Geometric configuration-limited metallocene catalyst and preparation method and application thereof

Abstract

The invention provides a limited geometric configuration metallocene catalyst as well as a preparation method and application thereof. The metallocene catalyst is selected from at least one of compounds with a structural formula shown in a formula (I): # imgabs0 # can adjust the solubility of the metallocene catalyst with the limited geometric configuration in a solvent through an electronic effect and a steric effect between cyclopentadiene and a pyrrole ring in the metallocene catalyst with the limited geometric configuration; the catalytic activity and catalytic efficiency of the catalyst are improved, and the usage amount of a cocatalyst is reduced. Meanwhile, the metallocene catalyst with the limited geometric configuration also has the characteristic of good hydrogen regulation sensitivity. The catalyst is especially suitable for preparing polyolefin elastomers, and the prepared elastomers are excellent in performance and have great application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallocene catalysts, and particularly relates to a constrained geometry metallocene catalyst, a preparation method thereof, and uses thereof. Background Art

[0002] Polyolefin elastomers were first industrially produced by The Dow Chemical Company in 1993. At present, the demand for polyolefin elastomers in China is large. Relying solely on domestic chemical enterprises cannot meet the current needs, and a large amount of imports are required, especially for high-performance polyolefin elastomers.

[0003] Existing olefin polymerization catalyst systems can be divided into Ziegler-Natta catalyst systems and metallocene catalyst systems. Among them, the metallocene catalyst system consists of a main catalyst and a cocatalyst. Generally, the main catalyst is a compound containing a transition metal as the main component, and the cocatalyst is generally a compound containing aluminum as the main component.

[0004] The main catalyst in the metallocene catalyst system has uniformly distributed active sites. Therefore, when this catalyst system is used in the preparation of polymers, the polymers obtained have good properties, and the copolymerization reaction of the polymers can be easily carried out, and the distribution of comonomers is uniform. However, there is still room for improvement when used in the preparation of high-performance polyolefin elastomers. That is, developing new catalysts and catalytic processes for preparing high-performance polyolefin elastomers is still a research direction with great challenges and significance. Summary of the Invention

[0005] In order to improve the deficiencies of the existing technology, the present invention provides a constrained geometry metallocene catalyst. By adjusting the electronic effect and steric effect between the cyclopentadiene and pyrrole ring in the constrained geometry metallocene catalyst, the solubility of the constrained geometry metallocene catalyst in the solvent can be adjusted, the catalytic activity and catalytic efficiency of the catalyst can be improved, and the usage amount of the cocatalyst can be reduced. At the same time, the constrained geometry metallocene catalyst also has the characteristics of good hydrogen response sensitivity. Further, the catalyst is particularly suitable for the preparation of high-performance polyolefin elastomers.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] A constrained geometry metallocene catalyst, wherein the metallocene catalyst is selected from at least one of the compounds having the structural formula shown in formula (I):

[0008]

[0009] Wherein, M is a transition metal;

[0010] X1 and X2 are the same or different, and are independently selected from Cl or alkyl;

[0011] R1 and R2 are the same or different and are each independently selected from hydrogen or an alkyl group, or R1 and R2 form a ring to form an aryl group;

[0012] R3 is selected from absent, substituted or unsubstituted alkyl groups. When substituted, the substituent is a halogen or an alkyl group;

[0013] R4 is selected from straight-chain alkyl groups.

[0014] A method for preparing the above constrained geometry metallocene catalyst, the method comprising the following steps:

[0015] After compound I-1 reacts with a lithium salt, a metal salt containing M is added to obtain compound I, that is, the compound having the structural formula shown in formula (I);

[0016]

[0017] Among them, R1, R2, R3, R4, X1, X2, and M each independently have the definitions described above.

[0018] The application of the above constrained geometry metallocene catalyst, which is used for the preparation of olefin polymers.

[0019] Advantages of the present invention:

[0020] The present invention provides a constrained geometry metallocene catalyst and its preparation method and use, especially for the preparation of high-performance polyolefin elastomers. By the electronic effect and steric effect between the cyclopentadiene and the pyrrole ring in the constrained geometry metallocene catalyst, the solubility of the constrained geometry metallocene catalyst in a solvent can be adjusted, the catalytic activity and catalytic efficiency of the catalyst can be improved, and the usage amount of the cocatalyst can be reduced. At the same time, the constrained geometry metallocene catalyst also has the characteristics of good hydrogen response sensitivity. The catalyst is particularly suitable for the preparation of polyolefin elastomers, and the prepared elastomers have excellent properties and great application prospects. Detailed implementation manners

[0021] As described above, the present invention provides a constrained geometry metallocene catalyst, and the metallocene catalyst is selected from at least one of the compounds having the structural formula shown in formula (I):

[0022]

[0023] Among them, M is a transition metal;

[0024] X1 and X2 are the same or different and are each independently selected from Cl or an alkyl group;

[0025] R1 and R2 are the same or different and are each independently selected from hydrogen or an alkyl group, or R1 and R2 form a ring to form an aryl group;

[0026] R3 is selected from absent, substituted or unsubstituted alkyl, and when substituted, the substituent is halogen or alkyl;

[0027] R4 is selected from linear alkyl.

[0028] According to an embodiment of the present invention, M is Ti or Zr.

[0029] According to an embodiment of the present invention, X1 and X2 are the same or different and are independently selected from Cl or C 1-6 alkyl. Exemplarily, X1 and X2 are the same or different and are independently selected from Cl or C 1-3 alkyl.

[0030] According to an embodiment of the present invention, R1 and R2 are the same or different and are independently selected from hydrogen or C 1-6 alkyl, or R1 and R2 form a ring to form C 6-12 aryl. Exemplarily, R1 and R2 are the same or different and are independently selected from hydrogen or C 1-3 alkyl, or R1 and R2 form a ring to form C 6-8 aryl.

[0031] According to an embodiment of the present invention, R3 is selected from absent, substituted or unsubstituted C 1-6 alkyl, and when substituted, the substituent is halogen or C 1-6 alkyl. Exemplarily, R3 is selected from absent, substituted or unsubstituted C 1-3 alkyl, and when substituted, the substituent is halogen or C 1-3 alkyl.

[0032] According to an embodiment of the present invention, R4 is selected from C 3-12 linear alkyl. Exemplarily, R4 is selected from C 3-10 linear alkyl. Also exemplarily, R4 is selected from C 4-8 linear alkyl.

[0033] According to an embodiment of the present invention, M is Ti or Zr; R3 is selected from absent, substituted or unsubstituted C 1-6 alkyl, and when substituted, the substituent is halogen or C 1-6 alkyl; R4 is selected from C 3-12 linear alkyl; X1 and X2 are the same or different and are independently selected from Cl or C 1-6 alkyl; R1 and R2 are the same or different and are independently selected from hydrogen or C 1-6 alkyl, or R1 and R2 form a ring to form C 6-12 aryl.

[0034] According to an embodiment of the present invention, M is Ti or Zr; R3 is selected from absent, substituted or unsubstituted C1-3 An alkyl group, when being substituted, the substituent is a halogen or C 1-3 alkyl group; R4 is selected from C 3-10 linear alkyl group; X1 and X2 are the same or different and are independently selected from Cl or C 1-3 alkyl group; R1 and R2 are the same or different and are independently selected from hydrogen or C 1-3 alkyl group, or R1 and R2 form a ring to form C 6-8 aryl group.

[0035] According to an embodiment of the present invention, M is Ti or Zr; R3 is selected from absent, substituted or unsubstituted C 1-3 alkyl group, when being substituted, the substituent is a halogen or C 1-3 alkyl group; R4 is selected from C 4-8 linear alkyl group; X1 and X2 are the same or different and are independently selected from Cl or C 1-3 alkyl group; R1 and R2 are the same or different and are independently selected from hydrogen or C 1-3 alkyl group, or R1 and R2 form a ring to form a phenyl group.

[0036] According to an embodiment of the present invention, the metallocene catalyst is selected from at least one of the following compounds 1 - compound 4:

[0037]

[0038] According to an embodiment of the present invention, the constrained geometry metallocene catalyst with a novel structure of the present invention contains a pentacoordinate complex, and there is a silicon bridging structure and two other types of bridging structures in the pentacoordinate complex, such as two other types of bridging structures (pyridine - M - cyclopentadiene and pyridine - R - OR4 - M - cyclopentadiene) between the cyclopentadiene and pyrrole rings described in the formula (1). X - ray diffraction analysis reveals that due to the presence of the pentacoordination in the catalyst containing the pentacoordinate complex structure, there is a situation where the bridging structures cannot match, resulting in the continuous rocking vibration of the electronegative group OR4, so that the catalyst continuously undergoes ring - opening and ring - closing during the polymerization process, activating the activity of the transition metal active center. At the same time, it is also found that such a structure can significantly improve the solubility of the constrained geometry metallocene catalyst in the solvent, reduce the complexity between the catalyst and the catalyst system formed by the cocatalyst, and is beneficial to enhancing the catalytic activity and catalytic efficiency of the catalyst.

[0039] As described above, the present invention also provides a preparation method of the above - mentioned constrained geometry metallocene catalyst, and the method includes the following steps:

[0040] After compound I - 1 reacts with a lithium salt, a metal salt containing M is added to obtain compound I, that is, a compound having the structural formula shown in formula (I);

[0041]

[0042] Among them, R1, R2, R3, R4, X1, X2, and M independently have the definitions described above.

[0043] According to an embodiment of the present invention, the lithium salt may be selected from alkyl lithium reagents, such as butyl lithium (specifically, it may be n-butyl lithium, isobutyl lithium, or tert-butyl lithium, preferably n-butyl lithium), lithium diisopropylamide, etc., at least one of them.

[0044] According to an embodiment of the present invention, the metal salt containing M may be a halogen salt containing M, such as titanium tetrachloride or zirconium tetrachloride.

[0045] According to an embodiment of the present invention, compound I-1 is prepared by a method including the following steps:

[0046] (1) Compound I-3 reacts with compound I-4 to obtain compound I-2;

[0047] (2) Compound I-2 is deprotected to obtain compound I-1;

[0048]

[0049] Among them, R1, R2, R3, and R4 independently have the definitions described above; X is selected from halogens, such as Br, Cl, or I; PG is selected from N-protecting groups, such as Boc, Bn, Cbz.

[0050] As described above, the present invention also provides the use of the above constrained geometry metallocene catalyst for the preparation of olefin polymers.

[0051] According to an embodiment of the present invention, it is used as a catalyst in olefin polymerization reactions.

[0052] According to an embodiment of the present invention, the olefin is selected from at least one of ethylene and olefins having 3 to 10 carbon atoms.

[0053] According to an embodiment of the present invention, it is used for the preparation of polyolefin elastomers. That is, it is used for the polymerization of ethylene and comonomers to prepare polyolefin elastomers, and the comonomer is selected from at least one of propylene, 1-butene, 1-pentene, and 1-hexene.

[0054] According to an embodiment of the present invention, it is used as a catalyst in the preparation of polyolefin elastomers.

[0055] According to an embodiment of the present invention, the constrained geometry metallocene catalyst is used as the main catalyst, and alkylaluminum is used as the cocatalyst. The molar ratio of the main catalyst to the cocatalyst is 1:300 - 2000, for example, 1:500, 1:1000, 1:1500 or 1:2000.

[0056] According to an embodiment of the present invention, the alkylaluminum is preferably trimethylaluminum, triethylaluminum, triisobutylaluminum or a mixture thereof. Compared with aluminoxane cocatalysts, the constrained geometry metallocene catalyst of the present application can be well matched with alkylaluminum cocatalysts, and can achieve good olefin polymerization efficiency. More importantly, the cost of the production process can be significantly reduced.

[0057] As described above, the present invention also provides a method for preparing a polyolefin elastomer. The method includes polymerizing ethylene and a comonomer in the presence of the above-mentioned constrained geometry metallocene catalyst and cocatalyst to obtain a polyolefin elastomer.

[0058] According to an embodiment of the present invention, the method includes the following steps:

[0059] Inject the constrained geometry metallocene catalyst and the cocatalyst into the reaction kettle respectively, introduce the polymerization monomer and hydrogen, and carry out the polymerization reaction; the polymerization monomer includes ethylene and a comonomer.

[0060] According to an embodiment of the present invention, the polymerization reaction does not require activation treatment of the catalyst before the reaction because the catalyst of the present application has high solubility in the solvent, and the catalytic activity and catalytic efficiency obtained directly after use without additional activation treatment can still meet the requirements of olefin polymerization production.

[0061] According to an embodiment of the present invention, the temperature of the polymerization reaction is 25°C - 150°C, for example, 38°C, 58°C, 98°C, 128°C or 149°C.

[0062] According to an embodiment of the present invention, the pressure of the polymerization reaction is 0.1MPa - 5MPa, for example, 0.8MPa, 1.5MPa, 2.6MPa, 3.9MPa or 4.9MPa.

[0063] The preparation method of the present invention will be further described in detail below with specific examples. It should be understood that the following examples are only for illustrative explanation of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0064] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; unless otherwise specified, the reagents, materials, etc. used in the following examples can all be obtained from commercial sources.

[0065] The molecular weight of the polymer was measured using an Alliance GPC V2000 GPC analyzer.

[0066] The melt index of the polymer was measured using ASTM D1238-13 under the conditions of 190 °C / 5.0 kg.

[0067] Example 1

[0068]

[0069] Step 1: At -78 °C, 1.5 equivalents of lithium 2,2,6,6-tetramethylpiperidide were added to a solution of 10 g of compound 1a in tetrahydrofuran (100 mL) in a reactor. After the addition was complete, the temperature was raised to room temperature and the reaction was carried out for 3 h. Then, 1 equivalent of compound 1b was added to the reaction solution, and the stirring reaction was continued for 2 h. After the reaction was completed, saturated ammonium chloride was added to quench the reaction, and the mixture was extracted with ethyl acetate. After separation, the organic phases were combined and purified by silica gel column chromatography to obtain compound 1c (14.2 g).

[0070] Step 2: 10 g of compound 1c was dissolved in dichloromethane (80 mL), and then trifluoroacetic acid (20 mL) was added. The mixture was stirred at room temperature for 3 h. After concentration under reduced pressure, saturated sodium bicarbonate solution was slowly added dropwise to adjust the pH to 8-9. The mixture was extracted with dichloromethane, washed with saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated to obtain compound 1d (6.8 g).

[0071] Step 3: At -78 °C, a solution of 4.0 M of 2 equivalents of n-butyllithium in tetrahydrofuran was added dropwise to a solution of 2.0 g of ligand 1d in tetrahydrofuran (20 mL) in a reactor. After the addition was complete, the temperature was raised to room temperature and the reaction was carried out for 2 h. Then, 1.5 equivalents of titanium tetrachloride were added to the reaction solution, and the stirring reaction was carried out for 1 h. After adding 10 mL of water to quench the reaction, the stirring was continued for 0.5 h. The reaction solvent was removed under vacuum, the residue was dissolved in toluene, the insoluble matter was filtered off, and then the solvent was removed again. The obtained solid was recrystallized from dichloromethane and n-hexane to obtain compound 1 (1.65 g). Theoretical values: C 17 H 25 Cl2NOSiTi: C, 50.26; H, 6.20; Cl, 17.45; N, 3.45; O, 3.94; Si, 6.91; Measured values: C, 50.22; H, 6.96; Cl, 17.04; N, 3.11; O, 3.43; Si, 6.25.

[0072] Example 2

[0073]

[0074] Referring to the method of Example 1, only replace titanium tetrachloride in Step 3 with zirconium tetrachloride to obtain Compound 2. Theoretical values: C 17 H 25 Cl2NOSiZr: C, 45.42; H, 5.60; Cl, 15.77; N, 3.12; O, 3.56; Si, 6.25; Measured values: C, 45.31; H, 5.76; Cl, 15.04; N, 3.22; O, 3.32; Si, 6.02.

[0075] Example 3

[0076]

[0077] Referring to the method of Example 1, only replace Compound 1a in Step 1 with Compound to obtain Compound 3. Theoretical values: C 19 H 29 Cl2NOSiTi: C, 52.55; H, 6.73; Cl, 16.33; N, 3.23; O, 3.68; Si, 6.47; Measured values: C, 52.04; H, 7.00; Cl, 16.22; N, 3.04; O, 3.21; Si, 6.08.

[0078] Example 4

[0079]

[0080] Referring to the method of Example 1, only replace Compound 1a in Step 1 with Compound to obtain Compound 4. Theoretical values: C 21 H 27 Cl2NOSiTi: C, 55.28; H, 5.96; Cl, 15.54; N, 3.07; O, 3.51; Si, 6.15; Measured values: C, 54.92; H, 6.22; Cl, 15.34; N, 2.91; O, 3.27; Si, 5.96.

[0081] Comparative Examples 1 - 4

[0082] Referring to the methods of Examples 1 - 4, prepare Compounds D1, D2, D3, and D4 as shown below;

[0083]

[0084] Test Example 1

[0085] At room temperature and ambient pressure, a known mass of the catalysts prepared in the examples and comparative examples and a known volume of n-heptane were added to a 20 mL vial. A PTFE-coated magnetic stir bar was inserted into the vial, and the mixture was stirred for 1 hour. Then, the suspension was filtered through a 0.4 μm PTFE syringe filter into a peeled vial to obtain a known mass of the supernatant. The n-heptane was removed under reduced pressure to obtain the catalyst, which was weighed, and the solubility (wt%) was calculated therefrom. The test results are shown in Table 1.

[0086] Table 1 Solubility of the catalysts prepared in the examples and comparative examples in n-heptane

[0087]

[0088]

[0089] As can be seen from Table 1, the solubility of the catalysts of Examples 1-4 in alkanes was significantly improved, which significantly reduced the complexity between the catalyst systems and was beneficial to enhancing the catalytic activity and catalytic efficiency of the catalysts.

[0090] Test Example 2

[0091] The ethylene-1-hexene copolymerization reaction was carried out using the catalysts of the examples and comparative examples respectively

[0092] The specific polymerization method includes the following steps:

[0093] (1) Under a nitrogen atmosphere, 20 mL of n-heptane was added to a 350 mL polymerization reactor, and then the reactor was connected to the polymerization reaction device. The device was evacuated with a vacuum pump for more than 5 min to remove the oxygen in the pipeline of the polymerization device, and the temperature control device was adjusted so that the reaction temperature was 30 °C;

[0094] (2) 5 μmol of the above-prepared catalyst and 5 mol of triisobutylaluminum cocatalyst were weighed and injected into the reaction device respectively. After injection, the valve was closed, and 1-hexene comonomer was introduced into the reactor. Then hydrogen was added, and finally ethylene was continuously introduced to keep the total polymerization pressure constant at 2.0 MPa, and the reaction was carried out at 80 °C for 120 min;

[0095] (3) The reaction was terminated and cooled to room temperature, and the hydrogen content, the yield of the polymerization product, and the relevant properties were tested as shown in Table 2.

[0096] Table 2 Test results of the properties of the catalysts prepared in the examples and comparative examples (Test Example 2)

[0097]

[0098]

[0099] As can be seen from Table 2, the catalyst of the present invention has high polymerization activity and good hydrogen response sensitivity. As the hydrogen partial pressure increases, the melt index increases significantly while the polymerization activity decreases only slightly.

[0100] Test Example 3

[0101] The ethylene-1-hexene copolymerization reaction was carried out using the catalysts of the examples and comparative examples respectively.

[0102] The specific polymerization method includes the following steps:

[0103] (1) Under a nitrogen atmosphere, 20 mL of n-heptane was added to a 350 mL polymerization reactor, and then the reactor was connected to the polymerization reaction device. The device was evacuated with a vacuum pump for more than 5 minutes to remove the oxygen in the pipeline of the polymerization device. The temperature control device was adjusted so that the reaction temperature was 30 °C.

[0104] (2) 5 μmol of the catalysts prepared in Example 1 and Comparative Example 1 and x mol of triisobutylaluminum cocatalyst were weighed respectively and injected into the reaction device. After injection, the valve was closed and 1-hexene comonomer was introduced into the reactor. Then hydrogen was added, and finally ethylene was continuously introduced to keep the total polymerization pressure constant at 2.0 MPa. The reaction was carried out at 80 °C for 120 minutes.

[0105] (3) The reaction was terminated and cooled to room temperature. The hydrogen content, the yield of the polymerization product and related properties were tested as shown in Table 3.

[0106] Table 3 Performance test results of the catalysts prepared in the examples and comparative examples (Test Example 3)

[0107]

[0108] As can be seen from Table 3, the catalyst of the present invention can match a lower content of cocatalyst, which can significantly reduce the preparation cost of polyolefins. The reduction in the amount of cocatalyst used can also reduce environmental pollution.

[0109] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A constrained geometry metallocene catalyst, characterized in that, The metallocene catalyst is selected from at least one of the compounds having the structural formula shown in formula (I): Wherein, M is a transition metal; X1 and X2 are the same or different, and are independently selected from Cl or alkyl; R1 and R2 are the same or different, and are independently selected from hydrogen or alkyl, or R1 and R2 form a ring to form an aryl group; R3 is selected from absent, substituted or unsubstituted alkyl, and when it is substituted, the substituent is halogen or alkyl; R4 is selected from linear alkyl.

2. The constrained geometry metallocene catalyst according to claim 1, wherein M is Ti or Zr; and / or, X1 and X2 are the same or different and are each independently selected from Cl or C 1-6 alkyl; and / or, R1 and R2 are the same or different and each independently selected from hydrogen or C 1-6 alkyl, or R1 and R2 form a ring to form C 6-12 aryl; and / or, R3 is selected from absent, substituted or unsubstituted C 1-6 alkyl, and when substituted, the substituent is halogen or C 1-6 alkyl; and / or, R4 is selected from C 3-12 linear alkyl group.

3. The constrained geometry metallocene catalyst according to claim 1, wherein The metallocene catalyst is selected from at least one of the following compounds 1 - compound 4:

4. The method for preparing a constrained geometry metallocene catalyst according to any one of claims 1-3, characterized in that, The method includes the following steps: After compound I-1 reacts with a lithium salt, a metal salt containing M is added to obtain compound I, that is, a compound having the structural formula shown in formula (I); Wherein, R1, R2, R3, R4, X1, X2, and M independently have the definitions in any one of claims 1 - 3.

5. The preparation method according to claim 4, characterized in that, The lithium salt is selected from at least one of butyllithium or lithium diisopropylamide.

6. The preparation method according to claim 4 or 5, characterized in that, Compound I-1 is prepared by a method including the following steps: (1) Compound I-3 reacts with compound I-4 to obtain compound I-2; (2) Compound I-2 is deprotected to obtain compound I-1; Wherein, R1, R2, R3, R4, X1, X2, and M independently have the definitions in any one of claims 1 - 3; X is selected from halogen, such as Br, Cl or I; PG is selected from N-protecting groups, such as Boc, Bn, Cbz.

7. Use of the constrained geometry metallocene catalyst according to any one of claims 1 to 3, characterized in that, The catalyst is used for the preparation of olefin polymers. Preferably, it is used for the preparation of polyolefin elastomers.

8. The use according to claim 7, characterized in that, The constrained geometry metallocene catalyst is used as the main catalyst, and alkylaluminum is used as the cocatalyst. The molar ratio of the main catalyst to the cocatalyst is 1:300 - 2000.

9. A method for preparing a polyolefin elastomer, characterized in that, The method includes polymerizing ethylene and a comonomer in the presence of the constrained geometry metallocene catalyst and the cocatalyst described in any one of claims 1 - 3 to obtain a polyolefin elastomer.

10. The preparation method according to claim 9, wherein, The method includes the following steps: Inject the constrained geometry metallocene catalyst and the cocatalyst into the reaction kettle respectively, introduce the polymerization monomer and hydrogen, and carry out the polymerization reaction. The polymerization monomer includes ethylene and a comonomer. Preferably, the polymerization reaction does not require activation treatment of the catalyst before the reaction. Preferably, the temperature of the polymerization reaction is 25°C - 150°C, and the pressure of the polymerization reaction is 0.1MPa - 5MPa.

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