Paperboard Wet End Additive Sorption Mechanics and Chemical Retention Verification
Verify paperboard wet end additive retention using dynamic drainage jars and extraction GC-MS to ensure food contact compliance and prevent converting failures.
Dissolved and Colloidal Substances
Contaminant Matrix
Process water reuse in paper mills concentrates organic and inorganic material released from wood pulp or recycled paper stock. The collective term dissolved and colloidal substances refers to wood extractives, resin acids, pitch, hemicellulose, and chemical additives suspended in wet-end white water loops. Paper machine operators monitor these substances to prevent pitch deposition, reduce chemical additive consumption, and maintain sheet formation quality.
Accumulation Process
Process water circuit closure increases the concentration of non-retained organic material, destabilizing wet-end chemistry. Higher levels of dissolved and colloidal substances neutralize cationic wet-end additives like retention aids, sizing agents, and dry strength resins, forcing mills to increase chemical dosing rates. Testing methodologies employ centrifugal separation, total organic carbon analysis, and charge titration to measure sticky colloidal pitch and dissolved wood sugars.
Biological treatment systems, microfiltration units, and fixative polymers are deployed to charge-neutralize or remove these contaminants before they agglomerate into macro-stickies. Uncontrolled accumulation leads to wire blinding, press felt plugging, paper surface spots, and web breaks during high-speed manufacturing.
Deposition Limit
Precipitated colloidal particles adhere to machine surfaces when water temperature, pH, or salt concentrations exceed stability thresholds. Excessive accumulation impairs paper strength by interfering with inter-fibre hydrogen bonding across the forming sheet.