| Cellulose is an inexhaustible and unlimited supply of renewable organic resources in nature. Through photosynthesis it can produce 100 billion tons of cellulose every year, they are widely used to develop textile fiber materials. Cellulose molecules have many hydrogen bonds, complex aggregation structure and high crystallinity, which make the attainability of the solvent to cellulose low so it is difficult to be dissolved in common solvents. It limits cellulose's further development, so it is particularly important to explore the method of new use of cellulose and its derivatives.Etherification can weak the hydrogen bonds effect between cellulose molecules, which highly improved the dissolvability of etherification product. Hydroxyl ethyl cellulose(HEC), product of the etherification between cellulose and ethylene oxide(EO), could be divided into two types as water-soluble and alkali-soluble according to different mole degree of substitution(MS). HEC with low MS cannot be dissolved in water but can be dissolved in diluted alkali solution, has a unique alkali-solubility, the solution mass fraction can be amounted to 9%.This alkali-soluble HEC has a good process ability of making fibers and films, and it is promising to become another vital regenerated cellulose fiber.In this context, this paper used gas-solid reaction method to synthesize low MS HEC which has unique alkali-solubility. First of all, in the base of the alkali cellulose's crushing ratio is 3.20, etherification time is 100 min, etherification temperature is 40℃, the mass ratio of EO to cellulose is 0.05～0.50, we got the HEC with good alkali-solubility. By infrared spectrum(FTIR), nuclear magnetic resonance (NMR), X-ray diffraction, thermo-gravimetric analysis(TG) and so on, we characterize the microstructure and etherification degrees of HEC. The results showed that HEC is belong to celluloseⅡstructure, with the increase of mass ratio of EO to cellulose, MS increased, crystallinity decreased and thermal-stability reduced. Second, through the test of HEC's solubility, we discussed the influence of the ideal solution conditions and the etherification on cellulose's solubility. When the temperature is 0℃and the time is 7-8 hours, the HEC can be dissolved in sodium hydroxide solution whose density is 8% easily, and the maximum mass fraction of solute can reach up to 10%. With the MS increased, the dissolubility of HEC enhanced, the dissolve time reduced, and the apparent viscosity of HEC solution with the same mass fraction decreased. Put the HEC solution in the acetic acid solution with a concentration of 10% for solidification regeneration at room temperature, we got the regenerated HEC films with uniform structure. With the MS increased, the regeneration films' tensile stress dropped, and the tensile strain increased. After a comprehensive analysis, we argue that when the mass ratio of EO to cellulose is 0.30, the HEC's further research is more appropriate. To improve the mass fraction of the solution and get a regeneration HEC fiber with high property, we added urea and thiourea into sodium hydroxide solution as cosolvent, the results found that the solvent can improve the dissolubility of HEC obviously and the mass fraction of the solution could attain to 12%, and the stability of the solution improved.Finally, the static and dynamic theological properties of the HEC dissolved in different solvents system were studied, which provided a reliable basis to choose a appropriate spinning technology. The results showed that all the solution were non-Newtonian fluid with shear thinning, they were not sensitive to temperature changes. With the test temperature dropped and the mass fraction of the solution increased, the apparent viscosity of the solution increased, the Newton property enhanced, and the gel property increased. |
PDF Full Text Request