Ethylene / alpha-olefin copolymerization cluster catalytic system

Abstract

The invention discloses an ethylene / alpha-olefin copolymerization cluster catalytic system. The catalytic system comprises a main catalyst component A, a co-catalyst component B, a pure solvent component C and a performance additive component D which interacts with a main catalyst to form a cluster catalyst. Wherein the component D can form a cluster catalyst with the main catalyst component A in the form of coordination complexation or supramolecular assembly or covalent bonds. The cluster catalytic system can significantly improve the polymerization activity of ethylene / alpha-olefin and the insertion capacity of alpha-olefin, has good high-temperature stability, can effectively regulate and control the reactivity rate of ethylene and alpha-olefin, improves the product performance by regulating and controlling the chain segment structure of the product, and has good application prospects. The copolymer prepared by the cluster catalytic system has the characteristics of high light transmission and low haze, and has high technical economy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of olefin polymerization and catalysts, in particular to an ethylene / alpha-olefin copolymerization cluster catalyst system. BACKGROUND

[0002] POE is a high alpha-olefin content random copolymer obtained by copolymerization of ethylene and alpha-olefins (such as 1-octene, 1-hexene, 1-butene, etc.). Since the alpha-olefins are introduced into the polymer chain in a random manner, the crystalline structure of polyethylene is destroyed, forming an amorphous region (rubber phase) with elasticity, and the polyethylene segments that are not destroyed remain crystalline, forming a crystalline region (plastic phase) with physical crosslinking capability. Since the physical crosslinking (crystalline) structure is stable at room temperature and can be destroyed at a temperature higher than the melting point, POE maintains high elasticity as a rubber at room temperature and is easily molded at high temperature.

[0003] Compared with Ziegler-Natta catalysts, metallocene catalysts have the characteristics of good solubility, single active site, and transition metal atoms and ligand structures in the main ligand structure that can be controlled in a wide range, overcoming the shortcomings of traditional heterogeneous catalysts, such as difficulty in controlling the structure and wide molecular weight distribution of the obtained polymers. However, the catalytic activity of metallocene catalysts has the problem of local rapid polymerization rate in the polymerization system, which is unstable and releases during the polymerization time, resulting in uneven heat release during the polymerization process. This not only brings difficulties to the stable production of products, but also affects the microstructure parameters of the products. At present, the method to solve the above-mentioned defects is to load the metallocene compound as an active ingredient onto a corresponding carrier. CN02105140.2, CN102453159B, and CN1590413A provide methods for loading metallocene compounds onto different carriers. However, such supported catalysts have the defect of low activity. Although traditional CGC catalysts have high activity and comonomer insertion ability, the high-temperature resistance is not ideal. On the other hand, a large amount of methylaluminoxane (MAO) or modified methylaluminoxane (MMAO) is needed as a decontaminant and cocatalyst in the production of high-end polyolefins catalyzed by metallocenes, which not only has high cost but also limits the supply of high-end polyolefin products due to the serious global shortage of MAO and MMAO. CN201010577990 discloses a method for preparing a constrained geometry metallocene chromium catalyst, which no longer needs to use a large amount of methylaluminoxane, greatly reducing the cost of the metallocene catalyst system. However, the above-mentioned catalyst system has a low comonomer insertion rate when used for olefin polymerization.

[0004] In the field of metallocene catalyst technology, previous studies have mostly focused on the modification of ligand structures. The main ligand structure has a significant impact on the activity and catalytic performance of catalysts. The presence of electron-donating substituents on cyclopentadienyl ligands can stabilize the active center and improve the catalyst activity; more electron-donating groups result in higher catalyst activity. However, some studies have also found that introducing phenoxy groups [CN201510082857.7] and benzidine groups [CN201610342188.7] with strong electron-withdrawing capabilities into the structure of metallocene compounds can improve the thermal stability of metallocene catalysts. However, the preparation methods of the above catalytic systems are relatively complex and have high requirements for the active center and ligands. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an ethylene / α-olefin copolymer cluster catalytic system.

[0006] Without altering the homogeneous polymerization process, the cluster catalyst system provided by this invention can significantly reduce the amount of co-catalyst, change the polymerization kinetics of ethylene / α-olefin copolymerization, improve the high-temperature thermal stability of the catalytic system, and simultaneously achieve uniform exothermic reaction. It can significantly improve polymerization activity with the same amount of active centers. By selecting different co-catalysts to form different cluster catalysts with the metallocene catalyst, the molecular configuration of the main catalyst can be effectively controlled, altering the electronic effects of the central metal atom, bond lengths, bond angles, and steric hindrance with adjacent ligands, thereby controlling the copolymerization behavior of ethylene / α-olefins. Simultaneously, it can effectively control the reactivity ratios of ethylene and α-olefins, thus controlling the structure of the product chain segments and improving product performance. The catalytic system of this invention is particularly suitable for olefin copolymerization reactions. The copolymers prepared by this cluster catalytic system exhibit superior light transmittance and low haze performance, demonstrating high technical and economic efficiency.

[0007] The ethylene / α-olefin copolymerization cluster catalytic system provided by the present invention comprises a main catalyst component A, a co-catalyst component B, a pure solvent component C, and a copolymerization modification auxiliary component D; wherein the auxiliary component D and the main catalyst component A form a cluster catalyst through coordination complexation, supramolecular assembly, or covalent bonding. The main catalyst component A and the copolymerization modifier component D are dissolved in pure solvent component C and stirred under an inert gas environment for at least 100 min to obtain cluster catalyst S; the concentration of the main catalyst component A in the pure solvent component C is 500-1000 μmol / ml; by modifying the main catalyst A with copolymerization modifier component D, the molecular configuration of the main catalyst component A is regulated, and the electronic effect of the central metal atom, the bond length, bond angle and steric hindrance with adjacent ligands are changed, thereby regulating the copolymerization behavior of ethylene / α-olefin; Cluster catalyst S and co-catalyst component B are placed separately to form the ethylene / α-olefin copolymer cluster catalytic system.

[0008] The interaction between the ethylene / α-olefin copolymer cluster catalyst promoter component D and the main catalyst component A is shown in X-ray absorption fine structure spectroscopy (XPS). The ligand-X bond length (where X is the central metal atom) increases by 0.05 Å to 0.5 Å in the R space range of 1 Å to 4 Å. The atoms bonded to the central metal atom by the ligand are generally Cl, O, C, or N atoms. The cluster catalyst activated by promoter component B shows enhanced alkylation behavior, decreased absorption shoulder peak intensity, and enhanced signal transition from X-ligand to X-CH3 in XPS. The central metal element in the main catalyst component A of the cluster catalyst activated by promoter component B exhibits a double-peak signal in room-temperature electron paramagnetic resonance (EPR) testing, with a magnetic field strength between 345-365 mT and a g-factor between 1.96 and 2.10.

[0009] The central metal element of the main catalyst component A is selected from one or more of Ti(Ⅲ), Ti(Ⅳ), Ti(Ⅴ), V(Ⅳ), V(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).

[0010] The copolymerization modifier component D is selected from one or more siloxane organic compounds containing a Si-O-Si structure, and the main structure is one or more of planar, cage-like, semi-cage-like, conical, and trapezoidal types.

[0011] The cluster structure formed by the copolymerization modifier and the main catalyst can stabilize the active center, avoiding the problems of unstable release of activity and difficulty in controlling exothermic reactions in the early stage during polymerization, while also exhibiting better high-temperature stability. On the other hand, the interaction between the modifier and the active center of the main catalyst can regulate the steric hindrance and electronic effects of the ligand structure around the active center, creating different polymerization microenvironments for ethylene / α-olefin copolymerization, creating more favorable conditions for α-olefin insertion, and improving the α-olefin insertion rate.

[0012] Another advantage of this invention is that, while ensuring polymerization activity and α-olefin insertion rate, a more economical mixture of alkyl aluminum and methylaluminoxane (MAO) or modified methylaluminoxane (MMAO) can be used as a co-catalyst, avoiding the complete use of large quantities of expensive methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), which is of positive significance for reducing production costs.

[0013] As a preferred embodiment of the present invention, the ethylene / α-olefin copolymerization process based on the above-mentioned cluster catalytic system is as follows: The polymerization reactor is baked in a vacuum environment at at least 100 °C for 2-4 h. During the baking process, high-purity nitrogen or argon is switched at least 10 times. After the baking process, an appropriate amount of polymerization solvent E and comonomer α-olefin F are added and stirred for at least 10 min. When the reactor reaches the reaction temperature T, a certain amount of cocatalyst component B is added to remove impurities and prepare for subsequent activation of the main catalyst. Finally, a quantitative amount of the prepared cluster catalyst S is added, and ethylene is immediately introduced to carry out the copolymerization reaction. The polymerization pressure is P, and after a reaction time t, the polymerization product is discharged and the product is characterized.

[0014] As a preferred embodiment of the present invention, the ethylene / α-olefin copolymerization activity based on the above-mentioned cluster catalytic system is improved by at least 20%, the α-olefin insertion rate is improved by 2%-10%, the 1-octene reactivity r2 is improved by 10%-100%, the thermal stability is improved by more than 5°C, and the amount of methylaluminoxane MAO or modified methylaluminoxane MMAO used is reduced by 20%-60%.

[0015] In a preferred embodiment of the present invention, the pure solvent component C and the polymerization solvent E are selected from one or more alkanes, cycloalkanes, and benzenes, wherein the alkane solvent is C5-C6. 30 Saturated alkanes, C5-C 30 Alicyclic hydrocarbons, C5-C 30 Aromatic hydrocarbons, C5-C 30 One or more of saturated heterocyclic hydrocarbons or paraffin oils. The polymerization solvent E and the pure solvent component C can be the same component or different components.

[0016] In a preferred embodiment of the present invention, the concentration of the main catalyst component A in the pure solvent component C is 500-1000 μmol / ml, preferably 500-800 μmol / ml; the molar ratio of the main catalyst component A to the copolymerization modifier component D is 1:500-500:1, preferably 1:1.1-200:1; and the molar ratio of the main catalyst component A to the co-catalyst component B is 1:1-1:2000, preferably 1:1.1-1:500.

[0017] In a preferred embodiment of the present invention, the cocatalyst component B is one or more of alkylaluminum compounds, alkyllithium compounds, alkylzinc compounds, alkylboron compounds, modified alkylaluminum compounds, and borides.

[0018] In a preferred embodiment of the present invention, the ratio of the organic co-catalyst to the main catalyst component A, calculated as the molar ratio of Al to M (the active center element of the main catalyst, Al / M), is 1-2000, preferably 1.1-500; preferably, the ratio of the boriding agent to the metallocene catalyst, calculated as the molar ratio of B to M, is 1-2000, preferably 1.1-500; preferably, the amount of the main catalyst added, calculated as the molar concentration of M in the ultra-dry solvent component, is 1-200 μmol / L.

[0019] In a preferred embodiment of the present invention, the comonomer F is selected from one or more α-olefins, such as propylene, 1-butene, 1-decene, 4-methyl-1-decene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-eicosene, dicyclodecadiene, 1,4-butadiene, 1,5-decadiene, 1,6-hexadiene, styrene, α-methylstyrene, or divinylbenzene.

[0020] In a preferred embodiment of the present invention, the polymerization reaction temperature is selected from 0-250 ℃, preferably 50-200 ℃; the polymerization pressure is selected from 0-50 MPa, preferably 0.3-10 MPa; and the polymerization reaction stirring speed is 50-400 r / min, preferably 150-250 r / min.

[0021] In a preferred embodiment of the present invention, the insertion rate of the comonomer α-olefin is 0.1-35%, preferably 5-25%; the molecular weight of the copolymer is 10,000-300,000 g / mol, preferably 50,000-250,000 g / mol; and the density of the copolymer is 0.850-0.920 g / cm³. 3 The preferred concentration is 0.850-0.905 g / cm³. 3 Light transmittance is 90%-99%, preferably 93%-99%.

[0022] The present invention has the following outstanding gain effects: 1. The cluster structure formed by the copolymerization modifier and the main catalyst of this invention can stabilize the active center, avoid the problem of unstable release of activity and difficulty in controlling the early exothermic reaction during polymerization, and at the same time exhibit better high-temperature stability.

[0023] 2. The interaction between the auxiliaries and the active center of the main catalyst in this invention can regulate the molecular configuration of the main catalyst, change the electronic effects of the central metal atom, the bond length, bond angle and steric hindrance with adjacent ligands, create different polymerization microenvironments for ethylene / α-olefin copolymerization, thereby regulating the copolymerization behavior of ethylene / α-olefin, creating more convenient conditions for the insertion of α-olefin, and improving the insertion rate of α-olefin.

[0024] 3. Under the premise of ensuring polymerization activity and α-olefin insertion rate, a more economical mixture of alkyl aluminum and methylaluminoxane (MAO) or modified methylaluminoxane (MMAO) can be used as a co-catalyst, avoiding the use of large quantities of expensive methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), which is of positive significance for reducing production costs.

[0025] 4. Based on the above cluster catalytic system, the ethylene / α-olefin copolymerization activity is improved by at least 20%, the α-olefin insertion rate is improved by 2%-10%, the octene reactivity ratio r2 is improved by 10%-100%, the thermal stability is improved by more than 20℃, and the amount of methylaluminoxane MAO or modified methylaluminoxane MMAO used is reduced by 20%-80%. Attached Figure Description

[0026] Figure 1 This is a comparison of polymerization kinetics curves between non-clustered and clustered catalytic systems. Figure 2 The high-temperature carbon NMR resonance NMR pair of the copolymer of the non-clustered catalytic system and the clustered catalytic system is shown. Figure 3 A comparison of the copolymer composition curves of non-clustered catalytic systems and clustered catalytic systems; Figure 4 This is a schematic diagram of a cluster catalytic system; Figure 5 For the fine structure spectrum of X-ray absorption spectroscopy for different catalyst systems in R space; Figure 6 The K absorption edge of the fine structure X-ray absorption spectra of different catalyst systems; Figure 7 Comparison of electron paramagnetic resonance (EPR) results of cluster catalyst S after activation with alkylaluminum and borane at different concentrations. Detailed Implementation

[0027] The preferred embodiments of the present invention will be described in more detail below, further elaborating and illustrating the invention. These embodiments are merely illustrative and do not limit the scope of the invention. Unless otherwise specified, all materials, reagents, and instruments used in the examples below were purchased from commercially available sources; unless otherwise specified, the experimental methods used in the examples are conventional methods; and unless otherwise specified, all concentrations in the examples are molar concentrations.

[0028] Example 1: The copolymerization modifier component D is shown in Formula 1-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Ti(IV), where R is n-pentyl.

[0029] Preparation of cluster catalyst S: Take 250 μmol of copolymerization modifier D as shown in Formula 1-1 and 10 mmol of main catalyst component A in 20 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 2 h. All the above preparation operations are carried out in a glove box filled with inert gas. The obtained cluster catalyst S is reserved for ethylene-octene copolymerization for later use. Equation 1-1 Equation 1-2 A 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, during which it was purged with inert gas at least 20 times. After baking, 300 mL of heptane, the polymerization solvent, was added to the reactor, followed by 120 mL of octene. Then, 300 μmol of trioctylaluminum was added and stirred for at least 2 min to remove impurities from the reactor. 200 μmol of methylaluminoxane and 10 μmol of organoboronide were added as cocatalysts. Finally, 2 μmol of cluster catalyst S (the molar amount of cluster catalyst S was calculated from the content of the main catalyst component A) was added. Ethylene was then introduced to carry out the copolymerization reaction at a polymerization pressure of 4.0 MPa, a polymerization temperature of 140 °C, and a polymerization time of 10 min. The polymerization product was sprayed under high pressure and its properties were analyzed. The analysis results of the polymerization product are shown in Table 1.

[0030] Example 2: The copolymerization modifier component D is shown in Formula 1-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Ti(IV), where R is n-pentyl.

[0031] Preparation of cluster catalyst S: Take 250 μmol of copolymerization modifier D as shown in Formula 1-1 and 10 mmol of main catalyst component A in 16.5 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 2 h. All the above preparation operations are carried out in a glove box filled with inert gas. The obtained cluster catalyst S is reserved for ethylene-octene copolymerization for later use.

[0032] The polymerization experiment was the same as in Example 1, and the analysis results of the polymerization product are shown in Table 1.

[0033] Example 3: The copolymerization modifier component D is shown in Formula 1-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Ti(IV), where R is n-pentyl.

[0034] Preparation of cluster catalyst S: Take 250 μmol of copolymerization modifier D as shown in Formula 1-1 and 10 mmol of main catalyst component A in 12.5 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 2 h. All the above preparation operations are carried out in a glove box filled with inert gas. The obtained cluster catalyst S is reserved for ethylene-octene copolymerization for later use.

[0035] The polymerization experiment was the same as in Example 1, and the analysis results of the polymerization product are shown in Table 1.

[0036] Example 4: The copolymerization modifier component D is shown in Formula 1-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Ti(IV), where R is n-pentyl.

[0037] Preparation of cluster catalyst S: Take 250 μmol of copolymerization modifier D as shown in Formula 1-1 and 10 mmol of main catalyst component A in 10 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 2 h. All the above preparation operations are carried out in a glove box filled with inert gas. The obtained cluster catalyst S is reserved for ethylene-octene copolymerization for later use.

[0038] The polymerization experiment was the same as in Example 1, and the analysis results of the polymerization product are shown in Table 1.

[0039] Example 5: The copolymerization modifier D component is shown in Formula 1-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Ti(IV), where R is n-pentyl.

[0040] The preparation process and polymerization experiment of the cluster catalyst S were the same as in Example 2, except that the polymerization temperature was 150℃. The analysis results of the polymerization product are shown in Table 1.

[0041] Example 6: The copolymerization modifier component D is shown in Formula 1-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Ti(IV), where R is n-pentyl.

[0042] The preparation process and polymerization experiment of the cluster catalyst S were the same as in Example 2, except that the polymerization temperature was 160℃. The analysis results of the polymerization product are shown in Table 1.

[0043] Example 7: The copolymerization modifier D component is shown in Formula 2-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Zr(IV), where R is n-pentyl.

[0044] Preparation of cluster catalyst S: Take 500 μmol of copolymerization modifier D as shown in Formula 2-1 and 10 mmol of main catalyst component A in 16.5 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 2 h. All the above preparation operations are carried out in a glove box filled with inert gas. The obtained cluster catalyst S is reserved for ethylene-hexene copolymerization for later use. Equation 2-1 A 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, during which it was purged with inert gas at least 20 times. After baking, 250 mL of polymerization solvent hexane was added to the polymerization reactor, followed by 90 mL of hexene, and then 300 μmol of trioctylaluminum was added and stirred for at least 2 min to remove impurities from the polymerization reactor. 200 μmol of co-catalyst component methylaluminoxane and 10 μmol of organoboronide were added, and finally 2 μmol of cluster catalyst S (the molar amount of cluster catalyst S was calculated from the content of main catalyst component A) was added. Ethylene was then introduced to carry out the copolymerization reaction at a polymerization pressure of 3.5 MPa, a polymerization temperature of 140 °C, and a polymerization time of 10 min. The polymerization product was sprayed under high pressure and its performance was analyzed. The analysis results of the polymerization product are shown in Table 1.

[0045] Example 8: The copolymerization modifier D component is shown in Formula 3-1, and the ligand structure of the main catalyst component A is shown in Formula 3-2, with the central metal atom being Hf(IV), where R is n-pentyl.

[0046] Preparation of cluster catalyst S: Take 250 μmol of copolymerization modifier D as shown in Formula 3-1 and 10 mmol of main catalyst component A in 16.5 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 2 h. All the above preparation operations are carried out in a glove box filled with inert gas. The obtained cluster catalyst S is reserved for ethylene-octene copolymerization for later use. Equation 3-1 Equation 3-2 A 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, during which it was purged with inert gas at least 20 times. After baking, 400 mL of the polymerization solvent toluene was added to the polymerization reactor, followed by 150 mL of heptene, and then 300 μmol of trioctylaluminum was added and stirred for at least 2 min to remove impurities from the polymerization reactor. 200 μmol of the co-catalyst component methylaluminoxane and 10 μmol of organoboronide were added, and finally 2 μmol of cluster catalyst S (the molar amount of cluster catalyst S was calculated from the content of the main catalyst component A) was added. Ethylene was then introduced to carry out the copolymerization reaction at a polymerization pressure of 3.0 MPa, a polymerization temperature of 140 °C, and a polymerization time of 10 min. The polymerization product was sprayed under high pressure and its performance was analyzed. The analysis results of the polymerization product are shown in Table 1.

[0047] Example 9: The copolymerization modifier D component is shown in Formula 4-1, and the ligand structure of the main catalyst component A is shown in Formula 3-2, with the central metal atom being Co(III), where R is n-pentyl.

[0048] Preparation of cluster catalyst S: Take 250 μmol of copolymerization modifier D as shown in Formula 4-1 and 10 mmol of main catalyst component A in 16.5 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 2 h. All the above preparation operations are carried out in a glove box filled with inert gas. The obtained cluster catalyst S is reserved for ethylene-octene copolymerization for later use. Equation 4-1 A 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, during which it was purged with inert gas at least 20 times. After baking, 400 mL of heptane, the polymerization solvent, was added to the reactor, followed by 200 mL of octene. Then, 300 μmol of trioctylaluminum was added and stirred for at least 2 min to remove impurities from the reactor. 200 μmol of methylaluminoxane and 10 μmol of organoboronide were added as cocatalysts. Finally, 2 μmol of cluster catalyst S (the molar amount of cluster catalyst S was calculated from the content of the main catalyst component A) was added. Ethylene was then introduced to carry out the copolymerization reaction at a polymerization pressure of 2.5 MPa, a polymerization temperature of 140 °C, and a polymerization time of 10 min. The polymerization product was sprayed under high pressure and its properties were analyzed. The analysis results of the polymerization product are shown in Table 1.

[0049] Comparative Example 1: The ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Ti(IV), where R is n-pentyl.

[0050] The 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, and purged with inert gas at least 20 times during the baking process. After baking, 300 mL of polymerization solvent heptane was added to the polymerization reactor, followed by 120 mL of octene, and then 300 μmol of trioctylaluminum was added and stirred for at least 2 min to remove impurities from the polymerization reactor. 200 μmol of cocatalyst component methylaluminoxane and 10 μmol of organoboronide were added, and finally 2 μmol of main catalyst component A was added. Ethylene was then introduced to carry out the copolymerization reaction. The polymerization pressure was 4.0 MPa, the polymerization temperature was 140 °C, and the polymerization time was 10 min. The polymerization product was sprayed under high pressure and the product performance was analyzed. The analysis results of the polymerization product are shown in Table 1.

[0051] Comparative Example 2: The ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Zr(IV), where R is n-pentyl.

[0052] The 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, and purged with inert gas at least 20 times during the baking process. After baking, 250 mL of polymerization solvent hexane was added to the polymerization reactor, followed by 90 mL of hexene, and then 300 μmol of trioctylaluminum was added and stirred for at least 2 min to remove impurities from the polymerization reactor. 200 μmol of cocatalyst component methylaluminoxane and 10 μmol of organoboronide were added, and finally 2 μmol of main catalyst component A was added. Ethylene was then introduced to carry out the copolymerization reaction. The polymerization pressure was 3.5 MPa, the polymerization temperature was 140 °C, and the polymerization time was 10 min. The polymerization product was sprayed under high pressure and the product performance was analyzed. The analysis results of the polymerization product are shown in Table 1.

[0053] Comparative Example 3: The ligand structure of the main catalyst component A is shown in Formula 3-2, with the central metal atom being Hf(IV), where R is n-pentyl.

[0054] A 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, during which it was purged with inert gas at least 20 times. After baking, 400 mL of the polymerization solvent toluene was added to the polymerization reactor, followed by 150 mL of heptene, and then 300 μmol of trioctylaluminum was added and stirred for at least 2 min to remove impurities from the polymerization reactor. 200 μmol of the co-catalyst component methylaluminoxane and 10 μmol of organoboronide were added, and finally 2 μmol of the main catalyst component A was added. Ethylene was then introduced to carry out the copolymerization reaction. The polymerization pressure was 3.0 MPa, the polymerization temperature was 140 °C, and the polymerization time was 10 min. The polymerization product was sprayed under high pressure and the product performance was analyzed. The analysis results of the polymerization product are shown in Table 1.

[0055] Comparative Example 4: The ligand structure of the main catalyst component A is shown in Formula 3-2, with the central metal atom being Co(III), where R is n-pentyl.

[0056] A 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, during which it was purged with inert gas at least 20 times. After baking, 400 mL of heptane, the polymerization solvent, was added to the reactor, followed by 200 mL of octene. Then, 300 μmol of trioctylaluminum was added and stirred for at least 2 min to remove impurities from the reactor. 200 μmol of methylaluminoxane and 10 μmol of organoboronide were added as cocatalysts. Finally, 2 μmol of the main catalyst component A was added, and ethylene was introduced to carry out the copolymerization reaction. The polymerization pressure was 2.5 MPa, the polymerization temperature was 140 °C, and the polymerization time was 10 min. The polymerization product was sprayed under high pressure and its properties were analyzed. The analysis results of the polymerization product are shown in Table 1.

[0057] Comparative Example 5: The copolymerization modifier component D is shown in Formula 1-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2, with the central metal atom being Ti(IV), where R is n-pentyl.

[0058] Preparation of cluster catalyst S: Take 2.5 μmol of copolymerization modifier D as shown in Formula 1-1 and 100 μmol of main catalyst component A in 10 mL of toluene solution to form a homogeneous solution. Keep the homogeneous solution under stirring at 250 rpm for at least 2 h. All the above preparation operations are carried out in a glove box filled with inert gas. The obtained cluster catalyst S is reserved for ethylene-octene copolymerization for later use.

[0059] The difference between this comparative example and Examples 1-4 is that in the cluster catalyst S of Examples 1-4, the concentration of the main catalyst component A in the pure solvent component C is 500-1000 μmol / ml, while in the cluster catalyst S of this comparative example, the concentration of the main catalyst component A in the pure solvent component C is 10 μmol / ml, which is much lower than the concentration range in the examples. However, the molar dosage of the main catalyst component A in the polymerization experiment is exactly the same in this comparative example and Examples 1-4. The polymerization experiment is the same as in Example 1, and the analysis results of the polymerization product are shown in Table 1.

[0060] Comparative Example 6: A 1.2 L copolymerization reactor was baked at high temperature (above 130 °C) and under vacuum for at least 2 h, during which it was purged with inert gas at least 20 times. After baking, 300 mL of heptane, the polymerization solvent, was added to the reactor, followed by 120 mL of octene. Then, 300 μmol of methylaluminoxane was added and stirred for at least 2 min to remove impurities from the reactor. 700 μmol of the co-catalyst component methylaluminoxane and 10 μmol of organoboronide were added, and finally, 2 μmol of cluster catalyst S (the molar amount of cluster catalyst S was calculated from the content of the main catalyst component A) was added. Ethylene was then introduced to carry out the copolymerization reaction at a polymerization pressure of 4.0 MPa, a polymerization temperature of 140 °C, and a polymerization time of 10 min. The polymerization product was sprayed under high pressure and its performance was analyzed. The analysis results of the polymerization product are shown in Table 1.

[0061] Comparative Example 7: The main catalyst is modified by using other copolymerization modifiers not included in this invention. The modifier component D is shown in Formula 5-1, and the ligand structure of the main catalyst component A is shown in Formula 1-2. The central metal atom is Ti(IV), and R is n-pentyl. Formula 5-1 The cluster catalyst S was prepared in the same manner as in Example 2.

[0062] The polymerization experiment was the same as in Example 1, and the analysis results of the polymerization product are shown in Table 1.

[0063] Performance testing Molecular weight and molecular weight distribution test The molecular weight (Mw, Mn) and molecular weight distribution (PDI) of the polymer can be determined by high-temperature gel permeation chromatography (GPC). A polymer solution of 0.1–0.3 wt% was prepared at 160 °C using 1,2,4-trichlorobenzene as the solvent, and the determination was performed using narrowly distributed polystyrene (PS) as the standard.

[0064] density The density of a polymer can be determined using a density gradient column. After degassing the melt index sample, it is cut into 1 mm cylinders and dropped into the density gradient column. Once the 1 mm cylinders have stabilized, the density gradient column reading is taken, and the polymer density is calculated by a computer program.

[0065] Melt index The melt mass flow rate of the material can be determined using a melt flow indexer. The flow characteristics of the test sample were determined at a temperature of 190 °C and a standard load of 2.16 kg.

[0066] Comonomer insertion rate The average composition of the copolymer comonomers was determined using a high-temperature carbon NMR spectrometer at 125 °C. The polymer was prepared into a 10% (w / w) solution of deuterated o-dichlorobenzene at 150 °C and dissolved for 3 to 4 hours, with shaking every half hour to ensure homogenization. Instrument parameters were optimized as follows: pulse angle 90°, reverse proton decoupling, pulse delay time 8 s, collection time 1.3 s, and spectral width 8000 Hz. An average of at least 5000 scans were performed.

[0067] Light transmittance, haze The films required for transmittance and haze performance testing were obtained through hot pressing, with an average film thickness of 400 μm. Transmittance and haze measurements were performed using a transmittance and haze meter.

[0068] Table 1 Summary of analytical results of products from examples and comparative examples The above are the analysis and characterization results of the polymerization systems of Examples 1-9 and Comparative Examples 1-6, as well as the ethylene / α-olefin copolymer products.

[0069] By comparing the polymerization activities of Examples 1-4 and Comparative Example 1, as well as Examples 7-9 and Comparative Examples 2-4, it can be found that the polymerization activity of the cluster catalyst system based on different active centers is more than twice that of the original catalyst system. By comparing the comonomer insertion rates of Examples 1-4 and Comparative Example 1, and Comparative Examples 7-9 and Comparative Examples 2-4, and the appendix to this specification, Figure 2 The high-temperature carbon NMR spectrum of the products clearly shows that the product chain composition and distribution of the cluster catalytic system are significantly different from those of the original catalytic system, and the comonomer insertion ability of the products in the cluster catalytic system is significantly enhanced. By comparing the transmittance and density of Examples 1-4 and Comparative Examples 1-2, the copolymer products of the cluster catalytic system have the characteristics of higher transmittance and lower haze, and have significant advantages in optical performance. Comparing Examples 1-4 and Comparative Example 5, it can be seen that although the molar amount of the main catalyst added is exactly the same, the catalyst concentration has a significant impact on the activity of the cluster catalytic system. The catalyst system with a higher concentration (Examples 1-4) exhibits relatively higher activity, while the catalyst system with a lower concentration (Comparative Example 5) shows lower activity during polymerization. However, due to the influence of the solubility of each component, a higher concentration is not always better. Higher concentrations may lead to component analysis, causing the polymerization to change from homogeneous solution polymerization to heterogeneous polymerization, resulting in a decrease in activity. Additionally, [further details omitted]. Figure 7The electron paramagnetic resonance (EPR) results of Examples 1-4 and Comparative Example 5 after activation with alkylaluminum and borane are compared. It can be clearly seen that within the concentration range of the present invention, compared with the low configuration concentration (the concentration of the main catalyst component A in the cluster catalyst S in the pure solvent component C is 10 μmol / ml), the EPR signal is stronger, indicating that the activation process is more thorough and more trivalent titanium active centers are generated.

[0070] By comparing Example 2 and Comparative Example 6, it can be seen that, while ensuring polymerization activity and comonomer insertion rate, the present invention can significantly reduce the amount of methylaluminoxane and use lower-cost alkylaluminum for impurity removal, thus significantly improving economic efficiency. By comparing Example 1, Examples 5-6 and Comparative Example 1, it can be found that the interaction between the auxiliary component and the active center can improve the high-temperature stability of the active center. Although the activity decreased slightly when the polymerization temperature was increased by 20°C, it was still better than the non-clustered catalyst system. By comparing Example 2 with Comparative Example 1 and Comparative Example 7, it can be found that the use of siloxane compound auxiliary component D, which is not part of this invention, has a very limited effect on improving polymerization activity and product performance. In addition to the above examples and comparative examples, the inventors also conducted experiments with different ethylene-octene feed ratios on the two catalytic systems used in Example 1 and Comparative Example 1. The polymerization reactivity ratios of the two catalytic systems were obtained through copolymer composition equations and linear regression. The obtained polymerization reactivity ratio data were then extrapolated to obtain the following... (See attached...) Figure 3 Comparison of copolymer composition curves, where the 1-octene polymerization rate r in the cluster catalytic system of Example 1 is shown. 2团簇 =0.121; the 1-octene polymerization rate r in the non-clustered catalytic system of Comparative Example 1 2非团簇 =0.066, an increase of 83.3%; X-ray absorption fine structure spectroscopy (XAFS) studies of clustered and non-clustered catalysts revealed that the introduced promoter component D interacted significantly with the metal active center, altering the original catalyst's molecular structure. The bond length of the M-ligand changed markedly, and the molecular structure shifted towards a direction more favorable for comonomer insertion. (See appendix) Figure 5 Compared to non-clustered catalysts, clustered catalysts, after activation with alkylaluminum, show a clear transformation in the K absorption edge of the active center. It is evident that the introduced copolymerization modifier promotes the methylation process of the active center, which is beneficial for the release of activity. Taking metallocene catalysts containing Ti-Cl groups as an example, the change in the absorption edge around 4978 eV manifests as a transformation from Ti-Cl to Ti-CH3 (see appendix). Figure 6 ); In addition to the embodiments described above, this invention has many other embodiments, which are described in more specific and detailed manner, but should not be construed as limiting the scope of this invention. Without departing from the concept and essence of this invention, those skilled in the art can make certain changes and improvements based on this invention, and these changes should all fall within the protection scope of the claims of this invention.

Claims

1. An ethylene / α-olefin copolymer cluster catalytic system, characterized in that, It comprises a main catalyst component A, a co-catalyst component B, a pure solvent component C, and a copolymerization modification auxiliary component D; wherein the auxiliary component D is selected from one or more siloxane organic compounds containing a Si-O-Si structure, and forms a cluster catalyst with the main catalyst component A in the form of coordination complexation, supramolecular assembly, or covalent bond; The main catalyst component A and the copolymerization modifier component D are dissolved in the pure solvent component C, and stirred for at least 100 min under an inert gas environment to obtain the clustered catalyst S. The concentration of the main catalyst component A in the pure solvent component C is 500-1000 μmol / ml. By modifying the main catalyst A with the copolymerization modifier component D, the molecular configuration of the main catalyst component A is regulated, and the electronic effect of the central metal atom, the bond length, bond angle and steric hindrance with the adjacent ligands are changed, thereby regulating the copolymerization behavior of ethylene / α-olefin. Cluster catalyst S and co-catalyst component B are placed separately to form the ethylene / α-olefin copolymer cluster catalytic system.

2. The ethylene / α-olefin copolymer cluster catalytic system according to claim 1, characterized in that, The interaction between the auxiliary component D and the main catalyst component A resulted in a ligand-X bond length increase of 0.05 Å to 0.5 Å in the R space of the X-ray absorption fine structure spectrum within the range of 1 Å to 4 Å, where X is a central metal atom. The central metal element in the main catalyst component A of the cluster catalyst activated by the co-catalyst component B showed a double-peak signal in the room temperature electron paramagnetic resonance test, with the magnetic field strength between 345-365 mT and the g factor between 1.96-2.

10.

3. The ethylene / α-olefin copolymer cluster catalytic system according to claim 1, characterized in that, The central metal element of the main catalyst component A is selected from one or more of Ti(Ⅲ), Ti(Ⅳ), Ti(Ⅴ), V(Ⅳ), V(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).

4. The ethylene / α-olefin copolymer cluster catalytic system according to claim 1, characterized in that, The main structure of the siloxane organic compound containing the Si-O-Si structure is planar, cage-like, semi-cage-like, conical, or trapezoidal.

5. The ethylene / α-olefin copolymerization cluster catalytic system and copolymerization method according to claim 1, characterized in that, The pure solvent component C is selected from one or more alkanes, cycloalkanes, and benzenes, wherein the alkane solvent is C5-C. 30 Saturated alkanes, C5-C 30 Alicyclic hydrocarbons, C5-C 30 Aromatic hydrocarbons, C5-C 30 One or more of saturated heterocyclic hydrocarbons or paraffin oils.

6. The ethylene / α-olefin copolymer cluster catalytic system according to claim 1, characterized in that, The concentration of the main catalyst component A in the pure solvent component C is 500-800 μmol / ml; the molar ratio of the main catalyst component A to the copolymerization modifier component D is 1:500-500:1; and the molar ratio of the main catalyst component A to the co-catalyst component B is 1:1-1:2000.

7. The ethylene / α-olefin copolymer cluster catalytic system according to claim 1, characterized in that, The cocatalyst component B is one or more of the following: alkylaluminum compounds, alkyllithium compounds, alkylzinc compounds, alkylboron compounds, modified alkylaluminum compounds, and borides.

8. A method for ethylene / α-olefin copolymerization based on the cluster catalytic system according to any one of claims 1-7, characterized in that, The copolymerization reactor is baked in a vacuum environment at 100 °C or above for at least 2 hours. During this period, the space inside the copolymerization reactor is replaced with an inert gas. After the required baking time is reached, the polymerization solvent E and comonomer F are added, and stirring is started. After the temperature reaches the preset temperature, the cocatalyst component B is added to remove impurities and prepare for the subsequent activation of the main catalyst. Then, the prepared homogeneous catalytic system S is added, and ethylene is introduced to start the copolymerization reaction.

9. The copolymerization method according to claim 8, characterized in that, The comonomer F is selected from one or more α-olefins, such as propylene, 1-butene, 1-decene, 4-methyl-1-decene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-eicosene, dicyclodecadiene, 1,4-butadiene, 1,5-decadiene, 1,6-hexadiene, styrene, α-methylstyrene, or divinylbenzene; the polymerization solvent E is selected from one or more alkanes, cycloalkanes, and benzenes, wherein the alkane solvent is one or more of C5-C30 saturated alkanes, C5-C30 alicyclic hydrocarbons, C5-C30 aromatic hydrocarbons, C5-C30 saturated heterocyclic hydrocarbons, or paraffin oil.

10. The copolymerization method according to claim 8, characterized in that, The polymerization temperature is selected from 0-250 ℃, and the polymerization pressure is selected from 0-50 MPa; in the prepared ethylene / α-olefin, the insertion rate of the α-olefin comonomer in the copolymer is 0.1-35%; the molecular weight of the copolymer is 10,000-300,000 g / mol; and the density of the copolymer is 0.850-0.920 g / cm³. 3 Light transmittance is 90%-99%.

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