US3421954A - Melt explosive composition having a matrix of an inorganic oxygen supplying salt - Google Patents

Description

United States Patent Ofice 3,421,954 Patented Jan. 14, 1969 74,368 us. Cl. 149-17 5 Claims Int. (:1. C06b 1/04 ABSTRACT OF THE DISCLOSURE Melt explosive compositions normally comprise a matrix of an inorganic oxygen-supplying salt with a fuel such as a solid organic explosive, carbonaceous material or particulate light metal dispersed therein. Such explosives may be employed in a variety of commercial or military applications. It has now been found that the sensitivity of melt explosive compositions may be improved by incorporating therein a soluble lignosulphonate.

This invention relates to melt explosive compositions and in particular to a means whereby the sensitivity of melt explosives may be substantially improved.

By melt explosive is meant an explosive composition produced by the steps of melting under the influence of heat one or more inorganic oxygen-supplying salts and while molten, adding thereto a fuel, the resultant mixture thereafter being allowed to cool to solidify in shaped or cast for-m. Such melt explosives may find useful application in nearly all commercial blasting operations and are particularly useful as economic substitutes for blasting agents of the type commonly packaged in sealed metal containers.

It has now been found that the sensitivity of melt explosive compositions may be substantially improved by incorporating therein a soluble lignosulphonate. In addition, the polymeric nature of this additive leads to useful improvements in the strengths and physical integrities of the derived products.

It is therefore an object of the present invention to provide a melt explosive composition of improved sensitivity. This and other objects of the invention will become apparent from a consideration of the following description and claims.

The improved melt explosive composition of the invention comprises essentially at least one inorganic oxygen-supplying salt, a fuel and a soluble lignosulphonate. The ingredients are combined together while the oxygensupplying salt is in the molten state. the composition thereafter being cooled to solidification.

A preferred inorganic oxygen-supplying salt for use in the melt explosive of this invention is ammonium nitrate. It will in some cases be advantageous to replace some or all of the ammonium nitrate by other metal nitrates such as sodium, potassium, barium and calcium nitrate. It will be known by those skilled in the art, for example, that eutectic mixtures of ammonium nitrate and sodium nitrate can be melted at lower temperatures than can pure ammonium nitrate. The use of such an eutectic blend in the explosive of the present invention possesses the desirable characteristics of reducing the degree of loss of any fuel material employed which may be volatile or decomposable at the higher temperatures, removing the ignition hazard associated with the use of higher temperatures, and realizing a considerable saving in the amount of heat necessary for carrying out the intended process.

The fuel ingredient may be any one of the wide range of explosive fuels known to the art such as, for example, carbonaceous material, solid organic explosives, particulate light metal or metalloid, sulphur, carbon, urea, formate, thiocyanate, thiosulphate and sulphanate salts of hydrocarbon oils and waxes and mixture of these. Fuels such as urea and other amido-ammonium or bydroxy compounds possessing high solubilities in ammonium nitrate are of particular benefit in the temperature-reducing role described heretofore.

The soluble lignosulphonate sensitizer 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 are particularly suitable. Such lignin sulphonates are by-products of the pulp and paper industry and are produced from waste sulphite liquor. The lignosulphonates are employed in the dry powder or granular form.

Preferred melt explosive compositions of the invention contain from 50 to 98% by weight of at least one inorganic oxygen-supplying salt, up to 20% by weight of fuel and from 0.5 to 30% by weight of a soluble lignosulphonate. In addition the composition may also advantageously contain other inorganic additives which are capable of forming eutectics with the oxydizing salts and thus lowering the melting point of the mixture, crystal habit modifiers, pH adjusting additives and stabilizers to arrest thermal decomposition or reaction. Examples of such materials will be readily evident to those skilled in the art.

The composition may be prepared by melting the oxygen-supplying salt conveniently in admixture with an optional melting point depressant and while molten, adding thereto with stirring the fuel ingredient and the lignosul phonate sensitizer. The composition is thereafter cooled in cast form in, for example, a mold or package or alternatively, a grained, prilled or flaked product may be produced by known means.

The following example and table illustrate the improved melt explosive composition of this invention but the latter is in no manner to be limted in scope to the embodiments described.

Example A series of melt explosive compositions were prepared by melting one or more oxygen-supplying salts with or without the presence of a melting point depressant and dispersing in the molten mixture a fuel ingredient and, optionally, a lignosulphonate sensitizer. .A few minutes of vigorous aerating agitation is beneficial to the process of the invention and was conveniently performed with a standard stirrer equipped with a propeller shaft. The explosives were then cooled and cast in cartridge form and exposed to initiation by various priming means. The melt composition containing a fuel but devoid of lignosulphonate sensitizer failed to detonate. The compositions containing added lignosulphonate sensitizer were detonated by means of a dynamite primer. The results are exemplified in the table below wherein the quantities used are expressed as percent by weight of the total. The products containing the lignosulphonate additive exhi'bited a noticeable improvement in the reduction of the brittleness normally associated with previously known cast compositions.

soluble lignosulphonate is selected from the group consisting of calcium, sodium, and ammonium lignosulphonates and mixtures thereof.

TABLE Mix No 1 2 3 4 5 Arrunonium lignosulphonate 10. 0 8. 0 10. 0 5. 0 Ammonium nitrate (pure). 80. 0 90. 0 80. 0 71. 0 71. 0 Soduim nitrate (pure) 5. 0 10. 0 12. 0 12.0 Urea (fuel) 5. 0 7. 0 7. 0 Mineral 011 (fuel) 2. 0 Air atomized aluminum fuel) 10.0 2. 6 +5. 3 V2 2!! X 12!! 2 X 8 Detonation Fired Fired Fired Fired Failed l 1 No. 8 cap. 1 50% dynamite.

' 80 g. pentolite.

What I claim is:

1. A melt explosive composition comprising essentially a solidified matrix of at least one inorganic oxygensupplying salt, said matrix having dispersed therein a fuel and a soluble lignosulphonate.

2. A melt explosive as claimed in claim 1 wherein the fuel is selected from the group consisting of carbonaceous material, solid organic explosives, particulate light metal 25 and met-alloid, sulphur, carbon, urea, formates, thiocyanates, thiosulphates, sulphonates, hydrocarbon oils and waxes and mixtures thereof.

3. A melt explosive as claimed in claim 1 wherein the oxygen-supplying salt is selected from the group consist- 30 ing of the nitrates of ammonium, sodium, potassium, barium, calcium and mixtures thereof.

4. A melt explosive as claimed in claim 1 wherein the 5. A melt explosive composition comprising essentially a solidifier matrix of from about 50% to about 98% 20 by weight of at least one inorganic oxygen-supplying salt, said matrix having dispersed therein from 0 to about 20% by weight of a fuel and from about 0.5% to about 30% by weight of a soluble lignosulphonate.

References Cited UNITED STATES PATENTS 3,369,945 2/ 1968 Craig et al 149-41 X CARL D. QUARFORTH, Primary Examiner. S. J. LECHERT, JR., Assistant Examiner.

US. Cl. X.R. 149-44, 60, 61