JPH05879A - Gas generating agent tablet - Google Patents

Abstract

PURPOSE:To enhance the physical strength of the tablet and to maintain an initial combustion rate over a long period by compounding hydrotalcite into a gas generating agent compsn. for an air bag and tableting the mixture. CONSTITUTION:The tablets having 3 to 15mm diameter and 1 to 10mm thickness are obtd. by uniformly mixing 40 to 90wt.% (hereafter %) alkaline metal azide (e.g.: sodium azide), 10 to 60% inorg. oxidizing agent (e.g.: sodium nitrate) or metal oxide (e.g.: copper oxide), 0 to 40% material (e.g. silicon dioxide) which bring the mists of alkaline metals and their oxides byproduced after the generation of gaseous nitrogen by combustion of the alkaline metal azide and oxide into reaction and adsorb and solidify these mists, 0 to 5% lubricant (magnesium stearate), and a proper ratio inorg. binder (e.g.: dibasic calcium phosphate) as binder, 0.1 to 15% natural or synthetic hydrotalcite by a general mixer, such as ball mill or V-shaped mixer, and tableting the mixture by a single shot type or rotary type tableting machine at 3 to 15mm diameter and 1 to 10mm thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas generant tablet for inflating an airbag for protecting a vehicle driver and a passenger.

[0002]

Inflatable airbags for protecting drivers and passengers in vehicle accidents 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 fire to finally produce a gas generant composition. A mechanism for rapidly generating a large amount of gas by burning and forming an air cushion state by guiding this gas to a bag to support the body of the driver and passengers, thereby protecting the vehicle from the impact at the time of a collision. Has become.

Since it is necessary to operate the above-mentioned mechanism within a short time at the time of collision, the gas generant composition contains 30 to 60 parts.
It is necessary to have combustion characteristics that complete the reaction within a relatively short limited time of millisecond.

Generally, a gas generating agent is formed by molding a powder or granules by a tableting molding machine. When the gas generating agent is mounted in a vehicle as an airbag system for a long period of time, the tablet formed by vibration is worn out and powdered, or cracked when it is unacceptable. It may happen. In such a state, the above-mentioned combustion speed may be affected and an abnormally high combustion speed may be exhibited. Then, not only the airbag does not deploy at a desired time, but also the airbag itself may be ruptured or, if it is left unattended, the metal container containing the gas generating agent may explode and cause serious damage to an occupant.

Therefore, it is necessary to increase the strength of the tablet against vibration, but there are few matters relating to the strength of the tablet and the binder in the Japanese published patent of the gas generating agent, such as those disclosed in JP-A-49-113781, JP-A-49-113782 and JP-A-49-113782. 50-
72881, 63-2242987, 2-8848.
8, 2-2333577, 2-302388, 3-
65584 etc. Of these, the strength measurement of tablets is described in JP-A-49-113781 and JP-A-49-11378.
2, the measurement of the compressive strength of the tablet in the hut-type hardness type, and Erwek in JP-A-3-65584.
a) There is only a description of the tensile strength of the tablet depending on the device. Further, the method of measuring the strength cannot be said to be appropriate as a method of evaluating the durability of the tablet against vibration.

[0006]

SUMMARY OF THE INVENTION It is desired that the gas generant maintains stable combustion characteristics for a long period of time by strengthening the compression-molded gas generant tablet and preventing powdering and cracking against vibration.

[0007]

Means for Solving the Problems As a result of earnest research by the present inventors, by mixing a gas generating agent composition with a specific substance, and mixing and molding the mixture, the composition is vibrated more than the conventional gas generating agent tablet. The present invention has been accomplished by finding that it becomes possible to produce a tablet that is remarkably strong against the physical impact of. That is, the present invention is a gas generant tablet characterized by comprising hydrotalcite in a gas generant composition and compression molding.

The production of the gas generant tablet of the present invention is the same as that of a general gas generant tablet for an air bag, and the composition is uniformly mixed by a general mixer such as a ball mill or a V-type mixer, and a single shot type or With a rotary tablet press, the diameter is usually 3 ~
It is manufactured in the form of tablets having a thickness of 15 mm and a thickness of 1 to 10 mm.

The gas generant composition used in the present invention comprises, for example, an alkali metal azide as a main component and an inorganic oxidant and / or a metal oxide, as in the case of a general gas generant composition for airbags, and if necessary. These are blended with a substance that reacts and adsorbs mist of alkali metal or its oxide produced as a by-product after burning and nitrogen gas generation to solidify.

As the alkali metal azide, for example, sodium azide, potassium azide, etc. are used, and are usually used in the range of 40% by weight to 90% by weight, preferably 50% by weight, based on the total composition of the gas generating agent. Used in the range of up to 75% by weight. Examples of the inorganic oxidizing agent include alkali metal nitrates, alkali metal perchlorates, metal sulfates, and the like, and potassium nitrate, sodium perchlorate, aluminum sulfate and the like are used. Further, as the metal oxide, for example, copper oxide ferric oxide or the like is used. These oxidizing agents are usually used in the range of 10% by weight to 60% by weight, more preferably 15% by weight to 40% by weight, based on the total composition of the gas generating agent.
Used in the weight% range.

As the substance for reacting and adsorbing the mist of alkali metal or its oxide by-produced after the alkali metal azide and the oxidant are burned to generate nitrogen gas and solidify, a general formula (Al2O3) m (MxO) is used. n (SiO2) p ・ q
H2O

(Where M is Li, Na, K, Sr, Mg
Alternatively, it represents Ca, and X represents 1 or 2. m, n, p,
q represents 0 or a positive number. However, m, n, p, and q do not become 0 at the same time. )

The compounds represented by the following are used, for example, alumina Al2O3, silicon dioxide SiO2, magnesium aluminate Al2O3MgO, calcium silicate CaO.
SiO2, magnesium aluminosilicate Al2O3M
gO (SiO2) XH2O (X: indicates 0 to 10) and the like. The amount of the compound added is usually 0% to 40% by weight.
However, it is preferably used in the range of 10% by weight to 30% by weight.

It is also possible to add a stearate as a lubricant to the gas generant composition. Aluminum stearate, magnesium stearate, calcium stearate, etc. are used as stearates. Lubricant is usually 0% to 5% by weight based on the total composition of the gas generating agent.
However, it is preferably used in the range of 0.1% by weight to 1% by weight.

A common method of increasing tablet strength is to incorporate a binder into the composition. As the binder, there are an organic binder and an inorganic binder, but the organic binder has a stronger binding force. However, when the organic binder is mixed in the presence of gas generation, there is a possibility that harmful carbon monoxide may be generated at the time of combustion, so it can be said that the inorganic binder is preferable. As the inorganic binder, calcium hydrogen phosphate, calcium carbonate, magnesium aluminate silicate, etc. are generally used.

As a method for evaluating the strength of tablets, there is a description of measurement of compressive strength and tensile strength of tablets in the above-mentioned JP-A-49-113782 and JP-A-3-65584.
However, the wear due to vibration of the gas generant tablets in the airbag when mounted on an actual vehicle is due to contact between tablets and contact with the container, and it is unlikely that the above method shows the degree of wear due to vibration. .. Here, the present inventors conducted various examinations on the physical strength of tablets by contacting the tablets by dropping the tablets with a commercially available tablet friability tester, contacting with the container and measuring the powdering rate thereof. ..

As a result, in the case of a gas generant tablet using a general inorganic binder such as calcium hydrogen phosphate,
There was a tendency that the friability did not decrease below a certain level even though the tablet compressive fracture strength measured by a Monsanto hardness meter was improved. Therefore, it was judged that the method using the friability tester is more suitable as a substitute test for the tablet strength against vibration than the method using the compression mirror test.

The present inventors have found that, when a substance called hydrotalcite is added to the above-mentioned gas generant composition and tableted, the strength of tablets in a friability test is remarkably increased. ..

Hydrotalcite has the chemical formula Mg6Al2
A substance represented by (OH) 16CO3.4H2O, which may be a natural hydrotalcite or a synthetic hydrotalcite, is preferably a synthetic hydrotalcite. Hydrotalcite is generally used in the gas generant composition in the range of 0.1% to 15% by weight, but is preferably in the range of 2% to 6% by weight.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 60 parts by weight of sodium azide, 18 parts by weight of potassium nitrate, 22 parts by weight of silicon dioxide, 0.5 part by weight of magnesium stearate 5 parts by weight of synthetic hydrotalcite were mixed with a ball mill at a speed of 90 rpm. Mix for 20 minutes. After this, use a single-shot tableting machine (Kikusui Seisakusho 6B-2 type) with a diameter of 5 m
The tablets were formed into tablets having a thickness of 3 mm.

At this time, easiness of molding with a tableting machine,
The gloss of the tablet after tableting of 00 tablets and the compressive breaking strength of 20 tablets of the molded tablet were measured with a Monsanto hardness meter (manufactured by Kagaki Medical Science Co., Ltd.).

Further, the molded tablet was dried at 105 ° C. for 2 hours, 10 g of the tablet was taken out, and a friability tester (Kayagaki Medical Science Co., Ltd.) was run for 10 minutes to test the friability (dusting rate).
Was measured.

Example 2 57 parts by weight of sodium azide, 17 parts by weight of potassium perchlorate, 26 parts by weight of aluminum silicate, 1 part by weight of magnesium stearate and 3 parts by weight of synthetic hydrotalcite were prepared in the same manner as in Example 1. Mixed and compressed. Further Example 1
The strength and friability of the tablets were measured in the same manner as in.

Example 3 Sodium azide (70 parts by weight), copper oxide (30 parts by weight), magnesium stearate (1 part by weight) and synthetic hydrotalcite (5 parts by weight) were mixed and tableted in the same manner as in Example 1 and further as Example 1. The strength and friability of the tablets were measured by the same method.

Example 4 70 parts by weight of sodium azide, 22 parts by weight of aluminum sulfate, 8 parts by weight of silicon dioxide, 0.5 part by weight of magnesium stearate and 5 parts by weight of synthetic hydrotalcite were mixed in the same manner as in Example 1.・ Tablet was pressed. Further, the strength and friability of the tablets were measured in the same manner as in Example 1.

Comparative Example 1 60 parts by weight of sodium azide, 18 parts by weight of potassium nitrate and 22 parts by weight of silicon dioxide were mixed and tableted in the same manner as in Example 1. Further, the strength and friability of the tablets were measured in the same manner as in Example 1.

Comparative Example 2 60 parts by weight of sodium azide, 18 parts by weight of potassium nitrate, 22 parts by weight of silicon dioxide, 0.5 part by weight of magnesium stearate, and 8 parts by weight of calcium hydrogen phosphate were mixed in the same manner as in Example 1 Tableted. Further, the strength and friability of the tablets were measured in the same manner as in Example 1.

Comparative Example 3 57 parts by weight of sodium azide, 17 parts by weight of potassium perchlorate, 26 parts by weight of aluminum silicate and 8 parts by weight of calcium hydrogen phosphate were mixed and tableted in the same manner as in Example 1. Further, the strength and friability of the tablets were measured in the same manner as in Example 1.

Comparative Example 4 70 parts by weight of sodium azide, 30 parts by weight of copper oxide, 0.5 parts by weight of magnesium stearate and 8 parts by weight of calcium hydrogen phosphate were mixed and tableted in the same manner as in Example 1.
Further, the strength and friability of the tablets were measured in the same manner as in Example 1.

Comparative Example 5 70 parts by weight of sodium azide, 22 parts by weight of aluminum sulfate and 8 parts by weight of silicon dioxide were mixed and tableted in the same manner as in Example 1. Further, the strength and friability of the tablets were measured in the same manner as in Example 1.

The compositions of Examples 1 to 4 and Comparative Examples 1 to 5 are summarized in Tables 1 and 2. The numerical values in Table 1 and Table 2 are parts by weight. The measurement results of Examples 1 to 4 and Comparative Examples 1 to 5 are summarized in Tables 3 and 4.

From Table 2, the use of hydrotalcite in the present invention makes the friability value much smaller than that of the calcium hydrogen phosphate of the comparative example, even though the tablet has similar compressive strength. Therefore, it can be said that hydrotalcite imparts the physical properties necessary for practical use to the gas generant tablet for an air bag.

[0034]

Table 1 Example 1 2 3 4 Sodium azide 60 57 70 70 70 Potassium nitrate 18 Sodium perchlorate 17 Copper oxide 30 Aluminum sulfate 22 Silicon dioxide 22 8 Aluminum silicate 26 Magnesium stearate 0.5 0.5 1 0.5 Synthesis Hydrotalcite 5 3 5 3

[0035]

Comparative Example 1 2 3 4 5 Sodium azide 60 60 60 57 70 70 Potassium nitrate 18 18 Sodium perchlorate 17 Copper oxide 30 Aluminum sulfate 22 Silicon dioxide 22 22 8 Aluminum silicate 26 Magnesium stearate 0.5 0.5. 5 Calcium hydrogen phosphate 8 8 8

[0036]

[Table 3] Example 1 2 3 4 Moldability Good Good Good Good Good Surface gloss Yes Yes Yes Yes Strength Average 20.8 22.3 17.3 23.7 (Kg) Range 16-23 19-25 12-19 18 ~ 26 Friability (%) 0.30 0.28 0.35 0.24

[0037]

[Table 4] Comparative Example 1 2 3 4 5 Moldability Capping Good Capping Good Capping Yes Yes Yes Yes Surface gloss No side surface Yes No central part Yes No side surface Strength Average 13.5 21.0 17.5 16.4 11.8 ( kg) Range 8-19 14-25 14-22 14-199 9-14 Friability (%) 2.60 1.65 1.54 1.68 2.23

[0038]

Since the gas generant tablet of the present invention has remarkably high physical strength, the initial burning rate is maintained for a long period of time.

Claims (1)

Claims: 1. A gas generant tablet characterized by comprising hydrotalcite in a gas generant composition and tableting.