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Gas generant compositions

Gas generant compositions description/claims

This application claims the benefit of U.S. Provisional Application Ser. No. 60/875,300 filed on Dec. 15, 2006.

The present invention relates generally to gas generating systems, and to autoignition and booster compositions employed in gas generator devices for automotive restraint systems, for example.

The present invention relates to autoignition compositions that upon ignition provide the flame front and pressure front necessary to safely ignite gas generant compositions in combustible communication therewith. As known in the art, gas generators are typically provided with an autoignition composition that in the event of a fire ignites responsive to a desired threshold temperature. As a result, the gas generant is ignited prior to melting for example, thereby safely igniting the main gas generant composition to inhibit or prevent the likelihood of an explosive event once the gas generant begins to combust.

An ongoing challenge is to simplify the manufacture of a gas generator by reducing the constituents required in the production thereof. For example, in many gas generators used in vehicle occupant protection systems, several discrete compositions are provided to serve correspondingly discrete functions. These compositions often include a primary gas generating composition that when combusted is employed to provide sufficient quantities of gaseous products to operate the associated restraint device, such as an airbag or seatbelt pretensioner. A booster composition is utilized to elevate the pressure and heat within the gas generator prior to combustion of the primary gas generant, thereby creating favorable conditions within the inflator for acceptable combustion of the primary gas generant. Of course, still yet another composition is the auto-ignition composition employed to provide safe combustion of the other compositions in the event of a fire. The auto-ignition composition is designed to ignite at temperatures below the melting point of the primary gas generant for example, thereby ensuring the controlled combustion of the primary gas generant, as opposed to an explosive reaction perhaps.

The use of compositions containing cellulose acetate butyrate (CAB), nitroguanidine (NQ), and potassium perchlorate (KP) as gas generant compositions is known. These compositions provide relatively large amounts of gas and relatively small amounts of solids upon combustion. However, the ignition temperature is over 500 degrees Celsius. Seatbelt pretensioners utilizing this composition disassemble when subjected to DOT and BAM rapid heating tests. Even so, this composition is desirable given the relatively cheap costs and also because of the large amounts of gas produced. It would therefore be an improvement in the art to stabilize the ignition and combustion of a CAB composition to make it useful in smaller micro gas generators used in seatbelt devices, for example.

The above-referenced concerns and others may be resolved by gas generating systems including an autoignition/booster composition containing a first oxidizer selected from metal perchlorates, such as potassium perchlorate, at about 10-90 weight percent of the composition, and a fuel component of CAB and NQ that when taken together are provided at about 10-90 weight percent of the composition. In accordance with the present invention, a first additive of molybdenum trioxide is provided at about 0.1-3 wt % of the total composition. Alternatively, any compound that would liberate molybdenum trioxide in the same relative molar/weight amounts during combustion may also be provided as the first additive. These include molybdic acid, ammonium molybdate, sodium molybdate, phosphomolybdic acid, ammonium phosphomolybdate, and sodium phosphomolybdate. A second additive of 5-aminotetrazole is provided at about 0.1-5 wt % of the total composition. Alternatively, any azole-based fuel including metal salts of azole compounds, and azole compounds such as aminotetrazole, tetrazole, 5-nitrotetrazole, 5-nitroaminotetrazole, and bitetrazole, may be included in the same weight percent range, or, in the same molar-effective amounts. Alternatively, triazole-based compounds including 1,2,4-triazole-5-one or 3-nitro-1,2,4-triazole-5-one and metal salts of these compounds may also be employed either singularly or in conjunction with the tetrazole-based compounds in the same weight percent range, or in the same molar-effective amounts. Alternatively, guanidine nitrate, aminoguanidine nitrate, triaminoguanidine nitrate, nitroguanidine, dicyandiamide, triazalone, nitrotriazalone, and mixtures thereof may also be employed either singularly or in conjunction with tetrazole-based and/or triazole-based compounds in the same weight percent range of about 0.1-5 weight percent when taken as a whole, or in the same molar-effective amounts as the azole-based second additive.

In further accordance with the present invention, a gas generator and a vehicle occupant protection system incorporating the autoignition system are also included. A seat belt device as known in the art may also contain a composition as described above may also be included.

FIG. 1 is a cross-sectional side view showing the general structure of an inflator in accordance with the present invention.

FIG. 2 is a schematic representation of an exemplary vehicle occupant restraint system containing a gas generant composition in accordance with the present invention.

• Provisional Patent
• Utility Patent

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