Classifications

• • 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
• • 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
  • C06B29/22—Compositions containing an inorganic oxygen-halogen salt, e.g. chlorate, perchlorate the salt being ammonium perchlorate
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
  • C06B45/04—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive
  • C06B45/06—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component
  • C06B45/10—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component the organic component containing a resin

Definitions

• the present invention relates to pyrotechnic compounds gas generators and a method for obtaining them.
• Said pyrotechnic compounds present:
• the inflation surface flow rate is estimated by the product pxnx T x Vc, where p is the density of the material (in g / cm 3 ), n the gaseous molar yield of the combustion (in mole / g), T the combustion temperature (in K) and Vc the combustion rate in cm / s
• the inflation surface flow rate parameter is expressed in mol.K / cm 2 .s.
• the present invention is in the technical field of pyrotechnic generation of gas. It is particularly applicable in vehicle occupant protection systems, protection by means of damping cushions (so-called "airbags”), which are inflated by the combustion gases of pyrotechnic compounds.
• airbags damping cushions
• this type of composition has the following advantages: the low temperature makes it possible to limit the thickness of the bag; - the gaseous effluents are generally of good quality vis-à-vis the acceptable toxicity standards in force in the field (USCAR).
• compositions on the other hand, have drawbacks that can penalize certain applications:
• the swelling capacity is limited; - combustion emitting solid residues, filters are necessary to reduce the emission of particles. These filters further reduce the swelling capacity due to the thermal losses they induce. The filters further induce an increase in the volume and cost of the generator; in almost all cases, the cold compositions have low combustion rates. This cumulative point at low swelling power induces low inflation surface flow rates. These low inflation surface flow rates are compensated for by the use of thin pellets and small diameters which induce a strong initial surface of pyrotechnic product and a low loading density. In general, the high initial "cold" product surface at low combustion speed induces, in addition to the aforementioned drawbacks, the following difficulties: the combustion of the product is slowly initiated and a high ignition charge is required ;
• a composition with a high swelling capacity, a high inflating surface flow rate and without particles has many advantages with respect to the operation and miniaturization of airbag system gas generators. This miniaturization is required for reasons of cost, weight and integration inside the vehicles.
• compositions based on silicone binder were then proposed.
• Compositions based on binder "RTV" room temperature vulcanizable
• potassium perchlorate have been described in patent applications FR 2 190 776 and FR 2 213 254.
• Patent application FR 2 728 562 describes a version improved of these products, manufacturable by a process of kneading and continuous extrusion.
• the silicone binder is combined with a mixture of ammonium perchlorate and sodium nitrate; said sodium nitrate serving as a chlorine sensor.
• the compositions according to these documents exhibit an acceptable gas yield, a high combustion temperature and a high rate of combustion. The inflating surface flow rate is therefore relatively high.
• compositions based on nitrocellulose and nitroglycerine compared with compositions based on nitrocellulose and nitroglycerine, these compositions have the advantage of being very stable in temperature and can be adjusted to "oxygen balance" (balance in oxygen) to meet the standards of toxicity of gaseous effluents.
• these compositions have the disadvantage of emitting a high level of particles (approximately 30%), especially sodium chloride and silica, which requires the use of a bag having a high thickness and a coating of protection of the internal face of said bag.
• Patent application EP 1 216 977 describes an extrudable solvent-free composition essentially comprising a two-component oxygenated hydrocarbon binder (an elastomer (a rubber) and a plasticizer), a nitrogen-containing organic compound and oxidizing charges.
• the oxidizing charges are ammonium perchlorate and a chlorine sensor which may be sodium nitrate.
• Sodium nitrate comes into height of about 15 to 20% by weight in the composition. Its role is to capture chlorine from ammonium perchlorate to form sodium chloride.
• This composition has a high combustion temperature and a swelling capacity and a surface flow of the same order of magnitude as those of the silicone bases, due to a slightly lower combustion rate and a lower particle rate.
• the gas yield, and therefore the swelling capacity is limited by the presence of the chlorine sensor which induces the formation of a solid chlorine salt.
• the overall content of solid combustion residues of these compositions is about 14%.
• the burning rates of these compositions are about 20 to 40 mm / s at a combustion pressure of 20 HPa.
• compositions with a high combustion temperature generating few particles and toxic effluent (with the aim of increasing the swelling capacity and the inflating surface flow rate, so as to reduce the volumes of These compositions can advantageously be shaped by solvent-free extrusion, which makes it possible to produce a monolithic shape that facilitates loading, improving the charging density of the generator.
• the absence of solvent avoids the emission of VOCs (volatile organic compounds).
• the gas generator can be smaller, compact and less expensive.
• the progressiveness of the control of the flow rate of gas related to the operation of a monolithic block and the moderation of the energy released due to the small mass of pyrotechnic product needed should allow to use bags of moderate or low thickness.
• the fixed improvement objective has been achieved.
• the inventors currently propose high performance pyrotechnic compounds, with reference to the specification above, pyrotechnic compounds that perform better than those corresponding to the compositions of the application EP 1 216 977.
• the pyrotechnic compounds of the invention have a composition of the type of that of the compounds according to said application EP 1 216 977 in that it contains:
• an oxidizing charge which comprises at least one inorganic perchlorate (i.e. without carbon); and a crosslinked oxygenated hydrocarbon binder obtained by crosslinking an elastomer in the presence of at least one crosslinking agent and at least one oxygenated plasticizer of said elastomer; said elastomer having a molecular weight greater than 200,000 and preferably being selected from polyesters and polyacrylates.
• the plasticizer (s) is (are) obviously perfectly miscible (s) in the elastomer, so as not to exude temperature and thus lower the glass transition temperature of said elastomer.
• the pyrotechnic gas-generating compounds of the invention therefore comprise, in their composition, an oxidizing charge (without carbon) and an oxygenated hydrocarbon binder, of the above types.
• the oxidizing charge in question which is inorganic (carbon-free), which comprises at least one inorganic perchlorate, does not include a chlorine sensor and said at least one oxygenated plasticizer of the elastomer consists of:
• a plasticizer whose molecular mass is greater than 350 g / mol (its vapor pressure is thus negligible at 120 ° C.) and the oxygen balance equal to or greater than -230% (said oxygen balance can thus be balanced in combustion with the chosen fillers); or a mixture of such plasticizers with each other (of at least two plasticizers of this type); or a mixture of at least one such plasticizer with at least one other oxygenated plasticizer (of another type).
• Said at least one original oxygenated plasticizer present advantageously consists of at least one plasticizer with the properties stated above. Mixtures of such plasticisers with other oxygenated plasticizers (such as dioctyladipate and / or dioctylazelate) may however also be present.
• the inventors have demonstrated that it is possible to compensate for the suppression of the additional oxidizing charge constituted by the chlorine sensor (in particular sodium nitrate) according to the teaching of application EP 1 216 977, by the presence of a new Oxygen plasticizer, which provides the amount of oxygen necessary for good combustion, thus avoiding the production of CO (whose concentration must be limited according to the standards in force, for the type of application).
• This result was not acquired in advance.
• the compounds of the invention generally have the disadvantage of emitting hydrogen chloride. At the end of combustion, said hydrogen chloride condenses with the water formed by the combustion and can be captured by the bag.
• the level of hydrogen chloride emitted by the compounds according to the invention is approximately 0.2 g / g.
• the bag can be coated with chlorine sensors.
• the pyrotechnic gas-generating compounds of the invention are therefore characterized in that their composition does not contain a chlorine sensor (complementary oxidant) but at least one specific oxygenated plasticizer (which compensates for the absence of said complementary oxidant).
• Said at least one specific oxygenated plasticizer is advantageously chosen from the family of oxygenated diesters, more specifically diesters with ether functions.
• Said at least one oxygenated plasticizer is very advantageously chosen from: dibutoxyethoxyethyl adipate (DBEEA),
• DOE dioctyladipate
• the oxidizing charge comprises at least one inorganic perchlorate. It generally represents from 64 to 94% by weight of the total mass of the compound, advantageously from 72 to 82% by weight of said total mass. It is the main constituent of the compounds of the invention.
• Said oxidizing charge advantageously comprises potassium perchlorate and / or ammonium perchlorate.
• Said oxidizing charge very advantageously comprises ammonium perchlorate. Preferably, it consists of ammonium perchlorate.
• Said ammonium perchlorate is advantageously used in several granulometries so as to improve the incorporation and distribution in the polymer and to reduce the toxicity of the gaseous effluents during combustion.
• the crosslinked oxygenated hydrocarbon binder generally represents from 6 to 20% by weight of the total mass of the compound. It advantageously represents from 8 to 16% by weight of the total mass. It comprises the crosslinked elastomer and said at least one original oxygenated plasticizer of the invention.
• the elastomer in question is a high molecular weight elastomer: Mw> 200,000 g / mol. It is preferentially chosen in the family of polyesters and polyacrylates.
• the polyacrylates may have reactive terminations of the chlorine / carboxyl, chlorine, hydroxyl or epoxy type.
• the polyesters may have hydroxyl-type reactive terminations. They advantageously have such hydroxyl-type reactive terminations.
• a crosslinking agent advantageously consists of a diisocyanate or triisocyanate.
• said at least one elastomer and said at least one crosslinking agent represent from 3 to 10% by weight, advantageously from 4 to 8% by weight, of the total mass of the compounds of the invention; and / or, advantageously and, said at least one plasticizer represents from 3 to 10% by weight, advantageously from 4 to 8% by weight, of the total mass of said compounds.
• the compounds of the invention may comprise, in their composition, the additional constituents:
• At least one nitrated organic compound whose oxygen balance is greater than -30% (which allows in particular to increase the gas yield).
• Such at least one compound is advantageously chosen from nitrogen nitrates and dinitramides. It consists very advantageously of guanidine nitrate (NG) or guanyl urea dinitramide (GUDN).
• NG guanidine nitrate
• GUIDN guanyl urea dinitramide
• at least one compound is between 0 (1) and 10%, advantageously between 3 and 8%, by weight within the compounds of the invention; at least one ballistic catalyst (which makes it possible, among other things, to improve the rate of combustion).
• a ballistic catalyst consists of a transition metal oxide with a high specific surface area (which accelerates the decomposition of the oxidizing charge).
• Such at least one ballistic catalyst is advantageously selected from copper oxide, iron oxide, manganese oxide and cobalt oxide. Generally, such at least one ballistic catalyst intervenes between 0 (0.1) and 6%, advantageously between 0 (0.1) and 2%, very advantageously between 1 and 2%, by weight within the compounds of the invention;
• At least one wetting agent chosen from organosiloxanes and titanates.
• Such at least one wetting agent is advantageously chosen from vinyltris- (2-methoxyethoxy) silane / tris- (3-trimethoxysilylpropyl) isocyanurate, ⁇ -glycidoxypropyltrimethoxysilane, diethoxydiacetoxysilane, diacetoxydiethoxysilane and dibutoxyethoxymethylsilane.
• Such at least one wetting agent makes it possible to reduce the viscoelasticity and the residual porosity of the compound.
• such at least one wetting agent intervenes between 0 (0.1) and 4%, advantageously between 0.2 and 3%, by weight within the compounds of the invention.
• the constituents (oxidizing charge + crosslinked oxygenated hydrocarbon binding agent + optional constituents chosen from those identified above) of the composition of the compounds of the invention, listed above, represent at least 95% by weight of said compounds, generally at least 98 % by weight of said compounds.
• the complement, if any, is generally composed of additives, such as auxiliaries (aids) manufacturing.
• the compounds of the invention can be of different types. These are monolithic compounds that can be full, mono- or multiperforated. These compounds typically contain, in their composition, an original oxygenated plasticizer as described above.
• Said compounds are particularly effective.
• Their composition is high gaseous (about 36 mol / kg) with combustion temperatures around 3000 K (it is indeed so-called hot compositions).
• Their burning rate is fast, about 45 mm / s at a pressure of 20 MPa. Because of their composition, they generate very few solid particles ( ⁇ 2%).
• Their composition is also likely, according to advantageous variants, to have an oxygen balance value of between -2% and -3%, ie that they generate only a very small amount of toxic gas and that they are quite suitable for an application in the field of airbags.
• the inflating surface flow rates of the compositions of the compounds of the invention are very interesting. They are about 830 mol.K / cm 2 .s.
• the process for obtaining the compounds of the invention is advantageously a process by analogy, as described in patent application EP 1 216 077. It is very advantageously a process carried out continuously, without a solvent, in a twin-screw mixer-extruder.
• said method comprises:
• said at least one plasticizer consists of or comprises an original plasticizer of the invention.
• said mixing and extrusion are advantageously carried out in a twin screw mixer-extruder.
• crosslinked loadings compounds of the invention.
• the twin screw extruder includes a mixing and mixing chamber, a compression chamber and an extrusion head.
• the solid and liquid constituents are introduced into the mixing and kneading compartment by two different feed openings, a solids supply opening and a liquid feed opening, and then transported and kneaded, followed by the homogeneous paste thus formed. is degassed in the compression compartment, then extruded with the aid of an extrusion head in the form of rods, and finally the rods thus formed are cut into loads using a cutting apparatus, and then these loads are crosslinked at a temperature generally between 100 0 C and 15O 0 C.
• the charges thus formed find their preferential application as a pyrotechnic charge in gas generators intended to inflate a protective cushion for occupants of a motor vehicle. Indeed, the burning rate of these loads, as well as the rate of solid residues produced and the rate of carbon monoxide and nitrogen oxides produced are particularly suitable (see above).
• compositions of pyrotechnic compounds have been evaluated by means of thermodynamic calculations and physical measurements.
• Composition A so-called cold, of the prior art
• composition without binder, contains: - 49% by weight of guanidine nitrate,
• pellets were prepared.
• composition with binder, contains:
• acrylic elastomer - 15% by weight of acrylic elastomer, crosslinking agent and plasticizer.
• composition is a composition according to patent application EP 1 216 077. It is extruded and crosslinked to generate compounds.
• Composition 1 of a compound of the invention It contains:
• the oxygen balance of this composition is -2.3%. Its theoretical density is 1.73 g / cm 3 .
• Its combustion temperature is about 3000 K at 20 MPa and its molar yield is 36.1 mol / kg.
• the particle content is less than 2%.
• the burning rate of the compounds (extruded) is between 40 and 50 mm / s at 20 MPa (see table below).
• Composition 2 of a compound of the invention It contains: - 79.9% by mass of ammonium perchlorate,
• DBEEA plasticizer
• vinyitris- (2-methoxyethoxy) silane 1.6% by weight of DBEEA (plasticizer), 1.6% by weight of vinyitris- (2-methoxyethoxy) silane,
• the oxygen balance of this composition is -2.4%. Its theoretical density is 1.72 g / cm 3 . Its combustion temperature is about 3000 K to 20 MPa and its molar yield is 36 mol / kg.
• the particle content is less than 2%.
• the burning rate of the compounds (extruded) is between 40 and 50 mm / s at 20 MPa (see table below).
• compositions A, B, 1 and 2 and those of the corresponding compounds are given in Table 1 below.
• the much higher burning rate of the compounds of the invention gives a surface flow rate of inflation greater than that of the reference compounds.
• the characteristic dimension of the object to be burned may be doubled to ensure an operating period "equivalent.
• the extruded block made from the compositions of the invention may therefore be very compact and allow the development
• the gas generators employing the compounds of the invention may be to some extent free of particulate filters. , the thermal losses of the gases are reduced.
• the compounds of the invention generally have the disadvantage of emitting hydrogen chloride.
• said hydrogen chloride condenses with the water formed by the combustion and can be captured by the bag.
• the level of hydrogen chloride emitted by the compounds of the invention is about 0.2 g / g.
• the bag can be coated with chlorine sensors.
• the vents can be reduced to increase the capture rate by condensation of acidified water in the atmosphere. bag. After operation, the bag naturally deflates under the effect of the drop in temperature and condensation of condensables.
• a conductive airbag (side) gas generator containing a compound according to the invention (14 g) emits 2.8 g of hydrogen chloride.
• the hydrogen chloride level is of the order of 700 ppm in a cabin of 2.8 m 3 .

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

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• 2007
  • 2007-05-02 FR FR0754809A patent/FR2915746B1/fr not_active Expired - Fee Related
• 2008
  • 2008-04-30 US US12/598,323 patent/US20110041969A1/en not_active Abandoned
  • 2008-04-30 AT AT08805727T patent/ATE527227T1/de not_active IP Right Cessation
  • 2008-04-30 WO PCT/FR2008/050773 patent/WO2008145935A2/fr not_active Ceased
  • 2008-04-30 CN CN2008800193613A patent/CN101679139B/zh not_active Expired - Fee Related
  • 2008-04-30 EP EP08805727A patent/EP2139828B1/de not_active Not-in-force
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