A narrow-distribution low-branching polyethylene wax and its preparation method

Abstract

The present invention relates to a narrow-distribution low-branching polyethylene wax and a preparation method thereof. A solvent, ethylene, a catalyst and a cocatalyst are added into a reaction kettle for polymerization reaction. After the polymerization reaction is completed, post-treatment is carried out to obtain a polyethylene wax product. The catalyst is a late transition metal catalyst with isatin as the skeleton, the cocatalyst includes an alkylaluminoxane, and the molar ratio of the catalyst to the cocatalyst is 1:100-600. Compared with the prior art, the present invention uses a late transition metal catalyst with high activity and high thermal stability to prepare a polyethylene wax with excellent performance. The obtained polyethylene wax has a moderate molecular weight, a narrow molecular weight distribution and a small degree of branching.

Description

Technical Field

[0001] The present invention relates to the field of new materials, and particularly to a narrow-distribution low-branching polyethylene wax and a preparation method thereof. Background Art

[0002] Polyethylene wax (PE-wax) is a high-molecular material polymerized from ethylene monomers, with an appearance of white granular / flaky structure. Its molecular weight ranges from 1000 to 10000, and the relatively low molecular weight endows polyethylene wax with properties different from those of conventional polyethylene. Polyethylene wax has characteristics such as low viscosity, high softening point, and high hardness, which enable it to be widely used in the field of plastic processing. In addition, polyethylene wax has properties such as non-toxicity, thermal stability, and low volatility, expanding its application in extreme environments such as low temperature and high heat. Finally, polyethylene wax has excellent dispersing ability for pigments, which can not only promote the uniform distribution of pigments, but also enhance the external lubricity of materials and provide excellent lubrication effects inside the materials, significantly improving the production efficiency of dye processing. Therefore, polyethylene wax has become a high-end material in polyethylene products.

[0003] Currently, there are mainly three methods for preparing polyethylene wax in industry: by-product refining, polyethylene cracking, and direct polymerization of ethylene. Among them, the by-product refining process refines and separates the oligomer components in the previous stage of polyethylene production, while the polyethylene cracking process obtains polyethylene wax by catalytic degradation of high-molecular-weight polyethylene. The polyethylene wax products obtained by the above two methods have a wide molecular weight distribution, many impurities, and poor performance in various aspects, making it difficult to meet the requirements of modern high-end fields. Only the polyethylene wax produced by the polymerization method can meet the requirements, and the polymerization method also meets the requirements of modern chemical industry for high efficient atom utilization rate and green production.

[0004] Chinese Patent CN112745409B discloses a narrow-distribution polyethylene wax and a preparation method thereof. This patent obtains polyethylene wax through a polymerization reaction using a metallocene catalyst Ph2PN[CH(CH3Ph)]PPh2·CrCl3 or Ph2PN(CHPh2)PPh2·CrCl3. The molecular weight of the prepared polyethylene wax is 500 - 2000, and the PDI is 1.4 - 3.0. This patent uses a metallocene catalyst, which has a high cost and a large amount of cocatalyst used.

[0005] Post-transition metal catalysts have unique catalytic properties for ethylene polymerization. Post-transition metal catalysts are formed by coordinating post-transition metals such as Fe, Co, Ni, Pd, etc. with ligands containing elements such as N, O, P, etc. to form metal-organic catalysts. They are prone to β-H elimination reaction to generate low-molecular-weight polymers. Compared with Ziegler-Natta (Z-N) catalysts that mainly produce high-molecular-weight polyethylene and metallocene catalysts with high costs, they are catalysts with potential for industrial production of polyethylene wax. For example, Chinese Patent CN 110092744A discloses a tert-butyl-containing asymmetric diimine pyridine transition metal complex for preparing polyethylene wax, which has a single catalytic active center. However, the polyethylene wax prepared by this patent has a wide molecular weight distribution and a large amount of cocatalyst used (Al / Fe≥1000), which hinders its practical application. Therefore, for the production of high-quality polyethylene wax products by ethylene polymerization, further research is still needed. Summary of the Invention

[0006] The purpose of the present invention is to provide a narrow-distribution and low-branching polyethylene wax and its preparation method to solve the above problems.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A preparation method of a narrow-distribution and low-branching polyethylene wax, specifically: adding a solvent, ethylene, a catalyst, and a cocatalyst into a reaction kettle for polymerization reaction, and performing post-treatment after the polymerization reaction to obtain a polyethylene wax product;

[0009] Among them, the catalyst is a post-transition metal catalyst with isatin as the skeleton;

[0010] The cocatalyst includes alkylaluminoxane;

[0011] The molar ratio of the catalyst to the cocatalyst is 1:100 - 600.

[0012] As a preferred technical solution of the present invention, the pressure in the reaction kettle is controlled by ethylene gas, and the pressure in the reaction kettle is controlled at 0.1 - 10 Mpa, preferably 0.1 - 5 MPa, more preferably 0.1 - 2 MPa, and even more preferably 0.1 - 0.5 Mpa;

[0013] The temperature in the reaction kettle is controlled at 45 - 120 °C, preferably 60 - 85 °C, more preferably 60 - 75 °C.

[0014] As a preferred technical solution of the present invention, the solvent is an inert organic solvent, which is a linear alkane, cycloalkane, or benzene aromatic derivative that is liquid at room temperature, has low viscosity, a boiling point not exceeding 120 °C, and low solubility for polyethylene wax. Toluene, xylene, and chlorobenzene are preferably used;

[0015] And / or, the cocatalyst is selected from methylaluminoxane, modified methylaluminoxane, isobutylaluminoxane, and the molar ratio of the catalyst to the cocatalyst is 1:400 - 600;

[0016] And / or, the catalyst and the cocatalyst are diluted with a solvent into a catalyst dilution solution and then added to the reaction kettle.

[0017] As a preferred technical solution of the present invention, the polymerization reaction is carried out in an anhydrous and anaerobic environment;

[0018] And / or, the post-treatment is to add acidic methanol to inactivate the catalyst. After collecting the product and drying it, a polyethylene wax product is obtained.

[0019] As a preferred technical solution of the present invention, the catalyst is a nickel metal catalyst with isatin as the skeleton, and its structural formula is:

[0020]

[0021] In the above formula, R 1～ At least one of R5 is an electron-donating group, selected from C1-C6 alkyl, C1-C6 alkoxy, aromatic phenyl, R 6～ R8 is selected from H, C1-C6 alkyl, halogen, and X is chlorine or bromine.

[0022] As a preferred technical solution of the present invention, among R1-R5, at least one of R1, R2, and R5 is selected from C1-C6 alkyl, and the rest are H; more preferably, R2 is an electron-donating group and the rest are H. As a preferred embodiment, the isatin derivative with R2 being methyl, methoxy or isopropyl, and R1, R3, R4, R5 being H.

[0023] R6-R8 are each independently selected from H or C1-C6 alkyl. Further preferably, the aniline derivative in which at least one of R6, R7, and R8 is an electron-donating group, that is, at least one of R6, R7, and R8 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl. More preferably, R6 is methyl, isopropyl or methoxy, and / or R7 is methyl, isopropyl or methoxy, and / or R8 is methyl, isopropyl or tert-butyl.

[0024] As a preferred technical solution of the present invention, the catalyst is prepared by the following method:

[0025] Under anhydrous and anaerobic conditions, add a diimine ligand with isatin as the skeleton and an anhydrous nickel salt to a reaction vessel containing a solvent, and react at 15-80 °C for 12-36 hours. Among them, the molar ratio of the diimine ligand to the anhydrous nickel salt is 2-3:1. After the reaction is completed, the catalyst solid is obtained through treatment;

[0026] The solvent includes acetonitrile;

[0027] The nickel salts include nickel chloride and nickel bromide.

[0028] As a preferred technical solution of the present invention, the diimine ligand has the structure shown in formula L:

[0029]

[0030] In formula L, R 1～ At least one of R5 is an electron-donating group, selected from C1-C6 alkyl, C1-C6 alkoxy, and aromatic phenyl. R 6～ R8 is selected from H, C1-C6 alkyl, and halogen.

[0031] As a preferred embodiment of the present invention, the diimine ligand is selected from any one of the following diimine ligand compounds of formula L1 to formula L10:

[0032]

[0033]

[0034]

[0035] The diimine ligand of the formula L structure uses isatin and its derivatives as the backbone. There is a six-membered ring and an N-heterocyclic five-membered ring structure in isatin, which has a certain rigidity and improves the thermal stability of the late transition metal catalyst when coordinated with the metal to form a catalyst. In addition, there is an N-heterocyclic five-membered ring in isatin. The N atom has a stronger electronegativity than the C atom, and there are lone pairs of electrons on the N atom that can conjugate with the benzene ring and the diimine structure to further optimize the electronic structure of the catalyst.

[0036] As a preferred technical solution of the present invention, the diimine ligand is prepared by the following method:

[0037] A 1,2-diketone compound and an aromatic amine are dissolved in an organic aprotic polar solvent, and a non-oxidizing organic strong acid is added as a catalyst. The reaction is carried out at 100-200 °C, preferably 120-160 °C, for 12-36 hours. The solvent in the reaction mixture is removed to obtain a solid product, which is purified to obtain the product;

[0038] The molar ratio of the 1,2-diketone compound to the aromatic amine is 1:2-2.5;

[0039] The organic aprotic polar solvent includes a mixture of toluene and dimethyl sulfoxide;

[0040] The organic strong acid includes p-toluenesulfonic acid.

[0041] A narrow-distribution and low-branching-degree polyethylene wax prepared by the above-described preparation method, wherein the polyethylene wax has a weight-average molecular weight of 3,800 - 8,000, a molecular weight distribution between 1.1 - 1.5, and a branching degree of 10 - 50 / 1000C.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The nickel metal catalyst prepared by the present invention with a novel structure of diimine ligand is based on isatin as the backbone, which has higher rigidity and more appropriate electron cloud density compared with the traditional 1,2-diketone structure, and can greatly improve the catalytic performance and stability of the catalyst. The synthesized late transition metal catalyst can have high catalytic activity in a wide range of 45 - 120°C. When preparing polyethylene wax, the obtained polyethylene wax product has the characteristics of narrow molecular weight distribution (PDI < 1.5) and low branching degree (< 50 / 1000C), and belongs to the high-quality polyethylene wax required by the market. Detailed Embodiments

[0044] The present invention will be described in detail below with reference to specific embodiments, but it is by no means a limitation to the present invention.

[0045] The inventors have found through research that when the late transition metal catalyst based on isatin is used for ethylene polymerization to produce polyethylene wax, it can maintain high catalytic activity in a wide range of 45 - 120°C, especially high-temperature stability. When used to prepare polyethylene wax, the polyethylene wax product has the characteristics of narrow molecular weight distribution (PDI < 1.5), low branching degree (< 50 / 1000C), and good chemical and physical properties. The possible reasons speculated by the inventors are as follows: When isatin is used as the backbone, there is a six-membered ring and an N-heterocyclic five-membered ring structure in isatin, which has a certain rigidity and can improve the thermal stability of the late transition metal catalyst. There is an N-heterocyclic five-membered ring in isatin. The N atom has stronger electronegativity than the C atom, and there are lone pair electrons on the N atom that can conjugate with the benzene ring and the diimine structure to further optimize the electronic structure of the catalyst. Compared with the traditional 1,2-diketone structure, it has higher rigidity and appropriate electron cloud density, and can improve the catalytic performance and stability of the catalyst.

[0046]

Preparation Example

[0047] The late transition metal catalyst with Ni as the active center is formed by coordinating a diimine ligand compound with a nickel salt, and its structural formula is:

[0048]

[0049] This catalyst is prepared by the following method:

[0050] Under anhydrous and anaerobic conditions, a ligand and an anhydrous nickel salt (nickel chloride, nickel bromide, preferably nickel chloride) are added to a reaction vessel containing a solvent (such as ultra-dry acetonitrile), and the reaction is carried out at 15-80 °C for 12-36 hours. Among them, the molar ratio of the ligand to the anhydrous nickel salt is 2-3:1. After the reaction is completed, the catalyst solid is obtained through treatment (after cooling to room temperature, concentration by reduced pressure evaporation, filtering out the solvent, and washing multiple times with dry n-hexane). The reaction formula is as follows:

[0051]

[0052] Among them, the diimine ligand is prepared by the following method:

[0053] A 1,2-diketone compound and an aromatic amine (molar ratio 1:2-2.5) are dissolved in an organic aprotic polar solvent (such as a mixture of toluene and DMSO), and a non-oxidizing organic strong acid (such as p-toluenesulfonic acid) is added as a catalyst. The reaction is carried out at 100-200 °C, preferably 120-160 °C for 12-36 hours. After the reaction, the solvent of the mixture is removed (such as by rotary evaporation), and the obtained solid product is purified (such as by recrystallization) to obtain the ligand. The reaction formula is as follows:

[0054]

[0055] Taking L1 as an example, the synthesis steps are as follows:

[0056]

[0057] Add about 100 ml of a mixed solution (V 甲苯 :V DMSO = 9:1) as the solvent to a 250 ml three-necked flask. Subsequently, add an isatin derivative (R1-methyl-substituted isatin, 10 mmol) and an aniline derivative (aniline, 21 mmol), mix them evenly, then add a catalytic amount of p-toluenesulfonic acid (10 μmol), and carry out a water-separating reflux at 120 °C for 24 hours. The solvent of the reaction mixture is removed by rotary evaporation, and the obtained solid is recrystallized to obtain the ligand L1.

[0058] The ligands L1-L10 are prepared respectively according to the above method. For specific details, see Table 1.

[0059] The specific information of the reagents used is as follows (taking R1-methyl-substituted erythrosine as an example, indicating that R1 is methyl and the rest of the groups are H).

[0060] R1-methyl-substituted erythrosine (CAS: 2058-74-4 Sigma-Aldrich)

[0061] R2-methyl-substituted erythrosine (CAS: 1127-59-9 Leyan Reagent)

[0062] R5-Methyl-substituted erythrosine (CAS: 1127-59-9 Mecklin)

[0063] R2-Isopropyl-substituted isatin (CAS: 66232-59-5 obtained by synthesis)

[0064] Sodium sulfate (CAS: 7757-82-6 Sigma-Aldrich)

[0065] Chloral hydrate (CAS: 302-17-0 Sigma-Aldrich)

[0066] Hydroxylamine sulfate (CAS: 10039-54-0 Sigma-Aldrich)

[0067] Concentrated hydrochloric acid (CAS: 7647-01-0 Sigma-Aldrich)

[0068] m-Isopropylaniline (CAS: 108-44-1 Aladdin)

[0069] R6-Methyl-substituted aniline (CAS: 87-62-7 Sigma-Aldrich)

[0070] R6-Bromo-substituted aniline (CAS: 608-3-0 Sigma-Aldrich)

[0071] R6-Isopropyl-substituted aniline (CAS: 24544-04-5 Sigma-Aldrich) R7-Methyl-substituted aniline (CAS: 108-69-0 Sigma-Aldrich)

[0072] R8-Methyl-substituted aniline (CAS: 106-49-0 Sigma-Aldrich)

[0073] 2,6-Diacetylpyridine (CAS: 1129-30-2 Sigma-Aldrich)

[0074] Salicylaldehyde (CAS: 90-02-8 Sigma-Aldrich)

[0075] Bis(triphenylphosphine) nickel(II) chloride (CAS: 14264-16-5 Sigma-Aldrich) Tetrahydrofuran (CAS: 109-99-9 Sigma-Aldrich)

[0076] n-Hexane (CAS: 110-54-3 Sigma-Aldrich)

[0077] Diethyl ether (CAS: 60-29-7 Aladdin)

[0078] Concentrated sulfuric acid (CAS: 7664-39-9, Aladdin)

[0079] Toluene (CAS: 108-88-3, Sigma-Aldrich)

[0080] Dimethyl sulfoxide (CAS: 67-68-5, Sigma-Aldrich)

[0081] Ethanol (CAS: 64-17-5, Sigma-Aldrich)

[0082] Acetonitrile (CAS: 75-05-8, Sigma-Aldrich)

[0083] p-Toluenesulfonic acid (CAS: 6192-52-5, Sigma-Aldrich)

[0084] Unless otherwise specified, all solvents involved in the present invention need to be treated to remove water.

[0085] Table 1 Raw materials for preparing ligands L1 - L10

[0086]

[0087]

[0088]

[0089] Ligand L1

[0090] Add 100 ml of a mixed organic solvent (V 甲苯 :V DMSO = 9:1) into a 250 ml three-necked flask. Subsequently, add R1-methyl-substituted erythrosine (10 mmol) and aniline (21 mmol) into the flask and mix evenly. Then add a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol), and reflux the reaction at 120 °C for 24 h. After the reaction is completed, distill off the solvent under reduced pressure, and then recrystallize and purify the product with an ethanol solution to obtain ligand L1 with a final yield of 87%. ( 1 H 300 MHz, DMSO): 7.62 - 6.81 (m, 14H, Ar-H), 3.55 (s, 3H, CH3). C 21 H 17 N3: Calculated values of elemental analysis (%): C, 81.00; H, 5.50; N, 13.49. Measured values (%): C, 81.24; H, 5.52; N, 13.41.

[0091] Ligand L2

[0092] Add 100 ml of a mixed organic solvent (V 甲苯 :V DMSO = 9:1) to a 250 ml three-necked flask. Subsequently, add R2-methyl-substituted erythrosine (10 mmol) and aniline (21 mmol) to the flask and mix well. Then add a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol), and reflux the reaction at 120 °C for 24 h. After the reaction is completed, distill off the solvent under reduced pressure, and then recrystallize and purify the product with an ethanol solution to obtain the ligand L2 with a final yield of 81%. ( 1 H 300 MHz, DMSO): 11.11 (s, 1H, N-H), 7.55 - 6.82 (m, 13H, Ar-H), 2.75 - 1.88 (m, 3H, CH3). C 21 H 17 N3: Calculated values (%) for elemental analysis: C, 81.00; H, 5.50; N, 13.49. Measured values (%): C, 81.15; H, 5.54; N, 13.47.

[0093] Ligand L3

[0094] Add 100 ml of a mixed organic solvent (V 甲苯 :V DMSO = 9:1) to a 250 ml three-necked flask. Subsequently, add R5-methyl-substituted erythrosine (10 mmol) and aniline (21 mmol) to the flask and mix well. Then add a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol), and reflux the reaction at 120 °C for 24 h. After the reaction is completed, distill off the solvent under reduced pressure, and then recrystallize and purify the product with an ethanol solution to obtain the ligand L3 with a final yield of 85%. ( 1 H 300 MHz, DMSO): 11.24 (s, 1H, N-H), 7.45 - 6.02 (m, 13H, Ar-H), 2.83 - 1.95 (m, 3H, CH3). C 21 H 17 N3: Calculated values (%) for elemental analysis: C, 81.00; H, 5.50; N, 13.49. Measured values (%): C, 81.07; H, 5.62; N, 13.53.

[0095] Ligand L4

[0096] Add 100 ml of a mixed organic solvent (V 甲苯 :V DMSO= 9:1), and then 10 mmol of R2-isomethyl-substituted erythrosine and 21 mmol of aniline were added to the flask and mixed evenly. Subsequently, a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol) was added, and the reaction was refluxed at 120 °C for 24 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified with an ethanol solution to obtain ligand L4 with a final yield of 77%.( 1 H 300 MHz, DMSO): 10.96 (s, 1H, N-H), 7.56 - 6.90 (m, 13H, Ar-H), 3.05 - 2.08 (m, 7H, CH(CH3)2). C 23 H 21 N3: Calculated values (%) for elemental analysis: C, 81.38; H, 6.24; N, 12.38. Measured values (%): C, 81.46; H, 6.39; N, 12.40.

[0097] Ligand L5

[0098] 100 ml of a mixed organic solvent (V 甲苯 :V DMSO = 9:1) was added to a 250 ml three-necked flask, and then 10 mmol of R2-tert-butyl-substituted erythrosine and 21 mmol of aniline were added to the flask and mixed evenly. Subsequently, a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol) was added, and the reaction was refluxed at 120 °C for 24 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified with an ethanol solution to obtain ligand L5 with a final yield of 72%.( 1 H 300 MHz, DMSO): 11.23 (s, 1H, N-H), 7.61 - 6.75 (m, 13H, Ar-H), 2.95 - 1.05 (m, 9H, C(CH3)3). C 24 H 23 N3: Calculated values (%) for elemental analysis: C, 81.55; H, 6.56; N, 11.89. Measured values (%): C, 81.58; H, 6.59; N, 11.90.

[0099] Ligand L6

[0100] 100 ml of a mixed organic solvent (V 甲苯 :V DMSO= 9:1), and then add R2-isopropyl-substituted erythrosine (10 mmol) and R6-methyl-substituted aniline (21 mmol) into the flask and mix them evenly. Then add a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol), and reflux the reaction at 120 °C for 24 h. After the reaction is completed, distill off the solvent under reduced pressure, and then recrystallize and purify the product with an ethanol solution to obtain the ligand L6 with a final yield of 82%.( 1 H 300 MHz, DMSO): 11.40 (s, 1H, N-H), 7.44 - 6.92 (m, 9H, Ar-H), 3.11 - 2.38 (m, 19H, CH(CH3)2). C 27 H 29 N3: Calculated values (%) for elemental analysis: C, 81.99; H, 7.39; N, 10.62. Measured values (%): C, 82.06; H, 7.49; N, 10.57.

[0101] Ligand L7

[0102] Add 100 ml of a mixed organic solvent (V 甲苯 :V DMSO = 9:1) into a 250 ml three-necked flask. Then add R2-isopropyl-substituted erythrosine (10 mmol) and R6-bromo-substituted aniline (21 mmol) into the flask and mix them evenly. Then add a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol), and reflux the reaction at 120 °C for 24 h. After the reaction is completed, distill off the solvent under reduced pressure, and then recrystallize and purify the product with an ethanol solution to obtain the ligand L7 with a final yield of 80%.( 1 H 300 MHz, DMSO): 11.27 (s, 1H, N-H), 7.60 - 6.81 (m, 9H, Ar-H), 3.31 - 1.48 (m, 7H, CH(CH3)2). C 23 H 17 N3Br4: Calculated values (%) for elemental analysis: C, 42.17; H, 2.62; N, 6.42; Br, 48.79. Measured values (%): C, 42.16; H, 2.69; N, 6.47; Br, 48.77.

[0103] Ligand L8

[0104] Add 100 ml of a mixed organic solvent (V 甲苯 :V DMSO= 9:1), and then 10 mmol of R2-isopropyl-substituted isatin and 21 mmol of R6-isopropyl-substituted aniline were added to the flask and mixed evenly. Subsequently, a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol) was added, and the reaction was refluxed at 120 °C for 24 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L8 with a final yield of 77%.( 1 H 300 MHz, DMSO): 11.15 (s, 1H, N-H), 7.77 - 6.92 (m, 9H, Ar-H), 3.19 - 1.35 (m, 35H, CH(CH3)2). C 35 H 45 N3: Calculated values (%) for elemental analysis: C, 82.79; H, 8.93; N, 8.28. Measured values (%): C, 82.86; H, 8.97; N, 8.47.

[0105] Ligand L9

[0106] 100 ml of a mixed organic solvent (V 甲苯 :V DMSO = 9:1) was added to a 250 ml three-necked flask, and then 10 mmol of R2-isopropyl-substituted isatin bromide and 21 mmol of R7-methyl-substituted aniline were added to the flask and mixed evenly. Subsequently, a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol) was added, and the reaction was refluxed at 120 °C for 24 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L9 with a final yield of 72%.( 1 H 300 MHz, DMSO): 11.29 (s, 1H, N-H), 7.45 - 6.93 (m, 9H, Ar-H), 3.34 - 1.55 (m, 19H, CH(CH3)2). C 27 H 29 N3: Calculated values (%) for elemental analysis: C, 81.99; H, 7.39; N, 10.62. Measured values (%): C, 82.02; H, 7.47; N, 10.66.

[0107] Ligand L10

[0108] 100 ml of a mixed organic solvent (V 甲苯 :V DMSO= 9:1), and then R2-isopropyl-substituted erythrosine (10 mmol) and R8-methyl-substituted aniline (21 mmol) were added to the flask and mixed evenly. Subsequently, a catalytic equivalent of p-toluenesulfonic acid (about 10 μmol) was added, and the reaction was refluxed at 120 °C for 24 h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified with an ethanol solution to obtain the ligand L10 with a final yield of 89%.( 1 H 300 MHz, DMSO): 11.50 (s, 1H, N-H), 7.52 - 6.88 (m, 11H, Ar-H), 3.16 - 1.37 (m, 13H, CH3CH(CH3)2). C 25 H 25 N3: Calculated values (%) for elemental analysis: C, 81.71; H, 6.96; N, 11.43. Found values (%): C, 81.78; H, 7.02; N, 11.59.

[0109] Preparation of catalysts C1 - C10

[0110] The above-obtained ligands were respectively coordinated with NiCl2, and the reaction equations are as follows:

[0111]

[0112] Specific steps: Under anhydrous and anaerobic conditions, about 100 ml of ultra-dry acetonitrile was added to a three-necked flask, and the ligands L1 - L10 (8.4 mmol) and anhydrous NiCl2 (4 mmol) were added respectively. The reaction temperature was controlled at 55 °C, and the reaction time was 24 hours. After the reaction, it was cooled to room temperature, concentrated by distillation under reduced pressure, the solvent was filtered out, and it was washed with dry n-hexane several times and dried to obtain catalysts C1 - C10.

[0113] Preparation of catalysts C1'-C3'

[0114] As a comparison, the catalysts C1'-C3' were prepared in the present invention.

[0115] Catalyst C1'

[0116] Preparation of ligand L1': 2,3-Butanedione (10 mmol) and aniline (22 mmol) were dissolved in 100 ml of toluene solution in a 250 ml three-necked flask, and a catalytic amount of p-toluenesulfonic acid (about 10 μmol) was added. The reaction was refluxed with water separation at 100 °C for 24 h. After the reaction, the solvent toluene was removed by distillation under reduced pressure, and the solid product was recrystallized with a hot ethanol solution, and the final yield was 86%.

[0117]

[0118] Synthesis of catalyst C1': Add the synthesized ligand (5 mmol) and anhydrous NiCl2 (11 mmol) to a single-necked flask, and then add anhydrous acetonitrile. Purge with nitrogen three times and reflux at 55 °C for 24 h. After the reaction, cool to room temperature, concentrate under reduced pressure, filter to obtain a solid, and wash with n-hexane. The final yield is 77%. The reaction formula is as follows:

[0119]

[0120] Catalyst C2'

[0121] Preparation of ligand L2': Add 3 mmol of 2,6-diacetylpyridine and 3.4 mmol of aniline to a 150 ml three-necked flask, then add 50 ml of toluene and heat with stirring under reflux. After reacting for half an hour, add a catalytic amount of p-toluenesulfonic acid (about 10 μmol) and continue the reaction for 12 h. Cool to room temperature and rotary evaporate to remove the solvent. Then perform column chromatography elution on a basic alumina column (eluent V 石油醚 : V 乙酸乙酯 = 100:1) to finally obtain the pyridinediimine ligand with a yield of 48%.

[0122]

[0123] Synthesis of catalyst C2': Add the above-prepared pyridinediimine ligand (1 mmol) and FeCl2·4H2O (1.2 mmol) to a 50 ml single-necked flask. Then purge with nitrogen three times to create an anhydrous and anaerobic environment. After that, add it to freshly distilled anhydrous ethanol and stir at room temperature. After reacting for 12 h, filter and wash with ether. The yield of the final product is 95%.

[0124]

[0125] Catalyst C3'

[0126] Preparation of ligand L3': Under an argon protection environment, add salicylaldehyde (0.2 mol) and 60 ml of anhydrous ethanol to a 250 ml three-necked flask. While stirring, use a constant pressure dropping funnel to add aniline (0.02 mol) to the flask, and then add formic acid (0.5 ml). Heat to 80 °C and react for 2 h. After cooling to room temperature, distill under reduced pressure and cool to precipitate the product. The yield of the final product is 88%.

[0127]

[0128] The synthesis steps of R2-isopropyl-substituted indirubin are as follows: A mixture of sodium sulfate (0.915 mol), distilled water (120 ml), chloral hydrate (0.109 mol), hydroxylamine sulfate (0.079 mol), 8.6 ml of concentrated hydrochloric acid (37%), and m-isopropylaniline (0.1 mol) dissolved in 60 ml of distilled water was gradually heated to 70 °C. Subsequently, 100 ml of ethanol was added, and the mixture was heated under reflux. After reacting for 1 h, the mixture was poured into ice water, and the solid of 3-isopropylisonitrosoacetanilide was collected by filtration, washed with water, and the final yield of 3-isopropylisonitrosoacetanilide was 81%. Subsequently, under magnetic stirring at room temperature, 3-isopropylisonitrosoacetanilide (17 mmol) was slowly added to concentrated sulfuric acid (9 ml). After reacting for 15 minutes, the reaction mixture was poured into crushed ice, collected by filtration, and a mixture of product 1 and product 2 was obtained. Subsequently, a crystallization method was used to purify product 2: The mixture of product 1 and product 2 was dissolved in a very small amount of DMSO, and DMSO was slowly dropped into a large amount of n-hexane solution. Due to the polarity difference, the solid of product 1 would precipitate. The filtration was repeated several times. Finally, the product 2 dissolved in n-hexane was rotary evaporated and washed with distilled water, and the final yield of R2-isopropyl-substituted indirubin was 45%.

[0129]

[0130] Synthesis of catalyst C3’: 40 ml of freshly distilled THF and NaH (4 mmol) were added to a 100-ml three-necked flask, and nitrogen was evacuated and filled three times. Subsequently, the salicylaldimine ligand was slowly dropped into the flask using a constant-pressure dropping funnel and stirred at room temperature for 3 h. The unreacted NaH was removed by filtration. Finally, 40 ml of toluene and (Ph3)2PhNiCl (1.5 mmol) were added and stirred at room temperature for 12 h. The filtrate was concentrated, and a n-hexane solution was slowly added until crystals precipitated. Finally, recrystallization was carried out with toluene and n-hexane solution, and the yield of the final product was 70%.

[0131]

[0132]

Example

[0133] The preparation method of polyethylene wax is specifically as follows:

[0134] A 250 ml stainless steel reactor was heated under vacuum at 150 °C for 2 hours and then cooled to ambient temperature. The reactor was then pressurized with ethylene to 1.2 atm, vented, and pressurized again with ethylene three times to ensure that the reactor was filled with an ethylene atmosphere. A cocatalyst MAO (1 mmol) was dissolved in about 100 ml of dry toluene and injected into the reactor. The mixture was continuously stirred for 5 min under an ethylene pressure of 1.2 atm. Finally, 50 ml of a toluene dilution of catalysts C1 - C10 (containing about 2 μmol of catalyst) was added to the reactor with a syringe and stirred evenly. Gaseous ethylene was continuously fed throughout the reaction process, and the ethylene pressure was maintained at 10 atm. The reaction temperature was controlled at 45 - 120 °C during the polymerization experiment. After 1 h of reaction, the polymerization process was completed. During post-treatment, acidic methanol (ethanol / hydrochloric acid with a mass ratio of 95:5) was added to inactivate the catalyst. The resulting precipitated polymer was collected, separated by liquid separation and rotary evaporation, and dried to a constant weight in vacuo at 40 °C to obtain polyethylene wax.

[0135] Using the same method as above, an ethylene polymerization experiment was carried out with catalysts C1'-C3' as catalysts.

[0136] The catalytic activities of each catalyst at different reaction temperatures were tested. The catalytic activity was calculated based on the yield of the polyethylene wax sample, expressed as g polyethylene wax / (mol catalyst × h). The specific results are shown in Table 2.

[0137] Table 2 Catalytic activities of different catalysts at different temperatures (10 6 g PE / mol cat h)

[0138]

[0139]

[0140] Note: "--" in Table 2 indicates not carried out.

[0141] As can be seen from Table 2, catalysts C1 - C10 have relatively high catalytic activities at 45 °C - 120 °C. The catalytic activity of the electron-donating group catalyst is better than that of the electron-withdrawing group catalyst (catalyst C7). From the perspective of the catalyst structure, when the substituents on R2 and R6 have a certain steric hindrance effect and electron-donating effect, the two interact with each other. For example, catalyst C8 shows the best catalytic activity, with a catalytic activity of up to 11.45×10 6 gPE / g cat h at 75 °C and still having a catalytic activity of 6.35×10 6 gPE / g cat h at a relatively high temperature of 120 °C, far exceeding other non-isatin skeleton late transition metal catalysts.

[0142] Example 1

[0143] The polyethylene wax was prepared according to the following steps: A 250 ml stainless steel reactor was heated under vacuum at 150 °C for 2 hours, and then cooled to ambient temperature. The reactor was then pressurized with ethylene to 1.2 atm, vented, and then pressurized again with ethylene, repeating three times to ensure that the reactor was filled with an ethylene atmosphere. Then, the cocatalyst MAO (1 mmol) was dissolved in about 100 ml of dry toluene and injected into the reactor. The mixture was continuously stirred for 5 min under an ethylene pressure of 1.2 atm. Finally, 50 ml of a toluene dilution of catalyst C1 (containing about 2 μmol of catalyst) was added to the reactor with a syringe and stirred evenly. Gaseous ethylene was continuously fed throughout the reaction process, and the ethylene pressure was maintained at 10 atm. The reaction temperature was controlled at 45 °C during the polymerization experiment. After 2 h of reaction, the polymerization process was completed. Acidic methanol (mass ratio 95:5 ethanol / hydrochloric acid) was added to inactivate the catalyst. The resulting precipitated polymer was collected, separated by liquid separation and rotary evaporation, and dried to a constant weight in vacuo at 40 °C to obtain the polyethylene wax sample E1.

[0144] Example 2

[0145] The same method as in Example 1 was used, except that: Polymerization was carried out at 60 °C using catalyst C2 to obtain the polyethylene wax sample E2.

[0146] Example 3

[0147] The same method as in Example 1 was used, except that: Polymerization was carried out at 75 °C using catalyst C3 to obtain the polyethylene wax sample E3.

[0148] Example 4

[0149] The same method as in Example 1 was used, except that: Polymerization was carried out at 60 °C using catalyst C5 to obtain the polyethylene wax sample E4.

[0150] Example 5

[0151] The same method as in Example 1 was used, except that: Polymerization was carried out at 75 °C using catalyst C6 to obtain the polyethylene wax sample E5.

[0152] Example 6

[0153] The same method as in Example 1 was used, except that: Polymerization was carried out at 60 °C using catalyst C7 to obtain the polyethylene wax sample E6.

[0154] Example 7

[0155] The same method as in Example 1 was used, except that: Polymerization was carried out at 75 °C using catalyst C8 to obtain the polyethylene wax sample E7.

[0156] Example 8

[0157] Using the same method as in Example 1, except that: Polymerization was carried out at 45 °C using catalyst C10 to obtain polyethylene wax sample E8.

[0158]

Comparative Example

[0159] Comparative Example 1

[0160] Using the same method as in Example 1, except that: Polymerization was carried out at 60 °C using catalyst C1’ to obtain polyethylene wax sample E1’.

[0161] Comparative Example 2

[0162] Using the same method as in Example 1, except that: Polymerization was carried out at 45 °C using catalyst C2’ to obtain polyethylene wax sample E2’.

[0163] Comparative Example 3

[0164] Using the same method as in Example 1, except that: Polymerization was carried out at 75 °C using catalyst C3’ to obtain polyethylene wax sample E3’.

[0165] Comparative Example 4

[0166] Using the same method as in Example 1, except that: Polymerization was carried out at 75 °C using catalyst C4’ to obtain polyethylene wax sample E4’, where catalyst C4’ is metallocene catalyst dichlorodicyclopentadienyltitanium.

[0167] Comparative Example 5

[0168] Polyethylene wax was prepared by free radical initiation of an initiator. The specific preparation method was as follows: A 250 ml stainless steel reactor was heated under vacuum at 150 °C for 2 hours, and then cooled to ambient temperature. Then the reactor was pressurized with ethylene to 1.2 atm, vented, and pressurized with ethylene again, repeating three times to ensure that the reactor was filled with an ethylene atmosphere. 5 μmol of initiator benzoyl peroxide (BPO) was dissolved in about 100 ml of dry toluene and injected into the reactor. Gaseous ethylene was continuously fed throughout the reaction process, and the ethylene pressure was maintained at 100 atm. The reaction temperature was controlled at 85 °C during the polymerization experiment. After 2 h of reaction, the polymerization process was completed. The resulting precipitated polymer was collected, separated by liquid extraction and rotary evaporation, and dried to a constant weight in vacuo at 40 °C to obtain polyethylene wax sample E5’.

[0169]

Testing of Polyethylene Wax Samples

[0170] The performance of polyethylene wax samples E1 - E8 and samples E1’ - E5’ was tested by the following methods:

[0171] (1) Molecular weight determination

[0172] Molecular weight determination includes weight-average molecular weight (Mw) and number-average molecular weight (Mn): It is determined by gel permeation chromatography in accordance with GB / T 27843-2011 "Determination of Low Molecular Weight Components in Chemical Polymer - Gel Permeation Chromatography (GPC)". The molecular weight distribution index (PDI) of polyethylene wax is determined by the ratio of the determined weight-average molecular weight to the number-average molecular weight.

[0173] (2) Degree of branching determination

[0174] The degree of branching of polyethylene wax is calculated from the nuclear magnetic resonance hydrogen spectrum.

[0175] (3) Drop melting point viscosity determination

[0176] The drop melting point is determined in accordance with GB / T 8026-2014 "Method for Determination of Drop Melting Point of Petroleum Wax and Petroleum Grease".

[0177] For specific test results, see Table 3.

[0178] Table 3 Determination of properties of polyethylene wax samples

[0179]

[0180]

[0181] As can be seen from Table 3, the weight-average molecular weight of the polyethylene wax prepared in the present invention is on average between 3800 and 8000, the molecular weight distribution is between 1.12 and 1.48 (narrow distribution), the degree of branching is between 10 and 50 / 1000C (<50 / 1000C, low degree of branching), and it belongs to polyethylene wax with excellent performance. Compared with polyethylene wax obtained by other types of late transition metal catalysts, it has a moderate molecular weight, a narrow molecular weight distribution, and a small degree of branching. The comprehensive performance is better than that of the comparative examples and can meet the market demand. Among the comparative examples, sample E4’ is prepared from metallocene catalyst dichlorodicyclopentadienyltitanium, with high catalyst cost, poor high-temperature resistance, and intolerance to polar solvents. Samples E1’, E2’, E3’, E5’, etc. have relatively high molecular weight distribution indices and poor product consistency.

[0182] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of narrow-distribution and low-branching polyethylene wax, characterized in that a solvent, ethylene, a catalyst and a cocatalyst are added to a reaction kettle for polymerization reaction, and after-treatment is carried out after the polymerization reaction is completed to obtain a polyethylene wax product; wherein, the cocatalyst includes alkylaluminoxane; the molar ratio of the catalyst to the cocatalyst is 1:100-600; the catalyst is a nickel metal catalyst with isatin as the skeleton, and its structural formula is: , wherein R 1~ At least one of R5 is an electron-donating group, selected from C1-C6 alkyl, C1-C6 alkoxy, aromatic phenyl, R 6~ R8 is selected from H, C1-C6 alkyl, halogen, and X is chlorine or bromine.

2. The preparation method of a narrow-distribution and low-branching-degree polyethylene wax according to claim 1, characterized in that, the pressure in the reaction kettle is controlled by ethylene gas, the pressure in the reaction kettle is controlled at 0.1-10 Mpa, and the temperature in the reaction kettle is controlled at 45-120 °C.

3. The preparation method of a narrow-distribution and low-branching-degree polyethylene wax according to claim 2, wherein, the pressure in the reaction kettle is controlled at 0.1-5 MPa, and the temperature in the reaction kettle is controlled at 60-85 °C.

4. The preparation method of a narrow-distribution and low-branching-degree polyethylene wax according to claim 1, wherein, the solvent is an inert organic solvent, which is a chain alkane, cycloalkane, or benzene aromatic derivative that is liquid at room temperature, has low viscosity, a boiling point not exceeding 120 °C, and low solubility in polyethylene wax; and / or, the cocatalyst is selected from methylaluminoxane, modified methylaluminoxane, and isobutylaluminoxane, and the molar ratio of the catalyst to the cocatalyst is 1:400-600; and / or, the catalyst and the cocatalyst are diluted with a solvent into a catalyst dilution solution and then added to the reaction kettle.

5. The preparation method of a narrow-distribution and low-branching-degree polyethylene wax according to claim 1, characterized in that, the polymerization reaction is carried out in an anhydrous and anaerobic environment; and / or, the post-treatment is to add acidic methanol to inactivate the catalyst, collect the product and dry it to obtain a polyethylene wax product.

6. The preparation method of a narrow-distribution and low-branching-degree polyethylene wax according to claim 1, characterized in that, Among R1~R5, at least one of R1, R2, and R5 is selected from C1-C6 alkyl, and the rest are H; R6~R8 are each independently selected from H or C1-C6 alkyl.

7. The preparation method of a narrow-distribution and low-branching-degree polyethylene wax according to claim 1, characterized in that, The catalyst is prepared by the following method: Under anhydrous and anaerobic conditions, a diimine ligand with isatin as the skeleton and an anhydrous nickel salt are added to a reaction vessel containing a solvent, and the reaction is carried out at 15~80 °C for 12~36 hours, wherein the molar ratio of the diimine ligand to the anhydrous nickel salt is 2~3:

1. After the reaction is completed, the catalyst solid is obtained through treatment; the solvent includes acetonitrile; the nickel salt includes nickel chloride and nickel bromide.

8. The preparation method of a narrow-distribution and low-branching-degree polyethylene wax according to claim 7, wherein The diimine ligand has the structure shown in formula L: , in formula L, R 1~ At least one of R5 is an electron-donating group, selected from C1-C6 alkyl, C1-C6 alkoxy, aromatic phenyl, R 6~ R8 is selected from H, C1-C6 alkyl, halogen.

9. The preparation method of a narrow-distribution and low-branching-degree polyethylene wax according to claim 8, wherein The diimine ligand is prepared by the following method: A 1,2-diketone compound and an aromatic amine are dissolved in an organic aprotic polar solvent, and a non-oxidizing organic strong acid is added as a catalyst. The reaction is carried out at 100~200 °C for 12~36 hours. After the reaction, the solvent in the mixture is removed to obtain a solid product, which is purified to obtain the product; the molar ratio of the 1,2-diketone compound to the aromatic amine is 1:2~2.5; the organic aprotic polar solvent includes a mixture of toluene and dimethyl sulfoxide; the organic strong acid includes p-toluenesulfonic acid.

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