Copolymer microspheres and methods for making the same

Abstract

The present application relates to the field of polymer synthesis, and discloses a kind of copolymer microspheres and its preparation method, after the mixed solution of polymer monomer, initiator is dissolved in organic solvent to obtain in protective atmosphere, polymerization reaction is carried out, and the copolymer emulsion suspension obtained is separated to obtain the copolymer microspheres;Polymer monomer is monomer I shown in formula (I), monomer II shown in formula (II) and monomer III shown in formula (III);Organic solvent is compound shown in formula (IV);With the total molar amount of polymer monomer as benchmark, the amount of monomer I is 27-48mol%, the amount of monomer II is 27-48mol%, and the amount of monomer III is 9-45mol%.The yield of the copolymer microspheres of the preparation method is high, the surface of the obtained copolymer microspheres is clean and pollution-free, the morphology is excellent, and has good uniformity.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis, and more specifically, to a copolymer microsphere and its preparation method. Background Technology

[0002] Traditional methods for preparing polymer microspheres include emulsion polymerization, suspension polymerization, soap-free emulsion polymerization, dispersion polymerization, and precipitation polymerization. Emulsion polymerization, suspension polymerization, and dispersion polymerization typically require the addition of emulsifiers, stabilizers, and other additives to the reaction system to achieve the preparation of polymer microspheres and their stability in the dispersion medium. These additives can have negative effects in certain applications and need to be removed. Soap-free emulsion polymerization and precipitation polymerization can prepare polymer microspheres without the addition of external stabilizing agents. Soap-free emulsion polymerization is usually carried out in an aqueous system and requires the participation of special initiators or comonomers to achieve microsphere preparation and stabilization. Precipitation polymerization is another polymerization method for preparing polymer microspheres. Traditional precipitation polymerization usually involves a low concentration of monomers, resulting in low efficiency in preparing polymer microspheres. Self-stabilizing precipitation polymerization is a novel method for preparing polymer microspheres. The choice of dispersion medium is crucial to the formation, morphology, particle size, and stability of the microspheres. Commonly used solvents include mixed solvents of organic acid alkyl esters, ketones and alkanes, or mixed solvents of ketones and other organic media (Chen Dong et al. Principles, methods and applications of self-stabilizing precipitation polymerization, Science in China: Chemistry, 2020, Vol. 50, No. 7: 732-742). The choice of solvent has a significant impact on the properties of the microspheres and the preparation process, and is also important for the stability of the process and subsequent drying (Zhu Xiaoli et al. Exploring the boundary conditions for the precipitation polymerization of TMPTA-St in ethanol-water mixed solvent to form monodisperse polymer microspheres based on Hansen three-dimensional solubility parameters, Acta Polymerica Sinica, 2013, 8: 1099-1107).

[0003] Existing technologies often employ ester solvents containing alkyl esters of organic acids, which typically have an odor. This odor is present in both the production environment and the resulting products. Using mixed solvents as dispersion media requires careful control of the solvent composition, complicating process control and resulting in low yields of copolymerized microspheres, which also increases manufacturing costs to some extent. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of complex process and low yield of copolymer microspheres caused by using mixed solvents as dispersion media, and to provide copolymer microspheres and their preparation method. The copolymer microspheres prepared by this method have a high yield, and the obtained copolymer microspheres have a clean and uncontaminated surface, excellent morphology, and good uniformity.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing copolymer microspheres, wherein the preparation method includes: dissolving a polymeric monomer and an initiator in an organic solvent in a protective atmosphere to obtain a mixed solution, and then carrying out a polymerization reaction, and separating the resulting copolymer emulsion suspension to obtain the copolymer microspheres;

[0006] The polymer monomers are monomer I as shown in formula (I), monomer II as shown in formula (II), and monomer III as shown in formula (III);

[0007]

[0008] Where R1 is H or C 1-5 The alkyl group; R2, R3 and R4 are each independently H, methyl or ethyl; R5 and R6 are each independently H or C. 1-3 Alkyl groups;

[0009] The organic solvent is a compound represented by formula (IV);

[0010]

[0011] Among them, R7 and R8 are independently H and C. 1-10 At least one of alkyl, phenyl and benzyl groups, and R7 and R8 are not both H;

[0012] Based on the total molar amount of the polymerizable monomers, the amount of monomer I is 27-48 mol%, the amount of monomer II is 27-48 mol%, and the amount of monomer III is 9-45 mol%.

[0013] A second aspect of the present invention provides a copolymer microsphere, wherein the copolymer microsphere is prepared by the above-described method for preparing copolymer microspheres.

[0014] Through the above technical solution, the copolymer microspheres and their preparation method provided by the present invention have the following beneficial effects.

[0015] This invention, by selecting a specific organic solvent and combining it with a specific amount of monomer, enables the polymerization reaction system to form a self-stabilizing system without the need for any stabilizers or co-stabilizers added during the polymerization process. The resulting copolymer microspheres are uniformly dispersed in the organic solvent without aggregation. The obtained copolymer microspheres have a clean, uncontaminated surface, excellent morphology, and good uniformity. This invention overcomes the problems of complex process control and increased manufacturing costs associated with using mixed solvents as dispersion media, which require controlling the solvent composition. Attached Figure Description

[0016] Figure 1This is the infrared spectrum of the copolymer microspheres from Example 1;

[0017] Figure 2 This is a scanning electron microscope image of the copolymer microspheres from Example 1. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The first aspect of the present invention provides a method for preparing copolymer microspheres, wherein the preparation method includes: dissolving a polymeric monomer and an initiator in an organic solvent in a protective atmosphere to obtain a mixed solution, and then carrying out a polymerization reaction, and separating the resulting copolymer emulsion suspension to obtain the copolymer microspheres;

[0020] The polymer monomers are monomer I as shown in formula (I), monomer II as shown in formula (II), and monomer III as shown in formula (III);

[0021]

[0022] Where R1 is H or C 1-5 The alkyl group; R2, R3 and R4 are each independently H, methyl or ethyl; R5 and R6 are each independently H or C. 1-3 Alkyl groups;

[0023] The organic solvent is a compound represented by formula (IV);

[0024]

[0025] Among them, R7 and R8 are independently H and C. 1-10 At least one of alkyl, phenyl and benzyl groups, and R7 and R8 are not both H;

[0026] Based on the total molar amount of the polymerizable monomers, the amount of monomer I is 27-48 mol%, the amount of monomer II is 27-48 mol%, and the amount of monomer III is 9-45 mol%.

[0027] In this invention, by selecting a specific organic solvent and combining it with a specific amount of monomer, the polymerization reaction system can form a self-stabilizing system without the need to add any stabilizers or co-stabilizers during the polymerization process. The resulting copolymer microspheres are uniformly dispersed in the organic solvent, and no aggregation occurs between the microspheres. The obtained copolymer microspheres have a clean, uncontaminated surface, excellent morphology, and good uniformity. This invention overcomes the problems of complex process control and increased manufacturing costs associated with using mixed solvents as dispersion media, which require controlling the solvent composition.

[0028] In this invention, the total amount of monomer I, monomer II, and monomer III is 100 mol%.

[0029] Furthermore, R1 is H or C. 1-3 Alkyl groups.

[0030] Furthermore, in equation (IV), R7 is C 1-4 Alkyl or phenyl, R8 is C 1-7 Alkyl groups.

[0031] Furthermore, the organic solvent is selected from at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and methyl butyl carbonate.

[0032] In this invention, when the above-mentioned organic solvent is used, the obtained copolymer microspheres have no special odor.

[0033] Furthermore, based on the total molar amount of the polymerizable monomers, the amount of monomer I is 35-47 mol%, the amount of monomer II is 35-47 mol%, and the amount of monomer III is 9-25 mol%.

[0034] According to a preferred embodiment of the present invention, the molar ratio of monomer I to monomer II is 0.9-1.1:1.

[0035] In this invention, when the amounts of monomer I and monomer II meet the above-mentioned range, it is more beneficial to obtain copolymer microspheres with good uniformity.

[0036] According to the present invention, the mass-to-volume ratio of the polymeric monomer to the organic solvent is 0.1-0.3 g / mL.

[0037] In this invention, when the mass of the polymerizing monomer and the amount of the organic solvent meet the above-mentioned range, the polymerization reaction is stable and controllable, and the resulting milky white dispersion system has good stability and is not easy to settle, which is conducive to obtaining copolymer microspheres with high uniformity.

[0038] Furthermore, the mass-to-volume ratio of the polymeric monomer to the organic solvent is 0.1-0.2 g / mL.

[0039] According to the present invention, the initiator is an organic peroxide and / or an azo compound.

[0040] Further, the organic peroxide is selected from at least one of benzoyl peroxide, dicumyl peroxide, ditert-butyl peroxide, dodecyl peroxide, tert-butyl peroxide, diisopropyl peroxide, and dicyclohexyl peroxide.

[0041] Furthermore, the azo compound is azobisisobutyronitrile and / or azobisisoheptanenitrile.

[0042] According to the present invention, the content of the initiator is 0.1 wt% to 5 wt%, based on the total weight of the polymerizing monomer and the initiator.

[0043] Furthermore, based on the total weight of the polymerizing monomer and the initiator, the content of the initiator is 0.3wt%-3.5wt%.

[0044] Furthermore, based on the total weight of the polymerizing monomer and the initiator, the content of the initiator is 0.3wt%-1wt%.

[0045] According to the present invention, the polymerization reaction temperature is 45-120°C and the polymerization reaction time is 3-20h.

[0046] Furthermore, the polymerization reaction is carried out at a temperature of 50-90°C for 3-8 hours.

[0047] In this invention, the protective atmosphere is not particularly limited and can be provided by conventional protective gases in the prior art, such as nitrogen.

[0048] In this invention, a water bath and / or an oil bath are used to provide the heat required for polymerization.

[0049] In this invention, the separation can be a conventional solid-liquid separation method in the art, such as centrifugation or filtration.

[0050] In this invention, when centrifugation is used, the centrifugation speed is 2000-10000 rad / min and the centrifugation time is 5-40 min.

[0051] A second aspect of the present invention provides a copolymer microsphere, wherein the copolymer microsphere is prepared by the above-described method for preparing copolymer microspheres.

[0052] In this invention, the obtained copolymer microspheres have a clean and uncontaminated surface and good uniformity.

[0053] According to the present invention, the copolymer microspheres include structural unit A shown in formula (1), structural unit B shown in formula (2) and structural unit C shown in formula (3);

[0054]

[0055] Where R1' is H or C 1-5 The alkyl group; R2', R3' and R4' are each independently H, methyl or ethyl; R5' and R6' are each independently H or C. 1-3 Alkyl groups.

[0056] Furthermore, R1' is H or C. 1-3 Alkyl groups.

[0057] According to the present invention, based on the total molar amount of each structural unit in the copolymer, the molar content of structural unit A is 27-48 mol%, the molar content of structural unit B is 27-48 mol%, and the molar content of structural unit C is 9-45 mol%.

[0058] Furthermore, based on the total molar amount of each structural unit in the copolymer, the molar content of structural unit A is 35-47 mol%, the molar content of structural unit B is 35-47 mol%, and the molar content of structural unit C is 9-25 mol%.

[0059] According to a preferred embodiment of the present invention, the molar ratio of structural unit A to structural unit B is 0.9-1.1:1.

[0060] According to the present invention, the average particle size of the copolymer microspheres is 200-1800 nm.

[0061] Furthermore, the average particle size of the copolymer microspheres is 200-1500 nm.

[0062] According to the present invention, the particle size distribution coefficient of the copolymer microspheres is 1.01-1.2.

[0063] Furthermore, the particle size distribution coefficient of the copolymer microspheres is 1.02-1.1.

[0064] The present invention will be described in detail below through examples. In the following examples, the polymerization yield (C) is calculated according to the following formula. p ) perform calculations

[0065] C p =Mp×100% / Mm

[0066] Where Mp is the mass of the obtained polymer; Mm is the total mass of the added monomers.

[0067] The morphology and size of the copolymer microspheres were observed and measured using scanning electron microscopy (SEM).

[0068] The infrared spectrum of the copolymer was measured using FI-IR.

[0069] The particle size distribution coefficient was determined by analyzing SEM images using image analysis software. The calculation method for the particle size distribution coefficient is as follows:

[0070] Number-average particle size is,

[0071] Where n is the number of particles, and di is the particle size of the i-th particle;

[0072] The weight-average particle size is,

[0073] Where n is the number of particles, and di is the particle size of the i-th particle;

[0074] The particle size distribution coefficient is P = Dw / Dn.

[0075] The content of each structural unit in the copolymer is obtained by analyzing the composition of the solution after polymerization and then calculating the content of each monomer.

[0076] Monomer I, having the structure shown in formula (I), was purchased from Bailingwei Technology Co., Ltd.

[0077] Monomer II has the structure shown in formula (II), where R1 is H, and is purchased from Bailingwei Technology Co., Ltd.

[0078] Monomer III, having the structure shown in formula (III), wherein R2 is H, R3 is H, R4 is H, R5 is H, and R6 is H, was purchased from Bailingwei Technology Co., Ltd.

[0079] Example 1

[0080] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 3.9 g of comonomer III, and 100 mL of dimethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 5000 rad / min for 20 minutes to obtain 13.3 g of polymer microspheres A1, corresponding to a polymer yield of 95%. The particle size of the polymer microspheres was 320 nm.

[0081] Example 2

[0082] 7.35 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 7.8 g of comonomer II, 5.9 g of comonomer III, and 100 mL of dimethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 67 °C water bath for polymerization for 9 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 6000 rad / min for 20 minutes to obtain 18.9 g of polymer microspheres A2, corresponding to a polymer yield of 94.3%. The particle size of the polymer microspheres was 735 nm.

[0083] Example 3

[0084] 7.35 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 7.8 g of comonomer II, 1.95 g of comonomer III, and 100 mL of dimethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 6 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 4000 rad / min for 20 minutes to obtain 15.7 g of polymer microspheres A3, corresponding to a polymer yield of 91.8%. The particle size of the polymer microspheres was 1800 nm.

[0085] Example 4

[0086] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 1.3 g of comonomer III, and 100 mL of dimethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 5000 rad / min for 20 minutes to obtain 10.4 g of polymer microspheres A4, corresponding to a polymer yield of 91.2%. The particle size of the polymer microspheres was 1520 nm.

[0087] Example 5

[0088] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 2.6 g of comonomer III, and 100 mL of dimethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 5000 rad / min for 20 minutes to obtain 11.6 g of polymer microspheres A5, corresponding to a polymer yield of 91.3%. The particle size of the polymer microspheres was 1215 nm.

[0089] Example 6

[0090] 5.39 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 2.6 g of comonomer III, and 100 mL of dimethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 8000 rad / min for 20 minutes to obtain 11.4 g of polymer microspheres A6, corresponding to a polymer yield of 86.4%. The particle size of the polymer microspheres was 1210 nm.

[0091] Example 7

[0092] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile, 5.72 g of comonomer II, 2.6 g of comonomer III, and 100 mL of dimethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The three-necked flask was then placed in a 52 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 7000 rad / min for 20 minutes to obtain 11.5 g of polymer microspheres A7, corresponding to a polymer yield of 87%. The particle size of the polymer microspheres was 1225 nm.

[0093] Example 8

[0094] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 2.6 g of comonomer III, and 100 mL of methyl ethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 5000 rad / min for 20 minutes to obtain 11.7 g of polymer microspheres A8, corresponding to a polymer yield of 92.1%. The particle size of the polymer microspheres was 1180 nm.

[0095] Example 9

[0096] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 2.6 g of comonomer III, and 100 mL of methyl propyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 5000 rad / min for 20 minutes to obtain 11.8 g of polymer microspheres A9, corresponding to a polymer yield of 92.9%. The particle size of the polymer microspheres was 1150 nm.

[0097] Example 10

[0098] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 2.6 g of comonomer III, and 100 mL of methyl butyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 5000 rad / min for 20 minutes to obtain 11.8 g of polymer microspheres A10, corresponding to a polymer yield of 92.9%. The particle size of the polymer microspheres was 1150 nm.

[0099] Example 11

[0100] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 2.6 g of comonomer III, and 100 mL of dibutyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath and reacted for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 5000 rad / min for 20 minutes to obtain 11.7 g of polymer microspheres A1, corresponding to a polymer yield of 92.1%. The particle size of the polymer microspheres was 1135 nm.

[0101] Example 12

[0102] 3.5 g of comonomer I, 0.1 g of azobisisobutyronitrile (AIBN), 5.2 g of comonomer II, 2.6 g of comonomer III, and 100 mL of dimethyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The flask was then placed in a 70 °C water bath for polymerization for 5 hours. After the reaction was completed, the resulting polymer emulsion suspension was centrifuged at 5000 rad / min for 20 minutes to obtain 8 g of polymer microspheres A2, corresponding to a polymer yield of 70.7%. The particle size of the polymer microspheres was 451 nm.

[0103] Comparative Example 1

[0104] 4.9g of comonomer I, 0.1g of azobisisobutyronitrile, 5.2g of comonomer II, 12g of comonomer III and 100mL of methyl propyl carbonate were added to a 250mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The three-necked flask was then placed in a 70℃ water bath and reacted for 5 hours. After the reaction was completed, the system became a solid and a dispersion of polymer microspheres could not be obtained.

[0105] Comparative Example 2

[0106] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile, 5.2 g of comonomer II, 0.4 g of comonomer III and 100 mL of methyl propyl carbonate were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The three-necked flask was then placed in a 70 °C water bath and reacted for 5 hours. After the reaction was completed, the system became a viscous liquid and a dispersion of polymer microspheres could not be obtained.

[0107] Comparative Example 3

[0108] 4.9 g of comonomer I, 0.1 g of azobisisobutyronitrile, 5.2 g of comonomer II, 1.3 g of comonomer III and 100 mL of NN-dimethylformamide were added to a 250 mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The three-necked flask was then placed in a 70 °C water bath and reacted for 5 hours. After the reaction was completed, the system was a transparent solution and a dispersion of polymer microspheres could not be obtained.

[0109] Comparative Example 4

[0110] 4.9g of comonomer I, 0.1g of azobisisobutyronitrile, 5.2g of comonomer II, 2.6g of comonomer III, 10mL of acetone and 90mL of toluene were added to a 250mL three-necked flask. After the materials were mixed evenly, nitrogen gas was purged for 20 minutes. The three-necked flask was then placed in a 70℃ water bath and the polymerization reaction was carried out for 5 hours. After the reaction was completed, the system was solidified and a dispersion of polymer microspheres could not be obtained.

[0111] Table 1

[0112]

[0113]

[0114] Continued from Table 1

[0115]

[0116] Continued from Table 1

[0117]

[0118]

[0119] The results show that the preparation method of the present invention yields high copolymer microspheres and produces products with uniform particle size.

[0120] Depend on Figure 1 It can be known that 1786cm -1 1890cm -1 The characteristic absorption peak of the anhydride group is 709 cm⁻¹. -1The absorption peak of the phenyl functional group indicates that the polymer prepared in Example 1 contains maleic acid structural units, styrene structural units, and divinylbenzene structural units.

[0121] Figure 2 The image shows an SEM image of the copolymer microspheres from Example 1. As can be seen from the image, the copolymer microspheres are uniform in size and the particle surfaces are clean and uncontaminated.

[0122] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the preparation of copolymeric microspheres, characterized in that, The preparation method comprises: dissolving polymer monomers and an initiator in an organic solvent to obtain a mixed solution in a protective atmosphere, and then performing a polymerization reaction to obtain a copolymer microsphere. The polymer monomers are monomer I shown in formula (I), monomer II shown in formula (II) and monomer III shown in formula (III). Formula (I); Formula (II); Formula (III); wherein R1is H or C 1-5 alkyl; R2, R3, and R4are each independently H, methyl, or ethyl; R5and R6are each independently H or C 1-3 alkyl; The organic solvent is a compound shown in formula (IV). Formula (IV); wherein R7and R8are each independently C 1-10 alkyl; The amount of the monomer I is 27-48 mol%, the amount of the monomer II is 27-48 mol%, and the amount of the monomer III is 9-45 mol% based on the total molar amount of the polymer monomers. The molar ratio of the monomer I to the monomer II is 0.9-1.1:

1. The mass-volume ratio of the polymer monomers to the organic solvent is 0.1-0.2 g / mL.

2. The production method according to claim 1, wherein R1is H or C 1-3 alkyl.

3. The production method according to claim 1, wherein In the formula (IV), R7is an alkyl group or a phenyl group, and R8is an alkyl group. 1-4 In the formula (IV), R7is an alkyl group or a phenyl group, and R8is an alkyl group. 1-7 In the formula (IV), R7is an alkyl group or a phenyl group, and 4. The production method according to claim 3, wherein The organic solvent is at least one selected from dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate and methyl butyl carbonate.

5. The production method according to claim 1 or 2, wherein The amount of the monomer I is 35-47 mol%, the amount of the monomer II is 35-47 mol%, and the amount of the monomer III is 9-25 mol% based on the total molar amount of the polymer monomers.

6. The production method according to claim 1, wherein The initiator is an organic peroxide and / or an azo compound.

7. The production method according to claim 6, wherein The organic peroxide is at least one selected from dibenzoyl peroxide, dicumyl peroxide, ditert-butyl peroxide, dilauryl peroxide, tert-butyl peroxybenzoate, diisopropyl peroxydicarbonate and dicyclohexyl peroxydicarbonate.

8. The production method according to claim 6, wherein The azo compound is azobisisobutyronitrile and / or azobisisoheptyl nitrile.

9. The production method according to claim 1, wherein The content of the initiator is 0.1wt%-5wt% based on the total weight of the polymer monomers and the initiator.

10. The production method according to claim 9, wherein The content of the initiator is 0.3wt%-3.5wt% based on the total weight of the polymer monomers and the initiator.

11. The production method according to claim 10, wherein The content of the initiator is 0.3wt%-1wt% based on the total weight of the polymer monomers and the initiator.

12. The method of producing according to claim 1, wherein, The temperature of the polymerization reaction is 45-120℃, and the polymerization reaction time is 3-20h.

13. The method of making according to claim 12, wherein, The temperature of the polymerization reaction is 50-90℃, and the polymerization reaction time is 3-8h.

14. The method of producing according to claim 1, wherein, The copolymer microspheres comprise structural unit A shown in formula (1), structural unit B shown in formula (2) and structural unit C shown in formula (3). Formula (1); Formula (2); Formula (3); wherein R1' is H or C 1-5 alkyl; R2', R3', and R4' are each independently H, methyl, or ethyl; R5' and R6' are each independently H or C 1-3 alkyl.

15. The method of making according to claim 14, wherein, R1' is H or C 1-3 alkyl.

16. The method of making according to claim 14, wherein, The molar content of the structural unit A is 27-48 mol%, the molar content of the structural unit B is 27-48 mol%, and the molar content of the structural unit C is 9-45 mol% based on the total molar amount of the structural units in the copolymer.

17. The method of making according to claim 16, wherein, The molar content of the structural unit A is 35-47 mol%, the molar content of the structural unit B is 35-47 mol%, and the molar content of the structural unit C is 9-25 mol% based on the total molar amount of the structural units in the copolymer.

18. The method of making according to claim 14, wherein, The molar ratio of the structural unit A to the structural unit B is 0.9-1.1:

1.

19. The method of producing according to claim 1, wherein, The average particle size of the copolymer microspheres is 200-1800nm.

20. The method of making according to claim 19, wherein, The average particle size of the copolymer microspheres is 200-1500nm.

21. The method of producing according to claim 1, wherein, The particle size dispersion coefficient of the copolymer microspheres is 1.01-1.

2.

22. The method of making according to claim 21, wherein, The particle size dispersion coefficient of the copolymer microspheres is 1.02-1.1.

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