EP0059178B1 - Use of a solution for extinguishing fires and simultaneously flame-proofing the surroundings of the fire - Google Patents

Description

The present invention relates to the use of a solution which can not only be used to extinguish fires or fires, but also for, in particular, short-term and / or temporary flame-proofing of a wide variety of materials, such as wood, textiles or porous plastic objects , is suitable.

It is already known to use solutions of inorganic salts, such as, for example, alkali or alkaline earth metal salts of carbonic acid, phosphoric acid, boric acid and the like, to extinguish fire. Relatively concentrated solutions are used, whereby the dissolved salts support the extinguishing effect of the water on the fires in so far as either inert gases are released during the heating process, which does not release the fire-maintaining gases (such as C0 ₂ in the case of carbonates) or the salts during heating melt and in turn cover the burning materials with a melt that prevents oxygen access. In this way, the pure extinguishing effect of the water is significantly supported. The disadvantage of these previously known solutions is that they are not suitable as such for short-term and / or temporary flame-resistant impregnation of various substances, since in the case of fire fighting with such solutions after extinguishing the fire or with a temporary impregnation on the sprayed objects which have not been destroyed by the flames, a coating which is difficult to remove sticks, so that it can be said in particular that the extinguishing or impregnation process usually causes additional damage.

The present invention has set itself the goal of finding a solution for extinguishing fire which does not have the above-mentioned disadvantage and which, moreover, is also already prophylactic, due to this fact. H. for short-term or temporary flame retarding of materials.

The present invention thus relates to the use of, in addition to optionally alkali metal hydrogen carbonate and / or optionally volatile or gaseous blowing agent, exclusively alkali metal citrate in a concentration of 10% by weight up to the saturation concentration having an aqueous solution for extinguishing fire and at the same time flaming the surroundings of the source of the fire .

As already mentioned in the introduction, the solution used according to the invention is not only suitable for fire fighting, but also for preventive fire protection on the one hand, the environment of a fire by fire-retardant impregnation and, on the other hand, of objects which are to be temporarily protected from possible fires. For these purposes in particular, it is essential that the fire protective applied solution, after it has served its purpose, can be removed from the object in question easily and without leaving any damage or discoloration of the object. It is known that fire fighting by the extinguishing agent can often cause greater damage than the actual fire; this applies in particular to relatively small fires, for their safe fighting relatively large amounts of extinguishing agent must be used, which in turn - in the case of the use of conventional fire extinguishing agents - damage or ruin the surroundings of the source of the fire. These disadvantages can be avoided by the solution used according to the invention.

In particular, the solution used according to the invention is also suitable for use in automatic fire extinguishers in which, as in the case of a sprinkler system, for example, extinguishing liquid is sprayed automatically when smoke or when a certain temperature increase occurs. If the solution is used according to the invention, not only is the necessary consumption of extinguishing agent reduced compared to pure water, so that no additional water damage occurs, it is also much easier to clean the room in question after the fire has been extinguished, since the solution used according to the invention after drying can be easily removed from the objects in the vicinity of the source of the fire (for example by brushing or by suction or the like). This easy removability of the agent after achieving the desired effect is lost if further salts (sodium chloride, sodium sulfate or the like) are added to the solution: a hard, firmly adhering coating is then formed which is only washed off from the objects or, if appropriate, at all cannot be removed.

The essential effect of the solution used according to the invention is that it can be easily removed again after it has served its purpose, without requiring a substantial amount of work and, above all, without affecting the objects from which it is to be removed. any permanent damage occurs.

Finally, the solution used according to the invention is particularly suitable for the flame-resistant impregnation of objects which in turn are only used for a short time; In particular, it is thought of the impregnation of Christmas trees, which every year around the turn of the year, when they are already very dry due to the relatively high room temperature, when trying to find them to light candles, catch fire, usually afterwards at least the room in which they are placed becomes a robbery of the flames. Spraying with the solution used according to the invention is easy to carry out since it is completely harmless to health and certainly prevents the formation of a dreaded Christmas tree fire, even if the tree itself has already dried out to a large extent and is therefore inherently flammable.

If hydrogen carbonate and citric acid are used in the mixing, the pressure required to spray the solution can be built up by the constituents themselves in the closed vessel.

As a further advantage of the solution used according to the invention, it should be mentioned that it is completely harmless to health, in fact - if pure substances are used - it could easily be drunk.

From AT-A 298 254 it has already become known to add an alkali carbonate to an extinguishing liquid for extinguishing fires of those substances from which harmful gases are released in the event of fire or heating, when fires are combated in which acid gases are released if a fire is to be combated in which alkaline substances are released, u. a. Add sodium citrate. According to this proposal, however, alkali carbonates, on the one hand, and sodium citrate, on the other hand, should never be used in combination with one another, but should only be used to combat or bind the acidic or alkaline gases released during the fires. In addition, according to this proposal, the substances specified should not be used for fire fighting per se, but only for binding the released gases, which means that these substances are added to the extinguishing liquid in a relatively small proportion. It is expressly stated that the substances are preferably used in a proportion of 1%. In contrast to this, the proposal according to the invention is based on using the alkali metal citrate, possibly in a mixture with the bicarbonate, as such for fighting fires, the salts being provided in substantially larger proportions in the extinguishing water.

From US-A 1 278 716 it is already known to provide fillings for fire extinguishers which consist of high-percentage solutions of tertiary alkali metal citrate with a more than 3-molar excess of alkali metal hydrogen carbonate. These solutions must also necessarily contain further salts, in particular alkali metal sulfate or alkali metal chloride, when they are applied to the source of the fire, since they are intended to be used in fire extinguishers in which the reaction of the alkali metal metal bicarbonate present with a suitable acid, such as sulfuric acid or hydrochloric acid , C0 ₂ arises, which supplies the pressure necessary for spraying the agent. It should be expressly pointed out that with such solutions which, when sprayed, in addition to the alkali metal citrate or, if appropriate, also alkali metal hydrogen carbonate, also contain sulfate or chloride or the rest of another salt-forming acid, the effect which can be achieved according to the invention, namely the easy removal of the residues after the quenching of the Fire, cannot be achieved. Experiments have shown that when sulfates, chlorides or, for example, phosphates are added to the solution used according to the invention, hard, firmly adhering coatings remain on the sprayed objects after the water has evaporated, which coatings can be removed only with difficulty and mostly with damage to the respective objects can. The surprising moment according to the invention is therefore primarily that if one or more of the constituents which have always been present are omitted from known mixtures or solutions for fire-fighting purposes, a special and surprising effect which could not be predicted in any way is achieved can.

The following examples are intended to explain the present invention in more detail, without, however, being restricted thereto.

All examples were carried out using a spray which was prepared in aqueous solution from 420 ml (= 37.80 g) sodium hydrogen carbonate and 400 ml (= 36 g) citric acid per liter of water. The spray was sprayed by means of an atomizer pump or from a spray can, a conventional, non-flammable fluorine-chlorinated hydrocarbon being used as the propellant. A propane gas flame at approx. 1,000 ° C was used as the pilot flame.

example 1

A wooden board, 20 x 20 cm, 2.5 cm thick, was smeared with the flame for 30 minutes, the board burned to about 2/3 of its volume. When spray-impregnated, the surface only browned. The fire protection agent turns white when it is exposed to fire and later also black, thereby forming a glaze over the entire surface. After a 1/2 hour use of the propane gas flame, there were no effects of fire, except for the brown surface and the black glaze with the fire protection agent.

Example 2

This experiment was carried out with a cleaning rag. Without impregnation with the spray, the cleaning rag burned after a few seconds. After impregnation with the spray, the same symptoms appeared again; when the flame strikes the surface turns white and then black again after prolonged exposure to the flame. The cloth is after the Impregnation hard, the surfaces of the pores are closed. The addition of citric acid is clearly noticeable here. The sodium hydrogen carbonate alone does not give such a hard surface and therefore does not provide this protection against flammability. The sodium bicarbonate alone does not create a surface as closed as with the solution used according to the invention. Immediately at the flame core, the cloth became black, outside the flame area the cloth remains as it was originally, but somewhat stiff and hard due to the impregnation. When the flame is withdrawn, there is no further burning, neither in the flame area nor outside the flame. After the test was completed, the impregnation could be removed by rubbing or brushing or washing out. This made the cloth supple again.

Example 3

This experiment was carried out with a plastic carpet. All plastic carpets would go up in 5 to 10 s when the flame strikes. The surface of the carpet melts and gives a black hard surface, whereby the lower foam of the carpet also burns immediately. The flames are very aggressive and spread very quickly, especially when there is wind. Half of a test carpet was sprayed with the spray and the progress of the flames was interrupted at the border. The surface had turned very little black, despite being exposed to a flame for half an hour. The non-impregnated part of the carpet was completely burned and melted away. All that was left was the impregnated part, the surface of which retained the entire structure. When spraying these carpets you hardly notice any change. Only after the water has evaporated does this surface become a little hard. All pores of the hair are thus closed, which alone significantly reduces the combustible surface of the carpet. By closing all of the pores in the hair of the carpet, the dangerous toxic gases which are produced in the event of a fire are prevented from escaping. Since the impregnating agent does not emit any gases apart from a little carbonic acid when extinguishing and the gas development during carpet fire is severely hampered, gas poisoning during fire fighting is avoided. When exposed to the flame, the impregnated carpet turns white on the surface and black if it burns further. This black layer forms the insulating surface against the underlying material.

Example 4

A cup with a diameter of 30 cm and a height of approx. 2 cm was filled with oil, set on fire and then extinguished when sprayed for the first time. When sprayed, the pressure of the liquid sprayed on the oil blows the fire aside. The subsequent fire protection agent then closes the surface of the oil with this agent; this will extinguish the fire. Immediately when spraying, a white film is formed on the oil surface, which comes from the fire protection agent. In this fire test, the solution used according to the invention was inflated onto the oil by a small atomizer.

Example 5

This experiment was carried out with rubber. About 1/2 kg of rubber waste was lit. Only when the flame was correct, about 60 cm high, was the spray sprayed for 1 to 2 s; the flame went out immediately. A white layer was again visible as residue. Since nothing else burned, the fire protection agent could not melt and absorb carbon released during the fire.

In all of the tests, it was found that all flammable materials that were sprayed with this spray did not burn afterwards. Since only small quantities were used in the fire tests, it was found that very little material is required to fight the fire. The white surface already mentioned is just so far visible that it results in a very thin white layer, similar to a layer of icing sugar. Since this layer is sticky, fire protection or fire fighting can be carried out in any position; this is in contrast to the possibility with normal foam extinguishers, where the foam cannot be used overhead.

From these examples it can be seen that when sprayed with the solution used according to the invention as a fire protection agent, a moist impregnation is initially formed on the surface. When exposed to fire, the water evaporates, the salts are separated and form a thin white layer. This layer is hard and becomes harder with further exposure to flame until it begins to melt. It turns black and ductile until it becomes brittle when exposed to further flames. The flammable material underneath can carbonize in extreme cases, but there is no ignition.

Claims (2)

1. The use of an aqueous solution comprising additionally to optionally present alkali metal hydrogen carbonate and/or optionally present volatile and gaseous propellant exclusively alkali metal citrate in a concentration from 10 % by wieght up to the saturation concentration for extinguishing fire and simultaneously rendering flame and fireproof the neighborhood of the fire center.

2. The use of an aqueous solution of a mixture of secondary and tertiary sodiumcitrates for the purpose mentioned in claim 1.