WO2003104362A1

WO2003104362A1 - Firelighters

Info

Publication number: WO2003104362A1
Application number: PCT/GB2003/002463
Authority: WO
Inventors: Michael Cox
Original assignee: Swedish Match UK Ltd
Current assignee: Republic Technologies UK Ltd
Priority date: 2002-06-11
Filing date: 2003-06-09
Publication date: 2003-12-18
Anticipated expiration: 2004-12-11
Also published as: GB2389858B; AU2003244778A1; GB0213293D0; GB2389858A; GB0313186D0

Abstract

A firelighter comprising a porous material and a wrapper enclosing the porous material, said porous material having been impregnated with a volatile liquid fuel, wherein the wrapper is laminate, comprising at least two layers, the layers comprising a first polymeric layer and a second non-polymeric layer, wherein the polymer layer is on the fuel side (the inside layer) of the wrapper. The polymeric layer is preferably laminate and comprises at least a first polyethylene layer and a second layer of non-polyolefinic material such as polyamide. The non-polymeric layer is paper. The volatile liquid fuel is biodiesel or kerosene. The porous material is fibreboard or compressed wood chips. The wrapper is sealed to prevent leakage of the fuel.

Description

Firelighters

The present invention relates to firelighters, that is devices that can be ignited easily and are used to light fires, such as barbeques, wood or coal fires.

Firelighters are ideally composed of a material that is easy to ignite and burns for a reasonable length of time so that the burning firelighter ignites the firewood or coal etc of the main fire. Dry kindling such as paper or twigs is often used to light fires, but such material often burns too quickly and at too low a temperature to ignite the fuel, such as logs or coal. Commercially available firelighters usually comprise gelled kerosene or less commonly, paraffin wax blocks.

The object of the present invention is to provide a firelighter which is easy to light and burns efficiently so it can be used to effectively light a fire, whilst also being environmentally friendly, by reusing recycled materials. Other advantages shall become apparent as the invention is described.

According to the present invention there is provided a firelighter comprising a porous material and a wrapper enclosing the porous material, said porous material having been impregnated with a volatile liquid fuel, wherein the wrapper is laminate, comprising at least two layers, the layers comprising a first polymeric layer and a second non-polymeric layer.

Preferably the polymer layer is on the fuel side (the inside layer) of the wrapper. Preferably the polymeric layer is polyethylene or is laminate, comprising at least two layers. Preferably the polymeric layer comprises a first polyethylene layer and a second layer of non-polyolefinic material. Preferably the non-polyolefinic material is polyamide. Preferably the polymeric layer comprises a polyethylene layer of thickness greater than 50 microns and less than 80 microns and a polyamide layer of thickness greater than 10 microns and less than 20 microns.

Preferably the non-polymeric layer is paper. Preferably the porous material has a porosity of more than 50 % and less than 80 %. Preferably the thickness of the firelighter (t) is less than half the width (w) and the depth (d) of the firelighter. Preferably the volatile liquid fuel is biodiesel or kerosene. Preferably the porous material is fibreboard. Preferably the wrapper is sealed to prevent leakage of the fuel.

According to another aspect of the present invention there is provided a firelighter comprising a porous material and a wrapper enclosing the porous material, said porous material having been impregnated with a volatile liquid fuel and characterised in that the volatile liquid fuel is biodiesel.

Advantages of the present invention are that the firelighter's paper wrapper is very easy to light and the volatile liquid fuel impregnated within the porous medium burns steadily and for a reasonable length of time. The wrapper ensures that the firelighter is clean to handle. The flat shape of the firelighter allows fast absorption of the volatile liquid fuel into the porous medium.

The firelighter is preferably made from environmentally friendly materials, as the fibreboard or compressed wood chips, biodiesel, paper wrapper and polymer coating may all be derived from waste materials.

A firelighter embodying the invention will now be described by way of example, with reference to the drawings, of which:

Figure 1 is a cross-sectional view of the firelighter, showing a cross-section between the two points marked A of figure 3 Figure 2 is a perspective view of the firelighter without the wrapper

Figure 3 is perspective view of the firelighter

Figure 4 is a cross-sectional view of an alternative embodiment of the firelighter.

Referring to figure 1, the firelighter comprises a core of porous material 10, impregnated with a volatile liquid fuel, and enclosed in a combustible wrapper 11. The core should be made of any combustible, porous, low density material. For example fibreboard (made by compressing fibrous material) or compressed wood chips could be used, the advantages of these materials being that they can be made from waste materials and are therefore inexpensive. In the embodiment shown in figure 1, the core is composed of fibreboard, having a density of around 0.3 g/cm³ and a porosity of 80 %, allowing the fibreboard to absorb 80 % fuel by volume. Fibreboard of density 0.8 g/cm³ or greater and porosity 50 % or less would be insufficiently porous. If there is insufficient fuel absorbed, the firelighter will be difficult to ignite and will provide insufficient energy to light the main fire. Increasing the porosity above 80 % does not significantly increase the volume of fuel absorbed by the fibreboard.

The fibreboard is impregnated with a volatile liquid fuel by immersing it in the fuel. The fibreboard is left soaking in the fuel until the board has absorbed sufficient fuel or until it is saturated. Referring to figure 2, the fibreboard 10 should have a thickness (t) that is less than half the width (w) and also less than half the depth (d). Due to its flat shape, the fibreboard has a high surface area to volume ratio, which allows it to absorb the volatile fuel faster than if it were cuboid with the thickness, width and depth of the fibreboard roughly equal. The firelighter burns fast with large flame height, due to the flat shape of the fibreboard block.

Long strips of 70 mm wide and 7 mm thick fibreboard are immersed in the fuel. After immersion the strips are cut into 70 mm squares, having surface area 11,760 mm . Alternatively large sheets of fibreboard could be soaked then cut or the fibreboard could be cut into pieces of the desired size before fuel impregnation. The pieces can of course be cut to any size, depending on the desired burning time of the firelighter. Before impregnation with fuel, a 70 mm square, 7 mm thick piece of fibreboard has a mass of about 10 g. After soaking in fuel it has a mass of about 30g. A 70 mm square, 7 mm thick piece of fibreboard, having a porosity of 80 % can absorb roughly up to 27 cm³ of biodiesel.

The fuel used to impregnate the core should be of low viscosity, so as to have a fast absorption time. The volatility should not be too high that the firelighter burns too vigorously, causing a hazard. The vapours of very volatile fuels are also difficult to contain. If the fuel has too low a volatility, the firelighter will be difficult to ignite.

In a preferred embodiment, biodiesel is used as the fuel as it has a suitable volatility (it has a flash point of around 100 °C). It also has a low viscosity of 4.7 centistokes (at 40 °C) therefore it takes only a short time for fibreboard to absorb sufficient fuel. Typically it takes around 30 seconds to saturate 7 mm thick strips of fibreboard with biodiesel.

Biodiesel is a renewable liquid fuel produced from the transesterification of the fatty acids in vegetable oils. It is composed of methyl esters produced from the transesterification of triglycerides with methanol, or it may be composed of ethyl esters from the transesterificatoin of triglycerides with ethanol. Fuel resulting from the transesterification of vegetable oils with lower alcohols other than methanol and ethanol would also be suitable, however such fuels are not currently commercially available. The firelighter fuel can be made from any vegetable oil, for example rape oil or the used cooking oil from fast food restaurants. As it is derived from vegetable sources it is environmentally sustainable and does not contribute to the release of carbon into the atmosphere. In the case of waste cooking oil, the production of biodiesel recycles an otherwise waste material. Biodiesel has a calorific value just less than that of normal mineral fuels. It is odourless and it produces less smoke during burning than mineral oil. Unlike mineral fuels biodiesel is non-tainting therefore can be used in firelighters for cooking fires or barbeques. Biodiesel has been commercially available for a number of years, primarily as methyl esters.

Raw vegetable oils could also be used to impregnate the fibreboard, however they are much more viscous than biodiesel, therefore vegetable oils would take a longer time to absorb into the fireboard. Raw vegetable oils also have a much a higher flash point than biodiesel, so would be more difficult to set alight.

The wrapper is a paper-polymer laminate comprising paper 12 coated with a thin polymer layer 13, the polymer layer being on the inside of the wrapper, adjacent to the fibreboard 10. The inner polymer layer is combustible, and impermeable to the biodiesel, therefore it retains the liquid fuel and its vapours. The polymer layer ensures that the firelighter is clean to the touch and does not have a strong odour. A wrapper of paper alone is unsuitable for containing liquid fuels as paper is permeable and would allow liquid fuels to leak through the wrapper and evaporate.

The outer layer is made of paper so that the firelighter is quick and easy to light. The paper also adds an extra layer of protection to prevent the inner polythene layer from being punctured or torn. Kraft paper (a coarse paper made from wood pulp) is used as it has high strength. The Kraft paper is typically 40 - 80 gsm, and preferably 60 gsm Kraft paper is used. Other combustible material such as cardboard can be used for the outer layer.

The polymer layer of the paper-polymer laminate wrapper must be sufficiently impervious to the liquid fuel in order to prevent leakage and also impervious to the fuel vapour to prevent evaporation of the fuel. The polymer layer of the wrapper comprises a polyethylene layer of thickness 50 - 80 microns and a polyamide layer of thickness 10 - 20 microns. The paper- polymer laminate wrapper is around 100 - 150 gsm in total. Polyethylene is used in the wrapper as it is flexible and tough and has a low softening point, so the wrapper can be heat sealed to form a leak tight package. However, polyolefm films are not completely impervious to hydrocarbons and hydrocarbon derivatives. Polyamide films have better barrier properties to hydrocarbons than polyolefins, therefore the polymer layer also includes a thin layer of polyamide film to enhance the barrier properties. Alternatively a polyester film could be used in place of the polyamide film as polyesters also have superior barrier properties than polyolefins. Of course, other materials which are tough, combustible and have good barrier properties can be used in the inside layer of the wrapper.

The ratio of the thicknesses of the paper and polymer layers should be chosen to ensure that the wrapper is strong and tear resistant, that it is easy to light and that once set alight, the firelighter bums well. Preferably the wrapper comprises a layer of 60 gsm Kraft paper, a polyethylene layer of 60 micron thickness and a polyamide layer of 12 micron thickness.

Thermoplastic polymer films such as polyethylene films are difficult to ignite because the plastic melts away from the source of the heat when ignition is attempted. Once the polymer is alight it burns with a small flame since most of the hot material drips away from the flame front. Small flames are more likely to be extinguished by wind or a small draught. The outer paper layer 12 in the paper-polymer laminate wrapper can easily be ignited and the paper provides a wick for the molten polymer to absorb into, preventing the polymer from dripping away from the flame. The polymer is retained at the flame front and therefore gives bigger flames which are less sensitive to draughts.

The polymer-paper laminate can be made by several different processes. In a first process, the polymer is extruded through a slot die as a film and then immediately pressed onto a paper substrate whilst the polymer is still hot and molten, so that the polymer adheres to the paper. The polyethylene layer can be adhered onto the paper first followed by the polyamide film on top of the polyethylene film, or vice versa. In a second process, a preformed cold polymer film is brought into contact with the paper and then heated to bond the polymer and paper together. The polyethylene layer can be bonded to the paper first, followed by the polyamide film or vice versa. Structured laminates comprising two or more polymer films can be formed in this way. Rather than using polymer-coated paper, separate layers of paper and polymer film may be used. The paper and polymer film may be glued together by use of adhesive and additional layers of polymer or paper may be added.

The paper-polymer laminate wrapper has many advantages over a wrapper comprising merely paper or plastic. The wrapper is tougher and less easy to puncture or tear than a single layer wrapper. It can be ignited easily, it bums well and it is impervious to the volatile liquid fuel contained in the firelighter.

The impregnated core is wrapped in a rectangular piece of the polymer- coated paper, the polymer layer forming the inner layer, adjacent to the fibreboard. Referring to figure 3, the wrapper is folded around the impregnated fibreboard, and sealed to form an envelope around the core, preventing leakage of the fuel. The impregnated fibreboard is placed in the center of a rectangular sheet of the wrapper (polyethylene side next to the fibreboard), having an area of around 110 mm by 170 mm, with the fibreboard edges parallel to the wrapper edges. The opposite, shorter sides of the rectangular sheet are folded over the fibreboard and brought together over the board, leaving around a 10 mm overlap of the polyethylene coated paper. A seal 32 is formed at the overlap either by means of a strip of pressure sensitive adhesive or by heating the area of overlap, thus melting the polyethylene and adhering the paper. Polyethylene has a low softening point and therefore the paper-polymer laminate wrapper can easily be heat sealed. There is an overlap 31 of around 10 mm at each of the two edges of the firelighter that run perpendicular to the seal 32. The two opposite ends 31 of the firelighter are then sealed in the same way.

Sheets of polymer coated paper of different sizes or shapes can be used to package the impregnated fibreboard, provided there is sufficient overlap of the wrapper to form strong seals, to prevent leakage of the fuel.

During use, the firelighter is placed amongst the fuel of the fire to be lit

(eg the briquettes of a barbeque). It should be placed reasonably centrally within the pile of fuel so as to ignite as much of the fuel as possible. The firelighter should be left accessible so that it can be lit, for example with a match or lighter, and it should also not be completely enclosed by the fuel so that there a good supply of air to allow it to bum for as long as possible. The wrapper is ignited, which then causes the core to catch alight. The firelighter of this embodiment will bum for around 12 minutes.

Referring to figure 4, in another embodiment, the firelighter comprises a large core made of compressed wood chips 41, saturated in kerosene. The wood chips are compressed, using a mould, into a cylindrically shaped block of length 150 mm, diameter 50 mm and mass 300 g. The compressed wood chips have a density of around 1.0 g/cm³ and a porosity of around 33 %. Kerosene is more volatile than biodiesel, having a flash point between 50 and 150 °C, therefore it is very easy to ignite. The block is immersed in kerosene for three minutes, in which time it absorbs around 12-14 % kerosene by volume. A minimum absorption of 10 % kerosene is necessary for the block to ignite and bum efficiently. The firelighter bums for around 40 minutes and can therefore be used to start large fires, which require a longer burning firestarter. The impregnated block is wrapped in a paper-polymer laminate wrapper comprising paper 43 coated by a layer of polymer 42, the polymer being adjacent to the wood chip block 41.

Claims

1. A firelighter comprising a porous material and a wrapper enclosing the porous material, said porous material having been impregnated with a volatile liquid fuel, wherein the wrapper is laminate, comprising at least two layers, the layers comprising a first polymeric layer and a second non-polymeric layer.

2. A firelighter according to claim 1 wherein the polymeric layer is on the fuel side (the inside layer) of the wrapper.

3. A firelighter according to claims 1 or 2 wherein the polymeric layer is polyethylene.

4. A firelighter according to claims 1 or 2 wherein the polymeric layer is laminate, comprising at least two layers.

5. A firelighter according to claim 4 wherein the polymeric layer comprises a first polyethylene layer and a second layer of a non-polyolefinic material.

6. A firelighter according to claim 5 wherein the polymeric layer comprises a first polyethylene layer and a second polyamide layer.

7. A firelighter according to claim 6 wherein the polymeric layer comprises a polyethylene layer of thickness greater than 50 microns and less than 80 microns and a polyamide layer of thickness greater than 10 microns and less than 20 microns.

8. A firelighter according to any previous claim wherein the non-polymeric layer is paper.

9. A firelighter according to any preceding claim wherein the porous material has a porosity of more than 50 % and less than 80 %.

10. A firelighter according to any preceding claim wherein the thickness of the firelighter (t) is less than half the width (w) and the depth (d) of the firelighter.

11. A firelighter according to any preceding claim wherein the volatile liquid fuel is biodiesel.

12. A firelighter according to claim any of claims 1 to 10 wherein the volatile liquid fuel is kerosene.

13. A firelighter according to any preceding claim wherein the porous material is fibreboard.

14. A firelighter according to any preceding claim wherein the wrapper is sealed to prevent leakage of the fuel.

15. A firelighter comprising a porous material and a wrapper enclosing the porous material, said porous material having been impregnated with a volatile liquid fuel and characterised in that the volatile liquid fuel is biodiesel.