Preparation method of polyacrylonitrile-based carbon fiber precursor

Abstract

The invention belongs to the technical field of polyacrylonitrile-based fibers, and relates to a polyacrylonitrile-based carbon fiber precursor preparation method, which comprises: carrying out a polymerization reaction on acrylonitrile, a comonomer, fumaronitrile and an initiator under a protective atmosphere to obtain the polyacrylonitrile-based carbon fiber precursor. Compared with the prior art, the method has the advantages that the fumarone dinitrile copolymerization modification process is simple, the initial heat release temperature of the acrylonitrile copolymer can be reduced by introducing a proper amount of fumarone dinitrile, and the carbon yield is remarkably increased. Compared with blending or dipping modification, the prepared precursor has few defects and is beneficial to preparation of high-performance carbon fibers.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyacrylonitrile-based fibers and relates to a method for preparing a polyacrylonitrile-based carbon fiber precursor. Background Art

[0002] In the preparation of polyacrylonitrile (PAN)-based carbon fibers, due to the concentrated heat release during the oxidation process of acrylonitrile homopolymer, the fibers are prone to fusion, breakage, and even fire, making it difficult to directly use them as precursors. Industrially, a certain amount of comonomer is usually added to improve the thermal behavior of homopolymer PAN. Most existing studies use acrylic acids, acrylic esters, acrylamides, vinyls containing sulfonic acid groups, etc. as modifying monomers, which have a certain effect on promoting cyano cyclization and alleviating the heat release during the oxidation process. During the spinning process, the role of ester monomers is to reduce the interaction force between cyano groups of PAN macromolecules, thereby reducing the aggregation density between macromolecules and the secondary transition point of the polymer, which is beneficial for drawing. Carboxylic acid monomers are mainly used to improve hydrophilicity.

[0003] During the oxidation and carbonization process, especially during the low-temperature carbonization process, as the macromolecular chains break and non-carbon elements are removed in the form of small molecules, the fiber weight loss can reach about 50%. Some studies have found that by improving the heat resistance of the fibers, the carbon yield can be increased to a certain extent, thereby reducing production costs. In recent years, with the increasingly fierce price competition in carbon fibers, carbon fiber production enterprises are facing huge cost reduction pressures, and research on improving the carbon yield has become a hot topic in the industry.

[0004] Chinese Patent CN201310100469.8 uses a pre-treatment process before low-carbonization to increase the carbon yield. By increasing the degree of low-temperature carbonization reaction and improving the heat resistance of the fibers, the purpose of increasing the carbon yield is achieved, but this method is essentially an extension of low-temperature carbonization.

[0005] Chinese Patents CN202011540059.1 and CN202010762400.1 propose methods for increasing the carbon yield of PAN-based carbon fibers by impregnating and modifying the precursor filaments. However, the inventors have found that in some methods, the modifier is easily lost, and in some methods, it is difficult to distribute evenly. Especially for the post-modification process, an additional impregnation process is required, which will have a certain impact on the distribution of the sizing agent on the surface of the precursor filaments.

[0006] Chinese Patent CN202211386442.5 proposes a scheme for blending and modifying acrylonitrile copolymer solutions with guanidine salts. The introduction of guanidine salts can promote the cyclization rate, increase the cross-linked structure, and improve the heat resistance of the fibers. Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing a polyacrylonitrile-based carbon fiber precursor, which can effectively improve the carbonization yield and is suitable for the preparation of high-performance carbon fibers. The introduction of an appropriate amount of fumarodinitrile structure can not only reduce the reaction activation energy but also increase the carbon yield. The modification method is simple and efficient, without major modifications to the production line, and is easy to implement.

[0008] The object of the present invention can be achieved by the following technical solutions:

[0009] A method for preparing a polyacrylonitrile-based carbon fiber precursor, comprising:

[0010]

[0011] Carrying out a polymerization reaction on acrylonitrile, a comonomer, fumarodinitrile, and an initiator under a protective atmosphere to obtain a polyacrylonitrile-based carbon fiber precursor.

[0012] Further, the reaction solvent used is selected from one or more of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, aqueous sodium thiocyanate solution, and aqueous zinc chloride solution.

[0013] Further, the comonomer is selected from one of vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, acrylamide, itaconic acid, monomethyl itaconate, monoethyl itaconate, monon-propyl itaconate, monoisopropyl itaconate, monon-butyl itaconate, monoisobutyl itaconate, monotert-butyl itaconate, ammonium itaconate, maleic acid, methyl maleic acid, maleic anhydride, fumaric acid, methyl fumaric acid, N-vinylimidazole / salt.

[0014] Further, the mass content of the comonomer in the acrylonitrile and comonomer mixture does not exceed 10%.

[0015] Further, the mass content of the comonomer in the acrylonitrile and comonomer mixture is 0.1-8%.

[0016] Further, the initiator is selected from one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, or dimethyl azobisisobutyrate, and the addition amount is 0.1-0.15 g / 20 g of acrylonitrile.

[0017] Further, the addition amount of the fumarodinitrile is 0.1-5% of the mass of acrylonitrile.

[0018] Further, the addition amount of the fumarodinitrile is 0.1-1% of the mass of acrylonitrile.

[0019] Further, the reaction conditions of the polymerization reaction are: the polymerization temperature is 40-80°C; the polymerization time is 8-24 h.

[0020] Further, the reaction conditions for the polymerization reaction are as follows: the polymerization temperature is 50-70 °C; the polymerization time is 10-18 h.

[0021] In some preferred embodiments, the monomer conversion rate is 75-99%, preferably 80-95%.

[0022] Compared with the prior art, the present invention has the following characteristics:

[0023] The fumarodinitrile copolymerization modification process in the present invention is simple. The introduction of an appropriate amount of fumarodinitrile can reduce the initial exothermic temperature of the acrylonitrile copolymer and significantly increase the carbon yield. Compared with blending or impregnation modification, the as-prepared precursor filaments of the present invention have fewer defects, which is beneficial to the preparation of high-performance carbon fibers. Description of the Drawings

[0024] Figure 1 Shows the influence of the fumarodinitrile content on the char residue rate of the acrylonitrile copolymer in the examples;

[0025] Figure 2 Shows the DSC curve of the copolymer with 0.5% fumarodinitrile content in Example 1;

[0026] Figure 3 Shows the DSC curve of the copolymer with 5% fumarodinitrile content in Example 4. Detailed Embodiments

[0027] The present invention will be described in detail below with reference to the drawings and specific embodiments. The following embodiments are implemented on the premise of the above technical solutions of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0028] Example 1:

[0029] A method for preparing a polyacrylonitrile-based carbon fiber precursor, comprising:

[0030] Put 79 g of dimethyl sulfoxide (DMSO) into a reaction kettle and start stirring. Put 20 g of acrylonitrile, dissolve 0.1 g of fumarodinitrile in 1 g of DMSO, then put it into the polymerization reaction kettle, stir and heat up to 65 °C, add 0.12 g of azobisisobutyronitrile, and react at a constant temperature for 24 h to obtain a copolymer solution with a solid content of 19% and an intrinsic viscosity of 1.79 dl / g.

[0031] Example 2:

[0032] A method for preparing a polyacrylonitrile-based carbon fiber precursor, which is only different from Example 1 in that:

[0033] The copolymer solution with a solid content of 18.3% and an intrinsic viscosity of 1.81 dl / g was obtained by using fumaronitrile accounting for 1% of the mass of acrylonitrile, and the rest was the same as in Example 1.

[0034] Example 3:

[0035] A preparation method of a polyacrylonitrile-based carbon fiber precursor is only different from that in Example 1 in that:

[0036] The copolymer solution with a solid content of 18.6% and an intrinsic viscosity of 1.78 dl / g was obtained by using fumaronitrile accounting for 2% of the mass of acrylonitrile, and the rest was the same as in Example 1.

[0037] Example 4:

[0038] A preparation method of a polyacrylonitrile-based carbon fiber precursor is only different from that in Example 1 in that:

[0039] The copolymer solution with a solid content of 17.8% and an intrinsic viscosity of 1.77 dl / g was obtained by using fumaronitrile accounting for 5% of the mass of acrylonitrile, and the rest was the same as in Example 1.

[0040] Example 5:

[0041] A preparation method of a polyacrylonitrile-based carbon fiber precursor is only different from that in Example 1 in that:

[0042] The copolymer solution with a solid content of 16.2% and an intrinsic viscosity of 1.75 dl / g was obtained by using fumaronitrile accounting for 10% of the mass of acrylonitrile, and the rest was the same as in Example 1.

[0043] Comparative example:

[0044] A preparation method of a polyacrylonitrile-based carbon fiber precursor is only different from that in Example 1 in that:

[0045] Without adding fumaronitrile, and the rest was the same as in Example 1, a homopolymer solution with a solid content of 19.2% and an intrinsic viscosity of 1.82 dl / g was obtained.

[0046] The samples of the examples and the comparative example were tested by Netzsch TG 209F3 and DSC 200F3 (nitrogen atmosphere, heating rate 10 °C / min), and the results are shown in Table 1 and Figure 2-3 as follows. The addition of 1% fumaronitrile can significantly increase the TGA char residue rate and shift the DSC exothermic peak forward. However, when the fumaronitrile content reaches 5%, a double peak appears in the DSC and shifts significantly backward. When the fumaronitrile content reaches 10%, the DSC exothermic peak further shifts backward and the char residue rate decreases.

[0047] Table 1

[0048]

[0049] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention as disclosed should be within the protection scope of the present invention.

Claims

1. A method for preparing a polyacrylonitrile-based carbon fiber precursor, characterized in that, comprising: Performing a polymerization reaction on acrylonitrile, a comonomer, fumaronitrile, and an initiator under a protective atmosphere to obtain a polyacrylonitrile-based carbon fiber precursor.

2. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 1, characterized in that, The reaction solvent used is selected from one or more of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, aqueous sodium thiocyanate solution, and aqueous zinc chloride solution.

3. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 1, characterized in that, The comonomer is selected from one of vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, acrylamide, itaconic acid, monomethyl itaconate, monoethyl itaconate, monon-propyl itaconate, monoisopropyl itaconate, monon-butyl itaconate, monoisobutyl itaconate, monoter-butyl itaconate, ammonium itaconate, maleic acid, methyl maleic acid, maleic anhydride, fumaric acid, methyl fumaric acid, N-vinylimidazole / salt.

4. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 3, characterized in that, The mass content of the comonomer in the acrylonitrile and comonomer mixture does not exceed 10%.

5. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 4, characterized in that, The mass content of the comonomer in the acrylonitrile and comonomer mixture is 0.1 - 8%.

6. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 1, characterized in that, The initiator is selected from one or more of azobisisobutyronitrile, azobisisopentanenitrile, azobisisoheptanenitrile, or dimethyl azobisisobutyrate, and the addition amount is 0.1 - 0.15 g / 20 g acrylonitrile.

7. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 1, characterized in that, The addition amount of the fumaronitrile is 0.1 - 5% of the mass of acrylonitrile.

8. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 7, characterized in that, The addition amount of the fumaronitrile is 0.1 - 1% of the mass of acrylonitrile.

9. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 1, characterized in that, The reaction conditions of the polymerization reaction are: the polymerization temperature is 40 - 80 °C; the polymerization time is 8 - 24 h.

10. The method for preparing a polyacrylonitrile-based carbon fiber precursor according to claim 9, characterized in that, The reaction conditions of the polymerization reaction are: the polymerization temperature is 50 - 70 °C; the polymerization time is 10 - 18 h.

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