METHOD OF CELLULOSE BLEACHING Russian patent published in 1999 - IPC

FIELD: production of cellulose; may be used in production of bleached cellulose without molecular chlorine. SUBSTANCE: method includes treatment of nonbleached cellulose with solution of potassium permanganate in acid medium at pH 1.2-2.1. Acid medium is used in the form of sulfuric acid or acid reactor residues of chlorine dioxide production. Potassium permanganate is taken in quantity of not more than 1% of weight of absolutely dry cellulose. Pulp is held at room temperature up to complete absorption of potassium permanganate with cellulose mass separated from solution and neutralized. Then, it is subjected to four-stage bleaching. The first and third stages are carried out in the presence of hydrogen peroxide in alkali medium at temperature of 70-100 C with consumption of hydrogen peroxide in the amount of 1.5-2.0% of absolutely dry cellulose weight. At the second and fourth stages, the bleached cellulose is treated with solution of chlorine dioxide at temperature of 50-70 C with total consumption of chlorine of 1.1-1.3% of absolutely dry cellulose mass. EFFECT: higher degree of whiteness of bleached cellulose. 3 cl, 1 tbl