US 3621917 A
Description (OCR text may contain errors)
United States Patent Meyer R. Rosen Irvington;
Samuel Sterman, Chappaqua; Eric G. Schwarz, Somers, all of N.Y.
Apr. 30, 1968 Nov. 23, 1971 Union Carbide Corporation Inventors Appl. No. Filed Patented Assignee METHOD OF EXTINGUISIIING LIQUID HYDROCARBON FIRES AND COMPOSITION THEREFOR COMPRISING SILICONE 2,514,310 7/1950 Busse et a1. 252/3 2,529,211 11/1950 Bussc et a1. 252/3 3,258,423 6/1966 Tuve et a1. 252/3 3,278,465 10/1966 Twitchett 260/4488 3,381,019 4/1968 Morehouse.. 260/3409 3,507,897 4/1970 Kanner et a1. 260/4481 3,513,183 5/1970 Morehouse 260/4482 Primary Examiner-l0hn T. Goolkasian Assistant Examiner-D. J. Fritsch Anarneys-Paul A. Rose, Aldo John Cozzi, Reynold J Finnegan, George A. Skoler and Eugene C. Traut1ein ABSTRACT: Anionic and/or amphoteric siloxanes in the 1iquid phase of fire extinguishing foams, with or without other materials as foam promoters. stabilizers or special purpose additives, provide rapid extinguishment of flames, form vaporsecuring films over the burning hydrocarbon liquid to prevent reignition upon foam rupture or disintegration, and impan compatibility of the foam with dry chemical extinguishing agents.
METHOD OF EXTINGUISI'IING LIQUID HYDROCARBON FIRES AND COMPOSITION THEREFOR COMPRISING SILICONE SURFACT ANTS This invention relates to methods of extinguishing liquid hydrocarbon fires and to compositions for use therein. The invention also relates to methods and compositions for preventing the ignition or reignition of low flash point flammable liquids for extended periods.
The extinguishment of low flash hydrocarbon liquid and fuel oil fires by the application of an aqueous base foam blan' ket is well known. The technique involves spreading a continuous, free flowing floating foam over the burning hydrocarbon, thus forming a tough, air excluding blanket. This blanket seals off volatile, combustible vapor from the ambient air and prevents reignition. As the water in the foam drains it cools the hydrocarbon.
One class of fire fighting foam which has gained wide acceptance is known as mechanical foam. It is usually generated by the aspiration of a gas (e.g., air) into a stream of water and a surface active agent which promotes and stabilizes the foam.
Another class of fire fighting foam is the chemical foam which is generated by the reaction, to produce carbon dioxide, of an alkali metal carbonate such as sodium bicarbonate with an acid compound such as aluminum sulfate. When combined with a suitable foam stabilizer, such as, licorice, saponin, glue, glycerin, glucose, sodium sulfonate, quillaia bark, and the like, a stable foam is produced.
A type of mechanical foam which is well known in the art consists of hydrolyzed animal or vegetable protein as foamformer, water and sundry additives, such as, buffers, freezing point depressants, additional foam stabilizers, bacteriocides and anticorrosive agents.
Many types of protein have been used to produce the proteinaceous foam-formers and these include keratins, albumins, globulins, hemoglobulins, seed meals and the like (US. Pat. No. 2,361,057; 2,368,623; 2,481,875 and 2,405,438). Typical sources of these proteins include horns, hoofs, hair, feathers, blood, soya bean meal, pea flower, cotton seed meal and peanut cakes. These proteins are usually degraded with a hydrolyzing agent in the form of an alkaline earth metal oxide or hydroxide, such as, magnesium, calcium or barium oxide. The hydrolysis proceeds, for example, as described in US. Pat. No. 2,324,951, until a minimum of 25 percent of the nitrogen present is converted to the peptone form.
One type of foam stabilizer commonly used for proteinaceous foams is a salt, e.g., ferrous sulfate, which on dilution or formation of the foam, will hydrolyze to an insoluble hydroxide, e.g., ferrous hydroxide, as described in US. Pat. No. 2,361,057. Another type of foam stabilizer is a soluble phosphated inorganic salt containing a fatty alcohol, such as a soluble, phosphated sodium lauryl sulfate as described in US. Pat. No. 2,193,541.
Mechanical foam, of the hydrolyzed protein type, has the advantage of being relatively inexpensive; however, it suffers from several disadvantages. A heavy blanket of foam is required, and the hydrocarbon is subject to reignition if the foam blanket is ruptured by the action of wind or other forces in the presence of an ignition source. Even the footprints of the firefighter as he moves through the foam, disrupt the foam body and permit the possibility of reignition.
Another disadvantage of foams based on hydrolyzed protein is lack of compatibility with dry chemical extinguishing agents. Dry chemical extinguishing agents are finely divided powders consisting of, for example, potassium bicarbonate, sodium bicarbonate or ammonium dihydrogen phosphate coated with materials, such as, aluminum stearate, magnesium stearate (Brit. Pat. 836,465) or silicones (Brit. Pat. 824,107) which impart moisture resistance and free flowing, fluid properties permitting the spraying of such powders on the fire.
The dispersion of such dry chemicals into the combustion zone of a fire rapidly extinguishes the flames. The use of dry chemicals alone in combating liquid hydrocarbon fires is severely limited because no means exist for cooling the hydrocarbon and suppressing the evolution of flammable vapor. If the flames are not completely extinguished, or if sparks and burning debris are present, reignition of the flammable vapor will occur.
The dual use of a dry chemical as the primary extinguishing .agent in conjunction with an oxygen excluding foam which will smother the fire and prevent further vaporization of flammable vapor is very desirable. However, the combined use of the highly efficient silicone treated dry chemicals with a hydrolyzed protein system, heretofore resulted in rapid disintegration of the protein foam. This phenomenon may be explained, since certain silicones are well known to be defoamers when used in conjunction with finely divided solids.
The use of certain fluorocarbons in combination with the hydrolyzed protein partially overcomes the disadvantages of the hydrolyzed protein system. The resulting foam is compatible with silicone treated potassium bicarbonate, commercially known as Purple K powder, but still requires a heavy foam blanket which, if ruptured, will allow flammable vapor to escape and reignition to occur.
More recently, mechanical foams have been generated by the use of perfluorocarbon surfactants which are not silicones in combination with a high molecular weight synthetic polymer. This system, known as light water" (US. Pat. No. 3,258,423) is limited to the use of certain ingredients and leaves little or no latitude in the selection of useable materials.
Certain types of silicones have previously been used in compositions for extinguishment and/or prevention of liquid hydrocarbon fires. The addition of a nonionic liquid alkyl silicone polymer to a chemical foam generated by sodium bicarbonate and aluminum sulfate, stabilized with licorice (US Pat. No. 2,790,502) is stated to have the effect of increasing the flash point and fire point by migrating into the surface of the liquid. lt is asserted that the composition may be used both as a preventative and extinguishing agent for organic oil fires.
In another application, a nonionic alkyl silicone-kerosene system (US. Pat. No. 2,543,672) is added to fuel oil to inhibit foaming. Water is applied to the burning liquid and the heat vaporizes the water to steam. The patent asserts that the presence of the silicone prevents boil-over of the burning fuel by inhibiting foaming which would result from the generation of steam within the fuel body. It is alleged that the steam rises to the surface and acts as a smothering barrier between the flammable vapors and oxygen.
it has been found that the use of nonionic alkyl silicones as disclosed in the two above-mentioned patents in fire fighting does not result in the formation of vapor-securing films and in some cases they act as antifoams to destroy the fire-smothering foam.
The present invention relates to foams and provides novel methods and foam compositions which have proven to be effective in extinguishing fires when utilized singly or in combination with other fire extinguishing agents. The present foam compositions display a remarkable effect in their ability to protect newly extinguished flammable fuel surfaces from possible recurrence of fire. ln this respect, the novel foams have been found to be especially useful in combating fires in gasoline, naphtha, toluene, benzene and other combustible hydrocarbon having highly flammable vapors. They are also useful in combating fires in other hydrocarbons, which are capable under the heat conditions of the fire to give off considerable flammable vapor, for example, kerosene, jet fuels, diesel oils, etc.
The present invention utilizes anionic and/or amphoteric silicone surfactants in the liquid phase of a fire fighting foam. These silicone surfactants reduce the surface tension of water in the foam to exceptionally low values and foams containing them are stable in contact with the hydrocarbon as well as during exposure to the heat generated in a typical hydrocarbon fire.
These silicone surfactants, when added in small amounts to heretofore known foam systems and compatible therewith, e.g., hydrolyzed protein foam systems, unexpectedly impart 1) resistance to the defoaming effects of dry chemical extinguishing agents such as Purple K powder, and (2) the ability of forming spreading vapor-securing films.
The liquid draining from aqueous foams containing these surfactants has the property of forming a surfactant-water film which spreads over the liquid hydrocarbon surface and forms a vapor-securing barrier film. This film effectively seals ofi' the hydrocarbon from radiant energy input from an ignition source, if present. The film also prevents further release of flammable vapor after the flames have been suppressed. It has the property of spreading under the flames and rapidly sealing off any exposed liquid hydrocarbon surface which may occur as a result of mechanical disruption of the foam blanket, as by falling debris, wind, etc.
The formation of a vapor-securing film is an unexpected property of the specific classes of anionic and amphoteric silicone surfactants disclosed herein. In contrast, similar foam promoting, low surface tension silicone surfactants which are cationic and other anionic and amphoteric silicone surfactants do not perform satisfactorily. For example, they do not form vapor-securing films under comparable conditions and/or are extremely poor in resistance to radiant heat attack, etc.
The anionic and/or amphoteric silicones themselves, when used in the relatively higher concentrations, act as the major foam-former and no substantial amounts, if any, of other known foam-formers, such as, hydrolyzed protein, licorice, etc., are needed. Alternatively, the known foam-formers can be employed as the primary or major foam-former and the anionic and/or amphoteric silicone is used in the relatively lower concentrations, i.e., about 0.] percent or less, for imparting to the foam the capability of forming the spreading vapor-securing film.
The foam containing the anionic and/or amphoteric silicone surfactants also exhibits complete compatibility with dry chemical extinguishing agents such as Purple K powder. This compatibility overcomes the inherent disadvantages of using Purple K powder as an extinguishing agent in conjunction with foams. The dual use of the anionic or amphoteric silicone foam with Purple K powder provides both the rapid flame extinguishment characteristics of the powder and the vapor suppression properties of the foam.
Certain of the amphoteric silicone surfactants are especially useful with hydrolyzed protein foam systems and provide the above-mentioned advantages even when used in very small amounts as will be explained more fully hereinafter. Most surprising is the ability of even small amounts of such silicone surfactants to render hydrolyzed protein foam systems compatible with dry chemical agents such as purple K powder.
The concentration of the amphoteric and/or anionic silicone surfactant employed in this invention is not narrowly critical. The liquid solutions from which foams are made according to this invention form the foam lamella or liquid phase upon mixing with air or other suitable gas. In order to impart to the foam the capability of forming spreading, vapor-securing films, it is highly desirable to use at least about 0.01 percent of the silicone based on the total weight of the liquid phase of the foam. When the silicone surfactant is employed as the major foam-former or -stabilizer, the liquid phase preferably contains from about 0.4 to about percent, more preferably about 0.5 to about 1 percent, of the silicone surfactant based on the total weight of the liquid solution. When employed in systems wherein the major foam-forming action is provided by a known foam-former, e.g., hydrolyzed protein foam systems, less than about 0.4 percent and as little as 0.01 percent of the silicone surfactant on the same weight basis provides spreading, vapor-securing films on the surface of liquid hydrocarbons.
The spreading surfactant-water, vapor-securing film of this invention is supplied by drainage of liquid from the foam lamella. Thus, the rate of drainage is important. in the heretofore known hydrolyzed protein foam systems, drainage is undesirable since this reduces the water content and the resistance of the foam to radiant heat attack.
In foams produced by amphoteric or anionic silicone surfactants in accordance with this invention, the rate of liquid drainage is more rapid than in the known hydrolyzed protein foams. More rapid drainage is necessary if the vapor-securing properties of the spreading films of this invention are to be utilized to their fullest advantage and extent.
If the drainage from foams produced by amphoteric or anionic silicone surfactants is too rapid, the draining aqueous liquid film formed is thicker and the resulting denser surfactant-water film may settle beneath the hydrocarbon surface. At excessive drainage rates the foam itself may be caused to collapse. If the drainage is retarded somewhat, however, a continuous supply of liquid over a longer time period will be made available for film formation and spreading. The rate of drainage should not be too slow or loss of film, due to evaporation and possible solubilization in the liquid hydrocarbon, may exceed the input of film-forming liquid to the surface.
Drainage rates of aqueous foams generated by amphoteric and anionic silicone surfactants are effectively retarded by the addition of a suitable organic or inorganic material, such as, asbestos, bentonite clay, etc., or water-soluble or waterdispersible organic polymers, to the foam liquid. These materials and polymers increase the bulk viscosity and surface plasticity of the foam lamellae. Useful polymers comprise any water-soluble or water-dispersible polymer, among which are included carboxymethyl cellulose, hydroxy ethyl cellulose, polyoxyethylene, polyvinyl alcohol, sodium polyacrylate, and the like. It has been found that, for any given polymer, the most effective foam stabilization appears to be obtained with low concentrations of the higher molecular weight polymers. Similar but apparently not quite as effective retardation is obtained with higher concentrations of the lower molecular weight polymers. Polymer concentrations in the liquid phase of the foam have been found to be most effective in the range of about 0.03 to 5.0 percent by total weight of the liquid phase.
Foams generated according to this invention by the use of amphoteric and/or anionic silicone surfactants with or without one or more of the drainage retarding polymers mentioned above can be applied to liquid hydrocarbon fires by either or both of two general methods, surface application or subsurface injection. ln the surface application method, the foam is applied to the surface of the burning liquid hydrocarbon and the flames are smothered as the fluid foam flows across the surface. Foam breakdown at the foam-flame front takes place during foam application, liberating some liquid. This liquid spreads as a film across the hydrocarbon surface under the flames and acts as a vapor suppressing barrier. The covering of a burning, exposed hydrocarbon area by the spreading film is enough to extinguish the flame. This extinguishing action is separate and distinct from the smothering effects of the foam itself. Upon extinguishment, the vapor-securing properties of the film, which is replenished and supplied by the foam, continue in effect. As long as there is liquid remaining in the foam it can drain due to gravitational action and the supply of liquid for film formation is assured. The film exhibits great mobility and travels rapidly to close any ruptures caused by mechanical agitation of the foam-film blanket, thus possessing self-healing properties. The mobility and self-healing properties of the vapor-securing film are obtained throughout the entire range of concentrations of anionic and amphoteric silicone surfactants given above and the foam can be formed and stabilized by any suitable means.
The second application technique, subsurface foam injection, is useful for liquid hydrocarbon tank fires since existing product inlet lines at the tank base can be used rather than installing costly foam lines on the tank side for delivery to the hydrocarbon surface. Upon reaching the surface, the foam blanket and vapor-securing film action is similar to that described for the surface application.
Introduction of a stream of air or other gas into the surfactant systems to form the fire-fighting foam having cell walls can be conveniently accomplished by the use of an aqueous concentrate containing the silicone surfactant and other additives, e.g., drainage retardant, hydrolyzed protein, licorice. etc. The water-silicone surfactant concentrate forms an active foamable solution on dilution with water. The concentrate can also contain a nonsolvent for the drainage retardant such as isopropanol (about l to about 80 weight percent based on the total weight of the concentrate) to reduce the viscosity and stabilize the drainage retarding polymer, if used, against ox- 'idative degradation. It can also contain freezing point depressants, antibacterial agents and other special purpose additives. The amount of silicone surfactant in the concentrate can vary from about 1.5 to about 80 percent and the amount of watersoluble polymer capable of retarding drainage of liquid from said cell walls can vary from about 4.5 to about 40 percent said percentages being based on the total weight of the concentrate a When the amphoteric silicone surfactants are used in accordance with this invention, they are most efiective in a pH range of greater than 7 to about 10. The anionic surfactants used in accordance with this invention are most useful and effective at a pH of about 7. Any suitable buffers of pH adjusting materials can be used which are not reactive with the materials employed in the system. For example, a useful buffer for the anionic surfactants is a suitable mixture of potassium dihydrogen phosphate and sodium hydroxide. Suitable pH adjusting materials for the amphoteric surfactants are the mineral acids, such as, hydrochloric acid, sulfuric acid and any suitable organic acid. From the standpoint of avoiding excessive corrosive effects, it appears desirable to avoid pHs which are deep in the acid or basic ranges.
The ratio of foam volume to liquid weight in the foam is defined as the foam expansion. Foam expansion is adjusted by mechanically controlling the volume of air or other gas mixed with the foam solution. Generally speaking, foam expansions between about four and about 1 l are most useful for the purposes of the invention. Foam expansion is also important in controlling the rate of liquid drainage and the foam fluidity.
Low expansion foams, for example, below about four, may be thin and watery and may be extremely poor in their resistance to heat. High expansion foams, for example, about [5, have high apparent viscosities and may not be fluid enough to spread across the burning liquid hydrocarbon surface. As the expansion of a foam is increased by incorporation of more air into the system, the rate of drainage decreases. The molecular weight, type and concentration of drainage retarding polymer also affects drainage rates and thus the optimum foam expansion varies in accordance therewith. The optimum expansion for a given foam solution, corresponding to optimum foam fluidity and drainage rate will be that which gives minimum extinguishment time and lowest drainage rate to obtain longest film duration.
Air, nitrogen, carbon dioxide, Freon-l2 or other suitable gaseous media can be used to expand and form the foam from the water-silicone surfactant concentrate.
The silicone surfactants used herein, preferably have only limited, if any, solubility in liquid hydrocarbons with which they would be expected to come into contact. The solubility can be varied, for example, by changing the nature of the hydrophilic group attached to the silicone backbone and/or solubility can be decreased by increasing the ratio of hydrophilic to hydrophobic portions of the silicone surfactant. The lower the solubility in the hydrocarbon, the longer is the effective life of the vapor-securing film provided the surfactant still lowers surface tension.
Many variations are possible in the constitution of the foamforming concentrate and a wide variety of special purpose additives, i.e., bacteriocides, antifreeze agents, anticorrosive agents, etc., can be added. However, it is preferable to select the ingredients of the foam producing concentrate so that they are substantially mutually compatible and little, if any, precipitates are formed. For example, Me SiO[OSi(Me)-C HIKOCH2(:H(OH)CH2N(MC)C2H-|SO:I a lLlsiMefl is fill ly compatible with National Aer-Q-Foam 3 percent Regular. n hydrolyzed protein concentrate.
An important embodiment of this invention is the dual use, in extinguishing fires, of a foam as described herein and a dry chemical extinguishing agent, such as Purple K powder. The foam and dry chemical can be applied concurrently or the dry chemical can be applied to extinguish the fire followed by ap plication of the foam or the fire can be extinguished with the foam followed by application of the dry chemical. Typical dry chemicals are disclosed in British Patents Nos. 824,l07 and 836,465. Such dry chemicals usually comprise finely divided fire extinguishing powders, such as, potassium bicarbonate, sodium bicarbonate, ammonium dihydrogen phosphate, potassium sulfate, and the like, which are mixed or coated with a flow-promoting agent, such as, water-repellent waxes, water-insoluble metallic soaps, e.g., aluminum stearate and magnesium stearate, water-repellent silicones, mica, talc,
. heavy magnesium oxide, porous silica, starch having a low bulk density and the like. The total amount of flow-promoting agent can be as little as 0.25 percent of the total weight of dry chemical agent and as much as 20 percent of the mica or talc if used as the flow-promoting agent, as much as 10 percent of the silica or starch, if used, as much as 5 percent of the wax, if used, or as much as 1.5 percent of the silicone or metallic soap, if used. The silicone can be formed in situ on the fireextinguishing powder by applying an organosilicone compound of the formula: RSiX or a mixture of organosilicon compounds of the formulas: R SiX and RQSiX- or R,'Si,,O,,X wherein R is a monovalent hydrocarbon group of one to 18 carbon atoms, X is hydrogen, halogen, alkoxy or hydroxy, and x and y are integers and by the application of heat causing the organosilicon compound to cross-link on the surface of the powder in the presence of 0.05 percent to 1.5 percent water and 0.5 percent to 50 percent, preferably 15 percent, of a porous catalyst, such as, Fullers earth, silica gel, silica-alumina and the like, the percentages being based on the total weight of the powder, the organosilicon compound, water and porous catalyst.
Anionic and amphoteric silicone surfactants useful in the present invention include siloxanes or siloxane mixtures having the average formula:
AB,,A I wherein n is an integer of at least 1 and preferably varies from 1 to 3.
In this formula, B is an amphoteric or anionic siloxy unit illustrated by the formula:
wherein R is a monovalent hydrocarbon group free of aliphatic unsaturation having one to 18 carbon atoms, w is an integer of l to 3, x is an integer of l to 3, y is an integer ofO to 1, preferably 1, z is an integer of l to 3, x+z is an integer of 2 to 4, X is a multivalent organic radical having a valence of rl-z, Y is a divalent group selected from the class consisting of anionic and amphoteric radicals, M is a member from the class consisting of monovalent, divalent, trivalent and tetravalent, preferably monovalent and divalent, cations, a is an integer of l to 4, preferably 1 to 2, and is equal to w times the valence of M divided by .r.
In formula l, the As are siloxy units of the formula:
wherein Z is monovalent hydrocarbon groups free of aliphatic unsaturation and having one to 18 carbon atoms. A, M, Y, X, R, a, w, x, y and 1 each may be the same or different in each unit lll and/0r molecule. Typical of the units represented by formula III are the trimethylsiloxy, and triphenylsiloxy units.
Preferably, the anionic and amphoteric silicone surfactants represented by fonnula l are linear as shown by the following formula:
wherein Z, R, and n are as defined above, M is a monovalent cation and L is a divalent organic linking group selected from the class consisting of R groups as hereinafter described and RN(R)R- groups as hereinafter described wherein R is bonded to silicon.
More specifically, anionic siloxy units, B, of formula I include those of the formula:
HO CHg-OCHgCHg-CH:, and the like.
Preferred anionic siloxy units are those of the formula:
MO SR'Si(R)O Vl wherein M is ammonium or an alkali metal, R and R defined above.
Amphoteric siloxy units, B, of the formula I include those of the formula:
are as VIII wherein M is an alkali metal or ammonium and R is alkylene or phenylene. Typical e R NR groups consist of five to 20 carbon atoms with the hydroxyl group and the amino nitrogen attached to vicinal carbon atoms as shown by the formula:
Alkyl (RH CHNCHCR- RI! RI! X wherein g is an integer of 2 to Alkyl bonded to nitrogen has one to eight carbon atoms; the R" groups are selected VIL from the class consisting of hydrogen, alkyl groups of one to eight carbon atoms, and, when taken together with the carbon atoms to which they are attached, cycloalkyl groups of six to 12 carbon atoms; and R is selected from the class consisting of alkylene -C,,H oxyalkylene OC,,l-l and alkyleneoxyalkylene C,,H R" and g need not be the same throughout the same R group. Typical alkyleneamino, hydroxy-substituted groups include alkyleneamino, hydroxysubstituted l alkyleneoxyalkylene groups, such as,
I I C3H6NCH2CHCH2OCH2CH2CH2, and the like; (2) cycloalkylene groups, such as,
(3) alkylene groups, such as and (4) eycloalkyloneoxyalkylene groups, s uch as HO CHzOClIzCl-IzCll2 Mo S and the like. When L contains amino nitrogen the siloxy unit IV and siloxanes containing it exhibit amphoteric properties and when amino nitrogen is absent the siloxy unit IV and siloxanes containing it exhibit anionic properties.
The cation M is typified by alkali metal cations, e.g., sodium, potassium, lithium, rubidium or cesium, ammonium or alkylor aryl-substituted ammonium cations wherein the alkyl substituents have one to 18 atoms, e.g., tetramethyl ammonium cation, tetraethyl ammonium cations or wherein the aryl substituents have six to 18 carbon atoms, e.g., phenyltrimethyl ammonium chloride, the cuprous cation, divalent metal cations, e.g., barium, calcium, strontium, cobalt, nickel, copper, tin, lead mercury, zinc, cadmium, magnesium, iron and the like. trivalent metal cations, e.g., cobalt, iron, aluminum, and the like, and tetravalent metal cations, e.g., tin.
Typical anionic radicals represented by Y are -O ,S-, O,-,SO, and the like, and typical amphotheric radicals are Typical monovalent hydrocarbon groups represented by R, Z and 'R and alkyl or cycloaliphatic groups, such as, methyl, ethyl, propyl, cyclopentyl, butyl, amyl, octyl, cyclohexyl, isopropyl, tert-butyl, octa-decyl, isooctyl and the like, aryl groups, such as phenyl, biphenyl, naphthyl and the like, aralkyl groups, such as, benzyl, beta-phenylethyl, beta-phenylpropyl, alkaryl groups such as tolyl, and the like.
The groups R, R" and 2 can be each the same or diiTerent throughout the same unit. When a is more than I, the groups R, X, Y and Z and the integers x and y each can be the same or different throughout the same unit. The cation M, the groups R, X, Y and Z and the integers .t and y each can be the same or different throughout the same molecule. The siloxane surfactant can contain two or more different units of formula ll and/or formula III in the same molecule or all units of formula ll and/or lll may be the same throughout the same molecule.
Representative alkyl groups represented by R. and Alkyl and cycloalkyl groups as represented by the R" groups when taken together in the above formulas are as listed above for R, Z and R. Typical alkylene groups as represented by R' in the above formulas include ethylene, l,4-butylene l,5.-pentylene and the like. Typical alkyleneoxyalkylene groups represented by R in the above formulas include ethyleneoxyethylene, l,2-propyleneoxy-1,2-propylene and the like. Oxyalkylene groups represented by R include oxyethylene, l,2oxypropylene and the like. The groups, radicals and integers set forth in the above formulas may respectively be the same or different in the same molecule and, where more than one such group, radical or integer appears in each unit, it may be the same or different in the same unit.
Amphoteric siloxanes and methods for making them are disclosed in U.S. Application No. 725,524, Siloxane Amino Hydroxy Sulfonates filed concurrently herewith by Edward L. Morehouse. Anionic siloxanes and methods for making them are disclosed in applications Ser. No. 565,745, filed July 18, 1966 now US. Pat. 3,507.897; Ser. No. 632,534 filed Apr. 21, 1967, now US. Pat. 3,531,507 Ser. No. 632,554, filed Apr. 21, 1967, now US. Pat. 3,531,417 and Ser. No. 574,576, filed Aug. 24, 1966 now US. Pat. No. 3,513,183. The anionic siloxanes disclosed in U.S. Pat. No. 3,278,465 can also be employed in this imgntion. u A
The following examples are presented wherein, unless otherwise indicated, Me means methyl, percentages and parts are by weight, temperatures are in degrees Centigrade, viscosities are centipoises at 25 D.
EXAMPLE 1 The presence of a vapor-securing film was clearly demonstrated by the addition of sodium fluorescein to a 1.13 weight percent solids solution of a compound of the average formula Me SiOIaO SCH Cl-l(H)Cl-1 OC H,,SiMeO]SiMe in water. This system was shaken to produce an air-expanded foam. The liquid draining from the foam was removed and added dropwise to the surface of a sample of high test motor grade gasoline and observed under ultraviolet light. The green flow of a film spreading over the gasoline surface was clearly visible. Similar results may be produced by employing a compound having the average formula Me SiolNaO sCl-l Cl-flol-bCl-l l-l siMeO] ,--SiMe EXAMPLEZ The action of the vapor-securing film was demonstrated in the following example. A control sample of high test motor grade gasoline was placed on a balance and the rate of evaporation was recorded as a function of time. A fresh sample of gasoline was then placed on the balance and several grams of a liquid, which had drained from an air foam made from a 1.13 weight percent solids aqueous solution of the silicone set forth in example 1, was gently applied to the surface of the gasoline. The rate of gasoline evaporation decreased to almost zero for several minutes.
EXAMPLE 3 The extinguishing and vapor-securing film-forming ability of the silicone set forth in example 1 was demonstrated in the following example. A 2 square foot pan was filled to 3 inches height with a water layer and 1 gallon of high test motor grade gasoline was added on top of the water layer. The gasoline was ignited and after a to seconds prebum, an air-expanded foam generated from a 1.13 weight percent solids aqueous solution of said silicone was gently delivered to the surface of the burning hydrocarbon. An application rate of 0.1 gal. of liq./ft. min. at a foam expansion of l 1.3 was used to obtain a fluid foam. The fire was extinguished in 1.4 minutes and the amount of water required to extinguish the fire, i.e., application density. was 0.14 gal./ft. The flame from a propane torch was passed over the foam surface at the hot metal wallfoarn interface to determine how long the foam acted as an effective barrier to the flammable vapors. This was defined as the resistance-to-reignition time and in this case was 4 minutes. At the onset of reignition, the time required for the flames to completely destroy the foam-film blanket and for the gasoline to burn freely, defined as the bumback time, was measured. In this case, the reignited gasoline burned as a can dlelike flame even though the entire surface was free of foam. This evidenced the existence of the vapor-securing film on the surface of the gasoline. The ga soline had gradually become apparently exposed as a result of foam drainage and breakdown during the preceding 4 minute period. As the burning area slowly grew in size, the flames eventually overcome the surface forces which maintained them in the initial candlelike appearance. The time required to completely overcome the effects of the film (bumback time) was 4 minutes. This example clearly demonstrated the formation and action of the vapor-securing film during fire extinguishment. As shown above, the film action was independent of the vapor-securing properties of the foam itself.
EXAMPLE 4 The effect of a stabilizing polymer on the air foam generated with the silicone set forth in example 1 was demonstrated by the following example. The identig1l procedure was employed in this example as was used in example 3. The aqueous foaming solution contained said silicone at a concentration of 0.69 percent solids and carboxy methyl cellulose, a 1 percent aqueous solution of which has a viscosity of 10,000 c.p.s. at 25 C. (Union Carbide Corporation, P75 X H), at a concentration of0. weight percent solids. At an expansion of 6.7, the fire was extinguished in 1.1 minutes, using an application density of 0.12 gal. liq./ft. The foam-film blanket had a resistance-to-reignition time of 32 minutes and a bumback time of 1.3 minutes. The effects of the proper choice of drainage retarding polymer, molecular weight and concentration are clearly evident by comparison of the 32 minutes resistance-to-reignition time of this example with the 4 minute time of example 3.
EXAMPLE 5 In an identical fire extinguishment procedure as in example 3, an air foam made from an aqueous solution of a silicone of the average formula: Me SiO[NaO SC H,N(Me)CH CH(OH)CH OC, Si(Me:)O]SiMe;,, at a concentration of 0.77 weight percent solids and a polyethylene oxide polymer, a 1 percent aqueous solution of which has a viscosity of 30 c.p.s. at 25 C. (Union Carbide Corporation Polyox WSRN750), at a concentration of 0.54 weight percent, was delivered to the surface of the burning gasoline at a foam expansion of 8.9. The fire was extinguished in 0.92 minutes and 0.09 gal. of liq./ft. was required. The foam-film blanket had a resistance-to-reignition time of 22.1 minutes and a 0.2 minute bumback time.
EXAMPLE 6 The compatibility of an air foam made from the silicone set forth in example 5, with Purple K powder (silicone treated KHCO and ABC powder (silicone treated ammonium dihydrogen phosphate) was demonstrated in the following example. The test in example 5 was repeated using the same foam solution. Upon extinguishment of the fire, Purple K powder and ABC powder were liberally sprinkled over the foam surface and no foam breakdown occurred. The flame of a propane torch was then repeatedly agitated in the gasoline with consequent rupturing of the foam blanket. No ignition resulted for 6 minutes.
EXAMPLE 7 Using the extinguishing procedure of example 3, an air foam made from an aqueous solution of a silicone mixture of the average formula: Me SiO[ NaO SC H,N( Me )CH CH(OH)CH OC Si(Me)O], -SiMe at a solids concentration of 0.75 percent and the polyethylene oxide polymer used in example 5 at a solids concentration of 0.6 weight percent, extinguished the fire in 0.8 minute. A foam expansion of 8.8 and an application density of 0.08 gal. liq./ft. were used. The resistance-to-reignition time was 17.5 minutes and burnback time was 03 minute.
EXAMPLE 8 The advantages of subsurface injection of foams of the present invention were demonstrated in the following example. The same foam as used in example 7 was used. The foam was injected into the center-bottom of the tank and rose through the water and gasoline to the burning surface. Extinguishment was accomplished in 0.47 minute using an expansion of 8.8 and an application density of 0.047 gal./ft. The foam-film blanket had a resistance-to-reignition time of 15.4 minutes. Comparison of this data with that of example 7 shows that the subsurface technique required a lower application density and extinguished the fire in a shorter period of time flei s i a arel s methoii EXAMPLE9 The incompatibility of a hydrolyzed protein foam (National Aer-O-Foam 3 percent Regular) with dry chemical extinguishing agents is demonstrated in this example which does not illustrate this invention. The failure of this type of foam to prevent reignition resulting from foam rupture, in the presence of an ignition source, was demonstrated in this example.
A 2 square foot pan was filled to 3 inches height of water and 1 gallon of high test motor grade gasoline was added. The gasoline was lighted and after a ten second prebum, air-expanded foam was gently delivered to the surface of the burning hydrocarbon. The foam lamella consisted of a commercial hydrolyzed protein system, 3 percent by volume in water. An application rate of 0.1 gal. of liq./ft. min. at a foam expansion of 5.9 was used to obtain a fluid foam.
The fire was extinguished in 1 minute 17 seconds and the amount of water required to extinguish the fire, or application density was 0. l28 gal./ft. The flame of a propane torch was passed over the foam surface at the hot metal wall interface to determine how long the foam acted as an effective barrier to the flammable vapors. This was defined as the resistance-toreignition time and in this case was 58 seconds. At the onset of reignition, the time required for the flames to completely destroy the foam blanket and for the gasoline fully to burn freely (bumback time) was 6 minutes, 45 seconds.
The test was repeated and upon extinguishment of the fire, several grams of Purple K powder (silicone treated KHCO,) and ABC powder (silicone treated ammonium dihydrogen phosphate) were sprinkled over the foam surface. Foam treated with Purple K powder immediately shrank up and was destroyed. The ABC powder slowly ate holes in the foam. A torch passed into the foam blanket ignited the gasoline.
EXAMPLE l The effects of a silicone surfactant on the protein system (National Aer-O-Foam, 3 percent Regular) used in Example 9 were demonstrated in this example as follows. The foam solution again consisted of 3 percent by volume of hydrolyzed protein with 0.075 percent by weight of an amphoteric silicone surfactant of the formula: Me SiO[N aO SC l-I N(Me)CH CH(OH)CH OC H Si(Me)O]SiMe and air was used to produce the foam. The identical fire same hydrolyzed procedure was performed as in example 9. A foam expansion of 12.9 was employed to achieve a fluid foam and the fire was extinguished in 58 seconds. An application density of 0.095 gal. liq./ft. was used. The resistance-to-reignition time was 10 minutes and 18 seconds compared to 58 seconds in example 9 wherein no silicone was present. After about 9 minutes, almost all of the foam was gone and what appeared to be exposed gasoline remained. However, no ignition could be obtained for about another 1% minutes. The effect of the vaporsecuring film, then, was visibly effective for about 3 minutes. The bumback time was 41 seconds.
The fire was again extinguished with the foam and several grams of Purple K powder and ABC powder were sprinkled onto the foam. No foam degradation was observed. The dry chemicals remained at the foam surface with no change in the foam appearance. Agitation with the flame of a propane torch did not induce ignition of the gasoline.
EXAMPLE 1 l The identical extinguishing test used in example 9 was repeated in this example using an air-expanded foam made from an aqueous solution of 0.02 percent by weight of the amphoteric silicone used in example 10 and 3 percent volume of the same hydrolyzed protein system. The fire was extinguished in 1 minute and 5 seconds using a foam expansion of 8.4. An application density of 0.107 gal/ft. was necessary to obtain extinguishment. The resistance-to-reignition time was 5 minutes, 17 seconds and the bumback time was 37 seconds. Addition of Purple K and ABC powders to the foam produced holes in the foam, wherever dry chemical had fallen, but did not cause complete foam breakdown. The effects of a vaporsecuring film were observed, but not to the extent seen in example 10.
Table 1 summarizes the results of examples 9-] 1.
EXAMPLE 12 served and when a small flame was placed above the gasoline surface the gasoline did not ignite.
Next it was attempted to produce a mechanical foam using Aer-O-Foam 3 percent Regular protein foam-forming material and 0.5 percent of the above-mentioned dimethyl silicone oil. The ability of the protein foam-forming material to fonn a stable foam was almost completely destroyed by the dimethyl silicone. When the resulting system was applied to the surface of gasoline and a small flame held above the surface, immediate ignition resulted.
EXAMPLE 13 This example demonstrates the superiority of high molecular weight polymers as drainage retardants as compared to the lower molecular weight polymers.
A foaming solution was made containing 0.1 percent of a hydroxyethyl cellulose having a 1 percent aqueous solution' viscosity of 40 c.p.s. at 25 C. and 0.85 percent solids of an amphoteric surfactant having the formula, Me SiO[NaO;, SC H N(CH )Ch Ch(OH)CH OC -,H.,Si( Me )OlSiMe A mechanical foam having a foam expansion of 6.5 was prepared from the above-mentioned solution. The quarter time of the foam, i.e., the time required for drainage of one quarter of the weight of liquid from the foam, was measured and found to be 1.8 minutes.
Another foaming solution was made containing 0.1 percent of a higher molecular weight hydroxyethyl cellulose having a 1 percent aqueous solution viscosity of 8,000 c.p.s. at 25 C. and containing 0.85 percent solids of the above-mentioned silicone. A mechanical foam having a foam expansion of 6.5 was prepared from this solution and its quarter time was measured as 4.5 minutes.
EXAMPLE 14 securing film-forming properties and heat resistance.
In each of these tests, 24.5 grams of distilled water, 24.5 grams of gasoline and one gram of silicone surfactant were shaken and then the mixture was allowed to separate and each phase was analyzed. As the cationic silicone surfactant there was used a material having the fonnula. (Me,SiO) Si(Me)C H OCH CH(OH)CH N(Me) "'HOC(CH;,) O, and as the amphoteric silicone surfactant there was used the surfactant TABLE I Application Extinguish- Application Resistanee- Burnbaek Expanmerit time,
density, reignitlon, time, PKP oomsion min. See. gaL/l't. min. sec. min. see. patibility Vaporseeurlng film formation C oneenrate, tration, gaL/ft. wt percent min Foam solution Example 6: 15 No. No. :41 Yts Yes-about 3% mins. effective. 0237: Yes Yes.
1 Not to the extent of Example 10. 1 MesSiOlNaOfiC2II4N(Me)CH2CH(OH)CH:0O;HuSi(Me)0lLsSlMm.
set forth in example l0. The relative gasoline and water solubilities are set forth in the table below:
Gasoline Phase, Water Phase,
The above data illustrate that the amphoteric silicone surfactant has considerably greater water solubility and that the cationic silicone surfactant has a considerably greater gasoline 15 solubility.
EXAMPLE 15 The ability of five surfactants to form vapor-securing films was investigated. In each of these tests an anionic silicone surfactant having the following formula was used: Method 3SiO[NaOSCH CH(OH)CH OC H,,Si(Me)O1,.[Si(Me)O] ,,SiMe wherein x is, respectively, 1, 2 and 4 and y is 0 and wherein x is, respectively 2 and 4 and y is 5. A 1 percent solids solution of each surfactant was prepared and foamed on a Waring Blender and the foam was delivered to the surface of gasoline. It was found that in the foam could not be formed. A flame was applied to each of the formed foams could not be formed. A flame was applied to each of the formed foams and 3 when the gasoline surface became exposed as the result of foam breakdown the presence of a vapor-securing film was looked for. This was evidenced by the nonignition, or ignition and self-extinguishment of the flame over a short period of time. It was found that only those two surfactants wherein y is 0 and x is respectively 1 and 2 produced vapor-securing film as observed by the above procedure.
Solutions of each of the above-mentioned surfactants whereinx is 4 andy is 0.x is 4 and y is 5, andx is 2 andy is 5, at concentrations of 3 to 4 percent, were applied to the surface of gasoline and and visual observations were made in an attempt to detect the presence of a spreading film, but no such film was observed. A small flame was held above the gasoline surface in each case and immediate ignition resulted. When a 1 percent solution of the surfactant where x is l and y is 0 was applied to the surface of gasoline, a spreading film was readily observed and ignition did not occur upon application of the small flame over a period of several minutes.
Aqueous solutions of each of the above surfactants at concentrations of about 3 to 4 percent were applied. respectively,
to the surfaces of benzene and toluene instead of gasoline. Only two surfactants, one wherein x is l and y is 0 an d the other wherein x is 2 and y is 0, were observed to form vaporsecuring films using both visual observation test and the test wherein a small flame is held above the benzene or toluene.
in systems utilizing the hydrolyzed protein or other known foam stabilizer as the major foaming and stabilizing agent, the hydrolyzed protein or other known stabilizer is preferably used in those amounts conventionally used in previous hydrolyzed protein systems. Other known stabilizers include powdered licorice extract, glue, saponin, glycerin, glucose, sodium sulfonate and quillaia bark and, when each is used in placed of the Aer-O-Foam of example 10 on a weight for weight basis, results similar to those of example 10 are obtained. The known foam stabilizers, especially the hydrolyzed protein stabilizers, impart additional durability or persistency to the foam. Similarly, the drainage retardant polymers impart durability or persistency.
It is preferred that the drainage retarding organic polymer employed herein be such that a 1 weight percent aqueous solution thereof has a viscosity of about 2 to about 10,000 c.p.s. at 25 C.
What is claimed is: 1. A process for extinguishing burning liquid hydrocarbons or preventing the ignition of flammable hydrocarbons, which LII comprises l providing on the surface of the liquid hydrocarbon a self-healing, vapor-securing film of an aqueous liquid containing a silicone surfactant that is at least partially soluble therein and reduces the surface tension thereof, said surfactant having the average formula:
AB,,A wherein n is an integer of l to 3, A is a siloxy unit ofthe formula:
wherein Z is a methyl radical, and B is an unit of the formula:
wherein R is a methyl radical, X is amultivalent organic group having a valence of x+2, said organic group being composed of atoms selected from the class consisting of carbon, hydrogen and oxygen, Y is a divalent amphoteric group selected from the class consisting of O .,SR N(R'-)- or O;,SORN(R) where R is a divalent hydrocarbon group and R is a radical selected from the class consisting of hydrogen and monovalent hydrocarbon radicals, M is selected from the class consisting of monovalent, divalent, trivalent and tetravalent cations, w is an integer of l to 3, x is an integer of l to 3, y is l, 1 is an integer of l to 3, x+z is an integer of2 to 4, a is an integer of l to 4 and is equal to w times the valence of M divided by .r, and (2) providing an aqueous foam in contact with an immediately above the film of aqueous liquid, wherein the cell walls of the aqueous foam comprise an aqueous liquid containing said silicone surfactant and said film is formed by drainage of said liquid from said foam.
2. Process as claimed in claim 1 wherein a dry chemical extinguishing agent is first applied to the surface of the burning liquid hydrocarbon and thereafter steps (1) and (2) are carried out.
3. The process as claimed in claim 1 wherein said silicone surfactant has the average formula:
wherein Z, R and n are as defined in claim 1, M' is a monovalent cation and L is a divalentR N(R)R-group, wherein R is a divalent group having three to l8 carbon atoms and is selected from the class consisting of hydroxy-substituted alkylene groups, hydroxy-substituted cycloalkylene groups, hydroxy-substituted alkylene-oxyalkylene groups and hydroxy-substituted cycloalkyleneoxyalkylene groups, R is a divalent hydrocarbon group having two to 10 carbon atoms and R is a member of the class consisting of hydrogen and a monovalent hydrocarbon group having 1 to 8 carbon atoms, the hydroxyl substituent of R being bonded to a carbon atom vicinal to the carbon atom bonded to nitrogen.
4. The process as claimed in claim 3 wherein the silicone surfactant is more soluble in water than in the liquid hydrocarbon.
5. The process as claimed in claim 3 wherein the aqueous liquid in the cell wall consists essentially of water and said silicone surfactant as the major foaming and foam stabilizing agent.
6. The process as claimed in claim 3 wherein the aqueous liquid consists essentially of water, said silicone surfactant and a foam former.
7. The process as claimed in claim 5 wherein the foam former is a partially hydrolyzed protein.
8. Process as claimed in claim 6 wherein said surfactant is present in the amount of about 0.01 percent to about 0.4 percent based on the total weight of said aqueous liquid.
9. Process as claimed in claim 3 wherein n is 1.5.
10. Process as claimed in claim 3 wherein n is 2.
11. Process as claimed in claim 5 wherein said aqueous liquid comprises water and a mixture of a major amount of said foam former and a minor amount of said silicone surfactant.
12. Process as claimed in claim 5 wherein said aqueous liquid comprises water and a mixture of a minor amount of amphoteric siloxy said foam former and a major amount of said silicone surfactant.
13. Process as claimed in claim 3 wherein said surfactant is the major foaming and foam-stabilizing agent and is present in amounts of about 0.4 to about 10 percent based on the total weight of said aqueous liquid.
14. Process as claimed in claim 6 wherein said surfactant is present in amounts of about 0.5 to about 1 percent based on the total weight of said aqueous liquid.
15. Process as claimed in claim 3 wherein said surfactant has the average formula: Me,SiO[NaO SC H,N(Me)CH CH(OH)CH OC H,,SiMeO]Si 16. Process as claimed in claim 3 wherein said surfactant has the average formula:
17. An aqueous liquid concentrate for the production of a fire-fighting foam having cell walls comprised of an aqueous liquid, said concentrate comprising, water, about 1.5 to about percent of a silicone surfactant having the average formula:
wherein Z, R and n are as defined in claim 1, M is a monovalent cation and L is a divalent-RN(R")R'group, wherein R is a divalent group having three to 18 carbon atoms and is selected from the class consisting of hydroxy-substituted alkylene groups, hydroxy-substituted cycloalkylene groups, hydroxy-substituted alkyleneoxyalkylene groups and hydroxy-substituted cycloalkyleneoxyalkylene groups, R is a divalent hydrocarbon group having two to 10 carbon atoms and R is a member of the class consisting of hydrogen and a monovalent hydrocarbon group having one to eight carbon atoms, the hydroxyl substituent of R being bonded to a carbon atom vicinal to the carbon atom bonded to nitrogen, and about 4.5 to about 40 percent of a water-soluble polymer capable of retarding drainage of liquid from said cell walls, said percentages being based on the total weight of said concentrate.
18. Aqueous liquid concentrate as claimed in claim 17 wherein M is a monovalent cation selected from the class consisting ofammonium and an alkali metal.
19. An aqueous, fire-extinguishing foam having cell walls comprised of an aqueous liquid containing about 0.01 to about 10 percent of a silicone surfactant having the average formula:
wherein Z, R and n are as defined in claim 1, M is a monovalent cation and L is a divalent-RN(R)R'-group, wherein R is a divalent group having three to 18 carbon atoms and is selected from the class consisting of hydroxy-substituted alkylene groups, hydroxy-substituted cycloalkylene groups, hydroxysubstituted alkyleneoxyalkylene groups and hydroxy-substituted cycloalkyleneoxyalkylene groups, R is a divalent hydrocarbon group having two to l0 carbon atoms and R is a member of the class consisting of hydrogen and a monovalent hydrocarbon group having one to eight carbon atoms, the hydroxyl substituent of R being bonded to a carbon atom vicinal to the carbon atom bonded to nitrogen, based on the total weight of said liquid.
20. Aqueous liquid concentrate as claimed in claim 17 wherein said concentrate also contains a hydrolyzed protein.
21. Aqueous liquid concentrate as claimed in claim 20 wherein said surfactant is present in an amount adequate to provide about 0.0l to about 0.4 percent of said surfactant in said cell walls, said percentage being based on the total weight of aqueous liquid in said cell walls.
22. Aqueous liquid concentrate as claimed in claim 17 wherein said surfactant is the major foaming and foam stabilizing agent and is present in an amount adequate to provide about 0.4 to about 10 percent of said surfactant in the aqueous liquid in said cell walls, said percentage being based on the total weight of said aqueous liquid in said cell walls.
23. Aqueous liquid concentrate as claimed in claim 17 wherein said surfactant has the average formula: Me SiO[NaO SC H N(Me)CH CH(OH)Cl-l OC H siMeOlSi polymer is polyoxyethylene glycol.
27. Foam as claimed in claim 25 wherein said watersoluble polymer is carboxy methyl cellulose.
28. Foam as claimed in claim 19 wherein M is a monovalent cation selected from the class consisting of ammonium and an alkali metal.
29. The process as claimed in claim 3 wherein M is a monovalent cation selected from the class consisting of ammonium, and an alkali metal.
# t t i l PO-WPIO UNITED STATES PATENT OFFICE 6 CERTIFICATE OF CORRECTION Patent No. 3 621 91? Dated NOV. 23, 1971 I Inventor(s) M.R. Rosen et a1.
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Claim 1, column 15, line 17, "x+2" should read x+z Claim 1, column 15, line 21 that portioa of the formula shown as "R should read R Claim 1, column 15, line 31 "an" should read and Claims 7, 11 and 12, line 1 of each claim, the number "5" should be 6 Claims 8 and 14, line 1 of each claim the number "6" should be 7 Signed and sealed this 16th day of May 1972.
'ARD' II.FLE.UCHEH ,JR ROBERT GOTTSCHALK F121: 1; testing Officer Commissioner of Patents