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Description  |
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This invention relates to an improved water-in-oil emulsion explosive,
incorporating an improved emulsifier which contributes substantially to
the effectiveness and operation of the explosion composition, and to a
method of forming same.
BACKGROUND OF THE PRESENT INVENTION
Water-in-oil emulsion explosives are well-known. For example, such
explosive compositions are disclosed in U.S. Pat. Nos. 4,356,044;
4,322,258; 4,141,763; 3,447,978 and 3,161,651. Emulsion explosives are
found to have certain advantages over conventional aqueous slurry
explosives which have a continuous aqueous phase, as for example described
in U.S. Pat. No. 4,141,767. Further explosive compositions are known from
Australian patent specifications Nos. 29932/89 (612,787); 67382/89; and
83316/87.
One inherent problem with emulsion explosives however is their relative
instability, due to the fact that they include a thermodynamically
unstable dispersion of supercooled solution or melt droplets in an
oil-continuous phase. If the emulsion remains stable, these supercooled
droplets are prevented from crystallising or solidifying into a lower
energy state. However, if the emulsion weakens or becomes unstable, then
crystallisation or solidification of the droplets results and the
explosive composition generally loses some of its sensitivity to
detonation and often becomes too viscous to handle for certain blasting
operations. Moreover, it is relatively common to add solid components to
emulsion explosives, for example in the form of glass microspheres for
density reduction and prills or particles of oxidizer salt (such as for
example porous prilled ammonium nitrate (AN) for increased energy. These
solid components do however in many cases tend to destabilize emulsions.
It is common to use emulsion explosives as a repumpable explosive. That is,
as an explosive that is formulated at a facility, and thereafter loaded or
pumped into a bulk container and then transported in such a container to a
blasting site, where it is repumped form the container into a bore hole.
Alternatively, such an explosive may be delivered or repumped into a
centrally located storage tank from which it will be further repumped into
a vehicle for transportation to a blasting site and the again repumped
into a bore hole.
It is therefore important that emulsion explosives remain stable even after
being subjected to repeated handling or shearing action which normally
tends to destabilise and emulsion. Further the viscosity of such emulsions
must remain sufficiently low enough to allow for repumping at reasonable
pressures and at a relatively low ambient temperature such as may be
experienced during colder months of the year. Repeated handling or
shearing action tends to increase an emulsion's viscosity.
It is an object of at least one aspect of the present invention to provide
an explosive composition including an emulsifier, which goes some way
towards overcoming or minimising the problems associated with explosive
compositions known up until this time.
It is a further aspect of at least one aspect of this invention to provide
a method of forming an explosive composition.
Other objects of the present invention will become apparent from the
following description.
BRIEF SUMMARY OF THE PRESENT INVENTION
According to one aspect, the present invention provides an explosive
composition including a hydrocarbyl polyamine emulsifier characterised by
a straight link between said hydrocarbyl group and said polyamine.
According to a further aspect of this invention there is provided an
explosive composition including a hydrocarbyl polyamine emulsifier
characterised by a straight link between hydrocarbyl group and said
polyamine, wherein said emulsifier is a compound of formula:
##STR1##
where R is a hydrocarbyl group containing at least 20 carbon atoms; R' is
an amino substituted hydrocarbyl group and R" is a hydrogen atom or an
alkyl group containing 1 to 4 carbon atoms.
According to a further aspect of this invention there is provided a method
of forming an explosive composition, which includes a hydrocarbyl
polyamine emulsifier, characterised by a straight link between said
hydrocarbyl group and said polyamine, wherein said emulsifier is produced
by reacting an alkanolamine with a hydrocarbyl halide.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE PRESENT INVENTION
The present invention relates to an improved explosive composition and more
particularly a water-in-oil emulsion explosive composition which, as
indicated above, sets out to overcome or minimize problems associated with
such explosive compositions known and used up until this time. In
preferred forms of the invention, the emulsion explosive composition of
the present invention provides improved stability and compatibility with
ingredients dissolved in oxidizer aqueous solution and with solids added
to the formed emulsion.
The term "water-in-oil" as used throughout the specification and claims
means a dispersion of droplets of an aqueous solution for water-miscible
melt (a discontinuous phase) in an oil or water-immiscible organic
material (a continuous phase).
The term "explosive" means both cap-sensitive explosives and
non-cap-sensitive explosives.
In a preferred form of the invention, the water-in-oil emulsion explosives
of the present invention contain a water-immiscible organic fuel as the
continuous phase and a substantially emulsified inorganic oxidizer salt
solution or melt as the discontinuous phase. The term "oxidizer",
"solution" or "melt" hereinafter used throughout the specification and
claims shall be interchangeable.
The term "solids" means a dry addition of "AN-prill" ANFO or sensitizing
microspheres or an auxiliary fuel-type granules or other known additives.
Such oxidizers, fuel phases and added solids react with one another upon
initiation by a blasting cap and/or booster to produce an effective
detonation.
The explosive composition of the present invention is particularly
characterised in that it includes a composition which comprises a
hydrocarbyl polyamine emulsifier characterised in that a straight link
entends between the hydrocarbyl group and the polyamine.
The explosive composition, in one form of the present invention, includes
an emulsifier in the form of a polybutene polyamine alcohol, which is a
compound of formula:
##STR2##
where R is a hydrocarbyl group containing at least 20 carbon atoms; R' is
an amino substituted hydrocarbyl group and R" is a hydrogen atom or an
alkyl group containing 1 to 4 carbon atoms.
The group R preferably contains from 20 to 500 carbon atoms, most
preferably from 30 to 150 carbon atoms.
R is preferably a hydrocarbyl group derived from the polymerization of an
olefin. Suitable olefins includes ethylene, propylene, butylenes, and
4-methylpentene-1. The preferred olefin is isobutylene. The preferred
materials are those ranging from about 800 to 3000 molecular weight with
the most preferred materials having a polyisobutenyl radical of 1000 to
1500 molecular weights.
In general, these compositions will contain from about 4.6 to 0.5 percent
by weight of nitrogen.
R' is preferably a polymethylene group containing 2 to 5 carbon atoms which
is associated with an amino group, e.g. of formula:
--CH.sub.2 CH.sub.2 NHCH.sub.2 --
or
--CH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.2 --
R" is preferably hydrogen.
In preferred forms of the invention reactants and build-up components of
formula (I) are:
A. an alkanolamine (a compound in which nitrogen is attached by a straight
link, to the carbon of an alkyl alcohol) of formula:
##STR3##
and specifically here, the preferred alkanolamine is N-(2-aminoethyl)
ethanolamine
with
B. a hydrocarbyl halide of formula:
R--X where X=chloride or bromide and R is a hydrocarbyl group as defined
hereinbefore.
A preferred olefin is polyisobutylene.
Preferably the molar ratio of alkanolamine to hydrocarbyl halide is in the
ratio 2:1 to 5:1.
Preferably the hydrocarbyl halide contains an average between 1.4 to 2.0
halogen atoms per molecule of hydrocarbyl halide.
One preferred emulsifier according to one form of the invention is a long
chain polyolefin (poly)amine alcohol produced through reaction of A with B
(as referred to hereinbefore).
A preferred emulsifier used in this invention is available and marketed as
an additive under the brand name ADX250 with an average molecular weight
of 1100. It should however be appreciated that the additive marketed under
the brand name ADX250 is primarily used in the lubricant industry and it
has been found that the use of this additive as an emulsifier has
particular advantages in so far as explosive compositions are concerned.
These advantages are referred to and described in detail herein, and such
an emulsifier has not previously been used in the explosives industry.
Other emulsifiers according to the present invention can, however, be used
to advantage.
The present invention incorporating a hydrocarbyl polyamine emulsifier, has
substantial advantages and in particular adds stability to the explosive
emulsion.
The immiscible organic fuel forming the continuous phase of the composition
is present in an amount of from about 3% to about 12%, and preferably in
an amount of from about 4% to about 8% by weight of the composition. The
actual amount used can be varied depending upon the particular immiscible
fuel(s) used and upon the presence of other fuels, if any. The immiscible
organic fuels can be aliphatic, alicyclic, and/or aromatic and can be
saturated and/or unsaturated, so long as they are liquid at the
formulation temperature. Preferred fuels include tall oil, mineral oil,
waxes, paraffin oils, benzene, toluene, xylenes, mixtures of liquid
hydrocarbons generally referred to as petroleum distillates such as
gasoline, kerosene and diesel fuels, and vegetable oils such as corn oil,
cotton seed oil, peanut oil, and soybean oil. Particularly preferred
liquid fuels are mineral oil, No. 2 fuel oil, paraffin waxes,
microcrystaline waxes, and mixtures thereof. Aliphatic and aromatic
nitrocompounds also can be used. Mixtures of the above can be used. Waxes
must be liquid at the formulation temperature.
Optionally, an in addition to the immiscible liquid organic fuel, solid or
other liquid fuels or both can be employed in selected amounts. Examples
of solid fuels which can be used are finely divided aluminum particles;
finely divided carbonaceous materials such as gilsonile or coal; finely
divided vegetable grain such as wheat; and sulfur. Miscible liquid fuels,
also functioning as liquid extenders, are listed below. These additional
solid and/or liquid fuels can be added generally in amounts ranging up to
15% by weight. If desired, undissolved oxidizer salt can be added to the
composition along with any solid or liquid fuels.
The inorganic oxidizer salt solution forming the discontinuous phase of the
explosive generally comprises inorganic oxidizer salt, in an amount from
about 45% to about 95% by weight of the total composition, and water
and/or water-miscible organic liquids, in an amount of from about 2% to
about 30%. The oxidizer preferably is primarily ammonium nitrate, but
other salts may be used preferably in amounts up to about 50%. The other
oxidizer salts are selected from the group consisting of ammonium, alkali
and alkaline earth metal nitrates, chlorates and perchorates. Of these,
sodium nitrate (SN) and calcium nitrate (CN) are preferred. From about 10%
to about 65% of the total oxidizer salt may be added in particle or prill
form.
Water generally is employed in an amount of from about 2% to about 30% by
weight based on the total composition. It is however preferably employed
in an amount up to about 30% by weight based on the total composition,
although in one form of the invention in the range of about 5% to about
30% by weight based on the total composition. Water-miscible organic
liquids can partially replace water as a solvent for the salts, and such
liquids also function as a fuel for the composition. Moreover, certain
organic liquids reduce the crystallisation temperature of the oxidizer
salts in solution. Miscible liquid fuels can include alcohols such as
methyl alcohol glycols such as ethylene glycols, amides such as formamide,
and analogous nitrogen-containing liquids. As is well known in the art,
the amount and type of liquid(s) used can vary according to desired
physical properties.
The emulsifier of the present invention is a product of a long chain
polyolefin and an alkanolamine both combined in a straight linkage.
As described hereinbefore, a particularly preferred derivative is the
commercially available ADX250 which is a compound product of a
polyisobutylene and N-(2-aminoethyl)-ethanolamine preferably carried in an
organic solvent.
The emulsifier of the present invention can be used singly or in
combination with other emulsifiers such as sorbitan fatty esters, glycol
esters, substituted oxazalines, alkyl amines or their salts, other
derivatives of polypropene or polybutene, derivatives thereof and the
like.
The compositions of the present invention preferably are reduced for their
actual densities to within the range of from about 0.5 to about 1.5 q/cc.
The commonly known density reducing agents that may be used include glass
spheres, plastic spheres, perlite, chemical gassing agents, foaming
agents. These are by way of example.
Thickening and crosslinking agents are not necessary for stability and
water resistancy, but can be added if desired.
The explosives of the present invention may be formulated in a conventional
manner. Typically, the oxidizer salt(s) first is dissolved in water (or
aqueous solution of water and miscible liquid fuel) at an elevated
temperature of from about 25.degree. C. to about 90.degree. C. or higher
depending upon the crystallisation temperature of the salt solution
The aqueous solution then is added to a solution of the emulsifier and the
immiscible liquid organic fuel, which solutions preferably are at the same
elevated temperature, and the resulting mixture is stirred sufficiently to
produce a water-in-oil emulsion. Stirring should be continued until the
formulation is uniform.
The solid ingredients, if any, then are added and stirred throughout the
emulsion.
The formulation process also can be accomplished in a continuous manner as
is known in the art.
It is advantageous to preblend the emulsifier in the liquid organic fuel
prior to adding the organic fuel to the aqueous solution. This way the
emulsion forms quickly and with minimum agitation.
Sensitivity and stability of the composition may be improved slightly by
passing then through a high-shear system to break the dispersed phase into
even smaller droplets prior to adding the density control agent.
We now refer to the following table I which further illustrates the
invention and in particular the advantages thereof. In table I, examples
3, 6, 7 and 10 all relate to explosive compositions containing
SMO-Sorbitan Monooleate, a commonly used emulsifier. Examples 1, 8 and 12
contain SMO-PIBSA-derivative combination, wherein PIBSA is Polyisobutenyl
Succinic Anyydride. In table I, examples 2, 4, 5, 9, 11 and 13 all relate
to explosive compositions incorporating an emulsifier according to the
present invention.
The study products were matrixes, sensitized (solids, gassed) and blends
with ANFO. Both booster sensitive and cap-sensitive (No 8 detonator)
formulations were tested. All samples were stored for an extended period
of time and observed/tested regularly. Values shown in table I are
reported as weeks stability at 20.degree. C. with observation on the
degree of crystallization. Table I also illustrates the improved
shelf-life storage stability provided by an emulsifier of the present
invention. Example 2 is for a cap-sensitive product while examples 4, 5
and 9 are for booster-sensitive formulations. Examples 11 and 13
illustrate also the improved stability for blends of emulsion matrixes
with ANFO.
TABLE I
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MIX EXAMPLE No:
INGREDIENTS
1 2 3 4 5 6 7 8 9 10 11 12 13
__________________________________________________________________________
AN 72.0
72.0
64.0
64.0
64.0
77 77 77 77 44.8
44.8
53.9
53.9
NHCN 14.0
14.0
14.0 9.8 9.8
SN 10.0
10.0
H.sub.2 O 10.0
10.0
15.0
15.0
15.0
16 16 16 16 10.5
10.5
11.2
11.2
DFO No 2 5.5 5.5 5.5 5.5 5.5 3.85
3.85
Mineral Oil
0.9 1.0 5.5 5.5 3.85
3.85
SMO - Emulsifier
1.0 1.5 1.5 1.5 1.4 1.05 0.98
PIBSA - co emulsifier
0.1 0.1 0.07
PIB - Alkanolamine
1.0 1.5 1.0 1.5 1.05 1.05
(ADX250)
WAX 3.0 3.0
(Paraffin/Microcr)
Q-719 3.0 3.0
Gassing Additives 0.4
ANFO 30.0
30.0
30.0
30.0
Density (g/cc)
1.18
1.18
1.40
1.40
1.15
1.33
1.33
1.33
1.33
1.35
1.35
1.30
1.30
Storage Temp
20 20 20 20 20 20 20 20 20 20 20 20 20
No Cycles 10 20 -- -- -- -- -- -- -- -- -- -- --
[1 cycle =
-20.degree.(24 h) +
20.degree.(24 h)]
Degree of
Crystallisation
After Cycling
1 week None
None
None
None
None
Mod Slight
Slight
None
Slight
None
Slight
None
2 weeks Heavy
Mod Slight Mod
3 weeks Slight
None
Mod Heavy
None
Heavy
Slight
4 weeks Heavy
None
None Heavy
Mod
8 weeks Slight Slight Mod
12 weeks
16 weeks None
20 weeks Mod None None Mod
30 weeks
40 weeks Slight None
Slight
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The invention will now be described and illustrated by way of example only
(without limitation) with reference to example 2, 5 and 11 as shown in the
above table I. By way of example, the parts and percentages are expressed
by weight.
EXAMPLE 2 (Cap-sensitive formula)
A mixture of technical grade ammonium nitrate (72.0 parts), sodium nitrate
(10.0 parts) and water (10.0 parts) was heated with stirring to a
temperature of about 95.degree. C. to give an aqueous solution. The hot
salt solution was then poured, with rapid stirring, into a hot solution
(90.degree. C.) of 1.0 part of ADX 250 (commercially available
polyisobutene alkanolamine) mixed with 3.0 parts of microcrystalline and
paraffin waxes and 1 part of mineral oil. Stirring was continued until a
uniform emulsion was obtained. A solid bulking agent (Q-719 glass
microspheres from PQ AUSTRALIA) as sensitizer was also added (3 parts) and
a cap-sensitive explosives was formed.
The explosive while still hot was placed in .0.25.times.200 mm plastic film
for evaluation of stability.
EXAMPLE 5 (Booster sensitive formula)
A mixture of technical grade ammonium nitrate (64 parts), Norsk Hydro
Calcium nitrate (14 parts) and water (15.1 parts) was heated with stirring
to a temperature of about 75.degree. C. to give an aqueous solution. The
solution was then poured, with rapid stirring and after pH adjustment,
into a hot solution (70.degree. C.) of 1.0 part of ADX250 mixed with 5.5
parts of No 2 fuel oil. Stirring was continued until a uniform emulsion
was obtained. A gassing additive was added to bring the density down to
ca. 1.15 g/cc. The product sample was then taken for observations and
evaluation against similar products but based on conventional SMO
(sorbitan monooleate)--example 3; or SMO/PIBSA-derivative
products--example 8.
EXAMPLE 11 (Booster sensitive formula in blend with ANFO)
The procedure of example 5 was repeated except that 1.5 parts of the ADX250
was used and non-gassing components were added. The formed emulsion was
blended then with dry ANFO blend in 70:30 ratio.
The examples 11 and 13 showed the improved storage stability provided by
the ADX250 of the invention compared to a conventional emulsifier in
examples 10 and 12.
It should be appreciated that the composition of the present invention can
be used in a conventional manner and compositions can be used both as
packaged, small diameter products or as bulk products. Generally the
compositions may be extrudable and/or pumpable.
The invention has been described by way of example only and it should be
appreciated that modifications and improvements may be made thereto
without departing from the scope of the invention as defined by the
appended claims.
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Description |
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