Study on the Bleaching of Wood Pulp

Abstract

The oxidative degradation of red pine holocellulose by peracetic acid (PA) or calcium hypochlorite (HC) was carried out under the comparatively rigid conditions. The yield of the oxidized holocellulose thus obtained was about 60% by degrading with the two reagents for four hours. Under the above conditions, hemicellulose present in red pine holocellulose was faster degraded than cellulose. It was also cleared that araban and xylan in the holocellulose are more unstable than mannan or glucan, and cellulose for degrading with PA or HC. The formation of carbonyl and carboxyl groups in red pine holocellulose was accelerated by the attack with HC, while the formation of these groups by PA degradation of it was in small quantities. On determining on the viscosity of a cuoxam solution of red pine holocellulose oxidized with PA or HC, it was found that the chain rupture of polysaccharides in the holocellulose occurs during the oxidative degradation, which gives a lower viscosity motivated by decreasing the actual degree of polymerization of original polysaccharides. The decrease of viscosity of a holocellulose cuoxam solution was more remarkable by degrading with HC than by oxidizing with PA. A lower-viscosity holocellulose prepared by oxidative degradation with HC contained 40m mol. of ketone, 10m mol. of aldehyde and 30m mol. carboxyl groups per 100g. of oxidized holocellulose, whereas the contents of these groups in PA-degraded holocellulose were about 27, 4 and 13m mol. per 100 g, respectively. It was also cleared that mannan present in red pine hemicellulose is more stable than xylan and glucan degraded by PA, while mannan and glucan were similary more stable than xylan during degrading with HC.