Bleaching of esp. recycled lignocellulose fibres - using hydrogen peroxide, ozone or per:acids, useful in paper, board and cardboard mfr. from old news print and magazines

摘要

Bleaching of recycled fibres with H2O2 is effected in a stock using ozone and a peracid or salts thereof. The peracid is pref. organic and is esp. peracetic acid, partic. distilled. equilibrium peracetic acid prepd. in-situ by reacting H2O2 with tetraacetylethylenediamine (TAED). t least some of the H2O2 is added with the peracid or salts. The stock is alkaline, having a pH of 8-12 and the amt. of peracid or salts is 10-750 mg/l of stock, based on 100% peracid. Stock temps. are pref. 10-75 deg.C and bleaching is performed during the defibration of waste paper, where the concn. of fibre in the stock is 20 wt.%.