Pinacol borane metallocene compound, preparation method thereof and application of pinacol borane metallocene compound in polyolefin elastomer synthesis

Abstract

The invention provides a pinacol borane metallocene compound, a preparation method thereof and application of the pinacol borane metallocene compound in polyolefin elastomer synthesis. The POE catalyst composition is prepared from the pinacol borane metallocene compound serving as a main catalyst and aluminum alkyl (or aluminum alkyl oxide) serving as a cocatalyst, POE products with different comonomer contents and molecular weights can be synthesized by regulating and controlling polymerization conditions, and the melting temperature and the melting index of the products can be flexibly adjusted.

Description

Technical Field

[0001] The invention belongs to the technical field of polyolefin elastomer synthesis, and particularly relates to a pinacol borane metallocene compound and a preparation method thereof and application thereof in the synthesis of polyolefin elastomer. Background Art

[0002] Polyolefin elastomer (POE) usually refers to polyolefin materials prepared by copolymerization of ethylene and α-olefins, such as 1-butene, 1-hexene or 1-octene. It has excellent mechanical properties, resilience, low temperature resistance and weather resistance, etc. It is mainly used in automotive parts, daily consumer goods, wires and cables, footwear, household appliances and photovoltaic films. The industrial production of POE mainly adopts metallocene catalysts combined with high-temperature solution polymerization technology (CN1328580A, CN1049849A, US5132381A, CN1324370A, CN115772240A, CN115677895A, etc.). High temperature can ensure that POE is completely dissolved during the polymerization process, avoid precipitation, and reduce the viscosity of the system. Catalysts with high catalytic activity and high temperature resistance are crucial to POE production and are the core of POE polymerization technology. The selection of polymerization process conditions such as pressure, temperature and comonomer concentration depends largely on the catalyst, and the catalyst also directly affects the structure, performance and application of polyolefin products. Metallocene catalysts are organic metal complexes formed by the coordination of transition metal atoms such as titanium, zirconium, and hafnium with functional groups containing cyclopentadienyl groups. They need to be used in conjunction with methylaluminoxane or borate as a co-catalyst. Compared with Ziegler-Natta catalysts, they have the advantages of high catalytic activity, narrow product molecular weight distribution, high copolymer monomer content and more uniform distribution.

[0003] Exxon was the first company to use metallocene catalysts to industrially produce polyolefins, including non-bridged dimetallocene and bridged dimetallocene catalysts. By changing the bridging group and the substituents on the cyclopentadienyl group, the steric hindrance of the active center can be adjusted, thereby regulating the catalytic activity, product structure and molecular weight. Subsequently, Exxon and Dow Chemical registered bridged semi-metallocene catalysts, which have good thermal stability, high catalytic activity at high temperatures, can accurately control the polymer chain structure, and introduce long-chain branched structures, so that POE has excellent melt strength and rheological processing properties.

[0004] Dow patent WO9314132 uses a metallocene catalyst with restricted geometry (Me 2 Si(C 5 Me 4 )(N t -Bu)TiCl 2) as the main catalyst and co-catalyst MAO, ethylene / 1-octene copolymerization was carried out under the conditions of 3.1 MPa, 120-160℃, and IsoparE solvent, and the catalytic activity was greater than 1.2×10 7 g / (mol Ti h), the density of the copolymer is 0.897-0.923 g / cm 3 .

[0005] Exxon's Chinese patent CN99812381.1 discloses a bridged metallocene catalyst with excellent solubility in aliphatic solvents, which is particularly suitable for olefin solution polymerization. Under the conditions of 190°C and 8.5 MPa, hexane is used as the solvent. p -Et 3 Si-Ph) 2 C(2,7-Di t Bu-Flu)(Cp)HfMe 2 The main catalyst is tri-n-octyl aluminum as a co-catalyst. The 1-octene content of the obtained polymer is 17 wt %, molecular weight distribution 2.3.

[0006] Patent CN116162185A discloses a metallocene catalyst and preparation method, in which the catalyst uses a bridged benzene ring as a bridge to connect phenol and cyclopentadiene, and then the metal atom and cyclopentadiene are complexed. This type of catalyst performs well in high-temperature solution polymerization, and the prepared copolymer also has the characteristics of a high-content long-chain branched polymer.

[0007] Patent CN112552433 A discloses a novel restricted geometry metallocene catalyst, which uses pyrrole N heterocycle to replace tert-butylamine in the traditional restricted geometry metallocene catalyst as an electron donor. Since the pyrrole group has stronger electron-withdrawing property, the metal-N bond is longer, so that the angle between the indenyl group, the metal central atom and the pyrrole group is smaller than that of the general alkyl N electron donor CGC, which is conducive to the attack of α-olefins. The catalyst is easy to prepare and can flexibly control the catalytic activity and the insertion rate of α-olefin monomers when used to catalyze the copolymerization of ethylene and α-olefins.

[0008] Patent CN118184711A adopts a microchannel continuous flow reactor to prepare metallocene catalysts. The microchannel reactor is used at -20°C to 60°C to achieve continuous preparation of metallocene catalysts. The reaction conditions are mild and the operation is simple. It not only improves the stability and safety of the metallocene catalyst synthesis process, but also improves production efficiency.

[0009] Patent CN111171189A discloses a high temperature resistant catalyst system and its application. The catalyst system uses a non-cyclopentadienyl main catalyst in combination with a co-catalyst and an activator. When used in ethylene / α-olefin solution copolymerization reactions, it exhibits high polymerization activity and copolymerization performance, and is particularly outstanding in high temperature tolerance.

[0010] Existing metallocene catalysts often have the following defects: (1) Poor high temperature resistance, o After C, the catalytic activity and polymer molecular weight drop rapidly, and the product performance is poor; (2) The synthesis steps are cumbersome and the conditions are harsh, requiring multiple steps of reaction, producing a large number of by-products, and the catalyst yield is low; (3) The POE product that can be prepared by a single catalyst has a narrow melt index range, and the copolymer monomer content and product melting temperature are difficult to accurately control. Summary of the invention

[0011] In view of the problems existing in the prior art, the present invention develops a class of metallocene compounds with excellent high temperature resistance, simple and efficient synthesis method, and flexible adjustment of product comonomer content and product performance, which can be used for industrial ethylene / alpha-olefin copolymerization to efficiently produce POE. The structure of this class of metallocene compounds is shown in Formula 1, with one end of the metal center being complexed with a cyclopentadienyl ring, and the other end being connected to pinacol borane. B and heteroatoms in pinacol borane change the electronic effect of the metal center, which can not only enhance the coordination ability of the metal active center to the double bond, but also stabilize the metal active center during the chain growth process, with strong high temperature resistance and high activity. The steric hindrance is small and the comonomer insertion rate is high. The catalyst structure is novel, easy to prepare, and has good solubility. Since B and heteroatoms are introduced into this class of pinacol borane metallocene compounds, the electrical properties are suitable. The present invention is composed of pinacol borane metallocene compounds, alkyl aluminum (or alkyl oxide aluminum) or borate to form a POE catalyst composition, which can regulate the polymerization conditions to synthesize POE products with different comonomer contents and molecular weights, and the product melting temperature and melt index can be flexibly adjusted.

[0012] Formula 1 The present invention adopts the following technical solution: The invention discloses the synthesis of a pinacol borane metallocene compound and its use in ethylene / alpha-olefin copolymerization to prepare a polyolefin elastomer. The compound has a simple synthesis method and mild conditions, and the polyolefin elastomer prepared by using the compound has the advantages of high catalytic activity, excellent high temperature resistance, and flexible adjustment of the copolymer monomer content and melt index.

[0013] A pinacol borane metallocene compound, wherein the pinacol borane metallocene compound has the structural formula: Wherein, M is selected from any one of Ti, Zr and Hf; and X is selected from any one of O and S.

[0014] Application: The pinacol borane metallocene compound is used in the synthesis of polyolefin elastomers. The pinacol borane metallocene compound is used as a main catalyst a and a co-catalyst b to form a catalyst composition for the synthesis of polyolefin elastomers; wherein the co-catalyst b is selected from one of methylaluminoxane, modified methylaluminoxane, triisobutylaluminum, triethylaluminum, and trimethylaluminum.

[0015] Preferably, the catalyst composition further includes a borate c; the borate c is selected from one of trityltetrakis(pentafluorophenyl)borate, N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate, and N,N-dioctadecylmethylaminotetrakis(pentafluorophenyl)borate.

[0016] Preferably, the molar ratio of the main catalyst a to the co-catalyst b is 1:50~10000.

[0017] Preferably, the molar ratio of the main catalyst a, the co-catalyst b and the borate c is 1:50~10000:0.1~10.

[0018] Preferably, the synthesis process of the polyolefin elastomer comprises the following steps: the reaction of ethylene and α-olefin is carried out in an inert solvent; each component in the catalyst composition is weighed in proportion and diluted with a solvent respectively, and then the inert solvent and α-olefin are added to the reaction system, and each component of the diluted catalyst composition is injected into the reaction system in turn or mixed in advance and then injected into the reaction system, and then ethylene is charged to carry out ethylene / α-olefin copolymerization.

[0019] Preferably, the polymerization reaction conditions are: temperature 25-200° C., pressure 0.1-10 MPa, time 5-60 min, and main catalyst a concentration of 0.1-100 μmol / L based on the liquid volume in the reactor.

[0020] Preferably, the α-olefin includes one of propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene.

[0021] Preferably, the inert solvent includes a straight chain alkane, isoalkane, cycloalkane or arylalkane having 4 to 10 carbon atoms.

[0022] Preferably, the catalyst preparation solvent is selected from one of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-decane, Isopar E, toluene and xylene.

[0023] The advantages of the present invention are: (1) Pinacol borane metallocene compounds were used as main catalysts for the preparation of polyolefin elastomers for the first time; (2) Pinacol borane metallocene compounds, due to the introduction of B and O or S atoms, have strong coordination ability, suitable electrical properties, stable metal center in the compound, strong high temperature resistance and high catalytic activity; (3) The steric hindrance is small, and POE products with different comonomer contents and molecular weights can be synthesized according to the reaction conditions. The melting temperature and melt index of the product can be flexibly adjusted; (4) The main catalyst has a novel structure, is easy to prepare and has good solubility. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Pinacol borane-pentamethylcyclopentadienyltitanium dichloride 1 H NMR spectrum. DETAILED DESCRIPTION

[0025] The present invention claims a synthesis of a pinacol borane metallocene compound and its use in the synthesis of a polyolefin elastomer. The metallocene compound is used in the synthesis of a polyolefin elastomer and needs to be combined with a co-catalyst to form a catalyst composition, which is as follows: Main catalyst a: Pinacol borane CGC compound structure is: ; Wherein M is selected from any one of Ti, Zr, and Hf; X is selected from O or S; Cocatalyst b: The cocatalyst of the present invention is selected from methylaluminoxane, modified methylaluminoxane, triisobutylaluminum, triethylaluminum, trimethylaluminum; Borate c: trityltetrakis(pentafluorophenyl)borate, N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate, N,N-dioctadecylmethylaminotetrakis(pentafluorophenyl)borate, etc.

[0026] Preferably, the molar ratio of the main catalyst a, the co-catalyst b and the borate c is 1:50~10000:0~10; The synthesis process of the polyolefin elastomer is as follows: an ethylene / α-olefin reaction is carried out in an inert solvent, a main catalyst a, a co-catalyst b and a borate c are weighed in proportion and diluted with a solvent, then an inert solvent and an α-olefin are added into the reaction system, and the diluted co-catalyst b, the main catalyst a and the borate c are injected into the reaction system in sequence or mixed uniformly in advance, and then ethylene is charged to make it fully contact with the reactants to carry out ethylene / α-olefin copolymerization, and the reaction conditions are: temperature 25-200°C, pressure 0.1-10MPa, time 5-60min, and the concentration of the main catalyst a is 0.1-100μmol / L based on the liquid volume in the reactor.

[0027] Preferably, the α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene; Preferably, the inert solvent comprises a straight chain alkane, isoalkane, cycloalkane or aromatic alkane having 4 to 10 carbon atoms; Preferably, the catalyst preparation solvent is preferably n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-decane, Isopar E, toluene, and xylene.

[0028] In order to make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

[0029] Example 1: Synthesis of Pinacol Borane-Pentamethylcyclopentadienyl Titanium Dichloride: Under anhydrous and oxygen-free conditions, a dichloromethane solution (20 mL) of pinacol borane (0.063 g, 0.5 mmol) and sodium hydride (24.0 mg, 1.0 mmol) were added to a 100 mL Schlenk bottle in sequence. The mixture was stirred at room temperature for 12 hours, and then pentamethylcyclopentadienyltitanium trichloride (CpTiCl) dissolved in 10 mL of dichloromethane was added dropwise to the above solution at -78 °C. 3 (110 mg, 0.5 mmol) solution. After stirring at room temperature for 5 hours, CH 2 Cl 2 , then add 20 mL of toluene to obtain a suspension, filter to remove the insoluble sodium salt, and remove the solvent under vacuum. Add 10 mL of n-hexane to the residue to obtain a suspension, filter it and then vacuum dry it for 12 hours to obtain an orange-red powder product, pinacol borane-pentamethylcyclopentadienyl titanium dichloride 0.089 g, with a yield of 58%. The NMR spectrum is shown in Figure 1 shown. 1 H NMR (400 MHz, DMSO-d6) δ 2.48 (s, 12H), 2.10-2.01 (m, 3H), 1.14 (s, 12H).

[0030] Application Example 1: After sealing and vacuuming a 2L reactor and maintaining pressure overnight, heat it to 140°C, fill it with nitrogen, repeat vacuuming-nitrogen filling three times, remove impurities such as water and oxygen remaining in the polymerization system, and ensure that the air has been replaced cleanly. Then use a vacuum pump to remove nitrogen and fill it with ethylene, repeat three times to ensure that the kettle is full of ethylene. Then set the temperature to 80°C and cool it down through the condensation system. Under stirring, inject 1L of toluene and 400mL of 1-octene into the reactor in sequence. After the temperature stabilizes to 80°C, inject 5mL of toluene solution of methylaluminoxane (including 1mmol of methylaluminoxane) and 1mL of toluene solution of main catalyst pinacol borane-pentamethylcyclopentadienyl titanium dichloride (including 2μmol of main catalyst) respectively, adjust the pressure to 3MPa, close the air inlet valve after 20 minutes of reaction, unload the ethylene pressure, add ethanol, and cool the reactor to about 60°C through the circulating condensation system. The reactor was then opened and the product was precipitated in 2L of ethanol. The precipitate was filtered and washed with anhydrous ethanol, then filtered and vacuum dried overnight. The white product collected was ethylene / 1-octene copolymer. The reaction conditions are listed in Table 1, and the test results of the product are shown in Table 2.

[0031] Application Example 2: Same as Application Example 1, except that the reaction temperature is 100° C. The reaction conditions are listed in Table 1, and the data results are shown in Table 2.

[0032] Application Example 3: Same as Application Example 1, except that the reaction temperature is 130° C. The reaction conditions are listed in Table 1, and the data results are shown in Table 2.

[0033] Application Example 4: Same as Application Example 1, except that the reaction temperature is 150° C. The reaction conditions are listed in Table 1, and the data results are shown in Table 2.

[0034] Application Example 5: Same as Application Example 1, except that the reaction temperature is 170° C. The reaction conditions are listed in Table 1, and the data results are shown in Table 2.

[0035] Application Example 6: Same as Application Example 3, except that the feed amount of octene-1 is increased to 600 mL. The reaction conditions are listed in Table 1, and the data results are shown in Table 2.

[0036] Application Example 7: Same as Application Example 3, except that the reaction pressure is 5 MPa. The reaction conditions are listed in Table 1, and the data results are shown in Table 2.

[0037] Application Example 8: Same as Application Example 3, except that 5 mL of methylaluminoxane toluene solution is replaced with 3 μmol N,N-dioctadecylmethylaminotetrakis(pentafluorophenyl)borate (MDOAB, CAS No.: 197308-04-6) and 1 mL of triisobutylaluminum-n-hexane solution (commercial triisobutylaluminum is a 2 mol / L Isopar E solution, a certain amount of which is dissolved in n-hexane to prepare a 1 mol / L triisobutylaluminum-n-hexane solution). The reaction conditions are listed in Table 1, and the data results are shown in Table 2.

[0038] Application Comparative Example 1: Same as Application Example 2, except that a typical CGC catalyst (structure as shown in Formula 2, synthesis process reference EP0416815A2) is selected as the catalyst. The data results are shown in Table 2.

[0039] Application Comparative Example 2: Same as Application Example 5, except that a typical CGC catalyst (Formula 2) is used as the catalyst. The data results are shown in Table 2.

[0040] Formula 2 Table 1 Reaction conditions of application examples and comparative examples Table 2 Data results of application examples and comparative examples From the results in Table 2, it can be seen that the use of the pinacol of the present invention as a POE catalyst, in combination with alkoxyaluminum or boron salt / alkylaluminum, has a relatively high catalytic activity. o C up to 170 o C, the catalytic activity first slowly increased, then slowly decreased, without any change in magnitude, and the molecular weight of the product also slowly decreased. o C up to 170 o C, the reaction activity is from 4.8×10 7 g·mol -1 ·h -1 Rapidly decreased to 0.8×10 7 g·mol -1 ·h -1, decreased by 83%, while the molecular weight of the product decreased rapidly. Under the same conditions, using the pinacol catalyst system of the present invention, the catalytic activity only decreased by 36%. The 1-octene insertion rate in the POE products obtained using the two catalyst systems was 30%-50%, and the melt index could be adjusted according to the octene insertion rate and the remaining conditions. It can be seen that the pinacol of the present invention is used to synthesize the catalyst of POE, which has more excellent high temperature resistance. In the high temperature solution method system, the viscosity of the system can be further reduced, which is conducive to improving the yield.

[0041] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A pinacol borane metallocene compound, characterized in that: The structural formula of the pinacol borane metallocene compound is: Wherein, M is selected from any one of Ti, Zr and Hf; and X is selected from any one of O and S.

2. The use of the pinacol borane metallocene compound according to claim 1 in the synthesis of polyolefin elastomers, characterized in that: The pinacol borane metallocene compound is used as a main catalyst a and a co-catalyst b to form a catalyst composition for the synthesis of a polyolefin elastomer; wherein the co-catalyst b is selected from one of methylaluminoxane, modified methylaluminoxane, triisobutylaluminum, triethylaluminum and trimethylaluminum.

3. The use according to claim 2, characterized in that: The catalyst composition also includes borate c; the borate c is selected from one of trityl tetrakis (pentafluorophenyl) borate, N,N-dimethylanilinium tetrakis (pentafluorophenyl) borate, and N,N-dioctadecylmethylamino tetrakis (pentafluorophenyl) borate.

4. The use according to claim 2, characterized in that: The molar ratio of the main catalyst a to the co-catalyst b is 1:50-10000.

5. The use according to claim 3, characterized in that: The molar ratio of the main catalyst a, the co-catalyst b and the borate c is 1:50~10000:0.1~10.

6. The use according to any one of claims 2 to 5, characterized in that: The synthesis process of the polyolefin elastomer comprises the following steps: the reaction of ethylene and α-olefin is carried out in an inert solvent; each component in the catalyst composition is weighed in proportion and diluted with a solvent respectively, then the inert solvent and α-olefin are added into the reaction system, and each component of the diluted catalyst composition is injected into the reaction system in turn or mixed in advance and then injected into the reaction system, and then ethylene is charged to carry out ethylene / α-olefin copolymerization.

7. The use according to claim 6, characterized in that: Polymerization reaction conditions: temperature 25-200°C, pressure 0.1-10MPa, time 5-60min, main catalyst a concentration 0.1-100μmol / L based on the liquid volume in the reactor.

8. The use according to claim 6, characterized in that: The α-olefin includes one of propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene.

9. The use according to claim 6, characterized in that: The inert solvent includes a straight-chain alkane, isoalkane, cycloalkane or arylalkane having 4 to 10 carbon atoms.

10. The use according to claim 6, characterized in that: The catalyst preparation solvent is selected from one of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-decane, Isopar E, toluene and xylene.

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