Effect of deinking chemicals on the deposition of fines and fillers on an air-water interface

The deposition of precipitated CaCO3 (PCC) fillers and thermomechanical fines onto an air-water interface was studied by the impinging jet technique. It was found that, in the absence of deinking chemicals, PCC deposits on the air-water interface while fines do not. In the presence of sodium oleate and calcium chloride, an appreciable deposition of fines and fillers occurred. The mechanism of deposition is the same as that for ink particles depositing on an air bubble: calcium soap particles, which can adsorb onto fillers, fines and an air-water interface form a bridge between fines or fillers and the air-water interface. The rate of deposition of fillers can be reduced by dispersants. Fibrillated fines form entangled webs in the interface in which larger particles can be captured. Fines can be removed from the air-water interface by high shear.