Patent Application
20190023629
The present disclosure relates to pyrotechnic compositions, such as priming mix compositions and propellant compositions, and in particular to low and no lead pyrotechnic compositions.
This section provides background information related to the present disclosure which is not necessarily prior art.
Pyrotechnic compositions such as priming mixes, detonating mixtures, propellants, initiators, and similar compositions usually include substances to increase their performances such as sensitivity, propagation, and smoothness of burning (for propellant compositions, meaning without self-extinguishing or transition into detonation). For variety of reasons, private industries and the Government, for example, have tried to replace lead azide in detonating mix, to replace lead styphnate in priming mixes, and to find a black powder substitute. Thus far, the success has been limited or left with desires in terms of performance, safety, cost, etc. For priming composition, one common ingredient for this purpose is lead styphnate, C6HN3O8Pb also known as lead 2,4,6-trinitroresorcinate. While lead styphnate is highly effective in these pyrotechnic compositions there are environmental and health and safety concerns over the presences of lead. Efforts have been made to reduce or eliminate lead styphnate without detracting from the performance of the pyrotechnic compositions in which it is used.
For example, for decades, numerous efforts from the ammunition industry and the government have tried to replace lead styphnate based priming mixes and propellants with unleaded mixtures. These efforts included using nanoparticles (MIC or Meta Interstitial Composition) of fuel and oxidizer which later evolved into using fine particles of, in addition to fuel and oxidizer, less sensitive explosives such as RDX, HMX or PETN etc. However, among other things these nanoparticles are very reactive, creating both fire/explosion risks and health hazards in the production environment.
These efforts have also included the use of known and established lead-free initiating explosives such as dinol (diazodinitrophenol or DDNP) and KDNBF (potassium dinitrobenzofuroxane). However, dinol, although the main stay of lead-free priming mixes, is not as thermally stable as lead styphnate, and thus dinol is usually relegated to “training” rounds, as distinguished from “duty” rounds, because of possible degradation from uncontrolled heat conditions.
These efforts have also included using newer lead free initiating explosives such as KDNP, or derivatives of nitrotetrazoeles. However the performance of these “new” initiating explosives is not necessarily better than existing materials, especially regarding safety. While the reactivity hazards are easily assessed, the health hazards are much harder to evaluate. Furthermore manufacturing procedures often include the use of organic solvents which are costly and can have significant environmental impact.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
Generally embodiments of this invention provide pyrotechnic compositions with satisfactory sensitivity and propagation with low levels or no levels (other than as inherent impurities) of lead, through the inclusion of a metallocene, and in particular ferrocene. The pyrotechnic compositions according to the various embodiments of this invention generally include a fuel, an oxidizer, and metallocene, a burn modifier, in an amount effective to provide the desired sensitivity and propagation. In the most preferred embodiments the metallocene is ferrocene, or a mixture of metallocenes including ferrocene.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Example embodiments will now be described more fully.
Generally, embodiments of this invention provide pyrotechnic compositions designed to produce an effect by heat, light, sound, gas/smoke or a combination of these, from non-detonative self-sustaining exothermic chemical reaction, generally without reliance on oxygen from external sources to sustain the reaction. These compositions comprise flash powders, gunpowders, propellants, pyrotechnic initiators, gas generators, ejection charges, burst charges, smoke compositions, delay compositions; pyrotechnic heat sources, and flares. Broadly, pyrotechnic compositions according to the principles of this invention include at least a fuel, an oxidizer, and an amount of at least one metallocene effective to improve sensitivity of the composition. This metallocene preferably is or includes ferrocene.
A first embodiment pyrotechnic composition in accordance with the principles of this invention is a priming mix for example for a primer for a centerfire cartridge, and comprises a primary explosive, a propagation aid, an oxidizer, and a fuel. In the preferred embodiment the primary explosive can comprise between about 30% and about 60%, and more preferably between about 35% and about 50%, of at least one of KDNBF, dinol, and Tetrazene. The propagation aid can comprise between about 10% and about 35%, and more preferably between about 10% and about 30%, of a metallocene. This metallocene is preferably Ferrocene. The oxidizer can comprise between about 5% and about 40%, and more preferably of at least one nitrate, peroxide, or oxide. The oxidizer is preferably at least one of Ba(NO3)2, Sr(NO3)2, KNO3. Finally the fuel can comprise between about 5% and about 25% of at least one of nitrocellulose or PETN as a reactive fuel, and at least one other fuel. This fuel is preferably at least one of boron, aluminum, carbon, metal shavings, or metal sulfides.
A second preferred embodiment of the pyrotechnic mix according to the principles of this invention also is a priming mix for example for a primer for a centerfire cartridge, similar to the priming mix of the first preferred embodiment. However, the primary explosive comprises between about 30% and about 50%, and more preferably between about 35% and about 45%, KDNBF as a primary explosive; the sensitizer comprises between about 2% and about 8% of Tetrazene as a sensitizer; between about 10% and about 30% of a metallocene, such as ferrocene, as a propagation aid; between about 5% and about 40% of an oxidizer, such as at least one of Sr(NO3)2 and KNO3; and between about 5% and about 20% of a reactive fuel such as powder fines, such as SMP111, and/or PETN; and at least one other fuel, such as boron, aluminum, carbon, metal shavings, or metal sulfides.
A third preferred embodiment of the pyrotechnic mix of this invention, is also a priming mix for example for a primer for a centerfire cartridge similar to the first and second embodiments, in which the primary explosive can comprise between about 35% and about 45% KDNBF; the sensitizer can comprise between about 3% and about 7% of Tetrazene; the propagation aid can comprise between about 12% and about 18% of Ferrocene; the oxidizer can comprise between about 25% and about 35% of Sr(NO3)2 as an oxidizer; the fuel can include between about 8% and about 12% of PETN, and preferably at least one of boron, aluminum, carbon, metal shavings, or metal sulfides.
The use of KDNBF is preferred over dinol, which has a DSC peak decomposition temperature of around 160° C. KDNBF's decomposition temperature is much higher, around 210° C.—in the similar range for nitrocellulose or PETN, used in leaded priming mixes. In comparative hot storage tests at 100° C. for up to three days, the KDNBF/ferrocene based lead free primers of the preferred embodiments performed as good as or better than prior leaded priming mixes, while dinol-based priming mixes became non-functional.
However, KDNBF may not be as sensitive as lead styphnate. The inventors have found that the sensitivity of a KDNBF mixture can be adjusted by including either a stronger reducing agent (fuel), or a stronger oxidizer, or both. In particular, the use of a strong reducing agent such as a metallocene like ferrocene, increases the sensitivity of KDNBF mixtures. Ferrocene readily loses electrons, which are available to other oxidizers such as KDNBF, reducing the activation energy for the explosive reaction and thus increasing the mixture's sensitivity.
While this effect has been demonstrated for ferrocene, the inventors believe that other ferrocene derivatives and even other metallocenes with similar reducing potential are also effective in increasing the sensitivity of KDNBF mixtures.
Red phosphorous, like ferrocene, can also sensitize KDNBF based priming mixes, producing excellent mix sensitivity. However, wet phosphorous can generate small amounts of highly toxic phosgene, which can be costly to mitigate, control or monitor phosgene, and dispose of red phosphorous in the production waste stream.
A fourth embodiment of the pyrotechnic composition according to the principles of this invention is a priming mix for a rim fire cartridge. The rim fire priming mix comprises a primary explosive, a propagation aid, an oxidizer, a fuel, and a frictionator. In the preferred embodiment the primary explosive can comprise between 25-35% of KDNBF; an optional sensitizer can comprise between 3-7% Tetrazene; the propagation aid can comprise between 10-20% of Ferrocene; the oxidizer can include up to 30% of Sr(NO3)2; up to 25% reactive fuel such as propellant powder fines, and the frictionator can comprise of 30-45% glass shards or beads.
Examples of priming mixes according to the compositions in the Table were prepared by pre-weighing all of the ingredients and adding them in layers to a mixing bowl. A proper level of moisture was maintained to ensure safe handling of the mix. The layering separates oxidizers from fuels and the reactive components from the sensitizers. Additional moisture was added as necessary to maintain the final moisture content of the mixture at around 25%. The mixing was carried out remotely and closely monitored. After mixing, the thoroughly mixed and uniformed wet priming mix was removed from the mixing bowl, and pellets of a predetermined volume of the wet mix are made and charged into primer cups, followed by the installation of the anvils. Finally, the assembled primers are dried in an oven before tests.
After primers from each example were dried, they were subject to sensitivity test, a standard test which has been employed by the ammunition industry. To set up, a primer or a primed shell case is installed into a steel die fitted with a firing pin. A steel ball of fixed weight (typically 1.92 oz. for center fire primers) is dropped on to the firing pin, which in turn hits the primer. By varying the drop height of the ball, the energy of firing pin is controlled. A series of drop tests is performed. A primer either fires or not. The sensitivity of the primer is then quantified statistically by H bar where 50% of the primers will fire, and S, the standard deviation. A sensitivity specification of a primer is based on the H and S system. Typically, a specification gives a range where H+4S and H-2S must fit. A typical sensitivity (H+4S; H-2S) bracket for pistol primer is (9.2″; 2″). Against that, the KDNBF/ferrocene LF502 primer from Example 1 has (7.63; 4.8), Example 3 (9.0; 4.35); Example 4 (9.7; 3.82), Example 5A has (10.87; 3.65), Example 5B has (10.05; 4.75); Example 6 has (13.3; 3.70); and Example 7 has (14.88, 3.75).
In addition to the sensitivity test, the primers were also subjected to full ballistic tests. Results of such tests showed a total transparency by swapping the control (“leaded”) primer with the Exhibit 1 (LF502) primer. Thus the use of metallocenes, and in particular ferrocene can result in lead-free and substantially lead-free pyrotechnic compositions such as priming mixes with properties equaling or exceeding their leaded counter parts.
The inventors believe that ferrocene will work with any types of explosives containing a nitro, nitrate ester or nitroso group will work with ferrocene. During an (explosion) reaction, nitro, nitrate ester or nitroso group tends to grab electrons, beginning with the easiest source, in our case, ferrocene. Such explosive could be dinol, or PETN, TNT, RDX, HMX, or any other suitable explosive.
Ferrocene could also work with other oxidizers in addition to strontium nitrate, such as nitrates, oxides, dioxides, and/or peroxides.
The above mentioned (LF503) is an alternative of (LF502) of Example 1, which uses nitrocellulose instead of PETN. And in another Example, Example 4 (LF495) uses barium nitrate instead of strontium nitrate (9.64; 5.64). Barium is not as toxic as lead, and there is lead free ammunition which still contains barium, but still it is considered as heavy metal.
A composition of a priming mix is based upon practicality and governed by sensitivity of the mix, and by the ignition requirements. The initiating explosive (dinol, lead styphnate, KDNBF, etc.) content usually has to be above some threshold to maintain adequate mix sensitivity. This percentage varies depending on the type of initiating explosive and the other ingredients. For most initiating explosives, the minimum percentage runs above 20%. Anything less, the mix will not have a required sensitivity. Tetrazene is a sensitizer and only to be needed at a low level, typically 2-6%. Since tetrazene is a poor energy generator, too much of it reduces the mix performance.
PETN or nitrocellulose/nitroglycerin ensures the burn transition from initiating explosive to fuel/oxidizer mixture. The explosive usually burns too fast to allow fuel/oxidizer mixture to catch on. PETN or nitrocellulose/nitroglycerin is like kindling, they are easily ignited but burn slower. Typically, they are in the range from about 5% to about 10%, but can be higher.
The ingredients described above are fuel rich, meaning they have insufficient oxygen to burn all carbon to carbon dioxides. Furthermore, their combustion products are mostly gasses, which are not the most efficient form to transfer energy to a propellant bed. Adding fuel and oxidizer generates hot particles which physically touch propellant grains and causing them to ignite much more quickly. Also, they can affect the sensitivity of a mix to a large extent by being a strong fuel or a strong oxidizer. The percentage of fuel and oxidizer varies greatly depending on their chemical composition and a mix's application. Fuel typically is presented at a smaller percentage as the energetics (explosives, PETN, nitrocellulose/nitroglycerin, etc.) in a mix are already fuel rich. As a result, fuel typically runs between 5 to 20%. Oxidizer will then take up the rest of the percentages and are usually at higher percentage, from 25 to 45%.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
This application claims priority to U.S. provisional application Ser. No. 62/404,624 filed on Oct. 5, 2016. The disclosure of the above-referenced application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62404624 | Oct 2016 | US |
