D - Textiles – Paper – 21 – C
Patent
D - Textiles, Paper
21
C
D21C 9/10 (2006.01) D21C 9/16 (2006.01)
Patent
CA 2395824
The present invention relates to a method for bleaching mechanical and chemithermomechanical pulp including that an advancing pulp suspension obtained after that the fibres are laid free is prebleached by adding reductive bleaching agent to the pulp suspension in a location just after the fibres are laid free and that the bleaching is carried out under given conditions in the form of high temperature and minimized oxygen access in respect of said adding location and immediately downstream of said location, characterized in, that the in the described manner prebleached pulp is subjected to at least one further bleaching treatment including that the pulp is bleached with an oxidizing bleaching agent, preferably peroxide bleaching agent, reinforced with borohydride.
La présente invention concerne un procédé de blanchiment de pâtes cellulosiques par voies mécaniques et thermomécanochimiques. Une suspension de pâtes cellulosiques en mouvement, obtenue après séparation de la lignine, est préblanchie par adjonction d'un agent de blanchiment réducteur à la suspension de pâtes, à un emplacement donné, juste après séparation de la lignine. Le blanchiment est réalisé dans des conditions déterminées, sous la forme d'un accès, à température élevée et oxygène minimal, audit emplacement d'adjonction et immédiatement en aval de l'emplacement. Le procédé se caractérise en ce que la pâte préblanchie est soumise à au moins un nouveau traitement de blanchiment dans lequel on utilise un agent de blanchiment oxydant, de préférence un agent de blanchiment peroxyde, renforcé de borohydrure.
Ni Yonghao
Wang Shuyu
Zhang Yijing
Holmen Aktiebolag
Macrae & Co.
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