Explosive and thermic compositions or charges – Containing inorganic nitrogen-oxygen salt
Reexamination Certificate
1999-06-28
2002-07-09
Carone, Michael J. (Department: 3641)
Explosive and thermic compositions or charges
Containing inorganic nitrogen-oxygen salt
C149S046000, C149S061000
Reexamination Certificate
active
06416599
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a gas generating agent for air bags, and particularly, to a novel gas generating agent having excellent capabilities of collecting slag and generating reduced harmful gas.
BACKGROUND ART
An airbag system, which is a rider protecting system, has been widely adopted in recent years for improving safety of the riders in an automobile. The airbag system operates on the principle that a gas generator is operated under control of signals from a sensor detecting a collision, to inflate an airbag between riders and an car body. The gas generator is required to have a function to produce a required and sufficient amount of clean gas containing no harmful gas in a short time.
On the other hand, the gas generating agents are press-formed into a pellet form for stability to the burning, and the pellets and equivalent are required to maintain their initial flammability characteristics over a long time even under various harsh environments. In the event that the pellets deform or decrease in strength due to deterioration with age, change of environments and the like, the flammability of the explosive compositions will exhibit at an abnormally earlier time than the initial flammability, so there is a fear that the airbag or the gas generator itself may be broken with the abnormal combustion in case of a collision, to fail in accomplishing the aim of protecting the riders or oven cause them injury. To satisfy those required functions, gas generating agents containing metallic compound azide, such as sodium azide and potassium azide, as their major component have been used hitherto. These known gas generating agents are widely used in terms of their advantages that they are burnt momentarily; that the component of combustion gas is substantially nitrogen gas only, so that no harmful gas such as CO (carbon monoxide) or NOx (nitrogen oxide) is produced; and that since the burning velocity is little influenced by the environment or the structure of the gas generator, it is easy to design the gas generator. However, the azide produced by contact of the metallic compound azide and the heavy metal has the nature of being easily exploded by impact and friction, so that it must be handled with the greatest possible caution. Further, the metallic compound azide itself is a harmful material and further has a notable disadvantage that it can decompose in the presence of water and acid to produce harmful gas.
Accordingly, as the substitution of metallic compound azide, gas generating agents containing tetrazoles, azodicarbonamides and other nitrogenous organic compounds as fuel components have been proposed by, for example, Japanese Laid-open Patent Publications No. Hei 2(1990)-225159, No. Hei 2(1990)-225389, No. Hei 3(1991)-20888, No. Hei 5(1993)-213687, No. Hei 6(1994)-80492, No. Hei 6(1994)-239684 and No. Hei 6(1994)-298587. The tetrazoles in particular have a high proportion of atoms of nitrogen in their molecular structure and inherently have the function to suppress the production of CO such that production of CO can be suppressed, so that almost no CO is produced in the combustion gas, as in the case of the metallic compound azide. Besides, the tetrazoles are superior to the abovesaid metallic compound azide in far less danger and toxicity.
Chlorates, such as alkaline metals or alkaline earth metals, perchlorates or nitrates are generally used for oxidizing agents using the nitrogenous organic compounds as fuel to be burnt. The alkaline metals or the alkaline earth metals produce oxides as a result of the burning reaction, and the oxides are harmful materials for a human body and environment such that they must be in the form of easily collectable slag to be collected in the gas generator so that they can be prevented from being released into the air bag. However, since many of the gas generating agents using the nitrogenous organic compounds as fuel to be burnt have the heat of combustion as high as 2,000-2,500 joule/g or more, the gas generated becomes high in temperature and pressure. As a result of this, the slag which is a by-product obtained in the burning of the gas generating agents increase in temperature and thus increase in flowability. In a conventional type of gas generator, a filter fitted therein tends to reduce its slag collection efficiency. For increase of the slag collection efficiency, a method of increased number of filtering members being set in the filter to cool and solidify the slag may be practical, but such a method has a disadvantage of increasing the size of the gas generator, going against the trend toward the size reduction and weight reduction of the gas generator.
Also, various methods of addition of slag forming agents have been proposed for collecting the oxide of alkaline metal or alkaline earth metal in the form of the slag to be easily collected in the filtering part with efficiency. In these methods, silicon dioxide or aluminum oxide is in principle added as an acid substance or a neutral substance easily slag-reactable with the oxides which are basic substances. The proposed methods are conceptually the same as the conventional slag-forming method for the gas generating agent using metallic compound azide as the fuel. The proposed method is the method in which silicate or aluminate is used as the oxide and is converted into a high-viscosity or high-melting, glassy substance, to collect the oxide as the slag. Japanese Laid-open Patent Publication No. Hei 4(1992)-265292, in particular, discloses the method in which a low-temperature slag-forming substance as typified by silicon dioxide and a high-temperature slag-forming forming agent (e.g. alkaline earth metal or transition-metallic oxide) which produces a solid having a melting point close to or more than the reaction temperature are both added to allow high-melting particles, which are solid matters produced by burning reaction, to react with low-temperature slag-forming agents in molten condition and the resultant particles are fused among themselves to improve the collecting efficiency.
However, the addition of the large amounts of substances that do not contribute to the generation of gas causes reduction of a relative proportion of the fuel components of the gas generating components, so that a rate of gasification is high, as compared with the known metallic compound azide, so that the advantage of the nitrogenous organic compound base fuels of holding promise of reducing the size of the gas generator may be impaired.
It is the primary object of the invention to solve the slag collecting problem which stands in the way of commercially practicing the nitrogenous organic compound base fuels. It is the secondary object of the invention to promote the size reduction of the gas generator through the full use of high rate of gasification of the nitrogenous organic compound base fuels. Further, it is the tertiary object of the invention to provide a gas generating agent molded member which is strong and stable with age by improving heat resistant properties and formability of the nitrogenous organic compound base fuels which are poor compared with the metallic compound azide of an inorganic matter.
DISCLOSURE OF THE INVENTION
The present invention provides means to solve these problems. A basic construction of the present invention comprises a fuel component of nitrogenous organic compound and an oxidizing agent as its major components, to which at least one metal nitride or metal carbide is added as a slag forming agent. The metal nitride and the metal carbide are allowed to react with a metallic component or an oxide thereof contained in the fuel component or the oxidizing agent, to form slag.
Another basic construction of the gas generating agent comprises a fuel component of nitrogenous organic compound and an oxidizing agent as its major components, to which at least one metal nitride or metal carbide and a slag forming metallic component that is allowed to react with a metallic component of the metal nitride or the metal carbide or an oxide thereof, to fo
Ikeda Kenjiro
Iwasaki Makoto
Kanamaru Moriyoshi
Kanda Takeshi
Kubo Dairi
Baker Aileen J.
Carone Michael J.
Nippon Kayaku Kabushiki-Kaisha
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