Wet spinning is one of the main spinning methods of chemical fiber.
The wet spinning process includes:
(1) preparation of spinning stock solution;
(2) extrusion of stock solution from spinneret hole to form fine flow;
(3) solidification of stock solution into primary fiber;
(4) roll or directly post-treatment of primary fiber.
The solution with certain composition, certain viscosity and good spinnability can be obtained by dissolving the fiber-forming polymer in a proper solvent, which is called spinning solution. The spinning solution can also be directly obtained by homogeneous solution polymerization. The polymer swells before dissolving, that is, the solvent penetrates into the polymer first, which makes the distance between the macromolecules increase continuously, and then dissolves to form a uniform solution. The whole process takes a long time, and the speed of swelling process has an important influence on the dissolution rate. Before spinning, the polymer solution must be prepared by mixing, filtering and defoaming before spinning, so as to make the properties of the spinning fluid homogeneous and uniform, remove the gel blocks and impurities contained therein and remove the bubbles in the solution. In the production of viscose fiber, the preparation before spinning also includes the maturing process, so that the viscose has the necessary spinnability.