Bleaching of cellulose pulps with reduced chlorine use - involving an initial degradation stage using strongly alkaline peroxide

摘要

In a several stage process for the complete bleaching of cellulose pulps using little chlorine, the succession of stages, possibly combined with a partial chlorination, is preceded by a degradation process using strongly alkaline peroxide, pref. under normal pressure, and at a temp. between 20 degrees C and the b.pt. of the bleaching bath. The process is carried out using pulp densities of 5-35, pref. 10-20%. The amt. of peroxide used is 0.2-10 wt.%, calculated on H2O oxygenated at 100%, w.r.t. the dry cellulose pulp. The amt. of alkali used is 2-15 pref. 4-8%, calculated for the substance at 100%, w.r.t. the dry cellulose pulp. The bleached cellulose pulps are used partic. in the prodn. of paper. Waste waters are obtd. which can be evaporated and regenerated without provoking corrosion.