Styrene-butadiene copolymer containing highly randomly-segmented styrene-butadiene block and preparation method of styrene-butadiene copolymer

Abstract

The invention discloses a preparation method of a styrene-butadiene copolymer containing a highly randomly-segmented styrene-butadiene block, and belongs to the field of styrene-butadiene rubber synthesis. The method comprises the following steps: in an anionic polymerization solution system containing aluminum salt and an initiator, continuously and uniformly adding a mixed monomer of styrene I and butadiene I to initiate and carry out copolymerization, immediately, continuously and uniformly adding butadiene II to continue copolymerization after the mixed monomer is added, and adding styrene II to carry out homopolymerization after the copolymerization is completed. According to the method, the styrene-butadiene copolymer with uniformly and alternately distributed styrene-butadiene copolymer blocks can be obtained, and vulcanized rubber of the styrene-butadiene copolymer has relatively good tear strength and good comprehensive physical properties.

Description

Technical Field

[0001] This invention relates to a styrene-butadiene copolymer, particularly to a styrene-butadiene copolymer containing highly randomly distributed styrene-butadiene blocks, and also to its preparation method, belonging to the field of styrene-butadiene rubber synthesis. Background Technology

[0002] With advancements in synthetic rubber technology, the sequence distribution and types of styrene-butadiene copolymers (SBRs) are increasing, and their applications are becoming more widespread. The discovered styrene-butadiene polymer structures include block structures, structures containing graded segments, and random structures containing indeterminate segments. Among these, block structures are the most regular and exhibit high stability in industrial production and application. However, graded and random structures are difficult to control industrially and are unstable, resulting in significant fluctuations in product performance. Consequently, they are not widely used in many high-end applications. Currently, many patented technologies related to styrene-butadiene block polymers have been reported. For example, Chinese patent CN1241582A and European patent WO96 / 25442 disclose methods for preparing styrene-butadiene polymers containing graded segments. The graded segments are formed by extending the butadiene feeding time, changing the butadiene feed from continuous to discontinuous, and the styrene feed from discontinuous to continuous, while controlling the polymerization temperature. This method involves a long feeding time and achieves alternating control. US Patent 4939208A discloses a method for preparing a multi-block copolymer containing styrene-diene random blocks, which requires a complex multi-stage feeding process. CN101319029A discloses a method for preparing a butadiene-styrene random copolymer that is essentially free of styrene microblocks using a continuous solution polymerization process. This method mainly involves adding reactants after a certain reaction time. If the timing of the addition is inappropriate, microblock structures can still be generated. Furthermore, during continuous feeding, small amounts of microblocks and gradient structures may also be produced, thus only ensuring a certain degree of randomness. Chinese Patent CN101903409A relates to a method for preparing a copolymer of 1,3-butadiene and styrene, wherein the copolymer contains a random segment in its main chain, followed by a block with a structure different from the main chain. This block is homopolymerized or copolymerized, functionalized, and the resulting product. Chinese patent CN107286292B discloses a method for preparing solution-polymerized styrene-butadiene rubber with random distribution and high vinyl content in styrene. The method involves adding butadiene monomer immediately after the mixed monomers are added to continue the polymerization reaction in order to control the randomness. During this reaction process, some irregular structures will still be produced. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a styrene-butadiene copolymer containing highly randomly distributed styrene-butadiene blocks. This copolymer has uniformly alternating styrene-butadiene copolymer blocks, which can ensure that its surface is non-sticky, and its vulcanizate has good tear resistance and good comprehensive physical properties.

[0004] The second objective of this invention is to provide a method for preparing a styrene-butadiene copolymer containing highly randomly distributed styrene-butadiene blocks. This method is simple to operate, has easily controllable conditions, and is mild, meeting the requirements of industrial production.

[0005] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing a styrene-butadiene copolymer containing highly randomly distributed styrene-butadiene blocks. The method involves first continuously and uniformly adding a mixture of styrene I and butadiene I monomers to an anionic polymerization solution system containing aluminum salt and an initiator to initiate copolymerization. After the mixed monomers are added, butadiene II is immediately and uniformly added to continue copolymerization. After copolymerization is completed, styrene II is added to homopolymerize.

[0006] The key to preparing the styrene-butadiene copolymer containing highly randomly distributed styrene-butadiene blocks in this invention lies in selecting a suitable randomization modifier and combining it with a specific feeding sequence to control the polymerization reactivity ratio of butadiene and styrene, thereby obtaining highly randomly distributed styrene-butadiene blocks. Firstly, aluminum salts are used as randomization modifiers. The role of aluminum salts is to adjust the reaction rates of butadiene and styrene to be more similar, thus obtaining polymer blocks with a high degree of randomness during their copolymerization reaction. Secondly, continuously and uniformly feeding premixed butadiene and styrene can further increase the randomness of the polymer blocks. Thirdly, a suitable amount of butadiene is slowly added in the later stages of polymerization to compensate for the defect of gradual block formation that easily occurs in the later stages of styrene-butadiene copolymerization, thereby effectively improving the randomness of the styrene-butadiene copolymer blocks.

[0007] As a preferred embodiment, the aluminum salt is AlR3 or RnAlX. 3-n Alternatively, R3Al2X2, where R is an alkyl group, x is a halogroup, and n = 1, 2, or 3. Preferred aluminum salts are organoaluminum salts or dimers containing at least one alkyl group. R is a short-chain alkyl group, such as a C1-C5 alkyl group. The alkyl group can be a straight-chain alkyl group, and when the number of carbon atoms exceeds 3, the alkyl group can be a branched alkyl group, specifically, for example, ethyl, isobutyl, etc. A further preferred aluminum salt is AlR3, which has better tunability.

[0008] As a preferred embodiment, the amount of aluminum salt added to the anionic polymerization solution system is 10–200 mg / kg. If the content of the aluminum salt in the anionic polymerization solution system is too low, its adjustment capability is low; if the content is too high, aluminum element will be introduced, making subsequent removal difficult. Therefore, the amount of aluminum salt added to the anionic polymerization solution system is further preferably 10–100 mg / kg.

[0009] As a preferred embodiment, the mass of styrene I accounts for 6-20% of the total mass of butadiene I, butadiene II, and styrene I. As another preferred embodiment, the mass percentage composition of butadiene I and butadiene II is 50-80%:20-50%. Due to the different polymerization rates of styrene and butadiene, controlling the concentrations of the two monomers in the anionic polymerization solution system during copolymerization is crucial for the synthesis of highly randomly distributed styrene-butadiene blocks. Therefore, adding the butadiene monomer in two parts and controlling the ratio of butadiene I, butadiene II, and styrene I is beneficial for regulating the randomness of the copolymerization.

[0010] As a preferred embodiment, the addition time of the mixed monomers is controlled within the range of 20–60 min. The addition time of butadiene II is controlled within the range of 10–30 min. The concentration ratio of the two monomers in the anionic polymerization solution system can be adjusted by controlling the polymerization rate of the monomers.

[0011] As a preferred embodiment, the mass of butadiene II accounts for 4% to 30% of the total mass of styrene I, butadiene I, butadiene II, and butadiene II.

[0012] As a preferred embodiment, the initiation temperature is 30–50°C, and the maximum copolymerization temperature does not exceed 120°C.

[0013] As a preferred embodiment, the anionic polymerization solution system further comprises an activator and a nonpolar organic solvent. The activator is, for example, tetrahydrofuran, used in an amount of 80–300 mg / kg, and the nonpolar organic solvent is, for example, cyclohexane or n-hexane.

[0014] The present invention also provides a styrene-butadiene copolymer containing highly randomly distributed styrene-butadiene blocks, which is obtained by the preparation method described above.

[0015] The styrene-butadiene copolymer provided by this invention comprises two blocks: one block is a random copolymer block of styrene and butadiene, in which butadiene and styrene are evenly distributed, and the mass content of styrene in this block ranges from 6% to 20%; the other block is a homopolymer block of styrene, with a mass content of 3% to 30% of the total polymer mass. The molecular weight of the copolymer is 5*10. 4 ~15*10 4The polymer contains styrene homopolymer blocks and a highly randomized styrene-butadiene structure. The styrene-butadiene copolymer with this structure has a non-sticky surface, and after vulcanization, it ensures the tear strength, tensile strength and elongation of the vulcanized rubber. The prepared hot melt adhesive does not shrink after coating and has good low-temperature performance.

[0016] As a preferred embodiment, the number-average molecular weight of the styrene-butadiene copolymer is 5 × 10⁻⁶. 4 ~15×10 4 .

[0017] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0018] The styrene-butadiene copolymer containing highly randomly distributed styrene-butadiene blocks provided by this invention can be used as a vulcanizate or hot melt adhesive because it contains highly randomly distributed blocks. After vulcanization, it has high tear strength, and the hot melt adhesive made from it has good low-temperature performance and coating properties.

[0019] This invention achieves a uniform, alternating distribution of styrene and butadiene by mass ratio by controlling conditions such as the feeding process during styrene-butadiene copolymerization, thus minimizing the formation of microblock and gradient segment structures.

[0020] The preparation process of the styrene-butadiene copolymer containing highly randomly distributed styrene-butadiene blocks provided by this invention is simple, easy to control, and has mild conditions, making it easy to achieve industrial production. Attached Figure Description

[0021] Figure 1 The image shows the 1H NMR spectrum of the styrene-butadiene copolymer in Example 1.

[0022] Figure 2 The image shows the 1H NMR spectrum of the styrene-butadiene copolymer in Example 2. Detailed Implementation

[0023] The following specific embodiments are intended to further illustrate the content of the present invention, but are not intended to limit the scope of protection of the claims of the present invention.

[0024] Example 1 (Control Sample):

[0025] After nitrogen purging and deoxygenation, 3000 mL of solvent was metered and pressurized into the polymerization reactor under nitrogen pressure. Then, 100 ppm of tetrahydrofuran and 10 mL (0.4 mol / L) of butyllithium were added. The mixture was heated to 60°C, and 22.5 g of styrene and 225 g of butadiene were mixed and continuously added to the reactor, with the maximum temperature controlled to not exceed 120°C. After reacting for 40 minutes, 52.5 g of styrene was added and reacted for another 25 minutes. Samples were taken to analyze the relative molecular mass, distribution, and microstructure of the copolymer. The copolymer was discharged, 0.5% antioxidant was added, and the mixture was condensed with water vapor and dried to obtain the polymer. Using gel permeation chromatography (GPC), the molecular weight of the product was determined to be 80026 g / mol, with a molecular weight distribution of 1.03.

[0026]

[0027] Example 2:

[0028] After nitrogen purging and deoxygenation, 3000 mL of solvent was metered and pressurized into the polymerization reactor under nitrogen pressure. Then, 100 ppm tetrahydrofuran, 30 ppm triethylaluminum, and 10 mL (0.4 mol / L) butyllithium were added. The temperature was raised to 50°C. 22.5 g of styrene and 135 g of butadiene were mixed and then continuously added to the reactor over 40 minutes. Immediately afterward, 90 g of butadiene was added continuously over 20 minutes, with the maximum temperature controlled to not exceed 120°C. After reacting for 40 minutes, another 52.5 g of styrene was added, and the reaction was continued for 25 minutes. Samples were taken to analyze the relative molecular mass, distribution, and microstructure of the copolymer. The copolymer was discharged, 0.5% antioxidant was added, and the mixture was condensed with water vapor and dried to obtain the polymer. Using gel permeation chromatography (GPC), the molecular weight of the product was determined to be 78509 g / mol, with a molecular weight distribution of 1.02.

[0029]

[0030] Example 3:

[0031] After nitrogen purging and deoxygenation, 3000 mL of solvent was metered and pressurized into the polymerization reactor under nitrogen pressure. Then, 100 ppm tetrahydrofuran, 10 ppm triisobutylaluminum, and 10 mL (0.4 mol / L) butyllithium were added. The mixture was heated to 50°C, and then 22.5 g of styrene and 180 g of butadiene were mixed and continuously added to the reactor over 40 minutes. Immediately afterwards, 45 g of butadiene was added continuously over 20 minutes, with the maximum temperature controlled to not exceed 120°C. After reacting for 40 minutes, 52.5 g of styrene was added again for a further 25 minutes. Samples were taken to analyze the relative molecular mass, distribution, and microstructure of the copolymer. The copolymer was discharged, 0.5% antioxidant was added, and the mixture was condensed with water vapor and dried to obtain the polymer. Using gel permeation chromatography (GPC), the molecular weight of the product was determined to be 78106 g / mol, with a molecular weight distribution of 1.02.

[0032]

[0033] Example 4

[0034] The reaction was carried out according to Example 2, except that the initiation temperature was adjusted to 30°C and the copolymerization reaction time was extended by 10 minutes. The test results are as follows.

[0035]

[0036] Example 5

[0037] After nitrogen purging and deoxygenation, 3000 mL of solvent was metered and pressurized into the polymerization reactor under nitrogen pressure. Then, 100 ppm tetrahydrofuran, 20 ppm triethylaluminum, and 8 mL (0.4 mol / L) butyllithium were added. The temperature was raised to 45°C. 22.5 g of styrene and 180 g of butadiene were mixed and continuously added to the reactor over 30 minutes. Immediately afterward, 45 g of butadiene was added continuously over 25 minutes, with the maximum temperature controlled to not exceed 120°C. After reacting for 40 minutes, another 52.5 g of styrene was added, and the reaction was continued for 25 minutes. Samples were taken to analyze the relative molecular mass, distribution, and microstructure of the copolymer. The copolymer was discharged, 0.5% antioxidant was added, and the mixture was condensed with water vapor and dried to obtain the polymer. Using gel permeation chromatography (GPC), the molecular weight of the product was determined to be 83050 g / mol, with a molecular weight distribution of 1.03.

[0038]

[0039] Example 6

[0040] After nitrogen purging and deoxygenation, 3000 mL of solvent was metered and pressurized into the polymerization reactor under nitrogen pressure. Then, 100 ppm tetrahydrofuran, 30 ppm triethylaluminum, and 10 mL (0.4 mol / L) butyllithium were added. The temperature was raised to 35°C. 36 g of styrene and 126 g of butadiene were mixed and continuously added to the reactor over 45 minutes. Immediately afterward, 54 g of butadiene was added continuously over another 35 minutes, with the maximum temperature controlled to not exceed 120°C. After reacting for 40 minutes, another 84 g of styrene was added, and the reaction was continued for 30 minutes. Samples were taken to analyze the relative molecular mass, distribution, and microstructure of the copolymer. The copolymer was discharged, 0.5% antioxidant was added, and the mixture was condensed with water vapor and dried to obtain the polymer. Using gel permeation chromatography (GPC), the molecular weight of the product was determined to be 82710 g / mol, with a molecular weight distribution of 1.03.

[0041]

[0042] Example 7

[0043] After nitrogen purging and deoxygenation, 3000 mL of solvent was metered and pressurized into the polymerization reactor under nitrogen pressure. Then, 100 ppm tetrahydrofuran, 80 ppm triisobutylaluminum, and 12 mL (0.4 mol / L) butyllithium were added. The temperature was raised to 35°C. 36 g of styrene and 90 g of butadiene were mixed and continuously added to the reactor over 40 minutes. Immediately afterward, another 90 g of butadiene was added over 15 minutes, with the maximum temperature controlled to not exceed 120°C. After reacting for 40 minutes, 84 g of styrene was added again for a further 30 minutes. Samples were taken to analyze the relative molecular mass, distribution, and microstructure of the copolymer. The copolymer was discharged, 0.5% antioxidant was added, and the mixture was condensed with water vapor and dried to obtain the polymer. Using gel permeation chromatography (GPC), the molecular weight of the product was determined to be 72710 g / mol, with a molecular weight distribution of 1.03.

[0044]

[0045] Example 8

[0046] After nitrogen purging and deoxygenation, 3000 mL of solvent was metered and pressurized into the polymerization reactor under nitrogen pressure. Then, 100 ppm tetrahydrofuran, 40 ppm triisobutylaluminum, and 7 mL (0.4 mol / L) butyllithium were added. The temperature was raised to 35°C. 31.5 g of styrene and 153 g of butadiene were mixed and continuously added to the reactor over 40 minutes. Immediately afterward, 102 g of butadiene was added over 20 minutes, with the maximum temperature controlled to not exceed 120°C. After reacting for 40 minutes, another 13.5 g of styrene was added, and the reaction was continued for 20 minutes. Samples were taken to analyze the relative molecular mass, distribution, and microstructure of the copolymer. The copolymer was discharged, 0.5% antioxidant was added, and the mixture was condensed with water vapor and dried to obtain the polymer. Using gel permeation chromatography (GPC), the molecular weight of the product was determined to be 142710 g / mol, with a molecular weight distribution of 1.03.

[0047]

[0048] Example 9

[0049] The compounding and vulcanization formula is as follows: 40 parts BR, 60 parts styrene-butadiene copolymer (Examples 1-8), 3 parts zinc oxide, 1 part stearic acid, 50 parts silica, 3 parts sulfur, 15 parts white mineral oil, and 4 parts other minor ingredients such as accelerator.

[0050] Compounding process: Weigh styrene-butadiene rubber (SBR) and corresponding fillers and additives. At 25℃, first plasticize the SBR and BR9000 on a two-roll mill with a 0.8mm roll gap for 2 minutes. Then add ZnO and stearic acid and continue plasticizing for 1.5 minutes. Next, add silica and white mineral oil in three batches and mix for 3 minutes each. After mixing, let it stand for 2 hours. Finally, adjust the roll gap to 0.15mm, perform a triangular wrapping process 9 times, and finally adjust the roll gap to 2.2mm. Sheet the rubber and let it stand for 4 hours. The compounded rubber is vulcanized using a flat vulcanizing apparatus at 160℃ and 10.0MPa for t90+2min to obtain the compounded vulcanized rubber sheet.

[0051]

Claims

1. A process for the preparation of a butadiene-styrene copolymer containing a high degree of randomly distributed butadiene blocks, characterized in that: In the anionic polymerization solution system containing aluminum salt and initiator, the mixed monomers of styrene I and butadiene I are continuously and uniformly added first to initiate and copolymerize, after the mixed monomers are added completely, butadiene II is continuously and uniformly added immediately to continue copolymerization, and after the copolymerization is completed, styrene II is added to homopolymerize.

2. A process for the preparation of a butadiene-styrene copolymer containing highly randomly distributed butadiene blocks according to claim 1, characterized in that: The aluminum salt is AlR3, R n AlX 3-n or R3Al2X2, wherein R is an alkyl group, x is a halide group, and n = 1, 2, or 3.

3. Process for the preparation of a butadiene-styrene copolymer containing highly randomly distributed butadiene blocks according to claim 1 or 2, characterized in that: The aluminum salt is added in the anionic polymerization solution system in an amount of 10-200 mg / kg.

4. A process for the preparation of a butadiene-styrene copolymer containing highly randomly distributed butadiene blocks according to claim 1, characterized in that: The mass of the styrene I accounts for 6-20% of the total mass of butadiene I, butadiene II and styrene I.

5. A process for the preparation of a butadiene-styrene copolymer containing highly randomly distributed butadiene blocks according to claim 1, characterized in that: The mass percentage composition of the butadiene I and the butadiene II is 50-80%:20-50%.

6. The preparation method of the butadiene-styrene copolymer containing highly random butadiene-styrene block according to claim 1, characterized in that: The adding time of the mixed monomers is controlled in the range of 20-60 min; The adding time of the butadiene II is controlled in the range of 10-30 min.

7. A process for the preparation of a butadiene-styrene copolymer containing highly randomly distributed butadiene blocks according to claim 1, characterized in that: The mass of the butadiene II accounts for 4%-30% of the total mass of styrene I, butadiene I, butadiene II and butadiene II.

8. A process for the preparation of a butadiene-styrene copolymer containing highly randomly distributed butadiene blocks according to claim 1, 2, 4, 5, 6 or 7, characterized in that: The temperature of the initiation is 30-50 ℃, and the highest temperature of the copolymerization does not exceed 120 ℃.

9. A styrene butadiene copolymer containing highly randomly distributed butadiene blocks, characterized in that: The preparation method obtained from any one of claims 1-6.

10. A styrene butadiene copolymer containing highly random butylene styrene blocks according to claim 7, characterized by: The number average molecular weight of the butylphenyl copolymer is 5 x 10 4 ~ 15 x 10 4 .

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