JP3940557B2 - High gas yield non-azide gas generator - Google Patents

Description

【００２７】
式Ｉに示されるテトラゾールの一般的非金属塩は、陽イオン性アミン成分Ｚ、およびテトラゾール環およびテトラゾール環の５位に置換したＲ基を含む陰イオン性成分を含む。式ＩＩに示されるようなトリアゾールの一般的非金属塩は、陽イオン性成分Ｚおよびトリアゾール環およびトリアゾール環の３位および５位に置換した２つのＲ基を含む陰イオン性成分を含有し、Ｒ_１はＲ_２と構造的に同類であっても、なくてもよい。Ｒ成分は、水素、またはアミノ、ニトロ、ニトロアミノ、または直接的、またはアミン、ジアゾまたはトリアゾ基を介して置換された式ＩまたはＩＩのそれぞれテトラゾリルおよびトリアゾリル基等の窒素含有化合物を含む群から選択される。化合物Ｚは、いずれの式の１位の水素を置換することによって陽イオンを形成し、アンモニア、ヒドラジン、グアニジン、アミノグアニジン、ジアミノグアニジン、トリアミノグアニジン、およびニトログアニジン等のグアニジン化合物；ジシアンジアミド、ウレア、カルボヒドラジド、オキサミド、オキサミン酸ヒドラジド、ビス−（カルボンアミド）アミン、アゾジカルボンアミドおよびヒドラゾジカルボンアミドを含むアミド類；および３−アミノ−１，２，４−トリアゾール、３−アミノ−５−ニトロ−１，２，４−トリアゾール、５−アミノテトラゾール、３−ニトロアミノ−１，２，４−トリアゾール、および５−ニトロアミノテトラゾールを含む置換アゾール類；メラミン等のアジン類を含むアミン群から選択される。
【００２８】
テトラゾールまたはトリアゾールの前記非金属塩を相安定化硝酸アンモニウム（ＰＳＡＮ）と乾燥混合する。ＰＳＡＮを一般的に、全ガス発生組成物の約４６−８７重量％、そしてより好ましくは５６−７７重量％の濃度で用いる。硝酸アンモニウムを、実施例１６に記載されるているように、そして“アジド無しのガス発生組成物の製造方法”と題し、１９９６年７月２日付与され、ここに参照して含める共有米国特許No.5,531,941に教えられるように硝酸カリウムによって安定化する。ＰＳＡＮは、ＡＮ８５−９０％およびＫＮ１０−１５％を含み、ＡＮ とＫＮ の共結晶化等の適当な手段で形成され、それで−４０℃と１０７℃の間で純粋な硝酸アンモニウム（ＡＮ）において起る固体−固体相変化を防ぐ。ＫＮを純粋なＡＮを安定化するために好ましく使用するが、当業者は他の安定化剤がＡＮと一緒にして使用できることを容易に理解するであろう。
【００２９】
ガス発生剤はさらに、アルカリ金属およびアルカリ土類金属の硝酸塩および過塩素酸塩から選択される金属性酸化剤を含有する。当業者は、金属性酸化物、亜硝酸塩、塩素酸塩、パーオキシド、およびヒドロキシド等の他の酸化剤も使用してもよいことを容易に理解するであろう。金属性酸化剤は、ガス発生組成物の約０．１−２５重量％、そしてより好ましくは０．８−１５重量％で存在する。
【００３０】
ガス発生剤はまたさらに、ケイ酸塩、シリコン、珪藻土、およびシリカ、アルミナおよびチタニア等のオキシド類を含む群から選択される不活性鉱物のような不活性成分を含有する。ケイ酸塩は、タルクおよび、粘土や雲母のケイ酸アルミニウム等の層構造を有するケイ酸塩；アルミノシリカート；ボロシリカート；およびケイ酸ナトリウムおよびケイ酸カリウム等の他のケイ酸塩を含むが、限定されるものではない。不活性成分は、ガス発生組成物の約０．１−８重量％、そしてより好ましくは０．１−３重量％で存在する。
【００３１】
好ましい態様は、５０−７７％のＰＳＡＮ、２３−２８％の５，５´−ビ−１Ｈ−テトラゾールのジアンモニウム塩（ＢＨＴ−２ＮＨ_３）、０．８−１５％の硝酸ストロンチウム、および０．１−３％の粘土を含有する。
金属性酸化剤と不活性成分との組み合わせは、金属性酸化剤から金属を含有する鉱物の生成となる。例えば、主としてケイ酸アルミニウム（Al₂Si₄ O₁₀)および石英（SiO₂)である粘土を硝酸ストロンチウム（Sr(NO₃)₂)の組み合わせは、主としてケイ酸ストロンチウム（SrSiO₄およびSr₃SiO₅)からなる燃焼生成物となる。この方法がガス発生燃焼を全ての圧力で持続させるのを助け、従って膨張器を“不燃”にならないようにするものと思われる。
【００３２】
上に定義されたような非金属塩、ＰＳＡＮ、アルカリ土類金属酸化剤、および不活性成分を含有するガス発生剤の燃焼速度は低い（１０００ｐｓｉで約０．３０ｉｐｓ）ものであり、１０００ｐｓｉで０．４０ｉｐｓの工業基準を下回る。従って、これらの組成物は全く予期されなかったことであるが、点火され、１０００ｐｓｉで０．４０ｉｐｓよりも低い燃焼速度をもつ他のガス発生剤に較べてさらに容易に燃焼を持続し、０．４０ｉｐｓ より大きい燃焼速度を有するガス発生剤を上回る機能を示す場合もある。
【００３３】
本発明と組み合わせて使用される任意の点火助剤を、トリアゾール、トリアゾロン、アミノテトラゾール、テトラゾールまたはビテトラゾール、またはここに参照して示すものを含めるＰｏｏｌｅの米国特許No.5,139,588に記載されているような他のものを含む非アジド燃料から選択する。 テトラゾールまたはトリアゾールに基づく燃料、相安定化硝酸アンモニウム、金属性酸化剤、および不活性成分を含有するガス発生剤が推進剤の改善された点火性を示し、且つまた再現性のある燃焼性能をもつ持続した燃焼速度をあたえるので、 BKNO₃等の通常の点火助剤はもはや必要でない。
【００３４】
本発明のガス発生組成物の成分が組み合わされ、そして混合される方法および順序は、均一な混合物が得られる限り重大ではなく、混合を用いられる成分の分解を起さない条件下に行う。例えば、材料を湿めらせて配合しいても、乾燥配合してもよく、ボールミルまたはRed Devilタイプのペイント撹拌器でつぶし、次いで圧縮成形してペレット化する。材料を別々または一緒に流体エネルギーミル、スエコ振動エネルギーミルまたはバンタム微粉末機で粉砕し、次いで配合するか、またはさらに圧縮の前にｖ−ブレンダーで配合してもよい。
【００３５】
本発明を以下の実施例によって説明し、ここでは特に記載がない限り成分を全組成物の重量パーセントで定量する。実施例１−３および１６−２０の値は実験的に得られた。実施例１８−２０は、実施例１−３で発見されたのと同等な化合物のパーセントを与え、比較する目的および実験室での結果を確認するために含めたものである。実施例４−１５の値が、示された組成に基づいて得られる。主たるガス生成物は、Ｎ_２、Ｈ_２ＯおよびＣＯ_２であり、固体を形成する成分は、一般的にそれらの最も普通の酸化状態で存在する。酸素バランスは、化学量論的にバランスされた生成物を生成するために必要とされるか、または遊離される組成物中の酸素の重量パーセントである。従って、負の酸素バランスは、酸素不足の組成物を表し、一方正の酸素バランスは、酸素に富む組成物を表わす。
【００３６】
組成物を処方するとき、燃料に対するＰＳＡＮの比を、酸素バランスが上記のように組成物の酸素−４．０重量％から＋１．０重量％であるように調整する。より好ましくは、燃料に対するＰＳＡＮの比を、組成物の酸素バランスが組成物の酸素−２．０重量％から０．０重量％であるように調整する。 ＰＳＡＮと燃料の相対的な量は、ＰＳＡＮを作るために使用される添加剤並びに選択された燃料の性質に依存するであろうことは理解できる。
【００３７】
下の表１と２において、ＰＳＡＮは星印をつけたもの以外の全ての場合において全酸化剤成分の１５％のＫＮで相安定化される。その場合においては、 ＰＳＡＮが全酸化剤成分の１０％のＫＮで相安定化される。
本発明によれば、これらの処方物は、熱的にも容量的にも−４０℃と１１０℃の温度範囲で安定であり；多量の無毒ガスを生成し；最小の固体微粒子を生成し；容易に点火し、そして繰り返し可能な燃え方をし；有毒な、感光性の、または爆発性の出発材料を含まず；そして最終形状において無毒、非感光性で、非爆発性である。
【表１】

【表２】

【００３８】
例１６ − 記述のみ
硝酸アンモニウム（AN)８５重量％および硝酸カリウム（KN)１５重量％からなる相安定化硝酸アンモニウム（PSAN)を以下のように製造した。乾燥ＡＮ２１２５ｇおよび乾燥ＫＮ３７５ｇを熱せられたジャッケットの２重遊星状ミキサーに加えた。蒸留水を、全てのANとKNが溶け、溶液温度が６６−７０℃になるまで混合しながら加えた。混合を、乾燥した白色粉末が生成されるまで大気圧で続けた。この製造物がPSANであった。PSANをミキサーから取りだし、薄い層に延ばし、８０℃で残留水分を除くために乾燥させた。
【００３９】
例１７ − 説明例
実施例１６で製造されたPSANを、純粋なANで普通起る望ましくない相変化が除かれたかどうかを決定するために純粋なＡＮと比較して試験した。両方をＤＳＣ中０℃から２００℃で試験した。純粋なANは、固体−固体相変化に対応して約５７℃および約１３３℃で吸熱、並びに約１７０℃で融点吸熱を示した。PSANは、約１１８℃で固体−固体相転移に対応する吸熱および約１６０℃でPSANの溶融に対応する吸熱を示した。
純粋なANおよび実施例１６で製造されたPSANを、直径１２ｍｍ、厚さ１２ｍｍスラグに圧縮し、−４０℃から１４０℃の温度範囲で体膨張計測器で容積膨張を測定した。−４０℃から１４０℃で加熱すると、純粋なANは、約−３４℃で始まる容積収縮、約４４℃で始まる容積膨張、および９０℃で始まる容積収縮および約１３０℃で始まる容積膨張を経過した。 PSANは、−４０℃から１０７℃で加熱したとき、容積変化を経過しなかった。それは約１１８℃で始まる容積膨張を経過した。
【００４０】
純粋なANおよび実施例１６で製造されたPSANを、直径３２ｍｍ、厚さ１０ｍｍスラグに圧縮し、乾燥剤と一緒に湿気を閉じたバッグに置き、温度を−４０℃から１０７℃の間で循環した。１サイクルは、サンプルを１時間１０７℃に保ち、約２時間かけて一定速度で１０７℃から−４０℃へ移行し、１時間−４０℃に保ち、そして約１時間かけて一定速度で−４０℃から１０７℃へ移行することから成り立っている。６２の全サイクル後、サンプルを取り出し、観察した。純粋なＡＮスラグは実質的に粉末に崩壊したが、PSANスラグは、亀裂または欠陥がなく完全に原形のままであった。
上記の例は、 ＫＮの添加とそれがANとKNの共沈殿混合物の１５重量％を含むことが−４０℃から１０７℃の自動車適用範囲でANに存在する固体−固体相転移を取り除いていることを示している。
【００４１】
例１８
重量％で以下の組成物： PSAN７６．４３％およびBHT・2NH₃２３．５７％を有するPSANとBHT・2NH₃の混合物を製造した。目方を計ったそして乾燥した成分を配合し、ボールミルジャー中セラミックシリンダーを用い、回転によって細かい粉末へ粉砕した。粉末を粉砕シリンダーから離し、材料の流動性を改善するために顆粒にした。顆粒を、高速回転プレスで圧縮してペレットに成形した。この方法でつくられたペレットは、格別の品質と強度であった。
組成物の燃焼速度は１０００ｐｓｉで１秒あたり０．４８インチであった。燃焼速度を一定圧力で、知られた長さの円柱状ペレットを燃やすために要する時間を測定することによって決定した。ペレットを１０トン加重して直径１／２“ダイ（die)に成形し、次いで側に沿っての燃焼を防ぐエポキシ／チタニウムジオキシド阻害剤で側に被覆した。
【００４２】
回転プレスでつくられたペレットはガス発生器アセンブリーに積まれ、そして容易に点火し、固体、空中微粒子、および生成される毒性ガス最小にしてエアバッグを満足に膨張させことが分かった。ガス発生剤の約９５重量％がガスへ転換された。使用された点火助剤は、BKNO₃等の促進剤を含まず、米国特許No.5,139,588に記載されているものような高ガス収率非アジドペレットのみを含有した。
鉱物衝撃装置の標準協会で試験すると、この混合物の衝撃感度は３００ｋｐ・ｃｍよりも大きかった。米国D.O.T.手順にしたがって試験すると、直径０．１８４″そして厚さ０．０８０″のペレットは、No.8の工業雷管（blasting cap)で開始したとき、爆燃も爆発もしなかった。
【００４３】
例１９
重量％で以下の組成： PSAN７５．４０％およびBHT・2NH₃２４．６０％を有するPSANとBHT・2NH₃の混合物を製造した。組成物は実施例１８のようにして製造され、再び格別の品質と強度のペレットを生成した。組成物の燃焼速度は１０００ｐｓｉで１秒あたり０．４７インチであった。
【００４４】
回転プレスでつくられたペレットはガス発生器アセンブリーに積んだ。ペレットは容易に点火し、固体、空中微粒子、および生成される毒性ガス最小にしてエアバッグを満足に膨張させことが分かった。ガス発生剤の約９５重量％がガスへ転換された。
鉱物衝撃装置の標準協会で試験すると、この混合物の衝撃感度は３００ｋｐ・ｃｍよりも大きかった。米国運輸局の手順にしたがって試験すると、直径０．２５０″そして厚さ０．１２５″のペレットは、No. 8の爆破キャップで開始したとき、爆燃も爆発もしなかった。
【００４５】
例２０
重量％で以下の組成： PSAN７２．３２％およびBHT・2NH₃２７．６８％を有する PSAN とBHT・2NH₃の混合物を製造した。組成物を、粉末に対する粉砕媒体の重量比を３倍にした以外は、実施例１８のようにして製造した。組成物の燃焼速度は１０００ｐｓｉで１秒あたり０．５４インチであった。鉱物衝撃装置の標準協会で試験すると、この混合物の衝撃感度は３００ｋｐ・ｃｍよりも大きかった。この例は、本発明の組成物の燃焼速度をより強烈に粉砕することによって増加できることを示している。米国D. O. T.手順にしたがって試験すると、直径0.184″そして厚さ0.090″のペレットは、No. 8の工業雷管で開始したとき、爆燃も爆発もしなかった。
本発明によれば、硝酸アンモニウムをベースとする推進剤は相安定化されており、大気圧以上で燃焼を維持し、豊富な無毒ガスを与え、一方微粒子形成を最小にする。テトラゾールおよびトリアゾールの非金属塩は、ＰＳＡＮと組み合わさって容易に点火するので、BKNO₃等の通常の点火助剤を燃焼を開始するために必要としない。
【００４６】
さらに、光感度が低下しているため、および米国Ｄ．Ｏ．Ｔ．規制にしたがっているため、組成物は、エアバッグ膨張器内で使用するため最適にデザインされた推進錠剤のサイズで容易にキャップ試験に通る。このように、本発明の顕著な利点は、無害で且つ非爆発性の出発材料を含有しており、また、これらのすべてがほとんど制限なく輸送できることである。
先行技術の比較データおよび本発明のそれを、PSANと一緒にしたテトラゾールおよびトリアゾールのアミン塩を利用することのガス発生の有利さを説明するために表３に示す。
【表３】

【００４７】
表３に示されるように、そして本発明の通り、PSANおよびテトラゾールおよびトリアゾールのアミン塩は、先行技術の組成物に比べてガス発生剤容積の１立方センチメートルあたり有意に多量のガスを生成する。このことは、必要とされるガス発生剤のより少ない量のためより小さい膨張器の使用を可能にする。より多くのガス生成のため、固体の生成が最小となり、それによってより小さい膨張器の使用にも役立つより小さくて且つより簡単なろ過方法を可能にする。
本発明のまた別の態様において、PSANおよび、テトラゾールの非金属塩またはトリアゾールの非金属塩を含有するいくつかのガス発生組成物は、乏しい点火性と不完全燃焼を示し、それによってガス生成の不適当な速度および／または“不燃”となることが見い出されている。表４の例２１−２７に示されるように、ケイ酸塩が生成され、それによって点火性を改善し、且つ全ての圧力で燃焼を持続する。
【表４】

【００４８】
例２１−２７
例２１−２７において、相安定化硝酸アンモニウム（PSAN)は、KN１０重量％を含有し、約８０℃で飽和水溶液から共結晶化によって製造された。５，５′−ビ−１Ｈ−テトラゾールの二アンモニウム塩（BHT-2NH₃)、硝酸ストロンチウム、粘土およびニトログアニジン（NQ)を外部の供給者から購入した。
各材料を１０５℃で別々に乾燥した。乾燥された材料は次いで、一緒に混合され、大きなボールミルジャー中アルミナシリンダーで転摩された。アルミナシリンダーを離した後、最終物は１５００グラムの均一で且つ粉砕された粉末となった。粉末は、流動性を改善するために顆粒にされ、次いで高速錠剤プレスでペレット（径０．１８４″、厚さ０．０９０″）に圧縮成形された。錠剤を膨張器の積み、６０Lタンクおよび１００ft³タンク内で点火した。６０Lタンクは、時間に亘る圧力を決定し、進行中膨張器から排出される固体の量を測定するために使用された。１００ft³タンクは、いくつかのガスのレベル並びに膨張器によって生成される空中の微粒子の量を決定するために使用された。表１は組成物の結果を要約している。
【００４９】
例２１−２４は、比較の目的で示されている。例２１はPSANおよびBHT-2NH₃を含有する。例２２はPSAN、BHT-2NH₃およびNQを含有する。例２3はPSAN、BHT-2NH₃および硝酸ストロンチウム（金属性酸化剤）を含有する。例２４はPSAN、BHT-2NH₃および粘土（不活性成分）を含有する。例２５および２６は、本発明に従い、PSAN、BHT-2NH₃、金属性酸化剤としての硝酸ストロンチウム、および不活性成分としての粘土を含有する。最後に、例２７は、 PSAN、BHT-2NH₃、金属性酸化剤としての硝酸ストロンチウム、および不活性成分としての粘土を含有するが、上記とは異なる量である。本出願人は、例２１と２２の組成物（及び上に示したものと似た組成物）に金属性酸化剤および不活性成分を加えるとは、持続する燃焼と最適な点火性につながることを見出した。しかし、当業者は、例えば、より高い圧力で運転させるように膨張器を再デザインすることが、自動車のエアバッグ適用において、例２１と２２の組成物をいっそう有用にするであろうことを容易に理解するであろう。
【００５０】
表４に示すように、例２１−２７は、最少の固体微粒子をもつ大きい容量のガスを生成する典型的な高収率ガス発生剤である。ガス変換は、燃焼後ガスへ変換される固体ガス発生剤の重量％である。例２５および２６のガス変換は、例２１−２４および２７よりわずかに低いが、６０Lタンク中の膨張器によって生成される固体の量には有意な差はない。このことは、例２５および２６の組成物が、例２１−２４および２７に較べてガス変換においてわずかに減少しているが、本質的に高収率ガス発生剤であることを示している。表４に挙げられたすべての例は、熱的にも容量的にも−４０℃から１１０℃で安定であり、非爆発性成分を含有するものである。
いくつかの膨張器デザインにおいて、例２１−２３（および上記と似た組成物）の組成物は時々“不燃”状態を経過することが見い出された。これは、特定の速度のガス生成を要求するエアバッグ運転には許容できず、従ってより高い圧力で運転できるより複雑な膨張器が要求される。一方、例２５−２７の組成は、しっかり点火されると、遅滞なく完全燃焼となる。
【００５１】
燃焼速度データを、PSAN、テトラゾールの非金属塩またはトリアゾールの非金属塩、金属性酸化剤、および不活性成分を組み合わせる利点をさらに記載するために挙げる。燃焼速度モデルR_b=aPⁿが適用されるとすると、式中Rb=燃焼速度、 a=定数、P=圧力、そしてn=圧力指数である。燃焼速度と圧力の関係、従ってa およびn は圧力の関数として変化できることに注目されたい。これが起れば、圧力に対する燃焼速度カーブにおける“中断”があり、異なる燃焼メカニズムへの変化を示す。理想的には、ガス発生組成物は、全膨張器運転圧力で単一の燃焼メカニズムをもつべきである。さらに、ガス発生剤は容易に点火し、且つこれらの圧力で燃焼を持続すべきである。図１は、ガス発生剤の圧力指数における“中断”を説明している。図１において、例２１−２３および２６の圧力に対する燃焼速度カーブが表わされている。例２６の組成物は、燃焼時“中断”を示すことなく、それによって単一の燃焼メカニズムがすべての膨張器運転圧力で維持され、起っていることをを示すことに注目されたい。
【００５２】
約３０００ｐｓｉを超える圧力では、全ての組成物が容易に点火し、そして燃焼を持続する。圧力が２０００−３０００ｐｓｉ より減少すると、例２１−２３は圧力指数における有意な上昇を経過する。これは、圧力により大きく依存する燃焼メカニズムへの変化を示す。この点で、圧力の少しの減少が、ガス発生剤の燃焼する速度を劇的に減少し、結局それを消させることになり得る。事実、組成物２１−２３を含むいくつかの膨張器は時々、ガス発生剤の少しの部分しか消費されないので、適切には機能しないことが分かった。この現象はまた、非常に低い圧力で観察された。プロパン炎を用いて常圧で点火すると、組成物２１−２３は燃え出すが、常に消えた。さらに、これらの組成物は燃焼速度装置内で試験すると、１００ｐｓｉで点火せず且つ完全に燃焼しない。
【００５３】
対照的に、図１に示されるように（組成物２６のカーブに“中断”の無いことに注目されたい）、組成物２６は点火し、容易に燃焼し、そして０−４５００ｐｓｉで同じ圧力指数を有する。プロパン炎を用いて常圧で点火すると、組成物２６は容易に点火し、ゆっくりと完全に燃焼した。燃焼速度装置内の１００ｐｓｉで、組成物２６は点火し、完全に燃焼した。組成物２６を含有する膨張器は、すべての場合に、容易な点火性、そしてガス発生剤の完全且つ安定した消費をもって機能した。膨張器運転特性は、組成物２５が使用されたときと概ね同一であった。低いレベルの金属性酸化剤と不活性成分、そして組成物２１−２３に似た燃焼速度性にもかかわらず、組成物２７は、膨張器レベルでガス発生剤の完全な消費をもって機能していることに注目されたい。
【００５４】
組成物２４は、PSAN、第１の燃料(BHT-2NH₃)および不活性成分を含有する。“不燃”または燃焼の遅れは、膨張器レベルで問題でなかった。しかし、この処方物は高いレベルの望ましくないガスを生成する。例２１−２３および例２５−２７に較べて、組成物２４は、似たCOレベルをもつが、はるかに高いレベルのアンモニア、NO、およびNO₂を有し、この組成物を自動車適用に不適当にする。これは毒性ガスの生成を防ぐことにおける金属性酸化剤の重要性を示している。
【００５５】
Ｘ線回折（XRD)を組成物２３−２６からの固体残渣について実行した。主たるフェーズを表４に表わす。組成物２３におけるSr(NO₃)₂のみの使用は、膨張器レベルで高レベルの毒性放出物の問題とともに主としてK₂CO₃の生成となる。組成物２５および２６におけるSr(NO₃)₂および粘土の使用が、“不燃”または高い毒性放出物レベルを起すことなく、主としてケイ酸ストロンチウムSr₂SiO₄の生成となる。
【００５６】
要約すると、例２１−２７は、PSANおよび第１の燃料に金属性酸化剤と不活性成分の両方の添加が燃焼過程中の金属ケイ酸塩を形成するために必要であることを示している。その結果が、容易に点火でき、全運転圧力で完全に燃焼し、しかもできるだけ少ない固体微粒子およびできるだけ少ない毒性ガスを生成する高ガス収率発生剤になる。
前記実施例は、好ましい燃料および酸化剤の使用を説明しているが、本発明の実施は説明された具体的な燃料および酸化剤に限定されるものではなく、且つ同様に上述および以下の特許請求項によって定義されるような、他の添加剤の包含を除外するものではない。
【図面の簡単な説明】
【図１】ガス発生剤の圧力指数における“中断”を説明している。[0001]
Background of the Invention
The present invention relates to a non-toxic gas generating composition that quickly generates a gas useful for inflating an occupant's safety restraint system in a vehicle, and specifically, the present invention provides an acceptable level of toxicity. It relates to a non-azide gas generant that not only produces a combustion product having a relatively high gas volume for solid particulates at an acceptable flame temperature. Furthermore, the composition of the present invention ignites easily and sustains combustion at a combustion rate that was previously considered too low to be applied to an automobile airbag.
[0002]
The evolution of azide-based gas generants to non-azide gas generants is well known in the prior art. The advantages of non-azide gas generating compositions compared to azide gas generating agents are described in detail in, for example, U.S. Patent Nos. 4,370,181; 4,909,549; 4,948,439; 5,084,118; 5,139,588 and 5,035,757, the discussion of which is hereby incorporated by reference. Included as literature.
[0003]
In addition to combustible components, pyrotechnical non-azide gas generators can be used to supply the oxygen necessary for rapid combustion or to reduce the amount of toxic gases generated, and to toxic oxides of carbon and nitrogen toxic oxides. And components such as slag forming components that agglomerate solid and liquid products formed during and immediately after combustion into filterable particulates such as clinker. Other optional additives such as combustion rate accelerators, firing modifiers and ignition aids are used to control the ignitability and flammability of the gas generant.
[0004]
One of the drawbacks of known non-azide gas generating compositions is the amount and physical properties of the solid residue formed during combustion. Solids produced as a result of combustion must be filtered or otherwise kept out of contact with the vehicle occupant. Therefore, it is highly preferred to develop a composition that produces an adequate amount of non-toxic gas to produce the smallest solid particulates and yet inflate the safety device at high speed.
[0005]
The use of ammonium nitrate as an oxidant is known to help gas generation with minimal solids. However, in order to be useful, automotive gas products must be thermally stable after more than 400 hours at 107 ° C. The composition must also maintain structural integrity when cycled between −40 ° C. and 107 ° C.
[0006]
In general, gas generating compositions using ammonium nitrate have unacceptably high levels, such as CO and NO, depending on the composition of coexisting additives such as plasticizers and binders._xThis is a thermally unstable propellant that produces toxic gases. Known ammonium nitrate compositions are also subject to low ignitability, slow burning rates and severe performance fluctuations. Several prior art compositions containing ammonium nitrate have been developed to solve this problem._ThreeWell-known ignition aids such as But BKNO_ThreeIs not desirable because it is a very sensitive and energy rich compound.
[0007]
Another problem that must be considered is that the US Department of Transportation (DOT) requires “cap testing” for gas generants. Because of the sensitivity to fuel explosions often used with ammonium nitrate, many propellants containing ammonium nitrate will not pass the capping test unless they are formed into large disks, thus making the expander design less flexible.
[0008]
Therefore, many non-azide propellants based on ammonium nitrate cannot meet the requirements for automotive applications. Two notable exceptions are disclosed in US Pat. No. 5,531,941 which shows the use of ammonium nitrate, triaminoguanidine nitrate and oxamide, and US Pat. No. 5,545,272 which shows the use of phase stabilized ammonium nitrate and nitroguanidine. ing. Although they are useful for automotive applications, these compositions still have problems that make transport requirements and difficult to pass the cap test because triaminoguanidine nitrate and nitroguanidine are explosive fuels. is there. In addition, due to poor ignitability and relatively low burning rates, nitroguanidine compositions are sensitive and energy-rich BKNO_ThreeConventional ignition aids such as
[0009]
Certain gas generant compositions containing ammonium nitrate are thermally stable but have a lower burning rate than desired for use in a gas expander. To be useful in occupant safety inflation applications, gas generant compositions generally require a combustion rate of at least 0.4 ips (inches / second) at 1000 psi. In general, gas generants with a combustion rate of less than 0.4 ips at 1000 psi do not ignite stably and are often “non-combustible” in the expander, with some of the gas generant burning. Even with complete combustion, poor ignitability results in gas production rates that are too slow for automotive airbag applications.
[0010]
Description of prior art
The gas generating composition described in US Pat. Nos. 4,909,549 and 4,948,439 to Poole et al. Comprises tetrazole or triazole compounds as metal oxide and oxidant compounds (alkali metals, alkaline earth metals and pure ammonium nitrate or ammonium perchlorate. ) And a relatively unstable generator that decomposes at low temperatures. Produces significant toxic products and particulates upon combustion. Both patents are BKNO as ignition aids_ThreeShows the use of.
[0011]
Although the gas generant composition described in US Pat. No. 5,035,757 to Poole results in a solid product that can be more easily filtered, the gas yield is not unsatisfactory.
Chang et al., No. 3,954,528, describes a synthetic polymeric binder in combination with triaminoguanidine nitrate (“TAGN”) and an oxidizing material. Although phase stabilized ammonium nitrate (“PSAN”) is not suggested, the oxidizing material includes ammonium nitrate (“AN”). This patent shows the manufacture of propellants for use in guns or other devices where large amounts of carbon monoxide and hydrogen are acceptable and desirable.
[0012]
Grubaugh's US Patent No. 3,044,123 describes solid propellant pellets containing AN as a major component. This method requires the use of oxidizable organic binders (eg cellulose acetate, PVC, PVA, acrylonitrile and styrene-acrylonitrile), then compression molding the mixture to produce pellets and heating to process the pellets To do. Since a commercially available AN is used, these pellets will certainly be damaged by temperature cycling and the claimed composition will produce large amounts of carbon monoxide.
[0013]
Becuwe US Pat. No. 5,034,072 is based on the use of 5-oxo-3-nitro-1,2,4-triazole as a replacement for other explosive materials (HMX, RDX, TATAB, etc.) in propellants and gun powders . This compound is also referred to as 3-nitro-1,2,4-triazol-5-one (“NTO”). This claim covers a gun powder composition containing NTO, AN and an inert binder, which composition is less hygroscopic than a propellant containing ammonium nitrate. Although referred to as inert, the binder produces carbon monoxide upon entering the combustion reaction and is unsuitable for airbag inflation.
[0014]
Lund et al., US Pat. No. 5,197,758, describes a gas generant composition comprising a non-azide fuel that is a transition metal complex of aminotetrazole, although it is particularly useful for inflating automobile restraint system airbags. A copper and zinc complex of 5-aminotetrazole and 3-amino-1,2,4-triazole that produces excess solids.
[0015]
US Pat. No. 4,931,112 to Wardle et al. Describes an automotive airbag gas generating formulation consisting essentially of NTO (5-nitro-1,2,4-triazol-3-one) and an oxidizing agent, The formulation is anhydrous.
Ramnarace US Patent No. 4,111,728 is useful as a gas generator for inflating liferafts and similar devices, or as a rocket propellant comprising a fuel selected from ammonium nitrate, polyester-type binder and oxamide and guanidine nitrate The thing is described.
[0016]
Boyars US Pat. No. 4,124,368 describes a method for preventing the explosion of ammonium nitrate by using potassium nitrate.
US Patent No. 4,552,736 to Mishra and US Patent No. 5,098,683 to Mehtratra et al. Describe the use of potassium fluoride to eliminate the expansion and contraction of transition phase ammonium nitrate.
[0017]
Chi U.S. Pat. No. 5,074,938 describes the use of phase-stabilized ammonium nitrate as a propellant oxidant containing boron and useful in rocket motors.
Canterbury et al., U.S. Patent No. 4,925,503, describes an explosive composition comprising a high energy material such as ammonium nitrate and a polyurethane polyacetal elastomer binder, the latter component being the focus of the invention.
[0018]
Hass, US Pat. No. 3,071,617, describes a long-known idea regarding oxygen balance and exhaust gas.
US Pat. No. 4,300,962 to Stinecipher et al. Describes an explosive containing ammonium nitrate and an ammonium salt of nitroazole.
Prior US Pat. No. 3,719,604 describes a gas generating composition comprising an aminoguanidine salt of azotetrazole or ditetrazole.
[0019]
Poole US Pat. No. 5,139,588 describes a non-azide gas generant useful in automotive restraint systems including fuel, oxidant and additives.
US Pat. No. 3,909,322 to Chang et al. For the use of pure nitroaminotetrazole salts and ammonium nitrate as gun propellants and for applications in gas-powered machinery such as engines, electric generators, motors, turbines, pneumatic equipment and rockets. The gas generating agent for is described.
U.S. Pat. No. 5,198,046 to Bucerius et al. Discloses KNO as an oxidant for use in generating environmentally friendly, non-toxic gases and providing excellent thermal stability._ThreeTogether with the use of diguanidinium-5,5'-azotetrazole.
[0020]
Onishi et al., U.S. Pat. No. 5,439,251, is a cationic amine and an anionic tetrazole group having 1-3 alkyls, chlorine, hydroxyl, carboxyl, methoxy, aceto, nitro, or a tetrazole ring at the 5-position of the tetrazole ring. The use of tetrazoleamine salts as airbag gas generants containing other tetrazolyl groups substituted via diazo or triazo groups is shown. The focus of this invention is on improving the physical properties of tetrazoles with respect to impact and friction sensitivity, and does not indicate a combination of tetrazoleamine salts with other compounds.
[0021]
Lund et al., US Pat. No. 5,501,823, teaches the use of anhydrous non-azide tetrazole, its derivatives, salts, complexes and mixtures thereof for use in airbag inflaters.
US Pat. No. 5,516,377 to Highsmith et al. Describes a salt of 5-nitraminotetrazole, BKNO._ThreeEtc., and the use of pure ammonium nitrate as an oxidant, but not the use of phase stabilized ammonium nitrate.
[0022]
Accordingly, the object of the present invention is to produce a large volume of non-toxic gas with minimal solid particulates, which is thermally and volumetrically stable from -40 ° C to 110 ° C, and does not contain explosive components. And providing a high yield (gas / mass> 90%) gas generant composition that ignites without delay and sustains combustion in a reproducible manner.
[0023]
Summary of invention
The foregoing problems are solved by providing a non-azide gas generant for a vehicle occupant restraint system that uses ammonium nitrate as the oxidant and potassium nitrate as the ammonium nitrate phase stabilizer. The fuel combined with the phase stabilized ammonium nitrate is selected from the group consisting of amine salts and other non-metallic salts of tetrazole and triazole with nitrogen-containing cationic and anionic components. The anionic component includes a tetrazole or triazole ring and an R group substituted at the 5-position of the tetrazole ring, or two R groups substituted at the 3- and 5-positions of the triazole ring. The R group is selected from hydrogen and nitrogen-containing functional groups such as amino, nitro, nitramino, tetrazolyl and triazolyl groups. Cationic components include ammonia, hydrazine; guanidine compounds such as aminoguanidine, diaminoguanidine, triaminoguanidine and nitroguanidine; dicyandiamide, urea, carbohydrazide, oxamide, oxamic acid hydrazide, bis- (carbonamido) amine, azodicarbonamide And amides including hydrazodicarbonamide; and 3-amino-1,2,4-triazole, 3-amino-5-nitro-1,2,4-triazole, 5-aminotetrazole, 3-nitroamino- Substituted azoles including 1,2,4-triazole and 5-nitroaminotetrazole; formed from the group including azines such as melamine.
[0024]
The gas generant further contains a metallic oxidant selected from alkali metal and alkaline earth metal nitrates and perchlorates. One skilled in the art will readily appreciate that other oxidizing agents such as metal oxides, nitrites, chlorates, peroxides, and hydroxides may also be used. The metallic oxidant is present at about 0.1-25% by weight of the gas generant composition, and more preferably 0.8-15%.
[0025]
The gas generant also further contains inert components such as silicates, silicon, diatomaceous earth, and inert minerals selected from the group comprising oxides such as silica, alumina and titania. Silicates include talc and silicates having a layer structure such as clay and mica aluminum silicate; aluminosilicates; borosilicates; and other silicates such as sodium silicate and potassium silicate, It is not limited. The inert component is present at about 0.1-8%, and more preferably 0.1-3% by weight of the gas generant composition.
[0026]
Detailed Description of the Preferred Embodiment
According to the present invention, preferred high nitrogen non-azides used as the first fuel of the gas generating composition are in particular monoguanidinium salts of 5,5′-bi-1H-tetrazole (BHT · 1GAD), 5, Diguanidinium salt of 5′-bi-1H-tetrazole (BHT · 2GAD), monoaminoguanidinium salt of 5,5′-bi-1H-tetrazole (BHT · 1AGAD), 5,5′-bi-1H-tetrazole Diaminoguanidinium salt (BHT · 2AGAD), monohydrazinium salt of 5,5′-bi-1H-tetrazole (BHT · 1HH), dihydrazinium salt of 5,5′-bi-1H-tetrazole (BHT · 2HAD) 2HH), monoammonium salt of 5,5′-bi-1H-tetrazole (BHT · 1NH₃), 5,5′-bi-1H-tetrazole diammonium salt (BHT · 2NH)₃), 5,3′-bi-1H-tetrazole mono-3-amino-1,2,4-triazolium salt (BHT · 1ATAZ), 5,5′-bi-1H-tetrazole di-3-amino- 1,2,4-triazolium salt (BHT · 2ATAZ), diguanidinium salt of 5,5′-azobis-1H-tetrazole (ABHT · 2GAD) and monoammonium salt of 5-nitramino-1H-tetrazole (NAT · 1NH)₃A) Non-metallic salts of ammonium, amine, amino, and amides of tetrazole and triazole selected from the group comprising. The first fuel generally comprises 13-38%, more preferably 23-28% by weight of the gas generant composition.
[Chemical 1]

[0027]
Common non-metallic salts of tetrazole shown in Formula I include a cationic amine component Z and an anionic component that includes a tetrazole ring and an R group substituted at the 5-position of the tetrazole ring. Common non-metallic salts of triazoles as shown in Formula II contain a cationic component Z and an anionic component comprising a triazole ring and two R groups substituted at the 3- and 5-positions of the triazole ring; R₁Is R₂And may or may not be structurally similar. The R component is from hydrogen or a group comprising nitrogen-containing compounds such as tetrazolyl and triazolyl groups of formula I or II, respectively, substituted directly or via an amine, diazo or triazo group, or amino, nitro, nitroamino, or Selected. Compound Z forms a cation by substituting hydrogen at the 1-position of any formula, and guanidine compounds such as ammonia, hydrazine, guanidine, aminoguanidine, diaminoguanidine, triaminoguanidine, and nitroguanidine; dicyandiamide, urea Amides, including carbohydrazide, oxamide, oxamic hydrazide, bis- (carbonamido) amine, azodicarbonamide and hydrazodicarbonamide; and 3-amino-1,2,4-triazole, 3-amino-5- Substituted azoles containing nitro-1,2,4-triazole, 5-aminotetrazole, 3-nitroamino-1,2,4-triazole, and 5-nitroaminotetrazole; from amine groups containing azines such as melamine Selected.
[0028]
The non-metal salt of tetrazole or triazole is dry mixed with phase stabilized ammonium nitrate (PSAN). PSAN is generally used at a concentration of about 46-87%, and more preferably 56-77% by weight of the total gas generant composition. Ammonium nitrate was applied as described in Example 16 and entitled “Method for Producing Azide-Free Gas Generating Composition”, Jul. 2, 1996, and is hereby incorporated by reference. Stabilized with potassium nitrate as taught in .5,531,941. PSAN contains 85-90% AN and 10-15% KN and is formed by any suitable means such as co-crystallization of AN and KN, so it occurs in pure ammonium nitrate (AN) between -40 ° C and 107 ° C Prevent solid-solid phase change. Although KN is preferably used to stabilize pure AN, those skilled in the art will readily understand that other stabilizers can be used in conjunction with AN.
[0029]
The gas generant further contains a metallic oxidant selected from alkali metal and alkaline earth metal nitrates and perchlorates. One skilled in the art will readily appreciate that other oxidizing agents such as metallic oxides, nitrites, chlorates, peroxides, and hydroxides may also be used. The metallic oxidant is present at about 0.1-25% by weight of the gas generant composition, and more preferably 0.8-15%.
[0030]
The gas generant also further contains inert components such as silicates, silicon, diatomaceous earth, and inert minerals selected from the group comprising oxides such as silica, alumina and titania. Silicates include talc and silicates having a layer structure such as clay and mica aluminum silicate; aluminosilicates; borosilicates; and other silicates such as sodium silicate and potassium silicate, It is not limited. The inert component is present at about 0.1-8%, and more preferably 0.1-3% by weight of the gas generant composition.
[0031]
A preferred embodiment is 50-77% PSAN, 23-28% diammonium salt of 5,5′-bi-1H-tetrazole (BHT-2NH₃), 0.8-15% strontium nitrate, and 0.1-3% clay.
The combination of a metallic oxidant and an inert component results in the production of a metal-containing mineral from the metallic oxidant. For example, mainly aluminum silicate (Al₂Si_Four O_Ten) And quartz (SiO₂) Strontium nitrate (Sr (NO_Three)₂The combination of strontium silicate (SrSiO)_FourAnd Sr_ThreeSiO_Five). It seems that this method helps sustain gas generating combustion at all pressures and thus keeps the expander from becoming "non-combustible".
[0032]
Non-metal salts as defined above, PSAN, alkaline earth metal oxidizers, and gas generants containing inert components have low burning rates (about 0.30 ips at 1000 psi) and 0 at 1000 psi. Below the industry standard of 40 ips. Thus, although these compositions were totally unexpected, they were ignited and sustained combustion more easily than other gas generants having a combustion rate lower than 0.40 ips at 1000 psi, and 0. It may also perform better than a gas generant having a combustion rate greater than 40 ips.
[0033]
Optional ignition aids used in conjunction with the present invention are described in Poole's US Pat. No. 5,139,588, including triazole, triazolone, aminotetrazole, tetrazole or bitetrazole, or those shown by reference herein. Choose from non-azide fuels including others. Fuels based on tetrazole or triazole, phase-stabilized ammonium nitrate, metallic oxidizers, and gas generants containing inert components show improved propellant ignitability and also have reproducible combustion performance BKNO_ThreeConventional ignition aids such as are no longer necessary.
[0034]
The manner and order in which the components of the gas generating composition of the present invention are combined and mixed is not critical as long as a uniform mixture is obtained, and the mixing is performed under conditions that do not cause decomposition of the components used. For example, the material may be wet blended or dry blended, crushed with a ball mill or Red Devil type paint stirrer and then compression molded into pellets. The materials may be ground separately or together in a fluid energy mill, a sco vibration energy mill or a bantam fine powder machine and then blended, or further blended in a v-blender prior to compression.
[0035]
The invention is illustrated by the following examples in which the ingredients are quantified in weight percent of the total composition unless otherwise stated. The values for Examples 1-3 and 16-20 were obtained experimentally. Examples 18-20 give percent of compounds equivalent to those found in Examples 1-3 and are included for comparison purposes and to confirm laboratory results. The values of Examples 4-15 are obtained based on the composition shown. The main gas product is N₂, H₂O and CO₂The components that form solids are generally present in their most common oxidation state. Oxygen balance is the weight percent of oxygen in the composition that is required or liberated to produce a stoichiometrically balanced product. Thus, a negative oxygen balance represents an oxygen deficient composition, while a positive oxygen balance represents an oxygen rich composition.
[0036]
When formulating the composition, the ratio of PSAN to fuel is adjusted so that the oxygen balance is from -4.0% to + 1.0% by weight of the composition as described above. More preferably, the ratio of PSAN to fuel is adjusted so that the oxygen balance of the composition is from -2.0% to 0.0% by weight of oxygen in the composition. It can be appreciated that the relative amounts of PSAN and fuel will depend on the additives used to make the PSAN as well as the nature of the fuel selected.
[0037]
In Tables 1 and 2 below, PSAN is phase stabilized with 15% KN of the total oxidizer component in all cases except those marked with an asterisk. In that case, PSAN is phase stabilized with 10% KN of the total oxidant component.
According to the present invention, these formulations are stable in the temperature range of −40 ° C. and 110 ° C. both thermally and volumetrically; produce large amounts of non-toxic gases; produce minimal solid particulates; Easily ignited and repeatable burning; free of toxic, photosensitive or explosive starting materials; and non-toxic, non-photosensitive and non-explosive in final form.
[Table 1]

[Table 2]

[0038]
Example 16-Description only
A phase stabilized ammonium nitrate (PSAN) consisting of 85 wt% ammonium nitrate (AN) and 15 wt% potassium nitrate (KN) was prepared as follows. 2125 g of dried AN and 375 g of dried KN were added to a heated jacketed double planetary mixer. Distilled water was added with mixing until all the AN and KN were dissolved and the solution temperature was 66-70 ° C. Mixing was continued at atmospheric pressure until a dry white powder was produced. This product was PSAN. The PSAN was removed from the mixer, spread into a thin layer and dried at 80 ° C. to remove residual moisture.
[0039]
Example 17-Illustration
The PSAN produced in Example 16 was tested in comparison to pure AN to determine if the undesirable phase changes that normally occur with pure AN were eliminated. Both were tested in DSC from 0 ° C to 200 ° C. Pure AN exhibited endotherms at about 57 ° C. and about 133 ° C., and a melting point endotherm at about 170 ° C. corresponding to the solid-solid phase change. PSAN exhibited an endotherm corresponding to a solid-solid phase transition at about 118 ° C. and an endotherm corresponding to melting of PSAN at about 160 ° C.
Pure AN and the PSAN produced in Example 16 were compressed into 12 mm diameter, 12 mm thick slag, and volume expansion was measured with a body dilatometer in the temperature range of −40 ° C. to 140 ° C. When heated from −40 ° C. to 140 ° C., the pure AN has undergone a volumetric shrinkage beginning at about −34 ° C, a volumetric expansion beginning at about 44 ° C, and a volumetric shrinkage beginning at 90 ° C and a volumetric expansion beginning at about 130 ° C. . PSAN did not undergo volume change when heated from −40 ° C. to 107 ° C. It has undergone a volume expansion starting at about 118 ° C.
[0040]
Pure AN and the PSAN produced in Example 16 were compressed to 32 mm diameter, 10 mm thick slag, placed in a closed bag with desiccant and circulated between -40 ° C and 107 ° C. did. One cycle keeps the sample at 107 ° C. for 1 hour, transitions from 107 ° C. to −40 ° C. at a constant rate over about 2 hours, keeps it at −40 ° C. for 1 hour and −40 at a constant rate over about 1 hour. It consists of a transition from ℃ to 107 ℃. Samples were removed and observed after 62 total cycles. Pure AN slag collapsed substantially into powder, while PSAN slag remained completely intact with no cracks or defects.
The above example eliminates the solid-solid phase transition present in AN in automotive applications from -40 ° C to 107 ° C that the addition of KN and it contains 15% by weight of the coprecipitation mixture of AN and KN It is shown that.
[0041]
Example 18
The following composition by weight: PSAN 76.43% and BHT · 2NH_ThreePSAN with 23.57% and BHT · 2NH_ThreeA mixture of was prepared. The measured and dried ingredients were blended and ground to a fine powder by rotation using a ceramic cylinder in a ball mill jar. The powder was separated from the grinding cylinder and granulated to improve the fluidity of the material. The granules were compressed into high speed rotary presses and formed into pellets. The pellets made by this method were of exceptional quality and strength.
The burn rate of the composition was 0.48 inches per second at 1000 psi. The burning rate was determined by measuring the time taken to burn a cylindrical pellet of known length at a constant pressure. The pellets were weighted to 10 tons and formed into ½ "diameter dies and then coated on the sides with an epoxy / titanium dioxide inhibitor that prevented burning along the sides.
[0042]
Pellets made with a rotary press were loaded into the gas generator assembly and were found to ignite easily and satisfactorily inflate the airbag with minimal solids, airborne particulates, and toxic gases produced. About 95% by weight of the gas generant was converted to gas. The ignition aid used was BKNO_ThreeAnd only high gas yield non-azide pellets such as those described in US Pat. No. 5,139,588.
When tested at the Mineral Impactor Standards Association, the impact sensitivity of this mixture was greater than 300 kp · cm. When tested according to the US D.O.T. procedure, the 0.184 "diameter and 0.080" thick pellets did not deflagrate or explode when started with a No. 8 industrial blasting cap.
[0043]
Example 19
The following composition by weight: PSAN 75.40% and BHT · 2NH_Three24.60% PSAN and BHT · 2NH_ThreeA mixture of was prepared. The composition was prepared as in Example 18 and again produced exceptional quality and strength pellets. The burn rate of the composition was 0.47 inches per second at 1000 psi.
[0044]
Pellets made with a rotary press were loaded into the gas generator assembly. The pellets were found to ignite easily and satisfactorily inflate the airbag with minimal solids, airborne particulates, and toxic gases produced. About 95% by weight of the gas generant was converted to gas.
When tested at the Mineral Impactor Standards Association, the impact sensitivity of this mixture was greater than 300 kp · cm. When tested in accordance with US Department of Transportation procedures, the 0.250 "diameter and 0.125" thick pellets did not detonate or explode when started with a No. 8 blast cap.
[0045]
Example 20
The following composition by weight: PSAN 72.32% and BHT 2NH_ThreePSAN with 27.68% and BHT · 2NH_ThreeA mixture of was prepared. A composition was prepared as in Example 18 except that the weight ratio of grinding media to powder was tripled. The composition burn rate was 0.54 inches per second at 1000 psi. When tested at the Mineral Impactor Standards Association, the impact sensitivity of this mixture was greater than 300 kp · cm. This example shows that the burning rate of the composition of the present invention can be increased by more intense grinding. When tested according to the US D. O. T. procedure, pellets of diameter 0.184 "and thickness 0.090" did not deflagrate or explode when started with a No. 8 industrial detonator.
According to the present invention, propellants based on ammonium nitrate are phase stabilized and maintain combustion above atmospheric pressure, providing abundant non-toxic gases while minimizing particulate formation. Since non-metallic salts of tetrazole and triazole easily ignite in combination with PSAN, BKNO_ThreeNormal ignition aids such as are not required to initiate combustion.
[0046]
In addition, the photosensitivity has decreased, and O. T. T. et al. Because of compliance, the composition easily passes the cap test with a propellant tablet size that is optimally designed for use in an airbag inflator. Thus, a significant advantage of the present invention is that it contains harmless and non-explosive starting materials, and all of these can be transported with little restriction.
Comparative data of the prior art and that of the present invention are shown in Table 3 to illustrate the gas evolution advantage of utilizing tetrazole and triazole amine salts with PSAN.
[Table 3]

[0047]
As shown in Table 3, and in accordance with the present invention, PSAN and tetrazole and triazole amine salts produce significantly higher amounts of gas per cubic centimeter of gas generant volume compared to prior art compositions. This allows the use of smaller expanders due to the smaller amount of gas generant required. Because of the more gas production, the production of solids is minimized, thereby allowing a smaller and simpler filtration method that also helps the use of smaller expanders.
In yet another aspect of the present invention, some gas generant compositions containing PSAN and a non-metal salt of tetrazole or triazole exhibit poor ignitability and incomplete combustion, thereby Inappropriate speed and / or "non-flammability" has been found. As shown in Examples 21-27 of Table 4, silicate is produced, thereby improving ignitability and sustaining combustion at all pressures.
[Table 4]

[0048]
Example 21-27
In Examples 21-27, phase stabilized ammonium nitrate (PSAN) was prepared by co-crystallization from a saturated aqueous solution at about 80 ° C. containing 10% by weight KN. Diammonium salt of 5,5'-bi-1H-tetrazole (BHT-2NH_Three), Strontium nitrate, clay and nitroguanidine (NQ) were purchased from external suppliers.
Each material was dried separately at 105 ° C. The dried materials were then mixed together and rolled on an alumina cylinder in a large ball mill jar. After releasing the alumina cylinder, the final product was 1500 grams of uniform and ground powder. The powder was granulated to improve flow and then compression molded into pellets (diameter 0.184 ", thickness 0.090") with a high speed tablet press. Pills on inflator stack, 60L tank and 100ft^ThreeI ignited in the tank. The 60 L tank was used to determine the pressure over time and measure the amount of solids that were discharged from the inflator during the process. 100ft^ThreeThe tank was used to determine several gas levels as well as the amount of airborne particulates produced by the inflator. Table 1 summarizes the results of the composition.
[0049]
Examples 21-24 are shown for comparison purposes. Example 21 is PSAN and BHT-2NH_ThreeContaining. Example 22 is PSAN, BHT-2NH_ThreeAnd NQ. Example 23 is PSAN, BHT-2NH_ThreeAnd strontium nitrate (a metallic oxidant). Example 24 is PSAN, BHT-2NH_ThreeAnd clay (inactive ingredients). Examples 25 and 26 are in accordance with the present invention PSAN, BHT-2NH_Three, Strontium nitrate as a metallic oxidant, and clay as an inert component. Finally, Example 27 is for PSAN, BHT-2NH_Three, Strontium nitrate as a metallic oxidant, and clay as an inert component, but in a different amount. Applicants believe that adding metallic oxidizers and inert components to the compositions of Examples 21 and 22 (and compositions similar to those shown above) will lead to sustained combustion and optimal ignitability. I found. However, those skilled in the art will readily recognize that redesigning the inflator to operate at higher pressures, for example, would make the compositions of Examples 21 and 22 more useful in automotive airbag applications. Will understand.
[0050]
As shown in Table 4, Examples 21-27 are typical high yield gas generants that produce large volumes of gas with minimal solid particulates. Gas conversion is the weight percent of solid gas generant that is converted to gas after combustion. The gas conversion of Examples 25 and 26 is slightly lower than Examples 21-24 and 27, but there is no significant difference in the amount of solids produced by the expander in the 60 L tank. This indicates that the compositions of Examples 25 and 26 are slightly reduced in gas conversion compared to Examples 21-24 and 27, but are essentially high yield gas generants. All examples listed in Table 4 are stable at -40 ° C to 110 ° C, both thermally and capacitively, and contain non-explosive components.
In some inflator designs, the compositions of Examples 21-23 (and similar compositions above) were found to sometimes go through a “non-flammable” state. This is unacceptable for airbag operation requiring a specific rate of gas production, and therefore requires a more complex inflator that can operate at higher pressures. On the other hand, the composition of Examples 25-27, when ignited well, complete combustion without delay.
[0051]
Burn rate data is listed to further describe the benefits of combining PSAN, tetrazole or non-metal salts of triazole, metallic oxidizer, and inert components. Burning rate model R_b= aPⁿWhere Rb = burning rate, a = constant, P = pressure, and n = pressure index. Note that the relationship between burning rate and pressure, and thus a and n, can vary as a function of pressure. When this happens, there is an “interruption” in the burn rate curve versus pressure, indicating a change to a different combustion mechanism. Ideally, the gas generant composition should have a single combustion mechanism at full expander operating pressure. Furthermore, the gas generant should ignite easily and continue to burn at these pressures. FIG. 1 illustrates the “interruption” in the pressure index of the gas generant. In FIG. 1, the combustion rate curves for the pressures of Examples 21-23 and 26 are represented. Note that the composition of Example 26 does not exhibit “interruption” during combustion, thereby indicating that a single combustion mechanism is maintained and occurs at all expander operating pressures.
[0052]
At pressures above about 3000 psi, all compositions ignite easily and continue to burn. As the pressure decreases below 2000-3000 psi, Examples 21-23 undergo a significant increase in pressure index. This indicates a change to the combustion mechanism that is highly dependent on pressure. At this point, a slight decrease in pressure can dramatically reduce the rate at which the gas generant burns, eventually turning it off. In fact, it has been found that some expanders containing compositions 21-23 do not function properly because sometimes only a small portion of the gas generant is consumed. This phenomenon was also observed at very low pressures. When ignited at normal pressure with a propane flame, compositions 21-23 burned out but always disappeared. Furthermore, these compositions do not ignite at 100 psi and do not burn completely when tested in a burn rate apparatus.
[0053]
In contrast, as shown in FIG. 1 (note that there is no “interruption” in the curve of composition 26), composition 26 ignites, burns easily, and has the same pressure index at 0-4500 psi. Have When ignited at normal pressure using a propane flame, composition 26 ignited easily and burned slowly and completely. At 100 psi in the burn rate apparatus, composition 26 ignited and burned completely. The inflator containing composition 26 functioned in all cases with easy ignitability and complete and stable consumption of the gas generant. Inflator operating characteristics were generally the same as when composition 25 was used. Despite the low levels of metallic oxidizers and inert components, and burn rate similar to compositions 21-23, composition 27 is functioning with full consumption of gas generant at the expander level. Note that.
[0054]
Composition 24 consists of PSAN, first fuel (BHT-2NH_Three) And inactive ingredients. “Non-combustible” or combustion delay was not a problem at the expander level. However, this formulation produces high levels of undesirable gases. Compared to Examples 21-23 and Examples 25-27, Composition 24 has similar CO levels, but much higher levels of ammonia, NO, and NO.₂Which makes this composition unsuitable for automotive applications. This demonstrates the importance of metallic oxidants in preventing the production of toxic gases.
[0055]
X-ray diffraction (XRD) was performed on the solid residue from compositions 23-26. The main phases are shown in Table 4. Sr (NO in composition 23_Three)₂The only use is mainly K with the problem of high level toxic emissions at the inflator level.₂CO_ThreeIs generated. Sr (NO in compositions 25 and 26_Three)₂And the use of clay, mainly without flammability or high toxic emission levels, without strontium silicate Sr₂SiO_FourIs generated.
[0056]
In summary, Examples 21-27 show that the addition of both a metallic oxidant and an inert component to PSAN and the first fuel is necessary to form a metal silicate during the combustion process. . The result is a high gas yield generator that can be ignited easily, burns completely at full operating pressure, and produces as few solid particulates and as little toxic gas as possible.
While the above examples illustrate the use of preferred fuels and oxidants, the practice of the present invention is not limited to the specific fuels and oxidants described, and likewise the patents mentioned above and below. The inclusion of other additives as defined by the claims is not excluded.
[Brief description of the drawings]
FIG. 1 illustrates “interruption” in the pressure index of a gas generant.

Claims (6)

A gas generating composition for inflating an automotive airbag automatic safety system comprising:
Formula I
[Outside 1]

Where
R is selected from the group consisting of hydrogen, amino, nitro, nitroamino, tetrazolyl and triazolyl groups;
Z is selected from the group consisting of ammonia, hydrazine, guanidine compounds, amides , substituted azoles and azines.
A non-metallic salt of tetrazole represented by:
Formula II
[Outside 2]

Where
R ₁ and R ₂ are each independently selected from the group consisting of hydrogen, amino, nitro, nitroamino, tetrazolyl and triazolyl groups;
Z is selected from the group consisting of ammonia, hydrazine, guanidine compounds, amides , substituted azoles and azines.
A high nitrogen fuel selected from the group consisting of non-metallic salts of triazole represented by:
Phase-stabilized ammonium nitrate,
Said composition comprising a mixture of strontium nitrate and clay. Fuel is used at a concentration of 13% to 38% by weight of the gas generant composition, phase-stabilized ammonium nitrate is used at a concentration of 46% to 87% by weight of the gas generant composition, and strontium nitrate is 0% of the gas generant composition. The gas generant composition of claim 1, wherein the gas generant composition is used at a concentration of 1 wt% to 25 wt%, and the clay is used at a concentration of 0.1 wt% to 8 wt% of the gas generant composition. The fuel is a monoguanidinium salt of 5,5'-bi-1H-tetrazole, a diguanidinium salt of 5,5'-bi-1H-tetrazole, or a monoaminoguanidinium of 5,5'-bi-1H-tetrazole. Salt, diaminoguanidinium salt of 5,5′-bi-1H-tetrazole, monohydrazinium salt of 5,5′-bi-1H-tetrazole, 5,5 Dihydrazinium salt of '-bi-1H-tetrazole, monoammonium salt of 5,5'-bi-1H-tetrazole, diammonium salt of 5,5'-bi-1H-tetrazole, 5,5'-bi-1H- Mono-3-amino-1,2,4-triazolium salt of tetrazole, di-3-amino-1,2,4-triazolium salt of 5,5′-bi-1H-tetrazole A composition according to claim 1 or 2, selected from the group consisting of 1,5'-azobis-1H-tetrazole diguanidinium salt and 5-nitroamino-1H-tetrazole monoammonium salt. 56-77% phase-stabilized ammonium nitrate, 23-28% diammonium salt of 5,5′-bi-1H-tetrazole (BHT-2NH ₃ ), 0.8-15% strontium nitrate, and 0.1-3% clay, wherein the% is based on the weight of the gas generating composition. The vehicle occupant restraint system provided with the gas generating composition in any one of Claims 1-4. The expander provided with the gas generating composition in any one of Claims 1-4.

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