CN101528642A

CN101528642A - Extrudable gas generant

Info

Publication number: CN101528642A
Application number: CNA2007800392152A
Authority: CN
Inventors: 伊万·V·门登豪; 罗伯特·D·泰勒
Original assignee: Autoliv ASP Inc
Current assignee: Autoliv ASP Inc
Priority date: 2006-08-28
Filing date: 2007-08-16
Publication date: 2009-09-09
Also published as: EP2061736A1; US20060289096A1; JP2010502544A; EP2061736A4; US20090008001A1; WO2008027204A1

Abstract

The invention provides extrudable gas generant compositions which, upon combustion, produce or result in an improved effluent and related methods for generating inflation gas for use in an inflatable restraint system. Such extrudable gas generant compositions include a non-azide, organic, nitrogen-containing fuel, at least one copper-containing compound, a perchlorate additive and a polymeric binder material. The at least one copper-containing compound may be selected from basic copper nitrate, cupric oxide, a copper dianunine-ammonium-nitrate mixture wherein the ammonium nitrate is present in the mixture in a range of about 3 to about 90 weight percent, and/or a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate. The perchlorate additive is present in an amount effective to result in a gaseous effluent, when the gas generant composition is combusted, having a reduced content of at least one species selected from carbon monoxide, ammonia, nitrogen dioxide and nitric oxide, as compared to a same gas generant free from the perchlorate additive. The polymeric binder material is effective to render the gas generant composition extrudable.

Description

Extrudable gas generant composition

Technical Field

The present invention relates to materials for gas generation, such as the generation of inflation gases for inflating inflatable devices such as airbags for automotive inflatable restraint systems, and more particularly, to extrudable perchlorate-containing gas generant compositions which produce or result in a gaseous effluent having a reduced content of various undesirable constituents and which are advantageous or readily manufacturable by an extrusion process.

Background

Generally, when a vehicle is rapidly decelerated, such as in a collision accident, a cushion or a bag, such as an airbag, which is inflated or expanded by gas, is used to protect a vehicle occupant. Such airbag restraint systems typically include: one or more airbags in an uninflated and folded state to reduce the space occupied; one or more impact sensors disposed on the vehicle frame or body for detecting sudden deceleration of the vehicle; an activation system electronically activated by the crash sensors; and an inflator that generates or supplies gas to inflate the airbag. In the event of a rapid deceleration of the vehicle, the crash sensors activate the activation system which in turn activates the inflator device to inflate the airbag cushion in milliseconds.

Various inflator devices for inflating one or more airbags of inflatable restraint systems have been disclosed in the art. Inflator devices that form or produce an inflation gas by combustion of a pyrotechnic gas-generating material, such as a gas generant composition, are well known. For example, inflator devices are known that utilize the high temperature combustion products of the combustion of a gas generant composition, including additional gas products, to provide a reserve and pressurized gas to inflate one or more airbags. In other known inflator devices, the combustion products produced by the combustion of the gas generant composition may be the only or substantially the only source of inflation gas used to inflate the airbag cushion. Typically, such inflator devices include a screen that removes dust or particulate matter from the inflation gas produced during combustion of the gas generant composition to limit or prevent occupant exposure to undesirable and/or toxic combustion byproducts.

Based on increasing concerns about passenger safety and injury avoidance, many automobiles typically include several inflatable restraint systems, each including one or more inflators. For example, a vehicle may include a driver airbag, a passenger airbag, one or more seatbelt tensioners, one or more knee protectors and/or one or more inflatable seatbelts, each provided with an associated inflator to protect the driver and passenger from frontal impacts. The vehicle may also include one or more head/chest cushions, and/or curtains, each provided with at least one associated inflator device, to protect the driver and passengers from side impacts. Generally, the gas flow or inflation gas produced by all of the inflator devices in a particular vehicle, as a whole, is required to meet stringent content limits to meet current industry safety requirements. It is therefore desirable that gas generant compositions used in such inflator devices produce as little undesirable gaseous effluent as possible, such as hydrogen chloride, carbon monoxide, nitrogen dioxide and nitric oxide.

Many gas generant compositions include perchlorate additives, such as ammonium perchlorate and/or alkali metal perchlorates, as an oxidizer. Such perchlorate additives are commonly used in gas generant compositions as a source of oxygen to enhance the combustion efficiency of the gas generant composition, such as the complete conversion of carbon to carbon dioxide, hydrogen to water, and nitrogen to nitrogen. However, perchlorate additives also tend to produce hydrogen chloride as a gaseous byproduct of combustion, and too high a concentration of hydrogen chloride can be toxic and/or corrosive. Hydrogen chloride can be removed from the combustion gas stream by adding an alkali or alkaline earth metal salt to the gas generant composition. Such alkali or alkaline earth metal salts are reacted with hydrogen chloride to form the weakly or non-toxic alkali or alkaline earth metal chlorides, such as sodium chloride or potassium chloride. However, such alkali or alkaline earth metal chlorides disadvantageously form fine particles or dust which can escape from the inflator. In addition, the addition of perchlorate additives generally increases the combustion temperature of pyrotechnic gas generant compositions, often resulting in elevated levels of undesirable and potentially toxic gaseous effluents such as ammonia and carbon monoxide.

One technique for controlling the composition of the gas stream resulting from the combustion of a gas generant composition involves the control of equivalence ratios, such as by varying the concentration of an oxidizer in the gas generant composition. While equivalence ratio control of gas generant materials is a technique conventionally employed to adjust gas generant effluent levels, such control tends to effect adjustment, sometimes referred to as equivalence ratio balancing. That is, as the equivalence ratio decreases, incompletely oxidized species such as carbon monoxide (CO) and ammonia (NH)₃) Increased and peroxidized substances such as Nitric Oxide (NO) and nitrogen dioxide (NO)₂) And (4) reducing. The opposite is true as the equivalence ratio increases.

In view of the above, there is a need for gas generant compositions that advantageously produce or result in low levels of undesirable effluents such as carbon monoxide, ammonia, nitrogen dioxide and nitric oxide, as well as low levels of finely divided particulate matter.

Typically, such gas generant compositions are produced using a spray drying process. In such spray drying processes, the gas generant compositions are typically prepared as a slurry of particulate material in a carrier fluid such as water or alcohol. The gas generant in slurry form is then sprayed into a fine spray such that the carrier fluid is simultaneously dried to form a powdered material. The powdered material is then pressed by a high speed press into gas generant bodies in the form of pellets, tablets, cakes and the like. However, those skilled in the art will recognize and appreciate that these two-step processes, such as spray drying and compression molding, result in increased production time and costs due to the use of multiple processing steps and/or systems to form the final gas generant composition product. Accordingly, it is desirable to produce gas generant compositions for use in such inflator devices in an economical and/or efficient manner.

For example, processes for more efficiently preparing solid gas generant bodies for use in inflator devices include extrusion processes. Such extrusion processes typically involve the mixing and extrusion of a viscous or paste-like gas generant composition into a desired shape. Each individual gas generant body may be formed by cutting or otherwise severing the gas generant body as it is extruded. Such gas generant bodies may be cut into various desired volumes, such as to allow multiple bodies to be disposed within a combustion chamber of an inflator device, or alternatively, to allow a single pellet to be disposed within the combustion chamber. Thus, those skilled in the art will recognize that such extrusion processes may be advantageously used to reduce manufacturing costs by reducing separate manufacturing and compression molding steps and reducing equipment costs.

In addition to the advantageous properties and characteristics described above, gas generant materials used in automotive inflation restraint applications must be sufficiently reactive such that upon initiation of an appropriate reaction, the resulting gas generation or reaction occurs sufficiently rapidly to permit proper inflation of an associated inflatable airbag cushion and to provide advantageous protection to the vehicle occupant.

Gas generant compositions useful in extrusion processes typically include a binder material that binds the components of the gas generant composition and increases the rigidity and/or strength of the extruded particles. However, such adhesive materials can adversely reduce the burn rate of the gas generant composition, thereby adversely affecting the rate at which inflation gas is produced and/or the total amount of inflation gas used to inflate an associated airbag cushion.

In view of the foregoing, there is a need and a demand for a pyrotechnic gas generant composition that can be extruded and formed into a plurality of individual gas generant bodies or individual pellet pieces that, when used in an airbag inflator device, can rapidly, reliably and/or efficiently produce a desired amount of gas flow at a combustion rate to inflate an associated airbag cushion.

Disclosure of Invention

It is a primary object of the present invention to provide an improved gas generant composition.

It is a more specific object of the invention to overcome one or more of the above problems.

The main object of the present invention can be achieved or at least partially achieved by the following technical solutions: an extrudable gas generant composition includes a non-azide, organic, nitrogen-containing fuel, at least one copper-containing compound, a perchlorate additive, and a polymeric binder effective to render the gas generant composition extrudable. The at least one copper-containing compound is selected from the group consisting of basic copper nitrate, cupric oxide, a mixture of copper diammine dinitrate and ammonium nitrate having ammonium nitrate present in the range of about 3 to about 90 weight percent, copper diammine bitetrazole, a copper-nitrate complex resulting from the reaction of 5-aminotetrazole with basic copper nitrate, or a mixture of the foregoing copper-containing compounds. The perchlorate additive includes at least one perchlorate material selected from alkali metal perchlorates and ammonium perchlorate. The perchlorate additive is present in an amount effective to result in a gaseous effluent having a reduced content of at least one of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide when the gas generant composition is combusted, as compared to an identical gas generant composition without the perchlorate additive.

The prior art generally fails to provide gas generant compositions which permit or facilitate the addition of one or more perchlorate additives while preventing or reducing the generation or levels of undesirable gases such as carbon monoxide, ammonia, nitrogen dioxide and nitric oxide. The prior art has further tended to fail to provide gas generant compositions including one or more perchlorate additives that can be extruded to form a plurality of individual gas generant bodies or a monolithic grain that can be rapidly and reliably combusted at an effective combustion rate to produce a gaseous effluent for inflating an associated airbag cushion.

The present invention further comprises an extrudable gas generant composition comprising:

a non-azide, organic, nitrogen-containing fuel in an amount of 5% to 60% by weight of the gas generant composition;

copper-containing compounds selected from the group consisting of basic copper nitrate, cupric oxide, a mixture of copper diammine dinitrate and ammonium nitrate having ammonium nitrate present in the range of 3 to 90 weight percent, copper diammine bitetrazole, a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate and mixtures of the foregoing copper-containing compounds, at least one of the copper-containing compounds being present in an amount of 10 to 80 weight percent based on the weight of the gas generant composition;

a perchlorate additive comprising at least one perchlorate material selected from the group consisting of alkali metal perchlorates and ammonium perchlorate in an amount of from 1 to about 10 percent by weight of the gas generant composition, the perchlorate additive being effective to result in a gaseous effluent having a reduced content of at least one of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide when the gas generant composition is combusted as compared to an identical gas generant composition without the perchlorate additive; and

a polymeric binder material in an amount of 1% to 20% by weight of the gas generant composition effective to render the gas generant composition extrudable, the polymeric binder material selected from the group consisting of cellulosic materials, natural rubber, polyacrylates, polyacrylamides, polyurethanes, polybutadienes, polystyrenes, polyvinyl alcohols, polyvinyl acetates, silicones and combinations of two or more thereof.

guanidine nitrate in an amount of 5% to 60% by weight of the gas generant composition;

a copper-containing compound selected from the group consisting of basic copper nitrate, cupric oxide, a mixture of copper diammine dinitrate and ammonium nitrate wherein ammonium nitrate is present in the mixture in a range of about 3 to about 90 weight percent, copper diammine bitetrazole, a copper-nitrate complex resulting from the reaction of 5-aminotetrazole with basic copper nitrate and mixtures thereof in an amount of 10 to 80 weight percent based on the weight of the gas generant composition;

a perchlorate additive comprising at least one perchlorate material selected from alkali metal perchlorates and ammonium perchlorate in an amount of 1 to 10% by weight of the gas generant composition; and

a polymeric binder material in an amount of 1% to 20% by weight of the gas generant composition, the polymeric binder material selected from the group consisting of cellulosic materials, natural rubber, polyacrylates, polyacrylamides, polyurethanes, polybutadienes, polystyrenes, polyvinyl alcohols, polyvinyl acetates, silicones and mixtures of two or more thereof.

Additionally, the present invention provides a corresponding or related method of generating an inflation gas for inflating an airbag of an inflatable restraint system of an automotive vehicle. These methods generally involve igniting a particular extrudable gas generant composition to produce a quantity of inflation gas and then inflating the airbag cushion with the inflation gas.

The term "equivalence ratio" as used herein refers to the ratio of the number of moles of oxygen in a gas generant composition or formulation to the number of moles of oxygen required to convert hydrogen to water, carbon to carbon dioxide, and any metal to a thermodynamically predictable metal oxide. Thus, gas generant compositions having an equivalence ratio greater than 1 are over-oxidized, gas generant compositions having an equivalence ratio less than 1 are under-oxidized, and gas generant compositions having an equivalence ratio equal to 1 are desirably oxidized.

As used herein, "substantially free", in reference to possible gas stream constituents such as hydrogen chloride, carbon monoxide, ammonia, nitrogen dioxide and nitric oxide, similarly refers to a gas stream or an expanding gas comprising such constituents in amounts equal to or less than those permitted or allowed by existing industry standards (american society for automotive research specifications). For example, for an automobile having an airbag with an inflator including a gas generant composition, when the inflator is activated in a 100 cubic foot container, the gas stream or inflation gas produced by the combustion of the gas generant composition is considered substantially free of hydrogen chloride if it includes about 5 parts per million or less hydrogen chloride; when the gas generator is activated in a 100 cubic foot vessel, the gas stream or inflation gas produced by igniting the gas generant composition is considered substantially free of carbon monoxide if it contains about 461 parts per million or less carbon monoxide; when the gas generator is activated in a 100 cubic foot container, the gas generator is considered substantially free of ammonia gas if the gas stream or inflation gas produced by igniting the gas generant composition includes about 35 parts per million or less ammonia gas; when the gas generator is activated in a 100 cubic foot container, the gas stream or inflation gas produced by igniting the gas generant composition is considered substantially free of nitrogen dioxide if it includes about 5 parts per million or less of nitrogen dioxide; when the gas generator is activated in a 100 cubic foot container, the gas stream or inflation gas produced by igniting the gas generant composition is considered substantially free of nitric oxide if it includes about 75 parts per million or less nitric oxide.

Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the appended claims and drawings.

Drawings

FIG. 1 is a simplified schematic illustration, partially broken away, showing the inflation of an airbag from an airbag component assembled within an automobile, according to one embodiment of the invention.

Detailed Description

The present invention provides an improved gas generant composition. More specifically, it has been discovered that by adding one or more perchlorate additives to a gas generant composition, a gas generant composition can be substantially improved (e.g., the resulting gas effluent can have a substantially reduced content of undesirable materials such as one or more of carbon monoxide, ammonia, nitrogen dioxide, and nitric oxide). Still further, it has been discovered that such gas generant compositions may be rendered extrudable without an undesirable decrease in burn rate by the addition of a polymeric binder material and at least one copper-containing compound.

As discussed above, perchlorate additives are particularly effective oxidizing agents for gas generant compositions used in the inflation of automotive inflatable restraint systems. However, the use of such perchlorate additives often results in the formation of undesirable by-products such as hydrogen chloride or finely divided solid particles (e.g., sodium chloride) when alkali or alkaline earth metal scavengers are also used. In the present invention, it has been discovered that the use of copper-containing compounds in extrudable gas generant compositions results in improved gas flow or inflation gases. In particular, it has been found that the formation of leachable copper chloride by-products often results in a reduction in the content of certain undesirable substances in the gas stream or expansion gas. Furthermore, it has been found to be advantageous that the formation of a leachable copper chloride by-product results in a reduced level of particulates escaping the inflator.

Moreover, it has been unexpectedly discovered that an gas generant composition including a perchlorate additive and at least one copper-containing compound does not result in an undesirable increase in the level of carbon monoxide in the gaseous effluent or inflation gas resulting from the combustion of the gas generant composition. This finding is unexpected because it has generally been found that gas generant compositions including perchlorate additives tend to result in elevated combustion temperatures and, in turn, elevated levels of carbon monoxide in the gaseous effluent or inflation gas. Furthermore, it has been surprisingly found that the carbon monoxide content is lower than expected without the usually occurring counteracting increase in the content of undesirable oxides of nitrogen, such as nitrogen monoxide or nitrogen dioxide.

Still further, it has been unexpectedly discovered that the predominant chlorine-containing species found in the gaseous effluent or inflation gas resulting from the combustion of an extrudable gas generant composition including a perchlorate additive and a copper-containing compound is copper chloride (CuCl)₂) Little or no hydrogen chloride was detected. This finding was unexpected because computer programs that perform standard thermodynamic calculations, such as the Naval Weapons Center Propellant Evaluation Program (PEP), generally predict that the major chlorides in the gas stream or expanded gas produced by the combustion of such extruded gas generant compositions will be cuprous chloride and cuprous chloride trimers with some hydrogen chloride.

Similarly, as discussed above, the addition of an amount of polymeric binder material effective to render the gas generant composition extrudable generally has a deleterious effect on the burn rate of the extrudable gas generant composition. However, in addition to providing an extrudable gas generant composition that combusts to produce an improved gas stream, it has also been discovered that the burn rate of an extrudable gas generant composition in accordance with the invention can be improved. Improved burn rates can be achieved by catalyzing the decomposition of perchlorate additives without adversely affecting the quality of the gas stream. Advantageously, a variety of materials may be used to enhance the burn rate of an extrudable explosive or gas generant composition including a perchlorate additive.

As indicated above, the present invention is directed to an extrudable gas generant composition including at least one non-azide, organic, nitrogen-containing fuel, at least one copper-containing compound, a perchlorate additive, and a polymeric binder material effective to render the gas generant composition extrudable. The perchlorate additive is present in an amount effective to result in a gaseous effluent having a reduced content of at least one of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide when the gas generant composition is combusted as compared to an identical gas generant composition lacking the perchlorate additive.

In practice, the extrudable gas generant composition can include about 5 to about 60 composition weight percent of at least one non-azide, organic, nitrogen-containing fuel, about 10 to about 80 composition weight percent of at least one copper-containing compound, about 1 to about 20 composition weight percent of a perchlorate additive, and about 1 to about 20 composition weight percent of a polymeric binder material.

Non-azide, organic, nitrogen-containing fuels useful in the extrudable gas generant composition include: amine nitrates (amine nitrates), nitramines, nitro heterocyclic compounds, tetrazole compounds, and mixtures thereof. While various non-azide, organic, nitrogen-containing fuels may also be used in extrudable gas generant compositions, in accordance with certain preferred embodiments, the non-azide, organic, nitrogen-containing fuel is preferably guanidine nitrate. In general, guanidine nitrate may be considered for its good thermal stability, low cost and high gas yield on combustion.

The extrudable gas generant composition can include about 5 to about 60 composition weight percent of at least one non-azide, organic, nitrogen-containing fuel. In accordance with certain embodiments, the extrudable gas generant composition can include about 5 to about 30 composition weight percent of at least one non-azide, organic, nitrogen-containing fuel. In accordance with other embodiments, the extrudable gas generant composition can include about 5 to about 20 composition weight percent of at least one non-azide, organic, nitrogen-containing fuel.

In accordance with certain embodiments, the extrudable gas generant composition may include about 5 to about 60 composition weight percent guanidine nitrate. In another embodiment, the extrudable gas generant composition may include about 5 to about 30 composition weight percent guanidine nitrate. In another embodiment, the extrudable gas generant composition may include about 5 to about 20 composition weight percent guanidine nitrate.

The extrudable gas generant composition also includes at least one copper-containing compound. Although a variety of copper-containing compounds may be used in the extrudable gas generant composition, suitable copper-containing compounds are selected from the group consisting of copper-nitrate complexes (e.g., copper-nitrate complexes resulting from reaction of 5-aminotetrazole with basic copper nitrate), basic copper nitrate, cupric oxide, mixtures of copper diammine dinitrate and ammonium nitrate wherein ammonium nitrate is present in the mixture in a range of about 3 to about 90 weight percent, copper diammine bitetrazole, and combinations thereof.

In accordance with certain embodiments, the extrudable gas generant composition can include about 10 to about 80 composition weight percent of at least one copper-containing compound.

Suitable copper-containing compounds for use in the practice of the present invention include copper-nitrate complexes resulting from the reaction of 5-aminotetrazole with basic copper nitrate. In particular, the copper-nitrate complex formed by the reaction of 5-aminotetrazole with basic copper nitrate is believed to be a 5-aminotetrazole copper hydroxy nitrate complex (a copper, hydroxy nitrate 1H-tetrazol-5-amine complex).

In accordance with one embodiment, the extrudable gas generant composition may include about 10 to about 60 composition weight percent of a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate. In accordance with another embodiment, the extrudable gas generant composition may include about 20 to about 60 composition weight percent of a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate. In another embodiment, the extrudable gas generant composition may include about 30 to about 60 composition weight percent of a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate.

In accordance with other embodiments, the extrudable gas generant composition may include a mixture of basic copper nitrate and a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate. In particular, the copper-nitrate complex resulting from the reaction of 5-aminotetrazole with basic copper nitrate is believed to be a 5-aminotetrazole copper hydroxy nitrate complex.

In accordance with one embodiment, the extrudable gas generant composition can include about 10 to about 80 composition weight percent of a combination of basic copper nitrate and the copper-nitrate complex. In accordance with another embodiment, the extrudable gas generant composition may include about 30 to about 80 composition weight percent of a combination of basic copper nitrate and the copper-nitrate complex. In another embodiment, the extrudable gas generant composition may include about 50 to about 80 composition weight percent of a combination of basic copper nitrate and the copper-nitrate complex.

In practice, the combination of basic copper nitrate and the copper-nitrate complex resulting from the reaction of 5-aminotetrazole with basic copper nitrate includes from about 20% to about 80% by weight of the combination of basic copper nitrate and from about 20% to about 80% by weight of the combination of the copper-nitrate complex. In accordance with another embodiment, the mixture of basic copper nitrate and the copper-nitrate complex includes from about 20% to about 40% basic copper nitrate by weight of the mixture and from about 60% to about 80% of the copper-nitrate complex by weight of the mixture.

The extrudable gas generant composition also includes a perchlorate additive in an amount effective to result in a gaseous effluent having a reduced level of at least one of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide when combusted as compared to the same gas generant composition without the perchlorate additive. The perchlorate additive includes at least one perchlorate material selected from the group consisting of alkali metal perchlorates and ammonium perchlorate. In practice, the gas generant composition can include about 1 to about 10 composition weight percent perchlorate additive.

In accordance with certain examples, the perchlorate additive includes at least one alkali metal perchlorate such as, for example, perchlorates of lithium, sodium, potassium, rubidium, and cesium. In fact, sodium perchlorate and potassium perchlorate are believed to be particularly desirable alkali metal perchlorates for use in the present invention, with potassium perchlorate being preferred for efficiency and cost, at least in part because of its lower moisture absorption.

In combination with other embodiments, the perchlorate additive is ammonium perchlorate. In practice, the gas generant composition can include about 1 to about 10 composition weight percent ammonium perchlorate.

In practice, it may be desirable and/or advantageous to utilize non-uniformities in the extrudable gas generant composition. Theoretically, larger particles of perchlorate additive incorporated into extrudable gas generant compositions in accordance with the invention will result in higher levels of non-uniformity. As a result, greater impact on effluent toxicity has been observed due to the inclusion of the sized perchlorate additive in a particular extrudable gas generant composition. In theory, the effectiveness of the perchlorate additive in reducing the formation of undesirable species in the gaseous effluent produced upon combustion of an extrudable gas generant composition is diminished as the perchlorate-containing gas generant composition becomes more uniform. For example, the use of perchlorate particles having an average particle size of less than 100 microns results in an extrudable gas generant composition having reduced heterogeneity and reduced effectiveness in preventing the formation of undesirable species in the gaseous effluent.

More specifically, in conjunction with the specific examples, it has been discovered that the addition of a perchlorate additive having an average particle size in excess of 100 microns and an average particle size of at least about 200 microns in an extrudable gas generant composition significantly improves the effluent resulting from the combustion of an extrudable gas generant composition containing such sized perchlorate additive particles as compared to the effluent resulting from the combustion of the same gas generant composition but without such sized perchlorate additive particles. In combination with at least other embodiments of the present invention, it has been found advantageous to add perchlorate additives to extrudable gas generant compositions having particles with an average particle size in the range of about 350 to about 450 microns.

The extrudable gas generant composition further includes a polymeric binder material effective to render the gas generant composition extrudable. In practice, the extrudable gas generant composition includes about 1 to about 20 composition weight percent polymeric binder material. In accordance with certain embodiments, the extrudable gas generant composition can include about 3 to about 10 composition weight percent polymeric binder material. In accordance with other embodiments, the extrudable gas generant composition can include about 3 to about 6 composition weight percent polymeric binder material.

Suitable polymeric binder materials for use in the extrudable gas generant compositions include, but are not limited to, cellulosic materials, natural rubber, polyacrylates, polyacrylamides, polyurethanes, polybutadienes, polystyrenes, polyvinyl alcohols, polyvinyl acetates, silicones and combinations of two or more thereof. In connection with specific embodiments, the polymeric binder material may be a cellulosic material selected from the group consisting of ethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, and mixtures of two or more thereof. In combination with other embodiments, the polymeric binder material may be a natural rubber selected from the group consisting of guar gum, xanthan gum, gum arabic, and mixtures of two or more thereof.

In accordance with one embodiment, the gas generant composition includes about 1 to about 20 composition weight percent guar gum. In accordance with certain embodiments, the extrudable gas generant composition can include about 3 to about 10 composition weight percent guar gum. In accordance with more specific embodiments, the extrudable gas generant composition can include about 3 to about 6 composition weight percent guar gum.

If desired, extrudable gas generant compositions in accordance with the invention may preferably include at least one metal oxide burn rate enhancing and slag formation additive. Such metal oxide additives may be added to increase the burn rate of the extrudable gas generant composition or to assist in the removal of undesirable combustion byproducts by forming leachable particulates or slag. In practice, the extrudable gas generant compositions of the invention may include up to about 10 composition weight percent of at least one such metal oxide additive. Suitable metal oxide additives include, but are not limited to, silica, alumina, zinc oxide, and mixtures thereof. In accordance with certain embodiments, the extrudable gas generant composition includes about 1 to about 5 composition weight percent of at least one such metal oxide additive. In accordance with other embodiments, the extrudable gas generant composition preferably includes about 1.5 to about 5 composition weight percent aluminum oxide metal oxide burn rate enhancing and slag formation additive and up to about 1 composition weight percent silicon dioxide metal oxide burn rate enhancing and slag formation additive.

In particular embodiments, the extrudable gas generant composition may preferably include at least one compound effective to enhance combustion of the perchlorate additive. In practice, the extrudable gas generant compositions of the invention may include up to about 10 composition weight percent of at least one such oxidizer. Suitable perchlorate additive combustion promoters include, but are not limited to, iron oxide, copper chromite, ferricyanide/ferricyanide dyes, and mixtures thereof.

In particular embodiments, the extrudable gas generant composition preferably includes at least one ferricyanide/ferricyanide dye. Such ferricyanide/ferricyanide dyes, also referred to as "ferriblue dyes", are generally understood to mean dyes of this class, family or variants based on microcrystalline ferrocyanide complexes. According to the results obtained by X-ray and infrared spectroscopy, the general chemical formula of the iron blue dye is:

Me(I)Fe(II)Fe(III)(CN)₆·H₂O (1)

in this formula, Me (I) means potassium, sodium or ammonium, and it is believed that the alkali metal ion plays a decisive role in the color quality of iron blue. Iron blue dyes, sometimes also referred to as "ferrocyanides," have been produced or sold under a variety of different names based on their location of production or their optical properties. Examples of such different names are berlin Blue, cyanotic Blue, chinese Blue, milori Blue, non-cyanotic Blue, paris Blue, prussian Blue, cohun Blue (corning Blue) and turner Blue.

Those skilled in the art and guided by the teachings herein provided will appreciate that there are numerous specific or particular iron blue dye ferrocyanide materials available for selection, as described above. The MANOX-Blue 4050 iron Blue dye ferrocyanide material produced or sold by Degussa corporation is the presently preferred iron Blue dye material for use in the present invention.

Other additives such as processing aids and/or lubricants may also be added to the extrudable gas generant composition to improve the processability of the gas generant composition. Typically, such additives may be added to the extrudable gas generant composition in relatively small concentrations, such as no more than about 5 composition weight percent.

In view of the foregoing, in accordance with certain embodiments, an extrudable gas generant composition may include:

at least one non-azide, organic, nitrogen-containing fuel in an amount of 5% to 60% by weight of the gas generant composition;

at least one copper-containing compound selected from the group consisting of basic copper nitrate, cupric oxide, a mixture of copper diammine dinitrate and ammonium nitrate wherein ammonium nitrate is present in the mixture in an amount of about 3 to about 90 weight percent, copper diammine bitetrazole, a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate and mixtures of the foregoing copper-containing compounds, the at least one copper-containing compound being present in an amount of about 10 to about 80 weight percent based on the weight of the gas generant composition.

A perchlorate additive of at least one perchlorate material selected from the group consisting of alkali metal perchlorates and ammonium perchlorate, the perchlorate additive being effective to result in a reduction in the level of at least one of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide in a gaseous effluent upon combustion of the gas generant composition in an amount of 1 to 10 composition weight percent of the gas generant composition as compared to an identical gas generant composition without the perchlorate additive; and

from 1% to 20% by weight of the gas generant composition of a polymeric binder material effective to render the gas generant composition extrudable, the polymeric binder material selected from the group consisting of cellulosic materials, natural rubber, polyacrylates, polyacrylamides, polyurethanes, polybutadienes, polystyrenes, polyvinyl alcohols, polyvinyl acetates, silicones and combinations of two or more thereof.

Further, in view of the above, in accordance with certain embodiments, an extrudable gas generant composition may include about 5 to about 60 composition weight percent guanidine nitrate, about 10 to about 80 composition weight percent of a combination of basic copper nitrate and a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate, about 1 to about 10 composition weight percent ammonium perchlorate, and about 1 to about 20 composition weight percent guar gum. The ammonium perchlorate is effective to result in a gas generant composition having a reduced level of at least one of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide in a gas stream upon combustion of the composition as compared to an identical gas generant composition without the ammonium perchlorate.

Further, in view of the above, in accordance with certain embodiments, an extrudable gas generant composition may include about 5 to about 60 composition weight percent guanidine nitrate, about 10 to about 60 composition weight percent of a copper nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate, about 1 to about 10 composition weight percent ammonium perchlorate, and about 1 to about 20 composition weight percent guar gum.

The present invention further includes a method of inflating an airbag of an inflatable restraint system of an automotive vehicle including the steps of igniting an extruded gas generant composition to produce a quantity of inflation gas and then inflating the airbag with the inflation gas. The expanded gas is seen to have a reduced content of at least one of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide.

It will be appreciated that the extrudable gas generant compositions of the invention may be combined, utilized or otherwise applied in conjunction with a variety of different structures, assemblies and systems. As shown in the drawings, a vehicle (10) has an interior structure 12 which contains an inflatable vehicle occupant safety restraint system, generally indicated at 14. It will be apparent that certain standard details that are not necessary for an understanding of the present invention may have been deleted or removed from the drawings for ease of illustration and understanding.

The vehicle occupant safety restraint system 14 includes an open reaction vessel 16 forming a housing containing an inflatable vehicle occupant safety restraint 20, such as an inflatable airbag, and a means, generally designated 22, for generating or providing inflation for inflating the associated occupant restraint. This gas generating device is generally referred to as an "inflator" in accordance with the above definition.

The inflator 22 includes a quantity of a gas generant composition of the invention such as described above. The inflator 22 also includes an igniter, as is known in the art, that is in igniting communication with the gas generant composition to initiate combustion of the gas generant composition. It will be appreciated that the particular configuration of the inflator device does not limit the broader applicability of the invention, and that such inflator devices may be configured in a variety of ways, as is known in the art.

In fact, the deploying airbag 20 advantageously provides protection for a vehicle occupant 24 by restraining the occupant from moving forward (i.e., to the right in the drawings) of the vehicle.

The invention will be described in more detail by the following examples which illustrate or simulate various aspects relevant to the application of the invention. All changes that do not depart from the gist of the invention are intended to be protected and the invention is not limited to these examples.

Comparative examples 1-4 and example 1:

five gas generant compositions were prepared, example 1(EX1) and comparative examples 1-4(CE1-CE4), as shown in table 1 below. Values for all compounds are given as weight percent of the gas generant composition.

Table 1

Wherein,

5-ATN/bCN complex is copper nitrate complex generated by reaction of 5-aminotetrazole and basic copper nitrate; and

the burn rate @3000 pounds per square inch-inch per second.

More specifically, for comparative examples 1 and 2, guanidine nitrate, a copper-containing compound, and alumina were mortar mixed and then spray dried to form a powdered precursor. The resulting powdery precursor is then suitably compressed into tablets by a conventional tabletting process.

For comparative example 3, comparative example 4 and example 1, guanidine nitrate, a copper-containing compound and alumina were mortar mixed and then spray dried to form a powdered precursor. The powdered precursor was dry blended with guar gum and for example 1, ammonium perchlorate was also included. The dry-blended mixture was wetted with water, dried and granulated. The granulated mixture is then suitably compressed into tablets using conventional tabletting procedures.

The burn rate data in table 1 was obtained by first pressing the corresponding gas generant composition sample into a 0.5 inch diameter cylinder. Typically, a sufficient amount of gas generant composition is compressed to provide a cylinder of 0.5 inches in length. Subsequently, all surfaces of the cylinders except the upper surface were coated with Krylon (Krylon) flame retardant to ensure linear combustion in the test apparatus. In each example, the coated cylinder was placed in a 1 liter closed tube or test chamber capable of being pressurized with nitrogen to several thousand pounds per square inch and equipped with a pressure gauge to accurately measure the pressure in the test chamber. A small sample of the ignition agent was placed on top of the cylinder and a nichrome wire was passed through the ignition powder and connected to the electrodes on the hatch cover of the test chamber. The test chamber was then pressurized to the desired pressure and the sample was passed through nichromeThe current of the gold wire was ignited. Pressure versus time data was collected as each sample was combusted. Because the combustion of each sample produced gases, the test chamber pressure rose indicating the start of combustion and the pressure leveled off indicating the end of combustion. The time required for combustion being equal to t₂-t₁Wherein t is₂Is the time of combustion end and t₁Is the time at which combustion begins. The weight of the sample divided by the burn time was used to determine the burn rate (grams per second). The burn rate is typically measured at four pressures: 900. 1350, 2000, and 3000 pounds per square inch (6205, 9308, 13790, and 20684 kilopascals, respectively). The log of burn rate versus the log of mean pressure is plotted, from which the burn rate at any pressure can be calculated using the following burn rate formula:

r_b＝K(P)ⁿ

wherein,

r_brate of combustion (linear)

K is constant

P is pressure

n is the pressure constant.

Discussion of the results

As can be seen from Table 1, the addition of the copper-nitrate complex (5-ATN/bCN) formed by the reaction of 5-aminotetrazole with basic copper nitrate has a very important effect on the burn rate of the gas generant composition. For example, when 5-ATN/bCN was added to the gas generant composition of comparative example 1 to produce the gas generant composition of comparative example 2, the burn rate increased from 0.82 inches/sec to 2.11 inches/sec (about 2.08 cm/sec to 5.36 cm/sec). Similarly, when 5-ATN/bCN was added to the extrudable gas generant composition of comparative example 3 to produce the extrudable gas generant composition of comparative example 4, the burn rate increased from 0.33 inches/sec to 1.32 inches/sec (about 0.84 cm/sec to about 3.35 cm/sec).

However, as can be seen from table 1, the addition of guar gum adversely affects the burn rate of the gas generant composition. For example, when guar gum was added to the gas generant composition of comparative example 1 to produce the gas generant composition of comparative example 3, the burn rate decreased from 0.82 inches/second to 0.33 inches/second (about 2.08 cm/second to 0.84 cm/second). Similarly, when guar gum was added to the extrudable gas generant composition of comparative example 2 to produce the extrudable gas generant composition of comparative example 4, the burn rate decreased from 2.11 inches/second to 1.32 inches/second (about 5.36 cm/second to about 3.35 cm/second).

In contrast, the extrudable gas generant composition of the invention (e.g., example 1) was found to have a burn rate of 2.30 inches/second (about 5.84 cm/second). It is theorized that the addition of the ammonium perchlorate additive results in a reduction in the undesirable component content of the gas stream while the addition of the 5-ATN/bCN counteracts the reduction in burn rate caused by the addition of the polymeric binder material. Thus, extrudable gas generant compositions such as example 1 have both improved effluent compositions and improved burn rates as compared to extrudable or non-extrudable gas generant compositions such as those of comparative examples 1-4 without ammonium perchlorate.

The present disclosure illustratively may be practiced in the absence of any element, part, step, component, or additive that is not specifically disclosed herein.

While in the foregoing detailed description this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that the details described herein can be varied considerably without departing from the basic principles of the invention.

Claims

1. An extrudable gas generant composition comprising:

at least one non-azide, organic, nitrogen-containing fuel;

at least one copper-containing compound selected from the group consisting of basic copper nitrate, cupric oxide, a mixture of copper diammine dinitrate and ammonium nitrate wherein ammonium nitrate is present in the mixture in a range of about 3 to about 90 weight percent, copper diammine bitetrazole, a copper-nitrate complex resulting from the reaction of 5-aminotetrazole with basic copper nitrate, and mixtures thereof;

a perchlorate additive comprising at least one perchlorate material selected from the group consisting of alkali metal perchlorates and ammonium perchlorate, the perchlorate additive being effective in an amount to result in a reduction in the level of at least one of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide in a gaseous effluent when the gas generant composition is combusted as compared to the same gas generant composition without the perchlorate additive; and

a polymeric binder material effective to render the gas generant composition extrudable.

2. The extrudable gas generant composition of claim 1 wherein the polymeric binder material is selected from the group consisting of cellulosic materials, natural rubber, polyacrylate, polyacrylamide, polyurethane, polybutadiene, polystyrene, polyvinyl alcohol, polyvinyl acetate, silicone, and combinations of two or more thereof.

3. The extrudable gas generant composition of claim 2 wherein the polymeric binder material is a cellulosic material selected from the group consisting of ethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, and combinations of two or more thereof.

4. The extrudable gas generant composition of claim 2 wherein the polymeric binder material is a natural rubber selected from the group consisting of guar gum, xanthan gum, gum arabic and combinations of two or more thereof.

5. The extrudable gas generant composition of claim 1 wherein the polymeric binder material is present in an amount of about 1 to about 20 composition weight percent.

6. The extrudable gas generant composition of claim 1 wherein the at least one non-azide, organic, nitrogen-containing fuel comprises guanidine nitrate.

7. The extrudable gas generant composition of claim 1 wherein the at least one non-azide, organic, nitrogen-containing fuel is present in an amount of about 5 to about 60 composition weight percent.

8. The extrudable gas generant composition of claim 1 wherein the at least one copper-containing compound is present in an amount of 10 to 80 composition weight percent.

9. The extrudable gas generant composition of claim 1 wherein the perchlorate additive is present in an amount of about 1 to about 10 composition weight percent.

10. The extrudable gas generant composition of claim 1 wherein the perchlorate additive is selected from the group consisting of ammonium perchlorate, potassium perchlorate, sodium perchlorate and mixtures thereof.

11. An extrudable gas generant composition comprising:

at least one copper-containing compound selected from the group consisting of basic copper nitrate, cupric oxide, a mixture of copper diammine dinitrate and ammonium nitrate wherein ammonium nitrate is present in the mixture in a range of about 3 to about 90 weight percent, copper diammine bitetrazole, a copper-nitrate complex resulting from the reaction of 5-aminotetrazole with basic copper nitrate, and mixtures thereof; the at least one copper-containing compound is present in an amount of from 10% to 80% by weight of the gas generant composition;

a perchlorate additive comprising at least one perchlorate material selected from alkali metal perchlorates and ammonium perchlorate; the perchlorate additive present in an amount of from 1 to 10 percent by weight of the gas generant composition is effective to result in a gaseous effluent having a reduced content of at least one gas selected from the group consisting of carbon monoxide, ammonia, nitrogen dioxide and nitric oxide when the gas generant composition is combusted, as compared to an identical gas generant composition without the perchlorate additive; and

a polymeric binder material present in an amount of from 1% to 20% by weight of the gas generant composition and effective to render the gas generant composition extrudable; the polymeric binder material is selected from the group consisting of cellulosic materials, natural rubber, polyacrylates, polyacrylamides, polyurethanes, polybutadienes, polystyrenes, polyvinyl alcohols, polyvinyl acetates, silicones and mixtures of two or more thereof.

12. The extrudable gas generant composition of claim 11 wherein the polymeric binder material is a natural rubber selected from the group consisting of guar gum, xanthan gum, gum arabic and combinations of two or more thereof.

13. The extrudable gas generant composition of claim 11 wherein the polymeric binder material is guar gum.

14. The extrudable gas generant composition of claim 11 wherein the at least one non-azide, organic, nitrogen-containing fuel comprises guanidine nitrate.

15. The extrudable gas generant composition of claim 11 wherein the perchlorate additive comprises ammonium perchlorate.

16. The extrudable gas generant composition of claim 11 wherein the perchlorate additive has a particle size of at least about 200 microns.

17. The extrudable gas generant composition of claim 11 wherein the copper-containing compound is a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate.

18. The extrudable gas generant composition of claim 11 wherein the copper-containing compound is a mixture of basic copper nitrate and a copper-nitrate complex resulting from reaction of 5-aminotetrazole with basic copper nitrate.

19. The extrudable gas generant composition of claim 11 additionally comprising a burn rate enhancing and slag formation metal oxide additive selected from the group consisting of silica, alumina, zinc oxide and combinations thereof.

20. The extrudable gas generant composition of claim 11 additionally comprising a combustion enhancer selected from the group consisting of iron oxide, copper chromite, iron blue dye and combinations thereof.

21. An extrudable gas generant composition comprising:

at least one copper-containing compound selected from the group consisting of basic copper nitrate, cupric oxide, a mixture of copper diammine dinitrate and ammonium nitrate with ammonium nitrate in a range of about 3 to about 90 weight percent, copper diammine bitetrazole, a copper-nitrate complex resulting from the reaction of 5-aminotetrazole with basic copper nitrate and mixtures thereof in an amount of 10 to 80% by weight of the gas generant composition;

a perchlorate additive in an amount of 1 to 10 percent by weight of the gas generant composition, the perchlorate additive including at least one perchlorate material selected from the group consisting of alkali metal perchlorates and ammonium perchlorate; and

a polymeric binder material in an amount of 1% to 20% by weight of the gas generant composition, the polymeric binder material being effective to render the gas generant composition extrudable; the polymeric binder material is selected from the group consisting of cellulosic materials, natural rubber, polyacrylates, polyacrylamides, polyurethanes, polybutadienes, polystyrenes, polyvinyl alcohols, polyvinyl acetates, silicones and mixtures of two or more thereof.