Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
2000-02-17
2002-07-02
Langel, Wayne (Department: 1754)
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
C149S124000, C540S552000, C540S554000, C544S180000, C588S253000
Reexamination Certificate
active
06414143
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the extraction and recovery of nitramine oxidizers from energetic materials, especially solid propellants, explosives, and pyrotechnics, and more particularly to an extraction and recovery process that is performed in the absence of organic solvent.
2. Description of the Related Art
Demilitarization has created a need for the economical and environmentally friendly non-hazardous disposal of solid explosives and propellants commonly found in rockets and ballistic missiles. An example of a propellant that is commonly found in rocket motors and missiles subject to demilitarization is Class 1.1 solid propellants. Generally, Class 1.1 solid propellants contain combinations of polymeric binders, plasticizers such as nitrate ester plasticizers, ballistic additives, chemical stabilizers, curing agents and catalysts, metal powders, and inorganic and/or organic oxidizers.
One class of organic oxidizer that has found wide acceptance in the rocket propulsion, explosive, and pyrotechnic arts comprises nitramine oxidizers. Common nitramine oxidizers include, for example, cyclotetramethylenetetranitramine (also known as HMX and 1,3,5,7-tetranitro-1,3,5,7-tetraaza-cyclooctane), cyclotrimethylenetrinitramine (also known as RDX and 1,3,5-trinitro-1,3,5-triaza-cyclohexane), and combinations thereof, as well as TEX (4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo-[5.5.0.0
5,9
0
3,11
]-dodecane), and HNIW (also known as CL-20) (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo [5.5.0.0
5,9
0
3,11
]-dodecane). These nitramines are commonly among the most expensive and highly explosive ingredients of conventional energetic compositions, making their successful and efficient recovery for subsequent re-use highly desirable.
A method for the extraction and recovery of nitramine oxidizers from solid propellants is disclosed in U.S. Pat. No. 5,284,995 to Melvin, which discloses the use of a liquid ammonia extraction agent for extracting HMX and RDX from rocket motor solid propellants. The use of liquid ammonia in nitramine recovery techniques introduces several complexities and expenses, especially in a closed system, including high capital expenditures required as outlay to obtain equipment capable of operating at the high-pressures (5 to 40 Kpsi) at which liquid ammonia is handled. The presence of liquid ammonia also creates other problems, such as worker safety issues, since contact between the ammonia and human skin can cause severe chemical burns to the handler. Additionally, liquid ammonia is combustible, and presents a severe inhalation hazard if not handled correctly. Another disadvantage of the process of U.S. Pat. No. 5,284,995 is that subjecting energetic materials, such as Class 1.1 propellants containing nitramine oxidizers, to pressurized environments as described in the '995 patent increases the risk of accidental detonation, as well as the accompanying catastrophic consequences that an accidental detonation or explosion often has on human life and property.
Techniques for decomposing pyrotechnic materials with a combination of organic solvents and mineral acids are disclosed in U.S. Pat. No. 4,098,627 to Tompa et al. Representative mineral acids include hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and perchloric acid, which function to decompose cross-linked or linked polymeric binders present in the pyrotechnic materials. The organic solvent functions either to swell the organic polymeric binder present in the pyrotechnic material or to dissolve filler material present in the pyrotechnic material. Organic solvents reportedly suitable in the process are toluene, xylene, dioxane, and tetrahydrofuran. The decomposition technique is carried out at 80° to 120° C. In practice, however, these organic solvents raise a host of safety concerns, including flammability, VOC emissions, environmentally sound and cost-effective waste disposal, and handling expenses.
Two additional approaches for dissolution of pyrotechnic materials having polymeric binders are disclosed in U.S. Pat. No. 4,389,265 to Tompa et al. The first approach utilizes a solution of 2-aminoethanol in a mixture of an aromatic solvent and an alcohol. The second approach is performed with a solution of a mineral acid, other than nitric acid, water, and an organic solvent. The 2-aminoethanol employed in the first approach and the combination of mineral acid and organic solvent employed in latter approach serve to breakdown or dissolve the polymeric binder. Examples of aromatic solvents for the first approach include benzene, toluene, xylene, ethylbenzene, and diethylbenzene. Examples of organic solvents used in the second approach include acetone, methylethylketone, tetrahydrofuran, and mixtures thereof. Hydrochloric, sulfuric or phosphoric acid in concentrations from 2N to 6N are combined with one or more of the above-listed organic solvents. The presence of these aromatic and organic solvents raises safety concerns over such issues as flammability, volatile emissions, and waste disposal.
There is therefore a long-felt need in the art to develop a method for the recovery of nitramine oxidizers from energetic materials such as solid propellants, explosives, and pyrotechnics (hereinafter collectively referred to as “PEP formulations” or “PEP materials”) in which there is no need for the use of either liquid ammonia under increased pressure or hazardous organic solvents that are volatile and/or flammable.
SUMMARY OF THE INVENTION
An object of this invention is to provide a nitramine-recovery method that addresses the above-described long-felt need in the art, is inexpensive and efficient, does not require the use of organic solvents as processing agents, and is suitable for the recovery of reusable nitramine oxidizers from PEP formulations, especially solid propellants of rocket motors such as ballistic missiles.
In accordance with the principles of this invention, the above and other objects are attained by the provision of a process in which nitramine oxidizers are extracted from PEP formulations with concentrated aqueous mineral acids, especially at least 70 wt. % nitric acid, in the absence of an organic solvent.
In accordance with one embodiment of this invention, the PEP formulation is treated in an acid bath comprising the concentrated aqueous mineral acid heated to a temperature sufficiently high to obtain a nitramine-containing solution. The solution is then filtered to generate a liquid filtrate containing the dissolved nitramine oxidizer. The filtrate is then diluted with a diluent such as water and/or treated with an acid-neutralizing agents such as aqueous sodium bicarbonate or sodium hydroxide or ammonia gas, which will cause the nitramine to precipitate out. The filtration of the nitramine-containing solution is performed at a temperature sufficiently high to keep the nitramine dissolved in the nitric acid solution. The nitramine oxidizer is then precipitated and isolated, for example, by filtering, drying, and washing the precipitate to yield the desired reusable nitramine oxidizer.
Suitable mineral acids for use in the aqueous concentrated mineral acid bath include, for example, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, perchloric acid, and combinations thereof. Nitric acid is preferred as the mineral acid because of the high solubilility of nitramines in nitric acid, especially nitric acid in a concentration of from about 70 to about 98 wt. %, preferably nitric acid at a concentration of up to 90 wt. % is utilized.
In accordance with a specific embodiment of this invention, in which the PEP formulation comprises a nitrate ester plasticizer, the process can also further comprise pre-treating the PEP formulation with a hydrolysis agent to hydrolyze the nitrate ester prior to addition of the PEP formulation to the heated acid bath.
The nitramine oxidizer is recovered in yields typically on the order of 60 wt. % or higher based on the amount of oxidizer present in the PE
Cannizzo Louis
Huntsmann Lew
Alliant Techsystems Inc.
Sullivan Law Group
LandOfFree
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