Chemical Polymer
Positively charged polymer derived from natural sources used to improve the dry strength and drainage of a paper web. Application of cationic starch hydrocolloid occurs primarily at the wet end of the paper machine where it binds to the negatively charged cellulose fibres and fine particles. It provides a bridge between fibres that enhances the internal bond strength of the resulting sheet.
Functional Mechanism
Electrostatic attraction drives the retention of the additive within the pulp slurry. Because most fillers and fibres carry an anionic charge, the introduction of a cationic starch hydrocolloid creates a stable network that reduces the loss of material through the forming wire. This interaction helps to maintain a clean white water system and prevents the build up of deposits in the machinery.
Higher levels of substitution in the starch molecule lead to stronger bonds but require careful monitoring of the zeta potential to avoid over-cationising the system, resulting in poor formation.
Operational Constraint
Effectiveness of the polymer depends on the overall charge balance of the mill water system. If the system contains too much anionic trash, the cationic starch hydrocolloid neutralises before it can bind to the fibres properly. Precise dosing ensures that the paper achieves the required burst and tensile strength without causing foam or drainage issues during production.
