ONE AND 2-STAGE APTMP((TM)) - A ROUTE TO HIGH-BRIGHTNESS PULP

Pilot studies on low-level chemical APTMP processes that utilized eith er one or two stages of impregnation prior to primary refining of heml ock/true fir chips from the Smurfit Newsprint, Newberg, OR, mill are r eported. Results of this work indicate that two-stage impregnation is more efficient in terms of brightness gains attainable at a given chem ical charge. Up to 14 points ISO were gained using less than 2.0% H2O2 with two stages. With two-stage impregnation, tear index improved by 28%. One-stage impregnation did not improve tear. Large reductions in shive content, 61% and 83%, could be realized by one- or two-stage APT MP treatment, respectively. Other strength properties and specific ene rgy requirements were minimally affected. This may have been due to th e relatively low alkali charges used to ensure adequate brightening.