桉木AS-AQ蒸煮及木质素特性研究

AS -AQ PULPING OF EUCALYPTUS WOOD AND THE STRUCTURAL CHANGE OF LIGNIN DURING PULPING

实验结果表明 ,桉木AS -AQ蒸煮到 14 5℃以前 ,木质素磺化反应占主导地位 ,温度升高木质素大量溶出 ;蒸煮后期 ,残余木质素和溶出木质素发生缩合反应 ,从而导致纸浆的KMnO4值上升 ,白度下降。通过实验 ,论证了纸浆中残余木质素含量高的原因。

AS -AQ pulping of eucalyptus (Leizhou No.1) wood and the structural change of lignin during pulping were studied. It was found that the lignin in eucalyptus has guaiacyl-syringyl-p-hydroxylphenyl (G -S -H) structural characteristics. The ratio of S∶G is 1.25∶1. The M_w is 6 784,M_n is 5 585.The guaiacyl groups in lignin was dissolved faster than syringyl groups in lignin during AS -AQ pulping .The sulfonation reaction and delignification rate of lignin in secondary walls(S) were slower than that in cell corner (CC) and compound middle lamella (CML) during AS -AQ pulping, so that residual lignin content in AS -AQ pulp was higher. Condenzation of lignin was occurred at the end of cooking, so that the permanganate number of pulp was raised and the brightness of pulp was reduced.