Processes for preparing mechanical pulps having high brightness

Details Processes for preparing mechanical pulps having high brightness Processes for preparing mechanical pulps having high brightness

D - Textiles, Paper

21

C

D21C 1/06 (2006.01) D21B 1/16 (2006.01) D21C 9/10 (2006.01) D21H 11/08 (2006.01)

Patent

CA 2453131

The present invention provides a process for preparing bleached mechanical pulp having high brightness from wood chips consisting essentially of the steps, in order, of impregnating wood chips having low bleachability with a chemical liquor consisting essentially of an aqueous solution of an alkaline inorganic compound and a chelating agent at a pH range of 7 to 12 and then removing said impregnating chemical liquor from said chips, next followed by the sequential steps, in order, of (a) defibration by primary refining, bleaching, and beating by secondary refining, or (b) defibration by primary refining, beating by secondary refining and bleaching.

La présente invention fournit un procédé de préparation de pâte mécanique blanchie qui présente un degré de blancheur élevé, à partir de copeaux de bois, et qui comprend essentiellement les étapes qui suivent, dans l'ordre indiqué. L'imprégnation de copeaux de bois qui présentent une faible aptitude de la pâte au blanchiment avec une solution chimique constituée essentiellement d'une solution aqueuse de composé inorganique alcalin et d'un chélateur dont la plage de pH est comprise entre 7 à 12. Ensuite est éliminée ladite solution chimique d'imprégnation desdits copeaux de bois; puis sont effectuées, dans l'ordre indiqué, les étapes qui suivent. a) la défibration par raffinage primaire, le blanchiment et le raffinage en pile par raffinage secondaire; ou b) la défibration par raffinage primaire, le raffinage en pile par raffinage secondaire et le blanchiment.

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