Compositions – Oxidative bleachant – oxidant containing – or generative – Plural oxidants
Reexamination Certificate
1999-11-12
2001-08-14
Anthony, Joseph D. (Department: 1714)
Compositions
Oxidative bleachant, oxidant containing, or generative
Plural oxidants
C252S186200, C252S186440, C252S187310, C149S019910, C149S047000, C149S062000, C149S076000, C149S078000, C280S741000
Reexamination Certificate
active
06274064
ABSTRACT:
TECHNICAL FIELD
The present invention relates to gas-generating compositions for generating a particulate-free, non-toxic, odorless and colorless gas. The present invention is particularly useful in vehicle occupant restraints and aircraft chutes.
BACKGROUND ART
The present invention relates generally to inflator compositions and more particularly to solid inflator compositions useful as gas generators. Gas generating compositions must satisfy various criteria for optimal effectiveness. Gas generating compositions for use in vehicle occupant restraints, e.g., automobile or aircraft airbags must satisfy stringent criteria including toxicity requirements which are of concern in solid propellants for military or propulsion systems. Conventional gas generating compositions are plagued with problems, including a high pressure exponent, a low burning rate, poor combustion stability, and inadequate age-life stability. The inferior ballistic properties disadvantageously result in low gas yields and unburned, energetic residues which remain at the end of the normal burn interval. Not surprisingly, great demand has recently arisen for gas generating compositions which yield a high volume of gas and a low volume of solid particulates, and which exhibit a low pressure exponent and have low pressure combustion stability.
Attempts to improve existing gas generating compositions to impart these properties have been unsuccessful for various reasons. For example, the addition of certain modifiers such as organometallic and certain oxides produce exhaust products that are toxic in man-rated environments. Other additives previously utilized, while not producing toxic exhaust products, have not successfully improved low pressure combustion efficiency. Also, other traditional techniques to solve these problems involve the use of relatively expensive degflagrative additives that interfere with the thermal or chemical stability of the overall formulation during long term thermal soak or thermal cycling conditioning.
Those skilled in this art have experienced difficulty in selecting among the many possible additive candidates for gas generating compositions intended for airbag applications to obtain compositions where smoke and ash are considered unacceptable consequences.
Moreover, propellant compositions are typically compacted into the form of grains of a suitable shape. Such propellant grains must be capable of sustaining thermal and tensile shock during igniter functioning, and must exhibit sufficient strength to remain intact during gas generator functioning if ballistic performance is to remain unaffected. The grains must retain such capability after aging and cycling.
There exists a continuing need for gas generating compositions, particularly gas generating compositions for air bag utility, which exhibit a low pressure exponent, high burning rate and good combustion efficiency at low pressures.
DETAILED DESCRIPTION OF THE INVENTION
Ammonium nitrate (AN), is conventionally employed as an oxidizer in gas generating compositions which include, as a component, guanidine nitrate (GN) because of its low cost, availability and safety. For example, a commercially available gas generating composition is ARCAIR 102A which is disclosed in U.S. Pat. No. 5,726,382 and includes guanidine nitrate, ammonium nitrate, potassium nitrate and polyvinyl alcohol.
Another commercially available gas generating composition is ARCAIR 102B which is disclosed in application Ser. No. 08/663,012 filed Jun. 7, 1996 now U.S. Pat. No. 5,850,053, and includes guanidine nitrate, ammonium nitrate, potassium perchlorate, and polyvinyl alcohol. A conventional airbag gas generating composition is disclosed in U.S. Pat. No. 5,538,567 to Olin. The '567 gas generating composition includes guanidine nitrate, an oxidizer, a flow enhancer and a binder. However, conventional airbag gas generating compositions such as the one disclosed in the patent might exhibit one or more disadvantages such as a high pressure exponent, a low burning rate, and poor combustion efficiency.
The present invention addresses and solves such problems by incorporating a strategically selected additive such as a metal oxide, e.g., iron oxide, in AN/GN compositions which surprisingly and unexpectedly improves the ballistic properties of AN-oxidized propellants, in particular, those containing GN or guanidine derivatives as highly oxygenated fuel sources. The composition, when in the form of a pressed pellet provides a generator to produce a particulate-free, non-toxic, odorless and colorless gas for inflating an air bag, without the tendency of the pellet to crack and with reduced phase change of the AN due to temperature cycling. Also, the pressure exponent is lowered, and low pressure combustion efficiency is improved. Furthermore, the addition of iron oxide does not adversely affect thermal stability of the base mix.
Accordingly, it is an object of the present invention to provide a gas generating composition which exhibits a lower pressure exponent and sustains combustion at pressures between ambient and 200 psi.
Another object of the present invention is to provide a method of generating a particulate-free, non-toxic, odorless and colorless gas.
According to the present invention, the foregoing and other objects are achieved in part by a gas generating composition comprising ammonium nitrate and a non toxic metal oxide.
Another object of the present invention is a method of generating a gas comprising the steps of a) providing an enclosed pressure chamber having an exit port, b) disposing within said chamber, a gas generating composition comprising ammonium nitrate and a non-toxic metal oxide, and c) providing means for igniting said composition upon detection of the pressure chamber being subjected to a sudden deceleration, whereby gas is instantly generated and conducted through the exit port of said pressure chamber.
Additional objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment of the invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.
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Anthony Joseph D.
Atlantic Research Corporation
Nixon & Vanderhye P.C.
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