Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02242614 1998-07-09
WO 97!29927 PCTJUS97I00358
NONAZIDE GAS GENERATING COMPOSITIONS
BACKGROUND OF THE INVENTION
The present invention relates to relatively nontoxic
gas generating compositions which on combustion rapidly
generate gases that are useful for inflating occupant safety
restraints in motor vehicles, commonly referred to as
automotive air bags, and more particularly to nonazide gas
generants that produce combustion products having not only
acceptable toxicity levels, but also higher gas volume to solid
particulates at comparable flame temperatures than heretofore
obtained with commercially available nonazide compositions.
One of the disadvantages of nonazide gas generant
compositions is the amount and physical nature of the solid
residues formed during combustion. The solids produced as a
i5 result of combustion must be filtered and otherwise kept away
from contact with the occupants of the vehicle. It is
therefore highly desirable to develop compositions that produce
a minimum of solid particulates while still providing adequate
quantities of a nontoxic gas to inflate the safety device at a
high rate.
In addition to the fuel constituent, pyrotechnic
compositions employed in inflating occupant safety restraints
contain ingredients such as oxidizers to provide the required
oxygen for rapid combustion and reduce the quantity of toxic
gases generated, a catalyst to promote the conversion of toxic
oxides of carbon and nitrogen to innocuous gases, and a slag
forming constituent to cause the solid and liquid products
formed during and immediately after combustion to agglomerate
into filterable klinker like particulates. Other optional
additives, such as burning rate enhancers or ballistic
modifiers and ignition aids, which are used to control the
ignitability and combustion properties of the gas generant
composition have also been developed.
Other advantages and disadvantages of prior art
nonazide gas generant compositions in comparison with other gas
generants containing azides, have been extensively described in
the patent literature such as U.S. Patents No. 4,370,187_;
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4,909,549; 4,948,439; 5,084,118; 5,139,588 and 5,035,757
The objects of the present invention are to provide
nonazide gas generant compositions for inflating automotive air
bag safety restraints which provide higher volumes of nontoxic
gas with correspondingly lower concentrations of solid
decomposition products, than have been possible with prior art
nonazide gas generant compositions, and still maintain reduced
toxic gas formation and filterable slag formation.
SUMMARY OF THE INVENTION
The objects of the present invention are accomplished
by employing certain derivatives and compounds of guanidine and
other high nitrogen-containing compounds, alone or in
combination with other high nitrogen nonazides as fuels in gas
generant compositions.
More specifically, the present invention comprises
the use of one or more high nitrogen nonazides selected from
the group consisting of nitroguanidine, nitroaminoguanidine,
guanidine nitrate, guanidine perchlorate, guanidine picrate,
cyanuric hydrazide, and diammonium bitetrazole, alone or in
combination with other high nitrogen nonazides, such as
tetrazoles, bitetrazoles, triazines, and triazoles. From a'
practical standpoint the compositions of the present invention
also include some of the additives heretofore used with
nonazide gas generant compositions such as oxidizers, gas
conversion catalysts, ballistic modifiers, slag formers,
ignition aids and compounding aids.
The gas generant compositions of this invention are
prepared by the methods heretofore employed for prior art
compositions and generally, but not exclusively, involve the
dry blending and compaction of comminuted ingredients selected
for combination. However, certain gas generant compositions of
this invention are prepared when desired using a novel process
involving incorporation of wetted aqueous or nonaqueous high
nitrogen nonazide constituents during the preparation and
manufacturing stages. This allows the use of materials which
are classified as flammable solids rather than explosives by
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the U.S. Department of Transportation during the more hazardous
processing stages of manufacture.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention the
preferred high nitrogen nonazides employed as primary fuels in
gas generant compositions for automotive air bag safety
restraint systems include in particular guanidine compounds,
either separately or in combination, selected from the group
consisting of guanidine nitrate, aminoguanidine nitrate,
diaminoguanidine nitrate, triaminoguanidine nitrate (wetted or
unwetted), guanidine perchlorate (wetted or unwetted),
triaminoguanidine perchlorate (wetted or unwetted), guanidine
picrate, triaminoguanidine picrate, nitroguanidine (wetted o~r
unwetted), and nitroaminoguanidine (wetted or unwetted). Other
preferred high nitrogen nonazides employed as fuels in the gas
generant compositions of this invention, either separately or
in combination with the above described guanidine compounds,
include 2,4,6-trihydrazino-s-triazine (cyanuric hydrazide);
2,4,6-triamino-s-triazine (melamine); and diammonium 5,5'
bitetrazole.
The foregoing preferred primary high nitrogen
nonazide fuels can be suitably combined with other known
secondary high nitrogen nonazide fuels without sacrificing the
benefits resulting from their use. The secondary high nitrogen
nonazide fuels which can be combined with the preferred primary
high nitrogen nonazide guanidine, triazine, and tetrazole fue7.s
specifically discussed above, include other guanidine compounc'ts
such as the metal salts of nitroaminoguanidine, metal salts of
nitroguanidine, nitroguanidine nitrate, nitroguanidine
perchlorate, tetrazoles such as 1H-tetrazole, 5-aminotetrazole,
5-nitrotetrazole, 5-nitroaminotetrazole, 5,5'-bitetrazole,
diguanidinium-5,5'-azotetrazolate, triazoles, such ass
nitroaminotriazole, 3-nitro-1,2,4-triazole-5-one, triazines
such as melamine nitrate; and metallic and nonmetallic salts of
the foregoing tetrazoles, triazoles, and triazines. Tk~e
secondary high nitrogen nonazide fuels of the present invention
are employed in a concentration of at least 10~ by weight of
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the total multiple fuel composition and preferably in the range
of 25 to 75% by weight of the total multiple fuel composition.
The preferred multiple fuel compositions of the
gresent invention permit greater variability in the design of
fuels useful in gas generants for automobile air bag safety
restraint systems. Thus, it was discovered that the high gas ,
volumeJlow combustion solids ratios of the guanidine compounds
can be combined with other fuels having advantageous
properties, such as lower ignition threshold temperatures,
easier ignitability and improved burning rate tailoring
capability without sacrificing the desirable properties of the
individual components to provide synergistically improved
superior fuels. Practical gas generant compositions, involve
in addition to the fuel, various other components to achieve
specific improvements in the performance of the nonazide fuels.
When used in combination with other materials the preferred
primary or primary/secondary nonazide singular or multiple fuel
of the present invention, taken as a whole, should be used in
a concentration of at least 15% by weight of the total gas
generant composition.
The foregoing guanidines, alone or in combination
with other known high nitrogen nonazides, are generally
employed in combination with an oxidizer, which is designed to
supply most if not all of the oxygen required for combustion.
Suitable oxidizers are known in the art and generally comprise
inorganic nitrites, nitrates, chlorites, chlorates,
perchlorates, oxides, peroxides, persulfates, chromates, and
perchromates. Preferred oxidizers are alkali metal and
alkaline earth metal nitrates, chlorates, perchlorates such as
strontium nitrate, potassium nitrate, sodium nitrate, barium
nitrate, potassium chlorate, potassium perchlorate and mixtures
thereof. The oxidizer is generally employed in a concentration
thereof. The oxidizer is generally employed in a concentration
of about 10 to 85% by weight of the total gas generant
composition and preferably in a concentration of 25 to 75% by
weight of the total gas generant composition.
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The combustion of the fuels of the present invention
can be controlled by the addition of ballistic modifiers which
influence the temperature sensitivity and rate at which the
propellant burns. Such ballistic modifiers were primarily
3eveloped for solid rocket propellants but also have been found
useful in gas generants for inflatable devices. Ballistic
modifiers useful in the compositions of the present invention
include cyanoguanidine; and inorganic and organic salts of
cyanoguanidine including the alkali, alkaline earth, transition
metal, ammonium, guanidine, and triaminoguanidine salts; and
mixtures ,thereof. It has been discovered that mixtures of
cyanoguanidine and cyanoguanidine salts are also very useful as
ballistic modifiers for the gas generant compositions of this
invention. Inorganic ballistic modifiers which can be suitably
employed include oxides and halides of Group 4 to 12 of the
Periodic table of Elements (as developed by IUPAC and published
by CRC Press, 1989); sulfur, and metal sulfides; transition
metal chromium salts; and alkali metal and alkaline earth metal
borohydrides. Guanidine borohydrides and triaminoguanidine
borohydrides have also been used as ballistic modifiers.
Organometallic ballistic modifiers include metallocenes,
ferrocenes and metal acetyl acetonates. Other preferred
ballistic modifiers include nitroguanidine, guanidine chromate,
guanidine dichromate, guanidine trichromate, and guanidine
perchromate. The ballistic modifiers are employed in
concentrations varying from about 0.1 to 25~ by.weight of the
total gas generant composition.
In order to reduce the formation of toxic carbon
monoxide and nitrogen oxides it may be desirable to include in
the compositions of the present invention a catalyst which aids
in the conversion of carbon monoxide and nitrogen oxides formed
in the combustion to carbon dioxide and nitrogen. Compounds
which are useful as catalysts include in particular alkali
metal, alkaline earth metal and transition metal salts of
' 35 tetrazole, bitetrazole, and triazole. Transition metal oxides
themselves have also found utility as catalysts for tYr.e
described gas conversions. The catalysts are normally employed
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in concentrations of 0.1 to 20~ by weight of the total gas
generant composition.
Filterable slag formation can be enhanced by the
addition of a slag former. Suitable slag formers include lime,
borosilicates, vycor glasses, bentonite clay, silica, alumina,
silicates, aluminates, transition metal oxides and mixtures ,
thereof .
Another additive found to aid in the temperature of
ignition and' resulting combustion of the fuel used in
inflatable safety devices is an ignition aid. Ignition aids
include finely divided elemental sulfur, boron, carbon,
magnesium, aluminum, and Group 4 transition metal, transition
metal oxides, hydrides and sulfides, the hydrazine salt of 3-
nitro-1,2,4-triazole-5-one and mixtures thereof. Preferred
ignition aids include elemental sulfur, transition metal
oxides, magnesium and hafnium, titanium hydride, the hydrazine
salt of 3-nitro-1,2,4-triazole-5-one and mixtures thereof. The
ignition aids are normally employed in concentrations of 0.1 to
15~ by weight of the total fuel composition.
As indicated above the fuel compositions of the
present invention are prepared by physically blending the
desired components, such as by ball milling. It may be
desirable to add compounding agents to facilitate the
compounding and obtain homogeneous mixtures. Suitable
processing or compounding aids include molybdenum disulfide,
graphite, boron nitride, alkali metal, alkaline earth and
transition metal stearates, polyethylene glycols, polyacetals,
polyvinyl acetate, fluoropolymer waxes commercially available
under the trade name "Teflon" of "Viton" and silicone waxes.
The compounding aids are normally employed in concentrations of
about 0.1 to 15~ by weight of the total gas generant
composition.
The manner and order in which the components of the '
fuel composition of the present invention are combined and
compounded is not critical so long as a uniform mixture is
obtained and the compounding is carried out under conditions
which do not cause decomposition of the components employed.
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For example, the materials may be wet blended, or dry blended
and attrited in a ball mill or Red Devil type paint shaker and
then pelletized by compression molding. The materials may also
be ground separately or together in a fluid energy mill, sweco
vibroenergy mill or bantam micropulverizer and then blended or
further blended in a v-blender prior to compaction. However,
a significant discovery has been made involving the use of
wetted aqueous or nonaqueous nitroguanidine rather than the dry
material which allows processing to be carried on during the
manufacturing stage with nitroguanidine classified as a
Department of Transportation classified 4.1 flammable solid.
The various components described hereinabove for use
with the novel fuels of the present invention have been used
heretofore in other nonazide fuel compositions. References
involving nonazide fuel compositions describing various
additives useful in the present invention include U.S. Patents
No. 5,035,757; 5,084,118; 5,139,588; 4,948,439; 4,909,549; and
4,370,181,. As taught in that art and as will be apparent to
those skilled in the art it is possible to combine the
functions of two or more additives into a single composition.
Thus, alkaline earth metal salts of tetrazoles, bitetrazoles
and triazoles not only function as fuel components but can also
be~used as slag formers. It has been discovered that strontium
nitrate acts not only as an oxidizer and a slag former, but
also is effective as a ballistic modifier ignition aid
densifier and processing aid.
The process of the invention can utilize conventional
gas generator mechanisms of the prior art. These are referred
to in U.S. Patent No. 4,369,079. Generally, the methods of the
prior art involve the use of a hermetically sealed metallic
cartridge containing fuel, oxidizer, slag former, initiator and
other selected additives. Upon initiation of combustion by the
firing of a squib, the sealing mechanism ruptures. This allows
gas to flow out of the combustion chamber through several
orifices and into an aspirating venturi through which outside
air is drawn into
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the gas formed by combustion so that the gas utilized to
inflate the air bag is a mixture of the gas generated by the
combustion and outside air.
The present invention is further illustrated by the
following representative examples, wherein the components are
quantified in weight percent of the total composition unless
otherwise stated. Thus, the quantities of the fuels and
oxidizers illustrated are by weight percentages of the total
gas generant composition and the gaseous exhaust components are
stated as weight percentages of the total gaseous exhaust
either in the combustion chamber or in the exhaust from the
combustion chamber. The analysis is based on the
Thermochemical Propellant Evaluation Program developed by the
NASA Lewis Research Center at a chamber pressure of 1000 psi
and exhausting at atmospheric pressure.
EBAMPLEB 1-9
In Examples 1 to 9 the compositions of the present
invention are compared to the prior art compositions based on
5-aminotetrazole (Example 1, Table 1) as the sole nonazide
fuel. The components of the compositions of the examples are
set forth in the attached Tables 1 and 2. The oxidizer
employed is strontium nitrate. The Tables further show the
flame temperature in degrees Kelvin, the quantity and
composition of the exhaust gases generated upon combustion and
the quantity of gas in moles generated from 100 g of the fuel
composition.
TABLE 1
EXAMPLES 1 2 3 4 5
5-aminotetraaoie 28.60 16.19 11.29 14.30 9.53
3 O Guanidine nitrate --- 23.24 32.40 29.26 39.00
Nitrogusnidine --- --- --- --- --_
Nitroaminoguanidine --- --- --- --- -_-
Strontium nitrate 71.40 60.57 56.31 56.44 51.47
Stoichiometric system yes yes yes yes no
Fiame temp., Chmbr, K 2089 2124 2136 2208 2248 0
N02, Chmbr/Exh, 96 .008/0 .005/0 004/0 .004/0 .003/0
CO, Chmbr/Exh, 6 .014/0 .025!0 .028!0.165/0 .215/0
Nitrogen, Exh, 96 50.73 45.25 43.42 45.66 43.97
Oxygen, Exh, ~ 12.55 8.57 7.24 8.45 7.08 t
4 0 C02, Exh, 96 22.75 23.87 24.24 24.61 25.23
Water Vapor, Exh, 96 13.97 22.32 25.10 23.24 26.33
Gas Mass Fraction, Exh, 96 65.04 70.34 71.47 72.37 74.81
Moles of Gas/100g, Exh 2.27 2.57 2.73 2.68 2.81
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- TABLE 2
EXAMPLES 6 7 8 g
5-aminotetrazole 16.47 11.56 14.30 9.53
Guanidine nitrate 1 1.82 16.60 --- ---
Nitroguanidine 10.08 14.15 --- ---
Nitrvaminoguanidine --- --- 21.45 28.60
Strontium nitrate 61.63 57.69 64.25 61.87
' Stoichiometric system yes yes yes yes
Flame temp., Chmbr, K 2193 2227 2236 2287
NO2, ChmbNExh, 96 .005/0 .006/0.008/0.007/0
CO, Chmbr/Exh, 6 .052/0 .064/0.067/0.085/0
Nitrogen, Exh, 96 46.32 44.84 48.12 47.25
Oxygen, Exh, 6 8.53 7.19 11.25 10.28
C02, Exh, 96 24.54 25.13 24.08 24.52
Water Vapor, Exh, 96 20.46 22.62 18.25 19.67
Gas Mass Fraction, Exh, 96 72.55 72.55 70.99 72.97
Motes of Gas/100g, Exh 2.66 2.66 2.47 2.53
Example to
A uniform mixture of 16.27$ nitroaminoguanidine,
36.93 guanidine nitrate and 46.8 of strontium nitrate that
was analyzed resulted in the following properties:
EXAMPLE 10
Flame temp., Chmbr, K 2374
NOz, Chmbr/Exh, 96 .002/0
CO, Chmbr/Exh, 96 .167/0
Nitrogen, Exh, 96 42.43
Oxygen, Exh, 96 3.30
CO~, Exh, 96 25.07
Water Vapor, Exh, 96 29.19
3 0 Gas Mass Fraction, Exh, 77.09
96
Motes of Gas/100g, Exh 2.94
Examples 11-13
Mixtures of guanidine and strontium nitrate
nitrate
in the percentages indicated resulted
in
the
following
properties:
EXAM PLES 1 1 12 13
Guanidine nitrate 53.51 58.51 48.51
Strontium nitrate 46.49 41.49 51.49
Flame temp., Chmbr, K 2159 2328 1952
' 40 NOZ, Chmbr/Exh, 96 .002/0 0/0 .003/0
CO, Chmbr/Exh, k .035/0 .315/0 .004/0
Nitrogen, Exh, % 39.76 40.59 38.93
Oxygen, Exh, 96 4.59 4.35 9.04
C02, Exh, 96 24.98 26.47 23.42
Water Vapor, Exh, 96 30.67 32.51 28.61
Gas Mass Fraction, Exh, 74.68 79.69 74.68
96
Moles of GasI100g, Exh 2.96 3.08 2.83
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Example 14
A uniform mixture of 42.90 of nitroaminoguanidine
and 57.10 of strontium nitrate that was analyzed resulted in
the following properties:
EXAMPLE 14
Flame temp., Chmbr, K 2386
NO~, Chmbr/Exh, 96 .007/0
CO, Chmbr/Exh, 96 .12/0
Nitrogen, Exh, 96 45.51
Oxygen, Exh, 96 9.95
C03, Exh, 96 25.40
Water Vapor, Exh, 96 22.52
Gas Mass Fraction, Exh, 96 76.94
Moles of Gas/100g, Exh 2.66
Examples 15-16
Mixtures of nitroaminoguanidine, 5-aminotetrazole,
potassium nitrate and strontium nitrate in the percentages
indicated were analyzed and resulted in the following
properties:
EXAMPLES 15 16
Nitroaminoguanidine 23.02 18.02
5-aminotetrazole 16.44 21.44
Potassium nitrate 19.54 19.54
Strontium nitrate 41.00 41.00
Flame temp., Chmbr, K 2226 2321
NO2, ChmbrIExh, 96 .003/0 .002/0
CO, Chmbr/Exh, 96 .041 /0 .097!0
Nitrogen, Exh, 96 51.35 52.14
Oxygen, Exh, g6 6.81 4.38
3 0 C02, Exh, % 19.53 20.81
Water Vapor, Exh, 96 19.94 18.94
Gas Mass Fraction, Exh, 96 68.55 69.76
Moles of Gasll00g, Exh 2.49 2.50
Examples 17-18
Uniform mixtures of nitr oguanidine, guanidine nitrate
and strontium nitrate were pr epared in the percentages
indicated were analyzed resultingin the following properties:
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EXAMPLES 17 18
Nitroguanidine 23.75 18.75
Guanidine nitrate 27.85 32.85
Strontium nitrate 48.40 48.40
Flame temp., Chmbr, K 2296 2252
NOz, Chmbr/Exh, 96 .002/0 .002/0
CO, Chmbr/Exh, 96 .089/0 .064/0
Nitrogen, Exh, 96 41.90 41.38
Oxygen, Exh, 36 4.51 5.14
COz, Exh, 96 26.32 25.91
Water Vapor, Exh, 96 26.94 27.57
Gas Mass Fraction, Exh, 96 76.30 76.30
Moles of Gas/100g, Exh 2.85 2.87
Example 19
A uniform mixture comprising 28.90% diammonium
bitetrazole and 71.10% strontium nitrate was analyzed and
resulted in the following properties:
EXAMPLE 19
Flame temp., Chmbr, K 2129
2 0 N02, ChmbrlExh, 96 .005/0
CO, Chmbr/Exh, 96 .024/0
Nitrogen, Exh, ~6 50.51
Oxygen, Exh, 96 8.27
COz, Exh, 96 22.67
Water Vapor, Exh, 96 18.56
Gas Mass Fraction, Exh, 96 65.19
Moles of Gas/100g, Exh 2.35
Example 20, Table 5-2 (LTS-3): A mixture of 5-
aminotetrazole (5AT), guanidine nitrate, and strontium nitrate
was prepared having the following composition in percent by
weight: 25.00% SAT, 25.00% guanidine nitrate, and 50.00%
strontium nitrate. These powders were ground separately and
dry blended. When ignited at atmospheric pressure with a fuse
and a small ignition charge of Dupont 4227 smokeless powder,
the composition burned thoroughly leaving a hard, porous
klinker like residue which is easily filterable. The pH of an
800 ml aqueous rinse was 11.
Example 21, Table 5-2 (LTS-3): The composition of
Example 20 was again ignited at atmospheric pressure, but with
U
more difficulty, with only a fuse, and without the Dupont 4227
ignition charge. Again, the mixture burned and left a hard
porous klinker like residue which is easily filterable.
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Example 22, Table 1-1 or Table 5-1 (LTS-5): A
baseline mixture of 5AT and strontium nitrate was prepared
having the following composition in percent by weight: 28.60%
5AT and 71.40% strontium nitrate. These powders were prepared ,
and burned as in Example 20 with a fuse and ignition charge,
and burned as in Example 21 with only a fuse and without an ,
ignition charge with essentially identical results. However,
the pH of an 800 ml aqueous rinse was 7-8.
Example 23, Table 1-1 or Table 5-1 (LTS-5): The
mixture from Example 22 was, ignited at atmospheric pressure
with a propane torch. The composition burned completely
leaving a hard porous klinker like residue.
Example 24, Table 5-6 (LTS-11): A mixture of SAT,
guanidine nitrate, and strontium nitrate was prepared having
the following composition in percent by weight: 23.26% SAT,
16.08% guanidine nitrate, and 60.66% strontium nitrate. These
powders were ground separately and dry blended. When ignited
at atmospheric pressure with a fuse and a small ignition charge
of Dupont 4227 smokeless powder, the mixture burned smoothly
and completely and left a hard porous klinker like residue
which is readily filterable.
Example 25, Table 5-6 (LTS-11): The same mixture as
Example 24, when ignited at atmospheric pressure with only a
fuse, and without the Dupont 4227 ignition charge, burned
smoothly and thoroughly and left an easily filterable hard
porous klinker like residue.
Example 26, Table 5-5 (LTS-13): A mixture of SAT,
guanidine nitrate, and strontium nitrate was prepared having
the following composition in percent by weight: 20.60% SAT,
24.12% guanidine nitrate, and 55.28% strontium nitrate. These
powders were ground separately and dry blended. When ignited
at atmospheric pressure with a fuse and a small ignition charge
of Dupont 4227 smokeless powder, the mixture burned smoothly
and completely and left a hard porous klinker like residue
which is readily filterable. The pH of an 800 ml aqueous rinse
was 11.
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Example Z7, Table 5-5 (LTS-13): The same mixture as
Example 26, when ignited at atmospheric pressure with only a
fuse, and without the Dupont 4227 ignition charge, burned
smoothly and thoroughly and left an easily filterable hard
porous klinker residue.
Example 28, Table 5-4 {LTS-12): A mixture of SAT,
guanidine nitrate, and strontium nitrate was prepared having
the following composition in percent by weight: 26.79% 5AT,
12.49% guanidine nitrate, and 60.72% strontium nitrate. Th.e
powders were ground separately and dry blended. When ignited
at atmospheric pressure with a propane torch, the composition
burned completely forming a hard residue which was somewhat
porous and readily filterable.
Example 29, Table 1-2 or Table 5-3 (LTS-7): A
mixture of 5AT, guanidine nitrate, and strontium nitrate was
prepared having the following composition in percent by weight:
16.19% 5AT, 23.24% guanidine nitrate, and 60.57% strontium
nitrate. The powders were ground separately and dry blended.
When ignited with only a fuse, fuse and Dupont 4227 smokeless
2o powder, or a propane torch, the composition burned to
completion leaving a hard porous readily filterable klinker
like residue.
Example 30, Table 3-4 (LTS-22): A mixture of
nitroguanidine and strontium nitrate was prepared having the
following composition in percent by weight: 50.00%
nitroguanidine and 50.00% strontium nitrate. These powder's
were ground separately and dry blended. When ignited at
atmospheric pressure with only a fuse, fuse and Dupont 4227
smokeless powder, or a propane torch, the composition burned to
completion leaving a hard porous readily filterable klinker
like residue. The pH of an 800 m1 aqueous rinse Was 7-8.
Example 31, Table 3-2 {LTS-24): A mixture of
nitroguanidine and strontium nitrate was prepared having the
following composition in percent by weight: 40.00%
nitroguanidine, 60.00% strontium nitrate. These powders were
ground separately and dry blended. When ignited at atmospheric
pressure with only a fuse, fuse and Dupont 4227 smokele~~s
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powder, or a propane torch, the composition burned to
completion leaving a hard porous readily filterable klinker
like residue. The pH of a 800 ml aqueous rinse was 7-8. In
this example, it will be observed by those skilled in the art
that the flame temperature is 131 degrees cooler and the
nontoxic gas output is significantly greater than the baseline ,
nonazide 5-aminotetrazole formulation shown in Example 1,
Table 1.
Example 32, Table 4-2 (LTS-23): A mixture of
to nitroguanidine and guanidine nitrate and strontium nitrate was
prepared having the following composition in percent by weight:
25.00% nitroguanidine, 25.00% guanidine nitrate,
50.00% strontium nitrate. These powders were ground separately
and dry blended. When ignited at atmospheric pressure with
only a fuse or a propane torch the ignitabiiity was marginal.
When ignited with a combination fuse and Dupont 4227 smokeless
powder the ignitability was acceptable, the composition burned
to completion leaving a hard porous readily filterable klinker
like residue.
Example 33, Table 5-7 (LTS-15): A mixture of 5-
aminotetrazole, guanidine nitrate, nitroguanidine and strontium
nitrate was prepared having the following composition in
percent by weight: 16.47% 5-aminotetrazole, 11.82% guanidine
nitrate, 10.08% nitroguanidine, and 61.63% strontium nitrate.
These powders were ground separately and dry blended. When
ignited at atmospheric pressure with only a fuse, or fuse and
Dupont 4227 smokeless powder, the composition burned to
completion leaving a hard porous readily filterable klinker
like residue. Ignition with only a propane torch was marginal.
3o The pH of a 800 ml aqueous rinse was 7-8.
Exaatple 3~, Table 5-8 (LTS-16): A mixture of 5-
aminotetrazole, guanidine nitrate, nitroguanidine and strontium
nitrate was prepared having the following composition in
percent by weight: 11.56% 5-aminotetrazole, 16.60% guanidine
nitrate, 14.15% nitroguanidine, and 57.69% strontium nitrate.
These powders were ground separately and dry blended. When
ignited at atmospheric pressure with only a fuse, or fuse and
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Dupont 4227 smokeless powder, the composition burned to
completion leaving a hard porous readily filterable klinker
like residue. Ignition with only a propane torch was marginal.
The pH of a 800 mI aqueous rinse was 7-8.
Example 35, Table 3-1 (LTS-25): A mixture of
nitroguanidine and strontium nitrate was prepared having the
r
following composition in percent by weight: 35.00%
nitroguanidine and 65.00% strontium nitrate. These powders
were ground separately and dry blended. When ignited at
atmospheric pressure with only a fuse, fuse and Dupont 4227
smokeless powder, or a propane torch, the composition burned to
completion leaving a hard porous readily filterable klinker
like residue. The pH of an 800 ml aqueous rinse was 7-8. It
will be obvious to those skilled in the art that the
composition evaluated in this example provides a comparable
nontoxic gas output to the baseline 5-aminotetrazole
composition, but achieves it at a flame temperature which is
448° lower than the baseline composition.
Example 36, (LTS-27): A mixture of nitroguanidine, 5
2o aminotetrazole, strontium nitrate, and potassium nitrate was
prepared having the following composition in percent by weight:
20.72% nitroguanidine, 16.39% 5-aminotetrazole, 42.23%
strontium nitrate, and 20.22% potassium nitrate. These powders
were ground separately and dry blended. When ignited at
atmospheric pressure with only a fuse or a fuse and Dupont 4227
smokeless powder, the composition burned to completion and
appeared to burn faster than a composition using only strontium
nitrate as the oxidizer. A hard solid mass resulted.
Example 37, (LTS-29): A mixture of nitroguanidine
3o and barium nitrate was prepared having the following
composition in percent by weight: 60.00% barium nitrate and
_ 40.00% nitroguanidine. These powders were ground separately
and dry blended. When ignited at atmospheric pressure with a
fuse and Dupont 4227 smokeless powder, the composition burned
very smoothly in a uniform manner to completion. A hard mass
resulted after burning the composition.
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_ WO 97/29927 PCT/US97/00358
Example 38, (LTS-30): A mixture of guanidine
nitrate, 5-aminotetrazole, potassium perchlorate, and strontium
nitrate was prepared having the following composition in
percent by weight: 19.90% guanidine nitrate, 22.40% 5-
aminotetrazole, 14.70% potassium perchlorate, and 43.00%
strontium nitrate. These powders were ground separately and
dry blended. When ignited at atmospheric pressure with a fuse
and Dupont 4227 powder, the composition burned rapidly to
completion with an audible roar leaving a hard solid mass on
completion of combustion.
Example 39, (LTS-31): A mixture of barium nitrate,
sulfur, and nitroguanidine was prepared having the following
composition in percent by weight: 51.00% barium nitrate,
15.00% sulfur, and 34.00% nitroguanidine. These powders were
ground separately and dry blended. When ignited at atmospheric
pressure with a fuse and Dupont 4227 smokeless powder, the
composition burned rapidly to completion leaving a hard mass.
The composition appeared to burn more rapidly with the
incorporation of the sulfur.
Example 40, (LTS-32): A mixture of barium nitrate,
nitroguanidine, the sodium salt of cyanoguanidine, and
cyanoguanidine was prepared having the following composition in
percent by weight: 51.00% barium nitrate, 34.00%
nitroguanidine, 10.00% sodium salt of cyanoguanidine, and 5.00%
cyanoguanidine. These powders were ground separately and dry
blended. When ignited at atmospheric pressure with a fuse and
Dupont 4227 smokeless powder, the composition burned very
rapidly in a uniform manner to completion leaving a hard mass.
Example 41, (LTS-33): A mixture of guanidine
3o nitrate, 5-aminotetrazole, potassium chlorate, and strontium
nitrate was prepared having the following composition in
percent by weight: 19.90% guanidine nitrate, 22.40% 5
aminotetrazole, 20.00% potassium chlorate, and 37.70% strontium
nitrate. These powders were ground separately and dry blended.
When ignited at atmospheric pressure with a fuse and Dupont
4227 smokeless powder, the composition burned quickly and
erratically.
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_ WO 97/29927 PCT/US97/00358
TABLE 3
LTS-25 LTS-24 LTS-22
EXAMPLES 1 2 3 4 5
Nitroguanidine 35 40 45 50 55
Strontium Nitrate 65 60 55 50 45
Flame temp., Chmbr, K 1641 1958 2235 2467 2621
N02, Chmbr/Exh, 96 .007/0 .007/0.006/0.003/0 .001
/0
CO, Chmbr/Exh, 96 0/0 .005/0.054/03.32/0 1.58/.001
Gas Mass Fraction, Exh, 96 65.57 70.62 73.07 75.52 77.97
l0 Moles of Gas/100g, Exh 2.28 2.53 2.54 2.75 2.86
pH of aqueos Rinse of
combustion products 7-8 7-8 ___ 7_g 7_g
-17-
CA 02242614 1998-07-09 _
WO 97/29927 PCT/US97/00358
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CA 02242614 1998-07-09
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19
CA 02242614 1998-07-09
WO 97/29927 PCTIUS97/00358
The foregoing examples demonstrates that a
significant increase in nontoxic gas output is realized at
acceptable and comparable flame temperatures when compared with
a very high gas output state of the art baseline composition ,
containing 5-aminotetrazole and strontium nitrate. The
substitution of guanidine nitrate for the baseline
5-aminotetrazole fuel component (Examples 11-13) results in a
much higher gas mass fraction. This allows a lower weight and
volume of propellant to be required in a volume-limited
application. In addition because of the decreased
concentration of particulates formed during the decomposition
fewer solids need to be filtered out of the gas stream. It
will also be apparent to those skilled in the art that
insignificant levels of toxic gases such as nitrogen oxides and
carbon monoxide are formed during the combustion by the
preferred compositions without the use of a catalyst as shown
by the foregoing examples.
Even when the 5-aminotetrazole fuel of the
stoichiometric baseline nonazide composition is only partially
substituted with guanidine nitrate (Examples 2, 3, 4 and 5 of
Table 1), a significant increase in the gas mass fraction and
moles of gas results at comparable flame temperatures.
same result is also accomplished by substituting nitroguanidine
alone (Examples 1-5 of Table 3) or in combination with
guanidine nitrate for the baseline aminotetrazole component
(Examples 17 and 18). Again a significant improvement in gas
yield results at slightly higher but acceptable flame
temperatures. The flame temperature can also be reduced by
substitution of more guanidine nitrate for nitroguanidine with
essentially no change in gas fraction or yield. The use of
nitroguanidine and/or nitroaminoguanidine is attractive for
increasing the overall density of the gas generant composition
for use in volume limited applications. In addition, when
nitroguanidine is used as the fuel constituent, the flame
temperature of the gas generant composition is significantly
lower at a comparable molar gas output when compared to the
state of the art 5-aminotetrazole based composition. When the
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CA 02242614 1998-07-09
WO 97/29927 PCT/LTS97/00358
aminotetrazole fuel of the baseline composition is partially
substituted with nitroguanidine or a combination of
nitroguanidine and guanidine nitrate, a significant increase in
the moles of gas per 100 g of propellant at comparable f lame
temperatures results (Examples 6 and 7).
It has also been discovered that when nitroguanidin~e
is incorporated into all of the experimental gas generant
compositions used as examples of this invention, that the
ignitability of the compositions is greatly improved as well as
the burning rate. In addition to a significant increase in gas
yield and moles of gas formed, when compared with either prior
art azide or nonazide gas generant compositions, the use of
combinations of guanidine nitrate and nitroguanidine or
nitroaminoguanidine with 5-aminotetrazole as a multiple
constituent fuel for the gas generant allows greater precision
for tailoring the burning rate, burning rate pressure exponent,
ignitability, and the amount and physical form of the slag and
klinkers produced on combustion. The use of a multiple
ingredient fuel containing constituents with different
densities such as guanidine nitrate and/or nitroguanidine
and/or nitroaminoguanidine and/or 5-aminotetrazole as described
in the examples of this invention further allows a greater
capability for tailoring and adjusting the resultant gas
generant composition density while maintaining the required
reactant stoichiometry, as that exhibited with. prior art
singular fuels.
The discovery of the foregoing desirable and unique
characteristics of nitroguanidine and guanidine nitrate
discussed above for use in multiple or singular fuels for the
gas generant compositions disclosed in this invention is
considered to be a very important finding. Nitroguanidine can
therefore be classified as either a fuel constituent or a
r multipurpose fuel/ballistic modifier/ignition aid, catalyst and
densifier for the purposes of this invention.
Example 19 demonstrates that diammonium bitetrazole
when evaluated with strontium nitrate as the oxidizer provides
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WO 97/29927 PCTlUS97/00358
a fuel that yields a - gas mass fraction at comparable
temperature to 5-aminotetrazole.
While the foregoing examples illustrate the use of
preferred fuels and oxidizers it is to be understood that the ,,
practice of the present invention is not limited to the
particular fuels and oxidizers illustrated and similarly doss
not exclude the inclusion of other additives as described above
and as defined by the following claims.
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