Fire Fighting Foaming Compositions

Abstract

A fire fighting composition according to the invention comprises a first surfactant selected from alkyl group-containing amphoteric surfactants, wherein the alkyl group contains at least 8 carbon atoms, and alkyl group-containing zwitterionic surfactants, wherein the alkyl group contains at least 8 carbon atoms, and mixtures thereof, and a second surfactant selected from alkyl group-containing anionic surfactants, wherein the alkyl group contains at least 8 carbon atoms, and wherein the weight ratio of the surfactant to the second surfactant is in the range of from 3:1 to 1:1.5, wherein the fire fighting foaming composition is essential free of fluorine. Typically, the first surfactant is selected from alkyl amine oxides, betaines and N-alkyl pyrrolidones. Typically, the second surfactant is selected from alkyl sulphates, alkyl phosphates, dialkylsulphosuccinates, sodium alkyl ether sulphates and alkyl carboxylates. The compositions which are essentially-free of fluorine or fluorine-containing compounds give a good combination of fire fighting properties, such as burn back performance and extinguishing capability.

Claims

1. A fire fighting foaming composition comprising a first surfactant selected from alkyl group-containing amphoteric surfactants, wherein the alkyl group contains at least 8 carbon atoms, and alkyl group-containing zwitterionic surfactants, wherein the alkyl group contains at least 8 carbon atoms, and mixtures thereof, and a second surfactant selected from alkyl group-containing anionic surfactants, wherein the alkyl group contains at least 8 carbon atoms, and wherein the weight ratio of the first surfactant to the second surfactant is in the range of from 3:1 to 1:1.5, and wherein the said fire fighting foaming composition is essentially free of fluorine.

2. A composition according to claim 1, wherein the first surfactant is selected from alkyl amine oxides, betaines and N-alkyl pyrrolidones and mixtures thereof.

3. A composition according to claim 2, wherein the first surfactant is an alkyl amine oxide wherein the alkyl group contains 10 or more carbon atoms, preferably 10 to 16 carbon atoms, more preferably 12 to 14 carbon atoms.

4. A composition according to any one of claims 1 to 3, wherein the second surfactant is selected from alkyl sulphates, alkyl phosphates, dialkylsulphosuccinates, sodium alkyl ether sulphates, alkyl carboxylates and mixtures thereof.

5. A composition according to claim 4, wherein the second surfactant is an alkyl sulphate wherein the alkyl group contains 10 or more carbon atoms, preferably 10 to 16 carbon atoms, more preferably 12 to 14 carbon atoms.

6. A composition according to claim 4 or claim 5, wherein the water-soluble alkyl sulphate is an ammonium salt, an alkali metal salt or an alkaline earth metal salt.

7. A composition according to claim 6, wherein the water-soluble alkyl sulphate is an ammonium salt or a sodium salt.

8. A composition according to any one of claims 1 to 7, wherein the weight ratio of first surfactant to second surfactant in the composition is in the range of from 2.5:1 to 1:1.2.

9. A composition according to claim 8, wherein the weight ratio of first surfactant to second surfactant is in the range of from 2.2:1 to 1:1.2.

10. A composition according to claim 9 comprising, as first surfactant, an alkyl amine oxide and, as second surfactant, an alkyl sulphate, wherein the weight ratio of alkyl amine oxide to alkyl sulphate is about 2:1.

11. A composition according to claim 9 comprising, as first surfactant, an alkyl amine oxide and, as second surfactant, an alkyl sulphate, wherein the weight ratio of alkyl amine oxide to alkyl sulphate is about 1:1.

12. A composition according to any one of claims 1 to 11, wherein the first surfactant is dimethyl dodecyl amine oxide.

13. A composition according to any one of claims 1 to 12, wherein the second surfactant is dodecyl sulphate sodium salt.

14. A composition according to any one of claims 1 to 13, wherein the water is present in the composition in an amount of from 22 to 88% (w/w).

15. A composition according to any one of claims 1 to 14, which additionally comprises at least one solvent selected from glycols, glycol ethers and 1-8C alkanols.

16. A composition according to claim 14, which additionally comprises at least one solvent selected from glycols and glycol ethers, wherein the solvent is present in the composition in an amount of from 5 to 30% (w/w).

17. A composition according to either claim 15 or claim 16, wherein the solvent is selected from hexylene glycol, 2-(2-butoxyethoxy) ethanol and diethylene glycol.

18. A composition according to claim 1, comprising dodecylsulphate sodium salt about 24% (w/w) dimethyl dodecyl amine oxide about 24% (w/w) and about 30% (w/w) of a solvent selected from glycols and glycol ethers.

19. A composition according to claim 1, comprising dodecylsulphate sodium salt about 8% (w/w) dimethyl dodecyl amine oxide about 8% (w/w) and about 10% (w/w) of a solvent selected from glycols and glycol ethers.

20. A composition according to claim 1, comprising dodecylsulphate sodium salt about 4% (w/w) dimethyl dodecyl amine oxide about 4% (w/w) and about 5% (w/w) of a solvent selected from glycols and glycol ethers.

21. A composition according to claim 1, comprising dodecylsulphate sodium salt about 16% (w/w) dimethyl dodecyl amine oxide about 32% (w/w) and about 30% (w/w) of a solvent selected from glycols and glycol ethers.

22. A composition according to claim 1, comprising dodecylsulphate sodium salt about 5.3% (w/w) dimethyl dodecyl amine oxide about 10.7% (w/w) and about 10% (w/w) of a solvent selected from glycols and glycol ethers.

23. A composition according to claim 1, comprising dodecylsulphate sodium salt about 2.7% (w/w) dimethyl dodecyl amine oxide about 5.3% (w/w) and about 5% (w/w) of a solvent selected from glycols and glycol ethers.

24. A composition according to any one of claims 18 to 23, wherein the solvent is selected from hexylene glycol, 2-(2-butoxyethoxy)ethanol and diethylene glycol.

25. A composition according to any one of claims 1 to 24 which additionally comprises one or more additives selected from corrosion inhibitors, divalent metal salts, buffers, stabilisers, anti-freeze agents and thickening agents, wherein thickening agents are ones that do not contain polymerised sugars or polysaccharide gums.

26. A composition according to claim 25, which comprises one or more corrosion inhibitor.

27. The use of a composition according to any one of claims 1 to 26 in preparing a composition for application to a fire.

Description

EXAMPLES

[0052] The compositions shown in the Tables below were prepared by simple mixing of the ingredients. Unless otherwise stated, the water used was fresh water. The compositions were evaluated for their extinction times and burn-back performance.

[0053] The evaluations were carried out according to the testing procedure described in British Standard EN 1568-3:2008 using Avtur (aviation kerosene) fires. Briefly, the testing procedure was as follows:

Apparatus

[0054] A circular fire tray of brass was used having an internal diameter (at rim) of about 565 mm, height (of vertical wall) of about 150 mm, height (of conical base) of about 30 mm and thickness of vertical wall of about 1.2 mm. The fire tray had a turned over rim and a drain point, with valve, at the centre of the conical base and had an area of about 0.25 m.sup.2. The fire tray was supported approximately 1 m above the ground on a steel frame with four legs and placed beneath a suitable fume extraction hood to extract the smoke without interfering with the fire.

[0055] For the burn-back testing, a brass burn-back pot was used having an internal diameter (at rim) of about 120 mm, internal depth of about 80 mm and a wall thickness of about 1.2 mm. The pot had a turned over rim, and was fitted with four studs at the base to give an overall height of about 96 mm. A chain, fitted to the rim, allowed the pot to be lifted using a metal rod.

[0056] Foam making nozzle had a nominal flow rate of 5.01/min at 7 bar when tested with water. It was fitted with an adjustable collar to allow foam to be ejected from the side of the nozzle and thus vary the foam flow rate through the outlet. It was, also, possible to control the foam flow rate by adjusting the pressure applied to the foam solution.

Test Procedure

Test Conditions

[0057] The test was carried out under the following conditions:

a) air temperature (15±5°) C.;
b) fuel temperature (17.5±2.5°) C.;
c) foam solution temperature (17.5±2.5°) C.

Set Up

[0058] The foam nozzle was positioned horizontally with the by-pass holes in the adjustable collar facing downwards at a height of (150±5) mm above the rim of the fire tray.

[0059] The nozzle pressure was set to 7 bar and the foam flow rate to (0.75±0.025) kg/min by adjusting the collar and, if necessary reducing the nozzle pressure. It was convenient to collect the foam in a tared vessel for 6 s and to weigh it to calculate the flow rate.

[0060] The nozzle was positioned while keeping it horizontal so that the foam struck the centre of the fire tray. Shut off the foam discharge. Clean the tray and close the drain valve.

Fire Test

[0061] (9±0.1) l of fuel were placed in the tray, and (0.3±0.01) l of fuel in the burn-back pot.

[0062] (120±2) s after fuelling the fuel was ignited and allowed to burn for (60±2) s before starting foam application. Foam was applied for (120±2) s to the centre of the tray and the times recorded from the start of foam application to 90% control, 99% control, and complete extinction.

[0063] At the end of foam application the fuel was ignited in the burn-back pot, and (60±2) s after the end of foam application the pot was lowered into the centre of the tray with a metal rod, taking care not to allow foam to enter the pot. The time taken from positioning of the burn-back pot to permanent full reinvolvement of the fire tray surface in flames was recorded as the burn-back time.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 C10 sulphate 2.4 C12 sulphate 2.4 2.4 2.4 C12-14 sulphate C12-16 sulphate C10 amine oxide 2.4 C12 amine oxide 2.4 2.4 2.4 C14 amine oxide Cocamidopropylamine .24 oxide Butyl carbitol 10 10 10 10 10 Water to 100 to 100 to 100 to 100 to 100 Extinction (min) 1.23 X X 2.10 1.55 Burnback (min) 9.00 4.50 3.30

TABLE-US-00002 TABLE 2 Example 6 7 8 9 10 11 12 C10 sulphate 2.4 C12 sulphate 2.4 2.4 C12-14 sulphate 2.4 2.4 C12-16 sulphate 2.4 2.4 C10 amine oxide 2.4 C12 amine oxide 2.4 2.4 2.4 C14 amine oxide 2.4 2.4 2.4 Coca Butyl carbitol 10 10 10 10 10 10 10 Water to 100 to 100 to 100 to 100 to 100 to 100 to 100 Extinction (min) X 1.35 1.23 1.24 1.37 1.32 1.42 Burnback (min) 9.00 7.20 8.00 8.00 7.00 6.45

TABLE-US-00003 TABLE 3 13 14 15 16 17 18 19 C10-C12 sulphate 2.4 C12 sulphate 2.4 2.4 C12 amine oxide 2.4 2.4 2.4 2.4 2.4 2.4 2.4 C12-14 Triethanolamine 2.4 alkyl sulphate C12-16 ammonium alkyl 2.4 sulphate Sodium lauryl ether 2.4 Dioctyl sulpho succinate 1 2.4 Alkyl phosphate ester 1 Butyl carbitol 10 10 10 10 10 10 10 Water to 100 to 100 to 100 to 100 to 100 to 100 to 100 Extinction (min) X 1.55 1.52 X 1.33 1.35 X Burnback (min) 2.30 3.27 5.17 5.15

TABLE-US-00004 TABLE 4 20 21 22 23 24 25 26 C10 sulphate 2.4 C12 sulphate 2.4 2.4 2.4 2.4 2.4 C12-14 sulphate 2.4 Cocamidopropylbetaine 2.4 0.3 Cap amine oxide 2.7 2.4 Alkyl diMe betaine 2.4 C1012 amine oxide 2.4 C12 amine oxide C10 alkyl pyrollidone 2.4 Xanthan gum Butyl carbitol 10 10 10 10 10 10 10 Water to 100 to 100 to 100 to 100 to 100 to 100 to 100 Extinction (min) X X 1.27 X 3.05 X X Burnback (min) 5.41 X

[0064] Tables 1 and 2 show clearly that performance is reliant on the combination of a first surfactant and a second surfactant.

[0065] Tables 3 and 4, below, show the performance of compositions containing commercially available surfactants different from those used in the compositions of Tables 1 and 2.

Evaluation Using Formulations Diluted in Sea Water

[0066] All testing was done based on the Defence Standard simulated sea water which contains 27 g/L Sodium Chloride and 10 g/L Magnesium Sulphate, which is a close replication of sea water that can be approximated as: 27 g/L Sodium Chloride, 6.5 g/L Magnesium Sulphate 1.5 g/L miscellaneous ions.

[0067] The compositions described in Table 5 were prepared by simple mixing of the ingredients wherein the water used was the simulated sea water described above and evaluated using the procedure described above.

TABLE-US-00005 TABLE 5 27 28 29 30 31 C10 sulphate C12 sulphate 1.6 1.2 1.8 2.4 C12-14 sulphate 1.6 Cocamidopropylbetaine Cap amine oxide 0.3 Alkyl diMe betaine C1012 amine oxide C12 amine oxide 3.1 3.1 2.4 2.4 2.4 C10 alkyl pyrollidone Butyl carbitol 10 10 10 10 10 Water to 100 to 100 to 100 to 100 to 100 Extinction (min) 1.31 1.22 X X 1.42 Burnback (min) 5.15 5.45 3.30

Example 32

[0068] A composition according to the invention was formulated as follows:

TABLE-US-00006 % by weight C.sub.12 sulphate 5.6 C.sub.12 amine oxide 10.4 Morpholine salt of octanoic 0.5 and decanoic acids Butyl carbitol (solvent) 10.0 Water to 100

[0069] The formulation above was tested in the ICAO B test at 3% in fresh water on Jet A1 fuel. The ICAO test is a standard test, well known in the art. The fire test method for performance level A, B or C fire fighting foams is described in ICAO Doc. 9137-AN/898, Airport Services Manual (ASM), Part 1, Rescue and Fire Fighting, Chapter 8. The results for 99% control, 100% extinguishment and burn-back were:—

TABLE-US-00007 Standard Example 99% control <60 s 48 s (pass) 100% extinguishment <120 s <120 s (pass) Burn-back >5 minutes 6 minutes and 5 s (pass)

[0070] It is known in the art that conventional foams containing fluorocarbon surfactants are able to lower surface tension sufficiently to give negative spreading energy on hydrocarbon fuels, i.e. they are able to form films on such fuels. Film forming properties are important since they allow the foam to spread over the surface of a burning fuel and thus cool it down and prevent the passage of oxygen to the fuel. This gives rapid control and extinguishment of the fire.

[0071] It is generally believed that foams based purely on hydrocarbon surfactants cannot give a negative spreading energy on a hydrocarbon fuel. We have found, surprisingly, that compositions according to the invention can form films on aviation fuel, or Avtur.

[0072] The composition having the formulation above (called ‘A’) was sprayed on to Jet A1 fuel. For comparison, two different prior art fluorine-free fire fighting foaming compositions (B and C), not in accordance with the subject matter claimed herein, were each tested separately on Jet A1 fuel under identical conditions (20° C.). The composition ‘A’ of the invention was also tested at 30° C. The results are shown below in Table 6.

TABLE-US-00008 TABLE 6 Spreading Water Water/fuel Fuel coefficient = surface interfacial surface yw + yf/ Exam- tension tension yf/w, tension w − yf, ple yw, mN/m mN/m yf, mN/m mN/m Temp ° C. A 24.0 0.2 28 −3.8 20 B 27.7 4 28 +3.7 20 C 29.4 4 28 +5.4 20 A 24.0 0.2 24.5 −0.3 30

[0073] Surface and interfacial tensions were measured using a White ‘OS’ Type torsion balance with a 1 cm diameter platinum du Noüy ring.

[0074] The prior art formulations B and C both had positive spreading coefficients on Jet A1 fuel and, so, neither was able to form an aqueous film on the surface of the fuel. Composition A (of the invention), however, has a negative spreading coefficient and forms a film at both 20° C. and 30° C.