JP3952424B2 - Gas generant composition - Google Patents

Description

ここで生成した窒素ガスは、燃料成分の燃焼によって生成した窒素ガスや炭酸ガスと共にエアバッグ内に放出されてエアバッグの展開に有効に利用され、酸素ガスは、燃料成分の燃焼に利用される。
【００２７】
尚、（１）式では、説明の便宜上、各１分子のＳｉ₃ Ｎ₄ ＋Ｓｒ（ＮＯ₃ ）₂ との反応式を示したが、実際には酸化剤として添加される硝酸ストロンチウムの量は、スラグ捕集のために添加される窒化珪素よりも圧倒的に多量であるから、化学量論的には上記反応は部分的には成立するも、次の（２）式で示される硝酸ストロンチウムの分解によって生成する酸化ストロンチウム粒子の表面層に、次式の（３）式で示す如き一般式で示されるストロンチウム珪酸塩が生成すると考えられる。
２Ｓｒ（ＮＯ₃ ）₂ →２ＳｒＯ＋２Ｎ₂ ＋５Ｏ₂ ・・・・・・・・・（２）
ＳｒＯ＋ＳｒＳｉＯ₃ →Ｓｒ_x ＳｉＯ_y ・・・・・・・・・・・・・（３）
〔ここで、（ｘ，ｙ）＝（２，４），（３，５）；反応式中の係数は省略〕
【００２８】
又、硝酸ストロンチウムの分解によって生成する酸化ストロンチウムは、高融点（２４３０℃）の酸化物であり、ガス発生器内では微細な固体粒子として燃焼過程で生成するが、上記（１），（３）式の反応によって、その粒子表面部に融点が１６００℃前後の各種珪酸塩が形成される。この珪酸塩は、反応環境温度の下では高粘度の溶融状態にあるので、各微粒子が互いに融着して凝集し、大きな粒子となってガス発生器内のフィルタ部材で捕集され易くなる。
【００２９】
又、前記金属窒化物が窒化アルミニウム（ＡｌＮ）の場合には、上記（１），（３）式は次の様に書き換えられる。尚、（５）式の係数は省略している。

ここで生成するアルミン酸塩も、上記珪酸塩と同様に、固形スラグ（ＳｒＯ）の表面に高粘度のスラグ層を形成し、スラグ微粒子を融着凝集してフィルタで濾過し易い形態のスラグを形成する。
【００３０】
これら金属窒化物の添加量は、ガス発生剤組成物全体に対して０．５〜１０％の範囲が好ましく、０．５％以下では、上記したスラグ捕集効果が期待できなくなり、又、１０％を越えると、燃料や酸化剤の添加量が制限されるので、発生ガス量不足や不完全燃焼を生じるおそれが出てくる。又、これらの粒径は、細かい程その効果が期待し易いので、個数基準５０％平均粒径で５μｍ以下、好ましくは１μｍ以下が良い。尚、個数基準５０％平均粒径とは、個数基準で粒度分布を表す方法であり、全粒子の個数を１００としたとき、小さい方から積算して５０個に達したときの粒度をいう。この金属窒化物の微粒子を、前記燃料成分や酸化剤成分の粉砕時に少量添加しておけば、これら粉砕成分の固結防止剤の作用をなすと共に酸化剤や燃料中に均一に分散させる事ができ、前記スラグ反応の均一化も期待できる。尚、これら金属窒化物を固結防止剤として使用する際に、二酸化珪素の微粉末である微粒化シリカと併用する事も可能である。
【００３１】
尚、金属窒化物をガス発生剤に用いた例としては、特公平６−８４２７４号に記載されたものがあるが、このガス発生剤は、従来のアジ化金属化合物に代えて窒化アルミニウム，窒化硼素，窒化珪素或いは遷移金属窒化物を用いるものであって、いわゆる燃料成分としてこれら金属窒化物を用いるものであり、本発明のスラグ捕集性を向上させるために金属窒化物を用いるものとは、根本的に思想が異なるものである。
【００３２】
次に、前記金属窒化物と同様に、本発明においてスラグ捕集剤として使用する金属炭化物について説明する。本発明で使用する金属窒化物としては、炭化珪素（ＳｉＣ），炭化硼素（Ｂ₄ Ｃ），炭化アルミニウム（Ａｌ₄ Ｃ₃ ），炭化マグネシウム（ＭｇＣ₂ ／Ｍｇ₂ Ｃ₃ ），炭化モリブデン（ＭｏＣ／Ｍｏ₂ Ｃ），炭化タングステン（ＷＣ／Ｗ₂ Ｃ），炭化カルシウム（ＣａＣ₂ ），炭化バリウム（ＢａＣ₂ ），炭化ストロンチウム（ＳｒＣ₂ ），炭化亜鉛（ＺｎＣ₂ ），炭化ナトリウム（Ｎａ₂ Ｃ₂ ），炭化銅（Ｃｕ₂ Ｃ₂ ），炭化チタン（ＴｉＣ），炭化マンガン（Ｍｎ₃ Ｃ），炭化バナジウム（ＶＣ），炭化ニッケル（Ｎｉ₃ Ｃ），炭化コバルト（Ｃｏ₂ Ｃ，ＣｏＣ₂ ），炭化鉄（Ｆｅ₂ Ｃ／Ｆｅ₃ Ｃ），炭化ジルコニウム（ＺｒＣ），炭化クロム（Ｃｒ₃ Ｃ₂ ／Ｃｒ₇ Ｃ₃ ／Ｃｒ₂₃Ｃ₆ ），炭化タンタル（ＴａＣ），炭化ニオブ（ＮｂＣ），炭化セリウム（ＣｅＣ₂ ），炭化スカンジウム（ＳｃＣ₂ ），炭化イットリウム（ＹＣ₂ ）及び炭化ゲルマニウム（ＧｅＣ）の群から選ばれた１種以上が使用される。
【００３３】
これらの内、炭化珪素，炭化硼素，炭化モリブデン，炭化タングステン，炭化チタン，炭化バナジウム，炭化ジルコニウム，炭化クロム，炭化タンタル，炭化ニオブ等は、ファインセラミックスと呼ばれているものであり、熱的にも安定で高強度の耐熱材料として使用されているものであるが、高温の酸化性雰囲気下では、他の炭化金属と同様に燃焼する性質がある。本発明は、この燃焼する性質を利用してスラグ形成とガス発生の両方の作用を同時に行うものである。例えば、炭化珪素の場合には、次の（６）式の如き酸化反応によって炭酸ガスと二酸化珪素を生成する。

ここで生成した炭酸ガス及び窒素は、燃料成分の燃焼によって生成した窒素ガス，炭酸ガス及び水蒸気と共にエアバッグ内に放出されて、エアバッグの展開に有効に利用され、酸素は、燃料成分の燃焼に利用される。
【００３４】
一方、副生した珪酸塩は、硝酸ストロンチウムの分解によって生じる燃焼残渣としてのＳｒＯと前記反応式（３），（５）の如き反応によってガス発生器内のフィルタ内で捕集し易い高粘性のスラグを形成する事は、前述の場合と同様である。即ち、燃焼残渣として生じるＳｒＯは、上記（６）式で生成する炭酸ガスと次式に示す反応によって炭酸ストロンチウムを生成する。
ＳｒＯ＋ＣＯ₂ →ＳｒＣＯ₃ ・・・・・・・・・・・・・・・・・・（７）
この炭酸ストロンチウムも、前述のストロンチウム珪酸塩と同様に、１５００℃程度で高粘性の溶融状態になるので、高融点粒子である固体の酸化ストロンチウムの表面に高粘性の炭酸ストロンチウムを形成して燃焼残渣の微粒子を融着凝集し、大きな粒子となってガス発生器内のフィルタ部材で捕集され易くする作用をなす。
【００３５】
これら金属炭化物の添加量は、前記金属窒化物と同様に、ガス発生剤組成物全体に対し、０．５〜１０％の範囲が好ましく、０．５％以下では、上記したスラグ捕集効果が期待できなくなり、又、１０％を越えると、燃料や酸化剤の添加量が制限されるので、発生ガス量不足や不完全燃焼を生じるおそれが出てくる。更に、これらの粒径は、細かい程その効果が期待し易いので、個数基準５０％平均粒径で５μｍ以下、好ましくは１μｍ以下が良い。これらの金属炭化物の微粒子を、前記燃料成分や酸化剤成分の粉砕時に少量添加しておけば、これら粉砕成分の固結防止剤の作用をなすと共に酸化剤や燃料中に均一に分散させる事ができ、前記スラグ反応の均一化も期待できる。尚、これら金属炭化物を固結防止剤として使用する際に、二酸化珪素の微粉末である微粒化シリカと併用すれば、スラグ捕集効率を一層高められる事は前述の通りである。又、この金属炭化物を前述の金属窒化物と併用してもよい事はいうまでもない。
【００３６】
次に、本発明で使用する他の添加剤としては、バインダとしての次の一般式で示されるヒドロタルサイト類がある。
〔Ｍ²⁺ _1-x Ｍ³⁺ _x （ＯＨ）₂ 〕^x+〔Ａ^n- _x/n ・ｍＨ₂ Ｏ〕^x-
ここで、Ｍ²⁺：Ｍｇ²⁺，Ｍｎ²⁺，Ｆｅ²⁺，Ｃｏ²⁺，Ｎｉ²⁺，Ｃｕ²⁺，Ｚｎ²⁺等の２価金属。
Ｍ³⁺：Ａｌ³⁺，Ｆｅ³⁺，Ｃｒ³⁺，Ｃｏ³⁺，Ｉｎ³⁺等の３価金属。
Ａ^n-：ＯＨ^- ，Ｆ^- ，Ｃｌ^- ，ＮＯ₃ ^- ，ＣＯ₃ ^2- ，ＳＯ₄ ^2- ，Ｆｅ（ＣＮ）₆ ^3- ，ＣＨ₃ ＣＯＯ^- ，蓚酸イオン，サリチル酸イオン等のｎ価のアニオン。
ｘ ：０＜ｘ≦０．３３
【００３７】
このヒドロタルサイト類は、結晶水を有する多孔質の物質であって、含窒素有機化合物系のガス発生剤のバインダとして極めて有効である。即ち、ヒドロタルサイト類をバインダとして含有するガス発生剤は、本発明の出願人の先願に係る特願平８−２７７０６６号に詳細に記載されている様に、低い打錠圧力においても、特に、アミノテトラゾールを主成分を燃料成分とした場合には、一般のアジド系ガス発生剤の錠剤硬度１０〜１５ｋｇ（モンサント型硬度計）よりも遙かに高い硬度（２５〜３０ｋｇ）を得る事が可能となる。これは、ヒドロタルサイト類が共通して水分を吸着し易い性質を有しており、この性質が組成物の各成分を強固に結合させる作用をなすものと考えられる。又、このバインダを用いた錠剤は、高温・低温の繰り返しによる熱衝撃に対しても錠剤の特性及び燃焼特性に変化がなく、従って実際に車両に搭載した後の経年変化が少なく、極めて特性の安定した錠剤を得る事が可能となる。
【００３８】
尚、ヒドロタルサイト類の代表的なものとしては、
化学式：Ｍｇ₆ Ａｌ₂ （ＯＨ）₁₆ＣＯ₃ ・４Ｈ₂ Ｏで表される合成ヒドロタルサイト、又は、
化学式：Ｍｇ₆ Ｆｅ₂ （ＯＨ）₁₆ＣＯ₃ ・４Ｈ₂ Ｏで表されるピロウライトがあるが、入手の容易性及び価格面から合成ヒドロタルサイトが好ましい。
【００３９】
このヒドロタルサイト類は、ガス発生剤の燃焼に際し、例えば合成ヒドロタルサイトの場合には、次の反応式に示す様に分解するので、有害ガスを発生せず、又、反応自体は吸熱反応であるので、ガス発生剤の発熱量を低減させる効果もある。
Ｍｇ₆ Ａｌ₂ （ＯＨ）₁₆ＣＯ₃ ・４Ｈ₂ Ｏ
→ ６ＭｇＯ＋Ａｌ₂ Ｏ₃ ＋ＣＯ₂ ＋１２Ｈ₂ Ｏ・・・・・・・・・（８）
更に、分解反応で得られるＭｇＯやＡｌ₂ Ｏ₃ は、前記スラグ形成性金属成分の高融点の酸化物であり、前記窒化物や炭化物中に含有される金属成分の珪酸塩（例えばＳｒ_x ＳｉＯ_y ）と前記合成ヒドロタルサイトの分解により生じるＭｇＯとが次式の如く反応して容易にフィルタで濾過可能なガラス状のマグネシウムの珪酸塩の複塩がスラグとして生成される。
ＭｇＯ＋Ｓｒ_x ＳｉＯ_y →ＭｇＯ・Ｓｒ_x ＳｉＯ_y ・・・・・・・・（９）
又、合成ヒドロタルサイトの分解生成物自体も、次式に示す酸・塩基反応であるスラグ反応によって容易に濾過可能なスピネルを形成する。
ＭｇＯ＋Ａｌ₂ Ｏ₃ →ＭｇＡｌ₂ Ｏ₄ ・・・・・・・・・・・・・（１０）
【００４０】
このヒドロタルサイト類をバインダとして添加する場合には、ガス発生剤組成物全体に対して、２〜１０重量％の範囲で含有させる。２％より少ないとバインダとしての機能が達成し難く、１０％を越えると、他の成分の添加量が少なくなってガス発生剤組成物としての機能が果たし難くなるからである。特に３〜８％の範囲で添加されるのが好ましい。
【００４１】
次に、ガス発生剤組成物は、直径４〜１０ｍｍ，厚さ２〜５ｍｍの錠剤或いは適宜寸法のディスク状に成形して使用されるのが一般的であり、その成形時の粉体の流動性を改善する目的で、例えば、ステアリン酸，ステアリン酸亜鉛，ステアリン酸マグネシウム，ステアリン酸カルシウム，ステアリン酸アルミニウム，二硫化モリブデン，グラファイト，窒化硼素の群から選択された１種以上の滑剤を、ガス発生剤全体に対して０．１〜１％添加するのが好ましい。これにより成形性を一層改善する事が可能となる。
【００４２】
又、上記成形して得られたガス発生剤成形体を、成形後に１００〜１２０℃の温度で２〜２４時間程度熱処理する事により、経時変化の少ないガス発生剤を得る事ができる。特に１０７℃×４００時間の過酷な耐熱老化試験を行う場合に、この熱処理は極めて有効である。尚、熱処理時間は、２時間未満では熱処理が不十分であり、２４時間を越えると、それ以上は意味のない熱処理となるので、２〜２４時間の範囲で適当に選定するのが良い。好ましくは５〜２０時間が良い。又、熱処理温度は、１００℃以下では効果が少なく、１２０℃を越えると却って劣化のおそれがあるので、１００〜１２０℃の範囲で適当な値を選定する事になる。好ましくは１０５℃〜１１５℃程度が良い。
【００４３】
次に、本発明の各成分の好ましい組み合わせについて説明する。先ず、燃料成分としては、安定で且つ安全性の高い物質であり、分子構造中の窒素原子の比率が高く、その結果分解して多量の窒素ガスを放出し、しかも有害なＣＯの発生を本質的に抑制する機能を有する５−アミノテトラゾールが好ましい。又、酸化剤としては、ＮＯ_x 発生を抑制する作用を有する硝酸塩が好ましく、特に、捕集し易い高粘性スラグを生成する硝酸ストロンチウムと、ＮＯｘの低減効果及びアミノテトラゾールと三酸化モリブデンとの組み合わせで自動発火機能を発現させる硝酸カリウムとの混合物が最適である。尚、これらの含有量については、前述の通りである。
【００４４】
又、金属窒化物としては窒化珪素が好ましく、又、金属炭化物としては炭化珪素が好ましい。これは珪素分が燃焼過程で二酸化珪素を生成し、この二酸化珪素が、硝酸ストロンチウムから生成する酸化ストロンチウム、或いはバインダとして添加するヒドロタルサイト類に含有されている金属成分とスラグ反応を生じて容易に捕集し易い高粘性のスラグを形成するからである。尚、これらの添加量については前述の通りである。
【００４５】
次に、これらの粒子混合物を結合して成形するためのバインダとしては、高融点酸化物であるＭｇＯとＡｌ₂ Ｏ₃ を生成し得る合成ヒドロタルサイトが最も好ましい。これらは窒化珪素又は炭化珪素から生じる得る二酸化珪素とスラグ反応を生じて、ガス発生器のフィルタ部で捕捉され易い高粘性のスラグを生成する。又、成形性を改善するための滑剤としては、ステアリン酸マグネシウムが最適である。尚、これらの添加量については前述の通りである。
【００４６】
【実施例】
以下に本発明の実施例について説明する。尚、実施例中の％は全て重量％である。
〔実施例１〕
燃料成分としての５−アミノテトラゾールを３２．２％と、酸化剤としての硝酸ストロンチウムを５３．４％と硝酸カリウムを５．８％（酸化剤中の硝酸ストロンチウム含有率：９０．２％）と，触媒成分としての三酸化モリブデンを０．５％と、金属窒化物としての窒化珪素を３．３％と、バインダとしての合成ヒドロタルサイトを４．６％及び滑剤としてのステアリン酸マグネシウムを０．２％とを夫々配合し、Ｖ型混合機により乾式混合した。尚、混合に際し、予め５−アミノテトラゾールと硝酸ストロンチウムと硝酸カリウムには、夫々窒化珪素の微粉末（個数基準５０％平均粒径で０．２μｍ）を、夫々の重量に応じて略比例配分した量を添加し、個数基準５０％平均粒径で１２μｍ程度に粉砕処理した。この混合物を、回転式打錠機でプレス成形して直径５ｍｍ，厚さ２．３ｍｍ，重量１００ｍｇのガス発生剤の錠剤を得た。次に、この錠剤を１１０℃で１０時間、熱処理を行った。
【００４７】
得られた錠剤４６ｇを、図１に示す構造の試験用ガス発生器１に装填した。この試験用ガス発生器１は、点火器２と伝火薬３とが配置された中央点火室７と、その周囲の、ガス発生剤４が装填された燃焼室８と、更に、その外側の金属フィルタ５が配置された冷却フィルタ室９とから構成され、燃焼ガスは、冷却フィルタ室９を経て、ハウジングのガス噴出孔６から外部に噴出する様になっている。このガス発生器１を用いて６０リットルタンクテストを行った。このテストは、内容積６０リットルの高圧容器内にガス発生器を装着して作動させ、容器内にガスを放出させて、図２に示す如き容器内圧力の時間的変化と、容器内への流出スラグ量の測定を行うものである。尚、図２において、縦軸は容器内圧力Ｐ，横軸は時間ｔであり、Ｐ１は容器内の最大到達圧力（Ｋｐａ），ｔ１は点火器２への通電からガス発生器の作動開始までの時間（ｍｓ：ミリ秒），ｔ２はガス発生器の作動からＰ１に至るまでの所要時間（ｍｓ）を示している。この６０リットルタンクテストの結果を表１に示す。又、この試験用ガス発生剤を用いて自動発火性試験も行い、その結果も併せて表１に示す。
【００４８】
【表１】

【００４９】
表１において、スラグ流出量は、前記試験用ガス発生器のガス放出孔６から噴出した固体残渣を容器内から集めた重量（ｇ）を示している。又、人体に有害なガスとしてＣＯとＮＯ_x （ＮＯ及びＮＯ₂ を含む）の量（ｐｐｍ）は、ガス発生器作動後の６０リットル容器内に溜まったガスを、所定のガス検知管による分析によって求めた。更に、ＡＩ機能は、自動発火機能を意味するもので、前記試験用ガス発生器を、外部火災試験と呼ばれる方法で試験し、火災等に対する自動発火機能の有無を示している。尚、外部火災試験は、積み上げた木材の上に試験用ガス発生器を載置し、木材に灯油をかけて着火し、火炎の中にガス発生器を１０〜３０分間放置しておき、ガス発生剤の燃焼によってガス発生器が破損するか否かを試験する方法である。因みに、実施例１の試験用ガス発生器の場合には、木材に着火後、約８分後にガス発生剤の燃焼が生じたが、ガス発生器は破損せず、実施例１のガス発生剤組成物は、自動着火機能を有する事が確認された。
【００５０】
〔実施例２〕
燃料成分としての５−アミノテトラゾールを３２．２％と、酸化剤としての硝酸ストロンチウムを４８．４％と硝酸カリウムを１０．８％（酸化剤中の硝酸ストロンチウム含有率：８１．８％）と、三酸化モリブデンを０．５％と、窒化珪素を３．０％と、合成ヒドロタルサイトを４．９％及びステアリン酸マグネシウムを０．２％とを夫々配合し、実施例１と同様の方法で混合及び成形を行い、ガス発生剤の錠剤を得た。尚、混合に際し、予め５−アミノテトラゾールと硝酸ストロンチウムと硝酸カリウムには、夫々窒化珪素の微粉末（個数基準５０％平均粒径で０．２μｍ）を、夫々の重量に応じて略比例配分した量を添加し、個数基準５０％平均粒径で１２μｍ程度に粉砕処理している。得られた錠剤を用いて実施例１と同様の試験を行い、その結果を上記表１に示す。
【００５１】
〔実施例３〕
燃料成分としての５−アミノテトラゾールを３２．０％と、酸化剤としての硝酸ストロンチウムを５０．４％と硝酸ナトリウムを９．０％（酸化剤中の硝酸ストロンチウム含有率：８４．３％）と、三酸化モリブデンを０．５％と、窒化珪素を３．６％と、合成ヒドロタルサイトを４．３％及びステアリン酸マグネシウムを０．２％とを夫々配合し、実施例１と同様の方法で混合及び成形を行い、ガス発生剤の錠剤を得た。尚、混合に際し、予め５−アミノテトラゾールと硝酸ストロンチウムと硝酸ナトリウムには、夫々窒化珪素の微粉末（個数基準５０％平均粒径で０．２μｍ）を、夫々の重量に応じて略比例配分した量を添加し、個数基準５０％平均粒径で１２μｍ程度に粉砕処理している。得られた錠剤を用いて実施例１と同様の試験を行い、その結果を上記表１に示す。
【００５２】
〔実施例４〕
燃料成分としての５−アミノテトラゾールを３１．６％と、酸化剤としての硝酸ストロンチウムを５３．６％と過塩素酸カリウムを６．２％（酸化剤中の硝酸ストロンチウム含有率：９０．５％）と、三酸化モリブデンを０．５％と、窒化珪素を４．０％と、合成ヒドロタルサイトを３．９％と滑剤としてのステアリン酸マグネシウムを０．２％とを夫々配合し、実施例１と同様の方法で混合及び成形を行い、ガス発生剤の錠剤を得た。尚、混合に際し、予め５−アミノテトラゾールと硝酸ストロンチウム及び過塩素酸カリウムには、夫々窒化珪素の微粉末（個数基準５０％平均粒径で０．２μｍ）を、夫々の重量に応じて略比例配分した量を添加し、個数基準５０％平均粒径で１２μｍ程度に粉砕処理している。得られた錠剤を用いて実施例１と同様の試験を行い、その結果を上記表１に示す。
【００５３】
〔比較例１〕
燃料成分としての５−アミノテトラゾールを３２．２％と、酸化剤としての硝酸ストロンチウムを５９．２％（その他の酸化剤を含まず）と、三酸化モリブデンを０．５％と、窒化珪素を３．３％と、合成ヒドロタルサイトを４．６％と滑剤としてのステアリン酸マグネシウムを０．２％とを夫々配合し、実施例１と同様の方法で混合及び成形を行い、ガス発生剤の錠剤を得た。尚、混合に際し、予め５−アミノテトラゾールと硝酸ストロンチウムには夫々窒化珪素の微粉末（個数基準５０％平均粒径で０．２μｍ）を、夫々の重量に応じて略比例配分した量を添加し、個数基準５０％平均粒径で１２μｍ程度に粉砕処理している。得られた錠剤を用いて実施例１と同様の試験を行い、その結果を上記表１に示す。
【００５４】
〔比較例２〕
燃料成分としての５−アミノテトラゾールを３２．２％と、酸化剤としての硝酸ストロンチウムを３０．２％と硝酸カリウムを２９．０％（酸化剤中の硝酸ストロンチウム含有率：５１．０％）と、三酸化モリブデンを０．５％と、窒化珪素を３．３％と、合成ヒドロタルサイトを４．６％及び滑剤としてのステアリン酸マグネシウムを０．２％とを夫々配合し、実施例１と同様の方法で混合及び成形を行い、ガス発生剤の錠剤を得た。尚、混合に際し、予め５−アミノテトラゾールと硝酸ストロンチウム及び硝酸カリウムには、夫々窒化珪素の微粉末（個数基準５０％平均粒径で０．２μｍ）を、夫々の重量に応じて略比例配分した量を添加し、個数基準５０％平均粒径で１２μｍ程度に粉砕処理している。得られた錠剤を用いて実施例１と同様の試験を行い、その結果を上記表１に示す。
【００５５】
〔比較例３〕
燃料成分としての５−アミノテトラゾールを３３．７％と、酸化剤としての硝酸カリウムを５６．６％（酸化剤中に硝酸ストロンチウム含有せず）と、三酸化モリブデンを０．５％と、窒化珪素を４．２％と、合成ヒドロタルサイトを４．８％と滑剤としてのステアリン酸マグネシウムを０．２％とを夫々配合し、実施例１と同様の方法で混合及び成形を行い、ガス発生剤の錠剤を得た。尚、混合に際し、予め５−アミノテトラゾールと硝酸カリウムには、夫々窒化珪素の微粉末（個数基準５０％平均粒径で０．２μｍ）を夫々の重量に応じて略比例配分した量を添加し、個数基準５０％平均粒径で１２μｍ程度に粉砕処理している。得られた錠剤を用いて実施例１と同様の試験を行い、その結果を上記表１に示す。
【００５６】
上記表１から明らかな様に、全ての実施例及び比較例の燃料成分が同一であり、いずれも良好に燃焼する条件での組成物を選択しているので、ｔ２及びＰ１に関しては大差は見られない。同様に、ＣＯについても、燃料成分が全て５−アミノテトラゾール（５−ＡＴＺ）であり、前述の通り、構造的にＣＯの発生を抑制する性格を有しているので、いずれの例においても大差は見られず且つ人体に有害なレベルではない。
【００５７】
次に、酸化剤としての硝酸ストロンチウムと硝酸カリウムについて見ると、酸化剤として硝酸ストロンチウムのみを使用した比較例１では、スラグ流出量を低く抑える効果があるが、ＮＯｘは無視し得ぬレベルにある。一方、酸化剤として硝酸カリウムのみを使用した比較例３では、ＮＯｘ発生量は低い値に抑えられているが、スラグ流出量は、高い値を示している。この事は、前述した通り、両者の関係が二律背反の関係にある事を示している。
【００５８】
そこで、酸化剤としての硝酸ストロンチウムと硝酸カリウムの混合によるＮＯｘ低減効果について見ると、酸化剤中の硝酸ストロンチウム含有量が０％であり硝酸カリウムが１００％の比較例３では、ＮＯｘ含有量は、最低の８０ｐｐｍであり、酸化剤中の硝酸ストロンチウムが１００％の比較例１では、最高の６５０ｐｐｍである。一方、両酸化剤を約半々に混合している比較例２を見ると、両酸化剤の混合比率とＮＯｘ発生量との間に加成性が成立するならば、比較例２の場合には、両者の中間の３６０〜３７０ｐｐｍ程度を示す事になるが、実際には１２０ｐｐｍであり、両酸化剤の混合によるＮＯｘの発生量は、加成性のラインから大きく外れて、予期せぬ低減効果が確認された。これは、実施例１，２の、酸化剤中の硝酸ストロンチウム含有量が、８０〜９０％の高比率の場合でも、ＮＯｘ含有量は１５０〜１７０ｐｐｍと、前記加成性のラインからＮＯｘの低能度側に大きく外れている事が分かる。又、硝酸ストロンチウムと併用する酸化剤が、硝酸ナトリウム（実施例３）及び過塩素酸カリウム（実施例４）の場合でも、同様に、前記加成性のラインからＮＯｘの低能度側に大きく外れており、これらの酸化剤の併用でも有効な事が分かる。
【００５９】
次に、スラグ流出量について見ると、全ての実施例及び比較例に、スラグ捕集剤としての窒化珪素を適量配合しているので、いずれの場合にも、極端なスラグ流出量は認められない。そこで、前述のＮＯｘの場合と同様に、酸化剤中の硝酸ストロンチウムと硝酸カリウムとの配合比率とスラグ流出量との関係について見ると、酸化剤中の硝酸ストロンチウム含有量が０％（硝酸カリウムが１００％）の比較例３では、スラグ流出量は、最高の８．０ｇであり、酸化剤中の硝酸ストロンチウムが１００％の比較例１では、最低の１．４ｇである。一方、両酸化剤を約半々に混合している比較例２を見ると、両者の中間の４．６ｇであり、この領域では、両酸化剤の混合とスラグ流出量との間に加成性が成立すると見られるが、実施例１，２における酸化剤中の硝酸ストロンチウム含有量が、８０〜９０％の高比率の領域では、スラグ流出量は１．８〜２．２ｇと、前記加成性のラインからスラグ流出量の低減側に外れており、スラグ流出量においても、両酸化剤の混合に、予期せぬ効果が確認された。尚、硝酸ストロンチウムと併用する酸化剤が、硝酸ナトリウム（実施例３）及び過塩素酸カリウム（実施例４）の場合でも、同様に、スラグ流出量は、低い値に抑えられている事が分かる。
【００６０】
因みに、ＣＯについて見ると、酸化剤として硝酸ナトリウムを併用した場合には（実施例３）、他の例に比してＣＯ発生量の低減効果がある事が分かる。又、酸化剤として過塩素酸カリウムを併用した場合には（実施例４）、ｔ２が最も小さな値を示し、燃焼速度の向上に有効である事が分かる。
【００６１】
次に、自動発火性能について見ると、実施例１〜３のものは、外部火炎試験において、ガス発生器を破壊する事なく、木材に点火後１０分以内にガス発生剤の燃焼が生じている。比較例２，３についても同様である。一方、比較例１の場合には、木材に点火後２３分を経過した時点で、大音響と共に爆発し、ガス発生器は粉々になって破片が飛び散っていた。この事から、自動発火性触媒の三酸化モリブデンの存在下でも、酸化剤が硝酸ストロンチウム単独では、その効果が期待できず、三酸化モリブデンと硝酸カリウム／硝酸ナトリウム／過塩素酸カリウムの共存下で、自動発火機能が生じる事が分かる。
【００６２】
〔実施例５〕
次に、自動発火機能についての各種試験結果について説明する。前述の実施例１と同一のガス発生剤組成物、即ち、燃料成分としての５−アミノテトラゾールを３２．２％と、酸化剤としての硝酸ストロンチウムを５３．４％と硝酸カリウムを５．８％と、自動発火性発現触媒成分としての三酸化モリブデンを０．５％と、金属窒化物としての窒化珪素を３．３％と、バインダとしての合成ヒドロタルサイトを４．６％及び滑剤としてのステアリン酸マグネシウムを０．２％とを用いて、実施例１と同様にして成形したガス発生剤の錠剤と、上記実施例１の組成の内、燃料成分（Ｘ），酸化剤中の硝酸カリウム（Ｙ）及び触媒成分としての三酸化モリブデン（Ｚ）を他の成分に１種類づつ変更し、実施例１と同様にして成形したガス発生剤の錠剤とを用いて自動発火性能試験を行い、その結果を表２に示す。検討した成分としては、燃焼成分（Ｘ）では、アミノテトラゾール，ニトログアニジン，ジシアンジアミド，アゾジカルボンアミドの４種類であり、酸化剤（Ｙ）では、硝酸カリウム，硝酸ナトリウム，硝酸ストロンチウム，硝酸バリウム，過塩素酸カリウムの５種類であり、触媒成分（Ｚ）では、三酸化モリブデン，酸化鉄，四三酸化鉄，酸化ニッケル，五酸化バナジウム，酸化銅，酸化カルシウム，二酸化マンガン，酸化タングステン，酸化クロム，過マンガン酸カリウム，モリブデン酸，モリブデン酸ナトリウム，リンモリブデン酸アンモニウム，二硫化モリブデン，硫化鉄，硫化亜鉛，アルミニウム，鉄，モリブデン，硫黄，活性炭，グラファイトの２１種類である。
【００６３】
自動発火性能試験の方法は、図３に示した自動温度調節装置付きシリコンオイルバス１１を用意し、ヒータ１２によって自動温度調節可能になっているオイルバス１４中に、内径２ｃｍ，長さ２０ｃｍの有底鉄管１０を浸漬し、オイルバスの温度が２００±２℃に安定している状態で、該鉄管１０内に、前記各種ガス発生剤の錠剤１粒を投入し、発火するまでの時間を測定して自動発火性能を確認した。自動発火試験の判定結果として、表２には、錠剤投入後、３分以内で発火したものを○，５分以内のものを△，それ以外のものを×で示している。尚、図３中、１３は温度計である。
【００６４】
【表２】

【００６５】
表２から明らかな様に、燃料成分がアミノテトラゾールで、酸化剤が硝酸ストロンチウムと硝酸カリウム／硝酸ナトリウム／硝酸バリウム／過塩素酸カリウムで、触媒成分が三酸化モリブデン／モリブデン酸／モリブデン酸ナトリウム／リンモリブデン酸アンモニウムの組み合わせにおいてのみ、自動発火性能が確認されている。尚、モリブデン酸，モリブデン酸ナトリウム及びリンモリブデン酸アンモニウムの場合には、２００℃の加熱によって分解し、三酸化モリブデンが生成するため、その時点から自動発火性能が生じるものと考えられ、そのため、三酸化モリブデンとして添加した場合に比べて、発火時間が多少遅れている。
【００６６】
【発明の効果】
以上説明した様に、本発明のガス発生剤組成物によれば、以下の如き顕著な効果が期待できる。即ち、
（１）有害ガスであるＣＯの発生を基本的に抑制できるアミノテトラゾールを燃料成分にもちいているので、ＣＯの発生の少ないクリーンなガスでエアバッグの展開が行われ、乗員に対する安全性が向上する。
（２）アミノテトラゾールと酸化剤とを主成分とするガス化率の高いガス発生剤において、酸化剤の主成分を硝酸ストロンチウムとなし、これにスラグ捕集剤として金属窒化物或いは金属炭化物を添加する事により、生成スラグの捕集性が著しく高まり、スラグ流出量が少なくなって、クリーンなガスでエアバッグの展開を行う事が可能となる。更に、スラグ捕集のためのフィルタ部材の量も少なくできるので、ガス発生器の小型化・軽量化に寄与する事になる。
（３）又、金属窒化物或いは金属炭化物は、分解して窒素ガスや炭酸ガスを生成するが、これは、エアバッグ展開に有用なガス成分としてエアバッグの展開に寄与するので、燃料成分としてのアミノテトラゾールの含有量を節約でき、この結果、ガス発生器の小型化，軽量化に寄与する事が期待できる。
（４）硝酸ストロンチウムをベースとする酸化剤に、少量の硝酸カリウム，硝酸ナトリウム，硝酸バリウム又は過塩素酸カリウムを添加した混合酸化剤となす事により、硝酸ストロンチウムのみでは抑制困難であったＮＯｘの発生を大幅に低減させる事が可能となる。
（５）更に、上記組成物に、少量の三酸化モリブデン又は加熱して三酸化モリブデンを生成するモリブデン化合物を添加しておく事により、ガス化率を落とす事なくガス発生剤自体に自動発火機能を発現させる事が可能となるので、従来の様にガス発生器内に別途自動発火機構を設ける必要がなくなり、ガス発生器の構造の簡素化とコストダウンが可能となる。
【図面の簡単な説明】
【図１】本発明の実施例で使用したガス発生器の概略断面図である。
【図２】６０リットルタンクテストにおける時間（ｔ）と容器内圧力（Ｐ）との関係を示すグラフである。
【図３】本発明の実施例で使用した自動発火性試験装置の概略断面図である。
【符号の説明】
１ ガス発生器
２ 点火器
３ 伝火薬
４ ガス発生剤
５ 冷却フィルタ部材
６ ガス放出孔
７ 中央点火室
８ 燃焼室
９ 冷却フィルタ室
１０ 有底鉄管
１１ シリコンオイルバス
１２ ヒータ
１３ 温度計
１４ オイルバス
Ｐ１ 最大到達圧力
ｔ１ 作動開始までの時間
ｔ２ 作動からＰ1 に到るまでの時間[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a gas generating agent for an air bag, and more particularly to a non-azide gas generating agent for an air bag, which has a low content of nitrogen oxides and carbon monoxide, which are harmful components in the generated gas, and slag. The present invention relates to a novel gas generant composition that is excellent in trapping property and further has autoignition properties.
[0002]
[Prior art]
The air bag device is an occupant protection device that has been widely adopted in recent years as one of the measures for improving the safety of occupants of automobiles, and its principle is that a gas generator is operated by a signal from a sensor that detects a collision. Thus, the airbag is deployed between the occupant and the vehicle body. This gas generator is required to have a function of generating clean gas without containing harmful substances and generating necessary and sufficient gas in a short time.
[0003]
On the other hand, in order to stabilize combustion, the gas generant is pressure-molded into tablets, and these tablets maintain their initial combustion characteristics over a long period of time even in various harsh environments. Things are required. If the shape of tablets, etc. collapses due to aging or environmental changes, or the strength decreases, the explosive properties of these explosive compositions exhibit abnormally faster combustion characteristics than the initial combustion characteristics. In the event of a car collision, the airbag may be torn due to abnormal combustion, or the gas generator itself may be damaged, and not only the purpose of occupant protection cannot be achieved, but there is even the risk of injury to the occupant.
[0004]
Therefore, as a material satisfying these functions, a gas generating agent mainly composed of a metal azide compound such as sodium azide or potassium azide has been conventionally used. This gas generating agent burns instantaneously and the combustion gas component is substantially only nitrogen, does not generate harmful gases such as CO (carbon monoxide) and NOx (nitrogen oxide), and has a burning rate. The azide generated by contact with heavy metals is not used because it is difficult to be influenced by the influence of the surrounding environment, that is, the structure of the gas generator, and the design of the gas generator is easy. It has the property of exploding easily due to friction and friction, and the utmost care was required for its handling. Further, the metal azide compound itself is a harmful substance, and further has a great problem that it decomposes in the presence of water or acid to generate a toxic gas.
[0005]
Therefore, as an alternative to the metal azide compound, for example, JP-A-2-225159, JP-A-2-225389, JP-A-3-20888, JP-A-5-213687, JP-A-6-80492. Japanese Laid-Open Patent Publication No. 6-239684, Japanese Laid-Open Patent Publication No. 6-298487, and the like have proposed a gas generating agent containing tetrazole, azodicarbonamide and other nitrogen-containing organic compounds as fuel components. Tetrazoles in particular, among various nitrogen-containing organic compounds, are thermally stable and have a high ratio of nitrogen atoms in the molecular structure, and therefore have the property of essentially suppressing the generation of CO. There is a problem with the generation of NOx. For this reason, as seen in the above-mentioned JP-A-2-225159 and JP-A-3-20888, venturi means are provided in the gas generator to introduce air into the combustion gas from the outside, whereby the concentration of NOx Although a method for lowering the relative value has been proposed, it is not an essential solution.
[0006]
In addition, as an oxidant for using these nitrogen-containing organic compounds as fuel and combusting them, alkali metal or alkaline earth metal chlorates, perchlorates or nitrates are generally used. These alkali metals and alkaline earth metals produce oxides as a result of the combustion reaction, but these oxides are harmful to the human body and the environment, so they are not released into the airbag. It is necessary to collect in the gas generator because it is easy to collect slag. However, many of the gas generating agents that use these nitrogen-containing organic compounds as fuel have a high combustion heat of 2000 to 2500 Joules / g or more, so that the generated gas becomes a high temperature and a high pressure. As a result, the temperature of the slag produced as a by-product during combustion increases, and the fluidity of the slag also increases, and the slag collection rate tends to decrease in a filter built in a conventional gas generator. . Therefore, in order to increase the slag collection rate, a method of loading more filter members and cooling and solidifying the slag can be considered, but in this case, the size of the gas generator increases, and the gas generator It goes against the trend of miniaturization and weight reduction.
[0007]
Further, various methods of adding a slag forming agent have been proposed in order to efficiently collect the alkali metal and alkaline earth metal oxides as slag that is easily collected in the filter section. The basic method is to add silicon dioxide or aluminum oxide as an acidic or neutral substance that easily causes a slag reaction with these basic oxides. The slag formation method in the case of the gas generating agent is not different from the idea. That is, the oxide is collected as silicate or aluminate instead of a highly viscous or high melting point glassy substance. In particular, Japanese Patent Laid-Open No. 4-265292 discloses a low temperature slag forming material typified by silicon dioxide and a high temperature slag forming agent that generates a solid having a melting point near or above the reaction temperature (for example, oxidation of alkaline earth metals and transition metals). The high melting point particles as solids produced by the combustion reaction are reacted with the molten low temperature slag forming agent, and the particles resulting from the reaction are fused together to increase the collection efficiency. A method for enhancing is disclosed.
[0008]
As the above-mentioned oxidizing agent having a high temperature slag forming property, strontium nitrate is disclosed as a particularly suitable substance in the above-mentioned JP-A-4-265292, JP-A-5-111700 and JP-A-5-21368. ing. Certainly, it is an effective means from the aspect of high-temperature slag formation, but when strontium nitrate is used as the oxidizing agent, the NOx concentration is desirable no matter how the stoichiometric ratio with the fuel component is changed. There is a practical problem that it does not drop to the level. As a countermeasure, the above-mentioned Japanese Patent Application Laid-Open No. 5-117070 discloses the use of a fuel component as an alkali metal salt or an alkali metal carbonate as a chemical additive. This leads to a decrease in the gasification rate of the gas generating agent and is not a preferred method.
[0009]
On the other hand, when potassium nitrate is used instead of strontium nitrate, it is possible to reduce the NOx concentration to a level acceptable to the human body, but it is caused by white smoke-like mist derived from potassium oxide generated from potassium nitrate. The amount of slag outflow was so great that the air bag could be melted by this mist, and in the worst case, a hole could be made and burn the passenger. Therefore, by adding a large amount of slag forming material such as silicon dioxide and further increasing the thickness of the filter member in the gas generator, the slag collection performance is lower than in the case of strontium nitrate, but it is considerably It is possible to reduce the amount of slag outflow. However, this method has a practical problem because it goes against the trend of reducing the size and weight of the gas generator.
[0010]
As described above, if strontium nitrate is used, the slag outflow can be reduced, but NOx increases beyond the allowable limit, and if potassium nitrate is used to suppress the generation of NOx, this time the slag outflow is increased. It was very difficult to solve this contradictory problem.
[0011]
Further, as a container material of the gas generator, use of aluminum instead of conventional stainless steel (SUS) is widely used in order to reduce the weight of the gas generator. In case of SUS, it has excellent high-temperature strength, so it is possible to burn the internal explosive composition without destroying the container even when the temperature rises during fires for vehicles or incineration of gas generators. However, in the case of aluminum, the high-temperature strength is significantly reduced, so if the gas generator is exposed to flame due to a vehicle fire etc. and the internal explosive composition burns, it cannot withstand the combustion pressure. If the container breaks, debris scatters around and the passengers and people around them may be killed. Thus, among the items required for the gas generator for an air bag, it is mentioned that a dangerous state such as destruction of a container does not occur even under such a situation. As a countermeasure, USP 4,561,675 proposes a method in which an explosive that automatically ignites at a temperature lower than the temperature at which the strength of aluminum is lowered is placed in close contact with the inner surface of the container when an aluminum container is used. Has been. The auto-ignition agent used here is composed mainly of nitrocellulose, and nitrocellulose itself lacks long-term stability at high temperatures and may even spontaneously ignite due to its deterioration. there were.
[0012]
The auto-ignition temperature is preferably 150 to 210 ° C. from the viewpoint of the strength of aluminum, and substances that ignite below that have a problem in stability during long-term storage. Examples of such autoignition compositions include JP-A-4-265289, JP-A-7-232929, JP-A-8-508972, and JP-A-8-511233, which are the same as the previous US patents. In addition, it is necessary to attach some structure to the inside of the gas generator, or to incorporate it into an igniting agent, a transfer agent, etc., which has been a cause of complicated structure and increased cost. In addition to those described in JP-A-8-508972, chlorates that are sensitive to oxidants are used, so there is a problem in the risk during production. Further, the gas generating agent itself has an autoignition property as described in JP-A-7-257986. A specific example of this composition is 70% by weight. Since it contains an inorganic oxide, the gas generation rate is low, and it is difficult to reduce the size and weight of the gas generator.
[0013]
[Problems to be solved by the invention]
As described above, nitrogen-containing organic compounds effective as a solution to the problem of the harmfulness of conventional metal azide compounds, in particular, problems related to the selection of the oxidant component of the gas generant that uses aminotetrazole as a fuel component, That is, the object is to solve the problems of the generation of toxic gas such as NOx and CO and the problem of slag trapping and to solve the problems of the conventional automatic ignition mechanism at once.
[0014]
Specifically, the generation amount of NOx and CO, which are harmful gas components in the generated gas, is low, the gasification rate is high, the slag outflow amount is small, and in addition, the gas generating agent itself has an automatic ignition function. It is another object of the present invention to provide a novel gas generant composition.
[0015]
[Means for Solving the Problems]
The present invention solves such a problem, and is a gas generant composition containing, as main components, a fuel component, an oxidant, and an auto-ignitable expression catalyst component, wherein 20 to 45% of aminotetrazole is used as the fuel component. (% By weight, the same unless otherwise specified) 50-75% oxidizer, 0.05-5% molybdenum trioxide as an auto-ignitable expression catalyst component, and the oxidant includes strontium nitrate It consists of nitrate or perchlorate of alkali metal or barium, and the strontium nitrate content in the oxidizing agent is 75 to 95%. As a result, the amount of NOx generated and the amount of slag outflow are both small, and the gas generating composition has an automatic ignition function. Instead of molybdenum trioxide, a molybdenum compound that generates molybdenum trioxide by heating such as molybdic acid, sodium molybdate, ammonium phosphomolybdate, and the like was contained in an amount of 0.05 to 5% in terms of molybdenum trioxide. It may be a thing.
[0016]
It is also preferable that the composition comprising the fuel component, the oxidant, and the catalyst component is mixed with 2 to 10% of the hydrotalcite represented by the following formula as a binder and molded. It is.
[M²⁺ _1-xM³⁺ _x(OH)₂]^{x +}[A^n- _{x / n}・ MH₂O]^x-
here,
M²⁺: Mg²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺Divalent metals such as
M³⁺: Al³⁺, Fe³⁺, Cr³⁺, Co³⁺, In³⁺Trivalent metals such as
A^n-: OH^-, F^-, Cl^-, NO_Three ^-, CO_Three ^2-, SO_Four ^2-, Fe (CN)₆ ^3-, CH_ThreeCOO^-, N-valent anions such as oxalate ion and salicylate ion
x: 0 <x ≦ 0.33
[0017]
In addition, as the hydrotalcite,
Chemical formula: Mg₆Al₂(OH)₁₆CO_Three・ 4H₂A synthetic hydrotalcite represented by O, or
Chemical formula: Mg₆Fe₂(OH)₁₆CO_Three・ 4H₂Pyrolite represented by O is preferably used.
[0018]
Further, the above composition may be mixed with 2 to 10% of one or more metal nitrides or metal carbides as a slag collecting agent to improve the slag collecting property, or the above One or more of magnesium stearate, zinc stearate, graphite, boron nitride and molybdenum disulfide as a lubricant is mixed with the composition in an amount of 0.1 to 1% to improve the moldability. This is also a preferable method. In particular, if the metal nitride or the metal carbide is mixed at the time of grinding one or both of the fuel component and the oxidizer, the metal nitride and the metal carbide are uniformly dispersed to make the slag reaction uniform. At the same time, the effect of acting as an anti-caking agent can be expected.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. The basic structure of the gas generating agent of the present invention contains, as main components, aminotetrazole as a fuel component, an oxidant mixture that burns the aminotetrazole, and molybdenum trioxide for exhibiting autoignition. And a hydrotalcite as a binder and other additives as appropriate.
[0020]
First, aminotetrazole used as a fuel component in the present invention will be described. Aminotetrazole has a structure in which the ratio of nitrogen atoms in the molecular structure is high and has a structure that basically suppresses the generation of harmful CO, and is easy to handle, including stability and safety. However, it is inexpensive and is the most preferable substance among various nitrogen-containing organic compounds. The content of aminotetrazole is preferably 20 to 45% with respect to the entire composition. If it is less than 20%, the amount of gas generated is small, and there is a possibility of causing poor development of the airbag. If it is added over 45%, the amount of oxidant added is relatively small, causing incomplete combustion and harmful. This is because a large amount of CO gas may be generated, and in an extreme case, unburned matter may be generated.
[0021]
Next, the oxidizing agent used in the gas generating agent of the present invention will be described. As described above, the combination of aminotetrazole and strontium nitrate increases NOx generation, and the combination of aminotetrazole and potassium nitrate reduces NOx generation but increases slag outflow. However, as a result of various studies, the present inventors have found that when strontium nitrate and potassium nitrate are mixed and used, in a certain range of mixing ratio, the mixture predicted by the additivity of both It has been found that NOx reduction effect and slag outflow reduction effect that are greatly different from the effect are manifested. The range is 75 to 95% strontium nitrate and 5 to 25% potassium nitrate with respect to the entire oxidizing agent. The same effect can be obtained by using other alkali metal or barium nitrate or alkali metal or barium perchlorate instead of potassium nitrate, but potassium nitrate is most preferable. Further, the content of the oxidizing agent is preferably 50 to 75% with respect to the entire gas generant composition. If the oxidizer content is less than 50%, the amount of supplied oxygen will be insufficient, causing incomplete combustion, producing harmful CO gas, and in extreme cases, producing unburned material in the fuel, which will lead to airbag deployment. Necessary gas is not supplied, and there is a risk of causing poor deployment of the airbag. On the other hand, if it exceeds 75%, there is a risk that the fuel component will be insufficient. Similarly to the case described above, the gas required for airbag deployment may not be supplied, and the airbag may be poorly deployed.
[0022]
Next, the catalyst component for automatic ignition expression used in the present invention will be described. When adding various metal oxides, metal sulfides and metal powders to the composition system of aminotetrazole, strontium nitrate and potassium nitrate as described above, and examining whether or not the automatic ignition function is given, surprisingly, Only molybdenum trioxide was found to have the property of developing an auto-ignition function. It was also found that the auto-ignition function was developed even when the addition amount was as small as 0.05%, and that the function hardly changed up to 5%. Therefore, the addition amount of molybdenum trioxide as a catalyst component for imparting automatic ignition is preferably in the range of 0.05% to 5%. If it is less than 0.05%, the automatic ignition function does not appear, and 5 If it exceeds 50%, the gasification rate will decrease.
[0023]
In addition, when it was confirmed whether or not the auto-ignition function was exhibited even in the combination of molybdenum trioxide and other fuel components or in combination with other oxidants, the fuel components were nitroguanidine, dicyandiamide and azodicarbonamide. In this case, the auto-ignition function does not appear, and when the oxidizing agent is a combination of strontium nitrate and potassium nitrate, it exhibits the best auto-ignition function, and other alkali metal or barium nitrate or perchlorate and nitric acid. An automatic ignition function was also confirmed in combination with strontium, but an automatic ignition function was not confirmed with strontium nitrate alone. In this sense, molybdenum trioxide is a unique catalyst that develops an auto-ignition function only when the fuel component is aminotetrazole and the oxidant is a combination of strontium nitrate and an alkali metal or barium nitrate or perchlorate. It can be said.
[0024]
Also, instead of molybdenum trioxide, even molybdenum compounds that produce molybdenum trioxide by heating below 180 ° C below the degradation temperature of aluminum, such as molybdic acid, sodium molybdate, and ammonium phosphomolybdate, are automatically It has been confirmed that an ignition function can be obtained, and in the present invention, these molybdenum compounds can be used. In addition, when using these molybdenum compounds in place of molybdenum trioxide, it is important that the amount added is within the range of 0.05 to 5% in terms of the generated molybdenum trioxide. .
[0025]
Next, other additive components used in the present invention will be described. One of the additives used in the present invention is a metal nitride or metal carbide as a slag scavenger. First, the metal nitride will be described. Another additive used in the present invention is a metal nitride as a slag collecting agent, and silicon nitride (Si) can be used as the metal nitride._ThreeN_Four), Boron nitride (BN), aluminum nitride (AlN), magnesium nitride (Mg)_ThreeN₂), Molybdenum nitride (MoN / Mo₂N), tungsten nitride (WN)₂/ W₂N, W₂N_Three), Calcium nitride (Ca_ThreeN₂), Barium nitride (Ba_ThreeN₂), Strontium nitride (Sr)_ThreeN₂), Zinc nitride (Zn_ThreeN₂), Sodium nitride (Na_ThreeN), copper nitride (Cu_ThreeN), titanium nitride (TiN), manganese nitride (Mn_FourN), vanadium nitride (VN), nickel nitride (Ni_ThreeN / Ni_ThreeN₂), Cobalt nitride (CoN / Co₂N / Co_ThreeN₂), Iron nitride (Fe₂N / Fe_ThreeN / Fe_FourN), zirconium nitride (ZrN), chromium nitride (CrN / Cr₂N), tantalum nitride (TaN), niobium nitride (NbN), cerium nitride (CeN), scandium nitride (ScN), yttrium nitride (YN), and germanium nitride (Ge)_ThreeN_Four1) or more selected from the group of). Of the above metal nitrides, sodium nitride (Na_ThreeN) and sodium azide (NaN) which has been conventionally used as a fuel for gas generants_Three) Is basically a different compound, and the metal nitride referred to in the present invention does not contain sodium azide.
[0026]
Among these, silicon nitride, boron nitride, aluminum nitride, molybdenum nitride, tungsten nitride, titanium nitride, vanadium nitride, zirconium nitride, chromium nitride, tantalum nitride, niobium nitride, etc. are called fine ceramics, Although it is used as a heat-resistant material that is thermally stable and has high strength, it has a property of burning in the same manner as other metal nitrides in a high-temperature oxidizing atmosphere. The present invention makes use of this burning property to simultaneously perform both slag formation and gas generation. For example, in the case of silicon nitride, nitrogen gas, silicate, and oxygen are generated by an oxidation reaction with strontium nitrate represented by the following formula (1). In addition, the coefficient of the reaction formula is omitted.

The nitrogen gas generated here is released into the airbag together with nitrogen gas and carbon dioxide generated by the combustion of the fuel component and is effectively used for the deployment of the airbag, and the oxygen gas is used for the combustion of the fuel component. .
[0027]
In the formula (1), for convenience of explanation, one molecule of Si each_ThreeN_Four+ Sr (NO_Three)₂The amount of strontium nitrate added as an oxidizing agent is actually much larger than that of silicon nitride added for slag collection, so stoichiometrically. Although the above reaction is partially established, the surface layer of the strontium oxide particles produced by the decomposition of strontium nitrate represented by the following formula (2) is represented by a general formula as represented by the following formula (3). Strontium silicate is considered to be produced.
2Sr (NO_Three)₂→ 2SrO + 2N₂+ 5O₂(2)
SrO + SrSiO_Three→ Sr_xSiO_y(3)
[Where, (x, y) = (2, 4), (3, 5); the coefficients in the reaction formula are omitted]
[0028]
Further, strontium oxide produced by decomposition of strontium nitrate is an oxide having a high melting point (2430 ° C.), and is produced in the combustion process as fine solid particles in the gas generator. (1), (3) By the reaction of the formula, various silicates having a melting point of around 1600 ° C. are formed on the particle surface. Since this silicate is in a high-viscosity molten state under the reaction environment temperature, the respective fine particles are fused and aggregated with each other, and become large particles that are easily collected by the filter member in the gas generator.
[0029]
When the metal nitride is aluminum nitride (AlN), the above equations (1) and (3) can be rewritten as follows. In addition, the coefficient of (5) Formula is abbreviate | omitted.

The aluminate produced here also forms a slag in a form that forms a high-viscosity slag layer on the surface of solid slag (SrO), melts and aggregates slag fine particles, and is easy to filter with a filter, as in the case of the silicate. Form.
[0030]
The addition amount of these metal nitrides is preferably in the range of 0.5 to 10% with respect to the entire gas generant composition, and if it is 0.5% or less, the above-described slag collecting effect cannot be expected. If the amount exceeds 50%, the amount of fuel or oxidant added is limited, and there is a risk of insufficient gas generation or incomplete combustion. Further, the smaller the particle size, the more easily the effect can be expected. Therefore, the number-based 50% average particle size is 5 μm or less, preferably 1 μm or less. The number-based 50% average particle size is a method of expressing the particle size distribution on the number basis. When the number of all particles is 100, it means the particle size when 50 particles are accumulated from the smallest. If a small amount of the metal nitride fine particles is added during the pulverization of the fuel component or the oxidant component, it can act as an anti-caking agent for the pulverized component and be uniformly dispersed in the oxidant or fuel. In addition, the slag reaction can be expected to be uniform. When these metal nitrides are used as anti-caking agents, they can be used in combination with finely divided silica which is a fine powder of silicon dioxide.
[0031]
An example of using a metal nitride as a gas generating agent is described in Japanese Patent Publication No. 6-84274. This gas generating agent can be replaced with a conventional metal azide compound, aluminum nitride, nitride. What uses boron, silicon nitride, or transition metal nitride, and uses these metal nitrides as so-called fuel components, and what uses metal nitrides to improve the slag collecting property of the present invention The idea is fundamentally different.
[0032]
Next, similarly to the metal nitride, the metal carbide used as the slag collecting agent in the present invention will be described. Examples of the metal nitride used in the present invention include silicon carbide (SiC) and boron carbide (B_FourC), aluminum carbide (Al_FourC_Three), Magnesium carbide (MgC₂/ Mg₂C_Three), Molybdenum carbide (MoC / Mo₂C), tungsten carbide (WC / W)₂C), calcium carbide (CaC₂), Barium carbide (BaC)₂), Strontium carbide (SrC₂), Zinc carbide (ZnC₂), Sodium carbide (Na₂C₂), Copper carbide (Cu₂C₂), Titanium carbide (TiC), manganese carbide (Mn_ThreeC), vanadium carbide (VC), nickel carbide (Ni_ThreeC), cobalt carbide (Co₂C, CoC₂), Iron carbide (Fe₂C / Fe_ThreeC), zirconium carbide (ZrC), chromium carbide (Cr_ThreeC₂/ Cr₇C_Three/ Cr_{twenty three}C₆), Tantalum carbide (TaC), niobium carbide (NbC), cerium carbide (CeC)₂), Scandium carbide (ScC₂), Yttrium carbide (YC)₂And at least one selected from the group of germanium carbide (GeC).
[0033]
Among these, silicon carbide, boron carbide, molybdenum carbide, tungsten carbide, titanium carbide, vanadium carbide, zirconium carbide, chromium carbide, tantalum carbide, niobium carbide, etc. are called fine ceramics and are thermally Is used as a stable and high-strength heat-resistant material, but has the property of burning in the same manner as other metal carbides in a high-temperature oxidizing atmosphere. In the present invention, both the slag formation and the gas generation are performed at the same time by utilizing this burning property. For example, in the case of silicon carbide, carbon dioxide gas and silicon dioxide are generated by an oxidation reaction such as the following equation (6).

Carbon dioxide and nitrogen produced here are released into the airbag together with nitrogen gas, carbon dioxide and water vapor produced by the combustion of the fuel component, and are effectively used for the deployment of the airbag. Oxygen is the combustion of the fuel component. Used for
[0034]
On the other hand, the by-produced silicate is highly viscous and easily collected in the filter in the gas generator by the reaction of SrO as a combustion residue generated by decomposition of strontium nitrate and the reaction formulas (3) and (5). The formation of the slag is the same as that described above. That is, SrO produced as a combustion residue produces strontium carbonate by the reaction shown in the following equation with the carbon dioxide gas produced by the above equation (6).
SrO + CO₂→ SrCO_Three(7)
This strontium carbonate is also in a highly viscous molten state at about 1500 ° C., similar to the above strontium silicate, so that high-viscosity strontium carbonate is formed on the surface of solid strontium oxide, which is a high melting point particle, and combustion residue The fine particles are fused and aggregated to form large particles that are easily collected by the filter member in the gas generator.
[0035]
The addition amount of these metal carbides is preferably in the range of 0.5 to 10% with respect to the entire gas generant composition, as in the case of the metal nitrides. If it cannot be expected, and if it exceeds 10%, the amount of fuel or oxidant added is limited, and there is a risk that the amount of generated gas will be insufficient or incomplete combustion will occur. Further, the smaller the particle size, the more easily the effect can be expected. Therefore, the number-based 50% average particle size is 5 μm or less, preferably 1 μm or less. If these metal carbide fine particles are added in a small amount at the time of pulverization of the fuel component and the oxidant component, they can act as an anti-caking agent for these pulverized components and be uniformly dispersed in the oxidant and fuel. In addition, the slag reaction can be expected to be uniform. As described above, when these metal carbides are used as an anti-caking agent, the slag collection efficiency can be further enhanced if used in combination with finely divided silica that is a fine powder of silicon dioxide. Needless to say, this metal carbide may be used in combination with the aforementioned metal nitride.
[0036]
Next, as other additives used in the present invention, there are hydrotalcites represented by the following general formula as a binder.
[M²⁺ _1-xM³⁺ _x(OH)₂]^{x +}[A^n- _{x / n}・ MH₂O]^x-
Where M²⁺: Mg²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺Divalent metals such as
M³⁺: Al³⁺, Fe³⁺, Cr³⁺, Co³⁺, In³⁺Trivalent metals such as
A^n-: OH^-, F^-, Cl^-, NO_Three ^-, CO_Three ^2-, SO_Four ^2-, Fe (CN)₆ ^3-, CH_ThreeCOO^-, N-valent anions such as oxalate ion and salicylate ion.
x: 0 <x ≦ 0.33
[0037]
These hydrotalcites are porous substances having crystal water, and are extremely effective as binders for nitrogen-containing organic compound-based gas generants. That is, the gas generant containing hydrotalcite as a binder is described in detail in Japanese Patent Application No. 8-277666, which is a prior application of the applicant of the present invention, even at a low tableting pressure. In particular, when aminotetrazole is used as a fuel component, a hardness (25-30 kg) much higher than a tablet hardness of 10-15 kg (Monsanto hardness tester) of a general azide-based gas generating agent can be obtained. Is possible. This is because hydrotalcites have the property of easily adsorbing moisture, and this property is considered to function to firmly bind the components of the composition. In addition, tablets using this binder have no change in tablet characteristics and combustion characteristics even with thermal shock caused by repeated high and low temperatures, and therefore, there is little change over time after actual mounting in a vehicle. A stable tablet can be obtained.
[0038]
In addition, as a typical thing of hydrotalcite,
Chemical formula: Mg₆Al₂(OH)₁₆CO_Three・ 4H₂A synthetic hydrotalcite represented by O, or
Chemical formula: Mg₆Fe₂(OH)₁₆CO_Three・ 4H₂Although there is pyrolite represented by O, synthetic hydrotalcite is preferable from the viewpoint of availability and price.
[0039]
These hydrotalcites are decomposed when the gas generating agent burns, for example, in the case of synthetic hydrotalcite, as shown in the following reaction formula, so that no harmful gas is generated, and the reaction itself is an endothermic reaction. Therefore, there is also an effect of reducing the calorific value of the gas generating agent.
Mg₆Al₂(OH)₁₆CO_Three・ 4H₂O
→ 6MgO + Al₂O_Three+ CO₂+ 12H₂O ... (8)
Furthermore, MgO and Al obtained by decomposition reaction₂O_ThreeIs a high melting point oxide of the slag-forming metal component, and a silicate (for example, Sr) of the metal component contained in the nitride or carbide._xSiO_y) And MgO produced by the decomposition of the synthetic hydrotalcite react as shown in the following formula, and a glassy magnesium silicate double salt that can be easily filtered by a filter is produced as slag.
MgO + Sr_xSiO_y→ MgO · Sr_xSiO_y(9)
Further, the decomposition product of the synthetic hydrotalcite itself forms a spinel that can be easily filtered by a slag reaction that is an acid / base reaction represented by the following formula.
MgO + Al₂O_Three→ MgAl₂O_Four(10)
[0040]
When adding these hydrotalcites as a binder, it is made to contain in 2-10 weight% with respect to the whole gas generating composition. When the content is less than 2%, the function as a binder is difficult to achieve. When the content exceeds 10%, the amount of other components added is small, and the function as a gas generant composition is hardly achieved. In particular, it is preferably added in a range of 3 to 8%.
[0041]
Next, the gas generant composition is generally used after being formed into a tablet having a diameter of 4 to 10 mm and a thickness of 2 to 5 mm or a disc having an appropriate size. For example, one or more lubricants selected from the group consisting of stearic acid, zinc stearate, magnesium stearate, calcium stearate, aluminum stearate, molybdenum disulfide, graphite, and boron nitride are used for gas generation. It is preferable to add 0.1 to 1% with respect to the whole agent. This makes it possible to further improve the moldability.
[0042]
Moreover, the gas generating agent obtained by the above molding can be heat-treated at a temperature of 100 to 120 ° C. for about 2 to 24 hours after molding to obtain a gas generating agent with little change with time. This heat treatment is extremely effective particularly when a severe heat aging test at 107 ° C. × 400 hours is performed. Note that the heat treatment time is less than 2 hours, and the heat treatment is insufficient. If the heat treatment time exceeds 24 hours, the heat treatment is meaningless. Preferably 5 to 20 hours is good. The heat treatment temperature is less effective at 100 ° C. or less, and if it exceeds 120 ° C., there is a risk of deterioration. Therefore, an appropriate value is selected in the range of 100 to 120 ° C. Preferably about 105 to 115 degreeC is good.
[0043]
Next, preferred combinations of the components of the present invention will be described. First, as a fuel component, it is a stable and highly safe substance, and the ratio of nitrogen atoms in the molecular structure is high. As a result, it decomposes and releases a large amount of nitrogen gas, and it is essential to generate harmful CO. 5-aminotetrazole having a functionally suppressing function is preferred. In addition, as an oxidizing agent, NO_xNitrate having an action of suppressing generation is preferable, in particular, strontium nitrate that generates high-viscosity slag that is easy to collect, and potassium nitrate that expresses an NOx reduction effect and an automatic ignition function by a combination of aminotetrazole and molybdenum trioxide. A mixture of is optimal. In addition, about these content, it is as above-mentioned.
[0044]
Further, silicon nitride is preferable as the metal nitride, and silicon carbide is preferable as the metal carbide. This is because silicon generates silicon dioxide in the combustion process, and this silicon dioxide easily causes slag reaction with metal components contained in strontium oxide generated from strontium nitrate or hydrotalcite added as a binder. This is because a highly viscous slag that is easy to collect is formed. These addition amounts are as described above.
[0045]
Next, as a binder for bonding and molding these particle mixtures, high melting point oxides MgO and Al₂O_ThreeMost preferred are synthetic hydrotalcites capable of producing. These cause a slag reaction with silicon dioxide, which can arise from silicon nitride or silicon carbide, to produce a highly viscous slag that is easily captured by the filter section of the gas generator. As a lubricant for improving moldability, magnesium stearate is optimal. These addition amounts are as described above.
[0046]
【Example】
Examples of the present invention will be described below. In addition, all% in an Example is weight%.
[Example 1]
52.2% 5-aminotetrazole as a fuel component, 53.4% strontium nitrate as an oxidant, and 5.8% potassium nitrate (strontium nitrate content in the oxidant: 90.2%), 0.5% of molybdenum trioxide as a catalyst component, 3.3% of silicon nitride as a metal nitride, 4.6% of synthetic hydrotalcite as a binder, and magnesium stearate as a lubricant of 0. 2% was blended and dry-mixed with a V-type mixer. In mixing, 5-aminotetrazole, strontium nitrate, and potassium nitrate were each preliminarily proportionally distributed with fine powder of silicon nitride (number-based 50% average particle size 0.2 μm) according to the respective weights. Was added and pulverized to about 12 μm with an average particle size of 50% based on the number. This mixture was press-molded by a rotary tableting machine to obtain a gas generant tablet having a diameter of 5 mm, a thickness of 2.3 mm, and a weight of 100 mg. Next, this tablet was heat-treated at 110 ° C. for 10 hours.
[0047]
The obtained tablet 46g was loaded into the test gas generator 1 having the structure shown in FIG. The test gas generator 1 includes a central ignition chamber 7 in which an igniter 2 and a charge transfer agent 3 are arranged, a combustion chamber 8 around which a gas generating agent 4 is loaded, and an outer metal. A cooling filter chamber 9 in which the filter 5 is disposed is configured so that the combustion gas is ejected to the outside through the cooling filter chamber 9 and from the gas ejection hole 6 of the housing. Using this gas generator 1, a 60 liter tank test was conducted. In this test, a gas generator was installed in a high-pressure container having an internal volume of 60 liters, and the gas was discharged into the container. As a result, the time-dependent change in the container pressure as shown in FIG. The amount of slag is measured. In FIG. 2, the vertical axis represents the pressure P in the container, the horizontal axis represents time t, P1 represents the maximum pressure (Kpa) in the container, and t1 represents the time from energization of the igniter 2 to the start of operation of the gas generator. (Ms: milliseconds), t2 indicates the required time (ms) from the operation of the gas generator to P1. The results of this 60 liter tank test are shown in Table 1. In addition, an auto-ignitability test was also conducted using this test gas generating agent, and the results are also shown in Table 1.
[0048]
[Table 1]

[0049]
In Table 1, the slag outflow amount indicates the weight (g) of collecting the solid residue ejected from the gas discharge hole 6 of the test gas generator from the inside of the container. Also, CO and NO are harmful gases to the human body._x(NO and NO₂(Ppm) was determined by analyzing the gas accumulated in the 60-liter container after the gas generator was activated using a predetermined gas detector tube. Further, the AI function means an automatic ignition function, and the test gas generator is tested by a method called an external fire test, and indicates the presence or absence of an automatic ignition function for a fire or the like. In the external fire test, a test gas generator is placed on the stacked wood, and fire is ignited with kerosene on the wood, and the gas generator is left in the flame for 10 to 30 minutes. This is a method for testing whether or not the gas generator is damaged by combustion of the generating agent. Incidentally, in the case of the test gas generator of Example 1, the gas generating agent burned about 8 minutes after ignition of the wood, but the gas generator was not damaged, and the gas generating agent of Example 1 was not damaged. It was confirmed that the composition had an automatic ignition function.
[0050]
[Example 2]
32.2% 5-aminotetrazole as a fuel component, 48.4% strontium nitrate as an oxidant and 10.8% potassium nitrate (strontium nitrate content in the oxidant: 81.8%), The same method as in Example 1 with 0.5% molybdenum trioxide, 3.0% silicon nitride, 4.9% synthetic hydrotalcite, and 0.2% magnesium stearate, respectively. Were mixed and molded to obtain a gas generant tablet. In mixing, 5-aminotetrazole, strontium nitrate, and potassium nitrate were each preliminarily proportionally distributed with fine powder of silicon nitride (number-based 50% average particle size 0.2 μm) according to the respective weights. And is pulverized to about 12 μm with a 50% average particle size. Using the obtained tablets, the same test as in Example 1 was performed, and the results are shown in Table 1 above.
[0051]
Example 3
52.0% of 5-aminotetrazole as a fuel component, 50.4% of strontium nitrate as an oxidizing agent, and 9.0% of sodium nitrate (the content of strontium nitrate in the oxidizing agent: 84.3%) In the same manner as in Example 1, 0.5% molybdenum trioxide, 3.6% silicon nitride, 4.3% synthetic hydrotalcite, and 0.2% magnesium stearate were blended. Mixing and molding were carried out by the method to obtain a gas generant tablet. In addition, when mixing, fine powder of silicon nitride (50% average particle diameter of 0.2% in number basis) was distributed approximately proportionally to 5-aminotetrazole, strontium nitrate, and sodium nitrate in accordance with the respective weights. The amount is added and pulverized to about 12 μm with a 50% average particle diameter based on the number. Using the obtained tablets, the same test as in Example 1 was performed, and the results are shown in Table 1 above.
[0052]
Example 4
51.6% of 5-aminotetrazole as a fuel component, 53.6% of strontium nitrate as an oxidizing agent, and 6.2% of potassium perchlorate (the content of strontium nitrate in the oxidizing agent: 90.5%) ), 0.5% molybdenum trioxide, 4.0% silicon nitride, 3.9% synthetic hydrotalcite, and 0.2% magnesium stearate as a lubricant. Mixing and molding were carried out in the same manner as in Example 1 to obtain a gas generant tablet. When mixing, preliminarily proportional to 5-aminotetrazole, strontium nitrate and potassium perchlorate, respectively, fine powder of silicon nitride (number-based 50% average particle size 0.2 μm) according to the weight of each. The distributed amount is added and pulverized to about 12 μm with an average particle size of 50% based on the number. Using the obtained tablets, the same test as in Example 1 was performed, and the results are shown in Table 1 above.
[0053]
[Comparative Example 1]
52.2% 5-aminotetrazole as a fuel component, 59.2% strontium nitrate as an oxidant (excluding other oxidants), 0.5% molybdenum trioxide, silicon nitride A gas generating agent was prepared by mixing 3.3%, 4.6% of synthetic hydrotalcite, and 0.2% of magnesium stearate as a lubricant, and mixing and molding in the same manner as in Example 1. Pills were obtained. In addition, when mixing, a quantity of silicon nitride fine powder (number-based 50% average particle diameter 0.2 μm) in proportion to each weight was added to 5-aminotetrazole and strontium nitrate in advance. The pulverization process is performed to about 12 μm with a 50% average particle diameter based on the number. Using the obtained tablets, the same test as in Example 1 was performed, and the results are shown in Table 1 above.
[0054]
[Comparative Example 2]
32.2% 5-aminotetrazole as a fuel component, 30.2% strontium nitrate as an oxidant, and 29.0% potassium nitrate (strontium nitrate content in the oxidant: 51.0%), Example 1 was formulated with 0.5% molybdenum trioxide, 3.3% silicon nitride, 4.6% synthetic hydrotalcite, and 0.2% magnesium stearate as a lubricant. Mixing and molding were performed in the same manner to obtain a gas generant tablet. In mixing, 5-aminotetrazole, strontium nitrate, and potassium nitrate were each preliminarily proportionally distributed with fine powder of silicon nitride (number-based 50% average particle size 0.2 μm) according to the respective weights. And is pulverized to about 12 μm with a 50% average particle size. Using the obtained tablets, the same test as in Example 1 was performed, and the results are shown in Table 1 above.
[0055]
[Comparative Example 3]
53.7% 5-aminotetrazole as a fuel component, 56.6% potassium nitrate as an oxidizing agent (not containing strontium nitrate in the oxidizing agent), 0.5% molybdenum trioxide, silicon nitride Of 4.2% of synthetic hydrotalcite, 4.8% of synthetic hydrotalcite and 0.2% of magnesium stearate as a lubricant were mixed and molded in the same manner as in Example 1 to generate gas. Drug tablets were obtained. In addition, when mixing, in advance to 5-aminotetrazole and potassium nitrate, an amount of silicon nitride fine powder (number-based 50% average particle diameter of 0.2 μm) approximately proportionally distributed according to the respective weights is added, It is pulverized to about 12 μm with a 50% average particle diameter based on the number. Using the obtained tablets, the same test as in Example 1 was performed, and the results are shown in Table 1 above.
[0056]
As is clear from Table 1 above, since the fuel components of all the examples and comparative examples are the same, and the compositions are selected under the conditions of good combustion, there is no significant difference regarding t2 and P1. I can't. Similarly, as for CO, the fuel component is all 5-aminotetrazole (5-ATZ), and, as described above, structurally has the property of suppressing the generation of CO. Is not seen and is not harmful to the human body.
[0057]
Next, regarding strontium nitrate and potassium nitrate as oxidizing agents, Comparative Example 1 using only strontium nitrate as an oxidizing agent has an effect of reducing the slag outflow amount, but NOx is at a level that cannot be ignored. On the other hand, in Comparative Example 3 using only potassium nitrate as the oxidizing agent, the NOx generation amount is suppressed to a low value, but the slag outflow amount shows a high value. This indicates that the relationship between the two is a trade-off, as described above.
[0058]
Therefore, when the NOx reduction effect by mixing strontium nitrate and potassium nitrate as an oxidizer is seen, in Comparative Example 3 in which the strontium nitrate content in the oxidizer is 0% and the potassium nitrate is 100%, the NOx content is the lowest In Comparative Example 1 in which the strontium nitrate in the oxidizing agent is 100%, the maximum is 650 ppm. On the other hand, looking at Comparative Example 2 in which both oxidants are mixed in about half, if additivity is established between the mixing ratio of both oxidants and the amount of NOx generated, in the case of Comparative Example 2, In the meantime, it shows about 360 to 370 ppm, but the actual amount is 120 ppm, and the amount of NOx generated by mixing the two oxidants deviates significantly from the additivity line, resulting in an unexpected reduction effect. Was confirmed. This is because, even when the strontium nitrate content in the oxidizing agent of Examples 1 and 2 is a high ratio of 80 to 90%, the NOx content is 150 to 170 ppm, and the low ability of NOx from the additive line. You can see that it is far off to the degree side. Similarly, even when the oxidizing agent used in combination with strontium nitrate is sodium nitrate (Example 3) and potassium perchlorate (Example 4), the NOx low-efficiency side greatly deviates from the additive line. It can be seen that a combination of these oxidizing agents is also effective.
[0059]
Next, with regard to the slag outflow amount, since an appropriate amount of silicon nitride as a slag collecting agent is blended in all the examples and comparative examples, no extreme slag outflow amount is observed in any case. . Therefore, as in the case of the above-mentioned NOx, the relationship between the mixing ratio of strontium nitrate and potassium nitrate in the oxidant and the slag outflow amount is 0% (potassium nitrate is 100%). In Comparative Example 3), the maximum slag outflow amount is 8.0 g, and in Comparative Example 1 in which 100% of strontium nitrate in the oxidizing agent is used, the minimum amount is 1.4 g. On the other hand, looking at Comparative Example 2 in which both oxidizers are mixed approximately in half, it is 4.6 g in the middle of both. In the region where the content of strontium nitrate in the oxidizing agent in Examples 1 and 2 is a high ratio of 80 to 90%, the slag outflow amount is 1.8 to 2.2 g. The slag outflow amount was reduced to the side where the slag outflow was reduced, and an unexpected effect on the mixing of both oxidants was also confirmed in the slag outflow. In addition, even when the oxidizing agent used together with strontium nitrate is sodium nitrate (Example 3) and potassium perchlorate (Example 4), it can be seen that the slag outflow amount is suppressed to a low value. .
[0060]
Incidentally, when looking at CO, when sodium nitrate is used in combination as an oxidizing agent (Example 3), it can be seen that there is an effect of reducing the amount of CO generated as compared with other examples. In addition, when potassium perchlorate is used in combination as an oxidizing agent (Example 4), t2 shows the smallest value, and it can be seen that it is effective for improving the combustion rate.
[0061]
Next, regarding the automatic ignition performance, in Examples 1 to 3, in the external flame test, combustion of the gas generating agent occurs within 10 minutes after ignition on the wood without destroying the gas generator. . The same applies to Comparative Examples 2 and 3. On the other hand, in the case of the comparative example 1, when 23 minutes passed after igniting the wood, it exploded with a loud sound, the gas generator was shattered, and fragments were scattered. Therefore, even in the presence of molybdenum trioxide, an auto-ignitable catalyst, the effect of strontium nitrate alone cannot be expected. In the presence of molybdenum trioxide and potassium nitrate / sodium nitrate / potassium perchlorate, It can be seen that an automatic ignition function occurs.
[0062]
Example 5
Next, various test results regarding the automatic ignition function will be described. The same gas generant composition as in Example 1 described above, that is, 32.2% 5-aminotetrazole as a fuel component, 53.4% strontium nitrate as an oxidant, and 5.8% potassium nitrate. 0.5% molybdenum trioxide as an auto-igniting catalyst component, 3.3% silicon nitride as a metal nitride, 4.6% synthetic hydrotalcite as a binder, and stearin as a lubricant A gas generant tablet formed in the same manner as in Example 1 using 0.2% magnesium oxide, and among the compositions of Example 1 above, fuel component (X), potassium nitrate (Y ) And molybdenum trioxide (Z) as the catalyst component are changed one by one to the other components, and an auto-ignition performance test is performed using a gas generant tablet formed in the same manner as in Example 1. Is shown in Table 2.As the components examined, the combustion component (X) includes four types of aminotetrazole, nitroguanidine, dicyandiamide, and azodicarbonamide, and the oxidizing agent (Y) includes potassium nitrate, sodium nitrate, strontium nitrate, barium nitrate, and perchlorine. There are five types of potassium acid, and catalyst components (Z) include molybdenum trioxide, iron oxide, iron tetroxide, nickel oxide, vanadium pentoxide, copper oxide, calcium oxide, manganese dioxide, tungsten oxide, chromium oxide, There are 21 types of potassium manganate, molybdate, sodium molybdate, ammonium phosphomolybdate, molybdenum disulfide, iron sulfide, zinc sulfide, aluminum, iron, molybdenum, sulfur, activated carbon, and graphite.
[0063]
The automatic ignition performance test method includes a silicon oil bath 11 with an automatic temperature control device shown in FIG. 3, and an oil bath 14 having an inner diameter of 2 cm and a length of 20 cm in an oil bath 14 that can be automatically temperature controlled by a heater 12. In a state where the bottomed iron pipe 10 is immersed and the temperature of the oil bath is stable at 200 ± 2 ° C., a time until a single tablet of the various gas generating agents is put into the iron pipe 10 to ignite. The auto-ignition performance was confirmed by measurement. As determination results of the automatic ignition test, Table 2 shows ◯ for those that ignited within 3 minutes, △ for those within 5 minutes, and × for those other than those that ignited within 3 minutes. In FIG. 3, reference numeral 13 denotes a thermometer.
[0064]
[Table 2]

[0065]
As is apparent from Table 2, the fuel component is aminotetrazole, the oxidant is strontium nitrate and potassium nitrate / sodium nitrate / barium nitrate / potassium perchlorate, and the catalyst component is molybdenum trioxide / molybdate / sodium molybdate / phosphorus. Only in combination with ammonium molybdate, automatic ignition performance has been confirmed. In the case of molybdic acid, sodium molybdate, and ammonium phosphomolybdate, it decomposes by heating at 200 ° C. to produce molybdenum trioxide, so that it is considered that automatic ignition performance occurs from that point. Compared to the case where it is added as molybdenum oxide, the ignition time is somewhat delayed.
[0066]
【The invention's effect】
As described above, according to the gas generant composition of the present invention, the following remarkable effects can be expected. That is,
(1) Since aminotetrazole, which can basically suppress the generation of CO, which is a harmful gas, is used as a fuel component, airbags are deployed with clean gas with little CO generation, improving safety for passengers To do.
(2) In a gas generator with a high gasification rate mainly composed of aminotetrazole and an oxidizing agent, the oxidizing agent is mainly composed of strontium nitrate, and a metal nitride or a metal carbide is added thereto as a slag collector. By doing so, the trapping property of the generated slag is remarkably increased, the amount of slag outflow is reduced, and the airbag can be deployed with clean gas. Furthermore, since the amount of the filter member for collecting slag can be reduced, it contributes to the reduction in size and weight of the gas generator.
(3) In addition, metal nitride or metal carbide decomposes to generate nitrogen gas or carbon dioxide gas, which contributes to the deployment of the airbag as a gas component useful for airbag deployment. The content of aminotetrazole can be saved, and as a result, it can be expected to contribute to the reduction in size and weight of the gas generator.
(4) By using a mixed oxidant with a small amount of potassium nitrate, sodium nitrate, barium nitrate or potassium perchlorate added to an oxidant based on strontium nitrate, it is possible to prevent the generation of NOx, which was difficult to suppress with strontium nitrate alone. It can be greatly reduced.
(5) Further, by adding a small amount of molybdenum trioxide or a molybdenum compound that generates molybdenum trioxide by heating to the above composition, the gas generating agent itself has an automatic ignition function without reducing the gasification rate. Therefore, it is not necessary to provide a separate automatic ignition mechanism in the gas generator as in the prior art, and the structure of the gas generator can be simplified and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a gas generator used in an embodiment of the present invention.
FIG. 2 is a graph showing the relationship between time (t) and container internal pressure (P) in a 60-liter tank test.
FIG. 3 is a schematic cross-sectional view of an automatic ignition test apparatus used in an example of the present invention.
[Explanation of symbols]
1 Gas generator
2 igniters
3 Gunpowder
4 Gas generating agent
5 Cooling filter members
6 Gas discharge hole
7 Central ignition chamber
8 Combustion chamber
9 Cooling filter chamber
10 Bottomed iron pipe
11 Silicon oil bath
12 Heater
13 Thermometer
14 Oil bath
P1 Maximum ultimate pressure
t1 Time to start operation
Time from t2 operation to P1

Claims (9)

A gas generant composition comprising a fuel component, an oxidant and a catalyst component as main components, wherein the fuel component is 20 to 45% by weight of aminotetrazole, 50 to 75% by weight of oxidant, and exhibits automatic ignition The catalyst contains 0.05 to 5% by weight of molybdenum trioxide as a catalyst component, and the oxidizing agent comprises strontium nitrate and an alkali metal or barium nitrate, or strontium nitrate and an alkali metal or barium perchlorate. A gas generating composition characterized in that the strontium nitrate content in the oxidizing agent is 75 to 95% by weight 2. The gas generant composition according to claim 1, comprising a molybdenum compound that generates molybdenum trioxide by heating instead of the molybdenum trioxide, in an amount of 0.05 to 5% by weight in terms of molybdenum trioxide. The gas generating composition according to claim 2, wherein the molybdenum compound is at least one selected from the group consisting of molybdic acid, sodium molybdate, and ammonium phosphomolybdate. Claims formed by adding 2 to 10% by weight of a hydrotalcite represented by the following formula as a binder to the composition comprising the fuel component, the oxidant, and the catalyst component, and mixing them. Item 4. The gas generant composition according to any one of Items 1 to 3 [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x−
here,
M ²⁺ : Divalent metal such as Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ M ³⁺ : Al ³⁺ , Fe ³⁺ , Cr ^{3 +,} Co ^3+, 3-valent metal of in ^3+, etc. ^{a n-: OH -, F -} , Cl -, NO 3 -, CO 3 2-, SO 4 2-, Fe (CN) 6 3-, CH ₃ n-valent anion x such as COO ⁻ , oxalate ion, salicylate ion, etc .: 0 <x ≦ 0.33 The hydrotalcites are
A synthetic hydrotalcite represented by a chemical formula: Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O, or
The gas generant composition according to claim 4, which is a pyrolite represented by the chemical formula: Mg ₆ Fe ₂ (OH) ₁₆ CO ₃ · 4H ₂ O. 6. The composition according to claim 1, wherein one or more metal nitrides or metal carbides as a slag scavenger are mixed in the composition in an amount of 2 to 10 wt% based on the entire composition. Gas generant composition The gas generant composition according to claim 6, wherein the number-based 50% average particle size of the metal nitride or metal carbide is 5 µm or less. The gas generant composition according to claim 7, wherein the metal nitride or metal carbide has a number-based 50% average particle size of 1 μm or less and is mixed when pulverizing one or both of the fuel component and the oxidizer. object As a lubricant, one or more selected from the group consisting of magnesium stearate, zinc stearate, graphite, boron nitride and molybdenum disulfide are mixed in the composition in an amount of 0.1 to 1% by weight based on the whole composition. A gas generant composition according to any one of claims 1 to 8.

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