PROPERTIES OF CANDIDATE INTERNAL SIZING AGENTS VERSUS SIZING PERFORMANCE

In this study various fatty acids, with either alum or polyallylamine as a mordant, and isocyanate sizing agents were used to determine the effect of the candidate sizing agent on sizing performance and strengt h properties of bleached hardwood pulp. A variety of observations were made. Sizing agents with 6 or 7 carbon atoms do not give sizing even when they are used in excess and they are well anchored to the fiber s urface. Fatty acids with 18 or more carbon atoms may give poor perform ance if they are not well dispersed. Bulky hydrophobic molecules, such as abietic acid, help to protect the sizing agent-alum-fiber linkage from attack by formic acid. Perfluorinated fatty acid sizing agents do not impart good sizing with either polyallylamine or alum as mordants . Gas chromatographic analysis of stearic acid showed that the passage of time allows free stearic acid to become bound and thereby improve the sizing performance.