Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Chemical treatment after start or completion of mechanical...
Patent
1982-06-04
1985-03-05
Alvo, Steve
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Chemical treatment after start or completion of mechanical...
162 28, 162 55, 162 84, 162149, D21C 304, D21C 326
Patent
active
045029180
ABSTRACT:
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.degree.-160.degree. C. and maintaining the particles in the temperature 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 temperature in the range of about 100.degree.-160.degree. C. for a period of time in the range of about 2-120 minutes; refining the cooked sodium sulfite treated reject fraction; and recombining at least part of the refined reject fraction with at least part of the accept fraction.
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Joyce Peter
Mackie David M.
Alvo Steve
MacMillan Bloedel Limited
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