GAS GENERANT COMPOSITIONS COMPRISING MELAMINE OXALATE FOR USE IN AUTOMOTIVE RESTRAINT DEVICES

Abstract

A gas generant composition for passive inflatable restraint systems (e.g., airbags) for automobiles is provided that comprises a melamine oxalate compound. The gas generant may be a cool burning gas generant composition that comprises a melamine oxalate compound, a co-fuel, such as guanidine nitrate, and an oxidizer, such as basic copper nitrate. The gas generant composition has advantageous combustion properties, including a maximum flame temperature at combustion (T.sub.c) of about 1700 K (1,427 C.), a linear burn rate of about 18 mm per second at a pressure of about 10 megapascals (MPa), a gas yield of the gas generant composition of about 5.7 moles/100 cm.sup.3, and a linear burn rate pressure exponent of about 0.35.

Claims

1. A gas generant composition for an automotive inflatable restraint system comprising a melamine oxalate compound.

2. The gas generant composition of claim 1, wherein the melamine oxalate compound comprises a molar ratio of melamine to oxalic acid ranging from about 1:1 to about 2:3.

3. The gas generant composition of claim 1, wherein the melamine oxalate compound is selected from the group consisting of: melamine monoxalate, dimelamine trioxalate, and combinations thereof.

4. The gas generant composition of claim 1 having a linear burn rate of greater than or equal to about 18 mm per second at a pressure of about 10 megapascals (MPa).

5. The gas generant composition of claim 1 having a linear burn rate pressure exponent of less than or equal to about 0.35.

6. The gas generant composition of claim 1 having a maximum flame temperature at combustion (T.sub.c) of less than or equal to about 1700 K (1,427 C.).

7. The gas generant composition of claim 1 having a maximum flame temperature at combustion (T.sub.c) of greater than or equal to about 1400 K (1,127 C.) to less than or equal to about 1600 K (1,327 C.).

8. The gas generant composition of claim 1 having a gas yield of the gas generant of greater than or equal to about 5.7 moles/100 cm.sup.3.

9. A cool burning gas generant composition for an automotive inflatable restraint system comprising: a melamine oxalate compound; a co-fuel; and an oxidizer, wherein the gas generant composition has a maximum flame temperature at combustion (T.sub.c) of less than or equal to about 1700 K (1,427 C.), a linear burn rate of greater than or equal to about 18 mm per second at a pressure of about 10 megapascals (MPa), a gas yield of the gas generant composition of greater than or equal to about 5.7 moles/100 cm.sup.3, and a linear burn rate pressure exponent of less than or equal to about 0.35.

10. The cool burning gas generant composition of claim 9, wherein the melamine oxalate compound comprises a molar ratio of melamine to oxalic acid ranging from about 1:1 to about 2:3.

11. The cool burning gas generant composition of claim 9, wherein the melamine oxalate compound is selected from the group consisting of: melamine monoxalate, dimelamine trioxalate, and combinations thereof.

12. The cool burning gas generant composition of claim 9 having a maximum flame temperature at combustion (T.sub.c) of greater than or equal to about 1400 K (1,127 C.) to less than or equal to about 1600 K (1,327 C.).

13. The cool burning gas generant composition of claim 9, wherein the melamine oxalate compound is present at greater than or equal to about 5% by weight to less than or equal to about 30% by weight of the total gas generant composition.

14. The cool burning gas generant composition of claim 9, wherein the co-fuel is selected from the group consisting of: guanidine nitrate, diammonium 5,5-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diammine bitetrazole, and combinations thereof.

15. The cool burning gas generant composition of claim 9, wherein the oxidizer is selected from the group consisting of: basic copper nitrate, alkali metal or alkaline earth metal nitrates, alkali metal, alkaline earth metal, or ammonium perchlorates, metal oxides, and combinations thereof.

16. The cool burning gas generant composition of claim 9, wherein the co-fuel comprises guanidine nitrate present at greater than or equal to about 10% to less than or equal to about 50% by weight of the gas generant composition.

17. The cool burning gas generant composition of claim 9, wherein the oxidizer comprising basic copper nitrate is present at greater than or equal to about 30% to less than or equal to about 70% by weight of the gas generant composition.

18. The cool burning gas generant composition of claim 9, wherein the melamine oxalate compound is present at greater than or equal to about 5% by weight to less than or equal to about 30% by weight of the total gas generant composition, the co-fuel is present at greater than or equal to about 10% to less than or equal to about 50% by weight of the total gas generant composition; the oxidizer is present at greater than or equal to about 30% to less than or equal to about 70% by weight of the total gas generant composition; and greater than or equal to 0% to less than or equal to about 10% by weight of the total gas generant composition of one or more gas generant additives.

19. A cool burning gas generant composition for an automotive inflatable restraint system comprising: a melamine oxalate compound; guanidine nitrate; and basic copper nitrate, wherein the gas generant composition has a maximum flame temperature at combustion (T.sub.c) of less than or equal to about 1700 K (1,427 C.), a linear burn rate of greater than or equal to about 18 mm per second at a pressure of about 10 megapascals (MPa), a gas yield of the gas generant of greater than or equal to about 5.7 moles/100 cm.sup.3, and a linear burn rate pressure exponent of less than or equal to about 0.35.

Description

EXAMPLE 1

[0077] A comparison of the properties of the formulations containing a melamine oxalate compound and other cool burning co-fuels similar to melamine oxalate are shown in Table 1 below. Six gas generant mixes are prepared with the formulations specified and tested for purposes of comparison. Mixes 1 and 2 contain melamine oxalate at different concentrations. Mixes 3-6 contain alternative co-fuels that appear to provide cool burning gas generants. The slagging agent is glass fibers and the co-oxidizer is ammonium perchlorate. Flame combustion temperature (T.sub.c) K, gas yield (G.sub.n) in moles/100 g, volumetric gas yield (G.sub.v) in moles 100 cm.sup.3, mass density, linear burn rate (R.sub.b) at 21 MPa, and slope of pressure sensitivity (n) are measured.

[0078] The burning rates in Table 1 are lower than the desired burn rate of at least about 18 mm/second; however, the measured burning rates are from hand mixes, which are typically lower than burning rates obtained in the spray dry production process. Thus, the burn rates in Table 1 do not necessarily represent enhanced burn rates that will be achieved from production processes, but are provided for comparison purposes.

TABLE-US-00001 TABLE 1 Property Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6 % bCN 59.65 58.62 48.94 52.01 30.82 58.90 % GuNO.sub.3 20.15 18.18 39.56 30.49 37.18 24.85 % Co-fuel 17.70 20.70 9 15 29.50 13.75 1:1 melamine 2:3 melamine urea biuret cupric melamine oxalate oxalate oxalate oxalate oxalate cyanurate (melamine (dimelamine monoxalate) trioxylate) % Slagging 1 1 1 1 1 1 Agent % Co-oxidizer 1.5 1.5 1.5 1.5 1.5 1.5 T.sub.c K 1600 1600 1600 1600 1600 1600 G.sub.n moles/ 2.51 2.49 2.86 2.73 2.51 2.56 100 cm.sup.3 Density g/cm.sup.3 2.33 2.32 2.13 2.16 2.23 2.27 G.sub.v moles/100 5.85 5.78 6.09 5.90 5.60 5.81 cm.sup.3 R.sub.b at 10 MPa 13.82 9.69 8.72 9.15 10.71 9.77 mm/sec Slope 0.350 0.314 0.469 0.386 0.331 0.352

[0079] As shown in Table 1, melamine oxalate in Mixes 1 and 2 (having melamine monooxalate and dimelamine trioxylate co-fuels) meets various goals of high gas yield and good ballistic properties at cool combustion flame temperatures. Mix 1 (1:1 melamine: oxalate) has high burn rates and low burn rate slope. While the burning rate of Mix 2 is lower, the burn rate slope is desirably the lowest value of all those tested. For Mixes 3 and 4 having urea oxalate and biuret oxalate as the co-fuel, the pressure sensitivity/slopes are too high, while concurrently the burn rates are relatively low. For Mix 5 having cupric oxalate co-fuel, the volumetric gas yield is too low. For Mix 6 having melamine cyanurate as the co-fuel, the burning rate is acceptable, while the burn rate slope is relatively small.

EXAMPLE 2

[0080] A comparison of the properties of the formulations containing a melamine oxalate compound and other cool burning co-fuels similar to melamine oxalate are shown in Table 2 below. Four gas generant mixes are prepared with the formulations specified and tested for purposes of comparison. Mix 7 contains melamine oxalate (dimelamine trioxylate), while Mixes 8-10 contain alternative co-fuels that appear to provide cool burning gas generants. The slagging agent is glass fibers and the co-oxidizer is ammonium perchlorate. Flame combustion temperature (T.sub.c) K, gas yield (G.sub.n) in moles/100 g, volumetric gas yield (G.sub.v) in moles 100 cm.sup.3, mass density, linear burn rate (R.sub.b) at 21 MPa, and slope of pressure sensitivity (n) are measured.

[0081] The burning rate of Mix 7 in Table 1 is lower than the desired burn rate of at least about 18 mm/second; however, the measured burning rates are from hand mixes, which are typically lower than burning rates obtained in the spray dry production process. Thus, like the burn rates in Table 1, the burn rates in Table 2 do not necessarily represent enhanced burn rates that will be achieved from production processes, but are provided for comparison purposes.

TABLE-US-00002 TABLE 2 Property Mix 7 Mix 8 Mix 9 Mix 10 % bCN 55.47 50.04 63.44 53.74 % GuNO.sub.3 26.03 29.76 15.93 18.5 % Co-fuel 16 11.25 18.13 18.5 2:3 melamine urea oxalate Melamine Biuret oxalate cyanurate oxalate (dimelamine trioxylate) % Slagging Agent 1 1 1 1 % Co-oxidizer 1.5 1.5 1.5 1.5 T.sub.c K 1520 1520 1520 1520 G.sub.n moles/100 g 2.6 2.82 2.41 2.66 Density g/cm.sup.3 2.24 2.17 2.41 2.66 G.sub.v moles/100 cm.sup.3 5.83 6.12 5.81 5.88 R.sub.b at 10 MPa 13.84 11.34 9.6 13.81 mm/sec Slope 0.344 0.468 0.313 0.401

[0082] As shown in Table 2, melamine oxalate in Mix 7 (having dimelamine trioxylate co-fuel) meets various goals of high gas yield and good ballistic properties at cool combustion flame temperatures, including a high burn rate and low burn rate slope. For Mixes 8 and 10 having urea oxalate and biuret oxalate as the co-fuel, the pressure sensitivity/slopes are too high. For Mix 9 having melamine cyanurate co-fuel, the burn rate is too low.

[0083] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.