A bimetallic compound, its preparation method and application

Abstract

This invention provides a bimetallic compound, its preparation method, and its applications. The bimetallic compound provided by this invention, through the design of including Cr and a Group IVB bimetal and specific ligands, exhibits excellent catalytic activity, high-temperature stability, and high α-olefin insertion rate in the reaction of ethylene polymerization to prepare polyolefin elastomers. The polyolefin elastomers obtained by catalysis have the advantages of high molecular weight and high 1-octene insertion rate, and can achieve a better balance between rigidity and toughness and resistance to low-temperature brittleness, and have good application prospects.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of olefin polymerization, and relates to a bimetallic compound and a preparation method and application thereof. BACKGROUND

[0002] Polyolefin materials are various and are widely used in people's daily life. However, with the development of society, traditional polyolefin materials cannot meet people's daily needs. Polyolefin materials develop towards the functional direction, and polyolefin elastomer (POE) is a kind of elastomer material mainly obtained by copolymerization of ethylene and alpha-olefin (such as 1-butene, 1-hexene, 1-octene, etc.), which combines the high elasticity of rubber and the processing performance of polyolefin plastic, and is widely used in the fields of automobiles, packaging materials, electric wires and cables, and medical devices.

[0003] At present, the process for producing POE in industry mainly comprises the following steps: adding monomer ethylene and comonomer alpha-olefin into a reactor, adding a certain amount of diluent to avoid polymer sticking, activating an auxiliary catalyst, and making the main metal catalyst catalyze the copolymerization of ethylene and alpha-olefin, and hydrogen can also be introduced as a molecular weight regulator to regulate the molecular weight of the polymer. After the copolymerization is completed, the polymer, diluent and monomer are separated. However, in the reported methods, high-carbon alpha-olefin is needed as a comonomer, and the cost of such monomer is high, which leads to high cost of industrial production of polyolefin elastomer.

[0004] Therefore, it is of great significance to avoid the use of high-carbon alpha-olefin and to prepare polyolefin elastomer with excellent performance only by using ethylene as a monomer. SUMMARY

[0005] The application provides a bimetallic compound, a preparation method thereof and application thereof in the field of olefin polymerization. The bimetallic compound provided by the application exhibits excellent catalytic activity, high-temperature stability and high alpha-olefin insertion rate in the reaction of preparing polyolefin elastomer by ethylene polymerization through the design of Cr and group IVB bimetal and specific ligands. The polyolefin elastomer catalyzed has the advantages of high molecular weight and high 1-octene insertion rate, can achieve better rigid-flexible balance and low-temperature cold brittleness resistance, and has good application prospect.

[0006] The first aspect of the application provides a bimetallic compound having the structure shown in formula I:

[0007] Formula I

[0008] In formula I, M is selected from group IVB metal; R1~R 14each independently selected from one of C1-C20 alkyl, C3-C20 cycloalkyl, C1-C20 alkoxy, C3-C20 cycloalkoxy, C1-C20 alkylamino, C3-C20 cycloalkylamino, hydrogen, halogen, aryl, aryloxy, arylamino; X is selected from one of methyl, chloro, dimethylamino, benzyl; Ar1, Ar2, Ar3are each independently selected from one of phenyl, C1-C6 alkyl-substituted phenyl, C1-C6 alkoxy-substituted phenyl, naphthyl, anthryl.

[0009] The bimetallic compound as described above, wherein R1-R 14 each independently selected from one of hydrogen, C1-C6 alkyl, C3-C10 cycloalkyl, benzhydryl, halogen, dibenzoheptanyl, fluorenyl, indenyl, anthryl;

[0010] Preferably, R1-R 14 each independently selected from one of hydrogen, tert-butyl, isopropyl, benzhydryl, halogen.

[0011] The second aspect of the present application provides a preparation method of the bimetallic compound as described above, comprising the following steps:

[0012] carrying out a first complexation reaction of the compound shown in formula II with MX4 to obtain a compound shown in formula III;

[0013] carrying out a second complexation reaction of the compound shown in formula III with chromium trichloride to obtain the compound shown in formula I;

[0014]

[0015] In formula II and formula III, R1-R 14 , Ar1, Ar2, Ar3, X1, X2, and M are defined the same as R1-R 14 , Ar1, Ar2, Ar3, X, and M are defined the same as R1-R

[0016] The third aspect of the present application provides an olefin polymerization catalyst, comprising a main catalyst and a cocatalyst, wherein the main catalyst comprises the bimetallic compound as described above.

[0017] The olefin polymerization catalyst as described above, wherein the cocatalyst comprises one or more of tris(pentafluorophenyl)boron, triphenylcarbenium tetrakis(pentafluorophenyl)borate, methylbis(octadecyl)ammonium tetrakis(pentafluorophenyl)borate, aluminoxane, alkylaluminum, and chloroalkylaluminum.

[0018] The olefin polymerization catalyst as described above, wherein the aluminoxane comprises one or more of methylaluminoxane, ethylaluminoxane, isobutylaluminoxane;

[0019] And / or, the aluminum alkyl includes one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum;

[0020] And / or, the aluminum alkyl includes one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum;

[0021] The olefin polymerization catalyst as described above, wherein the mole ratio of aluminum metal in the co-catalyst to the metal M and Cr in the main catalyst, Al / (Cr+M), is (1-5000):1, preferably (300-2000):1.

[0022] The fourth aspect of the present application provides a method for preparing a polyolefin elastomer, comprising: using the olefin polymerization catalyst provided by the third aspect of the present application to catalyze the polymerization reaction of ethylene monomers, to obtain a polyethylene elastomer.

[0023] The method for preparing as described above, wherein the temperature of the polymerization reaction is 0-250℃, the pressure is 0.1-5MPa, and the time is 2-120min.

[0024] Preferably, the temperature of the polymerization reaction is 140-220℃, the pressure is 1-5MPa, and the time is 10-60min.

[0025] The method for preparing as described above, wherein the solvent of the polymerization reaction includes one or more of toluene, hexane, heptane, Isopar E, and methylcyclohexane.

[0026] The implementation of the present application has at least the following advantages:

[0027] 1) The present application provides a bimetallic compound with Group IVB metal and Cr, wherein the Group IVB metal has good copolymerization activity of ethylene and α-olefin, and the metal Cr has good ethylene oligomerization activity. In the ethylene polymerization reaction, the metal Cr active center in the compound can promote the ethylene oligomerization to obtain α-olefins such as 1-butene, 1-hexene, and 1-octene, and the active center of the Group IV metal is conducive to promoting the copolymerization of the generated α-olefin and ethylene, thereby obtaining α-olefin-inserted polyolefin elastomers. In addition, the present application also designs a specific ligand structure around the bimetallic active center of the Group IVB metal and Cr, so that the metal M and the metal Cr active center have a suitable distance, which is conducive to the diffusion of the oligomers formed near the Cr to the vicinity of the M metal active to participate in the copolymerization with ethylene, so that the rates of oligomerization and copolymerization reach a higher balance, which is beneficial to the insertion of the oligomers. The rigid structure of the pyridine ring and the benzene ring containing substituents in the ligand not only enhances the stability of the bimetallic compound by using the rigid structure to make the bimetallic compound maintain good activity in high-temperature solution polymerization, but also regulates the electron cloud density of the metal active center through electronic effect and steric hindrance effect, thereby enhancing the catalytic activity of the bimetallic catalyst.

[0028] 2) The olefin polymerization catalyst provided by the present application has a main catalyst comprising the above-mentioned bimetallic compound with good thermal stability, high α-olefin insertion activity, and polymerization activity, so that the olefin polymerization catalyst applied to the preparation of high-molecular-weight, highly branched polyolefin elastomers from ethylene as a raw material exhibits excellent catalytic activity and thermal stability.

[0029] 3) The preparation method of the polyolefin elastomer provided by the present application, since the high-catalytic-activity, high-α-olefin-insertion-selectivity, and high-stability olefin polymerization catalyst is used to catalyze the polymerization reaction of ethylene, the prepared polyolefin elastomer has the advantages of high branching and high molecular weight, and the 1-octene insertion rate of the prepared polyolefin elastomer is as high as 40% or more, which exhibits excellent mechanical properties and low-temperature cold brittleness resistance. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0031] Definitions and explanations of terms :

[0032] Unless otherwise explained, all technical and scientific terms herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It is to be understood that the foregoing description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed. In this application, the use of "including" as well as other forms such as "comprising," "containing" and "having" are intended to cover a non-exclusive inclusion such that the process, method, article, composition or apparatus that comprises such elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, composition or apparatus.

[0033] The term "Group IVB metal" refers to a metal located in Group IVB of the Periodic Table of the Elements, including titanium (Ti), zirconium (Zr), hafnium (Hf), and the like.

[0034] The term "C1-C20 alkyl" refers to a straight or branched chain saturated hydrocarbon group having from 1 to 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, sec-butyl, pentyl, neopentyl, hexyl, heptyl, nonyl, decyl, and the like.

[0035] The term "C3-C20 cycloalkyl" refers to a non-aromatic cyclic hydrocarbon group having from 3 to 20 ring carbon atoms and zero heteroatoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like.

[0036] The term "C1-C20 alkoxy" refers to a group consisting of an alkyl group having from 1 to 20 carbon atoms and an oxygen atom, such as methoxy, ethoxy, propoxy, butoxy, and the like.

[0037] The term "C3-C20 cycloalkoxy" refers to a group formed by a cycloalkyl group having from 3 to 20 carbon atoms attached to an oxygen atom, such as cyclopropoxy, cyclobutoxy, cyclopentoxy, cyclohexoxy, cycloheptoxy, cyclooctoxy, and the like.

[0038] The term "C1-C20 alkylamino" refers to a group formed by an alkyl group having from 1 to 20 carbon atoms attached to an amino group, such as methylamino, ethylamino, propylamino, butylamino, pentylamino, hexylamino, and the like.

[0039] The term "C3-C20 cycloalkylamino" refers to a group formed by a cycloalkyl group having from 3 to 20 carbon atoms attached to an amino group, such as cyclopropylamino, cyclobutylamino, cyclopentylamino, cyclohexylamino, and the like.

[0040] The term "halogen" refers to fluorine, chlorine, bromine, and iodine.

[0041] The term "aryl" refers to a group satisfying the 4n+2 aromatic ring system, preferably a monocyclic, bicyclic or tricyclic aryl group, such as phenyl, biphenyl, indenyl, naphthyl, fluorenyl, anthryl, and the like. The aryl group can also be optionally substituted by one or more substituents, forming different substituted phenyl groups. The substituents can be alkyl, alkoxy, cycloalkyl, halogen, and the like.

[0042] The term "aryloxy" refers to a radical formed from an aryl group attached to an oxygen atom, such as phenoxy. The hydrogen atoms on the aryl ring can also be replaced by other substituents, forming different substituted aryloxy groups. The other substituents can be alkyl, alkoxy, cycloalkyl, halogen, etc.

[0043] The term "arylamino" refers to a radical formed from an aryl group attached to an amino group, such as phenylamino. The hydrogen atoms on the aryl ring can also be replaced by other substituents, forming different substituted arylamino groups. The other substituents can be alkyl, alkoxy, cycloalkyl, halogen, etc.

[0044] Polyolefin elastomer (POE) is a polyolefin material obtained by copolymerization of ethylene and α-olefin. Due to the presence of both polyethylene crystalline segments and amorphous regions formed by random copolymerization of α-olefin and ethylene in the molecular chain, POE has both the thermoplasticity of plastic and the high elasticity of rubber. Its unique molecular structure and physical and chemical properties make polyolefin elastomer have excellent mechanical properties and aging resistance. At present, the preparation process of POE mainly uses metallocene catalyst to catalyze the solution coordination polymerization of ethylene and α-olefin. However, the cost of α-olefin is relatively high, resulting in high cost of industrial production of polyolefin elastomer. It is of great significance to avoid the use of high-carbon α-olefin and prepare polyolefin elastomer only with ethylene as a monomer.

[0045] In view of the above problems, the prior art usually regulates the reactivity of ethylene homopolymerization and copolymerization by using special catalysts to obtain polyethylene elastomer with certain branching and high molecular weight. The commonly used catalyst in this type of reaction is α-diimine nickel / palladium complex. This complex has a unique "chain walking" polymerization mechanism, which can adjust the branching density and type in the main chain structure of the polymer, and can realize the preparation of highly branched polyethylene elastomer with ethylene as a single monomer. Despite the above advantages, α-diimine nickel / palladium complex has poor thermal stability at high temperatures, especially α-diimine nickel catalyst, which is easily deactivated at temperatures above 60°C, limiting its industrial application. Therefore, how to design the structure of the catalyst to obtain a catalyst that can catalyze ethylene to prepare polyolefin elastomer with high branching degree and high molecular weight with good thermal stability is a technical problem to be solved by the present application.

[0046] Based on this, the first aspect of the present application is a bimetallic compound having the structure shown in formula I:

[0047] Formula I

[0048] In formula I, M is selected from the group consisting of Group IVB metals; R1~R 14each independently selected from one of C1-C20 alkyl, C3-C20 cycloalkyl, C1-C20 alkoxy, C3-C20 cycloalkoxy, C1-C20 alkylamino, C3-C20 cycloalkylamino, hydrogen, halogen, aryl, aryloxy, arylamino; X is selected from one of methyl, chloro, dimethylamino, benzyl; Ar1, Ar2, Ar3 are each independently selected from one of phenyl, C1-C6 alkyl-substituted phenyl, C1-C6 alkoxy-substituted phenyl, naphthyl, anthryl.

[0049] In formula I, " represents a coordination bond.

[0050] The present application uses specific ligand structure to make chromium metal and group IVB metal combine to form a bimetallic compound. In catalyzing ethylene polymerization, the Cr metal exhibits excellent ethylene oligomerization activity, which can promote the formation of oligomers such as 1-butene, 1-hexene, 1-octene, etc. from ethylene; and the group IVB metal exhibits excellent ethylene homopolymerization and copolymerization activity, which can promote the copolymerization of ethylene and the oligomers such as 1-butene, 1-hexene, 1-octene, etc. formed from the oligomerization, and further obtain polyolefin elastomer material with high α-olefin insertion rate.

[0051] In formula I, " represents a coordination bond.

[0050] The present application uses specific ligand structure to make chromium metal and group IVB metal combine to form a bimetallic compound. In catalyzing ethylene polymerization, the Cr metal exhibits excellent ethylene oligomerization activity, which can promote the formation of oligomers such as 1-butene, 1-hexene, 1-octene, etc. from ethylene; and the group IVB metal exhibits excellent ethylene homopolymerization and copolymerization activity, which can promote the copolymerization of ethylene and the oligomers such as 1-butene, 1-hexene, 1-octene, etc. formed from the oligomerization, and further obtain polyolefin elastomer material with high α-olefin insertion rate.

[0052] It can be understood that the types of substituents are important factors for adjusting the coordination environment, electronic effect and steric effect of the bimetallic compound. Through experimental research, it is found that R1-R 14Each of R1-R6 is independently hydrogen, C1-C6 alkyl, C3-C10 cycloalkyl, benzhydryl, halogen, dibenzoheptane, fluorenyl, indenyl, anthracenyl, and more preferably, each of R1-R6 is independently hydrogen, t-butyl, isopropyl, benzhydryl, halogen. When each of R1-R6 is independently hydrogen, t-butyl, isopropyl, benzhydryl, halogen, the bimetallic compound has higher catalytic activity in ethylene polymerization, and the polyolefin elastomer has higher comonomer insertion rate and higher molecular weight.

[0053] The second application of the application provides a preparation method of the bimetallic compound, comprising the following steps:

[0054] The compound shown in formula II is subjected to a first complexation reaction with MX4 to obtain a compound shown in formula III;

[0055] The compound shown in formula III is subjected to a second complexation reaction with chromium trichloride to obtain the compound shown in formula I;

[0056]

[0057] In formula II and formula III, R1-R6, Ar1, Ar2, Ar3, X and M have the same definitions as R1-R6, Ar1, Ar2, Ar3, X and M in the compound shown in formula I. 14 In formula II and formula III, R1-R6, Ar1, Ar2, Ar3, X and M have the same definitions as R1-R6, Ar1, Ar2, Ar3, X and M in the compound shown in formula I. 14 In formula II and formula III, R1-R6, Ar1, Ar2, Ar3, X and M have the same definitions as R1-R6, Ar1, Ar2, Ar3, X and M in the compound shown in formula I.

[0058] Based on the electronic orbital characteristics of Cr element and Group IVB element, the Group IVB metal can preferentially react with the phenolic hydroxyl group in the compound shown in formula II to obtain the compound shown in formula III, and then chromium trichloride is added to coordinate the Cr metal with the P atom in the compound shown in formula III to obtain the compound shown in formula I.

[0059] The source of the compound shown in formula II is not specifically limited in the application, and the compound can be prepared by reasonable design according to the conventional synthesis strategy in organic synthesis and in combination with the properties of different substituents.

[0060] In a specific embodiment, the compound shown in formula II can be prepared according to the following synthesis route:

[0061]

[0062] Referring to the above reaction formula, aniline compound a is reacted with hydrogen bromide to obtain an ammonium hydrobromide salt compound b, 2-bromomagnesium-1-methoxybenzene and Ar3MgBr are reacted with phosphorus tribromide to obtain compound c1, and Ar1MgBr and Ar2MgBr are reacted with phosphorus tribromide to obtain compound c2; the prepared compound b, compound c1 and compound c2 are reacted under the action of triethylamine to obtain compound d; then compound d is reacted with n-butyllithium reagent and triisopropyl borate to convert the bromine atom on compound d into a boronic acid group, and the preparation of intermediate e is completed.

[0063] Among them, 2-bromomagnesium-1-methoxybenzene, Ar3MgBr, Ar1MgBr and Ar2MgBr can be prepared by Grignard reaction.

[0064]

[0065] Referring to the above reaction formula, compound f and compound g are respectively reacted with benzyl chloride to protect the phenolic hydroxyl group, and then the obtained compound h and compound j are respectively reacted with n-butyllithium reagent and triisopropyl borate to convert the bromine atom on compound d into a boronic acid group, to obtain compound k and compound m respectively; then compound k, compound m and compound n are subjected to a coupling reaction to obtain compound o; compound o is brominated with liquid bromine to obtain compound p; then compound p is continuously reacted with n-butyllithium reagent and triisopropyl borate to convert the bromine atom into a boronic acid group, to obtain compound q; compound q is subjected to a coupling reaction with p-dibromobenzene, and the preparation of intermediate r is completed.

[0066]

[0067] Referring to the above reaction formula, intermediate r is subjected to a coupling reaction with intermediate e to obtain compound s; then compound s is subjected to catalytic hydrogenation under hydrogen condition, and the benzyloxy group is deprotected and reduced to a phenolic hydroxyl group, to obtain the compound shown in formula II.

[0068] The first complexation reaction and the second complexation reaction are both carried out under inert gas protection, such as nitrogen atmosphere.

[0069] In order to make the second complexation reaction proceed more smoothly, chromium trichloride tetrahydrofuran complex can be used to provide chromium trichloride reactant to the reaction. Compared with chromium trichloride, the complex formed by chromium trichloride and tetrahydrofuran has higher solubility in organic solvents, and can reduce the degradation of chromium trichloride in air and moisture, which is conducive to storage and use.

[0070] The first complexation reaction and the second complexation reaction can be carried out in an organic solvent. Specifically, the solvent of the first complexation reaction can be one or more of n-hexane, toluene, tetrahydrofuran, diethyl ether, butyl ether, isopropyl ether, and cyclopentyl methyl ether; and the solvent of the second complexation reaction can be one or more of dichloromethane, tetrahydrofuran, dioxane, and diethyl ether.

[0071] In a specific embodiment, the temperature of the first complexation reaction and the second complexation reaction can be -80-25℃; and the time of the first complexation reaction and the second complexation reaction can be 3-16h.

[0072] In a specific embodiment, the molar ratio of the compound of formula II to MX4 in the first complexation reaction is 1:(0.8-1.2), and the molar ratio of the compound of formula III to chromium trichloride in the second complexation reaction is 1:(0.8-1.2).

[0073] After the completion of the first complexation reaction and the second complexation reaction, a process of purifying the reaction system is further included.

[0074] After the completion of the first complexation reaction, the compound of formula III can be precipitated from the reaction solution, and thus the process of purifying the reaction system can be completed by filtration.

[0075] After the completion of the second complexation reaction, the reaction solution can be concentrated, and then crystallized at low temperature, so that the compound of formula I is precipitated, and the process of purifying the reaction system is completed.

[0076] The third aspect of the present application provides an olefin polymerization catalyst, which comprises a main catalyst and a cocatalyst, wherein the main catalyst comprises the bimetallic compound provided in the first aspect of the present application.

[0077] The main function of the main catalyst in the olefin polymerization catalyst is to provide active sites, so that the olefin monomers can form metal-carbon bonds at these sites, thereby initiating the polymerization reaction.

[0078] The olefin polymerization catalyst provided by the present application has a main catalyst comprising the bimetallic compound with good thermal stability, high α-olefin insertion activity and polymerization activity, and thus the olefin polymerization catalyst applied to the reaction for preparing a high molecular weight, highly branched polyolefin elastomer from ethylene as a raw material exhibits excellent catalytic activity and thermal stability.

[0079] The main function of the cocatalyst in the olefin polymerization catalyst is to reduce the metal in the main catalyst from a high oxidation state to a low oxidation state, so that the main catalyst is in an activated state.

[0080] The kind of the co-catalyst is not particularly limited in the present application, and can be selected from the co-catalysts commonly used in the field of olefin polymerization, including but not limited to one or more of triphenylphosphine boron, triphenylcarbenium tetrakis(pentafluorophenyl)borate, tetra(pentafluorophenyl)borate-methylbis(octadecyl)ammonium salt, aluminoxane, alkylaluminum and chloroalkylaluminum.

[0081] Compared with other types of co-catalysts, aluminoxane, alkylaluminum and chloroalkylaluminum have higher thermal stability and hydrolysis resistance, which is beneficial to prolong the service life of the catalyst and improve the efficiency of the polymerization reaction.

[0082] Specifically, the aluminoxane includes one or more of methylaluminoxane, ethylaluminoxane and isobutylaluminoxane; the alkylaluminum includes one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum and tri-n-hexylaluminum; and the chloroalkylaluminum includes one or more of dichlorodiethylaluminum, trichlorotriethylaluminum, hemi-dichlorodiethylaluminum and ethylaluminum dichloride.

[0083] In the present application, the combination of the main catalyst and the co-catalyst can be reasonably optimized within the above range to achieve precise control of the polymerization activity, selectivity, product molecular weight and its distribution, so as to obtain a polyolefin elastomer that meets specific needs.

[0084] The ratio of the main catalyst and the co-catalyst also has a significant impact on the efficiency of the polymerization reaction, the activity stability of the catalyst and the properties of the generated polymer. A proper co-catalyst can activate the main catalyst to the greatest extent and improve its activity. Generally, increasing the amount of the co-catalyst is beneficial to the generation of more active centers, and thus is beneficial to the increase of the polymer molecular weight, but too large co-catalyst concentration can also lead to the occurrence of chain transfer reaction, thereby leading to chain termination and being not conducive to the increase of the polymer molecular weight.

[0085] Based on the above considerations, the molar ratio of aluminum in the co-catalyst to the metals M and Cr in the main catalyst, Al / (Cr+M), is controlled to be (1~5000):1, preferably (300~2000):1.

[0086] For example, the molar ratio of Al / (Cr+M) can be 1:1, 1:300, 1:500, 1:1000, 1:1500, 1:2000, 1:2500, 1:3000, 1:3500, 1:4000, 1:4500, 1:5000 or a range formed by any two of the above molar ratios.

[0087] In a specific embodiment, when the co-catalyst is selected from boron-containing compounds such as triphenylboron, triphenylcarbenium tetrakis(pentafluorophenyl)borate, methylbis(octadecyl)ammonium tetrakis(pentafluorophenyl)borate, etc., the molar ratio of B element in the co-catalyst to M and Cr in the main catalyst, B / (Cr+M), is controlled to be (0.5-3):1, more preferably (0.8-1.5):1.

[0088] For example, the molar ratio of B / (Cr+M) can be 0.5:1, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1, or a range formed by any two of the above.

[0089] The fourth aspect of the present application provides a method for preparing a polyolefin elastomer, which comprises: using the olefin polymerization catalyst provided by the third aspect of the present application to catalyze the polymerization reaction of ethylene monomers, to obtain a polyolefin elastomer.

[0090] In the above preparation method, since the olefin polymerization catalyst with high catalytic activity, high α-olefin insertion selectivity, and high stability is used to catalyze the polymerization reaction of ethylene, the prepared polyolefin elastomer has the advantages of high branching and high molecular weight, and exhibits excellent mechanical properties and low-temperature cold brittleness resistance.

[0091] With the increase of the content of α-olefin and other comonomers in the polyolefin elastomer, the density and crystallization properties of the polyolefin elastomer gradually decrease, which is beneficial to obtain a polyolefin material that is lighter and more flexible. Compared with α-olefins such as 1-butene and 1-hexene, 1-octene segments are softer and can make the material lighter, and are more suitable for fields with higher requirements for the rigidity and toughness balance of the material. The preparation method of the present application can prepare a polyolefin elastomer with a 1-octene insertion rate of 40 wt% or higher by selecting a specific olefin polymerization catalyst and combining with specific polymerization conditions.

[0092] In a specific embodiment, the polymerization reaction temperature is 0-250°C, the pressure is 0.1-5 MPa, and the time is 2-120 min. The temperature, pressure, and time of the polymerization reaction can be adjusted within the above ranges according to the different requirements for the catalytic activity of the catalyst, the molecular weight, and the insertion rate of the product.

[0093] As mentioned above, the bimetallic compound provided by the present application has good thermal stability and can maintain good catalytic activity in high-temperature solution polymerization. High temperature and high pressure are beneficial to increasing the molecular motion speed and solubility of ethylene, so that more ethylene monomers can be dissolved in the reaction medium and the reaction rate is accelerated, which is beneficial to the improvement of the polymerization product and efficiency and the reduction of the production cost of the polyolefin elastomer. Therefore, the temperature of the polymerization reaction can be further preferably 140-220°C, the pressure can be 1-5 MPa, and the time can be 10-60 min within the above ranges, so that the reaction has high yield and efficiency.

[0094] For example, the temperature of the polymerization reaction can be 140°C, 160°C, 180°C, 200°C, 220°C, or a range formed by any two of the above values; the pressure of the polymerization reaction can be 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, or a range formed by any two of the above values; and the time of the polymerization reaction can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, or a range formed by any two of the above values.

[0095] The solvent for the polymerization reaction is not specifically limited in the present application and can be selected from the solvents commonly used in ethylene polymerization, including but not limited to one or more of toluene, hexane, heptane, Isopar E, and methylcyclohexane.

[0096] Hereinafter, the present application will be further described through specific examples.

[0097] 1. Reagent Description

[0098] In the following examples, the raw materials and reagents used are commercially available unless otherwise specified, and the specific information is shown in Table 1.

[0099] Table 1

[0100]

[0101] 2. Test Method

[0102] A. In the following examples, the compounds were characterized by nuclear magnetic resonance (Brucker ARX-400). 1 H NMR.

[0103] B. Molecular weight M w and molecular weight distribution M w of the polymers n were tested by PL-GPC220 at 150°C, using three PLgel 10 μm MIXED-B separation columns connected in series and 1,2,4-trichlorobenzene as the solvent.

[0104] C. Polymer glass transition temperature T g According to the DSC (2000) method;

[0105] D. The polymerization activity of the main catalyst was calculated according to the following formula: Polymerization activity = polymer mass / (metal content of catalyst x polymerization time).

[0106] E. The 1-octene insertion rate in the polymer was measured according to the method in the reference (Macromolecules 1999, 32, 3817) by high temperature 13 C. NMR test obtained at high temperature 13 C. NMR test obtained at 120 °C using Brucker DMX 300 MHz with 1,1,2,2,- tetrachloroethane as solvent, obtaining 13 C. NMR spectrum, after the spectrum, the 1-octene insertion rate in the polymer was calculated;

[0107] F. Tensile strength and elongation at break: determined according to GB / T 1040.1-2006.

[0108] Synthesis Example 1

[0109] Synthesis of compound 1, the synthesis route is as follows:

[0110]

[0111] 1) Under a nitrogen atmosphere, 3-bromoaniline (17.21 g, 100 mmol) was mixed with hydrogen bromide (8.09 g, 100 mmol) in 200 ml of diethyl ether, stirred at room temperature for 30 min, filtered to obtain the ammonium bromide salt;

[0112] 2) Under a nitrogen atmosphere, 2-bromomethoxybenzene (18.7 g, 100 mmol) was heated to reflux with magnesium chips (2.4 g, 100 mmol) in 300 ml of tetrahydrofuran for 3 h, filtered, and to the filtrate, phosphorus tribromide (13.5 g, 50 mmol) was added dropwise in an ice water bath, stirred at room temperature for 2 h, filtered, and the filtrate was concentrated under vacuum, supplemented with triethylamine 300 ml as solvent, added ammonium bromide salt (12.65 g, 50 mmol), stirred at room temperature for 30 min, filtered, and the filtrate was concentrated under vacuum to obtain a concentrated solution including intermediate compound 1-a;

[0113] 3) To the concentrated solution of intermediate compound 1-a, add tetrahydrofuran 300 ml as solvent, under ice water bath, add n-butyllithium in n-hexane solution (1.6 M) 33 mL dropwise, stir for 30 min at this temperature, add triisopropyl borate (9.4 g, 50 mmol) to the reaction system, stir for 5 h at room temperature, remove the solvent under vacuum, extract with water and ethyl acetate, dry and concentrate the separated organic phase, and then perform column chromatography separation (eluent: petroleum ether and ethyl acetate in a volume ratio of 1-30:1) to obtain 25.5 g of compound 1 with a yield of 81.5%.

[0114] Synthesis of compound 1 1 H NMR (400 MHz, CDCl3): δ 7.39 (t, 4H), 7.22-7.11 (m, 9H), 6.96 (dd, 4H), 6.84 (dd, 1H), 6.71 (s, 1H), 4.32 (s, 2H), 3.98 (s, 13H).

[0115] Synthesis Example 2

[0116] Synthesis of compound 2, the synthesis route is as follows:

[0117]

[0118] 1) Under a nitrogen atmosphere, mix 2-bromophenol (17.3 g, 100 mmol) and benzyl chloride (19 g, 150 mmol) in 200 mL of acetone, stir for 3 h at room temperature, remove the solvent under vacuum, add 100 mL of water, extract with 100 mL of ethyl acetate, separate the layers, and remove the ethyl acetate under vacuum to obtain a concentrated solution;

[0119] 2) To the concentrated solution of step 1), add tetrahydrofuran 200 mL, and under ice water bath, add n-butyllithium 68.8 mL dropwise, stir for 30 min, add triisopropyl borate (18.8 g, 100 mmol) under ice water bath, react for 3 h at room temperature, remove the solvent under vacuum to obtain a concentrated solution;

[0120] 2) To the concentrated solution of step 2), add ethylene glycol dimethyl ether 300 mL as solvent, add 2,6-dibromopyridine (11.8 g, 50 mmol), heat to reflux for 4 h, add bromine (4 g, 25 mmol), stir for 5 h at room temperature, remove the solvent under vacuum to obtain a concentrated solution;

[0121] 3) To the concentrated solution of step 3), add tetrahydrofuran 300 mL, drop in n-butyllithium 34 mL under ice water bath, stir for 30 min, add triisopropyl borate (9.4 g, 50 mmol) under ice water bath, react for 3 h at room temperature, remove the solvent under vacuum, add water 100 mL, add ethyl acetate 200 mL, extract and separate, dry and concentrate the separated organic phase, and then perform column chromatography separation (eluent: petroleum ether and ethyl acetate at a volume ratio of 1-30:1), to obtain 21.7 g of compound 2, with a yield of 87.3%.

[0122] Synthesis of compound 2 1 H NMR (400 MHz, CDCl3): δ 8.82 (d, 2H), 7.85 (dd, 1H), 7.41-7.22 (m, 15H), 6.74 (d, 2H), 5.16 (s, 4H), 4.26 (s, 2H).

[0123] Synthesis Example 3

[0124] Synthesis of compound 3, with the following synthesis route:

[0125]

[0126] Under a nitrogen atmosphere, mix compound 2 (48.7 g, 100 mmol) and p-dibromobenzene (23.6 g, 100 mmol) in 300 mL of ethylene glycol dimethyl ether, heat to reflux for 5 h, add compound 1 (100 mmol) to the reaction system, heat to reflux for 5 h, remove the solvent under vacuum, add ethanol 300 mL, add target carbon, pass in H2, react for 3 h at 4 MPa and 80°C, filter, remove the solvent under vacuum, perform column chromatography separation on the concentrated solution (eluent: petroleum ether and ethyl acetate at a volume ratio of 1-30:1), to obtain 82.3 g of compound 3, with a yield of 89.5%.

[0127] Synthesis of compound 3 1 H NMR (400 MHz, CDCl3): δ 9.41 (s, 2H), 8.74 (dd, 1H), 8.61 (dd, 1H), 7.92 (dd, 1H), 7.39-7.15 (m, 29H), 6.74 (dd, 2H), 3.83 (s, 12H).

[0128] Synthesis Example 4

[0129] Synthesis of compound Z1

[0130]

[0131] The synthesis steps include:

[0132] Compound 3 (91.9 g, 100 mmol) and zirconium tetrachloride (24.5 g, 100 mmol) were mixed in 300 mL of n-hexane under nitrogen atmosphere, stirred at room temperature for 3 hours, filtered, the filter cake was dissolved in 300 mL of dichloromethane, chromium trichloride tetrahydrofuran complex (37.5 g, 100 mmol) was added, stirred at room temperature for 3 hours, the reaction solution was concentrated to 50 mL, crystallized at -20°C to obtain compound Z1, white solid 112.4 g, yield 91%.

[0133] Synthesis of compound Z1 1 H NMR (400 MHz, CDCl3): δ 8.74 (dd, 1 H), 8.61 (dd, 1 H), 7.92 (dd, 1 H), 7.39-7.15 (m, 29 H), 6.74 (dd, 2 H), 3.83 (s, 12 H).

[0134] Synthesis Example 5

[0135] Synthesis of compound H1

[0136]

[0137] The synthesis steps refer to synthesis example 4, except that zirconium tetrachloride (24.5 g, 100 mmol) is replaced by hafnium tetrachloride (32 g, 100 mmol). 123.2 g of compound H1 is obtained, yield 93%.

[0138] Synthesis of compound H1 1 H NMR (400 MHz, CDCl3): δ 8.74 (dd, 1 H), 8.61 (dd, 1 H), 7.92 (dd, 1 H), 7.39-7.15 (m, 29 H), 6.74 (dd, 2 H), 3.83 (s, 12 H).

[0139] Synthesis Example 6

[0140] Synthesis of compound T1

[0141]

[0142] The synthesis steps refer to synthesis example 4, except that zirconium tetrachloride (24.5 g, 100 mmol) is replaced by titanium tetrachloride (18.9 g, 100 mmol). 123.2 g of compound H1 is obtained, yield 93%.

[0143] Synthesis of compound H1 1 H NMR (400 MHz, CDCl3): δ 8.74 (dd, 1 H), 8.61 (dd, 1 H), 7.92 (dd, 1 H), 7.39-7.15 (m, 29 H), 6.74 (dd, 2 H), 3.83 (s, 12 H).

[0144] Synthesis Example 7

[0145] Synthesis of compound Z2

[0146]

[0147] The synthesis step refers to the patent CN110698513B.

[0148] Synthesis of compound Z2 1 H NMR (400 MHz, CDCl3): δ 8.61 (dd, 1 H), 7.64 (dd, 1 H), 7.19 (t, 1 H), 6.99 (dd, 2 H), 6.74 (dd, 1 H), 3.83 (q, 1 H), 2.81 (hept, 2H), 2.12 (s, 6 H), 1.93-1.88 (m, 4H), 0.91 (s, 9H).

[0149] The following examples and comparative examples respectively use the compounds Z1, compound H1, compound T1 and compound Z2 prepared by the above synthesis examples as the main catalyst to catalyze the polymerization of ethylene, and the polymerization steps are as follows:

[0150] A 1L polymerization reactor was continuously dried at 120°C for 6 hrs, and then vacuumized and replaced with N2 for 3 times while hot. After cooling to room temperature, 500 mL of Isopar-E and MMAO were added, and the reactor was heated to 220°C. Then 10 mL of toluene solution of the main catalyst (0.1 μmol / mL) was added, the ethylene pressure was adjusted to 4 MPa, and the pressure was kept constant. The reaction was stirred vigorously for 30 min.

[0151] After the reaction was completed, the temperature was cooled to room temperature, and the pressure was released. The reaction solution was neutralized with 5% hydrochloric acid acidified ethanol solution to obtain a polymer precipitate, which was washed with ethanol and water several times, and vacuum dried to constant weight to obtain the polymer.

[0152] The molar ratio of Al element in the MMAO added during the polymerization to the Cr in the main catalyst and the M metal (the M metal in the compound Z1 is Zr, the M metal in the compound T1 is Hf, and the M metal in the compound T1 is Ti) is 2000:1:1 when the compound Z1, the compound H1, and the compound T1 are used as the main catalyst. The molar ratio of Al element in the MMAO added during the polymerization to the Zr in the main catalyst is 1000:1 when the compound Z2 is used as the main catalyst.

[0153] The reaction conditions of the above examples and comparative examples are shown in Table 2.

[0154] Table 2

[0155]

[0156] As can be seen from Table 2, the catalytic system composed of the complex provided by the application as the main catalyst and the cocatalyst exhibits high catalytic activity, and the obtained polymer has higher molecular weight, better thermal stability, and higher comonomer insertion rate, which is suitable for high-temperature solution polymerization. In addition, the 1-octene insertion rate of the polymer of Examples 1-3 is more than 40 wt%, so the polymer is softer, and has higher elongation at break.

[0157] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application, but not to limit it; although the application has been described in detail with reference to the above examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the above examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A bimetallic compound characterized in that, having a structure shown in Formula I: Formula I In formula I, M is selected from the group consisting of Group IVB metals; R1~R 14 each independently selected from the group consisting of C1~C20alkyl, C3~C20cycloalkyl, C1~C20alkoxy, C3~C20cycloalkoxy, C1~C20alkylamino, C3~C20cycloalkylamino, hydrogen, halogen, aryl, aryloxy, arylamino; X is selected from the group consisting of methyl, chlorine, dimethylamino, benzyl; Ar1, Ar2, Ar3are each independently selected from the group consisting of phenyl, C1~C6alkyl-substituted phenyl, C1~C6alkoxy-substituted phenyl, naphthyl, anthryl.

2. The bimetallic compound of claim 1, wherein, R1~R 14 each independently is selected from one of hydrogen, C1~C6alkyl, C3~C10cycloalkyl, benzhydryl, halogen, dibenzocycloheptane, fluorenyl, indenyl, anthryl.

3. The bimetallic compound of claim 1 or 2, wherein, R1~R 14 each independently is selected from one of hydrogen, tert-butyl, isopropyl, benzhydryl, halogen.

4. A method of producing the bimetallic compound according to any one of claims 1 to 3, characterized in that, comprising the following steps: carrying out a first complex reaction of a compound shown in Formula II with MX4 to obtain a compound shown in Formula III; carrying out a second complex reaction of the compound shown in Formula III with chromium trichloride to obtain the compound shown in Formula I; In formula II and formula III, R1~R 14 , Ar1, Ar2, Ar3, X and M have the same definitions as R1~R 14 , Ar1, Ar2, Ar3, X and M have the same definitions as R1~R 5. An olefin polymerization catalyst comprising a procatalyst and a cocatalyst, characterized in that, the main catalyst comprises the bimetallic compound according to any one of claims 1-3.

6. The olefin polymerization catalyst of claim 5, wherein, the cocatalyst comprises one or more of tri(pentafluorophenyl)boron, triphenylcarbenium tetrakis(pentafluorophenyl)borate, methylbis(octadecyl)ammonium tetrakis(pentafluorophenyl)borate, aluminoxane, alkylaluminum and chloroalkylaluminum.

7. The olefin polymerization catalyst according to claim 6, wherein the aluminoxane comprises one or more of methylaluminoxane, ethylaluminoxane and isobutylaluminoxane; and / or, the alkylaluminum comprises one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum and tri-n-hexylaluminum; and / or, the chloroalkylaluminum comprises one or more of diethylaluminum chloride, triethylaluminum dichloride, diethylaluminum sesquichloride and ethylaluminum dichloride.

8. The olefin polymerization catalyst of claim 7, wherein, a molar ratio of the metal aluminum in the cocatalyst to the metals M and Cr in the main catalyst Al / (Cr+M) is (1-5000):

1.

9. The olefin polymerization catalyst according to claim 7 or 8, characterized in that, a molar ratio of the metal aluminum in the cocatalyst to the metals M and Cr in the main catalyst Al / (Cr+M) is (300-2000):

1.

10. A process for the preparation of a polyolefin elastomer, characterized in that, comprising: polymerizing ethylene monomers using the olefin polymerization catalyst according to any one of claims 5-9 to obtain the polyolefin elastomer.

11. The method of claim 10, wherein, the polymerization reaction is carried out at a temperature of 0-250℃, a pressure of 0.1-5 MPa and for a time of 2-120 min.

12. The production method according to claim 10 or 11, characterized by, the solvent for the polymerization reaction comprises one or more of toluene, hexane, heptane, Isopar E and methylcyclohexane; and / or, the polymerization reaction is carried out at a temperature of 140-220℃, a pressure of 1-5 MPa and for a time of 10-60 min.

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