EP0052552B1 - Process for the production of fine propulsive powders by granulation, and the powders so obtained - Google Patents

Description

The present invention relates to the field of propellant powders in grains. More precisely, the present invention relates on the one hand to a new process for the production of fine granular powders by granulation of the basic energetic materials in a granulating tray, and on the other hand as new industrial products the fine propellant powders obtained thanks to this new process.

In the past, attempts have been made to produce fine propellant powders for small arms by granulation in a rotating nitrocellulose apparatus in the presence of large quantities of water. Nitrocellulose grains are thus obtained which are recovered and reprocessed during a second granulation with a nitrocellulose solvent. The manufacturing process of these powders which are commonly called "Bulk powders" is for example described in the work "The Chemistry of Powder and Explosives", by Tenney L. Davis, Ph. D., published in New York in 1943 by John Wiley and Sons, Inc. However, this manufacturing process has the major disadvantage of leading to powders which are only partially gelatinized and therefore of dangerous use, due to the presence in the grain of non-nitrocellulose powder. gelatinized in a fibrous state.

Also partially gelatinized powders have been gradually abandoned in favor of completely gelatinized powders.

This is how fine propellant powders for small arms are, as a rule, in our time, nitrocellulose-based powders produced according to the so-called solvent process. According to this process, nitrocellulose, possibly mixed with other energy bases, is kneaded with solvents until it forms a homogeneous paste which is then spun with the press and cut into grains which are then wrung out, soaked, dried, smoothed and graphics if applicable. This process is well described in the work of MM. Louis VENNIN, E. BURLOT and H. LECORCHE, "Les Poudres et Explosifs", published in 1932 at the Librairie Polytechnique Ch. BERANGER, pages 578 et seq. This process leads to very good powders but is heavy and expensive to use because it uses a spinning press and cutting machines and requires heavy investment for safety reasons. Furthermore, the passage of the dough through a spinning press constitutes a "bottleneck" in the process which limits the possibilities in terms of flow rates.

If a porous powder is to be produced by this process, large quantities of soluble salt, such as potassium nitrate, which will be removed during soaking, should be introduced into the dough for kneading. to give as a by-product large quantities of salt water which are a source of pollution. Now it turns out that porous powders are brighter than non-porous powders and that for many applications porous powders are sought despite the additional disadvantage of their manufacture. The liveliness of a powder characterizes both its speed of combustion and the quantity of gas emitted in a given time of combustion.

Those skilled in the art are therefore looking for a method of manufacturing propellant powders which is relatively simple, which does not have, if possible, too great limitations in terms of flow rates and which makes it possible to obtain powders of liveliness. correct without having the drawbacks inherent in the previous processes for manufacturing porous powders.

Various researches have already been done to try to get rid of the press and the cutter. This research essentially led to the manufacturing process of so-called "spherical" powders. According to this process, a nitrocellulose collodion is produced which is dispersed in water, the aqueous dispersion is heated so as to cause the evaporation of the solvent and grains of gelatinized nitrocellulose are recovered. This process is for example described in French patents 1,268,986, 1,213,125, 1,195,187, 1,177,887, 1,168,167, or even in American patents 3,200,092, 3,235,420, 3,251,823, 3,563 977.

This method has the advantage of allowing large production rates, but has the major drawback of consuming a lot of energy because it requires heating large amounts of water, moreover it has drawbacks in terms of pollution due to the large quantities of gum-containing water that is left as a by-product.

The problem of a process for manufacturing fine live propellant powders which is simple, inexpensive, which does not have these disadvantages of pollution and which allows large flow rates remains therefore posed and has not so far been resolved in a way fully satisfactory.

The object of the present invention is precisely to provide a simple and inexpensive method for manufacturing fine propellant powders in grains for small arms and which have good vicacity.

The method according to the invention consists in carrying out in a rotating apparatus the granulation of wet base materials (with a humidity level close to 20%), sprinkled with solvent, in carrying out a first partial drying of the granules thus obtained and in finishing the finishing of said granules in a rounder possibly in the presence of solvent. The method according to the invention can be carried out batchwise or continuously depending on the needs and capacities of the available equipment.

The invention also relates, as a new industrial product, to propellant powders grains obtained using the process according to the invention.

• La figure 1 représente de façon schématique l'installation nécessaire à la mise en oeuvre en continu du procédé selon l'invention.
• La figure 2 est un diagramme indiquant l'ensemble des opérations nécessaires dans un exemple de fabrication en continu selon l'invention.

The description which follows illustrates in detail the implementation of the invention with reference to FIGS. 1 and 2.

• FIG. 1 schematically represents the installation necessary for the continuous implementation of the method according to the invention.
• FIG. 2 is a diagram indicating all the operations necessary in an example of continuous manufacturing according to the invention.

As mentioned above, the process according to the invention consists first of all in carrying out in a rotating apparatus the granulation of the finely ground base materials sprinkled with a solvent. The finely ground base materials are thus agglomerated using the solvent in the form of granules of essentially spherical shape. The rotating device is advantageously a "granulating tray" also sometimes called "granulating plate" widely used in the fertilizer or cement industry, but any equivalent device can also be used. The granulator tray is regularly supplied with base material and the solvent is sprayed very finely onto the granules being formed.

• - par le temps de séjour des granulés dans le plateau, temps qui est fonction à la fois de la vitesse de rotation du plateau et de son inclinaison: plus le plan de rotation du plateau est proche de la verticale et plus les granulés sont petits, on préférera en général une inclinaison selon laquelle le plan de rotation du plateau fait un angle voisin de 60° avec le plan horizontal,
• - par le taux de solvant: plus il y a de solvant, plus gros sont les granulés.

The tray is emptied by overflow of the largest granules which have formed there. The diameter of the granules leaving the tray depends on the starting raw materials and their grinding and can be adjusted as follows:

• - by the residence time of the granules in the tray, a time which is a function of both the speed of rotation of the tray and its inclination: the closer the plane of rotation of the tray is to the vertical, the smaller the granules, we generally prefer an inclination according to which the plane of rotation of the plate makes an angle close to 60 ° with the horizontal plane,
• - by the solvent content: the more solvent, the larger the granules.

• - de la nitrocellulose provenant soit directement de la nitration de la cellulose, soit obtenue à partir de poudres régénérées,
• - des poudres de récupération, qu'il s'agisse de poudres à simple base ou de poudre multibases,
• - des déchets de fabrication des poudres à double base fabriquées selon le procédé dit »sans dissolvant« et encore appelées »poudres SD« et notamment les copeaux d'usinage des blocs de poudre SD,
• - de la »galette« c'est à dire le mélange nitrocellulose-nitroglycérine utilisé pour la préparation des poudres SD.

The base materials agglomerated by the process according to the invention consist of the various solid energy bases which can be used in the manufacture of propellant powders in grains. The following bases can thus be used alone or in admixture:

• - nitrocellulose originating either directly from the nitration of the cellulose, or obtained from regenerated powders,
• - recovery powders, whether single base powders or multibase powders,
• - waste from the manufacture of double base powders produced according to the process known as "without solvent" and also called "SD powders" and in particular the machining chips from SD powder blocks,
• - "pancake", ie the nitrocellulose-nitroglycerin mixture used for the preparation of SD powders.

Before recovery, the basic recovery materials are ground very finely, the average diameter of the ground particles being preferably less than 300 microns for weapons of common calibers. For safety reasons, the grinding takes place under water as well as the mixing of the ground materials and the unmilled materials. The mixture of base materials is then drained to a humidity level of around 20% before passing over the granulating plate.

The agglomeration of the basic materials on the granulator tray is done using a solvent. All the solvents of one of the solid bases can be used, but preference is given, for reasons of convenience of recovery, to the solvents which are insoluble or poorly soluble in water. This is how we will use as solvents when we are in the presence of nitrocellulose, ketones such as methyl ethyl ketone, methyl isobutyl ketone, esters such as ethyl acetate, acetate d isopropyl, isobutyl acetate, nitroparaffins such as nitromethane.

The solvent must be finely sprayed on top of the granules. A stabilizer can be added to it in solution if it has not been added initially to the base materials and possibly a plasticizer. According to a preferred embodiment of the invention, a diluent is added to the solvent which must be non-solvent for nitrocellulose, but soluble in the solvent used. By way of example, mention may be made, as diluent, of light hydrocarbons such as white spirit or petrol A which is a petrol containing less than 1% of aromatic compounds and at least 80% of linear aliphatic hydrocarbons and the distillation temperature of which is between 40 and 100 ° C. The advantage of the diluent is that it allows easier regulation of the ballistic properties of the granules while avoiding excessive gelatinization.

On leaving the granulator tray, the granules then undergo a first partial drying intended to remove part of the water and of the solvents and are then terminated in a rounder in the possible presence of solvent.

The first drying can be carried out either in a conventional dryer, or in equivalent installations such as for example a fluidized bed. The granules are then finished in a rounder, this latter operation being absolutely necessary for obtaining a propellant powder in grains having acceptable properties. Rounder means any rotating device, fitted or not brewing tools, in which the outer surface of the granules is worked. It is advantageous to use as a rounder a granulator plate similar to that used for the actual granulation, but it is also possible to use any other commercial device fulfilling the desired function. In the case of a discontinuous process, it is advantageously possible to use as a rounder the granulator plate used for the granulation of the basic materials.

The rounding treatment is advantageously carried out in the presence of solvent and possibly of diluent. Advantage can be taken of the passage through the rounder to add the constituents which can be fixed to the surface of the grains such as for example combustion moderators or anti-static agents such as graphite.

The total watering rate in solvent, excluding diluent, between the granulator plate and the rounder is generally between 60 and 140% by weight relative to the weight of dry base material to be treated and is preferably between 80 and 120 %. In the case where a diluent is used, the solvent / diluent weight ratio is preferably between 90/10 and 70/30.

The granules leaving the rounder are wrung and dried. Spinning consists essentially of removing the solvent and optionally the diluent and is preferably carried out at room temperature while drying essentially consists of removing the water contained in the granules and is preferably carried out with hot air. The granules are then sieved, the granules having the desired particle size are stored while the others are recycled after possibly undergoing grinding under water. A first sieving can advantageously take place after the first drying and before the treatment in the rounder.

FIG. 1 schematically represents an installation necessary for the continuous implementation of the method according to the invention.

A storage tank 21 contains the basic materials which must be ground in the crusher 23. After grinding, these materials are mixed in the hopper 24 with the materials which do not require prior grinding from the storage tank 22. The mixture basic material is transported by means of a conveyor belt 25 onto a heavy belt 26 and from there into a crumbler 27 before falling into a granulator plate 11 sprayed with a solvent coming from the tank 35.

The granules formed are recovered on a conveyor belt 12 and pass over a sieve 13 before undergoing a first drying in a fluidized bed 14, they are then conveyed by a conveyor belt 15 in a rounder 16, at their exit from the rounder 16 the granules are transported by a conveyor belt 17 in a storage hopper 18 before undergoing the last treatments.

FIG. 2 is a diagram representing a possibility of complete implementation of the continuous process according to the invention.

The basic materials are stored in storage tanks 21 and 22. The basic materials stored in the tank 21 are ground under water in the grinder 23 before being mixed in the mixer 24 with the materials coming from the tank 22. The mixture of basic materials then undergoes partial elimination of the water in the dryer 26 so as to have a suitable humidity and then passes through the emitter 27 before being introduced into the granulator tray 11.

The tray 11 is sprayed with a liquid coming from a mixing tank 35 supplied from four tanks 31, 32, 33 and 34 respectively containing the plasticizer in solution, the solvent, the diluent and the stabilizer in solution. At their exit from the granulator plate 11 the granules are sieved on the sieve 13 and undergo a first drying in the fluidized bed 14 before being reprocessed in the rounder 16. The rounder 16 is supplied with liquid from a tank mixture 36 containing solvent and diluent from tanks 32 and 33 as well as the combustion moderator from tank 37. Graphite from a tank 38 is also added continuously to the rounder. as they exit the rounder, the granules are drained and then dried in the enclosure 41 before being screened on the screen 42. The solvents are recovered and recycled to the mixing tank 35. The granules having a correct particle size are stored in a hopper 43 while the finest granules are recycled into the mixer 24 and the largest granules are sent to the mill 23.

• - il est simple et court et nécessite beaucoup moins de main d'oeuvre qu'un procédé classique,
• - il utilise des technologies éprouvées qui ne nécessitent que peu d'entretien,
• - il est sûr car, dans la mesure où les matières de base sont humides, on ne manipule de poudre sèche qu'en fin de procédé à partir du séchage final. Sinon, pendant toutes les opérations précédant ce séchage la poudre contient de l'eau, ce qui limite considérablement les risques de prise en feu,
• - il est économique puisqu'il ne nécessite que peu de main d'oeuvre et peu de matériels complexes, qu'il est bien adapté au travail en continu et peut ainsi être fortement automatisé et commandé à distance,
• - enfin ce procédé est très souple et permet d'utiliser une large gamme de matières de base permettant ainsi l'obtention de poudres propulsives fines en grains de nature très diverses, il permet notamment la réutilisation de produits déclassés ou de produits de récupération.

The method according to the invention has the following advantages:

• - it is simple and short and requires much less manpower than a conventional process,
• - it uses proven technologies that require little maintenance,
• - it is safe because, since the basic materials are wet, dry powder is only handled at the end of the process from the final drying. Otherwise, during all the operations preceding this drying, the powder contains water, which considerably limits the risks of catching fire,
• - it is economical since it requires little labor and few complex materials, it is well suited to continuous work and can thus be highly automated and controlled remotely,
• - Finally, this process is very flexible and makes it possible to use a wide range of base materials, thus making it possible to obtain fine propellant powders in very diverse grains, it allows in particular the reuse of downgraded products or of recovery products.

The invention also relates, as a new industrial product, to the fine propellant powders obtained by the process according to the invention. It is indeed one of the surprising aspects of the invention to allow the production of propellant powder grains of good liveliness without the use of soluble salt. The grains of powders are obtained at the exit of the rounder and it is also surprising to note that the first passage on the granulator plate does not allow obtaining a propellant powder correctly adjusted but that it is only after a first drying and a treatment in the rounder that a product is obtained having the characteristics of a propellant powder usable in small and medium caliber commercial weapons and mainly in hunting rifles.

• - par la composition des matières de base: plus le potentiel de ces matières est élevé, plus la poudre sera vive,
• - par le taux de solvant utilisé, plus ce taux est bas et plus la poudre sera vive,
• - par la granulométrie, plus le diamètre des granulés est faible, plus vive sera la poudre, on recherchera de préférence une granulométrie comprise entre 300 et 1600 micrometers,
• - par le temps de séjour dans le plateau granulateur, plus ce temps est long, moins la poudre sera vive,
• - par la présence d'un diluant.

The ballistic performance of the powders according to the invention depends on the nature of the base materials and their adjustment can be done as follows:

• - by the composition of the base materials: the higher the potential of these materials, the brighter the powder,
• - the rate of solvent used, the lower this rate and the brighter the powder,
• - by the particle size, the smaller the diameter of the granules, the more vivid the powder, we will preferably seek a particle size between 300 and 1600 micrometers,
• - by the residence time in the granulator tray, the longer this time, the less the powder will be lively,
• - by the presence of a diluent.

The powders according to the invention can be described as heterogeneous in the sense that when viewed in section under a microscope, a homogeneous mass is not observed but a slightly porous heterogeneous mass is observed in which the elements belonging to each of the materials are recognized individually. basic.

The present invention will be better understood with the aid of the examples of implementation given below without implied limitation.

Example 1

• nitrocellulose: 62 parties en poids
• nitroglycérine: 38 parties en poids
• centralite: 1 partie en poids

et 15% de copeaux de poudre SD finement broyés.85% by weight of pancake having the following composition was used as base material:

• nitrocellulose: 62 parts by weight
• nitroglycerin: 38 parts by weight
• centrality: 1 part by weight

and 15% finely ground SD powder shavings.

The base material has a humidity of 20%, and the solvent used is ethyl acetate with a watering rate of 98%.

These basic materials are granulated in a granulating tray having a diameter of 600 mm and a plate height of 200 mm. The plane of rotation of the plate is inclined by 62 ° relative to the plane of the horizontal and the speed of rotation of the plate is 24 revolutions / minute. The feed rate of the granulator tray is 6 kg / hour of dry counted base material. The granules obtained are dried for 3 hours at room temperature and are then reprocessed in a second granulator tray similar to the first and under the same conditions of flow rate and speed of rotation.

• - charge de plomb: 32g g
• - charge poudre: 1,85 g
• - bourre feutre

A powder of potential 1140 cal / g (4770 J / g) is thus obtained with an apparent density of 650 kg / m ³ for the particle size cut between 1250 and 1600 micrometers. This powder is fired in a 12 mm caliber hunting rifle, under the following conditions:

• - lead charge: 32g g
• - powder charge: 1.85 g
• - felt fill

• - vitesse initiale des plombs: 370 m/s
• - pression maximale dans l'arme: 530 bars

The firing results are as follows:

• - initial sinker speed: 370 m / s
• - maximum pressure in the weapon: 530 bars

Example 2

• - 100% de galette de composition
  • nitrocellulose: 50 parties
  • nitroglycérine: 31 parties
  • dinitrotoluène: 18 parties
  • centralite: 1 partie

The operation is carried out with the equipment of Example 1 and under the same operating conditions but with the following materials:

• - 100% composition pancake
  • nitrocellulose: 50 parts
  • nitroglycerin: 31 parts
  • dinitrotoluene: 18 parts
  • centrality: 1 part

• - humidité: 20%
• - solvant: acétate d'éthyle
• - taux d'arrosage: 70%
• - débit d'alimentation: 8 kg/h

The operating conditions are:

• - humidity: 20%
• - solvent: ethyl acetate
• - watering rate: 70%
• - feed rate: 8 kg / h

• - charge de plomb: 32 g
• - charge de poudre: 2 g
• - bourre feutre

A powder is thus obtained having a potential of 988 cal / g (4134J / g) and an apparent density of 550 kg / m ³ for the particle size section between 800 and 1250 micrometers. This powder is shot in a 12 mm caliber shotgun under the following conditions:

• - lead charge: 32 g
• - powder charge: 2 g
• - felt fill

• - vitesse initiale des plombs: 394 m/s
• - pression maximale dans l'arme: 557 bars

The firing results are as follows:

• - initial sinker speed: 394 m / s
• - maximum pressure in the weapon: 557 bars

Example 3

• - 60% de galette de composition
  • nitrocellulose: 60 parties
  • nitroglycérine: 40 parties
• - 10% de copeaux de SD broyés
• - 30% de poudre à simple base à la nitrocellulose, broyée.

The operation is carried out with the equipment of Example 1 and under the same operating conditions but with the following materials:

• - 60% composition pancake
  • nitrocellulose: 60 parts
  • nitroglycerin: 40 parts
• - 10% of crushed SD chips
• - 30% of nitrocellulose simple base powder, crushed.

• - humidité: 12%
• - solvant: acétate d'isobutyle
• - diluant: essence A
• - rapport solvant/diluant: 70/30
• - stabilisant: 1% de centralite introduite dans le solvant
• - taux d'arrosage: 60%
• - débit d'alimentation: 6,4 kg/h

The operating conditions are:

• - humidity: 12%
• - solvent: isobutyl acetate
• - thinner: petrol A
• - solvent / diluent ratio: 70/30
• - stabilizer: 1% of centrality introduced into the solvent
• - watering rate: 60%
• - feed rate: 6.4 kg / h

• - charge de plomb: 32 g
• - charge de poudre: 1,65 g
• - bourre feutre

A powder is thus obtained having a potential of 1040 cal / g (4351 J / g) and an apparent density of 680 kg / m ³ for the particle size section between 500 and 800 micrometers. This powder is shot in a 12 mm caliber shotgun under the following conditions:

• - lead charge: 32 g
• - powder charge: 1.65 g
• - felt fill

• - vitesse initiale des plombs: 375 m/s
• - pression maximale dans l'arme: 580 bars

The firing results are as follows:

• - initial sinker speed: 375 m / s
• - maximum pressure in the weapon: 580 bars

Example 4

• nitrocellulose: 62 parties
• nitroglycérine: 38 parties
• centralite: 1 partie

The composition slab is used as the basic material:

• nitrocellulose: 62 parts
• nitroglycerin: 38 parts
• centrality: 1 part

The humidity is 20% and the solvent used is butyl acetate.

This cake is granulated in a granulating tray having a diameter of 1200 mm and a height of plate of 250 mm. The plane of rotation of the plate is inclined by 57 ° relative to the plane of the horizontal and the speed of rotation is 20 revolutions per minute. The feed rate is 12 kg / hour of dry counted base material with a watering rate of 72%. The granules are dried for 3 hours at room temperature and are then reprocessed in a second granulator tray under similar conditions.

• - charge de plomb: 32 g
• - charge de poudre: 2,0 g
• - bourre feutre

A powder of potential 1185 cal / g (4958 J / g) is thus obtained with an apparent density of 650 kg / m ³ for the particle size section between 1240 and 1600 micrometers. This powder is fired in a 12 mm caliber hunting rifle, under the following conditions:

• - lead charge: 32 g
• - powder charge: 2.0 g
• - felt fill

• - vitesse initiale des plombs: 395 m/s
• - pression maximale dans l'arme: 510 bars

The firing results are as follows:

• - initial sinker speed: 395 m / s
• - maximum pressure in the weapon: 510 bars

Example 5

This example shows the influence of too high a moisture content in the base materials on the performance of the powder.

• - nitrocellulose: 67 parties
• - nitroglycérine: 19,5 parties
• - dinitrotoluène: 2,5 parties
• - centralite: 1 partie

Granulate in the apparatus and under the conditions of Example 1 of the composition cake:

• - nitrocellulose: 67 parts
• - nitroglycerin: 19.5 parts
• - dinitrotoluene: 2.5 parts
• - centrality: 1 part

The moisture content of the wafer is 40%, the solvent used in the me _t hyl ethyl ketone with a spray rate of 140%.

A powder is thus obtained having a potential of 1045 cal / g (4372 T / g) but whose grain vivacity for the particle size cutting between 800 and 1600 micrometers is too high for normal use in a hunting weapon. This powder could be suitable for very specific applications, for example for very low lead charges.

Claims (12)

1. Process for the manufacture of fine granular propellant powders by granulation of the wet base materials in a rotating apparatus (11), characterised in that the base materials have a moisture content in the region of 20% and are wetted during the granulation by a solvent for one of the solid bases, and in that the granules obtained are subjected to a partial drying and are then completed in a rounder (16).

2. Process according to Claim 1, characterised in that the said rotating apparatus (11) is a granulating tray.

3. Process according to Claim 2, characterised in that the said rounder (16) is a granulating tray.

4. Process according to any one of Claims 1 to 3, characterised in that the said solvent is a solvent for nitrocellulose.

5. Process according to Claim 4, characterised in that the said solvent is sparingly suluble or insoluble in water.

6. Process according to Claim 5, characterised in that the said solvent is chosen from the group comprising methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, isopropyl acetate, isobutyl acetate and nitromethane.

7. Process according to any one of Claims 4 to 6, characterised in that the total wetting level in respect of solvent is between 60 and 140%.

8. Process according to any one of Claims 4 to 7, characterised in that a diluent is added to the said solvent.

9. Process according to Claim 8 characterised in that the said diluent is a volatile hydrocarbon.

10. Process according to any one of Claims 1 to 9 characterised in that it is a batch process.

11. Process according to any one of Claims 1 to 9 characterised in that it is continuous.

12. By way of a new industrial product, the granular propellant powder obtained by the process according to any one of Claims 1 to 11.

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