METHOD OF BLEACHING OF BISULFITE PULP Russian patent published in 2014 - IPC D21C9/10 

FIELD: textiles, paper.

SUBSTANCE: method comprises delignification by hydrogen peroxide in an acidic medium in the presence of sodium molybdate catalyst at a flow rate of H₂O₂ 1.0-4.0%, H₂SO₄ 0.5-1.0%, Na₂MoO₄ 0.05-0.5% by weight of absolutely dry pulp, the temperature of 70-98°C for 70-180 minutes, and the concentration of mass of 10%, then alkaline treatment is carried out at a flow rate of NaOH 1.5% by weight of absolutely dry pulp, at a temperature of 60-70°C for 60-90 minutes. Final bleaching is carried out in two stages: the first stage of final bleaching - by sodium chlorite at its flow rate of 0.5-1.5% and the flow rate of hydrochloric acid of 1.0-2.0% by weight of absolutely dry pulp, at a temperature of 60-90°C for 120 -240 minutes; the second stage - by alkaline solution of hydrogen peroxide in the presence of a complexing agent Trilon C at a flow rate of H₂O₂ 1.0-2.5%, NaOH 1.0-2.0%, Na₂SiO₃ 3.0%, Trilon C 0.1-0.5% by weight of absolutely dry pulp, at a temperature of 60-80°C for 120-180 minutes.

EFFECT: increase of whiteness and improvement of mechanical properties of the pulp.

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