A method for preparing spherical zinc 5,5'-azotetrazolate

Abstract

The application discloses a method for preparing spherical zinc azotetrazolate, wherein a bottom liquid and zinc azotetrazolate particles with a certain particle size are added into a container as seed crystals, a zinc salt solution and a sodium azotetrazolate solution are stirred and added at a certain temperature, and the spherical zinc azotetrazolate is obtained after a reaction for a period of time. The method does not need to introduce an additional crystal form control agent, and the PH of the solution is controlled to control crystallization. The obtained zinc azotetrazolate particles present a spherical shape, and the flowability and the loose bulk density are greatly improved. By controlling the particle size of the added seed crystals, the preparation of large-particle spherical zinc azotetrazolate with a particle size in the range of 80-200 mu m can be realized.

Description

Technical Field

[0001] This invention belongs to the field of energetic material crystallization, specifically relating to a method for preparing spherical 5,5'-azotetrazole zinc (ZnATZ). Background Technology

[0002] 5,5'-Azotetrazole zinc is an initiating explosive that does not contain toxic metals or environmentally harmful components such as perchlorate. Sun Yanling, Zhu Shunguan, et al. published a method for synthesizing azotetrazole zinc (Sun Yanling, Yan Donglin, Zhu Shunguan, et al. Synthesis and characterization of 5,5'-Azotetrazole zinc [J]. Energetic Materials, 2012, 20(3):5.). The target compound ZnATZ is synthesized in two steps. First, 5-aminotetrazole is used as a raw material and oxidized to sodium 5,5'-azotetrazole (NaATZ) using the Thiele alkaline oxidation method. 5,5'-Azotetrazole zinc is synthesized from pentaaminotetrazole. Its components do not contain toxic metals or environmentally harmful components such as perchlorate. Its decomposition products are only zinc oxide and nitrogen. Compared with the traditional initiating explosive lead stemonate, azotetrazole zinc has comparable flame sensitivity, impact sensitivity, and electrostatic sensitivity, and is expected to replace lead stemonate as a component of green initiating explosives. However, the azotetrazole zinc prepared by the above synthesis method suffers from poor flowability and low bulk density. During the mixing with other components to form a formulation, it is difficult to achieve uniform mixing and is prone to stratification. Furthermore, during loading, floating charges are easily generated, leading to safety issues. The crystal morphology of the azotetrazole zinc prepared by the above method exhibits a flower-like structure formed by the accumulation of plate-like crystals, and the particles are not dense, which is one of the reasons for the low bulk density and high sensitivity. In addition, since azotetrazole zinc is insoluble in water and other common solvents, controlling the crystallization process is difficult. Therefore, researching and improving the crystal morphology and particle size of azotetrazole zinc is of great significance for the use of this initiating explosive. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing spheroidized azotetrazole zinc. By preparing spheroidized azotetrazole zinc, the problems of low packing density, poor flowability, and high sensitivity of azotetrazole zinc obtained by existing preparation methods are successfully solved.

[0004] This invention discloses a method for preparing spherical azotetrazole zinc. A base liquid and azotetrazole zinc particles of a certain size are added to a container as seed crystals. At a certain temperature, a zinc salt solution and azotetrazole sodium solution are added while stirring. After reacting for a period of time, spherical azotetrazole zinc is obtained.

[0005] Preferably, zinc azotetrazole particles of a certain size refer to particles with a diameter not exceeding 100 micrometers.

[0006] Ideally, the base liquid should be water.

[0007] Preferably, the mass ratio of zinc azotetraazole particles of a certain size to the base liquid is 0.08:60.

[0008] Ideally, a certain temperature is 50-75℃, preferably 65-75℃.

[0009] Ideally, the zinc salt solution should be added within 20-30 minutes.

[0010] Preferably, the time for adding the sodium azotetrazole solution should be controlled within 25-35 minutes.

[0011] Ideally, the reaction time is 10-20 minutes.

[0012] Compared with existing technologies, this method does not require the introduction of additional crystal form control agents or the control of solution pH to control crystallization. The resulting azotetrazole zinc particles exhibit a spherical shape, with significantly improved flowability and loose packing density. By controlling the particle size of the added seed crystals, large-particle spherical azotetrazole zinc with a particle size range of 80-200 μm can be prepared. Attached Figure Description

[0013] Figure 1 The effect of different seed contents on crystal morphology.

[0014] Figure 2 The effect of different temperatures on crystal morphology.

[0015] Figure 3 The effect of different feed times on crystal morphology.

[0016] Figure 4 Comparison of the morphology of zinc azotetrazole: (a) by literature method, (b) by the method of this invention. Detailed Implementation

[0017] This disclosure will be more readily understood by referring to the following description, taken in conjunction with the accompanying drawings and examples, all of which form part of this disclosure. It should be understood that this disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Furthermore, the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting, unless otherwise stated.

[0018] It should also be understood that, for clarity, certain features of this disclosure may be described herein in the context of individual embodiments, but may also be provided in combination with each other in individual embodiments. That is, unless obviously incompatible or specifically excluded, each individual embodiment is considered to be combinable with any other embodiment, and such combination is considered to represent another different embodiment. Conversely, for brevity, various features of this disclosure described in the context of individual embodiments may also be provided individually or in any sub-combination. Finally, while a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure may also be considered an independent embodiment in itself.

[0019] Example 1

[0020] Weigh out 1.72g of zinc acetate dihydrate and 1.78g of sodium azotetrazole and dissolve them in 60ml of aqueous solution. Add 60ml of deionized water to the reaction vessel, and add 40mg, 60mg, 80mg and 100mg of seed crystals respectively. Heat the bottom solution to 65℃ with stirring, and then add the materials separately using a peristaltic pump. Add the zinc acetate dihydrate solution 1min first, and then add the sodium azotetrazole solution. Add the zinc acetate dihydrate solution after 20min, and add the sodium azotetrazole solution after 30min. After the feeding is completed, keep the reaction at the temperature for 10min, and then cool, filter, wash and dry.

[0021] Table 1. Bulk density and angle of repose for different seed contents

[0022]

[0023]

[0024] Note: A - Feed time of zinc acetate solution; B - Feed time of zinc azotetrazole; A' - Feed time of zinc acetate solution before sodium azotetrazole solution; M - Content of seed crystals added; ρ - Loose packing density; θ - Angle of repose

[0025] As shown in Table 1, the presence of seed crystals has a significant effect on the loose packing density and the angle of repose. When the seed crystal content is 80 mg, the prepared spherical azotetrazole zinc has the highest loose packing density, and the angle of repose indicates that the flowability is the best at this time. Figure 1 The ZnATZ morphology in the scanned electron microscope showed that the morphology of ZnATZ changed after the addition of seed crystals, exhibiting a spherical pattern. When the seed crystal content was 80 mg, the particle size of ZnATZ in the scanned electron microscope field of view showed better uniformity.

[0026] Example 2

[0027] 1.72 g of zinc acetate dihydrate and 1.78 g of sodium azotetrazole were dissolved in 60 ml of aqueous solution, respectively. 60 ml of deionized water and 80 mg of seed crystals were added to a reaction vessel. The mixture was heated to different temperatures with stirring. The zinc acetate dihydrate solution was added first, followed by the sodium azotetrazole solution 1 min later. The zinc acetate dihydrate solution was added after 20 min, and the sodium azotetrazole solution after 30 min. After the addition was complete, the reaction was maintained at this temperature for 10 min, then cooled, filtered, washed, and dried. The effect of higher temperatures on the crystallization of spheroidal azotetrazole zinc was investigated. The crystal morphology, bulk density, and flowability data are shown in Table 2. Figure 2 As shown:

[0028] Table 2. Bulk density and angle of repose for different seed contents

[0029]

[0030] Note: T - reaction temperature; ρ - loose bulk density; θ - angle of repose

[0031] Table 2 shows that the difference in bulk density and angle of repose between the products obtained under reaction conditions of 65℃ and 70℃ is negligible, indicating that the products obtained under both conditions have good bulk density and flowability. However, the products obtained under reaction conditions of 75℃ have poorer flowability and bulk density.

[0032] Depend on Figure 2 It can be seen that the spheroidized azotetrazole zinc particles are uniform in size at the three different temperatures, but the surface morphology of the particles is different. Under the reaction conditions of 75℃, the azotetrazole zinc particles are not spherical, but generally exhibit a serrated shape. Under the reaction conditions of 65℃ and 70℃, the particles appear to be more spherical, and at 70℃, the surface is smoother.

[0033] Example 3

[0034] Under the conditions of 80 mg seed crystals and a reaction temperature of 70 °C, different feeding times (20:30, 30:30, 30:0) were set for zinc acetate solution (A) and sodium azotetrazole solution (B) to simplify the feeding method and investigate the effect of feeding time on crystallization. When the feeding time was 0:30, the reaction solution was an emulsion after the addition was completed, and no product was obtained. Crystal morphology, bulk density, and flowability data are as follows: Figure 3 As shown in Table 3:

[0035] Depend on Figure 3 It can be seen that when the zinc acetate solution is fully fed into the reaction, the resulting azotetrazole zinc particles are uniform and have relatively regular morphology, tending to be spherical. However, when sodium azotetrazole is used as the base liquid, the reaction solution eventually becomes an emulsion and is difficult to filter, so large azotetrazole zinc particles cannot be obtained.

[0036] Table 3. Bulk density and angle of repose at different feed times

[0037]

[0038] Note: A:B - Feed time ratio of zinc acetate solution to sodium azotetrazole solution; ρ - Loose bulk density; θ - Angle of repose

[0039] Table 3 shows that as the feeding time of zinc acetate solution (A) increases, the bulk density of the obtained azotetrazolium zinc gradually increases and the angle of repose gradually decreases. When the feeding time of both solutions is 30 min, the flower-shaped azotetrazolium zinc has the highest bulk density and the lowest angle of repose, indicating that under this condition, the product has the best flowability and the highest bulk density. A comparison of the morphology of ZnATZ obtained under this condition with that obtained according to the literature method is shown below. Figure 4 As shown, the ZnATZ prepared by this method clearly exhibits a spherical structure, with the particle size increasing from 20 μm in the literature method to 100 μm. The angle of repose indicates that the ZnATZ prepared by this method has a significantly improved flowability.

Claims

1. A method for preparing spherical azotetrazole zinc, characterized in that, Add the base liquid water and azotetrazole zinc particles with a particle size of no more than 100 micrometers as seed crystals to the container. Control the mass ratio of azotetrazole zinc particles to the base liquid to be 0.08:

60. After heating the base liquid to 50~75℃ by stirring, add the following materials separately using a peristaltic pump: add the zinc acetate dihydrate solution first, and then add the azotetrazole sodium solution 1 minute later. The zinc acetate dihydrate solution is added after 20-30 minutes, and the azotetrazole sodium solution is added after 25-35 minutes. After reacting for 10-20 minutes, spherical azotetrazole zinc is obtained.

2. The method as described in claim 1, characterized in that, Start the stirrer and heat the base liquid to 65~75℃.

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