Wide molecular weight distribution polyethylene and preparation method thereof

Abstract

The invention relates to wide molecular weight distribution polyethylene and a preparation method thereof, and the method comprises the following steps: in a first reaction kettle, in a first organic solvent, carrying out a solution polymerization reaction of ethylene by taking an alpha-diimine metal complex as a main catalyst; and in a second reaction kettle and a second organic solvent, carrying out a solution polymerization reaction of ethylene by taking the metallocene complex as a main catalyst, and removing the solvent from the obtained polymer solution to obtain the wide molecular weight distribution polyethylene. The polyethylene has excellent processability and mechanical properties.

Description

Technical Field

[0001] The present application relates to the field of olefin polymerization, and in particular to a polyethylene with a wide molecular weight distribution and a preparation method thereof. Prior art

[0002] Catalysts are the core of the polyolefin industry. With the continuous advancement of catalyst technology, polyolefin materials with different performance are also being innovated. Metallocene catalysts are the second-generation olefin polymerization catalysts after Ziegler-Natta catalysts. Compared with traditional catalysts, metallocene catalysts have many advantages, such as: high catalyst activity, narrow molecular weight distribution of the resulting polymer, more uniform distribution of comonomers in the polymer backbone, and stronger ability to catalyze copolymerization. The single-center characteristics of metallocene catalysts give the resulting polymers an extremely narrow molecular weight distribution, but also greatly reduce the processing performance of the polymers, which to a certain extent inhibits the promotion and application of metallocene catalysts.

[0003] In order to solve the problem of poor processing performance of metallocene polyethylene, polymers with different molecular weights are usually melt blended, but this method consumes a lot of energy and also causes polymer degradation. Another method is to add processing aids, which not only increases production costs, but also affects its application performance due to the precipitation of a large amount of additives during use. A more advantageous method is to use a composite catalyst to prepare polyethylene with a bimodal distribution or a wide distribution, which significantly improves its processing performance without affecting its application performance.

[0004] Chinese patent CN1247875A discloses a composite metallocene catalyst for catalyzing ethylene polymerization to prepare branched polyethylene with a wide molecular weight distribution. By using two metallocene catalysts with different structures to catalyze ethylene polymerization, branched polyethylene with short chain branches is obtained, and the processing performance is improved. However, the polyethylene obtained by this method has a small number of branches on the main chain and only short branches, lacking long branches, so that the melt strength is low, and its processing performance and application performance cannot be significantly improved. Summary of the invention

[0005] The purpose of the present application is to provide a polyethylene with a wide molecular weight distribution and a preparation method thereof, wherein the polyethylene has excellent processing properties and mechanical properties.

[0006] In order to achieve the above object, on the one hand, the present application provides a method for preparing polyethylene with a wide molecular weight distribution, comprising the following steps:

[0007] 1) In a first reaction vessel, in a first organic solvent, a solution polymerization reaction of ethylene is carried out using an α-diimine metal complex as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminum halide, aryl borane and aryl borate as a co-catalyst;

[0008] 2) in a second reaction vessel, in a second organic solvent, using a metallocene complex as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminoxane, aryl borane and aryl borate as a co-catalyst, to carry out a solution polymerization reaction of ethylene,

[0009] Optionally, at least a portion of the polymer solution obtained in the first reactor is introduced into the second reactor for reaction or at least a portion of the polymer solution obtained in the second reactor is introduced into the first reactor for reaction; and

[0010] 3) combining the polymer solution obtained in the first reaction kettle or its remaining part with the polymer solution obtained in the second reaction kettle or its remaining part, removing the solvent, and obtaining the polyethylene with wide molecular weight distribution.

[0011] On the other hand, the present application provides a wide molecular weight distribution polyethylene, wherein the weight average molecular weight of the polyethylene is 1-1 million g / mol, the polymer dispersibility index (PDI) is 6-35, and the degree of branching is 10-100 / 1000C, wherein the number of long chain branches (LCB) above C6 in the branched chains of the polyethylene accounts for 5-25%.

[0012] Compared with the prior art, the polyethylene of the present application not only has a wider molecular weight distribution, but also has a certain amount of long side chains with more than 6 carbon atoms on the polymer main chain, which can significantly improve the melt strength of the polyethylene and give the polymer more excellent processing performance and mechanical properties. Moreover, the olefin polymerization method provided in the present application is simple and easy to operate, does not require harsh reaction conditions, and is easy to realize industrial production. DETAILED DESCRIPTION

[0013] The specific implementation methods of the present application are described in detail below, but it should be noted that the protection scope of the present application is not limited by these specific implementation methods, but is determined by the claims in the appendix.

[0014] Any specific numerical value disclosed herein (including the endpoint of the numerical range) is not limited to the exact value of the numerical value, but should be understood to also cover values ​​close to the exact value, such as all possible numerical values ​​within the range of ±5% of the exact value. In addition, for the disclosed numerical range, the endpoint values ​​of the range, the endpoint values ​​and the specific point values ​​in the range, and the specific point values ​​can be arbitrarily combined to obtain one or more new numerical ranges, and these new numerical ranges should also be regarded as specifically disclosed herein.

[0015] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0016] In the context of this application, unless otherwise expressly defined or the meaning is beyond the comprehension of a person skilled in the art, hydrocarbon or hydrocarbon derivative groups having more than 3 carbon atoms (such as propyl, propoxy, butyl, butane, butene, butenyl, hexane, etc.) have the same meaning when not preceded by the prefix "n". For example, propyl is generally understood to be n-propyl, and butyl is generally understood to be n-butyl, unless otherwise expressly defined.

[0017] In this application, except for the contents clearly stated, any matters or items not mentioned are directly applicable to the aspects 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 deemed to be part of the original disclosure or original record of this application, 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.

[0018] All patent and non-patent literature, including but not limited to textbooks and journal articles, mentioned herein are incorporated herein by reference in their entirety.

[0019] As described above, in the first aspect, the present application provides a method for preparing a polyethylene with a wide molecular weight distribution, comprising the following steps:

[0020] 1) In a first reaction vessel, in a first organic solvent, a solution polymerization reaction of ethylene is carried out using an α-diimine metal complex (also referred to as catalyst A in the present application) as a main catalyst and at least one selected from alkyl aluminum, halogenated alkyl aluminum, aryl borane and aryl borate as a co-catalyst;

[0021] 2) in a second reaction vessel, in a second organic solvent, a solution polymerization reaction of ethylene is carried out using a metallocene complex (also referred to as catalyst B in the present application) as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminoxane, aryl borane and aryl borate as a co-catalyst,

[0022] Optionally, at least a portion of the polymer solution obtained in the first reactor is introduced into the second reactor for reaction or at least a portion of the polymer solution obtained in the second reactor is introduced into the first reactor for reaction; and

[0023] 3) combining the polymer solution obtained in the first reaction kettle or its remaining part with the polymer solution obtained in the second reaction kettle or its remaining part, removing the solvent, and obtaining the polyethylene with wide molecular weight distribution.

[0024] In certain preferred embodiments, at least a portion of the polymer solution obtained in the first reactor is introduced into the second reactor for reaction; and in step 3), the remaining portion of the polymer solution obtained in the first reactor is combined with the polymer solution obtained in the second reactor, and the solvent is removed to obtain the wide molecular weight distribution polyethylene.

[0025] In a further preferred embodiment, the first reactor and the second reactor are connected in series, and the polymer solution obtained in the first reactor is introduced into the second reactor for reaction; and in step 3), the polymer solution obtained in the second reactor is desolventized to obtain the wide molecular weight distribution polyethylene. In this case, the method comprises the following steps:

[0026] 1') in a first reaction vessel, in a first organic solvent, using an α-diimine metal complex as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminum halide, aryl borane and aryl borate as a co-catalyst, to carry out a solution polymerization reaction of ethylene;

[0027] 2') in a second reaction vessel, in a second organic solvent, using a metallocene complex as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminoxane, aryl borane and aryl borate as a co-catalyst, to carry out a solution polymerization reaction of ethylene,

[0028] Wherein, all the polymer solution obtained by the reaction in the first reaction kettle is introduced into the second reaction kettle for reaction; and

[0029] 3') removing the solvent from the polymer solution obtained by the reaction in the second reactor to obtain the polyethylene with wide molecular weight distribution.

[0030] In certain preferred embodiments, at least a portion of the polymer solution obtained in the second reactor is introduced into the first reactor for reaction; and in step 3), the polymer solution obtained in the first reactor is combined with the remaining portion of the polymer solution obtained in the second reactor, and the solvent is removed to obtain the wide molecular weight distribution polyethylene.

[0031] In a further preferred embodiment, the second reactor and the first reactor are connected in series, and the polymer solution obtained by the reaction in the second reactor is introduced into the first reactor for reaction; and in step 3), the solvent is removed from the polymer solution obtained by the reaction in the first reactor to obtain the wide molecular weight distribution polyethylene. In this case, the method comprises the following steps:

[0032] 1″) in a first reaction vessel, in a first organic solvent, using an α-diimine metal complex as a main catalyst and at least one selected from alkyl aluminum, halogenated alkyl aluminum, aryl borane and aryl borate as a co-catalyst, to carry out a solution polymerization reaction of ethylene;

[0033] 2″) in a second reaction vessel, in a second organic solvent, using a metallocene complex as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminoxane, aryl borane and aryl borate as a co-catalyst, to carry out a solution polymerization reaction of ethylene,

[0034] wherein all the polymer solution obtained by the reaction in the second reaction kettle is introduced into the first reaction kettle for reaction; and

[0035] 3″) removing the solvent from the polymer solution obtained by the reaction in the first reaction kettle to obtain the wide molecular weight distribution polyethylene.

[0036] In some other preferred embodiments, the first reactor and the second reactor are connected in parallel, and in step 3), the polymer solution obtained by the reaction in the first reactor is combined with the polymer solution obtained by the reaction in the second reactor, and the solvent is removed to obtain the wide molecular weight distribution polyethylene. In this case, the method comprises the following steps:

[0037] 1″′) in a first reaction vessel, in a first organic solvent, using an α-diimine metal complex as a main catalyst and at least one selected from alkyl aluminum, halogenated alkyl aluminum, aryl borane and aryl borate as a co-catalyst, to carry out a solution polymerization reaction of ethylene;

[0038] 2″′) in a second reaction vessel, in a second organic solvent, using a metallocene complex as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminoxane, aryl borane and aryl borate as a co-catalyst, to carry out a solution polymerization reaction of ethylene; and

[0039] 3”′) combining the polymer solution obtained in the first reaction kettle with the polymer solution obtained in the second reaction kettle, removing the solvent, and obtaining the polyethylene with wide molecular weight distribution.

[0040] In a preferred embodiment, the α-diimine metal complex is selected from one or more metal complexes represented by general formula (I):

[0041]

[0042] In formula (I), R 1 -R 6are independently hydrogen, C1-C4 alkyl, C1-C4 haloalkyl, C2-C4 alkenyl, halogen, C1-C4 alkoxy or C6-C10 aryl, or adjacent groups, such as R 1 and R 2 , can also be connected together with the connected carbon atoms to form a ring, such as a 5-7 membered ring; R 7 , R 11 , R 12 and R 16 R is independently C1-C6 alkyl, C3-C6 cycloalkyl, unsubstituted or substituted phenyl or phenyl-substituted C1-C4 alkyl; 8 , R 9 , R 10 , R 13 , R 14 and R 15 are independently hydrogen, C1-C6 chain alkyl, C3-C6 cycloalkyl, unsubstituted or substituted phenyl, C1-C4 alkyl substituted with phenyl, halogen, C1-C4 alkoxy, nitro, substituted amino or mercapto; M is nickel or palladium; each X is independently selected from halogen, C1-C6 alkyl or C2-C6 alkenyl, wherein the substituted phenyl has 1-5 substituents selected from the group consisting of halogen, C1-C4 alkyl and C1-C4 haloalkyl.

[0043] In a further preferred embodiment, the α-diimine metal complex is selected from at least one of the metal complexes represented by general formula (IIa) or (IIb):

[0044]

[0045] In formula (IIa) or (IIb), R' 1 and R' 2 are independently hydrogen, C1-C4 alkyl, C1-C4 haloalkyl, halogen or C1-C4 alkoxy; R' 3 , R' 4 , R' 6 and R' 7 are independently C1-C6 alkyl, C3-C6 cycloalkyl, unsubstituted or substituted phenyl or phenyl-substituted C1-C4 alkyl; R' 5 and R' 8 are independently hydrogen, C1-C6 chain alkyl, C3-C6 cycloalkyl, unsubstituted or substituted phenyl, C1-C4 alkyl substituted with phenyl, halogen or C1-C4 alkoxy; M is nickel or palladium; X is halogen, wherein the substituted phenyl has 1-5 substituents selected from the group consisting of halogen, C1-C4 alkyl and C1-C4 haloalkyl.

[0046] In a particularly preferred embodiment, as the α-diimine metal complex, for example, the following metal complexes can be cited as specific examples:

[0047]

[0048] It should be noted that these metal complexes can be used alone or in any proportion.

[0049] In a preferred embodiment, the metallocene complex is selected from one or more metal complexes represented by general formula (III) or general formula (IV):

[0050]

[0051] In formula (III), R' is a C1-C8 straight or branched alkylene group, a C13-C21 diaryl alkylene group, a C2-C8 dialkylsilylene group or a C12-C20 diaryl silylene group, preferably a C1-C4 straight or branched alkylene group, a C13-C17 diaryl alkylene group, a C2-C4 dialkylsilylene group or a C12-C16 diarylsilylene group, more preferably a methylene group, an ethylene group, an isopropylidene group, a diphenylmethylene group, a dimethylsilylene group or a diphenylsilylene group; and Each independently represents a cyclopentadienyl, fluorenyl or indenyl group which is unsubstituted or substituted by 1 to 4 substituents selected from halogen, C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy or C6-C10 aryl; M is a Group IVB metal; each X is independently selected from halogen, C1-C6 alkyl or C2-C6 alkenyl,

[0052]

[0053] In formula (IV), and Each independently represents a cyclopentadienyl, fluorenyl or indenyl group, R" and R'" are each independently selected from hydrogen, C1-C8 straight chain or branched alkyl, preferably selected from hydrogen, C1-C4 straight chain or branched alkyl; M is a Group IVB metal; each X is independently selected from halogen, C1-C6 alkyl or C2-C6 alkenyl.

[0054] In a preferred embodiment, the structural formula of the alkyl aluminum as a co-catalyst is as shown in formula (Va),

[0055] Al(R) 3 (Va)

[0056] Wherein, each group R is independently selected from C1-C8 alkyl, preferably selected from methyl, ethyl, propyl, butyl and isobutyl, more preferably selected from ethyl and isobutyl. The alkyl aluminum can be used alone or in any combination of any proportion.

[0057] Specifically, as the alkyl aluminum, for example, trimethyl aluminum (Al(CH 3 ) 3 ), triethylaluminum (Al(CH 3 CH 2 ) 3 ), tri-n-propylaluminum (Al(nC 3 H 7 ) 3 ), triisopropylaluminum (Al(iC 3 H 7 ) 3 ), triisobutylaluminum (Al(iC 4 H 9 ) 3 )、tri-n-pentyl aluminum (Al(nC 5 H 11 ) 3 )、tri-n-hexyl aluminum (Al(nC 6 H 13 ) 3 ), diethyl methylaluminum (Al(CH 3 )(CH 3 CH 2 ) 2 ), and dimethylethylaluminum (Al(CH 3 ) 2 (CH 3 CH 2 )), etc., preferably selected from trimethylaluminum, triethylaluminum, and triisobutylaluminum.

[0058] In a preferred embodiment, the general structural formula of the alkylaluminoxane used as a co-catalyst is as shown in formula (Vb) or (Vc),

[0059]

[0060] Wherein, each group R is independently selected from C1-C8 alkyl, preferably selected from methyl, ethyl, propyl, butyl and isobutyl, more preferably selected from methyl and ethyl, and n is any integer in the range of 1-50, preferably any integer in the range of 10-30. The alkylaluminoxane can be used alone or in combination in any proportion.

[0061] Specifically, the alkylaluminoxane is preferably selected from methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, n-butylaluminoxane, modified methylaluminoxane and modified ethylaluminoxane, and more preferably selected from methylaluminoxane and modified methylaluminoxane.

[0062] In a preferred embodiment, the structural formula of the alkyl aluminum halide as a co-catalyst is as shown in Formula (Vd),

[0063] Al(R) n X 3-n (Vd)

[0064] Wherein, each group R is independently selected from C1-C8 alkyl, preferably selected from methyl, ethyl, propyl, butyl and isobutyl, more preferably selected from ethyl and isobutyl, X is halogen, preferably selected from chlorine and bromine, and n is 1 or 2. The halogenated alkylaluminum can be used alone or in combination in any proportion.

[0065] Specifically, as the alkyl aluminum halide, for example, dimethyl aluminum chloride (Al(CH 3 ) 2 Cl), dichloromethylaluminum (Al(CH 3 )Cl 2 ), diethylaluminum monochloride (Al(CH 3 CH 2 ) 2 Cl), ethylaluminum dichloride (Al(CH 3 CH 2 )Cl 2 )Dipropylaluminum monochloride (Al(C 3 H 7 ) 2 Cl), dichloropropylaluminum (Al(C 3 H 7 )Cl 2 ))、Di-n-butylaluminum monochloride (Al(nC 4 H 9 ) 2 Cl), n-butylaluminum dichloride (Al(nC 4 H 9 )Cl 2 ), diisobutylaluminum monochloride (Al(iC 4 H 9 ) 2 Cl), dichloroisobutylaluminum (Al(iC 4 H 9 )Cl 2 ), di-n-pentylaluminum monochloride (Al(nC 5 H 11 ) 2 Cl), dichloropentyl aluminum (Al(nC5 H 11 )Cl 2 ), diisopentylaluminum monochloride (Al(iC 5 H 11 ) 2 Cl), dichloroisopentylaluminum (Al(iC 5 H 11 )Cl 2 ), di-n-hexylaluminum monochloride (Al(nC 6 H 13 ) 2 Cl), dichlorohexyl aluminum (Al(nC 6 H 13 )Cl 2 ), diisohexylaluminum monochloride (Al(iC 6 H 13 ) 2 Cl), dichloroisohexylaluminum (Al(iC 6 H 13 )Cl 2 ), ethylaluminum monochloromethyl (Al(CH 3 )(CH 3 CH 2 )Cl), monochloromethylpropylaluminum (Al(CH 3 )(C 3 H 7 )Cl), monochloromethyl n-butylaluminum (Al(CH 3 )(nC 4 H 9 )Cl), monochloromethyl isobutyl aluminum (Al(CH 3 )(iC 4 H 9 )Cl), ethylpropylaluminum monochloride (Al(CH 2 CH 3 )(C 3 H 7 )Cl), ethyl n-butylaluminum monochloride (Al(CH 2 CH 3 )(nC 4 H 9 )Cl), ethyl isobutyl aluminum monochloride (Al(CH 2 CH 3 )(iC 4 H 9 )Cl) and the like, preferably selected from diethylaluminum monochloride, ethylaluminum dichloride, di-n-butylaluminum monochloride, n-butylaluminum dichloride, diisobutylaluminum monochloride, isobutylaluminum dichloride, di-n-hexylaluminum monochloride and n-hexylaluminum dichloride, further preferably selected from diethylaluminum monochloride and ethylaluminum dichloride.

[0066] In a preferred embodiment, the arylborane and arylborate as cocatalyst are selected from triphenylboron, tri(pentafluorophenyl)boron, triphenylcarbon tetra(pentafluorophenyl)borate, N,N-dimethylanilinium tetra(pentafluorophenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, 1-butyl-3-methylimidazole tetrafluoroborate, ferrocene tetrafluoroborate, trimethylammonium tetraphenylborate, triethylammonium tetraphenylborate, triisopropylammonium tetraphenylborate, tri-n-butylammonium tetraphenylborate, trimethylammonium tetra(4-methylphenyl)borate, triisopropylammonium tetra(4-methylphenyl)borate, ) borate, trimethylammonium tetrakis(2,4-dimethylphenyl)borate, triethylammonium tetrakis(2,4-dimethylphenyl)borate, trimethylammonium tetrakis(4-trifluoromethylphenyl)borate, tri-n-butylammonium tetrakis(4-trifluoromethylphenyl)borate, tri-n-butylammonium tetrakis(pentafluorophenyl)borate and N,N-diethylanilinium tetrakis(pentafluorophenyl)borate, more preferably one or more selected from tris(pentafluorophenyl)boron, triphenylcarbon tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate and triethylammonium tetrakis(pentafluorophenyl)borate.

[0067] In a preferred embodiment, in step 1), the molar ratio of the total amount of the co-catalyst alkylaluminum and halogenated alkylaluminum, calculated as aluminum atoms, to the amount of the α-diimine metal complex, calculated as central metal atoms, is (10-2000):1, preferably (100-1500):1, more preferably (200-1000:1; and / or the molar ratio of the total amount of the co-catalyst arylborane and aryl borate, calculated as boron atoms, to the amount of the α-diimine metal complex, calculated as central metal atoms, is (1-10):1, preferably (2-5):1.

[0068] In a preferred embodiment, in step 2), the molar ratio of the total amount of the co-catalyst alkylaluminum and alkylaluminoxane, calculated as aluminum atoms, to the amount of the metallocene complex, calculated as central metal atoms, is (10-5000):1, preferably (100-2000):1, more preferably (500-1000):1; and / or the molar ratio of the total amount of the co-catalyst arylborane and aryl borate, calculated as boron atoms, to the amount of the metallocene complex, calculated as central metal atoms, is (1-10):1, preferably (2-5):1.

[0069] In a preferred embodiment, the first organic solvent and the second organic solvent are each independently selected from at least one of aromatic hydrocarbons, alkanes and halogenated alkanes, preferably selected from one or more of toluene, dichloromethane, n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane, n-octane and Isopare series solvents, more preferably selected from one or more of n-pentane, n-hexane, cyclohexane, toluene and dichloromethane.

[0070] In a preferred embodiment, the conditions for the polymerization reaction in the first reactor include: a polymerization temperature of 0-100°C, preferably 50-80°C; a polymerization pressure of 0.1-4.0Mpa, preferably 0.5-3.0Mpa; and / or the conditions for the polymerization reaction in the second reactor include: a polymerization temperature of 40-150°C, preferably 70-130°C; a polymerization pressure of 0.1-4.0Mpa, preferably 0.5-3.0Mpa.

[0071] In addition, the cocatalyst alkylaluminum, alkylaluminoxane, halogenated alkylaluminum, arylborane or arylborate is generally used in the form of a solution. When preparing the solution of the cocatalyst, there is no particular limitation on the solvent used, as long as it can dissolve the cocatalyst. The solvent is generally selected as an alkane solvent, such as n-pentane, isopentane, cyclopentane, neopentane, etc., or an aromatic solvent, such as toluene, ethylbenzene, xylene, etc. According to the present application, in order to facilitate subsequent separation, it is preferred to use a solvent that is the same as the polymerization solvent; or a solvent that is the same as one of the solvents in the mixed solvent for polymerization.

[0072] In the second aspect, the present application provides a wide molecular weight distribution polyethylene having a weight average molecular weight of 100,000-1,000,000 g / mol, a polymer dispersibility index (PDI) of 6-35, and a degree of branching of 10-100 / 1000C, wherein the number of long chain branches (LCB) above C6 in the branched chains of the polyethylene accounts for 5-25%.

[0073] In a preferred embodiment, the weight average molecular weight of the wide molecular weight distribution polyethylene is 100,000-500,000 g / mol, the polymer dispersibility index (PDI) is 10-28, and the degree of branching is 20-80 / 1000C, wherein the number of long chain branches (LCB) above C6 in the polyethylene branches accounts for 8-22%.

[0074] In a more preferred embodiment, the weight average molecular weight of the wide molecular weight distribution polyethylene is 150,000-300,000 g / mol, the polymer dispersibility index (PDI) is 10-20, and the degree of branching is 22-73 / 1000C, wherein the number of long chain branches (LCB) above C6 in the polyethylene branches accounts for 10-20%.

[0075] In a preferred embodiment, the broad molecular weight distribution polyethylene is prepared by the method for preparing broad molecular weight distribution polyethylene of the present application.

[0076] Example

[0077] The embodiments of the present application will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be construed as limiting the scope of the present application.

[0078] The test method for the molecular weight and distribution of the polymers obtained in the following examples and comparative examples is as follows: The polymer molecular weight is measured using a PL-220 gel permeation chromatograph from 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 measurement temperature of 150° C., and a sample concentration of 2.0 mg / mL. The polymer dispersity index (PDI) is calculated based on the measured weight average molecular weight and number average molecular weight.

[0079] The branching degree and the ratio of branches of different lengths of the obtained polymers in the following examples and comparative examples were calculated based on the carbon nuclear magnetic resonance spectrum. The specific method is as follows: the microstructure of the polyethylene sample was determined using a Bruker Avance 600M nuclear magnetic resonance spectrometer. The sample was dissolved in deuterated o-dichlorobenzene to prepare a solution. The test temperature was 120°C, and the nuclear magnetic resonance hydrogen spectrum was obtained by scanning 2000 times and 6000 times respectively. 1 H-NMR) and carbon nuclear magnetic resonance spectroscopy ( 13 C-NMR).

[0080] The melt strength of the polymers obtained in the following examples and comparative examples was tested by using a Gottfert RT2000 advanced capillary rheometer equipped with a Rheotens module. The die length was 20 mm, the inner diameter was 2 mm, the plunger movement speed was 0.2 mm / s, the test temperature was 210°C, the initial pulling speed was 11.3 mm / s, and the acceleration was 6 mm / s. 2 The melt tension when the melt filament breaks is the melt strength of the polymer.

[0081] Example 1

[0082] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (5.5 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B1 (rac-vinylbisindenyl zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (11 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B1 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A1 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at a speed of 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B1 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P1 was weighed. The polymer test results are shown in Table 1.

[0083]

[0084] Example 2

[0085] In a glove box, the above-mentioned catalyst A1 (0.022 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (11 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B1 (rac-vinylbisindenyl zirconium dichloride) (0.0055 mmol), dichloromethane (10 mL), and methylaluminoxane (5.5 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B1 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A1 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at a speed of 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B1 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P2 was weighed. The polymer test results are shown in Table 1.

[0086] Example 3

[0087] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (5.5 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B1 (rac-vinyl bis-indenyl zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (11 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B1 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100° C. for 2 hours, hexane (1 L) and the above-configured catalyst A1 solution were added to the kettle in sequence. When the reactor was heated to 60° C., 2.0 MPa of ethylene was introduced, and the polymerization reaction was carried out for 15 minutes under stirring at 200 rpm. At the same time, the second high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, and then hexane (1L) and the above-configured catalyst B1 solution were added to the kettle in sequence. When the reactor was heated to 100°C, 2.0MPa ethylene was introduced, and the polymerization reaction was carried out for 15 minutes under stirring at 200rpm. After the reaction was completed, the polymer solutions in the first polymerization reactor and the second reactor were transferred to the collection tank at the same time. After adding the acidified ethanol solution to the collection tank, the solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to constant weight, and the obtained polymer P3 was weighed. The polymer test results are shown in Table 1.

[0088] Example 4

[0089] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (5.5 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B2 (dimethylsilyl-bis-(1-indenyl) zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (11 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B2 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A1 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at a speed of 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B2 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P4 was weighed. The polymer test results are shown in Table 1.

[0090] Example 5

[0091] In a glove box, the above-mentioned catalyst A3 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (5.5 mmol) were sequentially added to a 100 mL conical flask, stirred and mixed to form a catalyst A3 solution for standby use. Catalyst B2 (dimethylsilyl-bis-(1-indenyl) zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (11 mmol) were sequentially added to another 100 mL conical flask, stirred and mixed to form a catalyst B2 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A3 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B2 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding the acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P5 was weighed.

[0092] The polymer test results are shown in Table 1.

[0093]

[0094] Example 6

[0095] In a glove box, the above-mentioned catalyst A6 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (5.5 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A6 solution for standby use. Catalyst B2 (dimethylsilyl-bis-(1-indenyl) zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (11 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B2 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A6 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B2 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding the acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P6 was weighed.

[0096] The polymer test results are shown in Table 1.

[0097]

[0098] Example 7

[0099] In a glove box, the above-mentioned catalyst A3 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (5.5 mmol) were sequentially added to a 100 mL conical flask, stirred and mixed to form a catalyst A3 solution for standby use. Catalyst B3 (di(tert-butylcyclopentadienyl)zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (11 mmol) were sequentially added to another 100 mL conical flask, stirred and mixed to form a catalyst B3 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A3 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B3 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P7 was weighed. The polymer test results are shown in Table 1.

[0100] Example 8

[0101] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (5.5 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B1 (rac-vinylbisindenyl zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (11 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B1 solution for standby use. After the second high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst B1 solution were added to the kettle in sequence. When the reactor was heated to 100°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at a speed of 200rpm, the polymer solution in the second reactor was transferred to the first reactor, and then the above-configured catalyst A1 solution was added to the first reactor. When the temperature reached 60°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the first reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P7 was weighed. The polymer test results are shown in Table 1.

[0102] Example 9

[0103] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (3.3 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B1 (rac-vinylbisindenyl zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (5.5 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B1 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A1 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at a speed of 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B1 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P9 was weighed. The polymer test results are shown in Table 1.

[0104] Example 10

[0105] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (11 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B1 (rac-vinylbisindenyl zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and methylaluminoxane (5.5 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B1 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A1 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at a speed of 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B1 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P10 was weighed. The polymer test results are shown in Table 1.

[0106] Embodiment 11

[0107] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and diethylaluminum monochloride (5.5 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B1 (rac-vinylbisindenyl zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), and modified methylaluminoxane (11 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B1 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A1 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at a speed of 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B1 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P11 was weighed. The polymer test results are shown in Table 1.

[0108] Example 12

[0109] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and ethylaluminum dichloride (5.5 mmol) were added to a 100 mL conical flask in sequence, stirred and mixed to form a catalyst A1 solution for standby use. Catalyst B1 (rac-vinylbisindenyl zirconium dichloride) (0.011 mmol), dichloromethane (10 mL), triphenylcarbon tetrakis (pentafluorophenyl) borate (0.022 mmol) and triisobutylaluminum (11 mmol) were added to another 100 mL conical flask in sequence, stirred and mixed to form a catalyst B1 solution for standby use. After the first high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst A1 solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0MPa ethylene was introduced. After the polymerization reaction was carried out for 15 minutes under stirring at a speed of 200rpm, the polymer solution in the first reactor was transferred to the second reactor, and then the above-configured catalyst B1 solution was added to the second reactor. When the temperature was raised to 100°C, 2.0MPa ethylene was introduced to continue the reaction for 15 minutes. After the reaction was completed, the polymer solution in the second reactor was transferred to a collection tank. After adding an acidified ethanol solution to the collection tank, a solid polymer was precipitated. After filtering and washing, the polymer was vacuum dried at 60°C to a constant weight, and the obtained polymer P12 was weighed. The polymer test results are shown in Table 1.

[0110] Comparative Example 1

[0111] In a glove box, the above-mentioned catalyst A1 (0.011 mmol), dichloromethane (10 mL), and dichloroethylaluminum (5.5 mmol) were added to a 100 mL conical flask in sequence, mixed and set aside. After the 2L high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst solution were added to the kettle in sequence. When the reactor was heated to 60°C, 2.0 MPa of ethylene was introduced, 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 the obtained polymer P13 was weighed. The polymer test results are shown in Table 1.

[0112] Comparative Example 2

[0113] In a glove box, catalyst B1 (rac-vinylbisindenyl zirconium dichloride) (0.011mmol), dichloromethane (10mL), and methylaluminoxane (11mmol) were added to a 100mL conical flask in sequence, mixed and set aside. After the 2L high-pressure polymerization kettle was purged with high-purity nitrogen at 100°C for 2 hours, hexane (1L) and the above-configured catalyst solution were added to the kettle in sequence. When the reactor was heated to 100°C, 2.0MPa ethylene was introduced, 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 the obtained polymer P14 was weighed. The polymer test results are shown in Table 1.

[0114] Table 1 Polymer test results of various embodiments and comparative examples

[0115]

[0116] By comparing the examples with the comparative examples, it can be seen that the polyethylene prepared by the method provided in the present application not only has a wider molecular weight distribution, but also contains more long side chains on the polymer main chain, which can significantly improve the melt strength of the polymer, thereby giving the polymer more excellent processing performance and mechanical properties.

[0117] Although the specific implementations of the present application have been described in detail above in conjunction with the embodiments, it should be pointed out that the protection scope of the present application 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 application, and these changed implementations are obviously also included in the protection scope of the present application.

Claims

1. A method for preparing polyethylene with a wide molecular weight distribution, comprising the following steps: 1) In a first reaction vessel, in a first organic solvent, a solution polymerization reaction of ethylene is carried out using an α-diimine metal complex as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminum halide, aryl borane and aryl borate as a co-catalyst; 2) in a second reaction vessel, in a second organic solvent, using a metallocene complex as a main catalyst and at least one selected from alkyl aluminum, alkyl aluminoxane, aryl borane and aryl borate as a co-catalyst, to carry out a solution polymerization reaction of ethylene, in, Optionally, at least a portion of the polymer solution obtained by the reaction in the first reactor is introduced into the second reactor for reaction, or at least a portion of the polymer solution obtained by the reaction in the second reactor is introduced into the first reactor for reaction; and 3) combining the polymer solution obtained in the first reaction kettle or its remaining part with the polymer solution obtained in the second reaction kettle or its remaining part, removing the solvent, and obtaining the polyethylene with wide molecular weight distribution.

2. The preparation method according to claim 1, wherein at least a portion of the polymer solution obtained in the first reactor is introduced into the second reactor for reaction; and in step 3), the remaining portion of the polymer solution obtained in the first reactor is combined with the polymer solution obtained in the second reactor, and the solvent is removed to obtain the polyethylene with a wide molecular weight distribution; Preferably, the first reactor and the second reactor are connected in series, and the polymer solution obtained in the first reactor is introduced into the second reactor for reaction; and in step 3), the solvent is removed from the polymer solution obtained in the second reactor to obtain the wide molecular weight distribution polyethylene.

3. The preparation method according to claim 1, wherein at least a portion of the polymer solution obtained in the second reactor is introduced into the first reactor for reaction; and in step 3), the polymer solution obtained in the first reactor is combined with the remaining portion of the polymer solution obtained in the second reactor, and the solvent is removed to obtain the wide molecular weight distribution polyethylene. Preferably, the second reactor and the first reactor are connected in series, and the polymer solution obtained in the second reactor is completely introduced into the first reactor for reaction; and in step 3), the solvent is removed from the polymer solution obtained in the first reactor to obtain the wide molecular weight distribution polyethylene.

4. The preparation method according to claim 1, wherein the first reactor and the second reactor are connected in parallel, and in step 3), the polymer solution obtained by the reaction in the first reactor is combined with the polymer solution obtained by the reaction in the second reactor, and the solvent is removed to obtain the wide molecular weight distribution polyethylene.

5. The preparation method according to any one of claims 1 to 4, wherein The α-diimine metal complex is selected from one or more metal complexes represented by general formula (I): In formula (I), R1-R6 are independently hydrogen, C1-C4 alkyl, C1-C4 haloalkyl, C2-C4 alkenyl, halogen, C1-C4 alkoxy or C6-C10 aryl, or adjacent groups, such as R1 and R2, may also be linked together with the connected carbon atoms to form a ring, such as a 5-7 membered ring; R7, R 11 , R 12 and R 16 are independently C1-C6 alkyl, C3-C6 cycloalkyl, unsubstituted or substituted phenyl or phenyl-substituted C1-C4 alkyl; R8, R9, R 10 , R 13 , R 14 and R 15 are independently hydrogen, C1-C6 chain alkyl, C3-C6 cycloalkyl, unsubstituted or substituted phenyl, C1-C4 alkyl substituted with phenyl, halogen, C1-C4 alkoxy, nitro, substituted amino or mercapto; M is nickel or palladium; each X is independently selected from halogen, C1-C6 alkyl or C2-C6 alkenyl, wherein the substituted phenyl has 1-5 substituents selected from the group consisting of halogen, C1-C4 alkyl and C1-C4 haloalkyl.

6. The preparation method according to claim 5, wherein the α-diimine metal complex is selected from at least one of the metal complexes represented by general formula (IIa) or (IIb): In formula (IIa) and (IIb), R'1 and R'2 are independently hydrogen, C1-C4 alkyl, C1-C4 haloalkyl, halogen or C1-C4 alkoxy; R'3, R'4, R'6 and R'7 are independently C1-C6 chain alkyl, C3-C6 cycloalkyl, unsubstituted or substituted phenyl or phenyl-substituted C1-C4 alkyl; R'5 and R'8 are independently hydrogen, C1-C6 chain alkyl, C3-C6 cycloalkyl, unsubstituted or substituted phenyl, phenyl-substituted C1-C4 alkyl, halogen or C1-C4 alkoxy; M is nickel or palladium; X is halogen, wherein the substituted phenyl has 1 to 5 substituents selected from the group consisting of halogen, C1-C4 alkyl and C1-C4 haloalkyl, Preferably, the α-diimine metal complex is selected from one or more of the following metal complexes:

7. The preparation method according to any one of claims 1 to 6, wherein The metallocene complex is selected from one or more metal complexes represented by general formula (III) or general formula (IV): In formula (III), R' is a C1-C8 straight or branched alkylene group, a C13-C21 diaryl alkylene group, a C2-C8 dialkylsilylene group or a C12-C20 diaryl silylene group, preferably a C1-C4 straight or branched alkylene group, a C13-C17 diaryl alkylene group, a C2-C4 dialkylsilylene group or a C12-C16 diarylsilylene group, more preferably a methylene group, an ethylene group, an isopropylidene group, a diphenylmethylene group, a dimethylsilylene group or a diphenylsilylene group; Each independently represents a cyclopentadienyl, fluorenyl or indenyl group which is unsubstituted or substituted by 1 to 4 substituents selected from halogen, C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy or C6-C10 aryl; M is a Group IVB metal; each X is independently selected from halogen, C1-C6 alkyl or C2-C6 alkenyl, In formula (IV), Each independently represents a cyclopentadienyl, fluorenyl or indenyl group, R" and R'" are each independently selected from hydrogen, C1-C8 straight chain or branched alkyl, preferably selected from hydrogen, C1-C4 straight chain or branched alkyl; M is a Group IVB metal; each X is independently selected from halogen, C1-C6 alkyl or C2-C6 alkenyl.

8. The preparation method according to any one of claims 1 to 7, wherein: The general structural formula of the co-catalyst alkyl aluminum is shown in formula (Va), Al(R)3(Va) wherein each group R is independently selected from a C1-C8 alkyl group, preferably selected from a methyl group, an ethyl group, a propyl group, a butyl group and an isobutyl group, and more preferably selected from an ethyl group and an isobutyl group; The general structural formula of the co-catalyst alkylaluminoxane is as shown in formula (Vb) or (Vc), wherein each group R is independently selected from C1-C8 alkyl, preferably selected from methyl, ethyl, propyl, butyl and isobutyl, more preferably selected from methyl and ethyl, and n is any integer in the range of 1-50, preferably any integer in the range of 10-30; The general structural formula of the co-catalyst halogenated alkylaluminum is shown in formula (Vd), Al(R)X3-n(Vd) wherein each group R is independently selected from C1-C8 alkyl, preferably selected from methyl, ethyl, propyl, butyl and isobutyl, more preferably selected from ethyl and isobutyl, X is halogen, preferably chlorine or bromine, and n is 1 or 2; The cocatalyst arylborane and aryl borate are selected from triphenylboron, tri(pentafluorophenyl)boron, triphenylcarbon tetra(pentafluorophenyl)borate, N,N-dimethylanilinium tetra(pentafluorophenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, 1-butyl-3-methylimidazole tetrafluoroborate, ferrocene tetrafluoroborate, trimethylammonium tetraphenylborate, triethylammonium tetraphenylborate, triisopropylammonium tetraphenylborate, tri-n-butylammonium tetraphenylborate, trimethylammonium tetra(4-methylphenyl)borate, triisopropylammonium tetra(4-methylphenyl)borate, trimethyl One or more of tris(pentafluorophenyl)boron, triphenylcarbon tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate and triethylammonium tetrakis(pentafluorophenyl)borate.

9. The preparation method according to any one of claims 1 to 8, wherein: In step 1), the molar ratio of the total amount of the co-catalyst alkylaluminum and halogenated alkylaluminum, calculated as aluminum atoms, to the amount of the α-diimine metal complex, calculated as central metal atoms, is (10-2000):1, preferably (100-1500):1, more preferably (200-1000):1; and / or the molar ratio of the total amount of the co-catalyst arylborane and aryl borate, calculated as boron atoms, to the amount of the α-diimine metal complex, calculated as central metal atoms, is (1-10):1, preferably (2-5):1; and In step 2), the molar ratio of the total amount of the co-catalyst alkylaluminum and alkylaluminoxane, calculated as aluminum atoms, to the amount of the metallocene complex, calculated as central metal atoms, is (10-5000):1, preferably (100-2000):1, more preferably (500-1000):1; and / or the molar ratio of the total amount of the co-catalyst arylborane and aryl borate, calculated as boron atoms, to the amount of the metallocene complex, calculated as central metal atoms, is (1-10):1, preferably (2-5):

1.

10. The preparation method according to any one of claims 1 to 9, wherein The first organic solvent and the second organic solvent are each independently selected from at least one of aromatic hydrocarbons, alkanes and halogenated alkanes, preferably selected from one or more of toluene, dichloromethane, n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane, n-octane and Isopare series solvents, more preferably selected from one or more of n-pentane, n-hexane, cyclohexane, toluene and dichloromethane.

11. The preparation method according to any one of claims 1 to 10, wherein The conditions of the polymerization reaction in the first reactor include: a polymerization temperature of 0-100° C., preferably 50-80° C.; a polymerization pressure of 0.1-4.0 MPa, preferably 0.5-3.0 MPa; and / or The conditions for the polymerization reaction in the second reactor include: a polymerization temperature of 40-150° C., preferably 70-130° C.; and a polymerization pressure of 0.1-4.0 MPa, preferably 0.5-3.0 MPa.

12. A polyethylene with a wide molecular weight distribution, wherein the weight average molecular weight of the polyethylene is 100,000-1,000,000 g / mol, preferably 100,000-500,000 g / mol, more preferably 150,000-300,000 g / mol, the polymer dispersibility index (PDI) is 6-35, preferably 10-28, more preferably 10-20, the degree of branching is 10-100 / 1000C, preferably 20-80 / 1000C, more preferably 22-73 / 1000C, wherein the number of long branches of C6 or above in the branched chains of the polyethylene accounts for 5-25%, preferably 8-22%, more preferably 10-20%.

13. The broad molecular weight distribution polyethylene according to claim 12, which is prepared by the method according to any one of claims 1 to 11.

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