Influence of pulping method on the wettability of pulps prepared from pine and spruce

Abstract

The main objective of this research work was to study the wettability of thermomechanical pulps (TMP) prepared from heart- and sapwood of Scots pine ( Pinus sylvestris [ L.]). The TMP were prepared at different pulping temperatures (150 degrees C, 180 degrees C). Furthermore, thermomechanical ( TMP) and chemothermomechanical pulps ( CTMP) from Norway spruce ( Picea abies [ Karst.]) were also investigated. In this case both TMP and CTMP were prepared at 140 degrees C and 180 degrees C. Sheets of all pulps were prepared according to a method developed by Roffael et al. ( 2002). Sheets of TMP pulps from pine sapwood showed much better wettability compared with their counterparts from heartwoods. Pulps from heartwood experienced a dramatic decrease in their wettability when increasing the pulping temperature from 150 degrees C to 180 degrees C. In contrast increasing the temperature from 150 degrees to 180 degrees C seems to have no deleterious effect on the wettability of pulps prepared from sapwood. This phenomenon has been explained by the higher extractive content in pine wood. Comparing TMP and CTMP pulps from Norway spruce leads to the result that in general CTMP pulps are of higher wettability. This can be attributed to the high hydrophobic extractive content in TMP pulps on the one hand and to the higher alkalinity of CTMP pulps on the other hand.