EP0460991A1 - Use of a fluoroalkane-based composition as a fire-extinguishing agent - Google Patents

Abstract

The use of a composition comprising at least one perfluoroalkane and at least one hydrofluoroalkane is proposed to replace extinguishing agents such as trifluorobromomethane and difluorobromochloromethane. The composition, optionally pressurised with an inert gas, can be employed for the protection of premises by the so-called total-flooding technique.

Description

The present invention relates to a composition which can be used for fire fighting.

The invention relates in particular to the use of an extinguishing composition comprising at least one perfluoroalkane and at least one hydrogenofluoroalkane.

In the field of extinction and fire fighting, chlorobromofluoroalkanes and bromofluoroalkanes are mainly used.

Trifluorobromomethane, difluorochlorobromomethane and 1,1,2,2-tetrafluoro 1,2-dibromoethane are used in particular.

These compounds have high extinguishing efficiency and very low human toxicity. They are used in particular for the protection of premises that staff may have difficulty evacuating.

They are also used in premises where there are electrical and electronic equipment susceptible to corrosion (computer room, telephone exchanges, engine room on board ships).

However, these compounds are suspected of being responsible for the reduction of the stratospheric ozone layer which provides protection against certain radiations. They have high ODP (Ozone Depletion Potential) and are therefore listed in the Montreal Protocol. This protocol is the result of recent international discussions on the environment and commits the signatory countries to reduce the production and consumption of such compounds.

dans laquelle a est un nombre entier allant de 1 à 6, b étant égal à 2 ou 0 ;
et au moins un hydrogénofluoroalcane de formule : $${\text{C}}_{\text{n}}{\text{H}}_{\text{m}}{\text{F}}_{\text{p}}$$

dans laquelle n est un nombre entier allant de 1 à 4, m et p sont des nombres entiers au moins égaux à 1, la somme (m + p) est égale à 2n ou 2n + 2 et le rapport $$\frac{\text{m}}{\text{n}}$$

varie de 0,25 à 1;
à l'exclusion de la composition azéotropique constituée de 63,2 % en volume de perfluoropropane et de 36,8 % en volume de 1,1,1,2-tétrafluoroéthane.We have now found that these ecotoxic compounds can be replaced by an extinguishing composition which is not very destructive of the stratospheric ozone layer, this composition being characterized in that it comprises at least one perfluoroalkane of formula: $${\text{VS}}_{\text{at}}{\text{F}}_{\text{2a}}{\text{+}}_{\text{b}}$$

in which a is an integer ranging from 1 to 6, b being equal to 2 or 0;
and at least one hydrogenofluoroalkane of formula: $${\text{VS}}_{\text{not}}{\text{H}}_{\text{m}}{\text{F}}_{\text{p}}$$

in which n is an integer ranging from 1 to 4, m and p are whole numbers at least equal to 1, the sum (m + p) is equal to 2n or 2n + 2 and the ratio $$\frac{\text{m}}{\text{not}}$$

varies from 0.25 to 1;
excluding the azeotropic composition consisting of 63.2% by volume of perfluoropropane and 36.8% by volume of 1,1,1,2-tetrafluoroethane.

By way of illustration of perfluoroalkanes of formula I, mention may in particular be made of perfluoromethane, perfluoroethane, perfluoropropane, perfluoro n-butane, perfluorocyclopropane, perfluorocyclobutane and mixtures comprising at least two perfluoroalkanes listed above.

Among these compounds, the invention relates very particularly to perfluoroethane and / or perfluoropropane.

The composition according to the invention comprises an amount of perfluoroalkane (s) of formula I at least equal to 10% by volume. Preferably, it comprises an amount between 15% and 80% by volume.

Mention may in particular be made, by way of illustration of hydrogenofluoroalkanes of formula II, of trifluoromethane, 1,1,1,2-tetrafluoroethane, pentafluoroethane, 1,1,1,3,3,3-hexafluoropropane, 1, 1,1,2,3,3,3-heptafluoropropane, 1,1,1,2,2,3,3,4,4-nonafluorobutane, 1,1,2,2-tetrafluorocyclopropane, 1,1 , 2,2,3,4-hexafluorotranscyclobutane and mixtures comprising at least two hydrogenofluoroalkanes listed above.

Among these compounds, preference is given to trifluoromethane and / or 1,1,1,2-tetrafluoroethane.

The composition according to the invention comprises an amount of hydrogenofluoroalkane (s) of formula II at most equal to 90% by volume and preferably an amount between 85% and 20% by volume.

The compositions according to the invention have low Cup Burner values (generally less than 10%) and therefore have a high extinguishing power.

For purely indicative purposes, trifluorobromomethane, which is currently the most widely used extinguishing agent, has a Cup Burner value equal to 4.2% but is cited in the Montreal protocol.

The extinguishing effectiveness of the compositions according to the invention is measured according to the so-called "Cup Burner" method.

This method indicates the minimum percentage of extinguisher compound (measured by volume) in an air plus extinguisher compound mixture required to extinguish an ignited liquid fuel. The lower the value of the Cup Burner, the more effective the extinguishing compound.

The compositions according to the invention have the advantage of exhibiting the phenomenon of pseudosynergy, or even true synergy. In fact, it can be seen that for certain proportions of the compounds of formulas I and II, Cup Burner values of the composition are obtained which are lower than the Cup Burner value of the most effective extinguishing compound entering said composition.

The compositions according to the invention are practically devoid of destructive effect with respect to the stratospheric ozone layer, they have zero ODPs.

They also have very low human toxicity and are little or not corrosive.

They can be used to fight fires using the same techniques as trifluorobromomethane and difluorochlorobromomethane.

Thus, they can be advantageously used for the protection of premises by the technique known as total flooding, where the risk of fire is difficult to determine. The compositions according to the invention can also be pressurized with inert gases such as nitrogen, which makes it possible to increase their unloading speed.

They can also be used in portable extinguishing techniques.

The following examples illustrate the invention.

EXAMPLES 1 to 3

Perfluoropropane (FC 218) and trifluoromethane (HFC 23) compositions are produced according to the proportions given in Table 1.

Extinguishing efficiency is measured by the so-called Cup Burner method described in the draft ISO / DIS 7075-1 standard. The liquid fuel used is ethanol.

The results are reported in Table 1.

Composition 3 presents a phenomenon of true synergy while compositions 1 and 2 present a phenomenon of pseudosynergy.

EXAMPLES 4 and 5

Perfluoroethane (FC 116) and trifluoromethane (HFC 23) compositions are produced according to the proportions given in Table 2.

The results are reported in Table 2.

Composition 4 presents a phenomenon of true synergy while composition 5 presents a phenomenon of pseudosynergy.

EXAMPLES 6 and 7

Perfluoroethane (FC 116) and 1,1,1,2-tetrafluoroethane (HFC 134a) compositions are produced according to the proportions given in Table 3.

The results are reported in Table 3.

Compositions 6 and 7 show a phenomenon of true synergy.

Claims (14)

Use as extinguishing agent of a composition characterized in that it comprises at least one perfluoroalkane of formula: $${\text{VS}}_{\text{at}}{\text{F}}_{\text{2a + b}}$$

in which
a is an integer ranging from 1 to 6, b being 2 or 0;
and at least one hydrogenofluoroalkane of formula: $${\text{VS}}_{\text{not}}{\text{H}}_{\text{m}}{\text{F}}_{\text{p}}$$

in which n is an integer ranging from 1 to 4, m and p are whole numbers at least equal to 1, the sum (m + p) is equal to 2n or 2n + 2 and the ratio $$\frac{\text{m}}{\text{not}}$$

varies from 0.25 to 1;
excluding the azeotropic composition consisting of 63.2% by volume of perfluoropropane and 36.8% by volume of 1,1,1,2-tetrafluoroethane. Use according to claim 1 of a composition which comprises an amount of perfluoroalkane (s) of formula I at least equal to 10% by volume. Use according to claim 2 of a composition which comprises an amount of perfluoroalkane (s) of formula I between 15% and 80% by volume. Use according to claim I of a composition which comprises an amount of hydrogenofluoroalkane (s) of formula II at most equal to 90% by volume. Use according to claim 4 of a composition which comprises an amount of hydrogenofluoroalkane (s) of formula II of between 85% and 20% by volume. Use according to claim 1 of a composition in which the perfluoroalkanes of formula I are perfluoroethane and / or perfluoropropane. Use according to claim 1 of a composition in which the hydrogenofluoroalkanes of formula II are trifluoromethane and / or 1,1,1,2-tetrafluoroethane. Extinguishing composition characterized in that it consists of a mixture of a perfluoroalkane of formula: $${\text{VS}}_{\text{at}}{\text{F}}_{\text{2a + b}}$$

in which
a is an integer ranging from 1 to 6, b being 2 or 0; and a hydrogen fluoride alkane of formula: $${\text{VS}}_{\text{not}}{\text{H}}_{\text{m}}{\text{F}}_{\text{p}}$$

in which n is an integer ranging from 1 to 4, m and p are whole numbers at least equal to 1, the sum (m + p) is equal to 2n or 2n + 2 and the ratio $$\frac{\text{m}}{\text{not}}$$

varies from 0.25 to 1;
excluding the azeotropic composition consisting of 63.2% by volume of perfluoropropane and 36.8% by volume of 1,1,1,2-tetrafluoroethane. Composition according to Claim 8, characterized in that it comprises an amount of perfluoroalkane of formula I at least equal to 10% by volume. Composition according to Claim 9, characterized in that it comprises an amount of perfluoroalkane of formula I of between 15% and 80% by volume. Composition according to Claim 8, characterized in that it comprises an amount of hydrogenofluoroalkane of formula 11 at most equal to 90% by volume. Composition according to Claim 11, characterized in that it comprises an amount of hydrogenofluoroalkane of formula 11 of between 85% and 20% by volume. Composition according to Claim 8, in which the perfluoroalkanes of formula I are perfluoroethane or perfluoropropane. Composition according to Claim 8, in which the hydrogenofluoroalkanes of formula II are trifluoromethane or 1,1,1,2-tetrafluoroethane.