SOLUBILITY OF WOOL WAX IN SUPERCRITICAL CARBON-DIOXIDE

The solubility of raw wool wax in supercritical carbon dioxide was mea sured over a pressure and temperature range of 250-650 atm and 31-150 degrees C. Above 60 degrees C, the solubility increased Substantially with increasing pressure and temperature, but below 60 degrees C the s olubility of the wool wax reached a maximum at 475 atm. As the extract ion proceeded, the solubility decreased and the composition oi-the ext ract changed. The earliest fractions contained mainly 'free' wool wax acids and alcohols with only small amounts of the wool wax esters. The solubility of these acids and alcohols in the presence of wool wax wa s much lower than expected, and was attributed to a partitioning mecha nism. In the later fractions, the molecular weight of wool wax esters increased as the extraction proceeded. The degree of extraction obtain ed varied with pressure from 98% at 650 atm to 30% at 250 atm. While t he bulk of the wool wax extracted had no odour and only a pale colour, it did not appear possible to preferentially remove the wool wax acid s sufficiently to produce a pharmaceutical-grade lanolin by supercriti cal carbon dioxide extraction processes alone. (C) 1997 Elsevier Scien ce B.V.