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CN-121975058-A - Acrylonitrile binary copolymer and preparation method thereof

CN121975058ACN 121975058 ACN121975058 ACN 121975058ACN-121975058-A

Abstract

An acrylonitrile binary copolymer and a preparation method thereof relate to the technical field of preparation of high polymer materials and solve the problems that the prior polyacrylonitrile-based precursor has concentrated heat release, severe reaction, difficult control of temperature, uneven structure and the like in the preoxidation process. Under the protection of inert gas, acrylonitrile and 3-acrylamide-phenol are dissolved in an organic solvent, a free radical initiator is added for solution polymerization reaction after uniform stirring, and after the reaction is finished, the obtained polymerization solution is subjected to precipitation, washing, filtering and drying to obtain the acrylonitrile binary copolymer, wherein the mass ratio of the acrylonitrile to the 3-acrylamide-phenol is 99-96:1-4. The copolymer obtained by the invention can be used for preparing high-strength and high-compactness carbon fiber precursor, can reduce the exothermic peak strength in the pre-oxidation stage, promote the uniform cyclization reaction, inhibit the local overheating and melting phenomena, and improve the structural uniformity and mechanical properties of oxidized fibers and final carbon fibers.

Inventors

  • LI MING
  • ZHANG XINHENG
  • MA JUNMING
  • WANG QI

Assignees

  • 长春工业大学

Dates

Publication Date
20260505
Application Date
20260304

Claims (10)

  1. 1. The preparation method of the acrylonitrile binary copolymer is characterized by comprising the following steps: Under the protection of inert gas, acrylonitrile and 3-acrylamide-phenol are dissolved in an organic solvent, stirred uniformly, and added with a free radical initiator to carry out solution polymerization reaction; after the reaction is finished, precipitating, washing, filtering and drying the obtained polymerization solution to obtain an acrylonitrile binary copolymer; wherein the mass ratio of the acrylonitrile to the 3-acrylamide-phenol is 99-96:1-4.
  2. 2. The method for producing an acrylonitrile copolymer according to claim 1, wherein the inert gas is nitrogen.
  3. 3. The method for producing an acrylonitrile binary copolymer according to claim 1, wherein the organic solvent is one of dimethyl sulfoxide, N-dimethylformamide, and N, N-dimethylacetamide.
  4. 4. The method for producing an acrylonitrile copolymer according to claim 1, wherein the radical initiator is azobisisobutyronitrile.
  5. 5. The method for preparing an acrylonitrile binary copolymer according to claim 1, wherein the amount of the radical initiator is 0.1 to 2.0wt% of the total mass of acrylonitrile and 3-acrylamido-phenol.
  6. 6. The method for preparing an acrylonitrile binary copolymer according to claim 1, wherein the total mass of acrylonitrile and 3-acrylamido-phenol accounts for 16-30wt% of the total mass of the reaction system.
  7. 7. The method for preparing an acrylonitrile copolymer according to claim 1, wherein the temperature of the solution polymerization reaction is 55-70 ℃.
  8. 8. The method for preparing an acrylonitrile binary copolymer according to claim 1, wherein the time of the solution polymerization reaction is 8-12 hours.
  9. 9. The method for preparing the acrylonitrile copolymer according to claim 1, wherein the washing is performed 3 to 5 times by using absolute ethyl alcohol and warm water, the drying temperature is 50 to 60 ℃, and the drying time is 24 to 48 hours.
  10. 10. An acrylonitrile binary copolymer, characterized in that the acrylonitrile binary copolymer is prepared by the preparation method according to claims 1-9; The relative molecular weight of the acrylonitrile binary copolymer is 2.05X10 5 ~2.55×10 5 , and the molecular weight distribution is 2.01-2.46.

Description

Acrylonitrile binary copolymer and preparation method thereof Technical Field The invention relates to the technical field of preparation of high polymer materials, in particular to an acrylonitrile binary copolymer and a preparation method thereof. Background Carbon fiber has high specific strength, high specific modulus, excellent high temperature resistance, corrosion resistance and good dimensional stability, and is widely applied to the fields of aerospace, national defense and military industry, rail traffic, new energy equipment, high-end civil industry and the like. Among them, polyacrylonitrile (PAN) -based carbon fiber occupies the dominant position of the global carbon fiber market due to its excellent comprehensive properties, mature process and stable mechanical properties. As a key precursor material for carbon fiber preparation, the molecular structure, molecular weight and distribution of PAN-based fibrils have a decisive influence on the properties of the final carbon fiber. The preparation of PAN-based carbon fibers generally includes processes such as precursor preparation, pre-oxidation stabilization, and high temperature carbonization. Wherein the pre-oxidation stage is a key step in determining the microstructure and properties of the final carbon fiber. At this stage, the nitrile groups in the polyacrylonitrile molecular chain undergo cyclization reaction to form a trapezoid structure, which is a precondition for forming a stable graphitized structure in the subsequent carbonization process. Thus, the structural regularity of the PAN molecular chain, the cyclisation reaction initiation temperature and the cyclisation exotherm behaviour directly influence the controllability of the pre-oxidation process and the structural homogeneity of the carbon fibre. Although the traditional acrylonitrile homopolymer has higher crystallinity and mechanical property, the traditional acrylonitrile homopolymer still has certain limitation in practical application. For example, the initial temperature of the cyclization reaction is higher, the heat release is concentrated, local overheating and even fiber structure defects are easily caused, and meanwhile, the problems of difficult solubility regulation and control, narrow rheological property window and the like of the homopolymerized PAN in the solution spinning process influence the quality stability of the precursor. In addition, the force between the molecular chains of the homopolymer is strong, gel or microphase separation phenomenon easily occurs in the processing process, and continuous and stable preparation of high-quality precursor is not facilitated. To improve the above problems, researchers have generally employed a method of copolymerization modification to introduce a second monomer into the acrylonitrile main chain, and improve the solubility, spinnability, and thermal reaction behavior of the polymer by adjusting the copolymerization composition. Common comonomers include Methyl Methacrylate (MMA), acrylic Acid (AA), itaconic Acid (IA), and the like. Such monomers can reduce the crystallinity of the polymer to some extent, increase the solution stability, and provide a modulating effect on the cyclisation behaviour. However, the existing copolymerization system still has the following defects that (1) part of carboxyl-containing monomers are easy to ionize in the polymerization process, so that the free radical polymerization reaction rate is influenced, the molecular weight is reduced or the molecular weight distribution is widened, (2) certain comonomers can generate side reaction in the pre-oxidation process, so that the cyclization uniformity is influenced, (3) the promotion effect on the cyclization reaction is limited, the effect that the cyclization initial temperature is obviously reduced and the exothermic behavior is controllable is difficult to realize, and (4) part of the system is sensitive to metal ions or residual impurities, so that the post-treatment difficulty is increased. In recent years, it has been revealed that by introducing a functional monomer having a phenolic hydroxyl group or an amide structure into the PAN molecular chain, an acceleration effect on the cyclisation reaction of a nitrile group can be produced by intermolecular hydrogen bonding or local electron effect, thereby lowering the cyclisation initiation temperature and increasing the degree of cyclisation reaction. In addition, the functional monomer structure is reasonably designed, and the regularity of the polymer chain segment can be improved and the thermal stability of the pre-oxidation stage can be improved on the premise of not obviously reducing the molecular weight. However, there are relatively few studies on acrylonitrile binary copolymerization systems of monomers containing phenolic hydroxyl groups and amide difunctional structures, and particularly, there is still a lack of a mature and stable process route in terms of compromise of