WO1998050114A1

WO1998050114A1 - Foamable composition and method and apparatus for making an air foam from the same

Info

Publication number: WO1998050114A1
Application number: PCT/US1998/008086
Authority: WO
Inventors: John Edward Balkiewicz; David Kalkstein
Original assignee: Protein Foams, Inc.
Priority date: 1997-05-09
Filing date: 1998-05-11
Publication date: 1998-11-12
Also published as: AU7468098A

Abstract

A foamable composition comprising a metal based salt and a hydrolyzed protein, which when mixed with suitable amounts of air and water under pressure, produces a stable foam, and an apparatus for making a long lasting foam, which apparatus (10) includes an injection chamber (12), an expansion chamber (14) and a coiled hose (16) which extends therebetween, the coiled hose including a plurality of turns. A pressure generating pump (not shown) is provided to force a stream of foam solution into the injection chamber where it is mixed with a pressurized stream of air and passed through the injection chamber, the coiled hose, and the expansion chamber to yield a foam having desirable stability and expansion characteristics.

Description

FOAMABLE COMPOSITION AND METHOD AND APPARATUS FOR MAKING AN AIR FOAM FROM THE SAME

Field of the Invention

This invention relates to a foamable protein composition and a method for making the same. More particularly, the invention relates to such a foamable composition which, when mixed with suitable amounts of air and water, produces a compressed air foam which is sufficiently stable to be used as an effective daily cover for landfills. The invention also relates to an apparatus designed to produce a compressed air foam from the foamable composition. Background of the Invention

Pursuant to federal, state and local laws, municipal solid waste (MSW) landfills are required to be covered by an earthen or other approved cover for wastes deposited therein at the close of each working day. The use of earthen material as a cover imposes two significant costs on the landfill operator. First, the material must be purchased and, even when available on site, must be physically transported to the landfill and then spread evenly over the compacted trash. The transporting of the earthen material requires large and expensive earth moving equipment as well as substantial man power. Secondly, the earthen material takes up valuable volume which could otherwise be sold to customers. More specifically, the use of earthen material can consume as much as 15 to 20 percent of landfill volume. This deprives the landfill operator of significant potential revenue and profit. Further, the landfill capacity wasted by the earthen material reduces the useful life of the facility, thereby resulting in the need for landfills of increased size or the development of new sites. Accordingly, there is a need for a material which can be used to effectively cover a landfill without requiring expensive purchase and/or transportation costs. Further, there is a need for such a material which does not consume substantial amounts of valuable landfill volume. Such a material would significantly reduce the operating costs for the approximately 3000 landfills in the United States alone as well as the thousands of landfills abroad.

In recognition of the foregoing, a number of states have allowed foams to be used as covers if they meet certain statutorily provided requirements. For example, the covers must prevent the emission of certain volatile organic compounds and odors. The covers must also prevent the dispersal of loose trash at the landfill site and its vicinity. Foams replace the aggregate material in earthen materials with air. Thus, the use of foams as covers for landfills in place of the earthen material is desirable in that the foams do not take up as much volume as the earthen material and, therefore, are of economic value to the landfill operator. Moreover, such foams are typically less costly and easier to apply than other alternative daily cover methods or products.

Various air foam compositions have been in use for fire fighting purposes for many years. Examples of such foam compositions are disclosed in U.S. Patent Nos. 3,849,315, 4,099,574, 4,594,167, 5,207,932, and 5,225,094. Three prevalent fire fighting foam compositions comprise either partially hydrolyzed protein, detergents or film forming foam compositions based on perfluorinated hydrocarbons. The detergent foams are generally used as high expansion systems for rapidly flooding large spaces in order to extinguish fires in warehouses, hangers or the like. The perfluorinated hydrocarbon based foams, known as aqueous film forming foams (AFFF), are useful for rapidly spreading an extinguishing film over a burning liquid. Protein based air foam systems provide stable extinguishing foams of relatively greater stability and a practical expansion factor of 10 when used in a 3 or 6% by volume solution of the foam producing composition in conjunction with typical foam generating apparatus.

None of the existing foam systems mentioned above can be used effectively as a daily cover for municipal solid waste (MSW) landfills. More specifically, such foam systems do not remain stable for the period between the day's end of disposal operations and the beginning of the operations the following day. Further, such existing foam systems have expansion factors which are not adequate for use on landfills. An additional problem with existing foam systems is that the apparatus

__• utilized to discharge the foam fail to provide a sufficiently reliable discharge pattern or distance, tnereby necessitating the use of costly additional equipment.

Air foams, protein or film forming types, produced with aspirating discharge nozzles, as are common in the fire protection industry, generally have an expansion factor of 10. This is the case with both 3 and 6% by volume solutions. The injection of compressed air into the foam solution instead of drawing air in by way of aspirating nozzles has been seen to raise the expansion factor to about 15. In most systems that utilize compressed air injection, the foam thus created is forced by pressure through a series of screens within a chamber. As the foam is passed through these screens, bubbles in the foam are reduced in size. A drawback with this process is that some of the fragile foam bubbles are destroyed as they pass through the screens. This reduces the amount of foam produced and, therefore, the expansion factor.

An additional drawback with the process described above is that the velocity of the foam as it is discharged is reduced as it passes through the systems due to contact with the series of screens. This results in a tube like stream of foam being created. When this tube like stream is discharged into the air, the tube like shape is maintain, thereby limiting the foam's exposure to air. The limited air exposure has an adverse impact on the expansion factor of the foam.

Summary of the Invention

The present invention is designed to overcome the deficiencies of the prior art discussed above. It is an object of the present invention to provide a foamable protein composition which, when mixed with suitable amounts of air and water, produces a foam which remains stable for an extended period of time. It is a further object of the invention to provide such a foamable composition which is relatively inexpensive to manufacture.

It is still another object of the invention to provide a method and apparatus for producing an air foam from the foamable composition.

In accordance with the illustrative embodiments, demonstrating features and advantages of the present invention, there is provided a foamable composition which comprises a metal based salt and a hydrolyzed protein. The foamable composition, when mixed with suitable amounts of air and water, produces a foam which is stable for at least about lS hours and, preferably, for at least about 18 hours and, more preferably, for at least about 24 hours.

Accordingly, the foam provides an effective daily cover for landfills and the like. Further, the foam can be utilized to provide a cover for hazardous and other wastes while such materials are in transit. It can also be used for fire fighting applications where extended stability is required, such as with forest or tire fires. Other applications include utilizing the foam to: insulate freshly poured concrete or agricultural crops; reduce or eliminate odor and other emissions from agricultural waste, apply fertilizer to the leaves of plants.

This invention also provides an apparatus for generating the protein foam from the foamable composition. The apparatus includes an injection chamber, an expansion chamber and at least one coiled hose which extends therebetween. The coiled hose includes a plurality of turns. Pressure generating pumps are provided to draw the foamable composition, which is preferably in liquid form, and water in a proper proportion and force a stream of the resulting foamable solution into the injection chamber where it is mixed with a pressurized stream of air and passed through the injection chamber, through the coiled hose, through the expansion chamber, through a length of hose and finally out a discharge nozzle in order to yield the desired air foam. The invention further provides a method of preparing the foamable composition described above.

Other objects, features and advantages of the invention will be readily apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the drawings.

Brief Description of the Drawings

For the purpose of illustrating the invention, there is shown in the accompanying drawings one form which is presently preferred, it being understood that the invention is not intended to be limited to the precise arrangements and instrumentalities shown. FIG. 1 is a side perspective view of the foam producing apparatus in accordance with the present invention. FIG. 2 is a side cross-sectional view of the injection chamber as shown in FIG. 1. ^*

Detailed Description of the Invention

Referring now to the drawings in detail wherein like reference numerals have been used throughout the various figures to designate like elements, there is shown in FIG. 1 a foam producing apparatus constructed in accordance with the principles of the present invention and designated generally as 10.

The foam producing apparatus 10 essentially comprises an injection chamber 12, an expansion chamber 14, and first and second hydraulic coiled hoses 16 and 18 extending therebetween. The injection chamber 12 includes first and second inlet openings 20 and 22, respectively, and an outlet opening 24 (FIG. 2). A bushing 28 is preferably threadably secured to and extends outwardly from the first inlet opening 20 of the injection chamber 12. In the preferred embodiment, an elongated tubular member 30 extends into the first inlet opening 20 and passed the outlet opening 24. The bushing 28 secures the tubular member 30 in place. The tubular member 30 preferably has a significantly smaller inner diameter than the inner diameter of the injection chamber 12. In the preferred embodiment, the inner diameter of the injection chamber is approximately 2" and the inner diameter of the tubular member is approximately 0.75".

A bushing 32 is preferably threadably secured to and extends outwardly from the second inlet opening 22. Extending outwardly from the bushing 32 is a tubular member 34 which has an inner diameter of approximately 1". Secured to the free end of the tubular member 34 is an elbow 36. The preferred inner diameter of the elbow is also preferably about 1". Extending outwardly from the outlet opening 24 is a connector segment 40, which has an inner diameter of approximately 2" and is approximately 4" long. The elongated tubular member 30 partially extends into the connector segment 40.

A coupling 44 is secured to and extends from the free end of the connector segment 40. The preferred inner diameter of the coupling 44 is also 2". A Y-shaped connector member 46, which includes an input end 48 and first and second output ends 50 and 52, is provided. The connector member 46 preferably has an inner diameter of 1.5". The input end 48 of the Y-shaped connector member 46 is secured to the coupling 44 via a bushing

54 and a 1.5" inner diameter connector 55 as shown in FIG. 1. The expansion chamber 14 includes an input end 60 and a discharge end 62. The expansion chamber 14 further includes a segment (or bell reducer) 64 which diverges from the input end 60 thereof and a segment (or bell reducer) 66 which converges toward the discharge end 62 thereof. The preferred length of the expansion chamber is approximately 16" and the maximum diameter is approximately 4". A Y- shaped connector member 70, which includes two input ends 74 and 76 and an output end 78, is provided. The output end 78 of the Y-shaped connector member is secured to the input end 60 of the expansion chamber with a 1.5" inner diameter connector 79. The first coiled hose 16 extends between the output end 50 of the Y-shaped connector member 46 and the input end 74 of Y-shaped connector member 70. Similarly, the second coiled hose 18 extends between the output end 52 of the Y-shaped connector member 46 and the input end 76 of the Y-shaped connector segment 70. Each end of the coiled hose is secured an end of a corresponding one of the Y-shaped connector members by means of a bushing. In the preferred embodiment, each of the coiled hoses has an inner diameter of approximately 1", is approximately 8.5" long, and includes five turns. The total distance between the turns of each coiled hose is preferably about 5.75".

The apparatus described above can be effectively used to process a foamable protein composition, which is preferably in liquid form and is comprised of a metal based salt and a hydrolyzed protein, into a long lasting air foam. The apparatus is used to mix the foamable composition with suitable amounts of water and compressed air in order to yield a foam which is stable for at least about 16 hours and, preferably, for at least about 18 hours and, more preferably, for at least about 24 hours. The metal salt is preferably ferrous sulfate and, more preferably, ferrous sulfate heptahydrate crystal. However, other salts, such as ferric iron and aluminum salts could also be utilized. The addition of a salt in a dry, stable form has lead to a reduction in the number of steps required to produce a desired foam composition. The apparatus 10 enhances the performance of existing detergent based foam liquids and concentrates by generating foams with higher expansion factors than typically obtained with prior art machines.

In the preferred method, the foamable composition is obtained by pouring specific amounts of ferrous sulfate heptahydrate crystal (FeSO₄ 7H₂O) into a solution of hydrolyzed protein while stirring with an appropriate mixer. Various amounts of ferrous sulfate heptahydrate crystal have been found to create a foamable composition in accordance with the present invention. From a practical standpoint, however, it has been found tnat admixing one part of the ferrous sulfate heptahydrate crystal to approximately 24 parts of hydrolyzed protein results in a liquid foamable composition which has particularly desirable stability characteristics. It has also been found that adding ferrous sulfate until the pH of the mixture fall within the range of from about 6.0 to about 7.0 yields a preferred foamable composition. The addition of the ferrous sulfate in dry form, as opposed to first being added into a solution with water or taking the form of ferric sulfate, results in reduced exposure of the iron in the form of ferrous sulfate to air. This is desirable since the effectiveness of the foam is increased if the exposure to air and the resulting creation of a rust like ferric hydroxide takes place after the foam is discharged. The hydrolyzed protein can be obtained from a number of sources including, by way of example and not limitation, feather meal, animal hide, and hoof and horn meal.

In order to facilitate an understanding of the principles associated with the foregoing apparatus, its operation will now be briefly described. The foamable composition is combined with water and the resultant solution is pumped into the injection chamber 12 through the tubular member 30 by conventional pressure generating means. In the preferred embodiment, the solution comprises 1 part foamable composition and 30 parts water. Air is simultaneously pumped through the elbow 36, through the tubular member 34 and into the injection chamber 12 through the inlet opening 22 therein. The air is pumped in at a higher pressure than solution. Preferably, about 185 cubic feet per minute of air is pumped in under about 85 to about 95 psi while about 4.13 cubic feet per minute of solution is pumped in at about 65 psi.

As the solution is ejected out of the tubular member 30, it combines with the stream of air, which is pumped in at a higher pressure. The air flowing by the end of the tubular member 30 creates an area 90 of negative or lower than surrounding pressure

(FIG. 1). As the stream of air passes the end of the tubular member, the solution is drawn into the air stream, thereby mixing the two mediums together. The air infused foam solution is then passed into the Y-shaped connector member 46. Thereafter, a stream of the air infused foam solution is pumped through the output end 50 of the connector member 46 and through the coiled hose 16 while a second stream of the air infused foam solution is forced through the output end 52 of the connector member 46 and through the coiled hose 18. As each stream of solution is spiraled through the respective coiled hoses, a homogenized substance is formed. The infusion of air causes the volume of the solution to exparid against the inside of the corresponding coiled hose and turn into a foam. Accordingly, the coiled hoses create a compression zone by retarding the expansion. As the two streams of compressed foam are combined in the Y-shaped connector member 70 and the combined stream is passed into the expansion chamber, the 4.13 cubic feet per minute of solution becomes 185 cubic feet per minute of foam. While the theoretical expansion is 45.79 (4.13 ftVmin (sol.) / (185 ft min (air) + 4.13 ft /bin (sol.))), the actual expansion is typically around 25 to 40 due to energy loss and damage from he discharge hose and nozzle and the coiled hoses (compression coils) 16 and 18. The foam is discharged from the discharge end 66 of the expansion chamber. In the preferred embodiment, a 1.5" inner diameter hose (not shown), which is equipped with a 1.5" discharge nozzle, extends from the discharge end 66 of the expansion chamber 14. It should be noted that the discharge hose could be branched into two or more smaller discharge hoses or the foam could be discharged by a spray bar or other means. The foam, which is discharged from the discharge nozzle under pressure, has a practical throw of approximately 75 to 100 feet. Further, the resultant stream of foam can be thrown for a substantial distance with considerable accuracy taking the form of a stream of large flake like pieces. This is due to the fact that the spiraling motion of the foam created by the coiled hoses continues passed the discharge nozzle up to approximately 1/3 of the discharge distance of the foam. Such spiraling motion and the flake-like form of the discharged foam increases contact of the iron in the foam (ferrous iron) and air (oxygen) which results in the formation of water solution ferric hydroxide. It is ferric hydroxide specifically which provides durability and strength to the bubbles created from proteinaceous matter in the foam composition and which forms the skeleton of the foam's structure. The resultant foam, when applied, has been found to remain stable for up to about 28 hours. Accordingly, the foam has definite utility for covering MSW landfills overnight. Further, it has been found that the useful life of the foam cover can be increased to as long as approximately 60 hours by increasing the thickness of the same. The resultant foam has other uses. By way of example, the foam can be utilized to provide a cover for hazardous and other wastes while such materials are in transit. It can also be used for fire fighting applications where extended stability is required, such as with forest or tire fires. Other applications include utilizing the foam to: insulate freshly poured concrete or agricultural crops; reduce or eliminate odor and other emissions from agricultural waste, apply fertilizer to the leaves of plants.

Additional applications of the instant inventing foams include the following: Agricultural:

Protection from Frost:

Foam produced by the inventive system has sufficient durability to provide insulation for row and orchard crops. Because of the durability of the foam, relatively small amounts are required to provide overnight insulation. This has been tested. Using tomatoes, it was found that a layer of foam, one quarter of an inch thick, covering 50% or more of the leaves on the top of the plants, maintained a 15 degree temperature differential for a period of 14 hours. Temperatures measured at the core of the tomatoes covered by foam produced by the system were 60 degree F; those unprotected were 45 degree F. Foams have been used for this before but none are now known as commercially viable. Because of the ability of the system to produce a very stable foam at an efficient rate, it is estimated that the invention provides a commercially viable solution for most moderate and all high value crops. The system's range of discharge enables it to be deployed for orchard or row crops.

The commercially available system will produce foam at a rate of 50,000 gallons per hour. This yield equals 6,700 cubic feet. A cover area of one quarter of an inch thick covering 50% of exposed leaf area would equal 643,200 square feet, or about 16 acres, in an hour. At a retail cost of $18.00 per gallon, the cost of the foam material required is about $62.00 per acre.

Distribution of Water Soluble Agro-Chemicals: In this use the foam system replaces tractor drawn tanks equipped with booms that spray atomized water from a series of nozzles. The farmer doses the water with various chemical additives in proportions proscribed by the chemical manufacturers. The common contention by the farmers is that up to 50% of the materials they purchase is lost to evaporation and wind. The loss rate is very high as the evaporation rate for atomized water is a function of the exposed surface area relative to mass; therefore the smaller the droplet of water, the faster the evaporation process. An additional concern is that materials are transported by wind surpassing distances and can effect damage on neighboring crops.

For any water soluble material that is designed to be applied on leaves without necessarily covering 100% of their surface area (known as "systemic foliar application") foam produced by the inventive system provides the advantage of a) assuring that 100% of the agro chemical lands on the plants and does not evaporate rapidly; b) will not be susceptible to loss by wind except in high wind velocities. The foam duration may be modified to optimize the application by reducing the concentration of foam liquid in solution. In this application there is no value to the foam surviving more than an hour or two. Therefore the coverage rate is expanded considerably beyond that which was cited above for frost protection. At a 1% concentration in solution (other applications require a 3% concentration) the system will deliver coverage as follows: 150,000 gallons of foam, or 20,100 cubic feet. At a one quarter inch thickness covering 50% of the leaf surface area, a 55 gallon drum of purchased material would yield 1,929,000 square feet, or 45 acres. Using the same $18.00 per gallon cost, the cost per acre of the foam liquid required to do this would be $22 per acre. Fire Fighting:

Principal advances (in this and other applications) provided only by foam produced by the inventive system derive from the form taken by the expanded foam as it is discharged from the system. Upon discharge, the foam takes the form of small clusters measuring from about 1/4" rough diameter to 3/4". This form has never before been obtained by any foam used in fire fighting. Prior art produced foams that either ooze forcefully or splatter around with short range, or in the case of perfluorinated hydrocarbon surfactant based products, in a liquid stream. The foam clusters enable the iron content of the foam to be efficiently exposed to air and begin to form ferrous oxide (rust). Thus the enhanced stability of the foam. This is done most effectively by the inventive system in that the small cluster has a high ratio of exposed surface area to mass. In a sense the foam becomes reinforced with iron. No other foam has ever done this. These clusters accumulate rapidly and form a barrier between flammable vapor and air. In essence, an air barrier is created, and air has long been proved to be a superlative insulator. Properly applied, the cluster form is such that a high percentage of the foam surface area engages fire compared to other foams. Other protein foams slowly form a blanket which spreads over the fire in a way that reduces the amount of fire fighting agent that actually engages fire. Perfluorinated hydrocarbon surfactant based foams create fragile films which in favorable circumstances separate fuel from air. In practice they do not work which is why one sees firefighters close on to fires instead of far away. 5 Fire Extinguishment Efficiency:

The most common measure of fire fighting efficiency of foam agents is the Foam Solution Application Rate. This defines the amount of foam solution (not foam) that is required to extinguish fires. It is calculated by dividing the foam system's output in gallons per minute by the surface area of the fire. Thus a typical system currently in use 0 will require a Foam Solution Application Rate of .01 gpm/ft sq. (current US military and NFPA practice for perfluorinated hydrocarbon surfactant based foams; note this exceeds the specification rate, which won't put out fire). The system has extinguished 7000 square ft tires within the proscribed time frame at Foam Solution Application Rates as low as 0.005 gpm/ft.sq. (System discharges 33 gallons of foam solution in the form of over 900 5 gallons of foam).

Burnback:

Burnback is what happens when an extinguishant cannot permanently put out a fire; thus the fire re-ignites and starts all over again. It is a measure of both the stability of a foam and its efficacy. Military and other specifications and standards require

20 that a reignited fire covered by foam spread, in a specified amount of time, over a limited percentage of the fire area. Currently the US military Specification requires that in six minutes a fire not spread over 25% of a small test area. (The reason the military people rely on small test areas is that the material they use does not scale up and works very poorly). Foam produced this system does not burn back in 15 minutes. The reason we say 25 15 minutes is that when we have tested for burnback the fuel burned up before the fire destroyed the foam. This saves lives and is critical.

Discharge Range:

The unique thing here is that foam produced by the inventive system does not lose significant range when discharged from elevation, as in aerial systems. We have

30 tested discharge ranges of foam produced by this system at 35 and 100 ft elevations. Loss of range is less than 5% at 100'. The reason for this unique ability is the fact that the foam produced by the inventive system is very stable even though it is 97% air. Thus little energy is lost moving it through a hose to an elevated height. Water by contrast loses one pound per inch of pressure every 27 inches of elevation. Other foams, having much pound per inch of pressure every 27 inches of elevation. Other foams, having much higher water content, cannot match this property without either significant loss of range or much greater amounts of energy.

Insulation for Concrete During Construction:

This application utilizes the foam system, to produce an insulating cover for concrete and other construction materials that can be impacted by temperature variation during their curing process. A prime example is paving roads, in which freezing temperatures have a damaging effect on uncured concrete. The current practice is to avoid paving operations during cold months. The inventive system can be used to deploy insulation over curing concrete to prevent freezing as in the above agricultural application.

This application may be economically feasible as the high volume of expanded foam and the stability thereof have not heretofore been available.

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 the foregoing specification as indicating the scope of the invention.

Claims

What is claimed is:

1.^" A foamable composition comprising: a metal based salt, and a hydrolyzed protein; said foamable composition, when mixed with suitable amounts of air and water under pressure, produces a foam which is stable for at least about 16 hours.

2. The foamable composition of claim 1 wherein said metal based salt is selected from the group consisting of iron or aluminum salt.

3. The foamable composition of claim 1 wherein said metal based salt is an iron salt.

4. The foamable composition of claim 1 wherein said metal based salt is ferrous sulfate.

5. The foamable composition of claim 1 having a pH in the range of from about 6 to about 7.

6. The foamable composition of claim 1 including about one part of said metal salt and about 24 parts of said hydrolyzed protein.

7. The foamable composition of claim 1 having an expansion factor of from about 25 to about 45 when mixed with suitable amounts of water and air under pressure.

8. An apparatus for making a long lasting foam comprising: an injection chamber having an inlet opening and an outlet opening; hollow coil means having first and second ends; coupling means for connecting said outlet opening of said injection chamber to said first end of said coil means; an expansion chamber having an input end and a discharge end, said second end of said coil means being connected to said input end of said expansion chamber, and pressure generating means for passing a quantity of a foam solution through said injection chamber, through said coil means, and through said expansion chamber in order to yield a long lasting foam.

9. The apparatus of claim 8 wherein said coil means comprises a coiled hose which extends between said injection chamber and said expansion chamber.

10. The apparatus of claim 9 wherein said coiled hose includes at least about three turns.

11. The apparatus of claim 8 wherein said coil means comprises two coiled hoses, each of said hoses extends between said injection chamber and said expansion chamber.

12. The apparatus of claim 11 wherein each of said coiled hoses includes at least about three turns.

13. The apparatus of claim 9 further including an elongated tubular member extending into said injection chamber through said inlet opening thereof, said foam solution passing into said injection chamber through said elongated tubular member.

14. The apparatus of claim 13 wherein said injection chamber further includes an air inlet opening therein and pressure generating means for passing a stream of air over said tubular member and allowing said foam solution to be mixed with said stream of air as said foam solution is ejected from said tubular member.

15. A method of making a foam utilizing an apparatus which includes an injection chamber, an expansion chamber, and coil means extending between said injection chamber and said expansion chamber, said method comprising the steps of: providing a quantity of a hydrolyzed protein; admixing a suitable quantity of a metal based salt with said hydrolyzed protein until a foamable composition having a pH in the range of from about 6 to about 7 is obtained; admixing a suitable quantity of water with said foamable composition until a foam solution including approximately 3% of said foamable composition by volume is obtained; forcing a stream of said solution under pressure through said injection chamber, through said coil means, and through said expansion chamber in order to obtain a foam which lasts for at least about 16 hours.

16. The method of claim 15 further including the step of combining said stream of said solution with a pressurized stream of air in said injection chamber.

17. The method of claim 16 wherein said foamable composition has an expansion factor of from about 25 to about 45.

18. The method of claim 16 wherein said metal based salt is ferrous sulfate.

19. The method of claim 16 wherein said foam composition includes about one part of said metal salt and about 24 parts of said hydrolyzed protein.