Reduction of HF

Details Reduction of HF Reduction of HF

2002-12-13

2004-05-18

Anthony, Joseph D. (Department: 1714)

Compositions

Fire-extinguishing

Volatile or gas charged liquids containing

C252S002000, C252S003000, C252S007000, C252S008050, C252S004000

Reexamination Certificate

active

06736989

ABSTRACT:

FIELD OF THE INVENTION
The Invention relates to a composition to control, reduce or eliminate hydrogen fluoride (HF). Documents cited herein in the following text are incorporated by reference.
BACKGROUND OF THE INVENTION
The literature is replete with descriptions of fire-extinguishing compositions. Included in such compositions are gelled compositions comprising dry solid chemicals for extinguishing flames and inhibiting oxidation (for example sodium and potassium bicarbonate) and vaporizing organic liquids like brominated hydrocarbons. The latter compounds also extinguish flames very effectively. The mechanism by which brominated hydrocarbons extinguish flames is two-fold. The primary mechanism involves the termination of free radical ion reactions that sustain combustion and a secondary mechanism is heat abstraction associated with a high vapor heat capacity and a high heat of vaporization.
A number of perfluorocarbons, chlorofluoro-carbons (CFC) and hydrofluorocarbons (HFC) by themselves have been identified as potentially useful to extinguish fires in flooding applications, and being free of bromine content or low in chlorine content, have little or no ozone depletion potential (ODP). Representative of these perfluorocarbons, chlorofluorocarbons and hydrofluorocarbons are 2-chloro-1,1,1,2-tetrafluoroethane, pentafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoro-ethane, 1,1,1-trifluoroethane, perfluorocyclopropane, perfluoropropane, perfluorocyclobutane and the like; see U.S. Pat. No. 5,135,054, which is incorporated herein by reference. The chlorofluorocarbon compounds are also referred to by the “CFC” system of nomenclature, and the hydrofluorocarbons by the “HFC” system. Under these systems, the first digit represents the number of carbon atoms minus one (and is omitted if zero); the second digit represents the number of hydrogen atoms plus one; and the third digit represents the number of fluorine atoms. For example, HFC-125 represents pentafluoroethane.
U.S. Pat. No. 5,833,874 relates to fire-extinguishing compositions of low ozone depletion potential comprising dry particles of fire-extinguishing agents dispersed in a gel of liquefied volatile perfluorocarbons, chlorofluorocarbons or hydrofluorocarbons. The dry particles are compatibilized with the carrier gel by the presence of a surfactant system composed of a non-ionic surfactant, a film forming fluorocarbon surfactant and a phosphorus containing antiflocculent. The compositions of the patent are hybrids, i.e., gelled formulations of dry powder agents delivered in liquefied hydrofluorocarbons and chlorofluorocarbons.
Extinguishing open flames within a confined space such as a room in a building, an engine compartment in a vehicle, aircraft interiors, enclosed fuel storage areas, electric control boxes, storage containers, hazardous material storage facilities and the like has always posed problems of speed in extinguishing and clean-up requirements after the flame is extinguished. The first problem is related to placement of a fire extinguishing composition at the flame site, in sufficient quantity to extinguish a flame rapidly and on demand. The second problem is related to the nature of the fire extinguisher composition and its residues after flame extinction.
Normally, the HFC, PFC and HCFC gases that are developed to replace halons generate unacceptable high quantities of hydrogen fluoride when putting out fires, thereby running the risk of killing the persons in the “occupied” space from which the fire emanated even when the fire is put out. There are no HFC, PFC or HCFC gases that are exceptions to this statement. This covers the list of gases that are now EPA permitted to be used for fire extinguishment.
Thus there is a need for gaseous halon replacements that have demonstrated a greater affinity for HF production in fire scenarios. There is also a need for gas-based extinguishants for automatic fire extinguishers for moving vehicles, planes, ships, and electronics which are enclosed or semi-enclosed and thus need the elimination of HF to occur relatively rapidly.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore a principal object of the invention to overcome the shortcomings of the prior art heretofore mentioned.
It is a further object of the invention to provide a method for reducing HF to EPA accepted levels.
In accordance with one embodiment of the present invention, a method is provided for formulating a substantially non-aqueous, flame-extinguishing composition which uses a fluorocarbon gas to extinguish a fire to reduce the amount of HF given off when the fluorocarbon gas is applied to the fire, comprising providing a first amount of a fluorocarbon gas which produces HF when exposed to a fire; providing a gelled powder additive, said additive comprising salts of weak acids which decompose at the temperature.
In accordance with another embodiment of the present invention, a substantially non-aqueous, flame-extinguishing composition used to extinguish a fire is provided, comprising: a fluorocarbon gas in admixture with approximately 3-7% by weight of a gelled powder additive, said additive comprising salts of weak acids which decompose at the temperature of the fire.
In accordance with a further embodiment of the present invention, a substantially non-aqueous, flame-extinguishing composition used to extinguish a fire is provided, comprising a flame extinguishing fluorocarbon gas component comprising at least one hydrofluorocarbon gas, which produces HF gas when exposed to fire, in admixture with approximately 3-20% by weight of a gelled salt of a weak acid which decomposes when exposed to fire and which reduced the amount of HF gas produced by the hydrofluorcarbon gas, the relative quantities of salt and hydrofluorcarbon gas selected to reduce HF gas production to within a preselected limit.
In accordance with a yet another embodiment of the present invention, a method is provided for formulating a substantially non-aqueous, flame-extinguishing composition which uses a fluorocarbon gas to extinguish a fire, to reduce the amount of HF given off when the fluorocarbon gas is applied to the fire, comprising: providing a first amount of a fluorocarbon gas which produces HF when exposed to a fire; providing a gelled powder additive, said additive comprising salts of weak acids which decompose at the temperature of the fire; selecting a maximum HF emission target level; and adjusting the relative amounts of the additive and the fluorocarbon gas so that when the fluorocarbon gas is mixed with the additive and applied to a fire, no more than the target HF emission is given off, wherein the salt is an ammonium polyphosphate, and wherein the additive comprises 15-20% by weight of the admixture.
In accordance with a still further embodiment of the present invention, a method is provided for formulating a substantially non-aqueous, flame-extinguishing composition which uses a fluorocarbon gas to extinguish a fire, to, reduce the amount of HF given off when the fluorocarbon gas is applied to the fire, comprising: providing a first amount of a fluorocarbon gas which produces HF when exposed to a fire; providing a gelled powder additive, said additive comprising salts of weak acids which decompose at the temperature of the fire; selecting a maximum HF emission target level; and adjusting the relative amounts of the additive and the fluorocarbon gas so that when the fluorocarbon gas is mixed with the additive and applied to a fire, no more than the target HF emission is given off, wherein the salt is sodium bicarbonate and wherein the additive comprises 3-7% by weight of the admixture.
These and other embodiments of the invention are provided in or are obvious from the following detailed description of the invention.


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