Catalyst for synthesizing polyolefin elastomer, polyolefin elastomer and preparation method

Abstract

The present invention provides a catalyst for the synthesis of a polyolefin elastomer, a polyolefin elastomer, and a preparation method, and specifically relates to the technical field of polyolefin elastomers. The present invention uses a metallocene catalyst (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride as a main catalyst and triisobutylaluminum as a co-catalyst, and adopts a continuous polymerization process to polymerize ethylene and α-olefin comonomers at high temperature to prepare a polyolefin elastomer. The polyolefin elastomer prepared by the present invention has a high molecular weight and a narrow molecular weight distribution, a low glass transition temperature, simplifies the polymerization process, and greatly saves costs.

Description

Technical Field

[0001] The present invention relates to the technical field of polyolefins, and in particular to a catalyst for synthesizing a polyolefin elastomer, a polyolefin elastomer and a preparation method thereof. Background Art

[0002] Polyolefin elastomer (POE) is a rapidly developing synthetic polymer that can replace a series of polymers such as ethylene-propylene copolymer (EPM), ethylene-propylene diene monomer (EPDM), ethylene-vinyl acetate copolymer (EVA), styrene block copolymer (SBC), and ethylene-methyl acrylate copolymer (EMA). POE has certain versatility. Therefore, POE is widely used in medical packaging materials, automotive parts, wires and cables, daily necessities, and toys.

[0003] The emergence of POE products is inseparable from the development of homogeneous metal catalysts. At present, the co-catalysts for the preparation of POE elastomers are generally alkyl aluminum and boron compounds, but the synthesis cost of boron compounds is relatively high. Summary of the Invention

[0004] In view of the above shortcomings of the prior art, the present invention provides a catalyst for synthesizing a polyolefin elastomer, a polyolefin elastomer and a preparation method, which simplifies the polymerization process of POE and greatly reduces the cost.

[0005] To achieve the above-mentioned and other related purposes, the present invention provides a catalyst for synthesizing a polyolefin elastomer, wherein the catalyst is a single-active-center metallocene catalyst, and the structural formula of the metallocene catalyst is as follows:

[0006] .

[0007] The second aspect of the present invention provides a method for preparing a polyolefin elastomer, which comprises: under anhydrous and oxygen-free conditions, using the above-mentioned catalyst as the main catalyst, polymerizing ethylene and α-olefin comonomers under the action of the main catalyst and a co-catalyst to prepare the polyolefin elastomer.

[0008] In one example of the present invention, the preparation method includes at least the following steps: pre-treating the reaction device to make the reaction chamber of the reaction device free of water and oxygen; storing the solvent, main catalyst, co-catalyst, ethylene and α-olefin comonomer in the feeding tank of the reaction device respectively; preheating the reaction device to the required temperature, and inputting the solvent, main catalyst, co-catalyst, ethylene and α-olefin comonomer into the reaction chamber for polymerization reaction to obtain the polyolefin elastomer.

[0009] In one example of the present invention, the feed concentration of the main catalyst is 0.0015~0.09 μmol / mL, and the molar ratio of the co-catalyst to the main catalyst is (100~1000):1; the feed concentration of the α-olefin comonomer is 4.3~7.8 mol / L, and the feed molar ratio of the α-olefin comonomer to the ethylene is (0.3~10):1.

[0010] In one example of the present invention, the feed molar ratio of the α-olefin comonomer to the ethylene is preferably (0.8-5):1.

[0011] In one example of the present invention, the α-olefin comonomer and ethylene need to be dehydrated and deoxygenated before use.

[0012] In one example of the present invention, the co-catalyst is selected from triisobutylaluminum; and the α-olefin comonomer is a linear or branched α-olefin having 3 to 20 carbon atoms.

[0013] In one example of the present invention, the α-olefin comonomer is selected from one or more of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, decene, 1-dodecene, and 1-hexadecene.

[0014] In one example of the present invention, the reaction temperature of the polymerization reaction is 90-170° C., the reaction pressure is 2-10 MPa, and the reaction time is 0.05-1 h.

[0015] In one example of the present invention, the reaction temperature of the polymerization reaction is 120-170° C., the reaction pressure is 4-8 MPa, and the reaction time is 0.1-0.4 h.

[0016] A third aspect of the present invention provides a polyolefin elastomer, which is prepared using the above-mentioned preparation method.

[0017] In one example of the present invention, the weight average molecular weight of the polyolefin elastomer is 5*10 4 ~30*10 4 g / mol, molecular weight distribution index is 1~8, melt index is 0.5~30g / 10min, density is 0.859~0.895g / cm 3 .

[0018] The present invention provides a single-active-site metallocene catalyst with high catalytic activity. Using this catalyst as the main catalyst and triisobutylaluminum as a cocatalyst, ethylene and α-olefin comonomers are polymerized at high temperatures to produce a polyolefin elastomer. The preparation method of the present invention does not require a boron compound, simplifying the polymerization process and significantly reducing costs. The resulting polyolefin elastomer exhibits a high molecular weight, a narrow molecular weight distribution, and a low glass transition temperature (Tg) below -60°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 FIG. 1 is a flow chart of a method for preparing a polyolefin elastomer in one embodiment of the present invention.

[0021] Figure 2 This is the NMR spectrum of the metallocene catalyst provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0023] It should be noted that, unless conflicting, the features in the following examples and embodiments may be combined with each other. It should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments, rather than to limit the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers. For simplicity, only some numerical ranges are explicitly disclosed herein, and each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit, or can be combined with other lower limits or upper limits to form an unspecified range.

[0024] The present invention provides a catalyst for the synthesis of polyolefin elastomers, which is (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride. The (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride is a single-active-site metallocene catalyst, and its structural formula is shown below:

[0025] .

[0026] The catalyst has high catalytic activity and is used as a main catalyst to synthesize polyolefin elastomers. The obtained product has high molecular weight and narrow molecular weight distribution.

[0027] (Phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride was prepared by the following method:

[0028] (1) Fluorene and 2,5-dichloro-2,5-dimethylhexane were dissolved in an appropriate amount of nitromethane, and the obtained solution was injected into an argon-purged reaction flask. Aluminum chloride / nitromethane solution was added to the above reaction flask within 10 minutes to obtain a purple solution. The solution was stirred and reacted for 20 hours, and then slowly poured into an appropriate amount of ice water; the precipitate was collected by filtration and refluxed in ethanol for 2 hours. After cooling, the solid was collected by filtration and refluxed in hexane for 2.5 hours. The solid was cooled and filtered to collect the solid, and then dried in a vacuum to obtain octamethyloctahydrodibenzofluorene.

[0029] (2) Octamethyloctahydrodibenzofluorene was placed in a flask, evacuated, and added with ether. At 0°C, n-butyl lithium was injected over 3 minutes, followed by the addition of 6-phenyl-6-indenyl-methyleneindene and condensed ether. The reaction was stirred at room temperature for 5 days. Then, aqueous ammonium chloride was slowly added at 0°C. The organic layer was separated, and the aqueous layer was extracted with ether. The combined organic layers were dried over MgSO4, filtered, and spun to provide a crude product in quantitative yield. It was then purified by recrystallization from ethanol to obtain (6-phenyl-6-indenyl-methyleneindene)-octahydrooctamethyldibenzofluorene.

[0030] (3) Place (6-phenyl-6-indenyl-methyleneindenyl)-octahydrooctamethyldibenzofluorene and n-butyllithium in another flask. Add ether at -78°C, stir and allow to warm naturally to room temperature, then add tetrahydrofuran. After 45 hours, drain the solvent and add ZrCl4. Add petroleum ether at -78°C, drain the solvent after 47 hours, and purify to obtain (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride.

[0031] It should be noted that the ratio between the reactants in each step can be set according to the ratio of each group in the product.

[0032] The present invention provides a method for preparing a polyolefin elastomer. The method comprises: under anhydrous and oxygen-free conditions, using (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride as a main catalyst, polymerizing ethylene and α-olefin comonomers under the action of the main catalyst and a co-catalyst to prepare the polyolefin elastomer.

[0033] See also Figure 1 , a method for preparing a polyolefin elastomer, comprising at least the following steps:

[0034] S1. Pre-treating the reaction device to make the reaction chamber of the reaction device free of water and oxygen;

[0035] S2. The solvent, the main catalyst, the co-catalyst, the ethylene and the α-olefin comonomer are stored in the feed tanks of the reaction device respectively.

[0036] S3. Preheating the reaction device to a desired temperature, inputting a solvent, a main catalyst, a co-catalyst, ethylene and an α-olefin comonomer into the reaction chamber for polymerization reaction to obtain the polyolefin elastomer.

[0037] Specifically, the reaction apparatus in step S1 can be any apparatus that meets the conditions for polyolefin production. For example, the reaction apparatus can be a reactor, which typically includes a reactor body, a stirring mechanism, and a heating mechanism. The reactor body includes a reaction chamber, a plurality of feeding tanks connected to the reaction chamber are located at the top of the reactor body, and a discharge port is located at the bottom of the reactor body. The stirring mechanism is installed in the reactor body. During the reaction process, the stirring mechanism continuously stirs the material in the reaction chamber, thereby ensuring a more complete and efficient reaction. The heating mechanism can provide heat to the reaction chamber. The heating mechanism can provide heat to the reaction chamber in various forms, such as a heating jacket wrapped around the outside of the reactor body.

[0038] The purpose of pre-treating the reaction apparatus in step S1 is to remove moisture and oxygen from the reaction chamber, rendering it free of water and oxygen to prevent adverse effects of moisture or oxygen on the subsequent polymerization reaction. The specific operation is as follows: High-purity nitrogen is introduced into the reaction chamber at a temperature of 140°C to 150°C. The nitrogen is then replaced three to five times to ensure that the reactor is free of water and oxygen.

[0039] The main catalyst in step S2 is (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride. The preparation method thereof is described above and will not be described in detail here. The structural formula of the main catalyst is:

[0040] .

[0041] The co-catalyst is selected from triisobutylaluminum; the α-olefin comonomer is a linear or branched α-olefin having 3 to 20 carbon atoms. Furthermore, the α-olefin comonomer is selected from one or more of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, decene, 1-dodecene, and 1-hexadecene, that is, the α-olefin comonomer can be any one of the monomer types listed above, for example, 1-octene, or 1-butene, or decene, etc.; the α-olefin comonomer can also be a combination of two or more of the monomer types listed above in any proportion, such as a combination of propylene and 1-butene, or a combination of 1-pentene, 1-hexene and 1-octene, or a combination of decene, 1-dodecene and 1-hexadecene, etc., which are not listed here one by one. Of course, the α-olefin comonomer includes but is not limited to the monomer types listed above, and monomers that meet the conditions not listed above can also be selected. The solvent is mainly used to provide a reaction solvent to control the reaction process. The solvent can be a general organic solvent, preferably an isomeric alkane, such as toluene, hexane, etc.

[0042] Step S2: The above-mentioned solvent, main catalyst, co-catalyst, ethylene and α-olefin comonomer are stored in the feed tank of the reactor respectively. It should be noted that the main catalyst and co-catalyst need to be made into a solution and stored in the feed tank to control the feed concentration and rate of the main catalyst and co-catalyst during the reaction. For example, the main catalyst and toluene are made into a solution and stored in one feed tank; the co-catalyst triisobutylaluminum and hexane are made into a solution and stored in another feed tank, and the solvent, ethylene and α-olefin comonomer are stored in another feed tank. Preferably, the above-mentioned α-olefin comonomer and ethylene need to be dehydrated and deoxygenated before use.

[0043] In step S3, the reaction apparatus (reactor and pipeline) is preheated to the desired temperature, the speed of the stirring device in the reactor is adjusted to a set speed, for example, 1000 r / min, the ethylene feed valve on the top of the reactor is opened, the ethylene in the feed tank is introduced into the reactor, and the pressure in the reactor is controlled within a reasonable range; the chemical metering pump is turned on, and the feed valves for the solvent, main catalyst, co-catalyst and α-olefin comonomer on the top of the reactor are opened at the same time, so that the solvent, main catalyst, co-catalyst and α-olefin comonomer are continuously fed into the reactor at the set flow rate to carry out the polymerization reaction.

[0044] Among them, the feed concentration of the main catalyst is 0.0015~0.09μmol / mL, further, the feed concentration of the main catalyst is 0.01~0.08μmol / mL; for example, 0.03μmol / mL, 0.05μmol / mL, 0.07μmol / mL, and so on; the molar ratio of the co-catalyst to the main catalyst is (100~1000):1, further, the molar ratio of the co-catalyst to the main catalyst is (300~800):1, for example, 400:1, 500:1, 600:1 or 700:1, and so on.

[0045] The feed concentration of the α-olefin comonomer is 4.3 to 7.8 mol / L. Furthermore, the feed concentration of the α-olefin comonomer is 5.0 to 7.0 mol / L, for example, 5.0 mol / L, 6.0 mol / L, or 7.0 mol / L, etc. The feed molar ratio of the α-olefin comonomer to ethylene is (0.3 to 10):1. Furthermore, the feed molar ratio of the α-olefin comonomer to ethylene is (0.8 to 5):1, for example, 1:1, 3:1, or 5:1, etc. The residence time of the materials in the reactor is 3 to 60 minutes, for example, 10 minutes, 30 minutes, 50 minutes, etc. The α-olefin comonomer and ethylene are copolymerized in the presence of a primary catalyst and triisobutylaluminum.

[0046] The polymerization reaction in step S3 is carried out at a temperature of 90 to 170°C, preferably 120 to 170°C, for example, 120°C, 150°C, or 170°C. The reaction pressure is 2 to 10 MPa, preferably 4 to 8 MPa, for example, 4 MPa, 6 MPa, or 8 MPa. The reaction time (i.e., the residence time of the material in the reactor) is 0.05 to 1 hour, preferably 0.08 to 1 hour, preferably 0.1 to 0.4 hours, for example, 0.1 hour, 0.2 hour, 0.3 hour, or 0.4 hour. After the reaction is completed, the reaction product is washed with a large amount of acid and alcohol, filtered and dried, and dried in a vacuum drying oven to obtain a polyolefin elastomer.

[0047] The obtained copolymer was tested by high temperature gel permeation chromatography. The weight average molecular weight Mw was 5*104~30*104 g / mol, the molecular weight distribution index PDI was 1~8, the melt index was 0.5~30 g / 10min, and the density was 0.859~0.895 g / cm3.

[0048] The technical solutions of the present invention are described in detail below through several specific examples and comparative examples. Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art, and the instruments used in the examples are all commercially available.

[0049] It should be noted that the main catalysts used in Examples 1 to 12 are all (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride, and the structural formula is shown below:

[0050] .

[0051] The preparation process of (phenyl, indenyl)-methylene bridged (indenyl, fluorenyl) zirconium dichloride is as follows:

[0052] (1) Dissolve fluorene (210 mmol) and 2,5-dichloro-2,5-dimethylhexane (430 mmol) in an appropriate amount of nitromethane and inject into an appropriate amount of reaction bottle purged with argon; add 100 mL of aluminum chloride / nitromethane solution within 10 minutes to obtain a purple solution, and continue to stir and react for 20 hours; then slowly pour into an appropriate amount of ice water, filter and collect the precipitate, and reflux in 500 mL of ethanol for 2 hours; after cooling, filter and collect the solid, and reflux in 400 mL of hexane for 2.5 hours, cool and filter to collect the solid, and dry in a vacuum to obtain octamethyloctahydrodibenzofluorene.

[0053] (2) Octamethyloctahydrodibenzofluorene (30 mmol) was placed in a 300 mL flask, evacuated, and 120 mL of diethyl ether was added. At 0°C, n-butyl lithium (34 mmol) was injected over 3 min, followed by the addition of 6-phenyl-6-indenyl-methyleneindene (31 mmol), condensed diethyl ether (150 mL) and stirred at room temperature for 5 days, followed by the slow addition of 60 mL of aqueous ammonium chloride solution at 0°C. The organic layer was separated, and the aqueous layer was extracted with diethyl ether. The combined organic layers were dried over MgSO4, filtered, and spun to provide a crude product in quantitative yield. (6-phenyl-6-indenyl-methyleneindene)-octahydrooctamethyldibenzofluorene was then purified by recrystallization from ethanol.

[0054] (3) (6-Phenyl-6-indenyl-methyleneindenyl)-octahydrooctamethyldibenzofluorene (16 mmol) and n-butyllithium (32 mmol) were placed in a 250 mL flask. 75 mL of ether was added at -78°C. After stirring and naturally warming to room temperature, 25 mL of tetrahydrofuran was added. After 45 h, the solvent was dried and ZrCl4 (16.5 mmol) was added. 75 mL of petroleum ether was added at -78°C. After 47 h, the solvent was dried and purified to obtain (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride.

[0055] The product was tested by nuclear magnetic resonance spectrometer, and the obtained spectrum was as follows: Figure 2 As shown, the test spectrum proves that the structural formula of the product is as shown above.

[0056] Example 1

[0057] In this example, the primary catalyst used was (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride, the cocatalyst was triisobutylaluminum, the α-olefin comonomer was 1-octene, and the solvent was hexane. Before the experiment, the 500 mL reactor was purged three times with high-purity nitrogen at 150°C. A solution of the primary catalyst and toluene was stored in a feed tank, while a solution of triisobutylaluminum and hexane was stored in another feed tank. Hexane, 1-octene, and ethylene were stored in separate feed tanks.

[0058] The reactor and piping were preheated to the desired temperature. The reactor speed was set to 1000 rpm. The ethylene feed valve at the top of the reactor was opened, and the pressure within the reactor was controlled within a certain range. The chemical metering pump and the top feed valve were simultaneously opened. Hexane, the primary catalyst, triisobutylaluminum, and 1-octene were then continuously introduced into the reactor at the set flow rates. Once the reactor was fully filled, the materials overflowed from the reactor overflow port. The liquid level in the reactor was controlled by a pneumatic valve, and the materials were continuously discharged. The primary catalyst feed concentration was 0.003 μmol / mL, the molar ratio of triisobutylaluminum to primary catalyst was 100:1, the 1-octene feed concentration was 5.2 mol / L, and the molar ratio of 1-octene to ethylene was 1.25:1. The reactor temperature was maintained at 140°C and the pressure at 4 MPa during steady-state operation. The material residence time in the reactor was 10 minutes. The material continuously discharged from the product tank was washed with a large amount of acid and alcohol, filtered, and dried in a vacuum oven at 140°C for at least 4 hours.

[0059] Example 2

[0060] The difference between this embodiment and embodiment 1 is that the main catalyst feed concentration is 0.003 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 500:1, the 1-octene feed concentration is 5.2 mol / L, the molar ratio of 1-octene to ethylene is 3.27:1, and the temperature in the reactor is controlled at 160°C when stable.

[0061] Example 3

[0062] The difference between this embodiment and embodiment 1 is that the main catalyst feed concentration is 0.003 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 100:1, the 1-octene feed concentration is 5.2 mol / L, the molar ratio of 1-octene to ethylene is 0.3:1, and the temperature in the reactor is controlled at 120°C when stable.

[0063] Example 4

[0064] The difference between this embodiment and Example 1 is that the main catalyst feed concentration is 0.003 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 1000:1, the 1-octene feed concentration is 5.2 mol / L, the molar ratio of 1-octene to ethylene is 5:1, the temperature in the reactor is controlled at 170°C during stability, the pressure is 6 MPa, and the residence time of the material in the reactor is 16 min.

[0065] Example 5

[0066] In this example, the primary catalyst used was (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride, the cocatalyst was triisobutylaluminum, the α-olefin comonomer was 1-hexene, and the solvent was hexane. Before the experiment, the 500mL reactor was purged three times with high-purity nitrogen at 150°C. A solution of the primary catalyst and toluene was stored in a feed tank, a solution of triisobutylaluminum and hexane was stored in another feed tank, and 1-hexene and ethylene were stored in separate feed tanks.

[0067] The reactor and piping were preheated to the desired temperature. The reactor speed was set to 1000 rpm. The ethylene feed valve at the top of the reactor was opened, and the pressure within the reactor was controlled within a specified range. The chemical metering pump and the top feed valve were simultaneously opened. Hexane, the primary catalyst, triisobutylaluminum, and 1-hexene were then continuously introduced into the reactor at the set flow rates. Once the reactor was fully filled, the materials overflowed from the reactor overflow port. The liquid level in the reactor was controlled by a pneumatic valve, allowing for continuous discharge. The primary catalyst feed concentration was 0.05 μmol / mL, the molar ratio of triisobutylaluminum to the primary catalyst was 100:1, the 1-hexene feed concentration was 4.3 mol / L, and the molar ratio of 1-hexene to ethylene was 7.1:1. The reactor temperature was maintained at 120°C and the pressure at 4 MPa during steady-state operation. The residence time in the reactor was 10 minutes. The material continuously discharged from the product tank was washed with a large amount of acid and alcohol, filtered, drained, and dried in a vacuum oven at 140°C for at least 4 hours.

[0068] Example 6

[0069] The difference between this embodiment and embodiment 5 is that the main catalyst feed concentration is 0.05 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 100:1, the 1-hexene feed concentration is 4.3 mol / L, the molar ratio of 1-hexene to ethylene is 10:1, and the temperature in the reactor is controlled at 140°C when stable.

[0070] Example 7

[0071] The difference between this embodiment and embodiment 5 is that the main catalyst feed concentration is 0.05 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 100:1, the 1-hexene feed concentration is 4.3 mol / L, the molar ratio of 1-hexene to ethylene is 1.98:1, and the temperature in the reactor is controlled at 160°C when stable.

[0072] Example 8

[0073] The difference between this embodiment and Example 5 is that the main catalyst feed concentration is 0.05 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 100:1, the 1-hexene feed concentration is 4.3 mol / L, the molar ratio of 1-hexene to ethylene is 1.88:1, the temperature in the reactor is controlled at 140°C when stable, the pressure is 8 MPa, and the residence time of the material in the reactor is 24 min.

[0074] Example 9

[0075] In this example, the main catalyst used was (phenyl, indenyl)-methylene-bridged (indenyl, fluorenyl) zirconium dichloride, the cocatalyst was triisobutylaluminum, the α-olefin comonomer was 1-dodecene, and the solvent was hexane. Before the experiment, the 500mL reactor was purged three times with high-purity nitrogen at 150°C. A solution of the main catalyst and toluene was stored in a feed tank, while a solution of triisobutylaluminum and hexane was stored in another feed tank. Hexane, 1-dodecene, and ethylene were stored in separate feed tanks.

[0076] The reactor and piping were preheated to the desired temperature. The reactor speed was set to 1000 rpm. The ethylene feed valve at the top of the reactor was opened, and the pressure within the reactor was controlled within a certain range. The chemical metering pump and the top feed valve were simultaneously opened. Hexane, the primary catalyst, triisobutylaluminum, and 1-dodecene were then continuously introduced into the reactor at the set flow rates. Once the reactor was fully filled, the materials overflowed from the reactor overflow port. The liquid level in the reactor was controlled by a pneumatic valve, and the materials were continuously discharged. The primary catalyst feed concentration was 0.09 μmol / mL, the molar ratio of triisobutylaluminum to primary catalyst was 100:1, the 1-dodecene feed concentration was 7.8 mol / L, and the molar ratio of 1-dodecene to ethylene was 1.9:1. The reactor temperature was maintained at 120°C and the pressure at 4 MPa during steady-state operation. The material residence time in the reactor was 20 minutes. The material continuously discharged from the product tank was washed with a large amount of acid and alcohol, filtered, drained, and dried in a vacuum oven at 140°C for at least 4 hours.

[0077] Example 10

[0078] The difference between this embodiment and Example 9 is that the main catalyst feed concentration is 0.09 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 100:1, the 1-dodecene feed concentration is 7.8 mol / L, the molar ratio of 1-dodecene to ethylene is 1.85:1, and the temperature in the reactor is controlled at 140°C when stable.

[0079] Example 11

[0080] The difference between this embodiment and Example 9 is that the main catalyst feed concentration is 0.09 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 100:1, the 1-dodecene feed concentration is 7.8 mol / L, the molar ratio of 1-dodecene to ethylene is 1.93:1, and the temperature in the reactor is controlled at 160°C when stable.

[0081] Example 12

[0082] The main catalyst feed concentration is 0.09 μmol / mL, the molar ratio of triisobutylaluminum to the main catalyst is 100:1, the 1-dodecene feed concentration is 7.8 mol / L, the molar ratio of 1-dodecene to ethylene is 1.82:1, the temperature in the reactor is controlled at 140°C when stable, the pressure is 4 MPa, and the residence time of the material in the reactor is 60 min.

[0083] Comparative Example 1

[0084] In this comparative example, the main catalyst used was diphenylcarbonyl-cyclopentadienyl-(2-dimethylamino-fluorenyl) zirconium dichloride, the cocatalysts used were triisobutylaluminum and a boron compound, and the α-olefin comonomer was 1-octene. Before the experiment, the 500mL reactor was purged three times with high-purity nitrogen at 150°C. A solution of the main catalyst in toluene was stored in a feed tank, a solution of triisobutylaluminum in hexane was stored in a feed tank, and a solution of the cocatalyst (boron compound) in toluene was stored in a feed tank. 1-Octene and ethylene were stored in two separate feed tanks.

[0085] The reactor and piping were preheated to the desired temperature. The reactor speed was set to 1000 rpm. The ethylene feed valve at the top of the reactor was opened. The pressure in the reactor was controlled within a reasonable range. The chemical metering pump and the feed valve at the top of the reactor were simultaneously opened. The primary catalyst, triisobutylaluminum, cocatalyst (boron compound), and 1-octene were simultaneously and continuously introduced into the reactor at the set flow rates. Once the reactor was fully filled, the materials overflowed from the reactor overflow port. The liquid level in the reactor was controlled by a pneumatic valve, and the materials were continuously discharged. The primary catalyst feed concentration was 0.003 μmol / mL, the molar ratio of triisobutylaluminum to primary catalyst was 100:1, the molar ratio of cocatalyst (boron compound) to primary catalyst was 1.5:1, the 1-octene feed concentration was 5.2 mol / L, and the molar ratio of 1-octene to ethylene was 1.23:1. When stable, the temperature in the reactor is controlled at 140°C, the pressure is 4 MPa, and the residence time of the material in the reactor is 10 minutes. The material continuously flowing out of the product tank is washed with a large amount of acid and alcohol, filtered and dried, and dried in a vacuum drying oven at 140°C for more than 4 hours.

[0086] The polyolefin elastomers prepared in Examples 1 to 12 and Comparative Example 1 were subjected to performance tests. The test results are shown in Table 1.

[0087] Table 1: Properties of polyolefin elastomers obtained in Examples 1 to 12 and Comparative Example 1

[0088]

[0089] The main catalyst used in Comparative Example 1 is diphenylcarbonyl-cyclopentadienyl-(2-dimethylamino-fluorenyl)zirconium dichloride, rather than the main catalyst of the present invention. The test results in Table 1 clearly show that even with the addition of triisobutylaluminum and a boron compound as co-catalysts in Comparative Example 1, its catalytic activity is far lower than that in Examples 1 to 12. Furthermore, the polyolefin elastomers produced in Examples 1 to 12 have high weight-average molecular weights and narrow molecular weight distributions, and their glass transition temperatures are below -60°C.

[0090] The present invention utilizes a continuous polymerization process, where a novel metallocene catalyst, a co-catalyst, ethylene, and an α-olefin comonomer are simultaneously and continuously injected into a reaction apparatus for polymerization to produce a polyolefin elastomer. This method is simple, easy to operate, and cost-effective. The resulting polyolefin elastomer has a high molecular weight, a narrow molecular weight distribution, and a low glass transition temperature (Tg) of below -60°C. Therefore, the present invention effectively overcomes several practical issues in the prior art, thus possessing high utility and significance.

[0091] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing a polyolefin elastomer, characterized in that: include: Under anhydrous and oxygen-free conditions, a single-active-center metallocene catalyst is used as a main catalyst and triisobutylaluminum is used as a co-catalyst to polymerize ethylene and α-olefin comonomers under the action of the main catalyst and the co-catalyst to prepare a polyolefin elastomer; wherein the structural formula of the metallocene catalyst is as follows: 。 2. The preparation method according to claim 1, characterized in that At least the following steps are included: Pre-treating the reaction device to make the reaction chamber of the reaction device free of water and oxygen; The solvent, the main catalyst, the co-catalyst, the ethylene and the α-olefin comonomer are stored in the feed tanks of the reaction device respectively; The reaction device is preheated to a desired temperature, and the solvent, main catalyst, co-catalyst, ethylene and α-olefin comonomer are introduced into the reaction chamber for polymerization reaction to obtain the polyolefin elastomer.

3. The preparation method according to claim 2, characterized in that The feed concentration of the main catalyst is 0.0015~0.09 μmol / mL, and the molar ratio of the co-catalyst to the main catalyst is (100~1000):1; the feed concentration of the α-olefin comonomer is 4.3~7.8 mol / L, and the feed molar ratio of the α-olefin comonomer to the ethylene is (0.3~10):

1.

4. The preparation method according to claim 1, characterized in that The α-olefin comonomer is a linear or branched α-olefin having 3 to 20 carbon atoms.

5. The preparation method according to claim 4, characterized in that The α-olefin comonomer is selected from one or more of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, decene, 1-dodecene, and 1-hexadecene.

6. The preparation method according to claim 2, characterized in that The polymerization reaction has a reaction temperature of 90-170° C., a reaction pressure of 2-10 MPa, and a reaction time of 0.05-1 h.

7. The preparation method according to claim 6, wherein The polymerization reaction has a reaction temperature of 120-170° C., a reaction pressure of 4-8 MPa, and a reaction time of 0.1-0.4 h.

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