Selectivity improvement during oxygen delignification by adsorption of a sugar-based polymer, Journal of Pulp and Paper Science, February 2003, Vol. 29(2) (974KB)

Pulp strength loss during oxygen delignification is caused by cellulose depolymerization resulting from attack by radicals generated during delignification reactions. The objective was to investigate the use of radical-scavenging polymer additives that adsorb on cellulose surfaces where protection from radicals is needed. Increases in lignin–cellulose selectivity were observed for guar galactomannan as the adsorbed additive at charges as low as 0.3% on pulp. At 2.0% guar on pulp, the selectivity improvement was ~30%, with a similar reduction in the loss of wet zero-span breaking length. The cellulose depolymerization, expressed as the number of chain scissions, and kappa number were corrected for alkali extraction in the absence of oxygen. This analysis provides a fundamental understanding of the mechanism of oxygen delignification. Guar adsorption on pulp was measured using high-performance chromatography. Selectivity and wet zero span measurements were then related to the adsorbed amount of guar.