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 invention relates to a particle-free gas-generating mixture for use in gas generators for safety devices, in particular in gas generators for vehicle occupant restraint systems.
• Gas generators for safety devices usually contain a solid fuel based on sodium azide as a gas supplier Main component.
• sodium azide is toxic and can become easily with heavy metals forming extremely dangerous and violent implement reacting connections. Therefore, both in manufacturing the gas-generating mixtures as well as in the disposal Defective or unused gas generators require special measures.
• blowing agents containing sodium azide also a range of solids through suitable filter devices removed from the gas flow in the gas generator or in the gas generator have to be held back. There have therefore been attempts to Production of blowing agents which burn off essentially without residues undertaken.
• US-A-5 545 272 describes a gas generating composition which consists essentially of 35 to 55 wt .-% nitroguanidine and about 45 to 65 wt .-% phase-stabilized ammonium nitrate.
• phase stabilizing agents are potassium salts, e.g. Potassium nitrate and potassium perchlorate, but also potassium dichromate, Potassium oxalate and mixtures thereof in an amount from 5 to about 25 % By weight, preferably 10 to 15%.
• the gas generating composition of US-A-5 545 272 can due to the relatively high proportion of phase stabilizing additives not residue-free for the ammonium nitrate, i.e. without solid combustion residues burn down.
• phase stabilizing additives not residue-free for the ammonium nitrate, i.e. without solid combustion residues burn down.
• smoke formation caused by filter devices in the gas generator can only be suppressed incompletely.
• the known mixture is difficult to ignite and has a relative low burning rate.
• the high proportion of ammonium nitrate also leads to a high hygroscopicity, which occurs during processing. Storage and use in the gas generator an increased Effort requires an undesirable change in the fuel mixture to prevent.
• DE 195 05 568 A1 discloses a propellant for gas generators, the fuel as at least one compound from the group Tetrazoles, triazoles, triazines, cyanic acid, urea, their derivatives, Descendants or their salts, at least three as oxidizing agents Compounds from the group of peroxides, nitrates, chlorates or Perchlorate, as well as combustion moderators and the proportion of toxic Contains gas reducing supplements. Can be used as urea derivatives Biuret, guanidine, nitroguanidine, guanidine nitrate, aminoguanidine, Aminoguanidine nitrate, thiourea and triaminoguanidine nitrate be used.
• the invention accordingly provides an acid-free, particle-free burning, gas generating mixture for use in a gas generator ready for a safety device, which consists of a high-energy Fuel with an oxygen value of not less than -35%, with an oxidizer mixture of ammonium nitrate and ammonium perchlorate an ammonium nitrate content of 35 to 50 wt .-% and an ammonium perchlorate content of between 3 and 10% by weight, based in each case on the Total weight of the mixture, possibly a phase stabilizing one Additive for the ammonium nitrate in a proportion of at most 5% by weight, based on the weight of the ammonium nitrate, Burning moderators in a proportion of 0 to 3 wt .-%, based on the Total weight of the mixture and processing aids in one Proportion of 0 to 5% by weight, based on the total weight of the mixture, consists.
• the total water content of the gas-generating mixture is at most 0.3%.
• the ammonium nitrate content is preferably between 40 and 50%, particularly preferably between 40 and 45%.
• the ammonium perchlorate content is preferably in the range between 3 and 7% by weight.
• the high-energy fuel is preferably from guanidine nitrate, Nitroguanidine, triaminoguanidine nitrate, urea nitrate, Nitro urea, nitropenta, nitrotriazalon, hexogen, octogen or their mixtures selected existing group. Particularly preferred is the fuel guanidine nitrate and / or nitroguanidine. The latter is the most preferred fuel.
• the ammonium nitrate used in the invention can be small amounts contain phase stabilizing additives to increase storage stability, those made of copper oxide, zinc oxide, complex zinc compounds or mixtures of existing groups are selected. It it has been found that, in contrast to those in US-A-5 545 272 required amounts of 10 to 15% of potassium compounds for phase stabilization in the application according to the invention at most 5% of the mentioned additives are needed. Surprisingly, was found. that while controlling the water content of the overall mixture the proportion of phase-stabilizing additives reduced to zero can be. While phase stabilizing at water contents of 0.1 to 0.3% Additions of 3 to 5% to ensure storage stability can be used if the water content is below 0.1% phase-stabilizing additives are completely dispensed with. All in all this results in a reduction in solid emissions compared to US Pat. No. 5,545,272 by the mixture according to the invention from 50 to 100%.
• the compounds known in the art can be used as the combustion moderator. These include transition metal compounds and carbon black.
• the transition metal compounds can be selected from the group of transition metal oxides, hydroxides, nitrates, carbonates and organometallic compounds of the transition metals. Exemplary examples of this are iron oxides, copper oxides, chromium oxides, zinc oxide, copper chromite, basic copper nitrate, zinc carbonate, copper resorcylate and ferrocene.
• carbon black as a combustion moderator, optionally in a mixture with transition metal compounds, is preferred, however, because carbon black is inexpensive on the one hand and burns off without residue with the formation of CO 2 .
• processing aids are added, which from the from the Pressing aids, trickling aids or lubricants existing group selected are.
• processing aids are Polyethylene glycol, cellulose, methyl cellulose, graphite, wax, magnesium stearate, Zinc stearate, boron nitride, talc, bentonite, silicon dioxide or molybdenum sulfide.
• Ammonium nitrate content ensures that the inherently unfavorable properties, such as. the low structural stability, hygroscopicity, the poor willingness to ignite and the slow burning rate of mixtures containing ammonium nitrate through the addition of ammonium perchlorate can be compensated.
• an ammonium perchlorate content of less than 3% there is no significant improvement with regard to the willingness to ignite and the burning rate of the Fuel.
• An ammonium perchlorate content of above 10% by weight leads to the formation of free hydrogen chloride, which is due to the strict toxicity requirements for propellant gases for occupant protection systems is undesirable.
• ammonium perchlorate leads also in the small proportion of 3 to 10% by weight Increase in the willingness to ignite and burning rate of the invention Propellant. Due to the higher oxygen content of Ammonium perchlorate can also the ammonium nitrate in the Mixture can be reduced more.
• the invention thus creates a gas yield of up to 100 percent burning gas-generating mixture from which an essentially particle-free gas mixture is released and that physiologically is harmless.
• the use of an oxidizer mixture Ammonium nitrate and ammonium perchlorate also ensure good Willingness to ignite and a high burning rate. At the same time points the mixture according to the invention has high thermal and chemical stability on.
• a temperature storage test at 110 ° C. was also carried out with the mixture carried out over 400 h.
• the measured weight loss was below 0.8%; the mixture is therefore sufficiently stable.
• a thermal shock test was also carried out on tablets with different moisture contents.
• the tablets were first dried in vacuo ( ⁇ 1 mbar) at 100 ° C for 18 hours, then part of it was in a desiccator over 8 hours at 45% rel. Moisture again moistened in a defined way.
• the H 2 O content of the dried tablets was 0.08%, the H 2 O content of the moistened tablets was 0.30%.
• the tablets were hermetically sealed in an aluminum container and subjected to a temperature change between - 35 ° C and + 85 ° C (56 cycles). While the tablets with the increased moisture content swelled strongly after the test, were partially broken and thus had become unusable for the intended use, the dry tablets showed no change in their mechanical properties.
• Example 1 The tablets with a moisture content of 0.20% were the in Example 1 subjected to thermal cycling. After The tablets showed no change when the stress was complete their mechanical properties.
• Example 1 Tablets processed and ignited in a gas generator 51.5 g dried nitroguanidine, 40.0 g dried ammonium nitrate, 8.0 g of dried ammonium perchlorate, 2 g of copper chromite and 0.5 g of carbon black was added in the manner described in Example 1 Tablets processed and ignited in a gas generator.
• the average burning rate at 200 bar was 23 mm / s.

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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)

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Citations (9)

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• 1997
  • 1997-09-24 DE DE19742203A patent/DE19742203A1/de not_active Withdrawn
• 1998
  • 1998-09-23 EP EP98118023A patent/EP0905108B1/fr not_active Expired - Lifetime
  • 1998-09-23 DE DE59806422T patent/DE59806422D1/de not_active Expired - Lifetime
  • 1998-09-24 US US09/159,917 patent/US5989367A/en not_active Expired - Lifetime

Patent Citations (10)

Non-Patent Citations (2)

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