GAS GENERATING COMPOSITION
The present invention is a gas generating composition including fuel and an oxidizing agent, which can be used for an inflator of a vehicle airbag apparatus, wherein the oxidizing agent includes basic copper carbonate, the gas generating composition having the content of the basic copper carbonate of more than 40% by mass and 60% by mass or lower, and satisfying the following requirements (a) to (c): (a) the burning rate is 7.0 mm/sec or above; (b) the gas output is 2.30 mol/100 g or above; and (c) the calorific value per mol of generated gas is 100 kJ/mol or lower.
The present invention relates to a gas generating composition that can be used for an inflator of a vehicle airbag apparatus.
BACKGROUND ARTSA combustion temperature of a gas generating agent needs to be reduced in order to obtain a small and light inflator for a vehicle airbag apparatus, which is highly demanded in recent years. However, reducing the combustion temperature of the gas generating agent often leads to a decrease in burning rate and an amount of generated gas. In order to mend this problem, a method for increasing the amount of the gas generating agent for charging an inflator is considered, but with this method, a small and light inflator cannot be obtained. In order to solve such a problem, it is desired to use “calorific value per mol of generated gas” as an index. It is normally desired that appropriate burning rate or gas output be realized, while keeping a calorific value per mol of generated gas of. approximately 100 kJ/mol or less.
In JP-A No. 2004-155645, basic metal nitrate is disclosed as an oxygen-containing oxidizing agent, which is selected from among basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, basic manganese nitrate, basic iron nitrate, basic molybdenum nitrate, basic bismuth nitrate and basic cerium nitrate, and it is described that the calorific value can be suppressed by adding aluminum hydroxide thereto.
In JP-A No. 2001-220282, it is described that basic metal nitrate selected from among basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, basic manganese nitrate, basic iron nitrate, basic molybdenum nitrate, basic bismuth nitrate and basic cerium nitrate can be used as an oxidizing agent.
In JP-B No. 3907548, it is described that an oxygen-containing oxidizing agent selected from among metal nitrate, ammonium nitrate, a metal perchlorate salt, ammonium perchlorate, metal nitrite, metal chlorate, basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, and basic manganese nitrate.
In JP-A No. 2006-76849, such a gas generating composition is disclosed that the content of basic copper carbonate exceeds 20% by weight, but is equal to or lower than 40 wt %, but because the content of the basic copper carbonate in the embodiments is only 22.0 wt %, the effects obtained in the cases including 30 or more wt % basic copper carbonate are not confirmed.
SUMMARY OF THE INVENTIONThe present invention provides a gas generating composition for use in an inflator of a vehicle airbag apparatus and the like, such that a reduction of the calorific value per mol of generated gas is achieved without impairing burning rate or gas output, and the gas generating composition having no problem with the amount of mist or harmful gas concentration generated in combustion, solving such problems that have not been fully solved in the above prior arts.
The invention 1 provides a gas generating composition, containing fuel and an oxidizing agent, the oxidizing agent comprising basic copper carbonate, the composition having the content of the basic copper carbonate of more than 40% by mass and 60% by mass or lower, satisfying the following requirements (a) to (c):
-
- (a) the burning rate is 7.0 mm/sec or above;
- (b) the gas output is 2.30 mol/100 g or above; and
- (c) the calorific value per mol of the generated gas is 100 kJ/mol or lower.
The gas generating composition of the present invention can reduce the calorific value per mol of generated gas without impairing the burning rate or the gas output, by utilizing a predetermined amount of basic copper carbonate, and is free of problems regarding the amount of mist or harmful gas concentration generated in combustion. Therefore, the gas generating composition of the present invention is useful for an inflator of a vehicle airbag apparatus.
The present invention includes the following preferred embodiments 2 to 6:
2. The gas generating composition according to the invention described above, wherein the content of the basic copper carbonate is 42 to 60% by mass.
3. The gas generating composition according to the invention described above, wherein the oxidizing agent is a combination of the basic copper carbonate and a basic metal nitrate and/or a nitrate, and the total content of the oxidizing agent is 50 to 80% by mass.
4. The gas generating composition according to the invention described above, wherein the oxidizing agent is a combination of the basic copper carbonate and basic copper nitrate and/or strontium nitrate, and the total content of the oxidizing agent is 50 to 80% by mass.
5. The gas generating composition according to the invention described above, further including a carboxymethyl cellulose salt as a binder.
6. The gas generating composition according to the invention described above, further including aluminum hydroxide.
The gas generating composition of the present invention or a molded article obtained therefrom can be used for, for example, an airbag inflator of a driver's side, an airbag inflator of a passenger side next to the driver, a side airbag inflator, 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 a gas generator for a pretensioner, of various vehicles.
The gas generating composition of the present invention or an inflator that uses a molded article obtained from the gas generating composition may be of a pyrotechnic type in which a gas supply source is only a gas generating agent or of a hybrid type that uses both compressed gas, such as argon, and a gas generating agent.
Furthermore, the gas generating composition of the present invention or a molded article obtained therefrom can be also used as an igniting agent called an enhancer or a booster, which serves to transmit the energy of a detonator or a squib to the gas generating agent.
<Fuel>
The fuel used in the present invention can be a known fuel for a gas generating composition, for example, at least one selected from guanidine compounds, tetrazole compounds, triazine compounds, purine compounds, and amino-acid derivatives.
Preferred guanidine compounds include guanidine nitrate, nitroguanidine, and guanylurea dinitramide. Preferred tetrazole compounds include 5-aminotetrazole and bitetrazole ammonium salt. Preferred triazine compounds include melamine, melamine cyanurate, melamine nitrate, melamine perchlorate, trihydrazinotriazine, and a nitrocompound of melamine. Preferred purine compounds include 8-azaguanine. Preferred amino-acid derivatives include glycine.
The fuel used in the present invention can be two or more types of mixtures if necessary. A mixture of two or more guanidines or a mixture of guanidines and another substance, is preferred. For example, in the case of using only guanidine nitrate, problems are caused in the burning rate and the ignition ability of the gas generating composition, although the calorific value thereof can be made relatively low. In the case of using only nitroguanidine, the gas output of the gas generating composition becomes relatively low, although there are no problems in the burning rate or the ignition ability thereof. In order to handle these problems, the guanidine nitrate and the nitroguanidine can be mixed to obtain a fuel that takes the advantages of the guanidine nitrate and the nitroguanidine and overcomes the disadvantages thereof.
The content of the fuel used in the present invention is preferably 20 to 60% by mass, more preferably 25 to 55% by mass, or even more preferably 30 to 50% by mass, in the gas generating composition.
<Oxidizing Agent>
The oxidizing agent used in the present invention contains basic copper carbonate. The content of the basic copper carbonate exceeds 40% by mass but is equal to or lower than 60% by mass, or preferably 42 to 60% by mass, in the gas generating composition. The basic copper carbonate in an amount of 40% by mass or lower cannot exert the effect of reducing the calorific value, and the basic copper carbonate exceeding 60% by mass impairs the ignition ability.
An average particle diameter of the basic copper carbonate is preferably equal to or less than 5 μm, more preferably equal to or less than 3 μm, or even more preferably equal to or less than 1 μm. When the average particle diameter is large, the burning rate slows down, deteriorating the ignition ability. The average particle diameter was measured by particle size distribution measurement method based on laser scattering. A particle size meter MICROTRAC, Model No. 9320-X100, manufactured by Neede+Northrop Company, was used for the measurements. A sample was dispersed in ion-exchange water and irradiated with 50-W ultrasonic waves for 60 seconds. The 50% accumulated value of particle volume was obtained. Average values obtained by two measurements were taken as average particle diameters.
The oxidizing agent can further contain known oxidizing agent, such as one or more selected from among nitrate, basic metal nitrate, ammonium nitrate, metal perchlorate, ammonium perchlorate, metal nitrite, metal chlorate and the like.
Examples of basic metal nitrate include one or more selected from among basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, basic manganese nitrate, basic iron nitrate, basic molybdenum nitrate, basic bismuth nitrate and basic cerium nitrate. Among these, basic copper nitrate is preferred.
Examples of nitrate include one or more selected from among alkali metal nitrates such as potassium nitrate and sodium nitrate, as well as alkaline earth metal nitrates such as strontium nitrate. Among these, strontium nitrate is preferred.
The total content of the oxidizing agent used in the present invention is preferably 50 to 80% by mass, more preferably 50 to 75% by mass, or even more preferably 50 to 70% by mass in the gas generating composition.
<Binder>
The gas generating composition according to the present invention can contain a known binder of a gas generating composition, if necessary. Examples of the binder include one or more selected from among carboxymethyl cellulose (CMC), carboxymethyl cellulose sodium salt (CMCNa), carboxymethyl cellulose potassium salt (CMCK), carboxymethyl cellulose ammonium salt (CMCNH4), cellulose acetate, cellulose acetate butyrate (CAB), methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), ethyl hydroxyethyl cellulose (EHEC), hydroxypropyl cellulose (HPC), carboxymethyl ethyl cellulose (CMEC), microcrystalline cellulose, polyacrylamides, aminated compounds of polyacrylamide, polyacryl hydrazide, a copolymer of acrylamide and a metal salt of acrylic acid, a copolymer of polyacrylamide and a polyacrylic acid ester compound, polyvinyl alcohol (PVA), acryl rubber, guar gum, starch, and silicone.
Water-soluble cellulose derivatives (CMC, CMCNa, CMCK, CMCNH4, MC, EC, HEC, EHEC, HPC, CMEC), which are water-soluble binders, microcrystalline cellulose, PVA, guar gum, and starch are preferred as the binder. Above all, the water-soluble cellulose derivatives are preferred, CMC, CMCNa, CMCK and CMCNH4 are more preferred, and CMCNa is even more preferred.
The content of the binder used in the present invention is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, or even more preferably 2 to 15 parts by mass, with respect to a total of 100 parts by mass of the fuel and the oxidizing agent.
<Additives>
The gas generating composition according to the present invention can include a known additive of a gas generating composition, such as a combustion catalyst, a heat absorbing agent, a slag forming agent, a lubricant or the like, according to necessity. Examples of the known additive include metal oxides such as copper oxide, iron oxide, zinc oxide, cobalt oxide, manganese oxide, molybdenum oxide, nickel oxide, bismuth oxide, silica, and alumina; metal hydroxides such as aluminum hydroxide, cobalt hydroxide, iron hydroxide, and magnesium hydroxide; metal carbonates or basic metal carbonates such as cobalt carbonate, calcium carbonate, and basic zinc carbonate; complex compounds of metal oxides or hydroxides, such as Japanese acid clay, kaolin, talc, bentonite, diatomaceous earth, and hydrotalcite; ammonium dihydrogenphosphate, ammonium polyphosphate, metal acid salts such as sodium silicate, mica molybdate, cobalt molybdate, and ammonium molybdate; silicone, molybdenum disulfide, calcium stearate, silicon nitride, silicon carbide, boric acid, metaboric acid, anhydrous boric acid, and the like.
The additive used in the present invention may be in such an amount that does not have a great impact on the advantageous effects of the present invention in the calorific value, the gas output and the burning rate. The content of the additive is preferably 0.5 to 30 parts by mass, more preferably 1 to 25 parts by mass, or even more preferably 2 to 20 parts by mass, with respect to a total of 100 parts by mass of the fuel and the oxidizing agent.
The gas generating composition according to the present invention satisfies the following requirements (a) to (c), and preferably, also satisfies a requirement (d):
-
- (a) The burning rate is preferably 7.0 mm/sec or above, or more preferably 7.4 mm/sec or above;
- (b) The gas output is 2.30 mol/100 g or above, or more preferably 2.37 mol/100 g or above;
- (c) The calorific value per mol of generated gas is 100 kJ/mol or lower, or more preferably 90 kJ/mol or lower; and
- (d) The combustion temperature is preferably 2000 K or lower, or more preferably 1800 K or lower.
The composition according to the present invention can be molded into a desired shape, and a cylindrical molded article, a cylindrical molded article with a single hole, a perforated cylindrical molded article, or a pellet-shaped molded article can be obtained.
These molded articles can be manufactured by a method in which water or an organic solvent is added to and mixed with the composition and the obtained mixture is extrusion-molded (into the cylindrical molded article, the cylindrical molded article with a single hole, or a perforated cylindrical molded article), or by a compression-molding method using a pelletizer or the like (the pellet-shaped molded article).
EXAMPLES<Measuring the Burning Rate>
[Method for Forming a Measuring Strand]
The components of the gas generating composition were adequately mixed in the proportions shown in Table 1, and thereafter 30 g thereof was obtained. Water in an amount of 6 g was added thereto, which was then mixed in an antistatic plastic bag for 5 minutes or longer. The resultant mass was pulverized into small pieces and dried at 110° C. for two hours. The resultant product was then pulverized into powder in a mortar. 1.7 to 2.2 g of the powder was poured into a mold and the pressure of approximately 220 MPa (2250 kgf/cm2) was applied with a hydraulic pump, which was maintained for five seconds, to obtain a cylindrical strand (with a outer diameter of 9.55 mm and a length of 12.70 mm).
[Method of Measurement]
The measuring strand obtained in the manner described above was left in a temperature of 110° C. for 16 hours to eliminate water therefrom. Subsequently, an epoxy resin adhesive “Bond Quick 30” was applied twice to the side surface and one side of the measuring strand so as to ignite and combust the measuring strand from an end surface thereof. The resultant strand was installed in an SUS sealed bomb (internal volume thereof was 1 L), and the bomb was pressurized up to 7 MPa, while the inside thereof was purged with nitrogen. After the pressure inside the bomb was stabilized, a voltage of 12 V was applied to a nichrome wire in contact with the end surface of the measuring strand, thereby igniting and combusting the measuring strand by means of the fusing energy of the nichrome wire. The length of the measuring strand obtained prior to the combustion was divided by the time that has elapsed since the start of the combustion until when the peak of pressure rise was obtained, and the value obtained by this calculation was taken as the burning rate.
[Calculating the Gas Output, the Calorific Value Per Mol of Generated Gas, and the Combustion Temperature]
The gas output, the calorific value per mol of generated gas, and the combustion temperature were calculated through a simulation using a thermochemical equilibrium calculation program “NEWPEP.”
[Method for Measuring Friction Sensitivity and Drop-Hammer Sensitivity]
Powdered ingredients to include in the gas generating composition were each weighed such that the mass of the gas generating composition would be 1 g, and they were mixed adequately. The friction sensitivity and the drop-hammer sensitivity of the obtained powder sample were measured based on the explosive performance test method disclosed in Japanese Industrial Standard (JIS) K4810-1979.
[Method for Measuring Decomposition Temperature]
The same gas generating composition as the one used in the method for measuring the friction sensitivity and the drop-hammer sensitivity was used to perform thermogravimetry by using a thermobalance (TGDTA6300 manufactured by Seiko Epson Corporation). The temperature at which the mass is reduced was taken as a decomposition temperature.
[Method for Measuring Exhaust Gas Concentration]
After the measuring strand (with an outer diameter of 9.55 mm and mass of 2.00 g) obtained in the same method as the one described above was left in a temperature of 110° C. for 16 hours to eliminate water therefrom, the measuring strand was installed in an SUS sealed bomb (internal volume thereof was 1 L), and the bomb was pressurized up to 7 MPa, while the inside thereof was purged with nitrogen. After the pressure inside the bomb was stabilized, a predetermined current was passed into a nichrome wire in contact with the end surface of the measuring strand, thereby igniting and combusting the measuring strand by means of the fusing energy of the nichrome wire. Thus generated exhaust gas was obtained 60 seconds later, and the concentration thereof was measured using a gas detector (GV-100S manufactured by Gastec Corporation) and a gas detection tube (No. 10: for NO, No. 3L and 3M: for detecting NH3, No. 1L: for CO, manufactured by Gastec Corporation).
EXAMPLES AND COMPARATIVE EXAMPLESThe compositions shown in Table 1 were measured in the manners shown in Table 1.
It was confirmed in any of Examples 1 to 23 that the calorific value per mol of generated gas was sufficiently controlled (to 100 kJ/mol or lower) without impairing the practical burning rate (7.0 mm/sec or above) and the gas output (2.30 mol/100 g or above), in spite of the use of a large amount of basic copper carbonate (exceeding 40% by mass but equal to or lower than 60% by mass), which has a great heat absorption effect. However, Comparative Examples 1 to 8 show that either the gas output or the burning rate is not enough, causing a problem in practicality of these compositions.
The compositions shown in Table 2 were measured in the manners shown in Table 2.
According to Table 2, the friction sensitivities were, according to the JIS grades, Grade 7, indicating that the compositions are in the safest level, or Grade 6, indicating that the compositions can be handled safely. The drop-hammer sensitivities were, according to the JIS grades, Grade 8, indicating that the compositions are in the safest level. Furthermore, a decomposition start temperature was 150° C. or above, which is in a decomposition start temperature range where the compositions can withstand during welding for manufacturing an inflator. Therefore, it is confirmed that all of the compositions are less dangerous, can be manufactured safely, and are practical.
The compositions shown in Table 3 were measured in the manners shown in Table 3.
According to Table 3, it is confirmed that there are no problems in the concentrations of the hazardous exhaust gases NO, NH3 and CO.
Claims
1. A gas generating composition, comprising fuel and an oxidizing agent, the oxidizing agent comprising basic copper carbonate, the composition having the content of the basic copper carbonate of more than 40% by mass and 60% by mass or lower, satisfying the following requirements (a) to (c):
- (a) the burning rate is 7 0 mm/sec or above;
- (b) the gas output is 2.30 mol/100 g or above; and
- (c) the calorific value per mol of the generated gas is 100 kJ/mol or lower.
2. The gas generating composition according to claim 1, wherein the content of the basic copper carbonate is 42 to 60% by mass.
3. The gas generating composition according to claim 1, wherein the oxidizing agent is a combination of the basic copper carbonate and a basic metal nitrate and/or a nitrate, and the total content of the oxidizing agent is 50 to 80% by mass.
4. The gas generating composition according to claim 1, wherein the oxidizing agent is a combination of the basic copper carbonate and basic copper nitrate and/or strontium nitrate, and the total content of the oxidizing agent is 50 to 80% by mass.
5. The gas generating composition according to claim 1, further comprising a carboxymethyl cellulose salt as a binder.
6. The gas generating composition according to claim 1, further comprising aluminum hydroxide.
Type: Application
Filed: May 14, 2010
Publication Date: Mar 8, 2012
Inventor: Syouji Kobayashi (Hyogo)
Application Number: 13/321,426
International Classification: C06B 31/00 (20060101); C06B 45/10 (20060101); C06B 43/00 (20060101);
