EP2616413B1 - Pyrotechnic gas generator compounds - Google Patents

Pyrotechnic gas generator compounds Download PDF

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Publication number
EP2616413B1
EP2616413B1 EP11773097.8A EP11773097A EP2616413B1 EP 2616413 B1 EP2616413 B1 EP 2616413B1 EP 11773097 A EP11773097 A EP 11773097A EP 2616413 B1 EP2616413 B1 EP 2616413B1
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EP
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Prior art keywords
combustion
compound according
advantageously
pressure
compounds
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EP11773097.8A
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German (de)
French (fr)
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EP2616413A2 (en
EP2616413B8 (en
Inventor
Frédéric MARLIN
Stéphane BESOMBES
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ArianeGroup SAS
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ArianeGroup SAS
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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
    • C06B23/007—Ballistic modifiers, burning rate catalysts, burning rate depressing agents, e.g. for gas generating
    • 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
    • C—CHEMISTRY; METALLURGY
    • C06—EXPLOSIVES; MATCHES
    • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
    • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
    • C06B21/0033—Shaping the mixture
    • C06B21/0066—Shaping the mixture by granulation, e.g. flaking
    • 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
    • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
    • C06B29/00—Compositions containing an inorganic oxygen-halogen salt, e.g. chlorate, perchlorate
    • C06B29/02—Compositions containing an inorganic oxygen-halogen salt, e.g. chlorate, perchlorate of an alkali metal
    • C06B29/08—Compositions containing an inorganic oxygen-halogen salt, e.g. chlorate, perchlorate of an alkali metal with an organic non-explosive or an organic non-thermic component
    • 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
    • C06D5/02—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets by decompressing compressed, liquefied or solidified gases
    • 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 pyrotechnic gas-generating compounds, suitable for use in systems for protecting occupants of motor vehicles, more especially for the inflation of damping cushions (called “airbags”) and more particularly for the inflation of airbags.
  • airbags damping cushions
  • side cushioning cushions so-called side “airbags” (see below)).
  • Side airbag systems differ from front airbag systems essentially by the time required for deployment and installation of the airbag. Typically, this time is shorter for a side airbag (of the order of 10-20 ms, against 40-50 ms for a front airbag).
  • a side airbag the functional need to inflate the bag over a short period of time requires the use of a pyrotechnic composition having a sufficiently high combustion speed (typically equal to or greater than 30 mm / s, or even 35 mm / s, at 20 MPa ) over the operating pressure range in the combustion chamber of the generator, in order to obtain a sufficient inflation surface flow value (product pxnx Tc x Vc).
  • the pyrotechnic composition must also have good ignitability characteristics. Also, taking into account the generally declining surface profile of the loadings employed (of the pellet type), the composition should ideally exhibit a stable and sufficiently high combustion rate at low pressure.
  • the side airbags is more restrictive than that for the front airbags. Obviously, any technological advance in the field of said side airbags can also advantageously be applied in the field of front airbags.
  • a pressure P such as: 0.1 ⁇ P ⁇ 10 MPa, by medium pressure, a pressure P such that: 10 MPa ⁇ P ⁇ 30 MPa, by high pressure, a pressure P such that: P ⁇ 30 MPa.
  • the desired increase in the combustion rate of the pyrotechnic compound in question is therefore not only necessary to increase the gas flow rate in order to achieve the inflation time specifications, but also to ensure the ignitability of the compound without resorting to the use of a relay charge and the harmlessness of the combustion products.
  • said combustion temperature must not be too high (it must at least remain below 2400 K, more favorably below 2350 K) so that the temperature of the gases in the damping pad does not affect the integrity. occupant's physical condition.
  • a low combustion temperature makes it possible, on the one hand, to limit the thickness of the bag and, on the other hand, to simplify the design of the gas generator by making it possible to reduce the presence of baffles and filters within it. this.
  • the side airbag systems can use two types of gas generators: those called entirely pyrotechnic (the gas generation is then ensured exclusively by the combustion of a pyrotechnic charge) and those called “hybrid” (the gases then coming from a joint combustion of a pyrotechnic charge and a volume of neutral gas stored under pressure in a sealed tank).
  • gas generators those called entirely pyrotechnic (the gas generation is then ensured exclusively by the combustion of a pyrotechnic charge) and those called “hybrid” (the gases then coming from a joint combustion of a pyrotechnic charge and a volume of neutral gas stored under pressure in a sealed tank).
  • the pyrotechnic charge must not have a combustion temperature that is too low so that the combustion gases are hot enough to compensate for the temperature drop caused by the expansion of the volume of the pre-compressed neutral gas. .
  • combustion temperatures above 2000 K are required.
  • pyrotechnic compounds which are suitable for use in fully pyrotechnic gas generators or in hybrid generators, more particularly intended for side airbags, that is to say simultaneously having a moderate combustion temperature of the order of 2000-2400 K, more favorably 2000-2350 K, and a high combustion rate over the entire operating pressure range (especially greater than 30 mm / s at 20 MPa, more favorably greater at 35 mm / s at 20 MPa) , including at low pressure .
  • the basic ingredients of the compounds be pyrotechnically non-hazardous.
  • ingredient (s) belonging to the class of explosives such as nitroguanidine, hexogen (RDX), octogen (HMX).
  • Explosive ingredients are understood to mean ingredients classified in risk division 1.1 according to standard NF T 70-502 (see also UN - Recommendations on the Transport of Dangerous Goods - Manual of Tests and Criteria, Fourth Revised Edition, ST / SG / AC.10 / 11 / Rev.4, ISBN 92-1-239083-8ISSN 1014-7179 and STANAG 4488 ).
  • Guanidine nitrate and potassium perchlorate, taken separately, are not ingredients classified in this risk division. They do not constitute explosive ingredients, in particular within the meaning of the invention.
  • These compounds also include in their composition a low level of a ballistic catalyst, consisting of an oxygenated compound of a transition metal, advantageously with a high specific surface area, traditionally used in the field of propellants to increase the combustion rate at medium and high pressure (this catalyst accelerates the decomposition of the oxidizing charge).
  • a ballistic catalyst consisting of an oxygenated compound of a transition metal, advantageously with a high specific surface area, traditionally used in the field of propellants to increase the combustion rate at medium and high pressure (this catalyst accelerates the decomposition of the oxidizing charge).
  • Gas micro-generators for belt tensioner devices as described in said patent US 6,893,517 (and in its priority request EP 1 275 629 ) operate in pulses, which requires a high rate of combustion at medium and high pressure.
  • a strong exponent of pressure at low pressure and the non-combustion at atmospheric pressure of the compounds in question do not pose a problem, insofar as the pressure does not drop, in the context of use of said compounds, to a low level before the end of pyrotechnic operation.
  • This application for belt tensioner devices does not require, for the gas generator, requirements as severe as those required in the context of the present invention (airbags, and more particularly side airbags), in particular a high combustion speed. at low pressure, a lowering of the combustion pressure limit threshold (as close as possible to atmospheric pressure) and a low pressure exponent over the entire combustion range (especially at low pressure).
  • the pyrotechnic compounds which offer a good compromise, in terms of gas temperature, gas yield, rate of particles emitted and toxicity, contain, as main ingredients, guanidine nitrate (NG) in as a reducing filler and basic copper nitrate (BCN) as an oxidizing filler.
  • NG guanidine nitrate
  • BCN basic copper nitrate
  • said patent describes the need to add to the mixture of guanidine + ammonium perchlorate type a metal compound of iron oxide type in order to neutralize the hydrochloric acid present in the combustion gases, which has the consequence of reducing the gas yield value of the compound.
  • thermodynamic and ballistic characteristics of such a compound (reference compound 1), whose composition ("binary") contains only guanidine nitrate (NG) and potassium perchlorate (KClO 4 ), are presented in Table 1 below.
  • Table 1 Ingredients Guanidine nitrate % by mass 68.0 Potassium perchlorate % by mass 32.0 Characteristics Oxygen balance % -3 Density g / cm 3 1.67 T combustion at 20MPa K 2351 Gas yield at 1bar - 1000 K Mole / kg 33.2 Burning rate at 8MPa (low pressure) mm / s 20.6 Burning rate at 20MPa (medium pressure) mm / s 26.3 Burning rate at 50MPa (high pressure) mm / s 34.9 Pressure exponent determined between 6 and 52 MPa 0.26 Gas rate at 1 bar - 1000 K % 82.5 KCl level % 17.1 Combustion limit pressure (1) MPa 1.7 (1): the value given is a relative pressure. A zero combustion limit pressure correspond
  • Reference compound 1 exhibits numerous advantages among those expected from a compound for a gas generator for an airbag system.
  • the basic ingredients are simple and easily obtainable, inexpensive, non-hazardous in terms of pyrotechnics (no constituent belonging to the class of explosive compounds) and non-toxic.
  • the thermodynamic performance (gas yield, particle rate) is good and the combustion temperature remains moderate and therefore acceptable.
  • the particles emitted by combustion are non-toxic (mainly KCl).
  • the combustion speed of the order of 26 mm / s at 20 MPa is only increased by 20 to 30% compared to that of a compound based on Guanidine nitrate (NG) and basic copper nitrate (BCN), and remains low compared to the specifications set.
  • NG Guanidine nitrate
  • BCN basic copper nitrate
  • the ingredients of the first three types above generally represent more than 90% by mass of the total mass (of the composition) of the compounds of the invention, very generally at less 94% by mass, or even more than 98% by mass.
  • additive such as processing aids (calcium stearate, silica for example)
  • the ingredients of the three types above can quite represent 100% by mass of the total mass of the compounds of the invention.
  • Guanidine nitrate representing 60 to 70% of the total mass, is among other things used for pyrotechnic safety reasons and for its rheo-plastic behavior, suitable for the implementation of the compaction phases and possible pelletizing of the lane process.
  • dry see below
  • the manufacture of compounds by the dry process comprises up to four main steps (see below), which have in particular been described in the patent application WO 2006/134311 .
  • Potassium perchlorate is present, in the composition of the compounds of the invention, at an intermediate, moderate content (from 26 to 33% by mass, advantageously from 26 to 30% by mass), most particularly with reference to the combustion temperature, "ignitability" and high pressure burning rate referred to.
  • the combustion modifiers selected by the inventors, develop particularly interesting (unexpected) properties with reference to the three points of improvement sought (see above).
  • Said at least one combustion modifier is chosen from transition metal oxides, precursors of such oxides and mixtures thereof.
  • a precursor of such an oxide leads to the formation of such an oxide (generates such an oxide) during its temperature decomposition during the combustion of the pyrotechnic compound.
  • basic copper nitrate (Cu (NO 3 ) 2 ⁇ 3Cu (OH) 2 ) decomposes into copper oxide (CuO) (see below).
  • Said at least one combustion modifier is present in a sufficient quantity ( ⁇ 2.5% by mass), to be effective (with reference to the three points of improvement above), and not excessive ( ⁇ 6% by mass) so as not to affect the gas yield.
  • a single combustion modifier is generally present but the presence of at least two such additives is expressly provided for within the scope of the present invention.
  • said at least one combustion modifier is chosen from zinc oxide (ZnO), iron oxide (Fe 2 O 3 ), chromium oxide (Cr 2 O 3 ), manganese (MnO 2 ), copper oxide (CuO), basic copper nitrate (Cu (NO 3 ) 2 ⁇ 3Cu (OH) 2 ) and their mixtures.
  • Copper oxide and basic copper nitrate, a precursor of said copper oxide are particularly efficient.
  • the compounds of the invention therefore contain, as a modifier of combustion, copper oxide and / or basic copper nitrate. The use of these combustion modifiers makes it possible to obtain compounds of the invention having a pressure exponent value less than or equal to 0.1 over the pressure range 6-52 MPa.
  • said at least one combustion modifier according to the invention has a specific surface area greater than 3 m 2 / g, advantageously greater than 10 m 2 / g, very advantageously greater than 25 m 2 / g.
  • the pyrotechnic compounds of the invention may contain, at a low mass content (less than or equal to 6%, generally of at least 0.1%), at least one additive, in particular at least one additive facilitating their obtaining (shaping, during their obtaining), such as calcium or magnesium stearate, graphite and / or at least an additive improving the aggregation of the solid products of their combustion, chosen from refractory oxides at a softening or melting temperature suitable for the composition, such as silica or alumina.
  • at least one additive in particular at least one additive facilitating their obtaining (shaping, during their obtaining), such as calcium or magnesium stearate, graphite and / or at least an additive improving the aggregation of the solid products of their combustion, chosen from refractory oxides at a softening or melting temperature suitable for the composition, such as silica or alumina.
  • silica generally introduced in fine pulverulent form (advantageously of micrometric dimension, very advantageously of nanometric dimension) having a high specific surface area. (advantageously 100 m 2 / g or more) or in the form of silica fibers of small diameter (1 to 20 microns) and a few tens or hundreds of microns (20 to 500 microns) in length.
  • silica at levels of between 0.5 and 6% by mass, advantageously between 0.5 and 3.5% in mass, also has a very significant effect of lowering the combustion limit pressure.
  • the at least one additive intervenes with the constituent ingredients (NG, KClO 4 + at least one combustion modifier of the aforementioned type) (at the start of the manufacturing process) or is added, further downstream, in the manufacturing process of the compounds of invention.
  • compositions of the compounds of the invention do not contain an explosive ingredient (see the NF standard and the UN recommendations specified above), and this, in particular with reference to the parameters: pyrotechnic safety and combustion temperature. It should also be noted that the masses of pyrotechnic compounds required for the inflation of an air bag, in particular a side air bag, are greater than those required for the inflation of a belt retractor device according to the patent. US 6,893,517 (said inflations not being of the same type: inflation time greater than 10-20 ms / per pulse).
  • the pyrotechnic compounds of the invention can be obtained by a wet process.
  • said method comprises the extrusion of a paste containing the constituents of the compound.
  • said process includes a step of dissolving all the (or some of the) main constituents in aqueous solution comprising a solubilization of at least one of said main constituents (oxidant and / or reducing agent) and then obtaining d 'a powder by spray drying, adding to the powder obtained the constituent (s) which have not been put into solution, then shaping the powder in the form of objects by the usual dry processes.
  • the pyrotechnic compounds of the invention can also be obtained in the dry process, for example by simple pelletizing of the powder obtained by mixing their constituents.
  • the constituent ingredients of the compounds of the invention advantageously have a fine particle size, less than or equal to 20 ⁇ m.
  • Said particle size (value of the median diameter) is generally between 3 and 20 ⁇ m.
  • the compounds described in the present invention express their full potential if they are obtained by a dry process from powders having a median diameter of between 10 and 20 ⁇ m for KClO 4 and 5 to 15 ⁇ m for guanidine nitrate .
  • the present invention relates to a pulverulent composition (mixture of powders), precursor of a compound of the invention, the composition of which therefore corresponds to that of a compound of the invention (see above ).
  • the present invention relates to gas generators containing at least one pyrotechnic compound of the invention.
  • Said generators are perfectly suitable for airbags, in particular side airbags (see above).
  • Table 2 shows examples of compositions of compounds of the present invention, as well as the performances of said compounds compared with those of the reference compound of the prior art 1.
  • the compounds were evaluated by means of thermodynamic calculations or by means of thermodynamic calculations. from physical measurements carried out on granules or pellets made from the compositions via the mixing process of powders - compacting - granulation - and possibly dry pelletizing.
  • the reference compound 1 of the prior art contains guanidine nitrate and potassium perchlorate and does not contain a combustion modifier within the meaning of the invention.
  • the compounds of Examples 1 to 7 contain in their composition, in addition to the two constituents of the reference compound 1, such a combustion modifier.
  • the levels of the major constituents were adjusted in order to maintain an oxygen balance value close to -3%, so as to be able to directly compare the performance of the compounds in Table 1.
  • said addition leads jointly to a very significant lowering of the pressure exponent, very low pressure exponent over the entire operating pressure range (beyond 6 MPa), of the combustion limit pressure and to a significant increase in the rate of combustion at low pressure.
  • CuO is the compound which, added to Reference Composition 1, provides the most significant improvements (see Example 2).
  • the pressure exponent is almost zero over the entire operating range, the operating limit pressure is almost equal to atmospheric pressure.
  • Table 3 shows the second surprising effect demonstrated by the inventors, namely the very significant reduction in the combustion limit pressure (measured on granules) when silica is introduced at a moderate rate into the gas. composition of the compounds of the invention. This same effect, obtained with another refractory metal oxide such as alumina, is not of sufficient magnitude to be of interest.
  • TABLE 3 Examples Ref. 1 Ex. 8 Ex. 9 Ingredients unity Guanidine nitrate % 68.0 65.0 65.0 Potassium perchlorate % 32.0 30.0 30.0 Alumina % - 5.0 - Silica % - - 5.0 Characteristic Combustion limit (relative) pressure MPa 1.7 1.5 0.5

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

Description

La présente invention a pour objet des composés pyrotechniques générateurs de gaz, convenant pour une utilisation dans des systèmes de protection d'occupants de véhicules automobiles, plus spécialement pour le gonflage de coussins amortissants (dits "airbags") et tout particulièrement pour le gonflage de coussins amortissants latéraux (dits "airbags" latéraux (voir ci-dessous)).The present invention relates to pyrotechnic gas-generating compounds, suitable for use in systems for protecting occupants of motor vehicles, more especially for the inflation of damping cushions (called "airbags") and more particularly for the inflation of airbags. side cushioning cushions (so-called side "airbags" (see below)).

Le domaine technique relatif à la protection des occupants de véhicules automobiles a connu un essor très important durant les vingt dernières années. Les véhicules de dernière génération intègrent dorénavant au sein de l'habitacle plusieurs systèmes de sécurité, de type coussin gonflable amortissant (dit "airbag") dont le fonctionnement est assuré par les gaz de combustion de composés pyrotechniques. Parmi les systèmes de type coussin amortissant, on distingue principalement les airbags frontaux pour choc frontal et les airbags latéraux pour choc latéral.The technical field relating to the protection of occupants of motor vehicles has experienced a very significant development during the last twenty years. The latest generation vehicles now integrate several safety systems in the passenger compartment, of the damping airbag type (called "airbag"), the operation of which is ensured by the combustion gases of pyrotechnic compounds. Among the cushioning cushion-type systems, a main distinction is made between front airbags for frontal impact and side airbags for side impact.

Les systèmes airbags latéraux se différencient des systèmes airbags frontaux essentiellement par le temps requis pour le déploiement et la mise en place du coussin gonflable. Typiquement, ce temps est plus court pour un airbag latéral (de l'ordre de 10-20 ms, contre 40-50 ms pour un airbag frontal). Pour un airbag latéral, le besoin fonctionnel de gonflage du sac sur un temps court impose de recourir à une composition pyrotechnique présentant une vitesse de combustion suffisamment élevée (typiquement égale ou supérieure à 30 mm/s, voire 35 mm/s, à 20 MPa) sur la plage de pression de fonctionnement dans la chambre de combustion du générateur, ceci afin d'obtenir une valeur de débit surfacique de gonflage (produit p x n x Tc x Vc) suffisante. Par ailleurs, afin d'assurer une mise en régime satisfaisante du système, la composition pyrotechnique doit également présenter de bonnes caractéristiques d'allumabilité. Aussi, compte tenu du profil de surface généralement dégressif des chargements employés (de type pastille), la composition doit idéalement présenter une vitesse de combustion stable et suffisamment élevée à basse pression. En fait, l'homme du métier n'ignore pas que le cahier des charges des airbags latéraux est plus contraignant que celui des airbags frontaux. Bien évidemment, toute avancée technologique dans le domaine desdits airbags latéraux peut aussi avantageusement se décliner dans le domaine des airbags frontaux.Side airbag systems differ from front airbag systems essentially by the time required for deployment and installation of the airbag. Typically, this time is shorter for a side airbag (of the order of 10-20 ms, against 40-50 ms for a front airbag). For a side airbag, the functional need to inflate the bag over a short period of time requires the use of a pyrotechnic composition having a sufficiently high combustion speed (typically equal to or greater than 30 mm / s, or even 35 mm / s, at 20 MPa ) over the operating pressure range in the combustion chamber of the generator, in order to obtain a sufficient inflation surface flow value (product pxnx Tc x Vc). Furthermore, in order to ensure satisfactory start-up of the system, the pyrotechnic composition must also have good ignitability characteristics. Also, taking into account the generally declining surface profile of the loadings employed (of the pellet type), the composition should ideally exhibit a stable and sufficiently high combustion rate at low pressure. In fact, those skilled in the art are aware that the The specification for the side airbags is more restrictive than that for the front airbags. Obviously, any technological advance in the field of said side airbags can also advantageously be applied in the field of front airbags.

Dans le présent texte, on définit par basse pression, une pression P telle que : 0,1 ≤ P < 10 MPa, par moyenne pression, une pression P telle que : 10 MPa ≤ P < 30 MPa, par haute pression, une pression P telle que : P ≥ 30 MPa.In this text, by low pressure, we define a pressure P such as: 0.1 ≤ P <10 MPa, by medium pressure, a pressure P such that: 10 MPa ≤ P <30 MPa, by high pressure, a pressure P such that: P ≥ 30 MPa.

Il est par ailleurs d'usage de compenser les faibles vitesses de combustion des composés pyrotechniques utilisés dans les générateurs de gaz pour airbag actuels, en ayant recours à des chargements composés de pastilles de très faibles dimensions. Bien que n'étant pas économiquement intéressant du fait du faible débit massique de production des machines de pastillage et des coûts d'outillage induits, ceci permet, dans une certaine mesure, de pallier en partie le manque de vitesse de combustion. Cette solution accentue toutefois deux autres inconvénients :

  • la difficulté d'allumage, qui est augmentée du fait de la forte surface initiale du chargement, ce qui nécessite alors l'emploi d'un allumeur renforcé ou l'ajout d'une charge supplémentaire faisant office de relais d'allumage ;
  • une forte dégressivité de la surface en combustion du fait de la dimension réduite des pastilles, ce qui induit une longue queue de combustion à basse pression. Cette longue queue de combustion à basse pression est la source de l'émission de la majorité des espèces toxiques présentes dans les gaz servant à gonfler le coussin.
It is also customary to compensate for the low combustion rates of the pyrotechnic compounds used in current airbag gas generators, by having recourse to charges made up of pellets of very small dimensions. Although not economically advantageous due to the low mass flow rate of production of the pelletizing machines and the resulting tooling costs, this makes it possible, to a certain extent, to partially compensate for the lack of combustion speed. However, this solution accentuates two other drawbacks:
  • the difficulty of ignition, which is increased due to the large initial surface area of the load, which then requires the use of a reinforced igniter or the addition of an additional load acting as an ignition relay;
  • a strong degressivity of the combustion surface due to the reduced size of the pellets, which induces a long combustion tail at low pressure. This long tail of combustion at low pressure is the source of the emission of the majority of the toxic species present in the gases used to inflate the cushion.

Il convient donc de noter que l'augmentation recherchée de la vitesse de combustion du composé pyrotechnique en cause, sur toute la plage de pression, y compris à basse pression, est donc non seulement nécessaire pour accroître le débit de gaz afin d'atteindre les spécifications de délai de gonflage, mais aussi pour assurer l'allumabilité du composé sans recourir à l'emploi d'une charge relais et l'innocuité des produits de combustion.It should therefore be noted that the desired increase in the combustion rate of the pyrotechnic compound in question, over the entire pressure range, including at low pressure, is therefore not only necessary to increase the gas flow rate in order to achieve the inflation time specifications, but also to ensure the ignitability of the compound without resorting to the use of a relay charge and the harmlessness of the combustion products.

De surcroit, il existe des contraintes en référence à la température de combustion.In addition, there are constraints with reference to the combustion temperature.

De façon générale, ladite température de combustion ne doit pas être trop élevée (elle doit a minima rester inférieure à 2400 K, plus favorablement inférieure à 2350 K) afin que la température des gaz dans le coussin amortissant ne porte pas atteinte à l'intégrité physique de l'occupant. Une température de combustion basse permet, d'une part, de limiter l'épaisseur du sac et, d'autre part, de simplifier la conception du générateur de gaz en permettant de diminuer la présence de chicanes et de filtres au sein de celui-ci.In general, said combustion temperature must not be too high (it must at least remain below 2400 K, more favorably below 2350 K) so that the temperature of the gases in the damping pad does not affect the integrity. occupant's physical condition. A low combustion temperature makes it possible, on the one hand, to limit the thickness of the bag and, on the other hand, to simplify the design of the gas generator by making it possible to reduce the presence of baffles and filters within it. this.

Les systèmes airbags latéraux peuvent faire appel à deux types de générateurs de gaz : ceux dits entièrement pyrotechniques (la génération de gaz étant alors assurée exclusivement par la combustion d'un chargement pyrotechnique) et ceux dits "hybrides" (les gaz provenant alors de façon conjointe de la combustion d'un chargement pyrotechnique et d'un volume de gaz neutre stocké sous pression dans un réservoir étanche). Pour les générateurs de type "hybride", le chargement pyrotechnique ne doit pas présenter une température de combustion trop basse afin que les gaz de combustion soient suffisamment chauds pour compenser la baisse de température engendrée par l'expansion de volume du gaz neutre pré-comprimé. Idéalement, des températures de combustion supérieures à 2000 K sont requises.The side airbag systems can use two types of gas generators: those called entirely pyrotechnic (the gas generation is then ensured exclusively by the combustion of a pyrotechnic charge) and those called "hybrid" (the gases then coming from a joint combustion of a pyrotechnic charge and a volume of neutral gas stored under pressure in a sealed tank). For "hybrid" type generators, the pyrotechnic charge must not have a combustion temperature that is too low so that the combustion gases are hot enough to compensate for the temperature drop caused by the expansion of the volume of the pre-compressed neutral gas. . Ideally, combustion temperatures above 2000 K are required.

Ainsi, l'homme du métier est à la recherche de composés pyrotechniques qui conviennent pour une utilisation dans des générateurs de gaz entièrement pyrotechniques ou dans des générateurs hybrides, plus particulièrement destinés à des airbags latéraux, c'est-à-dire présentant simultanément une température de combustion modérée de l'ordre de 2000-2400 K, plus favorablement 2000-2350 K, et une vitesse de combustion élevée sur toute la plage de pression de fonctionnement (notamment supérieure à 30 mm/s à 20 MPa, plus favorablement supérieure à 35 mm/s à 20 MPa), y compris à basse pression.Thus, those skilled in the art are looking for pyrotechnic compounds which are suitable for use in fully pyrotechnic gas generators or in hybrid generators, more particularly intended for side airbags, that is to say simultaneously having a moderate combustion temperature of the order of 2000-2400 K, more favorably 2000-2350 K, and a high combustion rate over the entire operating pressure range (especially greater than 30 mm / s at 20 MPa, more favorably greater at 35 mm / s at 20 MPa) , including at low pressure .

En outre, les composés pyrotechniques pour airbags doivent aussi tendre à satisfaire conjointement aux exigences suivantes :

  • les gaz générés par la combustion du chargement pyrotechnique (comprenant un composé ou n composés) doivent être non toxiques, c'est-à-dire présenter une teneur faible en monoxyde de carbone, en oxydes d'azote et en composés chlorés ;
  • le rendement gazeux (c'est-à-dire la quantité de gaz généré par la combustion) doit être élevé afin de conduire à un fort pouvoir de gonflage ;
  • la quantité de particules solides générées par la combustion, susceptibles de constituer des points chauds pouvant endommager la paroi du coussin gonflable, doit demeurer faible ;
  • l'exposant de pression doit être le plus faible possible, notamment à moyenne et haute pression (typiquement inférieur à 0,35 ainsi que décrit dans l'art antérieur) mais aussi à basse pression. Un faible exposant de pression permet en effet de réduire de manière très significative la variabilité du fonctionnement entre la température extrême basse (vers
  • 40°C) et la température extrême haute (vers 90°C) requises dans le domaine d'utilisation. La reproductibilité du fonctionnement est de ce fait améliorée et la dimension de la structure métallique du générateur peut être avantageusement réduite ;
  • leur pression limite de combustion doit être aussi proche que possible de la pression atmosphérique.
In addition, pyrotechnic compounds for airbags must also tend to meet the following requirements together:
  • the gases generated by the combustion of the pyrotechnic charge (comprising one compound or n compounds) must be non-toxic, that is to say have a low content of carbon monoxide, nitrogen oxides and chlorinated compounds;
  • the gas yield (that is to say the quantity of gas generated by the combustion) must be high in order to lead to a high inflation power;
  • the quantity of solid particles generated by the combustion, likely to constitute hot spots which could damage the wall of the airbag, must remain low;
  • the pressure exponent must be as low as possible, in particular at medium and high pressure (typically less than 0.35 as described in the prior art) but also at low pressure. A low pressure exponent makes it possible to very significantly reduce the variability of the operation between the extreme low temperature (towards
  • 40 ° C) and the extreme high temperature (around 90 ° C) required in the field of use. The reproducibility of the operation is thereby improved and the dimension of the metal structure of the generator can be advantageously reduced;
  • their combustion limit pressure must be as close as possible to atmospheric pressure.

Il est aussi vivement souhaitable que les ingrédients de base des composés soient non dangereux sur le plan pyrotechnique. On évite avantageusement la présence d'ingrédient(s) appartenant à la classe des explosifs tels que la nitroguanidine, l'hexogène (RDX), l'octogène (HMX). On entend par ingrédients explosifs les ingrédients classés en division de risque 1.1 selon la norme NF T 70-502 (voir aussi ONU - Recommandations relatives au Transport des marchandises dangereuses - manuel d'épreuves et de critères, Quatrième édition révisée, ST/SG/AC.10/11/Rev.4, ISBN 92-1-239083-8ISSN 1014-7179 et STANAG 4488 ). Le nitrate de guanidine et le perchlorate de potassium, pris séparément, ne sont pas des ingrédients classés dans cette division de risque. Ils ne constituent pas des ingrédients explosifs, notamment au sens de l'invention.It is also highly desirable that the basic ingredients of the compounds be pyrotechnically non-hazardous. Advantageously avoids the presence of ingredient (s) belonging to the class of explosives such as nitroguanidine, hexogen (RDX), octogen (HMX). Explosive ingredients are understood to mean ingredients classified in risk division 1.1 according to standard NF T 70-502 (see also UN - Recommendations on the Transport of Dangerous Goods - Manual of Tests and Criteria, Fourth Revised Edition, ST / SG / AC.10 / 11 / Rev.4, ISBN 92-1-239083-8ISSN 1014-7179 and STANAG 4488 ). Guanidine nitrate and potassium perchlorate, taken separately, are not ingredients classified in this risk division. They do not constitute explosive ingredients, in particular within the meaning of the invention.

Il faut à ce stade signaler que l'incorporation d'ingrédients hautement énergétiques explosifs tels que la nitroguanidine, même à des taux réduits, contribue de façon préjudiciable à augmenter la température de combustion des composés, au-delà du seuil limite de 2350 K fixé par le besoin d'amélioration technique recherché par les inventeurs. Ainsi, des composés tels que décrits dans le brevet US 6 893 517 , consistant principalement en un mélange d'un dérivé de la guanidine (préférentiellement du nitrate de guanidine), d'un composé azoté explosif (préférentiellement de la nitroguanidine) et d'un oxydant inorganique (tel le perchlorate d'ammonium ou le perchlorate de potassium) ne répondent pas aux exigences du cahier des charges de la présente invention. Ces composés incluent en outre dans leur composition un faible taux d'un catalyseur balistique, constitué d'un composé oxygéné d'un métal de transition, avantageusement à haute surface spécifique, traditionnellement utilisé dans le domaine des propergols pour augmenter la vitesse de combustion à moyenne et haute pression (ce catalyseur accélère la décomposition de la charge oxydante). Les micro-générateurs de gaz pour dispositifs pour rétracteur de ceinture tels que décrits dans ledit brevet US 6 893 517 (et dans sa demande prioritaire EP 1 275 629 ) fonctionnent par impulsions, ce qui nécessite une forte vitesse de combustion à moyenne et haute pression. Un fort exposant de pression à basse pression et la non combustion à pression atmosphérique des composés en cause ne posent pas de problème, dans la mesure où la pression ne redescend pas, dans le contexte d'utilisation desdits composés, à un niveau bas avant la fin du fonctionnement pyrotechnique. Cette application pour des dispositifs de rétracteur de ceinture ne requiert pas, pour le générateur de gaz, des exigences aussi sévères que celles requises dans le contexte de la présente invention (airbags, et tout particulièrement airbags latéraux), tout particulièrement une vitesse de combustion élevée à basse pression, un abaissement du seuil limite de pression de combustion (au plus proche de la pression atmosphérique) et un faible exposant de pression sur toute la plage de combustion (notamment à basse pression).At this stage, it should be pointed out that the incorporation of high energy explosive ingredients such as nitroguanidine, even at reduced rates, adversely contributes to increasing the combustion temperature of the compounds, beyond the limit threshold of 2350 K set. by the need for technical improvement sought by the inventors. Thus, compounds as described in the patent US 6,893,517 , consisting mainly of a mixture of a derivative of guanidine (preferably guanidine nitrate), an explosive nitrogen compound (preferably nitroguanidine) and an inorganic oxidant (such as ammonium perchlorate or perchlorate of potassium) do not meet the requirements of the specifications of the present invention. These compounds also include in their composition a low level of a ballistic catalyst, consisting of an oxygenated compound of a transition metal, advantageously with a high specific surface area, traditionally used in the field of propellants to increase the combustion rate at medium and high pressure (this catalyst accelerates the decomposition of the oxidizing charge). Gas micro-generators for belt tensioner devices as described in said patent US 6,893,517 (and in its priority request EP 1 275 629 ) operate in pulses, which requires a high rate of combustion at medium and high pressure. A strong exponent of pressure at low pressure and the non-combustion at atmospheric pressure of the compounds in question do not pose a problem, insofar as the pressure does not drop, in the context of use of said compounds, to a low level before the end of pyrotechnic operation. This application for belt tensioner devices does not require, for the gas generator, requirements as severe as those required in the context of the present invention (airbags, and more particularly side airbags), in particular a high combustion speed. at low pressure, a lowering of the combustion pressure limit threshold (as close as possible to atmospheric pressure) and a low pressure exponent over the entire combustion range (especially at low pressure).

Actuellement, pour les airbags frontaux, les composés pyrotechniques qui offrent un bon compromis, en termes de température de gaz, de rendement gazeux, de taux de particules émises et de toxicité, contiennent, comme ingrédients principaux, du nitrate de guanidine (NG) en tant que charge réductrice et du nitrate basique de cuivre (BCN) en tant que charge oxydante. Les brevets US 5 608 183 et US 6 143 102 décrivent de tels composés.Currently, for front airbags, the pyrotechnic compounds which offer a good compromise, in terms of gas temperature, gas yield, rate of particles emitted and toxicity, contain, as main ingredients, guanidine nitrate (NG) in as a reducing filler and basic copper nitrate (BCN) as an oxidizing filler. Licences US 5,608,183 and US 6,143,102 describe such compounds.

Ces composés présentent toutefois des vitesses de combustion relativement faibles, inférieures ou égales à 20 mm/s à 20 MPa, ainsi qu'un faible rendement gazeux. Ils sont également difficiles à allumer.However, these compounds exhibit relatively low combustion rates, less than or equal to 20 mm / s at 20 MPa, as well as a low gas yield. They are also difficult to light.

Dans l'optique d'améliorer l'allumabilité de ce type de composés, on a proposé, selon l'art antérieur, l'ajout de perchlorate dans leur composition à base de nitrate de guanidine (NG) et de nitrate basique de cuivre (BCN). Ainsi, la demande de brevet EP 1 526 121 décrit l'ajout d'un perchlorate (notamment du perchlorate de potassium), à faible taux (moins de 5 % en masse), pour améliorer l'allumage de ces composés. Toutefois, l'incorporation de perchlorate à un taux aussi faible ne permet pas d'accroître suffisamment la vitesse de combustion du composé pour une utilisation satisfaisante au sein de générateurs de gaz pour airbags latéraux.With a view to improving the ignitability of this type of compound, it has been proposed, according to the prior art, to add perchlorate to their composition based on guanidine nitrate (NG) and basic copper nitrate ( BCN). Thus, the patent application EP 1 526 121 describes the addition of a perchlorate (in particular potassium perchlorate), at a low rate (less than 5% by mass), to improve the ignition of these compounds. However, the incorporation of perchlorate at such a low rate does not make it possible to increase the combustion rate of the compound sufficiently for satisfactory use in gas generators for side air bags.

Les demandes WO 2007/042735 et WO 2009/126702 décrivent des composés présentant des compositions, du même type, qui renferment du nitrate de guanidine (NG), à titre de charge réductrice, du nitrate basique de cuivre (BCN), à titre de charge oxydante principale et, en sus, une seconde charge oxydante, qui consiste avantageusement en du perchlorate de potassium (KClO4). Ces documents associent les bonnes performances desdits composés, notamment une vitesse de combustion élevée à haute pression, à la composition mais aussi au procédé de fabrication spécifique desdits composés (procédé qui inclut une étape de compactage à rouleaux en voie sèche pour WO 2007/042735 et deux étapes successives de séchage par atomisation et de compression pour WO 2009/126702 ).Requests WO 2007/042735 and WO 2009/126702 describe compounds having compositions, of the same type, which contain guanidine nitrate (NG), as reducing charge, basic copper nitrate (BCN), as main oxidizing charge and, in addition, a second charge oxidizing agent, which advantageously consists of potassium perchlorate (KClO 4 ). These documents associate the good performance of said compounds, in particular a high combustion rate at high pressure, with the composition but also with the specific manufacturing process of said compounds (process which includes a dry roller compacting step for WO 2007/042735 and two successive stages of spray drying and compression for WO 2009/126702 ).

Dans l'optique d'améliorer le rendement gazeux et la vitesse de combustion, on a également proposé, selon l'art antérieur, des composés à base d'un (ou plusieurs) réducteur(s) azoté(s) associé(s) à un oxydant fort de type perchlorate.With a view to improving the gas yield and the combustion rate, according to the prior art, compounds based on one (or more) associated nitrogen reducing agent (s) have also been proposed. to a strong oxidant such as perchlorate.

Dans la demande de brevet US 2006/0137785 , il est décrit l'association d'un réducteur de type guanidine (nitroguanidine ou nitrate de guanidine) et de perchlorate d'ammonium, ce dernier étant nécessairement incorporé à un taux significativement élevé (30% à 60% en masse). L'incorporation de perchlorate d'ammonium à un taux aussi élevé conduit à deux inconvénients majeurs qui sont, d'une part, une augmentation significative de la température de combustion (supérieure à 2800 K) et, d'autre part, la génération de chlorure d'hydrogène (lequel est un gaz toxique et hautement corrosif), ledit chlorure d'hydrogène se retrouvant alors présent dans les effluents gazeux. Pour pallier ce problème, il est décrit dans ledit brevet la nécessité d'adjoindre au mélange de type guanidine + perchlorate d'ammonium un composé métallique de type oxyde de fer afin de neutraliser l'acide chlorhydrique présent dans les gaz de combustion, ce qui a pour conséquence de diminuer la valeur de rendement gazeux du composé.In the patent application US 2006/0137785 , the association of a guanidine-type reducing agent (nitroguanidine or guanidine nitrate) and ammonium perchlorate is described, the latter necessarily being incorporated at a significantly high rate (30% to 60% by weight). The incorporation of ammonium perchlorate at such a high rate leads to two major drawbacks which are, on the one hand, a significant increase in the combustion temperature (greater than 2800 K) and, on the other hand, the generation of hydrogen chloride (which is a toxic and highly corrosive gas), said hydrogen chloride then being present in the effluents gaseous. To overcome this problem, said patent describes the need to add to the mixture of guanidine + ammonium perchlorate type a metal compound of iron oxide type in order to neutralize the hydrochloric acid present in the combustion gases, which has the consequence of reducing the gas yield value of the compound.

L'incorporation de perchlorate de potassium à la place du perchlorate d'ammonium présenterait l'avantage de conduire à la formation de chlorure de potassium (KCl) à la place de chlorure d'hydrogène (HCI) (mais l'inconvénient de réduire le rendement gazeux). En tout état de cause, l'incorporation de KClO4 à des taux aussi élevés (jusqu'à 60% en masse) produirait une augmentation de la température de combustion rédhibitoire dans le contexte de l'application visée.The incorporation of potassium perchlorate instead of ammonium perchlorate would have the advantage of leading to the formation of potassium chloride (KCl) instead of hydrogen chloride (HCl) (but the disadvantage of reducing the gas yield). In any event, the incorporation of KClO 4 at such high rates (up to 60% by mass) would produce an unacceptable increase in combustion temperature in the context of the intended application.

De façon logique, l'homme du métier s'est donc tourné vers des composés consistant en un mélange contenant du nitrate de guanidine (NG, seul ou associé à un co-réducteur) et du perchlorate de potassium (KClO4) à des taux intermédiaires d'environ 25% à 45% en masse, tel que décrit dans la demande de brevet WO 95/25709 et les brevets US 5 854 442 , US 5 997 666 , ledit mélange permettant d'obtenir des composés répondant partiellement aux exigences essentielles du domaine d'application visé par la présente invention, à savoir :

  • un bon rendement gazeux ;
  • une température de combustion modérée ;
  • une non toxicité intrinsèque des effluents particulaires ; et
  • une vitesse de combustion vers 20 MPa légèrement accrue par rapport aux compositions formulées à base nitrate de guanidine (NG) et nitrate basique de cuivre (BCN), mais qui demeure insuffisante pour une utilisation dans des airbags latéraux.
Logically, those skilled in the art have therefore turned to compounds consisting of a mixture containing guanidine nitrate (NG, alone or combined with a co-reducing agent) and potassium perchlorate (KClO 4 ) at levels intermediates of about 25% to 45% by mass, as described in the patent application WO 95/25709 and patents US 5,854,442 , US 5,997,666 , said mixture making it possible to obtain compounds partially meeting the essential requirements of the field of application targeted by the present invention, namely:
  • good gas yield;
  • a moderate combustion temperature;
  • intrinsic non-toxicity of particulate effluents; and
  • a combustion rate of around 20 MPa slightly increased compared to the compositions formulated based on guanidine nitrate (NG) and basic copper nitrate (BCN), but which remains insufficient for use in side airbags.

Les caractéristiques thermodynamiques et balistiques d'un tel composé (composé de référence 1), dont la composition ("binaire") renferme uniquement du nitrate de guanidine (NG) et du perchlorate de potassium (KClO4), sont présentées dans le tableau 1 ci-après. Tableau 1 Ingrédients Nitrate de guanidine % en masse 68,0 Perchlorate de potassium % en masse 32,0 Caractéristiques Oxygène balance % -3 Densité g/cm3 1,67 T combustion à 20MPa K 2351 Rendement gazeux à 1bar - 1000 K Mole /kg 33,2 Vitesse de combustion à 8MPa (basse pression) mm/s 20,6 Vitesse de combustion à 20MPa (moyenne presssion) mm/s 26,3 Vitesse de combustion à 50MPa (haute pression) mm/s 34,9 Exposant de pression déterminé entre 6 et 52 MPa 0,26 Taux de gaz à 1 bar - 1000 K % 82,5 Taux de KCl % 17,1 Pression limite de combustion (1) MPa 1,7 (1) : la valeur donnée est une pression relative. Une pression limite de combustion nulle correspond à la pression atmosphérique. The thermodynamic and ballistic characteristics of such a compound (reference compound 1), whose composition ("binary") contains only guanidine nitrate (NG) and potassium perchlorate (KClO 4 ), are presented in Table 1 below. Table 1 Ingredients Guanidine nitrate % by mass 68.0 Potassium perchlorate % by mass 32.0 Characteristics Oxygen balance % -3 Density g / cm 3 1.67 T combustion at 20MPa K 2351 Gas yield at 1bar - 1000 K Mole / kg 33.2 Burning rate at 8MPa (low pressure) mm / s 20.6 Burning rate at 20MPa (medium pressure) mm / s 26.3 Burning rate at 50MPa (high pressure) mm / s 34.9 Pressure exponent determined between 6 and 52 MPa 0.26 Gas rate at 1 bar - 1000 K % 82.5 KCl level % 17.1 Combustion limit pressure (1) MPa 1.7 (1): the value given is a relative pressure. A zero combustion limit pressure corresponds to atmospheric pressure.

Le composé de référence 1 présente de nombreux avantages parmi ceux attendus d'un composé pour générateur de gaz pour système airbag. Les ingrédients de base sont simples et aisément approvisionnables, peu coûteux, non dangereux sur les aspects pyrotechniques (pas de constituant appartenant à la classe des composés explosifs) et non toxiques. Les performances thermodynamiques (rendement gazeux, taux de particules) sont bonnes et la température de combustion demeure modérée donc acceptable. Les particules émises par la combustion sont non toxiques (essentiellement KCl).Reference compound 1 exhibits numerous advantages among those expected from a compound for a gas generator for an airbag system. The basic ingredients are simple and easily obtainable, inexpensive, non-hazardous in terms of pyrotechnics (no constituent belonging to the class of explosive compounds) and non-toxic. The thermodynamic performance (gas yield, particle rate) is good and the combustion temperature remains moderate and therefore acceptable. The particles emitted by combustion are non-toxic (mainly KCl).

Toutefois, un tel composé ne présente pas l'ensemble des performances attendues, notamment pour une application airbag latéral. Tout d'abord, la vitesse de combustion de l'ordre de 26 mm/s à 20 MPa, n'est accrue que de 20 à 30% par rapport à celle d'un composé à base de nitrate de guanidine (NG) et de nitrate basique de cuivre (BCN), et reste faible par rapport au cahier des charges fixé. Ensuite, lors d'essais avec cette formulation de référence, il est apparu que la substitution totale de l'oxydant nitrate basique de cuivre (BCN) par du perchlorate de potassium (KClO4), si elle permet d'accroître la vitesse de combustion au dessus de 5 MPa et aussi d'améliorer l'allumabilité, induit en contrepartie, et de façon fortement préjudiciable, un très fort exposant de pression à basse pression (supérieur à 0,55 sur la plage 6 à 10 MPa et une non combustion à pression atmosphérique (des essais complémentaires ont montré que la pression limite de fonctionnement se situe vers 1,7 MPa, alors qu'un composé formulé à base de nitrate de guanidine (NG) et de nitrate basique de cuivre (BCN) présente avantageusement une combustion non nulle à pression atmosphérique).However, such a compound does not exhibit all of the expected performances, in particular for a side airbag application. First of all, the combustion speed of the order of 26 mm / s at 20 MPa is only increased by 20 to 30% compared to that of a compound based on Guanidine nitrate (NG) and basic copper nitrate (BCN), and remains low compared to the specifications set. Then, during tests with this reference formulation, it appeared that the total substitution of the oxidant basic copper nitrate (BCN) by potassium perchlorate (KClO 4 ), if it makes it possible to increase the combustion rate above 5 MPa and also to improve ignitability, induced in return, and in a highly detrimental manner, a very strong pressure exponent at low pressure (greater than 0.55 over the 6 to 10 MPa range and non-combustion at atmospheric pressure (additional tests have shown that the operating limit pressure is around 1.7 MPa, while a compound formulated based on guanidine nitrate (NG) and basic copper nitrate (BCN) advantageously exhibits a non-zero combustion at atmospheric pressure).

En partant des performances connues du mélange nitrate de guanidine (NG) / perchlorate de potassium (KClO4), les inventeurs ont souhaité proposer des composés pyrotechniques générateurs de gaz améliorés, convenant tout particulièrement pour utilisation dans des airbags latéraux. Ils se sont plus particulièrement fixés pour objectif, tout en conservant ou en améliorant les autres caractéristiques, d'améliorer significativement les trois points suivants :

  • diminution de la pression limite de combustion,
  • diminution de l'exposant de pression (<0,26), avantageusement une forte diminution (≤0,2), très avantageusement une très forte diminution (≤0,1) à partir de 6 MPa,
  • accroissement de la vitesse de combustion sur toute la plage de pression, notamment à basse pression.
On the basis of the known performances of the guanidine nitrate (NG) / potassium perchlorate (KClO 4 ) mixture, the inventors wished to propose improved pyrotechnic gas-generating compounds, particularly suitable for use in side airbags. They have more particularly set themselves the objective, while maintaining or improving the other characteristics, to significantly improve the following three points:
  • reduction of the combustion limit pressure,
  • decrease in the pressure exponent (<0.26), advantageously a strong decrease (≤0.2), very advantageously a very strong decrease (≤0.1) from 6 MPa,
  • increased combustion rate over the entire pressure range, especially at low pressure.

De façon totalement inattendue, il s'est avéré que la présence, au sein de la composition des composés de l'invention, d'un faible taux d'(au moins) un composé oxygéné d'un métal de transition (un oxyde d'un métal de transition ou un composé précurseur d'un tel oxyde), avantageusement à haute surface spécifique, (traditionnellement utilisé en tant que catalyseur balistique dans le domaine des propergols pour augmenter la vitesse de combustion à haute pression (en accélérant la décomposition de la charge oxydante)), a (aussi) des effets majeurs sur les trois points d'amélioration recherchés ci-dessus (à savoir, l'augmentation de la vitesse de combustion (aussi) à basse pression, la diminution de la pression limite de combustion et la diminution de l'exposant de pression sur toute la plage de pression).Completely unexpectedly, it turned out that the presence, within the composition of the compounds of the invention, of a low level of (at least) one oxygen-containing compound of a transition metal (an oxide of 'a transition metal or a precursor compound of such an oxide), advantageously with a high specific surface area, (traditionally used as a ballistic catalyst in the field of propellants to increase the rate of combustion at high pressure (by accelerating the decomposition of the oxidizing charge)), has (also) major effects on the three points of improvement sought above (namely, increasing the combustion rate (also) at low pressure, decreasing the limiting combustion pressure and decreasing the pressure exponent over the entire pressure range).

Les compositions des composés pyrotechniques générateurs de gaz de l'invention (convenant tout particulièrement pour des applications airbag, notamment latéraux) consistent en:

  • du nitrate de guanidine,
  • du perchlorate de potassium.
  • au moins un modificateur de combustion, et
  • éventuellement au moins un additif,
caractérisées en ce que, exprimées en pourcentages massiques, elles renferment :
  • 60 à 70 % de nitrate de guanidine,
  • 26 à 33 %, avantageusement 26 à 30 %, de perchlorate de potassium,
  • 2,5 à 6 % d'au moins un modificateur de combustion choisi parmi les oxydes de métal de transition, les précurseurs de tels oxydes et leurs mélanges,
  • 0 à 6 % d'au moins un additif, et
ne renferment pas d'ingrédient explosif.The compositions of the gas-generating pyrotechnic compounds of the invention (very particularly suitable for airbag applications, in particular sideways) consist of:
  • guanidine nitrate,
  • potassium perchlorate.
  • at least one combustion modifier, and
  • optionally at least one additive,
characterized in that, expressed as percentages by mass, they contain:
  • 60 to 70% guanidine nitrate,
  • 26 to 33%, advantageously 26 to 30%, of potassium perchlorate,
  • 2.5 to 6% of at least one combustion modifier chosen from transition metal oxides, precursors of such oxides and mixtures thereof,
  • 0 to 6% of at least one additive, and
do not contain explosive ingredients.

Les ingrédients des trois premiers types ci-dessus (nitrate de guanidine, perchlorate de potassium et modificateur de combustion spécifique) représentent généralement plus de 90% en masse de la masse totale (de la composition) des composés de l'invention, très généralement au moins 94 % en masse, voire plus de 98% en masse. L'éventuelle présence d'additif(s), tels des auxiliaires de fabrication (stéarate de calcium, silice par exemple), est expressément prévue. Les ingrédients des trois types ci-dessus peuvent tout à fait représenter 100% en masse de la masse totale des composés de l'invention.The ingredients of the first three types above (guanidine nitrate, potassium perchlorate and specific combustion modifier) generally represent more than 90% by mass of the total mass (of the composition) of the compounds of the invention, very generally at less 94% by mass, or even more than 98% by mass. The possible presence of additive (s), such as processing aids (calcium stearate, silica for example), is expressly provided for. The ingredients of the three types above can quite represent 100% by mass of the total mass of the compounds of the invention.

Le nitrate de guanidine, représentant de 60 à 70 % de la masse totale, est en autres retenu pour des raisons de sécurité pyrotechnique et pour son comportement rhéo-plastique, adapté à la mise en œuvre des phases de compactage et éventuel pastillage du procédé voie sèche (voir ci-après), assurant une bonne densification de la composition pyrotechnique pulvérulente de départ tout en limitant l'effort de compression à appliquer. La fabrication des composés par le procédé voie sèche comprend jusqu'à quatre étapes principales (voir ci-après), qui ont notamment été décrites dans la demande brevet WO 2006/134311 .Guanidine nitrate, representing 60 to 70% of the total mass, is among other things used for pyrotechnic safety reasons and for its rheo-plastic behavior, suitable for the implementation of the compaction phases and possible pelletizing of the lane process. dry (see below), ensuring good densification of the starting powdery pyrotechnic composition while limiting the effort of compression to apply. The manufacture of compounds by the dry process comprises up to four main steps (see below), which have in particular been described in the patent application WO 2006/134311 .

Le perchlorate de potassium est présent, dans la composition des composés de l'invention, à une teneur intermédiaire, modérée (de 26 à 33 % massique, avantageusement de 26 à 30 % massique), tout particulièrement en référence à la température de combustion, "l'allumabilité" et la vitesse de combustion à haute pression visées.Potassium perchlorate is present, in the composition of the compounds of the invention, at an intermediate, moderate content (from 26 to 33% by mass, advantageously from 26 to 30% by mass), most particularly with reference to the combustion temperature, "ignitability" and high pressure burning rate referred to.

Au sein des mélanges NG + KClO4, les modificateurs de combustion, sélectionnés par les inventeurs, développent des propriétés particulièrement intéressantes (inattendues) en référence aux trois points d'amélioration recherchés (voir ci-dessus).Within the NG + KClO 4 mixtures, the combustion modifiers, selected by the inventors, develop particularly interesting (unexpected) properties with reference to the three points of improvement sought (see above).

Ledit au moins un modificateur de combustion est choisi parmi les oxydes de métal de transition, les précurseurs de tels oxydes et leurs mélanges. Un précurseur d'un tel oxyde conduit à la formation d'un tel oxyde (génère un tel oxyde) lors de sa décomposition en température au cours de la combustion du composé pyrotechnique. Ainsi le nitrate basique de cuivre (Cu(NO3)2·3Cu(OH)2) se décompose-t-il en oxyde de cuivre (CuO) (voir ci-après).Said at least one combustion modifier is chosen from transition metal oxides, precursors of such oxides and mixtures thereof. A precursor of such an oxide leads to the formation of such an oxide (generates such an oxide) during its temperature decomposition during the combustion of the pyrotechnic compound. Thus, basic copper nitrate (Cu (NO 3 ) 2 · 3Cu (OH) 2 ) decomposes into copper oxide (CuO) (see below).

Ledit au moins un modificateur de combustion est présent en une quantité suffisante (≥ 2,5 % en masse), pour être efficace (en référence aux trois points d'amélioration ci-dessus), et non excessive (≤ 6 % en masse) pour ne pas nuire au rendement gazeux. Un seul modificateur de combustion est généralement présent mais la présence d'au moins deux tels additifs est expressément prévue dans le cadre de la présente invention.Said at least one combustion modifier is present in a sufficient quantity (≥ 2.5% by mass), to be effective (with reference to the three points of improvement above), and not excessive (≤ 6% by mass) so as not to affect the gas yield. A single combustion modifier is generally present but the presence of at least two such additives is expressly provided for within the scope of the present invention.

De façon préférée, ledit au moins un modificateur de combustion est choisi parmi l'oxyde de zinc (ZnO), l'oxyde de fer (Fe2O3), l'oxyde de chrome (Cr2O3), le dioxyde de manganèse (MnO2), l'oxyde de cuivre (CuO), le nitrate basique de cuivre (Cu(NO3)2·3Cu(OH)2) et leurs mélanges. L'oxyde de cuivre et le nitrate basique de cuivre, précurseur dudit oxyde de cuivre (en ce sens que le BCN conduit à la formation d'oxyde de cuivre CuO lors de sa décomposition en température), sont particulièrement performants. De façon particulièrement préférée, les composés de l'invention renferment donc, à titre de modificateur de combustion, l'oxyde de cuivre et/ou le nitrate basique de cuivre. L'utilisation de ces modificateurs de combustion permet d'obtenir des composés de l'invention présentant une valeur d'exposant de pression inférieure ou égale à 0,1 sur la plage de pression 6-52 MPa.Preferably, said at least one combustion modifier is chosen from zinc oxide (ZnO), iron oxide (Fe 2 O 3 ), chromium oxide (Cr 2 O 3 ), manganese (MnO 2 ), copper oxide (CuO), basic copper nitrate (Cu (NO 3 ) 2 · 3Cu (OH) 2 ) and their mixtures. Copper oxide and basic copper nitrate, a precursor of said copper oxide (in the sense that BCN leads to the formation of copper oxide CuO during its decomposition at temperature), are particularly efficient. Particularly preferably, the compounds of the invention therefore contain, as a modifier of combustion, copper oxide and / or basic copper nitrate. The use of these combustion modifiers makes it possible to obtain compounds of the invention having a pressure exponent value less than or equal to 0.1 over the pressure range 6-52 MPa.

De façon préférée, ledit au moins un modificateur de combustion selon l'invention présente une surface spécifique supérieure à 3 m2/g, avantageusement supérieure à 10 m2/g, très avantageusement supérieure à 25 m2/g.Preferably, said at least one combustion modifier according to the invention has a specific surface area greater than 3 m 2 / g, advantageously greater than 10 m 2 / g, very advantageously greater than 25 m 2 / g.

On comprend que la fonction dudit au moins un modificateur de combustion spécifique (choisi parmi les oxydes de métal de transition, leurs précurseurs et leurs mélanges) au sein de la composition des composés de l'invention est, non seulement, comme dans l'art antérieur (voir notamment l'enseignement du brevet US 6 893 517 rappelé ci-dessus) d'augmenter la vitesse de combustion à haute et moyenne pression, mais aussi, de façon surprenante, de conférer aux composés pyrotechniques :

  • une combustion stable et auto-entretenue à basse pression (voire à une pression quasi égale à la pression atmosphérique),
  • une vitesse de combustion à basse pression plus élevée que celle des compositions de l'art antérieur,
  • un exposant de pression faible, voire quasi nul, à basse, moyenne et haute pression, significativement plus faible que celui des compositions de l'art antérieur ;
et ce, avec une "bonne" allumabilité" desdits composés, sans générer trop de particules solides à la combustion, et une température de combustion avoisinant les 2300 K.It is understood that the function of said at least one specific combustion modifier (chosen from transition metal oxides, their precursors and their mixtures) within the composition of the compounds of the invention is, not only, as in the art earlier (see in particular the teaching of the US 6,893,517 recalled above) to increase the combustion rate at high and medium pressure, but also, surprisingly, to give the pyrotechnic compounds:
  • stable and self-sustaining combustion at low pressure (or even at a pressure almost equal to atmospheric pressure),
  • a combustion rate at low pressure higher than that of the compositions of the prior art,
  • a low pressure exponent, or even almost zero, at low, medium and high pressure, significantly lower than that of the compositions of the prior art;
and this with a "good" ignitability "of said compounds, without generating too many solid particles on combustion, and a combustion temperature of around 2300 K.

On peut indiquer ici que les composés de l'invention, dont la composition a été précisée ci-dessus, présentent :

  • une température de combustion inférieure à 2350 K,
  • une pression (relative, c'est-à-dire en référence à la pression atmosphérique) limite de combustion inférieure ou égale à 1,5 MPa, avantageusement inférieure à 0,2 MPa, très avantageusement égale à 0,1 MPa,
  • un exposant de pression inférieur ou égal à 0,25, avantageusement inférieur ou égal à 0,2, très avantageusement inférieur ou égal à 0,1, pour une pression entre 6 et 52 MPa,
  • une vitesse de combustion :
    • + supérieure à 24 mm/s, avantageusement supérieure à 36 mm/s, à basse pression,
    • + supérieure à 30 mm/s, avantageusement supérieure à 35 mm/s, à moyenne pression,
    • + supérieure à 37 mm/s, avantageusement supérieure à 45 mm/s, à haute pression.
It can be indicated here that the compounds of the invention, the composition of which has been specified above, exhibit:
  • a combustion temperature below 2350 K,
  • a pressure (relative, that is to say with reference to atmospheric pressure) combustion limit less than or equal to 1.5 MPa, advantageously less than 0.2 MPa, very advantageously equal to 0.1 MPa,
  • a pressure exponent less than or equal to 0.25, advantageously less than or equal to 0.2, very advantageously less than or equal to 0.1, for a pressure between 6 and 52 MPa,
  • a combustion rate:
    • + greater than 24 mm / s, advantageously greater than 36 mm / s, at low pressure,
    • + greater than 30 mm / s, advantageously greater than 35 mm / s, at medium pressure,
    • + greater than 37 mm / s, advantageously greater than 45 mm / s, at high pressure.

On se doit d'insister ici sur les valeurs d'exposant de pression, basses, voire très basses, des composés de l'invention.We must insist here on the pressure exponent values, low, or even very low, of the compounds of the invention.

Les meilleurs résultats indiqués ci-dessus (variantes avantageuses et variantes très avantageuses) ont notamment été obtenus avec l'oxyde de cuivre et le nitrate basique de cuivre comme modificateur de combustion. A l'appui de cette affirmation, on peut se référer aux exemples ci-après.The best results indicated above (advantageous variants and very advantageous variants) have in particular been obtained with copper oxide and basic copper nitrate as combustion modifier. In support of this assertion, reference may be made to the examples below.

Dans le cadre de la présente invention, au sein de la composition des composés de l'invention, il est donc proposé une utilisation originale (tout particulièrement en référence aux paramètres ci-dessus) aux oxydes et précurseurs d'oxydes en cause (originale, par rapport à celle classique de catalyseur balistique connue, au sein de compositions différentes).In the context of the present invention, within the composition of the compounds of the invention, there is therefore proposed an original use (very particularly with reference to the above parameters) for the oxides and precursors of oxides in question (original, compared to the conventional ballistic catalyst known, within different compositions).

En sus des constituants ci-dessus (NG + KClO4 + au moins un modificateur de combustion du type précisé), les composés pyrotechniques de l'invention peuvent renfermer, à un faible taux massique (inférieur ou égal à 6 %, généralement d'au moins 0,1 %), au moins un additif, notamment au moins un additif facilitant leur obtention (la mise en forme, lors de leur obtention), tel que le stéarate de calcium ou de magnésium, le graphite et/ou au moins un additif améliorant l'agrégation des produits solides de leur combustion choisi parmi les oxydes réfractaires à température de ramollissement ou de fusion adaptée à la composition tels que la silice ou l'alumine. Il s'agit avantageusement de la silice, généralement introduite sous forme pulvérulente fine (avantageusement de dimension micrométrique, très avantageusement de dimension nanométrique) présentant une haute surface spécifique (avantageusement de 100 m2/g ou plus) ou sous forme de fibres de silice de faible diamètre (1 à 20 microns) et de quelques dizaines ou centaines de microns (20 à 500 microns) de longueur. De façon surprenante, il s'est avéré que la présence, au sein des composés pyrotechniques de l'invention, de silice, à des taux compris entre 0,5 et 6 % en masse, avantageusement entre 0,5 et 3,5 % en masse, a aussi un effet très significatif d'abaissement de la pression limite de combustion.In addition to the above constituents (NG + KClO 4 + at least one combustion modifier of the type specified), the pyrotechnic compounds of the invention may contain, at a low mass content (less than or equal to 6%, generally of at least 0.1%), at least one additive, in particular at least one additive facilitating their obtaining (shaping, during their obtaining), such as calcium or magnesium stearate, graphite and / or at least an additive improving the aggregation of the solid products of their combustion, chosen from refractory oxides at a softening or melting temperature suitable for the composition, such as silica or alumina. It is advantageously silica, generally introduced in fine pulverulent form (advantageously of micrometric dimension, very advantageously of nanometric dimension) having a high specific surface area. (advantageously 100 m 2 / g or more) or in the form of silica fibers of small diameter (1 to 20 microns) and a few tens or hundreds of microns (20 to 500 microns) in length. Surprisingly, it turned out that the presence, within the pyrotechnic compounds of the invention, of silica, at levels of between 0.5 and 6% by mass, advantageously between 0.5 and 3.5% in mass, also has a very significant effect of lowering the combustion limit pressure.

Il est donc aussi du mérite des inventeurs d'avoir mis en évidence cet effet de la silice au sein de compositions type NG + KClO4 (voir le tableau 3 ci-après), et donc au sein des compositions de l'invention (type NG + KClO4 + au moins un modificateur de combustion) où ledit effet se cumule avec ceux (englobant celui de l'abaissement de la pression limite de combustion) du au moins un modificateur de combustion présent.It is therefore also to the credit of the inventors to have demonstrated this effect of silica in NG + KClO 4 type compositions (see Table 3 below), and therefore within the compositions of the invention (type NG + KClO 4 + at least one combustion modifier) where said effect is cumulative with those (including that of lowering the combustion limit pressure) of at least one combustion modifier present.

Le au moins un additif intervient avec les ingrédients constitutifs (NG, KClO4 + au moins un modificateur de combustion du type précité) (au début du procédé de fabrication) ou est ajouté, plus en aval, dans le procédé de fabrication des composés de l'invention.The at least one additive intervenes with the constituent ingredients (NG, KClO 4 + at least one combustion modifier of the aforementioned type) (at the start of the manufacturing process) or is added, further downstream, in the manufacturing process of the compounds of invention.

On rappelle que les compositions des composés de l'invention ne renferment pas d'ingrédient explosif (voir la norme NF et les recommandations ONU précisées ci-dessus), et ce, notamment en référence aux paramètres : sécurité pyrotechnique et température de combustion. On note par ailleurs que les masses de composés pyrotechniques requises pour le gonflage d'un air-bag, notamment d'un air-bag latéral, sont plus importantes que celles requises pour le gonflage d'un dispositif rétracteur de ceinture selon le brevet US 6 893 517 (lesdits gonflages n'étant pas du même type : temps de gonflage supérieur à 10-20 ms / par impulsion).It is recalled that the compositions of the compounds of the invention do not contain an explosive ingredient (see the NF standard and the UN recommendations specified above), and this, in particular with reference to the parameters: pyrotechnic safety and combustion temperature. It should also be noted that the masses of pyrotechnic compounds required for the inflation of an air bag, in particular a side air bag, are greater than those required for the inflation of a belt retractor device according to the patent. US 6,893,517 (said inflations not being of the same type: inflation time greater than 10-20 ms / per pulse).

Les composés pyrotechniques de l'invention peuvent être obtenus suivant un procédé voie humide. Selon une variante, ledit procédé comprend l'extrusion d'une pâte contenant les constituants du composé. Selon une autre variante, ledit procédé inclut une étape de mise en solution aqueuse de tous les (ou certains des) constituants principaux comprenant une solubilisation d'au moins l'un desdits constituants principaux (oxydant et/ou réducteur) puis l'obtention d'une poudre par séchage par atomisation, l'ajout à la poudre obtenue du ou des constituants qui n'auraient pas été mis en solution, puis la mise en forme de la poudre sous la forme d'objets par les procédés usuels en voie sèche.The pyrotechnic compounds of the invention can be obtained by a wet process. According to one variant, said method comprises the extrusion of a paste containing the constituents of the compound. According to another variant, said process includes a step of dissolving all the (or some of the) main constituents in aqueous solution comprising a solubilization of at least one of said main constituents (oxidant and / or reducing agent) and then obtaining d 'a powder by spray drying, adding to the powder obtained the constituent (s) which have not been put into solution, then shaping the powder in the form of objects by the usual dry processes.

Les composés pyrotechniques de l'invention peuvent aussi être obtenus en voie sèche, par exemple par simple pastillage de la poudre obtenue par mélange de leurs constituants.The pyrotechnic compounds of the invention can also be obtained in the dry process, for example by simple pelletizing of the powder obtained by mixing their constituents.

Le procédé d'obtention préférentiel des composés pyrotechniques de l'invention inclut une étape de compactage à sec d'un mélange des ingrédients constitutifs en poudre desdits composés (excepté pour ledit au moins un additif qui peut être ajouté au cours du procédé). Le compactage à sec est généralement mis en oeuvre, de façon connue per se, dans un compacteur à cylindres, à une pression de compactage comprise entre 108 et 6.108 Pa. Il peut être mis en œuvre selon différentes variantes (avec une étape caractéristique de compactage "simple" suivie d'au moins une étape complémentaire, avec une étape caractéristique de compactage couplée à une étape de mise en forme). Ainsi, les composés pyrotechniques de l'invention sont susceptibles d'exister sous différentes formes (notamment au fil du procédé de fabrication conduisant aux composés finaux):

  • à l'issue d'un compactage à sec couplé à une mise en forme (par utilisation d'au moins un cylindre de compactage, dont la surface externe présente des alvéoles), on obtient des plaques avec motifs en relief que l'on peut casser pour l'obtention directe d'objets pyrotechniques formés ;
  • à l'issue d'un compactage à sec suivi d'une granulation, on obtient des granulés ;
  • à l'issue d'un compactage à sec suivi d'une granulation puis d'un pastillage (compression à sec), on obtient des pastilles ;
  • à l'issue d'un compactage à sec suivi d'une granulation puis du mélange des granulés obtenus avec un liant extrudable et de l'extrusion dudit liant chargé en lesdits granulés, on obtient des blocs monolithiques extrudés (chargés avec lesdits granulés).
The preferential process for obtaining the pyrotechnic compounds of the invention includes a dry compacting stage of a mixture of the constituent ingredients in powder form of said compounds (except for said at least one additive which can be added during the process). Dry compaction is generally carried out, in a manner known per se, in a roller compactor, at a compaction pressure of between 10 8 and 6.10 8 Pa. It can be carried out according to different variants (with a characteristic step "simple" compaction followed by at least one additional step, with a characteristic compacting step coupled with a shaping step). Thus, the pyrotechnic compounds of the invention are likely to exist in different forms (in particular over the course of the manufacturing process leading to the final compounds):
  • after dry compaction coupled with shaping (by using at least one compacting cylinder, the outer surface of which has cells), plates are obtained with relief patterns that can be breaking for the direct obtaining of formed pyrotechnic objects;
  • after dry compaction followed by granulation, granules are obtained;
  • after dry compaction followed by granulation and then pelletizing (dry compression), pellets are obtained;
  • at the end of a dry compaction followed by a granulation then of the mixing of the granules obtained with an extrudable binder and of the extrusion of the said binder loaded with the said granules, extruded monolithic blocks are obtained (loaded with the said granules).

Les composés pyrotechniques de l'invention sont donc notamment susceptibles d'exister sous la forme d'objets de type:

  • granulés,
  • pastilles,
  • blocs monolithes.
The pyrotechnic compounds of the invention are therefore particularly likely to exist in the form of objects of the type:
  • granules,
  • lozenges,
  • monolithic blocks.

De façon nullement limitative, on peut indiquer ici que:

  • les granulés de l'invention présentent généralement une granulométrie (un diamètre médian) comprise entre 200 et 1400 µm (ainsi qu'une masse volumique apparente comprise entre 0,8 et 1,2 g/cm3;
  • les pastilles de l'invention présentent généralement une épaisseur comprise entre 1 et 3 mm.
In no way limiting, we can indicate here that:
  • the granules of the invention generally have a particle size (a median diameter) of between 200 and 1400 μm (as well as a bulk density of between 0.8 and 1.2 g / cm 3 ;
  • the pellets of the invention generally have a thickness of between 1 and 3 mm.

Lorsque les composés de l'invention sont obtenus par un procédé en voie sèche, les ingrédients constitutifs des composés de l'invention présentent avantageusement une granulométrie fine, inférieure ou égale à 20 µm. Ladite granulométrie (valeur du diamètre médian) est généralement comprise entre 3 et 20 µm. Les composés décrits dans la présente invention expriment tout leur potentiel s'ils sont obtenus par un procédé en voie sèche à partir de poudres présentant un diamètre médian compris entre 10 et 20 µm pour le KClO4 et 5 à 15 µm pour le nitrate de guanidine.When the compounds of the invention are obtained by a dry process, the constituent ingredients of the compounds of the invention advantageously have a fine particle size, less than or equal to 20 μm. Said particle size (value of the median diameter) is generally between 3 and 20 μm. The compounds described in the present invention express their full potential if they are obtained by a dry process from powders having a median diameter of between 10 and 20 μm for KClO 4 and 5 to 15 μm for guanidine nitrate .

Selon un autre de ses objets, la présente invention concerne une composition pulvérulente (mélange de poudres), précurseur d'un composé de l'invention, dont la composition correspond donc à celle d'un composé de l'invention (voir ci-dessus).According to another of its subjects, the present invention relates to a pulverulent composition (mixture of powders), precursor of a compound of the invention, the composition of which therefore corresponds to that of a compound of the invention (see above ).

Selon un autre de ses objets, la présente invention concerne les générateurs de gaz contenant au moins un composé pyrotechnique de l'invention. Lesdits générateurs conviennent parfaitement pour les airbags, notamment latéraux (voir ci-dessus).According to another of its objects, the present invention relates to gas generators containing at least one pyrotechnic compound of the invention. Said generators are perfectly suitable for airbags, in particular side airbags (see above).

On se propose maintenant d'illustrer, de façon nullement limitative, l'invention.It is now proposed to illustrate, in no way limiting, the invention.

Le tableau 2 ci-après présente des exemples de compositions de composés de la présente invention, ainsi que les performances desdits composés comparées à celles du composé de l'art antérieur de référence 1. Les composés ont été évalués au moyen de calculs thermodynamiques ou à partir de mesures physiques menées sur des granulés ou des pastilles fabriqués à partir des compositions via le procédé de mélange de poudres - compactage - granulation - et éventuellement pastillage en voie sèche.Table 2 below shows examples of compositions of compounds of the present invention, as well as the performances of said compounds compared with those of the reference compound of the prior art 1. The compounds were evaluated by means of thermodynamic calculations or by means of thermodynamic calculations. from physical measurements carried out on granules or pellets made from the compositions via the mixing process of powders - compacting - granulation - and possibly dry pelletizing.

Le composé de référence 1 de l'art antérieur (voir le tableau 1 ci-dessus) renferme du nitrate de guanidine et du perchlorate de potassium et ne contient pas de modificateur de combustion au sens de l'invention. Les composés des exemples 1 à 7 renferment dans leur composition, en plus des deux constituants du composé de référence 1, un tel modificateur de combustion.The reference compound 1 of the prior art (see Table 1 above) contains guanidine nitrate and potassium perchlorate and does not contain a combustion modifier within the meaning of the invention. The compounds of Examples 1 to 7 contain in their composition, in addition to the two constituents of the reference compound 1, such a combustion modifier.

Les taux des constituants majeurs ont été ajustés afin de conserver une valeur de balance en oxygène proche de -3%, de manière à pouvoir directement comparer les performances des composés du tableau 1.The levels of the major constituents were adjusted in order to maintain an oxygen balance value close to -3%, so as to be able to directly compare the performance of the compounds in Table 1.

Les résultats du tableau 2 montrent, comme attendu selon l'enseignement de l'art antérieur (enseignement du brevet US 6 893 517 et celui du domaine des propergols), que l'ajout d'un modificateur de combustion au sens de l'invention dans une composition du type de celle du composé de référence 1 conduit à une augmentation de la vitesse de combustion à moyenne et haute pression sans modification significative de la température de combustion.The results of Table 2 show, as expected according to the teaching of the prior art (teaching of the patent US 6,893,517 and that of the field of propellants), that the addition of a combustion modifier within the meaning of the invention in a composition of the type of that of the reference compound 1 leads to an increase in the combustion rate at medium and high pressure without significant change in combustion temperature.

De façon surprenante, ledit ajout conduit de manière conjointe à un abaissement très important de l'exposant de pression, exposant de pression très faible sur toute la plage de pression de fonctionnement (au delà de 6 MPa), de la pression limite de combustion et à une augmentation importante de la vitesse de combustion à basse pression.Surprisingly, said addition leads jointly to a very significant lowering of the pressure exponent, very low pressure exponent over the entire operating pressure range (beyond 6 MPa), of the combustion limit pressure and to a significant increase in the rate of combustion at low pressure.

Le CuO est le composé qui, ajouté à la composition de référence 1, apporte les améliorations les plus significatives (voir l'exemple 2). L'exposant de pression est quasi nul sur l'ensemble de la plage de fonctionnement, la pression limite de fonctionnement est quasiment égale à la pression atmosphérique.CuO is the compound which, added to Reference Composition 1, provides the most significant improvements (see Example 2). The pressure exponent is almost zero over the entire operating range, the operating limit pressure is almost equal to atmospheric pressure.

Dans la mesure où un complexe de métal tel que le BCN se décompose au cours des réactions exothermiques de combustion en générant in situ du CuO de haute surface spécifique (ce qui a été vérifié expérimentalement), le CuO peut donc être remplacé par du BCN comme modificateur de combustion avec des résultats qui sont équivalents à ceux du CuO (voir l'exemple 7).Insofar as a metal complex such as BCN decomposes during exothermic combustion reactions generating high specific surface area CuO in situ (which has been verified experimentally), CuO can therefore be replaced by BCN as combustion modifier with results which are equivalent to those of CuO (see Example 7).

Le CuO et le BCN, permettent, lorsqu'ils sont incorporés à un taux réduit (5% dans les exemples), de conserver une valeur avantageuse de rendement gazeux (>32 g/mol) et conduisent au final à une amélioration très significative de la valeur de débit surfacique de gonflage (de plus de 40%) par rapport à la composition de référence NG / KClO4 du composé de référence 1. Tableau 2 Exemples Réf. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex 7 Ingrédients Nitrate de guanidine % 68,0 65,0 65,7 65,7 65,0 65,0 67,3 66,7 Perchlorate de potassium % 32,0 30,0 29,3 29,3 30,0 30,0 29,7 28,3 Oxyde de zinc (ZnO) % - 5,0 - - - - - - Oxyde de cuivre (CuO) % - - 5,0 - - - - - Oxyde de manganèse (MnO2) % - - - 5,0 - - - - Oxyde de Chrome (Cr2O3) % - - - 5,0 - - - Oxyde de Fer (Fe2O3) % - - - - - 5,0 - Nitrate basique de cuivre (BCN) % - - - - - - 3,0 5,0 Exemples Réf. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex 7 Caractéristiques Vitesse de combustion à 8MPa (basse pression) mm/s 20,6 26,7 36,2 24,9 27,0 25,8 34,5 38,1 Vitesse de combustion à 20MPa (moyenne pression) mm/s 26,3 31,9 38,0 31,5 31,1 31,2 36,4 39,3 Vitesse de combustion à 50MPa (haute pression) mm/s 34,9 38,0 45,7 39,5 37,8 41,5 44,7 47,8 Température de combustion K 2351 2237 2303 2285 2304 2294 2312 2296 Exposant de pression déterminé sur plage 6 - 52 MPa - 0,26 0,16 0,07 0,19 0,17 0,25 0,09 0,10 Pression (relative) limite de combustion MPa 1,7 1,5 0,1 1 0,5 0,25 0,1 0,1 Balance en oxygène % -3,0 -2,8 -3,1 -3,1 -2,8 -2,8 -3,1 -3,1 Densité g/cm3 1,67 1,73 1,72 1,72 1,73 1,73 1,69 1,70 Rendement gazeux à 1bar - 1000 K mole/kg 33,2 31,6 32,1 32,1 31,6 31,6 33,1 33,0 Débit surfacique de gonflage (pxnxTcxVc) à 20MPa mole.K /cm2.s 344 391 485 397 391 390 470 505 The CuO and the BCN, when they are incorporated at a reduced rate (5% in the examples), make it possible to retain an advantageous gas yield value (> 32 g / mol) and ultimately lead to a very significant improvement in the value of the surface inflation rate (of more than 40%) relative to the reference composition NG / KClO 4 of the reference compound 1. Table 2 Examples Ref. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex 7 Ingredients Guanidine nitrate % 68.0 65.0 65.7 65.7 65.0 65.0 67.3 66.7 Potassium perchlorate % 32.0 30.0 29.3 29.3 30.0 30.0 29.7 28.3 Zinc oxide (ZnO) % - 5.0 - - - - - - Copper oxide (CuO) % - - 5.0 - - - - - Manganese oxide (MnO 2 ) % - - - 5.0 - - - - Chromium oxide (Cr 2 O 3 ) % - - - 5.0 - - - Iron Oxide (Fe 2 O 3 ) % - - - - - 5.0 - Basic copper nitrate (BCN) % - - - - - - 3.0 5.0 Examples Ref. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex 7 Characteristics Burning rate at 8MPa (low pressure) mm / s 20.6 26.7 36.2 24.9 27.0 25.8 34.5 38.1 Burning rate at 20MPa (medium pressure) mm / s 26.3 31.9 38.0 31.5 31.1 31.2 36.4 39.3 Burning rate at 50MPa (high pressure) mm / s 34.9 38.0 45.7 39.5 37.8 41.5 44.7 47.8 Combustion temperature K 2351 2237 2303 2285 2304 2294 2312 2296 Pressure exponent determined over the range 6 - 52 MPa - 0.26 0.16 0.07 0.19 0.17 0.25 0.09 0.10 Combustion limit (relative) pressure MPa 1.7 1.5 0.1 1 0.5 0.25 0.1 0.1 Oxygen balance % -3.0 -2.8 -3.1 -3.1 -2.8 -2.8 -3.1 -3.1 Density g / cm 3 1.67 1.73 1.72 1.72 1.73 1.73 1.69 1.70 Gas yield at 1bar - 1000 K mole / kg 33.2 31.6 32.1 32.1 31.6 31.6 33.1 33.0 Inflation surface flow (pxnxTcxVc) at 20MPa mole.K / cm 2 .s 344 391 485 397 391 390 470 505

Le tableau 3 ci-après montre le deuxième effet surprenant mis en évidence par les inventeurs, à savoir la diminution très significative de la pression limite de combustion (mesurée sur des granulés) lorsque l'on introduit de la silice à un taux modéré dans la composition des composés de l'invention. Ce même effet, obtenu avec un autre oxyde réfractaire de métal tel que l'alumine, n'est pas d'une ampleur suffisante pour présenter un intérêt. TABLEAU 3 Exemples Réf.1 Ex. 8 Ex.9 Ingrédients unité Nitrate de guanidine % 68,0 65,0 65,0 Perchlorate de potassium % 32,0 30,0 30,0 Alumine % - 5,0 - Silice % - - 5,0 Caractéristique Pression (relative) limite de combustion MPa 1,7 1,5 0,5 Table 3 below shows the second surprising effect demonstrated by the inventors, namely the very significant reduction in the combustion limit pressure (measured on granules) when silica is introduced at a moderate rate into the gas. composition of the compounds of the invention. This same effect, obtained with another refractory metal oxide such as alumina, is not of sufficient magnitude to be of interest. TABLE 3 Examples Ref. 1 Ex. 8 Ex. 9 Ingredients unity Guanidine nitrate % 68.0 65.0 65.0 Potassium perchlorate % 32.0 30.0 30.0 Alumina % - 5.0 - Silica % - - 5.0 Characteristic Combustion limit (relative) pressure MPa 1.7 1.5 0.5

Claims (12)

  1. A solid pyrotechnic gas generator compound, the composition of which consists of:
    - guanidine nitrate,
    - potassium perchlorate,
    - at least one combustion modifier, and
    - optionally at least one additive,
    characterized in that its composition, expressed in weight percentages, comprises from:
    - 60 to 70% of guanidine nitrate,
    - 26 to 33%, advantageously 26 to 30%, of potassium perchlorate,
    - 2.5 to 6% of at least one combustion modifier chosen from transition metal oxides, the precursors of such oxides and mixtures thereof,
    - 0 to 6% of at least one additive, and
    does not comprise an explosive ingredient.
  2. The compound according to claim 1, characterized in that its composition consists of at least 94 % by weight, advantageously at least 98 % by weight, or even 100 % by weight of said guanidine nitrate, potassium perchlorate, and at least one combustion modifier.
  3. The compound according to claim 1 or 2, characterized in that said at least one combustion modifier is chosen from zinc oxide (ZnO), iron oxide (Fe2O3), chromium oxide (Cr2O3), manganese dioxide (MnO2), copper oxide (CuO), basic copper nitrate (Cu(NO3)2·3Cu(OH)2) and mixtures thereof.
  4. The compound according to any one of claims 1 to 3, characterized in that said at least one combustion modifier consists of copper oxide and/or basic copper nitrate.
  5. The compound according to claim 4, characterized in that it has a pressure exponent of less than or equal to 0.1, for a pressure of between 6 and 52 MPa.
  6. The compound according to any one of claims 1 to 5, characterized in that said at least one combustion modifier has a specific surface area of greater than 3 m2/g, advantageously greater than 10 m2/g and very advantageously greater than 25 m2/g.
  7. The compound according to any one of claims 1 to 6, characterized in that its composition comprises silica as additive.
  8. The compound according to claim 7, characterized in that said silica is in pulverulent form having a high specific surface area, advantageously of 100 m2/g or more, and of micrometric size, advantageously of nanometric size, or in the form of silica fibers of from 1 to 20 microns in diameter and from 20 to 500 microns in length.
  9. The compound according to any one of claims 1 to 8, characterized in that it is obtained by means of a dry process, which comprises a step of compacting a pulverulent mixture comprising the constituent ingredients of said compound in powder form, optionally followed by a granulation step, itself optionally followed by a step of forming by pelletizing.
  10. The compound according to any one of claims 1 to 9, characterized in that it is in the form of granules, pellets or monolithic blocks.
  11. A pulverulent composition, which is a precursor of a compound according to any one of claims 1 to 10, the composition of which corresponds to that of a compound according to any one of claims 1 to 8.
  12. A gas generator, suitable for an airbag, characterized in that it contains at least one compound according to any one of claims 1 to 10.
EP11773097.8A 2010-09-15 2011-09-15 Pyrotechnic gas generator compounds Active EP2616413B8 (en)

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FR1057353A FR2964656B1 (en) 2010-09-15 2010-09-15 PYROTECHNIC COMPOUNDS GENERATORS OF GAS
PCT/FR2011/052125 WO2012035271A2 (en) 2010-09-15 2011-09-15 Pyrotechnic gas generator compounds

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DE112015002666T5 (en) * 2014-06-05 2017-03-16 Tk Holdings, Inc. Improved booster composition
CN114988974A (en) * 2014-06-05 2022-09-02 Tk控股公司 Improved pressurized compositions
FR3037812B1 (en) 2015-06-29 2017-08-04 Herakles FIRE EXTINGUISHER
CN107573199A (en) * 2016-11-03 2018-01-12 湖北航天化学技术研究所 A kind of voltage-controlled heat production gas generating agent of high security
FR3077989B1 (en) 2018-02-20 2021-11-19 Arianegroup Sas FIRE EXTINGUISHER
CN108752154B (en) * 2018-06-08 2020-08-28 中国科学技术大学 Composite gas generating agent with wheat scattering combustion effect and preparation method thereof
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JP2024037522A (en) * 2022-09-07 2024-03-19 株式会社ダイセル Gas generant composition

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WO2012035271A2 (en) 2012-03-22
MX2013002988A (en) 2013-06-24
FR2964656B1 (en) 2012-10-12
EP2616413B8 (en) 2021-12-08
US20130228254A1 (en) 2013-09-05
KR20140135087A (en) 2014-11-25
CN103180271A (en) 2013-06-26
BR112013006065A2 (en) 2016-06-07

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