OXPXP漂白中活化处理的机理和聚糖降解的机理

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乙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增加，聚糖分子量降低，分子量分布半漂浆范围较窄，全漂浆则出现双峰。

Mechanisms of the Activating Treatment and the Polysccharides Degradation in OXPXP Bleaching

Lignin content in the pulp descreases, while carbonyl and phenolic hydroxylgroups in the residual lignin increase, and so do carbonyl groups in polysaccharides,after theactivating treatment.The fragmentation of lignin molecules and the increase in phenolic hy-droxyl groups make the lignin reactivity strong,which is favourable to delignification andbleaching in the subsequent stage; The loss in viscosity after the activating treatment is main-ly not only from the activating treatment itself but also from the degradation caused by thecarbonyl groups during the measurenfent of viscosity.The polysaccharides can also be de-graded during H_2O_2 bleaching and the carbonyl groups produced during the activating treat-ment will lead to more degradation of polysaccharides. After bleaching there is an increase incrystallinity and a decrease in average molecular weight.The molecular weight distributionis narrow in the case of semi-bleached pulp but wide and has two peaks in the case of full-bleached pulp.