硫酸盐竹浆ECF和TCF漂白过程中木素结构的变化

Study on the Changes of Lignin Structure during ECF and TCF Bleaching of Bamboo Sulfate Pulp

利用紫外光谱、红外光谱、凝胶渗透色谱、核磁共振波谱技术，研究了氧脱木素后纸浆、CIO2漂白后纸浆中残余木素及氧脱木素溶出木素结构的变化。浆料经过CIO2漂白和氧脱木素后，残余木素紫外光谱中216nm处的吸收明显减弱（分别下降了30．7％和10．0％），表明氧脱木素和CIO2漂白过程木素结构单元中有些苯环开裂。通过红外光谱分析得知，浆料经CIO2漂白和氧脱木素后，代表羧基的1701～1718cm^-1峰强度显著增强，代表游离酚羟基的3420cm^-1峰强度稍有增强，代表甲氧基的1266cm^-1处吸收峰减弱。通过对残余木素分子质量测定得知，与未漂浆残余木素相比，经氧脱木素和CIO2漂白后，浆中残余木素及氧脱木素溶出木素的平均分子质量降低，多分散性也随之下降，但下降程度不大。由^1H-NMR和^13C-NMR分析得知，与未漂浆残余木素相比，CIO2漂白后木素结构中的对羟基苯基、愈创木基和紫丁香基结构单元受到降解，部分β-O-4、β-1和β-5连接发生断裂。CIO2漂白浆残余木素羚基、芳环取代碳原子以及与氧连接的脂肪碳原子含量升高，而芳环甲氧基含量降低。

The changes of the structure of residual lignin of oxygen delignified pulp and chlorine dioxide bleached pulp, dissolved lignin during oxygen delignification were studied by using UV, FT-IR, GPC ,NMR. The absorption intensity at 216 nm in UV spectrum of residual lignin of oxygen delignified pulp and chlorine dioxide bleached pulp decreased 10.0% and 30.7% respectively. It indicated that some of ben- zene rings of lignin have been destroyed. It was found from FT-IR analysis of lignin that the absorption intensity of carboxyl group and methoxyl group increased obviously, the absorption peak of phenolic hydroxyl increased slightly. Through measuring the molecular weight distribution, compared with residual lignin of unbleached pulp, the average molecular weight of oxygen delignifacation and chlorine dioxide bleaching residual lignin and the dissolved lignin during oxygen delignifacation decreased, and the polydispersity decreased slightly too, which indicated that lignin degraded and dissolved during bleaching, but some residual lignin with high molecular weight remained in the bleached pulp. From quantitative ^1H-NMR and ^13C-NMR analysis, it was found that, compared with residual lignin of unbleached pulp, hydroxyphenyl, guaiacyl and syringyl units of residual lignin of chlorine dioxide bleached pulp were degraded, some β-O-4,β-1 and β-5 link-ages were broken during bleaching. The content of carboxyl group, substituted aromatic C atom and aliphatic C atom linked to oxygen of residual lignin from chlorine dioxide bleached pulp increased, but the content of aromatic methoxyl decreased.