[0001] The present invention relates to explosive compositions comprising a sensitized blend
of a water-in-oil emulsion and solid particulate ammonium nitrate (AN). e.g.. AN prills
or granules which may be coated with fuel oil (ANFO), and more particularly to such
compositions in the form of storage-stable packaged products and bulk products adapted
to be pumped into boreholes. The invention also relates to a low-viscosity emulsion
particularly adapted to be blended with fuel-free or -deficient AN to form such a
blend.
[0002] Explosives which comprise a blend of a water-in-oil emulsion and solid particulate
AN (e.g., ANFO) have captured the interest of blasters in recent years owing to the
fact that they are able to offer the advantages of high bulk density, blasting energy,
and water resistance characteristic of emulsion explosives, while at the same time
resulting in cost reductions owing to the lower cost of the AN. Among the problems
that may be encountered in connection with the use of these blends, however, are those
of blend pumpability and blend stability, more particularly of the stability of the
blend's explosive properties. Some blends are not pumpable. or only difficultly pumpable.
Some must be pumped 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 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 short time.
[0003] 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.
[0004] 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
ANFO (to be blended with an oxygen-balanced emulsion), or fuel-deficient or fuel-free
solid AN (to be blended with an emulsion that contains most or all of the oil required
to oxygen-balance the blend).
[0005] In U.S. Patent 4,181,546, Clay describes 40/60 to 60/40 emulsion/AN blends having
completely filled interstices in and between the AN particles. This product is said
to contain too high a proportion of dry ingredient to be pumpable in conventional
slurry pumps, but is said to be deliverable to a borehole by an auger in the same
manner as dry ANFO. This patent advises minimizing the amount of emulsifier, and using
high shear mixing, to insure a stable emulsion. Clay describes sorbitan fatty acid
esters as being particularly suitable emulsifiers, and "Glycomul 0" (sorbitan monooleate)
as superior to most for his invention.
[0006] Butterworth describes 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 address themselves to such matters
as blend stability, i.e., the condition of the blend after it has been allowed to
stand for several days or weeks before or after packaging, or before delivery in bulk
form to a borehole.
[0007] The emulsion portion of Binet et al.'s explosive composition is termed a "microemulsion",
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 per se, described as a "liqui-liquid foam" 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 doping with further
fuel and energy-enhancing ingredients. The patentees discuss a destabilizing seeding
crystal effect in prior art emulsion explosives resulting from the presence of solid
oxidizer salts in the basic emulsion. According to Binet et al., their findings show
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 50°C followed by 2-3 days
at -17°C.
[0008] Binet et al.'s consideration of storage stability 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 is 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.
[0009] AN/emulsion blends having good storage stability, and a method of making such blends
which does not require 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 as detonable after having
been delivered into a borehole in packaged form after a period of about three months
or more from the time the blends were made.
SUMMARY OF THE INVENTION
[0010] 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 droplets 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 ammonium 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
is stored for 48 hours in dry air at 25°C, after which time the emulsion is analyzed
for water loss.
[0011] In a preferred method of the invention the described structure that hinders water
loss 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 tri-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 liquid
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 salt have been combined to form the emulsion.
With this emulsifying system a base, e. g., hydroxide, is present in the emulsion's
aqueous phase.
[0012] An alternative, or preferably supplemental, way of forming the structure that controls
water transport between the aqueous 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 c
m2/sec.
[0013] 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 3
0 percent by weight of particles of AN, e.g., ANFO 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 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 a salt, preferably
an alkali metal, ammonium, or alkylammonium salt, of a fatty acid (preferably selected
from the group consisting of saturated and mono-, di-, and tri-unsaturated monocarboxylic
acids containing about from 12 to 22 carbon atoms), as well as the free fatty acid,
the fatty acid and fatty acid salt, together with said oil, forming said liquid carbonaceous
fuel, said blend containing a sensitizing 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 lost from the aqueous solution droplets
in the emulsion when aged at 25°C 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.
[0014] The term "aged" is used herein to distinguish the packaged product of the invention
from products which are made at the site of use and delivered into a borehole in bulk
form. An "aged" product denotes herein a product which is packaged and transported
to the field site at some later date. usually at least several days, and often weeks,
after the time of manufacture.
[0015] 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 denotes
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 "ANFO", in which
the usual AN/FO weight ratio is about 94/6, and/or coated according to the method
of the invention, as will be described hereinafter.
[0016] 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 the 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 1/1 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.
[0017] 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.
[0018] In the emulsion product made by adding a pre-formed fatty acid salt to the system,
the "fatty 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.
[0019] The amount of inorganic oxidizing salt (the oxidizer) present in the emulsion of
the invention is insufficient for the complete combustion of the fuel therein, as
is evidenced by the emulsion's negative oxygen balance. This oxidizer-deficient emulsion
is converted into a product having a more positive oxygen balance and satisfactory
explosive properties by blending with fuel-deficient or, preferably, substantially
fuel-free AN prills. By virtue of its relatively low viscosity, the oxidizer-deficient
emulsion can be blended with these AN prills with low shear so as to produce a preferred
explosive emulsion/AN blend of the invention containing about from 20 to 70 percent
by weight 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
[0020] 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 DESCRIPTION
[0021] The present invention is based on the discovery that the transport of water from
the dispersed aqueous phase of the emulsion to the AN 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 of water
results in an increase in the water content of the particulate AN, perhaps to a level
of about 5 to 10 percent, and an increase in the salt 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.
[0022] In the method of the invention, the AN particles and the components of the emulsion,
by virtue of their chemical composition and physical properties (e.g., size and spatial
relationships), 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 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 presence of a fatty acid and a base, according
to the method described in U.S. Patent 4,287,010 (Owen). It has been suggested 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.
[0023] 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 12 to
22 carbon atoms), most preferably sodium, potassium, and/or ammonium oleate, according
to techniques described in the aforementioned Owen patent.
[0024] 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. suggest that stability is 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 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.
[0025] The above-described control of the emulsifying 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 25°C of less than about -5
10 . and preferably less than about 10
-8, cm
2/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 (FO) normally used in ANFO for
example. Examples of such materials are solid or semi-solid hydrocarbons including
paraffin wax and petrolatum-rosin-paraffin.
[0026] 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 salt solution of the emulsion and
the AN particles. A reduced chemical driving force minimizes the rate of 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 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 the stability of emulsion explosives
per 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 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.
[0027] Other factors also can be controlled to minimize water transport across the emulsion's
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 preferably substantially all, of the oil required to
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 ANFO 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 aqueous solution droplets, thereby giving water
transport a "head start". With the "high oil" 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.
[0028] As has been stated above, increasing the oil content of the emulsion so as to increase
the dimensional thickness of the emulsion's 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 the separation
or "creaming" of the oil.
[0029] 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 phase, can be achieved if the concentration of the emulsifying agent is
higher than that used in standard "low oil" emulsions, i.e., essentially oxygen-balanced
emulsions which are to be blended with ANFO. If the emulsifying agent is a salt 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.
[0030] 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 containing an emulsifying agent in a concentration that is sufficiently
high to preserve the emulsion structure are unstable with respect to viscosity levels
when the emulsifying agent is sorbitan monooleate. In the latter case, despite the
lower viscosity of the "high oil" 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 no longer pumpable and subsequently not detonable. This level may be reached within
a day or two. Accordingly, viscosity stability is not a characteristic of "high oil"
emulsion/AN blends in general, but is dependent upon the nature of the emulsifying
system present in the "high oil" emulsion.
[0031] Other benefits of forming blends of the "high 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.
[0032] 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 21 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 40/60
to 60/40 emulsion/AN prills, the emulsion's liquid fuel content ranges about from
9 to 15 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.
[0033] The amounts of inorganic oxidizing salt(s) and water present in the aqueous phase
of the "high oil" emulsion are within the broad ranges specified for these components
in U.S. Patent 4,287,010, i.e., about from 50 to 95 percent oxidizing salt(s) and
about from 5 to 25 percent water, by weight. However, within these ranges, 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" emulsions used in the present method and in the packaged product of the
invention will be as described in U.S. Patent 4,287,010.
[0034] In the preparation of the emulsifying system according to the in situ method described
in the aforementioned U.S. Patent 4,287,010, the disclosure of which is incorporated
herein by reference, a fatty acid, e.g., oleic acid, and a base are brought together
at the same time as an aqueous solution of an inorganic oxidizing salt and an oil,
whereby a fatty acid salt emulsifying agent forms in situ as a water-in-oil emulsion
forms. Present in the resulting emulsion is the fatty acid salt, together with the
fatty acid (in the oil phase). Base is also present, in the aqueous phase.
[0035] The fatty acid salt emulsifying agent used in the preferred embodiment of the present
method may be a salt 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 such acids are oleic, linoleic, linolenic. stearic, isostearic, palmitic.
myristic, lauric, and brassidic acids. The free fatty acid present may be selected
from this same class of monocarboxylic acids. Oleic and stearic acids are preferred
on the basis of availability. In "high oil" emulsions to be delivered in bulk form,
a fatty acid, e.g., oleic acid, which is liquid at the temperature at which the blend
is expected to be used should be selected. Usually, this 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.
[0036] 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 the higher emulsifier concentration
in the "high oil" 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 used (i.e., added) to form the emulsion, the weight of "fatty acid" 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 the "high oil" 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.
[0037] In the present invention, oils and aqueous inorganic oxidizing salt solutions known
to the explosive emulsion art may be employed, preferably those disclosed in the aforementioned
U.S. Patent 4.287.010. Most often, the inorganic oxidizing salt present in the emulsion's
aqueous phase will be an ammonium, alkali metal, or alkaline earth metal nitrate or
perchlorate, preferably ammonium nitrate, alone or in combination with, 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.
[0038] 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 emulsion of a selected viscosity.
In the preferred in situ system the base preferably is dissolved in the aqueous solution,
which is agitated with the oil solution of the fatty acid.
[0039] 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 convenient 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.
[0040] If the blend of "high oil" emulsion and AN prills is 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 so, the blend remains in a form suitable for pumping after such time
owing to its viscosity stability, as is shown in Example 7. The viscosity of a freshly
made blend of an emulsion made by the in situ method and containing 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.
[0041] The AN with which the "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 used for a packaged product.
[0042] The emulsion/prill blend of the invention, whether made with AN or ANFO 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 sensitizing 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 per 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.
[0043] As was mentioned previously, the fatty acid salt emulsifying system is the preferred
means of providing the structure that minimizes water loss and transport in the method
of the invention. This means is used to best advantage when the fatty acid salt emulsifying
system is used in conjunction with high oil content, cell size control, and/or AN
coating. etc. However, in the present method the latter techniques can be used with
other emulsifying systems.
[0044] The present method is used 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 less than about 20 percent AN. The AN content usually 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.
[0045] Explosives which are blends of a water-in-oil emulsion and AN or ANFO prills having
a physical and chemical structure that minimizes water loss and transport from the
emulsion's aqueous phase according to the method of the invention, and especially
blends of the "high oil" emulsion of the invention and AN prills, are useful in bulk
as well as packaged form. The emulsion/AN blend of the invention made with the low-viscosity
"high oil" emulsion, and particularly the preferred "in situ" emulsion, is especially
suited for pumping operations. A preferred technique for pumping the blend into a
borehole is to pump it through an annular stream of aqueous lubricating liquid, e.g..
naturally occurring water, flowing through the conduit used to transfer the blend
to the hole. Such a technique is described in European Patent Application No. 83 302
563.8 by D.L. Coursen, for pumping a Bingham solid, e.g., a water-in-oil emulsion
explosive. By use of a method and apparatus of the type described in the Coursen application,
the disclosure of which is incorporated herein by reference, 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.
[0046] When the pumping is carried out at temperatures above 0°C, 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.
[0047] 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 process 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 used to provide the lubricating liquid.
[0048] The method, emulsion, and emulsion/AN blends of the invention will now be described
by means of illustrative examples.
Example 1
[0049] The rate of absorption of water into samples of four different emulsions was measured
as an estimate of the relative 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 ANFO blends of this invention, were prepared by the method
described in Example 1 of U.S. Patent 4,287,010, with variations in mixer speeds as
will be described. The percentages given 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.

[0050] 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.
[0051] 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 23°C, and the viscosity of D 4550 poise at 23°C, 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.
[0052] 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
[0053] 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
aqueous 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.
[0054] 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 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.
Example 3
[0055] An emulsion of the following formulation was made by the method described in Example
1 of U.S. Patent 4,287,010:

[0056] The percentages given for oleic acid and sodium hydroxide represent the proportions
used to make sodium oleate in situ.
[0057] Two blends, A and B, were made with this emulsion:

[0058] A Differential Scanning Calorimeter (DSC) was used to determine the heat released
on crystallization of the unblended emulsion, and of the emulsion component of each
blend on cooling at 5°K/min. from 300°K down to 220°K. These measurements were made
when the samples were fresh and after 35 hours of storage at 49°C. 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:
Heat Released on Total Crystallization (cal/q)

[0059] The above data show that Blend A (the blend with ANFO) was 53% more crystallized
than the 100% emulsion sample after 35 hours at 49°C. On the other hand, Blend B (the
blend with ANWAX) was only 14% more crystallized, and therefore more stable.
Example 4
[0060] 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:

[0061] The stability 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:

Example 5
[0062] The following "high oil" emulsions (22.5 kg mixes) were prepared in a 19-liter mixer
by adding a 50% aqueous solution of sodium hydroxide to an aqueous solution of ammonium
nitrate at 77°C, and adding the base-containing aqueous nitrate solution slowly with
agitation to a 30°C solution of oleic acid in a 3/1, by weight, mixture of No. 2 fuel
oil and Gulf Endurance No. 9 oil. The agitator tip speed was 133 cm/sec during ingredient
addition, and 400 cm/sec during a subsequent 5-minute shear cycle. The emulsions were
then sheared further to reduce the cell size sufficiently to produce a viscosity comparable
to that achievable by mixing at 600 cm/sec for an additional 2 minutes.

[0063] Emulsions A through E (at ambient temperature) were mixed with AN prills to form
blends A through E respectively. The mixing was carried out in a cement mixer at medium
speed for 4 minutes.

[0064] A typical emulsion which would be blended in the same manner as emulsions A through
E above is formulated from the following ingredients:

Example 6
[0065] The importance of higher emulsifier levels in "high 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.

Example 7
[0066] The stability of the viscosity of blends of AN prills with the "high oil" emulsion
of the invention, in contrast to blends made with "high oil" emulsions containing
non-ionic emulsifying agents at sufficiently high levels to preserve emulsion stability
was demonstrated by measuring the viscosities of six emulsion/prill blends containing
37.6 percent AN prills and 62.4 percent emulsion by weight. Three emulsions (K, L,
and M) were according to the invention, and contained different amounts of emulsifying
agent all of which were sufficient to produce a stable emulsion. Three emulsions (N,O,
and P) were "high oil" control emulsions (i.e., they contained sufficient oil to oxygen-balance
the blend with AN prills) that contained a non-ionic emulsifier in three different
concentrations, only two of which (in emulsions 0 and P) were sufficient to prevent
"creaming" of the oil phase.
[0067] In these emulsions the aqueous phase was a solution which consisted of 69.6% ammonium
nitrate, 15.5% sodium nitrate (SN), and 14.9% water by weight. Emulsions K, L, and
M were prepared according to the procedure described in Example 6 (with the exception
that SN was included in the aqueous phase). Emulsions N, O, and P were prepared by
adding sorbitan monooleate to the oil, and the AN/SN solution to the oil solution.
In the preparation of all six emulsions, the extendospheres (fly ash) were added during
the addition of the AN/SN solution to the oil. Emulsion viscosities were measured
with a Brookfield viscometer at 29°C using a 2 rpm Type E spindle.
[0068] The blends were made by mixing the emulsion and AN prills with low shear, by hand
with a spatula.
[0069] The results are given in the following table, and plotted in FIG. 3.
Emulsion No.
[0070]

[0071] Viscosities were measured (as described for the emulsion except at 25°C) 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. All blends had initial viscosities in
the 2000-4000 poise range. However, 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
0 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 (crystallization in the aqueous phase) which characteristically
compromises the blend's ability to detonate. Conversely, blends K, L, and M showed
no visual evidence of crystallization and were suitable for pumping.
Example 8
[0072] 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 high-emulsifier emulsion of the invention. Three emulsions. Q, R,
and Q, 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 oil" 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 ANFO prills, i.e., AN prills lightly coated with
fuel oil in a 94/6 AN/oil weight ratio. Blending was carried out in a cement mixer
as described in Example 5. The results were as follows:

[0073] The detonation velocities (m/sec) were measured on 12.7-cm diameter, unconfined samples
initiated with a 0.45-kg booster. Although blend Q is 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.
1. 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, said AN particles and the components of said emulsion being formed
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 or Claim 2 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 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 cm 2 /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 described herein.
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.