MXPA01003695A - Foamed energetic igniters and air bag assemblies containing the same - Google Patents

Abstract

An air bag igniter including a foamed material, and an air bag assembly containing the same are disclosed. The foamed material is formed from a composition including, as ingredients, a polyfunctional isocyanate, a polymeric binder having a plurality of hydroxyl groups which are reactive with the polyfunctional isocyanate, a fuel source, an oxidizer, and a foaming agent which may or may not be retained in the foamed material.

Description

CELL ENERGY LIGHTS AND AIR BAG ASSEMBLIES CONTAINING THE SAME BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to lighters suitable for use in airbag applications, and to airbag assemblies equipped with ignition devices. More particularly, this invention relates to lighters of air pockets comprising a cellular lighter material. 2. Description of Related Art An important use for specifically formulated gas generating compositions is in the operation of inflatable safety fastening systems, commonly referred to as air bag assemblies. Airbag assemblies are gaining industrial and commercial acceptance to the point where many, if not most, new automobiles are equipped with such devices. Actually, many new vehicles are Ref.128420 equipped with multiple airbags to protect the driver and passengers, and contain multiple airbags for the protection of each occupant. During the actuation of a supplementary (or secondary) restraint or braking system during the impact of the vehicle in an accident or the like, a sufficient quantity of gas must be generated to fully inflate the airbag of the supplementary restraint system before the driver could otherwise be propelled against the steering wheel or dashboard. In general, the air bag should be inflated within the course of a fraction of a second. As a result, almost instantaneous gas generation is required. Typically, the generation of the amount of gas needed to inflate the airbag is achieved through sequential ignition of the specifically formulated compositions. This chain only starts with a detonator comprising two electrical terminals spaced apart and a conductive material still of high resistance connecting the terminals. During the application of a predetermined amount of electric power to the electrical terminals, the detonator generates a sufficient amount of heat to ignite a lighter material placed in an operative relationship with the detonator. The lit igniter material in turn ignites a gas-generating material, often in the form of microspheres, present in sufficient quantities to generate the gas to completely inflate the airbag, or deploy the inflation gas as in a so-called system hybrid. The appropriate gas generating materials and the airbag constructions are well known to those skilled in the art. For example, it is already known to use sodium azide gas generators although others are also known and are contemplated within the scope of the invention. scope of this invention. The granules of boron and potassium nitrate (BKN03) have been conventionally used as the lighter material. However, one disadvantage of the granules of BKN03 is that they tend to become friable or brittle when subjected to a continuous application of loads or pressures for prolonged periods of time. Deterioration of the granules increases the burn rate of BKN03, and can lead to overpressurization during ignition, which adversely affects performance.

Therefore, it could be a significant advance in the art to provide a lighter material that is relatively insensitive to high impact loads.

- "• - *" "- - BRIEF DESCRIPTION OF THE INVENTION Therefore, it is an object of this invention to provide a glowing composition that addresses a need long recognized in the art, which overcomes the aforementioned disadvantages associated with conventional lighter materials. In accordance with the principles of this invention, these and other objects are achieved with the lighter of the airbag of the invention, which comprises a cellular or alveolar material. According to a first embodiment of the invention, the alveolar or cellular material is formulated from a composition comprising, as ingredients, at least one polyfunctional isocyanate, at least one non-energetic curable binder having a plurality of functional groups which are reactive with the polyfunctional isocyanate, at least one fuel source, at least one oxidant, and at least one foaming agent which imparts porosity to the alveolar or cellular material and may or may not be retained in the cellular or alveolar material. According to a second embodiment of this invention, the cellular or cellular material is formulated from a composition comprising, as the ingredients, at least one polyfunctional isocyanate, one or more energetically curable binders having a plurality of functional groups which are reactive with the polyfunctional isocyanate, one or more fuel sources other than the energy curable binder (s), at least one oxidant, and at least one foaming agent which imparts porosity to the cellular or alveolar material and may or may not be retained in the alveolar or cellular material. According to a third embodiment of this invention, the alveolar or cellular material is formulated from a composition similar to that of the second embodiment, with the exception that it is free of any fuels other than the energy polymeric binder. It is also an object of this invention to provide an air bag assembly that can be fired with high confidence and a consistent predictability. In accordance with the principles of this invention, these and other objects of this invention are achieved by the provision of an air bag assembly comprising a gas generator (e.g., generating microspheres) and at least one of the igniter devices of the Air bag described above in cooperative association with the gas generator to allow the ignition of the gas generator with high reliability. This invention also relates to vehicles, such as automobiles, sports utility vehicles, and trailers, which comprise the assembly of the airbag positioned either (a) in a frontal position to protect the occupants of the vehicle. of the collision against the instrument panel or (b) in a lateral position to protect the occupants of the vehicle from impact against the door panel and / or the roof of the compartment. These and other objects, features, and advantages of the present invention will become apparent from the appended drawings and the following detailed description which illustrates and explains, by way of example, the principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate the embodiments of this invention. In such drawings: Figure 1 is a simplified schematic sectional view of an assembly of the air bag in accordance with this invention; and Figure 2 is a trace of the ignition pressure of the engine at low temperature (-45 ° C) for an assembly including a foam igniter device with a GAP binder.

DETAILED DESCRIPTION OF THE MODALITIES OF THE INVENTION Referring now more particularly to the drawings, there is shown in Figure 1 an air bag assembly 10 comprising a housing 12 containing a plurality of gas generating microspheres 14. Located concentrically within the chamber accommodating the generating microspheres of the gas 14 is a detonator 16 having electrical conductor wires 18. The detonator 16 is surrounded by a cellular or alveolar lighter 20. In operation, an electric charge sent to the detonator ignites the ignition device 20, which sends the hot gas through the openings 22 located in the housing 12. The hot gas serves to activate the gas generating microspheres 14, which generate the gas needed to inflate a folded air bag (not shown). The gas generating microspheres 14 can be made of several known and novel materials suitable for inflating an air pocket. The representative gas generating materials 14 that can be used with the ignition device of this invention include, by way of example, the sodium azide gas generating compositions and the sodium azide free compositions, including the following: comprise oxidizable borohydride fuels as described in US Pat. No. 5,401,340; compositions comprising basic metal carbonates and / or basic metal nitrates as described in U.S. Pat. do not. 5,429,691 and U.S. Pat. No. 5,439,537; gas generating compositions containing non-metallic salts of 5-nitrobarbituric acid, as described in U.S. Pat. No. 5,472,534; the compositions generating the anhydrous tetrazole gas as described in U.S. Pat. No. 5,472,647, U.S. Pat. No. 5,500,059, U.S. Pat. No. 5,501,823, and U.S. Pat. No. 5,516,377; and compositions comprising metal complexes as described in U.S. Pat. No. 5,592,812 and in U.S. Pat. No. 5,725,699. These gas generating materials are processable, and can be compressed in a microsphere or other usable form. Based on the reading of this description, the extent to which the compositions of these U.S. Pat. are compatible for use with the ignition device of the invention should be evident to those skilled in the art. With the exception of the lighter material and the placement of the lighter device of this invention, the air bag assembly may be of a conventional design. Therefore, conventional portions of the assembly do not need and will not be described in further detail here. The lighter material can also be used for a supplementary restraint system for impacts on the head and / or for side impacts. A general description of the structure and operation of such a supplemental restraint system is described in U.S. Pat. No. 5,441,303 and U.S. Pat. No. 5,480,181. These referred fastening systems are mentioned by way of example only to show the construction and general operation of the known systems. This invention is not limited to such systems. Based on reading this description, the extent to which these referenced systems are compatible with the foam lighter device of this invention should be apparent to those skilled in the art. The lighter device of the invention is easily adaptable for use with the technology of the airbag inflator, hybrid, conventional. The technology of the hybrid inflator is based on heating a stored inert gas (argon or helium) to a desired temperature by burning a small amount of the propellant. Hybrid inflators do not require the cooling filters used with pyrotechnic inflators to cool the combustion gases, because the hybrid inflators are capable of providing a lower temperature gas. The discharge temperature of the gas can be changed selectively by adjusting the ratio of the weight of the inert gas to the weight of the propellant. The higher the ratio of the weight of the gas to the weight of the propellant, the colder the discharge temperature of the gas will be. A hybrid gas generation system comprises a pressure tank that has a breakable opening; a predetermined quantity of the inert gas placed inside this pressure tank; a gas generating device for producing hot combustion gases and having means for breaking the breakable opening; and means for igniting the gas generating composition. The tank has a breakable opening which can be broken by a piston when the gas generating device is turned on. The gas generating device is configured and positioned in relation to the pressure tank so that the hot combustion gases are mixed with and heat the inert gas. Suitable inert gases include, among others, argon and helium and mixtures thereof. The hot and mixed gases leave the pressure tank through the opening and finally exit the hybrid inflator and deploy the airbag.

The devices for the generation of a hybrid gas for supplementary safety fastening applications are described in Frantom, Hybrid Airbag Inflator Technology, Airbag Int'l Symposium on Sophisticated Occupant Safety Systems (Weinbrenner-Saal, Germany, November 2-3, 1992) . The cellular or alveolar material of this invention is formulated from a composition comprising, as the ingredients, (a) a polymeric matrix formed of at least one polyfunctional isocyanate and at least one curable binder having a plurality of hydroxyl groups which they are reactive with the polyfunctional isocyanate and (b) a foaming agent (or blowing agent) capable of imparting a relatively high porosity to the cellular or cellular material. The polyfunctional isocyanate may be an aliphatic, aliphatic, or aromatic cyclic compound. Preferably, a cyclic aliphatic polyfunctional isocyanate, and more preferably a polyfunctional aromatic isocyanate is selected. Suitable aliphatic polyisocyanates include the hexamethylene diisocyanates and the isophorone triisocyanate. An exemplary cyclic aliphatic polyfunctional isocyanate is isophorone diisocyanate. Exemplary aromatic polyfunctional isocyanates are a mixture of diphenyl methyl diisocyanate, methylene bisphenyl isocyanate, and polymethylene polyphenyl isocyanate (also known as "PAPI"); toluene diisocyanate ("TDI"); and methylenebis (phenyl isocyanate) ("MDI"). The material of the alveolar ignition device or Cell # 5 of this invention is characterized by a relatively high porosity. The porous nature of the alveolar lighter becomes more tolerant to the impacts of large shocks. The high porosity of the lighter material of the invention is achieved by introducing one or more agents for the formation of foam in the polymeric matrix before and / or during the curing process. When referenced herein, foaming agents may include gas that originates from an internal source and / or an external source. More specifically, gases can be introduced Externally, such as, for example, introducing one or more gases (preferably inert with respect to the alveolar or cellular igniter composition) into the polymeric curing or precured matrix in a suitable container or device. The gases produced internally include those gases generated in situ by the reaction between the polyisocyanate and a foaming agent, such as water. This reaction occurs simultaneously with and competes with the curing of the polymer matrix. At first, it is possible to select a blowing agent appropriate chemical that breaks down the generation of gases - ^ - - »" «* tfe *» •? »^. in situ to generate the gases for the foam formation of the igniter composition. The external source can be, for example, nitrogen. The foaming agent is introduced into the composition to reduce the density of the cured polymer matrix. The reduction in density can be selected for the specific fastening system. In the beginning, the resulting density can be from about 34% to about 76% of the theoretical maximum calculated density of the cured polymer matrix. In other words, the volumetric growth of the porous polymer matrix is from about 1.3 times (corresponding to 76%) to about 3 times (corresponding to 34%) relative to the theoretical maximum calculated density. The maximum theoretical density can be calculated by techniques well known to those skilled in the art, obtaining the known densities of the ingredients and measuring the concentrations of the ingredients. The actual measured density can also be determined by techniques well known to those of ordinary experience in the art. By way of example, the actual measured density can be determined by the foaming of the material in a container of known weight and volume, and measuring the weight of the container and the portion of foam within the container, i.e. removing the portion of foam that expands beyond the limits or boundaries of the container. The mechanical and burn properties of the cellular or alveolar lighter material of this invention can be adapted to match the requirements of its proposed application by selecting the ingredients of the appropriate polymer matrix, including the additional ingredients, and controlling the amount and type of the Foaming agent. According to a first embodiment of the invention, the polymer matrix is non-energetic. In this first embodiment, the curable binder having a plurality of hydroxyl groups which are reactive with the polyfunctional isocyanate may be one or more polyols. Exemplary polyols include, by way of example and without limitation, the hydroxy-terminated polyenes that include the hydroxy-terminated polybutadiene ("HTPB"); polycaprolactone ("PCP"); poly (alkylene glycols), including poly (ethylene glycol) ("PEG'7), poly (propylene glycol) (" PPG "), and poly (glycol adipate) (" PGA "). In the second and third embodiments of the invention, the polymer matrix is energetic.These modalities are especially desirable in applications in which high energy operation and large amounts of gas combustion are desired.Example polyols include, by way of example and without limitation, the polymers of glycidyl azide "GAP" or poly (glycidyl azide)) and poly (glycidyl nitrate) ("PGN"). Binders of a high burn rate such as GAP provide improved performance, which may be highly desirable for some applications The production of GAP and PGN is known to those skilled in the art, as shown in US Patent No. 5,264,596 and US Patent No. 5,801,325, the full descriptions of which are incorporated give here for reference. Fuel sources suitable for use with the first and second embodiments include, by way of example and without limitation, metals such as aluminum, boron, magnesium, silicon, titanium, zirconium, and such alloys. like the magnesium / aluminum alloys. The fuel is preferably in the form of a powder, particle and / or microspheres with a high surface area. Preferably, the fuel is dispersed homogeneously within the polymer matrix. The composition also usually includes one or more oxidants. Suitable oxidants include perchlorates, such as potassium perchlorate and ammonium perchlorate, and nitrates, such as potassium nitrate, sodium nitrate, and ammonium nitrate.

The composition may further include one or more surfactants, including silicone-based surfactants such as DOW 193. The curing catalysts may be any .5 of those known in the art, including dialkyl tin carboxylates, including dibutyl tin dilaurate and dibutyl tin diacetate, and the bismuth and aryl compounds including triphenyl bismuth. Where excess gas generation is desired, The cellular or alveolar lighter material can be immersed in the gas generators, such as the generating microspheres, such as UIX-171 of Cordant Technologies Inc., previously known as Tio ol Corporation. The ignition material is preferably made by means of a solvent-free process.

EXAMPLES The alveolar or cellular lighters in the following 20 examples were prepared substantially in the same manner. The PAPI curing agent was weighed in the specified amount and placed in a mixing vessel containing the pre-weighted polymer binder. Next, the surfactant was added to the mixing vessel. A metal spatula was used • ~ - - - '? ÜeJ. * To manually stir the materials contained in the container at room temperature until they become homogeneous. Then water was added in the specified amount with an eye drop applicator and mixed with the spatula. The oxidant, the fuel, and / or the gas that generates the microspheres were then added in the amounts specified in the Tables below. Finally, the dibutyltin dilaurate as a curing catalyst was added to catalyze the exothermic reaction between the polyol and the polyisocyanate and between the water and the polyisocyanate. The resulting mixture was characterized by a high viscosity, but was still sprayable to allow it to be placed inside the housing of the air bag assembly. The mixture is preferably applied at the start in the foam formation process, which proceeds substantially to its complement in 1/2 hour.

TABLE 1 (Example 1) TABLE 2 (Example 2) TABLE 3 (Example 3) TABLE 4 (Example 4) TABLE 5 (Example 5) TABLE 6 (Example 6) A stroke of the pressure-time for Example 3 is shown in Figure 2. This trace shows the characteristics of a small amount of the cellular or alveolar lighter, for example, 5.83 grams, which successfully ignited a Test assembly that has a load of 0.454 kg (1 pound) of a propellant with a small smoke generation. In particular, the low pressure plateau means that a uniform distribution of the front of the high intensity wave is being supplied to the propellant before the accumulation of the pressure in the combustion chamber. A benefit of the pressure trace is the relatively low speed of the pressure change within the housing when the pressure increases. This feature is advantageous for applications in which the gas generating microspheres to be ignited are known to have dp / dt characteristics where combustion is extinguished after rapid changes in chamber pressure. The more gradual the change in pressure at the beginning of the increase in pressure, the less likely it is that the microspheres generating the gas will be extinguished after the lighter material has been consumed. The preceding detailed description of the preferred embodiments of the invention has been provided for the purpose of explaining the principles of the invention and their practical application, whereby it is possible for other persons skilled in the art to understand the invention for various modalities and with several modifications such as those that are suitable for the particular use contemplated. The foregoing detailed description is not intended to be exhaustive or to limit the invention to the precise embodiments described. The modifications and equivalents will be apparent to practitioners skilled in the art and are encompassed by the appended claims.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims (22)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A lighter for an airbag, characterized in that it comprises a cellular or cellular material formulated from a composition, characterized in that it comprises, as the ingredients : at least one polyfunctional isocyanate; at least one curable or non-energetic hardening binder having a plurality of functional groups which are reactive with the polyfunctional isocyanate; at least one fuel source; at least one oxidant; and at least one foaming agent for imparting porosity to the cellular or cellular material and is optionally retained in the cellular or alveolar material of the air bag lighter.
2. 2. The lighter for the air bag according to claim 1, characterized in that the binder comprises a polyol.
3. 3. The lighter for the air bag according to claim 2, characterized in that the polyol comprises the hydroxy-terminated polybutadiene.
4. 4. The lighter for the air bag according to claim 1, characterized in that the polyfunctional isocyanate comprises a mixture of diphenyl methyl diisocyanate, methylene bisphenyl isocyanate, and polymethylene polyphenyl isocyanate.
5. 5. The lighter for the air bag according to claim 1, characterized in that it also comprises at least one surfactant and at least one curing catalyst.
6. 6. The lighter for the air bag according to claim 5, characterized in that the curing catalyst comprises the dibutyl tin dilaurate.
7. 7. An air bag assembly, characterized in that it comprises a gas generator, solid, and the lighter for the air bag according to claim 1, characterized in that the lighter for the air bag is placed in operative relation with the air bag. gas generator, solid, so that, during ignition of the lighter for the airbag, the lighter for the airbag activates the gas generator, solid.
8. 8. A vehicle, characterized in that it comprises the assembly for the air bag according to claim 7.
9. 9. A lighter for the air bag, characterized in that it comprises a cellular or cellular material formulated from a composition comprising, as the ingredients: at least one polyfunctional isocyanate; at least one hardenable energy binder having a plurality of functional groups which are reactive with the polyfunctional isocyanate; at least one fuel source different from the energy binder; at least one oxidant; and at least one foaming agent for imparting porosity to the cellular or cellular material and is optionally in the cellular or alveolar material of the lighter for the air bag.
10. 10. The lighter for the air bag according to claim 9, characterized in that the energy binder comprises a polyol.
11. 11. The lighter for the air bag according to claim 10, characterized in that the polyol comprises a hydroxy-terminated glycidyl azide polymer.
12. 12. The lighter for the air bag according to claim 9, characterized in that the polyfunctional isocyanate comprises a mixture of diphenyl methyl diisocyanate, methylene bisphenyl isocyanate, and polymethylene polyphenyl isocyanate.
13. 13. The lighter for the air bag according to claim 9, characterized in that it further comprises at least one surfactant.
14. 14. An air bag assembly comprising a gas generator, solid, and the lighter of the air bag of claim 9, characterized in that the lighter of the air bag is positioned in operative relation with the gas generator. solid so that, during ignition of the lighter of the airbag, the lighter of the airbag activates the solid, gas generator.
15. 15. A vehicle, characterized in that it comprises the assembly of the air bag of claim 14.
16. 16. A lighter for an air bag comprising an alveolar or cellular material formulated from a composition comprising, as the ingredients: minus a polyfunctional isocyanate; At least one energy curable binder having a plurality of hydroxyl groups which are reactive with the polyfunctional isocyanate; at least one oxidant; and at least one foaming agent for imparting porosity to the cellular or alveolar material and is * ^ * ajMÍ * ^^ '^' - 1, - ^?., ~ * ut "optionally retained in cellular or alveolar material, characterized in that the composition is free of any fuel sources other than the energy binder.
17. 17. The lighter for the air bag according to claim 16, characterized in that the energy binder comprises a polyol.
18. 18. The lighter for the air bag according to claim 17, characterized in that the polyol comprises a hydroxy-terminated glycidyl azide polymer.
19. 19. The lighter for the air bag according to claim 16, characterized in that the polyfunctional isocyanate comprises a mixture of diphenyl methyl diisocyanate, methylene bisphenyl isocyanate, and polymethylene polyphenyl isocyanate.
20. 20. The lighter for the air bag according to claim 16, characterized in that it also comprises at least one surfactant.
21. 21. An airbag assembly comprising a gas generator, solid and the airbag lighter according to claim 16, characterized in that the lighter for the airbag is placed in an operative relation with the airbag generator. solid gas so that, during ignition of the lighter for the airbag, the lighter of the airbag activates the solid gas generator.
22. 22. A vehicle, characterized in that it comprises the assembly of the air bag of claim 21.