The Use of Cationic Agents to Increase the Efficiency of Titanium Dioxide in Paper

Handsheets were made with a bleached sulfite pulp, titanium dioxide and cationic agents. The optical properties of these sheets were studied in order to determine and compare the efficiency of the titanium dioxide retained. The cationic agents used in this study were a quaternary ammonium salt, a polyamide, cationic starches made with these two chemicals, and a commercial cationic starch. When the optical properties of handsheets made from these substances were compared, it was found that the quaternary ammonium salt gave the highest opacity but the lowest retention. The polyamide gave lower opacities but higher retentions. The cationic starches made from these cationic chemicals showed slightly lower opacities than the cationic chemicals by themselves but they gave much higher retentions. The commercial cationic starch gave intermediate retention but lower opacity. It was concluded that the quaternary ammonium salt gave the best dispersion of the titanium dioxide but gave the lowest cationic charge to the pigment. The polymide gave a slightly poorer dispersion but gave a much higher charge to the pigment. The cationic starches gave the best retention through a combination of mechanical and physio-chemical retention, but did not disperse the pigment too well