Polyolefin elastomer and preparation method therefor

Abstract

The present invention provides a polyolefin elastomer and a preparation method therefor. The preparation method comprises: in a solvent, using a metallocene catalyst to carry out a copolymerization reaction of ethylene and α-olefin to obtain a polyolefin elastomer, the structural formula of the metallocene catalyst being formula I. In the preparation method of the present invention, the polymerization temperature is relatively high, and the catalyst has high temperature resistance, significantly improving the solubility of the polymer in the solvent, reducing the viscosity of the solution system, preventing the precipitated polymer from clogging pipes, and facilitating the separation of the resulting product. The prepared polyolefin elastomer has a narrow molecular weight distribution and a high α-olefin insertion rate.

Description

A polyolefin elastomer and its preparation method

[0001] Cross-reference information

[0002] This application claims priority to Chinese Patent Application No. 202411546133.9, filed on October 31, 2024, entitled "A Polyolefin Elastomer and a Method for Preparing the Same", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a polyolefin elastomer and its preparation method, belonging to the field of olefin polymerization technology. Background Technology

[0004] Polyolefin elastomers (POEs) are a class of high-performance, high-value-added thermoplastic elastomer materials, copolymerized from ethylene and α-olefins. The crystalline regions of the polyethylene chains (resin phase) act as physical cross-linking points, exhibiting typical plastic properties. Introducing a certain amount of α-olefins (1-butene, 1-hexene, 1-octene, etc.) weakens the crystalline regions of the polyethylene chains, forming amorphous regions (rubber phase) exhibiting rubber elasticity, thus giving the product elastomer properties. Ethylene-octene copolymers are among the fastest-growing classes of polyolefin elastomers. POE possesses the dual characteristics of plastics and rubber, exhibiting excellent comprehensive performance. It is currently widely used in automotive parts, wires and cables, machine tools, household goods, toys, entertainment and sporting goods, shoe soles, seals, hot melt adhesives, and other fields. Simultaneously, due to the rapid development of solar energy and the continuous innovation of photovoltaic module technology, the encapsulation material industry is constantly upgrading. The demand for POE as a photovoltaic encapsulant film is continuously increasing. POE films can effectively ensure the stable operation of modules in high-temperature and high-humidity environments, making them an ideal material for photovoltaic encapsulants.

[0005] Due to their low crystallinity and scattered bundle morphology, polyolefin elastomers are typically prepared using solution polymerization. In solution polymerization systems, increasing the temperature not only significantly improves the polymer's solubility in the solvent and reduces the viscosity of the solution, preventing polymer precipitation and blockage of pipelines, but also facilitates the separation of subsequent products. High-temperature solution systems can directly flash-evaporate polyolefin elastomers without heating, reducing energy consumption and significantly improving economic efficiency.

[0006] In the prior art, CN116789883A provides a polyolefin elastomer composed of random or block polymers of ethylene and α-olefins, with a molecular weight M w=30,000-200,000, PDI is 1.5-3, monomer insertion rate is 10-65 wt%. However, this synthesis temperature is low, energy consumption is high, which is not conducive to cost control; CN117209639A provides a method for preparing polyolefin elastomers, including: ethylene, functional monomer A and functional monomer B undergo copolymerization reaction in solvent under the action of a first catalyst; α-olefin polymerization is carried out under the action of a second catalyst and a co-catalyst to obtain a copolymer. The polymer has excellent polarity, which can ensure that the battery module maintains a high level of power generation for a long time. However, this synthesis process requires the use of two catalysts, making cost control difficult, and the synthesis route is divided into two steps, making the process more complex.

[0007] Therefore, developing a method for preparing polyolefin elastomers, using a high-temperature resistant catalyst with a defined geometry in the polymerization reaction, to obtain polyolefin elastomer products with high molecular weight and α-olefin insertion rate, narrow molecular weight distribution, and excellent performance is of great significance for the industrialization of polyolefin elastomers. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a polyolefin elastomer and its preparation method. The polyolefin elastomer prepared by the present invention utilizes a high polymerization temperature, exhibits excellent high-temperature resistance of the catalyst, and results in a polyolefin elastomer with a narrow molecular weight distribution and a high α-olefin insertion rate.

[0009] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a polyolefin elastomer, comprising the following steps:

[0010] In a solvent, a metallocene catalyst is used to carry out the copolymerization reaction of ethylene and α-olefins to obtain polyolefin elastomers;

[0011] The metallocene catalyst has a structure as shown in formula (I):

[0012] In formula (I), M is selected from Ti or Zr, preferably Ti;

[0013] X1 and X2 are each independently selected from halogens or alkyl groups having 1 to 6 carbon atoms, and X1 and X2 may be the same or different;

[0014] R1 to R4 are each independently selected from hydrogen or alkyl groups having 1 to 2 carbon atoms, and R1 to R4 may be the same or different.

[0015] According to a specific embodiment of the present invention, preferably, in formula (I), X1 and X2 are each independently selected from alkyl groups having 1 to 3 carbon atoms; more preferably, Me.

[0016] According to a specific embodiment of the present invention, preferably, in formula (I), X1 and X2 are each independently selected from F, Cl or Br; more preferably Cl.

[0017] According to a specific embodiment of the present invention, preferably, in formula (I), R1 to R4 are each independently selected from hydrogen or Me; more preferably Me.

[0018] According to a specific embodiment of the present invention, preferably, in formula (I), M is selected from Ti; X1 and X2 are each independently selected from Cl or Me; R1 to R4 are selected from Me.

[0019] According to a specific embodiment of the present invention, preferably, the metallocene catalyst is a compound with the structure shown in the formula Ti1, Ti2, Zr1, or Zr2:

[0020] The metallocene catalyst of borneol amine, which possesses both high steric hindrance and flexibility, as described in this invention, enables highly active catalysis of the copolymerization of ethylene and 1-octene at high temperatures, yielding polyolefin elastomers with high monomer insertion rates. In comparison, the metallocene catalyst Ti2 exhibits even higher polymerization activity, resulting in copolymers with higher molecular weights.

[0021] According to a specific embodiment of the present invention, preferably, the preparation method of the metallocene catalyst includes the following steps:

[0022] Under a protective atmosphere, compound A was reacted with organolithium and metal halide M to prepare a metallocene catalyst with the structure shown in formula (I) above.

[0023] The structure of compound A is as follows:

[0024] R1 to R4 in compound A are the same as R1 to R4 in formula (I); the M metal halide is selected from halides of Ti or Zr.

[0025] According to a specific embodiment of the present invention, preferably, under a protective atmosphere, organolithium is added to a solution containing compound A at -78°C to -40°C, and then added to a solution of metal halide M at -78°C to -40°C, thereby preparing a metallocene catalyst of formula (I) through reaction; more preferably, under nitrogen protection, organolithium is added to a solution containing compound A at -78°C to obtain a lithium salt, and then the obtained lithium salt is added to a solution of metal halide M at -78°C for reaction. Adding organolithium at -78°C can improve the reaction yield, and the obtained lithium salt can be directly used for the next synthesis without separation.

[0026] According to a specific embodiment of the present invention, preferably, under a protective atmosphere, an organolithium compound is added to a solution containing compound A and reacted at room temperature for 2-8 hours, preferably 6 hours; then it is added to a solution of metal halide M and reacted at room temperature for 4-8 hours, preferably 6 hours; the reaction is carried out at room temperature for 6 hours, which can improve the separation yield and the purity of the final metallocene catalyst.

[0027] According to a specific embodiment of the present invention, preferably, after the reaction of compound A with organolithium and metal halide M is completed, post-treatment processes such as solvent washing and drying are also included. These are all conventional operations in the art and are not specifically limited here.

[0028] According to a specific embodiment of the present invention, preferably, the organolithium is selected from n-butyllithium and / or methyllithium; more preferably, the organolithium is n-butyllithium, and the metallocene catalyst prepared is a compound with the structure shown in Ti1 and Zr1; the organolithium is methyllithium, and the metallocene catalyst prepared is a compound with the structure shown in Ti2 and Zr2; the organolithium is further preferably a hexane solution of n-butyllithium and / or an ether solution of methyllithium.

[0029] According to a specific embodiment of the present invention, preferably, the M metal halide is selected from the chlorides of Ti or Zr; more preferably, it is TiCl4.

[0030] According to a specific embodiment of the present invention, preferably, the molar ratio of compound A, organolithium, and metal halide M is 1:(2-5):(1-2), more preferably 1:(3.0-4.5):(1.1-1.5), and even more preferably 1:(2.2-4.4):(1.2-1.5). Within the scope of the present invention, the conversion rate of the target product can be improved. High yields of metallocene catalysts can be obtained when the molar ratio of titanium tetrachloride to compound A is in the range of (1.2-1.5):1, with the highest yield observed when the molar ratio is 1.2:1.

[0031] According to a specific embodiment of the present invention, preferably, the solvent is selected from one or more combinations of tetrahydrofuran, diethyl ether, toluene, and n-hexane.

[0032] According to a specific embodiment of the present invention, preferably, the source of compound A is not specifically limited. For example, compound A can be prepared by the following steps:

[0033] Under a protective atmosphere, borneolamine was reacted with organolithium and compound 2 to prepare compound A;

[0034] The structure of compound 2 is as follows:

[0035] In compound 2, R1 to R4 are the same as R1 to R4 in formula (I).

[0036] According to a specific embodiment of the present invention, preferably, under a protective atmosphere, an organolithium-based solution of borneol is added at -78°C to -40°C; then, at -78°C to -40°C, it is added to a solution of compound 2, and the reaction yields compound A; more preferably, at -78°C, organolithium is added to a solution containing borneol to form a lithium salt, and then, at -78°C, the lithium salt is slowly added to a solution of compound 2. Because the reaction is relatively vigorous, the obtained lithium salt needs to be mixed with compound 2 at -78°C and reacted at room temperature for 6 hours, which can improve the separation yield and the purity of the final dimethylsilane-linked ligand. The obtained lithium salt can be used directly in the next synthesis without separation to improve the yield of the target product.

[0037] According to a specific embodiment of the present invention, preferably, the reaction requires the addition of a solvent selected from at least one of DME, THF, n-hexane, toluene, etc., and more preferably tetrahydrofuran, to reduce the occurrence of side reactions.

[0038] According to a specific embodiment of the present invention, preferably, the source of compound 2 is not specifically limited. For example, compound 2 can be prepared by the following steps:

[0039] Compound 1 was prepared by reacting it with organolithium and dimethyldichlorosilane under a protective atmosphere.

[0040] The structure of compound 1 is as follows:

[0041] R1 to R4 in compound 1 are the same as R1 to R4 in formula (I).

[0042] According to a specific embodiment of the present invention, preferably, under a protective atmosphere, at -78°C to -40°C, an organolithium salt is added to a solution containing compound 1 to form a lithium salt, and then, at -78°C to -40°C, it is added dropwise to a solution of dimethyldichlorosilane to react, thereby obtaining compound 2; more preferably, at -78°C, an organolithium salt is added to a solution containing compound 1, and then, at -78°C, the lithium salt is slowly added to a solution of dimethyldichlorosilane to react. Because the reaction is relatively vigorous, it is necessary to add the organolithium salt of compound 1 dropwise to dimethyldichlorosilane under low-temperature conditions and slowly raise the temperature to room temperature to reduce the generation of byproducts.

[0043] According to a specific embodiment of the present invention, preferably, under a protective atmosphere, organolithium is added to a solution containing compound 1 and reacted at room temperature for 2-8 hours, preferably 6 hours; then it is added to a solution of dimethyldichlorosilane and reacted at room temperature for 4-8 hours, preferably 6 hours, which can improve the yield of the target product.

[0044] According to a specific embodiment of the present invention, preferably, the molar ratio of compound 1, organolithium, and dimethyldichlorosilane is 1:(1-2):(2-5), more preferably 1:(1.2-1.5):3. Using an excess of dimethyldichlorosilane can improve the yield and facilitate subsequent product separation. When the molar ratio of dimethyldichlorosilane to compound 1 is 3, the yield of compound 2 obtained is the highest.

[0045] According to a specific embodiment of the present invention, preferably, the molar ratio of borneol, organolithium, and compound 2 is 1:(1-2):(0.8-2.0), more preferably 1:(1.2-1.5):(1-1.5). When the molar ratio of n-butyllithium to borneol is in the range of (1.2-1.5):1, a high yield of compound A can be obtained, wherein the yield of compound A is highest, reaching 90%, when the molar ratio is 1.2:1.

[0046] According to a specific embodiment of the present invention, preferably, the reaction formula for the preparation process of compound A is as follows:

[0047] According to a specific embodiment of the present invention, preferably, the source of compound 1 is not specifically limited. For example, when R1-R4 are methyl groups, tetramethylcyclopentenone can be reduced with lithium aluminum hydride to obtain tetramethylcyclopentenol, which can then be further dehydrated with p-toluenesulfonic acid to obtain tetramethylcyclopentadiene. The molar ratio of tetramethylcyclopentenone to lithium aluminum hydride is 1:(0.3-0.5), more preferably 1:0.3. The reaction is carried out in hexane or diethyl ether solvent and requires stirring at 50°C for 3 hours to improve the yield of the target product. The yield of product compound 1 is highest when the molar ratio of lithium aluminum hydride to tetramethylcyclopentenone is 0.3.

[0048] According to a specific embodiment of the present invention, preferably, the copolymerization reaction temperature is 50-250°C, more preferably, the copolymerization reaction temperature is 150-220°C; wherein, the catalytic activity for copolymerizing ethylene and 1-octene is highest at a temperature of 180°C. It still exhibits very high copolymerization activity at 220°C.

[0049] According to a specific embodiment of the present invention, preferably, the pressure of ethylene introduced in the copolymerization reaction is 0.5-6 MPa, more preferably, the pressure of ethylene introduced in the copolymerization reaction is 1-3 MPa; when the catalytic copolymerization process is carried out in the range of 1-3 MPa, the performance of the obtained polyolefin elastomer is better, and the catalytic activity of catalytic copolymerization of ethylene and 1-octene is the highest at a pressure of 2 MPa.

[0050] According to a specific embodiment of the present invention, preferably, the concentration of α-olefin is 0.5-10 mol / L, more preferably 2-8 mol / L, based on the total volume of materials in the copolymerization reaction (the total volume of materials includes α-olefin, metallocene catalyst, solvent, optional co-catalyst, etc.).

[0051] According to a specific embodiment of the present invention, preferably, the copolymerization reaction time is 2-60 min; more preferably, the copolymerization reaction time is 5-15 min; when the catalytic copolymerization process is carried out in the range of 5-15 min, the catalytic activity and the molecular weight of the copolymer are higher.

[0052] According to a specific embodiment of the present invention, preferably, the α-olefin is selected from one or more combinations of 1-butene, 1-hexene, 1-octene, and 1-decene; more preferably, the α-olefin is selected from 1-hexene or 1-octene. Among these, the product exhibits the highest molecular weight and narrowest molecular weight distribution when ethylene and 1-octene are copolymerized using a metallocene catalyst.

[0053] According to a specific embodiment of the present invention, preferably, in the copolymerization reaction, ethylene and α-olefins are copolymerized under the combined action of a metallocene catalyst and a co-catalyst.

[0054] According to a specific embodiment of the present invention, preferably, the cocatalyst is selected from organoboron compounds and / or alkylaluminoxane compounds; more preferably, the organoboron compound is selected from one or more combinations of tris(pentafluorophenyl)boron, triphenylcarbontetra(pentafluorophenyl)boron salt, and N,N-dimethylanilinetetra(pentafluorophenyl)borate; even more preferably, the alkylaluminoxane compound is selected from one or more combinations of methylaluminoxane, dried methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, and isobutylaluminoxane.

[0055] According to a specific embodiment of the present invention, preferably, the cocatalyst is selected from one or more combinations of methylaluminoxane (MAO), modified methylaluminoxane (MMAO), dried methylaluminoxane (dMAO), tris(pentafluorophenyl)boron (B(C6F5)3), and triphenylcarbontetra(pentafluorophenyl)boron salt ([Ph3C][B(C6F5)4]); more preferably, the cocatalyst is dried methylaluminoxane and / or triphenylcarbontetra(pentafluorophenyl)boron salt. The cocatalyst of a mixture of dMAO and [Ph3C][B(C6F5)4] exhibits better performance and higher activity when used in the copolymerization of ethylene and 1-octene with a metallocene catalyst.

[0056] According to a specific embodiment of the present invention, preferably, the molar ratio of the metallocene catalyst to the co-catalyst is 1:(1-500); more preferably, the molar ratio of the metallocene catalyst to dry methylaluminoxane is 1:(100-300), and the molar ratio of the metallocene catalyst to triphenylcarbontetra(pentafluorophenyl)boron salt is 1:(1-1.5), and even more preferably 1:1.2.

[0057] According to specific embodiments of the present invention, preferably, in the copolymerization reaction, the molar ratio of the co-catalyst alkylaluminoxane compound to the metallocene catalyst is (20-500):1, which can catalyze the copolymerization of ethylene and 1-octene with high activity. Specifically, the catalytic activity is higher when the molar ratio of the alkylaluminoxane compound to the metallocene catalyst is in the range of (100-300):1. For example, the catalytic activity is highest when the molar ratio of dMAO to Ti2 is 150:1. In the copolymerization reaction, when the molar ratio of the co-catalyst [Ph3C][B(C6F5)4] to the metallocene catalyst Ti2 is in the range of (1-1.5):1, it can catalyze the copolymerization of ethylene and 1-octene with high activity. Specifically, the catalytic activity is highest when the molar ratio of [Ph3C][B(C6F5)4] to Ti2 is 1.2:1.

[0058] According to a specific embodiment of the present invention, preferably, the solvent is selected from one or more combinations of n-hexane, n-heptane, n-octane, methylcyclohexane, isopentane, isohexane, isooctane, and isomeric saturated alkanes; more preferably, the solvent is selected from one or more combinations of n-hexane, n-heptane, and alkane mixtures. Among the isomeric saturated alkanes, metallocene catalysts exhibit the highest activity in catalyzing the copolymerization of 1-octene and ethylene, resulting in products with high molecular weight and high α-olefin insertion rate.

[0059] Secondly, the present invention also provides a polyolefin elastomer prepared by the above-described method for preparing polyolefin elastomers.

[0060] According to a specific embodiment of the present invention, preferably, the weight-average molecular weight of the polyolefin elastomer is 53.5-576.8 kg / mol; the molecular weight distribution of the polyolefin elastomer is 2.0-2.8; and the α-olefin insertion rate of the polyolefin elastomer is 7.6 mol%-19.1 mol%.

[0061] The present invention has the following beneficial effects:

[0062] The polyolefin elastomer prepared in this invention has a high polymerization temperature. During polymerization, a metallocene catalyst with a high-temperature resistant and defined geometry is used, along with borneol amine, a rigid skeleton with a large steric hindrance. The substituents of borneol have a steric hindrance effect that combines rigidity and flexibility. Through the steric hindrance and electronic effects on the cyclopentadienyl ring, and the strategy of combining rigidity and flexibility on the substituents of the amine, the high-temperature resistance of the catalyst is improved. This can significantly enhance the solubility of the polymer in the solvent, reduce the viscosity of the solution system, prevent polymer precipitation and blockage of pipelines, and also facilitate the separation of subsequent products. This greatly reduces energy consumption in industrial production and significantly improves economic efficiency.

[0063] The polyolefin elastomer of the present invention has high α-olefin insertion rate, high molecular weight, narrow molecular weight distribution, excellent performance, and wide applicability, which is of great significance to the industrialization of polyolefin elastomers. Attached Figure Description

[0064] Figure 1 is the carbon NMR spectrum of the copolymer of ethylene and 1-octene provided in Example 11.

[0065] Figure 2 is the 1H NMR spectrum of compound A.

[0066] Figure 3 shows the 1H NMR spectrum of the metallocene catalyst Ti1.

[0067] Figure 4 shows the single-crystal structure of the metallocene catalyst Ti2. Detailed Implementation

[0068] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0069] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0070] The preparation methods of metallocene catalysts Ti1 and Ti2 are as follows:

[0071] 1.58 g / 10 mmol of borneol was dissolved in tetrahydrofuran, and 4.8 mL / 12 mmol of n-butyllithium (2.5 M) was added dropwise at -78 °C (the molar ratio of n-butyllithium to borneol was 1.2). The mixture was then allowed to react at room temperature for 6 hours. 22.21 g / 10 mmol of the compound was dissolved in 20 mL of tetrahydrofuran and mixed with the borneol lithium salt obtained in the previous step. Triethylamine, a deacidifying agent, was added, and the mixture was allowed to react for 6 hours. After the reaction was complete, the solvent was removed under vacuum, and the product was extracted with n-hexane. The solvent was then removed under vacuum and distilled under reduced pressure to give 3.06 g / 9.0 mmol of a yellow-green oil, with a yield of 90%.

[0072] The structure of compound 2 is as follows:

[0073] 2 g / 6 mmol of the silicon-substituted cyclopentadiene compound A was dissolved in 30 mL of tetrahydrofuran. 8.3 mL / 13.2 mmol of a 1.6 M n-butyllithium solution in n-hexane was added dropwise at -78 °C. The mixture was then allowed to rise to room temperature and reacted under nitrogen protection for 6 hours. 1.36 g / 0.79 mL / 7.2 mmol of titanium tetrachloride (the molar ratio of titanium tetrachloride to compound A was 1.2) was dissolved in 20 mL of n-hexane. The lithium salt obtained in the previous step was added dropwise to the titanium tetrachloride solution in n-hexane at -78 °C. The mixture was allowed to rise to room temperature and reacted under nitrogen protection for 6 hours. After the reaction was complete, the solvent was removed by vacuum, the solution was extracted with toluene, concentrated, and recrystallized to obtain a black solid powder, Ti1. The 1H NMR spectrum of the metallocene catalyst Ti1 is shown in Figure 3.

[0074] 2 g / 6 mmol of compound A was dissolved in 30 mL of tetrahydrofuran. 16.5 mL / 26.4 mmol of a 1.6 M lithium methyl ether solution was added dropwise at -78 °C, and the reaction was allowed to proceed to room temperature under nitrogen protection for 6 hours. 1.36 g / 0.79 mL / 7.2 mmol of titanium tetrachloride (the molar ratio of titanium tetrachloride to compound A was 1.2) was dissolved in 20 mL of n-hexane. The lithium salt obtained in the previous step was added dropwise to the titanium tetrachloride n-hexane solution at -78 °C. The reaction was allowed to proceed to room temperature under nitrogen protection for 10–12 hours. After the reaction was complete, the solvent was removed by vacuum, the solution was extracted with n-hexane, concentrated, and recrystallized to obtain orange-yellow crystals of Ti₂. The 1H NMR spectrum of the metallocene catalyst Ti₂ is shown in Figure 4.

[0075] The structure of compound A is as follows:

[0076] The 1H NMR spectrum of compound A is shown in Figure 2.

[0077] The example provides a method for preparing a polyolefin elastomer, the synthesis method of which is as follows:

[0078] The polymerization was carried out in a stainless steel high-temperature and high-pressure reactor equipped with a stirrer. Before the polymerization reaction, the reactor was vacuum-dried at 200°C for at least 2 hours. After the reactor cooled to room temperature, freshly distilled solvent, α-olefin, and co-catalyst were sequentially injected through the feed valve. Ethylene gas was introduced to 1.5 MPa, and the reaction system was heated to the set polymerization temperature. The mixture was stirred thoroughly, and a metallocene catalyst solution was added through the feed valve, maintaining the total volume of the polymerization system at 100 mL. The ethylene pressure was increased to the set polymerization pressure and maintained constant throughout the polymerization process. After the polymerization reaction reached the set time, the ethylene supply was stopped, the pressure was slowly released, the reactor was opened, and ethanol was added to terminate the reaction. The polymer product was obtained by filtration, soaked in hydrochloric acid / ethanol, filtered, washed several times with anhydrous ethanol, and then dried in a vacuum drying oven at 60°C to constant weight.

[0079] Example 1

[0080] Example 1 provides a method for preparing the above-mentioned polyolefin elastomer, wherein the reaction conditions are as follows: the metallocene catalyst Ti1 is 1 μmol; the molar ratio of the co-catalyst dMAO to the metallocene catalyst Ti1 is 150:1; the molar ratio of the co-catalyst [Ph3C][B(C6F5)4] to the metallocene catalyst Ti1 is 1.2:1; the solvent is a mixture of isomeric saturated alkanes; the polymerization temperature is 180℃; the pressure of ethylene introduced is 2 MPa; the concentration of 1-octene is 2.0 mol / L; and the polymerization time is 10 minutes.

[0081] The preparation method of the polyolefin elastomer provided in Example 2 is different from that in Example 1 only in that the metallocene catalyst Ti2 is used to catalyze the copolymerization of ethylene and 1-octene. The specific reaction results are shown in Table 1.

[0082] Table 1. Copolymerization of ethylene and 1-octene using different metallocene catalysts

[0083] Table 1 shows that the metallocene catalyst of borneol amine, which possesses both high steric hindrance and flexibility, can catalyze the copolymerization of ethylene and 1-octene with high activity at high temperatures, yielding polyolefin elastomers with high monomer insertion rates. In contrast, the metallocene catalyst Ti2 exhibits higher polymerization activity, resulting in copolymers with higher molecular weights.

[0084] The preparation methods of polyolefin elastomers provided in Examples 3-7 differ from those in Example 2 only in that, in the copolymerization reaction, metallocene catalyst Ti2 and different co-catalysts are used to copolymerize ethylene with 1-octene. The specific reaction results are shown in Table 2.

[0085] Table 2. Copolymerization of ethylene and 1-octene using different co-catalysts

[0086] Table 2 shows that in the copolymerization reaction, under the combined action of metallocene catalyst and co-catalyst, the copolymerization of ethylene and α-olefins can be carried out. The co-catalyst can be selected from one or more combinations of methylaluminoxane, modified methylaluminoxane, dry methylaluminoxane, tris(pentafluorophenyl)boron, and triphenylcarbontetra(pentafluorophenyl)boron salt. Among them, the co-catalyst of dMAO and [Ph3C][B(C6F5)4] mixed with metallocene catalyst Ti2 has better effect and higher activity in the copolymerization of ethylene and 1-octene.

[0087] The preparation methods of polyolefin elastomers provided in Examples 8-17 differ from those in Example 2 only in that, in the copolymerization reaction, metallocene catalyst Ti2 and different proportions of co-catalysts are used for the copolymerization of ethylene and 1-octene. Specific reaction results are shown in Table 3, where the Al / Ti molar ratio represents the molar ratio of dMAO to the metallocene catalyst Ti2, and the B / Ti molar ratio represents the molar ratio of [Ph3C][B(C6F5)4] to the metallocene catalyst Ti2. The carbon NMR spectrum of the copolymer of ethylene and 1-octene provided in Example 11 is shown in Figure 1.

[0088] Table 3. Copolymerization of ethylene and 1-octene with different proportions of co-catalysts

[0089] Table 3 shows that in the copolymerization reaction, a molar ratio of dMAO to Ti2 (20-500):1 provides highly active catalysis for the copolymerization of ethylene and 1-octene. The catalytic activity is highest when the molar ratio of dMAO to Ti2 is in the range of 100-300:1, and reaches its peak at a ratio of 150:1. In the same copolymerization reaction, a molar ratio of [Ph3C][B(C6F5)4] to Ti2 (1-1.5):1 provides highly active catalysis for the copolymerization of ethylene and 1-octene, with the highest activity observed at a ratio of 1.2:1. Furthermore, using a mixed cocatalyst system can leverage the synergistic effect of the cocatalysts, leading to better copolymerization results.

[0090] The preparation methods of polyolefin elastomers provided in Examples 18-20 differ from those in Example 2 only in that different α-olefin monomers are copolymerized with ethylene using the metallocene catalyst Ti2. The specific reaction results are shown in Table 4.

[0091] Table 4 Copolymerization of different α-olefin monomers with ethylene

[0092] Table 4 shows that the metallocene catalyst Ti2 can catalyze the copolymerization of different α-olefin monomers, including 1-butene, 1-hexene, 1-octene, and 1-decene, with ethylene at high temperatures. The copolymerization products have high molecular weight and high α-olefin insertion rate. Among them, the product with the highest molecular weight (455.7 kg / mol) and narrow molecular weight distribution and PDI (2.1) is produced by the copolymerization of ethylene and 1-octene catalyzed by the metallocene catalyst Ti2.

[0093] The preparation methods of polyolefin elastomers provided in Examples 21-23 differ from those in Example 2 only in that the copolymerization of ethylene and 1-octene is carried out in different solvents using a metallocene catalyst Ti2. The specific reaction conditions and polymerization results are shown in Table 5.

[0094] Table 5. Copolymerization of ethylene and 1-octene in different solvents

[0095] The results in Table 5 show that in different solvents, such as n-hexane, n-heptane, methylcyclohexane, isooctane, or mixtures of isomeric saturated alkanes, the metallocene catalyst Ti2 can be used to copolymerize ethylene and 1-octene. Among them, in the mixture of isomeric saturated alkanes, the metallocene catalyst Ti2 has the highest activity in catalyzing the copolymerization of 1-octene and ethylene, with a high molecular weight of product and a high α-olefin insertion rate.

[0096] The preparation methods of polyolefin elastomers provided in Examples 25-28 differ from those in Example 2 only in that the copolymerization of ethylene and 1-octene is carried out using a metallocene catalyst Ti2 at different temperatures. The specific reaction conditions and polymerization results are shown in Table 6.

[0097] Table 6. Copolymerization of ethylene and 1-octene at different temperatures

[0098] Table 6 shows that the metallocene catalyst Ti2 exhibits high catalytic activity for the copolymerization of ethylene and 1-octene at high temperatures of 100-250℃. The copolymerization process is carried out within a high temperature range of 150-220℃, resulting in polyolefin elastomers with superior performance. The highest catalytic activity for the copolymerization of ethylene and 1-octene is observed at 180℃. Very high copolymerization activity is still maintained at 220℃.

[0099] The preparation methods of polyolefin elastomers provided in Examples 29-33 differ from those in Example 2 only in that the copolymerization of ethylene and 1-octene is carried out using a metallocene catalyst Ti2 under different pressures. The specific reaction conditions and polymerization results are shown in Table 7.

[0100] Table 7. Copolymerization of ethylene and 1-octene under different pressures.

[0101] The results in Table 7 show that the metallocene catalyst Ti2 can catalyze the copolymerization of ethylene and 1-octene with high activity under pressures of 1-6 MPa. When the catalytic copolymerization process is carried out in the range of 1-3 MPa, the polyolefin elastomers obtained have better performance. Among them, the catalytic activity for the copolymerization of ethylene and 1-octene is the highest at a pressure of 2 MPa.

[0102] The preparation methods of polyolefin elastomers provided in Examples 34-37 differ from those in Example 2 only in that the copolymerization of ethylene and 1-octene is carried out using a metallocene catalyst Ti2 at different polymerization times. The specific reaction conditions and polymerization results are shown in Table 8.

[0103] Table 8. Copolymerization of ethylene and 1-octene at different time points

[0104] Table 8 shows that the metallocene catalyst Ti2 can catalyze the copolymerization of ethylene and 1-octene with high activity in the range of 5-60 min. When the catalytic copolymerization process is carried out in the range of 5-15 min, the catalytic activity and the molecular weight of the copolymer are even higher.

[0105] Comparative Examples 1-4 provide examples of copolymerization of ethylene and 1-octene catalyzed by the classic CGC catalyst Ti3. The CGC titanium complex Ti3 was prepared according to the patent report (WO2000075151) with a yield of 60%. Compared to the classic CGC catalyst Ti3, the metallocene catalyst Ti2 of this invention is simpler to synthesize and yields a higher yield (over 75%). The reaction conditions and results of ethylene polymerization catalyzed by the metallocene catalyst Ti2 and the classic CGC catalyst Ti3 are shown in Table 9.

[0106] The structure of the above-mentioned catalyst Ti3 is as follows:

[0107] Table 9. Copolymerization of ethylene and 1-octene using metallocene catalyst Ti2 and classic CGC catalyst Ti3.

[0108] The results of Comparative Examples 1-4 and Examples 2, 25-27 show that the metallocene catalyst Ti2 has stronger thermal stability than the classic CGC catalyst Ti3. This demonstrates that the borneol amine, which adopts a rigid framework with large steric hindrance, has a steric hindrance effect that combines rigidity and flexibility. Through the steric hindrance and electronic effects on the cyclopentadienyl ring and the strategy of combining rigidity and flexibility on the substituents on the amine, the high temperature resistance of the metallocene catalyst of the present invention is improved.

[0109] As can be seen from the above embodiments, the polyolefin elastomer provided by the present invention has an α-olefin insertion rate as high as 19.1 mol% and a maximum molecular weight of 576.8 kg / mol. In particular, the metallocene catalyst used in the solution polymerization process still exhibits high catalytic activity (5.01 × 10⁻⁶) at a high temperature of 220°C. 7 g·mol -1 Ti·h -1 The polyolefin elastomer of the present invention has a high α-olefin insertion rate, high molecular weight, and narrow molecular weight distribution. At the same time, the high polymerization temperature significantly reduces the energy consumption of the reaction process, which is conducive to promoting the industrialization of polyolefin elastomers.

Claims

1. A method for preparing a polyolefin elastomer, wherein, Includes the following steps: In a solvent, a metallocene catalyst is used to carry out the copolymerization reaction of ethylene and α-olefins to obtain polyolefin elastomers; The metallocene catalyst has a structure as shown in formula (I): In equation (I), M is selected from Ti or Zr; X1 and X2 are each independently selected from halogens or alkyl groups having 1 to 6 carbon atoms, and X1 and X2 may be the same or different; R1 to R4 are each independently selected from hydrogen or alkyl groups having 1 to 2 carbon atoms, and R1 to R4 may be the same or different.

2. The method for preparing the polyolefin elastomer according to claim 1, wherein, In formula (I), M is selected from Ti; X1 and X2 are each independently selected from Cl or Me; R1 to R4 are selected from Me.

3. The method for preparing the polyolefin elastomer according to claim 1, wherein, The metallocene catalyst is a compound with the structure shown in the formula Ti1, Ti2, Zr1, or Zr2:

4. The method for preparing the polyolefin elastomer according to claim 1, wherein, The pressure of ethylene introduced in the copolymerization reaction is 0.5-6 MPa; the concentration of α-olefin is 0.5-10 mol / L based on the total volume of materials in the copolymerization reaction; the temperature of the copolymerization reaction is 50-250℃; and the time of the copolymerization reaction is 2-60 min.

5. The method for preparing the polyolefin elastomer according to claim 4, wherein, The pressure of ethylene introduced in the copolymerization reaction is 1-3 MPa; the concentration of α-olefin is 2-8 mol / L based on the total volume of materials in the copolymerization reaction; the temperature of the copolymerization reaction is 150-220℃; and the time of the copolymerization reaction is 5-15 min.

6. The method for preparing the polyolefin elastomer according to claim 1, wherein, The α-olefin is selected from one or more combinations of 1-butene, 1-hexene, 1-octene, and 1-decene.

7. The method for preparing the polyolefin elastomer according to claim 1, wherein, In the copolymerization reaction, ethylene and α-olefins are copolymerized under the combined action of metallocene catalysts and co-catalysts.

8. The method for preparing the polyolefin elastomer according to claim 7, wherein, The cocatalyst is selected from organoboron compounds and / or alkylaluminoxane compounds.

9. The method for preparing the polyolefin elastomer according to claim 7, wherein, The molar ratio of the metallocene catalyst to the co-catalyst is 1:(1-500).

10. The method for preparing the polyolefin elastomer according to claim 8, wherein, The organoboron compound is selected from one or more of tris(pentafluorophenyl)boron, triphenylcarbontetra(pentafluorophenyl)boron, and N,N-dimethylanilinetetra(pentafluorophenyl)borate.

11. The method for preparing the polyolefin elastomer according to claim 8, wherein, The alkylaluminoxane compound is selected from one or more combinations of methylaluminoxane, dried methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, and isobutylaluminoxane.

12. The method for preparing the polyolefin elastomer according to claim 7, wherein, The cocatalyst is dry methylaluminoxane and / or triphenylcarbontetra(pentafluorophenyl)boron salt.

13. The method for preparing the polyolefin elastomer according to claim 12, wherein, The molar ratio of the metallocene catalyst to dry methylaluminoxane is 1:(100-300).

14. The method for preparing the polyolefin elastomer according to claim 12, wherein, The molar ratio of the metallocene catalyst to triphenylcarbontetra(pentafluorophenyl)boron salt is 1:(1-1.5).

15. The method for preparing the polyolefin elastomer according to claim 1, wherein, The solvent is selected from one or more of the following: n-hexane, n-heptane, n-octane, methylcyclohexane, isopentane, isohexane, isooctane, and isomeric saturated alkane mixtures (Isopar-E).

16. A polyolefin elastomer prepared by a method for preparing a polyolefin elastomer as described in any one of claims 1-15.

17. The polyolefin elastomer according to claim 16, wherein, The weight-average molecular weight of the polyolefin elastomer is 53.5-576.8 kg / mol.

18. The polyolefin elastomer according to claim 16, wherein, The molecular weight distribution of the polyolefin elastomer is 2.0-2.

8.

19. The polyolefin elastomer according to claim 16, wherein, The α-olefin insertion rate of the polyolefin elastomer is 7.6 mol% to 19.1 mol%.

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