Classifications

• • 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
  • C06B45/105—The resin being a polymer bearing energetic groups or containing a soluble organic explosive
• • 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 field of automobile safety. More specifically, the invention relates to the protection, in the event of a collision, of the occupants of a motor vehicle by means of a bag which is inflated by gases originating from the combustion of a pyrotechnic composition.
• the invention relates to a composition generating non-toxic hot gases mainly consisting of an inorganic oxidant and a binder based on poly (glycidyl azide).
• compositions mainly generating, by combustion, nitrogen are favorite. These compositions generally consist of an alkali or alkaline earth azide and an oxidant. Such compositions are, for example, described in US Patents 3741585, 4203787 or 4547235. These compositions generate so-called "cold" gases whose temperature at the outlet of the combustion chamber is generally between 600 ° C and 800 ° C but which contain solid residues which must be filtered before the gases enter the bag. Such compositions require the use of complex generators, comprising one or more filtration and cooling chambers. Furthermore, these compositions have poor mechanical strength.
• pyrotechnic composition compositions based on nitrocellulose, optionally plasticized with nitroglycerin, which have the advantage of generating no solid residue and allow the use of very simple generators consisting essentially of an igniter and a combustion chamber without any filtration chamber.
• these nitrocellulose-based compositions have other drawbacks.
• the combustion gases of these compositions have a relatively high content of toxic products, in particular carbon monoxide, which makes certain motor vehicle manufacturers reluctant to use protective devices using these compositions.
• the combustion speed of these compositions very much depends on the pressure prevailing in the combustion chamber, the curve representing the combustion speed of such a composition as a function of the pressure having no "plateau" in the operating zone. .
• compositions essentially comprising a fully combustible oxidant and an organic binder which are known and used in the field of rocket propulsion have good resistance to aging and a combustion rate which is often not very dependent on pressure.
• compositions of this type known to date cannot be used in the automobile safety devices mentioned above because of the toxicity of their combustion gases or the presence, in the latter, of hot solid residues.
• US Pat. No. 5,074,938 describes propellants for self-propulsion constituted mainly by a binder of the polyadipate glycol type, by an energy plasticizer of this binder, by ammonium nitrate and by particles of boron.
• a binder of the polyadipate glycol type by an energy plasticizer of this binder, by ammonium nitrate and by particles of boron.
• Such a composition does indeed have a "plateau" effect with a curve of the combustion rate as a function of the pressure which reveals a low pressure exponent, but the gases generated are, by the very nature of the binder, rich in carbon monoxide and moreover they contain solid particles of boron.
• gases generated cannot be used, without a filtration device, to inflate a safety cushion for a motor vehicle.
• US Pat. No. 4,938,813 illustrates another type of such compositions which are mainly constituted by a binder based on glycidyl polyazide and by an oxidizing charge which is a nitramine such as hexogen or octogen.
• Compositions of this type have although a "plateau" effect with a combustion speed relatively little dependent on the pressure, but the presence of nitramines leads to a high toxicity of the combustion gases incompatible with the standards required for automobile safety.
• these compositions often contain lead additives which add solid residues as additives.
• compositions are mainly constituted by a binder based on a copolymer of glycidyl polyazide and polyepoxide and by a mineral filler which is either nitrate of ammonium, or ammonium perchlorate. These compositions do not exhibit a marked plateau effect and, moreover, the presence of polyepoxide units in the binder results in a significant content in the combustion gases of toxic products, in particular carbon monoxide.
• the object of the present invention is to provide a person skilled in the art with pyrotechnic compositions which generate hot gases which meet the requirements set out above without having the drawbacks which have just been mentioned.
• the invention therefore relates to pyrotechnic compositions generating non-toxic hot gases comprising in particular an organic binder carrying azide groups, an energetic plasticizer and an oxidizing charge characterized in that said binder consists of the reaction product of a polyazide of OH-terminated glycidyl glycidyl with at least one polyisocyanate and in that the said oxidizing charge is made up at least 85% of its weight by ammonium nitrate.
• the compositions contain at least one additive which is chosen from the group consisting of ammonium perchlorate, carbon black and m-methyl p-nitro aniline.
• the content by weight of additive represents up to 3% by weight of the total weight of the composition, the weight content of the energy binder / plasticizer assembly being between 30 and 40% by weight of the total weight of the composition while the weight content of the whole oxidizing charge / additives is between 70% and 60% by weight of the total weight of the composition.
• said energy plasticizer is chosen from the group consisting of butane triol 1,2,4 trinitrate, trimethylolethane trinitrate, triethylene glycol dinitrate, bis (2,2 dinitropropyl) acetal, bis (2,2 dinitropropyl) formal.
• compositions according to the invention burn, essentially giving off nitrogen without producing solid residues.
• combustion rates that are not very dependent on the pressure between 150 and 500 bars, ie between 15 and 50 MPa (Mega Pascal) and of a value compatible with automotive safety requirements.
• the compositions according to the invention therefore prove to be particularly well suited for pyrotechnic gas generators intended to inflate, in the event of a motor vehicle accident, protective cushions, and in particular they are well suited to generators without a filtration device which are very exposed to the sudden drop in pressure caused by the sudden deployment of the airbag.
• a composition according to the invention essentially comprises, as indicated above, a binder, an energy plasticizer, an oxidizing charge and optionally additives.
• the binder consists of the reaction product of a glycidyl polyazide with OH hydroxyl endings with at least one polyisoyanate.
• the glycidyl polyazides with OH hydroxyl endings which can be used in the context of the present invention are polyethers of general formula: in which C, H, O, N represent carbon, hydrogen, oxygen and nitrogen respectively and where n represents an integer between 5 and 100.
• polymers are generally obtained by reaction of sodium azide on a polyepichlorohydrin as described, for example, in US Patents 4,268,450, 4,379,894 or 4,486,351.
• glycidyl polyazides of which the molecular mass is between 600 and 7000 and we prefer those whose molecular mass is between 1500 and 2500.
• polyisocyanate aliphatic, cycloaliphatic or usual aromatics such as, for example, methyl-1 cyclohexane-2,4 diisocyanate, methyl-1 cyclohexane-2,6 diisocyanate, dicyclohexylmethane-4,4 'diisocyanate, isophorone diisocyanate, methylene diisocyanate, hexane-1 , 6 diisocyanate, trimethyl-2, 2,4 hexane-1,6 diisocyanate, toluene diisocyanate, the biuret trimer of hexamethylene diisocyanate, polymethylene polyphenyl isocyanate.
• aromatics such as, for example, methyl-1 cyclohexane-2,4 diisocyanate, methyl-1 cyclohexane-2,6 diisocyanate, dicyclohexylmethane-4,4 'diisocyanate, isophor
• the NCO: OH ratio is close to 1: 1.
• the composition contains an energy plasticizer for the binder.
• the preferred plasticizers are chosen from the group consisting of butane triol 1,2,4 trinitrate, trimethylol ethane trinitrate, triethylene glycol dinitrate, bis (2,2 dinitropropyl) acetal and bis (2,2 dinitropropyl ) formal.
• the content by weight of plasticizer will generally be between 70 and 80% by weight relative to the weight of glycidyl polyazide used.
• the weight content of the energy binder / plasticizer assembly is advantageously between 30 and 40% by weight relative to the total weight of the composition.
• the composition contains an oxidizing charge which is constituted for at least 85% of its weight by ammonium nitrate.
• All of the oxidizing charge can consist of ammonium nitrate, but it is essential in the context of the present invention that ammonium nitrate represents, by weight, at least 85% of the oxidizing charge.
• a stabilized ammonium nitrate will be used.
• the stabilizer could for example consist of a small amount of nickel oxide NiO.
• This quality of ammonium nitrate is sold commercially and generally contains 3% by weight of nickel oxide relative to pure ammonium nitrate.
• the expression "ammonium nitrate” covers the assembly constituted by pure ammonium nitrate and by the stabilizer possibly present.
• nickel oxide is noncombustible, its presence in small amounts proves to be not a problem in the context of the present invention.
• the oxidizing charge is not 100% made up of ammonium nitrate, it can be supplemented by triaminoguanidinium nitrate, by nitroguanidine or by a nitramine such as hexogen or octogen.
• the compositions preferred in the context of the present invention contain, as oxidizing charge, exclusively ammonium nitrate.
• a composition according to the invention may contain additives intended essentially to improve the combustion characteristics and in particular the plateau effect, that is to say the slight influence of the pressure on the combustion rate.
• the additives falling within the scope of the present invention exclude metals or metal compounds and are preferably chosen from the group consisting of potassium perchlorate, carbon black and m-methyl p-nitroaniline.
• the content by weight of additives can represent up to 3% by weight relative to the total weight of the composition.
• the weight content of the whole oxidizing charge / additives is advantageously between 70% and 60% by weight relative to the total weight of the composition.
• compositions according to the invention are advantageously carried out in the following manner.
• the basic constituents of the binder are incorporated, namely the glycidyl polyazide, the isocyanate, the energy plasticizer, the hardener and catalysts intended to promote the reaction of the isocyanate on the glycidyl polyazide, such as dibutyl dilaurate. tin or iron acetyl acetonate.
• the solid constituents are mixed, namely the oxidizing charge optionally stabilized and, where appropriate, the additives.
• the mixture of solid constituents is added in successive fractions until a homogeneous paste is obtained which is put into final form by casting, injection or extrusion followed by baking to complete the crosslinking of the binder.
• compositions according to the invention are generally in the form of pellets or else of solid or tubular blocks.
• compositions burn with combustion rates compatible with the requirements of automotive safety, and without producing solid residues. They also have the double advantage of having on the one hand a substantially constant combustion speed between 100 and 500 bars, that is to say between 10 and 50 MPa, and on the other hand providing combustion gases containing much less carbon monoxide than a traditional nitrocellulose-based composition.
• combustion gases of the compositions according to the invention contain practically no nitrogen oxides, despite a high proportion of nitrogenous constituents in the composition.
• compositions according to the invention can advantageously be used in pyrotechnic gas generators intended for devices for protecting the occupants of a motor vehicle by airbags.
• these compositions also produce hot gases, they find their preferred application in pyrotechnic hot gas generators comprising only one ignition chamber and one combustion chamber directly connected to an airbag operating in addition to a belt. of security.
• This composition gave the following combustion rates: 18 mm / s at 20 Mpa 20 mm / s at 24 MPa 24 mm / s at 36 MPa 26 mm / s at 40 MPa

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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)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (2)

Publications (2)

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Cited By (14)

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Citations (4)

• 1992
  • 1992-06-12 FR FR9207067A patent/FR2692257B1/fr not_active Expired - Fee Related
• 1993
  • 1993-06-07 JP JP5135757A patent/JPH0669916B2/ja not_active Expired - Fee Related
  • 1993-06-14 DE DE69305793T patent/DE69305793T2/de not_active Expired - Fee Related
  • 1993-06-14 EP EP93401513A patent/EP0576326B1/de not_active Expired - Lifetime

Patent Citations (4)

Non-Patent Citations (1)

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