SUPERVISORS: Thomas ROSENAU, Antje POTTHAST, Karin FACKLER

PROJECT ASSIGNED TO: Takaaki GOTO

Viscose (rayon) manufacture is one of the main production processes for man-made cellulosic fibers. In order to be able to be spun into filaments, cellulosic pulp is converted into a cellulose derivative, cellulose xanthogenate, which is dissolved and thus becomes spinnable. By introduction into an aqueous spinning bath, the cellulose is regenerated and the filaments processes into the whole width of rayon products. The chemical derivatization of the cellulose requires a highly pure cellulosic material (dissolving pulp); conventional (paper grade) pulps are not suitable.

In viscose manufacture, the pulp is steeped with sodium hydroxide, which converts the cellulose into sodium cellulose and removes by-products. These process lyes contain solubilized hemicelluloses as well as lower-molecular weight fragments of cellulose and a plethora of carbohydrate-derived low-molecular weight carboxylic acids, carbonyl compounds, and hydroxyacids. So far the potential of these lyes as a chemical pool of valuable compounds is not used, and the aim of the project is directly derived from this: to screen different approaches for a value-added utilization of process lyes and to further elaborate promising options. This covers a thorough characterization of the complex process streams, a possible pre-fractionation and a determination of chemical properties of individual components as well as combined fractions.

Scheme of viscose (rayon) fiber production (courtesy of Lenzing AG), the red arrow indicating where the process lye arises.