Synthesis method of solution polymerized styrene-butadiene

Abstract

The invention relates to the technical field of rubber synthesis, in particular to a synthesis method of solution polymerized styrene-butadiene. According to the synthesis method, butadiene and styrene are taken as monomers, a dilithium chelating initiator, a gradient polarity regulator and other raw materials are matched, and polymerization, end capping, coupling and post-treatment are performed to prepare the product. Wherein the double-lithium chelation initiator is prepared through o-phenylenediamine silicon group protection and lithiation reaction and contains a stable five-membered chelate ring; the gradient polarity regulator is prepared from triethylene glycol through silicon etherification and methylation and is in a three-section type polarity gradient, and polymerization controllability is synergistically improved through triethylene glycol and triethylene glycol. The synthesis method can accurately regulate and control the microstructure of the product, reduce ash content and volatile components, improve mechanical properties and processing stability, and is suitable for the field of high-performance rubber products.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber synthesis, in particular to a method for synthesizing solution-polymerized butadiene styrene. Background Art

[0002] Styrene-butadiene rubber (SBR), a key synthetic rubber produced through the copolymerization of styrene and butadiene, is widely used in tires, footwear, and industrial products due to its excellent wear and aging resistance and processing properties. It is one of the most produced and widely used rubber products in the rubber industry. Its overall performance can be optimized by adjusting the styrene-butadiene ratio and microstructure to meet the needs of different scenarios, and it plays a vital role in the national economy.

[0003] Among the many types of styrene-butadiene rubber (SBR), solution-polymerized styrene-butadiene rubber (SSBR) is produced through the copolymerization of styrene and butadiene in an organic solvent, using a solution polymerization process. Compared to traditional emulsion-polymerized styrene-butadiene rubber (ESBR), SSBR offers advantages such as a narrow molecular weight distribution and highly controllable microstructure (such as vinyl content and styrene sequence distribution). This allows it to better balance rubber properties such as hysteresis loss, wet skid resistance, and rolling resistance. Therefore, it demonstrates significant advantages in high-performance tires (especially green tires), becoming a key material for improving overall tire performance.

[0004] However, the current research and production of solution-polymerized styrene-butadiene rubber (SSBR) still faces numerous technical challenges. Regarding the initiation system, traditional monolithium initiators (such as n-butyl lithium) are prone to association, resulting in uneven distribution of active centers and large fluctuations in initiation efficiency. This, in turn, results in a wide molecular weight distribution and poor structural uniformity in the polymer, which in turn affects the stability of mechanical properties. Regarding microstructural regulation, common polarity regulators are mostly single structures, making it difficult to dynamically adapt to the requirements for monomer reactivity at each stage of polymerization. This results in insufficient control precision for vinyl content and uneven distribution of copolymer sequences of styrene and butadiene, restricting further improvements in key properties such as the rubber's modulus and tensile strength. Furthermore, issues such as precise control of coupling reaction efficiency and effective removal of impurities (such as ash and volatile matter) also adversely affect the processing performance and durability of SSBR, limiting its application in high-end fields.

[0005] While the method for preparing epoxidized solution-polymerized styrene-butadiene rubber (SPBR) disclosed in Chinese invention patent application number CN116162205A demonstrates some improvement in modification, hydrogen peroxide readily decomposes to form hydrogen during the reaction, posing significant safety risks in industrial production and hindering large-scale industrial application. The method for preparing functionalized SSBBR / silica gel composites disclosed in Chinese invention patent application number CN110387073B, while offering some advantages in modification, lacks significant advantages in addressing the polymerization activity of high-Mooney SSBRA and related chain-type and coupling issues, limiting the product's application in certain specific areas. The technologies related to difunctionalized styrene-butadiene polymers disclosed in Chinese invention patent application CN106565904B, as well as the initiators and polymerization methods described in the papers "Research Progress on Dilithium Initiators for Negative Ionic Polymerization" and "Preparation of Functionalized Polylithium Initiators and Their Application in Polymerization of Three Monomers," have failed to effectively address key issues inherent in prior art solution-polymerized styrene-butadiene rubber, including bonding with silica fillers, hydrolytic stability, and randomization due to high styrene content. Similarly, the silane coupling agent-modified chain-functionalized solution-polymerized styrene-butadiene rubber and its synthesis method, disclosed in Chinese invention patent application CN108017757B, have failed to fundamentally overcome the existing technical difficulties and address these core challenges. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings in the prior art and to propose a method for synthesizing solution-polymerized butadiene styrene.

[0007] Based on the above purpose, the present invention provides a solution-polymerized butadiene styrene, which is prepared by polymerization reaction of the following raw materials in parts by weight: butadiene: 70-80 parts, styrene: 20-30 parts, anhydrous cyclohexane: 300-400 parts, dilithium chelate initiator: 0.3-0.5 parts, gradient polarity regulator: 0.5-0.7 parts, end-capping agent: 0.1-0.3 parts, coupling agent: 0.05-0.15 parts, and antioxidant: 0.4-0.6 parts; The preparation method of the dilithium chelate initiator is as follows: (1) Under nitrogen protection, o-phenylenediamine and triethylamine were added to anhydrous tetrahydrofuran (THF), cooled to 0-5°C, and trimethylsilyl chloride was added dropwise for 1-2 hours. After the addition was completed, the mixture was returned to room temperature and reacted for 2-4 hours. After the reaction was completed, the mixture was filtered and the filtrate was concentrated under reduced pressure to obtain bis(trimethylsilyl)o-phenylenediamine, which was used directly in the next step without purification. The chemical reaction equation is as follows: , The nitrogen atom in the amino group of o-phenylenediamine contains a lone pair of electrons and is nucleophilic. It can attack the partially positively charged Si atom in trimethylchlorosilane (the Si-Cl bond is highly polar, and the high electronegativity of Cl makes Si positively charged), and a nucleophilic substitution reaction occurs. The generated HCl is neutralized by the acid-binding agent triethylamine to avoid the reversal of the reaction between HCl and amine. Because o-phenylenediamine contains two amino groups and trimethylchlorosilane is slightly excessive, both amino groups are silylated to form a double silicon-protected product. The product is then 1 H NMR and 29 Si NMR was used for characterization; (2) Under nitrogen protection, add bis(trimethylsilyl)-o-phenylenediamine to a mixed solution of anhydrous toluene and anhydrous THF, cool to -78°C, and add n-butyllithium in hexane solution dropwise for 1-2 hours. After the addition is complete, heat to -10-0°C and react for 1-3 hours. After the reaction is complete, quench the reaction with a mixed solution of ethanol and toluene. Wash the organic phase twice with a saturated ammonium chloride solution and once with a saturated sodium chloride solution. Combine the organic phases, dry over anhydrous sodium sulfate, filter, and concentrate the filtrate under reduced pressure to remove the solvent. The obtained crude product is recrystallized from a mixed solution of toluene and n-hexane and crystallized at -20-0°C for 12-24 hours to obtain a dilithium chelate initiator. The chemical reaction equation is as follows: , In the double silicon-protected product, the H atom on the amino group has a weak acidity due to the high electronegativity of N, and can be protoned by the strongly basic n-butyl lithium. In the generated -NLi-, N - With Li + The two -NLi- groups are located at the adjacent position of the benzene ring, and the spatial distance is suitable for Li + The coordination radius forms a five-membered chelate ring through the coordination bond, and the product is 1 H NMR was performed for characterization; The preparation method of the gradient polarity regulator is as follows: (a) Under nitrogen protection, triethylene glycol and imidazole were added to anhydrous N,N-dimethylformamide (DMF), cooled to -10-0°C, and trimethylchlorosilane was added dropwise for 1-2 hours. After the addition was completed, the mixture was returned to room temperature and reacted for 1-2 hours. After the reaction was completed, the reaction solution was transferred to a separatory funnel, washed with dilute hydrochloric acid three times and then with saturated sodium chloride solution once. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain a monosilyl ether intermediate. The chemical reaction equation is as follows: , The O atom in the hydroxyl group of triethylene glycol contains a lone pair of electrons, which is more nucleophilic than the ether bond and can attack the Si atom of trimethylchlorosilane to cause a nucleophilic substitution reaction. Due to the use of weak base imidazole and limited trimethylchlorosilane, only one hydroxyl group reacts first, and imidazole neutralizes the generated HCl to generate imidazole hydrochloride, avoiding the double silylation caused by trimethylchlorosilane (strong alkaline conditions easily induce double substitution, which can be inhibited by weak base imidazole). The product passes through 1 H NMR and 29 Si NMR was used for characterization; (b) Under nitrogen protection, the monosilyl ether intermediate, methyl iodide, and potassium carbonate were added to anhydrous acetone, heated to 55-65°C, and reacted for 3-5 hours. After the reaction, the mixture was cooled to room temperature and filtered. The filtrate was concentrated under reduced pressure to obtain a brown liquid. The brown liquid was added to a separatory funnel, anhydrous ether was added, and the mixture was washed three times with a saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain a gradient polarity regulator. The chemical reaction equation is as follows: , The remaining hydroxyl groups of the monosilyl ether intermediate generate potassium alcoholate under the action of weak base potassium carbonate. The strong base and weak acid salt promote the deprotonation. Potassium alcoholate acts as a nucleophile to attack the partially positively charged C atom in iodomethane. - As a good leaving group, the reaction proceeds through the SN2 mechanism. Iodomethane has little steric hindrance, which is conducive to the attack of nucleophiles, forming a gradient structure with a weak polar silyl ether at one end, a medium polar ether bond in the middle, and a strong polar methoxy group at the other end. The product is formed by 1 The samples were characterized by H NMR.

[0008] Preferably, the end-capping agent is one or both of dichlorodimethylsilane and butadiene.

[0009] Preferably, the coupling agent is tin tetrachloride.

[0010] Preferably, the antioxidant refers to one or both of antioxidant 1010 and antioxidant 168.

[0011] Preferably, the molar ratio of o-phenylenediamine, trimethylchlorosilane and triethylamine in (1) is 1:2-2.4:2-2.4, and the weight ratio of o-phenylenediamine and anhydrous THF is 1:8-12.

[0012] Preferably, the amino group of o-phenylenediamine in (1) has strong nucleophilicity. If it is not protected and directly reacts with n-butyllithium, it will cause polylithiation due to the high activity of the NH bond, destroying the dilithium symmetry of the initiator. After the trimethylsilyl group is connected through the Si-N bond, the electronegativity of silicon is lower than that of carbon, which reduces the electron cloud density of the N atom and retains only one NH bond that can be lithiated, ensuring the generation of a single dilithium structure. At the same time, due to the large volume of the silicon group, a spatial barrier is formed around the amino group, slowing down the attack speed of n-butyllithium on the NH bond, avoiding the instantaneous explosive generation of the initiator, and also enhancing the stability of the initiator.

[0013] Preferably, the molar ratio of bis(trimethylsilyl)-o-phenylenediamine to n-butyllithium in the hexane solution of n-butyllithium in (2) is 1:2-2.2.

[0014] Preferably, the weight ratio of bis(trimethylsilyl)-o-phenylenediamine added to the mixed solution of anhydrous toluene and anhydrous THF in (2) is 1:8-12.

[0015] Preferably, the hexane solution of n-butyl lithium in (2) refers to a hexane solution with a concentration of 2.5 M n-butyl lithium.

[0016] Preferably, the mixed solution of anhydrous toluene and anhydrous THF in (2) is prepared by mixing anhydrous toluene and anhydrous THF in a weight ratio of 19:1.

[0017] Preferably, the ethanol and toluene mixed solution in (2) refers to a mixture of ethanol and toluene in a weight ratio of 1:3.

[0018] Preferably, the mixed solution of toluene and n-hexane in (2) refers to a mixture of toluene and n-hexane in a weight ratio of 2:3.

[0019] Preferably, the two -NLi- groups in (2) are connected through the ortho position of the benzene ring to form a five-membered ring structure, which just matches Li + The coordination radius is larger than that of the non-chelating structure, which makes the active center less likely to decompose and solves the problem of traditional n-butyl lithium being easy to associate (forming dimers). In the initiation stage, the Li + Weak coordination occurs with the π electron cloud of the monomer double bond (butadiene and styrene), gradually breaking the constraints of the N-Li bond and forming a "chelate ring opening → Li + Transfer → active chain generation" step-by-step process, this slow release makes the molecular weight distribution narrower, which is better than the traditional system. Finally, each initiator molecule contains two active Li + , two polymer chains can be initiated at the same time, and the growth rate deviation of the two chains is small, ensuring the structural uniformity of the product.

[0020] Preferably, the molar ratio of triethylene glycol, trimethylchlorosilane and imidazole in (a) is 1:1-1.1:1-1.2.

[0021] Preferably, the weight ratio of triethylene glycol to anhydrous DMF in (a) is 1:8-12.

[0022] Preferably, the dilute hydrochloric acid in (a) refers to a hydrochloric acid solution with a concentration of 1 mol / L.

[0023] Preferably, the molar ratio of the monosilyl ether intermediate, methyl iodide and potassium carbonate in (b) is 1:1-1.2:1.2-1.5.

[0024] Preferably, the weight ratio of the monosilyl ether intermediate, anhydrous acetone and anhydrous ether in (b) is 1:10-14:5-9.

[0025] Preferably, the strongly polar end (methoxy) oxygen atom in the gradient polarity regulator (b) has high electronegativity and is + Forming a strong coordination bond, it preferentially binds to Li + The combination promotes the 1,2-addition of butadiene and increases the vinyl content; the ether bond density in the medium polar region (ether bond) is moderate, and the replacement regulation in the middle stage balances the insertion rate of the two monomers, which is conducive to the formation of random structure; the silicon group at the weak polar end (silyl ether) weakens the coordination ability of the oxygen atom, reducing the Li + To avoid chain termination caused by excessive regulation, as the polymerization temperature increases, the gradient regulator realizes the polarity difference with Li + "Thermal induced coordination".

[0026] Preferably, the “thermally induced coordination” is mainly based on the following principle: at different temperatures, the degree of thermal motion of molecules is different, and the different polar groups and Li + The coordination balance of the strong polar methoxy group and Li + The coordination bond formed can exist stably at low temperature due to its high coordination energy. When the temperature rises, the molecular thermal motion is enhanced, and the stability of this strong coordination bond is impacted. The ether chain with medium polarity has moderate coordination energy and can exist stably at slightly higher temperature with Li + The coordination competitiveness of the methoxy group and Li + At high temperature, the weakly polar silyl ether is more likely to react with Li due to the minimal interference of molecular thermal motion under the influence of temperature and its own coordination energy is low. + Combined, thus completing the entire thermally induced coordination process.

[0027] Furthermore, the present invention also provides a method for synthesizing the solution-polymerized butadiene styrene, comprising the following steps: S1. Anhydrous cyclohexane was pressurized into a stainless steel polymerization kettle using nitrogen. The feed valve was closed and a nitrogen atmosphere was maintained in the kettle. Butadiene and styrene were stirred uniformly in a monomer metering tank and added to the polymerization kettle at once. A gradient polarity regulator was then added and stirring was started. The contents in the kettle were heated to 35-45°C using a hot water jacket and stirred for 5-15 minutes. A dilithium chelate initiator was added to initiate polymerization and allowed to react for 10-20 minutes. The temperature was then raised to 45-55°C for 20-40 minutes, and then raised to 65-75°C at a rate of 0.5-1°C / min for 20-40 minutes to complete chain growth. S2. After the chain growth reaction is completed, the temperature in the reactor is lowered to 55-65 ° C, the end-capping agent is added, and the reaction is stirred for 15-25 minutes for end-capping. Then, the coupling agent is added and the temperature is raised to 60-70 ° C for 10-20 minutes to complete the coupling reaction; S3. After the coupling reaction is completed, the temperature in the kettle is lowered to 45-55°C, the reaction is quenched with methanol, stirred for 5-15 minutes, an antioxidant is added, and stirring is continued for 15-25 minutes. The discharge valve is opened, and the polymer solution is placed in a coagulation kettle. The polymer solution is stirred and coagulated in deionized water at 80-90°C to precipitate polymer particles. After washing three times with deionized water, the wet particles are sent to an extrusion dehydrator to remove moisture, and then dried in a drying oven to constant weight to obtain solution-polymerized butadiene styrene.

[0028] Beneficial effects of the present invention: 1. The present invention significantly improves the controllability of the polymerization reaction by employing a dilithium chelate initiator. This initiator, protected by a double silicon group of o-phenylenediamine, forms a stable five-membered chelate ring structure that precisely binds the active center, avoiding the chain growth disorder caused by the explosive release or association of the active center in traditional initiators. This results in more uniform molecular chain growth and a narrower molecular weight distribution, thereby enhancing the structural uniformity of the rubber and laying the foundation for its excellent mechanical properties. Furthermore, the dual-active center design allows for the simultaneous initiation of two molecular chains, further ensuring the consistency of the product structure and improving the processing stability of the rubber.

[0029] 2. The application of a gradient polarity modifier in this invention enables dynamic and precise control of the polymerization process. This modifier has a three-segment structure: a weakly polar silyl ether, a moderately polar ether bond, and a strongly polar methoxy group. Through a "thermally induced coordination" mechanism, it adapts the active center requirements at different polymerization stages: at low temperatures, the highly polar end promotes 1,2-addition of butadiene to increase vinyl content; at moderate temperatures, the moderately polar end balances the monomer insertion rate to optimize styrene distribution; and at high temperatures, the weakly polar end reduces chain termination. This dynamic control results in a more rational rubber microstructure, effectively balancing deformation resistance and flexibility.

[0030] 3. This invention significantly improves the purity and stability of the rubber by optimizing the synergistic effect of the initiator and modifier. The silicon-based protection and purification process of the dilithium chelate initiator reduces impurity generation, while the multiple washing steps with the gradient polarity modifier reduce the introduction of exogenous impurities. Combined with the post-polymerization coagulation in 80-90°C deionized water and three washes, this post-polymerization process effectively removes impurities such as residual metal salts and solvents, reduces ash and volatile matter content, and minimizes the interference of impurities on the interchain interactions, thereby improving the durability and performance stability of the rubber.

[0031] 4. The coupling reaction efficiency of this invention is more easily controlled within the optimal range. Through the precise reaction of the symmetrical dual active centers of the dilithium chelate initiator with the coupling agent, a stable multi-arm branched structure is formed. This moderate branching enhances molecular chain entanglement to improve strength while avoiding processing difficulties caused by excessive coupling efficiency. Furthermore, the use of an end-capping agent optimizes the molecular chain terminal structure, reduces rigidity defects, further improves the overall performance of the rubber, and broadens its application potential in high-end rubber products. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The bis(trimethylsilyl)-o-phenylenediamine prepared in Preparation Example 2 of the present invention 1 H NMR spectrum; Figure 2 The bis(trimethylsilyl)-o-phenylenediamine prepared in Preparation Example 2 of the present invention 29 Si NMR spectrum; Figure 3 The dilithium chelate initiator prepared in Preparation Example 2 of the present invention is 1 H NMR spectrum; Figure 4 The monosilyl ether intermediate prepared in Preparation Example 5 of the present invention 1 H NMR spectrum; Figure 5 The monosilyl ether intermediate prepared in Preparation Example 5 of the present invention 29 Si NMR spectrum; Figure 6 The gradient polarity regulator prepared in Preparation Example 5 of the present invention is 1 H NMR spectrum. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0034] The main sources of raw materials used in the present invention are as follows: Styrene (St): polymerization grade, Beijing Chemical Reagent Factory, purified by two vacuum distillations before use; Butadiene (Bd): polymerization grade, purity >99%, Qilu Petrochemical, dried over 4Å molecular sieves and purified by two distillations before use; Tin tetrachloride: analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.; Dichlorodimethylsilane: purity 99%, Shanghai MacLean Biochemical Technology Co., Ltd.; Antioxidant 1010: purity >98%, Shanghai MacLean Biochemical Technology Co., Ltd.; Antioxidant 168: 98%, Shanghai MacLean Biochemical Technology Co., Ltd.; o-phenylenediamine: 98%, Shanghai MacLean Biochemical Technology Co., Ltd.; Triethylamine: 99%, Shanghai MacLean Biochemical Technology Co., Ltd.; Trimethylchlorosilane: purity >98%, Shanghai MacLean Biochemical Technology Co., Ltd.; n-Butyllithium in hexane: 2.5 M solution in Hexanes, Shanghai Maclean Biochemical Technology Co., Ltd.; triethylene glycol: 99.5%, Shanghai Maclean Biochemical Technology Co., Ltd.; imidazole: 99%, Shanghai Maclean Biochemical Technology Co., Ltd.; iodomethane: 99.5%, Shanghai Maclean Biochemical Technology Co., Ltd.; potassium carbonate: 99%, Shanghai Maclean Biochemical Technology Co., Ltd.

[0035] Preparation Example 1: The specific preparation method of dilithium chelate initiator is as follows: (1) Under nitrogen protection, 100 g of o-phenylenediamine and 187.15 g of triethylamine were added to 800 g of anhydrous THF, cooled to 0 °C, and 200.92 g of trimethylsilyl chloride was added dropwise for 1 h. After the addition was completed, the mixture was returned to room temperature and reacted for 2 h. After the reaction was completed, the mixture was filtered and the filtrate was concentrated under reduced pressure to obtain bis(trimethylsilyl)o-phenylenediamine, which was used directly in the next step without purification. (2) Under nitrogen protection, 200 g of bis(trimethylsilyl)-o-phenylenediamine was added to 1.6 kg of a mixed solution of anhydrous toluene and anhydrous THF (mixed in a weight ratio of 19:1), cooled to -78 ° C, and 633.64 ml of a 2.5 M hexane solution of n-butyl lithium was added dropwise for 1 hour. After the addition was completed, the temperature was raised to -10 ° C and the reaction was continued for 1 hour. After the reaction was completed, the reaction was quenched with a mixed solution of ethanol and toluene (mixed in a weight ratio of 1:3). The organic phase was washed twice with a saturated ammonium chloride solution and once with a saturated sodium chloride solution. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The obtained crude product was recrystallized from a mixed solution of toluene and n-hexane (mixed in a weight ratio of 2:3). The crystallization was carried out at -20 ° C for 12 hours to obtain a dilithium chelate initiator.

[0036] Preparation Example 2: The specific preparation method of dilithium chelate initiator is as follows: (1) Under nitrogen protection, 100 g of o-phenylenediamine and 205.86 g of triethylamine were added to 1 kg of anhydrous THF, cooled to 3 °C, and 221.02 g of trimethylsilyl chloride was added dropwise for 1.5 h. After the addition was complete, the mixture was returned to room temperature and reacted for 3 h. After the reaction was completed, the mixture was filtered and the filtrate was concentrated under reduced pressure to obtain bis(trimethylsilyl)o-phenylenediamine, which was used directly in the next step without purification. (2) Under nitrogen protection, 200 g of bis(trimethylsilyl)-o-phenylenediamine was added to 2 kg of a mixed solution of anhydrous toluene and anhydrous THF (mixed in a weight ratio of 19:1), cooled to -78 ° C, and 665.32 ml of a 2.5 M hexane solution of n-butyl lithium was added dropwise for 1.5 h. After the addition was completed, the temperature was raised to -5 ° C and the reaction was carried out for 2 h. After the reaction was completed, the reaction was quenched with a mixed solution of ethanol and toluene (mixed in a weight ratio of 1:3). The organic phase was washed twice with a saturated ammonium chloride solution and once with a saturated sodium chloride solution. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The obtained crude product was recrystallized from a mixed solution of toluene and n-hexane (mixed in a weight ratio of 2:3). The crystallization was carried out at -10 ° C for 18 h to obtain a dilithium chelate initiator.

[0037] Preparation Example 3: The specific preparation method of dilithium chelate initiator is as follows: (1) Under nitrogen protection, 100 g of o-phenylenediamine and 224.58 g of triethylamine were added to 1.2 kg of anhydrous THF, cooled to 5 °C, and 241.11 g of trimethylsilyl chloride was added dropwise for 2 h. After the addition was complete, the mixture was returned to room temperature and reacted for 4 h. After the reaction was completed, the mixture was filtered and the filtrate was concentrated under reduced pressure to obtain bis(trimethylsilyl)o-phenylenediamine, which was used directly in the next step without purification. (2) Under nitrogen protection, 200 g of bis(trimethylsilyl)-o-phenylenediamine was added to 2.4 kg of a mixed solution of anhydrous toluene and anhydrous THF (mixed in a weight ratio of 19:1 for anhydrous toluene and anhydrous THF), cooled to -78 ° C, and 697 ml of a 2.5 M hexane solution of n-butyl lithium was added dropwise for 2 h. After the addition was completed, the temperature was raised to 0 ° C and the reaction was carried out for 3 h. After the reaction was completed, the reaction was quenched with a mixed solution of ethanol and toluene (mixed in a weight ratio of 1:3 for ethanol and toluene). The organic phase was washed twice with a saturated ammonium chloride solution and once with a saturated sodium chloride solution. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The obtained crude product was recrystallized from a mixed solution of toluene and n-hexane (mixed in a weight ratio of 2:3 for toluene and n-hexane). The crystallization was carried out at 0 ° C for 24 h to obtain a dilithium chelate initiator.

[0038] Preparation Example 4: The specific preparation method of the gradient polarity regulator is as follows: (a) Under nitrogen protection, 100 g of triethylene glycol and 45.47 g of imidazole were added to 800 g of anhydrous DMF, cooled to -10°C, and 72.34 g of trimethylchlorosilane was added dropwise for 1 hour. After the addition was complete, the mixture was returned to room temperature and reacted for 1 hour. After the reaction was completed, the reaction solution was transferred to a separatory funnel and washed three times with a 1 mol / L hydrochloric acid solution and once with a saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain a monosilyl ether intermediate; (b) Under nitrogen protection, 100 g of the monosilyl ether intermediate, 63.83 g of iodomethane, and 74.59 g of potassium carbonate were added to 1 kg of anhydrous acetone, heated to 55°C, and reacted for 3 h. After the reaction, the mixture was cooled to room temperature and filtered. The filtrate was concentrated under reduced pressure to obtain a brown liquid. The brown liquid was added to a separatory funnel, 500 g of anhydrous ether was added, and the mixture was washed three times with a saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain a gradient polarity regulator.

[0039] Preparation Example 5: The preparation method of the gradient polarity regulator is as follows: (a) Under nitrogen protection, 100 g of triethylene glycol and 49.87 g of imidazole were added to 1 kg of anhydrous DMF, the temperature was lowered to -5°C, and 75.96 g of trimethylchlorosilane was added dropwise over a period of 1.5 hours. After the addition was complete, the mixture was returned to room temperature and allowed to react for 1.5 hours. After the reaction was complete, the reaction solution was transferred to a separatory funnel and washed three times with a 1 mol / L hydrochloric acid solution and once with a saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain a monosilyl ether intermediate. (b) Under nitrogen protection, 100 g of the monosilyl ether intermediate, 70.22 g of iodomethane, and 83.91 g of potassium carbonate were added to 1.2 kg of anhydrous acetone, heated to 60°C, and reacted for 4 h. After the reaction, the mixture was cooled to room temperature and filtered. The filtrate was concentrated under reduced pressure to obtain a brown liquid. The brown liquid was added to a separatory funnel, and 700 g of anhydrous ether was added. The mixture was washed three times with a saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain a gradient polarity regulator.

[0040] Preparation Example 6: The preparation method of the gradient polarity regulator is as follows: (a) Under nitrogen protection, 100 g of triethylene glycol and 54.40 g of imidazole were added to 1.2 kg of anhydrous DMF, the temperature was lowered to 0°C, and 79.58 g of trimethylchlorosilane was added dropwise over 2 h. After the addition was complete, the mixture was returned to room temperature and allowed to react for 2 h. After the reaction was complete, the reaction solution was transferred to a separatory funnel and washed three times with 1 mol / L hydrochloric acid solution and once with saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain a monosilyl ether intermediate. (b) Under nitrogen protection, 100 g of the monosilyl ether intermediate, 76.60 g of iodomethane, and 93.23 g of potassium carbonate were added to 1.4 kg of anhydrous acetone, heated to 65°C, and reacted for 5 h. After the reaction, the mixture was cooled to room temperature and filtered. The filtrate was concentrated under reduced pressure to obtain a brown liquid. The brown liquid was added to a separatory funnel, and 900 g of anhydrous ether was added. The mixture was washed three times with a saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain a gradient polarity regulator.

[0041] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that step (1) is omitted, and o-phenylenediamine is directly reacted with n-butyllithium. The specific preparation method is as follows: The specific preparation method of the initiator includes the following steps: Under nitrogen protection, 100 g of o-phenylenediamine was added to 1 kg of a mixed solution of anhydrous toluene and anhydrous THF (prepared by mixing anhydrous toluene and anhydrous THF in a weight ratio of 19:1), the temperature was lowered to -78°C, and 739.78 ml of a 2.5 M hexane solution of n-butyllithium was added dropwise for 1.5 hours. After the addition was complete, the temperature was raised to -5°C and the reaction was allowed to proceed for 2 hours. After the reaction was completed, the reaction was quenched with a mixed solution of ethanol and toluene (prepared by mixing ethanol and toluene in a weight ratio of 1:3). The organic phase was washed twice with a saturated ammonium chloride solution and once with a saturated sodium chloride solution. The organic phases were combined, dried over anhydrous sodium sulfate, and filtered. The filtrate was concentrated under reduced pressure to remove the solvent. The crude product was purified by silica gel column chromatography and recrystallized from a mixed solution of toluene and n-hexane (prepared by mixing toluene and n-hexane in a weight ratio of 2:3). The initiator was crystallized at -10°C for 18 hours to obtain the initiator.

[0042] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that o-phenylenediamine is replaced by m-phenylenediamine.

[0043] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and Preparation Example 2 is that o-phenylenediamine is replaced by aniline.

[0044] Comparative Preparation Example 4: The difference between Comparative Preparation Example 4 and Preparation Example 5 is that step (b) is omitted and the amount of trimethylchlorosilane in step (a) is doubled.

[0045] Comparative Preparation Example 5: The difference between Comparative Preparation Example 5 and Preparation Example 5 is that step (a) is omitted. The specific preparation method is as follows: The specific preparation method of the polarity regulator is as follows: Under nitrogen protection, 100 g of triethylene glycol, 207.94 g of iodomethane and 230.09 g of potassium carbonate were added to 1.2 kg of anhydrous acetone, heated to 60 ° C, and reacted for 4 hours. After the reaction, it was cooled to room temperature and filtered. The filtrate was concentrated under reduced pressure to obtain a brown liquid. The brown liquid was added to a separatory funnel, 700 g of anhydrous ether was added, and the mixture was washed three times with a saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain a polarity regulator.

[0046] Example 1: A specific synthesis method of solution-polymerized butadiene styrene, comprising the following steps: S1. 3 kg of anhydrous cyclohexane was pressed into a stainless steel polymerization kettle by nitrogen, the feed valve was closed and the nitrogen atmosphere in the kettle was maintained, 700 g of butadiene and 300 g of styrene were stirred in a monomer metering tank and added to the polymerization kettle at one time, 5 g of the gradient polarity regulator prepared in Preparation Example 4 was added, stirring was started, the temperature of the material in the kettle was raised to 35 ° C by heating with a hot water jacket, stirred for 5 min, 3 g of the dilithium chelate initiator prepared in Preparation Example 1 was added to initiate polymerization, the reaction was allowed to proceed for 10 min, the temperature was subsequently raised to 45 ° C for 20 min, and then the temperature was raised to 65 ° C for 20 min at a rate of 0.5 ° C / min to complete the chain growth; S2. After the chain growth reaction is completed, the temperature in the reactor is lowered to 55 ° C, 1 g of dichlorodimethylsilane is added, and the reaction is stirred for 15 minutes for end capping. Subsequently, 0.5 g of tin tetrachloride is added and the temperature is raised to 60 ° C for 10 minutes to complete the coupling reaction; S3. After the coupling reaction is completed, the temperature in the kettle is lowered to 45°C, the reaction is quenched with methanol, stirred for 5 minutes, 4g of antioxidant 1010 is added, and stirring is continued for 15 minutes. The discharge valve is opened, and the polymer solution is placed in a coagulation kettle. The polymer solution is stirred and coagulated in deionized water at 80°C to precipitate polymer particles. After washing three times with deionized water, the wet particles are sent to an extrusion dehydrator to remove moisture, and then dried in a drying oven to constant weight to obtain solution-polymerized butadiene styrene.

[0047] Example 2: A specific synthesis method of solution-polymerized butadiene styrene, comprising the following steps: S1. 3.5 kg of anhydrous cyclohexane was pressed into a stainless steel polymerization kettle by nitrogen, the feed valve was closed and the nitrogen atmosphere in the kettle was maintained, 750 g of butadiene and 250 g of styrene were stirred in a monomer metering tank and added to the polymerization kettle at one time, and then 6 g of the gradient polarity regulator prepared in Preparation Example 5 was added, stirring was started, the temperature of the material in the kettle was raised to 40 ° C by heating the hot water jacket, stirred for 10 min, 4 g of the dilithium chelate initiator prepared in Preparation Example 2 was added to initiate polymerization, the reaction was carried out for 15 min, and then the temperature was raised to 50 ° C for 30 min, and then the temperature was raised to 70 ° C for 30 min at a rate of 0.75 ° C / min to complete the chain growth; S2. After the chain growth reaction is completed, the temperature in the reactor is lowered to 60°C, 2g of dichlorodimethylsilane is added, and the reaction is stirred for 20 minutes for end-capping. Subsequently, 1g of tin tetrachloride is added, and the temperature is raised to 65°C for 15 minutes to complete the coupling reaction; S3. After the coupling reaction is completed, the temperature in the kettle is lowered to 50°C, the reaction is quenched with methanol, stirred for 10 minutes, 5g of antioxidant 1010 is added, and stirring is continued for 20 minutes. The discharge valve is opened, and the polymer solution is placed in a coagulation kettle. The polymer solution is stirred and coagulated in deionized water at 85°C to precipitate polymer particles. After washing three times with deionized water, the wet particles are sent to an extrusion dehydrator to remove moisture, and then dried in a drying oven to constant weight to obtain solution-polymerized butadiene styrene.

[0048] Example 3: A specific synthesis method of solution-polymerized butadiene styrene, comprising the following steps: S1. 4 kg of anhydrous cyclohexane was pressed into a stainless steel polymerization kettle by nitrogen, the feed valve was closed and the nitrogen atmosphere in the kettle was maintained, 800 g of butadiene and 200 g of styrene were stirred in a monomer metering tank and added to the polymerization kettle at one time, and then 7 g of the gradient polarity regulator prepared in Preparation Example 6 was added, stirring was started, the temperature of the material in the kettle was raised to 45 ° C by heating the hot water jacket, stirred for 15 min, 5 g of the dilithium chelate initiator prepared in Preparation Example 3 was added to initiate polymerization, the reaction was allowed to proceed for 20 min, and then the temperature was raised to 55 ° C for 40 min, and then the temperature was raised to 75 ° C for 40 min at a rate of 1 ° C / min to complete the chain growth; S2. After the chain growth reaction is completed, the temperature in the reactor is lowered to 65 ° C, 3 g of butadiene is added, and the reaction is stirred for 25 minutes for end capping. Subsequently, 1.5 g of tin tetrachloride is added and the temperature is raised to 70 ° C for 20 minutes to complete the coupling reaction; S3. After the coupling reaction is completed, the temperature in the kettle is lowered to 55°C, the reaction is quenched with methanol, stirred for 15 minutes, 6 g of antioxidant 168 is added, and stirring is continued for 25 minutes. The discharge valve is opened, and the polymer solution is placed in a coagulation kettle. The polymer solution is stirred and coagulated in deionized water at 90°C to precipitate polymer particles. After washing three times with deionized water, the wet particles are sent to an extrusion dehydrator to remove moisture, and then dried in a drying oven to constant weight to obtain solution-polymerized butadiene styrene.

[0049] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the dilithium chelate initiator prepared in Preparation Example 1 is replaced by the initiator prepared in Comparative Preparation Example 1.

[0050] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the dilithium chelate initiator prepared in Preparation Example 1 is replaced by the initiator prepared in Comparative Preparation Example 2.

[0051] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the dilithium chelate initiator prepared in Preparation Example 1 is replaced by the initiator prepared in Comparative Preparation Example 3.

[0052] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the gradient polarity regulator prepared in Preparation Example 4 is replaced by the polarity regulator prepared in Comparative Preparation Example 4.

[0053] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the gradient polarity regulator prepared in Preparation Example 4 is replaced by the polarity regulator prepared in Comparative Preparation Example 5.

[0054] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that the gradient polarity regulator prepared in Preparation Example 4 is replaced by tetrahydrofuran.

[0055] Comparative Example 7: The difference between Comparative Example 7 and Example 2 is that the dilithium chelate initiator prepared in Preparation Example 2 is replaced by n-butyl lithium.

[0056] Comparative Example 8: The difference between Comparative Example 8 and Example 2 is that the dilithium chelate initiator prepared in Preparation Example 2 is replaced by n-butyl lithium, and the gradient polarity regulator prepared in Preparation Example 4 is replaced by tetrahydrofuran.

[0057] Performance testing: 1. According to the test requirements of GB / T8656-2018, the basic properties of the styrene-butadiene rubber prepared in Examples 1-3 and Comparative Examples 1-8 were tested, including Mooney viscosity, ash content, and volatile matter; then, the corresponding rubber mixes were prepared according to the test standards, and the 300% modulus stress, tensile strength, and elongation at break of the rubber mixes were tested. The experimental results are shown in Table 1.

[0058] 2. The styrene-butadiene rubbers prepared in Examples 1-3 and Comparative Examples 1-8 were measured using a gel permeation chromatograph equipped with a high-performance liquid chromatography pump model 1515 produced by Waters Technology Corporation of the United States. The GPC was equipped with three separation columns: HT4, HT5, and HT6. The molecular weight and molecular weight distribution data were measured using tetrahydrofuran as the mobile phase at a flow rate of 1 ml / min. The experimental results are shown in Table 2.

[0059] 3. The chemical shift of the styrene-butadiene rubber prepared in Examples 1-3 and Comparative Examples 1-8 was measured using a BRUKER nuclear magnetic resonance spectrometer (model: AV-600) at 600 MHz, solvent: CDCl 3 , internal standard: tetramethylsilane (TMs), δ=7.27. The vinyl content in styrene-butadiene rubber is calculated by the following formula: , Wherein, Bv,% (wt): represents the mass fraction of 1,2-structure in polybutadiene, that is, the target content we want to calculate; I(4.08-5.04): represents the integrated intensity of hydrogen nuclei with chemical shifts in the range of 4.08-5.04 in the nuclear magnetic resonance hydrogen spectrum, which corresponds to the signal of specific hydrogen in the 1,2-structure of polybutadiene; I(5.04): is the integrated intensity of hydrogen nuclei with a chemical shift of 5.4, corresponding to the signal of hydrogen related to the 1,4-cis structure in polybutadiene; I(5.54): refers to the integrated intensity of hydrogen nuclei with a chemical shift of 5.54, corresponding to the signal of hydrogen related to the 1,4-trans structure in polybutadiene; I(4.8-5.04): is the integrated intensity of hydrogen nuclei with chemical shifts in the range of 4.8-5.04, which is related to the structural characteristic hydrogen signals of polybutadiene. By calculating the integrated intensities in different intervals, the content of 1,2-structure can be obtained.

[0060] The polystyrene content in styrene butadiene copolymer is calculated by the following formula: , Among them, S,% (wt): represents the mass fraction of the polystyrene component in the styrene-butadiene copolymer, which is the calculation target; I(7.04) is the integrated intensity of the hydrogen nucleus at the chemical shift of 7.04, corresponding to the signal of the specific hydrogen on the polystyrene benzene ring; I(6.56): refers to the integrated intensity of the hydrogen nucleus at the chemical shift of 6.56, which is also related to the hydrogen signal of the polystyrene benzene ring; I(5.04): corresponds to the integrated intensity of hydrogen related to the 1,4-cis structure of polybutadiene; I(4.8-5.04): is the integrated intensity of hydrogen nuclei with chemical shifts in the range of 4.80-5.04, which is related to the hydrogen signal of the polybutadiene structure; the calculation of the polystyrene component content is realized through the calculation of these parameters and integrated intensities.

[0061] The experimental results are shown in Table 2.

[0062] 4. Using GPC data, the coupling efficiency (η c ), , where S1 is the peak area of ​​the coupled polymer and S2 is the peak area of ​​the uncoupled polymer. The experimental results are shown in Table 2.

[0063] Table 1 Basic performance test of styrene-butadiene rubber Mooney viscosity ML1+4 100℃ Ash / % Volatile matter / % 300% modulus of tensile stress, MPa, 35min Tensile strength, MPa, 35min Elongation at break%,35min Example 1 54.79 0.17 0.85 13.62 18.72 412.33 Example 2 58.14 0.15 0.76 14.23 20.21 432.86 Example 3 60.32 0.16 0.80 13.76 19.46 417.35 Comparative Example 1 51.20 0.22 0.92 11.83 16.44 385.25 Comparative Example 2 49.83 0.25 0.95 10.51 15.20 365.65 Comparative Example 3 43.51 0.30 1.10 8.27 12.53 320.23 Comparative Example 4 55.30 0.18 0.81 12.66 17.86 415.35 Comparative Example 5 53.66 0.17 0.79 13.10 18.39 425.38 Comparative Example 6 48.92 0.21 0.89 11.23 15.62 375.87 Comparative Example 7 47.22 0.24 0.98 10.34 14.74 355.92 Comparative Example 8 40.12 0.28 1.15 7.88 11.23 305.48 Table 2 Molecular weight, molecular weight distribution, vinyl content, polystyrene content and coupling efficiency of styrene-butadiene rubber Molecular weight / (g / mol) Molecular weight distribution index Vinyl content / % Polystyrene content / % Coupling efficiency / % Example 1 265,000 1.15 60.2 23.8 50.5 Example 2 278,000 1.09 62.5 24.2 52.6 Example 3 270,000 1.12 60.7 23.9 51.4 Comparative Example 1 242,000 1.68 53.1 22.5 42.6 Comparative Example 2 230,000 1.82 50.8 22.2 38.5 Comparative Example 3 205,000 2.10 46.2 21.0 30.1 Comparative Example 4 255,000 1.35 56.5 23.2 46.6 Comparative Example 5 260,000 1.28 59.3 23.5 49.1 Comparative Example 6 228,000 1.85 48.5 21.8 36.6 Comparative Example 7 217,000 1.98 47.0 22.2 32.0 Comparative Example 8 198,000 2.35 43.2 21.0 25.0 Performance Analysis: As can be seen from the experimental data of Table 1 and Table 2, the solution-polymerized butadiene styrene prepared by the present invention in Examples 1-3 all show a comprehensive characteristic that is better than that of the comparative example in various performance tests, wherein the key indices such as Mooney viscosity, 300% tensile stress, tensile strength, and elongation at break of Example 2 are optimal, and microstructure parameters such as molecular weight and distribution, vinyl content, and coupling efficiency are more balanced, and ash content and volatile matter are more strictly controlled, and comprehensive performance is significantly ahead. The following is an explanation of the reasons for the excellent performance of Example 2 from each performance test item: From the perspective of Mooney viscosity, the reason for the good performance of Example 2 may be that its molecular chain entanglement degree and regularity achieve the optimal balance. Mooney viscosity is directly related to molecular chain length, entanglement density and structural uniformity. The dilithium chelate initiator used in Preparation Example 2 is protected by o-phenylenediamine disilyl to form a stable five-membered chelate ring. This structure can accurately bind Li through coordination bonds. + , achieving "slow release" initiation, avoiding the non-silicon-based protection initiator in the comparative example (such as comparative example 1 and comparative example 7-8) due to Li + The chain growth disorder caused by the explosive release also overcomes the non-chelating initiator (such as Comparative Example 2-3) due to Li + At the same time, the three-stage structure of "weak polarity silyl ether-medium polarity ether bond-strong polarity methoxy" of the gradient polarity regulator in Preparation Example 5 dynamically regulates the chain growth rate at different polymerization stages through "thermal exchange coordination": at low temperatures, the strong polarity methoxy promotes chain initiation, at medium temperatures, the medium polarity ether bond maintains uniform chain growth, and at high temperatures, the weak polarity silyl ether reduces chain termination, making the molecular chain length more uniform and the entanglement moderate. This synergistic effect puts the molecular weight of Example 2 in the optimal range, the molecular chain entanglement is neither excessive nor too little, and the final Mooney viscosity is more adapted to the processing and performance requirements.

[0064] From the perspective of ash and volatile matter, the reason why Example 2 performs well may be due to the precise control of inorganic impurities during the entire synthesis process. + It is easier to transfer completely to the end of the polymer chain, reducing the residual free lithium salt; the gradient polarity regulator is washed multiple times with dilute hydrochloric acid and saturated sodium chloride solution, and very few exogenous inorganic impurities are introduced into the polymerization system. In the post-polymerization treatment, 85°C deionized water coagulation and three washings can efficiently dissolve and remove the coupling reaction by-products (such as tin salts), and the molecular chain has high regularity and uniform entanglement, reducing the wrapping of inorganic impurities. The comparative example has a high ash content due to the instability of the initiator active center, insufficient purification of the regulator or disordered molecular chains.

[0065] From the perspective of 300% modulus of tensile stress and tensile strength, the reason why Example 2 performs well may be that its molecular chain rigidity and interchain interaction achieve the best match. 300% modulus of tensile stress reflects the material's ability to resist deformation, while tensile strength is related to the molecular chain breakage energy, both of which depend on the rigid structure of the molecular chain and the interchain entanglement strength. In Example 2, the strongly polar methoxyl group of the gradient polarity regulator is connected to Li + The strong coordination effect of the vinyl group significantly promotes the 1,2-addition of butadiene, while the double-bond side groups in the vinyl structure increase the steric hindrance of the molecular chain and improve the chain segment rigidity; at the same time, the medium-polar ether chain balances the reactivity ratio of styrene and butadiene, so that the polystyrene segments are evenly distributed in the molecular chain, and the rigid structure of the benzene ring enhances the interaction force between the molecular chains through the interchain π-π stacking effect; in addition, the coupling efficiency of 52.6% forms a moderate multi-arm branched structure, and the entanglement between the branches further strengthens the cross-linking network. In contrast, the control ratio has low vinyl content, uneven polystyrene distribution or insufficient coupling due to defects in the initiator or regulator, weak interchain interaction, and naturally low tensile stress and tensile strength.

[0066] From the perspective of elongation at break, the reason why Example 2 performs well may be that its molecular chain has good flexibility and segment mobility while maintaining rigidity. Elongation at break depends on the slippage of the molecular chain and the stretchability of the segment, which requires a balance between rigid structure and flexible segment. In the gradient polarity regulator of Example 2, the medium polarity ether chain acts as a flexible spacer, which can both form a bond with Li-ion through ether bond and form a bond with Li-ion. + The weak coordination maintains the connection between the chain segments, and can also undergo rotational slip when subjected to force, alleviating the brittleness caused by the rigid structure; the symmetrical dual active centers of the dilithium chelate initiator make the structure of both ends of the molecular chain more uniform, and combined with the end-capping treatment, the rigid defects at the chain ends are reduced, making the chain segments easier to stretch along the direction of force; in contrast, in the comparative example, the single polarity regulator (such as tetrahydrofuran) leads to uneven distribution of vinyl groups, or the single lithium initiator makes the chain end structure disordered, the chain segment movement is hindered, and the elongation at break is significantly reduced.

[0067] From the perspective of molecular weight and molecular weight distribution, the reason for the good performance of Example 2 may be that its molecular chain growth process is more uniform, avoiding the problem of too large or too small molecular weight and too wide distribution. Molecular weight is related to initiator activity and chain growth rate, while molecular weight distribution depends on the stability of the active center and the synchronization of chain growth. In the dilithium chelate initiator of Example 2, the di-NLi- at ​​the ortho position of o-phenylenediamine is tightly bound to Li through a five-membered chelate ring. + This structure makes the spatial distance between the two active centers and the electronic environment highly symmetrical, ensuring that the two polymer chains are initiated and grown synchronously; the steric hindrance of the silicon base slows down the Li +The reaction rate with the monomer avoids the "instantaneous explosive growth" and makes the chain length more uniform; at the same time, the "thermal exchange coordination" of the gradient polarity regulator dynamically adjusts the Li + The activity of the polymer is good. At low temperatures, strong coordination ensures synchronous initiation, while at high temperatures, weak coordination avoids premature chain termination, ultimately stabilizing the molecular weight at 278,000. In the comparative example, the initiator has no chelating structure or the regulator has no gradient, resulting in uneven chain growth, wide molecular weight distribution, and large performance fluctuations.

[0068] From the perspective of vinyl content, the reason why Example 2 performs well may be that its gradient polarity regulator can accurately control the 1,2-addition reaction of butadiene, making the vinyl structure stable and the content moderate. The vinyl content is determined by the addition mode of butadiene. The 1,2-addition requires a polarity regulator and Li + Strong coordination to change the double bond electron cloud density. In the gradient polarity regulator of Preparation Example 5 used in Example 2, the oxygen atom of the strongly polar methoxy group has high electronegativity and is + The formation of strong coordination bonds effectively induces electron cloud deflection around the butadiene double bond, promoting 1,2-addition. As the polymerization temperature increases, the moderately polar ether chains, due to their moderate coordination energy, gradually take over the regulation, avoiding the sudden drop in coordination capacity of a single highly polar modifier (such as tetrahydrofuran) at high temperatures, thereby increasing the vinyl content. This high vinyl content increases the rigidity of the molecular chain nodes and improves the material's deformation resistance. In contrast, the comparative polymer, due to the lack of a strongly polar end or high-temperature deactivation of the modifier, has a low and fluctuating vinyl content, limiting performance.

[0069] In terms of polystyrene content, the superior performance of Example 2 may be due to the synergistic effect of its dilithium initiator and gradient modifier, which balances the reactivity ratios of styrene and butadiene, resulting in a more uniform distribution of polystyrene segments. Polystyrene content is not only determined by the feed ratio but is also influenced by the monomer reactivity ratios (butadiene is more active than styrene) and initiator selectivity. The dilithium chelate initiator in Example 2, due to silicon-based protection, reduces the electron cloud density of the nitrogen atom, resulting in a more balanced initiation activity for styrene and butadiene. The moderately polar ether chains of the gradient polarity modifier interact simultaneously with the double bonds of both monomers through a dipole-dipole interaction, weakening the preferential polymerization of butadiene and enabling more uniform embedding of the polystyrene segments within the butadiene backbone. This uniform distribution avoids localized excessive rigidity caused by polystyrene blocks and enhances interchain interactions. In contrast, in the comparative example, due to the initiator's preference for butadiene initiation or the lack of a moderately polar segment in the modifier, the polystyrene distribution is uneven, the content deviates from the designed value, and performance declines.

[0070] In terms of coupling efficiency, the superior performance of Example 2 may be due to the symmetrical structure of its dilithium chelate initiator, which reacts more fully with the coupling agent and achieves an optimal coupling efficiency. The coupling efficiency reflects the degree to which the molecular chain forms a branched structure through the coupling agent. The symmetrical dual active centers (-NLi-) of the dilithium initiator react symmetrically with tin tetrachloride (SnCl4) to form a stable multi-arm structure. The coupling efficiency of Example 2 is 52.6%, which is within the optimal range of 45%-55%. This branching increases the molecular chain entanglement density (improving strength) while avoiding excessive cross-linking (e.g., exceeding 60%) that can lead to processing difficulties. The five-membered chelate ring of the dilithium initiator stabilizes the active center and reduces side reactions in the coupling reaction. In contrast, the comparative example, due to the asymmetric or single active center of the initiator, reacts unevenly with the coupling agent, resulting in low coupling efficiency, ineffective branching, and inferior performance.

[0071] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A solution-polymerized butadiene styrene, characterized in that: The invention is prepared by polymerization reaction of the following raw materials in parts by weight: butadiene: 70-80 parts, styrene: 20-30 parts, anhydrous cyclohexane: 300-400 parts, dilithium chelate initiator: 0.3-0.5 parts, gradient polarity regulator: 0.5-0.7 parts, end-capping agent: 0.1-0.3 parts, coupling agent: 0.05-0.15 parts, antioxidant: 0.4-0.6 parts; The end-capping agent refers to one or both of dichlorodimethylsilane and butadiene, the coupling agent refers to tin tetrachloride, and the antioxidant refers to one or both of antioxidant 1010 and antioxidant 168; The preparation method of the dilithium chelate initiator is as follows: (1) Under nitrogen protection, o-phenylenediamine and triethylamine were added to anhydrous tetrahydrofuran, cooled to 0-5°C, and trimethylchlorosilane was added dropwise for 1-2 hours. After the addition was completed, the mixture was returned to room temperature and reacted for 2-4 hours. After the reaction was completed, the mixture was filtered and the filtrate was concentrated under reduced pressure to obtain bis(trimethylsilyl)o-phenylenediamine, which was used directly in the next step without purification. (2) Under nitrogen protection, add bis(trimethylsilyl)-o-phenylenediamine to a mixed solution of anhydrous toluene and anhydrous tetrahydrofuran, cool to -78°C, and add n-butyllithium in hexane solution dropwise for 1-2 hours. After the addition is complete, heat to -10-0°C and react for 1-3 hours. After the reaction is complete, quench the reaction with a mixed solution of ethanol and toluene. Wash the organic phase twice with a saturated ammonium chloride solution and once with a saturated sodium chloride solution. Combine the organic phases, dry over anhydrous sodium sulfate, filter, and concentrate the filtrate under reduced pressure to remove the solvent. The obtained crude product is recrystallized from a mixed solution of toluene and n-hexane and crystallized at -20-0°C for 12-24 hours to obtain a dilithium chelate initiator. The preparation method of the gradient polarity regulator is as follows: (a) Under nitrogen protection, triethylene glycol and imidazole are added to anhydrous N,N-dimethylformamide, the temperature is lowered to -10-0°C, and trimethylchlorosilane is added dropwise for 1-2 hours. After the addition is complete, the mixture is returned to room temperature and reacted for 1-2 hours. After the reaction is complete, the reaction solution is transferred to a separatory funnel, washed three times with dilute hydrochloric acid and once with saturated sodium chloride solution. The organic phase is dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain a monosilyl ether intermediate. (b) Under nitrogen protection, the monosilyl ether intermediate, iodomethane and potassium carbonate were added to anhydrous acetone, the temperature was raised to 55-65°C, and the reaction was carried out for 3-5 hours. After the reaction was completed, the mixture was cooled to room temperature and filtered. The filtrate was concentrated under reduced pressure to obtain a brown liquid. The brown liquid was added to a separatory funnel, anhydrous ether was added, and the mixture was washed three times with a saturated sodium chloride solution. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain a gradient polarity regulator.

2. A solution-polymerized butadiene styrene according to claim 1, characterized in that: The molar ratio of o-phenylenediamine, trimethylsilyl chloride and triethylamine in (1) is 1:2-2.4:2-2.4, and the weight ratio of o-phenylenediamine and anhydrous tetrahydrofuran is 1:8-12.

3. A solution-polymerized butadiene styrene according to claim 1, characterized in that: The molar ratio of n-butyl lithium in the hexane solution of bis(trimethylsilyl)-o-phenylenediamine and n-butyl lithium in (2) is 1:2-2.2, the weight ratio of the mixed solution of bis(trimethylsilyl)-o-phenylenediamine, anhydrous toluene and anhydrous tetrahydrofuran is 1:8-12, and the hexane solution of n-butyl lithium refers to a hexane solution with an n-butyl lithium concentration of 2.5 M.

4. A solution-polymerized butadiene styrene according to claim 1, characterized in that: The anhydrous toluene and anhydrous tetrahydrofuran mixed solution in (2) refers to a mixture of anhydrous toluene and anhydrous tetrahydrofuran in a weight ratio of 19:1, the ethanol and toluene mixed solution refers to a mixture of ethanol and toluene in a weight ratio of 1:3, and the toluene and n-hexane mixed solution refers to a mixture of toluene and n-hexane in a weight ratio of 2:

3.

5. The solution-polymerized butadiene styrene according to claim 1, characterized in that: In the above (a), the molar ratio of triethylene glycol, trimethylsilyl chloride and imidazole is 1:1-1.1:1-1.2, the weight ratio of triethylene glycol and anhydrous N,N-dimethylformamide is 1:8-12, and the dilute hydrochloric acid refers to a hydrochloric acid solution with a concentration of 1 mol / L.

6. The solution-polymerized butadiene styrene according to claim 1, characterized in that: The molar ratio of the monosilyl ether intermediate, methyl iodide and potassium carbonate in (b) is 1:1-1.2:1.2-1.5, and the weight ratio of the monosilyl ether intermediate, anhydrous acetone and anhydrous ether is 1:10-14:5-9.

7. The method for synthesizing solution-polymerized butadiene styrene according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Anhydrous cyclohexane was pressurized into a stainless steel polymerization kettle using nitrogen. The feed valve was closed and a nitrogen atmosphere was maintained in the kettle. Butadiene and styrene were stirred uniformly in a monomer metering tank and added to the polymerization kettle at once. A gradient polarity regulator was then added and stirring was started. The contents in the kettle were heated to 35-45°C using a hot water jacket and stirred for 5-15 minutes. A dilithium chelate initiator was added to initiate polymerization and allowed to react for 10-20 minutes. The temperature was then raised to 45-55°C for 20-40 minutes, and then raised to 65-75°C at a rate of 0.5-1°C / min for 20-40 minutes to complete chain growth. S2. After the chain growth reaction is completed, the temperature in the reactor is lowered to 55-65 ° C, the end-capping agent is added, and the reaction is stirred for 15-25 minutes for end-capping. Then, the coupling agent is added and the temperature is raised to 60-70 ° C for 10-20 minutes to complete the coupling reaction; S3. After the coupling reaction is completed, the temperature in the kettle is lowered to 45-55°C, the reaction is quenched with methanol, stirred for 5-15 minutes, an antioxidant is added, and stirring is continued for 15-25 minutes. The discharge valve is opened, and the polymer solution is placed in a coagulation kettle. The polymer solution is stirred and coagulated in deionized water at 80-90°C to precipitate polymer particles. After washing three times with deionized water, the wet particles are sent to an extrusion dehydrator to remove moisture, and then dried in a drying oven to constant weight to obtain solution-polymerized butadiene styrene.

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