GB544709A - Improvements in the manufacture of smokeless propellent powder - Google Patents

Abstract

544,709. Cellulose and starch nitrates explosives. WESTERN CARTRIDGE CO. Sept. 17, 1940, No. 14289. Convention date, Sept. 25, 1939. [Classes 2 (ii) and 2 (iii)] [Also in Group XXI] In the production of smokeless propellent powder grains, the powder base such as cellulose nitrate or starch nitrate is treated with sufficient solvent to form a lacquer. This lacquer is agitated in a non-solvent bath to form a dispersion of globules. A part only of the solvent is removed from the globules while the dispersion is maintained, and the partially solidified globules are removed from the bath while they still contain a substantial amount of solvent. The grains may then be subjected to further treatments to bring them into the final grain form desired. The solvent for the powder base is preferably immiscible or only slightly miscible with the non-solvent. The non-solvent bath may be chosen so that it washes out impurities from the lacquer, and it may contain substances of alkaline reaction. Nitrocellulose, after the nitration process, may be drowned in water, washed with hard water, and subjected to a displacement wash with very dilute sodium carbonate or bicarbonate solution. It is then treated with a water-immiscible solvent, e.g. ethyl acetate, isopropyl acetate, methyl isobutyl ketone. The cellulose nitrate lacquer obtained is then washed to remove remaining acid and other impurities. The washing liquid may be water and it may contain organic amines, sodium carbonate or bicarbonate, calcium carbonate, or other compounds of alkaline reaction. If desired, the cellulose nitrate may be treated with the solvent while it is suspended in the displacement wash liquid. If a liquid other than water is used for washing the lacquer, the solvent of the lacquer must be immiscible with that liquid. Washing is accompanied by agitation of the lacquer which thus becomes dispersed in the non-solvent. Stabilizers such as diphenylamine or a centralite such as diethyl diphenyl urea.may be added to the lacquer. An organic amine such as aniline red or urea may be present during the washing. The external aqueous phase may contain a solute such as sodium sulphate so as to facilitate, by differences of osmotic and vapour pressure, the migration of water from the lacquer particles to the exterior thereof. The two layers may be allowed to separate. Agitation may be resumed and a protective colloid or emulsifying agent may be added, e.g. gum arabic or starch. When globules of lacquer of the appropriate size have been obtained, the temperature is raised to remove solvent to the desired extent. The partially solidified grains of cellulose nitrate are removed from the suspension by screening, centrifuging, or settling. The surface water may be removed from the grains by treatment with alcohol. The grains or globules may be kneaded and then extruded to form cords, strips, or ribbons, or they may be passed through rollers, formed into sheets, and divided into strips or flakes. Residual solvent is removed by air drying. The powder grains may be subjected to coating or other treatments. Accelerators such as nitroglycerin, or deterrents such as dinitrotoluene, or dibutylphthalate may be incorporated with the cellulose nitrate lacquer, or may be added to the suspension of cellulose nitrate globules after removal of part of the solvent. The process is applicable to the treatment of surplus or deteriorated powder grains. Specification 473,057 is referred to. The Specification as open to inspection under Sect. 91 comprises also the complete evaporation of solvent from the lacquer globules while they are still suspended in the non-solvent liquid, and comprises also agitation in a non- solvent of nitrocellulose particles softened with limited proportions of solvent, so as to form dispersed agglomerates - which may then be subjected to further treatment to form powder grains without requiring any removal of solvent by distillation. This subject-matter does not appear in the Specification as accepted.