EP2407443A1

EP2407443A1 - Gas generant composition, molded object thereof, and gas generator using same

Info

Publication number: EP2407443A1
Application number: EP10750568A
Authority: EP
Inventors: Toshihiro Ogata; Eishi Sato
Original assignee: Nippon Kayaku Co Ltd
Current assignee: Nippon Kayaku Co Ltd
Priority date: 2009-03-13
Filing date: 2010-03-09
Publication date: 2012-01-18
Also published as: US20120000583A1; WO2010103811A1; EP2407443A4; JPWO2010103811A1; CN102414147A; JP5719763B2

Abstract

The present invention relates to a gas generant composition that has a high ignitability and combustibility and is capable of quickly responding to an electrical signal for starting combustion, and particularly to a gas generant composition comprising a nitrogen-containing organic compound as a fuel component (A), a metal nitrate and/or a basic metal nitrate (B-1) and a perchlorate (B-2) having a 50 percent particle diameter from 1 to 50µm as an oxidant component (B), the content of the perchlorate (B-2) in the total mass of the oxidant component (B) is 5 mass percent or more and less than 35 mass percent.

Description

TECHNICAL FIELD

The present invention relates to a gas generant composition and a molded article of the gas generant composition, and a gas generator using the molded article of the gas generant composition and, particularly to a gas generant composition that quickly responds to an electrical signal for starting combustion (that is, a high responsiveness to electrical signals for starting combustion) suitable for use in a gas generator for vehicle passenger safety equipment.

BACKGROUND ART

In a measure for improving safety of vehicles, recently, airbags and seatbelt pretensioners have widely been adopted as vehicle passenger safety equipment that uses gunpowder. The principle of the airbag equipment is that a gas generant filled in a gas generator is burned by electrical signals from a sensor that detects collision of a vehicle and a high volume of gas is produced, then an airbag is deployed between a passenger and a vehicle inner wall by the pressure of the gas. The principle is the same for seatbelt pretensioners, which is, a sensor detects a vehicle collision, a gas generant filled in a gas generator is burned by electrical signals from the sensor, and gas is produced. Then the pressure of the gas operates a seatbelt retracting mechanism, which increases a restraining force of the seatbelt, and thus a passenger is protected. When a vehicle collides, an extremely quick response to electrical signals from a collision sensor is required for a gas generator for vehicle passenger safety equipment. In other words, a gas generator is required to burn a gas generant responding to electrical signals from a collision sensor to produce gas and to reach a maximum pressure of the produced gas in tens of milliseconds.
In order to meet the needs for extremely quick response performance as a gas generator for vehicle passenger safety equipment, a gas generant having a high responsiveness is required. Specifically, a gas generant that can immediately ignite responding to an ignition flame from an igniter of gas generator, burn completely in a short time and produce gas, is required. Further, by using such gas generant having a high responsiveness, a gas generator that is suitable as a vehicle passenger safety equipment and shows a high responsiveness, that is, time from generating a starting signal by a collision to reaching a maximum pressure of the produced gas is extremely short, can be provided.
Moreover, with growing awareness of vehicle safety functions, recently, in addition to airbags for front collisions that have been conventionally provided for drivers and front-seat passengers, installation of airbags for collisions against vehicle inner walls, glass surfaces and vehicle inner ceiling surfaces and installation of airbags for protecting lower legs against collisions are in progress. The distances between a passenger and such side face, head face and face relative to the lower legs are close. Thus a high responsiveness for deploying an airbag more quickly than that for front collision is required, and development of gas generator for vehicle passenger safety equipment adaptable to such position is in progress.
Gas generants used for gas generators are generally prepared based on a composition which contains a mixture of fuel components and oxidant components as a major component. As fuel components, instead of metallic azide compound that has been used previously, a nitrogen-containing organic compound is used, and a non-azide based gas generant composition containing a combination of a nitrogen-containing organic compound and inorganic oxidant has been proposed. As a role of oxidant component, a function that improves combustibility by supplying oxygen to fuel components and reduces production of unfavorable gas components such as carbon monoxide, ammonia, nitric oxide, nitrogen dioxide, hydrogen chloride and the like is required. Herein, as oxidant components of a gas generant composition, various nitrates are widely used, and specifically, metal nitrate, basic metal nitrate, ammonium nitrate, phase-stabilized ammonium nitrate and the like are known. Further, as oxidant components, examples of gas generant compositions using such nitrate and perchlorate in combination are known. Patent Document 1 discloses a gas generant composition containing a nitrogen-containing compound, a basic metal nitrate and a chloric acid compound. Moreover, Patent Document 2 discloses a gas generant composition containing a nitrogen-containing fuel, a copper-containing compound and alkali metal perchlorate having a mean particle size in excess of 100 microns. Both of these patent documents relate to a gas generant composition capable of reducing production of toxic gas component such as nitrogen oxide, ammonia and the like contained in a produced gas component. However, the gas generant compositions described in these patent documents have no sufficient combustion speed.

RELATED ART DOCUMENTS

PATENT DOCUMENTS

Patent document 1: JP2005119926(A )
Patent document 2: US Patent Application Publication Number 2006/0016529

SUMMARY OF INVENTION

TECHNICAL PROBLEM

It is an object of the present invention to solve the problems of the above mentioned related arts and to provide a gas generant composition and a molded article of the gas generant composition having an improved ignitability and combustibility. Further, it is another object of the present invention to provide, by including the molded article of the gas generant composition, a gas generator that reaches the maximum pressure of produced gas in a very short time after sending out of an electrical signal for starting combustion, in other words, that indicates a high responsiveness.

SOLUTION TO PROBLEM

Inventors of the present invention earnestly worked on to achieve the above mentioned objects and found out that, in a gas generant composition containing a nitrogen-containing organic compound as a fuel component and a metal nitrate and/or a basic metal nitrate and perchlorate as an oxidant component, the ignitability and combustibility of the gas generant composition can be improved significantly by limiting a 50 percent particle diameter of the perchlorate to the range from 1 to 50µm and limiting the content of the perchlorate in the total mass of oxidant component to the range of 5 mass percent or more and less than 35 mass percent, and thus brought the present invention to completion.
In other words, the gas generant composition according to the present invention is characterized in that it contains a nitrogen-containing organic compound as a fuel component (A) and a metal nitrate and/or a basic metal nitrate (B-1) and a perchlorate (B-2) having a 50 percent particle diameter from 1 to 50µm as an oxidant component (B), the content of the perchlorate (B-2) in the total mass of the oxidant component (B) is 5 mass percent or more and less than 35 mass percent.
In a preferred example of the gas generant composition according to the present invention, the nitrogen-containing organic compound is at least one kind selected from a group consisting of guanidine, triazole, tetrazole, bitriazole, bitetrazole and derivatives thereof.
In another preferred example of the gas generant composition of the present invention, the metal nitrate and/or the basic metal nitrate (B-1) are at least one kind selected from a group consisting of potassium nitrate, sodium nitrate, strontium nitrate and basic copper nitrate.
In another preferred example of the gas generant composition of the present invention, the perchlorate (B-2) is at least one kind selected from a group consisting of potassium perchlorate, sodium perchlorate and ammonium perchlorate.
In the gas generant composition according to the present invention, it is preferable that the content of the nitrogen-containing organic compound is from 35 to 60 mass percent, the content of the metal nitrate and/or the basic metal nitrate (B-1) is from 20 to 50 mass percent and the content of the perchlorate (B-2) is from 1 to 20 mass percent. It is further preferable that the nitrogen-containing organic compound is guanidine nitrate, the metal nitrate and/or basic metal nitrate (B-1) is basic copper nitrate and the perchlorate (B-2) is potassium perchlorate.
In the gas generant composition according to the present invention, it is preferable that the perchlorate (B-2) has a 50 percent particle diameter from 1 to 30µm.
In another preferred example of the gas generant composition according to the present invention, a binder (C) is further contained.
In another preferred example of the gas generant composition according to the present invention, a slag former (D) is further contained.
Further, the molded article of the gas generant composition according to the present invention is a molded article of the above mentioned gas generant composition.
In a preferred example of the molded article of the gas generant composition according to the present invention, the molded article has a columnar shape and a diameter thereof is 4mm or less.
Moreover, the gas generator according to the present invention is characterized in that it has a molded article of the above mentioned gas generant composition and it is preferable that the gas generator according to the present invention has a long cylindrical housing.

ADVANTAGEOUS EFFECT OF INVENTION

According to the present invention, in a gas generant composition containing a nitrogen-containing organic compound as a fuel component and a metal nitrate and/or a basic metal nitrate and a perchlorate as an oxidant component, a gas generant composition and a molded article of the gas generant composition having a high ignitability and combustibility can be provided by limiting the 50 percent particle diameter of the perchlorate to the range from 1 to 50µm and by limiting the content of the perchlorate in the total mass of the oxidant component to the range of 5 mass percent or more and less than 35 mass percent, and the gas generant composition and a molded article thereof is suitable for use in a gas generator for vehicle passenger safety equipment. It should be noted that the gas generant composition and the molded article thereof according to the present invention also have a high thermal stability. Moreover, by including the molded article of such gas generant composition, a gas generator that can reach a maximum pressure of the produced gas in a very short time after sending out of an electrical signal for starting combustion, that is, a gas generator showing a high responsiveness, can be provided. It should be noted that, since the gas generant composition has a high ignitability, the gas generator according to the present invention requires no enhancer agent that is used for inflators and the like for conventional airbags, and thus a reduction in size of gas generator can be achieved, and the gas generator is suitable as a gas generator for airbag for side collision which requires specifically quick response. Further, due to a high combustibility of the gas generant composition, the gas generator according to the present invention can produce clean exhaust gas containing relatively low components of carbon monoxide, ammonia and nitrogen oxide, and furthermore, can produce clean exhaust gas containing almost no chlorine and hydrogen chloride.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view in accordance with an embodiment of a gas generator according to the present invention;
FIG. 2 is a cross sectional view in accordance with another embodiment of a gas generant according to the present invention; and
FIG. 3 shows a pressure-time curve of Example 3 and Comparative Example 3 obtained from Test Example 4 of combustibility test (28.3L tank test).

DESCRIPTION OF EMBODIMENTS

Detailed description of the present invention is given below. The gas generant composition according to the present invention is characterized in that it contains a nitrogen-containing organic compound as a fuel component (A) and a metal nitrate and/or a basic metal nitrate (B-1) and a perchlorate (B-2) having a 50 percent particle diameter from 1 to 50µm as an oxidant component (B), the content of the perchlorate (B-2) in the total mass of the oxidant component (B) is 5 mass percent or more and less than 35 mass percent, has a high ignitability and combustibility and is suitable for use in a gas generator for vehicle passenger safety equipment.
The fuel component (A) of the gas generant composition according to the present invention is an nitrogen-containing organic compound. Here, no particular compounds are specified as the nitrogen-containing organic compound, and the nitrogen-containing organic compounds normally used for the gas generant composition for gas generator for vehicle passenger safety equipment may be preferably used. However, guanidine or its derivatives, triazole or its derivatives, tetrazole or its derivatives, bitriazole or its derivatives, bitetrazole or its derivatives, azodicarbonamide or its derivatives, hydrazine or its derivatives, and hydrazide derivatives are preferred. More specifically, 5-oxo-1,2,4-triazole, tetrazole, 5-amino tetrazole, aminotetrazole nitrate, nitroamino tetrazole, bitetrazole (5, 5'-bi-1H-tetrazole), 5, 5'-bi-1H-tetrazole diammonium salt, azobis tetrazole, 5, 5'-azobis tetrazole diguanidium salt, guanidine, nitroguanidine, cyanoguanidine, triaminoguanidinenitrate, guanidine nitrate, aminoguanidine nitrate, biuret, azodicarbonamide, carbohydrazide, carbohydrazide nitrate complex, oxalic hydrazide, hydrazine nitrate complex, ammine complex and the like are preferably included. Among these nitrogen-containing organic compounds, tetrazole derivatives, bitetrazole derivative and guanidine derivatives are preferred because they are low cost and high-reactive and can be handled relatively easily. Nitroguanidine, guanidine nitrate, bitetrazole, azobis tetrazole and 5-aminotetrazole are further preferred. Among them, guanidine nitrate is particularly preferable because it has some advantages in that the amount of oxidant component can be reduced because the guanidine nitrate contains oxygen in molecules, a high thermal stability can be achieved and a low cost and high gas yield during combustion can be expected. It should be noted that these nitrogen-containing organic compounds may be used alone or in combination of two or more of them.
Moreover, the above mentioned nitrogen-containing organic compounds are easy to handle, thus it is preferable that they are in powder state or in granulated state. Further, the 50 percent particle diameter thereof is preferably from 5 to 80µm and more preferably from 10 to 50µm. It should be noted that, if the 50 percent particle diameter of the nitrogen-containing organic compound is too large, the strength of the molded article of the gas generant composition declines, and if it is too small, a lot of cost is required for crushing. It should be noted that, in the present invention, the 50 percent particle diameter means a 50 percent particle diameter of average particle diameter based on cumulative number of measured particles, and can be measured by, for example, a laser diffraction method, a laser scattering method and the like.
The content rate (compounding ratio) of nitrogen-containing organic compound in the gas generant composition of the present invention is preferably from 35 to 60 mass percent, and more preferably from 40 to 58 mass percent. If the content rate (compounding ratio) of the nitrogen-containing organic compound is less than 35 mass percent, it is likely that the number of gas moles generated per 100g of gas generant composition decreases and that generation of nitrogen oxide increases due to oxygen excess. On the other hand, if the content rate (compounding ratio) of the nitrogen-containing organic compound exceeds 60 mass percent, organic matter increases, and thus it is likely that the absolute specific gravity of the gas generant composition decreases, filler content per volume decreases, and generation of toxic carbon monoxide increases due to lack of oxidant component.
As the oxidant component (B) of the gas generant composition according to the present invention, metal nitrate and/or basic metal nitrate (B-1) and perchlorate (B-2) having a 50 percent particle diameter from 1 to 50µm are used in combination.
As the above mentioned metal nitrate and/or basic metal nitrate (B-1), metal salt selected from, for example, alkali metal, alkaline-earth metal, iron, copper, magnesium, cobalt, nickel, zinc and the like is included. Specifically, as alkali metal nitrates, sodium nitrate, potassium nitrate and the like are included and as alkaline-earth metal nitrates, magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate and the like are included. It should be noted that these metal nitrates may be used alone or in combination of two or more of them. As basic metal nitrates, basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, basic magnesium nitrate, basic iron nitrate and the like are included. Among them, basic copper nitrate is particularly preferable. It should be noted that these basic metal nitrates may be used alone or in combination of two or more of them.
Moreover, the above mentioned metal nitrate and/or basic metal nitrate (B-1) are easy to handle, and thus it is preferred that they are in powder state or in granulated state. Then the 50 percent particle diameter thereof is preferably from 1 to 80µm, and more preferably from 1 to 50µm. It should be noted that, if the 50 percent particle diameter of the metal nitrate and/or basic metal nitrate (B-1) is too large, the strength of the molded article of the gas generant composition declines, and if is it too small, a lot of cost is required for crushing.
As the above mentioned perchlorate (B-2), for example, alkali metal perchlorate, alkaline-earth metal perchlorate, ammonium perchlorate and the like are included. Specifically, as alkali metal perchlorate, sodium perchlorate, potassium perchlorate and the like are included and as alkaline-earth metal perchlorate, magnesium perchlorate, calcium perchlorate, barium perchlorate, strontium perchlorate and the like are included. It should be noted that these perchlorates may be used alone or in combination of two or more of them.
Further, as for the perchlorate (B-2), its contact area with the fuel component (A) increases as its particle diameter decreases, and the perchlorate shows a high responsiveness to the fuel component (A), thus allowing significant improvement of ignitability and combustibility of the gas generant composition. Therefore it is necessary to limit its 50 percent particle diameter to the range from 1 to 50µm, preferably from 1 to 30µm, more preferably from 5 to 30µm, and yet further preferably from 8 to 25µm. It should be noted that, if the 50 percent particle diameter of the above mentioned perchlorate (B-2) is less than 1µm, a lot of cost is required for crushing, and if it is more than 50µm, in addition to decline in the strength of the molded article of the gas generant composition, sufficient effect of improvement of gas generating properties such as ignitability, combustibility, and the like cannot be obtained.
As mentioned above, the perchlorate (B-2) has a high responsiveness to the fuel component (A). Thus, if all of the oxidant components required for the gas generant composition are the perchlorate (B-2), for example, it reacts too keen and its handling would be too difficult. Thus, in the gas generant composition according to the present invention, control of the content of perchlorate (B-2) in oxidant component is very important, and the inventors of the present invention tried to find the most appropriate content and found that it was necessary to limit the content of perchlorate (B-2) in the total mass of the oxidant component (B) to the range of 5 mass percent or more and less than 35 mass percent. In the gas generant composition according to the present invention, if the content of perchlorate (B-2) in the total mass of the oxidant component (B) is 35 mass percent or more, as mentioned above, it reacts too much and handling thereof would be too difficult, and further, the amount of chlorine-derived gas generated during operation increases and additive agent for collecting the gas component is required, which reduces the content of active component (burning component and oxidant component) of the gas generant composition. Thus such mass percent should be avoided. In addition, with such mass percent, a self-sustained combustion property will be lost and occasionally combustion may be interrupted. The self-sustained combustion property herein means a property in which a composition burns completely without being interrupted after ignition. On the other hand, if the content of perchlorate (B-2) in the total mass of oxidant component (B) is less than 5 mass percent, sufficient effect of improving gas generation property such as ignitability, combustibility and the like cannot be obtained. It should be noted that, in the gas generant composition according to the present invention, the content of perchlorate (B-2) in the total mass of the oxidant component (B) is, in light of further improvement of the gas generating property such as ignitability, combustibility and the like, preferably in the range of 8 mass percent or more and less than 35 mass percent, and more preferably, in the range of 10 mass percent or more and less than 35 mass percent.
Although the content rate (compounding ratio) of oxidant component (B) in the gas generant composition according to the present invention varies depending on the kind of the above mentioned fuel component (A), kind of additive agent, oxygen balance and the like, it is preferably from 30 to 65 mass percent, and more preferably from 35 to 60 mass percent. Here, the content (compounding ratio) of the metal nitrate and/or basic metal nitrate (B-1) in the gas generant composition according to the present invention is preferably from 20 to 50 mass percent, and more preferably from 25 to 50 mass percent. Further, the content (compounding ratio) of the perchlorate (B-2) in the gas generant composition according to the present invention is preferably from 1 to 20 mass percent, and more preferably from 3 to 18 mass percent.
The gas generant composition according to the present invention may further contain additive agent. As the additive agent, generally, additive agents available for gas generant composition for gas generator for vehicle passenger safety equipment may be used. For example, additive agents such as a binder (C) for giving a moldability and a shape preserving property for keeping a preferred combustibility, a slag former (D) for facilitating filtration of combustion residues, combustion modifier, lubricant and the like may be used. The contents of these additive agents vary depending on the application. However, in any applications, if the content of additive agent is too much, performance such as combustibility declines, thus the content of additive agent in the gas generant composition is preferably from 0.1 to 15 mass percent, and more preferably, from 0.1 to 10 mass percent.
The above mentioned binder (C) is an additive agent which gives a moldability and a shape preserving property for keeping a preferred combustibility. For example, when a gas generant composition contains a binder (C), a combustibility can be held even in a harsh environment where an inflator is used. As a binder (C), any kinds can be used without specific limitation unless combustion behavior of the gas generant composition is adversely affected to a large extent, and as preferred examples, for example, metal salt of carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methylcellulose, cellulose acetate, cellulose propionate, cellulose acetate butyrate, cellulose nitrate, microcrystalline cellulose, guar gum, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polysaccharide derivatives such as starch, stearate and the like are included as organic binders, and molybdenum disulfide, synthetic hydrotalcite, acid clay, talc, bentonite, diatomite, kaolin, silica, alumina and the like are included as inorganic binders. Among them, cellulose-based binders, acid clay and the like are particularly preferred. The content of a binder (C) in the gas generant composition according to the present invention is preferably from 1.0 to 10 mass percent, and more preferably from 1.0 to 5 mass percent. If the content of a binder (C) is high, the fracture strength of molded article can be increased, however, the number of carbon elements and hydrogen elements in a composition is increased, and thus the concentration of carbon monoxide gas, which is an incomplete combustion product of carbon element, increases. This declines the quality of generated gas or may interfere combustion. Therefore use in the minimum amount by which the shape of the gas generant composition can be maintained is preferred. In particular, when the content of binder (C) exceeds 10 mass percent, relative abundance ratio of the oxidant component is needed to be increased, and the relative abundance ratio of the fuel component (nitrogen-containing organic compound) in a gas generant composition declines, and thus practical use of a gas generator may become difficult.
The above mentioned slag former (D) is an additive agent which facilitates filtration of combustion residues produced after combustion of gas generant composition and is added to prevent the residues from being released outside an inflator. Specific examples of the slag formers (D) include, for example, natural minerals such as silicone nitride, silicon carbide, silicon dioxide, silicate, aluminum oxide, titanium oxide, acid clay, clay and the like. The content of a slag former (D) in the gas generant composition according to the present invention is preferably from 0.5 to 10 mass percent, and more preferably from 1.0 to 5.0 mass percent. If the content of a slag former (D) is high, a combustibility declines and further the number of moles of generated gas declines, and thus the occupant protection performance may not be exercised sufficiently.
The above mentioned lubricant is added to improve mixing property and fluidity of basic ingredients when preparing a gas generant composition. Specific examples of the lubricant include, for example, graphite, magnesium stearate, zinc stearate, calcium stearate, sodium stearate, boron nitride, highly dispersible silica (silica dioxide), talc and the like. Among them, the highly dispersible silica (silica dioxide) has a function of preventing adhesion and aggregation during mixing and of uniform dispersion and mixing of basic ingredients, thus it has an effect of maintaining particle property and acting of each component, and is especially useful. The content of lubricant in the gas generant composition according to the present invention is preferably from 0.1 to 5.0 mass percent, and more preferably from 0.1 to 2.0 mass percent. If the content of lubricant is high, decline in combustibility, decline in the number of moles of generated gas, and further increase in concentration of carbon monoxide in the generated gas may occur.
The above mentioned combustion modifier is an additive agent for modifying combustion of gas generant composition. Specific examples include metallic oxide such as iron oxide, nickel oxide, copper oxide, zinc oxide, manganese oxide, chromic oxide, cobalt oxide, molybdenum oxide, vanadium oxide, tungsten oxide and the like, metallic hydroxide such as copper hydroxide, cobalt hydroxide, zinc hydroxide, aluminum hydroxide and the like, and carbons such as activated carbon powder, graphite, carbon black and the like. The content of combustion modifier in the gas generant composition according to the present invention is preferably 10 mass percent or less, and more preferably 5 mass percent or less.
It is preferable that the gas generant composition according to the present invention is used as a molded article having an appropriate shape. Hereinafter a molded article of the gas generant composition is also referred to as a gas generant. It should be noted that the gas generant composition may be molded into various shapes responding to the combustion performance of the gas generant composition and the combustion property of the gas generator. The molding methods include a press molding and an extrusion molding. The shapes of the molded article of the gas generant composition according to the present invention are not specifically limited and include pellet, disc, spherical, bar, columnar, cylindrical, hard candy prickly ball (konpeitou) and tetrapod shapes and the like. Moreover, the molded article may be either nonporous or porous such as single hole or multiple holes (e.g. cylindrical shape with single hole or with multiple holes). Further, pellet or disc shaped molded article may be provided with one to a few pieces of projections on one side or both sides thereof. The shape of the projection is not specifically limited and includes, for example, columnar, cylindrical, cone, pyramid and the like.
In a pressure molded article of the gas generant composition according to the present invention, it was found out that, when the molded article has a columnar shape, combustibility of the gas generant can be significantly improved if the column diameter of the molded article is small. Moreover, it was found out that, if the diameter of the columnar molded article is small, a bulk density of the gas generant increases. When a gas generator is filled with the gas generant, improvement of gas generation property is expected with the same filling amount as that for the molded article having a large column diameter. Further, if a bulk density is high, the filling amount of gas generant per unit volume can be increased and thus a high-output gas generator can be provided. Therefore, a high bulk density is desirable. Moreover, in another aspect, if a bulk density is high, the space filled with the gas generant can be made smaller, thereby achieving reduction in size of a gas generator, thus high bulk density is desirable. Specifically, in a gas generator provided with a long cylindrical housing having a space filled with gas generant, the shape thereof is limited, improvement of the filling property of gas generant applied to the gas generator is an important point. Therefore, when a gas generator provided with a long cylindrical housing is filled with a molded article of the gas generant composition according to the present invention, in light of improvement of the filling property to the gas generator, it is preferable that the molded article has a columnar shape and the diameter of the column is smaller. Specifically, the diameter of the columnar molded article is preferably 4.0mm or less, more preferably 3.2mm or less, and yet further preferably 2.5mm or less. Moreover, the diameter of the columnar molded article is preferably 2.0mm or more, although it is not specifically limited thereto. Further, for the thickness (height) of the columnar molded article, when it is thin (low), the combustibility is improved, however the filling properly declines. On the other hand, when it is thick (high), the filling properly is improved, but the combustibility declines. Therefore a thickness/diameter ratio is preferably from 30 to 80 percent, and more preferably from 30 to 60 percent. In addition, when taking the combustibility, the filling property and the strength of the molded article into consideration, the thickness of the columnar molded article is preferably 3.0mm or less, more preferably 2.0mm or less and yet further preferably 1.5mm or less. Further, the thickness of the columnar molded article is preferably 1.0mm or more, although it is not specifically limited thereto. It should be noted that as a columnar molded article, a pressure molded article having a thickness of 2.0mm or less and a diameter of 4.0mm or less is most preferable. Moreover, a columnar molded article includes a shape that contains a curved shape on the surface thereof. The height of the curve is preferably 0.5mm or less, more preferably 0.3mm or less, and yet further preferably 0.1mm or less. Further, a chamfered molded article is also included.
A manufacturing method of the molded article of the gas generant composition according to the present invention by the pressure molding method is exemplified below. When a gas generant composition is molded into a tablet, pellet or disc shape by a pressure molding, fuel components, oxidant components and arbitrary various additive agents are mixed by a dry mixer such as a V-type mixer or a locking mixer and the like. When mixing, balls are dispersed and interposed in the mixture of the components, thus the forces by the balls are received in every detail by the powder of the components. Therefore each component is dispersed uniformly in the composition. With the use of a mixer such as a locking mixer that performs rolling and oscillating movements, a gas generant composition in which each component is dispersed more uniformly can be obtained, thus it is desirable. Solution (binder solution) containing binder (C) is added to the obtained gas generant composition (powder), and the gas generant composition is granulated by using a wet type granulator such as an agitating granulator. The additive amount of binder solution is, although that depends, from 5 to 20 mass percent to the mixed powder. Thereafter, the solution is subject to heat treatment at temperatures from 80 to 100°C to obtain granules. If the amount of water in granules after heat treatment exceeds 1percent, fluidity declines and the next process of the pressure molding may not be performed stably, thus the amount of water in granule is 1 mass percent or less, and preferably 0.5 mass percent or less. Thereafter, the granules are pressure molded into a desired shape by a rotary press. A lubricant such as magnesium stearate that is normally used may be added in the range from 0.1 to 5 mass percent when press molding is performed. The pressure molded article may be used as a gas generant after being subject to heat treatment at temperatures from 100 to 110°C for 5 to 20 hours. The amount of water in the gas generant after heat treatment is 1 mass percent or less, preferably 0.5 mass percent or less, and more preferably 0.3 mass percent or less.
On the other hand, when a molded article of the gas generant composition according to the present invention is manufactured by an extrusion molding method, fuel components, oxidant components and various additive agents are mixed by a mixer, and water or organic solvent from 10 to 20 mass percent of the obtained mixed powder is added externally to the obtained mixed powder, which is kneaded sufficiently to obtain wet composition with a viscosity. Thereafter, the wet composition is passed through a die capable of extruding in a desired shape, and the extrusion molded article is cut appropriately. The extrusion molded article is in a columnar shape, more preferably in a long columnar shape. The diameter thereof is 3.0mm or less, preferably 2.5mm or less, and more preferably 2.0mm or less. Further, the diameter is preferably 1.0mm or more, although it is not limited thereto. A length/diameter ratio is preferably from 130 to 350 percent, more preferably from 130 to 250 percent, and yet further preferably from 130 to 200 percent. In addition, in light of combustibility, filling property and the like, the length of the long columnar molded article is 6.5mm or less, preferably 4.5mm or less, and further preferably 2.5mm or less. Moreover, the length is preferably 2.0mm or more, although it is not limited thereto. As an extrusion molded article, a long columnar molded article having a length of 2.5mm or less and a diameter of 2.0mm or less is the most preferable. The extrusion molded article that is obtained in this manner is subject to heat treatment and may be used as a gas generant.
It should be noted that, in the above mentioned heat treatment, by performing heat treatment at temperatures from 50 to 150°C for 10 to 20 hours, a molded article of gas generant composition that deteriorates little with time can be obtained. In a manufacturing method using an extrusion molding, heat treatment at low temperatures for a long time is required for heat treatment of a molded article that contains 10 to 20 mass percent of water. In particular, to pass a harsh heat aging resistance test performed at a temperature of 107°C for 400 hours, this heat treatment is extremely effective. It should be noted that a heat treatment for a period of less than 10 hours is not sufficient, and there is no point in performing a heat treatment for a period exceeding 20 hours. Thus it is preferable to arbitrarily select in the range from 10 to 20 hours. Further, for heat treatment temperature, if it is less than 50°C, effect to improve the quality of molded article is small, and if it is over 80°C, water evaporates too fast, and bubbles generate in the molded article and a lack of strength of molded article and abnormal combustion may occur. Therefore, it is preferable to perform a primary heat treatment at temperatures from 50 to 70°C so that the amount of water in the gas generant becomes 7 percent or less, preferably 5 percent or less, and thereafter to perform a secondary heat treatment at temperatures from 80 to 150°C so that the amount of water in gas generant becomes 1 mass percent or less, preferably 0.5 mass percent or less.
The molded article of the gas generant composition according to the present invention is preferable for use in a gas generator for vehicle passenger safety equipment, and particularly for use in a gas generator for airbag equipment.
The gas generator of the present invention is described in detail below with reference to the drawings. The gas generator according to the present invention is characterized in that it has a molded article of the above mentioned gas generant composition. The gas generator according to the present invention has the molded article of the gas generant composition. Therefore the time from sending out of an electrical signal for starting combustion to reaching a maximum pressure of the produced gas is extremely short, and thus the gas generator is suitable as a gas generator for vehicle passenger safety equipment. It should be noted that, as a gas generator for vehicle passenger safety equipment, gas generators for airbag equipment shown in FIGS. 1 and 2, for example, are included, although it is not specifically limited thereto.
FIG. 1 is a cross sectional view of an embodiment of a gas generator according to the present invention. The gas generator is normally used for airbag equipment for front collision. The gas generator 1 shown in FIG. 1 has a housing 2 consisting of a metallic container provided with a plurality of gas release holes 6. The housing 2 forms an outer envelope. The interior of the housing 2 is equipped with an ignition device 3 and a filter 5, and is filled with gas generant 4. An ignition chamber 7 is provided in the proximity of the ignition device 3, and the ignition chamber is normally filled with enhancer agent that transmits an ignited flame generated from the ignition device 3 to the gas generant 4. It should be noted that the gas generant composition according to the present invention has a high ignitability, thus no enhancer agent is required or the amount of enhancer agent can be reduced. Therefore, the ignition chamber 7 is not needed and the volume thereof can be reduced, thereby achieving a compact, lightweight and low cost gas generator.
FIG. 2 is another cross sectional view of the gas generator according to the present invention. The gas generator has a long cylindrical housing and is suitably used for airbag equipment for side collision. The long herein means that a length (L) and cross-sectional diameter (D) ratio (L/D) is 3 or more. Further, when the shape of the cross section is other than circle, Heywood diameter is to be D. Cross sectional shapes of long cylindrical housing include, for example, triangle, rectangle, trapezoid, circular, oval and the like. The gas generator 11 shown in FIG. 2 has a long cylindrical housing 12 consisting of a metallic container provided with a plurality of gas release holes 16, and an outer envelope is formed by the housing 12. The interior of the housing 12 is equipped with an ignition device 13 and a filter 15, and is filled with gas generant 14. An ignition chamber 17 is provided in the proximity of the above mentioned ignition device 13, and the ignition chamber is normally filled with enhancer agent that transmits an ignited flame generated from the ignition device 13 to the gas generant 14. It should be noted that the gas generant composition according to the present invention has a high ignitability, thus no enhancer agent is required or the amount of enhancer agent can be reduced. Therefore, the ignition chamber 17 is not required and volume thereof can be reduced, thereby achieving a compact, lightweight and low cost gas generator. Moreover, the gas generator 11 shown in FIG. 2 can be made compact easier than the gas generator 1 shown in FIG. 1, and thus is suitable as a gas generator for airbag used in a small installation space in vehicles. Moreover, the gas generator according to the present invention shows a high responsiveness, thus the gas generator 11 shown in FIG. 2 is suitable especially as a gas generator for airbag equipment for side collision, lower leg protection or raising seat.

EXAMPLES

The present invention is described in detail below with reference to the examples and the comparative examples. However, it should be noted that the present invention is not limited thereto. Each test was performed in the following method.

1. Particle size measuring method

A 50 percent particle diameter was measured by using a laser diffraction/diffusion particle size measuring equipment (Microtrack MT3300II made by Nikkiso Co., Ltd.). The 50 percent particle diameter refers to, as described above, a 50 percent particle diameter of average particle diameter based on cumulative number of measured particles.

2. Environmental resistance test (high-temperature stability test)

The molded article of the gas generant composition (gas generant) was placed in an aluminum container and was sealed, after that the container was placed in a constant temperature bath controlled at 107°C and was left. Thereafter, the gas generant was taken out after an arbitrary time and the weight loss rate of the gas generant was measured to confirm if it was decomposed.

3. Combustibility test (18cc tank test)

A sealed container for combustion with a volume of 18cc was filled with 2.0g of molded article of the gas generant composition (gas generant), and the gas generant was burned to measure the maximum pressure and the time to reach the maximum pressure. Further, based on the measurement, a pressure generation speed was calculated.

4. Emission measurement (18cc tank test)

After the 18cc tank test, the gas in the tank was collected in a Tedlar® bag, and concentration of the produced gas component was analyzed by using a detector tube made by GASTEC.

5. Combustibility test (28.3L tank test)

A gas generator having a long cylindrical housing was filled with 9.9g of molded article of the gas generant composition (gas generant) to perform a 28.3L tank test, and a pressure-time curve was measured.

6. Ignitability test

0.5g of molded article of the gas generant composition (gas generant) was ignited by a burner in the atmosphere to confirm if the gas generant was ignited and burned.

(Example 1)

55 mass part of guanidine nitrate, 40 mass part of basic copper nitrate, 5 mass part of potassium perchlorate having a 50 percent particle diameter of 19.84µm and 0.4 mass part of high-dispersion silica were mixed and further, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Example 2)

56 mass part of guanidine nitrate, 34 mass part of basic copper nitrate, 10 mass part of potassium perchlorate having a 50 percent particle diameter of 19.84µm and 0.4 mass part of high-dispersion silica were mixed and further, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) of the present invention.

(Example 3)

45 mass part of guanidine nitrate, 31.2 mass part of basic copper nitrate, 15 mass part of potassium perchlorate having a 50 percent particle diameter of 19.84µm, 1.4 mass part of polyvinyl pyrrolidone, 2.2 mass part of hydroxypropyl methylcellulose, 0.4 mass part of high-dispersion silica and 4.8 mass part of acid clay were mixed and subsequently, 16 mass part of water and 3 mass part of denatured ethanol were added thereto. The mixture was kneaded by a universal mixer and was molded by an extruder into a columnar article having a diameter of φ1.5mm and a length of 2.5mm, followed by heat treatment at a temperature of 55°C for 8 hours and 110°C for 8 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Example 4)

55 mass part of guanidine nitrate, 40 mass part of basic copper nitrate, 5 mass part of potassium perchlorate having a 50 percent particle diameter of 14.89µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Example 5)

55 mass part of guanidine nitrate, 40 mass part of basic copper nitrate, 5 mass part of potassium perchlorate having a 50 percent particle diameter of 44.41µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Example 6)

56 mass part of guanidine nitrate, 34 mass part of basic copper nitrate, 10 mass part of potassium perchlorate having a 50 percent particle diameter of 19.84µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 3.2mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Example 7)

56 mass part of guanidine nitrate, 34 mass part of basic copper nitrate, 10 mass part of potassium perchlorate having a 50 percent particle diameter of 19.84µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 2.5mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Comparative example 1)

53 mass part of guanidine nitrate, 47 mass part of basic copper nitrate and 0.4 mass part of high-dispersion silica were mixed and subsequently, 12 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C to obtain the molded article of the gas generant composition (gas generant) for comparative example.

(Comparative example 2)

55 mass part of guanidine nitrate, 40 mass part of basic copper nitrate, 5 mass part of potassium perchlorate having a 50 percent particle diameter of 194.4µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Comparative example 3)

40.2 mass part of guanidine nitrate, 51 mass part of basic copper nitrate, 1.4 mass part of polyvinyl pyrrolidone, 2.2 mass part of hydroxypropyl methylcellulose, 0.4 mass part of high-dispersion silica and 4.8 mass part of acid clay were mixed and subsequently, 16 mass part of water and 3 mass part of denatured ethanol were added thereto. The mixture was kneaded by a universal mixer and thereafter was molded by an extruder into a columnar article having a diameter of φ1.5mm and a length of 2.5mm, followed by heat treatment at a temperature of 55°C for 8 hours and 110°C for 8 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Comparative example 4)

59 mass part of guanidine nitrate, 21 mass part of basic copper nitrate, 20 mass part of potassium perchlorate having a 50 percent particle diameter of 19.84µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Comparative example 5)

55 mass part of guanidine nitrate, 40 mass part of basic copper nitrate, 5 mass part of potassium perchlorate having a 50 percent particle diameter of 92.73µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Comparative example 6)

55 mass part of guanidine nitrate, 40 mass part of basic copper nitrate, 5 mass part of potassium perchlorate having a 50 percent particle diameter of 144.8µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

(Comparative example 7)

55 mass part of guanidine nitrate, 40 mass part of basic copper nitrate, 5 mass part of potassium perchlorate having a 50 percent particle diameter of 222.9µm and 0.4 mass part of high-dispersion silica were mixed and subsequently, 11 mass part of polyvinyl alcohol aqueous solution of 0.6 mass percent was sprayed thereto, followed by heat treatment at a temperature of 90°C for 5 hours to produce granule. Thereafter, 0.4 mass part of magnesium stearate was added to the granule, which was molded into a columnar article having a diameter of 4.0mm and a thickness of 1.50mm, followed by heat treatment at a temperature of 110°C for 10 hours to obtain the molded article of the gas generant composition (gas generant) according to the present invention.

The molded article of the gas generant composition of Example 2 was subject to an environmental resistance test performed at a temperature of 107°C for 400 hours, 800 hours and 1200 hours. Table 1 shows a weight loss rate calculated from the initial weight and the weight after the test. The weight loss rate of Example 2 is 1 percent or less, which shows that almost no decomposition occurred under high temperature conditions, thus it is confirmed that the molded article has a performance that is acceptable as a gas generant. Further, for the gas generant of Example 2 which was applied to the environmental resistance test, a performance evaluation was made by the above mentioned combustibility test (18cc tank test), and the results are shown in Table 2. For the gas generant of Example 2 after the environmental resistance test, maximum pressure (PMax), time to reach the maximum pressure (t Pmax) and pressure generating rate (dP/dt) did not change compared to those at the initial stage, which shows that the gas generant has a good high-temperature stability. Table 1

Testing time 400 hours 800 hours 1200 hours

Weight loss rate 0.023percent 0.028percent 0.057percent

Table 2

Testing time Initial (0 hour) 400 hours 800 hours 1200 hours

tPmax (msec) 24.02 23.80 23.76 24.06

PMax (MPa) 64.39 64.23 63.96 64.10

dP/dt(MPa/ms) 3.546 3.522 3.580 3.554

The 18cc tank test was performed for the gas generant composition molded article of Examples 1 and 2 and Comparative examples 1 and 2. Table 3 shows the results. For Examples 1 and 2, the time to reach the maximum pressure (t Pmax) is shorter and pressure rising rate (dP/dt) is higher than those of Comparative example 1, thus it is found out that a combustion speed increases. Further, Example 1 was compared with Comparative example 2. Each potassium perchlorate used for them has a different 50 percent particle diameter. Example 1 reaches the maximum pressure in less time (tPmax) and has a higher pressure rising rate (dP/dt), thus the results show that the combustion speed increases. Moreover, the results show that Example 1 has a maximum pressure (Pmax) which is higher than that of Comparative example 2. Table 3

Example 1 Example 2 Comparative example 1 Comparative example 2

tPmax (msec) 29.42 24.02 52.82 32.07

PMax (MPa) 59.59 64.39 49.57 57.81

dP/dt(MPa/ms) 2.488 3.546 1.244 2.276

Test example 3. Emission measurement (18cc tank test)>

For the gas generant composition molded articles of Examples 1 and 2 and Comparative examples 1 and 2, emission gas was collected after the 18cc tank test and the gas generated after burn was analyzed. Table 4 shows the results. It shows that, for Example 1, with respect to all of the generated gas components, the amount of generation is smaller than that of Comparative examples 1 and 2. Further, it shows that Example 2 can also obtain the same degree of results as those of Example 1. It should be noted that all of the gas generants produce no hydrogen chloride. Table 4

Example 1 Example 2 Comparative example 1 Comparative example 2

NO (ppm) 6.0 5 42.5 8.5

NO₂(ppm) 0 0 0 0

NH₃(ppm) 0 1.0 2.5 1.0

CO (ppm) 5.2 5.5 4.3 5.4

HCI(ppm) 0 0 0 0

Test example 4. Combustibility test (28.3L tank test)>

The 28.3L tank test was performed for the gas generant composition molded articles of Example 3 and Comparative example 3. Normally, an enhancer agent for enhancing a flame from an ignition tool is used for a gas generator. However, this test was performed by excluding an enhancer agent from the specifications. Fig. 3 shows the results. It shows that in Example 3, ignition is caused without an enhancer agent and the tank pressure increases, while in Comparative example 3, no ignition is caused, which shows that the gas generant of Example 3 has a high ignitability. Moreover, from the results of the obtained pressure-time curve, it is obvious that the gas generant of Example 3 has a high responsiveness and a gas generating property.

Test 5. Ignitability test>

The ignitability test using a burner was performed for the gas generant composition molded article of Examples 1, 2 and 3 and Comparative example 4. Table 5 shows the results. It shows that, for the gas generant of Comparative example 4, the content of potassium perchlorate in oxidant component is too high, and thus the self-sustained combustion is difficult.

Table 5

	Ignition/combustion status
Example 1	Stable combustion after ignition
Example 2	Stable combustion after ignition
Example 3	Combustion after ignition
Comparative example 4	Combustion interrupted after ignition

Test example 6. Combustibility test (18cc tank test): Influence of particle diameter of potassium perchlorate>

The 18cc tank test was performed for the gas generant composition molded articles of Examples 1, 4 and 5 and Comparative examples 5 to 7, each potassium perchlorate (PP) used for them has a different 50 percent particle diameter. Table 6 shows the results. As the 50 percent particle diameter of the potassium perchlorate used decreases, the time to reach the maximum pressure (tPmax) decreases and the pressure rising rate (dP/dt) increases, which shows that the combustion speed increases. Moreover, as the 50 percent particle diameter decreases, the maximum pressure (PMax) increases. In these examples, the content of potassium perchlorate in the oxidant component is the same, thus it is obvious that performance of the gas generant can be improved by decreasing a 50 percent particle diameter of the potassium perchlorate. Further, it is obvious that use of potassium perchlorate having a 50 percent particle diameter of 50µm or less can improve the combustibility of gas generant.

Table 6

	Particle diameter of PP(µm)	tPax (ms)	PMax (MPa)	dP/dt (MPa/ms)
Example 4	14.89	29.26	58.47	2.459
Example 1	19.84	29.42	58.48	2.447
Example 5	44.41	31.86	58.03	2.327
Comparative example 5	92.37	34.14	56.49	2.142
Comparative example 6	144.8	33.81	56.67	2.122
Comparative example 7	222.9	34.40	56.88	2.154

Test example 7. Combustibility test (18cc tank test): Influence of the shape of the molded article of the gas generant composition>

In the molded article of the gas generant composition according to the present invention, to verify the influence of the shape of molded article to the combustibility, the 18cc tank test was performed for the molded articles of the gas generant compositions of Examples 2, 6 and 7, each tablet molded article thereof has a different diameter. Table 7 shows the results. It shows that Examples 2, 6 and 7 have the same composition, however, as the diameter decreases, the time to reach the maximum pressure (tPmax) decreases, thus there is no specific difference among the maximum pressures (PMax). However, the results show that the pressure rising rate (dP/dt) increases.

Test example 8. Measurement of bulk density; Influence of the shape of the molded article of the gas generant composition>

For the molded articles of the gas generant compositions of Examples 2, 6 and 7, bulk density was measured by using a cylindrical reservoir having a volume of 100cc. Table 7 shows the measurement results. It shows that as the diameter of the gas generant decreases, the bulk density increases.

Table 7

	Example 2	Example 6	Example 7
Molded article diameter (mm)	4.0	3.2	2.5
tPmax (msec)	24.02	22.54	20.95
PMax (MPa)	64.39	65.30	64.98
dP/dt(MPa/ms)	3.546	4.169	4.755
bulk density (g/cm³)	1.13	1.14	1.15

The results of the test examples 7 and 8 with respect of the shape of the molded article of the gas generant composition show that the molded article of the gas generant composition in accordance with the present invention has a higher pressure rising rate as the columnar diameter decreases, and thus the combustibility can be improved. The reason thereof is not known, however, it is expected that, as the diameter of the molded article decreases, a surface area of the gas generant per unit mass of the gas generant increases, which contributes to improvement of combustibility.
Further, in the columnar molded article of the gas generant composition according to the present invention, the obtained results show that, as the diameter decreases, the bulk density increases. This shows that the filling property of the gas generant to the gas generator is improved, thus the filling amount of gas generant per unit volume can be increased, which produces an effect of achieving a high-output gas generator. Moreover, decrease in the diameter of the columnar molded article of the gas generant composition according to the present invention improves the filling property and leads to a high responsiveness, thus the filling volume of the gas generant to the gas generator can be decreased, which produces an effect of achieving a compact gas generator.

INDUSTRIAL APPLICABILITY

The gas generant composition according to the present invention has a high ignitability and combustibility. Therefore, the composition quickly responds to an electrical signal for starting combustion, then immediately ignites and generates a large amount of combustion gas, thereby extremely decreasing the time from sending out of the electrical signal to reaching the maximum pressure of the produced gas. Therefore, the composition is suitable for the use in a gas generator for vehicle passenger safety equipment requiring a high responsiveness, and is particularly suitable for a gas generator for airbags for side collision, low leg protection or raising seat.

REFERENCE SIGNS LIST

[0086]

1, 11: Gas generator
2, 12: Housing
3, 13: Ignition device
4, 14: Gas generant
5, 15: Filter
6, 16: Gas release hole
7, 17: Ignition chamber

Claims

A gas generant composition comprising a nitrogen-containing organic compound as a fuel component (A), a metal nitrate and/or a basic metal nitrate (B-1) and perchlorate (B-2) having a 50 percent particle diameter from 1 to 50µm as an oxidant component (B), wherein a content of the perchlorate (B-2) in a total mass of the oxidant component (B) is 5 mass percent or more and less than 35 mass percent.
The gas generant composition according to claim 1, wherein the nitrogen-containing organic compound is at least one kind selected from a group consisting of guanidine, triazole, tetrazole, bitriazole, bitetrazole and a derivative thereof.
The gas generant composition according to claim 1 or 2, wherein the metal nitrate and/or the basic metal nitrate (B-1) is at least one kind selected from a group consisting of potassium nitrate, sodium nitrate, strontium nitrate and basic copper nitrate.
The gas generant composition according to any one of claims 1 to 3, wherein the perchlorate (B-2) is at least one kind selected from a group consisting of potassium perchlorate, sodium perchlorate and ammonium perchlorate.
The gas generant composition according to any one of claims 1 to 4, wherein a content of the nitrogen-containing organic compound is from 35 to 60 mass percent, a content of the metal nitrate and/or basic metal nitrate (B-1) is from 20 to 50 mass percent and a content of the perchlorate (B-2) is from 1 to 20 mass percent.
The gas generant composition according to claim 5, wherein the nitrogen-containing organic compound is guanidine nitrate, the metal nitrate and/or basic metal nitrate (B-1) is basic copper metal nitrate and the perchlorate (B-2) is potassium perchlorate.
The gas generant composition according to any one of claims 1 to 6, wherein the perchlorate (B-2) has a 50 percent particle diameter of 1 to 30µm.
The gas generant composition according to any one of claims 1 to 7, wherein a binder (C) is further contained.
The gas generant composition according to any one of claims 1 to 8, wherein a slag former (D) is further contained.
A molded article of the gas generant composition according to any one of claims 1 to 9.
The molded article of the gas generant composition according to claim 10, wherein a shape of the molded article is a columnar shape and a diameter thereof is 4mm or less.
A gas generator comprising the molded article of the gas generant composition according to claim 10 or 11.
The gas generator according to claim 12, comprising a long cylindrical housing.