Low-moisture-absorption ADN material suitable for isocyanate curing system as well as preparation method and application of low-moisture-absorption ADN material

Abstract

The invention discloses a low-moisture-absorption ADN material suitable for an isocyanate curing system and a preparation method and application thereof.The preparation method comprises the following steps that the surfaces of ADN particles are evenly coated with isocyanate, and an ADN-isocyanate mixed prepolymer is obtained; placing the ADN-isocyanate mixed prepolymer in an environment with certain humidity and temperature, and storing for a certain time to promote the isocyanate to be cured into a film, so as to obtain an isocyanate-coated ADN composite material; and washing and drying the isocyanate-coated ADN composite material, and removing the unreacted isocyanate, so as to obtain the low-moisture-absorption ADN material with good compatibility with an isocyanate curing system. According to the method, the reaction characteristics of isocyanate, water and ADN are utilized, so that the strong acting force between composite material structures and the hydrophobicity of the composite material are enhanced, and the compatibility of the composite material and an isocyanate curing system is ensured.

Description

Technical Field

[0001] This invention relates to the field of explosives technology, specifically to a low-moisture-absorbing ADN material suitable for isocyanate curing systems, its preparation method, and its application. Background Technology

[0002] Ammonium dinitramide (ADN) contains both oxidant and fuel components in its molecular structure, has a high oxygen content, and a heat of formation of -148.4 to -149.6 kJ / mol. It can be used as both an explosive and an oxidant in solid propellants. Compared to traditional oxidants such as ammonium perchlorate (AP), ADN has significant advantages in terms of gas production and energy density. Furthermore, because it does not contain chlorine, ADN produces extremely low smoke and infrared radiation during combustion, effectively reducing the detectability of weapon systems and aligning with the trend of low-signature weapon development. However, ADN's strong hygroscopicity can lead to clumping and even decomposition during storage and use, affecting the stability and performance of the propellant. Additionally, the incompatibility between ADN and propellant curing agents (isocyanate curing systems) makes propellant curing difficult, severely restricting its practical application in solid propellants. Therefore, solving the hygroscopicity problem and improving the compatibility with propellant components is a bottleneck technology for the large-scale application of ADN in composite explosives and solid propellants. Summary of the Invention

[0003] To address the aforementioned problems, the first objective of this invention is to provide a method for preparing a low-hygroscopic ADN material suitable for isocyanate curing systems. ADN is chemically incompatible with polyisocyanates, ADN only physically adsorbs water molecules, and isocyanates react with water to self-polymerize and are hydrophobic. This yields a low-hygroscopic ADN material suitable for isocyanate curing systems. The polyisocyanate reacts chemically with the ADN surface and undergoes self-polymerization to form a hydrophobic shell. Not only is the interaction between the two strong, but the resulting shell also exhibits strong water-shielding ability in the shielding environment, thus reducing the hygroscopicity of ADN. Furthermore, the ADN composite material shows good compatibility with isocyanates.

[0004] The second objective of this invention is to provide a low-hygroscopic ADN material suitable for isocyanate curing systems. This low-hygroscopic ADN material, suitable for isocyanate curing systems, has a significantly reduced hygroscopicity because the polyisocyanate undergoes self-polymerization on the surface of the ADN to form a hydrophobic polymer. The surface of the composite material changes from hydrophilic to hydrophobic due to the hydrophilicity of the ADN. In addition, the ADN surface is a polyisocyanate self-polymer, which has natural chemical compatibility with polyisocyanates.

[0005] The first technical solution adopted in this invention is: a method for preparing a low-hygroscopic ADN material suitable for isocyanate curing systems, comprising the following steps:

[0006] S1: Isocyanate is uniformly coated on the surface of ADN particles to obtain an ADN-isocyanate mixed prepolymer;

[0007] S2: The ADN-isocyanate mixed prepolymer is placed in an environment with certain humidity and temperature and stored for a certain period of time to promote the curing of isocyanate into a film, thereby obtaining an isocyanate-coated ADN composite material.

[0008] S3: The isocyanate-coated ADN composite material is washed and dried to remove unreacted isocyanate, resulting in a low-moisture-absorbing ADN material with good compatibility with the isocyanate curing system.

[0009] The isocyanate is a polyisocyanate;

[0010] The polyisocyanate is one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polyphenylmethylene polyisocyanate (PAPI), 1,6-hexanediisocyanate (HDI), isophorone diisocyanate (IPDI), and dicyclohexane 4,4'-diisocyanate.

[0011] The isocyanate accounts for 0.5% to 5% of the mass of the ADN granules.

[0012] In step S1, the method for uniformly coating the isocyanate onto the surface of the ADN particles is either a solid-phase coating method or a liquid-phase coating method.

[0013] The solid-phase coating process steps are as follows:

[0014] Isocyanate was directly mixed with ADN particles, and mechanical force was used to uniformly coat the surface of the ADN particles with isocyanate. The mixing and coating time was 10-60 min and the temperature was 20-30℃, resulting in an isocyanate-coated ADN composite material.

[0015] The liquid phase coating process steps are as follows:

[0016] Isocyanate is dispersed in a poor solvent of ADN, and then ADN particles are added and mixed. After removing the poor solvent in a certain way, an isocyanate-coated ADN composite material is obtained.

[0017] ADN's unsuitable solvents are at least one of ethyl acetate, toluene, and dichloromethane;

[0018] It is dried in one of the following ways: natural evaporation, rotary evaporation, or spray drying.

[0019] In step S2, the curing temperature of the ADN-isocyanate mixed prepolymer is 20℃~50℃, the relative humidity is 20%~40%, and the curing time is 3~7 days.

[0020] Step S3 includes:

[0021] The isocyanate-coated ADN composite material was washed with solvent 3 to 5 times and vacuum dried for 6 to 12 hours at 40 to 70°C and a vacuum degree of -0.1 to -0.2 MPa to finally obtain a low moisture absorption ADN material with good compatibility with the isocyanate curing system.

[0022] The solvent is one of dichloromethane, trichloromethane, cyclohexane, or n-hexane.

[0023] A low-moisture-absorbing ADN material suitable for isocyanate curing systems is prepared by the above-mentioned technical solution. The low-moisture-absorbing ADN material has a core-shell structure, with the core being ADN and the outer layer being the product of the reaction of polyisocyanate with water and ADN.

[0024] The present invention also provides the application of a low-moisture-absorbing ADN material suitable for isocyanate curing systems prepared according to the preparation method of the above technical solution in solid propellants.

[0025] The beneficial effects of the above technical solution are as follows:

[0026] (1) The invention discloses a low moisture-absorbing ADN material suitable for isocyanate curing system and its preparation method. The invention innovatively utilizes the chemical incompatibility between ADN and polyisocyanate, the property that ADN only physically adsorbs water molecules, and the property that isocyanate can self-polymerize and is hydrophobic when it reacts with water. The invention obtains a low moisture-absorbing ADN material suitable for isocyanate curing system. In this material, polyisocyanate reacts chemically with the surface of ADN on the one hand and self-polymerizes on the other hand to form a hydrophobic shell. Not only is the interaction between the two strong, but the water in the shielding environment is also strongly resisted after molding, which reduces the moisture absorption of ADN. Moreover, the ADN composite material has good compatibility with isocyanate.

[0027] (2) The low moisture absorption ADN material disclosed in this invention is suitable for isocyanate curing systems. It has a compact structure, does not change the initial morphology of the ADN material, is simple to operate, has low cost, and strong versatility. At the same time, it can achieve moisture absorption and solve the problem of incompatibility with isocyanate by using only a very small amount of isocyanate and modified isocyanate, which is easy to industrialize.

[0028] (3) The preparation method disclosed in this invention is simple, selective, safe, low cost, one-step molding, and has good reproducibility; the material structure and properties are adjustable and controllable, and it is suitable for industrial production; moreover, the preparation method disclosed in this invention ensures both strong inter-structural forces and compatibility between the composite material and the commonly used curing agent system for propellants.

[0029] (4) The low moisture absorption ADN material disclosed in this invention is suitable for isocyanate curing systems and has low moisture absorption. It does not absorb moisture at a temperature of 20°C and a relative humidity of 60% (tested using GJB770A-97).

[0030] (5) The low moisture absorption ADN disclosed in this invention is suitable for isocyanate curing systems and is used in high-energy solid propellants. It has good drug-forming properties in isocyanate curing systems and meets the drug-forming performance requirements of high-energy solid propellants. This composite material has good application prospects in the fields of high-energy solid propellants, explosives, and pyrotechnics.

[0031] This invention combines the moisture-absorbing properties of ADN to create a low-humidity environment that avoids the chemical reaction between ADN and polyisocyanates, while allowing the polyisocyanates to react slowly with water in a gentler way to form a dense, moisture-proof layer.

[0032] This invention allows ADN to undergo a mild reaction with water and isocyanate at low temperatures to form a protective layer, thus preventing direct contact between ADN and isocyanate at high temperatures and the resulting chemical reaction that could lead to incompatibility. Attached Figure Description

[0033] Figure 1 The graph shows the moisture absorption rate-time results of the moisture absorption test on TDI-coated ADN material.

[0034] Figure 2 The graph shows the moisture absorption rate-time results of the moisture absorption test on spherical ADN.

[0035] Figure 3 This is a diagram showing the curing results of a drug development experiment using AP as a high-energy propellant oxidant.

[0036] Figure 4 This is a diagram showing the curing results of a drug development experiment using ADN as a high-energy propellant oxidant.

[0037] Figure 5 This image shows the curing results of a drug development experiment using TDI-coated ADN material as a high-energy propellant oxidant. Detailed Implementation

[0038] The present invention will be further illustrated below with specific embodiments. It should be noted that those skilled in the art can make several modifications and improvements without departing from the principle of the present invention, and these should also be considered to fall within the protection scope of the present invention.

[0039] Techniques, methods, and equipment known to those skilled in the art may not be described in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0040] Unless otherwise specified, the experimental and testing methods described in the following examples are conventional methods; the reagents and materials described are obtained commercially or prepared using conventional methods unless otherwise specified.

[0041] This invention discloses a low-moisture-absorbing ADN material suitable for isocyanate curing systems and its preparation method. By forming an ADN-isocyanate cured layer on the surface of ADN particles, a low-moisture-absorbing ADN material with good compatibility with isocyanate curing systems is obtained. The method includes the following steps:

[0042] Step S1: Coat the surface of ADN particles with isocyanate uniformly to obtain an ADN-isocyanate mixed prepolymer;

[0043] In step S1, the method of uniformly coating isocyanate onto the surface of ADN particles is divided into solid-phase coating and liquid-phase coating. Solid-phase coating includes acoustic resonance co-coating, dual-center centrifugal mixing coating, and spin coater coating; liquid-phase coating includes one of the following: natural evaporation coating, rotary evaporation coating, and spray drying coating.

[0044] Preferably, the acoustic resonance co-coating method (a coating method in which solid ADN powder particles and liquid isocyanate are added to an acoustic vibration coating device, and the liquid is coated onto the surface of the solid powder through efficient resonance mixing via acoustic resonance), the dual-center centrifugal mixing coating method (a coating method in which solid ADN powder particles and liquid isocyanate are added to a dual-center centrifugal coating device, and the liquid is coated onto the solid surface through centrifugal mixing via centrifugal force), and the spin coater coating method (a coating method in which solid ADN powder particles and liquid isocyanate are added to a spin coater, and the liquid is coated onto the solid surface through centrifugal mixing via centrifugal force) all directly mix a certain amount of isocyanate liquid with ADN particles, and use mechanical force to uniformly coat the polyisocyanate. On the surface of ADN particles, a mixing and coating time of 10-60 min and a temperature of 20-30℃ are used to obtain an isocyanate-coated ADN composite material. Other methods include natural evaporation coating (allowing the solvent to evaporate naturally, resulting in isocyanate precipitation and coating on the solid surface), rotary evaporation coating (removing the solvent through rotary evaporation, resulting in isocyanate precipitation and coating on the solid surface), and spray drying coating (removing the solvent through spray drying, resulting in isocyanate precipitation and coating on the solid surface). First, isocyanate is dispersed in a poor solvent for ADN (the mass ratio of isocyanate to poor solvent is 1:20-30), such as ethyl acetate, toluene, or dichloromethane. Then, it is mixed with ADN particles, and after removing the solvent in a certain way, an isocyanate-coated ADN composite material is obtained.

[0045] In step S1, the isocyanate is a polyisocyanate. Specifically, it is one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polyphenylmethylene polyisocyanate (PAPI), 1,6-hexanediisocyanate (HDI), isophorone diisocyanate (IPDI), and dicyclohexane 4,4'-diisocyanate.

[0046] In step S1, the polyisocyanate accounts for 0.5% to 5% of the mass percentage of ADN granules.

[0047] Step S2: Place the ADN-isocyanate mixed prepolymer in an environment with certain humidity and temperature for a certain period of time to promote the curing of isocyanate into a film, and obtain the isocyanate-coated ADN composite material.

[0048] Preferably, the curing temperature of the ADN-isocyanate mixed prepolymer is between 20°C and 50°C, the relative humidity is between 20% and 40%, and the curing time is between 3 and 7 days.

[0049] Step S3: The isocyanate-coated ADN composite material is washed and dried to remove unreacted isocyanate, resulting in a low-moisture-absorbing ADN material with good compatibility with the isocyanate curing system.

[0050] Preferably, in step S3, washing and drying refer to washing the composite material 3 to 5 times with solvents such as dichloromethane, trichloromethane, cyclohexane, and n-hexane, and then vacuum drying it for 6 to 12 hours at 40 to 70°C and a vacuum degree of -0.1 ± 0.01 MPa, ultimately obtaining a low-moisture-absorbing ADN material with good compatibility with the isocyanate curing system.

[0051] This invention also provides a low-moisture-absorbing ADN material with good compatibility with isocyanate curing systems. The material has a core-shell structure, with the core being ADN and the outer layer being the product of the reaction of polyisocyanate with water and ADN. It is prepared by the above-mentioned low-moisture-absorbing ADN material suitable for isocyanate curing systems and the preparation method.

[0052] The present invention also provides the application of a low-moisture-absorbing ADN material suitable for isocyanate curing systems in solid propellants.

[0053] Starting from the fundamental principle of incompatibility between ADN and isocyanate, a low-hygroscopic ADN material with good compatibility with the isocyanate curing system is obtained by forming a layer of ADN-isocyanate cured material on the surface of ADN particles. The preparation method of this material is simple, the product is stable, the coating amount is low, and the compatibility with the isocyanate system is greatly improved, which can greatly expand the application range of this material.

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Example 1

[0056] Step S1: Accurately weigh 10g of spherical ADN particles and 0.15g of TDI. Use a solid-phase coating method to uniformly coat the TDI onto the surface of the ADN particles. Specifically, use a spin coater to mix the two particles using a solid-phase coating method. The spin coater is set to intermittent mode, with a mixing time of 10 minutes and a temperature of 25°C. During this time, remove the sample and use a wooden stick to scrape off any ADN particles adhering to the bottle wall before continuing to mix. Repeat this mixing process three times until the surface of the ADN particles is uniformly wetted.

[0057] Step S2: The ADN-TDI mixed prepolymer is stored at 25°C and 33%RH (saturated magnesium chloride solution) for 4 days to allow TDI to solidify into a film, thus obtaining the TDI-coated ADN composite material.

[0058] Step S3: After taking out the TDI-coated ADN composite material obtained in step S2, wash it repeatedly with cyclohexane three times, and then vacuum dry it for 8 hours at 50°C and a vacuum degree of -0.1MPa to finally obtain a TDI-coated ADN material with good compatibility with the isocyanate curing system.

[0059] TDI-coated ADN material and spherical ADN were subjected to hygroscopicity tests at 20°C and 65% relative humidity (saturated sodium nitrite solution). The hygroscopicity-time graph of the TDI-coated ADN material is shown below. Figure 1 As shown, the moisture absorption rate-time graph of the TDI-coated ADN material is as follows: Figure 2 As shown, the results indicate that the 24-hour moisture absorption weight gain of spherical ADN was 0.52%, and the 168-hour (7-day) moisture absorption rate was 3.45%. The 24-hour moisture absorption weight gain of TDI-coated ADN was 0.02%, and the 168-hour (7-day) moisture absorption rate was 0.09%. The moisture absorption rate of ADN after TDI coating decreased by 97% (7 days), showing a significant reduction.

[0060] TDI-coated ADN material and spherical ADN were used as alternatives to the traditional oxidant ammonium perchlorate (AP). AP was used as a control group in a drug development experiment with a high-energy propellant. During weighing and mixing, the ambient temperature and humidity were controlled at approximately 25°C and 50% RH to expose the compatibility of the TDI-coated ADN material in the isocyanate curing system. The curing status of the AP blank drug block used as the oxidant in the high-energy propellant drug development experiment is shown below. Figure 3 As shown, the solidification of the blank ADN block used in the drug development experiment with spherical ADN as a high-energy propellant oxidant is as follows. Figure 4 As shown, the solidification of TDI@ADN drug blocks used as high-energy propellant oxidizers in drug development experiments is as follows: Figure 5 As shown, the results indicate that the high-energy propellant block containing AP has good curing properties and no pores; the high-energy propellant containing ordinary spherical ADN has more pores, indicating poor compatibility with the propellant system; while the high-energy propellant containing TDI-coated ADN material has significantly reduced pores, indicating that the compatibility of the TDI-coated ADN material with high-energy propellant (isocyanate curing system) is significantly improved.

[0061] Example 2

[0062] Step S1: Accurately weigh 10g of spherical ADN particles and 0.3g of PAPI. Use a solid-phase coating method to uniformly coat the ADN particle surface with PAPI. Specifically, use a dual-center centrifuge to mix the two particles. The centrifuge operates for 40 minutes at 1800 rpm and 21°C. During this time, remove the sample and scrape off any ADN particles adhering to the bottle wall with a wooden stick, then continue mixing. Repeat this mixing process 10 times until the ADN particle surface is uniformly wetted.

[0063] Step S2: The ADN-PAPI mixed prepolymer is stored at 23°C and 40%RH for 5 days to allow PAPI to solidify into a film, thus obtaining the PAPI-coated ADN composite material.

[0064] Step S3: After taking out the PAPI-coated ADN composite material obtained in step S2, wash it repeatedly with dichloromethane 4 times, and then vacuum dry it for 10 hours at 50°C and a vacuum degree of -0.1MPa to finally obtain the PAPI-coated ADN material with good compatibility with the isocyanate curing system.

[0065] PAPI-coated ADN material and spherical ADN were subjected to hygroscopicity tests at 20℃ and 65% relative humidity. The results showed that the 24-hour moisture absorption weight gain of spherical ADN was 0.52%, and the 168-hour (7-day) moisture absorption rate was 3.45%. The 24-hour moisture absorption weight gain of PAPI-coated ADN material was 0, and the 168-hour (7-day) moisture absorption rate was 0.06%. After PAPI coating, the moisture absorption rate of ADN (7 days) decreased by 98.3%, showing a significant reduction.

[0066] Example 3

[0067] Step S1: Accurately weigh 10g of spherical ADN particles and 0.1g of IPDI. Use a liquid-phase coating method to uniformly coat the IPDI onto the surface of the ADN particles. Specifically, using a liquid-phase coating method, dissolve the IPDI completely in 3g of toluene, then add the weighed spherical ADN particles and stir until the surface of the ADN particles is uniformly wetted. Then, use a natural evaporation method to place the mixture in a dry, ventilated environment and let it stand for 2 days until the toluene has completely evaporated.

[0068] Step S2: The ADN-IPDI mixed prepolymer is stored at 50°C and 20%RH for 3 days to allow IPDI to solidify into a film, thus obtaining the IPDI-coated ADN composite material.

[0069] Step S3: After taking out the IPDI-coated ADN composite material obtained in step S2, wash it repeatedly with dichloromethane three times, and then vacuum dry it for 8 hours at 70°C and a vacuum degree of -0.2MPa to finally obtain the IPDI-coated ADN material with good compatibility with the isocyanate curing system.

[0070] The hygroscopicity of IPDI-coated ADN material and spherical ADN was tested under conditions of 20℃ and 65% relative humidity. The results showed that the 24-hour moisture absorption weight gain of spherical ADN was 0.52%, and the 168-hour moisture absorption rate (7 days) was 3.45%. The 24-hour moisture absorption weight gain of IPDI-coated ADN material was 0.49%, and the 168-hour moisture absorption rate (7 days) was 0.82%. After IPDI coating, the moisture absorption rate of ADN (7 days) decreased by 76.2%, indicating a reduction in moisture absorption.

[0071] Example 4

[0072] Step S1: Accurately weigh 10g of spherical ADN particles and 0.5g of HDI. Use a solid-phase coating method to uniformly coat the surface of the ADN particles with HDI. Specifically, use a dual-center centrifuge to mix the two particles. The dual-center centrifuge operates for 60 minutes at a speed of 1800 r / min and a temperature of 25℃. During this time, remove the sample and use a wooden stick to scrape off any ADN particles adhering to the bottle wall before continuing mixing. Repeat this mixing process 20 times until the surface of the ADN particles is uniformly wetted.

[0073] Step S2: The ADN-HDI mixed prepolymer is stored at 30°C and 30%RH for 7 days to allow HDI to solidify into a film, thus obtaining the HDI-coated ADN composite material.

[0074] Step S3: After taking out the HDI-coated ADN composite material obtained in step S2, wash it repeatedly with cyclohexane three times, and then vacuum dry it for 12 hours at 40°C and a vacuum degree of -0.1MPa to finally obtain the HDI-coated ADN material with good compatibility with the isocyanate curing system.

[0075] Hygroscopicity tests were conducted on HDI-coated ADN material and spherical ADN under conditions of 20℃ and 65% relative humidity. The results showed that the 24-hour moisture absorption weight gain rate of spherical ADN was 0.52%, and the 168-hour (7-day) moisture absorption rate was 3.45%. The 24-hour moisture absorption weight gain rate of HDI-coated ADN material was 0.15%, and the 168-hour (7-day) moisture absorption rate was 1.74%. After HDI coating, the moisture absorption rate of ADN decreased by 49.6% (7 days), indicating a significant reduction in moisture absorption.

[0076] Example 5

[0077] Step S1: Accurately weigh 10g of spherical ADN particles and 0.2g of MDI. Use a liquid-phase coating method to uniformly coat the MDI onto the surface of the ADN particles. Specifically, using a liquid-phase coating method, completely dissolve the MDI in 4g of dichloromethane, then add the weighed spherical ADN particles and stir until the surface of the ADN particles is uniformly wetted. Then, set the rotary evaporator temperature to 35℃ and the vacuum degree to 0.08MPa to remove the solvent dichloromethane.

[0078] Step S2: The ADN-MDI mixed prepolymer is stored at 35°C and 35%RH (saturated magnesium chloride solution) for 7 days to allow MDI to solidify into a film, thus obtaining the MDI-coated ADN composite material.

[0079] Step S3: After taking out the MDI-coated ADN composite material obtained in step S2, wash it repeatedly with cyclohexane 5 times, and then vacuum dry it for 6 hours at 50°C and a vacuum degree of -0.1MPa to finally obtain the MDI-coated ADN material with good compatibility with the isocyanate curing system.

[0080] Moisture absorption tests were conducted on MDI-coated ADN material and spherical ADN under conditions of 20℃ and 65% relative humidity. The results showed that the 24-hour moisture absorption weight gain rate of spherical ADN was 0.52%, and the 168-hour moisture absorption rate (7 days) was 3.45%. The 24-hour moisture absorption weight gain rate of MDI-coated ADN material was 0.21%, and the 168-hour moisture absorption rate (7 days) was 1.22%. After MDI coating, the moisture absorption rate of ADN (7 days) decreased by 64.6%, showing a significant reduction.

[0081] PAPI-coated ADN material (Example 2), IPDI-coated ADN material (Example 3), HDI-coated ADN material (Example 4), and MDI-coated ADN material (Example 5) were used as oxidants in high-energy propellant experiments. During the weighing and mixing process, the ambient temperature and humidity were controlled at approximately 25°C and 50% RH. The results are shown in Table 1. The results indicate that the porosity of the high-energy propellant containing PAPI-coated ADN material (Example 2), IPDI-coated ADN material (Example 3), HDI-coated ADN material (Example 4), and MDI-coated ADN material (Example 5) was significantly reduced, indicating that the compatibility of the ADN materials coated with TDI, PAPI, IPDI, HDI, and MDI in the high-energy propellant (isocyanate curing system) was significantly improved.

[0082] Table 1

[0083]

[0084] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments; the above descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present invention without departing from the spirit and scope of the present invention, and all such modifications and improvements fall within the scope of the present invention; the scope of protection of the present invention is determined by the appended claims.

Claims

1. A process for the preparation of a low hygroscopic ADN material suitable for isocyanate curing systems, characterized in that, The method comprises the following steps: S1: uniformly coating isocyanate on the surface of ADN particles to obtain ADN-isocyanate mixed prepolymer; S2: placing the ADN-isocyanate mixed prepolymer in an environment with certain humidity and temperature, and storing for a certain time to promote the isocyanate to be cured into a film to obtain isocyanate-coated ADN composite material; S3: removing unreacted isocyanate by washing and drying the isocyanate-coated ADN composite material to obtain low-hygroscopic ADN material with good compatibility with isocyanate curing system.

2. The production method according to claim 1, characterized by, The isocyanate is a polyisocyanate. The polyisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, polyphenyl polymethylene polyisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate.

3. The production method according to claim 1 or 2, characterized by, The mass percentage of the isocyanate in the ADN particle powder is 0.5% to 5%.

4. The method of claim 1, wherein, In the step S1, the method for uniformly coating isocyanate on the surface of ADN particles is solid-phase coating or liquid-phase coating.

5. The preparation method according to claim 4, characterized in that, The process steps of the solid-phase coating method are as follows: The isocyanate is directly mixed with ADN particles, and mechanical force is used to uniformly coat the isocyanate on the surface of the ADN particles, the mixing and coating time is 10 to 60 minutes, and the temperature is 20 to 30°C, to obtain isocyanate-coated ADN composite material.

6. The preparation method according to claim 4, characterized in that, The process steps of the liquid-phase coating method are as follows: The isocyanate is dispersed in a poor solvent of ADN, and then ADN particles are added for mixing, and after removing the poor solvent in a certain way, isocyanate-coated ADN composite material is obtained; The poor solvent of ADN is at least one of ethyl acetate, toluene, and dichloromethane; The certain way is one of natural volatilization, rotary evaporation, or spray drying.

7. The preparation method according to claim 1, characterized in that, In the step S2, the curing film temperature of the ADN-isocyanate mixed prepolymer is 20 to 50°C, the relative humidity is 20% to 40%, and the curing time is 3 to 7 days.

8. The method of claim 1, wherein, The step S3 comprises: The isocyanate-coated ADN composite material is washed with a solvent for 3 to 5 times, vacuum dried at 40 to 70°C and a vacuum degree of -0.1 to -0.2 MPa for 6 to 12 hours, and finally low-hygroscopic ADN material with good compatibility with isocyanate curing system is obtained; The solvent is one of dichloromethane, trichloromethane, cyclohexane, and n-hexane.

9. A low hygroscopic ADN material suitable for isocyanate curing systems, characterized in that, The low-hygroscopic ADN material prepared by the preparation method of any one of claims 1 to 8 has a core-shell structure, and the inner core is ADN and the outer layer is the product of the reaction of polyisocyanate with water and ADN.

10. Application of the low-hygroscopic ADN material prepared by the preparation method of any one of claims 1 to 8 to an isocyanate curing system in a solid propellant.

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