METHOD OF CELLULOSE BLEACHING Russian patent published in 1998 - IPC

FIELD: production of bleached cellulose by ozone bleaching with preliminary treatment of nonbleached cellulose with oxygen in alkali medium. SUBSTANCE: method includes treatment of initial cellulose material in two stages. The first stage is conducted with use of aqueous alkali solution and withdrawal of a part of aqueous alkali solution between stages of treatment of cellulose mass with oxygen at high temperature and pressure, washing of treated material and subsequent ozonizing. The second stage of treatment of initial cellulose material is effected with water in the amount ensuring concentration of treated material of 7-15%. Withdrawal of a part of aqueous alkali solution is carried out to obtain concentration of treated material equalling 18-25%. EFFECT: higher efficiency. 2 cl, 3 tbl