Evaluation of cationic polymers to control pitch deposition

A wide range of cationic polymers of varying chemical structure, charge density and molar mass were evaluated for their effectiveness to control wood resin deposition. The ability of the polymers to attach model wood resin particles to thermo-mechanical pulp fibres and to maintain the wood resin in the colloidal phase was determined over a pH range of 4.75, 6.85 and 8.06. High molar mass poly-DADMAC, copolymer poly-(AM-co-DADMAC) and guar gum were found to be the best fixatives over the pH range investigated. The performance of poly-DADMAC was found to increase with molar mass and charge density. A conceptual model was proposed to explain the behaviour of the polymers based on their ability to stabilise the wood resin colloids, to attach the wood resins to pulp fibres and to affect the wood resin particle size.