Alcohol resistant aqueous film forming firefighting foam

BACKGROUND AND BRIEF SUMMARY OF THE INVENTION
Firefighting foam concentrates are mixtures of foaming agents, solvents and other additives. These concentrates are intended to be mixed with water usually at either a 3 or 6% concentration, the resulting solution is then foamed by mechanical means and the foam is projected onto the surface of a burning liquid.
A particular class of firefighting foam concentrates is known as an aqueous film-forming foam (AFFF). AFFF concentrates have the quality of being able to spread an aqueous film on the surface of hydrocarbon liquids, enhancing the speed of extinguishment. This is made possible by the perfluoroalkyl surfactants contained in AFFF. These surfactants produce very low surface tension values in solution (15-20 dynes cm.sup.-1) which permits the solution to spread on the surface of the hydrocarbon liquids.
AFFF foams are not effective on water soluble fuels, such as alcohols and the lower ketones and esters, as the foam is dissolved and destroyed by the fuel. There is a sub-class of AFFF foam concentrates known as alcohol resistant AFFF (ARAFFF). ARAFFF concentrates contain a water soluble polymer that precipitates on contact with a water soluble fuel providing a protective layer between the fuel and the foam. ARAFFF foams are effective on both hydrocarbons and water soluble fuels.
Typical AFFF concentrates contain one or more perfluoroalkyl surfactants which may be anionic, cationic, non-ionic or amphoteric, one or more non-fluorinated surfactants which may be anionic, cationic, amphoteric or nonionic, solvents such as glycols and/or glycol ethers and minor additives such as chelating agents, pH buffers, corrosion inhibitors and the like. Many U.S. Patents have disclosed such compositions, such as U.S. Pat. Nos. 3,047,619; 3,257,407; 3,258,423; 3,562,156; 3,621,059; 3,655,555; 3,661,776; 3,677,347; 3,759,981; 3,772,199; 3,789,265; 3,828,085; 3,839,425; 3,849,315; 3,941,708; 3,95,075; 3,957,657; 3,957,658; 3,963,776; 4,038,198; 4,042,522; 4,049,556; 4,060,132; 4,060,489; 4,069,158; 4,090,976; 4,099,574; 4,149,599; 4,203,850; and 4,209,407.
ARAFFF concentrates are essentially the same as AFFF's, only with the addition of a water soluble polymer. These compositions are disclosed in U.S. Pat. No. 4,060,489; U.S. Pat. No. 4,149,599 and U.S. Pat. No. 4,387,032.
A common element in all AFFF and ARAFFF compositions is the perfluoroalkyl surfactant. This type of surfactant represents 40-60% of the cost of the concentrate.
We have unexpectedly discovered that by the use of alkyl polyglycoside surfactants it is possible to reduce the necessary concentrations of the perfluoroalkyl surfactants in AFFF compositions by more than 40% without loss of firefighting performance. Similarly, in ARAFFF compositions, the use of alkyl polyglycoside surfactants has produced an unexpected improvement in firefighting performance on water soluble fuels and has made possible the use of less expensive water soluble polymers. The polymer commonly used in ARAFFF compositions is Kelco K8A13, produced by the Kelco Division of Merck and Company. This polymer is believed to be a chemically modified xanthan gum and costs approximately seven (7) times the cost of ordinary industrial grade xantham gum.
Using surfactant systems disclosed in the prior art, it has been impossible to attain satisfactory ARAFFF performance on water soluble fuels with industrial grade xanthan gum without using so high a concentration of the gum that the composition become unacceptably viscous. However, we have discovered that by the inclusion of alkyl polyglycosides as surfactants, ARAFFF compositions using ordinary industrial grade xanthan gum will perform as well as or better than the ARAFFF compositions made with Kelco K8A13 and the surfactant systems disclosed in the past.
Alkyl glycoside and alkyl polyglycosides are known surfactants. A particularly useful class of polyglycosides for purposes of the invention is that marketed by the Horizon Chemical Division of Henkel, Inc. under the tradename "APG".
A typical molecular structure is shown below. ##STR1##
The superior performance of the alkyl polyglycosides in the foam fighting compositions is totally unexpected because of the very low interfacial tension values of alkyl polyglycoside compositions with hydrocarbons. It is normally desirable to use co-surfactant systems with relatively high interfacial tension values to avoid emulsification of fuel in the foam. Exemplary interfacial tension values are set forth below.
TABLE I______________________________________ Interfacial TensionSurfactant Concentration Mineral Oil______________________________________C.sub.12-15 Polyglycoside 0.01% 0.9 dynes/cmC.sub.12 Linear alkane sulfonate 0.01% 7.2 dynes/cmC.sub.12-15.sup.-3EO ether sulfate 0.01% 7.4 dynes/cmC.sub.8-10 Imidazoline dicarboxylate 0.01% 15.8 dynes/cm(mona CCMM-40)______________________________________
Broadly the invention comprises, in one embodiment, an AFFF composition firefighting concentrate comprising a perfluoroalkyl surfactant, a solvent and an effective amount of an alkyl polyglycoside. The invention, in another embodiment, broadly comprises a ARAFFF firefighting concentrate composition having a perfluoroalkyl surfactant, a solvent, a water soluble polymer and an effective amount of an alkyl polyglycoside.
The phrase an effective amount, means the use of the poly alkylglycoside in an amount such that the composition when used as a firefighting concentrate, meets or exceeds those standards which determine the acceptability of the concentrate for firefighting purposes.

DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention comprises an AFFF composition containing an alkyl polyglycoside having the formula:
C.sub.n H.sub.2+1 O(C.sub.6 H.sub.10 O.sub.5).sub.x H
wherein n=4-18 preferably 6-12 and x=1-6 preferably 1-2.
Additionally these compositions preferably contain an amphoteric perfluoroalkyl surfactant of the formula:
R.sub.F CH.sub.2 CH.sub.2 SO.sub.2 NHCH.sub.2 CH.sub.2 CH.sub.2 N.sup.+ (CH.sub.3).sub.2 CH.sub.2 COO.sup.-
and/or
R.sub.F CH.sub.2 CH.sub.2 SO.sub.2 NHCH.sub.2 CH.sub.2 CH.sub.2 N(CH.sub.3).sub.2 .fwdarw.O
and/or
C.sub.6 F.sub.13 CH.sub.2 CH.sub.2 SO.sub.2 NHCH.sub.2 CH.sub.2 CH.sub.2 N(CH.sub.3).sub.2 CH.sub.2 CH.sub.2 COO.sup.-
where:
R.sub.F is a perfluoroalkyl chain of the formula C.sub.n F.sub.2n+1 where n=4 to 18; and an anionic surfactant of the formula:
C.sub.n H.sub.2n+1 OSO.sub.3 Na
wherein the value of n=8 to 18; and a glycol ether selected from the group consisting of:
1-Butoxy-2-ethanol
1-Ethoxy-2-ethanol
1-Butoxyethoxy-2-ethanol
1-Butoxyethoxy-2-propanol,
an a glycol selected from the group consisting of:
1,2 ethanediol
1,2 propanediol
1,3 propanediol
1,3 butanediol
1,4 butanediol; and
A nonionic surfactant of the formula ##STR2## wherein
R.dbd.octyl or nonyl and n.dbd.2 to 15; and a sequestering agent chosen from salts of ethylene diamine tetraacetic acid and salts of nitrilo-tris acetic acid; and a pH buffer such as Trishydroxymethylaminomethane and/or urea;
The invention further comprises ARAFFF compositions having, in addition to the foregoing, a polysaccharide polymer such as xanthan gum, gum tragacanth, locust bean gum, or guar gum; and a preservative such as orthophenylphenol or dichlorophene.
Relative ranges of the component of the compositions for:
______________________________________3% AFFF by weight______________________________________Perfluoroalkyl surfactant 0.5-3.0%, preferably 0.8-2.6%Magnesium sulfate 0-1.0%, preferably 0.2-0.6%Glycol 0-10%, preferably 2.0-7.0%Alkyl polyglycoside 1.0-10.0%, preferably 4.0-8.5%surfactantAnionic surfactant 2.0-6.0%, preferably 3.0-5.0%Glycol ether 4.0-20.0%, preferably 5.0-15.0%Nonionic surfactant 0.5-2.0%, preferably 0.7-1.5%Sequestering agent 0-1.0%, preferably 0.1-0.5%Buffering agent 0-2.0%, preferably 0.5-1.0%Corrosion inhibitors 0-2.0%, preferably 0.1-0.8%Water Balance______________________________________
It will be recognized by those skilled in the art that AFFF concentrates intended for mixing with water in percentages other than 3% can be made by multiplying the percentage compositions above by the factor 3/x where x represents the desired mixing percentages.
Relative ranges of the composition for:
______________________________________ARAFFF for use at 3% on hydrocarbon fuels andat 6% on water soluble fuels______________________________________Alkyl polyglycoside 1.0-10.0%, preferably 2.0-6.0%surfactantPerfluoroalkyl surfactant 0.8-2.0%, preferably 1.0-1.5%Anionic surfactant 2.0-5.0%, preferably 2.2-3.5%Glycol ether 2.0-5.0%, preferably 3.0-4.0%Glycol 0-5.0%, preferably 0-4.0%Nonionic surfactant 0Sequestering agent 0.1-1.0%, preferably 0.1-0.3%Buffering agents 0-2.0%, preferably 0-1.7%Magnesium sulfate 0-1.0%, preferably 0.2-0.7%Polysaccharide 0.5-1.5%, preferably 0.8-1.0%Water Balance______________________________________
Fire testing
In the examples below, the following tradename ingredients are used.
Forafac 1157N, an amphoteric perfluoroalkyl surfactant, manufactured by Atochem, Inc. a 27% active solution of R.sub.F CH.sub.2 CH.sub.2 SO.sub.2 NHCH.sub.2 CH.sub.2 CH.sub.2 N.sup.+ (CH.sub.3).sub.2 CH.sub.2 COO.sup.-
APG 300 and APG 325CS, 50% active alkyl polyglycosides manufactured by Horizon Chemical Division of Henkel, Inc.
Triton X-102, a non-ionic octylphenol ethoxylate manufactured by Rohm & Haas Company.
Forafac 1183N, an amphoteric perfluoroalkyl surfactant, manufactured by Atochem, Inc., a 40% active solution of ##STR3##
Surflon S831-2, a nonionic perfluoroalkyl surfactant manufactured by Asahi Glass Co.
Butyl Carbitol-1-butoxyethoxy-2-ethanol manufactured by Union Carbide Co.
NTA/Na.sub.3 =Nitrilo trisacetic acid trisodium salt manufactured by W.R. Grace Co.
Tris Amino - Tris (hydroxymethyl) amino methane manufactured by Angus Chemical Co.
IDC 810M, an imidazoline dicarboxylate amphoteric surfactant, sold by Mona Industries under the tradename "Monateric CCMM-40".
Givgard G-4-40, 40% active solution of dichlorophene manufactured by Givaudan, Inc.
Each concentrate was tested in a fire laboratory using miniaturized models of full scale fire tests described below.
Mil-Spec - Mil-F-24385C - MOD Test Procedure
The liquid concentrate is tested as a premixed solution containing 3 parts of concentrate with 97 parts of water according to the following procedure.
Three liters of regular leaded gasoline, conforming to VV-G-I690 is placed into a round fire pan that is 2.69 ft.sup.2 in area and 41/2" deep, containing 21/2" of water and ignited. After a 10 second preburn, a foam discharge delivering 0.108 gpm of solution is directed for 90 seconds over the center of the fire pan in a spray type pattern that produces a foam quality that conforms to requirement 4.7.5 of Mil-F-24385C. Immediately after the 90 second foam application, a jet (5/32" diameter) of propane gas is ignited and placed over the center of the foam blanket at the rate of 40 cc/m. metered by a full view Rotameter model 8900D, manufactured by Brooks Instrument Div. Emerson Electric Co., King of Prussia, Pa., or equivalent. The impingement of the propane flame commences two inches above the top of the tank and shoots downwardly over the foam blanket until 25% of the foam blanket has been consumed by fire. The resulting heat flux is monitored and recorded by means of a water cooled calorimeter such as model C-1301-A-15-072 manufactured by Hy-Cal-Engineering, Santa Fe Springs, Calif., or equivalent, and a suitable Strip Chart Recorder capable of handling 1-5 M.V.
The time required to completely extinguish the fire and the time required for the propane jet to destroy 25% of the foam blanket are recorded as "Extinguishment" and "Burnback" times respectively. This test is a model of the 50 ft2 fire test in U.S. Military Specification Mil-F-24385C.
U.L. 162 5th Edition - MOD Test Procedure
Isopropyl Alcohol Test
The liquid concentrate is tested as a premixed solution containing 6 parts of foam concentrate and 94 parts of water. 15 liters of 99% isopropyl alcohol is placed into a round pan that is 2.69 ft.sup.2 in area and 41/2" deep, and ignited. After one minute of free burning a foam discharge delivering 0.269 gpm's of solution is directed onto the far wall of the fire pan in a solid stream application for two minutes, (Type II Fixed Nozzle) application that produces a foam quality that conforms to UL 162 5th edition paragraphs 15-15.9. Immediately after the two minute foam application, a jet (5/32" diameter) of propane gas is ignited and discharged over the center of the foam blanket at the rate of 100 cc/m. metered by a full view Rotameter, Model 8900D as manufactured by Brooks Instrument Div. Emerson Electric Co., King of Prussia, PA or equivalent.
The impingement of the propane flame commences two inches above the top of the tank and shoots downwardly over the foam blanket. The resulting heat flux is monitored and recorded by means of a water cooled Calorimeter such as Model C-1301-A-15072 manufactured by Hy-Cal-Engineering, Santa Fe Springs, California, or equivalent and a suitable Strip Chart Recorder capable of handling 1-5 MV until 20% of the foam blanket has been consumed by fire.
This test is a model of the fire test described in UL 162 5th Edition. The time required for 90% control, extinguishment and 20% burnback are recorded.
UL 162 5th Edition MOD Test Procedure
Heptane Test
The liquid concentrate is tested as a premixed solution containing 3 parts of concentrate and 97 parts of water. The test equipment is the same as that used for the isopropyl alcohol test. The procedures differ in that the foam application is Type III, the fuel is n-heptane, the application rate is 0.108 gpm and the application time is 2 minutes. The times for 90% control and 20% burnback are recorded.
The concentrates were prepared according to standard practice, that is simply blending the materials in a mixer.
______________________________________Example I 500 mlMaterials A B C______________________________________1. Water 226 ml 242 ml 242 ml2. Forafac 1157N 33.8 g 33.8 g 33.8 g3. Forafac 1183N 16.9 g 16.9 g 16.9 g4. Butyl carbitol 67.4 ml 67.4 ml 67.4 ml5. IDC-810M 66.6 ml6. Sodium decylsulfate (30%) 83.2 ml 83.2 ml 83.2 ml7. Triton X-102 4.2 ml 4.2 ml 4.2 ml8. MgSO.sub.4 2.0 g 2.0 g 2.0 g9. Sodium benzoate 2.0 g 2.0 g 2.0 g10. Tolyl triazole 0.5 g 0.5 g 0.5 g11. APG 300 (light) -- 50 g -- (dark) -- -- 50 g12. Acetic acid to adjust to pH 7.4-7.8______________________________________Fire Test Results3% sea water on 3 liters gasoline Modified 0.04 gpmTotal 25% Mil-F-24385C 2.69 ft.sup. 2 tankSeconds Ext. Burnback Exp QDT______________________________________A. 106 0'51" 4'25" 10.29 2'30"B. 87 0'38" 5'30" 10.74 2'42"C. 90 0'42" 7'00" 10.56 2'58"Spec 0'50" max 5'00" min______________________________________ Exp = Expansion ratio of foam QDT = 25% drainage time of foam
Composition A of Example 1 was the control. In inventive formulations B and C, the standard amphoteric surfactant IDC-810M was deleted and the alkyl polyglycoside APG 300 light (b) and dark (c) substituted therefor. Compositions B and C demonstrated better results were achieved with the formulations of the invention. THe extinguishing times (Ext.) for compositions B and C were quicker and the burnback times were longer.
______________________________________Example 2 1 literMaterials A B C______________________________________1. Water 751 ml 757 ml 753 ml2. Urea 12.4 g 12.4 g 12.4 g3. Butyl carbitol 39 ml 39 ml 39 ml4. K8A13 11.3 g 10.2 g 9.0 g5. G-4-40 2.9 g 2.9 g 2.9 g6. Forafac 1157N 46.6 g 41.4 g 46.6 g7. APG-325 80 g 80 g 80 g8. Sodium decylsulfate 113 ml 113 ml 113 ml (30%)9. MgSO.sub.4 5.0 g 5.0 g 5.0 g10. NTA/Na.sub.3 1.6 g 1.6 g 1.6 g11. Acetic Acid/50% NaOH to adjust pH 7.6-8.00______________________________________Fire Test ResultsModified UL-1623% Seawater on 10 Liters Heptane 0.04 gpm 90% 2.69 ft.sup.2 tank Exp. QDT Control Ext. 20% Burnback______________________________________A 7.42 7'48" 0'35" -- 4'45"B 7.47 6'46" 0'33" -- 5'00"C 7.95 6'39" 0'45" -- 4'45"Spec 3.5 2'00" 0'50" N/A 3'00" min min max min______________________________________6% Seawater on 15 Liters IPA 0.10 gpm 2.69 ft.sup.2 tank______________________________________A 6.47 23'01" 1'06" 1'15" 1'51" 7'00"B 6.10 25'25" 0'38" 1'12" 1'47" 6'45"C 5.66 19'53" 0'48" 1'10" 1'55" 6'05"Spec 7.0 10'00" 1'15" 1'45" 2'00" 5'00" min min max max max max______________________________________
In Example 2, Composition A was the control. The polysaccharide K8A13 and the perfluorosurfactant were reduced 10% in Composition B and the polysaccharide K8A13 was reduced 20% in Composition C. With the presence of the alkyl polyglycoside the compositions of the invention still had satisfactory performances.
______________________________________Example 3 1 gallonMaterials A B C______________________________________1. Water 2201 ml 2245 ml 2092 ml2. Surflon S-831-2 12 g 10 g 9.6 g3. Butyl carbitol 200 ml 200 ml 200 ml4. Ethylene glycol 220 ml 220 ml 220 ml5. Forafac 1157N 284 g 242 g 227.2 g6. APG-325 488 g 488 g 586 g7. Triton X-102 44 ml 44 ml 53 ml8. NTA/Na.sub.3 6 g 6 g 6 g9. Tris Amino 12.5 g 12.5 g 12.5 g10. Urea 12.5 g 12.5 g 12.5 g11. Sodium decylsulfate 305 ml 305 ml 336 ml (30%)12. Acetic Acid to adjust 8.00 8.00 7.96 pH to 7.6-8.0______________________________________Fire Tests ResultsModified Mil Spec3% Seawater on 3.0 liters gasoline 0.04 gpm 2.69 ft.sup.2 tank Total Seconds Ext. 25% Burnback Exp. QDT______________________________________A 98 0'43" 4' 27" 8.04 2'22"B 79 0'37" 4'58" 7.23 2'39"C 88 0'38" 4'30" 7.20 2'48"______________________________________1.5% Seawater on 3.0 liters gasoline 0.07 gpm 2.69 ft.sup.2 tank______________________________________A 79 0'36" 7'43" 4.05 2'12"B 67 0'34" 7'07" 4.15 2'24"C 70 0'36" 6'40" 4.37 2'18"______________________________________
In Example 3, composition A was the control. In composition B, the perfluoro surfactants were decreased, the poly alkylglycoside remained the same. In the composition C, the poly alkylglycoside was increased and the perfluoro surfactants further decreased. Testing according to th e modified test Mil-F-24385C as described above for Example 1, equal or better results were achieved with the compositions of the inventions.
______________________________________Example 4 1 literMaterials A B C______________________________________1. Water 804 ml 804 ml 804 ml2. Butyl carbitol 38 ml 38 ml 38 ml3. Xanthan gum 13.2 g 10.9 g 8.5 g4. G-4-40 2.5 g 2.5 g 2.5 g5. Forafac 1157N 47.8 g 47.8 g 47.8 g6. APG-325 44.0 g 44.0 g 44.0 g7. Sodium decylsulfate 79 ml 79 ml 79 ml8. NTA/Na.sub.3 1.6 g 1.6 g 1.6 g9. Tris Amino 1.6 g 1.6 g 1.6 g10. Acetic Acid to adjust pH to 7.6-8.0______________________________________Viscosity 3 RPM 33,200 cps 23,440 cps 15,360 cpsCurves 6 RPM 17,280 cps 12,480 cps 8,440 cpsBrookfield 12 RPM 8,900 cps 6,460 cps 4,590 cpsSprindle 3 at 30 RPM 3,884 cps 2,848 cps 2,024 cps 60 RPM off scale 1,608 cps 1,118 cps______________________________________Fire Test ResultsModified UL-1623% Seawater on 10 Liters Heptane 25% 90% 20% 0.04 gpm Exp. drain Control Ext. Burnback 2.69 ft.sup.2 tank______________________________________A 7.3 6'42" 0'37" -- 3'59"B 7.58 7'35" 0'37" -- 5'00"C 6.97 4'20" 0'37" -- 4'20"Spec 3.5 2'00" 0'50" N/A 3'00" min min max min______________________________________6% Seawater on 15 Liters IPA (99%) 0.10 gpm 2.69 ft.sup.2 tank______________________________________A 9.83 20'46" 0'42" 1'05" 8'15"B 9.79 17'05" 0'38" 0'56" 9'00"C 9.67 13'10" 0'30" 0'53" 7'30"Spec 7.0 10'00" 1'15" 1'45" 2'00" 5'00" min min max max max min______________________________________Viscosity 3 RPM 33,200 cps 23,440 cps 15,360 cpsCurves 6 RPM 17,280 cps 12,480 cps 8,440 cpsBrookfield 12 RPM 8,900 cps 6,460 cps 4,590 cpsSprindle 3 at 30 RPM 3,884 cps 2,848 cps 2,024 cps 60 RPM off scale 1,608 cps 1,118 cps______________________________________
Fire tests were run pursuant to the modified UL tests previously described.
Composition A was a standard ARAFFF composition. As the amount of polymer (xanthan gum) decreased the viscosity decreased. Thus, less polymer could be used with better or superior results with the presence of the alkyl polyglycoside.
Having described our invention, what we now claim is:

Number	Name	Date
3772269	Lew	Nov 1973
4060489	Chiesa, Jr.	Nov 1977
4387032	Chiesa, Jr.	Jun 1983
4424133	Mulligan	Jan 1984
4439329	Kleiner et al.	Mar 1984
4565647	Llenado	Jan 1986
4859349	Clark et al.	Aug 1989

Alcohol resistant aqueous film forming firefighting foam

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