GB2401374A - Fuel gel - Google Patents

Abstract

A fuel gel composition comprising an alcohol, an oil, and a gelling agent. The fuel gel composition typically has a decreased evaporation rate of the component alcohol(s) than many known alcohol-based gels, and therefore burns slowly, evenly and consistently. The gel comprises an oil which may be edible and/or substantially non-toxic and is, preferably, a plant oil such as a seed, bean, fruit or nut oil. The fuel gel composition may be used in many applications, including: greenhouse heaters, chafing dishes, vineyard heaters, lamps, camping stoves and fireplaces or as a fire lighting fuel for the ignition of solid fuels, for example wood, coal or charcoal.

Description

A Fuel Gel The invention relates to fuel gel compositions, for example

suitable for use in greenhouse heaters, chafing dishes, vineyard heaters, lamps, camping stoves and fireplaces or as a firelighting fuel for the ignition of solid fuels, for example wood, coal or charcoal.

In many known fuel gel compositions, the flammable components are alcohols, often in admixture with a gelling agent. Alcohol-based gels are clean burning and generate relatively little soot, smoke or harmful vapours or combustion products. Examples of such fuel gels include those disclosed in US Patents US 3,148,958, US 4,084,939 and US 3,183,068. A particular advantage of ethanol-based gels is that ethanol has a relatively low toxicity. Examples of ethanol-based gels on the market at the time of filing are the products sold under the trade names AlcoGelO Horeca as supplied by AlcoGel of Bruxelles, Belgium; Magic Heat as supplied by CX3 Technology, Inc. of California, USA and GreenheatO Combustible Gel Fuel as supplied by Greenheat South Africa (Pty) Ltd. Gelling agents suitable for preparing gel fuels are known. Gel structures can be formed by simply mixing alcohol solutions with certain gelling agents, for example, mixing hydroxyethyl cellulose into a solution comprising ethanol and methanol as described in US 3,183,068. Alternatively, the gelling agent may be generated in situ as in the case of the in si to formation of sodium stearate described in US 4,436,525. Examples of other suitable known gelling agents include: carboxy vinyl polymers and other crosslinked polymers and co-polymers as described in US 3,148,958; sodium stearate and other fatty acid soap products as described in US 3,183,068; natural and synthetic gums such as cellulose and modified celluloses, i.e. methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, nitrocellulose and ethylene-acrylic acid copolymer dispersions as described in US 4,084,939.

A drawback of many known gel compositions comprising ethanol or other alcohols is that the alcohol components are highly volatile and therefore evaporate rapidly. This leads to rapid loss of the alcohol component from the gel prior to igniting, which is wasteful and produces alcohol vapours which are potentially intoxicating and explosive in confined spaces. Rapid vaporization of the alcohol components during burning may also lead to rapid, inefficient combustion of the alcohol vapours, which does not provide for a steady slow heat output as required for cooking, heating or lighting and/or igniting other flammable materials.

A further disadvantage of many known fuel gel compositions comprising ethanol is their low flash point rendering them highly flammable materials that can be dangerous to use, store and transport, requiring transportation and storage in expensive metal containers for safety. For example, AlcoGelO Horeca has a flash point of 13 C in a Tad closed cup test and that gel is thus supplied in a metal container. Other examples of known alcohol-based - 3 fuel gels that are supplied in metal containers include Magic Heat.

The invention provides for a fuel gel composition comprising an alcohol, an oil, and a gelling. The alcohol-based fuel gel of the invention can burn with a clean, largely soot-free flame with few substantially harmful combustion products.

An advantage of the fuel gel composition of the invention is that it typically has a decreased evaporation rate of the component alcohol(s) than many known alcohol-based gels, and therefore burns slowly, evenly and consistently. It has been found that the fuel gel of the invention burns at an average initial heat output of 22.8 kJ/hour for a 30 g sachet and a 30 g sachet of the fuel gel composition of the invention was found to burn for 25 minutes. It was found that 30 g of gel formulated according to the invention evaporated more slowly in a parallel test from a 70 mm diameter open cup than g of gel currently marketed as Greenheat Combustible Gel Fuel (available from Greenheat UK Limited), comprising approximately the same proportions of the same ingredients other than the oil.

Various health and safety bodies set limits for volatile organic compound (VOC) emission level maxima. The lower evaporation rates of the compositions of the invention facilitate the provision of gels that satisfy the regulatory requirements. It has been found that the invention provides for fuel gel compositions that may be more than 50% below some allowable regulatory levels. For example, it was found in a test that complies with the South Coast Air Quality Management District Rule 1174 Ignition Method Compliance Certification Protocol required by the Californian Environmental Protection Agency of the USA, that one gel fuel according to the invention generated an average of 20.3 ppm VOC emission when combusted.

Furthermore, the fuel gel according to the invention typically has a high flash point and is therefore relatively safe to transport, store and use. Typically, the gel according to the invention has a flash point in excess of 100 C in a closed cup. Preferably, the fuel gel has a flash point of greater than 120 C in a closed cup. It was found in a Pensky Martens Closed Cup test that a fuel gel according to the invention had a flash point of 266 F (130 C) (ASTM D93 test method). Furthermore the gel was found to have an auto ignition temperature of 793.4 F (423 C) in an ASTM E659 test.

Various health and safety bodies set regulatory limits on quantities of materials that can be stored and/or transported in a single unit. The lower flash points of the compositions of the invention facilitate the provision of gels that satisfy the regulatory requirements for materials that may be stored and/or transported in bulk. Regulations also dictate the type of containers, that flammable materials must be stored and/or transported in, for example, highly flammable materials are often required to be transported in metal containers. The higher flash points of the compositions - 5 of the invention facilitate the provision of gels that satisfy the regulatory requirements for materials that may be stored and/or transported in non-specialised containers, for example, in plastic bottles or sachets.

Preferably, the gel comprises an alcohol having from lto 6 carbon atoms, for example, methanol, ethanol, propanol, iso-propanol, n-butanol, isobutanol, tert-butanol or hexanol. More preferably, the alcohol component comprises methanol and/or ethanol and/or propanol and, most preferably, ethanol (ethyl alcohol).

Preferably, the gel comprises an oil that is edible and/or substantially non-toxic. Preferably, the oil is a plant oil. It may be a seed, bean, fruit or nut oil. The plant oil may be selected from bean oils, for example, soya oil; seed oils, for example, sesame seed oil, oil-seed rape oil, corn oil, linseed oil or sunflower seed oil; fruit oils, for example, olive oils nut oils, for example, walnut, hazelnut or groundnut oilsi plant extract oilsi flower oils, for example, star flower oil from the borage flower) vegetable oilsi or the like. More preferably, the plant oil is soya oiland/or corn oil. Preferably the plant oil is substantially odourless. Preferably, the oil has a relatively small proportion of volatile components having a vapour pressure of greater than 10 kPa at 25 C. Preferably, the oil comprises at least a major proportion of unsaturated fatty acids. The oil may be oil from a synthetic source, for example, derived from petrochemicals. The oil may be an animal oil or a mineral oil. The oil may be a mixture of oils from different sources. - 6

The term "oil" as used herein includes in particular glycerides, especially triglycerides, which may be natural triglycerides, especially those of plant oils, or synthetic analogies thereof.

As described above, it is found that the presence of the oil raises the flash point of the gel when compared to an equivalent gel composition in which the oil is omitted.

It is also found that the inclusion of an oil in a gel composition typically lowers the evaporation rate of the gel and/or the flammable volatile components of the gel when compared to a gel composition in which the oil is omitted.

The presence of an oil in the gel formulation may raise the surface tension of the gel. Without being bound by any particular theory, a possible explanation for those effects is that the plant oil forms a protective coating, film or miniscus on the surface of the gel, which may slow evaporation of any volatile flammable components, for example, alcohols.

Whereas the gel according to the invention will ignite if a naked flame touches the gel it will otherwise be difficult or impossible to light under normal operating temperatures; it does not emit sufficient vapours to ignite indirectly via the flammable vapours.

In order to form a good gel structure, gels comprising alcohols comprise a gelling agent. Many suitable gelling agents are known such as described in the prior art discussed above. The proportions of gelling agents present in a gel formulation vary according to the desired properties of the gel. In general high proportions of gelling agent (greater - 7 than 5% of the total weight) are required to make very viscous and/or substantially non-mobile gels. Increasing the proportion of gelling agent also often has the effect of lowering the rate of evaporation of the volatile and/or flammable gel components and/or of the gel.

It has been found that the gel of the present invention has a good gel structure when the composition comprises a cellulose-based gelling agent. Preferably the cellulose-based gelling agent is ethyl hydroxyethyl cellulose. More preferably it is ethyl hydroxyethyl cellulose with a degree of substitution of from 0.8 to 1.0 ethyl groups per anhydroglucose unit and a molar substitution of from 2.2 to 2.9 ethylene oxide molecules reacted with each anhydroglucose unit. Preferably the ethyl hydroxyethyl cellulose is of a particle size of 98% <425 am and a viscosity of 5000 mPa (+1000 mPA) at 20 C (Broofield LV) of a 1 solution. In practice, ethyl hydroxyethyl cellulose as supplied by Akzo Nobel Surface Chemistry AB under the trade marks of BERMOCOLL EBS 481 FQ and BERMOCOLL E 481 FQ have been found to be particularly suitable.

The precise composition of the fuel gel according to this invention with reference to the proportions of the alcohol, oil and gelling agent components is not critical.

It is to be understood that the proportions of those components are selected to comprise 100 or less of the total weight of the gel. Each of the components are given as a percentage weight of the total weight of the gel including any further optional ingredients. The gel typically comprises from 50% to 95% by weight alcohol, preferably from 60% to 90% by weight, and more preferably from 70% to 85% by weight. The gel typically comprises from trace amounts to 20% oil, preferably froO.5 to 5% oil, and more preferably from 1% to 3% oil. The gel typically comprises from 0.01% to 15% gelling agent, preferably from 0.50 to 8% gelling agent, more preferably from 1.5% to 3.5% gelling agent, and most preferably from 2% to 3gO gelling agent. If the sum total of these essential ingredients is less than 100% of the total weight of the gel, it is to be understood that the balance of the weight is made up of other optional ingredients, for example, a congealing agent, which will be discussed later.

Preferably, the oil is present at a level such that the flash point of the fuel gel is raised to greater than 40 C, for example, greater than 60 C or 80 C and especially greater than 100 C, 110 C, 120 C or 130 C. Preferably, the oil is present at a level at which the evaporation rate of the fuel gel is lowered to less than 80% and preferably less than 60% of that of a gel with identical proportions of alcohol, gelling agent and any congealing agent. Preferably the oil is present at a level at which the gel generates at 25 C and atmospheric pressure less than 100 ppm VOC emission, for example, less than 60 ppm or 40 ppm VOC emission and especially less than 30 ppm, 20 ppm or 15 ppm VOC emission. Preferably, the oil is present at a level at which the burn time of 100 g of fuel gel in a 70 mm diameter cup is increased to greater than 60 minutes, for example, greater than 80 minutes, 100 minutes, 120 minutes, 140 minutes, 160 minutes, 200 minutes, 240 minutes or 300 minutes.

It has been found that a degree of control over the following properties of the gel can be achieved by varying the proportion of oil in the gel composition: a) the evaporation rate of the gel and/or the alcohol component of the gel; b) the flash point of the gel; c) the rate of heat output of the gel and/or total heat output of the gel, when burnt; d) the total burning time of the gel.

By making fine adjustments to the proportion of plant oil present in the gel composition, the properties of the gel including those listed above can be tuned to provide a gel that is particularly suited to a particular application.

For example, a higher evaporation rate and heat output rate may be better for cooking; a slower rate may be more suitable for lighting.

When formulating a gel composition the proportions of ingredients may be adjusted until a composition that has the desired consistency is achieved. A drawback of many known gel compositions, including many comprising alcohols, is that they are unstable under combustion conditions, breaking down and/or melting. Gels that breakdown and/or melt and so become very mobile and non-viscous, have the disadvantage that they spread out forming a thin film which has a large combustion surface and thus burns very rapidly. A further disadvantage of gels that become very mobile on burning is that they flow away from where the heat is required, which is a particular disadvantage in fire lighting fuels.

It has also been found that fuel gel compositions comprising oil in accordance with the invention may be obtained possessing many of the desirable properties discussed above, with lower proportions of gelling agent than in prior art compositions. A disadvantage of many known gelling agents is that they do not enhance the burning characteristics of the gel and may require energy to burn or vaporise. Some gelling agents leave a residue. Therefore, fuel gel compositions comprising a low proportion by weight of gelling agent are desirable as they mitigate those disadvantages.

If desired, the gel may further comprise a congealing agent. A congealing agent may in some circumstances be required to enable the gel to develop a good gel structure.

A congealing agent may, or may not, be added in combination with the gelling agent discussed above. Preferably the congealing agent is water. Preferably, from 0.5% to 30% by weight of the gel is water and more preferably from 10% to 30% weight. Most preferably, approximately 20% by weight of the gel is water.

It is an advantage of the fuel gel composition of the invention that it may have a low proportion of congealing agent. A disadvantage of many known congealing agents is that they are not flammable, and therefore require energy to burn or vaporise. Hence, fuel gel compositions which contain a minimum proportion of congealing agent are desirable. An advantage of lowering the proportion of congealing agents - 11 is that the calorific output of the gel per gram is increased with respect to a gel with a higher proportion of congealing agent.

Advantageously the gel comprises a colorant for aesthetic or identification purposes. A range of non-limiting examples of suitable colorants includes the dyestuffs phenolphthalein, Rose Bengal dye, Fuchsine SPB dye and Waxoline dyes. Preferably the dye does not adversely affect the properties of the gel. Preferably a dye is present in very small quantities and preferably constitutes less than 0.02% of the total weight of the gel. Preferably the gel according to the invention comprises Waxoline Yellow, Waxoline Green and/or Waxoline Blue dye as supplied by Avecia Pigments and Additives Limited. Colouring the gels may provide for identification of gels for different applications or possessing different properties. For example a barbeque lighting gel may be coloured red to distinguish it from a gel more suitable for lamps which may be coloured blue.

Advantageously the gel comprises a flame colorant for safety and aesthetic purposes. Suitable flame colourants include, but are not limited to, metal salts, such as lithium, copper, sodium, potassium and barium salts, boron-containing compounds, alcohols with 3 to 6 carbon atoms (as described in US 3,148,958) and aromatic compounds such as benzoic acid derivatives (described in US 3,183,068). Preferably a flame colourant makes up less than 3% of the total weight of the gel and more preferably from 0.0001S to 2% by weight.

Preferably the gel according to the invention comprises sodium chloride as a flame colorant. Incorporation of a flame colorant may be desirable for a gel for use in a lamp that provides luminescence of an attractively coloured light. A barbeque lighting gel may advantageously incorporate a flame colorant for safety purposes so that the flame is visible in bright sunlight.

Advantageously the gel is of neutral pH. Acidic or alkaline gels have the disadvantage of increased rates of corrosion of gel storage containers and/or plant used in the manufacture of the gel. Where appropriate the gel may comprise a pH modifying agent. Preferably, a pH modifying agent present in the gel composition is sodium bicarbonate (sodium hydrogen carbonate). The gel may comprise a pH buffer.

Preferably, the pH modifying agent makes up from 0.0001% to 3% of the total weight of the gel and more preferably from 0.5 to 1.5% by weight.

Advantageously, the gel according to the invention comprises an ingredient which gives the gel a pleasant odour and/or causes a pleasant odour to be released on burning.

Advantageously, the gel comprises an ingredient which is an insect repellent, which may, or may not, also be a perfume.

Preferably the gel comprises a perfume and/or an insect repellent ingredient in a proportion of from 0% to 2go of the weight of the gel as defined earlier. More preferably the gel consists of from 0.5% to 1% by weight of a perfume and/or insect repellent ingredient.

Preferably the gel according to the invention comprises Citronella, which has a pleasant aroma and acts as an insect repellent. The term "Citronella" is one used in the art and is particularly used herein to describe the oil extracts of the plant Cymbopogon nardus (L. ) or synthetic equivalents, the natural oil typically contains approximately 30% citronella! and approximately 40% geraniol.

Advantageously, a gel for use outside, for example, in garden lamps, as barbeque lighter fuel, as a patio heater, vineyard heater, or in a greenhouse heater may comprise an insect repellent to keep biting insects way, to repel insects that may damage plants and crops, or to keep insects away from food. Advantageously, gels for use in gardens may incorporate a perfume or otherwise be scented to provide a attractive aroma. An unpleasant aroma may be used to discourage pets or children from eating the gel. Gels for use in lamps may comprise a perfume to scent a room, disguise other smells, aid relaxation or provide a reminder that the lamp is lit.

Advantageously a perfume and/or insect repellent ingredient does not adversely affect the properties of the gel. Preferably the abovementioned ingredient enhances the properties of the gel, the ingredient may increase the flash point of the gel and/or lower the evaporation rate of the gel and/or provide for a longer more even burn of the gel.

Advantageously the fuel gel may comprise a denaturant or flavorant to act as a deterrent to accidental ingestion of the gel by humans or animals. The denaturant may also be added to enable the gel to be sold without duties levied on sale of edible alcohol products. Suitable flavourings or - 14 denaturants include, for example, brucine, quassin, Bitrex and denatonium benzoate. Suitably the deterrent is present at a level of from 0.0001% to 0.1%, preferably at a level of 0.001% w/v.

There is a demand for increased use of environmentally friendly and/or renewable energy sources. The gel of this invention can predominantly comprise components manufactured from natural raw materials such as plant materials. Certain fuel gel compositions according to this invention can therefore meet that demand. Advantageously, the gel comprises alcohol generated by fermentation and distillation of plant material. The oil and a gelling agent may also be manufactured from raw materials derived from natural plant sources.

Advantageously, the gelling agent may be ethyl cellulose made from cellulose derived from wood pulp and ethanol derived from plant material. If a perfume is present, the perfume may be a plant extract perfume. Denaturants from natural sources may be used in the gel composition.

Advantageously, a fuel gel, according to the invention can be supplied, for example, in a burner, a lamp, a greenhouse heater, a vineyard heater, a cooker, a stove, a camping stove, a disposable cooker, a chafing dish, a sachet, a bottle, a carton, a tube or a tin. The fuel gel according to the invention can be supplied in the form of a fire lighting fuel and/or as a barbeque lighter fuel.

Advantageously, a fuel gel according to the invention can be manufactured by a method comprising the step of mixing an alcohol with a plant oil and a gelling agent. - 15

An illustrative general procedure for manufacturing a gel according the invention will now be described. Alcohol and plant oil are combined in a mixing vessel together with any optional dyestuffs. Optional flame colouring agents, perfumes, insect repellents, denaturants, flavourings and/or pH modifying agents may also be added at this stage, especially if they are miscible in the alcohol and/or plant oil. The mixture is agitated and an optional congealing agent may be added. If any optional flame colouring agents and/or pH modifying agents are more readily dissolved in any liquid congealing agent used, they may be pre-dissolved in the congealing agent and added as a solution. In order to speed up the rate of dissolution of any of the components of the gel, the mixture may be warmed. On formation of a homogeneous solution, a gelling agent may be added portion-wise to the mixture. Agitation and/or heating may be employed to enable rapid formation of a homogenous gel. At this stage any further optional ingredients not yet incorporated may be added to the mixture. The gel mixture may then be poured, injected, pumped or siphoned into containers. Suitable containers include cans, bottles, cartons, tubes and sachets. For gel consistencies that substantially retain their shape when set the mixture may be poured into moulds and allowed to set.

If necessary the mixture may be cooled to promote setting.

The set gels may then be removed from the mould and/or cut into desired shapes and packaged for sale. The components may be added in an order differing from that described. It has been found that gel according to the invention can be - 16 manufactured by a number of different processes, for example, a viable gel can be produced when soya oil is added to a premixed gel of ethanol and ethyl hydroxyethyl cellulose gelling agent.

The following examples illustrate the invention:

EXAMPLE A

L ethanol and 2 L soya oil were mixed in a mixing vessel.

The mixture was agitated and 1.75 mL of Waxoline Green 6GFW dye (1, 4bis(p-tolylamino)anthraquinone as supplied by Avecia Pigments and Additives Limited) were added.

Subsequently 1 kg of sodium bicarbonate (sodium hydrogen carbonate) and 1 kg of sodium chloride were added as an aqueous solution in 20 L of water and 750 mL of Citronella was added while agitation was continued. Subsequently 2.5 L of ethyl hydroxyethyl cellulose as supplied by Akzo Nobel as Bermocol] EBS 481 FQ was added portionwise over a period of 10 minutes during which agitation was continued. The mixture was agitated for a further 10 minutes at which time a stable homogeneous gel was formed. The gel was then transferred into squeezable bottles for use.

EXAMPLE B

L ethanol and 40 L of water were mixed in a mixing vessel.

The mixture was agitated and 10 g of salt (sodium chloride) was added. 1. 5 g Waxoline Green G6FW dye (1,4-bis(p-tolylamino)anthraquinone as supplied by Avecia Pigments and Additives Limited), 2 g Denatonium Benzoate NF18 - 17 (benzyldiethyl(2,6-xylylcarbamoyl-methyl)ammonium benzoate as supplied by Sigma-Aldrich Limited) and 20 L soya oil was added. 7 kg of ethyl hydroxyethyl cellulose (as supplied by Akzo Nobel as Bermocoll EBS 481 FQ) was added portionwise over a period of 15 minutes during which agitation was continued. The mixture was agitated for a further 15 minutes at which time a stable homogeneous gel was formed. The gel was then transferred into sachets for use. - 18

Claims (18)

1. Claims: 1. A fuel gel comprising an alcohol, an oil and a gelling agent.
2. 2. A fuel gel as claimed in claim 1, wherein the alcohol is ethanol.
3. 3. A fuel gel as claimed in any one of claims 1 or 2, wherein the oil is a plant oil.
4. 4. A fuel gel as claimed in claim 3, wherein the plant oil is soya oil.
5. 5. A fuel gel as claimed in any one of claims 1 to 4, with a flash point of greater than 60 C.
6. 6. A fuel gel as claimed in any one of claims 1 to 5, comprising cellulose or a derivative thereof.
7. 7. A fuel gel as claimed in claim 6, comprising ethyl hydroxyethyl cellulose.
8. 8. A fuel gel as claimed in any one of claims 1 to 7, comprising an acidity regulator.
9. 9. A fuel gel as claimed in any one of claims l to 8, comprising a flame colouring agent.
10. 10. A fuel gel as claimed in any one of claims l to 9, comprising a colourant.
11. 11. A fuel gel as claimed in any one of claims 1 to 10, comprising a perfume and/or insect repellent.
12. 12. A fuel gel as claimed in any one of claims 1 to 11, comprising water.
13. 13. A fuel gel as claimed in any one of claims 1 to 12, in which the plant oil is at a level at which the flash - 19 point of the fuel gel is greater than 60 C.
14. 14. A method of manufacturing a fuel gel, comprising the step of mixing alcohol with an oil and a gelling agent.
15. 15. A garden heater, greenhouse heater or vineyard heater containing a fuel gel as claimed in claims 1 to 13.
16. 16. A cooker, stove or chafing dish containing a fuel gel as claimed in claims 1 to 13.
17. 17. A sachet or bottle containing a fuel gel as claimed in claims 1 to 13.
18. 18. A fire lighting fuel or barbeque lighter fuel comprising a fuel gel as claimed in claims 1 to 13.