EP0944562B1 - Compositions a inflammation spontanee pour generateurs de gaz de dispositifs de gonflage - Google Patents

Compositions a inflammation spontanee pour generateurs de gaz de dispositifs de gonflage Download PDF

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Publication number
EP0944562B1
EP0944562B1 EP97937024A EP97937024A EP0944562B1 EP 0944562 B1 EP0944562 B1 EP 0944562B1 EP 97937024 A EP97937024 A EP 97937024A EP 97937024 A EP97937024 A EP 97937024A EP 0944562 B1 EP0944562 B1 EP 0944562B1
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EP
European Patent Office
Prior art keywords
autoignition
composition
weight
oxidizer
booster
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP97937024A
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German (de)
English (en)
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EP0944562A4 (fr
EP0944562A1 (fr
Inventor
Sean P. Burns
Larry A. Moquin
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Automotive Systems Laboratory Inc
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Automotive Systems Laboratory Inc
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Priority claimed from US08/906,496 external-priority patent/US6007647A/en
Application filed by Automotive Systems Laboratory Inc filed Critical Automotive Systems Laboratory Inc
Publication of EP0944562A1 publication Critical patent/EP0944562A1/fr
Publication of EP0944562A4 publication Critical patent/EP0944562A4/fr
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C06—EXPLOSIVES; MATCHES
    • C06C—DETONATING OR PRIMING DEVICES; FUSES; CHEMICAL LIGHTERS; PYROPHORIC COMPOSITIONS
    • C06C9/00—Chemical contact igniters; Chemical lighters
    • C—CHEMISTRY; METALLURGY
    • C06—EXPLOSIVES; MATCHES
    • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
    • C06B31/00—Compositions containing an inorganic nitrogen-oxygen salt
    • C06B31/02—Compositions containing an inorganic nitrogen-oxygen salt the salt being an alkali metal or an alkaline earth metal nitrate

Definitions

  • the present invention relates to autoignition compositions used in inflator bags of automobile passenger-restraint devices.
  • Steel canisters are commonly used as the inflator pressure vessel in a passenger-restraint system because of the relatively high strength of steel at elevated temperatures. Given the emphasis on vehicle weight reduction, it is desirable that metals such as aluminum, and smaller or lighter steel vessels be utilized in the pressure vessel.
  • nonazide gas generant compositions do not meet the gaseous effluent requirements met by current azide based inflators.
  • the autoignition material a fraction of the total gas generant, has been found to create excessive levels of undesirable gaseous effluents, particularly carbon monoxide and nitrogen oxides. If an autoignition composition can be developed that produces little or no noxious gases, then the nonazide autoignition compositions will conform more closely to the effluent levels currently achieved by azide fuels.
  • a further concern involves the industry drive to reduce the size of the inflator by eliminating or reducing the volume of its components.
  • Most inflator systems are deployed by the combustion of a gas generant composition comprising a booster, an autoigniter, and a main gas generant charge.
  • a gas generant composition comprising a booster, an autoigniter, and a main gas generant charge.
  • electrical initiation of a squib ignites the booster that in turn supplies sufficient energy to ignite the main gas generant charge thereby deploying the gas inflator.
  • a separate autoignition composition is placed in close proximity to the booster so that during a fire the autoigniter will ignite, thereby igniting the booster and deploying the gas inflator.
  • the booster and autoigniter are separate auxiliary components to the main gas generant, and as such, prior compositions have not significantly contributed to the overall gas generated.
  • the gas generants comprise a fuel such as 5-aminotetrazole, an oxidizer such as strontium nitrate and/or sodium nitrate, and an inert compound such as clay or silica.
  • a fuel such as 5-aminotetrazole
  • an oxidizer such as strontium nitrate and/or sodium nitrate
  • an inert compound such as clay or silica.
  • the gas generants described therein do not autoignite at or below 175°C.
  • EP-A-6 59715 discloses an autoignition gas generant comprising a tetrazole and/or triazole compound, a water-soluble fuel, a transition metal oxide and an alkali and/or alkaline earth metal nitrate.
  • the present invention solves the aforementioned problems by providing an autoignition composition that also functions as a combination autoignition-booster-gas generant within a single chemical charge.
  • the present invention provides an autoignition composition for a gas generator of a vehicle occupant restraint system, autoignitable at or below 175°C, the composition comprising a mixture of the following in weight % based on the weight of the composition :
  • the alkali metal nitrite with the high nitrogen fuel creates a higher reactivity at lower temperatures, thereby lowering the autoignition temperature and facilitating the use of a lightweight pressure vessel within the passenger restraint system.
  • the composition passes all high temperature aging tests with a thermal stability at temperatures up to 110°C.
  • the selected compositions are safer to handle and produce minimal noxious gases such as carbon monoxide or nitrogen oxides.
  • an autoignition composition that includes a fuel, a booster oxidizer, an autoignition oxidizer, and an optional inert component.
  • a fuel is selected from a group consisting of tetrazoles such as 1H-tetrazole, 5-aminotetrazole, 5-nitrotetrazole, 5-nitroaminotetrazole, 5,5'-bitetrazole, diguanidinium-5,5'-azotetrazolate, salts of tetrazoles, triazoles such as nitroaminotriazole, 3-nitro-1,2,4-triazole, 3-nitro-1,2,4-triazole-5-one, salts of triazoles, and mixtures thereof.
  • the preferred fuel is 5-aminotetrazole (5AT) because it is readily available in a pure form at a relatively low cost.
  • the fuel comprises 28 to 40% by weight of the autoignition compound.
  • a booster oxidizer is selected from the group consisting of alkaline earth metal nitrates, alkaline earth metal nitrites, and mixtures thereof.
  • the preferred booster oxidizer is strontium nitrate because it is also readily available in pure form at a relatively low cost. Furthermore, strontium nitrate forms an easily filterable slag upon combustion.
  • the booster oxidizer comprises 18 to 64% by weight of the autoignition compound.
  • An autoignition oxidizer is selected from the group consisting of alkali metal nitrites. Sodium nitrite is preferred due to its low melting point. The most preferred autoignition oxidizer is sodium nitrite because of its high reactivity at low temperatures when combined with the above fuel component or components.
  • the autoignition oxidizer comprises 1 to 30% by weight of the autoignition compound.
  • an optional inert component is selected from the group including clay, diatomaceous earth, talc, silica, and alumina.
  • Multifunctional bentonite clay is a preferred inert component because it can desensitize the composition, act as a binder to provide greater strength to the final form of the autoignition material, and aid in slag filterability by forming alkali metal and alkaline earth metal silicates and aluminates.
  • the inert component comprises 0 to 20% by weight of the autoignition compound.
  • An autoignition composition used in a vehicle occupant restraint system must be thermally stable up to 110°C and must rapidly autoignite at temperatures sufficiently low to prevent rupture of the pressure vessel and yet provide normal deployment of the inflator.
  • the temperature at which exothermic decomposition begins to occur is dependent upon the choice of fuel and autoignition oxidizer, and is specifically related to the melting or decomposition temperatures of the individual components.
  • the ratios of autoignition oxidizer to booster oxidizer, and of autoignition oxidizer to inert material, are directly related to the temperature at which autoignition occurs in the compositions of the present invention. It should be noted that the sensitivity of a composition of the present invention to both shock and impact increases as the relative amount of autoignition oxidizer increases.
  • the pressure generated during deployment is correspondingly kept to a minimum thereby permitting the use of a lightweight pressure vessel. Maintaining the autoignition temperature below the melting point of the primary gas generant prevents detonation or rapid deflagration of the primary gas generant.
  • compositions of the present invention when ignited, produce little or no toxic gases such as carbon monoxide or nitrogen oxides.
  • the compositions of the present invention can be formulated to be oxygen deficient (higher CO and lower NO x ) or oxygen rich (lower CO and higher NO x ). This is measured by the oxygen balance of the composition, which is the percent by weight of molecular oxygen in the composition which is needed (negative oxygen balance) or liberated (positive oxygen balance), to result in a stoichiometric reaction of the composition ingredients thereby forming nitrogen, carbon dioxide, water, and the most common oxides of other elements present.
  • an autoignition composition be utilized in which the oxygen balance can be easily tailored to meet individual customer requirements, and yet still retain a lower autoignition temperature.
  • the preferred oxygen balance of the compositions of the present invention is between -3.0% and 1.0% by weight.
  • the most preferred oxygen balance is between -2.0% and 0.0% by weight.
  • the mechanism that leads to autoignition in the present invention occurs with as little as 1.0% by weight of an alkali metal nitrite autoignition oxidizer.
  • an alkali metal nitrite is the only oxidizer, an excessively high burn rate will result leading to possible detonation or rapid deflagration if a minimum mass is autoignited under confinement in an inflator.
  • Example 6 given below, is illustrative. It is equally well known that the bulk of undesirable water-soluble particulate produced by both azide and nonazide inflators are alkali metal solids that come from the combustion of compounds containing alkali metals.
  • an alkaline earth nitrate or nitrite can be used in combination as a more stable booster oxidizer.
  • the burn rate of the compositions can be decreased to a safe level while still retaining autoignition at a significantly reduced temperature.
  • alkaline earth nitrates and nitrites as a major constituent of the oxidizer, water soluble particulate is minimized.
  • the preferred embodiment is utilized as an autoignition-booster in conjunction with a primary gas generant, thereby alleviating the need for a separate booster charge.
  • the compositions of the present invention generate gas at levels similar to common nonazide gas generants or approximately 2.4 moles of gas per 100 grams of generant.
  • the autoignition composition can actually function as a combination autoignition-booster-primary gas generant in an inflator system.
  • the autoignition composition may also be utilized as a separate autoignition component in conjunction with separate booster and separate primary gas generant components.
  • compositions of the present invention contain no individually explosive components and are therefore relatively insensitive to shock and impact thereby simplifying processing methods and raw material handling procedures.
  • Figures 1 and 2 were generated using a differential scanning calorimeter (DSC).
  • a downward peak indicates an endothermic process (melting or endothermic decomposition) while an upward peak indicates an exothermic process (ignition or exothermic decomposition).
  • Table 1 correlates the curves of Figures 1 and 2 with the respective compositions found in the related art and with those described in the examples given below.
  • an alkali metal nitrite such as sodium nitrite reduces the autoignition temperature within a given gas generant composition.
  • compositions not incorporating an alkali metal nitrite do not exhibit exothermic reactions culminating in an autoignition temperature below 175°C.
  • the Tammann temperature is used to describe the temperature at which there is enough vibrational freedom in the lattice of an inorganic oxidizer to allow for intimate mixing with a mobile, reactive fuel. This is considered to be the temperature at which a self-sustaining reaction is likely to occur with minimal energy input, and is quite low for most alkali metal nitrites, chlorates, and perchlorates. Of particular interest are common oxidizers such as sodium nitrite and potassium chlorate, which have Tammann temperatures of -1°C and 42°C respectively.
  • alkali metal nitrites have a lower Tammann temperature than common alkali metal chlorates and perchlorates, the decomposition of the disclosed oxidizers are not exothermic as with chlorates. Therefore, a small amount of energy, such as that provided from an impact or electrostatic discharge may activate a reaction, but is less likely to cause a self-propagating reaction due to the nature of the individual components, specifically the oxidizers that decompose endothermically rather than exothermically, in accordance with the present invention.
  • a mixture of 51.9% strontium nitrate Sr(NO 3 ) 2 , 36.4% 5-aminotetrazole (5AT), and 11.7% sodium nitrite (NaNO 2 ) was prepared. Each component was dried and ground separately and then mixed by dry-blending. The composition was tested on a differential scanning calorimeter (DSC) at a heating rate of 10°C per minute. Endothermic decomposition occurred with an onset at 137°C and a peak at 142°C. Exothermic decomposition followed immediately, with an initial onset at 154°C and a peak at 183°C. The onset of a given peak from a DSC scan is defined here as the intersection of the tangent to the baseline and the tangent at the maximum slope of the peak in question.
  • DSC differential scanning calorimeter
  • a mixture of 42.7% Sr(NO 3 ) 2 , 36.9% 5AT, and 20.4% NaNO 2 was prepared and tested as described in example 1. Endothermic decomposition occurred with an onset at 136°C and a peak of 142°C. Exothermic decomposition followed immediately, with an initial onset at 154°C and a peak at 180°C. This example demonstrates that the amount of NaNO 2 present does not significantly effect the mechanism which causes autoignition in the present invention.
  • a mixture of 53.0% Sr(NO 3 ) 2 , 37.0% 5AT, and 10.0% NaNO 2 was prepared and tested as described in example 1. Exothermic decomposition occurred with an onset at 156°C and a peak at 183°C. Impact sensitivity was tested using a standard Bureau of Explosives Impact Machine consisting of an eight pound weight dropped from a given height. The impact sensitivity of a composition as defined here is the minimum drop height at which initiation occurs in two of two tests. The impact sensitivity of this composition was found to be 3 inches, with complete combustion of the sample. Autoignition was tested using an aluminum fixture containing a small amount of composition (70-100mg) and a temperature probe.
  • the fixture was placed on a hot plate and heated at a given rate until autoignition occurred, at which point the temperature was measured. When heated at a rate of approximately 15°C per minute, this composition ignited vigorously at temperatures of 152°C, 161°C, and 165°C in three separate tests.
  • a mixture of 65.0% NaNO 2 and 35.0% 5AT was prepared and tested as described in examples 1 and 3. Exothermic decomposition occurred with an onset at 151°C and a peak at 166°C. Autoignition was tested three times at a heating rate of approximately 20°C per minute. In the first two tests, vigorous ignition occurred at 118°C and 141°C. In the third test the powder was slightly tamped and detonation occurred at 140°C. This example demonstrates the importance of using an alkaline earth nitrate or nitrite as the primary booster oxidizer.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Air Bags (AREA)

Claims (7)

  1. Composition à autocombustion pour générateur de gaz d'un système de retenue de l'occupant d'un véhicule, qui est autoinflammable à une température inférieure ou égale à 175 °C et qui comprend un mélange des constituants suivants, les pourcentages étant des pourcentages en poids par rapport au poids de la composition :
    1 % à 30 % d'oxydants d'autocombustion choisi parmi les nitrites de métal alcalin,
    0 % à 20 % d'un ou plusieurs constituants inertes, choisis parmi l'argile, la terre de diatomée, le talc, la silice et l'alumine,
    28 % à 40 % d'un ou plusieurs combustibles choisis parmi les tétrazolés, les sels de tétrazoles, les triazoles, les sels de triazoles, et leurs mélanges, et
    18 % à 64 % d'un oxydant accélérateur, choisi parmi les nitrates et les nitrites de métal alcalino-terreux, et leurs mélanges,
    lesdits combustibles et ledit oxydant accélérateur figurant à des niveaux tels que le bilan d'oxygène de la composition totale est compris entre -3,0 % et 1,0 %,
    étant entendu que ladite composition à autocombustion ne contient pas, en pourcentages en poids, 22 à 36 % de 5-aminotétrazole, 38 à 62 % de nitrate de strontium et 2 à 18 % d'argile ou 2 à 18 % de silice.
  2. Composition à autocombustion selon la revendication 1, pour laquelle ledit combustible est constitué de 5-aminotétrazole et représente 28 % à 40 % en poids de ladite composition, et ledit oxydant accélérateur est constitué de nitrate de strontium et représente 18 % à 64 % en poids de ladite composition.
  3. Composition à autocombustion selon la revendication 2, pour laquelle ledit combustible représente 33 % à 37 % en poids de ladite composition, et ledit oxydant accélérateur représente 42 % à 53 % en poids de ladite composition.
  4. Composition à autocombustion selon la revendication 3, pour laquelle ledit oxydant accélérateur comprend environ 52 % de nitrate de strontium, ledit combustible azoté comprend environ 36 % de 5-aminotétrazole, et ledit oxydant d'autocombustion comprend environ 12 % de nitrite de sodium, ces pourcentages indiqués étant des pourcentages en poids par rapport à ladite composition.
  5. Composition à autocombustion selon la revendication 3, pour laquelle ledit oxydant accélérateur comprend environ 43 % de nitrate de strontium, ledit combustible azoté comprend environ 37 % de 5-aminotétrazole, et ledit oxydant d'autocombustion comprend environ 20 % de nitrite de sodium, ces pourcentages indiqués étant des pourcentages en poids par rapport à ladite composition.
  6. Composition à autocombustion selon la revendication 3, pour laquelle ledit oxydant accélérateur comprend environ 53 % de nitrate de strontium, ledit combustible azoté comprend environ 37 % de 5-aminotétrazole, et ledit oxydant d'autocombustion comprend environ 10 % de nitrite de sodium, ces pourcentages indiqués étant des pourcentages en poids par rapport à ladite composition.
  7. Composition à autocombustion selon la revendication 1, pour laquelle les sels de triazoles sont choisis parmi les sels de nitroaminotriazole, les sels de 3-nitro-1,2,4-triazole, et leurs mélanges.
EP97937024A 1996-08-16 1997-08-06 Compositions a inflammation spontanee pour generateurs de gaz de dispositifs de gonflage Expired - Lifetime EP0944562B1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US70068196A 1996-08-16 1996-08-16
US700681 1996-08-16
US906496 1997-08-05
US08/906,496 US6007647A (en) 1996-08-16 1997-08-05 Autoignition compositions for inflator gas generators
PCT/US1997/013070 WO1998006683A1 (fr) 1996-08-16 1997-08-06 Compositions a inflammation spontanee pour generateurs de gaz de dispositifs de gonflage

Publications (3)

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EP0944562A1 EP0944562A1 (fr) 1999-09-29
EP0944562A4 EP0944562A4 (fr) 2000-02-23
EP0944562B1 true EP0944562B1 (fr) 2005-11-23

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EP97937024A Expired - Lifetime EP0944562B1 (fr) 1996-08-16 1997-08-06 Compositions a inflammation spontanee pour generateurs de gaz de dispositifs de gonflage

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EP (1) EP0944562B1 (fr)
JP (1) JP4021491B2 (fr)
WO (1) WO1998006683A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6214138B1 (en) 1997-08-18 2001-04-10 Breed Automotive Technology, Inc. Ignition enhancer composition for an airbag inflator
WO1999057083A1 (fr) * 1998-04-30 1999-11-11 Daicel Chemical Industries, Ltd. Composition ameliorante pour gonfleur
US20040140027A1 (en) * 2001-05-10 2004-07-22 Rainer Hagel Igniting agents
US20080217893A1 (en) 2004-06-17 2008-09-11 Nof Corporation Firing Agent for Gas Generating Device
JP2007176202A (ja) * 2005-12-27 2007-07-12 Daicel Chem Ind Ltd エアバッグモジュール

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3653994A (en) * 1954-05-24 1972-04-04 Aerojet General Co Propellant compositions containing a metal nitrite burning rate catalyst
US4369079A (en) * 1980-12-31 1983-01-18 Thiokol Corporation Solid non-azide nitrogen gas generant compositions
US5139588A (en) * 1990-10-23 1992-08-18 Automotive Systems Laboratory, Inc. Composition for controlling oxides of nitrogen
US5035757A (en) * 1990-10-25 1991-07-30 Automotive Systems Laboratory, Inc. Azide-free gas generant composition with easily filterable combustion products
US5386775A (en) * 1993-06-22 1995-02-07 Automotive Systems Laboratory, Inc. Azide-free gas generant compositions and processes
JPH09501138A (ja) * 1993-08-02 1997-02-04 サイオコル・コーポレーション 無水テトラゾール・ガス発生剤組成物を製造する方法
US5472647A (en) * 1993-08-02 1995-12-05 Thiokol Corporation Method for preparing anhydrous tetrazole gas generant compositions
US5682014A (en) * 1993-08-02 1997-10-28 Thiokol Corporation Bitetrazoleamine gas generant compositions
US5431103A (en) * 1993-12-10 1995-07-11 Morton International, Inc. Gas generant compositions
US5380380A (en) * 1994-02-09 1995-01-10 Automotive Systems Laboratory, Inc. Ignition compositions for inflator gas generators

Also Published As

Publication number Publication date
EP0944562A4 (fr) 2000-02-23
EP0944562A1 (fr) 1999-09-29
JP4021491B2 (ja) 2007-12-12
JP2001507325A (ja) 2001-06-05
WO1998006683A1 (fr) 1998-02-19

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