Note: Descriptions are shown in the official language in which they were submitted.
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GASSER COMPOSITION & METHOD OF GASSING
This invention relates to gassing compositions
and a method for the preparation of gassed water-in-oil
emulsion explosives compositions.
Emulsion explosives compositions are well known
in the explosives industry. The Water-in-oil emulsion
explosive compositions now in common use were first
disclosed in U.S. Patent no. 3,447,978 (Bluhm) and comprise
as components:
(a) a di~acontinuous aqueous phase comprising
discrete droplets of an aqueous solution of
inorganic oxygen-releasing salts:
(b) a continuous water-immiscible organic phase
throughout which the droplets are dispersed
(c) an emulsifier which forms an emulsion of the
droplets of oxidiser salt solution throughout the
continuous organic phases and optionally
(d) a discontinuous gaseous phase and/or closed
cell void material.
Emulsion explosives compositions are often
blended with a solid particulate oxidiser salt such as
ammonium nitrate (AN) prills or particles, which may be
coated with or contain fuel oil (FO) to form a low cost
explosive of excellent blasting performance. Such
compositions are described in U.S. Patent no.s 3,161,551
(Egly et al), 4,111,727 (Clay), 4,181,546 (Clay) and
4,357,184 (Binet et al).
In Water-in-oil emulsion explosives compositions,
emulsifiers are used to decrease interfacial tension
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between the agueous and oil phases. Molecules of the
emulsifier locate at the interface between the agueous
droplet and continuous hydrocarbon phase. The emulsifier
molecules are oriented with the hydrophilic headgroup in
the aqueous droplet and the lipophilic tail in the
continuous hydrocarbon phase. Emulsifiers stabilise the '
emulsion, inhibiting coalescence of the aqueous droplets
and phase separation. The emulsifier also inhabits
crystallisation of the oxidiser salt within the droplets
30 which crystallisation can lead to emulsion breakdown and
reduction in detonation sensitivity of the emulsion
explosive composition.
A variety of emulsifier types and blends are
known in the art. For example Australian Patent no.
40006/85 (Cooper & Baker) discloses water-in-oil emulsion
explosive compositions which contain a conductivity
modifier which may also act as an emulsifier. Included
among such conductivity modifiers are condensation products
of poly[alk(en)y11 succinic anhydride (PiBSA) with amines
such as ethylene diamine, diethylene triamine and
ethanolamine.
Such conductivity modifiers/emulsifiers enable
the preparation of particularly stable emulsions which are
suitable for blending with solid particulate oxidiser salts
such as ammonium nitrate (AN) or ammonium nitrate and fuel
oil blends (ANFO). The stability of emulsion explosives
compositions prepared using such poly[a1k(en)yl3succinic
anhydride derivatives as conductivity modifiers/emulsifiers
enables the preparation of unsensitised emulsion phase (EP)
compositions at a dedicated plant under controlled
conditions and transport of that EF to the mine site for
sensitisation and use.
In general Water-in-oil or melt-in-oil emulsion
cannot be detonated unless they are sensitised.
Sensitising may be carried out by mixing the emulsion with
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a high explosive such as trinitrotoluene or nitroglycerine
or by incorporating small voids into the emulsion which act
as hot spots in the detonation. The latter is the
preferred method for sensitising a water-in-oil or melt-in-
oil emulsion explosive composition.
The most common methods currently used to
incorporate voids and sensitise a water-in-oil emulsion
composition or emulsion/AN/ANFO blend include in situ
gassing using chemical agents, the incorporation of closed
cell void material such as microballoons or a mixture of
both.
Suitable chemicals for the in situ generation of
gas bubbles suitable for use in water-in-oil emulsion
explosives include peroxides such as hydrogen peroxide,
nitrite salts such as sodium nitrite, nitrosamines such as
N,N''-dinitrosopentamethylenetetramine, alkali metal
borohydrides such as sodium borohydride and bases such as
carbonates including sodium carbonate.
Perhaps the most widely used chemicals for the _in
situ generation of gas bubbles are nitrous acid and its
salts which react under conditions of acid pH to produce
nitrogen gas bubbles. Accelerators such as thiocyanate
salts, iodides, sulphamic acid or its salts or thiourea may
be used to accelerate the reaction of a nitrite gassing
agent. The accelerator may also be consumed in the
reaction.
One of the problems with this commonly used
gasser system of the prior art is that nitroso species
r
generated during the gassing reaction may react with
functional moieties on the headgroup of the emulsifier.
Functional moieties on the emulsifier headgroup such-as
certain primary and secondary amines, amides, carboxylic
acids, esters and anhydrides are particularly vulnerable to
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attack by aitroso species. Re.actioa by aitroso species
with the moieties of the haadQroup causes chemical chaa9es
is the emulsifier which my have a deleterious effect on
the emulsifying capability of the emulsifier. 118 a result
the iateriacial tension of the dsoplets of the
discontinuous aQueous phase my decrease, causing
crystallisation of the of oxidiser salt within the aQueous
phase droplets and degradation of the esulsioa, possibly
even to the point breakdown of the emulsion into separate
aQueaus and oil phases.
The problem of emulsifier reaction with QassiaQ
agents is referred to in Australian Patent 681,702 (application
published September 4, 1997). Australian Patent 681,702 relates
to chemical gassing using sodium nitrite and teaches that "The
commonly used chemical gassing reaction can thus not be used to
gas the known PiBSA-based explosive emulsions". In effect, this
may lead to the need for different EP's to be used for gassed and
ungassed products comprising emulsion explosives compositions and
preclude the use~of PiBSA derivative~emulsifiers in nitrite gassed
ZO emulsion explosives compositions and hence the emulsion stability
advantages provided by such emulsifiers.
,i~aother problem associated with gassing agents,
lacludiag nitrite gassing agents of the prior art is the
difficulty of evenly distributing the gassiap agent
throughout the eaulsioa. taternatiopal patent l~pplication
WO-89/02881 attempts to address this problem by a~isiaQ into
the main body of es~ulsion, a nitrite QassiaQ agent which is
also in the form of as emulsion.
one of the drawbacks of using an emulsion gassing
agent is that the esulsioa gassiap agent dilutes both the
aQueous and oil phases of the main body of eaulsioa,'
reducing the blasting power of the amn~lsion explosive
forssd.
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One of the other problems associated with the
gassing methods and gasser compositions of the prior art is
that they had to be added in extremely high proportions to
reduce emulsion density to very low densities such as,
below 1 g/cc. The presence of extremely high proportion of
gasser compositions often adversely affected emulsion
stability due to dilution of the continuous or
discontinuous phase of the emulsion. =f either or both of
these phases are overly diluted, there may not be
sufficient emulsifier present to maintain an emulsion
structure.
The present applicants have now found a new
gasser solution and method of gassing an emulsion which
reduces or eliminates the problem of emulsion breakdown
experienced using nitrite as the chemical gassing agent.
The invention further provides advantages in the
preparation of sensitised emulsion explosives compositions
in that it enables one emulsion to be used for the
preparation of sensitised emulsion explosives compositions
regardless of Whether they are sensitised using a nitrite
chemical gassing agent or using other sensitising means.
The gasser solution and method of gassing are particularly
effective in i~roving the stability of emulsifiers in
emulsion explosives compositions which comprise emulsifiers
which have headgroups which are vulnerable to attack by
nitroso species, such as PiBSA based emulsifiers.
Accordingly the present invention provides a
gassed emulsion explosive composition comprising an
emulsion, excluding micro-emulsions, in combination with a
gasser composition;
the emulsion having a discontinuous aqueous phase
comprising inorganic oxygen releasing salts, a continuous
water imiscible organic phase and an emulsifier having a
functional moiety which is vulnerable to chemical attack by
nitross species, and
AMENDED SHEET
I~EA/AU
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the gasser composition having a solution of an
inorganic nitrite, an ammonium species and optionally an
accelerator,
wherein the reaction betweea the inorganic nitrite and
ammonium species occurs Within droplets of the gasser
solution such that there is substantially no chemical'
attack on the emulsifier.
The present invention also provides a method of
forming the aforementioned gassed emulsion explosives
composition wherein the method of gassing an emulsion
comprises the steps of:
(a) forming a gasser solution comprising a
solution of an inorganic nitrite, an ammonium species and
optionally an accelerator,
(b) adding the gasser solution to an emulsion
and mixing such that droplets of 'gasser composition are
distributed throughout the emulsion, and
(c) allowing the gasser solution to react and
form gas which is distributed as bubbles throughout the
emulsion to form the gassed emulsion explosive composition.
In accordance with another aspect of the present
invention there is provided a method of forming a gassed
emulsion explosive composition, the method comprising the
steps of: (a) forming a gasser solution comprising a
solution of an inorganic nitrite, an ammonium species and
optionally an accelerator, (b) adding the gasser solution to
an emulsion explosive composition comprising a discontinuous
aqueous phase comprising inorganic oxygen releasing salts, a
continuous water immiscible organic phase and a
poly[alk(en)yl] succinic anhydride based emulsifier such that
droplets of gasser composition are distributed.throughout the
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emulsion, and (c) allowing the inorganic nitrite and
ammonium species of the gasser solution to react and form
gas which is distributed as bubbles throughout the emulsion
to form the gassed emulsion explosive composition, wherein
the gasser solution is formed during or immediately before
addition of the gasser solution to the emulsion explosive
composition by mixing the inorganic nitrite, ammonium
species and optionally the accelerator, and wherein the
reaction between the inorganic nitrite and the ammonium
species occurs within droplets of the gasser solution such
that there is substantially no chemical attack on the
emulsifier.
Where used herein the term emulsion may refer to
a water-in-oil or melt-in-oil emulsion which is
unsensitised or partially sensitised and which is suitable
as a component of an emulsion explosive composition.
The emulsion explosives composition which is
gassed by the method of the current invention may be
unsensitised or be partially sensitised by any means known
in the art. For example the emulsion explosive composition
may comprise glass or plastic microballoons. As such, the
gasser solution and method of the current invention may be
the sole source of sensitising gas bubbles for an emulsion
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~~ s;.
~~cE~vE~ - s ~~~ iss~
explosives composition or may be used a.n conjunction with
other gasser solutions or other gasser compositions and
gassing methods. In addition, closed cell void material
such as glass or plastic microballoons may be used to
further sensitise the emulsion explosives composition prior
to or after gassing by the method of the current invention.
Without wishing to be bound by theory, it is
believed that the gasser solution forms droplets within the
emulsion explosives composition and in the presence of the
acidic emulsion explosives composition the inorganic
nitrite and ammonium species react within the droplets of
the gasser solution to form gas bubbles and provide the
gassed emulsion explosives composition.
AMENDED SHEET
1P~A.lAI,J
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_ g
It is preferred that the ratio of inorganic
nitrite to ammonium species is between 10:1 and 1:10. It
is particularly preferred that the molar proportion of '
ammonium species present in the gasser solution is up to
10% greater than the molar proportion of inorganic nitrite
so that all of the nitrite is consumed by reaction With the
ammonium species within the gasser solution droplet. More
preferably the ammonium species and inorganic nitrite are
present in eguimolar quantities.
The ammonium species of the gasser solution of
the current invention may be any suitable ammonium species
known to those skilled in the art such as ammonia, primary
or secondary amines and the salts thereof. Preferred
ammonium species include ammonium salts such as ammonium
chloride, ammonium nitrate, ammonium chlorate, ammonium
perchlorate, ammonium thiocyanate and combinations thereof.
The ammonium species may be formed in situ in the droplet
of gasser solution, for example by the reaction of ammonia
or a primary or secondary amine with a mineral acid or
organic acid. The ammonium species may typically comprise
up to 25 wt% of the gasser solution.
The inorganic nitrite of the gasser solution of
the current invention may be any suitable nitrite salt
known to those skilled in the art such as an alkaline earth
nitrite, alkali metal nitrite or combinations thereof. =n
a particularly preferred embodiment the inorganic nitrite
is sodium nitrite. Preferably the inorganic nitrite
comprises up to 25 wt% of the gasser solution.
The accelerator may be any suitable accelerator
known to those skilled in the art such as thiourea, urea,
thiocyanate, iodide, cyanate, acetate or the like and
combinations thereof. The proportion of accelerator in the
gasser composition may be influenced by the solubility of
5i ~~.~~ _.. ~ iI~.~.~ °..9,-,~tf~'-i('~',\..~
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the accelerator but may commonly comprise up to 25 wt% of
the gasser composition. In a particularly preferred
embodiment the gasser composition comprises up to 3 wt% of
thiourea or thiocyanate as accelerator.
t The reaction between the nitrite species and
ammonium species a.s pH dependent, being faster in acid
conditions than in basin conditions. If the pH is too low,
the gasser solution tends to self-gas so quickly that the
gassing reaction and gas production may be close to
complete before the composition can be mixed into the
emulsion. Conversely if the pH is too high, the gassing
reaction may proceed too slowly. The pH of the gasser
solution is preferably between pH 5 and 9, more preferably
between pH 6 and 8 and most preferably relatively close to
neutral.
The emulsion may also be buffered, preferably to
a pH between pH 5 and 9.
The gasser solution may comprise any suitable
solvent but water a.s the preferred solvent. Other optional
additives may also be present.
As indicated above, the inorganic nitrite and
ammonium species should be mixed together in solution to
form the gasser solution of the present invention.
Separate addition of the inorganic nitrite and the ammonium
species directly to the emulsion explosives composition
does not provide the advantages of the invention which lie
in efficient gassing rates and the reduction of elimination
of the problem of emulsion breakdown experienced using
nitrite as the chemical gassing agent.
The gassing method and gasser solution of the
current invention provide a means for reducing emulsion
density well below Z.0 g/cc. It should be noted that
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reduction of emulsion density below 1.0 g/cc was not
readily achievable using the gassing methods and gasser
solutions and gasser compositions of the prior art. The
high proportion of prior art gasser solutions and gasser
composition which needed to be added to the emulsion to
obtain low density tended to promote emulsion breakdown and
phase separation. Using the gassing method and gasser
solution of the current invention relatively high
proportions of gasser solution can be added to the
emulsion, sufficient to reduce the emulsion density well
below 1.0 g/cc without significant adverse effects on
emulsion stability.
It should be noted that once the gasser solution
is formed by mixing together an inorganic nitrite, ammonium
species and accelerator, slow reaction and concomitant gas
production may occur. This is of no consequence in
situations where the gasser solution is made up and quickly
thereafter mixed with an emulsion to form an emulsion
explosive composition. However if the gasser solution is
stored for a relatively long period such as a matter of
hours or days, much of the gas product may be lost before
the gasser solution can be mixed into the emulsion. In
order to overcome this storage problem the inorganic
nitrite, ammonium species and accelerator may be stored
separately in soled or solution form and mixed to form the
gasser solution immediately prior to addition to the
emulsion. An accelerator may be stored separately or with
either the inorganic nitrite and/or the ammonium species.
Therefore the present invention also envisages
and includes mixing of the inorganic nitrite and the
ammonium species to form the gasser solution of the present
invention immediately before addition to the emulsion or
during actual addition to the emulsion. -
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Suitable oxygen releasing salts for use in 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. More preferably the oxygen releasing salt
comprises ammonium nitrate or a mixture of ammonium nitrate
and sodium or calcium nitrates.
Typically, the oxygen releasing salt component of
the compositions of the present invention comprise from 45
to 95 wt% and preferably from 60 to 90 wt% of the total
emulsion composition. In compositions wherein the oxygen
releasing salt 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
composition the oxygen releasing salt component comprises
from 45 to 90 wt°.s (of the total emulsion composition),
ammonium nitrate or mixtures of from 0 to 40 wt%, sodium or
calcium nitrates and from 50 to 90 wt% ammonium nitrate.
Typically the amount of water employed in the
emulsion compositions of the present invention is in the
range of from 0 to 30 wt% of the total emulsion
composition. Preferably the amount employed is from 4 to
25 wt% and more preferably from 6 to 20 wt%.
The water immiscible organic phase of the
emulsion composition of the present invention comprises the
continuous "oil" phase of the emulsion composition and is
the fuel. Suitable organic fuels include aliphatic,
aiicyclic and aromatic compounds and mixtures thereof which
are in the la.quid state at the formulation temperatu3re.
Suitable organic fuels may be chosen from fuel oil, diesel
oil, distillate, furnace oil, kerosene, naphtha, waxes such
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as microcrystalline wax, paraffin wax and slack wax,
paraffin oils benzene, toluene, xylenes, asphaltic
materials, polymeric oils such as the low molecular weight
polymers of olefines, animal oils, fish oils aad 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 organic fuel or continuous phase of
the emulsion explosive composition comprises from 2 to 15
wtgs and preferably 3 to 10 wt°~ of the total composition.
As indicated, the gasser solution of the present invention
provides advantages relating to stability of the emulsifier
and avoiding the problems of the prior art relating to
emulsion breakdown which can be experienced where
emulsifiers are vulnerable to attack by nitroso species
formed when nitrite gassing agents are used to gas emulsion
explosives compositions. The gasser solution of the
current invention is suitable for use with a variety of
emulsifiers having headgroups comprising functional
moieties such as primary and secondary amines, amides,
carboxylic acids, esters and anhydrides and other groups
which may be vulnerable to attack by nitroso species. These
may include for example, 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,
alkylsulphosuccinates, alkylarylsulphonates,
alkylsulphosuccinates, alkylphosphates, alkenylphosphates,
phosphate esters, and poly(12-hydroxystearic) acid, $nd
mixtures thereof.
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Amongst the preferred emulsifiers are the generic
family of poly(alk(en)yl~ succinic anhydride based
emulsifiers, and particularly polyisobutylene succinic
anhydride (PiBSA) based emulsifiers, produced by reaction
with amines such as alkanolamines and the like. Where
used, particularly preferred additional emulsifiers include
sorbitan esters such as sorbitan mon-oleate.
Typically the emulsifier of the water-in-oil of
the emulsion comprises up to 5 wt% of the emulsion. Higher
proportions of the emulsifying agent may be used and may
serve as supplemental fuel for the composition but in
general a.t is not necessary to add more than 5 wt% of
emulsifying agent to achieve the desired effect. 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 minium
reguired to form the emulsion. The preferred level of
emulsifying agent used is in the range of from 0.1 to 2.0
wt% of the emulsion.
If desired, other optional fuel materials,
hereinafter referred to as secondary fuels, may be
incorporated in to the emulsion composition in addition to
the water immiscible organic 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 agueous solvent for the oxygen releasing
salts. Examples of solid secondary fuels include finely
divided materials such as sulphur, aluminium 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,
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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 from
0 to 30 wt~ of the total composition. ,
It lies within the invention that there may also
be incorporated into the emulsion composition other
substances or mixtures of substances which are oxygen
releasing salts or which are themselves suitable as
explosive materials. For example the emulsion may be mixed
with grilled or particulate ammonium nitrate before or
after the emulsion has been gassed.
Other optional additives may also be added to the
emulsion explosive compositions hereinbefore described
including thickening agents and thickener crosslinl~ing
agents such as zinc chromate or a dichromate either as a
separate entity or a.s a component of a conventional redox
system such as for example, a mixture of potassium
dichromate and potassium antimony tartrate.
The emulsion composition may be prepared by a
number of methods. One preferred method of manufacture
includes: dissolving said oxygen releasing salts in water
at a temperature above the fudge point of the salt
solution, preferably at a temperature in the range from 20
to 110°C to give an aqueous salt solution; combining an
aqueous salt solution, a water immiscible organic phase,
and an emulsifier With rapid mixing to form a water-in-oil
emulsion; and mixing until the emulsion is uniform.
The invention is now demonstrated by but in no
way limited to the following Examples. In Examples i to 24
various gasser compositions were mixed into a standard
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emulsion and the performance of the gasser composition was
monitored.
The components of the gasser compositions used
are recorded a.n Table 1.
Example 1
Preparation of a PiBSA Based Water-in-Oil Emulsion
A water-in-oil emulsion of the following
composition was prepared;
Oxidiser solution - 91 wt% comprising
10, ammonium nitrate (78.9 wt%)
water (20.7 wt%)
buffer (0.4 wt%)
Fuel phase - 9 wt% comprising a
hydrocarbon oil/emulsifier
mix.
The emulsifier was a condensation product of an
ethanolamine and poly(isobutylene) succinic anhydride.
The emulsion was prepared by dissolving ammonium nitrate in
the water at elevated temperature (98°C) then adjusting the
Ph of the oxidiser solution so formed to 4.2. The fuel
phase was then prepared by melting the microcrystalline wax
and mixing it with the hydrocarbon oil/emulsifier mix. The
fuel phase was then added in a slow stream to the oxidiser
solution at 98°C with rapid stirring to form a homogeneous
water-a.n-oil emulsion.
Preparation of the Gasser Composition
A neutral pH gasser composition was prepared by
dissolving thiourea, sodium nitrite and ammonium nitrate in
water. The gasser composition had the following
cOmpO8ltl.On;
thiourea 3.0 wt%
sodium nitrite 6.9 wt%
ammonium nitrate 8.0 wt%
water 82.1 wt%
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The mole ratio of sodium nitrite to ammonium
nitrite was 1.1. When the components were added together,
small bubbles gradually appeared in the gasser composition,
indicating slow self-gassing. -
The water-in-oil emulsion was kept at a
temperature of 55-60°C as 0.4 wt% of gasser composition was
stirred into the, emulsion over a 30 second period. After
mixing the gasser composition with the emulsion a short
induction time followed before reasonably rapid gassing of
the emulsion was observed. After 20 minutes, a sample of
the emulsion was viewed by microscope. No evidence of
emulsion breakdown was observed. Microscopic examination
of samples of the gassed emulsion held in storage at
ambient temperature for a further 3 weeks showed no
evidence of emulsion breakdown or crystallisation.
The final density of the gassed water-in-oil
emulsion was 1.09 g/ce as compared with 1.4 g/cc for the
ungassed water-in-oil emulsion.
Exan~le 2
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that the ammonium nitrate
was replaced with ammonium sulphate. The gasser
composition had the following coanposition;
thiourea 3.0 wt%
sodium nitrite 6.9 wt°-s
ammonium sulphate 9.8 wt%
water 80.3 wt%
The mole ratio of sodium nitrite to ammonium sulphate was
maintained at 1:1. The gassed water-in-oil emulsion
explosives formulation produced was almost
indistinguishable from that of Example 1 and after 3-days
there was no evidence of emulsion breakdown or
crystallisation.
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Example 3
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
' composition of Example 1 except that the ammonium nitrate
was replaced with ammonium perehlorate. The gasser
composition had the following composition;
thiourea 3.0 wt%
sodium nitrite 6.9 wt%
ammonium perchlorate 11.4 wt%
water 78.7 wt%
The mole ratio of sodium nitrite to ammonium perchlorate
was maintained at 1:1. The gassed water-in-oil emulsion
explosives formulation produced was almost
indistinguishable from that of Example 1. and after 3 days
there was no evidence of emulsion breakdown or
crystallisation.
Example 4
The Water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that the ammonium nitrate
was replaced with an eguimolar mixture of ammonium nitrate
and ammonium perchlorate. The gasser composition had the
following composition;
thiourea 3.0 wt%
sodium nitrite 6.9 wt%
ammonium nitrate/
ammonium perchlorate 9.8 wt%
water 80.3 wt%
The mole ratio of sodium nitrite to ammonium cations was
maintained at 1:1. The gassed water-in-oil emulsion
explosives formulation produced was almost
indistinguishable from that of Example 1 and after 3 days
there was no evidence of emulsion breakdown or
crystallisation.
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Examples 1 to 4 illustrate that changing the
ammonium species of the gasser composition between ammonium
nitrate, ammonium sulphate and ammonium perchlorate does
not affect the efficacy of the gasser composition. '
Example 5
The water-in-oil emulsion of Example 1 was mixed
With a gasser composition which was the same as the gasser
composition of Example 1 except that no accelerator was
used. The mole ratio of sodium nitrite to ammonium nitrate
was maintained at 2:1.
There was little evidence of self gassing of the
gasser composition prior to its addition to the water-in-
oil emulsion composition and when the gasser composition
was mixed with the water-in-oil emulsion the rate of gas
formation was less than half that of the rate observed for
Example 1.. The gassed water-in-Oa.l emulsion explosives
formulation produced was almost indistinguishable from that
of Example 1 and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Example 6
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 2 except that no accelerator was
used. The mole ratio of sodium nitrite to ammonium
sulphate was maintained at 1:1. There was no evidence of
self gassing of the gasser composition prior to its
addition to the water-in-Oil emulsion composition and when
the gasser composition was mixed with the water-in-oil
emulsion the rate of gas formation was less'than half that
of the rate observed for Example 2.
The gassed water-in-oil emulsion explosive
formulation produced was almost indistinguishable from that
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of Example 1 or 2 and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Exami~le 7
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which Was the same as the gasser
composition of Example 2 except that an acetic acid/acetate
buffer had been used to achieve a gasser composition pH of
5.5. The mole ratio of sodium nitrite to ammonium nitrate
was maintained at 1:1. Immediately the gasser composition
components were mixed there was a great deal of gas bubble
formation within the gasser composition. Most of the
gassing reaction had finished before the gasser composition
could be mixed with water-in-oil emulsion.
The water-in-Oa.l emulsion explosives formulation
produced gassed unevenly and the extent of gassing was not
as great as that exhibited in Example 1. The density of
the gassed emulsion was 1.3 g/cc as compared with 1.4 g/cc
for the ungassed emulsion.
Example 8
~ The water-in-oil emulsion of Example I. was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that an acetic acid/acetate
buffer was used to achieve a gasser composition pH of 6.5.
The mole ratio of sodium nitrite to ammonium nitrate was
maintained at 1:1. Within 1 minute of mixing together the
components of the gasser composition vigorous bubble
evolution commenced. The gasser composition was then mixed
with the water-in-oil emulsion.
The gassed water-in-oil emulsion explosives
formulation produced was almost indistinguishable from that
of Example 1 and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Example 9
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The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that sodium hydroxide was
added to achieve a gasser composition pH of 7.1. The mole -
ratio of sodium nitrite to ammonium nitrate was maintained
at 1:l. ZTery slow bubble formation was observed for up to
5 minutes after mixing the gasser composition components.
The gasser composition was then mixed with the water-in-oil
emulsion.
The gassed water-in-oil emulsion explosives
formulation produced was almost indistinguishable from that
of Example l and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Examt~le 10
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that sodium carbonate was
used to achieve a gasser composition pH of 7.8. The mole
ratio of sodium nitrite to ammonium nitrate was maintained
at 1:1. After mixing together the gasser composition
components. no gas bubble formation was observed for 12
minutes. In the following 2 hours only small bubbles were
observed. A sample of freshly mixed gasser composition
mixed with the water-in-oil emulsioa gave a product which
was almost indistinguishable from that of example 1 and
after 3 days there was no evidence of emulsion breakdown or
crystallisation.
Example 11
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which Was the same as the gasser ,
composition of Example 1 except that an acetic acid/acetate
buffer had been used to achieve a gasser composition pH of
8.2. The mole ratio of sodium nitrite to ammonium nitrate
was'maintained at 1:1. A small amount of self-gassing of
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the gasser composition was observed for 24 hours after the
gasser composition components were mixed together.
A gassed water-in-oil emulsion produced using a
freshly mixed sample of the gasser composition took several
~ 5 days to gas fully however the emulsion produced was
extremely storage stable and 3 weeks after gassing had been
completed there was no evidence of emulsion breakdown or
crystallisation.
Example 1 and Examples 7 to 11 show the effect on
the gasser composition of maintaining the same composition
but changing the pH. The reaction between the nitrite
species and ammonium species is known to be pH dependent,
being faster in acid conditions than in basic conditions.
=f the pH is too low, the gasser composition self-gasses so
quickly that the reaction may be close to complete before
the composition can be mixed into the water-in-oil
emulsion. Conversely if the pH is too high, the gassing
reaction may proceed too slowly. The optimal range for pH
of the gasser composition lies between about pH 6 and pH 8.
Examx~le 12
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that solvent was 50:50
ethanol:water instead of just water. The mole ratio of
sodium nitrite to ammonium sulphate was maintained at 1:l.
The gassed water-in-oil emulsion explosives
formulation produced was almost indistinguishable from that
of Example 1 and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Example 13
The water-in-Oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
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composition of Example 1 except that solvent was 50:50
methanol:water instead of just water. The mole ratio of
sodium nitrite to ammonium sulphate was maintained at 1:1.
the gassed water-in-oil emulsion explosives
formulation produced was almost indistinguishable from that '
of Example 1 and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Examples 1, 12 and 13 illustrate that changing
the solvent of the gasser composition from water to ethanol
or methanol does little to change the efficacy of the
gasser composition.
Example 14
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that the sodium nitrite was
replaced with potassium nitrite. The gasser composition
had the following composition;
thiourea 3.0 wt°o
potassium nitrite 8.5 wt%
ammonium nitrate 8.0 wt%
water 80.5 wt%
The mole ratio of nitrite anion to ammonium cation was
maintained at 1:1. The gassed water-in-oil emulsion
explosives formulation produced was almost
indistinguishable from that of Example 2 and after 3 days
there was no evidence of emulsion breakdown or
crystallisation.
Example 15
the water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that the sodium nitrite was
replaced with m,a.gnesium nitrite. The gasser composition had
the following composition;
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thiourea 3.0 wt%
magnesium nitrite 11.6 wt%
ammonium nitrate 8.0 wt°~s
' water 77.4 wt°~
The mole ratio of nitrite anion to ammonium cation was
maintained at 1:1. The gassed water-in-oil emulsion
explosives formulation produced was almost
indistinguishable from that of Example 1 and after 3 days
there was no evidence of emulsion breakdown or
crystallisation.
Examples 1, 14 and 15 illustrate that the gasser
composition of the present performs equally well
irrespective of whether an alkaline earth metal nitrite or
alkaline earth nitrate is used.
Example 16
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that the thiourea
accelerator was replaced by an equimolar quantity of urea.
The gassed water-in-oil emulsion explosives
formulation produced was almost indistinguishable from that
of Example 1 and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Example 17
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that the thiourea
accelerator was replaced by an equimolar quantity of
ammonium thiocyanate.
The gassed water-a.n-oil emulsion explosives
formulation produced was almost indistinguishable from that
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of example 1 and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Example 18
The water-in-oil emulsion of Example 1 was mixed
with a gasser composition which was the same as the gasser
composition of Example 1 except that the thiourea
accelerator was replaced by an equimolar guantity of sodium
iodide.
The gassed water-in-oil emulsion explosives
formulation produced Was almost indistinguishable from that
of Example 1 and after 3 days there was no evidence of
emulsion breakdown or crystallisation.
Examples 1, 16, 17 and 18 illustrate that
different accelerator species can be used successfully in
the gasser composition of the current invention.
Example 19
d~. gasser solution was prepared by the same method
as described in example 1 but with a higher concentration
of ammonium nitrate and sodium nitrite. The gasser
composition had the following composition;
thiourea 3.0 wt°s
sodium nitrite 8.6 wt°o
ammonium nitrate 10.0 wt°s
water 78.4 wt%
The mole ratio of sodium nitrite to ammonium
nitrite was maintained at 1:1. Small bubbles rapidly
formed in the gasser composition, indicating self-gassing.
The gasser composition was added to the water-in-oil
emulsion in the manner described in Example 1.
lifter mixing the gasser composition with the
emulsion immediate, rapid gassing of the emulsion was
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observed. After 20 minutes a sample of the emulsion was
viewed by microscope. No evidence of emulsion breakdown
was observed. After a further 2 weeks another sample of
emulsion was viewed by microscope. No emulsion breakdown
or crystallisation was occurred.
The final density of the gassed water-in-oil
emulsion was 1.00 g/cc as compared with 1.14 g/cc for the
ungassed water-in-oil emulsion.
A comparison of Examples 1 and 19 shows that an
increase of concentration of nitrite and ammonium species
in the gasser composition increases the rate of gassing and
provides a gassed water-in-oil emulsion of lower density.
Example 20
A gasser composition was prepared by the same
method as described in example 1 but with a mole ratio of
sodium nitrite which Was 50% higher than that of ammonium
nitrate. The gasser composition had the following
composition;
thiourea 3.0 wt%
sodium nitrite 10.35 wt%
ammonium nitrate 8.0 wt%
water 78.65 wt%
The mole ratio of sodium nitrite to ammonium
nitrate was 1.5:1. The gasser composition was added to the
water-in-oil emulsion in the manner described in Example 1.
After mixing the gasser composition with the
emulsion immediately, rapid gassing of the emulsion was
observed. After 20 minutes. a sample of the emulsion was
viewed by microscope and no evidence of emulsion breakdown
was observed. After a further 2 weeks another sample of
emulsion was viewed by microscope. No emulsion breakdown
or crystallisation was observed.
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A comparison of Example 1 to Example 20 shows
that where the mole quantity of nitrite exceeds that of the
ammonium species there is no adverse affect on the
stability of the emulsion in the first few weeks of
storage.
Exami~le 21
A gasser composition was prepared by the same
method as described in example 1 but with a mole ratio of
sodium nitrite which was 50% lower than that of ammonium
nitrate. The gasser composition had the following
composition;
thiourea 3.0 wt°~
sodium nitrite 6.9 wt%
ammonium nitrate 12.0 wt%
water 7 8 .1 wt°-s
The mole ratio of sodium nitrite to ammonium
nitrite was 1:1.5. The gasser composition was added to the
water-in-oil emulsion in the manner described in Example 1.
After mixing the gasser composition With the
emulsion immediately the gassing reaction proceeded in the
same manner as described in Example I. The gassed emulsion
produced was almost indistinguishable from that of Example
1 and no differences in the gassing rate or extent of
gassing was observed. No emulsion breakdown or
crystallisation was observed even after 3 weeks of storage.
A comparison of Example 1 to Example 21 shows
that increasing the mole quantity of the ammonium species
so that a.t exceeds the mole quantity of the nitrite species
has no effect on the gassing reaction.
Comparative Exam 1e 1 (CE1)
Preparation of the Comparative Gasser Composition
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A gasser composition of the prior art was
prepared by dissolving sodium nitrite and sodium
thiocyanate in water. The gasser composition had the
following composition;
sodium nitrite 23.0 wt%
sodium thiocyanate 23.0 wt%
water 54.0 wt%
A water-in-oil emulsion prepared according to the
method and composition of example 1 was kept at a
temperature of 55-60°C as 0.4 wt% of gasser composition was
stirred into the emulsion over a 30 second period.
After mixing the gasser composition with the
emulsion a short induction time followed before reasonably
rapid gassing of the emulsion was observed. After 20
minutes, a sample of the emulsion was viewed by microscope.
No evidence of emulsion breakdown was observed.
The density of the gassed water-in-oil emulsion
was 1.00 g/ec as compared with 1.4 g/cc for the ungassed
water-in-oil emulsion.
A further sample examined by microscope 24 hours
later revealed some crystallisation but no emulsion
breakdown. After a further 3 days another sample of
emulsion was viewed by microscope. A large amount of
emulsion crystallisation and breakdown was observed.
Comparison of CE1 and Examples ~. and 19 shows
that the gasser composition of the current invention can be
used to achieve emulsion densities equivalent with those
obtained using the gasser composition of the prior art,
however the gasser compositions of the current invention
are less prone to causing crystallisation and emulsion
breakdown.
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Example 22
Two samples of PiBSA based water-in-oil emulsion
of Example 1 were mixed with grilled ammonium nitrate in a
ratio of 70:30 by weight. The gasser compositions of the '
current invention were then added to the grill doped
emulsion arid the gassing rate measured. The gasser
composition of the prior art as described in CE1 was added
to a separate sample of 70:30 grill doped water-in-oil
emulsion of Example 1 and the gassing rate measured to
provide a comparison.
The gasser compositions used were of the
following composition;
Component Example 22(a) Example 22(b)
Sodium nitrite I3.2 wt% 21_0 wt%
Ammonium nitrate 17.6 wt% 24.3 wt%
Both gasser composition comprised 5 wt% thiourea
as accelerator and water was the solvent.The results of the
gassing measurements are recorded in Figure 1.
Tt is clear from Figure 1 that the gassing rate
of the gasser composition of the current invention is
equivalent to that of the gasser composition of the prior
art.
Example 23
The water-ixa.-oil emulsion of example 1 was mixed
with grilled ammonium nitrate in the proportions of 80:20
by weight, emulsion:prill. Differing amounts of a gasser
composition of the current invention was added to four
samples of the grill doped emulsion and the densities of
the gassed emulsions were measured over time. The gasser
composition of the prior ast as described in CE1 was added
to a separate sample of the water-in-oil emulsion of
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example 1 and the density of the gassed emulsion was
measured over time to provide a comparison.
The gasser composition of the current invention was as
follows
Component Example 23
Sodium nitrite 18.0 wt%
Ammonium nitrate 21.0 wt%
Thiourea 3.0 wt%
Water 58.0 wt%
The proportions of gasser composition added to
the Water-in-oil emulsion were as follows;
Example 23(a) 0.75 wt°-s
Example 23(b) 1.5 wt%
Example 23(c) 2.0 wt%
The gasser composition of CE1 was added at a
proportion of 0.5 wt%. Density measurements using higher
proportions of the gasser composition of CE1 could not be
determined because of emulsion breakdown and phase
separation. It was noted that none of the emulsions gassed
with the gasser composition of the current invention
displayed any signs of emulsion breakdown and after 1 month
of storage microscopic examination of samples of the gassed
emulsion showed only a very small amount of
crystallisation.
The results of the density measurements are
recorded in Figure 2. The results show that the gasser
composition of the current invention can reduce emulsion
density well below 1.0 g/cc at a rate which is comparable
with the gassing rate of the gasser composition of the
prior art. The results also show that the density of the
gassed emulsion product can be controlled by adding
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different proportions of the gasser composition of the
current invention. W2xile the invention has been
explained in relation to its preferred embodiments it is to
be understood that various modifications thereof will '
become apparent to those skilled in the art upon reading
the specification. Therefore, a.t is to be understood that '
the invention disclosed herein is intended to cover such
modifications as fall within the scope of the appended
claims.
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-31-
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CA 02239095 1998-OS-28
WO 97124299 7PCT/AU96100839
-32-
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SUBSTITU TE SHEET (Rule 26)
'CA 02239095 1998-OS-28
WO 97/24299 PCTJAU96/00839
- 33 -
AN = ammonium nitrate
AP = ammonium perchlorate
AS = ammonium sulphate
AT = ammonium thiocyanate
blrlI = magnesium nitrite
PNI = potassium nitrite
SA = sodium acetate
SI = sodium iodide
SMO = sorbitan mono-oleate
1U SNI _- sodium nitrite
ST = sodium thiocyanate
T = thiourea
U = urea
.'t-~;:~~ ~. : E-~3.r ~~:~~dr.;
