A method for preparing high performance polyethylene-based carbon fiber composites in situ by ethylene polymerization

Abstract

The application discloses a diimine nickel complex, a preparation method and application in ethylene polymerization, and the structural formula of the diimine nickel complex is shown in the following formula: The application improves the mechanical property and chemical corrosion resistance of the original polyethylene. In-situ polymerization also enables the filler to be more fully and uniformly filled into the polyethylene elastomer, thereby realizing a novel composite material which is excellent in compression resistance, heat resistance and ductility, and further providing a new output path for diversified development of the polyolefin composite material and a new method for synthesizing the polyolefin composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a diimine nickel complex, a preparation method and an application thereof in preparing a high-performance polyethylene-carbon fiber composite material by ethylene polymerization. Background Art

[0002] As one of the important varieties in the plastics industry, polyethylene's production and market demand have maintained a rapid growth trend. According to statistics, polyethylene production accounts for about one-third of the world's total plastics. With the development of petrochemicals and the continuous emergence and application of new technologies, polyethylene production technology and product quality will be further improved and improved. Polyethylene composites can significantly improve the strength and rigidity of the material by compounding with other materials (such as resins, fillers, etc.), enabling them to meet application scenarios with higher performance requirements. Polyethylene materials themselves have good wear resistance, and composite materials can further enhance this property and extend the service life of the product. Polyethylene composites have excellent corrosion resistance to most chemicals such as acids, alkalis, and salts, and can maintain stable performance in harsh environments.

[0003] Carbon fiber is a high-strength, high-modulus fiber with a carbon content of over 90%, primarily composed of carbon. It is an inorganic polymer fiber with excellent physical and chemical properties, including low density, high strength, high-temperature resistance, high chemical stability, fatigue resistance, and friction resistance. Furthermore, carbon fiber exhibits excellent electrical and thermal conductivity, electromagnetic shielding properties, and a low coefficient of thermal expansion. Its low price and excellent performance have led to its widespread use in heavy industries such as aerospace, rail transit, and vehicle manufacturing.

[0004] When preparing carbon fiber reinforced polyethylene composites, an interfacial bond forms between the carbon fibers and the polyethylene matrix. Through appropriate process control, such as heat treatment and surface treatment, this interfacial bond can be optimized, allowing for more efficient load transfer between the carbon fibers and the polyethylene matrix, thereby improving the overall strength of the composite. Carbon fibers and polyethylene each possess unique performance advantages. The high strength and high modulus of carbon fibers provide excellent load-bearing capacity, while polyethylene offers excellent toughness and wear resistance. Combining the two can fully leverage their synergistic effects, forming a new material with both high strength and good toughness. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to improve the mechanical properties and chemical corrosion resistance of existing PE materials.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] The present invention provides a diimine nickel complex, the structural formula of which is shown below:

[0008]

[0009] Preferably, the diimine nickel complex belongs to the orthorhombic system, Pnma space group, and the unit cell parameter α=90°, β=90°, γ=90°.

[0010] Preferably, the diimine nickel complex is composed of an asymmetric diimine compound It is complexed with ethylene glycol dimethyl ether nickel bromide.

[0011] The present invention also provides a method for preparing the nickel diimide complex, comprising the following steps: The nickel diimide complex is obtained by reacting the nickel diimide complex with ethylene glycol dimethyl ether nickel bromide (DME) NiBr2 in dichloromethane at room temperature under an inert gas atmosphere, with a yield of more than 90%.

[0012] Preferably, the molar ratio of the ligand to ethylene glycol dimethyl ether nickel bromide is 1:1.

[0013] Preferably, the reaction is carried out under stirring conditions.

[0014] Preferably, the usage ratio of the asymmetric diimine compound and dichloromethane is 1 g:20 ml.

[0015] Preferably, the method for preparing the asymmetric diimine compound comprises the following steps:

[0016] S1. 4-methoxyaniline and tert-butyl substituted benzhydrol Friedel-Crafts reaction under the action of Lucas reagent to obtain compound

[0017] S2, compound and 2,3-butanedione As raw materials, ketone amine condensation reaction occurs under the catalysis of acetic acid to obtain compound

[0018] S3, compound and 2,6-diisopropylaniline as raw materials, and undergo condensation reaction under the catalysis of p-toluenesulfonic acid to obtain the asymmetric diimine compound.

[0019] Preferably, in S1, the molar ratio of the 4-methoxyaniline to the tert-butyl-substituted benzhydrol is 1:2.1, the reaction temperature is 160° C., and the reaction time is 0.5 h.

[0020] Preferably, in S2, and 2,3-butanedione The molar ratio is 1:1, the reaction temperature is 80°C, and the time is 24h.

[0021] Preferably, in S3, The molar ratio of aniline to 2,6-diisopropylaniline is 1:1.1, the reaction temperature is 140°C, and the reaction time is 12 hours.

[0022] The present invention also provides an application of the diimine nickel complex as an ethylene polymerization catalyst.

[0023] Preferably, during the ethylene polymerization process, carbon fiber is also added as a modifier.

[0024] The present invention also proposes a method for preparing a modified polyethylene composite material using the diimine nickel complex as a catalyst, comprising the following steps: mixing a co-catalyst, a solvent and carbon fibers, adding a diimine nickel complex solution after degassing, and introducing ethylene to react to obtain the modified polyethylene composite material.

[0025] Preferably, the co-catalyst is Et2AlCl; the solvent is toluene; and the solvent of the diimine nickel complex solution is dichloromethane.

[0026] Preferably, the molar ratio of the co-catalyst to the diimine nickel complex is 400:1; the reaction pressure is 8.0 atmospheres, the temperature is 30° C., and the reaction time is 10 minutes.

[0027] The present invention also provides a modified polyethylene composite material, which is prepared by a method for preparing the modified polyethylene composite material using the diimine nickel complex as a catalyst.

[0028] The synthetic routes of the asymmetric diimine compound and the complex of the present invention are as follows:

[0029]

[0030] The advantages of the present invention are:

[0031] (1) The present invention, based on a novel asymmetric [N,N] nickel diimide catalyst, employs in-situ polymerization to synthesize a composite material. The asymmetry of the novel metal catalyst changes the active center structure and steric hindrance of the catalyst, thereby increasing polymerization activity. In-situ polymerization also enables the carbon fibers to be more fully and evenly incorporated into the polyethylene elastomer, thereby achieving a novel composite material with excellent compressive resistance, heat resistance, and ductility. This provides a new output path for the diversified development of polyolefin composite materials and a new method for synthesizing polyolefin composite materials.

[0032] (2) The present invention uses inorganic non-metallic carbon fibers as fillers when modifying PE materials to prepare a new composite material with excellent mechanical properties.

[0033] (3) The carbon fibers and polyethylene used in the present invention each possess unique performance advantages. The high strength and high modulus of carbon fibers provide excellent load-bearing capacity, while polyethylene has good toughness and wear resistance. Combining the two can fully utilize their synergistic effects to form a new material that has both high strength, good toughness, and chemical resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 For compound C of Example 1 of the present invention 1 H NMR spectrum;

[0035] Figure 2 For compound C of Example 1 of the present invention 13 C NMR spectrum;

[0036] Figure 3 This is an X-Ray Crystallography image of Compound D of Example 1 of the present invention;

[0037] Figure 4 This is a SEM scanning electron microscope image of the modified PE material prepared in Example 5 of the present invention;

[0038] Figure 5 This is a cyclic stress-strain curve of the modified PE material prepared in Example 2 of the present invention;

[0039] Figure 6 This is a photo of the modified PE material prepared in Example 2 of the present invention after being soaked in strong acid and strong base for 30 days;

[0040] Figure 7 These are the tensile diagrams of the materials obtained from Examples 2-5 and Comparative Example 1 of the present invention (PE represents Comparative Example 1, CF-28%, CF-40%, CF-47%, and CF-52% represent Examples 2-5, respectively). DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0042] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0043] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0044] The performance test conditions of the products obtained in the following embodiments and comparative examples are as follows:

[0045] The tensile strength test used a tensile specimen with a model of (50.0 ± 5.0) mm × (4.0 ± 0.5) mm × (2.5 ± 0.2) mm and a tensile rate of 50 mm / min.

[0046] The notched cantilever beam impact strength test uses a notched cantilever beam impact strength specimen with a size of (80.0±5.0) mm×(10.0±0.5) mm×(4.0±0.2) mm. The notch is machined with a milling machine, and the notch depth is (2.0±0.2) mm.

[0047] Example 1

[0048] Preparation of nickel diimide catalyst

[0049] Step (1): Synthesis of compound A: Weigh 4-methoxyaniline (1.20 g, 10 mmol), tert-butyl substituted benzhydrol (6.51g, 21mmol) was added to a pressure-resistant bottle and placed in an oil bath at 120°C. After the two solids dissolved, zinc chloride solid (0.68g, 5mmol) was weighed and dissolved in 2ml of concentrated hydrochloric acid. The dissolved liquid was then added to the pressure-resistant bottle. The oil bath temperature was adjusted to 160°C and stirred. After the temperature reached, the reaction was continued for 0.5h. After the reaction was completed, the mixture was cooled to room temperature, extracted three times with CH2Cl2, and dried over anhydrous magnesium sulfate. The magnesium sulfate was filtered out, the filtrate was concentrated, and ethanol was added to precipitate the solid. The desired product was obtained by vacuum drying. The reaction formula is as follows:

[0050]

[0051] Step (2): Synthesis of Compound B: Compound A (3.4 g, 5 mmol) and 2,3-butanedione (0.44 g, 5 mmol) were added to 50 ml of acetonitrile solution and placed in an 80°C oil bath. After dissolution, 3 drops of acetic acid solution were added and the reaction was continued for 24 hours. The product after the reaction was concentrated and recrystallized from n-hexane solution to precipitate the solid. The product was dried in a vacuum drying oven to obtain the product. The reaction formula is as follows:

[0052]

[0053] Step (3): Synthesis of ligand C: Compound B (1.70 g, 2 mmol) and 2,6-diisopropylaniline (0.39 g, 2.2 mmol) were placed in a round-bottom flask, 100 ml of toluene solution was added, and the round-bottom flask was placed in an oil bath at 140°C, a water separator and a condenser were placed, and the drug was dissolved and refluxed for 15 minutes, and then 0.01 g of p-toluenesulfonic acid was added and the reaction was continued under reflux for 12 hours. The reactant was cooled to room temperature, concentrated, and recrystallized with n-hexane to obtain a bright yellow solid. After drying in a vacuum drying oven, the desired product C was obtained. The reaction formula is as follows: 1 H NMR spectrum, 13 C NMR spectrum Figure 1 、 Figure 2 As shown;

[0054]

[0055] Among them, R 1 It is isopropyl.

[0056] Step (4): Synthesis of the complex: Under a nitrogen atmosphere, the compound C1g synthesized in step (3) was reacted with (DME)NiBr2 in a CH2Cl2 (20 mL) solvent at room temperature (the molar ratio of compound C to (DME)NiBr2 was 1:1) for 6 h. After filtration, washing, and drying, a diimine nickel complex D with a diacetyl skeleton, i.e., a diimine nickel catalyst, was synthesized. The reaction formula is as follows:

[0057]

[0058] The X-ray Crystallography of diimine nickel complex D is shown in Figure 3 As shown;

[0059] Bond length of diimine nickel complex D Sum bond angle (°): Br(1)-Ni(1)=2.3304(5), Br(2)-Ni(1)=2.3305(5), Ni(1)-N(1)=1.995(4), Ni(1)-N(2)=2.006(4), N(1)-C(29)=1.293(6) ), N(1)-C(32)=1.458(6), N(2)-C(23)=1.455(6), N(2)-C(28)=1.292(6); Br(2)-Ni(1)-Br(1)=119.94(3), N(2)-Ni(1)-Br(1)=11 2.28(4), N(2)-Ni(1)-Br(2)=112.28(4), N(1)-Ni(1)-Br(1)=112.48(4), N(2)-Ni(1)-Br(2)=112.48(4), N(1)-Ni(1)-N(2)=80.9 4(15), C(29)-N(1)-Ni(1)=114.8(3), C(32)-N(1)-Ni(1)=123.0(3), C(29)-N(1)-C(32)=122.2(4), C(28)-N(2)-Ni(1)=114.2(3),

[0060] C(28)-N(2)-C(23)=121.4(4), C(23)-N(2)-Ni(1)=124.4(3)

[0061] The main crystallographic data are described in the following table:

[0062]

[0063]

[0064] Example 2

[0065] Preparation of modified PE material: A 350 mL thick-walled glass pressure vessel is loaded with the required amount of Et2AlCl (800 μmol), toluene (28 mL), a portion of carbon fiber with a mass of 0.5 g and a magnetic stirrer in a glove box. Connect the pressure vessel to a high-pressure polymerization line and degas the solution. Use an oil bath to heat the container to 30°C and allow it to equilibrate for 5 minutes. Use a syringe to inject the nickel diimide catalyst (2 μmol) in Example 1 above in CH2Cl2 (2 mL) into the container. Under stirring, ethylene is introduced into the reaction vessel for pressurization and maintained at 8.0 atmospheres of ethylene. After 10 minutes, the container is vented and the polymer is precipitated in acidified ethanol (ethanol / concentrated hydrochloric acid = 50:1 (volume ratio) mixture) and dried under vacuum at 50°C for 24 hours. The obtained polyethylene elastomer is a modified PE material polymerized in situ. (Its cyclic stress-strain curve is shown in Figure 2). Figure 5As shown, the sample was tested 10 times in a cycle, with a maximum strain of 300% and a reciprocating stretching rate of 75.5%, indicating that its elastic properties are excellent)

[0066] Note: The chemical formula of the nickel diimide catalyst used in this embodiment is

[0067] Example 3

[0068] Preparation of the modified PE material: A 350 mL thick-walled glass pressure vessel was placed in a glove box and charged with the required amount of Et2AlCl2 (800 μmol), toluene (28 mL), a 1.0 g portion of carbon fiber, and a magnetic stirrer. The pressure vessel was connected to a high-pressure polymerization line, and the solution was degassed. The vessel was heated to 30°C in an oil bath and allowed to equilibrate for 5 minutes. The nickel diimide catalyst (2 μmol) described in Example 1 above in CH2Cl2 (2 mL) was injected into the vessel via syringe. While stirring, the reaction vessel was pressurized with ethylene and maintained at 8.0 atmospheres for 10 minutes. The vessel was then vented, and the polymer was precipitated in acidified ethanol (ethanol / concentrated hydrochloric acid = 50:1 (volume ratio)) and dried under vacuum at 50°C for 24 hours. This yielded a polyethylene elastomer, i.e., the in situ polymerized modified PE material.

[0069] Example 4

[0070] Preparation of the modified PE material: A 350 mL thick-walled glass pressure vessel was placed in a glove box and charged with the required amount of Et2AlCl2 (800 μmol), toluene (28 mL), a 1.5 g portion of carbon fiber, and a magnetic stirrer. The pressure vessel was connected to a high-pressure polymerization line, and the solution was degassed. The vessel was heated to 30°C in an oil bath and allowed to equilibrate for 5 minutes. The nickel diimide catalyst (2 μmol) described in Example 1 above in CH2Cl2 (2 mL) was injected into the vessel via a syringe. While stirring, the reaction vessel was pressurized with ethylene and maintained at 8.0 atmospheres for 10 minutes. The vessel was then vented, and the polymer was precipitated in acidified ethanol (ethanol / concentrated hydrochloric acid = 50:1 (volume ratio)) and dried under vacuum at 50°C for 24 hours. This yielded a polyethylene elastomer, i.e., the in situ polymerized modified PE material.

[0071] Example 5

[0072] Preparation of modified PE material: A 350 mL thick-walled glass pressure vessel is loaded with the required amount of Et2AlCl (800 μmol), toluene (28 mL), a 2.0 g portion of carbon fiber and a magnetic stirrer in a glove box. The pressure vessel is connected to a high-pressure polymerization line to degas the solution. The container is heated to 30°C using an oil bath and allowed to equilibrate for 5 minutes. The nickel diimide catalyst (2 μmol) in Example 1 above in CH2Cl2 (2 mL) is injected into the container using a syringe. Under stirring, the reaction vessel is pressurized with ethylene and maintained at 8.0 atmospheres of ethylene for 10 minutes, after which the container is vented and the polymer is precipitated in acidified ethanol (a mixture of ethanol / concentrated hydrochloric acid = 50:1 (volume ratio)) and dried under vacuum at 50°C for 24 hours. The obtained polyethylene elastomer is a modified PE material polymerized in situ. The modified PE material obtained under these conditions was observed by SEM scanning electron microscopy (as shown in FIG. Figure 4 ), and found that carbon fibers were more evenly incorporated into polyethylene elastomers under in situ polymerization.

[0073] Comparative Example 1 (without adding carbon fiber)

[0074] Preparation of a comparative material: A 350 mL thick-walled glass pressure vessel was placed in a glove box and charged with the required amounts of Et2AlCl2 (800 μmol), toluene (28 mL), and a magnetic stirrer. The pressure vessel was connected to a high-pressure polymerization line, and the solution was degassed. The vessel was heated to 30°C using an oil bath and allowed to equilibrate for 5 minutes. The nickel diimide catalyst (2 μmol) described in Example 1 above in CH2Cl2 (2 mL) was injected into the vessel using a syringe. With stirring, the reaction vessel was pressurized with ethylene and maintained at 8.0 atmospheres of ethylene and 30°C for 10 minutes. The vessel was then vented, and the polymer was precipitated in acidified ethanol (ethanol / concentrated hydrochloric acid = 50:1 (volume ratio)) and dried under vacuum at 50°C for 24 hours. This produced a polyethylene elastomer.

[0075] The modified PE materials with carbon fiber doping mass ratios of 0%, 28%, 40%, 47% and 52% were obtained in Examples 2-5 and Comparative Example 1. The blending results showed that the doping was very uniform from the macroscopic morphology. The SEM observation showed that the carbon fiber doping mass ratios of 0%, 28%, 40%, 47% and 52% were obtained. The modified PE materials with carbon fiber doping mass ratios of 0%, 28%, 40%, 47% and 52% were obtained. The blending results showed that the carbon fiber doping was very uniform from the macroscopic morphology. The SEM observation showed that the carbon fiber doping mass ratios of 0%, 28% and 40% were obtained. The SEM observation showed that the carbon fiber doping mass ratios of 5% and 52% were obtained. Figure 4 ) found that carbon fibers were better doped in the gaps of polyethylene, indicating that the in-situ polymerization method enables the filler to be more evenly doped in polyethylene.

[0076] The prepared material was laminated into dumbbell-shaped specimens using a laminating machine for performance testing. The tensile and impact resistance test results are as follows: Figure 7 The test results are shown in the following table:

[0077] Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Fiber doping amount / % 0％ 28％ 40％ 47％ 52％ Tensile strength (Mpa) 5.69 12.90 16.92 21.00 22.38 Elongation at break (%) 320 1120 830 795 870 Compatibility - excellent excellent excellent excellent

[0078] Example 6

[0079] Prepare 10% H2SO4, 10% HCl, and 10% NaOH solutions by mass, place the modified PE material in Example 2 in the solution for 30 days, observe the phenomenon, and test the chemical corrosion resistance of the composite material. Figure 6 The test results and test pictures are: Figure 6 As can be seen, after immersion in a solution of 10% H2SO4, 10% HCl, and 10% NaOH by mass for 30 days, the modified PE material showed no noticeable changes, such as bubbles, on its surface, and maintained a certain degree of integrity. This indicates that the modified PE material has good chemical corrosion resistance in strong acids and alkalis.

[0080]

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. Use of a diimine nickel complex as an ethylene polymerization catalyst for preparing a modified polyethylene composite material, characterized in that: In the ethylene polymerization process, carbon fiber is also added as a modifier; the structural formula of the diimine nickel complex is shown below:

2. Use of the diimine nickel complex according to claim 1 as an ethylene polymerization catalyst for preparing a modified polyethylene composite material, characterized in that: The nickel diimide complex belongs to the orthorhombic crystal system, Pnma space group, unit cell parameters α=90°, β=90°, γ=90°.

3. Use of the diimine nickel complex according to claim 1 as an ethylene polymerization catalyst for preparing a modified polyethylene composite material, characterized in that: The preparation method of the diimine nickel complex comprises the following steps: The nickel diimide complex is obtained by reacting the nickel diimide complex with ethylene glycol dimethyl ether nickel bromide (DME) NiBr2 in dichloromethane at room temperature under an inert gas atmosphere.

4. Use of the diimine nickel complex according to claim 3 as an ethylene polymerization catalyst for preparing a modified polyethylene composite material, characterized in that: The molar ratio of the ligand to ethylene glycol dimethyl ether nickel bromide is 1:

1.

5. A method for preparing a modified polyethylene composite material using a diimine nickel complex as a catalyst, characterized in that: The following steps are involved: The co-catalyst, solvent and carbon fiber are mixed, degassed, and then a diimine nickel complex solution is added, and ethylene is introduced to react to obtain the modified polyethylene composite material. The structural formula of the diimine nickel complex is shown below:

6. The method for preparing a modified polyethylene composite material using a diimine nickel complex as a catalyst according to claim 5, characterized in that: The co-catalyst is Et2AlCl; the solvent is toluene; and the solvent of the diimine nickel complex solution is dichloromethane.

7. The method for preparing a modified polyethylene composite material using a diimine nickel complex as a catalyst according to claim 5 or 6, characterized in that: The molar ratio of the co-catalyst to the diimine nickel complex is 400:1; the reaction pressure is 8.0 atmospheres, the temperature is 30° C., and the reaction time is 10 minutes.

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