Aluminum diethylphosphinate nanofiber, preparation method and use thereof, and flame-retardant epoxy resin material

Abstract

The application discloses aluminum diethylphosphinate nanofibers, a preparation method and application thereof, and a flame-retardant epoxy resin material, wherein the preparation method comprises the following steps: providing a water solution of sodium diethylphosphinate with a preset temperature, and acidizing the water solution of the sodium diethylphosphinate; adding a template agent into the water solution of the sodium diethylphosphinate to obtain a reaction liquid; and adding a water solution of an aluminum salt into the reaction liquid drop by drop, so that the aluminum diethylphosphinate nanofibers are obtained after reaction. The preparation method can directly prepare the aluminum diethylphosphinate product with nanoscale fibrous morphology, and the application of the aluminum diethylphosphinate nanofiber product in the epoxy resin material can effectively enhance the flame-retardant performance and mechanical strength of the epoxy resin material.

Description

Technical Field

[0001] This application relates to the field of flame retardant technology, specifically to a diethylaluminum hypophosphite nanofiber, its preparation method and uses, and also to a flame retardant epoxy resin material. Background Technology

[0002] With the widespread application of polymer materials in industries such as construction, automotive, and electronics, their significant drawback of flammability has brought many safety hazards to these industries. Therefore, developing flame retardants to modify polymer materials for flame retardancy is particularly important. Traditional halogenated flame retardants are among the most widely used flame retardants due to their high flame retardant efficiency and low cost. However, halogenated flame retardants release carcinogenic substances such as dioxins during combustion, which does not meet current environmental protection requirements, greatly limiting the use of traditional halogenated flame retardants. Developing environmentally friendly halogen-free flame retardants has become an urgent need at present.

[0003] Aluminum diethylphosphite (ADP) is a new generation of green and environmentally friendly halogen-free flame retardant. Due to its high flame retardant efficiency, small dosage, good color, and high comparative tracking index (CTI), it meets the development requirements of the electronics, automotive, and other industries for lightweight, miniaturized, and high-efficiency production of plastic parts, and has broad application prospects. Studies have shown that aluminum diethylphosphite has good dispersion compatibility in nylon materials and is suitable for various thermoplastic and thermosetting materials. It exhibits good flame retardant effects in epoxy resins, nylon, polyesters, and thermoplastic elastomers, with minimal impact on the mechanical properties of the materials. For example, Exolit OP1311 and Exolit OP 1312, developed by Clariant in Germany, are based on aluminum diethylphosphite. The former is mainly used for flame retardant GRPA6, and the latter for flame retardant GRPA66. These flame retardant products have low density, require less flame retardant, have good mechanical properties, good color, low smoke density, and high CTI values, and have broad application prospects in the electronics and electrical industries. However, the relatively large particle size of its products, approximately 42μm, affects their compatibility with polymer materials. While the Exolit OP935 series products have smaller particle sizes, ranging from 3 to 4μm, they are produced by crushing large particles, resulting in enormous energy consumption and severe environmental pollution during production.

[0004] Therefore, there is a need in this field to develop a new method for synthesizing nanoscale diethylaluminum hypophosphite. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of the prior art and provide a method for preparing diethyl aluminum hypophosphite, wherein the prepared diethyl aluminum hypophosphite has a nanofiber morphology and a regular morphology. When the diethyl aluminum hypophosphite nanofibers are applied to epoxy resin materials, the flame retardant properties and mechanical strength of the epoxy resin materials can be effectively enhanced.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: a method for preparing diethylaluminum hypophosphite nanofibers, comprising: providing an aqueous solution of sodium diethylaluminum hypophosphite at a preset temperature and making the aqueous solution of sodium diethylaluminum hypophosphite acidic; adding a template agent to the aqueous solution of sodium diethylaluminum hypophosphite to obtain a reaction solution; adding an aqueous solution of aluminum salt dropwise to the reaction solution, and obtaining the diethylaluminum hypophosphite nanofibers after reaction.

[0007] In some embodiments of this application, the addition of the template agent to the aqueous solution of sodium diethylphosphite includes: adding a first template agent with coordination function and a second template agent with hydrophilic and lipophilic properties to the aqueous solution of sodium diethylphosphite and stirring.

[0008] In some embodiments of this application, the molar ratio of the first template agent to the sodium diethylphosphite is 1:(500-1000); the molar ratio of the second template agent to the sodium diethylphosphite is 1:(100-300).

[0009] In some embodiments of this application, the first template agent includes at least one of tetrahydropyrrole, ethylenediamine, urea, and n-butylamine; the second template agent includes at least one of polyethylene glycol-6000, sodium α-alkenylsulfonate, hexadecyltrimethylammonium bromide, and sodium dodecylbenzenesulfonate.

[0010] In some embodiments of this application, the molar ratio of diethyl hypophosphite in the sodium diethylphosphite to aluminum ions in the aluminum salt is (2.5-3.5):1.

[0011] In some embodiments of this application, the mass fraction of the sodium diethylphosphite in the aqueous solution is 20% to 40%; the mass fraction of the aluminum salt in the aqueous solution is 20% to 40%; and the aluminum salt is at least one of aluminum chloride, aluminum sulfate, and aluminum nitrate.

[0012] In some embodiments of this application, a method for making the aqueous solution of sodium diethylphosphite acidic includes adding an aqueous solution of sulfuric acid to the aqueous solution of sodium diethylphosphite to adjust the pH value of the aqueous solution of sodium diethylphosphite to 2-4.

[0013] In some embodiments of this application, the preset temperature is 80°C to 90°C; the aqueous solution of the aluminum salt is gradually added dropwise over 2 hours, and the reaction time is 0.5 hours to 2 hours.

[0014] In some embodiments of this application, the preparation method further includes: filtering the reaction system to obtain a precipitate; washing the precipitate in deionized water at 70°C to 90°C; and drying the washed precipitate under a vacuum of 0.07MPa to 0.09MPa and a temperature of 110°C to 130°C for 1 hour to 3 hours to obtain the powdered aluminum diethylphosphite nanofibers.

[0015] In addition, this application also provides diethylaluminum hypophosphite nanofibers, which are prepared by the above-described method for preparing diethylaluminum hypophosphite nanofibers.

[0016] This application also provides the use of the aforementioned diethylaluminum hypophosphite nanofibers as a flame retardant.

[0017] This application also provides a flame-retardant epoxy resin material, comprising, by total mass, 70% to 99.9% of an epoxy resin matrix, 0.05% to 10% of m-phenylenediamine, and 0.05% to 30% of the aforementioned diethylaluminum hypophosphite nanofibers.

[0018] Compared with the prior art, the diethylaluminum hypophosphite nanofibers and their preparation method of this application have the following beneficial effects:

[0019] The preparation method of this application uses sodium diethylphosphite and water-soluble aluminum salt as raw materials and a template agent as a morphology control agent to directly prepare nanoscale fibrous aluminum diethylphosphite products. The reaction conditions are mild, and secondary pulverization is not required, thus reducing energy consumption and environmental pollution. Equipment investment is low, and production efficiency is high. Furthermore, through the synergistic effect between the first template agent with coordination function and the second template agent with hydrophilic and lipophilic properties, the formation of crystal nuclei and the growth direction and process of particles can be effectively controlled, allowing aluminum diethylphosphite crystals to grow in one direction, ultimately forming a relatively regular nanofiber morphology. Furthermore, by controlling the amount of the first and second template agents added, aluminum diethylphosphite can exhibit a better nanofiber morphology.

[0020] The diethylaluminum hypophosphite nanofibers obtained by the preparation method of this application have a particle size in the nanoscale range, thus exhibiting excellent dispersibility in epoxy resins. At the same time, the regular fibrous morphology can effectively improve the flame retardant properties and mechanical strength of epoxy resins. Attached Figure Description

[0021] The following accompanying drawings describe in detail the exemplary embodiments disclosed in this application. The same reference numerals denote similar structures in several views of the drawings. Those skilled in the art will understand that these embodiments are non-limiting and exemplary, and the drawings are for illustrative purposes only and are not intended to limit the scope of this application. Other embodiments may similarly fulfill the inventive intent of this application. It should be understood that the drawings are not drawn to scale. Wherein:

[0022] Figure 1 This is a scanning electron microscope image of the diethylaluminum hypophosphite nanofiber product prepared in Example 1 of this application;

[0023] Figure 2 This is a scanning electron microscope image of the diethylaluminum hypophosphite nanofiber product prepared in Example 2 of this application;

[0024] Figure 3 This is a scanning electron microscope image of the diethylaluminum hypophosphite nanofiber product prepared in Example 3 of this application;

[0025] Figure 4 This is a scanning electron microscope image of the diethylaluminum hypophosphite nanofiber product prepared in Example 4 of this application;

[0026] Figure 5 This is a scanning electron microscope image of the diethylaluminum hypophosphite nanofiber product prepared in Example 5 of this application;

[0027] Figure 6 This is a scanning electron microscope image of the diethylaluminum hypophosphite nanofiber product prepared in Example 6 of this application;

[0028] Figure 7 This is a scanning electron microscope image of the diethylaluminum hypophosphite nanofiber product prepared in Example 7 of this application;

[0029] Figure 8 This is a scanning electron microscope image of the diethylaluminum hypophosphite product prepared in Comparative Example 1 of this application;

[0030] Figure 9 This is a scanning electron microscope image of the diethylaluminum hypophosphite product prepared in Comparative Example 2 of this application;

[0031] Figure 10 This is a scanning electron microscope image of the diethylaluminum hypophosphite product prepared in Comparative Example 3 of this application;

[0032] Figure 11 Thermogravimetric analysis of the diethylaluminum hypophosphite nanofiber product prepared in Example 2 of this application;

[0033] Figure 12 Thermogravimetric analysis diagram of the diethylaluminum hypophosphite product prepared in Comparative Example 1 of this application;

[0034] Figure 13 The X-ray diffraction pattern of the diethylaluminum hypophosphite nanofiber product prepared in Example 2 of this application;

[0035] Figure 14 The X-ray diffraction pattern of the diethylaluminum hypophosphite product prepared in Comparative Example 1 of this application is shown below.

[0036] Figure 15 The infrared spectrum of the diethylaluminum hypophosphite nanofiber product prepared in Example 2 of this application;

[0037] Figure 16 The infrared spectrum of the diethylaluminum hypophosphite product prepared in Comparative Example 1 of this application is shown. Detailed Implementation

[0038] The following description provides specific application scenarios and requirements for this application, intended to enable those skilled in the art to make and use the content of this application. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this application. Therefore, this application is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0039] Given the numerous drawbacks of current methods for preparing diethylaluminum hypophosphite, such as the large particle size of the prepared product affecting its compatibility with polymer materials, and the fact that reducing the particle size through pulverization would lead to huge energy consumption and serious environmental pollution, this application provides a method for preparing diethylaluminum hypophosphite nanofibers. Using sodium diethylaluminum hypophosphite and water-soluble aluminum salt as raw materials and a template agent as a morphology control agent, a diethylaluminum hypophosphite product with a nanoscale fibrous morphology can be prepared through a metathesis reaction. This diethylaluminum hypophosphite product has a large aspect ratio and a regular morphology, and when applied to epoxy resin materials, it can effectively enhance their flame retardant properties and mechanical strength.

[0040] In some embodiments of this application, the preparation method of the aluminum diethylphosphite nanofibers includes the following steps:

[0041] S1: Provide an aqueous solution of sodium diethylphosphite at a preset temperature, and make the aqueous solution of sodium diethylphosphite acidic;

[0042] S2: A template agent is added to the aqueous solution of sodium diethylphosphite to obtain a reaction solution;

[0043] S3: An aqueous solution of aluminum salt is added dropwise to the reaction solution, and the diethylaluminum hypophosphite nanofibers are obtained after the reaction.

[0044] In some embodiments of this application, in step S1, the mass fraction of sodium diethylphosphite in the aqueous solution of sodium diethylphosphite is 20% to 40%, for example, 20%, 25%, 30%, 35%, 40%, or all sub-ranges or all individual values ​​between the above nodes.

[0045] In step S1, adjusting the aqueous solution of sodium diethylphosphite to acidity can regulate the supersaturation of the aluminum diethylphosphite generated in the subsequent reaction in the reaction system, thereby controlling the crystal morphology of aluminum diethylphosphite. In some embodiments of this application, the method for making the aqueous solution of sodium diethylphosphite acidic includes: slowly adding an aqueous solution of sulfuric acid to the aqueous solution of sodium diethylphosphite to adjust the pH value of the aqueous solution of sodium diethylphosphite to 2-4. The mass fraction of the aqueous solution of sulfuric acid can be determined according to the actual situation, for example, 50%.

[0046] In some embodiments of this application, the preset temperature in step S1 is 80℃~90℃. The aqueous solution of sodium diethylphosphite needs to be heated in step S1 because the solubility of the aluminum diethylphosphite formed in the reaction is very low in aqueous solution. If the temperature is increased after adding the aluminum salt aqueous solution, it will result in a metathesis reaction before reaching the preset temperature, forming an aluminum diethylphosphite precipitate. The supersaturation of aluminum diethylphosphite in aqueous solution differs between the lower temperature and the preset temperature, which will adversely affect the morphology of the aluminum diethylphosphite.

[0047] During their research, the inventors discovered that the preparation of diethylaluminum hypophosphite nanomaterials typically involves two stages: the first stage is the formation of diethylaluminum hypophosphite crystal nuclei, and the second stage is the growth of these nuclei. The morphology, size, and distribution of diethylaluminum hypophosphite nanomaterials are determined by the nature of the reaction system and the kinetics of the reaction. Furthermore, the aggregation problem between diethylaluminum hypophosphite nanoparticles cannot be ignored, making it difficult to prepare diethylaluminum hypophosphite nanomaterials with uniform size and structure. Therefore, to obtain diethylaluminum hypophosphite nanoparticles with controllable size and no aggregation in solution, effective intervention in the chemical reaction process is necessary. In step S2 of this application, a template agent is added to the reaction system. This template agent can effectively intervene in the metathesis reaction process of sodium diethylaluminum hypophosphite and aluminum salt, thereby achieving the preparation of nanoscale fibrous diethylaluminum hypophosphite.

[0048] In the embodiments of this application, the selection of the template agent has a significant impact on the morphology of diethylaluminum hypophosphite. In some embodiments of this application, the template agent includes a first template agent and a second template agent. The first template agent is selected from compounds with coordination effects, and the second template agent is selected from compounds with hydrophilic and lipophilic properties. The coordination of the compounds with coordination effects with aluminum ions can effectively change the supersaturation of diethylaluminum hypophosphite in aqueous solution and affect the formation process of diethylaluminum hypophosphite crystal nuclei. The compounds with amphiphilic effects (i.e., hydrophilic and lipophilic properties) can adsorb onto the diethylaluminum hypophosphite crystal nuclei in aqueous solution, changing the growth direction of the diethylaluminum hypophosphite crystals. Therefore, the first template agent and the second template agent work together to effectively control the formation of diethylaluminum hypophosphite crystal nuclei and the growth direction and process of the particles, so that the diethylaluminum hypophosphite crystals grow in one direction, ultimately forming a relatively regular nanofiber morphology.

[0049] In some embodiments of this application, step S2, adding the template agent to the aqueous solution of sodium diethylphosphite, includes: adding a first template agent with coordination function and a second template agent with hydrophilic and lipophilic properties to the aqueous solution of sodium diethylphosphite, and stirring. The order of addition of the first and second template agents is not required. After adding each template agent, the system is stirred to ensure complete dissolution of the added template agent. The stirring time is, for example, 0.5 hours to 1 hour.

[0050] In some embodiments of this application, the first template agent includes at least one of tetrahydropyrrole, ethylenediamine, urea, and n-butylamine, and the second template agent includes at least one of polyethylene glycol-6000, sodium α-alkenylsulfonate, hexadecyltrimethylammonium bromide, and sodium dodecylbenzenesulfonate.

[0051] In some embodiments of this application, changing the amount of the first template agent has little effect on the morphology of the aluminum diethylphosphite, while changing the amount of the second template agent has a significant effect on the morphology of the aluminum diethylphosphite. That is, the first template agent is a co-templating agent, and the second template agent is the main template agent. In some embodiments of this application, the amount of the first template agent added is less than the amount of the second template agent added.

[0052] In some embodiments of this application, the molar ratio of the first template agent to the sodium diethylphosphite is 1:(500-1000), for example, 1:500, 1:600, 1:700, 1:800, 1:900, 1:1000, or any sub-range or any single ratio between the above ratios, and the molar ratio of the second template agent to the sodium diethylphosphite is 1:(100-300), for example, 1:100, 1:150, 1:200, 1:250, 1:300, or any sub-range or any single ratio between the above ratios, so that the aluminum diethylphosphite exhibits a more superior nanofiber morphology.

[0053] In some embodiments of this application, in step S3, the molar ratio of diethyl hypophosphite in the sodium diethylphosphite to aluminum ions in the aluminum salt is (2.5-3.5):1.

[0054] In some embodiments of this application, in step S3, the aluminum salt is at least one of aluminum chloride, aluminum sulfate, and aluminum nitrate. As an example, the aluminum salt is aluminum sulfate. In some embodiments of this application, the mass fraction of the aluminum salt in the aqueous solution is 20% to 40%, for example, 20%, 25%, 30%, 35%, 40%, or all sub-ranges or all individual values ​​between the aforementioned nodes.

[0055] In some embodiments of this application, in step S3, the aqueous solution of the aluminum salt is gradually added dropwise over 2 hours, and the reaction time is 0.5 hours to 2 hours.

[0056] In some embodiments of this application, the preparation method further includes the following steps:

[0057] S4: Filter the system after the reaction to obtain the precipitate;

[0058] S5: Wash the precipitate in deionized water at 70℃~90℃;

[0059] S6: The washed precipitate is dried for 1 to 3 hours under a vacuum of 0.07 MPa to 0.09 MPa and a temperature of 110°C to 130°C to obtain the powdered aluminum diethylphosphite nanofibers.

[0060] This application also provides diethylaluminum hypophosphite nanofibers prepared by the above preparation method, and the diethylaluminum hypophosphite nanofibers can be used as flame retardants, for example, they can be applied to the flame retardancy of epoxy resin materials to prepare flame retardant epoxy resin materials.

[0061] This application embodiment also provides the flame-retardant epoxy resin material, which, based on a total mass of 100%, comprises: 70% to 99.9% epoxy resin matrix, 0.05% to 10% m-phenylenediamine, and 0.05% to 30% diethylaluminum hypophosphite nanofibers prepared by the above preparation method.

[0062] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. Unless otherwise specified, the reagents and raw materials used can be purchased commercially. Experimental methods in the following embodiments that do not specify specific conditions are performed according to conventional methods and conditions, or according to the product instructions.

[0063] Preparation of diethylaluminum hypophosphite nanofibers

[0064] Example 1

[0065] 20 kg of a 20% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 90 °C. A 50% sulfuric acid aqueous solution was slowly added to adjust the pH to 2.0. 3.5 g of tetrahydropyrrole was added, and after stirring for 1 hour, 24.4 g of sodium α-olefin sulfonate was added. After stirring for another 0.5 hours, 7 kg of a 20% aluminum sulfate aqueous solution was slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the specified temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdery aluminum diethylphosphite nanofiber product. A scanning electron microscope image of the product is attached. Figure 1 The relevant parameters are shown in Table 1.

[0066] Example 2

[0067] 20 kg of a 20% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 90 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 3.0. 2.4 g of ethylenediamine was added, and after stirring for 1 hour, 59.3 g of hexadecyltrimethylammonium bromide was added. After stirring for another 0.5 hours, 7 kg of a 20% aluminum sulfate aqueous solution was slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the desired temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdery aluminum diethylphosphite nanofiber product. A scanning electron microscope image of this product is attached. Figure 2 The relevant parameters are shown in Table 1, and the thermogravimetric diagram is attached. Figure 11 The X-ray diffraction pattern is attached. Figure 13The infrared spectrum is attached. Figure 15 .

[0068] Example 3

[0069] 20 kg of a 20% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 80 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 3.0. 2.5 g of n-butylamine was added, and after stirring for 1 hour, 42.5 g of sodium dodecylbenzenesulfonate was added. After stirring for another 0.5 hours, 7 kg of a 20% aluminum sulfate aqueous solution was slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the desired temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdery aluminum diethylphosphite nanofiber product. A scanning electron microscope image of this product is attached. Figure 3 The relevant parameters are shown in Table 1.

[0070] Example 4

[0071] 20 kg of a 20% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 80 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 3.0. 1.8 g of urea was added, and after stirring for 1 hour, 11.9 g of polyethylene glycol-6000 was added. After stirring for another 0.5 hours, 7 kg of a 20% aluminum sulfate aqueous solution was slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the desired temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum drying oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdery aluminum diethylphosphite nanofiber product. A scanning electron microscope image of this product is attached. Figure 4 The relevant parameters are shown in Table 1.

[0072] Example 5

[0073] 20 kg of a 25% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 90 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 2.0. 2.8 g of n-butylamine was added, and after stirring for 1 hour, 20.4 g of sodium α-olefin sulfonate was added. After stirring for another 0.5 hours, 7 kg of a 25% aluminum sulfate aqueous solution was slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the desired temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdery aluminum diethylphosphite nanofiber product. A scanning electron microscope image of this product is attached. Figure 5 The relevant parameters are shown in Table 1.

[0074] Example 6

[0075] 20 kg of a 30% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 90 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 4.0. 2.7 g of ethylenediamine was added, and after stirring for 1 hour, 127.5 g of sodium dodecylbenzenesulfonate was added. After stirring for another 0.5 hours, 7 kg of a 30% aluminum sulfate aqueous solution was slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the desired temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdery aluminum diethylphosphite nanofiber product. A scanning electron microscope image of this product is attached. Figure 6 The relevant parameters are shown in Table 1.

[0076] Example 7

[0077] 20 kg of a 40% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 90 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 3.0. 4.3 g of tetrahydropyrrole was added, and after stirring for 1 hour, 88.9 g of hexadecyltrimethylammonium bromide was added. After stirring for another 0.5 hours, 7 kg of a 40% aluminum sulfate aqueous solution was slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the desired temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdery aluminum diethylphosphite nanofiber product. A scanning electron microscope image of this product is attached. Figure 7 The relevant parameters are shown in Table 1.

[0078] Comparative Example 1

[0079] 20 kg of a 20% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 90 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 3.0. 7 kg of a 20% aluminum sulfate aqueous solution was then slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the desired temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdered aluminum diethylphosphite product. A scanning electron microscope image of this product is attached. Figure 8 The relevant parameters are shown in Table 1, and the thermogravimetric diagram is attached. Figure 12 The X-ray diffraction pattern is attached. Figure 14 The infrared spectrum is attached. Figure 16 .

[0080] Comparative Example 2

[0081] 20 kg of a 30% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 90 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 3.0. 7 kg of a 30% aluminum sulfate aqueous solution was then slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the specified temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powder product. A scanning electron microscope image of this product is attached. Figure 9 The relevant parameters are shown in Table 1.

[0082] Comparative Example 3

[0083] 20 kg of a 40% sodium diethylphosphite solution was added to a 50 L reactor. The mixture was stirred and heated to 90 °C. A 50% sulfuric acid solution was slowly added to adjust the pH to 3.0. 7 kg of a 40% aluminum sulfate aqueous solution was then slowly added dropwise over 2 hours. After the addition was complete, the reaction was maintained at the desired temperature for 1 hour. The resulting white precipitate was washed three times in deionized water at 80 °C and then dried in a vacuum oven at 120 °C (0.09 MPa) for 2 hours to obtain a white powdered aluminum diethylphosphite product. A scanning electron microscope image of this product is attached. Figure 10 The relevant parameters are shown in Table 1.

[0084] Table 1. Relevant parameters of the products prepared in Examples 1-7 and Comparative Examples 1-3 of this application.

[0085]

[0086] Based on the scanning electron microscope images of Examples 1-7 and Comparative Examples 1-3, and Table 1, it can be seen that the diethylaluminum hypophosphite products prepared in Examples 1-7 of this application do indeed have a nanofiber morphology, and the morphology is relatively regular with a large aspect ratio. However, the diethylaluminum hypophosphite prepared in Comparative Examples 1-3 did not form a nanofiber morphology. This is because a template agent was added in Examples 1-7 of this application. This template agent can effectively interfere with the metathesis reaction process of sodium diethylaluminum hypophosphite and aluminum salt, resulting in the diethylaluminum hypophosphite exhibiting a nanofiber morphology. Furthermore, the template agents added in Examples 1-7 include both compounds with coordination effects and compounds with amphiphilic effects. The coordination of the compounds with coordination effects with aluminum ions can effectively change the supersaturation of aluminum diethylphosphite in aqueous solution and affect the formation process of aluminum diethylphosphite crystal nuclei. The compounds with amphiphilic effects can adsorb onto the aluminum diethylphosphite crystal nuclei in aqueous solution, changing the growth direction of the aluminum diethylphosphite crystals, so that the growth of aluminum diethylphosphite proceeds in one direction, ultimately giving aluminum diethylphosphite a better nanofiber morphology.

[0087] Comparing the thermogravimetric analyses of Example 2 and Comparative Example 1, it can be seen that the thermal stability of the diethylaluminum hypophosphite nanofiber product prepared in Example 2 is higher than that of the diethylaluminum hypophosphite product prepared in Comparative Example 1. Therefore, the addition of a template agent during the preparation process in Example 2 of this application can improve the thermal stability of the diethylaluminum hypophosphite product. This is because the thermal stability of nanomaterials is mainly affected by their crystallinity, particle size, and secondary agglomeration. The better the crystallinity, the smaller the particle size, and the weaker the secondary agglomeration of nanomaterials, the better their thermal stability. In Example 2 of this application, the addition of a template agent results in better crystallinity of the diethylaluminum hypophosphite, a smaller fiber diameter, and effectively improves the secondary agglomeration of particles (comparative example). Figure 2 and attached Figure 8 Therefore, it has good thermal stability.

[0088] Comparing the X-ray diffraction patterns and infrared spectra of Example 2 and Comparative Example 1, it can be seen that the preparation method of this application only changes the morphology of the diethylaluminum hypophosphite product, enabling it to exhibit a regular nanofiber structure, without destroying its original molecular composition and crystal structure.

[0089] Application of diethylaluminum hypophosphite nanofibers in flame-retardant epoxy resin materials

[0090] Example 8

[0091] Weigh 15.0g of the diethylaluminum hypophosphite nanofiber product prepared in Example 2 and ultrasonically disperse it in 200mL of acetone. Add 76g of bisphenol A epoxy resin, mix and stir for 1 hour, and then remove the solvent acetone by rotary evaporation at 60°C. Then add 9g of m-phenylenediamine as a curing agent, stir for 20 minutes, pour into a preheated mold, and cure in an 80°C drying oven for 4 hours. Cool and demold to obtain flame-retardant epoxy resin material.

[0092] Comparative Example 4

[0093] Weigh 15.0g of the diethylaluminum hypophosphite product prepared in Comparative Example 1 and ultrasonically disperse it in 200mL of acetone. Add 76g of bisphenol A epoxy resin, mix and stir for 1 hour, and then remove the solvent acetone by rotary evaporation at 60℃. Then add 9g of m-phenylenediamine as a curing agent, stir for 20 minutes, pour into a preheated mold, and cure in an 80℃ drying oven for 4 hours. Cool and demold to obtain flame-retardant epoxy resin material.

[0094] Comparative Example 5

[0095] It uses pure epoxy resin material.

[0096] Samples were prepared from the products obtained in Example 8, Comparative Example 4, and Comparative Example 5, and the following flame retardant and mechanical properties were tested:

[0097] Flame retardant performance test: The test was conducted according to the UL94 vertical burning test, based on the ANSI / UL-94-2010 standard, on a CZF-5 horizontal and vertical burning tester from Nanjing Jiangning Analytical Instrument Co., Ltd. The sample size was 130×13×3mm.

[0098] Mechanical performance testing: Impact and tensile tests were conducted. Impact tests were performed according to GB / T1043.1-2008 standard on a ZBC-1400A pendulum impact testing machine from MTS Corporation in China, using unnotched specimens. The impact energy was 4J, and the specimen size was 100×10×4mm. Tensile tests were performed according to ASTM D3039-08 standard on a YF-900 computer-controlled tensile testing machine, with a sample size of 100×10×4mm and a testing speed of 2.0mm / min. Five parallel samples were tested for each impact and tensile test, and the average value was taken. The mechanical performance test results are shown in Table 2.

[0099] The flame retardant performance test results showed that the flame retardant epoxy resin material obtained in Example 8 achieved UL94 V0, the flame retardant epoxy resin material obtained in Comparative Example 4 achieved UL94 V1, while the pure epoxy resin material in Comparative Example 5 did not possess flame retardant properties. Therefore, when using the diethylaluminum hypophosphite nanofiber product prepared in the examples of this application to prepare flame retardant epoxy resin materials, the flame retardant performance of the epoxy resin materials can be effectively improved.

[0100] Table 2 shows the mechanical properties of the products prepared in Example 8 and Comparative Examples 4-5.

[0101]

[0102] As shown in Table 2, the pure epoxy resin material of Comparative Example 5 has high tensile strength, but low elongation at break and low impact strength, making it a brittle material. Comparative Example 4 added the diethylaluminum hypophosphite product prepared in Comparative Example 1 to the epoxy resin material, resulting in a decrease in the impact strength, tensile strength, and elongation at break of the prepared flame-retardant epoxy resin material. However, Example 8 of this application, by adding the diethylaluminum hypophosphite nanofiber product prepared in Example 2 of this application to the epoxy resin material, significantly improves the impact strength, tensile strength, and elongation at break of the prepared flame-retardant epoxy resin material.

[0103] In summary, the diethylaluminum hypophosphite nanofibers prepared in the embodiments of this application can effectively enhance the flame retardant properties and mechanical strength of epoxy resin materials.

[0104] The above description of the embodiments is intended to enable those skilled in the art to understand and apply this application. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, this application is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A method for preparing diethylaluminum hypophosphite nanofibers, characterized in that, include: An aqueous solution of sodium diethylphosphite at a preset temperature is provided, and the aqueous solution of sodium diethylphosphite is made acidic. A template agent is added to the aqueous solution of sodium diethylphosphite to obtain a reaction solution; An aqueous solution of aluminum salt is added dropwise to the reaction solution, and the diethylaluminum hypophosphite nanofibers are obtained after the reaction. Adding a template agent to the aqueous solution of sodium diethylphosphite includes: adding a first template agent with coordination function and a second template agent with hydrophilic and lipophilic properties to the aqueous solution of sodium diethylphosphite and stirring; the molar ratio of the first template agent to the sodium diethylphosphite is 1:(500-1000), and the molar ratio of the second template agent to the sodium diethylphosphite is 1:(100-300); the first template agent includes at least one of tetrahydropyrrole, ethylenediamine, urea, and n-butylamine; the second template agent includes at least one of polyethylene glycol-6000, sodium α-alkenyl sulfonate, hexadecyltrimethylammonium bromide, and sodium dodecylbenzene sulfonate.

2. The method for preparing diethylaluminum hypophosphite nanofibers according to claim 1, characterized in that, The molar ratio of diethyl hypophosphite in the sodium diethylphosphite to aluminum ions in the aluminum salt is (2.5–3.5):

1.

3. The method for preparing diethylaluminum hypophosphite nanofibers according to any one of claims 1 to 2, characterized in that, In the aqueous solution of sodium diethylphosphite, the mass fraction of sodium diethylphosphite is 20% to 40%; in the aqueous solution of aluminum salt, the mass fraction of aluminum salt is 20% to 40%; the aluminum salt is at least one of aluminum chloride, aluminum sulfate, and aluminum nitrate.

4. The method for preparing diethylaluminum hypophosphite nanofibers according to any one of claims 1 to 2, characterized in that, A method for making the aqueous solution of sodium diethylphosphite acidic includes adding an aqueous solution of sulfuric acid to the aqueous solution of sodium diethylphosphite to adjust the pH value of the aqueous solution of sodium diethylphosphite to 2-4.

5. The method for preparing diethylaluminum hypophosphite nanofibers according to any one of claims 1 to 2, characterized in that, The preset temperature is 80℃~90℃; the aqueous solution of the aluminum salt is gradually added dropwise over 2 hours, and the reaction time is 0.5 hours to 2 hours.

6. The method for preparing diethylaluminum hypophosphite nanofibers according to any one of claims 1 to 2, characterized in that, The preparation method further includes: The system after the reaction was filtered to obtain a precipitate; The precipitate was washed in deionized water at 70℃~90℃; The washed precipitate was dried for 1 to 3 hours under a vacuum of 0.07 MPa to 0.09 MPa and a temperature of 110°C to 130°C to obtain powdered aluminum diethylphosphite nanofibers.

7. A diethylaluminum hypophosphite nanofiber, characterized in that, The nanofibers were prepared by the method described in any one of claims 1 to 6.

8. The use of the diethylaluminum hypophosphite nanofibers according to claim 7 as a flame retardant.

9. A flame-retardant epoxy resin material, characterized in that, Based on a total mass of 100%, it comprises: 70% to 99.9% epoxy resin matrix, 0.05% to 10% m-phenylenediamine, and 0.05% to 30% of the diethylaluminum hypophosphite nanofibers as described in claim 7.

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