A method for the synthesis of solution-polymerized styrene-butadiene

Abstract

The present application relates to the technical field of rubber synthesis, in particular to a kind of synthesis method of solution polymerized butadiene styrene.The synthesis method uses butadiene and styrene as monomer, cooperates double lithium chelate initiator, gradient polarity regulator and other raw materials, is prepared through polymerization, end-capping, coupling and post-processing step.Among them, double lithium chelate initiator is prepared by o-phenylenediamine silicon-based protection and lithiation reaction, contains stable five-membered chelate ring;Gradient polarity regulator is prepared by triethylene glycol through silylation and methylation, presents three-stage polarity gradient, and the controllability of polymerization is improved by the cooperation of the two.The synthesis method can accurately control the microstructure of the product, reduce ash content and volatile matter, improve mechanical properties and processing stability, and is suitable for the field of high-performance rubber products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rubber synthesis, and particularly relates to a solution polymerized styrene-butadiene rubber synthesis method. BACKGROUND

[0002] Styrene-butadiene rubber (SBR) is an important synthetic rubber, which is copolymerized by styrene and butadiene, and is widely used in the fields of tires, shoemaking, industrial products, etc. due to excellent wear resistance, aging resistance and processing performance. It is one of the most widely used varieties in the rubber industry, and its comprehensive performance can be optimized by adjusting the ratio of styrene and butadiene and the microstructure to meet the use requirements of different scenes, and it occupies an important position in the national economy.

[0003] Among the many types of styrene-butadiene rubber, solution polymerized styrene-butadiene rubber (SSBR) is prepared by copolymerization of styrene and butadiene in an organic solvent through a solution polymerization process. Compared with traditional emulsion polymerized styrene-butadiene rubber (ESBR), SSBR has the advantages of narrow molecular weight distribution, strong controllability of microstructure (such as vinyl content and styrene sequence distribution), etc., and can better balance the hysteresis loss, wet skid resistance and rolling resistance of rubber, etc. Therefore, it has shown significant advantages in high-performance tires (especially green tires), and has become a key material for improving the comprehensive performance of tires.

[0004] However, the current research and production of solution polymerized styrene-butadiene rubber still faces many technical challenges. In the initiation system, the traditional single lithium initiator (such as n-butyllithium) is prone to association, resulting in uneven distribution of active centers, large fluctuation of initiation efficiency, and then causing wide polymer molecular weight distribution, poor structure uniformity, and affecting the stability of mechanical properties; in the microstructure regulation aspect, ordinary polar regulators are mostly single structure, which is difficult to dynamically adapt to the demand of monomer reactivity at each stage of polymerization, resulting in insufficient control precision of vinyl content, uneven copolymerization sequence distribution of styrene and butadiene, and restricting the further improvement of key properties such as rubber modulus and tensile strength. In addition, the precise control of coupling reaction efficiency, the effective removal of impurities (such as ash and volatile matter), etc. also have adverse effects on the processing performance and durability of SSBR, limiting its application expansion in high-end fields.

[0005] The preparation method of the epoxidized solution polymerized styrene-butadiene rubber disclosed in Chinese patent application No. CN116162205A has certain performance in modification effect, but hydrogen gas is easily formed by decomposition of hydrogen peroxide in the reaction process, which brings great safety hazards to industrial production, and makes it difficult to realize large-scale industrial application. The method for preparing functionalized solution polymerized styrene-butadiene rubber / white carbon black composite material disclosed in Chinese patent application No. CN110387073B has certain advantages in modification effect, but there are obvious deficiencies in solving the problems of polymerization activity and related chain type and coupling of high Mooney solution polymerized styrene-butadiene rubber, which limits the application of the product in certain specific fields. The double-functionalized styrene-butadiene polymer related technology disclosed in Chinese patent application No. CN106565904B, and the initiators and polymerization methods involved in the papers "Research Progress of Negative Ion Polymerization Double Lithium Initiator" and "Preparation of Functionalized Multi-lithium Initiator and Its Application in Polymerization of Three Monomers" cannot effectively solve the key problems of solution polymerized styrene-butadiene rubber in combination with white carbon black filler, hydrolysis stability and randomization of high styrene content. The functionalized solution polymerized styrene-butadiene rubber modified by silane coupling agent and its synthesis method disclosed in Chinese patent application No. CN108017757B also cannot fundamentally break through the difficulties of the existing technology and solve the above core problems. SUMMARY

[0006] The purpose of the present application is to solve the problems existing in the prior art and to provide a synthesis method of solution polymerized styrene-butadiene.

[0007] To achieve the above purpose, the present application provides a solution polymerized styrene-butadiene prepared by polymerization reaction of the following raw materials by weight: butadiene 70-80 parts, styrene 20-30 parts, anhydrous cyclohexane 300-400 parts, double lithium 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.

[0008] The preparation method of the double lithium chelate initiator is as follows:

[0009] (1) Under nitrogen protection, o-phenylenediamine and triethylamine are added to anhydrous tetrahydrofuran (THF), cooled to 0-5℃, and then trimethylchlorosilane is added dropwise, the dropwise addition time is 1-2h, after the dropwise addition is completed, the room temperature is restored, the reaction is carried out for 2-4h, after the reaction is completed, filtration is carried out, and the filtrate is concentrated under reduced pressure to obtain bis(trimethylsilyl) o-phenylenediamine, which is directly used in the next step without purification, and the chemical reaction equation is as follows:

[0010]

[0011] ​The nitrogen atom in the amino group of o-phenylenediamine contains a lone pair of electrons, making it 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), resulting in a nucleophilic substitution reaction. The generated HCl is neutralized by the acid-binding agent triethylamine, preventing the reaction between HCl and the amine from reversing. Because o-phenylenediamine contains two amino groups, and trimethylchlorosilane is in slight excess, both amino groups undergo silylation, forming a bisily protected product. The product is then transported through... 1 H NMR and 29 Characterized by Si NMR;

[0012] (2) Under nitrogen protection, bis(trimethylsilyl)-o-phenylenediamine was added to a mixed solution of anhydrous toluene and anhydrous THF, and the temperature was lowered to -78°C. A hexane solution of n-butyllithium was added dropwise over 1-2 hours. After the addition was complete, the temperature was raised to -10-0°C and the reaction was allowed to proceed for 1-3 hours. After the reaction was completed, the reaction was quenched with a mixed solution of 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, and filtered. The filtrate was concentrated under reduced pressure to remove the solvent. The crude product was recrystallized from a mixed solution of toluene and n-hexane at -20-0°C for 12-24 hours to obtain the bis-lithium chelating initiator. The chemical reaction equation is as follows:

[0013] ,

[0014] In the bis-silicon-protected product, the H atom on the amino group exhibits weak acidity due to the high electronegativity of nitrogen (N), and can be protonated by the strongly basic n-butyllithium, resulting in -NLi-. - With Li + They are bonded by electrostatic interaction, and the two -NLi- groups are located in the ortho position of the benzene ring, with a spatial distance that is compatible with Li. + The coordination radius, through coordination bonds, forms a five-membered chelate ring, and the product is obtained through... 1 Characterized by 1H NMR;

[0015] The gradient polarity modifier is prepared as follows:

[0016] (a) Under nitrogen protection, triethylene glycol and imidazole were added to anhydrous N,N-dimethylformamide (DMF), and the mixture was cooled to -10 to 0 °C. Trimethylchlorosilane was added dropwise over 1-2 hours. After the addition was complete, the mixture was allowed to return to room temperature and reacted for 1-2 hours. After the reaction was complete, the reaction mixture was transferred to a separatory funnel, washed three times with dilute hydrochloric acid, and then washed 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. The chemical reaction equation is as follows:

[0017] ,

[0018] The O atom in the hydroxyl group of triethylene glycol contains a lone pair of electrons, and is more nucleophilic than an ether bond, and can attack the Si atom of trimethylsilyl chloride to undergo nucleophilic substitution reaction. Since a weak base imidazole and a limited amount of trimethylsilyl chloride are used, only one hydroxyl group preferentially reacts, the imidazole neutralizes the generated HCl to form imidazole hydrochloride, and trimethylsilyl chloride is avoided to cause disilylation (strong alkaline conditions easily induce double substitution, and the weak base imidazole can inhibit it). The product is characterized by 1 H NMR and 29 Si NMR.

[0019] (b) Under nitrogen protection, the monosilyl ether intermediate, iodomethane and potassium carbonate are added to anhydrous acetone, and the temperature is raised to 55-65°C, and the reaction is carried out for 3-5h. After the reaction is completed, it is cooled to room temperature, filtered, and the filtrate is concentrated under reduced pressure to obtain a brown liquid. The brown liquid is added to a separatory funnel, anhydrous diethyl ether is added, and it is washed with saturated sodium chloride solution for 3 times. The organic phase is dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain a gradient polarity regulator, and the chemical reaction equation is as follows:

[0020]

[0021] The remaining hydroxyl group of the monosilyl ether intermediate generates potassium alcohol under the action of weak base potassium carbonate, and the strong base weak acid salt promotes deprotonation. The potassium alcohol acts as a nucleophile to attack the partially positive C atom in iodomethane, and I - is a good leaving group, and the reaction proceeds through the SN2 mechanism. Iodomethane has small steric hindrance, which is beneficial to the attack of the nucleophile, and a gradient structure with a weakly polar silyl ether at one end, a medium-polarity ether bond in the middle, and a strongly polar methoxy group at the other end is formed. The product is characterized by 1 H NMR.

[0022] Preferably, the capping agent refers to one or both of dichlorodimethylsilane or butadiene.

[0023] Preferably, the coupling agent refers to tin tetrachloride.

[0024] Preferably, the antioxidant refers to one or both of antioxidant 1010 or antioxidant 168.

[0025] Preferably, the molar ratio of the (1) o-phenylenediamine, trimethylsilyl chloride and triethylamine is 1:2-2.4:2-2.4, and the weight ratio of o-phenylenediamine to anhydrous THF is 1:8-12.

[0026] ​Preferably, the amino group of the o-phenylenediamine in (1) is strongly nucleophilic. If not protected, it will directly react with n-butyllithium, resulting in multi-lithiation due to the high activity of the N-H bond, destroying the double-lithium symmetry of the initiator. The trimethylsilyl group is connected through an Si-N bond, and the electronegativity of silicon is lower than that of carbon, which reduces the electron cloud density of the N atom and leaves only one N-H bond that can be lithiated, ensuring the formation of a single double-lithium structure. At the same time, due to the large size of the silicon group, a spatial barrier is formed around the amino group, slowing down the attack speed of n-butyllithium on the N-H bond, avoiding the instantaneous explosive generation of the initiator, and also enhancing the stability of the initiator.

[0027] Preferably, the molar ratio of double (trimethylsilyl) o-phenylenediamine to n-butyllithium in the hexane solution in (2) is 1:2-2.2.

[0028] Preferably, the weight ratio of double (trimethylsilyl) o-phenylenediamine to anhydrous toluene and anhydrous THF mixed solution in (2) is 1:8-12.

[0029] Preferably, the hexane solution of n-butyllithium in (2) refers to a hexane solution of n-butyllithium with a concentration of 2.5M.

[0030] Preferably, the anhydrous toluene and anhydrous THF mixed solution in (2) refers to a mixture of anhydrous toluene and anhydrous THF with a weight ratio of 19:1.

[0031] Preferably, the toluene and n-hexane mixed solution in (2) refers to a mixture of toluene and n-hexane with a weight ratio of 2:3.

[0032] Preferably, the toluene and n-hexane mixed solution in (2) refers to a mixture of toluene and n-hexane with a weight ratio of 2:3.

[0033] 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 matches the coordination radius of Li + perfectly, and the coordination energy is higher than that of the non-chelating structure, making the active center not easy to decompose, solving the problem of easy association (forming dimers) of traditional n-butyllithium. In the initiation stage, Li + in the chelating ring weakly coordinates with the π electron cloud of the double bond of the monomer (butadiene and styrene), gradually breaking the constraint of the N-Li bond, forming a step-by-step process of "chelating ring opening → Li + transfer → active chain generation". This slow release makes the molecular weight distribution narrow, which is better than the traditional system. Finally, each initiator molecule contains two active Li + , which can simultaneously initiate two polymer chains, and the growth rate deviation of the two chains is small, ensuring the structural uniformity of the product.

[0034] Preferably, the molar ratio of triethylene glycol, trimethylchlorosilane and imidazole in (a) is 1:1-1.1:1-1.2.

[0035] Preferably, the weight ratio of triethylene glycol and anhydrous DMF in (a) is 1:8-12.

[0036] Preferably, the dilute hydrochloric acid in (a) refers to a hydrochloric acid solution with a concentration of 1 mol / L.

[0037] Preferably, the molar ratio of monosilylether intermediate, iodomethane and potassium carbonate in (b) is 1:1-1.2:1.2-1.5.

[0038] Preferably, the weight ratio of monosilylether intermediate, anhydrous acetone and anhydrous diethyl ether in (b) is 1:10-14:5-9.

[0039] Preferably, the strong polarity end (methoxy) oxygen atom of the gradient polarity regulator in (b) has high electronegativity, and has a strong coordination bond with Li + , which is preferentially combined with Li + at the initial stage of polymerization, promotes the 1,2-addition of butadiene, and improves the vinyl content; the moderate polarity region (ether bond) has moderate ether bond density, takes over the regulation at the middle stage, balances the insertion rates of the two monomers, and is beneficial to the generation of random structure; the weak polarity end (silylether) weakens the coordination ability of the oxygen atom, reduces the binding of Li + at the later stage, avoids chain termination caused by excessive regulation, and realizes "thermal coordination exchange" with Li + through the difference in polarity as the polymerization temperature rises.

[0040] Preferably, the "thermal coordination exchange" is mainly based on the following principle: at different temperatures, the degree of molecular thermal motion is different, which affects the coordination balance of different polar groups with Li + From the molecular level, the coordination bond formed by the strong polarity methoxy and Li + can exist stably at low temperature due to high coordination energy, when the temperature rises, the stability of this strong coordination bond is impacted by the enhanced molecular thermal motion, the coordination competitiveness of the moderate polarity ether chain with Li + is enhanced at slightly higher temperature, which gradually replaces the methoxy with Li + coordination, and at the high temperature stage, the weak polarity silylether is less affected by the molecular thermal motion under the influence of temperature, and its coordination energy is low, so it is easier to be combined with Li + , thereby completing the whole thermal coordination exchange process.

[0041] Further, the present application also provides a synthesis method of the above-mentioned solution-polymerized butadiene, comprising the following steps:

[0042] S1. Anhydrous cyclohexane is pressurized into a stainless steel polymerization kettle by nitrogen, the feed valve is closed and the nitrogen atmosphere in the kettle is maintained, after the monomer metering tank is stirred uniformly, butadiene and styrene are added into the polymerization kettle at one time, then the gradient polarity regulator is added, the stirring is started, the temperature of the kettle is raised to 35-45 DEG C by heating with hot water jacket, the stirring is carried out for 5-15 min, the double lithium chelate initiator is added to initiate polymerization, the reaction is carried out for 10-20 min, then the temperature is raised to 45-55 DEG C and the reaction is carried out for 20-40 min, then the temperature is raised to 65-75 DEG C at a rate of 0.5-1 DEG C / min and the reaction is carried out for 20-40 min, and the chain growth is completed;

[0043] S2. After the chain growth reaction is completed, the temperature in the kettle is reduced to 55-65 DEG C, the end-capping agent is added, the stirring is carried out for 15-25 min to carry out end-capping, then the coupling agent is added, the temperature is raised to 60-70 DEG C and the reaction is carried out for 10-20 min, and the coupling reaction is completed;

[0044] S3. After the coupling reaction is completed, the temperature in the kettle is reduced to 45-55 DEG C, the reaction is quenched with methanol, the stirring is carried out for 5-15 min, the antioxidant is added, the stirring is continuously carried out for 15-25 min, the discharge valve is opened, the polymerization liquid is put into a coagulation kettle, the stirring is carried out in 80-90 DEG C deionized water to coagulate, the polymer particles are precipitated, the wet particles are washed with deionized water for three times, then the wet particles are sent into an extrusion dewatering machine to remove water, then the particles are dried in a drying box to constant weight, and the solution polymerized butadiene styrene is obtained.

[0045] The beneficial effects of the present application are as follows:

[0046] 1. The present application significantly improves the controllability of polymerization by using a double lithium chelate initiator. The initiator forms a stable five-membered chelate ring structure by means of o-phenylenediamine bis-silyl protection, can precisely bind the active center, avoids the chain growth disorder caused by the explosive release or association of the active center of the traditional initiator, makes the molecular chain growth more uniform, the molecular weight distribution is narrower, and further improves the structural uniformity of the rubber, which lays a foundation for excellent mechanical properties. At the same time, the double active center design can simultaneously initiate two molecular chains, further ensuring the consistency of the product structure and improving the processing stability of the rubber.

[0047] 2. The application of the gradient polarity regulator used in the present application realizes the dynamic and precise regulation of the polymerization process. The regulator has a three-section structure of "weakly polar silyl ether-medium polar ether bond-strong polar methoxy group", which can adapt to the demand of the active center in different stages of polymerization through the "thermal coordination exchange" mechanism: the strong polar end promotes butadiene 1,2-addition at low temperature to improve the vinyl content, the medium polar section balances the monomer insertion rate at medium temperature to optimize the styrene distribution, and the weak polar end reduces the chain termination at high temperature. This dynamic regulation makes the microstructure of the rubber more reasonable, effectively balancing the deformation resistance and flexibility.

[0048] 3. This invention significantly improves the purity and stability of rubber by optimizing the synergistic effect of initiators and regulators. The silicon-based protection and purification process of the double lithium chelate initiator reduces impurity generation, and the multiple washing steps of the gradient polarity regulator reduce the introduction of exogenous impurities. Combined with the post-polymerization process of deionized water coagulation at 80-90℃ and three washings, residual metal salts, solvents and other impurities can be efficiently removed, reducing ash and volatile content, minimizing the interference of impurities on the intermolecular forces, and improving the durability and performance stability of the rubber.

[0049] 4. The coupling reaction efficiency of this invention is easier to control within the optimal range. Through the precise reaction between the symmetrical dual active centers of the double lithium chelating initiator and the coupling agent, a stable multi-arm branched structure can be formed. This enhances strength by moderately branching to strengthen molecular chain entanglement, while avoiding processing difficulties caused by excessively high coupling efficiency. Simultaneously, the use of the end-capping agent optimizes the molecular chain end structure, reduces rigidity defects, further improves the overall performance of the rubber, and broadens its application potential in the field of high-end rubber products. Attached Figure Description

[0050] Figure 1 The bis(trimethylsilyl)o-phenylenediamine prepared in Example 2 of this invention 1 H NMR spectrum;

[0051] Figure 2 The bis(trimethylsilyl)o-phenylenediamine prepared in Example 2 of this invention 29 Si NMR spectrum;

[0052] Figure 3 The double lithium chelating initiator prepared in Example 2 of this invention 1 H NMR spectrum;

[0053] Figure 4 The monosilyl ether intermediate prepared in Example 5 of this invention 1 H NMR spectrum;

[0054] Figure 5 The monosilyl ether intermediate prepared in Example 5 of this invention 29 Si NMR spectrum;

[0055] Figure 6 The gradient polarity modifier prepared in Example 5 of this invention 1 H NMR spectrum. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0057] The main sources of raw materials used in this invention are as follows:

[0058] Styrene (St): polymerization grade, Beijing Chemical Reagent Factory, purified by twice distillation under reduced pressure before use; Butadiene (Bd): polymerization grade, purity more than 99%, Qilu Petrochemical, dried by 4A molecular sieve, purified by twice distillation before use; Tin tetrachloride: analytical pure, Jiangsu Qiangsheng Functional Chemical Co., Ltd.; Dichlorodimethylsilane: purity 99%, Shanghai Macklin Biochemical Technology Co., Ltd.; Antioxidant 1010: purity more than 98%, Shanghai Macklin Biochemical Technology Co., Ltd.; Antioxidant 168: 98%, Shanghai Macklin Biochemical Technology Co., Ltd.; o-Phenylenediamine: 98%, Shanghai Macklin Biochemical Technology Co., Ltd.; Triethylamine: 99%, Shanghai Macklin Biochemical Technology Co., Ltd.; Trimethylchlorosilane: purity more than 98%, Shanghai Macklin Biochemical Technology Co., Ltd.; n-Butyllithium in hexane: 2.5 M solution in Hexanes, Shanghai Macklin Biochemical Technology Co., Ltd.; Triethylene glycol: 99.5%, Shanghai Macklin Biochemical Technology Co., Ltd.; Imidazole: 99%, Shanghai Macklin Biochemical Technology Co., Ltd.; Iodomethane: 99.5%, Shanghai Macklin Biochemical Technology Co., Ltd.; Potassium carbonate: 99%, Shanghai Macklin Biochemical Technology Co., Ltd.

[0059] Preparation Example 1: The specific preparation method of the double lithium chelating initiator is as follows:

[0060] (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 trimethylchlorosilane was added dropwise, the dropwise addition time was 1 h, after the dropwise addition was completed, the room temperature was restored, the reaction was carried out for 2 h, after the reaction was completed, filtration was carried out, and the filtrate was concentrated under reduced pressure to obtain bis(trimethylsilyl) o-phenylenediamine, which was directly used in the next step without purification;

[0061] (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 according to a weight ratio of 19:1), cooled to -78°C, and 633.64 ml of n-butyllithium hexane solution with a concentration of 2.5 M was added dropwise, the dropwise addition time was 1 h, after the dropwise addition was completed, the temperature was raised to -10°C, and the reaction was carried out for 1 h, after the reaction was completed, the reaction was quenched with a mixed solution of ethanol and toluene (mixed according to a weight ratio of 1:3), the organic phase was washed with saturated ammonium chloride solution for 2 times, and then washed with saturated sodium chloride solution for 1 time, the combined organic phase was dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent, to obtain a crude product, which was recrystallized from a mixed solution of toluene and n-hexane (mixed according to a weight ratio of 2:3), and the crystals were precipitated at -20°C for 12 h to obtain the double lithium chelating initiator.

[0062] Preparation Example 2: The specific preparation method of the double lithium chelating initiator is as follows:

[0063] (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, the dropwise addition time was 1.5 h, after the dropwise addition was completed, the room temperature was restored, the reaction was carried out for 3 h, after the reaction was completed, filtration was carried out, and the filtrate was concentrated under reduced pressure to obtain bis(trimethylsilyl) o-phenylenediamine, which was directly used in the next step without purification;

[0064] (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 according to a weight ratio of 19:1), cooled to -78°C, and 665.32 ml of n-butyllithium hexane solution with a concentration of 2.5 M was added dropwise, the dropwise addition time was 1.5 h, after the dropwise 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 according to a weight ratio of 1:3), the organic phase was washed with saturated ammonium chloride solution twice, and then washed with saturated sodium chloride solution once, the combined organic phase was dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent, to obtain a crude product, which was recrystallized from a mixed solution of toluene and n-hexane (mixed according to a weight ratio of 2:3), and the crystals were precipitated at -10°C for 18 h to obtain the double lithium chelating initiator.

[0065] Preparation Example 3: The specific preparation method of the double lithium chelating initiator is as follows:

[0066] (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, the dropwise addition time was 1.5 h, after the dropwise addition was completed, the room temperature was restored, the reaction was carried out for 3 h, after the reaction was completed, filtration was carried out, and the filtrate was concentrated under reduced pressure to obtain bis(trimethylsilyl) o-phenylenediamine, which was directly used in the next step without purification;

[0067] (2) Under nitrogen protection, 200 g of bis (trimethylsilyl) phenylenediamine was added to 2.4 kg of a mixed solution of anhydrous toluene and anhydrous THF (mixed according to a weight ratio of 19:1), and cooled to -78°C. 697 ml of n-butyllithium hexane solution with a concentration of 2.5M was added dropwise, and the dropwise addition time was 2h. After the dropwise addition was completed, the temperature was raised to 0°C, and the reaction was carried out for 3h. After the reaction was completed, the reaction was quenched with a mixed solution of ethanol and toluene (mixed according to a weight ratio of 1:3). The organic phase was washed with saturated ammonium chloride solution twice, and then washed with saturated sodium chloride solution once. 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 according to a weight ratio of 2:3), and the crystals were precipitated at 0°C for 24h to obtain a bis-lithium chelating initiator.

[0068] The specific preparation method of the gradient polarity regulator is as follows:

[0069] (a) Under nitrogen protection, 100 g of triethylene glycol and 45.47 g of imidazole were added to 800 g of anhydrous DMF, and cooled to -10°C. 72.34 g of trimethylchlorosilane was added dropwise, and the dropwise addition time was 1h. After the dropwise addition was completed, the reaction was carried out at room temperature for 1h. After the reaction was completed, the reaction solution was transferred to a separatory funnel, washed with 1 mol / L hydrochloric acid solution three times, and then washed with saturated sodium chloride solution once. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain a monosilylether intermediate.

[0070] (b) Under nitrogen protection, 100 g of the monosilylether intermediate, 63.83 g of iodomethane, and 74.59 g of potassium carbonate were added to 1 kg of anhydrous acetone, and the temperature was raised to 55°C. The reaction was carried out for 3h. After the reaction was completed, the reaction was cooled to room temperature, filtered, and 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 diethyl ether was added, washed with saturated sodium chloride solution three times, and then the organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain a gradient polarity regulator.

[0071] The specific preparation method of the gradient polarity regulator is as follows:

[0072] (a) Under nitrogen protection, 100 g of triethylene glycol and 45.47 g of imidazole were added to 800 g of anhydrous DMF, and cooled to -10°C. 72.34 g of trimethylchlorosilane was added dropwise, and the dropwise addition time was 1h. After the dropwise addition was completed, the reaction was carried out at room temperature for 1h. After the reaction was completed, the reaction solution was transferred to a separatory funnel, washed with 1 mol / L hydrochloric acid solution three times, and then washed with saturated sodium chloride solution once. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain a monosilylether intermediate.

[0073] (b) Under nitrogen protection, 100 g of the mono-silicon ether intermediate, 76.60 g of methyl iodide and 93.23 g of potassium carbonate were added into 1.4 kg of anhydrous acetone, and the temperature was raised to 65 °C, and the reaction was carried out for 5 h. After the reaction was completed, the temperature was cooled to room temperature, and the reaction solution was filtered. The filtrate was concentrated under reduced pressure to obtain a brown liquid. The brown liquid was added into a separatory funnel, 900 g of anhydrous ether was added, and the mixture was washed with saturated sodium chloride solution for 3 times. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain the gradient polarity adjusting agent.

[0074] Preparation Example 6: The gradient polarity adjusting agent was prepared according to the following method:

[0075] (a) Under nitrogen protection, 100 g of triethylene glycol and 54.40 g of imidazole were added into 1.2 kg of anhydrous DMF, and the temperature was lowered to 0 °C. 79.58 g of trimethylsilyl chloride was added dropwise, and the dropwise addition was carried out for 2 h. After the dropwise addition was completed, the temperature was restored to room temperature, and the reaction was carried out for 2 h. After the reaction was completed, the reaction solution was transferred into a separatory funnel, and the mixture was washed with 1 mol / L hydrochloric acid solution for 3 times, and then washed with saturated sodium chloride solution for 1 time. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain the mono-silicon ether intermediate.

[0076] (b) Under nitrogen protection, 100 g of the mono-silicon ether intermediate, 76.60 g of methyl iodide and 93.23 g of potassium carbonate were added into 1.4 kg of anhydrous acetone, and the temperature was raised to 65 °C, and the reaction was carried out for 5 h. After the reaction was completed, the temperature was cooled to room temperature, and the reaction solution was filtered. The filtrate was concentrated under reduced pressure to obtain a brown liquid. The brown liquid was added into a separatory funnel, 900 g of anhydrous ether was added, and the mixture was washed with saturated sodium chloride solution for 3 times. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain the gradient polarity adjusting agent.

[0077] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that step (1) is omitted, and the ortho-phenylenediamine is directly reacted with n-butyllithium. The specific preparation method is as follows: the initiator was prepared according to the following steps:

[0078] Under nitrogen protection, 100 g of o-phenylenediamine was added to a mixed solution of 1 kg of anhydrous toluene and anhydrous THF (mixed in a weight ratio of 19:1), cooled to -78°C, and 739.78 ml of n-butyllithium hexane solution with a concentration of 2.5M was added dropwise, the dropwise addition time was 1.5 h, after the dropwise 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 with saturated ammonium chloride solution twice, and then washed with saturated sodium chloride solution once. The combined organic phase was dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The obtained crude product was purified by silica gel column chromatography, recrystallized in a mixed solution of toluene and n-hexane (mixed in a weight ratio of 2:3), and crystallized at -10°C for 18 h to obtain the initiator.

[0079] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that o-phenylenediamine is replaced by m-phenylenediamine.

[0080] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and Preparation Example 2 is that o-phenylenediamine is replaced by aniline.

[0081] 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.

[0082] Comparative Preparation Example 5: The difference between Comparative Preparation Example 5 and Preparation Example 5 is that step (a) is omitted, and the specific preparation method is as follows: the specific preparation method of the polarity regulator is as follows:

[0083] Under nitrogen protection, 100 g of o-phenylenediamine was added to a mixed solution of 1 kg of anhydrous toluene and anhydrous THF (mixed in a weight ratio of 19:1), cooled to -78°C, and 739.78 ml of n-butyllithium hexane solution with a concentration of 2.5M was added dropwise, the dropwise addition time was 1.5 h, after the dropwise 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 with saturated ammonium chloride solution twice, and then washed with saturated sodium chloride solution once. The combined organic phase was dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The obtained crude product was purified by silica gel column chromatography, recrystallized in a mixed solution of toluene and n-hexane (mixed in a weight ratio of 2:3), and crystallized at -10°C for 18 h to obtain the initiator.

[0084] Example 1: A specific synthesis method of solution polymerized butadiene, comprising the following steps:

[0085] S1. 3 kg of anhydrous cyclohexane was pressured 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 uniformly in a monomer metering tank and then added into 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 materials in the kettle was raised to 35°C by heating with a hot water jacket, stirring was carried out for 5 min, 3 g of the double lithium chelate initiator prepared in Preparation Example 1 was added to initiate polymerization, the reaction was carried out for 10 min, then the temperature was raised to 45°C at a rate of 0.5°C / min and the reaction was carried out for 20 min, then the temperature was raised to 65°C at a rate of 0.5°C / min and the reaction was carried out for 20 min, and chain growth was completed;

[0086] S2. After the chain growth reaction was completed, the temperature in the kettle was reduced to 55°C, 1 g of dichlorodimethylsilane was added, and termination was carried out by stirring for 15 min, then 0.5 g of tin tetrachloride was added, the temperature was raised to 60°C and the reaction was carried out for 10 min, and coupling was completed;

[0087] S3. After the coupling reaction was completed, the temperature in the kettle was reduced to 45°C, methanol was added to quench the reaction, stirring was carried out for 5 min, 4 g of antioxidant 1010 was added, stirring was continued for 15 min, the discharge valve was opened, the polymerization liquid was placed into a coagulation kettle, coagulation was carried out by stirring in deionized water at 80°C, the polymer particles were precipitated, the wet particles were washed three times with deionized water, the wet particles were sent into an extrusion dewatering machine to remove water, then drying was carried out in a drying oven until the weight was constant, and solution-polymerized styrene-butadiene rubber was obtained.

[0088] Example 2: A specific synthesis method of solution-polymerized styrene-butadiene rubber, comprising the following steps:

[0089] S1. 3.5 kg of anhydrous cyclohexane was pressured 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 uniformly in a monomer metering tank and then added into the polymerization kettle at one time, 6 g of the gradient polarity regulator prepared in Preparation Example 5 was added, stirring was started, the temperature of the materials in the kettle was raised to 40°C by heating with a hot water jacket, stirring was carried out for 10 min, 4 g of the double lithium chelate initiator prepared in Preparation Example 2 was added to initiate polymerization, the reaction was carried out for 15 min, then the temperature was raised to 50°C and the reaction was carried out for 30 min, then the temperature was raised to 70°C at a rate of 0.75°C / min and the reaction was carried out for 30 min, and chain growth was completed;

[0090] S2. After the chain growth reaction was completed, the temperature in the kettle was reduced to 60°C, 2 g of dichlorodimethylsilane was added, and termination was carried out by stirring for 20 min, then 1 g of tin tetrachloride was added, the temperature was raised to 65°C and the reaction was carried out for 15 min, and coupling was completed;

[0091] S3. After the completion of the coupling reaction, the temperature in the reactor was reduced to 50°C, the reaction was quenched with methanol, stirred for 10 min, 5 g of antioxidant 1010 was added, and stirring was continued for 20 min. The discharge valve was opened, the polymerization solution was placed in a coagulation kettle, and the polymer particles were precipitated by stirring in deionized water at 85°C. After being washed three times with deionized water, the wet particles were sent to an extrusion dewatering machine to remove water, and then dried in a drying oven to a constant weight to obtain solution-polymerized styrene-butadiene rubber.

[0092] Example 3: A specific synthesis method of solution-polymerized styrene-butadiene rubber, comprising the following steps:

[0093] S1. 4 kg of anhydrous cyclohexane was pressurized into a stainless steel polymerization kettle by nitrogen, the feed valve was closed, and a nitrogen atmosphere was maintained in the kettle. 800 g of butadiene and 200 g of styrene were stirred uniformly in a monomer metering tank and then added to the polymerization kettle at one time. 7 g of the gradient polarity regulator prepared in Preparation Example 6 was added, stirring was started, and the temperature of the material in the kettle was raised to 45°C by heating with a hot water jacket. After stirring for 15 min, 5 g of the double-lithium chelate initiator prepared in Preparation Example 3 was added to initiate polymerization. After 20 min of reaction, the temperature was raised to 55°C for 40 min, and then the temperature was raised to 75°C at a rate of 1°C / min for 40 min to complete the chain growth;

[0094] S2. After the completion of the chain growth reaction, the temperature in the reactor was reduced to 65°C, 3 g of butadiene was added, and the reaction was stirred for 25 min to cap. Then 1.5 g of tin tetrachloride was added, the temperature was raised to 70°C, and the reaction was carried out for 20 min to complete the coupling reaction.

[0095] S3. After the completion of the coupling reaction, the temperature in the reactor was reduced to 55°C, the reaction was quenched with methanol, stirred for 15 min, 6 g of antioxidant 168 was added, and stirring was continued for 25 min. The discharge valve was opened, the polymerization solution was placed in a coagulation kettle, and the polymer particles were precipitated by stirring in deionized water at 90°C. After being washed three times with deionized water, the wet particles were sent to an extrusion dewatering machine to remove water, and then dried in a drying oven to a constant weight to obtain solution-polymerized styrene-butadiene rubber.

[0096] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the double-lithium chelate initiator prepared in Preparation Example 1 is replaced with the initiator prepared in Comparative Preparation Example 1.

[0097] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the double-lithium chelate initiator prepared in Preparation Example 1 is replaced with the initiator prepared in Comparative Preparation Example 2.

[0098] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the double-lithium chelate initiator prepared in Preparation Example 1 is replaced with the initiator prepared in Comparative Preparation Example 3.

[0099] Comparative Example 4: Comparative Example 4 differs from Example 2 in that the gradient polarity modifier prepared in Preparation Example 4 is replaced with the polarity modifier prepared in Comparative Preparation Example 4.

[0100] Comparative Example 5: Comparative Example 5 differs from Example 2 in that the gradient polarity modifier prepared in Preparation Example 4 is replaced with the polarity modifier prepared in Comparative Preparation Example 5.

[0101] Comparative Example 6: Comparative Example 6 differs from Example 2 in that the gradient polarity modifier prepared in Preparation Example 4 is replaced with tetrahydrofuran.

[0102] Comparative Example 7: Comparative Example 7 differs from Example 2 in that the double lithium chelating initiator prepared in Preparation Example 2 is replaced with n-butyllithium.

[0103] Comparative Example 8: Comparative Example 8 differs from Example 2 in that the double lithium chelating initiator prepared in Preparation Example 2 is replaced with n-butyllithium and the gradient polarity modifier prepared in Preparation Example 4 is replaced with tetrahydrofuran.

[0104] Performance test:

[0105] 1. The basic properties of the styrene-butadiene rubber prepared in Examples 1-3 and Comparative Examples 1-8, including Mooney viscosity, ash content, and volatile matter, were tested according to the test requirements of GB / T8656-2018. Then the corresponding rubber compounds were prepared according to the test standards, and the 300% modulus, tensile strength, and elongation at break of the rubber compounds were tested. The experimental results are shown in Table 1.

[0106] 2. The styrene-butadiene rubber prepared in Examples 1-3 and Comparative Examples 1-8 was measured using a gel permeation chromatograph with a high-performance liquid chromatograph pump model 1515 produced by the American waters technology company. The GPC has three separation columns HT4, HT5, and HT6. The molecular weight and molecular weight distribution data were measured with tetrahydrofuran as the mobile phase at a flow rate of 1 ml / min. The experimental results are shown in Table 2.

[0107] 3. The chemical shift of the styrene-butadiene rubber prepared in Examples 1-3 and Comparative Examples 1-8 was measured using a nuclear magnetic resonance instrument (model: AV-600) of BRUKER company. The frequency was 600 MHz, the solvent was CDCl3, the internal standard was tetramethylsilane (TMs), and δ = 7.27.

[0108] The vinyl content in the styrene-butadiene rubber was calculated by the following formula:

[0109] ,

[0110] 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): indicates the integral intensity of hydrogen nuclei in the chemical shift interval of 4.08-5.04 in the nuclear magnetic resonance hydrogen spectrum, which corresponds to the signal of a specific hydrogen in the 1,2-structure of polybutadiene; I(5.04): is the integral intensity of hydrogen nuclei at a chemical shift of 5.4, which corresponds to the signal of hydrogen related to 1,4-cis structure in polybutadiene; I(5.54): refers to the integral intensity of hydrogen nuclei at a chemical shift of 5.54, which corresponds to the signal of hydrogen related to 1,4-trans structure in polybutadiene; I(4.8-5.04): is the integral intensity of hydrogen nuclei in the chemical shift interval of 4.8-5.04, which is related to the signal of the structural hydrogen of polybutadiene. The content of 1,2-structure is obtained by calculating the integral intensity of different intervals.

[0111] The content of polystyrene component in styrene-butadiene copolymer is calculated by the following formula: ,

[0112] Wherein S, %(wt): represents the mass fraction of polystyrene component in styrene-butadiene copolymer, which is the target for calculation; I(7.04): is the integral intensity of hydrogen nuclei at a chemical shift of 7.04, which corresponds to the signal of a specific hydrogen on the benzene ring of polystyrene; I(6.56): refers to the integral intensity of hydrogen nuclei at a chemical shift of 6.56, which is also related to the signal of benzene ring hydrogen of polystyrene; I(5.04): corresponds to the integral intensity of hydrogen related to 1,4-cis structure in polybutadiene; I(4.8-5.04): is the integral intensity of hydrogen nuclei in the chemical shift interval of 4.80-5.04, which is related to the signal of structural hydrogen of polybutadiene; The calculation of the content of polystyrene component is realized by calculating these parameters and integral intensities.

[0113] The experimental results are shown in Table 2.

[0114] 4. Using GPC data, the coupling efficiency (η c ) is calculated by the following formula: Wherein S1 is the peak area of coupled polymer, and S2 is the peak area of uncoupled polymer. The experimental results are shown in Table 2.

[0115] Table 1 Basic performance test of styrene-butadiene rubber

[0116] Mooney viscosity ML1+4100°C Ash content / % Volatile content / % 300% modulus, MPa, 35 min Tensile strength, MPa, 35 min Elongation at break, %, 35 min 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

[0117] Table 2 Molecular weight, molecular weight distribution, vinyl content, polystyrene content and coupling efficiency of styrene-butadiene rubber

[0118] Molecular weight / (g / mol) Molecular weight distribution index Vinyl content / % Polystyrene content / % Coupling efficiency / % Example 1 2.65 million 1.15 60.2 23.8 50.5 Example 2 2.78 million 1.09 62.5 24.2 52.6 Example 3 2.7 million 1.12 60.7 23.9 51.4 Comparative Example 1 2.42 million 1.68 53.1 22.5 42.6 Comparative Example 2 2.3 million 1.82 50.8 22.2 38.5 Comparative Example 3 2.05 million 2.10 46.2 21.0 30.1 Comparative Example 4 2.55 million 1.35 56.5 23.2 46.6 Comparative Example 5 2.6 million 1.28 59.3 23.5 49.1 Comparative Example 6 2.28 million 1.85 48.5 21.8 36.6 Comparative Example 7 2.17 million 1.98 47.0 22.2 32.0 Comparative Example 8 1.98 million 2.35 43.2 21.0 25.0

[0119] Performance analysis:

[0120] As can be seen from the experimental data in Table 1 and Table 2, the solution-polymerized styrene-butadiene rubbers prepared in Examples 1-3 according to the present application all exhibit better comprehensive properties than the comparative examples in various performance tests. Among them, Example 2 has the best key indicators such as Mooney viscosity, 300% modulus, tensile strength, and elongation at break, and more balanced microstructure parameters such as molecular weight and distribution, vinyl content, and coupling efficiency, and more stringent control of ash content and volatile content, and significantly better comprehensive performance. The reasons for the excellent performance of Example 2 are described below from various performance test items:

[0121] In terms of Mooney viscosity, the reason for the good performance of Example 2 may be that the degree of molecular chain entanglement and regularity reaches the optimal balance. Mooney viscosity is directly related to molecular chain length, entanglement density, and structural uniformity. The double-lithium chelating initiator prepared in Preparation Example 2 is protected by o-phenylenediamine disilyl to form a stable five-membered chelate ring. This structure can precisely bind Li + through coordination bonds, realizing “slow-release” initiation, avoiding the chain growth disorder caused by the burst release of Li + in the un-silyl-protected initiators (such as Comparative Examples 1 and 7-8), and overcoming the uneven active centers caused by Li + association in non-chelating initiators (such as Comparative Examples 2-3). At the same time, the three-stage structure of “weakly polar silyl ether-moderately polar ether bond-strongly polar methoxy” in the gradient polarity regulator of Preparation Example 5 dynamically regulates the chain growth rate at different polymerization stages through “thermal-induced coordination exchange”: the strongly polar methoxy promotes chain initiation at low temperatures, the moderately polar ether bond maintains uniform chain growth at medium temperatures, and the weakly polar silyl ether reduces chain termination at high temperatures, resulting in more uniform molecular chain length and moderate entanglement. This synergistic effect makes the molecular weight of Example 2 in the optimal range, the molecular chain entanglement neither too much nor too little, and the Mooney viscosity more suitable for processing and performance requirements.

[0122] In terms of ash content and volatile content, the reason for the good performance of Example 2 may be that it precisely controls inorganic impurities throughout the synthesis process. The five-membered chelate ring structure of the double-lithium chelating initiator makes Li + more easily transferred to the end of the polymer chain, reducing the residual free lithium salt; the gradient polarity regulator is washed with dilute hydrochloric acid and saturated sodium chloride solution multiple times, so that there are very few exogenous inorganic impurities brought into the polymerization system. In the post-polymerization treatment, 85°C deionized water coagulation and three washes can efficiently dissolve and remove the coupling reaction by-products (such as tin salts), and the molecular chain regularity is high and the entanglement is uniform, reducing the wrapping of inorganic impurities. However, the comparative examples have high ash content due to unstable active centers of the initiators, insufficient purification of the regulators, or disordered molecular chains.

[0123] The reason for the good performance of Example 2 can be that the rigidity of the molecular chain and the inter-chain interaction are optimally matched in terms of the 300% modulus and tensile strength. The 300% modulus reflects the material's ability to resist deformation, and the tensile strength is related to the molecular chain breaking energy, both of which depend on the rigid structure of the molecular chain and the strength of the inter-chain entanglement. In Example 2, the strong polar methoxy group of the gradient polarity regulator significantly promotes the 1,2-addition of butadiene through strong coordination with Li + , and the double bond side group in the vinyl structure increases the steric hindrance of the molecular chain and improves the segment rigidity; at the same time, the moderate polarity ether chain balances the reactivity of styrene and butadiene, making the polystyrene segments evenly distributed in the molecular chain, and the rigid structure of the benzene ring enhances the inter-chain interaction force through inter-chain π-π stacking; in addition, the 52.6% coupling efficiency forms a moderate multi-arm branched structure, and the entanglement between the branches further strengthens the cross-linked network, while the comparative examples have low vinyl content, uneven distribution of polystyrene, or insufficient coupling due to initiator or regulator defects, resulting in weak inter-chain interaction, low modulus and tensile strength.

[0124] In terms of elongation at break, the reason for the good performance of Example 2 can be that the molecular chain has good flexibility and segment movement ability while maintaining rigidity. The elongation at break depends on the slip of the molecular chain and the stretchability of the segment, requiring a balance between rigid structure and flexible segment. In the gradient polarity regulator of Example 2, the moderate polarity ether chain serves as a flexible spacer, which can maintain segment connection through weak coordination with Li + , and can rotate and slip when stressed, relieving the brittleness caused by rigid structure; the symmetric double active center of the double lithium chelate initiator makes the structure of the molecular chain more uniform at both ends, combined with end-capping treatment, reducing the rigid defects at the chain ends, making the segment more easily stretched along the stress direction; in contrast, the single polarity regulator (such as tetrahydrofuran) in the comparative examples leads to uneven distribution of vinyl, or the single lithium initiator makes the chain end structure disorderly, hindering the movement of the segment, and the elongation at break is significantly reduced.

[0125] In terms of molecular weight and molecular weight distribution, the reason for the good performance of Example 2 can be that the molecular chain growth process is more uniform, avoiding problems of excessively large or small molecular weight and excessively wide distribution. The molecular weight is related to the initiator activity and chain growth rate, and the molecular weight distribution depends on the stability of the active center and the synchronicity of chain growth. In the double lithium chelate initiator of Example 2, the double-NLi- at the ortho position of the o-phenylenediamine tightly binds Li + through a five-membered chelate ring, which makes the spatial distance and electronic environment of the two active centers highly symmetric, ensuring synchronous initiation and synchronous growth of the two polymer chains; the steric hindrance of the silicon-based group slows down the movement of Li +The reaction rate with monomers avoids "instantaneous explosive growth", making the chain length more uniform; at the same time, the "thermal coordination exchange" of the gradient polarity regulator dynamically adjusts the activity of Li + at low temperature to ensure simultaneous initiation, and weak coordination at high temperature to avoid premature chain termination, ultimately stabilizing the molecular weight at 278,000. In contrast, the comparative examples have no chelating structure for the initiator or no gradient for the regulator, resulting in uneven chain growth, wide molecular weight distribution, and large performance fluctuations.

[0126] The reason for the good performance of Example 2 may be that its gradient polarity regulator can precisely 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, and 1,2-addition requires a polarity regulator to change the electron cloud density of the double bond by strong coordination with Li + The oxygen atom of the strong polarity methoxy in the gradient polarity regulator of Preparation Example 5 used in Example 2 has high electronegativity, forms a strong coordination bond with Li + , and can effectively induce the electron cloud of butadiene double bond to promote 1,2-addition; as the polymerization temperature rises, the moderately polar ether chain gradually takes over the regulation due to its moderate coordination energy, avoiding the problem of sudden drop in coordination ability of single strong polarity regulator (such as tetrahydrofuran) at high temperature, and increasing the vinyl content. This high vinyl content increases the rigid nodes of the molecular chain, improving the material's resistance to deformation, while the comparative examples have low and fluctuating vinyl content due to the lack of strong polarity end or high-temperature inactivation of the regulator, limiting their performance.

[0127] The reason for the good performance of Example 2 may be that its gradient polarity regulator can precisely 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, and 1,2-addition requires a polarity regulator to change the electron cloud density of the double bond by strong coordination with Li + The oxygen atom of the strong polarity methoxy in the gradient polarity regulator of Preparation Example 5 used in Example 2 has high electronegativity, forms a strong coordination bond with Li + , and can effectively induce the electron cloud of butadiene double bond to promote 1,2-addition; as the polymerization temperature rises, the moderately polar ether chain gradually takes over the regulation due to its moderate coordination energy, avoiding the problem of sudden drop in coordination ability of single strong polarity regulator (such as tetrahydrofuran) at high temperature, and increasing the vinyl content. This high vinyl content increases the rigid nodes of the molecular chain, improving the material's resistance to deformation, while the comparative examples have low and fluctuating vinyl content due to the lack of strong polarity end or high-temperature inactivation of the regulator, limiting their performance.

[0128] The reason for the good performance of Example 2 can be that the symmetric structure of the double lithium chelating initiator reacts more fully with the coupling agent, and the coupling efficiency is in the optimal range. The coupling efficiency reflects the degree of formation of branched structures by the molecular chain through the coupling agent, and the symmetric double active center (-NLi-) of the double lithium initiator can symmetrically react with tin tetrachloride (SnCl4) to form a stable multi-arm structure. The coupling efficiency of Example 2 is 52.6%, which is in the optimal range of 45%-55%, which not only increases the molecular chain entanglement density (improves the strength) by branching, but also avoids excessive crosslinking of the molecular chain (processing difficulty) caused by excessive coupling (such as more than 60%). The five-membered chelate ring of the double lithium initiator makes the active center more stable, reduces side reactions in the coupling reaction, and the comparative examples are not as good in performance because the initiator active center is not symmetric or single active center, and the coupling agent reacts unevenly, the coupling efficiency is low, and effective branching cannot be formed.

[0129] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes within the technical range disclosed by the present application according to the technical solutions and inventive concepts of the present application, which should be covered within the protection scope of the present application.

Claims

1. A solution-polymerized styrene-butadiene characterized in that, The raw materials are polymerized to obtain the product, and the raw materials include butadiene 70-80 parts, styrene 20-30 parts, anhydrous cyclohexane 300-400 parts, double lithium chelate initiator 0.3-0.5 parts, gradient polarity regulator 0.5-0.7 parts, capping agent 0.1-0.3 parts, coupling agent 0.05-0.15 parts and antioxidant 0.4-0.6 parts; The 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 double lithium chelate initiator is prepared by the following method: (1) Under nitrogen protection, o-phenylenediamine and triethylamine are added to anhydrous tetrahydrofuran, and the temperature is lowered to 0-5°C. Trimethylchlorosilane is added dropwise for 1-2 hours. After the addition is completed, the temperature is restored to room temperature, and the reaction is carried out for 2-4 hours. After the reaction is completed, filtration is carried out. The filtrate is concentrated under reduced pressure to obtain bis(trimethylsilyl) o-phenylenediamine. No purification is required, and the product is directly used in the next step. (2) Under nitrogen protection, bis(trimethylsilyl) o-phenylenediamine is added to a mixed solution of anhydrous toluene and anhydrous tetrahydrofuran, and the temperature is lowered to -78°C. n-Butyllithium hexane solution is added dropwise for 1-2 hours. After the addition is completed, the temperature is raised to -10-0°C, and the reaction is carried out for 1-3 hours. After the reaction is completed, the reaction is quenched with a mixed solution of ethanol and toluene. The organic phase is washed with saturated ammonium chloride solution for 2 times and saturated sodium chloride solution for 1 time. The combined organic phase is dried over anhydrous sodium sulfate, filtered, and the filtrate is concentrated under reduced pressure to remove the solvent. The obtained crude product is recrystallized from a mixed solution of toluene and n-hexane. Crystallization is carried out at -20-0°C for 12-24 hours to obtain the double lithium chelate initiator. The gradient polarity regulator is prepared by the following method: (a) Under nitrogen protection, triethylene glycol and imidazole are added to anhydrous N,N-dimethylformamide, and the temperature is lowered to -10-0°C. Trimethylchlorosilane is added dropwise for 1-2 hours. After the addition is completed, the temperature is restored to room temperature, and the reaction is carried out for 1-2 hours. After the reaction is completed, the reaction liquid is transferred to a separatory funnel, washed with dilute hydrochloric acid for 3 times, and washed with saturated sodium chloride solution for 1 time. The organic phase is dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain the monosilylether intermediate. (b) Under nitrogen protection, the monosilylether intermediate, iodomethane and potassium carbonate are added to anhydrous acetone, and the temperature is raised to 55-65°C. The reaction is carried out for 3-5 hours. After the reaction is completed, the temperature is cooled to room temperature, and filtration is carried out. The filtrate is concentrated under reduced pressure to obtain a brown liquid. The brown liquid is added to a separatory funnel, and anhydrous diethyl ether is added. The mixture is washed with saturated sodium chloride solution for 3 times. The organic phase is dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure again to obtain the gradient polarity regulator.

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

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

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

3.

5. A solution-polymerized styrene-butadiene rubber according to claim 1, wherein The molar ratio of the triethylene glycol, trimethylchlorosilane and imidazole in the (a) is 1:1-1.1:1-1.2, and the weight ratio of the 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 1mol / L.

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

7. The solution polymerized styrene-butylene synthesis method according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1. Anhydrous cyclohexane is pressurized into a stainless steel polymerization kettle by nitrogen, the feed valve is closed and the nitrogen atmosphere in the kettle is maintained, the butadiene and styrene in the monomer metering tank are stirred uniformly and then added into the polymerization kettle at one time, the gradient polarity regulator is then added, the stirring is started, the temperature of the materials in the kettle is raised to 35-45℃ by heating with a hot water jacket, the stirring is continued for 5-15min, the double lithium chelate initiator is added to initiate polymerization, the reaction is carried out for 10-20min, then the temperature is raised to 45-55℃ and the reaction is carried out for 20-40min, then the temperature is raised to 65-75℃ at a rate of 0.5-1℃ / min and the chain growth is completed; S2. After the chain growth reaction is completed, the temperature in the kettle is lowered to 55-65℃, the capping agent is added, the stirring is carried out for 15-25min to carry out capping, then the coupling agent is added, the temperature is raised to 60-70℃ and the reaction is carried out for 10-20min to complete the coupling reaction; S3. After the coupling reaction is completed, the temperature in the kettle is lowered to 45-55℃, methanol is used to quench the reaction, the stirring is carried out for 5-15min, the antioxidant is added, the stirring is continued for 15-25min, the discharge valve is opened, the polymerization liquid is put into a coagulation kettle, the stirring is carried out in deionized water at 80-90℃ to coagulate, the polymer particles are precipitated, the wet particles are washed with deionized water for three times, then the wet particles are sent into an extrusion dewatering machine to remove water, then the particles are dried in a drying oven until the weight is constant, and then the solution polymerized butadiene styrene is obtained.

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