Branched polyethylene with adjustable and controllable branching degree and preparation method thereof

Abstract

The invention discloses branched polyethylene with an adjustable and controllable branching degree and a preparation method of the branched polyethylene. The crystallinity of the branched polyethylene is less than 25%, the weight-average molecular weight is between 100,000 g / mol and 120,000 g / mol, the molecular weight distribution is between 1.5 and 3.5, and the branching degree is adjustable and controllable between 60 / 1000C and 200 / 1000C. In the preparation method, an alpha-diimine nickel metal complex is contacted and mixed with at least one organic boron compound selected from aryl boron, alkyl boron and borate, and then is contacted with at least one organic aluminum compound selected from alkyl aluminum, aluminoxane and halogenated alkyl aluminum to perform solution polymerization of ethylene. The polymerization method provided by the invention has the advantages of high polymerization activity, no use of a second polymerization monomer, simple process and low cost, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to an ethylene polymer and a preparation method thereof, in particular to a branched polyethylene with a controllable and adjustable branching degree, and a preparation method of the branched polyethylene obtained by polymerizing ethylene under solution polymerization conditions under the joint action of a late transition metal nickel complex and an organic boron compound. Background Art

[0002] The degree of branching, branch type and distribution of polyethylene have a significant impact on the performance and application of polyethylene. Branched polyethylene has the characteristics of low crystallinity, low density, good solubility, low viscosity in solution and molten state due to the presence of more branches on its carbon chain, and has more superior film-forming property, transparency, toughness and mechanical processing performance compared to conventional linear polyethylene. Usually, branched polyethylene is mainly prepared by copolymerization of ethylene with a small amount of high carbon α-olefins (1-butene, 1-hexene or 1-octene), but because the reactivity ratio of α-olefins is much lower than that of ethylene, the degree of branching of polyethylene obtained by this method is often relatively low, and it is difficult to obtain polyethylene with high branching degree. Moreover, high carbon α-olefins are relatively expensive, resulting in an increase in the cost of copolymers. Subsequently, scientists discovered that the use of α-diimine nickel catalysts can catalyze the homopolymerization of ethylene to prepare high molecular weight branched polyethylene. However, the α-diimine nickel catalyst has poor temperature resistance, and the branched polyethylene polymerized by this method generally has a low degree of branching (branching degree <80 / 1000C) and is difficult to control, which limits the application range of the branched polyethylene.

[0003] Brookhart, Guan et al. obtained polyethylene with different degrees of branching by changing the temperature or pressure of the polymerization reaction (Macromolecules, 2000, 33(7): 2320-2334; Chem. Eur. J. 2002, 8(14): 3086-3092). However, although large adjustments in reaction temperature and pressure are easy to achieve on a laboratory scale, they are major process changes on an industrial scale and are very difficult to achieve.

[0004] In Chinese patent CN110590980A, an α-diimine nickel catalyst with a large steric skeleton was designed and synthesized, which changed the electron distribution and spatial effect around the metal center of the catalyst, thereby achieving the goal of obtaining a polymer with high molecular weight and a widely controllable degree of branching at high temperature. However, the ligand structure of this α-diimine nickel catalyst is relatively complex, the synthesis process is cumbersome, and the preparation cost is high, which is not conducive to industrial application. Summary of the invention

[0005] Based on the prior art, the inventors have creatively discovered, after a large number of experiments, analyses and in-depth studies, that, under conditions where the polymerization reaction is not changed, a catalyst system prepared in a specific manner using an α-diimine nickel catalyst and at least one boron compound selected from alkyl boron, aryl boron and borate is used for the preparation of branched polyethylene, thereby achieving regulation of the branching degree of polyethylene, without requiring complex catalyst structure design and synthesis, with a large regulation space for the branching degree, a flexible production method, and no harsh reaction conditions, and being very suitable for industrial production, thereby solving the deficiencies in the prior art.

[0006] The purpose of the present invention is to solve the technical problems in the prior art that the branching degree of the branched polymer obtained by catalyzing ethylene polymerization with the catalyst is too low and the branching degree is difficult to control, while ensuring the thermal stability of the nickel catalyst and being able to catalyze ethylene polymerization to obtain high molecular weight branched polyethylene. Therefore, the present invention provides a branched polyethylene with adjustable and controllable branching degree and a preparation method thereof.

[0007] Specifically, the present invention provides a method for preparing branched polyethylene with adjustable and controllable branching degree, which comprises the following steps:

[0008] (1) mixing and contacting the α-diimine nickel metal complex represented by formula (I) with at least one organic boron compound selected from aryl boron, alkyl boron and borate in a first organic solvent to obtain a mixture;

[0009] (2) polymerizing ethylene in the presence of the above mixture and at least one organoaluminum compound selected from alkylaluminum, aluminoxane and halogenated alkylaluminum to obtain branched polyethylene,

[0010]

[0011] In formula (I), R1-R6 are the same or different and are each independently hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C1-C6 haloalkyl, optionally substituted C2-C6 alkenyl, halogen, optionally substituted C1-C6 alkoxy or optionally substituted C6-C 10 Aryl, or two adjacent groups in R1-R6 are bonded to each other and together with the carbon atoms to which they are attached form an optionally substituted C4-C8 ring; R7, R 11 , R 12 , R 16 are the same or different and are each independently an optionally substituted C1-C6 alkyl, an optionally substituted C3-C8 cycloalkyl, or an optionally substituted phenyl; R8, R9, R 10 , R 13 , R 14 , R 15the same or different, each independently representing hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted phenyl, halogen, optionally substituted C1-C6 alkoxy, nitro, amino, mercapto; X is halogen, wherein the substituent in the "optionally substituted" is a substituent selected from the group consisting of halogen, C1-C4 alkyl, C1-C4 haloalkyl, and phenyl.

[0012] The present invention also provides a branched polyethylene (also referred to as "polyethylene" or "branched ethylene polymer" in the present invention) prepared by the method for preparing branched polyethylene with adjustable and controllable branching degree of the present invention.

[0013] Technical Effects

[0014] Compared with the prior art, in the present invention, a catalytic system prepared in a specific manner can be used for ethylene polymerization to achieve regulation of the degree of branching of polyethylene and increase the degree of branching of polyethylene. At the same time, the polymerization activity of the catalytic system can also be effectively improved. Therefore, the purpose of the present invention can be achieved without a complex catalyst structure, harsh reaction conditions, or a significant change in the polymerization conditions.

[0015] The preparation method of the present invention has the advantages of being simple and easy to operate, having a large adjustable space, being flexible and changeable, and having low production cost, and is very conducive to realizing industrial production.

[0016] In addition, in the preparation method of the branched polyethylene of the present invention, ethylene is used as the only polymerization monomer to obtain branched polyethylene containing branches, without the need to use expensive high-carbon α-olefins as comonomers. Therefore, not only can the branching degree of the branched polyethylene be improved, but the preparation method also has the advantages of low production cost and simple polymerization process.

[0017] The preparation method of the present invention has a large control range for the branching degree of branched polyethylene, and can obtain polyethylene with adjustable and controllable properties in a wide range from amorphous polyethylene to polyethylene with a certain degree of crystallinity, thereby conveniently controlling the branching degree of polyethylene as needed, further enriching the application range of polyethylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the carbon nuclear magnetic resonance spectrum of the polyethylene obtained in Example 3 of the present invention.

[0019] Figure 2 This is the carbon nuclear magnetic resonance spectrum of the polyethylene obtained in Comparative Example 3 of the present invention.

[0020] Figure 3 This is the GPC spectrum of the polyethylene obtained in Example 3 of the present invention.

[0021] Figure 4This is the DSC spectrum of the polyethylene obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention are described in detail below. However, it should be noted that the protection scope of the present invention is not limited by these specific embodiments but is determined by the appended claims.

[0023] In the context of this specification, except for the contents explicitly described, any matters or items not mentioned are directly applicable to those known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new contents not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0024] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless the weight basis does not conform to the common understanding of those skilled in the art.

[0025] The specific embodiments of the present invention are described in detail below. However, it should be noted that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the appended claims.

[0026] In the context of the present invention, unless otherwise specified, the physical properties of a substance (such as boiling point) are measured at normal temperature (25° C.) and normal pressure (101325 Pa).

[0027] [α-Diimine Nickel Metal Complex]

[0028] In the present invention, the catalyst used for preparing branched polyethylene is an α-diimine nickel metal complex represented by the following formula (I):

[0029]

[0030] In formula (I), R1-R6 are the same or different and are each independently hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C1-C6 haloalkyl, optionally substituted C2-C6 alkenyl, halogen, optionally substituted C1-C6 alkoxy or optionally substituted C6-C 10 Aryl, or two adjacent groups in R1-R6 are bonded to each other and together with the carbon atoms to which they are attached form an optionally substituted C4-C8 ring; R7, R 11 , R 12 , R 16are the same or different and are each independently an optionally substituted C1-C6 alkyl, an optionally substituted C3-C8 cycloalkyl, or an optionally substituted phenyl; R8, R9, R 10 , R 13 , R 14 , R 15 the same or different, each independently representing hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted phenyl, halogen, optionally substituted C1-C6 alkoxy, nitro, amino, mercapto; X is halogen, wherein the substituent in the "optionally substituted" is a substituent selected from the group consisting of halogen, C1-C4 alkyl, C1-C4 haloalkyl, and phenyl.

[0031] In the present invention, "C1-C6 alkyl" means a straight or branched alkyl group having 1 to 6 carbon atoms, for example, it can be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl and its isomers, hexyl and its isomers. In the present invention, "C1-C6 alkyl" is preferably "C1-C4 straight or branched alkyl".

[0032] In the present invention, "C1-C6 haloalkyl" means a group in which at least one hydrogen atom in the above-mentioned C1-C6 alkyl is replaced by a halogen group, and the halogen group is selected from fluorine, chlorine, bromine, and iodine. The upper limit of the number of halogen groups in the haloalkyl is the upper limit of the number of hydrogen atoms that can be replaced in the C1-C6 alkyl, which can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and can also be 1-8, 1-6, 1-4 or 1-2. When there are multiple halogen groups, each halogen group can be the same or different. The halogen group in the "C1-C6 haloalkyl" is preferably fluorine, chlorine, bromine, and more preferably fluorine or chlorine.

[0033] In the present invention, "C2-C6 alkenyl" means a straight or branched alkenyl group having 2 to 6 carbon atoms, wherein the group may have 1, 2 or 3 double bonds, and preferably has 1 double bond. As "C2-C6 alkenyl", for example, it may be vinyl, 1-propenyl, 2-propenyl, 1-butenyl and isomers thereof, 1-pentenyl and isomers thereof, 1-hexenyl and isomers thereof. In the present invention, "C2-C6 alkenyl" is preferably "C2-C4 straight-chain branched alkenyl".

[0034] In the present invention, "C1-C6 alkoxy" means a group obtained by bonding the above C1-C6 alkyl group to an oxygen atom, for example, it can be methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy and isomers thereof, hexyloxy and isomers thereof. In the present invention, "C1-C6 alkoxy" is preferably "C1-C4 straight-chain branched alkoxy".

[0035] In the present invention, "C6-C 10 The term "aryl" refers to an aromatic hydrocarbon group having 6 to 10 carbon atoms, and specifically, it may be phenyl or naphthyl.

[0036] In the present invention, "C3-C8 cycloalkyl" refers to a cyclic alkyl group having 3 to 8 carbon atoms, for example, it may be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, or cyclooctyl.

[0037] In the present invention, "C4-C8 ring" means a cyclic group having 4-8 ring carbon atoms, which may be an unsaturated ring or a saturated ring, and may or may not be aromatic. When it is an unsaturated ring, it may have 1, 2 or 3 double bonds. When it is an aromatic ring, it may be a benzene ring.

[0038] In the present invention, "two adjacent groups in R1-R6 are bonded to each other, and together with the carbon atoms to which they are connected, form an optionally substituted C4-C8 ring" means that two groups in at least any one of the five groups of R4 and R3, R3 and R1, R1 and R2, R2 and R5, and R5 and R6 are bonded to each other, and together with the carbon atoms to which they are connected, form an optionally substituted C4-C8 ring.

[0039] In the present invention, the substituent in "optionally substituted" is at least one group selected from halogen, C1-C4 alkyl, C1-C4 haloalkyl and phenyl. The upper limit of the number of the substituent is the upper limit of the position that can be substituted on the substituted group, and the number of the substituent can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. For example, it can be 1-8, 1-6, 1-5, 1-4, 1-3, 1-2. When there are multiple substituents, each substituent can be the same or different.

[0040] In the present invention, "halogen" means fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine or bromine.

[0041] In the present invention, "halogenated" means at least one of the selected halogens is substituted, and the upper limit of the halogenated group is the upper limit of the position that can be substituted on the substituted group, which can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. For example, it can be 1-8, 1-6, 1-5, 1-4, 1-3, 1-2. When there are multiple halogen groups, each substituent can be the same or different.

[0042] In the present invention, the upper limit of the number of substituents in "optionally substituted by..." is the upper limit of the positions that can be substituted on the substituted group, and the number of substituents can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. For example, it can be 1-8, 1-6, 1-5, 1-4, 1-3, 1-2. When there are multiple substituents, each substituent can be the same or different.

[0043] In one embodiment of the present invention, R1-R6 in formula (I) are the same or different and are independently selected from any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, fluorine, chlorine, bromine, halomethyl, haloethyl, halopropyl, haloisopropyl, halobutyl, haloisobutyl, halosec-butyl, halotert-butyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, phenyl, pentafluorophenyl, pentachlorophenyl or diphenylmethyl.

[0044] In one embodiment of the present invention, R1-R6 in formula (I) are the same or different and are independently selected from any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, fluorine, chlorine, bromine, halomethyl, haloethyl, halopropyl, haloisopropyl, halobutyl, haloisobutyl, halosec-butyl, halotert-butyl, phenyl, or pentafluorophenyl.

[0045] In one embodiment of the present invention, in formula (I), at least one group of R4 and R3, R3 and R1, R1 and R2, R2 and R5, R5 and R6 are bonded to each other to form, together with the carbon atoms to which they are connected, a benzene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, a cyclopentene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, or a cyclopentadiene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl.

[0046] In one embodiment of the present invention, in formula (I), R1 and R2 are bonded to each other to form a benzene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, a cyclopentene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, or a cyclopentadiene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl.

[0047] In one embodiment of the present invention, in formula (I), R4 and R3 are bonded to each other to form a benzene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, a cyclopentene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, or a cyclopentadiene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl.

[0048] In one embodiment of the present invention, in formula (I), R5 and R6 are bonded to each other to form a benzene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, a cyclopentene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, or a cyclopentadiene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl.

[0049] In one embodiment of the present invention, in formula (I), R7, R 11 , R 12 , R 16 are the same or different and are each independently selected from hydrogen, optionally substituted methyl, optionally substituted ethyl, optionally substituted propyl, optionally substituted isopropyl, optionally substituted butyl, optionally substituted isobutyl, optionally substituted sec-butyl, optionally substituted tert-butyl, optionally substituted phenyl, pentafluorophenyl, pentachlorophenyl.

[0050] In one embodiment of the present invention, in formula (I), R7, R 11 , R 12 , R 16 the same or different, and each independently selected from hydrogen, methyl optionally substituted by at least one selected from halogen and phenyl, ethyl optionally substituted by at least one selected from halogen and phenyl, propyl optionally substituted by at least one selected from halogen and phenyl, isopropyl optionally substituted by halogen and phenyl, butyl optionally substituted by at least one selected from halogen and phenyl, isobutyl optionally substituted by at least one selected from halogen and phenyl, sec-butyl optionally substituted by at least one selected from halogen and phenyl, tert-butyl optionally substituted by at least one selected from halogen and phenyl, and phenyl optionally substituted by at least one selected from halogen and phenyl.

[0051] In one embodiment of the present invention, in formula (I), R8, R9, R 10 , R 13 , R 14 , R 15 are the same or different, and are each independently selected from any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, fluorine, chlorine, bromine, phenyl, or pentafluorophenyl.

[0052] In one embodiment of the present invention, in formula (I), R8, R9, R 10 , R 13 , R 14 , R 15 The same or different, each independently selected from any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl.

[0053] In one embodiment of the present invention, in formula (I), R8, R 10 , R 13 , R 15 The same or different, each independently selected from any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl.

[0054] In one embodiment of the present invention, in formula (I), R9, R 14 The same or different, each independently selected from any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl.

[0055] In one embodiment of the present invention, X in formula (I) is chlorine or bromine.

[0056] In one embodiment of the present invention, the α-diimine nickel metal complex represented by formula (I) may further include the following metal complexes.

[0057]

[0058]

[0059] It should be noted that in the present invention, the "α-diimine nickel metal complex" as a catalyst may be used alone or in combination of two or more.

[0060] It should be noted that, in the present invention, when measuring the "α-diimine nickel metal complex", unless otherwise specified, the content of the nickel element (Ni) contained therein is used.

[0061] [Organoboron compounds]

[0062] In the present invention, the organoboron compound is at least one selected from arylborons, alkylborons and borates. That is, in the present invention, the organoboron compound may be used alone or in combination of two or more.

[0063] In the present invention, the alkyl boron and aryl boron may be compounds having the following general formula (B-1):

[0064] B(R)3(B-1)

[0065] Wherein, each of the three R groups may be the same or different from each other, and each R is independently selected from C 1-6 Straight or branched alkyl and C 6-10 Aryl, each group is optionally substituted with one or more halogen atoms, halogenated C 1-6 Straight chain or branched alkyl or phenoxy substituted.

[0066] In one embodiment of the present invention, the R is preferably selected from methyl, ethyl, propyl, butyl, isobutyl, phenyl, tolyl, trifluoromethylphenyl and pentafluorophenyl.

[0067] In one embodiment of the present invention, specific examples of alkylborons include trimethylboron, triethylboron, triisobutylboron, tripropylboron or tributylboron. Specific examples of arylborons include triphenylboron, tris(pentafluorophenyl)boron and tris[3,5-bis(trifluoromethyl)phenyl]boron.

[0068] In the present invention, the borate may be a compound having the following general formula (B-2):

[0069] [L] + [BE4] m - (B-2)

[0070] Wherein L is a cationic group, each E may be the same or different, and each is independently selected from a halogen atom, C 6-10 Aryl, which is optionally substituted by one or more halogen atoms, C 1-6 Straight chain or branched alkyl, halogenated C 1-6 Straight or branched alkyl, C 1-6 The radical may be substituted by a straight-chain or branched alkoxy radical or a phenoxy radical.

[0071] In one embodiment of the present invention, E is preferably selected from fluorine, phenyl, trifluoromethylphenyl and pentafluorophenyl. m represents the valence value of the group in the L part.

[0072] In the general formula (B-2), [L] + The moiety may be a common cation in borates, for example, Li + 、Na + , K + , Ca 2+ Mg 2+ 、[Fe(C5H5)2] + (ferrocene group), etc. In addition, the L part can also be an organic amine, in which case the L part can be represented by N(R')3, and each R' is independently selected from H, C 1-6 Straight or branched alkyl and C 6-10 Aryl, but not H at the same time; or two R' and N can be bonded to each other to form an optionally C 1-6 A 5-7 membered nitrogen-containing heterocyclic ring substituted with a straight or branched alkyl group, preferably each R' is independently selected from H, C 1-4 A straight chain or branched alkyl group and a phenyl group, but not both H; or two R' and N may be bonded to each other to form a group optionally containing C 1-4A 5-7 membered nitrogen-containing heteroaromatic ring or heterocyclic hydrocarbon substituted with a straight or branched alkyl group. For example, as the L part, methylamine, ethylamine, propylamine, butylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, N,N-dimethylaniline, N,N-diethylaniline, imidazole, 1-butyl-3-methylimidazole, pyridine, piperidine, etc. can be cited. [L] + The moiety may also be a group carrying a carbenium ion, such as a trityl carbenium ion.

[0073] In one embodiment of the present invention, specific examples of borates include trimethylammonium tetraphenylborate, triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tributylammonium tetraphenylborate, trimethylammonium tetra(p-tolyl)borate, tripropylammonium tetra(p-tolyl)borate, trimethylammonium tetra(o-p-dimethylphenyl)borate, triethylammonium tetra(o-p-dimethylphenyl)borate, trimethylammonium tetra(p-trifluoromethylphenyl)borate, tributylammonium tetra(p-trifluoromethylphenyl)borate, tributylammonium tetra(pentafluorophenyl)borate, N,N-diethylanilinium tetraphenylborate, N,N-dimethylanilinium tetra(pentafluorophenyl)borate, N,N-diethylanilinium tetra(pentafluorophenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, triphenylcarbon tetra(pentafluorophenyl)borate, 1-butyl-3-methylimidazole tetrafluoroborate, and ferrocene tetrafluoroborate.

[0074] In one embodiment of the present invention, the organic boron compound is preferably at least one selected from tris(pentafluorophenyl)boron, triphenylcarbon tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, and triethylammonium tetrakis(pentafluorophenyl)borate.

[0075] It should be noted that, in the present invention, when measuring the organoborbide compound, unless otherwise specified, it is expressed as the content of the boron (B) element contained in the organoborbide compound.

[0076] [Organoaluminum compounds]

[0077] In the present invention, the organoaluminum compound is at least one organoaluminum compound selected from the group consisting of alkylaluminum, aluminoxane and halogenated alkylaluminum.

[0078] In the present invention, examples of the alkyl aluminum include compounds represented by the following formula (D):

[0079] Al(R 11 )3(D)

[0080] In the formula (D), the group R 11 The same or different from each other, each independently selected from C 1-6The alkyl group is preferably selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl and isohexyl.

[0081] In one embodiment of the present invention, the alkyl aluminum is preferably trimethyl aluminum (Al(CH3)3), triethyl aluminum (Al(CH2CH3)3), tri-n-propyl aluminum (Al(C3H7)3), tri-isobutyl aluminum (Al(i-C4H9)3), tri-n-butyl aluminum (Al(C4H9)3), tri-isopentyl aluminum (Al(i-C5H 11 )3), tri-n-pentyl aluminum (Al(C5H 11 )3) Tri-n-hexyl aluminum (Al(C6H 13 )3) Triisohexyl aluminum (Al(i-C6H 13 )3), diethylmethylaluminum (Al(CH3)(CH3CH2)2) and dimethylethylaluminum (Al(CH3CH2)(CH3)2), etc., more preferably trimethylaluminum, triethylaluminum, tri-n-propylaluminum and triisobutylaluminum, further preferably triethylaluminum and triisobutylaluminum, and most preferably triisobutylaluminum.

[0082] In the present invention, the alkyl aluminum halide may include, for example, a compound represented by the following formula (E):

[0083] Al(R 11 ) n X 3-n (E)

[0084] In the formula (E), the group R 11 The same or different from each other, each independently selected from C 1-6 Alkyl, preferably selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl and isohexyl, most preferably methyl or ethyl; the group X is halogen, for example fluorine, chlorine, bromine, iodine, preferably chlorine. n is an integer of 1 or 2.

[0085] In one embodiment of the present invention, as the halogenated alkyl aluminum, for example, specific examples include dimethylaluminum monochloride (Al(CH3)2Cl), dimethylaluminum dichloride (Al(CH3)Cl2)), diethylaluminum monochloride (Al(CH3CH2)2Cl), diethylaluminum dichloride (Al(CH3CH2)Cl2), dipropylaluminum monochloride (Al(C3H7)2Cl), dipropylaluminum dichloride (Al(C3H7)Cl2), di-n-butylaluminum monochloride (Al(C4H9)2Cl), di-n-butylaluminum dichloride (Al(C4H9)Cl2), diisobutylaluminum monochloride (Al(i-C4H9)2Cl), diisobutylaluminum dichloride (Al(i-C4H9)Cl2), di-n-pentylaluminum monochloride (Al(C5H 11)2Cl), dichloropentylaluminum (Al(C5H 11 )Cl2), diisopentylaluminum monochloride (Al(i-C5H 11 )2Cl), dichloroisopentylaluminum (Al(i-C5H 11 )Cl2), di-n-hexylaluminum chloride (Al(C6H 13 )2Cl), dichlorohexyl aluminum (Al(C6H 13 )Cl2), diisohexylaluminum monochloride (Al(i-C6H 13 )2Cl), dichloroisohexylaluminum (Al(i-C6H 13 )Cl2), chloromethyl ethylaluminum (Al(CH3)(CH3CH2)Cl), chloromethyl propylaluminum (Al(CH3)(C3H7)Cl), chloromethyl n-butylaluminum (Al(CH3)(C4H9)Cl), chloromethyl isobutylaluminum (Al(CH3)(i-C4H9)Cl), chloroethyl propylaluminum (Al(CH2CH3)(C3H7)Cl), chloroethyl n-butylaluminum (Al(CH2CH3)(C4H9)Cl) and chloroethyl isobutylaluminum (Al(CH2CH3)(i-C4H9)Cl), etc., among which diethylaluminum chloride, ethylaluminum dichloride, di-n-butylaluminum chloride, n-butylaluminum dichloride, diisobutylaluminum dichloride, isobutylaluminum dichloride, di-n-hexylaluminum chloride, and n-hexylaluminum dichloride are preferred, diethylaluminum chloride, ethylaluminum dichloride and di-n-hexylaluminum chloride are further preferred, and diethylaluminum chloride is most preferred.

[0086] In the present invention, the aluminoxane may be a linear aluminoxane represented by the following formula (F): (R)(R)Al-(Al(R)-O) n -O-Al(R)(R), and a cyclic aluminoxane represented by the following formula (G): -(Al(R)-O-) n+2 -.

[0087]

[0088] In the aforementioned formula (F) and formula (G), a plurality of radicals R are identical or different from each other and are independently selected from C1-C6 alkyl, wherein methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl are preferred, and methyl, ethyl and isobutyl are more preferred. n is any integer in the range of 1-50, preferably any integer in the range of 10-30.

[0089] In one embodiment of the present invention, the aluminoxane is preferably methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, n-butylaluminoxane, modified methylaluminoxane or modified ethylaluminoxane, and more preferably methylaluminoxane or modified methylaluminoxane.

[0090] It should be noted that in the present invention, when measuring the organoaluminum compound, unless otherwise specified, it is expressed as the content of the aluminum (Al) element contained in the organoaluminum compound.

[0091] [Method for preparing branched polyethylene]

[0092] The present invention provides a method for preparing branched polyethylene, which comprises the following steps:

[0093] (1) mixing and contacting the α-diimine nickel metal complex represented by the above formula (I) of the present invention with at least one of the above organoboron compounds of the present invention selected from arylborons, alkylborons and borates in a first organic solvent to obtain a mixture;

[0094] (2) Ethylene is polymerized in the presence of the above mixture and at least one organoaluminum compound selected from alkylaluminum, aluminoxane and halogenated alkylaluminum to obtain branched polyethylene.

[0095] In the present invention, the step (1) of the method for preparing branched polyethylene of the present invention is to mix and contact the α-diimine nickel metal complex of the present invention shown in the formula (I) with at least one of the above-mentioned organoboron compounds of the present invention selected from arylboron, alkylboron and borate in a first organic solvent to obtain a mixture. The inventors surprisingly found that before ethylene polymerization, by pre-mixing the α-diimine nickel metal complex of the present invention shown in the formula (I) with the above-mentioned organoboron compound of the present invention, and then coordinating with the organoaluminum compound, the catalytic performance of the catalyst system can be better exerted in the ethylene polymerization reaction to obtain branched polyethylene with excellent performance. Without being limited by any existing theory, the inventors of the present invention speculate that the reason may be that by contacting the organoboron compound with the α-diimine nickel metal complex, the organoboron compound can interact with the complex. Thereafter, when the ethylene polymerization reaction is carried out and the organoaluminum compound is added, the competition between the organoaluminum compound and the organoboron compound is avoided in the presence of the organoaluminum compound, thereby improving the catalytic performance of the catalyst.

[0096] In the present invention, there is no limitation on the first organic solvent in the above step (1), as long as it can disperse / dissolve the α-diimine nickel metal complex represented by formula (I) of the present invention and the above-mentioned organoboron compound of the present invention, and mix and contact the two.

[0097] In one embodiment of the present invention, the first organic solvent includes but is not limited to C 4-10 Alkanes (such as butane, pentane, hexane, heptane, octane, nonane or decane, etc.), halogenated C 1-10 Alkanes (e.g. dichloromethane, chloroform, ethyl chloride, dichloroethane, trichloroethane and their isomers), C 6-10Aromatic hydrocarbon solvents (such as toluene and xylene and their isomers), halogenated C 6-10 Aromatic hydrocarbon solvents (such as chlorobenzene, dichlorobenzene and its isomers, chlorotoluene, etc.). Among them, C 6-10 Aromatic hydrocarbon solvents, halogenated C 1-10 Alkanes, halogenated C 6-10 The aromatic hydrocarbon solvent is more preferably one or more selected from toluene, p-xylene, m-xylene, o-xylene, mesitylene, o-dichlorobenzene, dichloromethane, 1,2-dichloroethane, and trichloroethane, and is further preferably one or more selected from dichloromethane, toluene, p-xylene, or 1,2-dichloroethane.

[0098] In one embodiment of the present invention, in step (1), the molar ratio of the α-diimine nickel metal complex to the organic boron compound is 0.5-50:1, preferably 1-20:1, and more preferably 1-10:1, based on the boron (B) element in the organic boron compound and the active metal nickel (Ni) element in the metal complex.

[0099] In one embodiment of the present invention, in step (1), the contact time of the α-diimine metal complex and the organoboron compound in the first organic solvent is preferably 5 to 30 minutes, more preferably 10 to 20 minutes. If the contact time is too short, the α-diimine metal complex and the organoboron compound cannot fully interact with each other, thereby affecting the catalytic effect of the final catalytic system. On the other hand, if the contact time is too long, the active center formed by the complex and the organoboron may be easily affected by the long contact time with the outside world.

[0100] In the present invention, the contact temperature in step (1) is not particularly limited as long as it has no effect on the structure of the α-diimine metal complex, and can be 0°C-60°C, preferably 10°C-50°C, and more preferably 20°C-40°C.

[0101] In step (2) of the present invention, ethylene polymerization is carried out in the presence of the mixture obtained in step (1) and at least one organoaluminum compound of the present invention selected from alkylaluminum, aluminoxane and halogenated alkylaluminum.

[0102] In one embodiment of the present invention, in step (2), ethylene polymerization is carried out in a second organic solvent.

[0103] In one embodiment of the present invention, in step (2), the mixture obtained in step (1) and at least one of the above-mentioned organoaluminum compounds of the present invention selected from alkylaluminum, aluminoxane and halogenated alkylaluminum are added to a second organic solvent, and then ethylene is introduced into the solvent to carry out ethylene polymerization.

[0104] In one embodiment of the present invention, the second organic solvent may be a commonly used polymerization solvent in polyethylene polymerization, for example, including but not limited to C 4-10 Alkanes or cycloalkanes (such as isopropane, butane, pentane, hexane, heptane, octane, nonane, decane, cyclohexane, cycloheptane, etc.), aromatic hydrocarbon solvents (such as toluene and xylene and their isomers), etc. Among them, hexane, isopropane, cyclohexane, toluene or a mixture thereof is preferably used as the second organic solvent.

[0105] In one embodiment of the present invention, there is no limitation on the order of adding the mixture obtained in step (1) and the organoaluminum compound of the present invention to the second organic solvent. The mixture obtained in step (1) may be added first, and then the organoaluminum compound of the present invention may be added; the organoaluminum compound of the present invention may be added first, and then the mixture obtained in step (1) may be added; or the mixture obtained in step (1) and the organoaluminum compound of the present invention may be added simultaneously.

[0106] In one embodiment of the present invention, there is no particular limitation on the form of addition of the organoaluminum compound, and the compound can be added directly to the second organic solvent or in the form of a solution. Usually, the compound is added in the form of a solution dispersed in a solvent. The solvent used to disperse the organoaluminum compound is not particularly limited, as long as it can disperse the organoaluminum compound, and can usually be an alkane solvent such as n-hexane, n-pentane, isopentane, cyclopentane, neopentane, etc., or an aromatic solvent such as toluene, ethylbenzene, xylene, etc. According to the present invention, in order to facilitate subsequent separation, the same solvent as the first solvent and / or the second solvent is preferred; or the same solvent as at least one of the mixed solvents for the polymerization system.

[0107] In one embodiment of the present invention, the amount of the organoaluminum compound used is not particularly limited as long as it is the conventional amount of the organoaluminum compound used in ethylene polymerization.

[0108] In one embodiment of the present invention, for the ratio of the organoaluminum compound to the α-diimine nickel metal complex, the molar ratio of Al to Ni is 10-2000:1, preferably 100-1500:1, and more preferably 150-1000:1, based on the total aluminum (Al) element in the organoaluminum compound and the active metal nickel (Ni) element in the metal complex.

[0109] In the preparation of the branched polyethylene of the present invention, a chain transfer agent may be used or may not be used.

[0110] In one embodiment of the present invention, as the chain transfer agent, other metal alkyl compounds other than the organoaluminum compound and the organoboron compound of the present invention can be listed, for example, one or more of n-butyl lithium, diethyl zinc, dipropyl zinc, dibutyl zinc, diisobutyl zinc, diethyl magnesium, dibutyl magnesium or n-butyl ethyl magnesium can be listed. In one embodiment of the present invention, when the chain transfer agent is used, the molar ratio of the amount of the chain transfer agent calculated by the metal content of the chain transfer agent to the α-diimine nickel metal complex calculated by metal Ni is 5-300:1, preferably 10-200:1.

[0111] In the present invention, there is no particular limitation on the amount of the α-diimine metal complex, as long as it is the conventional amount of the catalyst in the preparation of branched polyethylene. In one embodiment of the present invention, the amount of the α-diimine metal complex added is relative to the total amount of solvent in the polymerization process (usually the sum of the first organic solvent and the second organic solvent and other optional solvents thereafter), and the volume ratio of the Ni molar content of the complex to the total amount of solvent in the polymerization process is (0.1-100)×10 -6 mol / L, preferably (0.5-50)×10 -6 mol / L.

[0112] In the present invention, there is no particular limitation on the conditions for ethylene polymerization, as long as they are conventional conditions for preparing branched polyethylene. In one embodiment of the present invention, the polymerization reaction conditions are: polymerization temperature is 0-90°C, preferably 20-80°C; polymerization pressure is 0.1-4.0Mpa, preferably 0.5-3.0Mpa.

[0113] In the present invention, the time for ethylene polymerization is not particularly limited, and varies according to the amount of the catalyst system used, the amount of ethylene, and the polymerization temperature, and can be adjusted arbitrarily by those skilled in the art as needed. For example, it can be 10 minutes to 2 hours, 20 minutes to 90 minutes, 30 minutes to 1 hour, etc.

[0114] The method for preparing the branched polyethylene of the present invention can be carried out in a continuous polymerization mode or in a batch polymerization mode.

[0115] The method for preparing the branched polyethylene of the present invention is preferably carried out by solution polymerization.

[0116] The solvent in the solution polymerization of the present invention is a mixed solvent of the first solvent and the second solvent. In one embodiment of the present invention, other solvents may be further added as needed. There is no particular limitation on other solvents, as long as they do not affect the polyethylene reaction of the present invention. In one embodiment of the present invention, it is preferred not to add the other solvents.

[0117] In the present invention, ethylene polymerization is carried out in the absence of other comonomers. That is, in the present invention, branched polyethylene is prepared by homopolymerizing ethylene in the presence of a specific catalyst system.

[0118] In the present invention, after the polymerization reaction is completed, the reaction can be terminated by a method known in the art. For example, the polymerization reaction can be terminated by adding hydrochloric acid to acidify ethanol in the polymerization solution, or the polymerization reaction solution can be poured into the hydrochloric acid acidified ethanol solution to terminate the polymerization reaction.

[0119] In the present invention, after the polymerization reaction is completed, the branched polyethylene can be obtained by separation in a conventional manner of the present invention.

[0120] [Branched polyethylene]

[0121] By using the preparation method of the present invention, the branched polyethylene of the present invention can be prepared by catalyzing ethylene homopolymerization under solution polymerization conditions.

[0122] The branched polyethylene of the present invention may have branches of various lengths.

[0123] In one embodiment of the present invention, the crystallinity of the branched polyethylene is less than 25%.

[0124] In one embodiment of the present invention, the weight average molecular weight of the branched polyethylene is between 100,000 g / mol and 1.2 million g / mol.

[0125] In one embodiment of the present invention, the molecular weight distribution of the branched polyethylene is between 1.5 and 3.5.

[0126] In one embodiment of the present invention, the branching degree of the branched polyethylene is between 60 / 1000C-200 / 1000C (i.e., 60-200 branches per 1000 carbon main chains), preferably 70 / 1000C-150 / 1000C (i.e., 70-150 branches per 1000 carbon main chains).

[0127] Example

[0128] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail by examples below. However, the scope of the present invention is not limited to these examples.

[0129] Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available products.

[0130] The testing method of the molecular weight of the polyethylene obtained in the following examples and comparative examples is as follows: The polymer molecular weight is measured by a PL-220 gel permeation chromatograph of Polymer Laboratories, using 1,2,4-trichlorobenzene as the mobile phase, polystyrene as the standard sample, a differential detector, a flow rate of 1.0 mL / min, a measuring temperature of 150°C, and a sample concentration of 2.0 mg / mL.

[0131] The degree of branching of the polyethylene obtained in the following examples and comparative examples is calculated based on the carbon nuclear magnetic resonance spectrum. The specific method is: the microstructure of the polyethylene sample is measured using a Bruker Avance 600M nuclear magnetic resonance spectrometer. The sample is dissolved in deuterated o-dichlorobenzene to prepare a solution. The test temperature is 120°C, and the nuclear magnetic resonance hydrogen spectrum is obtained by scanning 2000 times and 6000 times respectively. 1 H-NMR) and carbon nuclear magnetic resonance spectroscopy ( 13 C-NMR).

[0132] Example 1

[0133] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and co-catalyst triethylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 22.2g of polymer was obtained. The polymerization activity was 40.4×10 5 g / (molNi·h), the polymer weight average molecular weight is 260.4 kg / mol, and the degree of branching is 107.8 / 1000 carbon atoms.

[0134] Example 2

[0135] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and co-catalyst triisobutylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out for 30 minutes under stirring at 200rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 18.2g of the polymer was weighed. The polymerization activity was 33.1×10 5 g / (molNi·h), the polymer weight average molecular weight is 277.0 kg / mol, and the degree of branching is 97.5 / 1000 carbon atoms.

[0136] Example 3

[0137] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out for 30 minutes under stirring at 200rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 75.8g of the polymer was weighed. The polymerization activity was 137.8×10 5 g / (molNi·h), the polymer weight average molecular weight is 215.7kg / mol, and the degree of branching is 128.7 / 1000 carbon atoms. The nuclear magnetic resonance spectrum of the obtained branched polyethylene is as follows Figure 1 As shown, the GPC spectrum is as Figure 3 As shown, the DSC spectrum is Figure 4 shown.

[0138] Example 4

[0139] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst methylaluminoxane (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 39.0g of the polymer was weighed. The polymerization activity was 70.9×10 5 g / (molNi·h), the polymer weight average molecular weight is 497.0 kg / mol, and the degree of branching is 90.2 / 1000 carbon atoms.

[0140] Example 5

[0141] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst diethylaluminum chloride (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 34.8g of the polymer was weighed. The polymerization activity was 63.3×10 5 g / (molNi·h), the polymer weight average molecular weight is 257.1 kg / mol, and the degree of branching is 95.6 / 1000 carbon atoms.

[0142] Example 6

[0143] In a glove box, nickel catalyst C5 (0.011mmol), N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and stirred and mixed at 30°C for 10 minutes before use as a catalyst solution. Hexane (1L) and co-catalyst triisobutylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 21.3g of polymer was obtained. The polymerization activity was 38.7×10 5 g / (molNi·h), the polymer weight average molecular weight is 344.0 kg / mol, and the degree of branching is 105.2 / 1000 carbon atoms.

[0144] Example 7

[0145] In a glove box, nickel catalyst C5 (0.011 mmol), tri(pentafluorophenyl)borane (0.022 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and the mixture was stirred and mixed at 30 ° C for 10 minutes, and then used as a catalyst solution. Hexane (1 L) and co-catalyst triisobutylaluminum (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 30 minutes under stirring at 200 rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 19.2 g of the polymer was weighed. The polymerization activity was 34.9×10 5 g / (molNi·h), the polymer weight average molecular weight is 316.3 kg / mol, and the degree of branching is 94.8 / 1000 carbon atoms.

[0146] Example 8

[0147] In a glove box, nickel catalyst C5 (0.011 mmol), triethylammonium tetrakis(pentafluorophenyl)borate (0.022 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and the mixture was stirred and mixed at 30 ° C for 10 minutes, and then used as a catalyst solution. Hexane (1 L) and co-catalyst triisobutylaluminum (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out at 200 rpm for 30 minutes. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 16.4 g of polymer was obtained. The polymerization activity was 29.8×10 5 g / (molNi·h), the polymer weight average molecular weight is 253.7 kg / mol, and the degree of branching is 87.7 / 1000 carbon atoms.

[0148] Example 9

[0149] In a glove box, nickel catalyst C1 (0.011 mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and the mixture was stirred and mixed at 30 ° C for 10 minutes, and then used as a catalyst solution. Hexane (1 L) and co-catalyst dichloroethylaluminum (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 30 minutes under stirring at 200 rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 57.5 g of polymer was obtained. The polymerization activity was 104.5×10 5 g / (molNi·h), the polymer weight average molecular weight is 215.7 kg / mol, and the degree of branching is 118.7 / 1000 carbon atoms.

[0150] Example 10

[0151] In a glove box, nickel catalyst C7 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 65.8g of the polymer was weighed. The polymerization activity was 119.6×10 5 g / (molNi·h), the polymer weight average molecular weight is 174.2 kg / mol, and the degree of branching is 90.8 / 1000 carbon atoms.

[0152] Embodiment 11

[0153] In a glove box, nickel catalyst C8 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 80.3g of the polymer was weighed. The polymerization activity was 146.0×10 5 g / (molNi·h), the polymer weight average molecular weight is 247.0 kg / mol, and the degree of branching is 149.2 / 1000 carbon atoms.

[0154] Example 12

[0155] In a glove box, nickel catalyst C5 (0.011 mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.011 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and the mixture was stirred and mixed at 30 ° C for 10 minutes, and then used as a catalyst solution. Hexane (1 L) and co-catalyst dichloroethylaluminum (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out at 200 rpm for 30 minutes. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 60.1 g of polymer was obtained. The polymerization activity was 109.3×10 5 g / (molNi·h), the polymer weight average molecular weight is 252.8 kg / mol, and the degree of branching is 100.8 / 1000 carbon atoms.

[0156] Example 13

[0157] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.044mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 74.4g of the polymer was weighed. The polymerization activity was 135.3×10 5 g / (molNi·h), the polymer weight average molecular weight is 206.2 kg / mol, and the degree of branching is 133.4 / 1000 carbon atoms.

[0158] Embodiment 14

[0159] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (1.65mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 32.3g of the polymer was weighed. The polymerization activity was 58.7×10 5 g / (molNi·h), the polymer weight average molecular weight is 374.3 kg / mol, and the degree of branching is 95.2 / 1000 carbon atoms.

[0160] Embodiment 15

[0161] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (5.5mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 76.4g of the polymer was weighed. The polymerization activity was 138.9×10 5 g / (molNi·h), the polymer weight average molecular weight is 237.0 kg / mol, and the degree of branching is 131.5 / 1000 carbon atoms.

[0162] Example 16

[0163] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and the mixture was stirred and mixed at 30°C for 10 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (11mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out at 200rpm for 30min. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 68.1g of the polymer was weighed. The polymerization activity was 136.2×10 5 g / (molNi·h), the polymer weight average molecular weight is 185.2 kg / mol, and the degree of branching is 146.6 / 1000 carbon atoms.

[0164] Embodiment 17

[0165] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and stirred and mixed at 30°C for 5 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out for 30 minutes under stirring at 200rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 70.3g of polymer was obtained. The polymerization activity was 127.8×10 5 g / (molNi·h), the polymer weight average molecular weight is 238.1 kg / mol, and the degree of branching is 119.4 / 1000 carbon atoms.

[0166] Embodiment 18

[0167] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and stirred and mixed at 30°C for 40 minutes, and then used as a catalyst solution. Hexane (1L) and cocatalyst dichloroethylaluminum (3.3mmol) were added to a 2L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out for 30 minutes under stirring at 200rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 53.2g of polymer was obtained. The polymerization activity was 96.7×10 5 g / (molNi·h), the polymer weight average molecular weight is 200.5 kg / mol, and the degree of branching is 94.3 / 1000 carbon atoms.

[0168] Comparative Example 1

[0169] In a glove box, nickel catalyst C5 (0.011 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and after being fully stirred at 30 ° C for 10 minutes, they were used as catalyst solutions. Hexane (1 L) and co-catalyst triethylaluminum (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 30 minutes under stirring at 200 rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 3.5 g of polymer was obtained. The polymerization activity was 6.36×10 5 gPE / (molNi·h), the polymer weight average molecular weight is 341.8kg / mol, and the degree of branching is 85.3 / 1000 carbon atoms.

[0170] Comparative Example 2

[0171] In a glove box, nickel catalyst C5 (0.011 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and after being fully stirred at 30 ° C for 10 minutes, they were used as catalyst solutions. Hexane (1 L) and co-catalyst triisobutylaluminum (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 30 minutes under stirring at 200 rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 1.9 g of polymer was obtained. The polymerization activity was 3.45×10 5 gPE / (molNi·h), the polymer weight-average molecular weight is 532.4 kg / mol, and the degree of branching is 67.7 / 1000 carbon atoms.

[0172] Comparative Example 3

[0173] In a glove box, nickel catalyst C5 (0.011 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and after being fully stirred at 30 ° C for 10 minutes, they were used as catalyst solutions. Hexane (1 L) and co-catalyst dichloroethylaluminum (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 30 minutes under stirring at 200 rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 57.5 g of polymer was obtained. The polymerization activity was 104.5×10 5 gPE / (molNi·h), the polymer weight average molecular weight is 240.0kg / mol, and the degree of branching is 93.6 / 1000 carbon atoms. The NMR spectrum of the obtained branched polyethylene is as follows Figure 2 shown.

[0174] Comparative Example 4

[0175] In a glove box, nickel catalyst C5 (0.011 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and after being fully stirred at 30 ° C for 10 minutes, they were used as catalyst solutions. Hexane (1 L) and co-catalyst methylaluminoxane (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 30 minutes under stirring at 200 rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 20.0 g of polymer was obtained. The polymerization activity was 36.4×10 5 g / (molNi·h), the polymer weight average molecular weight is 524.0 kg / mol, and the degree of branching is 65.0 / 1000 carbon atoms.

[0176] Comparative Example 5

[0177] In a glove box, nickel catalyst C5 (0.011 mmol) and dichloromethane (10 mL) were added to a 50 mL conical flask in sequence, and after being fully stirred at 30 ° C for 10 minutes, they were used as catalyst solutions. Hexane (1 L) and co-catalyst diethylaluminum chloride (3.3 mmol) were added to a 2 L high-pressure polymerization kettle purged with nitrogen, and the catalyst solution prepared above was transferred to the polymerization kettle. 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 30 minutes under stirring at 200 rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60 ° C to constant weight, and 11.8 g of polymer was obtained. The polymerization activity was 21.5×10 5 g / (molNi·h), the polymer weight average molecular weight is 337.4 kg / mol, and the degree of branching is 66.5 / 1000 carbon atoms.

[0178] Comparative Example 6

[0179] In a glove box, nickel catalyst C5 (0.011mmol), triphenyl carbon tetrakis (pentafluorophenyl) borate (0.022mmol), cocatalyst dichloroethylaluminum (3.3mmol) and dichloromethane (10mL) were added to a 50mL conical flask in sequence, and stirred and mixed at 30°C for 10 minutes before use as a catalyst solution. Hexane (1L) and the above-prepared catalyst solution were added to a 2L high-pressure polymerization reactor purged with nitrogen, and 1.5MPa ethylene was introduced at 60°C. The polymerization reaction was carried out for 30 minutes under stirring at 200rpm. After the reaction was completed, the polymerization solution was poured into an acidified ethanol solution to precipitate a solid polymer. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and 38.1g of polymer was obtained. The polymerization activity was 69.3×10 5 g / (molNi·h), the polymer weight average molecular weight is 206.4 kg / mol, and the degree of branching is 83.0 / 1000 carbon atoms.

[0180] The results of each example and comparative example are summarized below.

[0181] Table 1 Polymerization test results

[0182]

[0183]

[0184] The above examples and comparative examples can fully prove that by adopting the specific polymerization method of the present invention, not only the polymerization activity of the catalyst can be significantly improved, but also the degree of branching of the obtained polyethylene can be significantly improved. It can be seen that the preparation method of the specific polymerization system of the present invention is an effective means to regulate the degree of branching of polyethylene, thereby achieving the adjustable and controllable degree of branching of polyethylene in a larger range.

[0185] At the same time, compared with the prior art method of regulating the degree of branching of polyethylene by changing the catalyst structure or significantly adjusting the polymerization temperature and pressure, the method of the present invention is more feasible, easy to operate, low in cost, and very conducive to industrial application.

[0186] In addition, from the comparison between Example 3, Comparative Example 3 and Comparative Example 6, it can be seen that if the organoaluminum compound and the organoborbane compound are mixed with the nickel metal complex simultaneously, the polymerization activity and the degree of branching of the obtained polymer will be significantly reduced.

[0187] Although the specific implementations of the present invention have been described in detail above in conjunction with the embodiments, it should be pointed out that the protection scope of the present invention is not limited by these specific implementations, but is determined by the appended claims. Those skilled in the art may make appropriate changes to these implementations without departing from the technical ideas and purposes of the present invention, and these changed implementations are obviously also included in the protection scope of the present invention.

Claims

1. A method for preparing branched polyethylene, comprising the following steps: (1) mixing and contacting the α-diimine nickel metal complex represented by formula (I) with at least one organic boron compound selected from aryl boron, alkyl boron and borate in a first organic solvent to obtain a mixture; (2) polymerizing ethylene in the presence of the above mixture and at least one organoaluminum compound selected from alkylaluminum, aluminoxane and halogenated alkylaluminum to obtain branched polyethylene, In formula (I), R1-R6 are the same or different and are each independently hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C1-C6 haloalkyl, optionally substituted C2-C6 alkenyl, halogen, optionally substituted C1-C6 alkoxy or optionally substituted C6-C 10 Aryl, or two adjacent groups in R1-R6 are bonded to each other and together with the carbon atoms to which they are attached form an optionally substituted C4-C8 ring; R7, R 11 , R 12 , R 16 are the same or different and are each independently an optionally substituted C1-C6 alkyl, an optionally substituted C3-C8 cycloalkyl, or an optionally substituted phenyl; R8, R9, R 10 , R 13 , R 14 , R 15 the same or different, each independently representing hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted phenyl, halogen, optionally substituted C1-C6 alkoxy, nitro, amino, mercapto; X is halogen, wherein the substituent in the "optionally substituted" is a substituent selected from the group consisting of halogen, C1-C4 alkyl, C1-C4 haloalkyl, and phenyl.

2. The preparation method according to claim 1, characterized in that: In formula (I), R1-R6 are the same or different and are independently selected from any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, fluorine, chlorine, bromine, halomethyl, haloethyl, halopropyl, haloisopropyl, halobutyl, haloisobutyl, halosec-butyl, halotert-butyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, phenyl, pentafluorophenyl, pentachlorophenyl or diphenylmethyl, or, At least one group of R4 and R3, R3 and R1, R1 and R2, R2 and R5, R5 and R6 are bonded to each other, and together with the carbon atoms to which they are connected, form a benzene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, a cyclopentene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl, or a cyclopentadiene ring optionally substituted by at least one selected from halogen and C1-C4 alkyl.

3. The preparation method according to claims 1 and 2, characterized in that: In formula (I), R7, R 11 , R 12 , R 16 are the same or different and are each independently selected from hydrogen, optionally substituted methyl, optionally substituted ethyl, optionally substituted propyl, optionally substituted isopropyl, optionally substituted butyl, optionally substituted isobutyl, optionally substituted sec-butyl, optionally substituted tert-butyl, optionally substituted phenyl, pentafluorophenyl, pentachlorophenyl, Preferably, R7, R 11 , R 12 , R 16 the same or different, and each independently selected from hydrogen, methyl optionally substituted by at least one selected from halogen and phenyl, ethyl optionally substituted by at least one selected from halogen and phenyl, propyl optionally substituted by at least one selected from halogen and phenyl, isopropyl optionally substituted by at least one selected from halogen and phenyl, butyl optionally substituted by at least one selected from halogen and phenyl, isobutyl optionally substituted by at least one selected from halogen and phenyl, sec-butyl optionally substituted by at least one selected from halogen and phenyl, tert-butyl optionally substituted by at least one selected from halogen and phenyl, and phenyl optionally substituted by at least one selected from halogen and phenyl.

4. The preparation method according to any one of claims 1 to 3, characterized in that: Formula (I), wherein R8, R9, R 10 , R 13 , R 14 , R 15 are the same or different, and are each independently selected from any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, fluorine, chlorine, bromine, phenyl, or pentafluorophenyl.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The α-diimine nickel metal complex represented by formula (I) is at least one selected from the following metal complexes, 6. The preparation method according to any one of claims 1 to 5, characterized in that: The alkyl boron and aryl boron are compounds represented by the following general formula (B-1): B(R)3 (B-1) Wherein, each of the three R groups may be the same or different from each other, and each R is independently selected from C 1-6 Straight or branched alkyl and C 6-10 Aryl, each group is optionally substituted with one or more halogen atoms, halogenated C 1-6 Straight chain or branched alkyl or phenoxy substitution; The borate is a compound represented by the following general formula (B-2): [L] + [BE4] m - (B-2) Wherein L is a cationic group, each E may be the same or different, and each is independently selected from a halogen atom, C 6-10 Aryl, which is optionally substituted by one or more halogen atoms, C 1-6 Straight chain or branched alkyl, halogenated C 1-6 Straight or branched alkyl, C 1-6 substituted by a straight-chain or branched alkoxy or phenoxy group, Preferably, the alkyl boron is at least one selected from trimethyl boron, triethyl boron, triisobutyl boron, tripropyl boron and tributyl boron; Preferably, the arylborone is at least one selected from triphenylboron, tris(pentafluorophenyl)boron and tris[3,5-bis(trifluoromethyl)phenyl]boron; Preferably, the borate is at least one selected from trimethylammonium tetraphenylborate, triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tributylammonium tetraphenylborate, trimethylammonium tetra(p-tolyl)borate, tripropylammonium tetra(p-tolyl)borate, trimethylammonium tetra(o-p-dimethylphenyl)borate, triethylammonium tetra(o-p-dimethylphenyl)borate, trimethylammonium tetra(p-trifluoromethylphenyl)borate, tributylammonium tetra(p-trifluoromethylphenyl)borate, tributylammonium tetra(pentafluorophenyl)borate, N,N-diethylanilinium tetraphenylborate, N,N-dimethylanilinium tetra(pentafluorophenyl)borate, N,N-diethylanilinium tetra(pentafluorophenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, triphenylcarbon tetra(pentafluorophenyl)borate, 1-butyl-3-methylimidazole tetrafluoroborate and ferrocene tetrafluoroborate.

7. The preparation method according to claims 1-6, characterized in that: The alkyl aluminum is a compound represented by the following formula (D): <h2 style=";text-align:left;direction:ltr">Al(R<h2 style=";text-align:left;direction:ltr"> 11 <h2 style=";text-align:left;direction:ltr"> 3(D) In the formula (D), the group R 11 The same or different from each other, each independently selected from C 1-6 Alkyl, preferably selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl and isohexyl; The halogenated alkylaluminum is a compound represented by the following formula (E): Al(R 11 ) n X 3-n (AND) In the formula (E), the group R 11 The same or different from each other, each independently selected from C 1-6 Alkyl, preferably selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl and isohexyl, most preferably methyl or ethyl; the group X is halogen, preferably chlorine, and n is an integer of 1 or 2; The aluminoxane is a linear aluminoxane represented by the following formula (F) or a cyclic aluminoxane represented by the following formula (G): In the aforementioned formula (F) and formula (G), the multiple groups R are the same or different from each other and are independently selected from C1-C6 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl, more preferably methyl, ethyl and isobutyl, n is any integer in the range of 1-50, preferably any integer in the range of 10-30, Preferably, the alkyl aluminum is selected from trimethyl aluminum (Al(CH3)3), triethyl aluminum (Al(CH2CH3)3), tri-n-propyl aluminum (Al(C3H7)3), tri-isobutyl aluminum (Al(i-C4H9)3), tri-n-butyl aluminum (Al(C4H9)3), tri-isopentyl aluminum (Al(i-C5H 11 )3), tri-n-pentyl aluminum (Al(C5H 11 )3) Tri-n-hexyl aluminum (Al(C6H 13 )3) Triisohexyl aluminum (Al(i-C6H 13 )3), at least one of diethyl methyl aluminum (Al(CH3)(CH3CH2)2) and dimethyl ethyl aluminum (Al(CH3CH2)(CH3)2); Preferably, the alkyl aluminum halide is selected from dimethyl aluminum chloride (Al(CH3)2Cl), dimethyl aluminum dichloride (Al(CH3)Cl2)), diethyl aluminum chloride (Al(CH3CH2)2Cl), diethyl aluminum dichloride (Al(CH3CH2)Cl2), dipropyl aluminum chloride (Al(C3H7)2Cl), dipropyl aluminum dichloride (Al(C3H7)Cl2), di-n-butyl aluminum chloride (Al(C4H9)2Cl), di-n-butyl aluminum dichloride (Al(C4H9)Cl2), diisobutyl aluminum chloride (Al(i-C4H9)2Cl), diisobutyl aluminum dichloride (Al(i-C4H9)Cl2), di-n-pentyl aluminum chloride (Al(C5H 11 )2Cl), dichloropentylaluminum (Al(C5H 11 )Cl2), diisopentylaluminum monochloride (Al(i-C5H 11 )2Cl), dichloroisopentylaluminum (Al(i-C5H 11 )Cl2), di-n-hexylaluminum chloride (Al(C6H 13 )2Cl), dichlorohexyl aluminum (Al(C6H 13 )Cl2), diisohexylaluminum monochloride (Al(i-C6H 13 )2Cl), dichloroisohexylaluminum (Al(i-C6H 13 )Cl2), chloromethyl ethylaluminum (Al(CH3)(CH3CH2)Cl), chloromethyl propylaluminum (Al(CH3)(C3H7)Cl), chloromethyl n-butylaluminum (Al(CH3)(C4H9)Cl), chloromethyl isobutylaluminum (Al(CH3)(i-C4H9)Cl), chloroethyl propylaluminum (Al(CH2CH3)(C3H7)Cl), chloroethyl n-butylaluminum (Al(CH2CH3)(C4H9)Cl) and chloroethyl isobutylaluminum (Al(CH2CH3)(i-C4H9)Cl); The aluminoxane is at least one selected from methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, n-butylaluminoxane, modified methylaluminoxane or modified ethylaluminoxane, more preferably methylaluminoxane and modified methylaluminoxane.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The first organic solvent is selected from C 4-10 Alkanes (such as butane, pentane, hexane, heptane, octane, nonane or decane), halogenated C 1-10 Alkanes (e.g. dichloromethane, chloroform, ethyl chloride, dichloroethane, trichloroethane and their isomers), C 6-10 Aromatic hydrocarbon solvents (such as toluene and xylene and their isomers), halogenated C 6-10 At least one of the aromatic hydrocarbon solvents (e.g., chlorobenzene, dichlorobenzene and its isomers, chlorotoluene); preferably, one or more selected from toluene, p-xylene, m-xylene, o-xylene, mesitylene, o-dichlorobenzene, dichloromethane, 1,2-dichloroethane, and trichloroethane.

9. The preparation method according to any one of claims 1 to 8, characterized in that: In step (1), the molar ratio of the α-diimine nickel metal complex to the organic boron compound is 0.5-50:1, preferably 1-20:1, and more preferably 1-10:1, based on the boron (B) element in the organic boron compound and the active metal nickel (Ni) element in the metal complex.

10. The preparation method according to any one of claims 1 to 9, characterized in that: In step (1), the contact time of the α-diimine metal complex and the organic boron compound in the first organic solvent is 5 to 30 minutes, preferably 10 to 20 minutes.

11. The preparation method according to any one of claims 1 to 10, characterized in that: In step (2), ethylene polymerization is carried out in a second organic solvent, wherein the second organic solvent is selected from C 4-10 At least one of a chain alkane or a cycloalkane (e.g., isopropane, butane, pentane, hexane, heptane, octane, nonane, decane, cyclohexane, cycloheptane), an aromatic hydrocarbon solvent (e.g., toluene and xylene and isomers thereof), preferably, hexane, isopropane, cyclohexane, toluene or a mixture thereof.

12. The preparation method according to any one of claims 1 to 11, characterized in that: Regarding the ratio of the organoaluminum compound to the α-diimine nickel metal complex, the molar ratio of Al to Ni is 10-2000:1, preferably 100-1500:1, and more preferably 150-1000:1, based on the total aluminum (Al) element in the organoaluminum compound and the active metal nickel (Ni) element in the metal complex.

13. The preparation method according to any one of claims 1 to 12, characterized in that: In step (2), the polymerization reaction conditions are: polymerization temperature is 0-90°C, preferably 20-80°C; polymerization pressure is 0.1-4.0Mpa, preferably 0.5-3.0Mpa.

14. The branched polyethylene obtained according to the preparation method described in any one of claims 1 to 13 satisfies at least one of the following characteristics: 1) The crystallinity of the branched polyethylene is less than 25%; 2) The weight average molecular weight of the branched polyethylene is between 100,000 g / mol and 1.2 million g / mol; 3) The molecular weight distribution of the branched polyethylene is between 1.5 and 3.5; 4) The branching degree of the branched polyethylene is between 60 / 1000C and 200 / 1000C, preferably between 70 / 1000C and 150 / 1000C.

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