Alkaline earth metal zirconium oxide additive useful for improving ballistic performance of gas generating compositions

Abstract

A gas generant composition for an automotive inflatable restraint system includes one or more: fuels, such as guanidine nitrate; oxidizers, such as basic copper nitrate; and an alkaline earth zirconium oxide. The gas generant composition is substantially free of potassium perchlorate. The alkaline earth zirconium oxide may be barium zirconate (BaZrO3), calcium zirconate (CaZrO3), and/or strontium zirconate (SrZrO3). The alkaline earth zirconium oxide may be present at ≥about 0.1% by mass to ≤about 6% by mass of the gas generant composition. Such gas generants may be cool burning (e.g., a maximum flame temperature at combustion (Tc) of ≤about 1700K (1,427° C.)), have a linear burn rate of ≥about 20 mm per second at a pressure of about 21 MPa and a linear burn rate pressure exponent (n) of ≤about 0.35. Method of making such gas generants are also provided.

What is claimed is: 
     
         1 . A gas generant composition for an automotive inflatable restraint system comprising:
 one or more fuels;   one or more oxidizers; and   an alkaline earth zirconium oxide, wherein the gas generant composition is substantially free of potassium perchlorate.   
     
     
         2 . The gas generant composition of  claim 1 , wherein the alkaline earth zirconium oxide is selected from the group consisting of: barium zirconate (BaZrO 3 ), calcium zirconate (CaZrO 3 ), strontium zirconate (SrZrO 3 ), and combinations thereof. 
     
     
         3 . The gas generant composition of  claim 1 , wherein the alkaline earth zirconium oxide is present at greater than or equal to about 0.1% to less than or equal to about 6% by mass of gas generant composition. 
     
     
         4 . The gas generant composition of  claim 1 , wherein the alkaline earth zirconium oxide is present at greater than or equal to about 0.5% to less than or equal to about 5% by mass of the gas generant composition. 
     
     
         5 . The gas generant composition of  claim 1  having a linear burn rate of greater than or equal to about 20 mm per second at a pressure of about 21 megapascals (MPa). 
     
     
         6 . The gas generant composition of  claim 1  having a linear burn rate pressure exponent (n) of less than or equal to about 0.35. 
     
     
         7 . The gas generant composition of  claim 1  having a maximum flame temperature at combustion (T c ) of less than or equal to about 1700K (1,427° C.) and a gas yield of greater than or equal to about 5.7 moles/100 cm 3 . 
     
     
         8 . The gas generant composition of  claim 1  that is substantially free of silicon dioxide, aluminum oxide, and combinations thereof. 
     
     
         9 . The gas generant composition of  claim 1 , wherein:
 the one or more fuels are selected from the group consisting of: guanidine nitrate, diammonium 5,5′-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diammine bitetrazole, a melamine oxalate compound, and combinations thereof; and   the one or more oxidizers are selected from the group consisting of: basic copper nitrate, alkali metal or alkaline earth metal nitrates, alkali metal, ammonium perchlorate, metal oxides, and combinations thereof.   
     
     
         10 . The gas generant composition of  claim 1 , wherein the one or more oxidizers comprises ammonium perchlorate at less than or equal to about 7% by mass of gas generant composition. 
     
     
         11 . The gas generant composition of  claim 1 , wherein:
 the one or more fuels comprise guanidine nitrate present at greater than or equal to about 30% to less than or equal to about 60% by mass of the gas generant composition;   basic copper nitrate present at greater than or equal to about 30% to less than or equal to about 60% by mass of the gas generant composition; and   further comprising one or more gas generant additives present at greater than or equal to 0% to less than or equal to about 8% by mass of the gas generant composition.   
     
     
         12 . A gas generant composition for an automotive inflatable restraint system comprising:
 guanidine nitrate;   basic copper nitrate; and   greater than or equal to about 0.1% to less than or equal to about 6% by mass of barium zirconate (BaZrO 3 ), wherein the gas generant composition is substantially free of potassium perchlorate.   
     
     
         13 . The gas generant composition of  claim 12 , wherein the barium zirconate (BaZrO 3 ) is present at greater than or equal to about 0.5% to less than or equal to about 5% by mass of the gas generant composition. 
     
     
         14 . The gas generant composition of  claim 12  having a linear burn rate of greater than or equal to about 20 mm per second at a pressure of about 21 megapascals (MPa) and a linear burn rate pressure exponent (n) of less than or equal to about 0.35. 
     
     
         15 . The gas generant composition of  claim 12  wherein the barium zirconate (BaZrO 3 ) is present at greater than or equal to about 4% to less than or equal to about 5% by mass of the gas generant composition and the gas generant composition has a linear burn rate of greater than or equal to about 23 mm per second at a pressure of about 21 megapascals (MPa) and a linear burn rate pressure exponent of less than or equal to about 0.34. 
     
     
         16 . The gas generant composition of  claim 12 , wherein:
 the guanidine nitrate is present at greater than or equal to about 30% to less than or equal to about 60% by mass of the gas generant composition; and   the basic copper nitrate is present at greater than or equal to about 30% to less than or equal to about 60% by mass of the gas generant composition.   
     
     
         17 . A method of forming a gas generant with reduced pressure sensitivity, the method comprising:
 mixing basic copper nitrate, guanidine nitrate, an alkaline earth zirconium oxide, and a liquid to form a mixture;   spray drying the mixture to form a powder; and   compacting the powder to form the gas generant having a linear burn rate of greater than or equal to about 20 mm per second at a pressure of about 21 megapascals (MPa) and a linear burn rate pressure exponent (n) of less than or equal to about 0.35.   
     
     
         18 . The method of  claim 17 , wherein:
 the alkaline earth zirconium oxide is present at greater than or equal to about 0.1% to less than or equal to about 6% by mass of the gas generant;   the guanidine nitrate is present at greater than or equal to about 30% to less than or equal to about 60% by mass of the gas generant;   the basic copper nitrate is present at greater than or equal to about 30% to less than or equal to about 60% by mass of the gas generant; and   the gas generant is substantially free of potassium perchlorate.   
     
     
         19 . The method of  claim 17 , wherein the alkaline earth zirconium oxide is selected from the group consisting of: barium zirconate (BaZrO 3 ), calcium zirconate (CaZrO 3 ), strontium zirconate (SrZrO 3 ), and combinations thereof.