Study On Wet Spinning Process Of Cellulose Fiber In The Solvent System Of Dilute Alkali Solution

Cellulose fiber attracts more and more attention these years because of its excellent physical properties.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.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 derivatives melt spinning technique.The production efficiency can be improved and the problem of environmental pollution can be solved by using these methods.A novel composite solvent NaOH/thiourea/urea aqueous solution was adopted as solvent to dissolve the cellulose.The rheological properties were studied,so as to get theoretical basis of wet spinning of cellulose in NaOH/thiourea/urea aqueous solutions.Cellulose solution showed non-newtonian fluid properties.Viscous flow activation energy and the structural viscosity index of the cellulose solution increased as the temperature and the mass fraction increased.The gel temperature of the cellulose solution got lower when the mass fraction increased,while the gel temperature of 7wt%cellulose solution was 30.4?.The gel point had a trend of moving to the high-frequency direction as the temperature increased.5-25 ? was a suitable temperature range for the cellulose solution wet spinning.The 7wt%cellulose solution was used for wet spinning,and effects of spinning conditions on the structure and properties of the fiber were also studied.The obtained cellulose fiber had a smooth surface and almost circular cross-section with the compact and uniform structure.The maximum breaking strength and elongation of the fiber reached 2.41cN/dtex and 10.5%,respectively.The degree of crystallinity was 60-65%with the crystal form of cellulose transformed into type ? from the original type ?,and the orientation factor reached 0.76.The Optimum spinning condition was as follows:coagulation bath was composed by 8-10%H2SO4/6%Na2SO4 under the temperature of 25 ?,while the jet stretch ratio was 0.97,and the first water bath drawing ratio was 1.2 with the second water bath drawing ratio was 0.96.The temperature of the water bath was 45-55 ?.The cellulose/NaOH/thiourea/urea/PEG solution system was adopted to proceed wet spinning under the above-mentioned the spinning conditions.The structure and properties of the fiber were studied to explore the impact of PEG on properties of the cellulose fiber.The results showed that adding lwt%PEG into the alkali compound solvent can improve the stability of the cellulose solution,while it had no much effect on the crystal transition and the morphology of the fiber.However,the breaking strength and elongation at break decreased after PEG was added,and the degree of crystallinity and thermal stability of the fibers also reduced.After adding 1wt%PEG,the breaking strength of the cellulose fiber was 1.54cN/dtex,and elongation at break was 7.36%with the crystallinity of 62.8%.