EP0194180B1 - Process for the solventless production of pyrotechnical products having a thermosetting binder - Google Patents

Description

The present invention relates to the field of composite pyrotechnic products and in particular to propellants for weapons and their manufacturing processes. More precisely, the invention relates to a new process for the manufacture, without solvent, of pyrotechnic composite products with thermosetting binder, that is to say of pyrotechnic products essentially consisting of an inert thermosetting binder and by at least one pulverulent oxidizing charge.

Known propellant powders are known as “homogeneous” consisting of one or more gelatinized energy bases having, seen in section, a homogeneous appearance, hence their name. Among the most well-known homogeneous propellant powders, mention may be made of “smoke-free” powders based on nitrocellulose alone or based on a nitrocellulose-nitroglycerine mixture. In order to improve the ballistic performance of these powders, attempts have been made to incorporate therein powdery mineral or organic oxidizing charges. These powders, seen in section, no longer have a homogeneous appearance, but have a heterogeneous appearance in which one distinguishes on the one hand the energetic binder and on the other hand the oxidizing charge, these powders are said to be “composite” or “heterogeneous” .

Such powders are for example described in French patent FR-B-2 488 246.

The use of energy binders such as nitrocellulose, however, has the disadvantage of making the powders vulnerable. Vulnerability means the fact that these powders can ignite and deflagrate under the effect of an unwanted random physical phenomenon such as the impact of a projectile. Vulnerability is a major challenge for powders intended to be loaded on board ships, planes or combat tanks. The development of modern combat machines therefore leads the skilled person to seek out poorly vulnerable propellants.

Composite powders with an inert binder consisting mainly of a synthetic resin and an inorganic or organic oxidizing charge have been found to be significantly less vulnerable than homogeneous or composite powders with an energy binder. However, because they contain an inert binder, these powders must, in order to present the necessary energy during ignition, contain very high charge rates, often close to 80% of the total weight of the powder. Composite powders with an inert binder thus have the characteristic, compared to other composite materials, of actually containing very little binder compared to the pulverulent filler. However, these powders must be able to be worked under fairly harsh conditions, they must in particular be able to be extruded through a die of relatively small diameter, usually comprising pins intended to create the channels present in the powder strand, and to keep then their geometric shape over time. It is precisely at the level of the use of composite propellant powders with an inert binder for weapons that a person skilled in the art has encountered numerous difficulties.

Inert binders of synthetic origin usable in composite pyrotechnic products can be classified, like any resin, into thermoplastic binders and thermosetting binders. It is, of course, first of all towards the use of thermoplastic binders that the skilled person has turned, these binders allowing mechanical work at temperature of the product to give it the desired geometry.

European patent application EP-A-0 036 481 thus describes a process for manufacturing composite explosives with a thermoplastic binder. However, the composite products with a thermoplastic binder described in this patent are not entirely satisfactory insofar as their geometry is too sensitive to thermal variations.

Those skilled in the art then turned to the use of inert thermosetting binders such as polyurethane binders or three-dimensional polyesters, allowing, after complete polymerization of the resin, to definitively freeze the geometry of the grain of powder. The manufacture on an industrial scale of such powders is however very difficult because on the one hand that the thermosetting resins have a limited "pot life" (by "pot life" is meant the period during polymerization of the resin during which the latter can be worked as a plastic) and on the other hand because of the high loading rate in composite powders, the binder must already have good mechanical strength at the time of extrusion to ensure the cohesion of the propellant paste.

To remedy drawbacks in the context of the use of thermosetting binders, those skilled in the art have sought to work in the presence of solvents as described for example in French patents FR-B-2 268 770 and FR-B-2 488 246. These techniques are however complex and costly to use which is not satisfactory on an industrial scale.

To operate without solvent with thermosetting binders, those skilled in the art have made extensive use of the technique known as “casting” or “global” which consists in simultaneously mixing in a kneader the liquid elementary constituents of the resin and the oxidizing charge and to pour, before polymerization, the mixture thus obtained in a mold to conduct the actual polymerization there. This technique which has been widely described, for example in French patents FR-B-2 109 102, FR-B-2 196 998, FR-B-2 478 623 and FR-B-2 491 455, may be suitable for manufacture of solid composite propellants for rocket or rocket engines, or the manufacture of composite explosives for machine heads which are most often used in the form of large diameter products, but prove to be unsuitable for manufacturing industrial large composite powders and totally unsuitable for the industrial manufacture of small diameter composite powders and more generally small diameter composite pyrotechnic products.

To make solvent-free composite pyrotechnic products of small diameter with inert binder thermosetting, the skilled person therefore has, at present, only the solution which consists in mixing in a kneader the constituents of the resin with the oxidizing charge, in initiating the polymerization of the resin and, in the process of polymerization, to be carried out, in a very short period of time, the extrusion of the product as described for example in French patents FR-B-1 409 203 and FR-B-2 159 826. This technique which does not allow the manufacture simultaneous large quantities of product is not satisfactory on an industrial scale, and moreover is in practice usable only for extrusions with large diameters.

Those skilled in the art are therefore looking for an industrial process for the manufacture, without solvent, of small-diameter composite pyrotechnic products with an inert thermosetting binder.

The object of the present invention is precisely to propose such a method.

• - dans une première étape on mélange ledit prépolymère polyhydroxylé avec ladite charge énergétique et avec une quantité de diisocyanate comprise entre 50% et 90% en masse de la quantité stoechiométrique nécessaire à la polymérisation complète de tous les groupes hydroxyles OH dudit prépolymère, et on effectue la réaction de condensation des groupes isocyanates NCO sur les groupes hydroxyles OH de manière à obtenir une pâte partiellement polymérisée,
• - dans une seconde étape on mélange à la pâte partiellement polymérisée ainsi obtenue le complément de diisocyanate nécessaire pour atteindre ladite quantité stoechiométrique nécessaire à la polymérisation complète et on extrude le mélange pâteux ainsi obtenu,
• - dans une troisième étape on achève par cuisson à chaud la réaction de condensation des groupes isocyanates NCO rajoutés au cours de la deuxième étape sur les groupes hydroxyles OH encore libres.

The invention therefore relates to a process for the manufacture of composite pyrotechnic products, and in particular composite propellant powders, consisting mainly on the one hand of a polyurethane binder obtained by reaction of a polyhydroxylated prepolymer with a diisocyanate and on the other hand of at least an inorganic or organic energy charge characterized in that said polyhydroxylated prepolymer has a number average molecular mass of between 2000 and 5000 and an average functionality in OH hydroxyl groups greater than 2 and less than 3, and in that:

• in a first step, said polyhydroxylated prepolymer is mixed with said energy charge and with an amount of diisocyanate of between 50% and 90% by mass of the stoichiometric amount necessary for the complete polymerization of all the hydroxyl groups OH of said prepolymer, and the condensation reaction of the NCO isocyanate groups with the OH hydroxyl groups so as to obtain a partially polymerized paste,
• in a second step, the diisocyanate supplement necessary to reach said stoichiometric quantity necessary for complete polymerization is mixed with the partially polymerized paste thus obtained, and the pasty mixture thus obtained is extruded,
• - In a third step, the condensation reaction of the NCO isocyanate groups added during the second step on the hydroxyl groups OH which are still free is completed by hot cooking.

The invention also relates to composite pyrotechnic products such as propellants for weapons, propellants, explosives obtained by the process according to the invention. The invention relates in particular to powders in which the binder is obtained by reaction of a hydroxytelechelic polybutadiene having an average functionality in OH hydroxyl groups close to 2.3 on a diisocyanate and the energy charge of which consists of hexogen.

The invention thus allows a person skilled in the art to have an industrial process for manufacturing solvent-free composite pyrotechnic products and in particular composite propellant powders, having an inert thermosetting binder. The choice of the functionality of the polyhydroxylated prepolymer in fact gives the resulting polyurethane the thermosetting character. The particular operating mode retained within the framework of the invention makes it possible, at the end of the first step, to have a partially polymerized paste having at this stage certain plastic properties making it extrudable including in small diameters, in particular after addition of the additional amount of diisocyanate. It has in fact been observed by the applicant that the pasty mixture obtained at the end of the second step is almost non-reactive at room temperature or slightly above room temperature and can be worked without precipitation and without fear of setting irreversible mass. It is only by the hot cooking provided for in the third step that the extruded product is frozen in its chemical structure. The process according to the invention which makes it possible to prepare large quantities of small diameter extrudable paste without solvent and which can be preserved over time thus makes possible the production on a truly industrial scale of strands of composite pyrotechnic products with small diameter thermosetting binder. . This process is very suitable for the manufacture of composite propellant powders.

A detailed description is given below of the implementation of the invention.

The invention therefore relates to a process for manufacturing composite pyrotechnic products, and in particular composite propellant powders, consisting mainly on the one hand of an inert thermosetting binder and on the other hand of at least one organic or mineral energy charge. The inert thermosetting binder usable in the context of the present invention is a polyurethane binder obtained by reaction of a polyhydroxylated prepolymer with a diisocyanate. The polyhydroxylated prepolymer, preferably liquid, has, and this is an essential characteristic of the invention, an average functionality in OH hydroxyl groups greater than 2 and less than 3, preferably close to 2.3. Such a prepolymer must be constituted by a mixture of polyfunctional hydroxytelechelic prepolymers, but the final functionality of the prepolymer must not be obtained by adding to an essentially difunctional prepolymer of short tri or tetrafunctional polyols with a molar mass of less than 400, for example trimethylol ethane. , trimethylol propane, or tetramethylol methane, contrary to what is often practiced in the industry of thermosetting polyurethane resins. Said polyhydroxylated prepolymer must moreover have a weight-average molecular mass of between 2000 and 5000 and preferably close to 4000. The polyhydroxylated prepolymers preferred in the context of the present invention are mixtures essentially consisting of polyhydroxylated polybutadienes.

Said polyurethane binder is obtained by reaction of said polyhydroxylated prepolymer with a diisocyanate. This is another essential characteristic of the invention, namely that the three-dimensional network of the thermosetting polyurethane is obtained by reaction of a polyhydroxylated prepolymer. of functionality greater than 2 with a diisocyanate, to the exclusion of any polyisocyanate whose functionality would be greater than 2. The Applicant will explain later in the description the fundamental importance of this condition in the implementation of the method according to the invention . As diisocyanate, it is possible to use the aliphatic, cycloaliphatic or aromatic diisocyanates usually used in the manufacture of pyrotechnic compositions using a polyurethane binder. Mention may thus be made of toluene-2,4 diisocyanate, toluene-2,6 diisocyanate, 1-methyl-cyclohexane - 2,6 diisocyanate, dicyclohexyl methane-4,4 'diisocyanate, isophorone diisocyanate, methylene diisocyanate , hexane-1,6 diisocyanate, trimethyl-2,2,4 hexane-1,6 diisocyanate, benzene - 1,3 diisocyanate, benzene-1, 4diisocyanate, diphenyl-4,4 'diisocyanate, diphenylmethane-4,4 'diisocyanate, dimethoxy-3,3' diphenyl-4,4 'diisocyanate.

The diisocyanates preferred in the context of the present invention are chosen from the group consisting of toluene-2,4 diisocyanate, toluene-2,6 diisocyanate, methyl-1 cyclohexane-2,4 diisocyanate, methyl-1 cyclohexane- 2.6 diisocyanate, 4-dicyochexylmethane diisocyanate, isophorone diisocyanate, hexane-1,6 diisocyanate, trimethyl - 2,2,4 hexane-1,6 diisocyanate. To obtain pyrotechnic compositions which release very little smoke during their combustion, the aliphatic or cycloaliphatic diisocyanates will preferably be chosen from the above list.

The polyhydroxylated prepolymer and the diisocyanate must have rheological properties allowing processing without solvent. Preferably they are liquid.

Polyurethane binder audit is mixed with at least one organic or mineral energy charge. As the mineral energy charge, it is possible to use the charges chosen from the group consisting of ammonium nitrate, ammonium perchlorate, alkaline nitrates, alkaline earth nitrates, alkaline perchlorates, alkaline earth perchlorates. As organic energy charge, it is possible to use the nitro organic compounds known as energy compounds and in particular cyclotrimethylene trinitramine (hexogen), cyclotetramethylene tetranitramine (octogen), pentantithritol tetranitrate (pentrite), triaminoguanidine nitrate.

In the context of the present invention, the ratio between the weight of energy charge relative to the weight of polyurethane binder is preferably close to 4.

In addition to the binder and the filler, the pyrotechnic products according to the invention generally contain the usual additives known to those skilled in the art and specific to the final application for which said products are intended, such as in particular plasticizers, agents wetting agent, antioxidant agents, anti-glow agents, anti-erosive agents, combustion catalysts, etc.

The process for manufacturing composite pyrotechnic products according to the invention is further characterized by the fact that one operates in three distinct stages.

In a first step, said polyhydroxylated polymer is preferably mixed with said energy charge in a kneader in the presence of the desired additives as described above and with an amount of diisocyanate of between 50% and 90% by weight of the stoichiometric amount necessary for the complete polymerization of all the hydroxyl groups OH of said polyhydroxylated prepolymer. After obtaining a homogeneous mixture, the condensation reaction of the NCO isocyanate groups on the OH hydroxyl groups is carried out so as to obtain a partially polymerized paste. It is at this first stage that the importance of the functional conditions previously stated regarding the polyhydroxylated prepolymer and the diisocyanate is situated. It has in fact been observed by the applicant that polyhydroxylated prepolymers having a functionality in OH hydroxyl groups of between 2 and 3 obtained by mixing functional prepolymers and trifunctional prepolymers to the exclusion of any short tri or tetrafunctional polyol, have statistically two OH hydroxyl groups which are more reactive than the third group serving to provide additional functionality. By adding in the first stage an amount of diisocyanate representing only 50% to 90% by weight of the total stoichiometric amount of diisocyanate necessary for the complete polymerization of all the OH hydraulic groups of said prepolymer, the diisocyanate will react preferentially with the two most reactive OH groups of the prepolymer according to an essentially linear polymerization. There is thus obtained, at the end of the first step, a partially polymerized paste, still having certain plastic properties and capable of being preserved over time. This result could not be obtained in the presence of short polyols or polyisocyanates containing more than 2 NCO groups. According to a preferred embodiment of the first step, the amount of diisocyanate introduced is between 70% and 80% by weight of said stoichiometric amount and the condensation reaction of the isocyanate NCO groups on the OH hydroxyl groups is carried out at a temperature between 50 and 80 ° C.

In a second step, the mixture of diisocyanate necessary to reach said stoichiometric quantity necessary for polymerization is mixed, preferably in a kneader-extruder, or in a twin-screw extruder, with the partially polymerized paste obtained at the end of the first step. complete with all the hydroxyl groups OH of said prepolymer, after homogenization, the pasty mixture thus obtained is extruded to the desired geometry. As has already been said above, one of the major advantages of the method according to the invention lies in the fact that the pasty mixture obtained in this second step while being of thermosetting nature is almost non-reactive at room temperature or even at slightly temperature higher than room temperature. It is therefore possible to work this pasty mixture without precipitation and without fear of irreversible solidification as long as one operates in practice at a temperature below 40 ° C. By the way, and this is where another advantage of the process according to the invention, this pasty mixture has both sufficient plastic properties to be able to be extruded, even in small diameters, through dies comprising pins and already sufficiently mechanical to preserve, after extrusion , its shape pending final hot crosslinking which constitutes the third step of the process according to the invention.

In a third step, therefore, the condensation reaction of the NCO isocyanate groups added during the second step with the hydroxyl OH groups still free of the prepolymer is completed by hot cooking. This cooking, which is preferably carried out at a temperature between 50 ° C. and 80 ° C., makes it possible to complete the three-dimensional crosslinking of the thermosetting binder and to definitively freeze the chemical structure of the pyrotechnic product obtained.

At the end of the third step, the product obtained can undergo the usual finishing treatments required for its final application after having possibly been put into its final form by machining or cutting.

The method according to the invention thus makes it possible to obtain composite pyrotechnic products with thermosetting binder without the use of solvent and by being freed from the disadvantages presented by the previous methods using mixtures having a limited pot life.

The method according to the invention is in particular well suited to obtaining composite propellant powders with thermosetting binder for weapons, and in particular for small caliber weapons. The method according to the invention makes it possible in particular to easily obtain cylindrical composite propellant powders having the conventional geometries with one hole, seven holes or nineteen holes used in small and medium caliber weapons. In this context, preferred powders are the powders obtained using as prepolymer a polyhydroxylated polybutadiene having an average functionality in OH hydroxyl groups close to 2.3 and using as filler hexogen. Particularly preferred powders are those obtained by using in addition as diisocyanate a diisocyanate chosen from the group consisting of aromatic diisocyanates and in particular toluene diisocyanate.

However, the method according to the invention is also applicable to obtaining composite propellants with thermosetting binder or composite explosives with thermosetting binder. The use of the method according to the invention, in this context, is particularly advantageous in the cases where it is desired to obtain composite propellants or extruded composite explosives of small diameter.

The examples which follow illustrate, in a nonlimiting manner, certain possibilities for implementing the invention.

Example 1

A granular powder was made in cylindrical geometry with 7 channels according to the process which is the subject of the present invention.

The composition of the powder is as follows:

The polybutadiene used has a weight average molar mass of 4000 and an average functionality in OH hydroxyl groups of 2.3 while the polyether used has a weight average molecular weight of 2000 and an average functionality in OH hydroxyl groups of 3.

• Première étape: homogénéisation sous vide à 60°C des divers ingrédients de la composition excepté le réticulant, ceci dans un malaxeur. Après deux heures d'homogénéisation, addition d'une fraction du réticulant de telle façon à obtenir un rapport NCO/OH = 0,78. Après homogénéisation, la pâte ainsi obtenue est préréticulée 5 jours à 60°C en étuve.

The process used for the manufacture of the powder is as follows:

• First step: homogenization under vacuum at 60 ° C of the various ingredients of the composition except the crosslinker, this in a mixer. After two hours of homogenization, addition of a fraction of the crosslinker so as to obtain an NCO / OH ratio = 0.78. After homogenization, the dough thus obtained is pre-crosslinked for 5 days at 60 ° C in an oven.

Second step: the pre-crosslinked dough, cut into a parallelepiped shape, is introduced into the tank of a mixer-extruder. After 10 minutes of mixing, the additional crosslinking agent is produced and then homogenized at 30 ° C. The dough is extruded after 20 minutes of mixing, through three dies which present the final geometry of the powder.

Third step: post baking in an oven is carried out on long extruded strands, for two days at 60 ° C. The grain cutting is then carried out, making it possible to have a directly usable bulk powder.

• géométrie cylindrique à 7 trous
• D = 5,4 mm (diamètre du grain)
• d : 0,6 mm (diamètre d'un trou)
• web : 0,9 mm
• longueur du grain L = 8,1 mm
• force : 1,06 MJ/kg
• température de flamme : 2429 K
• masse volumique : 1,59 g/cm3
• vitesse de combustion à 100 MPa : 45 mm/s

The characteristics of the powder obtained are as follows:

• 7-hole cylindrical geometry
• D = 5.4 mm (grain diameter)
• d: 0.6 mm (diameter of a hole)
• web: 0.9 mm
• grain length L = 8.1 mm
• force: 1.06 MJ / kg
• flame temperature: 2429 K
• density: 1.59 g / cm3
• combustion speed at 100 MPa: 45 mm / s

Example 2

Propellant powder strands of the same composition and according to the same process as in Example 1 were made, in geometries calculated a priori for a 30 mm medium caliber ammunition.

• - poudre cylindrique monotubulaire:
  • D = 1,20 mm (diamètre du grain)
  • d = 0,4 mm (diamètre du trou central)
  • web = 0,4 mm
  • L = 1,8 mm (longeur du grain)
• - poudre cylindrique heptatubulaire:
  • D = 2,3 mm (diamètre du grain)
  • d = 0,3 mm (diamètre d'un trou)
  • web = 0,35 mm
  • L = 3,45 mm (longueur du grain)

Two geometries have been produced:

• - cylindrical monotubular powder:
  • D = 1.20 mm (grain diameter)
  • d = 0.4 mm (diameter of the central hole)
  • web = 0.4 mm
  • L = 1.8 mm (grain length)
• - cylindrical heptatubular powder:
  • D = 2.3 mm (grain diameter)
  • d = 0.3 mm (diameter of a hole)
  • web = 0.35mm
  • L = 3.45 mm (grain length)

• - poudre monotubulaire:
  • - charge de poudre: 51,5 g
  • - pression maximale dans l'arme: 300 MPa (crusher)
  • - vitesse initiale de l'obus: 850 m/s
• - poudre heptatubulaire:
  • - charge de poudre: 55 g
  • - pression maximale dans l'arme: 300 MPa (crusher)
  • - vitesse initiale de l'obus: 890 m/s

These powders gave the following ballistic results in ammunition using a 245 g shell:

• - monotubular powder:
  • - powder charge: 51.5 g
  • - maximum pressure in the weapon: 300 MPa (crusher)
  • - initial shell speed: 850 m / s
• - heptatubular powder:
  • - powder charge: 55 g
  • - maximum pressure in the weapon: 300 MPa (crusher)
  • - initial shell speed: 890 m / s

Example 3

A granular powder in cylindrical geometry with 7 channels was produced according to the process which is the subject of the present invention.

The composition is the same as in Example 1 except the nature of the nitramine, the hexogen being replaced by octogen (0-100 μm).

• géométrie cylindrique 7 trous: D = 5,4 mm d = 0,6
• mm web = 0,9 mm
• longueur du grain: L = 8,1 mm
• force: 1,064 MJ/kg
• température de flamme: 2439 K
• masse volumique: 1,61 g/cm³
• vitesse de combustion à 100 MPa = 45 mm/s

The process used is the same as that of Example 1 except in the first step of the process where the pre-crosslinking of the binder is ensured for an NCO / OH ratio = 0.72. The characteristics of the powder obtained are as follows:

• 7-hole cylindrical geometry: D = 5.4 mm d = 0.6
• mm web = 0.9 mm
• grain length: L = 8.1 mm
• force: 1.064 MJ / kg
• flame temperature: 2439 K
• density: 1.61 g / cm ³
• combustion rate at 100 MPa = 45 mm / s

Example 4

A powder in cylindrical geometry grains comprising 7 channels was produced according to the process of the present invention.

The composition of the powder is as follows:

The polybutadiene and the polyether are those used in Example 1. The process used for the implementation of this composition is the same as that described in Example 1 except in the first step where the NCO / OH ratio was equal at 0.75.

• - même géométrie que la poudre décrite à l'exemple 1
• - force = 1,06 MJ/kg
• - température de flamme: 2429 K
• - masse volumique = 1,59 g/c_m ³
• - vitesse de combustion à 100 MPa = 55 mm/s

A powder was thus obtained having the following characteristics:

• - same geometry as the powder described in Example 1
• - force = 1.06 MJ / kg
• - flame temperature: 2429 K
• - density = 1.59 g / c _m ³
• - combustion speed at 100 MPa = 55 mm / s

Example 5

A powder in grains of cylindrical geometry comprising 7 channels was produced according to the process which is the subject of the present invention.

The composition of the powder is as follows:

The polybutadiene and the polyether are those used in Example 1. The process used for the implementation of this composition is the same as that described in Example 1 except in the first step where the NCO / OH ratio was equal at 0.70.

• - même géométrie que la poudre décrite à l'exemple 1
• - force: 1,024 MJ/kg
• - température de flamme: 2250 K
• - masse volumique: 1,51 g/cm3
• - vitesse de combustion à 100 MPa: 65 mm/s

A powder was thus obtained having the following characteristics:

• - same geometry as the powder described in Example 1
• - force: 1,024 MJ / kg
• - flame temperature: 2250 K
• - density: 1.51 g / cm3
• - combustion speed at 100 MPa: 65 mm / s

Example 6

A powder in grains of cylindrical geometry comprising 7 channels was produced according to the process which is the subject of the present invention.

The composition of the powder is as follows:

The hydroxytelechelic polyether has a weight average molar mass of 2800 and a functionality in OH hydroxyl groups close to 2, the polyether triol has a weight average molecular weight of 2000 and a functionality in OH hydroxyl groups equal to 3.

The process used for the implementation of this composition is the same as that described in Example 1 except in the first step where the NCO / OH ratio was equal to 0.69.

• - même géométrie que la poudre décrite à l'exemple 1
• - force: 1,09 MJ/kg
• - température de flamme: 2500 K
• - masse volumique: 1,63 g/c_m ³
• - vitesse de combustion à 100 MPa: 40 mm/s

A powder was thus obtained having the following characteristics:

• - same geometry as the powder described in Example 1
• - force: 1.09 MJ / kg
• - flame temperature: 2500 K
• - density: 1.63 g / c _m ³
• - combustion speed at 100 MPa: 40 mm / s

Example 7

A powder in grains of cylindrical geometry comprising 7 channels was produced according to the process which is the subject of the present invention.

The composition of the powder is as follows:

The hydroxytelechelic polyester has a weight-average molar mass of 3200 and a functionality in OH hydroxyl groups equal to 2.4, the polyether triol is the same as that used in Example 6.

The process used for the implementation of this composition is the same as that described in Example 1 except in the first step where the NCO / OH ratio was equal to 0.84.

• - même géométrie que la poudre décrite à l'exemple 1
• - force: 1,16 MJ/kg
• - température de flamme: 2861 K
• - masse volumique: 1,72 g/_cm ³
• - vitesse de combustion à 100 MPa: 38 mm/s

A powder was thus obtained having the following characteristics:

• - same geometry as the powder described in Example 1
• - force: 1.16 MJ / kg
• - flame temperature: 2861 K
• - density: 1.72 g / _cm ³
• - combustion speed at 100 MPa: 38 mm / s

Example 8

A powder in cylindrical geometry grains comprising seven channels was produced according to the process which is the subject of the present invention.

The composition of the powder is as follows:

The hydroxytelechelic polycarbonate has a weight-average molar mass of 3000 and a functionality in OH hydroxyl groups close to 2.7.

The process used for the implementation of this composition is identical in all respects to that described in Example 1.

• - même géométrie que la poudre décrite à l'exemple 1
• - force: 1,17 MJ/kg
• - température de flamme: 2671 K
• - masse volumique: 1,67 g/c_m ³
• - vitesse de combustion à 100 MPa: 30 mm/s

A powder was thus obtained having the following characteristics:

• - same geometry as the powder described in Example 1
• - force: 1.17 MJ / kg
• - flame temperature: 2671 K
• - density: 1.67 g / c _m ³
• - combustion speed at 100 MPa: 30 mm / s

Example 9

Hollow strands were made of composite propellant for the production of very short combustion duration loads according to the process of the present invention.

The composition of the propellant is as follows:

The hydroxytelechelic polybutadiene is the same as that used in Example 1.

The empolyé manufacturing process is the same as that described in Example 1 except in the first step where the NCO / OH ratio was equal to 0.75.

• diamètre extérieur: 10,2 mm
• diamètre du canal central: 6 mm
• longueur d'un brin: 137 mm

The characteristics of the strands obtained are as follows:

• outer diameter: 10.2 mm
• diameter of the central channel: 6 mm
• length of a strand: 137 mm

The load consists of 31 identical strands which are embedded in an inert sole.

• - pression: 44 MPa à +20°C
• - vitesse de combustion: 106 mm/s
• - coefficient d'autoserrage: 0,56
• - diamètre du col de la tuyère: 43,1 mm
• - impulsion de poussée palier: 664 newton X seconde

The performance of this load is as follows:

• - pressure: 44 MPa at + 20 ° C
• - combustion speed: 106 mm / s
• - self-tightening coefficient: 0.56
• - diameter of the nozzle neck: 43.1 mm
• - landing push pulse: 664 newton X seconds

Example 10

Composite explosive cylinders were made according to the process of the present invention.

• - polyester hydroxytéléchélique 13,90 %
• - polyéther triol 0,42 %
• - méthylène dicyclohexyl diisocyanate 3,13 %
• - carbonate de diéthyle et de butyle 5,23 %
• - graphite 0,77 %
• - acétyl acétonate de Fer 0,0005%
• - octogène (0-100 _Ilm) 76,5 %

The composition of this explosive is as follows:

• - hydroxytelechelic polyester 13.90%
• - polyether triol 0.42%
• - methylene dicyclohexyl diisocyanate 3.13%
• - diethyl and butyl carbonate 5.23%
• - graphite 0.77%
• - Iron acetyl acetonate 0.0005%
• - octogenous (0-100 _I lm) 76.5%

The polyester and polyether are the same as those used in Example 7. The process used for the implementation of this composition is the same as that described in Example 1, except in the first step where the NCO / OH was equal to 0.84.

• - masse volumique: 1,67 g/_cm ³
• - vitesse de détonation: 7915 m/s
• - propriétés mécaniques à 20°C
  • - en compression (1 mm/min)
    • . Sm = 2,8 MPa (contrainte maximale à la rupture)
    • . E = 29 MPa (module d'élasticité)
    • . em = 17,3% (écrasement maximum avant rupture)
  • - en traction (10 mm/min)
    • . Sm = 0,8 MPa

The characteristics measured on this product are:

• - density: 1.67 g / _cm ³
• - detonation speed: 7915 m / s
• - mechanical properties at 20 ° C
  • - in compression (1 mm / min)
    • . Sm = 2.8 MPa (maximum breaking stress)
    • . E = 29 MPa (modulus of elasticity)
    • . em = 17.3% (maximum crushing before rupture)
  • - in traction (10 mm / min)
    • . Sm = 0.8 MPa

Example 11

• - masse volumique: 1,67 g/cm³
• - vitesse de détonation: 8060 m/s
• - propriétés mécaniques à 20°C en compression: Sm = 5,9 MPa
  • E = 55,9 MPa
  • em = ₁₅,6%

A composite explosive was made with a composition identical to that of the powder cited in Example 8 and some of its characteristics were determined.

• - density: 1.67 g / cm ³
• - detonation speed: 8060 m / s
• - mechanical properties at 20 ° C in compression: Sm = 5.9 MPa
  • E = 55.9 MPa
  • em = _15, 6%

Claims (11)

1. Process for the manufacture of compound pyrotechnic products consisting chiefly, on the one hand, of a polyurethane binder obtained by reaction of a polyhydroxylated prepolymer with a diisocyanate and, on the other hand, of at least one inorganic or organic energetic charge, the said polyhydroxylated prepolymer having a weight average molecular mass of between 2000 and 5000 and an average hydroxyl group OH functionality higher than 2 and lower than 3 characterized in that:

- in a first step the said polyhydroxylated prepolymer is mixed with the said energetic charge and with a quantity of diisocyanate which has between 50% and 90% by weight of the stoichiometric quantity required for the complete polymerization of all the hydroxyl groups OH of the said prepolymer, and the condensation reaction of the isocyanate groups NCO with the hydroxyl groups OH is carried out so as to obtain a partially polymerized dough,

- in a second step, which is carried out at a temperature below 40°C, the partailly polymerized dough thus obtained is mixed with the remaining diisocyanate required to reach the said stoichiometric quantity required for complete polymerization, and the pasty mixture thus obtained is extruded,

- in a third step the condensation reaction of the isocyanate groups NCO added during the second step with the hydroxyl groups which are still free is completed by heating to a temperature above 40°C.

2. Process according to Claim 1, characterized in that the said polyhydroxylated prepolymer has an average hydroxyl group OH functionality close to 2.3.

3. Process according to either of Claims 1 and 2, characterized in that the said polyhydroxylated prepolymer has a weight average molecular mass close to 4000.

4. Process according to any one of Claims 1 to 3, characterized in that the said polyhydroxylated prepolymere is a polyhydroxylated polybutadiene.

5. Process according to any one of Claims 1 to 4, characterized in that the said diisocyanate is chosen within the group consisting of 2,4-toluene diisocyanate, 2,6-toleune diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, methylene diisocyanate, 1,6-hexane diisocyanate and 2,2,4-trimethyl-1 ,6-hexane diisocyanate.

6. Process according to any one of the Claims 1 to 5, characterized in that the said inorganic energetic charge is chosen within the group consisting of ammonium nitrate, ammonium perchlorate, alkali metal nitrates, alkaline-earth metal nitrates, alkali metal perchlorates and alkaline-earth metal perchlorates.

7. Process according to any one of Claims 1 to 6, characterized in that the said organic energetic charge is chosen within the group consisting of hexogen, octogen, pentrite and triaminoguanidine nitrate.

8. Process according to any one of Claims 1 to 7, characterized in that the relationschip between the weight of energetic charge relative to the weight of polyurethane binder is close to 4.

9. Process according to any one of Claims 1 to 8, characterized in that the quantity of diisocyanate introduced in the first step is between 70% and 80% by weight of the said stoichiometric quantity.

10. Process according to any one of Claims 1 to 9, characterized in that in the first step the condensation reaction of the isocyanate groups with the hydroxyl groups is carried out at a temperature of between 50°C and 80°C.

11. Process according to any one of Claims 1 to 10, characterized in that in the third step the heating is performed at a temperature between 50°C and 80°C.