JPH08283090A - Gas generating agent composition - Google Patents

Abstract

PURPOSE: To provide a gas generating agent ensuring a small amt. of solid residue flowing out of a combustion chamber and generating a small quantity of heat. CONSTITUTION: This gas generating agent compsn. contains an alkali metallic azide, ferrite represented by the formula MO-nFe2 O3 [where M is a divalent metal and (n) is a real number of 0.1-10], nitrate or perchlorate of an alkali metal, carbonate of an alkaline earth metal, silicon dioxide and a stearate. This compsn. enables the use of an air bag of a thin material. Since the rate of gas generation is increased, the size of an inflator can be made smaller.

Description

Detailed Description of the Invention

[0001]

This invention relates to gas generant compositions. More specifically, it relates to a gas generant composition for inflating an airbag for protecting a driver and a passenger of an automobile.

[0002]

2. Description of the Related Art An air bag as a safety device for protecting a driver and a passenger when a vehicle such as an automobile is in an accident such as a collision is already well known. Usually, these airbags detect a severe collision between a car and another object or vehicle by an electric or mechanical sensing device, and then ignite,
Using a combination of means such as flame transfer, the gas generant composition is finally burned to rapidly generate a large amount of gas, and this gas is introduced into a bag to form an air cushion state, thereby enabling the driver. Also, by supporting the body of the passenger, it is a mechanism that protects from the impact in the event of a collision. Therefore, the gas generating agent is required to have the following performance. a) 30 to 60 in order to operate the above-mentioned mechanism at the time of collision
Be able to complete the generation of gas within a millisecond time. b) Since the generated gas is released into the vehicle after supporting the body of the vehicle occupant as an air cushion, it has low toxicity and is non-corrosive. c) Do not generate high heat that may damage or burn the airbag itself or the vehicle occupants. In a conventional gas generating composition for an air bag, it is mainly composed of an alkali metal azide, an oxidizing agent or a metal oxide, and a substance which reacts with and adsorbs an alkali metal by-produced from the reaction of these substances or an oxide thereof. ing. JP-A-4
Japanese Patent Publication No. 9-50110 discloses a gas generating composition comprising sodium azide, potassium nitrate as an oxidizing agent, and silicon dioxide as a reaction / adsorption material. Although the composition has a sufficient burning rate, it has a drawback that the cooling means such as a wire mesh is melted due to the high calorific value at the time of burning, and high-temperature fine particles are easily generated as white smoke.
JP-A-50-105572 discloses a gas generating composition obtained by adding magnesium carbonate as a cooling agent to a composition using sodium azide and potassium permanganate or potassium dichromate as an oxidizing agent. ing. Although this composition has a low calorific value, it does not have a sufficient burning rate, and in the composition outside the theoretical reaction formula shown, a combustion residue with a low melting point is generated and this composition passes through a cooling means such as a wire mesh. There is a drawback that it does. This pass-through residue has the disadvantage that it contains harmful and dangerous metallic sodium.
The technique described in JP-A-5-238867 is an improvement over the drawbacks of the technique described in JP-A-49-50110. By using iron oxide as the main oxidant component, the calorific value is reduced. . However, in this example of the gas generating agent, the content of sodium azide is as small as 60 to 62%, and it is necessary to increase the amount of the gas generating agent in order to obtain a predetermined amount of gas. For this reason, it is necessary to enlarge the gas generating agent chamber, the number of cooling means such as wire mesh in the limited structural space is reduced, and as a result, combustion residues that have not been collected are released into the airbag. In extreme cases, the occupant may be burned or the airbag itself may be torn, and the occupant may not be protected. In a normal airbag, the inside of the bag itself is coated for thermal protection of its material.

[0003]

The airbag system is very effective as a safety device for vehicles and the like, and needs to be supplied at a low cost. In such a study, the material of the airbag itself is not required to be coated on the inside, or a thin material is required, and the residual outflow amount is reduced to reduce the thermal load on the airbag itself. There is a need to. The problem to be solved by the present invention is to develop a gas generant composition which, in combustion of the gas generant composition, has a small residual outflow amount and a small calorific value with respect to the gas generation amount.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted extensive studies on the constituent components of a gas generant composition containing an alkali metal azide as an essential component, and as a result of the present invention, Arrived

That is, the present invention provides (1) an alkali metal azide, a ferrite represented by MO.nFe ₂ O ₃ (M is a divalent metal, n is a real number from 0.1 to 10), and a nitrate of an alkali metal. Or perchlorate,
Gas generant composition containing alkaline earth metal carbonate, silicon dioxide and stearate (2) Gas generant composition according to item (1), wherein the alkali metal azide is sodium azide (3) MO · nFe ₂ The ferrite metal M represented by O ₃ is manganese, iron, magnesium, calcium, strontium, barium, copper, lead, nickel, cobalt,
The gas generating composition according to the above (1) to (2), which is zinc or cadmium (4) The above (1) to which the nitrate or perchlorate of an alkali metal is potassium nitrate or potassium perchlorate, respectively.
(3) Gas generating composition (5) Alkaline earth metal carbonate is magnesium carbonate,
The gas generant composition according to the above (1) to (4), which is calcium carbonate, strontium carbonate or barium carbonate (6) The above (1) to which the stearate is magnesium stearate, zinc stearate, or aluminum stearate. The gas generant composition according to (5). (7) The gas generant composition according to the above item 5, wherein the magnesium carbonate is basic magnesium carbonate. (8) The above items (1) to (7), wherein the ferrite represented by MO · nFe ₂ O ₃ is an isotropic structure barium ferrite. )
Of the gas generant composition described above.

The present invention will be described in detail. The gas generant composition of the present invention is a gas generant composition containing sodium azide as a main gas source, and includes ferrite, alkali metal nitrate or perchlorate, alkaline earth metal carbonate, and silicon dioxide. The use of stearates and stearates as essential components produces the following effects.

Alkaline earth metal carbonates such as magnesium carbonate and calcium carbonate are decomposed into carbon dioxide and magnesium oxide, carbon dioxide and calcium oxide at about 700 ° C. and about 900 ° C., respectively. At that time 426 kcal
It is known to carry out endotherms of / mol and 748 kcal / mol (calculated from the standard enthalpy of formation of simple substance and inorganic compound). The gas generant composition containing these alkaline earth metal carbonates decomposes these carbonates due to the high temperature at the time of combustion and absorbs part of the heat of combustion to lower the calorific value. Further, the carbon dioxide gas generated at this time is used together with the nitrogen gas generated from sodium azide or the like to deploy the air bag, and it is possible to increase the gas generation rate per unit weight. Further, since the basic magnesium carbonate has a function of preventing the hydrolysis reaction of sodium azide by carbon dioxide in the air, the basic magnesium carbonate is advantageous for the stability of the gas generant composition. Become. The sodium azide-based gas generant composition obtained by combining silicon dioxide with magnesium carbonate having such characteristics has a large amount of combustion residue remaining in the tablet combustion chamber as a solidified product and has a small calorific value. This has the effect of significantly reducing the thermal load during deployment.

A preferred example of the alkali metal azide used in the present invention is sodium azide. The combustion characteristics of the gas generant composition are mainly controlled by the particle size of sodium azide, and upon collision, it is necessary to complete the gas generation within a time of usually 60 milliseconds. Sodium has an average particle size of 10 to 60 μ.
In particular, those having a particle size of m, which are fine particles produced by a spray-dry manufacturing method, are preferable from the viewpoint of tableting property. Preferred specific examples of the alkaline earth metal carbonate used in the present invention are magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate. Particularly, basic magnesium carbonate is also preferable in terms of storage stability of the gas generating agent. preferable.

Preferred specific examples of the metal M of the ferrite represented by MO.nFe ₂ O ₃ are manganese, iron, calcium, magnesium, copper, lead, nickel, cobalt,
Zinc, cadmium, barium or strontium may be mentioned, but examples of particularly preferred ferrites are barium ferrite and strontium ferrite. MO ・ n
N in the ferrite represented by Fe ₂ O ₃ is 0.1 to
A real number of 4 to 8 is more preferable than 10. Barium ferrite has a specific surface area of about 1 to 5 m ² / g, and strontium ferrite has a specific surface area of 1
The most preferable ferrite has a thickness of about 5 m ² / g. Furthermore, since normal barium ferrite has an isotropic structure, the grain shape of each particle is closer to a spherical shape, and the spherical diameter is uniform, as can be seen from the scanning electron micrograph.
It has excellent fluidity, allows direct tableting, and is excellent in cost.

A preferred specific example of the alkali metal nitrate or perchlorate used in the present invention is potassium nitrate or potassium perchlorate.

Specific preferred examples of stearates used in the present invention include magnesium stearate, zinc stearate, aluminum stearate, and the like.
Particularly preferred is magnesium stearate.

In the gas generant composition of the present invention, the alkali metal azide is 50 to 80% by weight, preferably 65.
Used in the range of up to 75% by weight. Similarly, MO / nFe
₂ O ₃ ferrite is 5 to 30% by weight, more preferably 1
In the range of 0 to 20% by weight, the alkali metal nitrate or perchlorate is 0.1 to 20% by weight, more preferably in the range of 2 to 10% by weight, and the alkaline earth metal carbonate is 0.1 to 20% by weight. More preferably in the range of 2 to 15% by weight, 0.1 to 20% by weight of silicon dioxide, more preferably 5 to 15% by weight, and 0.1 to 2% by weight of stearate, more preferably 0.3. ˜1% by weight. Other additives usually added to the gas generant composition are added if necessary.

The gas generant composition of the present invention is uniformly mixed by using a mixer such as a ball mill or a V-type mixer in the same manner as a usual gas generant composition, and then a rotary tableting machine is used. A tablet having a diameter of 3 to 15 mm and a thickness of 1 to 10 mm is produced.

[0014]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. Further, in each example, “part” means “part by weight”.

Example 1 Sodium azide 68.0 parts by weight, barium ferrite 12.0 parts by weight, potassium nitrate 5.0 parts by weight, magnesium carbonate 10.0 parts by weight, silicon dioxide 5.0 parts by weight,
A mixture of 0.5 parts by weight of magnesium stearate was mixed in a ball mill at 60 rpm for 20 minutes. Then, it was molded into a tablet having a diameter of 5 mm and a thickness of 3 mm with a rotary tableting machine (RT-S-9 type, Kikusui Seisakusho) to obtain a gas generant composition (tablet) of the present invention. The performance test of this product was performed by the following method. As a combustion tester for gas generant tablets, a stainless steel orifice with 10φ × 7 holes at the boundary between the tablet combustion chamber 40cc and the residual collection chamber 960cc, and a stainless wire mesh (20 mesh wire) A stainless airtight container provided with three sheets of 0.4 mm in diameter and aluminum foil (150 μ) was prepared. 25 in tablet burning chamber
g of the tablet and an igniter having a mechanism for electrically igniting the boron-silver stone transfer charge is installed, a pressure sensor is attached to the residual collection chamber, and then the igniter is ignited to burn the gas generating agent. The test was conducted. To evaluate the gas generant, measure the time until the pressure of the gas generated by combustion reaches the maximum peak and the maximum pressure value with an oscilloscope, pass the gas in the closed container through a filter, and then measure the integrated gas flow meter. (SEF-51 manufactured by STEC Co., Ltd.) to measure the amount of generated gas [A (l)], and then the amount of the combustion residue remaining in the combustion chamber and the theoretical gas generation rate indicate the residue flowing into the residue collection chamber. The amount of residual effluent [B (g)] is determined to determine the residual amount of effluent [B / A] with respect to the amount of generated gas. (Cal / g) to calorific value [C
/ A]. The performance test by this method is shown in Table 1. The indication in the column of composition in Table 1 is parts by weight.

Example 2 70.0 parts by weight of sodium azide, 10.0 parts by weight of barium ferrite, 4.0 parts by weight of potassium perchlorate, 6.0 parts by weight of magnesium carbonate, 10.0 parts by weight of silicon dioxide, stearin A mixture of 0.5 part by weight of magnesium acid was mixed and tableted in the same manner as in Example 1 to obtain a gas generant composition (tablet) of the present invention. About this thing Example 1
A performance test was conducted in the same manner as in, and the results are shown in Table 1.

Example 3 72.0 parts by weight of sodium azide, 8.0 parts by weight of strontium ferrite, 5.0 parts by weight of potassium perchlorate,
A mixture of 5.0 parts by weight of calcium carbonate, 10.0 parts by weight of silicon dioxide, and 0.5 parts by weight of magnesium stearate was mixed and tableted in the same manner as in Example 1 to produce the gas generant composition (tablet) of the present invention. Got A performance test was conducted on this product in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 Sodium azide 57.0 parts by weight, potassium nitrate 17.
A mixture of 0 parts by weight, 26.0 parts by weight of silicon dioxide and 0.5 parts by weight of magnesium stearate was mixed and compressed in the same manner as in Example 1 to obtain a gas generant composition for comparison. A performance test was conducted on this product in the same manner as in Example 1, and the results are shown in Table 2. The indication in the column of composition in Table 2 is parts by weight.

Comparative Example 2 Sodium azide 66.0 parts by weight, potassium permanganate 17.0 parts by weight, magnesium carbonate 17.0 parts by weight,
A mixture of 0.5 parts by weight of magnesium stearate was mixed and compressed in the same manner as in Example 1 to obtain a gas generant composition for comparison. A performance test was conducted on this product in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 3 62.0 parts by weight of sodium azide and 4.0 of potassium nitrate
Parts by weight, ferric oxide 27.0 parts by weight, silicon dioxide 6.
A mixture of 0 parts by weight and 0.5 parts by weight of magnesium stearate was mixed and compressed in the same manner as in Example 1 to obtain a comparative gas generant composition. A performance test was conducted on this product in the same manner as in Example 1, and the results are shown in Table 2.

[0021]

Table 1 Table 1 Example 1 Example 2 Example 3 Composition Sodium azide 68 70 72 Barium ferrite 12 10 Strontium ferrite 8 Potassium nitrate 5 Potassium perchlorate 4 5 Magnesium carbonate 10 6 Calcium carbonate 5 Silicon dioxide 5 10 10 Stearin Magnesium oxide 0.5 0.5 0.5 Combustion test maximum peak time (ms) 57 53 50 Maximum peak pressure (atm) 58 61 61 A: Evolved gas amount (l) 9.95 10.25 10.15 B: Residual outflow amount (g) 5.72 4.43 5.51 Tablet shape Tablet shape Tablet shape C: Calorific value (cal / mol) 383 395 407 Residual outflow amount relative to the generated gas amount B / A 0.57 0.43 0.54 Calorific value relative to the generated gas amount C / A 38.5 38.5 40.1

[0022]

Table 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Composition Sodium azide 57 66 62 Potassium nitrate 17 4 Potassium permanganate 17 Ferric oxide 27 Magnesium carbonate 17 Silicon dioxide 26 6 Magnesium stearate 0.5 0.5 0.5 Combustion test Maximum peak time (ms) 35 85 57 Maximum peak pressure (atm) 74 53 56 A: Generated gas amount (l) 7.60 10.80 8.20 B: Residual outflow amount (g) Wire mesh breakage 9.73 4.50 Tablet shape C: Calorific value (cal) / mol) 741 407 395 Residual outflow relative to the amount of generated gas B / A ── 0.90 0.55 Calorific value relative to the amount of generated gas C / A 98.0 37.0 48.2

The following can be seen from Tables 1 and 2. In the comparative example, the one with a high calorific value melted the wire mesh and there was no combustion residue in the combustion chamber. In the other comparative examples, the slag outflow amount and the calorific value per generated gas amount are larger than those of the examples of the present application, although the fuel speed is slightly slow. In each of the examples, it was observed that tablet-shaped combustion residues were collected by the wire net in the combustion chamber. From these, it was found that the gas generating agent according to the present invention had a high gas generating ability because the combustion residue was easily collected.

[0024]

EFFECT OF THE INVENTION In a gas generating agent for expanding an inflator structure having a constant volume and an air bag having a constant volume,
The gas generant composition of the present composition having a high gas generating capacity and sufficient combustion residue trapping property reduces the thermal load on the airbag itself, so that the material of the airbag itself can be made thin and cooling means. Since it can be made smaller, the inflator structure can be made smaller.

Claims (8)

[Claims] 1. Alkali metal azide, MO.nFe ₂ O ₃
Contains ferrite represented by (M is a divalent metal, n is a real number from 0.1 to 10), an alkali metal nitrate or perchlorate, an alkaline earth metal carbonate, silicon dioxide and a stearate. A gas generant composition. 2. The gas generant composition according to claim 1, wherein the alkali metal azide is sodium azide. 3. The ferrite metal M represented by MO.nFe ₂ O ₃ is manganese, iron, magnesium, calcium, strontium, barium, copper, lead, nickel, cobalt, zinc or cadmium. Gas generating composition. 4. The gas generant composition according to claim 1, wherein the alkali metal nitrate or perchlorate is potassium nitrate or potassium perchlorate, respectively. 5. The gas generant composition according to claim 1, wherein the alkaline earth metal carbonate is magnesium carbonate, calcium carbonate, strontium carbonate, or barium carbonate. 6. The gas generant composition according to claim 1, wherein the stearate is magnesium stearate, zinc stearate or aluminum stearate. 7. The gas generant composition according to claim 5, wherein the magnesium carbonate is basic magnesium carbonate. 8. The ferrite represented by MO.nFe ₂ O ₃ is barium ferrite having an isotropic structure.
The gas generant composition of.