Method of forming gas generant fuel mixture

Abstract

A method of forming a fuel mixture for a gas generating composition according to various implementations comprises the step of providing a mixture of melamine and water and adding nitric acid to the mixture to form melamine nitrate. Guanidine carbonate is mixed in to form guanidine nitrate. The guanidine carbonate mixing step may be performed at room temperature for at least 10 minutes. The melamine nitrate and guanidine nitrate form a solid precipitate fuel mixture which is filtered and rinsed with water. The rinsed fuel mixture is then dried. The drying step may be performed at a temperature in the range of 100° C. to 110° C. The nitric acid may be added as an aqueous solution having a molarity of 0.1 to 0.25. Also disclosed is a gas generating composition for use in airbag gas generators comprising the melamine nitrate and guanidine nitrate fuel mixture.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 387,551, filed on Dec. 15, 2022, the entire contents of which are incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to safety devices for passenger vehicles. In particular, the disclosure relates to a method of forming a gas generant fuel mixture for use in airbag gas generators. Passenger vehicles may include, for example, automobiles, boats, trains, aircrafts, and spacecrafts.BACKGROUND

[0003] Airbag systems have been widely adopted for improving the safety of passengers in vehicles, such as automobiles. In these systems, a gas generator is operated by ignition signals from a crash sensor detecting a collision and inflates an airbag between a passenger and a portion of the automobile. The gas generator is required to produce a sufficient amount of gas to inflate the airbag in a very short time. Typical gas generating compositions used to generate gas in current gas generators contain, at least, an oxidizer and a fuel. The particular constituents used in a given composition, and the amount of these constituents, greatly affects the properties (e.g., ignition rate, burn rate, heat, sensitivity, etc.), cost, and suitability of a composition for inflating an airbag.

[0004] One example of a gas generating composition for use in airbags can be found in U.S. Pat. No. 10,358,393 granted to the applicant of the present application. Example fuels for use in such gas generating compositions include melamine nitrate and guanidine nitrate. Melamine nitrate and guanidine nitrate can be mixed with at least one oxidizer and optional additives to form the gas generating composition. However, each fuel is typically manufactured separately before being added to the gas generating composition, leading to higher cost and complexity. Also, producing melamine nitrate results in a high amount of waste acid which is difficult to properly manage from a safety and environmental standpoint. Therefore, an improved process for producing a fuel mixture of melamine nitrate and guanidine nitrate would be cost efficient and safer in many respects. Correspondingly, a gas generating composition using such a fuel mixture would also be more cost efficient and beneficial.SUMMARY

[0005] Various implementations include a method of forming a fuel mixture for a gas generating composition. The method comprises the steps of (a) providing a mixture of melamine and water; (b) adding nitric acid to the mixture in excess two molar equivalents relative to the melamine to form melamine nitrate; (c) mixing guanidine carbonate into the water, nitric acid, and melamine nitrate mixture to form guanidine nitrate; (d) filtering out the melamine nitrate and guanidine nitrate; (e) rinsing the melamine nitrate and guanidine nitrate filtered in step (d) with water; and (f) drying the rinsed melamine nitrate and guanidine nitrate from step (e). The mixing in step (c) is performed at room temperature for at least 10 minutes and the drying in step (f) is performed at a temperature in the range of 100° C. to 110° C. The nitric acid can be added as an aqueous solution having a molarity of 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3. In other implementations, a fuel mixture is made by the method disclosed above. In other implementations, a gas generator comprises a gas generating composition comprising the fuel mixture made by the method disclosed above.

[0006] In other implementations, a method of forming a gas generating composition comprises the steps of (a) providing a mixture of melamine and water; (b) adding nitric acid to the mixture in excess of the two molar equivalents relative to the melamine to form melamine nitrate; (c) mixing guanidine carbonate into the water, nitric acid, and melamine nitrate mixture to form guanidine nitrate; (d) filtering out the melamine nitrate and guanidine nitrate; (e) rinsing the melamine nitrate and guanidine nitrate filtered in step (d) with water; (f) drying the rinsed melamine nitrate and guanidine nitrate from step (e); and (g) mixing the dried melamine nitrate and guanidine nitrate from step (f) with an oxidizer. The mixing in step (c) is performed at room temperature for at least 10 minutes and the drying in step (f) is performed at a temperature in the range of 100° C. to 110° C. The nitric acid can be added as an aqueous solution having a molarity of 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3. In some implementations, the oxidizer is basic copper nitrate. In other implementations, a gas generating composition is made by the method disclosed above. In other implementations, a gas generator comprises the gas generating composition made by the method disclosed above.

[0007] In other implementations, a method of forming a fuel mixture for a gas generating composition comprises the steps of (a) mixing melamine, guanidine carbonate, and nitric acid in water to form melamine nitrate and guanidine nitrate; (b) filtering out the melamine nitrate and guanidine nitrate formed during step (a); (c) rinsing the melamine nitrate and guanidine nitrate filtered in step (b) with water; and (d) drying the melamine nitrate and guanidine nitrate from step (c). The mixing in step (a) is performed at room temperature for at least 10 minutes and the drying in step (d) is performed at a temperature in the range of 100° C. to 110° C. The nitric acid can be added as an aqueous solution having a molarity from 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3. In other implementations, a fuel mixture is made by the method disclosed above. In other implementations, a gas generator comprises a gas generating composition comprising the fuel mixture made by the method disclosed above.

[0008] In other implementations, a method of forming a gas generating composition comprises the steps of (a) mixing melamine, guanidine carbonate, and nitric acid in water to form melamine nitrate and guanidine nitrate; (b) filtering out the melamine nitrate and guanidine nitrate formed during step (a); (c) rinsing the melamine nitrate and guanidine nitrate filtered in step (b) with water; (d) drying the melamine nitrate and guanidine nitrate from step (c); and (e) mixing the dried melamine nitrate and guanidine nitrate from step (d) with an oxidizer. The mixing in step (a) is performed at room temperature for at least 10 minutes and the drying in step (d) is performed at a temperature in the range of 100° C. to 110° C. The nitric acid can be added as an aqueous solution having a molarity from 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3. In some implementations, the oxidizer is basic copper nitrate. In other implementations, a gas generating composition is made by the method disclosed above. In other implementations, a gas generator comprises the gas generating composition made by the method disclosed above.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings are merely exemplary to illustrate steps, structure, and certain features that can be used singularly or in combination with other features. The disclosure should not be limited to the implementations shown.

[0010] FIG. 1 is a cross-sectional view of an airbag gas generator for use with a gas generating composition formed by the methods disclosed herein.

[0011] FIG. 2 is a block diagram of method steps for forming a fuel mixture for the gas generating composition according to one implementation.

[0012] FIG. 3 is a block diagram of method steps for forming the gas generating composition using the fuel mixture formed by the method steps of FIG. 2.

[0013] FIG. 4 is a block diagram of method steps for forming a fuel mixture for the gas generating composition according to another implementation.

[0014] FIG. 5 is a block diagram of method steps for forming the gas generating composition using the fuel mixture formed by the method steps of FIG. 4.

[0015] FIG. 6 is an FTIR plot of a fuel mixture formed by to the method steps of FIG. 2 and a comparative fuel mixture.DETAILED DESCRIPTIONGas Generators

[0016] As shown in FIG. 1, an exemplary gas generator 10 comprises a single ignition chamber comprising a main gas generant 14. The gas generator 10 also comprises a booster chamber comprising a booster gas generant 12. When the gas generator 10 is deployed, booster gas generant 12 is ignited and thus causes ignition of the main gas generant 14, therefore providing inflation gas to a connected airbag. The fuel mixtures and gas generating compositions described herein may be used for either the booster gas generant 12 or the main gas generant 14, or both. Preferably, the fuel mixtures and gas generating compositions described herein are used for the main gas generant 14.Fuel Mixture

[0017] According to one implementation, a fuel mixture for a gas generating composition can be produced by the method 200 as shown in FIG. 2. In a first step 201, a mixture of melamine and water is provided. In step 202, nitric acid is added to the water in excess of two molar equivalents relative to the melamine to form melamine nitrate. At step 203, guanidine carbonate is mixed into the water, nitric acid, and melamine nitrate mixture so that remaining nitric acid reacts with the guanidine carbonate to form guanidine nitrate and carbon dioxide. The guanidine carbonate mixing step is performed for at least 10 minutes at room temperature. As used herein, room temperature is used to describe temperatures in the range of 15° C. to 25° C., inclusive of the end values of the range. The nitric acid can be added as an aqueous solution having a molarity from 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3.

[0018] Both melamine nitrate and guanidine nitrate will form a solid precipitate fuel mixture which can be filtered out in step 204. Filtering can be performed with standard laboratory or production scale filtering systems, such as filter paper or fine mesh sieve screens used in a vibratory sieve machine. In step 205, the filtered melamine nitrate and guanidine nitrate fuel mixture is rinsed with water. Finally, in step 206, the rinsed melamine nitrate and guanidine nitrate fuel mixture is dried at a temperature in the range of 100° C. to 110° C., inclusive of the end values of the range. This method results in a fuel mixture of melamine nitrate and guanidine nitrate ready for use in gas generating compositions for airbag gas generators. This method results in significantly less cost and the elimination of hazardous acid waste byproducts. By way of nonlimiting example, the reactions may be represented by the chemical equations below:

[0019] According to another implementation, a fuel mixture for a gas generating composition can be produced by the method 400 as shown in FIG. 4. In a first step 401, melamine, guanidine carbonate, and nitric acid are mixed in water so that the melamine and the guanidine carbonate react with the nitric acid to form melamine nitrate and guanidine nitrate, respectively. The mixing is performed for at least 10 minutes at room temperature. As used herein, room temperature is used to describe temperatures in the range of 15° C. to 25° C., inclusive of the end values of the range. The nitric acid can be added as an aqueous solution having a molarity from 0.1 to 0.25 In some implementations the molar ratio of melamine to guanidine carbonate is about 1:1 . . . . In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3.

[0020] Both melamine nitrate and guanidine nitrate will form a solid precipitate fuel mixture which can be filtered out in step 402. Filtering can be performed with standard laboratory or production scale filtering systems, such as filter paper or fine mesh sieve screens used in a vibratory sieve machine. In step 403, the filtered melamine nitrate and guanidine nitrate fuel mixture is rinsed with water. Finally, in step 404, the rinsed melamine nitrate and guanidine nitrate fuel mixture is dried at a temperature in the range of 100° C. to 110° C., inclusive of the end values of the range. This method results in a fuel mixture of melamine nitrate and guanidine nitrate ready for use in gas generating compositions for airbag gas generators. This method results in significantly less cost and the elimination of hazardous acid waste byproducts. By way of nonlimiting example, the reactions may be represented by the chemical equation below:Gas Generating Compositions

[0021] According to another implementation, a gas generating composition can be produced by the method 300 as shown in FIG. 3. In a first step 301, a mixture of melamine and water is provided. In step 302, nitric acid is added to the water in excess of two molar equivalents relative to the melamine to form melamine nitrate. At step 303, guanidine carbonate is mixed into the water, nitric acid, and melamine nitrate mixture so that remaining nitric acid reacts with the guanidine carbonate to form guanidine nitrate and carbon dioxide. The mixing is performed for at least 10 minutes at room temperature. As used herein, room temperature is used to describe temperatures in the range of 15° C. to 25° C., inclusive of the end values of the range. The nitric acid can be added as an aqueous solution having a molarity of 0.1 to 0.25. In some implementations the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3.

[0022] Both melamine nitrate and guanidine nitrate will form a solid precipitate fuel mixture which can be filtered out in step 304. Filtering can be performed with standard laboratory or production scale filtering systems, such as filter paper or fine mesh sieve screens used in a vibratory sieve machine. In step 305, the filtered melamine nitrate and guanidine nitrate fuel mixture is rinsed with water. In step 306, the rinsed melamine nitrate and guanidine nitrate fuel mixture is dried at a temperature in the range of 100° C. to 110° C., inclusive of the end values of the range. The resulting fuel mixture of melamine nitrate and guanidine nitrate is then mixed with an oxidizer in step 307 to form the gas generating composition. The gas generating composition at this point is typically in the form of a powder mixture. This powder may then be pressed into tablet or wafer form in step 308, as required by the needs of the particular gas generator.

[0023] According to another implementation, a gas generating composition can be produced by the method 500 as shown in FIG. 5. In a first step 501, melamine, guanidine carbonate, and nitric acid are mixed in water so that the melamine and the guanidine carbonate react with the nitric acid to form melamine nitrate and guanidine nitrate, respectively. The mixing is performed for at least 10 minutes at room temperature. As used herein, room temperature is used to describe temperatures in the range of 15° C. to 25° C., inclusive of the end values of the range. The nitric acid can be added as an aqueous solution having a molarity of 0.1 to 0.25. In some implementations the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3.

[0024] Both melamine nitrate and guanidine nitrate will form a solid precipitate fuel mixture which can be filtered out in step 502. Filtering can be performed with standard laboratory or production scale filtering systems, such as filter paper or fine mesh sieve screens used in a vibratory sieve machine. In step 503, the filtered melamine nitrate and guanidine nitrate fuel mixture is rinsed with water. In step 504, the rinsed melamine nitrate and guanidine nitrate fuel mixture is dried at a temperature in the range of 100° C. to 110° C., inclusive of the end values of the range. The resulting fuel mixture of melamine nitrate and guanidine nitrate is then mixed with an oxidizer in step 505 to form the gas generating composition. The gas generating composition at this point is typically in the form of a powder mixture. This powder may then be pressed into tablet or wafer form in step 506, as required by the needs of the particular gas generator.

[0025] In some implementations of the disclosed gas generating compositions, the oxidizer is selected from the group consisting of metal perchlorates, nonmetal perchlorates, metal nitrates, basic metal nitrates, nonmetal nitrates, and combinations thereof. In some implementations, the metal nitrate is potassium nitrate. In other implementations, the metal nitrate is a basic metal nitrate. A suitable basic metal nitrate can be chosen from a basic copper nitrate, a basic cobalt nitrate, a basic zinc nitrate, a basic manganese nitrate, a basic iron nitrate, a basic molybdenum nitrate, a basic bismuth nitrate, and a basic cerium nitrate. Specific examples of these suitable metal nitrates are Cu2(NO3)(OH)3, Cu3(NO3)(OH)5·2H2O, Co2(NO3)(OH)3, Zn2(NO3)(OH)3, Mn(NO3)(OH)2, Fe4(NO3)(OH)11·2H2O, MoO2(NO3)2, Bi(NO3)(OH)2 and Ce(NO3)3(OH)·3H2O. Among these, basic copper nitrate is preferable.EXAMPLES

[0026] Example 1: A fuel mixture was prepared according to method 200 disclosed herein with respect to FIG. 2, with a >90% yield by mass. Afterwards, the fuel mixture was analyzed using an FTIR instrument and compared to a comparative fuel mixture which was also analyzed using the FTIR instrument. The comparative fuel mixture was created by mixing separately produced melamine nitrate and guanidine nitrate in water and then drying the mixture overnight. As is shown in FIG. 6, the FTIR absorbance profile of the fuel mixture prepared according to method 200 indicated the formation of melamine nitrate and guanidine nitrate, confirming the viability of method 200 to produce a high-quality fuel mixture of melamine nitrate and guanidine nitrate at low cost and with limited acid waste byproducts.

[0027] A number of implementations have been described. The description in the present disclosure has been presented for purposes of illustration but is not intended to be exhaustive or limited to the implementations disclosed. It will be understood that various modifications and variations will be apparent to those of ordinary skill in the art and may be made without departing from the spirit and scope of the claims. Accordingly, other implementations are within the scope of the following claims. The implementations described were chosen in order to best explain the principles of the fuel mixture and gas generating composition and their practical application, and to enable others of ordinary skill in the art to understand the fuel mixture and gas generating composition for various implementations with various modifications as are suited to the particular use contemplated.

[0028] The terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,”“an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated steps, features, operations, elements, and / or components, but do not preclude the presence or addition of one or more other steps, features, operations, elements, components, and / or groups thereof.

Examples

examples

[0026]Example 1: A fuel mixture was prepared according to method 200 disclosed herein with respect to FIG. 2, with a >90% yield by mass. Afterwards, the fuel mixture was analyzed using an FTIR instrument and compared to a comparative fuel mixture which was also analyzed using the FTIR instrument. The comparative fuel mixture was created by mixing separately produced melamine nitrate and guanidine nitrate in water and then drying the mixture overnight. As is shown in FIG. 6, the FTIR absorbance profile of the fuel mixture prepared according to method 200 indicated the formation of melamine nitrate and guanidine nitrate, confirming the viability of method 200 to produce a high-quality fuel mixture of melamine nitrate and guanidine nitrate at low cost and with limited acid waste byproducts.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 387,551, filed on Dec. 15, 2022, the entire contents of which are incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to safety devices for passenger vehicles. In particular, the disclosure relates to a method of forming a gas generant fuel mixture for use in airbag gas generators. Passenger vehicles may include, for example, automobiles, boats, trains, aircrafts, and spacecrafts.BACKGROUND

[0003] Airbag systems have been widely adopted for improving the safety of passengers in vehicles, such as automobiles. In these systems, a gas generator is operated by ignition signals from a crash sensor detecting a collision and inflates an airbag between a passenger and a portion of the automobile. The gas generator is required to produce a sufficient amount of gas to inflate the airbag in a very short time. Typical gas generating compositions used to generate gas in current gas generators contain, at least, an oxidizer and a fuel. The particular constituents used in a given composition, and the amount of these constituents, greatly affects the properties (e.g., ignition rate, burn rate, heat, sensitivity, etc.), cost, and suitability of a composition for inflating an airbag.

[0004] One example of a gas generating composition for use in airbags can be found in U.S. Pat. No. 10,358,393 granted to the applicant of the present application. Example fuels for use in such gas generating compositions include melamine nitrate and guanidine nitrate. Melamine nitrate and guanidine nitrate can be mixed with at least one oxidizer and optional additives to form the gas generating composition. However, each fuel is typically manufactured separately before being added to the gas generating composition, leading to higher cost and complexity. Also, producing melamine nitrate results in a high amount of waste acid which is difficult to properly manage from a safety and environmental standpoint. Therefore, an improved process for producing a fuel mixture of melamine nitrate and guanidine nitrate would be cost efficient and safer in many respects. Correspondingly, a gas generating composition using such a fuel mixture would also be more cost efficient and beneficial.SUMMARY

[0005] Various implementations include a method of forming a fuel mixture for a gas generating composition. The method comprises the steps of (a) providing a mixture of melamine and water; (b) adding nitric acid to the mixture in excess two molar equivalents relative to the melamine to form melamine nitrate; (c) mixing guanidine carbonate into the water, nitric acid, and melamine nitrate mixture to form guanidine nitrate; (d) filtering out the melamine nitrate and guanidine nitrate; (e) rinsing the melamine nitrate and guanidine nitrate filtered in step (d) with water; and (f) drying the rinsed melamine nitrate and guanidine nitrate from step (e). The mixing in step (c) is performed at room temperature for at least 10 minutes and the drying in step (f) is performed at a temperature in the range of 100° C. to 110° C. The nitric acid can be added as an aqueous solution having a molarity of 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3. In other implementations, a fuel mixture is made by the method disclosed above. In other implementations, a gas generator comprises a gas generating composition comprising the fuel mixture made by the method disclosed above.

[0006] In other implementations, a method of forming a gas generating composition comprises the steps of (a) providing a mixture of melamine and water; (b) adding nitric acid to the mixture in excess of the two molar equivalents relative to the melamine to form melamine nitrate; (c) mixing guanidine carbonate into the water, nitric acid, and melamine nitrate mixture to form guanidine nitrate; (d) filtering out the melamine nitrate and guanidine nitrate; (e) rinsing the melamine nitrate and guanidine nitrate filtered in step (d) with water; (f) drying the rinsed melamine nitrate and guanidine nitrate from step (e); and (g) mixing the dried melamine nitrate and guanidine nitrate from step (f) with an oxidizer. The mixing in step (c) is performed at room temperature for at least 10 minutes and the drying in step (f) is performed at a temperature in the range of 100° C. to 110° C. The nitric acid can be added as an aqueous solution having a molarity of 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3. In some implementations, the oxidizer is basic copper nitrate. In other implementations, a gas generating composition is made by the method disclosed above. In other implementations, a gas generator comprises the gas generating composition made by the method disclosed above.

[0007] In other implementations, a method of forming a fuel mixture for a gas generating composition comprises the steps of (a) mixing melamine, guanidine carbonate, and nitric acid in water to form melamine nitrate and guanidine nitrate; (b) filtering out the melamine nitrate and guanidine nitrate formed during step (a); (c) rinsing the melamine nitrate and guanidine nitrate filtered in step (b) with water; and (d) drying the melamine nitrate and guanidine nitrate from step (c). The mixing in step (a) is performed at room temperature for at least 10 minutes and the drying in step (d) is performed at a temperature in the range of 100° C. to 110° C. The nitric acid can be added as an aqueous solution having a molarity from 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3. In other implementations, a fuel mixture is made by the method disclosed above. In other implementations, a gas generator comprises a gas generating composition comprising the fuel mixture made by the method disclosed above.

[0008] In other implementations, a method of forming a gas generating composition comprises the steps of (a) mixing melamine, guanidine carbonate, and nitric acid in water to form melamine nitrate and guanidine nitrate; (b) filtering out the melamine nitrate and guanidine nitrate formed during step (a); (c) rinsing the melamine nitrate and guanidine nitrate filtered in step (b) with water; (d) drying the melamine nitrate and guanidine nitrate from step (c); and (e) mixing the dried melamine nitrate and guanidine nitrate from step (d) with an oxidizer. The mixing in step (a) is performed at room temperature for at least 10 minutes and the drying in step (d) is performed at a temperature in the range of 100° C. to 110° C. The nitric acid can be added as an aqueous solution having a molarity from 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3. In some implementations, the oxidizer is basic copper nitrate. In other implementations, a gas generating composition is made by the method disclosed above. In other implementations, a gas generator comprises the gas generating composition made by the method disclosed above.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings are merely exemplary to illustrate steps, structure, and certain features that can be used singularly or in combination with other features. The disclosure should not be limited to the implementations shown.

[0010] FIG. 1 is a cross-sectional view of an airbag gas generator for use with a gas generating composition formed by the methods disclosed herein.

[0011] FIG. 2 is a block diagram of method steps for forming a fuel mixture for the gas generating composition according to one implementation.

[0012] FIG. 3 is a block diagram of method steps for forming the gas generating composition using the fuel mixture formed by the method steps of FIG. 2.

[0013] FIG. 4 is a block diagram of method steps for forming a fuel mixture for the gas generating composition according to another implementation.

[0014] FIG. 5 is a block diagram of method steps for forming the gas generating composition using the fuel mixture formed by the method steps of FIG. 4.

[0015] FIG. 6 is an FTIR plot of a fuel mixture formed by to the method steps of FIG. 2 and a comparative fuel mixture.DETAILED DESCRIPTIONGas Generators

[0016] As shown in FIG. 1, an exemplary gas generator 10 comprises a single ignition chamber comprising a main gas generant 14. The gas generator 10 also comprises a booster chamber comprising a booster gas generant 12. When the gas generator 10 is deployed, booster gas generant 12 is ignited and thus causes ignition of the main gas generant 14, therefore providing inflation gas to a connected airbag. The fuel mixtures and gas generating compositions described herein may be used for either the booster gas generant 12 or the main gas generant 14, or both. Preferably, the fuel mixtures and gas generating compositions described herein are used for the main gas generant 14.Fuel Mixture

[0017] According to one implementation, a fuel mixture for a gas generating composition can be produced by the method 200 as shown in FIG. 2. In a first step 201, a mixture of melamine and water is provided. In step 202, nitric acid is added to the water in excess of two molar equivalents relative to the melamine to form melamine nitrate. At step 203, guanidine carbonate is mixed into the water, nitric acid, and melamine nitrate mixture so that remaining nitric acid reacts with the guanidine carbonate to form guanidine nitrate and carbon dioxide. The guanidine carbonate mixing step is performed for at least 10 minutes at room temperature. As used herein, room temperature is used to describe temperatures in the range of 15° C. to 25° C., inclusive of the end values of the range. The nitric acid can be added as an aqueous solution having a molarity from 0.1 to 0.25. In some implementations, the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3.

[0018] Both melamine nitrate and guanidine nitrate will form a solid precipitate fuel mixture which can be filtered out in step 204. Filtering can be performed with standard laboratory or production scale filtering systems, such as filter paper or fine mesh sieve screens used in a vibratory sieve machine. In step 205, the filtered melamine nitrate and guanidine nitrate fuel mixture is rinsed with water. Finally, in step 206, the rinsed melamine nitrate and guanidine nitrate fuel mixture is dried at a temperature in the range of 100° C. to 110° C., inclusive of the end values of the range. This method results in a fuel mixture of melamine nitrate and guanidine nitrate ready for use in gas generating compositions for airbag gas generators. This method results in significantly less cost and the elimination of hazardous acid waste byproducts. By way of nonlimiting example, the reactions may be represented by the chemical equations below:

[0019] According to another implementation, a fuel mixture for a gas generating composition can be produced by the method 400 as shown in FIG. 4. In a first step 401, melamine, guanidine carbonate, and nitric acid are mixed in water so that the melamine and the guanidine carbonate react with the nitric acid to form melamine nitrate and guanidine nitrate, respectively. The mixing is performed for at least 10 minutes at room temperature. As used herein, room temperature is used to describe temperatures in the range of 15° C. to 25° C., inclusive of the end values of the range. The nitric acid can be added as an aqueous solution having a molarity from 0.1 to 0.25 In some implementations the molar ratio of melamine to guanidine carbonate is about 1:1 . . . . In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3.

[0020] Both melamine nitrate and guanidine nitrate will form a solid precipitate fuel mixture which can be filtered out in step 402. Filtering can be performed with standard laboratory or production scale filtering systems, such as filter paper or fine mesh sieve screens used in a vibratory sieve machine. In step 403, the filtered melamine nitrate and guanidine nitrate fuel mixture is rinsed with water. Finally, in step 404, the rinsed melamine nitrate and guanidine nitrate fuel mixture is dried at a temperature in the range of 100° C. to 110° C., inclusive of the end values of the range. This method results in a fuel mixture of melamine nitrate and guanidine nitrate ready for use in gas generating compositions for airbag gas generators. This method results in significantly less cost and the elimination of hazardous acid waste byproducts. By way of nonlimiting example, the reactions may be represented by the chemical equation below:Gas Generating Compositions

[0021] According to another implementation, a gas generating composition can be produced by the method 300 as shown in FIG. 3. In a first step 301, a mixture of melamine and water is provided. In step 302, nitric acid is added to the water in excess of two molar equivalents relative to the melamine to form melamine nitrate. At step 303, guanidine carbonate is mixed into the water, nitric acid, and melamine nitrate mixture so that remaining nitric acid reacts with the guanidine carbonate to form guanidine nitrate and carbon dioxide. The mixing is performed for at least 10 minutes at room temperature. As used herein, room temperature is used to describe temperatures in the range of 15° C. to 25° C., inclusive of the end values of the range. The nitric acid can be added as an aqueous solution having a molarity of 0.1 to 0.25. In some implementations the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3.

[0022] Both melamine nitrate and guanidine nitrate will form a solid precipitate fuel mixture which can be filtered out in step 304. Filtering can be performed with standard laboratory or production scale filtering systems, such as filter paper or fine mesh sieve screens used in a vibratory sieve machine. In step 305, the filtered melamine nitrate and guanidine nitrate fuel mixture is rinsed with water. In step 306, the rinsed melamine nitrate and guanidine nitrate fuel mixture is dried at a temperature in the range of 100° C. to 110° C., inclusive of the end values of the range. The resulting fuel mixture of melamine nitrate and guanidine nitrate is then mixed with an oxidizer in step 307 to form the gas generating composition. The gas generating composition at this point is typically in the form of a powder mixture. This powder may then be pressed into tablet or wafer form in step 308, as required by the needs of the particular gas generator.

[0023] According to another implementation, a gas generating composition can be produced by the method 500 as shown in FIG. 5. In a first step 501, melamine, guanidine carbonate, and nitric acid are mixed in water so that the melamine and the guanidine carbonate react with the nitric acid to form melamine nitrate and guanidine nitrate, respectively. The mixing is performed for at least 10 minutes at room temperature. As used herein, room temperature is used to describe temperatures in the range of 15° C. to 25° C., inclusive of the end values of the range. The nitric acid can be added as an aqueous solution having a molarity of 0.1 to 0.25. In some implementations the molar ratio of melamine to guanidine carbonate is about 1:1. In some implementations, 2-4 molar equivalents of nitric acid are added. In some implementations, 3 molar equivalents of nitric acid are added. In some implementations, the molar ratio of melamine:guanidine carbonate:nitric acid is 1:1:3.

[0024] Both melamine nitrate and guanidine nitrate will form a solid precipitate fuel mixture which can be filtered out in step 502. Filtering can be performed with standard laboratory or production scale filtering systems, such as filter paper or fine mesh sieve screens used in a vibratory sieve machine. In step 503, the filtered melamine nitrate and guanidine nitrate fuel mixture is rinsed with water. In step 504, the rinsed melamine nitrate and guanidine nitrate fuel mixture is dried at a temperature in the range of 100° C. to 110° C., inclusive of the end values of the range. The resulting fuel mixture of melamine nitrate and guanidine nitrate is then mixed with an oxidizer in step 505 to form the gas generating composition. The gas generating composition at this point is typically in the form of a powder mixture. This powder may then be pressed into tablet or wafer form in step 506, as required by the needs of the particular gas generator.

[0025] In some implementations of the disclosed gas generating compositions, the oxidizer is selected from the group consisting of metal perchlorates, nonmetal perchlorates, metal nitrates, basic metal nitrates, nonmetal nitrates, and combinations thereof. In some implementations, the metal nitrate is potassium nitrate. In other implementations, the metal nitrate is a basic metal nitrate. A suitable basic metal nitrate can be chosen from a basic copper nitrate, a basic cobalt nitrate, a basic zinc nitrate, a basic manganese nitrate, a basic iron nitrate, a basic molybdenum nitrate, a basic bismuth nitrate, and a basic cerium nitrate. Specific examples of these suitable metal nitrates are Cu2(NO3)(OH)3, Cu3(NO3)(OH)5·2H2O, Co2(NO3)(OH)3, Zn2(NO3)(OH)3, Mn(NO3)(OH)2, Fe4(NO3)(OH)11·2H2O, MoO2(NO3)2, Bi(NO3)(OH)2 and Ce(NO3)3(OH)·3H2O. Among these, basic copper nitrate is preferable.EXAMPLES

[0026] Example 1: A fuel mixture was prepared according to method 200 disclosed herein with respect to FIG. 2, with a >90% yield by mass. Afterwards, the fuel mixture was analyzed using an FTIR instrument and compared to a comparative fuel mixture which was also analyzed using the FTIR instrument. The comparative fuel mixture was created by mixing separately produced melamine nitrate and guanidine nitrate in water and then drying the mixture overnight. As is shown in FIG. 6, the FTIR absorbance profile of the fuel mixture prepared according to method 200 indicated the formation of melamine nitrate and guanidine nitrate, confirming the viability of method 200 to produce a high-quality fuel mixture of melamine nitrate and guanidine nitrate at low cost and with limited acid waste byproducts.

[0027] A number of implementations have been described. The description in the present disclosure has been presented for purposes of illustration but is not intended to be exhaustive or limited to the implementations disclosed. It will be understood that various modifications and variations will be apparent to those of ordinary skill in the art and may be made without departing from the spirit and scope of the claims. Accordingly, other implementations are within the scope of the following claims. The implementations described were chosen in order to best explain the principles of the fuel mixture and gas generating composition and their practical application, and to enable others of ordinary skill in the art to understand the fuel mixture and gas generating composition for various implementations with various modifications as are suited to the particular use contemplated.

[0028] The terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,”“an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated steps, features, operations, elements, and / or components, but do not preclude the presence or addition of one or more other steps, features, operations, elements, components, and / or groups thereof.

Examples

examples

[0026]Example 1: A fuel mixture was prepared according to method 200 disclosed herein with respect to FIG. 2, with a >90% yield by mass. Afterwards, the fuel mixture was analyzed using an FTIR instrument and compared to a comparative fuel mixture which was also analyzed using the FTIR instrument. The comparative fuel mixture was created by mixing separately produced melamine nitrate and guanidine nitrate in water and then drying the mixture overnight. As is shown in FIG. 6, the FTIR absorbance profile of the fuel mixture prepared according to method 200 indicated the formation of melamine nitrate and guanidine nitrate, confirming the viability of method 200 to produce a high-quality fuel mixture of melamine nitrate and guanidine nitrate at low cost and with limited acid waste byproducts.

Claims

1. A method of forming a fuel mixture for a gas generating composition comprising the steps of:(a) providing a mixture of melamine and water;(b) adding nitric acid to the mixture in excess of two molar equivalents relative to the melamine to form melamine nitrate;(c) mixing guanidine carbonate into the water, nitric acid, and melamine nitrate mixture to form guanidine nitrate;(d) filtering out the melamine nitrate and guanidine nitrate;(e) rinsing the melamine nitrate and guanidine nitrate filtered in step (d) with water; and(f) drying the rinsed melamine nitrate and guanidine nitrate from step (e).

2. The method of claim 1, wherein the mixing of step (c) is performed at room temperature for at least 10 minutes.

3. The method of claim 1, wherein the drying of step (f) is performed at a temperature in the range of 100° C. to 110° C.

4. The method of claim 1, wherein the nitric acid is added as an aqueous solution having a molarity of 0.1 to 0.25.

5. The method of claim 1, further comprising(g) mixing the dried melamine nitrate and guanidine nitrate from step (f) with an oxidizer.

6. The method of claim 5, wherein the mixing of step (c) is performed at room temperature for at least 10 minutes.

7. The method of claim 5, wherein the drying of step (f) is performed at a temperature in the range of 100° C. to 110° C.

8. The method of claim 5, wherein the nitric acid is added as an aqueous solution having a molarity of 0.1 to 0.25.

9. The method of claim 5, wherein the oxidizer is selected from the group consisting of metal perchlorates, nonmetal perchlorates, metal nitrates, basic metal nitrates, nonmetal nitrates, and combinations thereof.

10. The method of claim 9, wherein the oxidizer is basic copper nitrate.

11. The method of claim 5, further comprising the step of pressing the gas generating composition into tablets or wafers.

12. A gas generator for use with an airbag comprising the tablets or wafers of claim 11.

13. A fuel mixture for a gas generating composition made by a method comprising the steps of:(a) providing a mixture of melamine and water;(b) adding nitric acid to the mixture in excess of two molar equivalents relative to the melamine to form melamine nitrate;(c) mixing guanidine carbonate into the water, nitric acid, and melamine nitrate mixture to form guanidine nitrate;(d) filtering out the melamine nitrate and guanidine nitrate;(e) rinsing the melamine nitrate and guanidine nitrate filtered in step (d) with water; and(f) drying the rinsed melamine nitrate and guanidine nitrate from step (e).

14. The fuel mixture of claim 13, wherein the mixing of step (c) is performed at room temperature for at least 10 minutes.

15. The fuel mixture of claim 13, wherein the drying of step (f) is performed at a temperature in the range of 100° C. to 110° C.

16. The fuel mixture of claim 13, wherein the nitric acid is added as an aqueous solution having a molarity of 0.1 to 0.25.

17. The fuel mixture for a gas generating composition of claim 13, wherein the method further comprises the step:(g) mixing the dried melamine nitrate and guanidine nitrate from step (f) with an oxidizer.18-40. (canceled)41. A gas generating composition made by a method comprising the steps of:(a) mixing melamine, guanidine carbonate, and nitric acid in water to form melamine nitrate and guanidine nitrate;(b) filtering out the melamine nitrate and guanidine nitrate formed during step (a);(c) rinsing the melamine nitrate and guanidine nitrate filtered in step (b) with water; and(d) drying the melamine nitrate and guanidine nitrate from step (c); and(e) mixing the dried melamine nitrate and guanidine nitrate from step (d) with an oxidizer.42-44. (canceled)45. The gas generating composition of claim 41, wherein the oxidizer is selected from the group consisting of metal perchlorates, nonmetal perchlorates, metal nitrates, basic metal nitrates, nonmetal nitrates, and combinations thereof.

46. The gas generating composition of claim 45, wherein the oxidizer is basic copper nitrate.47-48. (canceled)

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