WO2000044691A1

WO2000044691A1 - METHOD FOR REDUCING NO¿x?

Info

Publication number: WO2000044691A1
Application number: PCT/JP2000/000419
Authority: WO
Inventors: Yo Yamato
Original assignee: Daicel Chemical Industries, Ltd.
Priority date: 1999-01-27
Filing date: 2000-01-27
Publication date: 2000-08-03
Also published as: JP2000211987A

Abstract

A method for reducing the amount of NOx generating on the burning of a gas-generating agent for an air bag which comprises burning simultaneously two or more types of gas-generating agents having different oxygen balances. The amount of NOx is reduced through the reaction of an oxidizing gas and a reducing gas. The employment of the method according to the invention reduces the amount of NOx generating on the burning of a gas-generating agent for an air bag, which results in the reduction of the probability for the use of an air bag to affect adversely the health of an occupant, and thus in improvement of the safety and reliability of an inflator system.

Description

Specification

NOx reduction method Technical field

The present invention relates to a NOX reduction method for reducing the amount of NOX generated by combustion of a gas generating agent for an airbag during an inflation of an airbag system provided for protecting a human body mounted on an automobile, an aircraft, or the like.

Conventional technology

At present, sodium azide is well known as a fuel component of a gas generating agent used in an airbag system. A gas generator using sodium azide has a decomposition temperature of at least 400 and is excellent in heat resistance, and has no particular problem with its combustion characteristics, and is widely used in practice. However, sodium azide generates explosive compounds by reacting with heavy metals, etc., and has a low oral toxicity LD50 of 27 mg / kg for mouse rats. It is known that there is a concern about environmental pollution.

As a means to solve these problems, compounds that replace sodium azide are being studied. For example, Japanese Patent Publication No. 6-57669 discloses a gas generating agent containing a transition metal complex of tetrazole and triazol; Japanese Patent Application Laid-Open No. 5-254977 discloses A gas generating agent containing triaminoguanidine nitrate is disclosed; Japanese Patent Application Laid-Open No. Hei 6-23963 discloses a gas generating agent containing carbohydrazide; Japanese Patent Application Laid-Open No. 7-61885 The gazette contains cellulose acetate and perchloric acid lime and nitrogen-containing nonmetallic compounds. US Pat. No. 5,125,684 discloses a gas generating agent containing 15 to 30% of a cellulosic binder such as nitrocellulose and an energy substance; No. 292 discloses a gas generating composition comprising a combination of a tetrazole and triazole derivative, an oxidizing agent and a slag forming agent.

In general, a gas generating composition comprising a nitrogen-containing organic compound emits a chemical equivalent in combustion, that is, an amount of oxygen necessary for burning carbon, hydrogen, and other oxidizable elements in the nitrogen-containing organic compound molecule. When using an oxidizing agent that generates enough, it generates a larger amount of heat, has a higher combustion temperature, has a lower linear burning rate, and generates a smaller amount of toxic gas than a gas generating composition using an inorganic azide compound. Has the disadvantage of doing so.

Of the gases generated by the combustion of the gas generating agent, CO 2 and NO x are particularly problematic, and these gases are almost always generated by the combustion of organic compounds. Although the absolute value differs depending on the type of organic compound and oxidizing agent used in the gas generating agent, if the amount of organic compound is larger than the stoichiometric total amount, the concentration of trace C0 in the generated gas will increase, and the oxidizing amount of the organic compound will increase. If it is lower than that, the concentration of trace NOX in the generated gas will increase. During combustion of the gas generant, the two do not become completely zero, and it is necessary to find a range in which the optimum balance between them is maintained. From the viewpoint of user protection, it is required to further reduce the concentration of C〇 and NOX generated, but at present, no effective reduction method has been put into practical use. Even if the mixing ratio of the organic compound and the oxidizing agent is changed, it does not decrease so much, and it is very difficult to reduce it.

As a method generally known as a NOX reduction method, there is a large-scale denitration technology using a boiler or a burner that burns heavy oil, light oil, coal, propane gas, and the like. One of the typical denitration technologies There is a selective reduction method using NH ₃ to remove NO x by the following reaction.

NO + NH ₃ + 1/4 〇 _{_{_{2 → N 2 + 3/2 H 2}}} 0 it is conceivable to use also in this selective reduction method Infure evening and at NH ₃ (boiling point one 3 3.4 a gas ) Cannot be directly used as a reducing agent.

However, this selective reduction method is used in inflation overnight.

98/06682. Certainly, NOx reduction effects can be seen, but the urea, ammonium carbonate and ammonium carbamide shown here have poor heat resistance, and will decompose and sublime in the high-temperature test required for infra-free. Cannot be put to practical use. In addition, ammonium chloride, ammonium sulfate, and ammonium fluoride are not preferable because a gas containing chlorine, fluorine, and sulfur is generated after decomposition. Thus, this technology also has problems and is not enough. Disclosure of the present invention

The present invention provides a method for reducing NOx that can reduce the amount of NOx generated by the combustion of a gas generating agent for an airbag and improve safety further from the viewpoint of user protection during the inflation of an airbag system. The purpose is to provide.

It is another object of the present invention to provide an inflation system that employs the NOx reduction method.

The inventors of the present invention have repeated studies focusing on the fact that the selective reduction method shows a certain effect as a method for reducing the amount of NOx. As a result, they found that the selective reduction method reduces the amount of N〇X due to the effective reaction between the gas generated by the combustion of the gas generating agent and the gas generated from the reducing substance. Was. By further developing this principle, they have found that an effective reaction between an oxidizing gas and a reducing gas can achieve the above object, and have completed the present invention. That is, the present invention provides a NOX reduction method characterized by reducing the amount of NOX generated by simultaneously burning two or more types of gas generating agents having different oxygen balances.

The present invention also provides an inflation system that employs the above-mentioned N〇X reduction method.

The present invention is a method for generating a gas in which the amount of generated NO X is reduced by simultaneously burning two or more types of gas generating agents having different oxygen balances in an air bag gas generator including the gas generating agent.

By applying the NO X reduction method of the present invention, the amount of NO X generated by combustion of the gas generating agent for an air bag can be reduced. As a result, the possibility of adversely affecting the user's health can be reduced, and the reliability and safety of the infra-system can be improved. Embodiment of the Invention

Normally, only one gas generant is put into inflation overnight. Fuels, oxidizing agents, binders, slag forming agents, and other additives whose types and amounts are adjusted to satisfy the characteristics required for gas generating agents are used. At this time, it is very important to find a range in which the optimal balance between the amounts of CO and NOX, which are trace amounts of toxic gases generated in the post-combustion gas, is maintained. In practice, adjusting these gas components involves adjusting the oxygen balance of the gas generating agent. Oxygen balance is the excess or deficiency of oxygen for the complete combustion of combustible components in explosives. Oxygen balance is expressed as excess or deficiency of oxygen (g) per gram of explosive. However, no further effective method of reducing toxic gases has been put to practical use. Therefore, as a result of research, it has been found that the amount of NOX generated can be reduced by simultaneously burning two or more gas generating agents having different oxygen balances as in the present invention.

In other words, this does not control combustion in the solid phase by means of a combustion catalyst or the like, but daringly generates oxidizing gas and reducing gas from two or more types of gas generating agents with different oxygen balances, and makes these effective reactions. By controlling it, we try to reduce the amount of N〇 x. During the period of inflation during which the gas generating agent is burning, the temperature is high and the pressure is high, which is favorable conditions for these gas reactions.

At this time, the oxygen balance of the two or more gas generating agents used may be any as long as it has an effect, but is preferably -0.2 to +0.2 g / g. It is particularly preferred that it is -0.1 to +0.1 lg / g.

Usually, it is preferable to perform this N〇 x reduction method using two types of gas generators, one having a negative oxygen balance and the other having a positive oxygen balance. The balance is preferably -0.2 to 0.2 Og / g and 0.0 to +0.2 g / g, -0.1 to 0.Og / g and 0.0 to + 0.lg / g. g is particularly preferred.

In the NOX reduction method of the present invention, the gas generating agent may be placed anywhere in the inflation bath if the combustion gas generated from two or more types of gas generating agents effectively reacts. Preferably, it is located in the gas generant combustion chamber.

Next is the separation or mixing of two or more gas generants during inflation, but this is not particularly limited. Two or more types of gas generating agents may be mixed well by a mixer, etc., and handled as if they were a single type of gas generating agent, or they may be completely separated and charged during inflation. . When confused, the gas generating agent is easy to handle and a more reliable gas reaction can be expected. In addition, when the gas generating agent is handled separately, there is an advantage that the amount of each gas generating agent can be measured more accurately.

Next, the non-azide gas generating composition used in the present invention will be described.

The non-azide gas generating composition used in the present invention is preferably composed of a nitrogen-containing compound, an oxidizing agent, if necessary, a slag forming agent and a binder.

The nitrogen-containing compound used in the present invention is selected from the group consisting of a guanidine derivative, a tetrazole derivative, a bititrazole derivative, a triazole derivative, a hydrazine derivative, a triazine derivative, an azodicarbonamide derivative and a disocyanamide derivative. Species or a mixture of two or more species. Specific examples of these include nitroguanidine, guanidine nitrate, 5-aminotetrazole, bittrazol diammonium salt, 5-year-old xo 1,2,4-triazolyl, cyanoguanidine, triaminoguanidine nitrate, Examples thereof include trihydrazinotriazine, biuret, azodicarbonamide, piurea, carbohydrazide, carbohydrazide nitrate complex, oxalic acid dihydrazide, hydrazine nitrate complex, and sodium disocyanamide.

Among these nitrogen-containing compounds, one or more members selected from the group consisting of a tetrazole derivative and a guanidine derivative are preferable, and nitroguanidine, cyanoguanidine and 5-aminotetrazole are particularly preferable. The mixing ratio of the nitrogen-containing compound in the gas generating composition according to the present invention varies depending on the number of carbon elements, hydrogen elements and other oxidized elements in the molecular formula, but is usually in the range of 20 to 70% by weight. Is preferred, and a range of 25 to 60% by weight is particularly preferred. Various oxidizing agents can be used as the oxidizing agent used in the gas generating composition according to the present invention, and nitrates, nitrites, and perchloric acids containing cations selected from the group consisting of alkali metal and alkaline earth metal are used. At least salt and chlorate

An oxidizing agent selected from one type is preferred. Examples of the nitrate containing a cation selected from an alkali metal or an alkaline earth metal include sodium nitrate, potassium nitrate, magnesium nitrate, strontium nitrate, and the like. The mixing ratio of the oxidizing agent in the gas generating composition according to the present invention varies in absolute value depending on the type and amount of the gas generating compound used, but is preferably in the range of 30 to 80% by weight, particularly 40 to 75% by weight. A range is preferred.

The function of the slag forming agent in the gas generating composition according to the present invention is as follows. The oxide of a metal or an alkaline earth metal formed by the decomposition of the oxidizer component in the gas generating composition. It is a function to change from a liquid to a solid to stop it in the combustion chamber in order to avoid releasing mist as an inflation outside the evening. It is possible to select a slag forming agent optimized by the difference in metal components.

Specific examples of slag forming agents include acid clay, silica, bentonite-based, kaolin-based, and other naturally-occurring clays mainly composed of aluminosilicates; synthetic myc, synthetic olinite, synthetic smectite Slag forming agents selected from at least one of alumina, aluminum hydroxide, and the like. Among them, acid clay, Alumina or silica is preferred.

In the present invention, the slag forming agent is not essential, but adding an appropriate amount to the gas generating composition is very effective. When the slag forming agent is added, the mixing ratio can be varied in the range of 1 to 20% by weight, but is preferably in the range of 3 to 10% by weight. If the amount is too large, the linear burning speed and the gas generation efficiency decrease, and if the amount is too small, the slag forming ability can be sufficiently exhibited. Absent.

As the binder in the gas generating composition according to the present invention, any binder can be used as long as it does not significantly affect the burning behavior of the composition. Specific examples of the binder used in the present invention include metal salts of carboxymethyl cellulose, hydroxyxethyl cellulose, cellulose acetate, cellulose propionate, cellulose acetate butyrate, nitrocellulose, microcrystalline cellulose, and polyvinyl alcohol. Polysaccharide derivatives such as guar gum and starch; organic binders such as calcium stearate; or inorganic binders such as molybdenum disulfide, acid clay, talc, bentonite, diatomaceous earth, kaolin, silica, and alumina.

In the present invention, the binder is not essential, but adding an appropriate amount to the gas generating composition is very effective. When the binder is added, the compounding ratio is preferably in the range of 0 to 15% by weight. The larger the amount, the stronger the fracture strength of the molded body, but as the amount increases, the number of carbon elements and hydrogen elements in the composition increases, and a small amount of CO gas, which is an incomplete combustion product of carbon elements It is not preferable because the concentration of methane increases or the linear burning rate decreases.

The gas generating composition of the present invention can be produced by a dry method in which a fuel for a gas generating agent, an oxidizing agent, and the like are mixed in a powder form, or a wet method in which the fuel and the oxidizing agent are mixed in the presence of water or an organic solvent.

Further, the gas generating composition of the present invention can be molded into a desired shape. For example, compression molding using a tableting machine to produce pellets, compression molding using a disk molding machine to produce discs, grinding pellets to discs, or granulation using daraniure Alternatively, it can be extruded using a drawing machine (extrusion molding machine) to make a drawn medicine (non-porous, single-hole, porous). Furthermore, it can be rolled and formed into a film or plate shape. These molding methods can be appropriately selected according to the properties to be imparted to the molded article of the gas generating composition. For example, when the compression molding method is applied, the binder does not need to be molded or only a small amount is required, so that there is a tendency that the flammability does not decrease. Also, when the extrusion molding method is applied, it is easier to mold a thin web than the compression molding method, so that a molded product can be obtained even with a composition having a slow burning rate. In addition, the extrusion molding method is suitable for mass production because molding can be performed in a relatively short time. In the case of a composition having a high burning rate, the size of the molded product can be increased, so that the production efficiency can be further increased. In addition, when the extrusion molding method is applied, a molded article having a complicated shape such as non-porous, single-pored, or porous can be manufactured, so that various combustion characteristics can be imparted.

The NOX reduction method according to the present invention provides an inflation system provided with a module case containing an inflation circuit and an airbag, a judgment circuit, a sensor, and the like, which are provided for protecting a human body mounted on an automobile, an aircraft, or the like. It can be applied to the overnight system. Example

Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.

Example 1

Nitoroguanijin a (NQ) and strontium nitrate _{_{(S r (N0 3) 2}} ) were mixed so that the compositions shown in Table 1. Then, about 2 g of the mixed powder was compression-molded with a hand brace machine. A strand having a diameter of 9.6 mm and a length of about 14 mm was obtained. table 1

Examples 2-3 and Comparative Examples 1-3

The strands of Example 1 were burned in the combinations shown in Table 2, and the gas after combustion was analyzed to confirm the NOX reduction effect of the present invention. The strand was burned in a 1 liter combustion vessel by energizing the nichrome wire. The inside of the container was replaced with nitrogen, and the pressure was 5 O kgi / cm ² .

Analysis of C O and N 0 X was performed using a detector tube immediately after ignition.

From these results, it was found that the gas generating agent having the oxygen balance of the brass and the gas generating agent having the negative oxygen balance of Examples 2 and 3 was smaller than the case of burning the gas generating agent having the oxygen balance of 0.000 g / g as in Comparative Example 1. It has been proved that NOx and CO can be reduced when mixed and burned.

In addition, when the gas generating agent having a negative or positive oxygen balance was burned alone as in Comparative Examples 2 and 3, NOX and C〇 increased remarkably. It was found that the gas composition did not become the same. That is, in Example 3, it was found that NOX and C 0 were reduced by the reaction of the gases generated from the two types of gas generating agents. Table 2

Claims

The scope of the claims

1. A NOx reduction method characterized by reducing the amount of NOx generated by simultaneously burning two or more gas generating agents with different oxygen balances.

2. The NOx reduction method according to claim 1, wherein the gas generating agent used is of two types: one having a negative oxygen balance and one having a positive oxygen balance.

3. The NOx reduction method according to claim 1, wherein the gas generating agent is a non-azide-based gas generating agent and contains a nitrogen-containing compound and an oxidizing agent.

4. The nitrogen-containing compound is one or more selected from a guanidine derivative, a tetrazole derivative, a bitetrazole derivative, a triazole derivative, a hydrazine derivative, a triazine derivative, an azodicarbonamide derivative, and a dicyanamide derivative. NOX reduction method described in 3.

5. An inkjet system employing the NOx reduction method according to any one of claims 1 to 4.

6. In a gas generator for an airbag containing a gas generating agent, a method of simultaneously burning two or more types of gas generating agents with different oxygen balances to generate a gas with reduced NO X emissions.