Polyfunctional isocyanate crosslinking agents for propellant binders

Claim 1

In a propellant composition comprising a binder prepolymer having pendant hydroxyl groups, an auxiliary crosslinking agent comprising nitrocellulose, an energetic plasticizer, oxidizer solids selected from inorganic and organic materials, a crosslinxing agent for said binder prepolymer and a curing catalyst for said propellant composition, the improvement comprising as the crosslinking agent a polyfunctional isocyanate composition having an average isocyanate functionality of at least 4, said polyfunctional isocyanate being made by a process comprising reacting (a) a polyol having a hydroxyl functionality of at least 4 dissolved in a solvent inert to reaction witn said polyol, and (b) a diisocyanate, at a temperature of from about room temperature (22° C.) to below about 50° C. forming a reaction mass, the initial ratio of isocyanate groups of the diisocyanate to the hydroxyl groups of the polyol being at least 4/1, said reaction being continued until substantially all of hydroxyl groups of the polyol in the reaction mass have reacted with the isocyanate groups of the diisocyanate and recovering polyfunctional isocyanates having an average isocyanate functionality of at least 4.