US2653130A - Fire extinguishing composition of cbrf or cfbrcfbr containing cf as a propellant - Google Patents

Description

Sept. 22, 1953 B. J. ElsEMAN, JR 2,653,130

FIRE EXTINGUISHING COMPOSITION OF CBJULF'LOR CFQJ BJU CF@ BJU CONTAINING CFq AS A PROPELLANT Filed May 17, 1951 A TTORNE Y.

Patented Sept. 22, 1953 NETE STAT PATENT GFFHCE FIRE EXTNGUSHING COMPOSITION OF CBrzFz R CFzBrCFzBr CONTAINING GF4 AS A PROPELLANT Ware Application May 17, 1951, Serial No. 226,921

7 Claims.

This invention relates to self-propelling liquid compositions, and particularly to compositions of such character which are adapted for use as lire extinguishants having exceptionally desirable properties for use at varying ambient temperatures.

It has been proposed to use propellants for lire extinguishants which are low in toxicity, are stable during storage and provide adequate pres- .'sure forV discharge at temperatures near room temperature. However, such propcllants are not operative at low temperatures because they do not provide suflicient pressures at such temperatures. By low temperatures, as employed herein, I means temperatures equal to or below cold winter temperatures in the temperate zone, including, particularly, arctic temperatures and 'the loW temperatures encountered at high alti- 'tudes by airplanes. A propellant, which is suitable for use at such low temperatures, must also be suitable for operation at high temperatures, such as the highest summer temperatures and the temperatures encountered in the desert and in the tropics, since the same extinguisher may be required to operate at both the low temperatures and the high temperatures as, for example, when employed in an airplane or the like.

. Some re extinguishants function mainly by Asmothering the flame, while others tend to suppresscombustion even though oxygen is present. The latter type is the more efective, and probably functions by quenching free radical activity which is believed to be necessary for maintaining combustion even in the presence of oxygen. The bromo-iiuoro alkanes, such as CBrFz, CBrzFz and CFzBrCFzBr, are examples of such latter type. Ii' therpropellant is ofthe former type, as is commonly the case, it should not be employed in such large proportions as to excessively dilute the more eiective extinguishant.

A re extinguishant composition, in order to be satisfactory for use under the varying temperature conditions hereinbefore referred to, must meet all of the following requirements:

1. Be low in toxicity; Y

2. Have high stability;v Y

3. The propellant must provide adequate pressure at 10W temperatures, preferably at least 100 pounds" per square inch gauge at '-.65 AF., with- 2 outl excessive dilution of the more effective propelled extinguishant;

4. Develop only moderate pressures at high temperatures;

5. The pressure-must be well maintained during the entire discharge, i. e., until the last of the liquid has been expelled from the extinguisher; and.

6. The propellant must be suiiicient in volume so that a brief accidental discharge of gas phase, while the extinguisher is inverted, will not lead to an excessive loss of pressure.

Ofhand, nitrogen would appear to be the obvious propellant for use at low temperatures, as it meets requirements 1 to 4 and also has the advantage of being low in cost. However, nitrogen does not meet requirements 5 and 6. This is because of the 10W solubility of nitrogen in the highly effective extinguishants which are suitable for use at low temperatures. Thus, there is little nitrogen present and, when a part of the nitrogen is expelled or lost, the pressure in the extinguisher drops rapidly. This latter result can be offset to some extent through the use of larger amounts of nitrogen, by employing higher pressures at the low temperatures or by employing a large gas space equivalent to an auxiliary tank above the liquid extinguishant, but these expedients are objectionable because the pressures become excessive at high temperatures and, in the case of a large gas space, requires large and bulky equipment. It is an object of the present invention to provide new self-propelling liquid compositions having unusual properties. Another object is to provide a new self-propelling liquid composition which is particularly adapted for use as a lire extinguishant composition and which is operable and useful. over a wide range of temperatures, and especially atlOW temperatures. A further object is to provide a method of applying such self-propelling liquid compositions. A still further object is to provide a package comprising a hermetically sealed container charged with such self-propelling liquid composition. Other objectsare to provide new compositions of matter and to advance the art. Still other objects will appear hereinafter. y

The above and other objects may be accom- Y`plished in'accordance with my invention which comprises a self-propelling liquid composition consisting essentially of a solution of carbon tetrafluoride (GF4) in at least one of GBrzFz and GF2BrGF2Br, in which the GF4 constitutes from about 2.5% to about by Weight of the liquid; the method of applying such composition to an object Which comprises maintaining such liquid composition in a hermetically sealed container under the vapor pressure thereof and expelling such composition under such pressure through a discharge oriiice and directing the expelled composition against such object; and a package which comprises a hermetically sealed container charged With such liquid composition under a pressure corresponding tothe vapor'pressurenof,

such composition. In such compositionsprthe GF4 acts as the propellant for expelling the liquid composition from the container. Such com-` positions are particularly adapted for use as 'selfpropelling re extinguishant compositions' in which the GBrzFz and GFzBrGFzBr act as the primary extinguishants and the GF4 also acts as a rire extinguishant, functioning by smothering the flame, as Well as the propellant.

GF4 boils at -127.9 G., GBrzFz boils at 24.5 C. andGFzBrGFzBr boilsat 47.4 C. GF4 is nontoxic and highly stable, even at quite high temperatures. I have found that solutions of GF4 in each of GBrzFz and GFzBrGFzBr have abnormally high vapor pressures at low temperatures, deviating Widely from'Raoults law, which vapor pressures could not be predicted. Such deviation apparently decreases with increase Vin temperature. Also, GF4 is quite soluble in each of GBrzFz and CF'zBrCFzBI'. ofy GF4 and solutions thereof in CBrzFz and CFzBrCFzBr, about 2.5% of GF4 by Weight of the liquidvvill provide suicient pressure at lovv temperatures (of the order of about 100, p. s. i. g. at

65 F.) to meet the requirements of a selfpropelling fire extinguishant liquid, and will develop only moderate pressures at high temperatures. Also, such amount yof'GF4 is suiicient to maintain the pressure to the degree required during the entire discharge, and so that a brief.

accidental discharge :of the4 gas phase, While kthe container is inverted, does not. lead to excessive loss of pressure. For most purposes and particularly for use as a re extinguishant, the liquid Will contain from about 2.5% to about 10% by Weight of GF4 and,'preferably, from about 5% to about 10% by Weight. For other purposes and particularly Where the composition is to be used only at atmospheric temperatures or above,

smaller proportions of GF4, down to about 1% by weight, may be used, 1% providing pressures of about 25 to 30 p. s. i. g. at 65 F. More than 10% by Weight of GF4 can be employed Where the resulting higher pressures are desired.

When liquids are dissolved in each other, the expected result is that the Vapor pressure exerted by each component (fpartial pressure) Will be approximately equal to the vapor pressure of the pure compone-nt multipliedby the mole fraction of that component present in the mixture (Raoults law), and that the total pressurebf the mixture will be the sum of the pressures of the individual components (the fpartial pressures). A1; 65 F., GF4 has avapor pressure of 420 pounds per squareinch absolute (p. s. i..a.). At this temperature, the vapor pressures lof GBrzFz and. GFzBrGFzBr are a small fraction yof one p. s. i. a. and are thus negligible, and. the vapor pressure of GBrFa (B. P. -60 C.) is approximately p. s; .i...a. -.GBrF3 represents the Because `of such properties.

4 expected case-only a small deviation from Raoults law; While, with GBr2F2 and CFzBrGFzBr, the actual pressure is 3 to 4 times that calculated by Raoults laW. This may be seen in the following Table I, Where observed and calculated vapor pressures in p. s. i. a. are compared:

The disadvantages of the normal case, as

represented by GBrF3, are the large proportion of the propellant required (above table) to give ade- 1 quate discharge pressure at lovv temperature and ythe highwpressure developed thereby at higher temperatures, as shown infthe following Table II,

wherein the. pressures are given in pounds per v square inch gauge (p. s. i. g.)

Table II Composition Observed Vapor Presof the sure, p. s. i. g.

Liquid Phase,

' Weight Percent Compounds The disadvantage of nitrogen lies in its deciency' in gaseous volume as compared to GF4. This is shown by the number or" Vessel volumes oigaseous propellant at F. and 100 p. s. i. g., i. e., the numberV `of times the propellant present in theparticular mixture would ll the vessel at -65 F.` if the pressure were. reduced to 100 p..s. i. g. The smaller the number of vessel volumes, the less effective is the propellant. The data aregiven in the following Tables III and IV forz a vessel liquid full at' 150 F., the values in `Table' IV being for 65 F. except Whe-re indicated otherwise:

Table IV l Vessel liquid full at 150 F.

Table V Composition of liquid Percent Compounds phase, Liquid P. s. 1. g

Weight Discharged percent CBr2F4 95.0 58 GF4 5- 0 100 103. 5 o erna 99. 7 5g 2% Nitrogen 0. 3 100 42 From such graph and calculations, it is apparent that the pressure during the discharge is much better maintained by GF4 than by nitrogen at low temperatures, when the discharge is slow so that there is equilibrium between the liquid and the gas during the discharge. The amount of GF4 in the system is much greater than the amount of nitrogen and, therefore, after a certain percentage of the solution has been expelled, there will be a much larger amount of propellant remaining in the container when the propellant is GF4 than when the propellant is nitrogen. Usually, in practice, the orice of the container is opened wide fairly quickly, resulting in a sudden rapid discharge so that the propellant equilibrium between the liquid and the Vapor cannot be maintained and, for a given amount of liquid discharged, the proportion of propellant expelled will be higher and the fall in pressure will be more rapid than shown by the graph. In such latter case, the advantage of GF4 over nitrogen would be even greater than that shown in the graph, because of the larger amount of the GF4 propellant available.

As is usual in the case of self-propelling compositions, the compositions of my invention will be maintained under pressure in a hermetically sealed container, such as a iire extinguisher, which is provided with a discharge orice and a valve for controlling the ow of material through the orice. The valve is normally closed to prevent passage of either gas or liquid through the orifice and is opened for expelling the liquid through the orifice and directing it against an object to which it is to be applied. Such containers are well known and conventional and any of them, that will withstand the pressures involved, may be used.

It will be understood that the specific solutions disclosed in the tables are given for illustrative purposes solely and that the proportions of GF4 dissolved therein may be varied as indicated in the general description. It is also apparent that mixtures of GBrzFz and CFzBrGFzBr, in any desired proportions, may be used and the GF4 can be dissolved therein in the same proportions as in the individual compounds.

From the preceding disclosure, it will be apparent that I have provided novel self-propelling liquid compositions having unusual properties and which are suitable for use over a very wide range of temperature conditions. Such compositions have exceptional and particularly desirable properties for use at low temperatures. Therefore, it will be apparent that my invention constitutes a very valuable contribution to and advance in the art.

I claim:

l. A self-propelling liquid composition consisting essentially of a solution of GF4 in a member of the group consisting of GBrzFz and GFgBrGFzBr, in which the GF4 constitutes from about 2.5% to about 10% by weight of the liquid, said composition being maintained in a confined space under a pressure corresponding to its vapor pressure.

2. A self-propelling liquid composition consisting essentially of a solution of GF4 in a member of the group consisting of CBr2F2 and CFeBrCFeBr, in which the GF4 constitutes from about 5% to about 10% by weight of the liquid, said composition being maintained in a confined space under a pressure corresponding to its vapor pressure.

3. A self-propelling liquid composition consisting essentially of a solution of GF4 in a member of the group consisting of GBr2F2 and GFzBrGFzBr, in which the GF4 constitutes from about 5% to about 6.4% by weight of the liquid, said composition being maintained in a conned space under a pressure corresponding to its vapor pressure.

4. A self-propelling liquid composition consisting essentially of a solution of GF4 in GBr2F2, in which the GF4 constitutes from about 2.5% to about 10% by weight of the liquid, said composition being maintained in a confined space under a pressure corresponding to its vapor pressure.

5. A self-propelling liquid composition consisting essentially of a solution of GF4 in CBrzFz, in

which the GF4 constitutes from about 5% to about 10% by weight of the liquid, said composition being maintained in a confined space under a pressure corresponding to its vapor pressure.

6. A self-propelling liquid composition consist- 7 ing essentially of a solution of GF4 in CFzBrCFzBr, in which the GF4 constitutes from about 2.5% to about 10% by Weight of the liquid, said composition being maintained in a coni-ined space under a pressure corresponding to its vapor pressure. 5

rI. A self-propelling liquid composition consisting essentially of a solution of GF4 in CFzBrCFzBr, in which the GF4 constitutes from about 5% to about 10% by Weight of the liquid, said composition being maintained in a confined space under 10 a pressure corresponding to its Vapor pressure. BERNHARDT J. EISEMAN, JR.

was@

References Cited in S'the le of this patent UNITED'STATES PATENTS Number

Claims (1)

1. A SELF-PROPELLING LIQUID COMPOSITION CONSISTING ESSENTIALLY OF A SOLUTION OF CF4 IN A MEMBER OF THE GROUP CONSISTING OF CBR2F2 AND CF2BRCF2BR, IN WHICH THE CF4 CONSTITUTES FROM ABOUT 2.5% TO ABOUT 10% BY WEIGHT OF THE LIQUID, SAID COMPOSITION BEING MAINTAINED IN A CONFINED SPACE UNDER A PRESSURE CORRESPONDING TO ITS VAPOR PRESSURE.

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