Comparative solubility investigations of anthraquinone disperse dyes in near- and supercritical fluids

The present study covers equilibrium solubilities of a homologous series of 1,4-bis-(alkylamino)-9,10-anthraquinones (with alkyl from methyl to octade cyl) and additionally of the more polar anthraquinone derivatives 1-amino-1 -hydroxy-2-phenoxy-9,10-anthraquinone (C. I. Disperse Red 60) and 1,4-diami no-2-methoxy-9,10-anthraquinone (C. I. Disperse Red 11) in several near- an d supercritical fluids. The solubilities of the 1,4-bis-(alkylamino) substi tuted anthraquinones except the octadecyl-derivative were measured by means of a supercritical fluid chromatograph (SFC) between 299 and 346 K and up to a maximum pressure of 20 MPa. On the contrary, the measurements of 1,4-b is-(octadecylamino)-9,10-anthraquinone as well the two Disperse Red represe ntatives 60 and 11 were performed using a static optical high-pressure auto clave within pressures from 7 to 180 MPa and temperatures up to 400 K. We r eflected on the results from three different points of view, namely the inf luence of different substituents, of the particular solid state, and of dif ferent solvent gases. A complex pattern of interrelations of these paramete rs determining equilibrium solubilities opened; decoupling and a separate v iew proved to be insufficient. (C) 2001 Elsevier Science B.V, All rights re served.