GB1601016A

GB1601016A - Fire extinguishing powders

Info

Publication number: GB1601016A
Application number: GB1356178A
Authority: GB
Original assignee: MAGYAR NEPHADSEREG HADITECHNIK; Elzett Muvek
Current assignee: MAGYAR NEPHADSEREG HADITECHNIK; Elzett Muvek
Priority date: 1977-04-07
Filing date: 1978-04-06
Publication date: 1981-10-21
Also published as: DE2814034A1; HU179694B

Description

(54) IMPROVEMENTS IN FIRE EXTINGUISHING POWDERS (71) We, ELZETT MUVEK, a body corporate organised under the laws of Hungary of 5, Madarasz utca, Budapest XIII, Hungary, and MAGYAR NEPHADSEREG HADITECHNIKAI INTEZET, a body corporate organised under the laws of Hungary of Szilagyi Erzsebet fasor 120/122, Budapest XII, Hungary, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to fire extinguishing powders possessing good flame and ember extinguishing properties when applied either alone or as a component of fire extinguishing powder compositions. The invention also provides a process for the preparation of such fire extinguishing powders and powder compositions.

The fire extinguishing powders are prepared, according to the invention, by reacting a substance of good flame or ember extinguishing properties (such as phosphate, sulfate or borate) or a mixture thereof with other appropriate substances or mixtures thereof. The reactions can be performed either in solid phase by heating the starting substances under elevated pressure, or in liquid phase at elevated temperatures (e.g. by spray drying). In this latter instance the reactions can also be performed on the surface of catalyst carrier particles of high specific surface area, introduced into the liquid phase.

Equipment and apparatus filled with fire extinguishing powders have become increasingly widespread in the extinguishing of fires of various origins. Fire extinguishing techniques have developed in harmony therewith, and the qualities and compositions of fire extinguishing powder mixtures have changed in accordance with more recent requirements.

The fire extinguishing effect of such powder mixtures resides basically in that they prevent air from coming into contact with the burning material. Most of the fire extinguishing powders are substances liable to thermal decomposition, from which inert gases are liberated upon decomposition. The diluting effect of the gases and the cooling caused by the decomposition process result in an additional extinguishing effect. Various other secondary effects appear as well.

In practice, the following compounds have been used as active principles of fire extinguishing powder compositions: alkali metal and alkaline earth metal bicarbonates and carbonates, ammonium phosphates, such as mono- or diammonium phosphate, borates or boric acid, ammonium carbonate and bicarbonate, sodium and potassium phosphate, potassium sulfate, alkali metal halides, such as potassium chloride, resinous substances or polymers, proteins and related substances.

The proper selection of the materials depends also on the purpose of application. When the powder is to be used to put out "B" class fires (flammable liquids), it may contain an alkali metal bicarbonate or carbonate as active principle.

Fire extinguishing powders to be used in putting out "A" class fires (solids burning with flame or ember) contain phosphates and sulfates as active agents. Powders containing alkali metal chlorides or ammonium chloride with borax are suggested primarily for putting out "D" class fires (fires caused by light metals). The fire extinguishing powders may also contain various additives, such as lubricants.

colourants and substances imparting hydrophobic properties.

The basic requirements looked for in fire extinguishing powder compositions are as follows: good extinguishing capacity (expressed as the weight of powder applied per m3 of flame in unit time), flowability, low liability to agglomeration, hydrophobic nature, inactivity towards propellants, good stability, inertness to the environment (they must not be corrosive or poisonous).

Fire extinguishing powders which are of greatest practical interest contain adducts of potassium bicarbonate and urea or adducts of potassium bicarbonate and dicyanodiamide (see British patent specificationsNos. 1,118,215, 1,168,092 and 1,190,132 and German patent specification Nos. 2,258,256, 2,348,926 and 1,941,060). When a mixture of 1 mole of potassium bicarbonate and 1.2 moles of urea is heated, a substance with the composition of KC2N2H3O3, having a powerful flame extinguishing effect, is formed. The extinguishing capacity of this substance is estimated as five times that of sodium bicarbonate-based powders and 2.5 times that of potassium bicarbonate-based ones. Similarly to the above, the molecules of potassium bicarbonate-dicyanodiamide adducts also containCOOM groups, wherein M represents sodium or potassium atom.Fire extinguishing powder mixtures containing such adducts in appropriate amounts can be applied with excellent results to put out "B" and "C" class fires (burning gases, such as propanebutane gas mixtures, hydrogen, or methane. They are, however, inappropriate for putting out "A" class fires when used alone. The method suggested in the German patent specification No. 1,941,060 aims at eliminating this disadvantage of potassium bicarbonate-urea adducts, by taking into account other aspects as well.

The addition of ammonium phosphates and sulfates results, however, in a considerable worsening of the flame extinguishing property of the powder mixture.

In order to retain the flame extinguishing properties the amount of the potassium bicarbonate-urea adduct in the powder mixture must not be decreased below 55 to 60% by weight. In such instances, however, no melt is formed from the fire extinguishing powder when sprayed onto the surface of glowing substances, but a friable mass with low adhesion and deep effect forms, i.e. the powder mixture remains inapplicable for extinguishing "A" class fires.

The invention has among its objects to provide (at least in its preferred embodiments) highly effective fire extinguishing powders in which the above disadvantages are reduced or avoided, which have efficient flame and ember extinguishing properties when applied either alone or as components of fire extinguishing powder mixtures (such as in admixture with potassium bicarbonate- urea adducts). Furthermore, the invention provides a process for the preparation of such fire extinguishing powders and powder mixtures.

According to the process of our invention, one or more of the substances (a) or (b) or mixtures thereof a) alkali metal or ammonium phosphates, sulfates, hydrogenphosphates or bisulfates, b) alkali metal borates or boric acid, is subjected to heat treatment at a temperature below 200"C together with c) one or more reactive amino or imino compounds containing at least one -NH2 or No group (such as urea, thiourea, dicyanodiamide, guanidine, melamine or semi-carbazide), if desired together with d) ammonium carbonate or bicarbonate.

The term "reactive amino or imino compound" indicates a compound containing at least one amino or imino group which is not protected or otherwise inhibited in its reactivity.

The materials (a) and (b) used in accordance with the invention are those possessing good flame and ember extinguishing capacities. As is known, various phosphates, sulfates and borates (a) and (b) well fit this requirement.

The invention is based on the recognition that the flame and ember extinguishing capacities of the above substances can be increased to a great extent when they are reacted under heating, either alone or in admixture with each other, with other appropriate substances (c) or mixtures thereof. The reactions can be performed either in solid phase by heating the mixture under elevated pressure, or in liquid phase at elevated temperatures (e.g. by spray-drying). The solvent may dissolve at least one of the reactants, e.g. methanol, ethanol or dimethylformamide, or all of the starting materials, e.g. water. The liquid phase reactions can also be performed on the surface of a catalyst carrier powder with high specific surface area, introduced into the liquid phase.

The reactions can be performed either in the presence or in the absence of phosphoric acid. The individual reactants may be present in a molar ratio of from 0.005:1 to 100:1, preferably from 0.05:1 to 1:1.

When the reactions are performed in solid phase, the treatment is carried out e.g. at 80 to 1900C (preferably 110 to 1600C) under a pressure of 5 to 7 kg/cm2. In order to increase the yield, it is advisable to homogenize the powder mixture prior to heat treatment.

When the treatment is performed by evaporating a solvent, e.g. by spray drying, the reactants are combined with a solvent which dissolves at least one of the reactants, the reactants forming e.g. 10 to 80% by weight of the suspension or solution, and optionally 5 to 85% by weight of a powdery catalyst carrier substance with high specific surface area is admixed with the suspension or solution. The mean particle size of the carrier powder (such as aluminium oxides, silicates, pearlite, zeolites, bentonite, or powdered asbestos), is e.g. below 400,u, preferable 70 to 200,u. If desired, other inert substances, such as barium sulfate or tricalcium phosphate can also be added to the mixture. In order to evaporate the solvent, preferably at a temperature of at least 1000C, the suspension or solution may be sprayed into a hot gas stream.The temperature of the gas entering the spraying chamber can e.g. be 200 to 5500C, preferably 250 to 4000 C, that of the exiting gas is e.g. 100 to 1900C, preferably 120 to 1600C. The gas is preferably air. The good efficiency of the reactions taking place between the starting substances is ensured partly by the presence of the catalyst with high specific surface area and partly by an atmosphere of water vapour containing carbon dioxide and ammonia, generated upon thermal decomposition of ammonium carbonate and/or ammonium bicarbonate. The residence time of the mixture in the spray-drying chamber amounts to e.g. 5 to 25 seconds.

The fire extinguishing powders or powder mixtures according to the invention may also contain 1 to 50% by weight of a condensation product. The term "condensation product" refers to a substance produced by condensing formaldehyde with a compound listed under c) above (such as urea, thiourea, dicyanodiamide, quanidine, melamine or semicarbazide) in the presence of an acid such as phosphoric acid.

The invention is further illustrated by the aid of the following non-limiting Examples. Percentages are by weight.

Example 1 A mixture of 100 g of 85% phosphoric acid, 300 g of urea and 600 g of potassium dihydrogenphosphate is subjected to heat treatment at 1 500C for 3 hours. The resulting substance is ground in a ball mill to an appropriate particle size, and thereafter admixed with 5% by weight of barium sulfate, 6% by weight of tricalcium phosphate, 3% by weight of silica gel, 2% by weight of powdered mica, 2 ó by weight of magnesium stearate and 1% by weight of dimethyldiethoxysilane.

The resulting fire extinguishing powder possesses effective flame and ember extinguishing properties.

Example 2 Ammonium dihydrogenphosphate and dicyanodiamide are ground separately to a mean particle size below 100 y. 1 mole of ammonium dihydrogenphosphate is admixed with 0.05 to 1 mole of dicyanodiamide, and the mixture is thoroughly homogenized. The mixture is filled into a sealable, pressure-fast tray and subjected to heat treatment at 153 to 155"C for 3 hours. The resulting substance is ground to an appropriate particle size in a ball mill, and admixed with 5 to 950;o by weight of a potassium bicarbonate-urea adduct, 2% by weight of silica gel and 1% by weight of mica. The resulting fire extinguishing powders possess excellent flame and ember extinguishing abilities.

Example 3 50 g of 85% phosphoric acid are admixed with 400 g. of urea and 200 g. of borax, the mixture is ground to a particle size below 100 , and then it is subjected to heat treatment at 145 to 1500C for 2.5 hours. The resulting substance is ground to a mean particle size of 70 , and admixed with additives e.g. as in Example 1. An effective fire extinguishing powder is obtained.

Example 4 A mixture of 0.5 mole of boric acid, 0.08 to 1 mole of dicyanodiamide and 0.05 to I mole of urea is subjected to heat treatment at 145 to 1500C for 3.5 hours. The resulting substance is ground to a particle size of 80 p, and admixed with additives and 5 to 95% of a conventional fire extinguishing material (such as an alkali metal carbonate or bicarbonate, an alkali metal phosphate, an ammonium phosphate, a borate, a sulfate or a halide.

Example 5 A mixture of 1 mole of ammonium sulfate, 0.05 to I mole of dicyanodiamide and 0.1 to 0.6 mole of ammonium carbonate is ground to a particle size below 100 ,a. The mixture is put into a sealable, pressure-fast tray and subjected to heat treatment at 145 to 155"C for 2.5 hours. The resulting substance is ground, and admixed with additives and 10 to 50% of a condensation product (see above). An effective fire extinguishing powder is obtained.

Example 6 A mixture of urea and diammonium hydrogenphosphate with a molar ratio of 1:1 to 2 is dissolved in the smallest possible amount of water, and 0.05 to 0.15 mole of phosphoric acid and 40 to 60% of a catalyst carrier powder are admixed with the aqueous solution. The suspension is poured into a metal crown and evaporated on an oil bath at 1500C. The heat treatment is continued for 15 minutes after the complete evaporation of water. The resulting substance, which is an effective fire extinguishing powder, is processed as described in the previous Examples.

Example 7 A mixture of ammonium dihydrogenphosphate and dicyanodiamide with a molar ratio of 1:0.05 to 1 is dissolved in water. The solution is poured into a glass container provided with a tap, and a heated endless stainless steel belt is moved below the tap. The belt is heated to 160 to 1650C. The liquid is dropped onto the belt from the container. The solid substance, remaining on the belt after the evaporation of water, is processed as described in the previous Examples.

Example 8 A mixture of borax, urea and ammonium carbonate with a molar ratio of 1:0.5 to 1.5:0.2 to 0.6 is dissolved in water, and 35 to 85% of a catalyst carrier powder is added to the aqueous solution. The mixture is processed in a spray-dryer, 1.8 m. in diameter. Hot air is fed into the chamber through drying equipment, and the flow rate of the solution is adjusted so that the following parameters are maintained: inlet temperature of air: 250 to 5500 C, outlet temperature of air: 100 to 1900C.

The residence time of the substance in the chamber varies between 10 and 25 seconds. The resulting powders are effective fire extinguishing agents.

Example 9 A mixture of urea, ammonium dihydrogenphosphate and dicyanodiamide with a molar ratio of 0.2 to 0.7:1 to 2:0.1 to 0.8 is admixed with methanol, and the resulting suspension is processed as described in Example 8. An effective fire extinguishing powder is obtained.

Example 10 Fire extinguishing powders or powder mixtures are prepared as described in any of the preceding Examples from the substances listed below: Composition 1: Dicyanodiamide-ammonium dihydrogenphosphate adduct 5 to 95% Additives 0 to 3 & 00 Composition 2: Urea--diammonium hydrogenphosphate-phosphoric acid adduct 5 to 95% Sodium chloride 5 to 95% Additives 0 to 30% Composition 3: Urea-boric acid adduct 5 to 95% Urea-potassium bicarbonate adduct 5 to 95% Condensation product 1 to 50% Additives 0 to 30% Composition 4:: Dicyanodiamide-diammonium hydrophosphate adduct 5 to 95% Urea-sodium bicarbonate adduct 5 to 95% Additives 0 to 30% Composition 5: Urea-borax-ammonium sulfate adduct 5 to 95% Potassium bicarbonate-dicyanodiamide adduct 5 to 95 Ó Additives 0 to 30% Composition 6: Dicyanodiamide-ammonium hydrogenphosphate adduct 5 to 95% Potassium or sodium bicarbonate 5 to 95% Additives 0 to 30% Composition 7:: Guanidine-diammonium hydrogenphosphate adduct 5 to 95% Ammonium bicarbonate 5 to 40% Barium sulfate 0 to 6% Calcium phosphate 0 to 6% Silica gel 0 to 4% Magnesium stearate 0 to 3 / Mica powder 0 to 2 X Silicone oil 0 to 1% Any of the compositions listed above can be prepared either by solid phase or by liquid phase reactions.

The fire extinguishing powder mixtures according to the invention may contain preferably 5 to 95% by weight of a fire extinguishing powder prepared according to the invention along with 95 to 5% by weight of one or more of the following fire extinguishing substances: (1) sodium, potassium or ammonium carbonate or bicarbonate, (2) sodium, potassium or ammonium phosphates, (3) sodium, potassium or ammonium sulfates, (4) borates and boric acid, (5) alkali metal halides, (6) resinous or polymeric substances, such as PVC, (7) starch and related substances, (8) proteins and related substances, (9) adducts of potassium carbonate, potassium hydroxide and potassium bicarbonate with urea (see e.g. our co-pending 1601017 Application No. 13562/78), (10) adducts of sodium carbonate, sodium hydroxide and sodium bicarbonate with urea, (11) sodium bicarbonate-dicyanodiamide adducts, (12) potassium bicarbonate-dicyanodiamide adducts.

The fire extinguishing powders or powder mixtures according to the invention may also contain preferably 1 to 50% by weight of a condensation product (prepared by condensing urea, thiourea, dicyanodiamide, guanidine, melamine, semicarbazide or related substance with formaldehyde in the presence of phosphoric acid), furthermore 0 to 30% by weight of one or more auxiliary agent(s), such as flowability-increasing agents, substances increasing the hydrophobic nature of the product, surfactants, substances ensuring compatibility with fire extinguishing foams, anti-caking agents, sprayability-increasing substances and/or substances for adjusting to an appropriate bulk density.

When the process according to the invention is performed in liquid phase, it is preferred to admix 5 to 85% by weight of one or more catalyst carrier powder(s) with the solution or suspension to be processed. As catalysts, preferably substances with high specific surface area, such as aluminium oxides, silicates, pearlite, zeolites, bentonite or powdered asbestos may be used. Furthermore, other inert substances, such as barium sulfate or calcium phosphate can also be admixed with the liquid to be processed. When such additives are also used, the reaction is performed preferably by spray-drying. This operation is described in detail in our copending Application No. 13562/78. (Serial No. 1601017).

The compositions according to the invention can also be applied to impart flame retardant properties to various substances. This can be done by impregnation (e.g. by immersing fabrics or foils into a suspension, emulsion or solution of the fire extinguishing agent), pressing, coating (e.g. for the treatment of wooden articles), smelting, etc. When semi-finished articles are produced, the compositions according to the invention can also be used as additives in the process of manufacture.

The compositions according to the invention may be packed into fire extinguishing apparatus comprising means for discharging the composition onto a fire.

WHAT WE CLAIM IS: 1. A process for the preparation of a fire extinguishing powder or powder mixture, wherein at least one of the substances (a) or (b) or mixtures thereof: (a) alkali metal or ammonium phosphates, sulfates, hydrogenphosphates or bisulfates, (b) alkali metal borates or boric acid, is subjected to heat treatment at a temperature below 200"C together with (c) one or more reactive (as defined herein) amino or imino compounds containing at least one -NH2 or =NH group.

2. A process as claimed in claim 1 wherein said reactive amino or imino compound comprises urea, thiourea, dicyanodiamide, guanidine, melamine or semicarbazide.

3. A process as claimed in claim 1 or 2 wherein phosphoric acid is included in the mixture which is subjected to heat treatment.

4. A process as claimed in any of the preceding claims wherein ammonium carbonate and/or bicarbonate is included in the mixture which is subjected to heat treatment.

5. A process as claimed in any of the preceding claims wherein the starting materials are admixed-with the exception of any phosphoric acid-in the solid phase, and the mixture is subjected to heat treatment.

6. A process as claimed in claim 5 wherein the heat treatment is performed at 80 to 1900C.

7. A process as claimed in claim 6, wherein the heat treatment is performed at 110 to 1600C.

8. A process as claimed in any of claims 5 to 7, wherein the reactants are ground together prior to heat treatment.

9. A process as claimed in any of claims 1--4 wherein the starting materials are admixed with a solvent dissolving at least one of the reactants and then the solvent is evaporated.

10. A process as claimed in claim 9 wherein said solvent is methanol, ethanol or dimethylformamide.

11. A process as claimed in claim 9, wherein a solvent dissolving all of the starting materials is used.

12. A process as claimed in claim 11, wherein water is used as solvent.

13. A process as claimed in any of claims 9-12 wherein 5 to 85% by weight of a carrier powder which catalyses the reaction of the starting materials is added to the suspension or solution to be processed.

14. A process as claimed in claim 13 wherein said carrier powder has a mean particle size below 400 fe.

15. A process as claimed in claim 14 wherein said carrier powder has a mean particle size of 70 to 200 ,.

16. A process as claimed in any of claims 13 to 15, wherein said carrier powder

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. extinguishing foams, anti-caking agents, sprayability-increasing substances and/or substances for adjusting to an appropriate bulk density. When the process according to the invention is performed in liquid phase, it is preferred to admix 5 to 85% by weight of one or more catalyst carrier powder(s) with the solution or suspension to be processed. As catalysts, preferably substances with high specific surface area, such as aluminium oxides, silicates, pearlite, zeolites, bentonite or powdered asbestos may be used. Furthermore, other inert substances, such as barium sulfate or calcium phosphate can also be admixed with the liquid to be processed. When such additives are also used, the reaction is performed preferably by spray-drying. This operation is described in detail in our copending Application No. 13562/78. (Serial No. 1601017). The compositions according to the invention can also be applied to impart flame retardant properties to various substances. This can be done by impregnation (e.g. by immersing fabrics or foils into a suspension, emulsion or solution of the fire extinguishing agent), pressing, coating (e.g. for the treatment of wooden articles), smelting, etc. When semi-finished articles are produced, the compositions according to the invention can also be used as additives in the process of manufacture. The compositions according to the invention may be packed into fire extinguishing apparatus comprising means for discharging the composition onto a fire. WHAT WE CLAIM IS:

1. A process for the preparation of a fire extinguishing powder or powder mixture, wherein at least one of the substances (a) or (b) or mixtures thereof: (a) alkali metal or ammonium phosphates, sulfates, hydrogenphosphates or bisulfates, (b) alkali metal borates or boric acid, is subjected to heat treatment at a temperature below 200"C together with (c) one or more reactive (as defined herein) amino or imino compounds containing at least one -NH2 or =NH group.

12. A process as claimed in claim 11, wherein water is used as solvent.

16. A process as claimed in any of claims 13 to 15, wherein said carrier powder

comprises aluminium oxides, silicates, pearlite, zeolites, bentonite or powdered asbestos.

17. A process as claimed in claim 16 wherein said carrier powder is admixed with inert substances.

18. A process as claimed in claim 17 wherein said inert substances comprise barium sulfate or tricalcium phosphate.

19. A process as claimed in any of claims 9 to 18, wherein the starting materials listed in claims 1 > form 10 to 80 ó by weight of the suspension or solution in said solvent.

20. A process as claimed in any of claims 9 to 19, wherein the liquid is evaporated at a temperature of at least 1000C.

21. A process as claimed in any of claims 9 to 20, wherein the solution or suspension of starting materials in said solvent is divided into discrete droplets prior to evaporation.

22. A process as claimed in claim 21, wherein said division is performed by spray-drying.

23. A process as claimed in claim 22, wherein said solution or suspension is sprayed into a chamber into which a stream of hot gas is introduced.

24. A process as claimed in claim 23, wherein the gas leaves the chamber at a temperature of 100 to 1900C.

25. A process as claimed in claim 24, wherein the gas leaves the chamber at a temperature of 120 to 1600C.

26. A process as claimed in any of claims 13 to 25, wherein the reaction of the starting materials takes place on said surface of the 5 to 85% by weight of catalyst carrier powder which has a high specific surface area.

27. A process as claimed in any of claims 22 to 26, wherein gas is introduced into the spray drier at a temperature of 200 to 5500C.

28. A process as claimed in claim 27, wherein gas is introduced into the spray drier at a temperature of 250 to 4000 C.

29. A process as claimed in claim 27 or 28, wherein said gas is air.

30. A process as claimed in any of the preceding claims, wherein the individual reactants are used in a molar ratio of from 0.005:1 to 100:1.

31. A process as claimed in claim 30, wherein said mole ratio is selected between 0.05 and 1:1.

32. A process as claimed in any of the preceding claims, wherein phosphoric acid, urea and potassium dihydrogenphosphate are used as starting materials.

33. A process as claimed in any of claims I to 31, wherein ammonium dihydrogenphosphate and dicyanodiamide are used as starting materials.

34. A process as claimed in any of claims 1 to 31, wherein phosphoric acid, urea and borax are used as starting materials.

35. A process as claimed in any of claims 1 to 31, wherein boric acid, dicyanodiamide and urea are used as starting materials.

36. A process as claimed in any of claims 1 to 31, wherein ammonium sulfate, dicyanodiamide and ammonium carbonate are used as starting materials.

37. A process as claimed in claim 1 substantially as described herein.

38. A process as claimed in claim 1 substantially as described herein with reference to any of Examples 1--5.

39. A process as claimed in claim 1 substantially as described herein with reference to Example 6 or 7.

40. A process as claimed in claim 1 substantially as described herein with reference to Example 8 or 9.

41. A fire extinguishing powder, whenever prepared by a process as claimed in any of the preceding claims.

42. A fire extinguishing powder mixture, comprising 5 to 95% by weight of one or more fire extinguishing powders as claimed in claim 41 and 5 to 95% by weight of one or more of the following substances: (1) sodium, potassium or ammonium carbonate or hydrocarbonate, (2) sodium, potassium or ammonium phosphates, (3) sodium, potassium or ammonium sulfates, (4) borates and boric acid, (5) alkali metal halides, (6) resinous or polymeric substances, (7) starch and related substances, (8) proteins and related substances, (9) adducts of potassium carbonate, potassium hydroxide and potassium bicarbonate with urea, (10) adducts of sodium carbonate, sodium hydroxide and sodium bicarbonate with urea, (11) sodium bicarbonate-dicyanodiamide adducts, (12) potassium bicarbonate-dicyanodiamide adducts, and (13) condensation products.

43. A fire extinguishing powder mixture as claimed in claim 42 wherein said substance (6) is PVC and/or said substance (13) is one produced by condensing urea, thiourea, dicyanodiamide, guanidine, melamine, semicarbazide or a related compound with formaldehyde in the presence of phosphoric acid.

44. A fire extinguishing powder mixture as claimed in claim 42 or 43 comprising 5 to 80% by weight of a fire extinguishing agent as claimed in claim 41 or a mixture thereof, 5 to 40% by weight of a conventional flame extinguishing agent and 0 to 30% by weight of an additive.

45. A fire extinguishing powder mixture as claimed in any of claims 42--44 which includes an additive in an amount less than 15% by weight.

46. A fire extinguishing powder mixture as claimed in claim 41, which comprises 30 to 70% by weight of a fire extinguishing agent prepared according to any of claims 1 to 8 and any of claims 30--36 and 30 to 70% by weight of another fire extinguishing agent.

47. A fire extinguishing powder mixture substantially as illustrated in Example 10.

48. A flame-retardant article which comprises an effective amount of the fire extinguishing powder of claim 41 or of the fire extinguishing powder mixture of any of claims 42--47.

49. Fire extinguishing apparatus comprising a container holding the fire extinguishing powder of claim 41 or the fire extinguishing powder mixture of any of claims 42--47, and means for discharging said powder or powder mixture onto a fire.