THE EFFECT OF HEMICELLULOSES ON THE PAPERMAKING PROPERTIES OF WHITE BIRCH

A fibrous holocellulose was isolated from white birch using hot acidified sodium chlorite solutions. Pulps of varying hemicellulose content were prepared by alkaline treatment, and their beating and sheetmaking properties compared with the original holocellulose. Tensile strength increased with hemicellulose content, whereas tearing resistance and fold endurance decreased. Bursting strength reached a maximum at about 15% alkali-extractable hemicellulose content. Pulps obtained in yields of 46–53%, i.e., containing 10–20% hemicellulose, possessed the best over-all strength.A bleached sulphite pulp prepared from the same chips in a yield of 43.6% contained 20.7% alkali-extractable hemicellulose. The over-all yield of α-cellulose was about 6% lower, based on the wood, than in the case of the holocellulose, thus indicating greater fiber damage during the sulphite process. Hand sheets made from the sulphite pulp were inferior to sheets made from a chlorite pulp of the same hemicellulose content in bursting and...