Extraction and recovery of plasticizers from solid propellants and

Abstract

A method to extract and recover plasticizers and their stabilizers from solid propellants, explosives, and pyrotechnics (PEP source compositions) employs near critical liquid (NCL) or supercritical fluid (SCF) CO.sub.2 as the solvent. The extraction and ingredient recovery method provides an environmentally acceptable alternative to traditional open burning and destruction of PEP source compositions. CO.sub.2 solvent is nontoxic, nonflammable, noncorrosive, inexpensive, and does not generate any additional toxic or hazardous wastes. The solvent is totally inert when it is confined, pressurized, and possibly heated in direct contact with an energetic propellant or munition within a rocket motor or similar pressure vessel. CO.sub.2 readily undergoes a gas-to-liquid phase change to NCL conditions when confined and compressed to a pressure of 831 psig or greater at ambient temperature. By further increasing the pressure and temperature of NCL CO.sub.2 to 1058 psig and 31.3.degree. C. or greater, respectively, SCF conditions of CO.sub.2 are obtained. Either NCL or SCF CO.sub.2 has the capability to be a selective solvent for soluble plasticizers (e.g., nitroglycerin) and their stabilizers (e.g., diphenylamines and nitroanilines) from double base and crosslinked double base propellants, munitions and pyrotechnics. All undissolved propellant and munition ingredients are filtered from the NCL or SCF CO.sub.2 solvent prior to the pressure reduction/volume expansion recovery cycle. The recovery of soluble plasticizers and stabilizers from a NCL or SCF CO.sub.2 solvent system is achieved by allowing the NCL or SCF solvent to undergo pressure reduction and phase change to the gaseous state. The gaseous CO.sub.2 is then recycled for additional use in the method.