EP0639547A1 - Composition for the production of smoke opaque to infrared radiation - Google Patents

Abstract

A composition generating a smoke opaque to IR in the form of a pressed article which has a density in the range from 0.9 to 1.5 g/cm<3> is described, containing 10 to 25 per cent by weight of magnesium powder, 5 to 35 per cent by weight of a fluorinated organic polymer, 5 to 15 per cent by weight of chloroparaffin and 35 to 65 per cent by weight of an aromatic compound of the formula I <IMAGE> wherein A and B independently of one another are <IMAGE> -S-, -CH2-, <IMAGE> R<1> and R<2> independently of one another are OH, X or an alkyl radical having 1 to 4 carbon atoms, m and n in this case are an integer from 0 to 2 and X is halogen, or of an aromatic compound of the formula II <IMAGE> wherein D and E independently of one another are <IMAGE> or -N= and R<1>, R<2>, X, m and n are as defined above, or of one of the compounds phthalic anhydride, 2-benzoylpyridine, fluorene, dibenzosuberenone or diphenylene sulphide or of derivatives thereof which are substituted by R<1>m and/or R<2>n radicals.

Description

The invention relates to a composition that generates an IR-opaque mist.

In the field of reconnaissance, target location, target tracking and weapon technology, IR sensors are increasingly being used, which are able to make the battlefield transparent to the enemy area, covering the entire area. An effective way to cancel or interfere with the effects of IR sensors is to block the line of sight with fog systems. The effect of these fog systems is based on the fact that the particles forming the fog scatter and / or absorb the incident infrared radiation, the effect by scattering being strongest when the effective diameter of the particles and the wavelength of the incident electromagnetic radiation are approximately the same. The modern IR sensors are effective in the range from 0.8 to 14 µm. So far there has been the problem that particles with diameters in this area sink to the ground very quickly and effective smoke screens cannot be produced. It was already known to use hexachloroethane and red phosphorus to generate fog. The resulting aerosols are liquid aerosols that can remain suspended in the atmosphere. However, they have an insufficient surface area and particle size and can therefore only absorb or scatter electromagnetic radiation in the visible range, ie at a wavelength of 0.4 to 0.7 µm, but not in the IR range. In contrast, solid aerosols combine a large relative surface with a microscopic distribution. Very small particles with a diameter of 10⁻³ µm to 1 µm do not sink over a longer period of time if they are distributed in a gas volume, but are kept in the gas space by the Braun molecular motion and the viscosity of the carrier gas. In the case of particles with a diameter of 10 µm and more, the molecular movement cannot have the effect of gravity balance more and the particles sink. This has the consequence that prefabricated solid aerosols, such as. As brass or copper dust, are unsuitable as active substances for a mist-producing composition, since the particles sink quickly and can no longer be whirled up from the ground, or are blown away immediately after application by air movement.

To solve this problem, DE-A 33 26 883 now proposes to use a solid aerosol for shielding infrared rays, in which soot particles are generated by thermal decomposition. Chlorinated aromatics, in particular the highly toxic hexachlorobenzene, are used as compounds producing soot particles. This known composition provides soot particles with a particle diameter in the range from a few microns to millimeter-sized flakes. However, this system is not very effective in the infrared range.

In order to provide effective protection against IR homing heads and laser-guided homing heads as well as thermal imaging, a smoke screen must be created that is at least 30 m away from the object to be protected and covers an area in the range of 100 m wide and 10 m high can. Furthermore, after activating the fog-forming composition, the fog should be generated within 10 seconds and then have a service life of up to 60 seconds. The mist must be IR emitting and absorbing and must be designed to cover wavelengths in the range of 0.4 to 14 µm.

It was therefore an object of the invention to provide a composition with which a mist can be generated, which on the one hand is impermeable to IR and laser beams and on the other hand has a sufficiently long service life.

worin A und B unabhängig voneinander

-S-, -CH₂-,

bedeuten,
   R¹ und R² unabhängig voneinander für OH, X oder einen Alkylrest mit 1 bis 4 Kohlenstoffatomen stehen,
   m und n jeweils eine ganze Zahl von 0 bis 2 ist und
   X Halogen bedeutet,
oder einer aromatischen Verbindung der Formel II

worin D und E unabhängig voneinander

oder -N= bedeuten und
   R¹, R², X, m und n wie oben definiert sind,
oder einer der Verbindungen Phthalsäureanhydrid, 2-Benzoylpyridin, Fluoren, Dibenzosuberenon oder Diphenylensulfid oder von Derivaten hiervon, die mit Resten R¹_m und/oder R²_n substituiert sind.This object is achieved according to the invention by an IR-impermeable mist-producing composition in the form of a compact which has a density in the range from 0.9 to 1.5 g / cm³, containing 10 to 25 percent by weight of magnesium powder, 5 to 35 percent by weight of a fluorinated organic polymer, 5 to 15 percent by weight of chlorinated paraffin and 35 to 65 percent by weight of an aromatic compound of the formula I.

where A and B are independent of each other

-S-, -CH₂-,

mean,
R¹ and R² independently of one another represent OH, X or an alkyl radical having 1 to 4 carbon atoms,
m and n are each an integer from 0 to 2 and
X is halogen,
or an aromatic compound of formula II

where D and E are independent of each other

or -N = mean and
R¹, R², X, m and n are as defined above,
or one of the compounds phthalic anhydride, 2-benzoylpyridine, fluorene, dibenzosuberenone or diphenylene sulfide or derivatives thereof which are substituted by radicals R¹ _m and / or R² _n .

This composition, when activated in the usual way, for example by pyrotechnic ignition, leads to the formation of an aerosol, the particle size of which is in the desired range and the service life of which is up to one minute. The composition according to the invention is both IR-absorbing and emitting. In contrast to the previously used fog agents, hexachloroethane and phosphorus, which are in the form of liquid aerosols, solid aerosols are produced according to the invention.

In order to keep the mist particles in the atmosphere over a long period of time, the solid aerosol according to the invention is generated in situ by a pyrotechnic reaction, so that the mist is replenished from the ground over the period of the pyrotechnic reaction.

, wobei ln T der natürliche Logarithmus der Transmission ist, x die Dicke der Aerosolwand in m und c die Aerosolkonzentration in g pro m³ ist. Nur wenn die α-Werte ≧ 1 m² pro Gramm sind, ist eine Wirkung im IR-Bereich zu erwarten. Die bisher bekannten nebelerzeugenden Mittel haben α-Werte, die teilweise weit unter 1 liegen.The composition according to the invention contains the components necessary for in situ aerosol production in the form of an aerosol supplier, an energy supplier and a combustion moderator, which also serves as a binder. Only when these three components are in an optimal relationship to each other is a fog created that has the desired properties. A parameter defined as a mass extinction coefficient is essential for the effect of the aerosol formed on electromagnetic radiation in the IR range. This parameter reflects the ability of the aerosol to weaken the electromagnetic radiation. The mass extinction coefficient is defined as $\text{α = ln T: x. c}$

, where ln T is the natural logarithm of the transmission, x is the thickness of the aerosol wall in m and c is the aerosol concentration in g per m³. An effect in the IR range can only be expected if the α values are im 1 m² per gram. The mist-producing agents known to date have α values which are in some cases far below 1.

The mass extinction coefficient is related to the means used as the aerosol supplier and the burning rate. If the pyrotechnic reaction is such that the burn rate is in the range of 15 g per second, the desired mass extinction coefficient of 1.0 to 1.8 is achieved. The response speed is too high, this produces finely divided soot, which is not suitable for the absorption of electromagnetic radiation in the IR range. If the burning rate is too low, large flakes are formed which are not optimally effective even in the IR range. This burning rate can be achieved when using the composition according to the invention. For this purpose, a mixture of magnesium powder and a fluorinated organic polymer is used as the energy supplier, these two substances preferably being used in approximately equal amounts up to a weight ratio of 3: 1 and particularly preferably in a ratio of 1.5 to 2: 1.

The magnesium powder used for the composition according to the invention should be as fine as possible, since the activity increases with the size of the specific surface. A magnesium powder is preferably used in which more than 90 percent by weight have a particle size of less than 63 μm.

The fluorinated organic polymer provides the other part of the energy-providing reaction, in which energy is released by the reaction of magnesium with fluorine. As the fluorinated organic polymer, the commercially available fluorinated aliphatic and aromatic hydrocarbons can be used. Polytetrafluoroethylene and polyvinylidene fluoride are particularly suitable.

To control the energy-supplying reaction, a combustion moderator is added as a further component, with the aid of which the combustion temperature of the energy supplier can be controlled and kept constant. A chlorinated paraffin is used for this. Chlorinated paraffins are chlorinated aliphatic hydrocarbons. The commercially available chlorinated paraffins usually consist of mixtures of compounds with carbon skeletons of different lengths and different degrees of chlorination. From processing technology For reasons of the invention, a chlorine paraffin which is solid at the processing temperature is preferably used. Chlorine paraffin with a higher chlorine content is preferably used, particularly preferably with a chlorine content of more than 60 percent by weight.

worin A und B unabhängig voneinander

-S-, -CH₂-,

bedeuten,
   R¹ und R² unabhängig voneinander für OH, X oder einen Alkylrest mit 1 bis 4 Kohlenstoffatomen stehen,
   m und n jeweils eine ganze Zahl von 0 bis 2 ist und
   X Halogen bedeutet,
oder eine aromatische Verbindung der Formel II

worin D und E unabhängig voneinander

oder -N= bedeuten und
   R¹, R², X, m und n wie oben definiert sind,
oder eine der Verbindungen Phthalsäureanhydrid, 2-Benzoylpyridin, Fluoren, Dibenzosuberenon oder Diphenylensulfid oder von Derivaten hiervon, die mit Resten R¹_m und/oder R²_n substituiert sind.The third essential component of the composition according to the invention is the aerosol supplier. According to the invention, an aromatic compound of the formula I is used for this

where A and B are independent of each other

-S-, -CH₂-,

mean,
R¹ and R² independently of one another represent OH, X or an alkyl radical having 1 to 4 carbon atoms,
m and n are each an integer from 0 to 2 and
X is halogen,
or an aromatic compound of formula II

where D and E are independent of each other

or -N = mean and
R¹, R², X, m and n are as defined above,
or one of the compounds phthalic anhydride, 2-benzoylpyridine, fluorene, dibenzosuberenone or diphenylene sulfide or derivatives thereof, which are substituted by radicals R¹ _m and / or R² _n .

Due to the energy released during the pyrotechnic reaction, dehydrobenzene is produced from the compounds of the aerosol supplier through decarbonylation, decarboxylation, desulfurization, etc. responds. These polymers are the active substances of the aerosol according to the invention. They represent a mixture that accumulates to form agglomerates that have a fibrous new structure and that are highly porous and fissured by the CO and CO₂ formed during the reaction. For this reason, these particles have a very high specific surface area, which is very advantageous for their function. Suitable aromatic compounds include anthracene, anthraquinone, alizarin, acridine, anthrone, 8-bromoanthracene, thianthrene, thioxanthrone, thiodiphenylamine, phenazine, dihydroanthracene, 2-chlorothiodiphenylamine, phthalic anhydride, fluorene, 2-benzoylphenyl sulfide, diphenylbenzene sulfide. Since the toxicity of aromatic halogenated hydrocarbons is sometimes very high, the preferred aerosol supplier is the compounds which have no halogen atoms in their structure. Another aspect when choosing the aerosol supplier is the availability, which is particularly great for the compounds phthalic anhydride, anthracene and anthraquinone, so that these compounds are preferred for the composition according to the invention for economic reasons. Mixtures of different compounds of the formula I can also be used for the composition according to the invention.

The various components of the composition according to the invention are used in such an amount that 10 to 25 percent by weight, preferably 15 to 20 percent by weight magnesium powder, 5 to 35 percent by weight, preferably 10 to 30 percent by weight of the fluorinated polymer, 5 to 15 percent by weight, preferably 10 to 15 percent by weight chloroparaffin , and 35 to 65 percent by weight, preferably 40 to 60 percent by weight, of the aromatic compound serving as the aerosol supplier are present.

The individual components are mixed in the usual way and then pressed. The mixture containing the constituents necessary according to the invention is preferably pressed into a container, for example an aluminum container. The mixture is pressed at such a pressure that a body is formed which has a density in the range from 0.9 to 1.5 g / cm 3, preferably 1.1 to 1.4 g / cm 3. It was surprisingly namely found that the density of the composition according to the invention is an essential parameter by which the burning rate and thus the particle size of the aerosol supplier are influenced. Only if the compact has a density in the specified range will the spectrum of particle sizes from 1 to 15 µ be covered when it burns. If the density is too high, the burning rate increases so that only finely divided soot is produced, which cannot perform the task.

The composition according to the invention can additionally contain an IR-emitting component, the onset of action of which begins almost immediately after ignition and the effect of which continues until the action of the composition of the invention begins. Such systems are known to the person skilled in the art. Typical such compositions contain, for example, 25% of a fluorine-containing polymer, 25% of magnesium and 50% of an organic compound.

The composition is ignited in a manner known per se, the composition according to the invention for example by means of an ignition charge which, for. B. Si / Pb₃O₄ or an equivalent pyrotechnic mixture can be ignited, while the IR-emitting composition by an ignition decomposition charge, the ignition and decomposition take place simultaneously, for. B. Ba (NO₃) ₂ is ignited.

According to the invention, a composition is made available which generates an IR-proof mist, which fully meets the requirements and in which the use of toxic components is not necessary.

The invention is illustrated by the following examples:

example 1

180 g of magnesium powder with a sieve analysis of ≦ 10% larger than 71 µm, ≦ 60% larger than 40 µm, ≧ 30% larger than 25 µm, rest smaller than 25 µm and 240 g Hostaflon TF 9202 (polytetrafluoroethylene) were mixed intensively in a bowl. Then 480 g of anthraquinone sieved through a 1 mm sieve were added and mixed well again. Finally, 100 g of chlorinated paraffin with a degree of chlorination of 70 percent by weight and an average molecular weight of 516 were added and mixed again intensively. The powder mixture was then pressed into a container of 50 to 80 mm to a density of 1.1 to 1.4 g / cm³.

Example 2

The following composition was prepared according to the procedure of Example 1: Hostaflon TF 1640 (polytetrafluoroethylene), 10% by weight; Magnesium powder (as in Example 1), 20 weight percent; Anthraquinone, 60 weight percent; Chlorinated paraffin (as in Example 1), 10 percent by weight.

Example 3

The following composition was prepared using the procedure described in Example 1: Hostaflon TF 1640 (polytetrafluoroethylene), 10 percent by weight; Magnesium powder (as in Example 1), 20 weight percent; Anthraquinone, 55 weight percent; post-chlorinated PVC, chlorine content 62%, 15 weight percent.

Example 4

The following composition was prepared using the procedure described in Example 1: Hostaflon TF 9202 (polytetrafluoroethylene), 24 percent by weight; Magnesium powder (as in Example 1), 18 weight percent; Fluorene, 48 weight percent; Chlorinated paraffin (as in Example 1), 10 percent by weight.

Example 5

The following composition was prepared using the procedure described in Example 1: Hostaflon TF 9202 (polytetrafluoroethylene), 20 percent by weight; Magnesium powder (as in Example 1), 20 weight percent; Phthalic anhydride, 45 weight percent; Chlorinated paraffin (as in Example 1), 15 percent by weight.

Example 6

The following composition was prepared using the procedure described in Example 1: polyvinylidene fluoride with a fluorine content of 59 percent by weight (Vidar), 22 percent by weight; Thiodiphenylamine, 48 weight percent; Polyvinyl chloride, 10% by weight.

Example 7

The following composition was prepared using the procedure described in Example 1: polyvinylidene fluoride (as in Example 6), 30 weight percent; Magnesium powder (as in Example 1), 15% by weight; Acridine, 40 weight percent; Chlorinated paraffin (as in Example 1), 15 percent by weight.

Example 8

The following composition was prepared using the procedure described in Example 1: polyvinylidene fluoride (as in Example 6), 30 weight percent; Magnesium powder (as in Example 1), 15% by weight; Thianthrene, 40 weight percent; Chlorinated paraffin (as in Example 1), 15 percent by weight.

Example 9

In order to test the performance of the composition according to the invention in the spectral range from 1 to 14 μm, a fog wall was produced which should be suitable for protecting armored vehicles against thermal imaging, IR target seekers and laser-guided target seekers. For this purpose, 8 munitions were fired with an angle fan of 14 ° - 14 ° - 14 ° - 14 ° - 14 ° - 9 ° - 4 °. The mist ammunition each contained a mixture of the composition according to the invention from Example 1 and a mist-producing composition which contained 25% fluorinated organic polymer, 25% magnesium powder and 50% phthalic anhydride within 2 seconds. The following results were achieved: Measurement data Goal 1 Average goals 2 to 5 Setup time (VIS) / sec 4th Tool life (VIS) / sec 79 Setup time (IR) / sec 7 7 Tool life (IR) / sec 34 33 Service life (IR) / service life (VIS) 43% 42% Relative coverage (IR) 95% 100% Contrast attenuation 8 to 14 µm 91% Contrast attenuation 3 to 5 µm 95% Cross wind speed 3 m / s Relative humidity 84%

Claims (9)

IR-opaque mist-producing composition in the form of a compact which has a density in the range from 0.9 to 1.5 g / cm 3, containing 10 to 25% by weight of magnesium powder, 5 to 35% by weight of a fluorinated organic polymer, 5 to 15% by weight of chlorinated paraffin and 35 to 65 percent by weight of an aromatic compound of formula I.

where A and B are independent of each other

-S-, -CH₂-,

mean,
R¹ and R² independently of one another represent OH, X or an alkyl radical having 1 to 4 carbon atoms,
m and n are each an integer from 0 to 2 and
X is halogen,
or an aromatic compound of formula II

where D and E are independent of each other

or -N = mean and
R¹, R², X, m and n are as defined above,
or one of the compounds phthalic anhydride, 2-benzoylpyridine, fluorene, dibenzosuberenone or diphenylene sulfide or derivatives thereof which are substituted by radicals R¹ _m and / or R² _n . Composition according to Claim 1, characterized in that it contains 15 to 20% by weight of magnesium powder, 10 to 30% by weight of fluorinated organic polymer, 10 to 15% by weight of chlorinated paraffin and 40 to 60% by weight of the aromatic compound. Composition according to one of the preceding claims, characterized in that the ratio of magnesium powder to fluorinated organic polymer is 1.5 to 2: 1. Composition according to one of the preceding claims, characterized in that a magnesium powder is used in which more than 90% have a particle size of less than 70 µm. Composition according to one of the preceding claims, characterized in that polytetrafluoroethylene or polyvinylidene fluoride is used as the fluorinated organic polymer. Composition according to one of the preceding claims, characterized in that the aromatic compound has no halogen atoms as substituents. Composition according to one of the preceding claims, characterized in that phthalic anhydride, anthracene or anthraquinone is used as the aromatic compound. Composition according to one of the preceding claims, characterized in that a chlorinated paraffin is used whose degree of chlorination is above 60% by weight. Composition according to one of the preceding claims, characterized in that the density of the compact is in the range from 1.1 to 1.4 g / cm³.