The effect of dissolved and colloidal substances released from TMP on the properties of TMP fines

An experimental method to manufacture a model "white water" from mechanical pulp by leaching of the pulp in distilled water is presented. This water, which contains dissolved and colloidal substances "DCS", is fractionated into two fractions: a fraction which contains solely dissolved substances, "DS", and a fraction enriched in colloidal particles, "CS". The major part of the lipophilic extractives were found in the "CS" fraction and had a similar composition as the extractives in the non-fractionted water sample, the "DS" fraction contained no detectable amounts of neutral components and small amounts of fatty and resin acids. Galactoglucomannan was the dominating dissolved polysaccharide, Arabinose or Xylose were not detected in the water. The effect of these types of "white water" on the characteristics of TMP was studied by addition of different amounts to cationised TMP fines prior to sheet making. Fines were chosen as a model system because they are probably more susceptible to adsorption of "DCS" than coarser fractions, due to higher specific surface area. It was shown that water containing colloidal particles decreased the tensile strength of handsheets and that this decrease becomes more pronounced if the addition of colloial particles is increased. It is suggested that this decrease is linked to the amount of lipophilic extractives present on the surface of the fines and it is shown that the decrease begins to occur at a surface coverage of about 45%, as calculated from ESCA data. The tensile index was not affected by addtion of "DS" under the experimental conditions used. The light absorption coefficent of the sheets increased upon addition of all water fractions, which indicates that the dissolved substances are an important reason for the observed darker colour.