Novel branched polyethylene and preparation method thereof

Abstract

The invention discloses branched polyethylene and a preparation method thereof. The preparation method of the branched polyethylene comprises the following steps: taking an alpha-diimine nickel catalyst as a main catalyst, wherein the alpha-diimine nickel catalyst is shown in a formula (1); the method comprises the following steps of: polymerizing ethylene by using at least one selected from aluminoxane, modified aluminoxane, alkyl aluminum, alkyl aluminum hydrolysate, halogenated alkyl aluminum, aryl boron, alkyl boron and borate as a cocatalyst and using a polymerization solvent containing a halogenated organic solvent under the conditions that the polymerization reaction temperature is 60-85 DEG C and the polymerization pressure is 1.2-3.0 MPa to obtain the branched polyethylene. Compared with the traditional EPDM, the branched polyethylene prepared by the method provided by the invention has the advantage that the low-temperature impact performance of a polypropylene base material is improved very well.

Description

Technical Field

[0001] The invention relates to a novel branched polyethylene, a preparation method of the branched polyethylene, a polyolefin composition containing the branched polyethylene and use of the branched polyethylene for improving the low-temperature impact performance of polyolefin. Background Art

[0002] Branched polyethylene has branches on its carbon chain, so it has low viscosity in solution and molten state, and exhibits good mechanical properties, melt stretchability, transparency and good processing properties, becoming a major variety of polyolefin products.

[0003] Branched polyethylene has better processing performance, better film-forming properties and film light transmittance than linear polyethylene. Moreover, when the degree of branching increases, the glass transition temperature Tg decreases. Therefore, at room temperature, branched polyethylene appears as a rubbery elastomer, and thus has great industrial application value.

[0004] At present, the conventional method for preparing branched polyethylene is to use a late transition metal catalyst. In 1995, Professor Brookhart of North Carolina State University in the United States first reported that the (α-diimine) nickel catalyst I shown below with chain walking ability can prepare high molecular weight, branched polyethylene. Subsequent researchers have synthesized catalysts with other structures (Catal. Sci. Technol. 2013, 3, 1172; Macromolecules 42, 2009, 7789; Angew. Chem. Int. Ed. 2004, 43, 1821; J. Am. Chem. Soc. 2013, 135, 16316; Organometallics 23, 2004, 3276-3283), such as the (α-diimine) nickel catalysts II to VII shown below, the thermal stability of this type of catalyst has been improved to a certain extent.

[0005]

[0006] On the other hand, polyethylene materials, especially polypropylene, will become brittle at low temperatures. Therefore, during transportation, construction, and use in cold northern regions, brittle damage easily occurs, which limits the application of polyolefins, especially polypropylene. Therefore, improving the low-temperature impact performance of polyolefins, especially polypropylene, has always been the goal of many scientific researchers.

[0007] The structural characteristics of branched polyethylene determine that it can be used as a toughening modifier to improve the impact resistance of polypropylene. However, in actual production, there has been no report on an industrial-scale branched polyethylene production process, and there are even fewer reports on the toughening modification of polypropylene by branched polyethylene. In addition, the differences in the specific structures of the polymers will also lead to large differences in their toughening modification effects. Summary of the invention

[0008] In view of the technical problems of the prior art, the inventors of the present invention have conducted in-depth research and found that the low-temperature impact properties of polyolefins, especially polypropylene, can be greatly improved by using the branched polyethylene of the present invention as an additive, thereby expanding the application range of polyolefins, especially polypropylene, and improving its mechanical properties.

[0009] Specifically, the inventors have conducted in-depth research based on the prior art and found that the branched polyethylene of the present invention can be prepared by controlling specific polymerization conditions, using specific polymerization catalysts, and specific polymerization solvents. The branched polyethylene of the present invention can significantly improve the low-temperature impact properties of polyolefins, especially polypropylene. Thus, the present invention is completed.

[0010] More specifically, the present invention relates to the following aspects.

[0011] The method for preparing branched polyethylene is characterized by comprising the following steps:

[0012] The α-diimine nickel catalyst represented by the following formula (1) is used as a main catalyst; at least one selected from aluminoxane, modified aluminoxane, alkyl aluminum, alkyl aluminum hydrolyzate, halogenated alkyl aluminum, aryl boron, alkyl boron and borate is used as a co-catalyst, and ethylene is polymerized at a polymerization temperature of 60-85° C. (preferably 65-70° C.) and a polymerization pressure of 1.2-3.0 MPa (preferably 1.4-2.3 MPa) using a polymerization solvent containing a halogenated organic solvent to obtain a branched polyethylene:

[0013]

[0014] In formula (1), R1 and R2 are each independently selected from hydrogen, C 1-4 A straight or branched hydrocarbon group, or R1 and R2 together with the carbon atom to which they are bonded form a 5-6 membered ring; R3, R5, R7, R8, R 10 , R 12 Each independently selected from C 3-10 Straight or branched hydrocarbon group, R4, R6, R9, R 11 are each independently selected from hydrogen, C 1-4 A straight chain or branched hydrocarbon group, X is a halogen.

[0015] A polyolefin composition comprises a polyolefin and the branched polyethylene of the present invention.

[0016] The branched polyethylene of the present invention is used for improving the low-temperature impact property of polyolefin.

[0017] Technical Effects

[0018] The branched polyethylene prepared by the method of the present invention can greatly improve the low-temperature impact strength of polyolefin (polypropylene) when added as an additive to polyolefin, especially polypropylene to prepare a polyolefin composition, and the tensile strength is maintained or even improved to a certain extent. Moreover, compared with EPDM, the polyolefin composition of the present invention has a more obvious effect of improving the low-temperature impact strength of polyolefin, and the improvement of the tensile strength is also better than EPDM. DETAILED DESCRIPTION

[0019] The specific embodiments of the present invention are described in detail below, but it should be pointed out that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the claims in the appendix.

[0020] 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.

[0021] 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.

[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 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).

[0024] [Method for preparing branched polyethylene]

[0025] The present invention provides a method for preparing branched polyethylene, characterized in that it comprises the following steps:

[0026] The α-diimine nickel catalyst represented by the following formula (1) is used as a main catalyst; at least one selected from aluminoxane, modified aluminoxane, alkyl aluminum, alkyl aluminum hydrolyzate, halogenated alkyl aluminum, aryl boron, alkyl boron and borate is used as a co-catalyst, and ethylene is polymerized at a polymerization temperature of 60-85° C. (preferably 65-70° C.) and a polymerization pressure of 1.2-3.0 MPa (preferably 1.4-2.3 MPa) using a polymerization solvent containing a halogenated organic solvent to obtain a branched polyethylene:

[0027]

[0028]

[0029] In formula (1), R1 and R2 are each independently selected from hydrogen, C 1-4 A straight or branched hydrocarbon group, or R1 and R2 together with the carbon atom to which they are bonded form a 5-6 membered ring; R3, R5, R7, R8, R 10 , R 12 Each independently selected from C 3-10 Straight or branched hydrocarbon group, R4, R6, R9, R 11 are each independently selected from hydrogen, C 1-4 A straight chain or branched hydrocarbon group, X is a halogen.

[0030] As the main catalyst of the present invention, an α-diimine nickel catalyst represented by the following formula (1) is used.

[0031]

[0032] In formula (1), R1 and R2 are each independently selected from hydrogen, C 1-4 A straight or branched hydrocarbon group, or R1 and R2 together with the carbon atom to which they are bonded form a 5-6 membered ring; R3, R5, R7, R8, R 10 , R 12 Each independently selected from C 3-10 Straight or branched hydrocarbon group, R4, R6, R9, R 11 are each independently selected from hydrogen, C 1-4 A straight chain or branched hydrocarbon group, X is a halogen.

[0033] In one embodiment of the present invention, R1 and R2 are each independently selected from hydrogen, C 1-4 Straight chain or branched chain alkyl.

[0034] In one embodiment of the present invention, R1 and R2 are each independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl.

[0035] In one embodiment of the present invention, R1 and R2 are each independently selected from hydrogen, methyl, and ethyl.

[0036] In one embodiment of the present invention, R1 and R2 together with the carbon atom to which they are bonded form a 5-6 membered ring, whereby the compound of formula (1) may form a structure represented by the following formula (2) or formula (3):

[0037]

[0038] In one embodiment of the present invention, R4, R6, R9, R 11 are each independently selected from hydrogen, C 1-4 Straight chain or branched chain alkyl.

[0039] In one embodiment of the present invention, R4, R6, R9, R 11 Each is independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl.

[0040] In one embodiment of the present invention, R4, R6, R9, R 11 Each is independently selected from hydrogen, methyl, and ethyl.

[0041] In one embodiment of the present invention, R3, R5, R7, R8, R 10 , R 12 Each independently selected from C 3-10 Straight or branched alkyl, more preferably selected from C 3-6 Straight chain or branched chain alkyl.

[0042] In one embodiment of the present invention, R3, R5, R7, R8, R 10 , R 12 Each is independently selected from propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers.

[0043] It should be noted that, unless otherwise specified, in the present invention, the molar amount of the main catalyst of the present invention is based on the molar amount of the Ni element.

[0044] In the present invention, the co-catalyst may be selected from aluminoxane, modified aluminoxane, alkyl aluminum, alkyl aluminum hydrolyzate, halogenated alkyl aluminum, borofluorane, alkyl boron, alkyl boron ammonium salt or a mixture thereof.

[0045] The aluminoxane used as a co-catalyst may be, for example, a linear aluminoxane represented by the following general formula (I): (R)(R)Al-(Al(R)-O) n-O-Al(R)(R), and a cyclic aluminoxane represented by the following general formula (II): -(Al(R)-O-) n+2 -.

[0046]

[0047] In the aforementioned general formulae (I) and (II), the groups R are identical or different (preferably identical) to each other, and are independently selected from C1-C8 alkyl, preferably methyl, ethyl, propyl, butyl and isobutyl, most preferably methyl and isobutyl; n is any integer in the range of 1-50, preferably any integer in the range of 10-30.

[0048] As the aluminoxane, methylaluminoxane, ethylaluminoxane, isobutylaluminoxane and n-butylaluminoxane are preferred, and methylaluminoxane and isobutylaluminoxane are more preferred.

[0049] These aluminoxanes may be used alone or in combination of two or more in any ratio.

[0050] As the alkyl aluminum, for example, there can be mentioned the compound represented by the following general formula (III):

[0051] Al(R)3 (III)

[0052] In the general formula (III), the groups R are the same or different (preferably the same) and are each independently selected from C1-C8 alkyl, preferably methyl, ethyl, propyl, butyl and isobutyl, most preferably methyl and isobutyl.

[0053] Specifically, examples of the alkyl aluminum include trimethyl aluminum (Al(CH3)3), triethyl aluminum (Al(CH3CH2)3), tri-n-propyl aluminum (Al(C3H7)3), tri-isopropyl aluminum (Al(i-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., among which trimethylaluminum, triethylaluminum, tripropylaluminum and triisobutylaluminum are preferred, and triethylaluminum and triisobutylaluminum are most preferred.

[0054] These aluminum alkyls may be used alone or in combination of two or more in any ratio.

[0055] As the halogenated alkyl aluminum, for example, there can be mentioned the compound represented by the following general formula (IV):

[0056] Al(R) n X 3-n (IV)

[0057] In the general formula (IV), the groups R are the same or different (preferably the same) and are each independently selected from C1-C8 alkyl, preferably methyl, ethyl, propyl, butyl and isobutyl, most preferably methyl and isobutyl; X represents fluorine, chlorine, bromine or iodine; n represents 1 or 2.

[0058] Specifically, as the halogenated alkyl aluminum, for example, there can be mentioned 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 (AlCH2CH3)(C4H9)Cl), chloromethyl isobutylaluminum (Al(CH2CH3)(i-C4H9)Cl), etc., among which diethylaluminum chloride, ethylaluminum dichloride, di-n-butylaluminum chloride, n-butylaluminum dichloride, diisobutylaluminum chloride, isobutylaluminum dichloride, di-n-hexylaluminum chloride, and n-hexylaluminum dichloride are preferred, and diethylaluminum chloride, ethylaluminum dichloride and di-n-hexylaluminum chloride are further preferred, and diethylaluminum chloride is most preferred.

[0059] These alkylaluminum halides may be used alone or in combination of two or more in any ratio.

[0060] In the present invention, the alkyl boron and aryl boron may be compounds represented by the following general formula (V):

[0061] B(R')3(V)

[0062] In the general formula (V), 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 Preferably, the R' is selected from methyl, ethyl, propyl, butyl, isobutyl, phenyl, tolyl, trifluoromethylphenyl and pentafluorophenyl.

[0063] 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.

[0064] These alkylboranes and arylboranes may be used alone or in combination of two or more in any ratio.

[0065] In the present invention, the borate may be a compound represented by the following general formula (VI):

[0066] [L] + [BE4] m - (VI)

[0067] In the general formula (VI), 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 L group is substituted by a straight or branched alkoxy group or a phenoxy group. m represents the valence value of the group in the L portion. Preferably, the E is selected from fluorine, phenyl, trifluoromethylphenyl and pentafluorophenyl.

[0068] In the general formula (VI), [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 1-4 A 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.

[0069] 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-methylimidazolium tetrafluoroborate, and ferrocene tetrafluoroborate.

[0070] These borates may be used alone or in combination of two or more in any ratio.

[0071] In addition, according to the present invention, the co-catalyst may be used alone or in combination of multiple co-catalysts in any proportion as required. Moreover, there is no particular limitation on the proportion of each component in the mixture and it can be selected as required.

[0072] According to the present invention, the cocatalyst 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 at this time, as long as it can dissolve the cocatalyst, and generally an alkane solvent such as n-pentane, isopentane, cyclopentane, neopentane, etc., or an aromatic solvent such as toluene, ethylbenzene, xylene, etc. is selected. According to the present invention, in order to facilitate subsequent separation, the same solvent as the polymerization solvent is preferred; or the same solvent as at least one solvent in the mixed solvent for polymerization.

[0073] It should be noted that, unless otherwise specified, in the present invention, when the co-catalyst is aluminoxane, modified aluminoxane, alkyl aluminum, alkyl aluminum hydrolyzate, or halogenated alkyl aluminum, the molar amount of the co-catalyst is calculated based on the molar amount of the Al element; when the co-catalyst is alkyl boron, aryl boron, or borate, the molar amount of the co-catalyst is calculated based on the molar amount of the B element.

[0074] In one embodiment of the present invention, the main catalyst is preferably selected from aluminoxane, alkylaluminum, halogenated alkylaluminum or a mixture thereof, and more preferably selected from alkylaluminum, halogenated alkylaluminum or a mixture thereof.

[0075] In one embodiment of the present invention, the molar ratio of the co-catalyst calculated in terms of aluminum and / or boron to the main catalyst calculated in terms of metal Ni is 50-500:1, preferably 80-300:1.

[0076] In the preparation of the branched polyethylene of the present invention, a chain transfer agent may be used or not. As the chain transfer agent, other metal alkyl compounds other than the co-catalyst of the present invention may 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 may be listed. In one embodiment of the present invention, when a chain transfer agent is used, the molar ratio of the amount of the chain transfer agent based on the metal content of the chain transfer agent to the main catalyst based on metal Ni is 5-300:1, preferably 10-200:1.

[0077] In the method for preparing branched polyethylene of the present invention, the polymerization solvent is a polymerization solvent comprising a halogenated organic solvent. More specifically, the polymerization solvent of the present invention is a polymerization solvent comprising a halogenated organic solvent among conventional polymerization solvents commonly used in the preparation of polyethylene.

[0078] The conventional polymerization solvent may be a commonly used polymerization solvent in polyethylene polymerization reaction, for example, including but not limited to C 4-10 Alkanes (such as butane, hexane, heptane, octane, nonane or decane, etc.), C 6-10 Aromatic hydrocarbon solvents (such as toluene and xylene), etc. Among them, hexane, heptane, toluene, etc. are preferably used as the general polymerization solvent.

[0079] The halogen organic solvent refers to an organic solvent containing a halogen element, and specifically, halogenated C 1-10 Alkanes, halogenated C 6-10 Aromatic hydrocarbons, preferably halogenated C 1-4 Alkanes, halogenated benzenes. The halogen element is selected from fluorine, chlorine, bromine, and iodine, and is more preferably chlorine.

[0080] As chloro-C 1-10 Examples of alkanes include methyl chloride, dichloromethane, trichloromethane, ethyl chloride, dichloroethane and its isomers (e.g., 1,1-dichloroethane, 1,2-dichloroethane), trichloroethane and its isomers (e.g., 1,1,1-trichloroethane, 1,1,2-trichloroethane, etc.). 6-10 Aromatic hydrocarbons include chlorobenzene, dichlorobenzene and its isomers, chlorotoluene, etc. 1-10 Alkanes, Fluorinated C 6-10 Aromatic hydrocarbons, brominated C 1-10 Alkanes, Brominated C 6-10 Aromatic hydrocarbons, iodinated C 1-10 Alkanes, iodinated C 6-10 Aromatic hydrocarbons include the above-mentioned chlorinated C 1-10 Alkanes, Chloro-C 6-10 Compounds obtained by replacing the chlorine in aromatic hydrocarbons with fluorine, bromine, or iodine, respectively.

[0081] The inventors of the present invention surprisingly found that by including a halogenated organic solvent in the polymerization solvent, the prepared branched polyethylene exhibits excellent toughening properties for polyolefins (especially polypropylene).

[0082] In the present invention, the amount of the halogenated organic solvent used relative to the conventional polymerization solvent (i.e., the polymerization solvent before the halogenated organic solvent is added) is, by volume ratio, 0.001 to 0.2 parts by volume, preferably 0.003 to 0.1 parts by volume, and more preferably 0.005 to 0.05 parts by volume. In the present invention, if the content of the halogenated organic solvent is too little, such a specific branched polyethylene of the present invention cannot be obtained. On the other hand, if the content of the halogenated organic solvent is too much, it will have an adverse effect on the polymerization reaction and the post-treatment of the product, affecting the performance of the branched polyethylene.

[0083] In the present invention, the source of the halogenated organic solvent may be a halogenated organic solvent added to a conventional polymerization solvent alone, or may be a halogenated organic solvent added to a conventional polymerization solvent together with the main catalyst and / or co-catalyst as a solvent for the main catalyst and / or co-catalyst, as long as the polymerization solvent contains the halogenated organic solvent when the ethylene polymerization reaction is carried out.

[0084] In the present invention, it is preferred that the α-diimine nickel catalyst represented by formula (1) and at least one selected from aluminoxane, modified aluminoxane, alkyl aluminum, alkyl aluminum hydrolyzate, halogenated alkyl aluminum, aryl boron, alkyl boron and borate are dissolved in the above-mentioned halogen organic solvent of the present invention, and then added into the polymerization solvent to carry out ethylene polymerization reaction.

[0085] In the present invention, the polymerization temperature is 60-85° C., preferably 65-70° C. If the polymerization temperature is too low, the obtained branched polyethylene cannot provide sufficient toughening effect. On the other hand, if the polymerization temperature is too high, the stability of the catalyst is greatly affected, and the obtained branched polyethylene cannot provide sufficient toughening effect.

[0086] In the present invention, the polymerization pressure is 1.2-3.0 MPa, preferably 1.4-2.3 MPa. If the polymerization pressure is too low, the obtained branched polyethylene cannot provide sufficient toughening effect, and if the polymerization pressure is too high, the branched polyethylene of the present invention cannot be obtained.

[0087] 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.

[0088] The method for preparing the branched polyethylene of the present invention is preferably carried out by solution polymerization.

[0089] In the present invention, it is preferred that only ethylene is used as the olefin raw material in the production method of the present invention. That is, in the production method of the present invention, ethylene is homopolymerized.

[0090] In the present invention, by using the main catalyst represented by the above formula (1) of the present invention, combined with the specific polymerization conditions and specific polymerization solvent of the present invention, the branched polyethylene prepared can effectively improve the low-temperature impact properties of polyolefins, especially polypropylene.

[0091] 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.

[0092] In the present invention, after the polymerization reaction is completed, the reaction can be terminated by a method known in the art. For example, ethanol hydrochloride can be used to terminate the polymerization reaction, and the ethanol hydrochloride is prepared by mixing concentrated hydrochloric acid and ethanol. The volume percentage of the concentrated hydrochloric acid relative to ethanol can be 1v / v%-25v / v%, or 3v / v%-20v / v%, for example, 5v / v%.

[0093] 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.

[0094] In addition, the density of the branched polyethylene of the present invention is low, usually 0.85 g / cm 3 -0.87g / cm 3 .

[0095] The branched polyethylene of the present invention generally has a kinematic viscosity at 260° C. of 400,000 to 4,000,000 CP.

[0096] [Polyolefin composition]

[0097] The present invention also provides a polyolefin composition, in particular a polypropylene composition.

[0098] The polyolefin composition of the present invention comprises the branched polyethylene of the present invention. Relative to the total amount of the composition, the amount of the branched polyethylene is 1wt%-50wt%, preferably 3wt%-30wt%, more preferably 5wt%-25%, and particularly preferably 5wt%-20wt%. If the content of the branched polyethylene is too little, the toughening effect cannot be fully exerted, and if the content of the branched polyethylene is too much, it will have a certain adverse effect on the tensile strength of the polyolefin.

[0099] When the branched polyethylene of the present invention is added as an auxiliary agent to polyolefin, especially polypropylene, the low-temperature impact strength of the polyolefin can be greatly improved while maintaining or further improving the tensile strength.

[0100] The present invention also provides a use of the branched polyethylene of the present invention for improving the low-temperature impact properties of polyolefins, especially polypropylene.

[0101] Example

[0102] The present invention is further described in detail below using examples, but the present invention is not limited to these examples.

[0103] In the present invention, the methyl content in the side chain is determined by nuclear magnetic resonance carbon spectroscopy. 13 C NMR, the test temperature is 120℃, the polymer sample is dissolved in deuterated o-dichlorobenzene to make a 20wt% solution, and the sample is scanned 3000 times at 120℃ to obtain the 13 CNMR spectrum. 13 The peaks in C NMR determine the content of methyl branches in the branched polyethylene.

[0104] The preparation method of the polypropylene composition is to mix branched polyethylene and polypropylene in a specific ratio, add 0.05wt% antioxidant 1010 and 0.05wt% antioxidant 168 based on the total amount of the composition, wherein 1010 and 168 are both commercially available products. The uniformly mixed mixture is granulated by twin-screw extrusion, and the tensile strength and Izod notched low-temperature impact strength of the granules are measured.

[0105] Impact performance test

[0106] The Izod notched impact strength of all samples was tested using an impact tester.

[0107] The polypropylene composition was made into 80×10×4 mm specimens with a notch depth of 2 mm. The test temperature of all samples was -30°C, and five sets of data were tested for each sample to obtain the average value.

[0108] Tensile strength determination

[0109] The tensile strength of the sample was measured using a universal tensile testing machine. The sample was measured at room temperature and a tensile speed of 50 mm min-1. The sample was dumbbell ph-shaped, with a gauge length of 25 mm and an average size of 50×5×2 mm. Five sets of data were tested for each sample and the average value was taken.

[0110] In the application examples and comparative examples, the catalyst shown in the following formula is used. The catalyst is synthesized by conventional means in the art. For example, the method in CN201710919796.4 can be used.

[0111]

[0112] Application Example 1

[0113] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.2 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 73.44 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0114] Application Example 2

[0115] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (10 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and mixed to be used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.4 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 72.05 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0116] Application Example 3

[0117] In a glove box, M1 (16.04 μmol), 1,2-dichloroethane (8 ml) and ethylaluminum dichloride (3.22 mmol) were added to a 50 ml conical flask in sequence, mixed and used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 85.81 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0118] Application Example 4

[0119] In a glove box, M1 (14.25 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, mixed and used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.9 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 71.04 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0120] Application Example 5

[0121] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 2.3 MPa ethylene was introduced at 60 ° C. The polymerization reaction was carried out under stirring at 300 rpm for 0.5 hours. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 65.19 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0122] Application Example 6

[0123] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (7 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 2.5 MPa ethylene was introduced at 60 ° C. The polymerization reaction was carried out under stirring at 300 rpm for 0.5 hours. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 59.11 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0124] Application Example 7

[0125] In a glove box, M1 (16.04 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.22 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.5 MPa ethylene was introduced at 65 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 81.16 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0126] Application Example 8

[0127] In a glove box, M1 (16.04 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.22 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.5 MPa ethylene was introduced at 70 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 50.69 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0128] Application Example 9

[0129] In a glove box, M1 (16.04 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.22 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.5 MPa ethylene was introduced at 75 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 47.16 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0130] Application Example 10

[0131] In a glove box, M1 (16.04 μmol), dichloromethane (50 ml) and ethylaluminum dichloride (3.22 mmol) were added to a 50 ml conical flask in sequence, and mixed to be used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 1.5 MPa ethylene was introduced at 80 ° C. The polymerization reaction was carried out under stirring at 300 rpm for 0.5 hours. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 24.78 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0132] Application Example 11

[0133] In a glove box, M1 (16.04 μmol), dichloromethane (15 ml) and ethylaluminum dichloride (2.32 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 1.5 MPa ethylene was introduced at 60°C. The polymerization reaction was carried out under stirring at 300 rpm for 0.5 hours. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50°C to constant weight to obtain 76.91 g of polymer. The obtained polymer was used to prepare a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0134] Application Example 12

[0135] In a glove box, M2 (16.04 μmol), dichloromethane (5 ml) and ethylaluminum dichloride (3.22 mmol) were added to a 50 ml conical flask in sequence, and mixed to be used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 1.5 MPa ethylene was introduced at 65 ° C. The polymerization reaction was carried out under stirring at 300 rpm for 0.5 hours. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 68.09 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0136] Application Example 13

[0137] In a glove box, M2 (16.04 μmol), o-dichlorobenzene (20 ml) and ethylaluminum dichloride (3.22 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 2.5 MPa ethylene was introduced at 75°C, and the polymerization reaction was carried out under stirring at 300 rpm for 0.5 hours. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid, and the polymer was filtered and washed, and then vacuum dried at 50°C to constant weight to obtain 52.29 g of polymer. The obtained polymer was used to prepare a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0138] Comparative Example 1

[0139] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 0.75 MPa ethylene was introduced at 60 ° C. The polymerization reaction was carried out under stirring at 300 rpm for 0.5 hours. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 36.58 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0140] Comparative Example 2

[0141] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 3.5 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 40.29 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0142] Comparative Example 3

[0143] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 2.3 MPa ethylene was introduced at 30 ° C. The polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 56.45 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0144] Comparative Example 4

[0145] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, mixed and used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 2.3 MPa ethylene was introduced at 90 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 12.8 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0146] Comparative Example 5

[0147] The vulcanization characteristics of EPDM4045 were measured according to the above method.

[0148] Comparative Example 6

[0149] In a glove box, M1 (13.99 μmol), toluene (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and the mixture was used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, and 1.4 MPa ethylene was introduced at 60°C, and the polymerization reaction was carried out under stirring at 300 rpm for 0.5 hours. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid, and the polymer was filtered and washed, and then vacuum dried at 50°C to constant weight to obtain 67.5 g of polymer. The obtained polymer was used to prepare a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0150] Comparative Example 7

[0151] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (250 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and mixed to be used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.4 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 67.08 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0152] Comparative Example 8

[0153] In a glove box, M1 (13.99 μmol), 1,2-dichloroethane (0.5 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and mixed to be used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.4 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 67.29 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the properties were measured.

[0154] Comparative Example 9

[0155] In a glove box, M3 (13.99 μmol), 1,2-dichloroethane (15 ml) and ethylaluminum dichloride (3.96 mmol) were added to a 50 ml conical flask in sequence, and mixed to be used as a catalyst solution. Hexane (1 L) and the above-prepared catalyst solution were added to a 2 L high-pressure polymerization reactor replaced with nitrogen in sequence, 1.4 MPa ethylene was introduced at 60 ° C, and the polymerization reaction was carried out for 0.5 hours under stirring at 300 rpm. The polymerization solution was terminated with ethanol containing 5% hydrochloric acid. After filtering and washing, the polymer was vacuum dried at 50 ° C to constant weight to obtain 56.59 g of polymer. The obtained polymer was prepared into a composition according to the preparation method of the polypropylene composition and the performance was measured.

[0156] Table 1 Summary of results

[0157]

[0158]

[0159] ① PP is YPM-2203T, and PE is the branched polyethylene in each embodiment and comparative example;

[0160] ②When PP / PE=100 / 0, the -30℃ Izod notched impact strength is 8.23KJ / m 2 (0.05 wt% antioxidant 1010 and 0.05 wt% antioxidant 168 were added based on the total composition);

[0161] ③ When PP / PE=100 / 0, the tensile strength is 29.81 MPa (0.05wt% antioxidant 1010 and 0.05wt% antioxidant 168 are added based on the total amount of the composition).

[0162] The results of the above embodiments and comparative examples fully demonstrate that, through the specific aggregation method of the present invention, not only does the catalyst system exhibit excellent catalytic activity, but also the obtained branched polyethylene has a significant effect of improving the impact strength of polypropylene.

[0163] In contrast, when the specific polymerization method of the present invention is not satisfied, the catalyst system exhibits poor catalytic activity and the obtained branched polyethylene has limited effect of improving the impact strength of polypropylene.

[0164] 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, characterized in that: The following steps are involved: The α-diimine nickel catalyst represented by the following formula (1) is used as a main catalyst; at least one selected from aluminoxane, modified aluminoxane, alkyl aluminum, alkyl aluminum hydrolyzate, halogenated alkyl aluminum, aryl boron, alkyl boron and borate is used as a co-catalyst, and ethylene is polymerized at a polymerization temperature of 60-85° C. (preferably 65-70° C.) and a polymerization pressure of 1.2-3.0 MPa (preferably 1.4-2.3 MPa) using a polymerization solvent containing a halogenated organic solvent to obtain a branched polyethylene: In formula (1), R1 and R2 are each independently selected from hydrogen, C 1-4 A straight or branched hydrocarbon group, or R1 and R2 together with the carbon atom to which they are bonded form a 5-6 membered ring; R3, R5, R7, R8, R 10 , R 12 Each independently selected from C 3-10 Straight or branched hydrocarbon group, R4, R6, R9, R 11 are each independently selected from hydrogen, C 1-4 A straight chain or branched hydrocarbon group, X is a halogen.

2. The preparation method according to claim 1, characterized in that: In formula (1), R1 and R2 are each independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, or R1 and R2 together with the carbon atom to which they are bonded form a 5-membered ring; R4, R6, R9, R 11 Each is independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl; R3, R5, R7, R8, R 10 , R 12 Each is independently selected from propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers.

3. The preparation method according to claim 1 or 2, characterized in that: The α-diimine nickel catalyst represented by formula (1) is at least one compound selected from the group consisting of the following compounds represented by formula (2) or formula (3):

4. The preparation method according to any one of claims 1 to 3, characterized in that The aluminoxane is a linear aluminoxane represented by the following general formula (I) or a cyclic aluminoxane represented by the following general formula (II), In the general formulae (I) and (II), the groups R are identical or different (preferably identical), and are independently selected from C1-C8 alkyl, preferably methyl, ethyl, propyl, butyl and isobutyl, and most preferably methyl and isobutyl; n is any integer in the range of 1-50, preferably any integer in the range of 10-30, Preferably, the aluminoxane is at least one selected from methylaluminoxane, ethylaluminoxane, isobutylaluminoxane and n-butylaluminoxane.

5. The preparation method according to any one of claims 1 to 3, characterized in that The alkyl aluminum is a compound represented by the following general formula (III): Al(R)3(III) In the general formula (III), the groups R are identical or different (preferably identical) to each other, and are independently selected from C1-C8 alkyl, preferably methyl, ethyl, propyl, butyl and isobutyl, most preferably methyl and isobutyl, Preferably, the alkyl aluminum is selected from trimethyl aluminum (Al(CH3)3), triethyl aluminum (Al(CH3CH2)3), tri-n-propyl aluminum (Al(C3H7)3), triisopropyl aluminum (Al(i-C3H7)3), triisobutyl aluminum (Al(i-C4H9)3), tri-n-butyl aluminum (Al(C4H9)3), triisopentyl 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).

6. The preparation method according to any one of claims 1 to 3, characterized in that The alkyl aluminum halide is a compound represented by the following general formula (IV): Al(R) n X 3-n (IV) In the general formula (IV), the groups R are identical or different (preferably identical) and are independently selected from C1-C8 alkyl, preferably methyl, ethyl, propyl, butyl and isobutyl, most preferably methyl and isobutyl; X represents fluorine, chlorine, bromine or iodine; n represents 1 or 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 (AlCH2CH3)(C4H9)Cl), and chloromethyl isobutylaluminum (Al(CH2CH3)(i-C4H9)Cl).

7. The preparation method according to any one of claims 1 to 3, characterized in that The alkyl boron and aryl boron are compounds represented by the general formula (V): B(R')3(V) In the general formula (V), 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 The substituted straight or branched alkyl or phenoxy group, preferably, the R' is preferably selected from methyl, ethyl, propyl, butyl, isobutyl, phenyl, tolyl, trifluoromethylphenyl and pentafluorophenyl, Preferably, the alkyl boron is at least one selected from trimethyl boron, triethyl boron, triisobutyl boron, tripropyl boron or tributyl boron; Preferably, the arylborone is at least one selected from triphenylboron, tris(pentafluorophenyl)boron, and tris[3,5-bis(trifluoromethyl)phenyl]boron.

8. The preparation method according to any one of claims 1 to 3, characterized in that The borate is a compound represented by the following general formula (VI): [L] + [BE4] m - (WE) In the general formula (VI), 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 is substituted by a straight-chain or branched alkoxy or phenoxy group, m represents the valence value of the group in the L portion, and the E is selected from fluorine, phenyl, trifluoromethylphenyl and pentafluorophenyl, 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.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The molar ratio of the co-catalyst calculated in terms of aluminum and / or boron to the main catalyst calculated in terms of metal Ni is 50-500:1, preferably 80-300:

1.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The halogenated organic solvent is selected from halogenated C 1-10 Alkanes, halogenated C 6-10 At least one of the aromatic hydrocarbons is preferably selected from at least one of monochloromethane, dichloromethane, trichloromethane, monochloroethane, dichloroethane and its isomers (e.g., 1,1-dichloroethane, 1,2-dichloroethane), trichloroethane and its isomers (e.g., 1,1,1-trichloroethane, 1,1,2-trichloroethane), chlorobenzene, dichlorobenzene and its isomers, and chlorotoluene.

11. The preparation method according to any one of claims 1 to 10, characterized in that: The polymerization solvent is selected from C 4-10 Alkanes and C 6-10 The at least one aromatic hydrocarbon solvent is preferably at least one selected from hexane, heptane and toluene.

12. The preparation method according to any one of claims 1 to 11, characterized in that: The volume ratio of the halogenated organic solvent to the polymerization solvent is 0.001 to 0.2 parts by volume, preferably 0.003 to 0.1 parts by volume, and more preferably 0.005 to 0.05 parts by volume.

13. The preparation method according to any one of claims 1 to 11, characterized in that: Further comprising the steps of: After dissolving the α-diimine nickel catalyst represented by formula (1) and at least one selected from aluminoxane, modified aluminoxane, alkyl aluminum, alkyl aluminum hydrolyzate, halogenated alkyl aluminum, aryl boron, alkyl boron and borate in a halogenated organic solvent, a polymerization solvent is added to carry out an ethylene polymerization reaction.

14. Branched polyethylene, obtained by the preparation method according to any one of claims 1 to 13, having a density of 0.85 g / cm 3 -0.87g / cm 3 , the kinematic viscosity at 260°C is 400,000-4,000,000 CP.

15. A polyolefin composition comprising the branched polyethylene according to claim 14, wherein the amount of the branched polyethylene is 1 wt%-50 wt%, preferably 3 wt%-30 wt%, more preferably 5 wt%-25%, and particularly preferably 5 wt%-20 wt%, relative to the total amount of the composition.

16. A polypropylene composition comprising the branched polyethylene according to claim 14, wherein the amount of the branched polyethylene is 1 wt%-50 wt%, preferably 3 wt%-30 wt%, more preferably 5 wt%-25%, particularly preferably 5 wt%-20 wt%, relative to the total amount of the composition.

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