A method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength

Abstract

This invention discloses a method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength. The method involves dispersing ground raw materials and hollow glass microsphere byproducts in water, then adding 4-8% (by weight) of water glass to the mixture under stirring. After room temperature aging, drying, pulverizing, and grading, microporous precursor particles are obtained. These microporous precursor particles are then hollowed into spheres under a reducing atmosphere to obtain hollow glass microspheres with a floatability >97%. The hollow glass microspheres are then subjected to pressure and ultrasonic buoyancy separation to obtain hollow glass microspheres with a floatability >99%. Finally, the surface of these hollow glass microspheres is uniformly coated with a silicon-containing compound in a solvent, and after drying, high-floatability hollow glass microspheres with a floatability greater than 99.5% are obtained. The hollow glass microspheres prepared by this invention possess excellent characteristics such as low density, high compressive strength, high floatability, low ion precipitation, and low cost, and can be used in aerospace ablation-resistant materials, deep-sea floating body materials, automotive adhesives, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of functional inorganic filler material preparation technology, specifically relating to a method for preparing high-floatability hollow glass microspheres with a floating rate greater than 99.5% in an aqueous medium. The prepared high-floatability hollow glass microspheres can be widely used in military, building materials, petroleum, chemical and other fields, and are especially suitable for deep-sea floating bodies, aerospace, rail transportation, automobile manufacturing, 5G base stations and other fields. Background Technology

[0002] Hollow glass microspheres (HGM) are hollow, thin-walled, high-strength, and lightweight micron-sized glassy spheres. They possess superior properties unmatched by other fillers, such as low density, high strength, high temperature resistance, low thermal conductivity, low dielectric constant, and excellent dispersibility. As a filler material, they can not only reduce product costs but also endow products with new functions, making them the mainstream of new filler materials in the 21st century.

[0003] my country generates a large amount of waste glass every year, but the recycling rate is low due to differences in raw material sources, uses, and production mechanisms. Furthermore, glass is a non-degradable material, and its accumulation puts enormous pressure on environmental protection and resource utilization. Patents from 3M Inc. in the United States, such as CN103415481A and CN102811965AD, disclose methods for preparing hollow glass microspheres (HGM) using waste glass as raw material; however, the prepared HGM has high true density but low compressive strength, failing to meet application requirements.

[0004] With the continuous expansion of HGM applications, higher requirements are being placed on HGM performance, mainly in terms of true density, compressive strength, and buoyancy. True density and compressive strength are interdependent. The compressive strength of HGM is determined by factors such as material strength, aspect ratio (radius to wall thickness), surface condition, and buoyancy, and is negatively correlated with aspect ratio. Therefore, the lower the true density of HGM and the thinner the shell wall, the lower the compressive strength. Because lower HGM true density results in lighter and lower-cost products at the same addition amount, and the special functional properties imparted by HGM are more significant, maintaining high compressive strength is necessary to meet process and product performance requirements. Therefore, the preparation of low-density, high-compressive-strength, and high-buoyancy hollow glass microspheres has become a major key problem that needs to be solved. In specialized fields, such as aerospace ablation-resistant materials and deep-sea floating bodies, and in some application areas, international regulations (such as the EU REACH regulation) impose strict requirements on HGM ion precipitation.

[0005] In addition, hollow glass microspheres currently prepared from waste glass still have defects such as surface defects and ion precipitation.

[0006] To reduce production costs, Chinese patent application 201510177509.8 discloses a method for manufacturing hollow glass microspheres using waste glass. The method involves washing and crushing the waste glass, adding 3-10% feldspar, 0-6% talc, 1-3% soda ash, 1-5% limestone, 1-3% water glass, 1-3% zinc sulfate, and 1-3% calcium sulfate by weight of the waste glass. The mixture is then ball-milled, and a paste containing cellulose and other additives is added. The mixture is then spray-dried and heated to 1100-1200℃ for spheroidization to obtain hollow glass microspheres. However, the hollow glass microspheres produced by this method have a suspension rate of only 95% in water, and the breakage rate in compressive strength tests at 30 MPa is as high as 14% and 16%.

[0007] To further improve the floatability of hollow glass microspheres and effectively control their compressive strength and true density, Chinese patent ZL201910972403.5 discloses a method for preparing hollow glass microspheres with high floatability. The basic raw materials are a mixture of quartz, borax, calcium carbonate, sodium carbonate, sodium sulfate, and sodium phosphate. When the total mass of each component is calculated as 100%, the content of each component is: quartz 60.30~61.15%, borax 14.00~14.90%, calcium carbonate 19.15~20.80%, sodium carbonate 3.40~3.80%, sodium sulfate 0.22~0.81%, and sodium phosphate 0.41~1.25%. Stabilizing dispersants and surfactants also need to be added. However, the floatability of the hollow glass microspheres prepared by this method is still less than 98.5%, and the raw material cost and production cost are high. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing hollow glass microsphere preparation methods, such as high production cost, low yield, difficulty in controlling compressive strength and true density, uneven pore distribution of precursor particles, difficulty in controlling pore size, and severe surface defects and ion precipitation. This invention provides a method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength, solving the problems of low floatability, poor strength, and high ion precipitation in hollow glass microspheres prepared from waste glass. This method can be applied to aerospace ablation-resistant materials, deep-sea floating body materials, automotive adhesives, and other fields, and is of great significance for achieving the localization of high-end technological materials.

[0009] To achieve the above-mentioned objectives of this invention, a method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength is provided. Using waste glass powder as the main raw material, microporous precursor particles are prepared by adding hollow glass microsphere byproducts. Simultaneously, the hollow spheroidization process conditions are controlled to prepare high-floatability hollow glass microspheres. By coating the surface of the hollow glass microspheres with a silica layer, surface defects are repaired, ion precipitation is controlled, and the compressive strength of the hollow glass microspheres is improved. The specific process steps are as follows:

[0010] 1) Raw material pretreatment – ​​preparation of microporous precursor particles

[0011] When the total mass of the raw material components is calculated as 100%, the content of each component is as follows: waste glass 74.5-84.5%, quartz sand 4.1-8.9%, anhydrous borax 3.1-9.9%, calcium carbonate 3.2-6.7%, sodium sulfate 0.2-2.2%, lithium phosphate 0.1-1.2%, zinc phosphate 0.48-1.5%, and hollow glass microsphere by-product 1.1-1.98%; the hollow glass microsphere by-product refers to a true density of 1.0-1.8 g / cm³. 3 Hollow, porous glass beads with a particle size of less than 5μm; anhydrous borax can be converted into pentahydrate borax and decahydrate borax in the same proportion.

[0012] Waste glass, quartz sand, anhydrous borax, calcium carbonate, sodium sulfate, lithium phosphate, and zinc phosphate in the raw materials are ground to a particle size of less than 15 μm and mixed evenly. This mixture is then uniformly dispersed in water with hollow glass microspheres as a byproduct, yielding a mixture with a solid content of 65-73%. Then, 4-8% (by weight) of water glass is added to the mixture under stirring, causing gel solidification into a block structure. This block structure is then aged at room temperature, dried, pulverized, and classified to obtain microporous precursor particles with a particle size of 10-35 μm and an average pore size of less than 2.6 μm. Grinding achieves homogenization and particle refinement of the raw materials. An air jet mill or Raymond mill / ball mill-classification system is used to simultaneously complete pulverization and classification, reducing the generation of fine powder. The prepared microporous precursor particles have a narrower particle size range, improving the thermodynamic consistency during the hollow spheroidization process, which is beneficial for the preparation of high-floatability, high-strength hollow glass microspheres.

[0013] The content of all compounds in the waste glass, calculated as 100%, is as follows:

[0014] SiO2 60~90%;

[0015] Li₂O + Na₂O + K₂O 2~17%;

[0016] CaO + MgO 3~18%;

[0017] B2O3 0~15%;

[0018] SO30~2.8%

[0019] Al2O3 0~15%

[0020] ZnO + BaO + P2O5 + TiO2 + Balance 0~8%.

[0021] The purpose of adding hollow glass microspheres as a byproduct is to utilize their physical pores to form pore nuclei, making foaming easier. In the microporous precursor particles, they act as a physical foaming agent and nucleation agent, reducing the activation energy for bubble formation and increasing the hollow spherical proportion of the hollow glass microspheres.

[0022] The water glass is an aqueous solution of sodium silicate with no modulus limitation.

[0023] 2) Hollow spheroidization of microporous precursor particles

[0024] The microporous precursor particles prepared in step 1) are pre-dispersed in a combustion-supporting gas at 220~300℃, and then transported to a high-temperature spheroidizing furnace for hollow spheroidization under a reducing atmosphere. After being rapidly solidified and shaped by a cooling device, hollow glass microspheres with a floating rate of >97% are obtained.

[0025] In this step, the microporous precursor particles are first uniformly dispersed in a combustion-supporting gas with an initial temperature of 220~300℃, so that after being transported to the high-temperature spheroidizing equipment, the liquefaction rate of the particle surface is increased, energy consumption is reduced, heating is more uniform, and gas coating is achieved more efficiently. At the same time, hollow spheroidization is carried out under a reducing atmosphere. At a lower temperature, the glass liquid on the particle surface still has a lower surface tension, reducing energy consumption, bubble coalescence and expansion resistance, and finally preparing hollow glass microspheres with a floating rate of >97%.

[0026] 3) Strengthening of hollow glass microspheres: The hollow glass microspheres prepared in step 2) were subjected to pressure and ultrasonic buoyancy separation to obtain hollow glass microspheres with a buoyancy rate >99.3%; then, the pressure- and ultrasonically separated hollow glass microspheres were dispersed in a solvent containing silicon compounds and stirred for 20-45 min to uniformly coat the surface of the hollow glass microspheres with silicon compounds; after drying, the hollow glass microspheres coated with silicon compounds were heat-treated at 200-450℃ for 35-50 min to convert the silicon compounds into a silicon oxide layer, finally preparing a material with a true density of 0.12-0.40 g / cm³. 3 High-floatability hollow glass microspheres with compressive strength of 5.0~55 MPa, free boron content <500ppm, sodium ion content <100mg / L, and floatability greater than 99.5%.

[0027] The purpose of pressurization is to allow water to overcome resistance and enter the broken glass microspheres, increasing the density of the broken particles and causing them to sink during buoyancy separation, thereby improving the physical properties of hollow glass microspheres (increasing compressive strength and buoyancy rate).

[0028] In step 3), the silicon-containing compound is one or a mixture of two or more of silica sol, polysiloxane, and polysilazane. After high-temperature treatment, no residue remains except for the coated silica layer. The silicon-containing compound coats the surface of the hollow glass microspheres, and a silica layer is formed upon heating. The heating temperature is lower than the softening point of the hollow glass microspheres. The curing temperature is low, the curing time is short, the adhesion is strong, surface defects are repaired, and ion precipitation from the hollow glass microspheres is effectively prevented. The prepared hollow glass microspheres have excellent characteristics of high strength and low ion precipitation. Ultrasonic buoyancy separation can effectively improve the buoyancy separation efficiency and selection quality. Ultrasound promotes the detachment of broken particles and micro-powder particles from the attached hollow glass particles through physical force, allowing them to sink to the bottom of the solvent.

[0029] In step 3), the buoyancy separation medium used in ultrasonic buoyancy separation is water, ethanol, petroleum ether, or other substances with similar properties that do not chemically react with hollow glass microspheres and leave no residue after drying; the ultrasonic frequency used in ultrasonic buoyancy separation is 35~55kHz, with 40~50kHz being preferred.

[0030] Furthermore, the pressurization and ultrasonic buoyancy separation described in step 3) are carried out in a closed pressure vessel, with an applied pressure of 0.5~1.6MPa and an ultrasonic frequency of 35~55kHz.

[0031] Furthermore, in step 2), when the sum of the volume fractions of the combustion-supporting gases is calculated as 100%, the content of each component is preferably: oxygen 2~12%, hydrogen 2~5%, and air 85~94%.

[0032] As a preferred embodiment of the present invention, in step 1), grinding is performed using a ball mill or a vibratory mill, and drying is performed using one of a multi-layer belt dryer, a rotary drum dryer, or a fluidized bed dryer; in step 2), when the sum of the volume fractions of the combustion-supporting gases is calculated as 100%, the content of each component is: oxygen 4~10%, hydrogen 2~5%, and air 87~94%; in step 3), the buoyancy separation medium used in ultrasonic buoyancy separation is water, ethanol, petroleum ether, or other liquid substances with similar properties that do not chemically react with hollow glass microspheres and leave no residue after drying, and the ultrasonic frequency used in ultrasonic buoyancy separation is 40~50kHz.

[0033] The method of this invention can produce hollow glass microspheres with different true densities, compressive strengths, and buoyancy rates according to market demand.

[0034] To prepare a material with a compressive strength of several MPa and a true density ≤0.15 g / cm³ 3The hollow glass microspheres were prepared using raw materials with the following mass content (calculated as 100%): waste glass 74.5-76.5%, quartz sand 4.1-7.1%, anhydrous borax 5.7-9.7%, calcium carbonate 3.2-6.6%, sodium sulfate 1.2-2.2%, lithium phosphate 0.26-1.2%, zinc phosphate 0.48-1.4%, and hollow glass microsphere by-products 1.68-1.97%. The true density of the hollow glass microsphere by-products used was 1.0-1.25 g / cm³. 3 The true density of the prepared hollow glass microspheres was 0.12~0.15 g / cm³. 3 The compressive strength is 5.0~6.0MPa, the free boron content is <500ppm, the sodium ion content is <100mg / L, and the floatability is >99.70%.

[0035] To prepare a material with a compressive strength of 10~16 MPa and a true density of 0.17~0.22 g / cm³. 3 The hollow glass microspheres used, when the total mass of the raw material components is calculated at 100%, have the following mass contents: waste glass 75.3-79.8%, quartz sand 3.9-7.8%, anhydrous borax 6.2-9.2%, calcium carbonate 3.8-6.6%, sodium sulfate 0.86-1.18%, lithium phosphate 0.28-0.95%, zinc phosphate 0.49-0.98%, and hollow glass microsphere by-products 1.44-1.80%. The true density of the hollow glass microsphere by-products used is 1.21-1.54 g / cm³. 3 The true density of the prepared hollow glass microspheres was 0.17~0.22 g / cm³. 3 The compressive strength is 10~16MPa, the free boron content is <500ppm, the sodium ion content is <100mg / L, and the buoyancy rate is >99.80%.

[0036] To prepare hollow glass microspheres with a compressive strength of 30-40 MPa and a true density of 0.25-0.32, the raw material components, when calculated at 100% mass, contain the following: waste glass 77.8-81.8%, quartz sand 2.9-8.8%, anhydrous borax 5.4-8.6%, calcium carbonate 4.4-6.8%, sodium sulfate 0.64-0.92%, lithium phosphate 0.19-0.98%, zinc phosphate 0.79-1.28%, and hollow glass microsphere by-products 0.99-1.97%. The true density of the hollow glass microsphere by-products used is 1.52-1.76 g / cm³. 3 The true density of the prepared hollow glass microspheres was 0.25~0.32 g / cm³. 3 The compressive strength is 30~40MPa, the free boron content is <500ppm, the sodium ion content is <100mg / L, and the floatability is >99.8%.

[0037] To prepare hollow glass microspheres with a compressive strength of 45-55 MPa and a true density of 0.34-0.40, the raw material components, when calculated at 100% mass, contain the following: waste glass 79.8-83.7%, quartz sand 3.9-9.8%, anhydrous borax 3.9-7.8%, calcium carbonate 2.9-6.8%, sodium sulfate 0.19-0.68%, lithium phosphate 0.19-0.78%, zinc phosphate 0.99-1.57%, and hollow glass microsphere by-products 0.99-1.97%. The true density of the hollow glass microsphere by-products used is 1.21-1.54 g / cm³. 3 The true density of the prepared hollow glass microspheres was 0.34~0.40 g / cm³. 3 The compressive strength is 45~55MPa, the free boron content is <500ppm, the sodium ion content is <100mg / L, and the floatability is >99.75%.

[0038] It should be noted that the flotation rate here refers to the flotation rate of hollow glass microspheres in the water medium; the byproducts of hollow glass microspheres here are dust or a small amount of fine particle waste generated during the production process of hollow glass microspheres.

[0039] Compared with the prior art, the method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength of the present invention has the following beneficial effects:

[0040] (1) Using waste glass as the main raw material, on the one hand, the waste glass can be utilized with high added value, and on the other hand, the raw material cost is low. The amount of waste glass added is as high as 74.5~84.5%, which can significantly reduce the production cost of hollow glass microspheres.

[0041] (2) The present invention applies a pressure of 0.5~1.6MPa to hollow glass microspheres dispersed in solvent in a pressure vessel, and then performs ultrasonic buoyancy separation with an ultrasonic frequency of 40~50kHz, which can efficiently remove solid, porous, through-hole, broken and other defective particles.

[0042] (3) The present invention employs pressurization and ultrasonic buoyancy separation of the hollow glass microspheres prepared in step 2). This separation utilizes the difference in HGM particle density to effectively remove solid and thick-walled particles. Based on buoyancy separation, pressurization allows the solvent to overcome capillary forces, surface tension, viscous resistance, and other effects to enter the HGM containing micropores on the shell wall, promoting the sedimentation of particles with through holes. Simultaneously, the mechanical force generated by ultrasound peels off the fine particles and HGM shell fragments attached to the surface of the HGM shell. Not only does the prepared HGM have a floating rate >99.5%, but its compressive strength is also significantly improved due to the efficient removal of defective particles.

[0043] (4) The microporous precursor particles prepared by introducing the physical foaming agent "hollow glass microspheres as an adjunct" have uniform pore distribution and easy-to-control pore size. The hollow glass microspheres as an adjunct have a hollow or porous closed-cell structure with a particle size of less than 5 μm, and the pores are always covered by the spherical shell and maintain independent distribution.

[0044] (5) The tiny pores in the microporous precursor particles act as nuclei, which greatly reduces the activation energy for bubble formation and growth. At the same time, the surface tension is lower under a reducing atmosphere, which reduces the viscous resistance and surface tension that need to be overcome for gas coalescence and expansion, making it easier for the precursor particles to form a hollow structure. Combined with buoyancy separation, hollow glass microspheres with a floating rate of >99.5% are finally prepared, solving the problem of low yield of hollow glass microspheres prepared from waste glass powder.

[0045] (6) The hollow glass microspheres are uniformly coated with silicon-containing compounds, which can form a silicon dioxide layer at a low temperature. This not only leaves no residue and is safe and environmentally friendly, but also repairs the defects of the spherical shell on the surface of the hollow glass microspheres and improves the compressive strength. At the same time, the silicon dioxide layer effectively blocks the precipitation of ions inside the shell. Detailed Implementation

[0046] To describe the present invention, the following detailed description, in conjunction with embodiments, illustrates a method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength. However, the present invention is not limited to these embodiments.

[0047] The experiments were conducted according to the raw material mass ratios given in Table 1. In each experiment, the sum of the masses of each component in the raw materials was 1000 grams. Example 1

[0048] The specific implementation process is as follows:

[0049] (1) Preparation of microporous precursor particles: Weigh each component of the raw materials according to the proportion in Table 1, and grind them to obtain a mixture with a particle size of less than 10.15 μm; uniformly disperse the mixture and hollow glass microspheres in water to obtain a mixture with a solid content of 73%, and the true density of the hollow glass microspheres used is 1.16 g / cm³. 3 Then, water glass with a mass of 7.4% and a modulus of 2.45 was added to the mixture under stirring, and the gel solidified into a block structure. After aging at room temperature, drying, pulverizing and classifying, microporous precursor particles with a particle size D50 of 18 μm and an average pore size of 1.125 μm were obtained.

[0050] (2) Hollow spheroidization of microporous precursor particles: The microporous precursor particles prepared in step (1) are pre-dispersed in a combustion-supporting gas with an atmosphere composition of 6% oxygen, 5% hydrogen and 89% air at 260°C; then transported to a high-temperature spheroidizing furnace for hollow spheroidization in a reducing atmosphere, and finally rapidly solidified and shaped by a cooling device to obtain hollow glass microspheres with a floating rate of 97.8%.

[0051] (3) Strengthening of hollow glass microspheres: The hollow glass microspheres prepared in step (2) were subjected to pressure (0.7 MPa) and ultrasonic (40 kHz) buoyancy separation in petroleum ether as solvent; then the buoyancy-separated hollow glass microspheres were dispersed in a perhydropolysilazane solvent, stirred for 45 min, dried, and treated at 200℃ for 50 min to prepare a product with a true density of 0.134 g / cm³. 3 Hollow glass microspheres with a compressive strength of 5.2 MPa, a floatability of 99.77%, a free boron content of 403 ppm, and a sodium ion content of 79 mg / L. Example 2

[0052] The specific implementation process is as follows:

[0053] (1) Preparation of microporous precursor particles: Weigh each component of the raw materials according to the proportion in Item 2 of Table 1, and grind them to obtain a mixture with a particle size of less than 13.62 μm; uniformly disperse the mixture and hollow glass microspheres in water to obtain a mixture with a solid content of 71%, and the true density of the hollow glass microspheres used is 1.47 g / cm³. 3 Then, 5.6% by mass of water glass with a modulus of 3.1 was added to the mixture under stirring, and the gel solidified into a block structure. After aging at room temperature, drying, pulverizing, and grading, microporous precursor particles with a particle size D50 of 21 μm and an average pore size of 1.837 μm were obtained.

[0054] (2) Hollow spheroidization of microporous precursor particles: The microporous precursor particles prepared in step (1) are pre-dispersed in a combustion-supporting gas with an atmosphere composition of 10% oxygen, 2% hydrogen and 88% air at 300°C; then transported to a high-temperature spheroidizing furnace for hollow spheroidization in a reducing atmosphere, and finally rapidly solidified and shaped by a cooling device to obtain hollow glass microspheres with a floating rate of 98.5%.

[0055] (3) Strengthening of hollow glass microspheres: The hollow glass microspheres prepared in step (2) were subjected to pressure (1.0 MPa) and ultrasonic (45 kHz) buoyancy separation in ethanol as solvent; then the buoyancy-separated hollow glass microspheres were dispersed in silica sol solvent, stirred for 20 min, dried, and treated at 450℃ for 35 min to prepare a product with a true density of 0.17 g / cm³. 3Hollow glass microspheres with a compressive strength of 15 MPa, a floatability of 99.88%, a free boron content of 354 ppm, and a sodium ion content of 87 mg / L. Example 3

[0056] The specific implementation process is as follows:

[0057] (1) Preparation of microporous precursor particles: Weigh each component of the raw materials according to the proportion in Item 3 of Table 1, and grind them to obtain a mixture with a particle size of less than 8.96 μm; uniformly disperse the mixture and hollow glass microspheres in water to obtain a mixture with a solid content of 68%, and the true density of the hollow glass microspheres used is 1.6 g / cm³. 3 Then, water glass with a mass of 6.1% and a modulus of 2.1 was added to the mixture under stirring, and the gel solidified into a block structure. After aging at room temperature, drying, pulverizing and classifying, microporous precursor particles with a particle size D50 of 16 μm and an average pore size of 2.546 were obtained.

[0058] (2) Hollow spheroidization of microporous precursor particles: The microporous precursor particles prepared in step (1) are pre-dispersed in a 220°C combustion-supporting gas with an atmosphere composition of 4% oxygen, 2% hydrogen and 94% air; then transported to a high-temperature spheroidizing furnace for hollow spheroidization in a reducing atmosphere, and finally rapidly solidified and shaped by a cooling device to obtain hollow glass microspheres with a floating rate of 97.6%.

[0059] (3) Strengthening of hollow glass microspheres: The hollow glass microspheres prepared in step (2) were subjected to pressure (1.2 MPa) and ultrasonic (45 kHz) buoyancy separation in water as the solvent; then the buoyancy-separated hollow glass microspheres were dispersed in polypropylene siloxane solvent, stirred for 40 min, dried, and treated at 230℃ for 45 min to prepare a product with a true density of 0.26 g / cm³. 3 Hollow glass microspheres with a compressive strength of 39 MPa, a buoyancy of 99.81%, a free boron content of 265 ppm, and a sodium ion content of 66 mg / L. Example 4

[0060] The specific implementation process is as follows:

[0061] (1) Weigh each component of the raw materials according to the proportion in Serial No. 4 of Table 1, and grind them to obtain a mixture with a particle size of less than 14.32 μm; uniformly disperse the mixture and hollow glass microspheres in water to obtain a mixture with a solid content of 65%, and the true density of the hollow glass microspheres used is 1.8 g / cm³. 3Then, 4.5% water glass with a modulus of 3.3 by mass of the mixture was added under stirring, and the gel solidified into a block structure. After aging at room temperature, drying, pulverizing and classifying, microporous precursor particles with a particle size D50 of 23 μm and an average pore size of 1.390 μm were obtained.

[0062] (2) Hollow spheroidization of microporous precursor particles: The microporous precursor particles prepared in step (1) are pre-dispersed in a combustion-supporting gas with an atmosphere composition of 9% oxygen, 4% hydrogen and 87% air at 280°C; then transported to a high-temperature spheroidizing furnace for hollow spheroidization in a reducing atmosphere, and finally rapidly solidified and shaped by a cooling device to obtain hollow glass microspheres with a floating rate of 98.1%.

[0063] (3) Strengthening of hollow glass microspheres: The hollow glass microspheres prepared in step (2) were subjected to pressure (1.5 MPa) and ultrasonic (50 kHz) buoyancy separation in water as the solvent; then the buoyancy-separated hollow glass microspheres were dispersed in a perhydropolysilazane vinyl polysilazane solvent, stirred for 37 min, dried, and treated at 250℃ for 30 min to prepare a product with a true density of 0.35 g / cm³. 3 Hollow glass microspheres with a compressive strength of 55 MPa, a floatability of 99.81%, a free boron content of 337 ppm, and a sodium ion content of 75 mg / L.

[0064] Table 1. Mass fraction of each component in the raw materials of Examples 1-4

[0065]

[0066] This invention can also prepare materials with a true density of 0.29~0.34 g / cm³ by adjusting the raw material ratio and process parameters. 3 Hollow glass microspheres with a compressive strength of 20~30MPa, free boron content <500ppm, sodium ion content <100mg / L, and floatability >99.75%.

[0067] The upper and lower limits and ranges of the raw materials and process parameters involved in this invention can all achieve the present invention, and will not be listed one by one here.

Claims

1. A method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength, characterized in that... The following steps are to be taken: 1) Raw material pretreatment – ​​preparation of microporous precursor particles When the total mass of the raw material components is calculated as 100%, the content of each component is as follows: waste glass 74.5-84.5%, quartz sand 4.1-8.9%, anhydrous borax 3.1-9.9%, calcium carbonate 3.2-6.7%, sodium sulfate 0.2-2.2%, lithium phosphate 0.1-1.2%, zinc phosphate 0.48-1.5%, and hollow glass microsphere by-product 1.1-1.98%; the hollow glass microsphere by-product refers to a true density of 1.0-1.8 g / cm³. 3 Hollow, porous glass beads with a particle size of less than 5μm; Waste glass, quartz sand, anhydrous borax, calcium carbonate, sodium sulfate, lithium phosphate, and zinc phosphate in the raw materials are ground to a particle size of less than 15 μm and mixed evenly. Then, they are evenly dispersed in water with hollow glass microspheres as an adjunct to obtain a mixture with a solid content of 65-73%. Then, 4-8% by weight of water glass is added to the mixture under stirring, and the gel solidifies into a block structure. The block structure is aged at room temperature, dried, crushed, and graded to obtain microporous precursor particles with a particle size of 10-35 μm and an average pore size of less than 2.6 μm. 2) Hollow spheroidization of microporous precursor particles The microporous precursor particles prepared in step 1) are pre-dispersed in a combustion-supporting gas at 220-300℃, then transported to a high-temperature spheroidizing furnace for hollow spheroidization under a reducing atmosphere. The spheroids are then rapidly solidified and shaped using a cooling device to obtain hollow glass microspheres with a floating rate >97%. The content of each component, calculated as 100% of the total volume fraction of the combustion-supporting gas, is: oxygen 2-12%, hydrogen 2-5%, and air 85-94%. 3) Strengthening of hollow glass microspheres: The hollow glass microspheres prepared in step 2) are subjected to pressure and ultrasonic buoyancy separation to obtain hollow glass microspheres with a buoyancy rate >99.3%. The pressure and ultrasonic buoyancy separation are carried out in a closed pressure vessel, with an applied pressure of 0.5~1.6MPa and an ultrasonic frequency of 35~55kHz. Then, the pressure and ultrasonic buoyancy separated hollow glass microspheres are dispersed in a solvent containing silicon compounds and stirred for 20~45min to uniformly coat the surface of the hollow glass microspheres with silicon compounds. After drying, the hollow glass microspheres coated with silicon-containing compounds were heat-treated at 200–450 °C for 35–50 min to convert the silicon-containing compound coating into a silicon oxide layer, ultimately producing a product with a true density of 0.12–0.40 g / cm³. 3 High-floatability hollow glass microspheres with compressive strength of 5.0~55 MPa, free boron content <500ppm, sodium ion content <100mg / L, and floatability greater than 99.5%.

2. The method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength as described in claim 1, characterized in that: The content of all compounds in the waste glass, calculated as 100%, is as follows: SiO2 60~90%; Li₂O + Na₂O + K₂O 2~17%; CaO + MgO 3~18%; B2O3 0~15%; SO30~2.8% Al2O3 0~15% ZnO + BaO + P2O5 + TiO2 + Balance 0~8%.

3. The method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength as described in claim 1, characterized in that: In step 3), the silicon-containing compound is one or a mixture of two or more of the following: silica sol, polysiloxane, and polysilazane.

4. The method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength as described in claim 1, characterized in that: In step 1), grinding is performed using a ball mill or a vibratory mill, and drying is performed using one of the following: a multi-layer belt dryer, a rotary drum dryer, or a fluidized bed dryer; in step 3), the buoyancy separation medium used in ultrasonic buoyancy separation is water, ethanol, or petroleum ether that does not chemically react with hollow glass microspheres and leaves no residue after drying, and the ultrasonic frequency used in ultrasonic buoyancy separation is 40~50kHz.

5. A method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength as described in claims 1, 2, 3, or 4, characterized in that... When the total mass of the raw materials used is calculated as 100%, the mass content of each component is as follows: waste glass 74.5~76.5%, quartz sand 4.1~7.1%, anhydrous borax 5.7~9.7%, calcium carbonate 3.2~6.6%, sodium sulfate 1.2~2.2%, lithium phosphate 0.26~1.2%, zinc phosphate 0.48~1.4%, and hollow glass microsphere by-product 1.68~1.97%. The true density of the hollow glass microsphere by-product used is 1.0~1.25 g / cm³. 3 The true density of the prepared hollow glass microspheres was 0.12~0.15 g / cm³. 3 The compressive strength is 5.0~6.0MPa, the free boron content is <500ppm, the sodium ion content is <100mg / L, and the floatability is >99.70%.

6. A method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength as described in claim 1, 2, 3, or 4, characterized in that... When the total mass of the raw materials used is calculated as 100%, the mass content of each component is as follows: waste glass 75.3~79.8%, quartz sand 3.9~7.8%, anhydrous borax 6.2~9.2%, calcium carbonate 3.8~6.6%, sodium sulfate 0.86~1.18%, lithium phosphate 0.28~0.95%, zinc phosphate 0.49~0.98%, and hollow glass microsphere by-product 1.44~1.80%. The true density of the hollow glass microsphere by-product used is 1.21~1.54 g / cm³. 3 The true density of the prepared hollow glass microspheres was 0.17~0.22 g / cm³. 3 The compressive strength is 10~16MPa, the free boron content is <500ppm, the sodium ion content is <100mg / L, and the buoyancy rate is >99.80%.

7. A method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength as described in claim 1, 2, 3, or 4, characterized in that... When the total mass of the raw materials used is calculated as 100%, the mass content of each component is as follows: waste glass 77.8~81.8%, quartz sand 2.9~8.8%, anhydrous borax 5.4~8.6%, calcium carbonate 4.4~6.8%, sodium sulfate 0.64~0.92%, lithium phosphate 0.19~0.98%, zinc phosphate 0.79~1.28%, and hollow glass microsphere by-product 0.99~1.97%. The true density of the hollow glass microsphere by-product used is 1.52~1.76 g / cm³. 3 The true density of the prepared hollow glass microspheres was 0.25~0.32 g / cm³. 3 The compressive strength is 30~40MPa, the free boron content is <500ppm, the sodium ion content is <100mg / L, and the floatability is >99.8%.

8. A method for preparing high-floatability hollow glass microspheres with adjustable true density and compressive strength as described in claim 1, 2, 3 or 4, characterized in that... When the total mass of the raw materials used is calculated as 100%, the mass content of each component is as follows: waste glass 79.8~83.7%, quartz sand 3.9~9.8%, anhydrous borax 3.9~7.8%, calcium carbonate 2.9~6.8%, sodium sulfate 0.19~0.68%, lithium phosphate 0.19~0.78%, zinc phosphate 0.99~1.57%, and hollow glass microsphere by-products 0.99~1.97%. The true density of the hollow glass microsphere by-products used is 1.21~1.54 g / cm³. 3 The true density of the prepared hollow glass microspheres was 0.34~0.40 g / cm³. 3 The compressive strength is 45~55MPa, the free boron content is <500ppm, the sodium ion content is <100mg / L, and the floatability is >99.75%.

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