低密度調整剤の添加による紙の低密度化と空隙構造の変化

抄録

When the bulking promoter is added to pulp slurries at the wet end, the additive behaves like surface-active agent and partially prevents the formation of interfiber bonds in the handsheet. Therefore, an increase in paper thickness at the same basis weight could be performed. The tensile strength of the handsheets varied in proportion to the reduction of sheet density. Furthermore, considerable decreases in sheet density were observed for the acidic handsheets, compared with neutralized handsheets. The Page equation (1/T=1/F+1/B) was used to evaluate the strength contributions of single fiber and interfiber bond to tensile strength of handsheet. As a result, decreases in interfiber strength and only slight changes in zero-span tensile strength were obtained for both acidic and neutralized handsheets with addition of the bulking promoter. It was confirmed that the decrease in tensile strength of handsheet was dependent on the decrease in interfiber bond strength. Pore structures of the handsheets were characterized by mercury porosimetry. Addition of the bulking promoters caused increases in total pore volumes. Furthermore the major peak of control handsheet in the pore diameter 4 to 6μm region was broadened by addition of the bulking promoters. The light scattering coefficient of the handsheet reasonably increased because of its high porosity. Improvement of sheet thickness was confirmed by the SEM observation. The addition of the bulking promoters is capable of affecting not only in the interfibers but also in the pore structure of fiber wall.