US2988435A - Ammonium nitrate gas-generating compositions - Google Patents

Description

'5 ite 1 States 7 2,988,435 I AMMONIUM NITRATE GAS-GENERATING COMPOSITIONS William G. Stanley, Munster, and. Paul O. Marti, Jr., Seymour, IncL, assignors to Standard Oil Compan Chicago, 111., a corporation of Indiana I NoDrawing. Filed Apr. 30, 1956, Ser. No. 582,618 9 Claims. (Cl. 52-.5)

; ucts formed by burning a fuel with air in the gasgenerator to. drive a turbine which in turn drives an air compressor for supplying said air to burn said fuel. It is i possible to start the turbine of a jet engine to bring it to. required speed and temperature by an auxiliary starter, which utilizes a gaseprod'ucing grain composition for the production of large volumes of gas at, high temperature. The. composition of this invention may be fused in such service.

Ammonium nitrate is widely used as a component of high explosives, particularly the. so-called safe explosives, However, when ignited, ammonium nitrate alone does not. burn uniformlyandhas a tendency to go out. In order to improve the burning quality, to utilize the excess free oxygen available from the decomposition of the ammonium nitrate and to provide shaped grains suitable for use as described above, combustible binder material is used in the ammonium nitrate composition. However, the physical characteristics of the ammonium nitrate and the grain material produced therefrom introduce problems with respect to the choice of binder components. Thus solid ammonium nitrate exists in difierent crystalline forms at different temperatures, the transition from one form to a different form involving a volume change of the nitrate. Volume changes which occur at about 90 F. and also at about F. involve 3.5% and about 3%, respectively. It would, therefore, appear that an ammonium, nitrate-base composition could; be seriously affected by storage under variable conditions encountered in many. parts, of the world.

Heretofore, it has been known to use asphalt as, a;binder material for such oxygen producing materials as the perchlorates. However, when asphalt is used aloneas the sole binder material for ammonium nitrate, the gasproducing propellant compositions which have been shaped into grains tend to be brittle and non-resistant to shattering when subjected to shock at low temperatures. The brittleness of the asphalt in the composition at low temperatures is undesirable in that it produces weak grains which cannot tolerate cold temperatures. Another undesirable characteristic of a binder-material which eonsists of only asphalts is the tendency towardcold fiow-"at ambient temperatures. v

A requirement for a solid propellant grain suitable for military use is that it be ballistically stable after prolonged storage at temperatures as high as 170 orat temperatures as low as 75 F. Another requirement is that the grain will not shatter, crack or malperform ballistically afteirheing subjected to temperature extremes; that is, .170? F. followed immediately byv transfer to a cold zone Patented June 13, 1961 held at F. in a series of cycles. A thermal shock test wherein solid propellant grains are subjected suc cessively to these temperatures for periods of two hours is a measure of the ability of the grains to withstand deformation and fissuring as a result of temperature change. Still another requirement of solid propellant grains is that theyignite at temperatures down to 75 F. using an igniter charge which can be used at high temperatures.

An object of this invention is a gas-generating composition wherein ammonium nitrate is used as the principal gas-generating material. Another object of the invention is a shaped solid grain comprising ammonium nitrate, a combustion catalyst, and a binder material which grain will ignite at cold temperatures. Still another object of the invention is a shaped propellant grain comprising ammonium nitrate, which grain is dimensionally stable in the temperature range between about 170 and '75 F. A further object is a shaped propellant grain which withstands chemical change of the components thereof and change of shape under high temperature storage conditions. Other objects will be apparent from the description of the invention.

The composition of the invention comprises a combustible binder material consisting on a weight basis of (a) from about 30% to about 60% of a plasticizable mix ture of styrene-acrylonitrile copolymer containing from about 15 'r'nol percent to about 40 mol percent of my lonitrile units per molecule and a petroleum asphalt having a softening point of 200 F. to about 300 F. said mixture consisting on a Weight basis of (i) about 30 to of styrene-acrylonitrile copolymer and (ii) about 70 to about 10% by weight of the asphalt and (b) from about 70% to about 40% of at least one plasticizer selected from the class consisting of dinitrobenzene, dinitrotoluene, dinitrodiphenyl ether, bis (dinitrophenyl) triethylene glycol ether, dinitrophenyl propyl ether, bis (dinitrophenyl) propyl ether, dinitrophenyl allyl ether, dinitrostilbene and dinitroanisole and mixtures of at least one of the foregoing nitroaromatics with at least one ester selected from the class consisting of dialkyl phthalates having 1 to 8 carbon atoms per alkyl radical, triethylene glycol di-Z-ethylbutyrate, triethylene glycol di-2-ethylhexoate, triethyl'citrate, acetyl triethyl citrate and triacetin. Themixtures of plasticizer contain not more than 40% by weight of said ester.

The binder material is milled with finely ground ammonium nitrate, mixed with combustion catalyst, to produce the propellant composition. The propellant composition contains from about 65% to about 90% by weight of ammonium nitrate, about 8% to about 25% by weight of the binder material and about 1.0 to about 10.0% by weight of the combustion catlayst. Other components may be added to the propellant, that is, the grain composition to improve the burning properties and to improve the physical and chemical properties of the compositions as described hereinbelow.

The asphalt of this invention is solid at ambient temperatures and has a softening point within the range of from about 200 F. to about 300 F. preferably about 200 F. to about 250 F. and particularly in the range of about 215 F. to about 235 F. and a flash point of not less than 500 F. (Cleveland open cup). In the A.S-.T.M. penetrometer penetration test (D5-52) the penetration of the asphalt should be not less than 0.5 mm. at 32 F., not more than about 3.5 mm. at 77 and not more than about 6.0 mm. at F. The loss upon heating a 50 gram sample for a period of five hours at 325 F. should not 3 such as Gilsonite are not suitable due to low softening point and/or inorganic material content.

The styrene-acrylonitrile copolymer component of the binder is a synthetic resin, solid at normal atmospheric temperatures and is preferably reduced to small particle size before mixing with the asphalt. The copolymer contains from about 15 to about 40 mol percent, preferably about 29 mol percent of acrylonitrile units and from about 85 to about 60 percent preferably about 71 mol percent of styrene units per molecule. The binder material contains about 30 to about 60% of the plasticizable mixture of the styrene-acrylonitrile copolymer and asphalt the remaining 70% to about 40% of the binder material consisting essentially of plasticizer which contains a relatively high percent of oxygen. The mixture of styreneacrylonitrile copolymer and asphalt contains from about 30% to about 90% of a styrene-acrylonitrile copolymer the remaining 70% to about of the mixture being the above described asphalt.

The plasticizers of the binder material consist predominantly of nitroaromatic compounds the nitro substituent groups of the aromatic compounds being attached to the aromatic phenyl nuclei. The nitroaromatics contain from 1 to 2 phenyl groups per molecule and not more than 2 nitro substituent groups on any phenyl nucleus in the compound. Examples of these nitroaromatics are dinitrobenzenes, e.g., orthodinitrobenzene, the dinitrotoluenes particularly 2,4-dinitrotoluene, 2,4-dinitrodiphcnyl ether, bis (2,4-dinitrophenyl) triglycol ether, 2,4-dinitrophenyl propyl ether, bis (2,4-dinitrophenyl) propyl ether, 2,4-dinitrophenyl allyl ether, 2,4-dinitrostilbene and 2,4-dinitroanisole.

The dinitrodiphenyl ethers of the plasticizer may be prepared by reacting, in the alkali media, the appropriate nitro substituted chlorobenzene with phenol in a substantially equal molar concentration of the reactants according to the Williamson reaction. Likewise the nitrophenyl propyl ethers and nitrophenyl allyl ethers may be produced by reacting the alcohol with the nitro substituted chlorobenzene in alkali media. The bis (dinitrophenyl) propyl ether may be prepared by condensing 1 molecule of propylene glycol with 2 mols of the dinitrochlorobenzene in an alkali media and the bis (dinitrophenyl) triglycol ether may be prepared by condensing one mol of triethylene glycol ether with 2 mols of the dinitrochlorobenzene in alkali media. The dinitrostilbene is prepared by condensing 1 mol of dinitrotoluene preferably 2,4-dinitrotoluene with 1 mol of benzaldehyde. The phenyl nuclei and the aliphatic groups of the ethers as well as the dinitrostilbenes contain only nitro substituent groups.

To at least one of the nitroaromatic compound plasticizers may be added certain esters which are plasticizers but do not contain nitro substituent groups in the molecule thereof. Esters of polyhydric alcohols or esters of polycarboxylic acids are suitable non-nitro group containing plasticizers. Examples are dialkyl phthalates having from '1 to 8 carbon atoms in the alkyl groups thereof, triethylene glycol di-2-ethylbu-tyrate, triethylene glycol di-Z-ethylhexoate, triethyl citrate, acetyl triethyl citrate and triacetin. Normally liquid plasticizers such as the above esters must be compatible with styrene-acrylonitrile-asphalt-nitroaromatic component binders. Oxygen balance is important and esters of high oxygen content are preferred when they have no undesirable effects. Some plasticizers impart to the propellant grains good resistance to physical and chemical change as a result of impact, hot aging in storage, and cycling when subjected to extreme high or low temperatures. The nitroaromatic compounds improve the oxygen balance in the composition of the grain compositions with respect to producing water, carbon monoxide and carbon dioxide. The nitro compounds also contribute to the plasticity of the compound and improve the ignitability and burning rate of the compositions.

' The combustion catalyst of this invention may be inorganic catalyst or an organic catalyst depending on the primary use to which the gas-forming propellant composition is applied. Burning rates above about 0.05"/sec., preferably from about 0.08" to about 0.12"/sec. at 1000 p.s.i. are required for auxiliary turbine starter grains. Rates above about 0.10" per second at 1000 p.s.i. are required for assisted take-off and rocket propellant grains. Inorganic combustion catalysts are defined as the Prussian blue catalyst, ammonium dichromate and alkali metal dichromates. These are suitable for grain compositions of this invention when the projected service is that of propelling rockets and assist take-ofi of aircraft. Examples of the iron cyanide catalysts, that is Prussian blues which may be used in the compositions, are ferro ferrocyanide, ferric ferrocyanide, ferro ferricyanide, and ferric ferricyanide. The insoluble Prussian blues, that is, ferric ferrocyanide is preferred. Sodium, potassium-or ammonium chromates and/ or dichromates may be employed in the composition and mixtures of the iron cyanide catalysts with the chromate catalysts may be used. Ammonium dichromate is a preferred chromium inorganic catalyst.

Finely divided carbon functions as a catalyst in the combustion of the gas-forming compositions of this invention. Finely divided carbon which will pass through a #200 U.S. standard sieve, preferably to pass through a #325 U.S. standard sieve is used. Highly adsorptive activated carbons such as Norit and Nuchar, well known in the art as activated carbon made from residual organic material are one class of effective burning rate components.' Another class of carbon useful for increasing the burning rate of the compositions are the carbon blacks, roughly classified as the channel blacks and furnace blacks. The carbon blacks are characterized by having low ash content, that is, less than 0.5% and usually less than 0.15% and by having extremely small particle size, that is 50 to 500 A. To avoid dusting and afford convenience in handling, some carbon blacks are ronneu 1.0 the so-called bead type carbon blacks. A third type of carbon which may be used in the compositions of this invention is finely ground petroleum coke, particularly coke obtained as a residue in pipestilling of Mid-Continent heavy residuums. Such coke is low in ash content and hence, like the carbon blacks, is particularly suitable for use in gas-producing grains for service in starting the turbine of a jet engine where the solid inorganic particles in the combustion gas must be kept at a minimum. The coke is preferably ground to pass through a #325 U.S. standard sieve prior to incorporation in the gas-producing composition. Carbon is preferably added to the composition along with one or more of the inorganic or organic catalysts since the carbon not only functions as a catalyst but also increases the ignitibility of the compositions in the presence of the asphalt particularly at relatively low temperatures. When added to the compositions an amount within the range of from about 1 to about 3% of carbon 'is used along with the other catalytic material.

The organic catalysts are particularly suitable for service for starting of the turbine of jet engines since the combustion gas produced by the burning of propellant grains containing these catalysts can be impinged on metal surfaces with minimum. erosion effects. An example of an organic catalyst which may be used is aniline black. Another organic catalyst is the mono-alkali metal salt of barbituric acid. This catalyst is taught in the application of Walter W. Butcher, entitled Organic Combustion Catalyst, Serial No. 543,596, filed October 28, 1955, now abandoned. Other suitable organic rate promoters wich may be incorporated in propellant compositions oontaining the styrene-acrylonitrile-asphalt binder base material are the amine-N oxides particularly pyridine-N oxide. These rate promoters are taught and claimed in the copending application of Jack Linsk and Robert W. Todd, entitled Combustion Catalyst Promoter, Serial No. 574,063, filed March 21, 1956, now-Patout No. 2,936,225, issued May 10, 1960. When used as ing device for obtairing the burning rate. .of the test strips is painted with a liquid isobutylene polymet, with a layer of plasticized celluloseacetate or with he sole c taly i h ompos t onhe r anic atalys are. used in amounts within therange of about 1'% to about 5% by weight of the composition. The amount of catalyst in the propellant compositions which may be an inorganic combustion catalyst, carbon or an organic catalyst or mixtures of two or more of these may vary from about 1% to about preferably from about 2% to about 6% by weight of the composition when mixtures of the catalyst are used. It is preferred to use the finely divided carbon catalyst along with at least one of the other catalysts, inorganic or organic, and particularly with the organic catalyst.

An improvement in the gassing tendency of the compositions of this invention under high temperature conditions, i.e., as high as 170 F. is obtained by adding to the gas-forming composition from about 0.05 to about 2.0% by weight of an amine such as n-phenylenediamine. Other aromatic amines which are effective are .diphenylamine, dinaphthylamine, l-naphthylamine, the toluidenes, the xylidenes, dodecyl aniline,IN,N-dimethyl aniline and N-sec-butyl aniline. Diamino and triamin-o benzene and the corresponding amino toluenes are also effective to inhibit gassing 'of the composition under high temperature storage conditions.

Surface active agents such as the sorbi-tan oleates may be added in amounts within the range of 0.05 to about 0.5% by weight of the gas-forming composition as an aid to promote wetting of the nitrate with the other components of the composition and as an extrusion aid.

The term ammonium nitrate as used in this specificat-ion and in the claims is intended to mean either ordinary commercial grade ammonium nitrate, such as conventionally grained ammonium nitrate containing a small amount of impurities, which is generally coated with a small amount of moisture-resisting materialsuch as petrolatum or par-afiin, or to mean military grade ammonium nitrate or a mixture of minor amounts (usually less than 10%) of other inorganic nitrates such as sodium nitrate or potassium nitrate with the ammonium nitrate. Finely divided ammonium nitrate is preferred in order to reduce the voids to a minimum, thus to avoid the use of excess binder material.

In preparing the composition of this invention the binder material may be prepared first and the ammonium nitrate, in intimate admixture with the catalyst, is milled with the prepared binder. The binder may be prepared by heating and mixing the asphalt with the styrene-acrylonitrilecopolymer at a temperature below about 140 C. for a period of one to two hours, usually at a tempera- .tureof from about 110 C. to about 120 C. The burning-rate modifier and/or gassing inhibitor and/or surfactant may be added to the binder prior to addition of the ammonium nitrate. The catalyst, inorganic, organic and carbon are intimately mixed with the ammonium nitrate and added therewith to the binder. The .amrnonium nitrate with these admixed components is then milled into the binder material at a temperature below 110 C. and preferably at a temperature within the range of 90 C. to 105 C. Milling is continued until a product of uniform texture is obtained, after which the material is molded into shaped propellant grains and test strands at temperatures not in excess of 110 C.

The formulated compositions are molded at about :2000 psi. into rectangular strips of about 1" by three- .quarters inch cross-sectional dimension to form burning rate test strands. The molded strips are cut into Mi," x A test strands about 5" in length. If desired these. test strips may be prepared by extrusion. These test strips are provided with drilled holes 3" apart through which passed fusible wires connected to a tim- The surface a layer i of asphalt.

The. test strand is placed inapressurebomb elec trical connection of the fuse wires is made to the timing device which is started by the fusing, of one wire. As the test strand burns along its length the timing device is stopped by the fusing of the second wire. Thus the time for burning of a 3" length of the test strand is obtained. The test strand is ignited by means of a chrome resistance wire. Burning rates for the test strands are determined at a series of pressures under nitrogen pressure. These pressures and corresponding burning rates are plotted to obtain the slope of the burning ratepressure curve. Burning rates of the materials in specification are defined as the burning rates at 1000 pounds nitrogen pressure.

The gas-producing grains are prepared by extrusion or preferably by molding the compositions into cylindrical grains under a pressure of about 2000 to 4000 psi. The size and shape of the grains will depend upon their in: tended use; for starting the turbine of a jet engine the grains may be about 3 to 6 inches in diameter and about 3" to 6 in length. The grains are usually pro vided with internal apertures extending lengthwise of the grain to provide an opening which may be circular, starform, cruciform, etc. to afford increased internal burning surface; The external surface of the grain is covered with a thin coating of asphalt, with a mixture of carbon black and Vistanex or with plasticized cellulose acetate to restrict the burning surface of the grain.

The grains may be mounted in a conventional case and may be ignited or fired by electrical means, a charge of black powder or cannon powder being used as intermediate firing means. The temperature of the combustion gases produced by burning of the grain may be of the order of 1500 to 3500 F. and the pressure or impulse produced by the hot gases will be dependent upon the grain size, diameter of the gas-efflux nozzle and on the composition of the. grain. When employed in assist take-off service the nozzle may be a part of the grain case. When employed for starting the turbine of a jet engine, the nozzle may be incorporated 'in breech assembly in the motor itself. Since novelty in the method of using or firing the grain is not claimed, further description thereof is not necessary. The grain compositions may also be molded into disc form, stacks of the discs being used as gas-forming propellant material for rockets.

The following examples are illustrative of the gasforming compositions of this invention.

Example 1 A roofing coating asphalt was mixed with finely divided styrene-acrylonitrile copolymer containing about 29 mol percent of acrylonitrile units per molecule; the mixture contained approximately 2 parts of the sytreneacrylonitrile per 3 parts by weight of the asphalt. The as phalt was provided by oxidizing a Mid-Continent petroleum residuum having a softening point in the range of -90 F. The oxidized product coming within the 'following specification:

Flash, F. (Cleveland open cup Not less than 550 F. Softening point, A.S.T.M. ring and ball test 215235 F. Penetration: 1

At 32 F. Not less than 0.8 mm. At 77 F. 1.5-2.2 mm. At F. Not more than 4 mm. Percent loss of 50 grams heated 5 hours at 325 F. Not more than 0.5%.

A.S.T.M. penetrometer penetration tests (Di-.52).

To the milled mixture, heated to a temperature of l'30140 C. was added an equal weight of amixture of 2,4-dinitroluene and 2,4-dinitrodiphenyl ether plasticizer. The weight ratio of dinitrotoluene to dinitrodiphenyl ether in the mixed plasticizer was approximately 2. 1 to 3. There suiting mixture of asphalt, styrene-acrylonitrile 'copolymer having an acrylonitrile content of about 29 mol percent and plasticizer was milled for a period of about 2 hours following which the temperature of the mixture was lowered to about 110 C. To 18 parts by weight of this binder material, which was tough and flexible from which there was no tendency of separation of components at room temperatures, was added 82 parts by weight of a mixture containing 79 parts by weight of ammonium nitrate and 3 parts by weight of insoluble Prussi-an' blue catalyst after which the mixture of binder, ammonium nitrate'with catalyst was milled at a temperature of about 100-110" C. for a period of one hour to give a gas-producing composition consisting on a weight basis of 79% ammonium nitrate, 5.4% asphalt, 3.6% styreneacr'ylonitrile copolymer, 3.7% 2,4-dinitrotoluene, 5.3% 2,4-dinitrodiphenyl ether and 3.0% of insoluble Prussian blue catalyst. Cylindrical grains having a diameter of 2.75? and a. length of 4.0 were obtained by molding this material at about 3400 p.s.i. and about 100 C. These grains were provided with a starform internal aperture. They showed no tendency to cold flow or to undergo deformation by slumping when subjected to hot storage at 170 F. for a period of 30 days. The grains were successively thermally cycled at temperatures of 75 F. and +170 F. The grains showed no development of physical defects as a result of this thermal shock test and were fired in a rocket motor following the test, the external cylindrical surface of the grains being coated with a layer of asphalt to limit the combustion of the grain to internal and end surface burning. A part of the composition was molded to form 1" x Mi" burning test strands. These were burned in a pressure bomb according to the method described hereinabove. Test strands indicated a burning rate of 0.14" per second at 1000 p.s.i.

Example 2 A gas-burning composition was formulated according to the procedure used in Example 1 using only by weight of the composition as binder material. This low binder containing composition contained on a weight basis approximately 3.0% of the defined asphalt of Example 1 and 2.0% of the styrene-acrylonitrile copolymer having an acrylonitrile content of 29 mol percent, 3.0% of the dinitrodiphenyl ether, 2.0% of the dinitrotoluene, 3% of insoluble Prussian blue catalyst, 0.1% sorbitan sesquioleate as surfactant, and 86.9% of finely ground ammonium nitrate. The burning rate of a test strand .of this material at 1000 p.s.i. was 0.12" per second. Grains 4" in length, prepared as described in Example 1, were cycled through the thermal shock test with no damaging efiect on the ballistic properties of the grain. The grains were fired successfully after aging 30 days at 170 F.

Example 3 A gas-forming composition consisting of 16.2 parts by weight of the binder described in Example 1, 3.8% aniline black and 80% of ammonium nitrate was prepared according to the method described in Example 1. The finished composition consisted on a weight basis of about 4.9% of the same grade asphalt used in Example 1, 3.2% of the same grade styrene-acrylonitrile copolymer as used in Example 1, 4.8% 2,4-dinitrodiphenyl ether, 3.3% 2,4-dinitrotoluene, 3.8% aniline black organic catalyst and 80% ammonium nitrate. Burning rate test strands of this composition exhibited a burning rate of 0.10"/sec. at 1000 p.s.i. and a pressure exponent of the burning rate equal to 0.75. Burning rate test strands were molded from still another formulation prepared as These test strands showed a burning rate of 0.17 at 1000 p.s.i. The

incorporation of the an'inn'eua'cr along with teens-ai uble Prussian blue as catalyst gave an increased burning rate to the material.

Example 4 A gas-producing composition was formulated using the approximate 50% styrene-acrylonitrile plus asphalt-50% 2,4-dinitrodiphenyl ether plus 2,4-dinitrotoluene binder of Example 3. In this formulation a mixture of 78 parts by weight of the finely divided ammonium nitrate containing 3 parts by weight of carbon black were milled with 19 parts by weight of the binder material. The composition contained on a weight basis 3.8% of the styreneacrylonitrile, 5.7% of the asphalt, 5.7% of the 2,4-tlinitrodiphenyl ether, 3.8% of the 2,4-dinitrotoluene, 3% carbon black in the form of Micronex beads and 78% of finely divided ammonium nitrate, the finely divided carbon being the only catalyst in the composition. A molded burning rate test strand of this material showed a burning rate of 0.055"/sec. at 1000 p.s.i.

Example 5 In another experiment 74 parts by weight of finely clivided ammonium nitrate containing 3 parts by weight of carbon black in the form of Micronex beads was milled with 23 parts by weight of high styrene-acrylonitrile content binder. The styrene-acrylonitrile and asphalt used were samples of the same products used in Example 1. The finished composition consisted on a weight basis of 9.2% styrene-acrylonitrile copolymer, about 1.2% of the asphalt, about 3.4% of the 2,4-dinitrodiphenyl ether, about 4.6% of triethyl citrate, about 4.6% of his (2,4-dinitrophenyl) triglycol ether and 3% of the carbon black as the only catalyst in the composition and 74% of the finely divided ammonium nitrate. The burning rate of a test strand of this material was 0.043/sec. at 1000 p.s.i. Thus it was demonstrated that relatively slow-burning gas-producing propellant compositions may be obtained with relatively low binder content ammonium nitrate based compositions containing the asphalt-styrenc acrylonitrile based binder materials.

The above examples show that the ammonium nitratebased gas-generating compositions containing, as binder material, the defined styrene-acrylonitrile copolymerasphalt-binder base material, plasticized with the nitroaromatic components, with mixtures of the nitroaromatic components and with mixtures of the nitroaromatic components with non-nitro substituted plasticizers may be shaped into propellant grains which grains exhibit desirable physical properties and burning properties. Ammonium nitrate based grains containing the defined binder material may be subjected to extreme atmospheric temperature change in storage without undergoing chemical change, change of shape and without deterioration of ballistic properties.

Burning rates are expressed herein as burning rates at 1000 p.s.i. Percent compositions in this specification and in the claims are percents by weight unless specified otherwise.

Having thus described the invention what is claimed is:

1. A gas-producing composition comprising (1) from about 8% to about 25% by weight of a combustible binder, said binder consisting of (a) from about 30% to about 60% of a plasticizable mixture of styrene-acrylonitrile copolymer containing from about 15 mol percent to about 40 mol percent acrylonitrile units per molecule and a petroleum asphalt having a softening point of about 200 F. to about 300 F. said mixture consisting on a weight basis of (i) about 30% to about of the styrene-acrylonitrile copolymer and (ii) about 70% to about 10% by weight of asphalt and (b) from about 70% to about 40% of at least one plasticizer selected from the class consisting of dinitrobenzene, dinitrotoluene, dinitrodiphenyl ether, bis (dinitrophenyl) triglycol ether, dinitrophenyl propyl ether, bis (dinitrophenyl) propyl ether, dinitrophenyl allyl ether, dinitrostilbene and dinitroanisole and mixtures of at least one of the foregoing nitroaromatics with at least one ester selected from the class consisting of dialkyl phthalates having 1 to 8 carbon atoms per alkyl radical, triethylene glycol di-2- ethylbutyrate, triethylene glycol di-2-ethyl hexoate, triethyl citrate, acetyl triethyl citrate and triacetin said mixures containing not more than about 40% by weight of said ester, (2) from about 1 to about by weight of an ammonium nitrate combustion catalyst selected from the class consisting of Prussian blue, ammonium dichromate, alkali metal dichromate, finely divided carbon, aniline black, mono-alkali metal barbiturate and amine- N-oxidcs and (3) the remainder of said composition consisting essentially of ammonium nitrate.

2. The composition as described in claim 1 wherein the asphalt has a softening point within the range of about 200 to about 250 F.

3. The composition as described in claim 1 wherein the styrene-acrylonitrile copolymer contains about 29 mol percent of acrylonitrile units.

4. The composition of claim 1 wherein the binder consists of about 20% by weight of styrene-acrylonitn'le containing about 29 mol percent of acrylonitrile units, about 30% by weight of asphalt and the remainder of said binder consisting of 2,4-dinitrodiphenyl ether and 2,4-dinitrotoluene.

5. The composition as described in claim 1 wherein the catalyst consists of insoluble Prussian blue.

6. The composition as described in claim 1 wherein the catalyst consists of a mixture of insoluble Prussian blue and finely divided carbon.

7. The composition as described in claim 1 to which is 10 added about 0.05% to about 2% by weight of an aromatic hydrocarbon amine chemical stabilizer.

8. A shaped gas-producing propellant grain which comprises (1) about 8 to about 25% by weight of a combustible plastic binder, said binder consisting on a weight basis of (a) from about 30% to about of a plasticizable mixture of styrene-acrylonitn'le copolymer having an acrylonitrile content of about 29 mol percent acrylonitrile units and a petroleum asphalt having a softening point of about 200 to about 300 F. said plasticizable mixture containing on a Weight basis about 2 parts of said acrylonitrile to about 3 parts of said asphalt and (b) the remaining about to about 40% of said binder consisting of a mixture of 2,4-dinitrotoluene and 2,4-dinitrodiphenyl ether, said propellant composition also containing from about 1% to about 10% of at least one combustion catalyst selected from the class consisting of insoluble Prussian blue, ammonium dichromate, aniline black, carbon alkali metal dichromate, finely divided carbon, mono-alkali metal barbiturate and amine- N-oxide the total of said catalyst not exceeding 10% of the weight of said composition and the remainder of said composition consisting essentially of ammonium nitrate.

9. A shaped gas-producing propellant grain consisting on a weight basis of about 79% ammonium nitrate, 5.4% of petroleum asphalt having a softening point within the range of about 200 F. to 250 F., about 3.6% of styrene-acrylonitiile copolymer containing about 29 mol percent of acrylonitrile units, about 3.7% of 2,4-dinitrotoluene, about 5.3% of 2,4-dinitrodiphenyl ether and about 3.0% of insoluble Prussian blue catalyst.

No references cited.

Claims (1)

1. A GAS-PRODUCING COMPOSITION COMPRISING (1) FROM ABOUT 8% TO ABOUT 25% BY WEIGHT OF A COMBUSTIBLE BINDER, SAID BINDER CONSISTING OF (A) FROM ABOUT 30% TO ABOUT 60% OF A PLASTICIZABLE MIXTURE OF STYRENE-ACRYLONITRILE COPOLYMER CONTAINING FROM ABOUT 15 MOL PERCENT TO ABOUT 40 MOL PERCENT ACRYLONITRILE UNITS PER MOLECULE AND A PETROLEUM ASPHALT HAVING A SOFTENING POINT OF ABOUT 200* F. TO ABOUT 300* F. SAID MIXTURE CONSISTING ON A WEIGHT BASIS OF (I) ABOUT 30% TO ABOUT 90% OF THE STYRENE-ACRYLONITRILE COPOLYMER AND (II) ABOUT 70% TO ABOUT 10% BY WEIGHT OF ASPHALT AND (B) FROM ABOUT 70% TO ABOUT 40% OF AT LEAST ONE PLASTICIZER SELECTED FROM THE CLASS CONSISTING OF DINITROBENZENE, DINITROTOLUENE, DINITRODIPHENYL ETHER, BIS (DINITROPHENYL) TRIGLYCOL ETHER, DINITROPHENYL PROPYL ETHER, BIS (DINITROPHENYL) PROPYL ETHER, DINITROPHENYL ALLYL ETHER, DINITROSTILBENE AND DINITROANISOLE AND MIXTURES OF AT LEAST ONE OF THE FOREGOING NITROAROMATICS WITH AT LEAST ONE ESTER SELECTED FROM THE CLASS CONSISTING OF DIALKYL PHTHALATES HAVING 1 TO 8 CARBON ATOMS PER ALKYL RADICAL, TRIETHYLENE GLYCOL DI-2ETHYLBUTYRATE, TRIETHYLENE GLYCOL DI-2-ETHYL HEXOATE TRIETHYL CITRATE, ACETYL TRIETHYL CITRATE AND TRIACETIN SAID MIXTURES CONTAINING NOT MORE THAN ABOUT 40% BY WEIGHT OF SAID ESTER, (2) FROM ABOUT 1 TO ABOUT 10% BY WEIGHT OF AN AMMONIUM NITRATE COMBUSTION CATALYST SELECTED FROM THE CLASS CONSISTING OF PRUSSIAN BLUE, AMMONIUM DICHROMATE, ALKALI METAL DICHROMATE, FINELY DIVIDED CARBON, ANILINE BLACK, MONO-ALKALI METAL BARBITURATE AND AMINEN-OXIDES AND (3) THE REMAINDER OF SAID COMPOSITION CONSISTING ESSENTIALLY OF AMMONIUM NITRATE.