溶解浆的质量指标及生产技术述评

Quality specification of dissolving pulp and prospects of production technologies

溶解浆由高纯度纤维素组成,用于制造粘胶纤维、醋酸纤维、硝酸纤维、纤维素醚等材料,其重要的质量指标主要有α-纤维素含量、半纤维素含量、黏度、分子量分布等。因产品用途不同其质量指标要求存在较大差异,帘子线、醋酸纤维和粘胶长丝的α-纤维素质量分数一般为95%以上,含较少量的半纤维素及极微量的木质素。为提高产品质量,既要严格控制溶解浆中的半纤维素、木质素、灰分和金属离子含量,还需提高浆料的反应性能及纤维素分子量分布。阔叶木已成为目前溶解浆生产的主要纤维原料。溶剂法和离子液法制溶解浆技术,因可对纤维原料中纤维素、木质素和半纤维素组分进行综合利用,日益受到研究人员的重视。预水解硫酸盐法已成为主要的溶解浆生产工艺,设备系统由传统间歇蒸煮向现代DCS控制的置换蒸煮或连续蒸煮发展;氧碱脱木质素和Cl O2漂白的普及,推动了ECF、轻ECF甚至TCF等绿色漂白工艺在溶解浆生产中的应用。每种溶解浆生产技术与设备系统在中国均有应用实例。综合利用木质纤维素生物质三大组分的制浆工艺将成为下一代溶解浆生产技术的发展方向。选择不同的生产工艺和设备系统对生产线的盈利能力影响较大,新建生产线时应对原料的选择、主产品线和副产品线的定位、生产工艺和设备系统的选择进行科学论证。

The dissolving pulp is a special chemical pulp composed of high purity cellulose,which is mainly used in manufacturing the high-valued cellulose materials and products such as viscose fiber,acetate fiber,nitric acid fiber,cellulose ether products,etc.The alpha cellulose content,the hemicellulose content,the viscosity and the distribution of molecular weight are the most important quality indexes of the dissolving pulp.Different quality grade of dissolving pulps should be produced to meet the different quality specifications of end cellulose product,among which cord yarn,acetate fiber and viscose filament are liable to be manufactured from high-quality grades of dissolving pulp with alpha cellulose content being usually more than 95%.In order to produce finished products with high quality,the content of hemicellulose,lignin,ash and metal ions in dissolving pulp should be strictly controlled,and also,it is equally important for improving the chemical reactivity and the molecular weight distribution(MWD).Hardwood species has become the main raw material for the production of dissolving pulp at present.The dissolving pulp technology using solvent methods and ionic liquid methods have been attracting wide attentions for researchers because of comprehensive utilizing the cellulose,lignin and hemicelluloses components in fiber raw materials.The prehydrolysis kraft pulping technology has become the mainstream.It has being developed that the production equipment systems from the traditional batch cooking to the replacement cooking process and the continuous cooking process with modern DCS control system.With the popularization of oxygen alkali delignining and ClO 2 bleaching,the green bleaching technology,such as ECF,light ECF or even TCF technology,is widely used for the production of dissolving pulp.Each typical kind of dissolving pulp equipment system in the world can be found an application case in China.The production technology of dissolving pulp that can utilize three components,i.e.,cellulose,lignin and hemicellulose,in lignocellulosic resources simultaneously will be an important development direction in the future.The selection of different production processes and equipment systems has a great impact on the profitability of the production line.The selection of raw fiber materials,the positioning of the down products streams(including main products and byproducts),production process and equipment system should be discussed scientifically in setting up the new pulp production lines.