Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B25/00—Compositions containing a nitrated organic compound
  • C06B25/34—Compositions containing a nitrated organic compound the compound being a nitrated acyclic, alicyclic or heterocyclic amine
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06D—MEANS FOR GENERATING SMOKE OR MIST; GAS-ATTACK COMPOSITIONS; GENERATION OF GAS FOR BLASTING OR PROPULSION (CHEMICAL PART)
  • C06D5/00—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets
  • C06D5/06—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets by reaction of two or more solids

Definitions

• the present invention relates generally to gas-generant formulations for use in devices such as protective passive restraints or air bags used in motor vehicles, escape slide chutes, life rafts, and the like.
• inflators for inflating vehicle occupant passive restraint systems are known.
• air bags Various inflators for inflating vehicle occupant passive restraint systems
• air bags Various inflators for inflating vehicle occupant passive restraint systems
• a related type of inflator generates a gas source from a combustible gas- generating material which, upon ignition, provides a quantity of gas sufficient to inflate the air bag.
• the inflating air bag gas is provided by the combination of a stored compressed gas and the combustion products of the gas generating material.
• Inflators which depend entirely or partially on the generation of gases by virtue of combustion of combustible materials have several disadvantages.
• the burning of the propellant and the initiator materials in such inflators can result in the production of undesired particulate matter.
• using inflators with gas generant compositions which generate certain types of solid particuiates upon combustion as part of a passive restraint system in a vehicle could result in such undesirable particuiates being released into the occupant zone of the vehicle and thereby inhaled by the occupants.
• asthmatic reactions could possibly be caused by inhalation of soluble paniculate matter, creating a health risk for the occupants. Water insoluble particuiates are preferred over soluble particuiates, as the latter are believed to potentially cause a greater asthmatic reaction.
• Particuiates may arise from the energetic component, including gas generants and ignition systems, as well as through secondary combustion of inert inflator components. Reduction in the contribution of particuiates from one or more of these components will generate a beneficial reduction in particuiates for the whole inflator assembly.
• Gas generant formulations containing guanidine dinitramide generally are known from U.S. Patent No. 6,004,410 to Blomquist (the entire content of which is expressly incorporated hereinto by reference, and hereinafter referenced as "the Blomquist '410 patent”).
• the Blomquist '410 patent discloses gas generant compositions wherein the fuel component is a dinitramide salt having the formula X + [N(N0 2 )2Jn " and wherein n is equal to one or more, and X + is a cationic derivative of an organic compound having one or more tetravalent nitrogen atoms.
• a fuel component is guanidine dinitramide (GDN), while a preferred oxidizer is ammonium nitrate (AN).
• GDN guanidine dinitramide
• AN ammonium nitrate
• a phase stabilizer generally a potassium salt
• a burn rate exponent of about 2 or less is desirable for vehicle gas generant compositions. Improvements to GDN-containing formulations and gas generants in general are, however, still needed. For example, it would be highly desirable if GDN-containing formulations could be provided which exhibit decreased toxicity, improved ballistics and relatively low amounts of substantially water-insoluble combustion products. It is towards providing such improved GDN-containing formulations that the present invention is directed.
• the present invention relates to gas generant formulations containing guanidine dinitramide (GDN) which, upon combustion with alkaline earth metal nitrate salts, generate substantially water-insoluble particuiates.
• GDN guanidine dinitramide
• the alkaline earth metal nitrate salt is selected from nitrate salts of magnesium, calcium and strontium. Low toxicity, high purity strontium nitrate with a low barium content is especially preferred.
• the formulations of the present invention necessarily will include guanidine dinitramide (GDN) as a fuel component.
• GDN guanidine dinitramide
• the amount of the fuel component in the gas generant compositions of the present invention is that amount sufficient to achieve sustained combustion and an oxygen balance with the oxidizer such that essentially
• 100% of the combustion gases include carbon dioxide, nitrogen and water.
• the fuel component will be present in the formulations of the present invention in an amount between about 40 wt.% to about 90 wt.%. Unless noted to the contrary all weight percentages herein are expressed on the basis of the total formulation weight.
• compositions of this invention may also include an auxiliary-fuel, such as 5-aminotetrazole (5ATZ), nitroguanidine (NQ) (including high bulk density NQ, HBNQ), amino guanidine nitrate (AGN), guanidine nitrate (GN) and diammonium bitetrazole (DABT); and a coolant such as lithium carbonate (LC).
• auxiliary fuel and/or coolant if present, will most preferably be employed in the formulations in an amount up to about 60 wt.%, and more preferably between about 2 wt.% to about 20 wt.%.
• the formulations of the present invention will also necessarily include an oxidizer component, especially an alkaline earth metal nitrate oxidizer.
• the preferred alkaline earth metal nitrates include nitrate salts of magnesium, calcium and strontium. Most preferred is low toxicity high purity strontium nitrate (Sr(NO 3 ) 2 ) with a low barium content.
• the oxidizer will be present in the formulations of the present invention in amounts between about 10 wt % to about 60 wt %, and most preferably between about 25 wt % to about 45 wt. %.
• a standard grade of strontium nitrate for Grade B used in tracer compositions is not desirable for use in this invention because the maximum barium allowed is up to 1.5 wt.%.
• a "low barium content" in the low toxicity high purity strontium nitrate should not exceed about 0.05 wt.%.
• Typical barium content in the strontium nitrate will be between about 0.01 to about 0.03 wt.%.
• strontium nitrate according to Mil Spec Mil-S- 20322B Grade A or comparable is employed in the practice of the present invention.
• compositions of this invention may be used in the form of powders, granules, extruded, or compression-molded pellets or other formed configurations, and the like.
• the compositions are most preferably used in the form of a solid compression-molded mixture of the above components. It is important that the form of the invention have sufficient strength to withstand forces due to initiator shock or long term thermal aging and/or thermal cycling without loss of physical integrity.
• the compositions will therefore in their compressed or extruded configuration most preferably include a highly oxygenated polymeric binder in an amount sufficient to bind the components into a more durable, stronger solid form (e.g., pellet).
• Highly oxygenated binders may also be employed so as to achieve the low levels of solid combustion products required by new automotive specifications. Great emphasis is placed on airborne or suspended solids which may initiate asthmatic reactions, particularly in the water-soluble forms. Higher oxygen contents in the binder affect the quantity of solid ash produced by decreasing the amount of metal nitrate oxidizer required to maintain the necessary oxidizerfuel ratio (O:F).
• O:F ratio is defined as the ratio of the amount of oxygen present in the composition to the amount of oxygen required to fully burn all carbon and hydrogen to CO 2 and H 2 O, respectively, and all other elements to their corresponding steady state oxidized form.
• the oxidizer is the only major source of solid ash so that by minimizing oxidizer contents, the amount of solid ash is held to a minimum.
• the oxidizer strontium nitrate in the present invention yields strontium oxide, strontium hydroxide, and/or strontium carbonate solid ash.
• the ash is substantially insoluble (that is, at most minimally soluble) in water. As the oxygen content of the binder is increased, the amount of oxidizer is reduced and thus the amount of solid ash is reduced.
• the substantially water-insoluble ash that is generated on combustion by the formulations of the present inventions will be less than about 15% and preferably less than about 10.0 wt.%.
• the binder will typically be present in an amount based upon the total composition weight, of between 1 and 15 percent, and preferably between about 3 and 7 percent.
• the preferred binders are generally highly oxygenated and include cellulose acetate, cellulose acetate butyrate, methyl cellulose, polymethylmethacrylate (PMMA with about 32 wt. % oxygen), polyvinyl alcohols (PVA with about 36 wt. % oxygen), and/or polyalkylene carbonates.
• PMMA polymethylmethacrylate
• PVA polyvinyl alcohols
• polyalkylene carbonates examples of polyalkylene carbonates that may be employed in this invention are those that are commercially available from PAC Polymers, Inc. as polypropylene carbonate) copolymer (e.g., QPAC-40 containing about 47 wt. % oxygen) and poly(ethylene carbonate) copolymer (e.g., QPAC-25 containing about 54 wt. % oxygen).
• compositions of this invention may also include an ignition accelerator/augmentor in the form of a graphite powder.
• the preferred graphite powder has an average particle size of about 40 microns.
• One particularly preferred graphite powder is Microfyne Graphite commercially available from Joseph Dixon Crucible Company of Jersey City, New Jersey.
• the graphite accelerator/augmentor is present in the compositions of this invention in an amount between about 0.1 wt.% to about 2.0 wt.%, and more preferably between about 0.25 wt.% to about 0.5 wt.%.
• compositions of this invention may be uncatalyzed (i.e., the composition is void of a combustion catalyst), or may be catalyzed. That is, the composition may include a combustion catalyzing effective amount of a combustion catalyst.
• the formulation in accordance with the present invention yields a substantially lower amount of water-insoluble ash.
• all of the strontium exists as SrO(c), which is substantially insoluble, as the combustion products are expanded to atmospheric pressure.
• SrO (c) is converted to SrCO 3 (c), which is also substantially insoluble.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Air Bags (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

Applications Claiming Priority (3)

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• 2002
  • 2002-10-24 AU AU2002348016A patent/AU2002348016A1/en not_active Abandoned
  • 2002-10-24 WO PCT/US2002/033886 patent/WO2003037859A2/en not_active Ceased
  • 2002-10-24 EP EP02784228A patent/EP1448497A2/de not_active Withdrawn
  • 2002-10-24 JP JP2003540141A patent/JP2006502067A/ja not_active Withdrawn

Non-Patent Citations (1)

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