Abstract
In order to reduce pitch trouble of bleached sulfite pulp (softwood : hardwood = 50 : 50) in paper making, some investigations were carried out on the effects of acidification of pulp slurry and addition of aluminium sulfate suggested by Gustafsson et al (1), as well as (NaP03) 6 by Nagrodski et al (2) on reduction of sticky pitch produced during beating process. Contrary to the result of (1), acidification had no effect on the reduction of aluminium sulfate only exerted a bad influence at low pH in the case of the BSP (Fig. 1 & 2), although we also found the similar results to that of (1) in the case of unbleached soft wood sulfite pulp (Fig. 5). While aluminium sulfate had a noticeable effect if pH increased over ea. 5.5 by addition of NaOH (Fig. 3 & Tab. 1). It is supposed that the formation of flocky aluminium hydroxide and its combination with or occlusion of pitch particles may be necessary to the sticky pitch in BSP which chlorinated in bleaching process. The effect was more as addition of alum-inium sulfate increased. Higher temperature should be avoided, since increased the amount of pitch. (NaPO3) 6 was also effective, and its effect at 1.5 % addition for pulp was comparable to that of 0.5 % of aluminium sulfate. Addition of aluminium sulfate in beating process had no influence on rate of beating (Fig. 4) and sizing effect (Tab. 2).
