IGNITING LIQUID COMPRISING GAMMA-VALEROLACTONE AND ITS USE

TECHNICAL FIELD

The invention relates to a gamma-Valerolactone based igniting liquid and to the use of gamma-Valerolactone as an igniting liquid or igniting liquid additive.

BACKGROUND ART

In everyday use, igniting liquids are used for triggering the ignition of various materials, primarily when grilling, and they are also applied as an illuminating liquid in lamps and tea-lights. Furthermore, igniting liquids are accessories used by fire blowers or fire jugglers. In the industry, a large volume of igniting liquid, primarily petrol, is also used, mainly for the burning of wastes. Because the igniting liquids generally burn at a low temperature, plenty of carbon-monoxide is released during burning, which may lead to poisoning, and because of their low flash point, the storage and transportation of these liquids are dangerous.

Most frequently, petroleum-based igniting liquids are used, but in the literature new compositions of applicable igniting liquids are increasingly often described. There are attempts to make the new igniting liquids environmentally friendly and less risky or to produce them from such ingredients which burn cleanly and during their burning would not generate many such volatile organic compounds (VOC) ₁ which contaminate the environment and harms the health. Furthermore, in the case of igniting liquids it is an important consideration that they should have a pleasant smell or no odour at all.

One of the biggest problems of petroleum-based igniting liquids is their low flash point, the flaring up into flames, and their aromatic hydrocarbon content. Hence, many of these compounds could be highly hazardous to health.

There are several prior art approaches to replace petroleum based igniting liquids.

These materials comprise various terpenes, short chain (C1-C3) alcohols, detergents, various surfactants, thickening additives and water. Such an approach is described for example in US 6,843,812 B2. In this described mixture, the

proportions of constituents may change in a broad range. The terpene applied as a component is limonene, which has a low flash point (50 ⁰ C), consequently it can be easily set on fire, and it is a colourless liquid with a strong orange odour at room temperature, highly harmful to health and the environment. Due to its poisonous effect, an ingredient with an unpleasant flavour is added to protect children and animals. A non-ionic polymer or the esters of long chain alcohols are used as a surfactant, and the thickening agents are partly cross-linked ionic polymers or co-polymers, which make an impact if there is a change in the pH value. However, their shelf life is a few days only in many cases, because a phase separation takes place in the mixture. Although the original status can be restored by shaking, it is not a very comfortable approach to shake for example a lamp with all of its contents each time before it is ignited.

US 2005/0115145 A1 discloses an igniting liquid containing saturated fatty acid esters, methyl laurate (C12) and methyl stearate (C18), as well as ethyl alcohol. The methyl laurate content is 40 to 70 % by weight, the methyl stearate content is 10 to 30 % by weight and the ethyl alcohol content is between 5 and 25 % by weight.

Grilling is gaining increasing popularity today. However, the number of accidents caused by igniting liquids is also on the increase. Although a BBQ igniting liquid used on an everyday basis accelerates the process of creating glowing coals, the general view is spreading that the igniting liquid is such a chemical which is dangerous, pollutes the environment, harmful to health and even spoils the flavour of grilled food. In addition to the risk of carbon monoxide poisoning, the coals suddenly flaring up into flames may cause burns. A very fashionable example of other uses of igniting liquids is the application of various candles, torches, lamps and evocative tools. Earlier, mainly petroleum was used in lamps. However, petroleum has a very unpleasant odour and because of its low flash point and harmful effect on health and the environment, its transport is also more risky.

Of the physical and chemical characteristics of an ideal igniting liquid, especially important factors are for the user the pleasant smell, a density and viscosity which facilitate the pouring of the liquid, the igniting of the flame rapidly but not suddenly and without a flash, and the steady and continuous maintaining of fire without

smoke and odour even when the movement of air is not insignificant. Further important considerations are the lowest possible toxicity and minimising the negative effect on the environment. The regulation, control and statement of production, storage, transport and application of igniting liquid could be substantially facilitated if it is made of one or two well-defined materials.

DESCRIPTION OF THE INVENTION

According to the invention we have recognised that gamma-Valerolactone (alternative IUPAC name: 4-pentanolide) is excellently applicable as an igniting liquid or igniting liquid additive. The igniting liquid according to the invention contains at least 50 % by weight gamma-Valerolactone. Preferred embodiments of the invention are defined in the dependent claims.

gamma-Valerolactone

MODES FOR CARRYING OUT THE INVENTION

Gamma-Valerolactone has a flash point of 96 ⁰ C, and a boiling point of 206 ⁰ C.

According to the general point of view, these values are too high for application as an igniting liquid. Our experiments carried out with gamma-Valerolactone proved that a lit match has failed to ignite the gamma-Valerolactone liquid film on a charcoal surface even from a distance of a few millimetres. However, when the lit match contacted the gamma-Valerolactone liquid film on the charcoal surface, the ignition was triggered without flashing.

Because of its favourable physical and chemical characteristics, gamma- Valerolactone may be a renewable energy and raw material source and hence can play a decisive role according to the current results of research. Gamma- Valerolactone found in fruit and also applied as a food additive in food industry can be one of the most important raw materials, because it can be used for turning out energy and carbon-based products, can be produced from carbohydrates, and can

- A - be stored and transported easily and safely, because it has a low freezing point, and high boiling and flash points. Its mixing with water without any limitations, this substantially helps significantly its decomposition in the environment.

These physical and chemical characteristics of gamma-Valeroiactone make it especially suitable for application as an igniting liquid or igniting liquid additive. We have proven the successful application of gamma-Valerolactone as an igniting liquid by igniting charcoal available in trade and also by using it in a wick lamp. In our previous experiments, not only gamma-Valerolactone, but also various compositions of gamma-Valerolactone/bio-ethanol mixture were tested, thereby examining the applicability of gamma-Valerolactone as an additive. On the basis of our experiments it can be stated that gamma-Valerolactone can be used excellently both as an igniting liquid and an igniting liquid additive, because when ignited by a match, it does not burst into flames suddenly, the flame burns steadily and without soot. Further advantages are that the odour of this material is pleasant, an unpleasant smell is not generated during its burning and it will reliably burn even in a relatively high wind.

Experiment 1

In our experiment, we have injected 1 ml gamma-Valerolactone on about 3-4 g piece of charcoal, and then approached a lit match toward it. It took about 5 to 10 seconds to ignite the charcoal with the match flame, and after about 5 minutes the flame was blown out, but the charcoal continued to glow. It is important to emphasise that it is difficult to ignite gamma-Valerolactone with an open match flame, because it is not enough to put the flame in the gamma-Valerolactone vapours above the surface of the liquid, but it is necessary to touch directly the surface of the liquid with the flame and therefore a sudden flashing of the igniting liquid can be absolutely ruled out. It is important to note that charcoal cannot be ignited directly with a match without an igniting liquid.

It is a great advantage of the igniting liquid according to the invention, especially for the purpose of avoiding burns, that when the flame is positioned above the liquid, gamma-Valerolactone does not burst into flames; this only happens when the surface of the liquid is touched with the match flame and even then it is not ignited suddenly with a huge flame, but it starts to burn slowly and steadily on the

whole surface. Thanks to its high oxygen content, gamma-Valerolactone burns without generating smoke and soot, contrary to hydrocarbon based igniting liquids which emit a heavy dose of soot due to imperfect burning. As a result of its low vapour pressure, gamma-Valerolactone does not evaporate quickly, its odour is pleasant and sweetish, hence it does not spoil the flavour of grilled food either. It is not harmful to health since it is found in fruit also, and it is used by the food industry as a food additive. Because gamma-Valerolactone can be generated from renewable base materials, its application does not contribute to carbon-dioxide emission, in fact it reduces emission coming from the use of BBQs and this can be an important environmental benefit in light of the large number of users.

Since a lit match failed to ignite the gamma-Valerolactone liquid film on a charcoal surface even from a distance of a few millimetres, it seemed to be expedient to mix it with a low volume of another higher vapour pressure component, which accelerates the ignition of gamma-Valerolactone without contact. For this purpose, ethyl alcohol (bio-ethanol) seemed to be most suitable, because it is used broadly as an igniting liquid additive.

Therefore, the igniting liquid according to the invention preferably contains alcohol as well. The alcohol content may preferably go up to 50 % by weight. Above this ratio, the low flash point of the alcohol would dominate, that would make the igniting liquid dangerous. An alcohol ratio between 1 and 25 % by weight is especially preferable, because in this proportion the favourable characteristics of the ingredients are properly combined. Eventually, instead of ethyl alcohol methyl alcohol, propanol or butanol may be applied.

Bio-ethanol burns very well and is quickly ignited on its own, but it bursts into large flames suddenly, which can cause accidents. To avoid this, we have examined the gamma-Valerolactone/bio-ethanol mixtures primarily in such proportions where gamma-Valerolactone is dominant, i.e. its favourable effect prevails. Creating a single phase mixture, gamma-Valerolactone mixes with bio-ethanol, consequently it can be used as an excellent additive in ethanol based igniting liquids.

Experiment 2

When preparing the gamma-Valerolactone/bio-ethanol mixture, we have proceeded by using a 10ml syringe for dosing the required volume of gamma- Valerolactone into an Erlenmeyer-flask, and we have added bio-ethanol with the syringe in a suitable proportion, and after stirring for a few seconds, a semi- transparent homogenous solution was obtained. By injecting and igniting the mixture on charcoal, we have observed the slow spreading of the flame, and when was blown out, we saw the continued glowing of the charcoal.

When the ethyl alcohol dominated, i.e. when a 90/10 % by weight and a 80/20 % by weight mixture of ethyl alcohol and gamma-Valerolactone was examined, the ignition of the applied liquid and the charcoal was immediate, and it was not necessary to touch the match to the liquid, i.e. approaching the flame toward the surface was enough for ignition. The ignition proclivity of the mixture (flaring up into huge flames suddenly) is determined by the characteristics of ethyl alcohol in accordance with the proportions. The higher the alcohol content in the mixture, the more the mixture was liable to flare into high flames suddenly, which made the igniting liquid dangerous.

When examining a 90/10 % by weight and a 80/20 % by weight mixture of gamma- Valerolactone and ethyl alcohol, i.e. when gamma-Valerolactone was dominating, the favourable characteristics of lactone have become evident. The mixture was not ignited when the flame was approached, this only happened at the moment of direct touch, and no flaring was experienced, therefore avoiding any concerns about burns caused by ignition. The small bluish flame burnt in a modestly small size steadily and without any smoke.

Experiment 3 About 15 to 20 ml gamma-Valerolactone was filled into a wick lamp available in trade. We inserted the wick and waited for a few minutes until it soaked up the liquid, followed by ignition. The flame burnt uniformly without soot, there was no flickering, and the smell was pleasant, but not intensive.

Using gamma-Valerolactone as the igniting liquid of lamps, i.e. as an illuminating liquid is very favourable, because gamma-Valerolactone has a low vapour pressure, and if it is not in use the liquid will not evaporate with time and would not

emit an unpleasant odour. Due to its high oxygen content, it bums better than hydrocarbons, consequently there is no soot and no smoke is generated either. Of course, with further additives it can be made more colourful and more fragrant, which can make the igniting liquid even more attractive. By the use of various additives, the igniting liquid can be used as a fragrance or for repelling mosquitoes, flies, wasps and various insects.

The igniting liquid according to the invention may be produced also with further additives. Preferred additives are for example oxygenates, i.e. especially ethers (methyl-tert-butylether, ethyl-tert-butylether), esters (ethyl acetate, butyl acetate), carbonates (dimethyl carbonate, ethylene carbonate, diethyl carbonate) and hydrocarbons (less toxic alkanes, e.g. heptane, octane). The flash point of these additives is low and their vapour pressure is high; this is why it is preferable to mix them in a proportion so that the vapours of the resulting igniting liquid can be ignited from a max. distance of 1 cm within 2 seconds. To make sure that the favourable effect of gamma-Valerolactone is manifest and that the coals do not flare into flames suddenly when ignited, the proportion of these additives may not be higher than 50 % by weight either.

In addition to the ingredients above, the igniting liquid according to the invention may of course include the usual igniting liquid components like water, a surfactant and/or a thickening agent, for example in the proportions identified by prior art documents.

Of course, the invention is not limited to the preferred embodiments shown by way of example, but other variants are also possible within the range of protection defined in the claims.