Combustible propellant case

Abstract

Combustible propellant case for ammunition fired from a gun barrel, comprising - pulp, - Nitrocellulose, - 5 - 10 wt.% MO3 particles, based on the total weight of the propellant case, where M = Mo and / or W, and - 0.01 - 2 wt.% cationic surfactant, based on the total weight of the propellant case, wherein the average particle size d 50 the MO3 particles are 0.5 - 2.0 µm, the maximum particle size d 100 the MO3 particles are ≤ 15 µm, and the quotient of the average MO3 concentration in wt.% in a volume element of about 0.05 to 1.0 cm 3 (c VE ) at any point in the propellant case and the total MO3 concentration in wt.% (c] ges ) in the propellant case c VE : c ges = 0.80 - 1.20.

Description

[0001] The present invention relates to a combustible propellant case with MoO3 and / or WO3 particles and a method for producing the combustible propellant case.

[0002] When ammunition is fired from a gun barrel, the burning of the propellant powder creates high temperatures and pressures, which lead to severe wear on the gun barrels, especially in the case of large-caliber projectiles such as those used in artillery guns and tanks.

[0003] To reduce wear, erosion-reducing additives, such as wax or paraffin, can be added to the propellant powder or the combustible propellant case enclosing the propellant powder, as described in DE 39 27 400 A1.

[0004] EP 1 227 295 A2 describes that erosion-reducing additives can be added to a propellant case in the form of oxides of rare earth elements or one of the elements of the sixth subgroup of the periodic table or polyoxymethylene.

[0005] EP 1 647 538 A2 describes the addition of polyacetylene or a mixture of WO3 or MoO3 and CeO2 or La2O3 or Y2O3 in the form of particles to a propellant case to reduce erosion.

[0006] EP 1 319 919 B1 describes a method for producing a combustible casing for cartridge ammunition, wherein an aqueous pulp containing nitrocellulose and cellulose fibers is produced, from the pulp a raw felt is produced by dewatering the fiber material on a screen mold, and the raw felt is then pressed.

[0007] US 3 204 558 A describes wear-reducing additives for gun barrels.

[0008] Tungsten trioxide (WO3) and molybdenum trioxide (MoO3), when added to the propellant case, can reduce barrel erosion and thus barrel wear to a certain extent, presumably by trapping atomic hydrogen. However, barrel wear of this ammunition still needs to be improved to reduce maintenance requirements, increase the service life of the weapon barrels, and especially to improve the accuracy of firing the ammunition, as an eroded barrel significantly reduces firing accuracy.

[0009] Therefore, it is an object of the invention to reduce barrel wear in ammunition fired from a weapon barrel, in particular in artillery or tank barrels.

[0010] This object is achieved by a combustible propellant charge casing according to patent claim 1 and a method for producing a combustible propellant charge casing according to patent claim 9. Further features, embodiments and advantages emerge from the dependent claims and the description.

[0011] One aspect of the invention relates to a combustible propellant case for ammunition fired from a weapon barrel, comprising - pulp, - Nitrocellulose, - 5 - 10 wt.% MO3 particles, based on the total weight of the propellant case, where M = Mo and / or W, and - 0.01 - 2 wt.% cationic surfactant, based on the total weight of the propellant case, where the mean particle size d 50 the MO3 particles are 0.5 - 2.0 µm, the maximum particle size d 100the MO3 particles are ≤ 15 µm, and the quotient of the average MO3 concentration in wt.% in a volume element of about 0.05 to 1.0 cm 3 (c VE ) at any point in the propellant case and the total MO3 concentration in wt.% (c ges ) in the propellant case C VE : C ges = 0.80 - 1.20.

[0012] A further aspect of the invention relates to a method for producing a combustible propellant charge casing, comprising the steps (a) preparing a slurry of cellulose, nitrocellulose, MO3 particles, where M = Mo and / or W, and cationic surfactant in water, (b) mixing the slurry, (c) dewatering the slurry on a screen to produce a raw felt, (d) pressing the raw felt and (e) Drying to form a combustible propellant case.

[0013] According to the invention, MO3 particles are understood to mean MoO3 particles (molybdenum trioxide particles) or WO3 particles (tungsten trioxide particles). WO3 particles are preferred.

[0014] Within the scope of the invention, it was found that propellant charge cases of the prior art with metal oxide particles such as MoO3 or WO3 particles exhibit strong concentration fluctuations of the metal oxides in the propellant charge case and that this is at least one factor for the still excessive barrel wear after firing ammunition with corresponding propellant charge cases.

[0015] Surprisingly, the use of a cationic surfactant in the manufacturing process results in a relatively uniform and small particle size of the MoO3 and / or WO3 particles and a smaller concentration variation of the MoO3 and / or WO3 in the combustible propellant case, thus avoiding temperature and pressure peaks during firing and thereby reducing barrel wear.

[0016] Without being bound by the invention, it is assumed that the cationic surfactant, in conjunction with a relatively small particle size and narrow particle size distribution, counteracts sedimentation of the MoO3 and WO3 particles during the manufacturing process, thereby promoting effective recrystallization of the MoO3 and WO3 in the pulp (slurry) and thus enabling a relatively uniform particle size distribution. On the other hand, the dispersing effect of the surfactant, i.e. keeping the MoO3 and / or WO3 particles in suspension, promotes attachment of the particles to the fibers of the nitrocellulose and the pulp, thereby preventing the MoO3 and / or WO3 particles from sinking as a result of gravity. This leads to less fluctuation in the concentration of the MoO3 and / or WO3 particles in the finished propellant case.This is particularly relevant for the MoO3 and WO3 particles used in the invention, since the density of these substances is particularly high.

[0017] The particle size and particle size distribution are determined using laser diffraction in a wet measurement (Malvern system, Mastersizer E, wet measurement in water in a cuvette). This yields a particle size distribution curve. x means that x volume percent of the particles have a diameter that is smaller than the specified value. For a d 50 -value (average particle size) of, for example, 1 µm, 50 vol.% of the particles have a diameter ≤ 1 µm (micrometer). 100 -value (maximum particle size) of 10 µm, 100 vol.% of the particles have a diameter ≤ 10 µm.

[0018] For the purposes of the invention, a surfactant is understood to be a substance that is surface-active and thus reduces the surface tension of a liquid or the interfacial tension between two phases, thus supporting the formation of dispersions such as suspensions. Cationic surfactants have positively charged groups, such as quaternary ammonium groups.

[0019] For the purposes of the invention, polyamines are understood to be saturated, open-chain and / or cyclic organic compounds having terminal amino groups and optionally secondary and tertiary amino groups. Such a polyamine can be prepared, for example, by reacting ethylenediamine and / or propylenediamine with ethylene oxide with complete or almost complete substitution of the oxygen atoms. Furthermore, for example, a reaction of ethylenediamine and / or propylenediamine with epichlorohydrin with complete or almost complete substitution of the oxygen and chlorine atoms is possible. Such polyamines can be present in oligomeric or polymeric form. A cationic surfactant derived from a polyamine is, for example, the salt of a polyamine with an acid, such as acetic acid. Preferred is a surfactant available under the trade name Paragas.Paragas is a mixture of different compounds, essentially the salt of a polyethyleneamine / imine with an acid.

[0020] The combustible propellant case according to the invention contains 0.01 - 2 wt.% cationic surfactant, preferably 0.05 - 1 wt.%, more preferably 0.07 - 0.8 wt.%, even more preferably 0.1 - 0.6 wt.%, particularly preferably 0.3 - 0.5 wt.% cationic surfactant.

[0021] The combustible propellant case according to the invention is characterized in that the concentration of the MoO3 and / or WO3 particles in the propellant case is more constant than in propellant case of the prior art, in which the concentration fluctuates greatly within the propellant case and is also subject to strong fluctuations from case to case. A concentration difference of an average value of, for example, 8 wt.% of -3 wt.% within known propellant case, i.e. a minimum value of 5 wt.%, is usual. In the propellant case according to the invention, in contrast, the concentration fluctuations of the MoO3 and / or WO3 particles are smaller, preferably ≤ 1.5 wt.%, more preferably ≤ 1.0 wt.%, particularly preferably ≤ 0.7 wt.%, in particular ≤ 0.5 wt.%. In the axial direction of the propellant case, the concentration fluctuations are preferably even smaller, preferably ≤ 1.0 wt.%, more preferably ≤ 0.5 wt.%,

[0022] The MoO3 and WO3 concentrations are measured wet-chemically by cutting out, for example, a piece of the propellant case, e.g., punching it out, measuring 1 cm × 1 cm × the wall thickness of the propellant case (usually 3.3 mm). This piece is destroyed by fuming with concentrated nitric acid and then ashing in a muffle furnace at 800 °C. The ash content of the preliminary sample (nitrocellulose pulp and cellulose without WO3) as well as the loss on ignition of the tungsten trioxide are taken into account. By determining the residual moisture content in the sample, the analytical result can be expressed as a dry substance. w(talc,WO3)=moutweigh⋅106minitial weight⋅(100−w(H2O))⋅(100−GV)−w(ash) m Auswaage = Mass of the pellet used after annealing [g] m Einwaage = Mass of the pellet used before annealing [g] w(H2O) = water content of the pellet used[%] GV = Loss on ignition of talc or tungsten trioxide [%] w(ash) = ash content of the preliminary sample, calculated on dry matter [%]

[0023] To determine the total MoO3 and / or WO3 concentration, a wet-chemical measurement is carried out on the entire propellant case according to the above procedure. Alternatively, at least three wet-chemical measurements of approximately 0.05 to 1.0 cm each can be carried out according to the above procedure. 3 volume at randomly selected locations on the propellant case and the arithmetic mean is calculated. The total MoO3 and / or WO3 concentration (c ges ) in the propellant case is the total mass of MoO3 and / or WO3 in the propellant case divided by the total mass of the propellant case.

[0024] The quotient of the average MO3 concentration in wt% in a volume element of about 0.05 to 1.0 cm 3 (c VE) at any point in the propellant case and the total MO3 concentration in wt.% (c ges ) in the propellant case is c VE : C ges = 0.80 - 1.20, preferably 0.85 - 1.15, most preferably 0.90 - 1.10, with M = Mo and / or W, preferably W.

[0025] The volume element from 0.05 to 1.0 cm 3 preferably has a volume of about 0.1 to 0.8 cm 3 , more preferably about 0.2 to 0.6 cm 3 , in particular about 0.33 cm 3 More preferably, it is a continuous volume element. In a preferred embodiment of the invention, the volume element has the wall thickness of the propellant charge case. A propellant charge case typically has a length of approximately 30-90 cm (centimeters), a diameter of 100-160 mm (millimeters), and a wall thickness of approximately 2-4 mm, in particular 3.3 mm.

[0026] Preferably, the volume element for the determination of c VEa size of 0.5 cm × 0.5 cm × 0.2 cm to 1.5 cm × 1.5 cm × 0.4 cm, preferably 0.5 cm × 0.5 cm × 0.33 cm to 1.5 cm × 1.5 cm × 0.33 cm, particularly preferably 1.0 cm × 1.0 cm × 0.33 cm. These volume elements, which have the wall thickness of the propellant charge case as their thickness, thus reflect the deviations in the axial direction of the propellant charge case in several measurements. In the axial direction, the deviation from the mean value is particularly small. For a volume element for the determination of c VE with a size of 0.5 cm × 0.5 cm × 0.2 cm to 1.5 cm × 1.5 cm × 0.4 cm is c VE : C ges preferably 0.85-1.15, more preferably 0.90-1.10, particularly preferably 0.92-1.08. This reflects the concentration variation in the axial direction.

[0027] In a preferred embodiment of the propellant case according to the invention, the average particle size d 50 the MO3 particles 0.5 - 2.0 µm, the maximum particle size d 100of the MO3 particles ≤ 15 µm, and the quotient of the average MO3 concentration in wt.% in a volume element (c VE ) at any point in the propellant case and the total MO3 concentration in wt.% (c ges ) in the propellant case c VE : C ges = 0.85 - 1.15, preferably 0.90 - 1.10, particularly preferably 0.92 - 1.08, wherein the volume element has a size of 0.5 cm × 0.5 cm × 0.2 cm to 1.5 cm × 1.5 cm × 0.4 cm, wherein the propellant charge casing has a wall thickness and the 0.2 cm to 0.4 cm are the wall thickness of the propellant charge casing.

[0028] As an alternative to the wet-chemical determination described above, the MoO3 and / or WO3 concentration can be measured using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). For this purpose, a section of the propellant case is cut, and an SEM-EDX measurement is performed on an area of approximately 100 µm × 100 µm. The measurement is a surface measurement and reflects the MO3 and / or WO3 concentration in the upper layer of the section. It is expressed as a weight percent. The wet-chemical determination as described above is preferred.

[0029] In a preferred embodiment of the invention, the MoO3 and / or WO3 particles have a relatively uniform particle size, ie the particle size distribution is comparatively narrow. This is achieved by a low d 100 -value compared to d 50 -value is shown. The d 50The particle size of the MO3 particles (MoO3 and / or WO3 particles) is, according to the invention, 0.5 - 2.0 µm, preferably 0.7 - 1.6 µm, particularly preferably 0.8 - 1.4 µm and most preferably 0.9 - 1.1 µm. The d 100 -value of the MoO3 and / or WO3 particles is ≤ 15 µm, preferably ≤ 12 µm, more preferably ≤ 10 µm.

[0030] A uniform particle size in the sense of a narrow particle size distribution is achieved by mixing the slurry in the process according to the invention for at least 15 minutes in the presence of a cationic surfactant, preferably by stirring. Without being bound to this according to the invention, it is assumed that the cationic surfactant surrounds the regularly slightly negatively charged MoO3 and / or WO3 particles (MoO3 and WO3 are slightly acidic in an aqueous environment), whereby the MoO3 and / or WO3 particles are kept in suspension and thereby promotes recrystallization, i.e., dissolution and recrystallization. Even if a broad particle size distribution of the MoO3 and / or WO3 particles is used, after carrying out the process according to the invention, the particle size distribution in the propellant case is very narrow, for example d 50 = 0.5 to 2.0 µm with d 100≤ 15 µm, preferably ≤ 10 µm. This narrows the particle size distribution, ensuring more uniform thermal and pressure loading in the weapon barrel, thus avoiding thermal and pressure peaks and reducing barrel wear.

[0031] According to the invention, the average concentration of Mo3 in the propellant charge case (total Mo3 concentration) is 5-10 wt.%, preferably 6-9 wt.%, particularly preferably 7-8 wt.%, with M = Mo and / or W. M is preferably tungsten (W). In a preferred embodiment of the invention, the propellant charge case contains, in addition to the MoO3 and / or WO3 particles, less than 1 wt.%, preferably less than 0.5 wt.%, particularly preferably less than 0.1 wt.% of other metal oxide particles.

[0032] The combustible propellant case according to the invention preferably contains 45 - 65 wt.%, in particular 52 - 58 wt.%, nitrocellulose and / or 25 - 50 wt.%, in particular 33 - 40 wt.%, cellulose.

[0033] The method according to the invention comprises the steps (a) preparing a slurry of cellulose, nitrocellulose, MO3 particles, where M = Mo and / or W, and cationic surfactant in water, (b) mixing the slurry, preferably for at least 5 minutes, more preferably at least 20 minutes, most preferably 30 minutes to 2 hours. (c) dewatering the slurry on a screen to produce a raw felt, (d) pressing the raw felt and (e) Drying to form a combustible propellant case.

[0034] In a preferred embodiment of the invention, the slurry in step (a) contains 5 - 10 wt.% MO3 particles, based on the total weight of pulp, nitrocellulose, MO3 particles and cationic surfactant and / or 0.1 - 2 wt.% cationic surfactant, based on the total weight of pulp, nitrocellulose, MO3 particles and cationic surfactant.

[0035] The method according to the invention preferably comprises the steps (a) preparing a slurry (pulp) of cellulose, nitrocellulose, 5 - 10 wt.% MO3 particles, based on the total weight of the propellant case, where M = Mo and / or W, and 0.1 - 2 wt.% cationic surfactant, based on the total weight of the propellant case, in water, (b) mixing the slurry, preferably for at least 5 minutes, more preferably at least 20 minutes, most preferably 30 minutes to 2 hours. (c) dewatering the slurry on a screen to produce a raw felt, (d) pressing the raw felt and (e) Drying to form a combustible propellant case.

[0036] The surfactant preferably partially deposits on fibers, so that the amount of surfactant in the sleeve is preferably somewhat lower than in the slurry used.

[0037] In a preferred embodiment of the process according to the invention, in step (a) 45 - 65 wt% nitrocellulose, 25 - 50 wt% cellulose, 5 - 10 wt.% MoO3 and / or WO3 particles, A slurry is prepared in water containing 0.1-2 wt.% cationic surfactant, the wt.% in each case based on the total mass of nitrocellulose, cellulose, MoO3 and / or WO3 particles and / or cationic surfactant, and optionally additives, stabilizers, and / or binder resin. It is understood that the sum of the weight percentages of the individual components equals 100 wt.%. A preferred stabilizer is akardit.

[0038] The pressing of the raw felt in step (d) is preferably carried out at 20 - 175 °C, more preferably 100 - 175 °C, most preferably 120 - 150 °C.

[0039] Drying is preferably carried out under ambient conditions, in particular in a so-called standard climate.

[0040] In a preferred embodiment of the process according to the invention, a stabilizer is additionally added in step (a). The stabilizer is preferably acardite (diphenylamine). This stabilizer serves in particular to stabilize the nitrocellulose.

[0041] In a further preferred embodiment of the process according to the invention, a binder resin is additionally added in step (a). The binder resin can be added, for example, in the form of binder resin particles. During subsequent compression at elevated temperature, the binder resin melts and bonds the fibers together. The binder resin is preferably a polymer or a polymer blend of polystyrene-polybutadiene rubber (latex).

[0042] In a preferred embodiment of the invention, a lacquer is applied to the surface of the propellant case after step (e). A nitrocellulose lacquer is preferred. When using a lacquer, the binding resin described above is preferably added in step (a).

[0043] In a further preferred embodiment of the process according to the invention, a plastic is applied to the surface of the pressed raw felt between steps (d) and (e). The plastic is preferably a polyurethane (PU). This is preferably done by immersing the pressed raw felt in a bath of polyols with isocyanate crosslinking agents and subsequent drying, during which the polyurethane cures.

[0044] The method according to the invention preferably comprises the steps (a) preparing a slurry (pulp) of cellulose, nitrocellulose, MO3 particles, where M = Mo and / or W, and cationic surfactant in water, (b) mixing the slurry, preferably for at least 15 minutes, (c) dewatering the slurry on a screen to produce a raw felt, (d1) Pressing the raw felt, (d2) applying a plastic to the surface of the pressed raw felt, preferably a polyurethane and (e) Drying to form a combustible propellant case.

[0045] The method according to the invention also preferably comprises the steps (a) preparing a slurry (pulp) of cellulose, nitrocellulose and binder resin particles in water, adding MO3 particles, where M = Mo and / or W, and cationic surfactant in water, (b) mixing the slurry, preferably for at least 15 minutes, (c) dewatering the slurry on a screen to produce a raw felt, (d) pressing the raw felt and (e) drying to a combustible propellant case, (f) applying a varnish to the surface of the combustible propellant case, preferably a nitrocellulose varnish.

[0046] The slurry (pulp) is preferably mixed using conventional stirring tools, such as rotating blades. The slurry is dewatered by pouring it onto a sieve, allowing the water to flow through the holes in the sieve, possibly assisted by a vacuum. The raw felt is then pressed onto this sieve with a matching mating piece, thus producing a slightly moist propellant case. This propellant case is then dried to produce the combustible propellant case according to the invention.

[0047] The invention is further explained below using two examples: Example 1: Production of combustible shells for tank cannon ammunition 1. Pulp boards are pulverized into a pulp in water (2,627 liters of process water). This occurs in a container with a rotating blade at the bottom. The pulp weighs 78.8 kg. The pulp is then ground in a refiner. A further 1,200 liters of process water are added. 2. Nitrocellulose is stirred into the fiber pulp. The total weight is 120.0 kg. 3. Check the fabric density approx. 8% 4. Addition of another 1600 liters of process water. 5. Addition of Paragas: The Paragas is mixed with water and added to the mixture while stirring. 6. The stabilizer Akardite is added: The Akardite is suspended in water and ground. It is then added to the mixture while stirring. 7. 16.8 kg of WO3 particles are suspended in 32 liters of water and added to the mixture while stirring. 8. The mixture is pumped into the target container and diluted with process water. 9. The fibers are separated by suction onto sieve forms in special basins that are in communication with the target container. This creates the raw felt. 10. The raw felts are then pressed at approximately 170 °C. During the pressing process, the water from the raw felt is removed by vacuum. This step produces the core in its defined shape. 11. The pressed sleeves are PU-impregnated by briefly immersing them in a bath of polyols with isocyanate crosslinking agents and then drying and curing them in a drying tunnel. 12. Conditioning in standard climate (drying). 13. Mechanical cutting and chamfering. Example 2: Production of combustible casings for artillery ammunition

[0048] Steps 1-3 are identical.

[0049] Step 4 involves the addition of binding resin particles. These binding resin particles are later melted during compression and bond the fibers together. These are polymers made of polystyrene-polybutadiene latex.

[0050] Raw felt production and pressing analogous to the above process.

[0051] Step 11 is omitted here.

[0052] Steps 12 and 13 are carried out analogously.

[0053] The final step is painting. This is done with an NC paint containing the appropriate color pigment.

[0054] It is understood that the features mentioned above and those to be explained below can be used not only in the specified combinations, but also in other combinations or alone, without departing from the scope of the present invention. The advantages of features or combinations of several features mentioned are merely exemplary and can be used alternatively or cumulatively. The combination of features of different embodiments of the invention or of features of different patent claims is possible, deviating from the selected references to the patent claims.

Claims

[1] Combustible propellant case for ammunition fired from a gun barrel, comprising - pulp, - Nitrocellulose, - 5 - 10 wt.% MO3 particles, based on the total weight of the propellant case, where M = Mo and / or W, and - 0.01 - 2 wt.% cationic surfactant, based on the total weight of the propellant case, wherein the average particle size d 50 the MO3 particles are 0.5 - 2.0 µm, the maximum particle size d 100 the MO3 particles are ≤ 15 µm, and the quotient of the average MO3 concentration in wt.% in a volume element of about 0.05 to 1.0 cm 3 (c VE ) at any point in the propellant case and the total MO3 concentration in wt.% (c] ges ) in the propellant case c VE : c ges = 0.80 - 1.

20. [2] Combustible propellant case according to claim 1, characterized by that the mean particle size d50 the MO3 particles are 0.8 - 1.4 µm. [3] Combustible propellant case according to claim 1 or 2, characterized by that the d 100 -value of the MO3 particles is ≤ 12 µm. [4] Combustible propellant case according to one of the preceding claims, characterized by that the propellant case contains 7 - 8 wt.% MO3 particles and / or 0.05 - 1 wt.% cationic surfactant. [5] Combustible propellant case according to one of the preceding claims, characterized by that c VE : c ges = 0.85 - 1.

15. [6] Combustible propellant case according to one of the preceding claims, characterized by that the volume element has a size of approximately 0.5 cm × 0.5 cm × 0.2 cm to 1.5 cm × 1.5 cm × 0.4 cm, wherein the propellant charge case has a wall thickness of 0.2 cm to 0.4 cm being the wall thickness of the propellant charge case and c VE :c ges = 0.90 - 1.

10. [7] Combustible propellant case according to one of the preceding claims, characterized by that M = W. [8] Combustible propellant case according to one of the preceding claims, characterized by that the cationic surfactant contains two or more cationic groups, preferably the cationic surfactant is a salt of an organic polyamine with an acid. [9] A method for producing a combustible propellant case according to any one of claims 1-8, comprising the steps (a) preparing a slurry of cellulose, nitrocellulose, MO3 particles, where M = Mo and / or W, and cationic surfactant in water, (b) mixing the slurry, (c) dewatering the slurry on a screen to produce a raw felt, (d) pressing the raw felt and (e) Drying to form a combustible propellant case. [10] Method according to claim 9, characterized bythat the slurry in step (a) contains 5 - 10 wt.% MO3 particles, based on the total weight of pulp, nitrocellulose, MO3 particles and cationic surfactant and / or 0.1 - 2 wt.% cationic surfactant, based on the total weight of pulp, nitrocellulose, MO3 particles and cationic surfactant. [11] Method according to claim 9 or 10, characterized by that the cationic surfactant contains two or more cationic groups, preferably the cationic surfactant is a salt of an organic polyamine with an acid. [12] Method according to one of claims 9 to 11, characterized by that in step a) a stabilizer is added, preferably akardite.