A polyacrylonitrile spinning dope, its preparation method and application

Abstract

The present invention provides a polyacrylonitrile spinning dope, a preparation method thereof and an application thereof, belonging to the technical fields of textile chemicals and preparation of high-performance polyacrylonitrile fibers. The preparation method comprises the following steps: mixing acrylonitrile monomers, comonomers, a chain transfer agent and a photocatalyst in an aqueous sodium thiocyanate solution to form a mixed solution; and then carrying out a polymerization reaction on the mixed solution under a light source to obtain a polyacrylonitrile spinning dope; wherein the chain transfer agent is one or more of bis(carboxymethyl)trithiocarbonate, 2-(n-butyltrithiocarbonate)propionic acid, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid and 2-mercapto-S-thiobenzoyl acetic acid. The preparation method can synthesize a polyacrylonitrile spinning dope with high stability, high solid content and suitable viscosity, meeting the requirements for producing high-performance acrylic fibers.

Description

Technical Field

[0001] The present invention belongs to the technical fields of textile chemicals and the preparation of high-performance polyacrylonitrile fibers, and particularly relates to a polyacrylonitrile spinning dope, a preparation method thereof, and an application thereof. Background Art

[0002] Synthetic fibers have a wide range of uses in today's world. As one of the three major synthetic fiber varieties, acrylic fiber, due to its good physical and chemical stability, weather resistance, sunlight resistance, etc., on the one hand, its textiles can be directly used in fields such as clothing and decoration; on the other hand, as a raw material for producing carbon fiber, high-grade carbon fiber can be made through further processing.

[0003] The production processes of acrylic fiber mainly include two categories: one-step method and two-step method. The one-step method usually involves using an azo initiator to initiate acrylonitrile and comonomers, directly forming a polyacrylonitrile spinning dope through homogeneous solution polymerization, and then directly connecting to spinning after removing monomers and degassing to obtain polyacrylonitrile fibers. The two-step method usually adopts aqueous phase precipitation polymerization. The obtained polyacrylonitrile powder is washed, dried, and then dissolved in a solvent to prepare a polyacrylonitrile spinning dope. Then, the polyacrylonitrile spinning dope is degassed and spun to obtain polyacrylonitrile fibers.

[0004] However, due to the residue of azo initiators or the insufficient dissolution of polyacrylonitrile powder, and the sensitivity of polyacrylonitrile spinning dope prepared with organic solvents such as DMSO and DMAc to moisture in the air, bubbles or microgels will form in the polyacrylonitrile spinning dope, resulting in a decrease in the stability of the polyacrylonitrile spinning dope, thus bringing trouble to spinning, leading to unstable spinning state, poor production stability, and easy occurrence of phenomena such as hairiness and filament breakage.

[0005] In addition, traditional free radical polymerization technology cannot effectively control the polymer molecular weight and distribution. The obtained polyacrylonitrile has a relatively small molecular weight and a wide molecular weight distribution, and the solubility of polyacrylonitrile in the spinning dope is poor, resulting in a low solid content and low viscosity of the spinning dope, which is difficult to meet the requirements for producing high-performance acrylic fibers. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems in the related technologies to some extent. For this purpose, an embodiment of the present invention provides a polyacrylonitrile spinning dope, a preparation method thereof, and an application thereof. This preparation method can synthesize a polyacrylonitrile spinning dope with high stability, high solid content, and suitable viscosity, meeting the requirements for producing high-performance acrylic fibers.

[0007] In a first aspect, an embodiment of the present invention provides a method for preparing a polyacrylonitrile spinning dope, comprising the following steps: mixing acrylonitrile monomer, comonomer, chain transfer agent, and photocatalyst in an aqueous sodium thiocyanate solution to form a mixed solution; then carrying out a polymerization reaction on the mixed solution under a light source to obtain a polyacrylonitrile spinning dope;

[0008] Among them, the chain transfer agent is one or more of bis(carboxymethyl)trithiocarbonate, 2-(n-butyltrithiocarbonate)propionic acid, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, and 2-mercapto-S-thiobenzoylacetic acid.

[0009] The advantages and technical effects brought by the method for preparing a polyacrylonitrile spinning dope according to the embodiment of the present invention are as follows:

[0010] (1) In the method for preparing a polyacrylonitrile spinning dope according to the embodiment of the present invention, an inorganic aqueous sodium thiocyanate solution is used as a solvent, which can reduce the sensitivity of the polyacrylonitrile spinning dope to air, moisture, etc., and ensure that the polyacrylonitrile spinning dope maintains good stability for a long time.

[0011] (2) In the method for preparing a polyacrylonitrile spinning dope according to the embodiment of the present invention, the polymerization reaction process is initiated and controlled by light, the reaction conditions are mild, and the system products are pure.

[0012] (3) In the photo-controlled polymerization reaction system according to the embodiment of the present invention, a polyacrylonitrile spinning dope with a preset molecular weight and a narrow molecular weight distribution (PDI≤1.5) can be synthesized. The solubility of polyacrylonitrile in the aqueous sodium thiocyanate solution is relatively high, and the obtained spinning dope has high stability, high solid content, and suitable viscosity, and can be directly used for spinning after simple monomer removal and degassing.

[0013] (4) In the photo-controlled polymerization reaction system according to the embodiment of the present invention, by using the chain transfer agent of the defined type, the molecular weight and molecular weight distribution (PDI≤1.5) of the free radical polymer product can be effectively controlled, and the controllability is relatively strong.

[0014] In some embodiments, the molar ratio of the acrylonitrile monomer to the chain transfer agent is (100~20000):1.

[0015] In some embodiments, based on the total mass of the mixed solution being 100 wt%, the mass fraction of the acrylonitrile monomer is 5~40 wt%.

[0016] In some embodiments, based on the total mass of the acrylonitrile monomer and the comonomer being 100 wt%, the mass fraction of the comonomer is 0.5~20 wt%.

[0017] In some embodiments, the molar ratio of the photocatalyst to the chain transfer agent is 1:(5 - 500).

[0018] In some embodiments, based on the total mass of the mixed solution being 100 wt%, the mass fraction of sodium thiocyanate is 35 - 50 wt%.

[0019] In some embodiments, the light source is one or more of ultraviolet light, blue light, and white light; and / or, the light intensity of the light source is 0.2 - 20 mW·cm -2 。

[0020] In some embodiments, the photocatalyst is one or more of lithium phenyl(2,4,6 - trimethylbenzoyl)phosphate, eosin Y, and bengal red; and / or, the comonomer is one or more of vinyl acetate, butyl acrylate, itaconic acid, acrylic acid, methyl methacrylate, methyl acrylate, methacrylic acid, n - butyl methacrylate, isobutyl methacrylate, sodium itaconate, sodium acrylsulfonate, sodium methacrylsulfonate, acrylamido - 2 - methylpropanesulfonic acid sodium salt solution, 2 - acrylamido - 2 - methylpropanesulfonic acid, sodium styrenesulfonate, and acrylamide.

[0021] In a second aspect, an acrylonitrile spinning dope according to an embodiment of the present invention is obtained by the preparation method of the first aspect.

[0022] The advantages and technical effects brought by the acrylonitrile spinning dope of the embodiment of the present invention are as follows:

[0023] Due to the adoption of the preparation method of the acrylonitrile spinning dope in the first aspect, the acrylonitrile spinning dope of the embodiment of the present invention has high stability, high solid content, and suitable viscosity, and can be directly used for spinning after simple degassing of monomers and defoaming.

[0024] In a third aspect, an application of the acrylonitrile spinning dope according to the second aspect in the preparation of acrylonitrile fibers or carbon fibers.

[0025] The advantages and technical effects brought by the application of the embodiment of the present invention are as follows:

[0026] In the embodiment of the present invention, after the polymerization reaction is completed, the acrylonitrile spinning dope can be directly used for "one - step" spinning to prepare acrylic fibers or carbon fiber precursors after degassing of monomers and defoaming. Description of the Drawings

[0027] Figure 1 is the GPC spectrum of polyacrylonitrile obtained by the photocontrolled synthesis method of the acrylonitrile spinning dope in Example 3.

[0028] Figure 2It is the GPC spectrum of polyacrylonitrile obtained by the photo-controlled synthesis method of the polyacrylonitrile spinning dope of Comparative Example 1. Specific Embodiments

[0029] The embodiments of the present invention will be described in detail below. The examples are shown in the accompanying drawings. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0030] In comparison, using an inorganic sodium thiocyanate aqueous solution as a solvent can reduce the sensitivity of the polyacrylonitrile spinning dope to air, moisture, etc., and ensure that the polyacrylonitrile spinning dope maintains good stability for a long time. Based on the advantages of the sodium thiocyanate aqueous solution as a solvent in terms of non-toxicity and storage stability, etc., it can become a solvent for acrylic fiber production. However, the low solubility of polyacrylonitrile in the sodium thiocyanate aqueous solution and the easy generation of microgels during the two-step dissolution process are important factors restricting the preparation of high-performance polyacrylonitrile fibers.

[0031] Compared with traditional free radical polymerization techniques, controlled / living free radical polymerization techniques can effectively control the polymer molecular weight and distribution, improve the solubility of the polymer in solution, and are beneficial to obtaining a polyacrylonitrile spinning dope with a high solid content and appropriate viscosity, showing great application potential in the fields of high-quality acrylic fiber and carbon fiber preparation. At the same time, in recent years, the developed photo-controlled free radical polymerization technique, in addition to retaining the advantages of traditional controlled free radical polymerization such as designable molecular weight and narrow molecular weight distribution, its unique photo-switching effect can achieve two-dimensional spatio-temporal regulation of the polymerization system, and at the same time, the reaction conditions are milder, the energy consumption is lower, and the operation is more convenient. The above characteristics are of important value for stabilizing the polyacrylonitrile spinning dope after the polymerization reaction.

[0032] In a first aspect, an embodiment of the present invention provides a method for preparing a polyacrylonitrile spinning dope, including the following steps: mixing an acrylonitrile monomer, a comonomer, a chain transfer agent, and a photocatalyst in an aqueous sodium thiocyanate solution to form a mixed solution; and then carrying out a polymerization reaction on the mixed solution under a light source to obtain a polyacrylonitrile spinning dope;

[0033] Wherein, the chain transfer agent is one or more of bis(carboxymethyl)trithiocarbonate, 2-(n-butyltrithiocarbonate)propionic acid, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, and 2-mercapto-S-thiobenzoyl acetic acid.

[0034] The preparation method of the polyacrylonitrile spinning dope according to the embodiments of the present invention uses an inorganic sodium thiocyanate aqueous solution as a solvent, which can reduce the sensitivity of the polyacrylonitrile spinning dope to air, moisture, etc., and ensure that the polyacrylonitrile spinning dope maintains good stability for a long time. In addition, the preparation method of the polyacrylonitrile spinning dope according to the embodiments of the present invention utilizes photoinitiation to control the polymerization reaction process, the reaction conditions are mild, and the system products are pure. The photo-controlled polymerization reaction system according to the embodiments of the present invention can synthesize a polyacrylonitrile spinning dope with a preset molecular weight and a narrow molecular weight distribution (PDI≤1.5). The solubility of polyacrylonitrile in the sodium thiocyanate aqueous solution is relatively high, and the obtained spinning dope has high stability, high solid content and appropriate viscosity, and can be directly used for spinning after simple degassing and defoaming. In the photo-controlled polymerization reaction system according to the embodiments of the present invention, by using a chain transfer agent of a specified type, the molecular weight and molecular weight distribution (PDI≤1.5) of the free radical polymer product can be effectively controlled, and the controllability is relatively strong.

[0035] In some embodiments, the molar ratio of the acrylonitrile monomer to the chain transfer agent is (100~20000):1, such as 100:1, 1000:1, 2000:1, 5000:1, 10000:1, 15000:1, 20000:1, etc. When this molar ratio is too low, the molecular weight of the obtained polymer is too low, which is not conducive to spinning; when this molar ratio is too high, the molecular weight of the obtained polymer is too high, which is not conducive to improving the spinning efficiency.

[0036] In some embodiments, based on the total mass of the mixed solution being 100 wt%, the mass fraction of the acrylonitrile monomer is 5~40 wt%, such as 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, etc.; preferably, the mass fraction of the acrylonitrile monomer is 10~25 wt%. When the mass fraction of the acrylonitrile monomer in the mixed solution is too low, it is not conducive to increasing the solid content of the polyacrylonitrile spinning dope. When the mass fraction of the acrylonitrile monomer in the mixed solution is too high, the solid content of the polyacrylonitrile spinning dope is too high and the viscosity is too large, which is also not conducive to spinning.

[0037] In some embodiments, based on the total mass of the acrylonitrile monomer and the comonomer being 100 wt%, the mass fraction of the comonomer is 0.5~20 wt%, such as 0.5wt%, 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, etc.; preferably, the mass fraction of the comonomer is 2~5 wt%. When the mass fraction of the comonomer is too high or too low, it will have an adverse impact on the physical properties and processing properties of the polyacrylonitrile fiber.

[0038] In some embodiments, the comonomer is one or more of vinyl acetate, butyl acrylate, itaconic acid, acrylic acid, methyl methacrylate, methyl acrylate, methacrylic acid, n-butyl methacrylate, isobutyl methacrylate, sodium itaconate, sodium acrylsulfonate, sodium methallylsulfonate, sodium 2-acrylamido-2-methylpropanesulfonate solution, 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate, and acrylamide. Comonomers of the above types are beneficial to improving the physical properties, dyeing properties, processing properties, and functionality of polyacrylonitrile fibers, thereby meeting the requirements of different application fields.

[0039] In some embodiments, the molar ratio of the photocatalyst to the chain transfer agent is 1:(5 - 500), such as 1:5, 1:10, 1:100, 1:200, 1:300, 1:400, 1:500, etc. When this molar ratio is too low, the rate of the polymerization reaction is too slow, which is not conducive to the control of the polymerization reaction process and thus not conducive to improving the reaction efficiency. When this molar ratio is too high, the rate of the polymerization reaction is too fast, which is also not conducive to the control of the polymerization reaction process and further not conducive to improving the quality of the polymerization reaction product.

[0040] In some embodiments, the photocatalyst is one or more of lithium phenyl(2,4,6-trimethylbenzoyl)phosphate, eosin Y, and bengal red. The above several photocatalysts can effectively increase the rate of the photopolymerization reaction.

[0041] In some embodiments, based on the total mass of the mixed solution being 100 wt%, the mass fraction of sodium thiocyanate is 35 - 50 wt%, such as 35wt%, 36wt%, 38wt%, 40wt%, 42wt%, 45wt%, 48wt%, 50wt%, etc.; preferably, the mass fraction of sodium thiocyanate is 40 - 45 wt%. When the mass fraction of sodium thiocyanate in the mixed solution is too low, it is not conducive to the dissolution of the polymer.

[0042] In some embodiments, the light source is one or several of ultraviolet, blue light, and white light; preferably, the wavelength of the light source is 420 - 460 nm; and / or, the light intensity of the light source is 0.2 - 20 mW·cm -2 . The reaction system of the embodiments of the present invention does not require heating, and the reaction can be initiated using light with a lower energy density. The initiation conditions are mild, greatly saving energy consumption.

[0043] In the embodiments of the present invention, since the polymerization reaction is photo-initiated, there are no special restrictions on the reaction temperature. Preferably, the temperature of the polymerization reaction is 0 - 80°C, such as 0°C, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, etc., and more preferably, the temperature of the polymerization reaction is 15 - 35°C.

[0044] In some embodiments, the time of the polymerization reaction is 0.5 - 48 h, such as 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 48 h, etc. Preferably, the time of the polymerization reaction is 3 - 24 h.

[0045] In the reaction system of the embodiments of the present invention, by regulating one or several factors such as the illumination time, monomer concentration, and dosage of the chain transfer agent, the molecular weight and molecular weight distribution of the free radical polymer product can be controlled, and the controllability is relatively strong.

[0046] In a second aspect, the embodiments of the present invention provide a polyacrylonitrile spinning dope, which is obtained by the preparation method of the polyacrylonitrile spinning dope in the first aspect.

[0047] Due to the adoption of the preparation method of the polyacrylonitrile spinning dope in the first aspect, the polyacrylonitrile spinning dope of the embodiments of the present invention has high stability, high solid content, and suitable viscosity, and can be directly used for spinning after simple monomer removal and degassing.

[0048] In a third aspect, the application of the polyacrylonitrile spinning dope according to the second aspect in the preparation of polyacrylonitrile fibers or carbon fibers.

[0049] In the embodiments of the present invention, after the polymerization reaction is completed, the polyacrylonitrile spinning dope can be directly used for "one-step" spinning to prepare acrylic fibers or carbon fiber precursors after monomer removal and degassing.

[0050] The present invention will be described in detail below with reference to the embodiments and the drawings.

[0051] Example 1

[0052] This example provides a preparation method of a polyacrylonitrile spinning dope, which is a photo-controlled free radical polymerization method, and specifically includes the following steps:

[0053] The acrylonitrile monomer and methyl methacrylate were filtered with alumina powder. 1.2 g of acrylonitrile monomer, 0.1 g of methyl methacrylate, 5 mg of 2-(n-butyltrithiocarbonate)propionic acid (i.e., chain transfer agent), 0.2 mg of lithium phenyl(2,4,6-trimethylbenzoyl)phosphate (i.e., photocatalyst) and 3.0 mL of 50 wt% sodium thiocyanate aqueous solution were weighed. The above-mentioned several substances were mixed to obtain a mixed solution. Among them, the molar ratio of acrylonitrile monomer to chain transfer agent was 1080:1, and the molar ratio of photocatalyst to chain transfer agent was 1:31; based on the total mass of the mixed solution being 100 wt%, the mass fraction of acrylonitrile monomer was 23 wt%, and the mass fraction of sodium thiocyanate was 37.5 wt%; based on the total mass of acrylonitrile monomer and comonomer being 100 wt%, the mass fraction of comonomer was 7 wt%.

[0054] The mixed solution was added to a 10 mL quartz reaction tube, sealed with a rubber stopper, and purged with nitrogen for 10 min to remove excessive oxygen in the system. Under the irradiation of blue light with an intensity of 4 mW·cm -2 , the reaction was carried out at 25 °C for 16 hours to obtain a polyacrylonitrile spinning dope.

[0055] The polyacrylonitrile spinning dope was precipitated with a mixed solution of methanol and water. After suction filtration, it was washed and dried, and the final solid product was collected. The obtained solid product 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.

[0056] Example 2

[0057] This example provides a method for preparing a polyacrylonitrile spinning dope. This method is a photocontrolled radical polymerization method, and specifically includes the following steps:

[0058] The acrylonitrile monomer and methyl acrylate were filtered with alumina powder. 1.3 g of acrylonitrile monomer, 0.1 g of methyl acrylate, 0.05 g of itaconic acid, 6 mg of 2-mercapto-S-thiobenzoylacetic acid (i.e., chain transfer agent), 0.2 mg of lithium phenyl(2,4,6-trimethylbenzoyl)phosphate (i.e., photocatalyst) and 4.5 mL of 50 wt% sodium thiocyanate aqueous solution were weighed. The above-mentioned several substances were mixed to obtain a mixed solution. The mixed solution was added to a 10 mL quartz reaction tube, sealed with a rubber stopper, and purged with nitrogen for 10 min to remove excessive oxygen in the system. Under the irradiation of white light with an intensity of 5 mW cm -2 , the reaction was carried out at 25 °C for 12 hours to obtain a polyacrylonitrile spinning dope.

[0059] Using a mixed solution of ethanol and water as a precipitant to precipitate the polyacrylonitrile spinning dope, after suction filtration, it is washed, dried, and the final solid product is collected. The obtained solid product is dissolved in N,N-dimethylformamide, and parameters such as molecular weight and molecular weight distribution are measured using a gel permeation chromatography analyzer. The results are shown in Table 1.

[0060] Example 3

[0061] This example provides a method for preparing a polyacrylonitrile spinning dope. This method is a photo-controlled radical polymerization method, and specifically includes the following steps:

[0062] Filter acrylonitrile monomer and butyl acrylate with alumina powder. Weigh 1.5 g of acrylonitrile monomer, 0.1 g of butyl acrylate, 8 mg of bis(carboxymethyl)trithiocarbonate (i.e., chain transfer agent), 0.1 mg of eosin Y (i.e., photocatalyst), and 5.0 mL of 54 wt% sodium thiocyanate aqueous solution. Mix the above-mentioned substances to obtain a mixed solution. Add the mixed solution into a 10 mL quartz reaction tube, seal it with a rubber stopper, and purge with nitrogen for 10 min to remove excessive oxygen in the system. Under blue light irradiation of 3 mW cm -2 At 25 °C for 8 hours to obtain the polyacrylonitrile spinning dope.

[0063] Using a mixed solution of ethanol and water as a precipitant to precipitate the polyacrylonitrile spinning dope, after suction filtration, it is washed, dried, and the final solid product is collected. The obtained solid product is dissolved in N,N-dimethylformamide, and parameters such as molecular weight and molecular weight distribution are measured using a gel permeation chromatography analyzer. The results are shown in Table 1, and the GPC chromatogram is shown in Figure 1 .

[0064] Example 4

[0065] This example provides a method for preparing a polyacrylonitrile spinning dope. This method is a photo-controlled radical polymerization method, and specifically includes the following steps:

[0066] Filter acrylonitrile monomer and acrylamide with alumina powder. Weigh 1.3 g of acrylonitrile monomer, 0.05 g of acrylamide, 0.1 g of itaconic acid, 10 mg of 2-mercapto-S-thiobenzoyl acetic acid (i.e., chain transfer agent), 0.2 mg of rose bengal, and 4.0 mL of 56 wt% sodium thiocyanate aqueous solution. Mix the above-mentioned substances to obtain a mixed solution. Add the mixed solution into a 10 mL quartz reaction tube, seal it with a rubber stopper, and purge with nitrogen for 10 min to remove excessive oxygen in the system. Under blue light irradiation of 4 mW cm -2 At 25 °C for 10 hours to obtain the polyacrylonitrile spinning dope.

[0067] Using a mixed solution of methanol and water as a precipitant to precipitate the polyacrylonitrile spinning dope, followed by suction filtration, washing, and drying, and collecting the final solid product. The obtained solid product 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.

[0068] Example 5

[0069] This example provides a method for preparing a polyacrylonitrile spinning dope, which is a photo-controlled radical polymerization method, and specifically includes the following steps:

[0070] Filter acrylonitrile monomer and vinyl acetate with alumina powder, weigh 0.9 g of acrylonitrile monomer, 0.1 g of vinyl acetate, 0.05 g of itaconic acid, 4 mg of 2-(butyltrithiocarbonate) propionic acid (i.e., chain transfer agent), 0.1 mg of lithium phenyl(2,4,6-trimethylbenzoyl)phosphate (i.e., photocatalyst), and 3.0 mL of 52 wt% sodium thiocyanate aqueous solution. Mix the above-mentioned substances to obtain a mixed solution. Add the mixed solution into a 10 mL quartz reaction tube, seal it with a rubber stopper, and purge with nitrogen for 10 min to remove excessive oxygen in the system. Under the irradiation of blue light at 3 mW cm -2 , react at 25 °C for 12 hours to obtain the polyacrylonitrile spinning dope.

[0071] Using a mixed solution of ethanol and water as a precipitant to precipitate the polyacrylonitrile spinning dope, followed by suction filtration, washing, and drying, and collecting the final solid product. The obtained solid product 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.

[0072] Comparative Example 1

[0073] This comparative example provides a method for preparing a polyacrylonitrile spinning dope, which is a photo-controlled reversible addition-fragmentation chain transfer polymerization method. Its preparation method is the same as that of Example 1, except that dimethyl sulfoxide is used instead of sodium thiocyanate aqueous solution as the solvent.

[0074] Using a mixed solution of ethanol and water as a precipitant to precipitate the polyacrylonitrile spinning dope, followed by suction filtration, washing, and drying, and collecting the final solid product. The obtained solid product 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, and the GPC chromatogram is shown in Figure 2 .

[0075] Comparative Example 2

[0076] This comparative example provides a method for preparing a polyacrylonitrile spinning dope. This method is a photocontrolled reversible addition-fragmentation chain transfer polymerization method, and its preparation method is the same as that of Example 1, except that N,N-dimethylacetamide is used instead of an aqueous sodium thiocyanate solution as the solvent.

[0077] Table 1 Results of Photocatalytic Radical Polymerization of Acrylonitrile

[0078]

[0079] The experimental results of Example 1 prove that the photocatalytic reaction effect of its reaction system is good, the molecular weight of the obtained product is controllable, the molecular weight distribution is narrow, and it can be used for the spinning of the polymerization solution.

[0080] In the remaining examples, the photocatalytic reaction effect is good, the molecular weight of the obtained product is controllable, and the molecular weight distribution is narrow. The effects are equivalent to those of Example 1 and will not be listed one by one here.

[0081] The experimental results of Comparative Example 1 prove that when dimethyl sulfoxide is used as the solvent, the reaction efficiency is very low, and the molecular weight of the polymer is very low, only 5,160 (see Figure 2 ), and it cannot be used for the spinning of the polymerization solution.

[0082] The experimental results of Comparative Example 2 prove that when N,N-dimethylacetamide is used as the solvent, due to the easy occurrence of chain transfer in the N,N-dimethylacetamide solvent, the polymer product precipitates and cannot be directly used for spinning.

[0083] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the 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.

[0084] 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 polyacrylonitrile spinning solution, characterized in that: The following steps are involved: Mixing acrylonitrile monomer, comonomer, chain transfer agent and photocatalyst in a sodium thiocyanate aqueous solution to form a mixed solution; then subjecting the mixed solution to a polymerization reaction under a light source to obtain a polyacrylonitrile spinning stock solution; Wherein, the chain transfer agent is one or more of bis(carboxymethyl)trithiocarbonate and 2-mercapto-S-thiobenzoylacetic acid.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the acrylonitrile monomer to the chain transfer agent is (100-20000):

1.

3. The preparation method according to claim 1 or 2, characterized in that: Based on the total mass of the mixed solution being 100 wt %, the mass fraction of the acrylonitrile monomer is 5-40 wt %.

4. The preparation method according to claim 1 or 2, characterized in that: Based on the total mass of the acrylonitrile monomer and the comonomer as 100 wt %, the mass fraction of the comonomer is 0.5-20 wt %.

5. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the photocatalyst to the chain transfer agent is 1:(5-500).

6. The preparation method according to claim 1 or 2, characterized in that: Based on the total mass of the mixed solution being 100 wt %, the mass fraction of the sodium thiocyanate is 35-50 wt %.

7. The preparation method according to claim 1, characterized in that: The light source is one or more of ultraviolet light, blue light and white light; and / or the light intensity of the light source is 0.2-20 mW·cm -2 .

8. The preparation method according to claim 1, characterized in that: The photocatalyst is one or more of phenyl (2,4,6-trimethylbenzoyl) lithium phosphate, eosin Y and rose bengal; and / or the comonomer is one or more of vinyl acetate, butyl acrylate, itaconic acid, acrylic acid, methyl methacrylate, methyl acrylate, methacrylic acid, n-butyl methacrylate, isobutyl methacrylate, sodium itaconate, sodium propylene sulfonate, sodium methpropylene sulfonate, acrylamide-2-methylpropane sulfonic acid sodium salt solution, 2-acrylamido-2-methylpropane sulfonic acid, sodium styrene sulfonate and acrylamide.

9. A polyacrylonitrile spinning solution, characterized in that: Obtained by the method for preparing the polyacrylonitrile spinning solution according to any one of claims 1 to 8.

10. Use of the polyacrylonitrile spinning solution according to claim 9 in the preparation of polyacrylonitrile fibers or carbon fibers.

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