Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
  • C06B21/0033—Shaping the mixture
  • C06B21/0075—Shaping the mixture by extrusion
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
  • C06B45/04—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive
  • C06B45/06—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component
  • C06B45/10—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component the organic component containing a resin

Definitions

• 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.
• propellant powders are known as “homogeneous” consisting of one or more gelatinized energy bases having, seen in section, a homogeneous appearance, hence their name.
• 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.
• 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.
• 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.
• thermoplastic 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.
• EP-A-0 036 481 thus describes a process for manufacturing composite explosives with a thermoplastic binder.
• 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.
• 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.
• thermosetting binders 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.
• thermosetting binders 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.
• 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.
• the object of the present invention is precisely to propose such a method.
• 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.
• 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.
• diisocyanate it is possible to use the aliphatic, cycloaliphatic or aromatic diisocyanates usually used in the manufacture of pyrotechnic compositions using a polyurethane binder.
• 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.
• 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.
• 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.
• 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.
• the ratio between the weight of energy charge relative to the weight of polyurethane binder is preferably close to 4.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• a granular powder was made in cylindrical geometry with 7 channels according to the process which is the subject of the present invention.
• 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.
• 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.
• 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.
• a granular powder in cylindrical geometry with 7 channels was produced according to the process which is the subject of the present invention.
• composition is the same as in Example 1 except the nature of the nitramine, the hexogen being replaced by octogen (0-100 ⁇ m).
• a powder in cylindrical geometry grains comprising 7 channels was produced according to the process of the present invention.
• 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.
• a powder in grains of cylindrical geometry comprising 7 channels was produced according to the process which is the subject of the present invention.
• 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.
• a powder in grains of cylindrical geometry comprising 7 channels was produced according to the process which is the subject of the present invention.
• 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.
• a powder in grains of cylindrical geometry comprising 7 channels was produced according to the process which is the subject of the present invention.
• 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.
• a powder in cylindrical geometry grains comprising seven channels was produced according to the process which is the subject of the present invention.
• 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.
• Hollow strands were made of composite propellant for the production of very short combustion duration loads according to the process of the present invention.
• 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.
• the load consists of 31 identical strands which are embedded in an inert sole.
• 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.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Dispersion Chemistry (AREA)
• Molecular Biology (AREA)
• Polyurethanes Or Polyureas (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Powder Metallurgy (AREA)

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• 1985
  • 1985-02-27 FR FR8502796A patent/FR2577919B1/fr not_active Expired
• 1986
  • 1986-02-13 DE DE8686400307T patent/DE3663134D1/de not_active Expired
  • 1986-02-13 EP EP86400307A patent/EP0194180B1/fr not_active Expired
  • 1986-02-19 JP JP61033082A patent/JPS61201687A/ja active Granted
  • 1986-02-24 CA CA000502564A patent/CA1256702A/en not_active Expired
  • 1986-02-26 US US06/833,142 patent/US4657607A/en not_active Expired - Lifetime
  • 1986-02-26 KR KR1019860001346A patent/KR900000084B1/ko not_active IP Right Cessation
  • 1986-02-27 AU AU54148/86A patent/AU577250B2/en not_active Ceased

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