US3661776A - Composition comprising a foam-forming fluoroaliphatic compound and a film-forming fluoroaliphatic compound - Google Patents

Abstract

AN AQUEOUS COMPOSITION FOR EXTINGUISHING OR PREVENTING FLAMMABLE FUEL FIRES IS FORMULATED AS A 6% CONCENTRATE COMPOSITION AND COMPRISE WATER, A WATER-SOLUBLE FOAM-FORMING FLUOROALIPHATIC COMPOUND AT LEAST ONE WATER-SOLUBLE FILM-FORMING TWO-COMPONENT FLUOROALIPHATIC SALT, VIZ, ONE HAVING AN ACID COMPONENT AND A BASE COMPONENT. THE 6% CONCENTRATE COMPOSITION IS DILUTED WITH SIXTEEN PARTS WATER, BY WEIGHT, AND IS APPLIED ONTO A HYDROCARBON FUEL FIRE AS A BLANKETING FOAM.

Description

United States Patent Office- 3,661,776 Patented May 9, 1972 3,661,776 COMPOSITION COMPRISING A FOAM-FORMING FLUOROALIPHATIC COMPOUND AND A FILM- FORMING FLUOROALIPHATIC COMPOUND Robert B. Fletcher, Maplewood, and Kenneth W. Livermore, St. Paul, Minn., assignors to Minnesota Mining and Manufacturing Company, St. Paul, Minn.

No Drawing. Continuation of application Ser. No. 700,716, Jan. 26, 1968. This application Aug. 24, 1970, Ser. No. 66,595

Int. Cl. A6211 1/00 U.S. Cl. 252-3 4 Claims ABSTRACT OF THE DISCLOSURE An aqueous composition for extinguishing or preventing flammable fuel fires is formulated as a 6% concentrate composition and comprises water, a water-soluble foam-forming fluoroaliphatic compound and at least one water-soluble film-forming two-component fluoroaliphatic salt, viz, one having an acid component and a base component. The 6% concentrate composition is diluted with sixteen parts water, by weight, and is applied onto a hydrocarbon fuel fire as a blanketing foam.

This application is a continuation of our application Ser. No. 700,716 filed Jan. 26, 1968, and now abandoned.

This invention relates to improvements in foam compositions of the type disclosed in Tuve and Jablonski United States Pat. No. 3,258,423 for extinguishing liquid fuel fires or for blanketing newly extinguished fuel surfaces which are susceptible to fire fiashbadk.

The present invention provides novel 6% concentrate compositions, i.e., compositions which, when diluted with sixteen parts water and applied onto a flammable fuel fire, have proven to be effective in extinguishing fires by being present in either the liquid film-forming state or as a foam; the compositions can be utilized singly or in combination with other fire extinguishing agents. The present compositions displayed a remarkable elfect in their ability to protect newly extinguished flammable fuel surfaces from possible recurrence of fire. In this respect, the novel compositions have been found to be especially useful in combating fires in gasoline, naphtha, benzene and other combustibles which release a highly flammable vapor; they are also useful in combating fires in other hydrocarbons, which are capable under the heat conditions of a fire of giving considerable vapor, for example, kerosene, jet fuels, diesel oils, etc.

Thus, it is an object of the present invention to provide a more efficient composition in the form of a 6% concentrate for suppressing and extinguishing hydrocarbon fuel fires.

Another object of the invention is to provide a 6% concentrate composition that results in the formation of a water-containing surface film which inhibits the release of flammable vapor from a hydrocarbon surface.

Other objects and advantages of the invention will become more fully apparent from the following detailed description.

In accordance with the present invention, novel 6% concentrate compositions are formed from mixtures or solutions containing therein one or more foam-forming fiuoroaliphatic compounds and at least one film-forming two component fiuoroaliphatic salt, viz, one having an acid component and a base component. To be an effective film-forming agent, the salt must decrease the surface tension of an aqueous solution to less than about 25 dynes/cm. at a concentration no greater than 1% by weight at 25 C. At about 25 C., the acid component must be water soluble to the extent of at least 0.2% by weigh in aqueous solution and must have an ionization constant greater than about 1X10- At about 25 C., the base component must be soluble in aqueous solution of pH 5 or less to the extent of at least 0.2% by weight, must contain a trivalent basic nitrogen atom (e.g., a primary, secondary or tertiary amine) and must have a basic ionization constant in excess of about 1 l0- These 6% concentrate compositions are capable of forming a blanketing film or a frothy mass when blown or mixed with air, Freon-12, nitrogen, or other suitable gaseous media.

Preferred acids are represented by the general formula, R CO H and R SO H respectively, wherein R; is a monovalent aliphatic (including cycloaliphatic) radical free of unsaturation containing from 3 to about 21 carbon atoms, preferably 6 to 12 carbon atoms, in which the carbon atoms of the chain are substituted only by fluorine, chlorine or hydrogen atoms with no more than one hydrogen or chlorine atom for every two carbon atoms, and in which no more than one divalent oxygen or trivalent nitrogen atom, bonded only to carbon atoms, can be present in the chain for every two carbon atoms; a fluoroaliphatic radical containing a perfiuoro terminal group of at least 3 carbon atoms is, however, preferred.

Although any moderately water-soluble fluoroaliphatic compound tends to form foams in aqueous solutions, preferred Water-soluble foam-forming fluoroaliphatic compounds of the present invention are represented by the formula:

An especially preferred foam-forming fiuoroaliphatic compound is the following quaternary nitrogen compound which has in its molecular structure an intermediate amidopolymethylene linkage:

C1F15CONH CH N (CH CH CH COO (A) Typical water-soluble film-forming fluoroaliphatic twocomponent salts useful in the present invention, in which the fluoroaliphatic radical may be a substituent of either the acid or base component, may be represented bv the formulae:

Exemplary of these film-forming fluoroaliphatic twocomponent salts are the following sulfonic and carboxylic acid salts:

The B-alanine derivatives can be prepared by a variety of methods. The material designated as (A) was prepared by reaction of propiolactone with C'IF15CONH(CH2 3 H3) 2 in general accordance with procedure F of the article by Gresham et al., I. Am. Chem. Soc. 73 (3168) 1951; the material designated as (B) was prepared by reaction of propiolactone with (CH N(CH NH in general accordance with procedure A(c) of the same article, followed by neutralization of the product with perfiuorooctanoic' acid.

It has been found that, of the hereinabove listed twocomponent film-forming fluoroaliphatic salts, the carboxylic acid salts, i.e., compounds (B), (C), (D), (E) and (F), form more substantial and rapidly spreading films than the sulfonic acid salts and are, therefore, preferred. Compound (B) has been found to form films at extremely low concentrations, viz at concentrations as low as 0.04% by weight even in the absence of a foamforming compound and is an especially preferred filmforming salt for this invention.

The useful fluoroaliphatic compounds provide longchain surface active cations and/or anions which have a terminal fluoroaliphatic group of at least 3 carbon atoms, preferably at least 6 carbon atoms, that is both hydrophobic and oleophobic and therefore repellent to water and to hydrocarbons. The molecules are capable of concentrating on the surface of water or hydrocarbon fuel and form an oriented surface film with the fluoroaliphatic end pointed upward.

In the Tuve and Jablonski U.S. Pat. No. 3,258,423 at column 4, lines 69-75, the preferred fluoroaliphatic compounds, utilized in equal proportions, were represented by the following formulae:

It will be observed that the second of these compounds (N) is identical to the foam-forming compound (A) of the present invention. It will also be observed that the first listed of the foregoing compounds (M) is a fluoroaliphatic salt. Significantly, however, this salt is a quaternary salt and is not a film former.

Attempts to duplicate the results obtained by the patentees, i.e., a foam which upon disintegration formed a surface film on a hydrocarbon fuel surface, produced erratic and unpredictable results. In certain tests, excellent surface films were formed. In others, weak and barely discernible films were formed. In still other tests, no film formation was observed.

It has now been discovered that a definite and critical amount of a film-forming acid-base component salt, as herein defined, is required if surface film formation characteristics are to be assured. The presence, in varying degrees of one such two-component salt (Compound (B) herein) as an impurity was confirmed in each test solution of the patented composition which yielded a surface film upon foam degradation. In order to insure reliable and reproducible results in the fluoroaliphatic compositions of the present invention, with respect to surface film formation, it has been determined that the filmforming two-component fluoroaliphatic salt must be present in a concentration of at least about 2.5% by weight of the foam-forming fluoroaliphatic compounds; in amounts below about 4%, film-forming ability of the composition decreases in a geometric progression until the salt concentration drops below about 2.5%, when no film is formed. At salt concentrations above about 10%, the film-forming ability of the composition is not further enhanced by salt addition. In those instances, such as for preventive spraying of spills of flammable liquids, where the presence of foam is not critical but a vapor inhibiting film is desired, the film-forming salt may be present in concentrations equal to or even in excess of the foamforming compound.

Presently existing mobile foam-forming fire-fighting equipment is largely designed for use with so-called 6% concentrates, i.e., solutions wherein the fire-fighting agent is diluted with approximately sixteen parts water before it is foamed. This dilution may take place in a mixing tank or may be performed by metering valves in the foaming nozzle. Thus, to be economically and commercially useful, an improved fire-fighting composition must be compatible with the presently existing equipment.

One of the practical difficulties experienced with the foam compositions of Tuve and Jablonski, particularly a concentrate formulated to yield the preferred composition found in column 4, lines 69-75 of U.S. Pat. No. 3,258,423 has been its low dilution factor. It will be observed that said, preferred composition is the composition which is foamed and applied directly to the fire. Thus any concentrate of said preferred composition must be formulated to yield the requisite quantity (about 0.5% by Weight) of the active ingredients of the pre ferred composition for application to the fire. Following such a procedure, it was found that a satisfactory 25% concentrate, i.e., one which could be diluted with approximately 3 parts water to 1 part of foam concentrate, could be produced. However, it is obvious that a concentrate having such a low dilution factor could not be utilized in presently existing equipment without the necessity for extensive modification of such equipment.

Accordingly, in spite of the extreme usefulness of the aforesaid Tuve and J ablonski foam composition in fighting flammable fuel fires, a real and pressing need existed for a fire-fighting composition which could be utilized in existing mobile foam-forming fire-fighting equipment which are designed for use with 6% concentrates. It was early discovered that a 6% concentrate composition could not be obtained by the mere increase in concentration of the active components of the known aforenoted Tuve and Jablonski composition. For example, proportionately increasing the concentration of the constituents of the preferred composition yielded a concentrate having a viscosity which effectively preclude its use in the intended manner. Additionally, the constituent compounds were found to be stratified and precipitation was much in evidence at such concentrations.

It has now been discovered that stable effective 6% concentrates of manageable viscosities can be formulated by careful selection of the constituent compounds. Useful 6% concentrates have been prepared containing the foamforming perfluoroaliphatic compound (A) in concentrations of about 0.5 to about 10% by weight, with one or more film-forming fluorocarbon compounds in concentrations of about 4 to about 10% by weight of said foamforming compound, depending on the particular compound used for this purpose. Preferably, the 6% concentrate composition contains said foam-forming fluorocarbon compound in concentrations in the range of from about 2 to about 7% by weight of solution.

The compounds designated (A) and (B), when combined in a simple solution using about 5.8% of (A) and about 0.5 of (B) in a total concentration of about 6.3%, after being suitably diluted with sixteen parts water, have been found to be most effective in their ability to form resistant foams and blanketing films capable of protecting low flash point fuels from ignition or reignition for periods of from 5 to 10 minutes or more based on a final foam volume expansion of 8 to 10.

Improved stability in the present foams is obtained by means of additives which improve the resistance of the foam to heat and its capacity to maintain its surface liquid content. Foam improvers which may be advantageously combined in solution involve the high molecular weight water-soluble polymers of ethylene oxide, polyvinyl resins, polyglycols, carboxyl vinyl polymer, etc. An especially useful polyethylene oxide polymer (polyoxyethylene glycol) commercially available is the Polyox WSR N manufactured by the Union Carbide Chemical Co. (Polyox WSR N10 is a polyoxyethylene glycol with an average molecular weight of approximately 90,000.) Foam improvers of this type are usually present in amounts in the range of about 5 to by Weight of the concentrate composition.

Other useful foam stabilizers include the low molecular weight highly hydratable compositions such as ethylene glycol, diethylene glycol, glycerol, sorbitol and the like which not only serve as solubilizing agents for the higher molecular weight polymeric materials but also serve to decrease the rate of water evaporation from the foam surface. Stabilizers of this type are included in the range of about 15 to 50% by weight of the final concentrate solution.

A preferred 6% concentrate foaming composition in accordance with the invention has the following composition by weight:

The composition is prepared in a standard glass-lined or corrosion-resistant metal kettle, equipped for agitation and heating and cooling, as follows: The water plus ethylene glycol is charged to the kettle and heated to 160 F. with maximum agitation. The polyoxyethylene glycol, finely divided, is added slowly and mixing continued until it appears completely dissolved. With agitation continuing, the kettle contents are heated to 180 F. to insure completion of solution and then cooled rapidly to 125 F. Acetic acid is added in small amounts until the pH falls between 4.2 and 5.2 Agitation is continued and the fluorochemicals added. Agitation is continued for about minutes after which the kettle contents are filtered through a 25 micron filter and stored for subsequent use.

In use, the above 6% concentration is combined with sixteen parts Water by weight resulting in a solution containing about 0.4% of the active compounds (A) and (B) which is then expanded into a foam with conventional fire fighting equipment and applied onto the flammable fuel.

The foams formed from the 6% concentrate composition of the present invention constitute essentially airwater emulsions that display a substantial capability to distribute a thin surface layer of water in an active film. The oriented, surface-active film is capable of distributing a useful water content which does not drain rapidly from a hydrocarbon surface. This water-containing film with a specific gravity of about 1.0 is capable of floating on a hydrocarbon surface with a specific gravity of only 0.7 and of persisting thereon for an extended period of time. A further distinguishing feature of the present composition is its ability to form foam from very dilute'solutions containing small concentrations of the fluoroaliphatic foam-forming and film-forming materials. The distintegration of these foams results essentially in the deposition of a water-containing surface film on the hydrocarbon fuel surface.

As hereinbefore noted, the present fluoroaliphatic radical-containing compositions are conveniently formulated as 6% concentrates which are then diluted with sixteen parts water, by weight, to form the active foaming solution to generate the foam. The compositions usually also contain stabilizers and pour point depressants arid other additives.

The invention, therefore, makes possible the production of fluoroaliphatic compound-containing foams which have been found to be very advantageous in combating fuel fires, especially those involving hydrocarbon fuels with highly flammable vapors.

Obviously many modifications and variations of the present invention are possible in the light of the 'above teachings.

We claim:

1. An aqueous 6% concentrate composition for extinguishing or preventing flammable fuel fires consisting essentially of x (a) about 0.5 to about 10% by Weight of a water-soluble foam-forming fluoroaliphatic compound of the formula RgCONH (CH N+ (CH CH CH COO- wherein R is a monovalent fluoroaliphatic radical free of unsaturation containing from 3 to 21 carbon atoms in which the carbon atoms of the chain are substituted only by fluorine, chlorine or hydrogen atoms with no more than one hydrogen or chlorine atom for every two carbon atoms, and in which no more than one divalent oxygen or trivalent nitrogen atom, bonded only to carbon atoms, can be present in the skeletal chain for every two carbon atoms, (b) at least about 2.5% by weight of said foam-forming fluoroaliphatic compound of a two-component watersoluble film-forming fluoroaliphatic salt having (1) an acid component solu-ble to the extent of at least 0.2% by weight in aqueous solution and having an ionization constant greater than about 1X 10*, and (2) a base component soluble in aqueous solution of about pH 5 to the extent of at least 0.2% by weight and containing a trivalent basic nitrogen atom and havinga basic ionization constant in excess of about 1x10 selected from the group consisting of wherein R; is as defined hereinabove,

(c) about 5 to about 15% by weight of a polyoxyethylene glycol with an average molecular weight of about I 90,000, and

(d) about 15 to about by Weight water, said concentrate composition being capable of dilution with about sixteen parts by weight water,

said diluted composition being capable of forming a surface film on a hydrocarbon fuel surface, said film inhibiting flammable vapor release from said surface.

2. An aqueous 6% concentrate composition for extinguishing or preventing flammable fuel fires consisting essentially of (a) about 0.5 to about 10% by weight of a watersoluble foam-forming fluoroaliphatic compound of the formula R CONH (CH N+ (CH CH CH COO wherein R is a monovalent fluoroaliphatic radical free of unsaturation containing from 3 to 21 carbon atoms in which the carbon atoms of the chain are substituted only by fluorine, chlorine or hydrogen atoms with no more than one hydrogen or chlorine atom for every two carbon atoms, and in which no more than one divalent oxygen or trivalent nitrogen atom, bonded only to carbon atoms, can be present in the skeletal chain for every two carbon atoms,

(b) at least about 2.5 by weight of said foam-forming fiuoroaliphatic compound of a two-component watersoluble film-forming fiuoroaliphatic salt having (1) an acid component soluble to the extent of at least 0.2% by weight in aqueous solution and having an ionization constant greater than about 1X 10- and (2) a base component soluble in aqueous solution of about pH 5 to the extent of at least 0.2% by weight and containing a trivalent basic nitrogen atom and having a basic ionization constant in excess of about l 10- selected from the group consisting of:

wherein R; is as defined hereinabove,

() about to about 15% by weight of a polyoxyethylene glycol with an average molecular weight of about 90,000, and

((1) about 15 to about 95% by weight water, said concentrate composition being capable of dilution with about sixteen parts by weight water,

said diluted composition being capable of forming a surface film on a hydrocarbon fuel surface,

said film inhibiting flammable vapor release from said surface.

3. An aqueous 6% concentrate composition for extinguishing or preventing flammable fuel fires consisting essentially of (a) about 0.5 to about 10% by weight of a water-soluble foam-forming fluoroaliphatic compound of the formula:

(b) at least about 2.5% by weight of said foam-forming fluoroaliphatic compound of a two-component water-soluble film-forming fluoroaliphatic salt selected from the group consisting of (c) about 5 to about by weight of polyoxyethylene glycol with an average molecular Weight of about 90,000, and

(b) about 0.5 weight percent of a two-component water-soluble film-forming fluoroaliphatic salt of the formula (c) about 10 Weight percent of a polyoxyethylene glycol with an average molecular weight of about 90,000, (d) about 30 weight percent ethylene glycol, and (e) about weight percent water, said concentrate composition being capable of dilution with about sixteen parts by weight water,

said diluted composition being capable of forming forming a blanketing foam when blown with a gaseous media onto a hydrocarbon fuel surface,

said foam being capable of supplying a surface water film on said hydrocarbon fuel surface,

said film inhibiting flammable vapor release from said surface.

References Cited UNITED STATES PATENTS Brown et al. 252-355 Ahlbrecht 252-357 Ahlbrecht et al. 252-355 Furey 252-33.6 Tuve et al 252-6 OTHER REFERENCES Gresham et al. J. Am. Chem. Soc. 73 1951, pp. 3168- JOHN T. GOOLKASIAN, Primary Examiner D. J. FRITSCH, Assistant Examiner US. Cl. X.R.

STATES PATENT OFFEQE 'ctaimtflt or CORRECTWN Patent No. 3,661,776 Dated May 9', 1972 Inventor(s) Robert B. Fletcher and Kenneth W. Livermore It is certified thaterror appears in the above--identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 42, '"displayedY' should read display-.

Column 2, line 53, the formula reading [R so NH H McH c u oufm m "should be deleted.

Column l, line +2, preclude should read -prec1uded--.

Column 5, line 59, "distintegra should read --disintee;ra

Column 6, line M, that portion of the formula reading R CO H should. read R SO H Column 7, third line from bottom, after "of" insert --a-.

Column 8, line 27, forming" should be deleted.

Signed and sealed this 2nd day of January 1973.,

(SEAL) Attest;

EDWARD M..FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents QM FO-JOSO (10-69) USCOMM'DC 5037B-W59 a U 5. GOVERNMENT PRINTING OFFICE: "E59 O lliE-SSG UNI .STATES PATENT OFFICE CERT-IFTCATE CORRECTION Patent No. 3 6613776 ae d May 9,1972

Inventofls) Robert B. Fletcher and Kenneth W. Liver-morev It is certified that error appears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 1, line 42, displayed should read -display-.

Column 2, line 53, the formula reading sho 1d be del ted. [R SO NH H N(CH C H OH] N PO 11 e 3 Column l, line 2, prec1ude.should read -precluded--.

Column 5, line 59, "distintegra should'read disintegra v Column 6, line I I, that portion of the formula reading R CO H should read a R SO H Column 7, third line from bottom, after "of insert -a--.

Column 8, line 27, f'orming;" should be deleted.

Signed and sealed this 2nd day of January 1973.

(SEAL) Attest:

EDWARD M.,FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer 7 Commissioner of Patents QM PC1-1050 (10-69) USCDMM-DC 60376-1 69 w u s GOVERNIIENY PRINTING OFFICE: was o-3M-3u