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
• • 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
  • 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 compounds gas generators, suitable for use in protective systems of occupants of motor vehicles, more particularly for the inflation of damping cushions (so-called “airbags”) and particularly for the inflation of side damping cushions (so-called “side airbags” (see below)).
• airbags damping cushions
• side airbags side damping cushions
• the technical field relating to the protection of occupants of motor vehicles has grown considerably over the last twenty years.
• the latest generation of vehicles now include in the cabin several airbag-type airbag safety systems whose functioning is provided by the combustion gases of pyrotechnic compounds.
• the cushioning type of systems there are mainly frontal airbags for frontal impact and side airbags for side impact.
• Side airbag systems differ from frontal airbag systems primarily in the time required for deployment and placement 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 for inflation of the bag over a short time requires the use of a pyrotechnic composition having a sufficiently high combustion rate (typically equal to or greater than 30 mm / s, or even 35 mm / s, at 20 MPa ) over the operating pressure range in the generator combustion chamber, in order to obtain an inflated surface flow rate value (product pxnx Te x Vc) sufficient.
• the pyrotechnic composition in order to ensure satisfactory system operation, must also have good reliability characteristics. Also, given the generally decreasing surface profile of the loadings employed (pellet type), the composition should ideally have a stable and sufficiently high combustion rate at low pressure. In fact, those skilled in the art are aware that the . - specifications of the side airbags is more restrictive than that of the front airbags. Of course, any technological advance in the field of said side airbags can also advantageously be declined in the field of frontal airbags.
• a low pressure is defined as a pressure P such that: 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 rate of combustion 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 to reach the inflation time specifications, but also to ensure the ignitability of the compound without resorting to the use of a relay charge and the safety of the products of combustion.
• said combustion temperature should 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 cushioning cushion does not affect the integrity physical of the occupant.
• 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.
• those skilled in the art are in search of 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 presenting 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 higher at 35 mm / s at 20 MPa, v included at low pressure.
• pyrotechnic compounds for airbags must also tend to meet the following requirements together:
• the gases generated by the combustion of the pyrotechnic charge (comprising a compound or n compounds) must be non-toxic, that is to say have a low content of carbon monoxide, oxides of nitrogen and chlorinated compounds; . _
• the gas yield ie the quantity of gas generated by the combustion
• the pressure exponent must be as low as possible, especially 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 significantly reduce the variability of operation between the extreme low temperature (around -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 size of the metal structure of the generator can be advantageously reduced;
• the basic ingredients of the compounds be pyrotechnically non-hazardous.
• ingredient (s) belonging to the class of explosives such as nitroguanidine, hexogen (RDX), octogen (H X) is advantageously avoided.
• Explosive ingredients are 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 / ll / Rev.4, ISBN 92-1-239083-8ISSN 1014-7179 and STANAG 4488).
• Guanidine nitrate and potassium perchlorate, taken separately, are not ingredients in this risk division. They are not explosive ingredients, especially in the sense of the invention.
• These compounds also include in their composition a low level of a ballistic catalyst, consisting of an oxygen 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 oxygen 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 high exponent of low-pressure pressure and the non-combustion at atmospheric pressure of the compounds in question are not a problem, since the pressure does not fall back, in the context of use of said compounds, to a low level before the end of pyrotechnic operation.
• This application for belt retractor devices does not require, for the gas generator, requirements as severe as those required in the context of the present invention (airbags, and especially side airbags), especially a high rate of combustion. at low pressure, a lowering of the limit threshold of combustion pressure (closer to atmospheric pressure) and a low pressure exponent over the entire range of combustion (especially at low pressure).
• pyrotechnic compounds that offer a good compromise, in terms of gas temperature, gas yield, emitted particulate levels 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
• a combustion rate to 20 MPa slightly increased compared to compositions formulated based on guanidine nitrate (NG) and basic copper nitrate (BCN), but which remains insufficient for use in side airbags.
• NG guanidine nitrate
• BCN basic copper nitrate
• thermodynamic and ballistic characteristics of such a compound (reference compound 1), whose composition (“binary") contains only guanidine nitrate (NG) and potassium perchlorate (KCIO 4 ), are presented in Table 1 below. - -
• the given value is a relative pressure.
• a zero combustion pressure limit corresponds to the atmospheric pressure.
• Reference compound 1 has many of the advantages expected from a gas generator compound for an airbag system.
• the basic ingredients are simple and easily available, inexpensive, non-hazardous on the pyrotechnic aspects (no component of the class of explosive compounds) and non-toxic.
• the thermodynamic performances (gas yield, particle rate) are good and the combustion temperature remains moderate and therefore acceptable.
• the particles emitted by combustion are non-toxic (essentially KCl).
• the burning rate of the order of 26 mm / s to 20 MPa is only 20 to 30% higher than that of a compound based on _ Guanidine nitrate (NG) and basic copper nitrate (BCN), and remains low compared to the set specifications.
• NG Guanidine nitrate
• BCN basic copper nitrate
• compositions of the pyrotechnic gas-generating compounds of the invention (particularly suitable for airbag applications, especially lateral applications) contain:
• At least one combustion modifier chosen from transition metal oxides, precursors of such oxides and mixtures thereof,
• compositions of compounds of the invention consist (exclusively) in the ingredients listed above (NG + KCI0 4 + at least one combustion modifier + optionally at least one additive) taken at the levels indicated below. above.
• the ingredients of the first three types above generally represent more than 90% by weight of the total mass (of the composition) of the compounds of the invention, very generally at less than 94% by weight, or even more than 98% by weight.
• additive such as production auxiliaries (calcium stearate, silica, for example)
• the ingredients of the three types above can be quite 100% by weight of the total mass of the compounds of the invention.
• Guanidine nitrate representing 60 to 70% of the total mass, is also selected for reasons of pyrotechnic safety and for its rheoplastic behavior, suitable for the implementation of compaction phases and possible pelletization of the process.
• dry see - - hereinafter
• the manufacture of the compounds by the dry process process comprises up to four main steps (see below), which have been described in particular in the patent application WO 2006/134311.
• Potassium perchlorate is present in the composition of the compounds of the invention at a moderate intermediate level (from 26 to 33% by weight, advantageously from 26 to 30% by weight), particularly with reference to the combustion temperature, "ignitability" and the target high-pressure combustion rate.
• the combustion modifiers selected by the inventors, develop particularly interesting (unexpected) properties with reference to the three improvement points sought (see above).
• Said at least one combustion modifier is selected 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 decomposition in temperature during the combustion of the pyrotechnic compound.
• the basic copper nitrate (Cu (NO 3 ) 2 '3Cu (OH) 2 ) is decomposed into copper oxide (CuO) (see below).
• Said at least one combustion modifier is present in a sufficient amount (> 2.5% by weight), to be effective (with reference to the three improvement points above), and not excessive ( ⁇ 6% by weight) in order not to harm the gas yield.
• a single combustion modifier is generally present but the presence of at least two such additives is expressly provided for in the context of the present invention.
• said at least one combustion modifier is selected from zinc oxide (ZnO), iron oxide (Fe 2 O 3 ), chromium oxide ( ⁇ 2 ⁇ 3 ), manganese dioxide ( MnO 2 ), copper oxide (CuO), basic copper nitrate (Cu (NO 3 ) 2-3Cu (OH) 2 ) and mixtures thereof.
• the copper oxide and the basic copper nitrate, precursor of said copper oxide are - - particularly powerful.
• the compounds of the invention therefore contain, as a combustion modifier, copper oxide and / or basic nitrate of copper. The use of these combustion modifiers makes it possible to obtain compounds of the invention having a pressure exponent value of less than or equal to 0.1 over the pressure range 6-52 Pa.
• 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.
• a pressure (relative, that is to say with reference to atmospheric pressure) combustion limit less than or equal to 1.5 MPa, preferably less than 0.2 MPa, very advantageously equal to 0.1 MPa, - -
• the pyrotechnic compounds of the invention may contain, at a low mass level (less than or equal to 6%, generally at least 0.1%), at least one additive, especially at least one additive making it easier to obtain (shaping, when they are obtained), 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 with a softening or melting temperature adapted to the composition, such as silica or alumina.
• at least one additive especially at least one additive making it easier to obtain (shaping, when they are obtained), 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 with a softening or melting temperature adapted to the composition, such as silica or alumina.
• silica generally introduced in fine powder form (advantageously of micrometric size, 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.
• the at least one additive intervenes with the constituent ingredients
• compositions of the compounds of the invention do not contain any 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 airbag, in particular of a lateral airbag, are greater than those required for the inflation of a retractor device according to US Pat. 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 process comprises the extrusion of a paste containing the constituents of the compound.
• said process includes a step of aqueous dissolution of all (or some) of the main constituents comprising solubilization of at least one of said main constituents (oxidant and / or reducing agent) and then obtaining a powder by spray-drying, the addition to the powder obtained of the constituent (s) which would not have been dissolved, and the shaping of the powder in the form of objects by the usual processes in the dry process.
• the pyrotechnic compounds of the invention may also be obtained in the dry process, for example by simply pelletizing the powder obtained by mixing their constituents.
• the preferred method of obtaining the pyrotechnic compounds of the invention includes a dry compaction step of a mixture of powder constitutive ingredients of said compounds (except for said at least one additive which may be added during the process). Dry compaction is generally carried out, in a manner known per se, in a roller compactor, at a compacting pressure of between 10 8 and 6.10 8 Pa. It can be implemented according to different variants (with a characteristic step compaction "simple" followed by at least one complementary step, with a compaction characteristic step coupled to a shaping step). Thus, the pyrotechnic compounds of the invention are likely to exist in different forms (especially over the manufacturing process leading to the final compounds):
• pellets After dry compaction followed by granulation and then pelletizing (dry compression), pellets are obtained;
• the pyrotechnic compounds of the invention are therefore particularly likely to exist in the form of objects of the type:
• the granules of the invention generally have a particle size (a median diameter) of between 200 and 1400 ⁇ m (and an apparent density of between 0.8 and 1.2 cm 3 / g);
• the pellets of the invention generally have a thickness of between 1 and 3 mm.
• the constitutive ingredients of the compounds of the invention advantageously have a fine particle size, less than or equal to 20 ⁇ m. Said granulometry (value of the median diameter) is generally between 3 and 20 pm.
• 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 pm for KCl0 4 and 5 to 15 pm for guanidine nitrate. .
• the present invention relates to a powdery composition (mixture of powders), precursor of a compound of the invention, the composition of which 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 ideal for airbags, especially side airbags (see above).
• Table 2 gives examples of compositions of compounds of the present invention, as well as the performances of said compounds compared with those of the compound of the prior art of reference 1.
• the compounds were evaluated by means of thermodynamic calculations or from physical measurements on pellets or pellets made from the compositions via the mixing process of . . powders - compaction - granulation - and possibly dry pelletisation.
• 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 have been adjusted in order to maintain an oxygen balance value close to -3%, so that the performances of the compounds of Table 1 can be directly compared.
• said addition conjointly leads to a very significant lowering of the pressure exponent, a very low pressure exponent over the entire operating pressure range (beyond 6 MPa), of the combustion limit pressure and a significant increase in the low-pressure combustion rate.
• CuO is the compound which, added to the reference composition
• CuO and BCN allow, when incorporated at a reduced rate (5% in the examples), to retain an advantageous value of gas yield (> 32 g / mol) and ultimately lead to a very significant improvement in the surface flow rate value of inflation (by more than 40%) relative to the reference composition NG / KCIO4 of the reference compound 1.
• 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 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.

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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)

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• 2010
  • 2010-09-15 FR FR1057353A patent/FR2964656B1/fr active Active
• 2011
  • 2011-09-15 US US13/821,525 patent/US20130228254A1/en not_active Abandoned
  • 2011-09-15 EP EP11773097.8A patent/EP2616413B8/de active Active
  • 2011-09-15 KR KR1020137009591A patent/KR20140135087A/ko not_active Withdrawn
  • 2011-09-15 MX MX2013002988A patent/MX2013002988A/es not_active Application Discontinuation
  • 2011-09-15 JP JP2013528747A patent/JP2013541487A/ja active Pending
  • 2011-09-15 BR BR112013006065A patent/BR112013006065A2/pt not_active IP Right Cessation
  • 2011-09-15 CN CN2011800515939A patent/CN103180271A/zh active Pending
  • 2011-09-15 WO PCT/FR2011/052125 patent/WO2012035271A2/fr not_active Ceased

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