(512e) A New Recrystallization Method for Nitroguanidine

The objective to crystallize nitroguanidine is to obtain high bulk-density nitroguanidine because the needle shape crystal of nitroguanidine has low bulk-density. Normally the recystallization process is realized by lowing the temperature with different rate in hot water or other solvent systems with the help of specific additives. Recently a new process, anti-solvent recrystallization, is used for recrystallization of nitroguanidine, HMX, and RDX. A good recrystallizing process can obtain specific shaped, much smaller and more uniform nitroguanidine crystals. The shape and size of nitroguanidine crystals are determined by recrystallizing additives and conditions. Normally spherical nitroguanidine crystal is use as explosive charge and short column crystal is used as propellant. Recently the best commercially available nitroguanidine crystals made in German can be smaller than 20 microns, but the distributions of nitroguanidine crystals are still not satisfied because the controlling parameters in a bulk recrystallizing vessel are always limited and indirect for size control, even for the anti-solvent recrystallization process.

Different from other processes, this technology has realized generation of high uniform and much smaller nitroguanidine crystals. The size of nitroguanidine crystals can be controlled between 1 micron to 50 micron and all crystals are identical under microscope. During crystallizing procedure, the shape and size of nitroguanidine crystals are adjusted by different additive concentrations and different temperature decreasing rate. After the nitroguanidine crystals are obtained, the additives are removed to purify the nitroguanidine crystals. Application of the new nitroguanidine crystals in automobile industry shows high reliability. Also applications of the new nitroguanidine crystals in propellant (M60 or missile) show high reliability and enhanced power. The cost of the new process is much lower and the size is more controllable than the anti-solvent recrystallization process.