Recrystallization of HMX with compressed gases as anti-solvent

A ternary system consisting of cyclotetramethylene tetranitramine (octogen, HMX) as the solute, acetone or .gamma.-butyrolactone as solvents, and CO2 as the anti-solvent was used to investigate the formation of fine particles with the gas anti-solvent-(GAS)-process as well as the influence of the solvents upon the particle morphol. under the same operating conditions. The pptd. particles were examd. by IR , laser diffraction, and optical microscopy. The results show that HMX with a narrow particle size distribution was obtained. The crystals are of the same modification as the raw material and of high purity. The modification and the particle size are influenced by the solvent used for the recrystn.