MXPA99003942A - Autoignition propellant containing superfine iron oxide and method of lowering the autoignition temperature of an igniter - Google Patents

Abstract

An autoignition propellant (AIP) is disclosed for use in conjunction with gas generative compositions for air bags to reduce the autoignition temperature of said propellant without adversely affecting the AIP's storage thermal stability. Said AIP consists essentially of A) a mixture of a) about 60 to 80%by weight KClO3, b) about 15 to about 30%by weight lactose and c) about 1 to about 10%by weight of an aliphatic polycarbonate and B) and autoignition lowering effective amount of superfine iron in an amount up to 10%by weight based upon the combined weight of A) and B). A method of using the AIP to lower autoignition temperatures and an air bag inflator containing the AIP are also disclosed.

Description

PROPELLANT OF AUTOIGNITION CONTAINING SUPERFINE IRON OXIDE AND METHOD TO DECREASE THE TEMPERATURE OF AGREEMENT OF AN IGNITION DEVICE TECHNICAL FIELD "The present invention relates to inflators for devices such as passive protective restraints or airbags used in motor vehicles, exhaust ramps, rafts and the like .. More particularly, the present invention relates to an ignition device for the gas generating compositions used in inflators and a method for lowering the ignition temperature of an ignition device below its autoignition temperature.

PREVIOUS TECHNIQUE Many devices, such as protective passive restrictions or airbags used in motor vehicles, exhaust ramps, rafts and the like, are normally stored in a deflated state and are inflated with gas when needed. Such devices are usually stored and used very close to humans and, therefore, must be designed with a high security factor that is effective at all times. Inflation is usually carried out by means of a gas, such as air, nitrogen, carbon dioxide, helium and the like, which is stored under pressure _ and, in addition, pressurized and supplemented at the same time to be used by the addition of gaseous combustion products at high temperature, produced by the ignition of a gas generating composition. In some cases, the inflation gases are solely produced by the gas generating compositions. Obviously it is critical that the gas generating composition be able to be stored safely and reliably without decomposition or ignition at temperatures that are likely to be found in a motor vehicle or other storage environment. For example, temperatures as high as approximately 107 ° C (225 ° F) can be reasonably experienced. It is also important that substantially all combustion products generated during use are non-toxic, non-corrosive, and non-flammable, particularly when the device is used in a closed environment, such as in a passenger compartment of a motor vehicle. Ignition devices are known devices for igniting gas generating compositions in inflators for the passive protective constraints used in motor vehicles. Such ignition devices are burned by themselves by initiators, by example, electric detonators, which are activated after detecting an impact of the motor vehicle. U.S. Patent No. 4,561,675 to Ada s et al. and US Patent No. 4,858,951 to Lenzen, discloses ignition devices for protective passive restraints, in which each of the ignition and inflator devices is contained in an aluminum housing. As discussed in each of these patents, the use of aluminum has become prevalent to reduce weight. As discussed better in each of the patents, the use of aluminum housings has the disadvantage that when the housing is exposed to high temperatures, such as those that can be encountered in a fire, the mechanical strength of aluminum declines rapidly. In such cases, when the autoignition temperature of the ignition device is reached, the aluminum housings can break or explode, sending pieces and fragments flying in all directions. To avoid the serious damage that may result when the ignition devices and / or gas generating compositions self-ignite in heated aluminum housings, U.S. Patent Nos. 4,561,675 and 4,858,951 provide ignition devices, which have low autoignition temperatures. Adams et al. relies on the "intimate" thermal contact of the material ignition with the housing frame wall. Lenzen uses a homogeneous mixture of a reinforcement material and a self-igniting material, which is a powder that does not produce smoke that burns at a temperature in the range of 300 ° F (148.9 ° C) to 400 ° F (204.4 ° C). Although the prior art has recognized and solved the problem of the autoignition temperatures of the ignition devices and / or gas generating compositions, the compositions hitherto known which lower the ignition temperatures of the whole unit suffer disadvantageously, of extensive weight loss over the required storage temperatures, indicating thermal instability, which may adversely affect the required performance of those materials. Gas generating compositions of the type currently of interest are described by US Pat. No. 3,785,149, as well as divisions thereof, that is, 3,880,595 and 3,902,934. These patents describe compositions containing potassium chlorate and materials such as tartaric acid, wherein the tartaric acid is present in amounts of about 20-42% with a complementary amount of potassium chloride. On the other hand, in U.S. Patent No. 3,862,866, where the inventor of the first three patents is a co-inventor, the specification "describes the use of organic materials, for example, lactose, with potassium chlorate, the particle size of the oxidizing powder there is limited to below 25 microns and that of" cooling powder "below it. approximately 15 microns None of the foregoing describes or makes the invention of the present application obvious.

DESCRIPTION OF THE INVENTION Accordingly, an object of the present invention is to provide an improved self-ignition propellant (AIP) for inflation devices, which is particularly stable during storage for extended periods of time and extreme temperatures. The improved composition is stable at 225 ° F (approximately 107 ° C). Another object of the present invention is to provide a more effective ignition device, through a reduction in the autoignition temperature of the ignition device from about 195 ° C to 160 ° C. A further object of this invention is to provide a method for lowering the ignition temperature of the ignition device composition of the present application. This invention also provides a method for "lowering the autoignition temperature of a propellant consisting essentially of A) a mixture containing the following components: a) from about 60 to about 80% by weight of KC103; b) from about 15 to about 20% by weight of lactose; and c) from about 1 to about 10% by weight of an aliphatic polycarbonate; the method involves adding to the propellant, B) superfine iron oxide in an amount effective to decrease the ignition temperature of up to about 10% by weight based on the combined weight of A) and B).

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a conventional exciter side inflator, which can be used to practice the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 is a drawing of a pyrotechnic generator, in which the present invention can be employed. Since one part of the inflator is reserved for storage capacity, the device is smaller than its counterpart, the hybrid inflator. In this figure, there is an initiator (11) that will burn in response to a signal from a detector (not shown), which generates the signal as "the result of a change in conditions, example, a sudden deceleration of a vehicle (indicative of a crash), in which the inflator is installed. The initiator (11) gives rise to hot gases that burn the main generating charge (16), which is burned, generating a mixture of inflation gas. The mixture leaves the manifold (14) through the outlet gates (15). To make sure that the gas generator propellant (16) is well burned below its autoignition temperature (Tig) and well below that temperature, where the building materials of the physical components begin to weaken, a Self-ignition propellant (AIP) (13) having a suitably low Tg to burn the ignition charge (12), which then burns the propellant (16).

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to an ignition device for gas generating compositions. The ignition device or autoignition propellant of the present invention provides particular advantages over known ignition devices, including a self-ignition temperature, which is well below the temperatures at which the mechanical strength of the containers accommodating the The ignition device and the associated gas generating compositions deteriorate appreciably, and likewise, is below the autoignition temperatures of most gas generating loads. Also, autoignition temperatures are not relatively affected during a 17-day storage at 107 ° C. In the ignition device, part B), superfine iron oxide, is added to part A), a propellant mixture, at an ignition temperature which decreases the effective amount to approximately 10% based on the combined weight of A) and B) . The additional objects and advantages of the present invention will become readily apparent to those skilled in the art, from the following detailed description, in "where only the preferred embodiment of the invention is shown and described, simply by way of illustration of the best As contemplated, the invention is capable of other different embodiments, and its different details are capable of modifications in several obvious aspects, all without departing from the invention. DESCRIPTION OF THE PREFERRED EMBODIMENT The ignition device of the invention comprises A) a propellant, which is a mixture of potassium chlorate, lactose and an aliphatic polycarbonate, the portion that decreases the autoignition B) of the device. of ignition consists essentially of superfine iron hydroxide, known commercially as NANOCAT. This is produced by Mach I, King of Prussia, Pennsylvania (see Table I).

TABLE I - PROPERTIES OF NANOCAT VARIABLE NANOCAT EST NDAR11'- Particle size, nm 3 large rods surface area specific, m2gm 250 10-100 Apparent density, g / ml .05 56 Iron / oxygen ratio, 2/3 2/3 mol / mol ~ jtt As the MAPICO 516m The ignition device of the present, can be used to burn all known gas generating compositions. In this regard, the ignition device can be easily incorporated into known inflators, simply by replacing the new ignition device for the compositions of the ignition device or known ignition device systems. It should be understood that this ignition device can be used in conjunction with the inflators, which exclusively use fuel gas generating compositions, as well as those that use stored, compressed gases. The aliphatic polycarbonate binder helps compress the ignition material. However, the ignition device can be used either in the form of pellets of up to 0.3 grams, or in granular form. More particularly, the ignition propellant of the present invention is used in conjunction with a gas generating composition for inflating an inflatable device, such as an automobile air bag or an airplane exhaust ramp, and will provide a temperature of lower ignition, and will not lose effectiveness after a storage of 17 days ~ 107 ° C. The autoignition propellant consists essentially of A) a mixture containing the following components: a) from about 60 to about 80% by weight of KC103; b) from about 15 to about 30% by weight of lactose; and c) from about 1 to about 10% by weight of a polycarbonate to aliphatic; and B) superfine iron oxide, in an amount effective to decrease the ignition temperature of up to about 10% by weight based on the combined weight of A) and B). Preferably, the superfine iron oxide is present in an amount effective to decrease ignition of about 1 by weight, based on the combined weight of A) and B). The presence of superfine iron oxide reduces the autoignition temperature of the propellant of about 195 ° C, without the superfine iron oxide to about 160 ° C with iron oxide superfine The first part of the autoignition propellant, ie, A), preferably contains about 70% by weight of KC10; about 25"% by weight of lactose, and about 5% by weight of an aliphatic polycarbonate, such as is commonly known in the co-tech or" QPAC®. "The second part of the ignition device, ie, B) , contains superfine iron oxide in an amount of up to 10% by weight based on the combined weight of the two parts, preferably, in an amount of about 1% by weight based on the combined weight of A) and B) Not only is the auto-ignition temperature of the propellant ignition device reduced from 195 ° C to 160 ° C, but the auto-ignition temperature does not vary significantly from 160 ° C for a period of 17 days, during which the 2 parts of the ignition device are maintained at 107 ° C. It is critical for the thermal stability of the ignition device, that superfine iron oxide (SFIO) is used as a part to lower the autoignition temperature of the autoignition propellant. use of standard iron oxide (Fe203) grades having a surface area in the range of 10-20 m2 / gm, provides an initial reduction in the autoignition temperature, which approximates that produced by the superfine iron oxide, standard iron oxide does not maintain the temperature of Reduced autoignition for a period of 17 days at 107 ° C. This is demonstrated by the data in Table II described below.

TABLE II A) is a mixture of a) 70% / weight of KC103, b) 25% / weight of lactose and c) 5% / weight of QPAC * (Table III) TABLE III - QPAC PROPERTIES -40 TABLE III - PROPERTIES OF QPAC -40 (Continued) (1) QPAC -40 = Poly (propylene) carbonate such as that produced by PAC Polymers Inc. (QPAC is a registered trademark). From the foregoing, it is evident that the present invention functions as a mitigating device for the ignition device in the event of a bonfire or slow cooking. That is to say, by reducing the ignition temperature of the propellant composition, below its self-ignition temperature, catastrophic accidents are avoided. Only the preferred embodiment of the invention and a few examples of its versatility in the present description are shown and described. It should be understood that the invention is capable of using various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept expressed herein.

Claims (19)

1. CHAPTER CLAIMEDICATORÍO Having described the invention, it is considered as a novelty and, therefore, the content is claimed in the following CLAIMS: 1. A self-ignition propellant (AIP) to be used for a gas generating composition for inflating an inflatable device / the AIP exhibits a lower autoignition temperature which retains at the same time, its effectiveness after a storage period of 17 days at 107 ° C, the autoignition propellant is characterized in that it consists essentially of A) "a mixture containing the following components: a) from about 60 to about 80% by weight of KC103; b) from about 15 to about 30 % by weight of lactose, and c) from about 1 to about 10% by weight of an aliphatic polycarbonate, and B) superfine iron oxide, in an amount effective to decrease the ignition temperature of up to about 10% by weight in basis to the combined weight of A) and B).
2. 2. The autoignition propellant according to claim 1, characterized in that B) the superfine iron oxide is present in an amount effective to decrease autoignition of about 1% by weight based on the combined weight of A) and B).
3. The autoignition propellant according to claim 1, characterized in that the autoignition temperature is reduced from about 195 ° C without B), superfine iron oxide to about 160 ° C with B), superfine iron oxide. .
4. The autoignition propellant according to claim 1, characterized in that the components of A) are present in the following amounts a) about 70% by weight of KC103; b) about 25% "by weight of lactose, and c) about 5% by weight of an aliphatic polycarbonate, with B) superfine iron oxide in an amount effective to decrease the autoignition temperature from" up to "about 10% by weight weight based on the combined weight of A) and B)
5. 5. The autoignition propellant according to claim 4, characterized in that B), the superfine iron oxide, is present in an amount effective to decrease the autoignition temperature. from about 1% by weight based on the combined weight of A) and
6. 6. The autoignition propellant according to claim 1, characterized in that the AIP is in the form of a compressed load having a weight of up to about 3g 7.
7. A method for preparing an AIP by lowering the autoignition temperature of a propellant of autoignition for a gas generating composition, to inflate an inflatable device without adversely reducing the effectiveness of the AIP after a 17-day storage period at 107 ° C, the method consists essentially of adding B) to A) in a gas generator, wherein A) is a mixture containing the following compounds a) from about 60 to about 80% "by weight of ~ KC103; b) from about 15 to about 20% by weight of lactose, and c) from about 1 to about 10% by weight of an aliphatic polycarbonate, and B) is superfine iron oxide in an amount effective to decrease the autoignition temperature of up to about 10% by weight based on the combined weight of A) and B). "" "" 8.
8. The method according to the claim 7, "characterized in that B), the superfine iron oxide is added to A), the propellant, in an amount effective to decrease the autoignition temperature of about 1% by weight based on the combined weight of A) and B) 9.
9. The method according to claim 7, characterized in that B), the superfine iron oxide is added to A), the propellant, in an amount sufficient to reduce the autoignition temperature of the propellant of about 195. ° C without B), superfine iron oxide at approximately 160 ° C with B), superfine iron oxide.
10. The method according to claim 7, characterized in that the components of A) are present in the following amounts: a) about 70% by weight of KC103; b) about 25% by weight of lactose; c) about 5% by weight of an aliphatic polycarbonate; and B) superfine iron oxide is added thereto, in an amount sufficient to decrease the ignition temperature of up to 10% by weight based on the weight of A).
11. The method according to claim 10, characterized in that B), the superfine iron oxide is added to A) in an amount to decrease the autoignition temperature of about 1% by weight based on the weight combined from A) and B).
12. The method according to claim 7, characterized in that the inflatable device is an airbag of a vehicle occupant restraint device installed in an automobile.
13. The method according to claim 7, characterized in that the autoignition propellant is in the form of a compressed charge having a weight of up to about .3 gm.
14. 14. The method according to the claim 7, characterized in that the autoignition propellant is in the form of a dry powder mixture.
15. 15. In an inflator for an inflatable device, an inflator which includes an ignition composition, the improvement characterized in that the ignition composition is provided with A) a mixture containing the following components: a) approximately 60 to approximately 80% in weight of KC103; b) from about 15 to about 20% by weight of lactose; and c) from about 1 to about 10% by weight of an aliphatic polycarbonate; in combination with B) superfine iron oxide in an amount effective to decrease the autoignition temperature of up to about 10% by weight based on the combined weight of A) and B).
16. 16. The inflator according to claim 15, characterized in that the inflator includes a supply of compressed gas.
17. 17. The inflator according to claim 15, characterized in that the inflation gases are provided solely by the gas generating composition.
18. 18. The inflator according to claim 15, characterized in that the inflation device comprises an automobile airbag.
19. 19. The inflator according to claim 15, characterized in that the ignition composition is in the form of a compressed load having a weight of up to 0.3 g.