FRACTIONATING HIGH YIELD PULP INTO LONG-FIBRE AND FINE-FIBRE FRACTIONS

摘要

An improved high yield pulp, such as groundwood pulp, thermomechanical pulp, chemimechanical pulp and waste paper pulp having a widened field of use is produced by treating the raw material in a known manner, screening, thickening and bleaching, the pulp subsequent to being bleached at a low pulp consistency being mechanically worked and divided in a fractionating apparatus into a long-fibre fraction and a fine-fibre fraction. The freeness of the long-fibre fraction exceeds and freeness of the fine-fibre fraction by 150-600 ml C.S.F. and the fine-fibre fraction constituents 35-70 % by weight of the pulp quantity obtained after the bleaching stage.