Gas generating agent composition

Abstract

The present invention provides a gas generating composition comprising the following components (a) to (d), wherein the average particle diameter of the following (d) basic magnesium carbonate is 12 μm or less. (a) guanidine nitrate, (b) basic metal nitrate, (c) binder, (d) basic magnesium carbonate

Description

Technology Field

[0001] The present disclosure relates to a gas generating agent composition. Background Technology

[0002] Attempts are being made to ensure product reliability in inflators using gas generator compositions used in vehicle safety devices, such as airbag devices installed in vehicles. For example, attempts are being made to lower the combustion temperature of the gas generator composition to improve ignition properties while simultaneously reducing the pressure index (Patent Document 1). In addition, it is known that the combustion speed of the gas generator composition varies within a range of powers of the pressure index n as shown in the following equation, due to pressure fluctuations within the inflator.

[0003] The invention described in Patent Document 1 solves the problem by setting the ratio of melamine cyanurate to nitroguanidine to a specific range as a solution. Prior art literature

[0004] Japanese Patent Publication No. 2012-211064 The problem to be solved

[0005] One of the characteristics of a gas generator composition is combustion speed. If the combustion speed of a gas generator composition is low, it is necessary to reduce the size of the composition during molding to compensate for this drawback. However, reducing the size of the gas generator composition during molding can make the manufacturing process complicated. Furthermore, a gas generator composition with a low combustion speed cannot be used as a gas generator for inflators that require early development. In addition, the gas generator composition is required to possess good characteristics regarding ignition properties.

[0006] From these, the present disclosure aims to provide a gas generating agent composition having a high combustion rate and good ignition properties. means of solving the problem

[0007] As a result of repeated diligent research to solve the above problem, the inventors discovered that by using basic magnesium carbonate as an additive to the gas generator composition, and using one having an average particle diameter within a predetermined range, a gas generator composition having a high combustion speed and a short ignition time can be obtained.

[0008] In particular, regarding a gas generator composition comprising guanidine nitrate as a fuel and a basic metal nitrate as an oxidizing agent, it was found that the combustion rate of the gas generator composition increases when basic magnesium carbonate is added. Furthermore, it was found that when the average particle diameter of the basic magnesium carbonate in the gas generator composition is within a predetermined range, it exhibits a high combustion rate and good ignition properties. Additionally, in this specification, good ignition properties are synonymous with a short ignition time.

[0009] The present disclosure relates to the following contents.

[0010] [1] A gas generating composition comprising the following components (a) to (d), wherein the average particle diameter of the following (d) basic magnesium carbonate is 12 μm or less.

[0011] (a) Guanidine nitrate,

[0012] (b) basic metal nitrates

[0013] (c) Binder

[0014] (d) basic magnesium carbonate

[0015] [2] The above (a) content of guanidine nitrate is 20 mass% or more and 60 mass% or less, and

[0016] The content of the above (b) basic metal nitrate is 35 mass% or more and 75 mass% or less, and

[0017] The content of the above (c) binder is 0.1 mass% or more and 10 mass% or less, and

[0018] The above (d) gas generating agent composition described in [1], having a content of 6 mass% or less of basic magnesium carbonate.

[0019] [3] A gas generating composition as described in [1] or [2], wherein (b) the basic metal nitrate is basic copper nitrate and (c) the binder is carboxymethyl cellulose.

[0020] [4] A gas generating agent composition according to any one of [1] to [3], wherein the content of (d) basic magnesium carbonate is 0.1 mass% or more and 11 mass% or less.

[0021] [5] An inflator comprising a gas generating agent composition as described in any one of [1] to [4]. Effects of the invention

[0022] According to an embodiment of the present disclosure, a gas generating agent composition having a high combustion rate and good ignition properties can be provided. Brief explanation of the drawing

[0023] Figure 1 is a diagram showing the relationship between the content of basic magnesium carbonate and the combustion rate of the gas generator composition after molding. Figure 2 is a diagram showing the relationship between the content of basic magnesium carbonate and the ignition time of the gas generator composition after molding. Figure 3 is a diagram showing the relationship between the average particle diameter of basic magnesium carbonate and the combustion rate of the gas generator composition after molding. Figure 4 is a diagram showing the relationship between the average particle diameter of basic magnesium carbonate and the ignition time of the gas generator composition after molding. Figure 5 is a diagram showing the relationship between the content of basic magnesium carbonate with an average particle diameter of 12 μm or 13 μm and the combustion rate of the gas generator composition after molding. Figure 6 is a diagram showing the relationship between the content of basic magnesium carbonate with an average particle diameter of 12 μm or 13 μm and the ignition time of the gas generator composition after molding. Specific details for implementing the invention

[0024] The present disclosure will be explained below based on specific embodiments.

[0025] (a) Fuel

[0026] The fuel of component (a) according to the embodiment of the present disclosure comprises guanidine nitrate. Since guanidine nitrate contains oxygen in its molecule, the amount of oxidizing agent component can be reduced. Furthermore, it has good thermal stability and offers advantages such as low cost and a high gasification rate during combustion.

[0027] In the present disclosure, guanidine nitrate is preferably in powder or granular form for ease of handling, and the lower limit of the 50% particle size is typically 5 μm or more, and in one preferred embodiment 10 μm or more, and the upper limit is typically 80 μm or less, and in one preferred embodiment 50 μm or less. Furthermore, if the 50% particle size of guanidine nitrate is too large, the strength of the molded article of the gas generating agent composition decreases, whereas if it is too small, it requires a large cost for grinding. In addition, in the present disclosure, the 50% particle size refers to the 50% particle size based on the number of measured particles, and can be measured, for example, by laser diffraction and scattering methods.

[0028] The lower limit of the content (mixing ratio) of guanidine nitrate in the gas generating agent composition according to the embodiments of the present disclosure is typically 20 mass% or more, and in a preferred embodiment, 30 mass% or more, and the upper limit is typically 60 mass% or less, and in a preferred embodiment, 55 mass% or less. If the content (mixing ratio) of guanidine nitrate is less than 20 mass%, the number of moles of gas generated per 100 g of the gas generating agent composition decreases, and there is a tendency for the generation of nitrogen oxides to increase due to an excess of oxygen. On the other hand, if the content (mixing ratio) of guanidine nitrate exceeds 60 mass%, there is a tendency for a large amount of harmful carbon monoxide to be generated because the oxidizing agent component is insufficient.

[0029] In addition, other known fuels may be included to the extent that they can solve the problems of the present invention.

[0030] Other known fuels include one or more selected from tetrazol compounds including 5-aminotetrazole and bitetrazole ammonium salts; guanidine compounds including guanidine nitrate and dicyandiamide (excluding nitroguanidine); and triazine compounds including melamine, trimethylol melamine, alkylated methylol melamine, ammelin, ammeland, melamine nitrate, melamine perchlorate, trihydrazinotriazine, and nitrated melamine compounds.

[0031] (b) Oxidizing agent

[0032] The oxidizing agent of component (b) in the embodiment of the present disclosure comprises a basic metal nitrate and, if necessary, other oxidizing agents. By using a basic metal nitrate as component (b), the combustion temperature can be lowered.

[0033] Basic metal nitrates may include one or more selected from basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, and basic manganese nitrate, among which basic copper nitrate is preferred. Other oxidizing agents may include metal nitrates, ammonium nitrate, metal perchlorates, ammonium perchlorate, metal nitrites, metal chlorates, etc.

[0034] The content of the oxidizing agent is typically in the range of 35 mass% or more and 75 mass% or less with respect to the gas generating agent composition in one preferred embodiment, and in particular, in order to reduce the concentration of carbon monoxide and nitrogen oxides in the generated gas, it is more preferable to set it in the range of 40 mass% or more and 75 mass% or less in another preferred embodiment.

[0035] (c) Binder

[0036] As a binder of component (c) according to an embodiment of the present disclosure, one or more selected from carboxymethyl cellulose (CMC), carboxymethyl cellulose sodium salt (CMCNa), carboxymethyl cellulose potassium salt, carboxymethyl cellulose ammonium salt, cellulose acetate, cellulose acetate butyrate (CAB), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), microcrystalline cellulose, polyacrylhydrazide, acrylamide-metal acrylate copolymer, copolymer of polyacrylamide-polyacrylic acid ester compound, acrylic rubber, and silicone may be used. Among these, CMCNa is preferred.

[0037] The lower limit of the content of the binder of component (c) in the gas generating agent composition according to the embodiment of the present disclosure is typically 0.1 mass% or more, and in one preferred embodiment 1 mass% or more, and the upper limit is typically 10 mass% or less, and in one preferred embodiment 8 mass% or less.

[0038] (d) basic magnesium carbonate

[0039] The basic magnesium carbonate of component (d) in the embodiment of the present disclosure is added to ensure a high combustion rate of the gas generator composition.

[0040] The content of (d) basic magnesium carbonate in the gas generating agent composition according to the embodiment of the present disclosure is 11 mass% or less in one preferred embodiment, 10 mass% or less in another preferred embodiment, 6 mass% or less in another preferred embodiment, less than 5 mass% in another preferred embodiment, and less than 2 mass% in yet another preferred embodiment.

[0041] When a gas generator is combusted, the ignition ability can be improved by promoting the rate-limiting process of the combustion reaction through the base of basic magnesium carbonate. In particular, since basic magnesium carbonate can control the pH of the entire gas generator composition even in a relatively small amount, sufficient effect can be obtained even with a content of, for example, 6 mass% or less.

[0042] Meanwhile, if the content of basic magnesium carbonate exceeds 11 mass%, the combustion speed and ignition properties of the gas generator composition may decrease.

[0043] Meanwhile, in order to maintain good ignition properties of the gas generator composition, the content of basic magnesium carbonate is 0.1 mass% or more in one preferred embodiment.

[0044] The basic magnesium carbonate related to the embodiments of the present disclosure may be commercially available.

[0045] The average particle diameter of the basic magnesium carbonate according to the embodiments of the present disclosure is 12 μm or less. In a more preferred embodiment, it is 11 μm or less. In order to stably obtain the effect of improving ignition properties even when the amount of basic magnesium carbonate is small during scale-up, it is necessary to increase the contact between the fuel and the oxidizer and the basic magnesium carbonate. Therefore, by having an average particle diameter of 12 μm or less, which is equal to or less than the average particle diameter of the fuel and the oxidizer, the ignition properties of the gas generator composition, particularly ignition properties in a low-temperature environment, are improved. Meanwhile, the average particle diameter of the basic magnesium carbonate is typically 5 μm or more, and in a preferred embodiment, it is 8 μm or more.

[0046] The combustion of gas-generating compositions is susceptible to external environmental influences; generally, ignition and sustained combustion are less favorable in low-temperature environments compared to room or high temperatures. Therefore, improving ignition performance in low-temperature environments is important to minimize performance differences caused by temperature.

[0047] The average particle diameter of basic magnesium carbonate can be measured by a particle size distribution measuring device that uses the laser diffraction and scattering method. Specifically, it can be measured using a precision particle size distribution measuring device (such as the Microtrac HRA, 3000II, manufactured by Microtrac BEL Corp.).

[0048] The average particle diameter of basic magnesium carbonate can be adjusted during its manufacture, for example, by controlling the initial concentration of magnesium hydroxide used as a raw material and the reaction temperature when obtaining basic magnesium carbonate by reaction crystallization by the carbonation method.

[0049] (e) Other ingredients

[0050] The gas generating agent composition according to the embodiments of the present disclosure may contain various known additives for purposes such as adjusting the combustion speed of the gas generating agent composition and cleaning the combustion gas, to the extent that it can solve the problems of the present invention. Known additives include metal oxides such as copper(II) oxide, iron oxide, zinc oxide, cobalt oxide, manganese oxide, molybdenum oxide, nickel oxide, bismuth oxide, silica, and alumina; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, cobalt hydroxide, and iron hydroxide; cobalt carbonate and calcium carbonate; complex compounds of metal oxides or hydroxides such as acid clay, kaolin, talc, bentonite, and diatomaceous earth; and metal salts such as sodium silicate, molybdate mica, cobalt molybdate, and ammonium molybdate. Examples include molybdenum disulfide, calcium stearate, silicon nitride, silicon carbide, metaboric acid, boric acid, anhydrous boric acid, glass, etc.

[0051] The gas generating agent composition according to the embodiments of the present disclosure may not substantially contain phosphate. "Substantially not containing phosphate" means that the phosphate content in the gas generating agent composition is below the detection limit.

[0052] Examples of phosphates referred to in this specification include potassium dihydrogen phosphate, potassium monohydrogen phosphate, tripotassium phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, trisodium phosphate, calcium dihydrogen phosphate, calcium monohydrogen phosphate, tricalcium phosphate, magnesium dihydrogen phosphate, magnesium monohydrogen phosphate, trisodium phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, and magnesium ammonium phosphate.

[0053] In the gas generating agent composition according to the embodiment of the present disclosure, the combustion temperature does not rise above what is necessary even if phosphate is not included. Furthermore, when the gas generating agent composition according to the embodiment of the present disclosure does not include phosphate, ignition properties at low temperatures are improved.

[0054] The gas generating composition according to the embodiments of the present disclosure can be molded into a desired shape and may be a single-hole cylindrical, multi-hole cylindrical, or pellet-shaped molded body. These molded bodies can be manufactured by adding and mixing water or an organic solvent to the gas generating composition and then extruding (single-hole cylindrical or multi-hole cylindrical molded bodies) or by compression molding using a tablet press or the like (pellet-shaped molded bodies).

[0055] Since the gas generating agent composition according to the embodiment of the present disclosure has a high combustion rate, there is no need to make the molded body small, so the manufacturing process is not complicated.

[0056] The gas generating composition according to the embodiment of the present disclosure or the molded article obtained therefrom may be applied, for example, to an inflator for a driver's seat airbag, an inflator for a passenger seat airbag, an inflator for a side airbag, an inflator for an inflatable curtain, an inflator for a knee bolster, an inflator for an inflatable seat belt, an inflator for a tubular system, and an inflator for a pretensioner of various means of transportation. Among these, the gas generating composition according to the embodiment of the present disclosure or the molded article obtained therefrom may be preferably applied to an inflator for a side airbag that requires early deployment.

[0057] In addition, an inflator comprising a gas generator composition or a molded body obtained therefrom according to an embodiment of the present disclosure may be a pyrotype in which the gas is supplied solely from the gas generator, or a hybrid type in which both a compressed gas such as argon and the gas generator are supplied.

[0058] The gas generator composition or the molded body obtained therefrom according to the embodiments of the present disclosure may also be used as an ignition agent, referred to as an enhancer (or booster), for transferring energy from a detonator or squib to the gas generator.

[0059] Each component in each embodiment and combinations thereof are examples, and additions, omissions, substitutions, and other changes to the components may be appropriately made without departing from the well-known nature of the present invention. The present disclosure is not limited by the embodiments, but is limited only by the scope of the claims.

[0060] Examples

[0061] The present disclosure will be described in detail below with reference to examples. However, the present disclosure is not limited to the following examples.

[0062] <Preparation of Gas Generator Composition>

[0063] A pre-molding gas generator composition having the composition shown in Table 1 was prepared.

[0064]

[0065] The binder is carboxymethyl cellulose

[0066] **Average particle diameter of basic magnesium carbonate in Example 1: 10 μm, Average particle diameter of basic magnesium carbonate in Comparative Example 1: 14 μm

[0067] Formation into cylindrical strands

[0068] Water was added to each gas generator composition of the examples and comparative examples listed in Table 1 and mixed, and a single-hole molded body was obtained by extrusion molding, cutting, and drying.

[0069] The obtained single-hole molded body was crushed in an agate mortar and pestle, and the powder passed through a wire mesh with a mesh size of 500 μm was filled into the mortar side of a predetermined mold.

[0070] Next, the end surface of the tube was compressed and maintained at a pressure of 14.7 MPa for 5 seconds using a hydraulic pump, then removed and molded into a cylindrical strand with an outer diameter of 9.6 ± 0.1 mm and a length of 12.7 ± 1.0 mm to obtain a gas generating agent composition after molding.

[0071] Method for Measuring Combustion Speed

[0072] A cylindrical strand serving as a sample was installed inside a sealed SUS cylinder with a capacity of 1 L, and the cylinder was pressurized and stabilized to 5 MPa, 7 MPa, or 9 MPa while completely purging the cylinder with nitrogen. Subsequently, a predetermined current was passed through a nichrome wire in contact with the cross-section of the strand, and the strand was ignited and burned by the melting energy. The pressure behavior over time inside the cylinder was verified using a recorder chart, and the elapsed time from the start of combustion to the pressure rise peak was determined from the scale of the chart. The value calculated by dividing the length of the strand before combustion by this elapsed time was defined as the combustion rate. The respective test results of the examples and comparative examples are shown in Table 1.

[0073] Method for Measuring Wear Time

[0074] A predetermined amount of gas generator for evaluating a single-hole molded body obtained by extrusion molding was introduced into a 5 cc bomb test jig, and ignited with an ignition agent containing ZPP at a low temperature environment (-35℃) or at 26℃ under a room temperature environment, and the time to reach 10% of the maximum pressure was defined as the ignition time.

[0075] From the comparison of the results of Example 1 and Comparative Example 1 and Comparative Example 2 in Table 1, it was found that when basic magnesium carbonate was added to the gas generator composition, the combustion speed increased and the ignition time was shortened.

[0076] In addition, when comparing the results of Example 1 and Comparative Example 1, it was found that when the average particle diameter of the basic magnesium carbonate was 12 μm or less, the combustion speed of the gas generating agent composition was high and the ignition time was shortened.

[0077] Combustion Rate and Ignition Time When Changing the Content of Basic Magnesium Carbonate

[0078] A pre-molding gas generator composition having the composition shown in Table 2 was prepared. The preparation method is the same as that for the gas generator composition in Table 1. The materials used are the same as those listed in Table 1, and the average particle diameter of the basic magnesium carbonate is 10 μm. These pre-molding gas generator compositions were molded into cylindrical strands using the same method as in Example 1 above to obtain post-molding gas generator compositions. For each post-molding gas generator composition, the combustion speed and ignition time were measured using the method described above. The results are shown in Table 2.

[0079] In addition, regarding combustion speed and ignition time, the ratio (%) to the combustion speed (mm / sec) and ignition time (msec) of Comparative Example 3, respectively, was shown. Furthermore, the results of Examples 2 to 6 and Comparative Example 3 are summarized in Figures 1 and 2. In Figure 1, the horizontal axis represents the content of basic magnesium carbonate, and the vertical axis represents the rate of change (%) from Comparative Example 3 with respect to combustion speed. In Figure 2, the horizontal axis represents the content of basic magnesium carbonate, and the vertical axis represents the rate of change (%) from Comparative Example 3 with respect to ignition time.

[0080]

[0081] From the results in Table 2 and Figures 1 and 2, it was confirmed that adding basic magnesium carbonate resulted in an increase in combustion speed and a significant reduction in ignition time. In addition, when the content of basic magnesium carbonate was 3 mass% or more, a significant increase in combustion speed was observed.

[0082] Combustion Rate and Ignition Time When Average Particle Diameter of Basic Magnesium Carbonate Is Changed

[0083] A pre-molding gas generator composition having the composition shown in Table 3 was prepared. The preparation method is the same as that for the gas generator composition in Table 1. Materials other than basic magnesium carbonate are the same as those listed in Table 1, and the average particle diameter of the basic magnesium carbonate was varied. These pre-molding gas generator compositions were molded into cylindrical strands using the same method as in Example 1 above to obtain post-molding gas generator compositions. For each post-molding gas generator composition, the combustion speed and ignition time were measured using the method described above. The results are shown in Table 3.

[0084] In addition, regarding combustion speed and ignition time, the ratio (%) to the combustion speed (mm / sec) and ignition time (msec) of Example 9, respectively, was shown. Furthermore, the results of Examples 7 to 9 and Comparative Example 4 are summarized in Figures 3 and 4. In Figure 3, the horizontal axis represents the average particle diameter (μm) of basic magnesium carbonate, and the vertical axis represents the rate of change (%) from Example 9 with respect to combustion speed. In Figure 4, the horizontal axis represents the average particle diameter (μm) of basic magnesium carbonate, and the vertical axis represents the rate of change (%) from Example 9 with respect to ignition time.

[0085]

[0086] From the results in Table 3 and Figures 3 and 4, it was found that when the average particle diameter of basic magnesium carbonate exceeded 12 μm, the combustion rate dropped sharply and the ignition time increased sharply. On the other hand, when the average particle diameter of basic magnesium carbonate was 12 μm or less, both showed good combustion rates and short ignition times.

[0087] Combustion Rate and Ignition Time When Average Particle Diameter and Content of Basic Magnesium Carbonate Are Changed

[0088] Basic magnesium carbonate with average particle diameters of 12 μm and 13 μm was prepared, and by adjusting the content of basic magnesium carbonate in the gas generator composition to 0.1 mass%, 2 mass%, 6 mass%, 7 mass%, and 10 mass%, a gas generator composition before molding having the compositions shown in Table 4 was prepared. Materials other than basic magnesium carbonate were the same as those listed in Table 1. These gas generator compositions before molding were molded into cylindrical strands using the same method as in Example 1 above to obtain a gas generator composition after molding. For each gas generator composition after molding, the combustion speed and ignition time were measured using the method described above. The results are shown in Table 4.

[0089] In addition, regarding combustion speed and ignition time, the ratio (%) to the combustion speed (mm / sec) and ignition time (msec) of Comparative Example 5, respectively, was shown. Furthermore, the results of Examples 10 to 14 and Comparative Examples 5 to 10 are summarized in Figures 5 and 6. In Figure 5, the horizontal axis represents the basic magnesium carbonate content (mass%), and the vertical axis represents the rate of change (%) from Comparative Example 5 with respect to combustion speed. In Figure 6, the horizontal axis represents the basic magnesium carbonate content (mass%), and the vertical axis represents the rate of change (%) from Comparative Example 5 with respect to ignition time.

[0090]

[0091] From the results of Table 4 and Figures 5 and 6, when using basic magnesium carbonate with an average particle diameter of 12 μm, good combustion speed and short ignition time were observed in all cases. On the other hand, when using basic magnesium carbonate with an average particle diameter of 13 μm, short ignition time was not obtained depending on the content.

[0092] From the results of Tables 1 to 3 and Figures 1 to 6, it was found that in the gas generator composition, using basic magnesium carbonate with an average particle diameter of 12 μm or less is an important requirement for obtaining a good combustion rate and a short ignition time.

[0093] Industrial applicability

[0094] According to the present disclosure, a gas generating agent composition having a high combustion rate and a short ignition time can be provided.

Claims

Claim 1 A gas generating composition comprising the following components (a) to (d), wherein the average particle diameter of the following (d) basic magnesium carbonate is 12 μm or less, and the content of the said (d) basic magnesium carbonate is 0.1 mass% or more and 10 mass% or less. (a) guanidine nitrate, (b) basic metal nitrate, (c) binder, (d) basic magnesium carbonate Claim 2 A gas generating agent composition according to claim 1, wherein the content of (a) guanidine nitrate is 20 mass% or more and 60 mass% or less, the content of (b) basic metal nitrate is 35 mass% or more and 75 mass% or less, the content of (c) binder is 0.1 mass% or more and 10 mass% or less, and the content of (d) basic magnesium carbonate is 0.1 mass% or more and 6 mass% or less. Claim 3 A gas generating agent composition according to claim 1 or 2, wherein (b) the basic metal nitrate is basic copper nitrate and (c) the binder is carboxymethyl cellulose. Claim 4 An inflator comprising the gas generating agent composition described in paragraph 1 or 2. Claim 5 delete

Images