PROCESS FOR WHITENING DECIDUOUS SULFATE CELLULOSE Russian patent published in 1994 - IPC

FIELD: pulp-and-paper industry. SUBSTANCE: the process for whitening deciduous sulfate cellulose comprising treatment of the original cellulose suspension with a mineral acid at 70-95 C and a pH of 1.2-3.5, delignification with hydrogen peroxide with the addition of sodium hydroxide and sodium silicate, the amount of hydrogen peroxide of 0.5-2.5%, sodium hydroxide of 0.5-1.2% and sodium silicate of 2-5% based on the weight of the absolutely dry cellulose at a pH of 3.5-10.5 and subsequent washing of the with water. Prior to delignification with hydrogen peroxide, the cellulose suspension is pretreated with a sodium hydroxide-based alkali solution with the amount of 2-4% NaOH based on the weight of the absolutely dry cellulose for 1.1-2.0 hr at a pH of 10-11 followed by washing with water to a pH of 7-8. The process is carried out with the ratio of sodium hydroxide in the stages of pretreatment and delignification with hydrogen peroxide ranging from 1: 0.5 to 4: 0.5, respectively. The alkali solution is sodium hydroxide or a mixture thereof with the spent solution resulting from the stage of delignification with hydrogen peroxide; the mineral acid is sulfuric or hydrochloric acid or a mixture thereof with the spent acid in a 1:1 ratio. EFFECT: improved properties of the sulfate cellulose. 4 cl, 1 tbl