Peracetic acid Bleaching of Unbleached Sulfite Pulp

Abstract

This work was initiated in order to investigate peracetic acid (PA) bleaching different from NaClO₂, H₂O₂ and hypochlorite bleaching.
Active groups content, copper number, viscosity and hemicellulose content in various bleached pulps were measured.
Under same bleaching condition, PA bleaching showed higher viscosity of pulp than hypochlorite bleaching but it showed lower viscosity of pulp than H₂O₂ and NaClO₂ bleaching. It seemed that PA bleached pulps showed the lowest brightness among these bleached pulps, but hemicellulose content in PA bleached pulps showed high value.
At initial stage of PA bleaching CO group content in pulps increased, but it decreased with the progress of bleaching.
By means of mixing NaClO₂ with PA brightness was improved and showed higher viscosity than PA bleaching. At 80°C and 90°C PA bleaching proceeded speedily and made perfect in a few minutes, although it took about 2 or 3 hours at 60°C.