WO2016055814A1

WO2016055814A1 - Gel fuel

Info

Publication number: WO2016055814A1
Application number: PCT/GB2015/052979
Authority: WO
Inventors: Christopher Lewis BOWEN; Jonathan Richard HOWSE; Jacob Alexander LANE
Original assignee: Air Global Limited; The University Of Sheffield
Priority date: 2014-10-10
Filing date: 2015-10-12
Publication date: 2016-04-14
Also published as: GB201418002D0

Abstract

A gel fuel is provided for use in cooking, heating and especially fire lighting. The gel fuel is a chemically crosslinked gel fuel comprising a. one or more alcohols, b. a polymer and c. a chemical crosslinker. The crosslinked gel contains at least its own weight in liquid, exhibits no flow and as such can free stand, holding its shape indefinitely. The gel does not flow, even at temperatures at which it combusts.

Description

Gel Fuel

Technical Field of the Invention

The present invention relates to gel fuel. In particular it relates to a gel fuel for use in cooking, heating and especially firelighting. Background to the Invention

Fluid fuels (such as liquids and gases) are routinely used for heating and cooking purposes in circumstances where a transportable and easy to use fuel source is required. Such fuels can also be used in the domestic environment, for example in cases where a mains supply of gas and/or electricity is not available, or outdoors (for example, as part of camping equipment).

The use of fluid fuels, in contrast to the use of various solid fuels, has advantages including increased ease of combustion. Further, the combustion of fluid fuels (particularly liquids) typically provides a higher energy yield than combustion of naturally- occurring solid fuels (such as wood and coal). Nevertheless, although liquid fuels are typically easier to handle than gases, the high degree of flowability inherent in such substances creates significant risks associated with the potential for leakage during transport and use. Moreover, as flammable liquids are typically highly volatile, the use of most fluid fuels poses significant hazards resulting from the potential for the leakage of flammable gases. As an alternative to the use of fluid fuels, synthetic solid fuels have been developed. However, the use of hexamine fuel tablets has numerous disadvantages. For example, combustion of such fuel tablets is known to result in the production of highly toxic gases (such as formaldehyde, ammonia, nitrogen oxide and hydrogen cyanide), ingestion of which may lead to nausea, vomiting, gastrointestinal disturbances, kidney damage and, if ingested in sufficient quantities, death (see the Material Data Safety Sheet (MSDS) for Esbit (RTM)). The use of liquid fuels having increased viscosity has also been investigated. Such fuels have been produced, for example, through the use of thickening agents to create viscous solutions of ethanol and/or methanol. However, although such fuels are often referred to as "gels", these compositions are not gels in accordance with the true meaning of the term. This is because, although they may be highly viscous, they exhibit a degree of flow. As a result, such compositions do not eliminate disadvantages associated with fluid fuels. For example, these flammable compositions may leak from packaging materials and contaminate surrounding areas, thereby creating a risk to safety during transport and/or use.

In light of this, examples of compositions comprising alkyl cellulose derivatives and described as solids have been proposed in GB2500062. That document defines "true gels" as substantially dilute crosslinked systems that exhibit no flow. However, the examples defined therein are do not appear to be chemically cross-linked.

Two forms of cross-linking are known, one, as shown in figure 1 is referred to as physical cross linking. The other is chemical cross linking as described later in relation to the invention. In the case of physical cross linking, two or more polymer chains are sufficiently close enough together so as that the total interaction between them (and any additional additive) is equivalent to that of a chemical cross linker and holds the chains together, to form a "true gel" at room temperature, which does not flow. However, these interactions are reversible, and so melting is possible. This causes a problem, especially when it is the form of a fuel used as a firelighter and therefore not held in a container. It is also inherently more dangerous in terms of containment of any accidental fire, for the combusting material to be flowing. However, there are several advantages to the gel- form, such as being able to shape it and cut off slices with a knife, without the fuel crumbling. Currently, only solid fuels, fluid fuels, and gel fuels which do not flow at room temperature, but melt when burnt are known. An object of this invention is to provide a gel fuel that does not flow, even at temperatures at which it combusts.

Summary of the Invention

According to a first aspect of the invention, there is provided a chemically cross linked gel fuel comprising (a) one or more alcohols, (b) a polymer and (c) a chemical cross linker.

The term chemically cross linked gel as used herein defines a solid which contains at least its own weight in liquid, exhibits no flow and as such can free stand, holding its shape indefinitely. Preferably the gel fuel comprises 50-98% by volume of alcohol. More preferably the gel fuel comprises 80%> to 98%> by volume of alcohol and most preferably the gel fuel comprises from 95-98% by volume of alcohol.

Preferably the polymer and the chemical cross linker comprise between 2% and 30%) by mass of the gel fuel and more preferably between 8%> and 20% by mass of the gel fuel.

The alcohol may be one or more C1-C4 (e.g. Ci_6, C_1-5, C_1-4, C_1-3 or C_1-2, such as C^A or C 2) linear or, where possible, branched (e.g. linear) alkyl moieties substituted with at least one (such as two or, particularly, one) hydroxyl group(s). The skilled person will appreciate that alcohols (or mixtures of alcohols) that are particularly useful for the preparation of fuels are typically liquid at room temperature at atmospheric pressure (i.e. substances that have a melting point that is significantly lower than room temperature and a boiling point that is higher than room temperature).

Thus, in a particular embodiment, component (a) is one or more liquid alcohols. As used herein, the term liquid alcohols will be understood to refer to an alcohol, as defined herein, that is a liquid (i.e. a substance of definite volume but no fixed shape) at room temperature (i.e. around 20 degrees C) and at atmospheric pressure (i.e. around 100 kPa).

In a further embodiment, component (a) consists of one or more (e.g. one or two) alcohols selected from the group consisting of: n-butanol and, in particular, ethanol, methanol and 2-propanol; and/or the alcohol component of industrial methylated spirits.

Preferably the alcohol is ethanol, in particular bioethanol. Alternatively the alcohol may be butanol or isopropanol, preferably bio-butanol or bio-isopropanol.

Preferably the polymer is Poly(acrylic acid) (from acrylic acid monomers). Alternatively, the polymer may be based on another weak acid monomer, such as 2- propylacrylic acid, or 4-vinyl benzoic acid. As an alternative to the weak acid monomers, the polymer could be based on weak base monomers such as N,N- dimethylaminoethyl methacrylate (DMAEMA), Ν,Ν-diethylaminoethyl methacrylate (DEAEMA), 2-vinyl pyridine, or 4-vinyl pyridine. In a still further alternative, the polymer could be an acrylamide polymer, e.g diethyl acrylamide dimethyl acrylamide or diacetone acrylamide. In yet a further alternative the polymer could be glycerol mono(meth)acrylate, (methacryloyloxy)ethyl phosphoryl choline, N-vinyl pyrrolidone, propylene oxide (propylene glycol), ethylene oxide (ethylene glycol), vinyl butyral or 2- hydroxy ethyl methacrylate. Preferably the chemical cross linker is poly(ethylene glycol) dimethacrylate

(PEGDMA), most preferably PEGDMA (750g/mol). Alternatively, other difunctional cross linkers (especially lower weight PEGDMA cross linkers) may be used, for example, di(ethylene glycol) di(meth)acrylate, tetra(ethylene glycol) di(meth)acrylate poly(ethylene glycol) diacrylate (mn < 700 g mol^"1). Non-ethylene glycol based difunctional crosslinkers could be used, such as methylene bisacrylamide and 1,3- butanediol diacrylate. Altermatively the crosslinker could be trifunctional, for example, trimethylol propane trimethacrylate or trimethylol propane ethoxylate.

The gel fuel may further comprise one or more optional solvents, for example water. Preferably the solvent comprises up to 40% by volume of the gel, more preferably the solvent comprises 0-10% by volume of the gel and most preferably the solvent comprises about 5% by volume of the gel.

Preferably the alcohol comprises at least 40% of the liquid components of the gel (e.g. the alcohol and any solvent). More preferably the alcohol (e.g. ethanol comprises at least 60 % by volume of the liquid components in the system, and even more preferably the alcohol comprises at least 80 % by volume of the liquid components.

The gel fuel may include additional impurities, or one or more additives selected from the group consisting of colorants (such as methyl violet (also known as meths colorant) and/or malachite green), stabilizing agents and taste modifiers (such as bitter tasting substances, e.g. denatonium benzoate (Bitrex RTM).

The gel fuel may further comprise a polymerisation initiator. The polymerisation initiator may be a thermal initiator, preferably ammonium persulphate. Azobisisobutyronitrile (AIBN) can be used as an alternative to APS as athermal initiator. In a further alternative, the gel fuel may comprise a UV initiator, for example a photo initiator in the classes of benzyl ketal (Irgacure 184) and acyl-phosphineoxides (irgacure 819 and irgacure TPO).

Preferably the initiator : monomer ratio is between 0.5 and 2 w/w % The gel fuel may further comprise a base activator (especially where the polymer is based on an acid monomer), preferably 2-amino-2-methyl-l-propanol (AMP). This expands the polymer allowing the network to hold more solvent thus reducing the % w/w solids. Inclusion of AMP reduces % w/w solids required for the formation of a gelled network. Alternatively, any ethanol soluble substance that is basic can be used as a base activator.

Preferably the ratio of base activator to the monomer is between 60 and 100 molar %, most preferably about 80 molar %.

The gel fuel may further comprise a flashpoint modifier. Preferably the flashpoint modifier is a-terpinol. A flashpoint modifier raises the temperature at which combustion occurs in the presence of an ignition source. Industrially this is an attractive additive to add as the some air freight services only transport goods whose flashpoint is above 37.8 °C. Preferably the flashpoint modifier comprises less than 14 w/w % of the alcohol. The gel fuel may further comprise a viscosity modifier, for example, carbopol® EZ3. Preferably the viscosity modifier comprises less than 0.5% w/w of the liquid components of the gel.

Preferably the gel fuel comprises from 5 % w/w solids to 75 % w/w solids, preferably from 10 % w/w solids to 50 % w/w solids more preferably from 10 % w/w to 20 % w/w solids, especially about 15% w/w solids. These ranges provide the best compromise to obtain stability as a solid cross linked gel, rather than a weak gel which breaks easily, or an excessively fractured gel/brittle solid incorporating too little of the alcohol fuel. Preferably the mean degree of polymerisation of the polymer is from 10-100.

This tends to produce a preferable percentage of solids to form a true chemically cross linked gel which does not lose its form and melt when heated.

Preferably the a monomer : cross-linker molar ratio is between 10 and 100.

According to a second aspect of the invention, there is provided a method of forming a chemically cross linked gel fuel according to any of the preceding claims comprising mixing (a) at least one alcohol, (b) at least one monomers and (c) at least one chemical cross linker.

The components (a) to (c) may be mixed in any order. For example, at least some or all of components (b) and (c) may be mixed together first and then component (a) (and, if relevant, the remainder of components, (b) and (c)) added to the mixture so formed. As another example, at least some or all of components (a) to (c) may be mixed together simultaneously. Preferably the method further comprises the step of initiating a polymerisation reaction.

Preferably the method further comprises the step of adding a thermal initiator and heating the mixture, or adding a photoinitiator and irradiating the mixture. Preferably the method further comprises the step of adding a solvent, preferably water, to the mixture.

Preferably the method further comprises the step of adding a base activator to the mixture.

Preferably the method further comprises the step of adding a flashpoint modifier and/or a viscosity modifier to the mixture.

Any of the additional components added may be as defined in relation to the first aspect of the invention and all of the preferred and alternative features of the first aspect are preferred and alternative features of the second, third, fourth and fifth aspects of the invention. The method may further compri se the step of purging with an inert gas, preferably nitrogen.

The method may further comprise the step of cooling the mixture, preferably to 0 degrees C or below.

The method may further comprise the step of heating the mixture, preferably to at least 50 degrees C, most preferably about 60 degrees C. Most preferably cooling is carried out prior to heating. According to a third aspect of the invention there is provided a firelighter comprising a gel fuel as set out above.

A fourth aspect of the invention provides the use of a gel fuel as set out above as a fire lighter. According to a fifth aspect of the invention there is provided a product comprising a gel fuel as set out above contained in a packaging material, which is preferably flammable.

Detailed Description of the Invention

In order that the invention may be more clearly understood an embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 shows diagrammatically a physically cross-linked gel system of the prior art; and

Figure 2 shows diagrammatically a chemically cross-linked fuel gel system according to the invention.

With reference to figure 2, a chemically cross-linked fuel gel comprises polymer chains of polyacrylic acid 1, chemically bonded to one another by cross linkers 2 of PEGDMA. The voids contain bioethanol, as the fuel, as well as water (a solvent) and traces of a polymerisation initiator (APS), a base activator (AMP), and a flashpoint modifier (a-terpinol).

Examples In each example below, monomeric acrylic acid was obtained from Fisher Scientific Limited, Ammonium persulfate and poly(ethylene glycol) dimethacrylate were both supplied by Sigma Aldrich, and Ethanol was supplied by Brentagg. All reagents were used as purchased unless specified. Example 1 : PAAcm-PEGDMA cross-linked gel at 20 w/w % solids in a solvent system containing 95% ethanol by volume.

Synthesis:

Atypical polymerisation for the synthesis of PAAcio-PEGDMA cross-linked gel at 20 w/w % solids was carried out in the following manner. A reaction vessel was filled with monomeric acrylic acid (AAc; 2.06 g, 28.5 mmol), poly(ethylene glycol) dimethacrylate crosslinker (PEGDMA; 2.14 g, 2.85 mmol), ammonium persulphate initiator 2.0 w/w % in AAc (APS; 70 mg, 0.315 mmol) were dissolved in ethanol (20 ml) and water (1 ml). The reaction vessel was sealed and purged with nitrogen gas for 25 min. while immersed in an ice bath in order to reduce solvent evaporation. The deoxygenated solution was then placed in a pre-heated oven at 60 °C for 16 hours.

Results:

A clear gel was formed which rapidly lights when placed near an ignition source.

Example 2: PAAcm-PEGDMA cross-linked gel at 50 w/w % solids in a solvent system containing 95% ethanol by volume. Synthesis:

Atypical polymerisation for the synthesis of PAAcio-PEGDMA cross-linked gel at 50 w/w % solids was carried out in the following manner. A reaction vessel was filled with monomeric acrylic acid (AAc; 8.22 g, 0.114 mol), poly(ethylene glycol) dimethacrylate crosslinker (PEGDMA; 8.56 g, 11.4 mmol), ammonium persulphate initiator 2.0 w/w % in AAc (APS; 0.17 g, 0.735 mmol) were dissolved in ethanol (20 ml) and water (1 ml). The reaction vessel was sealed and purged with nitrogen gas for 25 min. while immersed in an ice bath in order to reduce solvent evaporation. The deoxygenated solution was then placed in a pre-heated oven at 60 °C for 16 hours.

Results:

A fractured gel was formed which lights when placed near an ignition source. When lit the flame spits. Example 3 : PAAcm-PEGDMA cross-linked gel at 12.5 w/w % solids with AMP base activator (obtained from Surfachem) and a solvent system containing 95% ethanol by volume.

Synthesis:

Atypical polymerisation for the synthesis of PAAcio-PEGDMA cross-linked gel at 12.5 w/w % solids was carried out in the following manner. A reaction vessel was filled with monomeric acrylic acid (AAc; 1.17 g, 16.3 mmol), poly(ethylene glycol) dimethacrylate crosslinker (PEGDMA; 1.22 g, 1.63 mmol), ammonium persulphate initiator 2.0 w/w % in AAc (APS; 2.4 mg, 0.105 mmol) and 2-amino-2-methyl-l- propanol (AMP; 1.16 g, 13 mmol) were dissolved in ethanol (20 ml) and water (1 ml). The reaction vessel was sealed and purged with nitrogen gas for 25 min. while immersed in an ice bath in order to reduce solvent evaporation. The deoxygenated solution was then placed in a pre-heated oven at 60 °C for 16 hours.

Results: A clear gel is form which rapidly lights when placed near an ignition source.

Example 4: PAAcm-PEGDMA cross-linked gel at 12.5 w/w % solids with AMP base activator, a-terpinol (flash point modifier, obtained from Alfa Aesar) and a solvent system containing 95% ethanol by volume. Synthesis:

Atypical polymerisation for the synthesis of PAAcio-PEGDMA cross-linked gel at 12.5 w/w % solids was carried out in the following manner. A reaction vessel was filled with monomeric acrylic acid (AAc; 1.17 g, 16.3 mmol), poly(ethylene glycol) dimethacrylate crosslinker (PEGDMA; 1.22 g, 1.63 mmol), ammonium persulphate initiator 2.0 w/w % in AAc (APS; 24 mg, 0.105 mmol) and 2-amino-2-methyl-l- propanol (AMP; 1.16 g, 13 mmol) were dissolved in ethanol (20 ml) and water (1 ml) with a-terpinol (1.58 g, 10 mmol). The reaction vessel was sealed and purged with nitrogen gas for 25 min. while immersed in an ice bath in order to reduce solvent evaporation. The deoxygenated solution was then placed in a pre-heated oven at 60 °C for 16 hours.

Results:

A clear relatively soft gel was formed which rapidly lights when placed near an ignition source.

Example 5: PAAcm-PEGDMA cross-linked gel at 12.5 w/w % solids with AMP base activator and a solvent system containing 60% ethanol by volume.

Synthesis: Atypical polymerisation for the synthesis of PAAcio-PEGDMA cross-linked gel at 12.5 w/w % solids was carried out in the following manner. A reaction vessel was filled with monomeric acrylic acid (AAc; 1.22 g, 17.0 mmol), poly(ethylene glycol) dimethacrylate crosslinker (PEGDMA; 1.27 g, 1.70 mmol), ammonium persulphate initiator 2.0 w/w % in AAc (APS; 25 mg, 0.109 mmol) and 2-amino-2-methyl-l- propanol (AMP; 1.21 g, 136 mmol) were dissolved in ethanol (12 ml) and water (8 ml). The reaction vessel was sealed and purged with nitrogen gas for 25 min. while immersed in an ice bath in order to reduce solvent evaporation. The deoxygenated solution was then placed in a pre-heated oven at 60 °C for 16 hours. Results:

A clear gel was formed which lights when placed near an ignition source.

Example 6: PAAcmn-PEGDMA cross-linked gel at 12.5 w/w % solids with AMP base activator and a solvent system containing 60% ethanol by volume.

Synthesis: Atypical polymerisation for the synthesis ofPAAcio-PEGDMA cross-linked gel at 12.5 w/w % solids was carried out in the following manner. A reaction vessel was filled with monomeric acrylic acid (AAc; 2.26 g, 31.4 mmol), poly(ethylene glycol) dimethacrylate crosslinker (PEGDMA; 0.24 g, 0.314 mmol), ammonium persulphate initiator 2.0 w/w % in AAc (APS; 25 mg, 0.109 mmol) and 2-amino-2-methyl-l- propanol (AMP; 2.24 g, 25.1 mmol) were dissolved in ethanol (12 ml) and water (8 ml). The reaction vessel was sealed and purged with nitrogen gas for 25 min. while immersed in an ice bath in order to reduce solvent evaporation. The deoxygenated solution was then placed in a pre-heated oven at 60 °C for 16 hours. Results:

A clear gel was formed which lights when placed near an ignition source.

Example 7: PAAcm-PEGDMA cross-linked gel at 12.5 w/w % solids with AMP base activator and a solvent system containing 95% ethanol by volume with a viscosity modifier (carbopol® EZ3 supplied by Lubrizol.

Synthesis:

Atypical polymerisation for the synthesis of PAAcio-PEGDMA cross-linked gel at 12.5 w/w % solids was carried out in the following manner. A reaction vessel was filled with monomeric acrylic acid (AAc; 1.17 g, 16.3 mmol), poly(ethylene glycol) dimethacrylate crosslinker (PEGDMA; 1.22 g, 1.63 mmol), ammonium persulphate initiator 2.0 w/w % in AAc (APS; 2.4 mg, 0.105 mmol) and 2-amino-2-methyl-l- propanol (AMP; 1.16 g, 13 mmol) were dissolved in ethanol (20 ml) and water (1 ml) with carbopol® EZ3 (0.04 g). The reaction vessel was sealed and purged with nitrogen gas for 25 min. while immersed in an ice bath in order to reduce solvent evaporation. The deoxygenated solution was then placed in a pre-heated oven at 60 °C for 16 hours.

Results:

A clear gel was formed which rapidly lights when placed near an ignition source. Example 8: Burn test

Gels formed by examples 1-7 were ignited and allowed to combust. During combustion they were observed to record whether the gel changed shape and flowed. In each case, the gel simply burnt away, with and did not flow. The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A chemically cross linked gel fuel comprising (a) at least one alcohol, (b) at least one polymer and (c) at least one chemical cross linker.

2. A chemically cross linked gel fuel according to claim 1 wherein the alcohol is ethanol, preferably bioethanol.

3. A chemically cross linked gel fuel according to claim 1 wherein the alcohol is butanol or isopropanol, preferably bio-butanol or bio-isopropanol.

4. A chemically cross linked gel fuel according to any of the preceding claims wherein the polymer is based on an acid monomer.

5. A chemically cross linked gel fuel according to any of the preceding claims wherein the polymer is based on a weak acid monomer.

6. A chemically cross linked gel fuel according to any of the preceding claims wherein the polymer is poly(acrylic acid).

7. A chemically cross linked gel fuel according to any of claims 1-5 wherein the polymer is poly(2-propylacrylic acid), or poly(4-vinyl benzoic acid).

8. A chemically cross linked gel fuel according to any of claims 1-3 wherein the polymer is based on a base monomer.

9. A chemically cross linked gel fuel according to claim 8 wherein the polymer is based on a weak base monomer.

10. A chemically cross linked gel fuel according to claim 9 wherein the monomer is selected from Ν,Ν-dimethylaminoethyl methacrylate (DMAEMA), N,N- diethyl aminoethyl methacrylate (DEAEMA), 2-vinyl pyridine and 4-vinyl pyridine.

11. A chemically cross linked gel fuel according to any of claims 1-3 wherein the polymer is an acrylamide polymer.

12. A chemically cross linked gel fuel according to any of claims 1-3 wherein the polymer is based on a monomer is selected from diethyl acrylamide dimethyl acrylamide, diacetone acrylamide, glycerol mono(meth)acrylate, (methacryloyloxy)ethyl phosphoryl choline, N-vinyl pyrrolidone, propylene oxide (propylene glycol), ethylene oxide (ethylene glycol), vinyl butyral and 2- hydroxy ethyl methacrylate.

13. A chemically cross linked gel fuel according to any of the preceding claims wherein the chemical cross linker is poly(ethylene glycol) dimethacrylate (PEGDMA).

14. A chemically cross linked gel fuel according to claim 13 wherein the chemical cross linker is PEGDMA (750g/mol).

15. A chemically cross linked gel fuel according to any of claims 1-12 wherein the cross linker is difunctional.

16. A chemically cross linked gel fuel according to claim 15 wherein the cross linker is selected from di(ethylene glycol) di(meth)acrylate, tetra(ethylene glycol) di(meth)acrylate, poly(ethylene glycol) diacrylate, methylene bisacrylamide and

1,3-butanediol diacrylate.

17. A chemically cross linked gel fuel according to any of claims 1-12 wherein the crosslinker is trifunctional.

18. A chemically cross linked gel fuel according to claim 17 wherein the cross linker is trimethylol propane trimethacrylate or trimethylol propane ethoxylate.

19. A chemically cross linked gel fuel according to any of the preceding claims further comprising one or more optional solvents.

20. A chemically cross linked gel fuel according to any of the preceding claims further comprising a polymerisation initiator.

21. A chemically cross linked gel fuel according to claim 20 wherein the polymerisation initiator may be a thermal initiator.

22. A chemically cross linked gel fuel according to claim 21 wherein the polymerisation initiator is ammonium persulphate.

23. A chemically cross linked gel fuel according to claim 20 wherein the polymerisation initiator is a UV initiator.

24. A chemically cross linked gel fuel according to claim 23 wherein the polymerisation initiator is a photo initiator in the classes of benzyl ketal and acyl- phosphineoxides.

25. A chemically cross linked gel fuel according to any of the preceding claims further comprising a base activator.

26. A chemically cross linked gel fuel according to claim 25 wherein the base activator is 2-amino-2-methyl-l-propanol (AMP).

27. A chemically cross linked gel fuel according to any of the preceding claims further comprising a flashpoint modifier.

28. A chemically cross linked gel fuel according to claim 27 wherein the flashpoint modifier is a-terpinol.

29. A chemically cross linked gel fuel according to any of the preceding claims further comprising a viscosity modifier.

30. A chemically cross linked gel fuel according to any of the preceding claims wherein the gel fuel comprises from 5 % w/w solids to 75 % w/w solids, preferably from 10 % w/w solids to 60 % w/w solids more preferably from 12.5 % w/w to 55 % w/w solids and most preferably from 15 % w/w to 50% w/w solids, especially about 20% w/w solids.

31. A chemically cross linked gel fuel according to any of the preceding claims wherein the mean degree of polymerisation of the polymer is from 10-100.

32. A method of forming a chemically cross linked gel fuel according to any of the preceding claims comprising mixing (a) at least one alcohol, (b) at least one monomers and (c) at least one chemical cross linker.

33. A method according to claim 32 further comprising the step of initiating a polymerisation reaction.

34. A method according to claim 33 further comprising the step of adding a

thermal initiator and heating the mixture, or adding a photoinitiator and irradiating the mixture.

35. A method according to any of claims 32-34 further comprising the step of adding a solvent, preferably water, to the mixture.

36. A method according to any of claims 32-35 further comprising the step of adding a base activator to the mixture.

37. A method according to any of claims 32-35 further comprising the step of adding a flashpoint modifier and/or a viscosity modifier to the mixture.

38. A firelighter comprising a gel fuel according to any of claims 1-31.

39. Use of a gel fuel according to any of claims 1-31 as a fire lighter.

40. A product comprising a gel fuel as claimed in any of claims 1-31 and

contained in a packaging material.

41. A product according to claim 40 wherein the packaging material is flammable.