Solubility, in Supercritical Carbon Dioxide, of Paraffin Waxes Used as Binders for Low-Pressure Injection Molding

Paraffin waxes, commonly used as binders in ceramic-forming processes, can be removed from ceramic bodies with supercritical carbon dioxide. Therefore, the solubility of three industrial paraffin waxes (melting at 42, 52, and 62 °C, respectively) in supercritical CO2 was investigated. The concentrations of these paraffin waxes in the solvent-rich phase in equilibrium with the paraffin-rich phase were measured at 343 K in the pressure range 12−30 MPa by using infrared absorption spectroscopy. Some n-alcane−CO2 binaries were also investigated. A model was developed by analogy with polydisperse polymers in solvents. It relates the concentration of the paraffin waxes to the concentration of the pure n-alcanes for n-alcane−CO2 binary systems. This model gives accurate overall concentration values for paraffin−CO2 mixtures and reproduces the n-alcane distribution in the solvent-rich phase.