US3369945A - Explosive composition containing an inorganic oxidizer salt,a soluble lignosulphonate,and mutual solvent therefor - Google Patents

Description

United States Patent 3,369,945 EXPLOSIVE CGMPCSITION CONTAINING AN INORGANEC OXIDLZER SALT, A SOLUBLE LEGNSSULFHONATE, AND MUTUAL SOL- VENT THEREFOR Joseph Francis McLean Craig, Beloeil, Quebec, and Errol Linton Falconer, St. Hilaire, Quebec, Canada, assignors to Canadian Industries Limited, Montreal, Quebec, Canada, a corporation of Canada No Drawing. Filed Oct. 14, 1966, Ser. No. 586,676 Claims priority, application Great Britain, Nov. 1, 1965, 46,133/65 8 Claims. (Cl. 149-39) ABSTRACT OF THE DISCLGSURE In lurry-type explosive compositions comprising oxygen-supplying salts, a fluid carrier and a sensitizer or fuel, optimum detonation and propagation has heretofore been possible only through the use of relatively large quantities of sensitizing materials and fuels. The present invention provides an explosive slurry composition of improved sensitivity, especially in small diameter charges, by incorporating in the composition a quantity of a soluble lignosulphonate which permits a reduction in the fuel and/or sensitizer content.

This invention relates to explosive compositions comprising essentially an inorganic oxygen-supplying salt, a sensitizer, a fuel, a thickener and a mutual solvent for the inorganic salt and the sensitizer. In particular, the invention relates to a means whereby the sensitivity of such explosive compositions may be substantially improved.

Explosive compositions comprising an oxygen-supplying salt such as, for example, ammonium nitrate, and a sensitizer and/or fuel together with a fluid solvent, disperser or carrier such as water, are known. These compositions are commonly referred to as slurry explosive compositions or, more generally, as slurry explosives. Such slurry explosives may range in degree of firmness or consistency from highly viscous, plastic-like extrudable compositions to less viscous pumpable or pourable fluidlike mixtures.

Slurry explosive compositions of the aforementioned types normally contain as essential ingredients widely known sensitizing and power enhancing materials and fuels such as, for example, finely divided .light metal, finely divided carbon and the like. In some cases, it is advantageous to add a self-explosive ingredient such as particulate TNT, PETN or smokeless powder to further improve the ensitivity or strength or both of the slurry explosives and thereby insure detonation and propagation. A wide range of such compositions are now known to the art.

For optimum reliability the known sensitizers employed in slurry explosives are either self-explosives or relatively expensive materials such as very finely divided light metal powders. Without such sensitizers, these slurry explosive compositions tend to be detonable only in large diameter charges with large primers. It has thus been necessary for the manufacturer of explosives to employ relatively large quantities of sensitizing material and fuel in slurry explosives in order to insure detonation and propagation. Such compositions, as well as being relatively expensive, are hazardous to handle and require special and costly precautions in manufacture, transportation, storage and use. Slurry explosive compositions containing self-explosives are, in turn, in most jurisdictions subject to regulatory restrictions in transportation and storage. Those that contain reactive sensitizers such as, for example, paintfine aluminum powder, tend to deteriorate and lose sensitivity on storage.

It has now been found that the aforementioned disadvantages may be overcome by employing as a sensitizer in slurry explosive compositions a soluble lignosulphonate.

It is, therefore, an object of the present invention to provide a means whereby the sensitivity of a slurry explosive composition may be increased.

Another object of the invention is to provide a slurry explosive composition which may be detonated in boreholes of small diameter.

Another object of the invention is to provide a sensitive slurry explosive composition which is devoid of any selfexplosives or other hazardous material.

A further object of the invention is to replace the known reliable sensitizers in slurry explosive compositions with a sensitizer that is much less costly and easily available.

Yet another object of the invention is to provide a sensitive slurry explosive composition that is stable and that does not deteriorate physically or become insensitive during storage.

These and other objects of the invention will become apparent from a consideration of the following description and claims.

The improved explosive composition of this invention comprises essentially at least one inorganic oxygensupply salt, at least one soluble lignosulphonate, a fuel, a thickener and a mutual solvent for the inorganic salt and the lignosulphonate.

The addition of a soluble lignosulphonate to a slurry explosive composition has the surprising and desirable effect of substantially increasing the sensitivity of the composition.

It is thus now possible to prepare useful and powerful, slurry explosive compositions which, though devoid of any self-explosive ingredient, may be detonated with ease in boreholes of small diameters. It is similarly now possible to prepare such compositions even containing additional sensitizing material such as, for example, finely divided aluminium, aluminium alloy, silicon, ferrosilicon or ferrophosphOrus or self-explosives which are more reliable to detonation and propagation than heretofore and which may be detonated in smaller diameter and with the use of smaller priming charges that has heretofore been possible.

Preferred blasting slurry explosive compositions of this invention contain from 30 to 90% by weight of at least one inorganic oxygen-supplying salt, from 0.1 to by weight of a soluble lignosulphonate from 1 to 3 by weight of a mutual solvent for the inorganic salt and the lignosulphonate from 0.1 to 10% by weight of thickener and from 0 to 40% by weight of fuel the proportions of the ingredients being such that the oxygen balance of the total composition is from +15 to 35 grams of oxygen per 100 grams of finished explosive.

A preferred inorganic oxygen-supplying salt for inclusion in the explosive compositions of this invention is ammonium nitrate. It is in some cases advantageous to replace some, suitably up to 50% or even up to of the ammonium nitrate by other metal nitrates such as sodium, barium, potassium and calcium nitrates. The particle size of the inorganic oxygen-supplying salts is not critical and powdered, granulated, or prilled forms may be used and part of the salts may be predissolved in all or part of the solvent.

A preferred mutual solvent for the oxidizing salt and the soluble lignosulphonate is water. However, other suitable mutual solvents such as, for example, formamide and dimethyl sulphoxide (DMSO) may be used in proportions up to total replacement of the water. Ethylene 3 glycol may be used in proportions up to 50% replacement of the water. These organic solvents are polar liquids, readily miscible with water in all proportions and are effective solvents for ammonium nitrate and other inorganic salts.

Where employed, the aluminium or aluminium alloy or other energetic metal or metallo-ids suitable for use in the explosive composition of this invention must be in finely divided form and may most suitably range from a fine dust to a form not coarser than that which will pass through a size 6 Tyler mesh screen. For example, relatively inexpensive air-atmozide aluminium powder, shredded foil or granules made from reclaimed scrap are suitable types. The use of the expensive paint-fine aluminium is not required to achieve high sensitivity in the explosive composition of this invention.

Useful particulate self-explosives which may be used in the explosive composition include, for example, trinitrotoluene (TNT) pentaerythritol tetranitrate (PETN), cyclotrirnethylenetrinitramine (RDX), composition B (mixture of TNT and RDX), pentolite (mixture of PETN and TNT), smokeless powder, nitrocellulose and mixtures of these.

The gel-forming or thickening agents employed in the aqueous slurry form of the explosive of the invention are preferably mannogalactans such as guar gum or carab seed. Guar gum of the self-cross-linking type recently made available on a commercial scale may be suitably employed. Where either dimethyl sulphoxide or formamide is employed alone as the mutual solvent in the slurry, hydroxyethyl cellulose may be used as a suitable thickener. Where dimethyl sulphoxide, formamide or ethylene glycol is used in combination with water, guar flour, tamarind flour or starch are suitable thickeners. A number of modified and synthetic materials useful as thickeners can be selected which are appropriate to the solvents employed and will be obvious to those skilled in the art. v

Metallic ch'romates suitable for use as cross linking agents for the polysaccharides in aqueous slurries are the same as those disclosed in Canadian Patent No. 729,555, issued on Mar. 8, 1966, that is, a metallic chromate selected from the group consisting of sodium and potassium dichromate and zinc and barium chromate.

The soluble lignosulphonate sensitizers may be any one of the wide range of lignin sulphonates commercially available. Any soluble salt of lignin sulphonic acid may be used and calcium, sodium and ammonium lignosulphonates have been found particularly suitable in the explosive composition of the invention. Such lignin sulphonates are by-products of the pulp and paper industry and are produced from waste sulfite liquor. The lignosulphonates may be employed either as a dry powder or alternatively as a solution. Where a lignosulphonate solution is employed, for example, an aqueous solution, the water of solution may be employed as all or part of the aqueous medium of the explosive composition.

The explosive composition may be prepared by processes well known in the art employing simple mixing procedures, the soluble lignosulphonate sensitizer being added at any convenient stage in the manufacture. The ligniosulphonate sensitizer may similarly be employed where a slurry explosive composition is prepared for use at the blasting site by means of the now well known slurry mix truck.

The following examples and tables illustrate the improved explosive composition of this invention but the latter is in no manner to be limited in scope to the embodiments described.

Example 1 An extrudable gelatinous explosive composition containing as essential ingredients ammonium nitrate, sodium nitrate, water, particulate TNT and particulate PETN was prepared. Additional softening or gelling material was also included in the composition. An 8" cartridge of 1 /2" diameter failed to be detonated with one No. 8 blasting cap. Two similar compositions in the same cartridge size containing in addition 0.5% by weight of sodium lignosulphonate and 1.0% by weight of ammonium lignosulphonate respectively were successfully detonated with one No. 8 blasting cap. The results are summarized in Table I, the quantities shown being expressed as percent by weight of the total.

TABLE I Mix No 1 2 3 4 Particulate PETN 10.0 10.0 4. 6 Particulate TNT 20.0 20. 0 20.0 23.0 Graincd ammonium nitrate 30. 0 30. 0 60. 0 34. 3 Grained sodium nitrate 33.0 33. 0 14. 0 e 31.0

1. 4 1. 4 1. 3 1. 6 Guar flour... O. 4 0. 4 0. 5 0. 4 Tamarind fl0ur. 0. 4 0. 4 0. 4 Sulphur 0. 7 Sodium lignosulphonate 0. 5 Ammonium lignosulphonate. 1.0 Oxygen balance +2. +2. 9 +0. 9 +0. 8 Detonation 1 Failed 1 No. 8 cap. 2 Fired 1 No. 8 cap. 3 Fired 5 No. 8 caps.

As can be seen from the above results Mix 1, devoid of lignosulphonate failed with one No. 8 cap while Mix 4, similarly devoid of lignosulphonate required five No. 8 caps for detonation. Mixes 2 and 3 containing lignosulphonate fired with a single No. 8 cap.

Example 2 TABLE 11 Mix No 1 Ammonium nitrate 5 Water 1 Paint-fine aluminium Calcium nitrate Carbon black Guar flour Ammonium lignosulphonat Oxygen balance Detonation 1 Failed with 1 No. 8 cap in 2 tests. 2 Fired with 1 No. 8 cap.

As can be seen from the above results Mix No. 1 containing sensitizing material but devoid of lignosulphonate failed to detonate while a similar mix containing ligno sulphonate was initiated with a single N0. 8 cap.

Example 3 An aqueous slurry explosive composition containing as essential ingredients, oxygen supplying salts, water, aluminium powder, pelleted TNT and thickener was prepared. A quantity of ammonium lignosulphonate was added to one batch of the composition, the other batch being devoid of lignosulphonate. The respective mixtures were packaged in 24 inch cartridges of 3 /2 inch diameter and exposed to initiation by 60 gram pentolite primers. The

compositions failed. The results are summarized in Table ities V below, the quantities being expressed as percent by Weight of the total.

TABLE V lignosulphonate failed to detonate.

ight of the total.

TABLE III mixture containing no The results are summarised in Table III, the quant being expressed as percent by We Mix N0.

Example 7 A series of five aqueous slurry explosive compositions were prepared containing as essential ingredients oxygensupplying salts, water, a fuel and a thickener. A range of lignin sulphonic acid salts was added to the compositions and each was cartridged and exposed to initiation by pentolite primer. In all cases detonation occurred and in one instance (Mix No. 5, Table VII) detonation was achieved in very small diameter charge. In all cases detonation of -a high order of detonation velocity resulted. The results are summarized in Table VII, the quantities shown being expressed as percent by weight of the total.

TABLE VII Mix N Ammonium nitrate Aluminum powder Sodium nitrate C alcium lignosulphonate (dry) 9. 0 C aleiumlignosulphonate (50% solution). Sodium lignosulphonate Ammonium lignosulphonate (49% soluon Oxygen balance. 29 -24 Density (gm /cc) 1.45 1.44 Cartridge size 6 x 24" x 24 Pentolite primer (g.) 680 680 Detonation velocity, M/S 1 3,110 1 4,400

1 Unconfined. 2 Confined in steel pipe.

Example 8 TAB-LE VIII Mix No 1 2 Particulate TNT 10. O 10. 0 Ammonium nitrate 39. 0 37. 0 Sodium nitrate 8. 0 8.0 15. 5 15. 5 25. 0 25. 0 1. 5 l. 5 1 0 1. 0 2. 0 24. 1

450 Detonation Fired Example 9 A series of slurry explosive compositions were prepared wherein a part or all of the normally used water Table IX, the quantities shown being expressed as percent by weight of the total.

TABLE IX Mix No Ammonium nitrate (AN) Sodium nitrate Pelleted TNT. Granular PETN- Tamarind flour- Pregelled starch. Hydroxyethyl cellul Water Ammonium lignosulphonate;

Density (gm/cc.) Minimum primer required 1:112 liquid at 25 C. 2 5 No. 8 caps.

! 1 No. 6 cap.

4 10 gm. pentalite.

Example 10 A series of explosive compositions were prepared wherein a part of the normally used Water solvent was replaced with for-mamide. The balance of the ingredients consisted essentially of oxygen-supplying salts and finely divided metal fuel together with known thickeners or density controllers. Quantities of ammonium lignosulphonate were contained in one group of compositions and a second group was devoid of lignosulphonate. Both types of compositions were packaged in cartridges of various diameters and exposed to initiation by various primers. The compositions containing lignosulphonate required sub stantially less primer initiation than did the non-lignosulphonate-containing compositions. The results are summarized in Table X, the quantities shown being expressed as percent by weight of the total.

TABLE X Ammonium nitrate- 71. 67. 0 Sodium nitrate" 8. 0 8.0 Urea Formamide 4. 0 4. 0 Granular aluminium.. 4. 0 4. 0 Air atomized aluminium. Ferrosilicon Gilsonite.--- 2. 2. 5 Sugar....- 4.0 Glyc 1. 0 Guar flour (thickener)- 0. 5 0. 7 0. 5

. l0. 0 l2. 8 10. O Ammonium lignosul honate- 7. 0 Density (gin/cc.) 1. 41 1.34 1.50 Cartridge diameter (inch)-... 6 6 6 Minimum primer required (g 1 320 320 1 680 1 Failed.

Example 11 Example 13 Two slurry explosive compositions were prepared wherein part of the normally used water solvent was replaced with dimethyl sulphoxide (DMSO). The balance of the essential ingredients consisted of oxygen supplying salts and known fuels, thickeners and stabilizers. To one of the compositions was added a quantity of ammonium lignosulphonate sensitizer. Packaged in 2 /2 inch and 3 inch diameter cartridges the lignosulphonate-containing composition was detonated by a 160 gm. pentolite primer while the composition devoid of lignosulphonate failed to detonate. The results are summarized in Table XI, the quantities shown being expressed as percent by weight of the total.

TABLE XI MixNo Ammonium nitrate Sodium uitrate.-..

1 Use to eliminate any large unstable air bubbles in the mix.

2 Detonation catalyst.

3 A similar composition using water solvent and devoid of DMSO was less sensitive.

Example 12 A field trial was carried out at an iron ore mine using a lignosulphonate sensitized aqueous slurry. The composition, prepared by a slurry mix pump vehicle, is shown as Mix 1 in Table XII below. It was loaded into 5 boreholes each filled with water. Each borehole was 9%" diameter x 42' deep. After days all the boreholes detonated successfully. Approximately 5,700 pounds of explosive compositions were loaded and initiated with 1 /2 pound pentolite primers. A similar composition but devoid of lignosulphonate was prepared as shown in Table XII, Mis 2. A cartridge 10" in diameter x pounds primed with 680 grams of pentolite failed to detonate. The results are summarized in Table XII, the quantities shown being expressed as percent by weight of the total.

TABLE XII Mix No Zinc ehromate Water Oxygen balance- Density (gm./cc.). Detonation ivwas gz rew pre CA) on (DQOKIOOS KIMO Q.

ayne TAB LE XIII Sample No 1 2 Ammonium nitrate 35. 0 Sodium nitrate 16.0 Water 14. 0 Ethylene glycol Guar flour (thickener)-- 0. 5 Ammonium lignosulpho 4. 5 Aluminium granules... 29. 0 Air atomized aluminium Paint-fine aluminium..... l 0

Segregation of ingredients I 1 Nil after 30 days storage. 2 Nil after 79 days storage.

As may be seen from the results shown in the preceding examples and tables, the addition of a soluble lignosulphonate to a slurry explosive composition has the surprising eifect of substantially increasing the sensitivity of the compositions. Slurry explosives of this type having an oxygen balance outside the range of +15 to 35 grams of oxygen per grams of finished explosive have failed to detonate consistently. It is preferred, therefore, that quantities of lignosulphonate sensitizer and fuel used be such that the oxygen balance of the composition is Within the range +15 to -35.

It will be appreciated by those skilled in the art that the principal advantage to be enjoyed through the use of the lignosulphonate sensitized slurry explosive compositions of the invention lies in the utilization of nonself-explosive slurry composition. That is, slurry compositions comprising oxygen-supplying salts, a solvent for the oxygen-supplying salts and a fuel may now, by the addition of a suitable quantity of lignosulphonate, be employed as practical and reliable commercial explosives possessing the additional advantages of low cost and great handling safety. Where it is desired to include in such compositions additional strength ingredients such as powdered light metal fuels or self-explosives, the use of the lignosulphonate sensitizers provides compositions which may be detonated in smaller diameter charges or with lower strength primers than has heretofore been possible.

It has also been found that the use of lignosulphonate sensitizers has no detrimental effect on the storage properties of aqueous slurry compositions; that is, compositions senitized with lignosulphonate will show no greater breakdown or segregation of ingredients than will similar compositions devoid or lignosulp'honate. As is well known, the presence of undesirable material such as, for example, impurities in powdered light metal in a slurry explosive has the effect of causing the composition to break down over long periods of storage into solids and a supernatent liquid layer. The use of lignosulphonate in no way accelle'rates this breakdown and may, in fact, provide a useful stabilizing function in such compositions. It has been noted that where lignosulphonates are employed as sensitizers in aluminum-cntaining slurry explosives, the use of stabilizers normally employed in such compositions is unnecessary.

The lignosulphonate sensitizers additionally function as effective agents in preventing or arresting the dissipation of minute bubbles of air which have been entrained or entrapped in the slurry mixture. Such air bubbles are normally incorporated in slurry explosive compositions by the lifting and folding of the mixture which occurs during the operation of the mechanical mixing of the ingredients or, alternatively, air is introduced into the mixture along with the dry ingredients. The quantity of such entrapped air provides a useful function in controlling the density of the explosive compositions.

What we claim is:

1. An explosive composition comprising essentially at least One inorganic oxygen-supplying salt, a soluble lignosulphonate, a mutual solvent for the inorganic oxygensupplying salt and the soluble lignosulphonate, a thickener and a fuel, the proportions of the ingredients being such that the oxygen balance of the total composition is from about +15 to. about -35 grams of oxygen per -100 grams of finished explosive.

2. An explosive composition as claimed in claim 1 wherein the fuel is selected from the group consisting of carbonaceous material, particulate nitrated organic explosive, particulate light metal or metalloids, sulphur, carbon, urea and mixtures thereof.

3. An explosive composition as claimed in claim 1 wherein the mutual solvent is selected from the group 12 consisting of water, formamide, dimethyl sulphoxide and mixtures thereof.

4. An explosive composition as claimed in claim 1 wherein the mutual solvent comprises a mixture of water and ethylene glycol in proportions such that the ethylene glycol represents not more than by weight of the total solvent.

5. An explosive composition as claimed in claim 1 wherein the oxygen supplying salt is selected from the group consisting of the nitrates of ammonia, sodium, potassium, barium, calcium and mixtures thereof.

6. An explosive composition as claimed in claim 1 wherein the soluble lignosulphonate is selected from the group consisting of calcium, sodium and ammonium lignosulphonate and mixtures thereof.

7. An explosive. composition as claimed in claim 2 wherein the particulate nitrated organic explosive is selected from the group consisting of trinitrotoluene, pentaerythritol tetranitrate, cyclotrimethylenetrinitramine, a blend of trinitrotoluene and cyclotrimethylenetrinitramine, a blend of trinitrotoluene and pentaer'ythritol' tetranitrate, smokeless powder, nitrocellulose and mixtures thereof.

8. An explosive composition comprising essentially between about 30% and about by weight of an inorganic oxygen-supplying salt, between about 0.1% and 25% by weight of a soluble lign'osul'phon-ate, from about 1% to about 30% by weight of a mutual solvent for the inorganic oxygen-supplying salt and the soluble'lignosulphonate, from about 011% to about 10% by weight of a thickener and from 0 to 40% by weigh-t of a fuel, the oxygen balance of the total composition being from about +15 to about 35 grams of oxygen per grams of finished explosive.

References Cited UNITED STATES PATENTS 3,132,061 5/1964 Walsh et a1 14941 CARL D. QUARFORTH, Primary Ex'aminer.

S. I. LECH'ERT, 111., Assistant Examiner.