Ammunition and explosives – Jacketed or cartridge gas generator – For gas-powered tools or means
Reexamination Certificate
1998-11-03
2003-01-14
Miller, Edward A. (Department: 3641)
Ammunition and explosives
Jacketed or cartridge gas generator
For gas-powered tools or means
C102S283000, C149S019910, C149S046000
Reexamination Certificate
active
06505562
ABSTRACT:
TECHNICAL FIELD
This invention relates to a gas generating composition adequately employed in air bag restraint systems in automobiles and a molded article thereof. More particularly, it relates to a gas generating composition containing fuels comprising a specific polymer compound and an ammonium nitrate-type oxidizing agent as the base together with other additives and a molded article thereof.
BACKGROUND ART
Compositions containing sodium azide have been frequently employed as gas generating compositions for air bags to be used in occupant crash protection systems in automobiles. However, there arises in recent years a problem that sodium azide is toxic to the human body and dangerous in handling. Accordingly, attempts have been made to develop gas generating compositions containing various nitrogen-containing organic compounds as so-called non-azide gas generating compositions with improved safety.
For example, U.S. Pat. No. 4,909,549 has disclosed compositions of hydrogen-containing tetrazole and triazole compounds with oxygen-containing oxidizing agents; U.S. Pat. No. 4,369,079 has disclosed compositions of hydrogen-free bitetrazole metal salts with oxygen-containing oxidizing agents; and JP-A 6-239683 has disclosed compositions of carbohydrazide with oxygen-containing oxidizing agents.
Most of these non-azide gas generating compositions consist of fuels comprising nitrogen-containing organic compounds such as metal salts of tetrazole and bitetrazole, triazole or carbohydrazide with oxidizing agents such as potassium nitrate, strontium nitrate or potassium perchlorate.
Moreover, U.S. Pat. No. 5,545,272 has disclosed gas generating compositions comprising ammonium nitrate phase-stabilized with 7 to 20% by weight of a potassium salt and nitroguanidine, while WO 96/27574 has disclosed gas generating compositions comprising nitroguanidine, phase-stabilized ammonium nitrate and a rubbery binder.
Furthermore, JP-A 7-330477 has disclosed gas generating compositions comprising acrylate-terminated polybutadiene, polybutadiene polycarboxylic acid or epoxy-modified polybutadiene with a hardening agent and an oxidizing agent. JP-A 6-92770 has disclosed gas generating compositions particularly containing an organic binder forming azide groups, an active plasticizer and an oxidizing filler and characterized in that the binder is a product obtained by the reaction between a hydroxylated polyglycidyl azide and at least one polyisocyanate and that ammonium nitrate amounts to at least 85% by weight of the oxidizing filler.
However, these gas generating agents of the azide-type or the non-azide type free from ammonium nitrate are both poor in gas-generation efficiency. For example, the azide-type gas generating agents can generate at most 1.5 mol of gas per 100 g thereof, while the non-azide type ones free from ammonium nitrate can generate at most 2.5 mol of gas per 100 g thereof. In addition, a large amount of residues, which are liquid or solid at high temperatures, are formed during the combustion of these gas generating agents. If such residues are discharged as they are from the inflator, they would damage the air bag, which causes not only a burst of the air bag from the air bag system or combustion of the air bag but also fatal harm to the occupants' breathing.
To minimize the combustion residues discharged from inflators, it is therefore necessary to pack a large amount of filters into the inflators, which interferes downsizing and lightening of the inflators and elevates the production cost thereof.
Although the above-mentioned gas generating compositions comprising phase-stabilized ammonium nitrate and nitroguanidine as described in U.S. Pat. No. 5,542,272 and WO 96/27574 have higher gas-generation efficiencies and produce less residues, the phase-stabilized ammonium nitrate and nitroguanidine would form together a eutectic at 120° C. or below. As a result, it is feared that the gas generating agents may be molten at the welding step in the process of manufacturing inflators. In addition, these compositions containing the phase-stabilized ammonium nitrate and nitroguanidine have high explosive sensitivities, which brings about some problems in qualities and safety during the production of the gas generating agents.
Furthermore, there have been disclosed gas generating agents with the use of energy binders such as azide polymers and ammonium nitrate or phase-stabilized ammonium nitrate which produce few residues (for example, EP No. 705809). However, these gas generating agents would form harmful carbon monoxide in a large amount during combustion. Therefore, it is problematic to simply apply them to gas generating compositions for automotive air bags, though they might be adequate for rocket propellants.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a gas generating composition which is less toxic or dangerous, can be easily handled, has a high combustion efficiency and a high gas-generation efficiency, produces few residues during combustion, can be safely manufactured, and exhibits a high molding strength in the molding step.
The present inventors have directed their attention to compositions of polymer compounds with ammonium nitrate which produce no or only a practically negligible amount of residues during combustion and have conducted intensive studies on the moldability, combustion properties, safety, practical availability, etc. thereof. As a result, they have found that gas generating compositions containing fuels comprising specific polymer compounds, ammonium nitrate-type oxidizing agents and oxyacid salts, optionally together with a combustion rate regulator such as carbon and a combustion-controlling catalyst such as metal oxides can be practically used solving the above problems. They have thus completed the present invention.
Accordingly, the present invention provides a gas generating composition characterized by containing the following components (a), (b) and (c):
(a) a fuel comprising at least one polymer compound selected from the group consisting of polyacrylic polymer compounds, polyacetal, urea resins, melamine resins, ketone resins and cellulose-based polymer compounds;
(b) an oxidizing agent selected from the group consisting of ammonium nitrate and phase-stabilized ammonium nitrate; and
(c) at least one combustion accelerator selected from the group consisting of oxyacid salts.
The present invention further provides a gas generating composition which contains, in addition to the above components (a), (b) and (c), one or more members selected from the group consisting of the following components (d) and (e):
The group consisting of
(d) a combustion rate regulator(s) selected from carbon and metallic powders; and
(e) a combustion-controlling catalyst(s) selected from the group consisting of metal oxides.
The present invention furthermore provides a molded article of a gas generating composition in the form of a single-hole or porous column obtained by extrusion-molding the above gas generating composition, a molded article of the gas generating composition in the form of pellets obtained by compression-molding the above gas generating composition, and a molded article of the gas generating composition in the form of a film obtained by molding the above gas generating composition into a film.
The present invention furthermore provides an inflator for air bags with the use of the above gas generating composition or the above molded article of the gas generating composition.
The present invention provides a gas generating composition for air bags to be used as occupant crash protection systems in automobiles and a molded article thereof. The present invention has made it possible to produce a gas generating composition which is less toxic or dangerous, can be easily handled, has a high combustion efficiency and a high gas-generation efficiency and produces few residue during combustion, and a molded articles thereof.
PREFERRED EMBODIMENT OF THE INVENTION
The polymer compound of the component (a) to be used in the present inve
Birch & Stewart Kolasch & Birch, LLP
Daicel Chemical Industries Ltd.
Miller Edward A.
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