Practical Aspects of Alkaline Sizing I on Kinetics of AKD Reactions Hydrolysis of AKD, 1990 Papermakers Conference Proceedings

Joseph Marton--Stability of AKD emulsions is adversely affected by elevated temperature, dilution, elevated pH, and the presence of accelerators. The main product of the hydrolytic changes is an inactive dialkyl ketone. Under average mill conditions, a significant part of the applied AKD may end up in this form in the sheet. The fate of AKD can be followed by combination of extraction, GLC, and IR spectroscopy methods described in this paper. Hydrolysis kinetics of AKD in two commercial preparations was studied. The apparent activation energy of AKD hydrolysis at pH 8 is 105 KJoule/mole, about double the activation energy published by Lindstrom for cellulose esterification with AKD. While the approximate rate constant of hydrolysis at around 3O’C is 25 times less than the rate constant of the esterification or cure, the rate gap is decreasing at elevated temperatures. Hydrolysis rate also is accelerated by the conventionally-used sizing promoters. The main byproduct of the diketene hydrolysis, ketone, is not innocuous, does not contribute much to hydrophobization of the sheet, and plays a role in its slipperiness.