Synthesis Of Cellulose Carbonate Compounds And Their Spinnability In Wet Spinning

As one of the important derivatives of cellulose,cellulose ester compounds have high dye uptake,high light transmittance,and excellent degradability,which greatly expands the application range of cellulose.Among them,cellulose carbonate is one of the important esterified derivatives of cellulose.It has high light transmittance,biodegradability,biocompatibility,etc.,and has a wide range of packaging materials,optical materials,and medical materials.Application prospects.However,the development of cellulose carbonates has been limited due to the complex synthesis process and the few types.In this paper,based on the DBU/DMSO/CO₂(1,8-diazabicycloundec-7-ene/dimethylsulfoxide/carbon dioxide)cellulose dissolution system,halogenated substances with different microscopic sizes,bromopropane,bromine Methylcyclopropane and benzyl bromide are used as electrophiles to attack the cellulose carbonate anion generated during the dissolution process,and undergo an electrophilic substitution reaction to generate stable cellulose carbonate compounds.Due to the different sizes of the side groups of the three halogenated molecules(benzyl>cyclopropylmethyl>propyl),cellulose carbonates with different inter-chain steric hindrance are generated.Explore the spinnability of this series of cellulose carbonates difference.At the same time,3wt%-6wt%of cellulose carbonate spinning solution was prepared for wet spinning,and the change of cellulose carbonate fiber from unspinable to spinnable as the concentration of the spinning solution increased was investigated.The rheological properties of the liquid are analyzed in focus.The above-mentioned research provides a strong basis for the spinning and forming of cellulose carbonate,and has far-reaching significance for the development and utilization of new cellulose fibers.The main research contents and conclusions are as follows:(1)The DBU/DMSO/CO₂ dissolution system was used to dissolve cellulose,and through halogenation reaction,cellulose carbonate compounds of different structural types were synthesized.Subsequently,the spinning performance of cellulose carbonate compounds at different concentrations of 3wt%-6wt%was explored.The results show that,at the same concentration,the viscosity of cellulose propyl carbonate solution is higher than that of cellulose benzyl carbonate and higher than that of cellulose cyclopropyl methyl carbonate.Among them,the concentration of the cellulose propyl carbonate solution must reach 4wt%,and the viscosity must be above 0.08 Pa·s,so that the wet spinning can be carried out smoothly.Cellulose benzyl carbonate solution comes next,with a concentration of 5wt%and a viscosity of 0.15 Pa·s or more.The spinnability of cellulose cyclopropyl methyl carbonate solution is poor,the concentration needs to reach 6wt%,and the viscosity is above 0.07Pa·s.(2)A series of basic properties of the spun cellulose carbonate fibers were explored.The three prepared cellulose carbonate-based fibers all have light yellow appearance and good transparency.By comparison with cellulose,it is found that in terms of crystallinity,the crystallinity of the above-mentioned cellulose carbonate fibers has been significantly reduced.Taking 6wt%cellulose propyl carbonate as an example,the crystallinity of the original cellulose is reduced from 76.39%.That's 24.92%.In terms of mechanical properties,among the three different types of carbonate fibers at the same concentration,the cellulose propyl carbonate fiber has the best mechanical properties.The breaking strength of 6wt%cellulose carbonate fiber is 0.35 c N/dtex and the elongation at break is 35.37.%.In terms of thermal stability,cellulose propyl carbonate fiber has the best thermal stability,with a decomposition temperature of 206°C,followed by cellulose benzyl carbonate at 161C,and cellulose cyclopropyl methyl carbonate is poor,only It is 142°C.Among the similar fibers spun,the cellulose carbonate fiber with a concentration of 6wt%has the best performance in all aspects.