Effect of PVOH or polyDADMAC addition on surface sizing with oxidized starch

Abstract

High loading of printing and writing grades with fillers has many advantageous aspects in papermaking because it allows decreasing fiber use and reducing manufacturing cost. High loading technology, however, has some disadvantageous aspects as well. It decreases physical properties of papers, especially strength properties. The problem associated with high loading can be reduced by applying surface sizing starch solution onto paper surface. It is important to control the penetration of the surface sizing starch solution into paper web to obtain the desired property improvement. In this study, the effect of the addition of two polymers into starch solution on paper properties has been examined. PVOH and polyDADMAC were used as polymeric additives for surface sizing with oxidized starch. Viscosity of starch solutions and surface roughness of dried starch films on glass slides showed that some interactions between polymeric additives and oxidized starch have been occurred and the most extensive interaction with starch solution was obtained with high molecular weight polyDADMAC. Low molecular weight PVOH was most effective in improving folding endurance and internal bond strength. On the other hand, polymer addition showed no effect on surface strength of paper. This indicates that not the level of starch holdout but the bonding strength of starch itself has predominant influence on surface strength of paper.