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Autoignition main gas generantRelated Patent Categories: Explosive And Thermic Compositions Or Charges, Metal Or Alloy Or Metalloid, Each In Particulate Form, With At Least One Metal Oxide, Inorganic Oxygen Containing Salt Or Organic Metal-oxygen SaltAutoignition main gas generant description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070169863, Autoignition main gas generant. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application claims the benefit of U.S. Provisional Application No. 60/761,017 having a filing date of Jan. 19, 2006. TECHNICAL FIELD [0002] The present invention relates generally to gas generating systems, and to gas generant compositions employed in gas generator devices for automotive restraint systems, for example. BACKGROUND OF THE INVENTION [0003] The present invention relates to nontoxic gas generating compositions that upon combustion rapidly generate gases that are useful for inflating occupant safety restraints in motor vehicles and specifically, the invention relates to thermally stable nonazide gas generants having not only acceptable burn rates, but that also, upon combustion, exhibit a relatively high gas volume to solid particulate ratio at acceptable flame temperatures. [0004] The evolution from azide-based gas generants to nonazide gas generants is well-documented in the prior art. The advantages of nonazide gas generant compositions in comparison with azide gas generants have been extensively described in the patent literature, for example, U.S. Pat. Nos. 4,370,181; 4,909,549; 4,948,439; 5,084,118; 5,139,588 and 5,035,757, the discussions of which are hereby incorporated by reference. [0005] In addition to a fuel constituent, pyrotechnic nonazide gas generants contain ingredients such as oxidizers to provide the required oxygen for rapid combustion and reduce the quantity of toxic gases generated, a catalyst to promote the conversion of toxic oxides of carbon and nitrogen to innocuous gases, and a slag forming constituent to cause the solid and liquid products formed during and immediately after combustion to agglomerate into filterable clinker-like particulates. Other optional additives, such as burning rate enhancers or ballistic modifiers and ignition aids, are used to control the ignitability and combustion properties of the gas generant. [0006] One of the disadvantages of known nonazide gas generant compositions is the amount and physical nature of the solid residues formed during combustion. When employed in a vehicle occupant protection system, the solids produced as a result of combustion must be filtered and otherwise kept away from contact with the occupants of the vehicle. It is therefore highly desirable to develop compositions that produce a minimum of solid particulates while still providing adequate quantities of a nontoxic gas to inflate the safety device at a high rate. [0007] The use of phase stabilized ammonium nitrate as an oxidizer, for example, is desirable because it generates abundant nontoxic gases and minimal solids upon combustion. To be useful, however, gas generants for automotive applications must be thermally stable when aged for 400 hours or more at 107 degree C. The compositions must also retain structural integrity when cycled between -40 degree C. and 107 degree C. Further, gas generant compositions incorporating phase stabilized or pure ammonium nitrate sometimes exhibit poor thermal stability, and produce unacceptably high levels of toxic gases, CO and NO.sub.x for example, depending on the composition of the associated additives such as plasticizers and binders. [0008] Yet another problem that must be addressed is that the U.S. [0009] Department of Transportation (DOT) regulations require "cap testing" for gas generants. Because of the sensitivity to detonation of fuels often used in conjunction with ammonium nitrate, many propellants incorporating ammonium nitrate do not pass the cap test unless shaped into large disks, which in turn reduces design flexibility of the inflator. [0010] Yet another concern includes slower cold start ignitions of typical smokeless gas generant compositions, that is gas generant compositions that when combusted result in at least 80 weight % of gaseous combustion products as compared to the overall weight of the combustion products. [0011] Many compositions containing phase stabilized ammonium nitrate contain an azole-based fuel such as a tetrazole. Although proven to be satisfactory in many applications, one concern is that azole-based fuels sometimes have a relatively shorter burnout time thereby complicating the inflation profile requirements. Furthermore, it is also an ongoing effort to economize the design of an inflator by increasing the functionality of a given composition, as an autoignition (less than 160 Celsius, perhaps) and primary gas generant for example. [0012] Accordingly, ongoing efforts in the design of automotive gas generating systems, for example, include other initiatives that desirably produce more gas and less solids without the drawbacks mentioned above. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 is an exemplary inflator incorporating a composition of the present invention. [0014] FIG. 2 is an exemplary gas generating system, in this case a vehicle occupant protection system, incorporating the inflator of FIG. 1. SUMMARY OF THE INVENTION [0015] The above-referenced concerns are resolved by gas generating systems including a gas generant composition containing phase stabilized ammonium nitrate, stabilized in a known manner, metal oxides including transitional metal oxides such as copper oxide, and a non-azole fuel, that is a fuel not containing tetrazole, triazoles, furazans, or azoles. Accordingly, typical fuels include amides and imides such as azodicarbonamide for example, or metal amine-based fuels such as copper diamine dinitrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) [0016] The above-referenced concerns are resolved by gas generating systems including a gas generant composition containing phase stabilized ammonium nitrate, stabilized in a known manner, metal oxides including transitional metal oxides such as copper oxide, and a fuel having non-azole character, that is a fuel not containing, or a fuel absent of any tetrazoles, triazoles, furazans, or azoles. Stated another way, the gas generant composition may be described as having a non-azole character because it does not contain an azole-based fuel as described herein. Accordingly, typical fuels include at least one of amides and imides such as dihydrazides, hydrazides, succinic dihydrazide, hydrazodicarbonamide, dicyandiamide, urea, carbohydrazide, oxamide, oxamic hydrazide, Bi-(carbonamide)amine, azodicarbonamide, derivatives thereof, d- or l-tartaric acid amide derivatives, and mixtures thereof, for example; metal amine-based fuels such as copper diamine di-nitrate; and mixtures thereof. Exemplary methods of stabilizing the phase stabilized ammonium nitrate include co-crystallization of the ammonium nitrate with potassium salts (e.g. KNO3 at about 10-15% by weight of the total weight of the PSAN), or by the solid-state melting of ammonium nitrate with transition metal oxides. [0017] Ammonium nitrate or phase stabilized ammonium nitrate (PSAN) is provided at about 60-80%, and more preferably at about 65-75% by weight of the total composition. A metal oxide is provided at about 2-10%, and more preferably at about 3-7%, by weight of the total composition. The fuel is provided at about 18-38% by weight of the total composition. It will be appreciated that the various percentages may be varied based on design requirements such as autoignition temperature and burn rate. [0018] One embodiment includes 68.27% PSAN, 3.25% copper oxide, and 27.50% azodicarbonamide. The resulting gas generation is 94.9% of the total combustion products. It will further be appreciated that a typical dry blend ratio of PSAN to the metal oxide is about 10 to 1 respectively, but may be modified as per the weight percents described above. Differential Scanning Calorimeter (DSC) laboratory results indicate a composition containing ammonium nitrate melt phase stabilized with copper oxide, combined with azodicarbonamide, exhibits an autoignition onset temperature of 150.20C, with a peak autoignition temperature of 155.48C. In contrast, nitrocellulose (smokeless powder) indicates an onset of 189.35C with a peak temperature of 214.19C. Accordingly, auto-ignition occurs relatively lower with compositions of the present invention. Continue reading about Autoignition main gas generant... Full patent description for Autoignition main gas generant Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Autoignition main gas generant patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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