New laboratory approach for evaluating kraft mill pitch deposit control additives

The deposition of synthetic pitch emulsions onto transparent plastic films was observed with a microscope. Direct counting of deposited particles versus time gave deposition kinetics. Without deposit control additives, almost every pitch droplet which approached the surface deposited. Treatment with nonylphenol ethoxylates, a standard class of pitch control additives, decreased the rate of deposition but failed to prevent it entirely. Consecutive surface treatment with cationic and anionic polymer not only inhibited deposition but gave deposits which were relatively easy to wash away.