US2937990A - Extinguishing agent for combustible metals - Google Patents

Description

I I Un te under conditions of a fire.

- cooling the burning mass. During the extinguishing'proc I 2,937,990 r EXTINGUISHING AGENT FOR ,COMBUSTIBLE William R. WainochdMeriomine, Mich, assignor. to

, Ansul Chemical Company, Marinette, Wis.,,a corpora- 'tion'of Wisconsin I No Drawing. Filed Sept. 28,-i9ss', ser. No: saints 8 claims. or. 252- This inventionrelates to a finely divided composition suitable for extinguishing fires in combustiblemetals and certain other substances. The invention is especially suitable for extinguishing fires in magnesium, sodium, potas siurn, calcium, lithium, uranium and their alloys.

. The increased use of combustible metals such as sodium, potassium, magnesium, and lithium has increased the'needfor a non-combustible extinguishing agent for thesemetals which will flow throughihose or pipe and can be applied in a controlled stream from a nozzle. At the present time, there areavailable a number of materials-which will extinguish fires in combustible metals These have'the disadvantages of being combustible them I selves or of being incapable of bein'g'conveyedrthrough hose and pipe. Combustible agents are usually high flash point liquids which will not react with the-burningmetal ess a portion of the extinguishing agent will be ignited by the ,burning metal, but if the quantity of agentused s great enough the cooling action will be sufiicient to extinguish the fire. It enough agent is not available a secondary flammable liquid fire will develop in the combustible' extinguishing agent.

I I 7 Because these combustible agents can increase the intensity of a metal fire their use is limited largely to small fires.

Non-combustible agents which cannot be applied through pipe or hose are also restricted in use on, com- I bustible metal fires. These materials are applied either by shoveling or by pouring from pails. In large fires or fires where presence of moisture causes spattering of the burning metal considerable danger is involved in appreaching close enough to the fire to apply the agent in either of these ways. In a confined space closevenou'gh approach for extinguishment could be difiicult without specialequipment for protectionagainst. the fumes produced by burning metal. The lack of a controlled stream would also make an extinguishing. agent diflicult to apply Overhead or in small spaces under or around equipment.

These disadvantages are overcome. by my present invention which provides an extinguishing composition which is non-combustible and can be applied through pipe or hose-in a controlled stream for extinguishing fires in combustible metals. By proper design of the 1 equipment my'composition can be applied at a considerable distance from. a fire. If the quantity of any agent used. on a fire is not sulficient for. complete extinguishment; the agent itself does not become involved and. there, is no danger of producing a fire more intense than before attempted extinguishment.

lt [yr novel composition. not only flows freely from extinguishing equipment but. also: is highly effective in extinguishing-.metalfires, I employga resin in. my composition which does not inhibit, free. flow of; the mixture at-i:.- mh ent-. Q 12Q l l 16-.;u Iia'lsur. utilize a, moistureeabsorbing material which has the ability to absorb consid- These agents extinguish by:

C atented ay 24. 196

erable moisture without-change in flow properties of. the

mixture.

- The resin used in my composition is of atype which is either plastic or thermosettingunder conditions encountered in fire extinguishment. The ability to become plastic'or thermosetting enables the resin-to bind the mass of fire-extinguishing agent into a coherent-fire smothering blanket. It also enables the extinguishing agent tocling to and blanket vertical surfaces to control fires which would be 'diflicult' to extinguish with'af'non absorbing agents.

TABLE I Moisture Average Min m m Maximum content discharge discharge discharge Moisture-absorbing agent Percent 'Perceut Percent Percent present 0.0859 89.9 86.0 92.3 Moisture-absorbingagent abv p sent 0.0853 79.7 66.14; 88 5 There was little difierenc'e i-h actual moisture content of' the mixes, butwiththe moisture-absorbingxagent present the average discharge was better and the range between the highest and lowest values was much narrower.

In addition to a resin having characteristics previously described and an inert. moisture-absorbing material, my

extinguishing composition also contains an inert salt and an agent which simultaneously improves the ilowof the mixture and imparts water repellency. Other flow-pro ducing agents may also be added if found desirable.

The bulk of my composition consists of ametallic salt. which is the basic extinguishing material. A salt shame] be chosen which will not react with'the burning metal under the conditions of the fire, which can be easily made water repellent and which has suitable flow properties.-

Sodium chloride is the inert salt preferred for my composition. Sodium chloride can be used for controlling} burning metals such as magnesium, sodium, potassium;

. calcium, uranium, alloys of these metals and wher in-- flammable substances, such as phosphorous, sulfur,organic substances:- and the like. An inert lithium salt can be used to replace sodium chloride in special prepara tions for use on lithium fires. Calcium fluoride is also a suitable extinguishing agent for certain metals.

The metallic salt used should be unagglomerated under ordinary conditions and should be capabl'eof being treat ed to produce water-repellency and free flow. A salt hav'-' ing the screen analysis shown in the following Table'll is advantageous, but wider ranges are not necessarily un-' satisfactory. T 3 1 TABLE II Mesh: Percent hf." Retained d 20 48 Pan. Y v I Metallic salt which. is too-fine does not flowiproperly if at all and it tends to produce an agent which'will drift away from the area to' which it is being applied. Be-

cause of the large amount of surface it also requiresv large quantities of the agent used for imparting waterrepellency. Salt that is too "coarse is not satisfactory because it will not flow well and .its large crystals are dif ficult to make water-repellent.

The moisture-absorbing material used in my fire-extinguishing composition should be capable of absorbing moisture from the salt and other ingredients without any appreciable change in physical properties. In the quantities used it should be substantially non-reacting with materials on which the extingiishing agent may be used. It should not deleteriously affect other desirable proper: ties of the extinguishing agent such as the ability when heated to bind into a coherent mass and cling to vertical surfaces.

My preferred composition contains fullers earth as the moisture-absorbing additive.- Talc and synthetic absorptive magnesium silicateare also satisfactory for this purpose. A composition incorporating magnesium carbonate is satisfactory but has increased bulkiness decreasing the amount of extinguishing agent which can be contained in a given extinguishing unit. 7

The preferred particle distribution of the fullers earth used should be such that atleast 95 percent of the material will pass through a 48 mesh screen and no more than 90 percent of the material will pass through a 200 mesh screen. Finer fullers earth satisfactorily absorbs moisture and gives desirable flow properties but inhibits the binding action produced by the resin. Coarser fullers earth, will not impartthe free-flow properties desired. The following Table III indicates the effect of particle size of fullers earth on the discharge from a standard extinguishing unit and on the binding properties imparted by the resin.

TABLE HI Agent with five percent fullers earth Grade fullers earth Preferred par- Fine Coarse ticle size Amount discharged-.. Discharge time H 26 sec Binding action Satisfactory--- The results show that when fine fullers earth is used the amount discharged and the time for complete discharge are satisfactory but the binding action is poor. Percentage discharge and binding action are good using coarse fullers earth, but the rate of discharge is low and the time for complete discharge is prolonged.

The quantity of moisture-absorbent material used may vary between one percent and ten percent by weight. Greater moisture absorption will be obtained with larger quantities of material, but these larger quantities will inhibit the binding action produced by the resin.

The binding agent used is a thermoplastic or thermosetting resin capable of binding the extinguishing powder into a coherent mass under the conditions of the fire. This binding agent should be solid, non-tacky and should not coalesce or lump at ambient temperatures. It should be self-extinguishing or non-flammable when exposed to an open flame. A copolymer of vinylidene chloride and acrylonitrile having suitable properties is the resin which I prefer for a binding agent. Various phenol-formaldehyde and vinyl chloride resins give satisfactory binding action when heated but are objectionable because of the strong odors produced. The particle size of the resin used should be such that the resin particles will not interfere with the flow of extinguishing agent. The best binding action is obtained with a fine grade of resin but of magnesium, zinc, calcium and other metals.

.4 coarser grades can be used if larger quantities are added to the mixture.

The quantity of resin used may vary over a considerable range. The larger thequantity the more effective the binding produced. Large quantities of resin affect other properties such as flow-ability. The preferred quantity of resin is 7 percent by weight, but the amount may vary between one percent and 20 percent by weight.

The water-repellency agent may consist of any suitable material such as metallic soaps of fatty acids. The agent may be applied in any suitable manner. Metallic soaps of fatty acids may be applied simply by mixing with the materials to be made water-repellent. The agent may also be applied in a solution with a volatile solvent or by, exposing-the extinguishing composition to the vapors of the agent.

The agents preferred for producing'water-repellency in my composition are metallic stearates including those These stearates may beobtained in grades ranging from dense to light and fluffy. Any of these grades may be used in proper quantity. With the dense grade as much as three percent may be necessary while less than one percent of the light grade may be needed.

Tricalcium phosphate may be used for improving flow of the agent. Quantities up to five percent by weight of tricalcium phosphate canbe used without greatly changing the properties of the mixture. Larger quantities of tricalcium phosphate will increase the bulkiness of the product.

My preferred composition for an agent for extinguishing metal fires contains the indicated percentage by weight of the following ingredients:

86% inert salt 7% copolymer of vinylidene chloride and acrylonitrile 5% fullers earth 1% magnesium stearate 1% tricalcium phosphate These ingredients in finely divided form are mixed or ground together by any suitable means to produce a homogeneous free-flowing composition; The proportions of the materials for this composition may however vary considerably. The proportions of the components of my composition may vary by weight as follows:

65-95% inert salt l20% copolymer of vinylidene chloride and acrylo nitrile l-10% fullers earth 1-3% magnesium stearate 0-5% tricalcium phosphate My composition will-flow freely and can be applied on metal fires from a safe distance. It may also be applied by shoveling or pouring from a pail if so desired. Normal quantities of moisture which the composition may take up during processing or storage will be absorbed by the moisture-absorbing agent present without deterioration of the flow properties. My composition can be discharged from pressurized vessels under normal conditions of operation.

I claim:

1. A finely divided composition for extinguishing fires in air-combustible metals consisting essentially of about 65 to about Weight percent metallic salt non-reactive with said burning metal, about 1 to about 10 weight percent solid inorganic moisture-adsorbing agent and about 1 to about 20 weight percent synthetic resin binder solid and non-tacky at ambient temperatures and self-extinguishing when exposed to an open flame.

2. The composition as defined in claim 1, wherein the moisture-adsorbing agent is selected from the group consisting of fullers earth, adsorptive magnesium silicate, talc and magnesium carbonate.

3. The composition as defined in claim 1, wherein the synthetic resin binder is selected from the group consisting of vinylidene chloride-acrylonitrile copolymers,

vinyl chloride polymers, and phenol formaldehyde poly- I mers.

4. The composition of claim 1 containing also less than about weight percent of tricalcium phosphate as flow improving agent.

' 5 The composition of claim 1 containing also less than about 3 weight percent of a metallic salt of a higher fatty acid as water-repellent agent.

6. The composition of claim 4 containing also less than about 3. weight percent metallic salt of a higher fatty acid as water-repellent agent.

,7. A finely divided composition for extinguishing fires in air-combustible metals consisting by weight of 86% sodium chloride, 7% copolymer of vinylidene chloride and acrylonitrile solid and non-tacky at ambient temperatures and self-extinguishing when exposed to an open flame, 5% fullers earth, 1% magnesium stearate and 1% tricalcium phosphate.

8. A finely divided composition for extinguishing fires in air-combustible metals consisting by weight of about to about percent sodium chloride, about -l to about 20 percent of a copolymer of vinylidene chloride and h acrylonitrile solid and non-tacky at ambient temperatures x and self-extinguishing when exposed to an open flame,

about 1 to about 10 percent fullers earth, less than about a 3 percent magnesium stearate, and less than about 5 percent tricalcium phosphate.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. 8. A FINELY DIVIDED COMPOSITION FOR EXTINGUISHING FIRES IN AIR-COMBUSTIBLE METALS CONSISTING BY WEIGHT OF ABOUT 65 TO ABOUT 95 PERCENT SODIUM CHLORIDE, ABOUT 1 TO ABOUT 20 PERCENT OF A COPOLYMER OF VINYLDENE CHLORIDE AND ACRYLONITRILE SOLID AND NON-TACKY AT AMBIENT TEMPERATURES AND SELF-EXTINGUISHING WHEN EXPOSED TO AN OPEN FLAME, ABOUT 1 TO ABOUT 10 PERCENT FULLER''S EARTH, LESS THAN ABOUT 3 PERCENT MAGNESIUM STEARATE, AND LESS THAN ABOUT 5 PERCENT TRICALCIUM PHOSPHATE.