Delignification of lignocellulosic material for paper - with alkali metal hydroxide, oxygen and opt. alkali metal sulphide

摘要

Cellulose having good bleaching props. is produced from a lignocellulosic material (deeidnous or comferours wood, straw, bagasse, etc.) in good yields by (1) treating the material in a closed reactor with a pulping liq. contg. an alkali metal hydroxide and opt. an alkali metal sulphide at 160-195 degrees C for is not 120 mins. so that a pulp yield of 55-65 wt% is obtained, (2) replacing the pulping liq. with 'white water' i.e. water or an aq. soln. of an alkali metal hydroxide (3) treating the material in an aq. suspension (concn. 2-30 wt%) with 2-20 wt% of an alkali metal hydroxide of 20-90 degrees C for 0.5-30 mins. (4) treating the alkaline material suspended in an aq. medium (concn. 3-35 wt%) with O2 (contg. gas) for 10-120 mins. at 80-140 degrees C under an O2 partial press of 2.1-14.0 kg/cm2 and (5) washing the material with water subsequently, bleaching by chlorination, alkaline extn. and ClO2-treatment is applied.