US2356149A - Blasting explosive composition and method - Google Patents

Description

"BL'Asr'rNGnxPLosrvn COMPOSITIONAND" 4 METHOD Olyde O. Daviawoodbury, N. J. asslgnor to E. I:

- du Pont de Nemours & Company, Wilmington,

Del; a corporation of Delaware No Drawing. Application September 18, 1940, .5

" fiSerial No. 357,287

" is ca m. (cits-#14) This inventionrelates teanewand'improved "enable those skilled in theart to duplicate mil form of explosive and particularly to a high exproduct:

plosive-free from nitroglycerin, possessing ia'vorq m p c able 'properties,'and in a form'convenlentfor use. 1 fouOwingmgr-ments were Weighed out v It has'long been recognized that black powder 6 aam designated: j

isan excellent coal-getting explosive in so far V Grams as its blasting effect is concerned. A'very deg 3500 sirable heaving effect is obtained with this ex- Sodium mtratp 300 plosive, which results in an increased amount of wv ulp 600 the desired lump coal rather than an-"undue S lf I 100 "shattering or the material. Th disadvantages I 1 1 I I ofblack powder are from the safety point of 1 1 10,000

name of considerable duration, which-tends to view,- sincesits explosion is accompanied by a Five hundred g m ld r addedto the ignite any inflammable gases present in the coal 16 andthe o nb o was intimately blended mine.

I by causing heavy, revolving wheels to pass Because of thesafety hazards with black'powthrough and'over it for a period of 80 gamut:

g y H to den-this has been largely. replaced in coal mines m l P 7 d n of h w e i f by permissible explosives, which possess a much m the ma into the w W d higher degreeofsafetyagainst gas and coal dust The caked material was then an agmnu' igmmma The permirssimesn commonlycompflse lated." The" fines passinga16-mesh screen were compositions high inrammonium nitrate content j discarded an'd'the grains'held on that. screen f'and containing sufflcient nitroglycerin to. .imj 3?? retained?" f g l f g gl ig part a proper degree of 'sensitiveness to theexa an p j 3 gi i 8 plosive.j Such compositions usuallyhave a highw l ff F Y S9 t f ;%i f n9 i er. velocity of detonation thanis desired, because Qnate-d-w t commem as ng vof the presence of the nitroglycerin, and the pres- 6 2 2222,! 9 55 95 IF P WQ 'W ence oi this latteringredient is a drawbackim p P Grams several respects 'The permissibles likewise are 1: 4 .or -'linaril y ofa pulverulent naturefso that spillgfiig g f ag 7"f"f 3% ing of some of the explosive is likely, if an at- Wood puln 1 800 temptism qde to use a portion of a cartridge. 1

. Aluminum powder .400 The objectof the present inventionis an im- TNT 500 proved explosive of relatively low velocityadapted) the blasting of coal A further objectgis an The first three of the above ingredients were explosive of relatively low velocity in a form mixed under revolving wheels for Period of 30 convenient for hand1mg. Agfwurther object is an m'inutes, after addition of 300 grams'ofwater. explosive possessing a .high degree of safety inv g ag g g gg g g ffgh im tm inflammable. atmospheres and constituting an da added 3 .3 5 g m improvement over granular permissibles. A still der the wheel f 33 m x .iurther object'is an explosive of convenient form mixed Q g 2g2; i fifg fi we adapted for. blasting down'coal without undue 1 I l shattering. Additional objects will be disclosed, Screen and added while damp-the warse' I as the invention is described more in detail here- 4 drygramsprepared'mithe'flrststw of the an inorganic oxidizing salt and at least one oxi- 'by a more sensitive explosive medium capableof ess, the-proportion of fines to grain being approximately 2 to 1. 'Theflne material was sensitive to the action of a blasting cap, hence served as a sensitizer for the grains.

The blend of coarsegrains and fine, material wastamped lightly intoa die or mold and, made "cohesive by compressing sufficiently to allow .removal from they mold. without disintegration.

.Ifhe die or mold was vprovided with a tapered rod or Pin vextending .coaxially{through it and atinafter.. p v v a The foregoing objects are accomplished according to my invention by producing a cohesive block of explosivecomprising a granulated blend of dlzable material, thesegrains being surrounded initiation by a commercial initiatoniOr example, a'blasting cap, and of propagation of the explo-' 'slon throughoutthe entire cohesive block of exbashed tqthe emoyable base oftheri'iold. 'I'his plosive.

rod or pin'with 'withdrawn after the :pellet was 1 ri us m thods may e f llow d n D p *formed,"leaving acoaxlal hole in the pellt." The invention. The following examples will serve as ins oh siveblocks of expl siv a cord lie-my llet waslhen'driedat120440" F. 'I'ne'penets weighed approximately 16.3 grams per linear illustrations of specific procedures which will inch (1% diameter), and when four pellets were 2 s,aso,14e

wrapped in paper to form an 8" cartridge the wrapped weight was 140 grams. The pellets were sufficiently sensitive to propagate the explosion across an' air gap of 6 inches, when shot with a blasting cap introduced into the center hole.

The

velocity of detonation, when shot confined in tin tubes, was 1980 meters per second, or about 1800 meters when shot unconfined.

Example 2 A granular form of explosive, inwhich the grain size was such that the material was held on a 16-mesh screen, was prepared from the following composition:

Per cent Ammonium nitrate 84 Sodium nitrate Wood pulp 6 The grains were prepared as in Example 1 and were insensitive to the action of a blasting cap.

The following composition was then incorporated in a mixing apparatus at 85 C. and subsequently cooled in the mixer to 45 C.: 7

Per cent Ammonium nitrate 76 Calcium cyanamide 3 TNT 20 Wood pulp 1 This blend of materials was screened through a 10-mesh sieve and mixed with the coarse, dry grains of .the first step of the process, in the proportion of 3 parts of the granular to 2 parts of the sensitizing explosive. The mixture was formed, as before, into pellets having longitudinal cenwr holes. No water was added to the mixture which was cohesive, as made, and which hardened on standing. The pellets made were. 1%" in diameter by 2" long, with a central hole of diameter. The pellets had a weight of 20 grams per linear inch. Four pellets were enclosed endto end in a paper wrapper and had a wrapped weight of 168 grams. The pelleted exhole of diameter. The mixture at; cohesive as made and hardened on standing. Four pellets were wrapped end to end in a paper wrap per to form a stick of explosive, which showed a velocity of detonation of 1350 meters per second when enclosed in paper' wrapper, and propagated the explosion across a 7" air gap.

In the foregoing examples, the blend of coarse grains and fine material was formed into cylindrical pellets by pressing lightly in a press. An-

grains and more sensitive surrounding explosive.

The composition of the grains of my product comprises at least one inorganic oxidizing salt and at least one oxidizable material. Various oxidizing salts are availablefor-such use and! prefer to employ an ammonium salt, for example, ammonium perchlorate or ammonium nitrate. Ammonium nitrate-is the preferred salt for use because of its known properties and its availability. Other salts, however, may be used such as sodium or potassium perchlorate; sodium nitrate, potassium nitrate, and the like. Various combustible ingredients are likewise suitable, such aswood pulp, various, meals and .iiours,

'starch and plant products generally, sulfur, finely plosive had a velocity of 2160 meters per second when shot in a tin tube, and propagated the explosion across a 1-inch air gap.

Example 3 A grain was prepared which would pass a 6- mesh screen but which. was held on a 16-mesh screen, the composition of the grain being as follows:

- Percent Ammonium-nitrate 80.6 Sodium nitr 8.9 Nitrocotton 4.5 Carbonaceous combustible material 6.0

The grains were prepared in the manner described in U. S. Patent 2,17l,3'l9, and were sensitive to the action of a" blasting cap.

A loose matrix composition was then prepared by'incorporating the following compositionin a mixing apparatus at 85 C. and cooling in the mixer to C.-:

Per cent Ammonium nitrate 76 Calcium cyanamide- 3 TNT 20 Wood pulp 1 divided metals, and theiike. It will be understood that more than one combustible ingredient may be used in the same composition. and more than one oxidizing agent. My preferred composition for grain, for exampleyincludes both ammonium and sodium nitrate. More than 50% ammonium nitrate will be present ordinarily in said grain, and preferably more than 75%. The

combustible ingredients'will desirably be present in an amount sufhcient approximately to utilize the available oxygen inthe oxidizing agent in burning to carbon dioxide and water.

' Any explosive composition sufliciently sensitive to be initiated by a commercial initiator and to cause propagation of the explosion throughout the entire block comes within the scope of my invention. Preferably, this sensitive compositionwil be free from nitroglycerin and other liquid explosives." I find here also an ammonium nitrate composition to be suitable, preferably one containing a relatively high percentage of this salt, for example, over'70%, and at least one sensitizing agent for the-ammonium nitrate, such as aluminum, trinitrotoluene, and thelike.

My explosive composition has been described as consisting of relatively coarse. grains of anexplosive mixture in intimate contact with a more sensitive matrix explosive. While I do not wish to be limited as to the size of grains, preferably they.are sufficiently large to be held on a 30- mesh screen. I find particularly desirable grains held on a 16-mesh screen. 1 Such grains by themselves are ordinarily not sufficiently sensitive to be detonated by is #6 or #a'blasting cap.

In the preparation of cohesive blocks of explosive according to my invention, it is necessary to add water to the more sensitive explosive matrix,

in order that the molded product shall possess sufficient cohesiveness. While various amounts of water may be introduced, we find it desirable to maintain in the mixture an amount of water amounting to at least 2% of this more sensitive portion. This water is removed in the subsequent drying of the pellet or other form of cohesive block.

In the foregoing I have described the embodiment of my invention which I greatly prefer to employ, namely, the cohesive block of the compositions noted. However, it is to be understood that I do not exclude from the broad scope of my invention the particular compositions themselves before they have been molded into block formation. Even these, due to the combined effect of the ingredients and their particular physical arrangement, namely, pellets surrounded by continuous matrix, offer extensive advantages over the compositions of the prior art, especially for the blasting of coal.

My invention is particularly applicable to detonating explosives, for example, those high in ammonium nitrate content. It should be understood, hc wever, that it is not necessarily limited to such explosives. While the invention has been described in detail in the foregoing, it will be understood that many variations may be introduced without departure from the spirit thereof. I wish to be limited only by the following patent claims.

I claim:

1. A detonatlng explosive comprising grains held on a 30-mesh screen and composed of an inorganic oxidizing salt and at least one oxidizable material and surrounding said grains a more sensitive explosive medium free from liquid explosive compounds and comprising a sensitized alkali nitrate composition said medium being capable of initiation by a commercial initiator the whole adhering together to form a cap sensitive cohesive block.

2. A detonating explosive comprising grains held on a 30-mesh screen composed of ammonium nitrate and at least one oxidizable material and surrounding said grains a more sensitive explosive medium free from liquid explosive compounds and comprising a sensitized ammonium nitrate composition said medium being capable of initiation by a commercial initiator the whole. adhering together to form a cap sensitive cohesive block.

3. A cohesive block of detonating explosive comprising a granulated blend of an inorganic oxidizing salt and at least one oxidizable material, said grains being substantially surrounded by a more sensitive explosive medium free from liquid explosive compounds and comprising a sensitized ammonium nitrate composition said medium being capable of initiation by a commercial initiator and of propagation of the explosion throughout the entire cohesive block.

4. A cohesive block of detonating explosive comprising a granulated blend of an oxygen-supplying ammonium salt and at least one oxidizable material, said grains being substantially surrounded by a more sensitive explosive medium free from liquidexplosive compounds and comprising a sensitized ammonium nitrate composition said medium being capable of initiation by a commerical initiator and of propagation of the explosion throughout the entire cohesive block.

5. The cohesive block of detonatlng explosive of claim 4. in which the ammonium salt is ammonium nitrate.

6. The cohesive block of detonating explosive of claim 4, in which the ammonium salt is ammonium perchlorate.

7. A cohesive block of detonatlng explosive of th detonating type comprising a blend of ammonium nitrate and at leastone oxidizable ma terial, said blend being in the form of grainssufficiently large to be held substantially on a 30- mesh screen, said grains being in intimate contact with a more sensitive explosive medium free from-liquid explosive compounds and comprising a sensitized ammonium nitrate composition said medium being capable of initiation by a commercial blasting cap and of propagation of the explosion throughout the entire cohesive block.

8. A detonatlng explosive of claim 'I, in which th cohesive block comprises a compressed cylindrical pellet.

9. The detonating explosive of claim 7, in which the cohesive block comprises a preformed, substantially cylindrical cartridge of combustible material substantially filled with the explosive mass compacted in situ.

10. The cohesive block of detonating explosive of claim 7, in which a substantially central perforation extends longitudinally throughout said block of explosive.

11. The method of preparing a detonating explosive which comprises forming a granulated blend of an inorganic oxidizing salt and at least one oxidizable material, intermingling said grains intimately with a more sensitive explosive medium free from liquid explosive compounds and comprising a sensitized ammonium nitrate composition said medium being capable of initiation by a commercial initiator and of propagation of the explosion throughout the mass, maintaining a water content amounting to at least 2% of the more sensitive explosive, forming said mixture into a cohesive block of explosive, and drying said cohesive block.

12. The method of preparing cohesive blocks of detonating explosive which comprises forming a granulated blend of an explosive ammonium salt and at least one oxidizable material, intermingling said grains intimately with a more sensitive explosive medium free from liquid explosive compounds and comprising a sensitized ammonium nitrate composition said medium being capable of initiation by a commercial initiator and of propagation of the explosion throughout the mass, maintaining a water content of at least 2% of the more sensitive explosive medium, forming said mixture into a cohesive block of explosive, and drying said cohesive block.

13. The method of preparing cohesive blocks of detonating explosive which comprises forming a compressed blend of ammonium nitrate and at least one oxidizable material, said blend being in the form of grains sufiiciently large to be held substantially on a 30-mesh screen, intermingling said grains intimately with a more sensitive explosive medium free from liquid explosive compounds and comprising a sensitized ammonium nitrate composition said medium being capable of initiation by a commercial blasting cap and of propagation of the explosion throughout the mass, maintaining a water content of at least 2% of the more sensitive explosive medium, forming said mixture into a cohesive block of explosive, and drying said cohesive block.

14. The method of producing substantially cylindrical, detonating explosive pellets, which comprises taming a blend of ammonium nitrate and at least one oxidizable material, said blend being in the Iorm 01' grains sumciently large to be held substantially on a '30-mesh screen, intermingling said grains intimately with a more sensitive explosive tree iromliquid explosive compounds and comprising a sensitized'ammonium nitrate composition said explosive being capable of initiation by a commercial blasting cap and 01' propagation of the explosion throughout the mass, maintaining a water content oi at least 2% of the more sensitive explosive, compressing said wet mixture into a 'substantially cylindrical pellet, and drying said pellet. r a

15. The method of producing a stickof cohesive detonating explosive, which comprises forming a blend of ammonium nitrate and at least one oxidizable material, said blend being in the form of grains sumcientlylarge to be held on a 30- mesh screen, intermingling said grains intimately with a more sensitiveexplosive free fromliquid explosive compounds-and comprising a sensitized ammonium nitrate composition said explosive being capable of initiation with a coin-i mercial blasting cap and of propagation of the explosion throughout the mass, maintaining a water content 02 at least 2% of the more sensiprior to the drying of said block.

cLYDE o. DAVIS.