JPH07309194A - Gas-forming agent for air bag - Google Patents

Abstract

PURPOSE:To restrain even an amino group including organic substance which forms ammonia by thermal decomposition, from generating NOx, and maintain a suitable reaction speed. CONSTITUTION:This gas-forming agent for an air bag, which comprises (a) amino group including substances, (b) oxidant mainly composed of nitrate, and (c) silicone resin included therein, where the silicone resin is granulated or molded as inclusions, and the gas generator preferably comprises (a) 20 to 50% amino group including organic substances by weight, (b) 40 to 70% oxidant by weight which includes more than the half of nitrate by weight, and (c) 2 to 20% silicone resin by weight included therein. And the addition of nitrate restrains the forming of NOx, and the addition of silicone resin maintains a reaction speed suitable.

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 for an air bag accommodated in a gas generator for inflating an air bag which is a vehicle occupant protection device.

[0002]

2. Description of the Related Art Gas generating agents for airbags of this type include
Since a moderate burning rate, good heat aging resistance, and harmlessness of generated gas are required, those containing sodium azide as a main component have been used.

That is, using sodium azide as a base, for example, an oxidizing agent [a metal oxide such as TiO ₂ , MnO ₂ or Fe ₂ O ₃ , a nitrate such as NaNO ₃ , KNO ₃ , Cu (NO ₃ ) ₂ or KClO]. ₄ , perchlorates such as NaClO ₄ ,
Chlorates such as KClO ₃ and NaClO ₃ ], metal reducing agents [Zr, Mg, Al, Ti, etc.], cooling agents [Na
₂ CO ₃ , K ₂ CO ₃ , CaCO ₃ , FeSO _4, etc.], pH adjusters [iron sulfide, etc.] Mechanical performance improvers [MoS ₂ , KBr, graphite, etc.] There is.

The gas generating agent containing sodium azide as a main component generates hydrazoic acid when it absorbs moisture. This hydrazoic acid is extremely sensitive to shock, explodes easily, and is extremely toxic to the human body. Therefore, the gas generating agent must be stored in a storage container such as an aluminum cup in a tightly sealed state so as not to come into contact with the atmosphere. Also,
An inspection is also required to confirm the sealed state.

Further, when sodium azide burns, a strong alkaline substance is produced. When this substance becomes mist and is discharged to the outside of the gas generator, holes are formed in the airbag. Therefore, a strict filter function is required to confine the mist in the gas generator through the double and triple filters. As a result, the internal pressure of the gas generator increases, and the container forming the gas generator becomes a pressure resistant container.

As described above, the soda azide-based gas generating agent is
In order to ensure its safety, it is necessary to store it in a sealed storage container and to release it from the gas generator through a strict filter function, so the structure of the gas generator is complicated. It has the drawback of

Since the above drawbacks of sodium azide are disliked, various non-sodium azide gas generating agents have been proposed. One of them is a gas generating agent containing azodicarbonamide as a main component, which has a very low risk of causing a fire by decomposition or combustion and has extremely low toxicity.

Japanese Unexamined Patent Publication No. 6-32689 proposes a gas generating agent for an air bag, which is composed of azodicarbonamide and oxohalogenate. In addition, JP-A-6-3
2690 discloses azodicarbonamide, oxohalogenates, and [ZnO, ZnCO ₃ , urea, MnO.
₂ , FeCl ₃ , CuO, Pb ₃ O ₄ , PbO ₂ , Pb
O, S, TiO ₂ , V ₂ O ₅ , CeO ₂ , Ho ₂ O ₃ ,
CaO ₂ and Yb ₂ O ₃ ] has been proposed as a gas generating agent for an air bag, which is composed of at least one combustion modifier. All of them utilize the reducibility of azodicarbonamide, and by reacting this directly with a specific oxidant called oxohalogenate, the impact ignitability, burning rate, and gas generation equivalent to those of the sodium azide-based gas generating agent are obtained. Amount and relatively low combustion temperature could be achieved.

[0009]

Although the aim of using azodicarbonamide as a main component is excellent, the reaction between azodicarbonamide and oxohalic acid salt far exceeds the permissible value for humans. An amount of NOx may be generated. The generation of NOx is described in, for example, Japanese Unexamined Patent Publication No. 50-189979, when CO, NH ₃ , NOx, and H ₂ O are generated by reacting an organic thermal decomposable substance that produces nitrogen gas by thermal decomposition with an oxidant. It has been suggested that some of the above may occur.

This azodicarbonamide has a structure shown in Chemical formula 1 and generates ammonia by thermal decomposition.

[0011]

[Chemical 1]

The reaction formula of potassium chlorate and potassium perchlorate, which are typical examples of the generated ammonia and oxohalogenate, is shown in Chemical formula 2.

[0013]

[Chemical 2]

No. 1 showing the reaction formula of potassium chlorate. No. 1 showing the reaction formulas of 1 and potassium perchlorate. Both of the _two have an equation a that produces N ₂ gas and an equation b that produces NO ₂ . The Gibbs free energy ΔGf ° for NO ₂ production in the equation b is as large as the Gibbs free energy ΔGf ° for the N ₂ gas production in the equation a. Moreover,
Similarly to the formula a, the formula b is an exothermic reaction in which the heat of formation ΔHf ° is minus, and the reaction is accelerated. That is, in the reaction of ammonia with potassium chlorate and potassium perchlorate, N ₂
NO ₂ is generated as easily as gas and NOx
Occurrence of is inevitable.

When NO reacts with water, it becomes nitrous acid, and NO
_{When 2} reacts with water, it becomes nitric acid, which is extremely harmful to the human body. The gas that inflates the airbag is quickly discharged to the outside of the airbag after the inflation. It is inevitable that the occupant will inhale a large amount of the exhausted gas, and a large amount of NO
The gas generating agent containing x cannot be used for an airbag.

The present invention was created in the process of theoretically pursuing the process of NOx generation as described above and also theoretically pursuing the process of reaction progress. Even with an amino group-containing organic substance that generates ammonia by thermal decomposition, such as dicarbonamide, NOx
It is an object of the present invention to provide a gas generant for an airbag that achieves impact ignitability, combustion speed, gas generation amount, and relatively low combustion temperature equivalent to those of a sodium azide-based gas generant while suppressing the generation of .

[0017]

That is, the gas generating agent for an air bag of the present invention comprises (a) an amino group-containing organic substance,
(B) An oxidizing agent containing a nitrate as a main component, and (c) a silicone resin, which are granulated or molded with the silicone resin as an inclusion. Preferably, (a) an organic compound containing an amino group: 20 to 50% by weight, (b) an oxidizing agent containing 1/2 or more by weight of nitrate: 40 to 70% by weight,
(C) Silicone resin: 2 to 20% by weight, and is granulated or molded with the silicone resin as an inclusion. More preferably, the content of silicone resin is 5 to 10% by weight.

The amino group-containing organic matter is a nitrogen gas generating component, and is accompanied by generation of ammonia by thermal decomposition in a normal combustion process. Such amino group-containing organic substances include azodicarbonamide, triaminoguanidine nitrate, and 5-aminotetrazole.

The oxidizer containing nitrate is an oxygen-supplying component, and its ignition temperature within a predetermined temperature range can be selected by combining it with an amino group-containing organic substance. Therefore, the quantitative ratio in the mixing of the amino group-containing organic matter and the oxidizing agent may be a stoichiometric amount that can completely burn the amino group-containing organic matter, but in order to adjust the burning rate, the burning temperature, the combustion gas composition, etc. Contains 20 to 50% by weight of amino group-containing organic matter.
On the other hand, the oxidizer is 40 to 70% by weight.

As the oxidizing agent, one or more of sodium nitrate, potassium nitrate, barium nitrate, strontium nitrate and the like can be used. Oxohalogenates include chlorates (potassium chlorate, sodium chlorate, barium chlorate, etc.), bromates (sodium bromate, potassium bromate, etc.), iodates (sodium iodate, potassium iodate). Etc.) and one or more of perchlorate, perbromate, periodate and the like can be used. The oxidizing agent may contain a metal peroxide such as K ₂ O ₂ or Na ₂ O ₂ .

The silicon resin which functions as a binder is most preferably room temperature curable silicone rubber. For granulation or molding, the content is preferably 2 to 20% by weight. If the content exceeds 20%, the ignitability deteriorates, and 2
If it is less than%, it becomes difficult to mold. Therefore, 5 is particularly preferable.
10 to 10% by weight.

Next, as endothermic decomposable substances added as necessary, ZnCO ₃ , CaCO ₃ , MgCO ₃
Metal carbonates such as _{NaHCO 3, MgC 2 O 4 ·} 2H 2
There are metal oxalates such as O. This endothermic decomposable substance is added to lower the temperature of the generated gas. When the gas temperature becomes high, the effect on the airbag cannot be ignored, so the temperature is adjusted with a sawtooth endothermic substance.

Further, in the composition of the present invention, various additives (the above-mentioned metal reducing agents, which are added to the conventional gas generating agent containing sodium azide as a main component, to the extent that the properties thereof are not impaired)
A pH adjusting agent and a mechanical performance improving agent) may be contained.

[0024]

In particular, it is essential that the oxidizing agent of the present invention contains nitrate as a main component in order to prevent NOx described above. That is, the reaction formula NO. 1 and 2 respectively N ₂ N
Looking at the reaction for producing O ₂ with sodium nitrate and potassium nitrate, which are typical examples of nitrates,
NO. Reaction formulas such as 3 and 4 are obtained. As is apparent from these equations, Gibbs free energy DerutaGf ° for NO ₂ generation equation b for generating NO ₂ is the value of a large positive, this reaction it is understood not to proceed in the normal.
On the other hand, Gibbs free energy ΔG for N ₂ gas generation
f ° is negative and it can be seen that the reaction proceeds easily. From this fact, when an organic compound containing an amino group is decomposed by using a nitrate as an oxidizing agent, NOx is not generated and harmless N
_It can be seen that only ₂ gases are generated.

In the present invention, it is essential to use this nitrate, but it is not necessary to use all the oxidizing agents as nitrates. That is, it is possible to add another oxidizing agent, for example, a general oxidizing agent such as an oxohalogenate, within a range in which NOx generation can be suppressed. This is because the Gibbs free energy ΔGf ° for NO ₂ production when nitrate is used is 3 as is clear from the reaction formulas of [Chemical Formula 2] and [Chemical Formula 3].
While it is from 0 to 530 [Kcal / mol], it is -100 [Kcal / mol] when using an oxohalogenate.
However, even if both are mixed, N in the overall reaction
In order for the Gibbs free energy ΔGf ° for O ₂ generation to become negative, the presence of a considerably large amount of oxohalogenate is required. Therefore, in the present invention, the addition of these oxohalogenates is allowed to the extent that the generation of NOx is not a problem. The amount of oxohalogenate added is
Although it naturally varies depending on the type of the amino group-containing organic substance to be decomposed, the type of oxohalogenate, etc., at least 50% by weight or more of the oxidizing agent should be nitrate. With this ratio, the amount of NO ₂ produced by the reaction between the oxohalogenate and ammonia can be suppressed to a level without problems. It should be noted that the effect of improving the reactivity of nitrate described below can be expected by adding such an oxohalogenate.

On the other hand, nitrate has a characteristic problem that it melts and absorbs heat before the reaction, so that it has a poor ignitability and a slow burning rate. As a method of compensating for the drawbacks of the nitrate, a method of adding a combustion accelerator containing a sulfur-based compound represented by black powder is common, but SOx such as sulfurous acid gas is generated by the combustion of the sulfur-based compound,
This causes a problem of odor as well as the problem of harmful gas as in the case of NOx. Therefore, the present invention has a great feature in adding a silicone resin as a means for solving the problems associated with the ignitability and combustibility of the nitrate. That is, the silicone resin has a three-dimensional structure represented by the structural formula shown in [Chemical Formula 4].

[0027]

[Chemical 4]

In the structure of this silicone resin, the Si group has an inorganic property and the R (alkyl group etc.) has an organic property. Therefore, the silicone resin is present between the organic substance containing an amino group and the nitrate salt which is an inorganic substance, and has a function of accommodating both and tightly binding both. As a result, heat conduction between the two becomes better,
The high temperature gas resulting from the combustion of the ignition charge immediately causes the melting of the nitrate and the decomposition of the amino group-containing organic matter, and at the same time promotes the above-mentioned reaction between ammonia and the nitrate generated by the decomposition of the amino group-containing organic matter and proceeds in a chain. By doing so, the gasification reaction will proceed explosively at once.

Further, in the present invention, since the silicone resin also functions as a binder, the silicone resin is added to the powdery amino group-containing organic substance and the powdery oxidizing agent to form granules or pellets or strands. Will be done. In this process, since the silicone resin itself is a thermally and chemically stable substance, there is no problem in working by using this as a binder and the quality of the obtained molded product is stable. There is.

[0030]

As the gas generating agent for an air bag of the present invention, a gas generating agent for an air bag based on an organic compound containing an amino group which does not require a strict sealing and a strict filter mechanism like sodium azide is practically used. There is an effect that can be realized. That is, when an amino group-containing organic substance that generates ammonia by thermal decomposition is subjected to an oxidation reaction with an ordinary oxidizing agent, N
Ox is generated, but the use of a specific oxidant, nitrate, as a main component prevents generation of NOx. However, since the melting before the ignition of nitrate is an endothermic reaction, the delay of the reaction is compensated by the binder of silicon resin to prevent the generation of NOx and maintain an appropriate reaction rate.

The present invention will be made clearer with reference to Examples and Comparative Examples below. However, the present invention is not limited to only these examples.

[Example 1] The combinations shown in Table 1 were mixed in the following proportions. Azodicarbonamide (ADCA) (Wako Pure Chemical Industries, Ltd.) 3.7 grams KNO ₃ (Wako Pure Chemical Industries, Ltd.) 3.5 grams KClO ₃ (Wako Pure Chemical Industries, Ltd.) 2.0 grams Silicon Resin (Si-RTV rubber; KE-441T manufactured by Shin-Etsu Chemical Co., Ltd.) 0.8 g To the above substances, 5 parts by weight of isoamyl acetate as a solvent was added, and the mixture was kneaded for 10 minutes, and then the diameter was 3 mm and the thickness was 3 mm.
The mold having the pores was placed and allowed to stand at room temperature for 24 hours for curing to give pellet-shaped tablets.

10 g of the tablets were ignited and burned in a 1 liter stainless steel container by using an igniter containing B / KNO ₃ and the change in generated pressure with time was recorded. The results are shown in Table 1.
Shown in. The ignition time was appropriate and the amount of NOx produced was within the permissible range for the human body. The ignition time is within 10 msec, and Pmax-tmsec is 10
Passes within 0 msec and NOx ppm within 200 ppm were passed.

[Example 2] Triaminoguanidine nitrate (TAGN) (manufactured by Chugoku Kayaku Co., Ltd.) was used in place of ADCA, tablets were formed in the same manner as in Example 1, and a 1-liter tank test was conducted. Is shown in Table 1. The ignition time was appropriate and the amount of NOx produced was within the permissible range for the human body.

Example 3 The same composition as in Example 1 was extruded from a punching metal having a large number of holes with a diameter of 2 mm to form a strand, and a 1 liter tank test was conducted. The results are shown in Table 1. . The ignition time was appropriate and the amount of NOx produced was within the permissible range for the human body.

Example 4 The same composition as in Example 2 was extruded from a punching metal having a large number of holes having a diameter of 2 mm to granulate it, and a 1 liter tank test was carried out. The results are shown in Table 1. Ignition time is appropriate and NO
The amount of x generated was within the allowable range for the human body.

Comparative Example 1 3.7 g of the above ADCA, 5.5 g of potassium chlorate, and 0.1 g of tragacanth rubber were used.
After adding 6 g and adding 5 parts by weight of isoamyl acetate as a solvent and kneading for 10 minutes, a diameter of 3 mm and a thickness of 3 mm
The mold having the pores was placed and allowed to stand at room temperature for 24 hours for curing to give pellet-shaped tablets. 1 gram of this tablet
Ignition and combustion were carried out using a igniter containing B / KNO ₃ in a liter stainless steel container, and changes in generated pressure with time were recorded. The results are shown in Table 1. Ignition time is appropriate,
Generates a large amount of NOx, which is harmful to the human body.

Comparative Example 2 Using the same composition as in Example 1 but using the same weight of tragacanth rubber (manufactured by Wako Pure Chemical Industries, Ltd.) as the binder instead of Si-RTV rubber, tablets were prepared and a 1 liter tank test was conducted. Carried out. The results are shown in Table 1. The pellets did not ignite, only the surface of the pellets burnt.

COMPARATIVE EXAMPLE 3 Using the same composition as in Example 2 but using the same weight of tragacanth rubber (manufactured by Wako Pure Chemical Industries, Ltd.) as the binder instead of Si-RTV rubber, tablets were prepared and a 1 liter tank test was conducted. Carried out. The results are shown in Table 1. The ignition speed is too slow to be put to practical use.

[Comparative Example 4] The same composition as in Example 3 was used, but instead of the Si-RTV rubber, the same weight of tragacanth rubber (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the binder, and the mixture was granulated and subjected to a 1 liter tank test. Was carried out. The results are shown in Table 1. Did not ignite.

Comparative Example 5 Using the same composition as in Example 4 but using the same weight of tragacanth rubber (manufactured by Wako Pure Chemical Industries, Ltd.) as the binder instead of Si-RTV rubber, granulation and 1 liter tank test Was carried out. The results are shown in Table 1. The ignition speed is too slow to be put to practical use.

[0042]

[Table 1]

Incidentally, N in Examples 1 to 4 and Comparative Examples 1 to 5
Ox was measured by NO + NO ₂ nitrogen oxide detector tube manufactured by Gastech Co., Ltd.

[Chemical 3]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location C09K 3/00 A (72) Inventor Michihisa Taguchi 3903-39, Abundant Town, Himeji City, Hyogo Prefecture Inside the Himeji Plant of Yakuhin Co., Ltd. (72) Inventor Kozo Ota 3903-39, Abundant Town, Himeji City, Hyogo Prefecture Nippon Kayaku Co., Ltd. Inside the Himeji Plant

Claims (7)

[Claims] 1. An air comprising (a) an organic compound containing an amino group, (b) an oxidizing agent containing a nitrate as a main component, and (c) a silicone resin, which is granulated or molded with the silicone resin as an inclusion. Gas generating agent for bags. 2. (a) Amino group-containing organic matter: 20 to 50
%, (B) Oxidizing agent containing 1/2 or more by weight of nitrate:
A gas generating agent for an air bag, which comprises 40 to 70% by weight and (c) a silicone resin: 2 to 20% by weight and is granulated or molded with the silicone resin as an inclusion. 3. The gas generating agent for an air bag according to claim 2, wherein the content of the silicone resin is 5 to 10% by weight instead of 2 to 20% by weight. 4. The organic substance containing an amino group is azodicarbonamide, triaminoguanidine nitrate, 5-
The gas generating agent for an airbag according to claim 1, which is one or more kinds of aminotetrazole. 5. The gas generating agent for an airbag according to claim 1, wherein the nitrate is one or more of sodium nitrate, potassium nitrate, barium nitrate and strontium nitrate. 6. The oxidant is, in addition to nitrate, chlorate, perchlorate, bromate, perbromate, iodate,
The gas generating agent for an air bag according to any one of claims 1 to 3, which contains an oxohalogenate composed of at least one kind of periodate. 7. (a) Amino group-containing organic substance, (b) Nitrate-based oxidizing agent, (c) Silicon resin, (d)
A gas generating agent for an air bag, which comprises an endothermic decomposable substance composed of one or more of metal carbonate and metal oxalate and is granulated or molded with the silicone resin as an inclusion.