OXPXP漂白中活化处理的机理和聚糖降解机理的探讨

Studies on mechanisms of the activating treatment and the polysccharides degradation in OXPXP bleaching

经活化处理后纸浆中木素含量降低，残余木素中的羰基和酚羟基增多，聚糖中的羰基也增多。木素大分子的降解和酚羟基的增多提高了木素的反应性能，因而有利于后续漂段木素的脱除和纸浆白度的提高。活化处理后聚糖中羰基的生成是导致铜二胺粘度降低的主要原因，也是导致后续漂段聚糖降解的主要原因之一。纸浆经漂白后结晶度提高，聚糖分子量降低，分子量分布半漂浆范围较窄，全漂浆范围较宽并出现双峰。

Lignin content in the pulp is lowered, carbonyl and phenolic hydroxyl groups in theresidual lignin increase and there is also an increased carbonyl groups in polysaccarides afterthe activating treatment. The fragmentation of lignin molecules and the increase in phenolichydroxyl groups make the lignin reactivity strong, which is favourable to delignification andbleaching in the subsequent stage. The loss in 'viscosity afterthe activating treatment ismainly not from the activating treatment itself but from the degradation caused by thecarbonyl groups during the measurement of viscosity' The polysaccharides can also bedegraded during H2O2 b1eaching and the carbonyl groups produced during the activatingtreatment wiU lead to a more degradation of polysaccharides. After bleaching there is anincrease in erystallinity and a decrease in average molecular weight. The molecular weightdistribution is narrow in the case of semi-bleached pulp but wide and has two peaks in thecase of full-bleached pulp.