NO126270B - - Google Patents

Description

Slurry explosive mixture.

The present invention relates to mud explosives or

as it is also called, slurry explosives, of the kind that include

uses a gas agent to regulate the density and thereby improve

re the sensitivity of the explosive.

Explosive mixtures containing an oxygen supplier

salt, e.g. ammonium nitrate, and a sensitizer and/or fuel together with a liquid solvent, dispersant

part or carrier, such as e.g. water, is known. These products are usually called slurry explosives or slurry explosives. Such slurry explosives can exhibit a varying degree of firmness or consistency, from highly viscous, extrudable products to less vis-

soft, pumpable or pourable liquid-like mixtures.

Slurry explosives of the above type contain

normally as essential components commonly known sensitizers and energy-increasing materials and fuels, e.g. finely divided light metal and finely divided carbon. In some cases, it is advantageous to add a self-exploding component, such as e.g. particulate trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN) or smokeless gunpowder to further improve sensibility

the ten or the styden or both parts of the slurry explosives, and here-

by ensuring the detonation and propagation. In general, the oxygen balance in the total product is within the range +15 to -35 g of oxygen per 100 g of the finished explosive. A large number of such products

ter is known.

It is common knowledge that the sensitivity of slurry explosives is improved by lowering their density. Regulated variations of the density without any significant change of the composition are further advantageous under certain conditions to achieve optimal blasting results. A number of density-reducing agents and methods for aeration are already generally known, but the reduced density thereby achieved is generally not maintained during prolonged storage.

It is an object of this invention to provide

means to increase the sensitivity of slurry explosives and to provide slurry explosives which will maintain sensitivity upon storage.

It has now been shown that the density and sensitivity of the slurry explosive can be advantageously regulated by in the product

introduce N,N'-dinitrospentamethylenetetramine. The explosives will thereby retain their sensitivity over long storage periods.

In accordance with the present invention, a slurry explosive thus comprises at least one inorganic oxygen-providing salt, a solvent for said salt, a thickening agent for the dissolution of the salt in the solvent, a fuel and as a density-regulating agent N,N'-dinitrospentamethylenetetramine.

Preferably, N,N<1->dinitrosopentamethylenetetramine is present

in an amount in the range of 0.01 to 1% by weight of the product.

Preferred slurry explosives according to the invention

then contains 15 to 83% by weight of at least one inorganic oxygen-donating salt, 10 to 30% by weight of solvent, 0.2 to

2.5% by weight of a thickener, 5 to 55% by weight of fuel and 0.01 to 1% by weight of N,N'-dinitrosopentamethylenetetramine.

The density of the product can be varied over wide limits by

to vary the amount of N,N'-dinitrosopentamethylenetetramine, and only a small amount is required to achieve a substantial reduction in density.

The inorganic oxygen-providing salt may conveniently comprise a salt of ammonia, sodium, potassium, barium or calcium or a mixture of two or more of the aforementioned nitrates.

The solvent preferably comprises water, formamide, dimethyl sulphoxide, ethylene glycol or mixtures thereof.

The fuel can suitably comprise particulate light metal or a metalloid, e.g. finely divided aluminium, aluminum alloy, silicon, ferrosilicon, ferrophosphorus, particulate organic explosive, an organic nitrate, e.g. isopropyl nitrate, sulfur or a carbonaceous material, e.g. carbon, urea, thiourea or sugar or a mixture thereof.

Useful particulate organic explosives that can be used in the products include e.g. TNT, PETN, cyclotrimethylene-trinitramine (RDX), composition B (mixture of TNT and RDX), pentolite (mixture of PETN and TNT), smokeless gunpowder, nitrocellulose, nitrostarch and mixtures thereof.

In aqueous slurry explosive products, the thickener may conveniently comprise a galactomannan, e.g. guar gum or locust bean gum. When dimethyl sulfoxide or formamide are used alone as the solvent, hydroxyethyl cellulose can be used as a thickener. When dimethyl sulfoxide is used in combination with water, guar gum, tamarind flour or starch are suitable thickeners.

The product can also advantageously contain crosslinking agents to crosslink the thickener. Suitable crosslinking agents for the polysaccharides in aqueous products include pentavalent antimony compounds, e.g. potassium pyroantimonate, or metal Icronates and dichromates, e.g. zinc chromate, sodium dichromate or potassium dichromate, advantageously in connection with a soluble antimony compound, e.g. potassium antimony tartrate.

Other additional components that are usually used in explosives, e.g. stabilizers, can be introduced into the products as desired.

The degree of density reduction by means of said aerating agent can be regulated by the pH of the slurry explosive.

The lower the pH, the higher the degree of reduction of the density, however

the final degree of density reduction depends only on the amount of N,N'-dinitrospentamethylenetetramine used. The pH is preferably in the range 3 to 6 and more preferably in the range 4.5 to 5.5.

The product can e.g. acidified with zinc nitrate or if the pH is already undesirably low, the pH can e.g. is increased using ammonium hydroxide or an amine.

The invention shall be further clarified by the following examples where all parts and percentages are based on weight. Examples 1, 3, 6 and 8 do not contain any N,N'-dinitrosopentamethylenetetramine and are listed for comparison.

EXAMPLES

In these examples, the following mixing method was used: The oxygen-providing salt, the solvent and the fuel were mixed in a so-called ribbon mixer until a homogeneous solution or suspension was obtained. The pH of the mixture was adjusted as desired by adding zinc nitrate or ammonium hydroxide. Guar gum dispersed in ethylene glycol was then added to the mixture and mixed until a thick gel was obtained. The required amount of N,N<1->dinitro-sopentamethylenetetramine (sold under the trade name "Vulcacel BN" by Imperial Chemical Industries Limited), crosslinking agent and stabilizers were then added and mixed until a homogeneous mixture was obtained.

The sensitivity of the slurry explosive product was investigated by determining the minimum charge of a series of test explosive chargers required to initiate 30 cm long cartridges of the product to detonation. The test explosive charges in ascending strength were:

Density was measured as bulk density.

Details regarding the composition and properties

are listed in the following tables:

Table 1 shows the effect of the introduction of different amounts of N,N<1->dinitrospentamethylenetetramine on the density and sensitivity of two products which contained no self-exploding sensitizer.

Table 2 shows the effect of the introduction of N,N'-dinitrosopentamethylenetetramine on the density and sensitivity of a product containing a self-exploding sensitizer.

Table 3 shows the storage properties of three typical slurry explosive products containing N,N'-dinitrospentamethylenetetramine without a self-exploding sensitizer.

Table 4 shows the effect of pH on the degree of reduction

of the density of a typical slurry explosive containing N,N'-dinitrosopentamethylenetetramine without a self-exploding sensitizer.

Examples 13 and 14

The composition of these examples was:

With the previously used expression "non-stressed"

(unconfined) is understood to mean that the explosives were tested with the specified charge diameters (1 or 2 inches, i.e. 2.5 or 5 cm) by detonation wrapped in containers of polyethylene film in the open and thus not with surrounding walls as in a borehole, or a simulated borehole, such as a steel pipe.

Claims (3)

1. Slurry explosive or so-called slurry explosive comprising at least one inorganic oxygen-providing salt, a solvent for said salt, a thickening agent1 for the dissolution of the salt in solvent and a fuel, characterized in that the explosive also contains N,N'-dinitrosopentamethyl-enetetramine as a density-regulating agent. 2. Explosive as stated in claim 1, characterized in that N,N'-dinitrosopentamethylenetetramine is present in an amount in the range of 0.01 to 1% by weight. 3. Explosive as specified in claim 1 or 2, characterized in that it contains 15 to 83% by weight of at least one inorganic oxygen-providing salt, 10 to 30% by weight of a solvent, o.2 to 2.5% by weight of a thickener, 5 to 55% by weight of fuel and 0.01 to 1% by weight of N,N1 - dinitrosopentamethylenetetramine.