H.sub.2 O.sub.2 /alkaline bleaching of wood pulps

Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Treatment with particular chemical

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162 90, D21C 916

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052961001

ABSTRACT:
High-yield lignocellulosic wood pulps are bleached by (i) first pretreating such pulp with a complexing agent for metal ions and next washing the pretreated pulp, and then (ii) bleaching such pretreated/washed pulp with an initial amount of hydrogen peroxide in an alkaline medium, including adding a supplementary bleaching amount of hydrogen peroxide and a supplementary amount of an alkaline agent to the pulp over the course of the bleaching step (ii) without interrupting same, at a point in time when from 60% to 85% of the initial amount of hydrogen peroxide has been consumed, and such supplementary amount of hydrogen peroxide being equal to or less than the initial amount thereof.

REFERENCES:
patent: 4732650 (1988-03-01), Michalowski et al.
patent: 4734161 (1988-03-01), Dubreux
Tappi Journal, vol. 70, No. 3, (Mar. 1987) by Lachenal.
Colodette et al., "The Effect of pH Control on Peroxide Brightening of Stoneground Wood Pulp", J. of Pulp and Paper, Mar. 1990, (162-78).
Anderson et al., "Optimized Hydrogen Peroxide Bleaching in Closed White Water Systems"; TAPPI, Apr. 1980, pp. 111-115 (162-78).

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