CA1176469A - Explosive composition - Google Patents
Explosive compositionInfo
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- CA1176469A CA1176469A CA000375777A CA375777A CA1176469A CA 1176469 A CA1176469 A CA 1176469A CA 000375777 A CA000375777 A CA 000375777A CA 375777 A CA375777 A CA 375777A CA 1176469 A CA1176469 A CA 1176469A
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Abstract
ABSTRACT
A gas-bubble-sensitised melt explosive com-position, which is not deleteriously affected by pumping, containing certain surfactants which inhibit the dis-engagement of the sensitising gas bubbles.
A gas-bubble-sensitised melt explosive com-position, which is not deleteriously affected by pumping, containing certain surfactants which inhibit the dis-engagement of the sensitising gas bubbles.
Description
~ ~'7~
This invention rleates to explosive compositions and to their preparation; in particular, it relates to . non-aqueous explosive compositions comprising an oxidiser salt, a fuel material miscible with the oxidiser salt in the liquid state and gaseous bubbles.
Such explosive compositions, which are alterna-tively termed melt explosive compositions, may be pump-able, pourable and flowable liquids or slurries~ or may be solids. However if they are solids it is implicit that they have been prepared in a liquid or slurry skate and solidified by cooling.
By 'miscible' we mean that the oxidiser salt and fuel material when mixed together in certain proportions, depending on their nature, and, if necessary heated, form a mobile melt. It is the presence of this me~k in non-aqueous explosive compositions which imparts the pumpable, pourable and flowable properties.
The oxidiser salt is not an ex~losive in its own right but it is explosive when mixed with the fuel.
Melt explosive compositions have been known ~or many years. Thus as early as 1934 in USA patent specifi-cation 2,063,572 there are descriptions o proces~es for making high density explosives by incorporating ammonium nitrate and a freezing point depressant to proauce a composition which had a relatively broad melting poin~
range and heatiny it to a temperature sufficient to liquify a portion only of the ammonium nitrate with -the freezing point depressant. The material so produced was compacted by extruding whilst it was hot and then pressed or tamped into containers wherein it cooled to a solid, high density explosive. In this document it was taught that ammonium nikrate by itself was not suf~iciently sensitive for use as an explosive cmd it was preferred that there be .inclucled in khe composition up to 25~ o~ a sensitizing agent such as trinitrotoluene or or pentaerythritol tetranitrate. In the USA patent specification 2,817,581 there is describea a cast ex-plosive composition comprising a solid mixture of 14 to 20 parts by weight of urea, 1 to 6 parts by weigh~ of a high explosive sensitizing component such as cyclo-trimethylene trinitramine and the remainder to 100 parts of ammonium nitrate~ In USA patent speci~ication
This invention rleates to explosive compositions and to their preparation; in particular, it relates to . non-aqueous explosive compositions comprising an oxidiser salt, a fuel material miscible with the oxidiser salt in the liquid state and gaseous bubbles.
Such explosive compositions, which are alterna-tively termed melt explosive compositions, may be pump-able, pourable and flowable liquids or slurries~ or may be solids. However if they are solids it is implicit that they have been prepared in a liquid or slurry skate and solidified by cooling.
By 'miscible' we mean that the oxidiser salt and fuel material when mixed together in certain proportions, depending on their nature, and, if necessary heated, form a mobile melt. It is the presence of this me~k in non-aqueous explosive compositions which imparts the pumpable, pourable and flowable properties.
The oxidiser salt is not an ex~losive in its own right but it is explosive when mixed with the fuel.
Melt explosive compositions have been known ~or many years. Thus as early as 1934 in USA patent specifi-cation 2,063,572 there are descriptions o proces~es for making high density explosives by incorporating ammonium nitrate and a freezing point depressant to proauce a composition which had a relatively broad melting poin~
range and heatiny it to a temperature sufficient to liquify a portion only of the ammonium nitrate with -the freezing point depressant. The material so produced was compacted by extruding whilst it was hot and then pressed or tamped into containers wherein it cooled to a solid, high density explosive. In this document it was taught that ammonium nikrate by itself was not suf~iciently sensitive for use as an explosive cmd it was preferred that there be .inclucled in khe composition up to 25~ o~ a sensitizing agent such as trinitrotoluene or or pentaerythritol tetranitrate. In the USA patent specification 2,817,581 there is describea a cast ex-plosive composition comprising a solid mixture of 14 to 20 parts by weight of urea, 1 to 6 parts by weigh~ of a high explosive sensitizing component such as cyclo-trimethylene trinitramine and the remainder to 100 parts of ammonium nitrate~ In USA patent speci~ication
2,814,555 there is described another cast solid explosive composition comprising 16-21 parts by weight of urea crystals, 1-3 parts o~ an adsorbent such as kaolin in admixture with an amount of ammonium nitrate sufficient to give 100 parts of an explosive composition.
In USA paten-t specification 3,135t637 there is described a solid blasting explosive comprising a re-action mixture of ammonium nitrate and a urea-aliphatic hydrocarbon cla~hrate. Still further in USA patent specification 3,247,033 there is describe~ solid ex-plosive compositions comprising ammonium nitrate and primary fuel material optionally in combination with secondary fuel material and modifying material. It is taught therein that the components of such CQmpOsitiOnS
should be heated to a temperature between 150C and 165C to form a molten mass which is then chilled rapidly to form a solid product which is subsequen~ly flaked, granulated and densified and which is said to be advantageous in that it contains a desirable crys-tal form, is less prone to segregation and non-homogeneity of the components and leads to enhanced contact between the components of the composition.
~he compositions xeferred to above are typical oE known melt explosive compositions and they have a common attribute in that they are solid compositions and it is taught in the documents describing them that they should be used in the solid state. Thus they are designed to be us0d in a manner similar to tha~ for the well known mixtures of ammonium nitrate and ~uel oil (ANFO). Whilst such compositions are satisfactory in many respects as explosives, they have suffere~ from the disadvantage that it has of*en been found to be difficult in practice to load -them into boreholes at commercially acceptable loading rates. Thus to achieve a ~esired packing density, and hence a desired available bulk energy, it is common to use vibrating or tamping means to locate dry explosive compositions in boreholes. Such means are sometimes not effec-tive when granular prior art compositions are loaded at high rates into large diameter boreholes, leading to reduced and nonhomogeneous packing densities. So as to overcome these deficiencies of solid explosives it has been proposed to use wa~er bear-iny explosive compositions which in general terms com-prise a mixture of oxidizing salt material, ~uel material and water in proportions such that the compositions are pourable or pumpable. These compositions, often re-ferred to as slurry explosives, have been useful but they suffer from the disadvantage that the ~ater com-ponent thereof acts as a diluent which contributes little to the energy which becomes available when the composition is detonated.
Water-bearing explosive compositions have a low energy to volume ratio and it is desirable, ~or some purposes, to provide a pumpable, pourable or flowable explosive compositions which is substantially water free.
Hence it has been proposed that explosive compositions having low solidi~ication points be made. Thus in USA
patent specification 3,926,696 provision is made for explosive compositions having as essential components an oxygen supplying salt such as ammonium nitrate, a metallic fuel such as aluminium or magnesium, and an eutectic mi~ture comprising an oxygen supplying salt and a combustible compound which lowers the solidi~ication ~ ~ 7~ 3 point o~ the salt and wherein the compositions are characterized in that they have solidification points below +10C and preferably below -10C. In US patent specification 3,996,078 which was derived from US
In USA paten-t specification 3,135t637 there is described a solid blasting explosive comprising a re-action mixture of ammonium nitrate and a urea-aliphatic hydrocarbon cla~hrate. Still further in USA patent specification 3,247,033 there is describe~ solid ex-plosive compositions comprising ammonium nitrate and primary fuel material optionally in combination with secondary fuel material and modifying material. It is taught therein that the components of such CQmpOsitiOnS
should be heated to a temperature between 150C and 165C to form a molten mass which is then chilled rapidly to form a solid product which is subsequen~ly flaked, granulated and densified and which is said to be advantageous in that it contains a desirable crys-tal form, is less prone to segregation and non-homogeneity of the components and leads to enhanced contact between the components of the composition.
~he compositions xeferred to above are typical oE known melt explosive compositions and they have a common attribute in that they are solid compositions and it is taught in the documents describing them that they should be used in the solid state. Thus they are designed to be us0d in a manner similar to tha~ for the well known mixtures of ammonium nitrate and ~uel oil (ANFO). Whilst such compositions are satisfactory in many respects as explosives, they have suffere~ from the disadvantage that it has of*en been found to be difficult in practice to load -them into boreholes at commercially acceptable loading rates. Thus to achieve a ~esired packing density, and hence a desired available bulk energy, it is common to use vibrating or tamping means to locate dry explosive compositions in boreholes. Such means are sometimes not effec-tive when granular prior art compositions are loaded at high rates into large diameter boreholes, leading to reduced and nonhomogeneous packing densities. So as to overcome these deficiencies of solid explosives it has been proposed to use wa~er bear-iny explosive compositions which in general terms com-prise a mixture of oxidizing salt material, ~uel material and water in proportions such that the compositions are pourable or pumpable. These compositions, often re-ferred to as slurry explosives, have been useful but they suffer from the disadvantage that the ~ater com-ponent thereof acts as a diluent which contributes little to the energy which becomes available when the composition is detonated.
Water-bearing explosive compositions have a low energy to volume ratio and it is desirable, ~or some purposes, to provide a pumpable, pourable or flowable explosive compositions which is substantially water free.
Hence it has been proposed that explosive compositions having low solidi~ication points be made. Thus in USA
patent specification 3,926,696 provision is made for explosive compositions having as essential components an oxygen supplying salt such as ammonium nitrate, a metallic fuel such as aluminium or magnesium, and an eutectic mi~ture comprising an oxygen supplying salt and a combustible compound which lowers the solidi~ication ~ ~ 7~ 3 point o~ the salt and wherein the compositions are characterized in that they have solidification points below +10C and preferably below -10C. In US patent specification 3,996,078 which was derived from US
3,926,696 there is described an eutectic composition consistiny essentially of an oxygen supplying sal-t, a combustible compound and at least 30% w/w o~ a nitrate or perchlorate of an alkanolamine, the composition hav-ing a solidification point below -10C.
In the realm of explosives manufacture it is considered to be desirable to use process conditions or components of compositions which lead to a minimum of hazard. Thus it is desirable that temperatures used in the preparation of explosive compositions are kept relatively low so as to avoid undesired detonation or burning of the compositions, hence use has been made o~
low melting eutectics of the oxidiser sa~ and ~uel material to provide the liquid phase in non-aqueous pumpable, pourable and ~lowable explosive composi~ions.
Frequently it is necessary to increase the . sensitivity to detonation of melt explosive compositions.
This can sometimes be ~chieved b~ the incorporation of high explosives such as trinitrotoluene, nitroglycerine, pentaerythritol tetranitrate, picric acid, nitro starch, cyclotrimethylenetrinitramine and the like. However, care has to be taken in using such high explosives, an~
: where for a particular purpose their use is unavoiaable~
the proportion thereof should be as small as possible.
There are other means o~ enhancing the sensitivity o~ non-aqueous explosive compositions which include the incorporation of such substances as the alkanolamine nitrates, alkanolamine perchlorates or unstabi.lized alkylene glycol nitratesr or inorganic materials like Einely div.ided aluminium, magnesium or ferrosilicon.
Another means of imparting sensitivity to melt explosive compositions is to incorporate a discontinuous gaseous phase therein. This may be achieved by the in-clusion of hollow particles, sometimes describe~ as microballoons, or porous particles. Alternatively the gaseous phase may take the form of gas bubbles homo-geneously dispersed throuyhout the composition: the composi-tions of the present invention are of this last type, namely 'gas-bubble-sensitised' melt explosive com-positions.
British Patent Specification 839,078 describesa gas-bubble-sensitised melt explosive composition in which the gas bubbles h~ave been generated by chemical means. Alternatively the gas bubbles can be introduced by mechanical aeration.
Melt explosive compositions provide a suitable means to supply bulk explosives. They are pumped into the boreholes and depending on the residence -time and ground temperature they may solidify and set, They may be initiated in the liquid or solid form. ~Iowever gas-bubble-sensitised melt explosives are liable to de-sensitisation by pumping because of disengagement of the gas bubbles from the composition. Furthermore gas bubble disengagement can also take place if the compositions stand for any length of time in a fluid or molten state~
This gas bubble disengagement manifests itself in an increase in the density of the composition. Usual:Ly it is necessary for a gas-bubble-sensitised e~plosive com-position to have a density not greater ~han 1~40 g./c.c.
If on pumping the clensity rises above this level, the composition is likely to be too insensitive to be ~
useful exp:Losive. In addit:ion to the loss of reduction in sensitivity associated with densification o~ the com-position, there is a further undesirable aspect associated with the Eact that explosive bulk energy 6~
is related -to density. Frequently it is desirable to modify the bulk energy of the charge even within the same borehole to accommodate compression of the charge by water head or explosive head and/or variations in the rock to be blasted, hence any uncontrollecl change in density which alters the bulk energy on ~he charge is undesirable.
We have now found tha-t gas-bubble-sensi-tised melt explosive compositions are stabilised against gas bubble disengagement by the inclusion of certaln cationic and non-ionic surfactants~ -Accordingly the present invention provides adensity-stabilised gas-b'ubble-sensitised melt explosive composition having a density not greater than 1.4 g./c.c.
characterised in that the said cornposition contains a foam-stabilising surfactant, as hereinaf-ter defined, in an amount in the range of 0.05 to 2~00 percent on a w~w basis.
The foam stabilising surfactant may consist of one or more surfactant species.
By 'density-stabilised' we mean that the said composition ini~s liquid or slurry state does not become substantially more dense on pumping or standing; nor do the gas bubbles grow or coalesce so that their sensitis-ing effect is lost. Desirably, any density increase isless than 10~ of the 'as-prepared' density.
The said gas-bubble-sensitised melt explosive compositions comprise essentially an oxygen releasing salt, a melt soluble fuel materiaL, a thickening agent, gas bubbles and the characterising foam stabilising suractant. 'tn addition, the said composition optionally comprise a cross-linking agent, water up to 3 percent w/w, and secondary ~uels, either in a liquid or solid form.
Suitable oxygen releasing salts for use in ~he ~:~'7~
compositions of this invention are alkali metal nitrates, alkaline earth metal nitrates, ammonium nitrate or their chlorate and perchlorate equivalents. Preferably the oxygen releasing salt component cons-ti-tutes between 60 and 80 percent w/w of the composition and is ~mmonium nitrate or a blend of ammonium nitrate and sodium nitrate.
The preferred composition range for such a blend is be-tween 5 and 20 parts by weight of sodium nitrate with 100 parts ammonium nitrate.
By melt soluble fuel material is meant a fuel material which is capable of forming a eutectic mixture with the oxygen releasing salt; the melting point of ~he eutectic mixture being less than the melting p~int of either the fuel material or the oxygen releasing salt.
It is desirable that the melt soluble fuel material be capable of forming a miscible melt with ammonium nitra~e, the preferred oxygen releasing salt~ Thus in the pre-ferred compositions containing ammonium nitrate the melt soluble fuel materials, hereinafter referred $o as the primary fuel, may be defined as an organic compound which i5 capable of forming a homogeneous eutectic melt with ammonium nitrate and of being oxidize~ by ammonium nitrate to form substantially all gaseous products. The primary fuel may be a single compound or a mixture of two or more compounds. Suitable primary ~uels inc:Lude carboxylates, thiocyanates, short chain amines, imides or amides. Typical useful primary fuels include ammonium acetate, ammonium formate, ammonium thiocyanage, hexa-methylene t~tramine, dicyanodiamide, thiourea, ace-tamide, urea and mixtures thereof. The preferred primary Euel is provide~ by between 15 and 30 percent w~w o~ urea.
The thickening agents are used in the compositions of the invention in amounts between 0.05 and 2 percent w/w. ~hey are suitably polymeric materials, especially g~ materials typified by the galactomannan gums such as locust bean gum or guar gum or derivatives -thereof such as hydroxypropyl guar gum. Other useful, but less pre-ferredl gums are the so called biopolymeric gums such as the heteropolysaccharides prepared by the microbial transformation of carbohydrate material, for example the treatment of glucose with a plant pathogen of the genus Xanthomonas typified by Xanthomonas campestris~
Polymeric materials derived from acrylamide are also use-ful thickeners.
In order that the composi-tions of the present invention will have the desired consistency, it is pre-ferable for the thickening agent to be crosslinked.
It is convenient for this purpose to use conventional crosslinklng agents such as zinc chromate or a dic~romate lS either as a separa-te entity or as a component of a con-ventional redox system for example a misture o~ potassium -dichromate and potassium antimony tartrate. Surprisinyly it has been found in many instances that the thickening agents do not re~uire the presence of water in the com-positions to be efficacious. Howe~er should it be con-sidered desirable that the solvation of gummy thickening agents or their crosslinking would be enhanced by the presence of small amounts of water or a water-bearing medium, it lies within the scope of the invention that there be present in the composition a sufficiency ~f water to enable such solvation or crosslinking to be effected, provided that the total water content of ~he composition does not exceed 3 percent on a w/w basis~
The gaseous bubbles may be introducel into the composition by mechanically aerating the compositi~n as it is being prepared or by adding a chemical, gassing agent such as a mixture of sodium nitrite and thiourea.
The amount of gaseous bubbles incorporated is such as to produce compositions oE density less than 1.~0 g~c,c.
Preferably it is such that the density is less than 1~35 g ~ /c . c ~
Although the stabilisation of foams in aqueous systems by surfactants is well known and the type of suitable surfactant is predictable, the use of sur-factants for foam stabilisation in non-aqueous systems~
such as are the composi-tions of this invention, is not well-known and suitable surfactants cannot be predicted.
However.we have found that there is a correlation ~etween the results obtained from a foam stabilisation tes-t, described hereinafter and the density stabilising effect of various surfactants on melt compositions containing air bubbles.
In the said foam stabilisation test 10 g of a eutectic composition consisting of 46.7% ammonium nitrate, 43.6~ urea and 9.7~ sodium nitrate, all on a w/w basis, is heated to 70C to form a melt in a graduated cylindrical vessel of 10 m.m. internal diameter. 0.5%
of the candidate surfactant or mixture of surfactants to be tested is adaed to the melt and the vessel is shaken for one minute. A foam forms on the surface of the melt. The height (f5) of this foam is measured after 5 minutes using the graduations on the vessel.
The foam height (f60) is measured again after 60 minutes, the vessel and melt being kept at 70C all the time. A
foam stability parameter is calculated from the foam heights according to the following formula:
foam height after sixty minu-tes, f60 ~5 foam height after five minutes, f5 By way of illustration of the appli.cation of the foam stabilisat:ion test, Table 1 records the results for a number of surfactants and surfactant mixtures.
7~
- 11 ~
Foam Stabilisation Tests -.
_ Co-surfactant Foam B Properties Surfactant ( I f B present f5 60 ratio w/w of A: ~I mm ~5 .
'Farmin' C (C12 amine) 11 0O73 'Farmin' O (oleylamine) 4 0.5 'Duomeen T (Tallow propylene diamine)8 0.63 'Armeen' HT (C18 amine) 7.5 0.8 'Armeen' 16D
(hexadecylamine) 4.5 0.78 'Armeen' 18D
(octadecylamine) 10 0.7 'Armac' 12D (C 2 amine acetate) 1 lQ~5 0.56 'Oxamin' ~O (C12 14 amine 3.5 0.57 'Emigen' AB (N-N-dimethyl . laurylamine) 12.5 0.44 'Farmin' DM40 (dimethyl myristyl amine) 2 0.5 'Farmin' DMC (dimethyl cocoamine) 7 0.43 'Farmin' DM86 (dimethyl : stearyl amine) 2~5 0.40 'Farmin' DM20 (N-N dimethyl laury1 amine) I 10.5 0.52 '~lkadet' 15 (C9 11 glucoside) ~ 6 0.8 'Dobanoll 91 (C9_11 glucose acetal) I 6 0.8 'Teric' 307 (C12 1~ ethoXYlated j phosphate) ~ 2 0~75 'Teric' CME3 (etho~ylated cocomonoethanolamide)* 1 1.5 0 , .
TABLE 1 continued . Co-surfact.ant Foam B Properties Surfactant . _ A (if B present ~5 60 ratio w/w of A: H Imm ~5 _ .
'Terie' CME7(ethoxylated eocomonoethanolamine)* 2 0 'Teriel 18M2 (ethoxylated C18 amine) 4 2.3 Terie' 12M2 (ethoxylated . 3 0.67 'Teric' 17A8 (ethoxylated .
C16-18 alcohol) 3 ~.8 'Teric' ALE25 (ethoxylated lauryl ether sulphate . 2 0.5 'Emi~en BB* (C12-14 9 5 0 10 betaine) .
Lauric Aeid* ) Sodium Stearate*
Caleium Stearate*
Sodium lauryl sulphate*
: IArmeen' 2HT (secondary ) : amine)* ) .
'Armeen' T08 (tertiary ) ~o foam formed amine*
'Armid' HT ~C18 amide)* ) 'Synprol' (C13 ~5 aleohol)*3 Oetadeeanol*
'Matexil' (sod.ium ) diisocctyl sulpho-sueeinate)*
'A~neen' HT Oetadeeanol 13.5 O.55 'Armeen' HT 'Teric' 307 21 0.62 . __ _ _ _ ,.
TABLE 1 continued _ . _ .
. Co-surfactant Foam B Properties SurEactant . . .
A (if B present f5 60 B - 5-1) ~I mm ~5 _ _ 'Armeen' HT 'Terici CME7 15.5 O.57 'Armeen' HT ITeric' ~LE25 16 0.66 'Armeen' HT 'Teric' 12A325 0.44 ~rmeen' HT 'Teric' CME324 D.48 'Teric' 18M2 'Teri.c' 3077 2.4+
'Teric' 18M2 'Teric' 12A33 2.7~
. _ . ._ ~'Farmin', 'Duomeen', 'Armeen', "Armac', IOxamin r r 'Emigen'l 'Alkadeti, IDobanol', 'Teric', 'Synprol', 'Armid', and '~atexil' are trade names).
(-~ In some instances ~he foam bubbles continue ~ rise to the surface o~ the test liquor after the fi~e minute reading. This can cause the value O~ 06 to be greater than unity).
The asterisks in Table 1 indicate those sur-factants unsuitable as density stabilisers. It has been found that only those surfactants or mixtures of sur factant species wh:ich gave an initial ~oam height, f5, result equal to or greater than 2 mm and had a stabilit~
parameter greater than 0.30 imparted the desirea density stabilisation effect which characterises the compositions of this invention, when included in gas-bubble-sensitised melt explosive compositions. Hence the foam-stabilising sur:Eactants oE the invention are aefined as those having an .f5 value e~ua]. to or greater than 2 mm and 05 greater than 0.3 by the foam stabilisation tést hereinbefore defined.
The pre:Eerred type of surfactant is a long r straight chain, organic primary amine containing at least 6 carbon a-toms in the molecular structure. More to be preferred are long, straight chain, organic primary amines containing between 12 and 22 inclusive carbon atoms in their molecular structure. Another preferred type of surfactant is an ethoxylated, straight chain organi.c amine containing at least 8 carbon atoms in the molecular structure.
It is not necessary to add more than 2.00% w/w of foam-stabilising surfactant to the melt explosive compositions of this invention for it to have the de-sired effect bu-t, of course, higher proportions will stabilise the foam. Economically, being a high-cost ingredient, it is desirable to keep the level of addition of foam stabilisiny surfactant to the minimum having the desired effect. The preferred level of addition i.s an amount in the range of 0.3 percent to 1.5 percent w/w on the basis of the whole composition.
In practice, the components used to make the explosive compositions of the invention ma~ contain water of crystallisation and/or free moisture, hence it is anticipated that there may be up to 3 percent w/w water in the said compositions~ Some watex may also be intro-duced in order to solvate th~ thickening sys-tem used as has been hereinbefore referred to. However the presence of water in the composition is undesirable because it detracts from the explosive properties of the composition and it is therefore kept to a practicable minimum~
Secondary fuel materials which are not melt soll~le may be chosen Erom a range of materials and in-clude :Eor instance sulphur alum.inium, silicon, carbon and uid or solid carbonaceou.s materials. Some liquid carbonaceous materi.als are unsuitable because they interfere with the density stabilising property of the surfactant. For this reason solid carbonaceous materials are used as secondary fuels, for example comminuted coke or charcoal, carbon black; resin acids such as abietic acid or derivatives thereof; sugars such as sucrose or dextrose' or other vegetable products such as s-tarch~
nut meal or wood pulp. Particulate aluminium is the preferred secondary fuel.
The process of making the gas-bubble-sensitised melt explosive compositions is essentially a mixing process and the sequence of addi-tion of the components to the mix is not critical. It is preferred, however.
to incorporate the gas bubbles as late as possible in the manufacture of the compositions because thereby the likelihood of disengagement of the gas bubbles is minimised and the mix is insensitive for a maximum time during the manufacture process; the gas bubbles being the sensitising agent.
A preferred method of preparation of the melt explosive compositions is to first prepare a pre-thickened melt comprising a portion of the oxygen .re-leasing salt component, the melt soluble fuel material, the thickening agent and the foam stabilising surfactant.
To this melt there is added a mixture comprising the remainder of the oxygen releasing salk component and optionally a crosslinking agent and/or secondary fuel.
If the gas bubbles are to be formed by chemical means, the chemical gassing agent is added to the mixture. If mechanical means are usecl to introduce the gas bubbles, a blend of the melt and the mixture is subjected to a mechanical aeration process, such as beating or uigorously stirr.iny.
The compositions of the invention are useful as fillings in explosiue cartridges and they are also eminently suitable for use in conjunction with - 16 ~
conventional pumping or mixing trucks designed ~or use with known water based explosives of the so-called slurry type. Thus for example a thickened melt component of the compositions of the invention may be placed in the solution tank of such a conventional mixing truck and the residual components of -the compositions may be added to and mixed with the melt in a conventional manner and thereafter the composition of the invention so prepared may be transferred to a borehole wherein it may be detonated.
The compositions of the invention have similar explosive bulk energy to other known non-aqueous com-positions which are pumpable, pourable or flowable with the advantage that they have stable densities. Moreover these new compositions are devoid, in terms of essential compoIients, of high explosive materials, per se.
The new compositions of the invention may ~e made having as wide a range of densities as 0.30 g./c.c~ to 1.40 g./c.c. The very low density ( 0.70 g./c.c.~
compositions are of particular utility when a low ex-plosive energy/volume explosive is desired, for instance when minimal backbreak is required during open pit bLasting.
One way of making such low density compositions is to mechanically aerate vigorously a suitable me:Lt composition until the desired density is achieved and then to add crosslinking agent to crosslink the thickening agent in the melt. Without the aadition o~
the characterising surfactant such compositions cannot ~0 be pumped or stored without considerable increase in density.
~, .
This invention is now illustrated by, but is not limited -to, the following examples, except examples 3, 4, 5 and 8. All parts and percentages are expressed on a weight basis unless otherwise specifie~.
A preferred composition was prepared as ~ollows.
Ammonium nitrate, sodi~n nitrate and urea were mixed according to proportions given below for Mixture A.
Mixture A Parts 10 ammonium nitrate 57.9 sodium nitrate 10.6 urea 31.5 sodium acetate 0.5 acetic acid (glacial) 0,5 15 surfactant 'Farmin C' 0.5 This mixture A was melted by heating and thickened by mixing in 0.1 parts by yuar gum at 65C
and standiny overnight.
To 61 parts of this mixture A 39 parts oF Mixture B ingredients were added in a planetary mixer.
Mixture B Ingredients Parts -ammonium nitrate prills 38.9 sodium nitrite as 33.33% aqueous solution 0.1 A sample of the resulting composition was re-circulated -through a pneumatically operated pis-ton pump five successive times~ The density oE the sample prior to pumping was 1.10 y/cc whilst ater pumping the density was 1.05 g/cc.
~his sample was then cooled to 20C an~ stored for a pexiod of one week.
The sample was then detonated in a 79 mm steel pipe usiny a 100 y pentolite booster. The VOD was measured to be 4.5 km/sec.
_XAMPLE 2 A composition was prepared acco~ding to the procedure already described for example 1. In this example the Mixture A contained 0.5 parts of the sur-factant 'Alkadet' 15 in place of 'Farmin C'. It wasthickened by addition of 0.1 parts guar gum and 0.2 parts starch.
Thirty nine parts of ammonium nitrate prills were added to sixty one parts of the thickened mixture A and the composition loaded into 79 mm diameter steel tubes.
The composition density was 1.31 g/cc. T~e sample was stored for 1 week and then detonated with a 140 g pentolite booster at a VOD of 3.1 km/sec.
-The compositions of these examples were i~entical in composition and preparation to that of Example 1 except for the variations listed in Table 2.
The densities of the compositions listed in Table 2 are those before storage. Experience has shown that such compositions are likely to increase in density on storage. However the ailure of the compositions of Examples 5 and 8 to initiate may also be due to gas bubble coalescence~
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A thickened melt solution containin~ the ingredients shown below as Mixture C was prepare~ by th~
procedure described for thickened Mixture ~ in Example 1.
5 Mixture C Parts ammonium nitrate 58.2 sodi~n nitrate 11~1 urea 26.0 water 3~0 10 guar gum 0.35 'Farmin C' 0.4 sodium acetate 0.4 acetic acid o,~
thiourea 0O005 To 76 parts of Mixture C were mixed 24 parts of the ingredients listed as Mixture D using a mixer of the type commonly employed on watergel explosive mix trucks.
Mixture D Parts __ ammonium nitrate prills 24.0 20 sodium nitrite as 33.33%
aqueous solution 0.15 sodium dichromate as 50%
aqueous solution ~.10 The density of the resulting mixture (C and D) was 1.00 g/cc. This mixture was pumped at 40 kg/min through a lobed gear pump after which the density was 0~96 g/cc. The stored mixture (density 1.02 g/cc) was then loaded into 140 mm cylindrical containers and stored for 30 days. The mi~ture then detonated satisfactorily ~ith a 30 g pentolite booster.
EXAMPI,E
To 70 parts o~ mixture C were added 30 parts of mixture E and the composition processed and stored as described for Example 11.
O ~
Mixture E Parts -ammonium nitrate prills 27,0 fuel grade, aluminium 3.0 sodium nitrite as 33.33%
aqueous solutio~ 0.15 sodium dichromate as 50%
aqueous solution 0.10 This mixture detonated satisfactorily after 30 days storage with a 20 g Pentolite booster.
EXAMPLES 1'3'AND 14 -Examples 11 and 12 were repeated in examples 13 and 14 respectively except that the ~Farmin C' surfact-ant in mixture C was replaced by 'Armeen' HT surfactant.
The products of these examples were processed and stored as described in Example 11. Subsequently they were satisfactorily detonated with a 20 g pen-tolite booster.
EXAMPI,E 15 An explosive composition similar to that o~
Fxample 14 but with 63 parts of mixture C, 30 parts ~f mixture E and 7 parts of fuel grade aluminium was made and satisfactorily detonated.
ExAMæLE 16 .
A thickened melt solution containing ~he in-gredients as Mixture C of example 11 was prepared except that 'Farmin C' in the mixture was replaced by 'Armeen' HT and thiourea was present in 0~02 pa.rts.
To 70 parts of this mixture were mixed 30 parts of Mixture D using a commercial explosive mix truck of the type generally used for water gel explosives.
Mixture D Parts ammonium nitrate prills 26.9 fuel grade aluminium 3.0 ~ ~`7~
~ 22 -MiXture D continued Parts .
sodium nitrite as 33.33% aqueous 0.20 solution sodium dichromate as 33~33~ a~ueous0~09 solution The densi-ty of the resulting mix~ure was 1.05 g/cc. 5 tonnes of this mixture was pumped into 15 blast holes (265 mm diameter by 14 metres deep) and success-fully detonated with 415 gm pentolite boosters.
Rock breakage and heave were observed to be excellent.
A thickened melt of composition F was prepared according to the procedure described in Exampl~ 1 for 15 thickened Mixture A.
Mixture F Parts ammonium nitrate 61.5 sodium nitrate 11.0 urea 24.5 20 water 3.0 soaium methyl naphthalene 0.5 (as a crystal habi-t sulphonate modifier) suxfactant 'Farmin DMC' 1.0 guar gum 0.4 After thickening this mixture was aerated by vigorous mixing to a density of 0.32 g~cc. To 100 parts of this composition was added 0.1 part of sodium di-chromate crosslinking solution.
The material was mixed and stored for three days prior to testing. The sample was detonated in a 170 mm cylindrical container underwater using a 140 g pentolite booster. A bubble energy yield oE 1.7 MJouleJky was measured.
.. . ,~
In the realm of explosives manufacture it is considered to be desirable to use process conditions or components of compositions which lead to a minimum of hazard. Thus it is desirable that temperatures used in the preparation of explosive compositions are kept relatively low so as to avoid undesired detonation or burning of the compositions, hence use has been made o~
low melting eutectics of the oxidiser sa~ and ~uel material to provide the liquid phase in non-aqueous pumpable, pourable and ~lowable explosive composi~ions.
Frequently it is necessary to increase the . sensitivity to detonation of melt explosive compositions.
This can sometimes be ~chieved b~ the incorporation of high explosives such as trinitrotoluene, nitroglycerine, pentaerythritol tetranitrate, picric acid, nitro starch, cyclotrimethylenetrinitramine and the like. However, care has to be taken in using such high explosives, an~
: where for a particular purpose their use is unavoiaable~
the proportion thereof should be as small as possible.
There are other means o~ enhancing the sensitivity o~ non-aqueous explosive compositions which include the incorporation of such substances as the alkanolamine nitrates, alkanolamine perchlorates or unstabi.lized alkylene glycol nitratesr or inorganic materials like Einely div.ided aluminium, magnesium or ferrosilicon.
Another means of imparting sensitivity to melt explosive compositions is to incorporate a discontinuous gaseous phase therein. This may be achieved by the in-clusion of hollow particles, sometimes describe~ as microballoons, or porous particles. Alternatively the gaseous phase may take the form of gas bubbles homo-geneously dispersed throuyhout the composition: the composi-tions of the present invention are of this last type, namely 'gas-bubble-sensitised' melt explosive com-positions.
British Patent Specification 839,078 describesa gas-bubble-sensitised melt explosive composition in which the gas bubbles h~ave been generated by chemical means. Alternatively the gas bubbles can be introduced by mechanical aeration.
Melt explosive compositions provide a suitable means to supply bulk explosives. They are pumped into the boreholes and depending on the residence -time and ground temperature they may solidify and set, They may be initiated in the liquid or solid form. ~Iowever gas-bubble-sensitised melt explosives are liable to de-sensitisation by pumping because of disengagement of the gas bubbles from the composition. Furthermore gas bubble disengagement can also take place if the compositions stand for any length of time in a fluid or molten state~
This gas bubble disengagement manifests itself in an increase in the density of the composition. Usual:Ly it is necessary for a gas-bubble-sensitised e~plosive com-position to have a density not greater ~han 1~40 g./c.c.
If on pumping the clensity rises above this level, the composition is likely to be too insensitive to be ~
useful exp:Losive. In addit:ion to the loss of reduction in sensitivity associated with densification o~ the com-position, there is a further undesirable aspect associated with the Eact that explosive bulk energy 6~
is related -to density. Frequently it is desirable to modify the bulk energy of the charge even within the same borehole to accommodate compression of the charge by water head or explosive head and/or variations in the rock to be blasted, hence any uncontrollecl change in density which alters the bulk energy on ~he charge is undesirable.
We have now found tha-t gas-bubble-sensi-tised melt explosive compositions are stabilised against gas bubble disengagement by the inclusion of certaln cationic and non-ionic surfactants~ -Accordingly the present invention provides adensity-stabilised gas-b'ubble-sensitised melt explosive composition having a density not greater than 1.4 g./c.c.
characterised in that the said cornposition contains a foam-stabilising surfactant, as hereinaf-ter defined, in an amount in the range of 0.05 to 2~00 percent on a w~w basis.
The foam stabilising surfactant may consist of one or more surfactant species.
By 'density-stabilised' we mean that the said composition ini~s liquid or slurry state does not become substantially more dense on pumping or standing; nor do the gas bubbles grow or coalesce so that their sensitis-ing effect is lost. Desirably, any density increase isless than 10~ of the 'as-prepared' density.
The said gas-bubble-sensitised melt explosive compositions comprise essentially an oxygen releasing salt, a melt soluble fuel materiaL, a thickening agent, gas bubbles and the characterising foam stabilising suractant. 'tn addition, the said composition optionally comprise a cross-linking agent, water up to 3 percent w/w, and secondary ~uels, either in a liquid or solid form.
Suitable oxygen releasing salts for use in ~he ~:~'7~
compositions of this invention are alkali metal nitrates, alkaline earth metal nitrates, ammonium nitrate or their chlorate and perchlorate equivalents. Preferably the oxygen releasing salt component cons-ti-tutes between 60 and 80 percent w/w of the composition and is ~mmonium nitrate or a blend of ammonium nitrate and sodium nitrate.
The preferred composition range for such a blend is be-tween 5 and 20 parts by weight of sodium nitrate with 100 parts ammonium nitrate.
By melt soluble fuel material is meant a fuel material which is capable of forming a eutectic mixture with the oxygen releasing salt; the melting point of ~he eutectic mixture being less than the melting p~int of either the fuel material or the oxygen releasing salt.
It is desirable that the melt soluble fuel material be capable of forming a miscible melt with ammonium nitra~e, the preferred oxygen releasing salt~ Thus in the pre-ferred compositions containing ammonium nitrate the melt soluble fuel materials, hereinafter referred $o as the primary fuel, may be defined as an organic compound which i5 capable of forming a homogeneous eutectic melt with ammonium nitrate and of being oxidize~ by ammonium nitrate to form substantially all gaseous products. The primary fuel may be a single compound or a mixture of two or more compounds. Suitable primary ~uels inc:Lude carboxylates, thiocyanates, short chain amines, imides or amides. Typical useful primary fuels include ammonium acetate, ammonium formate, ammonium thiocyanage, hexa-methylene t~tramine, dicyanodiamide, thiourea, ace-tamide, urea and mixtures thereof. The preferred primary Euel is provide~ by between 15 and 30 percent w~w o~ urea.
The thickening agents are used in the compositions of the invention in amounts between 0.05 and 2 percent w/w. ~hey are suitably polymeric materials, especially g~ materials typified by the galactomannan gums such as locust bean gum or guar gum or derivatives -thereof such as hydroxypropyl guar gum. Other useful, but less pre-ferredl gums are the so called biopolymeric gums such as the heteropolysaccharides prepared by the microbial transformation of carbohydrate material, for example the treatment of glucose with a plant pathogen of the genus Xanthomonas typified by Xanthomonas campestris~
Polymeric materials derived from acrylamide are also use-ful thickeners.
In order that the composi-tions of the present invention will have the desired consistency, it is pre-ferable for the thickening agent to be crosslinked.
It is convenient for this purpose to use conventional crosslinklng agents such as zinc chromate or a dic~romate lS either as a separa-te entity or as a component of a con-ventional redox system for example a misture o~ potassium -dichromate and potassium antimony tartrate. Surprisinyly it has been found in many instances that the thickening agents do not re~uire the presence of water in the com-positions to be efficacious. Howe~er should it be con-sidered desirable that the solvation of gummy thickening agents or their crosslinking would be enhanced by the presence of small amounts of water or a water-bearing medium, it lies within the scope of the invention that there be present in the composition a sufficiency ~f water to enable such solvation or crosslinking to be effected, provided that the total water content of ~he composition does not exceed 3 percent on a w/w basis~
The gaseous bubbles may be introducel into the composition by mechanically aerating the compositi~n as it is being prepared or by adding a chemical, gassing agent such as a mixture of sodium nitrite and thiourea.
The amount of gaseous bubbles incorporated is such as to produce compositions oE density less than 1.~0 g~c,c.
Preferably it is such that the density is less than 1~35 g ~ /c . c ~
Although the stabilisation of foams in aqueous systems by surfactants is well known and the type of suitable surfactant is predictable, the use of sur-factants for foam stabilisation in non-aqueous systems~
such as are the composi-tions of this invention, is not well-known and suitable surfactants cannot be predicted.
However.we have found that there is a correlation ~etween the results obtained from a foam stabilisation tes-t, described hereinafter and the density stabilising effect of various surfactants on melt compositions containing air bubbles.
In the said foam stabilisation test 10 g of a eutectic composition consisting of 46.7% ammonium nitrate, 43.6~ urea and 9.7~ sodium nitrate, all on a w/w basis, is heated to 70C to form a melt in a graduated cylindrical vessel of 10 m.m. internal diameter. 0.5%
of the candidate surfactant or mixture of surfactants to be tested is adaed to the melt and the vessel is shaken for one minute. A foam forms on the surface of the melt. The height (f5) of this foam is measured after 5 minutes using the graduations on the vessel.
The foam height (f60) is measured again after 60 minutes, the vessel and melt being kept at 70C all the time. A
foam stability parameter is calculated from the foam heights according to the following formula:
foam height after sixty minu-tes, f60 ~5 foam height after five minutes, f5 By way of illustration of the appli.cation of the foam stabilisat:ion test, Table 1 records the results for a number of surfactants and surfactant mixtures.
7~
- 11 ~
Foam Stabilisation Tests -.
_ Co-surfactant Foam B Properties Surfactant ( I f B present f5 60 ratio w/w of A: ~I mm ~5 .
'Farmin' C (C12 amine) 11 0O73 'Farmin' O (oleylamine) 4 0.5 'Duomeen T (Tallow propylene diamine)8 0.63 'Armeen' HT (C18 amine) 7.5 0.8 'Armeen' 16D
(hexadecylamine) 4.5 0.78 'Armeen' 18D
(octadecylamine) 10 0.7 'Armac' 12D (C 2 amine acetate) 1 lQ~5 0.56 'Oxamin' ~O (C12 14 amine 3.5 0.57 'Emigen' AB (N-N-dimethyl . laurylamine) 12.5 0.44 'Farmin' DM40 (dimethyl myristyl amine) 2 0.5 'Farmin' DMC (dimethyl cocoamine) 7 0.43 'Farmin' DM86 (dimethyl : stearyl amine) 2~5 0.40 'Farmin' DM20 (N-N dimethyl laury1 amine) I 10.5 0.52 '~lkadet' 15 (C9 11 glucoside) ~ 6 0.8 'Dobanoll 91 (C9_11 glucose acetal) I 6 0.8 'Teric' 307 (C12 1~ ethoXYlated j phosphate) ~ 2 0~75 'Teric' CME3 (etho~ylated cocomonoethanolamide)* 1 1.5 0 , .
TABLE 1 continued . Co-surfact.ant Foam B Properties Surfactant . _ A (if B present ~5 60 ratio w/w of A: H Imm ~5 _ .
'Terie' CME7(ethoxylated eocomonoethanolamine)* 2 0 'Teriel 18M2 (ethoxylated C18 amine) 4 2.3 Terie' 12M2 (ethoxylated . 3 0.67 'Teric' 17A8 (ethoxylated .
C16-18 alcohol) 3 ~.8 'Teric' ALE25 (ethoxylated lauryl ether sulphate . 2 0.5 'Emi~en BB* (C12-14 9 5 0 10 betaine) .
Lauric Aeid* ) Sodium Stearate*
Caleium Stearate*
Sodium lauryl sulphate*
: IArmeen' 2HT (secondary ) : amine)* ) .
'Armeen' T08 (tertiary ) ~o foam formed amine*
'Armid' HT ~C18 amide)* ) 'Synprol' (C13 ~5 aleohol)*3 Oetadeeanol*
'Matexil' (sod.ium ) diisocctyl sulpho-sueeinate)*
'A~neen' HT Oetadeeanol 13.5 O.55 'Armeen' HT 'Teric' 307 21 0.62 . __ _ _ _ ,.
TABLE 1 continued _ . _ .
. Co-surfactant Foam B Properties SurEactant . . .
A (if B present f5 60 B - 5-1) ~I mm ~5 _ _ 'Armeen' HT 'Terici CME7 15.5 O.57 'Armeen' HT ITeric' ~LE25 16 0.66 'Armeen' HT 'Teric' 12A325 0.44 ~rmeen' HT 'Teric' CME324 D.48 'Teric' 18M2 'Teri.c' 3077 2.4+
'Teric' 18M2 'Teric' 12A33 2.7~
. _ . ._ ~'Farmin', 'Duomeen', 'Armeen', "Armac', IOxamin r r 'Emigen'l 'Alkadeti, IDobanol', 'Teric', 'Synprol', 'Armid', and '~atexil' are trade names).
(-~ In some instances ~he foam bubbles continue ~ rise to the surface o~ the test liquor after the fi~e minute reading. This can cause the value O~ 06 to be greater than unity).
The asterisks in Table 1 indicate those sur-factants unsuitable as density stabilisers. It has been found that only those surfactants or mixtures of sur factant species wh:ich gave an initial ~oam height, f5, result equal to or greater than 2 mm and had a stabilit~
parameter greater than 0.30 imparted the desirea density stabilisation effect which characterises the compositions of this invention, when included in gas-bubble-sensitised melt explosive compositions. Hence the foam-stabilising sur:Eactants oE the invention are aefined as those having an .f5 value e~ua]. to or greater than 2 mm and 05 greater than 0.3 by the foam stabilisation tést hereinbefore defined.
The pre:Eerred type of surfactant is a long r straight chain, organic primary amine containing at least 6 carbon a-toms in the molecular structure. More to be preferred are long, straight chain, organic primary amines containing between 12 and 22 inclusive carbon atoms in their molecular structure. Another preferred type of surfactant is an ethoxylated, straight chain organi.c amine containing at least 8 carbon atoms in the molecular structure.
It is not necessary to add more than 2.00% w/w of foam-stabilising surfactant to the melt explosive compositions of this invention for it to have the de-sired effect bu-t, of course, higher proportions will stabilise the foam. Economically, being a high-cost ingredient, it is desirable to keep the level of addition of foam stabilisiny surfactant to the minimum having the desired effect. The preferred level of addition i.s an amount in the range of 0.3 percent to 1.5 percent w/w on the basis of the whole composition.
In practice, the components used to make the explosive compositions of the invention ma~ contain water of crystallisation and/or free moisture, hence it is anticipated that there may be up to 3 percent w/w water in the said compositions~ Some watex may also be intro-duced in order to solvate th~ thickening sys-tem used as has been hereinbefore referred to. However the presence of water in the composition is undesirable because it detracts from the explosive properties of the composition and it is therefore kept to a practicable minimum~
Secondary fuel materials which are not melt soll~le may be chosen Erom a range of materials and in-clude :Eor instance sulphur alum.inium, silicon, carbon and uid or solid carbonaceou.s materials. Some liquid carbonaceous materi.als are unsuitable because they interfere with the density stabilising property of the surfactant. For this reason solid carbonaceous materials are used as secondary fuels, for example comminuted coke or charcoal, carbon black; resin acids such as abietic acid or derivatives thereof; sugars such as sucrose or dextrose' or other vegetable products such as s-tarch~
nut meal or wood pulp. Particulate aluminium is the preferred secondary fuel.
The process of making the gas-bubble-sensitised melt explosive compositions is essentially a mixing process and the sequence of addi-tion of the components to the mix is not critical. It is preferred, however.
to incorporate the gas bubbles as late as possible in the manufacture of the compositions because thereby the likelihood of disengagement of the gas bubbles is minimised and the mix is insensitive for a maximum time during the manufacture process; the gas bubbles being the sensitising agent.
A preferred method of preparation of the melt explosive compositions is to first prepare a pre-thickened melt comprising a portion of the oxygen .re-leasing salt component, the melt soluble fuel material, the thickening agent and the foam stabilising surfactant.
To this melt there is added a mixture comprising the remainder of the oxygen releasing salk component and optionally a crosslinking agent and/or secondary fuel.
If the gas bubbles are to be formed by chemical means, the chemical gassing agent is added to the mixture. If mechanical means are usecl to introduce the gas bubbles, a blend of the melt and the mixture is subjected to a mechanical aeration process, such as beating or uigorously stirr.iny.
The compositions of the invention are useful as fillings in explosiue cartridges and they are also eminently suitable for use in conjunction with - 16 ~
conventional pumping or mixing trucks designed ~or use with known water based explosives of the so-called slurry type. Thus for example a thickened melt component of the compositions of the invention may be placed in the solution tank of such a conventional mixing truck and the residual components of -the compositions may be added to and mixed with the melt in a conventional manner and thereafter the composition of the invention so prepared may be transferred to a borehole wherein it may be detonated.
The compositions of the invention have similar explosive bulk energy to other known non-aqueous com-positions which are pumpable, pourable or flowable with the advantage that they have stable densities. Moreover these new compositions are devoid, in terms of essential compoIients, of high explosive materials, per se.
The new compositions of the invention may ~e made having as wide a range of densities as 0.30 g./c.c~ to 1.40 g./c.c. The very low density ( 0.70 g./c.c.~
compositions are of particular utility when a low ex-plosive energy/volume explosive is desired, for instance when minimal backbreak is required during open pit bLasting.
One way of making such low density compositions is to mechanically aerate vigorously a suitable me:Lt composition until the desired density is achieved and then to add crosslinking agent to crosslink the thickening agent in the melt. Without the aadition o~
the characterising surfactant such compositions cannot ~0 be pumped or stored without considerable increase in density.
~, .
This invention is now illustrated by, but is not limited -to, the following examples, except examples 3, 4, 5 and 8. All parts and percentages are expressed on a weight basis unless otherwise specifie~.
A preferred composition was prepared as ~ollows.
Ammonium nitrate, sodi~n nitrate and urea were mixed according to proportions given below for Mixture A.
Mixture A Parts 10 ammonium nitrate 57.9 sodium nitrate 10.6 urea 31.5 sodium acetate 0.5 acetic acid (glacial) 0,5 15 surfactant 'Farmin C' 0.5 This mixture A was melted by heating and thickened by mixing in 0.1 parts by yuar gum at 65C
and standiny overnight.
To 61 parts of this mixture A 39 parts oF Mixture B ingredients were added in a planetary mixer.
Mixture B Ingredients Parts -ammonium nitrate prills 38.9 sodium nitrite as 33.33% aqueous solution 0.1 A sample of the resulting composition was re-circulated -through a pneumatically operated pis-ton pump five successive times~ The density oE the sample prior to pumping was 1.10 y/cc whilst ater pumping the density was 1.05 g/cc.
~his sample was then cooled to 20C an~ stored for a pexiod of one week.
The sample was then detonated in a 79 mm steel pipe usiny a 100 y pentolite booster. The VOD was measured to be 4.5 km/sec.
_XAMPLE 2 A composition was prepared acco~ding to the procedure already described for example 1. In this example the Mixture A contained 0.5 parts of the sur-factant 'Alkadet' 15 in place of 'Farmin C'. It wasthickened by addition of 0.1 parts guar gum and 0.2 parts starch.
Thirty nine parts of ammonium nitrate prills were added to sixty one parts of the thickened mixture A and the composition loaded into 79 mm diameter steel tubes.
The composition density was 1.31 g/cc. T~e sample was stored for 1 week and then detonated with a 140 g pentolite booster at a VOD of 3.1 km/sec.
-The compositions of these examples were i~entical in composition and preparation to that of Example 1 except for the variations listed in Table 2.
The densities of the compositions listed in Table 2 are those before storage. Experience has shown that such compositions are likely to increase in density on storage. However the ailure of the compositions of Examples 5 and 8 to initiate may also be due to gas bubble coalescence~
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A thickened melt solution containin~ the ingredients shown below as Mixture C was prepare~ by th~
procedure described for thickened Mixture ~ in Example 1.
5 Mixture C Parts ammonium nitrate 58.2 sodi~n nitrate 11~1 urea 26.0 water 3~0 10 guar gum 0.35 'Farmin C' 0.4 sodium acetate 0.4 acetic acid o,~
thiourea 0O005 To 76 parts of Mixture C were mixed 24 parts of the ingredients listed as Mixture D using a mixer of the type commonly employed on watergel explosive mix trucks.
Mixture D Parts __ ammonium nitrate prills 24.0 20 sodium nitrite as 33.33%
aqueous solution 0.15 sodium dichromate as 50%
aqueous solution ~.10 The density of the resulting mixture (C and D) was 1.00 g/cc. This mixture was pumped at 40 kg/min through a lobed gear pump after which the density was 0~96 g/cc. The stored mixture (density 1.02 g/cc) was then loaded into 140 mm cylindrical containers and stored for 30 days. The mi~ture then detonated satisfactorily ~ith a 30 g pentolite booster.
EXAMPI,E
To 70 parts o~ mixture C were added 30 parts of mixture E and the composition processed and stored as described for Example 11.
O ~
Mixture E Parts -ammonium nitrate prills 27,0 fuel grade, aluminium 3.0 sodium nitrite as 33.33%
aqueous solutio~ 0.15 sodium dichromate as 50%
aqueous solution 0.10 This mixture detonated satisfactorily after 30 days storage with a 20 g Pentolite booster.
EXAMPLES 1'3'AND 14 -Examples 11 and 12 were repeated in examples 13 and 14 respectively except that the ~Farmin C' surfact-ant in mixture C was replaced by 'Armeen' HT surfactant.
The products of these examples were processed and stored as described in Example 11. Subsequently they were satisfactorily detonated with a 20 g pen-tolite booster.
EXAMPI,E 15 An explosive composition similar to that o~
Fxample 14 but with 63 parts of mixture C, 30 parts ~f mixture E and 7 parts of fuel grade aluminium was made and satisfactorily detonated.
ExAMæLE 16 .
A thickened melt solution containing ~he in-gredients as Mixture C of example 11 was prepared except that 'Farmin C' in the mixture was replaced by 'Armeen' HT and thiourea was present in 0~02 pa.rts.
To 70 parts of this mixture were mixed 30 parts of Mixture D using a commercial explosive mix truck of the type generally used for water gel explosives.
Mixture D Parts ammonium nitrate prills 26.9 fuel grade aluminium 3.0 ~ ~`7~
~ 22 -MiXture D continued Parts .
sodium nitrite as 33.33% aqueous 0.20 solution sodium dichromate as 33~33~ a~ueous0~09 solution The densi-ty of the resulting mix~ure was 1.05 g/cc. 5 tonnes of this mixture was pumped into 15 blast holes (265 mm diameter by 14 metres deep) and success-fully detonated with 415 gm pentolite boosters.
Rock breakage and heave were observed to be excellent.
A thickened melt of composition F was prepared according to the procedure described in Exampl~ 1 for 15 thickened Mixture A.
Mixture F Parts ammonium nitrate 61.5 sodium nitrate 11.0 urea 24.5 20 water 3.0 soaium methyl naphthalene 0.5 (as a crystal habi-t sulphonate modifier) suxfactant 'Farmin DMC' 1.0 guar gum 0.4 After thickening this mixture was aerated by vigorous mixing to a density of 0.32 g~cc. To 100 parts of this composition was added 0.1 part of sodium di-chromate crosslinking solution.
The material was mixed and stored for three days prior to testing. The sample was detonated in a 170 mm cylindrical container underwater using a 140 g pentolite booster. A bubble energy yield oE 1.7 MJouleJky was measured.
.. . ,~
Claims (21)
1. A density-stabilised gas-bubble-sensitised melt explosive composition of density not greater than 1.4 g/cc comprising an oxygen releasing salt, a primary fuel material capable of forming an eutectic mixture with the said oxygen releasing salt, thickening agent, gas bubbles, 0.0 to 3.0 per cent by weight of water and 0.05 to 2.0 per cent by weight of a surfactant selected from those surfactants which when subjected to a foam stabilisation test wherein (i) 0.5 per cent by weight of said surfactant is added to 10 g of a eutectic composition, consisting of 46.7 per cent by weight of ammonium nitrate, 43.6 per cent by weight of urea and 9.7 per cent by weight of sodium nitrate, in a 10 mm diameter tube;
(ii) the mixture is heated to 70°C; and (iii) the mixture is shaken for one minute;
produces a foam which: after standing for a period of 5 minutes, has a height (f5) greater than 2 mm; and after standing for a period of 60 minutes, has a ratio (??0), of foam height after 60 minutes (f60) to foam height after 5 minutes (f5), of greater than 0.3.
(ii) the mixture is heated to 70°C; and (iii) the mixture is shaken for one minute;
produces a foam which: after standing for a period of 5 minutes, has a height (f5) greater than 2 mm; and after standing for a period of 60 minutes, has a ratio (??0), of foam height after 60 minutes (f60) to foam height after 5 minutes (f5), of greater than 0.3.
2. An explosive composition according to Claim 1 wherein the said surfactant is a mixture of at least two surfactant species and wherein said mixture has a f5 value greater than 2 mm and ??0 value of greater than 0.3 according to said foam stabilisation test.
3. An explosive composition according to Claims 1 or 2 wherein the said surfactant constitutes between 0.3 and 1.5 per cent w/w inclusive of the composition.
4. An explosive composition according to Claim 1 wherein the said surfactant comprises a long straight chain primary amine containing at least six carbon atoms in its molecular structure.
5. An explosive composition according to Claim 4 wherein the said long straight chain primary amine contains between 12 and 22 inclusive carbon atoms in its molecular structure.
6. An explosive composition according to Claim 1 wherein the said surfactant comprises an ethoxylated straight chain organic amine containing at least eight carbon atoms in its molecular structure.
7. An explosive composition according to Claim 1 wherein said primary fuel comprises a fuel selected from the group of compounds consisting of ammonium acetate, ammonium formate, ammonium thiocyanate, hexamethylene tetramine, dicyanodiamide, thiourea, acetamide, urea and mixtures thereof.
8. An explosive composition according to Claim 1 which comprises as a primary fuel between 15 and 30 per cent w/w of urea.
9. An explosive composition according to Claim 1 which comprises a secondary fuel material selected from the group of fuels consisting of silicon, aluminium, sulphur, carbon, carbonaceous compounds and mixtures thereof.
10. An explosive composition according to Claim 9 which comprises as a secondary fuel between 0.5 and 10 per cent w/w of aluminium.
11. An explosive composition according to Claim 1 which additionally comprises a crosslinking agent capable of crosslinking the said thickener.
12. An explosive composition according to Claim 1 wherein the said oxygen releasing salt is selected from the group of salts consisting of alkali metal nitrates, alkaline earth nitrates, ammonium nitrate, alkali metal perchlorates, alkaline earth perchlorates, ammonium perchlorate, alkali metal chorates, ammonium chlorates and mixtures thereof.
13. An explosive composition according to Claim 12 which comprises as an oxygen releasing salt between 60 and 80 per cent w/w of ammonium nitrate.
14. An explosive composition according to Claim 11 which comprises as an oxygen releasing salt between 60 and 80 per cent w/w of a mixture consisting of 100 parts by weight of ammonium nitrate and between 5 and 20 parts by weight of sodium nitrate.
15. An explosive composition according to Claim 1 wherein the said thickening agent is selected from the group consisting of galactomannan gums, hydroxypropyl guar gum, polymeric materials derived from acrylamide and biopolymeric gums and constitutes between 0.05 and 2.0 per cent w/w of said composition.
16. A process for the manufacture of a density stabilized gas-bubble-sensitized melt explosive composition according to Claim 1 comprising forming a melt comprising an oxygen releasing salt, a melt soluble fuel material, a thickening agent and a foam stabilizing surfactant and intro-ducing gas bubbles into the melt.
17. A process according to Claim 16 wherein the gas bubbles are introduced by a mechanical aeration process.
18. A process according to Claim 16 wherein the gas bubbles are introduced chemically by means of gas generating agents.
19. A process as in Claim 16 including incorporating into said melt a crosslinking agent capable of crosslinking said thickening agent.
20. A process as in Claim 16 including incorporating into said melt further material selected from the group consisting of oxygen releasing salts, secondary fuels, gas generating agents and crosslinking agents capable of cross-linking said thickening agent.
21. A process for the manufacture of a density stabilized gas-bubble-sensitized melt explosive composition according to Claim 1 having a density less than 0.7 g/cc comprising forming a melt comprising an oxygen releasing salt, a melt soluble fuel material, a thickening agent and a foam stabilizing surfactant, aerating the melt mechanically until an aerated melt of the desired density is obtained and then adding a crosslinking agent to the aerated melt to crosslink the said thickening agent.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000375777A CA1176469A (en) | 1981-04-21 | 1981-04-21 | Explosive composition |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000375777A CA1176469A (en) | 1981-04-21 | 1981-04-21 | Explosive composition |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1176469A true CA1176469A (en) | 1984-10-23 |
Family
ID=4119767
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000375777A Expired CA1176469A (en) | 1981-04-21 | 1981-04-21 | Explosive composition |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1176469A (en) |
-
1981
- 1981-04-21 CA CA000375777A patent/CA1176469A/en not_active Expired
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