Key Influence Factors For The Stability Of Lyocell Spinning Dope

To replace the cotton with artificial cellulose fiber has been an economic policy from long since. So, until nowadays, China is still a country who has the biggest output of viscose fiber. However viscose fiber is doomed to be eliminated for its dismal environmental process. Solvent-spun cellulose fiber (Lyocell fiber) first appeared in the last century. But there isn’t any Lyocell plant in China because of the technology blockage. In recent years, the term of patent protection is coming to the end. So technology transfer begins. For a long time, the research on Lyocell fiber is focused on the fiber structure and forming process in China. So many problems on the stability of spinning dope need to be solved if we want to build our Lyocell plant. In a word, the research of side reaction in spinning solution is necessary.Three kinds of spinning solutions are prepared in laboratory. They are solution with no stabilizer, solution with single stabilizer and solution with composite stabilizers. The influence of metal ion, temperature and acid on the side reaction of spinning solution is studied. Apparent viscosity is used as a measure of cellulose degradation. And the ultraviolet-visible absorption spectroscopy (UV) of 4-Methylmorpholine N-oxide (NMMO) extracted from the spinning solution is used as a measure of NMMO decomposition. Apart from the influence, the mechanism of these factors is studied.From my search, that the spinning solution with no stabilizer is not suitable for Lyocell process for its instability in chemistry is proved. From the research on the solution with single stabilizer, hydroxylamine (HA) and Ethylene Diamine Tetraacetic Acid (EDTA) can restrain the decomposition of NMMO to some extent. However they can both accelerate the degradation of cellulose. Propyl Gallate (PG) can increase the stability of NMMO and cellulose. But the decomposition product of PG can color the spinning solution and the Lyocell fiber. To achieve the goal of preparing stable spinning dope, the use of composite stabilizer is the only choice.One typical composite stabilizer ratio is studied in this research. And the spinning solution with composite stabilizer is made. We have found in trails that this kind dope is very stable in 98℃ without disturbance. Also it is stable with the iron concentration of 0.050mg/g, or with the copper concentration of 0.098mg/g. The max temperature allowed by this dope is 110℃. The influence of volatile acid used by cellulose pretreatment is negligible.In this study, the mechanism of influencing factors is also studied. That the UV of NMMO extracted from the spinning solution undergoes changes with five stages is found. A better way of valuing the decomposition of NMMO is raised. The method is to use the absorbance under 280nm as the representation of NMMO. The mechanism of cellulose degradation is studied. And the difference catalytic effect between CUSO4 and Fe2O3 is found and analyzed in this study.