Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B31/00—Compositions containing an inorganic nitrogen-oxygen salt
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06D—MEANS FOR GENERATING SMOKE OR MIST; GAS-ATTACK COMPOSITIONS; GENERATION OF GAS FOR BLASTING OR PROPULSION (CHEMICAL PART)
  • C06D5/00—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets
  • C06D5/06—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets by reaction of two or more solids

Definitions

• This invention relates generally to gas generant materials such as used to inflate automotive inflatable restraint airbag cushions and, more particularly, to the enhancement of the rate at which such materials burn or otherwise react.
• Gas generant or generating materials are useful in a variety of different contexts .
• One significant use for such compositions is in the operation of automotive vehicle occupant restraints.
• a cushion or bag e.g., an "airbag cushion”
• the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements.
• Such systems typically also include one or more crash sensors mounted on or to the frame or body of the vehicle to detect sudden decelerations of the vehicle and to electronically trigger activation of the system.
• the cushion Upon actuation of the system, the cushion begins to be inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as an "inflator.”
• an airbag cushion is desirably deployed into a location within the vehicle between the occupant and certain parts of the vehicle interior, such as a door, steering wheel, instrument panel or the like, to prevent or avoid the occupant from forcibly striking such part(s) of the vehicle interior.
• Gas generant compositions commonly utilized in the inflation of automotive inflatable restraint airbag cushions have previously most typically employed or been based on sodium azide. Such sodium azide-based compositions, upon initiation, normally produce or form nitrogen gas. While the use of sodium azide and certain other azide-based gas generant materials meets current industry specifications, guidelines and standards, such use may involve or raise potential concerns such as relating to the safe and effective handling, supply and disposal of such gas generant materials. Certain economic and design considerations have also resulted in a need and desire for alternatives to azide-based pyrotechnics and related gas generants.
• non-azide fuels and oxidizers have been proposed for use in or as gas generant compositions.
• These non-azide fuels are generally desirably less toxic to make and use, as compared to sodium azide, and may therefore be easier to dispose of and thus, at least in part, found more acceptable by the general public.
• non-azide fuels composed of carbon, hydrogen, nitrogen and oxygen atoms typically yield all gaseous products upon combustion.
• fuels with high nitrogen and hydrogen contents and a low carbon content are generally attractive for use in such inflatable restraint applications due to their relatively high gas outputs (such as measured in terms of moles of gas produced per 100 grams of gas generant material).
• Gas generant compositions for automotive airbag applications generally preferably have a relatively high density and gas output (e.g., preferably producing at least about 3 moles of gas output per 100 grams of composition) and a relatively low combustion flame temperature (e.g., a combustion flame temperature of less than 2000 K), particulate output, lot to lot variability and cost.
• a relatively high density and gas output e.g., preferably producing at least about 3 moles of gas output per 100 grams of composition
• a relatively low combustion flame temperature e.g., a combustion flame temperature of less than 2000 K
• oxidizers known in the art and commonly employed in such gas generant compositions are metal salts of oxygen-bearing anions (such as nitrates, chlorates and perchlorates, for example) or metal oxides.
• oxygen-bearing anions such as nitrates, chlorates and perchlorates, for example
• metal oxides such as metal oxides.
• the metallic components of such oxidizers typically end up as a solid compound, such as an oxide, and thus reduce the relative gas yields realizable therefrom. Consequently, the amounts of such oxidizers in a particular formulation typically affect the gas output or yield from the formulation. If oxygen is incorporated into the fuel material, however, less of such an oxidizer may be required and the gas output of the formulation can be increased.
• gas generant materials desirably are relatively inexpensive, thermally stable (i.e., desirably decompose only at temperatures greater than about 160°C), and have a low affinity for moisture.
• Gas generant compositions for automotive airbag applications generally preferably provide or result in a burn rate in excess of 0.3 ips at 1000 psi, with higher bum rate compositions being generally preferred.
• Guanidine nitrate (CH 6 N 4 O 3 ) is a non-azide fuel with many of the above-identified desirable fuel properties.
• guanidine nitrate is commercially available, relatively low cost, non-toxic, provides excellent gas output due to a high content of nitrogen, hydrogen and oxygen and a low carbon content and has sufficient thermal stability to permit spray-dry processing, i view thereof, guanidine nitrate has found wide utilized in the automotive airbag industry.
• guanidine nitrate suffers from a lower bum rate than may be desired in many applications.
• an azide-free gas generant material that may more effectively overcome one or more of the problems or shortcomings described above.
• guanylurea nitrate advantageously has a relatively high theoretical density such as to permit a relatively high loading density for a gas, generant material that contains such a fuel component. Further, guanylurea nitrate exhibits excellent thermal stability, as evidenced by guanylurea nitrate having a thermal decomposition temperature of 216°C. In addition, guanylurea nitrate has a large negative heat of formation (i.e., -880 cal/gram) such as results in a cooler burning gas generant composition, as compared to an otherwise similar gas generant containing guanidine nitrate.
• a large negative heat of formation i.e., -880 cal/gram
• guanylurea nitrate in gas generant materials can serve to avoid reliance on the inclusion or use of sodium azide or other similar azide materials while providing improved bum rates and overcoming one or more of the problems, shortcomings or limitations such as relating to cost, commercial availability, low toxicity, thermal stability and low affinity for moisture, even further improvement in the bum rate of gas generant formulations may be desired or required for particular applications.
• a low gas generant formulation burn rate can be at least partially compensated for by reducing the size of the shape or form of the gas generant material such as to provide the gas generant material in a shape or form having a relatively larger reactive surface area.
• a general object of the invention is to provide an improved gas generant composition as well as either or both corresponding or associated methods of generating gas and methods for increasing the burn rate of a gas generant formulation.
• a more specific objective of the invention is to overcome one or more of the problems described above.
• such a general object of the invention can be attained, at least in part, through a gas generant composition that includes an oxidizer component and a fuel component including a transition metal complex of ethylenediamine 5,5'-bitetrazole.
• such a general object of the invention can be attained, at least in part, through a gas generant composition which includes: about 45 to about 90 weight percent cobalt HI nitrate complex with ligands selected from the group consisting of ammonia and water; about 2 to about 50 weight percent of a copper complex of ethylenediamine dinitrate; and about 5 to about 50 weight percent basic copper nitrate.
• a gas generant composition which includes: about 45 to about 90 weight percent cobalt HI nitrate complex with ligands selected from the group consisting of ammonia and water; about 2 to about 50 weight percent of a copper complex of ethylenediamine dinitrate; and about 5 to about 50 weight percent basic copper nitrate.
• the prior art generally fails to provide desirably lower cost non-azide based gas generant formulations having desirably increased or elevated burn rates as well as methods or techniques for increasing the bum rate of a gas generant formulation, particularly a non-azide based gas generant formulation
• the prior art generally fails to provide as effective as may be desired methods or techniques for the raising of the bum rate of a gas generant formulation, particularly a non-azide gas generant formulation, to a level sufficient and desired for vehicular inflatable restraint system applications and in a manner practical and appropriate for such applications. Further, the prior art also generally fails to provide corresponding or associated non-azide gas generant formulations that exhibit sufficiently and effectively elevated burn rates as may be desired for such vehicular inflatable restraint system applications.
• the prior art generally fails to provide gas generant compositions, such as for use in the inflation of automotive inflatable restraint airbag cushions, and which compositions simultaneously satisfy requirements for gas output and bum rate and which may also desirably satisfy other requirements such as related to combustion flame temperature, particulate output, lot to lot variability and cost.
• the invention further comprehends a method for increasing the bum rate of a gas generant formulation, the method involving adding, to the gas generant formulation, a quantity of at least one of a transition metal complex of ethylenediamine 5,5 '-bitetrazole and a copper complex of ethylenediamine dinitrate.
• the invention still further comprehends a method of generating gas, the method involving: igniting a gas generant composition comprising a fuel component including a transition metal complex of ethylenediamine 5,5'-bitetrazole and an oxidizer component.
• a gas generant composition which includes about 45 to about 90 weight percent hexammine cobalt IE nitrate; about 2 to about 50 weight percent copper bis ethylenediamine dinitrate; and about 5 to about 50 weight percent basic copper nitrate and wherein the composition provides a burn rate of in excess of 0.35 ips at 1000 psi.
• references to a specific composition, component or material as a "fuel” are to be understood to refer to a chemical that generally lacks sufficient oxygen to bum completely to CO 2 , H 2 O and N 2 .
• references herein to a specific composition, component or material as an "oxidizer” are to be understood to refer to a chemical generally having more than sufficient oxygen to burn completely to CO 2 , H 2 O and N 2 .
• references to a component or material as a "burn rate catalyst,” “burn rate enhancer” or the like are to be understood to refer to such a component or material, when added or included as a minor ingredient, i.e., typically in an amount of less than 20 weight percent and, more commonly, in an amount of less than 10 weight percent, produces or results in a significant effect on the bum rate of the composition in which the component or material has been added, where a significant effect on bum rate generally involves an increase in bum rate of at least about 20 percent. It will be understood that such bum rate catalyst or enhancer materials can and typically do undergo reaction when in normal use in a combustion reaction.
• Guanylurea nitrate C-NH 2 C(NH)NHC(O)NH 2 # HNO 3 ) is also commonly known as dicyandiamidine and amidinourea.
• FIG. 1 is a simplified schematic, partially broken away, view illustrating the deployment of an airbag cushion from an airbag module assembly within a vehicle interior, in accordance with one embodiment of the invention.
• the present invention provides improved gas generant compositions as well as methods for increasing the bum rate of a gas generant formulation and generating gas.
• improved gas generant composition desirably contains or includes a transition metal complex of ethylenediamine 5,5'-bitetrazole.
• Suitable transition metals for use in the practice of the invention include copper, zinc, cobalt, iron, nickel and chromium. Preferably, the transition metal has a valence of +2. These complexes generally have an empirical formula of M(C 2 H 8 N 2 ) 2 C 2 N g , where M is a transition metal of +2 valence.
• Preferred transition metals used in the practice of the invention include zinc and copper, with copper currently being a particularly preferred transition metal for such use as copper desirably forms copper metal whereas zinc may more likely form an oxide and thereby undesirably consume or use at least a portion of the gas generant oxidizer.
• a particularly preferred fransition metal complex of ethylenediamine 5,5 ' -bitetrazole for use in the practice of the invention has an empirical formula of Cu(C 2 H 8 N 2 ) 2 C 2 N 8 and is believed to be copper bis ethylenediamine 5,5'-bitetrazole.
• the transition metal complex of ethylenediamine 5,5 '-bitetrazole is present in the gas generant composition in a relative amount of between about 1 and about 100 wt.%> of the fuel component of the gas generant formulation.
• the transition metal complex of ethylenediamine 5,5' -bitetrazole is used as a bum rate enhancer in conj unction with a fuel material, sometimes hereinafter referred to as a "second" fuel material or a primary fuel or mixture or combination of primary fuel materials, in which the transition metal complex of ethylenediamine 5,5 '-bitetrazole comprises between about 1 and about 25 wt.% of the fuel component of the gas generant formulation, the primary fuel or mixture or combination of primary fuels comprises between about 75 and about 99 wt.% of the fuel component of the gas generant formulation.
• the invention can desirably be practiced via the inclusion of a sufficient quantity of at least one transition metal complex of ethylenediamine 5,5 '-bitetrazole to a gas generant formulation having a primary fuel to effect a desirable increase in the bum rate exhibited by the resulting formulation, as compared to the same formulation without the inclusion of such transition metal complex of ethylenediamine 5,5'-bitetrazole.
• a gas generant formulation in accordance with a preferred practice of the invention to include or incorporate the at least one transition metal complex of ethylenediamine 5,5 '-bitetrazole in a relative amount of at least 5 wt.%> and, more preferably, in a relative amount of at least 10 wt.% in order to provide gas generant formulations evidencing a sufficiently increased bum rate effective for such inflatable restraint system applications.
• gas generant formulations that contain or include guanidine nitrate, hexammine cobalt IE nitrate, copper bis-guanylurea dinitrate or a combination thereof as a primary fuel and a primary oxidizer selected from the group consisting of ammonium nitrate; basic metal nitrates such as basic copper nitrate (bCN), basic zinc nitrate and combinations thereof, for example; copper diammine dinitrate and combinations of two or more of such oxidizer materials.
• guanidine nitrate hexammine cobalt IE nitrate
• copper bis-guanylurea dinitrate or a combination thereof as a primary fuel
• a primary oxidizer selected from the group consisting of ammonium nitrate; basic metal nitrates such as basic copper nitrate (bCN), basic zinc nitrate and combinations thereof, for example; copper diammine dinitrate and combinations of two or more of such oxidizer materials.
• one preferred gas generant formulation for the incorporation or use of such a transition metal complex of ethylenediamine 5,5 '-bitetrazole in accordance with the invention includes ammonium nitrate as a primary oxidizer and copper bis guanylurea dinitrate as a primary fuel, hi accordance with certain preferred embodiments of the invention, the oxidizer component includes at least one basic metal nitrate such as basic copper nitrate (bCN), basic zinc nitrate and combinations thereof.
• bCN basic copper nitrate
• one preferred gas generant formulation for the incorporation or use of such a transition metal complex of ethylenediamine 5, 5 '-bitetrazole in accordance with the invention includes basic copper nitrate as a primary oxidizer and guanidine nitrate as a primary fuel.
• Another preferred gas generant formulation for the incorporation or use of such a transition metal complex of ethylenediamine 5,5 '-bitetrazole in accordance with the invention includes hexammine cobalt IE nitrate (HACN) and guanidine nitrate as fuels.
• basic metal nitrates are a prefe ⁇ ed oxidizer in combination with fuels and fuel combinations in accordance with this aspect of the present invention.
• gas generant compositions in accordance with this aspect of the invention may utilize a wide variety of oxidizers including alkali metal, alkaline earth metal, and ammonium salts of nitrates andperchlorates, transition metal oxides and hydroxides, basic metal nitrate salts (e.g., basic copper nitrate, basic zinc nitrate, etc.), basic metal carbonates, and transition metal complexes of ammonium nitrate and combinations thereof.
• the fuel and oxidizer are used at near stoichiometric relative amounts, i.e., within about 20 mole percent either side of stoichiometric equivalence.
• gas generant composition or formulation in accordance with this aspect of the invention may also contain other components such as known in the art, such as those used for slag formation, e.g., silica, alumina and other refractory oxides, and processing aids.
• other components such as known in the art, such as those used for slag formation, e.g., silica, alumina and other refractory oxides, and processing aids.
• various procedures or reaction schemes can be employed in the preparation of a transition metal complex of ethylenediamine 5,5 '-bitetrazole in accordance with this aspect of the invention.
• a currently preferred route for synthesizing the copper complex of ethylenediamine 5,5 '-bitetrazole is by reacting copper bitetrazole (produced by reacting cupric oxide or copper carbonate with bitetrazole) with ethylenediamine. Generally the complex is recovered as a monohydrate. The reaction to form the complex is: Cu(C 2 N 8 ) , 2H 2 O (copper bitetrazole) + C 2 H 8 N 2 (ethylenediamine) "4
• gas generant compositions or materials prepared in accordance with this aspect of the invention can be incorporated, utilized or practiced in conjunction with a variety of different stmctures, assemblies and systems.
• the Figure illustrates a vehicle 10 having an interior 12 wherein is positioned an inflatable vehicle occupant safety restraint system, generally designated by the reference numeral 14.
• an inflatable vehicle occupant safety restraint system generally designated by the reference numeral 14.
• certain standard elements not necessary for an understanding of the invention may have been omitted or removed from the Figure for purposes of facilitating illustration and comprehension.
• the vehicle occupant safety restraint system 14 includes an open-mouthed reaction canister 16 which forms ahousing for an inflatable vehicle occupant restraint 20, e.g., an inflatable airbag cushion, and an apparatus, generally designated by the reference numeral 22, for generating or supplying inflation gas for the inflation of an associated occupant restraint.
• an inflatable vehicle occupant restraint 20 e.g., an inflatable airbag cushion
• an apparatus generally designated by the reference numeral 22 for generating or supplying inflation gas for the inflation of an associated occupant restraint.
• an inflator is commonly referred to as an "inflator.”
• the inflator 22 contains a quantity of a gas generant composition or formulation in accordance with the invention and such as suited, upon ignition, to produce or form a quantity of gas such as to be used in the inflation the inflatable vehicle occupant restraint 20.
• a gas generant composition or formulation in accordance with the invention such as suited, upon ignition, to produce or form a quantity of gas such as to be used in the inflation the inflatable vehicle occupant restraint 20.
• the specific construction of the inflator device does not form a limitation on the broader practice of the invention and such inflator devices can be variously constructed such as is also known in the art.
• the airbag cushion 20 upon deployment desirably provides for the protection of a vehicle occupant 24 by restraining movement of the occupant in a direction toward the front of the vehicle, i.e., in the direction toward the right as viewed in the Figure.
• a lOpound sample of copper ethylenediamine 5, 5 '-bitetrazole can be prepared by charging a spray-dry mix tank with water (9080 ml). Bitetrazole dihydrate (2313.4 grams) can then be added to the spray-dry mix tank and partially dissolves. Basic copper carbonate (1486.85 grams) can then be added to the contents of the spray-dry mix tank and the temperature of the slurry canbe equilibrated at 190°F (88°C) andheld at that temperature until the reaction is complete (approximately 1 hour). Ethylenediamine can then be added gradually to the spray-dry mix tank contents and the complex will form immediately.
• Example 3 The gas generant compositions of each of Example 3 and Comparative Examples 1 and 2 were then tested.
• the burn rate and density (p) values identified in TABLE 3 below were obtained.
• the bum rate data was obtained by first pressing samples of the respective gas generant formulations into the shape or form of a 0.5 inch diameter cylinder using a hydraulic press (12,000 lbs. force). Typically enough powder was used to result in a cylinder length of 0.5 inch.
• the cylinders were then each coated on all surfaces except the top surface with a krylon ignition inhibitor to help ensure a linear bum in the test fixture, hi each case, the so coated cylinder was placed in a 1 -liter closed test vessel capable of being pressurized to several thousand psi with nitrogen and equipped with a pressure transducer for accurate measurement of pressure within the closed test vessel.
• a small sample of igniter powder was placed on top of the cylinder and a nichrome wire was passed through the igniter powder and connected to electrodes mounted in the test vessel lid.
• the test vessel was then pressurized to the desired pressure and the sample ignited by passing a current through the nichrome wire. Pressure vs. time data was collected as each of the respective samples were burned.
• r b burn rate at 1000 psi in inch per second (ips);
• n pressure exponent in the bum rate equation (1) identified above, where the pressure exponent is the slope of the plot of the log of pressure along the x-axis versus the log of the bum rate along the y-axis; and
• k the constant in the burn rate equation (1) identified above.
• Example 3 which gas generant composition contained the copper complex of ethylenediamine 5,5 '-bitetrazole in accordance with the practice of the invention, experienced a significantly increased burn rate (r b ) as compared to the gas generant composition of Comparative Example 1 which did not include any burn rate enliancer, and even compared to the gas generant composition of Comparative Example 2 containing copper complex of diammine 5,5 '-bitetrazole, described in the above-identified U.S. patent application No. 09/998,122 filed on 30 November 2001.
• Example 3 exhibited a lesser or reduced pressure sensitivity as compared to the gas generant composition of Comparative Example 1 , as evidenced by the lower or decreased pressure exponent (n) obtained therewith, and a pressure sensitivity comparable to the gas generant composition of Comparative Example 2.
• Example 4 and Comparative Examples 3 and 4 were then tested in a manner similar to that described above relative to Example 2 and Comparative Examples 1 and 2.
• the bum rate and density (p) values identified in TABLE 5 below were obtained.
• r b burn rate at 1000 psi in inch per second (ips);
• n pressure exponent in the bum rate equation (1) identified above, where the pressure exponent is the slope of the plot of the log of pressure along the x-axis versus the log of the bum rate along the y-axis; and
• k the constant in the burn rate equation (1) identified above.
• the gas generant composition of Example 4 which gas generant composition contained the copper complex of ethylenediamine 5, 5 '-bitetrazole in accordance with the practice of the invention, experienced a very significantly increased bum rate (r b ) as compared to the gas generant composition of Comparative Example 3 which did not include any burn rate enhancing co-fuel, and even compared to the gas generant composition of Comparative Example 4 containing copper complex of diammine 5, 5 '-bitetrazole, described in the above-identified commonly assigned U.S. patent application No. 09/998,122 filed on 30 November 2001.
• Example 4 exhibited a lesser or reduced pressure sensitivity as compared to the gas generant composition of Comparative
• Example 3 as evidenced by the lower or decreased pressure exponent (n) obtained therewith, and only slightly higher than that obtained with the gas generant composition of Comparative Example 4.
• the invention provides an effective method or technique for desirably raising or increasing of the burn rate of a gas generant formulation, particularly a non-azide gas generant formulation, to a level sufficient and desired for vehicular inflatable restraint system applications and in a manner practical and appropriate for such applications. Further, the invention also provides co ⁇ esponding or associated non-azide gas generant formulations which exhibit sufficiently and effectively elevated bum rates as may be desired for such vehicular inflatable restraint system applications.
• the present invention also generally provides an improved gas generant composition such as for use in the inflation of automotive inflatable restraint airbag cushions and which composition simultaneously satisfies requirements for gas output and bum rate and which may also desirably satisfy other requirements such as related to combustion flame temperature, particulate output, lot to lot variability and cost.
• Such gas generant compositions generally include a unique combination of a cobalt IE nitrate complex with ligands selected from the group consisting of ammonia and water, a copper complex of ethylenediamine dinitrate, and basic copper nitrate.
• formulations in accordance with a prefe ⁇ ed embodiment of this aspect of the invention generally include: about 45 to about 90 weight percent cobalt IE nitrate complex with ligands selected from the group consisting of ammonia and water; about 2 to about 50 weight percent of a copper complex of ethylenediamine dinitrate; and about 5 to about 50 weight percent basic copper nitrate.
• the cobalt IE nitrate complex is the main ingredient in the composition and as such is present in a greater relative amount than all the other ingredients of the composition combined.
• the cobalt El nitrate complex in the subject compositions generally serves or functions as a fuel, as defined above.
• the cobalt IE nitrate complex is a hexadentate cobalt IE nitrate complex, preferably a hexadentate neutral cobalt IE nifrate complex.
• Hexammine cobalt IE nitrate, pentammineaquo cobalt IE nitrate and mixtures thereof are particularly prefe ⁇ ed cobalt El nitrate complexes for use in the practice of the invention.
• a prefe ⁇ ed copper complex of ethylenediamine dinitrate for use in the practice of this aspect of the invention is copper bis ethylenediamine dinitrate.
• such copper complexes of ethylenediamine dinitrate can advantageously serve, function or otherwise operate as bum rate catalysts in the subject gas generant compositions.
• basic copper nitrate desirably serves or functions to provide oxygen needed or necessary to or for complete combustion of the copper complex of ethylenediamine dinitrate.
• gas generant compositions in accordance with this aspect of the invention have advantageously been found to provide or result in a bum rate of in excess of 0.35 ips at 1000 psi and, in accordance with at least certain prefe ⁇ ed embodiments, a burn rate of at least about 0.4 ips at 1000 psi.
• compositions in accordance with this aspect of the invention are desirably amenable to processing by relatively simple means.
• the copper complex of ethylenediamine dinitrate of such subject gas generant formulations can be formed, such as by reacting cupric nitrate with ethylenediamine, in situ, such as in a spray-dry mix tank.
• a gas generant composition in accordance with the invention is formed by: combining, a. the cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water with, b.
• the gas generant composition powder can then be appropriately press-fo ⁇ ned into a desired form, such as in the fo ⁇ n of a tablet or wafer, for example.
• gas generant compositions or materials prepared in accordance with this aspect of the invention can be incorporated, utilized or practiced in conjunction with a variety of different structures, assemblies and systems, such as representatively shown in the Figure described above.
• the Figure illustrates a vehicle 10 having an interior 12 wherein is positioned an inflatable vehicle occupant safety restraint system, generally designated by the reference numeral 14.
• the vehicle occupant safety restraint system 14 includes an open-mouthed reaction canister 16 which forms a housing for an inflatable vehicle occupant restraint 20, e.g. , an inflatable airbag cushion, and an apparatus, generally designated by the reference numeral
• such a gas generating device for generating or supplying inflation gas for the inflation of an associated occupant restraint.
• a gas generating device is commonly refe ⁇ ed to as an
• the inflator 22 contains a quantity of a gas generant composition or material in accordance with the invention and such as suited, upon ignition, to produce or form a quantity of gas such as to be used in the inflation the inflatable vehicle occupant restraint 20.
• inflator device does not form a limitation on the broader practice of the invention and such inflator devices can be variously constructed such as is also known in the art.
• the airbag cushion 20 upon deployment desirably provides for the protection of a vehicle occupant 24 by restraining movement of the occupant in a direction toward the front of the vehicle, i.e., in the direction toward the right as viewed in the Figure.
• the present invention is described in further detail in connection with the following examples which illustrate or simulate various features involved in the practice of the above-identified aspect of the invention. It is to be understood that all changes that come within the spirit of the invention are desired to be protected and thus the invention is not to be construed as limited by these examples.
• Example 5 a gas generant pyrotechnic composition in accordance with the invention and shown in TABLE 6 below (component values in terms of "wt %") was prepared and compared to the gas generant pyrotechnic compositions of Comparative Examples 5 and 6, also shown in TABLE 6, below.
• the gas generant pyrotechnic composition of each Example 5 and Comparative Examples 5 and 6 was then tested.
• the burn rate and density values identified in TABLE 7 below were obtained.
• the bum rate data was obtained first by pressing samples of the respective gas generant fo ⁇ nulations into the shape or form of a 0.5 inch diameter cylinder using a hydraulic press (12,000 lbs force). Typically enough powder was used to result in a cylinder length of 0.5 inch.
• the cylinders were then each coated on all surfaces except the top one with a krylon ignition inhibitor to help ensure a linear bum in the test fixture.
• the so coated cylinder was placed in a 1 -liter closed test vessel capable of being pressurized to several thousand psi with nitrogen and equipped with a pressure transducer for accurate measurement of the pressure within the closed test vessel.
• a small sample of igniter powder was placed on top of the cylinder and a nichrome wire was passed through the igniter powder and connected to electrodes mounted in the test vessel lid.
• the vessel was then pressurized to the desired pressure and the sample ignited bypassing a cu ⁇ ent through the nichrome wire.
• Pressure vs. time date was collected as each of the respective samples were burned. Since combustion of each of the samples generated gas, an increase in the test vessel pressure signaled the start of combustion and a "leveling off of pressure signaled the end of the combustion.
• the time required for combustion was equal to t 2 - t where t 2 is the time at the end of combustion and t j is the time at the start of the combustion.
• the sample weight was divided by combustion time to give a burning rate in grams per second. Burning rates were typically measured at four pressures (900, 1350, 2000, and 3000 psi). The log of bum rate vs the log of average pressure was then plotted. From this line the burn rate at any pressure can be calculated using the gas generant composition bum rate equation (1), identified above.
• the gas yield and flame temperature for the gas generant pyrotechnic composition of each of Example 5 and Comparative Examples 5 and 6 was calculated/determined and are also shown in TABLE 7.
• the gas generant pyrotechnic composition in accordance with the invention advantageously combined the advantages of the gas generant pyrotechnic composition of Comparative Examples 5 and 6 without also presenting or realizing the disadvantages normally associated with such compositions and without any appreciable difference in the density of the composition.
• the gas generant pyrotechnic composition in accordance with the invention e.g., Example 5 provided or resulted in higher a gas yield (consistent with the gas generant pyrotechnic composition of Comparative Example 5) while also providing or resulting in a higher bum rate and low lot to lot variability (consistent with the gas generant pyrotechnic composition of Comparative Example 6).
• the invention also provides gas generant compositions, such as for use in the inflation of automotive inflatable restraint airbag cushions, and which compositions simultaneously satisfy requirements for gas output (e.g., a gas output of at least about 3.0 moles per 100 grams of composition and, preferably, a gas output of about 3.3 moles or more per 100 grams of composition) and bum rate (e.g., a bum rate of in excess of 0.35 ips at 1000 psi and, preferably, a bum rate of at least about 0.4 ips at 1000 psi) and which compositions may also desirably satisfy other requirements such as related to combustion flame temperature, particulate output, lot to lot variability and cost.
• the invention illustratively disclosed herein suitably may be practiced in the absence of any element, part, step, component, or ingredient which is not specifically disclosed herein.

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