Bleaching of chemical pulp and treatment with a chelating agent

Details Bleaching of chemical pulp and treatment with a chelating agent Bleaching of chemical pulp and treatment with a chelating agent

D - Textiles, Paper

21

C

D21C 9/16 (2006.01) D21C 9/14 (2006.01) D21C 9/147 (2006.01)

Patent

CA 2310038

The invention relates to a process for the bleaching of chemical pulp, wherein the pulp is delignified and/or bleached with chlorine dioxide or with a combination of chlorine dioxide and a per- compound, and additionally the pulp is chelated in order to bind heavy metals, such as Fe, Mn and/or Cu, to a chelate complex. The chelate complex is selected from the group made up of N-bis-[(1,2-dicarboxylethoxy)-ethyl]-amine, N- bis[(1,2dicarboxylethoxy)-ethyl]-aspartic acid and N-tris-[(1,2-dicarboxylethoxy)-ethyl]-amine, and the alkali metal and earth- alkali metal salts of these, and the chelating treatments are carried out simultaneously by combining the chelating chemical with the pulp in the same bleaching stage as chlorine dioxide.

L'invention concerne un procédé pour le blanchiment de pâte chimique, dans lequel la pâte est délignifiée et/ou blanchie avec du dioxide de chlore ou bien avec une association de dioxide de chlore et d'un percomposé, et en outre, la pâte est chélatée en vue de fixer les métaux lourds, tels que Fe, Mn et/ou Cu, à un complexe de chélation. Ce dernier est choisi dans le groupe constitué de N-bis-[(1,2-dicarboxyléthoxy)-éthyl]-amine, acide N-bis [(1,2-dicarboxyléthoxy)-éthyl]-aspartique et N-tris-[(1,2-dicarboxyléthoxy)-éthyl]-amine, et des sels métalliques alcalins et métalliques alcalinoterrreux de ceux-ci, et les traitements de chélation sont réalisés simultanément par association du chélateur chimique avec la pâte dans le même étage de blanchiment que le dioxide de chlore.

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