Chlorine-free bleaching and delignifying of alkali cellulose - by bleaching with aq. peracid, extracting with alkaline soln.,bleaching with aq. peracid and bleaching twice with cyanamide-activated hydrogen peroxide soln.

摘要

The process comprises treating the alkali cellulose by a bleaching sequence comprising the stages (A)-(C)-(A)-(B)-(B) in which (A) is treatment with an aq. soln. of an organic peracid, (B) is bleaching with an alkaline cyanamide- or cyanamide salt-activated aq. H2O2 soln. and (C) is extn. of the lignin components with an alkaline aq. soln. USE/ADVANTAGE - The process allows prodn. of fully bleached cellulose with a good degree of delignification and whiteness with minimum degradation of the cellulose using relatively few bleaching stages and without using chlorine contg. bleaching agents. The prods. are useful e.g. for prodn. of high strength white papers.