Process for a two stage peroxide bleaching of pulp

Details Process for a two stage peroxide bleaching of pulp Process for a two stage peroxide bleaching of pulp

1986-04-07

1988-03-29

Alvo, Steve

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Treatment with particular chemical

162 80, 162 90, D21C 916

Patent

active

047341610

ABSTRACT:
A two-stage hydrogen peroxide bleaching treatment of chemical pulp at a temperature of about 90.degree.-100.degree. C. comprising subjecting said pulp in a first stage to hydrogen peroxide and to at least about 3 grams/1 of bath of a metal ion sequestering agent selected from nitrogen containing sequestering agents or agents derived from polyphosphoric or polyphosphonic acids at a pH of 8.5 to 9.5 so that hydrogen peroxide of about 0.3 to 2.5 wt. % relative to dry pulp weight is consumed, and subjecting said pulp in a second stage to hydrogen peroxide and to at least about 3.times.10.sup.-3 gram-atoms per 100 grams of dry pulp of magnesium in the form of magnesium hydroxide and a pH of at least about 11 so that about 2 to 5 weight % of hydrogen peroxide per weight of dry pulp is consumed during the two stages.

REFERENCES:
patent: 2865701 (1958-12-01), Shroeder
patent: 4187141 (1980-02-01), Ahrel
patent: 4294575 (1981-10-01), Kowalski

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