Novel Absorbing Fibres Based on Cellulose Acetate

Cellulose acetate having a degree of substitution (DS) of about 2.5 is known as a well-established technical product, which is processed to fibres, filter tow, membranes and thermoplastic materials. In general, the properties of this cellulose ester are strongly depending on the DS as it can be found for any cellulose derivative. Moreover, cellulose acetates cover a wider range of different properties that have not yet been used so far. These materials remain cellulose-like at very low DS-values, but become more and more hydrophilic as DS reaches about 1.5, accompanied by an enhanced swellability and water adsorption as borderline case. When exceeding this DS, the solubility characteristic turn back to hydrophobicity and finally approach that of commercial cellulose-2.5-acetates (thermoplastic, soluble in organic solvents). Nowadays, ionic liquids (IL), which have already attracted attention in cellulose research since a couple of years, provide the opportunity to combine both, chemical modification and physical shaping for the first time. With this cellulose acetate fibres with an adjustable DS-value are accessible without intermediate product isolation, because the used IL serves as solvent for reaction and shaping. In particular, the preparation of biodegradable absorbing fibres is described characterised by high retention behaviour for water and electrolyte solutions.