Chemical Retainer
Wet-end chemical addition in paper manufacturing regulates the ionic balance and bonding strength of the cellulose matrix. Correct cationic starch dosing ensures that the positively charged polymer binds effectively to the negatively charged wood fibres and fine particles during sheet formation. This ionic interaction helps to retain mineral fillers and strengthens the paperboard sheet.
Dry Strength
Fiber bonding is significantly enhanced when the starch molecules spread evenly across the slurry. In addition to dry strength improvement, this treatment reduces the release of dust and lint during subsequent printing processes. Excess addition, however, can reverse the charge of the system, causing the starch to remain in the process water and increasing the biological oxygen demand of the mill effluent.
Running the system at the optimal charge window protects both sheet integrity and water treatment efficiency.
Dosing Measurement
Monitoring the concentration of this additive is achieved through online charge analyzers that measure the streaming current of the white water. A precise dosing rate must be maintained to prevent spotty adhesion and poor surface picking resistance on offset printing presses. Papermakers adjust the flow rate of the liquid starch solution based on the incoming pulp wood species and the recycling content of the stock, as highly recycled furnishes require higher starch addition to compensate for degraded fibres.
This control ensures that the final packaging board meets the required internal bond strength while maintaining a clean, dust-free converting environment on the folders and gluers.
