US3328217A - Aqueous blasting compositions containining particulate smokeless powder and dinitrotoluene - Google Patents

Description

3,328,217 Patented June 27, 1967 3,328,217 AQUEOUS BLASTING COMPOSITIONS CONTAIN. ING PARTICULATE SMOKELESS POWDER AND DINITROTOLUENE John D. Ferguson, Wilmington, Del., assignor to Hercules Incorporated, a corporation of Delaware No Drawing. Filed July 20, 1965, Ser. No. 473,490 6 Claims. (Cl. 149-50) This invention relates to aqueous inorganic oxidizer salt type slurry blasting compositions of the nitrocarbonitrate type containing a combination of smokeless powder and dinitrotoluene as the sensitizer component.

Inorganic oxidizer salt type blasting compositions of the aqueous slurry type have had rather wide use in the explosives industry in recent years. These compositions comprise an inorganic oxidizer salt, water, a sensitizer, and generally a thickening agent in an amount to impart at least suificient body to the slurry to prevent settling of any of the various ingredients. Smokeless powder, single, double or triple base, and of particle size over a broad range, has been utilized extensively as one such sensitizer, as disclosed in the copending application of Clemens and Lawrence, Ser. No. 67,513, now U.S. Patent No. 3,235,- 425, filed Nov. 7, 1960, which is a continuation-in-part of application Ser. No. 800,634, filed Mar. 20, 1959, now abandoned.

A most important source of smokeless powder, from the economics standpoint, is that of war-surplus stocks made available to the industry from time to time. A considerable proportion of smokeless powder from this source is of such large grain size as to require grinding for use as a sensitizer in these slurry type compositions, and accordingly, even a part of the war-surplus stocks is not in suitable form for general use in these slurry compositions. Direct manufacture of smokeless powder for use in these slurry compositions has not been practical from the economics standpoint.

It is, therefore, of great importance that every step be taken to conserve use of smokeless powder in the above described slurries. This invention is based on the discovery that sensitivity and detonation rate of these aqueous inorganic salt slurry compositions, containing smokeless powder as the sensitizer component, are markedly increased by the presence of dinitrotoluene (DNT) The invention accordingly, provides for reduction in the amount of smokeless powder required heretofore for accomplishing a given detonation rate, or, alternatively, for accomplishing an increase in detonation rate for such a given amount of smokeless powder; and, also for direct use of smokeless powder heretofore of size and composition requiring grinding or the use of unduly large booster charges for detonation.

In accordance with the invention, inorganic oxidizer salt explosive compositions of the aqueous slurry type are provided which contain, on a weight basis, a combination of from 10 to 25 percent smokeless powder with from 2 to 15 percent dinit'ro'toluene (DNT), as the sensitizer component. The compositions of the invention generally comprise (Weight basis), from about 8 to 25 percent water, from about 30 to 75 percent of an inorganic oxidizer salt, the above described sensitizer component, and a thickener, usually in an amount of from 0.2 to 5 percent.

In a now preferred practice of the invention, the oxidizer salt component is either ammonium nitrate alone or together with sodium nitrate in a weight ratio to the sodium nitrate as low as about 0.5 :1, generally within the range of from about 2:1 to 8:1, and the thickener is guar gum in crosslinked (or gelled) form. The now preferred compositions of the invention contain (weight basis) from 12 to 20, and 3 to 10, percent smokeless powder and DNT respectively as a sensitizer component; from 12 to 18 percent water; from 30 to 65, and 5 to 15,

percentammonium nitrate and sodium nitrate respectively as'the oxidizer salt component; and from 0.2 to 2.0 percent guar gum as a thickener, preferably in crosslinked form.

By the term inorganic oxidizer salt, as is well known in the explosives art, is meant one which under the conditions of the detonation, liberates oxygen for the oxygen balance required.

Ammonium nitrate is in many instances the only inorganic oxidizer salt component. However, other inorganic oxidizer salts can be used, alone or with ammonium nitrate as a supplementary oxidizer salt. Of these supplementary salts, the alkali metal nitrates are now preferred. Often when ammonium nitrate is utilized with a supplementary salt, it comprises a major proportion of the total oxidizer salt, i.e., at least 50 percent of the total oxidizer salt. Exemplary inorganic oxidizer salts that can be used alone, or together with ammonium nitrate, are alkali metal and alkaline earth metal nitrates and perchlorates (including ammonium) as for example, sodium nitrate, magnesium nitrate, calcium nitrate, potassium nitrate, barium nitrate, sodium perchlorate, ammonium perchlorate, calcium perchlorate and magnesium perchlorate.

Particle size and type of the oxidizer salt ingredient are not generally critical. For example, ammonium nitrate can consist of prills such as used in fertilizers and which are substantially all on 20 mesh, or it can be granular and in that form, vary from coarse to fine. Other oxidizer salt ingredients are generally of comparable particle size.

The DNT component can be an oil, a solid, or an oilsolid mixture. As an oil, the DNT component is a mixture of DNT isomers and often has a freezing point in the range of about 20-35" C., and as a solid, it is essentially 2,4-dinitrotoluene.

By the term smokeless powder, it is meant the well known colloided nitrocellulose powders. Thus, the single base powder contains colloided nitrocellulose as the chief component, say in the order of from about 85 to 99 weight percent and the double base powder contains the same colloided nitrocellulose component but together with nitroglycerin or an equivalent liquid explosive nitric ester. Double base powders contain generally in the order of about colloided nitrocellulose and substantially the.

remainder nitroglycerin, with, of course, the usual supplemental ingredients. Triple base powders contain nitroguanidine .in addition to the colloided nitrocellulose, and nitroglycerin, in proportions generally at least about 40 to 50 percent nitroguanidine and substantially as the remainder colloided nitrocellulose and nitroglycerin, the latter two being in any suitable relative proportions, for example 1:1 to 4:1 of nitrocellulose to nitroglycerin. Smokeless powder is manufactured in the form of small flakes, strips, pellets, granules and cylindrical grains, the latter being generally perforated.

Exemplary of the smokeless powder formulations contemplated in the practice of the invention are:

Weight l e rcent I Single Base Double Base Triple Base Nitrocellulose 99. 0 83. 0 90. 0 93. 3 59. 0 78. 3 20. 0 Nitroguanidine 54. 7 Nitroglycerin. 5. O 40. 0 20. 0 19. 0 Diphenvlamine l 0 1. 0 1.0 0.7 0.7 Dinitrotoluene" 10. 0

Dibutyl pithalate 5. 0 Potassium sulfate. 1. 0 1.0 1.0 Ethyl centralite 1. 0 6. 0 Cryolite* 0. 3

The particle size of the smokeless powder ingredient generally varies from about 20 mesh (100 percent through 20-mesh screen), through medium and coarse to perforated grains as large as, say about 0.5 inch long by 0.25

The above examples demonstrate the marked supplementary effect of DNT on sensitivity and detonation rate of smokeless powder sensitized inorganic oxidizer salt slurries, in accordance with the invention. Thus, Ex-

inch in diameter. amples 1 and 2 show such a relationship in a composi- The thickener content can be as high as 5 percent tion sensitized with 15 percent 20 mm. smokeless powder, dependent upon the particular thickener and the desired there being an increase of over 1,000 m./sec. in detonaconsistency of the finished composition. Generally, 2. tion rate at the 475 and 160 gram booster levels, when thickener content up to about 2 percent is sufficient. DNT content is increased from 0 to 8 percent. Similarly, When the thickener content is within the range of 0.2 the compositions of Examples 3 and 4 sensitized with to 0.5 weight percent, there is sufiicient thickening to 20 percent smokeless powder demonstrate an increase prevent settling of the composition ingredients, although of 500 m./sec. at the 475 gram booster level and a additional thickener is often required in order to impart marked increase in sensitivity at the 40 gram booster a satisfactory degree of cohesiveness so that the comlevel, when DNT content is increased from 0 to 5 perposition retains its form as a unit mass, preferably cent. Examples 5 through 7 similarly demonstrate inplastic but deformable. Exemplary thickeners are sodium crease in sensitivity and detonation rate at the 15 percarboxymethylcellulose, karaya gum, water-soluble cent smokeless powder level when the DNT content is starches, locust bean meal, cereal products and the like. varied from 0 to 5 and then to 8 percent. Examples 8 When the thickener is guar gum in crosslinked form, through 10 demonstrate calcium nitrate, magnesium niin accordance with preferred practice, the guar content trate and sodium perchlorate as supplemental oxidizer is most advantageously within the range of from 0.5 to salts. 1.5 percent, under which conditions the finished com The amount of DNT advantageously utilized in the senposition is a plastic, rubbery, but deformable, mass. sitizer component, in the practice of the invention, is de- The compositions of the invention are in most instances pendent upon the particular smokeless powder. For a insensitive to detonating action of a No. 8 commercial given formulation, particle size of the smokeless powder is blasting cap but are, in all events, detonatable by conto a large extent determinative of the amount of DNT ventional booster charges of PETN (pentaerythritol utilized, the larger particle size requiring a correspondtetranitrate), RDX (cyclotrimethylenetrinitramine), Peningly larger proportion of DNT as supplemental sensitizer. tolite (PETN-TNT, 50/50), tetryl, Composition B DNT is less advantageously employed at the higher smoke- (RDX-TNT, 60/40) and the like. One booster advanless powder contents, say those exceeding about 25 pertageously employed is a dispersion of a crystalline high cent. In some instances, say at the level of 30 percent explosive, e.g., PETN or RDX in a plastic carrier such smokeless powder, DNT will generally be of no significant as described in the copending application of Alpheus M. advantage. In the preferred practice of the invention, Ball, Ser. No. 538,788, filed Oct. 5, 1955, and which is therefore, the compositions of the invention contain a detonated by either a commercial blasting cap or a maximum of about 25 weight percent smokeless powder detonating fuse. In general, these compositions are detoand often about 20 percent. Minimum smokeless powder natable in response to any secondary explosive. content is generally about 10 percent. These'values are The explosive compositions of the invention are of the correlated with DNT content in the order of from 2 to well known class of nitrocarbonitrates, by which term 15 percent. For example, when the composition contains it is meant there are no sensitizers which in themselves 40 about 10 percent, say of a single base ground smokeless are high explosives, and the mixtures will not detonate P DNT of from about 5 t0 8 Percent is advanwith a No. 8 blasting cap when packed for shipment. tageously employed. If a coarser smokeless powder is uti- The invention is illustrated with reference to the follized at that content level, a larger proportion of DNT lowing formulations, all on a weight percent basis. is generally employed, say as high as 8 to 12 percent.

TABLE 1 Number Water 16.0 16.0 16.0 16.0 18. 0 18. 0 18.0 16.0 16.0 16. 0 Ammonium Nitrate .9 .9 s 9 53 9 50.9 51.9

Calcium Nitrate Magnesium Nitrate Sodium Perchlorate Sodium Nitrate 3 Guar Guru 4 Smokeless Powder 5 DNT Density, grn./cc. Funnel Test 7 Flow Detonation Rate, rn./sec.

ggtonator, grams 8% DNT. Grains, 0.095 x 0039, single perforation. Runs 5, 6, 7Weight percent, nitrocellulose 85.0; DNT, 10.0; dibutyl phthalate 5.0.; 1 percent (l1phenylamine added. Runs 5, 6, 7 ground to about 25 percent on 25- lgesll; 2;? percent on 40-mesh; 35 percent on (SO-mesh; and 8 percent through -mes 5, 150 2, 000 4, 150 4, 4, 500 4, 600 4, 700 Failed 2,150

lfgtuns 2, 810, DNT added as a liquid; Runs 4, 6, 7 DNT added as so 1 7 Approximately 5,000 grams of slurry is poured into an aluminum funnel having 211% diameter x 1' orifice. When the orifice is opened to permit flow, the timing is begun. When light is visible through the orifice (looking down into the funnel), timing is stopped. The time difierence is designated as the flow time.

8 Measured as average detonation velocity over a 20 cm. length, at the end of a 28' long column of explosive. The explosive is confined in 5' diameter (nominal) black iron pipe (Schedule 40). The time tor detona; tion to proceed across the 20 cm. length of explosive is measured electronically by means of a counter-chronograph.

9 PentolitePETN:TNT=1:1.

When utilizing a double base or a triple base powder, particle size will be an important factor in correlation with amount of DNT to be utilized, but these powders Will require somewhat less DNT than the corresponding proportion of a single base powder.

The compositions of the invention can be prepared in accordance with any suitable sequence of mixing steps. However, when the DNT is an oil, it is advantageously premixed with at least a portion of the remaining solid ingredients as a coating and the resulting coated material then mixed with the remaining ingredients in any sequence desired.

In accordance with a now preferred procedure, crosslinkable guar gum, as the thickener component, is added in part to the water component together with a minor proportion of the oxidizer salt component and the resulting admixture maintained under agitation for several minutes at say 72100 F. Generally the amount of guar gum and oxidizer salt added are about 0.3 and 1 percent respectively based on the finished composition. The remaining portion of guar gum and oxidizer salt, along with the DNT component as a solid, are then added to the resulting admixture with continued stirring for a short time, say 2 to 3 minutes, and finally the smokeless powder component is added to the resulting DNT-containing admix ture. The pH of the system is regulated to inhibit hydration of the subsequent guar gum to permit final mixing and packaging under optimum flow conditions but to then permit hydration with subsequent gelation in storage. The thus inhibited mixture is packaged for final gelation in storage, for subsequent use.

As will be evident to those skilled in the art, various modifications can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

I claim:

1. An inorganic oxidizer salt type explosive composition of the aqueous slurry type containing as the sensitizer component from 10 to 25 weight percent colloided nitrocellulose smokeless powder particles in combination with from 2 to 15 weight percent dinitrotoluene.

2. An aqueous slurry type composition of claim 1 containing on a weight basis from 8 to 25 percent water, from to 75 percent of an inorganic oxidizer salt, and from 0.2 to 5 percent of a thickener.

3. An aqueous slurry type composition of claim 2 containing up to 2 percent guar gum as said thickener.

4. A composition of claim 3 containing from 12 to 18 percent water, from 30 to percent ammonium nitrate, from 5 to 15 percent sodium nitrate, from 12 to 20 percent smokeless powder, and from 3 to 10 percent dinitrotoluene.

5. A composition of claim 4 wherein said guar gum is in crosslinked form.

6. A composition of claim 1 wherein said oxidizer salt is ammonium nitrate together with at least one inorganic oxidizer salt selected from the group consisting of sodium nitrate, magnesium nitrate, calcium nitrate and sodium perchlorate.

References Cited UNITED STATES PATENTS 1,658,816 2/1928 Pratt 149-48 1,881,307 10/1932 Bashford 149-48 1,895,144 1/1933 Botts et al. 149-48 1,963,622 6/1934 Johnson et al. 149-48 2,537,039 1/1951 Downard 149-48 3,235,425 2/1966 Clemens et al 149-48 L. DEWAYNE RUTLEDGE, Primary Examiner. BENJAMIN R. PADGETI, Examiner.

S. J. LECHERT, JR., Assistant Examiner.

Claims (1)

1. AN INORGANIC OXIDIZER SLAT TYPE EXPLOSIVE COMPOSITION OF THE AQUEOUS SLURRY TYPE CONTAINING AS THE SENSITIZER COMPONENT FROM 10 TO 25 WEIGHT PERCENT COLLOIDED NITROCELLULOSE SMOKELESS POWDER PARTICLES IN COMBINATION WITH FROM 2 TO 15 WEIGHT PERCENT DINITROLUENE.