Gas generant igniter coating materials and methods

Abstract

Gas generant grains, such as tablets, granules or particulates, are coated with a dispersion of oxidizer particulates, metal fuel particulates, a fluoropolymer binder with which at least a portion of the metal fuel is reactive, and a solvent for the fluoropolymer.

What is claimed is:  
     
         1 . An ignition material comprising: 
 finely divided particulates of metal fuel, the metal fuel being reactive with fluorine moieties of a fluoropolymer,    finely divided oxidizer particulates, and    a fluoropolymer binder in which the finely divided particulates of metal fuel and the finely divided oxidizer particulates are substantially uniformly distributed.    
     
     
         2 . The ignition material of  claim 1  comprising the oxidizer particulates at between about 55 and about 75 wt. %, the metal particulates at between about 10 and about 40 wt. %, and the fluoropolymer binder at between about 1 and about 5 wt. %, said weight percentages being based on total weight of ignition material.  
     
     
         3 . The ignition material of  claim 1  wherein the metal fuel is selected from the group consisting of magnesium, aluminum, boron, beryllium, calcium, strontium, barium, sodium lithium, titanium and zirconium, mixtures of these metals and alloys of these metals.  
     
     
         4 . The ignition material of  claim 1  comprising magnesium.  
     
     
         5 . The ignition material of  claim 1  comprising aluminum.  
     
     
         6 . The ignition material of  claim 1  comprising boron.  
     
     
         7 . The ignition material of  claim 1  comprising a mixture or alloy of magnesium and aluminum.  
     
     
         8 . The ignition material of  claim 7  further comprising boron.  
     
     
         9 . The material of  claim 1  wherein the metal fuel comprises between about 20 and about 50 wt. % magnesium and between about 50 and about 80 wt. % aluminum, said weight percentages of magnesium and aluminum being based on total weight of magnesium and aluminum, and 0 to 20 wt. % boron, said weight percentage of being based on total weight of ignition material.  
     
     
         10 . The ignition material of  claim 9  containing at least 1 wt. % boron, said weight percentage of being based on total weight of ignition material.  
     
     
         11 . The ignition material of  claim 1  additionally comprising up to about 10 wt. % of a desensitizing additive, said weight percentage being based on total weight of ignition material.  
     
     
         12 . The ignition material of  claim 11  wherein the ignition material includes the desensitizing agent bentonite clay.  
     
     
         13 . The ignition material of  claim 1  in a form suitable for coating a substrate further comprising a solvent for said fluoropolymer binder in an amount sufficient to dissolve said fluoropolymer binder.  
     
     
         14 . A method of providing an ignition material-coated gas generant substrate comprising providing a gas generant substrate and coating the gas generant substrate with the ignition material of  claim 13 .  
     
     
         15 . The method of  claim 14  wherein the ignition material is coated on the gas generant substrate by spray coating.  
     
     
         16 . An ignition material-coated gas generant formulation comprising a gas generant having a coating of the ignition material of  claim 1 .  
     
     
         17 . The ignition material-coated gas generant formulation of  claim 16 , wherein the substrate is a gas generant grain having a maximum weight of about 3.0 grams and the ignition material-coated gas generant formulation is capable of self-ignition.  
     
     
         18 . An ignition material useful for coating a gas generant material substrate, the ignition material comprising oxidizer particulates, fuel particulates comprising metal fuel, and a fluoropolymer reactive with the metal fuel, the fluoropolymer being present at a level of between about 1 and about 5 wt. % of the ignition material.  
     
     
         19 . The ignition material of  claim 18  wherein the oxidizer particulates are present at a level of between about 55 and about 75 wt. % of ignition material and the metal particulates are present at between about 10 and about 40 wt. % of ignition material.  
     
     
         20 . The ignition material of  claim 19  additionally comprising up to about 10 wt. % of a desensitizing additive, said weight percentage being based on total weight of ignition material.  
     
     
         21 . An ignition material-coated gas generant comprising a gas generant material substrate having a coating of the ignition material of  claim 18 .  
     
     
         22 . The ignition material-coated gas generant of  claim 21 , wherein the gas generant material substrate is a gas generant grain having a maximum weight of about 3.0 grams and wherein the ignition material-coated gas generant is capable of self-ignition.  
     
     
         23 . A method of coating a gas generant material to provide an adherent ignition material film thereon; the method comprising, 
 dissolving a fluoropolymer in a solvent to form a fluoropolymer solution,    dispersing particulates of oxidizer and fuel in the fluoropolymer solution to form a dispersion, and    coating a gas generant substrate with the dispersion.    
     
     
         24 . The method of  claim 23  wherein the fluoropolymer comprises between about 1 and about 5 wt. % of the dispersion, exclusive of the solvent.  
     
     
         25 . The method of  claim 23  wherein the dispersion is coated onto the gas generant substrate by spray coating.  
     
     
         26 . The method of  claim 23  wherein the dispersion is coated onto the gas generant substrate by spray coating in a fluidized bed.  
     
     
         27 . The method according to  claim 23  wherein the gas generant substrate is a gas generant grain having a maximum weight of about 3.0 grams, the coated gas generant substrate is capable of self-ignition.