Note: Descriptions are shown in the official language in which they were submitted.
CA 02211~79 1997-08-13
~'Gas-producing mixtures~
Gas generators are being used to an increasing
extent, for example in motor vehicles for life-saving
purposes. The gas-producing mixture usually contains
sodium azide. Sodium azide as such is poisonous, and
it can readily react with heavy metals, e.g. copper and
lead, to form extremely dangerous and vigorously
reacting compounds. Special precautions must therefore
be taken in the production of the raw material and of
the gas charge mixture, in its processing and in
quality control. For this reason the disposal of the
sodium azide, for example when exchanging defective gas
generators or when scrapping vehicles, also presents a
particular problem. Improper use must also be reliably
prevented.
There has been no lack of attempts to use other
substances in place of sodium azide. A common feature
of all proposed replacements for sodium azide is that
they contain organic carbon compounds, and as a rule
also organic nitrogen compounds. EP 0 519 485
describes the use of tetrazole or a derivative or
derivatives of tetrazole, or the use of one or more
compounds from the group consisting of cyanic acid
derivatives and their salts, one or more compounds from
the group consisting of triazine and triazine
derivatives, the use of urea, its salts, derivatives
and salts of these compounds: these compounds can also
be present as mixtures. Ammonium nitrate and nitrates
of sodium, potassium, magnesium, calcium and iron,
and/or peroxides of zinc, calcium, strontium or
magnesium, can be used as oxidants. Other gas-
producing components, cooling agents, reducing agents,
catalysts and/or porosity producing agents can be
added.
EP 0 438 851 describes a non-toxic, non-azide
CA 02211~79 1997-08-13
pyrotechnic composition which is suitable for use in
the production of substantially non-toxic combustion
products that include a gas in order to fill an
accident cushion. The composition includes a mixture
of at least one tetrazole or tetrazole compound
containing hydrogen in its molecule, at least one
oxygen-containing oxidant and at least one metal oxide
selected from cobalt oxide, nickel oxide, chromium
oxide, aluminium oxide and boron oxide. In the
o combustion a substantially non-toxic primary gas
mixture and filterable solids are produced.
Aminotetrazole, together with oxidants which can
contain perchlorates as well as nitrates, is employed,
by way of example.
A similar formulation is disclosed in European
patent EP 0 372 733: the use of tetrazoles and
triazoles in mixtures with ammonium perchlorate and
alkali nitrate as oxidants, in combination with an
additive to control combustion.
PCT application WO 94/01381 describes a gas-
producing agent for airbags consisting of organic
nitrocompounds and halogenates. By halogenates are to
be understood, for example, alkali metal chlorates,
bromates and their per-compounds. The following are
mentioned, inter alia, as combustion-controlling
catalysts: oxides, chlorides, carbonates, sulphonates
of the 4th to 6th series of the periodic
classification.
When the above-mentioned gas charges undergo
reaction to inflate airbags for motor vehicle safety,
proportions of toxic gases such as, for example, carbon
monoxide or nitrogen oxides can be present besides non-
toxic working gases such as nitrogen, carbon dioxide
and hydrogen. Limits such as, for example, the maximum
allowable concentration (MAC) in the workplace, are set
having regard to peak loads for these gases. Their
CA 02211~79 1997-08-13
~ formation is thermodynamically and kinetically
connected, and in the case of carbon monoxide is
controlled e.g. by the producer gas equilibrium. It
has further been found that mixtures which contain
nitrogen- and carbon-containing compounds and evolve
small proportions of NOX during combustion-evolve large
proportions of C0, and vice versa. The establishment
of these equilibria is temperature and pressure-
dependent. It is known that a sufficiently effective
influencing of the composition of the reaction gases
towards the formation of non-toxic products cannot be
achieved solely by physical measures, for example
control of the reaction by pressure and/or temperature.
Processes are known from the literature which have
the object of reducing these components of the reaction
gases. Thus, for example, the equilibrium can be
displaced at the expense of carbon monoxide formation
by the formation of carbonates by the addition of
alkaline slag-forming agents to the gas charge. At the
same time nitrogen oxides are converted into nitrates
or nitrites.
However, these measures have the disadvantage that
the yield of gas is made substantially worse by the
high proportion of slag. In addition, the slag must be
separated at some expense from the gaseous constituents
by filters or other retaining systems before the
working gases can be used, for example for the
inflation of the airbag.
While the use of nitrogen-free systems does lead
to the formation of nitrogen-free gases, this is at the
expense of a lower yield of gas. The reason for this
is that, to displace the producer gas equilibrium in
the direction of CO2, an excess of slag-forming oxygen-
carrying agent must be used. Hence hybrid systems have
already been proposed in which the reactions described
above are brought about by compressed air instead of by
CA 02211~79 1997-08-13
slag-forming oxidants. However, these concepts suffer
from the disadvantage of the high weight of the system
and the need to control or supplement the compressed
air.
According to US patent 3 910 595, to improve the
- yield the gas forming in the reaction is passed through
a venturi nozzle so that ambient air can be drawn in to
assist in the inflation of the airbag. Here, however,
it must be taken into account that this ambient air
greatly cools the hot gases. Particularly at low
ambient temperatures the resulting loss in volume for
inflating the gasbag must be compensated for by the
pyrotechnic mixture. The resulting increased
proportion of toxic reaction gases in the interior of
the vehicle can no longer be sufficiently reduced by
dilution.
The present invention provides non-toxic, azide-
free mixtures for the production of gas by combustion.
These gas-producing mixtures can be used, inter alia,
in safety devices, for example in airbag systems for
inflation of airbags in motor vehicles and aircraft.
However, they are also suitable for lifting heavy loads
by inflation of bags placed under them, or for
expulsion of e.g. fire extinguishing powder, or for
other measures where the performance of work requires
rapid formation of gases.
The mixtures in accordance with the invention
contain:
a) as nitrogen-containing compound (fuel) at least
one compound from the group: tetrazole, triazole,
triazine, cyanic acid, urea, their derivatives or
their salts;
b) as oxidant, at least three compounds from the
group of the peroxides, nitrates, chlorates or
perchlorates;
c) combustion moderators which are capable of
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~ influencing the combustion and its rate by
heterogeneous or homogeneous catalysis; and
~ optionally also
d) additions which are capable of reducing the
proportion of the toxic gases.
The mixtures in accordance with the invention are
not toxic, and in contrast to azide-containing mixtures
are easy to handle. They therefore require less outlay
on safety in the production of the raw materials and
mixtures and in their shaping, storage or disposal.
The nitrogen-containing compounds to be used
according to the invention are those which, in the
mixture with oxidants, mainly form in their
thermal/chemical reaction CO2, N2, ~2 and H2O, but do not
evolve any gases such as CO or NOX in concentrations
that could endanger health.
The mixtures according to the invention preferably
contain as nitrogen-containing compounds (fuels) one or
more tetrazole derivatives of the formula:
N _ N
(R3-)N / C-R
N
(R2)
in which Rl and R2 or R3 can be the same or different,
with either R2 or R3 being present, and standing for
hydrogen, hydroxy, amino, carboxyl, an alkyl radical
with 1 to 7 carbon atoms, an alkenyl radical with 2 to
7 carbon atoms, an alkylamino radical with 1 to 10
carbon atoms, an aryl radical, optionally substituted
with one or more substituents which can be the same or
different and are selected from the amino group, the
nitro group, alkyl radicals with 1 to 4 carbon atoms or
an arylamino radical in which the aryl radical can
optionally be substituted, or the sodium, potassium and
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guanidinium salts of the said tetrazole derivatives.
In these compounds:
R1 preferably stands ~or hydrogen, amino, hydroxy,
carboxyl, a methyl, ethyl, propyl or isopropyl, butyl,
isobutyl or tert-butyl, n-pentyl, n-hexyl, or n-heptyl
radical, a methylamino, ethylamino, dimethylamino, n-
heptylamino, n-octylamino or n-decylamino radical, a
tetrazole radical, a phenylamino radical, a phenyl,
nitrophenyl or aminophenyl radical; and
R2 or R3 preferably stands for hydrogen, a methyl
or ethyl radical, a phenyl, nitrophenyl or aminophenyl
radical.
Particularly preferred compounds are the tetrazole
derivatives 5-aminotetrazole, lithium, sodium,
potassium, zinc, magnesium, strontium or calcium 5-
aminotetrazolate, 5-aminotetrazole nitrate, sulphate,
perchiorate and similar compounds, 1-(4-aminophenyl)-
tetrazole, 1-(4-nitrophenyl)-tetrazole, l-methyl-5
dimethylaminotetrazole, 1-methyl-5-methylamino
tetrazole, 1-methyltetrazole, 1-phenyl-5-
aminotetrazole, l-phenyl-5-hydroxytetrazole,
1-phenyltetrazole, 2-ethyl-5-aminotetrazole, 2-methyl-
5-aminotetrazole, 2-methyl-5-carboxytetrazole, 2-
methyl-5-methylaminotetrazole, 2-methyltetrazole, 2-
phenyltetrazole, 5-(p-tolyl)tetrazole, 5-diallylamino
tetrazole, 5-dimethylaminotetrazole, 5-ethylamino
tetrazole, 5-hydroxytetrazole, 5-methyltetrazole, 5-
methylaminotetrazole, 5-n-decylaminotetrazole,
5-n-heptylaminotetrazole, 5-n-octylaminotetrazole, 5-
phenyltetrazole, 5-phenylaminotetrazole or bis-
(aminoganidine)-azotetrazole and diguanidinium-5,5'-
azotetrazolate, as well as 5,5'-bitetrazole and its
salts, such as the 5,5'-bi-lH-tetrazole ammonium
compounds.
The mixtures may contain: as triazine derivatives,
1,3,5-triazine, as triazole derivatives, 1,2,4-
CA 02211~79 1997-08-13
triazole-5-one, 3-nitro-1,2,4-triazole-5-one, as cyanic
acid derivatives, sodium cyanate, cyanuric acid,
cyanuric acid esters, cyanuric acid amide (melamine),
l-cyanoguanidine, sodium dicyanamide, disodium
cyanamide, dicyanodiamidine nitrate, dicyanodiamidine
sulphate, and as urea derivatives biuret, guanidine,
nitroguanidine, guanidine nitrate, aminoguanidine,
aminoguanidine nitrate, thiourea; triaminoguanidine
nitrate, aminoguanidine hydrogen carbonate,
azodicarbonamide, tetracene, semicarbazide nitrate, as
well as urethanes, ureides such as barbituric acid, and
derivatives thereof.
5-aminotetrazole is used as a particularly
preferred component. When this component is used in
the mixture the preferred proportion is 10-40~ by wt.
As derivatives of 5-aminotetrazole, its salts in which
the acidic hydrogen atoms in 5-aminotetrazole are
replaced in ~alt-like manner by toxicologically
acceptable elements such as calcium, magnesium or zinc,
are used. However, compounds in which the cation is
ammonium, guanidinium and its amino derivatives can
also be used.
Oxidants which may be used according to the
1nventlon are:
- peroxides of alkali and alkaline earth
metals, zinc peroxide, and the
peroxodisulphates of the said elements and
ammonium peroxodisulphate;
- ammonium nitrate, nitrates of alkali and
alkaline earth metals, in particular lithium,
sodium or potassium nitrate, and strontium
nitrate;
- halogen oxycompounds of the alkali or
alkaline earth metals or of ammonium,
particularly preferably potassium perchlorate
or ammonium perchlorate.
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-8-
The oxidants can be used singly or in mixtures.
In order to reduce the proportion of nitrogen oxides in
the reaction mixture as far as possible, it is
advantageous to keep the proportion of nitrate in the
oxidant mixture as small as possible, since part of the
nitrate can undergo thermal decomposition.
A preferred combination of the oxidants consists
of zinc peroxide, potassium perchlorate and at least
one nitrate, preferably sodium nitrate or strontium
nitrate, mixed in the ratio 1:2:10 and in a total
amount of about 60~ by wt. in the gas-producing
mixture. The chlorine-containing compounds then react
during the combustion to form harmless sodium/potassium
chloride. Ammonium perchlorate can also be considered
as perchlorate, alone or mixed with another halogen
oxycompound, but an excess must be avoided in order to
prevent the formation of corrosive hydrochloric acid.
If ammonium perchlorate is used, the simultaneous
presence of zinc compounds is particularly
advantageous, since the risk of hydrochloric acid being
formed can thereby be avoided. An excess of sodium and
potassium compounds is acceptable, since these
compounds react with the reaction gases to form
harmless carbonates. The partial or complete
replacement of the alkali nitrate by strontium nitrate
leads to a marked reduction in the amount of slag.
The ratio of the nitrogen-containing compounds,
for example the tetrazoles and triazoles, to the
oxidants in the mixture is balanced so that, on
combustion of the gas charge mixture, an excess of
oxygen is formed. This excess of oxygen displaces the
CO/CO2 equilibrium in the direction of carbon dioxide.
Substances or mixtures thereof which are capable
by heterogeneous or homogeneous catalysis of
influencing the combustion and its rate are used as
combustion moderators. Moderators which intervene in
CA 02211~79 1997-08-13
the reaction through heterogeneous catalysis are
metals, metal oxides and/or metal carbonates and/or
metal sulphides. Preferred metals to use are boron,
silicon, copper, iron, titanium, zinc or molybdenum.
Calcium carbonate can also be used. Mixtures of these
- moderators can likewise be used.
Moderators which intervene in the reaction through
homogeneous catalysis are, for example, sulphur, boron,
silicon or ferrocene and its derivatives. These
moderators are vapourized into the vapour phase as a
result of the temperatures occurring in the reaction,
and thus can intervene in the reaction either as such
or as after-products. The proportion of these
substances in the mixture can amount to up to about 8~
Furthermore the mixture according to the invention
can contain gas-producing additions which are capable
of reducing the proportion of the noxious gases such as
nitrogen oxides and/or carbon monoxide. The proportion
of these noxious gases in the gas mlxture produced is
determined by
- the stoichiometric composition of the mixture,
- the temperature and pressure of the reaction,
- additives for influencing the reaction or the
after-reaction, and by the
- design of the generator in which the reaction
takes place.
While in a closed system, such as, for example, a
pressure bomb, it is relatively easy to reach the
composition of the gas mixture which approximates to
the thermodynamic calculations, this can no longer be
achieved under the actual operating conditions in the
generator, since during the few milliseconds duration
of the reaction the equilibrium cannot be established.
According to the invention, therefore, suitable
substances which can bring about a catalytic effect are
introduced into the mixture or into the region of the
CA 02211~79 1997-08-13
- 1 0 -
outflowing gases. For this purpose the combustionmoderators described above and oxides of precious
metals can be used. Further possibilities consist in
the use of noble metals such as palladium, ruthenium,
rhenium, platinum or rhodium, which employ the excess
oxygen in the reaction gases in a subsequent reaction
to convert the carbon monoxide. A preferred mode of
use contemplates applying the additive materials on
ceramic or electrodepositing them on metal grids as a
support. Using this method it is possible in
particular to reduce the proportion of carbon monoxide
in the gas mixture.
To reduce the proportion of NOX, additional
substances are used whose chemical properties catalyse
in particular the conversion of nitrogen oxides, for
example nitrogen dioxide, to nitrates or nitrites. In
principle, all more or less strongly basically reacting
substances are suitable.
These include, for example, oxides, hydroxides or
carbonates of non-toxic elements such as, for example,
those of the alkali and alkaline earth metals, those of
zinc, and mixtures of these compounds. When these
compounds are used, nitrates and nitrites of the
elements are mainly formed. Further suitable materials
for reaction with NO2 are urea, guanidine and its
derivatives, compounds having NH2 groups, such as, for
example, amidosulphonic acids, amido complexes and the
like, and amides. A particularly preferred embodiment
contemplates the use of peroxides in the outlet
openings of the generator. A particular advantage of
this is that, beside the reduction of the nitrogen
oxides by the reaction described above, oxygen is also
formed for the following catalytic reaction with carbon
monoxide.
The additions according to the invention, either
alone or together, can either be introduced directly
CA 02211~79 1997-08-13
~ into the gas-producing charge or be placed in the
outflow passages of the generator. For use in the
outlet passages of the generator the additions are
suitably used in a compacted form, for example in the
form of tablets, pellets or granules. The quantity of
the additions used in the charge amounts to about 10
by wt. In the outlet channels the quantity of the
additions can be as much as 75~ by wt., based on the
gas charge.
A reduction in the CO content can surprisingly
also be achieved if part of the fuel consists of the
salts, particularly the calcium, magnesium or zinc
salts, of the aminotetrazole, preferably of the
corresponding salts of 5-aminotetrazole, or of urea
derivatives. In these cases it suffices to use only
two oxidants.
To influence the rate and temperature of reaction
further additives can be added. Such additives can for
example be boron or metal powders, for example
titanium, aluminium, zirconium, iron, copper,
molybdenum, as well as their stable hydrides. Their
proportion in the additions is of the order of 5 ~ by
wt.
The production of the gas charge mixtures
according to the invention is carried out in known
manner. For example, the components are mixed dry,
sieved, divided into portions and pressed to tablets.
The adjustment of the rate of combustion can be
achieved through the shape and size of the grains of
the bulk material obtained by breaking and sieving out
the fragments. The bulk material can be produced in
large quantities and adapted to meet particular
combustion requirements by mixing fractions with
different dynamic liveliness. To improve the safety or
improve the results of mixing, premixtures of 2 or 3
components can also be used. A mixture of oxidant and
CA 02211~79 1997-08-13
additions may, for example, be made before it comes
into contact with the nitrogen-containing compounds.
However, the mixture can also be produced by
kneading water-moistened eomponents, followed by
granulating, e.g. by passage through sieves, extrusion
or the like. In this case binders, for example
waterglass, "inorganie rubber" (phosphorus
chloronitrile) or even small proportions of organie
binders such as acrylic resin, PTFE, or guar gum, can
be used. Since the components employed are neither
toxic nor particularly reactive, and can only be eaused
to reaet in the enelosed space with the aid of special
igniters, no special safety precautions are necessary.
The bulk material thus obtained ean be used
direetly. To avoid abrasion of the loose material in
contact with the generators, which would lead to
changes in the combustion characteristics and would
represent a safety risk through its vigorous
eombustion, the bulk material ean be surfaee-eoated.
This can be done through a varnish coating, whieh can
optionally be provided with ignition-promoting
additions to assist in the ignition. Ignition-
promoting additions that come into consideration are
oxidants such as zinc peroxide and metal powders such
as titanium and zirconium. The applieation ean be
effeeted by spraying-on the solvent-eontaining eoating
agent, e.g. in a drum while evaporating off the
solvent.
For speeial fields of applieation porous grain
struetures in the grains ean be used. The produetion
of sueh porous struetures ean be effected by
eonventional methods, for example by adding soluble
salts and subsequently dissolving them out with
suitable solvents or by addition of thermally
deeomposable substanees sueh as, for example, ammonium
biearbonate, acetone dicarboxylic acid, blowing agents,
CA 02211~79 1997-08-13
peroxides or azo-bisisobutyronitrile, which can then be
removed again in a subsequent process step by heating
and tempering at elevated temperature. The
characteristic is determined by quantity, grain size
and distribution. Such gas charges can, for example,
be used where gas charges which react in a strongly
progressive manner are required.
The ignition of the tailor-made gas charge can be
effected by the conventional methods. In doing so it
is important that no additional toxic reaction gas
components are set free from the igniter after the
reaction.
The gas charge mixture is insensitive in respect
of its safety characteristics, for example to the
effects of abrasion, shock and impact or to
ignitability by flame or cerium/iron sparks under
normal pressure. In an enclosure, however it burns
vigorously when suitably ignited. This provides
increased safety in manufacture and handling.
The mixtures according to the invention can, for
example, be used in gas generators for motor vehicle
safety with the electrically initiated ignition systems
conventionally employed there.
In contrast to generators based on an azide
charge, expensive filtering of the slag can be
dispensed with, since the slag contains no toxic
constituents. It consists mainly of carbonates and
chlorides of potassium and sodium, along with very
little nitrates/nitrites and zinc oxide. The discharge
of such non-toxic constituents is therefore generally
only limited by the limits set for the emission of
dust.
The following examples are intended to explain the
invention in more detail, but without limiting it.
The specified components for the gas charges
according to the invention are homogenised for 30
CA 022ll~79 l997-08-l3
-14-
minutes in the stated proportions by weight in plastic
containers in an eccentric tumbling mixer. Tabletting
of the mixtures to blanks with a diameter of about 6 mm
is then effected. 3.5 g of the tabletted samples are
caused to react using 0.2 g boron/potassium nitrate
(25:75 parts by wt.) as an igniting mixture and an
electrically heatable iron wire in a 25 ml stainless
steel pressure bomb. The pressure-time curve of the
reaction is recorded using a piezoelectric measuring
device. Combustion gases which are composed mainly of
H2O, CO2, N2 and ~2 and meet the toxicological
requirements set are formed in the exothermic reaction.
The gas charge mixtures described in the examples
are investigated, for example in a measuring apparatus
comprising a combustion chamber, gas flow diversion and
filter chamber, using specific mechanical
constructional conditions, to determine its combustion
characteristics. The gaseous reaction products are
collected and characterised in a 60 l volume vessel
(main constituents: H2O, CO2, N2 and O2).
Composition (wt. ~)
Example No. 1 2 3 4 5
5-aminotetrazole 33.133.1 34.0 33.1 34.2
sodium nitrate 52.352.3 61.5 52.3 64.8
- potassium
perchlorate 10.110.1 ---- 10.1 ----
zinc oxide4.0 3.01.0 ---- ----
zinc peroxide --- 1.0 3.0 4.0 ----
graphite 0.5 0.50.5 0.5 1.0
3 5 Example Heat of Friction Impact
explosionsensitivitysensitivity
(kJ/g) (N) (J)
13.61 > 360 10
23.69 ~ 360 10
33.70 ~ 360 10
43.82 ~ 360 7.5
53.82 ~ 360 10
CA 022llS79 l997-08-l3
-15-
Results of measurements in the ballistic pressure bomb
Example Maximum Time Cold gas2) CO
pressuredifferencel'
40-60~ p(max)
(bar) (ms) (l/g) (ppm)
1 715 6.7 0.41 1800
5 2 707 5.9 0.38 1100
3 729 6.1 0.41 2000
4 660 6.5 0.40 1800
730 6.7 0.41 3300
duration of the reaction at between 40 and 60~ of
the maximum pressure, in milliseconds
2) measured after cooling to room temperature.
Example 1 describes the reaction of 5-
aminotetrazole (5-ATZ) with a binary mixture of
oxidants. The reaction gas composition shows a content
of 1800 ppm CO in the reaction gases after combustion
in a closed pressure bomb. In Example 2 the addition
of only 1 ~ by wt. of zinc peroxide surprisingly leads
to a marked reduction in the proportion of CO to 1100
ppm with otherwise unchanged test parameters. The
changes in the composition of the mixtures in Examples
3 to 5 lead to poorer results.
Composition (wt ~)
Example No. 6 (=1) 7 8 9
5-aminotetrazole 33.1 25.4 16.6 10.7
3 5 sodium nitrate 52.3 52.7 52.7 52.7
potassium perchlorate10.1 10.2 10.2 10.2
Zn (5-ATZ) 2 - - - -11 . 2 ---- ____
Ca (5-ATZ) ---- ---- 20 0 25.9
zinc oxide 4.0 ---- ---- ----
graphite 0.5 0.5 0.5 0.5
CA 022ll~79 l997-08-l3
Example Heat of Friction Impact
explosion sensitivity sensitivity
(kJ/g) (N) (J)
6 (=)1 3.61 > 360 10
7 3.64 > 360 10
8 3 46 > 360 15
9 2.74 > 360 20
Results of measurements in the ballistic pressure bomb (25 ml):
Example Maximum Time Cold gas2~ CO
pressure differencel~
40-60~ p(max)
(bar) ~ms) (l/g) (ppm)
156 (=1) 715 6.70.41 1800
7 662 6.80.39 250
8 602 6.60.40 140
9 81 39.2 0.33 100
Results of measurements in the 60 l test canister:
Example CO reduction"Maximum pressure~
(~) (bar)
6 (=1) 0 2.2
7 10 2.1
8 40 1.7
9 95 < l.S
1) duration of the reaction between 40 and 60~ of the
maximum pressure in milliseconds
2) measured after cooling to room temperature
3) based on the test canister results, Example 1 or 6
4) mass of charge 40 g.
Examples 6 to 9 show that the addition of the Zn,
Ca and Mg salts of 5-aminotetrazole (Me(5-ATZ) 2) has a
favourable effect on the reaction gas composition. A
marked reduction is found in the proportion of CO. The
rate of reaction is also affected.
CA 022ll~79 l997-08-l3
-17-
Composition (wt. ~)
Example No.10 11 12 13
5-aminotetrazole 33.0 31.6 30.8 28.g
5 guanidine nitrate8.3 8.0 7.8 7.3
sodium nitrate 58.2 39.0 27.1 ----
strontium nitrate ---- 20.9 33.8 63.3
graphite 0.5 0.5 0.5 0.5
Example Heat ofFriction Impact Mass of
explosionsensitivitysensitivity residue3
(kJ/g) (N) (J) (g)
4.06 > 360 20 1.5
15 11 3.90 ~ 360 15 1.2
12 3.61 > 360 20 1.0
13 3.41 > 360 15 0.8
Results of measurements in the ballistic pressure bomb (25 ml):
Example Maximum Time Cold gas
pressuredifferencel'
40-60~ p(max)
(bar) (ms) (l/g)
25 10 779 6.1 0.46
11 767 7.0 0.41
12 723 7.3 0.42
13 620 8.6 0.39
duration of reaction at between 40 and 60~ of the
maximum pressure, in milliseconds
2) measured after cooling to room temperature
3) mass of solids in the 60 1 test canister after
combustion of 30 g gas charge in the experimental
generator.
Examples 10 to 13 differ in the proportion of
sodium nitrate/strontium nitrate used as oxidant. With
increasing proportions of strontium nitrate, the mass
of the slag emerging into the canister decreases. This
means that the filterability of the slag is improved by
the addition of strontium nitrate - after the
reaction - to the filter of the generator. At the
CA 02211579 1997-08-13
-18-
same time the proportion of CO in the reaction gas can
be favourably influenced.
