The Effect of Increasing Calcium Ion Concentration on Alkyl Ketene Dimer Sizing Efficiency

This thesis is a study of the relationship between calcium ions and the effectiveness of an alkaline sizing agent. Relationships between the increasing calcium ion concentration of a pure system and the sheet sizing based on the Hercule Size Tester are developed. It was determined that low addition levels of calcium ions increased the level of sizing developed and excessive calcium contents caused sizing response to deteriorate. Proposed mechanisms for this determination involve the compression or the fiber\u27s electrical double layer at low concentrations of calcium, and an adsorption competition between the size and calcium where high concentrations of calcium ions are found. High variability in sizing existed within· a large majority of the handsheets produced. Standard error for handsheet sizing reproducibility averaged around twenty percent. It is suggested that a handsheet sizing method be developed with reduced variability so that the pertinent results are not concealed by excessive error