Dissolution of HwBKP with [Bmim]Cl-DMF Solvent and Production of Cellulose Beads: Effect of Mixing Ratio of Solvents

Abstract

Hardwood bleached kraft pulp (HwBKP) was dissolved with 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and N,N-dimethylformamide (DMF) at 110℃, and cellulose beads were prepared by dropping the [Bmim]Cl/DMF/cellulose solution into water. The effects of the mixing ratio of [Bmim]Cl and DMF on the properties of the cellulose solution and beads are investigated in this paper. Increasing the DMF ratio decreased the viscosity and surface tension of the cellulose solution. Moreover, all cellulose solutions with various mixing ratios of [Bmim]Cl and DMF showed shear thinning behavior. The cellulose beads with 800-1500 μm diameters were prepared by varying the mixing ratio of [Bmim]Cl and DMF (the cellulose concentration was 3%; the inner diameter of a syringe needle was 0.41 mm). Increasing the DMF ratio increased the particle size of the cellulose beads, and increasing this ratio over 40% created a rough surface on the beads. During dissolution with [Bmim]Cl and DMF and regeneration in water, the cellulose crystal structure was changed to cellulose II and the crystallinity of the cellulose decreased. In addition, the thermal stability of the cellulose beads was slightly lower than that of the HwBKP.