A method for producing polyethylene wax using a metallocene catalyst and applications thereof

Abstract

The present application provides a method for preparing polyethylene wax by using metallocene catalyst, which comprises polymerizing ethylene in the presence of metallocene catalyst to prepare polyethylene wax; the metallocene catalyst comprises metallocene compound and activator selected from alkyl aluminum and / or borate. The polyethylene wax prepared by the method of the present application has a viscosity average molecular weight of 1000-10000 and a molecular weight distribution of 1.5-3; the polyethylene wax has a relatively narrow molecular weight distribution, and the preparation method is simple and economical, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of ethylene polymerization, and more specifically to a method for preparing polyethylene wax using a metallocene catalyst and its application. Background Technology

[0002] Polyethylene wax is a synthetic wax, a low molecular weight polyethylene with a relative molecular mass ranging from 1000 to 10000. It is non-toxic, odorless, and non-corrosive, appearing as a white or pale yellow powder, flakes, or block solid. Its melting point is between 90 and 130°C. At room temperature, polyethylene wax is virtually completely insoluble in any polar solutions, such as aqueous solutions, acid solutions, and alkaline solutions. At high temperatures, it is soluble in solutions containing benzene, xylene, n-heptane, turpentine, mineral oil, and paraffin oil. Polyethylene wax possesses many unique physicochemical properties compared to conventional polyethylene, such as low viscosity, low melting point, high crystallinity, high softening point, high hardness, good wear resistance, and low high-temperature volatility. Due to its excellent chemical stability, thermal stability, moisture resistance, low melt viscosity, and excellent electrical properties, polyethylene wax is widely used as a processing aid in rubber, plastics, fibers, coatings, inks, pharmaceuticals, food processing, and precision instrument casting.

[0003] Currently, there are three main methods for producing polyethylene wax on the market: the high molecular weight polyethylene (HMWPE) by-product method, the HMWPE thermal decomposition method, and the ethylene polymerization method. The HMWPE by-product method involves recovering polyethylene wax from a mixture of low molecular weight components and solvents obtained as by-products of polyethylene production from ethylene polymerization. This method produces polyethylene wax with low purity, a wide molecular weight distribution, a low melting temperature, and poor mechanical strength and heat resistance. The HMWPE thermal decomposition method is the simplest method for preparing polyethylene wax; it only requires heating polyethylene to a suitable decomposition temperature to obtain the desired product. However, due to the excessively high decomposition temperature, long reaction time, and difficulty in controlling reaction conditions, the produced polyethylene wax product is of low quality, containing a large number of branches and a wide molar mass distribution. The ethylene polymerization method refers to obtaining polyethylene wax products through chemical synthesis using ethylene as a raw material. This mainly includes high-pressure free radical polymerization, Ziegler-Natta catalytic polymerization, and metallocene catalytic polymerization. The polyethylene wax product synthesized by this method has a small relative molecular mass distribution, a narrow melting range, and higher product quality.

[0004] Metallocene-catalyzed polymerization uses metallocene catalysts with single active centers to catalyze the polymerization of ethylene to obtain polyethylene wax products. Compared with Ziegler-Natta (ZN) catalytic polymerization, this method has the advantages of high catalyst activity, low catalyst dosage, no need for a removal process, lower polymerization temperature, better economic efficiency, and a narrower molecular weight distribution. Utilizing the special polymerization properties and structural variability of the metallocene catalytic system, it is possible to produce polyethylene wax products with superior or entirely new properties. Existing technologies also disclose some methods for preparing polyethylene wax products using metallocene catalysts to catalyze the polymerization of ethylene, such as:

[0005] CN110139844A discloses a method for preparing polyethylene wax, the method comprising the steps of: providing a catalyst solution, wherein the catalyst solution comprises at least one activating compound, an alkylaluminoxane, and a metallocene complex, wherein the molar ratio of the activating compound to aluminum contained in the alkylaluminoxane is 0.0005 to 0.20; and polymerizing ethylene by contacting ethylene with the catalyst solution. The activating compound is selected from the group consisting of phenols, alcohols, sulfonic acids, sulfonates, boric acids, borates, heterocyclic compounds, amines, amides, and nitriles. The alkylaluminoxane is selected from methylaluminoxane, isobutylmethylaluminoxane, n-butylmethylaluminoxane, and n-hexylmethylaluminoxane. The metallocene complex contains at least one cyclopentadienyl ligand bonded to a transition metal selected from zirconium, titanium, and hafnium. The catalyst solution further comprises an aliphatic hydrocarbon solvent or an aromatic hydrocarbon solvent, or a mixture thereof. The prepared polyethylene wax has a molecular weight of 500 to 20,000 g / mol, a molecular weight distribution of 2 to 4, a density of 0.91 to 0.98 g / mL, and a viscosity of 10 to 25,000 cP.

[0006] CN115160462A discloses a catalyst composition for ethylene polymerization and a method for synthesizing polyethylene wax. The catalyst composition includes a main catalyst and a co-catalyst. The main catalyst includes a metallocene compound Cp1Cp2MXn. The co-catalyst is an organic compound containing aluminum or boron. The aluminum-containing organic compound is an alkylaluminum or alkylaluminoxane, and the boron-containing organic compound includes an organoborate ester or organoborate salt. This invention also provides a method for preparing polyethylene wax, using the above-described catalyst composition to prepare polyethylene wax. The catalyst composition is directly added to the polymerization system or added to the polymerization system in the form of a solution or suspension prepared with an inert solvent to produce the polyethylene wax product. The inert solvent includes one or more of the following: straight-chain alkanes with 4-12 carbon atoms, branched non-cyclic alkanes, cyclic alkanes without side chains or with side chains, toluene, or xylene. The polyethylene wax has the following properties: a narrower molecular weight distribution, with a number-average molecular weight Mn of 500-3500; a molecular weight distribution Mw / Mn ≤ 3.5, and in some embodiments, a molecular weight distribution Mw / Mn ≤ 1.8; at the same time, the polyethylene wax has high crystallinity and hardness, with a penetration of ≤ 2 d mm at room temperature and a melting point ≥ 110℃.

[0007] Although the methods described in the above patent documents can also prepare a polyethylene wax with a relatively narrow molecular weight distribution, the polyethylene wax prepared by them has a wider molecular weight distribution. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing polyethylene wax using a metallocene catalyst and its application. The polyethylene wax prepared by the method of the present invention has a viscosity-average molecular weight between 1,000 and 10,000 and a molecular weight distribution between 1.5 and 3. It has a narrow molecular weight distribution, and the preparation method is simple, economical, and has good prospects for industrial application.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing polyethylene wax using a metallocene catalyst, comprising preparing polyethylene wax by ethylene polymerization in the presence of the metallocene catalyst; wherein the metallocene catalyst comprises a metallocene compound and an activator, wherein the activator is selected from alkylaluminum and borates.

[0011] In some embodiments of the present invention, the metallocene compound is selected from any one or more cyclopentadienyl ligands bonded to a transition metal, preferably, the transition metal is selected from zirconium or hafnium.

[0012] In some embodiments of the present invention, the metallocene compound is selected from one or more of the following compounds:

[0013] Dimethylsilylbis(n-propyl)cyclopentadienyl zirconium dichloride;

[0014] Dimethylsilylbisindenylzirconium dichloride;

[0015] Diethylsilylbisindenylzirconium dichloride;

[0016] Diphenylsilyl bis(4,7-dimethylindenyl)zirconium dichloride;

[0017] Dimethylsilylbis(4,7-dimethylindenyl)zirconium dichloride;

[0018] Dimethylsilylbisindenylzirconium dichloride;

[0019] Diphenylsilylbis(2-methylcyclopentadienyl)zirconium dichloride;

[0020] Ethylene diindenyl zirconium dichloride;

[0021] Ethylene bis(2-methylindenyl)zirconium dichloride;

[0022] Dimethylsilylbis(2-methyl-3-butylcyclopentadienyl)zirconium dichloride;

[0023] Dimethylsilyldicyclopentadienyl zirconium dichloride;

[0024] Diethylmethylenecyclopentadienyl(3,5-dimethylphenylindenyl)zirconium dichloride;

[0025] Diethylmethylenecyclopentadienyl(4,7-dimethylindenyl)zirconium dichloride;

[0026] Dimethylmethylenecyclopentadienyl(4,7-dimethylindenyl)zirconium dichloride;

[0027] Dimethylsilylcyclopentadienyl(4,7-dimethylindenyl)zirconium dichloride;

[0028] Dimethylsilylcyclopentadienyl(3,5-dimethylphenylindenyl)zirconium dichloride;

[0029] Dimethylsilylbis(2-methylcyclopentadienyl)zirconium dichloride;

[0030] Dimethylsilylbis(2-methylindenyl)zirconium dichloride;

[0031] Dimethylsilylcyclopentadienyl(2-methylindenyl)zirconium dichloride;

[0032] Dimethylsilylbis(n-propyl)cyclopentadienyl hafnium dichloride;

[0033] Hafnium dichloride dimethylsilylbisindenyl chloride;

[0034] Diethylsilyldiindenyl hafnium dichloride;

[0035] Hafnium dichloride, diphenylsilylbis(4,7-dimethylindenyl)dichloride;

[0036] Hafnium dichloride dimethylsilylbis(4,7-dimethylindene)dichloride; Hafnium dichloride dimethylsilylbisindene;

[0037] Diphenylsilylbis(2-methylcyclopentadienyl)hafnium dichloride;

[0038] Ethylene diindenyl hafnium chloride;

[0039] Ethylene bis(2-methylindenyl) hafnium dichloride;

[0040] Hafnium dichloride dimethylsilylbis(2-methyl-3-butylcyclopentadienyl)dichloride;

[0041] Dimethylsilyldicyclopentadienyl hafnium dichloride;

[0042] Diethylmethylenecyclopentadienyl(3,5-dimethylphenylindenyl)hafnium dichloride;

[0043] Diethylmethylenecyclopentadienyl(4,7-dimethylindenyl)hafnium dichloride;

[0044] Hafnium dichloride, also known as dimethylmethylenecyclopentadienyl(4,7-dimethylindenyl)dichloride;

[0045] Hafnium dichloride, 2,4-dimethylsilylcyclopentadienyl(4,7-dimethylindenyl)dichloride;

[0046] Hafnium dichloride, 2,4-dimethylsilylcyclopentadienyl(3,5-dimethylphenylindenyl)dichloride;

[0047] Hafnium dichloride dimethylsilylbis(2-methylcyclopentadienyl)dichloride;

[0048] Hafnium dichloride, dimethylsilylbis(2-methylindenyl)dichloride;

[0049] Hafnium dichloride is a dimethylsilylcyclopentadienyl(2-methylindenyl)dichloride.

[0050] In some embodiments of the present invention, the alkylaluminum has the general formula AlR3, wherein R is C1-C2. 10 Alkyl; preferably, the alkyl aluminum is selected from one or more of trimethylaluminum, triethylaluminum, triisopropylaluminum, tri-n-propylaluminum, triisobutylaluminum, tri-n-butylaluminum, triisopentylaluminum, tri-n-pentylaluminum, triisohexylaluminum, tri-n-hexylaluminum, tri-n-heptylaluminum, tri-n-octylaluminum, tri-n-octylaluminum, tri-nonylaluminum, tri-nonylaluminum, tri-isodecylaluminum, and tri-decylaluminum.

[0051] In some embodiments of the present invention, the alkylaluminum is calculated as Al, the metallocene compound is calculated as the metal atoms therein (abbreviated as M), and the molar ratio of alkylaluminum to metallocene compound is 50:1 to 1000:1, preferably 100:1 to 800:1, and more preferably 200:1 to 500:1.

[0052] In some embodiments of the present invention, the borate is selected from one or more of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, tetra(pentafluorophenyl)borate diethylphenylammonium salt, tetra(pentafluorophenyl)borate dibutylphenylammonium salt, tetra(pentafluorophenyl)borate trimethylammonium salt, tetra(pentafluorophenyl)borate diethylammonium salt, and tetra(pentafluorophenyl)borate tributylammonium salt.

[0053] In some embodiments of the present invention, the borate is calculated as B, the metallocene compound is calculated as the metal atoms therein (abbreviated as M), and the molar ratio of borate to metallocene compound is 1:1 to 20:1, preferably 5:1 to 20:1, and more preferably 10:1 to 20:1.

[0054] In some embodiments of the present invention, the solvent for the polymerization reaction is an alkane and / or an aromatic solvent.

[0055] In some embodiments of the present invention, the solvent for the polymerization reaction is selected from one or more of hexaane, heptane, octane, nonane, decane, cyclohexane, benzene, toluene, and xylene.

[0056] In some embodiments of the present invention, the total pressure of the reactor for the polymerization reaction is 0.1 to 10 MPa; the partial pressure of ethylene is 0.1 to 10 MPa, preferably 0.1 to 1 MPa; and the partial pressure of hydrogen is greater than or equal to 1% of the partial pressure of ethylene in the reaction system. In some embodiments, the partial pressure of hydrogen for polymerization is greater than or equal to 50% of the partial pressure of ethylene in the reaction system. The hydrogen pressure can be adaptively adjusted according to the target molecular weight of the polyethylene wax product.

[0057] In some embodiments of the present invention, the reaction temperature of the polymerization reaction is 0°C to 100°C, preferably 30°C to 80°C, and more preferably 50°C to 80°C.

[0058] According to the method provided by the present invention, a method for preparing polyethylene wax using a metallocene catalyst specifically includes the following steps:

[0059] (1) First, inert gas is introduced into the reactor and the reactor is filled with inert gas. Then, solvent and metallocene catalyst are added into the reactor and hydrogen is introduced. The reactor is heated at a constant temperature of 0℃ to 100℃ for 20 min to 40 min.

[0060] (2) Ethylene is introduced into the reactor, and the reaction temperature inside the reactor is maintained at 0℃~100℃, so that ethylene is polymerized under the catalysis of a metallocene catalyst to form polyethylene wax. Preferably, the polymerization time is 20min~100min.

[0061] In some embodiments of the present invention, the reaction is terminated by adding a reaction terminator, preferably isopropanol.

[0062] In a second aspect, the present invention provides a polyethylene wax prepared by the method described in the first aspect.

[0063] The polyethylene wax provided by the present invention has a viscosity-average molecular weight of 1,000 to 10,000 and a molecular weight distribution between 1.5 and 3.

[0064] Thirdly, the present invention provides the application of the method described in the first aspect in the synthesis of polyethylene wax.

[0065] The beneficial effects of this invention are as follows:

[0066] This invention provides a method for preparing polyethylene wax by catalyzing the polymerization of ethylene with a metallocene catalyst. The polyethylene wax prepared by this method has a viscosity-average molecular weight of 1,000 to 10,000 and a molecular weight distribution between 1.5 and 3. It has a narrow molecular weight distribution and the preparation method is simple, showing good prospects for industrial application. Detailed Implementation

[0067] The following examples further illustrate the technology of the present invention. These examples are illustrative and exemplary of the present invention and do not limit the scope of the invention in any way.

[0068] Example 1

[0069] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0070] (1) First, nitrogen gas is introduced into the reactor and the reactor is filled with nitrogen gas. Then, 100 mL of cyclohexane, 25 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 35 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride are added into the reactor, and 25 mg of hydrogen gas is introduced. The reactor is heated at 80 °C for 30 min.

[0071] (2) Introduce ethylene at 1 MPa into the reactor, maintain the reaction temperature at 80°C for 60 min, and add a small amount of isopropanol to terminate the reaction.

[0072] (3) After cooling to room temperature, filter and dry to obtain 28.1g of white solid product. The obtained product was tested, and the results showed that the viscosity-average molecular weight was 9175 and the molecular weight distribution was 2.5.

[0073] Example 2

[0074] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0075] (1) First, fill the reactor with nitrogen gas and make the reactor full of nitrogen gas. Then add 100 mL of cyclohexane, 25 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 35 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride to the reactor and introduce 25 mg of hydrogen gas. Heat at 50 °C for 30 min.

[0076] (2) Introduce ethylene at 1 MPa into the reactor, maintain the reaction temperature at 50°C for 60 min, and add a small amount of isopropanol to terminate the reaction.

[0077] (3) After cooling to room temperature, filter and dry to obtain 35.3g of white solid product. The obtained product was tested, and the results showed that the viscosity-average molecular weight was 9469 and the molecular weight distribution was 2.1.

[0078] Example 3

[0079] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0080] (1) First, fill the reactor with nitrogen gas and make the reactor full of nitrogen gas. Then add 100 mL of cyclohexane, 25 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 35 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride to the reactor and introduce 25 mg of hydrogen gas. Heat at 100 °C for 30 min.

[0081] (2) Introduce ethylene at 1 MPa into the reactor, maintain the reaction temperature at 100°C for 60 min, and add a small amount of isopropanol to terminate the reaction.

[0082] (3) After cooling to room temperature, filter and dry to obtain 25g of white solid product. The product was tested and the results showed that the viscosity-average molecular weight was 6695 and the molecular weight distribution was 2.0.

[0083] Example 4

[0084] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0085] (1) First, fill the reactor with nitrogen gas and make the reactor full of nitrogen gas. Then add 100 mL of cyclohexane, 25 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 35 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride to the reactor and introduce 25 mg of hydrogen gas. Heat at 10 °C for 30 min.

[0086] (2) Introduce ethylene at 1 MPa into the reactor, maintain the reaction temperature at 10°C for 60 min, and add a small amount of isopropanol to terminate the reaction.

[0087] (3) After cooling to room temperature, filter and dry to obtain 15g of white solid product. The product was tested and the results showed that the viscosity-average molecular weight was 9582 and the molecular weight distribution was 1.6.

[0088] Example 5

[0089] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0090] (1) First, fill the reactor with nitrogen gas and make the reactor full of nitrogen gas. Then add 100 mL of cyclohexane, 32 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 40 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride to the reactor and introduce 50 mg of hydrogen gas. Heat at 80 °C for 30 min.

[0091] (2) Introduce ethylene at 1 MPa into the reactor, maintain the reaction temperature at 80°C for 60 min, and add a small amount of isopropanol to terminate the reaction.

[0092] (3) After cooling to room temperature, the product was filtered and dried to obtain 40.9g of white solid product. The product was tested, and the results showed that the viscosity-average molecular weight was 5693 and the molecular weight distribution was 2.1.

[0093] Example 6

[0094] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0095] (1) First, nitrogen gas is introduced into the reactor and the reactor is filled with nitrogen gas. Then, 100 mL of cyclohexane, 25 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 35 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride are added into the reactor, and 25 mg of hydrogen gas is introduced. The reactor is heated at 80 °C for 30 min.

[0096] (2) Introduce ethylene at 10 MPa into the reactor, maintain the reaction temperature in the reactor at 80°C for 60 min, and add a small amount of isopropanol to terminate the reaction.

[0097] (3) After cooling to room temperature, filter and dry to obtain 42g of white solid product. The product was tested and the results showed that the viscosity-average molecular weight was 9725 and the molecular weight distribution was 2.2.

[0098] Example 7

[0099] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0100] (1) First, nitrogen gas is introduced into the reactor and the reactor is filled with nitrogen gas. Then, 100 mL of cyclohexane, 25 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 35 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride are added into the reactor, and 25 mg of hydrogen gas is introduced. The reactor is heated at 80 °C for 30 min.

[0101] (2) Introduce 0.1 MPa of ethylene into the reactor, maintain the reaction temperature in the reactor at 80°C for 60 min, and add a small amount of isopropanol to terminate the reaction.

[0102] (3) After cooling to room temperature, filter and dry to obtain 22g of white solid product. The product was tested and the results showed that the viscosity-average molecular weight was 6295 and the molecular weight distribution was 1.8.

[0103] Example 8

[0104] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0105] (1) First, nitrogen gas is introduced into the reactor and the reactor is filled with nitrogen gas. Then, 100 mL of cyclohexane, 25 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 35 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride are added into the reactor, and 25 mg of hydrogen gas is introduced. The reactor is heated at 80 °C for 30 min.

[0106] (2) Introduce ethylene at 1 MPa into the reactor, maintain the reaction temperature at 80°C for 20 min, and add a small amount of isopropanol to terminate the reaction.

[0107] (3) After cooling to room temperature, filter and dry to obtain 15g of white solid product. The product was tested and the results showed that the viscosity-average molecular weight was 1610 and the molecular weight distribution was 1.5.

[0108] Example 9

[0109] A method for preparing polyethylene wax using a metallocene catalyst, the specific process of which is as follows:

[0110] (1) First, nitrogen gas is introduced into the reactor and the reactor is filled with nitrogen gas. Then, 100 mL of cyclohexane, 25 mg of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, 35 mg of trimethylaluminum and 2 μmol of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride are added into the reactor, and 25 mg of hydrogen gas is introduced. The reactor is heated at 80 °C for 30 min.

[0111] (2) Introduce ethylene at 1 MPa into the reactor, maintain the reaction temperature at 80°C for 100 min, and add a small amount of isopropanol to terminate the reaction.

[0112] (3) After cooling to room temperature, filter and dry to obtain 30g of white solid product. The obtained product was tested, and the results showed that the viscosity-average molecular weight was 9843 and the molecular weight distribution was 2.6.

[0113] Comparative Example 1

[0114] The reaction conditions and procedures were the same as in Example 1, except that diindene-zirconium dichloride was used instead of dimethylsilylbis(n-propyl)cyclopentadienylzirconium dichloride in step (1). 33g of a white solid product was obtained. Testing of the product showed that the viscosity-average molecular weight was 18206 and the molecular weight distribution was 4.2.

[0115] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The embodiments describe the present invention, and it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention.

Claims

1. A method for preparing polyethylene wax using a metallocene catalyst, characterized in that, The method includes preparing polyethylene wax by ethylene polymerization in the presence of a metallocene catalyst; the metallocene catalyst comprises a metallocene compound and an activator selected from alkylaluminum and borates.

2. The method according to claim 1, characterized in that, The alkylaluminum has the general formula AlR3, where R is C1-C2. 10 Alkyl; preferably, the alkyl aluminum is selected from one or more of trimethylaluminum, triethylaluminum, triisopropylaluminum, tri-n-propylaluminum, triisobutylaluminum, tri-n-butylaluminum, triisopentylaluminum, tri-n-pentylaluminum, triisohexylaluminum, tri-n-hexylaluminum, tri-n-heptylaluminum, tri-n-octylaluminum, tri-n-octylaluminum, tri-nonylaluminum, tri-nonylaluminum, tri-isodecylaluminum, and tri-decylaluminum.

3. The method according to claim 2, characterized in that, The alkylaluminum is calculated as Al, and the metallocene compound is calculated as the metal atoms therein. The molar ratio of alkylaluminum to metallocene compound is 50:1 to 1000:1, preferably 100:1 to 800:1, and more preferably 200:1 to 500:

1.

4. The method according to any one of claims 1-3, characterized in that, The borate is selected from one or more of tetra(pentafluorophenyl)borate dimethylphenylammonium salt, tetra(pentafluorophenyl)borate diethylphenylammonium salt, tetra(pentafluorophenyl)borate dibutylphenylammonium salt, tetra(pentafluorophenyl)borate trimethylammonium salt, tetra(pentafluorophenyl)borate diethylammonium salt, and tetra(pentafluorophenyl)borate tributylammonium salt.

5. The method according to claim 4, characterized in that, The borate is calculated as B, and the metallocene compound is calculated as the metal atoms therein. The molar ratio of borate to metallocene compound is 1:1 to 20:1, preferably 5:1 to 20:1, and more preferably 10:1 to 20:

1.

6. The method according to any one of claims 1-4, characterized in that, The solvent for the polymerization reaction is an alkane and / or an aromatic solvent, preferably one or more of hexaane, heptane, octane, nonane, decane, cyclohexane, benzene, toluene, and xylene.

7. The method according to any one of claims 1-6, characterized in that, The reaction temperature of the polymerization reaction is 0℃~100℃, preferably 30℃~80℃, and more preferably 50℃~80℃; And / or, the total pressure of the reactor for the polymerization reaction is 0.1 to 10 MPa; the partial pressure of ethylene is 0.1 to 10 MPa, preferably 0.1 to 1 MPa.

8. The method according to any one of claims 1-7, characterized in that, The method includes the following steps: (1) First, inert gas is introduced into the reactor and the reactor is filled with inert gas. Then, solvent and metallocene catalyst are added into the reactor and hydrogen is introduced. The reactor is heated at a constant temperature of 0℃ to 100℃ for 20 min to 40 min. (2) Introduce ethylene into the reactor and maintain the reaction temperature in the reactor at 0℃~100℃, so that ethylene is polymerized under the catalytic action of a metallocene catalyst to form polyethylene wax; preferably, the polymerization time is 20min~100min, and more preferably 40min~80min.

9. A polyethylene wax prepared by the method of any one of claims 1-8; preferably, the polyethylene wax has a viscosity-average molecular weight between 1,000 and 10,000 and a molecular weight distribution between 1.5 and 3.

10. The application of the method as described in any one of claims 1-8 in the synthesis of polyethylene wax.