Gas generating agent composition

Abstract

To provide a gas generating agent composition with a low pressure index.SOLUTION: A gas generating agent composition has a total content of at least 99 mass% of a nitrogen-containing organic compound as a fuel constituent, basic metal nitrate as an oxidant and synthetic hydrotalcite.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gas generant composition. [Background technology]

[0002] Airbag devices and seatbelt pretensioner devices are used as safety devices for protecting passengers in the event of a collision accident involving a vehicle, typically an automobile. In an airbag device, when a vehicle crashes, an electric signal is sent from a collision detection sensor to a gas generator for deploying an airbag, which burns a gas generating agent loaded in the gas generator to generate gas, and the gas pressure deploys the airbag.

[0003] On the other hand, in a seatbelt pretensioner device, when a sensor detects a vehicle collision, an electric signal is sent to combust a gas generating agent loaded in a gas generator for the seatbelt pretensioner to generate gas, and the gas pressure is used to activate a seatbelt winding mechanism. Various gas generating agent compositions, which are important components of the performance of the gas generators employed in such airbag devices and the like, have been developed.

[0004] For example, Patent Document 1 discloses a gas generating composition containing a tetrazole derivative, a guanidine derivative or a mixture thereof, a basic metal nitrate, and a binder and / or a slag forming agent. Patent Document 2 discloses a gas generating composition containing an organic compound as a fuel, an oxygen-containing oxidizing agent, magnesium hydroxide or a mixture of magnesium hydroxide and aluminum hydroxide, and further containing, as necessary, an additive selected from a binder, a metal oxide, and a metal carbonate, and a slag forming agent having a specific surface area of ​​100 to 500 m. 2 The present invention discloses a gas generant composition containing silicon dioxide having a content of 1 / g.

[0005] Patent Document 3 discloses a gas generating composition containing an organic compound as a fuel, an oxygen-containing oxidizing agent, aluminum hydroxide, and, if necessary, an additive selected from a binder, a metal oxide, and a metal carbonate, etc. Patent Document 4 discloses a gas generating composition containing a fuel, an oxidizing agent, and an additive selected from phosphoric acids and salts of phosphoric acids.

[0006] Patent Document 5 discloses an explosive composition for airbags that contains a combustion component, an oxidizer, and a binder that binds them together, and discloses a method for producing the explosive composition, in which the binder is a hydrotalcite represented by a specific formula.

[0007] Patent Document 6 discloses a gas generating composition containing guanidine nitrate as a fuel (A), a basic metal nitrate as an oxidizer (B), and a carboxymethylcellulose sodium salt as a binder (C), the carboxymethylcellulose salt having a viscosity of 1,000 mPa·s or more as measured by a B-type viscometer at 25°C in a 1% (w / w) aqueous solution. Furthermore, the gas generating composition contains a combustion modifier (D), and the content of the combustion modifier (D) is disclosed as being 4 to 10 mass%. It also discloses that the combustion modifier (D) contains one or more selected from the group consisting of synthetic hydrotalcite, aluminum oxide, silicon dioxide, diiron trioxide, triiron tetroxide, aluminum oxide hydroxide, kaolin, and acid clay. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2002-12493 A [Patent Document 2] JP 2005-126262 A [Patent Document 3] JP 2004-155645 A [Patent Document 4] JP 2006-076824 A [Patent Document 5] WO97 / 05087 [Patent Document 6] JP 2016-160152 A Summary of the Invention [Problem to be solved by the invention]

[0009] Attempts have been made to reduce the pressure exponent of gas generating compositions. Even in gas generating compositions that mainly contain guanidine nitrate as a combustion component and a basic metal nitrate as an oxidizer, various additives have been added to reduce the pressure exponent.

[0010] The pressure index is an index of the change in burning rate with respect to pressure fluctuations in a combustion system. In general, the burning rate depends on temperature and pressure, and increases with increasing temperature and pressure. Therefore, in order to obtain a stable burning rate with respect to pressure fluctuations during combustion in an inflator, it is preferable for the pressure index of the gas generating composition to be low. Under such circumstances, an object of the present invention is to provide a gas generating composition etc. having a small pressure exponent. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the following invention meets the above object, thereby completing the present invention.

[0012] <1> A gas generating composition, comprising a nitrogen-containing organic compound as a fuel component, a basic metal nitrate as an oxidizing agent, and synthetic hydrotalcite, the total content of which is 99 mass % or more. <2> the mass ratio (A):(B):(C) of the nitrogen-containing organic compound (A), the basic metal nitrate (B), and the synthetic hydrotalcite (C) is 42.6 to 46.6:48.1 to 52.1:3.3 to 7.3; <1> The gas generating composition according to claim 1. <3> The nitrogen-containing organic compound is guanidine nitrate (GN), and the basic metal nitrate is basic copper nitrate (BCN). <1> or <2> The gas generating composition according to claim 1. <4> The above <1> ~ <3> 2. A molded article of the gas generating composition according to claim 1 . <5> The above <4> A gas generator comprising the molded article according to claim 1 as a gas generating agent. Effect of the Invention

[0013] The gas generating composition of the present invention has a small pressure exponent and is suitable for use in gas generators and the like. [Brief description of the drawings]

[0014] [Figure 1] 13 is a graph showing the results of an experiment for determining a pressure index according to the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The following is a detailed description of the embodiments of the present invention, but the following description of the constituent elements is one example (representative example) of the embodiment of the present invention, and the present invention is not limited to the following content as long as the gist of the present invention is not changed. Note that in this specification, when the expression "~" is used, it is used as an expression including the numerical values ​​before and after it.

[0016] [Gas Generator Composition of the Present Invention] The gas generating composition of the present invention has a total content of the nitrogen-containing organic compound as a fuel component, the basic metal nitrate as an oxidizing agent, and the synthetic hydrotalcite of 99 mass % or more.

[0017] The present inventors have studied the composition of a gas generating composition and found that the pressure exponent can be reduced when a specific composition is used, and thus came up with the idea of ​​the present invention.

[0018] [Combustible components (flammable materials)] The present invention contains a nitrogen-containing organic compound as a fuel component. In the present application, the nitrogen-containing organic compound may be referred to as "component (A)". The nitrogen-containing organic compound is not particularly limited, and a nitrogen-containing organic compound that is usually used in a gas generating agent composition for a gas generator for a vehicle occupant safety device can be suitably used. Examples of the nitrogen-containing organic compound that are preferably used include guanidine or a derivative thereof or a salt thereof (guanidine compound), triazole or a derivative thereof or a salt thereof, tetrazole or a derivative thereof or a salt thereof, bitriazole or a derivative thereof or a salt thereof, bitrazole or a derivative thereof or a salt thereof, azodicarbonamide or a derivative thereof or a salt thereof, hydrazine or a derivative thereof or a salt thereof, and hydrazide derivative or a salt thereof.

[0019] More specifically, preferred examples of the compound include 5-oxo-1,2,4-triazole, tetrazole, 5-aminotetrazole, aminotetrazole nitrate, nitroaminotetrazole, bitetrazole (5,5'-bi-1H-tetrazole), 5,5'-bi-1H-tetrazole diammonium salt, azobistetrazole, 5,5'-azobistetrazole diguanidium salt, guanidine, aminoguanidine, diaminoguanidine, triaminoguanidine, nitroguanidine, aminonitroguanidine, cyanoguanidine, guanidine nitrate, aminoguanidine nitrate, diaminoguanidine nitrate, triaminoguanidine nitrate, nitroguanidine, aminonitroguanidine, biuret, azodicarbonamide, carbohydrazide, carbohydrazide nitrate complex, oxalic acid hydrazide, hydrazine nitrate complex, and ammine complex.

[0020] The guanidine compound is a concept including guanidine, guanidine derivatives and guanidine salts, and is a fuel component of the gas generating composition. Specific examples of the guanidine compound include guanidine, aminoguanidine, diaminoguanidine, triaminoguanidine, nitroguanidine, aminonitroguanidine and salts thereof (nitrates, carbonates, perchlorates, etc.), and one or more of them may be used in combination.

[0021] Among these, one or more selected from guanidine nitrate, aminoguanidine nitrate, diaminoguanidine nitrate, triaminoguanidine nitrate, nitroguanidine, and aminonitroguanidine are preferred, with guanidine nitrate being particularly preferred.

[0022] [Guanidine nitrate (GN)] The gas generating composition of the present invention preferably contains guanidine nitrate as a fuel component. Guanidine nitrate is said to have relatively high combustibility and generates little harmful gas, and is widely used as a fuel component of gas generating compositions. In addition, guanidine nitrate burns at low pressure. Therefore, a gas generator using this can be designed with a housing with low pressure resistance, which makes it easy to reduce the wall thickness of the gas generator and reduce its weight.

[0023] [Oxidizing agent] The present invention contains a basic metal nitrate as an oxidizing agent. In the present application, the basic metal nitrate may be referred to as "component (B)". Specific examples of the basic metal nitrate include basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, basic magnesium nitrate, and basic iron nitrate. Among these, basic copper nitrate, which has a low combustion temperature and good thermal stability, is particularly preferred.

[0024] [Basic copper nitrate (BCN)] The gas generating composition of the present invention preferably contains basic copper nitrate as an oxidizer. In the gas generating composition, an oxidizer is used to improve ignition ability and combustion sustainability. In the present invention, the composition preferably contains basic copper nitrate (BCN:Cu(NO3)2·3Cu(OH)2) as the oxidizer. Basic copper nitrate has high ignition ability and excellent oxygen supplying ability, and therefore when combined with guanidine nitrate, it can further reduce the amount of carbon monoxide generated.

[0025] [Synthetic hydrotalcite (HTS)] The gas generating composition of the present invention contains synthetic hydrotalcite. In the present application, the synthetic hydrotalcite may be referred to as "component (C)". Hydrotalcite is a compound having a Cl- It is a layered hydroxide with an anion exchange function such as those described above, and its general composition is expressed by the following formula: Synthetic hydrotalcite is also used as an antacid, adsorbent, resin stabilizer, flame retardant, etc. Mg6Al2(OH) 16 CO3 4H2O

[0026] [Gas Generator Composition] The gas generating composition of the present invention contains a nitrogen-containing organic compound as component (A), a basic metal nitrate as component (B), and a synthetic hydrotalcite as component (C), and the content of these components (A) to (C) is 99% or more. More preferably, it can be 99.5% by mass or more. The content of components (A) to (C) in the gas generating composition can be 100% by mass, that is, the gas generating composition can be composed essentially of only these components (A) to (C).

[0027] The additives blended in the gas generating composition of the present invention may be added as the balance of the components (A) to (C) to adjust the combustibility and control the burning rate, pressure exponent, generated gas composition, etc. On the other hand, if the content of the additives in the gas generating composition is high, problems arise such as a decrease in combustibility and an increase in the amount of residue generated by combustion. For this reason, it is preferable that the content of other components is low, such as less than 1 mass % or less than 0.5 mass %.

[0028] [Nitrogen-containing organic compounds:basic metal nitrates mass ratio] In the gas generating composition of the present invention, the mass ratio (A:B) of the nitrogen-containing organic compound as component (A) to the basic metal nitrate as component (B) is preferably 70:30 to 45:55. When guanidine nitrate is used as a representative nitrogen-containing organic compound and basic copper nitrate is used as the basic metal nitrate for components (A) and (B), the mass ratio of guanidine nitrate to basic copper nitrate (guanidine nitrate (GN): basic copper nitrate (BCN)) is preferably 70:30 to 45:55. Guanidine nitrate and basic copper nitrate are the main components of the gas generating composition. When the gas generating agent is burned, the gas components in the combustion gas change depending on the ratio of these. The oxygen balance between guanidine nitrate and basic copper nitrate is almost 0 when the molar ratio of GN / BCN is 9 / 4 (53 / 47 in mass ratio). When designed within this range as a reference, harmful gases in the combustion gas are particularly likely to be reduced.

[0029] According to the findings of the present inventors, the more the oxygen balance is positive (the higher the BCN ratio), the less CO and NH3 are generated. Also, the more the oxygen balance is negative (the higher the GN ratio), the less NOx is generated. In particular, in order to reduce the total amount of CO and NOx, the total amount of which should be controlled as harmful gases, it is preferable that the GN:BCN (mass ratio) is 70:30 to 45:55. From the viewpoint of reducing the amount of exhaust gas such as CO and NOx, it is more preferable to set the ratio to 65:35 to 50:50, and particularly preferable to set the ratio to 57:43 to 53:47.

[0030] The mass ratio of the content of the synthetic hydrotalcite, which is component (C) in the gas generating composition of the present invention (component (C) / total amount of gas generating composition) is preferably 1 to 10 mass%, more preferably 3 to 7 mass%, and particularly preferably 4 to 6 mass%.

[0031] In addition, the ratio of the contents of the components (A) to (C) is preferably such that the mass ratio (A):(B):(C) of the nitrogen-containing organic compound (A), the basic metal nitrate (B), and the synthetic hydrotalcite (C) is 42.6-46.6:48.1-52.1:3.3-7.3.

[0032] [Pressure Index] The pressure exponent can be expressed by the "Vieille's formula" shown below. This pressure exponent can be calculated from the results of measuring the burning rate at multiple pressures, as in the method of the examples described later. r=aP n r: burning rate, a: constant, P: ambient pressure, n: pressure exponent

[0033] The gas generating composition of the present invention exhibits a pressure index smaller than that of a combination of only "GN / BCN". For example, combustion behavior is ascertained under a plurality of pressures ranging from about 0.5 to 5 MPa or 1 to 3 MPa, and the results are applied to the Vielle formula to obtain the pressure index. More specifically, the pressure index of the gas generating composition of the present invention can be made lower than that of a gas generating composition consisting of only the two components GN / BCN.

[0034] The gas generating composition of the present invention is formed into a desired shape to form a molded article, which is then used as a gas generating agent to be incorporated into a gas generator. Hereinafter, the molded article of the gas generating composition may be referred to as a "gas generating agent".

[0035] [Gas generator] The gas generating agent of the present invention can be molded into various shapes according to the combustion performance and the combustion characteristics of the gas generator. The shape of the gas generating agent of the present invention is not particularly limited, and examples thereof include pellet-shaped, disk-shaped, spherical, rod-shaped, columnar, cylindrical, confetti-shaped, and tetrapod-shaped. The molded product may be non-perforated or may have a single hole or multiple holes (for example, a single-hole cylindrical or multiple-hole cylindrical). Furthermore, the pellet-shaped or disk-shaped molded product may have one or more protrusions on one or both sides. The shape of the protrusion is not particularly limited, and examples thereof include a columnar, cylindrical, conical, and polygonal pyramidal shape.

[0036] The gas generating agent of the present invention may be molded by a conventionally known method, for example, a method of extrusion molding the gas generating agent composition of the present invention, or a method of compression molding using a tablet machine or the like.

[0037] The gas generator of the present invention is a gas generator loaded with a gas generating agent, and uses a molded article (gas generating agent) made of the gas generating agent composition described above as the gas generating agent.

[0038] [Gas generator] The gas generator of the present invention is suitable as a gas generator for various vehicles including automobiles. Examples of gas generators for vehicles include a gas generator for an airbag and a gas generator for a pretensioner.

[0039] The gas generator of the present invention can have the same configuration as a conventionally known gas generator, except for the molded article obtained from the gas generating composition of the present invention, and is not particularly limited to a specific configuration, and any inflator having a structure that is normally mounted on a vehicle can be used without any particular limitation. A typical gas generator is configured by equipping an ignition device and, if necessary, a filter material inside an outer shell having an internal volume, and also filling it with a gas generating agent (a molded article obtained from a gas generating composition).

[0040] The gas generator of the present invention may be either a pyrotype in which gas is supplied only from a gas generating agent, or a hybrid type in which both a compressed gas such as argon and a gas generating agent are supplied. EXAMPLES

[0041] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples unless the gist of the present invention is changed.

[0042] 1. Raw material sample (a) Fuel components · Guanidine nitrate (GN): Guanidine nitrate (GN) was sieved to adjust the particle size to about 100 to 212 μm, and used as the guanidine nitrate (GN) for the gas generating composition of the examples and comparative examples. (b) Oxidizing agent Basic copper nitrate (BCN) (c) Additives The additives used were as follows, in accordance with the composition ratios of each of the Examples and Comparative Examples. Note that all additives were used after appropriate raw material selection and sieving to have a particle size of 100 μm before molding the gas generating composition samples. (c-1) Synthetic hydrotalcite ·Synthetic Hydrotalcite (HTS) (c-2) Iron oxide Iron oxide (Fe2O3) (c-3) Sodium carboxymethylcellulose Sodium carboxymethylcellulose (CMCNa)

[0043] 2. Production of gas generant composition A gas generating composition (a compact of a gas generating composition) was produced by mixing guanidine nitrate (GN), basic copper nitrate (BCN), and an appropriate additive, introducing the mixture into a pelletizer, and compression molding the mixture. When producing the composition using only GN and BCN, a total amount of about 4.0 g was weighed out as one gas generating composition, introduced into the pelletizer, and compression molded at 30 MPa. When further additives were used, a total amount of 4.0 g of GN, BCN, and additives was weighed out as one gas generating composition, and compression molded. After compression, the sample was shaped like a cylinder with a diameter of about 9.5 mm and a length of about 30 mm.

[0044] 3. Evaluation method 3.1 Chimney-type strand combustion device The samples were ignited by a nichrome wire in a chimney-type strand combustion apparatus, and the burning rate was measured (break wire method, high-speed camera). Experimental conditions: Nitrogen atmosphere (flow), measured at atmospheric pressure in the range of 1.0 to 3.0 MPa High-speed camera conditions: Resolution 1280 x 720, frame rate 500 FPS, exposure time 1900 μs (AMETEK PHANTOM MIRO C110)

[0045] 4. Composition ratio of gas generating agent composition The gas generating composition was prepared by mixing the ingredients in the ratios (mass %) shown below and in Table 1. Example 1: GN / BCN / HTS ·Comparative example 1: GN / BCN ·Comparative example 2: GN / BCN / Fe2O3 ·Comparative example 3: GN / BCN / CMCNa ·Comparative example 4: GN / BCN / Fe2O3 / CMCNa ·Comparative example 5: GN / BCN / HTS / CMCNa ·Comparative example 6: GN / BCN / HTS / Fe2O3

[0046] A gas generating composition was molded by mixing the components shown in Table 1, and a combustion test was conducted. The test results and the analysis results of the pressure index are shown in Fig. 1 and Table 1. Fig. 1 is a graph showing the measurement results of the ambient pressure (measurement range 1 MPa to 3 MPa) and the burning rate of Example 1 and Comparative Example 1, and an analysis example of the pressure index n.

[0047] When one or two types of compounding substances were added to the composition of Comparative Example 1, a significant reduction in the pressure index was observed only in the case of Example 1, which contained only HTS. Example 1 contained fewer components, so there was also less combustion residue.

[0048] [Table 1] [Industrial Applicability]

[0049] The gas generating composition of the present invention can be used in gas generators and is therefore industrially useful.

Claims

1. A gas generating composition comprising a nitrogen-containing organic compound as a fuel component, a basic metal nitrate as an oxidizing agent, and synthetic hydrotalcite, the total content of which is 99 mass % or more.

2. 2. The gas generating composition according to claim 1, wherein the mass ratio (A):(B):(C) of the mass (A) of the nitrogen-containing organic compound, the mass (B) of the basic metal nitrate, and the mass (C) of the synthetic hydrotalcite is 42.6 to 46.6:48.1 to 52.1:3.3 to 7.

3.

3. 2. The gas generant composition according to claim 1, wherein said nitrogen-containing organic compound is guanidine nitrate (GN) and said basic metal nitrate is basic copper nitrate (BCN).

4. A molded article of the gas generating composition according to any one of claims 1 to 3.

5. A gas generator comprising the molded article according to claim 4 as a gas generating agent.

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