Alkyl Ketene Dimer Wet End Hydrolysis in Alkaline Hardwood Furnish
Alkyl ketene dimer hydrolysis in alkaline hardwood stock converts active sizing wax into unreactive dialkyl ketone, raising chemical costs and felt deposits.
Wet End Hydrolysis
Chemical Degradation
Bond cleavage by water molecules occurs within the stock preparation area of paper production before the sheet formation phase. Wet end hydrolysis describes this irreversible breakdown of internal sizing agents or synthetic polymer additives when they remain in contact with acidic water over extended durations. Reaction rates increase when process temperatures rise or when the pH levels deviate from the alkaline neutral target range required for stability.
Processing Impact
Performance losses happen as the molecular weight of sizing agents drops, which prevents the proper orientation of hydrophobic chains on the cellulose fibre surfaces. Operators track this through the loss of Cobb sizing values and reduced water resistance in the finished board or paper product. High levels of chemical breakdown lead to excessive foaming in the headbox and the deposition of sticky contaminants on the wire mesh or press rolls.
Increased water temperature accelerates the cleavage of ester bonds within alkyl ketene dimer molecules. This reduction in sizing efficiency demands a higher dosing rate of chemical additives to maintain the required specifications for the substrate.
Systematic Control
Tight monitoring of retention aid performance and the stability of sizing emulsions prevents the premature exhaustion of active chemical species before they anchor to the fibres. Process engineers balance the dwell time of additives against the circulation rate to ensure that reactions with water molecules stay within manageable limits. Controlling the ionic charge balance in the aqueous suspension reduces the probability of rapid molecular decay.
Consistent thermal management at the stock inlet provides the primary protection against the accelerated chemical deterioration of paper additives.