JPH06298587A - Gas production agent composition - Google Patents

Abstract

PURPOSE:To enable the reduction in the amount of a coolant in a gas producer and miniaturize the gas producer substantially without producing carbon monoxide in a system without containing sodium azide by increasing the amount of a produced gas and suppressing the combustion temperature to a low value. CONSTITUTION:A pelletlike gas producing agent 7 is filled and arranged in a combustion chamber 3 in a gas producer 1. This gas producing agent composition consists essentially of cellulose acetate and potassium perchlorate and contains <=36wt.% metallic salt hydrate of bitetrazole. A manganese salt dihydrate of the bitetrazole is suitable as the metallic salt hydrate of the bitetrazole due to no formation of corrosive residues after burning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas generant composition used in a gas generator for inflating an air bag (hereinafter, simply referred to as a gas generator).

[0002]

2. Description of the Related Art An airbag is mounted on, for example, a steering wheel in a passenger compartment of an automobile and inflates in the event of a collision to protect an occupant. As a gas generating agent used to inflate this airbag, one containing sodium azide and various oxidants as main components is known, and by burning this, nitrogen gas is generated to generate an airbag. Inflate.

A gas generating agent containing sodium azide as a main component is preferable as a gas generating agent because it produces only clean nitrogen gas as a gas component when burned. However, sodium azide is highly toxic and easily forms a sensitive explosive substance when it comes into contact with an acid or a heavy metal. Therefore, it is necessary to pay particular attention during production and disposal. Further, since the gas generating agent containing sodium azide as a main component produces a large amount of corrosive sodium and sodium compounds after combustion, it is necessary to carry out these treatments at the time of disposal.

In order to solve this problem, gas generant compositions which do not use sodium azide have been studied in various fields. For example, Japanese Patent Publication No. 58-20919 discloses a composition comprising the following (a), (b) and (c). That is, the composition is (a) 78 to 92% by weight of an oxidizing agent which is a chlorate or perchlorate of an alkali metal or an alkaline earth metal, (b) cellulose acetate 7.9 to 17.2% by weight, (C) It is composed of a mixed explosive having 0.1 to 0.8% by weight of a combustion control agent containing carbon. As the carbon-containing combustion modifier, for example, acetylene black or graphite is used.
And this composition produces substantially no carbon monoxide,
A product gas consisting of water, carbon dioxide and oxygen is generated under standard conditions at about 0.36 liter / g.

[0005]

However, since the gas generant composition described in the above publication has a very high combustion temperature, when it is used by being incorporated in a gas generator,
It is necessary to sufficiently cool the produced gas in order to prevent the airbag from being burnt. Therefore, a large amount of coolant is required inside the gas generator, which is an obstacle to downsizing the gas generator.

[0006] In general, to reduce the size and weight of a gas generator, the required amount of gas generating agent per gas generator is reduced by increasing the amount of gas generated per unit weight of gas generating agent. Will be achieved at a higher level. However, such a reduction in size and weight has not yet been fully achieved.

The present invention has been made by paying attention to such a problem of the prior art. The purpose is a gas generant composition containing no sodium azide, which does not substantially generate carbon monoxide, produces a large amount of gas, and suppresses the combustion temperature to a low level, so that An object of the present invention is to provide a gas generant composition which can reduce the amount of a coolant and can reduce the size of a gas generator.

[0008]

In order to achieve the above object, in the gas generant composition of the present invention, cellulose acetate and potassium perchlorate are the main components, and a hydrate of bitetrazole metal salt is used. It is characterized by containing less than or equal to wt%.

Next, the respective constituents of the present invention will be described in order. Cellulose acetate is a combustible substance composed of carbon, hydrogen and oxygen, and when mixed with an oxidant and burned, it produces a large amount of carbon dioxide, water and oxygen. Cellulose acetate is soluble in a specific solvent and has a paste-like shape when dissolved, so when mixed with powder such as an oxidizing agent, it enters the gap between the powders and acts as a binder. It has the action of.

At this time, in order to fully exert the action as a binder, the blending amount of cellulose acetate is preferably 8% by weight or more. 8% by weight of cellulose acetate
If it is less than the above range, it is not suitable because it is difficult to completely cover the powder component such as the oxidizing agent with cellulose acetate. On the other hand, the upper limit of the blending amount of cellulose acetate is determined by the condition that carbon monoxide is not substantially generated when the gas generating composition is burned.

Here, the condition that carbon monoxide is not substantially produced is that the concentration of carbon monoxide in the produced gas is 50.
It means that it is less than 00 ppm. The upper limit of the blending amount of cellulose acetate for satisfying this condition varies depending on the blending ratio of potassium perchlorate and bitetrazole metal salt hydrate, and is preferably 26% by weight or less. Therefore, the preferable blending amount of cellulose acetate is in the range of 8 to 26% by weight.

[0012] Potassium perchlorate is an oxidizing agent. Among the oxidizing agents, the amount of oxygen released per unit weight is large, the thermal stability is excellent, the hygroscopicity is low, and most of the residue after combustion is not corrosive. Becomes potassium chloride. Therefore, potassium perchlorate is the most preferable as the oxidizing agent to be added to the gas generating composition. The particle size of potassium perchlorate is not particularly limited as long as it is in the range of 5 to 300 μm, but two or more kinds of powders having different particle sizes should be blended so as to have a close-packed structure. Is preferred. The amount of potassium perchlorate to be blended is preferably in the range of 55 to 87% by weight in order to produce 8% by weight or more of cellulose acetate without substantially producing carbon monoxide.

The hydrate of bitetrazole metal salt is a hydrate of a substance in which the hydrogen group of bitetrazole (C ₂ N ₈ H ₂ ) is replaced with a metal, and a typical example thereof is a hydrate of bitetrazole manganese salt. Hydrate (C ₂ N ₈ Mn 2H ₂ O), dihydrate of bitetrazole calcium salt (C ₂ N ₈ Ca 2
H ₂ O) etc. The hydrate of bitetrazole metal salt is
It has excellent thermal stability, and when mixed with potassium perchlorate and burned, it produces a large amount of nitrogen, carbon dioxide, water and oxygen. Among the hydrates of the bitetrazole metal salt, the dihydrate of the bitetrazole manganese salt is most preferable because it does not generate a corrosive residue after combustion.

The hydrate of the metal salt of bitetrazole may be not only dihydrate but also monohydrate or trihydrate or more. However, the anhydride is not suitable because it has no effect of suppressing the increase in combustion temperature.

The hydrate of bitetrazole metal salt is
Since the heat of formation is large, the combustion temperature can be suppressed to a low level by blending it with the above-mentioned gas generant composition comprising cellulose acetate and potassium perchlorate. That is, the combustion temperature of the gas generant composition is determined by the amount of heat generated by the reaction of cellulose acetate, hydrate of bitetrazole metal salt and potassium perchlorate. on the other hand,
This calorific value is calculated as a value obtained by subtracting the heat of formation of the hydrate of the bitetrazole metal salt of the base system from the heat of formation of the reaction product of the formation system. Therefore, when the heat of formation of the hydrate of the bitetrazole metal salt increases, the calorific value decreases, and as a result, the rise in combustion temperature is suppressed.

The combustion temperature can be further lowered as the amount of the hydrate of the bitetrazole metal salt compounded increases. However, when the content of this hydrate exceeds 36% by weight, the content of cellulose acetate is less than 8% by weight in order to substantially not generate carbon monoxide, and as described above, the cellulose acetate is powdered. Inability to completely cover body components. Therefore, the blending amount of the hydrate of this bitetrazole metal salt is
It is not more than 36% by weight, and is unsuitable if it exceeds 36% by weight.

The particle size of the hydrate of the bitetrazole metal salt is not particularly limited, but a particle size of 30 μm or less is preferable in order to obtain good combustion characteristics.
In the gas generant composition of the present invention, if necessary, a part of cellulose acetate may be triacetin (C ₃ H ₅ (OCOC).
H ₃ ) ₃ ), diethyl phthalate, dimethyl phthalate, and the like, and cellulose acetate can be substituted with a plasticizer having a good affinity with cellulose acetate. Of these plasticizers, triacetin is preferable because it has the highest oxygen content and does not require a large amount of oxidizing agent. If necessary, a combustion modifier such as metal powder or carbon black can be added.

Since the gas generant composition of the present invention constructed as described above does not contain sodium azide, it is easy to handle and there is no risk of producing corrosive sodium or sodium compounds. Further, since substantially no carbon monoxide is produced in the produced gas, safety is high, and moreover, the produced gas amount is large, so that the airbag can be surely deployed. In addition, since the combustion temperature of the gas generating agent can be kept low, it is possible to reduce the amount of the coolant in the gas generating apparatus, and the gas generating apparatus can be downsized.

[0019]

The gas generant composition of the present invention is a composition containing cellulose acetate and potassium perchlorate as main components, and as a means for producing a large amount of nontoxic gas and lowering the combustion temperature that is too high. , A hydrate of bitetrazole metal salt is used. The content of the hydrate of the bitetrazole metal salt is 36% by weight or less. Then, the hydrate of bitetrazole metal salt reacts with potassium perchlorate to produce a large amount of nontoxic gas. Further, since the heat of formation of the hydrate of the bitetrazole metal salt is large, the amount of heat generated by the reaction between the hydrate and potassium perchlorate is reduced, and the rise in combustion temperature can be suppressed.

[0020]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. (Example 1) As a raw material mixture, 11% by weight of cellulose acetate having a degree of acetylation of about 53% (manufactured by Teijin Ltd.), 4% by weight of triacetin (manufactured by Daihachi Chemical Industry Co., Ltd.) as a plasticizer,
55 wt% potassium perchlorate (manufactured by Japan Carlit Co., Ltd.) having an average particle size of 17 μm, and a bitetrazole manganese salt dihydrate having an average particle size of 22 μm (Toyo Kasei Co., Ltd.)
A composition of 30% by weight was prepared. A proper amount of a mixed solvent of acetone and methyl alcohol was added to this and mixed uniformly to prepare a drug mass.

Next, this drug mass was loaded into a companding machine. A die with a diameter of 4 mm is attached to the compander in advance.
The drug mass is extruded by being passed through this die by pressure and formed into a rod shape. The molded product was cut into a length of 2 mm and dried to obtain a pelletized gas generant composition.

This gas generating composition was prepared by Shimadzu Corporation
Pyrolysis Gas Chromatography (Model: GC-1
4A) was used to determine the composition of the produced gas at the time of combustion at 800 ° C. and the amount of produced gas in the standard state.

Separately from this, the pelletized gas generant composition was loaded into the gas generator shown in FIG. 1 so that the amount of produced gas in the standard state was about 30 liters. That is, in the figure, a gas generator 1 formed in a cylindrical shape has an ignition chamber 2 arranged at the center thereof,
A combustion chamber 3 concentrically formed on the outer periphery thereof and a cooling collection chamber 4 concentrically formed on the outer periphery thereof are provided.

The electric igniter 5 and the ignition charge 6 are arranged in the ignition chamber 2 and are ignited when energized. The pelletized gas generating agent 7 is loaded into the combustion chamber 3 and burns with a flame due to ignition of the ignition charge 6 to generate a gas such as nitrogen gas. The cooling and collecting materials 8 and 9 are arranged in the combustion chamber 3 and the cooling and collecting chamber 4, and cool the produced gas and filter and collect the solid combustion residue.

The plurality of ventilation holes 10 and 11 are provided in the partition wall between the ignition chamber 2 and the combustion chamber 3 and the partition wall between the combustion chamber 3 and the cooling collection chamber 4, respectively, and the flame is propagated or generated by the ignition of the ignition charge 6. Circulates gas. The gas ejection holes 12 are provided on the peripheral wall of the cooling / collecting chamber 4 so that the gas cooled in the cooling / collecting chamber 4 is ejected into an airbag (not shown).

When the ignition charge 6 is ignited by the igniter 5 on the basis of a signal at the time of a vehicle collision or the like, the flame is propagated to the combustion chamber 3 through the ventilation hole 10 and the combustion chamber 3
The gas generating agent 7 therein burns to generate gas. This generated gas is passed through the cooling / trapping material 8 and the ventilation hole 11 to cool the / trapping chamber 4
Will be introduced in. This gas is further ejected from the gas ejection hole 12 via the cooling and collecting material 9.

Next, the temperature inside the tank when this gas generator 1 was mounted in a tank of 60 liters and operated was measured with an alumel chromel type thermocouple having a wire diameter of 50 μm. The results are shown in Table 1. The amount of produced gas in Table 1 indicates the total volume of carbon dioxide, water, oxygen and nitrogen produced when 1 g of the gas generant composition is burned in the standard state. (Examples 2 to 5) With the composition shown in Table 1, a gas generant composition was produced in the same manner as in Example 1, and the respective properties were evaluated by the same method. The results are shown in Table 1. (Comparative Examples 1 and 2) With the composition shown in Table 1, a gas generant composition was produced in the same manner as in Example 1, and the respective characteristics were evaluated by the same method. The results are shown in Table 1. (Comparative Example 3) In Example 1, a bitetrazole manganese salt (anhydrous salt) obtained by firing a bitetrazole manganese salt dihydrate at 200 ° C instead of the bitetrazole manganese salt dihydrate. It was used. Otherwise, a gas generant composition was produced by the same method as in Example 1, and the respective characteristics were evaluated by the same method. The results are shown in Table 1.

[0028]

[Table 1]

As shown in Table 1, in each example, 36 wt% or less of a dihydrate of a bitetrazole manganese salt as a hydrate of the bitetrazole metal salt of the present invention was blended. Therefore, in any of the examples, the amount of produced gas is secured, the harmful CO concentration in the produced gas can be kept low, and the gas temperature in the tank can be kept low. Further, even when triacetin is not contained (Example 5), all the properties are well balanced and maintained well.

On the other hand, when the hydrate of the bitetrazole metal salt is not contained (Comparative Example 1), the gas temperature in the tank rises and the amount of produced gas is small. Further, when the amount of the hydrate of bitetrazole metal salt exceeds 36% by weight (Comparative Example 2), the CO concentration in the produced gas increases extremely. Furthermore, when an anhydrous salt of bitetrazole metal salt is used (Comparative Example 3), the CO concentration in the produced gas increases and the gas temperature in the tank rises.

[0031]

As described in detail above, the gas generant composition of the present invention is a gas generant composition containing no sodium azide, does not substantially generate carbon monoxide, and does not generate gas. Since the amount is large and the combustion temperature is kept low, the amount of the coolant in the gas generator can be reduced, and the gas generator can be downsized, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a gas generator containing a gas generant composition embodying the present invention.

[Explanation of symbols]

 1 ... Gas generator, 7 ... Gas generating agent.

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[Procedure amendment]

[Submission date] October 14, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

The hydrate of bitetrazole metal salt is
Since the heat of formation is small , the combustion temperature can be kept low by blending it with the above-mentioned gas generant composition comprising cellulose acetate and potassium perchlorate. That is, the combustion temperature of the gas generant composition is determined by the amount of heat generated by the reaction of cellulose acetate, hydrate of bitetrazole metal salt and potassium perchlorate. on the other hand,
This calorific value is the hydrate of the original bitetrazole metal salt.
It is calculated as a value obtained by subtracting the heat of formation of the reaction product, which is the generation system, from the heat of formation such as. Therefore, when the heat of formation of the hydrate of the bitetrazole metal salt decreases , the calorific value decreases, and as a result, the rise in combustion temperature is suppressed.

Claims (1)

[Claims] 1. A gas generant composition comprising cellulose acetate and potassium perchlorate as main components and containing a hydrate of bitetrazole metal salt in an amount of 36% by weight or less.