SPINNABILITY OF POLYNOSIC FIBERS IN THE WET-SPINNING

Abstract

Relationship between spinning conditions and spinnability of polynosic fibers in the wet spinning was investigated using a single hole spinning apparatus.
Maximum Jet Stretch (ν_2c/ν₁) and Maximum True Jet Stretch (ν_2c/ν_0c) were used for the criteria of spinnability, where ν_2c: maximum take up velocity of the filament without break, ν₁: average linear velocity of viscose filament in a spinnerette hole, ν_0c: velocity of viscose filament at maximum diameter (d₀) near the spinnerette surface at ν_2c.
In the case of the concentration of H₂SO₄ in the coagulating bath was sufficiently low, d₀ was generally larger than the diameter of the spinnerette hole at any stretch. Therefore, True Jet Stretch was higher than apparent Jet Stretch.
The relationship between H₂SO₄ concentration in the coagulating bath and ν_2c/ν₁ showed a curve having a maximum at lower H₂SO₄ concentration and a minimum at higher H₂SO₄ concentration (Maximum Jet Stretch Curve).
The Maximum True Jet Stretch Curve also showed a maximum and a minimum at lower and higher H₂SO₄ concentrations respectively, and the acid concentration at the maximum substantially coincided with that of the Maximum Jet Stretch Curve, whereas, at the minimum it shifted slightly to a higher acid concentration compared with that of the Maximum Jet Stretch Curve.
The H₂SO₄ concentrations where these two Jet Stretch Curves showed the maximum and minimum, varied depending on salt concentration, temperature of the coagulating bath, viscose feed rate, γ-value of viscose and spinnerette hole diameter.
The maximum diameter of the viscose filament just behind the spinnerette surface at Maximum Jet Stretch decreased as H₂SO₄ concentration in the coagulating bath increased, and became equivalent to the diameter of the spinnerette hole at the H₂SO₄ concentration where the Maximum True Stretch Curve showed the minimum. Therefore, it was considered that the stress of taking up the filaments just began to be transmitted to the spinnerette surface at this H₂SO₄ concentration.
The mechanism of the appearance of the minimum on Maximum True Jet Stretch Curves at the Maximum Jet Stretch Curves was discussed from a point of transmission of the stress for taking up the filaments.