What is wet non-woven fabric? The use of wet non-woven fabrics;
Wet non-woven fabric: it is to loosen the fiber raw materials placed in the water medium into single fibers, and at the same time mix different fiber raw materials to make fiber suspension slurry, which is transported to the mesh forming mechanism, the fiber is made into a net and then fixed into a cloth in a wet state. Wet spinning (Wet spinning)
One of the main spinning methods of chemical fibers, referred to as wet spinning. The process included in wet spinning is :(1)Preparation of spinning stock solution; (2)Press the stock solution out of the spray wire hole to form a trickle; (3)The stock solution trickle is solidified into a primary fiber; (4)The primary fiber is rolled or processed directly.
The synthetic fiber polymer is dissolved in a proper solvent to obtain a solution with a certain composition, a certain viscosity and good spinability, which is called spinning stock solution.
The spinning stock solution can also be directly obtained by polymerization of homogeneous solution.
The polymer swells before dissolving, that is, the solvent seeps into the polymer first, so that the distance between the macromolecular increases 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 go through pre-spinning preparation procedures such as mixing, filtration and defoaming to make the properties of the spinning stock solution uniform and consistent, remove the gel blocks and impurities contained in them and remove bubbles in the liquid.
In the production of viscose fiber, pre-spinning preparation also includes a ripening process to make the viscose have the necessary spinability.
The spinning stock solution is sent to the spinning machine by the circulating pipe, measured by the metering pump, and then enters the spray head through the candle filter and the connecting pipe (Cap).
The spray head is generally made of gold and platinum alloy or palladium alloy material.
A number of holes are regularly distributed on the spray head, and the aperture is 0. 05 ~ 0. 08mm.
The stock solution trickle pressed out from the spray hole enters the solidification bath, the solvent in the stock solution trickle spreads to the solidification bath, and the solidification agent penetrates into the trickle, thus making the stock solution trickle reach the critical concentration, it is precipitated in a solidified Bath to form fibers.
Diffusion and solidification in wet spinning are physical chemical processes, but some chemical fibers also undergo chemical changes during wet spinning.
For example, viscose fiber, cellulose yellow acid is decomposed into cellulose recycled fiber. Wet spinning speed (Refers to the speed of the first wire guide disc that rolls the newborn fiber)
Due to the limitation of the double diffusion speed of solvent and solidification agent and the fluid resistance of solidification bath, it is far lower than the melting speed.
The ratio of the linear velocity of the first wire guide plate to the extrusion velocity of the spinning stock solution is called the drawing ratio of the wire head.
The tensile ratio of wet spinning is generally negative, zero, or very small positive, in order to improve the stability of the forming process.
Spinning stock solution is a elastic adhesive with both viscosity and elasticity.
When the stock solution is pressed out of the spray wire hole, there is a hole expansion effect (Barles effect)
To make the diameter of the extrusion trickle larger than the hole diameter of the spray wire hole. In the wet spinning process, the expansion ratio is generally 1 ~ 2.
Under the tensile force of the first wire guide plate, the extrusion trickle gradually refines after crossing the maximum diameter, and the refining process continues until the stock solution trickle is completely cured.
The change of trickle diameter in wet spinning is not only the result of tensile deformation, but also related to the quality transfer process.
The spinning process from the spray head to the curing point is a fiber forming area, which is a key area for the formation of fiber structure.
Wet spinning primary fiber is swollen due to its large amount of liquid.
Macromolecular has great activity and low orientation, and its morphological structure is closely related to spinning process conditions.
The spinning process conditions are selected and controlled to 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 or double bath, deep bath or shallow bath, funnel forming or tube forming.
The winding device of wet filament spinning machine has centrifugal tank type or tube type.
When spinning short fibers, a spinning post-treatment combined machine is usually used, and the primary fibers formed at each spinning part are assembled into bundles for continuous post-treatment.
Wet spinning requires not only a wide variety of stock preparation and pre-spinning preparation equipment, but also solidification bath, circulation and recycling equipment, the process flow is complex, the investment cost of plant construction and equipment is high, and the spinning speed is low, so the cost is high.
The production capacity can be improved by using tens of thousands of hole spray heads or assembly spray heads when manufacturing cut fibers.
Generally, only synthetic fibers that cannot be spun by melt, such as polyvinyl fiber and polyvinyl alcohol fiber, are suitable for wet spinning with polymer solution to produce cut fibers and long silk bundles.
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