US2314810A - Explosive composition - Google Patents

Description

Patented Mar. 23, 1943 COMPOSITION Clarence Herman Winning, woodtury. N. 3., as-

signor to E. 1. du Pont de Nemonrs & Company, Wilmington, Deb, a corporation of Delaware No Drawing.

This invention relates to explosivecompositions containing a water-soluble inorganic salt, 7 and more particularly to ammoniumnitrate explosives. a

This application is'a continuation-in-part of my copending applications Serial No. 288,131, filed August 3, 1939, and Serial No. 354,825,1iled August 30, 1940.

Ammonium nitrate is a very extensively used ingredient in present day high exploslvesof the 12 Claims.

App ication February 18, 1941, Serial No. 379,445

My invention is applicable with advantage to V all explosive compositions containing a watersoluble salt, whether this salt is ammonium nitrate, sodium nitrate, a chlorate or perchlorate,

or other soluble salt. I find it particularly important in the case-of ammonium nitrate explosives, and especially in such compositions containlng an explosive nitric ester, nitroglycerin for dynamite type. It replaces nitroglycerine in increasingly larger proportions for a variety of reasons, particularly because it possesses high explosive strength, has outstanding safety proper-- ties, and is economically attractive. Ordinarily,

it is used with some particular sensitizing agent,

either explosive or non-explosive in nature. While ammonium nitrate explosives have been used with great success, one disadvantage of this ingredient has always been evident, namely, that it has a great amnity for water. Because of this fact, there is a tendency forexplosive compositions highin ammonium nitrate to become hard and set on storage in the presence of even small amounts of moisture. This brings about a decreased sensltiveness of the explosive and a lesser degree of uniformity in performance. The water resistance of ammonium nitrate explosives is generally low because of the presence of this very soluble salt.

An object ofthe present invention is an explosive composition containing at least one watersoluble salt and having improved water resistance. A further object is an ammonium nitrate explosive of enhanced water resistance. A still further object is an explosive containing ammonium nitrate wherein an ingredient is present which tends to prevent the harmful penetration of water. Additional objects willbe disclosed as the invention is described more at length hereinafter.

I haveiound that the foregoing objects are ac- 4 complished by including a grain sorghum derived intend to designate various types of cereals such as kafilr corn and broom corn; in other words, cereals that may be classified botanically, as "Andropogmz. sorghum." This will include any of certain grain sorghums derived from Sorghum vulaare, having stout, short-jointed, semi-juicy stalks and erect heads. They are cultivated for grain and forage in various regions of the United States and in other countries. Broom corn and kafllr corn are the two representatives of this group best known and most common in the United States.

example. It should be understood, however, that the intention is applicable as well to explosive compositions which contain no ingredient which is itself an explosive, for-example, compositions containing non-explosive sensitizing agents. Many compositions, for instance, contain am monium nitrate or other oxidizing agent sensitized with materials such as aluminum or other finely divided metals. Likewise, certain ammonium nitrate explosives are sensitized with various forms of carbon, and explosive and non-ex-- plosive nitrated hydrocarbons, for example parafiln, charcoal, dinitro-toluene, and the like. My-

invention is equally applicable to these compositions, since they contain the water-soluble salt which must be protected fromwet conditions in the field.

Th 'gdvantages of my invention are illustrated by the followi g specific embodiments, in which A and1B represent ammonia dynamites of similar compositions, A containing ordinary carbonaceous combustibles while B contains ground kaiilr com:

A is

N itroglycerln .Q ..percent 14. 0 l4. Ammonium nitrate .do-.-. 36. 5 36. Calcium stearate.. do 0. 3 0. Sodium nitrate. -do..- 35. 8 35. Wood pulp"... -do.. 1.0 1. Prior art meals do' 8. 9 0. Kalil: oorn do- 8. Sulfur ..do-. .3. 0 3. Chalk d0 0. 6 i 0.

' 100.0 '100. Densityctgs./ 50lbs.l% x 8" 112 10 The protection alforded the explosive by the ground kafiir com in sample B, was demonstrated by the results of a leaching test. Using 1%, x 8" cartridges of compositions A and B, these were partly opened and immersed in l /z'x 9" cans, iilled with water. The supernatant liquid in the two cases after 2'i hours amounted to and 00., respectively, for A and B, the respective specific gravities of said liquids being 1.140 and 1.025, showing the greater protection from loss of soluble salts in the case of the explosive containing the kafiir corn. The lesser degree of wet-' ness of the same powder is shown by the fact that A, after the leaching test, comprised 5%" of highly wet powder, 1 /4."'of moderately wet powder, and no slightly damp powder as .1;

responding quantities or 1", 3 and 2%" for B In a second leaching test, additional evidence was given of the improved resistance to water imparted by the presence of the kaflir com. Cartridges'of 4" x dimensions were used, and four holes of /3" diameter were made in the side wall at each end, the cartridges then being sub.- jected toa water pressure of lbs. per square inch for 24 hours. At the end of the test, dynamite A, containing meals of the prior art, had shrunk to a. column of highly wet material of 3 x 6 size. The weight of the cartridge had decreased from 2622 to 1563 grams, some of the latter weight being due to the water present.

In the case of dynamite B, containing kafiir corn, the weight of the cartridge had increased from 2680 to 2831 grams. Of the 4 diameter column of powder remaining, 2" was high Wet, 2" slightly damp, and 4" entirely dry. The explosive B was capable of detonation by a blasting cap at the end of the test.

The kaflir corn, when present in explosives of the type described, is capable of forming a cohesive and protective paste with the more or less dilute solutions produced when water comes in contact with the outer or exposed portions of explosives containing water-soluble salts. Ordinary flours, meals, and starches do not disperse satisfactorily and do not form protective pastes. As examples of these latter materials, I may mention untreaded wheat flour, corn meal, tapioca starch, and the like.

The dispersions formed by'mixture of ordinary starch products with relatively small amounts of either'water or dilute nitrate solutions, without application of heat, are such that there is a rapid separation of the flour, meal, starch, or the like. The ground kafilr corn acts differently in that the greater partof the material remains colloidally dispersed and suspended, on dilution of a relatively dry paste with dilute nitrate solution, even though no heat has been applied at any time.

When kafiir corn meal according to my invention is used in compositions suchas ammonia dynamites, it appears that the entrance of the first traces of water brings about a paste or gel formation. This gelatinization in the outer portion of the explosive-retards the rate of water penetration toward the interior of the explosive column. The gelatinous structure formed also prevents segregation of liquid or solid ingredients of the explosive such as would be caused by water penetration and softening of the composition. The cohesive gel or paste also decreases the loss of solid or liquid ingredients from partly opened cartridges by reason of gravity flow. The leaching of soluble salts is likewise lessened 'by the presence of the paste.

It will be understood that, in order to obtain the most favorable results. the kaiiir corn or broom corn meal, or similar meal, should be in finely divided condition. Preferably, said meal should be in a state of subdivision such that the major portion, that is more than 50%, will pass a Gil-mesh screen. Furthermore, the ground kaffir corn is desirably included in the explosive composition in pulverulent form during the manufacture of the explosive composition. no

- paste being formed at that time. I do not intend water-insoluble metal soap, such as calcium stearate, which will have a protective and coating efiect on the ammonium nitrate against water or moisture. The resence of this latter ingredient, together with the kamr corn meal, gives very beneficial results. fective, however, without the presence of the water-insoluble soap. Preferably, said kafllr corn meal will be used in an amount not greater than 15%, and I find aquantity between 1 and 9% to be advantageous. The invention is applicable with great advantage in ammonia dynamites containing ammonium nitrate and nitroglycerin in amounts not exceeding for example between 3 and 25%. It has important applications also in the case or compositions containing other high explosive compounds, such as nitrostarch, trinitrotoluene, and the like, in the presence of ammonium nitrate or other water-soluble salt. Furthermore, it is effective in the case of compositions in which the ammonium nitrate is sensitized by means of paraffin, dinitrotoluene, carbon, aluminum, other powdered metals and alloys, and many other materials.

The ground grain sorghum such as kailir corn or broom corn, according to my invention, has

been stated to be present preferably in pulverufrom the scope of the invention. I intend to be limited, therefore, only by the following patent claims. I

Iclaim: I

1. An explosive composition comprising a water-soluble oxygen-supplying inorganic salt, a

sensitizing agent, and a cereal meal of the species Andropogon sorghum in pulverulent form.

2. The explosive composition of claim 1, in which the cereal meal is kafllr corn.

3. The explosive composition of claim 1. in which the cereal meal is broom corn.

4. An, explosive composition comprising am- 'monium nitrate, a sensitizing agent, and a cereal monium nitrate, an explosive sensitizing agent,

and kaifir corn meal in pulverulent form.

8. The explosive composition of claim 7, wherein the sensitizing agent is nitroglycerin.

9. The explosive composition of claim 7, wherein the sensitizing agent is an aromatic nitrocompo 10. An explosive composition comprising ammonium nitrate. a non-explosive sensitizing agent and kaflir corn meal in pulverulent form.

11. The explosive composition oi claim 10, in which the sensitizing agent is a powdered metal.

12. An explosive composition comprising ammonium nitrate, between 3 and 25% of nitroglycerin, and not more than 15% of kafiir corn meal in pulverulent form.

The ground kafllr corn is ef-