Continuous cooking of cellulosic fibrous material with cold alka

Details Continuous cooking of cellulosic fibrous material with cold alka Continuous cooking of cellulosic fibrous material with cold alka

1995-02-08

1997-10-07

Czaja, Donald E.

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Continuous chemical treatment or continuous charging or...

162 41, 162 43, 162 62, 162237, D21C 326

Patent

active

056743599

ABSTRACT:
The pretreatment of cellulosic fibrous material is adjusted to improve pulp strength. The cellulosic material is initially pretreated with a low temperature alkaline liquid (e.g. 80.degree.-110.degree. C.), and then with a higher temperature (but still below cooking temperature), higher alkali concentration liquor. Only then is the material--which has alkali which has completely penetrated the cellulose fiber walls--subjected to cooking with white liquor at a temperature of about 150.degree.-180.degree. C. Green, white, or black liquor can be used in the first impregnation zone, while white liquor (with polysulfide addition) is preferably used in the second zone.

REFERENCES:
patent: 3654070 (1972-04-01), Pradt et al.
patent: 3802956 (1974-04-01), Backlund
patent: 5080755 (1992-01-01), Backlund
patent: 5522958 (1996-06-01), Li
Clayton, D. W. "Multi-stage polysulfide pulping processes", Pulp & Paper Magazine Canada, pp. T619-T630 Dec. 1967.
Norden S. "Modified kraft. . pulp", TAPPI, vol. 62. No. 7, pp. 49-51. Jul. 1979.
Disa Tormund, "New Findings on Sulfide . . . Liquors", May 1989, TAPPI Journal, pp. 205-210.

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