Cationic starch is a modified starch. The cationic starches mainly used as wet-end starch. Although native starch can be used as wet-end starch, but cationic starches are more preferable. As the cationic starches are positively charged, they are easily attracted by the negatively charged cellulose fiber and fillers. As a result fiber-to-fiber and fiber-to-filler bond are increased. Hence improved the retention of fines and filler and also increased paper sheet strength.
Commercially Available cationic starches are two types; quaternary ammonium type cationic starch and tertiary amino type cationic starch. Quaternary ammonium type starch is cationic in all pH range, whereas tertiary amino type starch is cationic only in the acidic range. It is the main problem of the application of tertiary amino type of cationic starch. Hence the applications of tertiary amino type of cationic starch are limited.
The quaternary ammonium containing group attached at the C6 position of the starch. Since the –OH group of this position is more active.
Benefit of Cationic Starch in Paper mill Industry:
Cationic starch enhances paper strength, water drainage, retention, improve paper quality; reduced dusting, linting and size addition; greater control of paper making process hence less paper web breaks and improve paper machine runnability as well as productivity. Cationic starch also allowed using more filler and more recycled fibers so reduce furnishes cost. As a surface size agent, cationic starch improves stiffness, opacity, printing quality and brightness.
Specification Of cationic starch
Physical state: odorless powder
Moisture Content % w/w (at 105°C-110°C): 14 max
pH value: 10% solution, 5-8
Viscosity 5% at 50℃: high (greater than 2200 cps)
Whiteness: 88% min.
Fineness (100 mesh): 99% min
Nitrogen content: up to 0.3%