Continuous preparation method of polyacrylonitrile resin with narrow molecular weight distribution

Abstract

The invention discloses a continuous preparation method of polyacrylonitrile resin with narrow molecular weight distribution, which is characterized in that acrylonitrile and a comonomer are used as raw materials, under the action of an initiator, a microchannel reactor is used for solution polymerization, and the polyacrylonitrile resin with narrow molecular weight distribution is obtained after the polymerization liquid is subjected to precipitation, suction filtration, washing and drying. The continuous preparation method of the polyacrylonitrile resin with narrow molecular weight distribution adopts the micro-channel reactor, has the characteristics of high polymerization reaction rate, low energy consumption, high yield and the like, and has the characteristics of greener, more environment-friendly and more efficient preparation process. By means of the preparation method disclosed by the invention, the polyacrylonitrile resin for the high-performance carbon fiber with the molecular weight distribution of 1.13-1.50 can be obtained on the premise of ensuring the high molecular weight.

Description

Technical Field

[0001] The invention relates to a continuous preparation method of polyacrylonitrile resin with narrow molecular weight distribution, belonging to the field of synthesis of polyacrylonitrile resin for carbon fiber. Background Art

[0002] Carbon fiber is a special high-performance fiber composed of carbon elements, with a carbon content of more than 90%, high specific strength and high specific modulus. It has a series of comprehensive properties such as low density, high temperature resistance, friction resistance, electrical conductivity, thermal conductivity, corrosion resistance, radiation resistance, and good damping, and is widely used in military and civilian fields. Among the three types of carbon fibers that have been industrialized, polyacrylonitrile-based carbon fiber has become the most used type of carbon fiber due to its excellent comprehensive properties such as strength, high carbonization yield, and simple production process, and its output accounts for more than 90% of the total carbon fiber.

[0003] The molecular weight distribution of polyacrylonitrile resin has a great influence on its material properties, spinning process conditions and final product quality. The molecular weight distribution is expressed as the ratio of weight average molecular weight to number average molecular weight (M w / M n ) indicates that a molecular weight distribution less than 1.5 is generally referred to as a narrow distribution, while a molecular weight distribution greater than 1.5 is referred to as a wide distribution. The wider the molecular weight distribution, the higher the polymer content with excessively high or low polymerization. Oligomers play a role of plasticization, destroying the orderliness of the original fiber structure. During the pre-oxidation process, a large amount of small molecular decomposition products and tar-like substances will be produced. These substances adhere to the fiber surface and cause pollution, which is not conducive to the subsequent pre-oxidation and energy transfer in the carbonization process. At present, the preparation of polyacrylonitrile resin with a narrow molecular weight distribution has become an important research topic in the field of polyacrylonitrile resin synthesis for carbon fiber.

[0004] There are many methods for preparing polyacrylonitrile resin, which are generally synthesized based on the traditional free radical polymerization mechanism, using solutions polymerization, emulsion polymerization, suspension polymerization and bulk polymerization. Among them, solution polymerization is a polymerization reaction carried out in a solvent that can dissolve both monomers and initiators and the polymers generated after the reaction. It is a commonly used polymerization method in the industrial production of polyacrylonitrile. However, traditional solution polymerization can only obtain polymers with a wide molecular weight distribution, which seriously affects the performance of the final product of polyacrylonitrile resin. At present, living polymerization technology is the most ideal process for controlling the molecular weight distribution of polymers, mainly including cationic polymerization, anionic polymerization and free radical living polymerization. The properties of acrylonitrile monomer itself make it impossible to achieve cationic living polymerization; anionic polymerization has very strict requirements on reaction conditions, and the reaction process is complicated, and the industrialization cost is high; the initiator or chain transfer agent used in free radical living polymerization is not easy to prepare and preserve, and is sensitive to oxygen or water. Chen Hou et al. published a method for preparing narrow molecular weight distribution polyacrylonitrile resin by reverse atom transfer radical active polymerization in a patent with authorization announcement number CN100532410C. This method uses organic acid and high-valent metal halide as the catalytic system, has strict reaction conditions, complex process and long reaction time.

[0005] At present, there have been many reports on the synthesis of polyacrylonitrile resin for carbon fiber, but the shortcomings of its preparation method are also obvious, such as: harsh reaction conditions, cumbersome operation, long reaction time, discontinuous reaction, low production efficiency, wide polymer molecular weight distribution, etc. In view of this, it is necessary to develop a simple, fast, efficient, economical and safe continuous process technology to achieve high-throughput production of polyacrylonitrile resin. Summary of the invention

[0006] The purpose of the present invention is to provide a continuous preparation method of polyacrylonitrile resin with narrow molecular weight distribution, which solves the problems of long reaction time, low production efficiency, wide polymer molecular weight distribution and the like in the prior art. The method adopted by the present invention can greatly improve the polymerization reaction rate, shorten the reaction time, realize efficient polymerization, and at the same time maintain the characteristic of narrow molecular weight distribution of polyacrylonitrile.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A continuous preparation method for a polyacrylonitrile resin with a narrow molecular weight distribution, characterized in that the method comprises the following steps:

[0009] 1. Prepare a copolymer system as a reaction liquid: acrylonitrile, a comonomer and an initiator are dissolved in a solvent, wherein the mass ratio of the comonomer to the solvent is 1:(1-9), and the mass ratio of the comonomer to the initiator is 100:(0.1-3.5); when the reaction liquid is a binary copolymer system, the mass ratio of acrylonitrile:the second monomer is (85-99.9):(0.1-15); when the reaction liquid is a ternary copolymer system, the mass ratio of acrylonitrile:the second monomer:the third monomer is (85-99.8):(0.1-10):(0.1-6);

[0010] 2. The reaction liquid is loaded into a raw material tank and enters a microchannel reactor with an inner diameter of 0.1-250 mm and a length of 1-1000 m under the action of a feed pump. After the reaction is complete, a polyacrylonitrile polymerization liquid is obtained. After precipitation, filtration, washing and drying, the polyacrylonitrile resin is obtained.

[0011] Preferably, the mass ratio of the comonomer to the solvent is (33-153):187, the mass ratio of the comonomer to the initiator is 100:(0.5-3.5), in the binary copolymer system, the mass ratio of acrylonitrile:the second monomer is (90-99):(1-10), and in the ternary copolymer system, the mass ratio of acrylonitrile:the second monomer:the third monomer is (90-99):(0.2-7):(0.1-5).

[0012] The second monomer is one of alkyl acrylate, alkyl methacrylate, vinyl acetate, vinyl propionate, styrene, vinyl chloride, vinyl dichloride or a mixture thereof, and the third monomer is one of itaconic acid and its derivatives, acrylic acid, methacrylic acid, maleic anhydride or a mixture thereof.

[0013] Preferably, the binary copolymer system is a copolymer system of acrylonitrile and methyl acrylate, and the ternary copolymer system is a copolymer system of acrylonitrile, methyl acrylate and itaconic acid.

[0014] The reaction temperature of the microchannel reactor is 40-200°C, the reaction pressure is 0.1-5.0 MPa, and the residence time is 1-120 min. Preferably, in the microchannel reactor, the reaction temperature is 65-155°C, the reaction pressure is 0.1-1.6 MPa, and the residence time is 5-60 min.

[0015] The solvent for the polymerization reaction is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc), preferably dimethyl sulfoxide (DMSO).

[0016] The initiator of the polymerization reaction is one or two of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), dimethyl azobisisobutyrate (AIBME) and azoisobutylcyanamide (V30), preferably azobisisobutyronitrile (AIBN).

[0017] The microchannel reactor is an annular microchannel reactor made of a 316L stainless steel coil, the inner diameter of the coil is 0.1-250 mm, the length is 1-1000 m, the coil is filled with internal components, and the internal components can be selected from at least one of spherical, ellipsoidal, cylindrical, truncated cone, annular, toothed, star-shaped, spring-shaped, vertical spiral, conical, and polyhedral shapes.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] 1. The present invention provides a continuous preparation method for a polyacrylonitrile resin with a narrow molecular weight distribution. Under the action of an initiator, the polyacrylonitrile resin is prepared in a microchannel reactor from acrylonitrile, a comonomer and a solvent. Compared with the traditional intermittent reaction conditions, the continuous reaction process can achieve precise control, good safety performance, significantly shortened reaction time, large output and high production efficiency. The stirring and shearing effects generated by the internal components in the reactor can promote material mixing. The method of the present invention has the characteristics of significantly shortened reaction time, significantly improved reaction efficiency and easy amplification, continuous production, simple operation and high safety. At the same time, the method of the present invention is simple to operate, has high production efficiency, low cost, can be produced continuously and uninterruptedly, and has stable product quality, so it has good industrial application prospects.

[0020] 2. The continuous preparation method of a polyacrylonitrile resin with a narrow molecular weight distribution provided by the present invention overcomes the defects of traditional solution polymerization. The weight average molecular weight of the prepared polyacrylonitrile resin is 60,000-472,000, and the molecular weight distribution is 1.13-1.50. It has the characteristics of high molecular weight and narrow molecular weight distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 The figure is a schematic flow diagram of a continuous preparation method of a polyacrylonitrile resin with a narrow molecular weight distribution according to the present invention, wherein numbers 1-7 correspond to a raw material storage tank, a plunger pump, a safety valve, a microchannel reactor, a cooling coil, a back pressure valve and a product storage tank, respectively;

[0023] Figure 2 is the GPC chart of the polyacrylonitrile resin in Example 1;

[0024] Figure 3 is the polyacrylonitrile resin in Example 1 1 H NMR spectra. DETAILED DESCRIPTION

[0025] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0026] Embodiment 1:

[0027] The total single mass concentration is controlled to be 25%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 98:2:0.5. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor filled with spherical stainless steel internal components with a coil inner diameter of 10mm and a length of 20m. The reaction temperature is controlled to be 95°C, the reaction pressure is 0.3MPa, and the residence time is 6.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 322,000, and the molecular weight distribution is 1.35.

[0028] Embodiment 2:

[0029] The total single mass concentration is controlled to be 30%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 98:2:1. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor filled with cylindrical stainless steel internal components with a coil inner diameter of 3mm and a length of 7.5m. The reaction temperature is controlled to be 125°C, the reaction pressure is 0.6MPa, and the residence time is 5.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 65,000, and the molecular weight distribution is 1.19.

[0030] Embodiment 3:

[0031] The total single mass concentration is controlled to be 45%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 96:4:0.8. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor filled with vertical spiral stainless steel internal components with a coil inner diameter of 30mm and a length of 10m. The reaction temperature is controlled to be 95°C, the reaction pressure is 0.5MPa, and the residence time is 10.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 459,000, and the molecular weight distribution is 1.47.

[0032] Embodiment 4:

[0033] The total single mass concentration is controlled to be 25%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 94:6:1.5. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor with a coil inner diameter of 20mm and a length of 40m filled with spring-shaped stainless steel internal components, and the reaction temperature is controlled to be 125°C, the reaction pressure is 0.6MPa, and the residence time is 5.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 91,000, and the molecular weight distribution is 1.37.

[0034] Embodiment 5:

[0035] The total single mass concentration is controlled to be 30%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 90:10:1.5. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor with a coil inner diameter of 30mm and a length of 20m filled with spring-shaped stainless steel internal components, and the reaction temperature is controlled to be 125°C, the reaction pressure is 0.8MPa, and the residence time is 2.5min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 61,000, and the molecular weight distribution is 1.50.

[0036] Embodiment 6:

[0037] The total single mass concentration is controlled to be 25%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 97:3:2. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor filled with spherical stainless steel internal components with a coil inner diameter of 50mm and a length of 10m. The reaction temperature is controlled to be 155°C, the reaction pressure is 1.4MPa, and the residence time is 2.5min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 132,000, and the molecular weight distribution is 1.35.

[0038] Embodiment 7:

[0039] The total single mass concentration is controlled to be 35%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 95:5:1. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor filled with cylindrical stainless steel internal components with a coil inner diameter of 100mm and a length of 5m. The reaction temperature is controlled to be 140°C, the reaction pressure is 1.0MPa, and the residence time is 5.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 119,000, and the molecular weight distribution is 1.43.

[0040] Embodiment 8:

[0041] The total single mass concentration is controlled to be 15%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 91:9:3. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor with a coil inner diameter of 20mm and a length of 100m filled with spring-shaped stainless steel internal components, and the reaction temperature is controlled to be 120°C, the reaction pressure is 1.0MPa, and the residence time is 8.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 60,000, and the molecular weight distribution is 1.26.

[0042] Embodiment 9:

[0043] The total single mass concentration is controlled to be 30%, acrylonitrile: methyl acrylate: azobisisobutyronitrile (mass ratio) = 94:6:0.5. According to the above ratio, acrylonitrile, methyl acrylate and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor with a spring-shaped stainless steel internal component filled with a coil inner diameter of 20mm and a length of 40m. The reaction temperature is controlled to be 145°C, the reaction pressure is 1.2MPa, and the residence time is 6.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 472,000, and the molecular weight distribution is 1.45.

[0044] Embodiment 10:

[0045] The total single mass concentration is controlled to be 25%, acrylonitrile: methyl acrylate: itaconic acid: azobisisobutyronitrile (mass ratio) = 98:1.7:0.3:1. According to the above ratio, acrylonitrile, methyl acrylate, itaconic acid and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor filled with spherical stainless steel internal components with a coil inner diameter of 3mm and a length of 15m. The reaction temperature is controlled to be 110°C, the reaction pressure is 0.6MPa, and the residence time is 5.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 213,000, and the molecular weight distribution is 1.23

[0046] Embodiment 11:

[0047] The total single mass concentration is controlled to be 20%, acrylonitrile: methyl acrylate: itaconic acid: azobisisobutyronitrile (mass ratio) = 96: 2.8: 1.2: 1.5. According to the above ratio, acrylonitrile, methyl acrylate, itaconic acid and azobisisobutyronitrile are dissolved in dimethyl sulfoxide and loaded in a raw material tank. Under the action of the feed pump, the reaction liquid enters a microchannel reactor filled with spherical stainless steel internal components with a coil inner diameter of 10mm and a length of 30m. The reaction temperature is controlled to be 125°C, the reaction pressure is 0.6MPa, and the residence time is 3.0min to obtain a polymer solution. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 76,000, and the molecular weight distribution is 1.30.

[0048] Comparative Example 1:

[0049] With azobisisobutyronitrile as initiator and dimethyl sulfoxide as solvent, acrylonitrile solution copolymerization is carried out in an intermittent reactor. The total single mass concentration is controlled to be 25%, and the mass ratio of acrylonitrile: methyl acrylate: azobisisobutyronitrile is 98:2:0.5. According to the above ratio, acrylonitrile, methyl acrylate and most of the solvent dimethyl sulfoxide are added to a three-necked flask under nitrogen protection, and azobisisobutyronitrile is dissolved in the remaining dimethyl sulfoxide. When the reaction temperature reaches 60°C, azobisisobutyronitrile solution is added and reacted at 60°C for 12 hours. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 299,000, and the molecular weight distribution index is 2.55.

[0050] Comparative Example 2:

[0051] With azobisisobutyronitrile as initiator and dimethyl sulfoxide as solvent, acrylonitrile solution copolymerization is carried out in an intermittent reactor. The total single mass concentration is controlled to be 25%, and the mass ratio of acrylonitrile: methyl acrylate: itaconic acid: azobisisobutyronitrile is 98:1.7:0.3:1. According to the above ratio, acrylonitrile, methyl acrylate, itaconic acid and most of the solvent dimethyl sulfoxide are added to a three-necked flask under nitrogen protection, and azobisisobutyronitrile is dissolved in the remaining dimethyl sulfoxide. When the reaction temperature reaches 60°C, azobisisobutyronitrile solution is added and reacted at a temperature of 60°C for 18 hours. The polymer solution is precipitated, filtered, washed and dried. The weight average molecular weight of the obtained polyacrylonitrile resin is 224,000, and the molecular weight distribution index is 2.98.

[0052] Compared with the results of comparative example 1, the polymerization reaction rate of Example 1 is greatly improved. The residence time of Example 1 is 6 minutes, while the reaction time of comparative example 1 is 12 hours. Under the premise of ensuring high molecular weight, the molecular weight distribution of the obtained polyacrylonitrile resin is narrower. The molecular weight distribution of the polyacrylonitrile resin obtained in Example 1 is 1.35, while the molecular weight distribution of the polyacrylonitrile resin obtained in comparative example 1 is 2.55. Compared with the results of comparative example 2, the polymerization reaction rate of Example 10 is also greatly improved. The residence time of Example 10 is 5 minutes, while the reaction time of comparative example 2 is 18 hours. Under the premise of ensuring high molecular weight, the molecular weight distribution of the obtained polyacrylonitrile resin is narrower. The molecular weight distribution of the polyacrylonitrile resin obtained in Example 10 is 1.23, while the molecular weight distribution of the polyacrylonitrile resin obtained in comparative example 2 is 2.98. By comparing the examples with the comparative examples, it can be found that the polyacrylonitrile resin obtained by the preparation method provided by the present invention has a narrower molecular weight distribution under the premise of ensuring high molecular weight. At the same time, the preparation method provided by the present invention greatly improves the polymerization reaction rate, is simpler to operate, has higher safety, and can achieve continuous production.

[0053] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A continuous preparation method for a polyacrylonitrile resin with a narrow molecular weight distribution, characterized in that: The method comprises the following steps: 1) Prepare a copolymer system as a reaction liquid: dissolve acrylonitrile, a comonomer and an initiator in a solvent to obtain a reaction liquid; wherein the mass ratio of the comonomer to the solvent is 1:(1-9), and the mass ratio of the comonomer to the initiator is 100:(0.1-3.5); when the reaction liquid is a binary copolymer system, the mass ratio of acrylonitrile:the second monomer is (85-99.9):(0.1-15); when the reaction liquid is a ternary copolymer system, the mass ratio of acrylonitrile:the second monomer is (85-99.8):(0.1-10):(0.1-6); 2) The reaction liquid is loaded into a raw material tank, and enters a microchannel reactor with an inner diameter of 0.1-250 mm and a length of 1-1000 m under the action of a feed pump. After the reaction is complete, a polymerization liquid of polyacrylonitrile is obtained. After precipitation, filtration, washing and drying, the polymerization liquid is obtained to obtain the polyacrylonitrile resin.

2. The continuous preparation method of polyacrylonitrile resin according to claim 1, characterized in that: The second monomer is one of alkyl acrylate, alkyl methacrylate, vinyl acetate, vinyl propionate, styrene, vinyl chloride, vinyl dichloride or a mixture thereof, and the third monomer is one of itaconic acid and its derivatives, acrylic acid, methacrylic acid, maleic anhydride or a mixture thereof.

3. The continuous preparation method of polyacrylonitrile resin according to claim 1, characterized in that: The solvent for the polymerization reaction is one or more of dimethyl sulfoxide, N,N-dimethylformamide and N,N-dimethylacetamide.

4. The continuous preparation method of polyacrylonitrile resin according to claim 1, characterized in that: The initiator of the polymerization reaction is one or two of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate and azoisobutylcyanamide.

5. The continuous preparation method of polyacrylonitrile resin according to claim 1, characterized in that: The reaction temperature of the microchannel reactor is 40-200° C., the reaction pressure is 0.1-5.0 MPa, and the residence time is 1-120 min.

6. The continuous preparation method of polyacrylonitrile resin according to claim 1 or 2, characterized in that: The binary copolymer system is a copolymer system of acrylonitrile and methyl acrylate, and the ternary copolymer system is a copolymer system of acrylonitrile, methyl acrylate and itaconic acid.

7. The continuous preparation method of polyacrylonitrile resin according to claim 1, characterized in that: The mass ratio of the comonomer to the solvent is (33-153):187, the mass ratio of the comonomer to the initiator is 100:(0.5-3.5), in the binary copolymer system, the mass ratio of acrylonitrile:the second monomer is (90-99):(1-10), and in the ternary copolymer system, the mass ratio of acrylonitrile:the second monomer:the third monomer is (90-99):(0.2-7):(0.1-5).

8. The continuous preparation method of polyacrylonitrile resin according to claim 3, characterized in that: The solvent for the polymerization reaction is dimethyl sulfoxide.

9. The continuous preparation method of polyacrylonitrile resin according to claim 4, characterized in that: The initiator of the polymerization reaction is azobisisobutyronitrile.

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