The Effect of Mill Closure on Properties of Mechanical Fines

Abstract

The effect of dissoloved and colloidal substances (DCS) in TMP (thermomechanical pulp) white water on the strength properties of handsheets and the flocculation capability of fines with retention aids were investigated.For this experiment, two types of fines were prepared. One is water-washed TMP fines and the other is white-water TMP fines which were fractionated with TMP white water. Breaking length and surface strength of the handsheets containing water-washed TMP fines were higher than that of the handsheets containing white water TMP fines. It is suggested that DCS adsorbed on white water TMP, fines had a detrimental influence on fiber bonding.The extent of flocculation of fines in the white water of a newsprint machine was measured by Photometric Dispersion Analyzer (PDA). The results of flocculation experiments showed that fines extracted with acetone were more easily flocculated with cationic retention aids than fines in white water. The molecular weight of retention aids affected the flocculation of the fines in white water.It is concluded that DCS has negative effects on sheet strength and on the flocculation of fines with retention aids.