Improving the strength of PGW pine pulp by alkaline peroxide treatment

In Nordic Countries the predominant softwood species used in mechanical pulping is Norway spruce. Utilization of Scots pine is restricted by its high extractive (resin) content. In addition, the strength properties of mechanical pine Pulps are not as good as those of the corresponding spruce pulps. A selective extractives removal from mechanical pine Pulps by solvent extraction results in a considerable improvement in the sheet strength properties. In this Study the possibilities of decreasing extractive content and improving the sheet strength properties of pressure groundwood (PGW) pine Pulp by alkaline peroxide treatment were examined. Dissolution of extractives of PGW pine pulp increased at high alkalinity. As both extractives and carbohydrates are dissolved under alkaline peroxide treatment, a selective removal of extractives of PGW Pine Pulp is hardly possible by washing of alkaline peroxide treated Pulps. Alkaline peroxide treatment Using high alkali charges resulted in improvements in fibre bonding. The results suggest that alkalinity rather than peroxide charge is the more dominant factor affecting the bonding ability. Although there was in increase in fibre flexibility, the increase in the bonding ability of fibre surfaces seemed to be the dominant factor relating to strength improvement. The results suggest, that the fibre bonding was affected not only by an increase in the number of carboxyl groups on the fibre surfaces but also by dissolution and washing Out of carbohydrates and extractives. Definition of relative importance of these factors on fiber bonding remains a Subject of subsequent studies. On the basis of the results, alkaline peroxide treatment with high alkali charges followed by washing Could be used for improving strength properties as well as for reducing the extractive content of the PGW pine pulp.