NEUTRAL SULPHITE SEMICHEMICAL PULP FROM HARD WOOD

We have obtained following results by the bleaching of birch NSSC pulp.Pulp of high α-cellulose content can be obtained by a smaller consumption of Cl2, from a more sufficiently cooked unbleached pulp rather than from an unsufficiently cooked pulp.The yield of bleached pulp based on chips was also higher in the former condition.By the bleaching of pulp of about 12% Cl2 absorption number by way of Cl2, NaOH and bleaching powder, bleached pulp of 86% α-cellulose content was easily obtained, but it was difficult to increase the a-cellulose content over 86%.If high α-collulose content is not needed, a bleached pulp of 82% α-cellulose content can be obtained by a smaller consumption of Cl2 (16%) and NaOH (5%).The yield of these bleached pulps based on chips is over 57%.