REMOVAL OF EXTRACTIVES DURING TCF BLEACHING OF RADIATA PINE BISULFITEPULP

Two-stage bleaching of radiata pine bisulfite pulp with totally chlori ne free chemicals was studied. A range of alkaline treatments was exam ined for the first stage. These included extraction with alkali, oxida tive extraction, alkaline peroxide and peroxide reinforced oxidative e xtraction. Peroxide under steep bleaching conditions was used for the second stage. The most practical way of preparing a high brightness pu lp with a low content of extractives was by the use of an alkali extra ction, followed by washing and then with steep bleaching.