Cationic starch and polyacrylamides for alkenyl succinic anhydride (ASA) emulsification for sizing of cellulosic fibers

Paper is composed of polysaccharides mainly cellulose and carbohydrates. The hydroxyl groups present in cellulose react with various substances added to fibrous slurry. Treating the cellulosic fibers chemically, which tends to develop the resistance to aqueous liquid absorption, is known as internal sizing of paper. The main internal alkaline sizing chemicals are alkyl ketene dimer and alkenyl succinic anhydride (ASA). In situ emulsification of ASA using cationic starch (CS) is conventionally practiced because of the low shelf life of ASA emulsion. In the present communication polyacrylamides (PAMs) have been used as an alternative chemical to cationic starch at very low dosages than cationic starch and varying ratios of ASA to polyacrylamides to stabilize the ASA droplets. The colloidal stability of ASA emulsions was measured in terms of particle size distribution, sizing performance, pH and percent hydrolysis of ASA with the passage of time. The ASA emulsions prepared with PAMs at very low dosage were observed with superior colloidal stability and sizing behaviour than the CS stabilized emulsion. Graphic abstract