Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06D—MEANS FOR GENERATING SMOKE OR MIST; GAS-ATTACK COMPOSITIONS; GENERATION OF GAS FOR BLASTING OR PROPULSION (CHEMICAL PART)
  • C06D5/00—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets
  • C06D5/06—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets by reaction of two or more solids

Definitions

• the present invention relates to an azide-free, gas-generating composition, in particular for use in safety devices for motor vehicles.
• 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.
• 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 2 -C 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.
• 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.
• 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.
• an additional fuel such as cyanuric acid for example
• cyanuric acid for example
• 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.
• the additionally used fuels have a lower oxygen balance than guanidine nitrate
• 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 leads to an increased proportion of solid matter in the gas mixture and hence to an increased particle output.
• 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.
• 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.
• guanidine carbonate guanidine nitrate, guanidine perchlorate, aminoguanidine nitrate, diaminoguanidine nitrate, triaminoguanidine nitrate, nitroguanidine or mixtures thereof are used as the guanidine compound.
• 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.
• 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 2 , H 2 O, Al 2 O 3 , B 2 O 3 etc. (O 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 2 deficit balance).
• the transition metal oxide present as a component of the oxidizer mixture can be selected from the group consisting of Cr 2 O 3 , MnO 2 , Fe 2 O 3 , Fe 3 O 4 , CuO, Cu 2 O or mixtures thereof.
• the oxidizer mixture preferably contains a mixture of Fe 2 O 3 and CuO, besides the further components of the oxidizer mixture.
• the Fe 2 O 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.
• the amount of toxic gases in the combustion products can be further reduced.
• 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.
• 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.
• part of the CuO can be replaced by Fe 2 O 3 .
• 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%.
• 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.
• 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 x proportions in the gas would rise unduly.
• 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.
• 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 x component of the generated gas measured in the test canister amounted to 1300 ppm.
• test data show that simultaneously using Fe 2 O 3 and CuO as one of the components of the oxidizer mixture result in a further reduction of the emission of toxic gases.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Organic Chemistry (AREA)
• Air Bags (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 1998
  • 1998-12-02 DE DE29821541U patent/DE29821541U1/de not_active Expired - Lifetime
• 1999
  • 1999-12-01 EP EP99123906A patent/EP1006096B1/fr not_active Expired - Lifetime
  • 1999-12-01 DE DE59902827T patent/DE59902827D1/de not_active Expired - Lifetime
• 2005
  • 2005-03-14 US US11/079,718 patent/US20050189052A1/en not_active Abandoned

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