CA2260144C - Thermally stable nonazide automotive airbag propellants - Google Patents
Thermally stable nonazide automotive airbag propellants Download PDFInfo
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Abstract
Thermally stable gas generant compositions incorporate a combination of nitroguanidine, one or more nonazide high-nitrogen fuels, and phase-stabilized ammonium nitrate or a similar nonmetallic oxidizer that, upon combustion, result in a greater yield of gaseous products per mass unit of gas generant, a reduced yield of solid combustion products, and acceptable bum rates, thermal stability, and ballistic properties. These compositions are especially suitable for inflating air bags in passenger-restraint devices.
Description
hY 8T I. NON BIDE l~rUTO OT AIRS G PROS hLANTS
_ _ _ _--.--- Bp~cICGRO~D Og ~ ICON
Field of the Inveatien The present invention relates to nontoxic gas generating compositions which upon combustion, rapidly generate gase~a 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 5 - _a. relatively high gas volume to solid particulate ratio at 'acce.ptable flame temperatures_ The evolution from azide-based gas generants to nona~zide gas generants is well-documented in the prior art.
The advantages of nonazide gas generant compositions in 10' co~aparison with azide gas generants have been extensively . described in the patent literature, for example, U.S. Patents No. 4,370,181; 4,909,549; 4,948,439; 5,084,118; 5,139,588 and . 5, 0:35, 757 ~'. -_ _ . _ ._ _ __ .____.__ __ _ In addition to a fuel constituent, pyrotechnic non~aaide 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 2o 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. '~
~otloer optional additives, such as burning rate enhancers yr ballistic modifiers and ignition aids, -are used. to control the .ig=~itability and combustion properties of the gas generant.
__ _ _ _ ..... ..
one of the disadvantages of known nonazide gas generant compositions is the amount and physical nature of the solid, residues formed during combustion. 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 therE:fore highly desirable to develop compositions that produce a ~ainimum of solid particulates while still providing adequate quantities of a nontoxic gas to inflate the safety device at a high rate.
The use of phase stabilized ammonium nitrate 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°C. The compositions must also retain structural integrity when cycled between -40°C
arid 107°C.
often, gas generant compositions incorporating phase stabilized or pure ammonium nitrate exhibit poor thermal stal:~i.lity, and produce unacceptably high levels of toxic gases, CO sand NOx for example, depending on the composition of the assc~c3ated additives such as-plasticizers and binders. 2n addition, ammonium nitxate contributes to poor ignitability, lower burn rates, and performance variability. Several known gas generant compositions incorporating ammonium nitrate uti:Lize weh known ignition aids such as 8xNO3 to solve this problem. However, the addition of an ignition aid such as BRN~~ is undesirable because it is a highly sensitive and energetic compound, and furthermore, contributes to thermal instability and an increase in the amount of solids produced.
Certain gas generant compositions comprised of armon~oni.um nitrate are thermally stable, but have burn rates less tha:n desirable for use .in gas _inflators. To be useful for passenger restraint inflator applications, gas generant compositions generally require a burn rate of at least .4 inc:h/second (ips) or store at 1000 psi. Gas generants with burn rates of less than 0.40 ips at 100o psi.do not ignite reliably and often result in "no-fires~~ in the inflator.
_ _ _ _--.--- Bp~cICGRO~D Og ~ ICON
Field of the Inveatien The present invention relates to nontoxic gas generating compositions which upon combustion, rapidly generate gase~a 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 5 - _a. relatively high gas volume to solid particulate ratio at 'acce.ptable flame temperatures_ The evolution from azide-based gas generants to nona~zide gas generants is well-documented in the prior art.
The advantages of nonazide gas generant compositions in 10' co~aparison with azide gas generants have been extensively . described in the patent literature, for example, U.S. Patents No. 4,370,181; 4,909,549; 4,948,439; 5,084,118; 5,139,588 and . 5, 0:35, 757 ~'. -_ _ . _ ._ _ __ .____.__ __ _ In addition to a fuel constituent, pyrotechnic non~aaide 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 2o 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. '~
~otloer optional additives, such as burning rate enhancers yr ballistic modifiers and ignition aids, -are used. to control the .ig=~itability and combustion properties of the gas generant.
__ _ _ _ ..... ..
one of the disadvantages of known nonazide gas generant compositions is the amount and physical nature of the solid, residues formed during combustion. 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 therE:fore highly desirable to develop compositions that produce a ~ainimum of solid particulates while still providing adequate quantities of a nontoxic gas to inflate the safety device at a high rate.
The use of phase stabilized ammonium nitrate 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°C. The compositions must also retain structural integrity when cycled between -40°C
arid 107°C.
often, gas generant compositions incorporating phase stabilized or pure ammonium nitrate exhibit poor thermal stal:~i.lity, and produce unacceptably high levels of toxic gases, CO sand NOx for example, depending on the composition of the assc~c3ated additives such as-plasticizers and binders. 2n addition, ammonium nitxate contributes to poor ignitability, lower burn rates, and performance variability. Several known gas generant compositions incorporating ammonium nitrate uti:Lize weh known ignition aids such as 8xNO3 to solve this problem. However, the addition of an ignition aid such as BRN~~ is undesirable because it is a highly sensitive and energetic compound, and furthermore, contributes to thermal instability and an increase in the amount of solids produced.
Certain gas generant compositions comprised of armon~oni.um nitrate are thermally stable, but have burn rates less tha:n desirable for use .in gas _inflators. To be useful for passenger restraint inflator applications, gas generant compositions generally require a burn rate of at least .4 inc:h/second (ips) or store at 1000 psi. Gas generants with burn rates of less than 0.40 ips at 100o psi.do not ignite reliably and often result in "no-fires~~ in the inflator.
Yet another problem that must be addressed is that the U.S. 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 nitr~3te, most propellants incorporating ammonium nitrate do not pass the cap test unless shaped into large disks, which in turn reduces design flexibility of the inflator.
Accordingly, many nonazide propellants based on ammonium nitrate cannot meet requirements for automotive to ~ appl,ications.
nescriptior~of the Related Art .--,., _ . . , U.S. patent No. 5,545,272 to Poole discloses the use of eras ~ generant compositions cons fisting of nitroguanidine (NQ) ., at a3 weight percent of 35%-55%, and phase stabilized ammonium nitrate (PSAN) at a weight percent of 45%-65%. NQ, as a fuel, is prEferred because it generates abundant gases and yet consists of very little carbon or oxygen, both of Which contribute to higher levels of Co and NOx in the combustion gases. According to Poole, the use of phase stabilized ammonium nitrate (PSAN) or pure ammonium nitrate is problematic because many gas generant compositions containing the oxidizer ._ are therutally unstable. Poole has found that combining NQ and 1~PSAN in the percentages given results in thermally stable gas gen.erant compositions. However, Poole reports burn rates of Z5 only .32 -,34 inch per second, at 1000 psi. As is we7.1 known;
. burn rates below .4 inch per second at 1000 psi are simply too lcw for confident use within an inflator.
In U.S. patent No. 5,531,941 to Poole, Poole teaches the: use of PSAN, and two or more fuels selected from a 3o specified group of nonazide fuels. Poole adds that gas generants using ammonium nitrate (AN) as the oxidizer are generally very slow~burning with burning rates at 1000 psi typically leas than~o.i inch per second. He further teaches that for air bag applications, burning rates of less than about 35 ' . - . , . . ~~ . .
Accordingly, many nonazide propellants based on ammonium nitrate cannot meet requirements for automotive to ~ appl,ications.
nescriptior~of the Related Art .--,., _ . . , U.S. patent No. 5,545,272 to Poole discloses the use of eras ~ generant compositions cons fisting of nitroguanidine (NQ) ., at a3 weight percent of 35%-55%, and phase stabilized ammonium nitrate (PSAN) at a weight percent of 45%-65%. NQ, as a fuel, is prEferred because it generates abundant gases and yet consists of very little carbon or oxygen, both of Which contribute to higher levels of Co and NOx in the combustion gases. According to Poole, the use of phase stabilized ammonium nitrate (PSAN) or pure ammonium nitrate is problematic because many gas generant compositions containing the oxidizer ._ are therutally unstable. Poole has found that combining NQ and 1~PSAN in the percentages given results in thermally stable gas gen.erant compositions. However, Poole reports burn rates of Z5 only .32 -,34 inch per second, at 1000 psi. As is we7.1 known;
. burn rates below .4 inch per second at 1000 psi are simply too lcw for confident use within an inflator.
In U.S. patent No. 5,531,941 to Poole, Poole teaches the: use of PSAN, and two or more fuels selected from a 3o specified group of nonazide fuels. Poole adds that gas generants using ammonium nitrate (AN) as the oxidizer are generally very slow~burning with burning rates at 1000 psi typically leas than~o.i inch per second. He further teaches that for air bag applications, burning rates of less than about 35 ' . - . , . . ~~ . .
0.4 to 0.5 inch per second are difficult to use. The use of PSAN is taught as desirable.because of its propensity to produce abundant gases and minimal solids, with minimal noxious gases.. Nevertheless, Poole recognizes the problem of low burn rates. and thus combines PsAN with a fuel component containing a majority of TAGN, and if desired one or more additional fuel.:. The addition of TAGN increases the burn rate of ammonium nitrate mixtures. According to Poole, TAGN/PSAN
compositions exhibit acceptable burn rates of .59-.83 inch/per l0 second. TAGN, however, is a sensitive explosive that poses safety concerns in processing and handling. In addition, TAGN
is classified as "forbidden" by the Department of Transportation, therefore complicating raw material requirexaents .
In U.S. Patent No, 5,500,059 to Lund et al., Lund states that burn rates in excess of 0.5 inch per second (ips) at 1, 000 psi, and preferably in the range of from about 1. 0 ips to about 1.2 ips at 1,000 psi, are generally desired. hand dxsc:loses gas generant compositions comprised of a 5-amir.~otetrazole fuel and a metallic oxidizer component. The use of a. metallic oxidizer reduces the amount of gas liberated per gram of gas generant, however, and increases the amount 0f_ solids generated upon combustion.
The gas generant compositions described in Foole et al, U. S. Patents No. 4, 909, 549 and 4, 948, 439, use tetrazole or triazole compounds in combination with metal oxides and oxidizer compounds (alkali metal, alkaline earth metal, and pure annnonium nitrates or perchlorates) resulting in a relatively unstable generant that decomposes at loGr 3o temperatures. Significant toxic emissions and particulate are formed upon combustion_ Both patents teach the use of BKN03 as an .ignition aid.
The gas generant compositions described in Poole, U.s_ patent No. 5,035,75?, result in more easily filterable solid products but the gas yie~.d is unsatisfactory..
Chang et al, U. S. Patent No. 3,~ 954, 525., describes the use of TAGN and a synthetic polymeric binder in combination with an oxidizing material. The oxidizing materials include pure AN although, the use of PsAN is not suggested. The patent teachea the preparation of propellants for use in guns or other devices where large amounts of carbon monoxide, nitrogen oxide.:, and hydrogen are acceptable and desirable. Because of the practical applications involved, thermal stability is not considered a critical parameter.
Grubaugh, U.S. Patent No. 3,044,123, describes a method of preparing solid propellant pellets containing AN as the major component. The method requires use o~ an oxidizable organ_~c binder (such as cellulose acetate, PVC, PVA, acrylonitrile and styrene-acrylonitrile), followed by comprcassion molding the mixture to produce pellets and by heat treating the pellets . These pellets would certainly be damaged by temperature cycling because commercial ammonium nitrate is used, and the composition claimed would produce. large amounts of carbon monoxide.
8ecuwe, U.S. Patent No. 5,034,072, is based on the use oi: 5-oxo-3-vitro-1, 2 , 4-triazole as a replacement for other explo~5ive materials (Iii, RDX, TATB, etc.) in propellants and gun powders. This compound is also called 3-vitro-1,2,4-triaz~~le-5-one ("NTO"). The claims appear to cover a gun powder composition which includes NTO, AN and an inert binder, where the composition is less hygroscopic than a propellant 2S containing ammonium nitrate. Although called inert, the binder would enter into the combustion reaction and produce carbon monoxide making it unsuitable for air bag inflation.
Land et al, U.S. Patent No. 5,197,758, describes gas generating compositions comprising a nonazide fuel which is a transition metal complex of an aminoarazole, and in particular are copper and zinc complexes of 5-aminotetrazole and 3-amino-1,2,4 -triazole which are useful for inflating air bags in automotive restraint systems, but generate excess solids.
wardle Et al, U. s. Patent No. 4, 931,112, describes an automotive air bag gas generant formulation consisting essentially of NTO (5-vitro-1,2,4-triazole-3--one) and an oxidizer wherein said formulation is anhydrous.
compositions exhibit acceptable burn rates of .59-.83 inch/per l0 second. TAGN, however, is a sensitive explosive that poses safety concerns in processing and handling. In addition, TAGN
is classified as "forbidden" by the Department of Transportation, therefore complicating raw material requirexaents .
In U.S. Patent No, 5,500,059 to Lund et al., Lund states that burn rates in excess of 0.5 inch per second (ips) at 1, 000 psi, and preferably in the range of from about 1. 0 ips to about 1.2 ips at 1,000 psi, are generally desired. hand dxsc:loses gas generant compositions comprised of a 5-amir.~otetrazole fuel and a metallic oxidizer component. The use of a. metallic oxidizer reduces the amount of gas liberated per gram of gas generant, however, and increases the amount 0f_ solids generated upon combustion.
The gas generant compositions described in Foole et al, U. S. Patents No. 4, 909, 549 and 4, 948, 439, use tetrazole or triazole compounds in combination with metal oxides and oxidizer compounds (alkali metal, alkaline earth metal, and pure annnonium nitrates or perchlorates) resulting in a relatively unstable generant that decomposes at loGr 3o temperatures. Significant toxic emissions and particulate are formed upon combustion_ Both patents teach the use of BKN03 as an .ignition aid.
The gas generant compositions described in Poole, U.s_ patent No. 5,035,75?, result in more easily filterable solid products but the gas yie~.d is unsatisfactory..
Chang et al, U. S. Patent No. 3,~ 954, 525., describes the use of TAGN and a synthetic polymeric binder in combination with an oxidizing material. The oxidizing materials include pure AN although, the use of PsAN is not suggested. The patent teachea the preparation of propellants for use in guns or other devices where large amounts of carbon monoxide, nitrogen oxide.:, and hydrogen are acceptable and desirable. Because of the practical applications involved, thermal stability is not considered a critical parameter.
Grubaugh, U.S. Patent No. 3,044,123, describes a method of preparing solid propellant pellets containing AN as the major component. The method requires use o~ an oxidizable organ_~c binder (such as cellulose acetate, PVC, PVA, acrylonitrile and styrene-acrylonitrile), followed by comprcassion molding the mixture to produce pellets and by heat treating the pellets . These pellets would certainly be damaged by temperature cycling because commercial ammonium nitrate is used, and the composition claimed would produce. large amounts of carbon monoxide.
8ecuwe, U.S. Patent No. 5,034,072, is based on the use oi: 5-oxo-3-vitro-1, 2 , 4-triazole as a replacement for other explo~5ive materials (Iii, RDX, TATB, etc.) in propellants and gun powders. This compound is also called 3-vitro-1,2,4-triaz~~le-5-one ("NTO"). The claims appear to cover a gun powder composition which includes NTO, AN and an inert binder, where the composition is less hygroscopic than a propellant 2S containing ammonium nitrate. Although called inert, the binder would enter into the combustion reaction and produce carbon monoxide making it unsuitable for air bag inflation.
Land et al, U.S. Patent No. 5,197,758, describes gas generating compositions comprising a nonazide fuel which is a transition metal complex of an aminoarazole, and in particular are copper and zinc complexes of 5-aminotetrazole and 3-amino-1,2,4 -triazole which are useful for inflating air bags in automotive restraint systems, but generate excess solids.
wardle Et al, U. s. Patent No. 4, 931,112, describes an automotive air bag gas generant formulation consisting essentially of NTO (5-vitro-1,2,4-triazole-3--one) and an oxidizer wherein said formulation is anhydrous.
Ramnarace, U.S. Patent No. 4,111,728, describes gas generators for inflating life rafts and similar devices or that are useful as rocket propellants comprising ammonium nitrate, a polyester type binder and a fuel selected from oxamide and guanidine nitrate. Ramnarace teaches that ammonium nitrate contr~lbutes to burn rates lower than those of other oxidizers and further adds that ammonium nitrate compositions are hygroscopic and difficult to ignite, particularly if small amounts of moisture have been absorbed.
Bucerius et al, U. S.~ Patent No. 5,198, 046, teaches the u~~e of diguanidinium-5,5~-azotetrazolate (GZT) with KNO3 as an ox:~dizer, for use in generating environmentally friendly, non-toxic gases. Bucerius teaches away from combining GZT with any chemically unstable and/or hygroscopic oxidizer. The use of other amine salts of tetrazole such as bis-(tria~minoguanldirlium) -5, 5 ~-azotetraaolate (TAGZT) or amp.noquanidirllum-5,5~-a2otetrazolate are taught as beiTlg much . less i:henaally stable when compared to GZT.
Boyars, U.S. Patent No. 4,124,368, describes a method for preventing detonation of ammonium nitrate by using - potassium nitrate.
Mishra, U.S. Patent No. 4,552,736, and Mehrotra et ~ al, U,.S. Patent No. 5,098,683, describe the use of potassium fluoride to eliminate expansion and contraction of ammonium nitrat:e in transition phase.
Chi, U.S. Patent No. 5,074,938, describes the use of phase stabilized ammona.um nitrate as an oxidizer in propellants conta~lning boron and as useful in rocket motors.
In U. S. Patent 5, 125, 684 to Cartwright, an extrudable 3o prope7Llant for use in crash bags is described as comprising an oxidi.:er salt, a cellulose-based binder and a gas generating component_ Cartwright also teaches the use of ~~at least one energeaic 'component selected from nitroguanidine (NG), triaminoguanidine nitrate, ethylene dinitramine, c y c 7. o t r i m a t h y 1 a n a t r i n i t r a m i n a ~ ( R D X ) , cyclot:etramethylenetetranitramine (HMX)_,--trinitrotoluene (TNT) , and ps:ntaerythritol tetranitrate (PETN)....~~
Bucerius et al, U. S.~ Patent No. 5,198, 046, teaches the u~~e of diguanidinium-5,5~-azotetrazolate (GZT) with KNO3 as an ox:~dizer, for use in generating environmentally friendly, non-toxic gases. Bucerius teaches away from combining GZT with any chemically unstable and/or hygroscopic oxidizer. The use of other amine salts of tetrazole such as bis-(tria~minoguanldirlium) -5, 5 ~-azotetraaolate (TAGZT) or amp.noquanidirllum-5,5~-a2otetrazolate are taught as beiTlg much . less i:henaally stable when compared to GZT.
Boyars, U.S. Patent No. 4,124,368, describes a method for preventing detonation of ammonium nitrate by using - potassium nitrate.
Mishra, U.S. Patent No. 4,552,736, and Mehrotra et ~ al, U,.S. Patent No. 5,098,683, describe the use of potassium fluoride to eliminate expansion and contraction of ammonium nitrat:e in transition phase.
Chi, U.S. Patent No. 5,074,938, describes the use of phase stabilized ammona.um nitrate as an oxidizer in propellants conta~lning boron and as useful in rocket motors.
In U. S. Patent 5, 125, 684 to Cartwright, an extrudable 3o prope7Llant for use in crash bags is described as comprising an oxidi.:er salt, a cellulose-based binder and a gas generating component_ Cartwright also teaches the use of ~~at least one energeaic 'component selected from nitroguanidine (NG), triaminoguanidine nitrate, ethylene dinitramine, c y c 7. o t r i m a t h y 1 a n a t r i n i t r a m i n a ~ ( R D X ) , cyclot:etramethylenetetranitramine (HMX)_,--trinitrotoluene (TNT) , and ps:ntaerythritol tetranitrate (PETN)....~~
In U.S. Patent 4,925,503 to Canterbury et al, an explosive composition Xs described as comprising a high energy material, e.g., ammonium nitrate and a polyurethane polyacetal elastaiaer binder, the latter component being the focus of the invention. Canterbury also teaches the use of a "high energy material useful in the present invention ... preferably one of the following high energy materials: RDX, NTO, TNT, HI~lX, TAGN, nitrogruanidine, or ammonium nitrate..."
Hess, U. s. Patent No. 3 , 0~1, 617, describes long known considerations as to oxygen balance and exhaust gases.
Stinecipher et al, U.S. Patent No. 4,300,962, describes explosives comprising ammonium nitrate and an ammonium salt of a nitroazole.
Prior, U.S. Patent No. 3,719,604, describes gas generating compositions comprising aminoguanidine salts of azotet.razole or of ditetrazole.
Poole, U.S_ Patent No_ 5,139,588, describes nonazide gas generants useful in automotive restraint devices comprising a fuel, an oxidizer and additives.
Hendrickson, U.S. Patent No. 4,798,637, teaches the use o~~ bitetrazole compounds, such as diammonium salts of bitetrazole, to lower the burn rate of gas generant - compositions. Hendrickson describes burn rates below .40 ips, and an 8% decrease in the burn rate when diammonium bitetrazole is used.
Chang et al, U.S. Patent No. 3,909,322, teaches the use of nitroaminotetrazole salts with oxidizers such as pure ammonium nitrate, I~MX, and 5-ATN. These compositions are used as gun,'propellants and gas generants for use in gas pressure actuated mechanical devices such as engines, electric generators, motors, turbines, pneumatic tools, and rockets. In contrast to the amine salts disclosed by Hendrickson, Chang teaches that gas generants comprised of 5-aminotetrazole nitrate and salts of nitrvaminotetrazole exhibit burn rates in excess of .40 ips. On the other hand, Chaiig also teaches that gas generants comprised of I3Mx and salts of nitroaminotetrazole exhibit burn rates of .243 ips to .360 ips. No data is given ' 1 4 y: r ' with regard to burn rates associated with pure AN and salts of nitroaminotetrazole.
Highsmith et al, U.S. Patent No. 5,516,377, teaches the us,e of a salt of 5-nitraminotetrazole, NQ, a conventional ignition aid such as BKNO3, and pure ammonium nitrate as an oxidizer, but does not teach the use of phase stabilized ammonium nitrate. Highsmith states that a composition comprised of ammonium nitraminotetrazole and strontium nitrate exhibits a burn rate of .313 ips. This is to low for automotive application. As such, Highsmith emphasizes the use of metallic salts of nitraminotetrazole.
Onishi et al, U.S. Patent No. 5,439,251, teaches the use off: a tetrazole amine salt as an air bag gas generating agent comprising a cationic amine and an anionic tetrazvlyl group having either an a11cy1 With carbon number 1-3, chlorine, hydroxyl, carboxyl, methoxy, aceto, vitro, or another tetrazolyl group substituted via diaao or triazo groups at the 5-position of the tetrazole ring. The inventive thrust is tQ
improve the physical, properties of tetrazoles with regard to 2o impact. and friction sensitivity, and therefore does not teach the combination of an amine or nonmetal tetrazole salt with any other chemical_ Lund et al, U.S. patent No. 5,501,823, teaches the use o;E nvnazide anhydrous tetrazoles, derivatives, salts, complexes, and mixtures thereof, far use in air bag inflators.
The use of bitetrazole-amines, not amine salts of bitetrazoles, is also taught.
Based on the above, the need remains for a PsAN-based gas generant which is thermally stable at 107C, ignites readily and without delay, has a burn rate at 1O00psi of greater than 0.40-0.5oips, and contains no sensitive explosive compounds.
SUMMARY OF THE INVENTION
The afc=ementioned problems are solved by a nonazide gas generant for a vehicle passenger restraint system comprising phase stabilized ammonium nitrate, nitroguanidine, and one or more nonazide fuels_ The nonazide fuels are -g-' selected from a group including guanidines; tetrazoles such as 5,5~bi.tetrazole, diammonium bitetrazole, diguanidinium-5,5~-azotetrazolate (GZT), and nitrotetrazoles such as 5-riitrot:etraaole; triazoles such as nitroaminotriazole, nitrot:riazoles, and 3-vitro-1,2,4 triazole-5-one; and salts of tetraz~~oles and triazolas_ A preferred fuels) is selected from the group consisting of amine and other nonmetal salts of tetra2oles and triazoles having a nitrogen containing cationic component and to a tetrazole and/or triazole anionic component. The anionic comporuent comprises a tetrazole or triazole ring, and an R
group substituted on the 5-position of the tetrazole ring, or two R groups substituted on the 3- and 5-positions of the triasole ring. The R groups) is selected from hydrogen and any nitrogen-containing compounds such as amino, vitro, nitramino, tetraaolyl and triazolyl groups. The cationic component is formed from a member of a group including amines, aminos~, and amides including ammonia, hydrazine, guanidine compounds such as guanidine, aminoguanidine, diaminoguanidine, triami.noguanidi.ne, dicyandiamide, nitroguanidine, nitrogen subsit,uted carbonyl compounds such as urea, carbohydraaide, oxamid,e, oxamic hydrazide, bis-(carbonamide) amine, azodicarbonamide, and hydrazodiearbonamide, and, amine azoles such as3-amino-1,2,4-triazole,3-amino-5-vitro-1,2,4-triazole, 5-ami~.otetraaole and 5-nitraminotetrazole. Optional inert additives such as clay, alumina, or silica may be used as a binder, slag former, coolant or processing aid. Optional ignition aids comprised of nonazide propellants may also be utilized in place of conventional ignition aids such as 8KNo3.
3o D~ETA=LSD DDSCRipTION OF T88 BREFSRRSD ~oD~NT(s) A nonazide gas generant comprises phase stabilized ammonium nitrate (PSAN), nitroguanidine (NQ), and one or more nonazide high-nitrogen fuels. One or more high-nitrogen fuels are selected from a group including tetrazoles such as 5-nitrotetrazole, 5,5~-bitetrazole, .triazoles such as nitroaminotriazole, nitrotriazoles, nitrotetrazoles, salts of -g-- tetrazoles and triazoles, and 3-nitro-1,2,4 triazole-5-one.
More specifically, salts of tetrazoles include in particular, amine, amino, and amide salts of tetrazole and triazole selected from the group including monoguanidinium salt og 5,5'-Bis-18-tetrazole (BHT~1GAD), diguanidinium salt of . 5, 5 ~-Ftis-113-tetraaole (BHT ~ 2GAD) , monoaminoguanidinium salt of 5,5'-Bis-1H-tetrazole (BHT~lAGAD), diami~noguanidinium salt of 5,5~-E~is-113-tetrazole (gHT~2AGAD), monohydrazinium salt of 5,5'-Bis-1H-tetrazole (BHT~1H8), dihydrazinium salt of 5,5'-His-1~1f-tetrazole (BHT~2HH), monoammonium salt of 5,5'-bis-1H
tetraz,ole (HHT ~ 1NH3) , diamalGllium salt of 5, 5' -bis-1H-tetraaole (BHT~2NH3), mono-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H
tetraz~ole (HHT ~ lATAZ) , di-3-amino--1, 2, 4-triazolium salt of 5,5'-bis-1H-tetrazole (BHT~2ATAZ), and diguanidinium salt of 5,5~-~,2obis~1H-tetraZOle (ABHT~2GAD).
Amine salts of triazoles include monoammonium salt of 3-vitro-1,2,4-triazole (NTA~1NH3), monoguanidinium salt of 3-nitro-1,2,4-tria2ole (NTA~1GAD), diammonium salt of dinitrobitriazole (DNBTR~2NH3), diguanidinium salt of dinitrobitriazole (DNBTR~2GAD), and monoammonium salt of 3,5-~dinitro-1,2,4-triazole (DNTR-iNH3).
N - N N - C
2 5 ~~ ~~ ~ Z ~~ ~~ ' Z
C N C N
\ / / \ /
R N RZ N
H H
Formula I Formula II
A ~generic nonmetal salt of tetrazole as shown in Formula I includes a cationic nitrogen containing component, Z, and an anionic component comprising a tetrazole ring and an R
group substituted on the 5-position of the tetrazole ring. A
generic nonmetal salt of triazole as shown in Formula II
includes a cationic nitrogen containing component, Z, and an anionic component comprising a triazole ring and two R groups substituted on the 3- and 5- positions~~of the triazole ring, wherein R1 may or may not be structurally synonymous with R2.
_10-- An R c:omponent is selected Pram a group including hydrogen or any nitrogen-containing compound such as an amino, nitro, nitramino, or a tetrazvlyl or triazolyl group as shown in Formu7.a I or II, respectively, substituted directly or via amine, diazo, or triazv groups. The compound Z is substituted at the 1-position of either formula, and is formed from a membex- of the group comprising amines, .aminos, and amides including ammonia, carbohydrazide, oxamic hydrazide, and hydra2;ine; guanidine compounds such as guanidine, amino~~uanidine, diaminoguanidine, triaminoguanidine, dicyandiamide and n.itroguanidine; nitrogen substituted carbonyl compdu~nds or amides such as urea, oxamide, bis-(carbonamide) amine, aaodicarbonamide, and hydrazodicarbonamide; and, amino azoles; such as 3-amino-1,2,4-triazole, 3-amino-5-vitro-1,2,4-triazole, 5-aminotetrazole, 3-nitramino-1,2,4-triazole, S-nitraminotetrazole, and melamine.
In accordance with the present invention, a preferred gas g~enerant composition results from the mixture of gas generant constituents including nitroguanidine, comprising s%-30% by weight of the gas generant composition, one or more amine salts of t etrazoles and/or triazoles, comprising 4%-40%
by weight of the gas generant composition, and psAN, comprising " 40%-85$ by weight of the gas generant composition. In the percentages given, an even more preferred embodiment results from 'the mixture of gas generant constituents consisting essentially of NQ, PSAN, and amine salts) of 5,5~-bis-1H-tetrazvle. In the percentages given, a most preferred composition results from the mixture of gas generant constituents consisting essentially of NQ, PSAN, and diammonium salt of 5,5~-bis-1H-tetrazole (BHT~2Nfi3). When combined, the fuel component consisting of NQ and one or more high nitrogen fuels as described herein, comprises 15%-60% by weight of the gas generant composition.
In accordance with procedures well known in the art, the foregoing nonazide fuels, and/or nonmetal salts of tetrazole or triazole, are blended with an oxidizer such as PSAN, .and NQ. The manner and order in which the components of the gas generant compositions of the present invention are combined and compounded is not critical so long as the proper particle size of ingredients are selected to ensure the desired mixture is obtained. The compounding is performed by one skilled in the art, under proper safety procedures for the preparation of energetic materials, and under conditions which will not cause undue hazards in processing nor decomposition of the components employed. For example, the materials may be wet blended, or dry blended and attrited in a ball mill or Red to Devil type paint shaker and then pelletiaed by compression molding. The materials may also be ground separately or together in a fluid energy mill, sweco vibroenergy mill or bantam, micropulveri2er and then blended or further blended in a v-blender prior to compaction.
Compositions having components more sensitive to friction, impact, and electrostatic discharge should be wet ground, separately followed by drying. The resulting fine powder of each of the components may~then be wet blended by tumbling with ceramic cylinders in a ball mill jar, for example, and then dried. Less sensitive components may be dry ,ground. and dry blended at'the same time.
Phase stabilx2ed ammonium nitrate is prepaxed as taught. in co-owned U. S. Patent No. 5, 531, 941 entitled, "Process For Preparing Azide-free Gas Generant Composition". Other nonmetal inorganic oxidizers such as ammonium perchlorate, or oxidizers that produce minimal solids when combined and combusted with the fuels listed above, may also be used. The ratio of oxidizer to fuel is preferably adjusted so that the amount. of oxygen allowed in the equilibrium exhaust gases is less than 3% by weight, and more preferably less than or equal to 2% by weight. The oxidizer comprises 40%-85% by weight of the gas generant composition.
The gas generant constituents of the present invention are commercially available. For example, the amine salts of tetrazoles may be purchased from Toyo Kasei Kogyo Company Limited, Japan_ rritroguanidine may be purchased from Nigu Chemie, and, the components used to synthesize PSAN, as described herein, may be purchased from Fisher or Aldrich.
Triazole salts may be synthesized by techniques, such as those described in U.S. Patent No. 4,Z3s,o14 to Lee et al.; in ~~New Explosives: Nitrotriazoles Synthesis and Explosive properties", by H.H. Licht, Fi_ Ritter, and H. Wanders, postfach 1260, D-79574 Weil am Rhein; and in ~~Synthesis of Nitro Derivatives of Triazoles", by Ou Yuxiang, Chen 8oren, Li Jiarong, Dong Shuan, Li Jianjun, and Jia Huiping, Heterocvcles, Vol. 38, No. 7, pps.
7.651-'1664, 1994. Other compounds in accordance with the present invention may be obtained as taught in the above-mentioned references, or from other sources well known to those skill~sd in the art, .
Ari optional burn rate modifier, from O-l0% by weight in tb.e gas generant composition, is selected ~xom a group including an alkali metal, an alkaline earth or a transition metal salt of tetrazoles or triazoles; an alkali metal or alKal:Lne earth nitrate or nitrite; TAGN; dicyandiamide, and alkali and alkaline earth metal salts of dicyandiamide; alkali 2o and alkaline earth borohydrides; or mixtures~thereof. An optional combination slag former and coolant, in a range of 0 to 10% by weight, is selected from a group including clay, . 5111ca, glass, and alumina, or mixtures thereof. When combining the optional additives described, or others known to those skilled in the art, care should be taken to tailor the additions with respect to acceptable thermal stability, burn rates,, and ballistic properties.
In accordance with the present invention, the combination of NQ, PSAN, and one or more nonazide high-nitrogen fuels,, as determined by gravimetric procedures, yields beneficial gaseous products ,equal to or greater than 90% of the total product mass, and solid products equal to or lesser than 10% of the total product mass_ Fuels suitable in practicing the present invention are high in nitrogen content and low in carbon content thereby providing a high burn rate and a minimal gener<ition of carbon monoxide.
The synergistic effect of the high-nitrogen fuels, in combination with an oxidizer producing minimal solids when combined with the fuels, results in several long-awaited benefits. Increased gas production per mass unit of gas generant results in the use of a smaller chemical charge.
Reduced solids production results in minimized filtration needs and therefore a smaller filter. Together, the smaller charge and smaller filter thereby facilitate a smaller gas inflator system. Furthermore, the gas generant compositions of the present invention have'burrt rates and ignitability that meet l0 and surpass performance criteria for use within a passenger restraint system, thereby reducing performance variability.
As shoran in Example 10, it has also been found that the use of nitroguanidine functions to retard the volumetric phase changes nonaally exhibited by pure ammonium nitrate, thereby further stabiliz~.ng the PsAN.
An unexpected benefit of the present chemical compositions is thermal stability. The thermal stability of the ga.s generants is unexpected based an the poor stability of other fuels and in particular, triazoles and tetrazoles, when combined with PSAN. In contrast to other thenaally stable compositions consisting of NQ and PSAN, these compositions ignite: readily and without delay and have a burn rate greater than 0.40-0.50 ips at 1000 psi. Furthermore, the amine salts of tetrazoles and triazoles are neither explosive nor flammable and ca.n be transported as non-hazardous chemicals.
The present invention is illustrated by the followung examples. All compositions are given in percent by weight.
EBASpZE 1 - comparative Example A mixture of ammonium nitrate (AN) , potassium nitrate (RN), and guanidine nitrate (GN) was prepared having 45.35%
Nfi4NO3, 8 . 0% KN, and 46 _ 65% GN. The amoononium nitrate was phase stabilized by coprecipitating with RN.
The mixture was dry-blended and ground in a ball mill. Thereafter, the dry-blended mixture was compression-melded into pellets, The burn rate of the composition was determined by measuring the time required to burn a cylindrical pellet of known length at constant pressure. The burn rate at 1000 pounds per square inch (psi) was .25~ inches per second (in/sec); the burn rate at 1500 psi was .342 in/sec. The corresponding pressure exponent was 0.702.
EYANP~B 2 - Comparative Example A mixture of 46.13% NI~NO3, 8.14% I~1, 35.73% GN, and 10.0% nitroguanidine (NQ) was prepared and tested as described in Example 1. The burn rate at 1000 psi was 0.282 in/sec and 20 the burn rate at 1500 psi was 0.368 in/sec. The corresponding pressure exponent was 0.657.
EZAMP1'~E 3 - Comparative Example A mixture of 46.91% NI~N03, 8.28% KN, 24.81% GN, and 20 . o% NQ was prepared and tested as described in Example 1.
The bL~trn rate at 1000 psi was 0.282 in/sec and the burn rate at 1500 psi was 0.3'73 in/sec. The corresponding pressure exponent was 0.,680.
E~Z~E 4 - Comparative Example A mixture of 52. 20% NIi~N03, 9. Z1% lai, 28. 59% GN, and ~ 10.0$ 5-aminotetrazole (5AT) was prepared and tested as described in Example 1. The burn rate at 1000 psi was 0.391 in/sec: and the burn rate at 1500 psi was 0.515 in/sec. The corresponding pressure exponent was 0.677.
AMPLE 5 - Comparative Example Table 1 illustrates the problem of thermal instability when typical nonazide fuels are combined with PSAN:
_ Table 1: Thermal Stability of PSAN - Non-Azide Fuel Mixtures Non-t~,zide Fuels) Thermal Stability Lrombi.ned ovith PSAN
5aaninotetrazole (5AT)Melts with108Conset and 1160 peak.
Decowposedwith6.74% weight loss when aged at 107C 336 hours. Poole '2~2 shows for melting with lass of NHS
when aged at 1070.
ethylene diamine Poole '272shows tneltiag at less than dinitrate, nitroguaslidine (NQ) SAT, NQ Melts with103Conset and 110C peak_ SAT,N~Q quaaidine Melts with93C
onset on peak_ nitrate (GN) 6N, N~Q Melts withlOOConset and 112C. Decomposed with 6.49%weight loss when aged at for 336 houre-GN, 3~-vitro-1,2,4- Melts withloseonset and 1100 peak.
triaz~ole (NTA) NQ, N'rA Melts withlilConset and 113C peak.
aminogusnidine nitrateMelts with1090onset and 110C peak.
1H-teltrazole (18T) Melts with109Conset and 110C peak.
diCyandiamide (DCDA) Melts with114Conset and 114C peak.
.GN, DI:DA Melts with104Conset Gild 105C peak.
NQ, DI~A Melts with1070onset and 115C peak.
Decomposedwith5.66% weight lose when aged at 107C hours.
for 336 2 0 SAT, GN Meits with70C
onset and peak.
magnelaium salt of Melts with100Conset and 111C peak.
(MSAT) In this example, I~decomposed~~ indicates that pellets of the given formulation were discolored, expanded, fractured, and/or stuck together (indicating melting), making them unsuitable for use in an air bag infl-ator. In general, any pSAN-nonazide fuel mixture with a melting point of less than t 1150 will decompose when aged at 1070. As shown, many compositions that comprise well known nonazide fuels and PSAN
are not fit for use within an inflator due to poor thermal stability.
N~:LE 6 - Comparative Example A mixture of 56.30% NI~NO3, 9.94% KN, 17.76% GN, and 16.0% 5AT was prepared and tested as described in Example 1.
The burn rate at 1000 psi was 0 _ 473 in/ sec and the burn rate at 1500 psi was 0.584 in/sec. The corresponding pressure exponent l0 Was 0.,518. The burn rate is acceptable, however, compositions containing GN, 5-AT, and PSAN are not thermally stable as shown in Table l, EXAMPLE 5.
BXANP1~E 7 Table 2: Gas Generating Characteristics of GZT, NQ, and PSAN.
PSAN (Wt%) 78.22 75.83 73.45 71.06 68.68 66.29 GZT (wt%) 21.78 19.17 16.55 13.94 11.32 8.71 NQ (wt%) 0.00 5.00 10.00 15_00 20.00 25.00 Gas Conversion (wt%;E 96.36 96.47 69.58 96.69 96.80 96.91 Gas afield (mol,/100g GG) 4.06 4.05 4.04 4_04 4.03 4.02 Gaseous NZ 37.8 37.7 37.6 37.5 37.5 37.4 Products C02 7.6 7.9 8.1 8.4 8.7 9.0 (vol.,%) HZO 54.7 54.5 54.3 54.0 53.8 53.6 Solid Products .
K20 (g/lOOg GG) 3.64 3.53 3.42 3.31 3.20 3.09 3 0 FlamE>_ Temperature (K) 2254 2275 2296 2317 2337 2358 As shown in table 2, gas generant compositions consisting essentially of GZT, N~, and PSAN generate mostly gas and minimal solids when combusted.
$~~r8 8 Table 3a: Gas generants comprising BHT-2NH3 or GZT, and PsAN.
PSAN 10%
KN (i~i'f%) 74. Z5 PSAN 15%
KN (ZNt%) 76.43 75.40 72.32 75.60 (wt%) 23.57 24.60 27.68 (wt%) 24.40 GZT (wt%) 25.75 NQ (wt%
Gas Yield 95 95 95 95 9?
Melting Point (C) 158 159 159 131 125 Aging at No No No No No 107C Deco. Deco. Deco. Deco. Deco.
Ignitability Exc. Exc. Exc. Exc. Exc.
Tailorability of Ballistic -Properties Marq. Marg. Marg. Marg. Mar Flame Temperature 21?9 2156 2U74 2052 2166 Rb1000 (ips) 0.48 0.47 0.52 0.57 0.51 table 3b. Gas aenerants com~risina BIiT-2NH~. PSAN. and NO.
PSAN
10% KN
wt% 64.40 7D.28 67.17 65.23 68.08 64.05 71.83 PSAN
% ICN
wt%
. B~-ilNH3 (wt%) 9.60 16.72 19.83 19.77 20.92 22.95 23.17 wt%
GZT
00t%
15 N wt% 26.00 13.00 13.00 15.00 11.00 13.00 5.00 Gas Yield 97 97 97 97 97 97 97 wt ~;
Melting ZO Point: 131 132 131 13Z 131 131 131 C
Aginch No No No No No No No a 107C Deco. Deco. Deco. Deco. Deco. Deco. Deco.
Ignitx- .
bilit Mar . Exc. Exc. Exc. Exc. Exc. Exc.
Tailos'-abilit;y of sallis~ticF.xc Exc Exc . Exc Exc . Exc . Exc . . _ .
Pro act.~
' Flame Tem . 2346 2274 2186 2167 2174 2093 2170 I
~
Rb1000 l s 0.43 0.49 0.52 0.49 0.54 0.52 0.54 Table Reference:
No Deco. - No Decomposition Exc. - Excellent Marg. - Marginal _19- . ,.
p~r~t~s 9 ~ ~ 12 5 ~1 2 ~ MAY, f~8 Applicants have found that it is difficult to tailor the ballistic performance of inflators containing gas generants consisting of PSAN and an amine or amide salts) of tetrazole or triazole. Applicants have also discovered that in addition to excellent burn rates and ignitability, the addition of nitroguanidine to these compositions facilitates simplified tailorability of ballistic performance, thezeby making inflator design much simpler. As shown in Tables 3a and 3b, the ballistic tailorability of compositions comprised of pSAN and amine salts l0 of tetrazoles is substantially improved by zhe addition of NQ.
Example 9 further illustrates this.
W When foz-mulating these compositions, it was unexpected wr that with the addition of nitroguanidine, the mixture would still be thermally stable at 1070, and experience essentially no decrease in ignitability or burn rate.
Table 4 illustrates the desirability of maintaining NQ
in percentages below 35%, and more preferably below 26s. Five curves illustrate the effect of increasing the percentage of NQ
from ~)-26 weight percent. Table 4 lists data corresponding to each curve, wherein NQ is combined with BI3T-2NFi3. These compositions were pressed into pellets, loaded into an airbag inflat:or, and fired in a 6oL tank.' In each of the following tests, all variables (pellet size, inflator configuration, etc.) were held constant, except for the formulation. Table 4 reflects testing that showed no significant change in any of the other desirable properties such as high gas yield, low solids, thermal stability, and burn rate.
1~~
:,~~~-L~~ 9 ? / ~ 2 ~ ~ Q
21 MAY 1~$ .
Table 4: Ballistic Tailorability Curve NQ BHT-ZNH3 Time to Maximum Peak (wt %) + PSAN 1 kPa Slvpe Tank P
(wt ~) (ms) (JcPa/ms) (kPa) 1 0 100 5.7 20.2 203.5 2 11 89 3.4 15.5 193.0 3 13 87 5.3 13.0 187.5 .4 15 85 4.2 11.3 176.5 5 1 26 ~ 74 ~ ~ 12.2 ~ 6.9 ~ 68.2 The time to a tank pressure of ZkPa (known as time to first gas in the industry), the maximum slope, and the peak tank pressure are all used to describe the ballistic performance of an airbag inflator. It can be seen that as the amount of NQ in the composition increases, both the maximum slope and the peak tank pressure decrease. The time to first gas is at an accept: able level of 3ms to 6ms in curves 1-4. The time to first gas in curve 5 is at an undesirable high level, and is indicative of a delay in ignition of the gas generant. This demonstrates the poor ignitability of gas generant compositions containing higher- percentages of NQ . The ignition delay seen in curve 5 -can be corrected by operating at a higher inflator internal combustion pressure. However, this would result in the need for a much more robust inflator stnzcture thereby increasing the size and weight of the inflator.
EB~PL~E 10 Another unexpected result is that nitroguanidine appears to help stabilize ammonium nitrate against volumetric phase changes during thermal cycling_ A composition containing 49% AN, 9% KN, and 43o NQ was prepared by grinding and blending the dry materials together. The AN in this composition was unstabilized since the AN and ~ were not combined to form a solution. This composition was tested by DSc and compared to pure Als_ At room temperature, Arz phase Iv exists. Upon heating phase IV changes into phase II at about 55°C. This is clearly seen om the DSc for pure AN. For the composition containing AN
~9 ..: r 7US 97i12579 21 MiIY liipg - and NrQ, the phase change has been eliminated and does not occur below 110°C. It is believed that lower amounts of NQ will provide the same benefit of AN phase-stabilization.
EXAadPLE l1 A composition resulting from the mixture of gas generant constituents consisting of 70.28% PSAN, 16.72% BAT-2NIi~, and 1:3 . 00% NQ was prepared and pressed into pellets . The pellets were placed in a covered, but unsealed container in a helium purged chamber and aged at 107°C_ In this way, any volatiles formed during decomposition would result in a weight loss in the sample>. After 408 hours of aging, the volatiles weight loss was ~J
0.30%. After 2257 hours of aging, the volatiles Weight loss was 0.97%.' After aging, the pellets showed no physical signs of decomposition. In addition, thermal analysis (DSC) showed no signii'icant differences in the pellets before and after aging.
The pellets which were aged for 2257 hours at 107°C were tested in an inflator and showed nv significant differences in ballistic perfox:~mance when Compared to unaged pellets_ EXAMPhE 12 A composition resulting from the mixture of _gas generant constituents consisting of 6~ _ 17% PSAN, 19 . 83% BHT-2NfI9, and 13.00% NQ was prepared and pressed into pellets. The PSAN
was a co-crystallized mixture of 90%~AN and 10% KN_ The pellets were placed in sealed inflators and temperature cycled. One ZS cycle consisted of holding the inflators at X05°C for two hours, cooling to -40°C in two hours, holding for two hours, and heating to 105.°C in two hours. After 50 cycles, the inflators were tested and showed no significant difference from the baseline units in ballistic performance. The physical appearance of the pellets after cycling was unchanged; there were nv expansion or cracks as is normally seen in unstabilized AN_ Although the components of the present invention have been described in their anhydrous form, it will be understood that the teachings herein encompass the hydrated forms as well.
AMEdI~D ~;
-z2-r.
While the foregoing examples illustrate and describe ~~~Ithe use of the present invention, they are not intended to limit the invention as disclosed in certain preferred embodiments herein. Therefore, variations and modifications commensurate - 5 with i~,.he above teachings and the skill and/or knowledge of the relevant art, are within the scope o~ the present invention.
_23_ - -- ..
Hess, U. s. Patent No. 3 , 0~1, 617, describes long known considerations as to oxygen balance and exhaust gases.
Stinecipher et al, U.S. Patent No. 4,300,962, describes explosives comprising ammonium nitrate and an ammonium salt of a nitroazole.
Prior, U.S. Patent No. 3,719,604, describes gas generating compositions comprising aminoguanidine salts of azotet.razole or of ditetrazole.
Poole, U.S_ Patent No_ 5,139,588, describes nonazide gas generants useful in automotive restraint devices comprising a fuel, an oxidizer and additives.
Hendrickson, U.S. Patent No. 4,798,637, teaches the use o~~ bitetrazole compounds, such as diammonium salts of bitetrazole, to lower the burn rate of gas generant - compositions. Hendrickson describes burn rates below .40 ips, and an 8% decrease in the burn rate when diammonium bitetrazole is used.
Chang et al, U.S. Patent No. 3,909,322, teaches the use of nitroaminotetrazole salts with oxidizers such as pure ammonium nitrate, I~MX, and 5-ATN. These compositions are used as gun,'propellants and gas generants for use in gas pressure actuated mechanical devices such as engines, electric generators, motors, turbines, pneumatic tools, and rockets. In contrast to the amine salts disclosed by Hendrickson, Chang teaches that gas generants comprised of 5-aminotetrazole nitrate and salts of nitrvaminotetrazole exhibit burn rates in excess of .40 ips. On the other hand, Chaiig also teaches that gas generants comprised of I3Mx and salts of nitroaminotetrazole exhibit burn rates of .243 ips to .360 ips. No data is given ' 1 4 y: r ' with regard to burn rates associated with pure AN and salts of nitroaminotetrazole.
Highsmith et al, U.S. Patent No. 5,516,377, teaches the us,e of a salt of 5-nitraminotetrazole, NQ, a conventional ignition aid such as BKNO3, and pure ammonium nitrate as an oxidizer, but does not teach the use of phase stabilized ammonium nitrate. Highsmith states that a composition comprised of ammonium nitraminotetrazole and strontium nitrate exhibits a burn rate of .313 ips. This is to low for automotive application. As such, Highsmith emphasizes the use of metallic salts of nitraminotetrazole.
Onishi et al, U.S. Patent No. 5,439,251, teaches the use off: a tetrazole amine salt as an air bag gas generating agent comprising a cationic amine and an anionic tetrazvlyl group having either an a11cy1 With carbon number 1-3, chlorine, hydroxyl, carboxyl, methoxy, aceto, vitro, or another tetrazolyl group substituted via diaao or triazo groups at the 5-position of the tetrazole ring. The inventive thrust is tQ
improve the physical, properties of tetrazoles with regard to 2o impact. and friction sensitivity, and therefore does not teach the combination of an amine or nonmetal tetrazole salt with any other chemical_ Lund et al, U.S. patent No. 5,501,823, teaches the use o;E nvnazide anhydrous tetrazoles, derivatives, salts, complexes, and mixtures thereof, far use in air bag inflators.
The use of bitetrazole-amines, not amine salts of bitetrazoles, is also taught.
Based on the above, the need remains for a PsAN-based gas generant which is thermally stable at 107C, ignites readily and without delay, has a burn rate at 1O00psi of greater than 0.40-0.5oips, and contains no sensitive explosive compounds.
SUMMARY OF THE INVENTION
The afc=ementioned problems are solved by a nonazide gas generant for a vehicle passenger restraint system comprising phase stabilized ammonium nitrate, nitroguanidine, and one or more nonazide fuels_ The nonazide fuels are -g-' selected from a group including guanidines; tetrazoles such as 5,5~bi.tetrazole, diammonium bitetrazole, diguanidinium-5,5~-azotetrazolate (GZT), and nitrotetrazoles such as 5-riitrot:etraaole; triazoles such as nitroaminotriazole, nitrot:riazoles, and 3-vitro-1,2,4 triazole-5-one; and salts of tetraz~~oles and triazolas_ A preferred fuels) is selected from the group consisting of amine and other nonmetal salts of tetra2oles and triazoles having a nitrogen containing cationic component and to a tetrazole and/or triazole anionic component. The anionic comporuent comprises a tetrazole or triazole ring, and an R
group substituted on the 5-position of the tetrazole ring, or two R groups substituted on the 3- and 5-positions of the triasole ring. The R groups) is selected from hydrogen and any nitrogen-containing compounds such as amino, vitro, nitramino, tetraaolyl and triazolyl groups. The cationic component is formed from a member of a group including amines, aminos~, and amides including ammonia, hydrazine, guanidine compounds such as guanidine, aminoguanidine, diaminoguanidine, triami.noguanidi.ne, dicyandiamide, nitroguanidine, nitrogen subsit,uted carbonyl compounds such as urea, carbohydraaide, oxamid,e, oxamic hydrazide, bis-(carbonamide) amine, azodicarbonamide, and hydrazodiearbonamide, and, amine azoles such as3-amino-1,2,4-triazole,3-amino-5-vitro-1,2,4-triazole, 5-ami~.otetraaole and 5-nitraminotetrazole. Optional inert additives such as clay, alumina, or silica may be used as a binder, slag former, coolant or processing aid. Optional ignition aids comprised of nonazide propellants may also be utilized in place of conventional ignition aids such as 8KNo3.
3o D~ETA=LSD DDSCRipTION OF T88 BREFSRRSD ~oD~NT(s) A nonazide gas generant comprises phase stabilized ammonium nitrate (PSAN), nitroguanidine (NQ), and one or more nonazide high-nitrogen fuels. One or more high-nitrogen fuels are selected from a group including tetrazoles such as 5-nitrotetrazole, 5,5~-bitetrazole, .triazoles such as nitroaminotriazole, nitrotriazoles, nitrotetrazoles, salts of -g-- tetrazoles and triazoles, and 3-nitro-1,2,4 triazole-5-one.
More specifically, salts of tetrazoles include in particular, amine, amino, and amide salts of tetrazole and triazole selected from the group including monoguanidinium salt og 5,5'-Bis-18-tetrazole (BHT~1GAD), diguanidinium salt of . 5, 5 ~-Ftis-113-tetraaole (BHT ~ 2GAD) , monoaminoguanidinium salt of 5,5'-Bis-1H-tetrazole (BHT~lAGAD), diami~noguanidinium salt of 5,5~-E~is-113-tetrazole (gHT~2AGAD), monohydrazinium salt of 5,5'-Bis-1H-tetrazole (BHT~1H8), dihydrazinium salt of 5,5'-His-1~1f-tetrazole (BHT~2HH), monoammonium salt of 5,5'-bis-1H
tetraz,ole (HHT ~ 1NH3) , diamalGllium salt of 5, 5' -bis-1H-tetraaole (BHT~2NH3), mono-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H
tetraz~ole (HHT ~ lATAZ) , di-3-amino--1, 2, 4-triazolium salt of 5,5'-bis-1H-tetrazole (BHT~2ATAZ), and diguanidinium salt of 5,5~-~,2obis~1H-tetraZOle (ABHT~2GAD).
Amine salts of triazoles include monoammonium salt of 3-vitro-1,2,4-triazole (NTA~1NH3), monoguanidinium salt of 3-nitro-1,2,4-tria2ole (NTA~1GAD), diammonium salt of dinitrobitriazole (DNBTR~2NH3), diguanidinium salt of dinitrobitriazole (DNBTR~2GAD), and monoammonium salt of 3,5-~dinitro-1,2,4-triazole (DNTR-iNH3).
N - N N - C
2 5 ~~ ~~ ~ Z ~~ ~~ ' Z
C N C N
\ / / \ /
R N RZ N
H H
Formula I Formula II
A ~generic nonmetal salt of tetrazole as shown in Formula I includes a cationic nitrogen containing component, Z, and an anionic component comprising a tetrazole ring and an R
group substituted on the 5-position of the tetrazole ring. A
generic nonmetal salt of triazole as shown in Formula II
includes a cationic nitrogen containing component, Z, and an anionic component comprising a triazole ring and two R groups substituted on the 3- and 5- positions~~of the triazole ring, wherein R1 may or may not be structurally synonymous with R2.
_10-- An R c:omponent is selected Pram a group including hydrogen or any nitrogen-containing compound such as an amino, nitro, nitramino, or a tetrazvlyl or triazolyl group as shown in Formu7.a I or II, respectively, substituted directly or via amine, diazo, or triazv groups. The compound Z is substituted at the 1-position of either formula, and is formed from a membex- of the group comprising amines, .aminos, and amides including ammonia, carbohydrazide, oxamic hydrazide, and hydra2;ine; guanidine compounds such as guanidine, amino~~uanidine, diaminoguanidine, triaminoguanidine, dicyandiamide and n.itroguanidine; nitrogen substituted carbonyl compdu~nds or amides such as urea, oxamide, bis-(carbonamide) amine, aaodicarbonamide, and hydrazodicarbonamide; and, amino azoles; such as 3-amino-1,2,4-triazole, 3-amino-5-vitro-1,2,4-triazole, 5-aminotetrazole, 3-nitramino-1,2,4-triazole, S-nitraminotetrazole, and melamine.
In accordance with the present invention, a preferred gas g~enerant composition results from the mixture of gas generant constituents including nitroguanidine, comprising s%-30% by weight of the gas generant composition, one or more amine salts of t etrazoles and/or triazoles, comprising 4%-40%
by weight of the gas generant composition, and psAN, comprising " 40%-85$ by weight of the gas generant composition. In the percentages given, an even more preferred embodiment results from 'the mixture of gas generant constituents consisting essentially of NQ, PSAN, and amine salts) of 5,5~-bis-1H-tetrazvle. In the percentages given, a most preferred composition results from the mixture of gas generant constituents consisting essentially of NQ, PSAN, and diammonium salt of 5,5~-bis-1H-tetrazole (BHT~2Nfi3). When combined, the fuel component consisting of NQ and one or more high nitrogen fuels as described herein, comprises 15%-60% by weight of the gas generant composition.
In accordance with procedures well known in the art, the foregoing nonazide fuels, and/or nonmetal salts of tetrazole or triazole, are blended with an oxidizer such as PSAN, .and NQ. The manner and order in which the components of the gas generant compositions of the present invention are combined and compounded is not critical so long as the proper particle size of ingredients are selected to ensure the desired mixture is obtained. The compounding is performed by one skilled in the art, under proper safety procedures for the preparation of energetic materials, and under conditions which will not cause undue hazards in processing nor decomposition of the components employed. For example, the materials may be wet blended, or dry blended and attrited in a ball mill or Red to Devil type paint shaker and then pelletiaed by compression molding. The materials may also be ground separately or together in a fluid energy mill, sweco vibroenergy mill or bantam, micropulveri2er and then blended or further blended in a v-blender prior to compaction.
Compositions having components more sensitive to friction, impact, and electrostatic discharge should be wet ground, separately followed by drying. The resulting fine powder of each of the components may~then be wet blended by tumbling with ceramic cylinders in a ball mill jar, for example, and then dried. Less sensitive components may be dry ,ground. and dry blended at'the same time.
Phase stabilx2ed ammonium nitrate is prepaxed as taught. in co-owned U. S. Patent No. 5, 531, 941 entitled, "Process For Preparing Azide-free Gas Generant Composition". Other nonmetal inorganic oxidizers such as ammonium perchlorate, or oxidizers that produce minimal solids when combined and combusted with the fuels listed above, may also be used. The ratio of oxidizer to fuel is preferably adjusted so that the amount. of oxygen allowed in the equilibrium exhaust gases is less than 3% by weight, and more preferably less than or equal to 2% by weight. The oxidizer comprises 40%-85% by weight of the gas generant composition.
The gas generant constituents of the present invention are commercially available. For example, the amine salts of tetrazoles may be purchased from Toyo Kasei Kogyo Company Limited, Japan_ rritroguanidine may be purchased from Nigu Chemie, and, the components used to synthesize PSAN, as described herein, may be purchased from Fisher or Aldrich.
Triazole salts may be synthesized by techniques, such as those described in U.S. Patent No. 4,Z3s,o14 to Lee et al.; in ~~New Explosives: Nitrotriazoles Synthesis and Explosive properties", by H.H. Licht, Fi_ Ritter, and H. Wanders, postfach 1260, D-79574 Weil am Rhein; and in ~~Synthesis of Nitro Derivatives of Triazoles", by Ou Yuxiang, Chen 8oren, Li Jiarong, Dong Shuan, Li Jianjun, and Jia Huiping, Heterocvcles, Vol. 38, No. 7, pps.
7.651-'1664, 1994. Other compounds in accordance with the present invention may be obtained as taught in the above-mentioned references, or from other sources well known to those skill~sd in the art, .
Ari optional burn rate modifier, from O-l0% by weight in tb.e gas generant composition, is selected ~xom a group including an alkali metal, an alkaline earth or a transition metal salt of tetrazoles or triazoles; an alkali metal or alKal:Lne earth nitrate or nitrite; TAGN; dicyandiamide, and alkali and alkaline earth metal salts of dicyandiamide; alkali 2o and alkaline earth borohydrides; or mixtures~thereof. An optional combination slag former and coolant, in a range of 0 to 10% by weight, is selected from a group including clay, . 5111ca, glass, and alumina, or mixtures thereof. When combining the optional additives described, or others known to those skilled in the art, care should be taken to tailor the additions with respect to acceptable thermal stability, burn rates,, and ballistic properties.
In accordance with the present invention, the combination of NQ, PSAN, and one or more nonazide high-nitrogen fuels,, as determined by gravimetric procedures, yields beneficial gaseous products ,equal to or greater than 90% of the total product mass, and solid products equal to or lesser than 10% of the total product mass_ Fuels suitable in practicing the present invention are high in nitrogen content and low in carbon content thereby providing a high burn rate and a minimal gener<ition of carbon monoxide.
The synergistic effect of the high-nitrogen fuels, in combination with an oxidizer producing minimal solids when combined with the fuels, results in several long-awaited benefits. Increased gas production per mass unit of gas generant results in the use of a smaller chemical charge.
Reduced solids production results in minimized filtration needs and therefore a smaller filter. Together, the smaller charge and smaller filter thereby facilitate a smaller gas inflator system. Furthermore, the gas generant compositions of the present invention have'burrt rates and ignitability that meet l0 and surpass performance criteria for use within a passenger restraint system, thereby reducing performance variability.
As shoran in Example 10, it has also been found that the use of nitroguanidine functions to retard the volumetric phase changes nonaally exhibited by pure ammonium nitrate, thereby further stabiliz~.ng the PsAN.
An unexpected benefit of the present chemical compositions is thermal stability. The thermal stability of the ga.s generants is unexpected based an the poor stability of other fuels and in particular, triazoles and tetrazoles, when combined with PSAN. In contrast to other thenaally stable compositions consisting of NQ and PSAN, these compositions ignite: readily and without delay and have a burn rate greater than 0.40-0.50 ips at 1000 psi. Furthermore, the amine salts of tetrazoles and triazoles are neither explosive nor flammable and ca.n be transported as non-hazardous chemicals.
The present invention is illustrated by the followung examples. All compositions are given in percent by weight.
EBASpZE 1 - comparative Example A mixture of ammonium nitrate (AN) , potassium nitrate (RN), and guanidine nitrate (GN) was prepared having 45.35%
Nfi4NO3, 8 . 0% KN, and 46 _ 65% GN. The amoononium nitrate was phase stabilized by coprecipitating with RN.
The mixture was dry-blended and ground in a ball mill. Thereafter, the dry-blended mixture was compression-melded into pellets, The burn rate of the composition was determined by measuring the time required to burn a cylindrical pellet of known length at constant pressure. The burn rate at 1000 pounds per square inch (psi) was .25~ inches per second (in/sec); the burn rate at 1500 psi was .342 in/sec. The corresponding pressure exponent was 0.702.
EYANP~B 2 - Comparative Example A mixture of 46.13% NI~NO3, 8.14% I~1, 35.73% GN, and 10.0% nitroguanidine (NQ) was prepared and tested as described in Example 1. The burn rate at 1000 psi was 0.282 in/sec and 20 the burn rate at 1500 psi was 0.368 in/sec. The corresponding pressure exponent was 0.657.
EZAMP1'~E 3 - Comparative Example A mixture of 46.91% NI~N03, 8.28% KN, 24.81% GN, and 20 . o% NQ was prepared and tested as described in Example 1.
The bL~trn rate at 1000 psi was 0.282 in/sec and the burn rate at 1500 psi was 0.3'73 in/sec. The corresponding pressure exponent was 0.,680.
E~Z~E 4 - Comparative Example A mixture of 52. 20% NIi~N03, 9. Z1% lai, 28. 59% GN, and ~ 10.0$ 5-aminotetrazole (5AT) was prepared and tested as described in Example 1. The burn rate at 1000 psi was 0.391 in/sec: and the burn rate at 1500 psi was 0.515 in/sec. The corresponding pressure exponent was 0.677.
AMPLE 5 - Comparative Example Table 1 illustrates the problem of thermal instability when typical nonazide fuels are combined with PSAN:
_ Table 1: Thermal Stability of PSAN - Non-Azide Fuel Mixtures Non-t~,zide Fuels) Thermal Stability Lrombi.ned ovith PSAN
5aaninotetrazole (5AT)Melts with108Conset and 1160 peak.
Decowposedwith6.74% weight loss when aged at 107C 336 hours. Poole '2~2 shows for melting with lass of NHS
when aged at 1070.
ethylene diamine Poole '272shows tneltiag at less than dinitrate, nitroguaslidine (NQ) SAT, NQ Melts with103Conset and 110C peak_ SAT,N~Q quaaidine Melts with93C
onset on peak_ nitrate (GN) 6N, N~Q Melts withlOOConset and 112C. Decomposed with 6.49%weight loss when aged at for 336 houre-GN, 3~-vitro-1,2,4- Melts withloseonset and 1100 peak.
triaz~ole (NTA) NQ, N'rA Melts withlilConset and 113C peak.
aminogusnidine nitrateMelts with1090onset and 110C peak.
1H-teltrazole (18T) Melts with109Conset and 110C peak.
diCyandiamide (DCDA) Melts with114Conset and 114C peak.
.GN, DI:DA Melts with104Conset Gild 105C peak.
NQ, DI~A Melts with1070onset and 115C peak.
Decomposedwith5.66% weight lose when aged at 107C hours.
for 336 2 0 SAT, GN Meits with70C
onset and peak.
magnelaium salt of Melts with100Conset and 111C peak.
(MSAT) In this example, I~decomposed~~ indicates that pellets of the given formulation were discolored, expanded, fractured, and/or stuck together (indicating melting), making them unsuitable for use in an air bag infl-ator. In general, any pSAN-nonazide fuel mixture with a melting point of less than t 1150 will decompose when aged at 1070. As shown, many compositions that comprise well known nonazide fuels and PSAN
are not fit for use within an inflator due to poor thermal stability.
N~:LE 6 - Comparative Example A mixture of 56.30% NI~NO3, 9.94% KN, 17.76% GN, and 16.0% 5AT was prepared and tested as described in Example 1.
The burn rate at 1000 psi was 0 _ 473 in/ sec and the burn rate at 1500 psi was 0.584 in/sec. The corresponding pressure exponent l0 Was 0.,518. The burn rate is acceptable, however, compositions containing GN, 5-AT, and PSAN are not thermally stable as shown in Table l, EXAMPLE 5.
BXANP1~E 7 Table 2: Gas Generating Characteristics of GZT, NQ, and PSAN.
PSAN (Wt%) 78.22 75.83 73.45 71.06 68.68 66.29 GZT (wt%) 21.78 19.17 16.55 13.94 11.32 8.71 NQ (wt%) 0.00 5.00 10.00 15_00 20.00 25.00 Gas Conversion (wt%;E 96.36 96.47 69.58 96.69 96.80 96.91 Gas afield (mol,/100g GG) 4.06 4.05 4.04 4_04 4.03 4.02 Gaseous NZ 37.8 37.7 37.6 37.5 37.5 37.4 Products C02 7.6 7.9 8.1 8.4 8.7 9.0 (vol.,%) HZO 54.7 54.5 54.3 54.0 53.8 53.6 Solid Products .
K20 (g/lOOg GG) 3.64 3.53 3.42 3.31 3.20 3.09 3 0 FlamE>_ Temperature (K) 2254 2275 2296 2317 2337 2358 As shown in table 2, gas generant compositions consisting essentially of GZT, N~, and PSAN generate mostly gas and minimal solids when combusted.
$~~r8 8 Table 3a: Gas generants comprising BHT-2NH3 or GZT, and PsAN.
PSAN 10%
KN (i~i'f%) 74. Z5 PSAN 15%
KN (ZNt%) 76.43 75.40 72.32 75.60 (wt%) 23.57 24.60 27.68 (wt%) 24.40 GZT (wt%) 25.75 NQ (wt%
Gas Yield 95 95 95 95 9?
Melting Point (C) 158 159 159 131 125 Aging at No No No No No 107C Deco. Deco. Deco. Deco. Deco.
Ignitability Exc. Exc. Exc. Exc. Exc.
Tailorability of Ballistic -Properties Marq. Marg. Marg. Marg. Mar Flame Temperature 21?9 2156 2U74 2052 2166 Rb1000 (ips) 0.48 0.47 0.52 0.57 0.51 table 3b. Gas aenerants com~risina BIiT-2NH~. PSAN. and NO.
PSAN
10% KN
wt% 64.40 7D.28 67.17 65.23 68.08 64.05 71.83 PSAN
% ICN
wt%
. B~-ilNH3 (wt%) 9.60 16.72 19.83 19.77 20.92 22.95 23.17 wt%
GZT
00t%
15 N wt% 26.00 13.00 13.00 15.00 11.00 13.00 5.00 Gas Yield 97 97 97 97 97 97 97 wt ~;
Melting ZO Point: 131 132 131 13Z 131 131 131 C
Aginch No No No No No No No a 107C Deco. Deco. Deco. Deco. Deco. Deco. Deco.
Ignitx- .
bilit Mar . Exc. Exc. Exc. Exc. Exc. Exc.
Tailos'-abilit;y of sallis~ticF.xc Exc Exc . Exc Exc . Exc . Exc . . _ .
Pro act.~
' Flame Tem . 2346 2274 2186 2167 2174 2093 2170 I
~
Rb1000 l s 0.43 0.49 0.52 0.49 0.54 0.52 0.54 Table Reference:
No Deco. - No Decomposition Exc. - Excellent Marg. - Marginal _19- . ,.
p~r~t~s 9 ~ ~ 12 5 ~1 2 ~ MAY, f~8 Applicants have found that it is difficult to tailor the ballistic performance of inflators containing gas generants consisting of PSAN and an amine or amide salts) of tetrazole or triazole. Applicants have also discovered that in addition to excellent burn rates and ignitability, the addition of nitroguanidine to these compositions facilitates simplified tailorability of ballistic performance, thezeby making inflator design much simpler. As shown in Tables 3a and 3b, the ballistic tailorability of compositions comprised of pSAN and amine salts l0 of tetrazoles is substantially improved by zhe addition of NQ.
Example 9 further illustrates this.
W When foz-mulating these compositions, it was unexpected wr that with the addition of nitroguanidine, the mixture would still be thermally stable at 1070, and experience essentially no decrease in ignitability or burn rate.
Table 4 illustrates the desirability of maintaining NQ
in percentages below 35%, and more preferably below 26s. Five curves illustrate the effect of increasing the percentage of NQ
from ~)-26 weight percent. Table 4 lists data corresponding to each curve, wherein NQ is combined with BI3T-2NFi3. These compositions were pressed into pellets, loaded into an airbag inflat:or, and fired in a 6oL tank.' In each of the following tests, all variables (pellet size, inflator configuration, etc.) were held constant, except for the formulation. Table 4 reflects testing that showed no significant change in any of the other desirable properties such as high gas yield, low solids, thermal stability, and burn rate.
1~~
:,~~~-L~~ 9 ? / ~ 2 ~ ~ Q
21 MAY 1~$ .
Table 4: Ballistic Tailorability Curve NQ BHT-ZNH3 Time to Maximum Peak (wt %) + PSAN 1 kPa Slvpe Tank P
(wt ~) (ms) (JcPa/ms) (kPa) 1 0 100 5.7 20.2 203.5 2 11 89 3.4 15.5 193.0 3 13 87 5.3 13.0 187.5 .4 15 85 4.2 11.3 176.5 5 1 26 ~ 74 ~ ~ 12.2 ~ 6.9 ~ 68.2 The time to a tank pressure of ZkPa (known as time to first gas in the industry), the maximum slope, and the peak tank pressure are all used to describe the ballistic performance of an airbag inflator. It can be seen that as the amount of NQ in the composition increases, both the maximum slope and the peak tank pressure decrease. The time to first gas is at an accept: able level of 3ms to 6ms in curves 1-4. The time to first gas in curve 5 is at an undesirable high level, and is indicative of a delay in ignition of the gas generant. This demonstrates the poor ignitability of gas generant compositions containing higher- percentages of NQ . The ignition delay seen in curve 5 -can be corrected by operating at a higher inflator internal combustion pressure. However, this would result in the need for a much more robust inflator stnzcture thereby increasing the size and weight of the inflator.
EB~PL~E 10 Another unexpected result is that nitroguanidine appears to help stabilize ammonium nitrate against volumetric phase changes during thermal cycling_ A composition containing 49% AN, 9% KN, and 43o NQ was prepared by grinding and blending the dry materials together. The AN in this composition was unstabilized since the AN and ~ were not combined to form a solution. This composition was tested by DSc and compared to pure Als_ At room temperature, Arz phase Iv exists. Upon heating phase IV changes into phase II at about 55°C. This is clearly seen om the DSc for pure AN. For the composition containing AN
~9 ..: r 7US 97i12579 21 MiIY liipg - and NrQ, the phase change has been eliminated and does not occur below 110°C. It is believed that lower amounts of NQ will provide the same benefit of AN phase-stabilization.
EXAadPLE l1 A composition resulting from the mixture of gas generant constituents consisting of 70.28% PSAN, 16.72% BAT-2NIi~, and 1:3 . 00% NQ was prepared and pressed into pellets . The pellets were placed in a covered, but unsealed container in a helium purged chamber and aged at 107°C_ In this way, any volatiles formed during decomposition would result in a weight loss in the sample>. After 408 hours of aging, the volatiles weight loss was ~J
0.30%. After 2257 hours of aging, the volatiles Weight loss was 0.97%.' After aging, the pellets showed no physical signs of decomposition. In addition, thermal analysis (DSC) showed no signii'icant differences in the pellets before and after aging.
The pellets which were aged for 2257 hours at 107°C were tested in an inflator and showed nv significant differences in ballistic perfox:~mance when Compared to unaged pellets_ EXAMPhE 12 A composition resulting from the mixture of _gas generant constituents consisting of 6~ _ 17% PSAN, 19 . 83% BHT-2NfI9, and 13.00% NQ was prepared and pressed into pellets. The PSAN
was a co-crystallized mixture of 90%~AN and 10% KN_ The pellets were placed in sealed inflators and temperature cycled. One ZS cycle consisted of holding the inflators at X05°C for two hours, cooling to -40°C in two hours, holding for two hours, and heating to 105.°C in two hours. After 50 cycles, the inflators were tested and showed no significant difference from the baseline units in ballistic performance. The physical appearance of the pellets after cycling was unchanged; there were nv expansion or cracks as is normally seen in unstabilized AN_ Although the components of the present invention have been described in their anhydrous form, it will be understood that the teachings herein encompass the hydrated forms as well.
AMEdI~D ~;
-z2-r.
While the foregoing examples illustrate and describe ~~~Ithe use of the present invention, they are not intended to limit the invention as disclosed in certain preferred embodiments herein. Therefore, variations and modifications commensurate - 5 with i~,.he above teachings and the skill and/or knowledge of the relevant art, are within the scope o~ the present invention.
_23_ - -- ..
Claims (13)
1. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of guanidines, tetrazoles, triazoles, salts of tetrazoles, and salts of triazoles; and phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture; said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, and, said phase stabilized ammonium nitrate comprises 40%-85% by weight of said mixture.
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of guanidines, tetrazoles, triazoles, salts of tetrazoles, and salts of triazoles; and phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture; said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, and, said phase stabilized ammonium nitrate comprises 40%-85% by weight of said mixture.
2. A gas generant composition as claimed in claim 1 further comprising:
a burn rate modifier selected from the group consisting of alkali and alkaline earth metal nitrates and nitrites, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide, alkali and alkaline earth. borohydrides, and mixtures thereof, wherein said burn rate modifier comprises not more than 10% by weight of said mixture.
a burn rate modifier selected from the group consisting of alkali and alkaline earth metal nitrates and nitrites, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide, alkali and alkaline earth. borohydrides, and mixtures thereof, wherein said burn rate modifier comprises not more than 10% by weight of said mixture.
3. A gas generant composition as claimed in claim 1 further comprising:
a combination slag former and coolant selected from the group consisting of clay, silica, glass, alumina, and mixtures thereof.
a combination slag former and coolant selected from the group consisting of clay, silica, glass, alumina, and mixtures thereof.
4. The composition of claim 1 wherein said at least one nonazide high nitrogen fuel is selected from the group consisting of 5-nitrotetrazole, 5,5'-bitetrazole, nitroaminotriazole, and 3-nitro-1,2,4 triazole-5-one.
5. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of monoguanidinium salt of 5,5'-Bis-1H-tetrazole, diguanidinium salt of 5,5'-Bis-1H-tetrazole, monoaminoguanidinium salt of 5,5'-Bis-1H-tetrazole, diaminoguanidinium salt of 5,5'-Bis-1H-tetrazole, monohydrazinium salt of 5,5'-Bis-1H-tetrazole, dihydrazinium salt of 5,5'-Bis-1H-tetrazole, monoammonium salt of 5,5'-bis'-1H-tetrazole, diammonium salt of 5,5'-bis-1H-tetrazole, mono-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H-tetrazole, di-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H-tetrazole, diguanidinium-5,5'-azotetrazolate, monoammonium salt of 3-nitro-1,2,4-triazole, monoguanidinium salt of 3-nitro-1,2,4-triazole, diammonium salt of dinitrobitriazole, diguanidinium salt of dinitrobitriazole, and monoammonium salt of 3,5-dinitro-1,2,4-triazole; and phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, raid nitroguanidine comprises 1%-26% by weight of said mixture, said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, and, said phase stabilized ammonium nitrate comprises 40%-85% by weight of said mixture.
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of monoguanidinium salt of 5,5'-Bis-1H-tetrazole, diguanidinium salt of 5,5'-Bis-1H-tetrazole, monoaminoguanidinium salt of 5,5'-Bis-1H-tetrazole, diaminoguanidinium salt of 5,5'-Bis-1H-tetrazole, monohydrazinium salt of 5,5'-Bis-1H-tetrazole, dihydrazinium salt of 5,5'-Bis-1H-tetrazole, monoammonium salt of 5,5'-bis'-1H-tetrazole, diammonium salt of 5,5'-bis-1H-tetrazole, mono-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H-tetrazole, di-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H-tetrazole, diguanidinium-5,5'-azotetrazolate, monoammonium salt of 3-nitro-1,2,4-triazole, monoguanidinium salt of 3-nitro-1,2,4-triazole, diammonium salt of dinitrobitriazole, diguanidinium salt of dinitrobitriazole, and monoammonium salt of 3,5-dinitro-1,2,4-triazole; and phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, raid nitroguanidine comprises 1%-26% by weight of said mixture, said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, and, said phase stabilized ammonium nitrate comprises 40%-85% by weight of said mixture.
6. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of nonmetal salts of triazoles substituted at the 1-, 3-, and 5-positions, and nonmetal salts of tetrazoles substituted at the 1- and 5-positions, said salts substituted at each position with a nitrogen-containing group; and phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixtures said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, and, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture.
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of nonmetal salts of triazoles substituted at the 1-, 3-, and 5-positions, and nonmetal salts of tetrazoles substituted at the 1- and 5-positions, said salts substituted at each position with a nitrogen-containing group; and phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixtures said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, and, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture.
7. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of 1-, 3-, 5-substituted nonmetal salts of triazoles, and 1-, 5- substituted nonmetal salts of tetrazoles, said salts substituted at each position with a nitrogen-containing compound; and phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture; said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture.
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of 1-, 3-, 5-substituted nonmetal salts of triazoles, and 1-, 5- substituted nonmetal salts of tetrazoles, said salts substituted at each position with a nitrogen-containing compound; and phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture; said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture.
8. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of guanidines, tetrazoles, triazoles, salts of tetrazoles, and salts of triazoles;
phase stabilized ammonium nitrate as an oxidizer, a burn rate modifier selected from the group consisting of alkali, alkaline earth, and transitional metal salts of tetrazole and triazole, triaminoguanidine nitrate, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide; alkali and alkaline earth borohydrides, and mixtures thereof; and a coolant selected from the group consisting of clay, silica, glass, and alumina, and mixtures thereof;
wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture; said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture, said burn rate modifier comprises 0-10% by weight of said mixture, and said coolant comprises 0-10% by weight of said mixture.
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of guanidines, tetrazoles, triazoles, salts of tetrazoles, and salts of triazoles;
phase stabilized ammonium nitrate as an oxidizer, a burn rate modifier selected from the group consisting of alkali, alkaline earth, and transitional metal salts of tetrazole and triazole, triaminoguanidine nitrate, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide; alkali and alkaline earth borohydrides, and mixtures thereof; and a coolant selected from the group consisting of clay, silica, glass, and alumina, and mixtures thereof;
wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture; said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture, said burn rate modifier comprises 0-10% by weight of said mixture, and said coolant comprises 0-10% by weight of said mixture.
9. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of monoguanidinium salt of 5,5'-Bis-1H-tetrazole, diguanidinium salt of 5,5'-Bis-1-tetrazole, monoaminoguanidinium salt of 5,5'-Bis-1H-tetrazole, diaminoguanidinium salt of 5,5'-Bis-1H-tetrazole, monohydrazinium salt of 5,5'-Bis-1H-tetrazole, dihydrazinium salt of 5,5'-Bis-1-tetrazole, monoammonium salt of 5,5'-bis-1H-tetrazole, diammonium salt of 5,5'-bis-1H-tetrazole, mono-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H-tetrazole, di-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H-tetrazole, diguanidinium-5,5'-azotetrazolate, monoammonium salt of 3-nitro-1,2,4-triazole, monoguanidinium salt of 3-nitro-1,2,4-triazole, diammonium salt of dinitrobitriazole, diguanidinium salt of dinitrobitriazole, and monoammonium salt of 3,5-dinitro- 1,2,4-triazole;
phase stabilized ammonium nitrate as an oxidizer, a burn rate modifier selected from the group consisting of alkali, alkaline earth, and transitional metal salts of tetrazole and triazole, triaminoguanidine nitrate, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide; alkali and alkaline earth. borohydrides, and mixtures thereof; and a coolant selected from the group consisting of clay, silica, glass, and alumina, and mixtures thereof;
wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture, said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40%-85% by weight of said mixture, said burn rate modifier comprises 0-10% by weight of said mixture, and said coolant comprises 0-10% by weight of said mixture.
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of monoguanidinium salt of 5,5'-Bis-1H-tetrazole, diguanidinium salt of 5,5'-Bis-1-tetrazole, monoaminoguanidinium salt of 5,5'-Bis-1H-tetrazole, diaminoguanidinium salt of 5,5'-Bis-1H-tetrazole, monohydrazinium salt of 5,5'-Bis-1H-tetrazole, dihydrazinium salt of 5,5'-Bis-1-tetrazole, monoammonium salt of 5,5'-bis-1H-tetrazole, diammonium salt of 5,5'-bis-1H-tetrazole, mono-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H-tetrazole, di-3-amino-1,2,4-triazolium salt of 5,5'-bis-1H-tetrazole, diguanidinium-5,5'-azotetrazolate, monoammonium salt of 3-nitro-1,2,4-triazole, monoguanidinium salt of 3-nitro-1,2,4-triazole, diammonium salt of dinitrobitriazole, diguanidinium salt of dinitrobitriazole, and monoammonium salt of 3,5-dinitro- 1,2,4-triazole;
phase stabilized ammonium nitrate as an oxidizer, a burn rate modifier selected from the group consisting of alkali, alkaline earth, and transitional metal salts of tetrazole and triazole, triaminoguanidine nitrate, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide; alkali and alkaline earth. borohydrides, and mixtures thereof; and a coolant selected from the group consisting of clay, silica, glass, and alumina, and mixtures thereof;
wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture, said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40%-85% by weight of said mixture, said burn rate modifier comprises 0-10% by weight of said mixture, and said coolant comprises 0-10% by weight of said mixture.
10. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of nonmetal salts of triazoles substituted at the 1-, 3-, and 5-positions, and nonmetal salts of tetrazoles substituted at the 1- and 5-positions, said salts substituted at each position with a nitrogen-containing group;
phase stabilized ammonium nitrate as an oxidizer, a burn rate modifier selected from the group consisting of alkali, alkaline earth, and transitional metal salts of tetrazole and triazole, triaminoguanidine nitrate, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide; alkali and alkaline earth. borohydrides, and mixtures thereof; and a coolant selected from the group consisting of clay, silica, glass, and alumina, and mixtures thereof;
wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture, said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40%-85% by weight of said mixture, said burn rate modifier comprises 0-10% by weight of said mixture, and said coolant comprises 0-10% by weight of said mixture.
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of nonmetal salts of triazoles substituted at the 1-, 3-, and 5-positions, and nonmetal salts of tetrazoles substituted at the 1- and 5-positions, said salts substituted at each position with a nitrogen-containing group;
phase stabilized ammonium nitrate as an oxidizer, a burn rate modifier selected from the group consisting of alkali, alkaline earth, and transitional metal salts of tetrazole and triazole, triaminoguanidine nitrate, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide; alkali and alkaline earth. borohydrides, and mixtures thereof; and a coolant selected from the group consisting of clay, silica, glass, and alumina, and mixtures thereof;
wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture, said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40%-85% by weight of said mixture, said burn rate modifier comprises 0-10% by weight of said mixture, and said coolant comprises 0-10% by weight of said mixture.
11. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of 1-, 3-, 5-substituted nonmetal salts of triazoles, and 1-, 5-substituted nonmetal salts of tetrazoles, said salts substituted at each position with a nitrogen-containing compound;
phase stabilized ammonium nitrate as an oxidizer, a burn rate modifier selected from the group consisting of alkali, alkaline earth, and transitional metal salts of tetrazole and triazole, triaminoguanidine nitrate, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide; alkali and alkaline earth. borohydrides, and mixtures thereof; and a coolant selected from the group consisting of clay, silica, glass, and alumina, and mixtures thereof;
wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture; said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture, said burn rate modifier comprises 0-10% by weight of said mixture, and said coolant comprises 0-10% by weight of said mixture.
nitroguanidine and at least one nonazide high-nitrogen fuel selected from the group consisting of 1-, 3-, 5-substituted nonmetal salts of triazoles, and 1-, 5-substituted nonmetal salts of tetrazoles, said salts substituted at each position with a nitrogen-containing compound;
phase stabilized ammonium nitrate as an oxidizer, a burn rate modifier selected from the group consisting of alkali, alkaline earth, and transitional metal salts of tetrazole and triazole, triaminoguanidine nitrate, dicyandiamide, alkali and alkaline earth metal salts of dicyandiamide; alkali and alkaline earth. borohydrides, and mixtures thereof; and a coolant selected from the group consisting of clay, silica, glass, and alumina, and mixtures thereof;
wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixture; said at least one nonazide high-nitrogen fuel comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said at least one nonazide high nitrogen fuel comprises 15%-60% by weight of said mixture, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture, said burn rate modifier comprises 0-10% by weight of said mixture, and said coolant comprises 0-10% by weight of said mixture.
12. A gas generant composition consisting of a hydrated or anhydrous mixture of:
nitroguanidine, diammonium salt of 5,5'-bis-1H-tetrazole, phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixtures said diammonium salt of 5,5'-bis-1H-tetrazole comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said diammonium salt of 5,5'-bis-1H-tetrazole comprises 15%-60% by weight of said mixture, and, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture.
nitroguanidine, diammonium salt of 5,5'-bis-1H-tetrazole, phase stabilized ammonium nitrate as an oxidizer, wherein said composition has a melting point of at least 115° C, the ammonium nitrate is phase stabilized by coprecipitating with potassium nitrate, said nitroguanidine comprises 1%-26% by weight of said mixtures said diammonium salt of 5,5'-bis-1H-tetrazole comprises 4%-40% by weight of said mixture, said nitroguanidine in combination with said diammonium salt of 5,5'-bis-1H-tetrazole comprises 15%-60% by weight of said mixture, and, said phase stabilized ammonium nitrate comprises 40-85% by weight of said mixture.
13. A gas generant composition according to any one of claims 1 to 12, wherein the at least one nonazide high-nitrogen fuel does not include salts of 5-nitraminotetrazole.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US68166296A | 1996-07-29 | 1996-07-29 | |
| US681,662 | 1996-07-29 | ||
| US851,503 | 1997-05-05 | ||
| US08/851,503 US6306232B1 (en) | 1996-07-29 | 1997-05-05 | Thermally stable nonazide automotive airbag propellants |
| PCT/US1997/012579 WO1998004507A1 (en) | 1996-07-29 | 1997-07-10 | Thermally stable nonazide automotive airbag propellants |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2260144A1 CA2260144A1 (en) | 1998-02-05 |
| CA2260144C true CA2260144C (en) | 2006-02-14 |
Family
ID=35892357
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002260144A Expired - Fee Related CA2260144C (en) | 1996-07-29 | 1997-07-10 | Thermally stable nonazide automotive airbag propellants |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2260144C (en) |
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1997
- 1997-07-10 CA CA002260144A patent/CA2260144C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| CA2260144A1 (en) | 1998-02-05 |
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