D - Textiles – Paper – 21 – C
Patent
D - Textiles, Paper
21
C
D21C 9/14 (2006.01)
Patent
CA 2719500
The present invention provides an improved process for chlorine dioxide bleaching of chemical pulps in an aque-ous suspension, which uses magnesium hydroxide or magnesium oxide. The process involves the addition of magnesium hydrox-ide or magnesium oxide to the pulp, in addition to chlorine dioxide, maintaining the mixture at a pH between about 2.5 to 7.5 for about 1 or more hours, most suitably between about 1 - 4 hours. This process can be used in the D1 or D2 stage of a typical D0E op D1E2D2 bleaching sequence, as well as in the chlorine dioxide brightening stage of other three, four, five, and six-stage bleaching sequences of either the so-called ECF process, or those containing elemental chlorine (Cl2). The temperature is between about 40 to about 90°C, and the pulp consistency is between about 1 to about 16%.
L'invention porte sur un procédé amélioré de blanchiment au dioxyde de chlore de pâtes chimiques en suspension aqueuse utilisant de l'hydroxyde de magnésium ou de l'oxyde de magnésium. Ledit procédé consiste: à ajouter de l'hydroxyde de magnésium ou de l'oxyde de magnésium à la pâte, en sus du dioxyde de chlore; à maintenir le mélange à un pH d'environ 2.5 à 7,5 pendant environ 1 heure ou plus et de préférence entre environ 1 et 4 heures. Le procédé le procédé peut être utilisé dans les étapes D1 ou D2 d'une séquence type de blanchiment D0EopD1E2D2 ainsi que dans l'étape d'azurage au dioxyde de chlore des séquences de blanchiment trois, quatre, cinq et six, soit dudit procédé ECF, soit de procédés utilisant du chlore élémentaire (Cl2). La température est comprise entre environ 40°C et environ 90°C, et la consistance de la pâte est comprise entre environ 1% et environ 16%.
He Zhibin
Ni Yonghao
Hill & Schumacher
University Of New Brunswick
LandOfFree
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