JP3819216B2 - Metal powder for ignition - Google Patents

Description

【００６５】
表１から、不定形状粒子に対する鱗片形状粒子の、インフレータ用イグナイタの点火剤としての優位性が明らかである。
【００６６】
即ち、不定形状粒子からなる粉末で、平均粒径が２０〜３０μｍ以上の場合（比較例２〜６）は、発火感度が低すぎ、燃焼速度も遅すぎる傾向である。取り扱い時における安全性は高いが、総合的に判断すると、インフレータ用イグナイタの点火剤としては不適当である。
【００６７】
平均粒径が１０〜２０μ以下の場合（比較例１及び７）は、逆に発火感度が非常に高くなり、燃焼速度が過大となって、エンハンサ剤の着火に対する確実性が低下する。しかも、取り扱い時における発火が問題になる。従って、この場合もインフレータ用イグナイタの点火剤としては不適当である。
【００６８】
これらに対し、鱗片形状粒子からなるジルコニウム粉末、チタニウム粉末の場合（実施例１〜６）は、広い粒径範囲で発火感度が適正であり、高い点火性能を維持しつつ、取り扱い時の高い安全性が確保される。しかも、燃焼速度が遅く、エンハンサ剤の着火に対する確実性が高いので、使用量の低減が可能となる。総合的に判断すると、インフレータ用イグナイタの点火剤として非常に好適である。
【００６９】
ただし、鱗片形状粒子からなるジルコニウム粉末、チタニウム粉末といえども、平均粒径が大きすぎたり、平均アスペクト比が小さすぎた場合（比較例８〜１１）は、インフレータ用イグナイタの点火剤としては、発火感度が低下し、燃焼速度も遅すぎる傾向となる。
【００７０】
【発明の効果】
以上に説明したとおり、本発明の点火用金属粉末は、ジルコニウム粉末、チタニウム粉末のうちの少なくとも１種以上からなり、その粉末形成粒子を鱗片形状としたことにより、点火性を損なうことなく、取り扱い時の安全性を高めることができる。また、燃焼継続時間の増大により、使用量を低減することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to ignition metal powder employed in the igniter igniting agent in airbags inflator for a motor vehicle.
[0002]
[Prior art]
An inflator, which is a device for generating gas used for deploying an automobile airbag, is generally composed of an igniter, an enhancer, and a gas generating agent. In this inflator, the gas for deployment of the air bag is generated through the process of ignition of the enhancer by ignition of the igniter, followed by heat generation of the enhancer, ignition of the gas generant by transmission, and finally combustion of the gas generant. To do.
[0003]
That is, the igniter is first ignited by the igniter due to the impact at the time of collision, and heat energy is generated. Next, in order to surely ignite the gas generating agent, the enhancer agent which is an amplifying agent of thermal energy is ignited, and finally the gas generating agent is ignited.
[0004]
There are two types of igniters: electrical ignition and mechanical ignition. In any case, explosives that can be ignited with minute energy are used as igniting agents. Specifically, a mixed drug of zirconium and potassium perchlorate (ZPP) or the like is used.
[0005]
As an enhancer, a mixture of boron and potassium nitrate is generally used. Sodium azide is used as the gas generating agent. This substance generates pure harmless nitrogen gas as a gaseous combustion product by combustion, but sodium azide itself is harmful and causes a problem during disposal. Therefore, development of a gas generating agent with low toxicity instead of sodium azide is in progress.
[0006]
[Problems to be solved by the invention]
As the igniter for the igniter, as described above, for example, a mixed drug (ZPP) of zirconium and potassium perchlorate is used. The metal used for this igniter is a fine powder, and besides zirconium, there are aluminum, magnesium, titanium and the like.
[0007]
In general, the finer the metal powder, the better the ignition performance. On the other hand, the risk of spontaneous ignition during handling increases and the safety decreases. In addition, the higher the ignition performance, the more rapid the combustion and the shorter the combustion duration time, so the certainty of the enhancer agent against ignition decreases. For this reason, a large amount of powder is required.
[0008]
From this point of view, the fine powder of zirconium usually used has excellent ignition performance, but has a high risk of spontaneous ignition during handling and a short combustion duration. In addition, in the case of titanium, for safety reasons, fine powders are not produced and have a relatively large particle size, so that the ignition performance is inferior.
[0009]
The objective of this invention is providing the metal powder for ignition which can improve the safety | security at the time of handling, and can increase a combustion continuation time, without impairing ignitability.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have focused on the specific surface area of the individual metal particles forming the metal powder, and have conducted various investigations and studies, particularly focusing on the particle shape that governs the specific surface area. It was. As a result, by making the metal particles into a flat scale shape, the combustion of the metal powder becomes mild, an appropriate combustion time is ensured, and the safety during handling is improved while maintaining excellent ignition performance. Turned out to be.
[0011]
The metal powder for ignition of the present invention has been developed based on such knowledge, and is a metal powder used as an igniter for an igniter in an inflator of an automobile airbag , and is one of zirconium powder and titanium powder. The metal particles comprising at least one kind and forming the powder have a scaly shape , an average diameter of 5 to 500 μm, and an aspect ratio of 10 or more .
[0012]
Generally, the metal powder used for the igniter of the igniter for inflators is made of amorphous metal particles produced by mechanical crushing. Since these metal particles are irregular in shape, they have a large specific surface area, are very active and easily ignite, and are extremely dangerous in handling. In particular, generally used fine powder of zirconium has a strong tendency.
[0013]
The present inventors paid attention to the shape of the individual metal particles forming the metal powder, and as a result of examination, the metal powder composed of scale-shaped metal particles is mildly combusted and the combustion speed is optimized. I found out. Conventional metal powder consisting of irregularly shaped metal particles tends to burn out immediately when ignited, but in the case of a flat scale shape, it burns while propagating on a relatively flat surface, so the combustion time can be extended There is. That is, metal powders composed of scale-shaped metal particles , particularly titanium powder and zirconium powder, have an appropriate burning rate. In addition, since the specific surface area of the scale-shaped metal particles is smaller than that of the irregular-shaped metal particles, the risk of ignition during handling can be reduced.
[0014]
The scale shape is a flat shape obtained by thinly extending the metal particles forming the metal powder. If spherical particles obtained by a gas atomizing method or the like are expanded without being broken by a ball mill or the like, thin disc-like scaly particles having a smooth periphery and surface can be obtained, and if broken, leaves with irregularities on the periphery -Like scale-shaped particles are obtained. Moreover, if a general irregular-shaped metal particle is extended, the leaf-shaped scale-shaped particle | grains of a tree with an unevenness | corrugation in a periphery will be obtained.
[0015]
Type of metal particles flake shape forming the ignition metal powder of the present invention is a two zirconium and titanium, alone powder consisting of particles, or may be used in combination of two or.
[0016]
As for the dimension of a metal particle, 5-500 micrometers is preferable at a diameter (particle diameter), and 10-200 micrometers is especially preferable. If the particle size is too small, the safety is deteriorated even in the scale shape, and the combustion rate is excessive. On the other hand, when the particle size is too large, the ignition performance decreases. Further, the aspect ratio (ratio of diameter to thickness) is preferably 10 or more, particularly preferably 30 or more. If the aspect ratio is too small, the effect of scale formation becomes insufficient. The upper limit of the aspect ratio is not particularly limited because it is preferably as large as possible from the viewpoint of the effect of scale formation. However, when it is extremely large, the strength for maintaining the scale shape becomes small and is easily destroyed. In addition, the manufacturing cost increases. From this viewpoint, 1000 or less is preferable, and 500 or less is particularly preferable.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0018]
When the metal powder used as a raw material is larger than a predetermined particle diameter, it is mechanically powdered by a ball mill or the like to obtain a metal powder having a predetermined particle diameter. The spherical powder obtained by the gas atomization method or the like does not need to be crushed, and a metal powder having a predetermined particle diameter is obtained by sieving.
[0019]
The obtained metal powder is put into a ball mill together with fats and oils such as oleic acid and mineral spirits, and a solvent such as alcohol, and spreads. Since the metal has ductility, it is expanded into a flat scale shape. When expanded to a predetermined particle size and aspect ratio, the oil and fat and solvent are washed with a volatile solvent such as asenton and alcohol and dried.
[0020]
The obtained scale-shaped metal powder is sieved to obtain a metal powder having a predetermined particle size.
[0021]
The reason why the fats and oils are used in the extending process of the metal powder is to prevent breakage of the particles by lubrication and to prevent the particles from being ignited by blocking the particles from the air.
[0022]
Examples of the apparatus used for spreading the metal powder include a stamp mill, a roll mill, a bead mill, and an attritor mill in addition to a rotary type, a vibration type or a planetary ball mill. The use of fats and oils and the selection of the operating conditions (for example, operating time) of the apparatus make it possible to expand the particles without breaking them.
[0023]
【Example】
Next, examples of the present invention will be shown, and the effects of the present invention will be clarified by comparing with comparative examples. In each example, the igniter for an inflator made of metal powder was evaluated as an igniter by the following burning rate test, friction sensitivity test, and electrostatic sensitivity test.
[0024]
[Burning rate test]
A powder sample is deposited on a magnetic plate in the form of a triangular prism with a short piece 3 mm, a long piece 20 mm, and a height 3 mm. The sample is ignited by a line explosion of the platinum bridge wire at one end surface in the long piece direction, and the combustion surface is advanced from one end surface to the other end surface, and a high-speed video is taken. An average combustion rate is calculated from each time until the combustion surface advances from the ignition end surface to 10 mm, 10 mm to 20 mm, and from the ignition end surface to 20 mm.
[0025]
A preferable average burning rate in this burning rate test is 0.1 to 1.0 m / s. If it is slower than 0.1 m / s, it takes too long to ignite the enhancer. If it is faster than 1.0 m / s, the certainty of the enhancer agent against ignition decreases, so that it is necessary to use a large amount of powder in order to extend the combustion time.
[0026]
(Friction sensitivity test)
A device comprising a pedestal on which a friction plate is mounted and capable of reciprocating at a low speed, and an arm that can adjust the load on the friction rod attached according to the weight of the weight and the hanging position is used. About 0.01 mL of the sample is placed on a 15 mm square, 5 mm thick ceramic friction plate. A friction rod made of porcelain having a rounded friction surface having a diameter of 10 mm and a length of 15 mm is attached to the arm. Both the friction plate and the friction rod have Shore hardness (JISZ2246) HS90 to 110 and surface roughness (JISB0601, JISB0651) of 15 μm.
[0027]
The friction rod is brought into contact with the sample, and a predetermined weight is suspended at a predetermined position of the arm and a predetermined load is applied. In this state, the friction plate is reciprocated once at a constant speed of 10 mm. The test is performed six times continuously with the same load, and a load at a so-called 1/6 ignition point, which is estimated to explode only once out of six times or to explode only once, is obtained.
[0028]
A preferable ignition load in this friction sensitivity test is 5 to 10 kgf. If the ignition load is less than 5 kgf, the ignition occurs too easily and may ignite during handling. On the contrary, if it is larger than 10 kgf, the ignitability with respect to the enhancer agent becomes a problem.
[0029]
[Electrostatic sensitivity test]
Use a proximity electrode type electric spark sensitivity tester for highly sensitive materials. A capacitor with a certain capacity is used according to the sensitivity of the sample. The battery is charged at a predetermined voltage according to the energy applied to the sample. Then, an electric spark is generated by discharging between the upper and lower electrodes.
[0030]
In the test, a sample of about 10 to 20 mg is deposited on the lower electrode, and the needle-like upper electrode is approached from above the sample and spontaneously discharged. Fire if sample emits sound, light or smoke. The discharge energy is obtained from the capacitor capacity and voltage when the sample ignites, and the sensitivity of the sample to electrostatic spark is obtained using this as a parameter.
[0031]
In this test, 50% ignition energy was determined by the up-and-down method. That is, the test is repeated about 20 to 30 times by changing the applied discharge energy at regular intervals, lowering the level by 1 when the sample ignites, and increasing by 1 level when the sample does not ignite. Deviation was determined. The interval between discharge energies was 0.1 increments on a logarithmic scale, and the number of tests was 20 times.
[0032]
A preferable ignition energy in this electrostatic sensitivity test is 5 to 15 mJ. If the ignition energy is less than 5 mJ, ignition may occur too easily and may ignite during handling. On the other hand, if it is larger than 15 mJ, the ignitability with respect to the enhancer becomes a problem.
[0033]
Example 1
100 g of powder composed of irregularly shaped zirconium particles having an average particle diameter of 50 μm was put in a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 2 hours in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scale-shaped zirconium particles having an average particle diameter of 100 μm and an average aspect ratio of 20.
[0034]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0035]
(Example 2)
100 g of powder composed of irregularly shaped titanium particles having an average particle diameter of 100 μm was put into a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 2 hours in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scaly titanium particles having an average particle diameter of 300 μm and an average aspect ratio of 30.
[0036]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0037]
Example 3
100 g of powder composed of spherical titanium particles having an average particle diameter of 50 μm was put in a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 2 hours in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scaly titanium particles having an average particle diameter of 100 μm and an average aspect ratio of 25.
[0038]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0039]
Example 4
100 g of powder composed of spherical titanium particles having an average particle diameter of 20 μm was put in a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 2 hours in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scaly titanium particles having an average particle size of 50 μm and an average aspect ratio of 25.
[0040]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0041]
(Example 5)
100 g of powder composed of spherical titanium particles having an average particle diameter of 18 μm was put in a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 1.5 hours in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scaly titanium particles having an average particle diameter of 20 μm and an average aspect ratio of 20.
[0042]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0043]
(Example 6)
50 g of powder composed of irregularly shaped zirconium particles having an average particle diameter of 50 μm and 50 g of powder composed of spherical titanium particles having an average particle diameter of 50 μm were placed in a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, And rotated for 1 hour. The obtained powder was washed with acetone, dried, and sieved to obtain a mixed powder composed of scale-shaped zirconium particles and titanium particles having an average particle diameter of 100 μm and an average aspect ratio of 20.
[0044]
The obtained mixed powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0045]
(Delete)
[0046]
(Delete)
[0047]
(Delete)
[0048]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0049]
(Comparative Example 1)
A powder composed of irregularly shaped zirconium particles having an average particle diameter of 10 μm was subjected to a burning rate test, a friction sensitivity test, and an electrostatic sensitivity test, and the average burning rate, ignition load, and ignition energy were measured. Table 1 shows the measured values.
[0050]
(Comparative Example 2)
The powder composed of irregularly shaped zirconium particles having an average particle diameter of 20 μm was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0051]
(Comparative Example 3)
A powder composed of irregularly shaped zirconium particles having an average particle size of 100 μm was subjected to a burning rate test, a friction sensitivity test, and an electrostatic sensitivity test, and the average burning rate, ignition load, and ignition energy were measured. Table 1 shows the measured values.
[0052]
(Comparative Example 4)
Powders composed of irregularly shaped titanium particles having an average particle diameter of 100 μm were subjected to a burning rate test, a friction sensitivity test, and an electrostatic sensitivity test, and the average burning rate, ignition load, and ignition energy were measured. Table 1 shows the measured values.
[0053]
(Comparative Example 5)
A powder composed of amorphous titanium particles having an average particle diameter of 50 μm was subjected to a burning rate test, a friction sensitivity test, and an electrostatic sensitivity test, and the average burning rate, ignition load, and ignition energy were measured. Table 1 shows the measured values.
[0054]
(Comparative Example 6)
Powders composed of irregularly shaped titanium particles having an average particle size of 30 μm were subjected to a burning rate test, a friction sensitivity test, and an electrostatic sensitivity test, and the average burning rate, ignition load, and ignition energy were measured. Table 1 shows the measured values.
[0055]
(Comparative Example 7)
A powder composed of irregularly shaped titanium particles having an average particle diameter of 20 μm was subjected to a burning rate test, a friction sensitivity test, and an electrostatic sensitivity test, and the average burning rate, ignition load, and ignition energy were measured. Table 1 shows the measured values.
[0056]
( Comparative Example 8 )
100 g of powder composed of irregularly shaped zirconium particles having an average particle diameter of 200 μm was put in a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 3 hours in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scale-shaped zirconium particles having an average particle diameter of 800 μm and an average aspect ratio of 40.
[0057]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0058]
( Comparative Example 9 )
100 g of powder composed of amorphous titanium particles having an average particle diameter of 200 μm was put into a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 3 hours in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scaly titanium particles having an average particle diameter of 700 μm and an average aspect ratio of 35.
[0059]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0060]
( Comparative Example 10 )
100 g of powder composed of irregularly shaped zirconium particles having an average particle diameter of 50 μm was put in a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 0.5 hour in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scale-shaped zirconium particles having an average particle diameter of 100 μm and an average aspect ratio of 5.
[0061]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0062]
( Comparative Example 11 )
100 g of powder composed of amorphous titanium particles having an average particle diameter of 50 μm was put in a pot together with 200 g of oleic acid, 50 g of mineral spirit, 10 g of ethyl alcohol and ball mill media, and rotated for 0.5 hour in a planetary mill. The obtained powder was washed with acetone, dried, and sieved to obtain a powder composed of scaly titanium particles having an average particle diameter of 150 μm and an average aspect ratio of 5.
[0063]
The obtained powder was subjected to a burning rate test, a friction sensitivity test and an electrostatic sensitivity test, and the average burning rate, ignition load and ignition energy were measured. Table 1 shows the measured values.
[0064]
[Table 1]

[0065]
From Table 1, the superiority of the scale-shaped particles over the irregular-shaped particles as an igniter for an inflator igniter is clear.
[0066]
That is, when the powder is composed of irregularly shaped particles and the average particle size is 20 to 30 μm or more (Comparative Examples 2 to 6), the ignition sensitivity tends to be too low and the combustion rate tends to be too slow. Although the safety at the time of handling is high, it is unsuitable as an igniter for an inflator igniter when comprehensively judged.
[0067]
When the average particle size is 10 to 20 μm or less (Comparative Examples 1 and 7), on the contrary, the ignition sensitivity becomes very high, the combustion rate becomes excessive, and the certainty of the enhancer agent against ignition decreases. Moreover, ignition during handling becomes a problem. Accordingly, in this case as well, it is unsuitable as an igniter for an inflator igniter.
[0068]
On the other hand, in the case of zirconium powder and titanium powder made of scale-shaped particles ( Examples 1 to 6 ), ignition sensitivity is appropriate in a wide particle size range, and high safety during handling is maintained while maintaining high ignition performance. Sex is secured. In addition, since the combustion rate is slow and the reliability of the enhancer agent against ignition is high, the amount of use can be reduced. Overall, it is very suitable as an igniter for an inflator igniter.
[0069]
However, even if the zirconium powder and the titanium powder are made of scale-shaped particles, if the average particle diameter is too large or the average aspect ratio is too small ( Comparative Examples 8 to 11 ), as an igniter for an inflator igniter, The ignition sensitivity tends to decrease and the combustion rate tends to be too slow .
[0070]
【The invention's effect】
As described above, the metal powder for ignition of the present invention is composed of at least one of zirconium powder and titanium powder, and the powder-forming particles are formed in a scale shape, so that the ignition property is not impaired. The safety at the time can be increased. Further, the amount of use can be reduced by increasing the combustion duration time.

Claims (1)

A metal powder used as an igniter for an igniter in an inflator of an automobile airbag, which is composed of at least one of zirconium powder and titanium powder, and the metal particles forming the powder have a scaly shape , A metal powder for ignition having an average diameter of 5 to 500 μm and an aspect ratio of 10 or more .