Preparation method for improving hydroxyl value of liquid rubber

Abstract

The invention discloses a preparation method for increasing the hydroxyl value of liquid rubber, which comprises the following steps: replacing a polymerization kettle with inert atmosphere gas, maintaining micro-positive pressure, sequentially adding a solvent, a regulator, a monomer and an initiator into the polymerization kettle, carrying out first reaction, adding an acidifying agent, adding an oxidizing agent, and carrying out second reaction, and after the reaction is finished, washing, vacuumizing to remove the solvent, and drying to obtain the polyhydroxy liquid rubber. According to the preparation method, the hydroxyl value of the liquid rubber can be increased, and the problem that the hydroxyl value content of the hydroxyl-terminated liquid rubber prepared by an anion solution method is low is solved.

Description

Technical Field

[0001] This invention belongs to the field of liquid rubber preparation, specifically relating to the preparation of conjugated diene liquid rubber by anionic solution method. Background Technology

[0002] Butadiene homopolymers or copolymers are among the most industrially mature types of polymers. Based on molecular weight, they are generally classified into solid rubbers or elastomers, such as polybutadiene rubber, styrene-butadiene rubber, and styrene-butadiene-styrene elastomers, as well as liquid rubbers, such as liquid polybutadiene rubber and liquid styrene-butadiene rubber.

[0003] Liquid rubber is commonly used in adhesives, modifiers, sealants, circuit board adhesives, rocket propellants, etc. Depending on its application, liquid rubber generally requires functionalization modification. Liquid polybutadiene rubber can be classified according to the type of functional groups into hydroxyl-terminated liquid polybutadiene rubber (HTPB), carboxyl-terminated liquid polybutadiene rubber (CTPB), hydroxyl-carboxyl-terminated liquid polybutadiene rubber (HCTPB), and epoxidized, amination-modified, and hydrogenated liquid rubbers. These terminally functionalized products are produced using two methods: free radical method and anionic method. The free radical method is simpler, but the product has a disordered microstructure, low functionality, and a wide molecular weight distribution. The anionic method is more complex, requires high-purity raw materials, and generally requires a dilithium initiator or a functionally protected alkyllithium initiator, resulting in higher costs. However, the product has a controllable microstructure, high functionality, narrow molecular weight distribution, and fewer impurities.

[0004] Liquid rubber was initially mainly used in the aerospace field, but with the research on liquid rubber application technology, its application field has gradually expanded to civilian use. Anionic solution polymerization, as one of the methods for preparing liquid rubber, has obvious advantages over free radical polymerization: (1) the polymer has good monodispersity, with a dispersion index close to 1.0; (2) the polymer molecular weight is controllable, and polymers with different molecular weights can be obtained by controlling the ratio of initiator and monomer; (3) the microstructure is tunable, and the microstructure of the polymer can be controlled by adjusting the initiator concentration, solvent polarity, and reaction temperature, and products with different properties can be obtained; (4) some functional polymers and block polymers can be synthesized conveniently and effectively. However, anionic polymerization also has obvious disadvantages: (1) the reaction conditions are strict and need to be carried out under completely anhydrous and oxygen-free conditions, which is difficult to operate and produce; (2) the price of bis-lithium initiators is high and they are difficult to store. At present, there are three main methods for synthesizing functionalized liquid rubber by anionic polymerization: one is the bis-lithium initiator method; the second is the oligomer bis-lithium initiator method; and the third is the method using a single lithium initiator with a protecting group. Currently, the hydroxyl functionality of hydroxyl-terminated liquid butadiene rubbers prepared via this route does not exceed 2.0. However, for hydroxyl-terminated liquid butadiene-modified polyurethanes, a higher hydroxyl functionality is desirable. This would generate more network-like urethane bonds in the polyurethane molecule structure formed with polyisocyanates, increasing intermolecular cohesion, improving tear strength, and giving the polyurethane higher mechanical abrasion resistance, toughness, hydrolysis resistance, and hydrophobicity when used as a coating material. Therefore, developing multi-hydroxyl liquid rubbers with a functionality exceeding 2 has broad application prospects.

[0005] Chinese patent CN101274972A discloses a method for preparing hydroxyl-terminated polybutadiene liquid rubber. This method uses an aliphatic alkyl lithium initiator with a silane protecting group, a non-polar solvent, and an epoxy compound as the end-capping agent. The mixture undergoes anionic polymerization followed by acid hydrolysis to obtain a series of hydroxyl-terminated polybutadiene liquid rubbers with narrow molecular weight distributions and controllable molecular weight. The average functionality of the hydroxyl-terminated polybutadiene liquid rubber prepared by this method is close to 2. However, the use of an epoxy compound as the end-capping agent results in low end-capping efficiency, leading to a low hydroxyl content.

[0006] Chinese patent CN113461837A discloses a method for preparing low-cis, high-vinyl-terminated hydroxyl-containing polybutadiene rubber. The preparation method includes the following steps: (1) preparation of a bifunctional initiator: reacting a bifunctional conjugated olefin with an alkali metal alkyl compound to obtain a bifunctional initiator; (2) preparation of active polybutadiene; (3) termination of polymerization by ring-opening reaction; (4) hydrolysis to obtain an alkaline hydroxyl-terminated polybutadiene solution; (5) alkaline neutralization by introducing carbon dioxide to obtain hydroxyl-terminated polybutadiene. The hydroxyl-terminated polybutadiene rubber obtained by the preparation method of this invention has a functionality of 1.8-2.1. However, this method uses a bifunctional initiator, so a bifunctional initiator needs to be prepared in the first step; in addition, this method uses ethylene oxide as a capping agent, but its capping efficiency is not high, resulting in a low hydroxyl content.

[0007] Chinese patent CN105601770A discloses a polyhydroxy polybutadiene liquid rubber and its controllable preparation method. This method prepares the polyhydroxy polybutadiene liquid rubber from commercially available cis-butadiene rubber via oxidative pyrolysis and reduction. The number-average molecular weight can be adjusted between 1000-15000 g / mol, the molecular weight distribution is between 1.2-3.0, the cis-1,4 content is greater than 90%, the glass transition temperature is -100 to -80℃, and the hydroxyl functionality is between 5 and 30. However, this method uses oxidative pyrolysis, resulting in a wide molecular weight range and making precise control of the polymer's microstructure impossible.

[0008] Chinese patent CN112979852A discloses a method for preparing high-functionality hydroxyl-terminated polybutadiene. The method involves reacting butadiene with a short-chain initiator in a polar solvent at 30–50°C for 3–5 hours, then lowering the temperature to 5–10°C. A sodium dodecyl oxide solution is then added, and the reaction continues for 1–1.5 hours. Ethylene oxide is then added, and the reaction continues at 0–10°C for 2–4 hours. Finally, acidification yields hydroxyl-terminated polybutadiene. The short-chain initiator is a bifunctional oligomeric isoprene dilithium. However, this method uses a bifunctional initiator; furthermore, while ethylene oxide is used as the end-capping agent, its end-capping efficiency is low, resulting in a low hydroxyl content. Summary of the Invention

[0009] The technical problem to be solved by this invention is the low hydroxyl content of terminal hydroxyl liquid rubber prepared by anionic solution method.

[0010] To solve the above-mentioned technical problems, the present invention provides a method for preparing liquid rubber with improved hydroxyl value, the method comprising the following steps:

[0011] The polymerization reactor was purged with an inert atmosphere to maintain a slight positive pressure. Solvent, regulator, monomer and initiator were added to the polymerization reactor in sequence to carry out the first reaction. Then an acidifier was added and an oxidant was added to carry out the second reaction. After the reaction was completed, the reactor was washed, vacuumed to remove the solvent and dried to obtain polyhydroxy liquid rubber.

[0012] In the preparation method of the present invention, preferably, the functionality of the polyhydroxy liquid rubber is greater than 2.

[0013] The preparation method of the present invention preferably adopts an anionic solution method, wherein the solvent is a nonpolar solvent, selected from at least one of hexaane, cyclohexane, cyclopentane, benzene, toluene, and tetrahydrofuran.

[0014] In the preparation method of the present invention, preferably, the initiator is selected from at least one of n-butyllithium, sec-butyllithium, and tert-butyllithium;

[0015] The molar ratio of the initiator to the monomer is 0.01-0.1:1.0.

[0016] In the preparation method of the present invention, preferably, the molar ratio of the initiator to the monomer is 0.015-0.03:1.0. In the preparation method of the present invention, preferably, the regulator is a Lewis base selected from at least one of the following: diethyl ether, anisole, dioxane, tetrahydrofuran, tetrahydrofurfuryl ether, dimethoxyethane (DME), diethylene glycol dimethyl ether (2G), tetramethylvinyldiamine (TMEDA), triethylamine, pentamethyldiethyltriamine (PMDETA), hexamethylphosphoryltriamine (HMPTA), dipiperidine ethane, dimorphidine ethane, 1,4-dichlorobenzenebicyclo[2,2,2]octane, 2,2-bis-(4,4,6-trimethyl-1,3-dichlorohexane) (DIDIOX), functional ethers, and cryptanes.

[0017] The molar ratio of the regulator to the monomer is 0.001-0.2:1.0.

[0018] In the preparation method of the present invention, preferably, the acidifying agent is at least one of formic acid and acetic acid;

[0019] The molar ratio of the acidifier to the monomer is 0.01-0.5:1.0.

[0020] In the preparation method of the present invention, preferably, the oxidant is hydrogen peroxide;

[0021] The molar ratio of the oxidant to the monomer is 0.01-0.5:1.0.

[0022] In the preparation method of the present invention, preferably, the monomer is at least one selected from butadiene, isoprene, and styrene;

[0023] The mass of the monomer is 1-30% of the mass of the solvent.

[0024] In the preparation method of the present invention, preferably, the inert atmosphere gas is selected from at least one of nitrogen and argon.

[0025] In the preparation method of the present invention, preferably, the temperature of the first reaction is 10-80℃ and the time is 10-200 minutes.

[0026] In the preparation method of the present invention, preferably, the temperature of the second reaction is 10-60℃ and the time is 0.5-5 hours.

[0027] Compared with the prior art, the preparation method of the present invention firstly does not require the preparation of a multifunctional initiator to obtain a multihydroxyl polymer, and secondly does not require end-capping with an epoxy compound. The prepared liquid rubber has a hydroxyl functionality greater than 2 and has a high hydroxyl value. The 1,2-structure content in the microstructure of the liquid rubber molecule prepared by the method of the present invention is controllable. Detailed Implementation

[0028] The examples below are selected to further illustrate the method of the present invention, but should not be limited to them in practical applications. Evaluation and analysis methods:

[0029] The hydroxyl content was determined using the acetic anhydride method;

[0030] Functionality (f) = number of moles of functional groups per gram of polymer / number of moles of polymer per gram.

[0031] Example 1

[0032] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. Then, 3600 g of hexane, 0.5 mol of tetrahydrofuran (a regulator), 400 g of butadiene, and 0.13 mol of n-butyllithium were added to the reactor sequentially. The temperature was raised to 40 °C to start the reaction, which lasted for 2 hours. Then, 1.5 mol of formic acid was added, followed by 1.6 mol of hydrogen peroxide. After reacting for 4 hours, the temperature was lowered, and the reactor was washed three times with deionized water. A sample was then taken, vacuumed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0033] Example 2

[0034] At room temperature, the polymerization reactor was solvent-cleaned and purged three times with argon to maintain a slight positive pressure. Then, 3400 g of hexane, 0.75 mol of tetrahydrofurfuryl ether (THF) as a regulator, 600 g of butadiene, and 0.20 mol of sec-butyllithium were added to the reactor sequentially. The temperature was raised to 40 °C to start the reaction, and the reaction was carried out for 2 hours. Then, 2.25 mol of formic acid was added, followed by 2.4 mol of hydrogen peroxide. After reacting for 4 hours, the temperature was lowered, and the reactor was washed three times with deionized water. A sample was taken, vacuumed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0035] Example 3

[0036] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. 3200g of cyclopentane, 1mol of diethylene glycol dimethyl ether (DME) as a regulator, 800g of butadiene, and 0.26mol of sec-butyllithium were added sequentially to the polymerization reactor. The temperature was raised to 40℃ to start the reaction, which lasted for 2 hours. Then, 3.2mol of acetic acid was added, followed by 2.4mol of hydrogen peroxide. After reacting for 4 hours, the temperature was lowered, and the reactor was washed three times with deionized water. Samples were taken, vacuumed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0037] Example 4

[0038] At room temperature, the polymerization reactor was solvent-cleaned and purged three times with argon gas to maintain a slight positive pressure. 3600 g of cyclopentane, 0.5 mol of tetramethylvinyldiamine (a regulator), 300 g of butadiene, 100 g of styrene, and 0.13 mol of n-butyllithium were added sequentially to the polymerization reactor. The temperature was raised to 40 °C to start the reaction, which lasted for 2 hours. Then, 2.25 mol of acetic acid was added, followed by 2.4 mol of hydrogen peroxide. After reacting for 4 hours, the temperature was lowered, and the reactor was washed three times with deionized water. Samples were taken, vacuumed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0039] Example 5

[0040] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. 3400 g of cyclohexane, 0.75 mol of tetrahydrofurfuryl ether (THF) as a regulator, 450 g of butadiene, 150 g of styrene, and 0.2 mol of tert-butyllithium were added sequentially to the reactor. The temperature was raised to 10 °C to initiate the reaction, which lasted 200 minutes. 4.5 mol of formic acid was added, followed by dropwise addition of 2.4 mol of hydrogen peroxide. After reacting for 4 hours, the temperature was lowered, and the reactor was washed three times with deionized water. A sample was then taken, vacuum-sealed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0041] Example 6

[0042] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. 3400 g of benzene, 1 mol of tetrahydrofurfuryl ether (THF) as a regulator, 400 g of butadiene, 200 g of styrene, and 0.26 mol of tert-butyllithium were added sequentially to the reactor. The temperature was raised to 80 °C to initiate the reaction. After 30 minutes, 6.75 mol of formic acid was added, followed by the dropwise addition of 1.14 mol of hydrogen peroxide. After reacting for 2 hours, the temperature was lowered, and the reactor was washed three times with deionized water. A sample was then taken, vacuum-sealed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0043] Example 7

[0044] At room temperature, the polymerization reactor was solvent-cleaned and purged three times with argon gas to maintain a slight positive pressure. Toluene 3600g, regulator 0.5mol, butadiene 400g, and n-butyllithium 0.13mol were added sequentially to the polymerization reactor. The temperature was raised to 40℃ to start the reaction, and the reaction was carried out for 1.5 hours. Formic acid 1.5mol was added, and hydrogen peroxide 1.6mol was added dropwise. After reacting for 4 hours, the temperature was lowered, and the reactor was washed three times with deionized water. A sample was taken, vacuumed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0045] Example 8

[0046] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. 3400 g of tetrahydrofuran, 0.75 mol of dimethoxyethane (a regulator), 600 g of butadiene, and 0.2 mol of n-butyllithium were added sequentially to the reactor. The temperature was raised to 40 °C to initiate the reaction. After 2 hours of reaction, 2.25 mol / mL of formic acid was added, followed by dropwise addition of 2.4 mol of hydrogen peroxide. After reacting for 4 hours, the temperature was lowered, and the reactor was washed three times with deionized water. A sample was then taken, vacuum-sealed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0047] Example 9

[0048] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. 3200 g of cyclopentane, 1 mol / mL of triethylamine as a regulator, 800 g of butadiene, and 0.26 mol of n-butyllithium were added sequentially to the polymerization reactor. The temperature was raised to 40 °C to start the reaction. After 2 hours of reaction, 3 mol / mL of acetic acid was added, followed by the dropwise addition of 3.2 mol of hydrogen peroxide. After 4 hours of reaction, the temperature was lowered, and the reactor was washed three times with deionized water. Samples were taken, vacuumed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0049] Example 10

[0050] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. 3400 g of cyclopentane, 0.75 mol of tetrahydrofurfuryl ether (THF) as a regulator, 450 g of butadiene, 150 g of styrene, and 0.2 mol of n-butyllithium were added sequentially to the reactor. The temperature was raised to 40 °C to initiate the reaction. After 2 hours of reaction, 2.25 mol of acetic acid was added, followed by dropwise addition of 2.4 mol of hydrogen peroxide. After 4 hours of reaction, the temperature was lowered, and the reactor was washed three times with deionized water. A sample was then taken, vacuum-sealed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0051] Example 11

[0052] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. Then, 3200g of hexane, 1mol of tetrahydrofurfuryl ether (THF) as a regulator, 400g of butadiene, 200g of styrene, and 0.26mol of n-butyllithium were added to the reactor sequentially. The temperature was raised to 40℃ to start the reaction. After 2 hours of reaction, 3mol of acetic acid was added, followed by 3.2mol of hydrogen peroxide. After 4 hours of reaction, the temperature was lowered, and the reactor was washed three times with deionized water. Samples were then taken, vacuumed to remove the solvent, dried, and their microstructure was analyzed.

[0053] Example 12

[0054] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. 3400 g of cyclopentane, 1 mol of tetrahydrofurfuryl ether (THF) as a regulator, 600 g of styrene, and 0.26 mol of tert-butyllithium were added sequentially to the reactor. The temperature was raised to 40 °C to start the reaction. After 2 hours of reaction, 6.75 mol of formic acid was added, followed by 1.14 mol of hydrogen peroxide. After another 2 hours of reaction, the temperature was lowered, and the reactor was washed three times with deionized water. Samples were taken, vacuumed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0055] Example 13

[0056] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. Then, 3400 g of hexane, 1 mol of tetrahydrofuran (a regulator), 600 g of isoprene, and 0.26 mol of tert-butyllithium were added to the reactor sequentially. The temperature was raised to 40 °C to start the reaction, and after 2 hours, 6.75 mol of formic acid was added, followed by 1.14 mol of hydrogen peroxide. After another 2 hours of reaction, the temperature was lowered, and the reactor was washed three times with deionized water. A sample was then taken, vacuumed to remove the solvent, and dried to obtain a polyhydroxy liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0057] Comparative Example 1

[0058] At room temperature, the polymerization reactor was solvent-cleaned and purged three times with argon to maintain a slight positive pressure. Then, 3400g of hexane, 0.75mol of tetrahydrofurfuryl ether (THF) as a regulator, 600g of butadiene, and 0.20mol of sec-butyllithium were added to the reactor sequentially. The temperature was raised to 40℃ to start the reaction. After 2 hours of reaction, 20ml of end-capping agent (ethylene oxide) was added. After 4 hours of reaction, 15ml of hydrochloric acid was added. After washing three times with deionized water, a sample was taken, vacuumed to remove the solvent, and dried to obtain liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0059] Comparative Example 2

[0060] At room temperature, the polymerization reactor was solvent-cleaned and purged with nitrogen three times to maintain a slight positive pressure. 3200g of cyclopentane, 1mol of diethylene glycol dimethyl ether (DME) regulator, 800g of butadiene, and 0.26mol of sec-butyllithium were added to the polymerization reactor sequentially. The temperature was raised to 40℃ to start the reaction. After 2 hours of reaction, 20ml of end-capping agent (ethylene oxide) was added. After 4 hours of reaction, 15ml of hydrochloric acid was added. After washing three times with deionized water, a sample was taken, vacuumed to remove the solvent, and dried to obtain liquid rubber. Its microstructure was analyzed, and the results are shown in Table 1.

[0061] Table 1

[0062]

[0063]

[0064] Comparing the results of Example 2 with Comparative Example 1, and Example 3 with Comparative Example 2, it can be seen that, compared with the method using ethylene oxide, the liquid rubber obtained by the preparation method of the present invention has higher hydroxyl functionality and hydroxyl value. The hydroxyl functionality of the liquid rubber of the present invention is greater than 2.

[0065] 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 method for preparing liquid rubber with increased hydroxyl value, characterized in that, Includes the following steps: The polymerization reactor was purged with an inert atmosphere to maintain a slight positive pressure. Solvent, regulator, monomer and initiator were added to the polymerization reactor in sequence to carry out the first reaction. Then an acidifier was added and an oxidant was added to carry out the second reaction. After the reaction was completed, the reactor was washed, vacuumed to remove the solvent and dried to obtain polyhydroxy liquid rubber.

2. The preparation method according to claim 1, characterized in that, The functionality of the polyhydroxy liquid rubber is greater than 2.

3. The preparation method according to claim 1, characterized in that, The solvent is selected from at least one of hexaane, cyclohexane, cyclopentane, benzene, toluene, and tetrahydrofuran.

4. The preparation method according to claim 1, characterized in that, The initiator is selected from at least one of n-butyllithium, sec-butyllithium, and tert-butyllithium; The molar ratio of the initiator to the monomer is 0.01-0.1:1.

0.

5. The preparation method according to claim 1, characterized in that, The regulator is a Lewis base selected from at least one of the following: diethyl ether, anisole, dioxane, tetrahydrofuran, tetrahydrofurfuryl ether, dimethoxyethane (DME), diethylene glycol dimethyl ether (2G), tetramethylvinyl diamine (TMEDA), triethylamine, pentamethyldiethyltriamine (PMDETA), hexamethylphosphoryltriamine (HMPTA), dipiperidine ethane, dimorphidine ethane, 1,4-dichlorobenzenebicyclo[2,2,2]octane, 2,2-bis-(4,4,6-trimethyl-1,3-dichlorohexane) (DIDIOX), methyl ether, and cryptane. The molar ratio of the regulator to the monomer is 0.001-0.2:1.

0.

6. The preparation method according to claim 1, characterized in that, The acidifying agent is at least one of formic acid and acetic acid; The molar ratio of the acidifier to the monomer is 0.01-0.5:1.

0.

7. The preparation method according to claim 1, characterized in that, The oxidant is hydrogen peroxide; The molar ratio of the oxidant to the monomer is 0.01-0.5:1.

0.

8. The preparation method according to claim 1, characterized in that, The monomer is at least one of butadiene, isoprene, and styrene; The mass of the monomer is 1-30% of the mass of the solvent.

9. The preparation method according to claim 1, characterized in that, The inert atmosphere gas is selected from at least one of nitrogen and argon.

10. The preparation method according to claim 1, characterized in that, The temperature of the first reaction is 10-80℃ and the time is 10-200 minutes; the temperature of the second reaction is 10-60℃ and the time is 0.5-5 hours.

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