JPH08169792A - Gas generating agent - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] Use of an organic compound as a component of the gas generant for airbags used to reduce the impact on passengers in the event of a vehicle collision Improve safety and functionality. [Structure] A nitrogen-containing organic compound and an oxidizing agent were contained, and the nitrogen-containing organic compound was made to pass through an endothermic process at the time of temperature rise. As a result, there is a risk of a fire during production, or the impact ignitability of the composition during use, and the burning rate are improved, and long-term stability is excellent, and the superiority of the generated gas amount and cost reduction can be achieved. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas generating agent, and more particularly to a gas generating agent for an airbag used for protecting an occupant in the event of a collision of an automobile. The gas generating agent improves safety and long-term stability, as well as impact ignitability and combustion. The purpose is to improve the speed, and also to achieve superiority of gas amount and cost reduction.

[0002]

2. Description of the Related Art Recently, it has been recognized by many people that it is effective to wear seat belts in order to prevent serious accidents such as death or injury of an occupant who is thrown out of the vehicle due to the impact of a vehicle collision. . However, even in that case, it is not possible to completely prevent a situation in which an occupant collides with the steering wheel portion or the windshield to cause serious injury. Therefore, in the event of a vehicle collision, the impact is mechanically or electrically sensed to ignite the gas generating agent, and by burning this, a large amount of gas is instantly generated to inflate the bag, and the cushioning action causes the occupant to occupy the occupant. The airbag system, in which an airbag designed to reduce the impact on the vehicle, is incorporated into the shaft center of the steering wheel or inside the dashboard, has come into the spotlight.

As a gas generating agent used in this airbag system, sodium azide has been mainly used so far, for example, titanium oxide, manganese dioxide, iron oxide, sodium nitrate, potassium nitrate, copper nitrate, potassium perchlorate, Oxidizing agents such as sodium perchlorate, potassium chlorate and sodium chlorate, metal reducing agents such as zirconium, magnesium, aluminum and titanium, cooling agents such as alkali and alkaline earth metal carbonates, pH adjustment of iron sulfate etc. It is known to contain additives such as agents, molybdenum disulfide, potassium bromide, graphite and the like.

[0004]

However, since the above-mentioned gas generant mainly containing sodium azica has the property of being easily decomposed, it is decomposed by a treatment such as mixing in the manufacturing process, Strict work control is required due to the risk of fire.

Secondly, sodium azide is not only a highly harmful substance itself, but also decomposes to generate sodium oxide or sodium hydroxide, so that special care must be taken in its handling during production. In addition, when this is used as a gas generating agent for an airbag system, it is necessary to separately take measures for removing or detoxifying harmful gas generated for safety, so that the entire structure of the gas generating device is complicated and It is inevitable that the cost will be extremely high.

Therefore, in an attempt to solve these problems,
Attempts have been made to use an organic gas generating agent in place of the above-mentioned sodium azide. For example, an airbag comprising an azodicarbonamide (hereinafter abbreviated as "ADCA") which is an easily decomposable organic substance, a metal oxidizing agent and an oxidizing agent. The gas generating agent for use is JP-B-40-21171, and the gas generating composition comprising ADCA and manganese oxide is JP-A-50-118.
No. 979, a gas generating agent for an air bag using ADCA and potassium perchlorate is further disclosed in JP-A-6-3268.
No. 9 and JP-A-6-32690, these ADCAs are excellent in combustion efficiency because they decompose especially at low temperatures, but they are not sufficient in terms of harmfulness and danger. It can't be said that it is.

Further, among the nitrogen-containing organic compounds, examples of the low-temperature decomposable nitrogen-containing organic compounds known so far include dinitrosopentamethylenetetramine (hereinafter referred to as “D”).
(Abbreviated as “PT”), and 4.4 ′ oxybisbenzenesulfonylhydragit, paratoluenesulfonylacetonehydrazone and the like. Since these are also low-temperature decomposable, they are effective for use as a gas generant, but since these molecules contain sulfur in addition to hydrogen, carbon, or oxygen, they can be contained in the gas generated during combustion. Sulfur compounds harmful to the human body may remain.

Generally, in order for the airbag system to function sufficiently, the airbag system has a high burning rate so that the bag can be inflated within a few tens of milliseconds, and the generated gas is finally discharged. It must not contain harmful ingredients as it is released outside the vehicle. From a safety point of view, the airbag system will not accidentally malfunction while it is not operating normally, and will not explode during manufacturing or when installed in a vehicle. Ignition is required to be as low as possible.

Further, since the airbag and the gas generating agent container (inflator) expanded by the gas generating agent come into direct or indirect contact with the body of the occupant, the combustion ignition temperature is as low as possible from the viewpoint of preventing the risk of burns. In addition, it is also desirable to have long-term stability that does not deteriorate even if left for a long time of 10 years or more in a vehicle in which the temperature often rises to a range exceeding 100 degrees Celsius. is there. The present invention is applicable to sodium azide and ADCA.
Solving the above-mentioned problems of conventional gas generating agents using
It is an object of the present invention to provide a gas generating agent that reduces the generation of harmful gas and is excellent in long-term stability while maintaining good flammability and impact resistance.

[0010]

In order to solve the above problems, the present invention contains a nitrogen-containing harmful compound and an oxidizing agent,
This nitrogen-containing organic compound is a gas generating agent that passes through an endothermic process at the time of temperature rise. In this configuration, it is conventionally considered that it is preferable to use, as the gas generating agent, a material having a low decomposition temperature for gas generation and also having a combustion enhancing action for prompt combustion of the generated gas. On the other hand, the present inventor has a wide temperature change range, and as a gas generating agent for an inflator of a vehicle-mounted airbag system having a characteristic of being stored for a long period of time, passes through an endothermic process at the time of temperature rise, It was realized for the first time by newly finding that a gas generating agent having an endothermic peak as a main peak is extremely effective. Further, a combustion accelerator or a combustion catalyst may be preferably added to this structure.

Here, HDCA (hereinafter abbreviated as "hydrazodicarbonamide") is a preferred example of the nitrogen-containing organic compound that undergoes an endothermic process at the time of temperature increase. Examples of suitable oxidizing agents include oxohalogenates and / or nitrates. Examples of the oxohalogenates include halogenates and / or perhalogenates, chlorates, perchlorates, and bromine. And at least one of the alkali metal salts of acid salts and perbromates. Of course, these items may be appropriately combined and used. DPT is preferably used as the combustion accelerator.

Further, suitable combustion catalysts include copper oxide, zinc oxide, titanium oxide, vanadium oxide, cerium oxide,
At least one of calcium oxide, manganese oxide and iron oxide is used. Of course, these may be appropriately combined and used. It should be noted that the above specific compound names are not limited at all, and other materials can be used alone or in combination as long as they have the same function.
That is, the first feature of the present invention is that a mixture of HDCA (hydrazodicarbonamide), which is an easily decomposable organic substance, and an oxohalogenate is used as a gas generating agent.

As a preferable characteristic of the gas generating agent so far, it is effective that it can be gasified in a state where the decomposition temperature is as low as possible and that the combustible gas in the generated gas can be quickly burned. Therefore, from such a viewpoint, it is disadvantageous to use HDCA as a gas generating agent for an inflator because it has a considerably higher decomposition temperature than that of ADCA described above and has a low gas generating efficiency as a gas generating agent. Has been expected. Despite that, the purpose of using the above HDCA is to use it in a very special situation that it is mounted on a vehicle, including environmental conditions. Especially under the severe conditions of high temperature and long-term use, This is because it has been judged that it can be used under special conditions that are not normally considered, such as maintaining stability and reliability.

Further, the HDCA has a composition of gas generated by combustion essentially of carbon dioxide, nitrogen, or water, containing almost no harmful substances, and a perchlorate as an oxidant for combustion. There are also advantageous conditions, such as the ability to use oxohalogenates such as chlorates. Among them, alkali metal salts such as sodium perchlorate, potassium perchlorate, sodium chlorate and potassium chlorate are particularly preferable. Further, perbromic acid and alkali metal salts of bromic acid can be used as well.

The amount of halogenate required for complete combustion of 1 mol of HDCA is 5/3 mol and the amount of perhalogenate is 5/4 mol. In this case, a generated gas containing no harmful substance can be obtained. In the case of ADCA used conventionally, 6 mol of gas generation can be obtained per mol, whereas in the case of using the HDCA of the present invention, a large amount of gas generation of 7 mol per mol can be obtained. It is also a feature that the quantity can be obtained.

Next, as a second means of the present invention, HDC
It is characterized by using a gas generating agent obtained by mixing DPT (dinitrosopentamethylenetetramine), which is an easily decomposable organic substance, in addition to A and oxohalogenate. In this case, the addition of DPT will improve the combustion speed and further increase the amount of generated gas. Incidentally, when the DPT in this case is used, a large amount of gas generation of 13 mol per mol is obtained by the complete combustion, and the obtained gas is the HDC of the first invention described above.
As with A, it contains only carbon dioxide, nitrogen, and water, with little other harmful effects. The amount of halogenate required for complete combustion of 1 mol of DPT is 13/4 mol, and the amount of perchlorate is 13/3 mol.

Further, as a third means of the present invention, HDC
A combustion catalyst is further added to A (hydrazodicarbonamide), DPT, and an oxohalogenate. In both cases of the first and second means described, the concentration used was a low concentration which did not adversely affect the human body, but the addition of the combustion catalyst resulted in even faster and more uniform combustion. In addition, the possibility of producing harmful gas such as carbon monoxide or ammonia due to incomplete combustion can be suppressed to a minimum.

The combustion catalyst used in this case is
Especially copper oxide, zinc oxide, titanium oxide, vanadium oxide,
It is preferable to use metal oxides such as cerium oxide, calcium oxide, and manganese oxide. In addition, various known combustion catalysts may be used alone or in combination of two or more. Although not shown in the above-mentioned first to third means, any nitrogen-containing compound other than HDCA can be used as long as its main peak shows an endothermic process.

[0019]

[Function] As described above, by using a nitrogen-containing organic compound that passes through an endothermic process at the time of temperature rise as a main component of a gas generating agent, a large amount of gas is stably generated for a long time while reducing the generation of harmful gas. To do. Further, it exhibits a combustion property that can be used as a gas generating agent and impact resistance. Further, by adding a combustion accelerator, the combustion speed is further improved and the gas generation amount is increased. Furthermore, by adding a combustion catalyst, higher-speed and uniform combustion is realized, and the generation of harmful gas due to incomplete combustion of carbon monoxide ammonia or the like is further suppressed. Here, when HDCA is used as the nitrogen-containing organic compound, the generated gas has a composition of carbon dioxide, nitrogen, water and the like, and does not substantially contain a harmful gas.

The HDCA has good compatibility with an oxidizing agent such as oxohalogenate. The amount of halogenate required to completely burn 1 mol of HDCA is 5/3 mol, and the amount of perhalogenate is 5/4 mol. In this case, no harmful gas is substantially generated. The conventional A
The gas generation amount of DCA was 6 mol per mol, whereas the gas generation amount of HDCA was 7 mol per mol, and a larger amount of gas was generated. When DPT is used as the combustion accelerator, it is 13 per mole.
It is expected that a large amount of moles of gas will be generated, the generated gas will only contain carbon dioxide, nitrogen, and water, and no harmful gas will be substantially generated. The amount of halogenate required for complete combustion per 1 mol of DPT is 13/4 mol, and the amount of perchlorate is 13/3 mol.

[0021]

【Example】

[Example 1] In this example, an experiment was conducted on long-term stability, which is an important item particularly for practical use of an airbag. Experimental method is 160 ± 5 ℃
This is an acceleration test in which the sample is left in the oven for 10 days and its weight change is observed. This acceleration test is based on HDCA (AD
(Although it is the same in the case of CA, etc.), when a weight change (decrease) occurs, there is a high possibility of decomposition due to the property used as a foaming agent, and lack of long-term stability. This was done focusing on the fact that it cannot be used in a harsh environment for a long time. Therefore, in this example, the weight loss rate, which is an extremely important item for evaluating the stability, was measured. ADCA is used for comparison, and HDCA alone or HDCA
The results of comparison with CA + DPT are as follows.

(Sample) (Sample) (Reduction rate (%)) Sample 1 HDCA 0.05 or less 2 〃 〃 Sample 3 HDCA / DPT 0.05 to 0.1 Comparative sample ADCA 0.51 or more In addition, since the weight reduction rate of HDCA is smaller than that of ADCA by about one digit, stability is very excellent in the first place. Furthermore, even when DPT having a combustion promoting function is added, the ADC is stable due to the excellent stability of HDCA.
Excellent stability is assured as compared to when added to A. Furthermore, even if an oxidizing agent or a catalyst is added to the above-mentioned HDCA, it has higher stability than the case of adding the same to ADCA.

Next, the physical properties of HDCA exhibiting excellent long-term stability will be examined as follows.
The present inventors believe that such stability is due to a difference in thermal characteristics, and therefore SC-DSC measurement (differential scanning calorimetry using a stainless steel sealed cell) is performed to consider the thermal characteristics of HDCA and ADCA. When performed, the endothermic main peak appears near 270 degrees Celsius as shown in FIG. On the other hand, for ADCA as well, SC
-When DSC measurement is performed, a main peak of heat generation appears near 200 degrees Celsius as shown in FIG.

Therefore, such endothermic process of HDCA is
In addition to the difference in decomposition temperature, it is considered to be one of the factors that have a significant effect on ADCA in long-term stability. In this example, long-term stability was confirmed, but in the following, flammability and impact resistance will be described as another confirmation item that is a practical gas generating agent that can be suitably used for an airbag system and the like. .

Example 2 Next, an experiment on the combustion characteristics of the present invention was tried. The sample used here was prepared by mixing the target composition and then dried and solidified by using a 4 mm mesh, and a 6 mm mesh was used to capture a 6 mm or less sample. It has a granular property in which particles of 3 mm or more are captured using a mesh. Therefore, in this embodiment, the particle size is 3 m.
This means that a sample of m or more and 6 mm or less was used.

In this example, the burning time was ignited by a nichrome wire using a steel pipe burning test device (60 mm diameter × 50 mm height). The burning time was defined as the time from smoke to extinction because the time from ignition to smoke is extremely short and can be ignored in the combustion processes of ignition, smoke generation, decomposition, combustion, and extinction. In the actual measurement, a video was taken of the combustion process, and the time from smoke emission to smoke extinction in the reproduced image was visually measured. The results are as follows. The oxidizer (KCIO3) is used in this embodiment to ensure the combustion.

(Sample) (Composition) (Duration) Sample 1 HDCA / KClO3 (35/65) 2.5 seconds Sample 2 HDCA / KClO3 (30/70) 2.1 seconds Sample 3 HDCA / KClO3 (25 / 75) 1.6 seconds Comparative sample ADCA / KClO3 (30/70) 1.1 seconds As is clear from the above, HDCA + oxidizer is ADCA.
+ Burning time is slightly longer than that of oxidizer, but this difference does not pose any practical problem. In addition, in HDCA and ADCA, it is generally considered that a combustion promoter such as DPT or a combustion catalyst is added in order to efficiently generate a combustion gas.
Combustibility comparable to that of CA is realized.

[Embodiment 3] Next, an experiment on safety in operation and use was tried. The experiment was evaluated by an impact ignitability test (in accordance with the method described in Industrial Explosives, Vol. 54, No. 2, 1983). The shorter the gap length (the distance between the impact source and the sample), the higher the safety. In this example, an oxidizing agent (KClO3,
The reason why KClO4, NaClO3) or the like is used is to evaluate the impact resistance under the condition where combustion is easy.

(Sample) (Composition) (Gap length) Sample 1 HDCA / KClO3 (35/65) 3 mm Sample 2 HDCA / NaClO3 (40/60) 3 mm Sample 3 HDCA / KClO3 (30/60/10) 5 mm sample 4 HDCA / KClO4 (35/55/10) 5 mm Comparative sample ADCA / KClO3 (40/60) 6 mm As is clear from the above, HDCA + oxidizer is ADCA.
+ Has a shorter gap length than oxidizer and has excellent impact resistance. In addition, in HDCA and ADCA, it is general to add a combustion promoter such as DPT or a combustion catalyst in order to efficiently generate combustion gas. Has excellent impact resistance.

[0030]

As described above, the typical structure of the present invention is H
Since it is a gas generating agent using a nitrogen-containing organic compound that passes through an endothermic process at the time of temperature rise, as typified by DCA, as shown by the experimental results in each of the above-mentioned examples, both stability and flammability are exhibited. In terms of the above, there is no practical problem, and by combining this HDCA with a so-called combustion aid such as an oxidizing agent or a catalyst, it is possible to use it as a gas generating agent composition that is even more practical.

Therefore, when this is used as, for example, a gas generating agent for an air bag of a vehicle, it sufficiently protects an occupant from the impact of a collision accident, and exhibits the following excellent operational effects. That is, firstly, it is less harmful as compared with sodium azide, and further has low decomposition or combustibility during processing for producing a gas generating agent,
It is extremely easy to handle and can be provided at low cost. Second, at the time of gas generation, it does not generate components harmful to the human body such as sodium oxide or sodium hydroxide as seen in sodium azide. It can be suppressed to a low concentration that has almost no effect on the human body.

The concentration of harmful gas can be further reduced by using a combustion catalyst. Thirdly, since the gas generating agent of the present invention has a lower combustion temperature as compared with the case of using sodium azide, it does not require special consideration such as heat resistance requirement for the material of the airbag. Not only can the cost be reduced, but also the risk of burns to the passenger can be eliminated. Fourth, ADC
As compared with the gas generating agent using A, it is possible to realize a gas generating agent that essentially has a large gas generation amount and is excellent in long-term stability and impact resistance.

As described above, since the organic gas generating agent is used as the composition of the present invention, compared with the gas generating agent using sodium azide, the handling safety in the manufacturing process and the composition It has advantages such as impact ignitability, burning rate, gas generation amount, and cost. Furthermore, by using HDCA, as an important reliability item that affects human life, it has excellent long-term stability that can always maintain specified characteristics even under severe conditions for 10 years or more, and can withstand long-term use of the vehicle. it can.

[Brief description of drawings]

FIG. 1 SC-D of HDCA used in the present invention
This is a graph showing the SC characteristics, where the horizontal axis represents temperature and the vertical axis represents the amount of heat.

FIG. 2 SC-D of ADCA used in the present invention
This is a graph showing the SC characteristics, where the horizontal axis represents temperature and the vertical axis represents the amount of heat.

Front page continuation (72) Inventor Yasuo Kudo 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Matsushita Giken Co., Ltd. (72) Hiroyuki Takahashi 1-1-1, Shimomachiya, Chigasaki City, Kanagawa Miyata Kogyo Co., Ltd. (72) Inventor Akihiko Fujii 1625 Hobukaicho, Hodogaya-ku, Yokohama-shi, Kanagawa Japan Carlit Co., Ltd. Hodogaya Plant

Claims (9)

[Claims] 1. A gas generating agent containing a nitrogen-containing organic compound and an oxidizing agent, wherein the nitrogen-containing organic compound passes through an endothermic process at the time of temperature rise. 2. The gas generating agent according to claim 1, further comprising a combustion promoter in addition to the nitrogen-containing organic compound and the oxidizing agent. 3. The gas generating agent according to claim 1, further comprising a combustion catalyst. 4. The gas generating agent according to claim 1, wherein the nitrogen-containing organic compound is hydrazodicarbonamide (HDCA). 5. The gas generant according to claim 1, wherein the oxidant is an oxohalogenate and / or a nitrate. 6. The gas generating agent according to claim 5, wherein the oxohalogenate is a halogenate and / or a perhalogenate. 7. The gas generating agent according to claim 5, wherein the oxohalogenate is at least one of chlorate, perchlorate, bromate, and alkali metal salt of perbromate. . 8. The gas generant according to claim 2, wherein the combustion accelerator is dinitrosopentamethylenetetramine (DPT). 9. A combustion catalyst comprising copper oxide, zinc oxide, titanium oxide, vanadium oxide, cerium oxide, calcium oxide,
The gas generating agent according to any one of claims 3 to 8, which is at least one of manganese oxide and iron oxide.