BE1025879B1 - Use of a halogenated salt of tetraphenyl phosphonium as a fumigant and fumigant pyrotechnic composition incorporating such material - Google Patents

Abstract

The subject of the invention is the use of at least one halogenated salt of tetraphenyl phosphonium as a fumigant in a pyrotechnic composition intended to ensure the concealment of an objective with respect to electromagnetic radiation in a given range of wavelengths. . The invention also relates to a fumigene pyrotechnic composition comprising at least one halogenated tetraphenyl phosphonium salt.

Description

Use of a halogenated salt of tetraphenyl phosphonium as a fumigant and fumigant pyrotechnic composition incorporating such a material.

The technical field of the invention is that of smoke-producing pyrotechnic compositions and more particularly smoke-producing compositions which can provide masking of an objective with respect to electromagnetic radiation in a given wavelength range.

Today we are looking for smoke bombs that can cover a wide spectrum of wavelengths, ranging from visible to far infrared, ie wavelengths from 0.7 micrometers to 14 micrometers.

Patent FR2583037 and FR2560186 disclose compositions combining an oxidant, a reducing agent and a material capable of generating masking particles which consists of a chlorinated aromatic compound. The masking particles generated are essentially carbon particles whose average particle size is close to the wavelengths of the radiation to be obscured.

These compositions are very effective from the point of view of masking, both for the visible spectrum and for the infrared domains: range from 3 to 5 micrometers and range from 8 to 12 micrometers. However, they have the drawback of using a substance, chlorinated naphthalene, which is today prohibited from manufacture and use by the European Union.

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There is thus a need to define, for the protection of land and naval forces, new pyrotechnic masking compositions which can ensure masking in a broad spectral range while using low-toxic components.

WO2015 / 132266 also discloses a smoke composition in which the material generating masking particles consists of a polyaromatic compound substituted with 1 to 3 bromine atoms, such as a dibromonaphthalene or a dibromoquinoline, and more particularly 1 , 4-dibromonaphthalene, 1,8dibromoquinoline or 4,7-dibromoquinoline.

This composition thus makes it possible, by replacing chlorine with bromine, to produce a smoke composition having substantially the performance of that known from chlorinated naphthalene while having less toxicity than the latter.

It is the aim of the invention to propose a new pyrotechnic composition which has a reduced toxicity but which has a certain masking efficiency, both in the visible and infrared range.

Thus, the subject of the invention is the use of at least one halogenated salt of tetraphenyl phosphonium as a fumigant in a pyrotechnic composition intended to mask an objective with respect to electromagnetic radiation in a range of wavelengths given.

These halogenated salts are commercially available and listed under the international CAS numbers:

BE2018 / 5007

2751 90 8 for tetraphenyl phosphonium bromide;

2001 45 8 for tetraphenyl phosphonium chloride;

2065 67 0 for tetraphenyl phosphonium iodide;

3587

1 for tetraphenyl phosphonium fluoride.

To date, they have never been used in pyrotechnic compositions, whether they are smoke-producing or not.

They are most often used as precursor or intermediate products in the synthesis of other compounds, in particular in the pharmaceutical field. Their structure facilitates the precipitation of organic molecules.

The Applicant has discovered that the combustion of these salts leads to the formation mainly of phosphonic acid and not of phosphoric acid like for most of the known organophosphorus.

This phosphonic acid is much less toxic than phosphoric acid and it leads to the production of masking clouds with reduced toxicity.

Furthermore, this combustion of organophosphates leads to the production of masking clouds having a high efficiency with respect to infrared radiation.

A halogenated salt of tetraphenyl phosphonium has the following structural formula in which X ^- denotes the halogen ion (Chlorine, Bromine, Iodine or fluorine).

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This molecule has four aromatic cycles which ensure during combustion the production of the carbon particles desired for masking.

The combustion will lead to the recombination of the halogen atoms with the other species: carbon or hydrogen, giving hydrogen halides or halogenated carbon derivatives.

Phosphorus recombines as phosphonic acid.

Preferably, the tetraphenyl phosphonium salt used is tetraphenyl phosphonium bromide.

This salt is of reduced cost and, as described in patent WO2015 / 132266, the use of bromine makes it possible to avoid the formation of hydrogen chloride during combustion, which reduces the toxicity of the fumes.

It would also be possible to use the other halogenated salts which will provide comparable masking performance. However, tetraphenyl phosphonium bromide or tetraphenyl phosphonium iodide will be preferred to reduce the toxicity of the cloud generated.

The invention also relates to a smoke pyrotechnic composition intended to ensure the masking of a

BE2018 / 5007 objective with respect to electromagnetic radiation in a given wavelength range and comprising at least one energetic material, such as an oxidation-reduction couple, as well as at least one smoke-generating agent generating masking particles, composition characterized in that it comprises as smoke agent at least one halogenated salt of tetraphenyl phosphonium.

An energetic material is a material or a composition which can be initiated and which provides sufficient energy to burn the fumigant and thus cause the emission of the masking particles, essentially carbon particles. Combustion will be carried out with sufficient speed to avoid the extinction of the smoke mass.

As an energetic material, it is possible to use an oxido-reducing couple, for example a couple combining, as reducing agent a metallic powder, and as oxidizing agent a fluoropolymer having in its molecular structure a percentage in fluorine greater than 60%.

The reducing agent can be chosen from the following bodies: aluminum, zirconium, magnesium, titanium, calcium silicide, boron.

The oxidant can be chosen from the following bodies: vinylidene fluoride and hexafluoropropylene di-polymer (for example the product sold by the company 3M under the brand Dyneon FC2230), polytetrafluoroethylene, tetrafluoroethylene or their mixture.

According to a particular embodiment, the composition may comprise: at least one organo-chlorinated compound in

BE2018 / 5007 a proportion less than 10% by mass. This chlorine compound allows more smoke to be deposited on the ground.

Indeed, chlorine will combine during combustion with carbonaceous species of the cloud, forming molecules of relatively large molar mass, this recombination will have a mechanical effect of increasing the cloud.

It has the advantage of increasing the duration of masking outdoors for a given mass of composition by avoiding too rapid dispersion of the smoke.

This chlorine compound will be added in small proportion so that the toxicity of the cloud is not increased excessively. We will choose a body incorporating a large number of chlorine atoms (chlorination rate greater than 60%) so that, despite the reduced mass, the recombination of chlorine has a significant effect.

We could for example use the compound marketed under the brand name Dechlorane plus by the American company Oxychem. This compound is a polyheteroaromatic used as a well-known flame retardant and is listed under the CAS number 13560-89-9. It has 12 chlorine atoms in its molecular structure.

More specifically, the masking composition according to the invention may combine:

from 10 to 40% in mass of material energy and of preference 20% to 30%, from 90% to 60% en masse of agent smoke and of preference 60% to 70%

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- from 0% to 10% by mass of chlorinated agent and preferably 0 to 7%,

- from 0% to 8% by mass of binder and preferably 0 to 5%.

The binder improves the mechanical strength of the composition block which will, for example, be implemented by compression.

The binder may consist of at least one epoxy-type resin added in a proportion of approximately 5% of the overall mass of the block (for a 100 gram block, 5 grams of binder are added).

In all cases the implementation by compression will be done with a relatively high compression ratio (17 Mega Pascals for a diameter of 125 mm for example).

For clarity, a few examples of compositions according to the invention and their uses are described below by way of illustration and without limitation, reference being made to the appended drawings in which:

- Figure 1 is a curve showing the evolution over time of the camouflage coefficient Cm for a composition according to Example 2 given below;

- Figure 2 shows the evolution over time of the camouflage coefficient Cm for a composition according to Example 3 given below;

- Figure 3 shows the evolution over time of the camouflage coefficient Cm for a composition according to Example 4 given below.

The Applicant has produced a certain number of compositions in accordance with the invention (proportions of

BE2018 / 5007 constituents given relative to the total mass of the composition) and proceeded to the evaluation of their masking performance.

Example 1

12% by mass of magnesium powder,

18% by mass of vinylidene fluoride and hexafluoropropylene di-polymer,

63% by mass of tetraphenyl phosphonium salt,

7% by mass of chlorinated agent.

This composition is put in the form of a block without binder. The block is produced by compression with the compression rate specified above (17 Mega Pascals for a diameter of 125 mm). Such a compression ratio is sufficient to ensure the cohesion of the block.

Example 2

12% by mass of magnesium powder,

12% by mass of vinylidene fluoride and hexafluoropropylene di-polymer,

69% by mass of tetraphenyl phosphonium salt,

7% by mass of chlorinated agent,

5% by mass of epoxy resin.

Example 3

15% by mass of magnesium powder,

15% by mass of vinylidene fluoride and hexafluoropropylene di-polymer,

69% by mass of tetraphenyl phosphonium salt,

5% by mass of epoxy resin.

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Example 4

15% by mass of magnesium powder,

15% by mass of vinylidene fluoride and hexafluoropropylene di-polymer,

62% by mass of tetraphenyl phosphonium salt,

7% by mass of chlorinated agent,

5% by mass of epoxy resin.

For each composition, a smoke block of approximately 800 grams was produced.

This block was positioned in an optronic tunnel at a distance of 6 meters from the optical measurement line.

The combustion of the block is done like a "cigarette". That is to say that the initiation is carried out at the level of the free upper surface of the block which is gradually consumed from its upper surface to its lower surface (bearing surface).

The smoke cloud generated was moved with a fan at a controlled speed of 3m / s so that it passed in front of the measuring equipment.

The measurement means include:

- a hot spring with a regulated temperature around 160 ° C;

- a cold source (constituted by the steel wall of the optronic tunnel);

- a thermal camera observing in band 3 (spectral window from 8 to 12μη).

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The masking is evaluated by comparing the effect of the passage of smoke in front of the thermal sources (cold and hot) on the temperature seen by the thermal camera.

For each pot tested, the camouflage coefficients Cm (in percentage) are calculated by applying the following formula:

/ = 100x 1V (Nb'-Nn ');

Formula in which:

Nb (t) and Nb 'are the digital levels measured by the camera at the level of the hot source, in the presence of smoke (Nb (t)) and in the absence of smoke (Nb');

Nn (t) and Nn 'are the digital levels measured by the camera at the level of the cold source, in the presence of smoke (Nn (t)) and in the absence of smoke (Nn').

As previously specified, the appended figures show the evolution over time on the abscissa of the camouflage coefficient Cm on the ordinate for various examples of composition.

FIG. 1 corresponds to the composition according to Example 2, FIG. 2 corresponds to the composition according to Example 3 and FIG. 3 corresponds to the composition according to Example 4.

It is noted when considering all the figures that the masking compositions according to the invention make it possible to obtain a camouflage coefficient greater than 45%

BE2018 / 5007 for a period of at least 90 seconds which is particularly advantageous.

Furthermore, the masking performances are very similar for the different compositions, which indicates a certain stability of operation even with a few% of formulation deviations.

We also note that the installation of the smoke curtain is quick.

It ranges from 3 seconds to 10 seconds.

It has also been noted, in the course of other tests, that the rate of combustion is a function of the magnesium level. Thus, the rate of combustion increases when the magnesium level increases. For example, a magnesium level of 15% will provide a block burning time of almost 52 seconds while a magnesium level of 12% will provide a burning time of 88 seconds.

This is not particularly visible in the figures which show the results of tests in the shooting tunnel.

It has also been observed that the addition of Dechlorane made it possible to increase the duration of the masking during combustion outdoors.

It is obvious that the invention is in no way limited to the examples described above but that numerous modifications can be made to the smoke-producing pyrotechnic composition and its use described above without departing from the scope of the invention as defined in the following claims.

Claims (17)

Claims. 1.- Use of at least one halogenated salt of tetraphenyl phosphonium as fumigant in a pyrotechnic composition intended to ensure the masking of an objective with respect to electromagnetic radiation in a given wavelength range. 2. Use according to claim 1, characterized in that the halogenated salt of tetraphenyl phosphonium used is tetraphenyl phosphonium bromide. 3. Use according to claim 1 to obtain a masking with a camouflage coefficient greater than 45% for a period of at least 90 seconds. 4.- Smoke pyrotechnic composition intended to ensure the masking of an objective with respect to electromagnetic radiation in a given range of wavelengths and comprising at least one energetic material, such as an oxidation-reduction couple, as well as at least one smoke-generating agent for masking particles, composition characterized in that it comprises as smoke-producing agent at least one halogenated salt of tetraphenyl phosphonium. 5.- Composition according to claim 4, characterized in that it comprises as smoke agent bromide or iodide of tetraphenyl phosphonium. 6.- Composition according to claim 5, characterized in that it comprises as energetic material a redox couple combining, as a metal powder reducer, and as an oxidizer a fluoropolymer. BE2018 / 5007 7.- Composition according to claim 6, characterized in that the fluoropolymer is a fluoropolymer having in its molecular structure a percentage of fluorine greater than 60%. 8.- Composition according to claim 6 or 7, characterized in that it comprises at least one reducing agent chosen from the following bodies: magnesium, aluminum, zirconium, titanium, calcium silicide, boron. 9.- Composition according to any one of claims 6 to 8, characterized in that it comprises at least one oxidant chosen from the following bodies: di-polymer of vinylidene fluoride and hexafluoro-propylene, polytetrafluoroethylene, tetrafluoro- ethylene or mixtures thereof. 10.- Composition according to any one of claims 6 to 9, characterized in that it comprises at least one chlorinated compound in a proportion of less than 10% by mass. 11.- Composition according to claim 10, characterized in that it comprises at least one organo-chlorinated compound with a chlorination rate greater than 60%. 12.- Composition according to one of claims 4 to 11, characterized in that it comprises: - 10% to 40% by mass of energetic material and preferably 20% to 30%, - 90% to 60% by mass of smoke-producing agent and preferably 60% to 70%, - 0% to 10% by mass of chlorinated agent and preferably 0 to 7 97%, - 0% to 8% by mass of binder and preferably 0 to 5%. BE2018 / 5007 13.- Composition according to claim 12, characterized in that the binder consists of at least one epoxy type resin added in a proportion of about 5% of the overall mass of the block. 14.- Composition according to claim 12, characterized in that it comprises: - 12% by mass of magnesium powder, - 18% by mass of vinylidene fluoride and hexafluoropropylene di-polymer, - 63% by mass of tetraphenyl phosphonium salt, - 7% by mass of chlorinated agent. 15.- Composition according to claim 12, characterized in that it comprises: - 12% by mass of magnesium powder, - 12% by mass of vinylidene fluoride and hexafluoropropylene di-polymer, - 69% by mass of tetraphenyl phosphonium salt, - 7% by mass of chlorinated agent, - 5% by mass of epoxy resin. 16.- Composition according to claim 12, characterized in that it comprises: - 15% by mass of magnesium powder, - 15% by mass of vinylidene fluoride and hexafluoropropylene di-polymer, - 69% by mass of tetraphenyl phosphonium salt, - 5% by mass of epoxy resin. 17.- Composition according to claim 12, characterized in that it comprises: - 15% by mass of magnesium powder, BE2018 / 5007 - 15% by mass of vinylidene fluoride and hexafluoropropylene di-polymer, - 62% by mass of tetraphenyl phosphonium salt, - 7% by mass of chlorinated agent, 5 - 5% by mass of epoxy resin.