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CN-122013340-A - Polyacrylonitrile precursor, preparation method thereof, polyacrylonitrile-based pre-oxidized fiber and polyacrylonitrile-based carbon fiber

CN122013340ACN 122013340 ACN122013340 ACN 122013340ACN-122013340-A

Abstract

The invention relates to the technical field of chemical fiber manufacturing, in particular to a polyacrylonitrile precursor, a preparation method thereof, a polyacrylonitrile-based pre-oxidized fiber and a polyacrylonitrile-based carbon fiber. The preparation method of the polyacrylonitrile precursor comprises the steps of dissolving polyacrylonitrile in a solvent to obtain a spinning solution, mixing dimethyl sulfoxide and water to prepare a basic coagulating bath, introducing a zinc source and an ammonia complexing agent, maintaining the pH value of the coagulating bath to be 9.5-10.5 to obtain a zinc-ammonia coordination coagulating bath, spraying the spinning solution into the zinc-ammonia coordination coagulating bath to be coagulated and formed to obtain a primary fiber, and then washing, hot water drafting, oiling, drying densification and steam drafting the primary fiber to obtain the polyacrylonitrile precursor. The invention can effectively improve the mechanical property, structural stability and pre-oxidation effect of the polyacrylonitrile precursor.

Inventors

  • ZHU YAOFENG
  • QIAN CHEN
  • FAN JIAZHONG
  • YANG ZHENHUA
  • XU XIANGYANG

Assignees

  • 浙江理工大学

Dates

Publication Date
20260512
Application Date
20260409

Claims (10)

  1. 1. The preparation method of the polyacrylonitrile precursor is characterized by comprising the following steps of: s1, dissolving polyacrylonitrile in a solvent to obtain spinning solution; wherein the polyacrylonitrile is a copolymer; S2, mixing dimethyl sulfoxide and water to prepare a basic coagulating bath, adding a zinc source into the basic coagulating bath, introducing a complexing agent, and maintaining the pH value of the coagulating bath to be 9.5-10.5 to obtain a zinc-ammonia coordination coagulating bath; Wherein the complexing agent is ammonia and/or ammonia water; S3, spraying the spinning solution obtained in the step S1 into the zinc-ammonia coordination coagulating bath obtained in the step S2 through spinning equipment to obtain nascent fibers; S4, washing, hot water drafting, oiling, drying densification and steam drafting are carried out on the nascent fiber to obtain polyacrylonitrile precursor; wherein steps S1 and S2 are not sequentially limited.
  2. 2. The method according to claim 1, wherein in step S2, the zinc source is at least one of zinc chloride and zinc oxide; the zinc source is added in an amount of 0.5 to 2.0wt% based on zinc ions.
  3. 3. The preparation method according to claim 1, wherein in the step S2, the complexing agent is ammonia and/or ammonia water; The mole ratio of NH 3 in the complexing agent to Zn in the zinc source is more than or equal to 4:1.
  4. 4. The preparation method of claim 1, wherein in the step S2, the mass ratio of dimethyl sulfoxide to water is 5:5-7:3.
  5. 5. The method according to claim 1, wherein in step S2, the temperature of the zinc-ammonia complex coagulation bath is 10 to 25 ℃.
  6. 6. The method according to claim 1, wherein in step S1: The polyacrylonitrile is a copolymer of acrylonitrile and itaconic acid, and the content of itaconic acid structure in the polyacrylonitrile is 1-5wt%; the solvent is dimethyl sulfoxide; the solid content of the spinning solution is 18-22wt%, and the viscosity at 50 ℃ is 50-150Pa.s.
  7. 7. The method according to claim 1, wherein in step S4: The washing is multistage washing, wherein the multistage washing comprises first-pass acid washing and subsequent water washing, wherein the washing liquid adopted by the first-pass acid washing is dilute acid liquid, the concentration of the dilute acid liquid is 0.5-2.0wt% and the pH value is 3-5; The temperature of the hot water drafting is 95-98 ℃, and the drafting multiple is 4.0-6.0 times; the temperature of the drying densification is 130-150 ℃; The steam pressure of the steam drafting is 0.3-0.7MPa, the steam temperature is 140-170 ℃, and the drafting multiple is 2.5-3.5 times.
  8. 8. A polyacrylonitrile precursor produced by the production process according to any one of claims 1 to 7.
  9. 9. A polyacrylonitrile-based preoxidized fiber is characterized by being prepared from polyacrylonitrile precursors through a preoxidation process, wherein the polyacrylonitrile precursors are the polyacrylonitrile precursors according to claim 8.
  10. 10. A polyacrylonitrile-based carbon fiber is characterized by being prepared from polyacrylonitrile precursors through preoxidation and carbonization, wherein the polyacrylonitrile precursors are the polyacrylonitrile precursors according to claim 8.

Description

Polyacrylonitrile precursor, preparation method thereof, polyacrylonitrile-based pre-oxidized fiber and polyacrylonitrile-based carbon fiber Technical Field The invention relates to the technical field of chemical fiber manufacturing, in particular to a polyacrylonitrile precursor, a preparation method thereof, a polyacrylonitrile-based pre-oxidized fiber and a polyacrylonitrile-based carbon fiber. Background Polyacrylonitrile (PAN) precursors are used as key precursors of high-performance carbon fibers and flame-retardant pre-oxidized fibers, and the uniformity of microstructure and surface integrity of the precursor directly determine the mechanical property, thermal stability and structural uniformity of the final product. In the spinning forming process of wet or dry-jet wet spinning, the double diffusion behavior of the coagulation bath is a core link for controlling the microstructure of the nascent fiber. The traditional PAN spinning technology generally adopts a neutral or weak acid coagulating bath system of solvent and water, and after the spinning solution trickles contact the coagulating bath, the organic solvent on the surface layer causes rapid precipitation of polymer molecular chains due to rapid diffusion to the coagulating bath, so that a compact skin layer structure is formed. This dense skin acts as a physical barrier, severely blocking the path of the core solvent outdiffusion, resulting in internal solvent retention and a severe imbalance in the sheath-core structure. Meanwhile, a large number of defects such as grooves, holes and folds are generated on the surface of the fiber in the rapid solidification process, and the defects become stress concentration points in the subsequent pre-oxidation and carbonization stages, so that the mechanical strength of the fiber is obviously weakened, the breakage rate is greatly improved, and finally the skin-core difference and the uneven structure of the product are aggravated To improve the coagulation process, the prior art has mainly slowed the rate of phase separation by adjusting the coagulation bath temperature or concentration (e.g. using low temperature or high concentration systems), or introduced alkaline additives to optimize the coagulation behaviour by precisely controlling the pH. Ammonium bicarbonate can form a buffer system under the weak alkaline condition, and partial ionization is generatedThe ionic strength of the coagulating bath can be regulated, and the double diffusion rate of DMSO and water is slowed down, so that the rapid densification of the cortex is inhibited to a certain extent. However, these methods can only perform limited macro-regulation of the coagulation process, and it is difficult to fundamentally solve the problem of clogging of the solvent channels caused by densification of the skin layer. While the alkaline environment helps to regulate the double diffusion behavior, improper pH control may initiate hydrolysis of the PAN cyano groups, resulting in polymer backbone breaks, significantly reducing the breaking strength and elongation of the fiber. In view of the coordination characteristic of cyano groups on PAN molecular chains, partial research attempts are made to introduce metal ions to build a temporary crosslinked network in a skin layer through coordination, but in practical application, because the coordination reaction is uncontrollable, the spinning solution is easily gelled in advance at a spinneret plate or the skin layer is excessively crosslinked, so that fiber brittleness is increased. The limitation of the prior art is that a mechanism capable of realizing accurate regulation and control of molecular scale is lacking, dynamic support cannot be formed on the cortex to maintain the permeability of the solvent, and balance between process stability and structural homogeneity is difficult to achieve, so that the difference of the fiber cortex and the fiber core is large and the surface defect is still obvious. Disclosure of Invention In view of the above, the invention provides a polyacrylonitrile precursor, a preparation method thereof, and a polyacrylonitrile-based pre-oxidized fiber and a polyacrylonitrile-based carbon fiber. The preparation method of the polyacrylonitrile precursor can effectively improve the mechanical property, structural stability and pre-oxidation effect of the polyacrylonitrile precursor. The invention provides a preparation method of polyacrylonitrile precursor, which comprises the following steps: s1, dissolving polyacrylonitrile in a solvent to obtain spinning solution; wherein the polyacrylonitrile is a copolymer; S2, mixing dimethyl sulfoxide and water to prepare a basic coagulating bath, adding a zinc source into the basic coagulating bath, introducing a complexing agent, and maintaining the pH value of the coagulating bath to be 9.5-10.5 to obtain a zinc-ammonia coordination coagulating bath; Wherein the complexing agent is ammonia and/or ammonia water; S3, spra