EP3114099B1 - Low-toxicity smoke pyrotechnic compositions for wide band masking - Google Patents

Description

The present invention relates to pyrotechnic compositions of low toxicity advantageously intended for the protection of land platforms (such as vehicles or armored vehicles), in particular against infrared guided threats. Said compositions make it possible to produce an effective camouflage cloud in the visible and infrared range.

The masking compositions currently used generally comprise an oxidizing / reducing couple, and a compound serving as fuel (fuel oil). During combustion, the fuel makes it possible to generate particles of shape and size adapted to ensure effective masking in the visible and infrared, in particular for the spectral window of between 3 and 14 μm. These compositions include chlorinated compounds, such as CLONACIRE® (composition comprising a mixture of chlorinated naphthalenes with a degree of substitution greater than 3) or hexachloroethane. These play the role of either an oxidizer or a particle generator product.

However, these strongly chlorinated compounds, during their degradation, form toxic products, in particular HCl (gaseous hydrochloric acid) in large quantities.

According to the evaluations of the Ministry of Ecology and Sustainable Development, Ministry of Health, Family and Handicapped Persons (INERIS sheet, 2003), the threshold for the first lethal effects and the threshold for irreversible effects associated with gaseous HCl for 10 minutes of exposure are 1300 ppm (threshold for first lethal effects, or 1937 mg / m ³ ), and 240 ppm (threshold for irreversible effects, or 358 mg / m ³ ).

There is therefore a need for pyrotechnic compositions exhibiting good masking performance with low toxicity.

The use of brominated compounds in pyrotechnic compositions is already known, in particular for applications as a decoy for the protection of aerial targets against infrared-guided threats, without however addressing the problem of the toxicity of said compositions. The effects sought in this case are generally not masking fumes but infra-red radiation imitating the radiation from the engine of aerial platforms.

Moreover, the patent US 5,389,308 , which relates to compositions generating opaque infrared fumes comprising magnesium powder, a fluorinated organic polymer, chloroparaffin and an aromatic compound, which may be a brominated aromatic compound such as 8-bromoanthracene, teaches that non-halogenated compounds are preferred because of their lower toxicity.

Likewise, patents US 3,498,925 and US 3,400,082 teach the use of metallic or organometallic compounds but not halogenated to reduce the toxicity of pyrotechnic compositions for masking in the visible. Requirement US 2012/0267016 , which relates to smoke-producing compositions for masking in the visible, for its part recommends the use of a mixture comprising melamine and polymethylated methylgallate. Furthermore, these compositions comprise sucrose as fuel, and a chlorate as oxidant. In addition, the patent US 4,238,254 describes pyrotechnic compositions for visible masking, including guanidine nitrate, which produces basic compounds capable of neutralizing hydrogen chloride (HCl) or phosphorus pentoxide produced in fumes. Requirement EP 1 876 161 teaches a pyrotechnic charge for the production of infrared radiation containing a brominated compound as fuel and / or as an oxidizing agent.

The prior art therefore consistently teaches that, in order to reduce or even eliminate the toxicity of pyrotechnic masking compositions, any use of halogenated product should be avoided, both as an oxidizing agent, reducing agent or fuel.

Surprisingly, the Applicant has however found that the use of a polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms as fuel in a pyrotechnic composition, preferably a fumigant, makes it possible to significantly reduce the toxicity of the pyrotechnic compositions. compared to those of the prior art, while retaining their masking performance both in the visible and in the infrared.

For the purposes of the present invention, the term “spectral window” is understood to mean a wavelength domain.

For the purposes of the present invention, the term “polyaromatic” compound is understood to mean a C10 to C14 hydrocarbon-based compound, consisting of 2 to 3 adjoining aromatic rings. As examples of polyaromatic compounds, mention may be made in particular of naphthalene, anthracene and phenanthrene. Preferably, it is naphthalene and anthracene, more preferably naphthalene.

For the purposes of the present invention, the term “polyheteroaromatic” compound means a compound consisting of 2 to 3 aromatic or heteroaromatic rings joined together and comprising at least one nitrogenous heteroaromatic ring. As examples of polyheteroaromatic compounds, mention may be made in particular of quinoline, isoquinoline and naphthyridine. Preferably, it is quinoline.

For the purposes of the present invention, the term “chlorinated compound” means an organic compound comprising at least one chlorine atom, in particular a compound comprising at least one chlorine carbon bond (C-Cl).

The present invention relates exclusively to chemically stable compounds.

Advantageously, the polyaromatic or polyheteroaromatic compounds substituted with 1 to 3 bromine atoms according to the invention do not contain chlorinated substituents.

Preferably, the polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms does not contain other substituents.

To determine the toxicity of a pyrotechnic composition, the potentially toxic species emitted during the combustion of the fumigant are determined. The quantities emitted during combustion are evaluated by thermodynamic calculation codes. For each toxic species identified, the literature is searched for the thresholds for the first lethal effects and the thresholds for irreversible effects. These two thresholds are evaluated as a function of the duration of exposure of the subject to the toxic substance, in this case gaseous HBr.

According to the report of the Toxicology Expert Group of the Ministry of Ecology, Energy, Sustainable Development and Regional Planning (April 15, 2008), the threshold for the first lethal effects and the threshold for the associated irreversible effects to gaseous HBr for 10 minutes of exposure are 3290 ppm (threshold for first lethal effects, or 11 054 mg / m ³ ), and 366 ppm (threshold for irreversible effects, or 1228 mg / m ³ ).

The present invention relates to the subject of the claims.

The present application firstly describes the use of a polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms as fuel in a pyrotechnic composition, preferably a fumigant, so that, during the combustion of said composition, the content of toxic substance in the gases emitted, such as hydrobromic acid, is less than 350 ppm, preferably less than 300 ppm.

• 5 à 25 % en poids de réducteur,
• 2 à 25 % en poids d'un liant, éventuellement en mélange avec un plastifiant, et
• 50 à 90 % en poids d'un combustible comprenant au moins un composé polyaromatique ou polyhétéroaromatique substitué par 1 à 3 atomes de brome,
• optionnellement 5% à 15% en poids d'oxydant,
• optionnellement de 2 à 10% en poids d'additifs

par rapport au poids total de la composition, la composition pyrotechnique ne contenant pas de composé chloré.The present invention relates to a pyrotechnic composition, preferably fumigant, comprising at least one reducing agent, a binder and at least one polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms as fuel, and optionally an oxidant, in the following proportions :

• 5 to 25% by weight of reducing agent,
• 2 to 25% by weight of a binder, optionally mixed with a plasticizer, and
• 50 to 90% by weight of a fuel comprising at least one polyaromatic or polyheteroaromatic compound substituted by 1 to 3 bromine atoms,
• optionally 5% to 15% by weight of oxidant,
• optionally from 2 to 10% by weight of additives

relative to the total weight of the composition, the pyrotechnic composition not containing any chlorinated compound.

The present invention further relates to a pyrotechnic device comprising said composition.

The present invention also relates to a method of masking a target comprising the production of a smoke screen preventing the transmission of infrared radiation between the target and the threat using a pyrotechnic composition, preferably smoke, comprising a polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms as fuel, in which the pyrotechnic composition is a composition according to the invention.

The present application describes the use of a polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms as defined above as fuel in a pyrotechnic composition, preferably a fumigant, in which, during the combustion of said composition, the content of toxic substance, in particular hydrobromic acid, of the gases emitted is less than 350 ppm, preferably less than 300 ppm.

Advantageously, the combustion of said composition offers a camouflage coefficient in the spectral window 8 to 12 μm greater than 50%, preferably greater than 60%, typically for 15 seconds, preferably for 20 seconds. Advantageously, the combustion of said composition offers a camouflage coefficient in the spectral window 3 to 5 μm greater than 60%, preferably greater than 70%, typically for 15 seconds, preferably for 20 seconds.

dans laquelle

• Nb(t) et Nb' sont les niveaux numériques respectivement avec et sans effet sur la source chaude ;
• Nn(t) et Nn' sont les niveaux numériques respectivement avec et sans effet sur la source froide.

For the purposes of the present invention, the term “camouflage coefficient” means the ratio Cm (t) expressed as a percentage calculated at time t according to the following formula: $${\mathrm{VS}}_m\left(t\right)=100\times \left(1-\frac{\left(\mathit{Nb}\left(t\right)-\mathit{Nn}\left(t\right)\right)}{\left(\mathit{Nb}\prime -\mathit{Nn}\prime \right)}\right)$$

in which

• Nb (t) and Nb 'are the digital levels respectively with and without effect on the hot source;
• Nn (t) and Nn 'are the digital levels respectively with and without effect on the cold source.

• une source chaude de type corps noir qui présente une température régulée autour de 200°C,
• une source froide (typiquement une plaque d'acier à température ambiante).

The camouflage coefficient is typically measured under controlled and reproducible conditions. The measuring devices used are transmitting means such as:

• a hot source of the black body type which has a regulated temperature of around 200 ° C,
• a cold source (typically a steel plate at room temperature).

• une caméra thermique travaillant en bande 2 (fenêtre spectrale 3-5 µm) ;
• une caméra thermique travaillant en bande 3 (fenêtre spectrale 8-12 µm).

And receiving measuring means such as:

• a thermal camera working in band 2 (spectral window 3-5 µm);
• a thermal camera working in band 3 (spectral window 8-12 µm).

Preferably, the smoke-producing composition does not contain a chlorinated compound.

Advantageously, the polyaromatic or polyheteroaromatic compound is substituted by 2 bromine atoms, even more advantageously, it is a dibromonaphthalene or a dibromoquinoline, even more advantageously 1,4-dibromonapthalene, 1,8-dibromoquinoline or 4,7-dibromoquinoline.

• 5 à 25 % en poids, de préférence 10 à 20% en poids, de réducteur,
• 2 à 25 % en poids d'un liant, éventuellement en mélange avec un plastifiant, et
• 50 à 90 % en poids, de préférence 60 à 80% en poids, d'un combustible comprenant au moins un composé polyaromatique ou polyhétéroaromatique substitué par 1 à 3 atomes de brome,
• optionnellement 5% à 15% en poids d'oxydant,
• optionnellement de 2 à 10% en poids d'additifs,

par rapport au poids total de la composition,The present invention relates to a pyrotechnic composition, preferably fumigant, comprising at least one reducing agent, a binder and at least one polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms as fuel, and optionally an oxidant, in the following proportions :

• 5 to 25% by weight, preferably 10 to 20% by weight, of reducing agent,
• 2 to 25% by weight of a binder, optionally mixed with a plasticizer, and
• 50 to 90% by weight, preferably 60 to 80% by weight, of a fuel comprising at least one polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms,
• optionally 5% to 15% by weight of oxidant,
• optionally from 2 to 10% by weight of additives,

relative to the total weight of the composition,

the composition not containing a chlorinated compound.

The weight of the binder is adjusted, if necessary, so that the percentages of the various elements added are equal to 100%. Thus the percentage of binder is adjusted relative to the mass percentages of reducing agent, fuel, optionally oxidant and additives, to obtain 100%.

The composition is devoid of chlorine compound.

Preferably, the polyaromatic or polyheteroaromatic compound is substituted with 2 bromine atoms. Advantageously, the polyaromatic or polyheteroaromatic compound is substituted by 2 bromine atoms, even more advantageously, it is a dibromonaphthalene or a dibromoquinoline, even more advantageously 1,4-dibromonapthalene, 1,8-dibromoquinoline or 4,7-dibromoquinoline.

Typically, the reducing agent is chosen from magnesium, aluminum, zirconium, titanium, silicon and boron or their mixtures, for example in the form of metal powder. Preferably, the reducing agent consists essentially of powder of magnesium or of a mixture of zirconium and magnesium.

• 5 à 25 % en poids de réducteur,
• 5 à 25 % , de préférence de 10 à 15 %, en poids d'un liant, éventuellement en mélange avec un plastifiant, et
• 50 à 90 %, de préférence 60 à 70 %, en poids d'un combustible comprenant au moins un composé polyaromatique ou polyhétéroaromatique substitué par 1 à 3 atomes de brome,
• optionnellement de 2 à 10% en poids d'additifs,

In a first embodiment, the binder also acts as an oxidant. In this embodiment, the compositions do not include an oxidizer in addition to the binder. In this first embodiment, the pyrotechnic composition, preferably smoke, according to the invention preferably comprises:

• 5 to 25% by weight of reducing agent,
• 5 to 25%, preferably 10 to 15%, by weight of a binder, optionally mixed with a plasticizer, and
• 50 to 90%, preferably 60 to 70%, by weight of a fuel comprising at least one polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms,
• optionally from 2 to 10% by weight of additives,

relative to the total weight of the composition.

The binder is then chosen from fluoroelastomers or their mixtures, advantageously polytetrafluoroethylene, poly (carbon monofluoride) (PMF, in English polycarbon mono fluoride) or a copolymer of vinylidene fluoride, hexafluoropropylene, perfluoromethylvinylether and / or tetrafluoroethylene (such as VITON®) or their mixtures.

In a second embodiment, the binder does not act as an oxidant. In this embodiment, the compositions according to the invention comprise between 5% and 15% by weight of oxidant, advantageously chosen from potassium chlorate, ammonium chlorate, potassium perchlorate, ammonium perchlorate, potassium nitrate or ammonium nitrate, or mixtures thereof. The oxidant can also be chosen from fluoroelastomers or their mixtures, advantageously polytetrafluoroethylene, poly (carbon monofluoride) (PMF, in English polycarbon mono fluoride) or a copolymer of vinylidene fluoride, hexafluoropropylene, perfluoromethylvinyl ether and / or tetrafluoroethylene or their mixtures.

The binder is then chosen from phenolic polymers, epoxy resins and polybutadiene. In particular, when the binder is an epoxy resin, the oxidant is advantageously chosen from polytetrafluoroethylene, poly (carbon monofluoride) (PMF, in English polycarbon mono fluoride) or a copolymer of vinylidene fluoride, hexafluoropropylene, perfluoromethyl vinyl ether and / or tetrafluoroethylene or their mixtures.

• 5 à 25 %, de préférence de 10 à 20%, en poids de réducteur,
• 2 à 10 %, de préférence de 3 à 5%, en poids d'un liant, éventuellement en mélange avec un plastifiant,
• 5 à 15 %, de préférence de 10 à 15%, en poids d'oxydant et
• 50 à 90 %, de préférence 60 à 80 %, en poids d'un combustible comprenant au moins un composé polyaromatique ou polyhétéroaromatique substitué par 1 à 3 atomes de brome,
• optionnellement de 2 à 10% en poids d'additifs,

par rapport au poids total de la composition.In this second embodiment, the pyrotechnic composition, preferably smoke, according to the invention preferably comprises:

• 5 to 25%, preferably 10 to 20%, by weight of reducing agent,
• 2 to 10%, preferably 3 to 5%, by weight of a binder, optionally mixed with a plasticizer,
• 5 to 15%, preferably 10 to 15%, by weight of oxidant and
• 50 to 90%, preferably 60 to 80%, by weight of a fuel comprising at least one polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms,
• optionally from 2 to 10% by weight of additives,

relative to the total weight of the composition.

The compositions according to the invention can also comprise additives, such as hardeners, combustion retarders, flame inhibitors. The combustion retarders are in particular chosen from diatoms and carbon graphite. An example of a preferred flame inhibitor is sodium hydrogencarbonate. The preferred additives are flame retardants and flame inhibitors.

The present invention also relates to a pyrotechnic device comprising a container in which is housed the payload of pyrotechnic composition according to the invention. Preferably, the pyrotechnic composition according to the invention is shaped by compression. The container is typically a smoke pot or a grenade capable of being launched by a launcher or manually.

The present invention also relates to a method of masking a target comprising the production of a smoke screen preventing the transmission of infrared radiation between the target and the threat using a pyrotechnic composition, preferably smoke, comprising a polyaromatic or substituted polyheteroaromatic compound with 1 to 3 bromine atoms as fuel, in which the pyrotechnic composition is a composition according to the invention.

DESCRIPTION OF FIGURES

• Figure 1 : curve representing the change in the camouflage coefficient for the 3-5 µm optical window for composition 1. The abscissa axis represents time in seconds, the ordinate axis represents the camouflage coefficient in%.
• Figure 2 : curve representing the change in the camouflage coefficient for the 8-12 µm optical window for composition 1. The abscissa axis represents time in seconds, the ordinate axis represents the camouflage coefficient in%.
• Figure 3 : curve representing the change in the camouflage coefficient for the 3-5 µm optical window for composition 2. The abscissa axis represents time in seconds, the ordinate axis represents the camouflage coefficient in%.
• Figure 4 : curve representing the change in the camouflage coefficient for the 8-12 µm optical window for composition 2. The abscissa axis represents time in seconds, the ordinate axis represents the camouflage coefficient in%.

EXAMPLES

The examples which follow are given by way of illustration, but should in no case be considered as limiting the present invention.

Example 1: toxicity assessment

The enthalpy of formation of 1,4-dibromonaphthalene was defined as being equal to 27.6 kCal / mol using Hyperchem software and data from the literature.

A simulation of the combustion of 1,4-dibromonaphthalene making it possible to determine the species emitted during combustion was carried out with the Coppelia software. The thermodynamic calculation was carried out in the absence of oxygen from the air, under 2 atmospheres of pressure and at a temperature of 2000K. The mass fractions of the species emitted resulting from this calculation mainly show a toxic species which is HBr. Its mass fraction is given by the Coppelia calculation as being equal to 0.3436.

From this result, the maximum concentration near the source of the smoke, i.e. the burning smoke pot of HBr can be estimated at 300 ppm. This concentration decreases rapidly by dilution as soon as one moves away from this source.

Toxicity thresholds described in the literature for the HBr molecule:

The data available concerning gaseous HBr (report of the Toxicologist Expert Group of the Ministry of Ecology, Energy, Sustainable Development and Regional Planning of April 15, 2008) describe the thresholds of the first lethal effects and the thresholds for irreversible effects associated with exposure times.

Example 2 : evaluation of masking performance Description of the compositions tested :

The compositions tested contain 1,4-dibromonaphthalene as fuel. It is this fuel which, associated with the oxidizing reducing couple, makes it possible to ensure the broadband masking performance.

In the case of composition 1, the binder used is a fluoropolymer of Viton® type. This binder also serves as an oxidant in the composition. The reducer used is magnesium. 1,4-dibromonaphthalene is present in the composition in an amount of approximately 70%, the Viton® binder represents 11% by weight of the composition, the reducing agent constitutes 19% of the mixture.

In the case of composition 2, the binder used is an epoxy resin associated with its hardener. The oxidant used in the composition is a fluoropolymer of the polytetrafluoroethylene type. The reducing agent used is magnesium. A combustion retarder is also used in the composition, it is graphite carbon. 1,4-Dibromonaphthalene is present in this composition at 68%, the binder at 3%, the reducing agent at 17%, the oxidant at 10% and the combustion retarder represents 2% in mass of the composition.

The compositions tested are compressed in the form of cylindrical smoke pots. The mass of composition contained in each jar is approximately 400g.

Description of the test means :

The test means make it possible to move the smoke cloud at a controlled speed so as to cause it to pass in a controlled and reproducible manner in front of the measuring means described below.

Description of the measuring means :

• The measurement means are made up of emitting sources which are:
  • a hot source of the black body type which has a regulated temperature of around 200 ° C,
  • a cold source (typically a steel plate at room temperature).

• une caméra thermique travaillant en bande 2 (fenêtre spectrale 3-5 µm)
• une caméra thermique travaillant en bande 3 (fenêtre spectrale 8-12 µm).

And receiving measuring means positioned opposite the sources which are:

• a thermal camera working in band 2 (spectral window 3-5 µm)
• a thermal camera working in band 3 (spectral window 8-12 µm).

Description of the implementation of the smoke pot :

The smoke curtain moves and passes in front of the measuring means, thus making it possible to measure the infrared performance of the smoke under controlled and reproducible conditions.

Description of the data analysis method:

For each pot tested, the following values are calculated from the luminance recordings obtained with the band 2 and band 3 thermal cameras.

dans laquelle

• Nb(t) et Nb' sont les niveaux numériques respectivement avec et sans effet sur la source chaude ;
• Nn(t) et Nn' sont les niveaux numériques respectivement avec et sans effet sur la source froide.

Cm = Camouflage coefficient (expressed as a percentage) calculated according to the following formula: $${\mathrm{VS}}_m\left(t\right)=100\times \left(1-\frac{\left(\mathit{Nb}\left(t\right)-\mathit{Nn}\left(t\right)\right)}{\left(\mathit{Nb}\prime -\mathit{Nn}\prime \right)}\right)$$

in which

• Nb (t) and Nb 'are the digital levels respectively with and without effect on the hot source;
• Nn (t) and Nn 'are the digital levels respectively with and without effect on the cold source.

The results obtained for compositions 1 and 2 in the 3-5 µm and 8-12 µm spectral windows are shown in the figures 1 to 4 .

It is noted that, both for composition 1 and for composition 2, the combustion of said composition offers a camouflage coefficient in the spectral window 8 to 12 μm and 3-5 μm greater than 50%, for at least 20 seconds.

More precisely, composition 1 offers a camouflage coefficient greater than 70% for 15 seconds in the 3-5 μm spectral band and greater than 60% for 15 seconds in the 8-12 μm spectral window.

Composition 2 provides a camouflage coefficient greater than 70% for 30 seconds in the 3-5 μm spectral band and greater than 60% for 20 seconds in the 8-12 μm spectral window.

Claims (9)

1. A pyrotechnic, preferably smoke, composition comprising at least one reductant, a binder and at least one polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms as fuel, and optionally an oxidant, in the following proportions:

   - 5 to 25% by weight of reductant,

   - 2 to 25% by weight of a binder, optionally mixed with a plasticizer, and

   - 50 to 90% by weight of a fuel comprising at least one polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms,

   - optionally 5% to 15% by weight of oxidant, and

   - optionally from 2 to 10% by weight of additives based on the total weight of the composition, the composition not containing a chlorinated organic compound.
2. The composition as claimed in claim 1, characterized in that the polyaromatic or polyheteroaromatic compound is substituted with 2 bromine atoms.
3. The composition as claimed in any one of claims 1 or 2, characterized in that the polyaromatic or polyheteroaromatic compound is a dibromonaphthalene or a dibromoquinoline.
4. The composition as claimed in any one of claims 1 to 3, characterized in that the reductant is selected from magnesium, aluminum, zirconium, titanium, silicon and boron or mixtures thereof, for example in the form of metal powder, preferably the reductant consists essentially of magnesium powder or a mixture of zirconium and magnesium.
5. The composition as claimed in any one of claims 1 to 4, characterized in that the oxidant is selected from potassium chlorate, ammonium chlorate, potassium perchlorate, ammonium perchlorate, potassium nitrate or ammonium nitrate, fluoroelastomers, or mixtures thereof.
6. The composition as claimed in claim 5, characterized in that the binder is selected from phenolic polymers, epoxy resins and polybutadiene.
7. The composition as claimed in any one of claims 1 to 4, characterized in that the binder also acts as an oxidant, and is advantageously selected from fluoroelastomers, advantageously polytetrafluoroethylene, poly(carbon monofluoride) or a copolymer of vinylidene fluoride, hexafluoropropylene, perfluoromethylvinylether and/or tetrafluoroethylene, or mixtures thereof.
8. A pyrotechnic device comprising a container, typically a smoke pot or grenade suitable for launching by a launcher or manually, in which is housed the pyrotechnic composition payload as claimed in any one of claims 1 to 7.
9. A process for masking a target comprising producing a smoke screen blocking transmission of infrared radiation between the target and the threat with a pyrotechnic, preferably smoke, composition comprising a polyaromatic or polyheteroaromatic compound substituted with 1 to 3 bromine atoms as fuel, said pyrotechnic composition being as defined in any one of claims 1 to 7.

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