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
  • C06B33/00—Compositions containing particulate metal, alloy, boron, silicon, selenium or tellurium with at least one oxygen supplying material which is either a metal oxide or a salt, organic or inorganic, capable of yielding a metal oxide

Definitions

• the present invention is directed to compositions for igniting gas generants for use in automotive airbag applications in conjunction with non-azide gas generants, particularly gas generant compositions containing both nitrogen and oxygen atoms and/or both nitrogen and hydrogen atoms and/or both nitrogen and carbon atoms.
• an airbag When an airbag is deployed, it must rapidly inflate, e.g., in the range of between 30 and 100 milliseconds, and then rapidly deflate. During deflation, the gases are vented into the passenger compartment of a vehicle, and undesirable by-product gases may present a hazard to the occupants of the vehicle. This is one of the major impediments in the commercialization of non-azide pyrotechnic inflators.
• a typical automotive airbag system consists of an airbag and a pyrotechnic inflator module in which the gases are produced which inflate the airbag.
• Inflators are described, for example, in U.S. Patents Nos. 4,943,086, 5,221,109, 5,241,910, the teachings of each of which are incorporated herein by reference.
• a remote sensor senses the force of a collision. The sensor is electrically connected to a squib in the inflator, and electrically generated heat in the squib ignites a small charge of pyrotechnic material in the squib. The pyrotechnic charge, in turn, produces heat that sets off a larger charge of igniter composition.
• a very common igniter material is B/KNO 3 , in which boron is the fuel and potassium nitrate the oxidizer.
• This composition is a standard ignitor composition in the inflator industry. This ignitor is generally proportioned to be fuel rich (that is oxygen-poor). Fuel-rich mixtures tend to have high burn temperatures, a feature desirable in igniting a gas generant composition. Furthermore, a fuel (boron)-rich ignitor composition ejects hot particles of boron or boron oxide which hasten combustion of the gas generant composition through direct thermal contact with the gas generant composition to be ignited.
• an igniter composition for a non-azide gas generant composition in which the gas generant composition contains any combination of C, H, O and/or N atoms which results in a reduction of undesired gas by-products produced by combustion of the gas generant composition.
• the igniter composition has a fuel component of which between about 5 and 100 wt% is a fuel selected from Mg, Ti, Al, TiH 2 , and mixtures thereof, and up to about 95 wt% of which comprises a combustible carbohydrate fuel, that is, a fuel which contains only the elements carbon, hydrogen and oxygen. Between about 35 and about 65 wt% of the carbohydrate fuel, if used, is oxygen content.
• the igniter composition further comprises an oxidizer component which does not contain nitrogen, particularly an oxidizer selected from the group consisting of KClO 3 , NaClO 3 , KClO 4 , NaClO 4 , and mixtures thereof.
• the igniter composition in accordance with the present invention is designed to burn with a sufficiently high temperature to ignite the gas generant composition.
• the igniter composition like the gas generant composition, produces gases upon combustion, this is not its primary purpose; hence, igniter compositions are not necessarily selected to maximize their gas output.
• the igniter composition is used at a very low mass ratio relative to the gas generant.
• a typical automotive driver side airbag inflator may contain about 2 grams of igniter composition and about 60 to 100 grams of gas generant composition. Passenger- side airbags and side airbags may have different amounts of gas generant material, but likewise contain a greater amount of gas generant material relative to igniter material.
• Non-azide gas generant compositions to which the invention is directed are those which contain the combinations of N plus O and/or N plus H, giving rise to NO x (especially NO and NO 2 ) and NH 3 combustion products.
• Such gas generant compositions commonly also contain carbon atoms, further giving rise to CO and HCN combustion products.
• the igniter composition contains oxidizer component in an amount sufficient so as to be at least stoichiometrically balanced with the fuel, i.e., have an oxygen-to-fuel ratio (O/F) of at least 1, and preferably is oxygen-rich, having an O/F stoichiometric ratio of at least about 1.05.
• the igniter composition must have an O/F ratio consistent with providing sufficient energy to ignite the gas generant composition.
• the igniter composition must be least stoichiometrically balanced. That is, there must be sufficient oxidizer to oxidize the metal or metal-containing fuel to the appropriate metal oxide and any carbohydrate fuel to CO 2 and H 2 O.
• the oxidizer-to-fuel ratio (O/F) is defined as equal to 1.0. If there is a 5% excess of oxidizer the O/F ratio is 1.05 and so forth.
• Preferred compositions have O/F greater than 1.05. This is in contrast to conventional B/KNO 3 igniter composition which is fuel rich (oxygen deficient).
• the combustion temperatures of the igniter compositions of the present invention are sufficiently high to ignite most non-azide gas generant compositions.
• the upper limit of O/F ratio is the point where the igniter composition no longer combusts hot enough to ignite the gas generant composition.
• igniter compositions in accordance with the invention will have O/F limits no higher than about 1.3 (i.e. 30 molar% over-oxidized).
• the fuel component may be entirely a metal or a metal hydride selected from the group consisting of Mg, Ti, Al, TiH 2 , and mixtures thereof. Of these, Ti is least preferred due to associated health risks. Mg and TiH 2 are currently preferred. While other metal hydrides, such as aluminum hydrides, might work as igniter fuels, they are generally considered to be too moisture-sensitive for automotive airbag inflators. TiH 2 , however, is found to have good moisture stability. Metals and metal hydrides have the important function in igniter compositions as producing metal oxide particulates, such as aluminum oxide or titanium oxide. Such particulates contribute to a rapid initial pressure by heating the gas generant composition by direct conduction.
• the fuel component may also include an organic C, H, O compound (carbohydrate) fuel having a relatively high oxygen content, i.e., between about 35 and about 65 wt%.
• the oxygen component is preferably high so as to require a relatively low corresponding amount of oxygen in the igniter mixture.
• the carbohydrate fuel is generally used at a level of at least about 20 wt% of the fuel component, more typically at a level of at least about 50 wt% of the fuel component, and most typically at a level of at least about 60 wt% of the fuel component, up to about 95% of the fuel component.
• the carbohydrate fuel if used, is included to produce high volumes of gas and therefore contribute to an initial high gas pressure within the inflator module, high pressure being believed to reduce levels of toxic gases.
• suitable carbohydrate fuels include, but are not limited to tartaric acid, succinic acid, malonic acid, lactose and mixtures thereof.
• the oxidizer component is a non-nitrogen-containing oxidizer.
• Preferred oxidizers are chlorates and perchlorates, such as potassium chlorate, sodium chlorate, potassium perchlorate, sodium perchlorate, or mixtures thereof.
• the identical composition was ignited using titanium hydride/potassium perchlorate (TiH 2 /KClO 4 ) igniter compositions with varying O/F ratios.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Air Bags (AREA)

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Cited By (6)

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Citations (7)

• 1996
  • 1996-09-05 EP EP96306440A patent/EP0763511A3/de not_active Withdrawn
  • 1996-09-13 JP JP8243580A patent/JPH09118580A/ja active Pending

Patent Citations (7)

Non-Patent Citations (1)

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