Low-fluorine synthetic fluorphlogopite powder and method for preparing the same

Abstract

The present application relates to a kind of low fluorine synthetic fluorophlogopite powder and its preparation method.The preparation method of the low fluorine synthetic fluorophlogopite powder of the present application is as follows: the raw material of synthetic fluorophlogopite powder is dispersed in deionized water, stirred, wetted completely, heated and kept warm, and stirred to obtain material body A;material body A is circulated through a shearing grinder while hot to obtain material body B;the pH of material body B is adjusted to 8-12 with an alkaline adjusting agent, and kept warm and ultrasonic stirring to obtain material body C;complexing stripping agent is added to material body C, kept warm and ultrasonic stirring to obtain material body D;complexing precipitating agent is added to material body D, kept warm and stirring to obtain material body E;material body E is dehydrated and washed to low conductivity, placed in an oven to dry to obtain material body F;material body F is calcined in a muffle furnace to obtain low fluorine synthetic fluorophlogopite powder.The synthetic fluorophlogopite powder prepared has not only free fluorine content controllable below 20 ppm, but also maintains the original whiteness, brightness, stability and mechanical strength of synthetic fluorophlogopite powder.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, and in particular to a low-fluorine synthetic fluorinated phlogopite powder and its preparation method. Background Technology

[0002] Mica powder includes both natural and synthetic mica. Natural mica can be further divided into muscovite, sericite, phlogopite, and biotite, among others. Natural mica is primarily derived from mica ore and has a layered silicate structure. It is mainly composed of silicon dioxide, aluminum oxide, potassium oxide, sodium oxide, water of crystallization, and small amounts of metallic impurities such as iron and manganese. Synthetic mica, on the other hand, is mainly synthesized artificially. It is primarily composed of silicon dioxide, aluminum oxide, magnesium oxide, and fluorine. Its composition is pure and controllable, and it does not contain metallic impurities such as iron and manganese. Synthetic mica possesses high insulation, high whiteness, high brightness, excellent chemical stability, and good mechanical strength, making it more practically advantageous than natural mica. However, because it contains fluorine, there are certain risks involved in its use. The fluorine in synthetic mica powder mainly consists of lattice fluorine and free fluorine. If the production process is not properly controlled during the production of synthetic mica powder, the content of free fluorine may be too high. Long-term exposure to free fluorine may lead to health risks such as dental fluorosis and skeletal fluorosis. Moreover, under certain extreme conditions, such as high temperature, strong acid, or incineration, hydrogen fluoride gas will be released. Hydrogen fluoride is a highly irritating and corrosive gas.

[0003] Patent CN113493209A describes a coating method for low-fluorine phlogopite. The method involves mixing phlogopite with deionized water, stirring to form a turbid liquid, then heating and stirring the mixture while adding a pH adjuster to adjust the pH to 7-11. Next, an aqueous solution containing a silicon compound is added dropwise to the mixture at a uniform rate. Heating is then stopped, and the mixture is stirred at room temperature, filtered, washed with water, and dried to obtain low-fluorine phlogopite. This patented method uses silicon to coat the fluorine in the synthesized mica, preventing its dissolution. However, silicon coating is a physical coating process and is not inherently reliable. It is prone to peeling off during subsequent processing (such as high-speed stirring), and the fluorine will still be released after the silicon coating layer peels off. Furthermore, the silicon-coated mica powder has altered surface properties, leading to decreased compatibility and dispersibility in other oils, coatings, etc., ultimately resulting in a decrease in the material's mechanical properties.

[0004] Therefore, there is an urgent need to find a new method for preparing synthetic fluorinated phlogopite powder with stable performance and low fluorine content. Summary of the Invention

[0005] To address the above technical problems, this invention provides a low-fluorine synthetic fluorinated phlogopite powder and its preparation method.

[0006] The first objective of this invention is to provide a method for preparing low-fluorine synthetic fluorinated phlogopite powder, comprising the following steps: S1. The synthetic fluorophlogopite powder is dispersed in deionized water by stirring, and then heated and stirred to obtain material A; S2. While the material A is still hot, shear and grind it to obtain material B; S3. Adjust the pH of material B to 8-12 using an alkaline regulator, and then heat and ultrasonically stir to obtain material C; S4. Add a coordination stripping agent to material C, keep it warm and ultrasonically stir to obtain material D; S5. Add a complexing precipitant to material D, keep warm and stir to obtain material E; S6. Dehydrate and wash material E until it has low electrical conductivity, then dry it to obtain material F; S7. Heat and calcine material F to obtain low-fluorine synthetic fluorinated phlogopite powder.

[0007] In some embodiments of the present invention, in step S1, the concentration of synthetic fluorophlogopite in material A is 1% to 60%, preferably 10% to 60%, and more preferably 20% to 50%; The heating and heat preservation temperature is 50℃~100℃, preferably 60℃~100℃, more preferably 80℃~100℃; the heat preservation time is 1~10 hours, preferably 2~8 hours, more preferably 3 hours.

[0008] In some embodiments of the present invention, in step S2, the number of shearing and grinding cycles is 1 to 10 times, preferably 2 to 8 times, and more preferably 3 to 5 times. The present invention wets and heats the synthesized fluorophlogopite powder in deionized water, allowing water molecules to penetrate the interlayer of the mica powder and weaken the interlayer forces (such as K...). + The electrostatic attraction of the mica powder is used, and then the high-speed shearing, impact, or grinding force of the shearing and grinding machine is used to peel off the weakened mica powder layers, thereby increasing the specific surface area and reactive sites of the mica powder. In some embodiments of the present invention, in step S3, the temperature of the heat preservation ultrasound is 50-100°C and the time is 1-10 hours; preferably 1-5 hours, more preferably 3 hours.

[0009] The alkalinity regulator includes one or more of sodium hydroxide, potassium hydroxide, ammonia, and triethanolamine, preferably sodium hydroxide or potassium hydroxide, and more preferably sodium hydroxide.

[0010] In some embodiments of the present invention, in step S4, the amount of the coordination stripping agent is 0.1% to 20 wt% of the synthetic fluorophlogopite powder. The coordination stripping agent is one or more of sodium citrate, sodium tartrate, sodium gluconate, sodium malate, disodium EDTA, tetrasodium EDTA, NTA (nitrotriacetic acid), ATMP (aminotrimethylmylate), ethylene glycol, glycerol, and sorbitol, preferably sodium citrate, sodium tartrate, disodium EDTA, or tetrasodium EDTA, and more preferably sodium citrate or disodium EDTA.

[0011] In some embodiments of the present invention, in step S5, the complexing precipitant is one or more of calcium chloride, magnesium chloride, aluminum nitrate, aluminum sulfate, aluminum chloride, magnesium sulfate, and magnesium nitrate; preferably calcium chloride, magnesium chloride, aluminum sulfate, and magnesium sulfate, and more preferably calcium chloride and magnesium chloride. The present invention utilizes a complexing precipitant (metal salt) to dissolve F... - It will react with metal ions (such as Ca). 2+ It rapidly complexes, forming calcium fluoride precipitate.

[0012] The amount of the complexing precipitant is 0.1-20 wt% of the synthetic fluorophlogopite powder; preferably 1%-20 wt%, more preferably 1-10 wt%; preferably 1-15 wt%, more preferably 1-10 wt%.

[0013] The time for heat preservation and stirring is 1 to 10 hours, preferably 1 to 5 hours, and more preferably 3 hours.

[0014] In some embodiments of the present invention, in step S6, the low conductivity is 0.1–100 μS / cm. Preferably, it is 1–50 μS / cm, more preferably 20 μS / cm. The drying temperature is 50–120°C, preferably 80–120°C, more preferably 100°C.

[0015] In some embodiments of the present invention, in step S7, the heating and calcination temperature is 300–1200°C, preferably 300–1000°C, and more preferably 400–800°C. The calcination time is 1–10 hours, preferably 3–8 hours, and more preferably 5 hours.

[0016] The second objective of this invention is to provide a low-fluorine synthetic fluorinated phlogopite powder, prepared by the preparation method described in the first objective.

[0017] In some embodiments of the present invention, the free fluorine content of the low-fluorine synthetic mica powder is 0.1–50 ppm, and exemplaryly, it can be 0.1–20 ppm, 20–50 ppm, etc. This maintains the original whiteness, stability, and mechanical strength of the synthetic mica powder.

[0018] The technical solution of the present invention has the following advantages compared with the prior art: This invention employs a combination of hydrothermal alkali dissolution, ion exchange, and high-temperature calcination to reduce and eliminate structural and free fluorine in synthesized fluorophlogopite powder. First, the synthesized fluorophlogopite powder is wetted and heated in deionized water, allowing water molecules to penetrate the interlayer spaces of the mica powder and weaken the interlayer forces (such as K+). + The process involves using electrostatic attraction, followed by high-speed shearing, impact, or grinding forces from a shearing and grinding machine to peel away the weakened mica powder layers, thereby increasing the specific surface area and reactive sites of the mica powder. Then, an alkaline regulator is used to introduce OH- ions. Under high temperature, OH- ions attack the Si-F bonds, undergoing a nucleophilic substitution reaction, causing fluorine to gradually dissolve as F- ions while OH- ions enter the structure. The addition of a coordination stripping agent accelerates this reaction process. Since fluoride ions do not exist independently in the synthesized fluorine-phlogopite powder but are firmly bonded to the "aluminum-oxygen octahedral" layer as coordinating atoms, and the coordination stripping agent contains negatively charged coordination groups (such as -COOH-), these coordination groups react with the Al in the synthesized mica in alkaline solution. 3+ A strong chelation reaction occurs, forming a water-soluble, stable organometallic complex. The fluoride ions, tightly bound to aluminum ions, lose their support, thus accelerating the exposure and release of fluoride ions from the crystal structure, transforming them into freely moving fluoride ions. Subsequently, a complexing precipitant (metal salt) is added, and the dissolved F- ions react with metal ions (such as Ca²⁺). 2+ The fluorine complex rapidly forms calcium fluoride precipitate, which is then washed, dried, and calcined at high temperature to remove residual fluorine-containing complexes and any organic impurities that may be introduced, thus obtaining a low-fluorine synthetic fluorinated phlogopite powder. The low-fluorine synthetic fluorinated phlogopite powder not only has a free fluorine content that can be controlled below 20 ppm, but also maintains the original whiteness, stability, and mechanical strength of the synthetic fluorinated phlogopite powder. Attached Figure Description

[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a schematic diagram of the experimental steps in Embodiment 9 of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0021] Unless otherwise specified, all materials and equipment used in this embodiment of the invention are commercially available. Example 1

[0022] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorinated phlogopite powder (initial fluorine content above 200ppm) to 200g of deionized water, stir to disperse and fully wet, then heat and stir at 80℃ for 3 hours to obtain material A. S2. While still hot, pass material A through a shearing and grinding mill three times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 80℃ for 3 hours to obtain material C; S4. Add 1g of sodium citrate to material C, and ultrasonically stir at 80℃ for 3 hours to obtain material D; S5. Add 1g of calcium chloride to material D, keep warm at 80℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 400°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 2

[0023] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 80℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 80℃ for 3 hours to obtain material C; S4. Add 1g of sodium citrate to material C, and ultrasonically stir at 80℃ for 3 hours to obtain material D; S5. Add 1g of calcium chloride to material D, keep warm at 80℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 400°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 3

[0024] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 80℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 80℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 80℃ for 3 hours to obtain material D; S5. Add 1g of calcium chloride to material D, keep warm at 80℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 400°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 4

[0025] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 80℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 80℃ for 3 hours to obtain material C; S4. Add 10g of sodium citrate to material C, and ultrasonically stir at 80℃ for 3 hours to obtain material D; S5. Add 1g of calcium chloride to material D, keep warm at 80℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 400°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 5

[0026] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 80℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 80℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 80℃ for 3 hours to obtain material D; S5. Add 5g of calcium chloride to material D, keep warm at 80℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 400°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 6

[0027] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 80℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 80℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 80℃ for 3 hours to obtain material D; S5. Add 10g of calcium chloride to material D, keep warm at 80℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 400°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 7

[0028] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 80℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 80℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 80℃ for 3 hours to obtain material D; S5. Add 5g of calcium chloride to material D, keep warm at 80℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 8

[0029] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 80℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 80℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 80℃ for 3 hours to obtain material D; S5. Add 5g of calcium chloride to material D, keep warm at 80℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 800°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 9

[0030] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 90℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 90℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 90℃ for 3 hours to obtain material D; S5. Add 5g of calcium chloride to material D, keep warm at 90℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 10

[0031] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 100℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 100℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 100℃ for 3 hours to obtain material D; S5. Add 5g of calcium chloride to material D, keep warm at 100℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 11

[0032] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 90℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 90℃ for 3 hours to obtain material C; S4. Add 5g of disodium EDTA to material C, and ultrasonically stir at 90℃ for 3 hours to obtain material D; S5. Add 5g of calcium chloride to material D, keep warm at 90℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained. Example 12

[0033] This embodiment provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder, as detailed below: S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 90℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 90℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 90℃ for 3 hours to obtain material D; S5. Add 5g of magnesium chloride to material D, keep warm at 90℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S7. After calcining material F in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained.

[0034] Comparative Example 1 This comparative example provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder. This comparative example is similar to Example 9, except that step S2 is omitted, i.e., the shearing and grinding operation is not performed.

[0035] S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 90℃ for 3 hours to obtain material A; S2. Adjust the pH of material A to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 90℃ for 3 hours to obtain material C; S3. Add 5g of sodium citrate to material C, and ultrasonically stir at 90℃ for 3 hours to obtain material D; S4. Add 5g of calcium chloride to material D, keep warm at 90℃ and stir for 3 hours to obtain material E; S5. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S6. After calcining material F in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained.

[0036] Comparative Example 2 This comparative example provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder. This comparative example is similar to Example 9, except that step S4 is omitted, i.e., no coordination stripping agent is added.

[0037] S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 90℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 90℃ for 3 hours to obtain material C; S4. Add 5g of calcium chloride to material C, keep warm at 90℃ and stir for 3 hours to obtain material D; S5. Dehydrate and wash material D until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material E; S6. After calcining material E in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained.

[0038] Comparative Example 3 This comparative example provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder. This comparative example is similar to Example 9, except that step S5 is omitted, i.e., no complexing precipitant is added.

[0039] S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 90℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 90℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 90℃ for 3 hours to obtain material D; S5. Dehydrate and wash material D until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material F; S6. After calcining material F in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained.

[0040] Comparative Example 4 This comparative example provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder. This comparative example is similar to Example 9, except that step S7 is omitted, i.e., calcination is not performed.

[0041] S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 90℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Adjust the pH of material B to 10 with 0.2g sodium hydroxide, and ultrasonically stir at 90℃ for 3 hours to obtain material C; S4. Add 5g of sodium citrate to material C, and ultrasonically stir at 90℃ for 3 hours to obtain material D; S5. Add 5g of calcium chloride to material D, keep warm at 90℃ and stir for 3 hours to obtain material E; S6. Dehydrate and wash material E until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain low-fluorine synthetic fluorinated phlogopite powder.

[0042] Comparative Example 5 This comparative example provides a method for preparing low-fluorine synthetic fluorinated phlogopite powder. This comparative example is similar to Example 9, except that step S3 is omitted, i.e., no alkaline regulator is added.

[0043] S1. Add 100g of synthetic fluorophlogopite powder to 200g of deionized water, stir to disperse and fully wet, then heat and keep warm at 90℃ for 3 hours to obtain material A; S2. While still hot, pass material A through a shearing and grinding mill 5 times to obtain material B; S3. Add 5g of sodium citrate to material B, and ultrasonically stir at 90℃ for 3 hours to obtain material C; S4. Add 5g of calcium chloride to material C, keep warm at 90℃ and stir for 3 hours to obtain material D; S5. Dehydrate and wash material D until its conductivity is 20 μs / cm, place it in an oven and dry it at 100℃ to obtain material E; S6. After calcining material E in a muffle furnace at 600°C for 5 hours, low-fluorine synthetic fluorinated phlogopite powder is obtained.

[0044] Test method for free fluorine: Take 5.0 g of this product and place it in a 300 mL round-bottom flask. Add 100 mL of water, attach a condenser, and heat under reflux for 1 hour. After cooling, filter using filter paper and a 0.45 μm filter membrane. Transfer all the filtrate to a distillation flask and distill according to the fluoride test method. Transfer the distillate to a volumetric flask, wash the receiver with a small amount of water, combine the washings with the distillate, and dilute to volume with water to prepare an accurate 200 mL solution, which will be used as the sample solution. Accurately take 20 mL each of the sample solution and the fluoride standard solution for the calibration curve, and place them in separate 50 mL volumetric flasks. Accurately add 5 mL of lanthanum-alizarin complexone solution and 20 mL of acetone to each flask, and add water to make 50 mL of each. Mix thoroughly, let stand for 90 minutes, and then measure the absorbance at a wavelength of 620 nm. Take another 20 mL of water, place it in a 50 mL volumetric flask, and perform the same procedure as with the test solution to prepare a control solution. The concentration of fluoride, a (μg / mL), is determined based on a pre-prepared calibration curve. The amount of fluoride dissolved (ppm) is then calculated using the following formula. Free fluoride content (ppm) = (a*200) / S, where a is the concentration of fluoride in the test solution (μg / mL) obtained from the self-calibration curve, and S is the sample amount (g). The results are shown in Table 1.

[0045] Table 1 shows the test results of Examples 1 to 12 and Comparative Examples 1 to 5. Blank raw materials / / / / / / / 286 Example 1 80 3 1 / 1 / 400 73.6 Example 2 80 5 1 / 1 / 400 71.9 Example 3 80 5 5 / 1 / 400 36.9 Example 4 80 5 10 / 1 / 400 35.2 Example 5 80 5 5 / 5 / 400 16.8 Example 6 80 5 5 / 10 / 400 12.3 Example 7 80 5 5 / 5 / 600 9.7 Example 8 80 5 5 / 5 / 800 9.5 Example 9 90 5 5 / 5 / 600 4.9 Example 10 100 5 5 / 5 / 600 5.2 Example 11 90 5 / 5 5 / 600 5.3 Example 12 90 5 5 / / 5 600 5.5 Comparative Example 1 90 / 5 / 5 / 600 99.5 Comparative Example 2 90 5 / / 5 / 600 88.3 Comparative Example 3 90 5 5 / / / 600 99.8 Comparative Example 4 90 5 5 / 5 / / 75.2 Comparative Example 5 90 5 5 / 5 / 600 78.9 Comparing Examples 1 and 2, the increased number of shearing and milling cycles resulted in a slight decrease in the free fluorine content. This is because shearing and milling reduces the interlayer forces of mica flakes, increasing the specific surface area of ​​the mica powder and providing reactive sites for subsequent alkali treatment. However, more shearing and milling cycles are not necessarily better. As the number of cycles increases, the particle size and flake thickness of the mica powder decrease, which can lead to a decline in the performance of the mica powder during subsequent use, such as reduced smoothness and toughness. In this embodiment of the invention, the optimal number of shearing and milling cycles (5 times) yielded the best results.

[0046] Comparing Examples 2 with Examples 3 and 4, the increase in the amount of coordination stripping agent can reduce the content of free fluorine to a certain extent. This is because the role of the coordination stripping agent here is to accelerate the transformation of fluorine in the crystal structure of mica powder into freely moving fluoride ions, which then undergo nucleophilic substitution with the basic regulator, causing the fluoride ions to dissolve and thus reducing its fluorine content. However, more coordination complexing agent is not necessarily better, because the ability of the coordination stripping agent is limited, and the amount of fluorine that can dissolve from the crystal structure of mica powder is also limited. In the embodiments of the present invention, the best effect is achieved when the amount of coordination stripping agent is 5 wt% of the amount of fluorine-phlogopite mica powder synthesized.

[0047] Comparing Examples 3 with Examples 5 and 6, the increase in the complexing precipitant significantly reduced the free fluoride content. This is because after the adjustment reaction with the alkaline regulator, the fluoride in the fluorophlogopite powder dissolves as fluoride ions. These fluoride ions can undergo a complexation reaction with the metal salt complexing precipitant, causing the fluoride precipitate to detach, thus ultimately reducing the free fluoride content. However, a larger amount of complexing precipitant is not always better, because the free fluoride in the fluorophlogopite powder is limited. If all the fluoride ions are complexed, there will be excess metal complexing precipitant remaining, which will increase the difficulty of subsequent processing and introduce excessive metal impurities. In the embodiments of this invention, the optimal effect is achieved when the amount of complexing precipitant is 5 wt% of the amount of fluorophlogopite powder used for synthesis.

[0048] Comparing Examples 5 with Examples 7 and 8, increasing the calcination temperature can reduce the free fluorine content to some extent. This is because high-temperature calcination can precipitate fluorine complexes and decompose some organic impurities, further removing free fluorine. However, a higher calcination temperature is not always better. Higher calcination temperatures will cause recrystallization and aggregation between mica powder layers, ultimately leading to hardening of the mica powder and affecting its performance. In the embodiments of this invention, the calcination temperature of 600℃ yielded the best results.

[0049] Comparing Examples 7 with Examples 9 and 10, the increase in the temperature of the heat preservation and stirring reduced the content of free fluorine to some extent. This is because the higher the temperature, the greater the probability of water molecules entering the mica powder layers, which in turn causes the mica powder layers to expand under pressure, reducing the interaction force between the mica powder layers and providing more active sites for subsequent alkali adjustment. However, higher temperatures are not always better. When the temperature reaches 100°C, it has reached the boiling point of water, at which point a large number of bubbles will be present in the water. The presence of these bubbles will affect the entry of water molecules into the mica powder layers and the subsequent alkali adjustment reaction. In the embodiments of this invention, the best effect was achieved when the heat preservation temperature was 90°C.

[0050] Comparing Example 9 and Example 11, the content of free fluorine is basically the same, indicating that the effects of sodium citrate and disodium EDTA as coordination strippers are basically the same.

[0051] Comparing Example 9 and Example 12, the content of free fluorine is basically the same, indicating that the effects of complexing precipitants, calcium chloride and magnesium chloride, are basically the same.

[0052] Comparing Example 9 with Comparative Example 1, the absence of shearing and grinding significantly impacts the subsequent removal of fluorine. This is because shearing and grinding reduces the interlayer forces of mica sheets, increases the specific surface area of ​​mica powder, provides reactive sites for subsequent alkali treatment, and thus affects the removal of fluorine.

[0053] Comparing Example 9 with Comparative Example 2, the absence of a coordination stripping agent significantly impacts the subsequent removal of fluoride. This is because the role of the coordination stripping agent here is to accelerate the transformation of fluoride in the mica powder crystal structure into freely moving fluoride ions, which then undergo nucleophilic substitution with the alkaline regulator, causing the fluoride ions to dissolve and thus reducing its fluoride content.

[0054] Comparing Example 9 with Comparative Example 3, the addition of the complexing precipitant can significantly eliminate the content of free fluorine. This is because the metal ions (such as Ca) in the complexing precipitant... 2+ It can rapidly complex with fluoride ions to form calcium fluoride precipitate, which can be completely removed by subsequent washing and calcination.

[0055] Comparing Example 9 with Comparative Example 4, the free fluorine content of the calcined mica powder is significantly lower. This is because calcination can decompose fluorine-containing complex precipitates and some organic impurities, thereby removing the free fluorine.

[0056] Comparing Example 9 with Comparative Example 5, the mica powder treated with alkaline conditioning had a significantly lower free fluoride content. This is because the alkaline conditioning agent introduces OH- ions during the alkaline conditioning process. - Under high temperature conditions, OH - It attacks the Si-F bonds in fluorophlogopite powder, leading to a nucleophilic substitution reaction, causing fluorine to react with F. - The form gradually dissolves, while OH... - Once fluorine enters the structure and dissolves in the form of fluoride ions, it can then undergo a complexation reaction with the complexing precipitant, ultimately reducing the amount of free fluorine.

[0057] Based on the above tests and results, Example 9 showed the best performance. Specifically, the best results were achieved when the heat preservation temperature was set at 90°C, the number of shearing and grinding cycles was 5, the pH was adjusted to 10 using an alkaline regulator, the amount of coordination stripping agent was 5 wt% of the amount of fluorophlogopite powder, the amount of complexing precipitant was 5 wt% of the amount of fluorophlogopite powder, and the muffle furnace calcination temperature was 600°C.

[0058] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing low-fluorine synthetic fluorinated phlogopite powder, characterized in that, Includes the following steps: S1. The synthetic fluorophlogopite powder is dispersed in deionized water by stirring, and then heated and stirred to obtain material A; S2. While the material A is still hot, shear and grind it to obtain material B; S3. Adjust the pH of material B to 8-12 using an alkaline regulator, and then heat and ultrasonically stir to obtain material C; S4. Add a coordination stripping agent to material C, keep it warm and ultrasonically stir to obtain material D; S5. Add a complexing precipitant to material D, keep warm and stir to obtain material E; S6. Dehydrate and wash material E until it has low electrical conductivity, then dry it to obtain material F; S7. Heat and calcine material F to obtain low-fluorine synthetic fluorinated phlogopite powder.

2. The method for preparing a low-fluorine synthetic fluorinated phlogopite powder according to claim 1, characterized in that, In step S1, the concentration of synthetic fluorinated phlogopite powder in material A is 1% to 60%; The heating and heat preservation temperature is 50℃~100℃, and the heat preservation time is 1~10 hours.

3. The method for preparing a low-fluorine synthetic fluorinated phlogopite powder according to claim 1, characterized in that, In step S2, the shearing and grinding cycle is 1 to 10 times.

4. The method for preparing a low-fluorine synthetic fluorinated phlogopite powder according to claim 1, characterized in that, In step S3, the temperature of the heat preservation ultrasound is 50-100℃, and the time is 1-10 hours; The alkalinity regulator includes one or more of sodium hydroxide, potassium hydroxide, ammonia, and triethanolamine.

5. The method for preparing a low-fluorine synthetic fluorinated phlogopite powder according to claim 1, characterized in that, In step S4, the amount of the coordination stripping agent is 0.1% to 20 wt% of the synthetic fluorophlogopite powder. The coordination stripping agent is one or more of sodium citrate, sodium tartrate, sodium gluconate, sodium malate, disodium EDTA, tetrasodium EDTA, hypozinotriacetic acid, aminotrimethylphosphonic acid, ethylene glycol, glycerol, and sorbitol.

6. The method for preparing a low-fluorine synthetic fluorinated phlogopite powder according to claim 1, characterized in that, In step S5, the complexing precipitant is one or more of calcium chloride, magnesium chloride, aluminum nitrate, aluminum sulfate, aluminum chloride, magnesium sulfate, and magnesium nitrate. The amount of the complexing precipitant used is 0.1-20 wt% of the synthetic fluorophlogopite powder. The time for heat preservation and stirring is 1 to 10 hours.

7. The method for preparing a low-fluorine synthetic fluorinated phlogopite powder according to claim 1, characterized in that, In step S6, the low conductivity is 0.1–100 μS / cm.

8. The method for preparing a low-fluorine synthetic fluorinated phlogopite powder according to claim 1, characterized in that, In step S7, the heating and calcination temperature is 300–1200℃, and the calcination time is 1–10 hours.

9. A low-fluorine synthetic fluorinated phlogopite powder, characterized in that, Prepared by the preparation method described in any one of claims 1 to 8.

10. The low-fluorine synthetic fluorinated phlogopite powder according to claim 9, characterized in that, The free fluorine content of the low-fluorine synthetic fluorinated phlogopite powder is 0.1–50 ppm.

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