Post-transition metal catalysts for the preparation of bimodal uhmwpe, ligands thereof, and methods of making and using the same

Abstract

The present application relates to a kind of diimine ligand with the general structure shown in formula L, the post-transition metal catalyst prepared by its coordination and its preparation method and application, wherein R1-R6 are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen. The present application constructs diimine post-transition metal catalyst with different chemical environment of bimetallic active site and rigid parent ring skeleton structure, not only improves catalytic activity and thermal stability, but also can be used for preparing bimodal UHMWPE by ethylene polymerization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyethylene, in particular to a post-transition metal catalyst for preparing bimodal UHMWPE, a ligand thereof, a preparation method and application thereof. BACKGROUND

[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 the fields of aerospace, marine engineering, petrochemical industry, new energy materials, etc. At present, there is a problem of overcapacity in the middle and low end of the industrial structure, while there is a serious shortage of high-end products. At present, UHMWPE needs to solve some key problems in its manufacturing process to promote UHMWPE to move towards 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, Z-N (Ziegler-Natta) catalyst and metallocene catalyst are two main types of catalysts. Z-N catalyst has become the mainstream choice because of its wide industrial application, but its multi-active center characteristics lead to poor consistency of the microstructure of polyethylene products, which is difficult to meet the increasingly strict requirements of the high-end market. To solve this problem, researchers have developed metallocene catalysts, which improve product consistency through a single active center. However, the synthesis process of metallocene catalysts is relatively complex, which to some extent limits its application in the polyethylene industry.

[0003] In view of the shortcomings of Z-N catalyst and metallocene catalyst, researchers further developed metal complex olefin catalysts with iron, cobalt, nickel, palladium and other late transition metal atoms as the core. This kind of catalyst has lower sensitivity to oxygen and moisture, and shows high activity in catalyzing olefin polymerization through structure regulation. Compared with Z-N catalyst and metallocene catalyst, late transition metal catalyst has higher stability, lower production cost, and can produce new polyolefin products with polar groups. Late transition metal catalyst is relatively simple to synthesize, has high yield, and the cost is much lower than that of Z-N catalyst and metallocene catalyst, showing great industrialization potential. However, the main obstacles hindering the industrial application of late transition metal catalysts are catalytic activity and thermal stability. Since the ethylene polymerization reaction 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 decrease at high temperatures. Chinese patent CN102775448B discloses a preparation method of late transition metal complex and polyethylene, but only at a lower temperature (≤60°C), and only low molecular weight polyethylene (molecular weight less than 2400) can be obtained.

[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: α-diimine Ni / Pd catalyst structure inhibits β-H elimination chain transfer reaction in olefin polymerization by increasing steric hindrance, and high molecular weight polyethylene (Single Strand Targeted Triplex Formation: Parallel-Stranded DNA Hairpin Duplexes for Targeting Pyrimidine Strands JACS., 1995, 117, 6416) is obtained. Researchers improve the catalytic activity and thermal stability by constructing rigid ring α-diimine structure with certain steric hindrance. Inspired by this, people mainly focus on improving the rigidity of the ligand structure and the steric hindrance to improve the thermal stability. For example, Chinese patent CN110092744A discloses a high-thermal-stability tertiary butyl-containing unsymmetrical diimine pyridine 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 cocatalyst used is large (Al / Fe≥1000), and it is used to prepare low molecular weight polyethylene wax.

[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 excellent mechanical properties and excellent processing performance. The high molecular weight part is used to ensure the 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 process for producing bimodal polyethylene mainly includes: (1) melt mixing method, that is, producing different molecular weight resins and then mixing, which has the problems of high cost and uneven product quality. (2) Sectional reaction method, that is, by using a series of reaction kettles, different conditions are controlled to generate bimodal polyethylene with different molecular weights, which is flexible in operation and has a wide range of grade adjustment, but the cost is higher. (3) Directly obtain bimodal polyethylene by one-stage reaction method, that is, by using catalyst to directly obtain bimodal polyethylene during polymerization, such as mixing different catalysts, using a catalyst system with multiple catalytic active sites, etc. This method is a relatively 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 alkyl aluminum cocatalyst to control the composition of the product. Patent document CN105440184B uses a two-component composite catalyst system to prepare bimodal molecular weight distribution polyethylene by olefin catalytic slurry polymerization in two series reactors. Patent document CN116640243A discloses a one-pot synthesis of bimodal polyethylene. In the polymerization process, by utilizing the two forms of retention and removal of H atoms, two active centers are generated in situ to synthesize bimodal polyethylene. Patent document CN117986424B prepares branched bimodal polyethylene by using a double-center metallocene catalyst, which includes metallocene chromium, metallocene zirconium 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 the catalyst is a metallocene compound or a non-metallocene catalyst.

[0007] Therefore, how to design and synthesize a post-transition metal catalyst for preparing bimodal UHMWPE, which has a stable rigid structure and can maintain excellent thermal stability at high temperatures to produce high-quality bimodal UHMWPE products, still needs further research. SUMMARY

[0008] The purpose of the present application is to provide a post-transition metal catalyst for preparing bimodal UHMWPE, its ligand, and its preparation method and application.

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

[0010] The purpose of the present application is achieved by the following technical solutions:

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

[0012]

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

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

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

[0016] The C6-C 12 The aryl is a monovalent aromatic carbocyclic ring system having at least one aromatic ring or a polycyclic ring with at least one ring being aromatic, for example, can 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 is H.

[0019] Further 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 C1-C4 alkyl or phenyl, for example selected from methyl, ethyl, n-propyl, isopropyl, t-butyl and the like or phenyl; and / or, at least one of R4-R6 is C1-C4 alkyl, for example selected from methyl, ethyl, n-propyl, isopropyl, t-butyl and the like, and the rest is H.

[0021] As a preferred embodiment of the present application, the diimine ligand is selected from any one of the following formula L1-L10 diimine ligand compounds:

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031] .

[0032] The diimine ligand of formula L of the present application 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 deactivation of the late transition metal catalyst at high temperature. On the other hand, the 1,10-phenanthroline skeleton has two N atoms, and the different electronegativity of N and C atoms 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 reaction with amines and metal coordination. The chemical environment between the two active sites is completely different, and can produce bimodal ultra-high molecular weight polyethylene.

[0033] The second aspect of the present application provides a preparation method of the above-mentioned diimine ligand. The diimine ligand is prepared by acid catalysis using 1,10-phenanthroline-5,6-dione derivatives of the general structure shown in formula I and aniline derivatives of the general structure shown in formula II as raw materials. The specific reaction formula is as follows:

[0034] .

[0035] 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, and are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, aromatic phenyl, aromatic naphthyl, aromatic biphenyl, halogen, etc. Preferably, 1,10-phenanthroline derivatives with electron-donating effect are used as the raw material of o-dicarbonyl, and further preferably 1,10-phenanthroline with electron-donating groups on R1 and R3 is used as the raw material of o-dicarbonyl. Further preferably, 1,10-phenanthroline with certain steric hindering electron-donating groups on R1 and R3 is used as the raw material of o-dicarbonyl. Further preferably, 1,10-phenanthroline with methyl on R1, isopropyl on R3, and methyl on R3 is used as the raw material of o-dicarbonyl.

[0036] In the embodiments of the present application, 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, 4,7-dimethyl-1,10-phenanthroline-5,6-dione, etc.

[0037] 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, primary amines with electron-donating effect are used as the amine raw material, and further preferably primary amines with certain steric hindering electron-donating groups are used as the amine raw material. Further preferably, methylamine, aniline, 3,5-dimethylaniline, and p-methylaniline are used as the amine raw material.

[0038] In the embodiments of the present application, the aniline derivative is selected from aniline, o-methylaniline, 3,5-dimethylaniline, p-methylaniline, p-bromoaniline, etc.

[0039] As a preferred technical solution, the present application provides a preparation method of diimine ligand, which comprises the following steps: 1,10-phenanthroline-5,6-dione derivative and aniline derivative are dissolved in aprotic polar organic solvent at a molar ratio of 1:2-2.5, and then a non-oxidizing strong organic acid is used as a catalyst (catalytic amount) for reaction at 40-150°C. After the reaction is completed, the mixture is subjected to solvent removal and purification to obtain the diimine ligand.

[0040] Preferably, the organic aprotic polar solvent can be a solvent commonly used in the art, such as benzene, toluene, etc. The non-oxidizing organic strong acid can be a substance of the organic strong acid class commonly used in the art, such as p-toluenesulfonic acid. The reaction temperature is preferably 60-100℃, and the reaction time is generally between 12-36 hours. The removal of the solvent can be carried out by conventional methods in the art, such as rotary evaporation. The purification of the product can be carried out by conventional methods in the art, such as recrystallization, column chromatography.

[0041] The third aspect of the present application provides a post-transition metal catalyst for preparing bimodal UHMWPE, which is a coordination compound formed by the diimine ligand described above and a post-transition metal salt.

[0042] The post-transition metal is selected from Fe, Co, Ni or Pd, and the post-transition metal salt can be a halide of the post-transition metal, such as chloride or bromide, including but not limited to ferric chloride, cobalt chloride, nickel bromide, nickel chloride, etc.

[0043] The inventors have found that the post-transition metal catalyst of the present application unexpectedly has high catalytic activity in a wide temperature range, especially excellent high-temperature stability. For example, when the reaction temperature is 80℃, the catalyst has a catalytic activity as high as 7.88×10 6 g / mol·h, and the specific mechanism is not fully clear. It is speculated that the post-transition metal catalyst with a 1,10-phenanthroline-5,6-dione skeleton has higher rigidity and more excellent electronic effect than the traditional 1,2-diketone structure, preventing the post-transition metal catalyst from deactivating at high temperatures. The 1,10-phenanthroline skeleton is different from phenanthrene, with two N atoms in the ring, and the difference in electronegativity between N 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 reaction with amines and metal coordination, and the chemical environment between the two active sites is completely different, which can produce bimodal ultra-high molecular weight polyethylene.

[0044] Preferably, the post-transition metal catalyst is a nickel metal catalyst with the general structure of formula C:

[0045] ,

[0046] wherein X is chlorine or bromine.

[0047] As a preferred embodiment of the present application, the nickel metal catalyst is selected from any one of formulas C1-C10:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057] .

[0058] The fourth aspect of the present application provides a preparation method of the above-mentioned post-transition metal catalyst, which can be prepared by a method of synthesizing a coordination compound. Taking a nickel metal catalyst with a general structure shown in formula C as an example, the following method can be used: the diimine ligand and a nickel salt are dissolved in anhydrous aprotic organic solvents in a molar ratio of 1:3-4, and reacted in an anhydrous and oxygen-free environment to obtain the nickel metal catalyst. The specific reaction formula is as follows:

[0059] .

[0060] Preferably, the nickel metal catalyst is prepared by the following method: the prepared ligand L and a nickel salt are dissolved in anhydrous aprotic organic solvents (for example, acetonitrile, toluene) in a molar ratio of 1:3-4, and reacted in an anhydrous and oxygen-free environment at a reaction temperature of 40-100°C for 12-36 hours. After the reaction is completed, the product is filtered, washed with distilled water for 2-3 times, and dried in a vacuum drying oven.

[0061] The fifth aspect of the present application provides an application of the above-mentioned post-transition metal catalyst in preparing bimodal UHMWPE. The post-transition metal catalyst, under the action of a cocatalyst, can obtain bimodal ultra-high molecular weight polyethylene with low pressure and high catalytic activity.

[0062] Further, 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.

[0063] Further, the selected solvent is mainly inert solvent, mainly including chain alkanes and cycloalkanes and benzene aromatic derivatives with boiling point not more than 120 DEG C. Preferably, benzene aromatic derivatives, alkanes with low viscosity and low boiling point not more than 110 DEG C and low solubility of ultra-high molecular weight polyethylene at normal temperature are used as solvents, such as toluene, xylene, chlorobenzene, hexane and the like.

[0064] Further, the selected co-catalyst is mainly alkyl aluminoxane, and further preferably methyl aluminoxane, modified methyl aluminoxane and isobutyl aluminoxane are used as co-catalysts, and the molar ratio of the late transition metal catalyst to the co-catalyst is 1:200-500.

[0065] Compared with the prior art, the present application has the following innovative points:

[0066] The present application designs and synthesizes a diimine late transition metal catalyst with different chemical environments of bimetallic active sites and rigid mother ring skeleton structure, and 1,10-phenanthroline-5,6-dione is used as the skeleton in the late transition metal catalyst, 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 late transition metal catalyst. In addition, two pyridine rings exist in 1,10-phenanthroline-5,6-dione, the pyridine ring and the benzene ring have obvious different electronic effects, and the lone pair 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, which can produce two metal active centers with completely different chemical environments, and can be applied to the low-pressure polymerization of ethylene to produce bimodal ultra-high molecular weight polyethylene. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 The molecular weight distribution diagram of the polyethylene sample E8. DETAILED DESCRIPTION

[0068] The present application will be described in detail below, and the technical solutions not described in detail are disclosed in the art.

[0069] The main reagents used in the examples are specifically as follows:

[0070] 1,10-phenanthroline-5,6-dione (CAS: 27318-90-7, Sigma-Aldrich)

[0071] 2,9-dimethyl-1,10-phenanthroline-5,6-dione (CAS: 102331-54-4, Henan Weiti Chemical)

[0072] 2,9-diphenyl-1,10-phenanthroline-5,6-dione (CAS: 1654020-68-4, Henan Li'en Chemical)

[0073] 2,9-diisopropyl-1,10-phenanthroline-5,6-dione (CAS: 1243254-92-3, Henan Li'en Chemical)

[0074] 4,7-dimethyl-1,10-phenanthroline (CAS: 3248-05-3, Leyue Reagent)

[0075] 4,7-dimethyl-1,10-phenanthroline-5,6-dione (CAS: 1713236-32-8, synthesized)

[0076] 2,3-butanedione (CAS: 431-03-8, Sigma-Aldrich)

[0077] 2,6-diacetylpyridine (CAS: 1129-30-2, Sigma-Aldrich)

[0078] salicylaldehyde (CAS: 90-02-8, Sigma-Aldrich)

[0079] methylaluminoxane (CAS: 120144-90-3, Jiuding Chemical)

[0080] high purity ethylene (CAS: 74-85-1, Shanghai Liquified Air)

[0081] aniline (CAS: 62-53-3, Sigma-Aldrich)

[0082] o-toluidine (CAS: 95-53-4, Sigma-Aldrich)

[0083] 3,5-dimethylaniline (CAS: 108-69-0, Sigma-Aldrich)

[0084] p-toluidine (CAS: 106-49-0, Sigma-Alrich)

[0085] p-bromoaniline (CAS: 106-40-1, Sigma-Aldrich)

[0086] p-toluenesulfonic acid (CAS: 6192-52-5, Sigma-Aldrich)

[0087] acetic acid (CAS: 64-19-7, Sigma-Aldrich)

[0088] ethanol (CAS: 64-17-5, Sigma-Aldrich)

[0089] dichloromethane (CAS: 75-09-2, Sigma-Aldrich)

[0090] Benzene (CAS: 71-43-2, Sigma-Aldrich)

[0091] Toluene (CAS: 108-88-3, Sigma-Aldrich)

[0092] Concentrated sulfuric acid 98% (CAS: 76664-93-9, Sigma-Aldrich)

[0093] Nitric acid (CAS: 7697-37-2, Sigma-Aldrich)

[0094] Sodium hydroxide (CAS: 1310-73-2, Sigma-Aldrich)

[0095] Hydrochloric acid (CAS: 7647-01-0, Sigma-Aldrich)

[0096] Acetonitrile (CAS: 75-05-8, Sigma-Aldrich)

[0097] Methanol (CAS: 67-56-1, Sigma-Aldrich)

[0098] The solvents involved in the examples must be anhydrous, unless otherwise specified.

[0099] Example 1

[0100] The catalyst sample 1 was prepared according to the following steps:

[0101] (1) The specific synthesis method of ligand L1 is as follows:

[0102]

[0103] 2.10 g of 1,10-phenanthroline-5,6-dione (10 mmol) was added to a 250 ml three-necked flask, about 100 ml of benzene 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 65°C, a condenser with a water separator was used, and the reaction was carried out for 24 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was purified by recrystallization 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 16N4: 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.

[0104] (2) Preparation of catalyst sample 1: the ligand L1 obtained is coordinated with NiCl2, and the specific steps are as follows: under anhydrous and anaerobic conditions, about 100 ml of super-dry acetonitrile is added to a three-necked flask, the ligand L1 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added, the reaction temperature is controlled at 55°C, and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by evaporation, the solvent is filtered out, washed with dry n-hexane for several times, and dried to obtain catalyst sample 1.

[0105] Example 2

[0106] Catalyst sample 2 is prepared as follows:

[0107] (1) The specific synthesis method of the ligand L2 is as follows:

[0108]

[0109] 2,9-dimethyl-1,10-phenanthroline-5,6-dione 2.38 g (10 mmol) is added to a 250 ml three-necked flask, about 100 ml of anhydrous acetic acid is added to dissolve it, then 2.14 g of aniline (23 mmol) and 7 μL of p-toluenesulfonic acid (about 50 μmol) are added. The three-necked flask is heated to 100°C, a condenser with a water separator is used, the reaction is carried out for 24 h, and then the solvent is removed by vacuum distillation after the reaction is completed. Ethanol is used to recrystallize and purify the product to obtain the ligand L2, and the final yield is 85% (2.4 g, 8.4 mmol). 1 H 300 MHz, DMSO): 8.84-7.30 (m, 14H, Ar-H); 2.95 (d, 6H, -CH3). C 26 H 20 N4: Elemental analysis calculated value (%): C, 80.39; H, 5.19; N, 14.42. Experimental determination value (%): C, 80.66; H, 5.29; N, 14.07.

[0110] (2) Preparation of catalyst sample 2: the ligand L2 obtained is coordinated with NiCl2, and the specific steps are as follows: under anhydrous and anaerobic conditions, about 100 ml of super-dry acetonitrile is added to a three-necked flask, the ligand L2 (8.4 mmol) and anhydrous NiCl2 (4 mmol) are added, the reaction temperature is controlled at 55°C, and the reaction time is 24 hours. After the reaction is completed, it is cooled to room temperature, concentrated by evaporation, the solvent is filtered out, washed with dry n-hexane for several times, and dried to obtain catalyst sample 2.

[0111] Example 3

[0112] Catalyst sample 3 was prepared as follows:

[0113] (1) The specific synthesis method of ligand L3 is as follows:

[0114]

[0115] 3.68 g of 2,9-dibromo-1,10-phenanthroline-5,6-dione (10 mmol) was added to a 250 ml three-necked flask, 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, the reaction was carried out for 24 h, after the reaction was completed, the solvent was removed by vacuum distillation, and the product was recrystallized with ethanol for purification, to obtain ligand L3, with a final yield of 71% (molar ratio). 1 H 300 MHz, 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 value (%): C, 55.77; H, 2.85; N, 10.71; Br, 30.73.

[0116] (2) Preparation of catalyst sample 3: The obtained ligand L3 was coordinated with NiCl2, and the specific steps were as follows: under anhydrous and anaerobic conditions, about 100 ml of ultra-dry acetonitrile was added to a three-necked flask, ligand L3 (8.4 mmol) and anhydrous NiCl2 (4 mmol) were added, the reaction temperature was controlled at 55°C, and the reaction time was 24 hours. After the reaction was completed, it was cooled to room temperature, concentrated under reduced pressure, the solvent was filtered out, washed with dry n-hexane for several times, and dried to obtain catalyst sample 3.

[0117] Example 4

[0118] Catalyst sample 4 was prepared as follows:

[0119] (1) The specific synthesis method of ligand L4 is as follows:

[0120]

[0121] Into a 250 ml three-necked flask, 3.62 g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10 mmol) was added to be dissolved in about 100 ml of anhydrous acetic acid, 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, and the reaction was carried out for 24 h using a condenser with a water separator. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was purified by recrystallization using ethanol to obtain the ligand L4, with a final yield of 88% (m.p. 230-232°C). 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 value (%): C, 84.69; H, 4.82; N, 10.57.

[0122] (2) Preparation of catalyst sample 4: The obtained ligand L4 was coordinated with NiCl2, and the specific steps were as follows: under anhydrous and anaerobic conditions, about 100 ml of ultradry acetonitrile was added to a three-necked flask, and the ligand L4 (8.4 mmol) and anhydrous NiCl2 (4 mmol) were added. The reaction temperature was controlled at 55°C, and the reaction time was 24 hours. After the reaction was completed, the reaction was cooled to room temperature, and then concentrated under reduced pressure. The solvent was filtered out, washed with dry n-hexane several times, and dried to obtain catalyst sample 4.

[0123] Example 5

[0124] Catalyst sample 5 was prepared as follows:

[0125] (1) The specific synthesis method of the ligand L5 is as follows:

[0126]

[0127] Into a 250 ml three-necked flask, 2.94 g of 2,9-diisopropyl-1,10-phenanthroline-5,6-dione (10 mmol) was added to be dissolved in 100 ml of anhydrous acetic acid, 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, and the reaction was carried out for 24 h using a condenser with a water separator. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was purified by recrystallization using ethanol to obtain the ligand L5, with a final yield of 91% (m.p. 230-232°C). 1 H 300MHz, DMSO): 8.79-7.52 (m, 14H, Ar-H); 3.95-1.77 (m, 14H, -CH(CH3)2). C 30 H28 N4: Elemental analysis calculated (%) : C, 80.39; H, 6.35; N, 12.60. Experimental determined (%) : C, 80.87; H, 6.43; N, 12.07.

[0128] (2) Preparation of catalyst sample 5: The obtained ligand L5 was coordinated with NiCl2, and the specific steps were as follows: under anhydrous and anaerobic conditions, about 100 ml of super-dry acetonitrile was added to a three-necked flask, the ligand L5 (8.4 mmol) and anhydrous NiCl2 (4 mmol) were added, the reaction temperature was controlled at 55°C, and the reaction time was 24 hours. After the reaction was completed, it was cooled to room temperature, concentrated by distillation, the solvent was filtered out, washed with dry n-hexane for several times, and dried to obtain catalyst sample 5.

[0129] Example 6

[0130] Catalyst sample 6 was prepared as follows:

[0131] (1) The specific synthesis method of ligand L6 was as follows:

[0132]

[0133]

[0134] First, 4,7-dimethyl-1,10-phenanthroline-5,6-dione was synthesized: 4,7-dimethyl-1,10-phenanthroline 1.35 g (6.5 mmol) and potassium bromide (7.5 g) were mixed, sulfuric acid (30 ml) was added dropwise at 0°C within 15 minutes, and then nitric acid (15 ml) was added to the reaction mixture within 15 minutes. The obtained mixture was heated at 80°C for 4 hours, and after the reaction was completed, the solution was cooled to 0°C. The cold acidic mixture was poured into ice. A 5% NaOH solution was added to the reaction mixture under vigorous stirring, and the pH value was adjusted to 3. The mixture was extracted with dichloromethane (3x300 ml), the organic phase was dried with MgSO4, the solvent was evaporated, and the obtained solid was dried under vacuum for use.

[0135] 2.38 g of 4,7-dimethyl-1,10-phenanthroline-5,6-dione (10 mmol) was added to a 250 ml three-necked flask, 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, the reaction was carried out for 24 h, and after the reaction was completed, the solvent was removed by vacuum distillation, and the product was purified by recrystallization with ethanol to obtain ligand L6, with a final yield of 75% (2.5 g, 10 mmol). 1H 300 MHz, 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 value (%): C, 80.42; H, 5.21; N, 14.37.

[0136] (2) Preparation of catalyst sample 6: The obtained ligand L6 was coordinated with NiCl2, and the specific steps were as follows: under anhydrous and anaerobic conditions, about 100 ml of super-dry acetonitrile was added to a three-necked flask, and the ligand L6 (8.4 mmol) and anhydrous NiCl2 (4 mmol) were added, and the reaction temperature was controlled at 55°C, and the reaction time was 24 hours. After the reaction was completed, it was cooled to room temperature, and then concentrated by evaporation, and the solvent was filtered out, and washed with dry n-hexane several times, and dried to obtain catalyst sample 6.

[0137] Example 7

[0138] Catalyst sample 7 was prepared as follows:

[0139] (1) The specific synthesis method of ligand L7 is as follows:

[0140]

[0141] 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, and then 2.46 g of o-toluidine (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, and the reaction was carried out for 24 h. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was recrystallized with ethanol for purification to obtain ligand L7, with a final yield of 68% (molar yield 68%). 1 H 300 MHz, DMSO): 8.52-7.49 (m, 22H, Ar-H); 2.50 (s, 6H, -CH3). C 38 H 28 N4: Elemental analysis calculated value (%): C, 84.42; H, 5.22; N, 10.36. Experimental value (%): C, 84.45; H, 5.26; N, 10.33.

[0142] (2) Preparation of catalyst sample 7: the ligand L7 obtained was coordinated with NiCl2, and the specific steps were as follows: under anhydrous and anaerobic conditions, about 100 ml of super-dry acetonitrile was added to a three-necked flask, the ligand L7 (8.4 mmol) and anhydrous NiCl2 (4 mmol) were added, the reaction temperature was controlled at 55°C, and the reaction time was 24 hours. After the reaction was completed, it was cooled to room temperature, concentrated by evaporation, the solvent was filtered out, washed with dry n-hexane for several times, and dried to obtain catalyst sample 7.

[0143] Example 8

[0144] Catalyst sample 8 was prepared as follows:

[0145] (1) The specific synthesis method of the ligand L8 was as follows:

[0146]

[0147] 3.62 g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10 mmol) was added to a 250 ml three-necked flask, about 100 ml of anhydrous acetic acid was added to dissolve it, then 2.78 g of 3,5-dimethylaniline (23 mmol) and 7 μL of p-toluenesulfonic acid (about 50 μmol) were added. The three-necked flask was heated to 100°C, and the condenser with a water separator was used for reaction for 24 h. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was recrystallized with ethanol for purification to obtain the ligand L8, and the final yield was 68% (molar ratio). 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 value (%): C, 84.51; H, 5.72; N, 9.77.

[0148] (2) Preparation of catalyst sample 8: the ligand L8 obtained was coordinated with NiCl2, and the specific steps were as follows: under anhydrous and anaerobic conditions, about 100 ml of super-dry acetonitrile was added to a three-necked flask, the ligand L8 (8.4 mmol) and anhydrous NiCl2 (4 mmol) were added, the reaction temperature was controlled at 55°C, and the reaction time was 24 hours. After the reaction was completed, it was cooled to room temperature, concentrated by evaporation, the solvent was filtered out, washed with dry n-hexane for several times, and dried to obtain catalyst sample 8.

[0149] Example 9

[0150] Catalyst sample 9 was prepared as follows:

[0151] (1) The specific synthesis method of ligand L9 is as follows:

[0152]

[0153] 3.62 g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10 mmol) was added to a 250 ml three-necked flask, about 100 ml of anhydrous acetic acid was added to dissolve it, then 2.46 g of p-methylaniline (23 mmol) and 7 μL of p-toluenesulfonic acid (about 50 μmol) were added. The three-necked flask was heated to 100°C, and the reaction was carried out for 24 h using a condenser with a water separator. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was recrystallized with ethanol for purification, to obtain ligand L9, with a final yield of 84% (1.8 g, 8.4 mmol). 1 H 300 MHz, 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 value (%): C, 84.55; H, 5.33; N, 10.30.

[0154] (2) Preparation of catalyst sample 9: The obtained ligand L9 was coordinated with NiC12, and the specific steps were as follows: under anhydrous and anaerobic conditions, about 100 ml of ultradry acetonitrile was added to a three-necked flask, ligand L9 (8.4 mmol) and anhydrous NiC12 (4 mmol) were added, the reaction temperature was controlled at 55°C, and the reaction time was 24 hours. After the reaction was completed, the reaction was cooled to room temperature, concentrated, and the solvent was filtered out. The product was washed with dry n-hexane for several times and dried to obtain catalyst sample 9.

[0155] Example 10

[0156] Catalyst sample 10 was prepared as follows:

[0157] (1) The specific synthesis method of ligand L10 is as follows:

[0158]

[0159] Into a 250 ml three-necked flask, 3.62 g of 2,9-diphenyl-1,10-phenanthroline-5,6-dione (10 mmol) was added to be dissolved in about 100 ml of anhydrous acetic acid, then 3.95 g of p-bromoaniline (23 mmol) and 7 μL of p-toluenesulfonic acid (about 50 μmol) were added. The three-necked flask was heated to 100℃, and the reaction was carried out for 24 h using a condenser with a water separator. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was purified by recrystallization with ethanol to obtain the ligand L10, with a final yield of 73% (C 1 H 300MHz, 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 value (%): C, 64.62; H, 3.33; N, 8.44; Br, 23.79.

[0160] (2) Preparation of catalyst sample 10: The obtained ligand L10 was coordinated with NiC12. Specifically, under anhydrous and anaerobic conditions, about 100 ml of ultradry acetonitrile was added to a three-necked flask, and the ligand L10 (8.4 mmol) and anhydrous NiC12 (4 mmol) were added. The reaction temperature was controlled at 55℃, and the reaction time was 24 hours. After the reaction was completed, the reaction was cooled to room temperature, concentrated by vacuum distillation, and the solvent was filtered out. The product was washed with dry n-hexane for several times and dried to obtain catalyst sample 10.

[0161] The catalysts and raw materials of Examples 1-10 are shown in Table 1.

[0162] Table 1 Catalysts and raw materials of Examples

[0163]

[0164] The present application also provides the following comparative examples.

[0165] Comparative Example 1

[0166] The catalyst sample a was prepared as follows.

[0167] (1) Synthesis of pyridine diimine ligand:

[0168]

[0169] The ligand L was obtained by dissolving 0.82 g of 2,6-diacetylpyridine (5 mmol) and 1.65 g of 4-amino-3,5-dimethylphenol (12 mmol) in 150 ml of methanol, adding 1 ml of formic acid, refluxing at 80°C for 12 hours, evaporating the solvent after the reaction was completed, and recrystallizing by adding n-hexane.

[0170] (2) Preparation of catalyst sample a:

[0171]

[0172] Under nitrogen, 1 mmol of ligand L was dissolved in 30 ml of THF and reacted for 1 hour, then FeCl2was added, and the reaction was carried out for 6 hours. The 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 value (%): C, 74.78; H, 6.73; N, 10.54; O, 8.02.

[0173] Comparative Example 2

[0174] Catalyst sample b: commercially available metallocene catalyst titanium dichloride (CAS: 1271-19-8), the structural formula of which is:

[0175]

[0176]

Catalyst performance test

[0177] The above catalysts were used for ethylene polymerization to prepare ultra-high molecular weight polyethylene, and the catalytic performance of the catalysts was tested.

[0178] The specific steps are as follows: 250 ml of a stainless steel reactor (with a cooling jacket) is vacuum heated at 150°C for about 30 min, then cooled to ambient temperature, pressurized with ethylene to 2 atm, vented and pressurized again with ethylene, and this is repeated three times to ensure that the reactor is filled with an ethylene atmosphere. The cocatalyst MAO (0.5 mmol) is dissolved in about 100 ml of dry hexane and injected into the reactor, continuously stirred for 5 min at an ethylene pressure of 1.2 atm, and finally 50 ml of a catalyst hexane dilution (containing about 2 μmol of catalyst) is added to the reactor and stirred uniformly. During the entire reaction process, gaseous ethylene is continuously injected, and the ethylene pressure in the reactor is maintained at 9-10 atm. The reaction temperature is controlled at 60-100°C, and the polymerization process is completed after 2 h of continuous reaction. Then, post-treatment is performed, the catalyst is inactivated by adding acidic methanol (mass ratio 95:5 of ethanol / hydrochloric acid), the obtained precipitated polymer is collected, separated by rotary evaporation, and dried to constant weight in a vacuum at 40°C to obtain a polyethylene sample which is weighed and detected.

[0179] The activity of the catalyst is calculated according to the yield of the polyethylene sample, in g of polyethylene / (mol of catalyst×h), and the catalytic activities of the various catalysts at different temperatures are listed in Table 2.

[0180] Table 2 Catalytic activities of different catalysts at different temperatures (unit: 10 6 g PE / mol cat h)

[0181]

[0182] Note: “--” means not performed.

[0183] As can be seen from Table 2, the 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 the catalytic activity is significantly weakened at 80°C or above. The catalytic activity of the comparative example 2, a metallocene catalyst titanium dichloride, is good at 70-80°C, but the catalytic activity is significantly weakened at 100°C. Compared with the comparative examples, except for the examples 3 and 10 with halogen as a substituent, the catalysts provided by the other examples exhibit excellent thermal stability (especially when the electron donor has a certain steric hindering effect), and maintain excellent ethylene catalytic activity at 80-100°C, indicating that the post-transition metal catalyst obtained by using 1,10-phenanthroline-5,6-dione as a diimine structural skeleton has high catalytic activity and thermal stability. For example, the catalytic activity of the example 8 is 7.88×10 6 gPE / g cat h at 90°C, and the catalytic activity is 4.57×10 6 gPE / g cat h at 100°C.

[0184]

Polyethylene sample performance test

[0185] Part of the polyethylene samples obtained above were selected for molecular weight determination: weight average molecular weight (Mw) and number average molecular weight (Mn): determined by gel permeation chromatography according to GB / T 27843-2011 "Chemicals - Determination of the content of low molecular weight components in polymers - Gel permeation chromatography (GPC)"; polyethylene molecular weight distribution index (PDI): determined by the ratio of the weight average molecular weight and the number average molecular weight; peak distribution: determined based on the GPC molecular weight distribution curve. The specific test results are shown in Table 3, Figure 1 The molecular weight distribution graph of polyethylene sample E8 is exemplarily listed.

[0186] Table 3 Polyethylene sample test results

[0187]

[0188] As can be seen from Table 3, high molecular weight and ultrahigh molecular weight polyethylene can be prepared at a relatively high polymerization reaction temperature according to the present application. Except for polyethylene samples E3 and E10 prepared by catalyst sample 3 and catalyst sample 10 with halogen as a substituent, the weight average molecular weight of polyethylene prepared according to the present application is 1.5-2 million, the PDI is 5-6, and it is all bimodal polyethylene, which performs more excellent in processing performance. Comparative Example 1 can only obtain low molecular weight polyethylene product and it is monomodal polyethylene, and the polyethylene prepared in Comparative Example 2 is monomodal polyethylene.

[0189] The above description of the embodiments is for the purpose of facilitating the understanding and use of the present application by those skilled in the art. Those skilled in the art can easily make various modifications to the embodiments and apply the general principles described herein to other embodiments without having to go through creative labor. Therefore, the present application is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art according to the disclosure of the present application without departing from the scope of the present application should be within the protection scope of the present application.

Claims

1. A diimine ligand having the general structure of formula L: ###0001### L wherein R1-R3 are independently selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl. ， wherein R1-R6are each independently selected from H, C1-C6alkyl, C1-C6alkoxy, C6-C10aryl, or halogen, and at least one of R1-R3is selected from C1-C6alkyl, C1-C6alkoxy, phenyl, or halogen. 12 R1-R6are each independently selected from H, C1-C6alkyl, C1-C6alkoxy, C6-C10aryl, or halogen, and at least one of R1-R3is selected from C1-C6alkyl, C1-C6alkoxy, phenyl, or halogen.

2. The diimine ligand of claim 1, wherein at least one of R1-R3 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl.

3. The diimine ligand of claim 2, wherein at least one of R1 and R3 is C1-C4 alkyl or phenyl.

4. The diimine ligand of claim 1, wherein at least one of R4-R6 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl.

5. The diimine ligand of claim 4, wherein at least one of R4-R6 is C1-C4 alkyl.

6. The diimine ligand of claim 1, wherein The diimine ligand is selected from any one of the following diimine ligand compounds of formula L2-L10: ###0002### L2 L3 L4 L5 L6 L7 L8 L9 L10 。 7. Process for the preparation of diimine ligands according to any one of claims 1 to 6, characterized in that, The diimine ligand is prepared by acid catalysis using a 1,10-phenanthroline-5,6-dione derivative of the general structure of formula I and an aniline derivative of the general structure of formula II as starting materials, and the specific reaction is as follows: ###0003### I II L 。 8. The method of claim 7, wherein the diimine ligand is prepared by the reaction of a diimine with a transition metal compound. The 1,10-phenanthroline-5,6-dione derivative is 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; The aniline derivative is aniline, o-methylaniline, 3,5-dimethylaniline, p-methylaniline, p-bromoaniline.

9. A post-transition metal catalyst for the preparation of a bimodal UHMW PE, characterized in that, The coordination compound is a nickel metal catalyst having the general structure of formula C: ###0004### C wherein X is chlorine or bromine. ， The coordination compound is prepared by dissolving the diimine ligand and a nickel salt in a molar ratio of 1:3-4 in anhydrous aprotic organic solvent and reacting in anhydrous and oxygen-free environment, and the specific reaction is as follows: ###0005### I II L C 10. The method of making a late transition metal catalyst according to claim 9, wherein, 11. Use of the late transition metal catalyst of claim 9 in the preparation of bimodal UHMWPE. 。 ​

Images