Surface Mechanical Treatment of TMP Pulp Fibers Using Grit Material

The authors studied surface mechanical treatments of thermomechanical pulp fibers using a grit material after first-stage refining and the treatment’s impact on second-stage refining. The surface mechanical treatment was performed using an ultra-fine friction grinder. The grit size of the grinding stone, the intensity of treatment and the rotational speed were optimized to accomplish rapid development and minimization of pulp fiber shorten-ing. The second stage of refining was carried out using a wing defibrator operated under typical TMP refining conditions. Surface mechanical treatment using a grinding stone with a grit diameter of 297-420 µm, operated at a contact point of the stones and a high rotational speed of 1500 rpm, provided an efficient disruption of pulp fibers with minimized cutting. A promising degree of fiber cell wall fracture was obtained when the energy applied during disruption was approximately 20% of the total refiner energy consumption. During second stage refining the disrupted pulp developed freeness more quickly while requiring 37% less energy. Laboratory sheets showed no significant differences in properties between the disrupted and non-disrupted pulps at a given freeness.