Low Temperature Alkali Activation Effect On Cellulose Structure And Properties

Cellulose fiber attracts more and more attention these years because of its excellent physical properties, such as the good hygroscopicity and permeability. So far, the main process to produce the regenerated cellulose fiber is the viscose process. However, the traditional viscose process is restricted by its disadvantages, such as energy consumption and high production costs. In addition, the traditional method cause serious pollution of the environment because in the process of production will produce a large number of waste water, waste residue and toxic gases such as CS2 and H2 S. Therefore, the development of an environmental friendly process has been widespread concerned. Some new technologies have been used to produce cellulose fibers these years, including NMMO solvent spinning technique, inorganic alkali aqueous solvent spinning cellulose and cellulose ionic liquid method spinning technique. The production efficiency can be improved and the problem of environmental pollution can be solved by using these methods.This paper studied alkali activation temperature, activation time base and the concentration of the alkali activator on the cellulose molecular structure, crystalline structure, degree of swelling, the degree of polymerization, the viscosity of cellulose systematically. In addition, this paper describes the dissolution degree of cellulose in new co-solvent NaOH/thiourea/urea aqueous solution as the solvent system. Research shows, alkali activated cellulose low temperature can be more effectively reduce cellulose crystallinity, and can increase the degree of the cellulose, and ultimately improve the solubility of cellulose. Optimal conditions for cellulose activation process: NaOH concentration was 9%, activation temperature was-5℃, activation time was 12 h. Twin screw directly cryogenic dissolved in NaOH / thiourea / urea solution as a solvent for dissolving cellulose pulp. Studies show that cellulose dissolved best by NaOH/thiourea/urea ratio of 9/6/6.5. Cellulose dope by filtration, degassing to improving the quality. On this basis, the process parameters in the wet spinning process is optimized. The best of the coagulation bath temperature was 15℃, the jet stretch ratio was 0.85, and the first water bath drawing ratio was 1.1 with the second water bath drawing ratio was 1.3. The temperature of the water bath was 55℃. The cellulose fiber fineness was 2.67 dtex, the breaking strength of the cellulose fiber was 1.43cN/dtex, and elongation at break was 8.09%.