Gas generant and manufacturing method thereof

Abstract

The present invention generally relates to gas generant compositions for inflators of occupant restraint systems, for example. An extrudable pyrotechnic composition includes polyvinylazoles for use within an airbag gas generator. The fuel may be selected from exemplary polyvinylazoles including 5-amino-1-vinyltetrazole, poly(5-vinyltetrazole), poly(2-methyl-5-vinyl) tetrazole, poly(1-vinyl) tetrazole, poly(3-vinyl) 1,2,5 oxadiazole, and poly(3-vinyl) 1,2,4-triazole. An oxidizer is combined with the fuel and preferably contains phase stabilized ammonium nitrate. A novel method of forming the compositions is also presented wherein the various constituents are wetted and/or dissolved, and then cured within the polyvinylazole matrix thereby forming a more intimate combination within the gas generant composition. A vehicle occupant protection system 180, and other gas generating systems, incorporate the compositions of the present invention.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application Ser. No. 60 / 557,279 filed on Mar. 29, 2004.TECHNICAL FIELD [0002] The present invention relates generally to gas generating systems, and to gas generant compositions employed in gas generator devices for automotive restraint systems, for example. BACKGROUND OF THE INVENTION [0003] The present invention relates to nontoxic gas generating compositions that upon combustion rapidly generate gases that are useful for inflating occupant safety restraints in motor vehicles and specifically, the invention relates to thermally stable nonazide gas generants having not only acceptable burn rates, but that also, upon combustion, exhibit a relatively high gas volume to solid particulate ratio at acceptable flame temperatures. [0004] The evolution from azide-based gas generants to nonazide gas generants is well-documented in the prior art. The advantages of nonazide gas generant comp...

AI Technical Summary

Benefits of technology

[0017] In yet another aspect of the invention, a method of manufacturing a gas generant composition incorporating a polyvinylazole is described. A vinyl azole is first added to a vessel. If necessary, an aqueous, organic, or aqueous / organic solvent is provided in an amount effective to dissolve all constituents to be added to the vessel. In preferred embodiments, a liquid vinyl azole will complete wet and / or facilitate the solubility of the other gas generant constituents without the use of a solvent. An oxidizer, preferably nonmetallic, is next added. Other constituents / solutes such as a secondary fuel(s), a secondary oxidizer(s), slag former(s), processing aid(s), coolant(s), and / or burn rate modifier(s) may be added to the slurry and stirred to a substantially uniform or homogeneous mixture. Next, an initiator is added to facilitate the curing or polymerization of the mixture. The mixture is then cured either statically, or without stirring, wherein a solid is then formed, or, while stirring wherein granules may then be formed. If cured statically, the mixture may be poured within molds, for example, to form the desired propellant shape(s). If cured while stirring, crushing and formation of the granules is not necessary given the inherent formation of the granules. Thermoplastic polymers facilitate melt processing for further shaping of the propellant if desired.

Problems solved by technology

One of the disadvantages of known nonazide gas generant compositions is the amount and physical nature of the solid residues formed during combustion.

Further, gas generant compositions incorporating phase stabilized or pure ammonium nitrate sometimes exhibit poor thermal stability, and produce unacceptably high levels of toxic gases, CO and NO.sub.x for example, depending on the composition of the associated additives such as plasticizers and binders.

Yet another problem that must be addressed is that the U.S. Department of Transportation (DOT) regulations require “cap testing” for gas generants.

Because of the sensitivity to detonation of fuels often used in conjunction with ammonium nitrate, many propellants incorporating ammonium nitrate do not pass the cap test unless shaped into large disks, which in turn reduces design flexibility of the inflator.

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