Influences of fatty acid anhydride components present in AKD wax on emulsion stability and paper sizing performance

The role of fatty acid anhydrides present as one of the by-products in commercial alkylketene dimer (AKD) waxes was studied in terms of AKD emulsion stability and paper sizing performance. Wax emulsions were prepared from mixtures of AKD waxes synthesized under different conditions and fatty acid anhydrides with various weight ratios, and subjected to stability tests and handsheet-making. Content of fatty acid anhydrides in total waxes varied from 5 to 45%. The presence of fatty acid anhydrides had little influence on zeta-potentials of the emulsion particles, sizing performance or AKD retention behavior in producing hand sheets containing AKD emulsions. However, the emulsion stability as measured by a temperature-shock stabilization treatment clearly decrease with increasing content of fatty acid anhydrides in the waxes, and there were clear increases in emulsion viscosity, particle size and scum weight.