SULFATE CELLULOSE BLEACHING PROCESS Russian patent published in 2003 - IPC

FIELD: paper-and-pulp industry. SUBSTANCE: in the first stage, unbleached coniferous cellulose with concentration 10-20 wt % is treated for 120 min with hydrogen peroxide in amount 2.5% of the weight of absolutely dry cellulose in alkali medium at pH 9.0-10.9 in presence of sodium silicate (consumed in amount 1%) at 80C. In the second and fourth stages, cellulose is treated at 70 C with chlorine dioxide consumed in amounts 1.2 and 0.4%, respectively. In the third and fifth stages, cellulose with the same concentration as in the first stage is treated for 120 min in each stage with hydrogen peroxide consumed in amounts 0.7% at 80 C and 1.0% at 80-90 C, respectively. EFFECT: increased whiteness of coniferous cellulose under chlorine-free conditions. 1 tbl, 6 ex