U.S. patent application number 10/348568 was filed with the patent office on 2004-07-29 for pyrotechnic compositions for gas generant applications.
Invention is credited to Mendenhall, Ivan V., Taylor, Robert D..
Application Number | 20040144455 10/348568 |
Document ID | / |
Family ID | 32735396 |
Filed Date | 2004-07-29 |
United States Patent
Application |
20040144455 |
Kind Code |
A1 |
Mendenhall, Ivan V. ; et
al. |
July 29, 2004 |
Pyrotechnic compositions for gas generant applications
Abstract
Pyrotechnic compositions which include a fuel material of cobalt
III nitrate complex with ammonia or water ligands, 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. Also provided are corresponding or
associated gas generating devices and inflatable vehicle occupant
safety restraint systems.
Inventors: |
Mendenhall, Ivan V.;
(Providence, UT) ; Taylor, Robert D.; (Hyrum,
UT) |
Correspondence
Address: |
James D. Erickson
Autoliv ASP, Inc.
3350 Airport Road
Ogden
UT
84405
US
|
Family ID: |
32735396 |
Appl. No.: |
10/348568 |
Filed: |
January 21, 2003 |
Current U.S.
Class: |
149/45 |
Current CPC
Class: |
C06B 31/00 20130101;
C06D 5/06 20130101 |
Class at
Publication: |
149/045 |
International
Class: |
C06B 031/00 |
Claims
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; 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.
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 wherein the composition
provides a burn rate of in excess of 0.35 ips at 1000 psi.
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. A gas generating device containing the pyrotechnic composition
of claim 1.
11. An inflatable vehicle occupant safety restraint system
comprising: the gas generating device of claim 10 connected in
association with an inflatable airbag cushion for inflating the
airbag cushion.
12. A pyrotechnic composition comprising: 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.
13. The pyrotechnic composition of claim 12 wherein the composition
provides a burn rate of at least about 0.4 ips at 1000 psi.
14. The pyrotechnic composition of claim 12 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.
15. The pyrotechnic composition of claim 14 wherein the powder form
of the pyrotechnic composition is press-formed into a desired
form.
16. A gas generating device containing the pyrotechnic composition
of claim 12.
17. An inflatable vehicle occupant safety restraint system
comprising: the gas generating device of claim 16 connected in
association with an inflatable airbag cushion for inflating the
airbag cushion.
Description
BACKGROUND OF THE INVENTION
[0001] 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.
[0002] 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.
[0003] 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.
[0004] In view of the above, gas generant compositions for
pyrotechnic automotive airbag applications generally preferably
have a relatively high burn rate, 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.
[0005] In general, the burn rate for a gas generant composition can
be represented by the equation (1), below:
r.sub.b=k(P).sup.n (1)
[0006] where,
[0007] r.sub.b=burn rate (linear)
[0008] k=constant
[0009] P=pressure
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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
[0014] A general object of the invention is to provide an improved
pyrotechnic composition.
[0015] A more specific objective of the invention is to overcome
one or more of the problems described above.
[0016] The general object of the invention can be attained, at
least in part, through a pyrotechnic composition which includes
[0017] about 45 to about 90 weight percent cobalt III nitrate
complex with ligands selected from the group consisting of ammonia
and water;
[0018] about 2 to about 50 weight percent of a copper complex of
ethylenediamine dinitrate; and
[0019] about 5 to about 50 weight percent basic copper nitrate.
[0020] 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.
[0021] 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.
[0022] 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 CO.sub.2, H.sub.2O and N.sub.2.
[0023] 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 CO.sub.2, H.sub.2O and
N.sub.2.
[0024] References to a component or material as a "burn rate
catalyst" 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 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.
[0025] Unless otherwise specifically noted, percentages when used
herein in conjunction with a composition ingredient or component
are to be understood to be in terms of weight percent.
[0026] 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
[0027] 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
[0028] 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.
[0029] 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 a
preferred embodiment of the invention generally include:
[0030] about 45 to about 90 weight percent cobalt III nitrate
complex with ligands selected from the group consisting of ammonia
and water;
[0031] about 2 to about 50 weight percent of a copper complex of
ethylenediamine dinitrate; and
[0032] about 5 to about 50 weight percent basic copper nitrate.
[0033] In accordance with one preferred embodiment 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.
[0034] 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.
[0035] 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 in the subject pyrotechnic
compositions.
[0036] 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.
[0037] 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.
[0038] 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:
[0039] combining,
[0040] a. the cobalt III nitrate complex with ligands selected from
the group consisting of ammonia and water with,
[0041] b. sufficient cupric nitrate and ethylenediamine to form the
copper bis ethylenediamine dinitrate and
[0042] c. the basic copper nitrate
[0043] to form a mixture and
[0044] spray drying the mixture to form a powder form of the
pyrotechnic composition.
[0045] 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.
[0046] 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.
[0047] 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."
[0048] 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.
[0049] 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.
[0050] 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
[0051] 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.
1 TABLE 1 Comparative Comparative Ingredient (wt %) Example 1
Example 1 Example 2 bCN 22.53 22.53 46.62 copper bis 10.00 -- --
ethylenediamine dinitrate HACN 67.47 73.5 -- GN -- -- 50.38 guar
gum -- 5.00 -- aluminum oxide -- -- 2.70 silicon dioxide -- -- 0.30
where, bCN = basic copper nitrate HACN = hexammine cobalt III
nitrate, and GN = guanidine nitrate
[0052] 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 vessel or bomb
capable of being pressurized to several thousand psi with nitrogen
and equipped with a pressure transducer for accurate measurement of
bomb 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 bomb lid. The
bomb 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 bomb 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 t.sub.2- t.sub.1 where t.sub.2
is the time at the end of combustion and t.sub.1 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.
2TABLE 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
low Variability dried/pressed) (extruded)
[0053] Discussion of Results
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
* * * * *