Dinuclear scandium catalyst and preparation method thereof, catalytic system, styrene-ethylene multi-block copolymer and preparation method thereof

Abstract

The invention relates to the technical field of olefin polymerization, and particularly provides a dual-core scandium catalyst and a preparation method thereof, a catalytic system, a styrene-ethylene multi-block copolymer and a preparation method thereof. The binuclear scandium catalyst has a structure as shown in a formula (1). The novel catalytic system and polymerization process provided by the invention can realize efficient and controllable copolymerization of styrene and ethylene, and accurately regulate and control the microstructure (such as sequence distribution and block characteristics) of the copolymer; therefore, the novel sPS-based copolymer with high strength, high toughness and good processability is prepared.

Description

Technical Field

[0001] This invention relates to the field of olefin polymerization technology, specifically providing a binuclear scandium catalyst and its preparation method, a catalytic system, and a styrene-ethylene multiblock copolymer and its preparation method. Background Technology

[0002] Polystyrene, as an important polymer material, has advantages such as low density, excellent electrical properties, and ease of processing in its general-purpose type (GPPS). However, its amorphous structure leads to poor heat resistance and mechanical strength, limiting its application in engineering fields. To overcome these limitations, syndiotactic polystyrene (sPS), produced by syndiotactic polymerization of styrene catalyzed by metallocene catalysts, has emerged. sPS possesses a highly ordered syndiotactic stereostructure, making it a crystalline engineering plastic. It not only retains the advantages of GPPS but also exhibits excellent heat resistance, chemical resistance, hydrolytic stability, and dimensional stability. Therefore, sPS has become a strong competitor in the global engineering plastics market, replacing traditional engineering plastics such as nylon (PA), polyester (PET, PBT), and polyphenylene sulfide (PPS), and is widely used in automotive, electronics, and medical devices.

[0003] Currently, the main methods for synthesizing sPS include solution polymerization and bulk polymerization. Solution polymerization is carried out in inert hydrocarbon solvents, which facilitates heat dissipation and stirring of the reaction system, and is one of the common industrial methods. Studies have shown that the choice of solvent has a significant impact on the final crystal form of sPS; for example, using C... 12 -C 30 Polymerization with long-chain hydrocarbon solvents at 40-80℃ can directly obtain the more thermodynamically stable γ-crystalline form, avoiding the complex post-processing problems caused by the inclusion of small molecules in the δ-crystalline form. However, solution polymerization suffers from problems such as solvent recovery, environmental pollution, and high production costs. On the other hand, bulk polymerization uses liquid styrene monomer itself as the reaction medium, requiring little or no solvent, making the process simpler. However, the inherent drawback of this method is that the viscosity of the system increases sharply as the reaction proceeds, leading to difficulties in heat dissipation and making it prone to gelation, sticking, blockage, and agglomeration, placing extremely high demands on the design and control of the reactor.

[0004] Despite the outstanding advantages of sPS, such as high strength, its inherent brittleness and poor processability severely restrict its further application and development. To improve the toughness of sPS, those skilled in the art typically employ copolymerization modification. Introducing flexible ethylene units into the rigid polystyrene backbone has proven to be an effective strategy. However, the successful implementation of this strategy highly depends on precise control over the regularity and sequence distribution of the copolymer segments. Without such control, the resulting copolymer often fails to significantly improve its impact resistance and toughness while maintaining the high strength of sPS, failing to achieve an ideal balance between strength and toughness.

[0005] Therefore, there is an urgent need in this field to develop a novel catalytic system and polymerization process that can achieve efficient and controllable copolymerization of styrene and ethylene, and precisely control the microstructure of the copolymer (such as sequence distribution and block characteristics) to prepare a novel sPS-based copolymer with high strength, high toughness and good processability, so as to overcome the above-mentioned defects of the prior art. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned technical problems and provide a novel catalytic system and polymerization process that can achieve efficient and controllable copolymerization of styrene and ethylene, and precisely control the microstructure of the copolymer (such as sequence distribution and block characteristics), thereby preparing a novel sPS-based copolymer with high strength, high toughness and good processing performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a binuclear scandium catalyst having the structure shown in formula (1): .

[0009] In a second aspect, the present invention provides a method for preparing a binuclear scandium catalyst, comprising the following steps: Step 1: React bromobenzene and magnesium in an ether solvent to generate a phenyl Grignard reagent; Step 2: React the phenyl Grignard reagent with 2,2-dichloropropane in an ether solvent to generate the ligand precursor CH3-C(C6H5)2-CH3; Step 3: React ScCl3 with di(trimethylsilyl)methane in tetrahydrofuran to produce [Sc(CH2Si(CH3)3)2]. + The solution; Step 4: Add [Sc(CH2Si(CH3)3)2] + The ligand precursor CH3-C(C6H5)2-CH3 obtained in step 2 was added to the solution, and the reaction was carried out to obtain the binuclear scandium catalyst shown in formula (1): .

[0010] In the preferred embodiment of the above preparation method, in step 2, the molar ratio of the phenyl Grignard reagent to 2,2-dichloropropane is (2.5-3.5):1; and / or, in step 2, the reaction is first carried out at -10 to 0°C for 0.5-1.5 hours, and then at 22-28°C for 2-4 hours; and / or, in step 4, the molar ratio of the ligand precursor CH3-C(C6H5)2-CH3 to the ScCl3 in step 3 is (0.5-0.7):1; and / or, in step 4, the reaction is carried out at 45-55°C for 5-7 hours.

[0011] In a third aspect, the present invention provides a catalytic system for copolymerizing styrene and ethylene, comprising: (i) the binuclear scandium catalyst described in the first aspect above, or the binuclear scandium catalyst prepared by the preparation method described in the second aspect above; and (ii) Metallocene catalysts.

[0012] In the preferred embodiment of the above catalytic system, the metallocene catalyst is pentamethylcyclopentadienyl titanium trichloride.

[0013] In the preferred embodiment of the above catalytic system, the molar ratio of the binuclear scandium catalyst to the metallocene catalyst is 1:(1-5).

[0014] In a fourth aspect, the present invention provides a method for preparing a styrene-ethylene multiblock copolymer, which employs the catalytic system described in the third aspect, and includes the following steps: S1. Hexane, styrene, tetrahydrofuran, modified methylaluminoxane, and the catalytic system are placed in a reactor and mixed to carry out the first stage of prepolymerization reaction; S2. Introduce ethylene gas into the reactor to carry out the second stage of copolymerization reaction; S3. Stop the ethylene supply, replace the gas in the reactor with inert gas, and maintain the temperature to carry out the third stage reaction; S4. Ethylene gas is introduced into the reactor again, and the fourth copolymerization reaction is carried out under the same conditions as the second stage. S5. After polymerization is complete, the reaction is terminated, and the styrene-ethylene multiblock copolymer is recovered from the reaction mixture.

[0015] In the preferred embodiment of the above preparation method, in step S1, the ratio of the number of moles of tetrahydrofuran [THF] to the total number of moles of all transition metal atoms in the catalytic system [M] is [THF]:[M] = (1~200):1.

[0016] In the preferred embodiment of the above preparation method, in step S1, the ratio of the number of aluminum atoms [Al] in the modified methylaluminoxane to the total number of transition metal atoms [M] in the catalytic system is [Al]:[M] = (1~500):1.

[0017] In the preferred embodiment of the above preparation method, in step S2, the second copolymerization reaction is carried out at a pressure of 2-3 MPa and a temperature of 80-100°C; and / or, the copolymerization time of steps S2 and S4 is independently 60-120 min; and / or, in step S1, the time of the first prepolymerization reaction is 5-30 min; and / or, in step S3, the time of the third reaction is 10-20 min.

[0018] In a fifth aspect, the present invention provides a styrene-ethylene multiblock copolymer prepared by the preparation method described in the fourth aspect above.

[0019] When the above technical solution is adopted, the present invention has the following beneficial effects: (1) Catalyst innovation: A novel dual-core scandium catalyst was designed and synthesized. Its unique bimetallic center and rigid bridging ligand structure exhibit excellent synergistic effect in a two-component catalytic system composed of metallocene catalysts, providing a core driving force for the controllable multi-block copolymerization of styrene and ethylene. (2) Process innovation: A unique multi-stage polymerization process (prepolymerization-copolymerization-displacement-repolymerization) was developed. By precisely controlling the feeding sequence and reaction environment of different monomers, the alternating growth of rigid styrene segments and flexible ethylene segments is guided at the molecular chain level, thereby directly synthesizing copolymers with multi-block structures. (3) Excellent product performance: The styrene-ethylene multiblock copolymer prepared by the method of the present invention has successfully achieved micro-phase separation of rigid segments and flexible segments, fundamentally solving the problems of high brittleness and poor processability of traditional sPS. Without sacrificing its high strength and heat resistance, it significantly improves the impact toughness and processing fluidity of the material, and has excellent comprehensive performance. (4) Process economy: The catalytic system, especially the modified methylaluminoxane co-catalyst, can still maintain high activity at extremely low [Al] / [M] ratios (1-500:1), which significantly reduces production costs and has significant industrial application value. Attached Figure Description

[0020] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which: Figure 1 This is a process flow diagram of the preparation method of the binuclear scandium catalyst of the present invention; Figure 2This is a process flow diagram of the preparation method of the styrene-ethylene multiblock copolymer of the present invention; Figure 3 This is the 1H NMR spectrum of the binuclear scandium catalyst of the present invention; Figure 4 This is the 1H NMR spectrum of the styrene-ethylene multiblock copolymer of the present invention; Figure 5 This is the carbon NMR spectrum of the styrene-ethylene multiblock copolymer of the present invention; Figure 6 This is a DSC diagram of the styrene-ethylene multiblock copolymer of the present invention. Detailed Implementation

[0021] Preferred embodiments of this application will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this application and are not intended to limit the scope of protection of this application.

[0022] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0023] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0024] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0025] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0026] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0027] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0029] As noted in the background section, existing technologies cannot achieve precise control over the regularity and sequence distribution of copolymer segments, making it difficult to significantly improve the impact resistance and toughness of the resulting copolymers while maintaining the high strength of sPS, thus failing to achieve an ideal balance between strength and toughness. This invention provides a novel catalytic system and polymerization process that enables efficient and controllable copolymerization of styrene and ethylene, precisely controlling the microstructure of the copolymer (such as sequence distribution and block characteristics), thereby preparing novel sPS-based copolymers that possess high strength, high toughness, and good processability.

[0030] Specifically, in a first aspect, the present invention provides a binuclear scandium catalyst having the structure shown in formula (1): .

[0031] The binuclear scandium catalyst provided by this invention, with its unique binuclear structure and specific ligand environment, can act as an independent active center when combined with metallocene catalysts, preferentially catalyzing the formation of soft polyethylene or ethylene-styrene random segments. This is an indispensable component in the formation of multi-block structures and makes a fundamental contribution to the excellent toughness of the final product.

[0032] In a second aspect, the present invention provides a method for preparing a binuclear scandium catalyst; please refer to [link to relevant documentation]. Figure 1 The preparation method includes the following steps: Step 1: React bromobenzene and magnesium in an ether solvent to generate a phenyl Grignard reagent; Step 2: React the phenyl Grignard reagent with 2,2-dichloropropane in an ether solvent to generate the ligand precursor CH3-C(C6H5)2-CH3; Step 3: React ScCl3 with di(trimethylsilyl)methane in tetrahydrofuran to produce [Sc(CH2Si(CH3)3)2]. + The solution; Step 4: Add [Sc(CH2Si(CH3)3)2] + The ligand precursor CH3-C(C6H5)2-CH3 obtained in step 2 was added to the solution, and the reaction was carried out to obtain the binuclear scandium catalyst shown in formula (1) above. The preparation method of the present invention is mild and can efficiently and selectively synthesize the binuclear scandium catalyst with well-defined structure and high purity, laying the foundation for the reliable preparation and widespread application of the catalyst.

[0033] In the preferred embodiment of the above preparation method, in step 2, the molar ratio of the phenyl Grignard reagent to 2,2-dichloropropane is (2.5-3.5):1; and / or, in step 2, the reaction is first carried out at -10 to 0°C for 0.5-1.5 hours, and then at 22-28°C for 2-4 hours; and / or, in step 4, the molar ratio of the ligand precursor CH3-C(C6H5)2-CH3 to the ScCl3 in step 3 is (0.5-0.7):1; and / or, in step 4, the reaction is carried out at 45-55°C for 5-7 hours.

[0034] This invention ensures high conversion and high selectivity in each step of the reaction by limiting key material molar ratios (e.g., Grignard reagent to dichloropropane ratio of 2.5-3.5:1, ligand to scandium ratio of 0.5-0.7:1) and reaction temperature and time, effectively suppressing the formation of monosubstituted byproducts or other heteronuclear complexes, thereby guaranteeing high yield and regularity of the final catalyst product.

[0035] In a third aspect, the present invention provides a catalytic system for copolymerizing styrene and ethylene, comprising: (i) the binuclear scandium catalyst described in the first aspect above, or the binuclear scandium catalyst prepared by the preparation method described in the second aspect above; and (ii) Metallocene catalysts.

[0036] The above-described catalytic system organically combines the binuclear scandium catalyst of this invention with a traditional metallocene catalyst, with the two having complementary functions and synergistic effects. The binuclear scandium center tends to generate flexible segments, while the metallocene center (such as pentamethylcyclopentadienyl titanium trichloride) is good at generating rigid syndiotactic polystyrene segments. The combination of the two is the key to realizing the one-pot direct synthesis of multiblock copolymers.

[0037] In the preferred embodiment of the above catalytic system, the metallocene catalyst is pentamethylcyclopentadienyl titanium trichloride.

[0038] The present invention specifically defines the metallocene catalyst as pentamethylcyclopentadienyl titanium trichloride, which is a known highly efficient catalyst for the syndiotactic polymerization of styrene. It has good compatibility with the binuclear scandium catalyst and a significant synergistic effect, making it the most preferred combination in this catalytic system.

[0039] In the preferred embodiment of the above catalytic system, the molar ratio of the binuclear scandium catalyst to the metallocene catalyst is 1:(1-5). For example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, or any value within the range described above.

[0040] This invention defines the optimal molar ratio of the two catalysts (1:1 to 1:5), which is the core of controlling the ratio of rigid to flexible segments in the copolymer. This ratio directly affects the balance of the mechanical properties of the final product and represents the most effective range for achieving a perfect combination of high strength and high toughness.

[0041] In a fourth aspect, the present invention provides a method for preparing a styrene-ethylene multiblock copolymer, which employs the catalytic system described in the third aspect. Please refer to [link to third aspect]. Figure 2 The preparation method includes the following steps: S1. Hexane, styrene, tetrahydrofuran, modified methylaluminoxane, and the catalytic system are placed in a reactor and mixed to carry out the first stage of prepolymerization reaction; S2. Introduce ethylene gas into the reactor to carry out the second stage of copolymerization reaction; S3. Stop the ethylene supply, replace the gas in the reactor with inert gas, and maintain the temperature to carry out the third stage reaction; S4. Ethylene gas is introduced into the reactor again, and the fourth copolymerization reaction is carried out under the same conditions as the second stage. S5. After polymerization is complete, the reaction is terminated, and the styrene-ethylene multiblock copolymer is recovered from the reaction mixture.

[0042] The multi-segment polymerization process described in this invention is a direct means of forming multi-block structures. By cyclically introducing ethylene, replacing it, and then introducing ethylene again, a reaction environment with periodic fluctuations in monomer concentration is artificially created, forcing the two catalysts to work in turn. This results in the sequential generation of segments with different properties on a single molecular chain, ultimately yielding a multi-block copolymer with a well-defined microphase separation structure.

[0043] In the preferred embodiment of the above preparation method, in step S1, the ratio of the molar number of tetrahydrofuran [THF] to the total molar number of all transition metal atoms in the catalytic system [M] is [THF]:[M] = (1~200):1. For example, it can be 10:1, 50:1, 100:1, 150:1, 200:1 or any value within the range.

[0044] This invention controls the total molar ratio of the tetrahydrofuran to all transition metal atoms in the catalytic system within the range of (1-200):1, which can finely adjust the electron cloud density and steric hindrance of the two catalyst active centers, thereby optimizing their polymerization rate against the two monomers, inhibiting homopolymerization, and promoting copolymerization. This is crucial for obtaining an ideal sequence distribution and multi-block structure.

[0045] In the preferred embodiment of the above preparation method, in step S1, the ratio of the number of moles of aluminum atoms [Al] in the modified methylaluminoxane to the total number of moles of all transition metal atoms [M] in the catalytic system [Al]:[M] = (1~500):1. For example, it can be 10:1, 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, 500:1 or any value within the range.

[0046] The catalytic system of this invention maintains high activity even with extremely low co-catalyst dosage ([Al] / [M] = 1~500:1). This significantly reduces the consumption of expensive alkylaluminoxane co-catalysts, substantially reduces production costs and the burden of subsequent waste treatment, demonstrating the enormous industrial application potential and economic value of this invention.

[0047] In the preferred embodiment of the above preparation method, in step S2, the second copolymerization reaction is carried out at a pressure of 2-3 MPa and a temperature of 80-100°C; and / or, the copolymerization time of steps S2 and S4 is independently 60-120 min; and / or, in step S1, the time of the first prepolymerization reaction is 5-30 min; and / or, in step S3, the time of the third reaction is 10-20 min.

[0048] The present invention optimizes and limits key process parameters such as polymerization pressure, temperature, and reaction time in each stage, ensuring that the polymerization process is stable, controllable, and reproducible, and can stably produce high-performance copolymers with predetermined molecular weight, composition, and microstructure.

[0049] In a fifth aspect, the present invention provides a styrene-ethylene multiblock copolymer prepared by the preparation method described in the fourth aspect above.

[0050] The styrene-ethylene multiblock copolymer of the present invention has a specific styrene content (10~90%), and its multiblock structure endows the material with excellent comprehensive properties, successfully solving the industry problem of difficulty in balancing strength and toughness. It is a new type of polymer material with broad application prospects.

[0051] The following detailed embodiments illustrate the binuclear scandium catalyst and its preparation method, catalytic system, styrene-ethylene multiblock copolymer and its preparation method of the present invention.

[0052] Example 1

[0053] This embodiment provides a dual-core scandium catalyst having the structure shown in formula (1) above.

[0054] The preparation method of the binuclear scandium catalyst includes the following steps:

[0055] Step 1: React bromobenzene and magnesium in an ether solvent to generate a phenyl Grignard reagent; Specifically as follows: In an anhydrous three-necked flask, 4.8 g of magnesium shavings and a small amount of iodine granules were added. Under argon protection, 50 mL of anhydrous diethyl ether was added. Then, a solution of 20.4 g of bromobenzene in 30 mL of anhydrous diethyl ether was slowly added dropwise through a constant-pressure dropping funnel. After initiation, the mixture was maintained at room temperature for 1 hour. The temperature was then raised to 40 °C and refluxed for 1 hour to obtain a brown phenyl Grignard reagent solution. The solution was then cooled to room temperature. The reaction equation is as follows: .

[0056] Step 2: React the phenyl Grignard reagent with 2,2-dichloropropane in an ether solvent to generate the ligand precursor CH3-C(C6H5)2-CH3; Specifically as follows: The brown phenyl Grignard reagent solution obtained in step 1 was cooled to 0°C in an ice bath. 4.9 g of 2,2-dichloropropane (CH3-CCl2-CH3) in 20 mL of anhydrous diethyl ether solution was slowly added dropwise over 0.5 h. After addition, the mixture was stirred at 0°C for 1 h, then heated to room temperature and stirred for 3 h. After the reaction was complete, 50 mL of saturated ammonium chloride solution was slowly added dropwise in an ice bath to quench excess Grignard reagent until no more bubbles were generated. The upper ether phase was collected by separation. The aqueous phase was extracted three times with diethyl ether. The combined organic phases were dried overnight with anhydrous sodium sulfate. After filtration, the diethyl ether was removed by rotary evaporation. The remaining solid was recrystallized from ethanol to obtain the ligand precursor CH3-C(C6H5)2-CH3. The reaction formula is as follows: .

[0057] Step 3: React ScCl3 with di(trimethylsilyl)methane in tetrahydrofuran to produce [Sc(CH2Si(CH3)3)2]. + The solution; Specifically as follows: In a 50 mL anhydrous Schlenk flask, under argon protection, 2 g of ScCl3 and 15 mL of anhydrous THF were added and stirred to dissolve. The mixture was then cooled to 0 °C in an ice bath, and 3.6 g of di(trimethylsilyl)methane in 10 mL of THF was slowly added dropwise. After the addition was complete, the mixture was allowed to react at room temperature for 2 h to form a mixture containing [Sc(CH2Si(CH3)3)2]. + A clear solution. The reaction equation is as follows: .

[0058] Step 4: Add [Sc(CH2Si(CH3)3)2] + The ligand precursor CH3-C(C6H5)2-CH3 obtained in step 2 was added to the solution and reacted to obtain the binuclear scandium catalyst shown in formula (1). Specifically as follows: To the above containing [Sc(CH2Si(CH3)3)2] + 1.8 g of the ligand precursor CH3-C(C6H5)2-CH3 was added to the clear solution, and the mixture was heated to 50 °C and stirred for 6 h. The solvent was removed by rotary evaporation under reduced pressure, and the residue was dissolved in 20 mL of n-hexane and filtered to remove insoluble matter. The filtrate was subjected to silica gel column chromatography, and the first yellow band was collected. After rotary drying, the target complex was obtained, and after vacuum drying for 2 h, the binuclear scandium catalyst shown in formula (1) was obtained. The reaction formula is as follows: .

[0059] The structure of the obtained binuclear scandium catalyst was confirmed, and its proton NMR spectrum is shown below. Figure 3 As shown, the five hydrogens on the benzene ring are non-equivalent hydrogens, but because the benzene ring is monosubstituted, it will exhibit multiple sets of multiple peaks with a chemical shift δ of about 6.3~8.0 ppm. The two Hs in Sc-CH2- that are connected to Sc are equivalent (one CH2 on each side, for a total of four Hs), and the adjacent Si(CH3)3 has no hydrogens (the CH3 on Si has no coupling ability), so it appears as a single peak; however, because Sc is a metal with weak electronegativity, the chemical shift δ of CH2 is around 1.0 ppm.

[0060] This embodiment also provides a catalytic system for copolymerization of styrene and ethylene, comprising 25 mg pentamethylcyclopentadienyl titanium trichloride and 15 mg of the binuclear scandium catalyst prepared by the above method.

[0061] This embodiment further provides a method for preparing a styrene-ethylene multiblock copolymer, wherein the raw materials are pretreated as follows before proceeding with the following preparation method:

[0062] Toluene was refluxed in the presence of sodium for 48 h, and then distilled under a nitrogen atmosphere. Styrene was purified by stirring overnight in the presence of calcium hydride and then distilling under reduced pressure. Modified methylaluminoxane (MMAO, 7 wt% aluminum in toluene) was dried as a white powder by removing the solvent under vacuum. The reactor was repeatedly cleaned and purged to ensure that the internal moisture and oxygen content was below 10 ppm.

[0063] Under nitrogen protection, the above catalytic system was dissolved in 10 mL of pretreated toluene in a reactor to prepare a catalyst solution.

[0064] The preparation method of the styrene-ethylene multiblock copolymer includes the following steps: S1. Hexane, styrene, tetrahydrofuran, modified methylaluminoxane, and the catalytic system are placed in a reactor and mixed to carry out the first stage of prepolymerization reaction; Specifically as follows: Add n-hexane (15 mL), pretreated styrene (20 mL), tetrahydrofuran (0.05 mL), and pretreated modified methylaluminoxane (650 mg) to the reactor and mix with the catalyst solution prepared above to carry out the first stage of prepolymerization reaction for 10 min.

[0065] S2. Introduce ethylene gas into the reactor to carry out the second stage of copolymerization reaction; Specifically as follows: Ethylene was introduced and kept at a constant pressure of 2.5 MPa. The temperature was controlled at 90°C, and stirring was continued to carry out the second stage of copolymerization reaction for 90 minutes.

[0066] S3. Stop the ethylene supply, replace the gas in the reactor with inert gas, and maintain the temperature to carry out the third stage reaction; Specifically as follows: The ethylene was replaced with nitrogen gas at a constant temperature, and the third stage of the reaction was continued for 15 minutes.

[0067] S4. Ethylene gas is introduced into the reactor again, and the fourth copolymerization reaction is carried out under the same conditions as the second stage. Specifically as follows: Ethylene was introduced and kept at a constant pressure of 2.5 MPa and temperature. Stirring was continued to carry out the fourth stage copolymerization reaction for 90 minutes.

[0068] S5. After polymerization is complete, terminate the reaction and recover the styrene-ethylene multiblock copolymer from the reaction mixture; Specifically as follows: Finally, the gas was vented, the solution was poured into acidified methanol, and the styrene-ethylene multiblock copolymer was collected by filtration and vacuum drying.

[0069] The structure of the obtained styrene-ethylene multiblock copolymer was confirmed, and its proton NMR spectrum is shown below. Figure 4 As shown: the strong peak at approximately 1.0–1.5 ppm indicates a high content of ethylene units in the copolymer; the hydrogen peak of the benzene ring at approximately 6.5–7.5 ppm is a characteristic signal of the sPS segment, proving the presence of the sPS structure in the copolymer. Its carbon NMR spectrum is shown below. Figure 5 As shown: the benzene ring contains 6 carbons, corresponding to a splitting peak at δ≈128-145ppm. Additionally, the aliphatic carbon peaks at δ≈40-45ppm (-CH- and -CH2- of the sPS backbone) are consistent with the characteristics of syndiotactic polystyrene (the backbone carbons of the syndiotactic structure exhibit specific chemical shifts due to steric hindrance). The peaks in this region are clear and without broadening, indicating that the sPS segments maintain the regularity of the syndiotactic sequence. The strong peak at δ≈25-30ppm is the main chain -(CH2)- of the PE segment. n The presence of a sharp carbon shift (characteristic carbon shift of polyethylene) indicates that the PE segment is a continuous long chain, not a randomly dispersed short unit. The aromatic carbons of sPS (125-145 ppm), the sPS main chain carbons (40-45 ppm), and the PE main chain carbons (25-30 ppm) are completely independent peak groups with no transition peaks. When the main chain carbons of the sPS segment (δ≈40-45 ppm) are connected to the terminal carbons of the PE segment, a specific "connection carbon shift" (usually in the δ≈42-45 ppm range) is generated, which is the covalent connection signal between the sPS main chain carbon and the PE terminal carbon. The carbon spectrum shows the simultaneous presence of typical sPS and PE characteristic signals, with a sharp PE methylene peak, indicating the simultaneous presence of a long, well-ordered sPS sequence and a long PE sequence in the copolymer.

[0070] Its DSC chart is as follows Figure 6As shown: one peak is located at 130-135℃, corresponding to the melting of the polyethylene (PE) segment; the other is located at 245-270℃, corresponding to the melting of the syndiotactic polystyrene (sPS) segment. The crystallization melting point of syndiotactic polystyrene is typically around 270℃, and fluctuations above 250℃ (close to 270℃) correspond to the melting peak of sPS (due to the block structure, peak broadening may occur). The two independent melting peaks indicate the presence of two independently crystallizing segments in this copolymer: crystalline polyethylene segments and crystalline syndiotactic polystyrene segments. This is a typical characteristic of microphase separation in block copolymers, as the two segments are thermodynamically incompatible and can each form their own crystalline regions. In contrast, styrene-ethylene random copolymers, due to their disordered sequence, typically struggle to form long-range ordered crystals, and DSC may not show obvious melting peaks or only broadened melting peaks.

[0071] Example 2 The only difference from Example 1 is that in step 2, the molar ratio of the phenyl Grignard reagent to 2,2-dichloropropane is 2.5:1.

[0072] Example 3 The only difference from Example 1 is that in step 2, the molar ratio of the phenyl Grignard reagent to 2,2-dichloropropane is 3.5:1.

[0073] Example 4 The only difference from Example 1 is that in step 2, the reaction is first carried out at -10°C for 1.5 hours, and then at 22°C for 4 hours.

[0074] Example 5 The only difference from Example 1 is that in step 2, the reaction is first carried out at 0°C for 0.5 hours, and then at 28°C for 2 hours.

[0075] Example 6 The only difference from Example 1 is that in step 4, the molar ratio of the ligand precursor CH3-C(C6H5)2-CH3 to the ScCl3 in step 3 is 0.5:1.

[0076] Example 7 The only difference from Example 1 is that in step 4, the molar ratio of the ligand precursor CH3-C(C6H5)2-CH3 to the ScCl3 in step 3 is 0.7:1.

[0077] Example 8 The only difference from Example 1 is that in step 4, the reaction is carried out at 45°C for 7 hours.

[0078] Example 9 The only difference from Example 1 is that in step 4, the reaction is carried out at 55°C for 5 hours.

[0079] Example 10 The only difference from Example 1 is that in step S1, the ratio of the number of moles of tetrahydrofuran [THF] to the total number of moles of all transition metal atoms in the catalytic system [M] is [THF]:[M] = 10:1.

[0080] Example 11 The only difference from Example 1 is that in step S1, the ratio of the number of moles of tetrahydrofuran [THF] to the total number of moles of all transition metal atoms in the catalytic system [M] is [THF]:[M] = 200:1.

[0081] Example 12 The only difference from Example 1 is that in step S1, the ratio of the number of aluminum atoms [Al] in the modified methylaluminoxane to the total number of transition metal atoms [M] in the catalytic system is [Al]:[M]=10:1.

[0082] Example 13 The only difference from Example 1 is that in step S1, the ratio of the number of aluminum atoms [Al] in the modified methylaluminoxane to the total number of transition metal atoms [M] in the catalytic system is [Al]:[M]=500:1.

[0083] Example 14 The only difference from Example 1 is that in step S2, the second copolymerization reaction is carried out at a pressure of 2 MPa and a temperature of 80°C for 60 min.

[0084] Example 15 The only difference from Example 1 is that in step S2, the second copolymerization reaction is carried out at a pressure of 3 MPa and a temperature of 100°C for 120 min.

[0085] Example 16 The only difference from Example 1 is that in step S1, the time for the first prepolymerization reaction is 5 minutes.

[0086] Example 17 The only difference from Example 1 is that in step S1, the time for the first prepolymerization reaction is 30 minutes.

[0087] Example 18 The only difference from Example 1 is that in step S3, the third reaction time is 10 minutes.

[0088] Example 19 The only difference from Example 1 is that in step S3, the third reaction time is 20 minutes.

[0089] Example 20 The only difference from Example 1 is that in the catalyst system, the molar ratio of the binuclear scandium catalyst to the metallocene catalyst is 1:1.

[0090] Example 21 The only difference from Example 1 is that in the catalyst system, the molar ratio of the binuclear scandium catalyst to the metallocene catalyst is 1:5.

[0091] Example 22

[0092] The only difference from Example 1 is that in step S1, the ratio of the number of moles of tetrahydrofuran [THF] to the total number of moles of all transition metal atoms in the catalytic system [M] is [THF]:[M] = 1:1.

[0093] Example 23

[0094] The only difference from Example 1 is that in step S1, the ratio of the number of moles of aluminum atoms [Al] in the modified methylaluminoxane to the total number of moles of all transition metal atoms [M] in the catalytic system is [Al]:[M]=1:1.

[0095] Comparative Example 1 The only difference from Example 1 is that the catalytic system contains only pentamethylcyclopentadienyl titanium trichloride and no binuclear scandium catalyst is added.

[0096] Comparative Example 2 The only difference from Example 1 is that the catalytic system contains only a binuclear scandium catalyst and does not contain pentamethylcyclopentadienyl titanium trichloride.

[0097] Comparative Example 3 The difference from Example 1 is that ethylene is not introduced, that is, steps S2, S3 and S4 are not carried out, and only the first stage of prepolymerization reaction in step S1 is carried out.

[0098] Experimental Example 1 This test example tested the mechanical properties of the products obtained from the various embodiments and comparative examples of the present invention.

[0099] Elongation at break: Tested according to ISO 527-2:2012; Impact resistance: Tested according to ISO 180:2023; Flowability: The melt index is used to characterize flowability. According to GB / T 3682.1-2018, the higher the melt index, the better the flowability.

[0100] The test results are shown in Table 1: Table 1. Test results of each embodiment and comparative example The results above show that: (1) This invention resolves the contradiction between "brittleness" and "strength retention": the impact strength of all embodiments is 56.2~97.0 kJ / m 2 Both were significantly higher than those of Comparative Example 1 (single metallocene, 25.6 kJ / m³). 2 ) and Comparative Example 2 (single dual-core scandium, 42.2 kJ / m 2 The impact strength of Example 1 was 3.7 times that of Comparative Example 1, indicating that the technical solution of the present invention effectively maintains high strength characteristics while significantly improving the toughness of the material. (2) This invention achieves "controllable copolymerization" and "precise sequence control": Comparative Example 3 (prepolymerization only, 12.5kJ / m 2 The impact resistance of the sample was the lowest among all samples. Combined with the results of Comparative Example 1 and Comparative Example 2, it shows that the complete catalytic system and multi-segment polymerization process of the present invention are the key to forming multi-block copolymers with excellent performance, and achieve effective control of copolymer sequence structure. (3) The present invention achieves a balance of "high strength, high toughness and good processing performance": as shown in Examples 1, 8 and 12, it achieves excellent impact strength (>93.3kJ / m). 2 While maintaining good elongation at break (>11.3%) and moderate processing fluidity (melt index 0.54-0.60 g / 10 min), it successfully overcomes the problem of balancing the properties of traditional sPS materials.

[0101] In summary, the catalytic system and polymerization process of this invention provide an effective technical solution to the problems of high brittleness of sPS materials, difficulty in precisely controlling copolymer structure, and inability to balance overall performance, opening up new avenues for the preparation of high-performance sPS-based copolymers.

[0102] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A dual-nuclear scandium catalyst, characterized in that, The binuclear scandium catalyst has the structure shown in formula (1): 。 2. A method for preparing a binuclear scandium catalyst, characterized in that, The preparation method includes the following steps: Step 1: React bromobenzene and magnesium in an ether solvent to generate a phenyl Grignard reagent; Step 2: React the phenyl Grignard reagent with 2,2-dichloropropane in an ether solvent to generate the ligand precursor CH3-C(C6H5)2-CH3; Step 3: React ScCl3 with di(trimethylsilyl)methane in tetrahydrofuran to produce [Sc(CH2Si(CH3)3)2]. + The solution; Step 4: Add [Sc(CH2Si(CH3)3)2] + The ligand precursor CH3-C(C6H5)2-CH3 obtained in step 2 was added to the solution, and the reaction was carried out to obtain the binuclear scandium catalyst shown in formula (1): 。 3. The preparation method according to claim 2, characterized in that, In step 2, the molar ratio of the phenyl Grignard reagent to 2,2-dichloropropane is (2.5–3.5):1; And / or, in step 2, the reaction is first carried out at -10 to 0°C for 0.5 to 1.5 hours, and then at 22 to 28°C for 2 to 4 hours; And / or, the molar ratio of the ligand precursor CH3-C(C6H5)2-CH3 in step 4 to the ScCl3 in step 3 is (0.5~0.7):1; And / or, in step 4, the reaction is carried out at 45–55°C for 5–7 hours.

4. A catalytic system for copolymerizing styrene and ethylene, characterized in that, The catalytic system includes: (i) the binuclear scandium catalyst of claim 1, or the binuclear scandium catalyst prepared by the preparation method of claim 2 or 3; and (ii) A metallocene catalyst, preferably pentamethylcyclopentadienyl titanium trichloride.

5. The catalytic system according to claim 4, characterized in that, The molar ratio of the binuclear scandium catalyst to the metallocene catalyst is 1:(1-5).

6. A method for preparing a styrene-ethylene multiblock copolymer, characterized in that, The preparation method uses the catalytic system as described in claim 4 or 5, and includes the following steps: S1. Hexane, styrene, tetrahydrofuran, modified methylaluminoxane, and the catalytic system are placed in a reactor and mixed to carry out the first stage of prepolymerization reaction; S2. Introduce ethylene gas into the reactor to carry out the second stage of copolymerization reaction; S3. Stop the ethylene supply, replace the gas in the reactor with inert gas, and maintain the temperature to carry out the third stage reaction; S4. Ethylene gas is introduced into the reactor again, and the fourth copolymerization reaction is carried out under the same conditions as the second stage. S5. After polymerization is complete, the reaction is terminated, and the styrene-ethylene multiblock copolymer is recovered from the reaction mixture.

7. The preparation method according to claim 6, characterized in that, In step S1, the ratio of the number of moles of tetrahydrofuran [THF] to the total number of moles of all transition metal atoms in the catalytic system [M] is [THF]:[M] = (1~200):

1.

8. The preparation method according to claim 6, characterized in that, In step S1, the ratio of the number of aluminum atoms [Al] in the modified methylaluminoxane to the total number of transition metal atoms [M] in the catalytic system is [Al]:[M] = (1~500):

1.

9. The preparation method according to claim 6, characterized in that, In step S2, the second copolymerization reaction is carried out at a pressure of 2-3 MPa and a temperature of 80-100°C; And / or, the copolymerization times of steps S2 and S4 are each independently 60–120 min; And / or, in step S1, the time for the first prepolymerization reaction is 5 to 30 minutes; And / or, in step S3, the third stage reaction time is 10 to 20 minutes.

10. A styrene-ethylene multiblock copolymer, characterized in that, It is prepared by the preparation method according to any one of claims 6 to 9.

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