Abstract:

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