radical polymerization of monomers,
the ATRP, RAFT and NMP processes which will be explained later
being counted among the free-radical processes in the context of
the invention, without any intention that this should impose a
restriction. In these processes, double bonds are opened up to form
covalent bonds. Accordingly, the repeat unit is obtained from the
monomers used.
[0033] The polymer comprising ester groups may contain 5 to 99.9%
by weight, especially 20 to 98% by weight and more preferably 30 to
60% by weight of repeat units derived from ester monomers having 7
to 15 carbon atoms in the alcohol radical.
[0034] In a particular aspect, the polymer comprising ester groups
may contain 0.1 to 90% by weight, preferably 5 to 80% by weight and
more preferably 40 to 70% by weight of repeat units derived from
ester monomers having 16 to 40 carbon atoms in the alcohol
radical.
[0035] In addition, the polymer comprising ester groups may contain
0.1 to 30% by weight, preferably 0.5 to 20% by weight, of repeat
units derived from ester monomers having 1 to 6 carbon atoms in the
alcohol radical.
[0036] The polymer comprising ester groups comprises preferably at
least 40% by weight, more preferably at least 60% by weight,
especially preferably at least 80% by weight and very particularly
at least 95% by weight of repeat units derived from ester
monomers.
[0037] Mixtures from which the inventive polymers comprising ester
groups are obtainable may contain 0 to 40% by weight, especially
0.1 to 30% by weight and more preferably 0.5 to 20% by weight of
one or more ethylenically unsaturated ester compounds of the
formula (I)
##STR00001##
in which R is hydrogen or methyl, R.sup.1 is a linear or branched
alkyl radical having 1 to 6 carbon atoms, R.sup.2 and R.sup.3 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.
[0038] 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.
[0039] The compositions to be polymerized preferably contain 5 to
98% by weight, especially 20 to 90% by weight and more preferably
30 to 60% by weight of one or more ethylenically unsaturated ester
compounds of the formula (II)
##STR00002##
in which R is hydrogen or methyl, R.sup.4 is a linear or branched
alkyl radical having 7 to 15 carbon atoms, R.sup.5 and R.sup.6 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.
[0040] 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-isopropylheptyl (meth)acrylate, nonyl
(meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate,
5-methylundecyl (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.
[0041] In addition, preferred monomer compositions comprise 0.1 to
90% by weight, preferably 5 to 80% by weight and more preferably 40
to 70% by weight of one or more ethylenically unsaturated ester
compounds of the formula (III)
##STR00003##
in which R is hydrogen or methyl, R.sup.7 is a linear or branched
alkyl radical having 16 to 40 and preferably 16 to 30 carbon atoms,
R.sup.8 and R.sup.9 are each independently hydrogen or a group of
the formula --COOR''' in which R''' is hydrogen or an alkyl group
having 16 to 40 and preferably 16 to 30 carbon atoms.
[0042] 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-butyl-3-vinylcyclohexyl (meth)acrylate,
2,3,4,5-tetra-t-butylcyclohexyl (meth)acrylate, and the
corresponding fumarates and maleates.
[0043] The ester compounds with a long-chain alcohol radical,
especially 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 rise to a mixture of esters, for example (meth)acrylates with
different long-chain alcohol radicals. These fatty alcohols include
Oxo Alcohol.RTM. 7911, Oxo Alcohol.RTM. 7900, Oxo Alcohol.RTM.
1100; Alfol.RTM. 610, Alfol.RTM. 810, Lial.RTM. 125 and Nafol.RTM.
types (Sasol); Alphanol.RTM. 79 (ICI); Epal.RTM. 610 and Epal.RTM.
810 (Afton); Linevol.RTM. 79, Linevol.RTM. 911 and Neodol.RTM. 25E
(Shell); Dehydad.RTM., Hydrenol.RTM. and Lorol.RTM. types (Cognis);
Acropol.RTM. 35 and Exxal.RTM. 10 (Exxon Chemicals); Kalcol.RTM.
2465 (Kao Chemicals).
[0044] Among the ethylenically unsaturated ester compounds, the
(meth)acrylates are particularly preferred over the maleates and
fumarates, i.e. R2, R3, R5, R6, R8 and R9 of the formulae (I), (II)
and (III) in particularly preferred embodiments are each
hydrogen.
[0045] The weight ratio of units derived from ester monomers having
7 to 15 carbon atoms, preferably of the formula (II), to the units
derived from ester monomers having 16 to 40 carbon atoms,
preferably of the formula (III), may be within a wide range. The
weight ratio of repeat units derived from ester monomers having 7
to 15 carbon atoms in the alcohol radical to repeat units derived
from ester monomers having 16 to 40 carbon atoms in the alcohol
radical is preferably in the range from 5:1 to 1:30, more
preferably in the range from 1:1 to 1:3, especially preferably
1.1:1 to 1:2.
[0046] Component (IV) comprises especially ethylenically
unsaturated monomers which can be copolymerized with the
ethylenically unsaturated ester compounds of the formulae (I), (II)
and/or (III).
[0047] However, particularly suitable comonomers for polymerization
according to the present invention are those which correspond to
the formula:
##STR00004##
in which R.sup.1* and R.sup.2* 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 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 CF.sub.3), .alpha.,.beta.-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
CH.sub.2.dbd.CCl--, 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(.dbd.Y*)R.sup.5*, C(.dbd.Y*)NR.sup.6*R.sup.7*,
Y*C(.dbd.Y*)R.sup.5*, SOR.sup.5*, SO.sub.2R.sup.5*,
OSO.sub.2R.sup.5*, NR.sup.8*SO.sub.2R.sup.5*, PR.sup.5*.sub.2,
P(.dbd.Y*)R.sup.5*.sub.2, Y*PR.sup.5*.sub.2,
Y*P(.dbd.Y*)R.sup.5*.sub.2, NR.sup.8*.sub.2 which may be
quaternized with an additional R.sup.8*, aryl or heterocyclyl
group, where Y* may be NR.sup.8*, S or O, preferably O; R.sup.5* is
an alkyl group having from 1 to 20 carbon atoms, an alkylthio
having 1 to 20 carbon atoms, OR.sup.15 (R.sup.15 is hydrogen or an
alkali metal), alkoxy of 1 to 20 carbon atoms, aryloxy or
heterocyclyloxy; R.sup.6* and R.sup.7* are each independently
hydrogen or an alkyl group having 1 to 20 carbon atoms, or R.sup.6*
and R.sup.7* 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.sup.8* is
hydrogen, linear or branched alkyl or aryl groups having 1 to 20
carbon atoms; R.sup.3*l and R.sup.4* are independently selected
from the group consisting of hydrogen, halogen (preferably fluorine
or chlorine), alkyl groups having 1 to 6 carbon atoms and
COOR.sup.9* in which R.sup.9* is hydrogen, an alkali metal or an
alkyl group having 1 to 40 carbon atoms, or R.sup.1* and R.sup.3*
together may form a group of the formula (CH.sub.2).sub.n' which
may be substituted by 1 to 2n' halogen atoms or C.sub.1 to C.sub.4
alkyl groups, or form the formula C(.dbd.O)--Y*--C(.dbd.O) where n'
is 2 to 6, preferably 3 or 4, and Y* is as defined above; and where
at least 2 of the R.sup.1*, R.sup.2*, R.sup.3* and R.sup.4*
radicals are hydrogen or halogen.
[0048] 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-dimethyl-1,6-hexanediol
(meth)acrylate, 1,10-decanediol (meth)acrylate; aminoalkyl
(meth)acrylates such as N-(3-dimethylaminopropyl)methacrylamide,
3-diethylaminopentyl 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,
methacryloylamidoacetonitrile,
2-methacryloyloxyethylmethylcyanamide, 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-methacryloylmorpholine,
N-methacryloyl-2-pyrrolidinone,
N-(2-methacryloyloxyethyl)-2-pyrrolidinone,
N-(3-methacryloyloxypropyl)-2-pyrrolidinone,
N-(2-methacryloyloxypentadecyl)-2-pyrrolidinone,
N-(3-methacryloyloxyheptadecyl)-2-pyrrolidinone; glycol
dimethacrylates such as 1,4-butanediol methacrylate, 2-butoxyethyl
methacrylate, 2-ethoxyethoxymethyl methacrylate, 2-ethoxyethyl
methacrylate; methacrylates 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
methacrylates 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, 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-methacryloyloxyethyl)-2-pyrrolidone; vinyl esters such as
vinyl acetate; styrene, substituted styrenes having an alkyl
substituent in the side chain, for example .alpha.-methylstyrene
and .alpha.-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-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine,
9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole,
1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone,
2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine,
N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran,
vinylthiophene, vinylthiolane, vinylthiazoles and hydrogenated
vinylthiazoles, vinyloxazoles 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 from those mentioned under (I), (II) and (III).
[0049] 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 can 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.
[0050] The comonomers (IV) and the ester monomers of the formulae
(I), (II) and (III) can each be used individually or as
mixtures.
[0051] Surprising advantages can be achieved, inter alia, with
polymers comprising ester groups 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,
polymers comprising ester groups for use 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
hydroxyalkyl (meth)acrylates and vinyl alcohols. These monomers
have been detailed above.
[0052] Similarly, surprisingly good efficiency is exhibited by
polymers comprising ester groups which comprise only a small
proportion, if any, of repeat units which derive from monomers
having oxygen-containing alcohol radicals of the formula (IV')
##STR00005##
where R is hydrogen or methyl, R.sup.10 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)
##STR00006##
in which R.sup.13 and R.sup.14 are each independently hydrogen or
methyl, R.sup.15 is hydrogen or an alkyl radical having 1 to 20
carbon atoms, and n is an integer of 1 to 30, R.sup.11 and R.sup.12
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 of the formula (VI)
##STR00007##
in which R.sup.13 and R.sup.14 are each independently hydrogen or
methyl, R.sup.15 is hydrogen or an alkyl radical having 1 to 20
carbon atoms, and n is an integer of 1 to 30.
[0053] The polymers comprising ester groups for use in accordance
with the invention have a molecular weight in the range of 5000 to
100 000 g/mol, preferably in the range of 10 000 to 70 000 g/mol
and more preferably in the range of 20 000 to 50 000 g/mol. These
values are based on the weight-average molecular weight M.sub.w of
the polydisperse polymers in the composition. This parameter can be
determined by GPC.
[0054] The preferred copolymers which can be obtained by
polymerizing unsaturated ester compounds preferably have a
polydispersity M.sub.w/M.sub.n in the range of 1 to 10, more
preferably 1.05 to 6.0 and most preferably 1.2 to 5.0. This
parameter can be determined by GPC.
[0055] The architecture of the polymers comprising ester groups is
not critical for many applications and properties. Accordingly, the
polymers comprising ester groups may be random copolymers, gradient
copolymers, block copolymers and/or graft copolymers.
[0056] 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 10 and
more preferably at least 30 monomer units.
[0057] 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).
[0058] 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 peroxy
compounds such as methyl ethyl ketone peroxide, acetyl-acetone
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
n-dodecyl mercaptan or 2-mercaptoethanol, or else chain
transferrers from the class of the terpenes, for example
terpinolene.
[0059] The ATRP process is known per se. It is assumed that it is a
"living" free-radical polymerization, without any intention that
the description of the mechanism should impose a restriction. 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 forms a
controlled polymerization system. The structure of the polymer, the
molecular weight and the molecular weight distribution can be
controlled correspondingly.
[0060] 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.
[0061] 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.
[0062] In addition, the inventive polymers are obtainable by NMP
processes (nitroxide-mediated polymerization), which are described,
inter alia, in U.S. Pat. No. 4,581,429.
[0063] These methods are described comprehensively, in particular
with further references, inter alia, in K. Matyjaszewski, T. P.
Davis, Handbook of Radical Polymerization, Wiley Interscience,
Hoboken 2002, to which reference is made explicitly for the
purposes of disclosure.
[0064] 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.degree.-200.degree. C., preferably
0.degree.-130.degree. C. and more preferably 60.degree.-120.degree.
C.
[0065] The polymerization may be carried out with or without
solvent. The term solvent is to be understood here in a broad
sense.
[0066] 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.
[0067] 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 odorants.
[0068] 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 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.
[0069] 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.
[0070] The ethylene copolymers preferably have molecular weights
which correspond to melt viscosities at 140.degree. 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 .sup.1H
NMR spectroscopy are preferably between 1 and 9 CH.sub.3/100
CH.sub.2 groups, in particular between 2 and 6 CH.sub.3/100
CH.sub.2 groups, for example 2.5 to 5 CH.sub.3/100 CH.sub.2 groups,
which do not stem from the comonomers.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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
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.
[0075] In addition to the components described above, a fuel
composition may comprise further components. These include
especially diesel fuels of mineral origin. For reasons of
environmental protection, the proportion of diesel fuels of mineral
origin may preferably be limited to at most 60% by weight, more
preferably at most 40% by weight and most preferably at most 15% by
weight.
[0076] The inventive fuel compositions have outstanding
low-temperature properties. Accordingly, the use of polymers which
comprise ester groups and 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 flow improvers in fuel compositions which
comprise at least one biodiesel fuel, constitutes a further aspect
of the present invention.
[0077] More particularly, the pour point (PP) to ASTM D97
preferably has values less than or equal to 12.degree. C.,
preferably less than or equal to 10.degree. C. and more preferably
less than or equal to 0.degree. C. Based on the biodiesel fuel
without addition of polymers for use in accordance with the
invention, it is unexpectedly possible to achieve improvements in
the pour point of 1.degree. C., preferably 3.degree. C. and most
preferably 5.degree. C.
[0078] The limit of the cold filter plugging point (CFPP) measured
to DIN EN 116 is preferably at most 12.degree. C., more preferably
at most 10.degree. C. and more preferably at most 0.degree. C. In
addition, the cloud point (CP) to ASTM D2500 of preferred fuel
compositions may assume values less than or equal to 12.degree. C.,
preferably less than or equal to 10.degree. C. and more preferably
less than or equal to 0.degree. C.
[0079] Surprisingly, it is especially possible to reduce the cloud
point with the polymers comprising ester groups for use in
accordance with the invention. This reduction is possible even in
the case of biodiesel fuels with a particularly high proportion of
long-chain saturated fatty acid units. This finding is surprising
especially because customary flow improvers, especially polymers
which have, for example, ethylene-vinyl acetate (EVA) units, which
have been developed to influence the CFPP, can cocrystallize with
the paraffins in the case of fossil diesel or the fatty acid alkyl
esters as the additized fuel is cooled. This prevents further
agglomeration of the individual crystals and ensures the
filterability of the fuel at relatively low temperatures. The
formation of the primary crystals and the temperature at which they
form are, however, not influenced by such additives. Since the
cloud point is by definition that point at which crystallization
sets in, it is obvious that the cloud point is barely influenced by
such additives. The present invention therefore also provides for
the use of polymers which comprise ester groups and 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, for improving the cloud
point of fuel compositions which comprise at least one biodiesel
fuel.
[0080] In this case, the cloud point can be reduced by at least
1.degree. C., preferably by at least 2.degree. C. or by at least
3.degree. C. and most preferably by at least 5.degree. C. These
figures are based on the cloud point of the biodiesel fuel without
the addition of polymers comprising ester groups for use in
accordance with the invention.
[0081] In the case of a surprisingly low use of up to 0.6% by
weight of polymers comprising ester groups, it is in many cases
possible to achieve improvements in the cloud point by at least
1.degree. C., preferably by at least 3.degree. C.
[0082] A further surprising aspect of the present fuel composition
is its outstanding low-temperature storability. Accordingly, the
inventive fuel compositions can be stored even at temperatures
below the cloud point without this being accompanied by any
significant separation of the fuel or significant formation of
precipitate. This aspect is essential especially in the case of
brief occurrence of unexpectedly low temperatures.
[0083] The cetane number to DIN 51773 of inventive fuel
compositions is preferably at least 50, more preferably at least
53, especially at least 55 and most preferably at least 58.
[0084] The viscosity of the present fuel compositions may lie
within a wide range, which may be adjusted to the intended use.
This adjustment can be effected, for example, through selection of
the biodiesel fuels. In addition, the viscosity can be varied by
the amount and the molecular weight of the polymers comprising
ester groups used. The kinematic viscosity of preferred fuel
compositions of the present invention is in the range from 1 to 10
mm.sup.2/s, more preferably 2 to 5 mm.sup.2/s and especially
preferably 2.5 to 4 mm.sup.2/s, measured at 40.degree. C. to ASTM
D445.
[0085] The present invention will be illustrated hereinafter with
reference to examples and comparative examples, without any
intention that this should impose a restriction.
EXAMPLES AND COMPARATIVE EXAMPLES
General Method for Preparing the Polymers
[0086] 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 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 l reaction flask of an apparatus with
sabre stirrer, condenser, thermometer, feed pump and N.sub.2 feed
line. The apparatus is inertized and heated to 100.degree. 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. Once the mixture in the reaction flask has attained a
temperature of 100.degree. 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.degree. 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.degree. C. for a further 2 h. A
60% clear concentrate is obtained.
[0087] The mass-average molecular weight M.sub.w and the
polydispersity index PDI of the polymers were determined by GPC.
The measurements were effected in tetrahydrofuran at 35.degree. C.
against a polymethyl methacrylate calibration curve composed of a
set of .gtoreq.25 standards (Polymer Standards Service or Polymer
Laboratories), whose M.sub.peak was distributed in a
logarithmically uniform manner over the range of 5.times.10.sup.6
to 2.times.10.sup.2 g/mol. A combination of six columns (Polymer
Standards Service SDV 100 .ANG./2x SDV LXL/2x SDV 100 .ANG./Shodex
KF-800D) was used. To record the signal, an RI detector (Agilent
1100 Series) was used.
TABLE-US-00001 TABLE 1 Properties of the polymers used Monomer
composition Mw PDI Polymer (weight ratio) [g/mol] (Mw/Mn) Example 1
SMA-LMA 98 300 2.25 60-40 Example 2 SMA-LMA 39 400 2.12 60-40
Example 3 SMA-LMA-BhMA-IDMA 44 000 2.25 40-40-10-10 Comparative
DPMA-HEMA 22 000 1.93 Example 1 90-10 Comparative DPMA 65 600 2.08
Example 2 100 SMA: alkyl methacrylate which has 16 to 18 carbon
atoms in the alkyl radical LMA: alkyl methacrylate which has about
10 carbon atoms in the alkyl radical, the alkyl radical being
predominantly linear BhMA: alkyl methacrylate which has about 22
carbon atoms in the alkyl radical IDMA: alkyl methacrylate which
has about 10 carbon atoms in the alkyl radical, the alkyl radical
being predominantly branched DPMA: alkyl methacrylate which has 12
to 15 carbon atoms in the alkyl radical HEMA: 2-hydroxyethyl
methacrylate
[0088] Subsequently, the polymers thus obtained were studied in
various biodiesel compositions. To this end, more particularly, a
fatty acid methyl ester formed from jatropha oil of Indian origin
with a proportion of palmitic acid methyl ester of 15.0% by weight
and a proportion of stearic acid methyl ester of 6.8% by weight
(JME), a fatty acid methyl ester formed from soya oil of North
American origin with a proportion of palmitic acid methyl ester of
10.7% by weight and a proportion of stearic acid methyl ester of
4.1% by weight (SME), and a fatty acid methyl ester formed from
palm oil of Malaysian origin with a proportion of palmitic acid
methyl ester of 43.7% by weight and a proportion of stearic acid
methyl ester of 4.4% by weight (PME), were used. The amount of
polymer used was in each case 600 ppm.
[0089] To study the low-temperature properties, the cloud point
(CP) to ASTM D2500 of the fuel compositions or the low-temperature
storability was determined.
[0090] In order to evaluate the influence of additives on the
storage of FAME, samples with and without additives were stored at
temperatures below the cloud point for 72 hours (cold storage test,
CST). This was done in a Julabo cryostat. After 24 and 72 hours,
the samples were assessed visually. The samples were rated on a
scale of 1-10. A methyl ester from soya oil (SME) of North American
origin and a methyl ester from palm oil (PME) of Malaysian origin
were used.
TABLE-US-00002 TABLE 2 Assessment of the biodiesel samples after
storage 1 sample has solidified completely 2 some liquid above a
solid block 3 significant amount (25%-50%) of liquid above a solid
layer 4 majority of the sample liquefied (50%+) over a solid layer
5 liquid layer but significant deposited solid layer 6 liquid layer
but small deposited solid layer 7 liquid layer over a small amount
of sediment 8 sample liquid but slightly cloudy with a small amount
of solid sediment 9 sample completely liquid but cloudy 10 sample
completely liquid and clear
[0091] The results obtained are shown in Table 3, 4 or Table 4.
TABLE-US-00003 TABLE 3 Cloud point (CP) of fuel compositions
Proportion of the Cloud point (CP) polymer in the Cloud point (CP)
to ASTM D2500 mixture to ASTM D2500 of PME Polymer used [% by wt.]
of JME [.degree. C.] [.degree. C.] unadditized -- 5 14 Example 1
0.6 1 11 Example 2 0.6 2 12 Example 3 0.6 1 11 Comparative 0.6 3 14
Example 1 Comparative 0.6 3 14 Example 2
TABLE-US-00004 TABLE 4 Storage of SME at -5.degree. C. Proportion
of Cold storage Cold storage the polymer in test (CST) test (CST)
the mixture assessment assessment Polymer used [% by wt.] after 24
h after 72 h unadditized -- 3 3 Example 1 0.6 8 8 Example 2 0.6 9 9
Example 3 0.6 8 8 Comparative Example 1 0.6 3 3 Comparative Example
2 0.6 3 3
TABLE-US-00005 TABLE 5 Storage of PME at 10.degree. C. Proportion
of Cold storage Cold storage the polymer in test (CST) test (CST)
the mixture assessment assessment Polymer used [% by wt.] after 24
h after 72 h unadditized -- 1 1 Example 1 0.6 6 5 Example 2 0.6 7 6
Example 3 0.6 6 5 Comparative Example 1 0.6 1 1 Comparative Example
2 0.6 1 1
[0092] The data shown above show clearly that the low-temperature
storability of fuel compositions with biodiesel components can
surprisingly be increased by the addition of polymers comprising
ester groups.
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