Composite oxalate modified pentaamino tetrazole gas generating agent and preparation method thereof

Abstract

The invention provides a composite oxalate modified pentaamino tetrazole gas generating agent and a preparation method thereof.The gas generating agent comprises a solid gas generating agent and a composite oxalate coolant, and the composite oxalate coolant comprises an oxalate compound A and an oxalate compound B, wherein the mass ratio of strontium oxalate in the composite oxalate coolant is 30%-40%. The composite oxalate modified pentaaminotetrazole gas generating agent is beneficial to slagging of the gas generating agent, the combustion temperature is obviously reduced, and the combustion performance is obviously improved.

Description

Technical Field

[0001] The invention belongs to the field of low combustion temperature gas generating agents and preparation thereof, and in particular relates to a composite oxalate modified pentaaminotetrazolyl type gas generating agent and a preparation method thereof. Background Art

[0002] Gas generating agent is mainly composed of oxidant and high-energy fuel. It can continuously burn in the absence of external oxidant and quickly produce a large amount of gas. Based on this characteristic, gas generating agent can be used as the main energy source and installed in solid rocket engine with a certain filling structure. It is widely used in military fields such as rockets and missiles, as well as civilian fields such as automobile airbags. In recent years, due to the continuous increase in accidents caused by airbags, the development of new gas generating agents with low combustion temperature, green combustion products and stable combustion performance is the main development trend in the future. In order to reduce the combustion temperature of gas generating agent, a certain amount of coolant is usually added to the gas generating agent formula to achieve the purpose of appropriately reducing the combustion temperature of gas generating agent. 5-aminotetrazole (CH3N5, abbreviated as 5AT) has the advantages of high nitrogen content and large gas production, and has shown great application potential in the field of gas generating agent. However, the traditional solid gas generating agent formula (5AT / Sr(NO3)2) has a high combustion temperature. Therefore, the present invention selects 5AT type gas generating agent as the research object, and reduces its combustion temperature and improves its combustion performance by adding a certain proportion of coolant to the 5AT type gas generating agent. The more common coolants are oxalates, carbonates, quaternary ammonium salts, etc. Among them, oxalates are more ideal performance improvers due to their low price and wide sources. However, the reduction of the combustion temperature of the gas generating agent is often accompanied by a reduction in the burning rate. In order to achieve a better balance between these two performance indicators of the gas generating agent, two oxalic acids are selected, one oxalate is used to reduce the combustion temperature, and the other oxalate (containing the same metal element as the oxidant in the gas generating agent) reduces the reduction of the combustion rate of the gas generating agent while reducing the combustion temperature. The composite oxalate prepared based on the two oxalates can be used as a coolant to achieve controllable combustion of the gas generating agent to a large extent. The existing composite preparation method of coolant and gas generating agent has different defects and is not suitable for the composite preparation of 5AT type gas generating agent. For example, the solvent-nonsolvent method has the problems of complex operation and low yield; the freeze-drying method has high requirements for equipment performance; the sol-gel method takes a long time; the most commonly used mechanical ball milling method has the advantages of simple operation and high yield, and many scholars have conducted 5AT-related research based on this method. Mechanical ball milling is divided into wet ball milling and dry ball milling. Since 5AT is easily soluble in water and alcohol, if a simple wet ball milling is used, the selection of solvents is required to be high, and a single dry ball milling is prone to agglomeration. Summary of the invention

[0003] In view of this, the present invention aims to overcome the defects in the prior art and proposes a composite oxalate-modified pentaaminotetrazole gas generating agent and a preparation method thereof.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0005] In a first aspect, the present invention provides a composite oxalate-modified pentaaminotetrazole gas generator, comprising a solid gas generator and a composite oxalate coolant, wherein the composite oxalate coolant comprises an oxalate compound A and an oxalate compound B, wherein the mass proportion of strontium oxalate in the composite oxalate coolant is 30%-40%.

[0006] Preferably, the oxalate compound A is strontium oxalate, and the oxalate compound B is one or a mixture of two or more of copper oxalate, ammonium oxalate, magnesium oxalate, calcium oxalate and cobalt oxalate.

[0007] Preferably, the added amount of the composite oxalate coolant is 1% to 5% of the total mass of the solid gas generating agent and the composite oxalate coolant.

[0008] Preferably, the solid gas generating agent is a mixture of 5-aminotetrazole and strontium nitrate.

[0009] Preferably, the 5-aminotetrazole and strontium nitrate are mixed in a ratio according to zero oxygen balance.

[0010] In a second aspect, the present invention also provides a method for preparing the composite oxalate-modified pentaaminotetrazole gas generating agent, comprising the following steps:

[0011] S1: the solid gas generating agent and the composite oxalate coolant are sieved and then wet ball milled;

[0012] S2: After the wet ball milling is completed, the ball milled product is taken out and placed in a vacuum oven for drying;

[0013] S3: dry ball milling the dried sample. After the dry ball milling is completed, the ball milling product is taken out, which is the composite oxalate-modified pentaaminotetrazole gas generating agent.

[0014] Preferably, a sieve with a mesh size of 80 to 120 is used in step S1.

[0015] Preferably, the solvent in the wet ball milling in step S2 is ethanol, ethyl acetate, or a mixture of the two. The solvent should be selected so that 5AT can be completely dissolved and other components are not dissolved.

[0016] Preferably, the rotation speed of the wet ball milling in step S2 is 250-350 r / min, and the ball milling time is 4-6 h.

[0017] Preferably, the drying temperature in step S2 is 35-50° C., and the drying time is 6-8 hours.

[0018] Preferably, the rotation speed of the dry ball milling in step S3 is 250-350 r / min, and the ball milling time is 4-6 h.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The gas generator of the present invention uses a composite oxalate prepared from two oxalates as a coolant for the 5AT type gas generator, wherein the oxalate compound A is an oxalate containing the same metal element as the oxidant in the gas generator (since the oxidant of the present invention is Sr(NO3)2, SrC2O4 is selected as one of the oxalates), which can reduce the combustion temperature while reducing the reduction in the combustion rate of the gas generator, and the oxalate compound B mainly plays a role in reducing the combustion temperature. Compared with the unmodified 5AT type gas generator, the combustion temperature is significantly reduced.

[0021] (2) The combustion residue of the gas generating agent of the present invention has a denser microstructure than that of the unmodified 5AT type gas generating agent, which indicates that the gas generating agent of the present invention is conducive to the slagging of the gas generating agent.

[0022] (3) The activation energy of the gas generating agent of the present invention is greater than that of the unmodified 5AT type gas generating agent, indicating that the pyrolysis stability is improved.

[0023] (4) The gas generating agent of the present invention has a combustion residue with a smaller particle size than the unmodified 5AT type gas generating agent.

[0024] (5) The preparation method of the gas generating agent of the present invention adopts the method of wet ball milling followed by dry ball milling, which solves the defects of difficult selection of solvent for single wet ball milling and easy agglomeration for single dry ball milling.

[0025] (6) The preparation method of the gas generating agent of the present invention adds a screening step before ball milling, so that the composite effect of multiple raw materials is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The SEM images of the combustion residues of the samples obtained in Example 1 and Comparative Example 1;

[0027] Figure 2 The laser particle size analyzer test diagram of the samples prepared in Example 1 and Comparative Example 1;

[0028] Figure 3 The thermocouple matrix temperature measurement curves of the samples prepared in Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0029] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0030] The present invention is described in detail below in conjunction with embodiments.

[0031] Example 1

[0032] In this embodiment, (5AT / Sr(NO3)2) is selected as the gas generating agent raw material, and composite oxalate is used as the coolant to prepare a gas generating agent with a lower combustion temperature, so as to achieve the purpose of modifying the gas generating agent. Then, the combustion performance test of the modified gas generating agent sample is carried out. The activation energy is calculated based on the TG-DSC test data, and the flame morphology and flame temperature partition of the gas generating agent sample are obtained based on the thermocouple matrix data combined with the high-speed camera data. Based on the laser particle size analyzer test and the scanning electron microscope (SEM) test data, the condensed phase combustion products and combustion efficiency of the gas generating agent are inferred. The specific steps are as follows:

[0033] 1) Weigh strontium nitrate and 5AT in a mass ratio of 36.48:63.52 for later use;

[0034] 2) Weigh 5% of the coolant (SrC2O4:CuC2O4=30%:70%), and sieve the coolant, strontium nitrate and 5AT to make the sample particle size within the range of 100-120 mesh;

[0035] 3) Add the sieved sample into a ball mill and add ethanol for wet ball milling;

[0036] 4) Turn on the ball mill, set the speed to 250r / min, and the ball milling time to 6h;

[0037] 5) After the wet ball milling is completed, take out the ball milled product and put it into a vacuum oven with the oven temperature set to 50°C and the drying time set to 8 hours;

[0038] 6) Place the dried sample in the ball mill again for dry ball milling;

[0039] 7) Turn on the ball mill, set the speed to 350r / min, and the ball milling time to 6h;

[0040] 8) After the dry ball milling is completed, the ball milling product, i.e., the composite oxalate-modified pentaaminotetrazole gas generating agent (sample 1), is taken out and stored for later use.

[0041] Example 2

[0042] The specific steps of the preparation method of the composite oxalate modified pentaaminotetrazole gas generating agent of this embodiment are as follows:

[0043] 1) Weigh strontium nitrate and 5AT in a mass ratio of 36.48:63.52 for later use;

[0044] 2) Weigh 1% of coolant (SrC2O4: (NH4)2C2O4 = 40%: 60%), sieve the coolant, strontium nitrate and 5AT to make the sample particle size within the range of 100-120 mesh;

[0045] 3) adding the sieved sample into a ball mill, adding ethyl acetate, and performing wet ball milling;

[0046] 4) Turn on the ball mill, set the speed to 350r / min, and the ball milling time to 6h;

[0047] 5) After the wet ball milling is completed, take out the ball milled product and put it into a vacuum oven with the oven temperature set to 50°C and the drying time set to 8 hours;

[0048] 6) Place the dried sample in the ball mill again for dry ball milling;

[0049] 7) Turn on the ball mill, set the speed to 250r / min, and the ball milling time to 6h;

[0050] 8) After the dry ball milling is completed, the ball milling product, i.e., the composite oxalate-modified pentaaminotetrazole gas generating agent (sample 2), is taken out and stored for later use.

[0051] Example 3

[0052] The specific steps of the preparation method of the composite oxalate modified pentaaminotetrazole gas generating agent of this embodiment are as follows:

[0053] 1) Weigh strontium nitrate and 5AT in a mass ratio of 36.48:63.52 for later use;

[0054] 2) Weigh 3% of coolant (SrC2O4:MgC2O4=35%:65%), sieve the coolant, strontium nitrate and 5AT to make the sample particle size within the range of 100-120 mesh;

[0055] 3) Add the sieved sample into a ball mill and add ethanol for wet ball milling;

[0056] 4) Turn on the ball mill, set the speed to 350r / min, and the ball milling time to 6h;

[0057] 5) After the wet ball milling is completed, take out the ball milled product and put it into a vacuum oven with the oven temperature set to 50°C and the drying time set to 8 hours;

[0058] 6) Place the dried sample in the ball mill again for dry ball milling;

[0059] 7) Turn on the ball mill, set the speed to 250r / min, and the ball milling time to 6h;

[0060] 8) After the dry ball milling is completed, the ball milling product, i.e., the composite oxalate-modified pentaaminotetrazole gas generating agent (sample 3), is taken out and stored for later use.

[0061] Example 4

[0062] The specific steps of the preparation method of the composite oxalate modified pentaaminotetrazole gas generating agent of this embodiment are as follows:

[0063] 1) Weigh strontium nitrate and 5AT in a mass ratio of 36.48:63.52 for later use;

[0064] 2) Weigh 3% of coolant (SrC2O4:CaC2O4=40%:60%), and sieve the coolant, strontium nitrate and 5AT to make the sample particle size within the range of 100-120 mesh;

[0065] 3) Add the sieved sample into a ball mill and add ethanol for wet ball milling;

[0066] 4) Turn on the ball mill, set the speed to 350r / min, and the ball milling time to 6h;

[0067] 5) After the wet ball milling is completed, take out the ball milled product and put it into a vacuum oven with the oven temperature set to 50°C and the drying time set to 8 hours;

[0068] 6) Place the dried sample in the ball mill again for dry ball milling;

[0069] 7) Turn on the ball mill, set the speed to 250r / min, and the ball milling time to 6h;

[0070] 8) After the dry ball milling is completed, the ball milling product, i.e., the composite oxalate-modified pentaaminotetrazole gas generating agent (sample 4), is taken out and stored for later use.

[0071] Example 5

[0072] The specific steps of the preparation method of the composite oxalate modified pentaaminotetrazole gas generating agent of this embodiment are as follows:

[0073] 1) Weigh strontium nitrate and 5AT in a mass ratio of 36.48:63.52 for later use;

[0074] 2) Weigh 3% of coolant (SrC2O4: CoC2O4 = 40%: 60%), and sieve the coolant, strontium nitrate and 5AT to make the sample particle size within the range of 100-120 mesh;

[0075] 3) Add the sieved sample into a ball mill and add ethanol for wet ball milling;

[0076] 4) Turn on the ball mill, set the speed to 350r / min, and the ball milling time to 6h;

[0077] 5) After the wet ball milling is completed, take out the ball milled product and put it into a vacuum oven with the oven temperature set to 50°C and the drying time set to 8 hours;

[0078] 6) Place the dried sample in the ball mill again for dry ball milling;

[0079] 7) Turn on the ball mill, set the speed to 250r / min, and the ball milling time to 6h;

[0080] 8) After the dry ball milling is completed, the ball milling product, i.e., the composite oxalate-modified pentaaminotetrazole gas generating agent (sample 5), is taken out and stored for later use.

[0081] Comparative Example 1

[0082] The preparation method of the gas generating agent in this comparative example omits step 2), and the remaining steps are exactly the same as those in Example 1. The prepared gas generating agent is sample 6.

[0083] Comparative Example 2

[0084] In the preparation method of the gas generating agent in this comparative example, the coolant is only SrC2O4, and the remaining steps are exactly the same as those in Example 1. The prepared gas generating agent is sample 7.

[0085] Comparative Example 3

[0086] In the preparation method of the gas generating agent of this comparative example, the coolant SrC2O4:CuC2O4=20%:80%, and the remaining steps are exactly the same as those in Example 1. The prepared gas generating agent is sample 8.

[0087] Comparative Example 4

[0088] In the preparation method of the gas generating agent of this comparative example, the coolant SrC2O4:CuC2O4=50%:50%, and the remaining steps are exactly the same as those in Example 1. The prepared gas generating agent is sample 9.

[0089] Comparative Example 5

[0090] In the preparation method of the gas generating agent in this comparative example, the amount of coolant added is 6%, and the remaining steps are exactly the same as those in Example 1. The prepared gas generating agent is sample 10.

[0091] Test example: Combustion performance test

[0092] The combustion performance test was conducted on samples 1 to 10. The specific test steps are as follows:

[0093] 1) TG-DSC test: For each test, 1-2 mg of sample was placed on an open alumina crucible and the temperature was (β = 5, 10, 15, 20 °C min -1 ) Four heating rates, the test temperature range is 100-800℃, and the test gas atmosphere is nitrogen.

[0094] 2) Based on the TG-DSC test data, the activation energy was calculated using the Kissinger-Akahira-Sunose (KAS) and other conversion rate methods to compare and analyze the thermal decomposition behavior and performance of the gas generating agent.

[0095] 3) Using spark ignition, the combustion temperature of the gas generator and the flame temperature zones were obtained based on the thermocouple matrix, and the effect of the coolant on the flame temperature of the gas generator was compared.

[0096] 4) The obtained combustion residue was subjected to SEM test to observe the microscopic morphology of the combustion products.

[0097] 5) The obtained combustion residue is tested by a laser particle size analyzer to observe the combustion residue of the gas generating agent. The SEM image of the combustion residue is as follows: Figure 1 As shown, the particle size distribution of the combustion residue is Figure 2 As shown, the thermocouple matrix temperature measurement curve is as follows Figure 3 The specific experimental results are shown in Table 1:

[0098] Table 1 Performance comparison of samples 1 to 10

[0099]

[0100] Comparing the sample without coolant (sample 6) with other samples with coolant, it can be seen that the maximum combustion temperature of sample 6 is the highest among all samples, indicating that the addition of coolant can effectively reduce the combustion temperature of the gas generator. Comparing sample 7 (single oxalate) with other samples with composite oxalate added, it can be seen that the maximum combustion temperature of sample 7 is significantly higher, indicating that composite oxalate has a better cooling effect than single oxalate. Further analysis found that among the samples with composite oxalate added, the maximum combustion temperature of the samples with a mass proportion of strontium oxalate of 30%-40% (samples 1-sample 5) was lower than that of other samples, indicating that 30%-40% is a better addition ratio.

[0101] It is worth mentioning that the maximum combustion temperature of sample 10 (coolant content is 6%) is the lowest among all samples, indicating that the content of coolant has a very important influence on the cooling effect. However, the reduction of combustion temperature must be accompanied by a reduction in combustion speed. The average combustion speed of sample 10 is significantly lower than that of other samples. Too low combustion speed will directly lead to insufficient power of the gas generator and its inability to play its due function. Therefore, the amount of coolant added needs to be between 1% and 5%. In addition, the reduction of the maximum combustion temperature is often accompanied by an increase in activation energy and a decrease in combustion residue (D50).

[0102] The above description shows that the composite oxalate-modified pentaaminotetrazolyl gas generating agent and the preparation method of the present invention have good effects. The coolant and the gas generating agent can be compounded by the method, and the compounding effect is good. After the gas generating agent is modified, its combustion temperature is significantly reduced and the combustion performance is significantly improved. The present invention can provide reference and suggestions for the preparation of new low combustion temperature gas generating agents and the combustion performance testing of gas generating agents.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite oxalate-modified pentaaminotetrazolyl gas generating agent, characterized in that: It comprises a solid gas generating agent and a composite oxalate coolant, wherein the composite oxalate coolant comprises an oxalate compound A and an oxalate compound B, wherein the mass proportion of strontium oxalate in the composite oxalate coolant is 30%-40%.

2. The composite oxalate-modified pentaaminotetrazolyl gas generating agent according to claim 1, characterized in that: The oxalate compound A is strontium oxalate, and the oxalate compound B is one or a mixture of two or more of copper oxalate, ammonium oxalate, magnesium oxalate, calcium oxalate and cobalt oxalate.

3. The composite oxalate-modified pentaaminotetrazolyl gas generating agent according to claim 1, characterized in that: The added amount of the composite oxalate coolant is 1% to 5% of the total mass of the solid gas generating agent and the composite oxalate coolant.

4. The composite oxalate-modified pentaaminotetrazolyl gas generating agent according to claim 1, characterized in that: The solid gas generating agent is a mixture of 5-aminotetrazole and strontium nitrate, wherein the 5-aminotetrazole and strontium nitrate are mixed in a ratio according to zero oxygen balance.

5. The method for preparing the composite oxalate-modified pentaaminotetrazolyl gas generating agent according to any one of claims 1 to 4, characterized in that: The steps include: S1: the solid gas generating agent and the composite oxalate coolant are sieved and then wet ball milled; S2: After the wet ball milling is completed, the ball milled product is taken out and placed in a vacuum oven for drying; S3: dry ball milling the dried sample. After the dry ball milling is completed, the ball milling product is taken out, which is the composite oxalate-modified pentaaminotetrazole gas generating agent.

6. The method for preparing the composite oxalate-modified pentaaminotetrazolyl gas generating agent according to claim 5, characterized in that: In the step S1, a sieve of 80 to 120 meshes is used.

7. The method for preparing the composite oxalate-modified pentaaminotetrazolyl gas generating agent according to claim 5, characterized in that: The solvent used in the wet ball milling in step S2 is ethanol, ethyl acetate or a mixture of the two.

8. The method for preparing the composite oxalate-modified pentaaminotetrazolyl gas generating agent according to claim 5, characterized in that: The rotation speed of the wet ball milling in step S2 is 250-350 r / min, and the ball milling time is 4-6 h.

9. The method for preparing the composite oxalate-modified pentaaminotetrazolyl gas generating agent according to claim 5, characterized in that: The drying temperature in step S2 is 35-50° C., and the drying time is 6-8 hours.

10. The method for preparing the composite oxalate-modified pentaaminotetrazolyl gas generating agent according to claim 5, characterized in that: In step S3, the rotation speed of the dry ball milling is 250-350 r / min, and the ball milling time is 4-6 h.

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