US3656553A - Flame-extinguishing substance comprising 1,2-dibromohexafluropropane - Google Patents

Abstract

A flame-estinguishing composition, especially for extinguishing fire upon a body of water, gasoline fires and hydrocarbon-fuel fires consisting at least in part of 1,2dibromohexafluoropropane.

Description

United States Patent Rainaldi et al.

[151 3,656,553 [451 Apr. 18, 1972 [54] F LAME-EXTINGUISHING SUBSTANCE COMPRISING 1,2- DIBROMOI-IEXAFLUROPROPANE [72] Inventors: Nicholino Rainaldi, Mestre; Pierluigi Fatutto, Venezia, both of Italy [73] Assignee: Montecatini Edison S.p.A., Milan, Italy [22] Filed: May 13, 1970 [21] Appl. No.: 36,937

[30] Foreign Application Priority Data May 16, 1969 Italy ..16892 A/69 [52] US. Cl. ..169/1 A, 252/3, 252/8 [51] Int. Cl. ..A62c l/14, A62d 1/00 [58] Field ofSearch ..252/2,3,8;169/1,1A,B; 239/601; 260/653.8

[56] References Cited UNITED STATES PATENTS 2,244,512 6/1941 Brandt ..252/3 X 2,653,130 9/1953 Eiseman, Jr. ..252/8 NDNEXPLOSIVE 7 k E U 5 5 2 3 g -4 R ii 3 L EXPLDJIVE ZONE 2,658,928 ll/1953 Simons et a1 ..260/653.8 2,678,953 5/1954 Conly ..260/653 8 2,959,359 11/1960 Casaletto ..239/601 X 3,212,998 10/1965 Doumas ..252/8 3,276,999 10/1966 Petit ..25 2/8 3,343,794 9/1967 Voitsekhovsky... ..239/601 X 3,479,286 11/ 1969 Gamboretto ..252/8 FOREIGN PATENTS OR APPLICATIONS $89,990 l/l960 Canada ..169/1 A OTHER PUBLICATIONS Hudlicky, Milos; Chemistry of Organic Fluorine Compounds, MacMillan Co., N.Y., 1962 p. 342

Primary Examiner--.Iohn T. Goolkasian Assistant Examiner-D. J. Fritsch Attorney-Karl F. Ross fuel fires consisting at least in part of 1,2-dibromohexafluoropropane.

5 Claims, 1 Drawing Figure NONE'XPLOSIVE %II-I-IEFT'ANE IN FUEL/NE MIXTURE PATENTEDAFR 18 I872 NONE X PL 05' I VE NDNEXPLOSIVE c5. 'CFBr wgm EXPL oslwr ZONE n-HEFTANE nv FUEL IAIR MIXTURE Nico/mo Raina/d. Pierluigi Fafuffo I N VEN TORS Attorney FLAME-EX'I'INGUISHING SUBSTANCE COMPRISING l ,Z-DIBROMOHEXAFLUROPROPANE position and agents and, more particularly, to bromine-con-.

taining fluorohydrocarbon fire-extinguishing agents.

BACKGROUND OF THE INVENTION It has been common knowledge in the fire-fighting field that fire extinction in industrial fires such as hydrocarbon fires and fires in automotive, aeronautical and missile plants, requires fire-fighting compositions of high potency and that halogen derivatives of lower hydrocarbons in the pure state or in mixtures provide high efiiciency and low toxicity. The selection of the best fire-extinguishing agent for a particular purpose, however, often depends upon other factors than the intrinsic firefighting or flame-quenching properties of the halogenated hydrocarbon. Pre-eminent among these other properties is the toxicity of the fire-extinguishing agent and/or its thermal decomposition products while another factor may be the ability of the product to prevent flashback, i.e. the tendency to reignition of an extinguished zone upon the formation of an opening in the blanket of fire-extinguishing material. Considerations of economic character are also relevant, these including the quantity of the fire-extinguishing agent consumed per unit time, per unit area or under the particular fire conditions, the nature, cost and stability of the product and the container in which it may be stored, and the nature of the discharge or distribution of the product.

OBJECT OF THE INVENTION It is an object of this invention to provide a flame-extinguishing composition which affords improved results by comparison with prior-art systems.

SUMMARY OF THE INVENTION This object and others which will become apparent hereinafter, are attained as a result of our surprising discovery based upon further efforts in the field of bromofluoroalkane fire-extinguishing agents, that there exists a compound which is far superior than the halogenated ethane derivatives previously known.

More particularly we have found that 1,2-dibromohexafluoropropane (CF BrCFBr-CF is a remarkable fireextinguishing compound which is rapidly acting and provides considerable assurance against flashback for hydrocarbon fires.

The l,2-dibromohexafluoropropane may be used directly as the sole flame-extinguishing agent but also can be incorporated in an amount ranging from 5 to 25 percent by weight in fire-extinguishing compositions: preferably, 7 to 15 parts by weight of the bromofluoropropane is employed per 100 parts by weight of the composition.

The composition may also include a surface-active agent, of which the most suitable are the organic sulfonates and sulfates, alkylarylpolyethylene glycol ethers, esters of alcohols such as sorbitol with higher fatty acids such as lauric, stearic and palmitic acids, and sodium or ammonium salts of sulfocarboxylic acids such as dialkyl sulfosuccinic acid having up to eight carbon atoms in the alkyl group. The composition should also include at least one, and possibly a plurality of propellants, capable of dispersing the fire-extinguishing agent over long distances, preferably an inert gas (i.e. a gas inert to chemical reaction with the components of the composition and with as low corrosivity with respect to the surface to be treated and the receptacle in which the composition is housed as possible) and/or a chlorofluoroalkane of the high-vaporpressure refrigerant type having a low boiling point (i.e. a boiling point well below ambient temperature so that the vapor pressure of the propellant will be substantial at ambient temperature and temperatures at which the compositions may be used).

Inert propellant gases suitable for the purpose of the present invention include nitrogen, carbon dioxide and sulfohexafluoride while the preferred chlorofluoroalkanes are those containing up to six halogen atoms and one or two carbon atoms, the halogens being exclusively chlorine and fluorine. Of greatest desirability are difluoromonochloromethane, difluorodichloromethane, trifluoromonochloromethane, i.e. chlorofluoromethane. It has been found to be suitable to use compressed or liquid nitrogen, compressed air or the like for relatively long spray jets, the propellant here acting as foaming agents as well. The composition may be displaced through the nozzle by pumps or compressors.

The composition can also contain one or more antifreezing agents, corrosion inhibitors, buffering agents, thickening and carrying agents and like components. We find especially useful in this connection polyalcohol antifreezing agents such as ethyleneglycol and propyleneglycol; corrosion inhibitors such as sodium nitrate, potassium nitrate, sodium phosphate, potassium phosphate, the corresponding polyphosphates and amino acids, such as triethanolamine. Functionally, the corrosion inhibitors act as bases which react with any acid which may be present and also serve as buffering agents. Thickening agents such as alkali (sodium or potassium) silicate may be used as the thixotropic or thickening agent.

DESCRIPTION OF THE DRAWING The invention is described in greater detail herein after with reference to the accompanying drawing and specific examples, the sole FIGURE of the drawing constituting a graph in which the minimum concentration of various extinguishing agents necessary to render a particular concentration of fuel in air nonexplosive is plotted along the ordinate, while the fuel-air composition is plotted along the abscissa.

SPECIFIC DESCRIPTION AND EXAMPLES In Examples I III supra, the efl'rcacy of the 1,2- dibromohexafluoropropane is given for fires of gasoline/kerosene/mixtures in rectangular containers. In all cases, the extinguishing materials were packed in sealed 5 kg vessels using nitrogen or chlorofluorohydrocarbon propellants (Example I) and equipped with spray nozzles discharging elliptical sprays (see our application Ser. No. 841,460 filed July 14, 1969) at a rate of 700-900 g per second over a distance of at least 5 m. In all cases the elliptical-section spray means and method of our application Ser. No. 841,460 filed July 14, 1969 is preferred.

EXAMPLE I A mixture of gasoline and gas oil in 1:1 proportion was poured into a 1.5 m metal pool.

After the mixture was ignited, 30 seconds were permitted to elapse so that the whole surface of the pool was homogeneously enveloped by the fire.

The extinguishing cylinder was charged with 216 B2 (1,2- dibromohexafluoropropane), mixed with difluoromonochloromethane (propellant): 2 seconds were necessary for the complete extinction of the tire, with consumption of 770 grams of material, equal to 510 g of 216 B2 per m EXAMPLE II The general operative conditions of the previous example were repeated, with the following changes:

the pool had an area of 0.4 m"; the fuel mixture was gasoline/gas oil in 2:1 proportion: the extinguishing cylinder was charged with 216 B2, pressurized with nitrogen at 14 atmospheres gauge.

After 30 seconds of precombustion, the fire was put out in 1 second, with a consumption of 450 grams (total), equal to 1,125 g/m of the active agent.

In another test, carried out under the same conditions, the consumption was 420 grams.

EXAMPLE Ill with the extinguishing cylinder used in the preceding test, but with a 4 in pool, and with a mixture gasoline/gas oil in 1:1 ratio, the extinction time, after 30 seconds of precombustion, was 3 seconds.

The consumption was 2,670 g, equal to 652 g/m EXAMPLE IV A flame extinguishing composition was prepared by intimately mixing 100 parts by weight of 1,2-dibromohexafluoropropane with 140 parts by weight of a surface-active agent in the form of a 30 percent aqueous solution of the sodium salt of lauritic-ether-sulfate, 120 parts by weight of ethyleneglycol antifreeze agent, 1.5 parts by weight of sodium nitrate corrosion inhibitor, 6.5 parts by weight of NAI-I PQ, buffering agent, 65 parts by weight of difluorodichloromethane and 55 parts by weight of difluoromonochloromethane propellants, 70 parts by weight of a 30 percent aqueous solution of potassium silicate and 442 parts by weight of water. When the composition was dispensed over a distance of about 5 m from pressurized containers having ejection connected to the container by hoses, the extinguishing time on a test area of 1.5 m in which the flames were produced by igniting a 1:1 gasoline/diesel-oil fuel, was less than seconds, the quantity of extinguishing composition employed was less than 2.6 kg, there was no indication of flashback and no combustion of the foam. Heat did not affect the foam blanket.

In FIG. 1, we have diagrammed the relative extinguishing powers of l,2-dibromohexafluoropropane and various conventional or prior-art flame-extinguishing substances. In the accompanying table, the peak values corresponding to the curves are given. FIG. 1 represents, along the abscissa, the concentration of n-heptane in a fuel/air mixture while the ordinate portrays the minimum concentration of the flameextinguishing agent necessary to render the mixture nonflammable. The tests were carried out at ambient temperature in a conventional 3-liter explosimetric glass burette equipped with an ignition device in the form of a 6-ohm nickel-chromium wire energized at 80 volts a-c. The level at which the extinguishing agent was introduced was kept constant and the general approach followed was that described by 1.1-1. SIMONS in Fluorine Chemistry, volume 5, page 356. The curves represent the boundary between the explosion zone within the curve and the nonexplosion zone externally of the curve, i.e. the explosive limit. As the peak of the curve is reduced, the quantity of inhibitor required to prevent explosion is correspondingly reduced and the more efficient is the fire-extinguishing agent.

From the curves of FIG. 1 and the peaks of Table 1, it can be seen that l,2-dibromohexafluoropropane (represented as 2 l 6-B2) is by far the most effective compound for the purpose indicated.

Table 1 also demonstrates the surprising superiority of asymmetric l,2-dibromohexafluoropropane by comparison with symmetrical l,3-dibromohexafluoropropane.

Using the apparatus described in Creitz in the Journal of Research of the National Bureau of Standards, 1961, the minimum concentration of fire extinguisher necessary to avoid conservation of the flame was determined. The results TABLE I.PEAKS OF INFLAM- MABILIIY TESTS WITH A 3 l IIER GLASS EXPLOSIMETRIC BURETTE Formula Peak Percent volume. Mg./ ee. air.

TABLE 2.--EXTINCTION TESTS CREITZ EQUIPMENT Extinguisher l CFyCFBr- CFzBl" F1181 CFzBr CF23! CFsBl' CF2CIB1' 0.42 0.80 1.68 1.40 Propane. 1. 40 1. 25 2. 30 2. 16 Acetone 1. 06 1. 22 2. 12 2. 66 Methanol. 3. 38 5. 20 4. 87 5. 40 Ethanol 0.97 1.84 2. 50 2.80 Benzene 1. 37 1. 29 3. 50 2. 99 Kerosene- 0. 97 1. M 2. 94 3. 47 rt-Heptane 1. 43 2. 20 2. 67 3. 92 Vlrgm-naphtha" 1. 24 1. 53 3. 20 H 1.10 1. 46 3. 56 3.10 1. 69 2. 00 3. 00 4. 00 1.10 1. 18 2. 55 3. 10

Percent extingu i sher by volume of the mixture air, fuel, extinguisher.

We claim:

1. A method of extinguishing a fire, comprising dispensing thereon a flame-extinguishing agent consisting at least in part of 1,2-dibromohexafluoropropane.

2. The method defined in claim 1, further comprising the step of propelling said composition onto said fire with a gaseous propellant selected from the group which consists of nitrogen and chlorofluorohydrocarbons.

3. The method defined in claim 2 wherein the flame extinguishing composition contains an aqueous solution of a surfactant agent.

4. The method defined in claim 1 wherein said 1,2- tclibromohexafluoropropane is dispensed directly upon the ire.

S. A fire-extinguishing composition consisting of 1,2- dibromohexafluoropropane, a gaseous propellant and an aqueous solution of a surfactant agent.

Claims (5)

1. A method of extinguishing a fire, comprising dispensing thereon a flame-extinguishing agent consisting at least in part of 1,2-dibromohexafluoropropane.

2. The method defined in claim 1, further comprising the step of propelling said composition onto said fire with a gaseous propellant selected from the group which consists of nitrogen and chlorofluorohydrocarbons.

3. The method defined in claim 2 wherein the flame extinguishing composition contains an aqueous solution of a surfactant agent.

4. The method defined in claim 1 wherein said 1,2-dibromohexafluoropropane is dispensed directly upon the fire.

5. A fire-extinguishing composition consisting of 1,2-dibromohexafluoropropane, a gaseous propellant and an aqueous solution of a surfactant agent.

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