Wet non-woven fabric: the fiber raw materials placed in the water medium are opened into single fibers, and different fiber raw materials are mixed at the same time to form a fiber suspension slurry, and the suspension slurry is transported to the web forming mechanism, and the fibers are netted in a wet state Then reinforce into cloth. Wet spinning Dissolve the fiber-forming polymer in an appropriate solvent to obtain a solution with a certain composition, a certain viscosity and good spinnability, called spinning dope. The spinning dope can also be obtained directly from homogeneous solution polymerization. The polymer swells before dissolving, that is, the solvent penetrates into the polymer first, so that the distance between the macromolecules continues to increase, 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-spin preparation steps such as mixing, filtration, and defoaming, so that the properties of the spinning dope are uniform and uniform, to remove gel blocks and impurities entrained therein, and to remove air bubbles in the solution. . In the production of viscose fibers, the preparation before spinning also includes the aging process, so that the viscose has the necessary spinnability. The spinning dope is sent to the spinning machine through the circulation pipeline, and is metered by the metering pump, and then enters the spinneret (cap) through the candle filter and 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 an aperture of 0.05-0.08 mm. The fine stream of raw liquid pressed out from the spinneret orifice enters the coagulation bath. The solvent in the fine stream of raw liquid diffuses into the coagulation bath, and the coagulant penetrates into the fine flow, so that the fine stream of raw liquid reaches a critical concentration, and precipitates in the coagulation bath to form fibers . Diffusion and solidification in wet spinning are physical and chemical processes, but some chemical fibers also undergo chemical changes during wet spinning. For example, viscose fiber, cellulose sodium flavate is decomposed into cellulose regenerated fiber. The wet spinning speed (referred to as the speed of the first godet for winding nascent fibers) is limited by the double diffusion speed of the solvent and coagulant and the fluid resistance of the coagulation bath, so it is much lower than the melt spinning speed. The ratio of the linear speed of the first godet to the extrusion speed of the spinning dope is called the spinneret draw ratio. The wet spinning draw ratio is generally negative, zero, or very small positive value, the purpose is to improve the stability of the forming process. The spinning dope is an elastic and viscous body with both viscosity and elasticity. When the original liquid is pressed out from the spinneret hole, there is an orifice swelling effect (Barers effect), so that the diameter of the extruded stream is larger than the spinneret hole diameter. During the wet spinning process, the expansion ratio is generally 1-2. Under the action of the stretching force of the first godet, the extruded stream gradually becomes thinner after crossing the maximum diameter, and the thinning process continues until the original liquid stream is completely solidified. The change of the fine flow diameter in wet spinning is not only the result of tensile deformation, but also related to the mass transfer process. The spinning process from the spinneret to the curing point is the fiber forming area, which is the key area for the formation of fiber structure. The wet-spun primary fiber is in a swollen state because it contains a lot of liquid. Macromolecules have great mobility, and the degree of orientation is very low, and their morphological structure is closely related to the spinning process conditions. Selecting and controlling the spinning process conditions can produce fibers with different cross-sectional shapes or special capillary pore structures and special properties. Wet spinning has various forming methods, and spinning machines also have various structures. For example, there are single bath method or double bath method, deep bath method or shallow bath method, funnel forming or tube forming. The winding device of the wet filament spinning machine has centrifugal tank type or bobbin type. When spinning short fibers, a spinning post-processing combination machine is usually used, and the primary fibers formed at each spinning part are collected into bundles, and post-processing is performed continuously. Wet spinning requires not only a wide variety of bulky liquid preparation and pre-spin preparation equipment, but also coagulation bath, circulation and recovery equipment. Its complicated process flow, large investment in plant construction and equipment, and low spinning speed, so the cost Higher. Tens of thousands of holes spinnerets or container spinnerets can be used to increase the production capacity when manufacturing cut fibers. Generally, only synthetic fibers that cannot be melt spun, such as polyacrylonitrile fibers and polyvinyl alcohol fibers, are suitable for wet spinning of polymer solutions to produce cut fibers and filament bundles. Pull and decoration are the cord's functions. 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wet spinning
One of the main spinning methods of chemical fibers, referred to as wet spinning. The wet spinning process includes:
(1) Preparation of spinning dope;
(2) Press the original solution out of the spinneret hole to form a thin stream;
(3) The fine stream of raw solution solidifies into primary fibers;
(4) Primary fiber package or directly post-processing.