Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Chemical treatment after start or completion of mechanical...
Patent
1986-03-12
1988-07-12
Chin, Peter
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Chemical treatment after start or completion of mechanical...
162 27, 162 28, 162 78, 162 90, D21B 102, D21B 104, D21C 300, D21C 910
Patent
active
047567996
ABSTRACT:
In accordance with the invention a chemimechanical pulp is produced from lignocellulosic material, for example wood chips, by subjecting the material to a process in which it is steamed, impregnated with alkali and peroxide, drained, pre-heated, refined and bleached. The material is impregnated in a single stage with a solution containing alkali and peroxide. Subsequent to passing an intermediate drainage and reaction stage, the material is pre-heated to a temperature of from about 50.degree. C., but not above 100.degree. C. The material is then refined in one or two stages. The material can be impregnated by immersing the same in the impregnating solution for a period of up to 20 minutes at a temperature of 15.degree.-60.degree. C., or by compressing the material in a screw press and permitting the compressed material to expand in the impregnating solution. The optimal brightness for a given peroxide charge is achieved by a balanced division of the peroxide charge between the chip impregnating stage and the bleaching stage.
REFERENCES:
patent: 4160693 (1979-07-01), Lindahl et al.
patent: 4187141 (1980-02-01), Ahrel
patent: 4486267 (1984-12-01), Prusas
patent: 4599138 (1986-07-01), Lindahl
Agnemo Roland
Bengtsson Goran
Simonson Rune
Bengtsson Goran
Chin Peter
Dang Thi
EKA AB
Simonson Rune
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