Fuel Paste

The present invention relates to a fuel paste, its use in indoor and outdoor applications and their manufacturing.

Fuel pastes are known and described in literature. For a convenient indoor and outdoor use, such pastes need to comply with a number of requirements. This includes good combustion properties, safety, low soot formation, low residue formation, none or positive smell, and others. Often, when improving one property other properties are adversely affected.

Fuel pastes based on an alcohol are known and commercially available, such as supplied by Firestar AG, Switzerland. Although considered reliable and convenient, such pastes show some drawbacks. For example, methanol or ethanol based fuel pastes burn with a slightly blue, almost invisible flame. Fuel pastes based on higher alcohols, such as butanol, burn with a more pleasant yellowish flame but give rise to extensive soot formation. It is also known to use flame colorants for obtaining intensely coloured flames. For example,

FR2690689 discloses a flame colouring system using an alcohol (optionally in gelled form) and metal salts, provided in a specific form to the burner. The flames produced by this method are considered artificial by the customer. Further, the components used for producing a coloured flame are considered hazardous and/or ecologically doubtful. Also, the set up consisting of burner, fuel gel, salt additive is considered inconvenient in use and expensive in manufacturing. In addition, such salt additives may cause ecological concerns and health issues.

There is a need for fuel pastes that combine the benefits of known fuel pastes and at the same time produces a pleasant flame colour. Often, a more brilliant flame is considered more pleasant.

Thus, it is an aim of the present invention to provide a fuel paste that overcomes the limitations and disadvantages of the currently known fuel pastes. In particular, it is aimed to provide a fuel paste that combines the advantages of the known fuel pastes and further provides a pleasant and/or brilliant flame color. It is also aimed that such fuel paste is versatile in that it is suitable for indoor uses and outdoor uses. Further, it is an aim of the present invention, to provide processes for obtaining such fuel pastes and uses for the fuel pastes provided.

These objectives are achieved by a fuel paste as defined in claim 1. Advantageous embodiments are disclosed in the specification and the dependent claims. Further aspects are disclosed in the independent claims an in the specification.

Accordingly, the invention relates in a first aspect to a fuel paste comprising or consisting of one or more Cl - C7 alcohols; water; one or more thickening agents; solid material containing lignin and/or cellulose of a size below 5 mm; and having a viscosity between 1500 and 10 000 mPas (20°C, measured according to the protocol given below) .

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. Further, it is understood that the various ranges, embodiments,

and preferences provided in this specification may be combined at will. Also, specific embodiments or preferences may not apply.

Unless otherwise stated, the following definitions shall apply in this specification:

The term "paste" refers to any composition having a viscosity between 1500 and lOOOOmPas at 2O ⁰ C. The viscosity is determined according to standard methods using e.g. a Brookfield viscosimeter. A suitable method is described in the examples. A paste may be a cream or gel type, preferably of gel type. As solid material is one component of the paste, a paste according to this invention will be heterogeneous. A "fuel paste" as described herein is to be distinguished from a fire lighter. While the purpose of the latter is to only start a fire (short burning time, high flame temperature) a fuel paste aims to provide a fire of its own. The term "indoor application" or "indoor use" refers to any use of the fuel paste in closed private or public premises, such as kitchen; living room, restaurant, shopping areas, etc.

The term "outdoor application" or "outdoor use" refers to any use of the fuel paste in open private or public areas, such as a patio, garden, public place, campground, sports facilities.

The following paragraphs provide a more detailed description of the components used in the fuel paste according to this invention.

As component a) one or more C1-C7 alcohols are used. The term C1-C7 alcohols includes methanol, ethanol, propanol, iso-propanol, butanol, pentanol hexanol and heptanol. Preference is given to methanol, ethanol, iso-propanol. C2-C7 alcohols suitable for a fuel

paste according to this invention may be of technical grade purity or better. Thus, the alcohols used may contain other compounds, in particular water and / or denaturating agents. The fuel paste of this invention may contain one or more C1-C7 alcohols. The following combinations are advantageous embodiments: ethanol; methanol / ethanol (e.g. 10 - 90 % methanol) ; ethanol / iso-propanol (e.g. 10 - 90 % iso-propanol) ; methanol / ethanol / iso-propanol (e.g. 10 - 50 % methanol and 10 - 50 % iso-propanol)

The selection of component a) influences many properties of the fuel paste such as flash point, soot formation, VOC emission, burning time, flame intensity.

As component b) water is used. No particular requirement as to the purity of the water is needed. However, to reduce residue formation water with a low content of minerals is advantageously. Further, it is recalled that a part or the total amount of water required may already be present in the C2-C7 alcohol of component a) .

It was found that the addition of water reduces soot formation and improves handling properties of the fuel paste. Further, water may improve gel formation and thus act as a congealing agent.

As component c) one or more thickening agents are used. Such thickening agents are known in the field and include gelling agents and Acetate Salts. Suitable gelling agents include: i) carboxy vinyl polymers and related crosslinked polymers and co-polymers; ii) in situ formed gelling agents such as obtained by formation of sodium stearate; iii) cellulose and modified cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, nitro cellulose, hydroxypropyl cellulose, methylhydroxybutyl cellulose; iv) polyacrylic acid and co-polymers thereof and related

crosslinked polymers; v) polyvinylpyrrolidones and related copolymers. Particular suitable thickening agents are selected from the group consisting of Carbopol 676 (CAS 0009003-01-4), Methocell 311 (Hydroxypropyl-Methyl- Cellulose) , 2-Amino-2-Methylpropanol (CAS 007732-18-5) , Ethomeen C25 (CAS 61791-14-8) .

It has been found that the fuel paste of the present invention has a good gel structure when the composition comprises a cellulose-based gelling agent.

Thus, in an advantageous embodiment, the cellulose-based gelling agent is Hydroxypropyl Methylcellulose . Preferably the Hydroxypropyl Methylcellulose is of a particle size of 100% <425 urn (18 u.s Std. Siev) urn and a 1 % solution shows a viscosity of 6000-8300 mPa (20 ⁰ C ; Broofield RTV) . In practice, Hydroxypropyl Methylcellulose as supplied by Dow Chemicals under the trade marks of Methocell 311 has been found particularly suitable. It has further been found that the fuel paste of the present invention has a good gel structure when the composition comprises an acrylic acid based gelling agent. Thus, in an advantageous embodiment, the acrylic acid -based gelling agent is Carbopol 676 (cas No 0009003-01-4), as supplied by Noveon Europe.

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 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. If desired, the fuel paste 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.

As component d) a solid material containing lignin and / or cellulose is used. For convenience, component d) will also be referred to as "solid material". The solid material may consist of natural material such as wood or plant material (e.g. waste material of plants like straw or chaff) or processed material such as paper, carton. Preferably, wood is used. The size of the solid material may be chosen in a wide range, also depending on the type of solid material used. Advantageously, the solid material is of a size below 5mm, much preferably in a size of 0.2 - 2 mm. The size of the solid material may be determined by standard methods, e.g. by using a sieve.

In an advantageous embodiment, wooden material like sawdust, wood shavings, wood fibres are used.

In an advantageous embodiment, wooden material is coniferous wood, like pine wood or fir wood.

It has been found that a degree of control over the following properties of the fuel paste can be achieved by varying the type and proportion of solid material in the gel composition: i) the colour of the flame, ii) the evaporation rate of the alcohol component of the paste; iii) the total burning time iv) the flash point; c) the rate of heat output. It is in particular surprising to obtain a significant colour change of the flame without an increase of soot formation and / or adverse effects of smell. The flame obtained by adding solid material was found to be "pleasant", "warm" and "natural" by customers. By making fine adjustments to the proportion of solid material present in the composition, its size and type, 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.

The precise composition of the fuel paste according to this invention with reference to the proportions of the alcohol (s), water, thickening agent (s) and solid material 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 fuel paste. Each of the components is given as a percentage weight of the total weight of the fuel paste including any further optional ingredients. The fuel paste typically comprises from 48 % to 93.5 % of component a),- (C]_—C7 alcohol), preferably from 71.5 % to 82.5 % by weight. The fuel paste typically comprises from 5 % to 30 % of component b) (water) , preferably from 15 % to 20 % by weight. The fuel paste typically comprises from 0.2 to 8 % of component c) (thickening agent), preferably from 0.5 % to 1.5 % by weight. The fuel paste typically comprises from 1 % to 10 % of component d) (solid material) , preferably from 2 % to 5 % by weight. 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. The fuel paste may comprise from trace amounts to 1 % of component e) (dyestuff) . The fuel paste may comprise from trace amounts to 3 % of component f) (additive) .

Further optional components of the fuel paste as disclosed herein are provided below:

As component e) one or more dyestuffs (paste colorants) may be added to the fuel paste for aesthetic

and / 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 (e.g. Waxoline Yellow, Waxoline Green, Waxoline Blue), preferably quinoline yellow (E104), sodium fluorescine and/or dyestuff ERKA S 3140 (red) . Preferably the dye does not adversely affect the properties of the fuel paste. Typically, the dyestuff is present in quantities below 1%, e.g. 0.1% of the total weight of the fuel paste. 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 orange to distinguish it from a gel more suitable for lamps which may be coloured green.

As component f) the fuel paste may comprise one or more additional flame colorants. Suitable flame colorants include, but are not limited to alkalimetal salts, such as hydroxides, carbonates, acetates.

Typically, the additional flame colorant is present in quantities below 3%, e.g. 1% of the total weight of the fuel paste.

Further optional components are i) pH modifiying agent (s) ; ii) perfume; iii) insect repellent

In a second aspect, the present invention relates to the use of a fuel paste as described herein.

Although possible to use the fuel paste as described herein for starting / igniting a fire (e.g. a wooden, charcoal or coal fire) , this is not the primary aim of the captioned fuel paste. The aim of the fuel paste is to provide a fire of its own, in particular for heating, warming or pleasure. One of the advantages of the present invention is to provide a fuel paste that is

suitable for indoor and outdoor applications. Thus, the invention relates in an advantageous embodiment to the use of a fuel paste as described above for cocking or warming dishes, to light or heat the environment. Consequently, the fuel paste as described herein may be used in connection with a burner (e.g. a cooker, camping cooker, disposable cooker), a heater (e.g. greenhouse heater, vineyard heater, camping stove, stove) a lamp, a mock fireplace.

For the uses as described above the fuel paste may be supplied in any convenient form (package) such as a sachet, carton, tube or tin. Advantageously, a tin as described in EP 1529004, which is incorporated by reference, is used. Thus, the invention also relates to a package containing a fuel paste as described herein.

In a third aspect, the present invention relates to a method of manufacturing a fuel paste as described herein.

The starting materials, i.e. the components as describe above, are commercially available or obtainable according to known methods .

General procedures for the manufacturing of fuel pastes are known, and may be applied to the fuel paste according to this invention.

In one embodiment, a method for manufacturing a fuel paste as described herein comprises the steps of mixing components a), b) e) (if present), f) (if present) , adding component d) to obtain a slurry and subsequently adding the thickening agent.

Gel structures can be formed by simply mixing a solution / suspension containing an alcohol with

certain gelling agents. In some cases - in particular of poor solubility properties of the thickening agent - it is advantageous to pre-swell the thickening agent with an alcohol or alcohol/water composition to improve gel formation.

The following examples illustrate the invention:

A Manufacturing of a fuel paste:

A fuel paste is obtained by mixing component a) with component c) for 15 min at r.t., adding water and stirring for an additional 15 min at r.t. and adding the remaining components and stirring for an additional period of 15 min. The thus obtained composition exhibits the final viscosity and is homogeneous.

Example 7 is manufactured for comparative purposes, mixing eethanol and iso-propanol prior to the addition of component c) . In this example, no component d) is present.

** quinoline yellow / fluorescine Na salt * technical grade, contains water

B Determination of viscosity: Viscosity is determined using a Brookfield viscometer and spindle S5 as a probe. General instructions of the manufacturer are observed. During set-up of the measuring unit, it is important to avoid formation of bubbles. This may be achieved e.g. by carefully dipping the probe into the paste in a oblique way prior to mounting at the viscometer. The rotational speed is adjusted in a way to obtain a momentum in the range of 10 - 100%; with preference to high values, as the viscometers error minimizes at higher values. The sample may be provided in any suitable container, e.g. a 600ml beaker. Care has to be taken that the sample is free of bubbles, dissolved gasses and shows homogeneity. Stirring and degassing is therefore recommended prior to measurement. As viscosity depends on temperature, it is recommended to control the temperature of the sample, e.g. by providing a water bath for maintaining constant temperature. The probe shall be dipped in the sample up to the centre of the nut, for avoiding measuring errors. The viscosity is noted, once a constant value is obtained. If a relative viscosity is of interest, a value may be taken after a pre-determined period of time.

The fuel pastes according to ex.l - ex.7 show viscosities within the range of 1500 - 10000 mPas at 20 ⁰ C.

C Assessment of fuel pastes:

The thus obtained fuel pastes are assessed as to their flame colour, soot formation and residue formation. Flame colour is assessed on a scale of 1 - 5, wherein 5 denotes a very intense flame color. Soot formation is assessed as yes or no. Residue formation is rated on a scale of 1 - 4 (low (1), medium, high, unacceptable high (4)).

As can be seen from the results, fuel pastes according to the invention show desiered properties, in particular with regards to flame color, soot formation and residue formation. Further, it is possible to avoid components that cause bad smell and are considered harmful .