NITROCELLULOSE EXPLOSIVE CONTAINING A CHARCOAL BINDER-OXIDIZER MIXTURE

3,473,982 NITROCELLULOSE EXPLOSIVE CONTAINING A CHARCOAL BINDE, R-OXIDIZER MIXTURE Ilermann Herzog, deceased, late of Kaufbeuren, Germa,,yy by Johanna Herzog, heir, Kaufbeuren, and Woldemar Hintze, Adolzfurt, Germany, assignors to Dynamit Nobel Aktiengesellschaft, lyoisdorf, Germany No Drawing. Continuation-in-part of application Ser. No. 573,472, Aug. 19, 1966. This application Mar. 1, 19(;R, Ser. No. 709,839 Claims priority, appfication Germany, Aug. 21, 1965, D 48,033 Int. Cl. C06b 1/00, 5102, 21102 U.S. Cl. 149-20 13 Claims 0 31473,982 United States Patent Office Patented Oct. 21, 1969 2 v elocity. These compositions find ready application in Powder-type propellants in rocket engines. However, they find little use in applications requiring a high detonating activity, a hi.-h reaction velocity as well as an improved stability at high temperatures. 5 S U M M A R Y O F T H E I N V E N T I O N ABSTRACT OF THE DISCLOSURE The present disclosure relates to an improved explosive composition which comprises about 20 to 80% by weight nitrocellulose @and about 80 to 20% by weight of a charcoal binder-oxidizer mixture containing about 5 to 30% by weight of the charcoal binder and about 95 to 70% by weight of the oxidizer. Advantageous, the explosive compositions of the present disclosure contains a high oxidizer content and contains up to about 1% by weight of nitroglycerin. The ptesentdisclosure is also directed to an improved method of manufacturing said explosive composition. BACKGROUND OF THE INVENTION This is a continuation-in-part of application Ser. No. 573,472, filed Aug. 19, 1966, now abandoned'. The present invention relates to improved explosive compositions and to a method of manufacturing said compositions. More particularly, the present invention concerns explosive compositions which exhibit a high detonatin,@ activity and reaction velocity and therefore are useful, for example, in propellant charges, prj'-mer char@,,es, ignitin.- charges, and the like. The use of black powder in the explosive industry is well known. Black powder, which is basically a mixture of saltpeter (potassium nitrate), carbon @and sulfur, is characterized by good ignitability, a constant igniting capacity and a uniform burning consumption. It is well known in the prior art that nitrocellulose can be mixed with black powder to produce an explosive composition which is capable of generating a greater amount of gas and heat than that generated by black powder alone, while maintaining @all of the other aforementioned advanta.escharacteristics of black powder. However, this mixture of nitrocellulose and black powder has many disadvanta-es, which include, for example, the undesirable influence (yf the sulfur contained in the black powder on the stability of nitrocellulose at hi.-her temperatures, say over 100' C., the formation of toxic sulfur reaction ptoducts, particularly hydrogen sulfide, during the buming of the blaek powder in the presence of nitrocellulose, which may involve considerable danger depending upon its place of use, and further the causing of heavy fouling on breech mechanisms and other firing components when black powder is fired as a mixture with nitrocellulose. It is also well known in the prior art to produce smokeless powder by using large amounts of nitroglycen'n content, for example at least 30% by weight and even as high as 50% by weight and higher. In addition, these known compositions contain small amounts of oxidizer, e.g., saltpeter and frequently use only carbon black as the carbonaceous binder, and in very small amounts. The advanta.-es of these compositions reside in that the powder exhibits a high mechanical sta:bility which eliminates powder breakup and loss with a resultant low-ertng, pf An object of the present invention is to produce an improved explosive composition which exhibits a high 10 detonating activity and reaction velocity and therefore is us&ful in propellant charges, primer or detonating charges, igniting charges, and the like. A further object of the present invention is to produce 15 an explosive composition which has all of the advantages of black powder and mixtures of black powder with nitr@ocellulose while substantially eliminatin.- the @disadvantages. A still 'further object of the present invention is to 20 provide an improved method for rrianufacturing the explosive composition of the present invention. Another object of the present invention is to produce an explosive composition which exhibits improved stability at high temperatures, the substantial elimination of the 25 formation of toxic sulfur reaction products while the explosive is being consumed, and an overall improvement in the operation of firing and breechmechanisms. Other objects and futther scope of applicability of the present invention will become apparent from the detailed 30 description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of i llustration-only, since various changes and modifications within the spirit and scope of the invention will become apparent to those 35 skilled in the aTt from this detailed description. Pursuant to the present invention, it has been found that the above-mentioned disadvantages may be elimi-@ nated and a much improved explosive composition and 40 method of manufacture may be obtained by the addition to nitrocellulose, a mixture containing a charcoal binder and an oxidizer such as saltpeter. Thus by eliminating the presence of black powder, and thus sulfur fr(ym the explosive composition of the present invention, the dis45 advantages enumerated above normally associated withexplosives containing sulfur-containing matetials are also eliminated. Furthermore, the improved explosive com@ positions of the present invention have not been obtained at the expense of its ballistic. values. For example, when 50 firing a weapon with an explosive composed of nitrocellulose and black powder (a mixture of potassium nitrate, sulfur, @and carbon) an initial velocity of 567 meters/see. was measured at a pressure of 1611 atmospheres. Using the same weapon, the same char-e and the 55 same projectile but substituting the explosive co@mposition of the present invention, an initial velocity of 577 meters/ sec. was measured at a pressure of 1622 atmospheres. These results show a substantially equivalent balli8tic performance for both explosive powders. 60 Unlike some of the prior art powders, the explosive composition of the present invention exhibits only a minor mechanical strength since the granules formed of saltpeter and charcoal therein, constituting a sulfur-free powder with specific properties, are adhered to each 65 other only slightly by the nitrocellulose. However, bei@au , se of the high oxidizer content, for example saltpeter, and the use of a charcoal, the explosive compositions oT detonating charge of the present invention exhibits a substantially higher detonating activity as well as a higher 70 reaction velocity. The advantage of using charcoal as compared to other carbon carriers, for example carbon black, is based on the high content of volatile components

3,473,982 3 in the charcoal which exert an accelerating effect upon the -reaction of the mixture. One of the -features of the present invention resides in the fact that the nitrates (oxidizer) which are - employed are first mixed and combined separately with the - charcoal 5 as a carbonaceous binder, and are manufactured in the form of a finely particulate, accurately dimensioned product, and are thereafter kneaded together with the alcohol-moist nitrocellulose to form a plastic mass. By using this kind of manufacturing method, the - specific 10 properties of the gun pgwder are particularly apparent, in addition to the specific properties of nitrocellulose, that is a hot flaine and a high amount of gas. The amount of nitrocellulose present with the chaTCoat binder-oxidizer mixture to form the explosive composition 15 of the present invention will vary depending upon the particular use for which it is intended. Advantageously, the explosive composition of the present invention will contain about 20 to 80% by weight, preferably 30 to 50% by weight, of nitrocellulose and about 80 to 20% by weight 20 preferably about 70 to 50% by weight, of the - charcoai binder-oxidizer mixture. The charcoal bi nder-oxidizer mixture may contain about 5 to 30% by weight of the charcoal binder and about 95 to 70% by weight of the oxidizer. More particularly, the binder is present in an 25 amount of about 10 to 25% by weight and the - oxidizer is an amount of about 90 to 75% by weight. The carbonaceous binder used in the present invention is limited to charcoal. The advantage of using - charcoal as compared to other carbon carriers, e.g. carbon black 30 is based on the high content of volatile components in the charcoal which exerts an accelerating effect upon the reaction of the mixture. The oxidizer employed in the composition of the present invention can be any of the inorganic nitrates such 35 as, for example, ammonium nitrate, and nitrates of the alkali and alkaline earth metals, such as sodium - nitrate, potassium nitrate (saltpeter), calcium nitrate, magnesium nitrate, strontium nitrate and beryllium nitrate. Of the oxidizers, potassium nitrate is preferred. Effective results 40 can also be obtained with mixtures of any one of the above nitrates, for example, a mixture of sodium nitrate with ammonium nitrate. As mentioned above, the amount of oxidizer used will vary depending upon the sensitivity and explosive effect desired, and these in turn are de- 45 pendent upon the particular nitrate or nitrates used. Because of the high oxidizer content and the use of charcoal, the explosive composition of the present invention has a substantially higher detonating activity and reaction velocity than compositions using small amounts of 50 oxidizdr and carbonaceous binders other than charcoal. The explosive compositions of the present invention can be mixed with various adjuvants such as solvents, plasticizers, stabilizers, ballistic modifiers, and the like. Suitable solvents include organic alcohols, such as for example, ethyl alcohol, isopropyl alcohol, te rtiary--butyl 5,5 alcohol, alkoxy alcohols, such as diethyline glycol, phenol, etc.; ethers, such as for example, ethyl ether, tertiarybutyl methyl ether, benzyl phenyl ether, etc.; - ketones, such as for example, acetones, ethylmethyl ketone diphenyl ketone, etc.; esters such as for example, @uty, 60 acetate and isopropyl acetate, and various other hydrocar'bons including, for example, benzene and toluene. Advantageously, plasticizers which can also act as solvents and energizing modifiers are added to the explosive . . 65 composition of the present invention. Suitably plasticizers include nitroglycerin, butane triol trinitrate, ethylene glycol dinitrate and the like. These materials may be mixed with one or more miscible deterrents, such as, butyl pht4alate, dimethylsebacate, dibutyl succinate, dibutyl 70 adipate, triacetin, ethyl diphenyl phosphate, tributyl phosphate, and the like. The preferred plasticizer is nitroglycerin which is advantageously present in an amount up to about I% by weight. Suitable stabilizing agents include diphenylamine, 2-ni- 75 4 trodiphe;iylamine, the centralites and many others. Other ingredients, such as dioetyl.phathalate, lead stearate, red lead, dinitrotoluene, and the like, may be incorporated in the explosive composition of the present invention to obtain particular ballistic properties, as desired. As recited above, the explosive mixture of the present invention is readily prepared by mixing the ingredients in a particular manner. Advantageously, the charcoal binderoxidizer mixture is in a finely granulated form before it is kiaeaded together with the nitrocellulose to form a plastic mass. The amount of solvent which can be used in the explosive composition of the present invention will vary, depending upon, for exam@ple, the amount of plasticizer present and also upon the desired consistency of the mixture, which can vary from a gelled oil or thick, barely pourable mixture, to a quick-flowing liquid. The ratio of the solvent to the explosive composition for example, can ran.-e from about I to I to about 20 to 1, and even higher, preferably about 3 to I to about 15 to 1. In one method of preparation, the explosive composition is prepared in gelatinous sheet form. Gelatinization is effected by rolling the explosive mixture with heat rolls, supplemented by intermediate kneading. Generally the production of such sheets requires a series of rolling stages, with the removal of volatile matter being accomplished during the final rolling steps, or by a subsequent drying treatment. The resulting sheet can then be inserted into an extruding dye where the composition may be extruded by conventional extrusion techniques. A typical method for producing suitable grains from explosive compositions is an extrusion technique in which the explosive composition, in a flowable forni is introduced into a hopper and the product extruded by screw extrusion into suitable grains. The extruded product can then be cut into the desired length and dried. The present invention is illustrated in detail by the following example which is not to be considered as limiting. Example I 2.8 kg. of nitrocellulose, moistened with ethyl alcohol, is kneaded with 2-3 liters of ethyl ether. Thereafter, 4.2 kg. of a mixture of potassium nitrate and charcoal, consisting of 80% by weight of potassium nitrate and 20'Yo by weight of charcoal, is added and the resultant mix is kneaded for about two hours. During the kneading procedure, 1% by weight of dibutyl phthalate (plasticizer) and 1% by weight of acardite (stabilizer) are added. The mass, kneaded into a compressible condition, is pressed through a nozzle, cut into pieces of desired length and dried. EXAMPLE H 2.1 kg. of nitrocellulose, moistened with ethyl alcohol, is kneaded with 2-2.5 liters of ethyl ether. Then, 4.9 kg. of a mixture of potassium nitrate and charcoal, the latter being in an extremely fine particulate form, containing about 75% by weight of potassium nitrate and 25% by weight of charcoal, as weli as 1% by weight of acardite 11 and about 1% by weight of nitroglycerin are added and the resultant mix is kneaded for about two hours to -form a compressible mass. The kneaded mass is pressed through a nozzle, cut into the desired length and dried. Acardite 11 is a urea derivative, similar to centralite, but having one less ethyl residue. The structural formula thereof is C6115-NH-C O-N-C6Ha I U2145 We claim1. An explosive composition which comprises about 20 to 80% by weight nitrocellulose and about 80 to 20% by weight of a charcoal binder-inorganic nitrate oxidizer salt mixture, said mixture containing about 5 to 30% by weight of the charcoal binder and about 95 to 70% by weight of the oxidizer.