A method for preparing nitrile rubber by solution polymerization

Abstract

The present invention discloses a method for preparing nitrile rubber by solution polymerization. The method comprises cooling a mixed solution containing butadiene and acrylonitrile, then adding an initiator to initiate a polymerization reaction to obtain a nitrile rubber solution. The mixed solution comprises a mixed solvent consisting of a benzene solvent and a ketone solvent. The solution polymerization method achieves a monomer conversion rate exceeding 85%. The prepared NBR raw rubber is colorless and transparent, has a wide molecular weight distribution (distribution index of 3.5 to 4.5), is free of impurities such as fatty acids, and exhibits excellent processing properties. The comprehensive physical properties of the vulcanized rubber exceed those specified in the national standards for existing emulsion-polymerized NBR. The method is simple to operate, low-cost, and highly efficient, making it suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a method for synthesizing nitrile rubber, in particular to a method for preparing NBR free of organic impurities such as fatty acids through solution polymerization, and belongs to the technical field of nitrile rubber synthesis. Background Art

[0002] Existing nitrile rubber is produced by initiating the copolymerization of acrylonitrile and butadiene in an emulsion with the aid of peroxides and other additives at low temperatures, typically between 4 and 30°C. For example, in "Study on Acrylonitrile-Butadiene-Isoprene Terpolymerization," by Gu Zhengwen, Dalian University of Technology, June 2011, and "Study on Factors Affecting the Properties of Nitrile-Butadiene Rubber," by Wang Zhongchao, Northwest Normal University, June 2012, dicumyl peroxide was used to initiate the polymerization of acrylonitrile and butadiene at temperatures below 8°C, using emulsifiers, activators, tetrasodium EDTA, and sodium ferric EDTA in desalted water. The results showed a monomer conversion rate of no more than 86%, and a polymerization reaction time of 15 to 22 hours. In addition, Chinese patents (CN103450397A) and (CN103665265A) disclose a method for preparing a nitrile rubber, specifically introducing a method for preparing a nitrile rubber by cold batch emulsion polymerization of butadiene and acrylonitrile. The method is characterized in that water, an emulsifier, an emulsifier aid, an emulsion stabilizer, and part of the acrylonitrile monomer in the formula are sequentially added into a polymerization kettle; when the temperature in the polymerization kettle drops to 5-10°C, an oxidant, a reducing agent, a secondary reducing agent, and a chelating agent of a redox initiator are sequentially added; and the remaining acrylonitrile monomer in the formula is added according to the acrylonitrile content requirements of nitrile rubber products of different specifications. The polymerization reaction time is controlled between 8-12 hours, and the monomer conversion rate is controlled between 65% and 80%. The technical indicators of the nitrile rubber obtained are: Mooney viscosity of 30-95, acrylonitrile content of 18-46% of the total monomer mass, vinyl unit content of 9-13%, and tensile strength of 10-22 MPa. A Chinese patent (CN104628955A) relates to a chemically modified nitrile rubber and its production method. The method involves copolymerizing 64-65 parts by weight of butadiene, 20-21 parts by weight of acrylonitrile, 0.30-0.31 parts by weight of butyl acrylate, 4.0-4.1 parts by weight of sodium oleate, and 0.18-0.19 parts by weight of dodecanethiol at 35-45°C for 15-22 hours. The technology does not describe initiators or activators. The resulting raw rubber has a Mooney viscosity of over 120 and a tensile strength of only 14.5 MPa. In other words, the aforementioned technologies are all emulsion polymerization processes.

[0003] Regarding solution polymerization, for example, in "Synthesis of Hydroxyl-Terminated Nitrile-Butadiene Rubber," Weng Lihua, Synthetic Rubber Industry, 1996, reported on the solution copolymerization of butadiene (Bd) and acrylonitrile (AN) in a stainless steel reactor, using H2O2 as the initiator, ethanol as the solvent, and AN / Bd = (10-40) / (90-60) for the synthesis of hydroxyl-terminated nitrile-butadiene rubber (HTBN). In "Rheological Properties of Nitrile-Butadiene Rubber-Chlorobenzene Solutions," Lei Hua, Synthetic Rubber Industry, 2002, a Haake rheometer was used to measure the rheological parameters of nitrile rubber-chlorobenzene solutions at various concentrations and temperatures under conditions similar to those used in the hydrogenation process for hydrogenated nitrile rubber. The results showed that under these conditions, the system behaved approximately like a Newtonian fluid, and a relationship between viscosity, temperature, and concentration was established.

[0004] In summary, the conventional preparation of NBR typically involves copolymerization of acrylonitrile and butadiene in an emulsion initiated by peroxide. The resulting raw rubber typically contains 3-5% fatty acids derived from acidified fatty acid soaps, which affects the basic physical properties and oil resistance of the vulcanized rubber product. However, there are no reports in the prior art of producing soap-free NBR using a solution process. Summary of the Invention

[0005] The NBR prepared by the existing emulsion polymerization process contains impurities such as 3-5% by mass of organic acid and residual soap and polymerization aids, which leads to the deterioration of the basic physical properties and oil resistance of NBR vulcanized rubber products. The purpose of the present invention is to provide a solution polymerization method that uses a special mixed solvent to achieve solution random copolymerization of butadiene and acrylonitrile to synthesize NBR, while reducing the introduction of organic impurities. The method can produce NBR vulcanized rubber products with higher basic physical properties and oil resistance, thereby meeting the needs of the more demanding industrial sealing and oil-resistant rubber product industries.

[0006] The endpoints of the ranges and any values ​​disclosed in the Summary of the Invention 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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the Summary of the Invention.

[0007] In order to achieve the above technical objectives, the present invention provides a method for preparing nitrile rubber by solution polymerization, wherein a mixed solution containing butadiene and acrylonitrile is cooled, and then an initiator is added to initiate a polymerization reaction to obtain a nitrile rubber solution; the mixed solution adopts a mixed solvent composed of a benzene solvent and a ketone solvent.

[0008] As a preferred solution, the mixed solution is cooled to below 8°C.

[0009] As a preferred scheme, the benzene solvent is at least one of benzene, toluene, dimethylbenzene, ethylbenzene and chlorobenzene. Further preferably toluene, ethylbenzene or chlorobenzene. Preferred benzene solvent not only can fully dissolve butadiene monomer and acrylonitrile monomer and realize uniform liquid phase polymerization, and the acrylonitrile-butadiene rubber polymer chain generated can be fully dissolved in the solvent, the acrylonitrile-butadiene rubber polymer chain can be fully stretched in the solvent, thereby fully exposing the active free radical polymerization end, it is kept higher chain growth activity, improve polymerization efficiency, and obtain higher molecular weight, if select non-benign solvent to the low solubility of acrylonitrile-butadiene rubber polymer chain, then the acrylonitrile-butadiene rubber polymer chain can not fully stretch and easily embed active free radical polymerization end and cause its deactivation, thereby be difficult to obtain the acrylonitrile-butadiene rubber polymer chain of high molecular weight, also easily produce cross-linked polymer gel.

[0010] As a preferred embodiment, the ketone solvent is a ketone compound having 3 to 5 carbon atoms. Examples include acetone and butanone. Preferred ketones are those with lower carbon atoms, as these ketone compounds have good water solubility. Since NBR is an oil-resistant polymer, insoluble in aliphatic hydrocarbons, but soluble in aromatic hydrocarbons and highly polar solvents, the present invention selects small-molecule ketone compounds as NBR polymerization solvents for use in conjunction with benzene solvents. This facilitates the formation of a homogeneous phase or fine particles with the aqueous additive solution, benzene solvent, and polymerized monomers, increasing the contact area between the reactants and the probability of molecular collisions, thereby accelerating the polymerization reaction rate. Therefore, even without the use of dispersants, organic acid soaps, and electrolytes, the monomers can still initiate and chain grow during the polymerization reaction. When the polymerization time is <14 hours, the monomer conversion rate is >85%, and the synthesized raw rubber Mooney viscosity is 35 to 90.

[0011] As a preferred embodiment, the mixed solvent comprises a benzene solvent and a ketone solvent in a mass ratio of (1-2):1. By adjusting the ratio of the benzene solvent to the ketone solvent within an appropriate range, the polarity of the mixed solvent can be controlled, thereby facilitating the random polymerization of butadiene and acrylonitrile.

[0012] As a preferred solution, the mass percentage composition of butadiene and acrylonitrile is (60-80%):(20-40%).

[0013] As a preferred solution, the amount of the mixed solvent relative to butadiene and acrylonitrile is (3.0-4.0) kg / kg.

[0014] As a preferred solution, the mixed solution further comprises a deoxidizer, a pH regulator, a reducing agent, an activator and a molecular weight regulator.

[0015] As a preferred embodiment, the pH adjuster is an aqueous sodium carbonate solution, and the amount of the pH adjuster used is sufficient to adjust the pH of the mixed solution to 9 to 11. The preferred pH environment is beneficial for increasing the polymerization rate of the polymerization reaction. The amount of the pH adjuster used relative to butadiene and acrylonitrile is 1.0 to 1.5 g / kg.

[0016] As a preferred solution, the deoxidizer is sodium dithionite, and the amount of the deoxidizer relative to butadiene and acrylonitrile is 0.01 to 0.05 g / kg. Sodium dithionite is added in the form of an aqueous solution.

[0017] As a preferred solution, the reducing agent is bleaching agent, the amount of the reducing agent relative to butadiene and acrylonitrile is 0.4 to 1.0 g / kg, and the bleaching agent is added in the form of an aqueous solution.

[0018] As a preferred embodiment, the activator is EDTA sodium iron salt, the amount of the activator relative to butadiene and acrylonitrile is 0.10-0.30 g / kg, and the EDTA sodium iron salt is added in the form of an aqueous solution.

[0019] As a preferred solution, the molecular mass regulator is tert-dodecyl mercaptan; the amount of the molecular mass regulator relative to butadiene and acrylonitrile is 4 to 8 g / kg.

[0020] As a preferred solution, the initiator is at least one of pinane hydroperoxide and p-menthane hydroperoxide; and the amount of the initiator relative to butadiene and acrylonitrile is 1.0 to 1.5 g / kg.

[0021] As a preferred solution, the polymerization reaction conditions are: temperature 4-8°C, time 12-14h, and pressure 0.2-0.5MPa. Under the preferred reaction conditions, a monomer conversion rate of >85% can be obtained.

[0022] After the polymerization reaction is completed, the rubber solution is discharged, the rubber solution is condensed with water vapor, the solvent is recovered, and the raw rubber is dried to finally obtain colorless and transparent NBR raw rubber.

[0023] The butadiene (B) and acrylonitrile (A) polymerization monomers used in the present invention are both fresh, with an inhibitor content of less than 1 mg / kg and an oxygen content of less than 1 mg / kg.

[0024] After the polymerization reaction is completed, the rubber solution is coagulated by using a rubber solution coagulation process of styrene-butadiene thermoplastic elastomer well known to technicians in the synthetic rubber industry, that is, the rubber solution is coagulated with water vapor, and the coagulation water temperature is preferably 85-98° C. Finally, the coagulated rubber is squeezed and dehydrated to obtain NBR dry rubber or raw rubber.

[0025] The NBR raw rubber prepared by the invention has a molecular weight distribution index of 3.5-4.5, a Mooney viscosity of 30-90, a combined acrylonitrile mass fraction of 25-42%, a vinyl mass fraction in butadiene of 9-45%, a gel content of less than 0.5% (mass content), and a polymer branching degree of 4.0-6.0.

[0026] The inorganic additives used in the polymerization environment of the present invention are generally added in the form of a solution. The water used to prepare the solution is deionized and deoxygenated water. The preparation must be carried out under nitrogen protection and isolated from the atmosphere, otherwise the polymerization efficiency will decrease.

[0027] The preferred method for preparing nitrile rubber by solution polymerization of the present invention is as follows: first, a mixture of a benzene solvent and a ketone solvent, butadiene, acrylonitrile, a deoxidizer, a pH regulator, a reducing agent, an activator, a molecular weight regulator, etc. is added to a polymerization kettle, and the polymer material is cooled to 4-8°C with chilled water, and then an initiator is added to initiate polymerization. The polymerization temperature is controlled to be no higher than 8°C, the pressure is 0.2-0.5 MPa, and the time is 10-14 hours. During this period, the Mooney viscosity of the polymer is sampled and measured until it reaches 35-90 and the monomer conversion rate is greater than 85%. The polymerization reaction is then stopped. After adding an antioxidant to the discharged polymer glue liquid, the glue liquid is condensed with water vapor and dried to obtain colorless and transparent NBR raw rubber.

[0028] Compared with the existing technology, the technical solution of the present invention has the following beneficial effects:

[0029] Compared with the conventional emulsion polymerization technology for synthesizing NBR in the prior art, the solution polymerization process adopted in the technical solution of the present invention unexpectedly found that the monomers in the polymerization reaction can still initiate and chain grow even in the absence of dispersants, organic acid soaps and electrolytes. The monomer conversion rate is >85% when the polymerization time is <14h, and the Mooney viscosity of the synthesized raw rubber is 35-90. This is due to the formation of a good microparticle polymerization environment between the polymerization aid and the benzene solvent and ketone solvent, which increases the contact area between the reaction materials and the collision probability between molecules, accelerates the rate of the polymerization reaction, and improves the random copolymerization efficiency between butadiene and acrylonitrile. After purification, water vapor condensation and drying, the synthesized rubber solution can obtain a colorless and transparent raw rubber. The vulcanized rubber has a 300% tensile stress of >12MPa, a tensile strength of >27MPa, and an elongation of >650%. The comprehensive basic physical properties are higher than those of the existing NBR vulcanized rubber formulated in GB / T 36089-2018 standard; at the same time, the oil resistance of the solution-polymerized nitrile vulcanized rubber of the technical solution of the present invention is much higher than that of the existing commercially available NBR, which is due to the fact that the NBR raw rubber of the present invention does not contain organic acids, soaps and low-molecular impurities such as organic and inorganic salts.

[0030] The method for preparing nitrile rubber by solution polymerization is simple to operate, low in cost, and conducive to large-scale production. The prepared NBR is a medium- and high-end material for industries such as sealing, oil-resistant molded rubber parts, high-elastic parts and rubber rollers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 NBR gel permeation chromatogram prepared in Example 1;

[0032] Figure 2 The NBR NMR prepared in Example 5 1 -NMR spectrum; chemical shift δ = 2.1 ~ 2.2 is the hydrogen proton on the carbon atom connected to the bound nitrile group; δ = 4.9 ~ 5.2 is the hydrogen proton on the vinyl group and the 1,4-addition unit.

[0033] Figure 3 Comparison of the vulcanization behavior of NBR, NBR3345C and emulsion ESBR1500 rubber compounds; Figure 3 It can be seen that compared with NBR3345C, the minimum Mooney viscosity of NBR is relatively low, and NBR3345C has the characteristics of rapid vulcanization. The vulcanization curve of emulsion ESBR1500 is flat, and it takes the longest time to reach the maximum Mooney viscosity, which shows that the vulcanization rate is slow. DETAILED DESCRIPTION

[0034] The following examples are intended to further illustrate the present invention, but are not intended to limit the scope of the claims.

[0035] In the following examples, the molecular weight distribution index of the polymer was determined by gel permeation chromatography (GPC); the Mooney viscosity of the polymer was determined by Mooney viscometer; and the H 1 -NMR spectroscopy quantitatively determines the microstructure of the polymer; an INSTRON tensile testing machine is used to determine the physical properties of the vulcanized rubber; and the mixing, vulcanization, and oil resistance testing of the raw rubber are carried out in accordance with the GB / T-34685-2017 standard.

[0036] Example 1

[0037] In a 5-liter polymerization kettle under nitrogen protection, 1.6 L of toluene and 1.5 L of butanone were added. Then, 3.5 mL of a 4.1% (weight) aqueous solution of EDTA sodium iron salt, 10 mL of a 10% (weight) aqueous solution of sodium carbonate, 3.5 mL of a 0.4% (weight) aqueous solution of sodium dithionite, 8 mL of a 6.2% (weight) aqueous solution of bleaching powder and 6 mL of tert-dodecyl mercaptan were added into the feeding sight glass respectively. The additives were then pressed into the polymerization kettle with nitrogen. 850 mL of butadiene and 200 g of acrylonitrile were pressurized into the polymerization kettle using nitrogen, stirring was started, and a circulating cooling water bath composed of ethylene glycol / water at 5°C was introduced to cool the materials to 5-8°C. Then, 0.88 mL of PMHP was pressurized into the polymerization kettle for initiation. The pressure was maintained at 0.2-0.5 MPa and the polymerization temperature was <8°C. After stirring for 12.5 hours, the Mooney viscosity of the polymer was measured to be 48.6 and the monomer conversion was 85.7%. The polymerization was stopped by discharging the material.

[0038] Add 2.5g of antioxidant 1520 to the leaked polymerized rubber liquid, stir evenly, and finally condense the rubber liquid with 98℃ steam, dehydrate the condensed rubber particles by extrusion, and dry to obtain colorless and transparent NBR raw rubber.

[0039] The molecular weight distribution index of the raw rubber was measured to be 3.7, the vinyl unit content was 11.6%, and the bound acrylonitrile content was 27.3%. The gel permeation chromatography (GPC) of the raw rubber was shown in FIG. Figure 1 .

[0040] Example 2

[0041] The relevant additives and process conditions in Example 1 were not significantly adjusted. Only 1.8 L of toluene, 1.3 L of butanone, 5.8 mL of dodecyl mercaptan, 0.90 mL of PMHP, 230 g of acrylonitrile, and 840 mL of butadiene were added. The total reaction time was 13 h, and the monomer conversion rate was 86.4%.

[0042] The molecular weight distribution index of the NBR raw rubber was measured to be 4.2, the Mooney viscosity was 53.8, the vinyl unit content was 12.6%, and the bound acrylonitrile content was 30.2%.

[0043] Example 3

[0044] The relevant additives and process conditions in Example 1 were not significantly adjusted. Only 2.0 L of ethylbenzene, 1.2 L of acetone, 5.7 mL of dodecyl mercaptan, 1.0 mL of PHP, 260 g of acrylonitrile, and 830 mL of butadiene were added. The total reaction time was 12 h, and the monomer conversion rate was 87.4%.

[0045] The molecular weight distribution index of the NBR raw rubber was measured to be 3.7, the Mooney viscosity was 58.4, the vinyl unit content was 11.5%, and the bound acrylonitrile content was 33.6%.

[0046] Example 4

[0047] The relevant additives and process conditions in Example 1 were not significantly adjusted. Only 1.7 L of benzene, 1.4 L of acetone, 5.5 mL of dodecyl mercaptan, 1.1 mL of PHP, 280 g of acrylonitrile, and 800 mL of butadiene were added. The total reaction time was 12 h, and the monomer conversion rate was 87.7%.

[0048] The molecular weight distribution index of the NBR raw rubber was measured to be 4.3, the Mooney viscosity was 63.6, the vinyl unit content was 11.2%, and the bound acrylonitrile content was 35.4%.

[0049] Example 5

[0050] The relevant additives and process conditions in Example 1 were not significantly adjusted. Only 1.9 L of chlorobenzene, 1.2 L of butanone, 5.4 mL of dodecyl mercaptan, 1.2 mL of PMHP, 325 g of acrylonitrile, and 750 mL of butadiene were added. The total reaction time was 14 h, and the monomer conversion rate was 88.7%.

[0051] The molecular weight distribution index of NBR raw rubber was measured to be 4.4, Mooney viscosity was 72.9, vinyl unit content was 10.7%, and bound acrylonitrile content was 41.1%. 1 -NMR spectrum is attached Figure 2 .

[0052] Comparative Example 1

[0053] The relevant additives and process conditions in Example 2 were not significantly adjusted. Only 2.5 L of toluene and 0.8 L of butanone were added, and the other materials remained unchanged.

[0054] Results After 13 h of stirring reaction with less ketone as cosolvent, the Mooney viscosity of NBR raw rubber was 27.8 and the conversion rate of monomer was 68.3%.

[0055] Comparative Example 2

[0056] The relevant additives and process conditions in Example 5 were not significantly adjusted. Only 2.9 L of chlorobenzene and 0.5 L of acetone were added, and the other materials remained unchanged.

[0057] Results After 14 hours of stirring reaction with less ketone as cosolvent, the Mooney viscosity of NBR raw rubber was 23.3 and the conversion rate of monomer was 57.6%.

[0058] Comparative Example 3

[0059] The relevant additives and process conditions in Example 1 were not significantly adjusted. Only 3.2 L of chlorobenzene was added, and no ketone was added as a co-solvent. Other materials remained unchanged.

[0060] Results After stirring and reacting for 13 hours without ketone as a cosolvent, the Mooney viscosity of the polymer was measured to be 22.5 and the monomer conversion rate was 24.4%.

[0061] Comparative Example 4

[0062] The relevant additives and process conditions in Example 2 were not significantly adjusted. Only 3.3 L of toluene was added, and no ketone was added as a co-solvent. Other materials remained unchanged.

[0063] Results After stirring and reacting for 14 hours without ketone as a cosolvent, the Mooney viscosity of the NBR raw rubber was measured to be 23.6 and the monomer conversion rate was 28.5%.

[0064] Example 6

[0065] Example 1, Example 2, Example 3, Example 4, Example 5 and commercially available emulsion ESBR1500, NBR1043N, NBR3345C and NBR1051 were mixed and vulcanized according to GB / T-34685-2017 standard. The basic physical properties of the vulcanized rubber are shown in Table 1; the oil resistance of the vulcanized rubbers of Example 1, Example 2, Example 3, Example 4, Example 5 and emulsion NBR1043N, NBR3345C and NBR1052 is shown in Table 2; the vulcanization characteristic behavior of the mixed rubbers of Example 1, Example 2, ESBR1500 and NBR3345C is shown in Table Figure 3 .

[0066] Table 1 Basic physical properties of vulcanized rubber

[0067]

[0068]

[0069] Note: “*” stands for fast-vulcanizing NBR.

[0070] As can be seen from Table 1, compared with emulsion rubber, solution NBR has higher strength and elongation at break.

[0071] Table 2 Oil resistance of different NBR vulcanizates**

[0072]

[0073] Note: “**” oil is n-octane, and “***” raw rubber does not contain rapid vulcanization accelerator.

[0074] As can be seen from Table 2, compared with emulsion polymerized NBR, solution polymerized NBR has excellent oil resistance.

Claims

1. A method for preparing acrylonitrile-butadiene rubber by solution polymerization, characterized in that: After cooling the mixed solution containing butadiene and acrylonitrile, an initiator is added to initiate a polymerization reaction to obtain a nitrile rubber solution; the mixed solution is a mixed solvent composed of a benzene solvent and a ketone solvent; The benzene solvent is at least one of benzene, toluene, xylene, ethylbenzene and chlorobenzene; The ketone solvent is a ketone compound having 3 to 5 carbon atoms; The mixed solvent is composed of a benzene solvent and a ketone solvent in a mass ratio of (1-2):1; The polymerization reaction conditions are: temperature of 4-8° C., time of 12-14 h, and pressure of 0.2-0.5 MPa.

2. The method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 1, wherein: The mass percentage composition of butadiene and acrylonitrile is (60~80%): (40~20%).

3. A method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 1, characterized in that: The amount of the mixed solvent relative to butadiene and acrylonitrile is (3.0-4.0) kg / kg.

4. The method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 1, wherein: The mixed solution also contains a deoxidizer, a pH regulator, a reducing agent, an activator and a molecular weight regulator.

5. A method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 4, characterized in that: The pH regulator is a sodium carbonate aqueous solution, and the amount of the pH regulator is used to adjust the pH value of the mixed solution to 9-11.

6. A method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 4, characterized in that: The deoxidizer is sodium dithionite, and the amount of the deoxidizer relative to butadiene and acrylonitrile is 0.01-0.05 g / kg.

7. A method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 4, characterized in that: The reducing agent is bleaching agent; the amount of the reducing agent relative to butadiene and acrylonitrile is 0.4-1.0 g / kg.

8. A method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 4, characterized in that: The activator is EDTA sodium iron salt; the amount of the activator relative to butadiene and acrylonitrile is 0.10-0.30 g / kg.

9. A method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 4, characterized in that: The molecular weight regulator is tert-dodecyl mercaptan; the amount of the molecular weight regulator relative to butadiene and acrylonitrile is 4-8 g / kg.

10. The method for preparing acrylonitrile-butadiene rubber by solution polymerization according to claim 4, wherein: The initiator is at least one of pinane hydroperoxide and p-menthane hydroperoxide; and the amount of the initiator relative to butadiene and acrylonitrile is 1.0-1.5 g / kg.

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