EP0212017B1

EP0212017B1 - Thixotropic fire suppressant composition containing carboxy polymer gelling agent

Info

Publication number: EP0212017B1
Application number: EP19850305735
Authority: EP
Inventors: William B. Tarpley; Gerald L. Ruscitto
Original assignee: CEASE FIRE Corp
Current assignee: C. F. VENTURE CORP.; CEASE FIRE CORPORATION
Priority date: 1983-06-21
Filing date: 1985-08-13
Publication date: 1990-01-17
Anticipated expiration: 2005-08-13
Also published as: JPH0214857B2; AU559312B2; EP0212017A1; JPS6244270A

Description

The present invention relates to a fire-suppressing composition, containing an ammonium salt in powder form in a non-polar liquid, which is thixotropically gelled by a carboxy polymer gelling agent.
Liquefied gases have been used to disseminate fine powders including pesticides, medicinal products, cosmetic products and fire extinguishing powders. To prevent packing and clogging of these powders, gelling agents such as "CAB-O-SIL" (Regd. Trademark of Cabot Corporation) have been used. Gelled liquid fire-suppressing suspensions, which may include ammonium salts, are disclosed in US-A 4 226 727 and US-A 4 234 432.
The aforesaid patents disclose the use of the following gelling agents: pyrogenic silica, montmorillonite clay, oleophilic vinyl addition polymer, pyrogenic titanium dioxide, aluminium or magnesium salts of fatty acids, colloidal attapulgite clay, colloidal quaternized bentonite, sub-micron magnesium oxide and sub-micron potassium bicarbonate.
Ammonium salts are useful fire-suppressing agents in powdered form. It has been found that a suspension of such powders having improved stability results from the addition of a carboxy polymer in small amounts as a gellant.
According to the invention, a non-aqueous thixotropically-gelled fire-suppressing composition is provided, which comprises a non-polar liquid, a carboxy polymer gelling agent in an amount effective to gel the liquid thixotropically and an ammonium salt. The composition may include as further additives either a viscosity modifier functional at low temperatures, a drying agent, or both.
The present invention also pertains to a method of extinguishing fires by applying the aforesaid composition.
Unless specified otherwise, all percentages stated herein are understood to be by weight.
A suspension of ammonium salts in powder form in a gelled non-polar liquid results from the present invention. A carboxy polymer gelling agent is used to form the suspension, which is thixotropic and exhibits excellent stability. A preferred feature of the invention resides in the provision of the composition in a form which contains by weight 0.5%-8.0% of the gelling agent, the balance being gelled liquid and ammonium salt.
The gelled liquid composition of the present invention preferably includes one or more fire-quenching liquids in combination with one or more fire-quenching liquefied gases and/or one or more overpressur- ized gases. If a fire-quenching liquefied gas (e.g. trifluorobromomethane) is used, the fire-quenching liquid may be omitted.
The gelled liquid composition must be capable of filling the interparticulate spaces in the suspension under pressure, i.e., when the suspension is at rest. Preferably, it is capable of expanding upon release of pressure to a gaseous vapour or droplet cloud carrying the fire-extinguishing particles. Finally, the gelled liquid composition must provide some measure of fire-quenching capability.
Fire-quenching liquids useful in the gelled liquid composition include, but are not limited to, the following: methylene bromide, methyl iodide, tetrafluorodibromoethane, trifluorotrichloroethane, fluorotrichloromethane, chloroform, bromoform, carbon tetrachloride and the like.
Liquefied gases which may be used according to the present invention include, but are not limited to, the following: trifluorobromomethane, difluorochlorobromomethane, perfluoropropane, perfluorocyclobutane, dichlorodifluoromethane, tetrafluoromethane, methyl bromide, trifluoromethane, trifluorochloromethane, hexafluoroethane and the like. Several of these gases have been designated as Halon materials "Halon" is the National Fire Protection Association designation for halogenated fire-extinguishing materials. Halon products are available from Great Lakes Chemical Company, DuPont Company, and ICI Americas, Inc. Halon 1211 (difluorochlorobromomethane), Halon 1301 (trifluorobromomethane) and mixtures thereof are useful. A mixture comprising 50% to 60% difluorochlorobromomethane and 40% to 50% trifluorobromomethane is particularly useful at low temperatures.
Overpressurizing gases useful in the gelled liquid component include nitrogen, carbon dioxide, helium, argon and the like.
In accordance with a preferred embodiment of the composition of the invention, this contains 70%-30% by weight of gelled liquid and 30% to 70% by weight of solids component containing the ammonium salt and the carboxy polymer gelling agent, the gelling agent itself constituting 0.5% to 8.0% by weight of the composition. The liquefied gases preferably comprise a blend of 50^%~60% difluorochloro-bro- momethane and 40%-50% trifluorobromomethane, while the gelling agent is a carboxy vinyl polymer and 35%-50% monoammonium phosphate is present.
The solids component, contains one or more powdered ammonium salts and one or more carboxy polymer gelling agents. The concentration of the gelling agent in the composition is preferably from 0.5% to 8.0% by weight. Nonlimiting examples of suitable powdered ammonium salts include mono-, di-, and triammonium phosphate, ammonium calcium phosphate sodium ammonium phosphate, ammonium sulphate, ammonium chloride and ammonium aluminium sulphate. Monoammonium phosphate (MAP) powder is particularly useful. ABC dry chemical fire-extinguishing powder, which is 90 to 95 percent MAP, is preferred.
Other fire-suppressing powders may be used in conjunction with one or more ammonium salts. Such powders include sodium bicarbonate, potassium bicarbonate, urea adducts of potassium bicarbonate such as are available from ICI under the Regd. Trademark "MONAX", sodium chloride, potassium chloride, and the like. Where a non-fire-suppressing agent is selected as the powdered ammonium salt, an auxiliary fire-suppressing powder is necessary.
The gelling agent is a polymer containing carboxyl groups in the free acid form. Excluded from the present invention are polymeric materials wherein carboxyl groups are substantially in neutralized or salt form. We have found these agents to be inadequate unless they undergo conversion to the free acid.
Included in the present invention are polymers which are functional derivatives of free polycarboxylic acids, e.g., polyacrylamides, wherein the functional groups have been substantially hydrolyzed to the free acid form. As an illustration, we have found that the 40% hydrolyzed polyacrylamide available from National Starch & Chemical Co. under the Regd. Trademark "POLYHALL 40-J" will satisfactorily gel the nonpolar liquid component of the present composition, in the presence of an ammonium salt. Forty percent of the nitrile groups in this polyacrylamide are hydrolyzed to the corresponding acid function. On the other hand, "POLYHALL 33-J", wherein only 33% of the nitrile groups are hydrolyzed, forms a much weaker suspension. For polymers having groups which are functional derivatives of carboxyl, those skilled in the art will be able to readily determine by routine experimentation the extent to which such groups must be first converted to the free acid form for gellation of the nonpolar liquid to occur.
The carboxy polymer acids useful in the present invention include carboxy vinyl polymers, such as those available from B.F. Goodrich under the "CARBOPOL" trademark; polysaccharides having pendant free carboxyl groups such as alginic acid and guar derivatives; hydrolyzed or partially hydrolyzed polyacrylamides such as "POLYHALL 40-J" (40% hydrolyzed); synthetic resins containing free carboxyl groups, such as the ionic exchange resins which are co-polymers or methacrylic acid and divinyl benzene available from Rohm & Haas Co., Philadelphia, Pa. under Regd. Trademark "AMBERLITE IPC-50". The "CARBOPOL" polymers used in the invention have an average equivalent weight of about 76±4, a molecular weight of from about 450,000 to about 4,000,000, and have the general structure:
(sold by B.F. Goodrich under the trademark "CARBOPOL" for water soluble resins). These polycarboxylated vinyl resins have Brookfield viscosities (cP) as measured on a Brookfield viscometer (model RVF or RVT) at approximately 25_°C in a range of from about 4,000 to 60,000 as measured on a 0.5% solution, and from about 3,000 to 7,000 as measured on a 1% solution. Particular "CARBOPOL" polymers have viscosities of from about 30,500 to 39,400 (average molecular weight about 3,000,000); 40,000 to 60,000 (average molecular weight about 4,000,000); and 4,000 to 11,000 (average molecular weight about 1,250,000) measured on a 0.5% solution; and 3,000 to 7,000 (average molecular weight about 750,000) measured on a 1% solution. "CARBOPOL" 941 has a Brookfield viscosity (cP) at 25_°C, 0.5% solution, of 4,000-11,000 (average molecular weight about 1,250,000). "CARBOPOL" 934 has a Brookfield viscosity at 25_°C, 0.5% solution, of 30,500-39,400 (average molecular weight about 3,000,000). "CARBOPOL" 941 and "CARBOPOL" 934 are particularly suitable. Other polymeric materials having free carboxyl groups, or having groups functionally equivalent to carboxyl which are readily convertible to the free acid form are known to those skilled in the art, and may be employed in the present invention. We have found that many excellent thickening and/or suspending agents which lack the free carboxyl function do not gel non-polar liquids in the presence of ammonium compound.
Without wishing to be bound by any theory or mechanism of action, we believe the suspending powder exerted over non-polar liquids by the carboxy polymer gelling agents described is due to a synergistic interaction between the free carboxyl function and the ammonium compound. Where the gelling agent was mixed with difluorochlorobromomethane, or a blend of difluorochlorobromomethane and trifluorobro-. momethane in the absence of ammonium compound, no gel formed. The gelling agent was insoluble in the liquid, and floated to the surface.
The preferred gelling agents are carboxy vinyl polymers. "CARBOPOL" 934 and 941 are particularly suitable. "CARBOPOL" is offered by the manufacturer to thicken and suspend insolubles, and to stabilize emulsions, primarily in aqueous systems. Where "CARBOPOL" is to be used with less polar liquids, the manufacturers recommend the addition of an amount of long fatty amine as a gelling adjuvant. We have found that "CARBOPOL" is ineffective as a gelling agent for the liquefied halogenated hydrocarbon gases which form the liquid component of the present composition, even in the presence of the recommended gelling adjuvants. What is surprising is that "CARBOPOL" will gel such non-polar liquids in the presence of an ammonium compound.
It has been discovered that if a carboxy polymer is added to the liquid component with an ammonium compound such as monoammonium phosphate (in the form of ABC powder), it gels the relatively non-polar fire-extinguishing liquids and liquefied gases constituting the gelled liquid component, without the need for polar gelling adjuvants. The resulting suspension is thixotropic and displays excellent performance as a fire-extinguishing composition, even after extended storage. Satisfactory storage stability has been demonstrated using "CARBOPOL" up to 18 months. Powdered MAP did not pack or clog but remained in suspension forming a thixotropic composition which could be easily disseminated. MAP loadings of 40 to 66 weight percent have been possible with 0.5 to 4.0 weight percent "CARBOPOL".
A composition of the present invention was prepared according to Example 1, containing 45% solids and 55% of the liquefied gases difluorochlorobromomethane and trifluorobromomethane.

Example 1

41.5% monoammonium phosphate
3.5% "CARBOPOL" 941
44.0% difluorochlorobromomethane
11.0% trifluorobromomethane

The above proportions of MAP, gellant and liquefied gas provided excellent fire extinction, as determined in a standard Underwriters Laboratory 2-B-rated fire test (0.4645 m2 (square feet) of burning heptane). The fire was extinguished in 3.5 seconds, using approximately 216 grams or 50 weight percent of extinguisher contents.
Performance declined as the weight percent solids in the composition was increased above 45%.. More extinguishant was needed to extinguish the same size fire, until a concentration of solids was reached that was so high that expulsion of the extinguisher contents by the action of the liquefied gases was prevented. As the level of solids was decreased below 45% (and the proportion of liquefied gas in the composition proportionately increased), the extinguisher began to act as a conventional Halon-type extinguisher, until it was unable to extinguish a 2-B rated fire.
A typical composition using a further fire extinguishing powder (KHC0₃) in addition to an ammonium salt is as follows:

Example 2

10% monoammonium phosphate
30% KHC0₃
4% "CARBOPOL" 941
44.8% difluorochlorobromomethane
11.2% trifluorobromomethane

The following experiments were performed, demonstrating the increased fire-extinguishing effectiveness of the present gelled concentrate composition in comparison with Halon or monoammonium phosphate, when used alone.

Example 3

To hundred grams of monoammonium phosphate (ABC powder) in nitrogen pressurized to 689.5 kN/m² (100 p.s.i) was released on an Underwriters Laboratory 1-B-rated fire (0.4645 m² (2.5 square feet) of burning heptane) (with 30 seconds pre-burn). The fire was not extinguished, despite expulsion of 95 weight percent of the contents of the containing vessel onto the fire.

Example 4

In extinguishing hardware identical to that used in Example 3, 200 grams of a blend containing 80% difluorochlorobromomethane and 20% trifluorobromomethane, by weight, were released on an identical fire. The fire was not extinguished, despite expulsion of 95 weight percent of the contents of the containing vessel onto the fire.

Example 5

In extinguishing hardware identical to that used in Examples 3 and 4, 200 grams of the composition according to Example 1 were released on an identical fire. The fire was extinguished upon expulsion of 71 weight percent of the vessel contents.
The synergistic interaction between MAP and various carboxy polymer gelling agents was demonstrated according to the following procedure.

Example 6

1.8 grams of "CARBOPOL" 941 were ground in a ball mill to a fine particle size and dry-mixed with 50 grams of MAP. The mixture was added to 78 grams of difluorochlorobromomethane, shaken and allowed to stand overnight. A uniform gell suspension was observed the next day.
Other agents were tested according to the procedure of Example 6, except that 2x-3x the amount of gelling agent was necessary to induce an initial suspension. The results appear in Table 1 below. A minus sign (-) indicates the complete absence of a suspension, where the MAP settled into a large mass at the bottom of the vessel. The mass resisted resuspension upon shaking. A plus sign (+) indicates gellation, with some settling of MAP overnight which was easily resuspended with only one or two gentle shakes of the hand. A double plus sign (++) indicates the presence of a highly uniform gell structure with either no settling or very slight observable settling of MAP. In the following Table 1, product names in capital letters indicated Regd. Trademarks and are followed by the names of the suppliers of the respective products.
Although "CARBOPOL 942" did not succeed in forming an acceptable suspension of ammonium alginate in difluorochlorobromomethane (Example 13), it is believed that the negative result is due not to the absence of interaction between ammonium alginate and the carboxyl vinyl gelling agent, but rather because of the hard, coarse nature of the sodium alginate powder, which was found very difficult to grind to the appropriate fine particle size necessary for suspension.
The ammonium salts used according to the present invention are hygroscopic. Monoammonium phosphate, in particular, readily absorbs moisture from the atmosphere, thereby adding water to the composition. The present of water is undesirable for two reasons. First, water promotes the formation of HBr and HF. At elevated temperatures, Halon materials will break down and react with any free water present to from these acids readily. HF and HBr are highly corrosive, and attack the metal components of the delivery vessel. Second, liquefied gases such as the Halon materials have a refrigerating effect. Any free water present in the composition readily freezes to form ice which clogs the delivery system. To protect against the formation of acid and ice, it is necessary that free water be kept from the composition.
Depending on the particular application, the composition therefore may include a drying agent in an amount sufficient to sequester any moisture in the system. Preferably, the drying agent is a non-corrosive material which will not harm the metal components of the delivery vessel. Suitable drying agents comprise metal salts and oxides. Molecular sieves may also be used for this purpose. Other drying agents are known to those skilled in the art. We have found that sodium sulphate, calcium sulphate, calcium chloride and calcium oxide are effective. Calcium oxide is preferred because of its secondary effect as a neutralizing agent in counteracting acids which may be generated through the breakdown of Halon materials.
Depending on the application, the fire-suppressing composition of the present invention may also include at least one viscosity modifier in an effective amount. Ideally, the viscosity modifier acts to prevent separation of the gel at temperatures as low as -40_°C (-40_°F), and prevents excessive thinning of the composition at temperatures up to 48_°C (120_°F). Chlorides of sodium, magnesium, aluminium and potassium may be used. Other metal salts may be used.
The same salt may function as both drying agent and viscosity modifier.
The gelled liquid compositions according to the present invention may be prepared by first mixing the various solid components with an intensive mixer, then adding the liquid component, with continued mixing. Alternatively, the solid component may be added to the liquid component, with intensive mixing.
The following Examples 14-24 are set forth to illustrate the present invention wherein the gelled liquid component comprises a mixture of difluorochlorobromomethane and trifluorobromomethane. Amounts of ingredients are expressed in grams.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims

1. A non-aqueous thixotropically-gelled fire-suppressing composition, characterized in that it comprises:

(a) a non-polar liquid;

(b) a carboxy polymer gelling agent in an amount effective to gel the liquid thixotropically; and

(c) an ammonium salt.

2. A composition according to claim 1, wherein the ammonium salt is selected from monoammonium phosphate, diammonium phosphate, triammonium phosphate, ammonium calcium phosphate, sodium ammonium phosphate, ammonium sulphate, ammonium chloride and ammonium aluminium sulphate.

3. A composition according to claim 1 or 2, wherein the gelling agent is selected from carboxyl vinyl polymers, polysaccharides, polyacrylamides, and synthetic resins having pendant free carboxyl groups or functional equivalents thereof which have been converted to the free acid to the extent necessary to induce gellation of the non-polar liquid.

4. A composition according to any preceding claim, which contains 70% to 30% by weight of gelled liquid and 30% to 70% by weight of solids component containing the ammonium salt and the carboxy polymer gelling agent, the gelling agent itself constituting 0.5% to 8.0% by weight of the composition.

5. A composition according to any preceding claim wherein a further additive is included, selected from drying agents, viscosity modifiers functional at low temperature and combinations thereof.

6. A composition according to any preceding claim, which includes a fire-suppressing powder selected from sodium bicarbonate, potassium bicarbonate, urea adducts of potassium bicarbonate, sodium chloride and potassium chloride.

7. A composition according to any preceding claim, which includes at least one fire-quenching liquid and at least one overpressurizing gas selected from nitrogen, carbon dioxide, helium and argon.

8. A composition according to any of claims 1-6, which includes at least one fire-quenching liquefied gas as the gelled liquid.

9. A composition according to claim 8, which includes at least one fire-quenching liquid and at least one fire-quenching liquefied gas as the gelled liquid.

10. A composition according to claim 7 or 9, wherein the fire-quenching liquid is selected from methylene bromide, methyl iodide, tetrafluorodibromoethane, trifluorotrichloroethane, fluorotrichloromethane, chloroform, bromoform and carbon tetrachloride.

11. A composition according to claim 8 or 9, wherein the fire-quenching liquefied gas is selected from trifluorobromomethane, difluorochlorobromomethane, perfluoropropane, perfluorocyclobutane, dichlorodifluoromethane, tetrafluoromethane, methyl bromide, trifluoromethane, trifluorochloromethane and hexafluoroethane.

12. A composition according to claim 11, wherein the gelled liquid is a blend of difluorochlorobromomethane and trifluorobromomethane.

13. A composition according to claim 12, wherein a blend of 50% to 60% difluorochlorobromomethane and 40% to 50% trifluorobromomethane is present.

14. A composition according to claim 12 or 13, wherein a carboxy vinyl polymer is present as the gelling agent.

15. A composition according to claim 14, which comprises 70%-30% of a liquefied gas which is a blend of 50%-60% difluorochlorobromomethane and 40%-50% trifluorobromomethane, 0.5%-8.0% of carboxy vinyl polymer gelling agent and 35%-50% monoammonium phosphate.

16. A composition according to claim 3 or 14, wherein the gelling agent is a polycarboxylated vinyl polymer having an average equivalent weight of 76±4, a molecular weight of 450,000 to 4,000,000, a Brookfield viscosity (cP) in the range from 4,000 to 60,000 as measured on a 0.5% solution and a Brookfield viscosity (cP) in the range from 3,000 to 7,000 as measured on a 1% solution, the polycarboxylated vinyl polymer having the general structure

and being present in an amount sufficient to gel the liquid.

17. A composition according to claim 16, wherein the polycarboxylated vinyl polymer has a Brookfield viscosity at 25_°C, as measured on a 0.5% solution, of 4,000-11,000 centipoise for an average molecular weight of about 1,250,000.

18. A composition according to claim 16, wherein the polycarboxylated vinyl polymer has a Brookfield viscosity at 25_°C, as measured on a 0.5% solution, of 30,500-39,400 centipoise for an average molecular weight of about 3,000,000.

19. A method of fire suppression, characterized by the application of a composition according to any of the preceding claims.