EP1857429A1 - Propulsive means for accelerating projectiles - Google Patents

Abstract

Propulsion system (I) for the acceleration of projectiles that is based on nitrocellulose, comprises a crystalline energy carrier on a nitramine base and one or many inert plasticizing additives, where at least one of the inert plasticizing additives is present, essentially homogeneously distributed, in a matrix of (I), and the one and/or another inert plasticizing additive has an increased concentration in zones near the surface. An independent claim is included for the preparation of (I), manufacturing a powder cake containing solvent, on the base of nitrocellulose and crystalline energy carrier on a nitramine base, and one or many inert plasticizing additives; extruding the powder cake containing a green grain solvent; surface treating with an inert plasticizing additive, so that the inert plasticizing additive in the zones near the surface has a weight proportion of not more than 10 wt.%. particularly less than 6 wt.%.

Description

Technical area

The invention relates to a drive for accelerating projectiles, which is based on nitrocellulose and a method for producing a drive.

State of the art

One important finding of ammunition manufacturers of the recent military conflicts is that the weapons and munitions platforms in operation can only offer inadequate protection against enemy attacks. These new threat scenarios essentially consist of enemy fire from light and medium armored vehicles, with their armor piercing relatively easily. The threat is further exacerbated by the fact that the weapons that pose the threat are easily transportable and in large numbers are circulating in an uncontrolled manner. There is thus a great need for improvement in the resistance to mechanical effects caused by bombardment of ammunition by e.g. a shaped charge jet, hot metal fragment splinters or bullets. Although the vulnerability of an ammunition is a system aspect, the propellant powder has a strong influence.

In addition, the recent past has shown that the risk of conflicts in warm climates can be classified as significantly increasing. Such "out-of-area" uses in warm climates generally require an improvement in the chemical stability of a propellant charge powder so that its safety during handling, use and storage is fully assured. Further examples, where an improvement in the chemical-thermal stability is required, are the extremely strong thermal cycling load of the ammunition with high temperature peaks of over 100 ° C ("almost cook-off"), which occurs in modern combat aircraft, or the resistance of an ammunition to fires ("slow cook-off"). The chemical stability of a propellant charge powder, which determines both its useful life and its "cook-off" temperature, hereby represents another field of activity with a need for improvement.

Therefore, for several years, developments aiming at high performance potential propellant powders and improved vulnerability (ie, mechanical impact) and "cook-off" (ie with regard to thermal effects). The challenge here is that a propellant charge powder to be used for military purposes must have the highest possible energy density, but at the same time should have the lowest possible vulnerability to mechanical and thermal effects. This requirement is of great importance for closed spaces such as tanks, armored personnel carriers or warships.

For some time now, attempts have been made to fulfill this requirement by means of so-called "insensitive ammunition" (IM), for which purpose new LOVA propellants (Low Vulnerability Ammunition) have been developed. These propellant powders typically contain between 60-80% by weight of a crystalline explosive and about 10-25% by weight of an inert or energetic binder. Typical explosives in LOVA propellants are cyclotetramethylene tetranitramine (HMX) and cyclotrimethylene trinitramine (RDX). Previous LOVA propellant charge powders typically consist of a synthetic inert or energetic elastomeric polymer binder in which the crystals of the respective explosive are embedded. Typical binders are CAB and HTPB (inert) and GAP, poly-AMMO and poly-BAMO.

In propellant charge powders (TLP) for weapons applications, a distinction is made between "homogeneous" and "composite" (heterogeneous) formulations, with homogeneous formulations comprising single and dibasic propellants. In-depth IM testing has shown that inert starch-based LOVA propellant powder has advantages over cook-off as compared to conventional powders. On the other hand, it has been shown that such formulations can detonate under mechanical action, hitherto preventing their widespread introduction and use (see, e.g., L. M. Barrington, Australian Defense Force (ADF), DSTO-TR-0097).

An example of a LOVA-TLP with an energetic synthetic binder is in US 6,228,190 wherein the binder consists of a nitratoalkyl-substituted alkyl ether prepolymer having reactive hydroxy end groups and a crosslinker based on a polyvalent isocyanate compound. It is known from practice that powders built up from such binders are cold-prone and that their production is very expensive and difficult.

LOVA-TLP with an elastomeric polyurethane-containing binder represent another known class of LOVA-TLP and are inter alia in US 4,925,503 . US 4,923,536 and US 5,468,312 described. The chain-extended polyurethanepolyacetal elastomer binder is obtained by reacting a dihydroxy terminated polyacetal homopolymer with an alkylenediisocyanate, then reacting the resulting isocyanate terminated prepolymer with a dihydroxy terminated polyacetal copolymer and finally reacting this elastomeric intermediate with an organic polyisocyanate. Since the preparation of this elastomeric binder system takes place via several synthesis steps, the costs are very high. In addition, it has been shown in the past that the reproducibility causes great problems, so that the obtained LOVA-TLP can not be manufactured with the desired uniformity of the product properties. For these reasons, LOVA-TLP have not been able to prevail on a broad front on this basis so far.

Another class of LOVA-TLP uses cellulose acetate or derivatives thereof (eg cellulose acetate butyrate, CAB) as elastomeric binders. Such formulations are, inter alia, in US 6,984,275 described.

The known LOVA formulations are unsatisfactory because their reproducibility is not sufficiently ensured and the production costs are relatively high. They are therefore practically not used.

Presentation of the invention

The object of the invention is to provide a drive belonging to the technical field mentioned above, which has a low sensitivity to mechanical effects, good "cook-off" properties and at the same time a high performance potential.

The solution of the problem is defined by the features of claim 1. According to the invention, the drive contains nitrocellulose as a base, as well as a crystalline energy carrier based on nitramine. In addition, an inert plasticizing additive is provided.

Surprisingly, by adding only relatively small amounts (e.g., <10% by weight) of inert plasticizing additives, the resistance to mechanical stimuli can be significantly improved. Depending on the application, it is also possible to use combinations of several inert additives to set the desired thermodynamic properties, such as performance or temperature characteristics. The grain structure of such drives is adapted to the specific application (setting the burn-up characteristic on pipe length, bullet weight, etc. of the weapon system).

To enhance or optimize the desired effects, optionally minor amounts (usually less than 5% by weight) of energetic plasticizers, e.g. based on Metyl-NENA (CAS No. 17096-47-0), Ethyl-NENA (CAS No. 85068-73-1) or Butyl-NENA (CAS No. 82486-82-6).

Comparable monobasic drives that do not contain the novel combination of additives have no IM properties.

Another major advantage of the drive according to the invention is its surprisingly high degree of energy conversion, which leads to a high internal ballistic performance. Thus it was found that the thermal efficiency, i. the proportion of TLP energy content converted into kinetic muzzle energy is up to 44% for full caliber ammunition. For subcaliber KE ammunition (KE = kinetic energy), i. in ammunition with a sabot, thermal efficiencies of up to 36% were found. This corresponds to an increase in energy conversion capacity of up to 10% at a comparable level of performance compared to conventional monobasic propellant powders. This manifests itself in the aforementioned increase in inside ballistic performance potential without deterioration of pipe erosion, since the flame temperature is practically not increased compared to a normal monobasic TLP.

The drives according to the invention are also characterized by a largely neutral temperature characteristic. This means that, regardless of the powder bed temperature over a wide temperature range, practically the same internal ballistic performance data is achieved, which makes it suitable for use in hot and cold climates is very desirable. For example, in a 30 mm full caliber ammunition for an airburst application, it has been found that the muzzle velocity varies only by 12 m / s within the temperature range of -32 ° C to + 52 ° C. The highest muzzle velocity is typically around 21 ° C and decreases with increasing warming resp. Cooling off continuously. An analogous course was also found for the peak gas pressure. Conventional monobasic TLPs typically exhibit a linear increase in muzzle velocity of 0.5 - 1.0 m / s per ° C, so with monobasic TLP, the muzzle velocity varies by 40-80 m / s over the same temperature range.

In contrast to the above-mentioned, previously known LOVA formulations, the drive according to the invention is not based primarily on the crystalline energy carrier. Rather, the proportion of nitrocellulose on the total weight (> 50 wt .-%, in particular> 60 wt .-%) predominates. The use of nitrocellulose ensures that the mean distances between the individual crystals of the crystalline energy carrier are sufficiently large, resp. that the individual crystals mostly do not touch. As a result, when external mechanical stimuli are applied, the shock pulse can not be passed from one explosive crystal to the adjacent crystals. It is prevented that the primary shock pulse is multiplied and transmitted over the entire amount of powder.

Another difference between the invention and the previously known LOVA formulations is that the hydrogen content in the combustion gases is not increased. Compared to the previously known LOVA formulations with crystalline energy sources, therefore, pipe erosion is avoided because of high proportions of hydrogen. It can easily be fired several thousand rounds, as prescribed by the usual acceptance conditions.

Nitrocellulose is obtained by nitration of cellulose (cotton linters, pulp) and has been the most important raw material for the production of one-, two- and three-base propellant powders for more than a hundred years. Nitrocellulose is available in large quantities at low prices and comes with a wide range of different chemical-physical properties such as nitrogen content, molecular weight or Viscosity offered. These differences allow nitrocellulose to be processed into the various homogeneous types of propellant charge powder. The energy content of nitrocellulose is adjusted via the nitrogen content. In monobasic formulations, nitrocellulose is the sole energy carrier, which means that the energy density of nitrocellulose is relatively high compared to other synthetic binder polymers.

In the context of the invention, it has now surprisingly been found that nitrocellulose can be used as starting material for the production of drives with IM properties. On the one hand, it has unexpectedly been found that the incorporation of relatively small proportions of a crystalline nitramine compound makes it possible to significantly improve the chemical stability in comparison with a nitramine-free drive. This massively improves the resistance to thermal stimuli, whereby the desired improvement of the cook-off temperature can be realized.

Another advantage is that the raw materials are inexpensive and readily available and that no exceptional ("exotic") process steps are required in the manufacturing process.

The drive is preferably designed in the form of grains (English: grain), which z. B. have a circular cylindrical geometry with axially extending longitudinal channels (e.g., 1 channel, or 7 or 19 channels). As a result, such a propellant powder is pourable, which is important for the industrial filling of pods. The propellant powder can thus be handled similar to a liquid during filling in the sleeves. For large caliber ammunition, the material can also be in the form of strips or extruded directly into a specific, suitable for guns form. (However, it's not about a large-volume, cast block, as it is used for solid rockets.)

The cylindrical powder grain has a ratio of length (L) to diameter (D) typically (but not necessarily) a value in the range of L / D = 0.25 to L / D = 5. The length of the circular cylinder is for example in the range of 0.3 - 10 mm and the diameter in the range of 0.3 - 10 mm.

Instead of cylindrical shapes, strip shapes can also be used. This typically includes shapes where the width is much smaller (e.g., at least 5 times or at least 10 times) than the length, and the thickness in turn is much smaller (e.g., at least 5 times or at least 10 times) than the width. (The thickness is, for example, 1-2 mm, the width is 10 mm or more, and the length is 100-150 mm.)

Also conceivable are so-called "shaped bodies", i. hollow cylindrical shapes for an ammunition in which the sleeve is missing or replaced by the arranged behind the ignition "moldings" is replaced.

Preferably, the crystalline nitramine compound contains a structural element of the general chemical structural formula RN-NO ₂ (R = radical). The proportion of the nitramine structural element in the total molecule should be as high as possible in order to achieve a correspondingly high energy content.

Instead of a nitramine compound of the type RO-NO ₂ , for example, a nitrate ester would be conceivable. However, the latter is chemically less stable than the nitramine compound.

The crystalline nitramine compound is preferably used in a concentration ranging from 1 to 35% by weight. Particularly preferred are concentrations in the range of 5-25 wt .-%. At higher proportions by weight of crystalline energy carrier, the crystals are statistically too close to each other and the vulnerability increases sharply. With weights up to 20%, vulnerability remains at a very low level.

With an inert plasticizing plasticizer in the grain matrix and / or a surface coating, the vulnerability may be somewhat mitigated for a given weight fraction of the crystalline nitramine compound. It is thus readily possible to work at the upper limit (i.e., at about 25% by weight crystalline nitramine).

It has been shown within the scope of the invention that RDX has two effects. First, it acts as an energy carrier or supplier (known property). Secondly, in the context according to the invention, it increases the chemical stability of the drive (new property). The stabilizing property is already from about 1 wt .-% to fruition. It increases thereafter with increasing weight proportion only insignificantly.

If the nitramine compound is provided as an energy carrier, then its proportion by weight in the powder grain will usually be more than 10%. For stabilization it is also possible to use per se known active substances, such as, for example, Akardit II can be used.

As the crystalline nitramine compound, hexogen (RDX, cyclotrimethylenetrinitramine, CAS # 121-82-4), octogen (HMX, tetramethylenetetranitramine, CAS # 2691-41-0, hexanitroisowurtzitane (CL-20, CAS # 14913-74-7 ), Nitroguanidine (NIGU, NQ, CAS # 70-25-7, N-methylnitramine (tetryl, N-methyl-N, 2,4,6-tetranitrobenzenamine, CAS # 479-45-8) and nitrotriazolone (NTO , CAS # 932-64-9) and triaminotrinitrobenzene (TATB, CAS # 3058-38-6) These compounds can be used singly or in combination with one another The crystalline nitramine compound is, for example, RDX with a mean particle size of 6 micrometers.

RDX is the most interesting of all these crystalline energy sources. It should be noted that the "insensitive" RDX offered on the market (also called I-RDX or RS-RDX) in the context according to the invention does not bring any improvement, although the I-RDX variant is offered precisely because of allegedly less vulnerability.

Octogen is relatively expensive compared to RDX. Other nitramine compounds (such as NIGU, etc.) have relatively little power compared to RDX.

The inert plasticizing additive (plasticizer) is basically distributed throughout the grain (i.e., in the grain matrix). He can be present in two different variants. It can be distributed more or less homogeneously in the grain matrix. But it can also be more concentrated in near-surface areas than inside the powder grain. The latter can increase the desired effect.

With a homogeneous distribution, the concentration of the inert plasticizing plasticizer in the grain matrix is in the range of 1.0-20% by weight. Preferably, the concentration is in the range of 1.0-10% by weight. In particular, already 1 to 5% by weight suffice. The lower the content of inert plasticizer, the higher the proportion of high-energy substances in the grain can be. With a homogeneous distribution of the plasticizing plasticizer, its weight fraction should be less than 10%, namely for medium caliber applications.

On the other hand, in small caliber applications, the weight fraction of the plasticizer may well increase to 15% by weight (due to the ratio of surface area to volume in the propellant charge powder).

The inert plasticizing plasticizer in the grain matrix may, for. B. a substantially water-insoluble organic polyoxo compound such. Example, a polyester or polyether compound having a molecular weight of 50 - 20,000 g / mol. If the inert plasticizer is enriched in the near-surface zone of the drive, it is a substantially water-insoluble organic compound (typically organic compound containing carboxyl groups (preferably camphor and / or aromatic urea compounds).

By being virtually insoluble in water, the plasticizer may be bathed in water during the production process to wash out the residual solvents (such as alcohol, diethyl ether or ethyl acetate) contained in the powder dough for extrusion. The water-insoluble plasticizer thus remains in the grain. Alternatively, the solvent can also be removed by air drying. It is then not necessary for the plasticizer to be water-insoluble.

Particularly suitable are water-insoluble citrate esters, adipic acid esters, sebacic acid esters or phthalic acid esters (or hydrogenated cyclohexyl derivatives thereof) having a molecular weight of 100-20,000 g / mol or combinations thereof.

In the plastics industry (see eg Handbook of Plasticizers, ISBN 1-895198-29-1 ) are known a variety of plasticizers, which are good gelatinators for nitrocellulose.

When the plasticizing additive is additionally incorporated in the near-surface zones of the powder grain, a carboxyl group-containing organic compound having a molecular weight of 100 to 5000 g / l is preferred. The proportion by weight of the total grain is preferably not more than 10% by weight, in particular less than 6% by weight.

However, concentration ranges of the inert plasticizer located in the near-surface zones of the drive below 15% by weight may also be suitable. However, with 1-2 wt .-% at medium caliber good results. Below 1.0 wt .-%, only an insufficient effect could be found.

The inert plasticizing additive located on the near-surface zones of the driver is preferably camphor (CAS # 76-22-2). Also included are aromatic urea derivatives such as diethyldiphenylurea (CAS # 85-98-3), dimethyldiphenylurea (CAS # 61 1-92-7), ethyldiphenylcarbamates (CAS # 603-52-1), N-methyl-N-phenylurethanes ( CAS # 2621-79-6) or ester compounds such as diethyl phthalate (CAS # 84-66-2), dibutyl phthalate (CAS # 84-74-2), diamyl phthalate (CAS # 131-18-0), di- n-propyl adipate (CAS # 106-19-4) in question or compounds analogous to those homogeneously distributed in the grain matrix. The inert plasticizing additive can also be applied as a combination of several individual compounds.

Examples of the inert plastic additive are acetyl triethyl citrate (CAS #: 77-89-4), triethyl citrate (CAS #: 77-93-0), tri-n-butyl citrate (CAS #: 77-94-1), Tributyl acetylcitrate (77-90-7), acetyltri-n-butyl citrate (CAS #: 77-90-7), acetyltri-n-hexyl citrate (CAS #: 24817-92-3), n-butyryltri-n -hexyl citrate (CAS #: 82469-79-2), di-n-butyl adipate, diisopropyl adipate (CAS #: 6938-94-9), diisobutyl adipate (CAS #: 141-04-8 ), Di-ethylhexyl adipate (CAS #: 103-23-1), nonyl undecyl adipate, n-decyl-n-octyl adipate (CAS #: 110-29-2), dibutoxyethoxy ethyl adipate, dimethyl adipate (CAS #: 627-93-0), hexyl octyl decyl adipate, diisononyl adipate (CAS #: 33703-08-1), di-n-butyl sebacate (CAS). #: 109-43-3), dioctyl sebacate (CAS #: 122-62-3), dimethyl sebacate (CAS #: 106-79-6), di-n-butyl phthalate (CAS # : 84-74-2), di-n-hexyl phthalate (CAS #: 84-75-3), di-nonyl undecyl phthalate (CAS No. 111381-91-0), nonyl undecyl phthalate (685-15-43-5), mixtures of largely linear C4-C11 alkyl phthalates (CAS #: 85507-79- 5, 111381-91-0, 68515-45-7, 68515-44-6, 68515-43-5, 111381-89-6, 111381-90-9, 28553-12-0), dioctyl terephthalate (CAS - #: 6422-86-2), dioctyl isophthalates (CAS #: 137-89-3), 1,2-cyclohexanedicarboxylic acid diisononyl ester (CAS #: 166412-78-8), dibutyl maleate (CAS #: 105-76-0), dinonyl maleate (CAS #: 2787-64-6), diisooctyl maleate (CAS #: 1330-76-3), dibutyl fumarate (CAS #: 105-75-9 ), Dinonyl fumarate (CAS #: 2787-63-5), dimethyl sebacate (CAS #: 106-79-6), dibutyl sebacate (CAS #: 109-43-3), diisooctyl sebacate (CAS #: 27214-90-0), dibutyl azelate (CAS #: 2917-73-9), diethylene glycol dibenzoate (CAS #: 120-55-8 ), Trioctyl trimellate (CAS #: 89-04-3), trioctyl phosphate (CAS #: 78-42-2), butyl stearate (CAS #: 123-95-5), glycerol triacetate (CAS # : 102-76-1), epoxidized soybean oil (CAS #: 8013-07-8), epoxidized linen seed oil (CAS #: 8016-11-3).

The inert plasticizing additives are also available in part under the following trade names: Hexamoll Dinch from BASF, Citroflex types from Reilly-Morflex Inc., Greensboro, North Carolina USA, and the like. A-2, A-4, A-6, C-2, C-4, C6, B-6, Paraplex types from C. P. Hall Co. Chicago, Illinois USA, et al. G25, G30, G51, G54, G57, G59, Santicizer types from the company Ferro Corporation, Cleveland, Ohio USA, 261, 278, palatinol types from BASF, Germany.

If the inert plasticizing additive is localized in the near-surface zones of the powder grain, it has a penetration depth of a few 100 micrometers. The penetration depth (i.e., the depth to which at least 95% by weight of the additive is contained) is e.g. maximum 400 microns. If the additive is introduced into the grain in this way, the greatest possible effect can be achieved with minimal amounts. This means that the grain volume contains no more inert substances than necessary, which results in a maximum amount of energy-containing material for a given amount of powder. Preferably, penetration depths in the range of 100-300 micrometers are used.

The drive according to the invention is excellently suited for small and medium caliber ammunition, i. the powder grains have a maximum geometric extension of 20 mm.

The geometric dimensions of the inventive propellant charge powder are determined primarily by the caliber range. Thus, the powder grains for small caliber applications (caliber range from about 5.56 to about 20 mm) on the one hand have cylindrical geometries with a diameter of about 0.5 - 3 mm, wherein the length of a powder grain is typically about 0.5-2.0x of the value of the respective grain diameter , In addition, cylindrical powders may contain longitudinal channels extending in the axial direction to influence the burning behavior. In practice, 1-, 7- and 19-hole geometries have particularly proven, wherein the diameter of the hole zones is typically between 0.05 to 0.5 mm.

For medium-caliber applications (caliber range from 20 mm to about 50 mm), experience has shown that the cylindrical grain geometry with a diameter of about 1.0 to 10 mm, wherein the length of a powder grain is typically about 0.5 to 2.0 times the value of the respective grain diameter , To control the Abbrandcharakteristik more extending in the axial direction longitudinal channels are normally included in the powder grain. Powder grains with 1, 7 or 19 longitudinal channels, whose diameters are typically 0.05-0.5 mm, have proven particularly useful.

For large caliber applications (caliber range from 60 mm to about 155 mm), the cylindrical grain geometry with a diameter of about 3 to 25 mm has been found to be useful, the length of a powder grain typically being 0.5 to 2 times the value of the respective grain diameter is. To control the Abbrandcharakteristik more extending in the axial direction longitudinal channels are normally included in the powder grain. Powder grains with 7, 19 and 51 longitudinal channels, whose diameters are typically 0.05 to 0.5 mm, have proven particularly useful. In addition, so-called strip powders have proven themselves for large-caliber applications. Their cross section is typically rectangular with a thickness of 0.5-5 mm and a width of 3.0-20 mm. The length is typically in the range of 5 - 50 cm.

The drive according to the invention can also be designed as a so-called shaped body. In this case, the drive additionally assumes the function of the sleeve and comes in so-called caseless ammunition used. Conceivable applications are in the caliber ranges of 4.6 - 155 mm, the geometry of such moldings is adapted to the particular application.

A method for producing a drive according to the invention is characterized in that a green grain is produced by pressing a solvent-containing powder dough of nitrocellulose and a crystalline energy carrier based on nitramine in a strand press or by extrusion.

The drives resulting from the combination according to the invention of a crystalline energy carrier based on nitramine with an inert additive in a grain matrix, the binder of which consists predominantly of nitrocellulose, can be produced on existing production facilities. The solid formulation components may e.g. be mixed with a solvent mixture. The resulting kneading dough can be kneaded in a kneader and then extruded in a press to the desired geometry. The completion to the desired drive can be done by washing, drying and cutting to the desired grain length. To improve the connection to the gelled nitrocellulose grain matrix and thus to optimize the desired effects, the crystalline nitramine compound may be subjected to a suitable pretreatment. The bulk densities of the novel drives are high and, depending on the geometry, can amount to well over 1060 g / l, which is important for achieving the high internal ballistic performance.

Preferably, a powder dough is used which results in a green grain having at least 60% by weight nitrocellulose, the nitrogen content of the nitrocellulose being between 11-13.5% by weight.

The nitrogen content of the nitrocellulose is particularly preferably between 12.6-13.25% by weight, the inert plasticizing plasticizer homogeneously distributed in the matrix is a polyester compound (preferably polyester compound having 2-10 ester groups per molecule such as citrates, phthalates, sebacinates and adipates having a molecular weight of 100 - 5000 g / mol, and the enriched in the near-surface zones of the drive inert plasticizer is an organic substance containing oxygen atoms and having a molecular weight of 100 - 5000 g / mol.

Of course, other additives known per se can also be used for the powder according to the invention. Sodium hydrogen carbonate (CAS #: 144-55-8), calcium carbonate (CAS #: 471-34-1), magnesium oxide (CAS #: 1309-48-4), acardite II (CAS #: 724-18-5), Centralit I (CAS #: 90-93-7), Centralit II (CAS #: 61 1-92-7), 2-Nitrodiphenylamine (CAS #: 836-30-6) and diphenylamine (CAS #: 122-39-4), for example, magnesium oxide (CAS #: 1303-48-4), molybdenum trioxide (CAS # : 1313-27-5), magnesium silicate (CAS #: 14807 -96-6), calcium carbonate (CAS #: 471-34-1) or titanium dioxide (CAS #: 13463-67-7), tungsten trioxide (CAS #: 1314-35-8), and, for fire suppression, for example, sodium oxalate (CAS #: 62-76-0), potassium bitarate (CAS #: 868-14-4), sodium bicarbonate (CAS #: 144-55-8), potassium bicarbonate (CAS #: 298-14-6), sodium oxalate (CAS #: 62-76-0), potassium sulfate (CAS #: #: 7778-80-5) or potassium nitrate (CAS #: 7757-79-1). Furthermore, the green powder may contain other known additives, for example for improving the ignition behavior and for modulating the burn-off behavior.

From the following detailed description and the totality of the claims, further advantageous embodiments and feature combinations of the invention result.

Brief description of the drawings

Fig. 1

Eine Munition nach der Einwirkung eines Hohlladungsstrahls;

Fig. 2

eine Munition nach der Einwirkung heisser Fragmente;

Fig. 3

eine Munition nach der Einwirkung eines Hohlladungsstrahls,

Fig. 4

eine Munition nach dem Kugeleinschuss (eng!. Bullet Impact) in einer 35 mm Stahlhülse;

The drawings used to explain the embodiment show:

Fig. 1

An ammunition after the action of a shaped charge jet;

Fig. 2

an ammunition after exposure to hot fragments;

Fig. 3

an ammunition after the action of a shaped charge jet,

Fig. 4

an ammunition after bullet impact (bullet impact!) in a 35 mm steel sleeve;

Ways to carry out the invention

In the examples explained below, all of the additives mentioned during the green-grain production have been added to the powder dough, ie they are uniformly distributed in the matrix. The total amount of these additives in the green grain is between 0-10 wt .-% compared to the nitrocellulose, preferably between 2-7 wt .-%. The production of the drives includes, among other things, the process steps "kneading with solvents", "extrusion through die", "drying" and "finishing" (surface treatment). The crystalline nitramine compound, which may need to be subjected to a pretreatment to improve the attachment to the matrix, and in the matrix homogeneously distributed inert plasticizing plasticizers are added to the putty. The inert plasticizing plasticizer located in the near-surface zone of the drive is applied either by impregnation of a "green grain" in aqueous emulsion or in a surface treatment process (finishing) together with other additives such as graphite.

example 1

There are 5 kg of heated to 60 ° C 7-hole green powder prepared by a powder dough from the solid portions of 25 wt .-% RDX, 1.8 wt .-% acardite II, 0.4 wt .-% potassium sulfate, 0.2 wt .-% lime, 0.1 wt .-% manganese oxide, 1.5 wt .-% of a phthalic acid ester (which consists mainly of linear C9-C11 alcohols having an average molecular weight of 450 g / mol and having an average dynamic viscosity at 20 ° C of 73 mPa * s constructed) and nitrocellulose with a nitrogen content of 13.20 wt .-% (supplement to 100%) are processed to a solvent-moist kneading dough and this pressed through a die (ie extruded) is. The extruded powder grains have 2.53 mm outer diameter, 3.08 mm length, 0.53 mm wall thickness and 0.12 mm hole diameter. The green powder thus prepared is placed in a preheated to 60 ° C polishing drum made of copper with about 50 liters of internal volume.

Subsequently, the powder mass 7.5 g of powdered graphite (0.15 wt .-%) are added, followed by a solution of 200 g of camphor in 225 ml of ethanol. Then allowed to act at a speed of 24 revolutions per minute for 2 hours, the solvent evaporates gradually through the open front opening. Thereafter, the powder is removed from the polishing drum and dried at 60 ° C for 24 hours.

The resulting bulk powder has the following properties:

Physical properties: Bulk density = 1024 g / l, heat content = 3580 J / g.

Chemical stability: deflagration temperature = 179 ° C. Heat flow calorimetry (STANAG 4582) = 12 J / g resp. 14.4 μW (requirement according to STANAG 4582: maximum heat development after 5 J / g: <114 μW).

Figure 1 shows that vulnerability to Bullet Impact results in a Type V (burn) reaction.

Fig. 2 illustrates the result when bombarded by hot fragments. Fig. 3 shows the result when bombarded with a shaped charge jet. It should be noted that in both cases there is a type V (burn-up) reaction. It remains a single piece, but the powder is burned.

Internal ballistic properties:

System: 30 mm full caliber ammunition with bullet mass of 405 g, sleeve 30 mm x 173, 30 mm Bushmaster II pressure tester (MANN-barrel), speed measurement optically in 2 m and 5 m after muzzle, pressure measurement Kistler 6215 piezoelectric.

Single-base comparison powder: length = 2.17 mm, diameter = 2.29 mm, wall thickness = 0.5 mm, hole diameter = 0.11 mm, energy content = 3403 J / g, bulk density = 1039 g / l. shelling temperature -54 ° C -32 ° C + 21 ° C + 52 ° C + 71 ° C Powder from Preparation Example 1 Charge mass = 174 g Muzzle velocity [m / s] 1099 1112 1124 1118 1103 Top gas pressure [bar] 3641 3933 4189 3951 3589 Monobasic comparison powder Charge mass = 174 g Muzzle velocity [m / s] 1091 Top gas pressure [bar] 4329

From the table it follows that the propellant charge powder according to the invention has a flat temperature profile. The speed variation of 12 m / s in the range of -32 ° C to + 52 ° C is low. Compared to the prior art (monobasic comparison powder), the muzzle velocity is higher by 30 m / s. In addition, the peak gas pressure is smaller, which allows a higher speed (about +50 m / s) with optimum utilization of the approved gas pressure.

Example 2:

Analogously to Example 1, a 7-hole green powder with 5.49 mm outer diameter, 13.60 mm length, 0.43 mm hole diameter and 1.05 mm wall thickness, composed of the solid portions of 10 wt .-% RDX, 2.0 wt .-% Akardit II, 2.0 wt .-% potassium sulfate, 5.0 wt .-% of a phthalic acid ester (which consists of predominantly linear C9-C11 alcohols having an average molecular weight of 450 g / mol and having an average dynamic viscosity (20 ° C) of 73 mPa * s and nitrocellulose having a nitrogen content of 12.6% by weight (supplement to 100%) in the manner mentioned by pressing a solvent-moist kneading dough through a die. The resulting powder has the following properties:

Physical properties: Bulk density = 855 g / l, heat content = 3190 J / g.

Chemical stability: deflagration temperature = 178 ° C. Heat flow calorimetry (STANAG 4582) = 7.8 J / g resp. 8 μW (requirement according to STANAG 4582: maximum heat development after 5 J / g: <114 μW). Stability test 132 ° C TL: 2.75 ml NaOH.

Vulnerability 1: Test: 35mm combination test (after Rheinmetall, Unterlüss, Germany). Action of shaped charge jet: reaction type V (burnup), action of hot fragments: reaction type V (burnup).

Example 3:

Analogously to Preparation Example 1, a 7-hole green powder with 2.05 mm outside diameter, 2.30 mm in length, 0.13 mm hole diameter and 0.41 mm wall thickness, composed of the solid portions of 25 wt .-% RDX, 1.5 wt .-% acardite II, 0.4 Wt .-% potassium sulfate, 2.5 wt .-% of a phthalic acid ester (composed of predominantly linear C9-C11 alcohols having an average molecular weight of 450 g / mol and having an average dynamic viscosity (20 ° C) of 73 mPa * s) and Nitrocellulose with a nitrogen content of 13.2 wt .-% (supplement to 100%) prepared by pressing a solvent-moist kneading dough through a die. Analogously to Example 1, 5 kg of this green powder in the polishing drum at 60 ° C with 10 g of graphite (0.2 wt .-%) and 125 g Camphor (2.5 wt .-%), dissolved in 180 ml of ethanol, treated. The resulting powder has the following properties:

Physical properties: Bulk density = 1042 g / l, heat content = 3808 J / g.

Chemical stability: deflagration temperature = 178 ° C. Stability 132 ° C TL: 5.52 ml NaOH.

4 shows a bullet impact ammunition in a 35 mm steel sleeve; There is a reaction type V (burnup).

Inner Ballistic Properties: Energy Content = 3824 J / g)

System: 25 mm APFSDS-T arrow ammunition with projectile mass of 129g (M919), sleeve 25mm x 137, 25mm Bushmaster M242 pressure tester (MANN-barrel), speed measurement optically in 4.2m and 14.9m after muzzle, pressure measurement Kistler 6215 piezoelectric. Charge mass = 100.0 g.

For comparison purposes, the propellant charge powder used in the M919 ammunition (energy content 3956 J / g) was shot with a charge mass of 101.0 g. Powder from Example 4, charge 100 g 21 ° C 50 ° C 71 ° C -54 ° C Muzzle velocity [m / s] 1430 1439 1445 1403 Top gas pressure [bar] 4135 4333 4409 3896 Action time [ms] 2.88 2.78 2.79 3.19 Thermal efficiency [%] 34.5 35.4 35.7 33.2 Comparative powder, charge 101 g 21 ° C 50 ° C 71 ° C -54 ° C Muzzle velocity [m / s] 1425 - 1430 1361 Top gas pressure [bar] 4150 - 4404 3436 Action time [ms] 3.12 - 2.87 3.62 Thermal efficiency [%] 32.7 - 33.0 29.9

It can be seen that the muzzle velocity despite higher energy content and lower charge mass at 21 ° C by 5 m / s higher than the introduced reference powder. In the cold region, the drop of V ₀ and Pmax is significantly lower, ie the temperature characteristic is advantageous. In addition, the action times and the thermal efficiencies (energy conversion) over the entire temperature range are clear better, which leads in practice to massive benefits (residue-free combustion, better hit pattern).

The action time is shorter, i. burnup is faster. The speed is 1430 m / s instead of only 1425 m / s. Particularly noteworthy is the better use of energy, e.g. 34.5% compared to 32.7%.

The test shows that, despite 130 J / g lower energy content compared to the prior art comparative example, one obtains outstanding performance at lower gas pressure.

Example 4

Analogous to Example 1, a 7-hole green powder with 2.32 mm outer diameter, 2.62 mm length, 0.14 mm hole diameter and 0.47 mm wall thickness, composed of the solid portions of 25 wt .-% RDX, 1.5 wt .-% Akardit II, 0.4% by weight potassium sulfate, 2.0% by weight of a phthalic acid ester (composed of predominantly linear C 9 -C 11 -alcohols having an average molecular weight of 450 g / mol and having an average dynamic viscosity (20 ° C.) of 73 mPas) and nitrocellulose having a nitrogen content of 13.2% by weight (supplement to 100%) by pressing a solvent-moist kneading dough through a die. Analogously to Example 1, 5 kg of this green powder are treated in the polishing drum at 60 ° C. with 12.5 g of graphite (0.25% by weight) and 100 g of camphor (2.0% by weight) dissolved in 170 ml of ethanol. The resulting powder has the following properties:

Physical properties: Bulk density = 1051 g / l, heat content = 3900 J / g.

• +21 °C: v₀ = 1151 m/s bei 4095bar. Aktionszeit t₄ = 3.55ms.
• +50°C: v₀= 1154m/s bei 4136bar. Aktionszeit t₄ = 3.50ms.
• +71 °C: v₀ = 1158m/s bei 4275bar. Aktionszeit t₄ = 3.43ms.
• -54°C: v₀ = 1150m/s bei 4084bar. Aktionszeit t₄ = 3.56ms.

Internal ballistic properties in 25 mm full caliber ammunition with a bullet mass of 205 g, sleeve 25mm x 137, 25mm Bushmaster M242 pressure tester (MANN-barrel), speed measurement optically in 12.5m and 17.2m after muzzle, pressure measurement Kistler 6215 piezoelectric. The charge mass was 92.0 g, which corresponds to a degree of filling of 0.939.

• +21 ° C: v ₀ = 1151 m / s at 4095bar. Action time t ₄ = 3.55ms.
• + 50 ° C: v ₀ = 1154m / s at 4136bar. Action time t ₄ = 3.50ms.
• +71 ° C: v ₀ = 1158m / s at 4275bar. Action time t ₄ = 3.43ms.
• -54 ° C: v ₀ = 1150m / s at 4084bar. Action time t ₄ = 3.56ms.

The muzzle velocity at + 21 ° C is about 70 m / s higher than with a normal monobasic TLP. In addition, the temperature characteristic over the very wide temperature range of -54 ° C to + 71 ° C is extremely flat. The t ₄ -action times are very short over the entire temperature range and serve as evidence for the surprisingly rapid thermal conversion of the new powder type. At + 21 ° C, the thermal efficiency is 40%, ie the internal energy of the new powder type is very well implemented.

Example 5:

• Physikalische Eigenschaften: Schüttdichte = 916 g/l, Wärmeinhalt = 3255 J/g.
• Chemische Stabilität: Verpuffungstemperatur = 179 °C. Wärmeflusskalorimetrie (STANAG 4582) = 12.1 J/g resp. 14 µW (Anforderung nach STANAG 4582: maximale Wärmeentwicklung nach 5 J/g: <114 µW).
• Verwundbarkeit 1: Test: 35mm-Kombinationstest (nach Rheinmetall, Unterlüss, Deutschland). Einwirkung Hohlladungsstrahl: Reaktion Typ A (V, Abbrand), Einwirkung heisse Fragmente: Reaktion Typ A (V, Abbrand)).
• Verwundbarkeit 2: Test: Bullet Impact Test in UN-Stahlrohr: Reaktion Typ V (Abbrand)

Analogous to Example 1, a 7-hole green powder with 5.56 mm outer diameter, 13.59 mm length, 0.48 mm hole diameter and 1.03 mm wall thickness, composed of the solid portions of 15 wt .-% RDX, 2.0 wt .-% Akardit II, 2.0% by weight potassium sulfate, 2.5% by weight of a phthalic acid ester (composed of predominantly linear C 9 -C 11 -alcohols having an average molecular weight of 450 g / mol and having an average dynamic viscosity (20 ° C.) of 73 mPas) and nitrocellulose having a nitrogen content of 12.6% by weight (100% completion) in the manner known in the powder art by compression of a solvent-wet kneading dough with a die. 5 kg of this green powder in the polishing drum at 60 ° C with 10 g of graphite (0.2 wt .-%) and 150 g camphor (3.0 wt .-%), dissolved in 200 mi Ethanoi, treated analogously to Example 1. The resulting powder has the following properties:

• Physical properties: Bulk density = 916 g / l, heat content = 3255 J / g.
• Chemical stability: deflagration temperature = 179 ° C. Heat flow calorimetry (STANAG 4582) = 12.1 J / g resp. 14 μW (requirement according to STANAG 4582: maximum heat development after 5 J / g: <114 μW).
• Vulnerability 1: Test: 35mm combination test (after Rheinmetall, Unterlüss, Germany). Action of shaped charge jet: reaction type A (V, burnup), action of hot fragments: reaction type A (V, burnup)).
• Vulnerability 2: Test: Bullet Impact Test in UN Steel Tube: Reaction Type V (burnup)

In summary, it should be noted that the nitrocellulose-containing propellant charge powders according to the invention, which contain a crystalline energy carrier based on nitramine and an inert plasticizing additive, in the caliber ranges from 5.56 mm (small caliber) to 155 mm (medium to large caliber, mortar) on a broad front Acceleration of the respective projectile can be used. The new drives have a high ballistic performance and can therefore be used in high-performance applications such as KE ammunition (arrow ammunition) or in full-caliber applications (airburst, ammunition in tanks, artillery and aircraft) without compromise.

The use of nitrocellulose as the main constituent of the grain matrix (= binder) offers advantages because the starting materials are freely available, renewable and inexpensive, because the production of the propellant charge powders can be produced with known processes in existing series plants, as well as better reproducibility (high uniformity) of the product properties entail.

The use of relatively high amounts of nitrocellulose in the matrix has a positive effect on the mechanical properties, in particular in the cold range at temperatures of <0 °. The mechanical properties of plastic-bonded LOVA-TLP with high levels of crystalline energy carrier filling are less good, i. Such TLPs are relatively brittle or become brittle as they age. In mechanical action, as occurs during the firing or by enemy bombardment of ammunition, such powder grains can break down, resulting in dangerous pressure increases resp. leads to detonative reactions. The new IM-TLPs to be protected hereby have advantages with regard to cold embrittlement. Dangerous pressure increases during the firing of ammunition and detonating implementations of the ammunition in enemy bombardment of the ammunition by hot fragments, balls or shaped charge jets are thus effectively prevented.

The new IM drives have better chemical stability compared to conventional monobasic and nitroglycerin-containing two- and three-base TLPs, resulting in Improvements in cook-off strength (shelf life at high temperatures) is reflected. This is of great advantage for applications in aircraft ammunition with high thermal load peaks or when using the ammunition in warm climates.

The new IM drives are characterized by the fact that their content of chemical energy (heat content) can be converted in high conversion rates into kinetic muzzle energy of the powered projectile. In sub-caliber ammunition types, the efficiencies are up to 36%, while maintaining the weapon-side system requirements, at a high speed level, as previously only available from TLPs, e.g. from EP 1'164'116 B1 ("EI®-TLP") has been achieved (i.e., about 50 m / s more than conventional monobasic TLP). In full-caliber applications, efficiencies of up to 44% are achieved, while maintaining weapon-side system requirements (compared to 39% with EI®-TLP).

The new IM drives are generally characterized by a very neutral temperature characteristic, which can be targeted and controlled via the layered structure. This means that the values of peak gas pressure and muzzle velocity at hot and cold temperatures differ only slightly compared to those recorded at 21 ° C. This causes the ammunition to be fired over virtually the entire temperature range with virtually the same internal ballistic performance regardless of the ambient temperature. This behavior, already familiar from EI®-TLP, brings advantages in terms of first hit probability, exploitation of system-related power reserves and constructive simplicity.

Claims (15)

Drive for accelerating bullets, which is based on nitrocellulose, characterized in that it contains a crystalline energy carrier based on nitramine and an inert plasticizing additive. Drive according to claim 1, characterized in that it consists of grains having a circular cylindrical geometry and extending in the axial direction of the longitudinal channels. Drive according to claim 1 or 2, characterized in that the crystalline energy carrier based on nitramine contains a nitramine compound of general chemical structural formula RN-NO ₂ , wherein R is a radical. Drive according to Claim 3, characterized in that the nitramine compound is present in a concentration in the range from 1 to 35% by weight, in particular in the range from 5 to 25% by weight. Drive according to one of claims 3 or 4, characterized in that the nitramine compound is RDX. Drive according to one of claims 1 to 5, characterized in that the inert plasticizing additive is present in a matrix of the drive substantially homogeneously distributed. Drive according to one of claims 1 to 6, characterized in that the inert plasticizing additive has a concentration in the range of 0.5 to 20 wt .-%. especially in the range of 1 - 5 wt .-% has. Drive according to one of claims 1 to 7, characterized in that the inert plasticizing additive is a substantially water-insoluble organic Polyoxoverbindung, in particular a polyester or polyether compound having a molecular weight of 50 - 20,000 g / mol. Drive according to Claim 8, characterized in that the inert plasticizing additive contains a water-insoluble citrate ester, an adipic acid ester, a sebacic acid ester or a phthalic acid ester and / or hydrogenated cyclohexyl derivatives thereof having a molecular weight of 100-20,000 g / mol. Drive according to one of claims 1 to 9, characterized in that it contains an increased concentration of inert plasticizing additive in near-surface zones and that in said near-surface zones of the inert plasticizing additive, a carboxyl-containing organic compound having a molecular weight of 100 - 5000 g / l is and has a concentration of not more than 10 wt .-%, in particular less than 6 wt .-%. Drive according to claim 9, characterized in that the inert plasticizing additive is essentially camphor. Drive according to one of claims 10 or 11, characterized in that the increased concentration of the inert plasticizing additive in the near-surface zones is limited to a penetration depth of a maximum of 400 microns. Drive according to one of claims 1 to 12, characterized in that it consists of grains of a maximum geometric extent of 20 mm. Process for the preparation of a drive based on nitrocellulose, characterized in that a solvent-based powder dough based on nitrocellulose and a crystalline energy carrier based on nitramine and an inert plasticizing additive is prepared and that a green grain is produced by extruding the solvent-containing powder dough. Process according to Claim 14, characterized in that the powder dough contains at least 60% by weight of nitrocellulose, the nitrogen content of the nitrocellulose being between 11-13.5% by weight.

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