METHOD OF SULFATE CELLULOSE WHITENING Russian patent published in 1996 - IPC

FIELD: paper and pulp industry. SUBSTANCE: cellulose mass is washed with 0.01-0.10 N sulfuric acid solution to pH 2.0-6.6, filtered and diluted with peroxymonosulfuric acid aqueous solution at concentration 0.3-1.7% of absolute dry cellulose mass or 0.01 N sulfuric acid, or water up to the mass concentration 1.9-34.0%. Cellulose mass is kept at 70-100 C for 0.5-3.0 hr at pH 1.5-6.6, washed to the neutral reaction followed by delignification with hydrogen peroxide at pH 10.0 ± 0.5 in the presence of sodium silicate at 60-100 C, concentration is 10-20%, consumption is 1-3% for 0.5-4.0 hr. EFFECT: improved method of whitening. 2 cl, 2 tbl