Dynamic modeling of dry-jet wet spinning of cellulose/[BMIM]Cl solution: complete deformation in the air-gap region

During the dry-jet wet spinning process of cellulose solutions with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as solvent, the special viscoelastic characteristics of the solution lead to a large air-gap distance where the extruded flow can extend completely before entering the coagulation bath. Therefore, online measurement of diameter and temperature can be carried out and the velocity on the spinning line determined reasonably. Therefore, a model of dry-jet wet spinning is proposed to simulate the extrusion and extending dynamics of cellulose/[BMIM]Cl solutions in the air-gap region with complete deformation. Material parameters such as the density and heat capacity were determined by experiment, and the heat transfer coefficient along the spin-line was evaluated by an inversion procedure involving online experimental data for temperature and diameter. A two-dimensional (2-D) approach in POLYFLOW was adopted to compute the dynamic parameters along both the axial and radial directions of the spinning line. The numerical results were verified by comparison with experimental data including temperature and diameter. It was found that the contraction flow in the spinneret orifice could not be neglected and use of a nonisothermal viscoelastic model in the constitutive equation gave better agreement between simulation and experiment.