MEASUREMENTS OF VELOCITY DISTRIBUTION AND DESWELLING OF FILAMENTS IN COAGULATING BATH IN THE WET-SPINNING OF POLYNOSIC FIBERS

Abstract

In order to investigate stretching and deswelling behaviors of viscose filaments in a coagulating bath during the wet spinning of polynosic fibers, a new method of measurement of velocity distribution of filaments in the coagulating bath was studied.
A single hole spinning apparatus was used, and the spinnerette was designed so that fine mercury particles were put into viscose at a constant rate at the stage of extrusion. The filament including mercury particles was photographed, and the velocity distribution was determined by measuring the distance of the mercury particles. Volume of the filament was calculated using the filament velocity and diameter.
Using this method, influences of sulfuric acid concentration in salt free coagulating baths and Jet Stretch on the diameter, volume and velocity of the filament were studied.
For the bath with H₂SO₄ concentration of 10g/l, the volume of the filament increased markedly compared with that of original viscose during the run of 200mm from the spinnerette surface in the coagulating bath.
This phenomenon may indicate the osmosis of the coagulating bath into the filament. For the bath with H₂SO₄ concentration of 20g/l, the same phenomenon was observed in lesser extent.
The velocity of the filament decreased just after passing the spinnerette surface from that in the spinnerette hole, and then recovered to a maximum velocity depending more or less on H₂SO₄ concentration in the coagulating bath. After reaching the maximum, the velocity of the filament decreased slowly to the take up speed by a longitudinal contraction of the filament. When Jet stretch was raised to 3.0, the velocity of the filament reached to maximum values at the distance of ca. 200mm from the spinnerette surface for the bath with H₂SO₄ concentration in 10g/l, and 20mm for the H₂SO₄ concentration in 30g/l. The stretching of the viscose filaments takes place in the paths 200mm or 20mm from the spinnerette surface depending on H₂SO₄ concentration.
These results show that the present method is applied on the spinning under a very slow coagulation rate.