Note: Descriptions are shown in the official language in which they were submitted.
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AMINE REACTED ALPHA, BETA-UNSATURATED CARBONYL
COMPOUND THICKENED EXPLOSIVE EMULSIONS
The present invention relates to emulsion explosives and, in particular, to
emulsion
explosives with desirable rheology characteristics. The present invention also
relates to
methods for producing such emulsion explosives, to their use and to methods of
blasting
that utilise them.
BACKGROUND TO THE INVENTION
Emulsion explosives are widely used in the explosives industry. They include
an aqueous
oxidizer phase dispersed in a fuel phase, or vice versa. A desirable property
of emulsion
explosives is that they are of low viscosity during processing and handling
but of high
viscosity in packaged cartridges or as a bulk product following loading into a
borehole.
This combination of viscosity properties facilitates efficient processing and
provides
excellent properties in the field. During processing low viscosities ease
pumping, improve
the flow of emulsion in pipes and hoses, and minimise adhesion to the walls of
tanks and
conduits of manufacturing systems. Higher viscosities in packaged products
permit good
tamping and allow cartridges to be cut cleanly. In bulk explosives high
viscosities
improve retention in boreholes inclined upwardly and prevent loss of product
in cracked
ground and in joints. The provision of a highly viscous bulk explosive with
enhanced
dimensional stability is particularly advantageous. Enhanced dimensional
stability lessens
stress on detonator leads when loading deep boreholes. It also reduces the
likelihood of
borehole collapse in soft ground, for example, in tar sands or coal.
The addition of natural wax such as bees wax, petroleum based waxes, polymeric
waxes or
polymeric resins to emulsion explosives in order to control emulsion rheology
is well
known. However, the use of such waxes and resins has a number of drawbacks.
For
example, during production of the emulsion explosive it is necessary to melt
the wax or
resin into the fuel phase of the emulsion. Accordingly, the rheology of an
emulsion
explosive that contains wax or resin is temperature dependent in accordance
with the
physical properties of the wax or resin. This can have practical implications
and
constraints on the use of such emulsions. In cold conditions the emulsion may
be too
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viscous to be pumpable. In hot conditions the emulsion may not be viscous
enough for the
intended use, such as in inclined or vertical boreholes where product
retention is required.
The present invention seeks to provide an alternative to the presently
available emulsion
explosives thickened using waxes and resins that does not suffer the practical
drawbacks
discussed above or, at least, a useful alternative thereto.
SUMMARY
Certain exemplary embodiments provide a method of producing a thickened
emulsion explosive,
which method comprises reacting in an emulsion explosive an amine compound and
an a,13-
unsaturated carbonyl compound such that thickening of the emulsion explosive
occurs, wherein
the a,13-unsaturated carbonyl compound is selected from aldehydes, ketones and
acrylates.
Certain exemplary embodiments further provide a thickened emulsion explosive
containing a
thickening agent comprising a reaction product of an amine compound and an
a,f3-unsaturated
carbonyl compound, wherein the a,13-unsaturated carbonyl compound is selected
from aldehydes,
ketones and acrylates.
Certain exemplary embodiments further provide a method of loading a borehole
with a bulk
thickened emulsion explosive, which method comprises: introducing an emulsion
explosive into
the borehole; and reacting in the borehole an amine compound and an a,13-
unsaturated carbonyl
compound in the emulsion explosive such that thickening of the emulsion
explosive occurs,
wherein the u,13-unsaturated carbonyl compound is selected from aldehydes,
ketones and
acrylates.
Certain exemplary embodiments further provide a method of producing a packaged
emulsion
explosive comprising: reacting in an emulsion explosive an amine compound and
an
unsaturated carbonyl compound such that thickening of the emulsion explosive
occurs; and
packaging the emulsion explosive, wherein the a43-unsaturated carbonyl
compound is selected
from aldehydes, ketones and acrylates.
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Accordingly, in a first aspect of the present invention there is provided a
method of producing a
thickened emulsion explosive, which method comprises reacting in an emulsion
explosive an
amine compound and an cl,13-unsaturated carbonyl compound such that thickening
of the
emulsion explosive occurs. The invention further provides a thickened emulsion
explosive
produced in accordance with this method.
In accordance with this aspect of the present invention it has been found that
certain amine and
a43-unsaturated carbonyl compounds can be reacted within a pre-formulated
emulsion explosive
in order to provide a rheological change, namely thickening, of the emulsion
explosive. As will
be explained in more detail below this rheological change has significant and
advantageous
practical implications with respect to the use of the emulsion explosive.
In accordance with the first aspect of the invention there is also provided a
thickened emulsion
explosive produced by the method of the present invention, i.e. containing a
thickening agent
comprising the reaction product of an amine compound and an a,13-unsaturated
carbonyl
compound.
Also provided is a method of loading a borehole with a thickened emulsion
explosive which
comprises introducing an emulsion explosive into the borehole and reacting (in
the borehole) an
amine compound and an a,13-unsaturated carbonyl compound in the emulsion
explosive such that
thickening of the emulsion explosive occurs.
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In accordance with the first aspect, further provided is a method of producing
a packaged
emulsion explosive, which method comprising reacting in an emulsion explosive
an amine
compound and an a,13-unsaturated carbonyl compound such that thickening of the
emulsion explosive occurs, and packaging the emulsion explosive.
In a second aspect of the present invention there is provided a method of
producing a
thickened emulsion explosive, which method comprises forming an emulsion
explosive by
mixing an aqueous oxidizer phase, a fuel phase and an amine compound and
reacting in
the emulsion explosive the amine compound and an 0-unsaturated carbonyl
compound
such that thickening of the emulsion explosive occurs. The amine compound and
the a,13-
unsaturated carbonyl compound are contacted and reacted whilst the emulsion
explosive is
being mixed in order to form a thickened emulsion explosive. In accordance
with this
aspect of the invention it has been found that certain amine compounds
function as an
emulsifier (and as a thickening agent in combination with certain 0-
unsaturated carbonyl
compounds), thereby removing the need to use a separate (conventional)
emulsifier. The
invention also provides a thickened emulsion explosive produced in accordance
with this
method.
Also provided is a method of loading a borehole with a thickened emulsion
explosive
which comprises forming an emulsion explosive by mixing an aqueous oxidizer
phase, a
fuel phase and an amine compound, introducing the emulsion explosive into the
borehole
and reacting (in the borehole) the amine compound and an a,3-unsaturated
carbonyl
compound emulsion such that thickening of the emulsion explosive occurs.
Another related aspect provides is a method of producing a packaged emulsion
explosive,
which method comprises forming an emulsion explosive by mixing an aqueous
oxidizer
phase, a fuel phase and an amine compound, reacting the amine compound and an
unsaturated carbonyl compound in the emulsion explosive such that thickening
of the
emulsion explosive occurs, and packaging the resultant emulsion explosive.
Further aspects of the invention provide a use in a blasting operation of a
thickened
emulsion explosive, and a method of blasting which comprises loading a
borehole with a
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thickened emulsion explosive in accordance with the invention, and detonating
the
thickened emulsion explosive.
BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments of the invention are described herein, by way of example
only, with
reference to the following drawings in which:
Figure 1 is a schematic illustrating implementation of an embodiment of the
present
invention;
Figure 2 is a schematic of a process for producing a packaged thickened
emulsion
explosive;
Figure 3 is a process flow diagram of a plant for producing a packaged
thickened emulsion
explosive;
Figure 4 is a graph of the compression test results for Example 4;
Figure 5 is a graph of the compression test results for Example 4;
Figure 6 is a graph of the compression test results for Example 4;
Figure 7 is a graph of the compression test results for Example 12;
Figure 8 is a graph of the compression test results for Example 12; and
Figure 9 is a graph of the compression test results for Example 12.
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DETAILED DESCRIPTION OF THE INVENTION
The first aspect of the present invention is based on the selection of
suitable amine and
a,13-unsaturated carbonyl compounds that will react with each other in an
emulsion
explosive to provide a desirable rheological effect, namely thickening of the
emulsion
explosive. The first aspect requires incorporation of appropriate amine and
a,r3-
unsaturated carbonyl compounds into the emulsion explosive in a suitable
manner and in
sufficient amounts to achieve a desired thickening of the emulsion explosive.
The degree of thickening that is achieved will depend upon a variety of
factors including
the selection of the a,-unsaturated carbonyl compound and the amine compound,
the
relative proportions of the a43-unsaturated carbonyl compound and the amine
compound to
each other and to the other components of the emulsion explosive, and the
extent to which
the amine and a43-unsaturated carbonyl compounds are dispersed in the emulsion
explosive. These parameters may be varied in order to control the degree of
rheological
change that takes place in accordance with this aspect of the present
invention.
Without wishing to be bound by theory, it is believed that the amine compound
and the
a,13-unsaturated carbonyl compound react within the body of the emulsion
explosive by a
Michael-type addition reaction resulting in the formation of a crosslinked
polymeric
network within the emulsion explosive. It is this crosslinked network that is
believed to
result in thickening of the (base) emulsion explosive. This may be because the
network in
some way binds or interacts with molecules of the fuel phase within the
emulsion
explosive thereby limiting mobility of such molecules. The extent to which
this network
forms will influence the extent to which the emulsion explosive is thickened.
At one
extreme the formation of the crosslinked network may be extensive enough to
result in a
continuous network extending through the emulsion explosive. In all aspects of
the present
invention, thickening includes polymerization.
The amine and a,3-unsaturated carbonyl compounds, and the amounts thereof, are
selected
on the basis of suitably reactive combinations. Thus, in the amounts used the
amine and
a,f3-unsaturated carbonyl compounds should react with each other at an
appropriate rate at
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the prevailing processing temperature. As will be apparent from following
discussion, in
embodiments of the first aspect of the invention it may be required for the
thickening
effect to take place very rapidly, even instantaneously, when the amine and
a,13-
unsaturated carbonyl compounds are contacted and react with each other. In
other
embodiments slower reaction of these compounds to achieve thickening may be
tolerated.
It is desirable for the reaction between the 4-unsaturated carbonyl compound
and the
amine compound to produce little to no exotherm, since significant temperature
increases
in the emulsion explosive are to be avoided, even if only localised in nature.
In addition,
the compounds selected should not destabilise or have a detrimental effect
upon the
properties of the emulsion explosive. In particular, the reaction of the amine
and 4-
unsaturated carbonyl compounds should not devalue the detonability or basic
explosive
energy of the emulsion explosive. In practice, suitable amine and a,13-
unsaturated
carbonyl compounds and the optimum amounts to be used may be determined
experimentally.
In principle, any amine compound and a,r3-unsaturated carbonyl compound that
undergo a
Michael-type addition reaction and that cause thickening of an emulsion
explosive may be
used in the present invention. However, there are practical constrains as
noted above and
these must be taken into account when considering compounds to use. The
following
provides a general description of compounds that are likely to be of use.
To be reactive with each other the amine compound and a,13-unsaturated
carbonyl
compound must have suitably available and reactive sites. Generally, each
compound
should have multiple reactive sites so that an extensive crosslinked network
can be
formed. For this reason it may also be preferred for a reactive site of the
amine or a,f3-
unsaturated carbonyl compound to be capable of reacting with more than one
molecule of
the complementary reactant. In that case the number of reactive sites per
molecule of the
respective compound may be reduced whilst retaining high crosslinking ability.
For
example, a lower degree of substitution may be required in an amine compound
substituted with primary amine reactive sites when compared to a compound
having
secondary amine reactive sites due to the increased capacity of a primary
amine to bond
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with an a,13-unsaturated carbonyl compound. Typically, the amine compound will
be a
polyamine having at least two primary amine functionalities that are suitably
reactive
towards the a,13-unsaturated carbonyl compound. The latter may also include
more than
one reactive site viz-a-viz the amine.
Suitably available reactive sites of the compounds are located so that
crosslinking
reactions are not sterically hindered. In this regard, at least one of the
amine or a,13-
unsaturated carbonyl compounds is generally substituted with terminal reactive
sites. For
example, an amine-terminated polymer may be selected as a suitable amine
compound. In
that case, it is likely to be beneficial, with respect to network formation,
that the amine
compound include at least two primary amine groups that are reactive toward
the a,13-
unsaturated carbonyl. Secondary amine functionalities may be present provided
they give
the requisite reactivity.
The amine compound may also include one or more functionalities that render
the amine
moieties more nucleophilic and thus reactive with respect to. the 0-
unsaturated carbonyl
compound. One skilled in the art would be familiar with such functionalities.
Examples of compounds that have been found to be useful in practice of the
first aspect of
the present invention include amine-terminated butadiene-acrylonitrile
copolymers of
formula:
NH2
NH2
in which m is about 10 - 170 and n is about 2 ¨ 60 and such that the
proportion of
acrylonitrile in the copolymer can range from about 10-30%. The amine-
terminated
butadiene-acrylonitrile copolymers found to be useful have molecular weights
of
approximately 4000. Accordingly, in those embodiments m is around 50-70 and n
is
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around 5-25. Such compounds are commercially available, for example Hycar
Reactive
Liquid Polymer ATBN 1300X21.
The a,13-unsaturated carbonyl compound may be an a,13-unsaturated aldehyde or
ketone, or
any other Michael-type acceptor. The general structure of an a,f3-unsaturated
carbonyl
compound is shown below.
Jw
Examples of readily available compounds that have been found to be useful in
practice of
the first aspect of the invention include a,13-unsaturated acrylates, such as
those derived
from epoxidized vegetable oils. Examples of epoxidized vegetable oils include
epoxidized
soya oil, expoxidized castor oil, expoxidized rape-seed oil and epoxidized
linseed oil. The
use of epoxidized soy oil acrylate may be preferred. An example of the
structure of a
typical epoxidized soy oil acrylate is shown below.
OH 0 0
OH 0 OH
OH
0
Lr
Alternatively, the a43-unsaturated acrylates may be derived from mineral oils,
for example,
the a, 13-unsaturated acrylates may be an ethoxylated trimethylopropane
triacrylate in which
the number of ethoxylated groups may be at least three and may be in excess of
20.
In some embodiments it may be desirable to use a polymeric a,13-unsaturated
acrylate.
Suitable polymeric a,f3-unsaturated acrylates may be selected from the group
consisting of
polyisoprene diacrylate, polybutadiene diacrylate, copolymers thereof and
mixtures
thereof
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It is possible to use one or more amine compounds and one or more a,13-
unsaturated
carbonyl compounds in order to achieve the desired effect in accordance with
the first
aspect of the present invention.
In some embodiments of the first aspect of the present invention the amine
compound is an
amine-terminated butadiene-acrylonitrile copolymer of the formula shown below
and the
a,[3-unsaturated carbonyl compound is epoxidized soy oil acrylate of the
formula shown
below. In this embodiment the value of m is approximately 67 and the value of
n is
approximately 8. The formula shown below only illustrates a single reactive
site of the
epoxidized soy oil acrylate. The epoxidized soy oil acrylate may have at least
two reactive
sites and will typically be derived from epoxidized soy oil with an average of
4.1 - 4.6
epoxy rings per triglyceride molecule. Reaction of these compounds is believed
to give a
product in which the amine compound is bonded to at least two, preferably
three or four,
molecules of the acrylate. This is illustrated in the following reaction
scheme in which the
reaction product includes three moieties derived from the acrylate bound to an
amine
molecule.
OH
\
NH2
NH2
INII
0
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I 0
0
OH OH
* \ /
0 _______________ HN
> C In
0
0
CD*
*'HOH
Usually the first aspect of the present invention is implemented by
formulating a modified
emulsion composition comprising the amine compound or a,13-unsaturated
carbonyl
compound, and by introducing into the modified emulsion the complementary
reactant
when thickening is required. Typically, the amine or a,13-unsaturated carbonyl
compound
is blended with the fuel component prior to formation of the emulsion, or it
may be added
externally after the base emulsion explosive has been formed. In the latter
case it is likely
that the reactant compound will migrate to the fuel phase. The base emulsion
may be of
conventional type and may be formulated in conventional manner. The emulsion
may be
an oil-in-water emulsion but the first aspect may have greater applicability
in relation to
water-in-oil emulsions. Generally, the a,-unsaturated carbonyl compound will
be the
reactant that is added to the fuel phase of the emulsion or externally to the
emulsion.
The base emulsion or the modified emulsion may be sensitized using
conventional
methods such as, for example, through the addition of glass or plastic
microspheres. It is
also possible to add substances or mixtures of substances which are oxygen
releasing salts
or which are themselves suitable as explosive materials. In addition, the
thickened
emulsion explosive may be a gassed product and/or the density of the product
may be
varied as appropriate using known techniques. However, the application of
these
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techniques, such as gassing the emulsion explosive, may need to be modified to
ensure that
adequate modification is performed prior to the completion of the thickening
reaction.
For successful implementation of the first aspect of the present invention it
is believed to
be important that the relevant reactant is thoroughly dispersed in the
emulsion explosive
composition prior to addition of the complementary reactant. As amine and a,f3-
unsaturated carbonyl compounds may constitute a relatively small proportions
of the
emulsion explosive composition, effective mixing may be very important to
ensure that the
reaction takes place throughout the composition. The appropriate degree of
mixing may
be achieved through the use of in-line static mixers.
If storage stable, the emulsion explosive composition containing the relevant
reactant may
be prepared and stored, and possibly transported, as necessary prior to use.
If stored it
may be desirable to agitate the emulsion explosive composition thoroughly
prior to use.
Addition of the amine or a,f3-unsaturated carbonyl compound to the base
emulsion
explosive (and thorough blending therewith) preferably does not cause any
significant
viscosity increase in itself. Some viscosity change can be tolerated provided
it does not
make subsequent handling and processing unduly difficult.
The complementary reactant is added to the formulated modified emulsion when
the
thickening effect is required to take place. At that time it is believed to be
important that
the complementary reactant is mixed thoroughly into the modified emulsion so
that
reaction between the amine and a,I3-unsaturated compounds takes place
throughout the
emulsion explosive composition. In this way localised thickening can be
avoided.
In order to enhance the ease with which the complementary reactant is
dispersed in the
modified emulsion it is possible to first dissolve or disperse the reactant
into a solvent
comprising the fuel as the fuel component, or materials compatible with the
fuel
component, for example corn oil. The complementary reactant may be combined
with the
solvent in a 50/50 ratio determined by weight.
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Usually, the ratio by weight of the amine compound to a43-unsaturated carbonyl
compound will be between 10:1 and 1:3, preferably the ratio is around 1:2.
Typically, the
total weight of amine and a,r3-unsaturated carbonyl compounds included or to
be included
in the emulsion explosive composition will be 0.4-2.5% based on the total
weight of the
emulsion explosive composition.
The thickened emulsion explosives in accordance with the first aspect of the
present
invention may be utilised in packaged or bulk explosives suitable for surface
or
underground applications. The thickened emulsion explosive may be prepared by
a
number of different methods, depending upon the ultimate use of the product.
When
preparing packaged product a relatively slow thickening effect may be
tolerated with the
full extent of the rheological change taking place prior to cutting and
packaging.
Alternatively, components may be mixed thoroughly just prior to packaging with
the
thickening effect developing within the packaging.
The thickening reaction will occur at the prevailing temperature used in the
production of
conventional emulsion explosives. In particular, the thickening reaction may
be occur
across a range of temperatures from about 15 C to about 100 C. The rate of
thickening
increases with temperature and at the upper end of the temperature range the
reaction may
be instantaneous. The rate of thickening may also be varied through the
addition of a
polyvalent inorganic salt or polyvalent organic salt. For example, the
addition of calcium
nitrate to the emulsion explosive can increase the rate of thickening.
The degree to which the resulting emulsion explosive is thickened can vary.
Thickening
includes an increase in viscosity and a degree of rheological change up to,
and including,
the formation of a thickened emulsion explosive with a non-fluid, deformable
rheology
such as a stiff gel. Typically, the thickened emulsion explosive composition
has a
viscosity of 40,000 ¨ 1,000,000+ cps, as measured a Brookfield Viscometer
using T bar E
or F. Preferably, it takes the form of a stiff gel. This property in
particular makes the
composition of great utility in bulk applications where up-hole retention is
required.
Embodiments of the thickened emulsion explosive may be thickened to such a
degree that
it may be possible to cut the stiff gel formed and have the cut product retain
its shape.
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Accordingly, it may be possible to further process the composition to form a
granulated
product. It is of course possible to manipulate the final viscosity as might
be required in
the field.
Once the thickening reaction has completed, the resulting degree of
rheological change can
be maintained across a range of temperatures. Thus, it may be possible to
expose the
thickened emulsion explosive to a broad range of temperatures without any
significant
reduction in the viscosity of the thickened emulsion explosive. Thus, the ease
with which
the thickened emulsion explosive may be cut is not usually significantly
affected over such
temperature ranges. Accordingly, the properties of a thickened emulsion
explosive in
accordance with the invention may not be sensitive to temperature
fluctuations.
When the thickened emulsion explosive is used as a bulk product it is
important that the
thickening effect takes place within a borehole that is being loaded rather
than in the
equipment used for formulation and pumping of the bulk product. If thickening
takes
place within this equipment, loading difficulties and fouling may occur.
When using the thickened emulsion explosive as a bulk product it may be
desirable for the
thickening effect to take place very rapidly and preferably instantaneously
when the
respective reactants come into contact with each other within the emulsion
explosive.
Rapid thickening is especially important when loading up-holes or upwardly
included
boreholes where product retention is vital. In such cases, if the thickening
effect
associated with this aspect of the invention is too slow, the bulk product
will not be
retained in place as required.
In this case, one loading hose may be used to deliver emulsion explosive
composition
containing one of the reactants into the borehole with a separate loading hose
delivering
the complementary reactant. Mixing of these individual components as they exit
the
respective loading hoses may be achieved using a suitable mixing nozzle. In
one
embodiment the loading hoses may be arranged in parallel along a common axis.
In a
preferred arrangement one component may be delivered down a loading hose
provided as
a centre-line within another larger diameter hose, i.e. as a concentric
arrangement. In both
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cases a nozzle mixer may be used to thoroughly blend the components as they
exit
respective loading hoses.
A schematic of a preferred loading hose (10) for the production of a thickened
bulk
product is shown in Figure 1. In an embodiment, a modified emulsion which
comprises a
preferred a,13-unsaturated carbonyl compound, epoxidized soy oil acrylate, is
pumped from
bulk emulsion storage tank (11) using a pump (12) and into the loading hose
(10). The
complementary reactant, the amine compound, is centre line injected using pump
(13)
through the complementary reactant line (14) into the loading hose. As
the
complementary reactant is pumped towards the nozzle (15) of the loading hose
(10) it
passes through a water ring injector (16). A static mixer (17) is positioned
at the nozzle
(15) and mixes the modified emulsion and complementary reactant together to
form the
thickened emulsion explosive.
Alternatively, it is possible to produce a packaged thickened emulsion
explosive by
producing the modified emulsion at a bulk emulsion plant and then transporting
the first
component to a packaging facility. The emulsion may be transported to a
packaging
facility (regional packaged plant) where it may be stored in silos. The
product may then
be pumped into the blender where it is sensitized. The sensitized emulsion may
also be
stored in a silo prior to use. At the packaging facility the modified emulsion
and
complementary reactant are combined to form the thickened product.
Alternatively, the
base emulsion may be produced at a bulk emulsion plant, then modified through
the
addition of a reactant at the packaging plant and stored prior to being
combined with the
complementary reactant.
The thickened emulsion explosive may be packaged to the desired diameter after
the
emulsion has thickened. Alternatively, the emulsion explosive composition may
be
packaged as the emulsion thickens. If a significant proportion of any reaction
between the
amine compound and the a43-unsaturated carbonyl compound takes place during
packaging, infrastructure costs may be reduced by removing the need to use the
cooling
bath that is often required for the production of explosive compositions
thickened using
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waxes. However, in embodiments it may be desirable for the majority of the
thickening to
occur after packaging.
In some embodiments, it may be desirable to pump the emulsion explosive
composition to
be packaged into the cartridge production unit using a nozzle similar to the
one described
above for forming a thickened bulk product. Accordingly, it is possible to
prepare the
product so that the reactants come into contact with each other as the product
is being
packaged. Mixing may be achieved using a nozzle mixer at the end of the
emulsion
explosive loading hose. Thus, the components are blended as they exit the
loading hose.
Figure 2 is a schematic of the process used to package the thickened emulsion
explosive in
accordance with the method previously described. In an embodiment, a modified
emulsion which comprises a preferred a,13-unsaturated carbonyl compound,
epoxidized
soy oil acrylate, is pumped from a bulk emulsion storage tank (18) using a
pump (not
shown) and into the emulsion line (20). The complementary reactant, the amine
compound, is centre line injected using pump (21) through the complementary
reactant
line (22) into the emulsion line (20). As the components are pumped through
the emulsion
line (20) into the cartridge production unit (19) they are combined using a
static mixer (23)
to produce the thickened emulsion explosive. The cartridges of the thickened
emulsion
explosive are transported by a conveyor belt (24) to the packaging unit (25).
Figure 3 illustrates a process flow diagram of a packaging plant suitable for
use in
accordance with the method previously described. In an embodiment, a modified
emulsion comprising an ad3-unsaturated carbonyl compound, for example a
epoxidized
soy oil acrylate, is pumped from a production plant transport truck (26) into
a bulk
emulsion storage tank (28) using a pump (27). Bulk sensitizing agents,
including
microballoons, other components, such as ammonium nitrate prills and
granulated
aluminium powder are transferred into respective feed hoppers (29), (30) and
(31). These
additives agents are then fed into a primary hopper (32) via their respective
transport lines
(34), (35) and (36). The first component is also pumped through line (38) into
the primary
hopper (32) using a feed pump (37).
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The modified emulsion and the sensitizing agents are combined using a ribbon
blender
(39) to produce a sensitized emulsion, which is transported from the ribbon
blender (39)
via a line (40) using an unloading pump (41). The sensitized emulsion is
pumped through
a line (42) into the sensitized emulsion storage tank (44). Samples of the
sensitized
emulsion may be collected using a sample port (43). The complementary
reactant, the
amine compound, is unloaded and weighed using scales (45) before being loaded
into the
complementary reactant storage tank (46). When the packaged thickened emulsion
explosive is produced, the sensitized emulsion is pumped into the flow line
(51) using a
feed pump (50). The complementary reactant is pumped through line (47) using
feed
pump (48) before being centre line injected into the flow line (51) using an
injector (49).
The modified emulsion and complementary reactant in the flow line (51) are
then
combined using static mixers (52) to produce the thickened emulsion explosive.
The
thickened emulsion explosive is transported via a line (53) into the packaging
machine
(54). The packaged thickened emulsion explosive is then transported using
conveyor belts
(55) and (56) to the boxing station (57) where it is prepared for
transportation.
The second aspect of the present invention and related embodiments are based
on the
selection of suitable amine compounds that will form an emulsion explosive
when mixed
with the aqueous oxidizer phase and a fuel phase. That is, in certain
embodiments the
amine compound functions as an emulsifier, thereby removing the need to use a
separate
(conventional) emulsifier to form an emulsion of the aqueous and fuel phases.
Furthermore, suitable amine compounds are ones that will react with suitable
a,13-
unsaturated carbonyl compounds to give a desirable rheological effect thereby
producing a
thickened emulsion explosive comprising the aqueous oxidizer phase and the
fuel phase
components. Embodiments in accordance with the second aspect of the invention
require
the addition of appropriate amine compounds to the aqueous oxidizer phase and
a fuel
phase in a suitable manner and in sufficient amounts to achieve the desired
emulsifying
effect to form an emulsion explosive. Furthermore, these embodiments then
require the
addition of an appropriate a,f3-unsaturated carbonyl compounds to the emulsion
explosive
in a suitable manner and in sufficient amounts to achieve a desired thickening
effect by
reaction in the emulsion of the amine compound and a,13-unsaturated carbonyl
compound.
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Thus, the second aspect of the present invention provides a method of forming
an emulsion
explosive followed by thickening of the emulsion explosive.
As discussed in relation to the first aspect of the present invention, the
degree of
thickening that is achieved will depend upon a variety of factors including
the selection of
the a,13-unsaturated carbonyl compound and the amine compound, the relative
proportions
of the a,13-unsaturated carbonyl compound and the amine compound to each other
and to
the other components of the emulsion explosive, and the extent to which the
amine and
a,13-unsaturated carbonyl compounds are dispersed in the aqueous oxidizer
phase and the
fuel phase. These parameters may be varied in order to control the degree of
rheological
change that takes place in accordance with the second aspect of the present
invention.
These parameters will also influence the degree of emulsification that occurs.
In relation to the second aspect, it is believed that the amine compound and
the a,13-
unsaturated carbonyl compound react by a Michael-type addition reaction, as
discussed
above in relation to the first aspect of the present invention, to form a
crosslinked
polymeric network in the finished emulsion explosive. The considerations
relating
selection of the reactants for the first aspect apply equally to embodiments
in accordance
with the second aspect. The same exemplary reactants as the first aspect may
be useful in
the second aspect of the invention.
Without wishing to be bound by theory, it is believed that the formation of a
crosslinked
polymeric network, which results in thickening of the emulsion explosive, also
assists in
achieving stable emulsification. This may be because the network in some way
binds or
interacts with molecules of the fuel phase thereby limiting mobility of such
molecules. The
limited mobility of the fuel phase molecules is believed to assist in
maintaining the
dispersion of the aqueous oxidizer phase and accordingly the formation of an
emulsion.
The amine compound may be used in conjunction with a conventional emulsifier
for
production of the emulsion explosive. However, emulsification will typically
be performed
without conventional emulsifiers.
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In this second aspect of the invention the emulsion explosive may be formed by
(vigorous)
mixing of known fuel phase and oxidiser phase combinations with one or more
appropriate
amine compounds. The emulsion is formed using the amine compound as
emulsifier,
with the complementary reactant, i.e. the a43-unsaturated carbonyl compound,
being
mixed into the emulsion explosive when thickening is required. Addition of the
a,f3-
unsaturated carbonyl compound may also refine the structure of the emulsion
formed
using the amine compound alone. For successful implementation of this second
aspect of
the present invention it is desirable to produce an emulsion using a suitable
amine
compound, the emulsion having the desired structure of the continuous and
discontinuous
phases prior the addition of the complementary reactant. The emulsion formed
using the
amine should be intact when the complementary reactant is added and mixed into
the
emulsion. The stability of the emulsion formed using the amine will therefore
influence
how the second aspect of the invention is implemented.
The bulkiness, molecular weight, degree of branching, number of functional
groups and/or
concentration of the amine compound may influence the viscosity
characteristics of the
emulsion explosive that is formed and its stability. Amine compounds with two
or more
terminal functional groups have been found to be particularly useful as
emulsifiers in
practice of the invention. Useful multi-functional amine compounds are
generally
polymeric with polar, hydrophilic head groups connected to lipophilic
hydrocarbon
segments. These polymeric amine compounds have sufficient conformational
freedom
and flexibility for each amine terminal (head) group to interact with the
aqueous phase of
the emulsion and for the lipophilic segments to interact with the fuel phase.
The effect of
these interactions is to stabilise the droplets of the discontinuous phase in
the continuous
phase and to limit or prevent coalescence of the droplets. For example, amine-
terminated
butadiene-acrylonitrile copolymers, as described above, have been found
useful.
If the molecular weight of the amine compound is too high, the viscosity of
the emulsion
explosive may increase significantly and blending in the a,13-unsaturated
carbonyl and
further processing may become difficult. Thus, the selection of an amine
compound with
relevant functionality and an appropriate molecular weight is particularly
important when
the amine compound is selected to act as an emulsifier.
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The amine compound may be blended with the fuel component prior to formation
of the
emulsion explosive, or it may be added externally after a precursor emulsion
comprising
the aqueous oxidiser and fuel phases has been formed. In the latter case it is
likely that the
amine compound will migrate to the fuel phase. The precursor emulsion may be
an oil-in-
water emulsion, but this aspect of the invention may have greater
applicability in relation
to water-in-oil emulsions.
As in the case of the thickened emulsion explosive of the first aspect, the
thickened
emulsion explosive may be sensitized or gassed using conventional methods.
Substances
or mixtures of substances which are oxygen releasing salts or which are
themselves
suitable as explosive materials may also be added. In addition, the thickened
emulsion
explosive may be a gassed product and/or the density of the product may be
varied as
appropriate using known techniques.
For successful implementation of the second aspect of the present invention it
is believed
to be important that the amine compound is thoroughly dispersed in the
emulsion
explosive prior to addition of the a,13-unsaturated carbonyl compound.
Thorough
dispersion of the amine compound will generally occur during formation of the
emulsion
explosive. The amine and a,13-unsaturated carbonyl compounds may constitute a
relatively
small proportion of the emulsion explosive and effective mixing may be very
important to
ensure that the reaction takes place throughout the explosive. The appropriate
degree of
mixing may be achieved through the use of in-line static mixers. -
The a4-unsaturated carbonyl compound is added to the emulsion when the
thickening
effect is required to take place. At that time it is believed to be important
that the a,13-
unsaturated carbonyl compound is mixed thoroughly into the emulsion so that
reaction
between the amine and a,13-unsaturated compounds takes place throughout the
emulsion.
In this way localised thickening can be avoided.
In order to enhance the ease with which the a4-unsaturated carbonyl compound
is
dispersed in the emulsion explosive it may be desirable to dissolve or
disperse the reactant
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into a suitable solvent, which may comprise the fuel as the fuel component, or
materials
compatible with the fuel component, for example corn oil. The a,-unsaturated
carbonyl
compound may be combined with the solvent in a 50/50 ratio determined by
weight.
The relative proportions of the amine or a,f1-unsaturated carbonyl compounds
are
generally the same as those for the first aspect of the invention. Similarly,
to the first
aspect the total weight of amine and a,[3-unsaturated carbonyl compounds to be
included in
the emulsion explosive composition will be 0.4-2.5% based on the total weight
of the
emulsion explosive composition. Adding the amine compound at a proportion of
around
1% based upon the total weight has been found useful when the amine compound
acts as
the emulsifying agent.
=
The thickened emulsion explosives in accordance with the second aspect may be
utilised
for the same applications as those in accordance with the first aspect. The
thickening
reaction and the resulting thickened emulsion explosive tend to have similar
characteristics
across all aspects of the invention.
A thickened emulsion explosive in accordance with the second aspect of the
invention may
be used as a bulk product. In this case, one loading hose may be used to
deliver a emulsion
explosive formed using the amine compound into the borehole with a separate
loading
hose delivering the a,13-unsaturated carbonyl compound. Mixing of the a,13-
unsaturated
carbonyl compound and the emulsion explosive as they exit the respective
loading hoses
may be achieved using a suitable mixing nozzle. In one embodiment the loading
hoses
may be arranged in parallel along a common axis. In a preferred arrangement
one
component may be delivered down a loading hose provided as a centre-line
within another
larger diameter hose, i.e. as a concentric arrangement. In each case a nozzle
mixer may be
used to thoroughly blend the components as they exit respective loading hoses.
Figure 1 may also be useful in illustrating implementation of the second
aspect of the
invention. In an embodiment, an emulsion explosive which comprises as
emulsifier an
amine compound, an amine-terminated butadiene-acrylonitrile copolymer, is
pumped from
bulk emulsion storage tank (11) using a pump (12) and into the loading hose
(10). While
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in the storage tank (11) the emulsion explosive may be agitated to prevent the
phases from
separating. The complementary reactant, the a43-unsaturated carbonyl compound
(e.g.
epoxidized soy oil acrylate), is centre line injected using pump (13) through
the
complementary reactant line (14) into the loading hose. As the a,f3-
unsaturated carbonyl
compound is pumped towards the nozzle (15) of the loading hose (10) it passes
through a
water ring injector (16). A static mixer (17) is positioned at the nozzle (15)
and mixes the
emulsion explosive and a,13-unsaturated carbonyl compound together to form the
thickened emulsion explosive.
The amine compound used to form the emulsion explosive should result in a
stable (intact)
emulsion. Otherwise, the phases of the emulsion may separate in the borehole.
Once in the
borehole the reactants will react thereby thickening the emulsion explosive.
Thus, in
accordance with this aspect of the invention it is possible to load the
borehole with an
emulsion explosive, which will continue to thicken once it is in the borehole.
Alternatively, it is possible to produce a packaged thickened emulsion
explosive by
producing an emulsion explosive using the amine as emulsifier, which may also
be
sensitized. At the packaging facility the emulsion explosive and a,r3-
unsaturated carbonyl
compound are combined to form a thickened product which is then packaged.
The thickened emulsion explosive may be packaged to the desired diameter after
the
majority of the thickened has occurred. Alternatively, the emulsion explosive
composition
may be packaged as the emulsion thickens. If a significant proportion of any
reaction
between the amine compound and the a,13-unsaturated carbonyl compound takes
place
during packaging, infrastructure costs may be reduced by removing the need to
use a
cooling bath. However, depending upon the relative stability of the emulsion
explosive, in
some embodiments it may be desirable for the majority reaction between the
reactants, and
accordingly the thickening, to occur after packaging.
In some embodiments, it may be desirable to pump the emulsion explosive
composition to
be packaged into the cartridge production unit using a nozzle similar to the
one described
above for forming a thickened bulk product. Accordingly, it is possible to
prepare the
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product so that the reactants come into contact with each other as the product
is being
packaged. Mixing may be achieved using a nozzle mixer at the end of the
emulsion
explosive loading hose. Thus, the components are blended as they exit the
loading hose.
The process illustrated in Figure 2, may be modified to produce a product in
accordance
with the method previously described for the second aspect of the invention.
In such an
embodiment, an emulsion explosive which comprises a preferred amine compound,
an
amine-terminated butadiene-acrylonitrile copolymer, is pumped from a bulk
emulsion
storage tank (18) using a pump (not shown) and into the emulsion line (20)
before
proceeding as described above to product the packaged thickened emulsion
explosive.
Figure 3 illustrates a process flow diagram of a packaging plant which may be
modified so
it is suitable for use in accordance with the method previously described for
the second
aspect of the invention. In such an embodiment, the emulsion explosive may be
produced
onsite rather than at a separate production plant. Accordingly, the production
plant
transport truck (26) would be replaced by amine compound, fuel phase component
and
oxidizer phase component storage tanks and blenders suitable for producing the
emulsion
explosive.
The emulsion explosive may be sensitized in the same manner as described
above.
However, the sensitized emulsion explosive may require agitation in the
sensitized
emulsion storage tank (44) to prevent phase separation. The remainder of the
manufacturing process may be performed as described above in relation to the
aspect
related to the first aspect of the present invention.
In addition to the first and second aspects of the present invention, it may
be possible to
select suitable amine and a,13-unsaturated carbonyl compounds that will form a
thickened
emulsion explosive when these compounds are added to and mixed with an aqueous
oxidizer phase and a fuel phase. In this case the thickened emulsion may be
formed in a
single step by mixing of the various components.
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In a further embodiment, a precursor emulsion may be formed using a
conventional
emulsifier or amine emulsifier as discussed herein. This precursor emulsion
may be formed
by (vigorous) mixing of known fuel phase and oxidiser phase combinations with
the
emulsifier(s). However, the precursor emulsion is not stable until the
addition of and
blending with the reactive amine and a,13-unsaturated carbonyl compounds to
produce a
thickened emulsion explosive.
Thus precursor emulsion may be formed so as to include either the amine
compound or
a,13-unsaturated carbonyl compound, with the complementary reactant, i.e. the
a,13-
unsaturated carbonyl compound or amine, being mixed into the precursor
emulsion when
thickening is required. Formation of the precursor emulsion with the amine
compound or
4-unsaturated carbonyl compound may result in increased emulsion stability.
In this case, the amine or a,13-unsaturated carbonyl compound may be blended
with the
fuel component prior to formation of the precursor emulsion, or it may be
added externally
after the precursor emulsion has been formed. In the latter case it is likely
that the reactant
compound will migrate to the fuel phase. The precursor emulsion may be an oil-
in-water
emulsion, but this aspect of the invention may have greater applicability in
relation to
water-in-oil emulsions. In some embodiments, the a,f3-unsaturated carbonyl
compound
will be the reactant that is added to the fuel phase or externally to the
precursor emulsion,
with the amine being blended into the precursor emulsion subsequently.
As in the case of the thickened emulsion explosive of the first and second
aspects, the
thickened emulsion explosive may be sensitized or gassed using conventional
methods.
For successful implementation of this aspect of the present invention it is
believed to be
important that the relevant reactant is thoroughly dispersed in the precursor
emulsion prior
to addition of the complementary reactant. As in other aspects, the amine and
4-
unsaturated carbonyl compounds may constitute a relatively small proportion of
the
emulsion explosive and effective mixing may be very important to ensure that
the reaction
takes place throughout the explosive.
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The addition of the amine or a,-unsaturated carbonyl compound to the relevant
component of the precursor emulsion, or the precursor emulsion itself, (and
thorough
blending therewith) preferably does not cause any significant viscosity
increase in itself.
Any viscosity change should not make subsequent handling and processing unduly
difficult.
The complementary reactant is added to precursor emulsion the when the
emulsifying and
thickening effects are required to take place. At that time it is believed to
be important
that the complementary reactant is mixed thoroughly into the precursor
emulsion so that
reaction between the amine and u43-unsaturated compounds takes place
throughout the
precursor emulsion. In this way localised thickening and/or emulsification can
be avoided.
In these alternative embodiments the relative and gross proportions of the
amine or
unsaturated carbonyl compounds are generally the same as those for the first
aspect of the
invention.
The thickened emulsion explosives in accordance with these alternative
embodiments may
be utilised for the same applications as those in accordance with the first
and second
aspects. The thickening reaction and the resulting thickened emulsion
explosive tend to
have similar characteristics across all aspects of the invention.
Thus, a thickened emulsion explosive in accordance with these alternative
embodiments
may be used as a bulk product. In this case, one loading hose may be used to
deliver a
emulsion explosive containing the amine compound into the borehole with a
separate
loading hose delivering the a,13-unsaturated carbonyl compound. Alternatively,
the fuel
phase component and the relevant reactant may be delivered using one hose and
the
aqueous oxidizer phase and the complementary component may be delivered in the
other.
Mixing of these individual components as they exit the respective loading
hoses may be
achieved using a suitable mixing nozzle. In one embodiment the loading hoses
may be
arranged in parallel along a common axis or, preferably, a concentric
arrangement.
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Depending upon the relative stability of the precursor emulsion, it may be
desirable for the
amine and a,13-unsaturated carbonyl compounds to react such that
emulsification of the
precursor emulsion occurs during mixing and as it is being pumped into the
borehole.
Otherwise, the phases of the precursor emulsion may separate in the borehole.
Ideally, the
precursor emulsion will be emulsified to form an emulsion explosive as the
reactants react
and as it is pumped into the borehole. Once in the borehole the reactants will
continue to
react thereby thickening the emulsion explosive. Thus, in accordance with this
aspect of
the invention it is possible to load the borehole with an emulsion explosive,
which will
continue to thicken once it is in the borehole.
Alternatively, it is possible to produce a packaged thickened emulsion
explosive by
producing the precursor emulsion, which may also be sensitized. At the
packaging facility
the precursor emulsion and complementary reactant are combined to form an
emulsified
and thickened product which is then packaged.
As discussed previously, the base emulsion or precursor emulsion used in
accordance with
all aspects of the present invention include the known fuel phase and oxidiser
phase
combinations for the production of conventional emulsion explosives. For
convenience,
unless otherwise stated, in the description below the term "emulsion" is taken
to include a
precursor emulsion.
Suitable oxygen releasing salts for use in the oxidizer phase of the emulsion
of the present
invention include the alkali and alkaline earth metal nitrates, chlorates and
perchlorates,
ammonium nitrate, ammonium chlorate, ammonium perchlorate and mixtures
thereof. The
preferred oxygen releasing salts include ammonium nitrate, sodium nitrate and
calcium
nitrate. However, the effect of calcium nitrate upon the rate of thickening
should be
considered when selecting salts. The oxygen releasing salt typically comprises
ammonium
nitrate or a mixture of ammonium nitrate and sodium nitrate.
If the emulsion is a water-in-oil emulsion, typically the oxygen releasing
salt component of
the oxidizer phase of the compositions of the present invention generally
comprises from
45 to 95 % w/w and preferably from 60 to 90 % w/w of the total thickened
emulsion
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explosive. In compositions wherein the oxidizer phase comprises a mixture of
ammonium
nitrate and sodium nitrate the preferred composition range for such a blend is
from 5 to 80
parts of sodium nitrate for every 100 parts of ammonium nitrate.
Therefore, in the preferred thickened emulsion explosive the oxygen releasing
salt
component of the oxidizer phase comprises from 45 to 95 % w/w (of the total
thickened
emulsion explosive) ammonium nitrate or mixtures of from 0 to 40 % w/w, sodium
or
calcium nitrates and from 50 to 95 % w/w ammonium nitrate.
Typically the amount of water employed in the oxidizer phase of the thickened
emulsion
explosives of the present invention is in the range of from 0 to 30 % w/w of
the total
emulsion composition. Preferably the amount employed is from 4 to 25 w/w and
more
preferably from 6 to 20 % w/w.
Suitable organic fuels for use in the fuel phase include aliphatic, alicyclic
and aromatic
compounds and mixtures thereof which are in the liquid state at the
formulation
temperature. Suitable organic fuels may be chosen from fuel oil, diesel oil,
distillate,
furnace oil, kerosene, naphtha, paraffin oils, benzene, toluene, xylenes,
asphaltic materials,
polymeric oils such as the low molecular weight polymers of olefines, animal
oils,
vegetable oils, fish oils and other mineral, hydrocarbon or fatty oils and
mixtures thereof
Preferred organic fuels are liquid hydrocarbons generally referred to as
petroleum
distillates such as gasoline, kerosene, fuel oils and paraffin oils.
Typically, the fuel phase
of the emulsion comprises from 2 to 15 w/w and preferably 3 to 10 % w/w of the
total
thickened emulsion explosive.
As discussed above, all aspects of the present may involve the use of
conventional
emulsifiers. The emulsifier may be chosen from the wide range of emulsifiers
known in the
art for the preparation of emulsion explosives. The emulsifier used may be one
of the well
known emulsifiers based on the reaction products of poly[alk(en)yl] succinic
anhydrides
and alkylamines, including the polyisobutylene succinic anhydride (PiBSA)
derivatives of
alkanolamines. Other suitable emulsifiers for use in the thickened emulsion
explosive of
the present invention include alcohol alkoxylates phenol 5 alkoxylates,
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poly(olyalkylene)glycols, poly(oxyalkylene)fatty acid esters, amine
alkoxylates, fatty acid
esters of sorbitol and glycerol, fatty acid salts, sorbitan esters,
poly(oxyalkylene) sorbitan
esters, fatty amine alkoxylates, poly(oxyalkylene)glycol esters, fatty acid
amines, fatty acid
amide alkoxylates, fatty amines, quaternary amines, alkyloxazolines,
alkenyloxazolines,
imidazolines, alkylsulphonates, alkylarylsulphonates, alkyl
sulpho succinates,
alkylarylsulpnonates, alkyl sulpho succinates,
alkylphosphates, alkenylphosphates,
phosphate esters, lecithin, copolymers of poly(oxyalkylene)glycols and poly(12-
hydroxystearic)acid and mixtures thereof.
Typically, the emulsifier of the emulsion comprises up to 5 w/w
of the thickened
emulsion explosive. Stable emulsions can be formed using relatively low levels
of
emulsifier and for reasons of economy it is preferable to keep the amount of
emulsifying
agent used to the minimum required to form the emulsion. The preferred level
of
emulsifying agent used is in the range of from 0.1 to 3.0 % w/w of the
thickened emulsion
explosive. However, lower levels of emulsifier may be used in certain
embodiments.
Alternatively or additionally, in the second aspect, the amine compound
functions as an
emulsifier.
If desired, other optional fuel materials, hereinafter referred to as
secondary fuels may be
incorporated into the emulsion in addition to the fuel phase. Examples of such
secondary
fuels include finely divided solids and water miscible organic liquids which
can be used to
partially replace water as a solvent for the oxygen releasing salts or to
extend the aqueous
solvent for the oxygen releasing salts in the oxidizer phase. Examples of
finely divided
materials include sulphur, aluminium, urea and carbonaceous materials such as
gilsonite,
comminuted coke or charcoal, carbon black, resin acids such as abietic acid,
sugars such as
glucose or dextrose and vegetable products such as starch, nut meal, grain
meal and wood
pulp. Examples of water miscible organic liquids include alcohols such as
methanol,
glycols such as ethylene glycol, amides such as formamide and urea and amines
such as
methylamine. Typically the optional secondary fuel component of the
composition of the
present invention comprises up to 30 % w/w of the total composition.
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It lies within the invention that there may also be incorporated into the
emulsion explosive
(prior to thickening) other substances or mixtures of substances which are
oxygen
releasing salts or which are themselves suitable as explosive materials. These
include
doping the emulsion with ammonium nitrate prills of low density or high
density, sodium
nitrate prills, calcium nitrate prills, sodium perchlorate prills and/or any
known oxidizers in
prill form, including those mixed with diesel oil and/or nitroalkane, for
example,
nitrotoluene etc; doping the emulsion with RDX, PETN, TNT, MAN, EAN, EDDN or
FIN
as organic nitrate sensitizer; and doping the emulsion with granulated
aluminum powder,
atomized aluminum, paint grade aluminum, foamed aluminum, nanoparticle
aluminum,
foam nickel, foamed iron, foamed silicon, foamed aluminum silicon alloy metal
etc.
The base emulsion or the modified emulsion may be sensitized using foamed
metal, foams
of natural or synthetic liquids or solids, foams of ammonium nitrate or oxygen
releasing
salts, water based foams, or oil based foam etc. Additionally or
alternatively, metal based
nano-materials, natural or synthetic nano-materials, or inorganic or organic
nano-materials
based upon amine nitrate, etc. may be used. Furthermore, the base emulsion or
modified
emulsion may be sensitized by gassing. Gassing my by performed using a number
of
compounds including nitrite compounds, organic carbonates, inorganic
carbonates,
peroxides, and nitrogen gas generating from an inorganic or organic compound.
The invention is now illustrated further by, but is in no way limited to, the
following
examples.
Examples
Throughout these examples the following abbreviations or acronyms are used:
ATBN amine terminated polybutadiene
acrylonitrile - Hycar 1300X21 polymer
ESOA epoxidized soybean oil acrylate
AN ammonium nitrate
SN sodium nitrate
CN calcium nitrate
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SMO sorbitan monooleate
SSO sorbitan sesquiolate
DN60 polyisobutylene succinic anhydride
derivative with diethanol amine from
Nelson Brothers
DN80 polyisobutylene succinic anhydride
derivative with diethylethanol amine from
Nelson Brothers
HT-22 ParaflexTM, highly purified mineral oil
from
PetroCanada
LZ2824S polyisobutylene succinic anhydride
derivative with diethanol amine from
LubrizolTM
SG1100 SoyGold 1100, fatty acid methyl ester of
soya bean oil, from Ag Environmental
Products L.L.0
VoD Velocity of Detonation (m.s-I)
Laboratory Synthesis of the Thickened emulsion explosive
Example 1
Table 1
Ingredient Proportion %w/w Mass (g)
ATBN 0.49% 10.0g
Mineral oil 7.46% 150.0g
AN 75.03% 1508.8g
Water 16.47% 331.2g
ESOA 0.55% 11.0g
The composition of the sample is shown in Table 1 and produced as follows. The
amine compound,
ATBN, was mixed into the mineral oil in a Hobart bowl at mixing at speed 2.
The ammonium nitrate
solution was produced by dissolving the ammonium
nitrate in the
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water. The ammonium nitrate solution was then slowly poured into the mixing
bowl while
the mixer is running. The mixture was then digested for 2 minutes and
continuously mixed
for another 3 minutes. The resulting precursor emulsion was very fluid,
globular and
unstable with a viscosity of 6000 cps at 75 C when measured using a Brookfield
Viscometer using spindle 7 at 20rpm. The a,j3-unsaturated carbonyl compound,
ESOA,
was mixed into the emulsion at speed 2 for 11 minutes. The resulting emulsion
was stable,
thick and gelled with a Brookfield viscosity at 75 C as shown in Table 2.
Table 2
Spindle Speed (rpm) Brookfield Viscosity (cps)
7 10 123000
7 20 90000
TbarE 5 240000
TbarE 10 170000
TbarE 20 110000
TbarE 50 46750
TbarE 100 29000
Example 2
Table 3
Ingredient Proportion %w/w Mass (g)
DN60 1.24% 24.8g
SMO 0.17% 3.4g
HT-22 2.32% 46.4g
Corn oil 0.72% 14.4g
ESOA 1.24% 24.8g
AN/SN/Water (77/11/12) 90.73% 1814.6g
K20 glass microballoons 2.86% 57.2g
ATBN 0.72% 14.4g
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In this example, a further composition was synthesized by weighing the
required DN60,
SMO, HT-22 and ESOA (shown in Table 3) into the Hobart mixing bowl, applying
steam
to the mixing bowl and mixing the components at speed 2. When the temperature
of the
oil mixtures reached 60 C, the AN/SN/Water solution was poured into the oil
mixture. It
took 2 minutes to digest the solution to form the water in oil emulsion. The
solution was
then mixed further at speed 2 for 3 minutes. Then the Brookfield viscosity was
taken.
Brookfield viscosity ¨ Spindle 7 at 10 rpm at 82 C=88400 cps
Spindle 7 at 20 rpm at 82 C=43800 cps
The Hobart bowl was placed back to the mixer and mixed further at speed 3 for
3 minutes
to refine the emulsion, before the Brookfield viscosity was measured again.
Brookfield viscosity ¨ Spindle 7 at 10 rpm at 76 C=250000 cps
Spindle 7 at 20 rpm at 76 C=135000 cps
Then K20 glass microballoons were added and mixed while the steam was still
running
through the bowl. The Brookfield viscosity was then measured.
Brookfield viscosity ¨ Spindle 7 at 10 rpm at 76 C=275000 cps
Spindle 7 at 20 rpm at 76 C=157000 cps
The ATBN was mixed with corn oil and then mixed into the emulsion. The
emulsion
gelled and became thick.
After 2 months storage at room temperature, a 25 mm diameter cartridge of the
resulting
thickened emulsion explosive at a density of 1.17 g/cc was shot with an
electric blasting
detonator. The velocity of detonation was measured using the point to point
target wire
method as 4504 m/sec.
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Example 3
Table 4
Ingredient Proportion %w/w Mass (g)
DN60 1.493% 29.86g
SMO 0.207% 4.14g
HT-22 2.810% 56.2g
ESOA 0.70% 14.0g
AN/SN/Water solution 94.79% 1895.8g
(77/11/12)
The required amount of DN60, SMO, HT-22 and ESOA, as shown in Table 4, was
weighed into a Hobart mixing bowl, steam was applied to the mixing bowl and
the
components were mixed at speed 2. When the temperature of the oil mixture
reached 60
C, the AN/SN/Water solution was poured into the oil mixture. The resulting
mixture was
then digested for 1 minutes and 30 seconds to form the water-in-oil emulsion.
The
emulsion was then mixed further at speed 2 for 3 minutes and 30 seconds. The
Brookfield
viscosity was then taken.
Brookfield viscosity ¨ Spindle 7 at 10 rpm at 84 C=72800 cps
Spindle 7 at 20 rpm at 84 C=38000 cps
The Hobart bowl was placed back into the mixer and mixed further at speed 3
for 3
minutes to refine the emulsion. Then the Brookfield viscosity was taken.
Brookfield viscosity ¨ Spindle 7 at 10 rpm at 71 C=220000 cps
Spindle 7 at 20 rpm at 71 C=114000 cps
T bar Eat 10 rpm at 71 C=140000 cps
Then 7.5 g of ATBN, mixed with 7.5 g of corn oil, was added and mixed into to
1000.0 g
of the sample emulsion. The Brookfield viscosity was then taken.
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Brookfield viscosity (time at zero) - T bar E at 10 rpm at 71 C=185000 cps
(after 30 minutes) T bar E at 10 rpm at 71 C=215000 cps
(after 4 hours) T bar Eat 10 rpm at 71 C=310000 cps
Example 4
Table 5
Ingredient Proportion %w/w Mass (g)
LZ2824S 0.636% 15.90g
Diesel Oil 2.542% 63.55g
SMO 0.497% 12.43g
AN 76.544% 1913.60g
Water 16.802% 420.05g
K-20 glass microballoons 2.979% 74.48g
The required amount of LZ2824S, SMO, Diesel Oil, as shown in Table 5, was
weighed
into a Hobart mixing bowl, the steam was applied to the mixing bowl and the
mixture was
mixed at speed 2. The AN and the water were mixed together to produce a
solution. '
When the temperature of the oil mixtures reached 50 C, the AN/Water oxidizer
solution
was poured into the oil mixture. The mixture was digested for 1 minute and 15
seconds to
form a water-in-oil emulsion. The emulsion was mixed further at speed 2 for 4
minutes.
Then the Brookfield viscosity was taken.
Brookfield viscosity ¨ Spindle 7 at 10 rpm at 78 C=31500 cps
Spindle 7 at 20 rpm at 78 C=17000 cps
The Hobart bowl was placed back to the mixer and mixed further at speed 3 for
3 minutes
to refine the emulsion. Then the Brookfield viscosity was taken.
Brookfield viscosity ¨ Spindle 7 at 10 rpm at 70 C=80000 cps
Spindle 7 at 20 rpm at 70 C=41500 cps
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Then K-20 glass microballoons were added and mixed into the emulsion while the
steam
was still running through the bowl.
A 2000g sample of the emulsion was divided into two equal parts. The following
materials were added into the emulsion and mixed at a temperature of between
70-75 C.
Sample 1 Sample 2
ESOA 2.02g 2.02g
SG1100 3.25g 3.25g
Corn Oil 3.25g 3.25g
The viscosity of sample 1 and sample 2 dropped slightly due to the additional
oil added
into the emulsion. The following materials were also added to the samples.
Sample 1 Sample 2
ATBN 3.50g 3.50g
LZ2824S 0.70g 0.70g
Diesel Oil 2.80g 2.80g
Calcium Nitrate (40%) 0.00g 10.0g
The ATBN was mixed into the emulsion resulting in the emulsion thickening and
gelling
in less than one minute. The samples were packaged into 25 mm diameter High
Density
Polyethylene (HDPE) film for compression tests. The samples had a length of
30mm and
were stored at room temperature prior to performing the compression tests. The
results of
the compression tests following 2 days, 4 days and 1 week of storage are shown
in Figures
4, 5 and 6, respectively.
Sample 1 and sample 2 test specimens were shot at room temperature with an
electric
blasting detonator. The results of the shooting tests are shown below in Table
6.
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Table 6
25mm dia After 1 Day After 4 Days After 9 Days After 2 month,
AN/W (82/18) 17 C shooting
temperature
Sample 1 VoD: 5427 VoD: 5000 VoD: 4961 VoD: 4433
Density: 1.118 Density: 1.128 Density: 1.133 Density:
1.120
Sample 2 VoD: 5163 VoD: 4739 VoD: 4774 VoD: 4550
Density: 1.101 Density: 1.119 Density: 1.123 Density:
1.122
Point to point VoD measurement of 63.5mm (2.5")
Example 5
Emulsions were prepared using a standard operating procedure for manufacturing
small-
scale laboratory mixes. The required amount of an aqueous oxidizer solution at
90 C was
added slowly for five minutes to the fuel phase containing ESOA at speed 2 in
a steam
jacketed mixing bowl. Additional emulsion refinement was required for the
packaged
emulsion formulations and achieved by mixing at speed 3 for 5 minutes. Once
the bulk or
packaged emulsion was refined to the desired viscosity and droplet size, the
product was
sensitized with plastic microspheres to the desired density. After the
addition of the
microspheres ATBN was then added to the emulsion and thoroughly mixed for
about two
minutes and then cartridged in plastic or cardboard containers.
The formulations used to manufacture the laboratory scale packaged and bulk
thickened
emulsion explosives are given below.
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Table 7: Bulk and Packaged formulations containing ESOA and ATBN
Ingredient Bulk Packaged
Oxidizer AN 77.646 72.610
SN 0.000 10.370
Water 17.044 11.320
Oil Phase DN80 0.645 0.000
Diesel Oil 2.597 0.000
SMO 0.504 0.000
Corn Oil 0.640 0.326
LZ28245 0.000 2.490
SSO 0.000 0.510
HT-22 0.000 1.104
ESOA 0.199 0.200
Sensitizer Microspheres 0.000 0.300
Other DN80 0.074 0.000
Diesel oil 0.298 0.000
LZ2824S 0.000 0.311
SSO 0.000 0.072
ATBN 0.372 0.375
Determining the Optimum Level of ESOA and ATBN
Example 8
Experimental laboratory batches of packaged and bulk emulsions were evaluated
to
determine the optimum level of ESOA and ATBN required to produce a cost
effective and
high quality thickened emulsion explosive compositions. The following table
shows the
process of reducing ESOA and ATBN to optimum levels. Thickened emulsion
explosive
samples with a nonfluid, deformable rheology are said to have polymerized.
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Table 8: Optimum Level of ESOA and ATBN in Polymerized Emulsions
Viscosity J
..: q;:=,.,-.,...,J.41.,.:,;: -:-:- =iiffiti,_., T bar Compress ion
"0 \A, AN (Vo v, Av Temp:-:( E at 5 rpm force after 1
. .. - . .. .
Matrix F S 0 A ,,,Ai I RN ' C)(10 3 cps ) d a V Comments
Product did not
Bulk 1.3 0.175 75 30 60 polymerize
Gelled, poor
Bulk 1.3 0.25 75 32.4 70 plasticity
Polymerization
Bulk 1.3 0.375 75 50 85 after 3 days
Polymerized after
Packaged 1.3 0.75 75 342 210 1 day
Polymerization
Bulk 1.3 0.5 75 53.8 100 after 2 days
_ _______________________________________________________________
Polymerized after
Packaged 1.3 0.375 75 213 150 2 days
Does not
Packaged 1.3 0.25 75 200 145 polymerize
Polymerization
Bulk 0.9 0.375 75 44 80 after 4 days
Bulk 0.9 0.31 75 53 130 Fair plasticity
Bulk -0.5 0.25 75 38 75 Fair plasticity
Good elasticity
and
polymerization
Bulk 0.2 0.375 75 47 85 after 3 days
Product did not
Bulk 0.2 0.25 75 53 175 polymerize
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The optimum level of ESOA and ATBN was found to be 0.2% and 0.375%,
respectively.
At 0.375% ATBN in the product, an acceptable rate of polymerization was
achieved. Any
level below 0.375% did not polymerize.
Tests of pure ESOA and ATBN indicated that a 30/70 blend gave the quickest
rate of
polymerization. Therefore, the amount of ESOA selected was 0.2%. This is a
35:65 ratio
of ESOA to ATBN. Higher ratios of ATBN will polymerize faster when the
chemicals are
combined as neat reactants. However, when mixed into a large volume matrix,
there must
be enough ESOA to disperse and polymerize with the ATBN. For this reason,
nothing
below 0.2% was tested.
Use of only ATBN in the emulsion without the a,13-unsaturated carbonyl
compound,
ESOA, caused it to thicken but with no plasticity. Emulsions containing only
ESOA but
no polymer will not gel or thicken in storage.
Oil used for Cleaning Process Equipment
Example 9
To determine how to clean the plant equipment after producing the thickened
emulsion
explosive, a solvent must be found that dissolves the product. Several oils
were used
experimentally to find the best solvent. In each test a mixture comprising
95.18% the
contemplated oil, 2.41% ESOA and 2.41% ATBN was mixed and observed. The oils
considered were: SG1100, SC1500 (biodegradable methyl esters derived from
soybean
oil), CE110 (biodegradable methyl ester derived from canola oil), Varsol 110,
HT-22,
Corn Oil, and Diesel oil.
The solubility of the mixture was determined visually in the laboratory. The
SG1100 was
the best solvent for the ESOA and ATBN product, and may be used for cleaning
plant
equipment. HT-22, corn oil, and diesel oil did not completely dissolve the
product.
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Emulsion Pilot Plant Trials
Example 10
The purpose of the Emulsion Pilot Plant Trials was to determine the
feasibility of
manufacturing thickened emulsion explosives in a non-laboratory setting.
Approximately one tonne of an explosive emulsion composition containing a
carbonaceous
fuel continuous phase, an aqueous discontinuous phase containing dissolved
oxidiser salt
and an emulsifier was produced in the EMMA II pilot plant using pin mill mixer
technology. ESOA was mixed into the matrix using a 125L Panocopter kitchen
mixer.
ATBN was delivered at the centre of the emulsion to obtain uniform mixing. A
blue dye
was added to the ATBN to help determine the dispersion within the matrix as it
was mixed
and to assist evaluating the amount of mixing.
The experiments were carried out using a 5m loading hose. All the flows were
calibrated
and curves were established. The emulsion matrix containing ESOA was pumped at
a rate
of 30 kg/min with 2.0% water lubrication. The addition of ATBN was delivered
at 2.0%
using the F5 method, in the centre of the emulsion. Two Sulzer static mixers
were
installed at the end of the loading hose to obtain uniform mixing with ATBN
additive. The
emulsion pumping pressure at a flow rate of 30kg/min was measured as 11 bars
and 14
bars of pressure at the ATBN pump.
Two plexiglass tubes (3.5 and 4 inch in diameter) were filled with the
thickened emulsion
explosive to evaluate up-hole retention properties. The thickened emulsion
explosive
stayed within the clear plexiglass tubes without slumping for over three
months.
Accordingly, the thickened emulsion explosive demonstrated excellent up-hole
retention
properties.
The gassing performance was also examined to determine if the thickened
emulsion
explosive could be chemically gassed. The thickened emulsion explosive was
capable of
being gassed to a cup density of 1.05 g/cc after 45 minutes at 250 C. Results
showed that
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the thickened emulsion explosive did not detrimentally affect the chemical
gassing
process.
The addition of ESOA externally to the matrix did not affect the consistency
of the matrix
produced. The addition of ESOA internally also did not affect the consistency
of the
matrix.
When ATBN was added, mixing was found to be a critical part of the product
production
process. If the emulsion was not mixed thoroughly, the thickening rate
reduced.
After the thickening had taken place, it was found that the product caked
inside the hopper
and it became very difficult to clean. For this reason, it became crucial to
find a solvent to
dissolve the polymer and clean the plant equipment.
New Concept in Manufacturing Packaged Emulsion
Example 11
In a field trial a bulk manufacturing plant was organized to examine the
feasibility
manufacturing a packaged thickened emulsion explosive. The matrix formulation
is listed
below:
Table 9: Formulation for Packaged Thickened emulsion explosive
Composition Formulation
Oil Phase DN60 56.99 2.85
SSO 12.02 0.601
HT-22 18.82 0.891
SG1100 4.61 0.231
Corn Oil 4.61 0.231
ESOA 0.40 0.198
Oxidizer AN 77.00 71.61
SN 11.00 10.23
Water 12.00 11.16
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Approximately 5,000 lbs of an emulsion matrix containing 0.2% ESOA in the oil
phase
was manufactured on the Stir-Pot-Static-Mixer. The matrix viscosity of the
base matrix
containing ESOA was measured at 82,000 cps with 2 DY static mixers with a
manufacturing pressure of 150 psi.
The optimum process parameters in manufacturing packaged emulsion matrix
through a
Stir-Pot-Static-Mixer emulsifier unit were determined and are summarized in
Table 10.
Table 10: Matrix Containing ESOA Manufacturing Process Conditions
Trial run (with ESOA) 5% 7%
AN / SN / water solution tank temp ( C) 93 93.3
AN / SN / water fudge point ( C) 74.8 74.8
AN / SN / water solution flow rate
(lb/min) 192.2 185.5
Surfactant / Oil Phase tank temp ( C) 60 60
Surfactant / Oil Phase run temp ( C) 57.7 57.7
Oil phase flow rate (lb/min) 10.2 14.1
Stir pot stirring speed 609 608
Number of mixers 2 2
Type of inline mixer DY DY
Transfer pump speed 203 285
Matrix pumping pressure (psi) 150 130
Matrix temperature ( C) 88 88
Matrix viscosity spindle 7 @ 20 rpm (cps) 82000 72000
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Thickened emulsion explosive Mine Trial
Example 12
Five 25 kg cases of packaged 25x300mm cartridge packaged thickened emulsion
explosive
were produced in the laboratory and shipped to a mine test site. The thickened
emulsion
explosive was evaluated against Magnafrac in an underground up-hole stope. The
main
purpose of the trial was to determine how the packaged thickened emulsion
explosive
performed when loading up-holes using a cartridge loader. The loading
operation was
conducted in the 1330 stope. The up-hole borehole diameter was 54 mm and 13.4
to 18.9
metres in length. In the 54 mm diameter up-holes the thickened emulsion
explosive
compacted as well as the Magnafrac packaged emulsion. Compaction measured for
the
Magnafrac product was 92% and the thickened emulsion explosive compacted
between 92
and 95%. Very little blow-back was observed when loading either the
composition or the
Magnafrac product. No product crystallization was observed when loading the
thickened
emulsion explosive product through the cartridge loader. Overall the trial was
a success,
which indicates that no foreseeable problems should be encountered when
loading the
packaged polymerized emulsion with a cartridge loader.
Cartridge Loader Operating Parameters:
25mm cartridge loader.
25mm grooved loading hose 30.5 metres in length.
72 psi operating pressure.
Approximately 1.5 metre standoff from the end of the loading hose to the
emulsion
Cup of water used in the cartridge loader when cartridges slowed down in the
hose
Trial results:
Loading was conducted in the 1330 up-hole stope. Tests were compared to
Magnafrac
emulsion cartridges used at the mine. For these tests, 25x300mm diameter
emulsion
cartridges were used. To ensure the cartridge loader was operating properly
and to set the
proper operating pressure the back rows were loaded with the Magnafrac product
prior to
loading the thickened emulsion explosive composition. When the loader was
operating
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properly, compaction tests were performed on the Magnfrac emulsion and the
thickened
emulsion explosive composition. Test results are shown in Table 11.
Table 11: Polymerized Compaction Results
Product Up-hole Borehole Weight Compaction
Diameter Length
Magnafrac 54 mm 10.67 meters 25 kg 92.4%
Magnafrac 54 mm 10.67 meters 25 kg 92.4%
Magnafrac 54 mm 9.45 meters 25 kg 104% (broke into
adjacent hole)
Thickened 54 mm 10.36 meters 25 kg 95%
Emulsion
Explosive
Thickened 54 mm 9.75 meters 25 kg 104% (broke into
Emulsion adjacent ring)
Explosive
Thickened 54 mm 10.67 meters 25 kg 92.4%
Emulsion
Explosive
Effect of Calcium Nitrate (CN) on Thickening Rate
Example 13
The effect of calcium nitrate on the thickening or polymerization rate was
studied as both
an external additive and an internal additive to the oxidizer phase. The
viscosities and
compression results were conducted at 1, 5, and 16-day intervals.
The experimental formulations are given below:
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Table 12: Formulations for Effect of CN on Polymerization Rate
Sample # 1055-57-1 1055-57-2 1055-58-1 1055-58-2 1055-59-1 1055-
59-2
SWOIL DN80
Oil Phase DO#2 3.1887 3.1572 3.1887 3.1572 3.1887
3.1572
SMO 0.4983 0.4933 0.4983 0.4933 0.4983
0.4933
ESOA 1.2656 1.2531 1.2656 1.2531 1.2656
1.2531
CORN OIL 0.0000 -0.0000 0.6328 0.6266 0.3164
0.3133
SG1100 0.6328 0.6266 0.0000 -0.0000 0.3164
0.3133
Oxidizer OXIDIZER 93.6701 92.7427 93.6701 92.7427 93.6701 92.7427
SWOIL DN80
Comp B DO#2 0.3722 0.3685 0.3722 0.3685 0.3722
0.3685
ATBN 0.3722 0.3685 0.3722 0.3685 0.3722
0.3685
External CN Sol'n
Addition (40%) 0.0000 0.9901 0.0000 0.9901 0.0000
0.9901
TOTAL 100.0000 100.0000 100.0000 100.0000 100.0000 100.0000
Results
The viscosity for each of the six formulae discussed above was tested at 1, 5,
and 16 days,
along with the compression data. The following data was taken with the T Bar E
using the
Brookfield viscometer, at 1 rpm and at room temperature.
Table 13: Results for Effect of Calcium Nitrate on Polymerization Rate
Brookfield Viscosity (104 cps) using T bar E at 1 rpm measured at room
temperature
Sample # 1055-57-1 1055-57-2 1055-58-1 1055-58-2 1055-59-1 1055-59-2
1 Day 153 200 169 229 153 200
5 Day 340 465 300 OVER 330 OVER
16 Day 414 OVER 298 OVER 330 OVER
This data shows that the addition of CN greatly increases the viscosity both
initially, and
over time, compared with the omission of CN.
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The compression data was taken at the same intervals, and the results are
shown in Figures
7-9.
The results show that the addition of CN into the oxidation phase or
externally, will
enhance the rate of polymerization and enhance plasticity of the product. Zinc
nitrate and
Urea did not have any effect on the rate of polymerization.
While calcium nitrate increases the rate of polymerization, it is not
recommended for use
due to the decreased sensitivity versus AN or SN. Additional microspheres are
needed
when calcium nitrate is used. Also, adding calcium nitrate increases the cost
of
production.
Zinc nitrate did not show the same polymerization effect as calcium nitrate,
even though it
also contains a di-cation (Ca+2 and Zn+2). This may be due to the pH
difference of Ca+2
and Zn+2 ions or the chelating property of calcium.
Rate of Polymerization
Example 14
When pure ESOA and ATBN are mixed, they form a polymerized resin. The rate at
which
the two components polymerized had a direct relationship to the ratio of ESOA
to ATBN.
The following percentages of ESOA and ATBN were mixed and the amount of time
before
polymerization is detected was recorded:
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Table 14: Set Times for Pure ESOA and ATBN
Set Time
ESOA% ATBN% (minutes)
30 70 35
40 60 45
50 50 60
60 40 120
70 30 240
This data was used to help determine the 0.2/0.375 ratio of ESOA to ATBN used
in the
formulation.
Embodiments have been described herein with reference to the figures and
examples.
However, some modifications to the described embodiments and/or examples may
be
made without departing from the spirit and scope of the described embodiments,
as
described in the appended claims.
The reference in this specification to any prior publication (or information
derived from it),
or to any matter which is known, is not, and should not be taken as an
acknowledgment or
admission or any form of suggestion that that prior publication (or
information derived
from it) or known matter forms part of the common general knowledge in the
field of
endeavour to which this specification relates.
Throughout this specification and the claims which follow, unless the context
requires
otherwise, the word "comprise", and variations such as "comprises" and
"comprising", will
be understood to imply the inclusion of a stated integer or step or group of
integers or steps
but not the exclusion of any other integer or step or group of integers or
steps.
=
