A solution-polymerized styrene-butadiene rubber having a terminal hydroxyl group and a method for preparing the same

Abstract

The application provides a kind of end with hydroxyl group solution polymerized butadiene rubber and its preparation method, the structural formula of solution polymerized butadiene rubber is as any one of formula (1), (2) shows;The application solves at least one of the following problems: in the existing SSBR functional modification technology, double lithium polymerization is easy to form false gel, system viscosity is large, increases the equipment load and production loss;RAFT technology cannot be mass-produced, and is difficult to be industrialized and applied;Weak polarity of initiator modification, limited performance improvement range;Liquid rubber modification is limited by prevulcanization process, and it is difficult to fully play the modification synergistic effect of rubber.

Description

Technical Field

[0001] This invention relates to the technical field of synthetic rubber, and more specifically, to a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups and its preparation method. Background Technology

[0002] With the technological iteration and upgrading of the rubber industry, the comprehensive performance requirements of rubber materials in various high-end fields are continuously increasing. By introducing functional groups into the molecular chain of solution-polymerized styrene-butadiene rubber (SSBR), material performance can be precisely optimized and application scenarios expanded. Currently, functionalized SSBR is widely used in the high-end tire field, while double-terminated hydroxyl polybutadiene rubber can be used as a soft segment of polyurethane elastomers, and modified liquid rubber can also be used as an adhesive for solid rocket propellants. Anionic polymerization is the core technology for preparing SSBR. Using alkyl lithium as an initiator, combined with a structure modifier, the 1,2-structure of butadiene can be precisely controlled to achieve random copolymerization of monomers. After polymerization, the molecular chain retains active species, and end-functionalization can be achieved through end-capping and coupling. Alternatively, the head end of the molecule can be modified with the help of a functionalizing initiator to prepare double-terminated SSBR, which is currently the mainstream technology for rubber modification.

[0003] Currently, various SSBR functionalization modification technologies have been developed in the industry. Existing research has yielded low molecular weight, double-terminated hydroxyl SSBR prepared through bilithium anionic polymerization, which is applied in the tire and polyurethane elastomer fields to effectively improve the overall performance of tires. Alternatively, RAFT technology is used to prepare chain-terminated epoxy SSBR, achieving precise control over styrene content and overcoming the challenge of SSBR chain-terminal functionalization. Another approach involves polymerizing SSBR using nitrogen-containing functionalized initiators and combining it with silane-oxygen end-capping to prepare bifunctionalized rubber, thereby improving tire performance. Finally, novel coupling agents can be prepared through graft modification of polybutadiene liquid rubber, which can isolate silica, reduce filler friction, and optimize various mechanical and wear-resistant properties of tires.

[0004] However, the relevant technologies have at least one of the following problems: In the existing SSBR functionalization modification technology, the double lithium polymerization is prone to forming pseudo-gels and the system viscosity is high, which increases the equipment load and production losses; RAFT technology cannot be mass-produced and is difficult to apply industrially; the polarity effect of initiator modification is weak and the performance improvement is limited; the modification of liquid rubber is limited by the pre-vulcanization process, making it difficult to give full play to the effect of rubber modification and enhancement. Summary of the Invention

[0005] The technical problems solved by this invention are: in existing SSBR functionalization modification technologies, double lithium polymerization is prone to forming pseudogels and the system viscosity is high, which increases equipment load and production losses; RAFT technology cannot be mass-produced and is difficult to apply industrially; the polarity effect of initiator modification is weak and the performance improvement is limited; and the modification of liquid rubber is limited by the pre-vulcanization process, making it difficult to fully exert the synergistic effect of rubber modification.

[0006] To address the aforementioned problems, in a first aspect, the present invention provides a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups, wherein the structural formula of the solution-polymerized styrene-butadiene rubber is shown in either formula (1) or (2): ; In equations (1) and (2), R1 represents C1~C 30 Straight-chain or branched alkanes; In equations (1) and (2), R2 represents C2~C 15 Straight-chain or branched alkanes; In equations (1) and (2), R3 represents C2~C 20 Straight-chain, branched, or cycloalkanes, R3 contains silicon, with a silicon content of 1 to 3 atoms; In formulas (1) and (2), a+b accounts for 55%~85% of the total molecular mass, a accounts for 30%~70% of the butadiene content (a+b), and c accounts for 15%~45% of the total molecular mass.

[0007] In one example of the present invention, the molecular weight of solution-polymerized styrene-butadiene rubber is 1,000 to 1,000,000; The molecular weight distribution of solution-polymerized styrene-butadiene rubber is 1.0~2.5.

[0008] Secondly, the present invention also provides a method for preparing a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups. The method is used to prepare a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups as in any of the above examples. The method includes: Preparation of functionalized initiators; In the polymerization system, a first solvent is first added, followed by the addition of a structure modifier, a mixture of styrene and butadiene monomers to the first solvent, and then an inert gas protection is applied. Under the inert gas protection, a functionalizing initiator is added to carry out the polymerization reaction. After the polymerization reaction is completed, an epoxy alkane or silane coupling agent is added for end-capping reaction; After the capping reaction is complete, a terminator is added to terminate the reaction; After the termination reaction is completed, a solution polymerized styrene-butadiene rubber solution with terminal hydroxyl groups is obtained; The solution-polymerized styrene-butadiene rubber solution was subjected to water washing and drying treatments in sequence to obtain solution-polymerized styrene-butadiene rubber with hydroxyl groups at the ends.

[0009] Compared with existing technologies, the technical advantages of this solution are as follows: This solution uses a functionalized initiator to regulate the polymerization reaction. The rubber molecular chain ends with hydroxyl groups, avoiding the defects of traditional double-lithium polymerization systems, such as the tendency to produce pseudo-gels and high system viscosity. This reduces the load on equipment during operation and the loss of raw materials and materials during production. Furthermore, it eliminates the need for RAFT modification technology, which is not suitable for mass production. This solution is based on a coherent and controllable mature anionic polymerization process, which can be directly integrated into existing industrial production lines, making its industrial application highly feasible.

[0010] Furthermore, this scheme introduces polar active sites at the beginning of the rubber molecular chain through a functionalized initiator, and achieves end-chain dihydroxyl functionalization by combining epoxy alkane or silane coupling agents. This thoroughly improves the shortcomings of traditional initiators, which have weak polarity and limited performance improvement, thereby enhancing the interfacial bonding ability between rubber and inorganic fillers such as carbon black and silica, and optimizing the rolling resistance, wet skid resistance, and abrasion resistance of the rubber compound. At the same time, this scheme completes the functionalization modification through in-situ polymerization end-chaining, eliminating the need for liquid rubber compounding and pre-vulcanization auxiliary processes, thus overcoming the limitations of pre-vulcanization processes. It can fully utilize the modification and synergistic effect of functional groups, avoid the problems of early crosslinking and uneven vulcanization of the rubber compound, and simultaneously improve the processing fluidity of the rubber compound and the mechanical properties of the vulcanized product.

[0011] In one embodiment of the present invention, the preparation of the functionalized initiator includes: Add the second solvent and raw material A1 to the reaction system, cool to -50℃ to -20℃, add the pulverized lithium sand to the reaction system, and react for 1 hour to 6 hours at -70℃ to 0℃. After the reaction is completed, filter out the unreacted lithium sand to obtain the functionalized initiator. The structural formula of the functionalized initiator is shown in formula (3): ; In equation (3), R1 represents C1~C 30 Straight-chain or branched alkanes.

[0012] Compared with existing technologies, the technical effects achieved by this solution are as follows: This solution prepares a functionalized initiator by reacting lithium sand with raw material A1 in a second solvent, and controls the reaction at -70℃ to 0℃ for 1 to 6 hours to ensure that the lithiation reaction is mild, complete and controllable. This avoids the problem of lithium sand easily agglomerating at high temperatures and producing side reactions that lead to impurities in the functionalized initiator. At the same time, the use of lithium sand increases the contact area between the raw material A1 and the lithium sand, so that the raw material A1 and lithium sand can react fully.

[0013] In one embodiment of the present invention, the second solvent includes one or two of cyclohexane, n-hexane, toluene, xylene, benzene, tetrahydrofuran, n-heptane, and n-octane.

[0014] In one embodiment of the present invention, the molar ratio of lithium sand to raw material A1 is 2.1:1 to 2.4:1, and the structural formula of raw material A1 is shown in formula (4): ; In equation (4), R1 represents C1~C 30 Straight-chain or branched alkanes.

[0015] In one embodiment of the present invention, the terminating agent has the structural formula shown in formula (5): ; In equation (5), R4, R5, and R6 represent C0~C10 respectively. 15 Straight-chain or branched alkanes.

[0016] In one embodiment of the present invention, the reaction temperature of the polymerization reaction is 30°C to 80°C; The reaction time for the polymerization reaction is 30 to 120 minutes; The reaction temperature for the end-capping reaction is -20℃ to 70℃; The reaction time for the end-capping reaction is 20 to 40 minutes; The processing temperature for the heating and / or drying treatment is 100℃~110℃; The polymerization methods of the polymerization reaction include batch polymerization, three-reactor continuous polymerization, and four-reactor continuous polymerization.

[0017] Compared with existing technologies, the technical advantages achieved by this solution are as follows: By limiting the polymerization reaction temperature to 30℃~80℃ and the polymerization reaction time to 30 minutes~120 minutes, this solution ensures a moderate copolymerization rate of styrene and butadiene monomers and sufficient reaction conversion, avoiding the problems of molecular chain breakage and increased thermal side reactions easily caused by high temperatures, as well as slow polymerization rates and high monomer residues at low temperatures. Furthermore, by limiting the end-capping reaction temperature to -20℃~70℃ and the end-capping reaction time to 20 minutes~40 minutes, this solution enables coupling of epoxide alkanes or silanes. The agent reacts fully and precisely with the active chain ends of the polymer, avoiding the problems of molecular chain cross-linking and increased system viscosity caused by excessively high end-capping temperature and time. It also prevents the defects of insufficient end-capping at low temperature and short time and low hydroxyl grafting rate, thereby improving the efficiency and uniformity of hydroxyl functionalization at the molecular chain ends. Furthermore, by limiting the drying treatment temperature to 100℃~110℃, residual solvents and small molecule impurities in the adhesive are thoroughly removed while avoiding the problems of thermal aging and performance degradation of solution-polymerized styrene-butadiene rubber caused by high temperature overheating, thus ensuring the purity and performance stability of the solution-polymerized styrene-butadiene rubber product.

[0018] In one embodiment of the present invention, the first solvent includes one or two of various aliphatic hydrocarbons and aromatic hydrocarbons such as cyclohexane, n-hexane, cyclopentane, n-heptane, benzene, toluene, and ethylbenzene; Structure modifiers include any one of ether modifiers and amine modifiers; And / or inert gases, including nitrogen or argon.

[0019] In one embodiment of the present invention, the ether modifier includes any one of tetrahydrofurfuryl ethyl ether, bistetrahydrofurfuryl propane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; Amine modifiers include any one of N,N,N',N'-tetramethylethylenediamine, pentamethyldiethylenetriamine, and triethylamine; The dosage of the structure modifier is 50ppm to 500ppm; The concentration of the mixed monomers of styrene and butadiene in the first solvent is 3% to 15%; Styrene accounts for 15% to 45% of the total mass of the mixed monomers of styrene and butadiene.

[0020] By adopting the technical solution of the present invention, the following technical effects can be achieved: This invention provides a solution-polymerized styrene-butadiene rubber (SBR) with terminal hydroxyl groups and its preparation method. By employing a functionalized initiator to regulate the polymerization reaction, the defects of traditional double-lithium polymerization systems, such as the tendency to produce pseudo-gels and high system viscosity, are avoided. This reduces the load on equipment during operation, as well as raw material and production process losses. Furthermore, it eliminates the need for RAFT modification technology, which is not suitable for mass production. This solution is based on a coherent and controllable mature anionic polymerization process, which can be directly integrated into existing industrial production lines, making its industrial application highly feasible. Furthermore, this scheme introduces polar active sites at the beginning of the rubber molecular chain through a functionalized initiator, and combines it with epoxy alkane or silane coupling agents to achieve dihydroxyl functionalization at the end of the molecular chain. This thoroughly improves the shortcomings of traditional initiator modification, which has weak polarity and limited performance improvement. As a result, it enhances the interfacial bonding ability between rubber and inorganic fillers such as carbon black and silica, and optimizes the rolling resistance, wet skid resistance, and abrasion resistance of the rubber compound. At the same time, this scheme completes the functionalization modification through in-situ polymerization end-capping, eliminating the need for liquid rubber compounding and pre-vulcanization auxiliary processes. This frees the rubber compound from the limitations of pre-vulcanization processes, fully utilizes the modification and synergistic effect of functional groups, avoids the problems of early crosslinking and uneven vulcanization of the rubber compound, and simultaneously improves the processing fluidity and mechanical properties of the vulcanized product. This invention prepares a functionalized initiator by reacting lithium sand with raw material A1 in a second solvent, and controls the reaction at -70℃ to 0℃ for 1 to 6 hours to ensure that the lithiation reaction is mild, complete and controllable. This avoids the problem that lithium sand is prone to rapid polymerization at high temperatures and produces side reactions that lead to impurities in the functionalized initiator. The use of lithium sand facilitates the removal of impurities by filtration after the reaction, improving the convenience of impurity removal and avoiding the problem of impurity residue causing gelation and abnormal viscosity fluctuations in the polymerization system. This invention limits the polymerization reaction temperature to 30℃~80℃ and the reaction time to 30 minutes~120 minutes to ensure a moderate copolymerization rate and sufficient conversion of styrene and butadiene monomers, avoiding the problems of molecular chain breakage and increased thermal side reactions caused by high temperatures, and slow polymerization rates and high monomer residues at low temperatures. Furthermore, by limiting the end-capping reaction temperature to -20℃~70℃ and the end-capping reaction time to 20 minutes~40 minutes, it ensures that the epoxy alkane or silane coupling agent fully and precisely binds to the active chain ends of the polymerization chain. The quasi-reaction process avoids the problems of excessively high end-capping temperature and time leading to molecular chain cross-linking and increased system viscosity, while also preventing defects such as insufficient end-capping at low temperatures and short time, resulting in low hydroxyl grafting rate. This improves the efficiency and uniformity of hydroxyl functionalization at the molecular chain ends. Furthermore, by limiting the drying process temperature to 100℃~110℃, residual solvents and small molecule impurities in the adhesive are thoroughly removed while avoiding thermal aging and performance degradation of solution-polymerized styrene-butadiene rubber caused by high-temperature overheating. This ensures the purity and performance stability of the solution-polymerized styrene-butadiene rubber product. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of the structure of a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups provided in an embodiment of the present invention; Figure 2 A flowchart illustrating a method for preparing solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups, provided in an embodiment of the present invention; Figure 3 This is a reaction process diagram of the polymerization reaction of solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups provided in an embodiment of the present invention. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] Firstly, such as Figure 1 As shown, the present invention provides a solution-polymerized styrene-butadiene rubber with hydroxyl groups at the end, the structural formula of which is shown in either formula (1) or (2): ; In equations (1) and (2), R1 represents C1~C 30 Straight-chain or branched alkanes; In equations (1) and (2), R2 represents C2~C 15 Straight-chain or branched alkanes; In equations (1) and (2), R3 represents C2~C 20 Straight-chain, branched, or cycloalkanes, R3 contains silicon, with a silicon content of 1 to 3 atoms; In formulas (1) and (2), a+b accounts for 55%~85% of the total molecular mass, a accounts for 30%~70% of the butadiene content (a+b), and c accounts for 15%~45% of the total molecular mass.

[0024] As a preferred embodiment, R1 in equations (1) and (2) is selected from C4~C 10 R1 is a straight-chain or branched alkane; R2 is a C2-C6 straight-chain or branched alkane; R3 is a C2-C5 straight-chain, branched, or cycloalkanes, wherein the silicon content is 1-3. c accounts for 18%-30% of the total molecular mass; a+b accounts for 70%-80% of the total molecular mass.

[0025] In some embodiments provided by the present invention, the molecular weight of solution-polymerized styrene-butadiene rubber is 1,000 to 1,000,000; preferably, in this embodiment, the molecular weight is 2,000 to 400,000. The molecular weight distribution of solution-polymerized styrene-butadiene rubber is 1.0~2.5.

[0026] Secondly, such as Figure 2 As shown, the present invention also provides a method for preparing a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups. The method is used to prepare a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups as described in any of the above embodiments. The method includes: S100: Preparation of functionalized initiators; S200: In the polymerization system, the first solvent is added first, and then the structure regulator, styrene and butadiene mixed monomers are added to the first solvent in sequence. After inert gas protection, the functional initiator is added under inert gas protection to carry out the polymerization reaction. S300: After the polymerization reaction is completed, add epoxy alkane or silane coupling agent to carry out the end-capping reaction; S400: After the capping reaction is complete, add a terminator to terminate the reaction; S500: After the termination reaction is completed, a solution polymerized styrene-butadiene rubber solution with hydroxyl groups at the end is obtained; S600: Solution-polymerized styrene-butadiene rubber (SBR) is subjected to sequential water washing and drying treatments to obtain solution-polymerized SBR with hydroxyl groups at the ends.

[0027] Understandably, this solution employs a functionalized initiator to regulate the polymerization reaction. The presence of hydroxyl groups at the head of the rubber molecular chain avoids the pitfalls of traditional double-lithium polymerization systems, such as the tendency to produce pseudo-gels and high system viscosity. This reduces the load on equipment during operation, as well as raw material and production losses. Furthermore, it eliminates the need for RAFT modification technology, which is not suitable for mass production. Based on a coherent and controllable mature anionic polymerization process, this solution can be directly integrated into existing industrial production lines, making its industrial application highly feasible.

[0028] Furthermore, this scheme introduces polar active sites at the beginning of the rubber molecular chain through a functionalized initiator, and achieves end-chain dihydroxyl functionalization by combining epoxy alkane or silane coupling agents. This thoroughly improves the shortcomings of traditional initiators, which have weak polarity and limited performance improvement, thereby enhancing the interfacial bonding ability between rubber and inorganic fillers such as carbon black and silica, and optimizing the rolling resistance, wet skid resistance, and abrasion resistance of the rubber compound. At the same time, this scheme completes the functionalization modification through in-situ polymerization end-chaining, eliminating the need for liquid rubber compounding and pre-vulcanization auxiliary processes, thus overcoming the limitations of pre-vulcanization processes. It can fully utilize the modification and synergistic effect of functional groups, avoid the problems of early crosslinking and uneven vulcanization of the rubber compound, and simultaneously improve the processing fluidity of the rubber compound and the mechanical properties of the vulcanized product.

[0029] The reaction process for preparing solution-polymerized styrene-butadiene rubber by polymerization is as follows: Figure 3 As shown, the first step involves the polymerization reaction of a bis-lithium initiator with styrene and butadiene. The bis-lithium initiator (Li-O-CH2-R1-CH2-Li) has carbon-lithium active sites at both ends and an ether bond in the middle of the molecular chain. It is a bifunctional anionic initiator that can initiate polymerization at one end while retaining the lithium active site at the other end, providing a hydroxyl precursor on one side of the final polymer. Styrene provides the hard segment of polystyrene, which improves the strength of solution-polymerized styrene-butadiene rubber. The conjugated diene polymerizes to form the soft segment of polybutadiene, which imparts elasticity to solution-polymerized styrene-butadiene rubber. Step 2: The activated lithium carbon terminal reacts with two types of reagents: monomolecular epoxy alkane and dihaloalkane, differentiating into two product routes: Route A: Single-end capping using a monomolecular epoxy alkane as a capping agent: epoxide three-membered ring undergoes ring-opening addition, forming a lithium-oxygen bond at the end, resulting in a single-ended dilithium macromolecule: Li-O-CH2R1-CH2-(Bd). a,b -[St] c -(R2)-O-Li; one side is lithium ether from the initiator, and the other side is lithium alkoxy generated by ring opening of the epoxy. The entire polymer has only one molecular chain. Route B: Bimolecular coupling using dihaloalkane (Cl-R3-Cl) as end-capping agent: The chlorine atoms at both ends of the dichloroalkane undergo nucleophilic substitution with the -C-Li of two molecules of active polylithium, removing LiCl, and R3 bridges the two polymer chains to obtain a symmetrical bilithium macromolecule: Li-O-CH2R1-CH2-(Bd). a,b -[St] c -R3-[St] c -(Bd) a,b -CH2R1-CH2-O-Li; the molecule is symmetrical, with -O-Li lithium oxygen active groups at both ends, and is a bifunctional lithium intermediate; Step 3: Protonation using a phenolic terminator: Phenol (Ar-OH) acts as a proton donor, and proton exchange occurs at the O-Li bond: RO-Li + Ar-OH → R-OH + ArOLi. Lithium is replaced by hydrogen, forming hydroxyl-terminated rubber, corresponding to two products: Product 1: Single-hydroxyl-terminated solution-polymerized styrene-butadiene: Derived from epoxy-terminated single-chain intermediates: the molecule has a hydroxyl terminal group on only one side, and the other end is an epoxy-derived hydroxyl group; The structure is shown in formula (1), consisting of a molecular chain with hydroxyl groups at both ends.

[0030] Product 2: Symmetrical solution-polymerized styrene-butadiene with dihydroxyl ends: From the dichloroane coupling double chain intermediate: the structure is shown in formula (2). The molecule is completely symmetrical from left to right, with a HO-CH2R1- hydroxyl group at each end, and R3 in the middle is the coupling bridge. The hydroxyl groups at both ends have higher functionality. In this designation, Bd represents butadiene, with the monomer structures CH2=CH-CH2-CH2- and -CH2-CH=CH-CH2-; St represents styrene, with the monomer structure C6H5-CH2=CH2; Ar represents phenol or alkylphenol; R represents a free radical; Cl represents chlorine; Li represents lithium; -OH represents a hydroxyl group; O represents oxygen; C represents carbon; and H represents hydrogen.

[0031] In some embodiments provided by the present invention, the preparation of the functionalized initiator includes: Add the second solvent and raw material A1 to the reaction system, cool to -50℃ to -20℃, add the pulverized lithium sand to the reaction system, and react for 1 hour to 6 hours at -70℃ to 0℃. After the reaction is completed, filter out the unreacted lithium sand to obtain the functionalized initiator. The structural formula of the functionalized initiator is shown in formula (3): ; In equation (3), R1 represents C1~C 30Straight-chain or branched alkanes, wherein R1 is preferably C4~C6. 10 Straight-chain or branched alkanes.

[0032] Understandably, this scheme prepares a functionalized initiator by reacting lithium sand with raw material A1 in a second solvent, and controls the reaction at -70℃ to 0℃ for 1 to 6 hours to ensure that the lithiation reaction is mild, complete and controllable. This avoids the problem of lithium sand easily agglomerating at high temperatures and producing side reactions that lead to impurities in the functionalized initiator. At the same time, lithium sand is selected to increase the contact area with raw material A1, so that raw material A1 and lithium sand can react fully.

[0033] Preferably, when preparing the functionalized initiator, the reaction conditions are between -50°C and -20°C for 2 to 4 hours.

[0034] In some embodiments provided by the present invention, the second solvent includes one or two of cyclohexane, n-hexane, toluene, xylene, benzene, tetrahydrofuran, n-heptane, and n-octane.

[0035] In some embodiments provided by the present invention, the molar ratio of lithium sand to raw material A1 is 2.1:1 to 2.4:1, and the structural formula of raw material A1 is shown in formula (4): ; In equation (4), R1 represents C1~C 30 Straight-chain or branched alkanes, wherein R1 is preferably C4~C6. 10 Straight-chain or branched alkanes.

[0036] In some embodiments provided by the present invention, the structural formula of the terminating agent is shown in formula (5): ; In equation (5), R4, R5, and R6 represent C0~C10 respectively. 15 Straight-chain or branched alkanes.

[0037] In some embodiments provided by the present invention, the reaction temperature of the polymerization reaction is 30°C to 80°C; The reaction time for the polymerization reaction is 30 to 120 minutes; The reaction temperature for the end-capping reaction is -20℃ to 70℃; The reaction time for the end-capping reaction is 20 to 40 minutes; The processing temperature for the heating and / or drying treatment is 100℃~110℃; The polymerization methods of the polymerization reaction include batch polymerization, three-reactor continuous polymerization, and four-reactor continuous polymerization.

[0038] Understandably, this scheme limits the polymerization reaction temperature to 30℃~80℃ and the reaction time to 30 minutes~120 minutes to ensure a moderate copolymerization rate of styrene and butadiene monomers and sufficient reaction conversion, avoiding the problems of molecular chain breakage and increased thermal side reactions easily caused by high temperatures, as well as slow polymerization rates and high monomer residues at low temperatures. Furthermore, by limiting the end-capping reaction temperature to -20℃~70℃ and the end-capping reaction time to 20 minutes~40 minutes, it ensures that the epoxy alkane or silane coupling agent binds to the active chain ends of the polymer. A thorough and precise reaction avoids the problems of excessively high end-capping temperature and time leading to molecular chain cross-linking and increased system viscosity, while also preventing defects such as insufficient end-capping at low temperatures and short time, resulting in low hydroxyl grafting rate. This improves the efficiency and uniformity of hydroxyl functionalization at the molecular chain ends. Furthermore, by limiting the drying process temperature to 100℃~110℃, residual solvents and small molecule impurities in the adhesive are thoroughly removed while avoiding thermal aging and performance degradation of solution-polymerized styrene-butadiene rubber caused by overheating. This ensures the purity and performance stability of the solution-polymerized styrene-butadiene rubber product.

[0039] Preferably, in this embodiment, the polymerization temperature is 40℃~55℃; the polymerization time is 40 minutes~60 minutes; the polymerization method is preferably batch polymerization; and the end-capping reaction temperature is 0℃~40℃.

[0040] In some embodiments provided by the present invention, the first solvent includes one or two of various aliphatic hydrocarbons and aromatic hydrocarbons such as cyclohexane, n-hexane, cyclopentane, n-heptane, benzene, toluene, and ethylbenzene; Structure modifiers include any one of ether modifiers and amine modifiers; And / or inert gases, including nitrogen or argon.

[0041] Preferably, in this embodiment, the first solvent is selected from one or two of cyclohexane, cyclopentane, benzene, and toluene.

[0042] In some embodiments provided by the present invention, the ether modifier includes any one of tetrahydrofurfuryl ethyl ether, bistetrahydrofurfuryl propane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; Amine modifiers include any one of N,N,N',N'-tetramethylethylenediamine, pentamethyldiethylenetriamine, and triethylamine; The dosage of the structure modifier is 50ppm to 500ppm; The concentration of the mixed monomers of styrene and butadiene in the first solvent is 3% to 15%; Styrene accounts for 15% to 45% of the total mass of the mixed monomers of styrene and butadiene.

[0043] Preferably, in this embodiment, the amount of structure modifier is 100ppm to 270ppm.

[0044]

Example 1

[0045] Preparation of solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups by polymerization initiated by functionalized initiators: A 10L high-pressure sealed polymerization reactor was selected. The reactor was pre-vacuumed and purged with nitrogen to ensure an anhydrous and oxygen-free environment. 5-7L of refined cyclohexane was added to the reactor as the first solvent. Subsequently, a structure modifier was added to the first solvent; in this example, bis(tetrahydrofurfuryl)propane was used at a concentration of 140 ppm relative to the solvent. After thorough stirring, a mixture of styrene and butadiene monomers was added. The monomer concentration in the cyclohexane solvent was 10% by mass; styrene accounted for 25% of the total mass of the mixed monomers, with the remaining component being butadiene. After the addition was complete, nitrogen was continuously purged to establish an inert gas protective atmosphere and remove air impurities from the reactor. The reactor temperature was maintained at 48°C, and the pre-prepared functionalized initiator was added to start the polymerization reaction. The polymerization temperature was controlled at 48°C, and the polymerization time was controlled at 50 minutes. After the mixed monomers have completely reacted, the temperature inside the reactor is adjusted to 20°C, and ethylene oxide is added as a capping agent to carry out the capping reaction. The reaction is kept at a constant temperature of 20°C for 20 minutes to complete the functionalization and capping modification of the rubber molecular chain ends. After the capping reaction is completed, a phenolic terminator or lithium alkoxy is added to the reaction system. The structural formula of the terminator is shown in formula (5). The reaction is stirred thoroughly until the system is completely reacted, and the polymerization reaction is terminated to finally obtain a solution-polymerized styrene-butadiene rubber solution with hydroxyl groups at the ends.

[0046] The polymerized solution-polymerized styrene-butadiene rubber (SBR) solution was transferred to a post-processing unit. The SBR solution was then slowly poured into boiling deionized water. The high temperature of the boiling water caused the cyclohexane solvent in the system to evaporate rapidly, precipitating rubber particles and forming an aqueous solution of the particles. The water-containing rubber particles were filtered out and placed on a 110°C open mill for drying. The drying and mixing continued until the volatile matter content of the rubber was below 0.6%, completely removing residual solvent and moisture, thus obtaining solution-polymerized SBR. The hydroxyl-terminated solution-polymerized SBR obtained in this embodiment has a molecular structure as shown in either formula (1) or (2).

[0047]

Example 2

[0048] The other steps are the same as in Example 1, and will not be repeated in this example.

[0049]

Example 3

[0050] The other steps are the same as in Example 1, and will not be repeated in this example.

[0051]

Example 4

[0052] The other steps are the same as in Example 1, and will not be repeated in this example.

[0053]

Example 5

[0054] The other steps are the same as in Example 1, and will not be repeated in this example.

[0055] Comparative Example 1 This embodiment prepares a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups, designed with a molecular weight of 330,000. The difference between this embodiment and Example 1 is: In this embodiment, solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups was prepared by initiating polymerization using n-butyllithium initiator, and 2,4,6-trimethylphenol was selected as the terminator. Other steps were the same as in Example 1, and will not be repeated here.

[0056] The structure and properties of the solution-polymerized styrene-butadiene rubbers with terminal hydroxyl groups prepared in Examples 1-5 and Comparative Example 1 are shown in Table 1: Table 1. Structure and property characterization of solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups. Mooney viscosity is an indicator of rubber performance. Too high a Mooney viscosity leads to high processing energy consumption, while too low a viscosity renders the rubber unprocessable. According to Table 1, the Mooney viscosities are all within a reasonable range (68.1-79.4). The molecular weights obtained in Examples 1-5 are almost identical to the designed molecular weights, indicating that the molecular weights are within the target range. Molecular weight distribution is the ratio of weight-average molecular weight to number-average molecular weight; a narrow distribution is a characteristic of anionic polymerization. Styrene content is related to the ratio of styrene monomer to butadiene monomer, and the styrene content is almost identical to the designed monomer ratio. Vinyl content is related to the type and amount of regulator, with regulators having the most direct impact on vinyl content.

[0057] The solution-polymerized styrene-butadiene rubber (SBR) with terminal hydroxyl groups provided by this invention can be applied in the fields of tires, polyurethane elastomers, and adhesives, including but not limited to waterproof membranes, modified plastics, and footwear materials. The following example illustrates the preparation of tire tread compound using the solution-polymerized SBR with terminal hydroxyl groups provided by this invention: [Example 6] The solution-polymerized styrene-butadiene rubber prepared in Example 1 was compounded and vulcanized to prepare tire tread material. The method for preparing the tread material is as follows: Set the temperature of the Hack mixer to 55°C and the speed to 50 rpm. First, put the solution-polymerized styrene-butadiene rubber and environmentally friendly aromatic oil into the mold cavity and mix for 2 minutes. Then, add the silica to the mold cavity of the mixer in four batches. Then, add the remaining silica, stearic acid, zinc oxide, antioxidant, and coupling agent into the mixer and mix for 5 minutes to ensure thorough mixing. Heat the Hack mixer to 150°C and adjust the speed to 25 rpm to heat-treat the compound for 5 minutes. Discharge the compound and cool it to room temperature. Finally, sulfur and accelerator were added to the rubber compound on a two-roll mill, and the compound was sheeted nine times to ensure thorough mixing of the components. The rubber compound samples were then tested using a rotorless vulcanizer to obtain vulcanization curves. The optimal vulcanization time for each sample was determined from these curves. Finally, tread rubber material performance test samples were prepared using different molds.

[0058]

Example 7

[0059]

Example 8

[0060] Comparative Example 2 The difference between this embodiment and embodiment 6 is that this embodiment uses the solution-polymerized styrene-butadiene rubber prepared in Comparative Example 1 for mixing and vulcanization to prepare the tire tread material. The method for preparing the tread material is the same as that in embodiment 6, and will not be repeated here.

[0061] The compounding formulations for Examples 6-8 and Comparative Example 2 are shown in Table 2: Table 2. Compound formulations for Examples 6-8 and Comparative Example 2 The performance characterization results of Examples 6-8 and Comparative Example 2 are shown in Table 3: Table 3. Performance characterization results of tread rubber materials The Payne effect reflects the dispersion effect of silica filler in the rubber matrix; the smaller the Payne effect value, the better the dispersion effect.

[0062] According to Table 3, the Payne effect values ​​of Examples 6-8 are significantly lower than those of Comparative Example 2, indicating that the filler dispersion effect of solution-polymerized styrene-butadiene rubber modified with dual-terminal hydroxyl end capping is significantly improved.

[0063] The reinforcing factor is the ratio of 300 constant elongation to 100 constant elongation, which reflects the bonding ability between rubber and silica. The larger the reinforcing factor, the stronger the bonding ability. The reinforcing factor comparison example 2 in Examples 6-8 shows that the solution-polymerized styrene-butadiene rubber with double-terminated hydroxyl end caps has a stronger bonding ability with silica.

[0064] The higher the tensile strength, the stronger the adaptability of the tread compound to harsh environments, indicating that the tread compound prepared by solution-polymerized styrene-butadiene rubber with double-terminated hydroxyl end-capping has a stronger adaptability to harsh environments.

[0065] Compression heat generation is a method for characterizing rolling resistance. It simulates the dynamic deformation of the tire during use, which causes internal friction in the material (internal friction is the cause of rolling resistance), resulting in an increase in material temperature. The higher the compression heat generation temperature, the greater the rolling resistance. The compression heat generation values ​​of Examples 6-8 are significantly lower than those of Comparative Example 2, indicating that the tread rubber prepared by solution polymerized styrene-butadiene rubber with dual-terminated hydroxyl end-capping has lower rolling resistance.

[0066]

Example 9

[0067]

Example 10

[0068]

Example 11

[0069] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups, characterized in that, The structural formula of the solution-polymerized styrene-butadiene rubber is shown in either formula (1) or (2): ； In equations (1) and (2), R1 represents C1~C 30 Straight-chain or branched alkanes; In equations (1) and (2), R2 represents C2~C 15 Straight-chain or branched alkanes; In equations (1) and (2), R3 represents C2~C 20 Straight-chain, branched, or cycloalkanes, R3 contains silicon, with a silicon content of 1 to 3 atoms; In formulas (1) and (2), a+b accounts for 55%~85% of the total molecular mass, a accounts for 30%~70% of the butadiene content (a+b), and c accounts for 15%~45% of the total molecular mass.

2. The solution-polymerized styrene-butadiene rubber according to claim 1, characterized in that, The molecular weight of the solution-polymerized styrene-butadiene rubber is 1,000 to 1,000,000; The molecular weight distribution of the solution-polymerized styrene-butadiene rubber is 1.0~2.

5.

3. A method for preparing solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups, characterized in that, The preparation method is used to prepare a solution-polymerized styrene-butadiene rubber with terminal hydroxyl groups as described in claim 1 or 2, and the preparation method includes: Preparation of functionalized initiators; In the polymerization system, a first solvent is first added, and then a structure modifier, a styrene and butadiene mixed monomer are added to the first solvent in sequence, followed by inert gas protection. Under the inert gas protection, the functionalized initiator is added to carry out the polymerization reaction. After the polymerization reaction is completed, an epoxy alkane or silane coupling agent is added for end-capping reaction; After the capping reaction is completed, a terminator is added to terminate the reaction; After the termination reaction is completed, the solution polymerized styrene-butadiene rubber solution with hydroxyl groups at the ends is obtained; The solution-polymerized styrene-butadiene rubber solution is subjected to water washing and drying treatment in sequence to obtain the solution-polymerized styrene-butadiene rubber with hydroxyl groups at the end.

4. The preparation method according to claim 3, characterized in that, The preparation of the functionalization initiator includes: Add a second solvent and raw material A1 to the reaction system, cool to -50°C to -20°C, add the pulverized lithium sand to the reaction system, and react for 1 hour to 6 hours at -70°C to 0°C. After the reaction is completed, filter out the unreacted lithium sand to obtain the functionalized initiator. The functionalized initiator has the structural formula shown in formula (3): ； In equation (3), R1 represents C1~C 30 Straight-chain or branched alkanes.

5. The preparation method according to claim 4, characterized in that, The second solvent includes one or two of cyclohexane, n-hexane, toluene, xylene, benzene, tetrahydrofuran, n-heptane, and n-octane.

6. The preparation method according to claim 4, characterized in that, The molar ratio of the lithium sand to the raw material A1 is 2.1:1 to 2.4:1, and the structural formula of the raw material A1 is shown in formula (4): ； In equation (4), R1 represents C1~C 30 Straight-chain or branched alkanes.

7. The preparation method according to claim 3, characterized in that, The structural formula of the terminator is shown in formula (5): ； In equation (5), R4, R5, and R6 represent C0~C10 respectively. 15 Straight-chain or branched alkanes.

8. The preparation method according to claim 3, characterized in that, The polymerization reaction temperature is 30℃~80℃; And / or the reaction time of the polymerization reaction is 30 minutes to 120 minutes; And / or the reaction temperature of the end-capping reaction is -20℃ to 70℃; And / or the reaction time of the end-capping reaction is 20 to 40 minutes; And / or the drying process is carried out at a temperature of 100°C to 110°C; And / or the polymerization method of the polymerization reaction includes batch polymerization, three-reactor continuous polymerization, and four-reactor continuous polymerization.

9. The preparation method according to claim 3, characterized in that, The first solvent includes one or two of various aliphatic hydrocarbons and aromatic hydrocarbons such as cyclohexane, n-hexane, cyclopentane, n-heptane, benzene, toluene, and ethylbenzene; The structure modifier includes any one of ether modifiers and amine modifiers; And / or the inert gas includes nitrogen or argon.

10. The preparation method according to any one of claims 3-9, characterized in that, The ether modifier includes any one of tetrahydrofurfuryl ethyl ether, bis(tetrahydrofurfuryl propane) ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; The amine modifier includes any one of N,N,N',N'-tetramethylethylenediamine, pentamethyldiethylenetriamine, and triethylamine; The dosage of the structure modifier is 50ppm to 500ppm; And / or the concentration of the styrene and butadiene mixed monomers in the first solvent is 3% to 15%; Styrene accounts for 15% to 45% of the total mass of the styrene and butadiene mixed monomers.

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