Post-transition metal catalyst for preparing bimodal UHMWPE (Ultra High Molecular Weight Polyethylene) as well as ligand, preparation method and application thereof

Abstract

The invention relates to a diimine ligand with a general formula structure as shown in a formula L, a late transition metal catalyst prepared by coordination of the diimine ligand, and a preparation method and application of the diimine ligand, wherein R1-R6 are respectively and independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C12 aryl or halogen. The diimine late transition metal catalyst with bimetal active sites in different chemical environments and a rigid mother ring skeleton structure is constructed, so that the catalytic activity and the thermal stability are improved, and the diimine late transition metal catalyst can be used for preparing bimodal UHMWPE through ethylene polymerization.

Description

Technical Field

[0001] The invention relates to the technical field of polyethylene, and in particular to a late transition metal catalyst for preparing bimodal UHMWPE, a ligand thereof, and a preparation method and application thereof. Background Art

[0002] Ultra-High Molecular Weight Polyethylene (UHMWPE) has extremely high wear resistance and self-lubricating properties, making it very popular in industrial applications such as conveyors, gears and guide rails. Secondly, UHMWPE has excellent impact resistance, which makes it widely used in the field of national defense and military industry. In addition, UHMWPE also has good chemical resistance and low temperature resistance, which makes it widely used in aerospace, marine engineering, petrochemical, new energy materials and other fields. At present, the industrial structure has the problem of overcapacity in the middle and low-end and serious shortage of high-end products. At present, UHMWPE urgently needs to solve some key problems in its manufacturing process to promote UHMWPE to the high-end market. Polymerization reaction is the core of UHMWPE production, and the choice of catalyst plays a decisive role in the final performance of UHMWPE. Researchers have made a lot of efforts in this field and have made some progress. At present, ZN (Ziegler-Natta) catalyst and metallocene catalyst are the two main types of catalysts. ZN catalysts have become the mainstream choice due to their wide industrial applications, but their multi-active center characteristics lead to poor consistency in the microstructure of polyethylene products, making it difficult to meet the increasingly stringent requirements of the high-end market. To solve this problem, researchers have developed metallocene catalysts, which use a single active center to improve product consistency. However, the synthesis process of metallocene catalysts is relatively complicated, which to some extent limits their application in the polyethylene industry.

[0003] In view of the shortcomings of ZN catalysts and metallocene catalysts, researchers have further developed metal complex olefin catalysts with late transition metal atoms such as iron, cobalt, nickel, and palladium as the core. This type of catalyst is less sensitive to oxygen and moisture, and exhibits high activity in catalyzing olefin polymerization through structural regulation. Compared with ZN catalysts and metallocene catalysts, late transition metal catalysts have advantages such as higher stability, lower production cost, and the ability to produce new polyolefin products with polar groups. The synthesis of late transition metal catalysts is relatively simple, the yield is high, and the cost is much lower than that of ZN catalysts and metallocene catalysts, showing great industrialization potential. However, the main obstacles to the industrial application of late transition metal catalysts are catalytic activity and thermal stability. Since ethylene polymerization is an exothermic reaction, most late transition metal catalysts are difficult to withstand high temperatures above 80°C, and the catalytic activity of late transition metal catalysts will also decrease at high temperatures. Chinese patent CN102775448B discloses a method for preparing late transition metal complexes and polyethylene, but it can only react at a lower temperature (≤60°C) and can only obtain low molecular weight polyethylene (molecular weight less than 2400).

[0004] α-Diimine-type late transition metal catalysts may be an effective strategy to solve the above problems. α-Diimine-type catalysts were discovered by Brookhart in 1995: the α-diimine Ni / Pd catalyst structure inhibits the β-H elimination chain transfer reaction in olefin polymerization by increasing steric hindrance, and obtains high molecular weight polyethylene (Single Strand Targeted TriplexFormation: Parallel-Stranded DNA Hairpin Duplexes for Targeting Pyrimidine Strands JACS., 1995, 117, 6416). The researchers improved the catalytic activity and thermal stability by constructing a rigid ring α-diimine structure with certain steric hindrance. Inspired by this, people mainly focus on improving the ligand rigid structure and steric hindrance to improve thermal stability. For example, Chinese patent CN110092744A discloses a highly thermally stable tert-butyl asymmetric diiminopyridine transition metal complex for preparing polyethylene wax, which has a single catalytic active center, high catalytic activity and good thermal stability. However, the amount of co-catalyst used is large (Al / Fe≥1000), and it is used to prepare polyethylene wax with a low molecular weight.

[0005] In addition, due to the high molecular weight of UHMWPE, there are many difficulties in subsequent processing by extrusion, granulation, stretching and other processes. Bimodal polyethylene has both excellent mechanical properties and excellent processing properties. Its high molecular weight part is used to ensure its physical and mechanical strength, and the low molecular weight part plays a lubricating role in the resin, which can improve the processing performance of the product. The current processes for producing bimodal polyethylene mainly include: (1) melt mixing method, that is, producing resins of different molecular weights separately and then mixing them, which has the problems of high cost and uneven product quality. (2) segmented reaction method, that is, by using a series of reactors to control different conditions to generate bimodal polyethylene with different molecular weights, it is flexible to operate and has a wide range of brand adjustment, but the cost is relatively high. (3) Directly obtain bimodal polyethylene through a one-stage reaction method, that is, directly obtain bimodal polyethylene by using a catalyst during polymerization, such as mixing different catalysts, using a catalytic system with multiple catalytic active points, etc. This method is a more ideal means.

[0006] Patent document CN104059184B uses a metallocene system to prepare bimodal polyethylene with adjustable molecular weight distribution, mainly by adjusting the addition concentration and addition time of the co-catalyst alkyl aluminum to regulate the composition of the product. Patent document CN105440184B uses a two-component composite catalytic system to prepare bimodal molecular weight distribution polyethylene by catalytic slurry polymerization of olefins in two series reactors. Patent document CN116640243A discloses a one-pot synthesis of bimodal polyethylene. During the polymerization process, two active centers are generated in situ by utilizing the two forms of retention and removal of H atoms to synthesize bimodal polyethylene. Patent document CN117986424B prepares branched bimodal polyethylene by using a dual-center metallocene catalyst, and its catalyst includes chromium metallocene, zirconium metallocene and modified silicon-based carrier. Patent document WO2023076208A1 discloses a method for preparing bimodal polyethylene by using a bimodal catalyst system and a trimming solution in a reactor, and its catalyst is a metallocene compound or a non-metallocene catalyst.

[0007] Therefore, how to design and synthesize a late transition metal catalyst for the preparation of bimodal UHMWPE so that it has a stable rigid structure and can maintain excellent thermal stability at higher temperatures to produce high-quality bimodal UHMWPE products still needs further research. Summary of the invention

[0008] The purpose of the present invention is to solve the above problems and provide a late transition metal catalyst for preparing bimodal UHMWPE, its ligand and its preparation method and application.

[0009] The present invention constructs a diimide post-transition metal catalyst with bimetallic active sites in different chemical environments and a rigid parent ring skeleton structure, which not only improves the catalytic activity and thermal stability, but also can prepare bimodal UHMWPE. It has original innovation and can improve the technical competitiveness of polyolefin materials.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] The first aspect of the present invention provides a diimine ligand having a general structure shown in Formula L:

[0012]

[0013] Wherein, R1-R6 can be the same or different groups, and R1-R6 are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen.

[0014] The C1-C6 alkyl group includes a linear or branched alkyl group, such as but not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl or hexyl, preferably methyl, isopropyl or tert-butyl.

[0015] The C1-C6 alkoxy group includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, pentyloxy or hexyloxy.

[0016] The C6-C 12 Aryl is a monovalent aromatic carbocyclic ring system having at least one aromatic ring or multiple condensed rings in which at least one ring is aromatic, for example, may be selected from phenyl, naphthyl or biphenyl.

[0017] As a preferred technical solution, at least one of R1-R3 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl;

[0018] And / or, at least one of R4-R6 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl, and the rest are H.

[0019] More preferably, at least one of R1-R2 is selected from C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Phenyl; at least one of R3-R4 is selected from C1-C3 alkyl, C1-C3 alkoxy; and / or at least one of R5-R6 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl.

[0020] As a preferred technical solution, at least one of R1 and R3 is a C1-C4 alkyl group or a phenyl group, for example, selected from a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a tert-butyl group, etc. or a phenyl group; and / or at least one of R4-R6 is a C1-C4 alkyl group, for example, selected from a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a tert-butyl group, etc., and the rest are H.

[0021] 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:

[0022]

[0023]

[0024]

[0025] The diimine ligand of the formula L structure of the present invention has a phenanthroline skeleton structure. On the one hand, the 1,10-phenanthroline skeleton has a certain rigidity and can provide a steric effect to prevent the late transition metal catalyst from being deactivated at high temperature; on the other hand, the 1,10-phenanthroline skeleton has two N atoms, and the different electronegativity of the N atom and the C atom helps to improve the electronic effect of the catalyst; in addition, the 1,10-phenanthroline-5,6-dione skeleton structure can form two active sites after metal coordination after reacting with amines, and the chemical environments between the two active sites are completely different, so that bimodal ultra-high molecular weight polyethylene can be produced.

[0026] The second aspect of the present invention provides a method for preparing the above-mentioned diimine ligand, using a 1,10-phenanthroline-5,6-dione derivative of the general structure shown in Formula I and an aniline derivative of the general structure shown in Formula II as raw materials through acid catalysis to prepare the diimine ligand, and the specific reaction formula is as follows:

[0027]

[0028] In the 1,10-phenanthroline-5,6-dione derivative of the general structure shown in Formula I, R1-R3 can be the same or different groups, independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, aromatic phenyl, aromatic naphthyl, aromatic biphenyl, halogen, etc. Preferably, a 1,10-phenanthroline derivative with an electron donating effect is used as an ortho-dicarbonyl raw material, and it is further preferred to use 1,10-phenanthroline with electron donating effect groups in R1 and R3 as an ortho-dicarbonyl raw material. It is further preferred that 1,10-phenanthroline with certain sterically hindered electron donating groups on R1 and R3 is used as an ortho-dicarbonyl raw material. It is further preferred that 1,10-phenanthroline with methyl, isopropyl, phenyl and R3 is methyl is used as an ortho-dicarbonyl raw material.

[0029] In the embodiment of the present invention, the 1,10-phenanthroline-5,6-dione derivative can be selected from 1,10-phenanthroline-5,6-dione, 2,9-dimethyl-1,10-phenanthroline-5,6-dione, 2,9-dibromo-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, 2,9-diisopropyl-1,10-phenanthroline-5,6-dione, -phenanthroline-5,6-dione, 4,7-dimethyl-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, and the like.

[0030] The aniline derivative of the general structure shown in Formula II has a primary amine as the main skeleton, and R4 can be the same or different H, C1-C6 alkyl, C1-C6 alkoxy, etc. Preferably, a primary amine with an electron-donating effect is used as the amine raw material, and more preferably, an electron-donating group primary amine with a certain steric hindrance effect is used as the amine raw material. Methylamine, aniline, 3,5-dimethylaniline, and p-methylaniline are further preferred as the amine raw materials.

[0031] In an embodiment of the present invention, the aniline derivative is selected from aniline, o-methylaniline, 3,5-dimethylaniline, p-methylaniline, p-bromoaniline and the like.

[0032] As a preferred technical solution, the preparation method of the diimine ligand of the present invention comprises the following steps: a 1,10-phenanthroline-5,6-dione derivative and an aniline derivative are dissolved in a non-protonic polar organic solvent at a molar ratio of 1:2 to 2.5, and then a non-oxidizing organic strong acid is used as a catalyst (catalytic level) to react at 40 to 150° C. After the reaction is completed, the solvent is removed from the mixture and purified to obtain the diimine ligand.

[0033] Preferably, the organic aprotic polar solvent can be a commonly used solvent in the art, such as benzene, toluene, etc. The non-oxidizing organic strong acid can be a commonly used solvent organic strong acid substance in the art, such as p-toluenesulfonic acid. The reaction temperature is preferably 60-100° C., and the reaction time is generally between 12-36 hours. The solvent can be removed by conventional methods in the art, such as rotary evaporation. The product can be purified by conventional methods in the art, such as recrystallization and column chromatography.

[0034] The third aspect of the present invention provides a late transition metal catalyst for preparing bimodal UHMWPE, which is a coordination compound formed by the above-mentioned diimine ligand and a late transition metal salt.

[0035] The late transition metal is selected from Fe, Co, Ni or Pd, and the late transition metal salt can be a halide of the late transition metal, such as a chloride or a bromide, including but not limited to ferric chloride, cobalt chloride, nickel bromide, nickel chloride, etc.

[0036] The inventors have found that the late transition metal catalyst of the present invention unexpectedly has high catalytic activity in a wide temperature range, especially excellent high temperature stability. For example, when the reaction temperature is 80°C, the catalyst has a high stability of 7.88×10 6 The specific mechanism is not very clear yet. The possible reason is speculated to be: the late transition metal catalyst with 1,10-phenanthroline-5,6-dione as the skeleton has higher rigidity and better electronic effect than the traditional 1,2-diketone structure, which prevents the late transition metal catalyst from being deactivated at high temperature. The 1,10-phenanthroline skeleton is different from phenanthrene. It has two N atoms in its ring. The different electronegativity of N atoms and C atoms also helps to improve the electronic effect of the catalyst; in addition, the 1,10-phenanthroline-5,6-dione skeleton structure can form two active sites after metal coordination after reaction with amines, and the chemical environment between the two active sites is completely different, which can produce bimodal ultra-high molecular weight polyethylene.

[0037] Preferably, the late transition metal catalyst is a nickel metal catalyst having a general structure shown in Formula C:

[0038]

[0039] Wherein X is chlorine or bromine.

[0040] As a preferred embodiment of the present invention, the nickel metal catalyst is selected from any one of the following formulas C1 to C10:

[0041]

[0042]

[0043]

[0044] The fourth aspect of the present invention provides a method for preparing the above-mentioned late transition metal catalyst. The late transition metal catalyst can be prepared by a method for synthesizing a coordination compound. Taking the nickel metal catalyst of the general structure shown in Formula C as an example, the following method can be used: the diimine ligand and the nickel salt are dissolved in an anhydrous aprotic organic solvent at a molar ratio of 1:3-4, and reacted in an anhydrous and oxygen-free environment. The specific reaction formula is as follows:

[0045]

[0046] Preferably, the nickel metal catalyst is prepared by the following method: dissolving the prepared ligand L and nickel salt in an anhydrous aprotic organic solvent (e.g., acetonitrile, toluene) in a molar ratio of 1:3-4, controlling an anhydrous and oxygen-free environment, and reacting at a reaction temperature of 40-100° C. for 12-36 hours. After the reaction is completed, filter, wash with distilled water 2-3 times, and dry the sample in a vacuum drying oven.

[0047] The fifth aspect of the present invention provides the use of the above-mentioned late transition metal catalyst in the preparation of bimodal UHMWPE. The late transition metal catalyst, under the action of a co-catalyst, obtains bimodal ultrahigh molecular weight polyethylene at a relatively low pressure and with high catalytic activity.

[0048] Furthermore, when producing ultra-high molecular weight polyethylene, the pressure is 0.1-10 MPa, preferably, the pressure is 0.1-2 MPa; further preferably, the pressure is 0.1-1 MPa.

[0049] Furthermore, the selected solvent is mainly an inert solvent, mainly including chain alkanes and cycloalkanes and benzene aromatic derivatives with a boiling point not exceeding 120° C. Preferably, benzene aromatic derivatives and alkanes that are liquid at room temperature, have low viscosity, have a boiling point not exceeding 110° C. and have low solubility in ultra-high molecular weight polyethylene are used, such as toluene, xylene, chlorobenzene, hexane, etc. as the solvent.

[0050] Furthermore, the selected co-catalyst is mainly alkylaluminoxane, and more preferably methylaluminoxane, modified methylaluminoxane, and isobutylaluminoxane as the co-catalyst. The molar ratio of the late transition metal catalyst to the co-catalyst is 1:200-500.

[0051] Compared with the prior art, the present invention has the following innovative features:

[0052] The present invention designs and synthesizes a diimine post-transition metal catalyst having a bimetallic active site with different chemical environments and a rigid parent ring skeleton structure. The post-transition metal catalyst uses 1,10-phenanthroline-5,6-dione as a skeleton. The phenanthrene ring structure in 1,10-phenanthroline-5,6-dione has a certain rigidity, which can improve the catalytic activity and thermal stability of the post-transition metal catalyst. In addition, there are two pyridine rings in 1,10-phenanthroline-5,6-dione, and the pyridine ring and the benzene ring have significantly different electronic effects. The lone pair of electrons on the N atom can be conjugated with the benzene ring and the diimine structure to further optimize the electronic structure of the catalyst, and can produce two metal active centers with completely different chemical environments, which can be applied to low-pressure polymerization of ethylene to generate bimodal ultra-high molecular weight polyethylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is the molecular weight distribution diagram of polyethylene sample E8. DETAILED DESCRIPTION

[0054] The present invention is described in detail below. All matters not described in detail in the present invention are technical solutions already disclosed in the art.

[0055] The specific sources of the main reagents used in the examples are as follows:

[0056] 1,10-Phenanthroline-5,6-dione (CAS: 27318-90-7, Sigma-Aldrich)

[0057] 2,9-Dimethyl-1,10-phenanthroline-5,6-dione (CAS: 102331-54-4, Henan Weitixi Chemical) 2,9-Diphenyl-1,10-phenanthroline-5,6-dione (CAS: 1654020-68-4, Henan Lien Chemical) 2,9-Diisopropyl-1,10-phenanthroline-5,6-dione (CAS: 1243254-92-3, Henan Lien Chemical) 4,7-Dimethyl-1,10-phenanthroline (CAS: 3248-05-3, Leyan Reagent)

[0058] 4,7-Dimethyl-1,10-phenanthroline-5,6-dione (CAS: 1713236-32-8, obtained by synthesis)

[0059] 2,3-Butanedione (CAS: 431-03-8, Sigma-Aldrich)

[0060] 2,6-Diacetylpyridine (CAS: 1129-30-2, Sigma-Aldrich)

[0061] Salicylaldehyde (CAS: 90-02-8, Sigma-Aldrich)

[0062] Methylaluminoxane (CAS: 120144-90-3, Jiuding Chemical)

[0063] High purity ethylene (CAS: 74-85-1, Shanghai Liquid Gas)

[0064] Aniline (CAS: 62-53-3, Sigma-Aldrich)

[0065] o-Toluidine (CAS: 95-53-4, Sigma-Aldrich)

[0066] 3,5-Dimethylaniline (CAS: 108-69-0, Sigma-Aldrich)

[0067] p-Toluidine (CAS: 106-49-0, Sigma-Alrich)

[0068] p-Bromoaniline (CAS: 106-40-1, Sigma-Aldrich)

[0069] p-Toluenesulfonic acid (CAS: 6192-52-5, Sigma-Aldrich)

[0070] Acetic acid (CAS: 64-19-7, Sigma-Aldrich)

[0071] Ethanol (CAS: 64-17-5, Sigma-Aldrich)

[0072] Dichloromethane (CAS: 75-09-2, Sigma-Aldrich)

[0073] Benzene (CAS: 71-43-2, Sigma-Aldrich)

[0074] Toluene (CAS: 108-88-3, Sigma-Aldrich)

[0075] Concentrated sulfuric acid 98% (CAS: 76664-93-9, Sigma-Aldrich)

[0076] Nitric acid (CAS: 7697-37-2, Sigma-Aldrich)

[0077] Sodium hydroxide (CAS:1310-73-2, Sigma-Aldrich)

[0078] Hydrochloric acid (CAS: 7647-01-0, Sigma-Aldrich)

[0079] Acetonitrile (CAS: 75-05-8, Sigma-Aldrich)

[0080] Methanol (CAS: 67-56-1, Sigma-Aldrich)

[0081] Unless otherwise specified, all solvents used in the examples must be anhydrous.

[0082] Example 1

[0083] Catalyst sample 1 was prepared as follows:

[0084] (1) The specific synthesis method of ligand L1 is as follows:

[0085]

[0086] 2.10g of 1,10-phenanthroline-5,6-dione (10mmol) was added to a 250ml three-necked flask, and about 100ml of benzene was added to dissolve it, followed by 2.14g of aniline (23mmol) and 7μL of p-toluenesulfonic acid (about 50μmol). The three-necked flask was heated to 65°C, and a condenser with a water separator was used to react for 24h. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was recrystallized and purified with ethanol, and dried to obtain ligand L1, with a final yield of 90%. ( 1 H 300MHz, DMSO): 9.12-7.11 (m, 16H, Ar-H). C 24 H 16 N4: Elemental analysis calculated value (%): C, 79.98; H, 4.47; N, 15.55. Experimental determination value (%): C, 80.11; H, 4.55; N, 15.41.

[0087] (2) Preparation of catalyst sample 1: The obtained ligand L1 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L1 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 1.

[0088] Example 2

[0089] Catalyst sample 2 was prepared as follows:

[0090] (1) The specific synthesis method of ligand L2 is as follows:

[0091]

[0092] 2.38 g (10 mmol) of 2,9-dimethyl-1,10-phenanthroline-5,6-dione was added to a 250 ml three-necked flask, and about 100 ml of anhydrous acetic acid was added to dissolve it, followed by 2.14 g of aniline (23 mmol) and 7 μL of p-toluenesulfonic acid (about 50 μmol). The three-necked flask was heated to 100°C, and a condenser with a water separator was used to react for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using ethanol to obtain ligand L2, with a final yield of 85% ( 1 H 300MHz, DMSO): 8.84-7.30 (m, 14H, Ar-H); 2.95 (d, 6H, -CH3). C 26 H 20N4: Elemental analysis calculated value (%): C, 80.39; H, 5.19; N, 14.42. Experimental determination value (%): C, 80.66; H, 5.29; N, 14.07.

[0093] (2) Preparation of catalyst sample 2: The obtained ligand L2 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L2 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 2.

[0094] Example 3

[0095] Catalyst sample 3 was prepared as follows:

[0096] (1) The specific synthesis method of ligand L3 is as follows:

[0097]

[0098] 3.68g of 2,9-dibromo-1,10-phenanthroline-5,6-dione (10mmol) was added to a 250ml three-necked flask, and about 100ml of anhydrous acetic acid was added to dissolve it, followed by 2.14g of aniline (23mmol) and 7μL of p-toluenesulfonic acid (about 50μmol). The three-necked flask was heated to 100°C, and a condenser with a water separator was used to react for 24h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using ethanol to obtain ligand L3, with a final yield of 71% ( 1 H 300MHz, DMSO): 9.14-7.22 (m, 14H, Ar-H). C 24 H 14 N4Br2: Elemental analysis calculated value (%): C, 55.63; H, 2.72; N, 10.81; Br, 30.84. Experimental determination value (%): C, 55.77; H, 2.85; N, 10.71; Br, 30.73.

[0099] (2) Preparation of catalyst sample 3: The obtained ligand L3 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L3 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 3.

[0100] Example 4

[0101] Catalyst sample 4 was prepared as follows:

[0102] (1) The specific synthesis method of ligand L4 is as follows:

[0103]

[0104] 3.62g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10mmol) was added to a 250ml three-necked flask, and about 100ml of anhydrous acetic acid was added to dissolve it, followed by 2.14g of aniline (23mmol) and 7μL of p-toluenesulfonic acid (about 50μmol). The three-necked flask was heated to 100°C, and a condenser with a water separator was used to react for 24h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using ethanol to obtain ligand L4, with a final yield of 88% ( 1 H 300MHz, DMSO): 9.33-7.42 (m, 24H, Ar-H). C 36 H 24 N4: Elemental analysis calculated value (%): C, 84.35; H, 4.72; N, 10.92. Experimental determination value (%): C, 84.69; H, 4.82; N, 10.57.

[0105] (2) Preparation of catalyst sample 4: The obtained ligand L4 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L4 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 4.

[0106] Example 5

[0107] Catalyst sample 5 was prepared as follows:

[0108] (1) The specific synthesis method of ligand L5 is as follows:

[0109]

[0110] 2.94g of 2,9-diisopropyl-1,10-phenanthroline-5,6-dione (10mmol) was added to a 250ml three-necked flask, and 100ml of anhydrous acetic acid was added to dissolve it, followed by 2.14g of aniline (23mmol) and 7μL of p-toluenesulfonic acid (about 50μmol). The three-necked flask was heated to 100°C, and a condenser with a water separator was used to react for 24h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using ethanol to obtain ligand L5, with a final yield of 91% ( 1 H 300MHz, DMSO): 8.79-7.52(m,14H,Ar-H); 3.95-1.77(m,14H,-CH(CH3)2). C 30 H 28 N4: Elemental analysis calculated value (%): C, 80.39; H, 6.35; N, 12.60. Experimental determination value (%): C, 80.87; H, 6.43; N, 12.07.

[0111] (2) Preparation of catalyst sample 5: The obtained ligand L5 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L5 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 5.

[0112] Example 6

[0113] Catalyst sample 6 was prepared as follows:

[0114] (1) The specific synthesis method of ligand L6 is as follows:

[0115]

[0116] First, synthesize 4,7-dimethyl-1,10-phenanthroline-5,6-dione: Mix 1.35g (6.5mmol) of 4,7-dimethyl-1,10-phenanthroline and potassium bromide (7.5g), add sulfuric acid (30ml) dropwise at 0°C within 15 minutes, and then add nitric acid (15ml, dripped within 15 minutes) to the reaction mixture. Heat the resulting mixture at 80°C for 4 hours, and cool the solution to 0°C after the reaction. Pour the cold acidic mixture onto ice. Add 5% NaOH solution to the reaction mixture under vigorous stirring and adjust the pH to 3. Extract the mixture with dichloromethane (3×300ml), dry the organic phase with MgSO4, evaporate the solvent, and vacuum dry the resulting solid for use.

[0117] 2.38 g of 4,7-dimethyl-1,10-phenanthroline-5,6-dione (10 mmol) was added to a 250 ml three-necked flask, and about 100 ml of anhydrous acetic acid was added to dissolve it. Then, 2.14 g of aniline (23 mmol) and 7 μL of p-toluenesulfonic acid (about 50 μmol) were added. The three-necked flask was heated to 100 ° C. A condenser with a water separator was used to react for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified with ethanol to obtain ligand L6. The final yield was 75% ( 1 H 300MHz, DMSO): 9.14-7.25(m,14H,Ar-H); 3.12-2.56(m,6H,-CH3). C 26 H 20 N4: Elemental analysis calculated value (%): C, 80.39; H, 5.19; N, 14.42. Experimental determination value (%): C, 80.42; H, 5.21; N, 14.37.

[0118] (2) Preparation of catalyst sample 6: The obtained ligand L6 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L6 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 6.

[0119] Example 7

[0120] Catalyst sample 7 was prepared as follows:

[0121] (1) The specific synthesis method of ligand L7 is as follows:

[0122]

[0123] 3.62 g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10 mmol) was added to a 250 ml three-necked flask, and about 100 ml of anhydrous acetic acid was added to dissolve it. Then, 2.46 g of o-methylaniline (23 mmol) and 7 μL of p-toluenesulfonic acid (about 50 μmol) were added. The three-necked flask was heated to 100 ° C. A condenser with a water separator was used to react for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified with ethanol to obtain ligand L7. The final yield was 68% ( 1 H300MHz, DMSO): 8.52-7.49 (m, 22H, Ar-H); 2.50 (s, 6H, -CH3). C 38 H28 N4: Elemental analysis calculated value (%): C, 84.42; H, 5.22; N, 10.36. Experimental determination value (%): C, 84.45; H, 5.26; N, 10.33.

[0124] (2) Preparation of catalyst sample 7: The obtained ligand L7 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L7 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 7.

[0125] Example 8

[0126] Catalyst sample 8 was prepared as follows:

[0127] (1) The specific synthesis method of ligand L8 is as follows:

[0128]

[0129] 3.62g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10mmol) was added to a 250ml three-necked flask, and about 100ml of anhydrous acetic acid was added to dissolve it, followed by 2.78g of 3,5-dimethylaniline (23mmol) and 7μL of p-toluenesulfonic acid (about 50μmol). The three-necked flask was heated to 100°C, and a condenser with a water separator was used to react for 24h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using ethanol to obtain ligand L8, with a final yield of 68% ( 1 H 300MHz, DMSO): 9.05-7.16 (m, 20H, Ar-H); 2.82-1.80 (m, 12H, -CH3). C 40 H 32 N4: Elemental analysis calculated value (%): C, 84.48; H, 5.67; N, 9.85. Experimental determination value (%): C, 84.51; H, 5.72; N, 9.77.

[0130] (2) Preparation of catalyst sample 8: The obtained ligand L8 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L8 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 8.

[0131] Example 9

[0132] Catalyst sample 9 was prepared as follows:

[0133] (1) The specific synthesis method of ligand L9 is as follows:

[0134]

[0135] 3.62g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10mmol) was added to a 250ml three-necked flask, and about 100ml of anhydrous acetic acid was added to dissolve it, followed by 2.46g of p-methylaniline (23mmol) and 7μL of p-toluenesulfonic acid (about 50μmol). The three-necked flask was heated to 100°C, and a condenser with a water separator was used to react for 24h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using ethanol to obtain ligand L9, with a final yield of 84% ( 1 H300MHz, DMSO): 8.99-7.58(m,22H,Ar-H); 2.91-1.77(m,6H,-CH3). C 38 H 28 N4: Elemental analysis calculated value (%): C, 84.42; H, 5.22; N, 10.36. Experimental determination value (%): C, 84.55; H, 5.33; N, 10.30.

[0136] (2) Preparation of catalyst sample 9: The obtained ligand L9 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L9 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 9.

[0137] Example 10

[0138] Catalyst sample 10 was prepared as follows:

[0139] (1) The specific synthesis method of ligand L10 is as follows:

[0140]

[0141] 3.62g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10mmol) was added to a 250ml three-necked flask, and about 100ml of anhydrous acetic acid was added to dissolve it, followed by 3.95g of p-bromoaniline (23mmol) and 7μL of p-toluenesulfonic acid (about 50μmol). The three-necked flask was heated to 100°C, and a condenser with a water separator was used to react for 24h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using ethanol to obtain ligand L10, with a final yield of 73% ( 1 H300MHz, DMSO): 9.23-7.67 (m, 22H, Ar-H). C 36 H 22 N4Br2: Elemental analysis calculated value (%): C, 64.50; H, 3.31; N, 8.36; Br, 23.84. Experimental determination value (%): C, 64.62; H, 3.33; N, 8.44; Br, 23.79.

[0142] (2) Preparation of catalyst sample 10: The obtained ligand L10 is coordinated with NiCl2. The specific steps are as follows: under anhydrous and oxygen-free conditions, about 100 ml of ultra-dry acetonitrile is added to a three-necked flask, and the ligand L10 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added. The reaction temperature is controlled to be 55°C and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by reduced evaporation, the solvent is filtered out, and the mixture is washed several times with dry n-hexane and dried to obtain catalyst sample 10.

[0143] The catalysts and raw materials of Examples 1 to 10 are detailed in Table 1.

[0144] Table 1 Catalysts and raw materials of Examples

[0145]

[0146] The present invention also provides the following comparative examples.

[0147] Comparative Example 1

[0148] Catalyst sample a was prepared according to the following steps.

[0149] (1) Synthesis of pyridine diimine ligand:

[0150]

[0151] 0.82 g of 2,6-diacetylpyridine (5 mmol) and 1.65 g of 4-amino-3,5-dimethylphenol (12 mmol) were dissolved in 150 ml of methanol, 1 ml of formic acid was added and refluxed at 80°C for 12 hours. After the reaction was completed, the solvent was evaporated and concentrated, and recrystallized by adding n-hexane to obtain ligand L.

[0152] (2) Preparation of catalyst sample a:

[0153]

[0154] Under nitrogen, 1 mmol of ligand L was dissolved in 30 ml of THF and reacted for 1 hour. Then FeCl2 was added and reacted for 6 hours. THF was removed by rotary evaporation to obtain catalyst a. The final yield was 85%. ( 1 H 300MHz, DMSO): 9.27(s,2H,-OH); 8.72-7.04(m,7H,-Ar-H); 2.68-2.11(m,18H,-CH3). C 25 H 27 N3O2: Elemental analysis calculated value (%): C, 74.79; H, 6.78; N, 10.47; O, 7.97. Experimental determination value (%): C, 74.78; H, 6.73; N, 10.54; O, 8.02.

[0155] Comparative Example 2

[0156] Catalyst sample b: commercially available metallocene catalyst titanocene dichloride (CAS: 1271-19-8), the structural formula of which is:

[0157]

[0158]

Catalyst performance test

[0159] The above catalysts were used for ethylene polymerization to prepare ultra-high molecular weight polyethylene, and the catalytic performance of the catalysts was tested.

[0160] The specific steps are as follows: a 250ml stainless steel reactor (with a cooling jacket) is heated in vacuum at 150°C for about 30min, then cooled to ambient temperature, the reactor is pressurized to 2atm with ethylene, and then vented and pressurized again with ethylene, and this is repeated three times to ensure that the reactor is filled with ethylene atmosphere. The cocatalyst MAO (0.5mmol) is dissolved in about 100ml of dry hexane and injected into the reactor, and stirred continuously for 5min under 1.2atm ethylene pressure. Finally, 50ml of catalyst hexane dilution (containing about 2μmol of catalyst) is added to the reactor with a syringe and stirred evenly. Gaseous ethylene is continuously added during the entire reaction process, and the ethylene pressure in the reactor is maintained at 9-10atm. The reaction temperature is controlled at 60-100°C during the polymerization process. The polymerization process is completed after the reaction is continued for 2h, and then post-treatment is performed, acidic methanol (mass ratio 95:5 ethanol / hydrochloric acid) is added to deactivate the catalyst, and the resulting precipitated polymer is collected, separated and rotary evaporated, and dried to a fixed weight in a vacuum at 40°C to obtain a polyethylene sample, which is weighed and tested.

[0161] The activity of the catalyst was calculated based on the yield of the polyethylene sample, in g polyethylene / (mol catalyst×h). Table 2 lists the catalytic activity of each catalyst at different temperatures.

[0162] Table 2 Catalytic activity of different catalysts at different temperatures (unit 10 6 g PE / mol cat h)

[0163] Serial number 60℃ 70℃ 80℃ 90℃ 100℃ Example 1 -- 1.42 1.25 1.02 -- Example 2 1.91 -- -- 6.34 3.04 Example 3 -- 0.23 0.44 -- 0.03 Example 4 3.33 -- 5.51 -- 3.26 Example 5 2.47 3.77 -- 6.40 -- Example 6 2.55 -- 4.79 -- 3.86 Example 7 -- 3.25 5.96 -- 3.93 Example 8 4.39 -- -- 7.88 4.57 Example 9 -- 3.87 6.37 -- 3.45 Example 10 0.27 -- 0.66 0.13 -- Comparative Example 1 3.75 1.43 0.04 -- -- Comparative Example 2 -- 5.86 4.19 -- 0.02

[0164] Note: “--” means not performed.

[0165] As can be seen from Table 2, Comparative Example 1 is a catalyst obtained from a pyridine diimine ligand (without a 1,10-phenanthroline-5,6-dione skeleton structure), which has poor thermal stability and its catalytic activity is significantly weakened at temperatures above 80°C. The metallocene catalyst dichlorotitacenene in Comparative Example 2 has good catalytic activity at 70-80°C, but its catalytic activity is significantly weakened after 100°C. Compared with the comparative examples, except for Examples 3 and 10 with halogen as substituents, the catalysts provided in other examples show excellent thermal stability (especially when donating electrons with a certain steric hindrance effect), and maintain excellent ethylene catalytic activity at temperatures of 80-100°C, indicating that the late transition metal catalyst obtained using 1,10-phenanthroline-5,6-dione as the diimine structure skeleton has high catalytic activity and thermal stability. For example, the catalytic activity of Example 8 at 90°C can reach 7.88×10 6 gPE / g cat h, catalytic activity at 100℃ is 4.57×10 6 gPE / g cat h.

[0166]

Polyethylene sample performance test

[0167] Select some of the polyethylene samples obtained above for molecular weight determination: weight average molecular weight (Mw) and number average molecular weight (Mn): determined by gel permeation chromatography in accordance with GB / T 27843-2011 "Determination of low molecular weight component content of chemical polymers by gel permeation chromatography (GPC)"; molecular weight distribution index (PDI) of polyethylene: determined by the ratio of the measured weight average molecular weight and number average molecular weight; peak distribution: determined based on the GPC molecular weight distribution curve. See Table 3 for specific test results. Figure 1 The molecular weight distribution profile of polyethylene sample E8 is exemplified.

[0168] Table 3 Polyethylene sample test results

[0169] Polyethylene samples catalyst Polymerization temperature <![CDATA[Mw(*10 4 )]]> PDI Peak distribution E1 Catalyst sample 1 80℃ 155 5.2 Twin Peaks E2 Catalyst sample 2 90℃ 177 5.3 Twin Peaks E3 Catalyst sample 3 80℃ 56 4.1 Twin Peaks E4 Catalyst sample 4 80℃ 180 5.5 Twin Peaks E5 Catalyst sample 5 90℃ 156 5.1 Twin Peaks E6 Catalyst sample 6 80℃ 158 5.1 Twin Peaks E7 Catalyst sample 7 80℃ 172 5.3 Twin Peaks E8 Catalyst sample 8 90℃ 197 5.9 Twin Peaks E9 Catalyst sample 9 80℃ 188 5.4 Twin Peaks E10 Catalyst sample 10 80℃ 67 4.2 Twin Peaks E11 Catalyst sample a 60℃ 6.7 2.3 Single Peak E12 Catalyst sample b 70℃ 152 2.4 Single Peak

[0170] As shown in Table 3, the present invention can prepare high molecular weight and ultra-high molecular weight polyethylene under relatively high polymerization reaction temperature conditions. Except for the polyethylene samples E3 and E10 prepared by catalyst samples 3 and 10 with halogen as substituents, the weight average molecular weight of the polyethylene of the present invention is distributed in the range of 1.5 to 2 million, the PDI is 5 to 6, and they are all bimodal polyethylenes, which have better processing performance. Comparative Example 1 can only obtain low molecular weight polyethylene products and are unimodal polyethylene, while Comparative Example 2 prepares unimodal polyethylene.

[0171] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. 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 work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A diimine ligand having the general structure shown in Formula L: in, R1-R6 are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen.

2. The diimine ligand according to claim 1, characterized in that: At least one of R1-R3 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl; And / or, at least one of R4-R6 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl.

3. The diimine ligand according to claim 2, characterized in that: At least one of R1 and R3 is a C1-C4 alkyl group or a phenyl group; And / or, at least one of R4-R6 is a C1-C4 alkyl group.

4. The diimine ligand according to claim 1, characterized in that: The diimine ligand is selected from any one of the following diimine ligand compounds of Formula L1 to Formula L10:

5. The method for preparing a diimine ligand according to any one of claims 1 to 4, characterized in that: The diimine ligand is prepared by acid catalysis using a 1,10-phenanthroline-5,6-dione derivative of the general structure shown in Formula I and an aniline derivative of the general structure shown in Formula II as raw materials. The specific reaction formula is as follows:

6. The method for preparing a diimine ligand according to claim 5, characterized in that: The 1,10-phenanthroline-5,6-dione derivatives include: 1,10-phenanthroline-5,6-dione, 2,9-dimethyl-1,10-phenanthroline-5,6-dione, 2,9-dibromo-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, 2,9-diisopropyl-1,10-phenanthroline-5,6-dione, 4,7-dimethyl-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione, 2,9-diphenyl-1,10-phenanthroline-5,6-dione; The aniline derivatives include: aniline, o-methylaniline, 3,5-dimethylaniline, p-methylaniline and p-bromoaniline.

7. A late transition metal catalyst for preparing bimodal UHMWPE, characterized in that The invention is a coordination compound formed by the diimine ligand as described in any one of claims 1 to 4 and a late transition metal salt.

8. The late transition metal catalyst according to claim 7, characterized in that A nickel metal catalyst having the general structure shown in Formula C: Wherein X is chlorine or bromine.

9. The method for preparing a late transition metal catalyst according to claim 8, characterized in that: The diimine ligand and the nickel salt are dissolved in an anhydrous aprotic organic solvent at a molar ratio of 1:3-4, and reacted in an anhydrous and oxygen-free environment to obtain the product. The specific reaction formula is as follows:

10. Use of the late transition metal catalyst according to claim 7 or 8 in the preparation of bimodal UHMWPE.

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