Bleaching method
AssigneeKemira Oyj
InventorsRisto Rahkola, Birgitta Peltopakka, Hannu Hämäläinen, Jonas Konn, Sari Vahlroos-Pirneskoski
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Abstract
Methods for treating lignocellulosic material or pigment with a reductive bleaching solution generally include washing the lignocellulosic material or pigment with a reducing agent of magnesium dithionite. The method includes at least one reductive stage and at least one peroxide stage. Also disclosed are methods for preparing dithionite solution wherein magnesium bisulfite is reduced with borohydride solution to obtain dithionite. Bleached lignocellulosic material or pigment obtained with the treatment methods are also disclosed.
Claims17
A method for treating lignocellulosic material or pigment with reductive bleaching solution in at least one reductive stage (Y), comprising:
- washing the lignocellulosic material or pigment in the at least one reductive stage (Y) with a reductive bleaching solution comprising magnesium dithionite;
- and
- washing the lignocellulosic material or pigment in at least one peroxide stage (P) with a peroxide.
A method for treating lignocellulosic material or pigment with a reductive bleaching solution in at least one reductive stage (Y), comprising:
- washing the lignocellulosic material or pigment in the at least one reductive stage (Y) with a reductive bleaching solution comprising magnesium bisulfite and borohydride;
- and
- washing lignocellulosic material or pigment with the method contains at least one peroxide stage (P) with a peroxide
Dependencies are inferred from the claim text.