DRYING BEHAVIOR OF ACETATE FILAMENT IN DRY SPINNING

Abstract

Drying behavior of acetate filament in dry spinning is investigated, including the elongational deformation of polymer solution thread in the early stage of drying. Variations of diameter, velocity, temperature, solvent concentration profile in the thread and tension distribution along the threadline in the spinning column, are calculated for spinning conditions encountered commercially by means of the equations of simultaneous momentum, heat and mass transfer between the thread and hot air flow in the spinning column. Concentration and temperature dependencies of the mutual diffusion coefficient from desorption experiment are correlated by the free volume theory. The elongational viscosity is estimated from the shear viscosity data using Krevelen theory. Residual acetone concentratio in the thread and tension at the exit of the spinning column are compared between the calculated results and the experimental data by a commercial apparatus; satisfactory agreement is found. Rapid decreases of temperature and surface concentration of the dope thread after extrusion confine the elongational deformation within several centimeters below the spinnerette. Initial elongational rate and die swell ratio are related to the winding velocity and tension at the exit of the spinning column. The tension is determined mainly by initial viscous force and air drag.

Keywords:

• Acetate fiber
• Cellulose acetate
• Concentration dependent diffusion coefficient
• Die swell
• Elongational viscosity
• Filament
• Polymer solution
• Solution spinning
• Elongational deformation

ACKNOWLEDGMENTS

The author gratefully acknowledges the dry spinning data provided by Mitsubishi Rayon Co. Ltd. and thanks Mr. K. Ishii (an old staff of Mitsubishi Rayon Co. Ltd.) for the promotion of this work. The author also thanks Dr. S. Kobuchi and Mr. M. Komichi for their collaborations.