Explosive and thermic compositions or charges – Structure or arrangement of component or product – Solid particles dispersed in solid solution or matrix
Reexamination Certificate
1999-04-20
2001-07-24
Jordan, Charles T. (Department: 3641)
Explosive and thermic compositions or charges
Structure or arrangement of component or product
Solid particles dispersed in solid solution or matrix
C149S019100, C149S021000, C149S109600
Reexamination Certificate
active
06264772
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to fire-prevention, in particular to fire-extinguishing agents containing pyrotechnical compositions, which generate a fire-extinguishing aerosol formed as a result of the thermal decomposition of said compositions at combustion.
Aerosol-forming compositions are used in fire-extinguishing systems for fires in enclosed and half-enclosed spaces, and namely in:
warehouses and garages;
office and factory rooms;
sections of transport media such as land vehicles, ocean-going and river ships, aeroplanes;
air-ventilator systems, etc.
DESCRIPTION OF THE BACKGROUND ART
Fire-extinguishing compositions must meet a whole complex of requirements:
a high fire-extinguishing efficiency;
a low toxicity of the combustion products;
a low temperature of the combustion products;
a simple, safe and low energy consuming preparation technology;
durability of the composition.
The maintenance of all the requirements interferes with the problems concerning the reciprocal, often conflicting with one another, effects of the factors related to the technology of preparation of fire-extinguishing compositions and their characteristics. For example, the requirement of high fire-extinguishing efficiency makes it necessary to use a large amount of solid fillers (oxidizing agents, combustible agents) in the compositions. However, the increase of the portion of solid fillers leads to an increased molding pressure, which in turn increases the hazardness of the process and its energy capacity. The high molding pressure leads due to the increased surface friction between the particles of the solid fillers to the appearance of stress at the contact point of the particles, the formation of pores and, consequently, to a decrease of the stability and also to a non-uniform distribution of the particles in the molded composition, which leads to its non-uniform combustion and, as a consequence, to a decrease of the fire-extinguishing efficiency.
For the development of novel compositions and the improvement of known compositions, the problem is said to meet the sum of present requirements or to significantly improve separate properties and characteristics.
A composition for extinguishing fires is known (RU 2001647), which contains as combustible binder an epoxide resin in an amount of 10-14.5% by weight, an isomethyltetrahydrophthalic anhydride curing agent in an amount of 12-15% by weight, potassium perchlorate in an amount of 2-25% by weight as oxidizing agent, as additives carbon or a pigment in an amount of 0.001-0.5% by weight, sulforicinate in an amount of 0.01-0.5% by weight, and potassium nitrate the balance. When said composition is used, the fire-extinguishing concentration amounts to 23-27 g/m
3
.
A composition for extinguishing fires is known (RU 2001648), which contains an epoxide resin in an amount of 1.5-15% by weight as combustible binder, isomethyltetrahydrophthalic anhydride in an amount of 1.5-15% by weight as curing agent, and additionally a polyether (polyester) resin in an amount of 7.5-30% by weight, methylethylketone peroxide in an amount of approximately 0.075% by weight, potassium perchlorate in an amount of 10-40% by weight as oxidizing agent, as additives sulforicinate or carbon in an amount of 0.001-0.5% by weight, and potassium nitrate the balance. The composition possesses an increased impact resistance if it contains the epoxy resin in an amount of 1.5% by weight and the polyether (polyester) resin in an amount of not more than 30% by weight. There exists also a lower content limit for the polyether (polyester) resin, i.e. 7.5% by weight, but in this case the epoxy resin must be present in an amount of up to 15% by weight.
The process for the preparation of the compositions for extinguishing fires according to RU 2001647 and RU 2001648 comprises the steps of successive charging and mixing of the components of the composition. Said process comprises:
Charging of the binder and the curing agent (epoxy resin and isomethyltetrahydrophthalic anhydride, and according to RU 2001648 additionally the polyether (polyester) resin and methylethylketone peroxide) and mixing within 30 minutes at a temperature of 20° C. with evacuation.
Charging of two doses of alkali metal nitrate with mixing for 10 minutes.
Charging of two doses of alkali metal perchlorate with mixing for 10 minutes and subsequent mixing of the components for 1 hour.
Charging of carbon or sulforicinate and mixing of all components for 30 minutes, whereby the last 20 minutes are carried out with evacuation.
The final composition is poured into forms and cured for 7-10 days at 80° C.
As a result, an article of predetermined shape is obtained, which may be used for extinguishing fires by means of its ignition by an initiating system.
Said compositions and the process for their preparation possess a series of essential disadvantages:
a high-energy capacity of the process due to the use of the epoxy resin with isomethyltetrahydrophthalic anhydride, which requires a prolonged curing of the composition (7-10 days at 80° C.). The use of polyethylene polyamine as curing agent allows to significantly (up to 1 hour) reduce the curing time, but at the same time there occurs an increase of the dynamic viscosity with such a velocity that it is not possible to prepare the composition at an industrial scale due to the loss of “survivability” at the stage of processing;
ecological hazardness due to the presence of uncured epoxy resin and isomethyltetrahydrophthalic anhydride in the composition, which may cause dermatitis and ulcers, if said components come in contact with the skin;
limited possibility to prepare compositions with a large content of solid phases (oxidizing agent, gas-aerosol-forming agent), because the reduction of the content of the binder leads to a drastic increase of the viscosity and the lack of flowability of the composition, furthermore, leads to difficulties in homogeneously dispersing the components and to an increase of the hazardness of the steps of mixing and molding articles from said composition. The use of high-weight portions of the binder in the composition leads to a low stability of the ignition and combustion of the composition, and also to a decrease of its fire-extinguishing efficiency;
the necessity to take additional steps in order to ensure the safeness during the processing of the composition for the case that methylethyleketone peroxide, which appears to be an explosive substance, is used in the composition. Furthermore, the provision of a stable composition is only possible in a narrow range of the proportion of epoxy resin and polyether (polyester) resin and correspondingly their curing agents, which affords very high demands on the accuracy of the dosing of the components and the necessity to observe a strict succession of the addition of the components;
a high dependence of the technological parameters (viscosity, flowability) of the composition and its fire-extinguishing concentration on minor changes in the preparation conditions and the concentration of the components. Thus, a change of the carbon content in the composition from 0.6 to 0.45% by weight leads to an increase of the viscosity by a factor of 10
3
(from 2×10
3
poise to 8×10
6
poise) and a decrease of the flowability coefficient (from 0.8 to 0.05), whereas the fire-extinguishing concentration increases from 24 to 27 g/m
3
.
Pyrotechnical compositions for use in a process for extinguishing voluminous fires are known (EP 0561035 B1). The first composition contains potassium perchlorate in an amount of 40-50% by weight, epoxy resin in an amount of 9-12% by weight, potassium chloride in an amount of 10-44% by weight, and magnesium powder in an amount of up to 4% by weight. A second composition contains potassium nitrate in an amount of 70-80% by weight, epoxy resin in an amount of 19-23% by weight and magnesium or aluminium powder in an amount of 2-4% by weight.
Said pyrotechnical compositions possess several essential disadvantages:
A high temperature of the combustion products;
harmful eff
Baker Aileen J.
Jordan Charles T.
R-Amtech International, Inc.
Rothwell Figg Ernst & Manbeck p.c.
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