WO1997046501A1

WO1997046501A1 - Gas generator compositions

Info

Publication number: WO1997046501A1
Application number: PCT/US1997/004588
Authority: WO
Inventors: Robert S. Scheffee; Brian K. Wheatley
Original assignee: Atlantic Research Corporation
Priority date: 1996-06-07
Filing date: 1997-03-21
Publication date: 1997-12-11
Also published as: AU2586197A

Abstract

A composition for generating a non-toxic, non-flammable, odorless gas is disclosed wherein the propellant of said composition is a mixture of about 25 % by weight to about 50 % by weight KClO4 with a complementary amount of guanidine nitrate or a gas-generating effective derivative thereof, the oxidation ratio of oxidizer to fuel being about 0.92 to about 0.98. The method of using said composition is also disclosed.

Description

GAS GENERATOR COMPOSITIONS

FIELD OF THE INVENTION

This invention involves a composition for generating a low particulate non-toxic, non-flammable, odorless and colorless gas. Said composition comprises a propellant mixture of an alkali perchlorate and guanidine nitrate or an effective gas generating derivative thereof with the optional inclusion of minor amounts of an organic binder. The composition finds particular use in generating gas to inflate an air bag in an occupant restraint in an automobile.

PRIOR ART

The substance of the present invention involves solid composite propellant compositions and their use as gas generators.

There is a continuing market for new compositions to generate, in a high volume, a gas that is non-toxic, cool burning, non-flammable and contains only a low concentration of solid particulates, said gas to be employed with air bags. Although some modification of earlier devices has resulted in increased production of cooler gases, such modifications have contributed to the formation of undesirable byproducts. Accordingly, neither the known materials nor the newly modified materials are recognized as increasing the evolution and lowering the temperature of generated gases for the instant purposes. Although many patents disclose lists of oxidizers that include the alkali and alkaline earth perchlorates and lists of materials that may be employed to serve as a fuel to be oxidized and thereby generate a gas, in general, potassium perchlorate is disclosed merely as a conventional oxidizer.

Exemplary of such disclosures, U.S. Patent 4,948,439 refers to a mixture of ammonium perchlorate and sodium nitrate in a 1 to 1 mole ratio as an especially useful oxidizer "compound". Other useful oxidizing compounds are described as salts, such as the ammonium, alkali metal, and alkaline earth metal nitrates and perchlorates. Furthermore, the patentee cautions that ammonium perchlorate, although a good oxidizer, is not useful as the sole oxidizer since it will produce hydrogen chloride or other toxic products if not balanced by the presence of metal, such as sodium or potassium. Thus, the reference advances the use of the perchlorate merely as a recognized oxidizer. In U.S. Patent 5,482,579, the patentee refers to a prior art composition as comprising three components, an oxidizing agent, a cellulose acetate and a carbon- containing combustion controller. The composition is said to contain 78% to 92% by weight of a chlorate or perchlorate of an alkali metal or alkaline earth metal as the oxidizing agent, 7.9 to 17.2% by weight of a cellulose acetate and 0.1 to 0.8% by weight of a carbon- containing combustion controller.

Cellulose acetate is described as a combustible material consisting of carbon, hydrogen and oxygen. The patentee notes that when cellulose acetate is mixed with a powder, such as an oxidizing agent, the cellulose acetate interposes the gaps between the powder particles and thus acts as a binder. At col. 4, beginning at line 20, the patentee identifies a nitrogen-containing non- metallic compound to control the combustion temperature as one selected from the group consisting of guanidine compounds, oximes, amides, tetrazole derivatives, aromatic nitro compounds and ammonium nitrate. Guanidine nitrate is specifically mentioned. In the tables, the weight percent of potassium perchlorate varies from approximately 45% to about 82%. Both the described patents relate to generating a gas to inflate a crash bag.

On the other hand, U.S. Patent 3,909,324 describes as the principal object of the invention therein the provision of a novel pyrotechnic composition for disseminating smoke dyes, pesticides, chemical warfare and the like agents. The compositions are aminoguanidinium nitrates or condensation products thereof, as a fuel, and inorganic oxidizers which are readily combustible at atmospheric pressures. In claim 1 of the patent, a pyrotechnic disseminating formulation is recited comprising about 8 to about 40 weight percent of aminoguanidinium nitrates or condensation products thereof and 8 to about 30 weight percent of an alkali metal or ammonium chlorate or perchlorate as oxidizer, the balance being an effective amount of a chemical warfare agent, an incapacitating agent, a smoke dye or a plant growth regulant to be disseminated. The subject matter of U.S. Patent 4,543,136 concerns a water-in-oil emulsion explosive composition. The composition includes an inorganic oxidizer salt which may be, for example, one of various nitrates, chlorates or perchlorates, including alkali metal or alkaline earth metal perchlorates. The inorganic oxidizer salts are used alone or in the admixture of at least two members. The oxidizer salt is generally 5 to 90 percent, preferably 40 to 85 percent and is used in the form of an aqueous solution. At col. 5, beginning at line 17, the patentee discusses sensitizers effective for improving the detonation liability and low temperature detonability of the resulting water-m-oil explosive. Among the various substances listed is guanidine nitrate. The compounding amount of the sensitizer is said to be 0 to 40 percent, preferably 0.5 to 30 percent.

BACKGROUND OF THE INVENTION

The invention of this application is designed to provide a composition for generating a particulate-free, non-toxic, non-flammable, odorless and colorless gas for various purposes, such as the inflation of an air bag in an automotive vehicle. The generation of the desired gas requires the provision of an enclosed pressure chamber having an exit port; a composition comprising a propellant of a guanidine nitrate and/or a gas-generative effective derivative thereof mixed with a perchlorate of an alkali metal or an alkaline earth metal, optionally with a binder, which composition is made into propellant grains of suitable shape by compaction. The guanidine nitrate compound/KC10₄/binder may be mixed with nitrates of alkali metals or alkaline earth metals as oxidizers and the composition used in an enclosed pressure chamber having an exit port so that upon ignition, the formulation, in response to a sudden deceleration being detected by a sensor device in the pressure chamber, substantially instantly generates a gas and conducts it through the exit port of said pressure chamber to accomplish a desired function, such as inflating an automotive vehicle air bag.

SUMMARY OF THE INVENTION

The gas-generating composition of the instant invention contains a propellant which is a mixture composed of about 50 percent to about 75 percent of a guanidine nitrate or a gas-generative derivative thereof with about 25 percent by weight to about 50 percent by weight of an alkali metal or alkaline earth metal perchlorate. The guanidine derivatives may include aminoguanidine nitrate and nitroguanidine as fuels. Alkali metal perchlorates, as well as alkali metal nitrate and alkaline earth metal perchlorates and nitrates can be used as oxidizers in the present invention. The oxidation ratio is maintained slightly fuel-rich, between 0.92 and 0.98.

The invention also includes the method of generating a gas by employing the propellant of the present invention, optionally together with suitable other gas generators for the production of non-toxic, non¬ flammable, odor-free gas. The method is carried out in a conventional air bag inflator.

BRIEF DESCRIPTION OF THE FIGURE Figure 1 is a pyrotechnic driver side inflator that may be used in practicing the method of the instant invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 is a drawing of the pyrotechnic generator of the instant invention. Since no part of the inflator is reserved for storage capacity, the device is smaller than its counterpart hybrid inflator. In said Figure 1, a cartridge (21) holds a generant (22) , which, for example, may be composed of 35% by weight potassium perchlorate and 65% by weight guanidine nitrate. At one end of said cartridge (21) is an initiator (23) that will combust in response to a signal from a sensor (not shown) which generates said signal as a result of a change in conditions, e.g., an excessive increase in temperature or a sudden deceleration of a vehicle (indicative of a crash) , in which the inflator is installed. The initiator (23) is kept in place by an initiator retainer (24) . An O-ring (25) serves as a gasket to render the inflator essentially gas tight in the end where the initiator (23) is located.

The end of the inflator opposite from that containing the initiator (23) holds a screen (27) upon which any particulates in the produced gas are retained, a spring (29) to maintain dimensional stability of the generant bed, and a burst disc (28) , which is ruptured when the gas pressure exceeds a predetermined value, permitting the gas to escape from the cartridge (21) . To ensure that the expelled gas is not released in an unduly strong stream, a diffuser (30) is affixed to the discharge end of the inflator.

Additional objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein only the preferred embodiment of the invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawing and description are to be regarded as illustrative in nature and not as restrictive. The present invention involves a composition for generating a particulate-free, non-toxic, non-flammable, odorless and colorless gas, said composition comprising a propellant mixture of about 50 to 75 percent by weight of guanidine nitrate (GN) and/or a gas-generative effective derivative thereof, such as aminoguanidine nitrate, nitroguanidine, triaminoguanidine nitrate, etc. with a complementary amount of a perchlorate of an alkali metal or an alkaline earth metal . The composition may also comprise a minor amount of an organic binder. Said organic binder may comprise cellulosics, such as cellulose acetate butyrate, polyvinyl alcohol (PVA) , hydroxy terminated polybutadiene (HTPB) , polyesters and epoxies, for example. In addition to the propellant mixture, the composition may also contain an oxidizer effective amount of a nitrate of an alkali metal or alkaline earth metal. Exemplary of the propellant compositions are those in which the ratio of GN:KC10₄ is 50/50, 65/35 and 75/25. Other ratios within the indicated range would also be expected to provide similar results. In the composition, the oxidation ratio is maintained slightly fuel-rich, the oxidizing compounds being in a ratio of 0.92 to 0.98 to the fuel. The composition preferably contains the propellant in the form of pressed grains of a suitable shape.

The inventive method involves generating a stable low particulate non-toxic, non-flammable, odorless and colorless gas comprising the following steps: providing an enclosed pressure chamber having exit ports; disposing within said chamber a gas-generative composition comprising a propellant mixture of about 50 to 75 percent by weight of GN and/or a gas-generative effective derivative thereof with a complementary amount of a perchlorate of an alkali metal or an alkaline earth metal, and providing means for igniting said gas- generative composition upon detection by a sensor of the pressure chamber being subjected to a sudden deceleration, whereby gas is substantially instantly generated and conducted through the exit ports of said pressure chamber. As previously noted, the gas- generative composition may comprise a minor amount of an organic binder which may be, for example, cellulose acetate butyrate or polyvinyl alcohol. Additionally, in the method described above, the gas-generative composition may include an oxidizing effective amount of a nitrate of an alkali metal or an alkaline earth metal. The oxidation ratio of the components in the gas- generative composition is maintained between 0.92 and 0.98. The propellant of the composition is compacted into the form of grains of a suitable shape. When the method is carried out in an automotive vehicle equipped with at least one air bag, the generated gas, conducted through the exit ports, thereafter enters said at least one air bag, which it substantially instantly inflates.

Only the preferred embodiment of the invention and but a few examples of its versatility are shown and described in the present disclosure. It is to be understood that the invention is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as is expressed herein.

Claims

We claim :

1. A composition for generating a low particulate non-toxic, non-flammable, odorless and colorless gas, said composition comprising a propellant mixture of about 50 to about 75 percent by weight of GN and/or a gas- generative effective derivative thereof with a complementary amount of a perchlorate of an alkali metal or an alkaline earth metal.

2. The composition of claim 1 also comprising a minor amount of an organic binder.

3. The composition of claim 2 wherein the binder is selected from the group consisting of cellulosics, PVA, HTPB, polyesters and epoxies.

4. The composition of claim 3 wherein the organic binder comprises cellulose acetate butyrate or polyvinyl alcohol .

5. The composition of claim 4 wherein the binder is PVA.

6. The composition of claim 1 further including an oxidizing effective amount of a nitrate of an alkali metal or an alkaline earth metal.

7. The composition of claim 1 wherein the ratio of GN to KC10₄ is about 65% by weight to about 35% by weight .

8. The composition of claim 1 wherein the propellant is in the form of pressed grains of a suitable shape.

9. The composition of claim 1 wherein the fuel is in a slight excess relative to the oxidizer.

10. The composition of claim 9 wherein the oxidation ratio is in the range of about 0.92 to about 0.98.

11. A method for generating a stable low particulate non-toxic, non-flammable, odorless and colorless gas comprising the steps of: a) providing an enclosed pressure chamber having exit ports; b) disposing within said chamber a gas-generative composition comprising a propellant mixture of about 50% to about 75% by weight of GN and/or a gas-generating effective derivative thereof with a complementary amount of a perchlorate of an alkali metal or an alkaline earth metal; and c) providing means for igniting said gas-generative composition upon detection by a sensor of the pressure chamber being subjected to a sudden deceleration, whereby said gas is substantially instantly generated and conducted through the exit ports of said pressure chamber.

12. The method of claim 11 wherein the gas- generative composition also comprises a minor amount of an organic binder.

13. The method of claim 12 wherein the binder is selected from the group consisting of celluloics, PVA,

HTPB, polyester and epoxies.

14. The method of claim 13 wherein the organic binder comprises cellulose acetate butyrate or polyvinyl alcohol .

15. The method of claim 14 wherein the organic binder is PVA.

16. The method of claim 11 wherein the gas- generative composition includes an oxidizing effective amount of a nitrate of an alkali metal or an alkaline earth metal .

17. The method of claim 11 wherein the oxidation ratio of the components in the gas-generative composition is maintained slightly fuel-rich, between 0.92 and 0.98.

18. The method of claim 11 wherein the propellant is compacted into the form of grains of a suitable shape.

19. The method of claim 11 wherein the ratio of GN to KC10₄ in said propellant mixture is about 65% by weight to about 35% by weight.

20. The method of claim 11, carried out in an automotive vehicle equipped with at least one air bag, wherein the generated gas, conducted through the exit ports, thereafter enters said at least one air bag, which it substantially instantly inflates.