双醛纤维素的制备及其对纸张强度的增强

Preparation of Dialdehyde Cellulose and Its Enhancement Effects on Paper Strength

目的采用球磨降低纤维素的结晶度,制备纤维素超细粉体;采用高碘酸钠氧化球磨后的纤维素,制备出双醛纤维素;利用双醛纤维素改善纸张的抗张强度。方法以微晶纤维素为原料,通过球磨粉碎处理,制备出微晶纤维素超细粉体。利用红外光谱、核磁光谱、X射线衍射和扫描电镜对不同处理时间的样品进行表征;利用高碘酸钠对球磨粉碎后的微晶纤维素超细粉体进行选择性氧化,制备双醛纤维素超细粉体;将双醛纤维素超细粉体加入纸浆中,研究其对纸张强度的影响。结果微晶纤维素经球磨粉碎后,结晶区被破坏,结晶度下降,会形成大小不一的超细粉状;纸张中双醛纤维素超细粉体的质量分数分别为0.8%和1.0%时,纸张干、湿强度提高到最大;微晶纤维素超细粉体与高碘酸钠的质量比为1∶3时,纸张湿抗张强度效果较好,从1.9 N·m/g增加至2.32 N·m/g,提高了22.1%。结论微晶纤维素超细粉体经高碘酸钠氧化后,纤维表面产生了大量醛基,在抄纸过程中会与纤维表面上的羟基形成半缩醛结构,使纸张的干、湿抗张强度得到改善。

The work aims to reduce the crystallinity of cellulose by ball milling to prepare cellulose ultrafine powder and produce dialdehyde cellulose by oxidation of milled cellulose with sodium periodate,so as to improve the strength of paper with dialdehyde cellulose.Microcrystalline cellulose was milled by ball milling to prepare cellulose ultrafine powder.The cellulose ultrafine powder samples treated for different time were characterized by IR,NMR,XRD and SEM.Dialdehyde cellulose ultrafine powder was prepared through the selective oxidation of the ultrafine powder of microcrystalline cellulose by sodium periodate.The dialdehyde cellulose ultrafine powder was added to the pulp to study its effect on paper strength.After the microcrystalline cellulose was crushed by ball milling,the crystalline area of cellulose was destroyed which resulted in the crystallinity of cellulose.At the same time,the ultrafine powders of different sizes were formed.When the fraction mass of dialdehyde cellulose in paper was 0.8%and 1.0%,respectively,the dry and wet strength of the paper increased to the maximum.On the condition that the mass ratio of microcrystalline cellulose and sodium periodate oxidation was 1∶3,the wet tensile strength of paper was the best,which increased from 1.9 N·m/g to 2.32 N·m/g,increasing by 22.1%.After the ultrafine powders of microcrystalline cellulose are oxidized by sodium periodate,a large number of aldehyde groups are produced on the surface of the fiber,which forms a semi-acetal structure with the hydroxyl groups on the surface of the fiber in the process of paper making,thus improving the dry and wet strength of the paper.