A granulation method for preparing high-spherical anti-hygroscopic ammonium dinitramide with the assistance of HMX

Abstract

The application discloses a granulation method for preparing high-spherical moisture-proof ammonium dinitramide (ADN) with the aid of HMX, and comprises the following steps: adding ADN crude product into an organic solvent, mixing, and then placing in an oil bath for heating and stirring to make the ADN completely melt into a uniform melt system; then adding an ultrasonic dispersion HMX crystal seed suspension into the melt system, and uniformly dispersing the crystal seeds under constant temperature stirring; then completing crystallization through rapid cooling, and performing filtering and drying treatment on the obtained crystalline particles to obtain smooth-surface and non-pore moisture-proof spherical ADN particles. The application introduces trace HMX as a crystal seed to regulate the crystallization result, effectively reduces the large amount of pores of the spherical ADN particles, and further improves the moisture-proof performance of the particles; the obtained spherical ADN particles have a particle size range of 50-500 microns, a sphericity of not less than 0.877, and a moisture absorption of less than 1.0% (20 DEG C, 55% relative humidity); the method for preparing the moisture-proof spherical ADN is simple, and has a good application prospect in the field of explosives and solid propellants.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials and relates to a granulation method for preparing highly spherical, moisture-resistant ammonium dinitramide (ADN) with the assistance of octogen (HMX). Specifically, it relates to a method for preparing smooth, non-porous, moisture-resistant spherical ADN with the assistance of HMX. Background Technology

[0002] The strong hygroscopicity of ADN particles severely limits their application in fields such as solid propellants. Researchers both domestically and internationally have conducted extensive research on everything from hygroscopic mechanisms to suppression methods. To address this issue, multiple research teams worldwide have carried out systematic studies. Currently, the main strategies for reducing ADN hygroscopicity include surface coating technology, eutectic technology, and spheroidization crystallization technology. Surface coating and eutectic technologies are essentially methods for modifying the crystal structure of ADN. Their core idea is to introduce new components into the ADN system, reducing the probability of water molecules contacting the functional groups on the ADN surface through physical shielding or chemical interactions, thereby effectively suppressing the hygroscopic behavior of ADN. For example, surface coating technology mainly involves coating the surface of ADN particles with anti-hygroscopic materials (GAP, polyurethane (PU), polyvinyl butyral (PVB), polyethylene glycol (PEG), stearic acid (SA), and HMX, etc.) to prevent direct contact between water molecules and ADN. Eutectic technology mainly utilizes a eutectic component with weak hygroscopicity to remove the highly hygroscopic NH4 from the ADN. + "Encapsulating" or shielding them weakens the direct interaction between water molecules and ADN. However, both of these technologies require the introduction of new compounds, which not only significantly diminish the advantages of ADN's high oxygen balance and high energy density but may also negatively impact its combustion performance in solid propellants.

[0003] Spheroidization crystallization technology is a moisture-wicking method centered on physical morphology control. It reconstructs rod- or sheet-like ADN crystals into spherical particles, reducing specific surface area and the interface accessible to water molecules. Existing technologies for ADN spheroidization mainly include various process routes such as melt spheroidization, spray spheroidization, ultrasonic-assisted spheroidization, micro-reaction spheroidization, and membrane emulsion spheroidization. The most significant advantage of this technology is that it does not introduce new chemical components, thus not altering the chemical composition or weakening the intrinsic properties of ADN, such as oxygen balance and high energy density. However, a significant drawback of spheroidization crystallization technology is that its ability to suppress moisture absorption is usually limited, making it difficult to achieve the improvements obtained through surface coating or eutectic methods. Morphology analysis reveals a large number of pores on the surface of spherical ADN, which is the main reason why its moisture-wicking performance cannot be further improved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a granulation method for preparing highly spherical, moisture-resistant ammonium dinitramide with HMX assistance. This method solves the problem that granules prepared by existing spherification methods often have porosity, making it difficult to effectively reduce their hygroscopicity. The present invention introduces trace amounts of nucleating seeds during the melt crystallization process to reduce particle porosity and improve moisture resistance. Under melt crystallization conditions, the addition of trace amounts of HMX as seeds significantly enhances the moisture resistance of spherical ADN particles.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance includes the following steps: Step 1: Add octogen HMX seed crystals to an organic solvent for dispersion. The resulting dispersion is then ultrasonically treated to obtain a uniformly dispersed seed crystal suspension for later use. Step 2: Add crude dinitramide ammonium (ADN) to the same organic solvent as in Step 1, and place the resulting solution in an oil bath and stir. Step 3: Heat the system from Step 2 to 95°C and stir at a constant temperature to completely melt the crude ADN. Step 4: While maintaining the stirring conditions and temperature at 95°C, slowly add the seed crystal suspension obtained in Step 1 to the molten ADN system obtained in Step 3, and continue stirring. Step 5: Remove the above molten ADN system from the oil bath and quickly place it in a cold water bath or ice-water mixture to cool it down to below 25°C, and keep it at that temperature to complete the crystallization process. Step 6: Filter and dry the crystalline particles obtained in Step 5 to obtain moisture-proof spherical ADN particles.

[0007] The present invention also includes the following technical features: Specifically, the HMX to ADN mass ratio is (0.001-0.01):1.

[0008] Specifically, the organic solvent is selected from at least one of decane or xylene.

[0009] Specifically, in step 1, the ultrasonic treatment conditions are: ultrasonic treatment at 100 W ultrasonic power for 5-15 minutes.

[0010] Specifically, in step 2, the obtained solution is placed in an oil bath and stirred for 10 minutes.

[0011] Specifically, in step 3, the constant temperature stirring time is 30 minutes; in step 4, the stirring time continues for 30 minutes.

[0012] Specifically, in step 5, the heat preservation time is 10 minutes.

[0013] Specifically, the obtained moisture-wicking spherical ADN particles have a particle size range of 50-500 μm, a sphericity of not less than 0.877, and a hygroscopicity of less than 1.0% at 25℃ and 50% relative humidity.

[0014] A type of moisture-resistant spherical ADN particle is prepared by the HMX-assisted granulation method for preparing highly spherical moisture-resistant ammonium dinitramide. The particle size range of the moisture-resistant spherical ADN particle is 50-500 μm, the sphericity can reach 0.933, and the moisture absorption performance at 25℃ and 50% relative humidity is as low as 0.085%.

[0015] The spherical ADN particles prepared by the HMX-assisted granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium are used to improve the combustion performance and long-term storage capacity of solid propellants.

[0016] Compared with the prior art, the present invention has the following technical effects: The HMX micro-seed-assisted melt crystallization process proposed in this invention prepares highly spherical, moisture-resistant ADN particles. At 25°C and 50% relative humidity, the hygroscopicity of the spherical ADN is less than 1.0%, which is significantly lower than that of the spherical ADN prepared by the original melt crystallization method. Attached Figure Description

[0017] Figure 1 The SEM image is a 0.01:1 HMX-ADN image. Figure 2 Original spherical ADN SEM image; Figure 3 The SEM image is 0.005:1 HMX-ADN. Figure 4 The SEM image is a 0.001:1 HMX-ADN image. Figure 5 The moisture absorption rate of spherical ADN. Detailed Implementation

[0018] This invention provides a granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance, comprising the following steps: Step 1: Add a small amount of HMX seed crystals to an organic solvent for dispersion. Place the resulting dispersion in an ultrasonic treatment device and ultrasonically treat it for 5 minutes under a set ultrasonic power of 100 W to obtain a uniformly dispersed seed crystal suspension for later use. Step 2: Add crude ADN to the same organic solvent as in Step 1, and place the resulting solution in an oil bath and stir for 10 min. Step 3: Heat the system from Step 2 to 95 °C and stir at a constant temperature for 30 min at a certain stirring speed to completely melt the crude ADN. Step 4: While maintaining stirring conditions and a temperature of 95°C, slowly add the seed crystal suspension obtained in Step 1 to the molten ADN system obtained in Step 3, and continue stirring for 30 min. Step 5: Remove the above molten ADN system from the oil bath and quickly place it in an ice-water mixture for cooling, so that the system temperature drops below 25°C, and keep it at that temperature for 10 minutes to complete the crystallization process. Step 6: Filter and dry the crystalline particles obtained in Step 5 to obtain high sphericity moisture-proof ADN particles.

[0019] Furthermore, the quality ratio of HMX to ADN is (0.001-0.01):1.

[0020] The organic solvent is selected from either decane or xylene.

[0021] The cooling crystallization method in step 5 is a water bath or an ice-water mixture.

[0022] The present invention also discloses a spherical ADN prepared by the above method.

[0023] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0024] In the following embodiments: Particle size was tested using the dry sieving method in GJB 772A-1997 403.1 Explosives Test Methods.

[0025] The sphericity test is performed using an image-based method.

[0026] The hygroscopicity of spherical ADN particles was determined using a constant temperature and humidity chamber and an analytical balance.

[0027] Example 1: This embodiment provides a granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance, including the following steps: Weigh 50 mg of HMX seed crystals and add them to 10 mL of decane solution. Disperse the resulting solution in an ultrasonic water bath and sonicate for 5 min at 100 W to obtain a uniformly dispersed HMX seed crystal suspension. Then, add 5 g of crude ADN to 90 mL of decane solution. Place the resulting system in an oil bath and stir for 10 min to ensure thorough mixing. Heat the system to 95°C and stir at 400 rpm for 30 min to completely melt the crude ADN in the decane solution, forming a homogeneous melt system.

[0028] While maintaining the system temperature at 95℃ and continuously stirring, the pre-prepared HMX seed suspension was slowly added to the molten system, and the mixture was stirred at a constant temperature for 30 min. The molten system was then removed from the oil bath and rapidly placed in an ice-water bath to cool it down to below 25℃, and maintained for 10 min to complete the crystallization process. Finally, the obtained crystalline particles were filtered and dried to obtain moisture-resistant spherical ADN particles, denoted as (0.01:1)HMX-ADN.

[0029] The spherical ADN particles prepared in this embodiment were tested and found to have a particle size range of 50–350 µm, a sphericity of 0.933, and a hygroscopicity of 0.085% (20°C, 55% relative humidity).

[0030] Structural Analysis 1. Scanning electron microscopy (SEM) analysis In this embodiment, SEM analysis was performed on the ADN raw material and the prepared spherical ADN, and the results are as follows: Figure 1 and Figure 2 As shown.

[0031] As can be seen from the figure: the original spherical ADN is mainly composed of aggregated sheet-like ADNs with many pores. Figure 1 In contrast, the ADN particles prepared in this embodiment have a high sphericity, with a sphericity of 0.933 (). Figure 2 ).

[0032] 2. Hygroscopicity In this embodiment, the hygroscopicity of the original spherical ADN and 0.01:1 HMX-ADN particles was analyzed, and the results are as follows: Figure 3 As shown.

[0033] As can be seen from the figure, under the conditions of 25℃ and 50% relative humidity, the hygroscopicity of the original spherical ADN is 3.19%, while that of 0.01:1 HMX-ADN particles is 0.085%, indicating that smooth and non-porous ADN can enhance the moisture-proof performance.

[0034] Example 2: Weigh 25 mg of HMX seed crystals and add them to 10 mL of decane solution. Disperse the resulting solution in an ultrasonic water bath and sonicate for 5 min at 100 W to obtain a uniformly dispersed HMX seed crystal suspension. Then, add 5 g of crude ADN to 90 mL of decane solution. Place the resulting system in an oil bath and stir for 10 min to ensure thorough mixing. Heat the system to 95°C and stir at 400 rpm for 30 min to completely melt the crude ADN in the decane solution, forming a homogeneous melt system.

[0035] While maintaining the system temperature at 95℃ and continuously stirring, the pre-prepared HMX seed suspension was slowly added to the molten system, and the mixture was stirred at a constant temperature for 30 min. The molten system was then removed from the oil bath and rapidly placed in an ice-water bath to cool it down to below 25℃, maintaining this temperature for 10 min to complete the crystallization process. Finally, the obtained crystalline particles were filtered and dried to obtain moisture-resistant spherical ADN particles, denoted as (0.005:1)HMX-ADN.

[0036] The spherical ADN particles prepared in this embodiment were tested and found to have a particle size range of 50–350 µm, a sphericity of 0.901, and a hygroscopicity of 0.43% (20°C, 55% relative humidity).

[0037] In this embodiment, the prepared 0.005:1 HMX-ADN was analyzed by SEM, and the results are as follows: Figure 3 As shown, spherical ADN particles also have a certain amount of porosity on their surface, which is why their hygroscopicity is higher than that of 0.01:1 HMX-ADN.

[0038] Example 3: Weigh 5 mg of HMX seed crystals and add them to 10 mL of decane solution. Disperse the resulting solution in an ultrasonic water bath and sonicate for 5 min at 100 W to obtain a uniformly dispersed HMX seed crystal suspension. Then, add 5 g of crude ADN to 90 mL of decane solution. Place the resulting system in an oil bath and stir for 10 min to ensure thorough mixing. Heat the system to 95°C and stir at 400 rpm for 30 min to completely melt the crude ADN in the decane solution, forming a homogeneous melt system.

[0039] While maintaining the system temperature at 95℃ and continuously stirring, the pre-prepared HMX seed suspension was slowly added to the molten system, and the mixture was stirred at a constant temperature for 30 min. The molten system was then removed from the oil bath and rapidly placed in an ice-water bath to cool it down to below 25℃, and maintained for 10 min to complete the crystallization process. Finally, the obtained crystalline particles were filtered and dried to obtain moisture-resistant spherical ADN particles, denoted as (0.001:1)HMX-ADN.

[0040] The spherical ADN particles prepared in this embodiment were tested and found to have a particle size range of 50–350 µm, a sphericity of 0.878, and a hygroscopicity of 0.64% (20°C, 55% relative humidity).

[0041] In this embodiment, the prepared 0.001:1 HMX-ADN was analyzed by SEM, and the results are as follows: Figure 4 As shown, the surface of spherical ADN particles also has more pores, which is why their hygroscopicity is higher than that of 0.01:1 HMX-ADN.

[0042] Example 4: Weigh 50 mg of HMX seed crystals and add them to 10 mL of decane solution. Disperse the resulting solution in an ultrasonic water bath and sonicate for 5 min at 100 W to obtain a uniformly dispersed HMX seed crystal suspension. Then, add 5 g of crude ADN to 90 mL of decane solution. Place the resulting system in an oil bath and stir for 10 min to ensure thorough mixing. Heat the system to 95°C and stir at 400 rpm for 30 min to completely melt the crude ADN in the decane solution, forming a homogeneous melt system.

[0043] While maintaining the system temperature at 95℃ and continuously stirring, the pre-prepared HMX seed suspension was slowly added to the molten system, and the mixture was stirred at a constant temperature for 30 min. The molten system was then removed from the oil bath and rapidly placed in a cold water bath (25℃) to cool it down to below 25℃, maintaining this temperature for 10 min to complete the crystallization process. Finally, the obtained crystalline particles were filtered and dried to obtain moisture-resistant spherical ADN particles, denoted as (0.01:1)HMX-ADN (25℃).

[0044] The spherical ADN particles prepared in this embodiment were tested and found to have a particle size range of 50–400 µm, a sphericity of 0.894, and a hygroscopicity of 0.17% (20°C, 55% relative humidity).

[0045] Example 5: Weigh 50 mg of HMX seed crystals and add them to 10 mL of xylene solution. Disperse the resulting solution in an ultrasonic water bath and sonicate for 5 min at 100 W to obtain a uniformly dispersed HMX seed crystal suspension. Then, add 5 g of crude ADN to 90 mL of xylene solution. Place the resulting system in an oil bath and stir for 10 min to ensure thorough mixing. Heat the system to 95°C and stir at 400 rpm for 30 min to completely melt the crude ADN in the toluene solution, forming a homogeneous molten ADN system.

[0046] Under conditions of maintaining the system temperature at 95℃ and continuous stirring, the pre-prepared HMX seed suspension was slowly added to the molten ADN system, and the mixture was stirred at a constant temperature for 30 min. The molten system was then removed from the oil bath and rapidly placed in a cold water bath to cool it down to below 25℃, and maintained for 10 min to complete the crystallization process. Finally, the obtained crystalline particles were filtered and dried to obtain moisture-resistant spherical ADN particles, denoted as (0.01:1)HMX-ADN (xylene).

[0047] The spherical ADN particles prepared in this embodiment were tested and found to have a particle size range of 50–400 µm, a sphericity of 0.885, and a hygroscopicity of 0.13% (20°C, 55% relative humidity).

[0048] Example 6: Weigh 50 mg of HMX seed crystals and add them to 10 mL of xylene solution. Disperse the resulting solution in an ultrasonic water bath and sonicate for 5 min at 100 W to obtain a uniformly dispersed HMX seed crystal suspension. Then, add 5 g of crude ADN to 90 mL of xylene and decane (volume ratio 1:1). Place the resulting system in an oil bath and stir for 10 min to ensure thorough mixing. Heat the system to 95°C and stir at 400 rpm for 30 min to completely melt the crude ADN in the decane solution, forming a homogeneous melt system.

[0049] While maintaining the system temperature at 95℃ and continuously stirring, the pre-prepared HMX seed suspension was slowly added to the molten system, and the mixture was stirred at a constant temperature for 30 min. The molten system was then removed from the oil bath and rapidly placed in a cold water bath to cool it down to below 25℃, maintaining this temperature for 10 min to complete the crystallization process. Finally, the obtained crystalline particles were filtered and dried to obtain moisture-resistant spherical ADN particles, denoted as (0.01:1)HMX-ADN (xylene / decane).

[0050] The spherical ADN particles prepared in this embodiment were tested and found to have a particle size range of 50–500 µm, a sphericity of 0.879, and a hygroscopicity of 0.24% (20°C, 55% relative humidity).

[0051] Comparative example: Add 5 g of crude ADN to 100 mL of decane solution, and place the resulting system in an oil bath and stir for 10 min to ensure thorough mixing. Heat the system to 95 °C and stir at 400 rpm for 30 min to completely melt the crude ADN in the decane solution, forming a homogeneous melt system.

[0052] While maintaining the system temperature at 95°C and continuously stirring, the pre-prepared HMX seed suspension was slowly added to the molten system, and stirring was continued at a constant temperature for 30 min. The molten system was then removed from the oil bath and rapidly placed in an ice-water bath for cooling, reducing the system temperature to below 25°C, and maintained for 10 min to complete the crystallization process. Finally, the obtained crystalline particles were filtered and dried to obtain moisture-resistant spherical ADN particles, denoted as ADN.

[0053] The spherical ADN particles prepared in this embodiment were tested and found to have a particle size range of 50–400 µm, a sphericity of 0.877, and a hygroscopicity of 3.19% (20°C, 55% relative humidity).

Claims

1. A granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance, characterized in that, Includes the following steps: Step 1: Add octogen HMX seed crystals to an organic solvent for dispersion. The resulting dispersion is then ultrasonically treated to obtain a uniformly dispersed seed crystal suspension for later use. Step 2: Add crude dinitramide ammonium (ADN) to the same organic solvent as in Step 1, and place the resulting solution in an oil bath and stir. Step 3: Heat the system from Step 2 to 95°C and stir at a constant temperature to completely melt the crude ADN. Step 4: While maintaining the stirring conditions and temperature at 95°C, slowly add the seed crystal suspension obtained in Step 1 to the molten ADN system obtained in Step 3, and continue stirring. Step 5: Remove the above molten ADN system from the oil bath and quickly place it in a cold water bath or ice-water mixture to cool it down to below 25°C, and keep it at that temperature to complete the crystallization process. Step 6: Filter and dry the crystalline particles obtained in Step 5 to obtain moisture-proof spherical ADN particles.

2. The granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance as described in claim 1, characterized in that, The HMX to ADN mass ratio is (0.001-0.01):

1.

3. The granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance as described in claim 1, characterized in that, The organic solvent is selected from at least one of decane or xylene.

4. The granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance as described in claim 1, characterized in that, In step 1, the ultrasonic treatment conditions are: ultrasonic treatment for 5-15 minutes at an ultrasonic power of 100 W.

5. The granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance as described in claim 1, characterized in that, In step 2, the resulting solution is placed in an oil bath and stirred for 10 minutes.

6. The granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance as described in claim 1, characterized in that, In step 3, the constant temperature stirring time is 30 min; in step 4, the stirring time is continued for 30 min.

7. The granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance as described in claim 1, characterized in that, In step 5, the heat preservation time is 10 minutes.

8. The granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance as described in claim 1, characterized in that, The resulting moisture-wicking spherical ADN particles have a particle size range of 50-500 μm, a sphericity of not less than 0.877, and a hygroscopicity of less than 1.0% at 25℃ and 50% relative humidity.

9. A moisture-resistant spherical ADN particle, characterized in that, The granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium with HMX assistance as described in any one of claims 1 to 8 was used to prepare the spherical dinitramide ammonium. The particle size range of the moisture-resistant spherical ADN particles is 50-500 μm, the sphericity can reach 0.933, and the moisture absorption performance at 25℃ and 50% relative humidity is as low as 0.085%.

10. The moisture-resistant spherical ADN particles prepared by the HMX-assisted granulation method for preparing highly spherical, moisture-resistant dinitramide ammonium according to any one of claims 1 to 8 are used for improving the combustion performance and long-term storage capacity of solid propellants.

Images