US3179588A - Powdered fire extinguishing composition - Google Patents

Description

United States Patent 3,179,588 POWDERED FIRE EXTINGUISHING COMPOSITION Timo Siimes, Riverside, Ontario, Canada, assignor, by

mesne assignments, to General Fire Extinguisher Corporation, Detroit, Mich., a corporation of Delaware No Drawing. Filed Dec. 19, 1960, Ser. No. 76,522 Claims. (Cl. 252-2) The present invention relates to a dry powder fire extinguishing material and, more particularly, relates to a non-caking, free flowing, finely powdered fire extinguishing composition having improved water repellency characteristics, good flow characteristics and reduced hygroscopicity characteristics, and which is suitable for use in extinguishing all kinds of fires including burning liquids,

live electrical fires, fires of solid substances such as Wood, rubber, etc., as well as combustible metal fires, such as magnesium.

. Heretofore, dry fire extinguishing chemicals have been formulated for extinguishing various types of fires and a few of such compositions have found commercial acceptance. In all known cases, however, prior compositions have had one or more deficiencies such as an undesirable tendency to cake on storage, poor flow characteristics, poor resistance to caking under elevated temperature conditions, undesirable hygroscopicity characteristics, poor waterv repellency or excessive cost. It will be appreciated that since materials employed to extinguish fires are discarded after one use that it is imperative for them to be relatively inexpensive. Suitably inexpensive materials which have employed in the past include the alkali metal salts of phosphoric, boric and sulfuric acids, the alkali metal carbonates and bicarbonates and such heretofore known compositions have relied at least partially on the liberation of carbon dioxide gas to assist in extinguishing the fires. Many of the combination materials of this type have been characterized by poor flow characteristics.

In accordance with this invention,, it has now been found that the advantageous fire extinguishing characteristics of the salts of phosphoric and sulfuric acids can be utilized effectively in a dry powder fire extinguishing composition when such powders are modified to improve their flow, hygroscopicity, and caking characteristics.

The basic components of the compositions of this invention are an alkali metal sulfate and an ammonium phosphate which may be either the diammonium or monoarrimonium phosphate. The modifying ingredients include .a silicone resin, a phenolic resin, a metal stearate and mica, The compositions may optionally include one or more of the alkaline earth metal salts of phosphoric and sulfuric acid such as barium sulfate and tri-calcium phosphate. Broadly, the compositions of this invention include the above stated ingredients, in the relative proportions specified.

FORMULATION I Component: Parts by weight Diammonium or mono-ammonium phosphate 35-90 All of the above ingredients should be in finely divided ,or powder form and at least about 75% of the particles should pass through a 325 mesh Tyler. screen, and the balance are preferably smaller than 100 mesh Tyler screen, although small quantities of particles larger than 100 mesh can be tolerated.

3,l?9,583 Patented Apr. 20, 1965 the resulting composition a more efiicient extinguishing medium for any and all types of fires which may be encountered.

A- preferred formulation having somewhat better overall characteristics is set forth as Formulation II.

FORMULATION II Component: Parts by weight Diammonium phosphate 65-82 Ammonium sulfate 8-14 Barium sulfate 10-16 Phenolic resin (B-stage) 2-5 Mica 1 /2-2 /2 Tri-calcium phosphate 1 /2-2 /2 Silicone resin 1-3 Magnesium stearate 1-2 substituted for by one or more of the named materials.

In either event, the total quantity of the mixture or separate substitute ingredients should be Within'therange specified in Formulation I for mica.

When the proportion of mica, or a substitute is below about /2 part by Weight, no substantial improvement in flow characteristics is detectable and when more than about 5 parts by weight of mica, or its substitute is present, the density of the extinguishing composition becomes too low to be practical. When, however, one of the heavier materials is substituted for mica, the upper limit of 5 parts by weight may be used or even exceeded without adetriment to the flow characteristics. For example, when molybdenum disulfide or tungsten disuliide is employed as a substitute, the upper limit may satisfaotorily range as high as 10-15 parts by weight without rendering the material too light or fluffy for good flow characteristics.

The phenolic resin component serves to modify the particle form of the powdered phosphate and sulfate metal salts :by both agglomeration of the extremely fine :particles and elimination of needle shaped particles. The

.furaldehyde or acrolein but is preferably formaldehyde, which may be supplied as paraformaldehyde or hexamethyltetramine for condensation with phenol in conven- 3 tional relative proportions and employing conventional reaction conditions to form B-stage reaction products.

The zinc or magnesium stearate component functions to form a moisture protective coating which keeps the particles dry and reduces hygroscopicity, particularly during the later stages of the compounding procedures and prior to the actual charging of the dry material into a fire extinguishing apparatus. The zinc or magnesium stearate can be replaced by other metallic stearates such as barium or other alkaline earth stearates, in whole or in part. The use of portions of zinc stearate, or its substitute in quantities above about three parts, in Formulation I, tends to cause lumping and decreases the smooth flow characteristics of the powder. Below about /2 part of the stearate component, the powder is undesirably hygroscopic. Magnesium stearate is superior to zinc stearate, particularly for use on extremely high temperature fires such as combustible metal fires and is the preferred ingredient for the purposes of this invention.

The silicone resin functions to form an external shell or envelope on all of the phosphate, sulfate and agglomerated particles, and this shell is continuous and imparts substantially complete water repellency to the individual particles. The powder therefore has extremely good resistance to caking during storage. The silicone materials which may be employed in the compositions of the present invention include organo-silicones and preferably are those which may be applied to the particles in a liquid form. It is possible to satisfactorily employ gaseous silicone materials such as trimethylchlorosilane, but these materials are more troublesome to handle and apply uniformly. The silicone is preferably a trifunctional silicone which is capable of cross-linking during polymerization on the surface of the particles, or agglomerants in the composition. The silicones which are suitable react to form a cross-linked polysiloxane having the general formula x y z)n wherein R is a hydrocarbon, x, y and z are whole numbers and n is the number of structural units in the surface formed by the polysiloxane. In these materials, the ratio of x/z should be less than 2 but not less than 2/ 3. Specific examples of suitable polysiloxane-producing materials which may be employed are the alkyl trihalosilanes, including methyltrichlorosilane, amyltrichlorosilane, octadecyltrichlorosilane, cyclohexyltrichlorosilane, etc., alkenyl trihalosilanes, including allyltrichlorosilane, vinyltrichlorosilane, etc., the aryl trihalosilanes, including phenyltrichlorosilane, etc., the alkyl alkoxysilanes, including methyltriethoxysilane, mono-methyl-diethoxysilane, etc., and alkenyl alkoxysilanes, including vinyltriethoxysilane, etc. These, starting materials are hydrocarbon substituted trifunctional silicone materials and include hydrocarbon substituted trihalosilane silicone materials.

Other polysiloxane-producing materials which are satisfactory are copolymers resulting from the partial hydrolysis of any of the above listed materials with difunctional silanes, such as dimethyl-diethoxysilane, dimethyldichlorosilane and diphenyldihydroxysilane. These materials are solid commercially by Dow Corning as DC-1107, DC-1108, by Linde Air Products Co. as X-21, X-22 and General Electric as SC-87. Particularly good results have been obtained from the use of Dow Corning DC- 1107, which is understood to be similar to dimethyl silicone fluid ((CH )SiO) except that many of the methyl groups have been replaced by hydrogen ator'ns. On heat curing, the polymers cross-link at the sites of hydrogen atoms to form a coating. DC-1107 is Water-white in color, has a specific gravity between 0.995 and 1.015, a viscosity at 25 C. Of 2040 centistokes, a minimum flash point of 200 F. and a maximum acid number of 0.02.

The compositions of this invention are compounded by first mixing the ammonium phosphate, the alkali metal sulfate, the phenolic resin, and the barium sulfate, when present, in a suitable mixing apparatus such as a ribbon mixer for 5-40 minutes. Thereafter, this mixture is pulverized in an impact pulverizer which fractures the phenolic resin particles and coats the surface of the phosphate and sulfate particles with the phenolic resin. After pulverizing, the mixture is classified, or screened, and the particles are selected which pass through a 325 mesh Tyler screen and particles which are retained on a 100 mesh screen are rejected. A blend is then made of these particles in which at least by weight of the total particles pass through a 325 mesh Tyler screen. The silicone resin is then admixed with a suitable solvent to convert it into a low viscosity liquid, for example, the normal viscosity of water at room temperature, and this is accomplished by admixing the silicone resin with about 25% to about 75% by volume of trichloroethylene, carbon tetrachloride, isopropyl alcohol or the like. The classified and mixed particles are then repositioned in a ribbon mixer and, while the mixer is rotating, the silicone resin-solvent blend is added to the mixture. The addition may be accomplished by slowly pouring in the silicone resin-solid liquid or by spraying or atomizing the silicone resin-solvent blend into the ribbon mixer. Somewhat more uniform application to the particles is obtained by using the spray or atomizing technique and this procedure is preferred. The material is mixed in the ribbon mixer with the silicone resin-solvent material for approximately 10 minutes and a catalyst for the silicone resin is then applied. A- suitablecatalyst for this purpose is a blend of 30 parts by weight of tin octoate (16% active ingredients) in admixture with 70 parts by weight of trichloroethylene. Other lrnown catalysts may be employed, such as iron octoate, Zinc 2-ethylhexoate, tin oleate, zinc naphthenate or triethanolamine and in any case an amount of catalyst to provide about 2% metal, based on the silicone solids in the diluted silicone resin solution, should be added. The proportion of trichloroethylene or other suitable solvent which is employed is not critical, but a sufiicient quantity should be employed to give a fairly thin liquid which will uniformly coat the previously coated particles. The catalyst may be applied in the same manner in which the silicone resin solvent material is applied and, for this purpose, application in the atomized spray form is also preferred. The material is tumbled in the mixer for 10-15 minutes and is then dried. During drying, the material is preferably slowly rotated and the temperature in the dryer is raised slowly to first remove the excess solvent and thereafter to effect curing of the silicone and the phenol formaldehyde resin coating on the surface of the particles. The mixture should be raised to a temperature of about 285 to about 310 F. and adequate curing is obtained in about 15 minutes to an hour with excellent results being obtained from curing for about 30 minutes. After curing, the material is taken out, again positioned in a ribbon mixer and the additional components, mica, zinc stearate, and tri-calcium phosphate are added to the mixer while the powder is still hot, preferably in the range of about 260 F.-275 F.

The addition of the zinc stearate to the hot powder assures uniform distribution of the zinc stearate throughout the mass and this mixing step is satisfactorily accomplished in about 20-30 minutes. After this final mixing, the blended materials are removed from the ribbon mixer, allowed to cool, and if desired, are screened to remove large particles, for example, particles larger than will pass through a 60 mesh Tyler screen. The following examples illustrate the method of compounding and the use of the compositions of this invention in greater detail.

Example I 87 parts of diammoniurn phosphate, 7 parts of ammonium sulfate and 8 parts of barium sulfate, 0.75 part of a phenol formaldehyde, B-stage resin, Durez resin No. 15,546, by weight, were added to a ribbon mixer and mixed for 10 minutes. Thereafter, the mixture was positioned in an impact pulverizer and screened through a 325 mesh screen.

A silicone resin-solvent mixture was prepared by admixing Dow Corning DC-1107, silicone fluid with trichloroethylene in a 50-50 mixture. With the mixed diammonium phosphate and ammonium sulfate particles rotating in the ribbon mixer, sufiicient of the silicone resin-solvent blend was atomized on the particles to equal 2 parts, by weight. The mixing was continued for about minutes and thereafter a catalyst for the silicone resin was added in the same manner. The catalyst blend contained 30 parts, by weight, of tin octoate (16% active ingredients) in admixture with 70 parts, by weight, of trichloroethylene and suflicient of this catalyst blend was added to represent A part, by weight, of the entire composition. The material was tumbled in the mixer for minutes and then slowly dried, and thereafter cured at 300. F. for minutes. While the material was still hot, and at a temperature in the range of 260 F.-275 F. and while rotating in the ribbon mixer, 2 parts of finely powdered mica, 2 parts of magnesium stearate and 2 parts of tri-calcium phosphate were added thereto and blended for 25 minutes. After cooling, the product was passed through a 60 mesh Tyler screen.

15 lbs. of this powdery composition were placed in a standard dry chemical fire extinguisher, pressurized with air at 170 psi and discharged on a wood crib Class A fire, in accordance with Underwriters Laboratories specifications. The powder was uniformly discharged and the fire was completely extinguished in 9 seconds.

Another standard dry chemical fire extinguisher was filled with 15 lbs. of the above powdery composition and pressurized in the same manner set forth above, and discharged on a Class B fire of white naphtha gasoline, in accordance with Underwriters Laboratories specifications. The fire was completely extinguished in an average time of 12 seconds in a series of such applications.

The powdery composition was tested in the extinguishing of a Class C fire for electrical conductivity in accordance with Underwriters Laboratories specifications and found to be non-conductive.

In another test, 20 lbs. of the above powdery material was placed in a standard dry chemical fire extinguisher and discharged on a fire of 15 lbs. of magnesium chips. The fire was extinguished by the use of 17 lbs. of the above powdery composition.

Example II A dry powder composition was prepared, using the same procedure as that described in detail in Example I, to contain 85 parts diammonium phosphate, 12 parts ammonium sulfate, 2 parts mica, 1 part magnesium stearate and 2 parts Dow Corning DC-1l07 silicone resin and 0.75 part phenol formaldehyde resin.

A standard dry chemical fire extinguisher was loaded with 15 lbs. of this powdery composition, placed under 170 p.s.i. air pressure and discharged on a wood crib Class A fire in accordance with Underwriters Laboratories specifications. The fire was completely extinguished in 16 seconds.

Example III A dry powder composition was prepared, having an identical composition to that set forth in Example I and different in the respect only that the silicone resin was applied to the mixed diammonium phosphate and ammonium sulfate particles coated with the phenol formaldehyde resin by introducing trimethylchlorosilane in heated vapor form to the interior of the rotating ribbon mixer.

An inspection of the resulting product and testing of it in a manner identical to that set forth in Example I showed that the material had comparable flow properties, water repellency properties and resistance to moisture pick-up in the atmosphere to that of the product of Example I. When the material was used to extinguish Class A, B and C fires, as set forth in Example I, substantially similar results were obtained in each case.

What is claimed is: 1

l. A dry powdery fire extinguishing composition which consists essentially of, by weight, -90 parts an alkali metal phosphate, 5-40 parts an alkali metal sulfate, /2-5 parts mica, /2-3 parts of a stearate selected from the group consisting of zinc, magnesium and alkaline earth metal stearates, /2-6 parts a silicone resin and /z-7 parts of a B-stage phenol aldehyde condensation product, said composition being in the form of discrete particles at least 75% of which are smaller than 325 Tyler screen mesh, said condensation product being present as a surface coating on said particles and said silicone resin overlying said condensation product surface coating.

2. A dry powdery fire extinguishing composition which consists essentially of, by weight, 65-82 parts an alkali metal phosphate, 8-14 parts an alkali metal sulfate, /2-2 /z parts mica, 1-2 parts of a stearate selected from the group consisting of Zinc, magnesium and alkaline earth metal stearates, 1-3 parts a silicone resin and 2-5 parts of a B-stage phenol aldehyde condensation product, said composition being in the form of discrete particles at least 75% of which are smaller than 325 Tyler screen mesh, said condensation product being present as a surface coating on said particles and said silicone resin overlying said condensation product surface coating.

3. A dry powdery fire extinguishing composition which consists essentially of, by weight, 35-90 parts an alkali metal phosphate, 5-40 parts an alkali metal sulfate, /2-5 parts mica, up to 30 parts barium sulfate, up to 5 parts tri-calcium phosphate and /2-3 parts of a stearate selected from the group consisting of zinc, magnesium and alkaline earth metal stearates, /z-6 parts a silicone resin and /2-7 parts of a B.-stage phenol aldehyde condensation product, said composition being in the form of discrete particles at least 75% of which are smaller than 325 Tyler screen mesh, said condensation product being present as a surface coating on said particles and said silicone resin overlying said condensation product surface coating. V

4. A-dry powdery fire extinguishing composition which consists essentially of, by weight, 65-82 parts an alkali metal phosphate, 8-14 parts an alkali metal sulfate, /2-2 /z parts mica, 10-16 parts barium sulfate, 1 /2-2 /z parts tri-calciurn phosphate, 1-2 parts of a stearate selected from the group consisting of zinc, magnesium and alkaline earth metal stearates, 1-3 parts a silicone resin and 2-5 parts of a B-stage phenol aldehyde condensation product, said composition being in the form of discrete particles at least 75 of which are smaller than 325 Tyler screen mesh, said condensation product being present as a surface coating on said particles and said silicone resin overlying said condensation product surface coating.

5. A method of combatting fires of burning combustible materials which comprises applying to said burning combustible materials, a solid, dry chemical fire extinguishing composition consists essentially of, by weight, 35-90 parts an alkali metal phosphate, 5-40 parts an alkali metal sulfate, /2-5 parts mica, /2-3 parts of a stearate selected from the group consisting of zinc, magnesium and alkaline earth metal stearates, /26 parts a silicone resin and /2-7 parts of a B-stage phenol aldehyde condensation product, said composition being in the form of discrete particles at least 75 of which are smaller than 325 Tyler screen mesh, said condensation product being present as a surface coating on said particles and said silicone resin overlying said condensation product surface coating.

6. A method of combatting fires of burning combustible materials which comprises applying to said burning combustible materials, a solid, dry chemical fire extinguishing composition consists essentially of, by weight, 65-82 parts an alkali metal phosphate, 8-14 parts an alkali metal sulfate, /2-2' /2 parts mica, 1-2 parts of a stearate selected from the group consisting of zinc, magnesium and alkaline earth metal stearates,- 1-3 parts a silicone resin and 2-5 parts of a B-stage phenol aldehyde condensation product, said composition being in the form of discrete particles at least 75% of which are smaller than 325 Tyler screen mesh, said condensation product being present as a surface coating on said particles and said silicone resin overlying said condensation product surface coating.

7. A method of combatting fires of burning combustible materials which comprises applying to said burning combustible materials, a solid, dry chemical fire extinguishing composition consists essentially of, by weight, 35-90 parts an alkali metal phosphate, 5-40 parts an alkali metal sulfate, /2-5 parts mica, up to 30 parts barium.

sulfate, up to 5 parts tri-calcium phosphate and /23 parts of a stearate selected from the group consisting of zinc, magnesium and alkaline earth metal stearates, /2-6 parts a silicone resin arid /2-7 parts of a B-stage phenol aldehyde condensation product, said composition being in the form of discrete particles at least 75 of which are smaller than 325 Tyler screen mesh, said condensation product being present as a surface coating on said particles and said silicone resin overlying said condensation product surface coating.

8. A method of combatting fires of burning combustible materials which comprises applying to said burning combustible materials, a solid, dry chemical fire extinguishing composition consists essentially of, by weight, 65-82 parts an alkali metal phosphate, 8-14 parts an alkali metal sulfate, /2-2 /2 parts mica, 10-16 parts barium sulfate, 1 /2-2 /2 parts tri-calcium phosphate, 1-2 parts of a stearate selected from the group consisting of Zinc,'magnesium and alkaline earth'metal stearates, 1-3 parts a silicone resin and 2-5 parts of a B-stage phenol aldehyde condensation product, said composition being in the form of discrete particles at least 75 of which are smaller than 325 Tyler screen mesh, said condensation product being present as a surface coating on said particles and said silicone resin overlying said condensation product surface coating.

9. A.niethod of making adry powdery: fire extinguishing composition which comprises the steps of (1), mixing, in parts by Weight, 35-90 parts of an alkali metal phosphate, 5-40 parts an alkali metal sulfate and /2 -7 parts a phenol formaldehyde resin, (2), screening the resulting mixture and discarding the particles which are retained on a mesh screen, (3), adding to the retained particles from step (2) about /2-6 parts of a silicone resin in a solvent while said particles are in motion, (4), adding a catalyst in an organic solvent to provide a metal concentration of about 2%, by Weight of the silicone resin solids, said metal being selected from the group consisting of tin, iron andzinc and being added in the form of a salt thereof and (5) slowly raising the temperature within the range of about 285 F. to about 310 F. to remove the excess solvent and to effect a cure of the silicone and phenol formaldehyde resin in said mixture.

10. A method in accordance with claim 9 wherein the product of step (5) is admixed, while at a temperature in the range of about 260 F.-275 F. with about /2-5 parts of mica, /2-3 parts of a stearate selected from the group consisting of zinc, magnesium and alkaline earth metal stearates, and about 1 /2-2 /2 parts tri-calcium phosphate.

References Cited by the Examiner UNITED STATES PATENTS 2,588,366 3/52 Dennett 260-291 2,647,892 8/53 La Brie et al. 252-384 X 2,734,002 2/56 Schoeld et al. 260-57 X 2,736,718 2/56 Webber 260-57 X 2,757,152 7/56 Solomon 260-465 X 2,866,760 12/58 Haessler et al. 252-383 2,881,138 4/59 Reiss 252-7 2,901,428 8/59 Schulenburg 252-7 3,017,348 1/62 Steppe et al. 252-7 X FOREIGN PATENTS 156,735 5/54 Australia. 815,712 7/59 Great Britain.

JULIUS GREENWALD, Primary Examiner.

Claims (2)

1.A DRY POWDERY FIRE EXTINGUISHING COMPOSITION WHICH CONSISTS ESSENTIALLY OF, BY WEIGHT, 35-90 PARTS AN ALKALI METAL PHOSPHATE, 5-40 PARTS AN ALKALI METAL SULFATE, 1/2-5 PARTS MICA, 1/2-3 PARTS OF A STEARTE SELECTED FROM THE GROUP CONSISTING OF ZINC, MAGNESIUM AND ALKALINE EARTH METAL STEARATES, 1/2-6 PARTS A SILICONE RESIN AND 1/2-7 PARTS OF A B-STAGE PHENOL ALDEHYDE CONDENSATION PRODUCT, SAID COMPOSITION BEING IN THE FORM OF DISCRETE PARTICLES AT LEAST 75% OF WHICH ARE SMALLER THAN 325 TYLER SCREEN MESH, SAID CONDENSATION PRODUCT BEING PRESENT AS A SURFACE COATING ON SAID PARTICLES AND SAID SILICONE RESIN OVERLYING SAID CONDENSATION PRODUCT SURFACE COATING.

9. A METHOD FO MAKING A DRY POWDERY FIRE EXTINGUISHING COMPOSITION WHICH COMPRISES THE STEPS OF (1), MIXING, IN PARTS BY WEIGHT, 35-90 PATS OF AN ALKALI METAL PHOSPHATE, 5-40 PARTS AN ALKALI METAL SULFATE AND 1/2-7 PARTS A PHENOL CORMALDEHYDE RESIN, (2) SCREENING THE RESULTING MIXTURE AND DISCARDING THE PARTICLES WHICH ARE RETAINED ON A 100 MESH SCREEN, (3), ADDING TO THE RETAINED PARTICLES FROM STEP (2) ABOUT 1/2-6 PARTS OF A SILICONE RESIN INA SOLVENT WHILE SAID PARTICLES ARE IN MOTION, (4), ADDING A CATALYST IN AN ORGANIC SOLVENT TO PROVIDE A METAL CONCENTRATION OF ABOUT 2%, BY WEIGHT OF THE SILICONE RESIN SOLIDS, SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF TIN, IRON AND ZONC AND BEING ADDED IN THE FORM OF A SALT THEREOF AND (5) SLOWING RAISING THE TEMPERATURE WITHIN THE RANGE OF ABOAUT 285*F. TO ABOUT 310*F. TO REMOVE THE EXCESS SOLVENT AND TO EFFECT A CURE OF THE SILICONE AND PHENOL FORMALDEHYDE RESIN IN SAID MIXTURE.