PROCEDURE FOR THE PRODUCTION OF IN ONES, TWO ONES OR DREIBASIGEN PROPELLANT POWDERS FOR TUBING WEAPON AMMUNITION

It is an object of the present invention to provide a propellant, and a method of producing the propellant, in which the maximum-pressure curve can easily be flattened in the temperature range for which the weapon is specified. This object and others are met by a composition of matter comprising propellants for gun ammunition surface treated with at least one of inert or energetic polymers and energetic, monomer softeners. The concept underlying the invention is to perform a surface treatment on conventional mono-, di- or tribasic powders using special desensitizers, namely only those that have little or no tendency to migrate. 29933-1 CA 02298513 2000-07-20 The desensitizers of the invention include inert or energetic polymers or large-volume monomers that practically do not migrate at all, and energetic, monomolecular substances, or mixtures of the components, that reduce the energy loss to a level that yields no perceptible decrease in performance capability during the firing of the weapon. The surface treatment of the propellants can be accomplished by any known method of surface treatment. For example, the surface treatment may be sprayed on, as a solution or an emulsion, in a treatment drum, particularly a rotating treatment drum, or an impregnation method may be performed, in which the propellant is incubated in the treatment solution or emulsion for a specified period of time. The following substances, used alone or as mixtures, have proven particularly advantageous for surface treatment : non-energetic polyesters, polyethers, polyurethanes, polyureas, polybutadienes, polyamides, cellulose esters (such as cellulose acetate, cellulose acetobutyrate, cellulose propionate); 2 9933-1 CA 02298513 200007-20 energetic polymers (e.g., poly-3-nitratomethyl-3- methyl oxetane (poly-NMMO), polyglycidylnitrate(poly- GLYN) , and glycidylazide polymer (GAP)); alkyl nitrato ethyl nitramines (e.g., methyl nitrato ethyl nitramine (methyl-NENA), ethyl nitrato ethyl nitramine (methyl-NENA), and butyl nitrato ethyl nitramine (methyl-NENA)); dinitro diazaalkanes; nitric acid esters (e.g., diethylene glycol dinitrate); nitroglycerine, triethylene glycol dinitrate, butane triol trinitrate, and metriol trinitrate; and bis(2,2-dinitropropyl) acetal (BDNPA), bis(2,2- dinitropropyl) formal (BDNPF). BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1 and 2 show the dependence of the maximum pressure and the muzzle velocity on the ambient temperature of a first propellant, with and without the surface treatment according to the invention. 29933-1 CA 02298513 2000-07-20 Figs. 3 and 4 show the temperature dependencies of the maximum pressure and muzzle velocity, as illustrated in Fig. 1, for a second propellant. Figs. 5 and 6 show the temperature dependencies of the maximum pressure and muzzle velocity, as illustrated in Fig. 1, for a third propellant. Fig. 7 is a plan view of a surface-treated powder, granule. Fig. 8 is a sectional view taken along line VIII - VIII of Fig. 7. Fig. 9 is a sectional view, similar to Fig. 8, of a further embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1: The propellant powder for which the surface treatment of the invention is to be performed is a dibasic propellant powders L 5460 used for 120-mm kinetic energy ammunition and has the following composition: Nitrocellulose 59.5% Nitroglycerine 14.9% Diethylene glycol dinitrate 24.8% Akardite II (Methyl Diphenylurea) 0.7% 29933-1 CA 02298513 2000-07-20 Other 0.1%. A 4% ethanolic solution of ethyl-NENA is sprayed onto the propellant powder L 54 60 in four portions in a conventional treatment drum. The surface-treated powder is dried and subsequently subjected to different firing tests. Figs. 1 and 2 illustrate the result of the temperature firing using the surface treated powder in a 40-mm simulator (curve a) in comparison to untreated L 5460 (curve b) . The maximum pressure (Pmax) of the combustion curve and the muzzle velocity (v0) are shown as a function of the temperature. The results indicate that the surface-treated L 5460 has a distinctly flattened temperature dependence of the maximum pressure and the muzzle velocity in the temperature range between 21'C and 63"C in comparison to the untreated powder. Example 2 : The dibasic L 5460 described above is used again as the propellant powder for surface treatment according to the invention. Palamoll 632, a polyester comprising adipic acid and propane-1,2-diol, is applied to the surface of L 5460 in an 29933-1 CA 02298513 2000-07-20 ethanolic emulsion (Palamoll: EtOH =1 : 3). The treatment with 1.5% of the polymer is effected in a rotating treatment drum at 45"C. The emulsion, divided into four portions, is successively added over a period of five hours; the solvent is simultaneously evaporated. Graphite is added multiple times during the treatment to prevent the granules from sticking. Figs. 3 and 4 show the firing results of this powder in a 40-mm simulator from -40 to +63°C, in comparison to an untreated L 54 60. The maximum pressure and the muzzle velocity are, again, shown as a function of the temperature. s In this case, a distinct flattening of the pressure and velocity curves once again can be seen between 21"C and +63°C (curve a) in comparison to the untreated propellant powder (curve b). Table 1 lists the specific energy for the powders described in the previous two examples. Table 1 Treatment Specific Energy [J/g] L 5460 ~~ 1165 29933-1 CA 02298513 2000-07-20 Example 1 4% ethyl-NENA 1165 Example 2 1.5% polyester 1145 The values for the specific energy indicate that the methods of the invention effect little or no loss in the performance capability of the propellants. Example 3 : A monobasic, 7-hole propellant powder C/M 0800 that was produced with nitrocellulose as the energy carrier and Centralite I as the stabilizer is incubated in an emulsion of nitroglycerine in water in a rotating drum at 30'C until the solution is clarified. The powder is then subjected to a second treatment in an emulsion of Palamoll 632 in water. In this way, 10% nitroglycerine and 2% Palamoll were applied. Figs. 5 and 6 show the results of a weapon firing with this powder in a 35-mm training ammunition (curve a), in comparison to a monobasic propellant powder B 6320 (curve b) normally used. While the conventional monobasic propellant B 6320 exhibits a significant increase in pressure and muzzle 29933-1 CA 02298513 2000-07-20 velocity between 21"C and 70"C, in the treated C/M 0800, a reduction in the temperature gradient is indicated in the range between 21"C and 52*C. Thus, a distinct improvement in performance capability in comparison to the conventional propellant powder can also be anticipated in the medium- caliber range with these treated powders. As microscopic examinations and tests involving combustion interruption in a ballistic bomb have shown, the desensitizer 1 deposits at the surface 2 of the respective powder granule represented by 3 in Figs. 7, 8 and 9. The inside holes 4 of the propellant powder are also partially (Fig. 8) or completely {Fig. 9) covered by the desensitizer 1, or can even be completely sealed by the desensitizer. This coating 1 of the propellant granules 3 presumably results in the desired change in the combustion behavior of the propellant, and thus in the observed reduction of the temperature gradient. The method can be used for known 1-, 7- and 19-hole propellants and those having cylindrical, hexagonal or rosette-shaped outer geometries. The powder that is surface-treated according to the invention further exhibits a reduced sensitivity to special stresses, as can occur, for example, during enemy firing, 29933-1 CA 02298513 2000-07-20 in comparison to untreated propellants of the same composition. It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims. 29933-1 CA 02298513 200007-20