MXPA94009331A

MXPA94009331A - Generating composition of

Info

Publication number: MXPA94009331A
Application number: MXPA/A/1994/009331A
Authority: MX
Inventors: D Taylor Robert; w barnes Michael; Hock Christopher; E Chandler Virginia; M Deppert Thomas; P Jordan Michael
Original assignee: Morton International Inc
Priority date: 1993-12-10
Filing date: 1994-12-02
Publication date: 1997-08-01

Abstract

The present invention relates to a gas generating composition comprising between about 20 and about 40% by weight of fuel, the fuel comprising a tetrazole and / or triazole compound in between about 50 and about 85% by weight of the fuel, and a water-soluble fuel in between about 15 and about 50% by weight of the fuel, between about 20 and about 80% by weight of oxidant, with at least about 20% by weight and up to 100% of the oxidant being transition metal oxide or a mixture of transition metal oxides, the rsto of this oxidant being a nitrate, chlorate, alkali metal and / or alkaline earth metal perchlorate or mixtures thereof, and any remaining components comprising components compatible with additional gas generators.

Description

GENERATING COMPOSITION OF GAS INVENTORS: CHRISTOPHER HOCK, MICHAE P. JORDAN, VIRGINIA E. CHANDLER, ROBERT D. TAYLOR, THOMAS M. DEPPERT and MICHAEL. BARNES, North Americans domiciled at 6846 S. Buena Vista Drive, Uintah, Utah 84463; 1191 N. Main st. # 4 Bountiful, Utah 84010; 1811 E. Wasatch, Ogden, Utah 84403, 356 South Rosewood Drive, Hyrum, Utah 84319; 660E 350 S., Brigham City, Utah 84302; and at 420N 300E, Brigham City, Utah 84302; -United States of North America, cede all rights to MORTON INTERNATIONAL, INC., A company duly organized and constituted in accordance with the Laws of the State of Indiana United States of North America, domiciled at 100 North Riverside Plaza, Randolph Street at the River, Chicago, Illinois 60606-1596 United States of America, for the invention that is described below.

The present invention relates to gas generating compositions for inflating automotive airbags and other devices in which rapid production of high volumes of gas is necessary. More particularly, the invention relates to these compositions wherein tetrazoles and triazoles are the fuel component and oxidants are selected to achieve a low combustion temperature to reduce the production of toxic oxides during combustion.

BACKGROUND OF THE INVENTION Most of the security systems consisting of airbags in automobiles, currently in use, use gas-generating compositions in which sodium azide is the main fuel. Due to the disadvantages with sodium azide, particularly the instability in the presence of metal impurities and toxicity, which presents a disposal problem for gas generators not exposed to fire, there is a desire to develop gas generating systems without azide , and a good amount of formulations without azide have been proposed. However, to date, gas generators without azide have not had an important commercial incursion. Alternatives for the azides that have been proposed, for example, in U.S. Patent No. 5,035,757, the teachings of which are incorporated herein by reference, include the azole compounds, which include the tretrazole and triazole compounds. The tetrazole compounds include 5-amino tetrazole (AT), tetrazole, bitetrazole and the metal salts of these compounds. The triazole compounds include 1, 2,4-triazol-5-one, 3-nitro, 1,2,4-triazol-5-one and the metal salts of these compounds. Although all of the above azole compounds are useful fuels in accordance with the present invention, AT is the most commercially important of these.

The gas generating systems include, in addition to the fuel component, an oxidant. Oxidants proposed for use in conjunction with azole fuels include the nitrate, chlorate and perchlorate salts of alkali metals and alkaline earth metals. A problem with the gas generant systems based on azole compounds proposed up to now, are their high combustion temperatures. The levels generated of toxic oxides, particularly CO and N0X depend on the combustion temperature of the gas generating reaction, the higher levels of these toxic gases are produced at higher temperatures. Therefore, it is desirable to produce gas generating mixtures that ignite at lower temperatures. Several processes for the processing of gas generators use water. The water treatment reduces the risks of the production of the gas generating materials. It is therefore desirable that gas generating compositions be formulated to facilitate the treatment of water. An example of water treatment, disclosed, for example, in U.S. Patent No. 5,015,309, the teachings of which are incorporated herein by reference, involves the steps of 1. The formation of a suspension of the generant ingredients, with water. 2. Spray drying of the suspension to form small spherical globules with a diameter of 100-300 microns. 3. The feeding of the small globules by means of gravity flow towards a high speed rotating press. To properly feed the tablet press, it is necessary to obtain the well-formed small spherical globules. Without small globules, filling or cavity formation in the feeding system is a common occurrence. Without the small globules, it is difficult to achieve high and uniform speed filling of the tablet press. These small globules will not form in the spray-drying stage without at least a portion of the generator that is soluble in water. Typical suspensions contain up to 35% water and it is preferred that at least 15% of the required solid ingredients are soluble in the suspension. Another common manufacturing technique, (e.g. in U.S. Patent 5,084,218) the teachings of which are incorporated herein by reference, involves the following steps: 1. The formation of a suspension of the generant ingredients with water. 2. The extrusion of the suspension to form strands similar to spaghetti. 3 .. The chopping and formation of spheres of the strands into small globules. 4. The rattle of the small globules as previously described. The step of chopping and forming spheres to form small globules will not be useful unless a portion of the generator is soluble in water.

SUMMARY OF THE INVENTION Gas generating compositions comprise between about 20 and about 40% by weight of a fuel and between about 20 and about 80% by weight of an oxidant; the rest are optional additional components. Between about 50 and about 85% by weight of the fuel is a triazole or tetrazole, between about 15 and about 50% by weight of the fuel is a water soluble fuel such as guanidine nitrate, ethylenediamine dinitrate or similar compounds. At least about 20% by weight of the oxidant up to 100%, preferably at least about 50% by weight, comprises a transition metal oxide; the rest are nitrates, chlorates or perchlorates of alkali metals and / or alkaline earth metals. The use of the transition metal oxides as an important oxidizing component results in lower combustion temperatures, and therefore a reduced production of toxic oxides. The compositions according to the invention self-ignite at temperatures in a range of about 170 ° C, whereby the use of these compositions as generators in the inflators can reduce the need for different self-ignition units, as they are generally used in inflators. contained in aluminum. Also, the compositions according to the invention can be used as auto-ignition materials in self-ignition units for inflators using conventional generators, such as azide-based generants.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of an inflator module adapted for use on the axis of a steering wheel, this inflator module does not have a separate self-ignition unit; and Figure 2 is a cross-sectional view of an inflator module adapted for use on the axis of a steering wheel, this inflator module having a self-ignition unit.

DETAILED DESCRIPTION OF CERTAIN PREFERRED MODALITIES In the present, unless stated otherwise, all percentages are by weight. While the major fuel component can be selected from any of the tetrazole and triazole compounds listed above and mixtures thereof, from a viewpoint of availability and cost, 5-aminatetrazole (AT) is currently the azole compound of choice, and the invention will be described primarily with reference to the AT. The purpose of the fuel is to produce carbon dioxide, water and nitrogen gas when burned with an oxidant and combination of suitable oxidants. The gases thus produced are used to inflate a car gas bag or other such device. As an example, the AT is burned to produce carbon dioxide, water and nitrogen according to the following equation: 2CH3N5 + 7/202? 2C02 + 3H20 + 5N2 To facilitate the process along with the water, a smaller portion of the fuel, ie between about 15 and about 50% by weight of the fuel, is soluble in water. While water-soluble oxidants, such as strontium nitrate, also facilitate the process in water, overconfidence in these water-soluble oxidants tends to undesirably produce high combustion temperatures. The specific desirable characteristics of water-soluble fuels are: The compound should be readily soluble in water, ie, at least about 30 g / ml H20 at 25 ° C; The compound must contain only elements selected from H, C, O and N; When formulated with an oxidant to produce carbon dioxide, nitrogen and water stequeometrically, the production of the gas must be greater than about 1.8 moles of the gas per 100 grams of the formulation; When formulated with an oxidant to produce carbon dioxide, water and nitrogen in a stoichiometric manner, the theoretical chamber temperature at 100 psi must be lower, preferably less than about 1800 ° K. The compounds that most ideally meet the above criteria are the nitrate salts of amines or substituted amines. Suitable compounds include, but are not limited to, the group consisting of guanidine nitrate, aminoguanidine nitrate, diamino guanidine nitrate, semicarbazide nitrate, triamine guanidine nitrate, ethylenediamine dinitrate, hexamethylenetetramine dinitrate and mixtures of these compounds . Guanidine nitrate is the currently preferred water soluble fuel. Generally any transition metal oxide would serve as an oxidant. Particularly suitable transition metal oxides include ferric oxide and cupric oxide. The preferred transition metal oxide is cupric oxide which, in combustion of the gas generator, produces copper metal as a slag component. The purpose of the oxidant is to provide the oxygen necessary to oxidize the fuel; for example, the CuO oxidizes the AT according to the following equation: 4CH3N5 + 14CuO? 14Cu + 4C02 + 6H20 + 10N2 The transition metal oxide may contain a single oxidant or may be used together with other oxidants including the nitrates, chlorates and perchlorates of alkali metals and alkaline earth metals and mixtures of these oxidants. Of these, nitrates (the alkali metal and / or alkaline earth metal salts) are preferred. Nitrate oxidants slightly increase gas production. The alkali metal nitrates are particularly useful as additives to promote ignition. It is often desirable to granulate the gas generating composition. If so, up to about 5% by weight, usually 0.2-5% by weight of a press auxiliary or binder can be used. This can be selected from materials known as useful for this purpose, which includes molybdenum disulfide, polycarbonate, graphite, viton, nitrocellulose, polysaccharides, polyvinylpyrrolidone, sodium silicate, calcium stearate, magnesium stearate, zinc stearate, talc , mica minerals, ventonite, molidobnite, and others known to those skilled in the art. A preferred binder / binder is molybdenum disulfide. If molybdenum disulfide is used, it is preferred that an alkali metal nitrate be included as a portion of the oxidant. The alkali metal nitrate in the presence of molybdenum disulfide results in the formation of alkali metal sulfate, instead of the toxic sulfur species. Accordingly, if molybdenum disulfide is used, the alkali metal nitrate is used as a portion of the oxidant in an amount sufficient to substantially convert all of the sulfur component of the molybdenum disulfide to alkali metal sulfate. This amount is at least the stoichiometric equivalent of molybdenum disulfide, but it is usually several times the equivalent of a stequeometric one. On a weight basis, an alkali metal nitrate is normally used between about 3 and about 5 times the weight of the molybdenum disulfide used. The gas generating composition may optionally contain a catalyst up to about 3% by weight, usually between about 1 and about 2% by weight. Boron hydrides and iron ferricyanide are these combustion catalysts. Certain transition metal oxides, such as copper chromate, chromium oxide and manganese oxide, in addition to the oxidizing function, act to catalyze combustion. To further reduce the reaction temperature, the coolants may also optionally be included in up to about 10% by weight, usually between about 1 and about 5% by weight. Suitable coolants include graphite, alumina, silica, metal carbonate salts, and transition metals and mixtures thereof. The cooling fluids may be in particulate form, although if available, the fiber form is preferred, for example, graphite, alumina and alumina / silica fibers. A further advantage of the compositions according to the invention is that they have a self-ignition temperature in a range around 170 ° C, that is between about 155 ° C and about 180 ° C. This corresponds to a particularly desirable autoignition temperature range for effecting autoignition in an aluminum inflator. With the self-igniting gas generating material in thermal communication with the cover, the gas generating material will self-ignite when the cover is exposed to abnormally high temperatures, such as in the range of about 240 ° C. U.S. Patent No. 4,561,675, the teachings of which are incorporated herein by reference, describe the risks of aluminum-covered chillers when subjected to temperatures that could be reached in a car fire. The aluminum shell weakens at a temperature below the temperature where conventional gas generating materials, particularly azide-based generants, self-ignite. Therefore, it would be possible that the cooler will explode or be destroyed, sending fragments through the air. However, U.S. Patent 4,561,675 faces this problem by providing a self-igniting device containing pyrotechnic material that self-ignites below the temperature at which the aluminum shell weakens and, in turn, ignites the main generating material. A unit that has a self-ignition unit is shown in Figure 2. Generally, all currently available aluminum inflators incorporate this self-ignition unit. Since the gas generating materials of the present invention self-ignite in a range around 170 ° C, there is no need to provide a separate self-ignition unit, as the same gas generator self-ignites at temperatures below the weakening temperatures of the gas. the aluminum cover. To eliminate the need for a separate self-ignition unit, costs are reduced. Also, greater design flexibility is allowed. Illustrated in FIG. 1 is a cut-off of an inflator unit 10 using the generator pellets 11, generated in accordance with the present invention, as a gas generator that also self-ignites. Filtering units in specific autoignition units are known in the art, for example, the patent 4,547,342, the teachings of which are incorporated herein by reference; however, these units that use generators which do not self-ignite below the weakening temperatures of aluminum pose a risk in fire situations. The cover is formed of two pieces of aluminum, a base 12 and a diffuser 13, welded together. The diffuser 13 is configured to define a central cylindrical chamber 14 and the annular chambers 15 and 16. Within the central chamber is an explosive charge 17 containing pyrotechnics. The explosive charge 17 is connected by an electrical connector 18 to a detector means, represented by a box 9, which detects when the vehicle is in collision, and the pyrotechnics in the explosive charge is ignited. Opposite the explosive charge 17 in the central chamber 14 is a cup 19 containing the ignition material, such as B and KN03. The explosive charge 17 with the ignition explodes, releasing gases that ignite the ignition material in the cup 19. The ignition cup 19 then explodes, releases gases through the diffuser conduits 20 to the annular chamber 15 where the granules 11 of the gas generating material. A device containing the generator 21 on the base side • of the chamber 15 is a construction device that holds the gas generator inside the diffuser 13 until it connects with the base 12. Surrounding the granules 11 is a screen or combustion filter 22, and coming to this is a metal tape seal with adhesive on the back 23 which seals the granules inside the inflator, protecting them from environmental conditions, such as humidity. When the generating pellets 11 are ignited, the gases pass through the screen 22, and break the metal seal 23 and pass out of the annular chamber 16 through the conduits 24. At the base end of the chamber 16 is a wire strap 25 to trap and retain the slag and particles formed during combustion. The gas is directed towards the filter 25 by means of a deflector ring 26. After passing through the filter 25, the gases pass around a screen 39, which bypasses the gases through a secondary filter 27, and exit through from ducts 28 to the air bag (not shown). Shown in Figure 2 is an inflator, similar to that of Figure 1, but using a gas generating composition of the present invention in a self-igniting unit 30 when the gas generating granules 11 'of the conventional composition, such as those based on azide, are used as primary generators. (In Figure 2, the identical parts are indicated with the same reference numbers used in Figure 1). The self-ignition unit 30 is a detonator at the end of the cup 14 that holds the ignition material. The upper part of the self-ignition unit 30 is in contact with the diffuser 13 in such a way that the self-igniting material is in thermal communication with the cover. The self-ignition material, that is to say the generating composition according to the invention, is separated from the ignition material by means of a fragile membrane 31, for example metal foil. The unit should be exposed to excessive temperatures, as could be found in a vehicle fire, the auto-ignition material ignites, burns the membrane 31, 'resulting in the events that lead to the generation of total gas according to the sequence previously established. The compositions of the present invention have stability for a long time. In this way, these are preferable to self-ignition materials, such as self-ignition materials based on nitrocellulose that degrade over time. The compositions are non-explosive, therefore they are preferable to explosive autoignition materials. The invention will now be described in great detail by means of the specific examples.

EXAMPLE 1-3 The gas generating compositions are formulated according to the following table (the amounts in parts by weight, including the molybdenum sulfide binder). The compositions were prepared by mixing the components in an aqueous suspension (approximately 70% solids), the composition was dried and the dry mixture was sieved. The degree of combustion of the coatings were pressed and the degree of combustion averaged at 1000 psi. 1 2 3 Guanidine Nitrate 9.84 10.84 11.82 Soluble Fuel Cupric Oxide 70.94 70.48 70.03 Oxidant 5 -Aminotetrazole 17.73 17.20 16.67 Fuel Sodium Nitrate 1.48 1.48 1.48 Oxidizer (low ignition temperature) Molybdenum disulfide 0.5 0.5 0.5 The properties of the compositions are the following: following: Degree of combustion at 1000 psi (ips) 0.78 0.79 0.79 Temp. of the chamber (<? K) 1653 1651 1648% Soluble (30% Suspension) 19.6 21.0 22.4 Well-formed slag (in all compositions) Autoignition temperature 160 ° C 160 ° C 160 ° C Example 4 Three inflators as shown in Figure 2 were assembled using the composition of Example 3 above. The inflators were placed on piles of firewood that was lit. After - for a period of time, the inflators were deployed normally due to the autoignition of the composition of the present invention, the autoignition propagated the rest of the ignition sequence.

Claims

Normally in a test of this type, an inflator in which the autoignition fails, is fragmented due to the reduction in the resistance of the cover to the temperature of the fire. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property; 1. A gas generating composition containing between about 20 and about 40% by weight of fuel, this fuel having a tetrazole and / or triazole compound in between about 50 and about 85% by weight of this fuel, and a soluble fuel in water in between about 15 and about 50% by weight of this fuel; between about 20 and about 80% by weight of oxidant, at least about 20% by weight and up to 100% of the oxidant is a transition metal oxide or a mixture of transition metal oxides, the remainder of this oxidant is a nitrate, chlorate, alkali metal and / or alkaline earth metal perchlorate or mixtures thereof; and any balance that contains the components compatible with the gas generant added.
2. The composition according to claim 1 further contains between about 0.2 and about 5% by weight of a binder material.
3. The composition according to claim 2, characterized in that the binder material is molybdenum sulphide.
The composition according to claim 3, characterized in that the oxidant contains sufficient alkali metal nitrate to convert substantially all of the sulfur component of the molybdenum sulfide to alkali metal sulfate during the combustion of the gas generating composition.
5. The composition according to claim 1, characterized in that the transition metal oxide is CuO.
The composition according to claim 1, characterized in that in addition to the transition metal oxide, the oxidant includes an alkali metal and / or alkaline earth metal nitrate.
The composition according to claim 1, characterized in that the water soluble fuel is selected from the group consisting of guanidine nitrate, aminoguanidine nitrate, diaminoguanidine nitrate, semicarbazide nitrate, triamine guanidine nitrate, ethylenediamine dinitrate, dinitrate haxamethyltetramine and mixtures of these.
The composition according to claim 7, characterized in that the water-soluble fuel is guanidine nitrate.
9. A method for producing high volumes of gas in an automobile air bag during a vehicular collision and also to produce the generation of high volumes of gas during the conditions of a vehicular collision, the method comprises the provision of an inflator unit that it contains a cover, the gas generator contained within this cover, the means for igniting the gas generator during a vehicular collision, and the means for sending the gases generated by the combustion of the gas generator to the air pocket, this generator of gas contains between about 20 and about 40% by weight of the fuel, this fuel contains a tetrazole and / or triazole compound in between about 50 and about 85% by weight of the fuel and a water soluble fuel in between about 15 and about 50% by weight of the fuel; between about 20 and about 80% of the oxidant, at least about 20% by weight and up to 100% of the oxidant is a transition metal oxide or a mixture of transition metal oxides, the remainder of this oxidant is a nitrate, chlorate, alkali metal and / or alkaline earth metal perchlorate or mixtures thereof; and any balance containing the components compatible with the additional gas generator, this self-igniting gas generator at temperatures between approximately 155 ° C and approximately 180 ° C, whereby self-ignition occurs in the absence of other auto-ignition material .
10. In an automobile air bag inflator comprising a cover, an electrically ignitable detonation means for generating hot gases, ignition material for producing additional hot gases, placed inside the cover to light during exposure to the hot gases generated by the detonation means, and a gas generating material to produce high volumes of gas, placed inside the cover to ignite during exposure to hot gases generated by the ignition material; a method for igniting the ignition material when the cover is exposed to abnormal high temperatures, the method comprising placing on the cover a self-igniting material in thermal communication with the housing and placed in order to ignite the ignition material when the material is on fire of self-ignition, the self-igniting material comprises: between about 20 and about 40% by weight of the fuel, this fuel contains a tetrazole and / or triazole compound in between about 50 and about 85% by weight of the fuel and a water-soluble fuel in between about 15 and about 50% by weight of the fuel; between about 20 and about 80% by weight of the oxidant, at least about 20% by weight and up to 100% of the oxidant such as a transition metal oxide or a mixture of transition metal oxides, the remainder of this oxidant as a nitrate, chlorate, alkali metal and / or alkaline earth metal perchlorate or mixtures thereof; and any balance that contains the components compatible with the additional gas generator. SUMMARY OF THE INVENTION The present invention relates to a gas generating composition containing as fuel a mixture of a larger portion of a triazole or tetrazole and of a minor portion of a water soluble fuel; and an oxidizing component, at least 20% by weight of this oxidizing component, a transition metal oxide, CuO. The generant compositions according to the invention self-ignite in a range around 170 ° C, providing auto-ignition of the generator without the need for separate self-ignition devices. Also, the generating compositions are useful as self-igniting pyrotechnics in self-igniting devices. In testimony of which, I have signed the above description and novelty of the invention as an appendix of MORTON INTERNATIONAL, INC., In Mexico City, Federal District, today, December 2, 1994. p.p.de MORTON INTERNATIONAL, INC. EDUARDO CORREA E.