Homogeneous metallocene catalytic system and ethylene / alpha-olefin copolymerization method thereof

Abstract

The invention belongs to the field of olefin polymerization, and discloses a homogeneous metallocene catalytic system and an ethylene / alpha-olefin copolymerization method thereof. The catalytic system comprises a metallocene compound A, an aluminoxane or modified aluminoxane component B1, an organic boron compound component B2, an aluminum alkyl compound component B3 and an ultra-dry solvent component C, according to needs, the composition further comprises a copolymerization modification auxiliary agent component D. The component B1 can protect the metal active center of the main catalyst A and initiate chain growth; the component B2 can effectively improve the copolymerization activity of the main catalyst A; and the component B3 can further significantly improve the copolymerization activity of the main catalyst A and regulate and control the average sequence length distribution of ethylene and alpha-olefin in the copolymer. The copolymerization performance of the main catalyst A can be changed by changing different modification auxiliary agent components D, and accurate regulation and control of a copolymer chain segment microstructure are realized.

Description

Technical Field

[0001] The present invention relates to the fields of olefin polymerization reaction and catalysts, and particularly to a homogeneous metallocene catalyst system and a method for copolymerizing ethylene / α-olefin. The catalyst system in the present invention is particularly suitable for olefin copolymerization reaction, significantly reducing the dosage of cocatalyst and having excellent polymerization activity in the copolymerization reaction. In particular, the introduced copolymerization modification additive can effectively change the coordination environment of metal active centers and regulate the microstructure of copolymer segments. Background Art

[0002] Polyolefin elastomer (POE) is a thermoplastic elastomer formed by random copolymerization of ethylene / α-olefin. Due to the insertion of α-olefin, a part of the crystalline structure of the polyethylene main chain is destroyed, forming an amorphous region (rubber phase) with high elasticity, and the undamaged polyethylene main chain continues to maintain the crystalline structure (plastic phase). Therefore, POE has both the characteristics of plastics and rubbers, is easy to process at high temperatures, and its excellent properties make it widely used in fields such as automotive parts, polymer modification, wire and cable, and photovoltaic encapsulation film. Generally, the ethylene / α-olefin polymerization process has three processes: gas-phase polymerization, slurry polymerization, and solution polymerization. Due to the high α-olefin insertion rate, the viscosity of the polymer will be too high, and it is difficult for the polymer to flow in the slurry reactor in granular form to achieve homogeneous polymerization. In addition, the low-melting-point polymer is easily swollen by the solvent and agglomerated, adhered, and will become sticky and block the pipeline, resulting in the problem of kettle blocking and wall hanging, so the gas-phase method and slurry method polymerization processes cannot be used for production. Therefore, the high-temperature solution polymerization process is still the main production method of polyolefin elastomers. On the one hand, the relatively high polymerization temperature is beneficial to reducing the viscosity of the materials in the reactor, ensuring good heat and mass transfer in the reactor, and overcoming the problem of material kettle blocking and wall hanging; on the other hand, high-temperature solution polymerization is beneficial to precisely regulating the microstructure of copolymer segments and realizing the targeted production of POE products with controllable chain segment molecular structure.

[0003] The homogeneous metallocene catalyst system uses transition metal (such as Ti, Zr, Hf) element complexes in Group ⅣB as the main catalyst, and uses alkylaluminoxane (such as MAO, MMAO) or organoboride (such as B(C 6 F 5 ) 3)A catalytic system composed of a cocatalyst, wherein the ligand of the transition metal element contains at least one cyclopentadienyl or cyclopentadienyl derivative. The development of metallocene olefin polymerization depends on the continuous improvement and large-scale industrial production of alkylaluminoxane. Unfortunately, there are technical bottlenecks in the production of the highly efficient cocatalyst alkylaluminoxane, resulting in a high cost of the metallocene catalytic system, relatively high prices of metallocene polyolefins and their products, and it is difficult for the end users to accept. This has also become a major bottleneck problem for the mass production of metallocene polyolefins. Therefore, how to improve the activity of the main catalyst and reduce the dosage of the cocatalyst is crucial for reducing production costs and getting rid of the problems of alkylaluminoxane. Chinese Patent CN201611231860.1 discloses a metallocene catalyst system and a method for catalytic olefin polymerization, which consists of three components: 1,3-bis(2,6-diisopropylphenyl)-imine imidazoline-isooctanoic acid-cyclopentadienyl titanium chloride main catalyst, modified alkylaluminoxane and triisobutylaluminum cocatalyst. The highest activity is 1.3×10 7 gpolymer·mol -1 ofTi·h -1 . However, although this catalytic system has relatively high activity, the polymerization temperature is low, propylene is used as a comonomer, and the copolymer yield is low, with a maximum of only 6.1 g. Chinese Patent CN202310860589.1 discloses a metallocene catalyst composition and its application. The metallocene composition consists of a metallocene complex and a cocatalyst. The metallocene catalyst is formed by coordinating a single cyclopentadienyl ligand containing N and P bidentate coordination with a transition metal, and the cocatalyst consists of any one or a mixture of several of an aluminum cocatalyst and / or a boron promoter. Although the activity is very high, up to 4.5×10 7 g polymer·mol -1 of Ti·h -1 . However, this method has many problems. On the one hand, a large amount of main catalyst and cocatalyst need to be used, which greatly increases the cost of the metallocene catalyst system. On the other hand, toluene is used as a solvent. Toluene not only has high toxicity, pollutes the environment, but also has a high price, and it is very difficult to remove toluene from the polymer. Therefore, this method is not suitable for industrial production.

[0004] As can be seen from the above, there are still the following deficiencies in the ethylene / α-olefin high-temperature solution polymerization process in terms of catalysts: (1) Although the single-site metallocene catalyst has high activity, a large amount of expensive alkylaluminoxane or modified alkylaluminoxane is required as a cocatalyst, which greatly increases the production cost and the ash content of the cocatalyst in the product is relatively high, reducing the economic benefits of the product; (2) The microstructure of the copolymer chain segment is uncontrollable, affecting the quality of the final product; (3) Using the environmentally polluting liquid toluene as a solvent results in high production costs and is not conducive to post-treatment for removing volatile components. Summary of the Invention

[0005] In view of the deficiencies of the existing metallocene catalyst systems, the present invention provides a homogeneous metallocene catalyst system and a method for copolymerizing ethylene / α-olefin.

[0006] According to the first aspect of the present invention, there is provided a homogeneous metallocene catalyst system for copolymerizing ethylene / α-olefin, the catalyst system comprising: a main catalyst component A, a first cocatalyst component B1, a second cocatalyst component B2, a third cocatalyst component B3, and an ultra-dry solvent component C; the component A is a metallocene compound, the component B1 is an aluminoxane or a modified aluminoxane, the component B2 is an organoboron compound, and the component B3 is an alkylaluminum compound.

[0007] After adding the component B1 and the component B2 to the catalyst system, the central metal element in the component A activated by the components B1 and B2 shows a doublet in the electron paramagnetic resonance test (EPR) at room temperature. The EPR spectrum shows that the magnetic field strength is between 345 - 365 mT, the g-factor is between 1.96 - 1.98 and 1.98 - 2.01 respectively, and multiple splitting peaks appear at the g-factor between 1.98 - 2.01. After adding the cocatalyst component B3 to the homogeneous metallocene catalyst system, more active centers with high activity and in the reduced valence state form are generated.

[0008] Further, the preparation method of the homogeneous metallocene catalyst system is as follows: the main catalyst component A is dissolved in the ultra-dry solvent component C from which water and oxygen have been removed to obtain a homogeneous solution of the main catalyst, and the cocatalyst components B1, B2, and B3 need to be stored for standby in an inert gas environment.

[0009] According to a preferred embodiment of the present invention, the homogeneous metallocene catalyst system further comprises a copolymerization modification additive component D; the copolymerization modification additive D is selected from one or more of organosilicon compounds such as siloxanes, organosilazanes, and fluorosilanes. The main structure of the copolymerization modification additive D is one or more of cage-shaped, semi-cage-shaped, and star-shaped structures. The organic groups in the molecular chain of the copolymerization modification additive D are selected from straight-chain alkyl groups of C 1 -C 10 ; cycloalkyl groups of C 1 -C 10 ; unsaturated hydrocarbon groups of C 1 -C 10 ; aryl groups of C 1 -C 10 ; aralkyl groups of C 1 -C 10 ; alkoxy groups of C 1 -C 10 ; alicyclic alkoxy groups of C 1 -C 10 ; and C 1 -C 10one or more of the aryloxy groups.

[0010] The homogeneous metallocene catalyst system of this preferred solution is configured as follows: The copolymerization modification auxiliary component D and the main catalyst component A are dissolved in the ultra-dry solvent component C from which moisture and oxygen have been removed, and stirring is maintained for at least 30 min under an inert gas environment for modification. The main catalyst component A and the copolymerization modification auxiliary component D exist in the form of coordination complexation, electrostatic adsorption, or molecular stacking. After modification, the main catalyst component is named A'. The cocatalyst components B1, B2, and B3 all need to be stored for standby under an inert gas environment. The concentration of the copolymerization modification auxiliary component D in the ultra-dry solvent component C is 0.01 - 500 μmol / mL, and the molar ratio of the copolymerization modification auxiliary component D to the main catalyst component A is 1:1000 - 1000:1.

[0011] Preferably, the general structural formula of the metallocene compound is L 1 HL 2 MX n , where L 1 and L 2 are selected from cyclopentadienyl, cyclopentadienyl derivatives, or a monodentate coordination anion group, and L 1 and L 2 can be the same or different; L 1 and L 2 each contain at least one substituent selected from one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, phenyl, naphthyl, anthracenyl, aralkyl, benzyl, phenethyl, alkoxy, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, vinyl, and propenyl.

[0012] Preferably, H is a bridging group connecting the two coordination groups of L 1 , L 2 , and may or may not exist depending on the different coordination groups of L 1 , L 2 . It is selected from the alkylene group of C 1 -C 10 , the substituted alkylene group of C 1 -C 10 , the arylene group of C 6 -C 14 , the substituted arylene group of C 6 -C 14 , the arylalkylene group of C 8 -C 15 , the alkylarylene group of C 8 -C 15 , the arylalkylene group of C 3 -C 20One or more of the sub-cycloalkyl groups, and the bridging atoms on the main chain are selected from one or more of Si, C, N, B, P, Al, Ge;

[0013] X is selected from halogen, C 1 -C 20 alkyl, C 1 -C 20 substituted alkyl, C 6 -C 30 aryl, C 6 -C 30 substituted aryl, C 1 -C 20 one or more of alkylamino;

[0014] M is an active center metal atom, selected from one or more of Ti(Ⅲ), Ti(Ⅳ), Ti(Ⅴ), Fe(Ⅱ), Fe(Ⅲ), Co(Ⅱ), Co(Ⅵ), Ni(Ⅱ), Cu(Ⅰ), Cu(Ⅱ), Zn(Ⅱ), Zr(Ⅱ), Zr(Ⅲ), Ru(Ⅱ), Ru(Ⅲ), Rh(Ⅱ), Rh(Ⅲ), Pd(Ⅱ), Pd(Ⅳ), Cr(Ⅳ), Zr(Ⅳ), Hf(Ⅲ) and Hf(Ⅳ);

[0015] n is the number of ligand X, determined according to the valence state and coordination of metal center M, and usually takes a value of 1-3.

[0016] Preferably, the cocatalyst component B1 is aluminoxane or modified aluminoxane, and its structural general formula is R(-Al(-R)-O) n -Al-R 2 ), where n is an integer, and each R can independently be C 10 -C 300 alkyl, aryl, alkoxy and aryloxy, and optionally two or more R groups can be linked together to obtain a specified cyclic structure, that is, two R groups can be an oxygen bridge between two aluminum atoms, preferably one or more of methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, n-propylaluminoxane, isopropylaluminoxane, n-butylaluminoxane, isobutylaluminoxane, neodecylaluminoxane, n-hexylaluminoxane and n-octylaluminoxane.

[0017] Preferably, the cocatalyst component B2 is an organoboron compound, selected from one or more of tris(pentafluorophenyl)borane, trityl tetrakis(pentafluorophenyl)borate, triphenylmethyl tetrakis(pentafluorophenyl)borate, tritylammonium tetrakis(pentafluorophenyl)borate, methylbis(octadecyl)ammonium tetrakis(pentafluorophenyl)borate, N,N-dioctadecylmethylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, bis(octadecyl)methylammonium tetrakis(pentafluorophenyl)borate, bis(hydrogenated tallow)methylammonium tetrakis(pentafluorophenyl)borate.

[0018] Preferably, the alkylaluminum compound B3 is selected from one or more of trimethylaluminum, triethylaluminum, tripropylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, triisohexylaluminum, trioctylaluminum, triphenylaluminum; preferably, the chloroalkylaluminum is selected from one or more of sesquimethylaluminum chloride, monochlorodimethylaluminum, dichloromethylaluminum, sesquietylaluminum chloride, monochlorodiethylaluminum, dichloroethylaluminum, monochlorodipropylaluminum, dichloropropylaluminum, monochlorodiisopropylaluminum, dichloroisopropylaluminum, sesquibutylaluminum chloride, monochlorodibutylaluminum, dichlorobutylaluminum, sesquibutylaluminum chloride, diisobutylaluminum chloride, dichloroisobutylaluminum, sesquibutylaluminum chloride, monochlorodibutylaluminum, dichlorobutylaluminum, sesquibutylaluminum chloride, diisobutylaluminum chloride, dichloroisobutylaluminum, sesquioctylaluminum chloride, monochlorodioctylaluminum, dichlorooctylaluminum.

[0019] Preferably, the super-dry solvent component C is selected from one or more of linear alkanes, cycloalkanes and benzenes, preferably C 4 -C 16 saturated alkanes, C 5 -C 10 alicyclic hydrocarbons, C 6 -C 300 aromatic hydrocarbons, C 4 -C 16 saturated heterocyclic hydrocarbons or paraffin oil.

[0020] According to the second aspect of the present invention, the present invention provides an ethylene / α-olefin copolymerization method using the homogeneous metallocene catalyst system, which is to bake the copolymerization reactor in a vacuum and at a temperature above 100 °C to remove moisture and oxygen in the reactor, and during this period, replace it with refined high-purity nitrogen and then add a solvent monomer for stirring. The solvent monomer includes a polymerization solvent E and an α-olefin F. When the reactor reaches the reaction temperature T, add the homogeneous metallocene catalyst system, and finally introduce ethylene for copolymerization reaction. After the reaction is completed, the polymerization product is discharged; the polymerization reaction temperature is 0-250 °C, and the polymerization pressure is 0-10 MPa.

[0021] More preferably, the addition of the homogeneous metallocene catalyst system is specifically as follows: the main catalyst component A is dissolved in the ultra-dry solvent component C to obtain a homogeneous main catalyst solution; when there is a copolymerization modification auxiliary component D, the main catalyst component A and the copolymerization modification auxiliary component D are dissolved in the ultra-dry solvent component C to obtain a homogeneous main catalyst solution; then the homogeneous metallocene catalyst system is added to the solvent monomer in one of the following ways:

[0022] (1) Add component B1, component B2, and component B3 to the solvent monomer in sequence, and then add the homogeneous main catalyst solution, where the addition order of component B1, component B2, and component B3 can be interchanged;

[0023] (2) Add the pre-mixed component B1 with component B2, component B3 to the solvent monomer, and then add the homogeneous main catalyst solution, where the addition order of the pre-mixed component B1 with component B2 and B3 can be interchanged;

[0024] (3) Add the pre-mixed component B1 with component B3, component B2 to the solvent monomer, and then add the homogeneous main catalyst solution, where the addition order of the pre-mixed component B1 with component B3 and B2 can be interchanged;

[0025] (4) Add the pre-mixed component B2 with component B3 to the solvent monomer, and then add component B1 and the homogeneous main catalyst solution in sequence, where the addition order of the pre-mixed component B2 with component B3 and B1 can be interchanged;

[0026] (5) Add component B2 and component B3 to the solvent monomer, and then add the pre-mixed component B1 and the homogeneous main catalyst solution, where the addition order of component B2 and component B3 can be interchanged;

[0027] (6) Add component B1 and component B3 to the solvent monomer, and then add the pre-mixed component B2 and the homogeneous main catalyst solution, where the addition order of component B1 and component B3 can be interchanged;

[0028] (7) Add component B1 and component B2 to the solvent monomer, and then add the pre-mixed component B3 and the homogeneous main catalyst solution, where the addition order of component B1 and component B2 can be interchanged;

[0029] (8) Add the pre-mixed component B1 with component B2 to the solvent monomer, and then add the pre-mixed component B3 and the homogeneous main catalyst solution;

[0030] (9) Add the pre-mixed component B1 with component B3 to the solvent monomer, and then add the pre-mixed component B2 and the homogeneous main catalyst solution;

[0031] (10) Add the pre-mixed component B2 and component B3 to the solvent monomer, and then add the pre-mixed component B1 and the homogeneous solution of the main catalyst;

[0032] (11) Add the pre-mixed component B1, component B2 and component B3 to the solvent monomer, and then add the homogeneous solution of the main catalyst;

[0033] (12) Add component B1 to the solvent monomer, and then add the pre-mixed component B2, component B3 and the homogeneous solution of the main catalyst;

[0034] (13) Add component B2 to the solvent monomer, and then add the pre-mixed component B1, component B3 and the homogeneous solution of the main catalyst;

[0035] (14) Add component B3 to the solvent monomer, and then add the pre-mixed component B1, component B2 and the homogeneous solution of the main catalyst;

[0036] (15) Add the pre-mixed component B1, component B2, component B3 and the homogeneous solution of the main catalyst to the solvent monomer.

[0037] As a preferred embodiment of the present invention, the ratio of the cocatalyst component B1 to the main catalyst component A is in terms of the molar ratio of Al element to M element (the active center element of the main catalyst) Al / M, which is 1:1 - 1:1000, and further preferably 1:1 - 1:200; preferably, the ratio of the cocatalyst component B2 to the main catalyst component A is in terms of the molar ratio of B element to M element B / M, which is 1:1 - 1:50, and further preferably 1:1 - 1:20; preferably, the ratio of the cocatalyst component B3 to the main catalyst component A is in terms of the molar ratio of Al element to M element Al / M, which is 1:0 - 1:250, and further preferably 1:0 - 1:100; preferably, the ratio of the copolymerization modifying agent component D to the main catalyst component A is in terms of the molar ratio of M element to substance D M / D, which is 1:1 - 1:200, and further preferably 1:1 - 1:50; preferably, the addition amount of the main catalyst is in terms of the molar concentration of M element in the ultra-dry solvent component, which is 1 - 200 μmol / L; the polymerization reaction temperature is 0 - 250 °C, and further preferably 50 - 200 °C; the polymerization reaction pressure is 0.3 - 10 MPa; the polymerization reaction stirring speed is 50 - 400 r / min, and further preferably 150 - 250 r / min; preferably, the cocatalyst component and the main catalyst component are pre-mixed in an inert gas environment and reserved for copolymerization, the mixing temperature is 0 °C - 50 °C, and further preferably 0 °C - 25 °C, and the mixing time is 1 min - 120 min, and further preferably 1 min - 30 min. As a preferred embodiment of the present invention, the high-temperature solution copolymerization method of ethylene / α-olefin using the homogeneous metallocene catalyst system, wherein α-olefin is preferably C3 -C 20 linear α-olefins, more preferably C 3 -C 9 linear α-olefins.

[0038] The homogeneous metallocene catalyst system proposed by the present invention and the ethylene / α-olefin copolymerization method bring the following beneficial effects:

[0039] (1) The copolymerization modifying additive component D and the main catalyst component A proposed by the present invention form a homogeneous solution in the ultra-dry solvent component C in the form of coordination complexation or electrostatic adsorption. The main catalyst component A and the copolymerization modifying additive component D exist in the form of coordination complexation, electrostatic adsorption or molecular stacking. The introduction of the copolymerization modifying additive component D can play a role in stabilizing the active center of the main catalyst, and different copolymerization modifying additives have different steric hindrance effects on the ligand structure. The steric hindrance of the ligand structure can be increased by using the copolymerization modifying additive, which can further prevent the attack of impurity small molecules and long-chain molecules on the active center, thereby inhibiting the deactivation reaction and enhancing the thermal stability and polymerization activity of the main catalyst.

[0040] (2) The copolymerization modifying additive component D and the main catalyst component A proposed by the present invention form a homogeneous solution in the ultra-dry solvent component C in the form of coordination complexation or electrostatic adsorption. Compared with the homogeneous catalyst system before modification, the coordination environment of the metal active center of the main catalyst changes after modification, and the active centers in the reduced valence state generated after activation are more evenly distributed. The unreduced active centers can also provide activity. The two active centers act synergistically, so that the heat release of the copolymerization reaction is more stable, avoiding the influence of "temperature runaway" on the branch distribution of the copolymer product and ultimately affecting the quality of the product. This method can effectively regulate the reactivity ratios of ethylene and α-olefin, thereby realizing the precise regulation of the microstructure of the copolymer chain segment.

[0041] (3) The addition of the cocatalyst component B3 makes it easier for the metal center element of the homogeneous metallocene catalyst to be reduced to a highly active active species. Compared with the case where the cocatalyst component B3 is not added, the activity can be increased by 0.3 - 1.5 times, and compared with the traditional constrained geometry metallocene catalyst (CGC), the activity can be increased by 1.5 - 4 times. At the same time, while increasing the activity, the amount of the cocatalyst methylaluminoxane or modified methylaluminoxane is greatly reduced, and the [Al] / [M] molar ratio is reduced from 500 - 1000 to 1 - 200, significantly reducing the production cost and breaking the limitation of the expensive methylaluminoxane cocatalyst on the industrial application of the ethylene / α-olefin copolymerization catalyst.

[0042] (4) The cocatalyst component B3 can also effectively regulate the average sequence lengths of ethylene and α-olefin in the copolymer molecular chain. Under the combined action of the catalyst component B3 and the copolymerization modifying additive component D, the microstructure of the copolymer chain segment is precisely regulated. Brief Description of the Drawings

[0043] Figure 1 It is the polymerization kinetic curve of Example 4 and Comparative Example 1.

[0044] Figure 2 It is the comparison of electron paramagnetic resonance results after activation of the homogeneous catalytic systems of Example 4 and Example 6. Detailed Description of the Invention

[0045] The preferred embodiments of the present invention will be described in more detail below to further explain and illustrate the present invention. It should be clear that the implementation cases are only used to illustrate the present invention and do not limit the scope of the present invention. In the following examples, if the materials, reagents and instruments used are not specified by the manufacturer, they are all purchased from commercial channels; the experimental methods used are all conventional methods without special instructions; the concentrations involved, without special instructions, are all molar concentrations.

[0046] The catalytic activity of the ethylene / α-olefin copolymerization reaction is calculated based on the amount of polymer produced per mole of the main catalyst A per hour, and the unit is g POE / (mol·h).

[0047] Performance Testing

[0048] Analysis of Chain Segment Structure:

[0049] The performance of the polymer material first depends on the microstructure of the polymer chain segments. The analysis of the chain segment structure is extremely important for the design of the material. The average composition of the comonomer in the copolymer can be measured by high-temperature nuclear magnetic resonance carbon spectrum ( 13 C-NMR).

[0050] Testing of Molecular Weight and Molecular Weight Distribution:

[0051] The molecular weight (M w , M n ) and molecular weight distribution (MWD) of the polymer can be measured by high-temperature gel permeation chromatography (GPC). Using 1,2,4-trichlorobenzene as the solvent, a polymer solution with a concentration of 0.1 - 0.3 wt% is prepared at 160 °C, and a narrow-distribution polystyrene (PS) is used as the standard sample for measurement.

[0052] Melt Index:

[0053] The melt mass flow rate of the material can be measured by a melt index instrument. The flow characteristics of the test material are measured under the conditions of a temperature of 190 °C and a standard load of 2.16 kg.

[0054] Density:

[0055] The density of the polymer can be determined by a density gradient column. After degassing the melt index spline, it is cut into 1 mm cylinders and thrown into the density gradient column. After the 1 mm cylinders are stable, the scale value of the density gradient column is read, and the density value of the polymer is calculated through a computer program.

[0056] Example 1:

[0057] The copolymerization modification auxiliary component D is tetramethylammonium-based cage-like polyhedral oligomeric silsesquioxane, and the structural general formula of the main catalyst component A is L 1 HL 2 MX n where L 1 and L 2 are tetramethylcyclopentadienyl, H is ethylidene, M is Ti(IV), X is methyl, and n = 2.

[0058] Prepare a homogeneous solution of the main catalyst component A': Take 12.5 μmol of the above copolymerization modification auxiliary D and 500 μmol of the above main catalyst component A in 5 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 120 min. The above preparation operations are all carried out in a glove box filled with inert gas. The obtained homogeneous solution of component A' is reserved for copolymerization.

[0059] Ethylene and 1-octene copolymerization experiment operation: First, bake a 1 L copolymerization reactor at a high temperature (above 130 °C) and in a vacuum state. During baking, it is replaced with refined high-purity nitrogen, and it is replaced 3 to 5 times every half hour. The baking time is not less than 120 min. After baking, then add 350 mL of the polymerization solvent hexane to the polymerization reactor, and then add 250 mL of the comonomer 1-octene. Turn on the stirring. When the temperature rises to about 130 °C, add 400 μmol of the cocatalyst component B1 (modified methylaluminoxane) and 1.2 μmol of the cocatalyst component B2 (N,N-dioctadecylmethylammonium tetrakis(pentafluorophenyl)borate) that have been premixed, and stir for at least 2 min to remove impurities in the polymerization reactor. Finally, add 2 μmol of the diluted homogeneous solution of the main catalyst component A' (the molar amount of the homogeneous solution of the main catalyst component A' is calculated from the content of component A), and introduce ethylene for copolymerization reaction. The polymerization pressure is 4.0 MPa, the polymerization temperature is 140 °C, and the polymerization time is 40 min. After the polymerization reaction is completed, the product is quenched in acidified ethanol by high-pressure spraying, and then it is placed in a fume hood and left standing overnight. The next day, it is dried to a constant weight under vacuum conditions and the product performance is analyzed. The analysis results of the polymerization products are shown in Table 2.

[0060] Example 2:

[0061] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the addition amount of the cocatalyst component B1 is changed to 300 μmol, and the addition amount of the cocatalyst component B2 is changed to 2.4 μmol. Under the condition that other conditions remain unchanged, the analysis results of the polymerization products are shown in Table 2.

[0062] Example 3:

[0063] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the addition amount of the cocatalyst component B1 is changed to 200 μmol, and the addition amount of the cocatalyst component B2 is changed to 3.6 μmol. Under the condition that other conditions remain unchanged, the analysis results of the polymerization products are shown in Table 2.

[0064] Example 4:

[0065] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the addition amount of the cocatalyst component B1 is changed to 100 μmol, and the addition amount of the cocatalyst component B2 is changed to 4.8 μmol. Under the condition that other conditions remain unchanged, the analysis results of the polymerization products are shown in Table 2.

[0066] Example 5:

[0067] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the addition amount of the cocatalyst component B1 is changed to 50 μmol, and the addition amount of the cocatalyst component B2 is changed to 6.0 μmol. Under the condition that other conditions remain unchanged, the analysis results of the polymerization products are shown in Table 2.

[0068] Example 6:

[0069] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the addition method of each component of the cocatalyst is changed to: first add 20 μmol of the cocatalyst B3 (trioctylaluminum), then add the pre-mixed 100 μmol of the cocatalyst component B1 and 4.8 μmol of the cocatalyst component B2, and finally add 2 μmol of the homogeneous catalytic system. The analysis results of the polymerization products are shown in Table 2.

[0070] Example 7:

[0071] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the addition method of each component of the cocatalyst is changed as follows: First, add 100 μmol of cocatalyst component B1 and 4.8 μmol of cocatalyst component B2 which are premixed, and then add 20 μmol of cocatalyst B3 and 2 μmol of the homogeneous catalytic system which are premixed. The analysis results of the polymerization products are shown in Table 2.

[0072] Example 8:

[0073] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the addition method of each component of the cocatalyst is changed as follows: First, add 20 μmol of cocatalyst B3, then add 50 μmol of cocatalyst component B1 and 4.8 μmol of cocatalyst component B2 which are premixed, and finally add 50 μmol of cocatalyst component B1 and 2 μmol of the homogeneous catalytic system which are premixed. The analysis results of the polymerization products are shown in Table 2.

[0074] Example 9:

[0075] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the addition method of each component of the cocatalyst is changed as follows: First, add 20 μmol of cocatalyst B3, then add 4.8 μmol of cocatalyst component B2, and finally add 100 μmol of cocatalyst component B1 and 2 μmol of the homogeneous catalytic system which are premixed. The analysis results of the polymerization products are shown in Table 2.

[0076] Example 10:

[0077] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the polymerization temperature is changed to 130 °C, and the addition method of each component of the cocatalyst is the same as that in Example 6. The analysis results of the polymerization products are shown in Table 2.

[0078] Example 11:

[0079] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1. Among them, the polymerization temperature is changed to 150 °C, and the addition method of each component of the cocatalyst is the same as that in Example 6. The analysis results of the polymerization products are shown in Table 2.

[0080] Example 12:

[0081] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1, except that the polymerization temperature is changed to 160 °C, and the addition method of each component of the cocatalyst is the same as that in Example 6. The analysis results of the polymerization products are shown in Table 2.

[0082] Example 13:

[0083] The preparation process of the homogeneous solution of the main catalyst component A' is the same as that in Example 1. Other operations in the copolymerization experiment of ethylene and 1-octene are the same as those in Example 1, except that the polymerization temperature is changed to 170 °C, and the addition method of each component of the cocatalyst is the same as that in Example 6. The analysis results of the polymerization products are shown in Table 2.

[0084] Comparative Example 1:

[0085] Prepare the homogeneous solution of the main catalyst component A: Take 500 μmol of the main catalyst component A (dimethylsilyl-tert-butylamido tetramethylcyclopentadienyl dimethyltitanium) in 5 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 120 min. The above preparation operations are all carried out in a glove box filled with inert gas. The obtained homogeneous solution of component A is reserved for copolymerization.

[0086] Operation of the copolymerization experiment of ethylene and 1-octene: First, bake a 1 L copolymerization reactor at a high temperature (above 130 °C) and in a vacuum state. During baking, replace it with refined high-purity nitrogen. Replace it 3 to 5 times every half hour, and the baking time is not less than 120 min. After baking, then add 350 mL of the polymerization solvent hexane into the polymerization kettle, and then add 250 mL of the comonomer 1-octene. Turn on the stirrer. When the temperature rises to about 130 °C, add 100 μmol of the cocatalyst component B1 and 4.8 μmol of the cocatalyst component B2 which are pre-mixed, and stir for at least 2 min to remove impurities in the polymerization kettle. Finally, add the diluted 2 μmol of the homogeneous solution of the main catalyst component A (the molar amount of the homogeneous solution of the main catalyst component A is calculated from the content of the main catalyst component A), and introduce ethylene for copolymerization reaction. The polymerization pressure is 4.0 MPa, the polymerization temperature is 140 °C, and the polymerization time is 40 min. After the polymerization reaction is completed, place the product in acidified ethanol through high-pressure spraying for quenching, and then let it stand in a fume hood overnight. The next day, dry it to a constant weight under vacuum conditions and conduct product performance analysis. The analysis results of the polymerization products are shown in Table 1.

[0087] Comparative Example 2:

[0088] Preparation of homogeneous solution of main catalyst component A': Take 12.5 μmol of copolymerization modifier D (sesquisiloxane) and 500 μmol of main catalyst component A (dimethylsilyl tert-butylamine tetramethylcyclopentadienyl titanium dichloride) and form a homogeneous solution in 5 mL of toluene solution. Keep the homogeneous solution under stirring at 250 rpm for at least 120 min. The above preparation operations are all carried out in a glove box filled with inert gas. The obtained homogeneous catalytic system is reserved for copolymerization.

[0089] Ethylene and 1-octene copolymerization experiment operation: First, bake a 1 L copolymerization reactor at high temperature (above 130 °C) and under vacuum. During baking, replace it with refined high-purity nitrogen. Replace it 3 to 5 times every half hour, and the baking time is not less than 120 min. After baking, then add 350 mL of polymerization solvent hexane into the polymerization reactor, and then add 250 mL of copolymerization monomer 1-octene. Turn on the stirrer. When the temperature rises to about 130 °C, then add 1000 μmol of cocatalyst component B1 (methylaluminoxane) and 10 μmol of cocatalyst component B2 (borane), stir for at least 2 min to remove impurities in the polymerization reactor. Finally, add 2 μmol of diluted homogeneous solution of main catalyst component A' (the molar amount of the homogeneous solution of main catalyst component A' is calculated from the content of main catalyst component A), introduce ethylene for copolymerization reaction. The polymerization pressure is 4.0 MPa, the polymerization temperature is 140 °C, and the polymerization time is 40 min. After the polymerization reaction is completed, place the product into acidified ethanol through high-pressure spraying for quenching, and then let it stand in a fume hood overnight. The next day, dry it to a constant weight under vacuum conditions and conduct product performance analysis. The analysis results of the polymerization products are shown in Table 1.

[0090] Table 1 Summary of the dosage ratios of main reagents in examples and comparative examples

[0091]

[0092] Table 2 Summary of product analysis results in examples and comparative examples

[0093]

[0094]

[0095] Comparative examples 14 - 20:

[0096] Examples 14 - 20 have the same preparation process of the homogeneous solution of main catalyst component A' as Example 1. The addition method of the homogeneous metallocene catalytic system and other operations of the ethylene and 1-octene copolymerization experiment are the same as those in Example 7. The remaining differences are shown in Table 3 below. The homogeneous metallocene catalytic system configured in this way has the same catalytic effect as that in Example 7. Table 3 Homogeneous metallocene catalytic system configured in Examples 14 - 20

[0097]

[0098] From the homogeneous metallocene catalyst systems of Examples 1-11 and Comparative Examples 1-2 above, and the analysis and characterization results of the ethylene / α-olefin copolymer products, combined with the attached Figure 1-2 , the following conclusions can be obtained:

[0099] (1) By comparing Examples 1-5, it is found that when the amount of cocatalyst component B1 is reduced from 400 μmol to 50 μmol and the amount of cocatalyst B2 is increased from 1.2 μmol to 6.0 μmol, the polymerization activities of Example 4 and Example 1 are not much different. However, compared with the amount of cocatalyst B2, the amount of cocatalyst component B1 is greatly reduced, significantly reducing the production cost. If the amount of cocatalyst B2 is continued to be increased, as can be seen from Example 5, the polymerization activity decreases instead, which will not only affect the physical properties of the copolymer but also ultimately affect the product quality. Generally speaking, the preferred amounts of cocatalyst component B1 and component B2 are those of Example 4.

[0100] (2) By comparing Example 4 with Comparative Example 1 and the attached Figure 1 polymerization kinetic curves, it is found that after introducing the copolymerization modification additive component D, the polymerization temperature of Example 4 is more stable, indicating that the copolymerization modification additive can change the coordination environment of the main catalyst metal active center and prevent impurity molecules from attacking the active center, thus playing a role in stabilizing the main catalyst active center.

[0101] (3) By comparing the polymerization activities of Examples 4, 6, and 7 and the attached Figure 2 it is found that after adding cocatalyst component B3, the polymerization activity is increased by 1.4 times. After pre-complexing cocatalyst component B3 with the main catalyst, the polymerization activity is increased by 1.8 times. Compared with the main catalyst used in Comparative Example 2, the polymerization activity is increased by 3 times, and the consumption of cocatalyst component B1 is reduced by 10 times. As can be seen from the attached Figure 2 , the reason for the increase in polymerization activity is that after adding cocatalyst component B3, the signal intensity in the electron paramagnetic resonance spectrum (EPR) of Example 6 is enhanced, indicating that more active centers in the reduced valence state with high activity are generated.

[0102] (3) By comparing the polymerization activities of Examples 6, 10, 11, 12, and 13, it is found that this homogeneous metallocene catalyst system shows excellent polymerization activity at high temperatures, and a temperature of 140 °C is the optimal reaction temperature.

[0103] (4) By comparing the polymerization activities of Examples 6, 7, 8, and 9, it was found that the pre-complexing effect of cocatalyst component B1 with main catalyst component A was inferior to that of cocatalyst component B3. This is because cocatalyst component B1 would rapidly activate main catalyst component A, resulting in the fact that once the pre-complexed main catalyst contacted ethylene before being added to the reaction kettle, the homopolymerization reaction of ethylene would be immediately initiated, ultimately causing blockage of the main catalyst pipeline.

[0104] (5) By comparing the average sequence lengths of ethylene and octene in Example 4, 7 and Comparative Example 1, it was found that after introducing the copolymerization modification additive component D into this catalytic system, n E decreased from 9.7 to 9.4, and n O remained unchanged. When both copolymerization modification additive component D and cocatalyst component B3 were added, n E decreased from 9.7 to 8.9, and n O increased from 1.4 to 1.5. Thus, it can be seen that by varying the ratio between copolymerization modification additive component D and cocatalyst component B3, the microstructure of the copolymer chain segments can be precisely regulated.

[0105] The present invention is not limited to the above-listed embodiments. In fact, there are also various other embodiments. Although the descriptions of these embodiments may be relatively specific and detailed, this does not mean that they constitute a limitation on the scope of the present invention patent. Without departing from the core concept and essence of the present invention, some modifications and improvements made by those of ordinary skill in the art based on the present invention are also covered within the protection scope defined by the claims of the present invention.

Claims

1. An ethylene / α-olefin copolymerization homogeneous metallocene catalyst system, characterized in that: The catalytic system comprises: a main catalyst component A, a first co-catalyst component B1, a second co-catalyst component B2, a third co-catalyst component B3 and an ultra-dry solvent component C; component A is a metallocene compound, component B1 is aluminoxane or modified aluminoxane, component B2 is an organic boron compound, and component B3 is an alkyl aluminum compound.

2. The ethylene / α-olefin copolymerization homogeneous metallocene catalyst system according to claim 1, characterized in that: The homogeneous metallocene catalyst system further comprises a copolymerization modification auxiliary component D; the copolymerization modification auxiliary component D is selected from one or more of siloxane organic compounds, silazane organic compounds, and ether compounds; the main structure of the copolymerization modification auxiliary component D is one or more of a cage type, a semi-cage type, and a star structure; the organic group in the molecular chain of the copolymerization modification auxiliary component D is selected from C1-C 10 Alkyl, C1-C 10 Cycloalkyl, C1-C 10 Unsaturated hydrocarbon groups, C1-C 10 Aryl, C1-C 10 Aralkyl, C1-C 10 Alkoxy, C1-C 10 Alicyclic alkoxy and C1-C 10 One or more of the aryloxy groups.

3. The ethylene / α-olefin copolymerization homogeneous metallocene catalytic system according to claim 1 or 2, characterized in that: The metallocene compound has the general structural formula L 1 HL 2 MX n , where L 1 With L 2 is selected from cyclopentadienyl, cyclopentadienyl derivatives or monodentate coordinating anion groups, L 1 With L 2 Can be the same or different; H is connected to L 1 , L 2 The bridging group of the two coordination groups, according to L 1 , L 2 The coordination group may be present or absent depending on the coordination group; M is the active center metal atom, selected from one or more of Ti(III), Ti(IV), Ti(V), Fe(II), Fe(III), Co(II), Co(VI), Ni(II), Cu(I), Cu(II), Zn(II), Zr(II), Zr(III), Ru(II), Ru(III), Rh(II), Rh(III), Pd(II), Pd(IV), Cr(IV), Zr(IV), Hf(III) and Hf(IV); X is selected from one or more of alkyl, cycloalkyl, aryl, aralkyl and halogen, wherein n is determined according to the valence state and coordination of the active center metal atom M.

4. The ethylene / α-olefin copolymerization homogeneous metallocene catalyst system according to claim 1 or 2, characterized in that: The co-catalyst component B1 is selected from one or more of methylaluminoxane, triisobutylaluminum-modified methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, isobutylaluminoxane, and trioctylaluminum-modified methylaluminoxane; the co-catalyst component B2 is selected from one or more of tri(pentafluorophenyl)borane, tetrakis(pentafluorophenyl)borate and their derivatives; the co-catalyst component B3 is selected from one or more of trimethylaluminum, triethylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tricyclohexylaluminum, and tri-n-octylaluminum.

5. The homogeneous metallocene catalyst system for ethylene / α-olefin copolymerization according to claim 2, characterized in that: The configuration method of the homogeneous metallocene catalytic system is as follows: a copolymerization modification auxiliary component D and a main catalyst component A are dissolved in an ultra-dry solvent component C from which water and oxygen have been removed, and the modification is carried out by maintaining a stirring state for at least 30 minutes under an inert gas environment. The main catalyst component A and the copolymerization modification auxiliary component D exist in the form of coordination complexation, electrostatic adsorption or molecular stacking. The modified main catalyst component is named A', and the auxiliary catalyst components B1, B2 and B3 are all required to be placed in an inert gas environment and retained for standby use. The concentration of the copolymerization modification auxiliary component D in the ultra-dry solvent component C is 0.01-500 μmol / mL, and the molar ratio of the copolymerization modification auxiliary component D to the main catalyst component A is 1:1000-1000:

1.

6. The ethylene / α-olefin copolymerization homogeneous metallocene catalytic system according to claim 1 or 2, characterized in that: In the homogeneous metallocene catalytic system, the concentration of the main catalyst component A in the ultra-dry solvent component C is 0.01-2000 μmol / mL; the molar ratio of the main catalyst component A to the co-catalyst component B1 is 1:1-1:2000; the molar ratio of the main catalyst component A to the co-catalyst component B2 is 1:1-1:50; and the molar ratio of the main catalyst component A to the co-catalyst component B3 is 1:1-1:1000.

7. An ethylene / α-olefin copolymerization method using the homogeneous metallocene catalyst system according to claim 1 or 2, characterized in that: The copolymerization reactor is baked under vacuum and above 100°C to remove moisture and oxygen in the reactor, during which it is replaced with refined high-purity nitrogen and then solvent monomers are added for stirring. The solvent monomers include polymerization solvent E and α-olefin F. After the reactor is heated to the reaction temperature T, a homogeneous metallocene catalyst system is added, and finally ethylene is introduced for copolymerization. After the reaction is completed, the polymerization product is discharged; the polymerization reaction temperature is 0-250°C, and the polymerization pressure is 0-10MPa.

8. The ethylene / α-olefin copolymerization method according to claim 7, characterized in that: The adding of the homogeneous metallocene catalyst system is specifically as follows: dissolving the main catalyst component A in the ultra-dry solvent component C to obtain a main catalyst homogeneous solution; when the copolymerization modification auxiliary component D is present, dissolving the main catalyst component A and the copolymerization modification auxiliary component D in the ultra-dry solvent component C to obtain a main catalyst homogeneous solution; and then adding the homogeneous metallocene catalyst system to the solvent monomer in one of the following ways: (1) Adding component B1, component B2, and component B3 to the solvent monomer in order, and then adding the main catalyst homogeneous solution, wherein the order of adding component B1, component B2, and component B3 can be reversed; (2) adding pre-mixed component B1, component B2, component B3, and then adding the homogeneous solution of the primary catalyst to the solvent monomer, wherein the order of adding the pre-mixed component B1, components B2 and B3 can be reversed; (3) adding pre-mixed component B1 and component B3, component B2, and then adding the homogeneous solution of the primary catalyst to the solvent monomer, wherein the order of adding the pre-mixed component B1 and components B3 and B2 can be reversed; (4) adding pre-mixed component B2 and component B3 to the solvent monomer, and then adding component B1 and the primary catalyst homogeneous solution in sequence, wherein the order of adding the pre-mixed component B2, component B3 and B1 can be reversed; (5) Adding component B2 and component B3 to the solvent monomer, and then adding the pre-mixed component B1 and the primary catalyst homogeneous solution, wherein the order of adding component B2 and component B3 can be reversed; (6) Adding component B1 and component B3 to the solvent monomer, and then adding the pre-mixed component B2 and the primary catalyst homogeneous solution, wherein the order of adding component B1 and component B3 can be reversed; (7) Adding component B1 and component B2 to the solvent monomer, and then adding the pre-mixed component B3 and the primary catalyst homogeneous solution, wherein the order of adding component B1 and component B2 can be reversed; (8) adding pre-mixed component B1 and component B2 to the solvent monomer, and then adding pre-mixed component B3 and the primary catalyst homogeneous solution; (9) adding pre-mixed component B1 and component B3 to the solvent monomer, and then adding pre-mixed component B2 and the primary catalyst homogeneous solution; (10) adding pre-mixed component B2 and component B3 to the solvent monomer, and then adding pre-mixed component B1 and the primary catalyst homogeneous solution; (11) adding pre-mixed component B1, component B2 and component B3 to the solvent monomer, and then adding the primary catalyst homogeneous solution; (12) adding component B1 to the solvent monomer, and then adding pre-mixed component B2, component B3 and a homogeneous solution of the main catalyst; (13) adding component B2 to the solvent monomer, and then adding the pre-mixed component B1, component B3 and the primary catalyst homogeneous solution; (14) adding component B3 to the solvent monomer, and then adding the pre-mixed component B1, component B2 and the primary catalyst homogeneous solution; (15) Add the pre-mixed component B1, component B2, component B3 and the primary catalyst homogeneous solution into the solvent monomer.

9. The method according to claim 7, characterized in that: The polymerization solvent E is selected from C4-C 16 Saturated alkanes, C5-C 10 Alicyclic hydrocarbons, C6-C 300 Aromatic hydrocarbons, C4-C 16 One or more of saturated heterocyclic hydrocarbons or paraffin oil; α-olefin F is selected from C3-C 10 One or more α-olefins, the ultra-dry solvent component C and the polymerization solvent E can be the same component or different components.

10. An ethylene / α-olefin copolymer product prepared by the method of claim 7, characterized in that: The insertion rate of the comonomer α-olefin is 0.1-30 mol%; the molecular weight of the copolymer product is 50000-300000 g / mol; the density of the copolymer product is 0.850-0.920 g / cm 3 .

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