3,274,105 United States Patent Office Patented Sept. 20, 1966 2 Such as carbon disulfide and percaptains). Nevertheless, 3,274,05 Within the above-mentioned limits, it is advisable to FIRE EXTENGUISHENG COMPOSITION choose the concentration of the solution according to the Norbert Mevel, Antony, France, assignor to Societe d’Etudes Chimiques poeir distrie et l'Agriculare nature of the fires to be dealt with: for fires of high boil S.E.C.P.I.A., Paris, France ing hydrocarbons and those of a large number of chem No Drawing. Filed July 5, 1963, Ser. No. 295,213 icals Such as alcohol, aldehydes, amines, petroleum ether, Claims priority, application France, Aag. 3, 1962, ethyl ether, etc., solutions containing from 300 to 400 905,979, Patent 1,338,454 g./l. of potassium acetate give the best results. But for 10 Clains. (C. 252-2) fires of low boiling hydrocarbons such as gasoline, solu O tions containing from about 500 to 600 g./l. are more This invention relates to fire extinguishing Solutions for effective to obtain complete extinction. use against dry fires and fires particularly difficult to ex It has also been found that by adding tetrapotassium tinguish such as those of hydrocarbons or inflammable pyrophosphate to acqueous solutions of potassium acetate, chemicals and mixed fires, that is to say, fires of con the extinguishing effect is considerably increased and that bustible solid substances (wood, paper, rags, etc.) soaked 5 the same results are obtained with a lower acetate con for example with hydrocarbons or chemicals. Centration. For example, a solution containing 300 g./I. It is well known that many potassium salts have inter of potassium acetate to which 100 to 200 g./I. of tetra esting fire extinguishing properties and may be used either potassium pyrophosphate have been added, has the same in the form of powder or in the form of aqueous Solutions eXtinguishing effect on a gasoline fire as a solution con to fight fires. In particular, it has been proposed to use 20 taining about 500 g/l. of potassium acetate alone. aqueous solutions of potassium acetate optionally mixed Solutions containing both acetate and tetrapotassium with other alkali metal salts and/or products such as pyrophosphate have outstanding extinguishing properties wetting agents and other surface active agents which make On mixed fires because this latter salt gives to the com the spraying easier. These solutions containing a rel bustible solid substances soaked with extinguishing liquid atively small quantity of potassium acetate are suitable 25 Such fireproof qualities that the risk of re-flashing is con to fight dry fires or fires generally easy to extinguish but siderably reduced or even avoided. they are not highly effective against fires of very inflam Although the addition of wetting agents does not better mable substances such as gasoline for instance. the Specific extinguishing properties of the solutions dis It is well known that as a general rule the effectiveness closed in the present invention, such products added in of a saline solution increases as the salt concentration is 3) Small quantities, by reducing the surface tension of the higher. However, when trying solutions containing more liquid, Will improve the dispersion of the droplets whereby than about 300 g./l. of potassium acetate, many tests the Spraying operation is made easier. Therefore, the have shown that during the Spraying operation a precipi use of a Wetting agent is mainly dependent upon the type tation occurs due to cooling and evaporation. This makes of Spraying apparatus chosen. Obviously, the wetting the liquid more difficult to disperse and causes a rapid agent must be compatible with the dissolved salts: for blocking of the spray nozzles through which the extin example, to the Solution disclosed in the present inven guishing solution is projected onto the fire. Thus, it is tion it is possible to add a wetting agent of oxyethylenic possible to put out a fairly small fire, but as the source alkylphenol type or a phosphate ester of non-ionic com of the fire grows, extinction becomes less certain and even pounds, preferably in quantity not exceeding 2% by totally impossible. 40 Weight of Solution. Specific examples of such wetting An object of this invention, therefore, is to provide agents are compounds of formula novel and more effective fire extinguishing solutions based on potassium acetate. Another object is to provide a method of extinguishing Where n is 6 to 15, R1 is H or CH and R an alkyl residue fires with the solutions of this invention. having 8 or 9 carbon atoms. it is a further object of this invention to provide a In addition to their excellent fire extinguishing proper new and improved process to prepare said extinguishing ties, the solutions disclosed in the present invention have Solutions. other outstanding advantages which are set forth here Upon further study of the specification and claims, below. other objects and advantages of the present invention will The freezing point of concentrated potassium acetate become apparent, 50 Solutions is very low, solutions containing about 600 g/l. It has now been found that an excellent extinguishing being practically non-freezing under all climates. effect is obtained without any risk of precipitation during It has been found that the freezing point of potassium the spraying by using solutions containing about 300 to acetate Solutions first decreases as the salt concentration about 600 g/l. of potassium acetate and having a pH rises up to about 600 g/l.; but if the salt concentration value of at least 7, and preferably ranging from about 55 continues to rise above 600 g/l., then the freezing point 7.5 to 8.5. The upper limit of the pH is unimportant, for increases. This fact is illustrated in the table hereunder. any higher pH is satisfactory to fight fires, but pH's lower Salt concentration in g./I. than 8.5 are preferred SO as to obtain solutions less cor -of potassium acetate: Freezing point (C.) rosive and less sensitive to wetting agents. 60 200 ------11 When the acetate concentration exceeds 600 g./I. there 290 ------18 is practically no improvement in extinguishing properties 400 ------32.5 While the risk of precipitation reappears even though the '90 ------45 pH is kept within the above-mentioned limits. The risk increases as the concentration rises and gets nearer to 550 ------60 potassium acetate saturation point which is very close to 65 603 ------95 1000 g/l. at room temperature. 620 ------82 It has been observed that solutions containing from 700 ------57 about 300 to about 600 g/l. of potassium acetate, main 900 ------25 tained at suitable pH, will very quickly extinguish fires of 70 The addition of tetrapotassium pyrophosphate to potas hydrocarbons or inflammable chemicals (excepting, how sium acetate solutions does not appreciably alter the ever, particularly rebellious fires of Sulfur compounds freezing points. For example, the freezing point of a

3,274,105 3 4. solution containing 400 g/l. of acetate and 100 g./l. of of the remainder of the specification and claims in any pyrophosphate is close to -40 C. way whatsoever. The fire extinguishing solutions disclosed in the pres Example I ent invention can thus be stored without any danger of A highly concentrated solution of potassium acetate was freezing, those having a freezing point equal or lower prepared as follows: to -40° C. being of course selected when climatic condi 171 kg. of technical grade potassium carbonate con tions are particularly severe. The extinguishing proper taining 96% K2CO3, 90 kg. of potassium hydroxide con ties of these solutions are not altered at low temperature taining 93% KOH, and 80 liters of water are put into a and they remain fluid enough to allow an effective Spray vessel. The mixture is stirred gently just enough to main ing operation with a suitable device. O tain the potassium carbonate in suspension therein while The fire extinguishing solutions herein set forth can be 300 liters of acetic acid of technical grade containing 80% produced by any known method but a particularly simple of CHCOOH are gradually added; the temperature rises method has been found to prepare them at low cost. up to 85 C. without external heating. At the end of the According to this method, potassium acetate solutions reaction 405 liters of a solution containing 900 g./l. of are prepared by the action of acetic acid on a mixture 5 potassium acetate are obtained. of potassium carbonate and hydroxide. Thus, neutraliza The solution thus obtained was used to prepare a tion is reached much more quickly and more easily than series of more dilute solutions at pH 7.5, containing re by the already known and generally used processes. The spectively 300, 400, 500 and 600 g./I. of potassium ace known processes comprise reacting acetic acid with either tate with which were carried out different field tests with potassium carbonate or potassium hydroxide, both known 20 hydrocarbon fires under the conditions hereafter de methods having serious drawbacks; in the first case the scribed. mixture must be heated and stirred vigorously in order to For each test 20 liters of "essence H' (mineral spirit facilitate the evolution of carbon dioxide; and in the Second having a boiling range from 35 to 200 C. under normal case, a strong cooling is necessary to eliminate the heat pressure) were poured into a round pan measuring 1.50 caused by neutralization of potassium hydroxide. 25 m. diameter and 0.20 m. high. The liquid was ignited The method of the present invention overcomes these and left to burn for one minute, then the solution was various drawbacks and allows manufacture of potassium projected onto the fire under 8 kg./cm. pressure through acetate without any external heating or cooling. This a hose nozzle, the time for complete extinction being method consists in gradually adding a quantity of acetic measured. Once the fire was out, the liquid was ignited acid sufficient to obtain neutralization to an aqueous Solu 30 a second time and left to burn for 30 seconds, the time tion of potassium hydroxide containing potassium car required for complete extinction again being measured bonate, the molar ratio K2CO3/KOH of the mixture being in the range of 0.5:1 to 1.25:1, preferably 0.6:1 to 0.8:1. The same operation was carried out three times. The gradual addition of acetic acid means that the whole The following table, whereins represents seconds, il amount of acetic acid is not added all at once to the aque lustrates the results obtained with the different acetate ous solution of potassium hydroxide containing potassium solutions: carbonate as it would cause a too sudden evolving of carbon dioxide. To prevent this from happening the ad Time necessary for complete extinction Concentration of the dition of acetic acid is made either step by step or con Solution, g.fl. Ignition 1st re- 2nd re- 3rd re tinuously at a rate sufficient to obtain a steady degasifying. ignition ignition ignition When operating as described above, the temperature of

the reaction mixture adjusts itself at a Suitable value 5 s 60s Os 3S 8s 5 s SS 3s which is from about 95 to about 60 C., preferably close 9s 36 S 9 S 4 S to 80-85 C, when the molar ratio K2CO3/KOH is com 26S 25 s 22 S Os prised between 0.6:1 and 0.8:1. Additionally, carbon dioxide evolves spontaneously without requiring any vigorous agitation for degasifying. Only a slight stirring Example 2 of the mixture is enough to obtain a slurry of potassium Laboratory tests were carried out on ethanol fires carbonate and to prevent it from collecting at the bottom with an apparatus giving a representative and homothetic of the reaction vessel. picture of field tests effected in a round pan measuring 1 According to this new method, fire extinguishing Solti m. diameter and 0.20 m. high with a horizontal bottom. tions can be prepared directly at the desired concentra With a 300 g/l. potassium acetate solution at pH 7.2, tion ready for spraying onto fires. But, should the site the fire was extinguished immediately (less than one sec of utilization be situated far from the manufacturing unit, ond) for first ignition as well as for the following ones. it is possible to prepare highly concentrated solutions 55 Similar results were obtained with a 500 g./l. potassium fairly close to saturation point, for instance solutions con acetate solution though the extinction is even more strik taining 800 to 1000 g/l. of potassium acetate, in order ing, the Smothering effect being instantaneous. to reduce transportation costs. These solutions can also Moreover, it was observed that the mists of both solu include the tetrapotassium phosphate and/or wetting agent tions prevented the ethanol from being ignited by an elec in the appropriate proportions, taking into account that 60 tric spark. the solutions will be eventually diluted to concentrations Example 3 of less than about 600 g/l. of KAc. Besides saving trans 10 liters of gasoline, some old rags and pieces of port costs, these highly concentrated solutions also have Wood Were placed in a round pan measuring 0.80 m. di the advantage of being much less corrosive than the more ameter and 0.20 m. high. These substances were ignited dilute ones and can hence be stored and transported with and left to burn for two minutes, the result being that out any damage to the containers. the whole stake was burning fiercely. A solution con The extinguishing solutions disclosed in the present in taining 300 g./I. of potassium acetate, 100 g./I. of tetra vention can be employed in any usual type of apparatus potassium pyrophosphate and 2% by weight of a wet for projecting or spraying Water under gas pressure. ting agent commonly sold under the trade-name of Without further elaboration, it is believed that one GAFAC RE 610 was then sprayed onto the blazing fire. skilled in the art can, using the preceding description, It took only one second to extinguish it completely in utilize the present invention to its fullest extent. The all cases, i.e., the first ignition and the following re following preferred specific embodiments are, therefore, ignitions. In fact, after the first re-ignition the wood does to be construed as merely illustrative, and not limitative 75 not catch fire again owing to the fireproof properties of 3,274,105 5 6 tetrapotassium pyrophosphate. Moreover, no spontane 200 grams/liter of tetrapotassium pyrophosphate, a wet ous flames reappear after the first extinguishing operation. ting agent compatible with the dissolved salts in a con From the foregoing description, one skilled in the art centration of less than 2% by weight of the solution, and can easily ascertain the essential characteristics of this sufficient water to make a liter of solution, said solution invention, and without departing from the spirit and 5 having a pH above 7. scope thereof, can make various changes and modifica 7. A process for the preparation of an aqueous potas tions of the invention to adapt it to various usages and sium acetate fire extinguishing solution, which process conditions. Consequently, such changes and modifica comprises gradually adding acetic acid to an aqueous tions are properly, equitable, and intended to be, within mixture of potassium carbonate and potassium hydroxide, the full range of equivalence of the following claims. the molar ratio K2CO3/KOH of the mixture being about What is claimed is: 0.5:1 to about 1.25:1, the quantity of acetic acid being 1. A method of extinguishing a fire, which method sufficient to neutralize said mixture, said solution having comprises the step of contacting the source of the fire a pH above 7. with an aqueous solution containing about 300-600 8. The process of claim 7, wherein the molar ratio grams/liter of potassium acetate and in addition a suf 5 K2CO3/KOH is about 0.6:1 to about 0.8:1. ficient quantity of tetrapotassium pyrophosphate to in 9. The process of claim 7, wherein the concentration crease the extinguishing effect of said potassium acetate, of potassium carbonate and potassium hydroxide in the said solution having a pH higher than 7. aqueous mixture is sufficient to yield a potassium acetate 2. The method of claim 1 wherein the concentration concentration of about 300-600 grams/liter. of potassium acetate is about 300-400 grams/liter and 20 10. The process of claim 7, wherein the concentration the concentration of tetrapotassium pyrophosphate is of potassium carbonate and potassium hydroxide in the about 100-200 grams/liter. aqueous mixture is sufficient to yield a potassium acetate 3. A method of extinguishing fires in climatic tem concentration of about 800-1000 grams/liter. peratures of below -40° C., which method comprises the step of, at said temperatures, contacting the source of 25 References Cited by the Examiner the fire with an aqueous solution containing about 400 grams/liter of potassium acetate and about 100 grams/ UNITED STATES PATENTS liter tetrapotassium pyrophosphate, said solution having a 1936,754 11/1933 Dreyfus et al. ------260-541 pH higher than 7. 2,624,706 1/1953 Maxcy et al. ------252-2 4. A fire extinguishing composition comprising, on the 30 2,876,118 3/1957 Jackson et al. ---- 252-8.1 XR basis of a liter of aqueous solution, about 300 to about 2,895,990 7/1959 Larrison et al. ... 260-541 XR 600 grams/liter of potassium acetate, a sufficient amount OTHER REFERENCES of tetrapotassium pyrophosphate to increase the ex tinguishing effect of said potassium acetate, and sufficient “Effect of Alkali-Metal Compounds on Combustion,' water to make a liter of solution, said solution having a 35 Thomas et al., Industrial and Engineering Chemistry, pH above 7. vol. 20, June 1928, pp. 575-577. 5. A fire extinguishing composition suitable for cli “Tetrapotassium Pyrophosphate,” Hooker Chemical matic conditions below -40° C., said composition com Corp., Jeffersonville, Indiana (February 1963). prising, on the basis of a liter of aqueous solution, about “The Use of Chemicals in Forest Fire Control,” Truax, 400 grams/liter of potassium acetate, about 100 grams/ 40 March 1956, U.S. Dept. of Agriculture, Forest Products liter of tetrapotassium pyrophosphate, and sufficient water Lab., Madison 5, Wis. (Table 1 relied on). to make a liter of solution, said solution having a pH above 7. LEON D. ROSDOL, Primary Examiner. 6. A fire extinguishing composition comprising, on the basis of a liter of aqueous solution, about 300 to about 45 JULIUS GREENWALD, Examiner. M. WEINBLATT, Assistant Examiner. 400 grams/liter of potassium acetate, about 100 to about