Explosive and thermic compositions or charges – Structure or arrangement of component or product – Solid particles dispersed in solid solution or matrix
Reexamination Certificate
1998-06-01
2003-11-11
Miller, Edward A. (Department: 3641)
Explosive and thermic compositions or charges
Structure or arrangement of component or product
Solid particles dispersed in solid solution or matrix
C149S036000, C149S096000, C149S097000, C149S098000, C149S100000
Reexamination Certificate
active
06645325
ABSTRACT:
FIELD OF INVENTION
The present invention is related to fast-burning nitrocellulose compositions comprising as additives substituted tetrazine compounds such as hydrazino tetrazines.
BACKGROUND OF THE INVENTION
Explosive decompositions of explosive compounds or mixtures are classified as either combustion or detonation. Explosives that decompose by combustion are known as deflagrating explosives or propellants, since they are often used to propel projectiles from guns. Those that detonate are known as detonating explosives, and may be divided into high or bursting explosives, blasting explosives, and priming explosives, depending upon whether they are used as bursting charges in shells or bombs, for breaking down or loosening minerals, rocks or other obstructions, or, in small quantities, in fuzes to initiate the explosion of much larger quantitites of other explosives. Explosives can be either chemical compounds (called chemical explosives) or mixtures of at least two different substances which may not themselves be explosive but form same in combination, called explosive mixtures. The oldest example of the latter is gunpowder.
Highly efficient propellants for aerospace propulsion, pyrotechnics, gas generation and the like depend upon the production of large volumes of low molecular weight gases. This has been accomplished for the most part with pyrotechnic and explosive compositions, but concerns which have received little attention are toxicity, storage stability and expense. A material which could solve many of the negative aspects of propellants commonly in use is nitrated cellulose, also known as nitrocellulose, cellulose nitrate or guncotton.
Nitrocellulose is used in great quantities in smokeless propellants for firearms, including artillery, and to some extent in combination with other propellants such as solid rocket propellants to help reduce their toxic gas production. Burning nitrocellulose generates nitrogen, carbon dioxide and water vapor, all non-toxic, low molecular weight gases. The problem is that nitrocellulose cannot be made to burn by itself rapidly enough to make it useful in most propellant applications without being mixed with other flammable or explosive materials to increase the reaction speed. Unfortunately, such additives, e.g. nitroglycerine, RDX, HMX, nitroglycol, ammonium perchlorate and the like, often create smoke and other disadvantages which the nitrocellulose was intended to overcome. Explosive and propellant compositions containing nitrocellulose in combination with other explosives are known, e.g. ballistite, composed of about 60 percent nitrocellulose and 40 percent nitroglycerine, and benite, containing about 60 parts of black powder in a matrix of about 40 parts of plasticized nitrocellulose and used as a propellant igniter.
Nitrocellulose is classified as a secondary explosive and used in many propellants. Single-base gun propellants are based primarily upon nitrocellulose, while double- and triple-base propellants contain significant quantities of additional energetic ingredients such as nitroglycerine and/or nitroguanadine. Nitrocellulose propellants are made with or without the incorporation of solvents as plasticizers by five processes—solvent extrusion, solvent emulsion, solventless extrusion, solventless rolling and casting (for rockets). These methods can produce propellants suitable for use in various guns, rockets, and the like. The methods are described in Kirk-Othmer's 4th Ed., infra, Vol. 10, at pp. 93-100. The same reference describes the production of ball powder, a single-base or double-base nitrocellulose propellant consisting of spherically shaped or flattened ellipsoidal grains and used primarily in small arms, at pp. 100-103.
For many applications of explosives and propellants, it is desirable to adjust the burning rate of the composition. See, e.g., U.S. Pat. No. 5,295,545, issued to the University of Colorado Foundation for a “Method of Fracturing Wells Using Propellants”. Considering the other properties of nitrocellulose, it would be desirable to cleanly increase its burning rate in explosive and propellant compositions. It has been reported that although the burning rate of nitrocellulose propellants at high gun pressures is not significantly affected by the presence of additives, the addition of small amounts of some metal salts to double-based propellants increases their burning rates at much lower rocket pressures. See Kirk-Othmer's
Encyclopedia of Chemical Technology
, 4th Ed., Vol. 10, p. 77 (John Wiley & Sons, NYC).
Various derivatives of 1,2,4,5-tetrazine, or s-tetrazine, are disclosed in U.S. Pat. No. 3,244,702, which is incorporated herein by reference. One such compound, 3,6-dihydrazino-1,2,4,5-tetrazine, has been reported to be useful in producing smokeless pyrotechnic compositions. Chavez & Hiskey, “High-Nitrogen Pyrotechnic Compositions,”
Journal of Pyrotechnics
, Vol. 7, pp. 11-14 (Summer 1998). Kirk-Othmer's Chapter 10, supra, reports at page 54 that 3,6-dinitro-s-tetrazine has been investigated as a high energy polymeric binder for use with RDX, HMX and higher energy explosives.
SUMMARY OF THE INVENTION
It is an aspect of the present invention to produce nitrocellulose compositions having accelerated burning rates to make them suitable for various propellant and explosive applications.
Another aspect is to produce propellant and explosive compositions which are stable under storage and relatively insensitive to friction and static electricity.
Other aspects of this invention will appear from the following description and appended claims.
In accordance with the invention, compositions of nitrocellulose are provided which contain small but effective amounts of substituted s-tetrazine compounds which increase the burning rates over those of pure nitrocellulose materials or compositions based thereon. The substituted s-tetrazine compounds disclosed in U.S. Pat. No. 3,244,702 can be used as such additives, either singly or in combination. Preferably, the additive comprises a hydrazine-substituted s-tetrazine, and most preferably, comprises dihydrazino-s-tetrazine. Depending upon the proportions of nitrocellulose, other propellants and/or explosives and the proportions of the additives, the compositions are useful as gas generators, airbag propellants, rocket propellants, fuels, fireworks propellants, industrial propellants and propellants for firearms, including artillery pieces.
Before explaining the disclosed embodiments of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular compositions disclosed, since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The compositions of the present invention are based upon nitrocellulose, and the effect of the invention is for the disclosed additives to increase the burning or detonation rate of the nitrocellulose compositions. Nitrocellulose is made by treating cellulose with nitric acid, using sulfuric acid as a catalyst. These processes are well known in the art, and various forms of nitrocellulose are commercially available. The manufacture of nitrocellulose is described in Kirk-Othmer's 4th Ed., supra, in Vol. 17, pp. 68-80 (“NITRATION”) and in Vol. 5, pp. 529-540 (“INORGANIC CELLULOSE ESTERS”). Both of these chapters are incorporated herein by reference. Cotton, alpha cellulose made from wood and other forms of cellulose can be used.
The cellulose repeating unit of the polymer molecule (C
6
H
10
O
5
) contains three hydroxyl groups, all of which can unite with molecules of nitric acid, acquiring the equivalent number of nitro groups. The degree of nitration, ranging from an average of one or less nitro groups per cellulose repeating unit to the theoretical maximum of three, determines whether the nitrocellulose is suitable for making plastics, lacquers, propellants or explosives. The number of nitro groups per repeating
Miller Edward A.
Poole, Esq. James K.
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