甲酸体系下纤维素酯化反应及纸浆的可漂性研究

Study on Esterification of Cellulose in a Formic Acid System and the Bleachability of Pulp

关键词:  甲酸  类木质素母体小分子  甲酸纤维素酯  

Key Words:formic acid  lignin parent small molecules  cellulose formate ester  

摘要:本研究应用类木质素母体小分子与甲酸与组成的蒸煮体系探究蒸煮反应对纤维素结构影响,同时应用微晶纤维素模拟微观实验,对蒸煮后纤维素结构进行表征,探究甲酸体系下纤维素酯键含量,推测酯化反应发生位置,构建纸浆白度与漂白体系pH的关系。结果表明：添加不同类木质素母体小分子与甲酸与组成的蒸煮体系蒸煮后纤维素酯化率在2%~7%左右；根据核磁分析推测纤维素酯化发生在C2,3和C6键。从微观层面发现甲酸与类木质素母体小分子组成的蒸煮体系蒸煮后,纤维素链上生成了酯键,得到漂白段NaOH用量增加的原因,对蒸煮后纸浆漂白前后进行性能表征；发现纸浆白度由71.3 %ISO漂白后增加到81.4 %ISO,抗张强度由31.5 N.m2^/g漂白后降低到26.9 N.m2^/g；同时发现添加类木质素母体小分子后蒸煮得到的纸浆与单一甲酸蒸煮得到的纸浆相比有相对较小的水接触角,说明单一甲酸蒸煮会在纤维素表面生成更多的酯键。

Abstract:In this study, the cooking system composed of lignin-like parent small molecules and formic acid was used to explore the effect of cooking reaction on cellulose structure. At the same time, the microcrystalline cellulose simulation micro-experiment was used to characterize the cellulose structure after cooking. The content of cellulose ester bond in formic acid system was explored, the position of esterification reaction was speculated, and the relationship between pulp whiteness and pH of bleaching system was constructed. The results showed that the esterification rate of cellulose was about 2%~7% after cooking in the cooking system with different types of lignin parent small molecules and formic acid. According to NMR analysis, it was speculated that cellulose esterification occurred in C2,3 and C6 bonds. From the microscopic level, it was found that the ester bond was formed on the cellulose chain after cooking in the cooking system composed of formic acid and lignin-like parent small molecules. The reason for the increase of NaOH dosage in the bleaching section was obtained, and the properties of the pulp before and after bleaching were characterized. It was found that the brightness of the pulp increased from 71.3 % ISO to 81.4 % ISO after bleaching, and the tensile strength decreased from 31.5 N.m2^/g to 26.9 N.m2^/g after bleaching. At the same time, it was found that the pulp obtained by adding lignin-like parent small molecules had a relatively small water contact angle compared with the pulp obtained by single formic acid cooking, indicating that single formic acid cooking would generate more ester bonds on the cellulose surface.