Surface characterization of rosin sizing agent on paper - Surface coverage ratio of rosin sizing agents on pulp fiber

Distribution of rosin size in handsheets, which were prepared from hardwood bleached kraft pulp added with either soap-type rosin size or emulsion-type rosin size, was studied using the following two methods: (A) back-scattering mode of scanning electron microscopy for handsheets pre-treated with OsO4 in the gas phase, and (B) ESCA angle-dependent technique. Rosin size components were observed as contrasted area from back-scattered electron images. No clear difference in areas due to rosin size components was observed between the handsheets dried at 20 degrees C and those heated at 170 degrees C for 20 sec., when the handsheets from L.BKP added with soap-type rosin were used as samples. In the case of handsheets prepared from L.BKP with emulsion-type rosin size, the areas due to size components decreased by heat treatment, suggesting that partial melting and spreading of the size components occurred on pulp fiber surfaces. On the other hand, when the ESCA angle-dependent technique was used, areas due to rosin size components clearly increased by the heat treatment at 170 degrees C for 20 sec. for the handsheets prepared with emulsion rosin size at any addition levels examined. The maximum coverage ratio of emulsion-type rosin size was calculated as about 48% on paper surface. The difference in coverage ratios obtained between the two methods may be ascribed to that in the detectable depth.