Process and principle of wet spinning

Wet spinning is one of the main spinning methods of chemical fibers. Wet spinning includes the following steps: (1) preparing spinning dope; (2) pressing the dope from the spinneret to form a trickle; (3) dope trickle Solidify into nascent fiber; (4) nascent fiber package or post-processing directly.

Let us understand the principle of wet spinning:

The fiber-forming polymer is dissolved in a suitable solvent to obtain a solution with a certain composition, a certain viscosity and good spinnability, which is called the spinning dope. The spinning dope can also be directly obtained by homogeneous solution polymerization. The polymer swells before it is dissolved, that is, the solvent penetrates into the polymer first to increase the distance between the macromolecules, and then dissolves to form a uniform solution. The entire process takes a long time, and the speed of the swelling process has an important influence on the dissolution rate. Before spinning, the polymer solution must undergo pre-spinning preparation processes such as mixing, filtering and defoaming to make the properties of the spinning dope uniform, remove the gel mass and impurities entrained in it, and remove the bubbles in the solution. . In the production of viscose fiber, the pre-spinning preparation also includes the maturation process, so that the viscose has the necessary spinnability.

The spinning dope is sent to the spinning machine by the circulating pipeline, measured by the metering pump, and then enters the spinneret (cap) through the candle filter and the connecting pipe. The spinneret is generally made of gold and platinum alloy or tantalum alloy material. A number of holes are regularly distributed on the spinneret, with a diameter of 0.05 to 0.08 mm. The trickle of stock solution pressed from the spinneret enters the coagulation bath, the solvent in the trickle of stock solution diffuses into the coagulation bath, and the coagulant penetrates into the trickle, so that the trickle of stock solution reaches a critical concentration and precipitates in the coagulation bath to form fibers . The diffusion and solidification in wet spinning are physical and chemical processes, but some chemical fibers also undergo chemical changes during the wet spinning process. For example, viscose fiber, sodium cellulose xanthate decomposes into cellulose regenerated fiber.