Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B23/00—Compositions characterised by non-explosive or non-thermic constituents
  • C06B23/02—Compositions characterised by non-explosive or non-thermic constituents for neutralising poisonous gases from explosives produced during blasting
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B29/00—Compositions containing an inorganic oxygen-halogen salt, e.g. chlorate, perchlorate
  • C06B29/22—Compositions containing an inorganic oxygen-halogen salt, e.g. chlorate, perchlorate the salt being ammonium perchlorate

Definitions

• This invention relates generally to gas generant compositions having improved effluent and, more particularly, to chlorine-containing gas generant compositions including a copper-containing chlorine scavenger compound.
• Such airbag restraint systems normally include: one or more airbag cushions, housed in an uninflated and folded condition to minimize space requirements; one or more crash sensors mounted on or to the frame or body of the vehicle to detect sudden deceleration of the vehicle; an activation system electronically triggered by the crash sensors; and an inflator device that produces or supplies a gas to inflate the airbag cushion.
• the crash sensors trigger the activation system which in turn triggers the inflator device which begins to inflate the airbag cushion in a matter of milliseconds.
• inflator devices which form or produce inflation gas via the combustion of a gas generating pyrotechnic material, e.g., a “gas generant,” are well known.
• gas generant a gas generating pyrotechnic material
• inflator devices that use the high temperature combustion products, including additional gas products, generated by the burning of the gas generant to supplement stored and pressurized gas to inflate one or more airbag cushions are known.
• the combustion products generated by burning the gas generant may be the sole or substantially sole source for the inflation gas used to inflate the airbag cushion.
• such inflator devices include a filter to remove dust or particulate matter formed during the combustion of a gas generant composition from the inflation gas to limit or prevent occupant exposure to undesirable and/or toxic combustion byproducts.
• a vehicle may include a driver airbag, a passenger airbag, one or more seat belt pretensioners, one or more knee bolsters, and/or one or more inflatable belts, each with an associated inflator device, to protect the driver and passengers from frontal crashes.
• the vehicle may also include one or more head/thorax cushions, thorax cushions, and/or curtains, each with at least one associated inflator device, to protect the driver and passengers from side impact crashes.
• the gaseous effluent or inflation gas produced by all of the inflator devices within a particular vehicle when taken as whole, are required to not include more than 5 parts per million hydrogen chloride in order to meet current industry safety guidelines.
• the gas generant compositions used in such inflator devices produce as little hydrogen chloride as possible.
• a number of gas generant compositions are known that include ammonium perchlorate as an oxidizer.
• Ammonium perchlorate is typically employed in gas generant compositions as a source of oxygen which promotes efficient combustion of the gas generant composition, e.g., complete conversion of carbon to carbon dioxide (CO 2 ), hydrogen to water (H 2 O) and nitrogen to nitrogen gas (N 2 ).
• CO 2 carbon dioxide
• H 2 O hydrogen to water
• N 2 nitrogen to nitrogen gas
• ammonium perchlorate also produces hydrogen chloride as a gaseous byproduct of combustion which, in too large a concentration, may be both toxic and corrosive.
• Hydrogen chloride gas can be “scavenged” or removed from the combustion gas stream by including a scavenger compound such as an alkali or alkaline earth metal nitrate such as sodium or potassium nitrate in the pyrotechnic gas generant composition.
• a scavenger compound such as an alkali or alkaline earth metal nitrate such as sodium or potassium nitrate in the pyrotechnic gas generant composition.
• alkali or alkaline earth metal nitrates react with the hydrogen chloride to produce less or nontoxic alkali or alkaline earth metal chlorides such as sodium or potassium chloride.
• alkali or alkaline earth metal chlorides may undesirably form as fine particulate matter or dust which can escape the inflator device.
• ammonium perchlorate typically increases the combustion temperature of the pyrotechnic gas generant composition often resulting in increased levels of undesirable and potentially toxic effluent gases such as ammonia and carbon monoxide.
• a pyrotechnic gas generant composition that takes advantage of the increased heat and oxygen provided by utilizing ammonium perchlorate as an oxidizer without increasing undesirable gaseous and particulate combustion byproducts in the inflation gas stream.
• a gas generant composition that includes a chlorine scavenger that is effective to remove hydrogen chloride from the gas stream within the inflator device.
• a gas generant composition that utilizes a metal-containing compound to provide a filterable metal chloride that effectively removes hydrogen chloride from the gas stream within the inflator and inhibits the formation of carbon monoxide and ammonia gases.
• a chlorine-containing gas generant composition that provides improved gas yields and burn rates.
• a general object of the invention is to provide a chlorine-containing gas generant composition the combustion of which results in an improved gaseous effluent or inflation gas.
• a more specific objective of the invention is to overcome one or more of the problems described above.
• the general object of the invention can be attained, at least in part, through a chlorine-containing gas generant composition including a nitrogen-containing fuel, ammonium perchlorate oxidizer, and a chlorine scavenger present in an amount effective to result in a gaseous effluent substantially free of hydrogen chloride when the gas generant is combusted, the chlorine scavenger containing at least about 98 weight percent of a copper-containing compound.
• the chlorine-containing gas generant composition contains no more than about 1 composition weight percent of a copper-free chlorine scavenger.
• the prior art generally fails to provide a chlorine-containing gas generant composition that takes advantage of the increased heat and oxygen provided by utilizing ammonium perchlorate as an oxidizer without increasing undesirable gaseous and particulate combustion byproducts in the inflation gas stream.
• the prior art fails to provide a chlorine-containing gas generant that utilizes ammonium perchlorate and a copper-containing compound that produces a filterable metal chloride to remove hydrogen chloride from a gaseous effluent resulting in an improved inflation gas.
• the invention further comprehends a method for inflating an airbag cushion of an inflatable restraint system of a motor vehicle including the steps of igniting a chlorine-containing gas generant composition that includes a nitrogen-containing fuel, ammonium perchlorate oxidizer, and an effective amount of a copper-compound to produce an inflation gas that is substantially free of hydrogen chloride, and inflating the airbag cushion with the inflation gas.
• a chlorine-containing gas generant composition that includes a nitrogen-containing fuel, ammonium perchlorate oxidizer, and an effective amount of a copper-compound to produce an inflation gas that is substantially free of hydrogen chloride
• the invention still further comprehends a chlorine-containing gas generant composition providing an improved gaseous effluent, including:
• references to “a chlorine scavenger” are to be understood to refer to a material, compound or composition that is capable of reacting with hydrogen chloride gas produced by the combustion of a chlorine-containing material, compound or composition to produce a filterable chlorine-containing material, compound or composition.
• the term “substantially free of hydrogen chloride” is understood to refer to a gaseous effluent or inflation gas that includes an amount of hydrogen chloride that is equal to or less than an amount of hydrogen chloride defined by current industry standards. For example, if a vehicle includes a single inflatable airbag cushion with a single inflator including a gas generant composition, the gaseous effluent or inflation gas produced by the combustion of the gas generant composition is substantially free of hydrogen chloride if it includes about 5 parts per million hydrogen chloride or less.
• filterable materials are to be understood to refer to a material, particle, or compound produced by combustion of a gas generant composition and that may be removed from a gaseous effluent or inflation gas stream such as by passing the gaseous effluent or inflation gas stream through a filter material or media such as a screen or mesh resulting in a decreased level of particulate matter exiting the inflator device.
• the term “equivalence ratio” is understood to refer to the ratio of the number of moles of oxygen in a gas generant composition or formulation to the number of moles needed to convert hydrogen to water, carbon to carbon dioxide, and any metal to the thermodynamically predicted metal oxide.
• a gas generant composition having an equivalence ratio greater than 1.0 is over-oxidized
• a gas generant composition having an equivalence ratio less than 1.0 is under-oxidized
• a gas generant composition having an equivalence ratio equal to 1.0 is perfectly oxidized.
• the present invention provides a chlorine-containing gas generant composition that includes a nitrogen-containing fuel, ammonium perchlorate oxidizer, and a chlorine scavenger in an amount effective to result in a gaseous effluent substantially free of hydrogen chloride.
• a chlorine scavenger in an amount effective to result in a gaseous effluent substantially free of hydrogen chloride.
• at least about 98 weight percent of the chlorine scavenger is a copper-containing compound.
• ammonium perchlorate is a particularly effective oxidizer for gas generant compositions used in the inflation of an automobile inflatable restraint system.
• the use of ammonium perchlorate typically results in the formation undesirable byproducts such as hydrogen chloride or fine particulate matter such as sodium chloride when an alkali or alkaline earth metal scavenger compound is also used.
• a filterable copper chloride byproduct is produced that results in a gaseous effluent or inflation gas that is substantially free of hydrogen chloride gas. Additionally, it has advantageously been found that a filterable copper chloride byproduct is produced that results in a reduction in the level of particulate that exits the inflator device
• the principal chlorine-containing species found in the gaseous effluent or inflation gas produced by the combustion of a gas generant composition including ammonium perchlorate and a scavenger compound predominantly containing a copper-containing compound is copper (II) chloride (CuCl 2 ) with little or no hydrogen chloride detected.
• standard thermodynamic prediction computer programs such as the Naval Weapons Center Propellant Evaluation Program (PEP) generally predict the principal chlorine species in the gaseous effluent or inflation gas produced by the combustion of such a chlorine-containing gas generant composition to be cuprous chloride (CuCl) and a trimer of cuprous chloride (Cu 3 Cl 3 ) with some hydrogen chloride.
• the gas yield and burn rates of the chlorine-containing gas generant composition in accordance with the invention can also be improved. Such improved gas yields and burn rates may be obtained as a result of catalyzing the decomposition of the ammonium perchlorate oxidizer without adversely affecting the quality of the gaseous effluent.
• materials that may be used to enhance the burn rate of pyrotechnic or gas generant compositions that contain ammonium perchlorate.
• the present invention is directed to a chlorine-containing gas generant composition including a nitrogen-containing fuel, ammonium perchlorate oxidizer; and a chlorine scavenger present in an amount effective to result in a gaseous effluent that is substantially free of hydrogen chloride when the gas generant combusted.
• a chlorine scavenger present in an amount effective to result in a gaseous effluent that is substantially free of hydrogen chloride when the gas generant combusted.
• at least about 98 weight percent of the chlorine scavenger is a copper-containing compound.
• the gas generant composition contains no more than about 1 composition weight percent of a copper-free chlorine scavenger.
• the chlorine-containing gas generant composition may include about 1 to about 20 composition weight percent ammonium perchlorate and about 80 to about 99 percent of a precursor blend containing the nitrogen-containing fuel and the chlorine scavenger.
• Useful nitrogen-containing fuels for use in the precursor blend include amine nitrates, nitramines, heterocyclic nitro compounds, and combinations thereof. While various nitrogen-containing fuels may be used in the chlorine-containing gas generant compositions of the invention, in accordance with certain preferred embodiments, the nitrogen-containing fuel may advantageously be guanidine nitrate. Generally, guanidine nitrate may be desirable due to its good thermal stability, low cost and high gas yield when combusted.
• the precursor blend may include about 30 to about 70 composition weight percent of a nitrogen-containing fuel.
• the precursor blend may include about 30 to about 70 composition weight percent guanidine nitrate.
• the precursor blend also includes a chlorine scavenger containing at least about 98 weight percent of a copper-containing compound.
• a chlorine scavenger containing at least about 98 weight percent of a copper-containing compound.
• the copper-containing compound is selected from copper nitrate complexes, basic copper nitrate, cupric oxide, and combinations thereof.
• Particularly suitable copper-containing compounds for use in the practice of this invention include copper diamine dinitrate and basic copper nitrate.
• the precursor blend includes about 30 to about 70 composition weight percent of a chlorine scavenger containing at least about 98 weight percent of a copper-containing compound.
• the precursor blend may include about 30 to about 68 composition weight percent copper diammine dinitrate.
• the precursor blend may include about 30 to about 60 composition weight percent basic copper nitrate.
• a chlorine-containing gas generant composition in accordance with the invention may advantageously contain at least one metal oxide burn rate enhancing and slag formation additive.
• metal oxide additives may be added to enhance the burn rate of the chlorine-containing gas generant composition or may be added to assist in the removal of undesirable combustion byproducts by forming filterable particulate material or slag.
• the chlorine-containing gas generant compositions of the present invention may include up to about 10 composition weight percent of at least one such metal oxide additive.
• Suitable metal oxide additives include, but are not limited to, silicon dioxide, aluminum oxide, zinc oxide, and combinations thereof.
• the chlorine-containing gas generant composition may desirably include at least one compound effective to enhance the combustion of the ammonium perchlorate oxidizer.
• the chlorine-containing gas generant compositions of the present invention may include up to about 10 composition weight percent of at least one such ammonium perchlorate combustion enhancer.
• Suitable ammonium perchlorate combustion enhancers include, but are not limited to, iron oxide, copper chromate, ferricyanide/ferrocyanide pigments, and combinations thereof.
• the chlorine-containing gas generant advantageously includes at least one ferricyanide/ferrocyanide pigment.
• ferricyanide/ferrocyanide pigments also referred to as “Iron Blue Pigments” are to be understood to generally refer to that class, family or variety of pigment materials based on microcrystalline Fe(II)Fe(III) cyano complexes. According to results obtained by X-ray and infrared spectroscopy, the basic general chemical formula for the Iron Blue Pigments is believed to be: Me(I)Fe(II)Fe(III)(CN) 6 .H 2 O.
• Me(I) stands for potassium, sodium or ammonium, with the alkali ion being believed to play a decisive role in the color properties of Iron Blue.
• Iron Blue Pigments also sometimes referred to as “iron ferricyanides,” have been produced or sold under a variety of different names related to either the place where the compound was made or to represent particular optical properties. Examples of such different names include: “Berlin Blue”, “Bronze Blue”, “Chinese Blue”, “Milori Blue”, “Non-bronze Blue”, “Paris Blue”, “Prussian Blue”, “Toning Blue” and “Turnbull's Blue”, for example.
• a chlorine-containing gas generant composition in accordance with certain preferred embodiments of the invention may include about 1 to about 20 composition weight percent ammonium perchlorate and about 80 to about 99 composition weight percent of a precursor blend containing about 30 to about 60 composition weight percent guanidine nitrate, about 30 to about 68 composition weight percent copper diammine dinitrate, and silicon dioxide in an amount of up to about 10 composition weight percent.
• a chlorine-containing gas generant composition in accordance with certain preferred embodiments of the invention may include about 1 to about 20 composition weight percent ammonium perchlorate and about 80 to about 99 composition weight percent of a precursor blend containing about 35 to about 60 composition weight percent guanidine nitrate, about 30 to about 60 composition weight percent basic copper nitrate, and at least one metal oxide additive in an amount up to about 5 composition weight percent.
• the precursor blend may further contain at least one ammonium perchlorate combustion enhancer in an amount up to about 5 composition weight percent.
• Additional additives such as processing aids may also be included in the chlorine-containing gas generant composition to improve processability of the composition.
• processing aids may also be included in the chlorine-containing gas generant composition in relatively minor concentrations such as no more than about 5 composition weight percent.
• a chlorine-containing gas generant composition, Example 1, in accordance with the invention and a chlorine-free gas generant composition, Comparative Example 1, having the same equivalence ratio were prepared as shown in TABLE 1.
• Each gas generant composition was pressed into 0.25 inch diameter by 0.070 inch thick tablets. Thereafter, each gas generant composition was tested by combusting 30 grams of tablets in a test apparatus into a 60-liter tank. The resulting gaseous effluent was analyzed by Fourier transform infrared spectroscopy (FTIR) to identify and quantify the trace species present in the effluent. The residual particles were analyzed using x-ray diffraction spectroscopy (XRF) to identify and quantify the metal species present in the residual particles.
• FTIR Fourier transform infrared spectroscopy
• XRF x-ray diffraction spectroscopy
• the gas generant composition of Example 1 included 0.13 moles of copper and 0.17 moles of chlorine and had an equivalence ratio of 1.0.
• the Naval Weapons Center Propellant Evaluation Program predicted that the gaseous effluent would include hydrogen chloride (HCl), cuprous chloride (CuCi) and a trimer of cuprous chloride (Cu 3 Cl 3 ).
• FTIR and XRF analysis of the combustion products of the gas generant composition of Example 1 indicated that no hydrogen chloride could be detected and that the principle copper species in the residual particles was copper (II) chloride (CuCl 2 ).
• a chlorine-containing gas generant composition, Example 2, in accordance with the invention and a chlorine-free gas generant composition, Comparative Example 2, having about the same equivalence ratio were prepared as shown in TABLE 3.
• Each gas generant composition was formed into tablets having a diameter of 0.25 inches and a thickness of 0.070 inches.
• the gas generant compositions were tested by combusting 42 grams of tablets in a standard passenger inflator into a 100 cubic foot tank. The resulting gaseous effluent was tested by FTIR to identify and quantify the trace species present in the effluent.
• Example 2 Based upon past experience, it was expected that the gas generant composition of Example 2 would produce a gaseous effluent with an increase in nitrogen oxides compared to gas generant composition of Comparative Example 2. However, analysis of the gaseous effluents of each gas generant composition, as shown in TABLE 4, indicated that the gas generating composition of Example 2 produced a gaseous effluent having no detectable hydrogen chloride, reduced carbon monoxide levels, and no significant increase in nitric oxide compared to the gas generating composition of Comparative Example 2. TABLE 4 Gas species (ppm) Example 2 Comparative Example 2 Carbon monoxide 144 161 Nitric oxide 24 22
• Example 3 in accordance with the invention A chlorine-containing gas generant composition, Example 3 in accordance with the invention and a standard chlorine-free gas generant composition, Comparative Example 3, that is similar were prepared as shown in Table 5.
• the burn rate date was obtained by first pressing samples of the respective gas generant compositions into the shape or form of a 0.5 inch diameter cylinder using a hydraulic press (12,000 lbs. force). Typically, enough powdered composition was used to result in a cylinder length of 0.5 inch. The cylinders were then each coated on all surfaces except the top surface with a krylon ignition inhibitor to help ensure a linear burn in the test apparatus. In each case, the so-coated cylinders were placed in a 1-liter closed vessel or test chamber capable of being pressurized to several thousand psi with nitrogen and equipped with a pressure transducer for accurate measurement of test chamber pressure.
• a small sample of igniter powder was placed on top of the cylinder and a nichrome wire was passed through the igniter powder and connected to electrodes mounted in the lid of the test chamber.
• the test chamber was then pressurized to the desired pressure and the sample ignited by passing a current through the nichrome wire.
• Pressure versus time data was collected as each of the respective samples were burned. Since combustion of each of the samples generated gas, an increase in test chamber pressure signaled the start of combustion and a “leveling off” of pressure signaled the end of combustion.
• the time required for combustion was equal to t 2 -t 1 , where t 2 is the time at the end of combustion and t 1 is the time at the start of combustion.
• the sample weight was divided by combustion time to determine the burning rate in grams per second.
• the invention provides chlorine-containing gas generant compositions having an improved effluent.
• the present invention provides a chlorine-containing gas generant including ammonium perchlorate oxidizer and a precursor blend containing a nitrogen-containing fuel and a chlorine scavenger in an amount effective to result in a gaseous effluent that is substantially free of hydrogen chloride when the gas generant composition is combusted, wherein at least about 98 weight percent of the chlorine scavenger is a copper-containing compound.
• the present invention provides a chlorine-containing gas generant composition that produces lower levels of undesirable trace gas species such as carbon monoxide and nitric oxide upon combustion.
• the present invention provides a chlorine-containing gas generant composition having an improved burn rate and gas yield when compared to an ammonium perchlorate-free gas generant composition.

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• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Air Bags (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

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• 2003
  • 2003-07-25 US US10/627,433 patent/US20050016646A1/en not_active Abandoned
• 2004
  • 2004-07-26 WO PCT/US2004/024016 patent/WO2005012208A2/en active Application Filing
  • 2004-07-26 EP EP04779190.0A patent/EP1648844B1/en not_active Expired - Lifetime
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