Pyrotechnical mixture for producing a smoke screen

Explosive and thermic compositions or charges – Metal or alloy or metalloid – each in particulate form – with... – Plural oxygen yielding compounds

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149 42, 149 43, 149 44, 149 61, 149 70, 149 77, 149 83, 102334, C06B 3314

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active

049683659

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a pyrotechnic mixture for producing a smoke screen.
Such mixtures are known per se. Hygroscopic compounds, such as metal chlorides (ZnCl.sub.2, FeCl.sub.3, AlCl.sub.3, TiCl.sub.4, SiCl.sub.4) or phosphorus oxides (P.sub.2 O.sub.3, P.sub.2 O.sub.5) are produced, evaporated and then hydrolyze with air to form smoke clouds suitable for camouflage. Regarding the mechanism of this method of smoke generation see H. Ellern, Military and Civilian Pyrotechnics, Chem. Publ. Comp., Inc., N.Y., 1968, pages 147-151; John A. Conkling, Chemistry of Pyrotechnics, Marcel Dekker Inc., N.Y., 1985, pages 174, 175.
Due to hydrolysis with humid air, the resulting smoke, particularly a smoke composed of hexachloroethane containing, so-called HC smoke, compositions, but also phosphorus smoke compositions, is highly acidic since it is primarily hydrochloric acid (HC smoke) or phosphorus acids (phosphorus smoke) that are formed. The smoke is therefore toxic and incompatible with plant life.
Moreover, in the smoke mixture most frequently employed which is based on hexachlorethane (HC) and zinc or zinc oxide, the heavy metal zinc is discharged into the environment.
There has been no lack of attempts to overcome these drawbacks. For example, the pyrotechnic smoke compositions disclosed in German Patents Nos. DE-PS 2,743,363 and DE-AS No. 2,819,850 are constructed in such a manner that the acid effect of the resulting smoke is partially or completely cancelled out by corresponding chemical complex formation or neutralization of the resulting ZnCl.sub.2 or of the phosphorus acids. However, toxic substances that are not compatible with the environment are still generated.


SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a smoke screen which is particularly suitable for training purposes and which is composed of a nontoxic aerosol which therefore is unable to produce a toxic effect on humans and animals and, is compatible with the environment. When NaCl is not employed as an additive, the smoke is primarily composed of macronutrients suitable for plants.
A pyrotechnic mixture for producing a smoke screen, the mixture comprising: producing compound and additive.
The invention as described above generates a non-toxic smoke of sufficient optical density for military training purposes.


BRIEF DESCRIPTION OF THE DRAWING

The drawing FIGURE shows the mixture of the invention as used in a smoke generating device.


DESCRIPTION OF THE PREFERRED EMBODIMENTS

Smoke generation occurs in the following way: the components magnesium powder, potassium nitrate and potassium perchlorate, when converted in a range of 2500.degree. C. will already produce smoke-like clouds. The density of the smoke is improved particularly by adding potassium chloride and/or sodium chloride whose sublimation boiling points are 1500.degree. C. and 1450.degree. C., respectively, far below the reaction temperature for the conversion of magnesium and potassium nitrate. The reaction products of the chemical reaction of magnesium with potassium nitrate, potassium perchlorate, calcium carbonate, etc. thus form with the sublimating potassium chloride or the evaporating sodium chloride a useful training smoke without toxic or environmentally damaging components.
The chemical reactions in the smoke composition can be represented in a simplified manner in the three equations below:
The energy (E) released in the three listed basic reactions serves to sublimate/evaporate the potassium chloride and sodium chloride.
To improve combustion control, substances such as azodicarbonamide, oxamide or dicyandiamide which produce nitrogen are preferably added to the mixture. This produces a continuous gas stream for better transport of the aerosol particles and an increased aerosol yield since the permanently formed gases prevent the slag from flowing together and enhance sublimation and evaporation by an enlarged surface area.
When the mixture burns, a pure, white aerosol results which is composed primarily of

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T. L. Davis, The Chemistry of Powder and Explosives, 1943, pp. 324-325.
H. Ellern, Military and Civilian Pyrotechnics, 1968, pp. 174-175.
J. A. Conkling, Chemistry of Pyrotechnics-Basic Principles and Theory, 1985, pp. 147-151.

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