EP1013311B1 - Extinguishing compositions - Google Patents

Description

The present invention relates to the field of fire extinguishing and more particularly relates to portable aerosol spray water containers which can be used to extinguish class B fireplaces (combustible liquids) and class A fireplaces (absorbent solid materials such as fabrics , paper, wood ...) as well as oil fires.

For the extinction of fires of absorbent or porous materials, combustion inhibitors are generally used such as, for example, ammonium phosphates or sulphates, which under the action of heat decompose endothermically. Decreasing the heat energy of the hearth, this decomposition inhibits the chain reaction mechanism of combustion and considerably reduces the emission of combustible gases. The flame retardancy mechanism by ammonium phosphates and sulfates has been described by S. SZONYI and A. CAMBON in the General Safety Review n ° 92, March 1990, pages 68-76, as well as in the work entitled " Ambient Extinguishing Agents and Inert Gas ”from the National Center for Prevention and Protection, 1982, chapter 3, pages 79-129.

Combustion inhibitor products are used in particular in aqueous solution or dispersion for extinguishing forest fires (long-term retardants). They are also used in the composition of many combustion inhibitor liquids for absorbent materials (US Patents 2,569,714, US 3,293,189. US 4,447,336, US 4,606,831, US 4,983,326, US 3,558,486, US 4,272 414, DE 2 724 162, DE 3 735 707, BE 895 993, BE 721 816, FR 2 019 890, FR 2 663 945 and DE 2 921 306).

Used in solid form, the ammonium phosphates and sulphates also constitute the basic elements of the ABC extinguishing powders as described in the patents DE 1 233 276, DE 1 542 506, DE 1 621 718, DE 2 625 351, DE 2 902,948. DE 3,321,174, DE 4,136,398, GB 1,410,469 and FR 1,510,555. US Pat. No. 3,553,127 describes the use of an extinguishing powder, the constituents of which (inorganic salts) are impregnated with a fluorinated surfactant to increase the resistance of the powder to re-ignition.

One of the well-known means for extinguishing fires of hydrocarbon liquids consists in projecting onto the hearth a foam obtained by mixing water under high pressure and an emulsifier based on hydrocarbon surfactants and a fluorinated surfactant. In this latter type of foam concentrate, known in the art as AFFF (Aqueous Film-Forming Foam) foam concentrate, the presence of the fluorinated surfactant makes it possible to produce a foam which, by decantation, forms an aqueous film floating on the surface of the oil. The purpose of this aqueous film is not only to extinguish the fire, but also to prevent possible re-ignition of the surface of the hydrocarbon. Foam concentrates of this type have been described in numerous patents, in particular the following: GB 1 258 299, US 5 086 785, FR 2 347 426, US 3 957 657, FR 2 040 316, US 4 350 206, FR 3 562 156, FR 2 148 442, FR 2 407 724, FR 2 385 413, US 3 772 195, FR 2 397 847, US 3 661 776, US 3 839 425, FR 2 103 669, US 3 957 657, US 3 963 776 and FR 2 296 625. AFFF foam concentrates produce, after dilution with water and addition of air, a foam forming, by decantation, an aqueous film which spreads over the entire surface of the hydrocarbon.

The first document dealing with the mixture between an inhibiting agent and an AFFF is the patent US Pat. No. 5,091,097. The main application of the formula described in this patent US Pat. No. 5,091,097 is the extinction of hydrocarbon fires and more particularly fires crude oil.

In patent EP 0 676 220 in the name of the applicant, a combustion inhibitor and an AFFF foam concentrate are also combined in a concentrate for portable extinguishers. This concentrate is intended to be diluted in water when using the extinguisher or when filling it.

In EP-A-0873768, an extinguishing composition is described comprising in aqueous solution at least one AFFF fire-fighting foam concentrate and at least one combustion inhibitor, as well as urea, citric acid and ethylene (or propylene) glycol. According to this document, this composition is in the form of a homogeneous and clear solution whose appearance is not changed, even after freezing. This composition is used as it is after dilution with water or is placed in a cartridge inside the extinguisher filled with water. In both cases, we are in the presence of a composition quite sensitive to frost, even if. after freezing and thawing, the appearance of this solution is not changed.

In the aforementioned cases, it would also be desirable for the compositions (concentrated or aqueous dilutes) to have a low gel point, typically down to -20 ° C. In fact, aerosols for domestic use, to which the invention particularly applies, must remain usable even if they are stored in a place not protected against frost (garage, shed, vehicle, etc.).

However, good extinguishing properties are difficult to obtain with a low freezing point formula. Indeed, the conventional way used to lower the freezing point of an aqueous composition to very low temperatures (down to -20 ° C.) consists in incorporating a water-soluble organic solvent therein playing the role of antifreeze. for example glycol. However, these compounds harm the extinguishing performance because they are flammable.

We are therefore looking for an extinguishing composition having good extinguishing properties while having a low freezing point, in particular intended for use in typically domestic aerosols (total capacity less than or equal to 2 liters) to extinguish incipient foci (for example foci of classes A and B described in standard NF 61-084 and oil fires).

Document DE-A-197 08 733 describes a composition comprising an ammonium salt, a fluorinated surfactant, a co-surfactant and an anti-freeze. The antifreeze comprises a polyol such as a glycol and preferably urea. The glycol: urea weight ratio is indicated as being between 4: 1 and 8: 1. The amount of anti-freeze in the composition of this document is 15 to 40% by weight, preferably 25 to 35% by weight, for a glycol content in the anti-freeze of 70 to 95% by weight ( and 30 to 5% urea).

In this document, the anti-freeze effect is obtained by the presence of a large amount of glycol. Even if it is indicated in this document that the compositions are extinguishing, they contain very large amounts of glycol, which are harmful. In addition, glycol is a relatively expensive compound that should be avoided as much as possible.

The invention therefore provides a composition having a low gel point. which is extinguishing and which contains a limited amount of glycol or anti-freeze solvent.

• a) au moins 1 % d'un émulseur AFFF ;
• b) au moins 5 % d'un inhibiteur de combustion ;
• c) de 3 à 20 % d'un solvant antigel ;
• d) au moins 10% d'urée, l'urée étant présente en une quantité au moins égale à celle du solvant anti-gel.

Thus, the invention provides such a composition, namely an aqueous extinguishing composition comprising, in% by weight relative to the weight of the composition:

• a) at least 1% of an AFFF foam concentrate;
• b) at least 5% of a combustion inhibitor;
• c) from 3 to 20% of an antifreeze solvent;
• d) at least 10% urea, the urea being present in an amount at least equal to that of the anti-freeze solvent.

• e) un tensioactif hydrocarboné, de préférence en une quantité d'au moins 0,10 % en poids, plus préférentiellement de 0,10 % à 0,5 % en poids.

According to one embodiment, the composition also comprises:

• e) a hydrocarbon surfactant, preferably in an amount of at least 0.10% by weight, more preferably from 0.10% to 0.5% by weight.

• a) de 1 à 3 % d'émulsion AFFF,
• b) de 5 à 15 % d'inhibiteur de combustion,
• c) de 5 à 15 % d'un solvant antigel, et
• d) de 15 à 30 % d'urée.

According to one embodiment, the composition comprises:

• a) from 1 to 3% of AFFF emulsion,
• b) from 5 to 15% of combustion inhibitor,
• c) from 5 to 15% of an antifreeze solvent, and
• d) from 15 to 30% urea.

• a) au moins 1 partie d'un émulseur AFFF ;
• b) au moins 5 parties d'un inhibiteur de combustion ;
• c) de 3 à 20 parties d'un solvant antigel ;
• d) au moins 10 parties d'urée, l'urée étant présente en une quantité au moins égale à celle du solvant anti-gel.

The subject of the invention is also a concentrated extinguishing composition (ie without water), comprising, by weight:

• a) at least 1 part of an AFFF foam concentrate;
• b) at least 5 parts of a combustion inhibitor;
• c) from 3 to 20 parts of an antifreeze solvent;
• d) at least 10 parts of urea, the urea being present in an amount at least equal to that of the anti-freeze solvent.

• e) un tensioactif hydrocarboné, de préférence en une quantité d'au moins 0,10 partie en poids, plus préférentiellement de 0,10 à 0,5 partie en poids.

According to one embodiment, the concentrated composition further comprises:

• e) a hydrocarbon surfactant, preferably in an amount of at least 0.10 part by weight, more preferably from 0.10 to 0.5 part by weight.

• a) de 1 à 3 parties d'émulseur AFFF,
• b) de 5 à 15 parties d'inhibiteur de combustion,
• c) de 5 à 15 parties d'un solvant antigel, et
• d) de 15 à 30 parties d'urée.

According to one embodiment, the concentrated composition comprises:

• a) from 1 to 3 parts of AFFF foam concentrate,
• b) from 5 to 15 parts of combustion inhibitor,
• c) from 5 to 15 parts of an antifreeze solvent, and
• d) from 15 to 30 parts of urea.

The invention also relates to an aerosol can comprising a composition according to the invention, under pressure.

The aerosol can can also comprise a concentrated composition according to the invention in a cartridge, and an aqueous solution, under pressure.

The aerosol can may also comprise in a first cartridge the components a), c), d) and optionally e) of a concentrated composition according to the invention, and in a second cartridge the component b) of a concentrated composition according to the invention. invention, and an aqueous solution, under pressure.

• a) au moins 1 % d'un émulseur AFFF ;
• b) au moins 5 % d'un inhibiteur de combustion ;
• c) de 3 à 20 % d'un solvant antigel ;
• d) au moins 10 % d'urée, l'urée étant présente en une quantité au moins égale à celle du solvant anti-gel;

avec une solution aqueuse.The subject of the invention is also a process for preparing an extinguishing composition comprising the mixture, in one or more stages, of the following compounds, in% by weight of the final composition:

• a) at least 1% of an AFFF foam concentrate;
• b) at least 5% of a combustion inhibitor;
• c) from 3 to 20% of an antifreeze solvent;
• d) at least 10% urea, the urea being present in an amount at least equal to that of the anti-freeze solvent;

with an aqueous solution.

The composition thus prepared advantageously has the preferred characteristics given in the present application.

The invention is now described in more detail in the description which follows.

The AFFF foam concentrate most often comprises an aqueous or hydroalcoholic solution, at least one fluorinated surfactant, at least one non-fluorinated surfactant, and at least one co-solvent such as a monoalkyl ether of mono- or di-ethylene- or propylene glycol. Preferably, an emulsifier is used whose content by weight of fluorinated surfactant (s) is between 5 and 25%, advantageously between 7 and 18%, that of surfactant (s) non fluorinated (s) ranging from 2 to 20%, preferably between 4 and 18%, and that of co-solvent can range from 20 to 50%, preferably from 30 to 45%.

• un agent antigel comme l'éthylèneglycol ou le propylèneglycol,
• un anticorrosif tel que le tolyltriazole ou le nitrile de sodium,
• un conservateur tel que le benzoate de sodium, le formaldéhyde, l'o-phénylphénol, ou le dichlorophène,
• un stabilisateur de pH tel que l'ammoniaque. la diéthanolamine, la triéthanolamine ou l'urée.

The foam concentrate can also contain various conventional additives in an amount which generally does not exceed 10% by weight:

• an antifreeze agent such as ethylene glycol or propylene glycol,
• an anticorrosive such as tolyltriazole or sodium nitrile,
• a preservative such as sodium benzoate, formaldehyde, o-phenylphenol, or dichlorophene,
• a pH stabilizer such as ammonia. diethanolamine, triethanolamine or urea.

The constituents of AFFF, namely the (at least one) fluorinated surfactant, the (at least one) non-fluorinated surfactant, the (at least one) co-solvent are described for example in the application on behalf of the applicant, published under No. EP-A-0 676 220, to which it is referred for more details.

In the context of the present invention, any of the known combustion inhibitors or a mixture of such inhibitors can be used. As nonlimiting examples of combustion inhibitor compounds. we can mention the orthophosphates of mono-, di-. or tri-ammonium, pyrophosphates of mono-, di-, tri- or tetra-ammonium, ammonium metaphosphate, ammonium polyphosphate, mixed salts of alkali metal ions and ammonium-orthophosphate, -pyrophosphate or -polyphosphate and ammonium sulfates and bisulfates. It is preferred to use orthophosphates and ammonium sulphates, in particular mono-ammonium orthophosphate, di-ammonium orthophosphate and ammonium sulphate or mixtures of these compounds.

The hydrocarbon surfactants which can be used in the formula can be anionic, nonionic or amphoteric compounds. Without limitation, mention may be made of the compounds of the following formula:

R _H -OSO ₃ M



R _H - (OC ₂ H _{4) q} -OSO ₃ M



R _H (OC ₂ H ₄ ) _q -OH



H (C ₆ H ₁₀ O ₆ ) _r -OR _H



R _H -CONH-C ₂ H ₄ -NH-C ₂ H ₄ OC ₂ H ₄ COOM



R _H -NH-C ₂ H ₄ -COOH



R _H -N (C ₂ H ₄ COOM) ₂

$${\text{R}}_{\text{H}}{\text{-N (CH}}_{\text{3}}{\text{)}}_{\text{2}}\text{→ O}$$ in which R _H represents an alkyl radical, linear or branched, containing from 4 to 18 carbon atoms, q is an integer ranging from 1 to 16, C ₆ H ₁₀ O ₅ denotes a glucoside group, r is an integer ranging from 1 to 6, preferably equal to 1 or 2 and M denotes an alkali metal ion or a quaternary ammonium.

The anti-freeze solvent is generally a polyol, advantageously a glycol, preferably ethylene glycol or propylene glycol.

The presence of urea in this aqueous composition has the effect of lowering its gel point. This antifreeze effect also makes it possible to reduce the amount of glycol type antifreeze to be used. In addition, urea makes it possible to obtain, in combination with the other constituents, a perfectly clear composition. The fact that this composition is clear, in opposition to a cloudy composition, guarantees the solubilization of each of the components and therefore the stability of the mixture.

Urea is preferably present in the composition in an amount at least equal to that of the anti-freeze solvent used, more preferably in an amount of at least 1.5 times.

Urea can be present in the form of a precursor which in contact with water turns into urea.

• a) l'émulseur ou l'inhibiteur est placé dans une cartouche à opercule,
• b) l'émulseur ou l'inhibiteur est placé séparé dans une cartouche à opercule, ou
• c) l'émulseur et l'inhibiteur sont placés tous deux dans une seule cartouche à opercule,

The constituents of the composition of the mixture according to the invention are typically used jointly in a conventional portable water spray extinguisher. They can all be there in premix with the water from the extinguisher, but also separately, for example according to one of the following methods:

• a) the foam concentrate or the inhibitor is placed in a cover cartridge,
• (b) the foam concentrate or inhibitor is placed separate in a cover cartridge, or
• c) the foam concentrate and the inhibitor are both placed in a single cover cartridge,

the other constituents being premixed either with one of the above constituents or with the water from the extinguisher.

An example of an aerosol container is a container which contains in a cartridge the AFFF, the antifreeze, the urea and optionally the additional surfactant and in another cartridge the inhibitor (for example in the form of a concentrated solution).

In practice, the various constituents are mixed with the water contained in the extinguisher at the time of use. Under the effect of the pressure, the mixture, that is to say the extinguishing composition, is expelled outside the body of the extinguisher and, by passing through the sprayer, forms a foam capable of extinguishing both class B fires (combustible liquids), class A fires (absorbent materials) and oil fires.

The pressure in the aerosol will be sufficient to obtain the formation of a foam (that is to say for the AFFF foam concentrate to play its role). The propellant is an inert gas such as nitrous oxide or nitrogen. Superior results have been obtained with a pressure in the aerosol can greater than or equal to 7 bars.

All the quantities expressed as a percentage are given by weight relative to the final weight of the compositions in question.

The following examples illustrate the invention without limiting it.

EXAMPLES

The foam concentrate is prepared under the following conditions:
At 40 ° C. and with moderate stirring, the following constituents are mixed by weight:
33.7 parts of a 31% aqueous solution of a mixture of fluorinated betaines of formula:

C _x F _{2x + 1} CH ₂ CH ₂ -SO ₂ NH-CH ₂ CH ₂ CH ₂ -N ^⊕ (CH ₃ ) ₂ CH ₂ COO ^⊖

before the following composition: x % 6 70 8 23 10 5 12 1.5 14 0.4 16 0.1
14.4 parts of a hydroalcoholic solution (35% ethanol) with 40% fluorinated amine oxide of formula: $${\text{VS}}_{\text{6}}{\text{F}}_{\text{13}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{-SO}}_{\text{2}}{\text{NH-CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{-N (CH}}_{\text{3}}{\text{)}}_{\text{2}}\text{→ 0}$$
15.2 parts of a 50% aqueous solution of alkyl (C ₈ and C ₁₀ ) amidoether propionate of formula:

alkyl-CONH-CH ₂ CH ₂ -NH-CH ₂ CH ₂ -OCH ₂ CH ₂ COONa

(Rewoteric AMVSF marketed by REWO),
4.7 parts of a 70% aqueous solution of alkyl (C ₈ and C ₁₀ ) -glucoside (Triton BG 10 sold by the company UNION CARBIDE), and
30 parts of diethylene glycol mono-n-butyl ether (C ₄ H ₉ -OC ₂ H ₄ -OC ₂ H ₄ -OH).

The mixture is then brought to pH 9.3 by addition of 2 parts of diethanolamine. The foam concentrate is thus obtained.

The combustion inhibitor is di-ammonium orthophosphate.

In the examples, the gel point is measured using the following procedure:

A DEWART with a capacity of 1 liter is filled with an acetone / dry ice mixture. A double-coated test tube is filled with the liquid compound for which the gel point is to be measured. A mercury thermometer and a system allowing the stirring of the liquid in this test tube are introduced. The test piece is then placed in the acetone / dry ice mixture. The contents of this test tube are regularly agitated so as to homogenize its temperature. The temperature drop is noted at regular intervals. The freezing point is characterized by a cessation of this drop in temperature, a sudden increase in the viscosity of the liquid and in some cases by the appearance of crystals. This operation is repeated three times for each liquid for which it is desired to obtain the freezing point.

Example 1

74 ml of water (74%) are poured into a 250 ml beaker and it is added thereto under slight stirring (magnetic bar 1 g (1%) of the abovementioned AFFF agent. 10 g (10%) of the above-mentioned combustion inhibitor and 15 g (15%) of 1,2-propanediol After a few minutes of stirring, the mixture is homogeneous and its gel point is measured according to the procedure given above. : -12 ± 1 ° C.

This composition is cloudy and is not extinguishing.

Examples 2 to 11

By proceeding as in Example 1, the mixtures in Table 1 given as a percentage by weight are produced. The gel points obtained for these mixtures as well as the appearance of the mixtures are shown in Table 1. TABLE 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 AFFF 1% 1% 1.5% 1.5% 1.5% 1.5% 1.5% Inhibitor 10% 10% 5.5% 5.5% 5.5% 10% 10% 10% 10% 10% Sodium octyl sulfate (42%) 0.35% 0.35% 0.35% 0.35% 0.35% Urea 15% 20% 25% 25% Ammonium nitrate 15% 1.2-propanediol 20% 25% 15% 20% 25% 15% 15% 15% 5% 15% Demineralized Water 69% 64% 79.5% 74.5% 69.5% 58.15% 53.15% 48.15% 58.15% 58.15% Frost point -14 ± 1 ° C -17 ± 1 ° C -11 ± 1 ° C -14 ± 1 ° C -16 ± 1 ° C -15 ± 1 ° C -18 ± 1 ° C -20 ± 1 ° C -5 ± 1 ° C -20 ± 1 ° C Product aspect Troub Troub Troub Troub Troub. Limp. Limp Limp Limp. Troub.

In Examples 7, 8, 9 and 10 in accordance with the invention, the combination of urea / 1,2-propanediol makes it possible to obtain a clear aqueous composition with a low gel point.

Examples 12 to 14 Hydrocarbon fire tests

The mixtures shown in Table 2 were prepared according to the procedure given in Example 1. TABLE 2 Ex. 12 Ex. 13 Ex. 14 AFFF 1% 1.5% 1.5% Inhibitor 10% 10% 10% Sodium octyl sulfate 42% 0.35% 0.35% Urea 25% 25% 1,2-propanediol 15% 25% 15% Demineralized Water 49% 63.15% 48.15%

The aerosols are 600 ml aluminum bottles filled with 240 ml of each of the compositions appearing in Table 2. The propellant gas used is nitrogen. The pressure of this gas in the aerosols is between 8 and 8.5 bars.

The aerosols thus obtained are evaluated according to the procedure below:

3 liters of water are poured into a circular tank 56 cm in diameter and then 2 liters of heptane. The extinction test with the aerosol can is only started 60 seconds after the fireplace is lit.

The aerosol is emptied by several successive presses on the diffuser button. For each test. note the completed emptying time of the aerosol as well as the control time at 90% of the hearth (time necessary for the flames to cover only 10% of the hearth's surface).

This series of tests was carried out outdoors with a temperature of 19.5 ° C and a wind of less than 3 ms ^-1 .

The results obtained are presented in Table 3. When the rows of this table include two series of results. this means that two tests were carried out with the same composition. TABLE 3 Mixture in aerosol Control time 90% Complete extinction Example 12 10 s 35s Example 13 <10 s no Example 14 <10 s
<10 s 15 s
25s

Examples 12 and 14, in accordance with the invention, are extinguishing compositions.

Example 15

300 ml of the composition of Example 14 are introduced into a 1 liter aerosol. The propellant is nitrogen. The pressure of this gas in the aerosol is between 8 and 8.5 bars. The aerosol is evaluated according to the procedure described in Examples 12 to 14. The only difference is that 5 liters of heptane are used instead of two. The results obtained are reported in Table 4. TABLE 4 Mixture in aerosol Control time 90% Complete extinction Example 15 <10 s 65s

Example 16

A test on type A fireplaces was carried out. The composition used for this test is shown in Table 6. TABLE 6 Ex. 16 AFFF 1.5% Inhibitor 10% Sodium octyl sulfate 42% 0.35% Urea 25% 1,2-propanediol 15% Demineralized Water 48.15%

The aerosol is an aluminum bottle filled with 600 ml with 250 ml of the composition shown in Table 7. The propellant used is nitrogen. The pressure of this gas in the aerosols is between 8 and 8.5 bars.

The aerosol thus obtained is evaluated according to the procedure described below:

The type A hearth consists of a stack of 12 Sylvestris pine logs 25 cm long and 4 x 4 cm in section. This stack consists of 4 stages of staggered logs. each stage being made up of 3 parallel sticks the most distant ends of which are 25 cm apart. This fireplace therefore has a floor area of 25 cm x 25 cm.

This fireplace is kept 21 cm from the ground on a metal support. A container 45 cm in diameter and 10 cm high is filled with 2 liters of water and 2 liters of heptane. This bin is lit then placed under the stack of wood. It is removed after 2 minutes of combustion. The wood fireplace is allowed to burn for an additional 6 minutes before starting the extinction test. The extinction is undertaken by projecting the composition on the hearth using successive presses on the button of the aerosol canister.

For each extinction test, note the time of complete emptying of the aerosol, the presence of flames after emptying, the presence of flame or red dots 3 minutes after extinction.

The result obtained is presented in Table 7 below. TABLE 7 Flames after emptying Presence of red dots Resumption of fire no no no

Example 17 Wood fireplace

The composition of Example 16 was evaluated on the type A hearth of standard NF 61-804. This fireplace is made up of 52 Carolina pine logs 20 cm long and 2.5 x 2.5 cm in section. This stack consists of 13 stages of staggered logs, each stage consisting of 4 parallel logs whose most distant ends are 20 cm apart. The fireplace therefore has a floor area of 20 cm x 20 cm.

The extinction is obtained with a 1 liter aluminum aerosol into which 300 ml of the composition of Example 16 has been introduced. The nitrogen pressure in the housing is between 8 and 8.5 bars. The extinction is obtained in less than a minute and no re-ignition is observed 3 minutes after the extinction.

Example 18 Oil fire test

One liter of peanut oil is poured into a 35 cm diameter container. The container is placed over a heptane fire. The oil ignites after about 25 minutes of heating. 30 seconds after the start of combustion, the jet of foam is directed at the oil. The intensity of the hearth immediately decreases, the fire goes out.

The extinction is carried out with an aerosol can containing 300 ml of composition from Example 16; less than 200 ml are used.

The compositions according to the invention are in particular free of citric acid, unlike the compositions according to document EP-A-0873768.

Claims (15)

1. Aqueous extinguishing composition comprising, as % by weight with respect to the weight of the composition:

   a) at least 1% of an AFFF emulsifier;

   b) at least 5% of a combustion inhibitor;

   c) from 3 to 20% of an antifreeze solvent;

   d) at least 10% of urea, the urea being present in an amount at least equal to that of the antifreeze solvent;

   the said composition being devoid of citric acid.
2. Composition according to Claim 1, additionally comprising:

   e) a hydrocarbonaceous surfactant, preferably in an amount of at least 0.10% by weight, more preferably of 0.10% to 0.5% by weight.
3. Composition according to Claim 1 or Claim 2, comprising, as % by weight with respect to the weight of the composition:

   a) from 1 to 3% of AFFF emulsion,

   b) from 5 to 15% of combustion inhibitor,

   c) from 5 to 15% of an antifreeze solvent, and

   d) from 15 to 30% of urea.
4. Concentrated extinguishing composition, comprising, by weight:

   a) at least 1 part of an AFFF emulsifier;

   b) at least 5 parts of a combustion inhibitor;

   c) from 3 to 20 parts of an antifreeze solvent;

   e) at least 10 parts of urea, the urea being present in an amount at least equal to that of the antifreeze solvent,

   the said composition being devoid of citric acid.
5. Composition according to Claim 4, additionally comprising:

   f) a hydrocarbonaceous surfactant, preferably in an amount of at least 0.10 part by weight, more preferably of 0.10 to 0.5 part by weight.
6. Composition according to Claim 4 or Claim 5, comprising, by weight:

   a) from 1 to 3 parts of AFFF emulsifier,

   b) from 5 to 15 parts of combustion inhibitor,

   c) from 5 to 15 parts of an antifreeze solvent, and

   d) from 15 to 30 parts of urea.
7. Composition according to any one of Claims 1 to 6, in which the AFFF emulsifier comprises from 5 to 25% by weight, preferably between 7 and 18%, of fluorinated surface-active agent(s), from 2 to 20% by weight, preferably between 4 and 18%, of nonfluorinated surface-active agent(s) and from 20 to 50% by weight, preferably between 30 and 45%, of cosolvent(s).
8. Composition according to any one of Claims 1 to 7, in which the inhibitor is chosen from monoammonium orthophosphate, diammonium orthophosphate and ammonium sulphate or the mixtures of these compounds.
9. Composition according to any one of Claims 2, 3 and 5 to 8, in which the hydrocarbonaceous surfactant is chosen from:
   
           R _H -OSO ₃ M
   
   
   
           R _H -(OC ₂ H ₄ ) _q -OSO ₃ M
   
   
   
           R _H (OC ₂ H ₄ ) _q -OH
   
   
   
           H(C ₆ H ₁₀ O ₅ ) _r -OR _H
   
   
   
           R _H -CONH-C ₂ H ₄ -NH-C ₂ H ₄ OC ₂ H ₄ COOM
   
   
   
           R _H -NH-C ₂ H ₄ -COOH
   
   
   
           R _H -N(C ₂ H ₄ COOM) ₂
   
   $${\mathbf{\text{R}}}_{\mathbf{\text{H}}}{\mathbf{\text{-N(CH}}}_{\mathbf{\text{3}}}{\mathbf{\text{)}}}_{\mathbf{\text{2}}}\mathbf{\text{→O}}$$ in which R_H represents a linear or branched alkyl radical comprising from 4 to 18 carbon atoms, q is an integer ranging from 1 to 16, C₆H₁₀O₅ denotes a glucoside group, r is an integer ranging from 1 to 6, preferably equal to 1 or 2, and M denotes an alkali metal ion or a quaternary ammonium.
10. Composition according to any one of Claims 1 to 9, in which the antifreeze solvent is a glycol, preferably ethylene glycol or propylene glycol.
11. Aerosol can comprising a composition according to any one of Claims 1 to 3 and 7 to 10, under pressure, preferably under a pressure of at least 7 bar.
12. Aerosol can comprising a composition according to any one of Claims 4 to 6 in a cartridge and an aqueous solution, under pressure, preferably under a pressure of at least 7 bar.
13. Aerosol can comprising, in a first cartridge, the components a), c), d) and optionally e) of a composition according to any one of Claims 4 to 6 and, in a second cartridge, the component b) of a composition according to any one of Claims 4 to 6, and an aqueous solution, under pressure, preferably under a pressure of at least 7 bar.
14. Process for the preparation of an extinguishing composition according to Claim 1, comprising the mixing, in one or more stages, of the following compounds, as % by weight of the final composition:

    a) at least 1% of an AFFF emulsifier;

    b) at least 5% of a combustion inhibitor;

    c) from 3 to 20% of an antifreeze solvent;

    d) at least 10% of urea, the urea being present in an amount at least equal to that of the antifreeze solvent;

    the said composition being devoid of citric acid,
    with an aqueous solution.
15. Process according to Claim 14, in which the extinguishing composition exhibits the characteristics of the composition according to any one of Claims 2, 3 and 7 to 10.