Note: Descriptions are shown in the official language in which they were submitted.
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METAL COMPLEXES FOR USE AS GAS GENERANTS
Field of the Invention
The present invention relates to
complexes of transition metals or alkaline earth
metals which are capable of combusting to generate
gases. More particularly, the present invention
relates to providing such complexes which rapidly
oxidize to produce significant quantities of
gases, particularly water vapor and nitrogen.
Background of the Invention
Gas generating chemical compositions are
useful in a number of different contexts. One
important use for such compositions is in the
operation of "air bags." Air bags are gaining in
acceptance to the point that many, if not most,
new automobiles are equipped with such devices.
Indeed, many new automobiles are equipped with
multiple air bags to protect the driver and
passengers.
In the context of automobile air bags,
sufficient gas must be generated to inflate the
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device within a fraction of a second. Between the
time the car is impacted in an accident, and the
time the driver would otherwise be thrust against
the steering wheel, the air bag must fully
inflate. As a consequence, nearly instantaneous
gas generation is required.
There are a number of additional
important design criteria that must be satisfied.
Automobile manufacturers and others have set forth
the required criteria which must be met in
detailed specifications. Preparing gas generating
compositions that meet these important design
criteria is an extremely difficult task. These
specifications require that the gas generating
composition produce gas at a required rate. The
specifications also place strict limits on the
generation of toxic or harmful gases or solids.
Examples of restricted gases include carbon
monoxide, carbon dioxide, NOx, SOx, and hydrogen
sulfide.
The gas must be generated at a
sufficiently and reasonably low temperature so
that an occupant of the car is not burned upon
impacting an inflated air bag. If the gas
produced is overly hot, there is a possibility
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that the occupant of the motor vehicle may be
burned upon impacting a just deployed air bag.
. Accordingly, it is necessary that the combination
of the gas generant and the construction of the
air bag isolates automobile occupants from
excessive heat. All of this is required while the
gas generant maintains an adequate burn rate.
Another related but important design
criteria is that the gas generant composition
produces a limited quantity of particulate
materials. Particulate materials can interfere
with the operation of the supplemental restraint
system, present an inhalation hazard, irritate the
skin and eyes, or constitute a hazardous solid
waste that must be dealt with after the operation
of the safety device . In the absence of an
acceptable alternative, the production of
irritating particulates is one of the undesirable,
but tolerated aspects of the currently used sodium
azide materials.
In addition to producing limited, if any,
quantities of particulates, it is desired that at
least the bulk of any such particulates be easily
filterable. For instance, it is desirable that
the composition produce a filterable slag. If the
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reaction products form a filterable material, the
products can be filtered and prevented from
escaping into the surrounding environment.
Both organic and inorganic materials have
been.proposed as possible gas generants. Such gas
generant compositions include oxidizers and fuels
which react at sufficiently high rates to produce
large quantities of gas in a fraction of a second.
At present, sodium azide is the most
widely used and currently accepted gas generating
material. Sodium azide nominally meets industry
specifications and guidelines. Nevertheless,
sodium azide presents a number of persistent
problems. Sodium azide is highly toxic as a
starting material, since its toxicity level as
measured by oral rat LDso is in the range of 45
mg/kg. Workers who regularly handle sodium azide
have experienced various health problems such as
severe headaches, shortness of breath,
convulsions, and other symptoms.
In addition, no matter what auxiliary
oxidizer is employed, the combustion products from
a sodium azide gas generant include caustic
reaction products such as sodium oxide, or sodium
hydroxide. Molybdenum disulfide or sulfur have
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been used as oxidizers for sodium azide. However,
use of such oxidizers results in toxic products
- such as hydrogen sulfide gas and corrosive
materials such as sodium oxide and sodium sulfide.
5 Rescue workers and automobile occupants have
complained about both the hydrogen sulfide gas and
the corrosive powder produced by the operation of
sodium azide-based gas generants.
Increasing problems are also anticipated
in relation to disposal of unused gas-inflated
supplemental restraint systems, e.g. automobile
air bags, in demolished cars. The sodium azide
remaining in such supplemental restraint systems
can leach out of the demolished car to become a
water pollutant or toxic waste. Indeed, some have
expressed concern that sodium azide might form
explosive heavy metal azides or hydrazoic acid
when contacted with battery acids following
disposal.
Sodium azide-based gas generants are most
commonly used for air bag inflation, but with the
significant disadvantages of such compositions
many alternative gas generant compositions have
been proposed to replace sodium azide. Most of
the proposed sodium azide replacements, however,
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fail to deal adequately with all of the criteria
set forth above.
It will be appreciated, therefore, that
there are a number of important criteria for
selecting gas generating compositions for use in
automobile supplemental restraint systems. For
example, it is important to select starting
materials that are not toxic. At the same time,
the combustion products must not be toxic or
harmful. In this regard, industry standards limit
the allowable amounts of various gases and
particulates produced by the operation of
supplemental restraint systems.
It would, therefore, be a significant
advance to provide compositions capable of
generating large quantities of gas that would
overcome the problems identified in the existing
art. It would be a further advance to provide a
gas generating composition which is based on
substantially nontoxic starting materials and
which produces substantially nontoxic reaction
products. It would be another advance in the art
to provide a gas generating composition which
produces very limited amounts of toxic or
irritating particulate debris and limited
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undesirable gaseous products. It would also be an
advance to provide a gas generating composition
which forms a readily filterable solid slag upon
reaction.
Such compositions and methods for their
use are disclosed and claimed herein.
Brief Summary of the Invention
The present invention is related to the
use of complexes of transition metals or alkaline
earth metals as gas generating compositions.
These complexes are comprised of a metal ration
and a neutral ligand containing hydrogen and
nitrogen. One or more oxidizing anions are
provided to balance the charge of the complex.
Examples of typical oxidizing anions which can be
used include nitrates, nitrites, chlorates,
perchlorates, peroxides, and superoxides. In some
cases the oxidizing anion is part of the metal
ration coordination complex. The complexes are
formulated such that when the complex combusts, a
mixture of gases containing nitrogen gas and water
vapor are produced. A binder can be provided to
improve the crush strength and other mechanical
properties of the gas generant composition. A co-
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oxidizer can also be provided primarily to permit
efficient combustion of the binder. Importantly,
the production of undesirable gases or
particulates is substantially reduced or
eliminated.
Specific examples of the complexes used
herein include metal nitrite ammines, metal
nitrate ammines, metal perchlorate ammines, metal
nitrite hydrazines, metal nitrate hydrazines,
metal perchlorate hydrazines, and mixtures
thereof. The complexes within the scope of the
present invention rapidly combust or decompose to
produce significant quantities of gas.
The metals incorporated within the
complexes are transition metals, alkaline earth
metals, metalloids, or lanthanide complexes. The
presently preferred metal is cobalt. Other metals
which also form complexes with the properties
desired in the present invention include, for
example, magnesium, manganese, nickel, titanium,
copper, chromium, zinc, and tin. Examples of
other usable metals include rhodium, iridium,
ruthenium, palladium, and platinum. These metals
are not as preferred as the metals mentioned
above, primarily because of cost considerations.
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The transition metal cation or alkaline
earth metal cation acts as a template or
coordination center for the transition metal
complex. As mentioned above, the complex includes
a neutral ligand containing hydrogen and nitrogen.
This neutral ligand is preferably ammonia or a
substituted ammonia ligand such as hydrazine or a
substituted hydrazine ligand. If carbon is
present in this neutral ligand, this neutral
l0 ligand is preferably aliphatic in nature rather
than aromatic. More preferably, the neutral
ligand is substantially or totally based on
nitrogen and hydrogen atoms and contains few if
any carbon atoms. Neutral ligands containing
hydrogen and nitrogen are described in F.A. Cotton
and G. Wilkinson's Advanced Inorganic Chemistry, A
Comprehensive Text, 4th Ed., Wiley-Inter-science,
1980, pages 118-132. Currently preferred neutral
ligands -are NH3 and N2H4. One or more oxidizing
anions may also be coordinated with the metal
cation. Examples of metal complexes within the
scope of the present invention include
Cu (NH3) 4 (N03) 2 (tetraamminecopper (II) nitrate) ,
Co (NH3) 3 (N02) 3 (trinitrotriamminecobalt ( III) ) ,
CO (NH3) 6 (Cl~q) 3
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(hexaamminecobalt(III) perchlorate), Co(NH3)6(N03)3
(hexaamminecobalt (III ) nitrate) , Zn (NZH4) 3 (N03) z
(tris-hydrazine zinc nitrate) , Mg (NzH4) z (C104) 2
(bis-hydrazine magnesium perchlorate), and
5 Pt (NOz) 2 (NHZNHZ) 2 (bis-hydrazine platinum ( II )
nitrite).
It is within the scope of the present
invention to include metal complexes which contain
a common ligand in addition to the neutral ligand.
10 A few typical common ligands include: aquo (H20),
hydroxo (OH) , carbonato (C03) , oxalato (Cz04) ,
cyano (CN), isocyanato (NC), chloro (Cl), fluoro
(F), and similar ligands. The metal complexes
within the scope of the present invention are also
intended to include a common counter ion, in
addition to the oxidizing anion, to help balance
the charge of the complex. A few typical common
counter ions include: hydroxide (OH-), chloride
(C1-) , fluoride (F') , cyanide (CN-) , carbonate (C03-
2) , phosphate (PO9-3) , oxalate (Cz04-2) , borate (B04-
5) , ammonium (NH9+) , and the like.
It is observed that metal complexes
containing the described neutral ligands and
oxidizing anions combust rapidly to produce
significant quantities of gases. Combustion can
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be initiated by the application of heat or by the
use of conventional igniter devices.
Detailed Description of the Invention
As discussed above, the present invention
is related to gas generant compositions containing
complexes of transition metals or alkaline earth
metals. These complexes are comprised of a metal
cation template and a neutral ligand containing
hydrogen and nitrogen. One or more oxidizing
anions are provided to balance the charge of the
complex. In some cases the oxidizing anion is
part of the coordination complex with the metal
cation. Examples of typical oxidizing anions
which can be used include nitrates, nitrites,
chlorates, perchlorates, peroxides, and
superoxides. The complexes can be combined with a
binder or mixture of binders to improve the crush
strength and other mechanical properties of the
gas generant composition. A co-oxidizer can be
provided primarily to permit efficient combustion
of the binder.
Metal complexes which include at least
one common ligand in addition to the neutral
ligand are also included within the scope of the
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present invention. As used herein, the term
common ligand includes well known ligands used by
inorganic chemists to prepare coordination
complexes with metal cations. The common ligands
are preferably polyatomic ions or molecules, but
some monoatomic ions, such as halogen ions, may
also be used. Examples of common ligands within .
the scope of the present invention include ague
(H20) , hydroxo (OH) , perhydroxo (OZH) , peroxo ~(Oa) ,
carbonate (C03) , oxalate (C204) , carbonyl (CO) ;
nitrosyl (NO), cyano (CN), isocyanato (NC),
isothiocyanato (NCS), thiocyanato (SCN), chloro
(C1) , fluoro (F) , amide (NHZ) , imdo (NH) , sulfate
(SO,), phosphate (POD), ethylenediaminetetraacetic
acid (EDTA), and similar ligands. See, F. Albert
Cotton and Geoffrey Wilkinson, Advanced Inor4anic
Chemistry, 2nd ed., John Wiley & Sons, pp. 139-
142, 1966 and James E. Huheey, Inoraanic
Chemistry, 3rd ed., Harper & Row, pp. A-97-A-107,
1983. Persons skilled in the art will appreciate
that suitable metal complexes within the scope of
the present invention can be prepared containing
a neutral ligand and other ligand not listed
above.
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In some cases, the complex can include a
common counter ion, in addition to the oxidizing
anion, to help balance the charge of the complex.
As used herein,.the term common counter ion
includes well known anions.and cations used by
inorganic chemists as counter ions. Examples of
common counter ions within the scope of the
present invention include, hydroxide (OH'); chloride
(C1') , fltioride (F') , cyanide (CN') , thiocyanate
( SCN' ) , carbonate ( C03-2 ) , sul f ate (SO,'2 ) , phosphate
(PO,'') , oxalate (CaO,'2) , borate (BO,'S) , ammonium
(NH,'), and the like. See, Whitten, K.W., and
Gailey, K.D., General Chemistry, Saunders College
Publishing, p. 167, 1981 and James E. Huheey,
Inorc~,anic Chemistry, 3rd ed., Harper & Row, pp. A-
97-A-103, 1983.
The gas generant ingredients axe
formulated such that when the composition com-
busts, nitrogen gas and water vapor are produced.
In some cases, .small amounts of carbon dioxide or
carbon monoxide are produced if a binder, co-
oxidizer, common ligand or oxidizing anion captain
carbon. The total carbon in the gas generant
composition is carefully controlled to prevent
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excessive generation of CO gas. The combustion of
the gas generant takes place at a rate sufficient
to qualify such materials for use as gas
generating compositions in automobile air bags and
other similar types of devices. Importantly, the
production of other undesirable gases or
particulates is substantially reduced or
eliminated.
Complexes which fall within the scope of
the present invention include metal nitrate
ammines, metal nitrite ammines, metal perchlorate
ammines, metal nitrite hydrazines, metal nitrate
hydrazines, metal perchlorate hydrazines, and
mixtures thereof. Metal ammine complexes are
defined as coordination complexes including
ammonia as the coordinating ligand. The ammine
complexes can also have one or more oxidizing
anions, such as nitrite (NOz-) , nitrate (N03-) ,
chlorate (C103-) , perchlorate (C104-) , peroxide (p2z-
), and superoxide (OZ-), or mixtures thereof, in
the complex. The present invention also relates
to similar metal hydrazine complexes containing
corresponding oxidizing anions.
It is suggested that during combustion of
a complex containing nitrite and ammonia groups,
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the nitrite and ammonia groups undergo a
diazotization reaction. This reaction is similar,
for example, to the reaction of sodium nitrite and
ammonium sulfate, which is set forth as follows:
5 2NaN0z + (NH4 ) ZS04 ~ NazS04 + 4H20 + 2N2
Compositions such as sodium nitrite and
ammonium sulfate in combination have little
utility as gas generating substances. These
materials are observed to undergo metathesis
10 reactions which result in unstable ammonium
nitrite. In addition, most simple nitrite salts
have limited stability.
In contrast, the metal complexes used in
the present invention are stable materials which,
15 in certain instances, are capable of undergoing
the type of reaction set forth above. The
complexes of the present invention also produce
reaction products which include desirable
quantities of nontoxic gases such as water vapor
and nitrogen. In addition, a stable metal, or
metal oxide slag is formed. Thus, the
compositions of the present invention avoid
several of the limitations of existing sodium
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azide gas generating compositions.
Any transition metal, alkaline earth
metal, metalloid, or lanthanide metal which is
capable of forming the complexes described herein
is a potential candidate for use in these gas
generating compositions. However, considerations
such as cost, reactivity, thermal stability, and
toxicity may limit the most preferred group of
metals.
The presently preferred metal is cobalt.
Cobalt forms stable complexes which are relatively
inexpensive. In addition, the reaction products
of cobalt complex combustion are relatively
nontoxic. Other preferred metals include
magnesium, manganese, copper, zinc, and tin.
Examples of less preferred but usable metals
include nickel, titanium, chromium, rhodium,
iridium, ruthenium, and platinum.
A few representative examples of ammine
complexes within the scope of the present
invention, and the associated gas generating
decomposition reactions are as follows:
Cu (NH3) 2 (N02) 2 -~ Cu0 + 3Hz0 + 2N2
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2Co (NH3) 3 (NOz) 3 -~ 2Co0 + 9H20 + 6N2 + ~
2 Cr (NH3 ) 3 (NOZ ) 3 -j Cr2O3 + 9H20 + 6Nz
[Cu (NH3) q] (N03) 2 -~ Cu + 3N2 + 6Hz0
2B + 3Co (NH3) 6Co (N02) 6 --> 6Co0 + B203 + 27H20
+ 18N2
Mg + Co (NH3) q (NOz) ZCo (NH3) 2 (NOz) q -j 2Co0 +
Mg0 + 9Hz0 + 6Nz
[Co (NH3) q (NOZ) 2] (NOz) + 2Sr (N03) 2 -~ lOCoO +
2Sr0 + 37N2 + 60H20
10 18 [Co (NH3) 6] (N03) 3 + 4Cu2 (OH) 3NO3 -~ 18Co0 +
8Cu + 83N2 + 168H20
2 [ Co ( NH3 ) ~ ] ( N03 ) 3 + 2NH9N03 -~ 2 Co0 + l lNz +
22H20
TiClq (NH3) 2 + 3Ba02 -j Ti02 + 2BaClz + Ba0 + 3H20
+ NZ
4 [Cr (NH3) SOH] (ClOq) z + [SnClq (NH3) z] -~ 4CrC13 + Sn0
+ 3 5H20 + llNz
10 [Ru (NH3) SNZ] (N03) 2 + 3Sr (N03) 2 -> 3Sr0 + lORu +
48N2 + 75H20
[Ni (Hz0) 2 (NH3) q] (N03) 2 -~ Ni + 3N2 + 8Hz0
2 [ Cr ( Oz ) 2 ( NH3 ) 3 ] + 4 NH4NO3 -~ 7N2 + 17H20 + Cr2O3
8 [Ni (CN) z (NH3) ] "C6H6+43KClOq -~
8Ni0+43KC1+64C02+12N2+36Hz0
2 [Sm(02) 3 (NH3) ] + 4 [Gd (NH,) g] (ClOq) 3 -~ SI11z03 +
4GdC13 + 19N2 + 57Hz0
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2Er (N03 ) 3 (NH3 ) 3 + 2 (Co (NH3 ) 6] (N03 ) 3 -~ Er203 + 12Co0
+ 60N2 + 117H20
A few representative examples of hydrazine
complexes within the scope of the present
invention, and related gas generating reactions
are as follows:
5Zn (NZH9) (N03) 2 + Sr (N03) 2 -~ 5Zn0 + 21N2 + 30Hz0
+ Sr0
Co (NZH4) 3 (N03) 2 -~ Co + 4NZ + 6Hz0
3Mg (NZHq) z (C104) z + 2S13N4 -j 6Si0z + 3MgC12 +
lON2 +12Hz0
2Mg (NZH4) 2 (N03) z + 2 [Co (NH3) 4 (NOz) 2] NOz -~ 2Mg0 +
2Co0 + l3Nz + 20H20
Pt {NOz) 2 (N2H4) 2 -~ Pt + 3Nz + 4H20
[Mn (NzHq ) 3 ] (N03 ) 2 + Cu ( OH ) 2 -> Cu + Mn0 + 4N2 +
7H20
2 [La (NZH9 ) 4 (N03 ) ] (N03 ) z + NH4NO3 ~ La203 + l2Nz +
18H20
While the complexes of the present invention
are relatively stable, it is also simple to
initiate the combustion reaction. For example, if
the complexes are contacted with a hot wire, rapid
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gas producing combustion reactions are observed.
Similarly, it is possible to initiate the reaction
by means of conventional igniter devices. One
type of igniter device includes a quantity of
B/KNO, granules or pellets which is ignited, and
which in turn is capable of igniting the
compositions of the present invention. Another
igniter device includes a quantity of
Mg/Sr(N03)2/nylon granules.
It is also important to note that many of the
complexes defined above undergo "stoichiometric"
decomposition. That is, the complexes decompose
without reacting with any other material to
produce large quantities of nitrogen and water,
and a metal or metal oxide. However, for certain
complexes it may be desirable to add a fuel or
oxidizer to the complex in order to assure
complete and efficient reaction. Such fuels
include, for example, boron, magnesium, aluminum,
hydrides of boron or aluminum, carbon, silicon,
titanium, zirconium, and other similar
conventional fuel materials, such as conventional
organic binders. Oxidizing species include
nitrates, nitrites, chlorates, perchlorates,
peroxides, and other similar oxidizing materials.
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Thus, while stoichiometric decomposition is
attractive because of the simplicity of the
composition and reaction, it is also possible to
use complexes for which stoichiometric~
5 decomposition is not possible.
As mentioned above, nitrate and perchlorate
complexes also fall within the scope of the
invention. A few representative examples of such
nitrate complexes include: Co(NH3)6(N03)3,
10 Cu (NH3) 4 (NO3) z, ~CO (NH3) 5 (NO3) ~ (NO3) zr
[Co (NH3) 5 (NOZ) l (N03) Z, [Co (NH3) 5 (H20) l (N03) 2. A few
representative examples of perchlorate complexes
within the scope of the invention include:
LCo (NH3) 6~ (C1O4) 3r ~Co (NH3) 5 (NOz) ] ClO4r
15 [Mg (NZH4) 2l (C104) z .
Preparation of metal nitrite or nitrate
ammine complexes of the present invention is
described in the literature. Specifically,
reference is made to Hagel et al., "The Triamines
20 of Cobalt (III). I. Geometrical Isomers of
Trinitrotriamminecobalt(III)," 9 Inorganic
Chemistry 1496 (June 1970); G. Pass and H.
Sutcliffe, Practical Inorctanic Chemistr~r, 2nd Ed. ,
Chapman & Hull, New York, 1974; Shibata et al.,
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"Synthesis of Nitroammine- and Cyanoammine-
cobalt(III) Complexes With Potassium
Tricarbonatocobaltate(III) as the Starting Materi-
al, " 3 Inorctanic Chemistry 1573 (Nov. 1964) ;
Wieghardt et al., "~e-Carboxylatodi-~,-hydroxo-
bis[triamminecobalt(III)] Complexes," 23 Inorganic
Synthesis 23 (1985); Laing, "mer- and fac-
[Co (NH3) 3N02) ~J : Do They Exist?" 62 J. Chem Educ. ,
707 (1985); Siebert, "Isomere des Trinitrotri-
amminkobalt(III)," 441 Z. Anora. AllQ. Chem. 47
(1978). Transition metal perchlorate ammine
complexes are synthesized by similar methods.
As mentioned above, the ammine complexes of the
present invention are generally stable and safe
for use in preparing gas generating formulations.
Preparation of metal perchlorate, nitrate,
and nitrite. hydrazine complexes is also described
in the literature.. Specific reference is made to
Patil et al., "Synthesis and Characterisation of
Metal Hydrazine Nitrite, Azide, and Perchlorate
Complexes," 12 Synthesis and Reactivity In
Inorganic and Metal Orczanic Chemistry,. 383 (1982);
Klyichnikov et al., "Preparation.of Some Hydrazine
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Compounds of Palladium," 13 Russian Journal of
Inorganic Chemistry, 416 (1968); Klyichnikov et
al., "Conversion of Mononuclear Hydrazine
Complexes of Platinum and Palladium Into Binuclear
Complexes," 36 Ukr. Khim. Zh., 687 (1970).
The described complexes can be processed into
usable granules or pellets for use in gas
generating devices. Such devices include
automobile air bag supplemental restraint systems.
Such gas generating compositions will comprise a
quantity of the described complexes and
preferably, a binder and a co-oxidizer. The
compositions produce a mixture of gases, princi-
pally nitrogen and water vapor, upon decomposition
or burning. The gas generating device will also
include means for initiating the burning of the
composition, such as a hot wire or igniter. In
the case of an automobile air bag system, the
system will include the compositions described
above; a collapsed, inflatable air bag; and means
for igniting said gas-generating composition
within the air bag system. Automobile air bag
systems are well known in the art.
Typical binders used in the gas generating
compositions of the present invention include
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binders conventionally used in propellant,
pyrotechnic and explosive compositions including,
but not limited to, lactose, boric acid, silicates
including magnesium silicate, polypropylene
. carbonate, polyethylene glycol, naturally
occurring gums such as guar gum, acacia gum,
modified celluloses and starches (a detailed
discussion of such gums is provided by C.L.
Mantell, The Water-Soluble Gums, Reinhold
Publishing Corp., 1947), polyacrylic acids, vitro-
cellulose, polyacrylaminde, polyamides, including
nylon, and other conventional polymeric binders.
Such binders improve mechanical properties or
provide enhanced crush strength. Although water
immiscible binders can be used in the present
invention, it is currently preferred to use water
soluble binders. The binder concentration is
preferably in the range from 0.5 to 12% by weight,
and more preferably from 2% to 8% by weight of the
gas generant composition.
Applicants have found that the addition of
carbon such as carbon black or activated charcoal
to gas generant compositions improves binder
action significantly perhaps by reinforcing the
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binder and thus, forming a micro-composite.
Improvements in crush strength of 50% to 150% have
been observed with the addition of carbon black to
compositions within the scope of the present
invention. Ballistic reproducibility is enhanced
as-crush strength increases. The carbon
concentration is preferably in the range of 0.1%
to 6% by weight, and more preferably from 0.3 to
3% by weight of the gas generant composition.
The co-oxidizer can be a conventional
oxidizer such as alkali, alkaline earth,
lanthanide, or ammonium perchlorates, chlorates,
peroxides, nitrites, and nitrates,~including for
example, Sr (N03) 2, NH9C10" FQ~T03, and (NH,) ~Ce (N03) s
The co-oxidizer can also be a metal
containing oxidizing agent such as metal oxides,
metal hydroxides, metal peroxides, metal oxide
hydrates, metal oxide hydroxides, metal hydrous
oxides, and mixtures thereof, including those
described in U.S. Patent No. 5,439,537 issued
August 8, 1995, titled ~~Thermite Compositions for
Use as Gas Generants". Examples of metal oxides
include, among others, the oxides of copper,
cobalt, manganese, tungsten, bismuth, molybdenum,
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and i ron, such as Cu0 , Co20, , Co~O~ , CoFe204 , Fe20, ,
Mo03, Bi2Mo06, and Bi203. Examples of metal
hydroxides include, among others, Fe(OH)3, Co(OH)3,
Co (OH) 2, Ni (OH) 2, Cu (OH) Z, and Zn (OH) 2 . Examples of
5 meta'i oxide hydrates and metal hydrous oxides
include , among others , Fez03' xH20, SnO~' xHzO, and
MoO,'H20. Examples of metal oxide hydroxides
include, among others, Co0 (OH) z, Fe0 (OH) Z, Mn0 (OH) Z
and Mn0 ( OH ) 3 .
10 The co-oxidizer can also be a basic metal
carbonate such as metal carbonate hydroxides,
metal carbonate oxides, metal carbonate hydroxide
oxides, and hydrates and mixtures thereof and a
basic metal nitrate such as metal hydroxide
15 . nitrates, metal nitrate oxides, and hydrates and
mixtures thereof, including those oxidizers
described in U.S: patent number 5,429,691, titled
~~Thermite Compositions for use as Gas Generants".
20 Table 1,, below, lists examples of typical
-basic metal carbonates capable of functioning as
co-oxidizers~in the compositions of the present
invention:
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Table 1
Basic Metal Carbonates
Cu (C03) ,-X' Cu (OH) zX, a . g. , CuC03' Cu (OH) z
(malachite)
Co(C03)1_X(OH)zX, e.g.,
2Co (C03) ' 3Co (OH) z' H20
CoXFeY ( C03 ) z ( OH ) z , a . g . ,
Coo.69Feo.3a (C03) o.z (OH) z
Na3 LCo (C03) 3] ' 3Hz0
Zn(C03)1_X(OH)ZX, e.g., Znz(C03) (OH)z
BiAMgs(C03)~(OH)D, e.g., BizMg(C03)z(OH)Q
Fe (C03) 1_X (OH) 3X, e.g. , Fe (C03) o.iz (OH) z.~s
Cuz_XZnX(C03)1_Y(OH)zY~ e.g.,
Cul.saZno.as (C03) (OH) z
Co Cu g .
y z-y (C03) 1_X (OH) zx. a .
COo.asCuo.si (C03) 0.43 (OH) 1.1
TiABi$ (C03) X (OH) Y (O) Z (Hz0) ~, e. g,
T13B14(C03)z(OH)z09(Hz0)z
(Bi0)zC03
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Table 2, below, lists examples of typical
basic metal nitrates capable of functioning as co-
oxidizers in the compositions of the present
invention:
Table 2
Basic Metal Nitrates
Cuz(OH)3N03 (gerhardite)
Coz ( OH ) 3N03
CuXCoz_X (OH) 3N03, e.g. , CuCo (OH) 3NO3
Znz ( OH ) 3NO3
Mn ( OH ) zN03
Fe (N03) n (OH) 3_n, e.g. , Fe9 (OH) 11N03~ 2H20
Mo (N03 ) zOz
BiON03~ H20
Ce (OH) (N03) 3- 3H20
In certain instances it will also be
desirable to use mixtures of such oxidizing agents
in order to enhance ballistic properties or
maximize filterability of the slag formed from
combustion of the composition.
The present compositions can also include
additives conventionally used in gas generating
compositions, propellants, and explosives, such as
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burn rate modifiers, slag formers, release agents,
and additives which effectively remove NOX.
Typical burn rate modifiers include Fez03, KzB1zH12,
BizMo06, and graphite carbon powder or fibers. A
number of slag forming agents are known and
include, for example, clays, talcs, silicon
oxides, alkaline earth oxides, hydroxides,
oxalates, of which magnesium carbonate, and
magnesium hydroxide are exemplary. A number of
additives and/or agents are also known to reduce
or eliminate the oxides of nitrogen from the
combustion products of a gas generant composition,
including alkali metal salts and complexes of
tetrazoles, aminotetrazoles, triazoles and related
nitrogen heterocycles of which potassium
aminotetrazole, sodium carbonate and potassium
carbonate are exemplary. The composition can also
include materials which facilitate the release of
the composition from a mold such as graphite,
molybdenum sulfide, calcium stearate, or boron
nitride.
Typical ignition aids/burn rate modifiers
which can be used herein include metal oxides,
nitrates and other compounds such as, for
instance, Fe203, FC2B1zH12' H20, Bi0 (N03) , Co203,
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CoFez04, CuMo04, BizMo06, MnOz, Mg (N03) z' xH20,
Fe (N03) 3' xHzO, Co (N03) z' xH20, and NHQN03. Coolants
include magnesium hydroxide, cupric oxalate, boric
acid, aluminum hydroxide, and silicotungstic acid.
Coolants such as aluminum hydroxide and silico-
tungstic acid can also function as slag enhancers.
It will be appreciated that many of the
foregoing additives may perform multiple functions
in the gas generant formulation such as a co-
oxidizer or as a fuel, depending on the compound.
Some.compounds may function as a co-oxidizer, burn
rate modifier, coolant, and/or slag former.
Several important properties of typical
hexaamminecobalt(III) nitrate gas generant
compositions within the scope of the present
invention have been compared with those of
commercial sodium azide gas generant compositions.
These properties illustrate significant
differences between conventional sodium azide gas
generant compositions and gas generant
compositions within the scope of the present
invention. These properties are summarized below:
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Property Typical Typical
Invention Sodium
Range Azide
Flame Temperature 1850-2050K 1400-1500K
Gas Fraction of 0.65-0.85 0.4-0.45
Generant
5 Total Carbon Content 0-3.5% trace
in Generant
Burn Rate of Gen- 0.10-0.35 ips 1.1-1.3 ips
erant at 1000 psi
Surface Area of 2.0-3.5 cm2/g 0.8-0.85 cm2/g
10 Generant
Charge Weights in 30-45 g 75-90 g
Generator
The term "gas fraction of generant" means the
weight fraction of gas generated per weight of gas
15 generant. Typical hexaamminecobalt(III) nitrate
gas generant compositions have more preferred
flame temperatures in the range from 1850°K to
1900°K, gas fraction of generant in the range from
0.70 to 0.75, total carbon content in the generant
20 in the range from 1.5% to 3.0% burn rate of
generant at 1000 psi in the range from 0.2 ips to
0.35 ips, and surface area of generant in the
range from 2.5 cm2/g to 3.5 cm2/g.
The gas generating compositions of the
25 present invention are readily adapted for use with
conventional hybrid air bag inflator technology.
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Hybrid inflator technology is based on heating a
stored inert gas (argon or helium) to a desired
temperature by burning a small amount of
propellant. Hybrid inflators do not require
cooling filters used with pyrotechnic inflators to
cool combustion gases, because hybrid inflators
are able to provide a lower temperature gas. The
gas discharge temperature can be selectively
changed by adjusting the ratio of inert gas weight
to propellant weight. The higher the gas weight
to propellant weight ratio, the cooler the gas
discharge temperature.
A hybrid gas generating system comprises a
pressure tank having a rupturable opening, a pre-
determined amount of inert gas disposed within
that pressure tank; a gas generating device for
producing hot combustion gases and having means
for rupturing the rupturable opening; and means
for igniting the gas generating composition. The
tank has a rupturable opening which can be broken
by a piston when the gas generating device is
ignited. The gas generating device is configured
and positioned relative to the pressure tank so
that hot combustion gases are mixed with and heat
the inert gas. Suitable inert gases include,
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among others, argon, helium and mixtures thereof.
The mixed and heated gases exit the pressure tank
through the opening and ultimately exit the hybrid
inflator and deploy an inflatable bag or balloon,
S such as an automobile air bag.
Preferred embodiments of the invention yield
combustion products with a temperature greater
than about 1800°K, the heat of which is
transferred to the cooler inert gas causing a
further improvement in the efficiency of the
hybrid gas generating system.
Hybrid gas generating devices for
supplemental safety restraint application are
described in Frantom, Hybrid Airbag Inflator
Technology, Airbag Int~l Symposium on
Sophisticated Car Occupant Safety Systems,
(Weinbrenner-Saal, Germany, Nov. 2-3, 1992).
An additional preferred embodiment of the
present invention is the incorporation of at least
one cool burning organic nitrogen compound such
as, for example, guanidine nitrate into the gas
generant composition. A cool burning organic
nitrogen compound is a compound having a
relatively low heat of formation. In general, the
cool burning compound's heat of formation can be
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less than about -400 cal/g, and preferably, less
than about -600 cal/g. The heat of formation for
guanidine nitrate, for example, is about -747
cal/g.
In this preferred embodiment, the cool
burning organic nitrogen compound is not the
primary fuel of the formulation but a secondary
fuel. Fuels already disclosed above such as, for
example, hexamminecobalt nitrate, may serve as the
primary fuel.
In addition, a substance such as guanidine
nitrate may also have some oxidizing capacity
because of the presence of, for example, the
nitrate group. However, the cool burning organic
nitrogen compound is not the principle oxidizing
agent. It may, however, act as a secondary
oxidizing agent or a co-oxidizer together with
other oxidizing or co-oxidizing substances noted
above such as, for example, basic copper nitrate.
Besides guanidine nitrate, additional cool
burning organic nitrogen compounds for this
preferred embodiment include guanidine salts such
as, for example, the carbonate salt and guanidine
derivatives such as, for example, aminoguanidine
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nitrate, diaminoguanidine nitrate, triaminogu-
anidine nitrate, nitroguanidine, urea, glycine,
glycine-ammonium nitrate complexes, and ethylene
diamine dinitrate. However, guanidine nitrate is
preferred. Mixtures of cool burning organic
nitrogen compounds may be used.
In principle, for this preferred embodiment,
the amount of cool burning organic nitrogen
compound incorporated into the composition can be
generally more than 0 wt.o and less than about 40
wt.%, and preferably, between about 5 wt.o and
about 30 wt.%, and more preferably, between about
10 wt.o and about 25 wt.%. This embodiment of
the present invention is not limited by theory,
however, and in practice, the amount can be
determined by a person skilled in the art
depending on what performance characteristics are
most important for the particular air bag
application.
In this preferred embodiment, use of the cool
burning organic nitrogen compound results in high
gas output with simultaneously improved
filterability of the slag produced from
combustion. Furthermore, the overall cost of the
composition can be reduced when a relatively less
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expensive cool burning organic nitrogen compound
such as guanidine nitrate replaces a relatively
more expensive ingredient such as, for example,
hexaamminecobalt nitrate. In principle, the
5 amount of NOX also may be reduced.
In this preferred embodiment, preferred gas
generant compositions comprise cool burning
organic nitrogen compounds, and in addition, also
comprise: 1) at least one one primary fuel such as
10 a metal complex like, for example,
hexamminecoabalt nitrate, Co(NH3)6(N03)3, which is
different than the cool burning organic nitrogen
compound, 2) a co-oxidizer such as, for example,
basic copper nitrate, Cuz(OH)3NO3, which is
15. different than the cool burning organic nitrogen
compound, and 3) a binder which is preferably a
water soluble binder such as, for example, guar
gum.
In general, in this preferred embodiment,
20 fuels, co-oxidizers, and binders can be used which
have previously been described herein. However,
preferred examples of fuels for this preferred
embodiment include cobalt ammine complexes, and
hexaammincobalt nitrate is particularly preferred.
25 Preferred examples of co-oxidizer include basic
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metal carbonates, basic metal nitrates, metal
oxides, metal nitrates, and metal hydroxides.
Basic copper nitrate is particularly preferred.
Preferred examples of binders include water
soluble or substantially water soluble polymers
including gums. Guar gum is particularly
preferred.
The amounts of the ingredients such as fuel,
co-oxidizer, and binder in this preferred
embodiment can be readily determined by a person
of skill in the art in view of the present
disclosure. In particular, however, the amount of
primary fuel, which is apart from the cool burning
organic nitrogen compound, generally can be
between about 30 wt.% and about 90 wt.%, and
preferably, between about 40 wt.% and about 75
wt.%. The sum of the amount of co-oxidizer, taken
together with the amount of cool burning organic
nitrogen compound, generally can be between about
10 wt.% and about 60 wt.%, and preferably, between
about 15 wt.% and about SO wt.%. The amount of
binder generally can be between about 0.5 wt.% and
about 12 wt.%, and preferably, between about 2
wt.% and about 10 wt.% and more preferably,
between about 3 wt.% and about 6 wt.%. Although
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in theory, compositions are generally used that
are stoichiometrically balanced, in practice,
compositions are often at least slightly fuel
rich, although slightly ox~~gen rich compositions
are possible in principle. Typically, the level
of ingredients is adjusted to give the best
balance of performance with respect to, for
example, effluent gases and slag characteristics.
Preferably, the composition also contains
small amounts of carbon such as, for example,
carbon black as a ballistic additive or burn rate
modifier, although. this is optional. The amount
of carbon black, typically, can be less than about
2 wt.o, and preferably, less than about 1 wt.%.
The cool burning organic nitrogen compound
can be used to replace partially the fuel
ingredient. In this case, the amount of co-
oxidizer can be increased to maintain the desired
stoichiometry. This may result in cost savings
because, for example, both basic copper nitrate
and guanidine nitrate are significantly less
costly than hexamminecobalt nitrate.
Surprisingly, however, the overall performance of
the generant is maintained despite the
replacement. The maintenance of overall
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performance is achieved from a volume perspective
because the density of the mixture increases as
the relative proportion of basic copper nitrate
increases.
In general, little if any chemical reaction
is believed to occur when guanidine nitrate is
mixed into the compositions, although the present
invention is not bound by such theory of chemical
reaction. Formulations can be prepared by
blending individual ingredients, or alternatively,
by preparing separate formulations and blending
these formulations. Blending individual
ingredients is generally preferred. Mixing can be
accomplished by conventional procedures with
conventional equipment known in the art, followed
by shaping or pelleting the composition.
EXAMPLES
The present invention is further described in
the following non-limiting examples. Unless
otherwise stated, the compositions are expressed
in weight percent.
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Example 1
A quantity (132 .4 g) of Co (NH3) 3 (NOz) 3,
prepared according to the teachings of Hagel et
al., "The Triamines of Cobalt (III). I.
Geometrical Isomers of Trinitrotriammineco-
balt(III)," 9 Inorganic Chemistry 1496 (June
1970), was slurried in 35 mL of methanol with 7 g
of a 38 percent by weight solution of pyrotechnic
grade vinyl acetate/vinyl alcohol polymer resin
commonly known as VAAR dissolved in methyl
acetate. The solvent was allowed to partially
evaporate. The paste-like mixture was forced
through a 20-mesh sieve, allowed to dry to a stiff
consistency, and forced through a sieve yet again.
The granules resulting were then dried in vacuo at
ambient temperature for 12 hours. One-half inch
diameter pellets of the dried material were
prepared by pressing. The pellets were combusted
at several different pressures ranging from 600 to
3,300 psig. The burning rate of the generant was
found to be 0.237 inches per second at 1,000 psig
with a pressure exponent of 0.85 over the pressure
range tested.
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Example 2
The procedure of Example 1 was repeated with
100 g of Co(NH3)3(NO2)3 and 34 g of 12 percent by
weight solution of nylon in methanol. Granulation
5 was accomplished via 10- and 16-mesh screens
followed by air drying. The burn rate of this
composition was found to be 0.290 inches per
second at 1,000 prig with a pressure exponent of
0.74.
10 Example 3
In a manner similar to that described in
Example 1, 400 g of Co(NH3)3(NOZ)3 was slurried with
219 g of a 12 percent by weight solution of
nitrocellulose in acetone. The nitrocellulose
15 contained 12.6 percent nitrogen. The solvent was
allowed to partially evaporate. The. resulting.,
paste was forced through an 8-mesh sieve followed
by a 24-mesh sieve. The resultant granules were
dried in air overnight and blended with sufficient
20 calcium stearate mold release agent to provide 0.3
percent by weight in the final product. A portion
of the resulting material was pressed into 1/2-
inch diameter pellets and found to exhibit a burn
rate of 0.275 inches per second at 1,000 psig with
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a pressure exponent of 0.79. The remainder of the
material was pressed into pellets 1/8-inch
diameter by 0.07-inch thickness on a rotary tablet
press. The pellet density was determined to be
1.88 g/cc. The theoretical flame temperature of
this composition was 2,358°K and was calculated to
provide a gas mass fraction of 0.72.
Example 4
This example discloses the preparation of a
reusable stainless steel test fixture used to
simulate driver's side gas generators. The test
fixture, or simulator, consisted of an igniter
chamber and a combustion chamber. The igniter
chamber was situated in the center and had 24,
0.10 inch diameter ports exiting into the combus-
tion chamber. The igniter chamber was fitted with
an igniter squib. The igniter chamber wall was
lined with 0.001 inch thick aluminum foil before -
24/+60 mesh igniter granules were added. The
outer combustion chamber wall consisted of a ring
with nine exit ports. The diameter of the ports
was varied by changing rings. Starting from the
inner diameter of the outer combustion chamber
ring, the combustion chamber was fitted with a
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0.004 inch aluminum shim, one wind of 30 mesh
stainless steel screen, four winds of a 14 mesh
stainless steel screen, a deflector ring, and the
gas generant. The generant was held intact in the
combustion chamber using a "donut" of 18 mesh
stainless steel screen. An additional deflector
ring was placed around the outside diameter of the
outer combustion chamber wall. The combustion
chamber was fitted with a pressure port. The
simulator was attached to either a 60 liter tank
or an automotive air bag. The tank was fitted
with pressure, temperature, vent, and drain ports.
The automotive air bags have a maximum capacity of
55 liters and are constructed with two 1/2 inch
- diameter vent ports. Simulator tests involving an
air bag were configured such that bag pressures
were measured. The external skin surface tempera-
ture of the bag was monitored during the inflation
event by infrared radiometry, thermal imaging, and
thermocouple.
Example 5
Thirty-seven and one-half grams of the 1/8-
inch diameter pellets prepared as described in
Example 3 were combusted in an inflator test
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device vented into a 60 L collection tank as
described in Example 4, with the additional
incorporation of a second screened chamber
containing 2 winds of 30 mesh screen and 2 winds
of 18 mesh screen. The combustion produced a
combustion chamber pressure of 2,000 psia and a
pressure of 39 psia in the 60 L collection tank.
The temperature of the gases in the collection
tank reached a maximum of 670°K at 20
milliseconds. Analysis of the gases collected in
the 60 L tank showed a concentration of nitrogen
oxides (NOX) of 500 ppm and a concentration of
carbon monoxide of 1,825 ppm. Total expelled
particulate as determined by rinsing the tank with
methanol and evaporation of the rinse was found to
be 1,000 mg.
Examt~ 1 a 6
The test of Example 4 was repeated except
that the 60 L tank was replaced with a 55 L vented
bag as typically employed in driver side
automotive inflator restraint devices. A
combustion chamber pressure of 1,900 psia was
obtained with a full inflation of the bag
occurring. An internal bag pressure of 2 psig at
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peak was observed at approximately 60 milliseconds
after ignition. The bag surface temperature was
observed to remain below 83°C which is an improve-
ment over conventional azide-based inflators,
while the bag inflation performance is quite
typical of conventional systems.
Example 7
The nitrate salt of copper tetraammine was
prepared by dissolving 116.3 g of copper(II)
nitrate hemipentahydrate in 230 mL of concentrated
ammonium hydroxide and 50 mL of water. Once the
resulting warm mixture had cooled to 40°C, one
liter of ethanol was added with stirring to
precipitate the tetraammine nitrate product. The
dark purple-blue solid was collected by
filtration, washed with ethanol, and air dried.
The product was conf firmed to be Cu (NH3 ) 4 (N03 ) z by
elemental analysis. The burning rate of this
material as determined from pressed 1/2-inch
diameter pellets was 0.18 inches per second at
1,000 psig.
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Exam~r~le 8
The tetraammine copper nitrate prepared in
Example 7 was formulated with various supplemental
oxidizers and tested for burning rate. In all
5 cases, 10 g of material were slurried with
approximately 10 mL of methanol, dried, and
pressed into 1/2-inch diameter pellets. Burning
rates were measured at 1,000 psig, and the results
are shown in the following table.
10 Copper Tetra- Oxidizer Burn Rate (ips)
ammine Nitrate
88% Cu0 (60) 0.13
Sr(N03)z (60)
92% Sr(N03)~ (8%) 0.14
90o NH4N03 (100) 0.25
15 78% Bi203 (22 0 ) 0 . 10
85% SrOz (15%) 0.18
Example 9
A quantity of hexaamminecobalt(III) nitrate
was prepared by a replacing ammonium chloride with
20 ammonium nitrate in the procedure for preparing of
hexaamminecobalt(III) chloride as taught by G.
Pass and H. Sutcliffe, Practical Inorganic
Chemistrv, 2nd Ed., Chapman & Hull, New York,
1974. The material prepared was determined to be
25 [Co(NH~)6](NOZ)3 by elemental analysis. A sample of
SUBSTITUTE SHEET (RULE 26)
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the material was pressed into 1/2-inch diameter
pellets and a burning rate of 0.26 inches per
second measured at 2,000 psig.
Example 10
The material prepared in Example 9 was used
to prepare three lots of gas generant containing
hexaamminecobalt(III) nitrate as the fuel and
ceric ammonium nitrate as the co-oxidizer. The
lots differ in mode of processing and the presence
or absence of additives. Burn rates were
determined from 1/2 inch diameter burn rate
pellets. The results are summarized below:
Formulation I Processing I Burn Rate
12 % (NH4) 2 [Ce (N03) 6] Dry Mix 0 . 19 ips
88 % [Co {NH3) 6] (N03) at 1690 psi
3
12 % (NHQ) 2 [Ce (N03) 6] Mixed with 0 .20 ips
88% [Co (NH3) 6] (N03) 3 35% MeOH at; .1690 psi
18 % (NH4) 2 [Ce (N03) 6] Mixed with 0 .20 ips
81 % [Co (NH3) 6] (N03) 10 % H20 at 1690 psi
3
1% Carbon Black
Example 11
The material prepared in Example 9 was used
to prepare several 10-g mixes of generant
compositions utilizing various supplemental
oxidizers. In all cases, the appropriate amount
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of hexaamminecobalt(III) nitrate and co-
oxidizers) were blended into approximately 10 mL
of methanol, allowed to dry, and pressed into 1/2-
inch diameter pellets. The pellets were tested
for burning rate at 1,000 psig, and the results
are shown in the following table.
Hexaammine- Co-oxidizer Burning Rate
cobalt (III) 1,000 psig
Nitrate
60 o Cu0 (40 0 ) 0 . 15
70% Cu0 (300) 0.16
83% Cu0 (10%) 0.13
Sr(N03)2 (7%)
88% Sr(N03)2 (12%) 0.14
70% Bi2O3 ( 30 0 0 . 10
)
83% NHQN03 (17%) 0.15
Example 12
Binary compositions of hexaamminecobalt(III)
nitrate ("HACN") and various supplemental
oxidizers were blended in 20 gram batches. The
compositions were dried for 72 hours at 200°F and
pressed into 1/2-inch diameter pellets. Burn
rates were determined by burning the 1/2 inch
pellets at different pressures ranging from 1000
to 4000 psi. The results are shown in the
following table.
SUBSTITUTE SHEET (RULE 2fi)
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48
Composition Rb (ips)at X Temp.
psi
Weight Ratio oK
1000 2000 3000 4000
HACN 0.19 0.28 0.43 0.45 1856
loo/o
HACN/Cu0 0.26 0.35 0.39 0.44 1861
90/10
HACN/Ce(NH4)z(NO,)60.16 0.22 0.30 0.38 -
88/12
HACN/Co20, 0.10 0.21 0.26 0.34 1743
90/10
HACN/Co (N03) 0.13 0.22 0 . 0. 41 1865
z6Hz0 35
90/10
HACN/Vz05 0.12 0.16 0.21 0.30 1802
85/15
HACN/FezO, 0.12 0.12 0.17 0.23 1626
75/25
HACN/Co,04 0.13 0.20 0.25 0.30 1768
81.5/18.5
HACN/MnOz 0.11 0.17 0.22 0.30 -
80/20
HACN/Fe (NO,) 0. 0.22 0. 31 0. 48 -
~9H20 14
90/10
HACN/A1 (NOD) 0.10 0.18 0.26 0.32 1845
z6H20
90/10
HACN/Mg (N03) 0.16 0.24 0. 32 0.39 2087
z2Hz0
90/10
Example 13
A processing method was devised for preparing
small parallelepipeds ("pps.") of gas generant on
a laboratory scale. The equipment necessary for
forming and cutting the pps. included a cutting
table, a roller and a cutting device. The cutting
SUBSTITUTE SHEET (RULE 26)
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49
table consisted of a 9 inch x 18 inch sheet of
metal with 0.5 inch wide paper spacers taped along
the length-wise edges. The spacers had a
cumulative height 0.043 inch. The roller
consisted of a 1 foot long, 2 inch diameter
cylinder of teflon. The cutting device consisted
of a shaft, cutter blades and spacers. The shaft
was a 1/4 inch bolt upon which a series of
seventeen 3/4 inch diameter, 0.005 inch thick
stainless steel washers were placed as cutter
blades. Between each cutter blade, four 2/3 inch
diameter, 0.020 inch thick brass spacer washers
were placed and the series of washers were secured
by means of a nut. The repeat distance between
the circular cutter blades was 0.085 inch.
A gas generant composition containing a
water-soluble binder was dry-blended and then 50-
70 g batches were mixed on a Spex mixer/mill for
five minutes with sufficient water so that the
material when mixed had a dough-like consistency.
A sheet of velostat plastic was taped to the
cutting table and the dough ball of generant mixed
with water was flattened by hand onto the plastic.
A sheet of polyethylene plastic was placed over
the generant mix. The roller was positioned
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parallel to the spacers on the cutting table and
the dough was flattened to a width of about 5
inches. The roller was then rotated 90 degrees,
placed on top of the spacers, and the dough was
5 flattened to the maximum amount that the cutter
table spacers would allow. The polyethylene
plastic was peeled carefully off the generant and
the cutting device was used to cut the dough both
lengthwise and widthwise.
10 The velostat plastic sheet upon which the
generant had been rolled and cut was unfastened
from the cutting table and placed lengthwise over
a 4 inch diameter cylinder in a 135°F convection
oven. After approximately 10 minutes, the sheet
15 was taken out of the oven and placed over a 1/2
inch diameter rod so that the two ends of the
plastic sheet formed an acute angle relative to
the rod. The plastic was moved back and forth
over rod so as to open up the cuts between the
20 parallelepipeds ("pps."). The sheet was placed
widthwise over the 4 inch diameter cylinder in the
135°F convection oven and allowed to dry for
another 5 minutes. The cuts were opened between
the pps. over the 1/2 inch diameter rod as before.
25 By this time, it was quite easy to detach the pps.
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from the plastic. The pps. were separated from
each other further by rubbing them gently in a
pint cup or on the screens of a 12 mesh sieve.
This method breaks the pps. into sinqlets with
some remaining doublets. The doublets were split
into singlets by use of a razor blade. The pps.
were then placed in a convection oven at 165-225°F
to dry them completely. The crush strengths (on
edge) of the pps. thus formed were typically as
great or greater than those of 1/8 diameter
pellets with a 1/4 inch convex radius of curvature
and a 0.070 inch maximum height which were formed
on a rotary press. This is noteworthy since the
latter are three times as massive.
Example 14
A gas generating composition was prepared
utilizing hexaamminecobalt(III) nitrate,
(NH3) sco] (N03) 3, powder (78. 07%, 39. 04 g) , ammonium
nitrate granules (19.93%, 9.96 g), and ground
polyacrylamide, MW 15 million (2.00%, 1.00 g).
The ingredients were dry-blended in a Spex
mixer/mill for one minute. Deionized water (12%
of the dry weight of the formulation, 6 g) was
added to the mixture which was blended for an
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additional five minutes on the Spex mixer/mill.
This resulted in material with a dough-like
consistency which was processed into
parallelepipeds (pps.) as in Example I3. Three
additional batches of generant were mixed and
processed similarly. The pps. from the four
batches were blended. The dimensions of the pps.
were 0.052 inch x 0.072 inch x 0.084 inch.
Standard deviations on each of the dimensions were
on the order of 0.010 inch. The average weight of
the pps. was 6.62 mg. The bulk density, density
as determined by dimensional measurements, and
density as determined by solvent displacement were
determined to be 0.86 g/cc, 1.28 g/cc, and 1.59
I5 g/cc, respectively. Crush strengths of 1.7 kg (on
the narrowest edge) were measured with a standard
deviation of 0.7 kg. Some of the pps. were
pressed into 1/2 inch diameter pellets weighing
approximately three grams. From these pellets the
burn rate was determined to be 0.13 ips at 1000
psi with a pressure exponent of 0.78.
Example 15
A simulator was constructed according to
Example 4. Two grams of a stoichiometric blend of
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Mg/Sr(N03)2/nylon igniter granules were placed into
the igniter chamber. The diameter of the ports
' exiting the outer combustion chamber wall were
3/16 inch. Thirty grams of generant described in
Example 14 in the form of parallelepipeds were
secured in the combustion chamber. The simulator
was attached to the 60 L tank described in Example
4. After ignition, the combustion chamber reached
a maximum pressure of 2300 psia in 17
milliseconds, the 60 L tank reached a maximum
pressure of 34 psia and the maximum tank
temperature was 640°K. The NOX, CO and NH3 levels
were 20, 380, and 170 ppm, respectively, and 1600
mg of particulate were collected from the tank.
Example 16
A simulator was constructed with the exact
same igniter and generant type and charge weight
as in Example 15. In addition the outer
combustion chamber exit port diameters were
identical. The simulator was attached to an
automotive safety bag of the type described in
Example 4. After ignition, the combustion chamber
reached a maximum pressure of 2000 psia in 15
milliseconds. The maximum pressure of the
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inflated air bag was 0:9 psia. This pressure was
reached 18 milliseconds after ignition. The
maximum bag surf ace temperature wad 67°C.
Example 17
. ~ A gas generating composition was prepared
utilizing hexaamminecobalt(III) nitrate powder
(76.29%, 76.29 g), ammonium nitrate granules
~,
(15.71%, 15.71 g, Dynamit Nobel, granule size:
<350 micron), cupric oxide powder formed
pyrometallurgically (5.00%, S.OO g) and guar gum .
(3.00%, 3.00 g). The ingredients were dry-blended
in a Spex mixer/mill for one minute. Deionized"
water (18% of the dry weight of the formulation, 9
g) was added to 50 g of the mixture which was
1.5 , blended for an additional five minutes on the Spex
mixer/mill. This resulted in material with a
dough-like consistency which was processed into
parallelepipeds (pps.) as in Example 13. The same
process was repeated for the othex 50 g of dry-
blended generant and the two batches of pps. were
blended together. The average,dimensions of the
blended pps. were 0.070 inch x 0.081 inch x ,0.088
. inch. Standard deviations on each of the
dimensions were ow the order of 0.010 inch. The
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average weight of the pps. was 9.60 mg. The bulk
density, density as determined by dimensional
measurements, and density as determined by solvent
displacement were determined to be 0.96 g/cc, 1.17
5 g/cc, and 1.73 g/cc, respectively. Crush
strengths of 5.0 kg (on the narrowest edge) were
measured with a standard deviation of 2.5 kg.
Some of the pps. were pressed into 1/2 inch
diameter pellets weighing approximately three
10 grams. From these pellets the burn rate was
determined to be 0.20 ips at 1000 psi with a
pressure exponent of 0.67.
Example 18
A simulator was constructed according to
15 Example 4. One gram of a stoichiometric blend of
Mg/Sr(N03)2/nylon and two grams of slightly over-
oxidized B/KN03 igniter granules were blended and
placed into the igniter chamber. The diameter of
the ports exiting the outer combustion chamber
20 wall were 0.166 inch. Thirty grams of generant
described in Example 17 in the form of parallele-
pipeds were secured in the combustion chamber.
The simulator was attached to the 60 L tank de-
scribed in Example 4. After ignition, the
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combustion chamber reached a maximum pressure of
2540 psia in 8 milliseconds, the 60 L tank reached
a maximum pressure of 36 psia and the maximum tank
temperature was 600°K. The NOX, CO, and NH3 levels
were 50, 480, and 800 ppm, respectively, and 240
mg of particulate were collected from the tank.
Example 19
A simulator was constructed with the exact
same igniter and generant type and charge weight
as in Example 18. In addition the outer
combustion chamber exit port diameters were
identical. The simulator was attached to an
automotive safety bag of the type described in
Example 4. After ignition, the combustion chamber
reached a maximum pressure of 2700 psia in 9
milliseconds. The maximum pressure of the
inflated air bag was 2.3 psig. This pressure was
reached 30 milliseconds after ignition. The
maximum bag surface temperature was 73°C.
Example 20
A gas generating composition was prepared
utilizing hexaamminecobalt(III) nitrate powder
(69.50%, 347.5 g), copper(II) trihydroxy nitrate,
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[Cuz (OH) 3NO3] , powder (21 . 5%, 107 . 5 g) , 10 micron
RDX (5.00%, 25 g), 26 micron potassium nitrate
(1.00%, 5 g) and guar gum (3.00%, 3.00 g). The
ingredients were dry-blended with the assistance
of a 60 mesh sieve. Deionized water (23% of the
dry weight of the formulation, 15 g) was added to
65 g of the mixture which was blended for an addi-
tional five minutes on the Spex mixer/mill. This
resulted in material with a dough-like consistency
which was processed into parallelepipeds (pps.) as
in Example 13. The same process was repeated for
two additional 65 g batches of dry-blended
generant and the three batches of pps. were
blended together. The average dimensions of the
pps. were 0.057 inch x 0.078 inch x 0.084 inch.
Standard deviations on each of the dimensions were
on the order of 0.010 inch. The average weight of
the pps. was 7.22 mg. The bulk density, density
as determined by dimensional measurements, and
density as determined by solvent displacement were
determined to be 0.96 g/cc, 1.23 g/cc, and 1.74
g/cc, respectively. Crush strengths of 3.6 kg (on
the narrowest edge) were measured with a standard
deviation of 0.9 kg. Some of the pps. were
pressed into 1/2 inch diameter pellets weighing
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58
approximately three grams. From these pellets the
burn rate was determined to be 0.27 ips at 1000
psi with a pressure exponent of 0.51.
Example 21
A simulator was constructed according to
Example 4. 1.5 grams of a stoichiometric blend of
Mg/Sr(NO3}2/nylon and 1.5 grams of slightly over-
oxidized B/KN03 igniter granules were blended and
placed into the igniter chamber. The diameter of
the ports exiting the outer combustion chamber
wall were 0.177 inch. Thirty grams of generant
described in Example 20 in the form of parallele-
pipeds were secured in the combustion chamber.
The simulator was attached to the 60 L tank de-
scribed in Example 4. After ignition, the
combustion chamber reached a maximum pressure of
3050 psia in 14 milliseconds. The NOX, CO, and NH3
levels were 25, 800, and 90 ppm, respectively, and
890 mg of particulate were collected from the
tank.
Example 22
A gas generating composition was prepared
utilizing hexaamminecobalt(III) nitrate powder
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(78.00%, 457.9 g), copper(II) trihydroxy nitrate
powder (19.00%, 111.5 g), and guar gum (3.00%,
17.61 g). The ingredients were dry-blended .and
then mixed with water (32.5~°a of the dry weight of
the formulation, 191 g) in a Baker-Perkins pint
,mixer for 30 minutes. To a portion of the
resulting wet cake (220 g), 9.2 additional grams
of copper(II) trihydroxy nitrate and 0.30
additional grams of guar gum were added as well as
. ~
~ 0.80 g of carbon black (Monarch 1100). This new
formulation was blended for 30 minutes on a Baker-
Perkins mixer. The wet cake was placed in a ram
extruder with a barrel diameter of 2 inches and a
die orifice diameter of 3/32 inch (0.09038 inch).
The extruded material was cut into lengths of
about one foot, allowed to dry under ambient .
conditions overnight, placed into an enclosed
container holding water in order to moisten and
thus soften the material, chopped into lengths of
about 0.1 inch and dried at 165°F. The dimensions
of the resulting extruded cylinders were an
average length of 0.113 inches and an average
diameter of 0.091 inches. The bulk density,
density as determined by dimensional measurements,
and density as determined by solvent displacement
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were 0.86 g/cc, 1.30 g/cc, and 1.61 g/cc,
respectively. Crush strengths of 2.1 and 4.1 kg
were measured on the circumference and axis,
respectively. Some of the extruded cylinders u:ere
5 pressed into 1/2 inch diameter pellets weighing
approximately three grams. From these pellets the
burn rate was determined to be 0.22 ips at 1000
psi with a pressure exponent of 0.29.
Example 23
10 Three simulators were constructed according
to Example 4. 1.5 grams of a stoichiometric blend
of Mg/Sr(N03)z/nylon and 1.5 grams of slightly
over-oxidized B/KN03 igniter granules were blended
and placed into the igniter chambers. The
15 diameter of the ports exiting the outer combustion
chamber wall were 0.177 inch, 0.166 inch, and
0.152 inch, respectively. Thirty grams of
generant described in Example 22 in the form of
extruded cylinders were secured in each of the
20 combustion chambers. The simulators were, in
succession, attached to the 60 L tank described in
Example 4. After ignition, the combustion
chambers reached a maximum pressure of 1585, 1665,
and 1900 psia, respectively. Maximum tank
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pressures were 32, 34, and 35 psia, respectively.
The NOX levels were 85, 180, and 185 ppm whereas
the CO levels were 540, 600, and 600 ppm,
respectively. NH3 levels were below 2 ppm.
Particulate levels were 420, 350, and 360 mg,
respectively.
Example 24
The addition of small amounts of carbon to
gas generant formulations have been found to
improve the crush strength of parallelepipeds and
extruded pellets formed as in Example 13 or
Example 22. The following table summarizes the
crush strength enhancement with the addition of
carbon to a typical gas generant composition
within the scope of the present invention. All
percentages are expressed as weight percent.
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Table 3
Crush Strength Enhancement with Addition of Carbon
%HACN %CTN %Guar %Carbon Fo~'cn Strength
65:00 30.00 5.00 0.00 EP 2.7 kg
64.75 30.00 4.50 0.75 EP 5.7 kg
78.00 19.00 3.00 0.00 pps. 2.3 kg.
72.90 23.50 3.00 0.60 pps. 5.8 kg
78.00 19.00 3.00 0.00 EP 2.3 kg
.
' 7 3.00 23.50 3.00 0.50 EP 4.1 kg
HACN = hexaamminecobalt(III) nitrate,
[ (NH3) 6Co] (N03) 3 (Thiokol)
CTN = copper (II) trihydroxy nitrate, (Cu2 (OH3) N03]
(Thiokol)
Guar = guar gum (Aldrich)
Carbon = °Monarch'~~1100" carbon black (Cabot)
EP = extruded pellet (see Example 22)
pps. - parallelepipeds (see Example 13)
strength = crush strength of pps. or extruded
pellets in kilograms.
Example 25
Hexaamminecobalt(III) nitrate was pressed
into.four gram pellets with a diameter of 1/2
inch. Qrie half of the pellets were weighed and
placed in a 95°C oven for 700 hours. After aging,
the pellets were weighed once again. No loss in
weight was observed. The burn rate of the pellets
held at ambient temperature was 0.16 ips at 1000
psi with a pressure exponent of 0.60. The burn
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rate of the pellets held at 95°C for 700 hours was
0.15 at 1000 psi with a pressure exponent of 0.68.
Example 26
A gas generating composition was prepared
utilizing hexaamminecobalt(III) nitrate powder
(76.00%, 273.6 g), copper(II) trihydroxy nitrate
powder (16.OOo, 57.6 g), 26 micron potassium
nitrate (5.00 0, 18.00 g), and guar gum (3.00%,
10.8 g). Deionized water (24.9% of the dry weight
of the formulation, 16.2 g) was added to 65 g of
the mixture which was blended for an additional
five minutes on the Spex mixer/mill. This
resulted in material with a dough-like consistency
which was processed into parallelepipeds (pps.) as
in Example 13. The same process was repeated for
the other 50-65 g batches of dry-blended generant
and all the batches of pps. were blended together.
The average dimensions of the pps. were 0.065 inch
x 0.074 inch x 0.082 inch. Standard deviations on
each of the dimensions were on the order of 0.005
inch. The average weight of the pps. was 7.42 mg.
The bulk density, density as determined by
dimensional measurements, and density as
determined by solvent displacement were determined
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to be 0.86 g/cc, 1.15 g/cc, and 1.68 g/cc, respec-
tively. Crush strengths of 2.1 kg (on the
narrowest edge) were measured with a standard
deviation of 0.3 kg. Some of the pps. were
pressed into ten, one half inch diameter pellets
weighing approximately three grams. Approximately
60 g of pps. and five 1/2 inch diameter pellets
were placed in an oven held at 107°C. After 450
hours at this temperature, 0.25% and 0.410 weight
losses were observed for the pps. and pellets,
respectively. The remainder of the pps. and
pellets were stored under ambient conditions.
Burn rate data were obtained from both sets of
pellets and are summarized in Table 4.
Table 4
Burn Rate Comparison Before and After Accelerated
Aging
Storage Conditions Burn Rate Pressure
at
1000 psi Exponent
24-48 Hours Q 0.15 ips 0.72
Ambient
450 Hours C 107C 0.15 ips 0.70
SUBSTITUTE SHEET (RULE 26)
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Example 27
Two simulators were constructed according to
Example 4. In each igniter chamber, a blended
mixture of 1.5 g of a stoichiometric blend of
5 Mg/Sr(N03)z/nylon and 1.5 grams of slightly over-
oxidized B/KN03 igniter granules were placed. The
diameter of the ports exiting the outer combustion
chamber wall in each simulator were 0.177 inch.
Thirty grams of ambient aged generant described in
10 Example 26 in the form of parallelepipeds were
secured in the combustion chamber of one simulator
whereas thirty grams of generant pps. aged at
107°C were placed in the other combustion chamber.
The simulators were attached to the 60 L tank
15 described in Example 4. Test fire results are
summarized in Table 5 below.
Table S
Test-Fire Results for Aged Generant
Aging Comb. Tank Tank NHS CO NOx Part.
2 0 Temp. Press.Press. Temp. Level Level Level Level
(psia)(psia) (K) (ppm) (ppm) (ppm) (mg)
Amb. 2171 31.9 628 350 500 80 520
107C 2080 31.6 629 160 500 100 480
SUBSTITUTE SHEET (RULE 26)
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Example 28
A mixture of 2Co (NH3 ) 3 (NOz ) 3 and
Co (NH3 ) 4 (NOz ) zCo (NH3 ) z (NOz ) 4 was prepared and pressed
in a pellet having a diameter of approximately
0.504 inches. The complexes were prepared within
the scope of the teachings of the Hagel, et al.
reference identified above. The pellet was placed
in a test bomb, which was pressurized to 1,000 psi
with nitrogen gas.
The pellet was ignited with a hot wire and
burn rate was measured and observed to be 0.38
inches per second. Theoretical calculations
indicated a flame temperature of 1805°C. From
theoretical calculations, it was predicted that
the major reaction products would be solid Co0 and
gaseous reaction products. The major gaseous
reaction products were predicted to be as follows:
Product Volume
Hz0 57 . 9
Nz 38.6
Oz 3.1
Example 29
A quantity of Co (NH3) 3 (NOz) 3 was prepared
according to the teachings of Example 1 and tested
using differential scanning calorimetry. It was
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observed that the complex produced a vigorous
exotherm at 200°C.
Example 30
Theoretical calculations were undertaken for
Co(NH3)3(NOZ)3. Those calculations indicated a
flame temperature of about 2,000°K and a gas yield
of about 1.75 times that of a conventional sodium
azide gas generating compositions based on equal
volume of generating composition ("performance
ratio"). Theoretical calculations were also
undertaken for a series of gas generating
compositions. The composition and the theoretical
performance data is set forth below in Table 6.
Table 6
Gas Generant Ratio Temp. Perf.
(C) Ratio
CO (NH,) 3 (NOZ) a - 1805 1 . 74
NH9 [Co (NH3) 2 (NOZ) 4] - 1381 1.81
NHQ [Co (NH3) 2 (NO2) ~] 99/1 1634 1 . 72
/B
Co (NH3) 6 (N03) 3 - 1585 2 . 19
[Co (NH3) 5 (N03) ] (N03) - 1637 2 . 00
2
[Fe (NzH4) 3] (N03) 2/Sr 87/13 2345 1 . 69
(N03) z
[Co (NH3) 6] (C104) 3/CaH286/14 2577 1.29
[Co (NH3) 5 (NOZ) ] (N03) - 1659 2 . 06
z
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Performance ratio is a normalized relation to a
unit volume of azide-based gas generant. The
theoretical gas yield for a typical sodium
azide-based gas generant (68 wt.% NaN3; 30 wt% of
MoSz; 2 wt % of S) is about 0 . 85 g gas/cc NaN3
generant.
Example 31
Theoretical calculations were conducted on
the reaction of [Co (NH3) 6] (C104) 3 and CaH2 as listed
in Table 6 to evaluate its,use in a hybrid gas
generator. If this formulation is allowed to
undergo combustion in the presence of 6.80 times
its weight in argon gas, the flame temperature
decreases from 2577°C to 1085°C, assuming 100%
efficient heat transfer. The output gases consist
of 86.8% by volume argon, 1600 ppm by volume
hydrogen chloride, 10.2% by volume water, and 2.9%
by volume nitrogen. The total slag weight would
be 6.1% by mass.
Example 32
Pentaamminecobalt(III) nitrate complexes were
synthesized which contain a common ligand in
addition to NH3. Aquopentaamminecobalt(III)
nitrate and pentaamminecarbonatocobalt(III)
nitrate were synthesized according to Inorg. Syn.,
vol. 4, p. 171 (1973).
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Pentaamminehydroxocobalt(III) nitrate was
synthesized according to H.J.S. King, J. Chem.
Soc., p. 2105 (1925) and O. Schmitz, et al., Zeit.
Anorg. Chem., vol. 300, p. 186 (1959). Three lots
of gas generant were prepared utilizing the
pentaamminecobalt(III) nitrate complexes described
above. In all cases guar gum was added as a
binder. Copper(II) trihydroxy nitrate,
[Cu2 (OH) 3N03] , was added as the co-oxidizer where
needed. Burn rates were determined from 1/2 inch
diameter burn rate pellets. The results are
summarized below in Table 7.
Table 7
Formulations Containing [Co (NH3) SX] (NOD) Y
Formulation %H20 Burn Rate
Added
97 . 0 0 [Co (NH3) 5 (HZO) 27% 0 . 16 ips
] (N03) 3
3% guar at 1000 psi
68 . 8% [Co (NH3) 5 (OH) ] 55 0 0 . 14 ips
(N03) 2
28.2% [Cuz (OH) 3N03] at 1000 psi
3.Oo guar
48 . 5 [Co (NH3) 5 (C03) ] 24 0 0 . 06 ips
(N03)
48 . 5 0 [Cuz (OH) 3N03 at 4150 psi
3.0% guar
Example 33
A formulation was prepared comprising the
following starting ingredients: 1) 72.84 wt.%
SUBSTITUTE SHEET (RULE 26)
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cobalthexaammine nitrate, 2) 21.5 wt.% basic
copper nitrate, 3) 5.0 wt.o guar gum, and 4) 0.66
wt.% carbon.
The formulation was processed as described in
5 Example 22 except a single screw extruder was
employed and the extruded cylinders incorporated a
0.035 inch center perforation. The formulations
were tested by the same procedure described in
Example 23 at various loadings ranging from 32 to
10 38 grams. The test results showed that
particulate values were between 0.6 g and 1.0 g
for all samples. The tank pressures ranged from
39 to 48 psia depending on load.
Example 34
15 A formulated blend to be extruded was
prepared comprising: 1) 38.75 wt.% basic copper
nitrate, 2) 36.38 wt.o hexaaminecobaltnitrate, 3)
19.5 wt.% guanidine nitrate, 4) 5.0 wt.% guar gum,
and 5) 0.37 wt.% carbon black. The blend was
20 prepared by mixing the ingredients according to
the procedure described in Example 33.
An initial test evaluation was carried out
with a 35 g sample of extruded material as
described in Example 23. The combustion pressure
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was 2808 psi, and the tank pressure was 39.9 psia.
The amounts of trace gas products were: ammonia
( 7 0 ppm) , NOX ( 4 0 ppm) , and CO ( 6 0 0 ppm) . The
particu~ate values were only 0.281 g. The
observed tank pressure of 39.9 psia compared to
that obtained with 33 g of formulation prepared
according to Example 33, whicr~ typically provided
39 to 40 psia under like conditions:
Example 35
A formulated blend to be extruded was
prepared~comprising: 1) 40.34 wt.% basic copper
nitrate, 2) 37.86 wt.% hexaaminecobaltnitrate, 3)
15.8 wt.% guanidine nitrate, 4) 5.7 wt.% guar gum,
and 5) 0.3 wt.% carbon black. The blend was
prepared by mixing the ingredients according to
the procedure described in Examples 33 and 34.
_ Results comparable to those of Example 34 were
expected and obtained.
Gas generants are described in U.S. Patent
~ Nos. 5,725,699 and 5,592,812.
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Summary
In summary the present invention provides gas
generating materials that overcome some of the
limitations of conventional azide-based gas
generating compositions. The complexes of the
present invention produce nontoxic gaseous
products including water vapor, oxygen, and
nitrogen. Certain of the complexes are also
capable of efficient decomposition to a metal or
metal oxide, and nitrogen and water vapor.
Finally, reaction temperatures and burn rates are
within acceptable ranges.
The invention may be embodied in other
specific forms without departing from its
essential characteristics. The described
embodiments are to be considered in all respects
only as illustrative and not restrictive. The
scope of the invention is, therefore, indicated by
the appended claims rather than by the foregoing
description.
