Lanthanum phosphite hollow microspheres, preparation method therefor, and use thereof

Abstract

The application discloses lanthanum hypophosphite hollow microspheres and a preparation method and application thereof. The lanthanum hypophosphite hollow microspheres are prepared by mixing an organic silicon template with an aqueous solution containing a lanthanum source and a hypophosphorous acid source to prepare a precursor, performing hydrothermal reaction on the precursor to prepare lanthanum hypophosphite microspheres, and removing the organic silicon template in the lanthanum hypophosphite microspheres by etching. The lanthanum hypophosphite hollow microspheres are prepared by using an organic silicon template assisted hydrothermal method and etching method, the particle size, shell structure and surface properties of the lanthanum hypophosphite hollow microspheres can be precisely controlled, the hollow microspheres have high crystallinity and rich mesopores, and have more active sites, so that the adsorption capacity and catalytic carbon formation capacity of the lanthanum hypophosphite hollow microspheres are significantly improved, and the application effect of the lanthanum hypophosphite hollow microspheres in the flame retardation field is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of lanthanum phosphite materials technology, and more particularly to lanthanum phosphite hollow microspheres, their preparation methods, and applications. Background Technology

[0002] With the widespread application of polymer materials in electronics, construction, transportation, and other fields, the fire hazards posed by their flammability are becoming increasingly prominent. Halogen-free, low-smoke, low-toxicity, and highly efficient flame retardant technologies have become a key focus of industry research and development. Traditional halogenated flame retardants have high flame retardant efficiency, but they easily release toxic hydrogen halide gases during combustion, posing environmental and health risks, and their use has been gradually restricted. Conventional phosphorus-based, nitrogen-based, and intumescent flame retardants (IFR) are environmentally friendly, but they generally suffer from problems such as large addition amounts, low flame retardant efficiency, and easy reduction of material mechanical properties, making it difficult to simultaneously meet the application requirements of high flame retardancy and high strength.

[0003] Lanthanum, a rare earth element, has a unique 4f electron layer structure and strong Lewis acidity, and possesses excellent catalytic crosslinking and char formation capabilities. Currently, it is mainly used in the form of lanthanum phosphate to achieve flame retardancy. However, there are still obvious shortcomings in the use of lanthanum phosphate for flame retardancy: (1) It is mostly used in combination for synergistic effect. When used alone as the main flame retardant, its efficiency is limited, and a high addition amount is required to achieve the ideal flame retardancy level; (2) Ordinary lanthanum phosphate powder has a large particle size and poor dispersibility, and it is easy to agglomerate in the polymer matrix, affecting the flame retardancy stability and material processing performance; (3) The flame retardancy mechanism research is not systematic, especially the char formation regulation and interfacial interaction law for different substrates are still unclear; (4) There is still room for improvement in the smoke suppression and anti-dripping performance at high temperature, which is difficult to meet the stringent fire protection requirements of high-end materials (such as new energy batteries and electronic packaging). Summary of the Invention

[0004] Therefore, it is necessary to provide a lanthanum phosphite microsphere with a hollow structure. By constructing hollow microspheres, the surface properties of lanthanum phosphite can be improved, thereby enhancing its application effect in the flame retardant field.

[0005] In a first aspect, this application provides a method for preparing lanthanum phosphite hollow microspheres, comprising the following steps:

[0006] A precursor was prepared by mixing an organosilicon template with an aqueous solution containing a lanthanum source and a phosphorous acid source.

[0007] The precursor was subjected to a hydrothermal reaction to prepare lanthanum phosphite microspheres.

[0008] Lanthanum phosphite hollow microspheres were prepared by etching to remove the organosilicon template from the lanthanum phosphite microspheres.

[0009] In some embodiments, the shape of the organosilicon template is spheres, and the particle size of the spheres is 200nm-500nm.

[0010] In some embodiments, the organosilicon template is prepared by reacting an organosilicon source dispersed in a solvent containing ethanol, water, and ammonia.

[0011] Optionally, the organosilicon source includes at least one of silicate ester organosilicon and organosilane;

[0012] Further optionally, the silicate ester organosilicon includes at least one of tetraethyl orthosilicate and methyl orthosilicate;

[0013] Further optionally, the organosilanes include octadecyltrimethoxysilane.

[0014] In some embodiments, at least one of the following conditions (1) to (5) is also satisfied:

[0015] (1) The volume ratio of the ethanol, the water and the ammonia in the solvent is (30-50):(5-15):(1-5);

[0016] (2) The volume ratio of the organosilicon source to the solvent containing ethanol, water and ammonia is (0.5-6):(50-60);

[0017] Optionally, the volume ratio of the organosilicon source to the solvent containing ethanol, water and ammonia is (2-6):(50-60).

[0018] (3) The lanthanum source includes one or more of lanthanum nitrate and lanthanum chloride;

[0019] (4) The phosphorous acid source includes one or more of phosphorous acid and its salts;

[0020] (5) The molar ratio of the lanthanum source to the phosphorous acid source is (0.5-1.5):(1-2).

[0021] In some embodiments, at least one of the following conditions (1) to (3) is also satisfied:

[0022] (1) The temperature of the hydrothermal reaction is 150℃-200℃;

[0023] Optionally, the hydrothermal reaction temperature is 160℃-200℃;

[0024] (2) The hydrothermal reaction time is 6 h-15 h;

[0025] Optionally, the hydrothermal reaction time is 8 h-15 h;

[0026] (3) The reaction vessel for the hydrothermal reaction is selected from a polytetrafluoroethylene reactor.

[0027] In some embodiments, the etching solution includes one or more of hydrofluoric acid solution and sodium hydroxide solution;

[0028] Optionally, the mass concentration of the etching solution is 1%-5%, and the etching time is 1h-5h.

[0029] Secondly, this application also provides a hollow lanthanum phosphite microsphere, which is prepared by the method for preparing hollow lanthanum phosphite microspheres provided in the first aspect.

[0030] In some embodiments, the particle size of the lanthanum phosphite hollow microspheres is 5 μm-20 μm; and / or, the thickness of the shell layer of the lanthanum phosphite hollow microspheres accounts for 60%-80% of the particle size of the hollow microspheres; and / or, the crystallinity of the shell layer of the lanthanum phosphite hollow microspheres is 65%-95%; and / or, the porosity of the shell layer of the lanthanum phosphite hollow microspheres is 30%-60%; and / or, the specific surface area of ​​the shell layer of the lanthanum phosphite hollow microspheres is 120 m². 2 / g -200 m 2 / g .

[0031] Thirdly, this application also provides a flame-retardant material, which includes the lanthanum phosphite hollow microspheres provided in the second aspect.

[0032] Fourthly, this application also provides the application of the lanthanum phosphite hollow microspheres provided in the second aspect in the preparation of flame retardants.

[0033] Compared with the prior art, the beneficial effects of the technical solution of this application are as follows:

[0034] This application provides a method for preparing hollow lanthanum phosphite microspheres. The method involves preparing a precursor by reacting an organosilicon template with an aqueous solution containing a lanthanum source and a phosphorous acid source, further forming lanthanum phosphite microspheres through a hydrothermal reaction, and then removing the organosilicon template from the lanthanum phosphite microspheres by etching, thereby obtaining lanthanum phosphite microspheres with a hollow structure. This application utilizes an organosilicon template-assisted hydrothermal method to prepare core-shell microspheres, wherein the shell material is lanthanum phosphite and the core is a silica sphere. The silica sphere serves as a hard template, enabling high controllability of the morphology and structure of the lanthanum phosphite microspheres. After etching to remove the template, hollow lanthanum phosphite microspheres are formed. This hollow structure provides a greater thermal barrier, delaying heat transfer to the material's interior. The hollow microspheres can also act as physical cross-linking points, enhancing melt strength and reducing dripping, thus significantly improving the morphological stability of the hollow lanthanum phosphite microspheres. Furthermore, the hollow microspheres possess excellent crystallinity, specific surface area, and abundant mesopores, forming numerous active sites on their surface. These sites effectively adsorb gases and capture free radicals, forming a dense carbon layer that effectively isolates oxygen and heat, significantly enhancing the flame-retardant effect of the hollow lanthanum phosphite microspheres. Attached Figure Description

[0035] Figure 1 The results of EDS energy dispersive spectroscopy analysis of the lanthanum phosphite hollow microspheres prepared in Example 1 of this application are shown.

[0036] Figure 2 XPS energy dispersive spectroscopy analysis results of lanthanum phosphite hollow microspheres (2 mLTEOS) prepared in Example 1 of this application.

[0037] Figure 3 Scanning electron microscope image of lanthanum phosphite hollow microspheres (2 mLTEOS) prepared in Example 1 of this application.

[0038] Figure 4 Scanning electron microscope image of lanthanum phosphite hollow microspheres (4 mLTEOS) prepared in Example 1 of this application.

[0039] Figure 5 This is a scanning electron microscope image of lanthanum phosphite prepared in Comparative Example 2 of this application.

[0040] Figure 6 This is a scanning electron microscope image of lanthanum phosphite prepared in Comparative Example 1 of this application. Detailed Implementation

[0041] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] As used herein, "optional," "optional," and "optional" refer to either "with" or "without" parallel options. If multiple "optional" entries appear in a technical solution, each "optional" entry is independent unless otherwise specified and there are no contradictions or mutual constraints. The term "and / or" as used herein includes any and all combinations of one or more related listed items. Unless otherwise specified, "multiple," "multiple," etc., as used herein refer to a quantity greater than 2 or equal to 2; for example, "one or more" indicates one, two, or more than two. In open-ended technical features or solutions described herein using words such as "containing," "including," and "comprising," unless otherwise specified, additional members beyond the listed members are not excluded. This can be considered as providing both a closed-ended feature or solution consisting of the listed members and an open-ended feature or solution that includes additional members beyond the listed members.

[0044] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0046] In recent years, researchers' studies on lanthanum substrates have focused on the preparation and application of lanthanum phosphate materials. However, there is a significant lack of research on the preparation of lanthanum phosphite, as well as its structure and surface properties. Lanthanum phosphite materials with hollow structures and their applications remain a research gap.

[0047] Based on this, this application aims to develop a method for preparing lanthanum phosphite microspheres with hollow structures, which can achieve precise control of structure and surface properties while forming hollow lanthanum phosphite microspheres, thus giving them excellent flame retardant properties.

[0048] In a first aspect, this application provides a method for preparing lanthanum phosphite hollow microspheres, comprising the following steps:

[0049] S1. Prepare a precursor by mixing an organosilicon template with an aqueous solution containing a lanthanum source and a phosphorous acid source.

[0050] S2. The precursor is subjected to a hydrothermal reaction to prepare lanthanum phosphite microspheres.

[0051] S3. Hollow lanthanum phosphite microspheres were prepared by etching to remove the organosilicon template from the lanthanum phosphite microspheres.

[0052] This application employs a hard template-assisted hydrothermal method and an etching method to remove the organosilicon template in order to prepare lanthanum phosphite microspheres with a hollow structure. The organosilicon template allows for precise control over the microsphere particle size, hollow structure, and surface performance parameters. The hydrothermal method facilitates the crystallization of lanthanum phosphite, forming a well-crystallized shell, avoiding the problem of poor stability of amorphous materials, and ensuring the integrity of the lanthanum phosphite shell material during the removal of the organosilicon template.

[0053] In some embodiments, the organosilicon template is spherical in shape, with a particle size of 200nm-500nm, including but not limited to 200nm, 300nm, 350nm, 400nm, 450nm, 500nm, or any combination thereof, and values ​​within that range. Further, the particle size of the spheres is 400nm-500nm. It should be understood that using a spherical organosilicon template with a particle size of 200nm-500nm is not only for achieving precise control of the particle size of the lanthanum phosphite hollow microspheres, but also to ensure reduced particle aggregation, ideal shell thickness and uniformity during the core-shell structure formation process, and improved shell performance, thereby ensuring shell stability and etching effect in subsequent etching processes.

[0054] In some embodiments, the organosilicon template is prepared by reacting an organosilicon source dispersed in a solvent containing ethanol, water, and ammonia. It should be understood that the organosilicon source undergoes alkaline-catalyzed hydrolysis and condensation reactions in the alcohol-water-ammonia system, ultimately generating silica spherical templates.

[0055] In some embodiments, the organosilicon source includes silicate-based organosilicones and / or organosilanes. Using silicate-based organosilicones and / or organosilanes enables the formation of structurally and structurally stable silica spheres, and the resulting hard template is more conducive to the preparation of lanthanum phosphite hollow microspheres. As a non-limiting example, silicate-based organosilicones include tetraethyl orthosilicate (TEOS) and / or methyl orthosilicate (TMOS); organosilanes include octadecyltrimethoxysilane (ODTMS).

[0056] In some embodiments, the volume ratio of ethanol, water, and ammonia in the solvent is (30-50):(5-15):(1-5), including but not limited to 30:5:1, 30:10:1, 30:15:1, 30:5:5, 30:10:5, 30:15:5, 40:5:1, 40:10:1, 40:15:1, 40:5:5, 40:10:5, 40:15:5, 50:5:1, 50:10:1, 50:15:1, 50:5:5, 50:10:5, 50:15:5, or any of the foregoing ranges and values ​​within those ranges. The mass fraction of ammonia is 25%-28%. Further, the volume ratio of ethanol, water, and ammonia in the solvent is (35-45):(8-12):(2-4). It is important to understand that the volume ratio of ethanol, water, and ammonia has a certain influence on the morphology and structure of the prepared organosilicon template. Since this application requires precise control of the structure of lanthanum phosphite hollow microspheres using organosilicon templates, controlling the ratio of ethanol, water, and ammonia in the reaction system can further regulate the solubility and catalytic activity of the reaction solvent system, thereby controlling the degree and rate of hydrolysis, as well as the degree and rate of polymerization. This allows for the acquisition of silica sphere templates with specific particle sizes and regular, uniform morphologies, thus achieving precise control over the structure and particle size of the lanthanum phosphite hollow microspheres. During the optimization process, it was found that when the volume ratio of ethanol, water, and ammonia exceeded the specified range, the solubility and catalytic activity of the reaction solvent system for the organosilicon source were significantly reduced. For example, when the ethanol-to-water ratio increased to 60:5, the hydrolysis rate of the organosilicon source was significantly slowed down, leading to an increase in the particle size of the organosilicon template and making it prone to aggregation. Conversely, excessively rapid hydrolysis resulted in a significant decrease in particle size. Simultaneously, when the ammonia content was higher than this range, the activity of the reaction system increased significantly, resulting in smaller organosilicon template particles with increased surface roughness; conversely, smaller ammonia content resulted in larger particle sizes and smoother surfaces. Therefore, this application optimized the reaction solvent system within this range through extensive experiments, enabling precise control of the structure and surface morphology of the organosilicon template, and ensuring a stable preparation process.

[0057] In some embodiments, the volume ratio of the organosilicon source to the solvent containing ethanol, water, and ammonia is (0.5-6):(50-60), including but not limited to 0.5:50, 1:50, 1:55, 1:60, 3:50, 3:55, 3:60, 5:50, 5:55, 5:60, 6:60, or any of the foregoing ranges and values ​​within those ranges. Further, the volume ratio of the organosilicon source to the solvent containing ethanol, water, and ammonia is (2-6):(50-60); even further, the volume ratio of the organosilicon source to the solvent containing ethanol, water, and ammonia is (4-6):(50-60), preferably (4-5):(50-55) within this range. It is important to understand that the ratio of the organosilicon source to the reaction solvent system has a significant impact on the hydrolysis and polycondensation rates of organosilicon during the preparation of organosilicon templates. By controlling the range of their ratio, suitable hydrolysis and polycondensation rates can be obtained, thereby regulating the nucleation and growth of the silica sphere template during its formation process, ultimately resulting in organosilicon templates with specific particle sizes, regular morphologies, and uniformity. The mass fraction of ammonia water is 25%-28%.

[0058] In some embodiments, the reaction time during the preparation of the organosilicon template is 5h-8h, including but not limited to 5h, 6h, 7h, 8h or any of the foregoing ranges and values ​​within that range.

[0059] As a non-limiting example, lanthanum sources include one or more of lanthanum nitrate and lanthanum chloride.

[0060] As a non-limiting example, sources of phosphorous acid include one or more of phosphorous acid and its salts, wherein the phosphite is selected from sodium phosphite.

[0061] It's important to understand that, unlike the preparation process of lanthanum phosphate, the preparation process of lanthanum phosphite is more prone to generating byproducts, which in turn affect crystallinity. This is mainly because the preparation of lanthanum phosphite involves a coordination reaction between lanthanum ions and phosphite ions. During this coordination process, the concentration and ratio of the coordinating ions, as well as the temperature and time of the coordination reaction, all influence the process. For example, the formation of normal or basic salts can affect the crystallinity and phase purity of the lanthanum phosphite material, thereby affecting the shell structure and properties of the microspheres, and further impacting the effectiveness of the template removal process.

[0062] In some embodiments, the molar ratio of lanthanum source to phosphorous acid source is (0.5-1.5):(1-2), including but not limited to 0.5:1, 0.5:2, 1:1, 1:2, 1.5:1, 1.5:2, or any of the foregoing ranges and values ​​within those ranges. Within this molar ratio range, a normal salt can be formed through coordination. However, if the lanthanum ion content is too high (e.g., a molar ratio of lanthanum source to phosphorous acid source of 2:1), the lanthanum ions will further react with hydroxide ions to form a basic salt, thus failing to obtain high-purity, high-crystallinity lanthanum phosphite. This results in insufficient stability of the shell structure of the lanthanum phosphite hollow microspheres, affecting the etching effect and potentially causing serious problems such as shell collapse and cracking. Furthermore, a molar ratio of lanthanum source to phosphorous acid source of (0.8-1.2):(1.2-1.8) can better achieve the technical effects of this application.

[0063] In some embodiments, the content of the lanthanum source in the aqueous solution is 0.01 mmol / mL to 0.1 mmol / mL, including but not limited to 0.01 mmol / mL, 0.03 mmol / mL, 0.05 mmol / mL, 0.08 mmol / mL, 0.1 mmol / mL, or any combination thereof and values ​​within such ranges. Further, the concentration of the lanthanum source in the aqueous solution is 0.01 mmol / mL to 0.05 mmol / mL.

[0064] In some embodiments, the concentration of the phosphorous acid source in the aqueous solution is 0.01 mmol / mL to 0.1 mmol / mL, including but not limited to 0.01 mmol / mL, 0.03 mmol / mL, 0.05 mmol / mL, 0.08 mmol / mL, 0.1 mmol / mL, or any range thereof and values ​​within that range. Further, the concentration of the phosphorous acid source in the aqueous solution is 0.03 mmol / mL to 0.06 mmol / mL.

[0065] It is important to understand that by reasonably controlling the amount of lanthanum source and phosphorous acid source added to the aqueous solution to form a suitable concentration, it is possible to ensure the ideal reaction rate while avoiding excessively high local concentrations that could lead to agglomeration, thereby improving the uniformity of the shell of the lanthanum phosphite hollow microspheres.

[0066] In some embodiments, the mass-to-volume ratio of the organosilicon template to the aqueous solution containing lanthanum and phosphorous acid sources is (30-50) mg:(30-50) mL, including but not limited to 30 mg:30 mL, 40 mg:30 mL, 50 mg:30 mL, 40 mg:30 mL, 40 mg:50 mL, 50 mg:30 mL, 40 mg:40 mL, or any of the foregoing ranges and values ​​within those ranges. Further, the mass-to-volume ratio of the organosilicon template to the aqueous solution containing lanthanum and phosphorous acid sources is (45-50) mg:(30-35) mL. It is understood that controlling the volume ratio can regulate the shell thickness and uniformity of the lanthanum phosphite hollow microspheres, reduce localized particle agglomeration, and enable the formation of high-purity and highly crystalline lanthanum phosphite materials through a uniform reaction system.

[0067] In some embodiments, the preparation process of the precursor (step S1) further includes ultrasound-assisted treatment; further, the ultrasound-assisted treatment time is 10 min-60 min.

[0068] In some embodiments, during the preparation of the precursor (step S1), the mixing time is 1 h to 6 h.

[0069] In some embodiments, the temperature of the hydrothermal reaction is 150°C-200°C, including but not limited to 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or any combination thereof and values ​​within that range. Further, the temperature of the hydrothermal reaction is 160°C-200°C; even further, the temperature of the hydrothermal reaction is 160°C-180°C.

[0070] In some embodiments, the hydrothermal reaction time is 6h-15h, including but not limited to 6h, 8h, 10h, 12h, 15h or any range formed by both of the foregoing and values ​​within that range. Further, the hydrothermal reaction time is 8h-15h; even further, the hydrothermal reaction time is 12h-15h.

[0071] It should be understood that this application achieves the crystallization of lanthanum phosphite through a hydrothermal reaction. During the crystallization process, by controlling the temperature and time of the hydrothermal reaction, a highly crystalline lanthanum phosphite material can be obtained better. Reaction within a temperature range of 160℃-200℃ for 8h-15h allows lanthanum ions and phosphite ions to fully coordinate and form a high-purity crystalline lanthanum phosphite material, and enables the precursor to grow slowly on the surface of the template, forming a uniform shell structure.

[0072] As a non-limiting example, the reaction vessel for the hydrothermal reaction is selected from a polytetrafluoroethylene (PTFE) reactor. It is understood that the PTFE reactor is a stainless steel reactor, and the PTFE reactor liner is made of PTFE material.

[0073] In some embodiments, etching includes chemical etching. As a non-limiting example, the chemical etching solution includes one or more of hydrofluoric acid solution and sodium hydroxide solution.

[0074] In some embodiments, the mass concentration of the etching solution is 1%-5%, and the etching time is 1h-5h. Further, the mass concentration of the etching solution is 1%-3%, and the etching time is 3h-4h.

[0075] This application utilizes a silica template method combined with a hydrothermal method to prepare lanthanum phosphite microspheres with hollow structures. This preparation method can form high-purity, high-crystallinity lanthanum phosphite materials, precisely control the particle size, structure, and surface performance parameters of the hollow lanthanum phosphite microspheres, and ensure the integrity of the shell structure and performance during the etching process.

[0076] Secondly, this application also provides a hollow lanthanum phosphite microsphere, which is prepared by the method for preparing hollow lanthanum phosphite microspheres provided in the first aspect.

[0077] In some embodiments, the particle size of the lanthanum phosphite hollow microspheres is 5 μm-20 μm, including but not limited to 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm or any of the foregoing ranges and values ​​within that range.

[0078] In some embodiments, the thickness of the shell of the lanthanum phosphite hollow microspheres accounts for 60%-80% of the particle size of the hollow microspheres.

[0079] In some embodiments, the crystallinity of the shell of the lanthanum phosphite hollow microspheres is 65%-95%; further, preferably 74%-86%; and even further, preferably 78%-86%.

[0080] In some embodiments, the porosity of the shell of the lanthanum phosphite hollow microspheres is 30%-60%; further, preferably 34%-55%; and even further, preferably 40%-50%.

[0081] In some embodiments, the specific surface area of ​​the shell of the lanthanum phosphite hollow microspheres is 120 m². 2 / g-200m 2 / g; further, preferably 140m 2 / g-182.5m 2 / g; more preferably 170m 2 / g-200m 2 / g.

[0082] Thirdly, this application also provides a flame-retardant material, which includes the lanthanum phosphite hollow microspheres provided in the second aspect.

[0083] Fourthly, this application also provides the application of the lanthanum phosphite hollow microspheres provided in the second aspect in the preparation of flame retardants.

[0084] For experimental parameters not specified in the following specific embodiments, please refer to the guidelines given in this application document first, or refer to experimental manuals or other experimental methods known in the art, or refer to the experimental conditions recommended by the manufacturer.

[0085] The raw materials and reagents involved in the following specific embodiments can be obtained commercially or prepared by those skilled in the art using known methods.

[0086] Example 1

[0087] This embodiment provides a method for preparing hollow lanthanum phosphite microspheres, the specific steps of which are as follows:

[0088] Preparation of silica sphere templates: 40 mL of anhydrous ethanol, 10 mL of deionized water and 3 mL of ammonia (25 wt%) were mixed to form a solution. 0.5 mL, 2 mL, 4 mL and 6 mL of tetraethyl orthosilicate (TEOS) were added dropwise to the solution under mechanical stirring. The reaction was carried out at room temperature for 6 hours. The mixture was collected by centrifugation, washed three times with ethanol, and dried at 60 °C to obtain 4 groups of silica sphere templates for later use.

[0089] Preparation of aqueous solution: Weigh 1 mmol of lanthanum nitrate (La(NO3)3·6H2O) and 1.5 mmol of phosphorous acid (H3PO3) and dissolve them in 30 mL of deionized water. Stir magnetically for 30 min until completely dissolved to form an aqueous solution.

[0090] Preparation of precursors: 50 mg of each of the four groups of silica sphere templates were dispersed in the above aqueous solution, sonicated for 30 min, and then stirred continuously at room temperature for 4 h to form four groups of mixed body fluids containing precursors.

[0091] Preparation of core-shell structured lanthanum phosphite microspheres: The four different mixtures containing precursors prepared above were transferred to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene, placed in an oven, and reacted at 160℃ for 12 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged to collect the precipitate, and washed twice with deionized water to obtain the precipitate, which is the core-shell structured lanthanum phosphite microspheres.

[0092] Preparation of lanthanum phosphite hollow microspheres: The lanthanum phosphite microspheres prepared above were dispersed in 50 mL of 2 wt% hydrofluoric acid (HF) aqueous solution and etched at room temperature for 4 h to completely remove the silica sphere template. After centrifugation, the precipitate was collected and washed three times with deionized water and anhydrous ethanol in sequence. Finally, the washed precipitate was dried in a vacuum drying oven at 60 °C for 6 h to obtain four groups of white powdery lanthanum phosphite hollow microspheres.

[0093] Example 2

[0094] This embodiment provides a method for preparing hollow lanthanum phosphite microspheres, the specific steps of which are as follows:

[0095] Preparation of silica sphere template: 40 mL of anhydrous ethanol, 10 mL of deionized water and 3 mL of ammonia (25 wt%) were mixed to form a solution. 2 mL of tetraethyl orthosilicate (TEOS) was added dropwise to the solution under mechanical stirring. The reaction was carried out at room temperature for 6 hours. The mixture was collected by centrifugation, washed three times with ethanol, and dried at 60 °C to obtain silica sphere template for later use.

[0096] Preparation of aqueous solution: Weigh 1 mmol of lanthanum nitrate (La(NO3)3·6H2O) and 1.5 mmol of phosphorous acid (H3PO3) and dissolve them in 30 mL of deionized water. Stir magnetically for 30 min until completely dissolved to form an aqueous solution.

[0097] Preparation of precursor: 50 mg of silica sphere template was dispersed in the above aqueous solution, sonicated for 30 min, and then stirred continuously at room temperature for 4 h to form a mixed body fluid containing the precursor.

[0098] Preparation of core-shell structured lanthanum phosphite microspheres: The above-prepared mixture containing precursors was transferred to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene and placed in an oven. The reactor was reacted at 180℃ for 8 h, 160℃ for 6 h, 180℃ for 15 h, 150℃ for 12 h, and 200℃ for 8 h, respectively. After the reaction was completed, the reactor was naturally cooled to room temperature, centrifuged to collect the precipitate, and washed twice with deionized water to obtain the precipitate, which is the core-shell structured lanthanum phosphite microspheres.

[0099] Preparation of lanthanum phosphite hollow microspheres: The lanthanum phosphite microspheres prepared above were dispersed in 50 mL of 2 wt% hydrofluoric acid (HF) aqueous solution and etched at room temperature for 4 h to completely remove the silica sphere template. After centrifugation, the precipitate was collected and washed three times with deionized water and anhydrous ethanol in sequence. Finally, the washed precipitate was dried in a vacuum drying oven at 60 °C for 6 h to obtain 5 groups of white powdery lanthanum phosphite hollow microspheres.

[0100] Example 3

[0101] This embodiment provides a method for preparing hollow lanthanum phosphite microspheres, the specific steps of which are as follows:

[0102] Preparation of silica sphere templates: 40 mL of anhydrous ethanol, 10 mL of deionized water and 3 mL of ammonia (25 wt%) were mixed to form a solution. 2 mL of tetraethyl orthosilicate (TEOS) was added dropwise to the solution under mechanical stirring. The reaction was carried out at room temperature for 6 hours. The mixture was collected by centrifugation, washed three times with ethanol, and dried at 60 °C to obtain 3 sets of silica sphere templates for later use.

[0103] Preparation of aqueous solution: Weigh 1 mmol of lanthanum nitrate (La(NO3)3·6H2O) and 1.5 mmol of phosphorous acid (H3PO3) and dissolve them in 30 mL of deionized water. Stir magnetically for 30 min until completely dissolved to form an aqueous solution.

[0104] Preparation of precursor: 50 mg of silica sphere template was dispersed in the above aqueous solution, sonicated for 30 min, and then stirred continuously at room temperature for 4 h to form a mixed body fluid containing the precursor.

[0105] Preparation of core-shell structured lanthanum phosphite microspheres: The above-prepared mixture containing precursors was transferred to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene and placed in an oven. The reactor was reacted at 160℃ for 12 h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the precipitate was collected by centrifugation and washed twice with deionized water to obtain the precipitate, which is the core-shell structured lanthanum phosphite microspheres.

[0106] Preparation of lanthanum phosphite hollow microspheres: The lanthanum phosphite microspheres prepared above were dispersed in 50 mL of 0.5 wt% and 5 wt% hydrofluoric acid (HF) aqueous solutions, respectively. The microspheres were etched at room temperature for 2 h (5 wt% HF aqueous solution) and 8 h (0.5 wt% HF aqueous solution) to remove the silica sphere template. The microspheres were centrifuged, the precipitates were collected, and washed three times with deionized water and anhydrous ethanol, respectively. Finally, the washed precipitates were dried in a vacuum drying oven at 60 °C for 6 h to obtain two groups of white powdery lanthanum phosphite hollow microspheres.

[0107] Comparative Example 1

[0108] Similar to the preparation method in Example 1, the amount of tetraethyl orthosilicate (TEOS) added was 2 mL. The preparation of lanthanum phosphite hollow microspheres and the removal of the silica sphere template were not carried out by etching. The lanthanum phosphite microspheres were calcined at 500°C for 5 h. The remaining preparation steps were the same as in Example 1.

[0109] Comparative Example 2

[0110] The preparation method is similar to that of Example 1, but silica ball templates are not used in the preparation process. All other preparation steps are the same as those in Example 1.

[0111] Experimental Example 1

[0112] The hollow lanthanum phosphite microspheres prepared by (2 mLTEOS) in Example 1 were analyzed by EDS and XPS spectroscopy. The results are shown in Table 1 and Appendix. Figure 1 and attached Figure 2 :

[0113] Table 1: EDS energy dispersive spectroscopy results of lanthanum phosphite hollow microspheres

[0114]

[0115] From the appendix Figure 1 According to the EDS results, the elemental content in the lanthanum phosphite hollow microsphere sample prepared in this application is close to the theoretical value of lanthanum phosphite. Figure 2 According to the XPS results, the phosphorus binding energy of the lanthanum phosphite hollow microsphere sample prepared in this application is around 133 eV and the oxygen binding energy is around 531.2 eV. Combined with the detection results of EDS and XPS, it is indicated that the hollow microspheres prepared in this application are lanthanum phosphite hollow microspheres.

[0116] Experimental Example 2

[0117] The morphology of the lanthanum phosphite products prepared in Examples 1-3 and Comparative Examples 1-2 was analyzed. See Appendix for some examples of product morphology. Figures 3-6 The scanning electron microscope (SEM) images show that the lanthanum phosphite prepared in this application is in the form of hollow microspheres, while the product prepared by calcination in Comparative Example 1 cannot obtain a hollow microsphere structure; the microsphere structure collapses at high temperature. (See attached image for details.) Figure 6 As shown; in Comparative Example 2, hollow microspheres could not be obtained without using a silica sphere template; see Appendix for details. Figure 5 As shown; further, to further analyze the effects of silica sphere template, hydrothermal reaction conditions, and etching conditions on the morphology and structure of lanthanum phosphite hollow microspheres during the preparation process, crystallinity was tested by XRD, porosity was determined by mercury intrusion porosimetry (GB / T21650.1-2026 standard), and specific surface area was determined by low-temperature nitrogen adsorption BET method (GB / T19587-2017 standard). The particle size and shell properties of the lanthanum phosphite hollow microspheres were analyzed, and the specific results are shown in Tables 2 to 4.

[0118] Table 2: Particle size and shell performance analysis results of lanthanum phosphite hollow microspheres prepared in Example 1

[0119]

[0120] Table 3: Particle size and shell performance analysis results of lanthanum phosphite hollow microspheres prepared in Example 2

[0121]

[0122] Table 4: Particle size and shell performance analysis results of lanthanum phosphite hollow microspheres prepared in Example 3

[0123]

[0124] Application Example 1

[0125] The products prepared in Examples 1-3 and Comparative Examples 1-2 were used for flame retardant testing of Nylon 66, and the application effect was verified. The specific test methods were: horizontal and vertical burning (UL94) and glow wire test (GB / T 5169.13-2024). The test results are shown in Table 5.

[0126] Table 5: Flame retardant test results of lanthanum phosphite hollow microspheres

[0127]

[0128] The results in Table 5 show that:

[0129] (1) The influence of hollow structure

[0130] Comparing the results of Comparative Example 1 and Examples 1-3, it can be seen that Comparative Examples 1-2 lacked hollow structures, failed UL94 Class V, and had relatively low GWIT values ​​of 675°C and 685°C, respectively. In contrast, Examples 1-3 were able to form microspheres with hollow structures, achieving a V-0 flammability rating and a GWIT value as high as 775°C. The hollow structure provides a greater thermal barrier, delaying heat transfer to the material's interior. The hollow microspheres can also serve as physical cross-linking points, enhancing melt strength and reducing dripping. The failure of Example 3 (sample 3-1) to pass Class V was mainly due to poor etching performance.

[0131] (2) Effect of specific surface area BET

[0132] Table 6: Effect of specific surface area on BET

[0133]

[0134] A high specific surface area provides more active sites, promoting the formation of a dense char layer in nylon 66 during combustion, effectively isolating oxygen and heat.

[0135] (3) Influence of shell thickness

[0136] Too thin [<7μm]: No. 2-1 (shell damaged), flame retardant effect decreased (V-1, GWIT 740℃).

[0137] Moderate [(7μm-12μm)]: No. 1-3 have the best flame retardant effect (V-0, GWIT 775℃).

[0138] Excessive thickness [>12μm]: No. 1-4, flame retardant effect slightly reduced (V-1, GWIT 750℃).

[0139] (4) Effect of crystallinity

[0140] Table 7: Crystallinity X c Impact

[0141]

[0142] Moderate crystallization (78%-86%) is beneficial for the formation of a stable carbon layer; excessive crystallization may lead to a decrease in porosity, affecting gas adsorption and free radical capture capabilities.

[0143] (5) Influence of porosity

[0144] Table 8: Effect of Porosity φ

[0145]

[0146] Mesoporous structures (40% < φ ≤ 50%) are beneficial for capturing free radicals generated during combustion and interrupting the combustion chain reaction; excessive porosity may lead to a decrease in the mechanical strength of the shell.

[0147] (6) Impact of template removal integrity

[0148] Template residue (No. 3-1): worst flame retardant effect (does not pass Class V, GWIT only 670°C).

[0149] Template completely removed (numbers 1-3): best flame retardant effect (V-0, GWIT 775°C).

[0150] Template residues occupy hollow spaces, reducing the effective active sites.

[0151] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0152] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing hollow lanthanum phosphite microspheres, characterized in that, Includes the following steps: A precursor was prepared by mixing an organosilicon template with an aqueous solution containing a lanthanum source and a phosphorous acid source. The precursor was subjected to a hydrothermal reaction to prepare lanthanum phosphite microspheres. Lanthanum phosphite hollow microspheres were prepared by etching to remove the organosilicon template from the lanthanum phosphite microspheres.

2. The method for preparing lanthanum phosphite hollow microspheres according to claim 1, characterized in that, The organosilicon template is spherical in shape, and the particle size of the sphere is 200nm-500nm.

3. The method for preparing lanthanum phosphite hollow microspheres according to claim 1 or 2, characterized in that, The organosilicon template is prepared by reacting an organosilicon source dispersed in a solvent containing ethanol, water, and ammonia. Optionally, the organosilicon source includes at least one of silicate ester organosilicon and organosilicon alkane; Further optionally, the silicate ester organosilicon includes at least one of tetraethyl orthosilicate and methyl orthosilicate; Further optionally, the organosilanes include octadecyltrimethoxysilane.

4. The method for preparing lanthanum phosphite hollow microspheres according to claim 3, characterized in that, It also satisfies at least one of the following conditions (1) to (5): (1) The volume ratio of the ethanol, the water and the ammonia in the solvent is (30-50):(5-15):(1-5); (2) The volume ratio of the organosilicon source to the solvent containing ethanol, water and ammonia is (0.5-6):(50-60); Optionally, the volume ratio of the organosilicon source to the solvent containing ethanol, water, and ammonia is (2-6):(50-60). (3) The lanthanum source includes one or more of lanthanum nitrate and lanthanum chloride; (4) The phosphorous acid source includes one or more of phosphorous acid and its salts; (5) The molar ratio of the lanthanum source to the phosphorous acid source is (0.5-1.5):(1-2).

5. The method for preparing lanthanum phosphite hollow microspheres according to claim 1 or 2, characterized in that, It also satisfies at least one of the following conditions (1) to (3): (1) The temperature of the hydrothermal reaction is 150℃-200℃; Optionally, the hydrothermal reaction temperature is 160℃-200℃; (2) The hydrothermal reaction time is 6 h-15 h; Optionally, the hydrothermal reaction time is 8 h-15 h; (3) The reaction vessel for the hydrothermal reaction is selected from a polytetrafluoroethylene reactor.

6. The method for preparing lanthanum phosphite hollow microspheres according to claim 1 or 2, characterized in that, The etching solution includes one or more of hydrofluoric acid solution and sodium hydroxide solution; Optionally, the mass concentration of the etching solution is 1%-5%, and the etching time is 1h-5h.

7. Hollow microspheres of lanthanum phosphite, characterized in that, The hollow lanthanum phosphite microspheres were prepared by the method described in any one of claims 1 to 6.

8. The hollow lanthanum phosphite microspheres according to claim 7, characterized in that, The lanthanum phosphite hollow microspheres have a particle size of 5 μm-20 μm; and / or, the thickness of the shell layer of the lanthanum phosphite hollow microspheres accounts for 60%-80% of the particle size of the hollow microspheres; and / or, the crystallinity of the shell layer of the lanthanum phosphite hollow microspheres is 65%-95%; and / or, the porosity of the shell layer of the lanthanum phosphite hollow microspheres is 30%-60%; and / or, the specific surface area of ​​the shell layer of the lanthanum phosphite hollow microspheres is 120 m². 2 / g -200 m 2 / g.

9. A flame-retardant material, characterized in that, The flame-retardant material includes the lanthanum phosphite hollow microspheres as described in claim 7 or 8.

10. The application of the lanthanum phosphite hollow microspheres as described in claim 7 or 8 in the preparation of flame retardants.

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