JPH06219881A - Gas generating agent composition - Google Patents

Abstract

PURPOSE:To obtain a gas generating agent composition free from the deterioration of performance eve in a severe environment for a long time by compounding an alkali metal azide or an alkali earth metal azide, an inorganic oxidizing agent and a fused silica. CONSTITUTION:The gas generating agent composition is obtained by compounding an alkali metal azide or on alkali earth metal azide (sodium azide is particularly preferable), an inorganic oxidizing agent (e.g. potassium nitrate) and a fused silica. By using the fused silica, the gas generating agent composition free from the deterioration of the performance even in severe environment for a long time, particularly the gas generating agent composition for automobile air bag to expand an air bag for protecting automobile drivers and companions is obtained.

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, and more particularly to a gas generant composition for an automobile airbag for inflating an airbag for protecting a vehicle driver and passengers.

[0002]

2. Description of the Related Art Inflatable air bags for protecting a driver and a passenger in a vehicle accident are already well known. Usually, these airbags detect a violent collision with another object or a vehicle by an appropriate electric or mechanical sensing device, and use a combination of means such as ignition and transfer to finally generate a gas generating composition. A large amount of gas is quickly generated by burning an object, and by guiding this gas to a bag, an air cushion state is formed, supporting the body of the driver and passengers, and protecting from the impact in the event of a collision. It is a mechanism to do.

Therefore, the following properties are required for the gas generating composition. a) Since it is necessary to operate the above-mentioned mechanism at the time of collision, 3
Complete the generation of gas within the time of 0 to 60 milliseconds. b) The generated gas is non-toxic and non-corrosive because it is released into the vehicle after supporting the body of the vehicle occupant as an air cushion. c) Do not generate much heat that could cause damage or burns to the airbag itself or the vehicle occupants. d) Capability of maintaining performance for a long period of at least 10 to 15 years. A conventional gas generating composition for an air bag is disclosed in JP-A-49-50.
110, 49-113781, 49-131977.
No. 51-126981, etc., mainly reacting an alkali metal azide with an oxidizing agent or a metal oxide and an alkali metal or its oxide by-produced from the reaction thereof.
It consists of substances that adsorb. A silicic acid compound is often used as a substance that reacts and adsorbs these oxides, and they contain water in the form of crystallization water, bound water, or adsorbed water.

Alkali metal azides, which are the main components of the gas generant composition, such as commonly used sodium azide, react with water to generate explosive and extremely toxic hydrogen azide gas. Generally, the gas generant composition for an air bag is placed in a closed container in order to prevent moisture absorption. However, when the vehicle is installed for a long period of time, water in the air in the closed container system and water in the composition decompose sodium azide to generate hydrogen azide gas.
When the amount of water is large, the internal pressure of the closed container rises due to the generation of gas and the temperature rise, and when it is excessive, the seal may be broken. In this case, since the sodium azide is further decomposed by its water content due to the inflow of air from the seal breaking portion, it is possible that the bag does not fully deploy or does not open at all when it is required to operate as an airbag system.

[0005]

SUMMARY OF THE INVENTION It is desirable to use substances free of water of crystallization, bound water and adsorbed water in order to minimize the water content in the gas generant composition.

[0006]

Means for Solving the Problems As a result of intensive studies by the present inventors, the case where a gas generant composition was stored under severe conditions for a long period of time by using silicic acid anhydride which is fused silica as a silicic acid compound. It was also found that the decomposition of sodium azide was extremely reduced. High-purity sodium azide has almost no hygroscopicity, and its loss on drying is 0.1
% Or less. As the substance used as the oxidizing agent, it is possible to select a substance having no hygroscopic property such as potassium nitrate and potassium perchlorate. However, as mentioned above, the silicic acid compound that reacts and adsorbs the by-produced alkali metal is crystal water.
Many of them contain water in the state of bound water / adsorbed water 50
Some exceed%. Generally, silica (hydrous silicon dioxide) has 8 to 10% of bound water / adsorbed water. Since these waters are gradually released by heating for a long period of time, when such a substance is used in the gas generant composition, sodium azide is decomposed, resulting in the malfunction of the airbag system as described above. Happens.

For the silicic acid anhydride, low specific gravity fine particles produced by vapor phase reaction synthesis such as the commonly known trade names “Aerosil” and “Cab-Osil”, and the high trade name “High Safer” (manufactured by Kinsei Kogyo Co., Ltd.) There are two types of high specific gravity fused silica obtained by melting and crushing pure silica. The low specific gravity fine particles are anhydrous at the time of production due to the presence of silanol groups on the surface, but absorb moisture during storage and have adsorbed water. However, since fused silica has no hygroscopicity, it does not have water such as adsorbed water.

In the case of fine particles of low specific gravity such as Aerosil, when a sufficient amount to react and adsorb the alkali component generated by the reaction of sodium azide and the oxidizing agent is mixed, the bulk specific gravity of the mixed powder is small and the desired weight is obtained. Is difficult to mold.
Further, since the difference in specific gravity from other raw materials is large and the powder is separated, the composition is changed and it cannot be used as a gas generant composition. On the other hand, since fused silica has the same specific gravity as other components, it does not cause any difficulty in tablet molding or powder separation.

That is, the present invention relates to a gas generant composition comprising an alkali metal azide or an alkaline earth metal azide, an inorganic oxidizing agent and fused silica.

Examples of the alkali metal azide or alkaline earth metal azide used in the present invention include sodium azide, potassium azide, magnesium azide, calcium azide, barium azide and strontium azide. Sodium is particularly preferred. These are preferably used in the range of 50 to 80% by weight based on the total amount of the gas generant composition.

The inorganic oxidizing agent used in the present invention includes
Examples thereof include one or a mixture of two or more of alkali metal or alkaline earth metal nitrates or perchlorates, alkaline earth metal or aluminum sulfates, transition metal oxides and the like.

Specifically, potassium nitrate, sodium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, potassium perchlorate, sodium perchlorate, magnesium perchlorate, calcium perchlorate, strontium perchlorate, magnesium nitrate, Calcium sulfate, strontium sulfate, aluminum sulfate, ferric oxide, nickel oxide, manganese dioxide, copper oxide, titanium dioxide, tin dioxide and the like can be mentioned, and potassium nitrate, potassium perchlorate, aluminum sulfate, ferric oxide, copper oxide. Etc. are particularly preferable. These are 10 to 4 relative to the total amount of the gas generant composition.
It is preferably used in the range of 0% by weight.

As the fused silica used in the present invention, both quartz glass and fused silica can be used, and they are used in the range of 1 to 40% by weight based on the total amount of the gas generating composition. preferable.

The production of the gas generating composition of the present invention is carried out in the same manner as in the production of a general gas generating composition for an air bag, for example, by uniformly mixing with a general mixer such as a ball mill or a V-type mixer, and a single shot. Diameter 3 by rotary type tablet machine or rotary tablet machine
It is produced in the form of tablets having a thickness of about 15 mm and a thickness of about 1 to 10 mm. However, if the tablets are compressed as they are, capping of the tablets and, in the worst case, laminating may occur, so if a lubricant such as talc, calcium stearate, or magnesium stearate is added thereto,
Very glossy or firm homogeneous tablets can be formed continuously for long periods of time. The lubricant is optionally used in the range of 5% by weight or less with respect to the total amount of the gas generating composition, but the range of 0.1% by weight to 2% by weight is particularly preferable.

[0015]

The present invention will be described in more detail with reference to the following examples. Example 1. 57 parts by weight of sodium azide, 17 parts by weight of potassium nitrate, and 26 parts by weight of fused silica (HISEFTER manufactured by Kinsei Kogyo Co., Ltd.) were mixed in a ball mill at a speed of 60 rpm for 20 minutes. Magnesium stearate 0.
After adding 5 parts by weight and mixing for 1 minute, a tablet having a diameter of 5 mm and a thickness of 3 mm was molded with a single-shot tableting machine (Kikusui Seisakusho 6B-2 type). The molded tablet was dried at 105 ° C. for 2 hours, and the heating loss was measured. In a 1000 cc hermetically sealed stainless steel container with a pressure sensor attached, 25 g of this tablet was taken out,
A combustion test was conducted to measure the maximum peak pressure and the time required to reach the maximum peak pressure of the generated gas by electrically igniting and burning the igniter of boron / silver stone. Then, the tablets are placed in a closed container, and a cycle test of 105 ° C. × 6 hours and 5 ° C. × 6 hours is performed for 500 cycles. After that, the change in weight of the tablet after the test and the burning test as described above were performed.

Example 2. 70 parts by weight of sodium azide,
22 parts by weight of aluminum sulfate, 8 parts by weight of fused silica and 0.5 part by weight of magnesium stearate were used in Example 1. Mixed and tableted in the same manner as. Further, the weight loss on heating, the combustion test, the cycle test and the weight loss were measured in the same manner as in Example 1.

Embodiment 3. 65 parts by weight of sodium azide,
23 parts by weight of ferric oxide, 12 parts by weight of fused silica and 0.5 parts by weight of magnesium stearate were mixed and tableted in the same manner as in Example 1. Further, the weight loss on heating, the combustion test, the cycle test and the weight loss were measured in the same manner as in Example 1.

Comparative Example 1. 57 parts by weight of sodium azide,
17 parts by weight of potassium nitrate, 26 parts by weight of hydrous silicon dioxide and 0.5 part by weight of magnesium stearate were used in Example 1.
Mixed and tableted in the same manner as. Further, the weight loss on heating, the combustion test, the cycle test and the weight loss were measured in the same manner as in Example 1.

Comparative Example 2. 70 parts by weight of sodium azide,
22 parts by weight of aluminum sulfate, 8 parts by weight of hydrous silicon dioxide and 0.5 part by weight of magnesium stearate were mixed and tableted in the same manner as in Example 1. Further, the weight loss on heating, the combustion test, the cycle test and the weight loss were measured in the same manner as in Example 1.

Comparative Example 3. 65 parts by weight of sodium azide,
23 parts by weight of ferric oxide, 12 parts by weight of hydrous silicon dioxide and 0.5 part by weight of magnesium stearate were mixed and tableted in the same manner as in Example 1. Further, the weight loss on heating, the combustion test, the cycle test and the weight loss were measured in the same manner as in Example 1. The compositions of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1.
Summarized in. (In Table 1, the unit is parts by weight.)

[0021]

Table 1 Table 1 Example 1 2 3 Comparative example 1 2 3 Sodium azide 57 70 65 57 70 65 Potassium nitrate 17 17 Aluminum sulfate 22 22 Ferric oxide 23 23 Fused silica 26 8 12 Hydrous silicon dioxide 26 8 12 Stearin Magnesium acid 0.5 0.5 0.5 0.5 0.5 0.5

Table 2 shows the weight loss on heating in Examples 1 to 3 and Comparative Examples 1 to 3, the maximum peak pressure and the maximum peak time in the initial combustion test, the weighting of the tablet after the cycle test, and the combustion test value.

[0023]

[Table 2]

The following can be seen from Table 2. The examples and comparative examples show equivalent characteristics in the initial combustion test.
Further, the results of the combustion characteristics and the weight after 500 cycles in the examples are hardly changed. On the other hand, the combustion characteristics after 500 cycles in the comparative example changed significantly,
Low pressure and low combustion. In addition, the weight reduction of the tablets is large as compared with the examples.

This is because the adsorbed water content contained in the tablets was removed as a heat loss during the initial heating, and the water content in the Examples was almost eliminated, so that the combustion characteristics and weight after the cycle test were hardly changed. However, in the comparative example, the bound water contained in silica (hydrous silicon dioxide) is released as water vapor into the system due to the high temperature environment,
During cooling, it condenses and reacts with sodium azide to decompose. Therefore, there is a possibility that the weight of the tablet is greatly reduced and the combustion characteristics are greatly changed, and the airbag does not deploy under desired conditions. Therefore, it can be seen that the use of fused silica in the gas generant composition greatly contributes to the stabilization of combustion characteristics for a long period of time.

[0026]

INDUSTRIAL APPLICABILITY According to the present invention, by using fused silica, a gas generant composition whose performance does not deteriorate even in a long-term harsh environment is obtained.

Claims (1)

[Claims] 1. A gas generating composition comprising an alkali metal azide or an alkaline earth metal azide, an inorganic oxidizing agent and fused silica.