Method for preparing polyacrylonitrile spinning solution with high solid content

Abstract

The invention relates to the technical field of polyacrylonitrile fiber preparation, in particular to a method for preparing a polyacrylonitrile spinning solution with high solid content. The method comprises the following steps: mixing a monomer, a chain transfer agent, hydrotropy salt and a photocatalyst in N, N-dimethylacetamide to obtain a mixed solution, and carrying out polymerization reaction under a light source; wherein the monomers comprise an acrylonitrile monomer and a comonomer; the hydrotropy salt comprises at least one of lithium chloride and calcium chloride. The method not only can overcome the problems of chain transfer and precipitation in traditional one-step polymerization with N, N-dimethylacetamide as a solvent, but also can realize accurate control of molecular weight distribution through a light control technology, and provides an efficient and environment-friendly solution for preparation of high-performance polyacrylonitrile.

Description

Technical Field

[0001] The present invention relates to the technical field of polyacrylonitrile fiber preparation, and particularly relates to a method for preparing a polyacrylonitrile spinning dope with a high solid content. Background Art

[0002] As an important polymer material, polyacrylonitrile (PAN) has been widely used in many fields due to its excellent physical and chemical stability and good processability. On the one hand, PAN can be used as the main precursor for preparing carbon fibers, which are processed into carbon fibers and their composites after spinning, pre-oxidation and carbonization, and have important applications in the fields of aerospace, high-end manufacturing, new energy, etc.; on the other hand, PAN can also be used to prepare hollow fiber membranes, synthetic fibers, etc., and has important uses in the fields of textiles, biomedicine, environmental protection, etc. However, the properties of PAN are closely related to its molecular weight distribution and molecular structure. Therefore, it is of great significance to develop an efficient polymerization method to control the composition and structure of PAN.

[0003] In the production of PAN, the commonly used polymerization methods include the one-step method and the two-step method: In the one-step method, the monomers are dissolved in a solvent, and the polymerization solution generated after solution polymerization is directly used for spinning. This method has a simple process, convenient operation and low requirements for equipment, but the resulting polymer has a low molecular weight and a wide distribution. The two-step method uses water as the reaction medium, and after precipitation and drying, it is dissolved in a solvent to prepare a spinning solution for spinning. This method can obtain a polymer with a relatively narrow molecular weight distribution, but the overall process flow is complex and the energy consumption is high. Although the one-step method has obvious process advantages, in the PAN polymerization system using N,N-dimethylacetamide (DMAc) as the solvent, the application of the one-step method is limited by the influence of solvent polarity and the like.

[0004] In industry, the two-step method process uses DMAc as the solvent mainly because the DMAc system allows a high spinning solid content and high production efficiency under the same spin viscosity. However, due to the high chain transfer coefficient of DMAc, there are deficiencies such as low monomer conversion rate and low polymer molecular weight in the one-step method process system. At the same time, due to the polarity differences between the monomer, the polymer and the solvent, when the solid content is high and the comonomer is unevenly distributed in the polymer main chain, the polymerization product is prone to precipitation during the reaction process. These technical difficulties restrict the application of the one-step polymerization in the DMAc system in the synthesis of PAN. Therefore, it is of great significance to develop a polymerization method that can overcome these problems. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present invention provides a method for preparing a polyacrylonitrile spinning dope with a high solid content. This method can not only overcome the chain transfer and precipitation problems in the traditional one-step polymerization using DMAc as a solvent, but also achieve precise control of the molecular weight distribution through a light control technique, providing an efficient and environmentally friendly solution for the preparation of high-performance PAN.

[0006] To this end, in a first aspect of the present invention, a method for preparing a polyacrylonitrile spinning dope with a high solid content is provided, and the method includes the following steps:

[0007] Mix a monomer, a chain transfer agent, a solubilizing salt, and a photocatalyst in N,N-dimethylacetamide to obtain a mixed solution, and carry out a polymerization reaction under a light source;

[0008] Wherein, the monomer includes an acrylonitrile monomer and a comonomer;

[0009] The solubilizing salt includes at least one of lithium chloride and calcium chloride.

[0010] The method provided by the present invention can achieve one-step polymerization of a system using DMAc as a solvent under high solid content conditions, and the obtained polymerization liquor has high stability and can be directly used for spinning after simple monomer removal and degassing treatment.

[0011] According to an embodiment of the present invention, the chain transfer agent includes at least one of methyl 2-((ethoxycarbonothioyl)thio)propionate, 2-cyano-2-propyl dodecyl trithiocarbonate, 2-cyanopropyl-N-methyl-N-(4-pyridyl)aminodithiocarbonate, and 4-cyano-4-(phenylthiocarbonothioyl)pentanoic acid.

[0012] According to an embodiment of the present invention, the photocatalyst includes at least one of zinc tetraphenylporphyrin, tris(2-phenylpyridine)iridium, and ruthenium(III) tris(2,2'-bipyridyl) dichloride.

[0013] According to an embodiment of the present invention, the comonomer includes at least one of methyl acrylate, vinyl acetate, butyl acrylate, itaconic acid, methyl methacrylate, methacrylic acid, n-butyl methacrylate, isobutyl methacrylate, sodium itaconate, sodium acrylsulfonate, sodium methallylsulfonate, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate, and acrylamide.

[0014] According to an embodiment of the present invention, the molar ratio of the monomer to the chain transfer agent is (500 - 10000):1, preferably (1000 - 5000):1.

[0015] According to an embodiment of the present invention, the content of the monomer in the mixed solution is 5 wt% - 40 wt%, preferably 15 wt% - 35 wt%.

[0016] According to an embodiment of the present invention, the content of the solubilizing salt in the mixed solution is 0.1 wt% - 1.5 wt%, preferably 0.2 wt% - 0.5 wt%.

[0017] According to an embodiment of the present invention, the molar ratio of the photocatalyst to the chain transfer agent is 1:(100 - 2000).

[0018] According to an embodiment of the present invention, the content of the comonomer in the monomer is 1 wt% - 15 wt%, preferably 3 wt% - 10 wt%.

[0019] According to an embodiment of the present invention, the intensity of the light source is 0.2 mW·cm -2 -20 mW·cm -2 。

[0020] According to an embodiment of the present invention, the light source includes at least one of ultraviolet light, blue light, and white light.

[0021] According to an embodiment of the present invention, the wavelength of the light source is 420 nm - 460 nm.

[0022] According to an embodiment of the present invention, the time of the polymerization reaction is 0.5 h - 72 h, preferably 12 h - 48 h.

[0023] The second aspect of the present invention provides a polyacrylonitrile spinning dope obtained by the method according to the first aspect, wherein the polydispersity index of the polyacrylonitrile in the polyacrylonitrile spinning dope is < 1.5, Mn is 40,000 Da - 250,000 Da, and Mw is 60,000 Da - 350,000 Da.

[0024] The polyacrylonitrile spinning dope can be prepared by the method provided by the present invention. The molecular weight of the polyacrylonitrile in the dope can be designed and the molecular weight distribution is narrow, and the polydispersity index (PDI) < 1.5.

[0025] The third aspect of the present invention provides the application of the polyacrylonitrile spinning dope obtained by the method according to the first aspect or the polyacrylonitrile spinning dope according to the second aspect in the preparation of acrylic fibers or carbon fiber precursors.

[0026] The method provided by the present invention is simple and easy to implement, suitable for industrial production, can greatly simplify the process flow, improve the quality and production efficiency of polyacrylonitrile fibers. The polyacrylonitrile spinning dope prepared by this method can be directly used for "one-step" spinning to prepare acrylic fibers or carbon fiber precursors after degassing and defoaming treatment.

[0027] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of embodiments in conjunction with the following drawings, in which:

[0029] Figure 1 It shows a schematic diagram of the molecular weight and molecular weight distribution of polyacrylonitrile in the polyacrylonitrile spinning dope provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Embodiments of the present invention will be described in detail below. The following described embodiments are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0031] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0032] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0033] To make the present invention easier to understand, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art to which the present invention pertains.

[0034] In this document, the term "comprising" or "including" is an open expression, that is, it includes the content specified by the present invention, but does not exclude other aspects.

[0035] In this document, the terms "optionally", "optional" or "option" generally mean that the subsequent event or condition may or may not occur, and this description includes the cases where the event or condition occurs and the cases where the event or condition does not occur.

[0036] Photo-controlled polymerization is a specific photochemical reaction driven by an external light source. By controlling the radical activation-deactivation process, the effective regulation of the polymer growth process can be achieved. In addition to being able to precisely control the composition, structure, molecular weight and distribution of the polymer, it also has the advantages of mild reaction conditions, low safety energy consumption, etc. In view of the deficiencies of the existing technology, it is of great significance to develop a method for synthesizing PAN by one-step through photo-controlled polymerization with DMAc as the solvent.

[0037] According to an embodiment of the present invention, a first aspect of the present invention provides a method for preparing a polyacrylonitrile spinning dope with a high solid content, and the method includes the following steps:

[0038] Mix a monomer, a chain transfer agent, a solubilizing salt, and a photocatalyst in N,N-dimethylacetamide to obtain a mixed solution, and carry out a polymerization reaction under a light source;

[0039] Wherein, the monomer includes an acrylonitrile monomer and a comonomer;

[0040] The solubilizing salt includes at least one of lithium chloride and calcium chloride.

[0041] The method provided by the present invention realizes the regulation of the uniformity of the comonomer distribution on the polymer chain segment through photo-controlled polymerization technology, and regulates the interaction between the polymer and the solvent by adding a solubilizing salt, effectively avoiding the occurrence of polymer precipitation under high solid content conditions, and finally obtaining a polymerization solution suitable for one-step spinning.

[0042] Specifically, the "high solid content" means that the solid content is greater than 22%.

[0043] According to a specific embodiment of the present invention, the type of the chain transfer agent is not particularly limited. As some specific examples, the chain transfer agent includes at least one of methyl 2-((ethoxycarbonothioyl)thio)propionate, 2-cyano-2-propyl dodecyl trithiocarbonate, 2-cyanopropyl-N-methyl-N-(4-pyridyl)aminodithiocarbonate, and 4-cyano-4-(phenylthiocarbonothioyl)valeric acid.

[0044] According to a specific embodiment of the present invention, the type of the photocatalyst is not particularly limited. As some specific examples, the photocatalyst includes at least one of zinc tetraphenylporphyrin, tris(2-phenylpyridine)iridium, and ruthenium(III) chloride tris(bipyridine).

[0045] According to specific embodiments of the present invention, the types of the comonomers are not particularly limited. As some specific examples, the comonomers include at least one of methyl acrylate, vinyl acetate, butyl acrylate, itaconic acid, methyl methacrylate, methacrylic acid, n-butyl methacrylate, isobutyl methacrylate, sodium itaconate, sodium acrylsulfonate, sodium methacrylsulfonate, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate, and acrylamide.

[0046] According to specific embodiments of the present invention, the molar ratio of the monomer to the chain transfer agent is (500 - 10000):1. As some specific examples, the molar ratio of the monomer to the chain transfer agent can be 500:1, 1000:1, 2000:1, 5000:1, 10000:1, etc., and preferably (1000 - 5000):1.

[0047] According to specific embodiments of the present invention, the content of the monomer in the mixed solution is 5wt% - 40wt%. As some specific examples, the content of the monomer in the mixed solution can be 5wt%, 10wt%, 15wt%, 20wt%, 35wt%, 40wt%, etc., and preferably 15wt% - 35wt%.

[0048] According to specific embodiments of the present invention, the content of the solubilizing salt in the mixed solution is 0.1wt% - 1.5wt%. As some specific examples, the content of the solubilizing salt in the mixed solution can be 0.1wt%, 0.2wt%, 0.3wt%, 0.5wt%, 1.0wt%, 1.5wt%, etc., and preferably 0.2wt% - 0.5wt%.

[0049] By regulating the monomer content, chain transfer agent content, and solubilizing salt content, the state, molecular weight, and distribution of the polymerization product can be controlled, and the controllability is relatively strong.

[0050] According to specific embodiments of the present invention, the molar ratio of the photocatalyst to the chain transfer agent is 1:(100 - 2000). As some specific examples, the molar ratio of the photocatalyst to the chain transfer agent can be 1:100, 1:200, 1:500, 1:1000, 1:1500, 1:2000, etc.

[0051] According to specific embodiments of the present invention, the content of the comonomer in the monomer is 1wt% - 15wt%. As some specific examples, the content of the comonomer in the monomer can be 1wt%, 3wt%, 5wt%, 10wt%, 15wt%, etc., and preferably 3wt% - 10wt%.

[0052] According to a specific embodiment of the present invention, the intensity of the light source is 0.2 mW·cm -2 -20 mW·cm -2 , as some specific examples, the intensity of the light source can be 0.2 mW·cm -2 , 0.5 mW·cm -2 , 1 mW·cm -2 , 2 mW·cm -2 , 5 mW·cm -2 , 10 mW·cm -2 , 15 mW·cm -2 , 20 mW·cm -2 etc. Specifically, by controlling the light intensity and time, the polymerization reaction process can be precisely regulated.

[0053] According to a specific embodiment of the present invention, the type of the light source is not particularly limited. As some specific examples, the light source includes at least one of ultraviolet light, blue light, and white light.

[0054] According to a specific embodiment of the present invention, the wavelength of the light source is 420 nm - 460 nm. As some specific examples, the wavelength of the light source can be 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, etc.

[0055] According to a specific embodiment of the present invention, the time of the polymerization reaction is 0.5 h - 72 h. As some specific examples, the time of the polymerization reaction can be 0.5 h, 1 h, 2 h, 5 h, 10 h, 12 h, 30 h, 48 h, 72 h, etc., and preferably 12 h - 48 h. Specifically, since the polymerization reaction is photo-initiated, there is no special limitation on the reaction temperature. For example, the temperature of the polymerization reaction can be 0 °C - 80 °C, and preferably 15 °C - 35 °C.

[0056] According to a specific embodiment of the present invention, the polymerization reaction is carried out under an inert atmosphere, for example, it can be carried out under a nitrogen atmosphere.

[0057] According to an embodiment of the present invention, a second aspect of the present invention provides a polyacrylonitrile spinning dope obtained by the method according to the first aspect. The polydispersity index of polyacrylonitrile in the polyacrylonitrile spinning dope is <1.5, Mn is 40,000 Da - 250,000 Da, and Mw is 60,000 Da - 350,000 Da.

[0058] The polyacrylonitrile spinning dope can be prepared by using the method provided by the present invention. The molecular weight of polyacrylonitrile in the dope can be designed and the molecular weight distribution is narrow, and the polydispersity index (PDI) <1.5.

[0059] According to an embodiment of the present invention, a third aspect of the present invention provides the use of the polyacrylonitrile spinning dope obtained by the method according to the first aspect or the polyacrylonitrile spinning dope according to the second aspect in the preparation of acrylic fibers or carbon fiber precursor filaments.

[0060] The solutions of the present invention will be explained below with reference to examples. Those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. For those not specifically noted in the examples regarding technical or conditions, the techniques or conditions described in the literature in the art or according to the product specifications are followed. For reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0061] Example 1

[0062] This example provides a polyacrylonitrile spinning dope and a preparation method thereof. The preparation method includes the following steps:

[0063] Filter the acrylonitrile monomer and vinyl acetate monomer with alumina powder. Weigh 19 g of acrylonitrile monomer, 1 g of vinyl acetate monomer, 18.6 mg of methyl 2-((ethoxycarbonothioyl)thio)propionate, 0.1 mg of zinc tetraphenylporphyrin, 0.2 g of lithium chloride, and 80 g of N,N-dimethylacetamide and add them to a 200 mL photoreactor. Evacuate and purge with nitrogen to remove oxygen in the system. Under blue light irradiation of 4 mW·cm -2 stir for 48 hours to obtain the polyacrylonitrile spinning dope. Use a mixed solution of methanol and water as a precipitant to precipitate the sample. After suction filtration, wash and dry. Dissolve the obtained solid in N,N-dimethylformamide and use a gel permeation chromatography (GPC) analyzer to test parameters such as molecular weight and molecular weight distribution. The results are shown in Table 1.

[0064] Example 2

[0065] This example provides a polyacrylonitrile spinning dope and a preparation method thereof. The preparation method includes the following steps:

[0066] Filter the acrylonitrile monomer and methyl acrylate monomer with alumina powder. Weigh 22.8 g of acrylonitrile monomer, 1.2 g of methyl acrylate monomer, 50 mg of 2-cyano-2-propyl dodecyl trithiocarbonate, 0.1 mg of zinc tetraphenylporphyrin, 0.4 g of lithium chloride, and 76 g of N,N-dimethylacetamide and add them to a 200 mL photoreactor. Evacuate and purge with nitrogen to remove oxygen in the system. Under blue light irradiation of 6 mW·cm -2Under the blue light irradiation, stir for 30 hours to obtain the polyacrylonitrile spinning dope. Use a mixed solution of methanol and water as a precipitant to precipitate the sample. After suction filtration, wash and dry it. Dissolve the obtained solid in N,N-dimethylformamide, and use a gel permeation chromatography analyzer to test parameters such as molecular weight and molecular weight distribution. The results are as Figure 1 shown in Table 1.

[0067] Example 3

[0068] This example provides a polyacrylonitrile spinning dope and a preparation method thereof. The preparation method includes the following steps:

[0069] Filter acrylonitrile monomer with alumina powder. Weigh 27.2 g of acrylonitrile monomer, 0.84 g of itaconic acid, 66 mg of 2-cyanopropyl-N-methyl-N-(4-pyridyl)aminodithiocarbonate, 0.2 mg of zinc tetraphenylporphyrin, 0.5 g of lithium chloride, and 72 g of N,N-dimethylacetamide and add them to a 200 mL photoreactor. Evacuate and purge with nitrogen to remove oxygen in the system. Under the blue light irradiation of 5 mW·cm -2 stir for 12 hours to obtain the polyacrylonitrile spinning dope. Use a mixed solution of methanol and water as a precipitant to precipitate the sample. After suction filtration, wash and dry it. Dissolve the obtained solid in N,N-dimethylformamide, and use a gel permeation chromatography analyzer to test parameters such as molecular weight and molecular weight distribution. The results are shown in Table 1.

[0070] Example 4

[0071] This example provides a polyacrylonitrile spinning dope and a preparation method thereof. The preparation method includes the following steps:

[0072] Filter acrylonitrile monomer and methyl methacrylate monomer with alumina powder. Weigh 26.3 g of acrylonitrile monomer, 1.7 g of methyl methacrylate monomer, 146 mg of 4-cyano-4-(phenylthiocarbonothioylthio)pentanoic acid, 0.2 mg of zinc tetraphenylporphyrin, 0.5 g of lithium chloride, and 72 g of N,N-dimethylacetamide and add them to a 200 mL photoreactor. Evacuate and purge with nitrogen to remove oxygen in the system. Under the blue light irradiation of 4 mW·cm -2 stir for 10 hours to obtain the polyacrylonitrile spinning dope. Use a mixed solution of methanol and water as a precipitant to precipitate the sample. After suction filtration, wash and dry it. Dissolve the obtained solid in N,N-dimethylformamide, and use a gel permeation chromatography analyzer to test parameters such as molecular weight and molecular weight distribution. The results are shown in Table 1.

[0073] Example 5

[0074] This example provides a polyacrylonitrile spinning dope and a preparation method thereof. The preparation method includes the following steps:

[0075] The acrylonitrile monomer and methyl acrylate monomer were filtered with alumina powder. 25.8 g of acrylonitrile monomer, 2 g of methyl acrylate, 0.3 g of itaconic acid, 140 mg of 2-cyano-2-propyl dodecyl trithiocarbonate, 0.4 mg of zinc tetraphenylporphyrin, 0.8 g of lithium chloride and 72 g of N,N-dimethylacetamide were added to a 200 mL photoreactor. The system was evacuated and purged with nitrogen to remove oxygen. Under blue light irradiation of 6 mW·cm -2 , it was stirred for 12 hours to obtain the polyacrylonitrile spinning dope. A mixed solution of methanol and water was used as a precipitant to precipitate the sample. After suction filtration, it was washed and dried. The obtained solid was dissolved in N,N-dimethylformamide, and parameters such as molecular weight and molecular weight distribution were measured using a gel permeation chromatography analyzer. The results are shown in Table 1.

[0076] Example 6

[0077] This example provides a polyacrylonitrile spinning dope and a preparation method thereof. The preparation method includes the following steps:

[0078] The acrylonitrile monomer, methyl acrylate monomer and sodium allylsulfonate monomer were filtered with alumina powder. 27 g of acrylonitrile monomer, 2.7 g of methyl acrylate monomer, 0.3 g of sodium allylsulfonate monomer, 146 mg of 2-cyano-2-propyl dodecyl trithiocarbonate, 0.3 mg of zinc tetraphenylporphyrin, 0.8 g of lithium chloride and 70 g of N,N-dimethylacetamide were added to a 200 mL photoreactor. The system was evacuated and purged with nitrogen to remove oxygen. Under white light irradiation of 5 mW·cm -2 , it was stirred for 16 hours to obtain the polyacrylonitrile spinning dope. A mixed solution of methanol and water was used as a precipitant to precipitate the sample. After suction filtration, it was washed and dried. The obtained solid was dissolved in N,N-dimethylformamide, and parameters such as molecular weight and molecular weight distribution were measured using a gel permeation chromatography analyzer. The results are shown in Table 1.

[0079] Example 7

[0080] This example provides a polyacrylonitrile spinning dope and a preparation method thereof. The preparation method includes the following steps:

[0081] The acrylonitrile monomer and methyl acrylate monomer were filtered with alumina powder. 30.8 g of acrylonitrile monomer, 4 g of methyl acrylate monomer, 0.2 g of itaconic acid, 200 mg of 2-cyano-2-propyl dodecyl trithiocarbonate, 0.5 mg of zinc tetraphenylporphyrin, 2.5 g of calcium chloride and 65 g of N,N-dimethylacetamide were added to a 200 mL photoreactor. The system was evacuated and purged with nitrogen to remove oxygen. Under light irradiation of 4 mW·cm -2Under white light irradiation, stir for 12 hours to obtain the polyacrylonitrile spinning dope. Use a mixed solution of methanol and water as a precipitant to precipitate the sample. After suction filtration, wash and dry it. Dissolve the obtained solid in N,N-dimethylformamide and use a gel permeation chromatography analyzer to test parameters such as molecular weight and molecular weight distribution. The results are shown in Table 1.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is only that: lithium chloride is not added.

[0084] It was found that: the sample without adding lithium chloride directly precipitated in the form of a white precipitate, and the feed liquid had no viscosity and could not be used for spinning.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 2 is only that: the dosage of lithium chloride is 0.08 g.

[0087] It was found that: part of the sample with a small amount of lithium chloride added precipitated in the form of a precipitate, and the feed liquid had no viscosity and could not be used for spinning.

[0088] Table 1

[0089] Light source <![CDATA[Illumination intensity / mW·cm -2 > Time / h <![CDATA[M n,GPC / Da]]> Mw / Da PDI Example 1 Blue light 4 48 232,500 330,100 1.42 Example 2 Blue light 6 30 130,900 184,600 1.41 Example 3 Blue light 5 12 106,300 142,400 1.34 Example 4 Blue light 4 10 64,200 82,200 1.28 Example 5 Blue light 6 12 65,600 92,500 1.41 Example 6 White light 5 16 74,600 93,300 1.25 Example 7 White light 4 12 53,300 70,300 1.32

[0090] As can be seen from Table 1, the molecular weight of the product obtained in the examples provided by the present invention is controllable and the molecular weight distribution is narrow; in addition, compared with the comparative examples, the examples provided by the present invention overcome the chain transfer and precipitation problems in the one-step polymerization using DMAc as a solvent.

[0091] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0092] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a high-solid content polyacrylonitrile spinning solution, characterized in that: The method comprises the following steps: The monomer, chain transfer agent, solubilizing salt and photocatalyst are mixed in N,N-dimethylacetamide to obtain a mixed solution, and a polymerization reaction is carried out under a light source; Wherein, the monomers include acrylonitrile monomers and comonomers; The dissolution-advantage salt includes at least one of lithium chloride and calcium chloride.

2. The method according to claim 1, characterized in that The chain transfer agent includes at least one of 2-((ethoxythiocarbonyl)thio) propionate methyl ester, 2-cyano-2-propyl dodecyl trithiocarbonate, 2-cyanopropyl-N-methyl-N-(4-pyridine)aminodithiocarbonate, and 4-cyano-4-(phenylthioformylthio) valeric acid; Optionally, the photocatalyst includes at least one of tetraphenylporphyrin zinc, tris(2-phenylpyridine)iridium, and terpyridine ruthenium chloride; Optionally, the comonomer includes at least one of methyl acrylate, vinyl acetate, butyl acrylate, itaconic acid, methyl methacrylate, methacrylic acid, n-butyl methacrylate, isobutyl methacrylate, sodium itaconate, sodium propylene sulfonate, sodium methpropylene sulfonate, sodium 2-acrylamido-2-methylpropane sulfonate, 2-acrylamido-2-methylpropane sulfonic acid, sodium styrene sulfonate, and acrylamide.

3. The method according to claim 1, characterized in that The molar ratio of the monomer to the chain transfer agent is (500-10000):1, preferably (1000-5000):

1.

4. The method according to claim 1, characterized in that: The content of the monomer in the mixed solution is 5wt%-40wt%, preferably 15wt%-35wt%.

5. The method according to claim 1, characterized in that The content of the dissolution-aiding salt in the mixed solution is 0.1wt%-1.5wt%, preferably 0.2wt%-0.5wt%.

6. The method according to claim 1, characterized in that The molar ratio of the photocatalyst to the chain transfer agent is 1:(100-2000).

7. The method according to claim 1, characterized in that The content of the comonomer in the monomer is 1 wt%-15 wt%, preferably 3 wt%-10 wt%.

8. The method according to claim 1, characterized in that The intensity of the light source is 0.2 mW·cm -2 -20mW·cm -2 ; Optionally, the light source includes at least one of ultraviolet light, blue light, and white light; Optionally, the wavelength of the light source is 420nm-460nm; Optionally, the polymerization reaction time is 0.5h-72h, preferably 12h-48h.

9. A polyacrylonitrile spinning solution obtained by the method according to any one of claims 1 to 8, characterized in that: The polydispersity index of the polyacrylonitrile in the polyacrylonitrile spinning solution is less than 1.5, the Mn is 40000Da-250000Da, and the Mw is 60000Da-350000Da.

10. Use of the polyacrylonitrile spinning solution obtained by the method according to any one of claims 1 to 8 or the polyacrylonitrile spinning solution according to claim 9 in the preparation of acrylic fibers or carbon fiber precursors.

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