USE OF A DYNAMIC SHEET FORMER (DSF) TO EXAMINE THE EFFECT OF FILLER ADDITION AND WHITE WATER RECIRCULATION ON FINE PAPERS CONTAINING HIGH-YIELD PULP

With increased interest in using high-yield pulps (HYP) in uncoated and coated wood-free paper, there is a need to evaluate the effects of HYP under the conditions similar to commercial paper machine operations. Such tests were carried out by means of a Dynamic Sheet Former (DSF) sheet with white water recirculation, considering the high fines content of HYP and the usually high filler content in fine papers. In this study, we evaluated the use of a DSF that is equipped with a white water recirculation tank for making oriented sheets under various conditions. The effects of different factors such as operational variables, use of retention aids, and recirculation of white water were examined and clarified in terms of retention of fines and fillers as well as their impact on paper properties. The effect of HYP content on filler retention was also examined.