Preparation and application of a core-shell structured hollow glass microsphere precursor microparticle

Abstract

This invention discloses the preparation and application of core-shell structured hollow glass microsphere precursor particles, comprising: mixing water glass with water, then removing sodium ions with a cation exchange resin to obtain a silicate aqueous solution; dissolving metal nitrate and boric acid into a saturated aqueous solution, adding it to the silicate aqueous solution under magnetic stirring to obtain a uniformly doped transparent mixed solution, and spray drying to obtain core-shell structured hollow glass microsphere precursor particles. This invention pre-forms relatively large pores within the precursor particles to obtain core-shell structured hollow glass microsphere precursor particles, which can effectively shorten the foaming and spheroidizing time, reduce incompletely foamed particles, and improve the yield and performance of hollow glass microspheres. This invention uses molecular-level water glass as the main raw material, completing part of the silicate formation and cross-linking reaction during the process, replacing the bonding and aggregation of particles prepared by traditional soft chemical methods with chemical bonding, thus enhancing the compressive strength of the precursor particles.

Description

Technical Field

[0001] This invention belongs to the field of hollow glass microsphere precursor particle preparation technology. More specifically, this invention relates to the preparation and application of core-shell structured hollow glass microsphere precursor particles. Background Technology

[0002] Hollow glass microspheres are hollow, spherical glass powders with diameters in the micrometer range. They possess advantages such as low density, high strength, good environmental stability, and easy dispersion. By designing and controlling the glass material composition of hollow glass microspheres, they can be endowed with functions such as corrosion resistance, radiation resistance, heat insulation, sound insulation, and electrical insulation. Therefore, they are widely used in cutting-edge technology fields such as aerospace and deep-sea exploration, as well as civilian fields such as petrochemicals.

[0003] The industrial preparation process of hollow glass microspheres mainly involves two stages: first, the preparation of precursor microparticles; and second, the foaming of these precursor microparticles into spheres at high temperatures. The properties of the precursor microparticles prepared in the first stage have a decisive impact on the efficiency of the foaming process and the performance of the final product. Currently, there are two mainstream industrial production methods for precursor microparticles: one is the glass powder method, which involves uniformly mixing raw materials such as quartz sand, limestone, and boric acid, then melting them at high temperatures (1200–1400℃) into a glass melt, followed by water quenching, drying, and pulverization to obtain precursor microparticle powder with a predetermined composition. This method, due to the high-temperature melting stage, allows the precursor microparticles to complete the chemical and physical processes of silicate formation and glass material formation, resulting in microspheres with high chemical stability and high compressive strength. However, it suffers from low foaming efficiency and high cost. Another method is the soft chemical method, which involves dispersing silica micro powder, inorganic salts, foaming agents, and stabilizing dispersants in water in a certain proportion to form a slurry, and then spray drying it to obtain precursor microparticles. In this method, the components of the precursor microparticles aggregate into microparticles under the binding effect of the stabilizing dispersant, and there is no chemical bonding between the components. Therefore, the precursor microparticles have low strength and metal salts are easy to precipitate.

[0004] The heat transfer, mass transfer, and morphological evolution of precursor microparticles during spheroidization were analyzed using fluid dynamics simulation. The entire process of precursor microparticle foaming and spheroidization can be decomposed into four stages: encapsulation, foaming, refining, and cooling and solidification. The foaming stage can be further divided into four processes: bubble nucleation, bubble growth, bubble coalescence, and bubble merging. The precursor microparticles evolved from solid particles, porous particles, core-shell particles, to hollow microspheres. Precursor microparticles obtained by the glass powder method and the soft chemical method are all solid particles, which suffer from incomplete foaming during the high-temperature vitrification spheroidization process. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these objectives and other advantages of the present invention, a method for preparing core-shell structured hollow glass microsphere precursor particles is provided, comprising the following steps:

[0007] Step 1: Mix water glass with water, and then use a cation exchange resin to remove sodium ions to obtain an aqueous solution of silicic acid.

[0008] Step 2: Dissolve the metal nitrate and boric acid into a saturated aqueous solution, and add it to the silicic acid aqueous solution obtained in Step 1 under magnetic stirring to obtain a uniformly doped transparent mixed solution.

[0009] Step 3: The transparent mixed solution obtained in Step 2 is spray-dried to obtain core-shell structured hollow glass microsphere precursor particles.

[0010] Preferably, in step one, the modulus of the water glass is 3.1 to 3.4; the mass-to-volume ratio of water glass to water is 1g:3 to 5mL.

[0011] Preferably, in step one, the cation exchange resin is a macroporous, strongly acidic styrene-type cation exchange resin D001.

[0012] Preferably, in step one, the mass ratio of cation exchange resin to water glass is 1.5 to 2.5:1.

[0013] Preferably, in step two, the magnetic stirring speed is 500-700 rpm.

[0014] Preferably, in step two, the amount of boric acid used is calculated based on the mass ratio of B2O3 in the target hollow glass microspheres.

[0015] Preferably, in step two, the metal nitrate includes lithium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, aluminum nitrate, and sodium nitrate.

[0016] Preferably, in step two, the amount of metal nitrate used is calculated based on the mass ratio of the corresponding oxide in the target hollow glass microspheres.

[0017] Preferably, in step three, the inlet air temperature of the spray dryer is 180–400°C, the feed rate is 5–10%, the inlet air volume is 60–80%, and the air flow rate is 500–700 L / h.

[0018] Preferably, step one further includes: using a radio frequency processor to assist the cation exchange resin in removing sodium ions; wherein the radio frequency processor has a frequency of 27.12MHz, a power of 6-9W, an electrode spacing of 100-140mm, and a time of 20-30min.

[0019] Preferably, step two further includes: subjecting the obtained transparent mixed solution to gamma irradiation treatment; wherein the irradiation dose rate is 600-800 Gy / min and the time is 10-20 min.

[0020] Application of core-shell structured hollow glass microsphere precursor particles prepared by the method described above in the preparation of hollow glass microspheres.

[0021] The present invention has at least the following beneficial effects: When preparing precursor microparticles, the present invention pre-forms large-sized pores in the precursor microparticles, and the resulting core-shell structured hollow glass microsphere precursor microparticles can effectively shorten the time for small bubbles to coalesce into large bubbles in the melt during foaming and spherical formation, reduce the number of incompletely foamed microspheres, and improve the yield and performance of hollow glass microspheres.

[0022] This invention uses molecular-level water glass as the main raw material. Partial silicate formation and cross-linking reactions are completed during solution doping and spray drying, eliminating the need for stabilizing dispersants. Chemical bonding replaces the agglomeration and bonding effects of traditional soft chemical methods for microparticle preparation, enhancing the compressive strength of the precursor microparticles. The solution doping method improves the doping uniformity of the precursor microparticles, further enhancing the microscopic uniformity of the glass material during vitrification and spheroidization, thus improving product performance.

[0023] In the reaction of water glass and cation exchange resin, this invention utilizes a radio frequency processor to promote the exchange of matter and energy between materials, thereby accelerating the reaction process and significantly shortening the ion exchange time. In the solution doping process, this invention performs gamma irradiation treatment to promote silicate formation and cross-linking reaction, further enhancing the compressive strength of the precursor particles.

[0024] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0025] Figure 1 Scanning electron microscope image of the core-shell structured hollow glass microsphere precursor particles prepared in Example 1;

[0026] Figure 2 Scanning electron microscope image of the internal cross-section of the core-shell structured hollow glass microsphere precursor particles prepared in Example 1 after grinding and crushing.

[0027] Figure 3 Scanning electron microscope image of hollow glass microspheres prepared from hollow glass microsphere precursor particles with solid structure as comparative example 1.

[0028] Figure 4 Simulation of bubble growth and aggregation during the foaming process of precursor microparticles into spheres;

[0029] Figure 5 The foaming time of hollow glass microsphere precursor particles with different pore sizes is given. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0031] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0032] Example 1

[0033] A method for preparing core-shell structured hollow glass microsphere precursor particles includes the following steps:

[0034] Step 1: Mix 300g of water glass with a silica content of 28.56% and a modulus of 3.3 with 1200mL of water, then add 600g of macroporous strong acid styrene-type cation exchange resin D001 to remove sodium ions. After soaking for 1 hour, separate the upper layer solution to obtain an aqueous solution of silicic acid.

[0035] Step 2: Dissolve the metal nitrates (aluminum nitrate nonahydrate: 7.6420g; calcium nitrate tetrahydrate: 76.5320g; magnesium nitrate hexahydrate: 16.5194g; lithium nitrate: 25.1633g; sodium nitrate: 9.9687g; potassium nitrate: 5.5849g) and 18.9078g boric acid in 300mL of water. Add the solution to the silicic acid aqueous solution obtained in Step 1 under magnetic stirring at 600rpm to obtain a transparent mixed solution with pH=2.5 and uniform doping.

[0036] Step 3: The transparent mixed solution obtained in Step 2 is spray-dried to obtain core-shell structured hollow glass microsphere precursor particles; the specific conditions for spray drying are: inlet air temperature of 180℃, feed rate of 7%, inlet air volume of 70%, and air flow rate of 600L / h.

[0037] The hollow glass microsphere precursor particles with a core-shell structure prepared in this embodiment and their internal cross-sections after grinding and crushing were characterized by scanning electron microscopy. The results are as follows: Figures 1-2 As shown, the hollow glass microsphere precursor particles prepared in this embodiment have enlarged pores inside, indicating that the present invention has successfully prepared core-shell structured hollow glass microsphere precursor particles.

[0038] Comparative Example 1

[0039] A method for preparing hollow glass microsphere precursor particles with a solid structure includes the following steps:

[0040] Step 1: Dissolve 104.3g of silica in 338ml of water and stir at 10000rpm for 5min using a homogenizer to obtain solution A;

[0041] Step 2: Dissolve the metal nitrates (aluminum nitrate nonahydrate: 7.6420g; calcium nitrate tetrahydrate: 76.5320g; magnesium nitrate hexahydrate: 16.5194g; lithium nitrate: 25.1633g; sodium nitrate: 9.9687g; potassium nitrate: 5.5849g) and 18.9078g boric acid in 300ml of water, and add the solution to solution A using a homogenizer while stirring at 10000rpm to obtain a doped emulsion;

[0042] Step 3: After stirring the doped emulsion for 5 minutes in a homogenizer at 10,000 rpm, spray dry it to obtain hollow glass microsphere precursor particles with solid structure. The specific conditions for spray drying are: inlet air temperature of 180℃, feed rate of 7%, inlet air volume of 70%, and air flow rate of 600 L / h.

[0043] The solid-structured hollow glass microsphere precursor particles prepared in this comparative example were foamed into spheres at 1200℃ with a feed rate of 15 kg / h to obtain hollow glass microspheres. Scanning electron microscopy images are shown below. Figure 3 As shown, it can be seen that hollow glass microspheres prepared from solid-structured hollow glass microsphere precursor particles contain microspheres that are not fully foamed.

[0044] Figure 4 This study simulates the bubble growth and coalescence process during the foaming of precursor microparticles into spheres. During the melt foaming process, based on the Laplace pressure inside the bubbles in the melt, Δp = 2γ / R, where a larger radius of curvature R results in a smaller Δp. As the precursor microparticles foam to form hollow glass microspheres, smaller bubbles continuously coalesce towards larger bubbles, eventually forming spherical hollow glass droplets. These droplets are then cooled and solidified to obtain hollow glass microsphere powder. The foaming time of the precursor microparticles with different pore sizes was studied using fluid dynamics simulation. The results are as follows: Figure 5 As shown, the present invention pre-forms large-sized pores in the precursor particles, which can effectively shorten the time for small bubbles to coalesce into large bubbles and improve foaming efficiency.

[0045] Example 2

[0046] A method for preparing core-shell structured hollow glass microsphere precursor particles includes the following steps:

[0047] Step 1: Mix 300g of water glass with a silica content of 28.56% and a modulus of 3.3 with 1200mL of water, then add 600g of macroporous strong acid styrene-type cation exchange resin D001. After treating the mixture with an RF processor for 30 minutes, separate the upper layer solution to obtain a silicic acid aqueous solution. The RF processor has a frequency of 27.12MHz, a power of 7W, and an electrode spacing of 140mm.

[0048] Step 2: Dissolve the metal nitrates (aluminum nitrate nonahydrate: 7.6420g; calcium nitrate tetrahydrate: 76.5320g; magnesium nitrate hexahydrate: 16.5194g; lithium nitrate: 25.1633g; sodium nitrate: 9.9687g; potassium nitrate: 5.5849g) and 18.9078g boric acid in 300mL of water. Add the solution to the silicic acid aqueous solution obtained in Step 1 under magnetic stirring at 600rpm to obtain a transparent mixed solution with pH=2.5 and uniform doping.

[0049] Step 3: The transparent mixed solution obtained in Step 2 is spray-dried to obtain core-shell structured hollow glass microsphere precursor particles; the specific conditions for spray drying are: inlet air temperature of 180℃, feed rate of 7%, inlet air volume of 70%, and air flow rate of 600L / h.

[0050] This embodiment utilizes a radio frequency processor to promote the reaction between water glass and cation exchange resin, significantly shortening the reaction time.

[0051] Example 3

[0052] A method for preparing core-shell structured hollow glass microsphere precursor particles includes the following steps:

[0053] Step 1: Mix 300g of water glass with a silica content of 28.56% and a modulus of 3.3 with 1200mL of water, then add 600g of macroporous strong acid styrene-type cation exchange resin D001. After treating the mixture with an RF processor for 30 minutes, separate the upper layer solution to obtain a silicic acid aqueous solution. The RF processor has a frequency of 27.12MHz, a power of 7W, and an electrode spacing of 140mm.

[0054] Step 2: Dissolve the metal nitrates (aluminum nitrate nonahydrate: 7.6420 g; calcium nitrate tetrahydrate: 76.5320 g; magnesium nitrate hexahydrate: 16.5194 g; lithium nitrate: 25.1633 g; sodium nitrate: 9.9687 g; potassium nitrate: 5.5849 g) and 18.9078 g of boric acid in 300 mL of water. Add this solution to the silicic acid aqueous solution obtained in Step 1 under magnetic stirring at 600 rpm to obtain a transparent mixed solution with pH = 2.5 and uniform doping. Irradiate the obtained transparent mixed solution with gamma rays at a dose rate of 700 Gy / min for 10 min.

[0055] Step 3: The treated transparent mixed solution is spray-dried to obtain core-shell structured hollow glass microsphere precursor particles; the specific conditions for spray drying are: inlet air temperature of 180℃, feed rate of 7%, inlet air volume of 70%, and air flow rate of 600L / h.

[0056] This embodiment utilizes a radio frequency processor to promote the reaction between water glass and cation exchange resin, significantly shortening the reaction time. Furthermore, the hollow glass microsphere precursor particles with a core-shell structure prepared in this embodiment are crushed and ground, resulting in fewer particle breakages and higher strength. This indicates that the gamma irradiation treatment of the mixed solution in this invention is beneficial to silicate formation and cross-linking reaction, further enhancing the compressive strength of the precursor particles.

[0057] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing core-shell structured hollow glass microsphere precursor particles, characterized in that, Includes the following steps: Step 1: Mix water glass with water, then remove sodium ions using a cation exchange resin to obtain a silicate aqueous solution; wherein the modulus of the water glass is 3.1~3.4; the mass-to-volume ratio of water glass to water is 1g:3~5mL; the cation exchange resin is macroporous strong acid styrene-type cation exchange resin D001; the mass ratio of cation exchange resin to water glass is 1.5~2.5:1; Step 2: Dissolve the metal nitrate and boric acid into a saturated aqueous solution, and add it to the silicic acid aqueous solution obtained in Step 1 under magnetic stirring to obtain a uniformly doped transparent mixed solution; wherein the metal nitrate is lithium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, aluminum nitrate and sodium nitrate; Step 3: The transparent mixed solution obtained in Step 2 is spray-dried to obtain core-shell structured hollow glass microsphere precursor particles.

2. The method for preparing core-shell structured hollow glass microsphere precursor particles as described in claim 1, characterized in that, In step two, the magnetic stirring speed is 500~700 rpm.

3. The method for preparing core-shell structured hollow glass microsphere precursor particles as described in claim 1, characterized in that, In step two, the amount of boric acid used is calculated based on the mass ratio of B2O3 in the target hollow glass microspheres.

4. The method for preparing core-shell structured hollow glass microsphere precursor particles as described in claim 1, characterized in that, In step two, the amount of metal nitrate used is calculated based on the mass ratio of the corresponding oxide in the target hollow glass microspheres.

5. The method for preparing core-shell structured hollow glass microsphere precursor particles as described in claim 1, characterized in that, In step three, the inlet air temperature of the spray dryer is 180~400℃, the feed rate is 5~10%, the inlet air volume is 60~80%, and the air flow rate is 500~700L / h.

6. The application of a core-shell structured hollow glass microsphere precursor microparticle prepared by the preparation method according to any one of claims 1-5 in the preparation of hollow glass microspheres.

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