THE CHARGE OF FINES ORIGINATING FROM DIFFERENT PARTS OF THE FIBRE WALL.

carbohydrates, mechanical pulp The amount and origin of charged groups in fines from different parts of the fibre wall have been determined. In order to produce the different fines, chips from mainly Norway spruce were refined in a pilot refiner. Most of the fines were removed from the pulp by washing before further refining. This procedure was executed four successive times, and the fibre wall thickness of the long fibre fraction was measured after each refining stage. The fines produced in the first refining stage had less fibrillar material and a higher amount of charged groups than the last fractions. The amount of charged groups was measured both by chemical analysis and polymer adsorption. Three uronic acids were responsible for 80-90 % of the charge, measured in terms of the adsorption of a small cationic polymer for the fines fractions