COMBINED TREATMENTS TO UPGRADE REPULPED LONG FIBER KRAFT PAPER

摘要

As known,increase in the number of chemical pulp utilization cycles diminishes the bonding capacity,which leads to papers with lower strength properties.Such properties are later on recovered industrially through refining mechanical actions,which generate more cellulose fines and thus reduce pulp drainage rate in the paper machine.The present work analyzes different alternatives to the treatment of long fibre kraft pulp recycled in the laboratory.To obtain synergistic improvements in upgrading the mentioned pulp,the effects of combined mechanical and chemical treatments were studied.The relative effects of treating the recycled pulp first with alkali and then by applying selective refining actions in a PFI mill-i.e.,radial (pure) compression and radial compression plus different axial shear levels -were particularly evaluated.Further on,the evolution of the properties under analysis was compared with those of the pulp without chemical treatment and with standard refining,respectively.Alkaline treatment with NaOH,combined with pure compression refining,seems to be the most convenient procedure to obtain a higher final drainability and a lower energy consumption for a given tensile strength index,compared with its counterpart,which adds shear actions.