EP0460992A1 - Use of a halogenoalkane-based composition as a fire-extinguishing agent - Google Patents

Abstract

A composition comprising at least one fluoroalkane and at least one hydrofluorohydroalkane is proposed for replacing especially trifluorobromomethane and difluorobromochloromethane. This composition can be employed for firefighting by the so-called total-flooding and portable extinguisher techniques.

Description

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

The invention relates in particular to the use of a composition comprising at least one fluoroalkane and at least one hydrogenofluorohalogenoalkane.

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).

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 ozone depletion potential (ODP) 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.

• a - les perfluoroalcanes de formule $${\text{C}}_{\text{a}}{\text{F}}_{\text{2a + b}}$$
  
  dans laquelle a est un nombre entier allant de 1 à 6, b étant égal à 2 ou 0 ;
• b - les hydrogénofluoroalcanes de formules $${\text{C}}_{\text{n}}{\text{H}}_{\text{m}}{\text{F}}_{\text{p}}$$
  
  dans laquelle n est un nombre entier allant de 1 à 6, m et p sont des nombres entiers au moins égaux à 1 et la somme (m + p) étant égale à 2n ou 2n + 2 ;

et d'un hydrogénofluorohalogénoalcane de formule $${\text{C}}_{\text{q}}{\text{H}}_{\text{r}}{\text{F}}_{\text{w}}{\text{Cl}}_{\text{x}}{\text{Br}}_{\text{y}}{\text{I}}_{\text{z}}$$

dans laquelle q est un nombre entier allant de 1 à 4, r et w sont des nombres entiers au moins égaux à 1, x, y et z sont des nombres entiers dont l'un au moins est différent de zéro, la somme (r + w + x + y + z) est égale à 2q ou 2q + 2 et r est inférieur ou égal à la somme (w + x + y + z).We have now found to replace these ecotoxic compounds an extinguishing composition which is not very destructive of the stratospheric ozone layer, characterized in that it consists of a mixture of a fluoroalkane chosen from the group consisting of

• a - the perfluoroalkanes of formula $${\text{VS}}_{\text{at}}{\text{F}}_{\text{2a + b}}$$
  
  in which a is an integer ranging from 1 to 6, b being equal to 2 or 0;
• b - hydrogenofluoroalkanes of formulas $${\text{VS}}_{\text{not}}{\text{H}}_{\text{m}}{\text{F}}_{\text{p}}$$
  
  in which n is an integer ranging from 1 to 6, m and p are whole numbers at least equal to 1 and the sum (m + p) being equal to 2n or 2n + 2;

and a hydrogen fluorofluorohaloalkane of formula $${\text{VS}}_{\text{q}}{\text{H}}_{\text{r}}{\text{F}}_{\text{w}}{\text{Cl}}_{\text{x}}{\text{Br}}_{\text{y}}{\text{I}}_{\text{z}}$$

in which q is an integer ranging from 1 to 4, r and w are whole numbers at least equal to 1, x, y and z are whole numbers at least one of which is different from zero, the sum (r + w + x + y + z) is equal to 2q or 2q + 2 and r is less than or equal to the sum (w + x + y + z).

By way of illustration of perfluoroalkanes of formula (I), mention may in particular be made of perfluoromethane, perfluoroethane, perfluoropropane, perfluoro n-butane and perfluorocyclobutane.

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

Mention may in particular be made, as illustration of hydrogenofluoroalkanes of formula (II), of trifluoromethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-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 and 1,1,2,2,3,4-hexafluorotranscyclobutane.

Among the compounds of formula (II), those in which m is equal to 1 or 2 are preferred.

Among these compounds, mention will be made more particularly of trifluoromethane, 1,1,1,2,3,3,3-heptafluoropropane or 1,1,1,3,3,3-hexafluoropropane.

By way of illustration of hydrogenofluorohaloalkanes of formula (III), mention may in particular be made of fluorodichloromethane, difluorobromomethane, difluorochloromethane, fluorochloromethane, 1,1,1,2-tetrafluoro 2-chloroethane, 1,1,2, 2-tetrafluoro 1-chloroethane, 1,1,1-trifluoro 2,2-dichloroethane, 1,1,1-trifluoro 2-chloroethane, 1-fluoro 1,1-dichloroethane, 1,1-difluoro 1 -chloroethane, 1,1,2-trifluoro 2-chloroethane, 1,2-difluoro 1,1-dichloroethane and 1,1,1-trifluoro 2-chloropropane.

Among the compounds of formula (III), those for which r is less than the sum (w + x + y + z) are preferred.

Among these compounds, mention will be made more particularly of difluorochloromethane, difluorobromomethane or 1,1,1,2-tetrafluoro 2-chloroethane.

The composition according to the invention comprises an amount of fluoroalkane chosen from the group consisting of the compounds of formula (I) or (II) at least equal to 10% by volume. Preferably, it comprises an amount between 15% and 80% by volume.

The composition according to the invention comprises an amount of hydrogenofluorohaloalkane of formula (III) 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 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. Indeed, it can be seen that for certain proportions of the compounds of formulas (I) or (II) and (III), values of Cup Burner of the composition are obtained lower than the value of Cup Burner of the most effective extinguishing compound entering said composition. .

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

Compositions of 1,1,1,2-tetrafluoro 2-chloroethane (HCFC 124) and perfluoroethane (FC 116) 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 ODP is defined as the ratio between the reduction in the ozone column recorded during the emission of a unit mass of substance and the same reduction for the trichlorofluoromethane chosen as reference (ODP = 1).

The values reported in these examples were calculated by the Lawrence Livermore National Laboratories (1-D Model). For purely indicative purposes, trifluorobromomethane has an ODP of 10 and 1,1,2,2-tetrafluoro 1,2-dibromomethane has an ODP of 6.

The ODP of a composition is equal to the sum of the contributions of each constituent of the composition. Thus, for example a composition which would contain 50% of trifluorobromomethane and 50% of 1,1,2,2, -tétrafluoro 1,2-dibromoéthane would have an ODP equal to:
10 X 0.5 + 6 X 0.5 or 8

The results are reported in Table 1.

It is noted that the compositions according to the invention exhibit a phenomenon of true synergy.

EXAMPLES 4 to 6

Compositions of 1,1,1,2-tetrafluoro 2-chloroethane (HCFC 124) and perfluoropropane (FC 218) are produced according to the proportions given in Table 2.

As in the previous examples, the fire extinguishing efficiency is measured by the Cup Burner method.

The results are reported in Table 2.

Compositions 5 and 6 exhibit a phenomenon of true synergy while composition 4 exhibits a phenomenon of pseudosynergy.

EXAMPLE 7

A composition is produced containing 28% (by volume) of 1,1,1,2- tetrafluoro 2-chloroethane (HCFC 124) and 72% (by volume) of 1,1,1,2,3,3,3- heptafluoropropane (HFC 227e).

The results are reported in Table 3.

EXAMPLES 8 and 9

Difluorochloromethane (HCFC 22) and perfluoropropane (FC 218) compositions are produced according to the proportions given in Table 4.

The results are reported in Table 4.

EXAMPLES 10, 11 and 12

Difluorobromomethane (22 B 1) and perfluoropropane (FC 218) compositions are produced according to the proportions given in table 5.

The results are reported in Table 5.

Claims (8)

Use as extinguishing agent of a composition characterized in that it consists of a mixture of a fluoroalkane chosen from the group consisting of a - the perfluoroalkanes of formula $${\text{VS}}_{\text{at}}{\text{F}}_{\text{2a + b}}$$

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

in which n is an integer ranging from 1 to 6, m and p are whole numbers at least equal to 1 and the sum (m + p) being equal to 2n or 2n + 2; and a hydrogen fluorofluorohaloalkane of formula $${\text{VS}}_{\text{q}}{\text{H}}_{\text{r}}{\text{F}}_{\text{w}}{\text{Cl}}_{\text{x}}{\text{Br}}_{\text{y}}{\text{I}}_{\text{z}}$$

in which q is an integer ranging from 1 to 4, r and w are whole numbers at least equal to 1, x, y and z are whole numbers at least one of which is different from zero, the sum (r + w + x + y + z) is equal to 2q or 2q + 2 and r is less than or equal to the sum (w + x + y + z). Use according to claim 1 of a composition in which the compound of formula (I) chosen is perfluoroethane or perfluoropropane. Use according to claim 1 of a composition in which the compound of formula (II) chosen is trifluoromethane or 1,1,1,2,3,3,3-heptafluoropropane. Use according to claim 1 of a composition in which the compound of formula (III) chosen is difluorochloromethane, difluorobromomethane or 1,1,1,2-tetrafluoro 2-chloroethane. Use according to claim 1 of a composition which comprises an amount of fluoroalkane chosen from the group consisting of compounds of formula (I) or (II) at least equal to 10% by volume. Use according to claim 5 of a composition which comprises an amount of fluoroalkane chosen from the group consisting of compounds of formula (I) or (II) of between 15% and 80% by volume. Use according to claim 1 of a composition which comprises an amount of hydrogenofluorohaloalkane of formula (III) at most equal to 90% by volume. Use according to claim 7 of a composition which comprises an amount of hydrogenofluorohaloalkane of formula (III) between 85% and 20% by volume.