A method for extracting ammonium perchlorate from solid propellant

Abstract

The present invention discloses a method for extracting ammonium perchlorate from a solid propellant, belonging to the field of composite solid propellant manufacturing. The method comprises the following steps: S1, subjecting the propellant to high and low temperature cycle treatment; S2, chopping the propellant and soaking it in a mixed solution of an organic reagent and an organic base; S3, adding an acidic solution to the propellant and stirring and crushing it; S4, subjecting the propellant to ultrasonic vibration to precipitate a preliminary extraction sample; S5, centrifuging the preliminary extraction sample and drying it to obtain ammonium perchlorate. The present invention avoids physical and chemical changes in the ammonium perchlorate filler during the overall process. Ammonium perchlorate is extracted from the propellant while maintaining its inherent state in the propellant as much as possible. The method can be used as a means of obtaining raw materials for studying changes in the properties of the ammonium perchlorate filler during the aging process of the propellant.

Description

Technical Field

[0001] The invention belongs to the field of composite solid propellant manufacturing, and particularly relates to a method for extracting ammonium perchlorate from solid propellant. Background Art

[0002] Solid propellants are essentially high-filling polymer-based particle-reinforced composite materials, in which the mass fraction of the oxidizer (typically ammonium perchlorate, AP) is generally above 60%. During service, propellants are subjected to the combined effects of complex loads such as ambient temperature, gravity, and vibration, inevitably leading to aging. When studying the aging performance of propellants, it is often desirable to comprehensively and meticulously characterize the changes in the physicochemical properties of the polymer matrix and the encapsulated solid filler (primarily ammonium perchlorate) to reveal the aging mechanism. However, the filler in solid propellants is encapsulated in a colloid matrix formed by the curing of the binder polymer. Current techniques only allow observation of the filler morphology and internal distribution at the propellant surface using instruments such as scanning electron microscopy and micro-CT. Further testing of the oxidizer's performance requires extracting the ammonium perchlorate from the propellant. The state and properties of the extracted ammonium perchlorate particles should closely resemble those in the propellant.

[0003] Existing methods for recovering ammonium perchlorate, a raw material for propellants, typically use water or liquid ammonia as a medium. This involves dissolving the ammonium perchlorate in the propellant to form a solution, which is then recovered through recrystallization. This method involves the ammonium perchlorate undergoing a dissolution-crystallization process, which inevitably differs significantly from its original state in the propellant (particle morphology, size, and structure), making it unsuitable for aging research. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a method for extracting ammonium perchlorate from a solid propellant. The extracted ammonium perchlorate has the same actual property state as the ammonium perchlorate in the propellant, thereby achieving in-situ characterization of the properties of the ammonium perchlorate in the propellant and meeting the requirements for in-situ testing of filler properties in propellant aging performance research.

[0005] The present invention includes a method for extracting ammonium perchlorate from a solid propellant, comprising the steps of:

[0006] S1. Perform high and low temperature cycle treatment on the propellant;

[0007] S2, chopping the propellant treated in step S1 and soaking it in a mixed solution of an organic reagent and an organic base;

[0008] S3, adding an acidic solution to the propellant treated in step S2, and stirring and crushing the propellant;

[0009] S4, subjecting the propellant treated in step S3 to ultrasonic vibration and precipitation to obtain a preliminary extraction sample;

[0010] S5. Centrifuge the preliminary extraction sample obtained in step S4 and dry it to obtain ammonium perchlorate.

[0011] Furthermore, in step S1 , the low temperature of the high-low temperature cycle treatment is below -50° C., the high temperature is above 60° C., and the number of cycles is 4 to 6 times.

[0012] Furthermore, in step S1, the high and low temperature cycle treatment is specifically to cyclically store the propellant between the ultra-low temperature test chamber and the high temperature oven.

[0013] Furthermore, in step S2, the organic agent has a solubility parameter similar to that of the propellant matrix but is incompatible with ammonium perchlorate.

[0014] Furthermore, in step S2, the organic reagent includes one of toluene, acetonitrile or tetrahydrofuran.

[0015] Furthermore, in step S2, at room temperature, the propellant is immersed in the mixed solution for more than 24 hours.

[0016] Furthermore, in step S3, the acidic solution is HCl, the molar ratio of Al to HCl in the solid propellant is ≤2, and a planetary stirrer is used for stirring for 4 h to 6 h.

[0017] Furthermore, in step S4, the ultrasonic oscillation time is 30 minutes to 60 minutes.

[0018] Furthermore, in step S5, the drying temperature is 60°C, and the preliminary extraction sample is dried until the weight is constant.

[0019] Furthermore, the propellant includes one of a 3,3-bisazidomethyloxytetramethylene and tetrahydrofuran copolyether-based solid propellant or a hydroxyl-terminated polybutadiene-based solid propellant.

[0020] Beneficial effects of the present invention:

[0021] The present invention utilizes the structural characteristics of the propellant, namely, the propellant matrix structure is a polymer network formed by the reaction of a hydroxyl-terminated adhesive macromolecular prepolymer and a curing agent, and ammonium perchlorate is used as a filler. The polymer matrix of the propellant interacts with the surface of the ammonium perchlorate through physical polar adsorption. The propellant is first subjected to high and low temperature cycling treatment. The polymer matrix has a larger thermal expansion coefficient than the filler, and the volume change of the matrix caused by temperature change is also much greater than that of the filler. During the high and low temperature cycling treatment, the matrix and filler undergo inconsistent volume changes due to repeated thermal expansion and contraction, which can effectively destroy the interfacial bonding between the filler and the matrix caused by physical adsorption. Then, an organic reagent is used to fully swell the matrix, making the polymer cross-linked network of the matrix sparse and fragile. An organic base is used to degrade the carbamate curing point structure in the matrix, thereby effectively disintegrating the matrix network and preliminarily separating the matrix from the filler. An acidic solution is added and stirred to remove Al in the filler. Then, ultrasonic vibration is performed to further remove the ammonium perchlorate filler particles from the polymer network of the matrix to obtain a preliminary extract of ammonium perchlorate. Finally, centrifugal separation and purification are performed to obtain pure ammonium perchlorate.

[0022] The invention provides a solid propellant ammonium perchlorate particle extraction process, which adopts physical processes such as high-low temperature cycle treatment, organic reagent swelling of the matrix, stirring and shaking peeling, and centrifugal separation. During the process, the ammonium perchlorate does not need to undergo a dissolution-crystallization precipitation process, thereby avoiding physical and chemical changes of the ammonium perchlorate filler in the overall process. The ammonium perchlorate is extracted from the propellant while maintaining the inherent state (particle size, specific surface area, and crystal structure) of the ammonium perchlorate filler in the propellant as much as possible. The extracted ammonium perchlorate has the same properties as the actual ammonium perchlorate in the propellant, thus achieving in-situ characterization of the properties of the ammonium perchlorate in the propellant and meeting the requirements for in-situ testing of filler properties in propellant aging performance research. The invention is suitable for use as a raw material acquisition method for studying changes in the properties of ammonium perchlorate fillers during propellant aging, and is also suitable for use in the recovery of raw materials from discarded composite solid propellants. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Attachment Figure 1 FIG1 is a process flow chart for extracting ammonium perchlorate from solid propellant according to one embodiment of the present invention;

[0024] Attachment Figure 2 This is the particle size distribution curve of ammonium perchlorate in the propellant raw material of Example 1 of the present invention;

[0025] Attachment Figure 3 This is the particle size distribution curve of ammonium perchlorate extracted in Example 1 of the present invention;

[0026] Attachment Figure 4 The XRD spectrum of ammonium perchlorate extracted from Example 1 of the present invention is

[0027] Attachment Figure 5This is the particle size distribution curve of ammonium perchlorate in the propellant raw material of Example 2 of the present invention;

[0028] Attachment Figure 6 This is the particle size distribution curve of ammonium perchlorate extracted in Example 2 of the present invention;

[0029] Attachment Figure 7 This is the XRD spectrum of ammonium perchlorate extracted in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0032] As attached Figure 1 As shown, the present invention provides a method for extracting ammonium perchlorate from a solid propellant, comprising the following steps:

[0033] S1. Subject the propellant to high and low temperature cycling treatment. The polymer matrix has a larger thermal expansion coefficient than the filler, and the volume change of the matrix caused by temperature change is also much greater than that of the filler. During the high and low temperature cycling treatment, the repeated thermal expansion and contraction will cause inconsistent volume changes of the matrix and filler, which can effectively destroy the bonding effect between the filler and the matrix caused by physical adsorption;

[0034] S2. Chopping the propellant treated in step S1 into small pieces and soaking it in a mixed solution of an organic reagent and an organic base; the organic reagent causes the matrix to fully swell, increasing the sample volume by 20 to 30 times or more, making the polymer cross-linked network of the matrix sparse and fragile, and the organic base degrades the carbamate solidification point structure in the matrix, thereby effectively disintegrating the matrix network and preliminarily separating the matrix from the filler;

[0035] S3, adding an acidic solution to the propellant treated in step S2, and stirring and crushing it. The propellant filler contains Al, and this step removes Al in the reaction system;

[0036] S4, ultrasonically vibrating the propellant treated in step S3 to obtain a preliminary extraction sample by precipitation, and further removing the ammonium perchlorate filler particles from the polymer network of the matrix to obtain a preliminary extraction sample of ammonium perchlorate;

[0037] S5. Centrifuge the preliminary extraction sample obtained in step S4 to remove impurities in the preliminary extraction sample, further purify it, and dry it to obtain pure ammonium perchlorate.

[0038] The embodiments of the present invention utilize the structural characteristics of the propellant, namely, the propellant matrix structure is a polymer network formed by the reaction of a hydroxyl-terminated adhesive macromolecular prepolymer and a curing agent, which interacts with the surface of ammonium perchlorate through physical polar adsorption. By adopting physical processes such as high and low temperature cycling, organic reagent swelling of the matrix, stirring and shaking exfoliation, and centrifugal separation, the ammonium perchlorate does not need to undergo a dissolution-crystallization process during the process, thereby avoiding physical and chemical changes in the ammonium perchlorate filler during the overall process. While maintaining the inherent state of the ammonium perchlorate filler in the propellant as much as possible (particle size, specific surface area, crystal structure), the ammonium perchlorate is extracted from the propellant. The extracted ammonium perchlorate has the same properties as the actual ammonium perchlorate in the propellant, achieving in situ characterization of the properties of ammonium perchlorate in the propellant and meeting the requirements for in situ testing of filler properties in propellant aging performance studies. The present invention is suitable for use as a raw material acquisition method for studying changes in the properties of ammonium perchlorate fillers during propellant aging, and is also suitable for use in the recovery of raw materials from discarded composite solid propellants.

[0039] Among them, in step S1, the number of cycles of high and low temperature cycle treatment is 4 to 6 times, and the storage time is not less than 20 minutes per time, so that the overall temperature of the sample reaches a predetermined value to ensure the effect, and the different volume expansion rates of the matrix and filler at high and low temperature differences are used to preliminarily destroy the bonding effect at the interface between the polymer matrix and the filler.

[0040] Among them, in step S1, the high and low temperature cycle treatment is specifically to cyclically store the propellant in an ultra-low temperature test box and a high temperature oven. The ultra-low temperature test box is set to a low temperature below -50°C, and the high temperature oven is set to a high temperature of 60°C to 70°C. The low temperature condition should be as low as possible below or close to the glass transition temperature of the propellant, and the high and low temperature difference should be as large as possible, but not higher than 70°C, so as to avoid the danger of overheating and decomposition of the propellant.

[0041] In step S2, the organic reagent has a solubility parameter similar to that of the propellant matrix but is insoluble in ammonium perchlorate.

[0042] Among them, in step S2, the organic reagent includes one of toluene, acetonitrile, tetrahydrofuran or chloroform. The specific selection needs to be determined according to the material of the propellant matrix. If the matrix is ​​HTPB, toluene is selected; if the matrix is ​​NEPE, acetonitrile is selected; if the matrix is ​​PBT, tetrahydrofuran or chloroform is selected.

[0043] Wherein, in step S2, at room temperature, the propellant is immersed in the mixed solution for more than 24 hours to ensure that the matrix is ​​fully swollen, which is conducive to the separation of the matrix and the filler.

[0044] In step S3, the acidic solution is HCl, wherein the molar ratio of HCl to Al in the solid propellant is ≥2, and a planetary stirrer is used for stirring for 4 h to 6 h to completely remove Al in the reaction system.

[0045] In step S4, the ultrasonic oscillation time is 30 minutes to 60 minutes, so that the ammonium perchlorate particles are completely removed from the polymer matrix, which is beneficial to improving the extraction rate of ammonium perchlorate and obtaining more ammonium perchlorate samples for aging research.

[0046] Wherein, in step S5, the drying temperature is 60° C., and the preliminary extraction sample is dried until the weight is constant.

[0047] Propellants applicable to the embodiments of the present invention include 3,3-bis-azidomethyloxytetramethylene and tetrahydrofuran copolyether (PBT)-based solid propellants and hydroxyl-terminated polybutadiene (HTPB)-based solid propellants.

[0048] Example 1

[0049] This embodiment provides a method for extracting ammonium perchlorate particles from a solid propellant, wherein the selected solid propellant is a PBT composite solid propellant, and its mass percentage is shown in Table 1.

[0050] Table 1 Mass percentage of solid propellant in Example 1

[0051] Components PBT matrix ammonium perchlorate Al Mass percentage 23 60 17

[0052] The extraction method of the present embodiment comprises the following steps:

[0053] (1) Weigh 100 g of PBT propellant billet and vacuum seal it in a polytetrafluoroethylene packaging bag. Then, place it in an ultra-low temperature test chamber (-50°C) and a high temperature oven (70°C) for four cycles of storage.

[0054] (2) The PBT propellant was taken out and cut into small pieces with a size of less than 2 mm × 2 mm × 2 mm, and then poured into a spherical glass flask. Tetrahydrofuran and an organic base were added to the glass flask and soaked for 24 hours to allow the matrix to fully swell and destroy the cross-linked network structure;

[0055] (3) Add HCl to a glass flask and stir with a planetary stirrer for 4 hours to break up the swollen propellant and allow the Al filler in the propellant to fully react with HCl;

[0056] (4) ultrasonically vibrating the reacted sample for 30 min to completely release the ammonium perchlorate particles from the polymer matrix and precipitate to obtain a preliminary ammonium perchlorate extraction sample;

[0057] (5) After removing impurities in the preliminarily extracted ammonium perchlorate by centrifugal separation, the ammonium perchlorate is dried in a vacuum oven to obtain pure ammonium perchlorate.

[0058] As attached Figure 2 -Attached Figure 4 As shown in the accompanying graph, the particle size distribution of ammonium perchlorate extracted in Example 1 is basically consistent with that of ammonium perchlorate in the propellant raw material, indicating that the particle structure of ammonium perchlorate is well maintained. Figure 4 As shown in the figure, the main diffraction peaks are all attributed to ammonium perchlorate, indicating that there are very few impurities in the extracted ammonium perchlorate, and there is basically no attached polymer matrix or Al.

[0059] As shown in Table 2, the volume average particle size D of the extracted ammonium perchlorate and the raw material ammonium perchlorate is 43 The relative difference is 1.43%, and the median particle size D 50 The relative difference is 1.46%, which is within 5%, further indicating that the ammonium perchlorate obtained by extraction can represent the actual state of ammonium perchlorate in the propellant.

[0060] Table 2 Example 1 raw material ammonium perchlorate and ammonium perchlorate particle size test data obtained by extraction

[0061] <![CDATA[D 10 / μm]]> <![CDATA[D 43 / μm]]> <![CDATA[D 50 / μm]]> <![CDATA[D 75 / μm]]> <![CDATA[D 90 / μm]]> Raw material ammonium perchlorate 147.9 307.0 293.7 391.7 498.1 Extraction of ammonium perchlorate 140.8 302.6 289.4 387.2 494.3

[0062] Example 2

[0063] This embodiment provides a method for extracting ammonium perchlorate particles from a solid propellant, wherein the solid propellant selected is an HPBT composite solid propellant, and its mass percentage is shown in Table 3.

[0064] Table 3 Mass percentage of solid propellant in Example 2

[0065] Components HPBT matrix ammonium perchlorate Al Mass percentage 23 60 17

[0066] The extraction method of the present embodiment comprises the following steps:

[0067] (1) Weigh 100 g of HTPB propellant billet and vacuum seal it in a polytetrafluoroethylene packaging bag. Then, place it in an ultra-low temperature test chamber (-50°C) and a high temperature oven (70°C) for four cycles of storage.

[0068] (2) The HTPB propellant was taken out and cut into small pieces with a size of less than 2 mm × 2 mm × 2 mm. The pieces were then poured into a spherical glass flask. Toluene and an organic base were added to the glass flask and the mixture was soaked for 24 hours to allow the matrix to fully swell and destroy the cross-linked network structure.

[0069] (3) Add HCl to a glass flask and stir with a planetary stirrer for 4 hours to break up the swollen propellant and allow the Al filler in the propellant to fully react with HCl;

[0070] (4) ultrasonically vibrating the reacted sample for 30 min to completely release the ammonium perchlorate particles from the polymer matrix and precipitate to obtain a preliminary ammonium perchlorate extraction sample;

[0071] (5) After removing impurities in the preliminarily extracted ammonium perchlorate by centrifugal separation, the ammonium perchlorate is dried in a vacuum oven to obtain pure ammonium perchlorate.

[0072] As attached Figure 5 -Attached Figure 7 As shown in the accompanying graph, the particle size distribution of the ammonium perchlorate obtained by extraction in Example 2 is basically consistent with that of the ammonium perchlorate in the propellant raw material, indicating that the ammonium perchlorate particle structure is well maintained. Figure 7 As shown, the main diffraction peaks are all attributed to ammonium perchlorate, indicating that there are very few impurities in the extracted ammonium perchlorate, and there is basically no attached polymer matrix or Al.

[0073] As shown in Table 4, the volume average particle size D of the extracted ammonium perchlorate and the raw material ammonium perchlorate 43 The relative difference is 2.72%, and the median particle size D 50 The relative difference is 3.48%, which is within 5%, further indicating that the ammonium perchlorate obtained by extraction can represent the actual state of ammonium perchlorate in the propellant.

[0074] Table 4 Example 2 Raw material ammonium perchlorate and ammonium perchlorate particle size test data obtained by extraction

[0075] <![CDATA[D 10 / μm]]> <![CDATA[D 43 / μm]]> <![CDATA[D 50 / μm]]> <![CDATA[D 75 / μm]]> <![CDATA[D 90 / μm]]> Raw material ammonium perchlorate 102.9 282.8 272.9 372.1 478.1 Extraction of ammonium perchlorate 98.97 290.5 282.4 381.9 489.5

[0076] Comparative Example 1

[0077] This comparative example provides a method for extracting ammonium perchlorate particles from a solid propellant, wherein the solid propellant selected is an HPBT composite solid propellant, and the formulation is consistent with that in Example 2, the only difference being that the processing time of steps 2 and 3 is shortened.

[0078] The extraction method of the present embodiment comprises the following steps:

[0079] (1) Weigh 100 g of HTPB propellant billet and vacuum seal it in a polytetrafluoroethylene packaging bag. Then, place it in an ultra-low temperature test chamber (-50°C) and a high temperature oven (70°C) for four cycles of storage.

[0080] (2) The HTPB propellant was taken out and cut into small pieces with a size of less than 2 mm × 2 mm × 2 mm. The pieces were then poured into a spherical glass flask. Toluene and an organic base were added to the glass flask and the mixture was soaked for 18 hours to allow the matrix to fully swell and destroy the cross-linked network structure.

[0081] (3) Add HCl to a glass flask and stir with a planetary stirrer for 2 hours to break up the swollen propellant and allow the Al filler in the propellant to fully react with HCl;

[0082] (4) ultrasonically vibrating the reacted sample for 30 min to completely release the ammonium perchlorate particles from the polymer matrix and precipitate to obtain a preliminary ammonium perchlorate extraction sample;

[0083] (5) After removing impurities in the initially extracted ammonium perchlorate by centrifugal separation, the ammonium perchlorate extraction sample is dried in a vacuum oven to obtain an ammonium perchlorate extraction sample.

[0084] Compared to Example 2, this comparative example shortened the processing time for steps 2 and 3. The resulting ammonium perchlorate-extracted sample was noticeably darker and sticky, indicating that a small amount of Al and matrix impurities remained in the sample, failing to achieve the desired extraction goal. The reaction time during the matrix and Al removal steps should meet the requirements to ensure effective ammonium perchlorate extraction.

[0085] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

[0087] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A method for extracting ammonium perchlorate from a solid propellant, characterized in that: The following steps are involved: S1. Perform high and low temperature cycle treatment on the propellant; S2, chopping the propellant treated in step S1 and soaking it in a mixed solution of an organic reagent and an organic base; At room temperature, the propellant is immersed in the mixed solution for more than 24 hours; S3, adding an acidic solution to the propellant treated in step S2, and stirring and crushing the propellant; The acidic solution is HCl, the molar ratio of Al to HCl in the solid propellant is ≤2, and a planetary stirrer is used for stirring for 4 h to 6 h; S4, subjecting the propellant treated in step S3 to ultrasonic vibration and precipitation to obtain a preliminary extraction sample; S5. Centrifuge the preliminary extraction sample obtained in step S4 and dry it to obtain ammonium perchlorate.

2. The method for extracting ammonium perchlorate from a solid propellant as claimed in claim 1, wherein: In step S1, the low temperature of the high and low temperature cycle treatment is below -50°C, the high temperature is above 60°C, and the number of cycles is 4.

3. The method for extracting ammonium perchlorate from a solid propellant according to claim 1 or 2, wherein: In step S1, the high-low temperature cycle treatment is specifically to cyclically store the propellant between an ultra-low temperature test chamber and a high-temperature oven.

4. The method for extracting ammonium perchlorate from a solid propellant as claimed in claim 1, wherein: In step S2, the organic agent has a solubility parameter similar to that of the propellant matrix but is incompatible with ammonium perchlorate.

5. The method for extracting ammonium perchlorate from a solid propellant as claimed in claim 4, wherein: In step S2, the organic reagent includes one of toluene, acetonitrile or tetrahydrofuran.

6. The method for extracting ammonium perchlorate from a solid propellant as claimed in claim 1, wherein: In step S4, the ultrasonic oscillation time is 30 minutes to 60 minutes.

7. The method for extracting ammonium perchlorate from a solid propellant as claimed in claim 1, wherein: In step S5, the drying temperature is 60° C., and the sample is dried until the initial extraction reaches a constant weight.

8. The method for extracting ammonium perchlorate from a solid propellant as claimed in claim 1, wherein: The propellant comprises one of a 3,3-bis-azidomethyloxybutylene and tetrahydrofuran copolyether-based solid propellant and a hydroxyl-terminated polybutadiene-based solid propellant.

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