Three main methods are used to produce the continuous filaments (primary spinning):
1. Melt spinning
Melt spinning: The polymer is melted in a melt-extruder. The liquid is forced through the
spinner opening under pressure and cooled by a jet of air to form the filament. A spinning
preparation (spin finish) is generally applied at the bottom of the spinning duct. The melting
process is suitable for thermoplastic fibres such as polyester, polyamide, polyolefins (e.g.
polypropylene) and glass fibre.
2. Dry spinning
Dry spinning: The polymer is dissolved in a solvent. The dissolved polymer is extruded through
a spinneret into a chamber of heated air or gas where the solvents evaporates and the filament
forms. This filament is further after-treated with a spin finish. The dry spinning process is
principally used for acetate, triacetate and polyacrilonitrile.
3. Wet spinning.
Wet spinning: The polymer is dissolved in solution. The solution is forced under pressure
through an opening into a liquid bath in which the polymer is insoluble. As the solvent is
dissipated the fibre forms. The solvent can be dissipated through extraction or by means of a
chemical reaction between the polymer solution and a reagent in the spinning bath (reactive
spinning). The residual solvent can be extracted by simple washing. After the thread is formed
and the solvent is washed out, a spin finish can be applied. Wet spinning produces viscose,
Manmade fibres are typically extruded into continuous filaments. The continuous filaments can
- Used directly (in general, following further shaping or texturing)
- Cut into staple length and then spun in a process resembling the one used for wool or cotton.
Following primary spinning, the applied treatments vary, depending on the final product and the
processed fibre. Two simplified process sequences can be identified for this stage:
- Process for the manufacturing of continuous filament in flat or texturised form
- Process for the manufacturing of staple fibres.