US3666707A

US3666707A - Slurry additive for ablative water fire extinguishing systems

Info

Publication number: US3666707A
Application number: US13179A
Authority: US
Inventors: William L Livingston
Original assignee: Factory Mutual Research Corp
Current assignee: Factory Mutual Research Corp
Priority date: 1970-02-20
Filing date: 1970-02-20
Publication date: 1972-05-30
Anticipated expiration: 1989-05-30

Abstract

A shelf stable slurry for injection into ablative water fire extinguishing systems comprises a uniform suspension of polyacrylamide polymer gelling agent in a polyoxyalkylene vehicle containing a stabilizing amount of silica suspending agent.

Description

I United States Patent 1151 3,666,707 Livingston 1 May 30, 1972 [54] SLURRY ADDITIVE FOR ABLATIVE 3,354,084 11/1967 Katzer 252/2 WATER FIRE EXTINGUISHING 2,892,730 6/1959 Kloepfer. 106/ 193 SYSTEMS 2,760,941 8/1956 Iler ..260/2.5

3,210,273 10/1965 Taulli ..252/28 [72] Inventor: William L. Livingston, Sharon, Mass. 3,474,061 10/1969 Benin at "260/29 6 73 Assigneez Factory Mutual Research Corporation, 3,514,500 3/1970 Osmond ..260/8 74 Turnpike, Mass. Primary E.xaminer-Morris Liebman [22] F'led: 1970 Assistant Examiner-Richard Zaitlen [21] AppL 13,179 Attorney-Lane,Aitken,'Dun'ner&Ziems [57] ABSTRACT [52] US. Cl.....' ..260/33.2, 252/2, 252/8,

260/295 A, 260/41 A A shelf stable slurry for injection into ablative water fire extin- [51] int. Cl ..C08g 51/42 gu g sy ems comprises a uniform suspension of [58] Field of Search ..260/33.2, 33.4, 41 A, 29.6 S; p lyacrylamide polymer gelling agent in a polyoxyalkylenc 106/30 vehicle containing a stabilizing amount of silica suspending agent. [56] References Cited UNITED STATES PATENTS 17 Claims Drawings 2,810,716 10/1957 Markus ..260/88.1

SLURRY ADDITIVE FOR ABLATIVE WATER FIRE EXTINGUISHING SYSTEMS CROSS REFERENCE TO RELATED APPLICATION William L. Livingston et al.

Serial No. 766,475

Filed Oct. 10, 1968 Entitled: Method of Controlling Fire BACKGROUND OF THE INVENTION In the aforementioned copending application, a method of fire protection is disclosed in which a gelling agent in the fonn of water swellable polymer is injected into a water main supplying the sprinkler heads of a fixed fire extinguishing system actuated to put out a fire in the enclosure within which the sprinkler heads are located. By so introducing the gelling agent into a flowing water stream in the water main, an ablative gel fire extinguishant is formed having significant advantages over plain water. Not only are the thermal absorption characteristics of the ablative gel greater than water, but equally as important, the gel is substantially more viscous than plain water and tends to cling to surfaces on which it is sprayed. As a result, much lesser quantities of the ablative extinguishant are required to put out a fire than is required with plain water, thereby enabling system designs with lower flow capacity, not to mention a significant reduction in water damage to the space protected.

Although systems embodying the method described in the aforementioned copending application have been found extremely effective in extinguishing actual fires, numerous and complex practical problems have been encountered in the achievement of proper gelling agent injection at the time the system is actuated to extinguish a fire. For example, the gelling agent itself is highly reactive to water and can create water stoppages in the fire extinguishing system over-injection occurs. Moreover, the powdered solid form of the gelling agent and the innate difiiculty of properly mixing a powder with a liquid stream under pressure is, at the very least, likely to provide large slugs of relatively rigid material, contributing further to the problem of pipe blockage. Obviously, even the most remote possibility of pipe blockages cannot be tolerated in fire extinguishing systems.

In the earlier stages of development, the problems of mixing the gelling agent with the flowing stream were solved in part by first mixing the powder with a separate liquid carrier such as anhydrous propyl alcohol to form a slurry, and introducing the slurry into the flowing water stream. Principally because of the very short shelf life of known slurries, actual formation of the slurry in systems heretofore available did not occur until after the fire extinguishing system had been been activated. One obvious shortcoming of this approach is as a result of the number of mechanisms which must be brought into operation before the desirable attributes of the ablative water system can be consummated. In this connection, moreover, it must be borne in mind that fixed fire extinguishing systems, by virtue of their being operated only during periods of dire emergency, remain inactive for long periods of time, often exceeding several years duration. Consequently, conventional items of hardware, capable of effecting first the mixture of the powdered solid gelling agent to form a slurry and then the introduction of the slurry into the water lines supplying the sprinkler heads of the fire extinguishing system, present an extremely high percentage of risk in terms of possible malfunction at the time they are called on to extinguish a tire. Hence, there is an acute need for a gelling agent containing slurry having a shelf life commensurate with the long dormant periods of fixed fire extinguishing systems and also which possesses such chemical and physical properties that the introduction thereof into a flowing pipe line can be effected very simply and reliably upon the existence of a fire without danger of pipe blockages.

SUMMARY OF THE INVENTION In accordance with the present invention, the problems heretofore experienced with the injection of gelling agents into a flowing water stream to form an ablative extinguishant are substantially alleviated by the uniform suspension of polyacrylamide polymer gelling agent in a polyoxyalkylene vehicle containing a stabilizing amount of silica suspending agent to form a shelf stable slurry. The terms slurry" and suspension" are used herein interchangeably.

DETAILED DESCRIPTION OF THE INVENTION The polyacrylamide polymer gelling agents for use herein are cross-linked, hydrolyzed compounds represented by the structural formula wherein n/m ranges from 2 to 4 with 2.5 to 3.5 preferred. These compounds have molecular weights ranging from 15,000 to 25,000 with 17,500 to 22,500 preferred. These gelling agents are conveniently utilized herein in particulate form having an average particle size ranging from through 50 mesh to through 325 mesh, preferably from through 230 mesh to through 325 mesh, U.S. Standard Seive Series. These gelling agents are readily commercially available. For example, a very suitable gelling agent within this class of compounds is sold under the trade name Gelgard M by Dow Chemical Company. Gelgard M has the above structural formula wherein n/m is approximately 3. It has an average molecular weight of about 20,000 and is in particulate form having a particle size of through 325 mesh, U.S. Standard Seive Series.

The polyoxyalkylene vehicles in which the gelling agents are suspended are polyoxyalkylene monohydroxy compounds which are aliphatic monoethers of polyoxyalkylene glycols. The aliphatic monoether groups contain one to four carbon atoms. The polyoxyalkylene portion of the molecule comprises a chain fonned predominantly of the oxyethylene group and the oxy-l, Z-propylene group. They are prepared utilizing a mixture of ethylene oxide and l,2-propylene oxide in which the weight ratio of ethylene oxide to l,2-propylene oxide ranges from 3:1 to 121.5, preferably 2:1 to 1:125. Useful compounds have viscosities ranging from 50 to Saybolt seconds at 100 F. (The viscosity is a measure of molecular weight.) and are water-miscible. These compounds are described in Roberts et al, U.S. Pat. No. 2,425,755. These compounds are readily commercially available. An especially useful compound within this class is sold under the tradename UCON 50 HB 100. This compound is believed to have its aliphatic monoether group derived from butanol (that is, containing 4 carbon atoms) and to be prepared utilizing a mixture of ethylene oxide and 1,2-propylene oxide with a weight ratio of ethylene oxide to l,2-propylene oxide of 1:1; it has a viscosity of 100 Saybolt seconds at 100 F. and is water-miscible.

The silica suspending agent useful herein is colloidal pyrogenic silica. It is conveniently prepared by high temperature that is vapor phase hydrolysis of silicon tetrachloride. Ordinarily it has a surface area ranging from 100 square meters per gram to 300 square meters per gram, preferably ranging from square meters per gram to 225 square meters per gram. Pyrogenic silica suitable for use herein is sold under the trade name Cab-o-sil by Cabot Corporation. An especially useful pyrogenic silica is sold under the trade name Cab-o-sil M-5. It has a surface area of 200 square meters per gram.

The gelling agent should be present in the slurry in an amount sufficient that the slurry may be efficiently stored and transported and efficiently injected to form ablative water for extinguishing purposes. In other words, if very little of the III gelling agent active is present percentagewise in the slurry, the storing and shipping costs will be increased and more pumping will be required to get the gelling agent where it is to operate compared to where a greater percentage of gelling agent is present. On the other hand, the amount of gelling agent present in the slurry should be insufficient for precipitation of the gelling agent from the slurry to occur. Ordinarily, these goals are obtained if the slurry comprises by weight from to 49 percent gelling agent, preferably from to 45 percent gelling agent.

The polyoxyalkylene vehicle should be present in amount sufficient for the gelling agent to remain in suspension but insufficient to dilute the slurry to the point where it is not economically handled. Ordinarily these goals are obtained if the slurry comprises by weight from 89 to 47 percent vehicle, preferably from 62.5 to 51.5 percent vehicle.

The' silica suspending agent should be present in an amount sufficient to stabilize the slurry, that is suspension, against separation of components resulting in settling of the gelling agent into a discrete body, but insufficient to thicken the slurry to the point where it is pumped with difficulty. Ordinarily these goals are obtained if the slurry comprises by weight from 1 to 4 percent suspending agent, preferably from 2.5 to 3.5 percent suspending agent.

The slurry of the present invention is conveniently prepared by first slowly blending the suspending agent into the vehicle until a homogenous mixture is achieved and then mixing in the gelling agent to provide a uniform slurry.

The resulting slurry is pourable and is easily pumped. When the slurry is mixed with water in an amount sufficient to provide 0.1 to 0.5 percent gelling agent in the resulting mixture, an ablative extinguishant is formed capable of putting out enclosed fires. The slurry is indefinitely shelf stable against separation of components resulting in settling of the gelling agent into a discrete body and against harmful viscosity change at temperatures normally encountered during shipping and storage in fire extinguishing systems previous to use.

The following example further illustrates a slurry additive within the scope of the present invention and its preparation and use.

EXAMPLE A 100-pound batch of slurry was made up as follows: 57 pounds of UCON 50 HB 100 was poured into a cement mixer. To the UCON 50 BB 100 in the cement mixer was added over a 5minute period 3 pounds of Cab-o-sil M-5. The cab-o-sil was blended in slowly so that no lumps were formed. After the Cab-o-sil was uniformly distributed through the UCON 50 HB 100, lbs. of Gelgard M was slowly blended in over a 30- minute period. After the blending was achieved, the mixing was stopped and a uniform slurry was provided. The slurry thus formed contained by weight 57% UCON 50 HB 100, 40% by weight Gelgard M, and 3% Cab-o-sil M-5.

The slurry thus formed was injected from a P-inch diameter copper tubing into the center of a water stream flowing in a 3- inch diameter steel pipe by means of a Moyno positive displacement slurry pump to form an ablative material which was directed on a 12-foot high pile of ignited pallets by spray nozzles centrally positioned above the top of the pile of pallets. Slurry was injected into the water stream so that the density of ablative material directed onto the blazing pile of pallets was approximately 0.2 gallons/minute/foot square. The amount of slurry added to the water was about 0.5 percent by weight, and since the Gelgard M represented about 40 percent by weight of the slurry, the amount of gelling agent actually added to the water was about 0.2 percent by weight. A square spray pattern was obtained by using a solid pattern square spray nozzle manufactured by the Spray Systems Co. under N0. 2H290SQ. The ablative maten'al extinguished the fire.

The slurry so formed remains useful in the above-described system even though retained in a slurry storage tank upstream of the injector for periods as long as 1 year. Thus, even 1 year after the slurry has been placed into the extinguishment system the slurry is still uniform, still has a pumpable viscosity, and is easily injected into a water stream to form an ablative material whereby fires in enclosures can be extinguished.

These same results are achieved when the composition of the slurry is by weight 52.3% UCON 50 HB 100, 45% Gelgard M, and 2.7% Cab-o-sil M-5.

Other polyacrylamide polymer gelling agents than Gelgard M, other polyoxyalkylene vehicles other than UCON 50 HB 100, and other pyrogenic silicas than Cab-o-sil M-5 can be utilized in the above example with similar results of shelf stability over long periods of storage in an extinguisher system prior to use resulting in pumpability and the formation of suitable ablative mixtures even after having remained in this system more than 1 year.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

1. A shelf stable slurry additive for ablative water automatic fixed fire extinguishing systems, said additive comprising a uniform suspension of polyacrylamide polymer gelling agent in a polyoxyalkylene vehicle containing an amount of silica suspending agent sufficient to stabilize said suspension.

2. The slurry additive of claim 1 wherein the silica suspending agent is colloidal pyrogenic silica.

3. The slurry additive of claim 2 wherein said pyrogenic silica has a surface area ranging from about square meters per gram to about 300 square meters per gram.

4. The slurry additive of claim 3 wherein said additive comprises by weight from about 1 to 4 percent pyrogenic silica.

5. The slurry additive of claim 4, said additive comprising by weight from about 2.5 to 3.5 percent pyrogenic silica.

6. The slurry additive of claim 1, wherein the gelling agent is a cross-linked, hydrolized compound having the structural formula wherein n/m ranges from about 2 to 4, said compound having a molecular weight ranging from about 15,000 to 25,000.

7. The slurry additive of claim 6 wherein said gelling agent is in particulate form having an average particle size ranging from through about 50 mesh to through about 325 mesh.

8. The slurry additive of claim 7 wherein the gelling agent particle size ranges from through about 230 mesh to through about 325 mesh.

9. The slurry additive of claim 6 wherein said additive comprises by weight from about 10 to 49 percent gelling agent.

10. The slurry additive of claim 9 wherein said additive comprises by weight from about 35 to 45 percent gelling agent.

11. The slurry additive of claim 1 wherein the polyoxyalkylene vehicle is a polyoxyalkylene monohydroxy compound which is an aliphatic monoether of a polyoxyalkylene glycol, the aliphatic monoether group containing 1 to 4 carbon atoms, the polyoxyalkylene portion of the molecule comprising a chain formed predominantly of the oxyethylene group and the oxyl ,2-propylene group.

12. The slurry additive of claim 11 wherein said vehicle is prepared utilizing a mixture of ethylene oxide and 1,2- propylene oxide in which the weight ratio of ethylene oxide to l,2-propylene oxide ranges from about 3:1 to 1:15, said vehicle having a viscosity ranging from about 50 to Saybolt seconds at 100 F., said vehicle being water-miscible.

13. The slurry additive of claim 12 wherein the weight ratio of ethylene oxide to 1,2-propylene oxide ranges from about 2:1 to 1:125 and wherein said vehicle has a viscosity ranging from about 75 to 125 Saybolt seconds at 100 F.

14. The slurry additive of claim 13 wherein said additive comprises by weight from about 47 to 89 percent vehicle.

15. The slurry additive of claim 14 wherein said additive comprises by weight from about 62.5 to 5 1.5 percent vehicle.

16. The slurry additive of claim 1 wherein the gelling agent is a cross-linked, hydrolzyed compound represented by the structural formula particulate form having a particle size of through about 325 mesh; said polyoxyalkylene vehicle being an aliphatic monoether of a polyoxylalkylene glycol, the monoether group being derived from butanol, the polyoxyalkylene portion of the molecule being derived from butanol, the polyoxyalkylene portion of the molecule being derived from a mixture of ethylene oxide and 1,2-propylene oxide with a weight ratio of ethylene oxide to 1,2-propylene oxide of about 1:1, said polyoxyalkylene vehicle having a viscosity of about Saybolt seconds at 100 F. and being water-miscible; the silica suspending agent being colloidal pyrogenic silica having a surface area of about 200 square meters per gram; said slurry additive comprising by weight from about 35 to 45 percent gelling agent, from about 51.5 to 62.5 percent vehicle, and from about 2.5 to 3.5 percent silica suspending agent.

17. A method for preparing the slurry additive of claim 1,

said method comprising the steps of first blending the W suspending agent into the vehicle until a homogenous mixture is achieved and then mixing in the gelling agent to provide a uniform slurry.

Claims

2. The slurry additive of claim 1 wherein the silica suspending agent is colloidal pyrogenic silica.
3. The slurry additive of claim 2 wherein said pyrogenic silica has a surface area ranging from about 100 square meters per gram to about 300 square meters per gram.
4. The slurry additive of claim 3 wherein said additive comprises by weight from about 1 to 4 percent pyrogenic silica.
5. The slurry additive of claim 4, said additive comprising by weight from about 2.5 to 3.5 percent pyrogenic silica.
6. The slurry additive of claim 1, wherein the gelling agent is a cross-linked, hydrolized compound having the structural formula
7. The slurry additive of claim 6 wherein said gelling agent is in particulate form having an average particle size ranging from through about 50 mesh to through about 325 mesh.
8. The slurry additive of claim 7 wherein the gelling agent particle size ranges from through about 230 mesh to through about 325 mesh.
9. The slurry additive of claim 6 wherein said additive comprises by weight from about 10 to 49 percent gelling agent.
10. The slurry additive of claim 9 wherein said additive comprises by weight from about 35 to 45 percent gelling agent.
11. The slurry additive of claim 1 wherein the polyoxyalkylene vehicle is a polyoxyalkylene monohydroxy compound which is an aliphatic monoether of a polyoxyalkylene glycol, the aliphatic monoether group containing 1 to 4 carbon atoms, the polyoxyalkylene portion of the molecule comprising a chain formed predominantly of the oxyethylene group and the oxy-1,2-propylene group.
12. The slurry additive of claim 11 wherein said vehicle is prepared utilizing a mixture of ethylene oxide and 1,2-propylene oxide in which the weight ratio of ethylene oxide to 1,2-propylene oxide ranges from about 3:1 to 1:1.5, said vehicle having a viscosity ranging from about 50 to 150 Saybolt seconds at 100* F., said vehicle being water-miscible.
13. The slurry additive of claim 12 wherein the weight ratio of ethylene oxide to 1,2-propylene oxide ranges from about 2:1 to 1: 1.25 and wherein said vehicle has a viscosity ranging from about 75 to 125 Saybolt seconds at 100* F.
14. The slurry additive of claim 13 wherein said additive comprises by weight from about 47 to 89 percent vehicle.
15. The slurry additive of claim 14 wherein said additive comprises by weight from about 62.5 to 51.5 percent vehicle.
16. The slurry additive of claim 1 wherein the gelling agent is a cross-linked, hydrolzyed compound represented by the structural formula
17. A method for preparing the slurry additive of claim 1, said method comprising the steps of first blending the suspending agent into the vehicle until a homogenous mixture is achieved and then mixing in the gelling agent to provide a uniform slurry.