中国制浆造纸研究院
硕士研究生毕业（学位）论文
桦木制备醋酸纤维浆粕方法的研究
THE STUDY ON THE PROCESS FOR PRODUCING CELLULOSE
ACETATE PULP FROM BIRCH
王月江
指导教师：刘文（教授级高工） 申请学位级别：工学硕士 专业名称：制浆造纸工程 论文提交日期：2011年5月 论文答辩日期：2011年6月
二〇一一年五月
桦木制备醋酸纤维浆粕方法的研究
摘 要
醋酸纤维素作为人造纤维素的一种，不仅在纺织行业得到广泛的应用，更是香烟过滤嘴丝束的首选材料。但是，制备醋酸纤维素的原料醋酸纤维浆粕的生产技术长期被国外少数国家所垄断，我国此项技术基本处于试验阶段。因此，研究醋酸纤维浆粕的制备方法就显得异常重要。它不仅够缓解我国纺织和香烟行业对进口的依赖性，减少国际市场对我国的冲击；还有利于进一步完善我国醋酸纤维工业的产业链，促进经济的发展。
醋酸纤维浆粕通常由木材或棉短绒制备，是α-纤维素含量高(96%)、白度高(90%ISO)且聚合度高的纸浆。本论文首先进行了预水解硫酸盐法制备醋酸纤维浆粕的研究。研究证实预水解工艺能够大幅降低硫酸盐纸浆中的聚戊糖含量，这有利于制备醋酸纤维浆粕。预水解硫酸盐浆经过漂白后，能够在白度、α-纤维素含量和聚合度方面达到醋酸纤维浆粕的指标要求。
由于预水解工艺在推广应用上存在一定的局限性，本论文研究了从硫酸盐浆制备醋酸纤维浆粕的方法。该部分先通过正交实验优化出桦木硫酸盐法蒸煮的最佳工艺(用碱量18%，最高温度170℃，保温时间90min，硫化度25%)。然后以在此工艺条件下制得的硫酸盐浆为原料进行漂白实验。漂白实验主要包括白度的提升、α-纤维素含量的提升和聚合度的调节三个方面。
第一，在提升白度方面：采用常规的多段漂白方法如二氧化氯漂白或过氧化氢漂白能顺利的将纸浆的白度提升至90%ISO，达到指标要求。第二，在提升α-纤维素含量方面：采用冷碱抽提的办法处理纸浆能够将其聚戊糖含量降到很低，从而间接的提高了α-纤维素含量。第三，在聚合度方面：可以采用次氯酸盐漂白的方法来调节纸浆的聚合度，以使其达到目标范围。在合理配置这三个步骤之后，实验制得了在各项主要指标上都符合醋酸纤维浆粕标准的产品。
另外，本论文还在硫酸盐浆制备醋酸纤维浆粕方案的基础上，考察了直接采用商品浆制备醋酸纤维浆粕的可行性。研究发现，在合理选用商品浆的情况下，直接由商品浆制备醋酸纤维浆粕是可能的。
关键词：醋酸纤维浆粕；桦木制浆；预水解；α-纤维素；聚合度；冷碱抽提
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Study on the Process for Producing Cellulose Acetate
Pulp from Birch
Abstract
As an artificial fiber, cellulose acetate not only being widely used in textile industries, but also being the best choice for the material of cigarette filter. However, the production technology of cellulose acetate pulp has been monopolized by a few developed countries for a long time, so we can hardly product it ourselves. Therefore, it is very important for us to study the production methods of the cellulose acetate pulp. On one hand, it can help our textile and cigarette industries to get rid of the dependence of import. On the other hand, the cellulose acetate production chain would be more completed, which is beneficial for our economy.
Cellulose acetate pulp, usually prepared from cotton linters and wood pulp, is class of pulp with high alpha cellulose content(more than 96%)and high brightness(more than 90%ISO) and uniform DP. In this work, the prehydrolyzed kraft pulp method of producing cellulose acetate pulp form birch is studied. According to this study, it is proved that the prehydrolyzed process is able to reduce the pentosans content of the pulp, which is beneficial for producing the cellulose acetate pulp. The bleaching experiment of the prehydrolyzed kraft pulp shows that the bleached prehydrolyzed kraft pulp is able to meet the standard of the cellulose acetate pulp. In other words, it is possible to produce cellulose acetate pulp form birch with a prehydrolyzed KP process.
Because of the wastewater caused by the predydrolyzed process is hard to treatment, and the cooking time of predudrplyzed process usually longer than 4 hours, this method can’t be accepted perfectly by many small-scale pulping mill. In this case, a new bleached process form ordinary kraft pulp is studied. According to this study, the best process for cooking birch is determined. The birch wood chips are cooked with 18 percent of sodium hydroxide and sodium sulfide. The sulfidity the of this process is 25% , the maximum
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cooking temperature is 170℃,and the time at maximum temperature is 90 min.
Based on the pulp process of birch ordinary kraft pulp, the bleach process is studied. There are there significant problems for producing cellulose acetate pulp form ordinary kraft pulp.Firstly, the brightness of the pulp. The brightness can be increased successfully to 90%ISO by the general bleached process such as ClO2 and H2O2. Secondly, the alpha cellulose content of the pulp. The pentosans content of the pulp can be decreased to a very low level by a 10% sodium hydroxide extraction process. Indirectly, the alpha cellulose content will be upgraded to more than 96%. Thirdly, the DP of the pulp. A common standard for reflecting DP is intrinsic viscosity. In order to control the intrinsic viscosity at an ideal level, the NaClO is used. Through arranging those there process reasonable, this experiment gets cellulose acetate pulp that all the mainly standards are able to meet the requirement.
Based on the 10%NaOH extraction process, a feasibility of producing cellulose acetate pulp directly from market pulp is tested. According to the test, it is possible to get qualified cellulose acetate pulp through this process if the suitable market pulp is chose.
KEY WORD: cellulose acetate pulp; birch pulp; predydrolyzed KP; NaOH extraction;DP;
Crystallinity
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