Method and composition for generating nitrogen gas

Abstract

A gas generating composition is disclosed wherein the combustible reactants are an alkali metal azide and a metal oxide which upon thermal initiation react to produce alkali metal oxide, metal and pure nitrogen gas which can be used to inflate an impact protection air cushion of an automotive restraint system.

I claim: 
     
       1. A solid composition for generating nitrogen gas substantially free of noxious and toxic impurities .Iadd.for inflating an air cushion in a vehicle passenger restraint system and capable of substantially fully inflating such cushion in the elapsed time between the occurrence of a primary collision of the vehicle with another object and secondary collisions occurring as a result thereof.Iaddend., comprising essentially a mixture of alkali metal azide and at least a stoichiometric amount of a metal oxide selected from the group consisting of iron, titanium and copper oxides and mixtures thereof, said metal oxide being capable of reacting exothermically with the alkali metal azide and wherein the metal of the oxide is lower in the electromotive series than the alkali metal of the azide and is a metal other than .[.the.]. .Iadd.an .Iaddend.alkali .Iadd.metal. .Iaddend. 
     
     
       2. The composition according to claim 1 wherein .[.: a..]. the alkali metal azide is sodium azide. 
     
     
       3. The composition according to claim 2 wherein: a. the alkali metal azide is sodium azide forming about 62 parts per hundred by weight of the total composition; and   b. the metal oxide is copper oxide forming the remainder of the composition.   
     
     
       4. The composition according to claim 2 wherein: a. the alkali metal azide is sodium azide forming about 70.9 parts per hundred by weight of the total composition; and   b. the metal oxide is iron oxide forming the remainder of the composition.   
     
     
       5. The composition according to claim 2 wherein: a. the alkali metal azide is sodium azide forming about 76.5 parts per hundred by weight of the total composition; and   b. the metal oxide is titanium dioxide forming the remainder of the composition.   
     
     
       6. A method for rapidly generating pure nitrogen gas .Iadd.to inflate an air cushion in a vehicle passenger restraint system whereby such cushion is substantially fully inflated between the occurrence of a primary collision of the vehicle with another object and secondary collisions occurring as a result thereof where such restraint system includes a gas generation apparatus having such air cushion attached to it, .Iaddend.comprising: a. .[.providing.]. .Iadd.placing in such gas generating apparatus .Iaddend.a homogeneous mixture comprising essentially solid granular alkali metal azide and at least a stoichiometric amount of a metal oxide in solid granular form selected from the group consisting of iron, titanium, and copper oxides and mixtures thereof, said metal oxide being capable of reacting exothermically with the alkali metal azide, the metal of the oxide being lower in the electromotive series than the alkali metal of the azide and the metal of the oxide being other than an alkali metal; and   b. raising the temperature of the mixture sufficiently to ignite it.   
     
     
       7. The method according to claim 6 wherein the alkali metal azide is sodium azide. 
     
     
       8. The method according to claim 7 wherein the metal oxide is copper oxide. 
     
     
       9. The method according to claim 8 wherein the particle size of the sodium azide is less than about 50 microns. .Iadd. 
     
     
       10.  The composition according to claim 1, wherein about 110 grams of said composition reacts substantially fully within an elapsed time of no more than about 60 milliseconds. .Iaddend. .Iadd.11. The composition according to claim 10, wherein about 110 grams of said composition reacts to generate at least about 2.6 cubic feet of nitrogen. .Iaddend. .Iadd.12. The composition according to claim 1, wherein about 250 grams of said composition reacts substantially fully within an elapsed time of no more 
     
     
        than about 60 milliseconds. .Iaddend. .Iadd.13.  The composition according to claim 12, wherein about 250 grams of said composition reacts to generate at least about 6.0 cubic feet of nitrogen. .Iaddend. .Iadd.14. The method according to claim 7, including the step of selecting the composition such that about 110 grams of said composition reacts substantially fully within an elapsed time of no more than about 60 milliseconds. .Iaddend. .Iadd.15. The method according to claim 14, including the step of selecting the composition such that about 110 grams of said composition reacts to generate at least about 2.6 cubic feet of nitrogen. .Iaddend. .Iadd.16. The method according to claim 7, including the step of selecting the composition such that about 250 grams of said composition reacts substantially fully within an elapsed time of no more than about 60 milliseconds. .Iaddend. .Iadd.17. The method according to claim 16, including the step of selecting the composition such that about 250 grams of said composition reacts to generate at least about 6.0 cubic feet of nitrogen. .Iaddend. .Iadd.18. The method according to claim 14 or claim 15, wherein said composition comprises essentially about 62 parts per hundred by weight of sodium azide, and copper oxide as the remainder of the composition. .Iaddend. .Iadd.19. A solid composition for generating nitrogen gas substantially free of noxious and toxic impurities for inflating an air cushion in a vehicle passenger restraint system and capable of substantially fully inflating such cushion in the elapsed time between the occurrence of a primary collision of the vehicle with another object and secondary collisions occurring as a result thereof, consisting essentially of a mixture of (a) an alkali metal azide and   (b) at least a stoichiometric amount of a metal oxide as an oxidizer, said metal oxide being selected from the group consisting of iron, titanium and copper oxides and mixtures thereof, said metal oxide being capable of reacting exothermically with the alkali metal azide and having sufficient available oxygen to substantially fully oxidize the alkali metal of the azide,   the metal of the metal oxide being lower in the electromotive series than the alkali metal of the azide and being a metal other than an alkali metal, and   said composition being capable of reacting substantially fully within the elapsed time between the occurrence of a primary collision of the vehicle with another object and secondary collisions occurring as a result thereof, and of generating sufficient nitrogen gas to inflate such air     
     
     
        cushion within said elapsed time. .Iaddend. .Iadd.20.  A method for rapidly generating pure nitrogen gas to inflate an air cushion in a vehicle passenger restraint system whereby such cushion is substantially fully inflated between the occurrence of a primary collision of the vehicle with another object and secondary collisions occurring as a result thereof and where such restraint system includes a gas generation apparatus having such air cushion attached to it, comprising: a. placing in such gas generating apparatus a homogeneous mixture consisting essentially of solid granular alkali metal azide and at least a stoichiometric amount of a metal oxide in solid granular from as an oxidizer, said metal oxide being selected from the group consisting of iron, titanium, and copper oxide and mixtures thereof, said metal oxide being capable of reacting exothermically with the alkali metal azide and having sufficient available oxygen to substantially fully oxidize the alkali metal of the azide,   the metal of the oxide being lower in the electromotive series than the alkali metal of the azide,   the metal of the oxide being other than an alkali metal, and   said mixture being selected to react substantially fully within the elapsed time between the occurrence of a primary collision and secondary collisions occurring as a result thereof, and to generate sufficient nitrogen gas to inflate such air cushion within said elapsed time; and     b. raising the temperature of the mixture sufficiently to ignite it.   
     
     
        .Iaddend. .Iadd.21.  The composition according to claim 19 wherein the alkali metal azide is sodium axide. .Iaddend. .Iadd.22. The composition according to claim 10 or 12 wherein: a. the alkali metal azide is sodium azide forming about 62 parts per hundred by weight of the total composition; and   b. the metal oxide is copper oxide forming the remainder of the composition. .Iaddend. .Iadd.23. The method according to claim 20 wherein the alkali metal azide is sodium azide. .Iaddend.