JPH0632689A - Gas-generating agent for air bag - Google Patents

Abstract

PURPOSE:To readily form a safe gas-generating agent at a low cost by adding azodicarbonamide (ADCA) and an oxohalogenic acid. CONSTITUTION:(A) One or more kinds of alkali metals halogenate salts are selected from NaClO3, KClO3, NaBrO3 and KBrO3. (B) An alkali metal perhalogenate salt is selected from KClO4, NaClO4, etc. The component A and/or the component B are compounded to obtain (C) an oxohalogenic acid salt. 100-400 pts.wt. of the oxohalogenic acid salt (C) is mixed with 100 pts.wt. of (D) azodicarbonamide and, if necessary, further with (E) a combustion temperature-controlling agent (e.g. sodium carbonate) and/or a combustion rate- controlling agent (e.g. aluminum sulfate) in an amount of approximately 10 pts.wt. per 100 pts.wt. of the sum of the components C and D to produce the gas-generating agent for air bags.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a gas generating agent for an air bag.

[0002]

2. Description of the Related Art When a vehicle such as an automobile collides at high speed, the vehicle is built into the steering wheel by detecting the collision in order to prevent the occupant from being killed or injured by colliding with the steering wheel or windshield of the vehicle. A so-called airbag system in which a nylon bag is inflated is rapidly increasing in demand as safety requirements for automobiles and the like further increase.

In an air bag system, after a collision is detected, it is instantly ignited electrically or mechanically to ignite and burn a gas generating agent to generate gas and inflate the bag. It is essential that such a gas generating agent has appropriate impact ignitability and burning rate. The impact ignitability is the ignition sensitivity to impact, and if it is too sensitive, the danger of explosion increases and it is not preferable for safety. Therefore, it is desirable that impact ignitability is as low as possible. On the other hand, if the burning speed is slow, the bag does not inflate instantly, and it is not useful as an airbag.

Further, the gas generating agent is required to have a not so high combustion temperature. I mean, usually an airbag
In order to absorb the impact when the occupant collides with the inflated airbag or to assist the occupant to escape, some gas is released immediately after the inflation and some contraction occurs, but if the combustion temperature is high The gas temperature rises, causing occupants to burn, etc., or making a hole in the bag to deteriorate its function,
This is because the danger of burning the bag and causing a vehicle fire increases.

Conventionally, as a gas generating agent for an airbag, sodium azide is used as a base, and for example, an oxidizing agent [TiO ₂ ,
Metal oxides such as MnO ₂ and Fe ₂ O ₃ , NaNO ₃ ,
Nitrate such as KNO ₃ and Cu (NO ₃ ) ₂ , KCl
Perchlorate such as O ₄ , NaClO ₄ , KClO ₃ , Na
Chlorates such as ClO ₃ ], metal reducing agents [Zr, M
g, Al, Ti, etc.], cooling agent [Na ₂ CO ₃ , K ₂ C
Those containing additives such as O ₃ , CaCO ₃ , FeSO _{4 and the} like], pH adjusters [iron sulfate and the like], mechanical performance improvers [MoS ₂ , KBr, graphite and the like] are known.

A gas generating agent based on sodium azide has been widely used as a gas generating agent for an air bag because of its excellent properties such as appropriate impact ignitability, burning rate, and relatively low burning temperature. There are problems as shown in.

(1) There is a risk of causing a fire due to decomposition or combustion. Therefore, there is a risk of fire during the manufacturing process (mixing with an oxidizing agent, granulation of the preparation, etc.), and therefore safety management must be strictly performed.

(2) Since it decomposes to produce toxic components such as Na ₂ O and its derivatives (NaOH, etc.), care must be taken in handling during the manufacturing process.

(3) Since the gas generated by the combustion or decomposition of sodium azide has a high nitrogen concentration and a very low concentration of toxic components, there is no problem in practical use, but for the sake of completeness, further reduction of the concentration of toxic components is possible. desired.

(4) Since it is a highly toxic and dangerous substance, there is a capital investment for ensuring safety.

In view of the above problems of sodium azide,
A gas generating agent for airbags, which has impact ignitability, burning rate, gas generation amount, etc. similar to or better than sodium azide, is less dangerous and toxic than sodium azide, and is cheaper is desired. There is.

On the other hand, Japanese Patent Publication No. 49-21171 discloses that
It is suggested that a gas generating agent for an airbag, which is composed of azodicarbonamide, an oxidizing agent such as potassium chlorate, and a metal reducing agent such as Zr or Mg, is not specifically disclosed. This composition thermally decomposes azodicarbonamide using the heat of redox reaction between an oxidizing agent and a metal reducing agent to generate a gas, and the gas generating agent is actually produced and tested. Therefore, it can be seen that the burning rate is insufficient and it cannot be used for an airbag. In addition, since the metal reducing agent itself has a very high impact ignitability, there is a problem that the handling risk is great. Further, theoretically, it is expected that the combustion temperature is very high.

Further, Japanese Patent Application Laid-Open No. 50-118979 discloses
Disclosed is a gas generating agent for an air bag, which comprises an azodicarbonamide and an oxidizing agent such as potassium permanganate, manganese dioxide, barium dichromate, barium peroxide. The impact ignitability and burning rate are not satisfactory when an agent is used, and when an oxidizing agent such as barium dichromate or barium peroxide is used, the generated gas contains a large amount of toxic components. Be done.

[0014]

As a result of intensive studies, the present inventors have focused on azodicarbonamide, which has a very low risk of causing a fire due to decomposition or combustion and has extremely low toxicity, in order to solve the above-mentioned problems of the prior art. , The thermal decomposition of azodicarbonamide using the heat of redox reaction 2
By utilizing the reducibility of azodicarbonamide and directly reacting this with a specific oxidant, rather than a subsequent reaction,
The inventors have completed the present invention by discovering that impact ignitability, combustion rate and gas generation amount, and relatively low combustion temperature, which are equal to or superior to those of sodium azide, can be achieved.

That is, the present invention relates to a gas generating agent for an air bag, which comprises azodicarbonamide and oxohalogenate.

In the present invention, azodicarbonamide is used as the gas generating base. Azodicarbonamide has hitherto been widely used, for example, as a foaming agent for resins, and has a low risk of causing a fire and low toxicity, and therefore a low risk of handling. As the azodicarbonamide, a commercially available product may be used as it is. The shape and size of azodicarbonamide are not particularly limited and may be appropriately selected and used.

Known oxohalogenates can be used. Among them, halogenates and perhalogenates are preferable, and their alkali metal salts are particularly preferable. As the alkali metal salt of a halogenate, for example,
Potassium chlorate, sodium chlorate, potassium bromate,
Examples thereof include chlorates and bromates such as sodium bromate. Examples of alkali metal perhalogenates include perchlorates and perbromates such as potassium perchlorate, sodium perchlorate, potassium perbromate, and sodium perbromate. In the present invention, one or more oxohalogenates can be used. The shape and size of the oxohalogenate salt are not particularly limited and may be appropriately selected and used.

In the composition of the present invention, the compounding amount of the oxohalic acid salt with respect to the azodicarbonamide is usually
The stoichiometric amount may be set so that azodicarbonamide can be completely oxidized and burned on the basis of the amount of oxygen, but by appropriately changing the mixing ratio of azodicarbonamide and oxohalogenate, the burning rate, the burning temperature, the burning Since the gas composition and the like can be adjusted arbitrarily, it may be appropriately selected from a wide range. For example, about 100 to 400 parts by weight, preferably about 120 to 240 parts by weight of oxohalogenate may be added to 100 parts by weight of azodicarbonamide.

The composition of the present invention may contain a combustion temperature adjusting agent and a combustion rate adjusting agent in addition to the above-mentioned essential components as long as the performance thereof is not impaired. Examples of the combustion temperature adjusting agent include carbonates such as Na, K, Ca and Mg, and bicarbonates. Further, examples of the burning rate adjusting agent include sulfates such as Al, Zn, Mn, and Fe. The blending amount of the burning temperature controlling agent and / or the burning rate controlling agent is usually 1 with respect to 100 parts by weight of the total amount of azodicarbonamide and oxohalogenate.
The amount may not exceed about 0 parts by weight, preferably about 5 parts by weight.

Further, the composition of the present invention may contain various additives which have been conventionally used in gas generators for airbags, as long as the performance thereof is not impaired.

The composition of the present invention is produced by mixing the above-mentioned components, and the resulting mixture may be used as it is as a gas generating agent, or may be used as a formulation. Formulation is performed according to a conventional method. For example, an appropriate amount of the composition of the present invention and a binder may be mixed and molded. A commonly used binder can be used. The shape of the preparation is not particularly limited and may be various shapes, for example, pellet shape, disk shape, spherical shape, sucrose shape, tetrapot shape and the like, and may be non-porous. It may have a hole shape (for example, briquette shape).

[0022]

The composition of the present invention has the following excellent effects.

(A) Since the composition has extremely low risk of decomposition or combustion to cause a fire and toxicity, the risk of handling in the manufacturing process is very low. Formulation is also easy.

(B) The present composition has impact ignitability equivalent to or lower than that of sodium azide, and is extremely safe.

(C) The composition has a burning rate and a gas generation amount equal to or higher than that of sodium azide.

(D) Since the composition has a relatively low combustion temperature, there is no danger of injuring an occupant or puncturing the bag, and the amount of toxic components in the generated gas is extremely small.

(E) The composition can be produced at a very low cost.

(F) This composition is easier to recycle than conventional gas generating agents.

[0029]

EXAMPLES The present invention will be further clarified with reference to the following examples and comparative examples.

Examples 1 to 4 and Comparative Examples 1 and 2 Azodicarbonamide (referred to as "ADCA" in the table below) and sodium chlorate (NaClO ₃ ) were mixed at the blending ratio (wt%) shown in Table 1 below. The composition of the present invention was obtained.

60 kg of this composition was produced by a hydraulic tablet press.
The pellet was pressed with a pressure of / cm ² to form a pellet (diameter 5 mm, height 5.0 mm), and the pellet was subjected to the following steel pipe combustion test with nozzle, and its ignitability and combustion time were evaluated. The results are also shown in Table 1.

For comparison, the current gas generating agent (Na
N ₃ -CuO) was subjected to steel combustion test with nozzle. The results are also shown in Table 1.

[Steel Tube Combustion Test with Nozzle I] 1. 5 g of a gas generating agent is placed in a flame-resistant steel container (a cylinder having an inner diameter of 50 mm and a height of 50 mm), a nichrome wire is set, and the lid is closed. The lid has a hole with a diameter of 7 mm.

2. Connect the nichrome wire to the slidac 1
A voltage of 0 V is applied to ignite the gas generant.

3. White smoke first emerges from the hole and then ignites. The flame duration (burn time) from the ignition to the extinction of the flame is measured visually and recorded.

[0036]

[Table 1]

In this test, if the combustion time is about 3 to 5 seconds, the actual inflation time of the airbag is about several tens of milliseconds, which is not a problem in practical use. Therefore, it can be seen from Table 1 that the composition of the present invention has the same performance as the current product containing sodium azide.

[Steel Tube Combustion Test II with Nozzle] In the steel tube combustion test I with nozzle, the ignitability and the combustion time were evaluated in the same manner as above except that the diameter of the nozzle hole was 5 mm. The results are shown in Table 2.

[0039]

[Table 2]

Examples 5 to 9 and Comparative Example 3 Azodicarbonamide (referred to as "ADCA" in the table below), sodium chlorate (NaClO ₃ ) and potassium chlorate (in the proportions (% by weight) shown in Table 3 below) KClO ₃ ) or sodium bromate (NaBrO ₃ ) was mixed to obtain the composition of the present invention.

The composition of the present invention and the current gas generant (Na
The _{N 3 -KClO 4 -Fe 3 O 4} ) was subjected to impact ignitability test. The results are also shown in Table 3.

[Impact Ignition Test] This test is a method for measuring the risk of ignition (impact sensitivity) of a gas generating composition due to impact. The experimental procedure will be described below with reference to FIGS.

1. [FIG. 1] 5 g of a powder sample (2) is weighed into a test stainless steel container (1). The stainless steel container (1) is a stainless steel (SUS304) cylinder with a bottom, and has an inner diameter of 31 mm and an outer diameter of 36.
mm, thickness 2.5 mm, and height 55 mm.

2. [Fig. 2] Place a polyethylene card (3) of the required thickness on the sample. The total thickness of the polyethylene card (3) is called the cap length.

3. [Fig. 3] Two 1 mm thick polyethylene cards (3 ') with a diameter of 6.5
A hole of mm is opened, a detonator (4) is inserted into this hole, and the hole is set in the stainless steel container (1). As the detonator, No. 0 electric detonator manufactured by Nippon Kayaku Co., Ltd. was used.

4. [FIG. 4] In the case of a gas generating agent containing sodium azide, the upper part of the stainless steel container (1) is covered with paraffin (5) to prevent moisture absorption.

5. This stainless steel container is fixed in a vise inside the explosion dome and energized to explode the detonator.

6. At this time, it is observed whether the sample ignites.

Table 3 shows the gap length at the time of ignition (ignition up to that gap length) and the gap length at the time of non-ignition (no ignition above that gap length).

In this test, the longer the gap length, the higher the sensitivity of impact ignitability. That is, the longer the ignition gap length, the higher the explosion sensitivity to impact and the greater the danger.

[0051]

[Table 3]

From Table 3, the composition of the present invention is
It can be seen that it is as safe as or higher than _3- KClO ₄ —Fe ₃ O ₄ ).

From the above results, it is understood that the composition of the present invention has both appropriate impact ignitability and burning rate and is suitable as a gas generating agent.

Examples 10 to 11 and Comparative Examples 4 to 5 Azodicarbonamide (referred to as "ADCA" in the table below)
200 parts by weight of sodium chlorate (NaClO ₃ ) 90
The parts by weight were mixed to obtain the composition of the present invention.

For comparison, a gas generating agent suggested in JP-B-49-21171 was produced. That is, 200 parts by weight of azodicarbonamide, 90 parts by weight of sodium chlorate and 10 parts by weight of Zr powder were mixed to obtain a comparative composition.

Each of these was molded into pellets (diameter 5 mm, height 5.0 mm) in the same manner as in Example 1 and subjected to a nozzle-equipped steel pipe combustion test and impact ignition test. that time,
Whether or not a flame was generated was also observed. The results are shown in Tables 4 and 5.

[0057]

[Table 4]

From Table 4, it can be seen that the safety of the gas generating agent is remarkably increased by adding the metal reducing agent such as Zr.
Further, the reaction (combustion) of the composition of the present invention is carried out without flame and at a low temperature, but the comparative composition containing Zr undergoes flammable combustion and the temperature of the reaction product (gas) becomes high. Therefore, it is not preferable to add a metal reducing agent such as Zr, Al or Mg to the composition of the present invention.

[0059]

[Table 5]

From Table 5, it can be seen that the comparative composition containing Zr burns with flame and the temperature of the reaction product (gas) increases.

Example 12 This composition was subjected to a strand burner test (see, for example, Industrial Explosives Association 1992 Annual Meeting, Proceedings, "Combustion Characteristics of Sodium Azide Gas Generating Agents", pp. 98-99). ) And examined its flammability.

1. First, 30 parts by weight of azodicarbonamide and 70 parts by weight of sodium perchlorate were mixed to obtain a composition of the present invention.

2. This composition has a prismatic shape (8 mm × 5 mm ×
Pressure molding to 50 mm (pressure: 1.25 t / c)
m ² ), and a silicone resin was applied as a restrictor to the side surface of this prism to prepare a sample.

3. A chimney-type strand combustion test device was used for this test. About 40m on the sample
Two holes (diameter 0.6 mm) were opened at intervals of m, and fixed in the device through a fuse (diameter 0.5 mm).

4. After setting the test temperature (20 ° C.) in this state, the sample was burned by igniting it from above with a nichrome wire, and the burning rate (mm / sec) was calculated from the difference in the fusing time of the two fuses and the gap between the holes. .

5. This measurement is performed at 10 kgf / cm ² and 4
It was carried out under a pressure of 0 kg / cm ² .

[0067] As a result, the misfire at the time of 10kgf / cm ^2, at the time of 40kgf / cm ² was 48.3mm / sec.

[Brief description of drawings]

FIG. 1 is a diagram showing a procedure of an impact ignition test.

FIG. 2 is a diagram showing a procedure of an impact ignition test.

FIG. 3 is a drawing showing a procedure of an impact ignition test.

FIG. 4 is a drawing showing a procedure of an impact ignition test.

[Explanation of symbols]

 1 Stainless steel container 2 Powder sample 3 Polyethylene card 3'Polyethylene card 4 Detonator 5 Paraffin

Claims (6)

[Claims] 1. A gas generating agent for an airbag, which comprises azodicarbonamide and an oxohalogenate. 2. The gas generating agent according to claim 1, wherein the oxohalogenate is a halogenate and / or a perhalogenate. 3. The gas generating agent according to claim 2, wherein the halogenate is an alkali metal halogenate. 4. The gas generating agent according to claim 3, wherein the alkali metal halide is at least one selected from potassium chlorate, sodium chlorate, potassium bromate and sodium bromate. 5. The gas generating agent according to claim 2, wherein the perhalogenate is an alkali metal perhalogenate. 6. The gas generating agent according to claim 5, wherein the alkali metal perhalogenate is at least one selected from potassium perchlorate, sodium perchlorate, potassium perbromate and sodium perbromate. .