JP2008174441A - Gas generating system and composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the production of a gas generating system by reducing a size, weight and numbers of elements required in their production and to provide a gas generating material composition to be used. <P>SOLUTION: The gas generating system with no booster chamber is provided. An inflator contains a composition containing a metal chlorate as a first oxidizing agent, a carboxylic acid, dicarboxylic acid or their mixture as a first fuel and a second oxidizing agent not having properties of a perchlorate. The metal chlorate of about 10-20 wt.%, the first fuel of about 15-45 wt.% and the second oxidizing agent of about 30-50 wt.% based on a weight of a total composition are provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

This application claims the benefit of US Provisional Application No. 60 / 848,682, filed September 30, 2006.

BACKGROUND OF THE INVENTION The present invention relates generally to gas generant systems and gas generant compositions used in gas generators, for example, for automotive restraint systems. As is known in the art, gas generation systems can be used to supply inflation or working gas to gas-activated elements of a vehicle occupant protection system. An ongoing challenge is to simplify the production of gas generation systems by reducing the size, weight, and number of elements required in its production. For example, in many gas generators used in vehicle occupant protection systems, several individual compositions are provided to serve corresponding individual functions. These compositions often include a first gas generant composition that, when burned, has a sufficiently large amount of gas product to activate a combined restraint device such as an air bag or seat belt pretensioner. I will provide a.

  The booster composition is utilized to increase the pressure and heat in the gas generator prior to combustion of the first gas generant, thereby facilitating efficient combustion of the first gas generant. Create a condition for.

  Other compositions are autoignition compositions that are used to provide safe combustion of other compositions during combustion. The autoignition composition is designed to ignite, for example, at a temperature below the melting point of the first gas generant, thereby ensuring controlled combustion of the first gas generant. The ignition of the autoignition composition provides the flame front and pressure front necessary to safely ignite the gas generant composition present in combustible communication with the autoignition composition. As a result, the main gas generant is safely ignited prior to melting.

  However, each individual composition contributes to the efficient and effective operation of the gas generation system, but each composition further increases the weight, cost (material and assembly time) and volume of the system. For example, typically stored in separate tubes or chambers to facilitate manipulation of each composition and prevent mixing between the various compositions, booster compositions, gas generants and autoignition compositions . Separate storage chamber equipment for each composition generally increases weight, cost, and assembly time required to construct a gas generation system. Furthermore, if a relatively larger amount of combustible material is combusted during system operation, a correspondingly larger amount of effluent material and heat will be generated by the combustion of the material. Therefore, it would be advantageous to reduce the number of gas generating system components and the number of compositions used during system operation.

SUMMARY OF THE INVENTION These and other problems include a first oxidant selected from a metal chlorate such as potassium chlorate, a carboxylic or dicarboxylic acid as the first fuel, a metal or non-metal nitrate, A second oxidant selected from nitrites, oxides, basic metal nitrates and other known oxidants, and any second selected from azoles including tetrazoles, triazoles and furazanes, and salts thereof. It can be solved by a gas generating system comprising a gas generating composition comprising two fuels. Other components, including extrusion aids such as fumed silica and / or graphite, can be included in relatively small amounts.

  The present invention further includes a gas generator and vehicle occupant protection system incorporating the gas generant / booster composition. The novel gas generant formulations as described herein perform the functions of both gas generant and booster compositions. Alternatively, the gas generant blend described herein can perform the functions of a gas generant, a booster composition, and an autoignition composition. Given the multifunctional benefits of the gas generant composition, the structure defining the booster and / or autoignition material and the chamber for containing the booster and / or autoignition material can be eliminated, thereby Inflator manufacturing is simplified.

DETAILED DESCRIPTION FIG. 1 shows a cross section of a known gas generation system 10 incorporating a separate booster and gas generation chamber therein. The embodiment of the gas generation system shown in FIGS. 1, 2 and 4 shows, for example, a form of inflator that can be used to inflate elements associated with a vehicle occupant protection system. However, such a gas generation system may be used for other applications. The structure and operation of the basic system elements described herein are well known in the art. In addition, the materials and techniques used to manufacture the structural elements of gas generation systems are known in the art.

The system 10 includes an outer housing 12 and an inner housing 14 disposed within the outer housing and including a predetermined amount of gas generant 16 therein. Inner housing 14 defines a combustion chamber for the gas generant. Inner housing orifice 18 provides fluid communication between the interior and exterior of inner housing 14. A fluid flow path is provided between the gas outlet opening 20 and the orifice 18 formed in the housing 12 and at the end or other portion of the housing 12.
The booster chamber 22 is formed by a booster cup 23 and a divider 28. Chamber 22 contains booster composition 24 therein. Divider 28 separates gas generant 16 and booster composition 24 to allow fluid communication between booster chamber and combustion chamber (via opening 28a) upon activation of the gas generating system and combustion of the booster composition. To do. The term “booster chamber” as used herein is understood to refer to any structure and / or element that performs the function of separating the booster composition from the gas generant composition. Initiator 32 is provided to initiate combustion of booster composition 24 upon receipt of the activation signal in a manner known in the art. The autoignition material 30 provides or is capable of providing fluid communication with the booster composition 24 upon exposure of the system to an external temperature high enough to cause ignition of the autoignition material (eg, as generated by a flame). Arranged to be.

  FIG. 2 shows a cross-sectional side view showing the general structure of a gas generation system 100 according to the present invention. Elements common to the systems shown in FIGS. 1, 2 and 4 have been given similar element numbers for simplicity and clarity. Comparing FIGS. 1 and 2, the individual booster composition 24 and booster chamber 22 shown in FIG. 1 have been removed in the system shown in FIG. This is achieved through the use of the gas generant composition 116 according to one of the embodiments described herein. Such a composition performs the function of both a gas generant and a booster composition, or the function of a gas generant, a booster and an autoignition composition, thereby requiring a separate composition and individual Eliminate structures required to separate and support the composition (eg, booster cups and dividers). This can reduce the system weight and shorten the length of the system envelope. When gas generants that function only as gas generants and booster compositions are formulated, as described above, a separate autoignition composition is used to ensure a safe operation of the system in the event of ignition. May still be provided at a suitable location within.

  In one embodiment, the gas generant composition according to the present invention comprises about 10-60% by weight of alkali metal, alkaline earth metal and transition metal chlorates, such as potassium chlorate, and mixtures thereof A first fuel selected from a carboxylic acid and a dicarboxylic acid, such as DL-tartaric acid; about 30-50% by weight, metal and non- A second oxidant selected from metal nitrates, nitrites, oxides and other known oxidants; and about 0-30% by weight selected from tetrazoles, triazoles, furazanes and their salts Contains a second fuel. The above weight percentages were calculated based on the total composition weight. Extrusion aids or processing additives such as graphite or fumed silica can be added in relatively small amounts, such as 0.1-2% by weight, based on the weight of the total composition.

  In another embodiment, the gas generant composition according to the present invention comprises a metal chlorate salt such as potassium chlorate; DL-tartaric acid, L-tartaric acid, D-tartaric acid, succinic acid, glutamic acid, adipic acid, mucoic acid, A first selected from carboxylic acids and dicarboxylic acids, including fumaric acid, oxalic acid, galactaric acid, citric acid, glycolic acid, L-malic acid, and compounds having at least one —COOH group, and mixtures thereof A second fuel selected from azoles, including tetrazoles, triazoles, furazanes, salts thereof and mixtures thereof; free of metallic and non-metallic nitrates and other perchlorates A second oxidizing agent selected from known oxidizing agents. However, it will be appreciated that all compositions with the multi-functional advantages of gas generants, boosters and (optionally) autoignition are contemplated.

  The carboxylic acid or dicarboxylic acid will preferably have primary hydrogen or a PKA of 3 or less. Nevertheless, it has been found that for certain fuels / salts, the pKa of the basic acid may be in the range of 5.0 or less.

  In certain embodiments, the sum of the fuel components including the carboxylic acid fuel and the second fuel is provided at about 20-45% by weight based on the weight of the total composition; the oxidant component is the total composition. The potassium chlorate or metal chlorate is provided at about 10-60% by weight based on the weight of the total composition. Here, the weight percentage of chlorate is calculated separately from the oxidizing agent. Compositions can be formed by mixing the components in granular form by dry or wet mixing in a known manner and then pelletizing or otherwise shaping the composition into a form suitable for further use. Ingredients can be provided by Fisher Chemical, Aldrich Chemical, GFS and other known suppliers. Embodiments of the invention are illustrated by the following examples:

Comparative Example 1
A known gas generant composition was prepared by intimately mixing 26.875 wt.% D-glucose of the dried granules with about 73.125 wt.% Potassium chlorate. % By weight was based on the weight of the total composition. The composition ignited at about 144 ° C. as determined by DSC analysis. The propellant formed from the components resulted in a gas yield of approximately 55.5%. In the Bruceton test, the impact sensitivity of this formulation had an HD50 of 2.0 inches.

Example 2
Exemplary formulations have been provided that act as booster compositions, autoignition compositions and gas generant compositions. The formulation comprises about 19.0% by weight 5-aminotetrazole, about 20.0% by weight DL-tartaric acid, about 35.0% by weight strontium nitrate and about 26.0% by weight potassium chlorate. . The ingredients were previously ground separately to a relatively small size by known methods. They were then dry mixed to form a substantially homogeneous composition. The composition autoignited at about 140 ° C. as determined by DSC analysis. The propellant formed from the components resulted in a gas yield of approximately 67%. In the Bluestone test, this formulation had an impact sensitivity of 11.5 inches HD50. After aging the composition at 107 ° C. for about 480 hours, the composition still ignited at about 145.1 ° C. as determined by DSC analysis.

Example 3
Exemplary formulations have been provided that act as booster compositions, autoignition compositions and gas generant compositions. The formulation comprises about 19.0% by weight 5-aminotetrazole, about 19.0% by weight DL-tartaric acid, about 50.0% by weight strontium nitrate and about 12.0% by weight potassium chlorate. . The ingredients were ground and dry mixed to form a substantially homogeneous composition. The composition autoignited at about 141 ° C. as determined by DSC analysis. The propellant formed from the components resulted in a gas yield of approximately 68.2%. In the Bluestone test, the impact sensitivity of this formulation had an HD50 of 8.8 inches. As shown in FIG. 3, the composition reflected a relatively good burn rate over several pressure ranges, in particular a burn rate of 0.8 inches per second (ips) and higher. Refer to FIG. 3 again. The composition is about 0.2 ips at about 200 psig, about 0.35 ips at about 550 psig, about 0.5 ips at about 1000 psig, about 0.55 ips at about 1500 psig, about 0.85 ips at about 2000 psig, about 0.005 at about 2500 psig. The combustion rate was about 0.85 ips at 9 ips, about 3000 psig, and about 1.2 ips at about 3900 psig. Thus, the compositions of the present invention exhibit satisfactory burning rates (typically greater than 0.4 ips at about 2500-3000 psig), thereby ensuring satisfactory function as the first gas generant. Indicated. The composition was aged at 107 ° C. for about 480 hours and still autoignited at about 174.7 ° C. as determined by DSC analysis.

Example 4
Exemplary formulations have been provided that act as booster compositions, autoignition compositions and gas generant compositions. The formulation includes about 28.0 wt% DL-tartaric acid, about 32.0 wt% strontium nitrate and about 30.0 wt% potassium chlorate, and 10% a second fuel. The ingredients were previously ground separately to a relatively small size by known methods. They were then dry mixed to form a substantially homogeneous composition. The composition autoignited at about 153 ° C. as determined by DSC analysis. The propellant formed from this component resulted in a gas yield of approximately 66.1%. In the Bluestone test, the impact sensitivity of this formulation was 8.1 inches HD50.

As demonstrated in Examples 1-4, the composition formed in accordance with the present invention (Example 2-4) preferably auto-ignites below about 180 ° C. and also provides a booster function. The composition of the present invention produces a greater amount of gas and exhibits a sufficient burning rate, thereby producing a sufficient amount of gas when activated. Compositions using a second oxidant such as strontium nitrate provide a relatively increased gas volume and improved sensitivity. The result of the bluestone sensitivity test with H50 = 3.9 or higher is U.S. Pat. S. D. O. Relieve packaging requirements with T rules. Thus, a composition having a sensitivity test result of 3.9 or greater provides substantial packaging advantages.
The use of a mixture of a second fuel, such as 5-aminotetrazole, with a carboxylic acid or dicarboxylic acid, a second oxidant, and potassium chlorate can produce large amounts of gas, acceptable autoignition temperature and booster function. To express. Thus, the composition thus formed is provided to replace one of three separate booster compositions, autoignition compositions, and gas generant compositions that are typically used in gas generators. Can be done.

Example 5-16
As shown in Table 1 below, the various acids shown show acceptable autoignition temperatures in various applications when converted to salts and mixed with stoichiometric amounts of potassium chlorate. . In some cases, the autoignition temperature exceeds 180 ° C., but is still useful in selected applications such as hybrid inflators and seat belt pretensioners. It will be appreciated that these examples reflect the autoignition properties provided by the resulting salts and potassium chlorate. As further shown, acids exhibiting a pKa of about 3.05 or less generally provide an autoignition temperature of less than 170-180 ° C. However, for example, if an autoignition temperature on the order of 250 ° C. is acceptable, an acid exhibiting a pKa of about 5.0 or less may still be acceptable. Certain acids, such as citric acid and malonic acid, may not fulfill the autoignition function when stoichiometrically combined with potassium chlorate. However, when combined with at least one second oxidant, it functions as a booster oxidant and a first gas generant. The use of a desiccant as described in co-pending US patent application Ser. No. 11 / 479,493, referenced and incorporated as part of this specification, may cause gasses under certain circumstances. Maintaining optimal environmental conditions within the generator, thereby facilitating the development of the tri-function of the composition when used as autoignition, booster and first gas generating composition.

  It will be appreciated that the present invention further contemplates gas generators manufactured as known in the art and vehicle occupant protection systems manufactured as known in the art. Let's go. As such, the autoignition composition of the present invention is used in gas generators, seat belt assemblies, and / or vehicle occupant protection systems. All of these are manufactured as known in the art.

In different aspects of the invention, the compositions of the invention can be used in gas generation systems. For example, as schematically shown in FIG. 3, a vehicle occupant protection system made in a known manner includes an air bag inflator in a steering wheel, and a crash sensor electrically connected to a seat belt assembly. including. The gas generant composition of the present invention can be used in a wider vehicle occupant protection system or in both subassemblies within the gas generant system. More specifically, each gas generating device used in an automobile gas generating system can include a gas generating composition as described herein. The extrusion aid can be selected from talc, graphite, borazine [(BN) ₃ ], boron nitride, fumed silica, and fumed alumina. The extrusion aid preferably comprises 0-10% of the total composition, more preferably 0-5% of the total composition.

  The composition can be dry or wet mixed using methods known in the art. The various components are generally provided in particulate form and are mixed with other gas generant components to form a uniform mixture.

  It should be noted that all percentages and weight percentages given herein are based on the total weight of the gas generant composition. The chemicals described herein are supplied by companies such as Aldrich Chemical Company.

  As shown in FIG. 4, another exemplary inflator 200 incorporates a single chamber inflator design for a driver side airbag module. In general, inflators including gas generant / booster 216 formed as described herein can be manufactured as known in the art. U.S. Pat. Nos. 6,422,601, 6,805,377, 6,659,500, 6,749,219 and 6,752,421 illustrate typical airbag inflator designs and are referenced herein. Is incorporated as part of According to the present invention, the gas generation system 200 does not incorporate a separate booster composition, and therefore does not incorporate a booster chamber. As mentioned above, the use of a composition that functions as a booster and gas generant facilitates simplification of the inflator design.

  Please refer to FIG. The exemplary inflator 10 described above can be incorporated into the airbag system 200. The airbag system 200 includes at least one airbag 202 and an inflator 10 that includes the gas generant composition 12 of the present invention, the inflator being associated with the airbag 202 in fluid communication with the interior of the airbag. The airbag system 200 includes or is connected to a crash sensor 210. The crash sensor 210 includes a known crash sensor algorithm and signals activation of the airbag system 200 in the event of a crash, for example by activation of the airbag inflator 10.

  Please refer to FIG. The airbag system 200 can be incorporated into a wider and more comprehensive vehicle occupant restraint system 180 that includes additional elements such as a safety belt assembly 150. FIG. 3 shows a schematic diagram of one exemplary embodiment of such a restraint system. Safety belt assembly 150 includes a safety belt housing 152 and a safety belt 100 extending from housing 152. A safety belt retractor mechanism 154 (eg, a spring-type mechanism) can be coupled to the end portion of the belt. Further, a safety belt pretensioner 156 including a propellant 12 can be coupled to the belt retractor mechanism 154 to start the retractor mechanism in the event of a collision. Exemplary seat belt retractor mechanisms that can be used with the safety belt embodiment of the present invention are US Pat. Nos. 5,743,480, 5,553,803, 5,667,161, 5,451,008, 4,558,832 and 4,597,546. These patents are referenced and incorporated as part of this specification. Examples of typical pretensioners with which safety belt embodiments of the present invention can be combined are disclosed in US Pat. Nos. 6,505,790 and 6,419,177. These patents are referenced and incorporated as part of this specification.

  The safety belt assembly 150 includes a crash sensor algorithm 158 (e.g., a known crash sensor algorithm that generates an activation signal for the belt pretensioner 156, e.g., upon activation of a pyrotechnic igniter (not shown) incorporated in the pretensioner. Inertial sensors or accelerometers) or can be connected thereto. US Pat. Nos. 6,505,790 and 6,419,177, referenced above and incorporated as part of this specification, provide examples of pretensioners that start in such a manner.

  Although the safety belt assembly 150, the airbag system 200, and the wider vehicle occupant protection system 180 are illustrated, the gas generation system contemplated by the present invention is not limited thereto.

  It will be further understood that the foregoing descriptions of embodiments of the present invention are for illustrative purposes only and do not limit the scope of the invention in any way. As such, the various structural operational features shown herein can be modified in many ways by those skilled in the art without departing from the scope of the invention as defined by the claims. .

FIG. 1 is a cross-sectional side view showing the general structure of a known gas generation system incorporating individual boosters and gas generation chambers; FIG. 2 is a cross-sectional side view showing the general structure of a gas generation system according to the present invention, with the booster chamber eliminated therein; FIG. 3 is a schematic diagram of an exemplary vehicle occupant restraint system including a gas generant composition according to the present invention; FIG. 4 is a cross-sectional side view showing the general structure of a gas generation system according to different embodiments of the present invention, with the booster chamber removed therein.

Claims (10)

Airbag inflator without booster chamber. A composition comprising: a metal chlorate as a first oxidant; a first fuel selected from carboxylic acids, dicarboxylic acids, and mixtures thereof; and a second oxidant not having perchlorate properties; The inflator according to claim 1, further comprising: Based on the weight of the total composition, the metal chlorate is provided at about 10-20% by weight; the first fuel is provided at about 15-45% by weight; the second oxidant is about 30-50 The inflator of claim 2 provided in weight percent. The inflator of claim 2, wherein the composition further comprises a second fuel selected from tetrazoles, triazoles and furazanes, and salts thereof in an amount of about 0.1-30 wt%. A vehicle passenger protection system comprising the inflator of claim 1. A gas generation system comprising the composition of claim 2. The primary fuel is tartaric acid and its isomers, succinic acid, glutamic acid, adipic acid, mucoic acid, oxalic acid, malonic acid, fumaric acid, galactaric acid, glycolic acid, citric acid, L-malic acid, and mixtures thereof. The inflator according to claim 2, which is selected. About 19-28% by weight DL-tartaric acid, about 12-30% by weight potassium chlorate, about 15-25% by weight 5-aminotetrazole, and about 30-50% by weight based on the weight of the total composition 5. The composition of claim 4 comprising 1% strontium nitrate. The composition of claim 2, wherein the second oxidant is selected from metal, basic metal or non-metal nitrates, nitrites, oxides, and chlorates. Housing without booster chamber;
Metal chlorate as first oxidant;
A gas generation system comprising a composition comprising: a first fuel selected from carboxylic acids, dicarboxylic acids, and mixtures thereof; and a second oxidant that does not have perchlorate properties;
Based on the weight of the total composition, the metal chlorate is provided at about 10-20% by weight; the first fuel is provided at about 15-45% by weight; the second oxidant is about 30-50 Gas generation system provided in weight percent.

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