A kind of preparation method of polyacrylonitrile-based carbon fiber precursor

Abstract

The invention discloses a method for preparing polyacrylonitrile-based carbon fiber precursors. The method comprises the following steps: firstly, the polyacrylonitrile spinning dope obtained after the pretreatment of the polyacrylonitrile solution is continuously fed from the main feed port of the twin-screw extruder; secondly, the modifying agent is fed from the side of the twin-screw extruder The feeding port is continuously fed according to the dose; finally, the polyacrylonitrile spinning dope fed from the main feeding port and the modifier fed from the side feeding port pass through the twin-screw extruder conveying section, degassing section, After the pressurized section, the modified polyacrylonitrile solution is obtained. The pressurized modified polyacrylonitrile solution passes through the spinneret to form an extrusion flow, enters the coagulation bath through the air dry section, and is solidified and formed, and is drawn out of the coagulation bath to prepare a primary product. fiber. The pretreated material is assisted by twin-screws to add modifiers online to ensure sufficient degassing and precision filtration of the material, improve the spinnability of polyacrylonitrile-based spinning dope, reduce fiber micropore defects, and improve process stability.

Description

technical field [0001] The invention belongs to the technical field of carbon fiber preparation, and in particular relates to a method for preparing polyacrylonitrile-based carbon fiber precursors. Background technique [0002] Carbon fiber is a very important material for structural and functional integration. It is widely used in aerospace, sports and leisure, transportation and industrial production. According to different raw materials, carbon fiber is divided into many varieties, and the most widely used is polymer Acrylonitrile-based carbon fiber. Traditional polyacrylonitrile carbon fiber precursor preparation methods are divided into wet spinning and dry-wet spinning. These two spinning forming methods may cause concentration changes due to double diffusion of solvent and non-solvent during the formation of primary fibers. ; The concentration change of solvent and non-solvent will produce phase separation, which will lead to the formation of larger hole defects in t...

AI Technical Summary

Problems solved by technology

Traditional polyacrylonitrile carbon fiber precursor preparation methods are divided into wet spinning and dry-wet spinning. These two spinning forming methods may cause concentration changes due to double diffusion of solvent and non-solvent during the formation of primary fibers. ;Changes in the concentration of solvent and non-solvent will produce phase separation, which will lead to the formation of larger void defects in the nascent fiber, which will be inherited to the final carbon fiber and is one of the main reasons for the degradation of the final product properties

Among them, the dry-wet spinning can usually be coagulated and formed at a lower coagulation bath temperature because the spinneret flow passes through the air dry section before entering the coagulation bath. Compared with wet spinning, the surface and internal defects of the fiber are reduced, but Lower coagulation bath temperature leads to higher energy consumption, and the spinneret flow is prone to breakage due to fluctuations in external conditions, and the suitable spinning process range is narrow

[0003] The advantage of using ultra-high molecular weight polymers for spinning is that the gelation temperature of the spinning liquid can be significantly increased, and it is easy to form a homogeneous structure of bicontinuous phases during the fiber coagulation forming process, but the one-step spinning process It is difficult to prepare ultra-high molecular weight polymers by solution polymerization, and because of the large molecular weight, it is necessary to use low-solid content spinning dope or large-aperture spinneret spinning, which may bring new defects; in the two-step spinning process, Add water or alcoholic substance as modifier (Chinese patent CN102154723A) in the process of dissolving dry resin, after mixing through stirring tank, ripen to form gel-like spinning dope in advance, then carry out gel spinning; Existing problem is: not only The process is complex, and ordinary stirring conditions cannot fully guarantee the uniformity of mixing. After further pre-adding modifiers, the viscosity of the resin system is high, resulting in difficulties in degassing and precision filtration.