Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B23/00—Compositions characterised by non-explosive or non-thermic constituents
  • C06B23/001—Fillers, gelling and thickening agents (e.g. fibres), absorbents for nitroglycerine
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
  • C06B45/04—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive
  • C06B45/06—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component
  • C06B45/10—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component the organic component containing a resin
• • 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 the pyrotechnic generation of gas, in particular for inflating protective cushions used in systems for protecting the occupants of a motor vehicle.
• the invention relates more particularly to pyrotechnic compositions generating, at temperatures acceptable for motor vehicle safety, clean, so-called "cold" gases, rich in nitrogen and non-toxic, as well as pyrotechnic compounds capable of being obtained from such compositions.
• the pyrotechnic gas generators must supply in extremely short times, of the order of thirty milliseconds, clean gases, that is to say free of particles.
• US Patent 5,608,183 discloses gas-generating pyrotechnic compositions comprising a reducing charge constituted by guanidine nitrate (NG) and an oxidizing charge constituted by basic copper nitrate (BCN) in predetermined proportions. These compositions are very advantageous because they burn at low temperatures below 2000 K, which allows them to be used in gas generators for protective cushion, and because they allow to obtain during their combustion high gas yields .
• NG guanidine nitrate
• BCN basic copper nitrate
• a gas-generating pyrotechnic composition comprising an oxidizing charge constituted by basic copper nitrate (BCN), a reducing charge constituted by guanidine nitrate (NG), as well as a binder, characterized in that it also includes:
• RDX hexogen
• H MX octogen
• PETN pentrite
• TAGN triaminoguanidine nitrate
• nitroguanidine 3-nitro-1, 2,4-triazol-5-one (ONTA) and mono- and bi-tetrazoles
• RDX hexogen
• H MX octogen
• PETN pentrite
• TAGN triaminoguanidine nitrate
• nitroguanidine 3-nitro-1, 2,4-triazol-5-one (ONTA) and mono- and bi-tetrazoles
• the basic copper nitrate (hereinafter BCN), of formula Cu (N ⁇ 3 ) 2 , 3Cu (OH) 2 , is chosen as oxidant because it has the advantage of being perfectly stable and, associated with a reducing agent, to burn, forming easily filterable copper residues.
• the BCN is insoluble in water which is advantageous when the composition uses a water-soluble binder allowing it to be manufactured by extrusion.
• BCN also has a satisfactory gas yield, higher than that of compounds such as copper oxide, and a relatively high oxygen balance (called OB for "Oxygen Balance") of + 30%.
• basic copper nitrate (BCN) is at a mass fraction of between 40 and 60% (very advantageously between 50 and 60%) of the total mass of the composition.
• the reducing charge chosen is guanidine nitrate (NG).
• NG guanidine nitrate
• NG is an organic compound rich in nitrogen, stable and inexpensive.
• guanidine nitrate has very good aging resistance measured by the 400 hour test at 107 ° C.
• the presence of guanidine nitrate (NG) in the composition improves the gas yield of the composition.
• Guanidine nitrate (NG) exhibits an enthalpy of negative formation which also has the effect of lowering the combustion temperature of the composition.
• guanidine nitrate (NG) is at a mass fraction of between 20 and 55% (very advantageously between 20 and 40%) of the total mass of the composition.
• the additional reducing charge in the composition of the invention makes it possible in particular to improve the gas yield and to facilitate the ignition of said composition, therefore to make it more reliable, and to be able to overcome the use of an ignition relay. Ignition relays are expensive products, the use of a composition according to the invention therefore makes it possible to reduce the cost of the gas generator.
• the additional reducing charge chosen is hexogen (RDX) or octogen (HMX). Said additional reducing charge, when it is present, is generally present at a mass fraction of less than 15% relative to the total mass of the composition.
• RDX hexogen
• HMX octogen
• guanidine nitrate a solid solution by substitution.
• This type of solid solution by substitution is per se known to those skilled in the art.
• the chemicals in question in this case, guanidine nitrate, on the one hand and the second oxidant, on the other hand must have: a close molecular size, the same type of crystal lattice, and the same valence ( or degree of oxidation).
• the inventors have, quite surprisingly, highlighted the great interest of this type of solution, within the framework of the invention.
• the impact on the rate of combustion is considerable.
• oxidants already used in pyrotechnics, therefore suitable, within the compositions of the invention, only those which form with guanidine nitrate a solid solution by substitution.
• Particularly suitable are ammonium perchlorate, potassium perchlorate, ammonium nitrate, sodium nitrate and potassium nitrate.
• Particularly suitable are ammonium perchlorate and potassium perchlorate. The intervention of ammonium perchlorate is particularly recommended. We return below to these particular oxidants.
• said additional oxidizing charge when it is present, is at a mass fraction of less than 15%, advantageously less than 10%, of the total mass of the composition.
• Ammonium perchlorate is a very strong oxidant and has a very good gas yield. Its strongly oxidizing nature makes it possible in particular to increase the proportion of reducing charge and therefore guanidine nitrate (NG) in the composition, the latter also having a very good gas yield.
• NG guanidine nitrate
• the presence of ammonium perchlorate in the composition makes it possible, like the additional reducing charge, to facilitate ignition of the composition.
• ammonium perchlorate makes it possible to lower the pressure exponent, which makes the composition less dependent on the pressure and therefore less dependent on the temperature.
• the pressure exponent is particularly low, well below 0.7, which makes it possible to be able to operate the pyrotechnic compound at temperatures between -35 ° C and 85 ° C.
• the composition according to the invention can therefore be used in a motor vehicle. Even if ammonium perchlorate or potassium perchlorate is a strong oxidant and has interesting properties in combustion, its use in a composition leads to obtaining high combustion temperatures and to the generation of combustion gases comprising a rate fairly high hydrogen chloride.
• compositions of the invention are moreover capable of containing a transition metal oxide to catalyze the decomposition of the additional oxidant.
• This transition metal oxide can in particular be an iron, copper or manganese oxide, generally present at a level of less than 5% by weight. It has been indicated that the compositions of the invention contain an additional reducing charge, as described above and / or an additional oxidizing charge, as described above.
• halogens such as, for example, trichlorethylene is regulated, which greatly complicates the manufacture of such a composition and increases its manufacturing cost.
• organic solvents such as that, for example, ketone type solvents (acetone, methyl ethyl ketone, etc.) leads to the implementation of complex solutions to control the emissions of volatile organic compounds (VOCs).
• VOCs volatile organic compounds
• high molecular weight is meant, in the present application and the appended claims, an average molecular weight greater than 250,000 g / mol, advantageously greater than or equal to 700,000 g / mol.
• Carboxymethylcellulose is effective in that it has:
• compositions must have a balanced oxygen balance (called OB for “Oxygen Balance”).
• OB Olygen Balance
• a composition is said to be balanced in oxygen when the composition contains enough oxygen so that after reaction, the various compounds of the composition are found in the form of CO 2 , H 2 O and N 2 .
• the oxygen balance of the binder should be as small as possible.
• Carboxymethylcellulose has a much higher oxygen balance than the oxygen balance of elastomeric binders.
• Carboxymethylcellulose a mixture of short fibers and long fibers, as defined above, is particularly effective in reference to granulation, compression and extrusion operations and is therefore perfectly suited for packaging the composition in the form of pellets, discs or monolithic blocks, mono- or even multi-perforated.
• the mixture of short fibers and long fibers makes it possible to obtain:
• the specific water-soluble binder as specified above, is generally present, within the compositions of the invention, at a mass fraction of between 2 and 15% of the total mass of the composition. Beyond 15%, its influence is likely to be damaging on the oxygen balance of the composition.
• the specificity of the binder of the compositions of the invention made it possible to obtain, by continuous extrusion, using a continuous twin-screw extruder, compounds, under a geometry described in the profession as a block (or grain ) monolithic with mono- or multi-perforations, with an outside diameter varying from a few millimeters to about twenty millimeters.
• the number of perforations can vary from 1 to 19, for perforations from 0.5 to 1.5 mm in diameter.
• the composition of the invention may also comprise additives and in particular additives playing the role of combustion catalysts or agents for trapping the solid particles emitted during combustion. Said agents make it possible to trap solid particles emitted during combustion so as to create residues of a size large enough to be able to be filtered.
• Additives well known in the field of compositions for automotive safety such as alumina or silica can be added to the composition according to the invention.
• the present invention relates to compounds capable of being obtained from the pyrotechnic compositions described above.
• pyrotechnic compounds having a composition as described above are produced and shaped by a process of pelletizing or of compression of discs.
• pyrotechnic compounds having a composition as described above are produced and shaped by an extrusion process.
• pyrotechnic compounds having a composition according to the invention can be produced at a high rate by compression of discs or by pelleting. Before the pelletizing operation, a step of preparing the powder must be carried out. This step cannot be reduced to a simple dry mixing of the various constituents. In fact, in order to be able to carry out the pelletizing operation, it is necessary to obtain a powder which flows well.
• This preparation step is a granulation operation consisting of starting from the various materials entering into the composition of the composition according to the invention and present in pulverulent form to make grains with a higher particle size of the order of a few hundred microns. Once this powder has been obtained, the pelletizing operation can be carried out. These pelletizing or compression processes are per se known to those skilled in the art. According to the invention, pyrotechnic compounds having a composition according to the invention can also be obtained by extrusion. Extrusion is made possible, even optimized, by the presence of the carboxymethylcellulose added with water. In the event that ammonium or potassium perchlorate is involved, care should be taken to incorporate a small amount of water so as to avoid the solubilization of said perchlorate.
• the process for obtaining pyrotechnic compounds by extrusion advantageously comprises a step of continuous supply of a kneading and extrusion apparatus, such as for example a twin-screw extruder, on the one hand with the charge (s) ( s) oxidizing (s) (BCN and optionally the additional oxidizing charge) and on the other hand with the reducing charge (s) (NG and possibly the additional reducing charge) premixed with the binder used (the specific binder used).
• a profiled rod is extruded which is hardened in an oven and then cut to the desired length, for example to form aggregates.
• the monolithic compounds obtained can be mono- or multi-perforated.
• the specificity of the binder (mixture of short fibers and long fibers) makes it possible to obtain such multi-perforated compounds.
• Table 1 presented below shows some examples of formulation of compositions according to the invention. The percentages given are percentages by mass.
• CMC-Na Sodium carboxymethylcellulose (quantity expressed in percent).
• the binder used is a mixture of CMC-Na with a high average molecular weight: Mw ⁇ 700,000 g / mol (BLANOSE ® from AQUALON HERCULES - grade 7H -) and CMC-Na with a low average molecular weight: Mw “90,000 g / mol (BLANOSE ® from AQUALON HERCULES - grade 12UL -).
• the mixtures in question are generally 85/15 mixtures (mass ratio: CMC-Na high molecular weight / CMC-Na low molecular weight).
• BCN Basic Copper Nitrate (quantity expressed in percent)
• NG Guanidine Nitrate (quantity expressed in percent)
• RDX Hexogenic (quantity expressed in percent)
• HMX Octogen (Quantity expressed in percent)
• ONTA 3-nitro-l, 2 , 4-triazol-5-one (quantity expressed in percent)
• OM Metallic Oxide (quantity expressed in percent) as SiO 2 or AI 2 O used in particular as a ballistic catalyst and / or particle trapping agent.
• SiO 2 or AI 2 O used in particular as a ballistic catalyst and / or particle trapping agent.
• Table 3 presents the results obtained for a shot in a 60-liter, 30-gram tank of a composition according to different examples in Table 1.
• Tt0.9 delay separating the ignition time from the moment at which the tank pressure is equal to 90% of the maximum pressure in the tank.
• the composition is ignited with 140 mg of TiPP powder (powder based on titanium hydride and potassium perchlorate) as well as with 450 mg of relay charge.
• ignition is carried out with only 140 mg of TiPP powder. This shows that the presence of ammonium perchlorate or RDX in the compositions makes it possible to greatly improve the ignition and to get rid of the ignition relay.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Dispersion Chemistry (AREA)
• Molecular Biology (AREA)
• Crystallography & Structural Chemistry (AREA)
• Air Bags (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

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• 2004
  • 2004-02-10 FR FR0401253A patent/FR2866022B1/fr not_active Expired - Fee Related
• 2005
  • 2005-02-09 JP JP2006552656A patent/JP4575395B2/ja not_active Expired - Fee Related
  • 2005-02-09 EP EP05717583A patent/EP1713745A2/de not_active Withdrawn
  • 2005-02-09 WO PCT/FR2005/000282 patent/WO2005077862A2/fr not_active Application Discontinuation
  • 2005-02-09 US US10/588,661 patent/US20070181236A1/en not_active Abandoned
  • 2005-02-09 CN CNB2005800045552A patent/CN100390110C/zh not_active Expired - Fee Related

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