CA1237581A

CA1237581A - Pyrotechnical smoke charges

Info

Publication number: CA1237581A
Application number: CA000438624A
Authority: CA
Inventors: Manfred Weber
Original assignee: Pyrotechnische Fabrik F Feistel GmbH and Co KG
Current assignee: Pyrotechnische Fabrik F Feistel GmbH and Co KG
Priority date: 1982-10-16
Filing date: 1983-10-07
Publication date: 1988-06-07
Also published as: FI76066C; FI833595A0; DK426783A; KR840006473A; EP0106334A3; ZA837647B; NO833739L; JPS59131592A; DK426783D0; KR910000506B1; DK164665B; ES8602564A1; DK164665C; EP0106334A2; DE3238444A1; NO158375B; AR231962A1; SG80491G; ES526488A0; IL69859A

Abstract

Pyrotechnical smoke charges, which produce impenetrable smoke in the visible and infrared spectra, are additionally admixed with cesium compounds which are dispersed during burn out and which absorb radiations in the IR spectrum.

Description

~ 1237581 PYROTECHNICAL SMOKE CHARGES N-Technical Field This invention relates to pyrotechnical smoke charges, which, in the visible and in the infrared spectra, generate substantially impervious smoke, as characterized in the claims.

Background Art Artificial smoke is used to keep frost away from plantations (especially orchards and vineyards). Smoke or oil mist is usually generated or a fine water mist is sprayed;
each is optionally stabilized by glycerin, a fatty alcohol, or a similar substance and is spread over crops to be protected in a more or less thick layer in order to reflect the heat radiated from the soil and thus to prevent cooling. In keeping with the purpose, these mists or clouds must be maintained over longer periods of time; any loss resulting from condensation and wind movement must be made up by continuing new smoke generation. This is why continually operating systems are employed in most cases for this purpose.
Artificial smoke is also used in the military sector to camouflage military installations, troop units and vehicles.
In particular, when providing protection for troop units and vehicles, it is important to preclude direct observation by the enemy of those units and vehicles for a short period of time, for which purpose a pyrotechnical charge is usually ?5 fired in the direction of the enemy; that charge is _ -1- ~ , distributed like shot fired from a shotgun and forms a multitude of smoke-generating particles which provide for very fast and uniform smokescreen coverage of larger surface areas [see DE-AS (German Patent Application published for opposition) 30 31 369 and the literature cited therein].
A large number of=uarious smoke and mist mixtures has become known for this purpose.. Such mixtures are based on, e.g., titanium tetrachloride, silicon tetrachloride or chlorosulfonic acid (or their combinations with ammoniaDr sulfur trioxide) as liquid smoke generators or red phosphorus, HC mixtures (hexachloroethane/zinc/zinc oxide) or ammonium _ perchlorate/zinc oxide as solid smoke generators. In an operational situation, these substances are converted either through a secondary combustion reaction or through suitable products which are released together during their mixing.
Decisive factors in the quality of smoke formation are speed of formation, concentration, and the manner of spread as well as the duration of smoke screen coverage. Suitable smoke mixtures are known for these purposes (see DE-AS 30 31 369).
See also, for example, DE-OS 25 56 256, DE-OS 25 09 539, DE-OS 18 12 027, DE-AS 12 46, 488, DE-OS 30 12, 405, DE-OS 27 29 055, DE-OS 27 43 363, DE-OS -19-13 790 [DE-OS -- German Patent Appliction published for inspection].
But these mixtures entail a critical disadvantage with ?5 respect to broad use in modern defense technology. In the past it was particularly important to generate a smokescreen which would be as dense as possible in visible light; however, present-day military observers, in addition, also 'have infrared detection, direction-finding and heat-generating 0 instruments which exploit the fact that military targets emit =

-2-very intensive heat radiation because of'their energy output and that radiation can be detected at great ranges. Because, - on account of atmospheric components, such as CO2 and water vapor, infrared radiation of certain wavelengths is absorbed $ selectively, these instruments work preferably in the so-called "windows" of the atmosphere which are at from 0.7 to 1.5 mp, from 2 to 2.5 mp, from 3 to 5 mp and from 8 to 12 mp.
In particular efforts are now being made to work in the 8 to mu range because, in that range, disturbances due to smoke, 10 haze and ordinary fog are minimal. It is therefore the purpose of pyrotechnical smoke charges, conversely, to guarantee the highest possible absorption or reflection of IR
radiation in this range.
Moreover, most pyrotechnical smoke charges contain corroding, toxic or highly acid components,.such as phosphorus pentoxide, hydrochloric acid, sulfuric acid, titanium or zinc salts, which are extraordinarily harmful to human beings and plants in the concentration found in smoke. Due to the addition of metal oxides, buffer substances and ammonium compounds, steps were therefore taken in most present-day smoke charges to make sure that the smoke generated is neutral or only as acid as absolutely necessary. One purpose of this invention also resides in modifying known smoke charges to preclude or minimize their reacting in an acid manner.

Summary of the Invention These problems are quite surprisingly solved by measures described in the claims, that is to say, by adding an appropriate cesium compound to known smoke charges.

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123=1 The invention has a number of related aspects, including the use of cesium in compound form to reduce the transparency of smoke generated by a pyrotechnic smoke charge to IR
radiation, corresponding smoke charges and their compositions and even the resulting generated smoke. Particularly advantageous results are obtained with charges comprising any one or any combination of the following components:
phosphorus, zirconium/nickel alloy, boron (particularly amorphous boron) and ammonium chloride.
Illustrative pyrotechnic smoke charges have from 0.5 to 50 percent by weight of cesium compound(s), preferably from 5 to 25 percent by weight. The cesium compound is, e.g., cesium chloride, cesium bromide, cesium nitrate, cesium oxide or any combination thereof. It is advantageous for the charge to be a hexachloroethane charge with metal powder, especially silicon and/or aluminum powder.
Such a charge has, e.g., from 50 to 70 percent by weight of hexachloroethane, from 20 to 40 percent by weight of silicon and/or aluminum metal powder and from 1 to 20 percent by weight of the cesium compound(s).
The invention is particularly advantageous with phosphorus-containing charges, especially those having at least about 50 percent by weight of phosphorus. Other advantageous charge components include zirconium/nickel alloys (e.g., in an amount of from 3 to 15 percent by weight), boron --(e.g., in an amount of from 5 to 20 percent by weight), aluminum-powder (e.g., in an amount of from 3 to 20 percent by =
weight), red phosphorus (e.g., in an amount of from 30-to 50 percent by weight) and ammonium chloride (e.g., in an amount of from 5 to 25 percent by weight). The charge components are

-4-optional, but are advantageou'sly incorporated in a pyrotechnic smoke charge of this invention either individually or in any combination.

The Invention By incorporating a cesium compound in a pyrotechnic smoke charge, quite surprisingly, transparency of the resulting smoke to IR light, especially IR light with wavelengths of from 3 to 5 or from 8 to 12 mp, is significantly reduced, although it has thus far been impossible to determine what this is based on. -Since cesium salts in the near IR spectrum of 12 m. do not reveal any absorption (which can be traced back to oscillation) in which the cesium ions participate (cesium halogenides do not reveal any oscillation, while cesium nitrate reveals merely the oscillation of the nitrate group at 7.2 mu), the possibility of direct absorption of the IR light is extremely remote. As the amount of cesium salt is relatively small, corresponding to an average of 25%, compared to the total quantity of smoke, and because, accordingly,the other smoke-forming components are present in smaller quantities; the=increase in the particle number of the dispersed system cannot be responsible for this effect.
Because, according to observations so far, the settling speed and condensability of the formed smoke clouds do not differ from those of the corresponding smoke charges without the addition of cesium salt, an improvement in the scatter effect of the generated particles also does not seem to be responsible for this effect. Assuming that Stokes' Law

-5-applies for these particles in a first approximation, that is to say, assuming that the settling speed is proportional to the square of the particle diameter, an enlargement of the particle diameter by 1 m u in the customary smoke charges to a figure of 10 mp -- which would be necessary for effective scatter in the IR range of from 8 to 12 mu -- would mean an increase in the settling speed by a factor of 100. It therefore remains reserved for further investigations to find a satisfactory theory as to why the pyrotechnical smoke charges according to the invention have satisfactory density both in the visible and in the IR spectra.
This invention furthermore is intended to increase the smoke yield of phosphorus-containing smoke charges.
The usually employed metals, magnesium and titanium, lead to an ash content of from 60 to 70% after the burnout of smoke charges.
Quite surprisingly, it is possible to increase the effectiveness of such smoke charges by using -- instead of magnesium and titanium -- a zirconium/nickel alloy, preferably with 70% zirconium and 30% nickel. The ash content of such charges can thus be reduced to 5%. Additions of boron work in the same direction and further improve IR absorption.
The effectiveness is further increased through the addition of ammonium chloride.
A great advantage of the subject smoke charges is that they act passively. That means that they do not reveal any heat tone of their own and thus do not alter the image of surroundings in IR sights.

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Examples .~ -In the following examples a series of smoke charges according to the invention is compared with corresponding smoke charges without the addition according to the invention.
Example 1.
Ammonium Perchlorate Smoke 1.7 kg of ammonium perchlorate, 1.5 kg of zinc oxide, 0.8 kg of polychloroisoprene, and 0.5 kg of ammonium chloride are made into a dough with a solution 0.5 kg dioctylphthalate in 1 liter of methanol. This mixture is forced through a sieve with a mesh width of from 0.3 to 0.5 mm and is dried on a screen. The dried granulate is then pressed under a pressure of 500 - 1500 bar according to DE-AS 30 31 369 to form blanks of about 50 g. Each time, 20 blanks are combined with an igni-tion charge, according to example 2 in DE-AS 30 31 369, in a synthetic or metal casing to form one charge.
The ignition charge consists of the components magnesium powder (1,2 kg), ferroprussiate (0,9 kg) amorphous boron (2,39 kg), chlorparaffine powder (0,8 kg) and black powder (4,71 kg). Magnesium powder and ferroprussiate were premixed, chlorparaffine solved in 2 liters of perchloroethylene was-. --added and mixed. The amorphous boron was added and mixing was repeated for 5 minutes. Finally the black powder was filled in, _-mexed with the other components for 10 minutes, dried and pressed under 1500 bar.
The same mixture as above is furthermore mixed with 0.4 kg =
of cesium nitrate and is processed in the same manner into blanks weighing about 50 g. As above, in each case 20 blanks are assembled with an ignition charge in a casing to form a single load.
. To judge the smoke effect, three white plates, heated to about 40 degrees Centigrade are set up out in a field at an interval of 10 m and are observed from a range of 100 m with IR and optical sights with wavelengths of 10 mp, 3.5 m-p and 0.6 m V. Smoke charges with the above composition are fired with a propellent charge at a point from about 40 to 50 m in front of the target, where, within a matter of seconds, a 3 to

- 7 -..-. 12375'8JL
15 m high and 25 to 40 m wide and deep smokescreen is formed.
At a temperature of 22 degrees Centigrade and a relative air - humidity of 48%, the coverage conditions given in the following table are then determined.
By "very good" we mean coverage of from 95 to 100%, that is to say, the target can no longer be distinguished from the background. By "good" we mean coverage of from 80 to 95%, that is to say, the target just about cannot be made out. By "moderate" we mean coverage of from 50 to 80%. By "poor" we 0 mean coverage of less than 50%, in which case the target- can still be clearly made out.
Table 1 IR Wavelength 0.6 u 3.5 u 10 U
Perchlorate good poor poor Perchlorate/CsNo3 very good good good Example 2.
Hexachloroethane Smoke 2.5 kg hexachloroethane, 0.8 kg zinc oxide, 0.4 kg silicon powder, 0.3 kg aluminum powder and 0.3 kg amorphous 0 boron are mixed intensively and are turned into a dough in a kneader with 2 kg of a 10% elastomer-like solution- in acetone.
The mixture is processed into blanks using the same method as in Example 1 and the blanks are insulated by means of an --~
additional coating of inethacrylic resin and are combined to 5 form smoke charges according to Example 1.
The same mixture as above, but with the addition of'l kg of cesium nitrate, is processed into smoke charges in the corresponding manner.
The elastomer consisted of butadiene. Polybutadiene is usable as well.

-8-`-- The smoke effect is determined according to Example 1 whereby the results given in the following Table 2 are obtained. The smoke formed has a pH value of from about 5 to 7.

Table 2 IR Wavelength 0.6u 3.5u l0u HC-mixture very good moderate moderate HC/CsCl very good very good very good Example 3.

Red Phosphorus Smoke 0.65 kg of red phosphorus, 0.15 kg of iron (III) oxide, 0.15 kg of aluminum powder, and 0.15 kg of magnesium powder are kneaded with 0.2 kg of 10% elastomer bonding agent and are processed into blanks according to Example 1.

Mixtures, which in addition contain 0.40 kg of cesium nitrate, are processed into blanks in the same manner.

The smoke effect is determined according to Example 1. The results obtained are shown in Table 3, below.
Table 3 IR Wavelength 0.6u 3.5u l0u Phosphorus very good poor poor Phosphorus/CsN03 very good very good very good Phosphorus/RbN03 very good very good good

- 9 -~.7 1y~-~ = ~~~~~ .
Example 4.
= 0.65 kg of hexachloroethane, 0.2 kg of silicon powder, and 0.15 kg of aluminum powder are mixed and, under light pressure, are pressed in a casing which is connected with a propellent and ignition charge.
Mixtures which, in addition, contain 0.01-0.10 kg cesium chloride are processed in the same manner.
The following smoke effects are obtained:
Table 4 ,0 IR Wavelength 0.6 u 3.5p 1011 HC-smoke good moderate moderate HC-CsCl very good very good very good.

Proven prescriptions are given in the following examples.
Compounding and other procedures are as set forth in the =5 preceding examples.
Butadiene (polybutadiene) is used as bonding agent.
Example S. 55% red phosphorus 23% cesium nitrate 0 12% zirconium/nickel alloy, 70:30 - -~

10% butadiene Example 6. 55% red phosphorus 20% cesium nitrate = ~

~

i '= ~ 4% manganese powder =
6% zirconium/nickel alloy, 70:30 = 5% fine aluminum powder 10% butadiene Example 7.
27% NH4C1O4 8% Zr/Ni 70:30 5% fine aluminum powder 25% CsN03 24% NH4C1 10% butadiene Example B.
43.75% red phosphorus 33.00$ CsN03 6.00% amorphous boron 4.75% titanium powder, smaller than 100 m u 12.50$ polybutadiene Example 9.
43.75% red phosphorus 33.00$ CsN03 6.00% amorphous boron 4.75% zirconium/nickel alloy, 70:30 - ~
12.50% macroplast B 202. (Butadiene in a solvent produced by Henkel, Dusseldorf, Germany) The invention and its advantages are readily understood ?5 from the foregoing description. Procedures, techniques, ingredients and details other than those specifically called

-11-JL23'7581 . for are conventional and well within the skill of the art.
,., Various changes may be made in the processes, formulations and = products without departing from the spirit and scope of the invention or sacrificing its material advantages. Examples provided herein are merely illustrative of preferred embodiments.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A metal-powder-containing pyrotechnic smoke charge capable of producing a smoke screen and comprising an effective amount of a cesium compound to increase absorption of infrared rays by generated smoke or to impede penetration of generated smoke by infrared rays.

2. A smoke charge according to claim 1 having from 0.5 to 50 percent by weight of the cesium compound.

3. A smoke charge according to claim 2 having from 5 to 25 percent by weight of the cesium compound.

4. A smoke charge according to claim 1 wherein the cesium compound comprises a member selected from the group consisting of cesium chloride, cesium bromide, cesium nitrate and cesium oxide.
5. A smoke charge according to claim 1 comprising a hexachloroethane charge.

6. A smoke charge according to claim 5 wherein the metal powder comprises silicon and aluminum.

7. A smoke charge according to claim 1 comprising from 50 to 70 percent by weight of hexachloroethane, from 20 to 40 percent by weight of metal powder wherein the metal is at least one member selected from the group consisting of silicon and aluminum, and from 1 to 20 percent by weight of the cesium compound.

8. A smoke charge according to claim 7 wherein the cesium compound comprises a member selected from the group consisting of cesium chloride, cesium bromide, cesium nitrate and cesium oxide.
9. A smoke charge according to claim 1 comprising phosphorus.

10. A smoke charge according to claim 9 having at least about 50 percent by weight of phosphorus.

11. A smoke charge according to claim 10 comprising from 5 to 25 percent by weight of ammonium chloride.

12. A smoke charge according to claim 10 comprising a zirconium/nickel alloy.

13. A smoke charge according to claim 12 wherein the alloy has a zirconium/nickel weight ratio of 70/30.

14. A smoke charge according to claim 12 comprising an amount of amorphous boron sufficient to increase IR absorption by smoke generated by the charge.

21. A process according to claim 18 wherein said charge comprises boron.

22. A process according to claim 18 wherein said charge comprises ammonium chloride.

23. A metal-powder-containing pyrotechnic smoke charge capable of producing a smoke screen according to claim 1, comprising from 5% to 50% by weight of a cesium compound to increase the absorption of infrared rays by generated smoke or to impede penetration of generated smoke by infrared rays, and further comprising 3% to 40% by weight of at least one metal powder of the group of silicon powder, aluminum powder, zirconium/nickel alloy powder, magnesium powder and titanium powder.