WO2016066945A1

WO2016066945A1 - Efficient composite pyrotechnic product with no pb in the composition thereof and preparation of same

Info

Publication number: WO2016066945A1
Application number: PCT/FR2015/052888
Authority: WO
Inventors: Fabienne Morin; Martine GOLFIER; Caroline CARAYON
Original assignee: Herakles
Priority date: 2014-10-28
Filing date: 2015-10-27
Publication date: 2016-05-06
Also published as: KR20170101897A; IL251766B; EP3212594A1; PL3212594T3; JP6510640B2; IL251766A0; FR3027597A1; JP2017538648A; FR3027597B1; US20180290945A1; EP3212594B1; KR102621576B1

Abstract

The main subject of the present invention is an efficient composite pyrotechnic product, with no lead in the composition thereof, the production of which on an industrial scale does not encounter a problem of pot life of the intermediate paste. Said product contains, in a plasticized binder, comprising a crosslinked energetic polymer and at least one energetic plasticizer, organic energetic fillers and a combustion catalyst. Characteristically, said crosslinked energetic polymer consists of a polyglycidyl azide (PAG), having a number-average molecular mass (Mn) of between 700 and 3000 g/mol, crosslinked, via its terminal hydroxyl functions, with at least one crosslinking agent of polyisocyanate type, and said combustion catalyst consists of bismuth citrate.

Description

PERFORMANT COMPOSITE PYROTECHNIC PRODUCT WITHOUT Pb IN ITS COMPOSITION AND PREPARATION

The present invention relates to composite pyrotechnic products, particularly suitable as solid propellants for rocket engine propellant charges. It is more precisely composite pyrotechnic products, containing a high rate of organic energy charges in an energy binder. Said products are particularly interesting in that their composition does not contain lead, in that they are efficient, particularly in terms of the rate of combustion, and in that the pot life (see definition below) of their mixture precursor (before crosslinking) is high (their obtaining on an industrial scale is greatly facilitated).

A composite type solid propellant comprises pulverulent solid charges (oxidizing charges, with, optionally, reducing charges) and various additives, including feasibility additives and performance additives, in a generally plasticized binder (a polymer matrix). solid - a crosslinked polymer - energetic or not, usually plasticized).

The binder is obtained from a liquid polymer

("Crosslinkable"), having chemically reactive terminations, capable of being crosslinked by at least one crosslinking agent (at least bi-functional) also liquid. At least one plasticizer and the other ingredients of the propellant, with the exception of the at least one crosslinking agent (and at least one crosslinking catalyst, if there is at least one plasticizer), are generally introduced into such a liquid polymer in an appropriate order. such at least one crosslinking catalyst (generally very sensitive to moisture) is used), then finally said at least one crosslinking agent (and said optional at least one crosslinking catalyst used). The polymer charged is then heat-treated ("cooked") at a temperature compatible with the energetic materials (loads min / m) present. The crosslinked polymer constitutes, with the plasticizer (s) present (s), the plasticized binder, which coats all the ingredients and in particular the pulverulent fillers, to finally form a solid body.

The method currently used to manufacture such composite pyrotechnic products in the form of blocks is a batch process, called "batch", consisting in preparing a certain amount of paste, casting said quantity (at least a part of it). ci) in a number of structures (at least one) and heat treatment the (s) load (s) thus obtained (to crosslink the polymer). In a first step, the various ingredients are therefore introduced in a proper order and carefully and long kneaded, under pressure conditions (usually under a partial vacuum) and temperature very precise. For the next step, the mixture, which is therefore in the form of a paste, is poured into at least one structure (said structure possibly being used with forming tools within it). The assembly then undergoes a heat treatment (baking) to ensure the crosslinking (hardening) of the polymer. The structure is in most cases the very envelope of the load.

The introduction of the at least one crosslinking agent (and optionally at least one crosslinking catalyst) into the mixture is carried out towards the end of the kneading step. Indeed, as soon as said introduction, the dough - already persian more or less viscous, depending on the nature of the polymer, depending on the rate of charge ... - begins to crosslink (to "harden"). Thus, the casting can be done for a limited time, called "pot life", during which the mixture remains fluid enough to be poured. It is imperative, for an industrial implementation, that the pot life of the the paste is sufficiently high (in order to have the necessary time for the various casting operations).

The pot life of a propellant paste is evaluated by measuring the evolution of the viscosity of said paste over time. It is considered that from a viscosity greater than 1.5 kPa.s = 15 kPo (15 kP), a propellant paste is no longer "flowable", and that a time less than 15 hours to reach this Viscosity prevents any industrialization of the process. A paste viscosity less than or equal to 1.5 kPa.s = 15 kPo after 15 hours is therefore the (necessary and sufficient) condition which ensures the flowability of said paste under industrial conditions. Those skilled in the art understand of course that the pot life of a paste depends on the exact conditions (temperature and pressure) of casting said paste.

In order to increase the burning rate of a solid propellant, it is known to add in the composition of said solid propellant agents which act as combustion catalysts (also known as ballistic catalysts). Organometallic lead salts and lead oxides have been used for this purpose in the past. Lead, because of its toxicity, has since been replaced by bismuth; hence the use of salts and oxides of bismuth as a catalyst for burning solid propellants.

The patent application FR 2 727 401 thus describes the use of bismuth salts, such as bismuth β-resorcylates, bismuth Y-resorylate, bismuth salicylate, bismuth citrate, bismuth stearate, and bismuth oxide, as combustion catalyst for double base solid propellants (nitrocellulose and at least one nitric ester such as nitroglycerine) or composite double base (fillers in an energetic binder based on a nitric ester). The use of these novel combustion catalysts, however, has a disadvantage insofar as these are also found to be catalysts for crosslinking and where therefore their use reduces the pot life (see above).

US Pat. No. 6,168,574 confirms that the presence of bismuth salts, particularly that of bismuth salicylate and that of a bismuth β-resorylate, in the composition of a composite propellant (with an energy binder (of the nitramine type: ORP-2 (see below)) or non-energetic (polyglycol adipate (PGA), caprolactones), cross-linked by a polyisocyanate) induces a significant decrease in pot life; the bismuth salt (combustion catalyst) also acting as a crosslinking catalyst. Said patent proposes "a process device" to limit this decrease in pot life. He proposes introducing the bismuth salt into a propellant paste (upstream) cooled to about 16 ° C (60 ° F), instead of about 32-38 ° C (90-100 ° F) according to the method. conventional. It is conceivable that the more substantial increase in the viscosity of the paste, inherent in this cooling of greater amplitude, inevitably complicates the further implementation of the process. In fact, the implementation of a process, including a temperature rise of the dough at such a low temperature, limits the choice as to the nature of the polymers suitable as binder precursors. Said polymers must be able to be cast at this low temperature.

US Pat. No. 6,168,677 confirms the teachings of US Pat. No. 6,168,574. It describes and evaluates polyisocyanate-crosslinked energetic composite propellants containing, in their composition, bismuth salicylate and / or bismuth citrate, as a catalyst. ballistic. The energetic binders described are nitramine type binders obtained from (acid) polymers of the ORP-2 type. (Poly (diethyleneglycol-4,8-dinitrazaundecanoate) and 9DT-NIDA (diethyleneglycol-triethyleneglycol-nitraminodiacetic terpolymer) Such polymers can be cast at low temperature, at 60 ° F ± 16 ° C (see Table 10 of the patent). US 6,168,677).

To date, the skilled person is still looking for a powerful propellant, highly energetic, incorporating, in its composition, a non-toxic ballistic catalyst (lead-free), which can be obtained, on an industrial scale, with a paste having a sufficiently long pot life and this under advantageous, simple operating conditions, in particular temperature management.

In such a context, the Applicant proposes a new specific energy-binding composite propellant (comprising a specific energy polymer (PAG) crosslinked with at least one polyisocyanate), containing a specific combustion catalyst (bismuth citrate) in its composition. This new composite propellant, whose composition does not contain lead, is energy efficient (it has a particular high speed of combustion) and its preparation process is particularly interesting. It is the merit of the Applicant to have selected a pair, precursor polymer energy binder / combustion catalyst, which, conventionally used with polyisocyanate (s), plasticizer (s) and organic energy charges, leads to a propellant whose dough , before crosslinking, has a pot life close to that of a similar propellant does not contain, in its composition, combustion catalyst or containing, in its composition, lead citrate as a combustion catalyst; and this, at a temperature of 35-55 ° C (temperature, higher than room temperature, perfectly suitable for a "simple" implementation of the process for preparing said propellant (see below)). According to its first object, the present invention therefore relates to new composite pyrotechnic products, highly energetic and not containing lead in their composition. They are of the crosslinked energy binder type containing organic energy charges. They contain, more specifically, in a plasticized binder, comprising a crosslinked energy polymer and at least one energetic plasticizer, organic energy charges and a combustion catalyst. Characteristically:

said crosslinked energy polymer consists of a glycidyl polyazide (PAG) having a number-average molecular weight

(Mn) of between 700 and 3000 g / mol, crosslinked, via its hydroxyl terminal functions, with at least one polyisocyanate crosslinking agent; and

the combustion catalyst consists of bismuth citrate. The structure of the composite pyrotechnic products of the invention therefore typically associates a specific binder and a specific combustion catalyst. This combination has proved to be particularly advantageous with reference to the specification which includes two stipulations that are a priori contradictory (combustion catalysts are generally also found as crosslinking catalysts (see above)): high energy performance (high combustion rates) ) of the product (requiring the presence of a combustion catalyst in an effective amount) and easy management of its production process (especially with reference to the problem of the life (of "pot life") of the dough to crosslink).

The nature of the binder (that of its precursor polymer) is therefore one of the key elements (of the composition) of the composite pyrotechnic products of the invention. Incidentally note here that the "a" glycidyl polyazide (= binder precursor polymer) should read "at least one" glycidyl polyazide throughout the present text. Indeed, it is in no way excluded from the scope of the invention to use a mixture of at least two glycidyl polyazides (having molecular weights (between 700 and 3000 g / mol) and / or different branching ratios). as precursor polymer of the binder of the products of the invention.

The energetic polymer selected as precursor of the binder of the products of the invention is therefore a polyazide, a glycidyl polyazide (PAG) which has terminal hydroxy functions (a hydroxytelechelic PAG); hence 1) its energetic properties and 2) its ability to be crosslinked with the polyisocyanate crosslinking agents.

Said polymer has an adequate molecular weight (in particular, with reference to its consistency (liquid) and the consistency of its mixture with essentially the charges (organic energy) and with reference to the relative content of the crosslinked binder in crosslinking agent (s) ), a number-average molecular weight (Mn) of between 700 and 3000 g / mol, advantageously between 1700 and 2300 g / mol.

It is the merit of the inventors to have identified (selected) this type (of precursor polymer) of binder, perfectly suitable for use with bismuth citrate as a combustion catalyst.

Crosslinking agents, of the polyisocyanate type (at least bifunctional), which are suitable for the crosslinking of such a hydroxytelechelic glycidyl polyazide (PAG), are known per se. It may especially be di- or triisocyanates. These are advantageously liquid polyisocyanates chosen from toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), dicyclohexylmethylene diisocyanate (MDCl), hexamethylene diisocyanate (HDI), trimer of said hexamethylene diisocyanate (notably marketed by Bayer under the trade name Desmodur ^® N 3300), biuret trihexane isocyanate (ΒΤΉΙ), 3,5,5-trimethyl-6-hexamethylene diisocyanate and mixtures thereof. In a particularly preferred manner, the trimer of hexamethylene diisocyanate is used.

Said crosslinking agents are conventionally used in an amount necessary and sufficient to ensure the crosslinking of the polymer (not excessive so as not to pollute the crosslinked product obtained). They are conventionally used in an amount such that the bridging ratio (NCO (of the crosslinking agent) / OH (of the polymer)) is between 0.8 and 1.4, or advantageously of 1.

The crosslinked energy polymer generally represents from 10 to 14% by weight of the total composition of the composite pyrotechnic products of the invention. The energy polymer per is generally involved for 8 to 12% by weight, the at least one crosslinking agent for about 2% by weight.

It is understood that the nature of the binder (of its precursor polymer) is not per se original but that the advantage of the invention lies in the combination of such a (precursor polymer) binder with a catalyst of specific combustion.

Conventionally, the energy binder is associated with at least one energetic plasticizer. The energy plasticizer (s) in question is (are) advantageously of the nitrate and / or nitramine type. The energy plasticizer (s) in question is (are) very advantageously selected from diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN), butanetriol trinitrate (BTTN) trimethylolethane trinitrate (TMETN), a mixture of 2,4-dinitro-2,4-diaza-pentane, 2,4-dinitro-2,4-diaza-hexane and 3,5-dinitro-3, 5-diaza-heptane (and especially DNDA 5.7), nitrate ethyl nitramines (especially methyl-2-nitratoethyl nitramine (methylNENA) and ethyl-2-nitratoethyl nitramine (ethylNENA)) and mixtures thereof.

The plasticizer (s) of the pyrotechnic products of the invention generally represent (s) from 10 to 30% by weight, more generally from 15 to 25% by weight, of the total composition of said products.

The energy charges present are organic charges.

The organic energy charges involved are not per se original. These are organic energy charges known per se and, for the most part, already packaged according to the prior art in crosslinked energy polymer binders (in particular of the PAG type). It is advantageously charges of hexogen (RDX), octogen (HMX), hexanitrohexaazaisowurtzitane (CL20), nitroguanidine (NGU), ethylene dinitramine (EDNA), dinitramide N-guanylurea (FOX 12 (GUDN)), 1,1-diamino-2,2-dinitroethylene (FOX 7 (DADE)), 5,5'-azotetrazolate bis (triaminoguanidinium) (TAGZT), 5,5'-azotetrazolate of dihydrazinium (DHDZT), 5,5'-bis (tetrazolyl) hydrazine (HBT), bis (2,2-dinitropropyl) nitramine (BDNPN), a nitropyrazole or a mixture of these fillers (organic energy ).

Within the composite pyrotechnic products of the invention, there is therefore a type of energy charge, advantageously chosen from the list above, or a mixture of at least two types of energy charge, advantageously chosen from the list above. . Preferably, there are energetic charges of RDX.

Organic energy charges are conventionally in the form of solid grains, distributed homogeneously within the plasticized crosslinked binder. These solid grains suitably have, in a known manner per se, several particle size distributions. The organic energy charges of the pyrotechnic products of the invention generally represent from 50 to 70% by weight, more generally from 55 to 65% by weight, of the total composition of said products. It is understood that said products are high load.

The presence of inorganic energy charges within the plasticized binder of the pyrotechnic products of the invention can not be totally excluded. In any case, such inorganic energy charges, present, are in small quantities (<4% by weight). They can be considered as additives (see below). Their presence may be appropriate, with reference to the ballistic properties of the product; however, it must not be responsible for the consequent formation of flue gases or flares.

The presence of metal fillers, within the plasticized binder of the pyrotechnic products of the invention, is, in turn, generally excluded. Such metal charges are indeed likely to generate particles during their combustion.

The nature of the present combustion catalyst therefore constitutes the other of the key elements (of the composition) of the composite pyrotechnic products of the invention. Said combustion catalyst consists of bismuth citrate. Said bismuth citrate, because of its lower toxicity, advantageously replaces the salts and lead oxides of the prior art. Moreover, surprisingly, said bismuth citrate, a specific combustion catalyst, within the plasticised binder specific for the pyrotechnic products of the invention, has a positive effect on the combustion (especially on the rate of combustion) without posing a problem. problem upstream during the preparation of the product (the preparation process being of an "easy" implementation, generally "at constant temperature" until the crosslinking of the polymer, in any state of cause which includes no substantial cooling (of the type of that described in US 6,168,574 and 6,168,677)), without pot life management problem). In this connection, the reader is invited to consider the results in Table 2 below.

Bismuth citrate (the combustion catalyst) is generally present in the composition of the pyrotechnic products of the invention at a mass ratio of 1 to 6%, very generally at a mass ratio of 3 to 5%.

The composite pyrotechnic products of the invention are also likely to contain, and generally contain in their binder (crosslinked precursor polymer), besides the plasticizer (s), organic energy charges and combustion catalyst (specific), at least one additive . It is more apt to speak of at least one other additive, combustion catalysts generally constituting additives. The combustion catalysts have now been isolated from the other additives insofar as they are at the basis of the technical problem currently considered and where the combustion catalyst (specific) retained constitutes a key element of the products of the invention.

Among the additives that are suitably present, the following conventional additives are preferred: the crosslinking catalysts and the stabilizing agents of the plasticizer (s) energy (s) present (s). Thus, according to an advantageous variant, the composite pyrotechnic products of the invention therefore contain in their composition, in addition to the crosslinked polymer (PAG), the plasticizers (s), organic energy charges and combustion catalyst (bismuth citrate), at least an additive; said at least one additive comprising at least one crosslinking catalyst and / or at least one stabilizing agent for the plasticizer (s) present. Said at least one polymerization catalyst may especially be chosen from triphenylbismuth and dibutyldilaurate of tin (DBTL). Present, it is generally at a content not exceeding 100 ppm. Said at least one stabilizing agent of the plasticizer (s) present may in particular consist of at least one aromatic amine, such as 2-nitrodiphenylamine (2-NDPA) and N-methylparanitroaniline (MNA). Present, it is generally at a content of about 1% by weight.

Other additives that may be present in the composition of the composite pyrotechnic products of the invention may especially consist of inorganic energetic charges (see above) and one or more implementing agents (auxiliaries). manufacturing). The said agent (s) is (are) generally present at a content of 1 to 2% by weight.

The additives which may be present (in view of the above remarks, it has been understood that generally several types of additive are present) generally represent a maximum of 4% by weight of the composition of the composite pyrotechnic products of the invention. They represent very generally 0.1 to 4% by weight of the composition of said composite pyrotechnic products of the invention.

In view of the above remarks, it is understood that the composite pyrotechnic products of the invention are not of a new type but that they are new by the combination, in their composition, of a specific binder (PAG cross-linked by at least one polyisocyanate) and a specific combustion catalyst (bismuth citrate).

In the context of an advantageous variant, the composition of the composite pyrotechnic products of the invention, expressed in percentages by weight, thus contains:

from 50 to 70%, advantageously from 55 to 65%, of organic energy charges, and from 10 to 14% of the energy polymer (of the hydroxytelechelic PAG type) crosslinked (via its terminal hydroxy functions with at least one polyisocyanate),

from 10 to 30%, advantageously from 15 to 25%, of at least one energetic plasticizer,

from 1 to 6%, advantageously 3 to 5%, of bismuth citrate, and

from 0 to 4%, advantageously from 0.1 to 4%, of at least one additive.

It is understood that the advantageous ranges indicated above can quite be considered independently of each other. Preferably, they are in combination with each other.

In the context of this advantageous variant, said composition is generally free of any other ingredient (especially any metallic filler) and therefore consists of the ingredients listed above, present in the amounts indicated above.

The great interest of the products of the invention is evident from the above remarks. The products are interesting per se (in terms of ballistic performance, also because of their mechanical properties, the weak signature of the generated plume (discretion) during their propellant combustion) and to the extent that the pot life of the dough (precursor ) containing the ingredients is similar to that of the paste of a similar propellant containing no bismuth citrate. More generally, the implementation of the preparation of the products of the invention is not difficult and is "optimized" in terms of temperature management.

According to its second object, the present invention therefore relates to a method for preparing a composite pyrotechnic product, as described above. This process comprises: - the constitution of a homogeneous paste by

a) incorporation, with agitation, at a temperature of between 35 and 55 ° C., into a suitable glycidyl polyazide (hydroxytelechelic PAG having a number-average molecular weight as specified above), at least one energetic plasticizer, organic energy charges and other constitutive ingredients of the desired composite pyrotechnic product (including the specific combustion catalyst: bismuth citrate) with the exception of any crosslinking agent and any crosslinking catalyst, and

b) stirring the resulting mixture, under partial vacuum, to a (preferably said) temperature of between 35 and 55 ° C;

under partial vacuum, at a temperature advantageously between 35 ° and 55 ° C., the incorporation into said homogeneous paste constituted by said at least one crosslinking agent and optionally at least one crosslinking catalyst, followed by stirring of the mixture formed;

pouring said mixture constituted (having been) stirred (= of the mixture obtained) into at least one structure; and

the heat treatment of said mixture constituted (having been) stirred in said at least one structure.

The partial vacuum mentioned is intended for degassing of the medium above which it is applied. It is usually 10 mm Hg. Incidentally, it is not necessarily constant intensity.

The heat treatment (of crosslinking (of the hydroxytelechelic PAG)) is generally carried out at a temperature between 30 and 60 ° C (30 ° C <T ≤ 60 ° C) for several days.

This method may be considered as a method by analogy, but, typically, by the specific nature of the (binder precursor polymer) and the specific nature of the combustion catalyst, its first stages are carried out at temperatures (preferably a temperature) between 35 and 55 ° C (35 ° C <T (s) ≤ 55 ° C) , (without cooling), without pot life problem (said polymer).

It is now proposed to illustrate the invention by the examples below. Examples A, B1 and B2, which illustrate the prior art, are more specifically described below, examples 1 and 2 illustrating the invention and comparative examples C1 and C2.

Examples 1 and 2 relate to propellants according to the invention comprising, in their composition, hexogen (RDX) charges, a binder based on a hydroxytelechelic PAG type energy polymer (sold by the company EURENCO (Mn)). (average molecular weight) = 1900 g / mol) cross-linked (for the trimer of hexamethylene diisocyanate commercially available from Bayer under the trademark Desmodur ^® N 3300), plasticized (by a mixture of two energetic plasticizers (BTTN / TMETN; 30/70 (% by mass))), stabilizers of said plasticizers (MNA / 2-NDPA, 75/25 (% by weight)) and bismuth citrate as a ballistic catalyst (at a mass ratio of 1 % for Example 1 and at a mass ratio of 4% for Example 2).

Said propellants of Examples 1 and 2 were compared to reference propellants, for one (Ref.1) without ballistic catalyst in its composition (Example A) and for the other (Ref.2) with lead citrate. as a ballistic catalyst, in its composition, at a mass ratio of 1% (Example B1) and 3.5% (Example B2).

Two comparative examples are also presented with propellants similar to that of Example 2 according to the invention but comprising, as a ballistic catalyst, sub-salicylate of bismuth (Cl) and bismuth carbonate (C2), in place of bismuth citrate.

The compositions of these propellants (more precisely that of their pulp before crosslinking) are presented in Table 1 below.

The same products were obviously used for all the examples. As for RDX loads, they consisted of 68% by weight of an RDX of a particle size class of 0 - 100 μιη and 32% by weight of an RDX with a particle size class of 2.5 - 5. μιτι.

Table 1

Thus, composite pyrotechnic products (propellants) having the mass compositions given in Table 1 above were prepared. For this purpose, the procedure specified below (see the paragraph below entitled "Preparation") has been implemented.

There was interest in the pot life of propellant pastes (middlings) prepared. Said pot life was determined by implementing the viscosity measurements as shown below (see the paragraph below titled "determining the pot life"). The results appear in the first part of Table 2 below.

Said Table 2 also contains, in its second part, combustion rate results measured at different pressures, on the finally obtained propellants. Preparation

In a kneader, the (glycidyl polyazide precursor polymer) was introduced, then the plasticizers (BTTN / TMETN) and the stabilizing agents (MNA / 2-NDPA) of said plasticizers. The mixture was kneaded for 15 minutes at a temperature of 40 ° C.

Was then added to said mixture, under stirring, the organic energetic charges (RDX), per serving, then the additives (other than the crosslinking agent and catalyst (Desmodur ^® N 3300 and DBTL)) and the combustion catalyst. Stirring was then continued for 2 h 30, still at the temperature of 40 ° C and under a vacuum of 10 mm Hg (which allowed the degassing of the medium), to obtain a homogeneous paste.

The crosslinking catalyst (DBTL (55 ppm)) was then added to said homogeneous paste and the medium was further stirred 30 minutes before the addition of the crosslinking agent of the binder. Said crosslinking agent (Desmodur ^® N 3300) was finally added and the medium was further stirred 15 min (still at 40 ° C and vacuum).

Thus, batches of 2 kg of propellant paste were prepared.

A sample of each of the propellant pastes thus prepared was taken for pot life determination.

The remainder of each of the prepared propellant pastes was then poured into a suitable structure and then subjected to the following heat treatment: baking for 75 hours at a temperature of 50 ° C.

Determining the pot life of pasta

The pot life was determined by measuring the viscosity of the propellant paste in question (containing the crosslinking agent and the crosslinking catalyst) over time, using a Brookfield viscometer (with the body). ° 3 (mobile C) rotated at 1 rpm) at a temperature of 40 ° C. The time for which the viscosity reached 15 kPo was recorded to determine if the propellant met the industrialization criterion, i.e., if the said time was greater than 15 hours.

Table 2

The following comments on the results in Table 2 are proposed.

Potty life

As expected, the pastes of the reference propellants, without a ballistic catalyst (example A) or containing lead citrate as a ballistic catalyst (examples B1 and B2) reached the (viscosity) value of 15 kPo beyond 24 hours, thus meeting the criterion of industrial flowability.

The propellant paste of Example 1 (according to the invention) incorporating bismuth citrate at a mass content of 1% has properties of flowability equivalent to those of the reference propellants A (without ballistic catalyst) and B1 (containing 1% by weight of Pb citrate).

Example 2 (according to the invention) shows that, even at a high mass level (4%) of bismuth citrate, the propellant paste has maintained a viscosity of at least 15 kPo for at least 16 h, which is beyond the minimum time of 15 hours (required to industrially ensure the operations of casting the dough).

The viscosity of propellant pastes of the comparative examples

Cl and C2 exceeded the maximum acceptable viscosity value (15 kPo) in less than one hour (which is well below the required 15 hours). This demonstrates the particularly relevant selection of the pair PAG / bismuth citrate, according to the invention.

Combustion speeds

Table 2 also shows that the ballistic catalyst (combustion catalyst), bismuth citrate, gives propellants according to the invention combustion rates, depending on the pressure, much higher than that of the reference propellant A (without a ballistic catalyst in its composition), and close to those of propellants B1 and B2 comprising, in their composition, lead citrate (toxic product) as a combustion catalyst.

Claims

1. Composite pyrotechnic product comprising, in a plasticized binder, comprising a crosslinked energy polymer and at least one energetic plasticizer, organic energy charges and a combustion catalyst, characterized in that:

said crosslinked energy polymer consists of a glycidyl polyazide (PAG), having a number-average molecular weight (Mn) of between 700 and 3000 g / mol, crosslinked, via its hydroxyl terminal functions, with at least one crosslinking agent of polyisocyanate type; and

said combustion catalyst consists of bismuth citrate.

2. Composite pyrotechnic product according to claim 1, characterized in that said glycidyl polyazide (PAG) has a number-average molecular weight (Mn) of between 1700 and 2300 g / mol.

3. composite pyrotechnic product according to claim 1 or 2, characterized in that said at least one energetic plasticizer is of the nitrate and / or nitramine type.

4. Composite pyrotechnic product according to any one of claims 1 to 3, characterized in that said organic energy charges are selected from the charges of hexogen, octogen, hexanitrohexaazaisowurtzitane, nitroguanidine, ethylene dinitramine, N-guanylurea dinitramide, 1,1-diamino-2,2-dinitroethylene, bis (triaminoguanidinium) 5,5'-azotetrazolate, dihydrazinium 5,5'-azotetrazolate, 5,5'-bis (tetrazolyl) hydrazine, bis (2,2-dinitropropyl) nitramine, a nitropyrazole and mixtures of such fillers.

5. Composite pyrotechnic product according to any one of claims 1 to 4, characterized in that it contains 1 to 6% by weight, preferably 3 to 5% by weight of said citrate bismuth.

6. composite pyrotechnic product according to any one of claims 1 to 5, characterized in that it further contains at least one additive.

7. Composite pyrotechnic product according to claim 6, characterized in that said at least one additive comprises at least one crosslinking catalyst and / or at least one stabilizing agent of the at least one energetic plasticizer.

8. Composite pyrotechnic product according to any one of claims 1 to 7, characterized in that its composition, expressed in percentages by weight, contains:

from 50 to 70%, advantageously from 55 to 65%, of said organic energy charges,

from 10 to 14% of said crosslinked energy polymer,

from 10 to 30%, advantageously from 15 to 25%, of said at least one energetic plasticizer,

from 1 to 6%, advantageously from 3 to 5%, of said citrate of bismuth, and

from 0 to 4%, advantageously from 0.1 to 4%, of at least one additive.

9. Process for preparing a composite pyrotechnic product according to any one of claims 1 to 8, characterized in that it comprises:

- the constitution of a homogeneous paste by

a) incorporation, at a temperature between 35 and 55 ° C, into said glycidyl polyazide, of said at least one energetic plasticizer, organic energy charges and other ingredients constituting the desired composite pyrotechnic product with the exception of any crosslinking agent and any crosslinking catalyst, and

b) stirring the resulting mixture, under partial vacuum, at a temperature between 35 and 55 ° C;

under partial vacuum, at a temperature of between 35 ° and 55 ° C., the incorporation, in said homogeneous paste constituted by said at least one crosslinking agent and optionally of at least one crosslinking catalyst, followed by stirring of the compound mixture;

pouring said stirred mixture into at least one structure; and

the heat treatment of said stirred mixture formed in said at least one structure.