A continuous flow-based polyacrylonitrile photo-controlled polymerization apparatus and production method

Abstract

This invention discloses a photocontrolled polymerization device and production method for polyacrylonitrile based on continuous flow. The invention employs a two-stage combined photocontrolled polymerization process: a batch reactor for prepolymerization and a tubular continuous flow reactor. The low-viscosity stage in the early polymerization phase takes place in a batch reactor with an internal light source, while the high-viscosity stage in the later polymerization phase occurs in a tubular continuous flow photoreactor. The light source can effectively penetrate the glass coil reactor, achieving efficient and controllable photocontrolled polymerization. This effectively overcomes the problems of difficult mass transfer due to increased material viscosity in the later stages of batch reactor polymerization, such as slower reaction efficiency and uneven illumination. Furthermore, the continuous flow photoreactor is divided into multiple independently controllable stages, allowing for precise adjustment of the light power density according to the reaction progress, achieving higher conversion rates in a shorter time.

Description

Technical Field

[0001] This invention relates to the field of polyacrylonitrile carbon fiber technology, and more specifically to a continuous flow-based photocontrolled polymerization equipment and production method for polyacrylonitrile. Background Technology

[0002] Carbon fiber is a lightweight, high-strength, high-performance fiber material that plays an irreplaceable role in aerospace, defense, and high-end equipment manufacturing. Based on the source of its raw materials and precursors, it can be classified into polyacrylonitrile (PAN)-based, pitch-based, and viscose-based carbon fibers. Among these, polyacrylonitrile carbon fiber has become the mainstream carbon fiber production technology due to its simple processing route and superior, stable product performance. Globally, over 90% of carbon fiber is obtained from spinning and carbonizing polyacrylonitrile. Therefore, synthesizing high-quality polyacrylonitrile is crucial for the final production of high-performance carbon fibers.

[0003] Currently, the mature industrial synthesis methods for polyacrylonitrile include two steps: one-step DMSO solution polymerization and two-step aqueous suspension polymerization. Both are based on traditional thermally initiated free radical polymerization technology. On the one hand, the slow initiation and rapid growth kinetics of these methods mean that the molecular weight and distribution cannot be precisely controlled. The molecular weight distribution (PDI) of the synthesized polyacrylonitrile is generally between 2.0 and 3.0, or even higher. A wide distribution means that the high molecular weight component will significantly increase the viscosity of the spinning solution, seriously affecting spinnability, while the low molecular weight portion will restrict the strength and modulus of the precursor and carbon fibers. On the other hand, the heat of polymerization of acrylonitrile is as high as -72.5 kJ / mol. Under the conditions of traditional free radical polymerization, if the heat of reaction is not removed in time, the system temperature will rise sharply, causing the reaction to runaway, i.e., "explosive polymerization." This not only easily forms gels, seriously affecting product quality, but also brings safety risks. The requirements for rapid heat removal and precise temperature control of the polymerization equipment are extremely high, resulting in higher equipment energy consumption and costs.

[0004] In recent years, novel light-driven controlled polymerization technology has begun to be applied to the synthesis of high-performance polyacrylonitrile. Compared with traditional free radical polymerization technology, it has the advantages of mild and safe reaction conditions, strong molecular weight controllability, and narrow molecular weight distribution. Patent CN 115947883B discloses a light-controlled polymerization technology for acrylonitrile composed of acrylonitrile monomer, chain transfer agent, and oxygen scavenger, carried out in the ultraviolet-visible wavelength range, which can obtain high molecular weight narrow distribution polyacrylonitrile with a molecular weight of over 400,000 and a molecular weight distribution of less than 1.5. Patent CN 118745234 A discloses a light-controlled polymerization technology using a two-dimensional cadmium-based phthalocyanine coordination polymer material as a photocatalyst, used to prepare polyacrylonitrile spinning solutions with narrow distribution, high solid content, and spinnability.

[0005] However, a common bottleneck in the aforementioned photocontrolled polymerization technologies lies in the limited effective penetration depth of the light source. During large-scale scaling, as the volume of traditional polymerization reactors increases, it becomes difficult to effectively guarantee the uniformity of illumination. This results in a high reaction rate near the light source and a relatively low reaction rate further away. Especially in the later stages of the polymerization reaction, as the system viscosity increases, mass transfer becomes more difficult, leading to a broadening of the molecular weight distribution in photocontrolled polymerized acrylonitrile during scale-up, and a significant decrease in performance compared to smaller-volume reactors. Simultaneously, the reaction rate for photocontrolled polymerization of polyacrylonitrile in traditional batch reactors is also relatively slow. Engineering scale-up and reaction efficiency have become bottlenecks restricting the large-scale industrial application of photocontrolled polymerization.

[0006] In summary, in order to overcome the problems of wide molecular weight distribution, easy risk of "explosive polymerization" in traditional free radical polymerization technology, and the difficulty in scaling up batch photocontrolled polymerization process, uneven illumination, and slow reaction rate, this invention provides a continuous flow-based photocontrolled polymerization equipment and production method for polyacrylonitrile, which has the advantages of producing polyacrylonitrile with narrow molecular weight distribution, uniform and stable product performance, and safe and efficient reaction. Summary of the Invention

[0007] In view of this, the present invention provides a photocontrolled polymerization device and production method for polyacrylonitrile based on continuous flow.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A continuous flow-based photopolymerization device for polyacrylonitrile includes: a preparation tank, a prepolymerization kettle, a first continuous flow photoreactor, a second continuous flow photoreactor, a third continuous flow photoreactor, a vacuum system, a high-purity nitrogen pipeline, and a collection kettle; The preparation tank, prepolymer reactor, and vacuum system are connected in sequence. A branch is provided in the pipeline between the prepolymerization vessel and the vacuum system, and the branch is connected to the collection vessel. The prepolymerization vessel is sequentially connected to the first continuous flow reactor, the second continuous flow reactor, the third continuous flow reactor, and the collection vessel; The first continuous flow reactor, the second continuous flow reactor, and the third continuous flow reactor are all connected to the branch; The preparation tank, prepolymerization kettle, and collection kettle are all connected to the high-purity nitrogen pipeline, which serves to replace and protect the nitrogen atmosphere.

[0010] Preferably, the vacuum system includes a vacuum pump and a condenser; the vacuum system serves to remove air. One end of the vacuum pump is connected to the prepolymerization vessel, and the other end is connected to the condenser.

[0011] Preferably, the preparation tank is equipped with a weighing and metering module and a stirring device, and the solvent, main monomer, comonomer and photoinitiator complex are mixed and metered in the preparation tank.

[0012] Preferably, the above-mentioned equipment further includes: a first discharge screw pump and a first disc filter; The prepolymer reactor, the first discharge screw pump, the first disc filter, and the first continuous flow reactor are connected in sequence. The prepolymerization reactor is equipped with a light source and a stirring device; the wavelength of the light source is 350~500 nm, and the optical power density is 3 mW / cm². 2 ~300 mW / cm 2 .

[0013] Preferably, the first continuous flow reactor, the second continuous flow reactor, and the third continuous flow reactor are all transparent coil reactors, and the ratio of the sum of their effective volumes V1 to the effective volume V of the prepolymerization vessel is 60:1 to 3:1, more preferably 30:1 to 10:1. The inner diameter of the transparent coil is 0.5 mm to 30 mm, more preferably 1 mm to 10 mm, and the transparent coil is made of borosilicate glass or quartz glass; The transparent coil contains a columnar light source with a wavelength of 350-500 nm and an optical power density of 3 mW / cm². 2 ~300mW / cm 2 The switching on and off and the optical power density of each continuous flow reactor can be controlled individually. A first static mixer is provided between the first continuous flow reactor and the second continuous flow reactor, and a second static mixer is provided between the second continuous flow reactor and the third continuous flow reactor. The high-purity nitrogen pipeline is also connected to the pipeline between the first disc filter and the first continuous flow reactor, the pipeline between the first static mixer and the second continuous flow reactor, and the pipeline between the second static mixer and the third continuous flow reactor.

[0014] Preferably, the above-mentioned equipment further includes: a second discharge screw pump and a second disc filter; The collecting vessel, the second discharge screw pump, and the second disc filter are connected in sequence. The prepolymer reactor is also connected to the pipeline between the second discharge screw pump and the second disc filter; The collecting vessel is equipped with a stirring device.

[0015] Another object of the present invention is to provide a method for the photocontrolled polymerization of polyacrylonitrile based on continuous flow, comprising the following steps: (1) The solvent, main monomer, comonomer and photoinitiator are mixed in a preparation tank and protected by nitrogen gas. After the mixture is homogeneous, it is introduced into the prepolymerization kettle by gravity flow combined with nitrogen pressurization to start the first stage of prepolymerization. (2) The prepolymer obtained is fed into the first continuous flow reactor, the second continuous flow reactor and the third continuous flow reactor in sequence through the first discharge screw pump and the first stacked plate filter for the second stage of polymerization; (3) After the second stage of polymerization, the acrylonitrile polymer solution is obtained and temporarily stored in the collection tank. After the acrylonitrile polymer solution is completely stored in the collection tank, the vacuum system is connected and the vacuum degree is controlled at -0.4~-0.8 bar to remove the air bubbles in the acrylonitrile polymer solution. If the molecular weight and viscosity of the polymer solution are low, it is returned to the prepolymerization tank through the second discharge screw pump and re-entered into the continuous flow reactor for supplementary polymerization.

[0016] Preferably, the solvent in step (1) is dimethyl sulfoxide; the main monomer is acrylonitrile; and the comonomer is itaconic acid or a combination of itaconic acid and methyl methacrylate. The photoinitiator complex comprises a photoinitiator and a chain transfer agent, wherein the molar ratio of the photoinitiator to the chain transfer agent is 1:100 to 1:500; The photoinitiator is an ultraviolet or visible light initiator, including 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; the chain transfer agent is one or more of 2-cyano-2-propyldodecyl trithiocarbonate, 2-(dodecyl trithiocarbonate)-2-methylpropionic acid, and 4-cyano-4-[(dodecylthiocarbonylthiocarbonyl)thioalkyl]valerate.

[0017] The molar ratio of the main monomer to the photoinitiator complex is (1000~10000):1; Based on the total mass of the mixture, the mass fraction of the main monomer is 10-35%; based on the mass of the main monomer, the mass fraction of the comonomer is 0.1-3%; The reaction parameters for the first prepolymerization stage are: reaction temperature 40~70℃, light source wavelength 350~500 nm, and light power density 3~30 mW / cm². 2 ; The obtained polymer solution has a Breuer rotational viscosity of 1,000 to 50,000 cps at a test temperature of 50°C, and is more preferably 2,000 to 20,000 cps.

[0018] Preferably, the conveying flow rate of the first discharge screw pump in step (2) is 0.2 kg / h to 100 kg / h, and more preferably 1 kg / h to 100 kg / h; The filtration accuracy of the first disc filter is 1μm ~ 10μm; The optical power density of the first continuous flow photoreactor is 10~100 mW / cm². 2 ; The optical power density of the second continuous flow photoreactor is 50~200 mW / cm². 2 ; The optical power density of the third continuous streamer reactor is 100~300 mW / cm². 2 .

[0019] Preferably, the temperature inside the collection vessel in step (3) is controlled at 40~60℃, and the stirring speed is controlled at 5~50 rpm; The acrylonitrile polymerization solution has a molecular weight of 100,000 to 500,000 and a molecular weight distribution of 1.1 to 1.6; the Breitfeld rotational viscosity at a test temperature of 50°C is 50,000 cps to 150,000 cps. The second discharge screw pump has a conveying flow rate of 50~500 kg / h; The second disc filter has a filtration accuracy of 0.1μm to 1μm.

[0020] As can be seen from the above technical solution, compared with the prior art, the present invention has the following technical effects: This photocontrolled polymerization process combines two stages: a batch reactor for prepolymerization and a tubular continuous flow reactor. The initial low-viscosity stage of polymerization takes place in a batch reactor with an integrated light source, while the later high-viscosity stage occurs in a tubular continuous flow reactor. The light source effectively penetrates the glass coil reactor, enabling efficient and controllable photocontrolled polymerization. This effectively overcomes the problems of difficult mass transfer, slower reaction efficiency, and uneven illumination caused by the increased material viscosity in the later stages of the batch reactor. Furthermore, the continuous flow reactor is divided into multiple independently controlled stages, allowing for precise adjustment of the light power density according to the reaction progress, achieving higher conversion rates in a shorter time.

[0021] The polymer solution obtained by this invention has moderate viscosity and narrow molecular weight distribution. It does not require additional precipitation, separation, dissolution, or other operations, and is free of gel, impurities, and bubbles. It can be directly used for subsequent spinning operations to obtain high-performance precursor fibers. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the device structure of the present invention; In the picture: 1-Preparation tank; 2-Prepolymerization kettle; 3-First discharge screw pump; 4-First disc filter; 5-First continuous flow reactor; 6-First static mixer; 7-Second continuous flow reactor; 8-Second static mixer; 9-Third continuous flow reactor; 10-Collection vessel; 11-Second discharge screw pump; 12-Second disc filter; 13-Vacuum pump; 14-Condenser; 15-High-purity nitrogen pipeline; A - Solvent; B - Main monomer; C - Comonomer; D - Photoinitiator complex; E - High-purity nitrogen. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1 This embodiment provides a continuous flow-based photopolymerization device for polyacrylonitrile, including: a preparation tank 1, a prepolymerization kettle 2, a first discharge screw pump 3, a first disc filter 4, a first continuous flow photoreactor 5, a second continuous flow photoreactor 7, a third continuous flow photoreactor 9, a vacuum system, a high-purity nitrogen pipeline 15, a collection kettle 10, a second discharge screw pump 11, and a second disc filter 12. The preparation tank 1, the prepolymerization reactor 2, and the vacuum system are connected in sequence; A branch is provided in the pipeline between the prepolymer reactor 2 and the vacuum system, and the branch is connected to the collection reactor 10; The prepolymer reactor 2 is connected in sequence to the first discharge screw pump 3, the first disc filter 4, the first continuous flow reactor 5, the second continuous flow reactor 7, the third continuous flow reactor 9, and the collection reactor 10. The first continuous flow reactor 5, the second continuous flow reactor 7, and the third continuous flow reactor 9 are all connected to the branch circuit; The preparation tank 1, the prepolymerization vessel 2, and the collection vessel 10 are all connected to the high-purity nitrogen pipeline 15.

[0026] The vacuum system includes a vacuum pump 13 and a condenser 14. One end of the vacuum pump 13 is connected to the prepolymer reactor 2, and the other end is connected to the condenser 14.

[0027] The preparation tank 1 is equipped with a weighing and metering module and a stirring device. Solvent, main monomer, comonomer and photoinitiator complex are mixed and metered in the preparation tank.

[0028] The prepolymerization reactor 2 is equipped with a light source and a stirring device; the wavelength of the light source is 350~500 nm, and the optical power density is 3 mW / cm². 2 ~300 mW / cm 2 .

[0029] The first continuous flow reactor 5, the second continuous flow reactor 7 and the third continuous flow reactor 9 are all transparent coil reactors, and the ratio of their sum of effective volumes V1 to the effective volume V of the prepolymerization vessel 2 is 60:1 to 3:1. The inner diameter of the transparent coil is 0.5 mm to 30 mm, and the transparent coil is made of borosilicate glass or quartz glass; The transparent coil contains a columnar light source with a wavelength of 350-500 nm and an optical power density of 3 mW / cm². 2 ~300mW / cm 2 The switching on and off and the optical power density of each continuous flow reactor can be controlled individually. A first static mixer 6 is provided between the first continuous flow reactor 5 and the second continuous flow reactor 7, and a second static mixer 8 is provided between the second continuous flow reactor 7 and the third continuous flow reactor 9.

[0030] The high-purity nitrogen pipeline 15 is also connected to the pipeline between the first disc filter 4 and the first continuous flow reactor 5, the pipeline between the first static mixer 6 and the second continuous flow reactor 7, and the pipeline between the second static mixer 8 and the third continuous flow reactor 9.

[0031] The collecting vessel 10, the second discharge screw pump 11, and the second disc filter 12 are connected in sequence; The prepolymer reactor 2 is also connected to the pipeline between the second discharge screw pump 11 and the second disc filter 12; A stirring device is installed inside the collecting vessel 10.

[0032] Example 2 This embodiment provides a continuous flow-based photocontrolled polymerization production method for polyacrylonitrile, including the following steps: (1) The following proportions are used to meter and feed the materials into the preparation tank 1: acrylonitrile mass fraction 15 wt%, the molar ratio of 2,4,6-trimethylbenzoyl diphenylphosphine oxide to 2-cyano-2-propyl dodecyl trithiocarbonate in the photoinitiator complex is 1:100; the molar ratio of the photoinitiator complex to acrylonitrile is 1:5000, the comonomers itaconic acid and methyl methacrylate each account for 0.5% of the mass fraction of acrylonitrile; the remaining components are dimethyl sulfoxide.

[0033] (2) After the nitrogen atmosphere is replaced in the prepolymer reactor 2, the first continuous flow photoreactor 5, the second continuous flow photoreactor 7, the third continuous flow photoreactor 9, and the collection vessel 10, the raw materials in the preparation tank 1 are introduced into the prepolymer reactor 2 by gravity flow combined with nitrogen pressurization to carry out the prepolymerization reaction at a reaction temperature of 45°C and 10 mW / cm². 2 After the light power reaction time is 6 h and the Brookfield viscosity reaches 10000 cps, the light is fed by the first discharge screw pump 3 at a flow rate of 2 kg / h, and then sequentially into the first continuous flow reactor 5, the second continuous flow reactor 7, and the third continuous flow reactor 9 through the first stacked plate filter 4 with a precision of 5 μm.

[0034] The first continuous flow optical reactor 5 has an optical power density set to 20 mW / cm². 2 ; The second continuous flow optical reactor 7 has an optical power density set to 60 mW / cm². 2 ; The third continuous flow optical reactor 9 has an optical power density set to 100 mW / cm². 2 ; The mixture passes through the first static mixer 6 and the second static mixer 8 in sequence, and then enters the collection vessel 10. Under vacuum degassing conditions of 50°C and -0.5 bar, the final acrylonitrile polymerization product is obtained.

[0035] Example 3 This embodiment provides a continuous flow-based photocontrolled polymerization production method for polyacrylonitrile, the specific steps of which are as follows: (1) The following proportions are used to meter and feed the materials into the preparation tank 1: the mass fraction of acrylonitrile is 10 wt%, the molar ratio of 2,4,6-trimethylbenzoyl diphenylphosphine oxide to 2-cyano-2-propyl dodecyl trithiocarbonate in the photoinitiator complex is 1:500; the molar ratio of the photoinitiator complex to acrylonitrile is 1:10000; only itaconic acid is used as the comonomer, accounting for 0.1 wt% of the mass fraction of acrylonitrile; the remaining components are dimethyl sulfoxide.

[0036] (2) After purging the prepolymer reactor 2, each continuous flow reactor and the collection vessel with nitrogen atmosphere, the raw material is introduced into the prepolymer reactor 2 by gravity flow combined with nitrogen pressurization for prepolymerization reaction. The reaction temperature is 40℃, and the reaction is carried out for 8 h at a light power density of 3 mW / cm² until the Brookfield viscosity reaches 2000 cps. Then, the raw material is introduced into the three continuous flow reactors by the first discharge screw pump 3 at a flow rate of 0.2 kg / h and through the first stacked plate filter 4 with a precision of 1 μm.

[0037] The first continuous flow optical reactor 5 has an optical power density set to 10 mW / cm². 2 ; The second continuous flow optical reactor 7 has an optical power density set to 50 mW / cm². 2 ; The third continuous flow optical reactor 9 has an optical power density set to 100 mW / cm². 2 ; The mixture passes through the first static mixer 6 and the second static mixer 8 in sequence before entering the collection vessel 10. Under vacuum degassing conditions of 40°C and -0.8 bar, the final acrylonitrile polymerization product is obtained.

[0038] Example 4 This embodiment provides a continuous flow-based photocontrolled polymerization production method for polyacrylonitrile, the specific steps of which are as follows: (1) The following proportions are used to meter and feed the materials into the preparation tank 1: the mass fraction of acrylonitrile is 35 wt%, the molar ratio of 2,4,6-trimethylbenzoyl diphenylphosphine oxide to 2-cyano-2-propyl dodecyl trithiocarbonate in the photoinitiator complex is 1:100; the molar ratio of the photoinitiator complex to acrylonitrile is 1:1000; the comonomers are itaconic acid and methyl methacrylate, each accounting for 1.5 wt% of the mass fraction of acrylonitrile; the remaining components are dimethyl sulfoxide.

[0039] (2) After the system is purged with nitrogen atmosphere, the raw materials enter the prepolymer reactor 2 for prepolymerization reaction at a reaction temperature of 70°C and a light power density of 30 mW / cm² for 4 h until the Brookfield viscosity reaches 20000 cps. Then, the raw materials are fed into the three continuous flow reactors by the first discharge screw pump 3 at a flow rate of 100 kg / h and through the first stacked plate filter 4 with a precision of 10 μm.

[0040] The first continuous flow optical reactor 5 has an optical power density set to 100 mW / cm². 2 ; The second continuous flow optical reactor 7 has an optical power density set to 200 mW / cm². 2 ; The third continuous flow optical reactor 9 has an optical power density set to 300 mW / cm².2 ; The mixture passes through the first static mixer 6 and the second static mixer 8 in sequence, and then enters the collection vessel 10. Under vacuum degassing conditions of 60°C and -0.4 bar, the final acrylonitrile polymerization product is obtained.

[0041] Comparative Example 1 (1) The following proportions are used to meter and feed the materials into the preparation tank 1: acrylonitrile mass fraction 15 wt%, the molar ratio of 2,4,6-trimethylbenzoyl diphenylphosphine oxide to 2-cyano-2-propyl dodecyl trithiocarbonate in the photoinitiator complex is 1:100; the molar ratio of the photoinitiator complex to acrylonitrile is 1:5000, the comonomers itaconic acid and methyl methacrylate each account for 0.5% of the mass fraction of acrylonitrile; the remaining components are dimethyl sulfoxide.

[0042] (2) After purging the prepolymerization reactor 2 with nitrogen atmosphere, the raw materials in the preparation tank 1 are introduced into the prepolymerization reactor 2 by gravity flow combined with nitrogen pressurization to carry out the prepolymerization reaction at a reaction temperature of 45℃ and a concentration of 10mW / cm³. 2 The reaction was carried out at a light power density of 120 h without entering a continuous flow reactor, directly yielding the final acrylonitrile polymerization product.

[0043] The comparison results between Examples 2-4 and Comparative Example 1 are shown in Table 1: Table 1

[0044] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0045] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A photocontrolled polymerization apparatus for polyacrylonitrile based on continuous flow, characterized in that, include: Preparation tank, prepolymerization kettle, first continuous flow photoreactor, second continuous flow photoreactor, third continuous flow photoreactor, vacuum system, high-purity nitrogen pipeline and collection kettle; The preparation tank, prepolymer reactor, and vacuum system are connected in sequence. A branch is provided in the pipeline between the prepolymerization vessel and the vacuum system, and the branch is connected to the collection vessel. The prepolymerization vessel is sequentially connected to the first continuous flow reactor, the second continuous flow reactor, the third continuous flow reactor, and the collection vessel; The first continuous flow reactor, the second continuous flow reactor, and the third continuous flow reactor are all connected to the branch; The preparation tank, prepolymerization vessel, and collection vessel are all connected to the high-purity nitrogen pipeline.

2. The photocontrolled polymerization equipment for polyacrylonitrile based on continuous flow according to claim 1, characterized in that, The vacuum system includes a vacuum pump and a condenser; One end of the vacuum pump is connected to the prepolymerization vessel, and the other end is connected to the condenser.

3. The photocontrolled polymerization equipment for polyacrylonitrile based on continuous flow according to claim 2, characterized in that, The preparation tank is equipped with a weighing and metering module and a stirring device, in which the solvent, main monomer, comonomer, and photoinitiator complex are mixed and metered.

4. The photocontrolled polymerization equipment for polyacrylonitrile based on continuous flow according to claim 2, characterized in that, Also includes: The first discharge screw pump and the first disc filter; The prepolymer reactor, the first discharge screw pump, the first disc filter, and the first continuous flow reactor are connected in sequence. The prepolymerization reactor is equipped with a light source and a stirring device; the wavelength of the light source is 350~500 nm, and the optical power density is 3 mW / cm². 2 ~300 mW / cm 2 .

5. The photocontrolled polymerization equipment for polyacrylonitrile based on continuous flow according to claim 4, characterized in that, The first, second, and third continuous flow reactors are all transparent coil reactors, and the ratio of their sum of effective volumes V1 to the effective volume V of the prepolymer reactor is 60:1 to 3:

1. The inner diameter of the transparent coil is 0.5 mm to 30 mm, and the transparent coil is made of borosilicate glass or quartz glass; The transparent coil contains a columnar light source with a wavelength of 350-500 nm and an optical power density of 3 mW / cm². 2 ~300 mW / cm 2 The switching on and off and the optical power density of each continuous flow reactor can be controlled individually. A first static mixer is provided between the first continuous flow reactor and the second continuous flow reactor, and a second static mixer is provided between the second continuous flow reactor and the third continuous flow reactor. The high-purity nitrogen pipeline is also connected to the pipeline between the first disc filter and the first continuous flow reactor, the pipeline between the first static mixer and the second continuous flow reactor, and the pipeline between the second static mixer and the third continuous flow reactor.

6. The photocontrolled polymerization equipment for polyacrylonitrile based on continuous flow according to claim 5, characterized in that, Also includes: Second discharge screw pump and second disc filter; The collecting vessel, the second discharge screw pump, and the second disc filter are connected in sequence. The prepolymer reactor is also connected to the pipeline between the second discharge screw pump and the second disc filter; The collecting vessel is equipped with a stirring device.

7. A method for producing polyacrylonitrile by photocontrolled polymerization based on continuous flow, characterized in that, Using the device according to claim 6, the steps include: (1) The solvent, main monomer, comonomer and photoinitiator are mixed in a preparation tank and protected by nitrogen gas. After the mixture is homogeneous, it is introduced into the prepolymerization kettle by gravity flow combined with nitrogen pressurization to start the first stage of prepolymerization. (2) The prepolymer obtained is fed into the first continuous flow reactor, the second continuous flow reactor and the third continuous flow reactor in sequence through the first discharge screw pump and the first stacked plate filter for the second stage of polymerization; (3) After the second stage of polymerization, the acrylonitrile polymer solution is obtained and temporarily stored in the collection tank. After the acrylonitrile polymer solution is completely stored in the collection tank, the vacuum system is connected and the vacuum degree is controlled at -0.4~-0.8 bar to remove the air bubbles in the acrylonitrile polymer solution. If the molecular weight and viscosity of the polymer solution are low, it is returned to the prepolymerization tank through the second discharge screw pump and re-entered into the continuous flow reactor for supplementary polymerization.

8. The method for producing polyacrylonitrile by photocontrolled polymerization based on continuous flow according to claim 7, characterized in that, The solvent in step (1) is dimethyl sulfoxide; the main monomer is acrylonitrile; the comonomer is itaconic acid or a combination of itaconic acid and methyl methacrylate; The photoinitiator complex comprises a photoinitiator and a chain transfer agent, wherein the molar ratio of the photoinitiator to the chain transfer agent is 1:100 to 1:500; The molar ratio of the main monomer to the photoinitiator complex is (1000~10000):1; Based on the total mass of the mixture, the mass fraction of the main monomer is 10-35%; based on the mass of the main monomer, the mass fraction of the comonomer is 0.1-3%; The reaction parameters for the first prepolymerization stage are: reaction temperature 40~70℃, light source wavelength 350~500 nm, and light power density 3~30 mW / cm². 2 ; The obtained polymer solution had a Breuer rotational viscosity of 1000~50000 cps at a test temperature of 50℃.

9. The method for producing polyacrylonitrile by photocontrolled polymerization based on continuous flow according to claim 7, characterized in that, In step (2), the conveying flow rate of the first discharge screw pump is 0.2 kg / h to 100 kg / h; The filtration accuracy of the first disc filter is 1μm ~ 10μm; The optical power density of the first continuous flow photoreactor is 10~100 mW / cm². 2 ; The optical power density of the second continuous flow photoreactor is 50~200 mW / cm². 2 ; The optical power density of the third continuous streamer reactor is 100~300 mW / cm². 2 .

10. The method for producing polyacrylonitrile by photocontrolled polymerization based on continuous flow according to claim 7, characterized in that, In step (3), the temperature inside the collection vessel is controlled at 40~60℃, and the stirring speed is controlled at 5~50 rpm; The acrylonitrile polymerization solution has a molecular weight of 100,000 to 500,000 and a molecular weight distribution of 1.1 to 1.6; the Breitfeld rotational viscosity at a test temperature of 50°C is 50,000 cps to 150,000 cps. The second discharge screw pump has a conveying flow rate of 50~500 kg / h; The second disc filter has a filtration accuracy of 0.1μm to 1μm.

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