Dissolving pulps are produced for manufacturing various cellulose-derived products, including regenerated cellulose fibers (e.g. viscose). The viscose capacity in Asia has been increasing enormously during recent years, which has resulted in an increase in dissolving pulp production. The annual production capacity of wood-based dissolving pulps is about 7 million tons globally. The processability of a dissolving pulp is often described as its reactivity towards derivatization. There are three reactive hydroxyl groups in each β-D-glucopyranose within the cellulose chain and the reactivity is related to the relative ease by which the hydroxyl groups can be substituted by the reactants. However, there is currently no single analytical method to reliably measure the quality (reactivity) of dissolving pulps. In this study we aim to investigate the reactivity of several commercial pulps by measuring the viscose filterability and the fiber wall pore size distribution. The viscose filterability method simulates the conversion process of the dissolving pulp to viscose (cellulose xanthate solution) on a laboratory scale. For this purpose, a bench-scale viscose plant has been developed according to a modified test plant as described by Treiber[1] where the conversion process is evaluated thoroughly step-by-step, until the viscose is finally filtrated using deep bed filtration. The accessibility of the cellulose molecules in both crystalline and amorphous domains are affected by the raw material properties and the different process concepts to remove non-cellulosic components during the dissolving pulp manufacture. The effects of the applied purification processes on the microfibrillar structure and dimensions of cellulose in different commercial dissolving pulps are investigated by solid-state NMR spectroscopy. Moreover, the fiber wall pore size is also investigated using fiber saturation point (FSP) and BET measurements. The results from these measurements are then related to the viscose filterability and to the overall quality of the dissolving pulp. 1. Treiber, E., et al., A small-scale laboratory viscose plant for testing rayon grade pulps. Das Papier, 1962. 16(3): p. 85-94.

Viscose filterability and fiber wall pore size as measures for pulp reactivity

251st National Meeting (2016)

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