Effect of Simultaneous Addition of Cationic Starch and Bentonite on Some Properties of Writing and Printing Paper

Nano and micro particle systems including a cationic polymer such as cationic starch and nanoparticle such as bentonite have been utilized as retention and drainage aid. In this research, the effect of simultaneous addition of cationic starch and bentonite nanoparticles on fine retention, and drainage of the pulp slurry and on some strength properties of hand sheets were investigated. A combination of the three levels (0.5, 1 and 1.5%) of cationic starch and one of the three levels (0, 0.2 and 0.4%) of bentonite were used. The results revealed that the highest fine retention was at 0.5% cationic starch addition, but the highest drainage was obtained adding 0.4% bentonite and 1.5% cationic starch. However, the interactive effect of the variables retention and drainage was not statistically significant. Application of 0.2% bentonite and 1% cationic starch; 0.2% bentonite and 1% cationic starch or 1.5% cationic starch produced the highest tensile strength index and tear strength index in hand sheets respectively. The highest burst strength index of the papers was related to the addition of only 1% cationic starch.