Alkaline Sizing of Mechanical Pulp

  • Kim, Bong-Yong (Department of Wood Science and Technology, College of Agriculture, Kyungpook National University) ;
  • Akira Isogai (Department of Biomaterial Science, Graduate School of Agricultural and Life Science, The University of Tokyo)
  • Published : 2000.12.01


Alkaline Sizing behavior and mechanism of handsheets, which were prepared from thermomechanical pulp (TMP) with alkylketene dimer (AKD), were studied in terms of the conditions of the handsheet-making. AKD content in the TMP handsheets was increased with increasing of AKD addition level and the addition of a polyamideamine-epichlorohydrin resin (PAE) clearly enhanced AKD retention as well as the resultant sizing performance of TMP handsheets. Although drying of the AKD sized TMP webs at $20^{\circ}C$ led to no or quite low sizing level, but TMP handsheets sized with AKD had higher sizing degrees with increasing of the temperature of heat treatment. Scanning electron microscopic observations of the AKD-sized TMP handsheets showed that AKD emulsion particles were present on pulp fiber surfaces independently without coagulation in the TMP handsheets dried at $20^{\circ}C$. Heat treatment of the AKD-sized handsheets resulted in disappearance of the AKD emulsion particles because of their melting and spreading. The addition of calcium carbonate filler to the TMP suspensions did not influence on AKD content in the TMP handsheets. Nevertheless, their sizing degrees clearly increased by the addition of $CaCO_3$filler. Probably, AKD molecules adsorbed on the $CaCO_3$filler particles contribute to the enhancement of sizing performance. Thus, AKD can give sizing features effectively to the TMP handsheets, when they are made under suitable conditions.



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