Cold combustion gas generator formulation for airbag with low combustion rate slope

Abstract

A gas generant formulation for a side impact airbag includes a primary fuel, a primary oxidant, a secondary fuel, and a secondary oxidant. The secondary fuel includes at least melamine nitrate in an amount ranging from about 1.00 wt% to about 10.00 wt%. The secondary oxidant includes at least potassium perchlorate in an amount ranging from about 1.00 wt% to about 10.00 wt%. The formulation provides a combustion rate of at least 50 mm / s at 40 MPa and a combustion rate slope equal to or less than 0.40.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Patent Application No. 17 / 886,536, filed on August 12, 2022. The entire disclosure of the above application is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a gas generating composition for an airbag, and an airbag including the gas generating composition. Background Art

[0004] This section provides background information related to the present disclosure which is not necessarily prior art.

[0005] Airbag systems have been used in vehicles for many years, and a great deal of research has been done on these systems. Generally, the goals associated with airbag system research are to improve performance, reduce the size and weight of the system, and reduce the cost of manufacturing the airbag system. More specifically, a great deal of research has been done to improve the functionality and reduce the cost of the gas generants used to inflate the airbags of the airbag system.

[0006] Optimized gas generant performance and subsequent system cost reduction can be achieved through pyrotechnic formulations that can burn at low flame temperatures with desired ballistic performance characteristics. Such desirable ballistic performance characteristics include fast burning rates and low burning rate slopes. Low flame temperatures and lower burning rate slopes allow for less required airbag cushion reinforcements and reduced wall thickness of pressure vessels (combustion chambers), thereby effectively reducing system cost and weight. However, the challenge of this approach is to reduce flame temperatures and slopes while maintaining a sufficiently high burning rate to inflate the airbag cushion within the required time.

[0007] The heat sink in the inflator is typically in the form of a metal screen assembly which also serves to filter solid combustion residues from the gas stream. In an efficient inflator design, the amount of screen assembly used will be sufficient to effectively filter the solid combustion products from the gas stream and cool the gases from the combustion flame temperature to a lower desired temperature that will cause minimal damage to the airbag. The desired combustion flame temperature for a "fast and cool" gas generant formulation for side applications is 1800K-1950K.

[0008] The prior art for side impact inflator applications is the combination of an alkali metal perchlorate co-oxidant (such as potassium perchlorate) with an alkaline copper nitrate oxidant, guanidine nitrate fuel and optional co-fuel. The burn rate achieved is a function of the amount of potassium perchlorate used. Unfortunately, the amount of potassium perchlorate used is also proportional to the combustion flame temperature. Reducing the amount of potassium perchlorate in the formulation will cool the flame temperature and ideally reduce the amount of condensable potassium chloride gas in the combustion products. Gaseous potassium chloride can pass through the filter and condense, and then form solids in the cushion itself, which makes it a challenge to meet customer restrictions on airborne particles. However, reducing the amount of potassium perchlorate to reach the target flame temperature will reduce the burn rate to a level sufficient to make it no longer useful in, for example, side impact applications. When added to the other ingredients of the formulation, additives that reduce the combustion flame temperature and have a positive impact on ballistics (which in turn makes it possible to reduce the amount of potassium perchlorate in the formulation) will be a "fast and cool" solution and an improvement in the art. Summary of the invention

[0009] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0010] According to a first aspect, the present disclosure provides a gas generant formulation for a side impact airbag, which may include a primary fuel; a primary oxidizer; a secondary fuel, which may include at least melamine nitrate in an amount ranging from about 1.00 wt % to about 10.00 wt %; a secondary oxidizer, which may include at least potassium perchlorate in an amount ranging from about 1.00 wt % to about 10.00 wt %, wherein the formulation has a burning rate of at least 50 mm / s at 40 MPa and a burning rate slope equal to or less than 0.40.

[0011] According to the first aspect, the main fuel may include at least guanidine nitrate, and the amount of the guanidine nitrate may be in the range of about 35 wt % to about 55 wt %.

[0012] According to the first aspect, the primary oxidant may include at least basic copper nitrate, and the amount of the basic copper nitrate is in a range of about 25 wt % to about 50 wt %.

[0013] According to the first aspect, the formulation may further include at least one additive in an amount of up to about 11.0 wt % configured to cool the temperature of gas produced by the formulation, improve slagging of the formulation, or act as a pressure aid for the formulation.

[0014] According to the first aspect, the formulation may include a slagging improving additive, and the slagging improving additive may include at least one of a metal oxide and / or a metal hydroxide.

[0015] According to a first aspect, the formulation may include an additive configured to act as a pressure aid, and the pressure aid may include at least one of a lubricant and / or a release agent. The lubricant may include at least one of molybdenum disulfide and graphite, and the release agent may include at least one of calcium stearate and magnesium stearate.

[0016] According to a second aspect of the present disclosure, a gas generant formulation for a side impact airbag is provided, which may include: a primary fuel comprising at least guanidine nitrate; a primary oxidant comprising at least basic copper nitrate; a secondary fuel comprising at least melamine nitrate in an amount ranging from about 5.00 wt % to about 10.00 wt %; and a secondary oxidant comprising at least potassium perchlorate in an amount ranging from about 5.00 wt % to about 10.00 wt %, wherein the combustion rate of the formulation is at least 50 mm / s at 40 MPa, and the combustion rate slope is equal to or less than 0.40.

[0017] According to the second aspect, the amount of guanidine nitrate can be in the range of about 35 wt % to about 55 wt %.

[0018] According to the second aspect, the amount of basic copper nitrate may be in the range of about 25 wt % to about 50 wt %.

[0019] According to a second aspect, the formulation may further include at least one additive in an amount of up to about 11.0 wt % configured to cool the temperature of gases generated by the formulation, improve slagging of the formulation, or act as a pressure aid for the formulation.

[0020] According to a second aspect, the formulation includes a slagging improving additive, and the slagging improving additive may include at least one of a metal oxide and a metal hydroxide.

[0021] According to a second aspect, the formulation comprises an additive configured to act as a pressure aid, the pressure aid may include at least one of a lubricant and / or a release agent, and the lubricant may include at least one of molybdenum disulfide and graphite, and the release agent may include at least one of calcium stearate and magnesium stearate.

[0022] Further areas of applicability will become apparent from the description provided herein.The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. DETAILED DESCRIPTION

[0023] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0024] The present disclosure provides a gas generating composition. Gas generating compositions (also referred to as propellants), gas generating materials, and pyrotechnic materials are used in inflators of airbag modules, which are used in vehicle occupant inflatable restraint systems. The selection of a gas generating composition or material involves various factors, including meeting current industry performance specifications, guidelines, and standards; producing safe gases or effluents; handling safety of the gas generating material; stability of the material over longer periods of time; and cost-effectiveness in manufacturing, among other considerations. Preferably, the gas generating composition is safe during handling, storage, and disposal.

[0025] Improved gas generator performance in an inflatable restraint system can be achieved in a variety of ways, many of which ultimately depend on the formulation of the gas generating composition to provide the desired properties. Ideally, the gas generating composition provides sufficient gas mass flow rate within the desired time interval to achieve the required working pulse of the inflatable device (e.g., airbag) within the inflatable restraint system. Although the temperature of the gas produced by the gas generating composition affects the amount of working gas that can be done, high gas temperatures may be undesirable because they can cause burns and related thermal damage. In addition, high gas temperatures can also potentially lead to excessive dependence or sensitivity of the gas to heat transfer and excessively rapid deflation characteristics, which may also be undesirable. Therefore, it is advantageous to minimize the flame temperature.

[0026] The desired combustion flame temperature of the "fast and cool" gas generating composition used in the side inflatable restraint system is in the range of 1800 degrees Kelvin to 1950 degrees Kelvin (i.e., 1526.85 degrees Celsius to 1676.85 degrees Celsius). Therefore, a high flame temperature can be considered to be any temperature exceeding about 1950 degrees Kelvin (1676.85 degrees Celsius) when burning. In order to mitigate the effects of high flame temperatures, the inflator may include a radiator, which may also be used as a filter or screen for the inflator. However, most of the mass of the inflator is generally attributed to the combination of the radiator, which affects the efficiency of the system and more significantly affects the weight of the inflator. In view of the above, one aspect of the present disclosure is to provide a gas generating composition for a side inflatable restraint system that can achieve high gas output at a high mass flow rate at a relatively low flame temperature (i.e., less than about 1950 degrees Kelvin). This aspect is achieved by using a gas generating composition comprising at least one primary oxidant, at least one secondary oxidant, at least one primary fuel and at least one secondary fuel. Although not required, the gas generant composition may also contain various additives.

[0027] Primary oxidant

[0028] According to the gas generating composition of the present disclosure, it includes at least one primary oxidant. Exemplary primary oxidants that can be used in the gas generating composition of the present disclosure include metal nitrates. Preferably, the at least one primary oxidant includes a basic metal nitrate. The amount of the primary oxidant may range between about 25.00 wt % and about 50.00 wt % (including the end values). Exemplary basic metal nitrates include basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, basic manganese nitrate, basic iron nitrate, basic molybdenum nitrate, basic bismuth nitrate and basic cerium nitrate. Although more than one primary oxidant can be used, it is particularly preferred that the primary oxidant includes at least basic copper nitrate.

[0029] Secondary oxidants

[0030] The gas generating composition of the present disclosure comprises at least one secondary oxidant. The at least one secondary oxidant may be present in an amount ranging between about 1.00 wt % and about 10.00 wt % (including the end values). Exemplary secondary oxidants include alkali metal and alkaline earth metal salts of perchloric acid. Specific examples of these materials suitable for use herein include ammonium perchlorate, sodium perchlorate, potassium perchlorate, magnesium perchlorate, and barium perchlorate. Although more than one secondary oxidant may be used, it is particularly preferred that the secondary oxidant includes at least potassium perchlorate.

[0031] Main fuel

[0032] The gas generating composition according to the present disclosure comprises at least one main fuel. The at least one main fuel may be present in an amount ranging between about 35.00 wt % and about 55.00 wt % (including end values). Exemplary main fuels may include nitrogen-containing organic compounds. In a specific example, the nitrogen-containing organic compound may be guanidine or a guanidine derivative. Guanidine derivatives may be selected from nitroguanidine, guanidine nitrate, aminoguanidine, aminoguanidine nitrate, biguanidine urea copper dinitrate (CuGUN) and aminoguanidine bicarbonate. Other examples of main fuels include tetrazole or tetrazole derivatives selected from aminotetrazole, bitetrazole, azobistetrazole, nitrotetrazole and nitroaminotetrazole. Although more than one main fuel may be used, it is particularly preferred that the main fuel at least includes guanidine nitrate.

[0033] Auxiliary fuel

[0034] The gas generating composition according to the present disclosure comprises at least one secondary fuel. The at least one secondary fuel may be present in an amount ranging from about 1.00 wt % to about 10.00 wt % (inclusive). Any of the above-mentioned main fuels may be used as a secondary fuel, although in a reduced amount compared to the amount of the main fuel. However, preferably, the secondary fuel comprises at least melamine nitrate.

[0035] additive

[0036] Although not required, the gas generating composition according to the present disclosure may contain at least one additive. If desired, the total amount of additives included in the gas generating composition may be up to about 11.00% by weight. Additives can be used to cool gas temperature, improve slagging, improve effluent, improve bonding, and improve powder flow. Additives for lubrication (i.e., press aids) can also be optionally added, which can allow improved powder flow during processing and pressing, and improve slagging.

[0037] Additives that may be used as coolants to reduce the temperature of the gas include materials such as basic copper carbonate or other suitable carbonates, copper glycolate, melamine copper oxalate, copper cyanurate dihydrate, and other suitable coolants.

[0038] As non-limiting examples, additives that may be used as pressure aids include lubricants and / or mold release agents such as molybdenum disulfide and graphite, metal salts of fatty acids such as calcium stearate and magnesium stearate, and / or graphite boron nitride. If used as an additive, the pressure aid may be present in the gas generating composition in an amount up to about 1% by weight.

[0039] Additives that can be used to improve slagging include metal oxides such as aluminum oxide, silicon dioxide, cerium oxide, iron oxide, zinc oxide, titanium oxide, zirconium oxide, bismuth oxide, molybdenum oxide, lanthanum oxide, e-glass, etc. Metal hydroxides (such as aluminum hydroxide) and other metal hydroxides known to those skilled in the art can also be used as additives to improve slagging. If used as an additive, the slagging generating agent can be present in the gas generating composition in an amount of up to about 10% by weight.

[0040] Although in some aspects it is preferred that the gas generating composition is substantially free of a binder, in some alternative aspects the gas generating composition may include an additive as a binder to improve crush strength without significantly compromising effluent and combustion characteristics. Exemplary additives that may be used as binders include carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, ammonium carboxymethyl cellulose, cellulose acetate, cellulose acetate butyrate, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl ethyl cellulose, fine crystalline cellulose, polyacrylamide, amine products of polyacrylamide, polyacrylic acid hydrazides, copolymers of acrylamide and metal salts of acrylic acid, copolymers of polyacrylamide and polyacrylate compounds, polyvinyl alcohol, acrylic rubber, guar gum, starch, and silicone.

[0041] As described above, the gas generating composition according to the present disclosure preferably comprises at least potassium perchlorate as a secondary oxidant and melamine nitrate as a secondary fuel. It has been found that the combined use of melamine nitrate and potassium perchlorate achieves a synergistic effect on ballistics when these materials are used together, and each of these materials is included in the gas generating composition in an amount ranging from about 1.00 wt. % to about 10.00 wt. %, including the end values. Preferably, each of these materials is included in the gas generating composition in an amount ranging from about 5.00 wt. % to about 10.00 wt. %, including the end values.

[0042] When the gas generating composition includes potassium perchlorate, the burning rate of the gas generating composition including potassium perchlorate can be a function of the amount of potassium perchlorate used. In addition, the amount of potassium perchlorate used can be proportional to the flame temperature. In other words, the burning rate and flame temperature increase with the increase of the amount of potassium perchlorate in the gas generating composition. Therefore, it can be expected that if the amount of potassium perchlorate in the gas generating composition is reduced, the flame temperature can be cooled while also reducing the amount of condensable potassium chloride gas produced as a combustion product (potassium chloride gas can pass through the filter of the inflator and condense to form solids in the cushion layer, which is generally desired to avoid in order to limit the amount of airborne particulates required by vehicle manufacturers). Unfortunately, it has been recognized that reducing the amount of potassium perchlorate in the gas generating composition will reduce the burning rate to the extent that the composition using a lower amount of potassium perchlorate cannot be used for side inflatable restraint systems. This is demonstrated by Table 1 below.

[0043]

[0044]

[0045] Table 1

[0046] Each of the above formulations was mixed and then spray dried. As can be seen in Table 1 above, when the amount of potassium perchlorate in the side aerator formulation was reduced from 12.52% to less than 7%, the slope decreased, but the formulation did not produce enough burn rate to match the baseline comparison, making the reduced amount of potassium perchlorate useless for the side aerator application.

[0047] However, as described above, when a reduced amount of potassium perchlorate as a secondary oxidant is used in combination with a reduced amount of melamine nitrate as a secondary fuel, a cold burning gas generant formulation having a low burn rate slope and a burn rate sufficient for side impact inflator applications is obtained. In this regard, as can be seen from Table 2 below, the use of potassium perchlorate as a secondary oxidant in a gas generant formulation comprising basic copper nitrate as a primary oxidant and guanidine nitrate as a primary fuel significantly increases the burn rate of the formulation, but also significantly increases the pressure sensitivity of the burn rate, as can be seen when comparing Formulation 1 and Formulation 2 in Table 2.

[0048] preparation 1 2 3 4 bCN% 46.62 30.51 49.10 36.82 Guanidine nitrate % 50.38 56.49 40.40 46.47 Potassium perchlorate% 0 10.00 0.00 8.76 Melamine Nitrate % 0 0 7.50 7.46 Slagging aid % 3.00 3.00 3.00 0.50 Rb*mm / s at 40MPa 15.81 35.55 18.36 39.96 Slope 0.37 0.54 0.39 0.40

[0049] Table 2. Effect of additives on the burning rate of bCN / guanidine nitrate formulations

[0050] Furthermore, it can be seen from Table 2 above that the addition of melamine nitrate as a secondary fuel to a gas generant formulation containing basic copper nitrate as a primary oxidant and guanidine nitrate as a primary fuel slightly increases each of the burn rate and the burn rate slope of the formulation, as can be seen when comparing Formulation 1 and Formulation 3 in Table 2. However, it can also be seen in Table 2 that when a combination of melamine nitrate and potassium perchlorate is added to a formulation containing basic copper nitrate as a primary oxidant and guanidine nitrate as a primary fuel, the burn rate of Formulation 4 is greater than that of Formulation 2. In addition, the slope achieved by Formulation 3 is maintained in Formulation 4, which shows a synergistic relationship between the use of melamine nitrate and potassium perchlorate in reduced amounts (i.e., in an amount ranging between about 1.00 wt % and about 10.00 wt %, and preferably in an amount ranging between about 5.00 wt % and about 10.00 wt %, inclusive).

[0051] It should be understood that each formulation in Table 2 was prepared as a subscale laboratory mixture and was not subsequently spray dried as in the formulations in Table 1. Nevertheless, the use of the subscale laboratory mixture is useful for relative comparisons between the formulations without potassium perchlorate and melamine nitrate (i.e., Formulation 1 in Table 2), the formulation containing each of potassium perchlorate and melamine nitrate (i.e., Formulation 4 in Table 2), and the formulation containing one of potassium perchlorate (i.e., Formulation 2 in Table 2) and melamine nitrate (i.e., Formulation 3 in Table 2).

[0052] However, when Formulation 4 in Table 2 was spray dried and compared to the baseline composition in Table 1, it can be seen that the flame temperature and slope were each reduced to levels suitable for use in a side impact inflator system as shown in Table 3 (below) without sacrificing burn rate. In formulations according to the present disclosure containing reduced amounts of potassium perchlorate and melamine nitrate, the burn rate was at least 50 mm / s at 40 MPa and the slope was less than or equal to 0.40.

[0053] preparation Baseline from Mixture 1 SD mixture 4 from Table 2 bCN% 28.47 36.73 Guanidine nitrate % 47.95 46.35 Potassium perchlorate% 12.52 8.74 Total fuel % 9.63CuGUN 7.43 Melamine Nitrate Slagging aid % 1.18 0.50 Pressure aid % 0.25 0.25 Tc(K) 2033 1950 Burning rate (at 40MPa) 62.03 54.85 Burning rate slope 0.54 0.37

[0054] Table 3 - Comparison of Spray-Dried Formulation 4 in Table 2 with the Baseline Comparative Formulation in Table 1

[0055] It will be appreciated that the amounts of the various components of Formulation 4 in Table 2 have been reduced to account for the addition of a compression aid required for the spray dried formulation.

[0056] As described above, the formulations of the present disclosure containing reduced amounts of potassium perchlorate and melamine nitrate are beneficial in terms of gas generant performance and reduce the overall cost of the system containing the formulation. In this regard, the lower flame temperature falls within the expected combustion flame temperature range of "fast and cool" gas generant formulations that can be used for side impact applications (i.e., 1800K-1950K), and the burning rate of at least 50mm / s at 40MPa and the slope of less than or equal to 0.40 allow for less required airbag cushion reinforcements and reduced wall thickness of the pressure vessel (combustion chamber), thereby effectively reducing system cost and weight. In addition, despite the lower flame temperature and burning rate slope, the burning rate remains at a sufficiently high level to inflate the airbag cushion within the required time.

[0057] The foregoing description of the embodiments has been provided for the purpose of illustration and description. It is not intended to be exhaustive or to limit the present disclosure. The individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where applicable and can be used in selected embodiments, even if not specifically shown or described. They can also be varied in a variety of ways. Such variations should not be considered as departing from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

Claims

1. A gas generant formulation for a side impact airbag, the formulation comprising: primary fuel; and Primary oxidant; Features: a secondary fuel comprising at least melamine nitrate in an amount ranging from about 1.00 wt % to about 10.00 wt %; and a secondary oxidant comprising at least potassium perchlorate in an amount ranging from about 1.00 wt % to about 10.00 wt %, The formulation has a burning rate of at least 50 mm / s at 40 MPa and a burning rate slope equal to or less than 0.

40.

2. The preparation according to claim 1, characterized in that The main fuel includes at least guanidine nitrate.

3. The preparation according to claim 2, characterized in that The amount of guanidine nitrate ranges from about 35 wt % to about 55 wt %.

4. Preparation according to one of the preceding claims, characterized in that The primary oxidant comprises at least basic copper nitrate.

5. The preparation according to claim 4, characterized in that The amount of basic copper nitrate ranges from about 25 wt % to about 50 wt %.

6. The preparation according to one of the preceding claims, further characterized in that At least one additive in an amount up to about 11.0 weight percent configured to cool the temperature of gases generated by the formulation, improve slagging of the formulation, or act as a compression aid for the formulation.

7. The preparation according to one of the preceding claims, further characterized in that The additive for improving slagging comprises at least one of metal oxides and / or metal hydroxides.

8. The preparation according to one of the preceding claims, further characterized in that A pressure aid additive, wherein the pressure aid additive includes at least one of a lubricant and / or a release agent.

9. The preparation according to claim 8, characterized in that The pressure aid additive includes at least one of a lubricant and / or a release agent, the lubricant includes at least one of molybdenum disulfide and graphite, and the release agent includes at least one of calcium stearate and magnesium stearate.

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