US2594985A - Fire extinguishing foam stabilizer - Google Patents

Description

Patented Apr. 29, 1952 FIRE EXTINGUISHIN G FOAM STABILIZER Joseph M. Perri, Philadelphia, Pa., assignor to National Foam System, Inc., Philadelphia, Pa., a corporation of Delaware N Drawing. Application September 9, 1948, Serial No. 48,529

This invention relates generally to fire extinguishing compositions and more particularly to such compositions as are capable, when combined with water, of producing a foam nonsupporting to combustion and which serves as a blanket to smother and so extinguish the flames produced by burning organic liquids having high capillary characteristics, such as alcohols, ethers, acetones, organic esters and the like. More specifically, the present invention relates to a chemical foam charge designed for use in portable extinguishers of the type containing solutions of acid and basic foam-forming agents which are normally maintained separate but are adapted to be mixed together to produce a stabilized fire extinguishing foam.

Heretofore and prior to this invention, various foam-forming compositions have been employed a in portable extinguishers for producing, upon reaction thereof, a foam satisfactory for the extinguishment of oil and gasoline fires. These compositions ordinarily comprise aqueous solutions of sodium bicarbonate and aluminum sulphate, into one orv the otherv of which is incorporated a suitable stabilizer for increasing the surface viscosity of the foam bubbles formed when the acid and basic reagents are mixed together.

While the foam produced by such conventional- 1y charged extinguishers is quite effective in extinguishing oil, gasoline and the like fires, experience has demonstrated that such foam is totally ineffective as an extinguisher of such fires as are produced by burning alcohols, esters, ketones, ethers, acetones and other such flammable organic liquids, this primarily for the reason that ordinary stabilized fire extinguishing foam is quickly broken down and disintegrated by organic liquids contacted by the foam.

In order to obviate this difficulty attempts have been made to incorporate as a stabilizer in one or the other of the aqueous acid and basic foamforming agents a material which results, upon reaction of said agents, in the formation of a water insoluble aluminum soap, it having been found that the presence of such soap in the reacted foam-forming solution produces a stabilized foam which is not. materially affected by alcohol and other such organic liquids and which will float freely upon the surface thereof in such quantities as to produce an effective fire extinguishing foam blanket. 7

It is known that an alkanol amino soap may be utilized for forming the desired Water insoluble aluminum soap, such soap being readily obtained by mixing coconut fatty acids with an amine,

3 Claims. (Cl. 252-6.5)

such as monoethanol amine, triethanolamine or diethanolamine. However, when such alkanol amino soap is mixed with water, as when incorporated in a water solution of bicarbonate of soda, there results the formation of an insoluble curd which is comprised of calcium or magnesium soap, when hard water is used, and some alkanol amine soap salted out by the saturated bicarbonate solution, such curd having a tendency to rise to the top of the solution in the form of a gel or liver. The presence of these curds in a water solution of the basic foam-forming agent in a portable extinguisher for chemically producing fire extinguishing foam seriously interferes with efiective operation of the extinguisher and for this reason it has been inadvisable and impractical to incorporate the alkanol amino soap as a foam stabilizer in portable fire extinguishers.

I have found that the above difiiculty may be overcome by incorporating lecithin with the alkanol amino soap in the water solution of the bicarbonate of soda. The lecithin, as employed in accordance with the present invention, prevents the formation of the undesired curds or gel by rendering the insoluble soap capable of being supported in solution in a colloidal condition. In the presence of the lecithin, the sub-microscopic particles of the alkanol amino soap are completely and homogeneously dispersed throughout the aqueous solution of the sodium bicarbonate in the extinguisher, thus maintaining the latter free of any gel or liver formation which might interfere with or constitute a hazard to eflicient operation of the extinguisher when said basic solution is combined with the acid (aluminum sulphate) solution to produce the desired fire extinguishing foam. I

In the preparation of the stabilizer of the pres- I ent invention, the several ingredients thereof are combined substantially in the following proportions and in accordance with the following procedure:

First, 25 grams of lecithin are dissolved in 30 cc. of isopropanol. To this solution is then added approximately 33 grams of coconut fatty acids, 10 cc. of monoethanolamine and 185 cc. of water, the whole being thoroughly mixed at a maintained temperature of between to degrees F. While this higher temperature is preferred for the mixing operation, the mixing may be efiected at room temperature, and accordingly it will be understood that thetemperature maintained during the mixing operation is not in any sense critical. In place of the monoethanol- 3 amine, either diethanolamine or triethanolamine may be employed.

The coconut fatty acids combine with the amine to form an alkanol amino soap, which latter is completely and homogeneously dispersed in the mixture prepared as above described by the action of the lecithin present in said mixture, the final mixture being in the form of a colloidal dispersion.

In the use of the stabilizer of the present invention in a 2 gallon acid-basic fire extinguisher, the following charge formula is preferred and recommended:

For the acid charge, 30 ounces of aluminum sulphate is dissolved in 2%; pints of water.

For the basic charge, 25 ounces of bicarbonate of soda is dissolved in 1% gallons of water and to this solution is added 4 ounces of the stabilizer prepared as above described.

Upon operation of the extinguisher, the acid and basic charges are combined and react .to produce a stabilized foam capable of extinguishing not only fires of gasoline and related petroleum products, but also fires of methanol, acetone, ethylacetate, isopropyl alcohol, isopropyl ether and other such polar liquids normally incapable of being extinguished by ordinary foam. The more or less water soluble alkanol .amino soap present in the basic charge and colloidally .dispersed therein by the lecithin to prevent the formation of any curds or gel which might interfere with efiicient operation of the extinguisher, upon reaction of said basic charge with the acid charge, is converted to a water insoluble aluminum soap which renders the foam capable of extinguishing fires of alcohol and other such flammable organic liquids of high capillary characteristics.

What is claimed as new and useful is:

1. A stabilizer for a fire-extinguishing foam obtained by combining an aqueous solution of aluminum sulphate with an aqueous solution of bicarbonate of soda, said stabilizer consisting of an alkanol amino soap colloidally dispersed by 4 lecithin in one of said foam-forming solutions.

2. In a method of extinguishing fires of alcohol and other such flammable organic liquids of high capillary characteristics, the steps comprising colloidally dispersing by lecithin an alkanol amino soap in an aqueous solution of bicarbonate of soda and then reacting said basic solution with an aqueous solution of aluminum sulphate to produce fire extinguishing foam.

3. In a method of extinguishing fires of flammable liquids, the steps comprising forming an aqueous solution of an alkanol amino soap colloidally dispersed by lecithin, introducing said aqueous colloidal dispersion in an aqueous solution of sodium bicarbonate, and reacting said solution containing said colloidal dispersion with aluminum sulphate to form fire extinguishing foam.

JOSEPH M. PERRI.

REFERENCES CITED The following references are of'recorcl in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,375,779 Crosby et al Apr. 26, 1921 1,624,389 Dunlap et a1 Apr. 12, 1927 1,833,899 Hoyt ,Dec. 1, 1931 2,002,885 Detwiler et a1 Sept. 9, 1932 2,020,517 Rewald Nov. 12, 1935 2,047,128 Park 1. July 7, 1936 2,057,695 Schwieger Oct. 20, 1936 2,168,468 Braun et al. Aug. 8, .1939 2,253,587 Goodner Oct. 14, 1941 FOREIGN PATENTS Number Country Date 517,812 Great Britain Feb. 9, 1940 OTHER REFERENCES Gregory: Uses and Applications of Chemicals and Related Materials, vol. II, pages 185, 186, Reinhold Publishing Corp., N. Y. (1944).

Claims (1)

1. A STABILIZER FOR A FIRE-EXTINGUISHING FOAM OBTAINED BY COMBINING AN AQUEOUS SOLUTION OF ALUMINUM SULPHATE WITH AN AQUEOUS SOLUTION OF BICARBONATE OF SODA, SAID STABILIZER CONSISTING OF AN ALKANOL AMONO SOAP COLLOIDALLY DISPERSED BY LECITHIN IN ONE SAID FOAM-FORMING SOLUTIONS.