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

• a subject of the present invention is pyrotechnic gas generator compounds, suitable for use in motor vehicle occupant protection systems, more especially for the inflation of airbags and most particularly for the inflation of side airbags (see below).
• the side airbag systems differ from the front airbag systems essentially due to the time required for the deployment and positioning of the airbag. Typically, this time is shorter for a side airbag (about 10-20 ms, compared with 40-50 ms for a front airbag).
• the functional requirement of inflation of the bag over a short time makes it necessary to resort to 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 combustion chamber of the generator, in order to obtain a sufficient value of the inflation rate per unit area (product ⁇ n ⁇ Tc ⁇ Vc).
• the pyrotechnic composition in order to ensure a satisfactory start-up of the system, the pyrotechnic composition must also have good ignitability characteristics. Also, given the generally tapered surface profile of the charges used (of pellet type), the composition should ideally have a combustion rate that is stable and high enough at low pressure. In fact, those skilled in the art are aware that the specifications for side airbags are more restrictive than those for front airbags. Of course, any technological advance in the field of said side airbags can also advantageously be available in the field of front airbags.
• the term “low pressure” is used to define a pressure P such that: 0.1 ⁇ P ⁇ 10 MPa
• the term “medium pressure” is used to define a pressure P such that: 10 MPa ⁇ P ⁇ 30 MPa
• the term “high pressure” is used to define a pressure P such that: P ⁇ 30 MPa.
• the desired increase in combustion rate of the pyrotechnic compound in question is therefore necessary not only to increase the gas flow rate in order to achieve the inflation delay specifications, but also to ensure the ignitability of the compound without recourse to the use of a relay charge and the innocuousness of the combustion products.
• said combustion temperature must not be too high (it must at a minimum remain less than 2400 K, more preferably less than 2350 K) so that the temperature of the gases in the airbag does not harm the physical integrity 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 of filters within said generator.
• the side airbag systems may call for two types of gas generators: those which are said to be entirely pyrotechnic (the gas generation then being exclusively provided by the combustion of a pyrotechnic charge) and those said to be “hybrid” (the gases then originating jointly from the combustion of a pyrotechnic charge and from a volume of neutral gas stored under pressure in a leaktight reservoir).
• gas generators those which are said to be entirely pyrotechnic (the gas generation then being exclusively provided by the combustion of a pyrotechnic charge) and those said to be “hybrid” (the gases then originating jointly from the combustion of a pyrotechnic charge and from a volume of neutral gas stored under pressure in a leaktight reservoir).
• the pyrotechnic charge must not have a too low combustion temperature so that the combustion gases are hot enough to compensate for the drop in temperature generated by the volume expansion of the precompressed neutral gas. Ideally, combustion temperatures above 2000 K are required.
• those skilled in the art are in search of pyrotechnic compounds which are suitable for use in entirely pyrotechnic gas generators or in hybrid generators, more particularly intended for side airbags, i.e. which simultaneously have a moderate combustion temperature of about 2000-2400 K, more preferably 2000-2350 K, and a high combustion rate over the entire operating pressure range (in particular greater than 30 mm/s at 20 MPa, more preferably greater than 35 mm/s at 20 MPa), including at low pressure.
• the pyrotechnic compounds for airbags must also aim to jointly meet the following requirements:
• explosive ingredients means ingredients classified in risk division 1.1 according to standard NF T 70-502 (see also UNO—Recommendations relating to the transport of dangerous goods—manual of tests and criteria, fourth revised edition, ST/SG/AC.10/11/Rev.4, ISBN 92-1-239083-8155N 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 oxygen-containing compound of a transition metal, advantageously with a high specific surface area, conventionally used in the field of propellants for increasing the combustion rate at medium and high pressure (this catalyst accelerates the decomposition of the oxidizing charge).
• a ballistic catalyst consisting of an oxygen-containing compound of a transition metal, advantageously with a high specific surface area, conventionally used in the field of propellants for increasing the combustion rate at medium and high pressure (this catalyst accelerates the decomposition of the oxidizing charge).
• the gas microgenerators for seatbelt tensioner devices as described in said U.S. Pat. No. 6,893,517 (and in its priority application EP 1 275 629) operate via pulses, which requires a high combustion rate at medium and high pressure.
• a high pressure exponent at low pressure and noncombustion at atmospheric pressure of the compounds in question does not pose a problem, since the pressure does not fall again, in the context of the use of said compounds, to a low level before the end of the pyrotechnic operation.
• This application for seatbelt tensioner devices does not need, for the gas generator, requirements as severe as those needed in the context of the present invention (airbags, and most particularly side airbags), most particularly a high combustion rate at low pressure, a drop in the cut-off combustion pressure threshold (as close as possible to atmospheric pressure) and a low pressure exponent over the entire combustion range (in particular at low pressure).
• the pyrotechnic compounds which offer a good compromise, in terms of gas temperature, gas yield, level of particles emitted and toxicity, contain, as main ingredients, guanidine nitrate (GN) as reducing charge and basic copper nitrate (BCN) as oxidizing charge.
• GN guanidine nitrate
• BCN basic copper nitrate
• patent application EP 1 526 121 describes the addition of a perchlorate (in particular potassium perchlorate), in a low amount (less than 5% by weight), for improving the ignition of these compounds.
• a perchlorate in particular potassium perchlorate
• the incorporation of perchlorate in such a low amount does not make it possible to sufficiently increase the combustion rate of the compound for satisfactory use in gas generators for side airbags.
• Patent application US 2006/0137785 describes the combination of a reducing agent of guanidine type (nitroguanidine or guanidine nitrate) and of ammonium perchlorate, the latter being necessarily incorporated in a significantly high amount (30% to 60% by weight).
• the incorporation of ammonium perchlorate in such a high amount results in two major drawbacks which are, firstly, a significant increase in the combustion temperature (above 2800 K) and, secondly, the generation of hydrogen chloride (which is a toxic and highly corrosive gas), said hydrogen chloride then being present in the gas effluents.
• 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 results in a decrease in the gas yield value for the compound.
• thermodynamic and ballistic characteristics of such a compound (reference compound 1), the (“binary”) composition of which contains only guanidine nitrate (GN) and potassium perchlorate (KClO 4 ), are given in table 1 hereinafter.
• Reference compound 1 exhibits many advantages among those expected of a compound for generating gas for an airbag system.
• the basic ingredients are simple and readily available, inexpensive, safe with regard to the pyrotechnic aspects (no constituent belonging to the explosive compounds class) and nontoxic.
• the thermodynamic performance (gas yield, particle content) is good and the combustion temperature remains moderate and therefore acceptable.
• the particles emitted by the combustion are nontoxic (essentially KCl).
• the combustion rate of about 26 mm/s at 20 MPa is increased only by 20 to 30% compared with that of a compound based on guanidine nitrate (GN) and on basic copper nitrate (BCN), and remains low with respect to the set specifications.
• GN guanidine nitrate
• BCN basic copper nitrate
• a transition metal a transition metal oxide or a compound which is a precursor of such an oxide
• compositions of the pyrotechnic gas generator compounds of the invention (which are most particularly suitable for airbag, in particular side airbag, applications) contain:
• compositions of compounds of the invention consist (exclusively) of the ingredients listed above (GN+KClO 4 +at least one combustion modifier+optionally at least one additive), taken in the contents indicated above.
• the ingredients of the first three types above generally represent more than 90% by weight of the total weight (of the composition) of the compounds of the invention, very generally at least 94% by weight, or even more than 98% by weight.
• additive(s) such as manufacturing aids (calcium stearate, silica, for example)
• the ingredients of the three types above can absolutely represent 100% by weight of the total weight of the compounds of the invention.
• the guanidine nitrate representing from 60 to 70% of the total weight, is in addition selected for pyrotechnic safety reasons and for its rheoplastic behavior, suitable for carrying out the compacting and optional pelletizing phases of the dry process (see hereinafter), ensuring a good densification of the starting pulverulent pyrotechnic composition while limiting the compressive load to be applied.
• the manufacture of the compounds via the dry process comprises up to four main steps (see hereinafter), which have in particular been described in patent application WO 2006/134311.
• the potassium perchlorate is present, in the composition of the compounds of the invention, in a moderate intermediate content (from 26 to 33% by weight, advantageously from 26 to 30% by weight), very particularly with reference to the combustion temperature, the “ignitability” and the combustion rate at high pressure that are targeted.
• the combustion modifiers selected by the inventors, develop particularly advantageous (unexpected) properties with reference to the desired three points of improvement (see above).
• Said at least one combustion modifier is chosen from transition metal oxides, the precursors of such oxides and mixtures thereof.
• a precursor of such an oxide results in the formation of such an oxide (generates such an oxide) at the time of its decomposition at temperature during the combustion of the pyrotechnic compound.
• the basic copper nitrate (Cu(NO 3 ) 2 .3Cu(OH) 2 ) decomposes to copper oxide (CuO) (see hereinafter).
• Said at least one combustion modifier is present in an amount which is sufficient ( ⁇ 2.5% by weight) to be effective (with reference to the three points of improvement above), and not excessive ( ⁇ 6% by weight) so as not to harm the gas yield.
• Such one combustion modifier is generally present, but the presence of at least two such additives is expressly envisioned in 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 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 which is a precursor of said copper oxide (in the sense that BCN results in the formation of copper oxide CuO at the time of its decomposition at temperature), are particularly effective.
• the compounds of the invention therefore contain, as combustion modifier, copper oxide and/or basic copper nitrate.
• the use of these combustion modifiers makes it possible to obtain compounds of the invention which have a pressure exponent value of 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 of greater than 3 m 2 /g, advantageously greater than 10 m 2 /g and very advantageously greater than 25 m 2 /g.
• the pyrotechnic compounds of the invention can contain, at a low content by weight (less than or equal to 6%, generally at least 0.1%), at least one additive, in particular at least one additive that facilitates the obtaining of said compounds (the forming during the obtaining thereof), such as calcium stearate or magnesium stearate, graphite and/or at least one additive for improving the aggregation of the solid products of their combustion, chosen from refractory oxides with a softening or melting point adapted to the composition, such as silica or alumina.
• at least one additive in particular at least one additive that facilitates the obtaining of said compounds (the forming during the obtaining thereof), such as calcium stearate or magnesium stearate, graphite and/or at least one additive for improving the aggregation of the solid products of their combustion, chosen from refractory oxides with a softening or melting point adapted to the composition, such as silica or alumina.
• silica generally introduced in fine pulverulent form (advantageously of micrometric size, very advantageously of nanometric size) having a high specific surface area (advantageously of 100 m 2 /g or more), or in the form of silica fibers of small diameter (1 to 20 microns) and some tens or hundreds of microns (20 to 500 microns) in length.
• silica at contents between 0.5 and 6% by weight, advantageously between 0.5 and 3.5% by weight, also has a very significant effect of drop in the cut-off combustion pressure.
• the at least one additive intervenes with the constituent ingredients (GN, KClO 4 +at least one combustion modifier of the above-mentioned type) (at the beginning of the manufacturing process) or is added, further downstream, in the process for manufacturing the compounds of the invention.
• compositions of the compounds of the invention do not contain an explosive ingredient (see the NF standard and the UNO recommendations specified above), this being in particular with reference to the parameters: pyrotechnic safety and combustion temperature. It is, moreover, noted that the weights of pyrotechnic compounds required for the inflation of an airbag, in particular of a side airbag, are greater than those required for the inflation of a seatbelt tensioner device according to U.S. Pat. No. 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 according to a wet process.
• said process comprises the extrusion of a paste containing the constituents of the compound.
• said process includes a step of placing all the (or some of the) main constituents in aqueous solution, comprising solubilization of at least one of said main constituents (oxidizing agent and/or reducing agent), and then the production of a powder by spray drying, the addition to the powder produced of the constituent(s) that were not placed in solution, and then the forming of the powder in the form of objects via the usual dry processes.
• the pyrotechnic compounds of the invention can also be obtained by dry process, for example by simple pelletizing of the powder obtained by mixing of their constituents.
• the preferential process for obtaining the pyrotechnic compounds of the invention includes a step of dry compacting 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).
• the dry compacting is generally carried out, in a manner known per se, in a roll compacter, at a compacting pressure of between 10 8 and 6 ⁇ 10 8 Pa. It can be carried out according to different variants (with a characteristic step of “simple” compacting followed by at least one additional step, with a characteristic step of compacting coupled to a forming step).
• the pyrotechnic compounds of the invention are capable of existing in various forms (in particular along the manufacturing process resulting in the final compounds):
• the pyrotechnic compounds of the invention are therefore in particular capable of existing in the form of objects of the following type:
• the constituent ingredients of the compounds of the invention advantageously have a fine particle size, of 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 all their 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), which is a 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 the 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 hereinafter gives examples of compositions of compounds of the present invention, and also the performances of said compounds compared with those of the reference prior art compound 1.
• the compounds were evaluated by means of thermodynamic calculations or on the basis of physical measurements carried out on granules or pellets manufactured from the compositions via the dry process of mixing of powders—compacting—granulation—and optionally pelletizing.
• the reference prior art compound 1 (see table 1 above) contains guanidine nitrate and potassium perchlorate and does not contain any combustion modifier within the meaning of the invention.
• the compounds of examples 1 to 7 contain such a combustion modifier in their composition, in addition to the two constituents of the reference compound 1.
• CuO is the compound which, when added to the reference composition 1, provides the most significant improvements (see example 2).
• the pressure exponent is virtually zero over the whole of the operating range, the cut-off operating pressure is virtually equal to atmospheric pressure.
• CuO and BCN make it possible, when they are incorporated in a low amount (5% in the examples), to preserve an advantageous gas yield value (>32 g/mol) and result, in the end, in a very significant improvement in the inflation rate per unit area value (of more than 40%) compared with the GN/KClO 4 reference composition of the reference compound 1.
• Table 3 hereinafter shows the second surprising effect demonstrated by the inventors, namely the very significant decrease in the cut-off combustion pressure (measured on granules) when silica is introduced at a moderate content into the composition of the compounds of the invention.
• This same effect, obtained with another refractory metal oxide such as alumina, is not of a sufficient size to be of interest.

Landscapes

• 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)

Applications Claiming Priority (3)

Publications (1)

Family

ID=43927666

Family Applications (1)

Country Status (9)

Cited By (2)

Families Citing this family (7)

Citations (3)

Family Cites Families (17)

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

Patent Citations (3)

Also Published As

Similar Documents

Legal Events