Dmitri Gorski¹, Kjell-Arve Kure², Kathrin Mörseburg³

¹ nsiFOCUS, Norske Skog ASA, Halden, Norway

² Norske Skog Saugbrugs, Halden

³ Paper and Fibre Research Institute, Trondheim

Development of fibre properties such as external and internal fibrillation, fibre split index and the quality of fines fraction is considered to be one of the goals of mechanical pulp refining. In this paper, these fibre properties were linked to critical printing paper properties such as tensile index, light scattering, air permeability, PPS and surface fibre roughening. The recently developed ATMP (Advanced Thermomechanical Pulp) process was compared to a TMP reference as well as an ATMP (aq.) reference, where no process chemicals were used. Both the equipment configuration in ATMP refining (mechanical pre-treatment in Impressafiner and Fiberizer and first stage refining at elevated intensity) and the addition of process chemicals (Mg(OH)₂ and H₂O₂ added to the first stage refiner) were found to have significant influence on the development of fibre properties. This conclusion was confirmed when the physical properties of the sheets made from whole pulp, long fibre fraction and model fibre fraction mixed with different fines fractions were examined. Better developed fines fraction did not contribute to decreased fibre roughening while it decreased air permeability somewhat and increased PPS significantly.