Gas generating composition
The present invention provides a gas generating composition comprising: (a) a fuel; (b) an oxidizer; and (c) a compound selected from the group consisting of a double salt of phosphoric acid.
Latest Daicel Chemical Industries, Ltd. Patents:
This nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2005-34759 filed in Japan on Feb. 10, 2005 and 35 U.S.C. § 119(e) on U.S. Provisional Application No. 60/653105 filed on Feb. 16, 2005, which are incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a gas generating composition for an airbag restraint system for automobiles, etc., and a molded article thereof.
2. Description of the Related Art
Compositions containing sodium azide have been widely used as a gas generating agent applied in the gas generator in air bags serving as vehicle occupant safety devices in the past. However, the toxicity of sodium azide in humans [LD50 (oral-rat)=27 mg/kg)] and danger during handling have been considered problematic, and safer gas generating compositions that contain various nitrogenous organic compounds, in other words, “non-azide gas generating compositions,” have been developed as an alternative.
U.S. Pat. No. 4,909,549 discloses a composition containing a tetrazole or triazole compound containing hydrogen in the molecule and an oxygen-containing oxidizer. U.S. Pat. No. 4,370,181 discloses a gas generating composition comprising a metal salt of a bitetrazole that does not contain hydrogen and an oxidizer that does not contain oxygen. U.S. Pat. No. 4,369,079 discloses a gas generating composition containing a metal salt of a bitetrazole compound that does not contain hydrogen and an alkali metal nitrate, an alkali metal nitrite, an alkaline earth metal nitrate, an alkaline earth metal nitrite or a mixture thereof. U.S. Pat. No. 5,542,999 discloses a gas generating agent comprising a fuel such as GZT, TAGN (triaminoguanidine nitrate), NG (nitroguanidine), NTO and the like, a basic copper nitrate, a catalyst to reduce toxic gases, and a coolant. U.S. Pat. No. 5,608,183 discloses a gas generating composition comprising a fuel such as guanidine nitrate and the like, a basic copper nitrate, and guar gum.
However, the above non-azide gas generating compositions produces a residue (mist) after combustion, and a filter should be used to prevent that residue from flowing into the airbag. In this case, it maybe applicable to prepare a composition that readily forms a slag that is easily trapped by the filter after combustion of the gas generating composition.
U.S. Pat. No. 6,143,102 discloses that silica is added, as a slag-forming agent, to a composition including a fuel such as guanidine nitrate, a basic copper nitrate, and a metal oxide such as alumina in order to form a good slag (clinker). JP-A No. 10-502610 discloses that the combustion temperature is lowered by the addition of glass powder to a fuel such as a tetrazole compound, and strontium nitrate, and as a result an amount of NOx and CO is decreased, and a solid slag is formed thereby. U.S. Pat. No. 5,104,466 (JP-A No. 5-70109) discloses that mist is reduced by using a mixture of an alkali metal azide, pellets containing an oxidizer, and granules containing a silica-containing material.
SUMMARY OF THE INVENTIONThe present invention provides a gas generating composition containing (a) a fuel, (b) an oxidizer, and (c) a compound selected from double salts of phosphoric acid.
The present invention also provides a gas generating composition molded article in a single-perforated cylindrical shape or a porous cylindrical shape, obtained by extruding and molding the above gas generating composition.
DETAILED DESCRIPTION OF THE INVENTIONAlthough it is possible to lower the combustion temperature and decrease an amount of NOx and the like by the addition of glass powder as disclosed in JP-A No. 10-502610, there is still room for improvement because not only is glass powder expensive, but also the burning rate decreases, ignitability suffers, and the weight of the gas generating agent increases and the like.
An aspect of the present invention is to solve the problems resulting from the addition of glass powder and to provide a gas generating composition and molded article thereof in which a slag forms easily, an amount of NOx, CO, and the like can be reduced, and the burning rate and ignitability are improved.
As one solution to the problem in the aforementioned prior art, the inventor have already filed an application for a combination of glass powder, aluminum hydroxide, and the like (EP-A1 No. 1415963 published on 6 May 2004).
Moreover, while conducting research for the above invention, the inventor noticed the properties of the post-combustion residue properties and the post-combustion levels of NOx, CO, and the like of the gas generating agent, and after additional research he discovered, in Japanese patent application 2004-262027 and equivalents in US and DE, that by using a phosphate he can obtain post-combustion residue properties and decreases in the amounts of NOx and CO equivalent to the inventions in which glass powder is used, and he filed an application therefor.
The present invention improves upon that invention even further.
The present invention relates to a gas generating composition suitable for an airbag restraint system for automobiles, etc., and a molded article thereof.
EMBODIMENT OF THE INVENTIONSince the gas generating composition and molded article thereof of the present invention contain a compound selected from a double salt of phosphoric acid, the combustion residue solidifies and form a slag. As a result, the combustion residue forms a mist, thereby being prevented from being discharged out of the inflator. Moreover, when the gas generating composition contains the above salt of phosphoric acid, the levels of post-combustion NOx and CO can be reduced, and the burning rate can also be increased.
Furthermore, in the gas generating composition and molded article thereof of the present invention, a double salt of phosphoric acid performs the role of a binder under a high temperature, and when the same is used in a gas generator, the filtering properties by the coolant/filter during combustion are excellent.
<Component (a)>
An example of the fuel of Component (a) used in the present invention includes at least one selected from tetrazole compounds, guanidine compounds, triazine compounds, and nitroamine compounds. The problems addressed by the present invention are solved and the effect of the invention can be obtained by using any of the items listed for Component (a).
Preferred tetrazole compounds are as follows: 5-aminotetrazole, ammonium salts of bitetrazole, and the like. Preferred guanidine compounds are as follows: nitrate salt of guanidine (guanidine nitrate), aminoguanidine nitrate, nitroguanidine, triaminoguanidine nitrate, and the like. Preferred triazine compounds are as follows: melamine, cyanuric acid, ammeline, ammelide, ammeland, and the like. The preferred nitroamine compounds include cyclo-1,3,5-trimethylene-2,4,6-trinitramine.
<Component (b)>
Preferably the oxidizer of Component (b), used in the present invention, includes at least one selected from Component (b-1) a basic metal nitrate, a nitrate salt, and ammonium nitrate; and Component (b-2) a perchlorate and chlorate. The problems addressed in the present invention are solved and the effect of the invention can be obtained by using any of the items listed for Component (b).
The basic metal nitrate salt of Component (b-1) includes at least one selected from 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.
To increase the burning rate, the average particle size of the basic metal nitrate is preferably 30 μm or less and more preferably 110 μm or less. The average particle size is measured by a particle size distribution method utilizing laser diffraction. A basic metal nitrate that has been dispersed in water, and then exposed to ultrasonic waves for 3 minutes is used as the measurement sample; the median particle size (D50) is determined, and the average of two measurements is considered to be the mean particle size.
The nitrate of Component (b-1) include alkali metal nitrates such as potassium nitrate, sodium nitrate, and alkaline earth metal nitrates such as strontium nitrate.
The perchlorate or chlorate of Component (b-2) is a component that not only has an oxidizing action but also a combustion promoting action. The term “oxidizing action” refers to an action that enables efficient combustion by generating oxygen during combustion and also reduces the generated amount of toxic gases such as ammonia, CO. On the other hand, the term “combustion promoting action” refers to an action whereby ignitability of the gas generating composition is improved and an action whereby the burning rate is improved.
The perchlorate or chlorate includes at least one selected from ammonium perchlorate, potassium perchlorate, sodium perchlorate, potassium chlorate, and sodium chlorate.
<Component (c)>
The double salt of phosphoric acid as Component (c), used in the present invention, is a component that traps the mist generated by combustion and forms a slag. Therefore, the combustion residue can be prevented from becoming a mist, being discharged outside of the inflator, and flowing into the airbag by including Component (c) in the gas generating composition.
In addition, because the double salt of phosphoric acid is insoluble in water, the double salt of phosphoric acid will not precipitate, nor cause chalking, on the surface of the molded article even if the molded article of the gas generating composition is manufactured using water. The term “insoluble in water” means that the solubility in 100 ml of pure water at 20° C. is 10 g/100 ml or less.
For Component (c), the following formula can be used: Ma(PO4)bMcXd wherein M is an alkali metal or alkaline earth metal such as Ca, Na; X is OH, CO3, PO4, SiO4, C2O4; and a, b, and c are positive numbers). The compounds Ca3(PO4)2.Ca(OH)2, 3Ca3(PO4)2.Ca(OH)2, 3Ca3(PO4)2.CaCl2, 3Ca3(PO4)2.CaCO3, 3CaNaPO4.CaSiO4 are preferred.
<Component (d)>
The present invention can also include aluminum hydroxide and/or magnesium hydroxide as Component (d). The aluminum hydroxide and magnesium hydroxide can each be used alone or in combination. The problems addressed by the present invention are solved and the effect of the invention can be obtained by using any of the items listed for Component (d).
The aluminum hydroxide and magnesium hydroxide of Component (d) have low toxicity, have a high temperature of initial decomposition, and when they do undergo thermal decomposition, they absorb a large amount of heat and generate aluminum oxide or magnesium oxide and water. The inclusion of aluminum hydroxide and/or magnesium hydroxide lowers the combustion temperature of the gas generating composition, and lowers the generated amounts of post-combustion toxic NOx and CO.
<Component (e)>
The present invention can also include a binder as Component (e). The problems addressed in the present invention are solved and the effect of the invention can be obtained by using any of the items listed for Component (e).
The binder of Component (e) is as follows: at least one selected from carboxymethyl cellulose (CMC), carboxymethyl cellulose sodium (CMCNa), carboxymethyl cellulose potassium, carboxymethyl cellulose ammonium, cellulose acetate, cellulose acetate butyrate (CAB), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl cellulose (HEC), ethylhydroxy ethylcellulose (EHEC), hydroxypropyl cellulose (HPC), carboxymethyl ethylcellulose (CMEC), microcrystalline cellulose, polyacrylamide, amino compounds of polyacrylamide, polyacryl hydrazide, acrylamide-acrylic acid metal salt copolymer, polyacrylamide-polyacrylic acid ester copolymer, polyvinyl alcohol, acrylic rubber, guar gum, starch, and silicone.
Among the above, carboxymethyl cellulose sodium (CMCNa) and guar gum are preferred in consideration of the cohesive properties, cost, ignitability, and the like of the binder.
<Component (f)>
The present invention can also include an additive as Component (f). The problems addressed in the present invention are solved and the effect of the invention can be obtained by using any of the items listed for Component (f).
The additive of Component (f) is as follows: at least one selected from metal oxides such as copper oxide, iron oxide, zinc oxide, cobalt oxide, manganese oxide, molybdenum oxide, nickel oxide, bismuth oxide, gallium oxide, silica, alumina; metal carbonates or basic metal carbonates such as cobalt carbonate, calcium carbonate, magnesium carbonate, basic zinc carbonate, basic copper carbonate; complexes of metal oxides or hydroxides such as Japanese acid clay, kaolin, talc, bentonite, diatomaceous earth, hydrotalcite; metal acid salts such as sodium silicate, mica molybdate, cobalt molybdate, ammonium molybdate; molybdenum disulfide, calcium stearate, silicon nitride, and silicon carbide. These additives can lower the combustion temperature of the gas generator, regulate the burning rate, and reduce the generated amounts of post-combustion toxic NOx and CO. Among these additives, copper oxide, iron oxide, and magnesium oxide are preferred.
<Content Ratio of Components in the Composition>
(1) First Combination
When the composition of the present invention includes three components, (a), (b), and (c), the following content ratio of the components is preferred from the standpoint of solving the problems addressed by the present invention.
The content ratio of the fuel of Component (a) is preferably 35 to 65 mass %, more preferably 40 to 60 mass %, and still more preferably 40 to 55 mass %.
The content ratio of the oxidizer of Component (b) is preferably 30 to 70 mass %, more preferably 35 to 65 mass %, and still more preferably 45 to 55 mass %.
The content ratio of the double salt of phosphoric acid of Component (c) is preferably 0.1 to 15 mass %, more preferably 0.2 to 10 mass %, and still more preferably 0.5 to 5 mass %.
(2) Second Combination
When the composition of the present invention contains four components, (a), (b), (c), and (d), the following content ratio of the components is preferred from the standpoint of solving the problems addressed by the present invention.
The content ratio of the fuel of Component (a) is preferably 30 to 60 mass %, more preferably 35 to 55 mass %, and still more preferably 35 to 50 mass %.
The content ratio of the oxidizer of Component (b) is preferably 35 to 70 mass %, more preferably 35 to 65 mass %, more preferably 40 to 60 mass %, and still more preferably 40 to 55 mass %.
The content ratio of the double salt of phosphoric acid of Component (c) is preferably 0.1 to 15 mass %, more preferably 0.2 to 10 mass %, and still more preferably 0.5 to 5 mass %.
The content ratio of aluminum hydroxide and/or magnesium hydroxide of Component (d) is preferably 0.5 to 15 mass %, more preferably 2 to 12 mass %, and still more preferably 3 to 10 mass %.
When the content of Component (d) lies within the above range, not only can the generated amount of toxic NOx and CO be lowered in association with the decrease in combustion temperature, but also when the composition of the present invention is utilized in an airbag inflator, a burning rate necessary for the expansion and deployment of the airbag within the desired time can be assured.
From the standpoint of increasing mist trapping effectiveness, the total content ratio of Component (c) and Component (d) is preferably 0.5 to 20 mass %, more preferably 2 to 15 mass %, and still more preferably 3 to 10 mass %.
Similarly, from the standpoint of increasing mist trapping effectiveness, the weight ratio of Component (c) and Component (d) [(d)/(c)] is preferably 1 to 20, more preferably 2 to 15, and still more preferably 3 to 10.
(3) Third Combination
When the composition of the present invention includes four components, (a), (b), (c), and (e), the following content ratio of the components is preferred from the standpoint of solving the problems addressed by the present invention.
The content ratio of the fuel of Component (a) is preferably 25 to 55 mass %, more preferably 30 to 55 mass %, and still more preferably 35 to 45 mass %.
The content ratio of the oxidizer of Component (b) is preferably 35 to 70 mass %, more preferably 40 to 60 mass %, and still more preferably 40 to 55 mass %.
The content ratio of the double salt of phosphoric acid of Component (c) is preferably 0.1 to 15 mass %, more preferably 0.2 to 10 mass %, and still more preferably 0.5 to 5 mass %.
The content ratio of the binder of Component (e) is preferably 0.5 to 20 mass %, more preferably 2 to 15 mass %, and still more preferably 3 to 10 mass %.
(4) Forth Combination
When the composition of the present invention includes four components, (a), (b), (c), and (f), the following content ratio of the components is preferred from the standpoint of solving the problems addressed by the present invention.
The content ratio of the fuel of Component (a) is preferably 25 to 55 mass %, more preferably 30 to 55 mass %, and still more preferably 35 to 45 mass %.
The content ratio of the oxidizer of Component (b) is preferably 35 to 70 mass %, more preferably 40 to 60 mass %, and still more preferably 40 to 55 mass %.
The content ratio of the double salt of phosphoric acid of Component (c) is preferably 0.1 to 15 mass %, more preferably 0.2 to 10 mass %, and still more preferably 0.5 to 5 mass %.
The content ratio of the additive of Component (f) is preferably 0.1 to 15 mass %, more preferably 0.5 to 10 mass %, and still more preferably 1 to 5 mass %.
(5) Fifth Combination
When the composition of the present invention contains five components, (a), (b), (c), (d), and (e), the following content ratio of the components is preferred from the standpoint of solving the problems addressed by the present invention.
The content ratio of the fuel of Component (a) is preferably 25 to 55 mass %, more preferably 30 to 55 mass %, and still more preferably 35 to 45 mass %.
The content ratio of the oxidizer of Component (b) is preferably 35 to 70 mass %, more preferably 40 to 60 mass %, and still more preferably 40 to 55 mass %.
The content ratio of the double salt of phosphoric acid of Component (c) is preferably 0.1 to 15 mass %, more preferably 0.2 to 10 mass %, and still more preferably 0.5 to 5 mass %.
The content ratio of aluminum hydroxide and/or magnesium hydroxide of Component (d) is preferably 0.5 to 15 mass %, more preferably 2 to 12 mass %, and still more preferably 3 to 10 mass %.
The content ratio of the binder of Component (e) is preferably 0.5 to 20 mass %, more preferably 2 to 15 mass %, and still more preferably 3 to 10 mass %. The above content ratio is preferred when Component (e) is used in combination with Component (d) because the combustion gas can be scrubbed with no loss of moldability.
(6) Sixth Combination
When the composition of the present invention includes five components, (a), (b), (c), (d), and (f), the following content ratio of the components is preferred from the standpoint of solving the problems addressed by the present invention.
The content ratio of the fuel of Component (a) is preferably 25 to 55 mass %, more preferably 30 to 55 mass %, and still more preferably 35 to 45 mass %.
The content ratio of the oxidizer of Component (b) is preferably 35 to 70 mass %, more preferably 40 to 60 mass %, and still more preferably 40 to 55 mass %.
The content ratio of the double salt of phosphoric acid of Component (c) is preferably 0.1 to 15 mass %, more preferably 0.2 to 10 mass %, and still more preferably 0.5 to 5 mass %.
The content ratio of aluminum hydroxide and/or magnesium hydroxide of Component (d) is preferably 0.5 to 15 mass %, more preferably 2 to 12 mass %, and still more preferably 3 to 10 mass %.
The content ratio of the additive of Component (f) is preferably 0.1 to 15 mass %, more preferably 0.5 to 10 mass %, and still more preferably 1 to 5 mass %.
(7) Seventh Combination
When the composition of the present invention contains six components, (a), (b), (c), (d), (e), and (f), the following content ratio of the components is preferred from the standpoint of solving the problems addressed by the present invention.
The content ratio of the fuel of Component (a) is preferably 25 to 55 mass %, more preferably 30 to 55 mass %, and still more preferably 35 to 45 mass %.
The content ratio of the oxidizer of Component (b) is preferably 35 to 70 mass %, more preferably 40 to 60 mass %, and still more preferably 40 to 55 mass %.
The content ratio of the double salt of phosphoric acid of Component (c) is preferably 0.1 to 15 mass %, more preferably 0.2 to 10 mass %, and still more preferably 0.5 to 5 mass %.
The content ratio of aluminum hydroxide and/or magnesium hydroxide of Component (d) is preferably 0.5 to 15 mass %, more preferably 2 to 12 mass %, and still more preferably 3 to 10 mass %.
The content ratio of the binder of Component (e) is preferably 0.5 to 20 mass %, more preferably 2 to 15 mass %, and still more preferably 3 to 10 mass %. The above content ratio is preferred when Component (e) is used in combination with Component (d) because the combustion gas can be scrubbed with no loss of moldability.
The content ratio of the additive of Component (f) is preferably 0.1 to 15 mass %, more preferably 0.5 to 10 mass %, and still more preferably 1 to 5 mass %.
<Composition Examples>
The gas generating composition of the present invention can be molded into a desired shape and can be prepared as a molded article with a single-perforated cylindrical shape, a porous cylindrical shape, or a pellet shape. The molded article can be manufactured by a method in which water or an organic solvent (preferably water) is added to and mixed with the gas generating composition, and then extrusion molding is performed (molded article with a single-perforated cylindrical shape or a porous cylindrical shape), or by a method in which compression molding is performed using a tablet machine, and the like (molded article in pellet form).
Even if water is used in the manufacture of the molded article, since the double salt of phosphoric acid of Component (c) included in the gas generating composition of the present invention is insoluble in water, it will not dissolve in water during the manufacturing process. In case that a water soluble salt is used, the salt that has dissolved in water precipitates on the surface of the molded article and dries to cause chalking. However in the present invention, the above situation is prevented, so that the ignitability of the molded article is not decreased by such powder on the surface of the molded article.
The gas generating composition of the present invention and the molded article obtained therefrom can be used, for example, in an air bag inflator for a driver side, airbag inflator for passenger side next to the driver, side airbag inflator, inflatable curtain inflater, knee bolster inflator, inflatable seatbelt inflator, tubular system inflator, and pretensioner gas generator in various types of vehicles.
Moreover, inflators using the gas generating composition of the present invention and the molded article obtained therefrom may be either a pyrotechnic inflator, in which the gas supply originates from the gas generating agent alone, or a hybrid type inflator, in which the gas supply originates from both a compressed gas such as argon and the like, and a gas generating agent.
Furthermore, the gas generating composition of the present invention and the molded article obtained therefrom can be used as an igniting agent referred to as an enhancer (or booster) and the like for transferring the energy of a detonator or squib to the gas generating agent.
EXAMPLES Example 12081 g of guanidine nitrate, 2319 g of basic copper nitrate, 150 g of CMCNa, 400 g of aluminum hydroxide, 50 g of 3Ca3(PO4)2.Ca(OH)2, and 735 g of water were mixed and kneaded in a 10 L kneader, molded by extrusion, and passed through cutting, drying and sieving process steps and the like to obtain a gas generating composition molded article in the single-perforated form having an outer diameter of 4.3 mm, an inner diameter of 1.1 mm and a length of 4.1 mm. The results of visual examination confirmed that no chalking was present on the surface of the molded article.
An amount of 39.9 g of the gas generating composition molded article was placed in a single type inflator for a driver side and subjected to a 60 L tank test (a widely known test method disclosed in Paragraph No. 98 of JP-A No. 2001-97176). As a result, a maximum tank pressure was 190 kPa and the amount of mist in the tank was 892 mg.
In addition, this inflator was actuated in a 2800 L tank, and the concentrations of NOx, CO, and NH3 in the exhaust gas inside the tank were measured. In the 2800 L tank test, the test inflator was placed in an iron tank with a capacity of 2800 L, and the concentrations of NO, NO2, CO, and NH3 inside the tank were measured at 3 minutes, 15 minutes and 30 minutes after the inflator was ignited. The mean value of the gas concentration at 3 minutes, 15 minutes and 30 minutes was used as the concentration for each gas.
The following results were obtained: NO2: 0 ppm, NO: 9 ppm, CO: 70 ppm, and NH3: 4 ppm. These results demonstrate that there was only a small amount of mist and the exhaust gas is clean.
Example 2 and Comparative Example 1 Molded articles were manufactured as in Example 1 using the gas generating compositions having the components shown in Table 1. The burning rate and pressure index were measured for the molded articles.
The invention thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Claims
1. A gas generating composition comprising:
- (a) a fuel;
- (b) an oxidizer; and
- (c) a compound selected from the group consisting of a double salt of phosphoric acid.
2. The gas generating composition according to claim 1, wherein the content ratio of (c) in the composition is 0.1 to 15 mass %.
3. The gas generating composition according to claim 1 or 2, further comprising (d) aluminum hydroxide and/or magnesium hydroxide.
4. The gas generating composition according to claim 1 or 2, further comprising (e) a binder and/or (f) an additive.
5. A gas generating composition molded article in a single-perforated cylindrical shape or a porous cylindrical shape, obtained by extruding and molding the gas generating composition according to claim 1 or 2.
Type: Application
Filed: Feb 9, 2006
Publication Date: Aug 31, 2006
Applicant: Daicel Chemical Industries, Ltd. (Sakai-Shi)
Inventor: Jianzhou Wu (Himeji-Shi)
Application Number: 11/349,964
International Classification: C06B 31/28 (20060101);
