US2358385A - Explosive - Google Patents

Description

Y? ls. g Face c ELOSEVE Clyde Gliver Davis and Walter Corneiius Holmes, Woodhury, N. 3., asslgnors to E. El du Pont de Nemours a Company, Wilmington, Bet, a corporation of Delaware no prawns. Application April 10, 1941,

Serial No. 387,915

7 Claims. (Cl. 52-11) This invention relates to a detonating explosive so that the explosive when once initiated will in granular form, and more particularly to a high function effectively. Various such explosive nidensity expiosive of high ammonium nitrate cont-rates are applicable advantageously, for examtent capable of efiective use in the presence of ple nitrostarch, nitrocellulose, ground smokeless powder, which consists mainly of nitrocellulose. f ree flowing explosives offer a number of adpentaerythritol tetranitrate, nitromannite, and vantages in use, particularly with respect to load the like. ing, since they can be poured into the borehole In addition to the foregoing ingredients, it is made to fill it completely without the necesdesirable that a binding agent be present, comoi cartridging or tamping. Black powder lo prising a plant product capable of forming a and ya 'ous explosives containing high ammonicohesive paste on contact with unheated water. um nit 'te contents are examples of free flowing The presence of this ingredient prevents disinteeXploslv-es of the prior art. Such compositions gration of the explosive grains during passage have been satisfactory from the viewpoint of through water. Various materials of this type loa g properties under dry conditions, but have may be used, for example a pregelatinized cereal been out of the question when the boreholes conproduct such as a flaked corn product in finely tained, or were filled with, water. Because of the divided condition, where the cereal product has high content of water-soluble salts in such an been preheated to an elevated temperature or plosives, largely sodium or ammonium nitrate, or otherwise treated so that it is capa e f o min both, such compositions not only lo much'of 2 a cohesive paste with cold'water. Other suitable their soluble content by leaching but cease to be p s eg Vegetable p oducts a e We flour, capable of functioning as explosives under wet ey fl r, t fl r, spelt e i s edm conditions. and the like. Preferably we employ linseed meal The object of the present invention is a high or barley flour, since these tend to cause a conexplosive of freefiowing nature, capable of fun strictive efiect on contact with water and formationing effectively after immersion in water. A tion of the cohesive protecti pasta s in further object is an ammonium nitrate explosive t tends to give an increased e tyhe in granular form which is compatible with wat r, formation of the paste-at the initial penetration A still further object is a high density explosive of water into the explosive tends to bind together of the foregoing type, possessing high strength. the materials and to prevent loss of the sensitiz- Additional advantages will be disclosed as the in agent from t e e p i e grain. ulverulent vention is described more fully hereinafter. p v s n inin u h in redients are We have found that the foregoing advantages claimed in the patent to Winning, United States are accomplished and the disadvantages of th PatentNo. 2,231,043. We find it desirable to use prior art overcome when we prepare pressed agthe pa t ma e a in n amount begregates or grains preferably of flowable size tween .5 and 10% of the entire composition. comprising an inorganic oxidizing agent, a solid Examples are given in the following o et ods explosive nitrate of an aliphatic polysaccharide, f r rryin o r n n i n and f r a nin and desirably a vegetable product capable of the desired free-flowing, water-compatible exforming a cohesive paste with unheated water. p s- The individual grains should have a density a greater than 1.0, or, in other words, should be sumcienfly heavy that they Wm sink in water The following ingredients were weighed in the a tions designated and were introduced into While we preierably employ ammonium nipropor trate as the inorganic oxidizing agent because of figure's gelatin dynamite mixing bowl Example I the additionalexplosive strength imparted by its Per cent use, this salt may be replaced completely or in Nltrostarch 22.0 part by other oxygen-supplying salts, such as Ammonium nitrate 58.0 sodium nitrate, potassium nitrate, various inor- Linseed meal 4.5 ganic perchlorates, and the like. Barley flour M 4.5

The presence of a certain amcuntof a solid- Sodium nitrate 10.0 explosive nitrate of an aliphatic polysaccharide aluminum powder 0.5 is necessary in the compressed aggregates ac- Chalk 0.5 cording to our invention in order to impart the desired degree of sensitiveness to propagation, 100.0

nitrostarch of 22.7% water content. After mix ture, the above composition formed a stiff gel. The material was removed from the mixer, pressed into flat layers about 1" thick, and then dried until firm, though not to absolute removal of water. The material was granulated through a 4-mesh screen on a suitable granulator and dried completely to hard grains.

The following velocities of detonation were obtained when tin tubes were filled with water and the explosive poured in until it reached the top of the tube:

Diameter Per cent Velocityof can water present meters/sec.

Inches From the foregoing results it is seen that the explosive is not only compatible with water and capable of detonation after immersion, but that greatly increased velocity resulted in the case of the immersed powder when this was in a 2-inch diameter column- A half-stick of 40% straight dynamite was used as primer in all cases.

Example II A mixing of the following composition was made in the same type of apparatus as used for Example I, and by the same procedure:

In this case, five parts of water was added with the ni-trocotton, based on the total weight of the mixing.

The granulated material was again poured into tin tubes filled with water, as in Example I, the water amounting to 33 of the total weight of the material in the can. Detonation was obtained. I

Example III A 7000 gram mixture was made of the following ingredientsin a figure-8 mixing bowl:

a Per cent Nitrostarch 30.0 Ammonium nitrate 56.5 Flaked corn product 4.5 Linseed meal 4.5 Wood pulp 4.0 Chalk 0.5

The above ingredients were first mixed dry for 5 minutes, then 400 grams of water was added. The mixing was continued for 5 minutes, at which time the composition had become a stiff gel. The

It was then granulated through a 6-mesh screen, and dried completely. The material that passed through a 16-mesh screen was removed. The grains were poured into 2" tin tubes. When initiated with a #6 cap, a velocity of detonation of 2200 meters per second was obtained. The powder, when in 3" cans containing 33 /a% water,

gave a complete detonation with a 40% straight dynamite primer. I

The foregoing examples illustrate specific embodiments of the explosive according to our invention. It will be seen that the invention permits the preparation of a free-flowing explosive that is capable of initiation and propagation of the detonation after immersion in water. In its ability togive satisfactory blasting execution after immersion in water for several hours,,our explosive is equaled only by the gelatin dynamites or ammonium nitrate explosives completely enclosed in metal or other water-proof containers. No other free-flowing explosive can approach it in this respect. Preferably we employ compositions containing more than 50% ammonium nitrate. Lower strength explosives are obtained when the above salt is replaced partly or entirely by sodium nitrate, the contents of solid organic nitrate being equal. In copending case, Serial No. 376,842, filed January 31, 1041, a granular explosive is disclosed compatible with water, which utilizes grains into which not less than 15% of nitroglycerin or other liquid explosive nitric ester has been absorbed sumciently to leave the grain dry and freeflowing. The explosive according to the present invention, containing no liquid explosive ingredient, has the advantage that the absorptiveness of the grain need not be considered; hence there is no limit to the density of the grain that can be used, and for use in water we would prefer a grain of the highest attainable density.

It will be understood that the exact solid ni-' trio ester used will control composition to a certain extent. Preferably we use nitrostarch as such solid nitric ester, as'this allows the preparation of a high density explosive without the necessity of a great amount of compressionbut merely granulation. This sensitizing ingredient preferably should be present in an amount not less than 15%. The presence of the pasteforming material, and its behavior on contact with water, not only aids in binding the materials of the grain together, but will in many cases tend to increase the density. High density, of course, means a greater bulk strength for the explosive, which is an important consideration. It has been stated that the individual grains should be suillciently dense to sink when poured into water. When using nitrostarch as sensitizer, we desirably employ-grains having a density greater than 1.25, and advantageously above Various methods may be used for manufacturing the foregoing explosive. ple, employ methods common to black powder manufacture and incorporate the blend under heavy revolving wheels, subsequently granulating material was removed from the bowl, spread on trays, pressed gently and dried partly at the wheelcake. A second method would consist in blending the ingredients in an ordinary dynamite mixing apparatus, preferably of the type used in the manufacture of gelatinous dynamites, after which the caked material could be put through a conventional granular. In both of the foregoing methods, the ingredients would be mixed in the presence of water. A third procedure would be to mix the blended materials in We may, for exam- 2,358,385 r h l 3 a substantially dry condition; containing for example less than 1% of water, and then to feed the blend through a tablet or pill machine. If a free-flowing powder is desired, it will be desirable to screen outthe fine particles. Preferably we use finished grainsof a degree of fineness such that substantially the greater part will pass a 3-mesh and be held on a iii-mesh screen.

A granular explosive of the type described herein will ordinarily be insensitive to the action or a blasting cap when free from fine dust, but will detonate when initiated with a suitable booster, especially mder water. The explosive, therefore, can be packed in bags and handled in accordance with this degree of insensitiveness.

would possess a high order of safety in'handling. It has been stated in the foregoi g that desir.

ably a binding agent is present comprisinga plant product capable of forming a cohesive paste on contact with imheated water. While such an ingredient aids in binding the grains together and is highly preferable, its presence is not essential. Sufllcient carbonaceous combustible material must be present, however, in addition to the organic sensitizer, to react with at least a portion oi the oxygen available from the ammonium nitrate or other inorganic oxi agent When the explosive of our invention is poured into water, the grains quickly become wet and sink rapidly to the bottom. While the soluble portion oi! the grains is dissolved and passes into the surrounding water, the grains retain their structure and appearance and no solid aliphatic nitrate is lost or segregated. Th dissolved ingredients appear to take part in the explosive chemical reactions during detonation-and contribute to the energy of the explosion.

While our invention has been described with considerable thoroughness in the foregoing, it will be understood that many departures may be made from the details of operations and the compositions cited without deviation from the scope oi the invention. We intend, therefore, to be limited only by the following claims.

We claim: I

.1. A free-flowing detonable explosive in granular form free irom liquid explosive ingredients comprising compressed blended aggregates of an inorganic oxidizing agent, at least of a solid explosive nitrate of an aliphatic polysaccharide. and a plant product capable of forming a cohesive paste withimheated water, the individual grains of said explosive having a density greater than 1.0.

2. A free-flowing detonable explosive in gran- -ular form free from liquid explosive ingredients comprising blended aggregates oi ammonium nitrate, at least 15% of a solid explosive nitrate of an aliphatic polysaccharide, and a vegetable product capable of forming a cohesive paste with unheated water, the individual grains of said ex- 15 plosive being comp essed to a density suflicient to In other words, the explosive of our invention cause them to sink in water.

3. The explosive oi claim 2, in which the solid aliphatic nitrate of an aliphatic polysaccharide is nitrostarch."

4. The explosive of claim 2, in which the solid aliphatic nitrate of an aliphatic polysaccharide is nitrocellulose.

5. The explosive or claim 2, in which the solid aliphatic nitrate of an aliphatic polysaccharide is ground smokeless powder.-

pressed blended aggregates of ammonium nitrate, at least 15% of a solid explosive nitrate of an aliphatic polysaccharide and a plant prod- 3 of said explosive having a density greater than '7. A free-flowing, granular detonatingexplosive capable of functioning efiectively after immersion in water, said explosive being free from 40 liquid explosive ingredients and comprising compressed blended aggre ates of not less than 15% nitrostarch, between 40 and 75% ammonium nitrate, and not less than 4% of a plant product capable of forming a cohesive paste with unheated water, the individual grains of said explosive having a density greater'than 1.25.

CLYDE OLIVER DAVIS. CORNEIIIUS HOLMES.