Chemical Modifier
Modified potato or corn starch carries a permanent positive charge that binds to negatively charged wood fibres and mineral fillers during papermaking. In modern alkaline systems, cationic wet-end starch functions as a dry-strength additive that improves both internal bond strength and surface pick resistance. The modification process involves etherification of natural starch granules to introduce quaternary ammonium groups.
This chemical change ensures that the polymer remains active across a broad pH range.
Retention Mechanism
Electrostatic attraction drives the interaction between the polymer and the cellulose surface. When cationic wet-end starch is added to the stock preparation system before the headbox, it accelerates the drainage of water from the forming web while keeping fine particles and mineral fillers securely suspended within the fibrous matrix. This dual action increases the running speed of the paper machine and optimizes the overall retention of costly additives.
High-speed corrugating lines rely on this treatment to maintain structural integrity in lightweight linerboard and fluting grades. The resulting board exhibits higher burst strength and resistance to edge crush.
Adsorption Limit
Saturation of the anionic fibre sites occurs when the chemical addition rate exceeds the natural binding capacity of the furnish. When this threshold is crossed, excess cationic wet-end starch remains in the process water and causes deposits on the press felt. Regular testing of the white water ensures that the dosage matches the electrical demand of the slurry.
