Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B43/00—Compositions characterised by explosive or thermic constituents not provided for in groups C06B25/00 - C06B41/00
• • 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

• 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.
• 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 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.
• 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.
• PCT application WO 94/01381 describes a gas-producing agent for airbags consisting of organic nitrocompounds and halogenates.
• halogenates are to be understood, for example, alkali metal chlorates, bromates and their per-compounds.
• combustion-controlling catalysts oxides, chlorides, carbonates, sulphonates of the 4th to 6th series of the periodic classification.
• the present invention provides non-toxic, azide-free mixtures for the production of gas by combustion.
• 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.
• safety devices for example in airbag systems for inflation of airbags in motor vehicles and aircraft.
• 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:
• 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 CO 2 , N 2 , O 2 and H 2 O, but do not evolve any gases such as CO or NO x 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: in which R 1 and R 2 or R 3 can be the same or different, with either R 2 or R 3 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 guanidinium salts of the said tetrazole derivatives.
• R 1 and R 2 or R 3 can be the same or different, with either R 2 or R 3 being present, and standing for hydrogen, hydroxy, amino,
• R 1 preferably stands for 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
• R 2 or R 3 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, perchlorate and similar compounds, 1-(4-aminophenyl)-tetrazole, 1-(4-nitrophenyl)-tetrazole, 1-methyl-5-dimethylaminotetrazole, 1-methyl-5-methylaminotetrazole, 1-methyltetrazole, 1-phenyl-5-aminotetrazole, 1-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-diallylaminotetra
• the mixtures may contain: as triazine derivatives, 1,3,5-triazine, as triazole derivatives, 1,2,4-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), 1-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.
• derivatives of 5-aminotetrazole its salts in which the acidic hydrogen atoms in 5-aminotetrazole are replaced in salt-like manner by toxicologically acceptable elements such as calcium, magnesium or zinc, are used.
• compounds in which the cation is ammonium, guanidinium and its amino derivatives can also be used.
• Oxidants which may be used according to the invention are:
• the oxidants can be used singly or in mixtures.
• 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/CO 2 equilibrium in the direction of carbon dioxide.
• Moderators which intervene in 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%
• 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 mixture produced is determined by
• additional substances are used whose chemical properties catalyse in particular the conversion of nitrogen oxides, for example nitrogen dioxide, to nitrates or nitrites.
• nitrogen oxides for example nitrogen dioxide
• nitrates or nitrites In principle, all more or less strongly basically reacting substances are suitable.
• 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.
• non-toxic elements such as, for example, those of the alkali and alkaline earth metals, those of zinc, and mixtures of these compounds.
• nitrates and nitrites of the elements are mainly formed.
• Further suitable materials for reaction with NO 2 are urea, guanidine and its derivatives, compounds having NH 2 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 can either be introduced directly into the gas-producing charge or be placed in the outflow 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.
• 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.
• 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.
• 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.
• premixtures of 2 or 3 components can also be used.
• a mixture of oxidant and additions may, for example, be made before it comes into contact with the nitrogen-containing compounds.
• the mixture can also be produced by kneading water-moistened components, followed by granulating, e.g. by passage through sieves, extrusion or the like.
• binders for example waterglass, “inorganic rubber” (phosphorus chloronitrile) or even small proportions of organic 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 caused to react in the enclosed space with the aid of special igniters, no special safety precautions are necessary.
• the bulk material thus obtained can be used directly.
• the bulk material can be surface-coated. This can be done through a varnish coating, which 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 application can be effected by spraying-on the solvent-containing coating agent, e.g. in a drum while evaporating off the solvent.
• porous grain structures in the grains can be used.
• the production of such porous structures can be effected by conventional methods, for example by adding soluble salts and subsequently dissolving them out with suitable solvents or by addition of thermally decomposable substances such as, for example, ammonium bicarbonate, acetone dicarboxylic acid, blowing agents, 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.
• 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 specified components for the gas charges according to the invention are homogenised for 30 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 H 2 O, CO 2 , N 2 and O 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: H 2 O, CO 2 , N 2 and O 2 ). Composition (wt. %) Example No.
• 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.
• 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.
• 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. Composition (wt. %) Example No.
• 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 same time the proportion of CO in the reaction gas can be favourably influenced.

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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)
• Catalysts (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
• Treating Waste Gases (AREA)
• Manufacture And Refinement Of Metals (AREA)

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• 1995
  • 1995-02-18 DE DE19505568A patent/DE19505568A1/de not_active Withdrawn
• 1996
  • 1996-02-13 CA CA002211579A patent/CA2211579A1/en not_active Abandoned
  • 1996-02-13 MX MX9706223A patent/MX9706223A/es active IP Right Grant
  • 1996-02-13 BR BR9607444A patent/BR9607444A/pt not_active IP Right Cessation
  • 1996-02-13 WO PCT/EP1996/000605 patent/WO1996026169A1/de active IP Right Grant
  • 1996-02-13 PL PL96321832A patent/PL183318B1/pl not_active IP Right Cessation
  • 1996-02-13 RU RU97116160/02A patent/RU2250207C2/ru not_active IP Right Cessation
  • 1996-02-13 KR KR1019970705691A patent/KR100417454B1/ko not_active IP Right Cessation
  • 1996-02-13 EP EP96902269A patent/EP0809616A1/de not_active Withdrawn
  • 1996-02-13 CZ CZ0262197A patent/CZ298208B6/cs not_active IP Right Cessation
  • 1996-02-13 CN CN96193147A patent/CN1183758A/zh active Pending
  • 1996-02-13 JP JP8525361A patent/JPH11500098A/ja active Pending
  • 1996-02-13 TR TR97/00813T patent/TR199700813T1/xx unknown
• 2006
  • 2006-11-17 US US11/561,128 patent/US20070102076A1/en not_active Abandoned

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