US2973255A

US2973255A - Preparation of acetonylacetone di-

Info

Publication number: US2973255A
Authority: US
Publication date: 1961-02-28
Anticipated expiration: 1978-02-28

Description

if I ired Patented Feb. as, est

PROPELLANT James R. Eiszner, Park Forest, Ill., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Filed Nov. 30, 1954, Ser. No. 471,993

7 Claims. (Cl. 52-.5)

This invention relates to a composition for the generation of gas, said composition containing ammonium nitrate as the principal gas-producing agent. More particularly, the invention relates to a novel composition usable with a binder material for a shaped explosive. Specifically the invention relates to a novel composition comprising ammonium nitrate gas-producing agent, a binder material,

of heat or by a blasting cap. Furthermore, when ignited,

ammonium nitrate does not burn uniformly and has a tendency to go out when used in the absence of other combustible organic material. Thus, to improve the burning quality, to increase the sensitivity and to utilize the excess free-oxygen vmade available by the decomposition of the ammonium nitrate, organic materials which also may function as binder material for the shaping of the ammonium nitrate into grains are admixed with the ammonium nitrate.

Modern warfare utilizes large quantities of rockets for ground-to-ground missiles, ship-to-shore missiles, air-toground and air-to-air missiles. These rockets are comprised essentially of thin-Wall casings, Which contain a combustion chamber in which is incorporated a quantity of solid propellant, a nozzle through which the decomposition gases pass, and thereby create the forward thrust; stabilizing vanes and a war head which contains high explosives. Military rockets heretofore have utilized double base powders such as bailastite as a solid propellant for use in such rockets. Rocket units have also been developed to assist in the take-oft of heavily loaded airplanes and to make possible the use of short runways. Such units are commonly known as JATO (jet assisted take-oil?) or ATO (assisted take-0E) units. A constant uniformly distributed assist impulse, with respect to time, is desirable for such take-ofi' service.

Economic considerations of cost and availability make the use of ammonium nitrate as the base material in solid propellants for rockets and ATO units quite attractive. Moreover the relatively low flame temperature of the form, particularly at temperatures of about 32 C. and also 18 C., i.e., temperatures common to storage conditions, a considerable volume change takes place in the ammonium nitrate. Thus the binder material used with the ammonium nitrate to form physically stable grains must be flexible to compensate for changes in volume in order that such volume changes will provide a minimum amount of voids and cracks in the grain. Moreover, the solid propellant grain suitable for military use must be ballistically stable after prolonged storage at temperatures as high as about 77C. and as low as about 60 C. Production of fissures in the grain, either internally or externally over the surface of the grain, creates additional burning surfaces which results in unpredictability of the ballistic performance of the rocket or ATO unit. Thus it becomes necessary to provide a binder material which will provide a shaped grain of satisfactory physical stability. Moreover, such grain must be capable of being ignited at extremely low or relatively high temperatures after being subjected to variable storage temperature conditions.

Finely powdered ammonium nitrate contains about 20% or more by volume of void space. This void space must be completely filled in order to obtain a shaped explosive grain of the desired physical characteristics. When the combustion catalyst is an organic material, a part of the void space is filled by the catalyst. However, when using an inorganic compound as the catalyst, the binder must not only fill the voids of the ammonium nitrate, but also the voids present in the finely powdered inorganic catalyst material. Another factor which contributes to the maintenance of uniform and smooth combustion of the propellant grain is that of maintenance of stoichiometric oxygen balance for the production of water, carbon monoxide and carbon dioxide in the combustion of the propellant grain. Hence, binder material components capable of furnishing a part of the oxygen for combustion of the grain are used to supply any oxygen deficiency in the composition.

For many military uses, an explosive is desired which has nondetonating characteristics rather than the detonating characteristics of ordinary ammonium nitrate explosives. The burning characteristics of nondetonating explosives are dependent upon the temperature and pressure in the combustion chamber. The relationship of burning rate and pressure at constant temperatures is expressed by R. N. Wimpress in Internal Ballistics of Solid Fuel Rockets (1950), as

wherein B is the linear burning rate at pressure p, ,8 is the linear burning rate for the composition at 1000 psi, p

. is the pressure in p.s.i. in the burning chamber and n is decomposition of ammonium nitrate (1730-2150 C.)'

the pressure exponent showing dependence of burning rate on pressure and is the numerical value equal to the slope of the curve of burning rate in inches per second obtained by plotting the burning rate versus pressure on log-log paper. Ammonium nitrate compositions usually have a pressure exponent of about 0.7 or higher. Smokeless powders, such as ballastite and oordite have pressure exponents between about 0.6 and 0.7. A composition having a pressure exponent of the order of 1.0 readily passes into detonation with only a small amount of shock. The lower the value of "n the less is the detonating character of the decomposition of the gas-producing component and the more even and smooth is the burning rate of the propellent grain. Thus a sustained thrust rather than a detonation is obtained by smooth burning of the grain. Propellant compositions having an exponent less than about 0.65 are preferred.

An object of this invention is the preparation of a gasgenerating composition using ammonium nitrate as the principal gas-generating material. Another object of the invention is the preparation of an explosive grain comprising ammonium nitrate, a combustion catalyst, and a plasticized thermoplastic synthetic polymeric material binder in 'an oxgenated binder which grain is dimensionally stable and non-fissuring over a wide range of storage temperatures. Still another object of the invention is the preparation of an ammonium nitrate explosive having readily ignitable properties. An additional object of the invention is the preparation of an ammonium nitrate explosive comprising ammonium nitrate and a combustible binder material, the combustion of which binder material is accomplished at a relatively uniform rate under conditions. of variable pressure. A still further object of the invention is to produce an ammonium nitrate-combustible binder propellant grain which will ignite at relatively low pressures and low temperatures. Another object of the invention is to produce a combustible ammonium nitrate propellant grain, the pressure exponent of the burning rate of which grain is less than about 0.65. Other objects will become apparent from the description of the invention hereinbelow. Y

I have discovered that a gas-producing propellant grain composition comprising a major proportion of ammonium nitrate, a combustion catalyst, a plasticized thermoplastic synthetic polymeric material binder, and at least one oxime having not more than 2 NCH groups per molecule, said =NOH groups of said oxime being attached to acyclic carbon atoms in said molecule, exhibits burning and ignition characteristics superior to burning and ignition characteristics of ammonium nitrate gasproducing propellant grains which contain no oxime, so defined, as a component of the gas-producing propellant grain. I have discovered that the presence of oxime during the combustion of the ammonium nitrate grain lowers the value of the exponent n in the above formula and/or increase the rate of burning of the grain. I have also discovered that the presence of the oxime, either when incorporated in the grain or when coated on that part of the grain exposed to burning, lowers substantially the ignition temperature of the ammonium nitrate propellant grain.

The explosive composition of my. invention consists essentially of:

(1) At least about 70% by weight of ammonium nitrate, usually from about 70% to about 82% by weight;

(2) An efiective amount of a combustion catalyst, generally from about 1% to about 8% by weight of the explosive graing,

(3) From about 10% to about 25% by weight of a binder, which binder consists essentially of: (a) Between about and 50% by Weight of at least one plasticizable thermoplastic synthetic polymeric material as the base material for the binder; and (b) From about 50% to about 85% by weight of at least one oxygencontaining plasticizer material capable of plasticizing the polymeric base material (a); and

(4) Associated with the components of the explosive composition at least one oxime having not more than two =NOH groups per molecule, the =NOH groups being attached to acyclic carbon atoms in the oxime molecule.

For purposes of this specification and claims based thereon theterm oxime group'is defined as the :NOH group, the double bond of the nitrogen being attached to an acyclic carbon atom of the molecule.

In addition to the above components of the explosive propellant composition, there may be added in relatively minor amounts up to about 2% based on the weight of the grain composition, such materials as surface active agentsas tergitols, dresinates; etc. (usually not more than about .2%) for the purpose of. improving the mixing, milling, and contact properties of the components of the explosive composition; tertiarybutyl catechol or metadiaminobenzene to stabilize the composition with respect to :gas evolution under hot storage conditions-(not usually more than about 2% by weight of the composition) and carbon black or activated carbon such as Norite which in general is added in amounts not more than about 5% based on the weight of the explosive composition as an adjunct catalyst. The composition also may have added thereto, insmall amounts up to about 2% by weight of magnesium oxide which is added to stabilize the composition against decomposition when stored under high temperature conditions.

The term ammonium nitrate as used in this specification and in the claims is intended to mean either ordinary commercial grade ammonium nitrate such as granular ammonium nitrate containing a small amount of impurities and which is then generally coated with a small amount of moisture-resistant material, such as petrolatum or parafiin, or military grade ammonium nitrate. The ammonium nitrate may contain minor amounts, usually not more than 20% and preferably not more than about 10% by weight of other gas-producing inorganic nitrates such as sodium nitrate and/or potassium nitrate along with the ammonium nitrate. The term substantially all ammonium nitrate as used in the specification and claims is defined to include not only ammonium nitrate per se but also associated therewith in the explosive composition, the above explosive inorganic nitrates and the minor amounts of additives to the grain to function as set out above.

The oximes suitable for incorporation in the binder material,;preferably should have boiling points at atmospheric pressure above about C. in order that they may be retained in the binder material during the process of manufacturing the binder material and the grain produced therefrom and also to avoid the loss of oxime component by evaporation from the grain during periods of storage under relatively high temperature conditions.

The oxime component or components of the explosive compositions may be associated with the composition in intimate admixture with binder material to which it may be added before the ammonium nitrate and catalyst are mixed with the binder material. The oxime also may be added, to the grain composition during the milling operation of ammonium nitrate with a binder material. Still av third method of incorporating the oxime with the binder is to coat with the oxime those surfaces of the grain subject to burning (usually produced by insets in producing the molded grain). I prefer to add the oxime to the binder material in an amount Within the range of from about 5% to about 15% based on the weight of the binder material with which it is associated.

The oxime component or components which constitutefrom. about 1% to about 5% by weight or" the explosive composition are selected from the class consisting of ketoximes, aromatic aldoximes and substituted aromatic aldoximes, the oxime groups of which class of oximes are attached to acyclic carbon atoms. Oximes corresponding to the formula below are preferred:

Int" n ort RC(CH2)=. CR

wherein R and R are selected from the class consisting of methyl, ethyl, phenyl and hydrogen; wherein R" is selected from the class consisting of oxygen and NOH and wherein x is an integer from 0 to 2. Specific examples of the oximes which correspond to the above efiective, particularly for increasing the burning rate of propellant grains are the aldoximes and substituted aldoximes which correspond to the general formula wherein R is selected from the class consisting of nitro substituted phenyl, amino substituted phenyl, hydroxy substituted phenyl, furyl and styryl. Representative examples of this class of effective oximes are m-nitrobenzaldoxime, o-aminobenzaldoxime, furaldoxime, salicylaldoxime and cinnamaldoxime. The relative effectiveness of the above oximes with respect to improvement in burning characteristics of explosive grain compositions is illustrated in the table below.

The combustion catalyst used in the grain formulations of this invention may be either organic or inorganic. Shiitable inorganic catalysts are ammonium dichromate catalysts and Prussian blue, either of the soluble or insoluble type. These iron-type catalysts are the subject matter of US. patent applications filed by Wayne A. Proell and Wm. G. Stanley, Serial No. 273,564, filed February 26, 1952, and Serial No. 288,065, filed May 15, 1952. Suitable organochromium type catalysts are described in US. patent application, Serial No. 279,968, filed April 1, 1952, by Wayne A. Proell and are the organochromium compounds selected from the chromate salts of the class consisting of aliphatic polyamines, cycloaliphatic polyamines and alicyclic secondary amines. Examples of these compounds are: ethylene-diamine chromate, triethylene tetramine chromate, hexamethylene diamine chromate and dimethyl piperazine chromate.

The iron-iron cyanide compounds known as soluble Prussian blues and insoluble Prussian blues are efiective catalysts for the purpose of this invention. The better soluble Prussian blues contain alkali metals such as potassium and sodium and/or the ammonium radical. Some of the iron cyanides which have been found to be effective catalysts are: ferro ferrocyanide, ferric ferrocyanide, ferro ferricyanide, ferric ferricyanide, potassium ferric ferrocyanide, sodium ferric ferrocyanide, ammonium ferric ferrocyanide, potassium soluble Prussian blue, sodium soluble Prussian blue and ammonium-sodium soluble Prussian blue.

The insoluble Prussian blues, that is the chemical compound ferri ferrocyanide or the commonly known insoluble Prussian blue, are more effective catalysts at high pressure operation than are the soluble Prussian blues. Thus when operating the combustion chamber containing a solid propellant at pressures between about 500 and 2000 p.s.i., a higher burning rate (inches per second) is obtainable when using in a given composition insoluble Prussian blue rather than soluble Prussian blue as the catalyst. The insoluble Prussian blue containing explosive compositions are diiiicult to ignite at atmospheric pressures when the amount of the catalyst is less than 6% by weight based on the weight of the grain. However, such compositions ignite readily when an elevated pressure is imposed on the combustion chamber at application of the igniting means. Ammoniated insoluble Prussian blue catalyst produced by exposing insoluble Prussian blue to the use of ammonia gas as taught in Serial No. 288,549, filed May 17, 1952, by Wayne A. Proell combines the ignition characteristics of soluble Prussian blue catalyst and the burning rate characteristics of insoluble Prussian blue catalyst in a single catalytic material. When using a chromium catalyst or a mixture of the iron cyanide catalyst above, between 1 and 8% by weight of catalyst should be present in the explosive composition,

preferably between 2 and 4% by weight of catalyst should be present in the propellant grain.

As indicated above, the binder material for the propelweight of the grain. The binder material serves several functions. Thus it serves to bind the ammonium nitrate into shaped forms, to supply organic material to be burned and thus provide additional energy, to modify the decomposition characteristics of the ammonium nitrate, to operate as a carrier for the oxime component described above and to furnish a part of the oxygen required for the burning of the binder material.

The binder material comprises essentially a base material capable of being plasticized, which base material consists essentially of a synthetic polymeric material, preferably an oxygen-containing synthetic polyineric material such as cellulose acetate, cellulose acetate-butyrate, and polyvinyl acetate. However, such synthetic polymers as polyvinyl chloride, styrene-acrylonitrile copolymer and quaternized polyvinylpyridine polymer may be used as plasticizable base material for the binder. I may also use as base synthetic polymer material in the binder, high molecular Weight polyesters of polyhydric alcohols with polycarboxylic acids, which polyesters may undergo cross-linking when heated. One example of such polyester is the polyesterification product of glycerol and/ or glycol with maleic acid.

A particularly suitable synthetic polymeric material is cellulose acetate. The preferred cellulose acetate used as a polymeric base material of this invention is known as a partially esterified cellulose acetate and is described as having an acetic acid content between about 51 and 57 weight percent. The term weight percent acetic acid denotes the amount of acetic acid obtained upon saponification of the cellulose acetate and is expressed as percent of the initial material. A particularly suitable cellulose acetate is one which analyzes between 54 and 56 weigh-t percent of acetic acid which cellulose acetate was used in formulating grain material described hereinbelow in the table. Lacquer grade cellulose acetate is particularly adaptable as base polymeric material for the binder. This grade is described, in addition to its acetic acid content, by its viscosity when dissolved in acetone. Viscosities within the range of 2 and S0 centipoises at 25 C. describe a suitable range. The preferred cellulose acetate of this invention has a viscosity of between 2 and 10 centipoises. A binder having the proper characteristics for use in preparing the shaped explosive composition of this invention contains between about 18 and 40 percent by weight of the defined cellulose acetate.

Another suitable synthetic polymeric base material for the binder of this invention is cellulose acetate-butyrate, which is known as a partially esterified cellulose acetatebutyrate and is described as having an acetic acid content between about 7 and 55 weight percent and a butyric acid content between about 16 and 61 percent. A particularly suitable cellulose acetate-butyrate is one which analyzes between about 25 and 31 weight percent of acetic acid and between about 31 and 35 weight percent butyric acid. As in the case of cellulose acetate, the cellulose acetate-butyrate commercial grades are described by viscosity when dissolved in acetone, 20% by weight of polymer in the acetone being used to determine the centipoise viscosity. The preferred cellulose acetate-butyrate polymer of this invention has a viscosity between about 10 and 40 centipoises. The binder having the characteristics suitable for preparing the shaped explosive composi tion of this invention contains from about 18 to about 40 percent by weight of the defined cellulose acetate-butyrate polymer. Preferably the binder contains between about 27% and 35% by weight of the defined cellulose acetatebutyrate.

The thermoplastic binder compositions contain, in addition to the above synthetic polymeric base material, at least one oxygen-containing plasticizer, which constitutes the plasticizer material for the base material. Since the plasticizer material is the predominant component of the binder material, cognizance of stoichiometric'oxygen ballant grain makes up from about 10% to about by 15 ance is taken in the choice of plasticizer material. Thus 7 plasticizers which provide a part of the oxygen requirement for the smokeless combustion of the explosive com position are generally preferred. Suitable plasticizers for the binder composition may be classified broadly as:

Illustrative examples of these plasticizers are tabulated below:

Polymeric esters;

Esters of polyhydric alcohols; Ethers of nitrophenols; Nitrornonocyclic aromatics; Esters of polycarboxylic acids; Alkyl ethers of polyglycols; and Polyglycols.

Polymeric esters:

Glycol maleate Diethylene glycol oxalate Ethylene glycol diglycolate Diethylene glycol diglycolate Esters of polyhydric alcohols:

Monoacetin Diacetin Triacetin Hydroxyethylacetate Ethylene glycol diacetate Diethylene glycol diacetate Triethylene glycol diacetate Triethylene glycol di-Z-ethylbutyrate Polyethylene glycol di-Z-ethylhexoate Nitromethylpropanediol diacetate Ethers of nitrophenols:

Dinitrophenyl propyl ether Dinitrophenyl allyl ether Nitrodiphenyl ethers Nitrornonocyclic aromatics:

Dinitrobenzene Nitrotoluene Dinitrotoluene Esters of polycarboxylic acids: .Methylcarbitol diglycolate Di-methylallyl diglycolate Dibutyl diglycolate Tributyl citrate Tripropyl citrate Triethyl citrate Trimethyl citrate Acetyl triethyl citrate Dimethyl phthalate Diethyl phthalate Dibutyl phthalate Dioctyl hthalate Ethyl glycolatyl methyl phthalate Dimethyl nitrophthalate Alkyl ethers of polyglycols:

Dimethoxy tetraglycol Diethoxy tetraglycol Polyglycols:

Diethylene glycol Triethylene glycol Polyethylene glycol (200) Dipropylene glycol ell) reaction in reacting achloronitrobenzene with phenolin the presence of caustic.- One suchexample is 2,4-dinitrodiphenyl other which is particularly effective as-a plasticizer when used in conjunction with other plasticizers such as ethylene glycol diglycolate. Dinitrotoluene is also a very effective plasticizer which may be used with nitrodiphenyl ether or with ethylene glycol diglycolate or with mixtures of ethylene glycol diglycolate and nitrodiphenyl ether. It may also be used alone to plasticize cellulose esters. r

The polyester plasticizer, ethylene glycol diglycolate, is the product of the polyester condensation of ethylene glycol with diglycolic acid wherein a molar excess of alcohol is used. The dihydric alcohols used in the preparation of such class of adjunct plasticizers may be selected from at least one of the class consisting of ethylene glycol, polyethylene glycol, propylene glycol, polypropyleneglycol, n-butylene glycol, and poly n-butylene glycol. The polyglycols must have a molecular weight of less than 400 in order to produce a polyester of the desired properties.

The dicarboxylic acids utilized in the preparation of this class of polyester plasticizers are selected from the class consisting of aliphatic dicarboxylic acids and aliphatic oxydicarboxylic acids, which acids have between 2 and 6 carbon atoms in the molecule. Examples of the oxydicarboxylic acids are diglycolic acid. i.e., oxydiacetic acid, oxyaceticpropanoic acid and oxydipropanoic acid. Examples of the dicarboxylic acids are malonic acid, succinic acid, glutaric acid and adipic acid. It is preferred to use the oxydicarboxylic acids in the preparation of this type of plasticizer. The molecular weight of the polyester condensation product obtained from ethylene glycol with diglycolic acid, is related to its efficiency as a plasticizer. A low molecular weight is desirable which low molecular weight is obtained by using a large molar excess of glycol, i.e., glycol to acid. The molar ratio of glycol to acidshould be between 1.03 and 1.3, preferably between about 1.1 and 1.2. The molecular weight of the polyester should be not more than about 1,000 and preferably not more than about 600.

In preparing the ethylene glycol diglycolate the desired amount of glycol and diglycolic acid are charged to a heated reaction zone wherein the temperature of the material is maintained at about 150 C. The Water evolved in the reaction is Withdrawn from the reaction zone by means of a condenser which refluxes back to the reaction zone any glycol and acid which may have vaporized. Preferably the reaction zone is operated under vacuum. The reaction is continued until the evolution of water is substantially complete. The plasticized thermoplastic polymeric material binder'rnay contain from about to about 40% by weight, preferably from about to about by weight of this polyester condensation product plasticizer when it is used in conjunction with nitrodiphenyl ether plasticizer for plasticizing celiulosc acetate.

Thus to recapitulate my novel composition of matter suitable for use as a gas-producing propellant consists of from about 10% to about 25% by weight of a plasticized thermoplastic synthetic polymeric material binder, from about 1% to about 5% by weight of at least one oxime having not more than 2 =NOH groups per molecule, said :NOH groups being attached to acyclic carbon atoms in said molecule, from about 1% to about 8% by weight of a combustion catalyst, and the remainder substantially all ammonium nitrate. As indicated' above, a major portion of the binder material of the composition is oxygen-containing plasticizer material,

that is, from about to about by weight of the plasticized binder material is oxygen-containing plasticizer.

used in the binder may be varied over a considerable range to obtain optimum physical properties and to obtain stoichiometric balance of oxygen afiording components in the grain. Usually when more than one plas- The relative amounts of different plasticizers 83. ticizer is used the individual plasticizer components are present in approximately equal weights.

The production of the preferred oxime of this invention that is, acetonylacetone dioxime, is illustrated in the example below.

PREPARATION OF ACETONYLACETONE DI- OXIME To 8 liters of water in a 12" battery jar was added 2492 grams of hydroxylammonium sulfate and 1500 grams of acetonylacetone was then added to the solution. Using a separatory funnel, a solution of 1200 grams of sodium hydroxide dissolved in 4 liters of water was added to the reaction mixture, the rate of addition being determined by the heat of reaction. A temperature of 65- 70 C; was maintained. After addition was complete, the mixture was cooled and stirring was continued until the reaction mixture came to room temperature. The precipitated dioxime was then filtered with suction and dried, after washing the precipitate with a small amount of water. The moisture content of the dried sample, determined by heating in avacuum oven (25" of mercury) at 125 C. for a period of 15 minutes was 1.12%. The ash content of the sample was 0.073%.

Acetonylacetone monooxime may be prepared by the same procedure by using only sufiicient hydroxylammonium sulfate to give the monooxime product. Acetylacetone oximes may also be prepared according to thistechnique using acteylacetone.

In preparing the compositions of this invention the binder material is first prepared and the ammonium nitrate and catalyst are milled with the plasticized binder. The binder is prepared by heating the plasticizer material at a temperature not in excess of about 150 C., usually within the range of from about 120 C. to about 140 C. The heated plasticizer material is stirred and the polymeric base material is added, heating and stirring being continued until a homogeneous mixture is obtained. The oxime is then added to the mixture of polymeric plasticizable component and plasticizer material of the binder and is thoroughly mixed therewith before the addition of the ammonium nitrate or the catalyst component of the finished grain. The catalyst may be added simultaneously with or immediately preceding the addition of the ammonium nitrate. The ammonium nitrate and catalyst are then milled into the plasticized mass at a temperature below about 120 C. and preferably at a temperature of about 110 C. Milling is continued until a product of uniform texture is obtained. Burning rate test strips are extruded or molded under pressure. The material is shaped into propellant grains.

The rate of burning of the grain material is determined at different pressures in an inert atmosphere. The test strands of materials for the determination of burning rates of compositions herein described were prepared by ram extrusion at about 110 C.

PREPARATION OF BURNING RAT TEST STRIPS In preparing the test strips the material, in a 1" diameter cylinder, was subjected to 2,000 pounds pressure and extruded in a strand through an aperture of about /8 inch diameter. After cooling the strand was cut'into test strips approximately long and these were then coated with lacquer grade cellulose acetate to inhibit surface burning along the strand. The test strip was drilled at two points 3 apart along its length and fusible wires were inserted in the drilled holes. The test piece was then placed in a pressure bomb, electrical connection of the fuse wires being made to a timing device. The timing device was started by the fusing of one wire and as the test piece burned along its length, the timing device was stopped by the fusing of the second wire. Thus the time for the burning of the 3 inches of the test piece was obtained. The test piece was ignited by means of a nichromeresistance wire placed in contact with one end of the test piece. Burning rates for the test pieces were determined at pressures of 600, 800, 1000, 1200, 1400, 1600 and 1800 pounds per square inch of nitrogen pressure. The burning rate in inches per second for the different pressures was plotted on log-log paper. The plot gave a straight line relationship. The slope of this line is defined as the exponent of the burning rate as related to pressure in the above formula. Burning rates of the materials in this specification are defined as the burning rates at 1000 pounds nitrogen pressure. Rates above 0.100 inch/sec. are generally required for propellant grains.

Grains were formulated according to the following procedure.

PREPARATION OF PROPELLANT GRAINS Approximately 250 grams of the binder material containing the plasticizable polymeric material and plasticizer were heated in a steam jacketed vessel with the steam at about 15 pounds pressure in the-jacket for a period of about 20 minutes. To this binder material, a mixture of about 240 grams of commercial grade ammonium nitrate and 30 grams of soluble Prussian blue were added.

The mixture was agitated for 15 minutes to obtain intimate contact of the ammonium nitrate and catalyst with the binder material after which the remainder of the nitrate was added, that is, about 480 grams, and the mixing was continued for 30 minutes followed by 15 minutes mixing under reduced pressure, that is, 20 inches of mercury as reduced pressure. The hot mix was then loaded into a 2%" diameter mold, maintained at a temperature of about C. The mold contained a'starform inset. The mold may be provided with insets of other shapes such as cylinders, triform, cruciform or uniform internal burning surface may be provided by a multiplicity of insets in the mold. The propellant composition may also be molded into disc-shaped grains, preferably perforated, for use in rockets and missiles. The mold was subjected to 10,000 p.s.i. ram pressure for about 5 minutes after which the ram pressure was re-' duced to 5,000 p.s.i. This pressure was maintained for an additional 15 minutes. The mold was removed from the press and allowed to cool to room temperature. The grain was removed from the mold and cut to 4" lengths and the surface of the cylindrical grain was machined to obtain a uniform and even surface. The grains were inhibited with respect to cylindrical surface burning by coating with vistanex-asphalt mixtures. Other non-burning material may be used.

The burning rate (at 1000 p.s.i.) and the burning rate exponent of propellant grain material consisting of about 72 to 75% ammonium nitrate and about 22 to 25% binder material containing different oximes and insoluble Prussian blue as catalyst is shown in the table below. The ammonium nitrate used in these formulations was dynamite grade and had a particle size by Rotap analysis as follows:

The insoluble Prussian blue catalyst was dry color grade. The binder material was made up of cellulose acetate (synthetic polymeric material) and, as plasticizer materials, ethylene glycol diglycolate and 2,4-dinitrodiphenyl ether. The cellulose acetate was lacquer grade and analyzed between 54 and 56 weight percent of acetic acid, and made up about 23% by weight of the binder got-3,255

material. The ethylene glycol diglycolate and 2,4-dinitrodiphenyl ether, prepared as described hereinabove, were present in equal amounts in the binder which contained 38.5% of each. The oximes of the table were added to the binder material in an amount to produce a binder containing 10% by weight of the oxime based on the total weight of binder and oxime. Thus the finished binder' contained: cellulose acetate 20.6, ethylene glycol diglycolate 34.7, 2,4-dinitrodiphenyl ether 34.7% and oxime 10% by weight.

Table Burning Oxime Rate Pressure (Inehes/ Exponent Second) 1 None 0. 105 0. 82 Ketoxirnes:

Acetonylacetone dioxime..- 118 0.59 Aeetonylaeetone monooxim 0 102 0. 58 Aeetylacetone dioxime. O 115 0. 58 Dimethylglyoxime. 0 101 0.65 Benzil dioxime-- 0. 135 0. 66 Quinone dioxime 0.110 0.78 Aldoxirnes:

Suecinaldehyde dioxime 0 130 0.72 Salicylaldoxime 0 105 0. 66 m-Nitrobenzaldoxime 0 125 0. 67 o-Aminobenzaldoxirne. 0 110 0.69 Cinnamaldoxime... 0 115 0. 69 Furaldoxime 0 119 0.67 Benzaldoxime 0. 095 0. 68

1 At 1000 psi.

The data in the above table shows that the acyclic ketoximes, particularly the acyclic ketodioximes are more effective for depressing the pressure exponent than are the aldoximes. The alicyclic quinone dioxime shows no appreciable effect either as a depressant for the exponent or as a burning rate accelerator. Acetonylacetone dioxime is particularly efiective and increases the burning rate about in addition to depressing the exponent. The substituted aromatic aldoximes are effective in increasing the burning rate and also in depressing the pressure exponent. Furaldoxime is also quite effective.

A grain formulation with acetonylacetone dioxime incorporated in the cellulose acetate-ethylene glycol diglycolate-2,4-dinitrodiphenyl ether binder was ignited at a temperature below -60 C. A grain formulated in the same way and containing the same components except that 'no oxime was present in the formulation cannot be ignited at this temperature. 1

v The oximes are effective in promoting the burning rate and depressing the pressure exponent of propellant grain material containing synthetic polymers other than the cellulose acetate. Thus the burning rates of grains made up of ammonium nitrate and binder material containing cellulose acetate-butyrate, as plasticizable material, are markedly improved and lower pressure exponents are manifested if the oximes are incorporated in such binder material. Thus a grain containing about 73% of the above commercial grade ammonium nitrate, 3% insoluble Prussian blue catalyst and 24% binder material consisting of 40% cellulose acetate-butyrate and 60% dinitrotoluene had a burning rate at 1000 pounds pressure of 0.108 and a pressure exponent of 0.66. The addition of sufficient acetonylacetone dioxime to give a binder containing 36%'cellulose acetate-butyrate, about 54% dinitrotoluene and 10% acetonylacetone dioxirne produced a grain material having a burning rate of 0.135 at 1000 pounds pressure and an exponent of 0.65. The cellulose acetate-butyrate synthetic polymeric base material of the binder contained about 50% butyric acid.

The plasticizer material of the binder can also be varied, the same polymeric material to be plasticized being used to obtain improved burning characteristics by the addition of oxime such as acetonylacetone dioxime. Thus grain material containing 72% ammonium nitrate, 3% insoluble Prussian blue catalyst and 25% binder material consisting of 25% lacquer grade cellulose acetate, 25% ethylene glycol diglycolate, 10% nitromethylpropanediol diacetate and 40% dinitrotoluene had a burning rate of 0.10 inch per second at 1000 pounds pressure and an exponent of 0.84. The addition of 8% acetonylacetone dioxime to this binder produced a grain material which had a burning rate of 0.140 inch/sec. at 1000 pounds pressure and an exponent of 0.63. Lowering the amount of insoluble Prussian blue catalyst to 2% in this grain material resulted in a finished grain material having a burning rate of 0.127 and an exponent of 0.63. Other materials may be used in small amounts in the binder material in order to improve the burning rate and/ or the exponent.

A propellant grain material containing ammonium nitrate and sodium nitrate as the explosive nitrate was prepared according to the above described procedure for preparing ammonium nitrate grains. The composition of the propellant material was as follows:

The burning rate at 1000 p.s.i. of this material was 0.21 inch per second and the pressure exponent was 0.75. A similar composition containing the above components in the same percents by weight except that no oxime component was present and containing 75% by weight of ammonium nitrate, had a burning rate of 0.24 and a pressure exponent of 0.87. Thus the exponent was depressed by the incorporation of only 2% oxime in the material without a substantial change in the burning rate.

A propellant grain material containing polyvinyl acetate as a component of the binder was prepared according to the above-described procedure. The composition was as follows:

percent Ammonium Diehroinate 1 00 Prussian blue (Insoluble). 2. 00 Mieronex Beads (Carbon 1. 50 Polyvinyl Acetate 5. Triethylene glycol Di-2-e 2.90 Dinitrophenyl propy1ether.- 4. 35 ZA-dinitrodiphenyl ether 1. 45 Magnesium Oxide (Stabilizer) 1.00

The burning rate of this composition was 0.146 inch per second. A similar composition made up of the above components in the same relative proportions except that acetonylacetone dioxime was added to the extent of 2% of the total weight of theabove formulation had a burning rate of 0.182. Thus, the burning rate was increased by about 25% by the incorporation of only 2% oxime in the material. A grain prepared from this oxime-containing material was ignited at 60 C. The grain without the oxime would not ignite at 60 C., using the same diameter motor nozzle even when 40% more igniter material was used than igniter material used to ignite the oxime-containing grain.

Although I have described my novel composition as applicable for use as a propellant grain composition in airplane take-off service and for the propulsion of rockets, I do not wish to be limited to such use. The composition may be used in the form of smokeless powder grains of sporting powder and the like. The compositions may also be used as blasting powder.

Having thus described my invention, What I claim is:

l. A gas-producing solid propellant consisting essentially of (1) (a) from about 10% to about 25% by weight of a binder consisting essentially of from about 15% to about 50% by weight of a synthetic polymeric base material selected from the class consisting of cellulose acetate, cellulose acetate butyrate, polyvinyl acetate, styrene-acrylonitrile copolymer, polyvinyl chloride, quaternized polyvinyl pyridine polymer and polyesters of polyhydric alcohols with polycarboxylic acids, and (b) between about 50% and 85% by weight of at least one oxygen containing plasticizer selected from the class consisting of glycol maleatc, diethylene glycol oxalate, ethylene glycol diglycolates, acetins, ethylene glycol di-lower alkanoates, nitromethyl propanediol diacetate, tri-loweralkyl citrates, di-lower-alkyl phthalates, acetyl triethyl citrate, dimethyl allyl diglycolate, nitrodiphenyl ethers, dinitrophenyl allyl ethers, nitrobenzenes, di-lower-alkoxy tetraglycol and poly-loWer-alkylene glycols, (2) from about 1% to about 8% of an ammonium nitrate combustion catalyst selected from the class consisting of Prussian blue and ammonium dichromate, (3) from about 1% to about 5% by weight of an oxime selected from the class of ketoximes corresponding to the formula wherein R and R are selected from the class consisting of oxygen and NOH and x is an integer from 0 to 2 and from the class of aldoximes corresponding to the formula NOH 3-0 wherein R is selected from the class consisting of nitro substituted phenyl, amino substituted phenyl, hydroxy substituted phenyl, furyl and styryl, and (4) the remainder essentially ammonium nitrate.

2. The composition of claim 1 wherein said catalyst is Prussian blue.

3. The composition of claim 1 wherein the oXime is acetonylacetone dioxime.

4. The composition of claim 1 wherein the oxime is acetylacetone dioxime.

5. The composition of claim 1 wherein the oxime is acetonylacetone monooxime.

6. The composition of claim 1 wherein the oxime is benzil dioxime.

7. A composition of matter suitable for use as a gasproducing propellant which consists of about 72% by weight of ammonium nitrate, about 5.2% by weight of cellulose acetate, about 8.6% by weight of ethylene glycol diglycolate, about 8.7% by Weight of 2,4-dinitrodiphenyl ether, about 3% by Weight of Prussian blue catalyst and about 2.5% by weight of acetonylacetone dioxime.

References Cited in the file of this patent UNITED STATES PATENTS 1,021,882 OBrien Apr. 2, 1912 2,159,234 Taylor May 23, 1939 2,165,263 Holm July 11, 1939 2,223,181 Miller et a1. Nov. 26, 1940 2,417,090 Silk et al. Mar. 11, 1947 2,692,195 Hannum et a1. Oct. 19, 1954 FOREIGN PATENTS 14,196 Great Britain 1897 429,763 Great Britain June 6, 1935

Claims

1. A GAS-PRODUCING SOLID PROPELLANT CONSISTING ESSENTIALLY OF (1) (A) FROM ABOUT 10% TO ABOUT 25% BY WEIGHT OF A BINDER CONSISTING ESSENTIALLY OF FROM ABOUT 15% TO ABOUT 50% BY WEIGHT OF A SYNTHETIC POLYMERIC BASE MATERIAL SELECTED FROM THE CLASS CONSISTING OF CELLULOSE ACETATE, CELLULOSE ACETATE BUTYRATE, POLYVINYL ACETATE STYRENE-ACRYLONITRILE COPOLYMER, POLYVINYL CHLORIDE, QUATERNIZED POLYVINYL PYRIDINE POLYMER AND POLYESTERS OF POLYHYDRIC ALCOHOLS WITH POLYCARBOXYLIC ACIDS, AND (B) BETWEEN ABOUT 50% AND 85% BY WEIGHT OF AT LEAST ONE OXYGEN CONTAINING PLASTICIZER SELECTED FROM THE CLASS CONSISTING OF GLYCOL MALEATE, DIETHYLENE GLYCOL OXALATE, ETHYLENE GLYCOL DIGLYCOLATES, ACETINS, ETHYLENE GLYCOL DI-LOWER ALKANOATES, NITROMETHYL PROPANEDIOL DIACETATE, TRI-LOWERALKYL CITRATES, DI-LOWER-ALKYL PHTHALATES, ACETYL TRIETHYL CITRATE, DIMETHYL ALLYL DIGLYCOLATE, NITRODIPHENYL ETHERS, DINITROPHENYL ALLYL ETHERS, NITROBENZENES, DI-LOWER-ALKOXY TETRAGLYCOL AND POLY-LOWER-ALKYLENE GLYCOLS, (2) FROM ABOUT 1% TO ABOUT 8% OF AN AMMONIUM NITRATE COMBUSTION CATALYST SELECTED FROM THE CLASS CONSISTING OF PRUSSIAN BLUE AND AMMONIUM DICHROMATE, (3) FROM ABOUT 1% TO ABOUT 5% BY WEIGHT OF AN OXIME SELECTED FROM THE CLASS OF KETOXIMES CORRESPONDING TO THE FORMULA