Patent Application
20240002311
The present disclosure relates to a gas-generating agent composition.
In an inflator using a gas-generating agent composition, which is used in a vehicle safety device such as an airbag device mounted on a vehicle, an attempt is being made to ensure the reliability of the product. For example, an attempt is being made to lower the burning temperature of a gas-generating agent composition, improve the ignitability, and reduce the pressure index (Patent Document 1). It is known that the burn rate of a gas-generating agent composition varies in a range of the power of a pressure exponent n as expressed by the following equation due to the pressure variation in the inflator.
The invention disclosed in Patent Document 1 solves the issue by setting a ratio between melamine cyanurate and nitroguanidine in a specific range as a solution.
Burn rate is one of the properties of a gas-generating agent composition. When a gas-generating agent composition has a low burn rate, it may be necessary for the shape of the gas-generating agent composition to be made small when molded to compensate for its disadvantage. When the shape of the gas-generating agent composition at the time of molding is made small, a production process may become complicated. Also, a gas-generating agent composition having a low burn rate cannot be used as a gas generating agent for an inflator which may require early deployment. In addition, a gas-generating agent composition is desirable to have good ignitability.
In view of the above, an object of the present disclosure is to provide a gas-generating agent composition having a high burn rate and good ignitability.
As a result of intensive studies to solve the above issues, the present inventors have found that a gas-generating agent composition having a high burn rate and a short ignition time can be obtained by using a basic magnesium carbonate as an additive for the gas-generating agent composition with an average particle size in a predetermined range.
In particular, it has been found that, in a gas-generating agent composition containing guanidine nitrate as a fuel and a basic metal nitrate as an oxidizing agent, the burn rate of the gas-generating agent composition increases when basic magnesium carbonate is added. In addition, it has been found that when the average particle size of the basic magnesium carbonate in the gas-generating agent composition is within a predetermined range, the gas-generating agent composition has a high burn rate and good ignitability. In the present specification, good ignitability is synonymous with short ignition time.
The present disclosure relates to the following contents:
[1] A gas-generating agent composition comprising components (a) to (d) below, wherein an average particle size of the following component (d) basic magnesium carbonate is 12 μm or less:
[2] The gas-generating agent composition according to [1], wherein
[3] The gas-generating agent composition according to [1] or [2], wherein (b) the basic metal nitrate is basic copper nitrate, and (c) the binder is carboxymethyl cellulose.
[4] The gas-generating agent composition according to any one of [1] to [3], wherein a content of (d) the basic magnesium carbonate is 0.1 mass % or more and 6 mass % or less.
[5] An inflator comprising the gas-generating agent composition according to any one of [1] to [4].
According to an embodiment of the present disclosure, a gas-generating agent composition having a high burn rate and good ignitability can be provided.
Hereinafter, an embodiment of the present disclosure will be described.
(a) Fuel
A fuel, which is a component (a) according to an embodiment of the present disclosure, comprises guanidine nitrate. Since guanidine nitrate contains oxygen in the molecule, there are advantages such as reducing a blending amount for an oxidizing agent component, obtaining good thermal stability, reducing costs, and being able to expect a high gasification rate during combustion.
In the present disclosure, the guanidine nitrate is preferably in the form of powder or granules because it is easy to handle, and the lower limit of the 50% particle size is usually 5 μm or more, and 10 μm or more in a preferred embodiment, and the upper limit is usually 80 μm or less, and 50 μm or less in a preferred embodiment. If the 50% particle size of guanidine nitrate is excessively large, the strength of the molded article of the gas-generating agent composition is lowered, whereas if it is excessively small, the cost of pulverization would be high. In the present disclosure, the 50% particle size means a 50% particle size based on the number of measured particles, which can be determined by, for example, a laser diffraction/scattering method.
The lower limit of the content percentage (blending ratio) of guanidine nitrate in the gas-generating agent composition according to an embodiment of the present disclosure is usually 20 mass % or more, and 30 mass % or more in a preferred embodiment, and the upper limit is usually 60 mass % or less, and 55 mass % or less in a preferred embodiment. When the content percentage (blending ratio) of guanidine nitrate is less than 20 mass %, the number of moles of generated gas per 100 g of the gas-generating agent composition decreases, and the generation of nitrogen oxides tends to increase due to excess oxygen. Meanwhile, when the content percentage (blending ratio) of guanidine nitrate exceeds 60 mass %, the amount of the oxidizing agent component becomes insufficient, so that an amount of harmful carbon monoxide to be generated tends to be large.
Further, other known fuels may be included within such a range that the issues of the present invention can be solved.
Examples of those other known fuels include one or more selected from tetrazole compounds including 5-aminotetrazole and bitetrazole ammonium salts; guanidine compounds including guanidine nitrate and dicyandiamide (excluding nitroguanidine); and triazine compounds including melamine, trimethylolmelamine, alkylated methylolmelamine, ammeline, ammeland, melamine nitrate, melamine perchlorate, trihydrazinotriazine, and melamine nitrated compounds.
(b) Oxidizing Agent
The oxidizing agent, which is the component (b) according to an embodiment of the present disclosure, includes a basic metal nitrate and optionally other oxidizing agents. By using a basic metal nitrate as the component (b), the burning temperature can be lowered.
Examples of the basic metal nitrate include one or more selected from basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, and basic manganese nitrate, and among them, basic copper nitrate is preferable. Examples of the other oxidizing agents include metal nitrate, ammonium nitrate, metal perchlorate, ammonium perchlorate, metal nitrite, and metal chlorate.
The oxidizing agent content is usually in a range of 35 mass % or more and 75 mass % or less with respect to the gas-generating agent composition in a preferred embodiment, and is more preferably set in a range of 40 mass % or more and 75 mass % or less in another preferred embodiment in order to reduce the concentrations of carbon monoxide and nitrogen oxide in the generated gas.
(c) Binder
Examples of the binder for the component (c) according to an embodiment of the present disclosure include one or more selected from carboxymethyl cellulose (CMC), a carboxymethyl cellulose sodium salt (CMCNa), a carboxymethyl cellulose potassium salt, a carboxymethyl cellulose ammonium salt, cellulose acetate, cellulose acetate butyrate (CAB), ethylcellulose (EC), hydroxyethylcellulose (HEC), microcrystalline cellulose, polyacrylhydrazide, an acrylamide-acrylic acid metal salt copolymer, a polyacrylamide-polyacrylic acid ester compound copolymer, acrylic rubber, and silicone. Among these, a CMCNa is preferable.
The lower limit of the content of the binder as the component (c) in the gas-generating agent composition according to an embodiment of the present disclosure is usually 0.1 mass % or more, and 1 mass % or more in a preferred embodiment, and the upper limit is usually 10 mass % or less, and 8 mass % or less in a preferred embodiment.
(d) Basic Magnesium Carbonate
Basic magnesium carbonate as the component (d) according to an embodiment of the present disclosure is added to ensure a high burn rate of the gas-generating agent composition.
The content of (d) the basic magnesium carbonate in the gas-generating agent composition according to an embodiment of the present disclosure is 11 mass % or less in a 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 still another preferred embodiment.
At the time of the combustion of the gas generating agent, the base from the basic magnesium carbonate promotes the rate-determining process of the combustion reaction, thereby improving the ignitability. In particular, since the pH of the entire gas-generating agent composition can be controlled even with a relatively small amount of basic magnesium carbonate, a sufficient effect can be obtained even with a content of, for example, 6 mass % or less.
Meanwhile, when the content of the basic magnesium carbonate is more than 11 mass %, the burn rate and ignitability of the gas-generating agent composition may decrease.
Meanwhile, from the viewpoint of maintaining good ignitability of the gas-generating agent composition, the content of the basic magnesium carbonate is 0.1 mass % or more in a preferred embodiment.
For the basic magnesium carbonate according to an embodiment of the present disclosure, a commercially available product can be used.
The average particle size of the basic magnesium carbonate according to an embodiment of the present disclosure is 12 μm or less. In a further preferred embodiment, it is 11 μm or less. In order to stably obtain the effect of improving ignitability even when the amount of the basic magnesium carbonate is small at the time of scale-up, it is necessary to increase the contact between the fuel and the oxidizing agent and the basic magnesium carbonate. Therefore, by having an average particle size of 12 μm or less, which is equal to or less than the average particle size of the fuel and the oxidizing agent, the ignitability of the gas-generating agent composition, particularly the ignitability in a low temperature environment, is improved. Meanwhile, the average particle size of the basic magnesium carbonate is usually 5 μm or more, and 8 μm or more in a preferred embodiment.
The combustion of the gas-generating agent composition is easily affected by the external environment, and in general, in a low temperature environment, ignition and combustion continuation are disadvantageous as compared with normal temperature and high temperature. In order to reduce the difference in performance depending upon the temperature, it is important to improve the ignitability in a low-temperature environment.
The average particle size of the basic magnesium carbonate can be measured by a particle size distribution measuring apparatus utilizing a laser diffraction/scattering method. Specifically, it can be measured using a precision particle size distribution measuring apparatus (Microtrac HRA, 3000 II manufactured by MicrotracBEL Corp., and the like).
The average particle size of the basic magnesium carbonate can be adjusted by controlling the initial concentration of the magnesium hydroxide used as a starting material and the reaction temperature when the basic magnesium carbonate is obtained by reactive crystallization by a carbonation method.
(e) Other Components
The gas-generating agent composition according to an embodiment of the present disclosure can include various known additives for the purpose of adjusting the burn rate of the gas-generating agent composition and cleaning the combustion gas within a range in which the issues of the present invention can be solved. Examples of those known additives include metal oxides such as cupric 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 oxide or hydroxide such as acid clay, kaolin, talc, bentonite and diatomaceous earth; metal acid salts such as sodium silicate, mica molybdate, cobalt molybdate, and ammonium molybdate; molybdenum disulfide, calcium stearate, silicon nitride, silicon carbide, metaboric acid, boric acid, boric anhydride, and glass.
The gas-generating agent composition according to an embodiment of the present disclosure may be substantially free of phosphate. The phrase “substantially free of phosphoric acid” means that the content of phosphate in the gas-generating agent composition is not more than the detection limit.
Examples of the phosphate referred to herein include potassium dihydrogen phosphate, potassium monohydrogen phosphate, potassium tertiary phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, sodium tertiary phosphate, calcium dihydrogen phosphate, calcium monohydrogen phosphate, calcium tertiary phosphate, magnesium dihydrogen phosphate, magnesium monohydrogen phosphate, magnesium tertiary phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, and ammonium magnesium phosphate.
Even if the gas-generating agent composition according to an embodiment of the present disclosure does not contain phosphate, the burning temperature does not become higher than necessary. In addition, when the gas-generating agent composition according to an embodiment of the present disclosure does not contain phosphate, ignitability at a low temperature is improved.
The gas-generating agent composition according to an embodiment of the present disclosure can be molded into a desired shape, and can be molded into a single-hole cylindrical shape, a porous cylindrical shape, or a pellet-like molded article. These molded articles can be produced by a method in which water or an organic solvent is added to and mixed with the gas-generating agent composition and a mixture is subjected to extrusion molding (molded articles having a single-hole cylindrical shape or a porous cylindrical shape) or compression molding using a tableting machine or the like (molded articles in the molded article of pellets).
Since the gas-generating agent composition according to an embodiment of the present disclosure has a high burn rate, it is not necessary to make the molded article small, and the manufacturing process does not become complicated.
The gas-generating agent composition according to an embodiment of the present disclosure or the molded article obtained therefrom can be applied to, for example, an inflator for a driver's seat airbag, an inflator for a front 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 vehicles. The gas-generating agent composition according to an embodiment of the present disclosure or a molded article obtained therefrom can be preferably applied to an inflator for a side airbag, which may require early deployment, among these.
In addition, the inflator including: the gas-generating agent composition according to an embodiment of the present disclosure; or the molded article obtained therefrom may be either a pyrotechnic type in which the gas is supplied only from the gas-generating agent or a hybrid type in which the gas is supplied from both a compressed gas such as argon and the gas generating agent.
The gas-generating agent composition according to an embodiment of the present disclosure or a molded article obtained therefrom can also be used as an ignition agent called an enhancer agent (or booster) or the like for transmitting energy of a detonator or squib to a gas generating agent.
Each of the configurations, combinations thereof, and the like in each embodiment are an example, and various additions, omissions, substitutions, and other changes may be made as appropriate without departing from the spirit of the present invention. The present disclosure is not limited by the embodiments and is limited only by the claims.
Hereinafter, the present disclosure will be specifically described with reference to examples. However, the present disclosure is not limited to the embodiments in the following examples.
A gas-generating agent composition before molding having the composition listed in Table 1 was prepared.
Molding into Cylindrical Strand
Water was added and mixed with each of the gas-generating agent compositions of examples and comparative examples listed in Table 1, and the mixture was subjected to extrusion molding, cutting, and drying to obtain a single-hole molded article.
The obtained single-hole molded article was ground in an agate mortar, and the powder passed through a wire mesh having an opening of 500 μm was filled in a mortar side of a predetermined mold.
Next, a punch-side end surface was compressed and held at a pressure of 14.7 MPa for 5 seconds by a hydraulic pump, and then taken out and molded into a cylindrical strand having 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.
Method for Measuring Burn Rate
The cylindrical strand as a sample was placed in an SUS-made closed bomb having an inner volume of 1 L, and the inside of the bomb was completely substituted with nitrogen gas while the pressure was stabilized to the 5 MPa, 7 MPa, or 9 MPa. Thereafter, a predetermined electric current was passed through the nichrome wire in contact with the end face of the strand, and the wire was ignited and fired by the fusing energy. The pressure behavior with time in the bomb was confirmed by a chart of a recorder, the elapsed time from the start of combustion to the pressure rise peak was confirmed from the scale of the chart, and the value calculated by dividing the strand length before combustion by this elapsed time was taken as the burn rate. The results of the examples and comparative examples are listed in Table 1.
Method for Measuring Ignition Time
A predetermined amount of a gas generating agent for evaluation of a single-hole molded article obtained by extrusion molding was charged into a 5 cc bomb test jig, and ignited with an ignition chemical containing ZPP at 26° C. under a low temperature environment (−35° C.) or a normal temperature environment, and the time when the gas generating agent reached 10% of the maximum pressure was defined as an ignition time.
From the comparison of the results from Example 1, Comparative Example 1, and Comparative Example 2 in Table 1, it was found that when basic magnesium carbonate was added to the gas-generating agent composition, the burn rate was increased and the ignition time was shortened.
When the results of Example 1 and Comparative Example 1 were compared, it was found that, when the average particle size of the basic magnesium carbonate was 12 μm or less, the burn rate of the gas-generating agent composition was high and the ignition time was short.
Burn Rate and Ignition Time when the Basic Magnesium Carbonate Content is Changed
A gas-generating agent composition before molding having the composition listed in Table 2 was prepared. The preparation method is the same as that of the gas-generating agent composition of Table 1. The materials used were the same as those listed in Table 1, and the average particle size of the basic magnesium carbonate was 10 μm. These gas-generating agent compositions before molding were molded into cylindrical strands in the same manner as in Example 1 and the like to obtain gas-generating agent compositions after molding. For each gas-generating agent composition after molding, the burn rate and ignition time were measured by the above-mentioned methods. The results are listed in Table 2.
The burn rate and the ignition time are listed as ratios (%) to the burn rate (mm/sec) and the ignition time (msec) of Comparative Example 3, respectively. Further, the results from Examples 2 to 6 and Comparative Example 3 are summarized in
From the results listed in Table 2 and
Burn Rate and Ignition Time when the Average Particle Size of Basic Magnesium Carbonate is Changed
A gas-generating agent composition before molding having the composition listed in Table 3 was prepared. The preparation method is the same as that of the gas-generating agent composition of Table 1. Materials other than the basic magnesium carbonate were the same as those listed in Table 1, and the average particle size of the basic magnesium carbonate was changed. These gas-generating agent compositions before molding were molded into cylindrical strands in the same manner as in Example 1 and the like to obtain gas-generating agent compositions after molding. For each gas-generating agent composition after molding, the burn rate and ignition time were measured by the above-mentioned methods. The results are listed in Table 3.
The burn rate and the ignition time are listed as ratios (%) to the burn rate (mm/sec) and the ignition time (msec) of Example 9, respectively. Further, the results of Examples 7 to 9 and Comparative Example 4 are summarized in
From the results of Table 3 and
Burn Rate and Ignition Time when the Average Particle Size and the Content of Basic Magnesium Carbonate is Changed
Basic magnesium carbonate having an average particle size of 12 μm and 13 μm was prepared, and the content of the basic magnesium carbonate in the gas-generating agent composition was adjusted to 0.1 mass %, 2 mass %, 6 mass %, 7 mass %, and 10 mass % to prepare gas-generating agent compositions before molding having the compositions listed in Table 4. The materials other than basic magnesium carbonate are the same as those listed in Table 1. These gas-generating agent compositions before molding were molded into cylindrical strands in the same manner as in Example 1 and the like to obtain gas-generating agent compositions after molding. For each gas-generating agent composition after molding, the burn rate and ignition time were measured by the above-mentioned methods. The results are listed in Table 4.
The burn rate and the ignition time are listed as ratios (%) to the burn rate (mm/sec) and the ignition time (msec) of Comparative Example 5, respectively. The results from Examples 10 to 14 and Comparative Examples 5 to 10 are summarized in
100%
From the results listed in Table 4 and
From the results of Tables 1 to 3 and
According to the present disclosure, a gas-generating agent composition having a high burn rate and a short ignition time can be provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-166757 | Oct 2020 | JP | national |
| 2021-068270 | Apr 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/036040 | 9/30/2021 | WO |
