Alkenyl Succinic Anhydride

The cationic starch solution used to emulsify ASA must be cooled below 38 Celsius (100 Fahrenheit) and have a pH of 4-4.5 to minimize ASA hydrolysis. If the starch viscosity is excessively high, poor emulsification may result, leading to poor ASA retention, but generally low starch viscosity leads to poor sizing with ASA. A low starch solution pH for emulsification of AKD can interfrere with the process, so the pH should be around 5-7. The starch intrinsic viscosity (4% starch solution at 150 Fahrenheit) should be low, around 1.0 to 1.1, when emulsifying AKD to give maximum sizing, which is the opposite of ASA. Quaternary ammonium starches work better than tetiary ammonium starches for alkaline sizing. Generally, 3:1 cationic starch (about 0.30% N) to ASA or AKD is used for emulsifaction, with an additional 8lb/ton cationic starch for papermaking.