Date of Award
Bachelor of Science
Pulp and Paper Technology
Dr. Stephen Kukolich
The effect of pH on the efficiency of the cationic agents, Kymene 557 (Epichlorohydrin) and Tydex (Polyethylenimine), was studied, and the efficiencies of the two cationic agents were compared.
The pH at which cationic agents are most effective, considering percent retention of titanium dioxide, is pH 5.7 at the time of titanium dioxide slurry addition. The pH for optimum opacity in a sheet is pH 6.0.
A pH that is controlled by alum, rather than independently of alum, produces higher titanium dioxide retentions and opacities. Maximum efficiency is not controlled by pH alone. An alum loading of about 3.5% should be present at the time of titanium dioxide addition.
Although the pH 5.7 produces the best results at the point just before the titanium dioxide-cationic agent slurry is added, if one retains this pH, by adjusting pH of dilution water, right up to the point of sheet formation, the efficiency of the cationic agent decreases.
Comparing Kymene and Tydex as cationic agents, Kymene produced the best retention of titanium dioxide and opacity in the sheet, when the cationic agent was added to the titanium dioxide particles. At pH 7.0 Kymene produced a zeta potential of +2.54mV on the titanium dioxide, and Tydex only produced +0.99mV.
Oakleaf, Stanley L., "The Effects of pH on Cationic Agents to Increase the Efficiency of TiO2 in Paper" (1970). Paper Engineering Senior Theses. 413.