EP3148957B1 - Initiated pyrotechnic blocks and method for producing same - Google Patents

Description

The present invention relates to primed pyrotechnic breads, their method of manufacture and their use. The pyrotechnic blocks or bars concerned by this invention comprise a priming composition integrated directly into said blocks, and are obtained by compression. They are advantageously used as infrared lures, typically in the conventional domain and the spectral domain.

BACKGROUND OF THE INVENTION

A pyrotechnic bread is a solid block, optionally decomposing into several subparts or layers, the composition, geometry and volume of which may differ, and comprising at least one layer of a pyrotechnic composition.

Pyrotechnic rolls can be characterized by radial combustion (from the outside to the inside), or by axial combustion (also called "cigarette type combustion"). The present invention is preferably aimed at pyrotechnic bars having a radial combustion.

Such pyrotechnic breads are intended for various civil or military applications, such as missile lure by infrared emission.

The combustion of an infra-red pyrotechnic bread is characterized by its luminance, its duration and its rising edge (speed and intensity on ignition). The luminance is directly related to the nature of the pyrotechnic composition itself. The duration of the combustion is not only a function of the nature of the composition, but also of the geometry of the bread. Finally, the rising edge is generally provided by the concomitant use of a priming composition.

The prior art describes in particular pyrotechnic breads called "primed", that is to say that these pyrotechnic rolls are shaped and generally grooved so as to receive in their free grooves the priming composition pasty form. An example of this is the pyrotechnic breads described in the patent FR 2,729,749 , which comprise a pyrotechnic composition in the form of a grooved block, in the grooves of which was deposited a priming composition.

• d'infrastructure : jusqu'à présent, des loges de travail doivent être spécifiquement dédiées à l'amorçage et équipées d'un mélangeur spécifique pour fabriquer la composition d'amorçage sous forme de pâte.
• de main d'oeuvre : après fabrication, la composition d'amorçage est déposée dans les rainures libres du bloc pyrotechnique, généralement manuellement ou automatiquement (pour des exemples de procédés automatiques voir notamment EP 0 665 415 , US 6,427,599 , EP 0 309 097 ).
• De logistique : une fois fabriquée, la composition d'amorçage est alors sous forme pâteuse et sous solvant. Elle dispose donc d'une durée de vie limitée, ce qui en limite l'utilisation. Cette durée d'utilisation limitée impose en outre une planification contraignante des différentes étapes de fabrication du pain pyrotechnique amorcé.

However, the method of priming pyrotechnic loaves is generally long and expensive, in particular in terms of:

• infrastructure: until now, work boxes have to be specifically dedicated to priming and equipped with a specific mixer to manufacture the priming composition in paste form.
• manpower: after manufacture, the priming composition is deposited in the free grooves of the pyrotechnic block, usually manually or automatically (for examples of automatic processes see particular EP 0 665 415 , US 6,427,599 , EP 0 309 097 ).
• Logistic: once manufactured, the priming composition is then in pasty form and under solvent. It therefore has a limited life, which limits the use. This limited duration of use also imposes a constraining planning of the various stages of manufacture of the pyrotechnic bread initiated.

In addition, in order to ensure the cohesion of the two compositions (priming and main), the initiating composition most often comprises a thermosensitive, thermosetting or thermoplastic crosslinking agent.

Moreover, the removal of the priming composition in the form of paste in the grooves of the pyrotechnic block generally results in a weak cohesion between the priming paste and the pyrotechnic block, which influences the physical and mechanical properties of the pyrotechnic bread initiated. This weak cohesion leads to poor transmission of (combustion) fires between the different layers, which generates a combustion profile and therefore non-optimal infrared emission.

The prior art further discloses primed pyrotechnic breads not intended for infrared decoy applications having axial combustion. We can quote in particular US 2001/013384 , US 8,465,606 , US 3,744,418 , US5,466,314 , US 2,868,129 , DE 876 822 and US 2013/0036932 , which furthermore do not mention the addition of grooves on the pyrotechnic bread.

There is therefore a need for a new process for producing, depositing and shaping pyrotechnic cracked bread having a radial combustion which significantly improves the adhesion of the priming on the block and the cohesion between the main compositions and priming so as to improve the combustion profile, less expensive, simplifying the implementation infrastructure. This concept not only makes it possible not to limit the duration of use of the priming compositions, but also to vary the priming compositions. This concept has the advantage of optimizing the IR performance by improving the luminescence of the blocks, in particular by a better fire transmission between the priming and the infrared composition of the block.

SUMMARY OF THE INVENTION

Surprisingly, the applicant has developed a method for producing pyrotechnic bread, primed, typically radial combustion, to overcome the problems of the prior art. In addition, this new manufacturing process makes it possible to access pyrotechnic rolls initiated in a few operations, with numerous advantages in terms of mechanical strength, integration (for example in the DSMF, Firing Safety Device). ), reduced vulnerability in particular to mechanical aggression (eg MURAT classification), cohesion between the block and priming, performance, time saving, while significantly reducing manufacturing costs and removal.

1. 1) disposition successive, dans un outillage de mise en forme, d'au moins:
   1. a) une couche (a) de composition d'amorçage, et
   2. b) une couche (b) de composition principale,
2. 2) mise en forme, de préférence par compression.

The present invention thus relates to a method of manufacturing a pyrotechnic bread primed in the form of a grooved multilayer block, said method comprising the following successive steps:

1. 1) successive arrangement, in a shaping tool, of at least:
   1. a) a layer (a) of priming composition, and
   2. b) a layer (b) of main composition,
2. 2) shaping, preferably by compression.

Thus, the method according to the invention is simplified compared to the methods of the prior art, since the priming composition is shaped at the same time as the main composition.

The present invention also relates to a particular texture of the priming composition, for obtaining an IR block initiated in a single compression operation, while maintaining its geometry and dimensions. The priming composition is no longer in the form of a paste, but in the same form as the main pyrotechnic composition, making it possible to overcome the problems of segregation or density.

1. a) une couche (a) de composition d'amorçage,
2. b) une couche (b) de composition principale,

susceptible d'être obtenu selon le procédé selon l'invention.The present invention also relates to a pyrotechnic bread, comprising at least:

1. a) a layer (a) of priming composition,
2. b) a layer (b) of main composition,

obtainable according to the process according to the invention.

The present invention also relates to a pyrotechnic device comprising a pyrotechnic bread according to the invention.

The present invention also relates to the use of a pyrotechnic bread or device according to the invention as infrared decoy.

DEFINITIONS

According to the present invention, the meaning of "bread or pyrotechnic block" means a solid block, optionally decomposing into several sub-parts or layers, whose composition, geometry and volume may differ. A pyrotechnic bread comprises at least one main composition. Preferably, the pyrotechnic bread according to the invention is intended for civil or military applications, such as missile lure by infrared emission, in particular in the classical and spectral domain. For the purposes of the present invention, a "main composition" comprises a mixture of at least one oxidant and at least one reducing agent, the combustion of which generates infrared-radiating chemical species. Thus, the main compositions produce, as a result of the combustion, a high emission in the infrared, according to a specific profile, and possibly gases and / or fumes, or a combination thereof. In the present invention, the term "main composition" will be used to refer to the term "infrared composition".

The main compositions can be either of "conventional" type or of "spectral" type.

The main conventional compositions are defined as compositions with strong reducing agents (magnesium for example) having a high combustion temperature with an IR emission of the black body type.

For the purposes of the present invention, the term "spectral principal composition" means compositions having a specific infrared radiation in particular IR bands (band I and band II) with a band II / band I ratio greater than the so-called conventional compositions.

According to the present invention, the meaning of "priming composition" or "ignition composition" means a composition for initiating the main pyrotechnic block, on a defined surface, in a defined time.

For the purpose of the present invention, the term "primed pyrotechnic bread (or block)" means a pyrotechnic bread (or block) comprising at least one main composition layer and a priming composition layer. Preferably, the primed multilayered bread is in the form of a multilayer block.

In the present invention, "radial combustion" is understood to mean combustion which takes place from the outside of the material burning towards the center of the pyrotechnic bread (from the outside to the inside, see figure 5a ). Thus, in the case of a cylindrical pyrotechnic roll, a radial combustion takes place along a radius of the cylinder, from the outside to the inside. By analogy, in the case of a parallelepipedal bread, a radial combustion also means a combustion which takes place from the outside of the parallelepiped towards its center, according to the transverse direction for example. Radial combustion opposes axial combustion, which takes place from an outer layer to an opposite outer layer of material along an axis thereof (see FIG. figure 5b ). Thus, in the case of a cylinder, axial combustion takes place from a circular base to the other circular base for example.

For the purposes of the present invention, the term "composition in the form of dry grains" is intended to mean that the composition (principal or initiator) is in the form of a granular solid (optionally powder) with a determined particle size, the composition comprising at most 5% by weight, for example between 3 and 4% by weight, of solvent relative to the total weight of the composition. "Solvent" means any organic and / or aqueous solvent compatible with the composition (main or priming), that is to say in particular any organic and / or aqueous solvent inert with respect to the composition and to obtain grains still slightly moist.

DETAILED DESCRIPTION Process

1. 1) disposition successive, dans un outillage de mise en forme, d'au moins:
   1. a) une couche (a) de composition d'amorçage, et
   2. b) une couche (b) de composition principale,
2. 2) mise en forme par compression.

The present invention thus relates to a method of manufacturing a pyrotechnic bread primed in the form of a multilayer block, said method comprising the following successive steps:

1. 1) successive arrangement, in a shaping tool, of at least:
   1. a) a layer (a) of priming composition, and
   2. b) a layer (b) of main composition,
2. 2) compression formatting.

Preferably, the primer pyrotechnic bread obtained by this process has a radial combustion.

Advantageously, the main layer is the majority layer of bread, that is to say, it represents the largest proportion by weight of the pyrotechnic bread initiated. In particular the main composition layer is between 60 and 95% by weight, especially between 80 and 92% by weight relative to the weight of the total primer pyrotechnic bread.

Formatting

For the purposes of the present invention, the term "formatting" means an operation to fix the final shape of the pyrotechnic bread. The formatting is implemented by compression. Particularly advantageously, the method according to the present invention comprises few operations compared to the methods of the prior art. The method according to the present invention thus essentially comprises a first stage of disposition of the main and priming compositions, typically in the form of grains, and then a compression forming step in order to obtain a primed pyrotechnic bread. Advantageously, the method according to the invention comprises a single shaping step, step (2). The method according to the invention makes it possible to obtain breads which are primed directly at the end of the shaping step (2). It therefore does not generally require a boot step or additional formatting. The primed bread obtained directly at the end of the shaping step (2) can thus be used as it is in a pyrotechnic device, the priming composition being already deposited on the main infrared composition in the bread (by compression unique).

The shaping is carried out in a compression tool capable of receiving the appropriate amounts of priming composition and main composition, and can withstand high pressure. It should be noted that the tools used are not specific of the process, but is identical to what is conventionally used in the art. As an example of tools, there may be mentioned: a compression mold having a main body having a volume capable of receiving the compositions, a compression piston equipped with adapted punches (in particular grooved) and a demolding piston; all being able to withstand strong pressures.

When the shaping is done by compression, the method according to the invention advantageously comprises a step 3) demolding the pyrotechnic bread.

Advantageously, the initiating composition and the main composition are in the form of solid powder or dry grains, having a calibrated particle size preferably between 0.5 and 5 mm, more preferably between 0.5 mm and 2 mm. more preferably between 0.8 and 1.2 mm. Advantageously, the compression is uniaxial. This typically takes place under a pressure of between 5 KPa and 50 KPa (5 tons and 50 tons) depending on the composition (s) used. The compression is advantageously carried out at ambient temperature or at a temperature of between 30 ° C. and 120 ° C., preferably between 30 ° C. and 80 ° C.

When shaping is carried out by casting, the process advantageously comprises a step 3 ') of drying the pyrotechnic bread. The drying is preferably carried out in an oven. In addition, the priming and main compositions have a texture and a viscosity compatible with a casting step.

grooving

The pyrotechnic bread obtained is grooved typically in the longitudinal direction. The presence of grooves makes it possible to better circulate the hot gases and thus to impart a more efficient combustion regime to the priming composition, with a homogeneous and rapid ignition of all the primed surfaces. Indeed, the grooves increase the contact surface between the hot air and the grooved bread, which ensures a better homogeneity of the radial combustion.

Grooving is particularly advantageous when radial combustion is desired.

The grooving is obtained through the shaping step by the use of tools equipped with punches having a suitable shape (including grooving). Thus, in a tool of compression, the compartment in which the compositions are poured priming and main is such that the shape obtained after compression corresponds to that of a grooved block.

Advantageously, in an extrusion tool, the section of the die has a grooved profile. For a casting process, the compositions are advantageously cast in molds having grooved imprints.

The method according to the invention does not require a shaping step other than step (2), the geometry of the bread at the end of this step (2), in particular as regards the number and the geometry grooves, generally corresponds to that of the finished product (pyrotechnic bread directly usable in a pyrotechnic device).

Thus, the method according to the invention makes it possible to obtain pyrotechnic loaves with "free" grooves of any composition, the priming composition being already integrated into the bread (see Figures 1 to 4 ).

Those skilled in the art will adapt the number and geometry of the grooves to the desired speed and combustion profile, taking into account in particular that the combustion will typically take place under dynamic conditions, ie the pyrotechnic bread initiated will be in motion during combustion.

Geometry of the pyrotechnic bread primed

In a particular embodiment, the pyrotechnic roll is shaped so as to obtain a parallelepipedal or cylindrical multilayer block, grooved, typically in the longitudinal direction. Advantageously, the grooved layer comprises or consists of the priming composition. An example of grooved parallelepiped pyrotechnic bread is given on the Figures 1 and 2 . An example of grooved cylindrical pyrotechnic bread is given on the Figures 3 and 4 .

Pyrotechnic bread primed bi- and tri-layer

The multilayer block according to the invention comprises at least two layers, the priming composition layer and the main composition layer.

1. 1) disposition successive dans cet ordre, dans un outillage de mise en forme, de:
   1. a) une première couche (a) de composition d'amorçage,
   2. b) une couche (b) de composition principale,
   3. c) une deuxième couche (c) de composition d'amorçage ;
2. 2) mise en forme par compression.

In a preferred embodiment, the resulting block is trilayer. In this embodiment, the pyrotechnic roll preferably comprises a central layer of a main composition, "sandwiched" or coated on two opposite sides (two opposite faces in the case of a parallelepiped, or two radially opposite layers in the case of a cylinder) or on both sides by a priming composition layer. The process according to the invention then comprises the following successive stages:

1. 1) successive arrangement in this order, in a shaping tool, of:
   1. a) a first layer (a) of priming composition,
   2. b) a layer (b) of main composition,
   3. c) a second layer (c) of priming composition;
2. 2) compression formatting.

In other words, in this embodiment, the step 1) further comprises the provision of a layer (c) of priming composition, so that the layer (b) of the main composition is coated on two sides of a priming composition (a) and (c).

According to a variant of this embodiment, the priming compositions are identical in layers (a) and (c). Typically, layers (a) and (c) contain the same amount by weight of initiator composition.

Preferably, the three-layer pyrotechnic roll obtained has grooves on at least two opposite faces, preferably on the faces of the priming composition.

Double priming

As indicated above, the method according to the invention makes it possible to obtain breads which are primed directly at the end of the shaping step (2). It therefore does not require an additional boot step in the general case. The primed roll obtained directly at the end of the shaping step (2) can thus be used as such in a pyrotechnic device.

In particular, in the case of grooved pyrotechnic breads, the method according to the invention makes it possible to obtain pyrotechnic loaves with "free" grooves of any composition, the priming composition being already integrated into the bread (see Figures 1 to 4 ).

According to one variant, the method according to the invention thus makes it possible to manufacture "double-initiated" pyrotechnic bars. Indeed, in one embodiment of the invention, the method comprises an additional step of depositing a composition additional priming element (a '), preferably in the form of a paste, in the grooves of the primed and grooved pyrotechnic bread according to the invention. The additional priming composition (a ') is identical to or different from the starting composition (s) used in the priming layer (s). The additional priming composition (a ') is for example manually deposited in the grooves of the pyrotechnic bread primed and grooved according to the invention. The doubly primed pyrotechnic roll thus has the advantage of providing a greater energy at the initiation of the block (high power on ignition) and thus to obtain a higher performance rising edge.

This particular embodiment (double priming) thus combines the advantages of the previously used methods and the method according to the invention, the latter making it possible to obtain a pyrotechnic bread primed with free grooves, which was not the case for certain processes of the prior art, which is filled with priming composition which is in the form of viscous paste on the first priming layer obtained by compression - hence the name "double priming".

Note that the methods of the prior art with manual removal of the priming layer in the grooves of the pyrotechnic bread, consisting only of main composition, did not allow to obtain "doubly primed" breads.

Advantageous embodiment

1. 1) disposition successive, dans un outillage de mise en forme, d'au moins:
   1. a) une couche (a) de composition d'amorçage, et
   2. b) une couche (b) de composition principale, typiquement classique ou spectrale,
2. 2) mise en forme par compression, notamment à l'aide de poinçons rainurés.

According to a preferred variant of the invention, this relates to a method of manufacturing a pyrotechnic bread primed in the form of a multilayer block typically grooved in the longitudinal direction, said method comprising the following successive steps:

1. 1) successive arrangement, in a shaping tool, of at least:
   1. a) a layer (a) of priming composition, and
   2. b) a layer (b) of main composition, typically conventional or spectral,
2. 2) compression forming, in particular using grooved punches.

Those skilled in the art will adapt the number and geometry of the grooves to the desired speed and combustion profile, taking into account in particular that the combustion will typically take place under dynamic conditions, ie the pyrotechnic bread initiated will be in motion during combustion.

The primer pyrotechnic bread obtained according to this variant advantageously retains a radial combustion.

Advantageously, the main layer is the majority layer of bread, that is to say, it represents the largest proportion by weight of the pyrotechnic bread initiated. In particular the main composition layer is between 60 and 95% by weight, especially between 80 and 92% by weight relative to the weight of the total primer pyrotechnic bread.

The shaping is carried out in a compression tool capable of receiving the appropriate amounts of priming composition and main composition, and can withstand high pressure. As an example of tools, there may be mentioned: a compression mold having a main body having a volume capable of receiving the compositions, a compression piston equipped with suitable punches (typically grooved punches) and a demolding piston; all being able to withstand strong pressures.

In this preferred embodiment, the method advantageously comprises a single compression forming step.

In this preferred embodiment, the method advantageously comprises a step 3) of demolding the pyrotechnic bread.

Advantageously, the main composition and the initiating composition are in the form of solid powder or dry grains, having a calibrated particle size preferably between 0.5 and 5 mm, even more preferably between 0.5 mm and 2 mm, more preferably between 0.8 and 1.2 mm. Advantageously, the compression is uniaxial. This typically takes place under a pressure of between 5 KPa and 50 KPa (5 tons and 50 tons) depending on the composition (s) used. The compression is advantageously carried out at ambient temperature or at a temperature of between 30 ° C. and 120 ° C., preferably between 30 ° C. and 80 ° C.

In this particular embodiment, the pyrotechnic bread can be shaped so as to obtain a parallelepipedal, or cylindrical, multilayer block.

The method may also include a further step of depositing an additional priming composition (a '), preferably in paste form, into the grooves of the primed pyrotechnic bread according to this preferred embodiment. The additional priming composition (a ') is identical to or different from the (or) starting composition (s) used in the (or) priming layer (s). The additional priming composition (a ') is for example manually deposited in the grooves of the primed pyrotechnic bread.

1. 1) disposition successive dans cet ordre, dans un outillage de mise en forme, de:
   1. a) une première couche (a) de composition d'amorçage,
   2. b) une couche (b) de composition principale,
   3. c) une deuxième couche (c) de composition d'amorçage ;
2. 2) mise en forme par compression, notamment à l'aide de poinçons rainurés.

Preferably, the block obtained is trilayer. According to this variant, the pyrotechnic roll preferably comprises a central layer of a main composition, "sandwiched" or coated on two opposite sides (two opposite faces in the case of a parallelepiped, or two radially opposite layers in the case a cylinder) or on both sides of a priming composition layer. The process then comprises the following successive steps:

1. 1) successive arrangement in this order, in a shaping tool, of:
   1. a) a first layer (a) of priming composition,
   2. b) a layer (b) of main composition,
   3. c) a second layer (c) of priming composition;
2. 2) compression forming, in particular using grooved punches.

The priming compositions in layers (a) and (c) may be the same or different. Typically, layers (a) and (c) contain the same amount by weight of initiator composition.

Preferably, the three-layer pyrotechnic roll obtained has grooves on at least two opposite faces, preferably on the faces of the priming composition.

Advantages of the process according to the invention

Thus, the process according to the invention makes it possible to significantly reduce the cost and the production time of the pyrotechnic primed loaves, in particular by reducing the number of operations carried out in the production process. In particular, a single compression step is sufficient to obtain a primed pyrotechnic roll, directly usable in a pyrotechnic device.

In addition, a single compression step is sufficient to obtain the cohesion of all layers of the pyrotechnic bread.

In addition, the process according to the invention makes it possible to reduce the amount of solvents used, since it is no longer necessary to work with a mixture with a controlled viscosity (mixture in the form of a paste, for example). Furthermore, the method according to the invention makes it possible to reduce or even to eliminate certain steps such as drying, especially in the case of compression shaping, when the compositions are thermoplastic (conventional lure).

The method according to the invention also makes it possible to manufacture pyrotechnic loaves of novel structure, and to improve the cohesion between the priming composition and main composition layers. Since the interface between the priming and main layers is more intimately connected, the combustion (generally radial) is more regular and there is a decrease or even a suppression of the transient combustion conditions.

The present invention also provides a method as described above, further comprising a step of crosslinking by heating, when the priming or main compositions are thermosetting (spectral decoy). In this case, the process according to the invention makes it possible, during the crosslinking, to create chemical bonds between the block and the priming, provided that the same type of binder (resin type) is used between the block and the priming. , thereby increasing the mechanical strength and the fire transmission between the block and the priming.

Pyrotechnic bread primed

The invention also proposes to provide pyrotechnic primed rolls, in the form of a grooved multilayer block, obtainable by the method according to the invention, comprising at least one priming composition layer and a composition layer. main. The pyrotechnic blocks initiated according to the invention have a particular arrangement. In fact, the step of priming the loaves is no longer performed after the shaping and baking step, but during the shaping step, preferably during the compression step. The composition of the pyrotechnic block is "sandwiched" between the priming composition which is typically in the form of dry grains in the compression tooling.
Primed pyrotechnic bread advantageously has a radial combustion.

Advantageously, the main layer is the majority layer of bread, that is to say, it represents the largest proportion by weight of the pyrotechnic bread initiated. In particular the main composition layer is between 60 and 95% by weight, especially between 80 and 92% by weight relative to the weight of the total primer pyrotechnic bread.

Classic main composition

According to a particular embodiment of the invention, the main composition of the bread or block is a classic decoy.

• entre 30 et 60% d'un réducteur, de préférence du magnésium, du zirconium, du bore ou leurs mélanges, et
• entre 30 et 40% d'un mélange d'au moins deux polymères fluorés, le premier polymère fluoré étant choisi parmi le polytétrafluoroéthylène, et le second polymère fluoré étant un fluoroélastomère avantageusement choisi parmi les copolymères de fluorure de vinylidène, hexafluoropropylène, perfluorométhylvinyléther et/ou tetrafluoroéthylène ou encore le PMF (polymonofluoride) .
• optionnellement, entre 2 et 20% de polymères carbonés ou leurs co-polymères tels que le polypropylène, la polybutadiène, le polycarbonate, le polyéthylène ou le polystyrène.

In this case, such a composition is preferably intended to emit in the infrared. Advantageously, such a main composition comprises an MTV mixture (magnesium, Teflon, Viton), typically comprising:

• between 30 and 60% of a reducing agent, preferably magnesium, zirconium, boron or mixtures thereof, and
• between 30 and 40% of a mixture of at least two fluorinated polymers, the first fluorinated polymer being chosen from polytetrafluoroethylene, and the second fluorinated polymer being a fluoroelastomer advantageously chosen from copolymers of vinylidene fluoride, hexafluoropropylene, perfluoromethylvinylether and / or or tetrafluoroethylene or PMF (polymonofluoride).
• optionally, between 2 and 20% of carbon polymers or their co-polymers such as polypropylene, polybutadiene, polycarbonate, polyethylene or polystyrene.

• entre 30 et 50% d'un réducteur, de préférence du magnésium, du zirconium, du bore ou leurs mélanges, et
• entre 30 et 40% d'un mélange d'au moins deux polymères fluorés, le premier polymère fluoré étant choisi parmi le polytétrafluoroéthylène, et le second polymère fluoré étant un fluoroélastomère avantageusement choisi parmi les copolymères de fluorure de vinylidène, hexafluoropropylène, perfluorométhylvinyléther et/ou tetrafluoroéthylène ou encore le PMF (polymonofluoride),
• optionnellement, entre 2 et 8% de polymères carbonés ou leurs co-polymères tels que le polypropylène, le polycarbonate, le polyéthylène ou le polystyrène.

Typically, the initiator composition used in combination with a conventional master composition is thermoplastic. Preferably, it comprises an MTV mixture (magnesium, Teflon, Viton), typically comprising:

• between 30 and 50% of a reducing agent, preferably magnesium, zirconium, boron or their mixtures, and
• between 30 and 40% of a mixture of at least two fluorinated polymers, the first fluorinated polymer being chosen from polytetrafluoroethylene, and the second fluorinated polymer being a fluoroelastomer advantageously chosen from copolymers of vinylidene fluoride, hexafluoropropylene, perfluoromethylvinylether and / or or tetrafluoroethylene or PMF (polymonofluoride),
• optionally, between 2 and 8% of carbon polymers or their co-polymers such as polypropylene, polycarbonate, polyethylene or polystyrene.

In this case, the block thus initiated during compression, can be directly integrated into the DSMF (Safety and Firing Device).

Main spectral composition

According to another embodiment of the invention, the main composition of the bread or block constitutes a spectral decoy.

• entre 5 et 15% d'une résine choisie parmi une résine polyester, époxy, polybutadiène ou ses co-polymères ;
• entre 1 et 4% d'un agent réticulant à fonction isocyanate tel que :IPDI (Isophoron de diisocyanate),
• entre 20 et 30% d'oxydant tel que le perchlorate d'ammonium, le nitrate d'ammonium, le nitrate de potassium, le chlorate de potassium ou le perchlorate de potassium,
• entre 2 et 5% de molécules énergétiques telles que RDX (1,3,5-Trinitroperhydro-1,3,5-triazine), HMX (cyclotétraméthylène-tétranitramine), et
• entre 10 et 30%, de réducteur tel que l'aluminium, le zirconium, ou leurs mélanges.

In this case, such a composition is intended to emit in the infrared range. Advantageously, such a main composition is a mixture comprising:

• between 5 and 15% of a resin chosen from a polyester resin, epoxy resin, polybutadiene resin or its co-polymers;
• between 1 and 4% of an isocyanate-functional crosslinking agent such as: IPDI (Isophoron diisocyanate),
• between 20 and 30% of oxidant such as ammonium perchlorate, ammonium nitrate, potassium nitrate, potassium chlorate or potassium perchlorate,
• between 2 and 5% of energy molecules such as RDX (1,3,5-Trinitroperhydro-1,3,5-triazine), HMX (cyclotetramethylene-tetranitramine), and
• between 10 and 30% of reducing agent such as aluminum, zirconium, or mixtures thereof.

• entre 5 et 15% d'une résine choisie parmi une résine polyester, époxy, polybutadiène ou ses co-polymères ;
• entre 1 et 4% d'un agent réticulant à fonction isocyanate tel que :IPDI (Isophoron de diisocyanate),
• entre 20 et 30% d'oxydant tel que le perchlorate d'ammonium, le nitrate d'ammonium, le nitrate de potassium, le chlorate de potassium ou le perchlorate de potassium,
• entre 2 et 5% de molécules énergétiques telles que RDX (1,3,5-Trinitroperhydro-1,3,5-triazine), HMX (cyclotétraméthylène-tétranitramine), et
• entre 10 et 30%, de réducteur tel que l'aluminium, le zirconium, ou leurs mélanges.

Typically, the initiator composition used in combination with a spectral main composition is a thermosetting resin. Preferably, it consists of a mixture comprising:

• between 5 and 15% of a resin chosen from a polyester resin, epoxy resin, polybutadiene resin or its co-polymers;
• between 1 and 4% of an isocyanate-functional crosslinking agent such as: IPDI (Isophoron diisocyanate),
• between 20 and 30% of oxidant such as ammonium perchlorate, ammonium nitrate, potassium nitrate, potassium chlorate or potassium perchlorate,
• between 2 and 5% of energy molecules such as RDX (1,3,5-Trinitroperhydro-1,3,5-triazine), HMX (cyclotetramethylene-tetranitramine), and
• between 10 and 30% of reducing agent such as aluminum, zirconium, or mixtures thereof.

In this case, the bread or primer block is placed in the oven after compression, to create chemical bonds between the block and the boot. The consequence is a clear improvement in the cohesion between the priming composition and the main composition, which further improves the profile of infrared emission during combustion (and overall decoy performance), in particular by suppressing the transient regimes during the passage of the combustion of the priming layer at the main layer.

grooves

The pyrotechnic bread primed according to the invention is grooved, as described above.

Double priming

In a particular embodiment, the pyrotechnic bread is "doubly primed". In this embodiment, it comprises an additional priming composition (a ') in the grooves of the primed and grooved pyrotechnic bread according to the invention. The additional priming composition (a ') is identical to or different from the starting composition (s) used in the priming layer (s).

Three-layered bread.

In a preferred embodiment, the resulting bread is three-layered. In this embodiment, the pyrotechnic roll preferably comprises a central layer of a main composition (b), "sandwiched" or coated on two opposite sides (two opposite faces in the case of a parallelepiped, or two layers radially opposite in the case of a cylinder) or on both sides of a layer of priming composition, layers (a) and (c). Advantageously, the priming composition is identical in layers (a) and (c). Typically, layers (a) and (c) contain the same amount by weight of initiator composition.

Preferably, the three-layer pyrotechnic roll obtained has grooves on at least two opposite faces, preferably on the faces of the priming composition.

In a particular embodiment, the pyrotechnic bread may also consist of several different main compositions sandwiched with the priming composition.

Within the meaning of the present invention, a main composition is the main composition of the bread. This composition will provide the effect requested during the combustion. The main composition is the majority composition of the pyrotechnic bread. The priming composition is the initiator composition of this main composition.

Specific embodiments

In a particular embodiment, the pyrotechnic bread may be partially sandwiched between the priming composition and the main composition (s) of the bread. Part of the block can thus be started.

In a particular embodiment, the pyrotechnic bread may be partially grooved (the groove makes it possible to circulate advantageously the ignition gases during the initiation of bread) and initiated. Part of the block can thus be sandwiched between the priming composition and the main composition of the bread.

In a particular embodiment, the pyrotechnic bread can be primed and not grooved. The entire block is primed where the main composition is "sandwiched" by the priming composition over the entire length.

In a particular embodiment, the pyrotechnic bread can be fully primed with several priming and grooved compositions. Indeed, the main composition is sandwiched with one or more priming compositions. In this embodiment, the first priming composition can be shaped at the same time as the main composition and the other priming compositions shaped in a second step. Thus, it is possible to have a priming composition A1 on a preferred part of the block, and then to have a starting composition A2 on the rest of the block. Thus, several different formulations can be used on all or part of the block depending on the performance demand.

Preferred embodiment

According to a preferred variant, the invention relates to a pyrotechnic bread primed in the form of a grooved multilayer block comprising at least one layer of priming composition and a main composition layer, obtainable by the process according to the invention. in which the shaping step is performed by compression.

Preferably, the primed pyrotechnic bread is of the "sandwich" type, that is to say that it comprises three layers: a typically conventional or spectral main composition layer, "sandwiched" or between two layers of composition boot.

The composition of the pyrotechnic block is sandwiched between the two layers of priming composition which is typically in the form of dry grains in the compression tooling.

Advantageously, the main layer is the majority layer of bread, that is to say, it represents the largest proportion by weight of the pyrotechnic bread initiated. In particular the main composition layer is between 60 and 95% by weight, especially between 80 and 92% by weight relative to the weight of the total primer pyrotechnic bread.

Advantages of pyrotechnic breads primed according to the invention

• amélioration de la transmission de feu entre le bloc et l'amorçage, résultant notamment en une suppression des régimes transitoires de combustion,
• propriétés physiques de l'amorçage nettement améliorées,
• amélioration des tenues mécaniques aux agressions extérieures du pain pyrotechnique.
• amélioration du rendement thermique de la combustion,
• augmentation de la durée de vie des compositions d'amorçage avant mise en forme,
• diminution des phases de fabrication de la composition d'amorçage.

The pyrotechnic breads primed according to the invention have several advantages over primed breads of the prior art:

• improvement of the fire transmission between the block and the priming, resulting notably in a suppression of the transient combustion regimes,
• significantly improved physical properties of priming,
• improvement of mechanical resistance to external attacks of pyrotechnic bread.
• improvement of the thermal efficiency of combustion,
• increase of the life of the priming compositions before forming,
• reduction of the manufacturing phases of the priming composition.

In particular, the pyrotechnic rolls according to the invention have excellent resistance to vibrations, especially with respect to pyrotechnic rolls manufactured according to the methods of the prior art, in particular the methods comprising manual or automatic removal of the priming composition.

Devices and Uses

The present invention also relates to a pyrotechnic device comprising a pyrotechnic bread according to the invention.

Preferably, the primed bread according to the invention is inserted into a pyrotechnic device. This pyrotechnic device is advantageously a cartridge, in which is typically added an initiation system. In one embodiment of the invention, the cartridge is mounted in a charger, to be used from an aircraft.

The present invention also relates to a use of the pyrotechnic bread according to the invention or the device according to the invention as infrared decoy.

DESCRIPTION OF THE FIGURES

• Figure 1 : Diagram of a pyrotechnic roll initiated in the form of a parallelepipedal trilayer block comprising a central layer of a main composition (b), "sandwiched" or coated on two opposite sides of a priming composition layer, layers (a) and (c). The bread is grooved on the priming composition layer faces, and the grooves (d) are longitudinal.
• Figure 2 : Photograph of a pyrotechnic bread initiated at the end of the production line in the form of a three-layer block comprising a central layer of a main composition (b), "sandwiched" or coated on two opposite sides of a layer of priming composition, layers (a) and (c), obtained according to Example 1, in parallelepipedal form.
• Figure 3 : Diagram of a pyrotechnic bread primed in the form of a cylindrical trilayer block comprising a central layer of a main composition (b), "sandwiched" or coated on two opposite sides with a priming composition layer, layers (a) and (c). The bread is grooved on the priming composition layer faces, and the grooves (d) are longitudinal.
• Figure 4 : Photograph of a pyrotechnic bread initiated at the end of the production line in the form of a three-layer block comprising a central layer of a main composition (b), "sandwiched" or coated on two opposite sides of a initiator composition layer, layers (a) and (c), obtained according to example 1, in cylindrical form.
• Figure 5 : diagram showing a radial (a) or axial (b) combustion profile. The arrows indicate the direction of combustion.
• Figure 6 : Radiometric measurement of spectral type infrared lures in dynamic configuration. Curve in solid lines: three-layer bread sandwich type according to the invention. Dotted curve: Bread made according to the prior art. There is a significant improvement in performance at the beginning of combustion, with an excellent fire transition between the block and the priming. The x-axis represents time. The y-axis represents luminance (in Watt per steradian).
• Figure 7 : Radiometric measurement of classic type infrared decoys in static configuration. Curve in solid lines: three-layer bread sandwich type according to the invention. Dotted curve: Bread made according to the prior art. There is a significant improvement in performance at the beginning of combustion, with an excellent fire transition between the block and the priming. The x-axis represents time. The y-axis represents luminance (in Watt per steradian).

EXAMPLES Example 1: IR Spectral Lure

Manufacture in planetary mixer, under solvent, the same day, compositions of the block then of the priming. The compositions are granulated to obtain a calibrated grain size of about 1.2 mm. Then the grains obtained are dried at 50 ° C for 2h, in order to evaporate the solvent. The compositions are thus obtained in the form of non-crosslinked dry grains.

• entre 5 et 15% d'une résine choisie parmi une résine polyester, époxy, polybutadiène ou ses co-polymères ;
• entre 1 et 4% d'un agent réticulant à fonction isocyanate tel que :IPDI (Isophoron de diisocyanate),
• entre 20 et 30% d'oxydant tel que le perchlorate d'ammonium, le nitrate d'ammonium, le nitrate de potassium, le chlorate de potassium ou le perchlorate de potassium,
• entre 2 et 5% de molécules énergétiques telles que RDX (1,3,5-Trinitroperhydro-1,3,5-triazine), HMX (cyclotétraméthylène-tétranitramine), et
• entre 10 et 30%, de réducteur tels que l'aluminium, le zirconium, ou leurs mélanges.

The priming composition is a mixture comprising:

• between 5 and 15% of a resin chosen from a polyester resin, epoxy resin, polybutadiene resin or its co-polymers;
• between 1 and 4% of an isocyanate-functional crosslinking agent such as: IPDI (Isophoron diisocyanate),
• between 20 and 30% of oxidant such as ammonium perchlorate, ammonium nitrate, potassium nitrate, potassium chlorate or potassium perchlorate,
• between 2 and 5% of energy molecules such as RDX (1,3,5-Trinitroperhydro-1,3,5-triazine), HMX (cyclotetramethylene-tetranitramine), and
• between 10 and 30% of reducing agent such as aluminum, zirconium, or mixtures thereof.

1. a) une première couche (a) de composition d'amorçage, coté poinçons rainuré,
2. b) une couche (b) de composition principale,
3. c) une deuxième couche (c) de composition d'amorçage, coté poinçon rainuré (voir figure 1).

In the compression tooling, provided with grooved punches on at least 2 opposite faces, the following layers are successively arranged:

1. a) a first layer (a) of priming composition, grooved punches side,
2. b) a layer (b) of main composition,
3. c) a second layer (c) of priming composition, side grooved punch (see figure 1 ).

About 4 grams of priming composition are uniformly distributed over the entire surface to form layer a). The priming composition of the layer a) is then on the side of the grooved punches. To form layer b), about 90 g of main composition is uniformly provided over layer a). Finally, the second priming layer c) is uniformly disposed over the entire surface over layer b). The priming composition of the layer c) is then on the side of the grooved punches.

The dosing of the compositions and their depositing in the compression tooling can be done automatically and the masses can be adjusted according to the gauges. The piston is then lowered on this series of layers to apply a compression ratio of 10 KPa (10 tons) for 10 seconds. The compression ratio is adapted to the caliber manufactured.

The whole is then demolded, by an automatic cycle of the press, by reverse thrust.

The primed IR block is thus obtained directly in a single compression step.

The primed block is then placed in an oven at 70 ° C for 5 days to undergo crosslinking to bind the main composition layer to the priming composition layers. Chemical bonds are thus created between the main composition layer and the priming composition layers.

A photograph of the bread thus obtained by the process according to the invention is given in figure 2 or 4 (depending on the shape of the compression tool).

It is no longer necessary to give it to the next workshop to be primed by manual or automatic cannula removal.

Then, the firing safety device (DSMF) is added to perform the cartridge integration.

Example 2: Performance of the blocks according to the invention

The performances of the blocks according to the invention were compared with those obtained with a block of the prior art (ie initiated by manual removal) during a dynamic shot for the "spectral" pyrotechnic bread of Example 1 and at the same time. a dynamic static shot for the "classic" pyrotechnic bread of Example 1.

Experimental apparatus :

After assembling the DSMF to the primed bread, everything is put together in a cartridge.

For dynamic shooting: The cartridge is positioned on a cart that will be launched at a certain speed on a rail, then the decoy cartridge will be launched to simulate an ejection under the plane.

Measuring means such as radiometers and thermographs are arranged to measure the infra-red performance of the breads, in dynamic shots.

For a static shot: The subassembly is fixed on a fixed support, the lure is initiated. Infrared performance is then measured using radiometers

Results

The figure 6 demonstrates on the one hand that the rising edge obtained with a block according to the invention is faster and higher than with a block according to the prior art and secondly, that the block / priming transition is no longer marked by a dip in performance (block according to the prior art) corresponding to a transient combustion regime, but a continuous measurement of the infrared signal (block according to the invention).

The findings are the same on the figure 7 .

Thus, figures 6 and 7 illustrate the disappearance of the transient regime obtained with the pyrotechnic breads primed according to the invention, both in dynamic or static fire conditions.

In conclusion, the loaves according to the invention make it possible to increase the rates, to simplify the process which requires much less means and personnel, to have a significant improvement in the transition of the combustion between the priming composition and the main composition (with elimination of transient combustion conditions), which makes it possible in particular to increase the rising edge, but also gives the priming composition a better mechanical strength (passage of vibration and shock tests and strong cohesion with the bread).

Claims (14)

1. A method for manufacturing an initiated pyrotechnic block in the form of a grooved multilayer block, said method comprising the following successive steps:

   1) successive arrangement, in a shaping tool, of at least:

   a) a layer (a) of initiating composition, and

   b) a layer (b) of main composition,

   2) shaping by compression.
2. The method of claim 1, characterized in that it comprises a single shaping step by compression.
3. The method of claim 1 or 2, characterized in that the initiating composition and the main composition are in the form of dry grains.
4. The method of any one of claims 1 to 3, characterized in that step 1) further comprises arrangement of a layer (c) of an initiating composition, such that the layer (b) of main composition is coated on two opposite sides with an initiating composition (a) and (c).
5. The method of any one of claims 1 to 4, characterized in that the main layer represents between 60 and 95% by weight, especially between 80 and 92% by weight relative to the total weight of the initiated pyrotechnic block.
6. The method of any one of claims 1 to 5, characterized in that it comprises a further step of depositing an additional initiating composition in the grooves of the initiated pyrotechnic block, the additional initiating composition preferably being in the form of a paste.
7. The method of any one of claims 1 to 6, characterized in that the obtained initiated pyrotechnic block has radial combustion.
8. An initiated pyrotechnic block in the form of a grooved multilayer block, obtainable by the method according to any one of claims 1 to 7 comprising at least one layer of initiating composition and a layer of main composition.
9. The initiated pyrotechnic block of claim 8, characterized in that it comprises a central layer of a main composition (b), coated on two opposite sides with a layer of initiating composition, layers (a) and (c).
10. The initiated pyrotechnic block of any one of claims 8 or 9, characterized in that the main layer represents between 60 and 95% by weight, especially between 80 and 92% by weight relative to the total weight of the initiated pyrotechnic block.
11. The initiated pyrotechnic block of any one of claims 8 to 10, characterized in that it comprises an additional initiating composition in the grooves of the initiated pyrotechnic block.
12. The initiated pyrotechnic block of any one of claims 8 to 11, characterized in that it has radial combustion.
13. A cartridge comprising an initiated pyrotechnic block according to any one of claims 8 to 12.
14. Use of the initiated pyrotechnic block according to any one of claims 8 to 12 or of the cartridge according to claim 13 as infrared decoy.

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