EP1173394B9 - Pyrotechnic active mass for producing an aerosol highly emissive in the infrared spectrum and impenetrable in the visible spectrum - Google Patents

Abstract

The invention relates to a pyrotechnic active mass which is impenetrable in the visible spectrum, highly emissive in the infrared spectrum and used for camouflage and decoy purposes. As principal ingredients said mass contains red phosphorus and an alkali metal nitrate or mixture of alkali metal nitrates and as secondary ingredients at least one transition metal or a metal-rich compound or alloy thereof, at least one metalloid and a binder.

Description

The present invention relates to a human and ecotoxicological compatible pyrotechnic active material consisting of red phosphorus, one metallic fuel from the group of transition metals, preferably Titanium, zirconium or iron, a moderator from the group of metalloids boron and silicon, an oxidizing agent from the group of the alkali metal nitrates is preferred Cesium nitrate and potassium nitrate, which are used to produce an im Infrared (3-5, 8-14 µm) highly emissive and visually impenetrable Aerosols are suitable.

Today, pyrotechnically generated aerosols are mainly used in the military Area used for camouflaging, deceiving, dazzling, simulating and marking.

While marking and simulating are preferably colored for use cases Aerosols based on organic azo dyes are used (white, orange, red, violet, green, blue) which are only in the visible range of the spectrum absorb, preferably used for camouflage, deception and blinding Aerosols, which also include the infrared region of the electromagnetic spectrum especially in the area of the atmospheric transmission window at 0.3 - 1.5; 1.6-1.8; 2.0-2.5; 3.0-5.0 and 8.0-14 µm through different mechanisms interrupt. These mechanisms include scattering, absorption and Radiation emission.

Scattering and absorption of radiation are described by the Lambert-Beer law. I = I 0 exp -α Cl

Where I describes the radiation intensity weakened by the interactions, I _{0 represents} the initial intensity. c corresponds to the concentration of the aerosol per unit volume, l is the path length of the isotropic density assumed by the aerosol cloud. α is the wavelength-dependent mass extinction coefficient of the aerosol particles, which is the sum of the scattering and absorption coefficients for a given substance: α (λ) = α str (λ) + α Section (Λ)

While the scattering process mainly depends on the particle morphology and size of the particles, the absorption is only determined by the chemical composition of the particles. Only the refractive index m of an aerosol, which is determined both by the physical and chemical properties, influences both the scattering and the absorption behavior.

According to Rayleigh , in order for aerosols to scatter radiation, the particle diameter, assuming the spherical morphology of the particles, and the wavelength of the radiation to be scattered must be identical. This means that for optimal scattering of radiation in the micrometer range there must be particles with particle diameters of 0.3 - 14 µm.

a) Verbrennung sauerstoffdefizienter, Kohlenstoff-reicher pyrotechnischer Sätze. Beim Abbrand entsteht dann aufgrund der schlechten Sauerstoffbilanz viel Ruß mit Partikeldurchmessern im relevanten Größenbereich (DD 301 646 A7, DE 3326884 C2)

b) Explosiv-Dissiminierung von vorkonfektionierten Partikeln vorzugsweise Messingstaub im geeigneten Größenbereich.

Such particles can be generated in an established manner by the following processes:

a) Combustion of oxygen deficient, carbon-rich pyrotechnic phrases. When burning, a lot of soot with particle diameters in the relevant size range is generated due to the poor oxygen balance (DD 301 646 A7, DE 3326884 C2)

b) Explosive dissimination of pre-assembled particles, preferably brass dust in the appropriate size range.

The aerosols described under a) and b) have a chemical composition to absorb infrared radiation. Both soot and Brass dust is electrically conductive and therefore for coupling infrared radiation suitable.

The disadvantages of the methods for generating infrared radiation described above shielding aerosol clouds consist in a) in the contamination of the produced soot particles with partly carcinogenic polyaromatic Hydrocarbons (PAH) and in the case of energetic halogenated ones Components in such pyrotechnic sentences in the contamination of the Carbon black particles with polyhalogenated oxyarenes such as e.g. Polyhalogendibenzofuranen and polyhalodibenzodioxins or also polyhalogenated Biphenyls.

So-called bird nesting always occurs with the explosive dispersion of pre-assembled particles. This means the hole with very low particle density caused by the explosion process in the aerosol cloud. At this point in the cloud, the line of sight (LOS) is not blocked. Furthermore, brass dust sinks to the ground very quickly, so that only unsatisfactory covering times are achieved. The toxic effects of brass dust on humans and the environment are also very considerable, so that mass application, especially for exercise purposes, has to be avoided.

In EP106334 active compositions are described which contain red phosphorus, CsNO ₃ , B, Ti or a Zr / Ni alloy and a binder.

In DE 40 30 430 an active mass is described, which by a coordinated Quantity ratio of magnesium powder, a fluorinated organic Polymer, chlorinated paraffin and an aromatic compound, in particular Anthracene or phthalic anhydride, aromatic radicals on burning generated, which react to polyaromatics, which as voluminous agglomerates with fibrous structure have diameters in the range of 1 - 20 µm, which for the IR radiation scattering and absorption are suitable and nevertheless due to the large specific surface suspended in the air. To the formation of To suppress finely divided soot instead of polyaromatics, one must Burning rate of approx. 15 g / sec. be observed so that the opaque effects appear relatively late. Therefore, this patent continues proposed a rapidly burning mixture of fluorine-containing polymer, Add magnesium powder and an organic binder, the short term when Burning off produces a strong IR emission and thus the initial one Cover gap closes.

A disadvantage of this process is that the polyaromatics formed are also contain carcinogenic substances, and the emissive effect due to use of magnesium subsides very quickly.

The main problem with conventional impenetrable aerosols of the type described above is the ineffectiveness of effectively protecting moving, warm targets (people, vehicles, armored platforms) against CLOS and SACLOS guided weapons (e.g. Milan, TOW, etc.). These guided missiles are controlled by wire or glass fiber by an operator who uses a thermal imaging device (8 - 14 µm) to aim at the target. After the target has been recognized, an operator can estimate the approximate position from the last perceived movement and continue to follow the emissive target through the transmission holes typically located in aerosol clouds and guide the missile to the target.

The object of the present invention was therefore to create a new camouflage fog develop, in addition to the impenetrability in the visible area also a long-lasting coverage in the IR range.

This object is achieved by the features of the main claim and promoted by that of the subclaim.

The main components of the mist sets according to the invention include red phosphorus, an alkali metal nitrate such as lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate and cesium nitrate, or a mixture thereof, and, as secondary components, a metallic fuel from the group of transition metals such as titanium, zirconium or iron or one metal-rich alloy or compound of these elements such as TiH, Zr / Ni, Zr / Fe or ZrSi ₂ , at least one metalloid such as boron or silicon or an electron-donating compound of these elements, and a polymeric organic binder.

It was previously known that the red phosphorus serves as a carrier for the transmission-damping effect in the visible range, but new is the knowledge that under certain circumstances the red phosphorus also acts as a carrier for the emissive effect in the infrared range. The red phosphorus is largely evaporated during the conversion of the energetic components nitrate / metal / metalloid (Eq. 3) and burns to phosphorus pentoxide in the presence of atmospheric oxygen according to equation (4). P _(red) + heat of combustion → P _{4 (g)} P _{4 (g)} + 5 O ₂ → 2 P ₂ O ₅ + heat

Phosphorus pentoxide reacts with the air humidity according to equation 5 to phosphoric acid. P ₂ O ₅ + 3 H ₂ O → 2 H ₃ PO ₄ + heat

The use of alkali metal nitrates as an oxidizing agent according to the invention provides alkali metal oxides during combustion, which in the presence of atmospheric moisture acc. GI. 6 react to the hydroxides. M ₂ O _(s) + H ₂ O → 2 MOH _(aq) + heat M = Na, K, Rb, Cs

These aerosol droplets deliver the corresponding dihydrogen phosphates in a strongly exothermic reaction with the phosphoric acid droplets. MOH + H ₃ PO _{4 (aq)} → 2 MH ₂ PO ₄ + H ₂ O + heat

The hydration of the dihydrogen phosphates is also an exothermic reaction and provides heat again. MH ₂ PO ₄ + n H ₂ O → MH ₂ PO ₄ · (H ₂ O) _n + heat

The aerosol droplets formed have a size of 0.01-2 µm and thereby high absorption and scattering coefficients in the visible and short-wave Infrared range from 0.3 - 1.9 µm and low attenuation values in the middle and long-wave infrared from 2 - 14 µm. Without prejudice to that, the Reactions 4 - 6 but especially heat generated in steps 7 and 8 for strong emission of the aerosol droplets in the middle and long-wave infrared, and thus compensates for the low scatter and Absorption coefficient. Contrary to the well known strong emission of Magnesium-containing active masses that occur directly during combustion and then quickly subsides, the heat development according to the invention occurs in part through chemical processes that are only delayed by the onset of education of the aerosol droplets become possible, so that this emissive effect 50 - 200 sec., I.e. for the time necessary for camouflage.

Through the use of transition metals according to the invention, their oxides have high levels of heat, such as zirconium and titanium, as well Metalloids such as boron and / or silicon have very high combustion temperatures reached, therefore the aerosol particles get a high thermal Energy, which increases the emission in the long-wave IR.

The use according to the invention of the transition metals and their alloys or metal-rich compounds continue to suppress the formation of Phosphanbildnern. The incineration due to oxygen underbalancing formed metal phosphides (e.g. zirconium phosphide or titanium phosphide have non-ionic character, which is why with humidity or acid Rain does not result in hydrolysis or acidolysis with the release of phosphines.

Therefore, fog sentences laboratoryized according to the invention are human and ecotoxicological compatible and considerably safer than conventional fog sets based on red phosphorus and light metal such as magnesium or aluminum. This is also typical for mist sets based on red phosphorus self-igniting of the combustion residues no longer occurs.

The following example is intended to illustrate the invention without, however, to restrict:

example

Made from 2750 g red phosphorus, 990 g potassium nitrate, 220 g silicon, 220 g boron, 220 g Zirconium and 990 g Macroplast binder (30% solids) is gradually removed Adding the components to the red phosphorus produces a doughy set. The solvent moist mass is sieved (7 mm mesh size) and 20 minutes in Vacuum dried at 40 ° C and 20 mbar. The 42 g of granules are mixed with a Pressing pressure of 20 tons into ring-shaped compacts with an edge height of 10 mm 57 mm outer diameter and 15 mm inner diameter pressed. A Tablet has a burning time of approx. 35 seconds and delivers one visually thick white fog.

Radiometric measurement of the resulting aerosol at a distance of 4 m from the source reveals the following radiation levels in the infrared range: Band V (8 - 14 µm) Band II (3 - 5 µm) > 100 W / sr> 25 s > 20 W / sr> 25 s > 60 W / sr> 75 s > 10 W / sr> 75 s.

FIG. 1 shows the radiant intensity of the aerosol clouds which are produced by burning off a compact of the mass 120 g, which has been processed according to the invention, at a distance of 5 m from the source. With the aerosol clouds generated according to the invention, very good irradiation (> 95%) of emissive targets, the color temperature 300 ° C., is achieved.

Claims (2)

1. Pyrotechnic active mass for camouflaging and decoy purposes impenetrable in visual.light and strongly emissive in infrared light which, as main components, there are contained red phosphorus, an alkali metal nitrate or a mixture of alkali metal nitrates and, as subsidiary components, at least one transition metal or a metal-rich compound or alloy thereof, at least one metalloid, as well as a binder, characterised in that there are contained 55% to 62% red phosphorus, 18% to 23% alkali metal nitrates, 10 to 18% subsidiary components of transition metals and metalloids and 5 to 7% of binders.
2. Pyrotechnic active mass according to claim 1, characterised in that there are contained 58.5% red phosphorus, 21.1% potassium nitrate, in each case 4.7% boron, silicon and zirconium, as well as 6.3% of a polychloroprene binder.

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