TWO-STAGE PURIFICATION OF FIBROUS CELLULOSE MATERIAL EMPLOYING GASEOUS CHLORINE DIOXIDE IN ONE STAGE AND A PEROXYGEN COMPOUND IN THE OTHER

摘要

A two stage process for bleaching an unbleached chemical cellulosic pulp in which the first stage comprises fluffing a pulp that has been adjusted in moisture content to a consistency of from about 20 to 60 percent, contacting the pulp with gaseous chlorine dioxide diluted with a non-reactive gas at a temperature of between 15 DEG and 100 DEG C. for a period of 20 seconds to 60 minutes, the pulp then being washed with water; and finally in the second stage adjusting the pulp moisture content to 5 percent and contacting the pulp with a peroxygen compound having a peroxygen content of from 0.025-1.5 percent by weight based on the weight of the dry pulp at a temperature up to 100 DEG C. for a period of from 1/2 to 5 hours.