Ultrahigh molecular weight polyethylene with low molecular chain entanglement and preparation method and application thereof

Abstract

The invention discloses ultra-high molecular weight polyethylene with low molecular chain entanglement and a preparation method and application thereof.The preparation method comprises the steps that a compound with the structure shown in the formula I serves as a main catalyst, an alkyl aluminum compound serves as a cocatalyst, and the main catalyst and the cocatalyst are subjected to a catalytic polymerization reaction with ethylene, and the viscosity average molecular weight of obtained ultra-high molecular weight polyethylene powder is 50-10 million g / mol; and the bulk density is 0.05-0.3 g / cm < 3 >. According to the present invention, the low molecular chain entanglement characteristic is provided, that is, the high-strength sample can be formed under the normal temperature and non-melting condition through pressurization, the sample can be stretched at the normal temperature, the stretching rate can achieve 5-550 times, preferably 30-350 times, and the stretching breaking strength can achieve 2-45 cN / dtex;

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ultra-high molecular weight polymers, and relates to a low molecular chain entangled ultra-high molecular weight polyethylene as well as a preparation method and application thereof. BACKGROUND

[0002] Ultra-high molecular weight polyethylene (UHMWPE) is a thermoplastic engineering plastic with high impact resistance, extremely high wear resistance, high corrosion resistance, self-lubricating property, environmental stress cracking resistance, safety and health, etc. It can be processed into various plates, pipes, fibers, films and other products, and applied to high-end fields such as military (e.g. bulletproof clothing, bulletproof helmet, bulletproof armor, cut-resistant gloves), aerospace, marine equipment, rail transportation, medical stents, fine filtration and lithium battery separators.

[0003] The molecular chain of low entangled ultra-high molecular weight polyethylene has a low entanglement characteristic before processing. A new low processing cost cold pressing and cold drawing processing method is reported in Petroleum and Chemical Industry, 2024, Vol. 53, No. 1, 121-129, to process it into a shape. The low entangled ultra-high molecular weight polyethylene is generally prepared by using a homogeneous N, O coordinated titanium (Ti) catalyst (such as FI catalyst, Talebi, S., R. Duchateau, S. Rastogi, J. Kaschta, G. W. M. Peters and P. J. Lemstra (2010). Macromolecules 43(6): 2780-2788.) or a semi-metallocene Cr catalyst (such as Romano, D., S. Ronca and S. Rastogi (2015). Macromolecular Rapid Communications 36(3): 327-331.). The disentanglement effect of the molecular chain of the low entangled ultra-high molecular weight polyethylene prepared by the Ti catalyst is better. The disentangled ultra-high molecular weight polyethylene can be shaped by cold pressing, and then stretched by cold stretching, which can generally be stretched to 30-70 times (3000%-7000%). However, the above two catalysts both use a homogeneous catalyst polymerization method when catalyzing ethylene polymerization, and the polymerization temperature is generally higher than 100℃. High polymerization reaction temperature reduces the polymerization reaction effect. In addition, the Ti catalyst catalyzes ethylene polymerization, which is a living polymerization characteristic, and the molecular weight distribution of the polyethylene obtained therefrom is generally between 1.0-3.0. Furthermore, the cost of the low entangled ultra-high molecular weight polyethylene prepared by the Ti catalyst and the Cr catalyst is high, and the cost of the methylaluminoxane used as a catalyst promoter is also high, which limits the application and development thereof. SUMMARY

[0004] To improve the above technical problems, the present application provides a kind of low molecular chain entanglement of ultra-high molecular weight polyethylene and its preparation method and application, the viscosity average molecular weight of the ultra-high molecular weight polyethylene of the present application is 50-1000 million g / mol, the bulk density is 0.05-0.3 g / cm 3 .

[0005] To achieve the above-mentioned purposes of the application, the present application adopts the following technical solutions:

[0006] The present application provides a kind of compound of structure shown in formula I:

[0007]

[0008] In formula I, R1, R2 and R3 are the same or different, and are independently selected from C1-C 18 Alkyl, C2-C6 alkenyl, C3-C 18 Cycloalkyl, C6-C8 aryl optionally substituted with one or more halogen, alkyl; R3 can also be selected from hydrogen;

[0009] X is selected from halogen (fluorine, chlorine, bromine, iodine), C1-C 18 Alkyl, benzyl optionally substituted with one or more alkyl, trimethylsilylmethylene, dialkyl (C1-C6) amine group, C1-C 18 Alkoxy and phenol group optionally substituted with one or more alkyl.

[0010] n is 1-4, and exemplarily, n is selected from 1, 2, 3 or 4.

[0011] According to an embodiment of the present application, the compound of the structure shown in Formula I can be any one of the following: titanium acetylacetonate trichloride, titanium acetylacetonate dichloride, titanium acetylacetonate monochloride, titanium tetraacetylacetonate, titanium bis(benzoylacetone) dichloride, titanium bis(dibenzoylmethane) dichloride, titanium tetrakis(dibenzoylmethane), titanium bis(3-ethyl-2,4-pentanedione) dichloride, titanium bis(3-n-propyl-2,4-pentanedione) dichloride, titanium bis(3-isopropyl-2,4-pentanedione) dichloride, titanium bis(3-isobutyl-2,4-pentanedione) dichloride, titanium bis(3-n-butyl-2,4-pentanedione) dichloride, titanium bis(3-n-pentyl-2,4-pentanedione) dichloride, titanium bis(3-cyclopentyl-2,4-pentanedione) dichloride, titanium bis(3-n-hexyl-2,4-pentanedione) dichloride, titanium bis(3-cyclohexyl-2,4-pentanedione) dichloride, titanium bis(3-phenyl-2,4-pentanedione) dichloride, titanium bis(3-benzylidene-2,4-pentanedione) dichloride, titanium bis(l,l,5,5-tetrafluoro-2,4-pentanedione) dichloride, titanium bis(l,l,l-trifluoro-2,4-pentanedione) dichloride, titanium bis(l,l,l-trifluoro-2,4-hexanedione) dichloride, titanium bis(l,l,l-trifluoro-5,5-dimethyl-2,4-hexanedione) dichloride, titanium bis(4,4,4-trifluoro-l-phenyl-l,3-butanedione) dichloride, titanium bis(4,4,4-trifluoro-l-(2-naphthyl)-l,3-butanedione) dichloride, titanium bis(stearoylbenzoylmethane) dichloride, titanium acetylacetonate bisphenoxide, titanium acetylacetonate bisdiisopropoxide, titanium acetylacetonate bis(dimethylamido), titanium acetylacetonate bisdimethyl, titanium acetylacetonate bisbenzyl, titanium acetylacetonate bis(trimethylsilylmethylene).

[0012] According to an embodiment of the present application, the compound of the structure shown in Formula I is prepared by reacting a compound of the structure shown in Formula 2 or an alkyl lithium with a titanium source such as TiCl4 or an organotitanium chloride,

[0013]

[0014] In Formula 2, R1, R2, and R3 are the same or different and are independently selected from C1-C6 alkyl, C2-C6 alkenyl, C3-C6 cycloalkyl, C6-C8 aryl optionally substituted with one or more halogens, alkyl, or aryl; R3 can also be hydrogen. 18 alkyl, C2-C6 alkenyl, C3-C6 cycloalkyl, C6-C8 aryl optionally substituted with one or more halogens, alkyl, or aryl; R3 can also be hydrogen. 18 alkyl, C2-C6 alkenyl, C3-C6 cycloalkyl, C6-C8 aryl optionally substituted with one or more halogens, alkyl, or aryl; R3 can also be hydrogen.

[0015] According to an exemplary embodiment of the present invention, the compound with the structure shown in Formula 2 may be selected from, but is not limited to, the following compounds: 3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, 3-allyl-2,4-pentanedione, 3-butyl-2,4-pentanedione, 2,2,4,6,6-pentamethyl-3,5-heptanedione, 3-methylnonane-2,4-dione, 3,7-diethyl-5-methylnonane-4,6-dione, 3-propyl-2,4-pentanedione, 4-methyl-3,5-heptanedione, 3-(1-methylethyl)pentane-2,4-dione, 3-methyl-2,4-hexanedione, 3-ethylidene-2,4-pentanedione, 3-methylene-2,4-pentanedione, 3-hexyl-2 4-Pentanedione, 3-(tert-butyl)pentane-2,4-dione, 3-pentyl-2,4-pentanedione, 4-ethyl-2,2,6,6-tetramethylheptane-3,5-dione, 2,5,8-trimethylnonane-4,6-dione, 3-isobutyl-2,4-pentanedione, 3-(3-methylbutyl)-2,4-pentanedione, 3,7-diethyl-3,5-dimethylnonane-4,6-dione, 3-octyl-2,4-pentanedione, 3,5-dimethyl-2,4-hexanedione, 3-sec-butyl-2,4-pentanedione, 2,4-dimethyl-3,5-heptanedione, 3-methyl-2,4-heptanedione, 3-(1-methyl-allyl)-2,4-pentanedione, 3-isopropylidene-2,4-pentanedione 3,6-Dimethyl-2,4-heptanedione, 5-ethylnonane-4,6-dione, 4,6-dimethyl-3,5-octanedione, 2,4,6-trimethyl-3,5-heptanedione, 3-ethyl-2,4-heptanedione, 4-allyl-2,2,6,6-tetramethyl-3,5-heptanedione, 4-isopropyl-2,2,6,6-tetramethylheptane-3,5-dione, 4-tert-butyl-2,2,6,6-tetramethyl-3,5-heptanedione, 3-butyl-pentane-2,4-dione (E)-enol homologues, 4-ethyl-3,5-heptanedione, 3-heptyl-2,4-pentanedione, 7-butyl-6,8-tetrazanedione, 2-isobutyrylhexanone, 3,3,7,7-tetramethyl-5-isobutyl-4 6-Nonanedione, 3,3,7,7-Tetramethyl-5-allyl-4,6-nonanedione, 2,2,6,6-Tetramethyl-4-hexyl-3,5-heptadecanedione, 2,2,7-trimethyl-4-isopropyl-3,5-octanedione, 2,2,6-trimethyl-4-tert-butyl-3,5-heptadecanedione, 2,2,7-trimethyl-4-tert-butyl-3,5-octanedione, 2,2,6,6-Tetramethyl-4-isobutyl-3,5-heptadecanedione, 2,2,6-trimethyl-4-isopropyl-3,5-heptadecanedione, 2,2,6,6-tetramethyl-4-butyl-3,5-heptadecanedione, 2,2,6,6-tetramethyl-4-propyl-3,5-heptadecanedione, 2,2,6-trimethyl-4-isobutyl-3,5-Hempanedione, 4-Allyl-3,5-Hempanedione, 3-Decyl-2,4-Pentanedione, 4-Allyl-2,6-Dimethyl-3,5-Hempanedione, 2,6-Dimethyl-4-Isopropyl-3,5-Hempanedione, 2,2,7-Trimethyl-4-Butane-3,5-Octanedione, 4,8-Dimethyl-6-Isopropyl-5,7-Undecanedione, 2,2,6-Trimethyl-4-Ethyl-3,5-Nonanedione, 4-Acetyl-3-Hempone, 3-Isopropyl-6-Methyl-2,4-Hempanedione, 9-Hexyl-8,10-Heptadecanedione, 3-Hexadecyl-2,4-Pentanedione, 2-Nonyl-1,3-Pentanedione, 2,6-Dimethyl-4-tert-Butyl-3,5-Hempanedione, 2,6-Dimethyl 4-Ethyl-3,5-heptadecanedione, 3-Isopropyl-2,4-heptadecanedione, 3-Methyl-2,4-octanedione, 4-Methyl-3,5-octanedione, 4-propyl-3,5-heptadecanedione, 3-Methyl-2,4-decanedione, 3-propyl-2,4-octanedione, 5-propyl-4,6-decanedione, 6-propylundecane-5,7-dione, 2,2,4-trimethyl-3,5-heptadecanedione, 3-Ethylnonane-2,4-dione, 3,7-Diethyl-5-isopropyl-4,6-nonanedione, 6-Methylundecane-5,7-dione, 5-Butylundecane-4,6-dione, 6-Butyl-5,7-dodecanedione, 3-Vinyl-2,4-pentanedione, 6-Allylundecane-5,7-dione 3-(3,3-dimethylbutyl)-2,4-pentanedione, 3-dodecyl-2,4-pentanedione, 4-propyl-3,5-nonanedione, 3-tetradecyl-2,4-pentanedione, 2,2,4,7-tetramethyl-3,5-octanedione, 2,2,4,7-tetramethyl-3,5-octanedione, 2,2,6-trimethyl-4-butyl-3,5-heptanedione, 2,2,4,6-tetramethyl-3,5-octanedione, 3-isopropyl-5-methyl-2,4-hexanedione, 3,3,5,7,7-pentamethyl-4,6-nonanedione, 2,6-dimethyl-4-butyl-3,5-heptanedione, 2-methyl-4-isopropyl-3,5-heptanedione, 3,7-dimethyl-5-isopropyl-4,6-nonanedione 1,3-Diphenyl-2-methyl-1,3-propanedione, 2-allyl-1,3-diphenyl-1,3-propanedione, 1,1-dibenzoylpropane, 4,4'-methoxy-tert-butyldibenzoylmethane, 1,3-di(p-methoxyphenyl)-2-methyl-1,3-propanedione, 1,3-diphenyl-2-isopropyl-1,3-propanedione, 3-hydroxy-2-methyl-1-phenyl-3-(4'-chlorophenyl)-1-propanone, 3-hydroxy-3-(4-methoxyphenyl)-2-methyl-1-phenyl-1-propanone, 1,3-di(p-methylphenyl)-2-methyl-1,3-propanedione, 2-methyl-1,3-bis(p-chlorophenyl)propane-1,3-dione, 2-methyl-1-phenyl-1,3-Butanedione, 2-allyl-1-phenylbutane-1,3-dione, 1-phenyl-2-methyl-1,3-pentanedione, 2-ethyl-1-phenyl-1,3-butanedione, 2-butyl-1-phenyl-1,3-butanedione, 2,4-dimethyl-1-phenyl-1,3-pentanedione, 1-phenyl-2-propyl-1,3-butanedione, 2-methyl-1-(p-tolyl)butane-1,3-dione, 3-benzoyl-2-octanone, 2-isopropyl-1-phenylbutane-1,3-dione, 2-methyl-1-o-chlorophenyl-1,3-pentanedione, 5-benzoyl-6-undecanone, 2-ethyl-1-phenyl-1,3-pentanedione, 2-heptyl-1-phenylbutane-1,3-dione, 2-heptyl-1 -Phenylacetane-1,3-dione, 2-ethyl-4-methyl-1-phenyl-1,3-pentanedione, 2-isobutyl-1-phenyl-1,3-butanedione, 2-isobutyl-1-phenyl-1,3-butanedione, 3-(4'-methoxyphenyl)-2,4-pentanedione, 3-(4-fluorophenyl)pentane-2,4-dione, 3-(4-chlorophenyl)pentane-2,4-dione, 3-(4-nitrophenyl)pentane-2,4-dione, 3-(4-acetylphenyl)-2,4-pentanedione, 3-(4-bromophenyl)-2,4-pentanedione, 3-(cyclohexyl-2-enyl)pentane-2,4-dione, 3-(3-oxocyclohexyl)pentane-2,4-dione, 3-(1-adamantyl)pentane-2,4- Diones, 3-p-toluenepentane-2,4-dione, 4-phenyl-2,2,6,6-tetramethylheptane-3,5-dione, 3-(2',4',6'-trimethylphenyl)-2,4-pentanedione, 2,6-dimethyl-4-cyclopentyl-3,5-heptanedione, 2,2,6,6-tetramethyl-4-cyclohexyl-3,5-heptanedione, 2,2,6,6-tetramethyl-4-cyclopentane-3,5-heptanedione, 3-cyclohexyl-2,4-pentanedione, 2,6-dimethyl-4-phenyl-3,5-heptanedione, 3-(a-naphthyl)2,4-pentanedione, 3-(cyclopentane-2-pentyl)pentane-2,4-dione, 3-(2,3,5,6-tetramethylphenyl)pentane-2,4-dione, 3-cyclopentylethyl Acrylacephenone, 3-(9-anthrayl)2,4-pentanedione, p-bis(3-acetylacetone)benzene, 3-(9-fluorenyl)-2,4-pentanedione, 3-(2'-methylphenyl)-2,4-pentanedione, 3-(3-methoxyphenyl)pentane-2,4-dione, 3-(3,5-dimethylphenyl)hexane-2,4-dione, 3-(tetrahydro-2H-pyran-2-yl)pentane-2,4-dione, 3-(tetrahydrofuran-2-yl)-2,4-pentanedione, 3-(5-methyl-2-furanyl)-2,4-pentanedione, 3-(4-pyridyl)pentane-2,4-dione, 2-(2-furanyl)acetoacetate, 3-(1-isochromyl)-2,4-dioxolane, 3-(pyridyl)pentane-2,At least one selected from 4-dione, 3-morpholino-2,4-pentanedione, and 3-octahydroquinazine-4-ylpentane-2,4-dione.

[0016] The present invention also provides a method for preparing a compound with the structure shown in Formula I, comprising: reacting a compound with the structure shown in Formula 2 or an alkyl lithium with a titanium source (such as TiCl4 or organotitanium chloride) to prepare a compound with the structure shown in Formula I.

[0017] According to an embodiment of the present invention, the reaction molar ratio of the compound or alkyl lithium with the titanium source (such as TiCl4 or organotitanium chloride) shown in Formula 2 is 1:1 to 5:1, with examples being 1:1, 2:1, 3:1, 4:1, and 5:1.

[0018] According to an embodiment of the present invention, the organotitanium chloride is selected, for example, from at least one of diacetylacetone titanium chloride, diphenol titanium chloride, diisopropoxy titanium chloride, and di(dimethylamino) titanium chloride.

[0019] According to an embodiment of the present invention, the alkyl lithium is selected from at least one of methyl lithium, benzyl lithium, and trimethylsilylmethylene lithium.

[0020] According to embodiments of the present invention, the reaction of the compound or alkyllithium with the titanium source according to Formula 2 is carried out in a solvent system such as an organic solvent. For example, the organic solvent may be selected from toluene or tetrahydrofuran.

[0021] According to an embodiment of the present invention, the reaction temperature is -78℃ to 40℃, exemplarily -78℃, room temperature, and 40℃; the reaction time is 1 to 48 hours, exemplarily 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 12 hours, 16 hours, 24 hours, 36 hours, and 48 hours.

[0022] According to an embodiment of the present invention, the preparation method further includes, after the reaction is complete, solid-liquid separation and drying to obtain a compound with the structure shown in Formula I. For example, the solid-liquid separation can be performed using methods known in the art, such as filtration.

[0023] The present invention also provides the use of compounds with the structure shown in Formula I as catalysts. For example, their use in the catalytic polymerization of ethylene to prepare polyethylene; preferably, their use in the catalytic polymerization of ethylene to prepare ultra-high molecular weight polyethylene; more preferably, their use in the catalytic polymerization of ethylene to prepare ultra-high molecular weight polyethylene with low molecular weight chain entanglement.

[0024] The present invention also provides a catalyst system comprising: a compound with the structure shown in Formula I as a main catalyst, and an alkylaluminum compound as a co-catalyst.

[0025] According to an embodiment of the present invention, the alkylaluminum compound is selected from at least one of alkylaluminum, alkoxyaluminum, and alkylaluminum halide; exemplaryly, the alkylaluminum compound is selected from at least one of triethylaluminum, trimethylaluminum, triisobutylaluminum, methylaluminoxane, diethylaluminum chloride, and ethylaluminum dichloride.

[0026] According to an embodiment of the present invention, the molar ratio of the alkylaluminum compound to the compound with the structure shown in Formula I is (1-10000):1, preferably (10-500):1; exemplary ratios are 1:1, 10:1, 50:1, 100:1, 500:1, 1000:1, 5000:1, 1000:1, 5000:1, and 10000:1.

[0027] The present invention also provides a method for preparing polyethylene, comprising catalytically polymerizing ethylene (preferably in an inert solvent) in the above-mentioned catalyst system to obtain ultra-high molecular weight polyethylene powder.

[0028] According to an embodiment of the invention, the inert solvent is selected from unsubstituted or optionally substituted C3-C solvents. 18 Alkanes, C3-C 18 Cycloalkanes, unsubstituted or optionally substituted with one or more halogens, C6-C 18 Aromatic hydrocarbons. Preferably selected from one, two or more of the following: n-propane, isopropane, n-butane, isobutane, n-pentane, isopentane, cyclopentane, n-hexane, methylpentane, cyclohexane, n-heptane, dichloromethane, toluene, xylene, chloroform, chloroethane, chlorobenzene, chlorobenzyl, toluene, and xylene.

[0029] According to an embodiment of the present invention, the method for preparing polyethylene includes mixing an inert solvent, an alkylaluminum compound, and a compound with the structure shown in Formula I to obtain a mixed solution, controlling the reaction temperature, introducing ethylene gas to start the reaction, cooling to remove heat (maintaining the temperature of the reaction system to be stable), adding a polymerization terminator after the polymerization reaction is completed, removing the inert solvent, and drying to obtain ultra-high molecular weight polyethylene powder.

[0030] According to an embodiment of the present invention, the concentration of the compound with the structure shown in Formula I in the mixed solution is 0.001 to 10 mmol / L, for example 0.001 mmol / L, 0.01 mmol / L, 0.1 mmol / L, 0.5 mmol / L, 1 mmol / L, 2 mmol / L, 5 mmol / L, and 10 mmol / L.

[0031] According to an embodiment of the present invention, the polymerization temperature is -50 to 110°C, preferably -30 to 80°C, and exemplary values ​​are -50°C, -30°C, -10°C, 0°C, 25°C, 40°C, 60°C, 80°C, and 110°C. In the polymerization reaction of the present invention, the temperature of the polymerization system fluctuates within ±5°C of a set value, preferably within ±3°C.

[0032] According to an embodiment of the present invention, the polymerization reaction pressure is 0.1 to 4.0 MPa, preferably 0.2 to 2.0 MPa, and exemplary pressures are 0.1 MPa, 0.2 MPa, 0.5 MPa, 1 MPa, 2 MPa, and 4 MPa.

[0033] According to an embodiment of the present invention, the cooling and heat removal method may be at least one of the following: reactor jacket cooling and heat removal, reactor internal cooling and heat removal, external solvent circulation heat removal, and heat removal by inert solvent evaporation.

[0034] According to an embodiment of the present invention, the polymerization terminator is a compound containing active hydrogen, preferably water, methanol or ethanol.

[0035] According to an embodiment of the present invention, the inert solvent can be removed by one of the following methods: solvent evaporation, filtration, pressure filtration, centrifugation, etc.

[0036] The present invention also provides polyethylene prepared by the above preparation method.

[0037] According to an embodiment of the present invention, the polyethylene is ultra-high molecular weight polyethylene, preferably ultra-high molecular weight polyethylene with low molecular weight chain entanglement. The polyethylene prepared by the present invention is in powder form.

[0038] In this invention, at room temperature, pressure is applied in a mold at a pressure of 5-50 MPa to process the polyethylene of this invention into a tensile specimen. This specimen is then stretched at room temperature, achieving a stretch ratio of 5-550 times, preferably 30-350 times. Exemplarily, the tensile breaking strength is 2-45 cN / dtex, preferably 30-40 cN / dtex.

[0039] According to an embodiment of the present invention, the viscosity-average molecular weight of the polyethylene is 500,000 to 10,000,000 g / mol.

[0040] According to an embodiment of the present invention, the bulk density of the polyethylene is 0.04–0.3 g / cm³. 3 Preferably, it is 0.04–0.1 g / cm³. 3 .

[0041] The present invention also provides applications of the above-mentioned polyethylene in military (such as bulletproof vests, bulletproof helmets, bulletproof armor, cut-resistant gloves), aerospace, marine equipment, rail transportation, medical stents, fine filtration and battery separators.

[0042] The present invention also provides an article containing or prepared from the above-mentioned polyethylene.

[0043] According to an embodiment of the present invention, the article can be one of sheet material, pipe material, fiber material, and film material.

[0044] Terminology Definitions and Explanations

[0045] Unless otherwise stated, the definitions of groups and terms recorded in this application specification and claims, including their definitions as examples, exemplary definitions, preferred definitions, definitions recorded in tables, and definitions of specific compounds in the examples, can be arbitrarily combined and combined with each other. Such combinations and combinations of group definitions and compound structures should fall within the scope of this application specification.

[0046] Unless otherwise stated, the numerical ranges described in this specification and claims correspond to at least each of the specific integer values ​​described herein. For example, the numerical range "1-6" corresponds to each of the integer values ​​in the numerical range "1-6", namely 1, 2, 3, 4, 5, and 6. It should be understood that in the use of "one" and "many" when describing substituents herein, "many" refers to integers ≥2, such as 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0047] The term "halogen" refers to fluorine, chlorine, bromine, and iodine.

[0048] The term "C1-C6 alkyl" refers to a straight-chain or branched saturated hydrocarbon group having 1, 2, 3, 4, 5, or 6 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, or 1,2-dimethylbutyl, or their isomers.

[0049] The term "C2-C6 alkenyl" should be understood to preferably refer to a straight-chain or branched hydrocarbon group containing one or more double bonds and having 2, 3, 4, 5, or 6 carbon atoms, for example, having 2 or 3 carbon atoms (i.e., C2-C6 alkenyl). 2-3Alkenyl). It should be understood that when the alkenyl group contains more than one double bond, the double bonds may be separable or conjugated. The alkenyl group is, for example, vinyl, allyl, (E)-2-methylvinyl, (Z)-2-methylvinyl, (E)-but-2-enyl, (Z)-but-2-enyl, (E)-but-1-enyl, (Z)-but-1-enyl, pent-4-enyl, (E)-pent-3-enyl, (Z)-pent-3-enyl, (E)-pent-2-enyl, (Z)-pent-2-enyl, (E)- Pentyl-1-enyl, (Z)-pentyl-1-enyl, hex-5-enyl, (E)-hex-4-enyl, (Z)-hex-4-enyl, (E)-hex-3-enyl, (Z)-hex-3-enyl, (E)-hex-2-enyl, (Z)-hex-2-enyl, (E)-hex-1-enyl, (Z)-hex-1-enyl, isopropenyl, 2-methylprop-2-enyl, 1-methylprop-2-enyl 2-Methylprop-1-enyl, (E)-1-methylprop-1-enyl, (Z)-1-methylprop-1-enyl, 3-methylbut-3-enyl, 2-methylbut-3-enyl, 1-methylbut-3-enyl, 3-methylbut-2-enyl, (E)-2-methylbut-2-enyl, (Z)-2-methylbut-2-enyl, (E)-1-methylbut-2-enyl, (Z)-1-methyl But-2-enyl, (E)-3-methylbut-1-enyl, (Z)-3-methylbut-1-enyl, (E)-2-methylbut-1-enyl, (Z)-2-methylbut-1-enyl, (E)-1-methylbut-1-enyl, (Z)-1-methylbut-1-enyl, 1,1-dimethylprop-2-enyl, 1-ethylprop-1-enyl, 1-propylvinyl, 1-isopropylvinyl.

[0050] The term "C3-C6 cycloalkyl" should be understood to refer to saturated monocyclic alkanes having 3, 4, 5, or 6 carbon atoms. Examples include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0051] The term "C6-C" 12 "Aryl" should preferably be understood to represent a monovalent aromatic or partially aromatic monocyclic, bicyclic, or tricyclic hydrocarbon ring ("C6-C") having 6, 7, 8, 9, 10, 11, or 12 carbon atoms. 12 Aryl), particularly a ring with 6 carbon atoms (“C6 aryl”), such as phenyl; or biphenyl, or a ring with 9 carbon atoms (“C9 aryl”), such as indenyl or indenyl, or a ring with 10 carbon atoms (“C9 aryl”). 10Aryl), such as tetrahydronaphthyl, dihydronaphthyl, or naphthyl. The above definition of the term "alkyl", such as "C1-C6 alkyl", also applies to other terms containing "C1-C6 alkyl", such as the terms "C1-C6 alkoxy", "C1-C6 haloalkyl", "halogenated C1-C6 alkoxy", etc.

[0052] The beneficial effects of this invention:

[0053] The ultra-high molecular weight polyethylene powder of this invention has a viscosity-average molecular weight of 500,000 to 10,000,000 g / mol and a bulk density of 0.05 to 0.3 g / cm³. 3 It has low molecular chain entanglement characteristics, that is, under pressure at room temperature and without melting, it can form a sample with strength. The sample can be stretched at room temperature, and the stretching ratio can reach 5-550 times, preferably 30-350 times. The tensile breaking strength can reach 2-45 cN / dtex. Detailed Implementation

[0054] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0055] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0056] Evaluation and analysis methods:

[0057] (1) Catalyst activity = [polymer yield (g)] / [catalyst mass (mol)]; the unit of catalyst activity is 10. 5 g PP / molCat;

[0058] (2) The viscosity-average molecular weight of polyethylene was determined according to GB / T32679-2016;

[0059] (3) Method for determining the bulk density of polyethylene: Using a 100mL graduated cylinder, allow the material to fall naturally from the opening, measuring 100mL. Weigh the polyethylene and divide the total weight by the volume to obtain the bulk density, expressed in g / mL or g / cm³. 3 .

[0060] Example 1: Synthesis of Catalyst

[0061] The preparation of titanium acetylacetone catalysts is as follows: At room temperature, a toluene solution of a diketone compound (concentration 0.2 mmol / mL) and a toluene solution of TiCl4 (concentration 0.1 mmol / mL) are mixed (wherein: the molar ratio of diketone compound to TiCl4 in the preparation of catalyst 3 is 3:1; the molar ratio of diketone compound to TiCl4 in the preparation of catalyst 4 is 4:1; and the molar ratio of diketone compound to TiCl4 in the preparation of the remaining catalysts is 2:1). The mixture is reacted for 6 hours, then filtered and dried to obtain catalysts 1-25 sequentially. The specific reaction conditions are shown in Table 1 below.

[0062] The preparation of catalysts 1-25 is basically the same as that of catalysts 1-25 above, except that TiCl4 is replaced with diphenol titanium dichloride, diisopropoxy titanium dichloride, and di(dimethylamino) titanium dichloride in sequence to prepare catalysts 26-28 in sequence. The specific reaction conditions and parameters are shown in Table 1 below.

[0063] Titanium diacetylacetone dichloride was dissolved in tetrahydrofuran (concentration of 0.1 mmol / mL), and alkyl lithium (methyl lithium, benzyl lithium, trimethylsilylmethylene lithium) was added dropwise at -78℃, wherein the molar ratio of alkyl lithium to titanium diacetylacetone dichloride was 3:1, to prepare the following catalysts 29-31. The specific reaction conditions are shown in Table 1 below.

[0064] The types of diketone compounds / alkyllithium, titanium sources, and the molar ratios of diketone compounds / alkyllithium and titanium sources used in the preparation of catalysts 1-31 are shown in Table 1 below.

[0065] Table 1

[0066]

[0067]

[0068] Example 2: Preparation of Ultra-High Molecular Weight Polyethylene

[0069] Catalysts 1-31 prepared in Example 1 were dissolved in toluene to obtain catalyst solutions with a concentration of 2 wt%. In a 5 L high-pressure reactor, a vacuum of 0.1 MPa was applied, nitrogen was introduced, and the mixture was circulated three times. 3 L of dry solvent was added, and heat transfer oil at a certain temperature was introduced into the reactor jacket. Once the reactor temperature reached the set temperature, 5 mmol of alkylaluminum co-catalyst diethylaluminum chloride was added, and the mixture was stirred for 3 min. Then, 0.2 mmol of the catalyst solution was added, and ethylene was continuously introduced into the reactor. Once the set pressure was reached, the pressure inside the reactor was maintained for polymerization. After reacting for 2 h, the ethylene introduction was stopped, and unreacted ethylene was removed (the reactor pressure was released to atmospheric pressure). 5 mL of water was added, and the reaction was stopped. After filtration, the material was vacuum dried and weighed to obtain polyethylene.

[0070] Its viscosity-average molecular weight was tested according to national standards. Specific reaction conditions (polymerization temperature, polymerization pressure, solvent type) and polyethylene performance results are shown in Table 2 below:

[0071] Table 2

[0072]

[0073]

[0074]

[0075] Example 3

[0076] The ultra-high molecular weight polyethylene obtained by polymerization of No. 6 in Table 1 above was added into a tensile sample mold and pressurized to 10 MPa at room temperature to obtain a sample. The sample was then stretched using a universal tensile testing machine at room temperature at a stretching rate of 1 mm / s. The sample was stretched to 220 times the breaking strength, and the breaking strength reached 35.5 cN / dtex.

[0077] The ultra-high molecular weight polyethylene obtained by polymerization of No. 27 in Table 1 above was added into a tensile sample mold and pressurized to 10 MPa at room temperature to obtain a sample. The sample was then stretched using a universal tensile testing machine at room temperature at a stretching rate of 1 mm / s. The tensile strength reached 38.2 cN / dtex when stretched to 250 times the breaking strength.

[0078] The ultra-high molecular weight polyethylene obtained by polymerization of No. 31 in Table 1 above was added into a tensile sample mold and pressurized to 10 MPa at room temperature to obtain a sample. The sample was then stretched using a universal tensile testing machine at room temperature at a stretching rate of 1 mm / s. The sample was stretched to 230 times the breaking strength, and the breaking strength reached 36.8 cN / dtex.

[0079] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compound of the structure of Formula I: ###0001### Formula I wherein n is 1-4, illustratively, n is selected from 1, 2, 3, or 4. R1, R2and R3are the same or different and independently of one another selected from the group consisting of C1-C6alkyl, C2-C6alkenyl, C3-C8cycloalkyl, C6-C8aryl, which are unsubstituted or optionally substituted by one or more halogen, alkyl; R3may also be selected from hydrogen; 18 R1, R2and R3are the same or different and independently of one another selected from the group consisting of C1-C6alkyl, C2-C6alkenyl, C3-C8cycloalkyl, C6-C8aryl, which are unsubstituted or optionally substituted by one or more halogen, alkyl; R3may also be selected from hydrogen; 18 R1, R2and R3are the same or different and independently of one another selected from the group consisting of C1-C6alkyl, C2-C6alkenyl, C3-C8cycloalkyl, C6-C8aryl, which are unsubstituted or optionally substituted by one or more halogen, alkyl; R3may also be selected from hydrogen; X is selected from one of the group consisting of halogen (fluorine, chlorine, bromine, iodine), C1-C 18 alkyl, benzyl, which is unsubstituted or optionally substituted by one or more alkyl groups, trimethylsilylmethylene, dialkyl(C1-C6)amino, C1-C 18 alkyloxy and phenol, which is unsubstituted or optionally substituted by one or more alkyl groups. which is any one of the following: titanium acetylacetonate trichloride, titanium acetylacetonate dichloride, titanium acetylacetonate monochloride, titanium acetylacetonate, titanium bis(benzoylacetone) dichloride, titanium bis(dibenzoylmethane) dichloride, titanium tetrakis(dibenzoylmethane), titanium bis(3-ethyl-2,4-pentanedione) dichloride, titanium bis(3-n-propyl-2,4-pentanedione) dichloride, titanium bis(3-isopropyl-2,4-pentanedione) dichloride, titanium bis(3-isobutyl-2,4-pentanedione) dichloride, titanium bis(3-n-butyl-2,4-pentanedione) dichloride, titanium bis(3-n-pentyl-2,4-pentanedione) dichloride, titanium bis(3-cyclopentyl-2,4-pentanedione) dichloride, titanium bis(3-n-hexyl-2,4-pentanedione) dichloride, titanium bis(3-cyclohexyl-2,4-pentanedione) dichloride, titanium bis(3-phenyl-2,4-pentanedione) dichloride, titanium bis(3-benzylidene-2,4-pentanedione) dichloride, titanium bis(l,l,5,5-tetrafluoro-2,4-pentanedione) dichloride, titanium bis(l,l,l-trifluoro-2,4-pentanedione) dichloride, titanium bis(l,l,l-trifluoro-2,4-hexanedione) dichloride, titanium bis(l,l,l-trifluoro-5,5-dimethyl-2,4-hexanedione) dichloride, titanium bis(4,4,4-trifluoro-l-phenyl-l,3-butanedione) dichloride, titanium bis(4,4,4-trifluoro-l-(2-naphthyl)-l,3-butanedione) dichloride, titanium bis(stearoylbenzoylmethane) dichloride, titanium acetylacetonate diphenoxide, titanium acetylacetonate diisopropoxide, titanium acetylacetonate bis(dimethylamido), titanium acetylacetonate dimethyl, titanium acetylacetonate dibenzyl, titanium acetylacetonate bis(trimethylsilylmethylene).

2. The compound of claim 1 having the structure of formula I, ###0001### I The compound of the structure of Formula I is prepared from a compound of the structure of Formula 2 or an alkyl lithium and a titanium source (such as TiCl4 or an organotitanium chloride) by a reaction, 3. The compound of claim 2 having the structure of formula I, ###0001### I The preparation method comprises: reacting a compound of the structure of Formula 2 or an alkyl lithium and a titanium source (such as TiCl4 or an organotitanium chloride) to prepare the compound of the structure of Formula I. In formula 2, R1, R2and R3are the same or different and independently of one another selected from the group consisting of C1-C6alkyl, C2-C6alkenyl, C3-C8cycloalkyl, C6-C8aryl, which are unsubstituted or optionally substituted by one or more halogen, alkyl; R3may also be selected from hydrogen. 18 alkyl, C2-C6alkenyl, C3-C8cycloalkyl, C6-C8aryl, which are unsubstituted or optionally substituted by one or more halogen, alkyl; R3may also be selected from hydrogen. 18 alkyl, C2-C6alkenyl, C3-C8cycloalkyl, C6-C8aryl, which are unsubstituted or optionally substituted by one or more halogen, alkyl; R3may also be selected from hydrogen. Preferably, the compound of the structure of Formula 2 can be selected from, but not limited to, the following compounds: 3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, 3-allyl-2,4-pentanedione, 3-butyl-2,4-pentanedione, 2,2,4,6,6-pentamethyl-3,5-heptanedione, 3-methylnonane-2,4-dione, 3,7-diethyl-5-methylnonane-4,6-dione, 3-propyl-2,4-pentanedione, 4-methyl-3,5-heptanedione, 3-(1-methylethyl)pentane-2,4-dione, 3-methyl-2,4-hexanedione, 3-ethylidene-2,4-pentanedione, 3-methylene-2,4-pentanedione, 3-hexyl-2,4-pentanedione, 3-(tert-butyl)pentane-2,4-dione, 3-pentyl-2,4-pentanedione, 4-ethyl-2,2,6,6-tetramethylheptane-3,5-dione, 2,5,8-trimethylnonane-4,6-dione, 3-isobutyl-2,4-pentanedione, 3-(3-methylbutyl)-2,4-pentanedione, 3,7-diethyl-3,5-dimethylnonane-4,6-dione, 3-octyl-2,4-pentanedione, 3,5-dimethyl-2,4-hexanedione, 3-sec-butyl-2,4-pentanedione, 2,4-dimethyl-3,5-heptanedione, 3-methyl-2,4-heptanedione, 3-(1-methyl-allyl)-2,4-pentanedione, 3-isopropylidene-2,4-pentanedione, 3,6-dimethyl-2,4-heptanedione, 5-ethyl-nonane-4,6-dione, 4,6-dimethyl-3,5-octanedione, 2,4,6-trimethyl-3,5-heptanedione, 3-ethyl-2,4-heptanedione, 4-allyl-2,2,6,6-tetramethyl-3,5-heptanedione, 4-isopropyl-2,2,6,6-tetramethylheptane-3,5-dione, 4-tert-butyl-2,2,6,6-tetramethyl-3,5-heptanedione, 3-butyl-pentane-2,4-dione (E)-enol isomer, 4-ethyl-3,5-heptanedione, 3-heptyl-2,4-pentanedione, 7-butyl-6,8-tridecanedione, 2-isobutyrylhexanone, 3,3,7,7-tetramethyl-5-isobutyl-4,6-nonanedione, 3,3,7,7-tetramethyl-5-allyl-4,6-nonanedione, 2,2,6,6-tetramethyl-4-hexyl-3,5-heptanedione, 2,2,7-trimethyl-4-isopropyl-3,5-octanedione, 2,2,6-trimethyl-4-tert-butyl-3,5-heptanedione, 2,2,7-trimethyl-4-tert-butyl-3,5-octanedione, 2,2,6,6-tetramethyl-4-isobutyl-3,5-heptanedione, 2,2,6-trimethyl-4-isopropyl-3,5-heptanedione, 2,2,6,6-tetramethyl-4-butyl-3,5-heptanedione, 2,2,6,6-tetramethyl-4-propyl-3,5-heptanedione, 2,2,6-trimethyl-4-isobutyl-3,5-heptanedione, 4-allyl-3,5-heptandione, 3-decyl-2,4-pentandione, 4-allyl-2,6-dimethyl-3,5-heptandione, 2,6-dimethyl-4-isopropyl-3,5-heptandione, 2,2,7-trimethyl-4-butane-3,5-octandione, 4,8-dimethyl-6-isopropyl-5,7-undecandione, 2,2,6-trimethyl-4-ethyl-3,5-nonandione, 4-acetyl-3-heptanone, 3-isopropyl-6-methyl-2,4-heptandione, 9-hexyl-8,10-heptadecandione, 3-hexadecyl-2,4-pentandione, 2-nonyl-1,3-pentandione, 2,6-dimethyl-4-tert-butyl-3,5-heptandione, 2,6-dimethyl-4-ethyl-3,5-heptandione, 3-isopropyl-2,4-heptandione, 3-methyl-2,4-octandione, 4-methyl-3,5-octandione, 4-propyl-3,5-heptandione, 3-methyl-2,4-decandione, 3-propyl-2,4-octandione, 5-propyl-4,6-decandione, 6-propylundecane-5,7-dione, 2,2,4-trimethyl-3,5-heptandione, 3-ethylnonane-2,4-dione, 3,7-diethyl-5-isopropyl-4,6-nonandione, 6-methylundecane-5,7-dione, 5-butylundecane-4,6-dione, 6-butyl-5,7-dodecandione, 3-vinyl-2,4-pentandione, 6-allylundecane-5,7-dione, 3-(3,3-dimethylbutyl)-2,4-pentandione, 3-dodecyl-2,4-pentandione, 4-propyl-3,5-nonandione, 3-tetradecyl-2,4-pentandione, 2,2,4,7-tetramethyl-3,5-octandione, 2,2,4,7-tetramethyl-3,5-octandione, 2,2,6-trimethyl-4-butyl-3,5-heptandione, 2,2,4,6-tetramethyl-3,5-octandione, 3-isopropyl-5-methyl-2,4-hexandione, 3,3,5,7,7-pentamethyl-4,6-nonandione, 2,6-dimethyl-4-butyl-3,5-heptandione, 2-methyl-4-isopropyl-3,5-heptandione, 3,7-dimethyl-5-isopropyl-4,6-nonandione, 1,3-diphenyl-2-methyl-1,3-propanedione, 2-allyl-1,3-diphenyl-1,3-propanedione, 1,1-dibenzoylpropane, 4,4'-methoxy-tert-butyldibenzoylmethane, 1,3-di(p-methoxyphenyl)-2-methyl-1,3-propanedione, 1,3-diphenyl-2-isopropyl-1,3-propanedione, 3-hydroxy-2-methyl-1-phenyl-3-(4'-chlorophenyl)-1-propanone, 3-hydroxy-3-(4-methoxyphenyl)-2-methyl-1-phenyl-1-propanone, 1,3-di(p-methylphenyl)-2-methyl-1,3-propanedione, 2-methyl-1,3-bis(p-chlorophenyl)propane-1,3-dione, 2-methyl-1-phenyl-1,3-butyldione, 2-allyl-1-phenylbutane-1,3-dione, 1-phenyl-2-methyl-1,3-pentanedione, 2-ethyl-1-phenyl-1,3-butyldione, 2-butyl-1-phenyl-1,3-butyldione, 2,4-dimethyl-1-phenyl-1,3-pentanedione, 1-phenyl-2-propyl-1,3-butyldione, 2-methyl-1-(p-tolyl)butane-1,3-dione, 3-benzoyl-2-octanone, 2-isopropyl-1-phenylbutane-1,3-dione, 2-methyl-1-o-chlorophenyl-1,3-pentanedione, 5-benzoyl-6-undecanone, 2-ethyl-1-phenyl-1,3-pentanedione, 2-heptyl-1-phenylbutane-1,3-dione, 2-heptyl-1-phenylbutane-1,3-dione, 2-ethyl-4-methyl-1-phenyl-1,3-pentanedione, 2-isobutyl-1-phenyl-1,3-butyldione, 2-isobutyl-1-phenyl-1,3-butyldione, 3-(4'-methoxyphenyl)-2,4-pentanedione, 3-(4-fluorophenyl)pentane-2,4-dione, 3-(4-chlorophenyl)pentane-2,4-dione, 3-(4-nitrophenyl)pentane-2,4-dione, 3-(4-acetylphenyl)-2,4-pentanedione, 3-(4-bromophenyl)-2,4-pentanedione, 3-(cyclohex-2-enyl)pentane-2,4-dione, 3-(3-oxocyclohexyl)pentane-2,4-dione, 3-(1-adamantyl)pentane-2,4-dione, 3-p-tolylpentane-2,4-dione, 4-phenyl-2,2,6,6-tetramethylheptane-3,5-dione, 3-(2',4',6'-trimethylphenyl)-2,4-pentanedione, 2,6-dimethyl-4-cyclopentyl-3,5-heptanedione, 2,2,6,6-tetramethyl-4-cyclohexyl-3,5-heptanedione, 2,2,6,6-tetramethyl-4-cyclopentane-3,5-heptanedione, 3-cyclohexyl-2,4-pentanedione, 2,6-dimethyl-4-phenyl-3,5-heptanedione, 3-(a-naphthyl)2,4-pentanedione, 3-(cyclopent-2-yl)pentane-2,4-dione, 3-(2,3,5,6-tetramethylphenyl)pentane-2,4-dione, 3-cyclopentylacetylacetone, 3-(9-anthryl)2,4-pentanedione, p-bis(3-acetylacetone)benzene, 3-(9-fluorenyl)-2,4-pentanedione, 3-(2'-methylphenyl)-2,4-pentanedione, 3-(3-methoxyphenyl)pentane-2,4-dione, 3-(3,5-dimethylphenyl)hexane-2,4-dione, 3-(tetrahydro-2H-pyran-2-yl)pentane-2,4-dione, 3-(tetrahydrofuran-2-yl)-2,4-pentanedione, 3-(5-methyl-2-furyl)-2,4-pentanedione, 3-(4-pyridyl)pentane-2,4-dione, 2-(2-furyl)acetylacetate, 3-(1-isochromyl)-2,4-dioxopentane, 3-(pyrid-2-yl)pentane-2,4-diketones, 3-morpholino-2,4-pentanedione and 3-octahydroquinolizine-4-yl pentane-2,4-dione.

4. Process for the preparation of a compound of the structure of formula I according to any one of claims 1 to 3, characterized in that, Preferably, the molar ratio of the compound of the structure of Formula 2 or the alkyl lithium and the titanium source (such as TiCl4 or an organotitanium chloride) is 1:1 to 5:

1.

5. Use of the compound of the structure of Formula I according to any one of claims 1 to 3 as a catalyst. For example, in the catalysis of ethylene polymerization to prepare polyethylene; preferably, in the catalysis of ethylene polymerization to prepare ultra-high molecular weight polyethylene; more preferably, in the catalysis of ethylene polymerization to prepare low molecular chain entangled ultra-high molecular weight polyethylene. The compound of the structure of Formula I according to any one of claims 1 to 3 is used as a main catalyst, and an alkyl aluminum compound is used as a cocatalyst.

6. A catalyst system characterized in that, Preferably, the alkyl aluminum compound is selected from at least one of an alkyl aluminum, an alkoxy aluminum, and an alkyl aluminum halide. ​ Preferably, the aluminum alkyl compound is selected from at least one of triethylaluminum, trimethylaluminum, triisobutylaluminum, methylaluminoxane, diethylaluminum chloride, and ethylaluminum dichloride, etc. Preferably, the molar ratio of the aluminum alkyl compound to the compound of the structure shown in Formula I is (1-10000):1, preferably (10-500):

1.

7. A process for the preparation of polyethylene, characterized in that The catalyst system described in claim 6 is used to catalytically polymerize ethylene to obtain an ultra-high molecular weight polyethylene powder.

8. The polyethylene prepared by the preparation method of claim 7. Preferably, the polyethylene has a viscosity average molecular weight of 50-100 million g / mol. Preferably, the bulk density of the polyethylene is between 0.04 and 0.3 g / cm 3 , preferably between 0.04 and 0.1 g / cm 3 .

9. The use of the polyethylene of claim 8 in the fields of military (such as bulletproof clothing, bulletproof helmets, bulletproof armor, and cut-resistant gloves), aerospace, marine equipment, rail transportation, medical stents, fine filtration, and battery separators, etc.

10. An article containing or prepared from the polyethylene of claim 8. Preferably, the article can be one of a plate, a pipe, a fiber, and a film, etc.

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