An ultrasonic-assisted NTO crystallization granulation method

Abstract

The application discloses an ultrasonic-assisted NTO crystallization granulation method, which comprises the following steps: (1) dissolving NTO in a solvent to prepare an NTO saturated solution; (2) adding an anti-solvent and a bridging agent into a crystallization reactor, stirring to uniformly disperse the bridging agent in the anti-solvent, and obtaining a bridging agent-anti-solvent system; (3) dropping the NTO saturated solution into the stirring bridging agent-anti-solvent system, and simultaneously performing ultrasonic treatment, so that an oil-in-water (O / W) microemulsion is formed, and NTO is precipitated; (4) stopping the ultrasonic treatment, and continuing to stir, so that the NTO single crystal particles are coalesced into spherical particles under the action of a shearing flow field; and (5) filtering, washing and drying to obtain NTO spherical particles. In the application, the ultrasonic treatment is coupled with the anti-solvent crystallization, the bridging agent is used to bond the ultrasonic fusion crystals, and large-particle spherical NTO explosive particles with different sizes are prepared, the surface of the prepared NTO spherical particles is smooth without sharp edges and corners, and the sphericity is as high as 90% to 93%.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials preparation technology, specifically an ultrasound-assisted NTO crystallization granulation method. Background Technology

[0002] 3-Nitro-1,2,4-triazol-5-one (NTO) plays an important role in energetic materials, with a density as high as 1.93 g / cm³. 3 With detonation energy comparable to cyclotrimethyltrinitramine (RDX) and sensitivity similar to 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), NTO is a simple and inexpensive insensitive explosive with great application potential. However, directly synthesized NTO is mostly serrated or irregular rod-shaped, with a particle size distribution ranging from tens to hundreds of micrometers. Its crystal quality is relatively low, its sensitivity is relatively high, and its powder processability is poor, limiting its application in explosive formulations and propellants.

[0003] Studies have shown that spherical explosive particles have fewer sharp edges, better flowability, and stronger processability, resulting in a very low probability of hot spots forming due to friction and impact. This leads to high safety performance and is beneficial for increasing charge density, improving processing and formulation mechanical properties, thereby optimizing the energy output of the explosive and improving its combustion and detonation performance. Therefore, the control of NTO particle morphology has always been a key focus. For example, patent CN201510673200.8 discloses a high crystal density spheroidized NTO crystal and its preparation method, which uses a mixed solvent cooling crystallization method to obtain NTO spheroid particles with a particle size of 120-200 μm; patent CN202211569676.3 discloses a recrystallization method for NTO crystals, which uses a cooling crystallization method to obtain near-spherical particles with a particle size of 200-400 μm; patent CN202210853143.1 discloses a spherical single crystal 3-nitro-1,2,4-triazol-5-one and its preparation method, which uses an additive-assisted cooling crystallization method to obtain spherical single crystal particles with a particle size of only a few micrometers; patent CN202111613994.0 discloses a spherical NTO crystal and its preparation method, which uses a mixed solvent cooling crystallization method to obtain NTO spheroids with a particle size of tens of micrometers. The methods described above all employ cooling crystallization to obtain single or polycrystalline particles of different sizes and sphericities, with only slight differences in solvent types and ratios, and the largest particle size is only a few hundred micrometers. No methods for preparing NTO particles with larger sizes and higher sphericity have been reported. Recent reviews of methods for preparing and characterizing spherical explosive crystals also do not report on methods for the aggregation of large spherical particles (D. Liao, M. Li, J. Wang, et al., Journal of Materials Research and Technology. 27(2023)3098-3118). Summary of the Invention

[0004] The purpose of this invention is to further improve the characteristics of NTO particles. An ultrasonic-assisted NTO crystallization and granulation method has been invented, which couples the explosive crystallization and granulation processes within one operating unit. This method has high preparation efficiency and low cost, and can obtain NTO particles of various sizes, with narrow particle size distribution and high sphericity. It is expected to significantly improve the flowability, stability and mechanical properties of the product and expand its applications.

[0005] This invention is the first to use a crystallization-granulation coupling method to prepare large-diameter NTO spherical particles with high sphericity. Many rod-shaped crystals of tens of micrometers are tightly aggregated together by a bridging agent to form larger particles.

[0006] This invention is achieved using the following technical solution:

[0007] An ultrasound-assisted NTO crystallization granulation method includes the following steps:

[0008] (1) Dissolve NTO in a solvent to prepare a saturated NTO solution;

[0009] (2) Add antisolvent and crosslinking agent to crystallization reactor, stir to make crosslinking agent uniformly dispersed in antisolvent, and obtain crosslinking agent-antisolvent system;

[0010] (3) Add the saturated NTO solution dropwise into the crosslinking agent-antisolvent system under stirring, and simultaneously sonicate it to form an oil-in-water (O / W) microemulsion, while NTO precipitates out.

[0011] (4) Stop the ultrasound and continue stirring. Under the action of the shear flow field, the NTO single crystal particles will agglomerate into spherical particles.

[0012] (5) Filter, wash and dry to obtain NTO spherical particles.

[0013] Optionally, the solvent is N-methylpyrrolidone; the antisolvent is selected based on differences in solubility and compatibility with the crosslinking agent, and the antisolvent is deionized water; the crosslinking agent, which acts as a binder between crystals, is toluene.

[0014] Optionally, the volume ratio of the crosslinking agent to the mass of the NTO is 0.6 to 1 ml: 1 g, and the volume ratio of the solvent to the antisolvent is 1:2 to 1:5.

[0015] Optionally, the stirring described in steps (2), (3), and (4) involves turning on an electric stirrer and controlling the speed to be between 300 and 900 rpm. The stirring rates in steps (2) and (3) are the same, and the stirring rate in step (4) is the same as or different from that in step (3).

[0016] Optionally, in step (3), the NTO saturated solution is added dropwise into the crosslinking agent-antisolvent system at a drip rate of 2.5 to 3.0 ml / min using a peristaltic pump.

[0017] The amount of crosslinking agent determines whether aggregates can be formed. Optionally, the frequency of ultrasound in step (3) is 40KHz and the time is 1min20s~3min20s.

[0018] Optionally, the stirring time in step (4) is controlled to be 30 to 60 minutes.

[0019] Preferably, the volume ratio of the solvent to the non-solvent is 1:3 to 1:4.

[0020] Preferably, the ultrasound duration is 2 min 50 s to 3 min 10 s.

[0021] Preferably, the volume ratio of the crosslinking agent to the mass ratio of NTO is 0.7-0.8 ml: 1 g.

[0022] The preferred drip rate of the peristaltic pump is 2.5–2.8 ml / min.

[0023] Ultrasound provides energy for the nucleation and growth of crystals. The duration of ultrasound also determines whether aggregates can be formed in the end. The time should not be too long. The ultrasound time can be 1 min 20 s to 3 min 20 s, and the preferred ultrasound time is 2 min 50 s to 3 min 10 s.

[0024] Stirring provides varying degrees of shear force, and the stirring speed determines the final size of the aggregated particles. The stirring speed is 300–900 rpm, preferably 350–900 rpm.

[0025] To obtain a dry NTO crystal product, the mixture was filtered, washed, and dried after stirring. Filtration was performed under vacuum, followed by washing with deionized water. Drying was carried out under vacuum at a temperature of 70–90°C for 6–10 hours.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] This invention utilizes ultrasonic and antisolvent coupling crystallization combined with a crosslinking agent to bond ultrasonically fused crystals to prepare large spherical NTO explosive particles of different sizes. The introduction of ultrasound and the crosslinking agent has a significant impact on crystal morphology and aggregation, directly determining the initial crystal morphology and the density of the aggregates. The prepared NTO spherical particles have smooth surfaces without sharp edges, with a sphericity as high as 90%–93%. The particle size can be adjusted in multiple specifications according to requirements (e.g., 556 μm, 965 μm, 1323 μm, 1788 μm, 6650 μm, etc.). Attached Figure Description

[0028] Figure 1 This is an electron microscope image of the NTO crystal used in this invention.

[0029] Figure 2 A photograph of the NTO crystal prepared in Example 1 (the smallest square in the figure is 1 mm in length).

[0030] Figure 3 This is an electron microscope image of the NTO crystal prepared by filtering immediately after stopping the sonication in Example 1.

[0031] Figure 4 (a) is a photograph of the NTO crystal prepared in Example 2 (the smallest square in the figure is 1 mm in length), (b) is an electron microscope image, and (c) is a surface microscope image of the particles.

[0032] Figure 5 (a) is a photograph of the NTO crystal prepared in Example 3 (the smallest square in the figure is 1 mm in length), (b) is an electron microscope image, and (c) is a surface microscope image of the particles.

[0033] Figure 6 (a) is a photograph of the NTO crystal prepared in Example 4 (the smallest square in the figure is 1 mm in length), (b) is an electron microscope image, and (c) is a surface microscope image of the particles.

[0034] Figure 7 (a) is a photograph of the NTO crystal prepared in Example 5 (the smallest square in the figure is 1 mm in length), (b) is an electron microscope image, and (c) is a surface microscope image of the particles.

[0035] Figure 8 (a) is an electron microscope image of particles filtered immediately after sonication was turned off, without the use of a crosslinking agent, which is a control example. (b) is an electron microscope image of the final particles of the control example without the use of a crosslinking agent. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] In the following implementation examples, the NTO crystal was provided by the Institute of Chemical Materials, China Academy of Engineering Physics; N-methylpyrrolidone was purchased from Shanghai Aladdin Biotechnology Co., Ltd.; toluene was purchased from Chengdu Kelong Chemical Co., Ltd.; and deionized water was prepared in the laboratory.

[0038] Example 1

[0039] An ultrasound-assisted NTO crystallization granulation method is as follows:

[0040] First, a saturated solution was prepared by dissolving 1.25g of NTO raw material in 4ml of N-methylpyrrolidone at 25℃. 12ml of deionized water was poured into the crystallization reactor, and the temperature of the crystallization reactor was controlled to be around 25℃. Then, 0.9ml of toluene was added, and the electric stirrer was turned on with a stirring speed of 350rpm. The 4ml saturated solution was dropped into the deionized water at a rate of 2.6ml / min using a peristaltic pump. At the same time, the ultrasonic treatment was turned on (frequency of 40KHz, the same below). After 1min30s, the ultrasonic treatment was turned off, and then the mixture was stirred at 500rpm for 50min. The solution was then filtered, washed, and dried to obtain NTO spherical aggregates.

[0041] Figure 2 Here are actual photographs of the NTO explosive particles prepared in this embodiment. Figure 2 It can be seen that the prepared NTO particles are uniform in size, with an average particle size of 6650 μm; the particles have no sharp edges, are spherical in shape, have a dense surface, and good flowability. Figure 3 The crystal sample obtained immediately after stopping ultrasonication in Example 1 was filtered. The measured average particle size was 26 μm, which shows that it is consistent with the crystal morphology on the surface of the final sample.

[0042] Example 2

[0043] An ultrasound-assisted NTO crystallization granulation method is as follows:

[0044] First, a saturated solution was prepared by dissolving 2.5g of NTO raw material in 8ml of N-methylpyrrolidone at 25℃. 24ml of deionized water was poured into the crystallization reactor, and the temperature of the crystallization reactor was controlled at 25℃. Then, 2ml of toluene was added, and an electric stirrer was turned on at a stirring rate of 600rpm. The 8ml of saturated solution was dropped into the deionized water at a rate of 2.8ml / min using a peristaltic pump. At the same time, the sonication was turned on and turned off after 3min10s. Then, the mixture was stirred at 500rpm for 60min. The solution was then filtered, washed, and dried to obtain NTO spherical aggregates.

[0045] Figure 4 (a) is a photograph of the obtained particles. Figure 4 (b) is an electron microscope image. Figure 4 (c) is an electron microscope image of the surface of the prepared NTO particles. It can be seen from the image that the prepared NTO particles are uniform in size, with an average particle size of 1788 μm and a sphericity of 91.1%. The particles have no sharp edges, high sphericity, dense surface, and good flowability.

[0046] Example 3

[0047] An ultrasound-assisted NTO crystallization granulation method is as follows:

[0048] First, 1.88g of NTO raw material was dissolved in 6ml of N-methylpyrrolidone at 25℃ to prepare a saturated solution. 24ml of deionized water was poured into the crystallization reactor, and the temperature of the crystallization reactor was controlled at 25℃. Then, 1.5ml of toluene was added, and the electric stirrer was turned on at a stirring rate of 700rpm. The 6ml of saturated solution was dropped into the deionized water at a rate of 2.8ml / min using a peristaltic pump. At the same time, the sonication was turned on and turned off after 3min. Then, the mixture was stirred at 500rpm for 55min. After filtration, washing, and drying, NTO spherical aggregates were obtained.

[0049] Figure 5 (a) is an image of the obtained sample. Figure 5 (b) is an electron microscope image of the sample. Figure 5 (c) is an electron microscope image of the surface of the prepared sample particles. It can be seen from the image that the prepared NTO particles are uniform in size, with an average particle size of 1323 μm and a sphericity of 93%. The particles have no sharp edges, high sphericity, uniform particle size, dense surface, and good flowability.

[0050] Example 4

[0051] An ultrasound-assisted NTO crystallization granulation method is as follows:

[0052] First, 2.5g of NTO raw material was dissolved in 8ml of N-methylpyrrolidone at 25℃ to prepare a saturated solution. 28ml of deionized water was poured into the crystallization reactor, and the temperature of the crystallization reactor was controlled at 25℃. Then, 1.8ml of toluene was added, and the electric stirrer was turned on at a stirring speed of 800rpm. The 8ml of saturated solution was dropped into the deionized water at a rate of 2.6ml / min using a peristaltic pump. At the same time, the sonication was turned on and turned off after 3min. Then, the mixture was stirred at 500rpm for 50min. The solution was then filtered, washed, and dried to obtain NTO spherical aggregates.

[0053] Figure 6 (a) is an image of the obtained NTO sample. Figure 6 (b) is an electron microscope image of the sample. Figure 6 (c) is an electron microscope image of the prepared sample particle surface. It can be seen from the image that the prepared NTO particles are uniform in size, with an average particle size of 1187 μm and a sphericity of 92.6%. The particles have no sharp edges, high sphericity, dense surface, and good flowability.

[0054] Example 5

[0055] An ultrasound-assisted NTO crystallization granulation method is as follows:

[0056] First, 2.5g of NTO raw material was dissolved in 8ml of N-methylpyrrolidone at 25℃ to prepare a saturated solution. 24ml of deionized water was poured into the crystallization reactor, and the temperature of the crystallization reactor was controlled at 25℃. Then, 1.9ml of toluene was added, and the electric stirrer was turned on at a stirring speed of 700rpm. The 8ml of saturated solution was dropped into the deionized water at a rate of 2.8ml / min using a peristaltic pump. At the same time, the sonication was turned on and turned off after 3min10s. Then, the stirring speed was adjusted to 900rpm and stirred for 1h. The solution was then filtered and dried to obtain NTO spherical aggregates.

[0057] Figure 7 (a) is a sample image of the obtained NTO. Figure 7 (b) is an electron microscope image of the sample. Figure 7 (c) is an electron microscope image of the surface of the prepared sample particles. It can be seen from the image that the prepared NTO particles are uniform in size, with an average particle size of 627 μm and a sphericity of 88.1%. The particles have no sharp edges, high sphericity, dense surface, and good flowability.

[0058] The control group did not use a crosslinking agent.

[0059] First, 2.5g of NTO raw material was dissolved in 8ml of N-methylpyrrolidone at 25℃ to prepare a saturated solution. 24ml of deionized water was poured into the crystallization reactor, and the temperature of the crystallization reactor was controlled at 25℃. The electric stirrer was turned on and the stirring speed was adjusted to 600rpm. The 8ml of saturated solution was dropped into the deionized water at a rate of 2.8ml / min using a peristaltic pump. At the same time, the sonication was turned on and turned off after 2min55s. Then, the mixture was stirred at 500rpm for 50min. The solution was then filtered, washed, and dried to obtain NTO aggregates.

[0060] Figure 8 (a) is an image of the prepared sample after sonication was turned off without the addition of a crosslinking agent. Figure 8 (b) is an electron microscope image of the final sample. It can be seen that after sonication, stirring for a certain period of time can also cause it to aggregate into irregular aggregates. Figure 8 (a) The average particle size is 27 μm. Figure 8 (b) The average particle size of the aggregates was 78 μm. The presence or absence of a bridging agent demonstrated that toluene played a crucial role in the crystal aggregation process.

[0061] Although the invention has been described herein with reference to illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter combination within the scope of this disclosure. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A method for ultrasound-assisted crystallization and granulation of 3-nitro-1,2,4-triazol-5-one, characterized in that, Includes the following steps: (1) Dissolve NTO in a solvent to prepare a saturated NTO solution; (2) Add antisolvent and crosslinking agent to crystallization reactor, stir to make crosslinking agent uniformly dispersed in antisolvent, and obtain crosslinking agent-antisolvent system; (3) Add the saturated NTO solution dropwise into the crosslinking agent-antisolvent system under stirring, and simultaneously sonicate it to form an oil-in-water microemulsion, while NTO precipitates out. (4) Stop the ultrasound and continue stirring to cause the NTO single crystal particles to aggregate into spherical particles; (5) Filter, wash and dry to obtain NTO spherical particles; The solvent is N-methylpyrrolidone, the antisolvent is deionized water, and the crosslinking agent is toluene; The stirring described in steps (2), (3), and (4) involves turning on the electric stirrer and controlling the speed at 300-900 rpm. The stirring rates in steps (2) and (3) are the same, and the stirring rate in step (4) is the same as or different from that in step (3). Step (3) The frequency of ultrasound is 40KHz and the time is 1min20s ~ 3min20s.

2. The ultrasound-assisted crystallization and granulation method for 3-nitro-1,2,4-triazol-5-one according to claim 1, characterized in that, The volume ratio of the crosslinking agent to the mass of the NTO is 0.6~1ml:1g, and the volume ratio of the solvent to the antisolvent is 1:2~1:

5.

3. The ultrasound-assisted crystallization and granulation method for 3-nitro-1,2,4-triazol-5-one according to claim 1, characterized in that, In step (3), the NTO saturated solution is added to the crosslinking agent-antisolvent system by a peristaltic pump at a dropping rate of 2.5~3.0 ml / min.

4. The ultrasound-assisted crystallization and granulation method for 3-nitro-1,2,4-triazol-5-one according to claim 1, characterized in that, In step (4), the stirring time is controlled to be 30~60 min.

5. The ultrasound-assisted crystallization and granulation method for 3-nitro-1,2,4-triazol-5-one according to claim 2, characterized in that, The volume ratio of the solvent to the antisolvent is 1:3 to 1:

4.

6. The ultrasound-assisted crystallization and granulation method for 3-nitro-1,2,4-triazol-5-one according to claim 1, characterized in that, The ultrasound duration is 2 min 50 s ~ 3 min 10 s.

7. The ultrasound-assisted crystallization and granulation method for 3-nitro-1,2,4-triazol-5-one according to claim 1, characterized in that, The volume ratio of the crosslinking agent to the mass of NTO is 0.7~0.8 ml: 1 g.

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