MXPA96006306A

MXPA96006306A - Non-azide gas generating compositions with an interconstru catalyst

Info

Publication number: MXPA96006306A
Application number: MXPA/A/1996/006306A
Authority: MX
Inventors: S Khandhadia Paresh
Original assignee: Automotive Systems Laboratory Inc
Priority date: 1995-04-14
Filing date: 1996-12-11
Publication date: 1997-06-01

Abstract

The present invention relates to: Non-azide gas generating compositions are formed from a non-azide fuel, an oxidant, a slag former, and an interconstructed catalyst comprising an alkali metal, alkaline earth metal, or metal salt of transition of tetrazoles, bitetrazoles and triazoles or transition metal oxide. The interconstructed catalyst promotes the conversion of nitrogen oxides (NOx) and carbon monoxide to nitrogen gas (N2) and carbon dioxide, respectively. The gas generators are therefore not toxic and are useful for inflating a system for vehicle occupant restriction

Description

NON-AZIDE GAS GENERATING COMPOSITIONS WITH AN INERCONSTRIDED CATALYST BACKGROUND OF THE INVENTION The present invention relates in general to gas generating compositions, used to inflate assemblies for safety restriction of occupants in motor vehicles and more particularly to non-azide gas generators, which provide combustion products with toxicity levels. acceptable in the case of exposure to the occupants of the vehicle. Inflatable occupant restraint devices for motor vehicles have been under development throughout the world for many years, including the development of gas generating compositions to inflate these assemblies for occupant restraint. Because the gasses produced by the gas generators must meet stringent transition requirements, most, if not all, of the gas generators now in use are based on alkali metal alkali or alkali metal azides, particularly sodium azide. . When reacted with an oxidizing agent, the sodium azide forms a relatively non-toxic gas consisting primarily of nitrogen. Furthermore, the combustion of azide-based gas generators occurs at relatively low temperatures, which allows the production of non-toxic inflating gas without the need for additives to reduce the combustion temperature.

However, azide-based gas generators are inherently difficult to handle and involve a relatively high risk in manufacturing and disposal. While the inflation gases produced by the azide-based gas generators are relatively non-toxic, the metal azides themselves, on the contrary, are highly toxic, resulting in extra expense and risk in the manufacture, storage and disposal of the generator. Of gas. In addition to direct contamination to the environment, metal azides also react easily with acids and heavy metals to form extremely sensitive compounds that can ignite or detonate spontaneously. In contrast, gas generators other than azide provide significant advantages over azide-based gas generators with respect to hazards related to toxicity during manufacture and disposal. Still further, most non-azide gas generating compositions typically provide a large yield of (moles of gas per gram of gas generator) than conventional azide-based occupant restriction gas generators. However, the known and used non-azide gas generators to date, produce unacceptably high levels of toxic substances upon combustion. The most difficult toxic gases to control are gases nitrogen oxide (NOx) and carbon monoxide (CO).

The reduction of a level of N0X and toxic CO before combustion of non-azide gas generator, has proved to be a difficult problem. For example, manipulating the oxidant / fuel ratio only reduces either N0X or CO. More specifically, increasing the ratio of oxidant to fuel minimizes the CO content before combustion because the extra oxygen oxidizes the CO carbon dioxide. Unfortunately, however, this approach results in increased amounts of N0X. Alternatively, if the oxidant / fuel ratio is reduced to remove excess oxygen and reduce the amount of N0X produced, increased amounts of CO are processed. The relatively high levels of NOx and CO produced by combustion of non-azide gas generators, as opposed to azide-based gas generators, are primarily due to the relatively high combustion temperatures exhibited by non-azide gas generators. . For example, the combustion temperature of an iron oxide / sodium azide gas generator is 969 ° C (1776 ° F), while non-azide gas generators they exhibit considerably higher combustion temperatures such as 1818 ° C (3304 ° F). The use of lower-energy non-azide fuels to reduce the combustion temperature is inefficient because the lower-energy non-azide fuels do not provide an extremely high gas generator velocity high enough to utilize the system for vehicle occupant restraint. The burning speed of the gas generator is important to ensure that the inflator operates easily and adequately. Another disadvantage created by the high combustion temperatures exhibited by the non-azide gas generators is the difficulty presented in forming solid combustion particles that easily coalesces into slag. Slag formation is convenient because the slag is easily filtered, resulting in relatively clean inflation gases. The gas generator based on azide, the lower combustion temperatures lead to solid formation. However, many common solid combustion products that can be expected from non-azide gas generators are liquids at the higher combustion temperatures exhibited by the non-azide gas generator, and therefore are difficult to filter out of the gas stream. . Therefore, there is a need for a non-azide gas generator that can produce inflation gases where toxic gases such as NOx and CO are minimized without compromising the desired burn rate of the gas generator. SUMMARY OF THE INVENTION The aforementioned problems in accordance with the present invention are solved by a non-azide gas generating composition which is itself non-toxic, and also produces combustion-inflating gases and exhibits reduced levels of NOx and CO. The manufacturing, storage and disposal hazards associated with unburned azide inflators are eliminated by the gas generators of the invention. The reduced content of toxic gases produced upon combustion allows the gas generators of the present invention to be used in systems for restraining the vehicle occupant, while protecting the occupants of the vehicle from exposure to toxic inflation gases such as N0X and CO, that to date have been produced with non-azide gas generators. Specifically, the present invention comprises a four component gas generator comprising a non-azide fuel, an oxidant, a slag former and a fuel catalyst. The non-azide fuel is selected from the group consisting of tetrazoles, bitetrazoles and triazoles. The oxidant is preferably selected from the group consisting of nitrates, chlorates, or inorganic perchlorates of alkali metals or alkaline earth metals. The slag-forming compound is selected from the oxide of alkali metals, hydroxides, perchlorates, nitrates, chlorates, silicates, borates or carbonates, or of hydroxides, perchlorates, nitrates, or chlorates of earth and transitional alkaline metals or of silicon dioxide, oxides of alkaline earth metals and naturally synthetically manufactured magnesium and aluminum silicate compounds, such as clay and talc, of natural origin or synthetically formulated.

According to the present invention, the interconstructed catalyst actively promotes the conversion of N0X and CO to nitrogen gas (N2) and CO2, respectively to reduce the toxicity of nitrogen gases produced by gas generators. The interconstructed catalyst is selected from the group consisting of salts of alkali metals, alkaline earth metals, and transition metals of tetrazoles, bitetrazoles and triazoles, and transition metal oxides. DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE PREFERRED EMBODIMENT According to the present invention, the fuel used in the non-azide gas generator is preferably chosen from compounds that maximize the nitrogen content of fuel and regulate the carbon and nitrogen content at moderate values. These fuels are typically chosen from azole compounds, particularly tetrazole compounds, such as aminotetrazole, tetrazole, 5-nitrotetrazole, 5-nitroaminotetrazole, bitetrazole and triazole compounds such as l, 2,4-triazol-5-one or 3-nitro-l , 2,4-triazol-one. A preferred embodiment uses 5-aminotetrazole as the fuel due to cost, availability and safety. Oxidants generally provide all or most of the oxygen present in the system. The oxidant actively supports combustion and also suppresses CO formation. The relative amounts of oxidant and fuel used are liquefied to provide a small access of oxygen to the combustion products, thus limiting the formation of CO, by oxidizing CO in carbon dioxide. The oxygen content in the combustion products should be in the range of 0.1% to about 5% and preferably to about 0.5% to 2%. The oxidant is selected from nitrates, chlorates and perchlorates of alkali metals, and nitrates, chlorates and perchlorates of earth alkaline metals. Strontium and barium nitrates are easy to obtain in the anhydrous state and are excellent oxidants. Strontium nitrate and barium nitrate are more preferred because of the more easily filtered solid products that are formed as described below. A slag former is included in the gas generator to facilitate the formation of solid particles which can then be filtered out of the gas stream. A convenient method of incorporating a slag former in the gas generator is by using an oxidant or a fuel that also serves a dual capacity as a slag former. The most preferred oxidant that also improves slag formation is strontium nitrate, but barium nitrate is also effective. In general, slag formers can be selected from numerous compounds, including hydroxides, nitrates, chlorates, and perchlorates, alkalis, alkaline earths and transition metals as well as silicates, borates, oxides and carbonates of alkali metals, in addition to silicon dioxide , oxides of alkaline earth metals and synthetically produced natural magnesium silicate compounds such as clay and talcum. In accordance with the present invention, the interconstructed catalyst comprises an alkali metal salt, alkaline earth metal salt, or transition metal salt of tetrazoles, bitetrazoles and triazoles or a transition metal oxide. The catalyst, which is directly mixed in the gas generating composition, actively promotes the conversion of NOx and CO to N2 and C02. More specifically, metals that are present in the form of a salt of a tetrazole, bitetrazole or triazole or in the form of a transition metal oxidant, catalyze two reactions. For example, a typical primary reaction is as follows: 2CO + 2NO? 2C02 + N2 It is also considered that the interconstructed catalyst also promotes a secondary decomposition reaction, as follows: 2N0? N2 + 02 The amount of catalyst that is included in the gas generating mixtures of the present invention, preferably is within a range of 5% by weight to about 15% by weight of the gas generating mixture. In general, the fuel is present in the gas generators of the present invention in a concentration of about 2% to about 50% by weight, the oxide is present in a concentration of about 30% to about 66% by weight, and the compound Slag former is present in a concentration of about 2% to about 10% by weight. A person skilled in the art will readily appreciate the manner in which the combinations of ingredients mentioned above combine to form the gas generating compositions of the present invention. For example, the materials can be mixed dry and subjected to attrition in a ball mill and then nodilized with compression molding. The present invention can be exemplified by the following representative examples within the components are quantified in weight percent. Example 1 a mixture of 5-aminotetrazole (5-AT), strontium nitrate [Sr (N03) 2], copper salt of 5-AT, and clay, having the following composition in weight percent: 28.62 is prepared % 5-AT, 57.38% Sr (N03) 2, 8.00% clay, 6.00% copper salt of 5-AT. The above materials are dry blended, subjected to attrition in a ball mill and nodilized by compression molding.

E eBPlQ 2 A mixture of (5-AT), Sr (N03) 2 talc and zinc salt of 5-AT is prepared as described in Example 1 having the following composition in percent by weight: 28.62% 5-AT, 57.38% Sr (N03) 2, 6.00% talc, and 8.00% zinc salt of 5- AT. a mixture of (5-AT), Sr (N03) 2 copper oxide and a copper salt of 5-AT is prepared, as described in Example 1 having the following composition in percent by weight: 28.62% of -AT, 57.38% of Sr (N03) 2, 6.00% of copper oxide and 8.00% of talc. Example 4 A mixture of (5-AT), Sr (N03) 2 zinc oxide and a copper salt of 5-AT is prepared, as described in Example 1 having the following composition in percent by weight: 28.62 % from -AT, 57.38% of Sr (N03) 2, and 8.00% of zinc oxide, 6.00% of clay. E enpjQ 5 A mixture of (5-AT), Sr (N03) 2 zinc oxide and a zinc salt of 5-AT, as described in Example 1, having the following composition in percent by weight is prepared : 28.62% 5-AT, 57.38% Sr (N03) 2, and 6.00% zinc oxide and 8.00% talcum.

While the preferred embodiment of the invention is described, it will be appreciated that the invention is susceptible to modification, without departing from the scope of the following claims.

Claims

CLAIMS 1.- A four component non-azide gas generating composition, which forms combustion gases, useful for inflating a safety restriction device for a vehicle occupant, characterized in that it comprises at least one material from each of the following groups Functional materials: (a) a fuel; (b) an oxidizing compound; (c) a slag-forming compound; and (d) a catalyst that promotes the conversion of toxic oxides of nitrogen and carbon monoxide to nitrogen gas (N2) and carbon dioxide, respectively, wherein the fuel comprises 5-aminotetrazole which is present in a concentration of approximately 26% at about 32% by weight, the oxidizing compound comprises strontium nitrate, which is present at a concentration of about 52% to about 58% by weight, the slag-forming compound comprises clay which is present at a concentration of about 2% by weight. about 10% by weight, and the catalyst comprises a zinc salt of 5-aminotetrazole, which is present in a concentration of about 5% to about 15% by weight.
2. A four-component non-azide gas generating composition, which forms gases before combustion, useful for inflating a safety restriction device for vehicle occupants, characterized in that it comprises at least one material from each of the following functional groups of Materials: (a) a fuel; (b) an oxidizing compound; (c) a rusting compound of slag; and (d) a catalyst that promotes the conversion of toxic oxides of nitrogen and carbon monoxide to nitrogen gas (N2) and carbon dioxide, respectively, wherein the fuel comprises 5-aminotetrazole which is present in a concentration of approximately 26% at about 32% by weight, the oxidizing compound comprises strontium nitrate, which is present at a concentration of about 52% to about 58% by weight, the slag-forming compound comprises talc which is present at a concentration of about 2% by weight. about 10% by weight, and the catalyst comprises a copper salt of 5-aminotetrazole, which is present in a concentration of about 5% to about 15% by weight.
3. A four component non-azide gas generating composition that forms gases before combustion, useful for inflating a vehicle occupant safety restriction device, characterized in that it comprises at least one material from each of the following functional groups of materials : (a) a fuel; (b) an oxidizing compound; (c) a slag-forming compound; and (d) a catalyst that promotes the conversion of toxic oxides of nitrogen and carbon monoxide to nitrogen gas (N2) and carbon dioxide, respectively, wherein the fuel comprises 5-aminotetrazole which is present at a concentration of approximately 26% at about 32% by weight, the oxidizing compound comprises strontium nitrate, which is present at a concentration of about 52% to about 58% by weight, the slag-forming compound comprises clay which is present at a concentration of about 2% by weight. about 10% by weight, and the catalyst comprises a copper salt of 5-aminotetrazole, which is present in a concentration of about 5% to about 15% by weight.
4. A four-component non-azide gas generating composition that forms gases before combustion, useful for inflating a vehicle occupant safety restriction device, comprising at least one material from each of the following functional groups of materials: (a) a fuel; (b) an oxidizing compound; (c) a slag-forming compound; and (d) a catalyst that promotes the conversion of toxic oxides of nitrogen and carbon monoxide to nitrogen gas (N2) and carbon dioxide, respectively, wherein the fuel comprises 5-a-inotetrazole which is present in a concentration of about 26. % to about 32% by weight, the oxidizing compound comprises strontium nitrate, which is present in a concentration of about 52% to about 58% by weight, the slag-forming compound comprises clay which is present in a concentration of about 2% to about 10% by weight, and the catalyst comprises a copper oxide of 5-aminotetrazole, which is present in a concentration of about 5% to about 15% in leso.
5. A four-component non-azide gas generating composition, which forms combustion gases, useful for inflating a vehicle occupant safety restriction device, characterized in that it comprises at least one material from each of the following functional groups of Materials: (a) a fuel; (b) an oxidizing compound; (c) a slag-forming compound; and (d) a catalyst that promotes the conversion of toxic oxides of nitrogen and carbon monoxide to nitrogen (N2) gases and carbon dioxide, respectively, wherein the fuel comprises 5-aminotetrazole which is present at a concentration of approximately 26% at about 32% by weight, the oxidizing compound comprises strontium nitrate, which is present in a concentration of about 52% to about 58% by weight, the slag-forming compound comprises talc which is present at a concentration of about 2% by weight. about 10% by weight, and the catalyst comprises a zinc oxide, which is present in a concentration of about 5% to about 15% by weight.