US 2434872 A
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mammal), 1948" t 2,434,8TIZ
. Jamea'l'aylor, Saltcoato, and John Whetstone, West-Kilbrlde, Scotland, asa'gnorl to Imperial Great mam Chemical Industries Limited, a corporation of wing." Application 12, 19 44,
No Dra Beral No.
. -'i Claims.
The present invention relates to a new or im:- proved method forthe manufacture of combustibleexplosive charges in compact form, characterised by a .high' gas yield and capable of proa proportion sumcient to obviate the formation 522,106. In Great Britain November of oxides of nitrogen, and. in the case of charges required for operating mechanical devices, sufficient to yield a high proportion of permanent duction' in forms of considerable web thickness, 5 cases in the gases formed. Suitable chromium for the generation of gas pressure, and to comcompounds are stated to include ammonium, alpact combustible gas producing explosive charges kall metal. nd rtain other chromates', bichrothereby obtained. mates and polychromates, theammonium and a Compact gas producing charges composed of a P ium ltsin P rticul rly ffe ive. combustible explosive material are frequently em- These are referred to hereinafter as chromate ployed for the actuation of gas pressure operated compounds. According to the aforesaid proposal mechanical devices and gas escape reaction acit is stated that the ingredients may be admixed tuated devices, for instance rockets. by a milling operation, and compact compositions Although it is known to use pellets of blackprepared by pressing mixtures containing ampowder, and although pellets of compositions 16 monium nitrate and ammonium bichromate with made from similar ingredients modified by the mineral jelly, bitumen, or paraformaldehyde as presence of inorganic or organic diluents have the oxidisable'material are exemplified. been suggested as charges for the production of Notwithstanding the sensitising effect of the gas pressure for such purposes, extruded charges chromate compounds generally on the thermal made from smokeless powders consisting essen- 20 decomposition of'ammonium nitrate we have now tially of gelatinised nitrocellulose compositions found that compact ammonium'nitrate charges are now commonly employed on account 01' their containing an oxidisable material and sensitised markedly superior gas'yield and other advantages. with a chromate compound and suitable for the It is, however, difllcult to produce charges of gela generation of ga p sure n e Produced y a tinised nitrocellulose compositions of any concasting operation involving at least partial fusion siderable web thickness if a volatile solvent is of the charge provided that there is included in used in their production, since the solvent evapothe composition suflicient .of at least one amrates only very slowly from the interior of the monium nitrate fusion promoting ingredient solid charge, and in practice it is usually necessary to at ordinary mp tur to r n er the mpo iemploy a composition containing nitroglycerine as tion pourable at a temperature not exceeding apgelatinis'ing agent in order to make and extrude proximat ly 110 to 1 Preferably h hr the composition without using a volatile solvent. mate compound is introduced into the composi- It would, however, be desirable to produce. tion on y after a mixture t a temperature-8t ast compact charges for the generation of gas presapproximating to pouring temperature has been sure for the aforesaid purposes without necessifo ed. comprising at least t o um nitating the use of pressing apparatus and also trate and the fusion promoting ingredients. The without consuming the organic nitrates required oxidisable material may or may not comprise an for the manufacture of smokeless powder. ammoniumznitrate fusion promoting ingredient. It has been proposed in British specification Other constituents can be introduced before or 453,210 to provide a charge for gas-pressure oper- 40 after the chromate compound, but the mainteated devices consisting essentially or largely of nance of compositions containing the chromate ammonium nitrate and containing as sensitiser of compound at high temperature should be avoided its thermal decomposition a chromium compound by casting the composition without unnecessary adapted to generate chromic oxide on heating in delay, otherwise it may show evidence of exother-, the presence of ammonium nitrate, so that the gas mic reaction. evolving composition is capable of undergoing-a The chromate compound may advantageously self sustained decomposition without detonation be an alkali metal or ammonium bichromate or when ignited locally and at ordinary pressure by a polychromate, and the proportion employed may non-detonating igniting element insufflcient of conveniently amount to from about 2 to 20 per itself to eflect any substantial general rise in temcent of the weight of the ammonium nitrate used. perature of the charge. By ammonium, nitrate fusion promoting in- According to this previous proposal it is degredients, solidat ordinary temperature, we mean sirable to include in the composition a material solid materials (other than chromate compounds) oxidisable by the ammonium nitrate so as to yield adapted when heated with ammonium nitrate to gaseous products, this material being present in temperatures substantially below the fusion point amen ' included in the composition. The quantity of the fusion promoting ingredients included in the composition, including any water not capable of being bound as water of crystallisation must be' sufiicient to render the mixture pourable at the aforesaid temperature, since above that temperature the thermal decomposition of the ammonium nitrate by the chromate compound may occur at an appreciable rate, and it will be understood that there must be used only such fusion promoting ingredients as are capable of being heated with ammonium nitrate and also with the chromate compound alone without undergoing any substantial decomposition leading to the formation of gaseous products, at a temperature not exceeding the aforesaid pouring temperature. Olive colouration indicates chro'mate destruction.
Subject to this proviso there may be used as fusion promoting ingredients a wide variety of organic or inorganic substances having the aforesaid properties, whether or not of oxidising or oxidisable character. It is frequently desirable to employ a plurality of fusion promoting ingredients and these may if desired be of differing chemical character.
It is often necessary that the amount of oxidisable material in the cast charge should be sufficient not merely to prevent the formation of any appreciable quantity of oxides of nitrogen, but
also to yield a high proportion of permanent gases, more particularly carbon monoxide and hydrogen, in the products of its combustion. On the other hand, the formation of an unoxidlsed carbon smoke is seldom desirable. The employment of ammonium nitrate fusion promoting ingredients of oxidisable organic or inorganic character in conjunction with ammonium nitrate fusion promoting ingredients of an oxidising character facilitates the production of cast charges of desirable oxygen balance at a low pouring temperature.
One useful group of ammonium nitrate fusion promoting ingredients includes saline and nonsaline compounds capable of forming eutectic mixtures with ammonium nitrate, whether or not of oxidising character, for instance alkali metal nitrates, alkaline earth metal nitrates, alkali metal chlorides, alkaline earth metal chlorides, magnesium sulphate and ammonium chloride, or other non-alkaline anhydrous salts. Likewise there may be used various non-saline organic compounds. A useful group of ammonium nitrate fusion promoters of oxidisable character is provided by weakly basic or non-basic organic amino derivatives, for instance dicyandi amide, guanidine nitrate, nitroguanidine, acetamide, guanidine and like compounds.
An especially useful category of fusion promoting ingredients is also provided by highly soluble non-alkaline salts containing water of crystallisation, whether or not of oxidising character. for instance magnesium, nitrate hexahydrate, Epsom salts, zinc nitrate hexahydrate, or calcium nitrate tetrahydrate, microcosmic salt and the like. The water of crystallisation liberated by such hydrated salts at raised temperature has the desirable effect of retarding thermal decomposition of the ammonium bichromate'in the melt. Instead of the hydrated salts containing water of crystallisation the anhydrous salts or salts of a lower degree by hydration and water in amounts up to that capable of being bound as water of crystallisation when the melt is cooled may alternatively be employed.
As oxidisable ingredents organic polyhydric compounds are frequently too easily oxidised by the polychromates or bichromates to be of service according to the present invention, but in addition to the fusion promoting ingredients there may be included in the cast composition suspended solid combustibles such as lamp black, graphite, resins or the like, and the cast composition may also include fusible oxidisable ingredients such as nitro-hydrocarbons, hydrocarbons, waxes or the like emulsified in the melt with the assistance of emulsifying agents such as bentonite or kieselguhr.
The invention is illustrated by the following examples, in which the parts are parts by weight.
Example 1 10 parts magnesium nitrate hexahydrate are fused in a kettle having a stirrer and a previously made mixture of 6'? parts powdered ammonium,
nitrate, and 15 parts dicyandiamide is then introduced into the kettle, which is heated to to 93 C. and stirred at this temperature until as much of the material as possible has fused. 8 parts finely crystalline ammonium bichromate are then stirred into the mixture, and the resulting mixture is poured at 90 to 95 C. into wooden moulds of the required shape, in which it is allowed to solidify. The resulting cast charge is thereafter removed from the moulds before it has completely cooled.
Example 2 10 parts magnesium nitrate hexahydrate are fused in a heated kettle fitted with stirring apparatus and a previously prepared mixture of 56 parts finely crystalline ammonium nitrate, 6 parts potassium nitrate and 8 parts dicyandiamide is then introduced and heated to C. 2 parts bentonite and 11 parts trinitrotoluene are then introduced into the mixture which is stirred until the molten trinitrotoluene has been well emulsifled. 6.5 parts finely crystalline ammonium bichromate are then stirred into the mixture, which is poured at 95 to 100 G. into wooden moulds of the required form, from which it is removed afterdsolidification, but before it has completely coole Example 3 A mixture of 71 parts finely crystalline ammonium nitrate, 10 parts nitroguanidine, and 7 parts acetamide are melted together with stirring in a kettle at 100 0., 8 parts finely crystalline ammonium bichromate are then introduced into the mixture, whereupon 2 parts bentonite and 2 parts carnauba wax introduced, and the mixture is stirred until the carnauba wax has been well emulsified. The resulting mixture is poured into wooden moulds of the required form from which it is removed after it has solidified, but before it is quite cold.
Example 4 A mixture of 69 parts finely crystalilne ammonium nitrate, 10 parts nitroguanidine, 2 parts magnesium nitrate hexahydrate and 7 parts acetamide are mcited'together with stirring in a kettle at 100 C.- 8 parts finely crystalline ammonlum bichromate are then introduced into the it is removed after it has solidified, but before it is quite cold.
Example 56 parts finely crystalline ammonium nitrate, 15.2 parts guanidine nitrate, 11.6 parts nitroguanidine, 2.parts magnesium nitrate hexahydrate and 7.2 parts dicyandiamide arefused together at a temperature of 105 0., whereupon 8 parts finely crystalline ammonium bichromat'e are introduced into the melt with stirring. The melt is then cast into cardboard moulds of the required form, in which it is allowed to solidify, and from which it is removed before the cast has completely cooled.
Example 58 parts finely crystalline ammonium nitrate, 15.2 parts guanidine nitrate, 11.6 parts nitroguanidine and 7.2 parts dicyandiamide are fused together at a temperature'of 105 C. whereupon 8 parts finely crystalline ammonium bichromate are introduced into the melt, with stirring. The melt is then cast into cardboard moulds of the required form, in which it is allowed to solidify. and from which it is removed before the cast has completely cooled. Examples 1-6 give orange coloured casts.
Example 2' 6* yielding a high gas evolution. In using them for the generation of pressure it is frequently desirable to employ a relatively small quantity of smokeless powder made from nitrocellulose of small web thickness, desirably in conjunction with a small quantity of 'blackpowder, to assist their ignition. It is not, however, essential to use smokeless powder. For instance, a cast tubular pellet having an external diameter of say 2 inches and an annular thickness of /4 inch, and weighing 2 to 3 lbs. could be ignited by means of an electric powder fuze containing about 15 to 20 grams of blackpowder inserted into the tube.
Having now particularly described and ascertained the nature of our said invention, and in what manner the same is to be performed, we declare that what we claim is:
1. A combustible explosive charge in compact form for the generation of gas pressure. which comprises ammonium nitrate in preponderating proportion, in intimate commixture with an oxidizable material, a chromate compound adapted to sensitize the thermal decomposition of the charge, and an ammonium nitrate fusion-promoting ingredient solid at ordinary temperatures and adapted to render the charge fluid at a temperature not exceeding 115 0.; said charge being compact and homogeneous due to solidification of the mixture from fused condition.
2. A process for the production of combustible explosive charges in compact form and suitable form in which it is allowed to solidify and from which it is removed before it has completely cooled.
It is sometimes convenient to cast the compositions into Celluloid containers which are left in place, and are burned oif in the operation of igniting the charge, instead of casting them into moulds from which they are removed. Charges of any desired web thickness in tubular or solid forms may be made according to the method of the present invention. Not only are the novel charges of the invention highly compact or dense as a result of having solidified from fused condition, but in addition they possess substantial homogeneity or uniformity of composition throughout, in degree characteristic of solidification from such fused condition. The chromate sensitizer is at least in part dissolved in the fluid ammonium nitrate phase at the temperature at which the melt is cast, and in any case becomes uniformly-distributed throughout the melt in extremely intimate and effective asso- The cast charges described in the foregoing examples are all capable of burning when ignited,
for the generation of gas pressure which comprises mixing ammonium nitrate with at least one fusion promoting ingredient solid at ordinary temperature, said ingredients being adapted to render the charge pourable at a temperature not exceeding about 0., rendering said mixture pourable by at least partial fusion at, a temperature not exceeding about 115 C., thereafter adding from 2 to 20% based on the weight of ammonium nitrate of a chromate compound adapted to sensitize the thermal decomposition of the charge, adding at som point during the mixing operation an oxidizable carbonaceous material sufllcient maximum to bind a preponderant proportion of the oxygen present in the combustion products of the charge in the form of'carbon monoxide, and casting the charge by pouring without appreciable delay after addition of the chromate compound.
3. Aprocess for the production of combustible explosive charges in compact form and suitable for the generation of gas pressure which comprises mixing ammonium nitrate with at least one oxidizabl carbonaceous fusion promoting ingredient, such ingredients being suificient in amount to bind a preponderant proportion of the oxygen present in the combustion products of the charge in the form of carbon monoxide and adapted to render the charge pourable at a temperature not exceeding about 115 rendering said mixture pourable by at least partial fusion at a temperature not exceeding about 115 (3., thereafter adding from 2 to 20% based on the weight a v I 7 fusion promoting ingredient consists oi mazne slum nitrate hexahydrate. I 1
6. A process as defined in claim 2 in which one fusion promoting ingredient consists or an alkali metal nitrate.
7. A- process as defined in claim 2 in which the fusion promoting ingredients comprise a mixture of (a) an organic amino derivative which is not more than weakly basic and (b) magnesium nitrate hexahydrate.
Number Name Date 422,514 Emmens Mar. 4, 1890 Number 1,671,792
Number 8 t Name Date Stoops May 29. 1928 Boyd Jan. 12, 1982 Stoops May 9, 1988 Spaeth Au. 1, 1938 Naoum July 81, 1934 Holm Apr.17,1937 Kirst Jan. 31, 1989 Cook Nov. 12, 1940 FOREIGN PATENTS Country Date Great Britain Feb. 12, 1920 Great Britain Mar. 11, 1936 Great Britain Feb. 15, 1938 Great Britain Apr. 20, 1942 Great Britain July 4, 1945