THE ACTION OF CATIONIC POLYMERS IN THE FIXATION OF DISSOLVED AND COLLOIDAL SUBSTANCES .2.

In order to find the optimum way of reducing the amount of dissolved a nd colloidal (DC) material in a papermaking furnish, a large number of cationic polyelectrolytes have been tested on a laboratory furnish. R emoval of DC material is essential if dry and wet strength aids are to be used efficiently in paper production. To clarify the detected effe cts, a limited model study with polystyrene latex and bleached chemica l cellulosic fibres was also conducted. The results of this investigat ion shaw that the removal efficiency of the polyelectrolytes was large ly influenced by the concentration of cellulosic fibres and the concen tration of DC material in the suspension to be treated. This is believ ed to be due to the fact that when polymers are adsorbed on colloids a nd cellulosic fibres, they rapidly adopt a flat configuration on the p articles. If the polymers have reconformed to this configuration befor e the particle meets another particle or a fibre there will be no brid ging type of flocculation. If the particle concentration is increased, the time between collisions is decreased and a bridging type of flocc ulation can take place. The results of the model experiments support t his hypothesis and from experiments with different modes of polymer ad dition it can be suggested that there is a fixation of latex particles (and DC material) to fibres at high concentrations of both latex (and DC material) and fibres.