U.S. patent application number 11/079718 was filed with the patent office on 2005-09-01 for azide-free, gas-generating composition.
This patent application is currently assigned to TRW Airbag Systems GmbH & Co. KG. Invention is credited to Hofmann, Achim, Rodig, Karl-Heinz, Schropp, Roland, Zeuner, Siegfried.
Application Number | 20050189052 11/079718 |
Document ID | / |
Family ID | 8066128 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050189052 |
Kind Code |
A1 |
Zeuner, Siegfried ; et
al. |
September 1, 2005 |
Azide-free, gas-generating composition
Abstract
The present invention relates to an azide-free gas-generating
composition, in particular for use in safety devices for motor
vehicles, comprising a fuel in a proportion of 20 to 60% by weight
and consisting of one or more components, and an oxidizer mixture
in a proportion of 40 to 80% by weight and consisting of at least
three components, each in relation to the total composition. In
accordance with the invention, the fuel consists of a guanidine
compound in a proportion of at least 95% by weight and a further
fuel component in a proportion of 0 to less than 5% by weight, each
in relation to the fuel, and the oxidizer mixture consists of one
or more transition metal oxides in a proportion of 20 to 80% by
weight, basic copper nitrate in a proportion of 0 to 50% by weight,
metal chlorate, metal perchlorate, ammonium perchlorate or mixtures
thereof in a proportion of 1 to 15% by weight and alkali metal
nitrate, alkaline earth metal nitrate or mixtures thereof in a
proportion of 1 to 15% by weight, each in relation to the oxidizer
mixture.
Inventors: |
Zeuner, Siegfried; (Munchen,
DE) ; Hofmann, Achim; (Polling, DE) ; Schropp,
Roland; (Tegernheim, DE) ; Rodig, Karl-Heinz;
(Kraiburg, DE) |
Correspondence
Address: |
TAROLLI, SUNDHEIM, COVELL & TUMMINO L.L.P.
526 SUPERIOR AVENUE, SUITE 1111
CLEVEVLAND
OH
44114
US
|
Assignee: |
TRW Airbag Systems GmbH & Co.
KG
|
Family ID: |
8066128 |
Appl. No.: |
11/079718 |
Filed: |
March 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11079718 |
Mar 14, 2005 |
|
|
|
09453134 |
Dec 2, 1999 |
|
|
|
Current U.S.
Class: |
149/45 |
Current CPC
Class: |
C06D 5/06 20130101 |
Class at
Publication: |
149/045 |
International
Class: |
C06B 045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 2, 1998 |
DE |
298 21 541 . 1 |
Claims
1. An azide-free gas-generating composition, in particular for use
in safety devices for motor vehicles, comprising a fuel in a
proportion of 20 to 60% by weight and consisting of one or more
components, and an oxidizer mixture in a proportion of 40 to 80% by
weight and consisting of at least three components, each in
relation to the total composition, wherein the fuel consists of a
guanidine compound in a proportion of at least 95% by weight and a
further fuel component in a proportion of 0 to less than 5% by
weight, each in relation to the fuel, and wherein the oxidizer
mixture consists of one or more transition metal oxides in a
proportion of 20 to 80% by weight, basic copper nitrate in a
proportion of 0 to 50% by weight, metal chlorate, metal
perchlorate, ammonium perchlorate or mixtures thereof in a
proportion of 1 to 15% by weight and alkali metal nitrate, alkaline
earth metal nitrate or mixtures thereof in a proportion of 1 to 15%
by weight, each in relation to the oxidizer mixture.
2. The composition according to claim 1, wherein the guanidine
compound is selected from the group consisting of guanidine
carbonate, guanidine nitrate, guanidine perchlorate, aminoguanidine
nitrate, diaminoguanidine nitrate, triaminoguanidine nitrate,
nitroguanidine or mixtures thereof.
3. The composition according to claim 1, wherein the further fuel
component is an organic compound which has an oxygen balance of
more than -90%.
4. The composition according to claim 1, wherein the further fuel
component is selected from the group consisting of cyanuric acid,
urea, oxamide, urazol, alloxane, alloxantine and parabanic acid or
mixtures thereof.
5. The composition according to claim 1, wherein the transition
metal oxide is selected from the group consisting of
Cr.sub.2O.sub.3, MnO.sub.2, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, CuO,
Cu.sub.2O or mixtures thereof.
6. The composition according to claim 1, further comprising
processing aids in a proportion of up to 5% by weight, in relation
to the total composition, the processing aids being selected from
the group consisting of trickling aids, pressurizing aids and/or
lubricants.
7. The composition according to claim 1, essentially consisting of
30 to 60% by weight guanidine nitrate, 0 to 3.15% by weight
cyanuric acid, 15 to 30% by weight CuO, 15 to 30% by weight basic
copper nitrate, 0.1 to 5% by weight ammonium perchlorate and 1 to
5% by weight alkali- and/or alkaline earth metal nitrate, each in
relation to the total composition.
8. The composition according to claim 1, wherein the oxidizer
mixture simultaneously contains Fe.sub.2O.sub.3 and CuO.
9. The composition of claim 8, wherein the Fe.sub.2O.sub.3 is
present in an amount of at least 4% by weight, in relation to the
total composition.
10. The composition of claim 7, wherein CuO is partly replaced by
Fe.sub.2O.sub.3.
Description
[0001] The present invention relates to an azide-free,
gas-generating composition, in particular for use in safety devices
for motor vehicles.
BACKGROUND OF THE INVENTION
[0002] Gas-generating compositions which are used in safety devices
for motor vehicles generally consist of a fuel based on sodium
azide and an oxidation agent. Owing to the toxicity of sodium
azide, however, a search for alternatives to the gas-generating
mixtures containing azide was already begun early on.
[0003] The U.S. Pat. No. 5,608,183 describes a gas-generating
mixture which contains between approximately 30 and 85% by weight
of a fuel and between approximately 15 and approximately 70% by
weight of an oxidation agent. At least 60% by weight of the fuel
consists of the nitrate salt of an acidic polyamine or of a
C.sub.2-C.sub.3-alkyl diamine, such as for example the nitrate
salts of urea, guanidine, aminoguanidine, diaminoguanidine,
semicarbazide, ethylene diamine, 1,3-propane diamine or 1,2-propane
diamine, or mixtures thereof. The oxidation agent comprises at
least 60% by weight basic copper nitrate and/or cobalt triamine
tri-nitrate. The processing of the mixtures takes place in a wet
process.
[0004] The gas-generating mixture known from the U.S. Pat. No.
5,608,183 has an insufficient readiness to ignite and also a
combustion rate which is too low. Owing to the high proportion of
basic copper nitrate, in addition an increased proportion of toxic
gases is to be found in the released gas mixture. The processing of
the mixture in a wet process requires additional drying stages and
is therefore cost-intensive.
[0005] The German Utility Model No. 298 06 504 provides a
gas-generating composition which comprises a fuel mixture
consisting of at least two components, in a proportion of 20 to 60%
by weight and an oxidizer mixture consisting of at least three
components in a proportion of 40 to 80% by weight, each in relation
to the total composition. The fuel mixture of the known composition
is composed of 5 to 95% by weight of a guanidine compound, 5 to 95%
by weight of a heterocyclic organic acid, for example cyanuric
acid, and 0 to 20% by weight of further fuels. The oxidizer mixture
of the known composition consists of one or more transition metal
oxides in a proportion of 20 to 70% by weight and 10 to 50% by
weight basic copper nitrate and 2 to 30% by weight metal chlorate,
metal perchlorate, ammonium perchlorate, alkali metal nitrate,
alkaline earth metal nitrate or mixtures thereof.
[0006] The use of an additional fuel, such as cyanuric acid for
example, in a proportion of more than 5%, however, results in a
distinctly reduced combustion rate of the composition. The
composition is therefore unsuitable for use in gas generators for
the driver's side, in which owing to the shorter distance between
the vehicle occupant and the vehicle components, high combustion
rates are preferred. As the additionally used fuels have a lower
oxygen balance than guanidine nitrate, in addition a higher
proportion of oxidizer must be used to balance out the mixture and
to achieve an optimally reduced emission of harmful gas. The higher
oxidizer proportion, however, leads to an increased proportion of
solid matter in the gas mixture and hence to an increased particle
output.
[0007] A need therefore continues to exist for improved azide-free,
gas-generating compositions for use in safety devices for motor
vehicles, with which a high combustion rate can be achieved with,
at the same time, a low particle output.
SUMMARY OF THE INVENTION
[0008] The present invention provides such a composition, which
comprises a fuel in a proportion of 20 to 60% by weight and
consisting of one or more components, and an oxidizer mixture in a
proportion of 40 to 80% by weight and consisting of at least three
components, each in relation to the total composition. The
composition is characterized in that the fuel consists of a
guanidine compound in a proportion of at least 95% by weight and of
a further fuel component in a proportion of 0 to less than 5% by
weight, each in relation to the fuel. In addition, the oxidizer
mixture consists of one or more transition metal oxides in a
proportion of 20 to 80% by weight, basic copper nitrate in a
proportion of 0 to 50% by weight, metal chlorate, metal
perchlorate, ammonium perchlorate or mixtures thereof in a
proportion of 1 to 15% by weight and alkali nitrate, alkaline earth
nitrate or mixtures thereof in a proportion of 1 to 15% by weight,
each in relation to the oxidizer mixture.
[0009] Preferably guanidine carbonate, guanidine nitrate, guanidine
perchlorate, aminoguanidine nitrate, diaminoguanidine nitrate,
triaminoguanidine nitrate, nitroguanidine or mixtures thereof are
used as the guanidine compound.
[0010] The further fuel component is preferably an organic compound
which has an oxygen balance of more than -90%. Particularly
preferred as further fuel component are cyanuric acid, urea,
oxamide, urazol, alloxane, alloxantine and parabanic acid or
mixtures thereof.
[0011] The "oxygen balance" is to be understood to mean the
quantity of oxygen in percentage by weight which becomes free with
complete conversion of a compound or of a mixture to CO.sub.2,
H.sub.2O, Al.sub.2O.sub.3, B.sub.2O.sub.3 etc. (O.sub.2 excess
balance). If the available oxygen is not sufficient for this, then
the missing quantity necessary for the complete conversion is
indicated with a minus sign (O.sub.2 deficit balance).
[0012] The transition metal oxide present as a component of the
oxidizer mixture can be selected from the group consisting of
Cr.sub.2O.sub.3, MnO.sub.2, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, CuO,
Cu.sub.2O or mixtures thereof.
[0013] The oxidizer mixture preferably contains a mixture of
Fe.sub.2O.sub.3 and CuO, besides the further components of the
oxidizer mixture.
[0014] Preferably, the Fe.sub.2O.sub.3 is present in an amount of
at least 4% by weight, and more preferably in an amount of at least
9% by weight, in relation to the total composition. By using
Fe.sub.2O.sub.3 and Cuo simultaneously, the amount of toxic gases
in the combustion products can be further reduced.
[0015] The composition can contain in addition conventional
processing aids in a proportion of up to 5% by weight in relation
to the total composition, the processing aids preferably being
selected from the group consisting of trickling aids, pressurizing
aids and/or lubricants.
[0016] A preferred composition according to the invention consists
of 30 to 60% by weight guanidine nitrate, 0 to 3.15% by weight
cyanuric acid, 15 to 30% by weight CuO, 15 to 30% by weight basic
copper nitrate, 1 to 5% by weight ammonium perchlorate and 1 to 5%
by weight alkali- and/or alkaline earth metal nitrate, each in
relation to the total composition. Preferably, part of the CuO can
be replaced by Fe.sub.2O.sub.3.
[0017] The compositions according to the invention are
distinguished compared with the mixtures known hitherto by an
improved combustion behavior and in particular by an extremely low
particle output in combination with a high combustion rate. They
are therefore particularly suitable for use in driver's airbag
systems. The improved combustion behavior of the compositions
according to the invention is promoted by the use of at least one
organic compound of the group of guanidine compounds as fuel. The
use of guanidine nitrate is particularly preferred owing to its
favorable oxygen balance of -26.2%.
[0018] Compared with other organic compounds or mixtures thereof
with guanidine nitrate, therefore less oxidizer is required to
balance out the mixture. Through this step, therefore, a lower
particle output is already achieved.
[0019] It is known that the addition of further fuel components,
such as cyanuric acid for example, to the guanidine compounds
exerts a favorable influence on the carbon monoxide and NO.sub.x
components in the released hot gas. Surprisingly, however, it was
found that the proportion of further fuel components has to be kept
below 5% by weight, in relation to the total quantity of fuel, in
order to keep the combustion rate sufficiently high and, at the
same time, to minimize the particle output. Higher proportions of
further fuel components result in an undue reduction of the
combustion rate and increase to the emitted particle quantity.
Depending on the requirements set for the gas-generating
composition, the addition of the further fuel components can also
be dispensed with entirely.
[0020] The proportion of basic copper nitrate in the oxidizer
mixture should in any case amount to a maximum of 50% by weight in
relation to the oxidizer mixture. In addition to a high burning
speed and extremely low carbon monoxide- and NO.sub.x emissions, a
good readiness of the mixture to ignite and also an excellent
retaining capability with regard to the solid combustion residues
are achieved. A higher proportion of basic copper nitrate is not
desired, because hereby in particular the NO.sub.x proportions in
the gas would rise unduly.
[0021] A gas-generating mixture which is particularly preferred
according to the invention consists of 40 to 55% by weight
guanidine nitrate, 0 to 2.9% by weight cyanuric acid, respectively
15 to 30% by weight copper oxide and basic copper nitrate and also
respectively 1 to 5% by weight ammonium perchlorate and alkali- or
alkaline earth metal nitrate. Owing to the low proportion of
cyanuric acid, this composition ensures a sufficient combustion
rate for driver's airbag systems. The simultaneous presence of
ammonium perchlorate and alkali- or alkaline earth metal nitrate in
a molar ratio of approximately 1:1 (alkali) or respectively 2:1
(alkaline earth) has proved to be particularly favorable for a
further reduction of the particle output, because through this
combination, compared with mixtures of the other oxidizers, to
achieve identical oxidation equivalents, the smallest quantities of
solid combustion residues are produced. At the same time, the
occurrence of HCl as toxic combustion product is prevented. The
addition of small quantities of ammonium perchlorate and metal
nitrate has, in addition, a favorable influence on the combustion
rate.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] The invention is described below with the aid of
particularly preferred working embodiments which, however, are to
be understood as being non-restrictive.
EXAMPLE 1
[0023] 473 g micronized guanidine nitrate, 20 g ground cyanuric
acid, 231 g each copper oxide and basic copper nitrate and 26 g
ammonium perchlorate and 19 g sodium nitrate were weighed in
together into a ball mill, ground for three hours and mixed with
each other. The obtained mixture was directly pressed into tablets
without further processing steps. Tests showed a very good
readiness to ignite with a combustion rate of 17 mm/s. The solid
component in the released gas mixture amounted to 1.7%.
EXAMPLE 2
[0024] 493 g micronized guanidine nitrate, 231 g each copper oxide
and basic copper nitrate and 26 g ammonium perchlorate and 19 g
sodium nitrate were weighed in together into a ball mill. In
addition 5 g calcium stearate were added to the preparation and
worked up as in Example 1. On firing of the obtained tablets, a
good ignition readiness resulted and a combustion rate of 17 mm/s,
with a solid component in the generated gas of 1.8%. The NO.sub.x
content of the generated gas, measured in a 60 l test canister,
amounted to 550 ppm.
COMPARATIVE EXAMPLE 1
[0025] 29.5 g micronized guanidine nitrate, 12.8 g cyanuric acid,
respectively 25.65 g copper oxide and basic copper nitrate and 6.4
g potassium perchlorate were mixed in a ball mill, as described in
Example 1, and pressed into tablets. In tests, the mixture showed
only moderate readiness to ignite; the combustion rate amounted to
10 mm/s. The solid component in the gas mixture amounted to 3.1%.
The NO.sub.x content determined in a 60 l test canister was 550
ppm.
COMPARATIVE EXAMPLE 2
[0026] A mixture of 47.1 parts guanidine nitrate and 52.9 parts
basic copper nitrate was produced according to the specification
described in Example 1 of the U.S. Pat. No. 5,608,183. The mixture
showed a poor ignition readiness and only a combustion rate. The
NO.sub.x component of the generated gas measured in the test
canister amounted to 1300 ppm.
EXAMPLE 3
[0027] 1147 g micronized guanidine nitrate, 612 g basic copper
nitrate, 316 g copper oxide (CuO), 242 g iron oxide
(Fe.sub.2O.sub.3), 103 g ammonium perchlorate, 75 g sodium nitrate
and 5 g calcium stearate were weighed in together into a ball mill
and processed as described in Example 1. The test also showed a
good readiness to ignit and a combustion rate of about 15 mm/s.
[0028] The analysis of toxic components in the combustion gases
showed that the combination of iron oxide and copper oxide as the
metal oxide component in the propellant mixture had a highly
favourable influence on the emission of carbon monoxide (CO) and
ammonia (NH.sub.3). The following emission of gases has been
determined by igniting gas generators having the typical
performance of gas generators for the driver's side (about 2.3 bar
in a 146 l canister):
1 Co concentration NH.sub.3-concentration [ppm] [ppm] Gas generator
loaded 541 266 with 150 g pro- pellant in accordance with
Comparative Example 1 Gas generator loaded 374 33 with 136 g pro-
pellant according to Example 3
[0029] The test data show that simultaneously using Fe.sub.2O.sub.3
and CuO as one of the components of the oxidizer mixture result in
a further reduction of the emission of toxic gases.
* * * * *