CA1217342A - Stable an/emulsion explosives and emulsion for use therein - Google Patents

Abstract

TITLE
Stable AN/Emulsion Explosives and Emulsion for Use Therein ABSTRACT OF THE DISCLOSURE
Explosives that are sensitized blends of a water-in-oil emulsion and AN particles, such as AN or ANFO prills, have improved stability when their structure hinders the loss of water from the aqueous emulsion phase and transportation of such water across the oil phase to the AN particles. Use of an anionic emulsifying agent comprising a fatty acid salt, e.g., as formed in situ during the formation of the emulsion, is the preferred way of forming such a blend-stabilizing structure. Emulsion/ANFO and emulsion/AN blends stabilized in this manner make satisfactory storage-stable packaged products.
Emulsion/AN blends made with a new low-viscosity emulsion containing essentially all of the oil required to oxygen-balance the blend and a proportionately larger amount of anionic emulsifying agent to stabilize the emulsion structure constitute preferred bulk products owing to their greater adaptability to pumping. Pumping the stabilized blends through an annular stream of aqueous lubricating liquid is advantageous.

Description

TITLE
Stable AN/Emulsion Explosives and Emulsion for U~e Therein BACKGROUND 0~ THE INVENTION
Field of the Invention The present invention relates to explosive compo6itions comprising a sensitized blend of a water-in-oil emul6ion and 601id particulate ammonium nitrate (AN), e.g., AN prill6 or granule6 which may be coated with fuel oil ~ANFO), and more particularly to 6uch compo6itions in the form of storage-6table packaged products and bulk products adapted to be pumped into boreholes. The invention also relates to a low-vi~cosity emulsion particularly adapted to be blended with fuel-free or -deficient AN to form such a blend.
DescriPtion of the Prior Art Explosive6 which compri~e a blend of a water-in-oil emul6ion and 601id particulate AN (e.g., ANFO) have captured the intere6t of blasters in recent year6 owing to the fact that they are able to offer the advantages of high bulk density, bla6ting energy, and water resi6tance characteristic of emulsion explosives, while at the 6ame time re6ulting in cost reductions owing to the lower co~t of the AN. Among the problem~ that may be encountered in connection with the use of these blend~, however, are those of blend pumpability and blend ~tability, more particularly of the 6tability of the blendls explosive properties. Some blends are not pumpable, or only difficultly pumpable. Some must be pumped `~

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immediately after they have been formed because they do not retain their pumpability even for a day or two. While there is no question but that the blend must have a sufficiently long shelf life as to be s detonable after it has been emplaced in a borehole, this matter has not been dealt with to any significant degree in most of the prior art sources on emulsion/AN blends. Nevertheless, it is a fact that not all packaged blends are detonable by the time they are to be used, even if the packages have been stored for only a ~hort time.
Emulsion/AN blends are described in U.S.
Patents 3,161,551 (Egly et al.); 4,111,727 (Clay);
4,181,546 (Clay); and 4,357,184 (Binet et al.), and British Patent 1,306,546 (Butterworth). Egly et al.
describe an emulsion/AN blend wherein the emulsion, said to be in a sensitized form, is employed as a sensitizer for the solid ammonium nitrate. Regarding the delivery of the blend into a borehole, the patentees describe forming the blend in the borehole itself, i.e., by dropping the AN into the hole and pouring the sensitized emulsion over it.
Clay, whose 10/90 to 40/60 emulsion/AN
blends in U.S. Patent 4,111,727 are sensitized only by the air entrapped in the AN, states that the emulsion and AN particles are combined by very simple procedures, preferably just prior to insertion into the borehole. Clay also states that sorbitan monooleate, sorbitan monostearate, and sorbitan monopalmitate are quite suitable emulsifiers for making his emulsion, and that the emulsifiers preferably are blended into the oil before the aqueous component is added. Clay's AN may be oxygen-balanced ANF0 (to be blended with an oxygen-balanced emulsion), or fuel-deficient or l;Zi73~ `

fuel-free solid AN (to be blended with an emul6ion that contains mo6t or all of the oil required to oxygen-balance t~e blend).
In U.S. Patent q,181,546, Clay de6cribes 40/60 to 60/40 emul6iontAN blends having completely filled inter6tice6 in and between the AN particle6.
Thi6 product is said to contain too high a proportion of dry ingredient to be pumpable in conventional slurry pumps, but i~ said to be deliverable to a borehole by an auger in the 6ame manner as dry ANPO.
This patent advises minimizing the amount of emulsifier, and u6ing high 6hear mixing, to insure a stable emulsion. Clay describe6 60rbitan fatty acid ester6 a6 being particularly suitable emul6ifier6, and Glycomul O* (sorbitan monoolsate) as su~erior to most for his invention.
Butterworth describe6 loading his blend into an 8.3-cm-diameter polyethylene tube, priming the charge with nitroglycerin, and detonating the charge one hour after mixing. Thus, Egly et al., Clay, and Butterworth do not addres6 themselve6 to such matters as blend stability, i.e., the condition of the blend after it ha6 been allowed to stand for several days or weeks before or after packaging, or before

2~ delivery in bulk form to a borehole.
The emulsion portion of Binet et al.ls explosive composition is termed a "microemul6ionll, and it contains an amphiphatic synthetic polymer emulsifier, along with a conventional water-in-oil emulsifier. Optionally, a phosphatide emulsion stabilizer is included. Binet et al.~s microemulsion Der 6e, described as a Illiqui-liquid foamll of very small cell size ranging from less than 1 micron to about 15 microns, is said to display exceptional long-term storage stability and to be tolerant to * denotes trade mark 12i~34Z

doping with further fuel and energy-enhancing ingredients. The patentees discuss a destabilizing seeding crystal effect in prior art emul6ion explosives re~ulting from the presence of solid oxidizer salts in the basic emulsion. According to Binet et al., their findings Chow that their microemulsion, when doped with 24 percent ground AN, was much more stable tO this seeding crystal effect than a prior art emulsion, and remained cap-sensitive for three cycles, each consisting of 3 days of storage at 50C followed by 2-3 days at -17C.
Binet et al.'s consideration of storage &tability is directed for the most part at the explosive emulsion itself. The patentees mention that all known prior art water-in-oil emulsions suffer from lack of stability owing to the seeding effect. Binet et al. also imply that the seeding effect i6 a problem in AN-doped emulsions, although they do not explain how this can be so in microemulsions containing relatively large AN
particles. Moreover, Binet et al. require an expensive polymeric emulsifier, and an optional emulsion stabilizer, to achieve improved stability in their microemulsion.
AN~emulsion blends having good storage 6tability, and a method of making such blends which does not reguire the use of expensive additives, of perhaps limited utility, are greatly needed to expand the spectrum of AN/emulsion products that can be made available to the public. In particular, blends are needed which are pumpable into a borehole even a few days after having been formed, as well a6 detonable after having been delivered into a borehole in packaged form after a period of about three mon~ths or more from the time the blends were made.

3~

SUMMARY OF THE INVENTION
. _ . . .
The present invention provides an improvement in a method of preparing an explosive composition by combining ammonium nitrate (AN) particles, e.g., AN or ANFO prills, with a water-in-oil emulsion comprising (a) a liquid carbonaceous fuel having components which form a continuous emulsion phase, (b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within the continuous phase, and (c~ an emulsifying agent to form a blend of the AN particles and the emulsion containing a sensitizing amount of dispersed gas bubbles or voids. The improvement of the invention comprises forming the AN particles and the components of the emulsion into a structure that minimizes the loss of water from the aqueous solution drople~s and the transportation of the water across the continuous phase to the AN particles mixed with the emulsion.
Preferably, this structure includes an emulsion which, when subjected to the following Water Diffusion Test, loses no more than about 4 percent of its original weight:
A cylindrical pan of 7.5 mm radius and 2.6 mm height is filled with 0.325 cc of freshly prepared emulsion, which is the same emulsion as that which has been used to prepare the mixture. The emulsion's flat exposed surface of 1.25 cm2 area is contacted with a cylindrical pellet of a~lmonium nitrate having the same cross-sectional area as the emulsion sample and a height of at least 1 cm. The ammonium nitrate is the same as that which has been used to prepare the mixture. The emulsion/AN sample i6 stored for 48 hours in dry air at 25C, after which time the emulsion is analyzed for water loss.

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In a preferred method of the invention the described structure that hinders water 106S and transport is formed by combining the AN particles with an emulsion which contains, in its emulsifying system, (a) a salt, preferably an alkali metal, ammonium, and/or alkylammonium salt, of a fatty acid (preferably selected from the group consisting of saturated and mono-, di-, and ~ri-unsaturated monocarboxylic acids containing about from 12 to 22 carbon atoms), as well as (b) the free fatty acid, the latter being in solution in an oil, the oil solution constituting the continuous emulsion phase, and the fatty acid and fatty acid salt, together with said oil, forming said liguid carbonaceous fuel.
Most preferably, the fatty acid salt emulsifying system is one which has been produced in situ from a fatty acid and a base when the oil and the aqueous solution of the inorganic oxidizing calt have been combined to form the emulsion. ~ith this emulsifying system a base, e. g., hydroxide, is present in the emulsion's aqueous phase.
An alternative, or preferably supplemental, way of forming the structure that controls water transport between the aqueou~ solution droplets and the AN particles is to provide a droplet cell size of at least about 1, and preferably no greater than about 4, microns. Still alternatively, or additionally, the structure will be formed by coating the AN particles with a substance in which water has a diffusion coefficient at 25~C of less than about 10-5 cm2/sec.
Also provided by this invention is a storage-stable packaged product made by one embodiment of the method of the invention and comprising an aged blend of preferably at least about 734~:

30 percent by weight of particles of AN, e.g., ANF0 prills, and preferably at least about 30 percent by weight of an emulsion comprising (a) a liquid carbonaceous fuel including an oil solution of a fatty acid, said solution forming a continuous emul~ion phase, (b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within the continuous phase, and (c) an emulsifying system including an emulsifying agent comprising a salt, preferably an alkali metal, ammonium, or alkylammonium salt, of a fatty acid ~preferably selected from the group consisting of satu~ated and mono-, di-, and tri-unsaturated monocarboxylic acids lS containing about from 12 to 22 carbon atoms), as well as the free fatty a~id, the fatty acid and fatty acid salt, together with said oil, forming said liquid carbonaceous fuel, said blend containing a ~ensitizing amount of dispersed gas bubbles or voids, e.g., an amount which is at least about 5 percent of the volume of the blend, and whose structure is such that the amount of water 106t from the agueous solution droplets in the emulsion when aged at 25C
for 2 days is no more than about 4, and preferably no more than about 3.5, percent of the original emulsion weight, as measured by the above-described Water Diffusion Test. In a preferred embodiment, the emulsion has a droplet cell size of at least about 1, and preferably no greater than about 4, microns.
The term "aged~' is used herein to distinguish the packaged product of the invention from products which ara made at the site of use and delivered into a borehole in bulk form. An llagedll product denotes herein a product which is packaged 3s and transported to the field site at some later date, 121~3~

usually at least several days, and often weeks, after the time of manufacture.
The term ~'ammonium nitrate particles~ as used herein tO describe the solid material that is present in the product of the invention in a blend with an emulsion denote~ ammonium nitrate in the form of granules or prills, e.g., fuel-free or fuel-deficient prills, or prills lightly coated with fuel oil, i.e., the well-known "ANF0", in which the usual AN/F0 weight ratio i~ about 94/6, andtor coated according to the method of the invention, as will be described hereinafter.
In a further embodiment, the present invention provides a water-in-oil emulsion adapted to be blended with AN prills by one embodiment of the method of the invention to form a stable explosive, said emulsion comprising (a) about from 7 to 21 percent, preferably about from 9 to 15 percent, by weight of a liquid carbonaceous fuel including an oil solution of a fatty acid, said solution forming a continuous emulsion phase;
(b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within the continuous phase; and (c) an emulsifying system comprising (1) said fatty acid and (2) a fatty acid salt, the oil, fatty acid, and the fatty acid salt together forming t~e liquid carbonaceous fuel, and the ratio of the amounts of oil and fatty acid added to form the emulsion being in the range of about from ltl to 3/1 by weight; said emulsion having an oxygen balance more negative than about -6 percent, e.g., as negative as about -50 percent.

12~342 In a preferred emulsion, in which the emulsifying system is one which has been produced in situ from the fatty acid and a base when the oil and the aqueous salt solution have been combined to form the emulsion, a base is also present, as a result of the addition of base and fatty acid in an equivalents ratio of about from 0.5/1 to 3~1, preferably about from 1.5/1 to 2/1. In the above-specified oil to fatty acid ratio in this particular emulsion, the fatty acid weight should be understood to be the weight of fatty acid added to form the emulsion.
Some of this becomes converted to the fatty acid salt emulsifier. This emulsion has a viscosity generally in the range of about from 500 to 10,000 poise, and about from 500 to 3,000 poise for bulk products. The emulsion structure is stable for a period of about 3 months or more.
In the emulsion product made by adding a pre-formed fatty acid salt to the system, the 'Ifatty acid" weight in the above-specified oil to fatty acid ratio should be understood to be the weight of fatty acid added plus the weight of fatty acid salt added when the emulsion is being made. In this product the ratio of the weight of fatty acid salt (added) to the weight of fatty acid (added) is at least about 0.5/1.
The amount of inorganic oxidizing salt (the oxidizer) present in the emul6ion of the invention is insufficient for the complete combustion of the fuel therein, as is evidenced by the emulsionls negative oxygen balance. This oxidizer-deficient emulsion is converted into a product having a more positive oxygen balance and 6atisfactory explosive properties by blending with fuel-deficient or, preferably, substantially fuel-free AN prills. By virtue of its relatively low visc06ity, the oxidizer-deficient emulsion can be blended with these AN prills wi~h low shear so as to produce a preferred explosive emulsion/AN blend of the invention containing about from 20 to 70 percent by ~eight of AN prills and a sensitizing amount of dispersed gas bubbles or voids (e.g., an amount which is at least about 5 percent based on blend volume), the blend being essentially oxygen-balanced, i.e., having an oxygen balance more positive than about -25 percent, and preferably in the range of about from -10 to ~5 percent. Blends made from the preferred in situ emulsion and about from 20 to 50 percent prills have a viscosity in the range of about from 2500 to 20,000 poise, a viscosity in this range being maintainable for a period of several days.
BRIEF DESCRIPTION OF THE DRAWING
In the accompanying drawing, which consists of plots of data obtained in the experiments described in Examples 1, 2, and 7:
FIG. 1 is a plot of the rate at which water is transported into an emulsion used in a product of this invention, as contrasted to an emulsion used in a product of the prior art;
FIG. 2 is a plot of the rate at which water is transported into solid ammonium nitrate from an emulsion used in a product of the invention, as contrasted to an emulsion used in a product of the prior art; and FIG. 3 is a plot of the viscosities of three blends of the invention and three control blends versus time.
DETAILED DESC~IPTION
The present invention is based on the discovery that the transport of water from the ~
dispersed aqueous phase of the emulsion to the AN

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particles that are intermixed with the emulsion in AN/emulsion blends plays a major role in the instability of these blends, leading to a deterioration of product performance. This transfer S of water results in an increase in the water content of the particulate AN, perhaps to a level of about 5 to 10 percen~, and an increase in the sal~
concentration in the dispersed aqueous phase, approaching the saturation limit and the possibility that the salt may crystallize out. These combined effects can cause the structure of the emulsion/AN
blend to deteriorate rapidly.
In the method of the invention, the AN
particles and the component~ of the emulsion, by lS virtue of their chemical composition and physical properties (e.g., size and spatial rela~ionships), are formed into a structure in the emulsion/AN blend that minimizes the loss of water from the droplets of aqueous salt solution, and transportation of the water across the emulsion's continuous phase to the AN particles. This structure provides a medium or barrier resistive to water-transport formed preferably by a substantially hydrophobic continuous emulsion phase, most preferably obtained when the emulsifying system contains a salt, preferably an alkali metal, ammonium, and/or alkylammonium salt, of a fatty acid (e.g., a saturated or mono-, di-, or tri-unsaturated monocarboxylic acid containing about from 12 to 22 carbon atoms), as well as the free 3~ fatty acid in solution in an oil, the oil solution of the acid forming the emulsion's continuous phase, and the oil, fatty acid, and fatty acid salt together forming the liquid carbonaceous fuel. Most preferably, this emulsifying system is formed in situ by combining the oil and the aqueous solution in the ~2:173~Z

presence of a fatty acid and a base, according to the method described in U.S. Patent 4,2~7,010 ~Owen). It has been ~uggested that the Owen in situ method may allow the fatty acid salt (soap) emulsifying agent to form at the oil/water interface, where it is present together with free fatty acid, whereby a stabilizing equilibrium is believed to be established between the acid/soap at the interface, fatty acid in the oil phase, and base in the aqueous phase.
In a most preferred embodiment of the method of the invention, therefore, the emulsifying system is one which has been produced by the in situ formation of a salt, preferably an alkali metal~
ammonium, or alkylammonium salt, of a fatty acid (preferably a saturated or mono-, di-, or tri-unsaturated monocarboxylic acid containing about from lZ to 22 carbon atoms~, most preferably sodium, potassium, and/or ammonium oleate, according to techniques described in the aforementioned Owen patent.
The importance (to the stability of emulsion/AN blends) of a blend structure provided by an emulsion containing a hydrophobic continuous emulsion phase, and more particularly a relatively nonpolar emulsifying system that produces such a continuous phase, has not heretofore been recognized. In fact, Clay (U.S. Patent 4,181,546) says that he found the (non-ionic) sorbitan oleate type to be among the most satisfactory emulsifiers.
Binet et al. 6uggest that stability i5 dependent on the presence of a graft, block, or branch polymeric emulsifier in combination with conventional emulsifiers. High concentrations of the polar non-ionic emulsifiers in the oil layer render it relatively hydrophilic and therefore capable of 1~73~2 transporting water to the AN particles at a rapid rate, leading to the product instability described above. The benefit of the hydrophobic oil layer, as contrasted to the more hydrophilic oil layer preferred by Clay, is shown in Examples 1 and 2 which follow.
The abo~e-described control of the emulsi,ying system is the preferred way of providing a structure wherein a hydrophobic medium is present between the aqueous droplets in the emulsion and the AN particles. An alternative method, useful with any emulsifying system but preferably in conjunction with the preferred emulsifying system described above, is to coat the AN particles with a substance in which water diffusivity is low, e.g., in which water has a diffusion coefficient at 25C of less than about 10 5, and preferably less than about 10 8, cm /sec. Preferred coating materials are those which, when used in an amount constituting 6-10 percent of the amount of solid AN used, can act as a fuel to oxygen-balance the solid AN. Such materials could replace the fuel oil (F0) normally used in ANF0 for example. Examples of such materials are solid or semi-solid hydrocarbons including paraffin wax and petrolatum-rosin-paraffin.
In a further preferred embodiment of the invention, the required structure formed by the AN
particles and the components of the emulsion is provided by controlling the cell size of the emulsion's internal phase (the aqueous salt solution droplets) so as to decrease the chemical driving force, i.e.. the difference between the chemical potential of the water in the dispersed aqueous 6alt solution of the emulsion and the AN particles. A
reduced chemical driving force minimizes the rate of ~Z~342 water transport from the aqueous emulsion phase to the AN particles. The chemical potential of the components in the dispersed aqueous phase increases in inverse proportion to the radius of curvature of 5 the cell (droplet). Therefore, smaller cell size increases the chemical potential of the water in the discontinuous phase, thereby increasing the driving force for water transport to the solid oxidizer. In the past, a smaller cell size (higher viscosity) has been recommended to increase ~he stability of emulsion explosives ~ se. For example, Clay (U.S.
Patent 4,181,546) recommends "a good shearing mixing"
as well as "a good emulsifier" (sorbitan oleate type) to obtain a good stable emulsion. As is discussed lS above, the situation is different for emulsion/AN
blends. The optimum cell size of the internal phase of an emulsion in a blend is the largest that will not crystallize on losing water over the goal shelf life of the product. This insures a minimum rate of water transfer, without premature crystallization of the emulsion. The optimum cell size generally is from about 1 to about 4 microns, decreasing as the aqueous phase water content decreases.
Other factors also can be controlled to minimize water transport across the emulsionls continuous phase. Since the rate of water transport not only is determined by the composition of the continuous phase but also is decreased when the dimensional thickness of this phase is greater, the continuous phase can be made dimensionally thicker by increasing the oil content of the emulsion.
Therefore, a preferred product of the invention, especially for use in bulk emulsion/AN blends, is a "high oil" emulsion that contains a portion, and 3s preferably substantially all, of the oil required to 1~7342 oxygen-balance the solid ammonium nitrate to be blended therewith. This is beneficial for several reasons. First, the added oil imparts a lower viscosity to the emulsion. Low viscosity is of great benefit in that it permits the formation of emulsion/AN blends with lower shear mixing, which has an advantageous effect on the stability of the blend. Lower shear mixing is especially important in making blends having a high content of solid AN or ANF0 because the movement of the particles past each other during mixing performs work on the emulsion between them which may break the oil film that separates the particles from the agueous solution droplets, thereby giving water transport a ~head start". With the "high oilll emulsion of the invention, and particularly the preferred emulsion in which the emulsifying system is formed in situ a more stable blend results because the components can be mixed with less shear than that used in blending a more viscous emulsion, and a less viscous, more easily pumpable blend results. Moreover, as will be explained more fully hereinafter, the lower viscosity of the blend is sufficiently stable, at least for several days, so that the advantage of ease of pumping is retained even if a few days elapse between the time when the blend is made and the time when it is pumped.
As has been stated above, increasing the oil content of the emulsion so as to increase the dimensional thickness of the emulsionls continuous phase will increase the resistance to the transport of water across the continuous phase to the AN
particles. However, the uncontrolled enlargement of the emulsion's continuous phase often causes t~e separation or "creaming" of the oil.

It now has been found that in certain specific systems a ~high oil~ emulsion having an emulsion structure that is stable, i.e., a structure in which there is no "creaming" of the oil pha6e, can be achieved if the concentration of the emul6ifying agent is higher than that used in standard ~low oil~
emulsions, i.e., essentially oxygen-balanced emulsions which are to be blended with ANF0. If the emulsifying agent is a ~alt of a fatty acid used in conjunction with the free fatty acid, which is in solution in the oil, and especially if the salt of a fatty acid has been formed in situ as described in U.S. Patent 4,287,010, the stable, low-viscosity emulsion (i.e., the "high oil~' emulsion which contains proportionately more emulsifying agent) forms blends with AN having a stable viscosity which remains low enough to facilitate pumping even if the blend "ages" a day or so before pumping.
Non-ionic emulsifying agents, such as those of the sorbitan fatty acid ester type, have been stated in the prior art, i.e., in U.S. Patent

4,181,546 (Clay), as having been found to be among the most satisfactory emulsifiers for emulsions, with respect to stability. A new finding, however, is that emulsion/AN blends made from "high oil"
emulsions containir.g an emulsifying agent in a concentration that is sufficiently high to preserve the emul~ion structure are unstable with respect to viscosity levels when the emulsifying agent is sorbitan monooleate. In the latter case, despite the lower viscocity of the "high oil'l emulsion used to form the blend, water transport from the aqueous phase and the possible crystallization of the salt therein can cause the blend viscosity to rise at an extremely rapid rate to a level at which the blend is ~2~34;~

no longer pumpable and subsequently not detonable.
This level may be reached within a day or two.
Accordingly, viscosity stability i~ not a charact~ristic of "high oil" emulsion/AN blends in general, but is dependent upon the nature of the emulsifying system present in the ~high oil~ emulsion.
Other benefits of forming blends of the llhigh oil" emulsion of the invention and oil-free or oil-deficient AN prills are that the void volume in the AN prills could be useful as sensitizing sites in the blend. In addition, inclusion of all of the required oil in the emulsion to begin with permits the oil to fatty acid ratio to remain essentially undisturbed in the transition from the unblended to the blended emulsion, hence preserving the required emulsifier level.
Assuming that the preferred "high oil"
emulsion of the invention is intended for blending with 20 to 70 percent AN prills, the amount of liquid carbonaceous fuel (oil plus fatty acid plus fatty acid salt) present in this emulsion generally will be in the range of about from 7 to Zl percent, based on the total emulsion weight. The amount of liquid carbonaceous fuel in this emulsion is higher as the AN prill content of the blend in which it is to be used is higher. In the preferred blend range of 40/50 to 60/4Q emulsion/AN prills, the emulsionls liquid fuel content ranges about from 9 to lS percent by weight, and is no more than about 13 percent in emulsions to be used in bulk products, in which it is beneficial to use no more than about 50 percent prills to facilitate pumping.
The amounts of inorganic oxidizing salt(s) and water present in the aqueous phase of the "~igh 3s oill' emulsion are within the broad ranges specified lZl~Z

for these components in U.S. Patent 4,287,010, i.e., about from 50 to 95 percent oxidizing salt(s) and about from S to 25 percent water, by weight.
However, within these range6, higher water concentrations, i.e., about from 12 to 20 percent, are preferred in this emulsion. The content of inorganic oxidizing salt(s), liquid carbonaceous fuel, and water of ~low oil~ emulsion6 used in the present method and in the pac~aged product of the invention will be as de6cribed in U.S. Patent 4,287,010.
In the preparation of the emul6ifying system according to the in 6itu method de6cribed in the aforementioned U.S. Patent 4,287,010, a fatty acid, e.g., oleic acid, and a ba6e are broug~t together at the same time as an aqueous 601ution of an inorganic oxidizing salt and an oil, whereby a fatty acid salt emulsifying agent form6 in ~itu as a water-in-oil emulsion forms. Pre6ent in the resulting emulsion i6 the fatty acid 6alt, together with the fatty acid (in the oil phase). Base i6 also present, in the aqueous pha6e.
The fatty acid 6alt emulsifying agent u6ed in the preferred embodiment of the present method may be a 6alt of a saturated or mono-, di-, or tri-unsaturated monocarboxylic acid containing at least about 12, and usually no more than about 22, carbon atoms. Examples of 6uch acids are oleic, linoleic, linolenic, stearic, iso6tearic, palmitic, myristic, lauric, and brassidic acids. The free fatty acid present may be selected from thi6 same class of monocarboxylic acids. Oleic and ~tearic acid6 are preferred on the basis of availability. In ~high oilll emulsion6 to be delivered in bulk form, a 3~Z

fatty acid, e.g., oleic acid, which is liquid at the temperature at which the blend is expec~ed to be u6ed 6hould be ~elected. Usually, thi6 will be an unsaturated monocarboxylic acid. The cation portion of the fatty acid salt preferably is an alkali metal (e.g., sodium, potassium, or lithium), ammonium, or mono-, di-, or trialkylammonium ion in which the alkyl group(s) preferably contain 1-3 carbon atoms.
Sodium, potassium, and ammonium oleates are preferred.
As may be seen from Example 6 which follows, the emulsion structure of the "high oil" emulsion of the invention is many times more stable than a comparable emulsion containing a lower emulsifier concentration. To provide tke higher emulsifier concentration in the "high oil'l emulsion, the weight ratio of oil to fatty acid added to form the emulsion should be in the range of about from 1/1 to 3/1. If pre-formed fatty acid salt is u6ed (i.e., added) to form the emulsion, the weight of 'Ifatty acidll in this ratio should be understood to be the weight of fatty acid added plus the weight of fatty acid salt added, and the ratio of fatty acid salt (added) to fatty acid (added), by weight, should be at least about 0.5/1. The base/acid equivalents ratio used to form z5 the llhigh oil'l emulsion by the in situ method should be in the range of about from 0.5/1 to 3/1, preferably about from 1.5/1 to 2/1.
In the present invention, oil6 and aqueous inorganic oxidizing salt 601ution6 known to the explosive emulsion art may be employed, preferably those disclo6ed in the aforementioned U.S. Patent 4,287,010. Most often, the inorganic oxidizin~ salt pre6ent in the emul6ion~s agueou6 pha6e will be an - ammonium, alkali metal, or alkaline earth metal nitrate or perchlorate, preferably ammonium nitrate, ~2~73g~

alone or in combination wi~h. for example, up to 50 percent sodium nitrate (based on the total weight of inorganic oxidizing salts in the aqueous phase).
Salts having monovalent cations are preferred, as explained in U.S. Patent 4,287,010. Suitable oils for use in the liquid carbonaceous fuel include fuel oils and lube oils of heavy aromatic, naphthenic, or paraffinic stock, mineral oil, dewaxed oil, etc.
The "high oil" emulsion of the invention is formed by agitating the aqueous oxidizing salt solution and the oil solution of the fatty acid in the presence of the fatty acid salt under conditions which result in a stable emul6ion of a selected viscosity. In the preferred in 6itu system the base preferably is dis601ved in the aqueous solution, which is agitated with the oil solution of the fatty acid.
This emulsion may be blended with AN prills (or granules) by pumping it into a mixer or into an auger conveying the AN. The latter mode is convenie~t for making a packaged product. The turning of the screw in the auger blends the emulsion and prills as well as transfers the blend into the package. The low viscosity of the emulsion allows the mixing to be done in a shorter auger length with less shear, resulting in improved shelf life over blends made with high shear.
If the blend of "high oil" emulsion and AN
prills i6 to be used in bulk form, e.g., by pumping it from a mixer and into a borehole, perhaps after standing in the mixer for a day or 60, the blend remains in a form suitable for pumping after such time owing to i~s visc06ity stability, as i6 shown in Example 7. The viscosity of a freshly made blend of an emulsion made by the in situ method and containing ~7342 about from 20 to 50 percent AN prills generally is in the range of about from 2500 to 20,000 poise, and the blend maintains a viscosity in this range for a period of several days, sufficient to enable pumping to be undertaken during such time.
The AN with which the l'high oil" emulsion is blended is an oil-deficient product, preferably substantially oil-free AN prills. To produce a blend which is to be pumped, sufficient prills are used to produce a blend having a prill content of about from 20 to 50 percent by weight. Up to 70 percent prills may be u~ed for a packaged product.
The emulsion/prill blend of the invention, whether made with AN or ANF0 prills, is in a sensitized form so that it is detonable by means customarily used to initiate explosives. For this reason the blend contains a fiensitizing amount, e.g., at least about 5 percent by volume, of dispersed gas bubbles or voids (based on blend volume). This void or gas volume can be that of the AN prills ~er se (see Example 5), or gas can be incorporated by adding other air-carrying solid materials, for example, phenol-formaldehyde microballoons, glass microballoons, fly ash, etc. If materials of the latter type are to be present in the blend, they may constitute a component of the emulsion or they may be added at the time of blending. Generally, with blends containing less than about 50 percent AN
prills, provision should be made for the express addition of gas bubbles or voids into the emulsion for the sensitization thereof.
As was mentioned previously, the fatty acid salt emulsifying system i6 the preferred means of providing the structure that minimizes water loss and transport in the method of the invention. This means 34~

i6 u6ed to be6t advantage when the fatty acid 6alt emul6ifying 6y6tem i6 u6ed in conjunction with high oil content, cell 6ize control, and/or AN coating, etc. However, in the pre6ent method the latter technique6 can be used with other emul~ifying ~y6tems.
The pre6ent method is u6ed to advantage in the preparation of blends which contain about from 20 to 70 percent AN particles by weight. The need for a water transport barrier and/or decreased chemical driving force generally is not great with blends containing le~s than about 20 percent AN. The AN
content u6ually will be in the range of about from 30 to 70 percent by weight for a packaged blend, and about from 20 to 50 percent by weight for a pumped blend.
Explosives which are blend6 of a water-in-oil emul6ion and AN or ANF0 prill6 having a phy6ical and chemical 6tructure that minimizes water 1066 and transport from the emul~ionls aqueou6 phase according to the method of the invention, and especially blends of the ~high oil~ emul6ion of the invention and AN prills, are useful in bulk as well as packaged form. The emul6ion/AN blend of the invention made with the low-visco6ity llhigh oil emul~ion, and particularly the preferred ~in 6itu emulsion, i~ especially 6uited for pumping operation~. A preferred technique for pumping the blend into a borehole i6 to pump it through an annular stream of aqueou6 lubricating liquid, e.g., naturally occurring water, flowing through the conduit used to transfer the blend to the ~ole. Such a technique is described in co-pending Canadian Patent Application Serial No. (Applicant's Case No.
PI-n339), filed May 10, 1984, by D. L. Coursen, for pumping a Bingham solid, e.g., a water-in-oil emulsion explosive. By use of a method ~lZ1~3~

and apparatus of the type described in the Coursen application, the resistance of the emulsion/AN blend to movement through a conduit is reduced by provision of an annular layer of liquid of low viscosity, e.g., water, around a central column of the blend in the conduit. An annulus of aqueous lubricating liquid, injected into the conduit through which the emulsion/AN blend is to be delivered to the borehole, provides lubrication sufficient to permit a column of the blend to slide through the conduit without undergoing appreciable deformation in shear, i.e~, movement in "plug flow", a distinct benefit for maintaining the emulsion structure of the blend. An additional benefit of using this apparatus is that it is more effective when used with small amounts of lubricant, which assures better control of the strength and sensitivity of the explosive blend owing to the decreased risk of dilution. A lubricating - liquid flow rate which is no greater than about 5~, and usually no greater than about 0.5-2~, of the emulsion/AN blend flow rate is used.
When the pumping is carried out at temperatures above 0C, water is the preferred lubricating liquid, on the basis of low cost, low viscosity, and immiscibility with the emulsion/AN
blend being pumped. Additives such as ethylene glycol may be added to the water to reduce its freezing point during cold weather. The water need not be of high purity or even potable. Therefore, any naturally occurring water available at the field site of use can generally be used even though such waters, whether from streams, wells, or the sea, invariably contain some dissolved salts.

1 Z1734~

The above-described annular lubricant method can be carried out with intermittent pumping, if desired, even in the case in which water is the lubricating liquid. In contrast to the proce6s described in U.S. Patent 4,259,977 for pumping emulsions, in the present process, in which the material being pumped is an emulsion laden with solid AN, plugging of the delivery conduit does not occur on stoppage of the pumping operation when a water annulus is used. It is believed that the avoidance of the swelling/plugging problem in the annular lubricant pumping method is related to the nature of the continuous phase in the explosive emulsion used in the present blend, and more particularly to the hydrophobicity thereof resulting from the emulsifying agent or system therein. It is possible that the fatty acid salt. and especially the equilibrium structure of the emulsifying system produced when the emulsifying agent is formed in situ, as is described in the aforementioned U.S. Patent 4,287,010, provide a uniquely hydrophobic environment between the lubricating liquid on the outer surface of the emulsion/AN blend and the aqueous phase droplets within the blend, thereby preventing the absorption of the lubricating liquid into the blend despite the presence of a concentration gradient between the lubricating liquid and the aqueous phase droplets.
In any event, a matching of such concentrations is unnecessary with the present blends, and any available water supply can be u6ed to provide the lubricating liquid.
The method, emulsion, and emulsion/AN blends of the invention will now be described by means of illustrative examples.

121~34Z

Example l The rate of absorption of water into samples of four different emulsions was measured as an estimate of the relati~e rates of water transport through these emulsions in emulsion/AN blends. The compositions of the samples are shown in the following table. Samples B, C, and D, which are samples of ~low oil~ emulsions that would be used, for example.
in packaged ANF0 blends of this invention, were prepared by the method described in Example l of U.S.
Patent 4,287,010, with variations in mixer speeds as will be described. The percentages gi~en for oleic acid and ammonium hydroxide represent the proportions used to prepare ammonium oleate in situ. Sample a is a sample of an emulsion of the type described in U.S.
Patent 3,447,978. in which a non-ionic emulsifying agent is present.

~.21734~

Sample a ~ C D
Ammonium Nitrate (dissolved), ~ 75.3 5~.9 72.9 72.9 Sodium Nitrate (dissolved), % - 13.2 - _ Water, % 16.3 5.915.1 15.1 Oil, % 6.0 3.9 3.9 3.9 10 ~leic Acid, % - ~.0 2.0 2.0 Ammonium Ilydroxide. % - 0.5 0.5 0.5 Sorbitan Mono-oleate, % 1.1 Glass Microspheres, % 1.3 Fly Ash, % - 5.6 5.6 5.6 Mole Fraction of Water in Aqueous Phase 0.49 0.49 0.48 0.48 Density, g/cc 1.25 1.30 1.29 1.29 Relative Cell Size: A < D ~ C ~ B
To test the water absorption rate, the samples were loaded into cylindrical pans of 7.5 mm radius and 2.6 mm height. The samples were submerged under 25.4 mm of water. At various time intervals, a sample was removed, excess water blotted off, and the moisture content measured by Karl Fischer analysis.
The results are shown in FIG. 1.
The effect of cell size on the rate of water absorption into the sample is seen by comparing the curves for C and D, which were the same emulsion sheared at different mixer tip speeds to yield different viscosities and cell sizes. The viscosity of C was 1900 poise at 23C, and the viscosity of D

lZ1~34~

4550 poise at 23C, representing the smaller cell size. Because of its smaller cell size, the aqueous phase of D had a higher chemical potential than the aqueous phase of C, resulting in a lower driving force for water transport into the emulsion. After 3 hours, C had gained about 18 percent more water than D.
The effect of the type of emulsifying system on the water absorption rate is more pronounced than the effect of cell size, as can be seen by comparing B, C, or D to A. Although A had the smallest cell size of all the samples (i.e., the least chemical driving force into the emulsion), it gained 49 percent more water than D, apparently because of the poor transport resistance of the continuous phase containing the polar, non-ionic emulsifier.
ExamPle 2 The rate of transfer of water from samples of emulsion a. c. and D, described in Example 1, to ammonium nitrate pellets in surface contact therewith was measured as an estimate of the relative rates of transport of water from the emulsion's discontinuous agueous phase to AN particles in emulsion/AN blends.
In this experiment, in which the Water Diffusion Test described previously was performed, the emulsion samples of Example 1 were contacted on the surface with a cylindrical ammonium nitrate pellet of the same cross-sectional area. The water which diffused from the emulsion into the AN pellet is plotted against time in FIG. 2.
A comparison of samples C and D shows that the smaller cells of D increased the driving force for water transport from the emulsion, sample D, after 43 hours, having lost 66 percent more water than sample C. Moreover, water loss was much higher ~2~734~
2~
in A than in C or D (losing 283 percent more water than C or D after 43 hours) because of the combined hydrophilicity of the continuous emulsion phase and the higher driving force. A high degree of water absorption by the solid AN results in instability of the emulsion/AN blend.
Exam~le 3 An emulsion of the following formulation was made by the method described in Example 1 of U.S.
Patent 4,287,010:
%_ Ammonium Nitrate 60.
(dissolved) Sodium Nitrate 13.5 (dissolved) Water 13.7 Oil 3-9 Oleic Acid 2.0 Sodium Ilydroxide 0.5 Fly Ash 5.6 The percentages given for oleic acid and sodium hydroxide represent the proportions used to make sodium oleate in situ.
Two blends, A and B, were made with this emulsion:
Blend A Blend B
Emulsion, % 50 50 ANFO ~94% AN prills 6% No. 2 Fuel oil), % 50 ANWAX (94% AN prills 6% Paraffin wax), % - 50 A Differential Scanning Calorimeter (DSC) was used to determine the heat released on crystallization of the unblended emulsion, and of the emulsion ~2~73~2 component of each blend on cooling at 5~/min. from ~00K down to 220K. These measurements were made when the samples were fresh and a~ter 35 hour~ of stora~e at 49C. Water transport from the emulsion causes concentration of salts in the dispersed aqueous phase and eventual crystallization of the cells. The relative degrees of crystallization present in each sample before cooling can be estimated by measuring the heat released on complete crystallization of the samples by DSC, higher heat release corresponding to less crystallization before cooling. The results were as follows:
IIeat Released on Total Crvstallization (cal/~
lIours at 49C 0 35 100% Emulsion 20.5 18.8 Blend A 15.4 8. a Blend B 17.5 16.2 The above data show that Blend A (the blend with ANFO) was 53% more crystallized than the 100% emulsion sample after 35 hours at 49C. On the other hand, Blend B (the blend with ANWAX) was only 14% more crystallized, and therefore more stable.
EXam~le 4 Emulsion/ANFO blends of various component ratios were prepared by mixing ANFO with an emulsion of the following formulation, prepared as described in Example 1 of U.S. Patent 4,287,010:
Ammonium Nitrate 60.8 (dissolved), %
Sodium Nitrate 13.6 (dissolved), %

~Z173~

Water, % 13.56 Oil, % 3.84 Oleic Acid, % 1.96 Sodium Ilydroxide, % 0.54 Microspheres, % 5.7 The stabili~y of the blends after aging was determined by detonating them with or without confinement, and measuring their detonation velocities. The results are shown in the following table:
Vel. of Detonation Emulsion ANFO Age at Temp. in 12.7 cm Temp.
(%) (%) (Davs) (C) diam. (m/sec) (C~
gO163 15 2670W 20 15 20 80 76 15 4011~ 20 75163 15 3250~ 20 70163 15 3235~ 20 60163 15 2375~ 20 50132 15 3950~ 20 20 50 sO101 -7 3890~ 5 59 41 40 15 2900~ 20 69 31 40 15 2900~ 20 79 21 40 15 4800~ 20 89 11 40 15 4800~ 20 ~Confined in steel pipe ~Unconfined ExamPle 5 The following "high oilll emulsions (22.5 kg mixes) were prepared in a l9-liter mixer by adding a 50% aqueous solution of sodium hydroxide to an aqueous solution of ammonium nitrate at 77C, and adding the base-containing aqueous nitrate solution 3~ slowly with agitation to a 30C solution of ole'ic ~Z~7342 acid in a 3/1, by weight, mixture of No. 2 fuel oil and Gulf Endurancet No. 9oil. The agitator tip ~peed was 133 cm/6ec during ingredient addition, and 400 cm/sec during a 6ubsequent 5-minute 6hear cycle. The emulsions were then sheared further to reduce the cell size 6ufficiently to produce a vi~c06ity comparable to that achievable by mixing at 600 cm/sec for an additional 2 minute6.
Emulsion No.
A B C D E
Emulsion ComPosition (wt.%) AN 71.4 70.0 68.2 65.3 60.7 water 19.8 19.4 18.9 13.1 16.~
oil 4.6 5.5 6.7 8.6 11.7 oleic acid~ 2.7 3.3 4.0 5.1 7.0 NaOM (50% aq.601n)~ 1.5 1.8 2.2 2.8 3.8 oxYqen Balance -9.3 -14.4 -20~9 -31.2 -48.2 ~Weight added to form oleate emulsifier in 6itu.
Emul6ions A through E (at ambient temperature) were mixed with AN prills to form blends A through E respectively. The mixing wa6 carried out in a cement mixer at medium 6peed for 4 minute6.
Blend No.
A B C D
Blend comPo~ition (wt.~) Emulsion 70 60 SO 40 30 AN Prills 30 40 50 60 70 OxYaen Balance -0.5 -0.6 -0.5 -0.5 -0.5 Blend No. Continued Detonation Velocit~ (m~6ec) A B C D
in 12.7-cm-diam. 6teel pipe 13 days after blending 3408 -- 3401 4130 418 t denotes trade mark A typical emulsion which would be blended in the same manner as emulsions A through E above is formulated from the following ingredients:
oil 6.7%
oleic acid 1.3%
sodium oleate 2.7%
Balance: 80% aq. AN solution ExamPle 6 The importance of higher emulsifier levels in ~Ihigh oil~ emulsions was established by preparing the following emulsions in 700-gram quantities by the procedure described in Example 5 except that shearing at 400 cm/sec was performed for only 1 minute. When necessary, the duration of shearing was varied to give emulsion viscosities of 1000 poise. Emulsion stability was measured by centrifuging the emulsion for 10 minutes at 2500 rpm each day for 3 days, at ambient temperature, and determining the weight loss of the continuous (oil) phase.
Emulsion No.
F G II I J~
Emulsion comPosition (wt.%)~
Oil 7.4 7.4 6.7 6.7 8.4 Oleic acid~ 3.0 3.0 4.0 4.0 2.0 NaOII (50% aq. soln.)~*~ 1.65 3.3 2.2 4.4 1.1 Oil/acid wt. ratio 2.5 2.5 1.7 1.7 4.2 Base/acid equiv. ratio 1.5 3.0 1.5 3.0 1.5 Wt. lo~s of oil Phase (%~ 2 1 0 0 27 ~Emulsion containing prior art emulsifier level ~Balance 80 weight-% AN solution ~Weight added to form oleate emulsifier in situ Example 7 The stability of the viscosity of blends of AN prills with the "high oilll emulsion of the invention, in contrast to blends made with ~high oil~

12~7342 emulsion~ containing non-ionic emul6ifying agents at sufficiently high level~ to pre6erve emul6ion 6tability was demon6trated by measuring the vi6co~itie6 of 6iX emul6ion/prill blend6 ~ontaining 37.6 percent AN prill6 and 62.4 percent emul6ion by weight. Three emulsion~ (K, L, and M~ were according to the invention, and contained different amounts of emulsifying agent all of which were 6ufficient to produce a stable emul6ion. Three emul6ions (N,0, and P) were "high oil" control emul6ion6 (i.e., they contained 6ufficient oil to oxygen-balance the blend with AN prill6) that contained a non-ionic emul6ifier in three different concentration~, only two of which (in emulsion6 0 and P) were 6ufficient to prevent "creaming" of the oil phase.
In the6e emul6ions the agueou6 pha6e was a solution which consi6ted of 69.6% ammonium nitrate, 15.5% ~odium nitra~e (SN), and 14.9% water by weight.
Emul6ions K, L, and M were prepared according to the procedure de6cribed in Example 6 (with the exception that SN was included in the aqueous phase). Emulsions _, 0, and P were prepared by adding 60rbitan monooleate to the oil, and the AN/SN solution to the oil 601ution. In the preparation of all six emulsion6, the extendospheres (fly ash) were added during the addition of the AN/SN 601ution to the oil. Emul6ion vi6co6itie6 were mea6ured with a Brookfield* viscometer at 29C using a 2 rpm Type E
6pindle.
The blend6 were made by mixing the emulsion and AN prills with low 6hear, by hand with a spatula.
The re6ult6 are given in the following ta~le, and plotted in FIG. 3.
* denotes trade m~rk :~2;i~34~

Emulsion No.
K k M N o p Emulsion ComPosition (wt.%) AN/SN Solution ~ 81.8 ~1.882.8 82.8 ~2.~
Oil 7.5 6.75 5.7510.9 lO.O 8.5 Oleic acid~ 4.0 4.75 5.75 NaOH (50% aq.soln.)~ 1.0 1.0 1.0 Sorbitan mono-oleate (SMO) - - -0.6 1.5 3.0 Extendospheres 5.7 5.7 5.7 5.7 5.75.7 Emulsion viscositY
_5~c~ 575 6~ 804 529 6291000 ~Weight added to form oleate emulsifier in situ.
Viscosities were measured (as described for the emulsion except at 25C) on the freshly made blends as well as on two- and six-day-old blends.
Plots of viscosity vs. time for blends K through P
are shown in FIG. 3. ~11 blends had initial 2~ viscosities in the 2000-4000 poise range. EIowever, while blends of the invention, i.e., blends K, L, and M, showed only a modest viscosity rise over a six-day period, reaching viscosities of only about 4500-5000 poise after six days, the control blends 0 and P
showed a rapid rise within only two days. Control blend N, made from emulsion N, which contained an SMO
concentration which was so low as to be insufficient to maintain emulsion stability, exhibited a low rate of viscosity rise over a two-day period, but rose rapidly in viscosity over the next four days. The extremely high viscosities of control blends O and P
after two days rendered the blends essentially unpumpable (specifically, unable to flow by gravity from a tank to the suction of a pump), and indicated a deleterious change in the emulsion structure 12~34~

(crystallization in the aqueous phase) which characteristically compromises the blend's ability to detonate. Conversely, blends K, k, and M showed no visual e~idence of crystalli2ation and were suita~le for pumping.
Exam~le ~
The following experiment shows that even stable emulsion/ANFO blends having minimized water transport according to the method of the invention can be improved by the use of the high-oil hig~-emulsifier emulsion of the invention. Three emulsions, ~, R, and 5, were prepared as described in Example 5 for the preparation of emulsions A through E (except that in emulsions Q and R sodium nitrate was included in the aqueous phase as in Example 7).
Emulsions R and S were the preferred "high oill' emulsions, and emulsion Q was an oxygen-balanced emulsion having a lower oil content and emulsifier content than emulsions R and S. Blends R and S were 50/50 emulsion/AN prills. Emulsion Q was blended in the same ratio with ANEO prills, i.e., AN prills lightly coated with fuel oil in a 94J6 AN/oil weight ratio. Blending was carried out in a cement mixer as described in Example 5. The results were as follows:
Emulsion No.
Q R S
Emulsion ComPosition (wt.%) AN 60.~55.7 67.45 SN 13.612.5 water 13.011.9 14.~
oil 3.~5~.0 7.5 oleic acid~ 1.954.0 3.0 NaOII (50% ag.soln.)~ 1.1 2.2 1.65 Extendospheres 5.75.7 5 7 ~eight added to form oleate emulsifier in situ.

Blend No.
Q R
Blend~Aoe Detonation VelocitY
13 days 3,097 3,097 3,690 39 days~ 1,618 3,306 3,284 ~60 days for Blend S
The detonation velocities (m/sec) were measured on 12.7-cm diameter, unconfined samples initiated wit~ a 0.45-kg booster. Although blend Q
i6 comparable to blends R and S at age 39 days in terms of confined detonation velocity, blends R and S
do not require confinement at this age (nor does blend S require it at age 60 days~ to detonate at acceptable velocities.

Claims (26)

WHAT IS CLAIMED IS:

1. In a method of preparing an explosive composition by combining ammonium nitrate (AN) particles with a water-in-oil emulsion comprising (a) a liquid carbonaceous fuel having components which form a a continuous emulsion phase, (b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within said continuous phase, and (c) an emulsifying agent to form a blend of said particles and said emulsion containing a sensitizing amount of dispersed gas bubbles or voids, the improvement comprising forming said AN particles and the components of said emulsion into a structure that minimizes the loss of water from said droplets and transportation thereof across said continuous oil phase to said AN particles.

2. A method of Claim 1 wherein said blend is formed and thereafter packaged.

3. A method of Claim 1 wherein said structure is formed by combining said AN particles with an emulsion which contains, in its emulsifying system, a salt of a fatty acid, as well as the free fatty acid in solution in an oil, said oil solution forming said continuous emulsion phase, and said fatty acid, said fatty acid salt, and said oil together forming said liquid carbonaceous fuel.

4. A method of Claim 3 wherein said fatty acid is selected from the group consisting of saturated and mono-, di-, and tri-unsaturated monocarboxylic acids containing about from 12 to 22 carbon atoms, and said salt is an alkali metal, ammonium, and/or alkylammonium salt.

5. A method of Claim 4 wherein said structure is formed by combining said AN particles with an emulsion that has been obtained by combining said oil and said aqueous solution with agitation in the presence of said fatty acid and a base so as to form said fatty acid salt emulsifying agent in situ.

6. A method of Claim 4 wherein AN prills are combined with an emulsion which contains liquid carbonaceous fuel in an amount sufficient to essentially oxygen-balance said AN prills and said inorganic oxidizing salt present in said aqueous solution, said AN prills constituting about from 20 to 70 percent by weight of said blend.

7. A method of Claim 6 wherein said structure is formed by combining said AN prills with an emulsion that has been obtained by combining said oil and said aqueous solution with agitation in the presence of a fatty acid and a base so as to form a fatty acid salt emulsifying agent in situ.

8. A method of Claim 7 wherein the amount of liquid carbonaceous fuel in said emulsion is about from 7 to 21 percent, based on the weight of said emulsion.

9. A method of Claim 8 wherein the amounts of fatty acid and base added to form said fatty acid salt in situ are sufficient that the ratio of the amount of oil added to the amount of fatty acid added is in the range of about from 1/1 to 3/1 by weight, and the equivalents ratio of the amount of base added to the amount of fatty acid added is in the range of about from 0.5/1 to 3/1.

10. A method of Claim 9 wherein said fatty acid is oleic acid, and said fatty acid salt is ammonium oleate and/or one or more alkali metal salts of oleic acid.

11. A method of Claim 1 wherein said structure is formed by mixing said particles and said emulsion at a rate and for a time sufficient to produce a cell size of said discontinuous emulsion phase in the range of about from 1 to 4 microns.

12. A method of Claim 1 wherein said structure is formed by coating said AN particles with an agent in which water has a diffusion coefficient at 25°C of less than about 10-5 cm2/sec.

13. An aged, storage-stable explosive product comprising, in a package, a blend of at least about 30 percent by weight of particles of ammonium nitrate (AN) and at least about 30 percent by weight of an emulsion comprising (a) a liquid carbonaceous fuel including an oil solution of a fatty acid, said solution forming a continuous emulsion phase, (b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within the continuous phase, and (c) an emulsifying system including an emulsifying agent comprising (1) an alkali metal, ammonium, or alkylammonium salt of a fatty acid containing about from 12 to 22 carbon atoms, as well as (2) the free fatty acid, said fatty acid, said fatty acid salt, and said oil together forming said liquid carbonaceous fuel, and said blend containing dispersed gas bubbles or voids comprising at least about 5 percent of its volume, said emulsion, when aged at 25°C for 2 days, losing no more than about 4 percent of its original weight when subjected to the Water Diffusion Test.

14. An explosive product of Claim 13 wherein said emulsion has been obtained by combining said aqueous solution and an oil with agitation in the presence of a fatty acid and a base so as to form said fatty acid salt in situ, said emulsifying system also containing base.

15. A water-in-oil emulsion adapted to be blended with ammonium nitrate prills to form an explosive, said emulsion comprising (a) about from 7 to 21 percent by weight of a liquid carbonaceous fuel including an oil solution of a fatty acid, said solution forming a a continuous emulsion phase:
(b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within said continuous phase; and (c) an emulsifying system comprising (1) said fatty acid and (2) a fatty acid salt, said oil, fatty acid, and fatty acid salt together forming said liquid carbonaceous fuel, and the ratio of the amounts of oil and fatty acid added to form said emulsion being in the range of about from 1/1 to 3/1 by weight;
said emulsion having an oxygen balance more negative than about -6 per cent.

16. An emulsion of Claim 15 wherein said emulsifying system is one which forms in situ from a fatty acid and a base as said oil and said aqueous solution are brought together to form said emulsion, the equivalents ratio of the amount of base added to the amount of fatty acid added to form said emulsifying system being about from 0.5/1 to 3/1, said emulsion having a viscosity in the range of about from 500 to 10,000 poise, and being stable in emulsion structure for a period of at least about 3 months.

17. An emulsion of Claim 15 wherein said emulsifying system is formed by adding a fatty acid and a salt of a fatty acid to the other components of the emulsion, said ratio of oil to "fatty acid" being understood to be the ratio of oil to fatty acid plus fatty acid salt added when the emulsion is being made, and the ratio of said fatty acid salt added to fatty acid added being at least about 0.5/1.

18. An emulsion of Claim 15 wherein said fatty acid salt is selected from alkali metal, ammonium, and alkylammonium salts of saturated and mono-, di-, and tri-unsaturated monocarboxylic acids containing about from 12 to 22 carbon atoms.

19. An emulsion of Claim 18 wherein said fatty acid is oleic acid, and said fatty acid salt is ammonium oleate and/or one or more alkali metal salts of oleic acid.

20. An emulsion of Claim 15 containing substantially no dispersed air-carrying solid materials.

21. An explosive product comprising a blend of about from 30 to 80 percent by weight of the emulsion of Claim 15 and about from 70 to 20 percent by weight of ammonium nitrate prills sufficient to essentially oxygen balance said emulsion, said blend containing a sensitizing amount of dispersed gas bubbles or voids.

22. An explosive product comprising a blend of about from 50 to 80 percent by weight of the emulsion of Claim 16 and about from 50 to 20 percent by weight of ammonium nitrate prills sufficient to essentially oxygen balance said emulsion, said blend containing a sensitizing amount of dispersed gas bubbles or voids, having a viscosity in the range of about from 2500 to 20,000 poise, and remaining in said viscosity range for a period of several days.

23. An explosive product of Claim 21 wherein said dispersed gas is the gas present in said ammonium nitrate prills.

24. An explosive product of Claim 21 wherein supplemental air-carrying solid materials are present.

25. A method of delivering the explosive product of Claim 22 to a borehole through a conduit comprising pumping said product to the borehole through an annular stream of aqueous lubricating liquid flowing through the conduit in the same direction as the explosive product, said product being adapted to resume flowing when pumping is resumed after extended periods of rest in said conduit, independently of the composition of said aqueous lubricating liquid.

26. A method of Claim 25 wherein said aqueous lubricating liquid is naturally occurring water.