WO1999011327A2 - Fire extinguishing composition - Google Patents

Abstract

A fire extinguishing composition including a salt which is either potassium acetate, potassium bicarbonate, lithium bicarbonate, or sodium bicarbonate; a boron-containing compound; and water. The fire extinguishing composition is non-corrosive to metals, has a desirable pH, and is particularly effective on grease fires.

Description

FIRE EXTINGUISHING COMPOSITION

Field of the Invention

The present invention relates generally to fire extinguishing compositions

and, more particularly, to fire extinguishing compositions for application to

hydrocarbon fires.

Background of the Invention

Numerous types of fire extinguishing compounds are known, such as

carbon dioxide, liquid extinguishing compounds, and various powder sprays.

Liquid compounds are generally corrosive to metals. This is of particular concern

in extinguishing fires on a cooking surface, e.g., a grease fire on a stove top.

Specifically, even if the fire is successfully extinguished before the fire can

damage the stove top surface, the stove top, which is typically a metal surface,

may be damaged due to corrosion caused by the extinguishing composition.

There is a continuing need to develop effective compositions for

extinguishing fires. Particularly, there is a need for effective liquid fire

extinguishing compositions. Liquid compositions are more easily transported,

stored, and applied than pressurized canisters, such as the traditional CO₂

canisters. Liquid compositions also have distinct advantages when fighting large

fires, since the liquid can be dispersed over a wide area using a suitable

dispenser.

Water has long been used as an effective liquid fire extinguishing

composition. Water has a number of disadvantages. For example, relatively

large quantities of water are required to extinguish a fire, and large quantities of water may not be readily available or practical. In addition, water is inefficient

forextinguishing hydrocarbon fuel fires. Hydrocarbons such as grease, oil, tar,

and the like, repel the water. Also, these fuels generally burn hotter and faster

than many other kinds of fires due to the efficiency of hydrocarbons as a fuel for

oxidation reactions. Compared to other available compositions, water is less

effective as a coolant when used to extinguish such fires.

Most stove-top fires result from ignition of cooking grease. These fires

annually result in about 2,000 deaths in the United States, and 6,000 deaths

world-wide. More than one million people are hospitalized each year due to

kitchen fires. When extinguishing grease fires of the type wherein a pan of

grease, or any other grease-bearing flammable medium, bursts into flame, the

various methods of extinguishment consist of fully covering the flaming body of

grease with a coating of fire extinguishing agent applied by spraying. This has

required a person to aim the fire extinguishing material, or if the material was

being applied by an automatic apparatus, the latter would have to cover a

relatively large expanse. If the fire extinguishing material did not completely

cover the fire, the fire was not effectively extinguished .

U.S. Patent No. 4,756,839 (hereinafter "the '839 patent") describes a

composition comprising potassium carbonate and a boron-containing component

which to some extent overcomes the above-mentioned problems. However, the

composition comprising potassium carbonate and the boron-containing

component of the '839 patent has the disadvantage of having high alkalinity,

e.g., having a pH between 1 1 .0 and 1 1 .5. In addition, the composition of the

'839 patent is not completely non-corrosive. After being applied to a surface, e.g., a metal stove top, to extinguish a fire, the potassium carbonate can be

corrosive if allowed to remain in contact with the surface for a period of several

hours. This corrosive effect can result from the high pH of the composition.

Further, relative to the composition of the subject invention, the composition of

the '839 patent can require up to three times as much material to extinguish an

identical fire.

Certain known fire extinguishing compositions employ the use of a

surfactant, separately applied, to reduce the surface tension of a fire

extinguishing composition and improve its ability to spread over the surface of a

fuel source of the fire. However, surfactants were previously incapable of being

successfully stored as part of the composition mixture due to their tendency to

separate from the extinguishing composition, which caused non-uniform

dispersion of the extinguishing composition and surfactant.

There is thus a need in the art for a liquid fire extinguishing composition

which is not corrosive to metals, for example, cooking equipment and utensils,

or metal dispensing means for dispensing a fire extinguishing composition. Such

can be accomplished by providing a composition having a component other than

potassium carbonate or a lower pH. There is also a need in the art for a fire

extinguishing composition which is capable of extinguishing grease or other

hydrocarbon fires without the need for completely covering the fire, i.e.,

requiring only small amounts of material to come in contact with the source of

the fire. Further, a composition which can extinguish a fire using less material is

advantageous and desired. In addition, a fire extinguishing composition

comprising a surfactant which does not separate from the other components of the mixture while being stored is unique and heretofore undescribed.

Brief Summary of the Invention

It is accordingly an object of the present invention to provide an

advantageous fire extinguishing composition which, for example, is not corrosive

to metals, and a method of extinguishing a hydrocarbon fire using a composition

of the subject invention.

It is another object of the invention to provide a fire extinguishing

composition, as above, which is effective in extinguishing grease fires. A

further object of the invention is to provide a composition which can effectively

be used to extinguish a grease fire, i.e., a high-end hydrocarbon, and a fire

fueled by a low-end hydrocarbon, e.g., gasoline, kerosene, or other so-called

"light" hydrocarbons.

It is yet another object of the invention to provide a fire extinguishing

composition which has a pH of less than 1 1 . A further object of the invention is

to provide a fire extinguishing composition which can extinguish a fire by using

less material, i.e., one-half or less as compared to known compositions. The

composition of the subject invention further has minimum volatility and excellent

reignition protection.

It is still another object of the invention to provide a fire extinguishing

composition which includes a surfactant which remains in solution during

storage of the composition.

These objects, and others described hereinafter, are achieved by an

aqueous fire extinguishing solution which comprises water, potassium acetate, and a boron-containing compound, wherein the potassium acetate and the

boron-containing compound are dissolved in the water to form the aqueous

solution, the solution being sprayable on the fire.

Detailed Description of the Preferred Embodiments

In one embodiment of the invention, an advantageous fire extinguishing

composition comprises a mixture of a specific potassium salt or a bicarbonate

compound, e.g., potassium acetate (KAc), a boron-containing compound, and

water. It has been found that when the composition is applied to a stove-top

fire, such as a grease fire, or to a charcoal fire, the fire is immediately

extinguished.

By dispensing a relatively small amount of the improved fire extinguishing

material anywhere in a flaming pan of grease, or an expanse of grease which is

burning, the flames will be extinguished immediately because of the interaction

of the material with the grease and the spreading of the material over the

surface of the grease. It is believed that the placement of a small area of fire

extinguishing compound into a large expanse of grease causes a matrix barrier

blanketing composition to be formed which seeks out grease and flame, then

covers the entire expanse of grease. The flames are thus extinguished by

shutting off the oxygen supply as well as interfering with the chemical reaction

of rapid oxidation. The composition is capable of ascending an incline in order

to seek out and blanket hot grease.

In a first embodiment of the invention, which comprises water, potassium

acetate, and the boron-containing compound, the potassium acetate is present in an amount of between about 20% and 60% by weight, more preferably

between about 35%-55% by weight, and most preferably at about 40% by

weight. It has also been found that potassium bicarbonate can be used in place

of the potassium acetate, but with relatively lower efficacy. Sodium or lithium

bicarbonate can also be used as a substitute for potassium acetate, and gives

results similar to the composition comprising potassium bicarbonate.

The boron-containing compound is preferably boric acid, but it may be any

other suitable boron-containing material in addition to or in place of boric acid,

including ammonium, sodium, potassium, calcium, iron, and zinc borates, boron

phosphate, boron, and boron oxide. Where the boron-containing compound of

the first embodiment is boric acid, it is preferably present in an amount of at

least 0.5% by weight, more preferably at least about 0.75 % by weight and

most preferably about 1 .5%-2.0% by weight, the remaining portion of the

composition being potassium acetate and water.

When one or more of the other boron compounds are used in addition to

or in place of the boric acid, the quantity should be such as to provide an

amount of boron equivalent to the amount that will be provided by the amounts

of boric acid disclosed above. In other words, one or more of the other boron

compounds listed above can be substituted in whole or in part for the foregoing

quantities of boric acid, provided that the amounts employed contain the ratio

equivalent stoichiometric quantities of boron that will be present in the above-

disclosed amounts of boric acid.

Converting the above amounts of boric acid to a boron basis, the amount

of boron is preferably at least 0.085 % by weight, more preferably at least 0.1 3% by weight, and most preferably between about 0.26% and 0.34% by

weight.

Advantageously, the composition of the subject invention has a pH lower

than most known compositions used commercially for extinguishing grease fires.

Potassium carbonate aqueous solution alone can have a pH of up to 1 3, which

can be hazardous to persons having to clean up the composition after a fire

unless protective clothing or other protective means is used.

An aqueous solution composed of potassium carbonate and boric acid can

have a pH as low as about 1 1 to about 1 1 .5. However, a solution of this pH

can be corrosive to metal if it remains in contact with the metal for an extended

period of time.

By contrast, the subject composition has a pH lower than 1 1 , typically in

the range closer to neutral pH, e.g., a pH of between about 7 and 1 0. In a

preferred embodiment, a composition according to the subject invention has a

pH of about 8. For example, a composition comprising 42% potassium acetate

has a pH of about 7.9. Thus, the subject composition is less likely to corrode

metal, even if it remains in contact with metal for a period of several hours to a

few days.

A further advantage of the subject composition having a pH of about 8 is

that clean-up of the material is facilitated. The composition, after successfully

extinguishing a fire, can be left to dry to a powder. This resulting powder

maintains a relatively low pH (about 8) which is not harmful or caustic to a

person performing clean-up after the fire, nor is it harmful or corrosive to the

surface on which it dries. In addition, the powder can be simply vacuumed up and disposed under normal conditions, i.e., there is no government regulation

requiring special disposal procedures.

Clean-up is also facilitated by the fact that relatively small amounts of

material are required to be used to extinguish a fire. This use of less material, as

compared to other known compositions, is also economically advantageous

because of its overall low cost. Moreover, the capability to use less material

which is accomplished by the subject composition enables the employment of a

comparatively smaller distribution means, e.g., automatic spray devices which

are triggered by heat of a fire. Use of a smaller distribution means facilitates use

by allowing such distribution means to be affixed above a home stove, e.g.,

under a ventilation hood.

The subject composition can also be used in small canisters or other

dispensing means which are placed in a manner to dispense the fire

extinguishing composition from a conventional sprinkler head used in fire

prevention in commercial buildings, e.g., hotels, or homes. This eliminates the

need for water-based systems and their consequent plumbing systems.

Moreover, the elimination of water-based fire sprinkler systems by use of the

subject composition in a compatible dispensing means can eliminate water

damage to the surrounding area when a dispensing means using the subject

composition is deployed.

Another advantage of the subject composition comprising potassium

acetate, a boron-containing compound, and water is the rapid reduction of the

heat of the fire. The subject composition lowers the heat of the fire immediately

upon contact with the fire fuel source which can accordingly reduce damage caused by the heat of the fire.

The solution of the subject composition can be dispensed from a

pressurized can or a mechanical pump or any other device from which the

solution can be projected. It has been found that the fire extinguishing solution

is non-corrosive, that is, it will not corrode aluminum, copper, steel, or other

metallic surfaces to which it has been applied during a fire extinguishing action,

nor will it corrode metallic containers or piping used for containing or dispensing

the solution. By contrast, most prior art aqueous fire extinguishing compositions

have tended to dissolve metal.

Furthermore, in spite of the fact that the composition is in aqueous form,

it will not cause detrimental splattering when it is applied to and reacts with a

flaming oil or grease. Rather, the composition forms a matrix in which the

composition is spread rapidly across the surface of the grease fire to rapidly

extinguish it. A crust can form on the surface of the grease after

extinguishment, which protects the surface from flashback. In addition, the

composition blocks, or prevents the escape of, vapors of the fire fuel source.

This is particularly advantageous if the vapors of the fire fuel source are harmful

or hazardous.

A composition of boric acid, water and potassium acetate which has been

found particularly effective comprises about 40% by weight potassium acetate,

about 2.0% by weight boric acid, and about 58% by weight water.

In another embodiment of the invention, the composition comprising

potassium acetate, a boron-containing compound, and water, as described

herein, can further include a surfactant or a suspension stabilizer. Surfactants and stabilizers are well known in the art and are commercially available.

Surfactants typically comprise at least one of a sulfate or phosphate. Preferred

surfactants include sodium decyl sulfate, sodium hexyl sulfate, or sodium oxyl

sulfate. These can typically be included at a concentration of about 6-1 2% of

the total composition. Other surfactants would be recognized by those of

ordinary skill in the art so long as they are compatible with a composition of the

subject invention as described herein and can help form a continuous layer of the

subject composition.

Suspension stabilizers are components which, as their name implies, help

to keep a mixture in suspension, i.e., prevent separation of the components or

precipitation of an ingredient. Suspension stabilizers are also known in the art

as "hydrotrobes. " Examples of suspension stabilizers useful with the subject

composition are NAXONATE 4L and NAXONATE 4XT. Typically, such solution

stabilizers are included at a concentration of between about 5-1 0% of the total

composition.

In a preferred embodiment, the composition comprises potassium acetate

or a bicarbonate salt as described herein, a boron-containing compound, water, a

surfactant, and a solution stabilizer. Advantageously, the solution stabilizer

prevents separation of the surfactant from the other components which form the

subject composition. This allows the surfactant to be evenly distributed with

the other components of the mixture when the composition is dispensed during

use. Accordingly, the subject composition which includes surfactant is capable

of being stored as a mixture and dispensed as a mixture from a single storage

container or dispenser. Following are examples which illustrate procedures for practicing the

invention. These examples should not be construed as limiting. All percentages

are by weight and all solvent mixture proportions are by volume unless

otherwise noted.

Example 1 :

An aqueous mixture comprising a final composition of approximately 40%

potassium acetate approximately 2.0% boric acid, and the balance (about 58%)

water was prepared. All components were in solution.

In testing the effectiveness of the subject composition, peanut oil was

ignited in a round pan, 1 1 " diameter x ¹ _ " deep, by heating the oil with a

bunsen burner to about 800° F. The peanut oil was allowed to burn 1 -2

minutes. Application of a single droplet (about 0.05 ml) of the subject

composition immediately extinguished the fire. An identical test using a known

composition (potassium carbonate/boric acid/water) required about 3 droplets

(0.1 5 ml) before the fire was extinguished. Thus, the subject composition

comprising sodium acetate, boric acid, and water is about three times as

effective as the known potassium carbonate, boric acid, and water composition

which previously was believed to be the most effective composition available for

grease fires.

In addition, when applying the subject composition to the grease fire, the

single droplet was applied at one edge of the pan. The composition immediately

spread across the entire surface of the grease and extinguished the fire. A layer

of the composition formed over the surface of the grease, thereby achieving a

further advantageous blocking effect on the vapors, preventing escape of vapors from the fuel source of the fire.

A similar test of the subject composition using a 3' x 2' pan of peanut oil

approximately 1 " deep was conducted. The peanut oil was heated to about

800° F to cause self-ignition. The peanut oil was allowed to burn for 1 -2

minutes. Using only 3-4 ounces of the subject composition, the fire was

extinguished in approximately 1 -2 seconds.

The composition and resulting reaction products from the fire were not

corrosive to either aluminum and copper components utilized in the apparatus

used to apply the composition or to metals, e.g., pans, involved in the fire.

It should be understood that the examples and embodiments described

herein are for illustrative purposes only and that various modifications or

changes in light thereof will be suggested to persons skilled in the art and are to

be included within the spirit and purview of this application and the scope of the

appended claims.

Claims

I claim:

I . A fire extinguishing composition comprising a salt selected from the

group consisting of potassium acetate, potassium bicarbonate, lithium

bicarbonate, and sodium bicarbonate; a boron-containing compound; and water.

2. The fire extinguishing composition of claim 1 , wherein the boron-

containing compound is selected from elemental boron, boric acid, ammonium

borate, potassium borate, calcium borate, iron borate, zinc borate, boron

phosphate, and boron oxide.

3. The composition of claim 1 , wherein said boron-containing

compound is boric acid.

4. The composition of claim 1 , wherein said salt is potassium acetate.

5. The composition of claim 1 , wherein said potassium acetate is

between about 20% and 60% by weight of the total composition.

6. The composition of claim 4, wherein said potassium acetate

comprises between about 35% and 55% by weight of the total composition.

7. The composition of claim 4, wherein said potassium acetate

comprises about 40% by weight of the total composition.

8. The composition of claim 4, wherein said potassium acetate

comprises about 42% by weight of the total composition.

9. The composition of claim 3, wherein said boric acid comprises at

least about 0.5% by weight of the total composition.

1 0. The composition of claim 3, wherein said boric acid comprises at

least about 0.75% by weight of the total composition.

I I . The composition of claim 3, wherein said boric acid comprises between about 1 .5% and about 2.0% of the total composition.

1 2. The composition of claim 4, wherein said potassium acetate

comprises about 40% of the total composition, boric acid comprises about 2.0%

of the total composition, and water comprises about 58% of the total

composition.

1 3. The composition of claim 1 , wherein said composition has a pH of

between about 7 and about 10.

1 4. The composition of claim 1 , wherein said composition has a pH of

about 8.

1 5. The composition of claim 1 , wherein said composition further

comprises a surfactant.

1 6. The composition of claim 1 5, wherein said surfactant is selected

from the group consisting of sodium hexyl sulfate, sodium octyl sulfate, and

sodium decyl sulfate.

1 7. The composition of claim 1 , wherein said composition further

comprises a solution stabilizer.

1 8. The composition of claim 1 7, wherein said suspension stabilizer is

selected from the group consisting of NAXONATE 4L and NAXONATE 4XT.

1 9. The composition of claim 1 , wherein said composition comprises a

surfactant and a solution stabilizer.

20. A method for extinguishing a hydrocarbon fire, said method

comprising the steps of:

(a) providing a composition which comprises a salt selected from

the group consisting of potassium acetate, potassium bicarbonate, lithium bicarbonate, and sodium bicarbonate; a boron-containing compound; and

water; and

(b) contacting a hydrocarbon fire with an effective amount of

said composition.

21 . The method of claim 20, wherein said composition is dispensed

from a sprinkler head.

22. The method of claim 20, wherein said salt is potassium acetate.

23. The method of claim 20, wherein said composition further

comprises a surfactant which remains in solution during storage and dispensing.