Two-stage chemical treatment of mechanical wood pulp

Details Two-stage chemical treatment of mechanical wood pulp Two-stage chemical treatment of mechanical wood pulp

D - Textiles, Paper

21

C

9/13

D21C 3/06 (2006.01) D21B 1/02 (2006.01) D21C 3/26 (2006.01)

Patent

CA 1177608

ABSTRACT OF THE DISCLOSURE A two-stage chemical treatment process is disclosed for increasing the density, strength and brightness properties of mechanical wood pulp. The method comprises the steps of: applying an aqueous solution of sodium sulfite in the range of about 1%- 10% sodium sulfite based on bone dry weight of wood to wood particles, the solution having a pH in the range of about 4.5-11; heating the sodium sulfite treated wood particles to a temperature in the range of about 100-160°C and maintaining the particles in the tem- perature range for a period of time in the range of about 20 seconds to 10 minutes; refining the heated sodium sulfite treated wood particles into mechanical wood pulp; separating the pulp into a reject fraction and an accept fraction, the reject fraction containing a higher proportion of shives and long fiber material; applying an aqueous solution of sodium sulfite, in the range of about 4%-50% sodium sulfite based on bone dry weight of wood, to the reject fraction, the solution having a pH in the range of about 4.5-11; cooking the sodium sulfite treated reject fraction at a tempera- ture in the range of about 100°-160°C for a period of time in the range of about 2-120 minutes; refining the cooked sodium sulfite treated reject fraction; and re- combining at least part of the refined reject fraction with at least part of the accept fraction.

404723

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