GB1111391A - Solid propellants - Google Patents

Abstract

Solid propellant is made by a continuous process in which a stream of resin binder is introduced into a moving stream of an oxidizing material, followed by mixing to obtain a uniform composition. The process prevents pressure build-up and short-circuiting of the resin, and reduces the danger of explosion. As shown in Fig. 1, the solid oxidizer is fed at a controlled rate from hopper 14 to screw conveyer 18 and mixer 26; the oxidizer may be recycled in a fluidized state via line 22. The mixer comprises a rotating screw-bladed shaft and stationary teeth 28. Components reacting to form a polyurethane binder are introduced into the mixer through inlet 30, the isocyanate ingredient from tank 32 which is at low pressure, and a slurry of additives in the polyol ingredient from vessel 38 in which an inert atmosphere is maintained. The inlet 30 extends into the stream of oxidizer and is constructed as shown in Fig. 4. The isocyanate feed enters at 105 and flows through tube 106; the polyol slurry enters at 112 and flows through annular space 114 around the tube 106 and so surrounds the isocyanate stream on introduction through inlet 30 into the mixer. A radioactive tracer may be added at 111, so that tests may be carried out to determine the efficiency of the mixing. The mixed propellant passes from the mixer through <PICT:1111391/C1/1> <PICT:1111391/C1/2> pipe 63, Fig. 1, to cooled deaerator 68 which is connected to a source of vacuum. The mixture is then tested in instrumentation section 80 and either passed to waste or to the curing section, for example being discharged directly into a rocket casing and cured in situ. Compositions.-Suitable compositions containing polyurethane are described in Specification 984,960. The Specification includes lists of suitable isocyanates, isothiocynates, hydroxy and thiol compounds, and cross-linking agents; preferably the isocyanate component is used in slight excess over the hydroxy or thiol component. The binder may also be asphalt, or polyester or other resins as described in Specifications 579,057 and 883,586 and United States Specification 2,563,265. Suitable oxidizing agents are chromates, dichromates, permanganates, nitrates, chlorates, and perchlorates of alkali or alkaline earth metals, ammonia, hydrazine, or guanidine. Aluminium powder may be included in the composition. Other standard additives specified are plasticizers, catalysts, burning rate modifiers, antioxidants, wetting agents, and antifoaming agents. A suitable igniter for the propellants is described in United States Specification 3,000,312.