A composite oxalate-modified pentaaminotetrazole gas generating agent and preparation method thereof

Abstract

The present invention provides a composite oxalate-modified pentaaminotetrazole gas generator and a preparation method thereof. The gas generator comprises a solid gas generator and a composite oxalate coolant. The composite oxalate coolant comprises oxalate compound A and oxalate compound B, wherein the mass fraction of strontium oxalate in the composite oxalate coolant is 30% to 40%. The composite oxalate-modified pentaaminotetrazole gas generator facilitates slagging, significantly reduces combustion temperature, and significantly improves combustion performance.

Description

Technical Field

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

[0002] Gas generators are primarily composed of an oxidizer and a high-energy fuel. They can continuously burn in the absence of an external oxidizer, rapidly producing large quantities of gas. Due to these properties, gas generators can serve as a primary energy source and, when incorporated into solid rocket engines with specific loading structures, are widely used in military applications such as rockets and missiles, as well as in civilian applications such as automotive airbags. In recent years, due to the increasing number of airbag-related accidents, the development of new gas generators with low combustion temperatures, green combustion products, and stable combustion performance has become a major trend. To lower the combustion temperature of gas generators, a certain amount of coolant is often added to the formulation to achieve this goal. 5-Aminotetrazole (CH3N5, abbreviated 5AT), with its high nitrogen content and high gas production, has shown great potential for application in the gas generator field. However, the traditional solid gas generating agent formula (5AT / Sr(NO3)2) has a relatively high combustion temperature. Therefore, the present invention selects 5AT type gas generating agents 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 include oxalates, carbonates, quaternary ammonium salts, etc. Among them, oxalates have become more ideal performance improvers due to their low price and wide availability. However, the reduction in 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 in the burning rate of the gas generating agent while reducing the combustion temperature. The composite oxalate prepared based on the two oxalates can achieve controlled combustion of the gas generating agent to a large extent as a coolant. 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 agents. For example, the solvent-nonsolvent method suffers from complex operation and low yields; freeze-drying requires high equipment performance; and the sol-gel method is time-consuming. The most commonly used mechanical ball milling method offers advantages such as ease of operation and high yield, and many researchers have conducted research on 5AT based on this method. Mechanical ball milling methods are divided into wet and dry ball milling. Because 5AT is easily soluble in water and alcohol, wet ball milling alone requires a high solvent selection, while dry ball milling alone 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 further 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 the 5AT is 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. Oxalate compound A is an oxalate containing the same metal element as the oxidant in the gas generator (since the oxidant in the present invention is Sr(NO3)2, SrC2O4 is selected as one of the oxalates). This can reduce the combustion temperature while also reducing the decrease in the gas generator's burning rate. Oxalate compound B primarily serves to reduce the combustion temperature. Compared to the unmodified 5AT type gas generator, the combustion temperature is significantly lowered.

[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 prepared in Example 1 and Comparative Example 1 are shown;

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

[0028] Figure 3 Graph showing the temperature measurement of the thermocouple matrix of the samples prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

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

[0030] The present invention is described in detail below with reference to the embodiments.

[0031] Example 1

[0032] In this example, (5AT / Sr(NO3)2) was selected as the gas generating agent raw material and composite oxalate was used as the coolant to prepare a gas generating agent with a low combustion temperature, achieving the purpose of gas generating agent modification. Combustion performance tests were then conducted on the modified gas generating agent samples. Activation energy was calculated based on TG-DSC test data, and flame morphology and flame temperature zoning of the gas generating agent samples were determined based on thermocouple matrix data combined with high-speed camera data. Laser particle size analyzer and scanning electron microscopy (SEM) test data were used to infer the gas generating agent's condensed phase combustion products and combustion efficiency. The specific steps are as follows:

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

[0034] 2) Weigh 5% of 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 to a ball mill and add ethanol for wet ball milling;

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

[0037] 5) After wet ball milling is completed, remove the ball-milled product and place it in a vacuum oven at 50°C for 8 hours;

[0038] 6) Place the dried sample back into the ball mill for dry ball milling;

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

[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 and set aside;

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

[0045] 3) Add the sieved sample to a ball mill and add ethyl acetate for wet ball milling;

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

[0047] 5) After wet ball milling is completed, remove the ball-milled product and place it in a vacuum oven at 50°C for 8 hours;

[0048] 6) Place the dried sample back into the ball mill for dry ball milling;

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

[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 and set aside;

[0054] 2) Weigh 3% coolant (SrC2O4:MgC2O4=35%:65%) and 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 to a ball mill and add ethanol for wet ball milling;

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

[0057] 5) After wet ball milling is completed, remove the ball-milled product and place it in a vacuum oven at 50°C for 8 hours;

[0058] 6) Place the dried sample back into the ball mill for dry ball milling;

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

[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 and set aside;

[0064] 2) Weigh 3% 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 to a ball mill and add ethanol for wet ball milling;

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

[0067] 5) After wet ball milling is completed, remove the ball-milled product and place it in a vacuum oven at 50°C for 8 hours;

[0068] 6) Place the dried sample back into the ball mill for dry ball milling;

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

[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 and set aside;

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

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

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

[0077] 5) After wet ball milling is completed, remove the ball-milled product and place it in a vacuum oven at 50°C for 8 hours;

[0078] 6) Place the dried sample back into the ball mill for dry ball milling;

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

[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 is to omit 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 of 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 of 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: 1-2 mg of sample was placed on an open alumina crucible for each test, and the temperature was adjusted to (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) conversion method 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 coolant on the flame temperature of the gas generator was compared.

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

[0097] 5) The obtained combustion residue is tested by 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 as follows 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 the 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 generating agent. Comparing sample 7 (single oxalate) with the other samples with compound oxalate added, it can be seen that the maximum combustion temperature of sample 7 is significantly higher, indicating that compound oxalate has a better cooling effect than single oxalate. Further analysis found that among the samples with compound oxalate added, the maximum combustion temperature of the samples with a mass proportion of strontium oxalate of 30%-40% (samples 1-5) were all lower than that of the other samples, indicating that 30%-40% is a better addition ratio.

[0101] It's worth noting that Sample 10 (with a 6% coolant content) has the lowest maximum combustion temperature of all samples, indicating that coolant content significantly influences the cooling effect. However, a decrease in combustion temperature is inevitably accompanied by a decrease in combustion rate. Sample 10's average combustion rate is significantly lower than that of the other samples. Excessively low combustion rates directly lead to insufficient power for the gas generator, preventing it from performing its intended function. Therefore, the coolant addition level should be between 1% and 5%. Furthermore, a decrease in maximum combustion temperature is often accompanied by an increase in activation energy and a decrease in combustion residue (D50).

[0102] The above demonstrates that the composite oxalate-modified pentaaminotetrazole gas generant and preparation method of the present invention demonstrate excellent results. This method allows for the effective compounding of a coolant and a gas generant. The modified gas generant significantly reduces its combustion temperature and improves its combustion performance. This invention provides valuable insights and recommendations for the preparation of novel low-combustion-temperature gas generants and for testing their combustion performance.

[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 principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A composite oxalate-modified pentaaminotetrazole gas generating agent, characterized in that: The invention 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%; 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.

2. The composite oxalate-modified pentaaminotetrazole 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.

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

4. The method for preparing the composite oxalate-modified pentaaminotetrazole gas generating agent according to any one of claims 1 to 3, 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.

5. The method for preparing the composite oxalate-modified pentaaminotetrazole gas generating agent according to claim 4, characterized in that: In the step S1, a sieve with a mesh size of 80 to 120 is used.

6. The method for preparing the composite oxalate-modified pentaaminotetrazole gas generating agent according to claim 4, characterized in that: The solvent used in the wet ball milling in step S2 is ethanol, ethyl acetate or a mixture of the two.

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

8. The method for preparing the composite oxalate-modified pentaaminotetrazole gas generating agent according to claim 4, characterized in that: The drying temperature in step S2 is 35-50° C., and the drying time is 6-8 hours.

9. The method for preparing the composite oxalate-modified pentaaminotetrazole gas generating agent according to claim 4, 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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