Preparation method of ADN spherical crystal

Abstract

The invention discloses a preparation method of ADN spherical crystals. The preparation method comprises the following steps: (1) uniformly dispersing a surfactant and a dispersing agent in a solvent 2, and adding a solvent 1 solution of ADN under a stirring condition to obtain a suspension; and (2) standing the suspension obtained in the step (1), replacing the supernate with a solvent 3 dispersed with a dispersing agent, and stirring to obtain the ADN spherical crystal. The ADN spherical crystal is prepared through anti-solvating-out crystallization in a solution phase, the process is simple, the operation temperature can be reduced to normal temperature, the condition is mild, and the safety is high. The prepared ADN spherical crystal product is compact in particle, high in sphericity degree, good in dispersity and adjustable in particle size, and can be widely applied to subsequent surface modification of ADN to improve the moisture absorption resistance and application adaptability of ADN.

Description

Technical Field

[0001] This invention relates to a method for preparing ADN spherical crystals, and further to a method for preparing ADN spherical crystals in a low-temperature solution phase, belonging to the field of energetic materials. Background Technology

[0002] Ammonium dinitramide (CAS: 140456-78-6), abbreviated as ADN, has the molecular formula NH4N(NO2)2. ADN is a typical third-generation energetic substance, first proposed and synthesized by the Soviet Union. As an oxidizer for solid rocket propellants or liquid unit propellants, it is a novel high-energy, green oxidizer. ADN contains no halogens, reducing the chemical signatures emitted by the propellant and lowering environmental pollution. Furthermore, its high oxygen and nitrogen content and high energy density significantly increase the specific impulse of the propellant, improving efficiency. Therefore, ADN is considered the most promising high-energy component of the next generation of solid propellants.

[0003] However, compared to other propellant oxidizers, ADN is extremely hygroscopic, which is a bottleneck limiting its application. Therefore, it is essential to develop a new ADN crystal and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned shortcomings of the prior art and provide a method for preparing spherical ADN crystals through reverse dissolution crystallization in a solution phase. This process is simple, the operating temperature can be reduced to room temperature, the conditions are mild, and the safety is high. The prepared spherical ADN crystals are compact, have high sphericity, good dispersibility, and adjustable particle size, and can be widely used in subsequent surface modification of ADN to improve its moisture-proof properties and application adaptability.

[0005] To achieve this objective, the present invention employs the following technical solution: One objective of this invention is to provide a method for preparing ADN spherical crystals, characterized in that the preparation method includes the following steps: (1) Disperse the surfactant and dispersant evenly in solvent 2, and add the ADN solvent 1 solution under stirring conditions to obtain a suspension; (2) Let the suspension obtained in step (1) stand, replace the supernatant with solvent 3 containing the dispersant, stir, and obtain ADN spherical crystals.

[0006] Preferably, the surfactant in step (1) is any one or a combination of at least two of Span 20, Span 40, Span 60, Span 80, Tween 20, Tween 40, Tween 60 or Tween 80; Preferably, the amount of surfactant added in step (1) is 5 to 20 wt% of the amount of ADN added, for example, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, etc.; Preferably, the dispersant in step (1) is nano-silica, and the average particle size of the nano-silica is 10~30nm, such as 10nm, 15nm, 20nm, 25nm, 30nm, etc.; Preferably, the amount of nano-silica added in step (1) is 1 to 2 wt% of the amount of ADN added, for example, 1 wt%, 1.5 wt%, 2 wt%, etc.

[0007] Preferably, solvent 1 in step (1) is any one or a combination of at least two of methanol, ethanol, acetone, acetonitrile, n-propanol or isopropanol; Preferably, the solvent 2 in step (1) is any one or a combination of at least two of n-hexane, cyclohexane, benzene, toluene, xylene or ethylbenzene; Preferably, in the solvent 1 solution of ADN in step (1), the concentration of ADN is 0.2~0.8g / mL, for example 0.2g / mL, 0.3g / mL, 0.4g / mL, 0.5g / mL, 0.6g / mL, 0.7g / mL, 0.8g / mL, etc.; Preferably, the dissolution temperature of the ADN in solvent 1 in step (1) is 20~55℃, for example 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, etc.; Preferably, the volume of solvent 2 added in step (1) is 5 to 50 times the volume of solvent 1 added in the ADN solvent 1 solution, for example, 5 times, 10 times, 15 times, 20 times, 25 times, 30 times, 35 times, 40 times, 45 times, 50 times, etc.

[0008] Preferably, the dispersion method in step (1) is ultrasound, and the power of the ultrasound is 600~1000W, such as 600W, 700W, 800W, 900W, 1000W, etc.; Preferably, the ultrasound is intermittent ultrasound irradiation, wherein the continuous irradiation time is 1~3s (e.g., 1s, 2s, 3s, etc.), the interval time is 3~5s (e.g., 3s, 4s, 5s, etc.), and the total intermittent irradiation time is 2~5min (e.g., 2min, 3min, 4min, 5min, etc.). Preferably, the stirring rate in step (1) is 300~700 rpm (e.g., 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, etc.), and the stirring time is 20~60 min (e.g., 20 min, 30 min, 40 min, 50 min, 60 min, etc.). Preferably, the stirring in step (1) is applied by a single-layer double-bladed anchor paddle; Preferably, during the stirring process in step (1), the temperature of the suspension is maintained at 5~25℃, for example, 5℃, 10℃, 15℃, 20℃, 25℃, etc.

[0009] Preferably, the preparation method of the solvent 3 containing the dispersant in step (2) includes: placing the dispersant in the solvent 3 and dispersing it; Preferably, the dispersant is nano-silica, and its addition amount is 0.5~1wt% of the ADN addition amount, for example 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, etc.; Preferably, solvent 3 is any one or a combination of at least two of dichloromethane, dichloroethane, trichloromethane, carbon tetrachloride, or tetrachloroethylene; Preferably, the volume of solvent 3 added is 0.5 to 4 times the volume of solvent 2 added, for example, 0.5 times, 1 time, 2 times, 3 times, 4 times, etc. Preferably, the dispersion method is ultrasound, and the power of the ultrasound is 600~1000W, such as 600W, 700W, 800W, 900W, 1000W, etc.; Preferably, the ultrasound is intermittent ultrasound irradiation, wherein the continuous ultrasound irradiation time is 1~3s (e.g., 1s, 2s, 3s, etc.), the intermittent time is 3~5s (e.g., 3s, 4s, 5s, etc.), and the total intermittent irradiation time is 2~5min (e.g., 2min, 3min, 4min, 5min, etc.).

[0010] Preferably, the stirring rate in step (2) is 200~300 rpm (e.g., 200 rpm, 220 rpm, 250 rpm, 280 rpm, 300 rpm, etc.), and the stirring time is 20~60 min (e.g., 20 min, 30 min, 40 min, 50 min, 60 min, etc.). Preferably, the stirring in step (2) is applied by a single-layer double-bladed anchor paddle; Preferably, during the stirring process in step (2), the temperature of the suspension is maintained at 5~25℃, for example, 5℃, 10℃, 15℃, 20℃, 25℃, etc.

[0011] Preferably, step (2) further includes sequentially performing solid-liquid separation, washing, and vacuum drying on the substance obtained after stirring; Preferably, the solid-liquid separation method is filtration; Preferably, the cleaning solvent is solvent 3 with a dispersant; it should be noted that the concentration and preparation method of the solvent 3 with a dispersant used here are the same as those of the solvent 3 with a dispersant in step (2). Preferably, the vacuum drying temperature is 40~60℃ (e.g., 40℃, 45℃, 50℃, 55℃, 60℃, etc.), and the drying time is 4~24h (e.g., 4h, 10h, 16h, 20h, 24h, etc.).

[0012] The second objective of this invention is to provide a preparation method as described in the first objective to prepare ADN spherical crystals.

[0013] Preferably, the average particle size of the ADN spherical crystals is 50-350 micrometers; Preferably, the average sphericity of the ADN spherical crystal is not less than 0.85; Preferably, the density of the ADN spherical crystal is 1.76~1.80 g / cm³. 3 .

[0014] A third objective of this invention is to provide an application of the ADN spherical crystal as described in objective two in the field of explosives, propellants, or fireworks agents.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention obtains high-quality spherical crystals by antisolvent crystallization of ADN in the solution phase, supplemented by the addition of surfactants and dispersants. The process is simple and efficient. At the same time, the particle size and sphericity of the crystal products are controlled and optimized by changing process parameters such as stirring rate, solvent ratio, and temperature.

[0016] (2) The present invention can complete the spheroidization of ADN at 20~55℃, and even without heating, which greatly reduces the operating temperature of the traditional melt granulation method and improves the safety and equipment adaptability of the preparation process.

[0017] (3) The ADN spherical crystal product obtained by the present invention has compact particles, high sphericity, and good dispersibility. It can be widely used in subsequent surface modification of ADN to improve its moisture-proof performance and application adaptability. Attached Figure Description

[0018] Figure 1 XRD powder diffraction pattern of ADN spherical crystals; Figure 2Optical microscope image of the ADN spherical crystal obtained in Example 1. Detailed Implementation

[0019] Example 1: (1) At 35℃, 4.5g of ADN was dissolved in 10mL of methanol to obtain an ADN solution; (2) Add 0.9g Tween 20 and 0.09g nano silica to 50mL cyclohexane, disperse by ultrasonication (power 800W, intermittent irradiation, continuous ultrasonic irradiation time / intermittent ultrasonic time is 2s / 4s, total time 3min) and maintain the temperature at 15℃. Add the ADN solution from (1) to it and stir at 500rpm for 30min to obtain the first suspension. (3) Disperse 0.045g of nano silica in 150mL of dichloromethane to obtain a mixture; let the suspension in (2) stand, replace the supernatant with the above mixture, maintain the temperature at 15℃, and stir at 300rpm for 30min to obtain a second suspension; (4) The suspension in (3) is filtered and washed with the same mixture as in step (3). The solid is then vacuum dried at 55°C for 8 hours to obtain ADN spherical crystal products.

[0020] The prepared ADN spherical crystal product was subjected to XRD powder diffraction testing (XRD diffractometer model D8 ADVANCE, Bruker, Germany), and the spectra are shown below. Figure 1 As shown, this indicates that the product is a stable crystal.

[0021] The prepared ADN spherical crystal products were observed using an optical microscope (model MGL6000, Shanghai Tianzhu Optical Instrument Factory, China). Figure 2 As shown, the product has a spherical shape.

[0022] The particle size of the prepared ADN spherical crystal product was tested (using a TopSizer laser particle size analyzer, Zhuhai Omec Instruments Co., Ltd., China), and the average particle size was 100 micrometers. The sphericity of the prepared ADN spherical crystal products was tested (based on microscopic images and analyzed using ImageJ image processing software), and the average sphericity was 0.9. The density of the prepared ADN spherical crystal product was tested (using a true density meter, Ultrapyc 5000, Anton Paar, Austria), and the density was 1.80 g / cm³. 3 ; The hygroscopicity of the prepared ADN spherical crystal product was tested (standard GJB770B-2005). The saturated hygroscopicity at 25℃ and 53% relative humidity was 0.71%.

[0023] Example 2: (1) At 55℃, 4.5g of ADN was dissolved in 10mL of ethanol to obtain an ADN solution; (2) Add 0.9g Span 60 and 0.09g nano silica to 300mL toluene, and ultrasonically disperse (power 600W, intermittent irradiation, continuous ultrasonic irradiation time / intermittent ultrasonic time is 2s / 4s, total time 5min) until uniform, and maintain its temperature at 5℃. Add the ADN solution from (1) to it and stir at 700rpm for 20min to obtain the first suspension. (3) Disperse 0.045g of nano silica in 300mL of tetrachloroethylene to obtain a mixture; let the suspension in (2) stand, replace the supernatant with the above mixture, maintain the temperature at 5℃, stir at 200rpm for 20min to obtain a second suspension; (4) The suspension in (3) is filtered and washed with the same mixture as in step (3). The solid is then vacuum dried at 50°C for 12 hours to obtain ADN spherical crystal products.

[0024] The ADN spherical crystal product obtained in Example 2 was subjected to the same tests as in Example 1. The product was a stable crystal with a spherical morphology, an average particle size of 170 micrometers, an average sphericity of 0.86, and a density of 1.76 g / cm³. 3 The saturated moisture absorption rate is 0.78% under the conditions of 25℃ and 53% relative humidity.

[0025] Example 3: (1) At 25℃, 3g of ADN was dissolved in 10mL of acetone to obtain an ADN solution; (2) Add 0.6g Span 80 and 0.06g nano silica to 50mL benzene, and disperse by ultrasonication (power 800W, intermittent irradiation, continuous ultrasonic irradiation time / intermittent ultrasonic time is 2s / 4s, total time 3min) until uniform, and maintain its temperature at 15℃. Add the ADN solution from (1) to it and stir at 500rpm for 30min to obtain the first suspension. (3) Disperse 0.03g of nano silica in 100mL of chloroform to obtain a mixture; let the suspension in (2) stand, replace the supernatant with the above mixture, maintain the temperature at 15℃, stir at 300rpm for 30min to obtain a second suspension; (4) The suspension in (3) is filtered and washed with the same mixture as in step (3). The solid is then vacuum dried at 55°C for 8 hours to obtain ADN spherical crystal products.

[0026] The ADN spherical crystal product obtained in Example 3 was subjected to the same tests as in Example 1. The product was a stable crystal with a spherical morphology, an average particle size of 80 micrometers, an average sphericity of 0.88, and a density of 1.79 g / cm³. 3 The saturated moisture absorption rate is 0.83% under the conditions of 25℃ and 53% relative humidity.

[0027] Example 4: (1) At 40℃, 2g of ADN was dissolved in 10mL of isopropanol to obtain an ADN solution; (2) Add 0.45g Span 40 and 0.09g nano silica to 150mL xylene, and disperse by ultrasonication (power 1000W, intermittent irradiation, continuous ultrasonic irradiation time / intermittent ultrasonic time is 2s / 4s, total time 3min) until uniform, and maintain its temperature at 25℃. Add the ADN solution from (1) to it and stir at 300rpm for 60min to obtain the first suspension. (3) Disperse 0.045g of nano silica in 150mL of dichloroethane to obtain a mixture; let the suspension in (2) stand, replace the supernatant with the above mixture, maintain the temperature at 25℃, and stir at 200rpm for 60min to obtain a second suspension; (4) The suspension in (3) is filtered and washed with the same mixture as in step (3). The solid is then vacuum dried at 40°C for 24 hours to obtain ADN spherical crystal products.

[0028] The ADN spherical crystal product obtained in Example 4 was subjected to the same tests as in Example 1. The product was a stable crystal with a spherical morphology, an average particle size of 330 micrometers, an average sphericity of 0.85, and a density of 1.76 g / cm³. 3 The saturated moisture absorption rate is 0.75% under the conditions of 25℃ and 53% relative humidity.

[0029] Example 5: (1) Dissolve 6g of ADN in 10mL of acetone at 50℃ to obtain an ADN solution; (2) Add 1.2g Tween 80 and 0.12g nano silica to 50mL toluene, and disperse by ultrasonication (power 800W, intermittent irradiation, continuous ultrasonic irradiation time / intermittent ultrasonic time is 2s / 4s, total time 3min) until uniform, and maintain its temperature at 15℃. Add the ADN solution from (1) to it and stir at 300rpm for 30min to obtain the first suspension. (3) Disperse 0.06g of nano silica in 150mL of chloroform to obtain a mixture; let the suspension in (2) stand, replace the supernatant with the above mixture, maintain the temperature at 15℃, and stir at 250rpm for 30min to obtain a second suspension; (4) The suspension in (3) is filtered and washed with the same mixture as in step (3). The solid is then vacuum dried at 60°C for 4 hours to obtain ADN spherical crystal products.

[0030] The ADN spherical crystal product obtained in Example 5 was subjected to the same tests as in Example 1. The product was a stable crystal with a spherical morphology, an average particle size of 140 micrometers, an average sphericity of 0.88, and a density of 1.79 g / cm³. 3 The saturated moisture absorption rate is 0.72% under the conditions of 25℃ and 53% relative humidity.

[0031] Example 6: (1) At 50℃, 2.5g of ADN was dissolved in 10mL of acetonitrile to obtain an ADN solution; (2) Add 0.15g Tween 40 and 0.06g nano silica to 50mL ethylbenzene, and disperse by ultrasonication (power 1000W, intermittent irradiation, continuous ultrasonic irradiation time / intermittent ultrasonic time is 2s / 4s, total time 2min) until uniform, and maintain its temperature at 15℃. Add the ADN solution from (1) to it and stir at 500rpm for 40min to obtain the first suspension. (3) Disperse 0.03g of nano silica in 100mL of carbon tetrachloride to obtain a mixture; let the suspension in (2) stand, replace the supernatant with the above mixture, maintain the temperature at 15℃, and stir at 250rpm for 40min to obtain a second suspension; (4) The suspension in (3) is filtered and washed with the same mixture as in step (3). The solid is then vacuum dried at 50°C for 12 hours to obtain ADN spherical crystal products.

[0032] The ADN spherical crystal product obtained in Example 6 was subjected to the same tests as in Example 1. The product was a stable crystal with a spherical morphology, an average particle size of 110 micrometers, an average sphericity of 0.85, and a density of 1.78 g / cm³. 3 The saturated moisture absorption rate is 0.75% under the conditions of 25℃ and 53% relative humidity.

[0033] Comparative Example 1: The saturated moisture absorption rate of untreated ADN raw material is 1.35% at 25°C and 53% relative humidity.

[0034] A comparison of the examples with Comparative Example 1 shows that the ADN spherical crystal product prepared by the present invention has significantly reduced hygroscopicity compared with the untreated ADN raw material.

[0035] This invention discloses and proposes a method for preparing ADN spherical crystals. Those skilled in the art can implement this method by appropriately modifying some steps, based on the content of this document. The method of this invention has been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the methods and products described herein without departing from the content, spirit, and scope of this invention to achieve the technical results of this invention. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included within the spirit, scope, and content of this invention.

Claims

1. A method for preparing ADN spherical crystals, characterized in that, The preparation method includes the following steps: (1) Disperse the surfactant and dispersant evenly in solvent 2, and add the ADN solvent 1 solution under stirring to obtain a suspension; (2) Let the suspension obtained in step (1) stand, replace the supernatant with solvent 3 containing the dispersant, stir, and obtain ADN spherical crystals.

2. The preparation method according to claim 1, characterized in that, The surfactant mentioned in step (1) is any one or a combination of at least two of Span 20, Span 40, Span 60, Span 80, Tween 20, Tween 40, Tween 60 or Tween 80; Preferably, the amount of surfactant added in step (1) is 5-20 wt% of the amount of ADN added; Preferably, the dispersant in step (1) is nano-silica, and the average particle size of the nano-silica is 10~30nm; Preferably, the amount of dispersant added in step (1) is 1 to 2 wt% of the amount of ADN added.

3. The preparation method according to claim 1, characterized in that, In step (1), solvent 1 is any one or a combination of at least two of methanol, ethanol, acetone, acetonitrile, n-propanol or isopropanol; Preferably, the solvent 2 in step (1) is any one or a combination of at least two of n-hexane, cyclohexane, benzene, toluene, xylene or ethylbenzene; Preferably, in the solvent 1 solution of ADN in step (1), the concentration of ADN is 0.2~0.8 g / mL; Preferably, the dissolution temperature of the ADN in solvent 1 in step (1) is 20~55℃; Preferably, the volume of solvent 2 added in step (1) is 5 to 50 times the volume of solvent 1 added in the ADN solvent 1 solution.

4. The preparation method according to claim 1, characterized in that, The dispersion method described in step (1) is ultrasound, and the power of the ultrasound is 600~1000W; Preferably, the ultrasound is intermittent ultrasound irradiation, wherein the continuous ultrasound irradiation time is 1~3s, the interval time is 3~5s, and the total intermittent irradiation time is 2~5min; Preferably, the stirring rate in step (1) is 300~700 rpm and the stirring time is 20~60 min; Preferably, the stirring in step (1) is applied by a single-layer double-bladed anchor paddle; Preferably, the temperature of the suspension is maintained at 5~25℃ during the stirring process in step (1).

5. The preparation method according to claim 1, characterized in that, The preparation method of the solvent 3 containing the dispersant in step (2) includes: placing the dispersant in the solvent 3 and dispersing it; Preferably, the dispersant is nano-silica, and its addition amount is 0.5~1wt% of the ADN addition amount; Preferably, solvent 3 is any one or a combination of at least two of dichloromethane, dichloroethane, trichloromethane, carbon tetrachloride, or tetrachloroethylene; Preferably, the volume of solvent 3 added is 0.5 to 4 times the volume of solvent 2 added; Preferably, the dispersion method is ultrasound, and the power of the ultrasound is 600~1000W; Preferably, the ultrasound is intermittent ultrasound irradiation, wherein the continuous ultrasound irradiation time is 1~3s, the interval time is 3~5s, and the total intermittent irradiation time is 2~5min.

6. The preparation method according to claim 1, characterized in that, The stirring speed in step (2) is 200~300 rpm, and the stirring time is 20~60 min; Preferably, the stirring in step (2) is applied by a single-layer double-bladed anchor paddle; Preferably, the temperature of the suspension is maintained at 5~25℃ during the stirring process in step (2).

7. The preparation method according to claim 1, characterized in that, Step (2) further includes sequentially performing solid-liquid separation, washing, and vacuum drying on the substance obtained after stirring; Preferably, the solid-liquid separation method is filtration; Preferably, the cleaning solvent is solvent 3 in which a dispersant is dispersed; Preferably, the vacuum drying temperature is 40~60℃ and the drying time is 4~24h.

8. ADN spherical crystals are prepared by the preparation method according to any one of claims 1-7.

9. The ADN spherical crystal according to claim 8, characterized in that, The average particle size of the ADN spherical crystals is 50~350 micrometers; Preferably, the average sphericity of the ADN spherical crystal is not less than 0.85; Preferably, the density of the ADN spherical crystal is 1.76~1.80 g / cm³. 3 .

10. The application of the ADN spherical crystal according to claim 8 or 9 in the field of explosives, propellants or fireworks agents.

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