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Publication numberUS20040216820 A1
Publication typeApplication
Application numberUS 10/838,884
Publication dateNov 4, 2004
Filing dateMay 4, 2004
Priority dateJan 21, 2003
Also published asCN1761637A, CN100357236C, US20040144455
Publication number10838884, 838884, US 2004/0216820 A1, US 2004/216820 A1, US 20040216820 A1, US 20040216820A1, US 2004216820 A1, US 2004216820A1, US-A1-20040216820, US-A1-2004216820, US2004/0216820A1, US2004/216820A1, US20040216820 A1, US20040216820A1, US2004216820 A1, US2004216820A1
InventorsIvan Mendenhall, Robert Taylor
Original AssigneeMendenhall Ivan V, Taylor Robert D
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Pyrotechnic compositions for gas generant apllications
US 20040216820 A1
Abstract
Pyrotechnic compositions which include about 45 to about 90 weight percent of a fuel material of cobalt III nitrate complex with ammonia or water ligands, and about 10 to about 55 weight percent of a combination of a combination of a burn rate catalyst of copper bis ethylenediamine dinitrate and an oxidizer of basic copper nitrate are provided to result in relatively high gas outputs and burn rates. The compositions desirably include the cobalt III nitrate complex in a greater relative amount than either the copper complex of ethylenediamine dinitrate or the basic copper nitrate; the copper complex of ethylenediamine dinitrate is present in a relative amount of at least about 2 weight percent and the basic copper nitrate is present in a relative amount of at least 1.5 times the relative amount of the copper complex of ethylenediamine dinitrate. Also provided are corresponding or associated gas generating devices and inflatable vehicle occupant safety restraint systems.
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Claims(20)
What is claimed is:
1. A pyrotechnic composition comprising:
about 45 to about 90 weight percent cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water and
about 10 to about 55 weight percent of a combination of: a) a copper complex of ethylenediamine dinitrate and b) basic copper nitrate;
wherein the composition includes the cobalt III nitrate complex in a greater relative amount than either the copper complex of ethylenediamine dinitrate or the basic copper nitrate; the copper complex of ethylenediamine dinitrate is present in a relative amount of at least about 2 weight percent and the basic copper nitrate is present in a relative amount of at least 1.5 times the relative amount of the copper complex of ethylenediamine dinitrate.
2. The pyrotechnic composition of claim 1 wherein the copper complex of ethylenediamine dinitrate is copper bis ethylenediamine dinitrate.
3. The pyrotechnic composition of claim 1 wherein the cobalt III nitrate complex is a hexadentate cobalt III nitrate complex.
4. The pyrotechnic composition of claim 3 wherein the hexadentate cobalt III nitrate complex is a hexadentate neutral cobalt III nitrate complex.
5. The pyrotechnic composition of claim 1 wherein the cobalt III nitrate complex is selected from the group consisting of hexammine cobalt III nitrate, pentammineaquo cobalt III nitrate and mixtures thereof.
6. The pyrotechnic composition of claim 1 formed by:
combining
a. the cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water with,
b. sufficient cupric nitrate and ethylenediamine to form the copper bis ethylenediamine dinitrate and
c. the basic copper nitrate to form a mixture and
spray drying the mixture to form a powder form of the pyrotechnic composition.
7. The pyrotechnic composition of claim 6 wherein the powder form of the pyrotechnic composition is press-formed into a desired form.
8. The pyrotechnic composition of claim 1 consisting essentially of:
the cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water;
the copper complex of ethylenediamine dinitrate; and
basic copper nitrate.
9. The pyrotechnic composition of claim 1 wherein the composition provides a burn rate of at least about 0.4 ips at 1000 psi.
10. The pyrotechnic composition of claim 1 wherein the pyrotechnic composition provides a gas output of at least about 3.3 moles per 100 grams of pyrotechnic composition.
11. A gas generating device containing the pyrotechnic composition of claim 1.
12. An inflatable vehicle occupant safety restraint system comprising:
the gas generating device of claim 11 connected in association with an inflatable airbag cushion for inflating the airbag cushion.
13. A pyrotechnic composition comprising:
about 45 to about 90 weight percent hexammine cobalt III nitrate;
about 2 to about 20 weight percent copper bis ethylenediamine dinitrate; and
basic copper nitrate in a relative amount of at least about 1.5 times that of the copper bis ethylenediamine dinitrate,
wherein the composition provides a burn rate of in excess of 0.35 ips at 1000 psi and a gas output of at least about 3.0 moles per 100 grams of the composition.
14. The pyrotechnic composition of claim 13 wherein the copper bis ethylenediamine dinitrate and the basic copper nitrate are present in total relative amount of about 10 to about 55 composition weight percent.
15. The pyrotechnic composition of claim 13 consisting essentially of: hexammine cobalt III nitrate, copper bis ethylenediamine dinitrate and basic copper nitrate.
16. The pyrotechnic composition of claim 13 wherein the composition provides a burn rate of at least about 0.4 ips at 1000 psi.
17. The pyrotechnic composition of claim 13 formed by:
combining
a. the hexammine cobalt III nitrate with,
b. sufficient cupric nitrate and ethylenediamine to form the copper bis ethylenediamine dinitrate and
c. the basic copper nitrate to form a mixture and
spray drying the mixture to form a powder form of the pyrotechnic composition.
18. The pyrotechnic composition of claim 17 wherein the powder form of the pyrotechnic composition is press-formed into a desired form.
19. A gas generating device containing the pyrotechnic composition of claim 13.
20. An inflatable vehicle occupant safety restraint system comprising:
the gas generating device of claim 19 connected in association with an inflatable airbag cushion for inflating the airbag cushion.
Description
CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. application Ser. No. 10/348,568, filed on 21 Jan. 2003. The co-pending parent application is hereby incorporated by reference herein in its entirety and is made a part hereof, including but not limited to those portions which specifically appear hereinafter.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to pyrotechnic compositions and, more particularly, to pyrotechnic compositions such as used in gas generant applications such as in the inflation of automotive inflatable restraint airbag cushions.

[0003] Pyrotechnic 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 involving the safe and effective handling, supply and disposal of such gas generant materials.

[0004] Certain economic and design considerations have also resulted in a need and desire for alternatives to azide-based pyrotechnics and related gas generants. For example, interest in minimizing or at least reducing the overall space requirements for inflatable restraint systems and particularly the space requirements related to the inflator component in such systems has stimulated a quest for gas generant materials which provide relatively higher gas yields per unit volume as compared to typical or usual azide-based gas generants. Further, automotive and airbag industry competition has generally lead to a desire for gas generant compositions which satisfy one or more conditions such as being composed of or utilizing less costly ingredients or materials and being amenable to processing via more efficient or less costly gas generant processing techniques.

[0005] In view of the above, gas generant compositions for pyrotechnic automotive airbag applications generally preferably have relatively high burn rates, densities, and gas outputs (e.g., preferably producing at least about 3 moles of gas output per 100 grams of composition) and relatively low combustion flame temperatures (e.g., a combustion flame temperature of less than 2000 K), particulate outputs, lot to lot variability and cost.

[0006] In general, the burn rate for a gas generant composition can be represented by the equation (1), below:

r b =k(P)n  (1)

[0007] where,

[0008] rb=burn rate (linear)

[0009] k=constant

[0010] P=pressure

[0011] n=pressure exponent, where the pressure exponent is the slope of a linear regression line drawn through a log-log plot of burn rate versus pressure.

[0012] 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 burn rate compositions being generally preferred.

[0013] Unfortunately, the development of new gas generant compositions for pyrotechnic automotive airbag applications oftentimes involves a tradeoff between gas output and burn rate. For example, efforts to compensate for the low burn rate of some previously developed non-azide gas generants has resulted in the use of solvent extrusion processing of such formulations into small perforated grains. Solvent extrusion processing, however, requires a drying step following the extrusion. The application of such a drying step has been shown to produce or introduce an undesired variability in resulting gas generant compositions in the form of differences in density in the extruded perforated grains. Consequently, it has proven difficult to develop alternatives to azide-based pyrotechnics and related gas generants and which alternatives simultaneously satisfy automotive airbag application requirements with respect to burn rate and gas output.

[0014] Thus, there is a need and a demand for pyrotechnic compositions which simultaneously satisfy requirements for gas output and burn rate and which compositions also desirably satisfy other requirements such as related to combustion flame temperature, particulate output, lot to lot variability and cost.

SUMMARY OF THE INVENTION

[0015] A general object of the invention is to provide an improved pyrotechnic composition.

[0016] A more specific objective of the invention is to overcome one or more of the problems described above.

[0017] The general object of the invention can be attained, at least in part, through a pyrotechnic composition which includes:

[0018] about 45 to about 90 weight percent cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water;

[0019] about 2 to about 50 weight percent of a copper complex of ethylenediamine dinitrate; and

[0020] about 5 to about 50 weight percent basic copper nitrate.

[0021] In accordance with one preferred embodiment of the invention, such a pyrotechnic composition desirably includes:

[0022] about 45 to about 90 weight percent cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water and

[0023] about 10 to about 55 weight percent of a combination of: a) a copper complex of ethylenediamine dinitrate and b) basic copper nitrate;

[0024] wherein the composition includes the cobalt III nitrate complex in a greater relative amount than either the copper complex of ethylenediamine dinitrate or the basic copper nitrate; the copper complex of ethylenediamine dinitrate is present in a relative amount of at least about 2 weight percent and the basic copper nitrate is present in a relative amount of at least 1.5 times the relative amount of the copper complex of ethylenediamine dinitrate.

[0025] The prior art generally fails to provide pyrotechnic compositions, such as for use in the inflation of automotive inflatable restraint airbag cushions, and which compositions simultaneously satisfy requirements for gas output and burn rate and which may also desirably satisfy other requirements such as related to combustion flame temperature, particulate output, lot to lot variability and cost.

[0026] The invention further comprehends a pyrotechnic composition which includes about 45 to about 90 weight percent hexammine cobalt III 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.

[0027] In accordance with another preferred embodiment of the invention, such a pyrotechnic composition desirably includes:

[0028] about 45 to about 90 weight percent hexammine cobalt III nitrate;

[0029] about 2 to about 20 weight percent copper bis ethylenediamine dinitrate; and

[0030] basic copper nitrate in a relative amount of at least about 1.5 times that of the copper bis ethylenediamine dinitrate,

[0031] wherein the composition provides a burn rate of in excess of 0.35 ips at 1000 psi and a gas output of at least about 3.0 moles per 100 grams of the composition.

[0032] As used herein, references to a specific composition, component or material as a “fuel” are to be understood to refer to a chemical which generally lacks sufficient oxygen to burn completely to CO2, H2O and N2.

[0033] Correspondingly, 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 CO2, H2O and N2.

[0034] References to a component or material as a “burn rate catalyst” or a “burn rate enhancer” 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 no more than about 20 weight percent and, more commonly in an amount of no more than about 10 weight percent, produces or results in a significant effect on the burn rate of the composition in which the burn rate catalyst has been added, where a significant effect on burn rate generally involves an increase in burn rate of at least about 20 percent. It will be understood that such burn rate catalyst materials can and typically do undergo reaction when in normal use in a combustion reaction.

[0035] Unless otherwise specifically noted, percentages when used herein in conjunction with a composition ingredient of component are to be understood to be in terms of weight percent.

[0036] Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0037] The FIGURE 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.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention generally provides an improved pyrotechnic composition and, more particularly provides an improved pyrotechnic composition such as for use in the inflation of automotive inflatable restraint airbag cushions and which composition simultaneously satisfies requirements for gas output and burn rate and which may also desirably satisfy other requirements such as related to combustion flame temperature, particulate output, lot to lot variability and cost.

[0039] Pyrotechnic compositions in accordance with the invention generally include a unique combination of a cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water, a copper complex of ethylenediamine dinitrate, and basic copper nitrate. In particular, formulations in accordance with certain preferred embodiments of the invention generally include:

[0040] about 45 to about 90 weight percent cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water;

[0041] about 2 to about 50 weight percent of a copper complex of ethylenediamine dinitrate; and

[0042] about 5 to about 50 weight percent basic copper nitrate.

[0043] Moreover, pyrotechnic compositions in accordance with certain preferred embodiments of the invention desirably consist essentially of a cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water; a copper complex of ethylenediamine dinitrate; and basic copper nitrate.

[0044] As detailed further below, formulations in accordance with certain particularly preferred embodiments of the invention generally include:

[0045] about 45 to about 90 weight percent cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water and

[0046] about 10 to about 55 weight percent of a combination of: a) a copper complex of ethylenediamine dinitrate and b) basic copper nitrate;

[0047] wherein the composition includes the cobalt III nitrate complex in a greater relative amount than either the copper complex of ethylenediamine dinitrate or the basic copper nitrate; the copper complex of ethylenediamine dinitrate is present in a relative amount of at least about 2 weight percent and the basic copper nitrate is present in a relative amount of at least 1.5 times the relative amount of the copper complex of ethylenediamine dinitrate.

[0048] Further, in accordance with certain preferred embodiments of the invention, the cobalt III 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. Those skilled in the art and guided by the teachings herein provided will also appreciate that the cobalt III nitrate complex in the subject compositions generally serves or functions as a fuel, as defined above.

[0049] In accordance with one preferred embodiment of the invention, the cobalt III nitrate complex is a hexadentate cobalt III nitrate complex, preferably a hexadentate neutral cobalt III nitrate complex. Hexammine cobalt III nitrate, pentammineaquo cobalt III nitrate and mixtures thereof are particularly preferred cobalt III nitrate complexes for use in the practice of the invention.

[0050] A preferred copper complex of ethylenediamine dinitrate for use in the practice of the invention is copper bis ethylenediamine dinitrate. Further, as detailed below, such copper complexes of ethylenediamine dinitrate can advantageously serve, function or otherwise operate as burn rate catalysts or burn rate enhancers in the subject pyrotechnic compositions. As indicated above, in the preferred practice of the invention, the inclusion in the formulation of at least about 2 weight percent of the copper complex of ethylenediamine dinitrate is generally preferred in order for the formulation to attain or realize significant or substantial burn rate enhancement in accordance with the invention.

[0051] In the pyrotechnic formulations of the invention, 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. More particularly, in such formulations, the cobalt III nitrate complex acts or serves as a near monopropellant. That is, the cobalt III nitrate complex is in and of itself in near stoichiometric balance such that the inclusion of a relatively small amount of additional oxidizer is required in order to stoichiometrically balance the cobalt III nitrate complex. In view thereof, those skilled in the art and guided by the teachings herein provided will appreciate that the amount of basic copper nitrate desirably included in such formulations is in large part dependent or proportional to the amount of the copper complex of ethylenediamine dinitrate also included in the formulation. Thus, as indicated above relative to a preferred practice of the invention, formulations wherein the basic copper nitrate is present in a relative amount of at least 1.5 times the relative amount of the copper complex of ethylenediamine dinitrate have been found to particularly attractive in the practice of the invention.

[0052] As detailed below, pyrotechnic compositions in accordance with the invention have advantageously been found to provide or result in a burn rate of in excess of 0.35 ips at 1000 psi and, in accordance with at least certain preferred embodiments, a burn rate of at least about 0.4 ips at 1000 psi.

[0053] While the broader practice of the invention is not necessarily limited by or to specific methods of preparation or processing, the compositions of the invention are desirably amenable to relatively simple processing. For example, the copper complex of ethylenediamine dinitrate of the subject pyrotechnic formulations can be formed, such as by reacting cupric nitrate with ethylenediamine, in situ, such as in a spray-dry mix tank. In accordance with one preferred embodiment of the invention, a pyrotechnic composition in accordance with the invention is formed by:

[0054] combining,

[0055] a. the cobalt III nitrate complex with ligands selected from the group consisting of ammonia and water with,

[0056] b. sufficient cupric nitrate and ethylenediamine to form the copper bis ethylenediamine dinitrate and

[0057] c. the basic copper nitrate

[0058] to form a mixture and

[0059] spray drying the mixture to form a powder form of the pyrotechnic composition.

[0060] The pyrotechnic composition powder can then be appropriately press-formed into a desired form, such as in the form of a tablet or wafer, for example.

[0061] As will be appreciated, pyrotechnic compositions or materials prepared in accordance with the invention can be incorporated, utilized or practiced in conjunction with a variety of different structures, assemblies and systems. As representative, 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. As will be appreciated, 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.

[0062] 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 22, for generating or supplying inflation gas for the inflation of an associated occupant restraint. As identified above, such a gas generating device is commonly referred to as an “inflator.”

[0063] The inflator 22 contains a quantity of a pyrotechnic 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. As will be appreciated, 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.

[0064] In practice, 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.

[0065] The present invention is described in further detail in connection with the following examples which illustrate or simulate various aspects involved in the practice 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.

EXAMPLES Example 1 and Comparative Examples 1 and 2

[0066] In Example 1, a gas generant pyrotechnic composition in accordance with the invention and shown in TABLE 1 below (component values in terms of “wt. %”) was prepared and compared to the gas generant pyrotechnic compositions of Comparative Examples 1 and 2, also shown in TABLE 1, below.

TABLE 1
Comparative Comparative
Ingredient (wt. %) Example 1 Example 1 Example 2
bCN 22.53 22.53 46.62
CuEDDN 10.00
HACN 67.47 73.5
GN 50.38
guar gum 5.00
aluminum oxide 2.70
silicon dioxide 0.30

[0067] The gas generant pyrotechnic composition of each of Example 1 and Comparative Examples 1 and 2 was then tested. The burn rate and density values identified in TABLE 2 below were obtained. In particular, the burn 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 one with a krylon ignition inhibitor to help ensure a linear burn in the test fixture. In 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 the test vessel pressure. 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. Since combustion of each of the samples generated gas, an increase in test vessel pressure signaled the start of combustion and a “leveling off” of pressure signaled the end of combustion. The time required for combustion was equal to t2−t1 where t2 is the time at the end of combustion and t1 is the time at the start of 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 burn 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 burn rate equation (1), identified above. In addition, the gas yield and flame temperature for the gas generant pyrotechnic composition of each of Example 1 and Comparative Examples 1 and 2 was calculated/determined and are also shown in TABLE 2.

TABLE 2
Comparative Comparative
PARAMETER Example 1 Example 1 Example 2
Gas Yield 3.3 3.3 2.9
(moles/
100 grams)
Flame 1800 1805 1850
Temperature
(K)
Burn Rate 0.40 0.25 0.4-0.5
(ips @
1000 psi)
Density (g/cc) 1.97 (pressed 1.95 (pressed 1.95 (pressed
pellet) pellet) pellet)
Particulate low low low
Lot to Lot low (spray high (extruded) low
Variability dried/pressed)

[0068] Discussion of Results

[0069] As shown by the results in TABLE 2, the gas generant pyrotechnic composition in accordance with the invention (i.e., Example 1) advantageously combined the advantages of the gas generant pyrotechnic compositions of Comparative Examples 1 and 2 without also presenting or realizing the disadvantages normally associated with such compositions and without any appreciable difference in the density of the composition. More specifically, the gas generant pyrotechnic composition in accordance with the invention (e.g., Example 1) provided or resulted in higher a gas yield (consistent with the gas generant pyrotechnic composition of Comparative Example 1) while also providing or resulting in a higher burn rate and low lot to lot variability (consistent with the gas generant pyrotechnic composition of Comparative Example 2). Those skilled in the art and guided by the teachings herein provided will appreciate the significance of the increased burn rate provided or resulting from the gas generant pyrotechnic composition in accordance with the invention (e.g., Example 1) such as compared to the gas generant pyrotechnic composition of Comparative Example 1 and such as for the reasons described above.

Examples 2-6

[0070] In Examples 2-6, gas generant pyrotechnic composition in accordance with the invention and shown in TABLE 3 below (component values in terms of “wt. %”) were each prepared via a laboratory mix in a beaker, in a manner similar to Example 1. That is, these example compositions were each prepared on a laboratory, rather than commercial, scale.

TABLE 3
(wt. %) Example 2 Example 3 Example 4 Example 5 Example 6
bCN 8.69 17.95 19.49 21.03 31.80
CuEDDN 5.00 7.00 8.00 9.00 20.00
HACN 86.31 75.05 72.51 69.97 48.40

[0071] The gas generant pyrotechnic composition of each of Examples 2-6 was then tested. The burn rate values identified in TABLE 4 below were obtained. In particular, the burn rate data was obtained first by 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 one with a krylon ignition inhibitor to help ensure a linear burn in the test fixture. In 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 the test vessel pressure. 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. Since combustion of each of the samples generated gas, an increase in 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 t2−t1 where t2 is the time at the end of combustion and t1 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 burn 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 burn rate equation (1), identified above. In addition, the gas yield for the gas generant pyrotechnic composition of each of Examples 2-6 was calculated/determined and are also shown in TABLE 4.

TABLE 4
PARAMETER Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6
Gas Yield (moles/100 grams) 3.7 3.4 3.4 3.3 3.1
Burn Rate (ips @ 1000 psi) 0.38 0.37 0.38 0.41 0.52

[0072] Discussion of Results

[0073] As shown by the results in TABLE 4, gas generant pyrotechnic compositions in accordance with the invention (e.g., Examples 2-6) provided or resulted in desirably high gas yields (e.g., a gas output of at least about 3.0 moles per 100 grams of composition and, in Examples 2-5, a gas output of at least about 3.3 moles or more per 100 grams of composition) and desirably high burn rates (e.g., a burn rate in excess of 0.3 ips at 1000 psi, preferably, a burn rate of in excess of 0.35 ips at 1000 psi and, at least with Examples 5 and 6, a burn rate of at least about 0.4 ips at 1000 psi).

[0074] Thus, the invention provides pyrotechnic 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 burn rate (e.g., a burn rate of in excess of 0.35 ips at 1000 psi and, preferably, a burn 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.

[0075] 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.

[0076] 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 certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7470337Mar 21, 2006Dec 30, 2008Autoliv Asp, Inc.Gas generation with copper complexed imidazole and derivatives
US7758709Jun 21, 2006Jul 20, 2010Autoliv Asp, Inc.Monolithic gas generant grains
US8057611Aug 13, 2007Nov 15, 2011Autoliv Asp, Inc.Multi-composition pyrotechnic grain
WO2008051274A2 *Mar 19, 2007May 2, 2008Autoliv Asp IncGas generation with copper complexed imidazole and derivatives
Classifications
U.S. Classification149/61
International ClassificationC06D5/06, C06B31/00
Cooperative ClassificationC06B31/00, C06D5/06
European ClassificationC06D5/06, C06B31/00
Legal Events
DateCodeEventDescription
May 4, 2004ASAssignment
Owner name: AUTOLIV ASP, INC., UTAH
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MENDENHALL, IVAN V.;TAYLOR, ROBERT D.;REEL/FRAME:015304/0591
Effective date: 20040503