Explosive and thermic compositions or charges – Structure or arrangement of component or product – Solid particles dispersed in solid solution or matrix
Reexamination Certificate
2000-04-26
2003-09-23
Miller, Edwatd A. (Department: 3641)
Explosive and thermic compositions or charges
Structure or arrangement of component or product
Solid particles dispersed in solid solution or matrix
C149S036000, C149S046000, C149S060000
Reexamination Certificate
active
06623574
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/JP99/05296 which has an International filing date of Sep. 28, 1999, which designated the United States of America.
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
This invention relates to a gas generating composition which is suited for an air bag restraining system of automobiles, and an inflator for an air bag using the same.
PRIOR ART
As a gas generating agent for an air bag as a passenger protecting device in automobiles, gas generating agents containing various nitrogen-containing organic compounds being safer non-azide compound fuels that replace sodium azide have been developed.
For example, U.S. Pat. No. 4,909,549 discloses a composition of hydrogen-containing tetrazole and triazole compounds and an oxygen-containing oxidizing agent; U.S. Pat. No. 4,369,079 discloses a composition of a hydrogen-free bitetrazole metal salt and an oxygen-containing oxidizing agent; and JP-A 6-239683 discloses a composition of carbohydrazide and an oxygen-containing oxidizing agent. Most of these non-azide gas generating compositions are made of nitrogen-containing organic compound fuels such as tetrazole, a bitetrazole metal salt, triazole, carbohydrazide and the like and oxidizing agents such as potassium nitrate, strontium nitrate, potassium perchlorate and the like.
Further, U.S. Pat. No. 5,545,272 discloses a gas generating composition of ammonium nitrate phase-stabilized with 7 to 20% by weight of a potassium salt and nitroguanidine; WO 96/27574 discloses a gas generating agent of a composition of nitroguanidine, phase-stabilized ammonium nitrate and a rubber-like binder; JP-A 7-330477 discloses a gas generating composition of acrylate-terminated polybutadiene, polybutadiene polycarboxylic acid, epoxy-modified polybutadiene, a curing agent and an oxidizing agent; JP-A 6-92770 discloses a gas generating composition especially containing an organic binder generating an azide group, an active plasticizer and an oxidation filler, the binder being made of a reaction product of polyglycidyl azide having a hydroxyl group and at least one polyisocyanate, and at least 85% by weight of the oxidation filler being ammonium nitrate; and JP-A 10-72273 discloses a gas generating agent made of ammonium nitrate, a reducing agent which is at least one of tetrazole, aminotetrazole, bitetrazole, a bitetrazole metal salt, bitetrazole ammonium salt, nitroguanidine, guanidine nitrate, dicyandiamide and the like, and a combustion controlling agent such as copper oxide, manganese dioxide or the like.
However, an amount of a gas generated per 100 g of the azide gas generating agent is 1.5 mol or less, and an amount of a gas generated per 100 g of a non-azide gas generating agent that does not use ammonium nitrate is 2.5 mol or less. Thus, in either case, there is a problem that a gas output is low. Further, large amounts of residues are generated in the combustion. Accordingly, when residues generated are released as such from an inflator, high-temperature liquid or solid residues might damage a bag and a bag might be separated from an air bag module or burned. In addition, it is sometimes harmful in breathing of passengers. In order to prevent the release of combustion residues from an inflator as much as possible, there is a method in which a large amount of a filter is packed in an inflator. However, this method is against downsizing of an inflator and reduction of its weight, and also increases the production cost.
Moreover, the gas generating composition of phase-stabilized ammonium nitrate and nitroguanidine disclosed in U.S. Pat. No. 5,545,272 and WO 96/27574 provides a high gas output and reduces amounts of residues generated. However, phase-stabilized ammonium nitrate and nitroguanidine form a low eutectic product, and the melting temperature thereof is as low as 120° C. or less. Thus, the gas generating agent might be melted during the welding step in the production of an inflator. Besides, the composition containing phase-stabilized ammonium nitrate and nitroguanidine has a high initiation sensitivity, which is problematic in the safety of the production of the gas generating agent.
Moreover, the gas generating composition made of ammonium nitrate, tetrazoles and a metal oxide, disclosed in JP-A 10-72273, is hard to mold because of the absence of a high polymer, and cannot endure a volume change when a phase of ammonium nitrate is changed, making it difficult to control combustion of the gas generating agent after the lapse of a long period of time.
Besides, gas generating agents in which an energy binder such as an azide polymer or the like and ammonium nitrate or phase-stabilized ammonium nitrate are used and amounts of residues generated are reduced are disclosed (for example EP 705809). However, these gas generating agents are problematic in that a large amount of hazardous carbon monoxide is generated in the combustion. Further, since a burning rate is low, it is difficult to simply apply the same to gas generating agents for an air bag of automobiles.
DISCLOSURE OF THE INVENTION
An object of this invention is to provide, upon solving the above-described problems, a gas generating composition which is excellent in a combustion efficiency and a gas output and in which amounts of residues generated are reduced in the combustion.
Another object of this invention is to provide an inflator for an air bag using the above-described gas generating composition.
This invention provides a gas generating composition comprising (a) 5 to 40% by weight of at least one high polymer selected from the group consisting of a polyacrylic derivative resin, a polyacetal, a urea resin, a melamine resin, a ketone resin and a cellulose-based high polymer, and (b) 95 to 60% by weight of ammonium nitrate or phase-stabilized ammonium nitrate.
Further, this invention provides an inflator for an air bag using the above-described gas generating composition.
The gas generating composition of this invention has a low toxicity and a high safety, is easy to handle, and is excellent in a combustion efficiency and a gas output, and amounts of residues generated are reduced. Accordingly, the gas generating composition of this invention is suitable as a gas generating agent for an air bag as a passenger protecting device in automobiles. Further, since the gas generating composition of this invention has a high thermal stability, an inflator for an air bag using the same can maintain a stable performance for a long period of time and can be downsized more.
PREFERRED EMBODIMENTS OF THE INVENTION
The high polymer as component (a) used in this invention is a component that acts as both a fuel and a binder in the gas generating composition.
With respect to the high polymer as component (a), in view of an oxygen balance and a combustibility of the high polymer, its thermal stability in the mixing with ammonium nitrate and the like, one type or a combination of two or more types selected from the group consisting of a polyacrylic derivative resin, a polyacetal, a urea resin, a melamine resin, a ketone resin and a cellulose-based high polymer which are solid in the use temperature range (−30° C. to 90° C.) of the gas generating agent can be proposed. Component (a) is described in detail below.
(1) Polyacrylic Derivative Resin
Polyacrylamide (LD
50
(peroral, mouse) is 1,200 mg/kg or more and there is no mutagenicity), aminated polyacrylamide, polyacrylhydrazide (LD
50
(peroral, mouse) is 3,800 mg/kg and there is no mutagenicity), a copolymer of acrylamide and ammonium acrylate, a copolymer of acrylamide and an acrylic acid metal salt, a copolymer of acrylamide and an acrylic acid ester compound and the like can be proposed.
As these polyacrylic derivative resins, the following compounds (i) to (v) are preferable.
(i) (CH
2
CHCONH
2
)
n
(ii) (CH
2
CHCONHNH
2
)
n
(iii) (CH
2
CHCONH
2
)
n
—(CH
2
CHCONHNH
2
)
p
(iv) (CH
2
CHCONH
2
)
n
—(CH
2
CHCOOM)
q
(v) (CH
2
CHCONH
2
)
n
—(CH
2
CHCOOR)
s
[wherein M represents a metal ion su
Daicel Chemical Industries Ltd.
Miller Edwatd A.
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