Studies on Beating

Abstract

Several commercial pulps were beaten by laboratory beaters with steel roll and stone roll, respectively, and the relations between air resistance of paper and beating state were investigated mainly from the viewpoint of the effect of fines produced during beating. 1) Drainage characteristics of pulp suspension and air resistance of sheet are both affected extremely by existence of fines produced during beating (Fig. 2, 3 and 6). Contribution of fibrillation and change in fiber length distribution to air resistance may be neglected as compared with that of fines. 2) The amount of fines produced varies with beating method and kind of pulp (Fig. 4), while air resistance decreases nearly with a certain ratio by removal of fines irrespective of beating method and kind of pulp (Fig. 6). 3) Wet heating results in less amount of fines and higher air resistance at the same amount of fines (Fig. 7). So, air resistance may be determined by both the amount and the quality of fines. Fines produced in wet beating process larger specific surface than free beating. 4) Air resistance increases exponentially with the increase of specific surface of wet pulp. At the same amount of specific surface, free beating results in higher air resistance (Fig. 9). 5) Relation between logarithm of air resistance and specific scattering coefficient of sheet is linear almost irrespective of beating method (Fig. 10). 6) At the same S-R beating degree, wet beating results in higher air resistance (Fig. 12). While, relation between logarithm of air resistance and that of slowness measured with improved slowness tester (Fig. 1) is nearly linear irrespective of beating method and kind of pulp (except NDKP) used in this experiment (Fig. 15). So, improved slowness is thought to be very effective measure for estimating air resistance.