High-entropy layered metal hydroxide composite material as well as preparation method and flame-retardant and smoke-suppression application thereof

Abstract

The invention discloses a high-entropy layered metal hydroxide composite material as well as a preparation method and flame-retardant and smoke-suppression application thereof. In order to solve the problems of single component limitation and function imbalance of traditional LDHs, the component limitation of the traditional LDHs is broken through high-entropy effect design, and a flame-retardant system which is stable in wide temperature range and high in smoke suppression efficiency is constructed through cooperation of multiple metals. The high-entropy metal hydroxide flame-retardant smoke-suppression composite material for the electric wires and cables has the characteristics of efficient flame retardance, smoke suppression, greenness, high mechanical strength and the like, achieves excellent flame-retardant, smoke-suppression and toxicity-reduction effects when being used in the processing process of thermoplastic polyurethane for the electric wires and cables, and is free of pollution to the environment and human bodies.

Description

Technical Field

[0001] The present invention belongs to the field of flame retardancy, and particularly relates to a high-entropy layered metal hydroxide composite material, a preparation method thereof, and a flame retardant and smoke suppression application thereof. Background Art

[0002] As a key component in the process of power transportation, wires and cables are prone to fire hazards during long-term use of electric current due to the instability of electricity. It seriously endangers property safety while threatening life and health. To address the potential hazards of smoke toxicity and insufficient flame retardant efficiency of wires and cables in fire scenarios, the development of composite materials with high smoke suppression, low toxicity, and wide-range flame retardant adaptability has become a key focus of industry technology research. Thermoplastic polyurethane (TPU), as a high-performance polymer material with excellent physical and chemical properties, is widely used in the materials of wires and cables. However, a large amount of smoke and harmful gases will be released during the processing and use of TPU.

[0003] Currently, the methods to improve the smoke suppression performance of TPU mainly include the modification of the internal structure of the polymer, blending and adding additives, surface in-situ coating, etc. Blending and adding additives is simple to operate, has strong universality, and is the most commonly used in industrialization. The added additives need to achieve high flame retardant and smoke suppression efficiency at low addition amounts and have a low impact on the mechanical properties of the polymer matrix. Among them, environmental friendliness and price are also important considerations. In the future, the development of environmentally friendly halogen-free and highly efficient TPU smoke suppression technologies will be a research hotspot, and more environmentally friendly and efficient methods will continue to be explored and widely applied in fields such as intelligent manufacturing and sustainable development.

[0004] In the prior art, layered double hydroxides (LDHs) have been widely used in the field of flame retardant modification due to the adjustable properties of their layers and the endothermic characteristics of thermal decomposition. The domestic market size of the hydrotalcite industry reached 1.456 billion yuan in 2023, and it is expected that the global industrial-grade hydrotalcite market size will reach 320 million US dollars in 2029. LDHs are very promising advanced materials. In recent years, in the research on LDHs for flame retardant and smoke suppression of TPU, it is mainly divided into three types: LDHs and traditional flame retardants (such as ammonium polyphosphate, aluminum diethyl phosphinate) synergistically flame retard and suppress smoke of TPU (Polym. Degrad. Stab, 2022, 202: 110043. Polym. Degrad.Stab, 2019, 165: 126-136.), LDHs and highly efficient phosphorus-containing flame retardants (such as DOPO, PEI) synergistically flame retard and suppress smoke of TPU (Appl. Clay Sci., 2024, 258: 107489. Polym. Degrad. Stab, 2020, 178:109179.), LDHs and inorganic lamellar materials (such as Mxene, MoS 2)Synergistic flame retardant and smoke suppression TPU (J. Polym. Sci., 2024, 62(24): 5693-5705., Constr. Build. Mater., 2024, 457: 139478.). However, there are still some problems in the application of traditional LDHs flame retardants and smoke suppressants:

[0005] 1. Limitation of component singularity: Traditional LDHs mostly adopt double / triple metal systems (such as Mg-Al, Zn-Cu). The limited types of metal in the layer board lead to low free radical capture efficiency (smoke density grade > 70%), and the layer board is prone to collapse at high temperatures (thermal stability < 300 °C);

[0006] 2. Problem of functional imbalance: Existing solutions mostly focus on optimizing the flame retardant performance (such as the heat release rate reduction > 30%), but the inhibition rates of toxic gases such as CO and HCN are insufficient (< 50%), making it difficult to meet the dual requirements of "low smoke and low toxicity" for wires and cables;

[0007] 3. Poor process economy: Multi-metal LDHs need to be co-precipitated or ion-exchanged step by step. The process flow is complex and the precision of metal ratio regulation is low (deviation > 15%), resulting in high large-scale production costs.

[0008] In view of the above technical bottlenecks, it is urgent to break the component limitations of traditional LDHs through high-entropy effect design, and use multi-metal synergy (≥5 kinds) to construct a flame retardant system with wide-temperature stability and high smoke suppression efficiency, which is of great significance for improving the fire safety and environmental friendliness of wires and cables.

[0009] There is certain research on the patent application of high-entropy metal hydroxides. For example, the application of high-entropy metal hydroxides as working electrodes (CN118422246A, CN 119029197A) shows that high-entropy metal hydroxides are very promising, and their multi-metal synergy has high catalytic activity and stability. However, the research on the application of high-entropy metal hydroxides in flame retardancy is relatively scarce, and there is still a lack of research on their flame retardant application for high-performance TPU materials. Designing a high-entropy layered metal hydroxide as a low-loading - high flame retardant and smoke suppression efficiency smoke and toxicity reduction hybrid material for TPU as a wire and cable material has great research value. Summary of the Invention

[0010] In view of the problems existing in current wire and cable materials, such as high cost, high toxicity, and poor flame retardancy, the present invention provides a high-entropy layered metal hydroxide composite material, a preparation method thereof, and a flame retardant and smoke suppression application. The high-entropy metal hydroxide flame retardant and smoke suppression composite material of the present invention has characteristics such as high-efficiency flame retardancy, smoke suppression, environmental friendliness, and high mechanical strength. When it is used in the processing of thermoplastic polyurethane for wire and cable, excellent flame retardant and smoke suppression and toxicity reduction effects can be achieved, and it is also pollution-free to the environment and human body. The preparation process of the smoke suppression and toxicity reduction composite material of the present invention has low cost, is simple, green, highly controllable, and can be prepared in batches.

[0011] In the present invention, different from traditional flame retardants that contain a large amount of toxic elements and may have a negative impact on the environment and health and may release a large amount of toxic gases during fire combustion. Aiming at the problems existing in traditional LDHs, the present invention focuses on the dual requirements of optimizing flame retardant performance and low smoke and low toxicity, realizes multiple effects of process economy and mechanical property optimization, and completes the balance process of synergistic flame retardancy and smoke suppression and other properties. The present invention designs a high-entropy layered metal hydroxide, and uses multi-metal synergy (≥5 kinds) to construct a flame retardant system with wide-temperature stability and high smoke suppression efficiency. The above technologies are the keys to preparing polyurethane materials for wire and cable with low cost, simple and green operation, low cost, strong controllability, and high-efficiency flame retardancy and smoke suppression.

[0012] In the high-entropy layered metal hydroxide composite material of the present invention, the metal active components include multiple ones among iron, cobalt, nickel, aluminum, magnesium, manganese, and zinc.

[0013] Furthermore, the number of types of metal elements in the metal active components ≥5 kinds.

[0014] Still further, in the metal active components, the molar ratio of divalent metal to trivalent metal is 2:1 to 3:1, preferably 2:1.

[0015] Exemplarily, in the metal active components, the ratio of iron, aluminum, nickel, cobalt, and magnesium is 1:1:2:2:2, the ratio of iron, aluminum, nickel, cobalt, and manganese is 1:1:2:2:2, and the ratio of iron, aluminum, nickel, cobalt, and zinc is 1:1:2:2:2.

[0016] Still further, the metal active components are selected from NiCoFeAlMg, NiCoFeAlMn, or NiCoFeAlZn.

[0017] Furthermore, the high-entropy layered metal hydroxide presents a granular structure or a lamellar structure, and the particle size is 50 - 200 nm.

[0018] The preparation method of the high-entropy layered metal hydroxide composite material of the present invention includes the following steps:

[0019] Step 1: Mix and dissolve a divalent metal salt and a trivalent metal salt in deionized water to obtain a mixed metal salt solution;

[0020] Step 2: Add a precipitating agent to the mixed metal salt solution obtained in Step 1, and continuously stir within the temperature range of 25 - 30 °C to obtain a suspension;

[0021] Step 3: Transfer the suspension obtained in Step 2 to a high-pressure reaction kettle, carry out a hydrothermal reaction at 100 °C - 150 °C, filter to obtain a precipitate product, wash it with ethanol and deionized water, and dry it to obtain a high-entropy layered metal hydroxide.

[0022] In Step 1, the divalent metal salt and the trivalent metal salt are chlorides of metal active components, such as magnesium chloride, cobalt chloride, nickel chloride, iron chloride, aluminum chloride, etc. The molar ratio of the divalent metal salt to the trivalent metal salt is between 2:1 and 3:1.

[0023] In Step 2, the precipitating agent is one or more of an aqueous sodium hydroxide solution and an aqueous sodium carbonate solution. The molar ratio of the amount of the precipitating agent added to the metal salt is between 2:1 and 4:1.

[0024] The present invention also provides a method for preparing an organic phosphate radical in-situ intercalated high-entropy layered metal hydroxide composite material, including the following steps:

[0025] Step 1: Mix and dissolve a divalent metal salt and a trivalent metal salt in deionized water to obtain a mixed metal salt solution;

[0026] Step 2: Add an organic phosphate radical compound and a precipitating agent to the mixed metal salt solution obtained in Step 1, and continuously stir within the temperature range of 25 - 30 °C to obtain a suspension;

[0027] Step 3: Transfer the suspension obtained in Step 2 to a high-pressure reaction kettle, carry out a hydrothermal reaction at 100 °C - 150 °C, filter to obtain a precipitate product, wash it with ethanol and deionized water, and dry it to obtain a high-entropy layered metal hydroxide.

[0028] In Step 1, the divalent metal salt and the trivalent metal salt are chlorides of metal active components, such as magnesium chloride, cobalt chloride, nickel chloride, iron chloride, aluminum chloride, etc. The molar ratio of the divalent metal salt to the trivalent metal salt is between 2:1 and 3:1.

[0029] In Step 2, the organic phosphate radical compound is phenylphosphinic acid (PPA) or diphenylphosphoric acid (DPA).

[0030] In Step 2, the precipitating agent is one or more of an aqueous sodium hydroxide solution and an aqueous sodium carbonate solution.

[0031] The molar ratio of the precipitant addition amount to the metal salt is between 2:1 and 4:1, and the molar ratio of the organic phosphate group to the metal salt is between 1:2 and 1:2.

[0032] The application of the high-entropy layered metal hydroxide composite material of the present invention is to add the high-entropy layered metal hydroxide as an auxiliary agent to thermoplastic polyurethane to improve the flame retardancy and smoke suppression performance of the composite material.

[0033] The application of the organic phosphate group in-situ intercalated high-entropy layered metal hydroxide composite material of the present invention is to add the organic phosphate group in-situ intercalated high-entropy layered metal hydroxide composite material as an auxiliary agent to thermoplastic polyurethane to improve the flame retardancy and smoke suppression performance of the composite material.

[0034] Further, when adding the high-entropy layered metal hydroxide as an additive to thermoplastic polyurethane, a melt blending method is used to construct a TPU composite material. The steps include:

[0035] (1) The TPU masterbatch is dried in an oven to remove moisture.

[0036] (2) The dried TPU masterbatch is added to a mixer for melting, and then the high-entropy layered metal hydroxide or the organic phosphate group in-situ intercalated high-entropy layered metal hydroxide composite material is added and mixed evenly to obtain a TPU composite material.

[0037] (3) The TPU composite material is hot-pressed on a flat vulcanizer to obtain regular plates.

[0038] Further, the addition amount of the high-entropy layered metal hydroxide or the organic phosphate group in-situ intercalated high-entropy layered metal hydroxide composite material is 1-3 wt% of the total mass of the polymer composite material.

[0039] The beneficial effects of the present invention are reflected in:

[0040] 1. Aiming at the problems of single-component limitation and functional imbalance of traditional LDHs, the present invention breaks the component limitation of traditional LDHs through high-entropy effect design, constructs an electron-rich structure using a multi-metal system, and through scientific interface regulation, constructs nano-fillers with multiple oxygen vacancies and metal defects. Through the high-entropy effect and slow diffusion effect, it has high activity, high structural stability, and component tunability, which is beneficial to the inhibition of pyrolysis products and the adsorption of toxic gases during combustion. Through efficient synergistic action for flame retardancy, it is used to prepare polyurethane composites, achieving low addition amount and high smoke suppression-flame retardancy efficiency.

[0041] 2. The composite material of the present invention is prepared by a one-step hydrothermal method, which has a short process route, uses inexpensive raw materials and does not involve flammable, explosive or hazardous reagents. The process is controllable, and the accuracy of metal ratio regulation is high, which has great reference significance for industrial production. When it is used in the processing and production of thermoplastic polyurethane elastomers for wire and cable, it can meet the dual requirements of high-efficiency flame retardancy optimization and low smoke and low toxicity, achieve multiple effects of process economy and mechanical property optimization, and is safe, environmentally friendly, can reduce environmental pollution, and can be used in the practical application of wire and cable.

[0042] 3. The preparation process of the present invention is simple, green, and has low production cost. The process is simple and has high efficiency. It constructs a flame retardant system with wide temperature range stability and high smoke suppression efficiency, has strong controllability, no "three wastes" pollution, requires less equipment investment, and the product is convenient to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0045] Figure 1 XRD pattern of NiFeCoAlMg high-entropy LDHs prepared in Example 1.

[0046] Figure 2 SEM images of NiFeCoAlMg, NiFeCoAlMn and NiFeCoAlZn high-entropy LDHs prepared in Examples 1-3 and Ni-Fe LDHs prepared in Comparative Example 1; a, b are SEM images of Ni-Fe LDHs, the material is rod-shaped, with a size of 100-200 nm; c, d are SEM images of NiFeCoAlMg, the material is rod-shaped, with a size of 1-5 μm; e, f are SEM images of NiFeCoAlMn, the material is a stacked lamellar structure, with a size of 30-100 nm; g, h are SEM images of NiFeCoAlZn, the material is a stacked lamellar structure, with a size of 100-500 nm.

[0047] Figure 3 N 2 adsorption and desorption diagram.

[0048] Figure 4 Microcalorimetry test results of the materials obtained by compounding NiFeCoAlMg high-entropy LDHs prepared in Example 1 with different proportions of TPU; the material with an addition amount of 3wt% has the lowest peak heat release, and an addition amount of 3wt% is preferably used for test research.

[0049] Figure 5 Cone calorimeter test results of NiFeCoAlMg, NiFeCoAlMn, and NiFeCoAlZn high-entropy LDHs prepared in Examples 1-3 and Ni-Fe LDHs prepared in Comparative Example 1 at 35 kW; a is the heat release rate curve of the material, b is the total heat release curve, c is the smoke release rate curve, d is the total smoke release curve, e is the CO generation rate curve, f is the CO 2 generation rate curve; the addition of high-entropy LDHs significantly reduces the heat release and smoke release of the composite material. Compared with Ni-Fe LDHs, the effect is further improved; NiFeCoAlMn / TPU has the best effect, with the peak heat release reduced by up to 40.76%, the total heat release reduced by 22.32%, and the total smoke release reduced by 45.79%. It is proved that the addition of high-entropy LDHs significantly reduces both the smoke and heat release of the polyurethane composite material.

[0050] Figure 6 Combustion smoke density test results of NiFeCoAlMg, NiFeCoAlMn, and NiFeCoAlZn high-entropy LDHs prepared in Examples 1-3 and Ni-Fe LDHs prepared in Comparative Example 1 at 25 kW; a is the smoke density curve of the material, b is the bar chart of the maximum smoke release value, c is the bar chart of the time to reach the maximum smoke release value. Before intercalation, the addition of high-entropy LDHs also reduces the combustion smoke density of the composite material. NiFeCoAlMn / TPU has the best effect, with a reduction of 13.5%, but the addition of all materials will cause premature combustion of TPU.

[0051] Figure 7 Tensile test data of NiFeCoAlMg, NiFeCoAlMn, and NiFeCoAlZn high-entropy LDHs prepared in Examples 1-3 and Ni-Fe LDHs prepared in Comparative Example 1. a is the tensile property diagram, b is the maximum tensile strength, and c is the elongation at break. Due to uneven distribution, the addition of high-entropy LDHs reduces the mechanical properties of the material.

[0052] Figure 8Cone calorimeter test results of NiFeCoAlMg / DPA, NiFeCoAlMn / DPA, NiFeCoAlZn / DPA, NiFeCoAlMg / PPA, NiFeCoAlMn / PPA and NiFeCoAlZn / PPA intercalated high-entropy LDHs prepared in Examples 4-9 at 35 kW; a is the heat release rate curve of the material, b is the total heat release curve, c is the smoke release rate curve, d is the total smoke release curve. After intercalating the high-entropy LDHs, the heat release and smoke release of the composite materials are further reduced. Among them, the effect of NiCoFeAlZn / PPA / TPU is the best, with the peak heat release reduced by up to 42.09% and the total smoke release reduced by 48.55%, indicating that the intercalation of organic acid radicals further improves the fire safety performance of the materials.

[0053] Figure 9 Combustion smoke density test results of NiFeCoAlMg / DPA, NiFeCoAlMn / DPA, NiFeCoAlZn / DPA, NiFeCoAlMg / PPA, NiFeCoAlMn / PPA and NiFeCoAlZn / PPA intercalated high-entropy LDHs prepared in Examples 4-9 at 25 kW; a is the smoke density curve of the material, b is the bar chart of the maximum smoke release, c is the bar chart of the time to reach the maximum smoke release. After intercalation, the smoke suppression effect of the high-entropy LDHs is significantly improved, with the maximum reduction of 61.6%, reflecting the excellent smoke and toxicity suppression effect of the intercalated high-entropy LDHs on the materials.

[0054] Figure 10 Tensile test data of NiFeCoAlMg / DPA, NiFeCoAlMn / DPA, NiFeCoAlZn / DPA, NiFeCoAlMg / PPA, NiFeCoAlMn / PPA and NiFeCoAlZn / PPA intercalated high-entropy LDHs prepared in Examples 4-9; a is the tensile property diagram, b is the maximum tensile strength, c is the elongation at break. After intercalating the materials, due to the presence of organic acid radicals, the mechanical properties of the materials are improved to a certain extent, indicating that the addition of organic acid radicals is beneficial to maintaining the overall performance of the materials.

[0055] Figure 11Cross-sectional scanning electron microscope images of the distribution of NiFeCoAlMg, NiFeCoAlMn, and NiFeCoAlZn high-entropy LDHs prepared in Examples 1-3 and Ni-Fe LDHs prepared in Comparative Example 1 in the TPU material. a, b, and c are SEM images of the quenched cross-section of TPU, and the cross-section is very smooth; d, e, and f are SEM images of the quenched cross-section of Ni-Fe LDHs / TPU, and there are a large number of pores on the cross-section, which affect the mechanical properties of the material; g, h, and i are SEM images of the quenched cross-section of NiFeCoAlMg / TPU, and the pores are significantly smaller; j, k, and l are SEM images of the quenched cross-section of NiFeCoAlMn / TPU, and the pores become smaller; m, n, and o are SEM images of the quenched cross-section of NiFeCoAlZn / TPU, and the pores become smaller, but still affect the mechanical properties.

[0056] Figure 12 Raman spectra of the char residues formed after combustion of the composites of NiFeCoAlMg, NiFeCoAlMn, and NiFeCoAlZn high-entropy LDHs and NiFeCoAlMg / PPA, NiFeCoAlMn / PPA, and NiFeCoAlZn / PPA intercalated high-entropy LDHs prepared in Examples 1-9 and Ni-Fe LDHs prepared in Comparative Example 1 in the TPU material. a is the Raman spectrum of the TPU char residue, I D / I G is 3.17, b is the Raman spectrum of the NiFeCoAlMg / TPU char residue, I D / I G is 4.11, c is the Raman spectrum of the NiFeCoAlMnTPU char residue, I D / I G is 4.03, d is the Raman spectrum of the NiFeCoAlZn / TPU char residue, I D / I G is 3.34, e is the Raman spectrum of the NiFeCoAlMg / DPA / TPU char residue, I D / I G is 3.05, f is the Raman spectrum of the NiFeCoAlMg / DPA / TPU char residue, I D / I G is 3.67, g is the Raman spectrum of the NiFeCoAlMg / DPA / TPU char residue, I D / I G is 3.98. I D / I G The larger the I

[0057] Figure 13SEM images of the carbon residues after combustion of the NiFeCoAlMg, NiFeCoAlMn, and NiFeCoAlZn high-entropy LDHs prepared in Examples 1-3 and the Ni-Fe LDHs prepared in Comparative Example 1 after being compounded in the TPU material. a, b, and c are SEM images of the TPU carbon residues, and the carbon residues are broken and loose; d, e, and f are SEM images of the Ni-Fe LDHs / TPU carbon residues; g, h, and i are SEM images of the NiFeCoAlMg / TPU carbon residues; j, k, and l are SEM images of the NiFeCoAlMn / TPU carbon residues; m, n, and o are SEM images of the NiFeCoAlZn / TPU carbon residues, and the carbon residues become dense. Detailed implementation manners

[0058] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following detailed description of the specific implementation manners of the present invention will be given in conjunction with the accompanying drawings. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0059] Unless otherwise indicated or shown in the operating examples, all numbers representing the amounts of components, physical and chemical properties, etc. used in the specification and claims are understood to be adjusted by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters listed in the above specification and the appended claims are approximate values, and those skilled in the art can appropriately change these approximate values in seeking to obtain the desired characteristics using the teachings disclosed herein. The use of numerical ranges expressed by endpoints includes all numbers within that range and any range within that range. For example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0060] Specifically, it includes the following steps:

[0061] S1. Prepare high-entropy layered metal hydroxides by combining the coprecipitation method and the hydrothermal method;

[0062] S11. Mix magnesium chloride, cobalt chloride, nickel chloride, iron chloride, and aluminum chloride (the molar ratio of divalent metal salts to trivalent metal salts is between 2:1 and 3:1, and the total metal salt content is 0.16 - 0.2 mol) and dissolve them in deionized water solution; use sodium hydroxide aqueous solution and / or sodium carbonate aqueous solution as a precipitating agent and add it to the mixed chloride salt solution, and continuously stir within the temperature range of 25 - 30 °C; exemplarily, magnesium chloride is 0.04 mol, cobalt chloride is 0.04 mol, nickel chloride is 0.04 mol, iron chloride is 0.02 mol, and aluminum chloride is 0.02 mol.

[0063] S12. Transfer the above suspension to a high-pressure reactor and carry out a hydrothermal reaction at 100 °C - 150 °C. Filter to obtain a precipitate product, wash it with ethanol and deionized water, collect the precipitate product, and dry it in a forced-air oven to prepare NiFeCoAlMg high-entropy LDHs.

[0064] S13. The preparation methods of NiFeCoAlMn high-entropy LDHs and NiFeCoAlZn high-entropy LDHs are similar, but there are certain differences in the selected metals. NiFeCoAlMn high-entropy LDHs select Ni, Fe, Co, Al, and Mn; NiFeCoAlZn high-entropy LDHs select Ni, Fe, Co, Al, and Zn.

[0065] S2. Use a phosphorus-containing organic acid to carry out in-situ intercalation on the high-entropy LDHs to prepare an organic acid root intercalated high-entropy LDHs.

[0066] S21. Select phenylphosphinic acid (PPA) and diphenylphosphoric acid (DPA) as the organic phosphate groups to carry out in-situ intercalation on the high-entropy layered metal hydroxide.

[0067] S22. Mix magnesium chloride, cobalt chloride, nickel chloride, iron chloride, and magnesium chloride (the molar ratio of divalent metal salts to trivalent metal salts is between 2:1 and 3:1, and the total metal salt content is 0.16 - 0.2 mol) and dissolve them in deionized water solution; use a sodium hydroxide solution containing organic phosphate groups and sodium carbonate aqueous solution as a precipitating agent and add it to the mixed chloride salt solution, and continuously stir within the temperature range of 25 - 30 °C; exemplarily, magnesium chloride is 0.04 mol, cobalt chloride is 0.04 mol, nickel chloride is 0.04 mol, iron chloride is 0.02 mol, aluminum chloride is 0.02 mol, and phenylphosphinic acid is 0.1 mol.

[0068] S23. Transfer the above suspension to a high-pressure reactor and carry out a hydrothermal reaction at 100 °C - 150 °C. Filter to obtain a precipitate product, wash it with ethanol and deionized water, collect the precipitate product, dry it in a forced-air oven, and prepare PPA-intercalated NiFeCoAlMg high-entropy LDHs, denoted as NiFeCoAlMg / PPA.

[0069] S24. The preparation methods of DPA-intercalated high-entropy LDHs and PPA-intercalated high-entropy LDHs are similar. The selected organic phosphate group is changed from phenylphosphinic acid (PPA) to diphenylphosphoric acid (DPA) to prepare DPA-intercalated NiFeCoAlMg high-entropy LDHs, denoted as NiFeCoAlMg / DPA.

[0070] S25. The preparation methods of organic phosphate-intercalated NiFeCoAlMn high-entropy LDHs and NiFeCoAlZn high-entropy LDHs are similar, but there are certain differences in the selected metals. For NiFeCoAlMn high-entropy LDHs, Ni, Fe, Co, Al, and Mn are selected, denoted as NiFeCoAlMn / PPA and NiFeCoAlMn / DPA; for NiFeCoAlZn high-entropy LDHs, Ni, Fe, Co, Al, and Zn are selected, denoted as NiFeCoAlZn / PPA and NiFeCoAlZn / DPA.

[0071] The following examples more specifically describe the content disclosed in the present invention. These examples are only for illustrative purposes, because various modifications and changes within the scope of the present invention are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0072] Example 1:

[0073] Select chloride salts of different metal precursors to prepare high-entropy LDHs. Taking the preparation of NiFeCoAlMg high-entropy LDHs as an example, the metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and magnesium chloride hexahydrate.

[0074] 1. Mix aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and magnesium chloride hexahydrate in a certain proportion (the molar ratio of divalent metal salt to trivalent metal salt is between 2:1 and 3:1, and the total metal salt content is 0.16 - 0.2 mol). Dissolve them in 200 ml of deionized water, and continuously stir to mix evenly. The stirring rate is 300 rpm, the stirring temperature is 25 °C, and the stirring time is 1 h. Denote this mixed solution as solution A.

[0075] 2. Dissolve 6 g of sodium hydroxide in 100 ml of deionized water. The stirring rate is 300 rpm, the stirring temperature is 25 °C, and the stirring time is 1 h. Denote this mixed solution as solution B.

[0076] 3. Dissolve 15.9 g of sodium carbonate in 100 ml of deionized water. The stirring rate is 300 rpm, the stirring temperature is 25 °C, and the stirring time is 1 h. Denote this mixed solution as solution C.

[0077] 4. Slowly add and dissolve solution A and solution B into solution C while maintaining the pH value of solution C at 10. The stirring rate for the whole reaction is 300 rpm, the stirring temperature is 25 °C, and the reaction stirring time is 10 min. Take 400 ml of the suspension produced by the coprecipitation reaction and transfer it to a Teflon-lined stainless-steel autoclave for hydrothermal reaction at 120 °C for 12 h. After the hydrothermal reaction, collect the precipitate product by centrifugation, wash it with ethanol and deionized water until the pH is approximately equal to 7. The centrifugation speed is 6000 rpm, and the centrifugation time is 5 min. Collect the obtained precipitate product and place it in a blast drying oven to dry for 12 h at a temperature of 60 °C. Obtain NiFeCoAlMg high-entropy LDHs.

[0078] Example 2:

[0079] Example 2 is basically the same as Example 1, and the main difference is that there are certain differences in the metal salt precursors, which are synthesized by changing the metal salts according to the stoichiometric ratio. The metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and manganese chloride tetrahydrate. Obtain NiFeCoAlMn high-entropy LDHs.

[0080] Example 3:

[0081] Example 3 is basically the same as Example 1, and the main difference is that there are certain differences in the metal salt precursors, which are synthesized by changing the metal salts according to the stoichiometric ratio. The metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and zinc chloride. Obtain NiFeCoAlZn high-entropy LDHs.

[0082] Example 4:

[0083] The high-entropy LDH is intercalated with a phosphorus-containing organic acid root to achieve high flame retardancy and maintain tensile properties. Phenylphosphinic acid (PPA) is selected for in-situ intercalation experiment of LDH. Taking the intercalated NiFeCoAlMg high-entropy LDH as an example. The metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate and magnesium chloride hexahydrate.

[0084] 1. Mix magnesium chloride hexahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate and aluminum chloride nonahydrate in a certain proportion (the molar ratio of divalent metal salt to trivalent metal salt is between 2:1 and 3:1, and the total metal salt content is 0.16 - 0.2 mol), dissolve them in 200 ml of deionized water, and continuously stir to mix evenly. The stirring rate is 300 rpm, the stirring temperature is 25 °C, and the stirring time is 1 h. This mixed solution is denoted as solution A.

[0085] 2. Dissolve 6 g of sodium hydroxide in 100 ml of deionized water, add phenylphosphinic acid PPA (the molar ratio of phenylphosphinic acid to LDH metal is 0.5 - 2), the stirring rate is 300 rpm, the stirring temperature is 25 °C, and the stirring time is 1 h. This mixed solution is denoted as solution B.

[0086] 3. Dissolve 15.9 g of sodium carbonate in 100 ml of deionized water, the stirring rate is 300 rpm, the stirring temperature is 25 °C, and the stirring time is 1 h. This mixed solution is denoted as solution C.

[0087] 4. Slowly add and dissolve solution A and solution B into solution C, while maintaining the pH value of solution C at 10. The stirring rate of the whole reaction is 300 rpm, the stirring temperature is 25 °C, and the reaction stirring time is 10 min. Take 400 ml of the suspension produced by the coprecipitation reaction, transfer it to a Teflon-lined stainless steel autoclave, and carry out a hydrothermal reaction at 120 °C for 12 h. After the hydrothermal reaction, collect the precipitate product by centrifugation, wash it with ethanol and deionized water until the pH is approximately equal to 7. The centrifugation speed is 6000 rpm, the centrifugation time is 5 min, collect the obtained precipitate product, and place it in a blast drying oven to dry for 12 h at a temperature of 60 °C. Obtain PPA-intercalated NiFeCoAlMg high-entropy LDHs, denoted as NiCoFeAlMg / PPA.

[0088] Example 5:

[0089] Example 5 is basically the same as Example 4, and the main difference lies in the difference in the phosphorus-containing organic acid. Diphenylphosphoric acid (DPA) was selected to conduct an in-situ intercalation experiment on LDH. The metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and magnesium chloride hexahydrate. DPA-intercalated NiFeCoAlMg high-entropy LDHs were obtained, denoted as NiCoFeAlMg / DPA.

[0090] Example 6:

[0091] Example 6 is basically the same as Example 4, and the main difference lies in the difference in the metal salt precursors. Synthesis was carried out by changing the metal salts according to the stoichiometric ratio. The metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and manganese chloride tetrahydrate. The selected organic phosphate groups are the same, all phenylphosphinic acid (PPA). PPA-intercalated NiFeCoAlMn high-entropy LDHs were obtained, denoted as NiCoFeAlMn / PPA.

[0092] Example 7:

[0093] Example 7 is basically the same as Example 5, and the main difference lies in the difference in the metal salt precursors. Synthesis was carried out by changing the metal salts according to the stoichiometric ratio. The metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and manganese chloride tetrahydrate. The selected organic phosphate groups are the same, all diphenylphosphoric acid (DPA). DPA-intercalated NiFeCoAlMn high-entropy LDHs were obtained, denoted as NiCoFeAlMn / DPA.

[0094] Example 8:

[0095] Example 8 is basically the same as Example 4, and the main difference lies in the difference in the metal salt precursors. Synthesis was carried out by changing the metal salts according to the stoichiometric ratio. The metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and zinc chloride. The selected organic phosphate groups are the same, all phenylphosphinic acid (PPA). PPA-intercalated NiFeCoAlZn high-entropy LDHs were obtained, denoted as NiFeCoAlZn / PPA.

[0096] Example 9:

[0097] Example 9 is basically the same as Example 5, and the main difference lies in the difference in the metal salt precursors. Synthesis was carried out by changing the metal salts according to the stoichiometric ratio. The metal salt precursors include aluminum chloride nonahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate, iron chloride nonahydrate, and zinc chloride. The selected organic phosphate groups are the same, all diphenylphosphoric acid (DPA). DPA-intercalated NiFeCoAlZn high-entropy LDHs were obtained, denoted as NiFeCoAlZn / DPA.

[0098] Comparative Example 1:

[0099] Comparative Example 1 is basically the same as Example 1, and the main difference lies in the metal salt precursors, which include nickel chloride hexahydrate and iron chloride nonahydrate. The prepared NiFe-LDH was compared with the other high-entropy LDHs in terms of effects.

[0100] Experimental Example 1:

[0101] The NiFeCoAlMg-LDH high-entropy LDHs prepared in Example 1 were analyzed by an XRD diffractometer. The composite sample of NiFeCoAlMg-LDH has the mixed characteristic peaks of NiFe LDH (PDF#40-0215), CoFe LDH (PDF#50-0235), and NiAl LDH (PDF#15-0087), indicating the successful preparation of NiFeCoAlMg high-entropy LDHs, which contain different LDHs.

[0102] Experimental Example 2:

[0103] The morphologies of the NiFeCoAlMg, NiFeCoAlMn, and NiFeCoAlZn high-entropy LDHs prepared in Examples 1-3 and the Ni-Fe LDHs prepared in Comparative Example 1 were analyzed by scanning electron microscopy. The Ni-Fe LDHs and NiFeCoAlMg high-entropy LDHs are rod-shaped structures with sizes ranging from 100 to 200 nm, and the NiFeCoAlMn and NiFeCoAlZn high-entropy LDHs are stacked lamellar structures with sizes ranging from 50 to 100 nm.

[0104] Experimental Example 3:

[0105] The specific surface areas and pore size distributions of the NiFeCoAlMg, NiFeCoAlMn, and NiFeCoAlZn high-entropy LDHs prepared in Examples 1-3 and the Ni-Fe LDHs prepared in Comparative Example 1 were analyzed by N 2 adsorption-desorption. The four synthesized LDHs are all mesoporous materials, and the N 2 adsorption-desorption diagrams are all type-IV hysteresis loops. The hysteresis loops of the Ni-Fe LDHs and NiFeCoAlMg high-entropy LDHs are the same, both being H3-type hysteresis loops, corresponding to the pores generated by stacked irregular rods. The hysteresis loops of the NiFeCoAlMn and NiFeCoAlZn high-entropy LDHs are the same, both being H4-type hysteresis loops, corresponding to the pores of irregular lamellae. The analysis results are the same as the conclusions of the scanning electron microscopy data.

[0106] Experimental Example 4:

[0107] The smoke suppression and toxicity reduction hybrid material is added to thermoplastic polyurethane as an additive. The composite material is constructed by melt blending method. After drying the TPU masterbatch, it is melted in a mixer, and then the LDHs smoke suppressant is added and mixed evenly to obtain the TPU composite material. The composite material is hot pressed on a flat vulcanizer to obtain regular plates.

[0108] (1)Dry the TPU masterbatch in an oven for 6 h to remove moisture for later use;

[0109] (2)Melt the dried TPU masterbatch in a mixer. The temperature of the mixer is 180 °C and the rotation speed is 140 rpm. After the TPU is melted, add the prepared LDHs smoke suppressant into the mixer under stirring conditions. The addition amount of the smoke suppressant is 3 wt%, and stir for 5 minutes to mix evenly, then the TPU composite material can be obtained.

[0110] (3)Hot press the obtained irregular TPU composite material to obtain regular plates. The specific material size and standard are determined according to the national standard of combustion test. The hot pressing process is carried out on a flat vulcanizer. The hot pressing temperature is 185 °C, the pressure is 10 MPa, the preheating time is 3 - 5 min, and the hot pressing time is 1 - 3 min.

[0111] The smoke suppressant materials are respectively selected from the Ni-Fe LDH powder prepared in Comparative Example 1, the NiFeCoAlMg-LDH powder prepared in Example 1, the NiFeCoAlMn-LDH powder prepared in Example 2, the NiFeCoAlZn-LDH powder prepared in Example 3, the NiCoFeAlMg / PPA powder prepared in Example 4, the NiCoFeAlMg / DPA powder prepared in Example 5, the NiCoFeAlMn / PPA powder prepared in Example 6, the NiCoFeAlMn / DPA powder prepared in Example 7, the NiCoFeAlZn / PPA powder prepared in Example 8, and the NiCoFeAlZn / DPA powder prepared in Example 9.

[0112] According to different smoke suppressant materials, the prepared composite materials are named Ni-Fe LDH / TPU, NiFeCoAlMg-LDH / TPU, NiFeCoAlMn-LDH / TPU, NiFeCoAlZn-LDH / TPU, NiCoFeAlMg / PPA / TPU, NiCoFeAlMg / DPA / TPU, NiCoFeAlMn / PPA / TPU, NiCoFeAlMn / DPA / TPU, NiCoFeAlZn / PPA / TPU, and NiCoFeAlZn / DPA / TPU.

[0113] The flame-retardant TPU composites prepared (Ni-Fe LDH / TPU, NiFeCoAlMg-LDH / TPU, NiFeCoAlMn-LDH / TPU, NiFeCoAlZn-LDH / TPU, NiCoFeAlMg / PPA / TPU, NiCoFeAlMg / DPA / TPU, NiCoFeAlMn / PPA / TPU, NiCoFeAlMn / DPA / TPU, NiCoFeAlZn / PPA / TPU, and NiCoFeAlZn / DPA / TPU) and the TPU material were tested for heat release rate, total heat release, smoke release rate, and total smoke release on a cone calorimeter at 35 kW. See Figure 5 and Figure 8 As shown, it shows the influence of different smoke suppressants on the combustion process of the TPU material. The addition of high-entropy LDHs significantly reduces the heat release and smoke release of the composite material. Compared with Ni-Fe LDHs, the effect is further improved; the effect of NiFeCoAlMn / TPU is the best, with the peak heat release reduced by up to 40.76%, the total heat release reduced by 22.32%, and the total smoke release reduced by 45.79%. It proves that the addition of high-entropy LDHs significantly reduces both the smoke and heat of the polyurethane composite material. When the high-entropy LDHs are intercalated, the heat release and smoke release of the composite material are further reduced. Among them, the effect of NiCoFeAlZn / PPA / TPU is the highest, with the peak heat release reduced by up to 42.09% and the total smoke release reduced by 48.55%, indicating that the intercalation of organic acid radicals further improves the fire safety performance of the material.

[0114] Experimental Example 5:

[0115] The combustion smoke density of the flame-retardant TPU composites prepared in Experimental Example 4 (Ni-Fe LDH / TPU, NiFeCoAlMg-LDH / TPU, NiFeCoAlMn-LDH / TPU, NiFeCoAlZn-LDH / TPU, NiCoFeAlMg / PPA / TPU, NiCoFeAlMg / DPA / TPU, NiCoFeAlMn / PPA / TPU, NiCoFeAlMn / DPA / TPU, NiCoFeAlZn / PPA / TPU, and NiCoFeAlZn / DPA / TPU) was tested. See the smoke density curves of the composite materials shown in Appendix Figure 6 and Appendix Figure 9 Before intercalation, the addition of high-entropy LDHs also reduces the combustion smoke density of the composite material. The effect of NiFeCoAlMn / TPU is the best, reducing it by 13.5%; after intercalation, the smoke suppression effect of high-entropy LDHs is significantly improved, reducing it by up to 61.6%, reflecting the excellent smoke and toxicity suppression effect of the intercalated high-entropy LDHs on the material.

[0116] Experimental Example 6:

[0117] The smoke density during combustion of the flame-retardant TPU composites prepared in Experimental Example 4 (Ni-Fe LDH / TPU, NiFeCoAlMg-LDH / TPU, NiFeCoAlMn-LDH / TPU, NiFeCoAlZn-LDH / TPU, NiCoFeAlMg / PPA / TPU, NiCoFeAlMg / DPA / TPU, NiCoFeAlMn / PPA / TPU, NiCoFeAlMn / DPA / TPU, NiCoFeAlZn / PPA / TPU, and NiCoFeAlZn / DPA / TPU) was tested. See the smoke density curves of the composites shown in Appendix Figure 6 and Appendix Figure 9 Before intercalation, the addition of high-entropy LDHs also reduced the combustion smoke density of the composites. The effect of NiFeCoAlMn / TPU was the best, reducing it by 13.5%. After intercalation, the smoke suppression effect of high-entropy LDHs was significantly improved, with a maximum reduction of 61.6%, demonstrating the excellent smoke and toxicity suppression effect of the intercalated high-entropy LDHs on the material.

[0118] Experimental Example 7:

[0119] The mechanical properties of the flame-retardant TPU composites prepared in Experimental Example 4 (Ni-Fe LDH / TPU, NiFeCoAlMg-LDH / TPU, NiFeCoAlMn-LDH / TPU, NiFeCoAlZn-LDH / TPU, NiCoFeAlMg / PPA / TPU, NiCoFeAlMg / DPA / TPU, NiCoFeAlMn / PPA / TPU, NiCoFeAlMn / DPA / TPU, NiCoFeAlZn / PPA / TPU, and NiCoFeAlZn / DPA / TPU) were tested by tensile test. See the mechanical curves of the composites shown in Appendix Figure 7 and Appendix Figure 10 Due to uneven distribution, the addition of high-entropy LDHs reduced the mechanical properties of the material. After intercalation of the material, due to the presence of organic acid radicals, the mechanical properties of the material were improved to a certain extent, indicating that the addition of organic acid radicals is beneficial to maintaining the overall properties of the material. The cross-section of the flame-retardant TPU composites prepared in Experimental Example 4 was tested by scanning electron microscopy. See Figure 11As can be seen from the mechanical curve of the composite material shown, due to uneven distribution, a large number of pores exist in the material with the addition of Ni-Fe LDH, which affects its mechanical properties; due to the metal dislocation effect with the addition of high-entropy LDHs, different lattice spacings result in a slight improvement in the mechanical properties of the material, but there is still a certain decrease compared to pure TPU. After organic acid root intercalation in the material, the addition of organic acid roots promotes the dispersion of the material, which is beneficial to the improvement of the mechanical properties. Organic acid root intercalated high-entropy LDHs can achieve high flame retardancy and retention of tensile strength at high filling levels.

[0120] Experimental Example 8:

[0121] The char residues after combustion of the flame-retardant TPU composite materials (Ni-Fe LDH / TPU, NiFeCoAlMg-LDH / TPU, NiFeCoAlMn-LDH / TPU, NiFeCoAlZn-LDH / TPU, NiCoFeAlMg / PPA / TPU, NiCoFeAlMg / DPA / TPU, NiCoFeAlMn / PPA / TPU, NiCoFeAlMn / DPA / TPU, NiCoFeAlZn / PPA / TPU, and NiCoFeAlZn / DPA / TPU) prepared in Experimental Example 4 were subjected to scanning electron microscopy (SEM) testing and Raman spectroscopy testing. Refer to Figure 12 and Figure 13 the SEM images and Raman spectra of the char residues shown. As can be seen from the figures, the addition of high-entropy LDHs makes the char residues after combustion of the material denser, which is beneficial to forming a barrier to achieve the flame-retardant effect. The result of I D / I G in the Raman spectrum can also prove this point. The larger the I D / I G , the higher the graphitization degree of the char residue, which is beneficial to forming a barrier during combustion.

[0122] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a high entropy layered metal hydroxide composite material, characterized in that The steps include: Step 1: Mix and dissolve a divalent metal salt and a trivalent metal salt in deionized water to obtain a mixed metal salt solution; Step 2: adding a precipitant to the mixed metal salt solution obtained in step 1, stirring continuously at a temperature range of 25-30° C. to obtain a suspension; Step 3: Transfer the suspension obtained in step 2 to a high-pressure reactor, perform a hydrothermal reaction at 100° C.-150° C., filter to obtain a precipitated product, wash with ethanol and deionized water, and dry to obtain a high-entropy layered metal hydroxide.

2. The preparation method according to claim 1, characterized in that: In step 1, the divalent metal salt and the trivalent metal salt are chlorides of metal active components, and the metal active components include multiple types of iron, cobalt, nickel, aluminum, magnesium, manganese, and zinc.

3. The preparation method according to claim 2, characterized in that: The number of metal elements in the metal active component is ≥5.

4. The preparation method according to claim 3, characterized in that: The metal active component is NiCoFeAlMg, NiCoFeAlMn or NiCoFeAlZn.

5. The preparation method according to claim 3 or 4, characterized in that: In the metal active component, the molar ratio of the divalent metal to the trivalent metal is 2:1 to 3:

1.

6. The preparation method according to claim 1, characterized in that: In step 2, the precipitant is one or more of sodium hydroxide and sodium carbonate, and the molar ratio of the precipitant added to the metal salt is between 2:1 and 4:

1.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In step 2, an organic phosphate compound and a precipitant are added to the mixed metal salt solution obtained in step 1, and the mixture is continuously stirred in a temperature range of 25-30° C. to obtain a suspension; and then, after a hydrothermal reaction in step 3, an organic phosphate in-situ intercalated high entropy layered metal hydroxide composite material is obtained.

8. The preparation method according to claim 7, characterized in that: In step 2, the organic phosphate compound is phenylphosphite or diphenylphosphoric acid, and the molar ratio of the organic phosphate to the metal salt is between 1:2 and 1:

2.

9. Application of the high entropy layered metal hydroxide composite material prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The high entropy layered metal hydroxide is added as an auxiliary agent to thermoplastic polyurethane to improve the flame retardant and smoke suppression properties of the composite material.

10. Use of the organophosphate in-situ intercalated high entropy layered metal hydroxide composite material prepared according to claim 7 or 8, characterized in that: The organic phosphate in-situ intercalated high entropy layered metal hydroxide composite material is added as an auxiliary agent into thermoplastic polyurethane to improve the flame retardant and smoke suppression properties of the composite material.

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