Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B25/00—Compositions containing a nitrated organic compound
  • C06B25/34—Compositions containing a nitrated organic compound the compound being a nitrated acyclic, alicyclic or heterocyclic amine
• • 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

• This invention relates to solid gas generator fuel compositions (gas generant mixtures) primarily for airbag inflator propellants and belt tensioners, the gas generator fuel compositions having very good long term thermal stability.
• An airbag essentially consists of a gas generator housing which is connected to the gas generator propellant, i.d.R. in tablet form, is filled, and a primer (Squib) to ignite the gas generator propellant, and a gas bag.
• a primer Squib
• Suitable detonators are described, for example, in US Pat. No. 4,931,111.
• the initially small folded airbag is filled after the initial ignition of the resulting gas during combustion of the gas generator propellant and reached in a period of about 10-50 ms its full volume.
• the escape of hot particles or melts from the gas generator into the gas bag must be largely prevented because it could lead to damage to the gas bag or injury to vehicle occupants. This is achieved by binding and filtering the slag resulting from the combustion of the gas generator propellant.
• DE-4435790 A which is assigned to the Applicant, discloses gas generator fuel compositions based on guanidine compounds on suitable carriers, which have substantially improved burn-off behavior and improved slag formation.
• the gas generator fuel composition described in DE-4435790 A comprises (A) at least one carbonate, bicarbonate or nitrate of guanidine, aminoguanidine, diaminoguanidine or triaminoguanidine in an amount of about 20-55% by weight based on the total amount of components (A ) and (B), (B) at least one alkali or alkaline earth metal nitrate or ammonium nitrate as oxidizing agent in an amount of about 80-45% by weight, based on the total amount of components (A) and (B) and for moderation of the burn-up and to improve the formation of slag in an amount of 5-45 wt .-% based on the total amount of components (A) and (B), (C1) at least one carrier selected from silica, alkali
• DE-4435790 A refers to the Holland test in which the gas generator fuel composition was heated to 105 ° C for 72 hours.
• the Holland test is a method developed in 1927 for the determination of the chemical Resistance of blowing agents.
• the weight loss is determined, which occurs after only 72 hours of heating at 105 ° C (polybasic propellant) or 110 ° C (monobasic propellant). The loss occurring here, less the weight loss that occurred in the first eight hours, may not exceed 2% (see J. Köhler and R. Meyer, Explosives, 9th revised and expanded edition 1998, Verlag Wiley-VCH, page 170).
• the refractory, substantially chemically inert slag scavenger in highly dispersed form, i. produced by flame hydrolysis, serves as an internal filter, whereby the formation and the discharge of dust-like particles from the gas generator housing is largely prevented.
• Part of the highly dispersed slag scavenger can serve as a carrier substance for catalyst metals. This document thus does not deal with the long-term stability of the gas generator fuel compositions under hot storage.
• the present invention is therefore based on the object to provide gas generator fuel compositions that meet the increasingly demanded by the automotive industry more stringent requirements for stability in hot storage for at least 400 hours at 110 ° C while maintaining the functionality.
• the present invention thus provides a gas generator fuel composition that can withstand hot storage at 110 ° C for at least 400 hours, thus meeting the ever-increasing demands of the automotive industry for gas generator propellant compositions for gas generator propellants in airbags.
• gas generator fuel compositions based on nitroguanidine as a fuel and the specified oxidizing agents or oxidizing agent mixtures in conjunction with one or more stabilizers of the type mentioned can surprisingly be formulated gas generator fuel compositions, which in a hot storage of 110 ° C over a storage period of 400 hours, preferably 1000 hours and in particular 3000 hours, a weight loss of less than 1%, preferably less than 0.5% and in particular less than 0.2%, while maintaining the operability of the gas generator fuel compositions.
• the stability results obtained are valid in open as well as in closed systems used in practice in the same way.
• the fuel is nitroguanidine (NIGU; NQ).
• NIGU nitroguanidine
• Nitroguanidine is virtually nontoxic, non-hygroscopic, poorly water-soluble, thermally stable, burning at low temperature and of low impact and friction sensitivity.
• the combustion gas yield is high, producing a large amount of nitrogen gas.
• a particularly preferred nitroguanidine according to the first and third embodiments of the present invention is a nitroguanidine containing 0.1 to 0.5% of nitroguanidinium hydrogensulfate and nitroguanidinium nitrate.
• Such acid-stabilized nitroguanidine will be referred to as stabilized nitroguanidine hereinafter.
• the pH of an aqueous extract (5 g of nitroguanidine per 200 ml of water, 20 ° C) of this stabilized nitroguanidine is 3.5 to 4.4.
• Such stabilized nitroguanidine is e.g. available as NIGU LBD SS from NIGU CHEMIE GmbH, Waldkraiburg, Germany.
• Conventional NIGU has a pH of 4.5-7.0 (5g nitroguanidine per 200 ml water, 20 ° C).
• alkali and alkaline earth nitrates such as lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate or barium nitrate
• alkali or alkaline earth chlorates and perchlorates such as lithium, sodium, potassium, magnesium
• mixtures of alkali or alkaline earth nitrate with ammonium perchlorate in particular mixtures of potassium nitrate or sodium nitrate with ammonium perchlorate.
• component (C) inorganic and organic acids can be used.
• a particularly preferred inorganic acid is boric acid.
• Particularly preferred organic acids are citric acid, tartaric acid, cyanuric acid, terephthalic acid and fumaric acid.
• Another suitable stabilizer is hydrophobic SiO 2 (available, for example, as Aerosil R812S from Degussa AG, Germany; hydrophobing agent: hexamethyldisilazane) when NIGU stabilized as a fuel is used.
• Hydrophobic SiO 2 is a material that is not wetted by water, ie it floats on the water surface (see infra, Kunststoffen Research, No. 11, page 55ff.).
• hydrophobic SiO 2 is present in combination with another stabilizer.
• the gaseous products produced during the combustion of the gas generator fuel compositions according to the invention consist essentially of carbon dioxide, nitrogen and water vapor. Any toxic gaseous combustion products, such as CO, NO x and NH 3 , are below the required limit values.
• Nitroguanidine component (A) is present in the gas generator fuel compositions of the invention in an amount of from about 33 to about 60 weight percent, preferably from about 40 to about 60 weight percent, and more preferably from about 45 to about 55 weight percent. % before, the oxidizing agent, component (B), is present in an amount of from about 35 to about 55 weight percent, preferably from about 38 to about 52 weight percent, and more preferably from about 40 to about 48 weight percent and the stabilizer component (C) is present in an amount of up to about 5% by weight, preferably up to about 3% by weight, more preferably up to about 1.6% by weight, and especially of about 0.5 to about 1.6 wt .-% before.
• the gas generator fuel compositions according to the invention contain further components.
• the gas generator fuel compositions according to the invention optionally contain as component (D) at least one Abbrandstabilisator or Abbrand modererator, which can also act as slag or Schlackenfnatureer.
• Abbrandstabilisator or Abbrand modererator which can also act as slag or Schlackenfnatureer.
• these are Al 2 O 3 , in particular highly dispersed Al 2 O 3 having a BET surface area (based on DIN 66131) of 100 ⁇ 15 m 2 / g (obtainable, for example, as aluminum oxide C from Degussa AG, Germany), Fe 2 O 3 , SiO 2 , iron acetylacetonate, mixtures thereof and mixtures of finely divided Al 2 O 3 and SiO 2 , for example a mixture of about 16% highly dispersed Al 2 O 3 and about 84% highly dispersed SiO 2 (available, for example, as Aerosil COK 84 of Degussa AG, Germany) (see series of publications Pigments, "Basics of Aero
• pyrogenic oxides are prepared by high temperature hydrolysis (flame hydrolysis) of the gaseous metal chloride (AlCl 3 ) under the influence of the resulting in the oxyhydrogen gas water and at the characteristic for such a reaction temperature (4 AlCl 3 + 6 H 2 + 3 O 2 ⁇ 2 Al 2 O 3 + 12 HCl) (see the series Pigments, "highly dispersed metal oxides according to the Aerosil® process", No. 56, 4th edition 1989, Degussa AG).
• the Abbrandstabilisatoren or -moderatoren, component (D) cause, inter alia, a linear burnup, ie an exponential increase in pressure and temperature during the burn is prevented.
• Fe 2 O 3 can serve under certain combustion conditions as an oxygen supplier.
• these compounds can also be used as slag formers to prevent the formation of dust-like Abbrandagen.
• Component (D) is present in an amount of up to about 7% by weight, preferably in an amount of up to about 5% by weight, and more preferably in an amount of about 0.4 to about 5% by weight in the Gas generator fuel composition.
• Highly dispersed Al 2 O 3 is present in the gas generant fuels of the present invention preferably in an amount of up to 5% by weight, preferably in an amount between 0.5-3% by weight and especially 2-3% by weight , This low content of Al 2 O 3 ensures a high gas yield.
• the gas generant fuel compositions of the present invention may contain as component (E) at least one binder.
• suitable binders are cellulose compounds, polymers of one or more polymerisable olefinically unsaturated monomers, a water-insoluble metal salt of stearic acid and graphite. Graphite is particularly preferred.
• cellulose compounds are cellulose ethers, such as carboxymethylcellulose, methylcellulose ethers, in particular Methylhydroxyethylcellulose, a well-usable methylhydroxyethylcellulose is CULMINAL® MHEC 30000 PR from Aqualon, suitable polymers with binding action are polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol and polycarbonates.
• the binder (E) serves as a desensitizer and as a processing aid in the production of granules or tablets from the gas generator fuel composition. It also serves to reduce the hydrophilicity of the gas generator fuel compositions.
• Component (E) is present in an amount of up to about 5% by weight, preferably of up to about 3% by weight, more preferably of up to 1% by weight and in particular of about 0.2 to about 0, 5 wt .-% before.
• Preferred gas generator fuel compositions according to the present invention comprise nitroguanidine, in particular stabilized nitroguanidine according to the invention as fuel (component (A)), Cu (NO 3 ) 2 .3Cu (OH) 2 , Sr (NO 3 ) 2 , KNO 3 or a mixture of KNO 3 and NH 4 ClO 4 as oxidizing agent (component (B)), at least one stabilizer selected from the group consisting of hydrophobic SiO 2 , and boric acid, citric acid, tartaric acid, cyanuric acid, terephthalic acid and fumaric acid, optionally in admixture with hydrophobic SiO 2 (Component (C)), highly dispersed Al 2 O 3 , optionally in admixture with iron (III) oxide as component (D) and graphite as component (E).
• fuel component (A)
• a gas generator fuel composition containing stabilized NIGU as fuel and Sr (NO 3 ) 2 or a mixture of NaNO 3 or KNO 3 with NH 4 ClO 4 as the oxidant even in the presence of burnup stabilizers / moderators and slag formers / scavengers has a good or excellent long-term stability under hot storage at 110 ° C.
• the addition of a stabilizer (component (C)) is not required for the stabilization of the gas generator fuel composition.
• gas generant fuel compositions and gas generator propellants have been manufactured according to the following procedure:
• the starting components (A), (B), (C), if necessary. (D) and optionally (E) were mixed and ground or precompressed by means of a ball mill.
• Granulating the gas generator fuel mixture was carried out in a vertical mixer by adding about 20% water while stirring and at an elevated to about 40 ° C temperature. After briefly flash drying or after predrying, the resulting mixed mass was rubbed at room temperature through a through-hole machine with an 1 mm sieve. The granules obtained in this way were dried for about 2 hours in a drying oven at about 80 ° C.
• the finished granules of the gas generator fuel composition (particle size distribution 0-1 mm) were then pressed into tablets (pellets) using a rotary press. These gas generator propellant pellets were post-dried at 80 ° C in a drying oven.
• the starting components (A), (B), (C), optionally (D) and optionally (E) are dry blended and then compacted under pressure, e.g. by means of a gear compactor.
• the compactate is then broken up into granules and tabletted with a rotary press.
• the tablets or pellets of the gas generator fuel composition used in the gas generators may be made by known methods, such as extrusion, in rotary presses or tableting machines.
• the size of the pellets or tablets depends on the desired firing time in the particular application.
• the gas generator fuel composition according to the invention consists of non-toxic, easily produced and inexpensive components whose processing is not a problem.
• the ignitability of the mixtures is good. They burn quickly and deliver high gas yields with very low CO, NO x and NH 3 levels below the maximum permitted lie.
• the gas generant fuels of the present invention have very good stability with a hot storage of 110 ° C for more than 400 hours.
• the mixtures according to the invention are therefore particularly suitable for use as gas generants in the various airbag systems, but also as extinguishing agents or propellants.
• the percentages are by weight.
• GuNO 3 is the abbreviation for guanidinium nitrate and serves as a lower energy auxiliary fuel.
• NIGU stabilized is nitroguanidine, which is stabilized with a total of 0.2% nitroguanidinium hydrogen sulfate and nitroguanidinium nitrate.
• Comparative Examples 1 to 5 demonstrate the conventional stability of gas generant fuel compositions based on conventional nitroguanidine as a fuel.
• the increasing instability of the gas generator fuel composition results in increasing content of highly dispersed Al 2 O 3 .
• the gas generator fuel composition contains no Al 2 O 3 and has a satisfactory long-term stability at a storage time of 400 hours and 1000 hours, respectively.
• such a gas generator fuel composition is unsuitable for practical use because burn-off performance is insufficient.
• the burning behavior improves with increasing content of Al 2 O 3
• the stability of the gas generator fuel composition decreases rapidly.
• a weight loss of 1.47% is already present for a storage time of 400 hours, and at a content of 5.0% by weight Al 2 O 3 , the weight loss for a storage time of 400 hours is 3.76%. These values are unacceptable for practical use.
• Comparative Example 4 the addition of hydrophobic SiO 2 shows a marked increase in stability. Compared to the formulation according to Comparative Example 5, for a tablet with 4 mm diameter and 2 mm height, there is only a weight loss of 0.62% for a storage period of 400 hours compared to. 1.45% in the formulation according to Comparative Example 5. Both formulations according to Comparative Example 4 and according to Comparative Example 5 contain a sufficient amount of 2.6 wt .-% Al 2 O 3 . However, this stability improvement is not enough to meet the demands of the automotive industry.
• Comparative Example 7 shows the instability of a gas generator fuel composition containing stabilized nitroguanadine in the presence of Cu (NO 3 ) 2 .3Cu (OH) 2 .
• Comparative Examples 8 and 9 an oxidizer mixture of Sr (NO 3 ) 2 and Cu (NO 3 ) 2 .3Cu (OH) 2 was used.
• the Al 2 O 3 additionally present in the formulation according to Comparative Example 9 in turn causes a decrease in the stability.
• Comparative Examples 10 and 11 the stability of stabilized nitroguanidine was examined in the presence of CuCO 3 and CuO, respectively.
• Comparative Example V12 in a gas generator fuel composition containing Al 2 O 3 as component (D), very good stabilization is obtained by the combination of stabilized NIGU as fuel and hydrophobic SiO 2 as stabilizer (see Example 1) with Comparative Examples 4 and 6).
• KNO 3 was used as the oxidizing agent (component (B)) in combination with Al 2 O 3 in highly dispersed form and ferric oxide as component (D).
• the formulation according to Comparative Example V20 contains KClO 4 as oxidizing agent (component (B)) and Aerosil COK 84 as component (D). Again, a very good stability is obtained for the granules.
• Examples 4 to 6 show that a stable gas generator fuel composition can be obtained even in the presence of Al 2 O 3 (see Example 14) without the addition of a stabilizer, if the oxidizing agent is a mixture of KNO 3 and NH 4 ClO 4 in Combination with stabilized NIGU is used as fuel.
• a comparison with Comparative Example 5 demonstrates that such good stability can not be obtained with conventional nitroguanidine as fuel and KNO 3 as oxidant in the presence of Al 2 O 3 .
• Example 6 demonstrates the good stability of gas generator fuel compositions which, in addition to nitroguanidine, also contain guanidinium nitrate (GuNO 3 ) as a lower energy auxiliary fuel.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Air Bags (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2000
  • 2000-12-22 DE DE10064285A patent/DE10064285C1/de not_active Expired - Fee Related
• 2001
  • 2001-12-17 WO PCT/EP2001/014901 patent/WO2002051773A1/de active IP Right Grant
  • 2001-12-17 DE DE50110079T patent/DE50110079D1/de not_active Expired - Lifetime
  • 2001-12-17 EP EP01272021A patent/EP1345872B1/de not_active Expired - Lifetime
  • 2001-12-17 JP JP2002552876A patent/JP3848257B2/ja not_active Expired - Fee Related
  • 2001-12-17 CZ CZ20031998A patent/CZ297751B6/cs not_active IP Right Cessation
  • 2001-12-17 US US10/451,436 patent/US20040108031A1/en not_active Abandoned
  • 2001-12-17 AT AT01272021T patent/ATE328854T1/de active

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