Oxygen Delignification and Bleaching of Industrial Hemp Pulps

The oxygen delignification of unbleached kraft pulps produced from industrial hemp stalks and hemp 'wood' was studied, as well as the susceptibility of such pulps to bleaching. Hemp stalk and wood pulp showed comparable susceptibility to delignification with oxygen in alkaline media and good bleachability in the elemental chlorine free (ECF) and the total chlorine free (TCF) bleaching processes. Good bleachability was also shown by hemp bast fibre pulp. The final yield and intrinsic viscosity of bleached pulps produced from industrial hemp were also determined and compared with the properties of pulps produced from tree wood. It was found that the final yield of bleached hemp stalk pulp was higher than that of conventional bleached birch- and pine papermaking pulps. However, the retention of high intrinsic viscosity in hemp pulps can be achieved by varying the conditions of the oxygen delignification and bleaching processes.