Density (Glcms)

US 20110132505A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2011/0132505 A1 Dlugogorski et al. (43) Pub. Date: Jun. 9, 2011

(54) METHOD FOR GASSING EXPLOSIVES (30) Foreign Application Priority Data ESPECIALLY AT LOW TEMPERATURES Jan. 10, 2007 (AU) ...... 2007900069 ( 75 ) Inventors: RagglmondBo dan Z gligrrace munt (AU)? Dlu olégric orski, Miles Publication. . Classi?cation. . Kennedy, The Hill (AU); Mark (51) Int. Cl. Stuart Rayson, Shortland (AU); C06B 21/00 (2006.01) Gabriel Da Silva, Carlton (AU) C06B 43/00 (2006.01) (52) US. Cl...... 149/109.4; 149/109.6 (73) Assignee: Newcastle Innovation Limited, Callaghan (AU) (57) ABSTRACT The invention provides a method for gassing an explosive to (21) APP1~ N05 12/522,626 sensitise the explosive and/ or modify the density of the explo sive. The method comprises reacting at least one oxidiser With (22) PCT Filed: Jan. 10, 2008 at least one nitrogen containing compound in the explosive to generate nitrogen gas. The explosive is formulated to effect (86) PCT NO; PCT/AU2008/000013 diffusion of the oxidiser and/or the compound into contact With each other, the nitrogen gas being generated by oxidation § 371 (c)(1), of the compound by the oxidiser. The invention extends to the (2), (4) Date; Feb, 24, 2011 explosive compositions themselves.

1.35

1.25 (glcms)Density

1.05

0.95

0.85 ||||I||||l||||l||||I||||I||||I||||l|||| 0 200 400 600 800 1000 1200 1400 1600 Time (s) —E|—NaOBr 30 °C —0-NaOC| 20 °C Patent Application Publication Jun. 9, 2011 Sheet 1 0f 7 US 2011/0132505 A1

1.35

1.3 (glcms)Density 1.25 1.2

0 400 800 1200 1600 2000 Time (s) —9—LiOC| —A—NaOBr/NaOH +ChloramineT

FIGURE 1

1.4

1.35

1.3 a

1.25 mg)Density(g/c

‘E;I

1.05

0.95

NaOBr/NaOH 30 OC LiOCI 30 OC FIGURE 2 LiOCI 12 OC NaOBr/NaOH 23 OC Patent Application Publication Jun. 9, 2011 Sheet 2 0f 7 US 2011/0132505 A1

1.4

1.35 ‘

1.3

1.25

(g/cm3)Density 1.2

0 100 200 300 400 500 600 Time (s)

—9— NaOCI 20 °C

FIGURE 3

(g/cm3)Density

1.05

0.95 0 500 1000 1500 Time (s) + 5 "C, 0% NaOH + 40 °C, 5% NaOH +18 °C, 2% NaOH

FIGURE 4 Patent Application Publication Jun. 9, 2011 Sheet 3 0f 7 US 2011/0132505 A1

(glcma)Density

0 1000 2000 3000 4000 5000 6000 Time (s) —9— 18 °C, 0% NaOH + 18 °C, 2% NaOH —El—40 °C, 5% NaOH

FIGURE 5

1.4

1.35

1.3

1 .25 (g/cm3)Density 'aQ

1.05

0.95

09 IllIllllll|llll|llIllllllllllllllllllllllllllllll 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Time (s) —0-Non-diffusing Buffer —E-E)iffusing Buffer

FIGURE 6 Patent Application Publication Jun. 9, 2011 Sheet 4 0f 7 US 2011/0132505 A1

1.4

1.35

1.3

1.25 (g/cm3)Density 1.2

1.05

0.95

0 9 l l l l l l l l l l I I I I l I I I I l I I I I l I I I I l I I I I 0 500 1000 1500 2000 2500 3000 3500 Time (s) +20 °C, 0% NaOH +40 °C, 5% NaOH

FIGURE 7

(g/cm3)Density

0-95 IIIIIIIllIIIIIIlllllIlllllllllllllllllllllll 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Time (s)

+NaOCI pH 6.25 + NaOCI pH 5

FIGURE 8 Patent Application Publication Jun. 9, 2011 Sheet 5 0f 7 US 2011/0132505 A1

F? E Q E 2 '6 C d) a

1||||l||||I||||l||||I||||I||||l||||l||||l|||| O 500 1000 1500 2000 2500 3000 3500 4000 4500 Time (s)

+ 5 °C, Acid Added —El-20 °C, Acid Added +20 °C, No Acid

FIGURE 9

F? E Q E) .2 '5 C d) a

I I I I l | | I I I I I I I l | | I I I I I I I I | | | I 0 200 400 600 800 1000 1200 Time (s)

FIGURE 10 Patent Application Publication Jun. 9, 2011 Sheet 6 0f 7 US 2011/0132505 A1

1.3

1.25

1.2 Density(g/cm3) 1.15 1.1

1.05

0.95

| | | | l | | | | l | | | | l | | | | l | | | | l | | | | l | | | | 0 500 1000 1500 2000 2500 3000 3500 Time (s)

FIGURE 11

1.4 1.35 ‘.1

1.3

1.25 Density(g/cm3) L;:

1.05

0.95 0 500 1000 1500 2000 2500 3000 3500 4000 Time (s) +40 "c, 5% NaOH—A— 20 “c, 0% NaOH

FIGURE 12 Patent Application Publication Jun. 9, 2011 Sheet 7 0f 7 US 2011/0132505 A1

1.35 “

1.25

(g/cm3)Density (5

1.05

0.95

0.85 I I I I l I I I I l I I I I l I I I I l I I I I l I I I I l I I I I O [\D O O .p O O O) O O 800 1000 1200 1400 1600 Time (s) —E|—NaOBr 30 "C —0—NaOCI 20 "C

FIGURE 13 US 2011/0132505 A1 Jun. 9, 2011

METHOD FOR GASSING EXPLOSIVES range of proportions. U.S. Pat. No. 4,737,207, for example, ESPECIALLY AT LOW TEMPERATURES discloses a convenient process to mix microballoons With emulsion explosives by means of suspensions. Glass micro FIELD OF THE INVENTION spheres still ?nd considerable application in sensitising higher cost packaged explosives, due to their stability, but are [0001] The invention relates to explosive compositions and cost inef?cient for use in bulk explosives When compared to particularly to methods of sensitising and/or modifying the loW cost chemical gassing technologies (vide infra). density of explosives by gas bubbles, including emulsion, gel, [0005] Other physical sensitisation technologies that have slurry and ANFO explosives. The invention ?nds particular found limited application notWithstanding their loWer cost, though not exclusive application in the mining industry. include the addition of bagasse piths, perlite, vermiculite, pumice, as Well as plastic microspheres (Which may be BACKGROUND OF THE INVENTION expanded in emulsion by heating above 850 C., as described [0002] Prior to detonating, emulsion, gel and heavy ammo in Us. Pat. No. 6,113,715), solid foams (e.g., polystyrene nium nitrate-fuel oil (ANFO) explosives require sensitisa based, U.S. Pat. No. 4,543,137), liquid foam (after addition to tion, and a number of technologies exist to perform this task. explosive, the foam itself breaks doWn With release of bubbles Originally, technologies requiring the addition of high explo Which disperse in the explosive matrix; European Patent sives Were employed, With examples of such explosives Application No. 514000), puffed rice and Wheat, and more including trinitrotoluene (TNT), nitroglycerine, nitrocellu recently expanded popcorn (US. Pat. No. 5,409,556) as Well lose (Which constitutes a major ingredient of smokeless poW as rice hulls (U.S. Pat. No. 6,995,731). der), nitrostarch, nitrocotton, nitroguanidine, hexamethyl [0006] Currently, the most industrially important route to enetetramine, ethylenediaminedinitrate, sensitising explosives to detonation comprises the so-called trinitrophenylmethylnitramine, mixtures of TNT and trim chemical gassing or foaming, involving the formation of ethylenetrinitramine, TNT and pentaerythritol tetranitrate, small bubbles of CO2, O2, H2, NO or N2 in situ in emulsions and TNT With ethylene dinitramine. Metal particles, such as and gel explosives by means of chemical reactions. U.S. Pat. those of aluminium, magnesium, boron or silicon, as Well as No. 6,261,393 also provides a brief reference to employing ferrophosphorous and ferrosilicon, can also be utilised to calcium carbide as a gassing reagent, presumably to generate enhance the sensitisation by high explosives. HoWever, these C2H2, but Without providing an example. For the most part, methods are expensive and require sensitising during emul these gassing technologies alloW transport of unsensitised sion or gel production, normally at the manufacturing plant, emulsions and gels, With the addition of bubble generating necessitating subsequent transportation of sensitised explo chemicals at the time of pumping the emulsions or gels into sives Which, of course, is highly undesirable. Because of these blastholes. Chemical gassing Was introduced in the late 1960s tWo considerations, cost and safety, the use of high explosives and early 1970s to provide alternative means of sensitising for emulsion and gel sensitisation has noW been largely aban gel explosives and then emulsion explosives (US. Pat. No. doned. Attempts to replace high explosives With nitrates of 3,447,978). With time, industry has converged on the use of aliphatic and phenolic amines (eg. U.S. Pat. No. 3,431,155, nitrogen gassing (U.S. Pat. No. 3,886,010), With N2 formed GB Patent No. 1,536,180) also appear to have met the same by reactions betWeen nitrites and ammonia, thiourea, or other fate. amines in the presence of catalysts and pH regulators. The [0003] Another group of technologies used to sensitise knoWn chemical gassing processes are further revieWed explosives involves entrapping air or adding light particles to beloW. slurries, emulsions and heavy ANFO by physical processes [0007] For instance, U.S. Pat. No. 3,288,658 describes the (eg. see U.S. Pat. No. 3,382,117) as a means to decrease the application of carbon dioxide to gassing explosive gels in a amount of high-explosive sensitisers or regulate distribution process involving mixing of an acid (such as hydrochloric, of explosive strength. U.S. Pat. No. 3,397,097 for instance is acetic, nitric or sulfuric) With a solution of ammonium or directed to the sensitisation of gel explosives by this method. alkali metal carbonate, particularly sodium or potassium To act as sensitisers the voids need to be small, at least less bicarbonate, at temperatures below 500 C. and pH beloW 6.5. than 1.6 mm in siZe and preferably, less than 100 pm. A shock Recently, CO2 gassing has been suggested as part of Water Wave travelling in the sensitised explosive compresses the resistant ANFO systems that transform themselves into sen voids adiabatically. This raises the local emulsion tempera sitised slurries in Water-logged blastholes (U.S. Pat. No. ture above that required to detonate the bulk explosive. Sen 6,261,393). From a chemical perspective, the process sitisation technologies involving the introduction of small involves a reduction in pH resulting in the protonation of voids can also function as density regulators, to decrease HCO3_, folloWed by the decomposition of H2CO3 and the blasting energy or to distribute explosive strength in a bore evolution of CO2. This method can be used to sensitise emul hole or over a set of boreholes. sion explosives provided that acetic acid or another organic [0004] Glass microspheres (microballoons) have been pre acid of similar pKa is employed as a proton donor. Unfortu ferred for emulsion explosive sensitisation especially at tem nately, the solubility of CO2 in blasting agents varies as a peratures beloW that suitable for chemical gassing based on function of pressure and the agent’s composition, making the nitrosation of ammonia or thiourea (vide infra), in spite of the adjustment of emulsion or slurry density With CO2 particu elevated cost of microballoons (in the order of AU$2,000/kg), larly dif?cult to regulate, especially for deep boreholes. handling dif?culty oWing to their loW density (<400 kg/m3, [0008] Oxygen gassing typically involves the decomposi but typically <200 kg/m3), and high shipping expenses per tion of hydrogen peroxide in the presence of catalysts, such as unit Weight. HoWever, their advantages include small siZe (on manganese dioxide, ferric nitrate, potassium iodide, ferrous average 65 pm, with particle siZes distributed betWeen 10 to sulphate, manganese sulphate, aluminium particles and even 175 um), provision of no additional fuel to the sensitised coarse sand, at temperatures in excess of 550 C. (eg., see U.S. material and ability to be mixed With explosives over a Wide Pat. No. 3,790,415). Other catalysts including carbonates, US 2011/0132505 A1 Jun. 9, 2011

bicarbonates, and nitrites as Well as oxidisers, such as ferric ogy. The use of copper complexes in emulsion explosive salts, and oxoanion oxidisers, such as permanganates, dichro systems has also been abandoned because of safety concerns, mates, peroxysulphates, hypohalites, can also effectively similarly to the use of peroxides as previously mentioned. decompose hydrogen peroxide. The sensitisation of slurry [0013] A recent development in nitrogen gassing involves explosives With lithium, sodium and potassium peroxides, is the application of toxic diaZonium salts generated by in-line described in US. Pat. No. 4,081,299. Oxygen gassing mixing of an amine, acid and a nitrite (U .S. Pat. No. 6,027, employing a pre-emulsi?ed solution of H2O2, With MnO2 588). At temperatures above 35° C., some diaZonium salts present in the discontinuous phase of the emulsion, has been decompose to N2 at rates signi?cantly faster than for a com also demonstrated as a viable technology (U .S. Pat. No. monly used foaming system composed of sodium nitrite With 5,397,399). HoWever, the US Code of Federal Regulation, 29 sodium thiocyanate catalyst (vide infra), With fast gassing CFR 1910.109 Explosives and Blasting Agents excludes the reported betWeen 50° C. and 70° C. use of peroxides in emulsion and gel systems (Clark, 1991). [0014] Nitrogen gassing via the nitrosation mechanism as [0009] The application of hydrogen to gassing of slurry and introduced to the ?eld of explosives by US. Pat. No. 3,660, emulsion explosives is based on the observation that H2 is 181 and US. Pat. No. 3,886,010, has dominated chemical released in reactions involving ammonium salts and alkali gassing, and emulsion explosive sensitisation as a Whole, over metal borohydrides (ie., lithium, sodium or potassium boro the last 30 years. The gassing process is initiated by mixing a hydrides); e.g., according to NH4++BH4_QH3NiBH3+H2, concentrated solution of nitrite ion (usually originating from at temperatures in excess of 40° C. A gassing process based on inexpensive NaNO2, With other options involving nitrous this reaction is described in US. Pat. No. 3,711,345. Safety acid and solutions of potassium and ammonium nitrites) With concerns relating to the use of alkali metal borohydrides and slurry or emulsion explosive. Citric or more frequently-used hydrogen itself, and possibly the loss of hydrogen from emul acetic acid diffusing from emulsion droplets then protonates sions oWing to rapid diffusion of H2 through the emulsion nitrite ions to form N2O3, Which subsequently transfers back matrix, has prevented further development and implementa across oil ?lms to react With ammonia (N2O3+NH3QN2+ tion of hydrogen foaming by industry. NO2_+H++H2O). Nitrosation of ammonia constitutes a sloW [0010] A nitric oxide gassing process involving the nitro reaction even at around 50° C. and in practice thiourea (or sation of chemical species (substrates) having an enol group, melamine, sulphamic acid or its salts; Canadian Patent No. or a deprotonated enolate form of the enol group, employing 2,239,095) is added to emulsion to act as a substrate for a nitrosating agent such as N2O3, ONCl, ONBr, ONSCN, nitrosation. In this mechanism, ON+ (from HNO2) acts as an ONI, nitrosothiourea, nitrosyl thiosulfate, HNO2, ON", effective nitrosating agent (HNO2+NH2CSNH2aN2+ ON"OH2 or inorganic nitrosyl complexes, is described in 2H2O+HSCN). Alternatively, a strong nucleophilic species, International Patent Application No. PCT/AU2006/0015 96). such as thiocyanate (e. g., NaSCN), iodide, bromide, chloride, The substrate used is preferably ascorbic acid or ascorbate nitrosothiourea, nitrosoamines (such as N,N'-dinitrosopen (vitamin C), and the reaction forms O-nitroso products Which tamethylenetetramine, see US. Pat. No. 4,409,044), can subsequently decompose to yield nitric oxide. The reaction serve as catalysts to affect the nitrosation of ammonia by ON+ rate is pH dependent, taking approx. 4 min to gas emulsion (e.g., ONSCN+NH3QN2+SCN_+H++H2O). Optimised for explosives at 25° C. and a pH beloW 3.9. HoWever, nitric mulations designed to operate at temperatures beloW 25° C. oxide may promote the production of so-called after-blast necessitate the use of both thiourea (as a substrate, added to fumes, although technologies exist, e.g., based on addition of emulsion) and thiocyanate (as a catalyst, added to gasser); silicon poWder, to alleviate this factor (U.S. Pat. No. 6,539, e.g., see European Patent Application 775,681. The mecha 870). nistic details of the nitrite gassing processes are noW rela [0011] Early attempts to introduce nitrogen gassing to tively Well understood (except, perhaps, for nitrosothiourea, slurry and emulsion explosives relied on adopting bloWing nitrosoamine and sulphamic acid systems), e.g., da Silva et al. agents (ie., agents that decompose to N2 at temperatures (2006). above 550 C.) as described in US. Pat. No. 3,713,919, and the [0015] Since the development of nitrite gassing, a number oxidation of hydrazine and its derivatives at temperatures in of important advances have been introduced to optimise the excess of about 40° C. as described in gassing technology, especially to accelerate the gassing rate [0012] US. Pat. No. 3,706,607. Examples of the applica and make the process operate at loWer temperatures and alloW tion of both technologies to gassing emulsion explosives are formation of gas bubbles of less than 100 um in siZe. They described in US. Pat. No. 3,770,522. Chemicals useful as include the use of microemulsions (European Patent Appli bloWing agents include N,N'-dimethyl- and N,N'-diethyl-N, cation No. 775,681), LeWis acids such as Zinc nitrate to facili N'-dinitrosoterephthalamide, benZensulphonyl hydraZide, tate the protonation of nitrite ions (U .S. Pat. No. 6,855,219), aZobisisobutyronitrile and p-tert-butylbenZaZide, as sum premixing nitrite and thiourea prior to adding to emulsion marised in US. Pat. No. 4,008, 108. A gassing process involv (U.S. Pat. No. 6,165,297, Canadian Patent No. 2,239,095), ing N,N'-dinitrosopentamethylenetetramine is also described nitrite as poWder (U .S. Pat. No. 4,997,494), pre-emulsi?ed in US. Pat. No. 3,713,919. Gassing Was reported for the gasser (U .S. Pat. No. 4,875,951, suggested independently in reaction of hydraZine monohydrate and other hydraZine PCT/US88/03354), calcium and strontium accelerants (U.S. derivatives With various oxidising agents including hydrogen Pat. No. 6,022,428), formation of small bubbles With organic peroxide, ammonium persulphate and copper(ll)nitrate. This additives (Canadian Patent No. 2,040,751), ?uorosurfactants gassing system inherently requires the process be carried out (U.S. Pat. No. 4,594,118) or high pressure (U.S. Pat. No. at high temperatures. This requires that either the gassing be 4,676,849). Technologies combining nitrite gassing With performed during or immediately after emulsion manufac other methods for regulating emulsion density and/or sensi ture, When the mixture is still hot, or subsequent heating of the tivity have also been developed, particularly for specialised explosive if the explosive is sensitised at a later time. These applications, such as shock resistant explosives (microbal practical limitations have prevented the use of this technol loons/nitrite, US. Pat. No. 5,017,251), porosity-modi?ed US 2011/0132505 A1 Jun. 9, 2011

ANFO (US. Pat. No. 5,240,524) and enhanced sensitivity to delay the onset of the gassing reaction to alloW more time explosives (high explosives/nitrite, US. Pat. No. 4,221,616). for mixing of the gasser into the explosive. [0016] However, in spite of its versatility and loW cost (in [0025] In addition, the explosive can comprise a proton the order ofAU$6/tonne), nitrite gassing cannot be effectively acceptor for maintaining pH above a predetermined loWer implemented for sensitising emulsions at sub or near Zero (ie., limit or Within a predetermined pH range to inhibit crystalli <0o C. or ~0o C.) temperatures, With the rate of gassing sation in the explosive. declining substantially beloW 25° C. Concerns have been also [0026] A pH regulating agent such as a pH buffer Which can raised over the health and environmental risks associated With act as both the proton donor and proton acceptor can be used. the use of nitrite salts, and over safety implications of pre A pH regulating agent can also act as a proton transfer agent mixing of nitrite and thiourea prior to adding the mix to the for transporting protons across fuel lamellae or into another emulsion. Furthermore, the identi?cation of the common phase of the explosive for increasing the rate of diffusion of accelerant thiourea as a possible human carcinogen means the oxidiser and/or the nitrogen compound. In the broadest that even chemical gassing at moderate temperature (ca. 250 sense, a proton transfer agent is to be taken to encompass an C.) using this compound may be phased out. agent that can act to transfer at least one proton across fuel lamellae and/or into another phase of an explosive for release SUMMARY OF THE INVENTION of the proton. [0017] In an aspect of the invention there is provided a [0027] Hence, in one or more embodiments of the inven method for gassing an explosive to sensitise the explosive tion, the explosive can comprise a proton transfer agent for and/ or modify the density of the explosive, comprising react transferring one or more protons across fuel lamellae of the ing at least one oxidiser With at least one nitrogen containing explosive or more generally, across phases of the explosive, to compound in the explosive to generate nitrogen gas, the increase the rate of diffusion of the oxidiser and/or the nitro explosive being formulated to effect diffusion of the oxidiser gen compound. and/ or the compound into contact With one another, the nitro [0028] It Will be understood that the invention is not limited gen gas being generated by oxidation of the compound by the to the particular nitrogen compound(s) utilised in the explo oxidiser. sive and any suitable nitrogen compound can be used. [0018] Typically, the oxidiser and/ or the nitrogen com [0029] In at least one form, the nitrogen gas is generated by pound diffuse across fuel lamellae in the explosive into con oxidation of ammonia/ammonium cation (NH3/NH4+) by the tact With one another. In at least some embodiments, essen oxidiser. Typically, though not exclusively, the oxidiser dif tially only the oxidiser diffuses across the fuel lamellae for fuses to the NH3/NH4+. In this embodiment, the explosive can reacting With the oxidiser. comprise a proton donor for protonating the oxidiser to pro [0019] The gassing of the explosive can be carried out over mote the diffusion of the oxidiser into contact With the NH3/ a range of temperatures and is particularly suitable for gassing NH4+ as indicated above. Desirably, the explosive Will also emulsion explosives, though not solely, at loW temperatures include a proton acceptor to maintain pH above a predeter including near or beloW 0° C. mined loWer limit to inhibit crystallisation in the explosive. [0020] Typically, the amount of nitrogen gas generated is Again, a pH regulating agent that acts as both the proton determined by the quantity of the oxidiser added to the explo donor and the proton acceptor can be employed. Altema sive. The oxidiser is normally added in the form of a compo tively, the pH can be elevated to increase the concentration of sition (gasser) containing the oxidiser. The gasser can be a NH3 (Which is in equilibrium With NH4+), to promote diffu solution of the oxidiser. sion of the NH3 e.g., across fuel lamellae. In this instance, the [0021] The terms “nitrogen containing compound” and oxidiser may be essentially non-diffusing in the context of the variations thereof such as “nitrogen compound” and the like invention. in the context of the invention are taken to mean any com [0030] In another form, the nitrogen gas is generated by pound containing nitrogen that is capable of producing nitro oxidation of an amine (eg., a primary amine), With the oxida gen gas via reaction With the oxidiser. tion of NH3/NH4+ occurring as a side reaction. In this instance [0022] The term “oxidiser” in the context of the invention is the majority of nitrogen gas is generated by reaction of the to be taken to mean a substance that removes one or more oxidiser With the amine. In general, the reaction betWeen an electrons from the nitrogen compound to produce the nitro oxidiser and a primary amine shoWs a higher selectivity gen gas from the nitrogen compound and/or species derived toWard the production of nitrogen gas than the reaction With from the compound. This is distinguished from inorganic NH3/NH4+. Thus reactions With a primary amine afford a oxidiser salts (such as ammonium nitrate) Which form part of reduction in the amount of oxidiser required to produce a prior art base explosive Wherein the term refers to the pres desired amount of gas in an explosive. Similarly, the explo ence of oxygen in the salts. In the present invention, the sive in this embodiment may contain a pH regulating agent oxidiser is generally added to the explosive folloWing the and/or proton transfer agent for protonating the oxidiser to manufacture of the explosive, normally When the explosive is promote the diffusion of the oxidiser through the fuel lamel ready to be gassed. lae of the explosive. [0023] The explosive can be formulated for protonation of [0031] In another form, the nitrogen gas is generated by the oxidiser to effect the diffusion of the oxidiser. oxidation of a nitrogen compound containing a hydraZine [0024] In at least some embodiments, the explosive can (iNHiNHz) group to produce the nitrogen gas, With the comprise a proton donor to control the rate at Which the oxidation of NH3/NH4+ occurring as a parallel side reaction. oxidiser diffuses to react With the nitrogen compound, In this instance, the nitrogen gas is primarily generated by the thereby controlling the gassing rate. Alternatively, or as Well, reaction betWeen the oxidiser and the hydraZine, With a loWer the pH of the gasser can be adjusted to alter or further in?u level of nitrogen gas generated by the parallel side reaction ence the rate of oxidiser diffusion. For example, the pH of the betWeen the oxidiser and NH3/NH4+. In general, at tempera gasser can be raised via the addition of an alkaline substance tures less than 400 C. hydrazine chemicals are essentially US 2011/0132505 A1 Jun. 9, 2011

non-diffusing across fuel lamellae, in that the amount of gas nitrogen compounds can be considered as essentially non produced from oxidiser molecules diffusing across the fuel diffusing under these conditions. lamellae to the hydrazine is substantially greater than the [0039] As Will be understood, the gassing of the explosive amount of gas produced from the hydrazine diffusing across by the generated nitrogen gas may be achieved by simply the fuel lamellae to the oxidiser. In comparison to the above alloWing the gas to foam the explosive. The gassing of the embodiment involving the oxidation of NH3/NH4+ and an explosive may also, or alternatively, involve stirring the amine, reduced amounts of oxidiser and pH regulator agent explosive during at least a part of the gassing process to can be utilised to achieve sensitisation of and/or density achieve substantially even distribution of the nitrogen gas modi?cation of the explosive. bubbles essentially throughout the explosive. Distribution of [0032] In yet another form, the nitrogen gas is generated by the gas bubbles throughout the explosive may also be oxidation of a nitrogen rich compound having 3 or more achieved by pumping of the emulsion explosive. nitrogen atoms for generation of the nitrogen gas, With the [0040] Methods embodied by the invention are particularly oxidation of NH3/NH4+ occurring as a parallel side reaction. suitable for gassing emulsion explosives. HoWever, it Will be Examples of suitable such nitrogen rich compounds include understood that at least some embodiments can be utilised to those containing a tetraZole or triaZole ring. In this instance, gas forms of explosives other than emulsion explosives, such the nitrogen gas is primarily generated by reaction of the as gel, slurry and ANFO explosives, and the invention oxidiser With the nitrogen compound, With a lesser amount of expressly extends to such further explosives. gas being produced by the oxidation of the NH3/NH4+. The presence of double bonds betWeen nitrogen atoms of triaZ [0041] Methods as described herein provide technologies oles, tetraZoles, and like such nitrogens compounds again for sensitisation and/or density modi?cation of explosives at reduces the amount of oxidiser required to produce the loW temperature as an alternative to conventional loW tem desired amount of nitrogen gas required to achieve sensitisa perature gassing methods such as those involving the use of tion and/or density modi?cation of the explosive. expensive glass microspheres. Advantageously, at least some gassing methods embodied by the invention require no heat [0033] In another aspect of the invention there is provided ing of the explosive prior to mixing With the oxidiser and/or an explosive comprising NH3/NH4+ and/ or at least one other substrate to above ambient temperatures, even temperatures nitrogen containing chemical, and at least one oxidiser for of 0° C. or beloW, affording a substantial advance in the art. reaction With the NH3/NH4+ and/or the nitrogen containing Moreover, various forms of methods embodied by the inven chemical to generate nitrogen gas for gassing the explosive. tion appear to be comparable in cost to nitrite-based gassing, [0034] In another aspect of the invention there is provided a Which for the previous three decades has been the preferred method for gassing an explosive to sensitise the explosive technology for sensitisation and/or density modi?cation of and/ or modify the density of the explosive, comprising react explosives. ing at least one oxidiser With at least one nitrogen containing [0042] Furthermore, at least some embodiments involving compound in the explosive to generate nitrogen gas, the oxi the use of hydraZine and/or derivatives thereof address a diser and the compound initially being in different phases of number of de?ciencies of prior art nitrogen gassing methods the explosive to one another, and the oxidiser and/or com employing these substrates. In particular, one or more pound diffusing into contact With each other Whereby nitro embodiments as described herein may alloW an emulsion gen gas is generated via oxidation of the nitrogen compound explosive to be gassed to a pre-determined density at a con by the oxidiser. trolled rate, by mixing one or more reagents such as the [0035] In another aspect there is provided an explosive oxidiser into the emulsion after its manufacture, rather than gassed by a method of the invention. during the manufacturing process as is the case in Us. Pat. [0036] In yet another aspect of the invention there is pro No. 3,706,607. This alloWs emulsion explosives to be manu vided an explosive, comprising at least one oxidiser and at factured in bulk and transported safely to mine sites before least one nitrogen containing compound, the explosive being being sensitised to detonation, reducing the risk of accidents formulated for effecting diffusion of the oxidiser and/ or the associated With transport of explosive materials. Further, one compound into contact With each other for oxidation of the or more embodiments of the invention provide methods that compound by the oxidiser to produce nitrogen gas from the alloW explosives formulated With nitrogen compounds to be compound for gassing of the explosive. gassed over a Wide temperature range by adjusting the pH of [0037] In still another aspect of the invention there is pro gasser solutions, removing the need for heating or cooling of vided an explosive, comprising at least one oxidiser and at the explosives to achieve desired gassing times. least one nitrogen containing compound, the oxidiser and the [0043] Throughout this speci?cation the Word “comprise”, compound being in different phases of the explosive to one or variations such as “comprises” or “comprising”, Will be another, and the explosive being formulated for diffusion of understood to imply the inclusion of a stated element, integer the oxidiser and/ or the compound into contact With each other or step, or group of elements, integers or steps, but not the for oxidation of the compound by the oxidiser to produce exclusion of any other element, integer or step, or group of nitrogen gas from the compound for gassing of the explosive. elements, integers or steps. [0038] In methods embodied by the invention, the rate of [0044] Any discussion of documents, acts, materials, the overall gassing process is governed by the rate of transfer devices, articles or the like Which has been included in this of the diffusing reagent and/or the nitrogen compound. In the speci?cation is solely for the purpose of providing a context instance that both the nitrogen compound and the oxidiser for the present invention. It is not to be taken as an admission diffuse, the rate of gassing is limited by the combined rate of that any or all of these matters form part of the prior art base diffusion of both these reagents. HoWever, the rate of oxidiser or Were common general knoWledge in the relevant ?eld of diffusion typically far exceeds that of most nitrogen com technology as it existed anyWhere before the priority date of pounds at loW temperature, and as such the vast majority of this application. US 2011/0132505 A1 Jun. 9, 2011

[0045] The features and advantages of the invention Will [0060] A typical emulsion explosive consists of (i) a dis become further apparent from the following detailed descrip continuous phase of a solution of nitrate salts, such as ammo tion of embodiments of the invention. nium nitrate in Water, and (ii) a continuous fuel phase includ ing an emulsi?er such as poly-isobutylene succinic anhydride BRIEF DESCRIPTION OF THE (PiBSA) and a carbonaceous fuel, such as diesel, para?in or ACCOMPANYING DRAWINGS bio oils. [0046] FIG. 1 is a graph showing gassing of an emulsion [0061] Explosive compositions embodied by the invention explosive in the absence of a pH regulating agent/proton Will normally include: (i) at least one nitrogen containing transfer agent; compound (also knoWn as the reductant(s) or substrate(s)) [0047] FIG. 2 is a graph shoWing gassing of emulsion Which is capable of producing nitrogen gas via reactions With explosives in the presence of a pH regulating agent/proton the oxidiser(s), and (ii) at least one oxidiser for removing transfer agent; electrons from the reductant(s) to produce the nitrogen gas, [0048] FIG. 3 is a graph shoWing gassing of an emulsion With the oxidiser being added to the emulsion to affect sen explosive containing a primary amine substrate in the pres sitisation and or density modi?cation at a point in time after ence of a pH regulating agent; the emulsion has been constructed. In one or more embodi [0049] FIG. 4 is a graph shoWing gassing of an emulsion ments of the invention the substrate is normally added to the explosive containing a cyclic hydraZide substrate in the pres discontinuous phase of the explosive (in the case of an emul ence of a pH regulating agent capable of transferring protons sion) during the manufacture of the base explosive, prior to from the emulsion to the gasser; subsequent addition of the oxidiser. The oxidiser is normally [0050] FIG. 5 is a graph shoWing gassing of an emulsion added to the explosive after manufacture and forms its oWn containing a cyclic hydraZide compound in the presence of a discrete droplets (phase) Within the emulsion. Therefore, non diffusing pH regulating agent; either the oxidiser or nitrogen compound must diffuse through fuel lamellae that separate their respective phases in [0051] FIG. 6 is a graph shoWing a comparison of gassing betWeen emulsions containing diffusing and non-diffusing order to come into contact With each other and react. pH regulating agents; [0062] Reactants (i) and (ii) Will normally be selected to [0052] FIG. 7 is a graph shoWing gassing of an emulsion react rapidly With one another, even at sub-Zero temperatures. containing a monohydraZide With non-diffusing pH regulat In addition, at least one of either the reductant or the oxidiser Will be capable of diffusing, or the explosive Will be formu ing chemical; lated to alloW diffusion, of the reductant or oxidiser through [0053] FIG. 8 is a graph shoWing a comparison of gassing betWeen emulsions at different pH With a non-diffusing pH oil or fuel ?lms (fuel lamellae) separating droplets of the reductant(s) and the oxidiser. As charged molecules are regulating agent; insoluble in the fuel ?lm, only neutral molecules are capable [0054] FIG. 9 is a graph shoWing a comparison of gassing of diffusing betWeen gasser and emulsion droplets. betWeen examples containing a non-diffusing pH regulating agent With and Without an additional proton transfer agent; [0063] The substrate can be any compound containing at least one nitrogen atom in a form capable of being oxidised to [0055] FIG. 10 is a graph shoWing the gassing ofan emul sion With a monohydraZide and diffusing pH regulating produce nitrogen gas. Such compounds include, but are by no means limited to ammonia/ammonium cations, ammonium agent; salts, and any alkyl, aryl and cyclic compound containing at [0056] FIG. 11 is a graph shoWing the gassing ofan emul least one or more of a combination of the folloWing functional sion With a monohydraZide and diffusing pH regulating moieties; amines including primary, secondary and tertiary agent; amines, hydraZines, hydraZides including dihydraZides, [0057] FIG. 12 is a graph shoWing the gassing ofan emul hydraZine hydrate and hydraZine dichloride, aZides, triaZoles sion containing a dihydraZide and a non-diffusing pH regu and/or tetraZoles, and derivatives, and salts thereof. lating agent; and [0064] Yet further nitrogen compounds that may be used in [0058] FIG. 13 is a graph shoWing the gassing ofan emul sion containing a tetraZole and a diffusing pH regulating one or more embodiments of the invention include aZo com agent. pounds (RiN:NiR) such as dimethyldiaZine, aZoben Zene and aZodicarboxamide, imidates such as ethyl formimi date hydrochloride, polyamines such as ethylene diamine, DETAILED DESCRIPTION OF EMBODIMENTS methylamine hydrochloride, parbamates such as methyl car OF THE INVENTION bamate, cyanides, nitriles, aZides such as ethyl aZidoacetate, [0059] The invention relates to methods for gassing an guanidines and salts thereof such as guanidine nitrate and explosive to sensitise the explosive to detonation and/or guanidine carbonate, hydraZones such as benZaldehyde semi modify the density of the explosive, comprising reacting at carbaZone, hydroxylamines such as N-methylhydroxylamine least one oxidiser With at least one nitrogen containing com hydrochloride, and imines such as formamidine acetate salt. pound in the explosive to generate nitrogen gas from the [0065] The oxidiser is typically able to diffuse from the compound. Methods embodied by the invention ?nd applica gasser droplets to the emulsion phase, or can be made able to tion in the gassing of emulsion explosives and particularly diffuse by accepting or releasing a proton/protons. Examples Water-in-oil emulsion explosives, and this type of emulsion is of such oxidisers include hypohalous acids such as hypochlo primarily exempli?ed beloW. HoWever, it Will be understood rous and hypobromous acids and their corresponding alkali that embodiments of methods of the invention also have metal or alkali earth metal salts, N-halo sulfonamides, such as application to other explosives including the gassing of melt N-chlorobenZenesulfonamide, N-chlorotoluenesulfonamide in-oil emulsion, gel, slurry andANFO explosives (commonly and their salts (Chloramine B and T respectively for referred to as heavy ANFO and Which comprises emulsion example), N-halosuccinamides, such as N-chlorosuccina explosives in combination With ammonium nitrate-fuel oil). mide and N-bromosuccinamide and their salts, chloric and US 2011/0132505 A1 Jun. 9, 2011

bromic acids and their salts, N-oxides such as N-methylmor [0070] The action of a proton transfer agent With a hypo pholine N-oxide, trimethylamine N-oxide or pyridine N-ox halite gasser is described beloW in the folloWing steps, With ide as Well as any alkali or alkali earth metal manganates. reference to the acetic acid/hypochlorite system, Which is [0066] In at least some embodiments, the oxidiser consists used in various examples of the present invention: of a solution containing one or more of the compounds com [0071] 1. Acetic acid present in the discontinuous phase prising any alkali metal and alkali earth metal hypochlorites, of the emulsion diffuses through the fuel ?lm to the hypobromites or hypoiodates, knoWn as hypohalites. Such gasser. oxidisers are capable of reacting rapidly With nitrogen com [0072] 2. The acetic acid is deprotonated by hypohalites pounds at loW temperature to produce nitrogen gas. Further present in the gasser, to produce hypohalous acid and more, hypohalites are Weak bases in solution, meaning that they can accept a proton to form corresponding hypohalous acetate as shoWn in the folloWing reaction. acids, Which, as neutral molecules, are able to diffuse rapidly [0073] 3. Hypochlorous acid diffuses to the emulsion, through fuel lamellae separating emulsion and droplets of Where it reacts With nitrogen containing chemicals to gasser solution. produce nitrogen gas. [0067] Hypohalous acids (eg HOCl, HOBr) exist in equi [0074] 4. Protons produced in the gassing reaction cause librium With the corresponding hypohalite anion, With the the formation of more acetic acid from acetate ions, and relative concentration of each species being determined by the process continues until either the proton transfer the pH of the solution. At loW pH (pH<7) the hypohalite exists agent or the hypochlorite is completely consumed. predominantly in the protonated form, Whist at high pH (pH>9) the majority exists as hypohalite anions. It is evident [0075] The amount of proton transfer agent(s) used should that in order for hypohalite gassers to diffuse through fuel be su?icient to transfer enough protons to protonate substan lamellae and react With nitrogen compounds, the pH of the tially all of the oxidiser molecules, thus ensuring that the gasser must be suf?ciently loW to increase the concentration entire contents of the gasser droplets are able to participate in of the hypohalous acid to a level that alloWs an adequate rate the gassing reaction. The amount of pH regulating agent used of gasser diffusion. Thus the pH of the gasser is a relevant also depends on hoW many protons are produced in the gas factor in determining the rate of gassing using hypohalite sing reaction, and should desirably be suf?cient to consume oxidisers, With gassers of loW pH having signi?cantly faster the majority of protons produced in the reaction, thereby gassing times than those With high pH. maintaining the emulsion at an essentially constant pH. Like [0068] In order to ensure e?icient use of hypohalite oxidis Wise, in the case that the gassing reaction consumes protons, ers, the pH of the gasser solution should be continuously suf?cient pH regulating agent(s) should be added to ensure loWered (or at least remain constant at a loW value) through that enough protons are available for the reaction to reach out the gassing process. This can occur via the transfer of completion and that the emulsion pH does not rise signi? protons (hydrogen cations) from the emulsion phase to the gasser and ensures that the entire contents of the gasser can cantly. participate in the gassing reaction. If proton transfer does not [0076] In another embodiment of the invention, at least one occur, hypohalite anions Will be trapped in the gasser droplets pH regulating agent is added to the gasser to either accelerate and unable to react With nitrogen containing compounds in or sloW the gassing process. For example, raising the pH of a the emulsion. Proton transfer in an emulsion explosive is hypohalite gasser With a soluble alkali metal hydroxide such generally relatively sloW, unless a proton transfer agent is as sodium hydroxide sloWs the gassing process, as the added included in the emulsion formulation. hydroxide must be neutralised by protons transferred from [0069] In a preferred embodiment of the invention, the the emulsion before gassing can occur. Similarly, the addition emulsion formulation Will contain a pH regulating agent of small amounts of an acidic substance, such as sulfuric, capable of transferring protons from the emulsion phase to hydrochloric, nitric or acetic acid (amongst others) to hypo the gasser, also knoWn as a proton transfer agent. In general, the term “a proton transfer agent” encompasses a Weak acid or halite gassers increases the concentration of hypohalous acid, base that When protonated, forms a neutral molecule Which thereby accelerating the gassing process. can diffuse rapidly through fuel lamellae separating emulsion [0077] At temperatures in excess of 35° C., gassing using and gasser droplets. Such molecules dissociate When they the above method can be very rapid. In order to sloW the reach the gasser droplets effecting the release of protons in the gassing process at higher temperatures, the proton transfer gasser and as such, are able to transfer protons from the agent may be replaced With a non-diffusing pH regulating emulsion to the gasser droplets. Examples of proton transfer agent. This produces sloW gassing rates, as proton transfer to agents Well suited to the present invention include the car the gasser is greatly reduced, alloWing the invention to be boxylic acids such as acetic acid and formic acid, Which exist used at higher temperatures. In the case that such an emulsion in equilibrium With their deprotonated anions, acetate and formulation needs to be gassed at a loW temperature, a proton formate. There are many other suitable compounds that can transfer agent such as acetic acid can be added to the emulsion be used as proton transfer agents, provided that the pH of the prior to the addition of the gasser to increase the gassing rate. emulsion phase is selected to ensure that a signi?cant propor tion of the compound exists in its protonated from. Examples [0078] The above mechanisms apply to the use of all nitro of such substances include citric, tartaric, furoic, fumaric, gen compounds and oxidisers as described herein. Further salicylic, malonic, phthalic, sulfanilic, mandelic, malic, details of the invention Will noW be discussed in relation to butyric and oxalic acids, and their salts. Typically, the proton four industrially important classes/groups of nitrogen com transfer agent Will be selected such that it does not react With pounds. HoWever, it Will be understood that the invention is the oxidiser used. not limited to the use of these nitrogen compounds. US 2011/0132505 A1 Jun. 9, 2011

Class 1 This means that the reaction betWeen such oxidisers and [0079] In one form, the substrate (nitrogen compound) for NH3/N H 4+ leads to a net increase in the number of protons, or, the oxidiser Will typically be the ammonium cation (NH4+) in other Words, protons are produced in the reaction. This is and ammonia (N H 3) Which exist in equilibrium in ammonium demonstrated in reactions [7] and [8]. Speci?c examples of solutions as folloWs: suitable oxidisers Which can be used include, but are not limited to, lithium, sodium, potassium, calcium and barium hypohalites (eg., hypochlorites, hypobromites and [0080] The ammonium cation and thereby ammonia can be hypoiodites). Examples of the relevant half reactions are as provided by the addition of one or more ammonium salts to folloWs: the explosive. Examples of suitable ammonium salts include, but are not limited to, ammonium nitrates, sulfates, phos phates, sul?des, chlorides, bromides, ?uorides, iodides, per chlorates, periodates, acetates, citrates, and tartarates. Typi cally, the ammonium salt Will be ammonium nitrate or [0087] Combining half reaction [3] With [5] and [4] With [6] ammonium perchlorate, Which are commonly employed in provides examples of the overall main and side reactions explosive compositions. In the case that these salts are already operating during the oxidation of NH4+ by hypochlorites as present in the explosive, additional nitrogen containing folloWs: chemicals are not required. [0081] The oxidiser Will normally diffuse through the fuel lamellae to reach the solution containing ammonium salt(s) and/ or other nitrogen containing chemicals as described above. Such oxidisers include but are not limited to hypoha lous acids such as hypochlorous and hypobromous acids and their corresponding alkali metal or alkali earth metal salts, [0088] For hypohalite and chloramine-type oxidisers, the N-halosulfonamides, such as N-chlorobenZenesulfonamide, reduction of the apparent pH to beloW unity is possible in the N-chlorotoluenesulfonamide and their salts (Chloramine B discontinuous phase of the emulsion. In the presence of unre and T respectively), N-halosuccinamides, such as N-chloro acted oxidisers this build-up of acidity, if left, may lead to succinamide and N-bromosuccinamide and their salts, chlo emulsion crystallisation as a result of the formation of ammo ric and bromic acids and their salts, N-oxides such as N-me nium nitrate crystals leading to a reduction in emulsion sta thylmorpholine N-oxide, trimethylamine N-oxide or pyridine bility. To preclude this, a commensurate amount of a proton N-oxide, and alkali or alkali earth metal manganates. acceptor such as sodium acetate is added to the discontinuous [0082] Alternatively, the pH of the solution of ammonium phase of the emulsion explosive to prevent pH from decreas can be increased by the addition of a proton donor to elevate ing substantially as demonstrated in Example 3 beloW. The the concentration of NH3 to achieve diffusion of the NH3 (a anion of Weak acids exists in equilibrium in solution and as neutral species) through the fuel lamellae. The increase in such, can also regulate pH by accepting protons from solution NH3 concentration occurs because at higher pH, feWer pro to avoid a decrease in pH beyond desired levels in at least tons are available, and the equilibrium of reaction [2] shifts to some methods embodied by the invention. Further examples the left, increasing the concentration of NH3 and thereby the of such pH regulating agents include, but are not limited to, NH3 concentration gradient across the fuel lamellae. salts of other Weak acids including food acids such as citric [0083] The oxidation of ammonia to nitrogen gas requires and tartaric acids. Additional examples of pH regulating the transfer of 6 electrons betWeen ammonia and the oxidiser agents useful in embodiments of the invention include furoic, as indicated in the folloWing half reaction: fumaric, salicylic, malonic, phthalic, sulfanilic, mandelic, malic, butyric and oxalic acids, as Well as their salts.

[0084] HoWever, the inventors have observed in Examples Class 2 2.1 and 2.2 described beloW, that to reach the pre-determined emulsion explosive density, about 1 1 electrons are consumed [0089] Another group of nitrogen compounds suitable for per mole of nitro gen evolved. Without Wishing to be bound by use in the present invention are primary amines. A primary theory, it is hypothesised that some of the NH4+ oxidises to amine is a chemical species With the structure RiNHZ, nitrate ions via a parallel side half reaction as folloWs: Where R represents any alkyl, aryl or cyclic substituent. Any such amine can be used as a constituent of the explosive in embodiments of the invention described herein. The amine [0085] It is further believed by the inventors that under the can contain one or more amino groups, for example NHZi conditions of reactions [3] and [4], approximately 75% of the RiNHZ, and can incorporate one or more heteroatoms such total NH4+ consumed is oxidised in the main reaction and the as O, S or N, and the use of such compounds is speci?cally remaining 25% in the side reaction. encompassed. Speci?c examples of amines Which may ?nd [0086] Relevantly, reactions [3] and [4] produce protons, use in embodiments of the invention include but are not leading to a signi?cant drop in pH. Although protons are limited to methylamine, ethanamide, ethanolamine, normally consumed by the decomposing oxidisers, the trisamine, aniline (aminobenZene), urea and thiourea. The present inventors have further found that in the case of NH3/ oxidation of amines is analogous to that of ammonia/ammo NH4+ this consumption is limited to three protons per mol nium cations requiring the removal of 6 electrons per mol ecule of evolved nitrogen gas for at least some types of oxi ecule of nitrogen gas produced, as shoWn in the folloWing half disers, such as alkali metal and alkali earth metal hypohalite equation. salts, Which are particularly effective in oxidising NH3/NH4+. US 2011/0132505 A1 Jun. 9, 2011

[0090] Combining reactions [5] and [9] provides an hydraZide by three groups of oxidisers found to be particu example of the oxidation of amines by hypochlorites as fol larly effective, namely hypohalites, halites and permangan loWs: ates:

[0091] The use of urea in particular ?nds Widespread appli cations in nitrosation based gassing technologies, Which are currently used to sensitise emulsion explosives. Unlike the nitrosation of urea that occurs only at high temperatures (>40° C.), the oxidation of urea (and other amines) proceeds rapidly at loW temperatures (<20° C.), thus alloWing the Wherein R denotes an optionally substituted alkyl, aryl or present invention to sensitise emulsions designed for nitrosa cyclic group, With or Without one or more heteroatoms tion of urea to be gassed at loW temperature, removing the present in their structure. It is noted that reaction [13] con need to heat the emulsion prior to gassing. The use of urea to sumes protons, and if these are not available, the oxidation of generate nitrogen gas With hypohalite oxidisers to sensitise the hydraZide by permanganates produces MnO2 rather than and/ or modify the density of an explosive is demonstrated in Mn3+, as indicated beloW: Example 3.1.

Class 3 [0095] HoWever, it is noted that permanganate is essentially [0092] Another group of nitrogen compounds With appli non-diffusing limiting its use in methods described herein. cation in the present invention are compounds containing a [0096] Side reactions may lead to production of side prod hydraZine group, iNHNHz and derivatives thereof. A par ucts including dimers, such as R4C(:O)iNHiNHi ticular class of hydraZines better suited to practical uses are NHiNHiC(:O)iR or R%(:O)iNHiNH% hydraZides, Which have substantially improved safety prop (:O)iR, and amides, such as R4C(:O)iNH2. erties compared to hydraZines. For this reason, hydraZides are HoWever, the selectivity of the oxidation reactions to produce of particular importance. HoWever, it should be understood N2 during oxidation of the hydraZide is substantially higher that the invention extends to all compounds and classes of than that for the direct oxidation of NH3/NH4+. Reactions compounds containing an iNHNHz group and derivatives [7] -[14] shoW that control of the availability of protons (ie., by thereof. regulating pH) during the oxidation process, is dependent on the oxidiser used. [0093] A hydraZide (including the sulfonyl hydraZides) is a [0097] The hydraZine gassing method described in US. chemical species that contains either the 4C(:O)iNHi Pat. No. 3,706,607 typically operates at temperatures of at NH2 or iS(:O)2iNHiNH2 group in its chemical struc least betWeen 32° C. (90° F.) and 54° C. (1300 F.), and in ture, i.e., it contains a carbonyl or sulfonyl group bonded to practice can require temperatures up to 71° C. (160° F.) to the hydraZine group Any optionally substituted suitable alkyl, sensitise emulsion explosives, as used in US. Pat. No. 3,770, aryl and cyclic hydraZides can be used as constituents in 522. In contrast, one or more embodiments of the invention embodiments of methods of the invention described herein. enable nitrogen gassing employing hydraZides and other The hydraZide can contain one or more hydraZide groups (ie., nitrogen compounds as the substrate at temperatures of 0° C. polyhydraZide), such as di- or trihydraZides, and can also or less as described above. contain various combinations of amino groups and hydraZine [0098] The use of hydraZides as a source of nitrogen for groups, for example, semicarbaZide and aminoguanidine. nitrogen based chemical gassing is demonstrated extensively HydraZides useful in the invention may also incorporate one in Examples 4 through 6. or more heteroatoms such as O, S or N, examples of Which include pyridinic nitrogen as in isonicotinic acid hydraZide, Class 4 and the use of all such hydraZides is expressly encompassed. [0099] Another group of nitrogen compounds Well suited to Speci?c examples of hydraZides Which may ?nd use in use in methods embodied by the invention are those knoWn as embodiments of the invention include, but are not limited to, “nitrogen rich” compounds. These compounds contain a high acetic acid hydraZide, formic acid hydraZide, oxalic acid percentage of nitrogen, Which reduce the amount of substrate dihydraZide, maleic acid hydraZide (3,6-dihydroxy required to release the desired amount of nitrogen gas. Often, pyridaZine), succinic acid dihydraZide, semicarbaZide, ami nitrogen rich compounds contain tetraZole and/or triaZole noguanidine, isonicotinic acid hydraZide, benZoic acid rings, and derivatives thereof, such as those used as propel hydraZide, o-, m- and p-hydroxybenZoic acid hydraZide and lants and as gas generators in automobile air bags, including o-, m- and p-methylbenZoic sulfonyl hydraZides. Further 5-aminotetraZole, bis(aminotetraZolyl)tetraZine, bisguani hydraZides suitable for use in embodiments of methods of the dinium aZotetraZole and bitetraZole. Such compounds con invention are described in US. Pat. No. 3,706,607, the con tain nitrogen-nitrogen double bonds, Which reduce the tents of Which is incorporated herein in its entirety by refer amount of oxidiser required to liberate a given amount of ence. nitrogen gas compared to other nitrogen compounds. The [0094] Without Wishing to be bound by theory, it is believed triaZoles include the various triaZole tautomers, such as the by the inventors that the main oxidation reaction of the 1H and 2H 1,2,3 triaZole tautomers and the 1H and 4H-1,2,4 hydraZide requires the transfer of 4 electrons per molecule of tautomers. TriaZole derivatives include mono, di and trisub nitrogen gas produced during hydraZide foaming, as illus stituted molecules containing any alkyl, aryl, sulfonyl, nitro, trated by the folloWing generic examples of oxidation of the thio or amino substituents. Speci?c examples include but are US 2011/0132505 A1 Jun. 9, 2011

by no means limited to 1,2,4-triaZole, 1H-1,2,3-triaZole, 1,2, HoWever, for processes that rely on simultaneous or consecu 4-triaZole-3-carboxylic acid, 3-amino-1,2,4-triaZole, 1H-1,2, tive generation of nitrogen gas both from oxidation of NH3/ 4-triaZole-3 -thiol, 3 ,5 -diamino-1,2,4-triaZole, and their alkali NH4+ and oxidation of the hydraZide, a more preferable range metal and alkali earth metal salts. is from 0 M to 0.1 M for monohydraZides and 0 M to 0.05 M [0100] TetraZoles that can be used include the 1H and 2H for dihydraZides. Similarly, for higher substituted hydraZides, tautomers, and their mono or di-substituted derivatives, tetraZoles or triaZoles containing multiple nitrogen atoms, the Which can include species substituted at the 1 and 2 positions preferred concentration is from 0 to 0.2/n M, Where n is the in the tetraZole ring, or the 5 position corresponding to the number of nitrogen atoms available in each molecule of the carbon atom. Substituents can include one or more or a com nitrogen compound. bination of any alkyl, aryl, sulfonyl, nitro, amino or thio [0106] For gassing systems relying only on the direct oxi groups. Speci?c examples of tetraZoles include but are by no dation of NH3/NH4+, the minimum concentration of NH4+ means limited to 5-amino-1H-tetraZole, bitetraZole, 5-me Will usually be about three times higher than the equivalent thyl-lH-tetrazole, 5-phenyl-1H-tetraZole, 1H-tetraZole-5 concentration of other nitrogen compounds. This does not acetic acid and 5-methylthio-1H-tetraZole, and their alkali present any di?iculties as present-day emulsion explosives metal and alkali earth metal salts. containing ammonium nitrate are typically characterised by [0101] The oxidation of the tetraZole ring requires the concentrations of NH4+ in the order of about 13 M. removal of four electrons to produce tWo molecules of nitro [0107] The amount of gas produced to regulate the density gen gas. HoWever, various substituents present in common of emulsion can be varied as a function of the emulsion tetraZoles can also be oxidised to produce nitrogen gas, location in a borehole. In such applications, an excess of the increasing the yield of nitrogen to greater than tWo molecules substrate (eg., hydraZide or other nitrogen compounds) can be per molecule of tetraZole. Such substituents also increase the used in the discontinuous phase of the emulsion, and the oxidiser requirement, With the level of increase determined amount of nitrogen gas released controlled by adjusting the by the nature of the substituent(s). The oxidation half equa amount of oxidiser mixed in the emulsion. tion for a common tetraZole derivative, 5 -amino-1H-tetraZole [0108] Any suitable oxidiser can be used to oxidise is shoWn beloW. hydraZides and other nitrogen compounds to nitrogen as described herein. Examples of representative oxidisers [0102] Combining reactions [15] and [6] yields the overall include, but are not limited to hypohalites such as hypochlo reaction betWeen 5-aminotetraZole and sodium hypobromite. rites, hypobromites and hypoiodites, chlorites, bromites, chlorates, bromates, iodates, perchlorates, perbromates, periodates, permanganates, manganates, ferrates, selenates, [0103] Reaction [16] shoWs that CO2 is produced at a ratio ruthenates, perborates, peroxodisulphates, and peroxomono of one molecule of CO2for every tWo and a half molecules of sulphates of ammonium, and corresponding acids, and alkali nitrogen gas. Without Wishing to be bound by theory, it is metal and alkali earth metal salts of the foregoing (eg., believed that the majority of CO2 generated remains dis sodium chlorite, sodium bromite, and lithium, sodium, potas solved in the aqueous phase of the emulsion as bicarbonates sium, magnesium and calcium hypobromite), and organic (i.e., HCO3), provided that the pH of this phase is suf?ciently cations, e.g. benZyltriethylammonium permanganate. Fur high, as is generally the case in embodiments of the invention. ther examples include, but are not limited to, hydrogen per It is evident that just 1.4 moles of hypohalite oxidiser are oxide, inorganic and organic peroxides, organic nitrates, such required per mole of nitrogen gas produced for 5-aminotet as benZoyl or peracetyl nitrate, salcomine, chloramine T and raZole, affording a substantial reduction in the oxidiser con B, nitrodisulfonates, N-oxides, such as N-methylmorpholine sumption compared to other nitrogen containing compound. N-oxide, trimethylamine N-oxide and pyridine N-oxide, [0104] The particular nitrogen compound employed Will sodium dichlorocyanurate, acids such as peroxodisulfuric depend on cost considerations, solubility, the amount of oxi acid, peroxomonosulfuric acid, trichloroisocyanuric acid, diser required for its oxidation and its ability to diffuse hypochlorous acid, iodic acid, selenious acid, vanadic acid, through fuel lamellae of the explosive. and salts of Cu(II), Fe(ll), Mn(lll), Co(lll), Ti(lV), Cr(Vl), [0105] The nitrogen compound Will normally be added to V02", lead oxide, manganese dioxide, N-halosulfonamides the discontinuous phase of the explosive emulsion at a con such as N-chlorotoluenesulfonamide and N-chlorobenZene centration up to about 0.1 M and more preferably, in a range sulfonamide, N-halosuccinamides such as N-bromosuccina of from 0.01 to 0.08 M in explosive formulations that do not mide and N-chlorosuccinamide, iodine monochloride, iodine rely on direct oxidation of NH3/NH4+. The precise concen bromide, ferricyanide, and dimethyl sulphoxide and its co tration of nitrogen chemical depends on (i) the type of nitro oxidants, and salts of the foregoing including their alkali gen chemical employed and in particular, the number of metal and alkali earth metal salts. It is noted that the US Code moles of nitrogen gas that can be evolved per mole of sub of Federal Regulation, 29 CFR 1910.109, prohibits any addi strate, (ii) the target density of the gassed explosive, (iii) the tion or use of chlorates and peroxides in blasting agents need to target the oxidation of the nitrogen compound rather (Clark, 1991). than NH3/NH4+, With higher concentrations promoting reac [0109] The use of oxidisers Which diffuse or can be made to tion With the nitrogen compound rather than NH3/NH4+, and diffuse through the fuel lamellae separating the gasser and the (iv) the temperature at Which foaming occurs. For example, in nitrogen compound(s) are typically employed, With the appli explosives in Which the nitrogen gas is produced essentially cation of non-diffusing oxidisers being limited to those only from the oxidation of a hydraZide at 200 C., to achieve instances in Which the nitrogen compound can diffuse rapidly the ?nal density of 1.05 g/cm3 of a typical ammonium nitrate across the fuel lamellae to the gasser at loW temperature. Thus emulsion displaying ungassed density of 1.33 g/cm3, a con the oxidisers most suitable for use in the invention include for centration of monohydraZide of around 0.021 M is required, example hypohalous acids such as hypochlorous, hypobro assuming 70% yield of the monohydraZide to nitrogen gas. mous and hypoiodic acids and their corresponding alkali US 2011/0132505 A1 Jun. 9, 2011

metal or alkali earth metal salts, N-halo sulfonamides, such as the second species of the foaming system (i.e., the oxidiser) N-chlorobenZenesulfonamide, N-chlorotoluenesulfonamide that is added to the emulsion should desirably be able to and their salts (Chloramine B and T respectively), salcomine, diffuse rapidly through the fuel lamellae. N-halosuccinamides, such as N-chlorosuccinamide and [0115] The nitrogen compound Will generally be dissolved N-bromosuccinamide and their salts, chloric and bromic in the discontinuous phase of the emulsion explosive, and acids and their salts, N-oxides such as N-methylmorpholine diffusion of the selected oxidiser through the fuel lamellae of N-oxide, trimethylamine N-oxide or pyridine N-oxide as Well the explosive can be achieved in a number of Ways. For as alkali or alkali earth metal manganates. example, the diffusion of the oxidiser can be accomplished [0110] Some oxidisers such as hydrogen peroxide and per by: oxosulfates, display kinetic limitation to oxidation requiring [0116] (i) Selection of an oxidiser that diffuses readily the use of catalysts (eg., sodium tungstate), Which is expressly under the gassing conditions, such as chloramine T or B, or encompassed by the invention. Examples of Cr(V I) oxidisers N-oxides. This is illustrated for chloramine T in Example include, but are not limited to, chromium oxide, chromates, 2.1; dichromates, including pyridinium dichromate, chromic [0117] (ii) Selection of an oxidiser Whose acid form exhib acid, dipyridine chromium oxide and pyridinium chlorchro its a high pKa value, such as hypochlorites, hypobromites, mate. hypoiodites, manganates or bromites. Anions of these salts [0111] The oxidation of NH3/NH4+ Will typically involve can be readily protonated oWing to proton transfer from the the use of strong to very strong oxidisers, including, but not discontinuous phase of the emulsion, e.g., by diffusion of a limited to, hypochlorites, hypobromites, hypoiodites, chlo pH regulating agent such as a Weak acid like acetic or rites, chloramine T and B, N-bromosuccinamide and N-chlo formic acid. In this case, the pH of the discontinuous phase rosuccinamide, permanganates and peroxosulphates. In gas and the type of the pH regulating agent should be selected sing systems involving nitrogen chemicals in addition to to accelerate the gassing process. Speci?cally, the pH regu NH4+, these oxidisers Will oxidise both nitrogen containing lating agent itself should be able to diffuse through the fuel chemicals and, albeit often at a sloWer rate, NH3/NH4+. lamellae (this point is demonstrated by comparing the mea Weaker oxidisers Will generally only oxidise nitrogen com surements of Examples 4.1 and 4.2 beloW). pounds rather than NH3/NH4+. [0118] Methods described herein have application in the [0112] The amount of the oxidiser used in preferred gassing of emulsion explosives (including melt-in-oil emul embodiments of the invention Will depend, inter alia, on: (i) sions) of explosive emulsion, gel, slurry and heavy ANFO target density of the foamed explosive composition; (ii) the compositions. For example, the gasser can be pre-emulsi?ed selectivity of the oxidiser to produce nitrogen gas in reactions or delivered to emulsion in the form of a micro-emulsion, a With NH3/NH4+ and other nitrogen compounds, in the pres LeWis acid catalyst may be added to make an oxidiser diffuse ence of side reactions; (iii) the concentration of the active through fuel lamellae or for instance, an oxidiser can be added species in the oxidiser; (iv) the need to oxidise NH3/NH4+ or as a poWder, as described for nitrite gassing in US. Pat. No. the hydraZide; (v) the number of electrons WithdraWn from 4,875,951, European Patent Application No. 775,681, US. substrate by each molecule of the oxidiser, i.e., the change in Pat. No. 6,855,219 and US. Pat. No. 4,997,494 respectively, the oxidation state; (vi) the presence of catalyst (since in the the contents of Which are incorporated herein in their entirety process of its activation, an oxidiser may accept an electron by cross-reference. from a catalyst rather than from the substrate); and (vii) the [0119] Water-in-oil emulsion explosives can be any emul temperature of foaming. If an oxidiser is added to an emulsion sion comprising a discontinuous phase of an aqueous oxidis explosive as a gasser solution, it is preferred that the mass of ing solution of inorganic salts dispersed in a continuous phase that solution is less than 4% W/W of the emulsion, With the of an organic fuel in the presence of one or more emulsifying content of the active species in the solution of betWeen 5% agents. Such emulsion explosives are Well knoWn in the art. W/W and 50% W/W. [0120] The oxidising salt can, for example, be selected [0113] For example, to foam an emulsion that contains from ammonium, alkali metal and alkaline earth nitrates, 0.015 M maleic hydraZide With sodium hypochlorite in Which perchlorates and mixtures of the foregoing. Typically, the the hydraZide is essentially entirely consumed, 2><0.015/0. oxidising salt Will comprise at least about 50% W/W of the 8:0.038 mol sodium hypochlorite (NaOCl)/L emulsion, or emulsion explosive composition, more preferably at least 0.038/1.33:0.028 mol/kg emulsion Would be required. The about 60%, 70% or 80% W/W and most preferably, at least factor of 0.8 corresponds to ef?ciency of gassing and the about 90% W/W of the explosive. In a particularly preferred factor of 2 signi?es the ratio of number of electrons required embodiment, the oxidising salt Will be ammonium nitrate by a molecule of hydraZide [11] to that provided by each alone or in combination With sodium nitrate, potassium molecule of the oxidiser [5]. Taking into account the molecu nitrate, calcium nitrate and/or ammonium, alkali metal and lar Weight of NaOCl and the concentration of NaOCl in alkaline earth metal perchlorates. commercially available solutions of 12.5% W/W, the calcula [0121] Proton transfer agents used herein can comprise one tion becomes 0.028><(22.99+35.5+16)/0.125:17 g/kg emul or more compounds selected from the group consisting of sion. By selecting a different oxidiser, and/or using more inorganic acids, organic acids, carboxylic acids, and salts concentrated solutions, the amount of gasser may be opti thereof, the explosive being formulated such that at least mised to less than 0.8% W/W of the emulsion. some of these compounds exist in the explosive in a neutral [0114] Normally, the species of a nitrogen compound form. More particularly, these agents can comprise one or foaming system that is included in the discontinuous phase of more compounds selected from the group consisting of alkyl the emulsion Will be at a relatively loW concentration. This carboxylic acids, acetic acid, formic acid, phosphoric acid, means that the diffusion of this species through the fuel lamel citric acid, tartaric acid, furoic acid, fumaric acid, salicylic lae Will be sloW, even if the species itself is soluble in the fuel acid, malonic acid, phthalic acid, sulfanilic acid, mandelic and displays high diffusivity in that phase. For faster gassing, acid, malic acid, butyric acid, oxalic acid, and salts thereof. US 2011/0132505 A1 Jun. 9, 2011

[0122] Non-diffusing pH regulating agents as described perature or Within any speci?c range of temperatures Within herein can comprise one or more compounds selected from the particular ranges speci?ed above (eg., 35° C., 15° C., 14° the group consisting of partially or completely deprotonated C. or 13° C., or eg., from 0° C. or beloW up to about 15° C.), forms of inorganic acids and carboxylic acids, and salts and all such speci?c temperatures and temperature ranges are thereof. In particular, these agents can comprise one or more expressly encompassed. of phosphoric acid, acetic acid, formic acid, citric acid, tar [0129] An example of an embodiment of the invention is as taric acid, furoic acid, fumaric acid, salicylic acid, malonic folloWs. Add to an emulsion explosive composition contain acid, phthalic acid, sulfanilic acid, mandelic acid, malic acid, ing a hydraZide compound (eg., acetyl hydraZide, maleic butyric acid, oxalic acid, and salts thereof. hydraZide etc., at a concentration betWeen 0.01 and 0.1 M) [0123] A melt-in-oil emulsion explosive can be any such and a pH regulating agent (eg., sodium acetate, approx 0.2 to explosive containing little or no Water in its formulation, and 1% of the composition) With the pH of the emulsion betWeen may solidify once the temperature decreases beloW the solidi 4.5 and 6, a solution of sodium hypochlorite (the solution ?cation point of the melt, Which usually lies betWeen 70° C. and 130° C. Normally, the melt-in-oil emulsion contains containing 10-20% NaOCl) and mix this solution into the ammonium nitrate and at least one other chemical added to emulsion for 5-15 s to disperse it and gas the emulsion. The decrease the melting point of ammonium nitrate. Melt-in invention Will noW be described beloW by reference to a Water emulsion explosives are also Well knoWn in the art (e. g., number of further non-limiting Examples. U.S. Pat. No. 4,790,891 and Us. Pat. No. 4,676,849). [0124] So-called heavy ANFO mixtures form an important EXAMPLE 1 part of industrial explosives consumption. In heavy ANFO, emulsion explosives are typically mixed With ANFO, that is, 1. Experimental Protocol With porous solid prilled ammonium salts With oil present in 1.1 Emulsions the porous space of the prills. Heavy ANFO may be suitably gassed by the methods described in this invention, and the use [0130] In all Examples, the discontinuous phase of explo of any such methods to sensitise and/or modify the density sive emulsions consisted of a super-saturated solution of this type of explosive is speci?cally encompassed. ammonium nitrate, containing approximately 400 g of [0125] Emulsi?ers commonly used in emulsion explosive ammonium nitrate per 100 g of Water. In Emulsions A and B, compositions include sorbitan monooleate (SMO), poly the continuous phase consisted of a mixture of diesel fuel and isobutane succinic anhydrides (PiBSA) and amine derivatives a PiBSA emulsi?er, such that the ratio of fuel to emulsi?er of PiBSA, and conjugated dienes and aryl-substituted ole?ns. Was approximately 70 parts of diesel fuel to 30 parts of U.S. Pat. No. 6,800,154 and Us. Pat. No. 6,951,589 provide PiBSA, by mass. The phase ratio for these emulsions Was 87 a particularly comprehensive summary of suitable emulsi? parts discrete phase to 13 parts continuous phase on a volu ers Which may be used, the contents of Which are incorporated metric basis. This corresponded approximately to 91.5 parts herein by reference in their entirety. of discrete phase to 8.5 parts of continuous phase on a mass [0126] The fuel used in the explosive can also be any fuel basis. In Emulsions C-K, the continuous phase consisted of a commonly utilised in explosive compositions. Examples of mixture of diesel fuel and PiBSA emulsi?er, such that the fuels that can be utilised include, but are not limited to, ratio of fuel to emulsi?er Was 80 parts diesel to 20 parts paraf?nic, ole?nic, napthenic, and paraf?n-napthenic oils, PiBSA by mass. The ratio phase ratio for Emulsions C-K Was animal oils, vegetable oils, synthetic lubricating oils, hydro 94 parts of discrete phase to 6 parts of continuous phase on a carbon oils in general and oils derived from coal and shale, as mass basis. The above compositions conform to those Well described in detail in Us. Pat. No. 6,951,589, the contents of knoWn in the art, such as those described in Us. Pat. No. Which is also incorporated herein by reference in its entirety. 4,409,044, U.S. Pat. No. 3,447,978 and Us. Pat. No. 3,770, [0127] Although gel explosives Were utilised by industry 522. prior to emulsion explosives, their use has declined in pref erence to emulsion explosives and heavy ANFO. Neverthe [0131] The discontinuous phase Was prepared by dissolv less, gel explosives are Well knoWn to the skilled addressee. ing ammonium nitrate in Water at a temperature of 75° C. Examples of gel explosives are for instance described in Us. Various combinations of pH regulating agents, such as Pat. No. 3,382,117, U.S. Pat. No. 3,660,181, U.S. Pat. No. sodium acetate, sodium hydroxide and tri-sodium citrate 3,711,345 and Us. Pat. No. 3,713,919. Were then added to control the pH of the system if required in [0128] Typically, the gassing of an explosive as described a particular emulsion. Some of these chemicals also serve as herein Will be achieved at ambient temperature although heat proton transfer agents during the gassing process. Nitrogen ing of the explosive to assist diffusion of the oxidiser and/or containing compounds such urea, 5-aminotetraZole, and vari nitrogen compound is not excluded. The gassing may for ous hydraZides/dihydraZides Were also added to some emul example be carried out at temperatures of about 70° C. or sions to improve the ef?ciency of the gassing process. The beloW, or at atemperature of60° C., 50° C., 40° C., 30° C., 25° apparent pH of the solution Was measured using a pH probe C., 20° C., 10° C., 5° C. or 0° C. or beloW, or in any range of (Hanna pH 213 meter With HI 1131B pH probe) prior to from 0° C. or beloW up to about 70° C. As Will also be addition to the continuous phase. Table 1 lists emulsions used understood, the gassing may be carried at any speci?c tem in the examples described beloW. US 2011/0132505 A1 Jun. 9, 2011 12

TABLE 1

Composition of emulsions

A B C D E F G H I J K

Discontinuous Phase

Ammonium nitrate (g) 1000 1000 600 600 600 400 600 600 600 600 600 Water (g) 250 250 150 150 150 100 150 150 150 150 150 Sodium acetate (g) i 14.83 4.96 3.29 i i i 3.28 3.29 i 3.28 Tri-sodium citrate (g) i i i 5.87 4.01 5.88 i i 5.87 i

Sodium dihyd.rogen i i i i i 0.24 i i i i citrate (g)

Maleic hydraZide (g) i i 1.13 1.14 i i i i i i

Succinic dihydraZide (g) i i i i 0.73 i Acetyl hydrazide (g) i i i i 0.58 0.83 0.83 0.83 i

5-AminotetraZole (g) i i i i i 4.47

Urea (g) i i 1.01 i i i i i i i i Sodium hydroxide i i 0.57 8.25 7.94 4.0 1.01 0.75 7.84 3.26 50% solution (g) Apparent pH 3.85 6.05 5.5 6.29 6.24 6.29 5.0 5.5 5 6.24 B 5.5 5.5 Continuous Phase

Diesel oil (g) 81.76 82.96 38.65 38.97 39.12 26.01 38.72 38.53 38.57 39.07 38.90 PiBSA (g) 35.26 35.67 9.66 9.74 9.78 6.5 9.68 9.63 9.64 9.77 9.73

Total mass (g) 1367.0 1383.5 804.9 811.4 813.8 541.1 805.4 803.3 803.1 813.3 809.6

[0132] Emulsions Were constructed by slowly adding the serve three to ?ve experiments. The gasser solution Was above solution containing ammonium nitrate to the continu mixed With the emulsion for 5-15 s at 300 rpm With an ous phase at a temperature of approximately 75° C. The tWo overhead stirrer to ensure an even distribution of the gasser phases Were mixed thoroughly using an overhead stirrer (IKA throughout the emulsion. In examples Where acetic acid Was Eurostar Digital) operating at approximately 300-450 rpm. added to the emulsion prior to gassing, the desired amount of Once the tWo phases had been completely combined, the acid Was mixed in the emulsion for 15 s, before adding the mixing speed Was increased to approximately 500-600 rpm gasser after a further 30 s had elapsed. The emulsion Was then and maintained at this speed until the emulsion had reached a transferred to a container of knoWn volume, such that the suitable viscosity. emulsion occupied completely the volume Within the con 1.2 Preparation of Gassers tainer. The container Was levelled at the top and Weighed at [0133] Five types of gasser chemicals Were used, including regular intervals as the gassing progressed in order to observe lithium and calcium hypochlorites (LiOCl and Ca(OCl)2, the density change and the rate of gassing. respectively), chloramite T, sodium hypochlorite (NaOCl) [0135] For experiments conducted at temperatures other and sodium hypobromite (NaOBr). Lithium and calcium than ambient, the emulsion temperature Was adjusted by hypochlorites as Well as chloramine T Were obtained as sol means of a constant-temperature refrigerated and heated ids, Whilst sodium hypochlorite and hypobromite Were Water bath before addition of the gasser solution. The con obtained as solutions. The solids Were Weighed into a 20 cm3 tainer employed in the experiment Was also placed in the beaker and distilled Water Was then added to affect the disso Waterbath before handling. Once the gasser solution hadbeen lution. The concentration of the gasser solution Was generally added to the emulsion, the container Was returned to the Water betWeen 10 and 20%; although higher concentration could bath at all times When not being Weighed. have been possible. To accelerate the dissolution of the sub stance, the beaker Was heated lightly (less than 50° C.), and then the solution Was cooled doWn prior to use. In the case of EXAMPLE 2 sodium hypochlorite and hypobromite, the gassing reactant Was present in a solution of approximately 10-12% by mass. [0136] 2.1 Oxidation of Ammonia in Emulsion Without Sodium hypobromite contained a small percentage (1-5%) of Proton Transfer Agent sodium hydroxide for enhanced shelf life, Whilst some [0137] This example demonstrates that ammonia/ammo examples utilised additional sodium hydroxide to delay the nium ions can be directly oxidised by various oxidisers in onset of the gassing process. For examples utilising addi order to produce nitrogen gas to sensitise and/or modify den tional sodium hydroxide in the gasser, stock solutions Were sity of an emulsion or gel explosive. It also demonstrates the made by adding the required mass of 50% sodium hydroxide in?uence of the gasser composition and pH on the rate of solution to a knoWn mass of sodium hypochlorite solution. gassing and indicates the desirability of appropriate pH selec The desired mass of solution for use in examples Was draWn into a syringe, con?rmed by Weighing, and used Without tion to achieve required sensitisation times. alteration. [0138] The methodutilised involved gassing of EmulsionA (With no pH control or proton transfer agent) using lithium 1.3 Gassing Procedure hypochlorite, sodium hypobromite and chloramine T, at 30° [0134] Gassing experiments Were conducted using 23012 g C. Table 2 shoWs the composition of gassing solutions and of emulsion, allowing each batch of emulsion of Table 1 to completion time for each example.