Chlorine-free bleaching and delignification of alkali cellulose - by first treating with aq. organic peracid soln. and then with cyanamide (salt) activated hydrogen peroxide soln.

摘要

A process for Cl-free bleaching and delignification of alkali cellulose comprises treating the alkali cellulose (a) with an aq. soln. of an organic peracid and subsequently (b) with an alkaline cyanamide- or cyanamide salt-activated aq. H2O2 soln.. Pref. the peracid used in stage (a) is peracetic acid or performic acid. The active H2O2 content of the peracid is pref. 0.1-3 wt. % w.r.t. the dry wt. of the cellulose. USE/ADVANTAGE - The process allows prodn. of semi-bleached cellulose with a good degree of delignification and a whiteness (ISO) grade of 65-80 %, 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.