Title of Invention

"A LOW TOXICITY PROPELLANT COMPOSITION AND PROCESS FOR PREPARING THEREOF"

Abstract

This invention relates to a process for preparing low toxicity propellant composition for small arm ammunition comprising of following steps: kneading dehydrated nitrocellulose with a stabiliser preferably diphenylamine and in the mixture of solvent wherein ether and alcohol are present in ratio of 20-24% to form a dough, extruding the dough to form shapes, coating the extruded grains with graphite, moderating as herein described the coated grains with camphor, water steeping the extruded propellant grains, drying the water treated propellant grains by hot air followed by polishing and sieving.

Full Text

FIELD OF INVENTION The present invention relates to a low toxicity propellant composition for small arms ammunition and a process for preparing thereof. PRIOR ART In small arms ammunition, single as well as double base propellants are utilised. These propellants basically comprise an energy releasing ingredient (nitrocellulose, nitroglycerine etc.), a stabiliser (diethyl diphenyl urea, diphenylamine etc.) and a moderant (dinitro toluene, diamylphthaiate etc.). In some cases; such small arms might be mounted on an armoured vehicle, and when fired, create fumes of various composition inside the enclosed environment of the vehicle. Mostly, these fumes comprise toxic oxides of nitrogen, carbon monoxide and ammonia which are left behind in the enclosed environment of the vehicle. In case of existing small arms ammunition, toxicity levels created by the toxic fumes present in the product gases of the propel1ant, are found to be beyond the human tolerance limit. The amount of such toxic gases, which arc released during th* combustion of the propellant, depend upon the various constituents of the prope11ant as well upon the pressure condition inside the gun chamber. However, the extent of toxic gases might be reduced by changing the composition of the propellant as well as by modifying the pressure conditions in*ide the gun chamber which affect the chemical reactions during combustion of the propellant. Conventionally, dinitrotoluene is used as a moderant in the small arms ammunition propellant. Dinitrotoluene is a weak surface moderant which does not affect the pressure conditions, significantly, inside the gun chamber. Further, dinitrotoluene, on decomposition during the propellant combustion, liberates oxides of nitrogen thereby further increasing the concentration of toxic fumes in the propel lant product gas. Many attempts have been made, in the past, to reduce the toxic level created by above Mentioned gases in the propellants used in the small arms ammunition gun propellant. In one such known process, urea (10%by weight of the propellant composition) is added to the propellant composition. However, this known method of reducing toxicity of the small arms ammunition propellant, utilising urea as an ingredient to reduce the toxicity level, suffers from following disadvantages. One major disadvantage of this known process for reducing the toxicity level of small arms propellants is that it reduces the energy level of the propellant. Another disadvantage of his known process for reducing the toxicity level of small arms propellants is that it reduces the velocity thus reducing the efficacy of the ammunition. Yet another disadvantage of this known process for reducing the toxicity level of the small arms ammunition propellant propellant is that it makes the propellant hygroscopic in nature thereby affecting the ballistic characteristics of the propellant. Still another disadvantage of this known process for reducing the toxicity level of small arms ammunition propellant is that use of urea affects the physical characteristics of the propellant, OBJECTS OF THE INVENTION Primary object of the invention is to provide a small arm propellant composition and a process for preparing thereof for providing small arm propellant with reduced toxicity. Another object of the invention is to provide a small arm propellant composition and a process for preparing thereof which uses camphor as a moderant in the propellant composition. Still object of the invention is to provide a small arm propellant composition and a process for preparing thereof wherein the pressure conditions inside the chamber can be controlled. Yet another object of the invention is to provide a small arm propellant composition and a process for preparing thereof which facilitates higher degree of gelatinisation thereby resulting in lower burn rate of the propellant. Still further object of the invention is to provide a small arm propellant composition and a process for preparing thereof which modifies the burning rate of the propellant to yield desired velocity at a controlled pressure. Yet another object of the invention is to provide a small arm propellant composition and a process for preparing thereof which is easy to adopt. Still another object of the invention is to provide a small arm propellant composition and a process for preparing thereof which is economically viable. Yet another object of the invention is to provide a small arm propellant composition and a process for preparing thereof which is safe. DESCRIPTION OF THE INVENTION According to this invention there is provided a process for preparing low toxicity propellant composition for small arm ammunition comprising of following steps: a) kneading dehydrated nitrocellulose with a stabiliser preferably diphenylamine and in the mixture of solvent wherein ether and alcohol are present in ratio of 20-24% to form a dough, b) extruding the dough to form shapes, c) coating the extruded grains with graphite, d) moderating the coated grains with camphor, e) water steeping the extruded propellant grains, f) drying the water treated propellant grains by hot air followed by polishing and sieving. In accordance with the present invention, the process of preparing small arms ammunition propellant comprises following steps: i) Preparation of dehydrated nitrocellulose from water wet nitrocellulose, having nitrogen content 13.15 - 13.30% and moisture content about 25 - 30 %, by replacing water content with ethanol. ii) Kneading dehydrated nitrocellulose in the sigma blade mixer along with required quantity of stabiliser diphenylamine and 110% ether-alcohol solvent mixture on the weight of nitrocellulose. Kneading was carried out for 2 - 3 hours at 20- 25°C followed by 1 hour at 10°C. iii) Subjecting the dough as formed above to the process of extrusion by hydraulic press followed by cutting and vacuum drying the grams. The mean cut length of these grains is from 1.1-1.2 mm The vacuum drying process is carried out for about 28-30 hours at around 50 degree °C to reduce the volatile matter content iv) Loading the vacuum dried grains in a rotating sweetie pan and coating the same with 0.05 parts graphite (weight wise). v) Moderating the partially coated grains with 2 parts of camphor (in alcohol solution) for every 100 parts of basic composition (weight wise) for a period of 2.0 hours in sweetie pan. Again coating the propellant grains with additional quantity of 0.15 parts of graphite for four hours. vi) Water steeping the propellant grains in hot water (15 liter water for 1 kg powder) for a period of 3 - 5 hours at 40 - 45°C followed by 3 - 5 hours at 45 - 50°C after unloading the moderated grains from sweetie pan. vii) Drying the water treated propellant grains at 35 - 40°C by hot air blowing till the volatile matter content is reduced to 1.0 to 1.2%. viii) Polishing the powder in the presence of wooden balls in a sweetie pan. ix) Sieving the powder through suitable sieve to remove higher and lower sized propellant grains after completion of polishing process The process of present invention will now be illustrated with a working example which is intended to be a typical example to illustrate the working of the invention and is not intended to be restrictively imply any limitation on the scope of the invention WORKING EXAMPLE The gun propellant composition: Nitrocellulose - 99.0 parts (N2% 13.15-13.30) Diphenylamine - 1.0 part Camphor - 2.0 parts over 100 parts Graphite - 0.2 parts over 100 parts 4.45 kg of dehydrated nitrocellulose having nitrogen content 13.15 -13.30 % and ether - alcohol solubility 20 - 24%, 45 g diphenyl amine and solvent mixture comprising of 2.80 kg diethyl ether and 1.87 kg ethyl alcohol were incorporated in a 40 liter overflow capacity sigma blade mixer and kneaded for 2-3 hours at 20-25 °C followed by kneading for 1.0 hour at 10 °C. The resulting dough was then extruded at a pressure of 150 kg/cm2 into tubular shape using suitable die-pin assembly and straining assemblies consisting of choke plate and 30, 20 and 10 BSS stainless steel wire meshes. The extruded strands were pre-dried for a period of 30 minutes at 35°C and cut in a Guillotine cutting machine to realise 1.1 to 1.2 mm mean cut length. The cut grains were then sieved through suitable sieve to remove undersize grains. The sieved grains were then vacuum dried for 28-30 hours at 50°C so that volatile matter content was not more than 1.5%. Two such batches of vacuum dried propellant grains were prepared. Next, these two batches of vacuum dried propellant, prepared in above manner, are moderated with camphor and surface coated with graphite. 7.2 kg of the vacuum dried powder recovered from the above two batches were transferred to a 50 kg capacity sweetie pan alongwith wooden balls constituting 30% of the weight of propellant grain. The propellant grains were initially coated with graphite in the rotating sweetie pan with 3.60 gin graphite (0.05 part by weight of the propellant composition) for a period of 30 minutes. The partially coated propellant grains were moderated by * camphor solution consisting of 142 gm camphor dissolved in 700 cc ethanol. The camphor solution was sprayed over the propellant grains while the sweetie pan was in rotation. Moderation process was continued for 2 hours. Next, 10.80 gm graphite (0.15 parts by weight of propellant composition) was coated over the propellant grains by adding it slowly in the sweetie pan and coating for a period of 4 - 6 hours. The moderated and coated propellant was unloaded from the sweetie pan in a cotton cloth bag and subjected to water steeping in about 100 liters hot water at 40 - 45°C for 3 - 5 hours. Water steeping was continued for another 3-5 hours with fresh water at 45°C - 50°C. During both the stages water used for steeping was saturated with camphor. There after, the water steeped propellant grains were dried in a hot air oven at 35°C - 40°C for a period of 6 - 8 hours, till the volatile matter content in the propellant grains were reduced to 1 - 1.2%. The dried propeliant grains were subjected to final polishing in a sweetie pan and sieved. The above small arm ammunition propellant, thus prepared was put to test by firing it inside a combat vehicle. After testing, it was found to generate lesser amount of toxic gases inside the combat vehicle as compared to known propellant. In the following table a comparison has been made between the amount of toxic gases generated by a known propellant (NC-1140) utilising dinitrotoluene as moderant and the present propellant utilising camphor as moderant. Type of ammunition No of rounds CO NO2 Used fired (ppm)(ppm) NC-1140 200 500 2.97 Present propellant 200 200 0.5 The result indicates that combustion products from the propellant prepared from the above mentioned process are less toxic than those known in the art. It is to be understood that the process of present invention is susceptible to adaptations, changes, modifications by those skilled in the art. Such adaptations, changes, modifications are intended to be within the scope of the present invention which is further set forth by the following claims. WE CLAIM; 1. A process for preparing low toxicity propellant composition for small arm ammunition comprising of following steps: a) kneading dehydrated nitrocellulose with a stabiliser preferably diphenylamine and in the mixture of solvent wherein ether and alcohol are present in ratio of 20-24% to form a dough, b) extruding the dough to form shapes, c) coating the extruded grains with graphite, d) moderating the coated grains with camphor, e) water steeping the extruded propellant grains, f) drying the water treated propellant grains by hot air followed by polishing and sieving. 2. A process as claimed in claim 1 wherein said kneading is carried out in a mixer as herein described with stabiliser diphenylamine and preferably in the mixture of solvent wherein ether and alcohol are present in ratio of 20-24% preferably for 2-3 hours at 20-25°C followed by kneading preferably at a lower temperature. 3. A process as claimed in claim 1 wherein said drying process is carried out in vacuum and preferably for 20-30 hours at 50°C. 4. A process as claimed in claim 1 wherein coating is done with preferably .05 parts of graphite over the weight of the propellant. 5. A process as claimed in claim 1 wherein said moderation is carried out for two hours with 2 parts of camphor over the weight of the propellant composition followed with coating with 0.15 parts of graphite for four hours. 6. A process as claimed in claim 1 wherein said water steeping is carried out preferably for 3-5 hours at 40-45°C followed by water steeping for 3-5 hours at 45-50°C. 7. A process as claimed in claim 1 wherein said drying of propellant grains is carried out preferably at 35-40°C. 8. A process as claimed in claim 1 wherein said nitrocellulose percentage weight wise is preferably 90%. 9. A process for preparing a low toxicity propellant composition substantially as herein described.

Documents:

476-del-2000-abstract.pdf

476-del-2000-claims.pdf

476-del-2000-correspondence-others.pdf

476-del-2000-correspondence-po.pdf

476-del-2000-description (complete).pdf

476-del-2000-form-1.pdf

476-del-2000-form-19.pdf

476-del-2000-form-2.pdf

476-del-2000-form-26.pdf