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Gas generating systemRelated Patent Categories: Explosive And Thermic Compositions Or Charges, Structure Or Arrangement Of Component Or Product, Solid Particles Dispersed In Solid Solution Or Matrix, Continuous Phase Contains Organic Material, Organic Material Contains Polysaccharide Resin Or Synthetic Resin, Resin Contains Oxirane Groups Or Interunit Ether Linkages, Polysaccharide Or Derivative ThereofGas generating system description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060219340, Gas generating system. 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 Ser. No. 60/666,964 having a filing date of Mar. 31, 2005. 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] Even so, the addition of additives such as binders is often necessary to retain the shape of the propellant or gas generant tablets, and inhibit fragmentation of the same over time. Certain water soluble binders, such as carboxyl cellulosic binders, exhibit hygroscopic properties given their water solubility. Accordingly, these types of binders result in compositions that often have poor thermal stability, and in particular with compositions containing preferred oxidizers such as phase stabilized ammonium nitrate. [0009] Accordingly, ongoing efforts in the design of automotive gas generating systems, for example, include initiatives that desirably produce more gas and less solids without the drawbacks mentioned above. SUMMARY OF THE INVENTION [0010] The above-referenced concerns are resolved by gas generating systems including a gas generant composition containing an alkyl cellulosic binder such as cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Stated another way, compositions of the present invention contain a primary cellulosic binder containing alkyl substitutions, an oxidizer, and an ignition catalyst or burn inhibitor selected from the group including molybdenum trioxide and other molybdenum compounds, dibutylthalates, dicyclohexourea, triacetin, and mixtures thereof. Known fuels, oxidizers, and other additives may be incorporated into these compositions as known in the art and as determined by design criteria. In accordance with the present invention, gas generating systems such as airbag inflators and vehicle occupant protection systems incorporate these gas generating compositions. [0011] Typical micro gas generators use nitrocellulose or smokeless powder compositions for gas generation in a device. These compositions often result in relatively higher amounts of carbon monoxide. Furthermore, ballistic tailoring is not readily accomplished with the use of nitrocellulose. These are non-nitrocellulose compositions containing an oxidizer, a fuel, and a binder. Performance characteristics (i.e. ballistic output) related to burning rate can be varied based on the particle size distribution of the oxidizer component. In general, as the particle size distribution of the oxidizer is reduced, the burning rate of the propellant composition increases thereby enhancing the ballistic properties. As the particle size increases, the burning rate decreases and thus the ballistic output is reduced. Accordingly, the ballistic properties may be tailored in this manner. Average particle size ranges from 10 to 150 microns. Combinations of particle size distributions within said range can also be considered for the purpose of modifying performance. Ballistic tailoring can also be achieved by varying the shape, size and surface treatment, or any combination thereof of the propellant grains. Various propellant processes and techniques affecting propellant grain density, porosity, and surface finish (i.e. high or low exposed burning surface area) can also be employed to tailor ballistic output, for instance to achieve a regressive burn profile. A discreet propellant geometry such as a small cylinder, processed in a particular way such as extrusion, exhibits a porous center and also exhibits a regressive type burn profile. Limiting damage to equipment incorporating gas generants, seatbelt pretensioners for example, is thereby facilitated. [0012] In sum, the present invention includes gas generant compositions that optimize the production of gas combustion products and minimize solid combustion products while retaining other design requirements such as reduced hygroscopicity and thermal stability. These and other advantages will be apparent upon a review of the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 is an exemplary airbag inflator containing a gas generant composition formed in accordance with the present invention. [0014] FIG. 2 is a schematic representation of an exemplary vehicle occupant restraint system incorporating the inflator of FIG. 1 and a gas generant in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) [0015] The present invention generally includes gas generant compositions that contain a fuel, an oxidizer, molybdenum trioxide, and a primary binder. The primary binder is selected from the group of cellulosic binders such as cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Stated another way, compositions of the present invention preferably contain a primary cellulosic binder containing alkyl substitutions. Alkyl substitutions include acetyl, propionyl, butyryl groups with hydroxyl groups. The primary binder is generally provided at about 5-30% by weight of the composition. [0016] In accordance with the present invention, burn inhibitors and burn suppressants may also be included and are selected from the group containing dibutylthalates, dicyclohexourea, triacetin, and other known burn inhibitors, and mixtures thereof. The burn inhibitor or ignition catalyst may be provided in a weight percent from about 0.1-20% by weight. By inhibiting the burn, potential damage to associated gas generating systems, seatbelt assemblies and pretensioners for example, are mitigated. In accordance with one aspect of the present invention, therefore, with the addition of the burn inhibitor it has been found that the overall ignition temperature is substantially reduced thereby preserving the integrity of associated equipment such as seatbelt pretensioners. EXAMPLE 1 [0017] A composition was homogeneously mixed in a known manner, the composition containing nitroguanidine, potassium perchlorate, and cellulose acetate butyrate. Upon applying heat from a hot plate, the composition did not autoignite at 320 C, and a black char resulted. Continue reading about Gas generating system... Full patent description for Gas generating system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Gas generating system 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. Start now! - Receive info on patent apps like Gas generating system or other areas of interest. ### Previous Patent Application: Non-toxic, metallic-metal free zinc peroxide-containing, ir tracer compositions and ir tracer projectiles containing same for generating a dim visibility ir trace Next Patent Application: Heavy metal free, environmentally green percussion primer and ordnance and systems incorporating same Industry Class: Explosive and thermic compositions or charges ### FreshPatents.com Support Thank you for viewing the Gas generating system patent info. IP-related news and info Results in 0.13183 seconds Other interesting Feshpatents.com categories: Medical: Surgery , Surgery(2) , Surgery(3) , Drug , Drug(2) , Prosthesis , Dentistry 174 |
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