Bleaching of deinked paper/wood pulp

Details Bleaching of deinked paper/wood pulp Bleaching of deinked paper/wood pulp

1993-03-01

1995-09-12

Knable, Geoffrey L.

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Waste paper or textile waste

162 7, 162 78, 162 84, D21C 910, D21C 916

Patent

active

054494362

ABSTRACT:
Deinked paper/wood pulps are improvedly bleached to high levels of whiteness by conjointly treating such pulps with a sulfite bleaching agent, e.g., Na.sub.2 SO.sub.3, NaHSO.sub.3 or mixture thereof, or SO.sub.2 and NaOH, and a reducing agent more electronegative than the sulfite ion, e.g., thiourea dioxide, sodium borohydride or sodium dithionite, in a reaction medium having an initial pH ranging from 6 to 12, advantageously followed by washing sulfite and reducing agent values from the bleached pulp and then treating the washed pulp with hydrogen peroxide in an aqueous alkaline medium.

REFERENCES:
patent: 3384534 (1968-05-01), Kindron et al.
patent: 3981765 (1976-09-01), Kruger et al.
patent: 3985674 (1976-10-01), Ellis et al.
patent: 4812206 (1989-03-01), Devic et al.
patent: 5143581 (1992-09-01), Devic

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