SULFATE CELLULOSE BLEACHING PROCESS Russian patent published in 2001 - IPC

FIELD: paper-and-pulp industry. SUBSTANCE: cellulose characterized by 84.3 permanganate units is subjected to alternate treatment with hydrogen peroxide in alkali medium and with chlorine dioxide. In the first stage, 10-20% cellulose is treated with hydrogen peroxide (pH 9.0-10.9) at 75-85 C for 60 min with hydrogen peroxide uptake 2% on the weight of absolutely dry cellulose. In the 3rd and 5th stages, cellulose in the same concentration is treated for 120 min at 70-100 C with hydrogen peroxide uptake 0.5 and 1.0%, respectively. The 2nd and 4th stages are carried out at 70 C with chlorine dioxide uptake 0.7-1.0 and 0.3%, respectively, depending on initial hardness of cellulose. Cellulose product is characterized by 86-88% whiteness, which depends on initial hardness of cellulose. EFFECT: enhanced bleaching efficiency. 1 tbl, 10 ex