A bimodal styrene butadiene copolymer and its preparation, use and articles

Abstract

The application belongs to the field of polymers, and specifically discloses a S→B-(S / B)-B→S polymer which is a triblock polymer, wherein the first segment is a S→B gradual change block, the second segment is a S / B random block, and the third segment is a B→S gradual change block; in the S→B-(S / B)-B→S polymer, the total molecular weight is 70-120 thousand, the styrene content is 30-60 wt.%, and the vinyl content is 15-40 wt%; wherein the S content in the first segment is 5-10 wt%, and the B content is 2-5 wt%; the S content in the second segment is 22-43 wt%, and the B content is 40-60 wt%. The application also includes preparation and application of the copolymer. The polymer has brand-new structural characteristics, and has excellent comprehensive performance.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to the field of styrene-butadiene copolymer technology. Technical Background

[0002] Traditional styrene-butadiene copolymers generally include two types of products: SBS and SSBR. These two types of products are manufactured using completely different processes for shoe sole production. SBS is typically manufactured using injection molding vulcanization, while SSBR is typically manufactured using high-pressure molding vulcanization. Each process has its own advantages: injection molding vulcanization of rubber offers high precision in material preparation, short operation time, and fast vulcanization speed, significantly reducing labor costs and improving economic efficiency. The rubber compound injected through the injection machine has a higher density, improved hardness, tensile strength, and elongation at break, and lower permanent deformation at break, positively impacting the performance of rubber products. Meanwhile, injection molding vulcanization offers shorter production cycles, higher efficiency, greater adaptability, and easier automation.

[0003] Vulcanized rubber soles are soft, highly elastic, resistant to aging and cracking, and heat-resistant, making them suitable for various sports. However, their manufacturing process is relatively complex. Injection-molded rubber soles are less prone to delamination. Due to their simpler manufacturing process, they are generally less refined in detail. Furthermore, the special composition of the sole makes it prone to cracking and hardening at lower temperatures. Additionally, the manufacturing process can easily create uneven, blocky soles, resulting in relatively lower wearing comfort.

[0004] For many years, the inventors have been dedicated to the research and development of styrene-butadiene copolymers, hoping to develop a styrene-butadiene copolymer material that is easy to process and has excellent performance, so as to combine the performance and processing advantages of SBS injection-molded vulcanized shoe soles and SSBR injection-molded vulcanized shoe soles, and meet the market's higher requirements for shoe materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this invention is to provide an S→B-(S / B)-B→S polymer (also referred to as a dual-gradient styrene-butadiene copolymer), which aims to provide a novel polymer that can be injection molded and vulcanized and possesses excellent dimensional stability and wear resistance.

[0006] The second objective of this invention is to provide a method for preparing the S→B-(S / B)-B→S polymer.

[0007] A third objective of this invention is to provide the application of the aforementioned S→B-(S / B)-B→S polymer in the preparation of vulcanized products such as shoe soles.

[0008] A fourth objective of this invention is to provide a polymer composition comprising the aforementioned S→B-(S / B)-B→S polymer and rubber articles thereof.

[0009] An S→B-(S / B)-B→S polymer is a triblock polymer, wherein the first segment is an S→B graded block, the second segment is an S / B random block, and the third segment is a B→S graded block.

[0010] The S→B-(S / B)-B→S polymer has a total molecular weight of 70,000-120,000, a styrene content of 30-60 wt.%, and a vinyl content of 15-40 wt%. Specifically, the first segment has an S content of 5-10 wt% and a B content of 2-5 wt%. The second segment has an S content of 22-43 wt% and a B content of 40-60 wt%.

[0011] This invention provides a novel polymer with a special dual-gradient structure of (S→B) and (B→S), and further, by controlling the S / B content and ratio of each segment, synergy can be achieved, which can unexpectedly enable injection molding vulcanization. Moreover, it is beneficial to improve the dimensional stability, wear resistance and many other properties of the prepared products.

[0012] In this invention, the S→B block mentioned in the first paragraph refers to a copolymer block formed by styrene and butadiene, wherein the starting segment is polystyrene, and the polystyrene content gradually decreases while the polybutadiene content gradually increases as the chain lengthens. The S / B random block mentioned in the second paragraph refers to a block formed by the random copolymerization of styrene and butadiene. The B→S block mentioned in the third paragraph refers to a copolymer block formed by styrene and butadiene, wherein the polybutadiene content gradually decreases while the polystyrene content gradually increases as the chain lengthens, and the terminal segment is a polystyrene structure.

[0013] In this invention, the special dual-gradient structure and the combined control of the S / B content in each segment are key to synergistically improving its performance.

[0014] In this invention, the content of S or B in each segment is based on the total monomer content of (S+B).

[0015] Preferably, the S content in the first segment is 5-10 wt.%, the S content in the second segment is 28-36 wt.%, and the balance is S in the third segment, with the total S content of the first to third segments being 40-50 wt.%. Additionally, the B content in the first segment is 2-5 wt%, the B content in the second segment is 40-55 wt.%, and the balance is B in the third segment.

[0016] Preferably, the molecular weight of the S→B gradient block (first segment) is 5000-12000, wherein the molecular weight of the initial polystyrene is 500-1000. The molecular weight of the second segment is 50000-80000. The molecular weight of the B→S gradient block (third segment) is 3000-6000, wherein the molecular weight of the terminal polystyrene is 200-1000.

[0017] The present invention also provides a method for preparing the S→B-(S / B)-B→S polymer, wherein a solution containing an initiator, a modifier, and styrene and butadiene required for the first stage is subjected to a first-stage polymerization at a temperature below 10°C (preferably -10°C to 10°C); then, a mixed monomer containing butadiene and styrene required for the second stage is continuously added to carry out a second-stage polymerization, wherein the temperature of the second-stage polymerization is 80°C to 130°C (preferably 100°C to 110°C); then, styrene and butadiene monomers required for the third stage are added to carry out a third-stage polymerization to obtain the S→B-(S / B)-B→S polymer, wherein the temperature of the third-stage polymerization is 65°C to 90°C.

[0018] To successfully prepare the aforementioned dual-gradient polymer and solve the challenges in its preparation, this invention innovatively provides a three-stage temperature-variable polymerization approach. This approach involves pre-polymerizing the required amounts of styrene and butadiene at a specified low temperature for the first stage, followed by increasing the temperature for the second and third stages. Furthermore, by coordinating the S / B addition method, ratio, and temperature control for each stage of polymerization, this approach effectively solves the polymer preparation challenges, facilitating the successful preparation of the dual-gradient polymer. Moreover, it also helps improve the properties of the resulting polymer.

[0019] In this invention, the combination of the temperature-variable polymerization method and the addition method and ratio of S / B during the preparation process is the key to the synergistic preparation of the novel polymer and the improvement of its performance.

[0020] In this invention, the S and B required for the first stage are mixed at once and then polymerized at low temperature under the presence of an initiator and a regulator. This facilitates the successful preparation of the dual-gradient polymer and improves its properties.

[0021] In this invention, the initiator can be a conventional anionic initiator in the industry, such as alkyl lithium, or more specifically, butyl lithium.

[0022] In this invention, the amount of initiator can be adjusted according to the polymerization requirements, for example, it can be 1.0-1.7 mmol / 100g dry gel.

[0023] In this invention, the solvent in the first polymerization stage can be conventional in the industry, such as at least one of n-hexane, cyclohexane, hexane, pentane, etc.

[0024] In this invention, the regulator can be at least one of the following well-known in the industry: THF, diethyl ether, anisole, crown ether, cryptane, dioxane, tetramethylethylenediamine, triethylamine, etc. Furthermore, the amount of regulator can be adjusted according to the requirements of the prepared 1,2 structure, for example, it can be 50-200 ppm (content in the solvent).

[0025] In this invention, the polymerization time for the first stage is 60 min to 90 min.

[0026] In this invention, during the first polymerization stage, styrene is used at 5-10 wt% of the total monomers, and butadiene is used at 2-5 wt% of the total monomers.

[0027] In this invention, after the first stage of polymerization is completed, a mixture of styrene and butadiene monomers is continuously added directly to the polymerization system, and the temperature is increased to carry out the second stage of polymerization. In this invention, the polymerization process progresses from a low temperature in the first stage to a relatively high temperature in the second stage. Combined with the controlled addition method and dosage of styrene and butadiene monomers, this facilitates the formation of a novel polymer with the aforementioned special structure and excellent properties.

[0028] In this invention, during the second polymerization stage, styrene is used at 22-43 wt% of the total monomers, and butadiene is used at 40-60 wt% of the total monomers.

[0029] In this invention, the polymerization time for the second stage is 30 min to 60 min.

[0030] In this invention, after the second stage of polymerization is completed, the remaining styrene and butadiene are added to carry out the third stage of polymerization.

[0031] In the third polymerization stage of this invention, the required styrene and butadiene monomers can be added all at once.

[0032] Preferably, the polymerization time for the third stage is 30 min to 60 min.

[0033] In this invention, the polymerization reaction can be quenched using existing methods to obtain the new polymer.

[0034] The present invention also provides the application of the aforementioned S→B-(S / B)-B→S polymer in preparing rubber products, preferably in preparing vulcanized rubber products, more preferably in preparing injection-molded vulcanized rubber products, and even more preferably in preparing injection-molded vulcanized shoe sole rubber products.

[0035] In this invention, the S→B-(S / B)-B→S polymer can be made into any desired product based on known principles and methods.

[0036] The present invention also provides a polymer composition comprising the aforementioned S→B-(S / B)-B→S polymer.

[0037] In this invention, the polymer composition may further include at least one of a crosslinking agent, a crosslinking aid, an antioxidant, a reclaimed rubber, and a filler.

[0038] For example, one example of the present invention is a polymer composition comprising an S→B-(S / B)-B→S polymer, a crosslinking agent, crosslinking aid A, crosslinking aid B, an antioxidant, reclaimed rubber, and a filler.

[0039] The crosslinking agent, crosslinking aid A, crosslinking aid B, antioxidant, reclaimed rubber, and filler mentioned herein can all be components known in the industry. For example, the crosslinking agent is at least one of BPO, DTBP, DCP, and BIBP. The crosslinking aid A is at least one of ZnO, MgO, stearic acid, etc. The crosslinking aid B is at least one of TMPTMA, TMPTA, EGDA, EGDMA, ZDMA, TAIC, etc. The antioxidant is at least one of antioxidant 1076, antioxidant 1010, antioxidant 168, or antioxidant 626. The filler is at least one of silica, carbon black, silicate, carbonate, etc.

[0040] The present invention further illustrates polymer composition embodiments in which the weight ratios of the components are as follows:

[0041] S→B-(S / B)-B→S polymer, 50 parts

[0042] Bridge-crossing agent 0.5-1.0 parts;

[0043] Crosslinking aid A: 0.5-2.0 parts

[0044] Crosslinking aid B: 0.5-2.0 parts

[0045] Antioxidant 0.1 to 0.5 parts

[0046] 10-20 parts of reclaimed rubber

[0047] 5-10 parts of filler.

[0048] The present invention also provides a vulcanized rubber article obtained by vulcanizing a polymer composition comprising the novel polymer described in the present invention.

[0049] In this invention, the polymer composition described herein can be vulcanized using known methods to obtain the desired product.

[0050] For example, in one embodiment of the present invention, the vulcanized rubber product is obtained by vulcanization through injection molding vulcanization process. Further, the vulcanized rubber product is a shoe sole formed by vulcanization through injection molding vulcanization process.

[0051] Beneficial effects

[0052] 1. This invention provides a novel polymer structure, which, based on a special double-gradient structure and the combined control of the S / B content and ratio in each segment, can achieve synergy and improve the polymer's performance. For example, the polymer has good processing fluidity, can meet the requirements of injection molding and performance, and the resulting product has good dimensional stability and good gloss.

[0053] 2. Based on the aforementioned three-stage temperature-controlled polymerization approach, this invention further combines monomer addition methods, proportions, and polymerization temperature control to achieve synergy, successfully solving the problems encountered in polymer preparation and successfully preparing the polymer. Moreover, it also helps to improve the performance of the obtained polymer.

[0054] 3. Products made from polymers with the novel structure described in this invention have excellent properties. For example, the resulting shoe soles have good tear resistance, abrasion resistance, dimensional stability, and transparency. They are easy to process and have low cost, and can be used to prepare high-end shoe materials that combine functionality and fashion.

[0055] In addition, the polymer described in this invention can be prepared by injection molding, which solves the shortcomings of traditional SSBR vulcanization, which requires the addition of sulfur (strong odor, not environmentally friendly) and high-pressure mold vulcanization molding process, resulting in complex processing and poor tear resistance. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0057] The present invention discloses a novel styrene-butadiene copolymer (labeled as: S→B-(S / B)-B→S polymer), which comprises a three-segment structure: a first segment is a styrene-butadiene gradient structure that initiates polystyrene (S→B segment), a second segment is a random copolymer of styrene-butadiene (S / B segment), and a third segment is a structure with a butadiene-styrene gradient end capped with polystyrene (B→S segment).

[0058] In the S→B-(S / B)-B→S polymer, the total bound styrene content is 30-60%, the total molecular weight is 70,000-120,000, and the vinyl content is 15-40%.

[0059] In one segment of the structure: the total styrene content is 5-10 wt.%, the amount of butadiene is 2-5 wt.%, the molecular weight of the initially initiated polystyrene is 500-1000, and the molecular weight of the styrene-butadiene gradient is 5000-12000.

[0060] In the two-segment structure, the total styrene content is 22-43 wt.%, the amount of butadiene is 40-60 wt.%, and it is a completely random structure with a molecular weight of 50,000-80,000.

[0061] In the three-segment structure: the remaining styrene and butadiene are combined in the three segments (for example, the total styrene content in the three segments is 3-7%, and the amount of butadiene is 5-10%), the butadiene-styrene gradient molecular weight is 3000-6000, and the molecular weight of the end-capped polystyrene is 200-1000.

[0062] The synthesis method for polymerizing the novel styrene-butadiene copolymer of this invention is, for example, as follows:

[0063] 1) Using alkyllithium as an initiator and tetrahydrofuran as a modifier, a styrene-butadiene mixed monomer is subjected to a single-stage polymerization. The initiation temperature is below 10°C, preferably -10°C to 10°C, and the reaction time is 60 min to 90 min.

[0064] 2) Then, a mixture of butadiene and styrene monomers is added for two-stage polymerization at a reaction temperature of 80℃~130℃ and a reaction time of 30min~60min.

[0065] 3) Add styrene to carry out three-stage styrene-butadiene mixed monomer polymerization at a reaction temperature of 65℃~90℃ for 30min~60min;

[0066] Comparative Example 1

[0067] Add 3000ml of cyclohexane and 0.3ml of tetrahydrofuran to a 5-liter stainless steel reactor with a stirrer, add 70g of styrene, adjust the temperature to 65℃, then add 11ml (0.4mol / L) of butyllithium initiator, react for 30 minutes, after the reaction is complete, add 210g of butadiene monomer, after the reaction is complete, add 70g of styrene monomer, react for 30 minutes, then discharge the material, add an antioxidant, condense water vapor, dry and set aside for later use.

[0068] Example 1

[0069] Add 3000ml of cyclohexane and 0.35ml of tetramethylvinyldiamine to a 5-liter stainless steel reactor equipped with a stirrer. Add 30g of styrene and 15g of butadiene. Adjust the temperature to -5℃, then add 11ml (0.4mol / L) of butyllithium initiator. React for 60 minutes. After the reaction is complete, raise the temperature of the reactor to 100℃, and then continuously add 90g of a mixed monomer of styrene and 185g of butadiene. After the reaction is complete, the temperature of the reactor is 80℃. Add another 20g of the mixed monomer of styrene and 10g of butadiene. React for 10-30 minutes and then discharge the product. Add an antioxidant, condense water vapor, and dry for later use.

[0070] Example 2

[0071] Add 3000ml of cyclohexane and 0.25ml of dioxane to a 5-liter stainless steel reactor equipped with a stirrer. Add 30g of styrene and 15g of butadiene. Adjust the temperature to -5℃, then add 11ml (0.4mol / L) of butyllithium initiator. React for 60 minutes. After the reaction is complete, raise the temperature of the reactor to 100℃, and then continuously add 125g of a mixed monomer of styrene and 150g of butadiene. After the reaction is complete, the temperature of the reactor is 80℃. Add another 20g of a mixed monomer of styrene and 10g of butadiene. React for 10-30 minutes and then discharge the product. Add an antioxidant, condense water vapor, and dry for later use.

[0072] Example 3

[0073] Add 3000ml of cyclohexane and 0.3ml of tetrahydrofuran to a 5-liter stainless steel reactor equipped with a stirrer. Add 30g of styrene and 15g of butadiene. Adjust the temperature to -5℃, then add 9ml (0.4mol / L) of butyllithium initiator. React for 60 minutes. After the reaction is complete, raise the temperature of the reactor to 100℃, and then continuously add 90g of a mixed monomer of styrene and 185g of butadiene. After the reaction is complete, the temperature of the reactor is 80℃. Add another 20g of the mixed monomer of styrene and 10g of butadiene. React for 10-30 minutes and then discharge the product. Add an antioxidant, condense water vapor, and dry for later use.

[0074] Example 4

[0075] Add 3000ml of cyclohexane and 0.5ml of tetrahydrofuran to a 5-liter stainless steel reactor equipped with a stirrer. Add 25g of styrene and 10g of butadiene. Adjust the temperature to -5℃, then add 10ml of 0.4mol / L butyllithium initiator. React for 60 minutes. After the reaction is complete, raise the temperature of the reactor to 100℃, and then continuously add 100g of a mixed monomer of styrene and 192g of butadiene. After the reaction is complete, the temperature of the reactor is 80℃. Add another 15g of a mixed monomer of styrene and 8g of butadiene. React for 10-30 minutes and then discharge the product. Add an antioxidant, condense water vapor, and dry for later use.

[0076] Example 5

[0077] Add 3000ml of cyclohexane and 0.3ml of tetrahydrofuran to a 5-liter stainless steel reactor equipped with a stirrer. Add 25g of styrene and 10g of butadiene. Adjust the temperature to -10℃, then add 10ml of 0.4mol / L butyllithium initiator. React for 60 minutes. After the reaction is complete, raise the temperature of the reactor to 110℃, and then continuously add 100g of a mixed monomer of styrene and 192g of butadiene. After the reaction is complete, the temperature of the reactor is 70℃. Add another 15g of a mixed monomer of styrene and 8g of butadiene. React for 10-30 minutes and then discharge the product. Add an antioxidant, condense water vapor, and dry for later use.

[0078] Comparative Example 2 (The first segment does not form a double gradient structure)

[0079] Add 3000ml of cyclohexane and 0.3ml of tetrahydrofuran to a 5-liter stainless steel reactor equipped with a stirrer, add 45g of styrene, adjust the temperature to 65℃, then add 11ml (0.4mol / L) of butyllithium initiator, react for 60 minutes, then continuously add 110g of a mixed monomer of styrene and 165g of butadiene. After the reaction is complete, the reactor temperature is 80℃, then add another 20g of a mixed monomer of styrene and 10g of butadiene, react for 10-30 minutes, then discharge the product, add an antioxidant, condense water vapor, dry, and set aside for later use.

[0080] Comparative Example 3 (the third segment does not form a double gradient structure)

[0081] Add 3000ml of cyclohexane and 0.3ml of tetrahydrofuran to a 5-liter stainless steel reactor equipped with a stirrer. Add 30g of styrene and 15g of butadiene. Adjust the temperature to -5℃, then add 11ml of 0.4mol / L butyllithium initiator. React for 60 minutes. After the reaction is complete, raise the temperature of the reactor to 100℃, and then continuously add 115g of a mixture of styrene and 170g of butadiene monomers. After the reaction is complete, add 30g of styrene monomer at once. Discharge the product after 10-30 minutes of reaction. Then add an antioxidant, condense the steam, and dry for later use.

[0082] Comparative Example 4 (S / B = 20 / 80)

[0083] Add 3000ml of cyclohexane and 0.3ml of tetrahydrofuran to a 5L stainless steel reactor equipped with a stirrer. Add 12g of styrene and 24g of butadiene. Adjust the temperature to -5℃, then add 11ml of 0.4mol / L butyllithium initiator. React for 60 minutes. After the reaction is complete, raise the temperature of the reactor to 100℃, and then continuously add 50g of a mixed monomer of styrene and 252g of butadiene. After the reaction is complete, the temperature of the reactor is 80℃. Add another 8g of a mixed monomer of styrene and 4g of butadiene. React for 10-30 minutes and then discharge the product. Add an antioxidant, condense the water vapor, and dry it for later use. It has no physical properties at room temperature.

[0084] Comparative Example 5 (the first stage of polymerization was not carried out at low temperature)

[0085] Add 3000ml of cyclohexane and 0.3ml of tetrahydrofuran to a 5L stainless steel reactor equipped with a stirrer. Add 30g of styrene and 15g of butadiene. Adjust the temperature to 65℃, then add 11ml (0.4mol / L) of butyllithium initiator. React for 60 minutes. After the reaction is complete, continuously add 125g of a mixed monomer of styrene and 150g of butadiene at approximately 60℃. After the reaction is complete again, add 20g of the mixed monomer of styrene and 10g of butadiene at approximately 75℃. React for 10-30 minutes, then discharge the product. Add an antioxidant, condense water vapor, and dry for later use. (Imperfect results may include uneven distribution in the middle section, poor tear resistance, and sticky sample.)

[0086] Table 1 shows the performance test results of the polymers prepared in each embodiment and comparative example.

[0087]

[0088] The following vulcanization studies were conducted on the polymers prepared for each case, where the polymer formulations are as follows:

[0089] 50 parts of styrene-butadiene copolymer prepared in each case

[0090] 1 part of crosslinking agent or crosslinking agent BPO / DTBP

[0091] Crosslinking aid ZnO, 1 part

[0092] Crosslinking aid TMPTMA, 1 part

[0093] Antioxidant 1076 / 1010, 0.2 parts

[0094] Antioxidant 168 or 626, 0.2 parts

[0095] Reclaimed rubber, 15 parts

[0096] 8 parts silica

[0097] In this invention, the polymer composition described herein can be vulcanized using existing methods to obtain the desired product. For example, a typical injection molding vulcanization process for a styrene-butadiene copolymer composition is as follows: a 600t injection vulcanizing machine is used; the bottom plate and top plate are installed into the mold and then closed; the compounded rubber is injected into the cavity through the injection vulcanizing machine. During production, the screw temperature is 60℃-110℃, the vulcanization (mold) temperature is (170±5)℃ for the upper plate and (170±5)℃ for the lower plate, the vulcanization time will be determined based on simulation analysis results, and the vulcanization pressure is 15MPa.

[0098] The test results are shown in Table 2:

[0099] Table 2 Performance of Polymerization Vulcanization in Examples

[0100]

[0101] It is evident that the vulcanized polymer prepared by the method of this invention possesses excellent comprehensive properties.

Claims

1. An S→B-(S / B)-B→S polymer, characterized in that, It is a triblock polymer, wherein the first segment is an S→B graded block, the second segment is an S / B random block, and the third segment is a B→S graded block; The S→B-(S / B)-B→S polymer has a total molecular weight of 70,000-120,000, a styrene content of 30-60 wt.%, and a vinyl content of 15-40 wt%. In the first segment, the S content is 5-10 wt% and the B content is 2-5 wt%. In the second segment, the S content is 22-43 wt% and the B content is 40-60 wt%.

2. The S→B-(S / B)-B→S polymer as described in claim 1, characterized in that, The molecular weight of the S→B graded block is 5000-12000.

3. The S→B-(S / B)-B→S polymer as described in claim 1, characterized in that, The molecular weight of the second segment is 50,000-80,000.

4. The S→B-(S / B)-B→S polymer as described in claim 1, characterized in that, The molecular weight of the B→S graded block is 3000-6000.

5. The S→B-(S / B)-B→S polymer according to any one of claims 1 to 4, characterized in that, The molecular weight of the polystyrene at the beginning of the first segment is 500-1000; the molecular weight of the polystyrene at the end of the third segment is 200-1000.

6. A method for preparing the S→B-(S / B)-B→S polymer according to any one of claims 1 to 5, characterized in that, The solution containing an initiator, a regulator, and styrene and butadiene required for the first stage is subjected to a first-stage polymerization at a temperature below 10°C. Then, a mixture of butadiene and styrene monomers required for the second stage is continuously added to carry out a second-stage polymerization at a temperature of 80°C to 130°C. Next, styrene and butadiene monomers required for the third stage are added to carry out a third-stage polymerization to obtain the S→B-(S / B)-B→S polymer, wherein the temperature of the third-stage polymerization is 65°C to 90°C.

7. The preparation method according to claim 6, characterized in that, The initiator is an alkyl lithium.

8. The preparation method according to claim 7, characterized in that, The amount of initiator used is 1.0-1.7 mmol / 100g dry gel.

9. The preparation method according to claim 6, characterized in that, The regulator is at least one of THF, diethyl ether, anisole, crown ether, cryptane, dioxane, tetramethylethylenediamine, and triethylamine.

10. The preparation method according to claim 9, characterized in that, The dosage of the regulator is 50-200 ppm.

11. The preparation method according to claim 6, characterized in that, In the first polymerization stage, styrene and butadiene are added at once. In the third polymerization stage, styrene and butadiene are added at once.

12. The preparation method according to claim 6, characterized in that, The first aggregation phase lasts 60 to 90 minutes. The second aggregation phase lasts for 30 to 60 minutes. The third polymerization time is 30 min to 60 min.

13. An application of the S→B-(S / B)-B→S polymer according to any one of claims 1 to 5, characterized in that, It is used to prepare rubber products.

14. The application of the S→B-(S / B)-B→S polymer as described in claim 13, characterized in that, It is used to prepare vulcanized rubber products.

15. The application of the S→B-(S / B)-B→S polymer as described in claim 14, characterized in that, It is used to prepare injection-molded vulcanized rubber products.

16. The application of the S→B-(S / B)-B→S polymer as described in claim 15, characterized in that, It is used to prepare injection-molded vulcanized rubber soles for shoes.

17. A polymer composition comprising the S→B-(S / B)-B→S polymer according to any one of claims 1 to 5.

18. The polymer composition of claim 17, characterized in that, It also includes at least one of the following: crosslinking agent, crosslinking aid, antioxidant, reclaimed rubber, and filler.

19. The polymer composition of claim 18, characterized in that, The composition comprises an S→B-(S / B)-B→S polymer, a crosslinking agent, crosslinking aid A, crosslinking aid B, an antioxidant, reclaimed rubber, and a filler.

20. The polymer composition of claim 19, characterized in that, The bridge-riding agent is at least one of BPO, DTBP, DCP, and BIBP; The crosslinking aid A is at least one of ZnO, MgO, and stearic acid; The crosslinking aid B is at least one of TMPTMA, TMPTA, EGDA, EGDMA, ZDMA, and TAIC. The antioxidant is at least one of antioxidant 1076, antioxidant 1010, antioxidant 168 or antioxidant 626; The filler is at least one of silica, carbon black, silicate, and carbonate.

21. The polymer composition according to claim 19 or 20, characterized in that, The weight ratio of each component is: S→B-(S / B)-B→S polymer, 50 parts Bridge-crossing agent 0.5-1.0 parts; Crosslinking aid A: 0.5-2.0 parts Crosslinking aid B: 0.5-2.0 parts Antioxidant 0.1~0.5 parts 10-20 parts of reclaimed rubber 5-10 parts of filler.

22. A vulcanized rubber product, characterized in that, It is obtained by vulcanization using any one of the polymer compositions of claims 17 to 21.

23. The vulcanized rubber product as described in claim 22, characterized in that, The vulcanized rubber product is obtained by vulcanization through injection molding.

24. The vulcanized rubber product as described in claim 23, characterized in that, The vulcanized rubber product mentioned above is a shoe sole formed by injection molding vulcanization.

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