At present, the spinning solution of wet spinning is developed in the direction of high concentration, high polymer and high viscosity in order to produce high quality carbon fiber precursor. The three high data are close to or equivalent to the parameters of dry spun spinning. The main technological parameters of wet spinning can be summed up as the following.
1, the spinning solution is high concentration. Dope concentration (solid content) roughly 20%-23% (mass fraction), the replacement amount of such a high solid content of coagulant in the solidification process of water decreased, to produce dense solidification strips and the high density of PAN precursor. High strength fibers with high molecular weight.
3, the diameter of the spinneret (spinneret hole) develops in a larger direction. The spinning aperture of spinning T300 grade PAN precursor is about 0.05mm or 0.055mm, and now it develops towards large aperture 0.07mm, which is suitable for the development direction of spinning liquid toward high concentration, high viscosity and polymer. The larger the spinning diameter, the greater the flow rate in the spinning solution at a unit time, which can improve the spinning speed. The general level of carbon fiber with PAN raw silk, the size is about 1.0-1.2d, when the polymerization conditions and the spinneret is fixed, and the discharge amount of Q roller speed V is proportional to the amount of Q, spit out the spinning faster, is conducive to improve the yield and reduce the production cost of children. The diameter of the spinneret is 0.075mm, and the wire collecting speed is up to 77m/min. For wet spinning, the spinning speed is faster. Under the condition of general wet spinning, the spinning speed is between 40-60m/min.
4, spinning temperature and coagulation bath temperature are relatively high. For Newton fluid flow, viscosity is the resistance of flow resistance inside the fluid, and is closely related to viscosity. The viscosity increases, the movement of macromolecules is accelerated, the intermolecular force is weakened, and it is easy to flow. So. The viscosity of the spinning liquid has a great influence on its spinnability. In spinning wet spinning high concentration, high viscosity and high molecular weight spinning fluid, increasing spinning viscosity can reduce viscosity and improve spinnability, and make spinning fluid evenly pass through spinneret hole with small aperture. It is one of the key factors for process stability and quality stability to regulate the spinning temperature and keep its viscosity in the best flow state. In the production site or in the laboratory, the determination of viscosity by the ball viscosity method is one of the most common methods for the spinning solution.
5, the tension in the solidification process is small. In the solidification phase separated into fiber, spun filament particularly delicate, “ ” molecular force is very small, not easy deformation, relatively large single axial pulling force. Or it will pull the yarn or filament and broken wires, causing irregular deformation, serious will break through the primary gel network. The solidification process of 200mg/ filament tension in the following as well, when more than this value will be generated when the filament, broken wire and weak wire tow to decrease the performance of weak wire here refers to the average performance is lower than the tow.
6, high fold drafting. Fiber forming is a physical process, drafting through the whole process. A total of 10-15 times the total drafting (hot or boiling water) and two drafting (high pressure steam drafting).
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