Note: Descriptions are shown in the official language in which they were submitted.
B 1 7 1 2 2
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SOLID WATER-IN-OIL EMULSION EXPLOSIVES
COMPOSITIONS AND PROCESSES
TECHN I CAL FI ELD
This invention relates to a solid water-in-oil
explosive composition and more particularly to such
explosive compositions and methods of formulating
same which may be rendered cap sensitive without the
need for high explosive sensitizing agents.
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BACKGROUND ART
There are a number of industrial applications in
which formulations of detonable oxidizing salts,
e.g., salts of nitric and perchloric acid, are
employed in formulating blasting agents. The most
widely used of these oxidizer salts is ammonium
nitrate which is commonly employed in admixture with
a light petroleum oil to produce the product termed
"ANFO" (ammonium nitrate and fuel oil). ANFO is an
economical and relatively safe explosive. However,
ammonium nitrate is highly hygroscopic and becomes
inert (deactivated to detonation) when contacted by
water. ThUs, unless special packaging steps are
taken, the use of ANFO in an environment in which
significant quantities of water are present is not
advisable.
Some of the problems and difficulties involved in
the use of ANFO and other oxidizer salt explosives
may be avoided through the use of emulsion-type
2~ blastinc~ agents. These a~ents comprise a
discontinuous ~internal) emulsion phase which is in
the form o an aqueous solution of an oxidizer salt
and a continuous (external) emulsion phase which is
in the form of a carbonaceous fuel component. The
`external phase or the continuous fuel phase may be
liquid semisolid, or solid. Thus, U.S. Patent No.
3,447,978 to Bluhm discloses an emulsion type
blasting agent in which the discontinuous emulsion
phase is an aqueous solution of ammonium nitrate,
optionally containing also a minor portion of a
second oxidi~er salt. The second oxidizer salt is
usually sodium nitrate although other alkali metal or
alkaline earth metal nitlates or perchlorat : may
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~3~39
, (' .
also be used. Also disclosed for this purpose are
ammonium chlorates or perchlorates, aluminum nitrate
or chlorate, zinc nitrate, chlorate, or perchlorate,
and organic oxidizing agents such as ethylene diamine
dichlorate and ethylene diamine diperchlorate. The
external emulsion phase comprises a wax and oil, a
wax and a polymeric material, or a wax and a
polymeric modified oil component. The external phase
is liquid during the emulsion forming stage and after
cooling may be a liquid/ paste, or solid at the
temperatures at which it is stored and used. The
explosive composition of Bluhm also includes an
occluded gas component dispersed within the emulsion
and characterized as forming a discontinuous emulsion
phase. The occluded gas component is incorporated in
the emulsion by aeration or by the addition of hollow
closed cells identified as microspheres, microbubbles
or microballoons.
In the explosive composition described in Bluhm,
the various component parts are present in amounts
hased upon 100 parts ammonium nitrate as a base.
Thus, water is present in the amount of 10-60 parts
by weight (preferably 1~-44 parts by weight) and the
carbonaceous fuel component in an amount within the
range of 4-45 parts by weight (preferably 5-17 parts
by wei~ht). The occluded gas provided by entrained
gas or closed cell voids is present in an amount of
at least 4 volume percent.
The composition disclosed in Bluhm is described
as being cap insensitive; that is, it is not subject
to direct detonation by an electric blasting cap
without the presence of a booster explosive
component. U.S. Patent No. 4,110,134 to Wade
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discloses a water-in-oil emulsion composition which
can be formulated to provide no. 6 cap~sensitive
explosive cartridges. In the Wade explosive
composition, the discontinuous emulsion phase is an
aqueous solution of an inorganic oxidizer salt
composed principally of ammonium nitrate. The water
concentraLion is about 10 to 22 weight percent of the
emulsion. The continuous emulsion phase is present
in an amount of about 3.5 to about 8 weight percent
and comprises a hydrocarbon fuel including an
emulsifier. Auxiliary fuels such as aluminum,
aluminum alloys and magnesium may also be added in
amounts up to about 15 weight percent. Also
incorporated in the explosive composition of Wade is
lS sufficient closed-cell void containing material
providing an ultimate emulsion density within the
range of about .9 to about 1.35 g/cc to render the
explosive composition sensitive to a no. 6 electric
blastincJ cap at a cartridge diameter of 1.25
~0 inches, The closed cell void materials employed in
Wade may be microspheres or microballoons of any
suitable type and may be gas filled or evacuated.
SuitablQ void cells include glass spheres, phenol
formaldehyde microballoons and saran microspheres.
The rnaximum density at which the explosive
forrnulation may be detonated by a no. 6 blasting cap
varies depending upon the water concentration and
also as a function of the fuel and inorganic oxidizer
content. Thus, the maximum density decreases as
water concentration increases`and also as wax in the
continuous phase decreases. The maximum density is
also decreased by replacing a secondary inorganic
perchlorate component with an inoryanic nitrate other
than ammonium nitrate.
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U.S. Patent No. 4,343,663 to Breza discloses a
solid water-in-oil emulsion explosive composition in
which the continuous fuel phase is provided by cross-
linking a liquid polymer to provide a thermoset
5 resin. Thus, the continuous emulsion phase may be
arrived at by cross-linking an unsaturated polyester
resin with an ethylenically unsaturated cross-linking
agent such as styrene monomer. The discontinuous
emulsion phase in Breza comprises an aqueous solution
10 of an oxidizer salt which is an ammonium, amine,
alkali metal, or alkaline-earth metal salt of nitric
acid or perchloric acid. The Breza explosive
composition also comprises a sensitizer material
dispersed in the matrix and/or the aqueous solution
15 for inducing or enhancing the detonability of the
solution-containing resin matrix. The sensitizer
material may be a solid high explosive e.g~
pentaerythritol tetranitrate, an organic nitrate
ester or nitramine or the sensitizer may be totally
20 nonexplosive, a dispersion of gas bubbles or voids,
or the sensitiæer material may be in part a dispersed
solid high explosive, The relative concentrations of
water in the discontinuous phase and resin in the
continuous fuel phase vary depending upon the type of
2S sensitizer employed. The resin content should be at
least ~ by weight and in the case of a nonexplosive
sensitized product, the resin content may not exceed
10% and preferably is no more than 8%. Where the
product is high explosive sensitized, the resin
30 content preferably is at least 12%. The water
content should be at least 5~ and generally at least
about 8~, but should not exceed 25% by weight.
~ j ~30~E~9~l (
As noted previously, all or part of the
- sensitizer in Breza can be provided by dispersed gas
bubbles or voids constituting at least about 5% of
the product volume, The voids can be formed by
direct gas injection, the in situ generation of gas,
by mechanical agitation, or by the addition of
particulate material such as phenol-formaldehyde or
glass microballoons, fly ash, or siliceous glass.
Preferred gas void volumes are in the range of about
5 to about 35~. The high explosive compositions in
Breza which are sensitized with a high explosive are
cap sensitive; that is, they may be directly
detonated by a no 8 electric blasting cap. However,
the explosive compositions sensitized with
microballoons, even with the presence of monomethyl-
amine nitrate are not directly cap sensitive, but are
cap sensitive only with the presence of a booster
such as Detaprime 16 or 33 gram boosters around the
cap well.
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DISCLOSURE OF THE INVENTION
In accordance with the present invention there
are provided new and improved solid water-in-oil
explosive compositions which may be formulated to be
sensitive to a no. ~ blasting caps. In one aspect of
the invention, there is provided a solid water-in-oil
emulsion explosive comprising a continuous emulsion
phase formed of a solid carbonaceous fuel which is
derived from an oleaginous liquid. The continuous
ln emulsion phase provides a self sustaining matrix.
The discontinuous emulsion phase of the explosive is
formed of an aqueous solution of a detonable oxidizer
salt~ The water content of the discontinuous aqueous
phase is present in the emulsion in a weight
concentration which is less than the weight
concentration of the carbonaceous fuel phase. The
explosive compositi.on further comprises a solid non-
hygroscopic oxidizer salt dispersed within the
emulsion in a solid ~ranular orm, Void cells are
dispersed within the emulsion in an amount to provide
a void cell volume in the emulsion of at least 5
volume percent, Preferably the void cell volume
expressed in terms of volume percent of the emulsion
is greater than the quantity of water in the emulsion
expressed in terms of weight percent of the emulsion.
In a further aspect of the invention there is
provided a water-in-oil emulsion explosive
composition comprising a continuous emulsion phase as
described previously and a discontinuous emulsion
phase formed of an aqueous solution of a detonable
oxidizer salt which includes ammonium nitrate as the
major component thereof. The composition includes
void cells to provide a void volume of at least 5
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volume percent as described previously and also
- includes ammonium perchlorate dispersed within the
emulsion in a solid granular form.
In a further aspect of the invention there is
provided a water-in-oil emulsion e~plosive comprising
a continuous emulsion phase as described previously
and a discontinuous emulsion phase formed of an
aqueous solution of a detonable oxidizer salt. The
composition includes void cells comprising a void
volume of at least 5 volume percent as described
above and includes a solid nonhygroscopic oxidizer
salt dispersed within the emulsion in a concentration
of at least 20 weight percent.
In another embodiment of the invention, there is
provided a solid water-in-oil emulsion explosive
which is in the form of unconsolidated particulate
material, but which is still cap sensitive. The
particulate solid emulsion explosive comprises a
discontinuous emulsion phase, formed as desaribed
previously, which is hydr,oph,o,b,"i,c and renders the
particulate explosive water repellant so that it can
be used Ln bore holes and the like which contain
water. In still a further embodiment of the
invention, there is provided a solid water-in-oil
emulsion explosive which is deformable under applied
stress while maintaining its integrity as a
continuous body. The deformable or flexible
explosive product, like the unconsolidated product,
may be employed in environments in which an explosive
is to be loaded into an irregularly shaped
containment zone.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIGURES 1 and 2 are graphs illustrating the
relationship between the void vol~lme and the
concentration of dispersed solid oxidizer salt on cap
sensitive and non cap sensitive emulsions prepared in
the course of experimental work relative to the
invention.
.
DESCRIPTION OF PREFERRED MODES
The present invention provides solid water-in-oil
emulsion explosives which can be rendered cap
sensitive through the proper selection and
distribution of detonable oxidizer salts in both the
continuous and discontinuous emulsion phases; and
selection of the proper relative proportions of solid
carbonaceous fuel in the continuous phase, water in
the discontinuous phase, and void cell volume in the
emulsion matrix.
Oxidizer salts which may be detonated and which
are useful in ~ormulating explosive compositions are
well known to those skilled in the art and are
disclosed in the aforementioned patents to Bluhm,
Wade and Breza. As a practical matter, it usually
will be preferred to employ ammonium nitrate as the
principle oxidiæer salt in aqueous solution in
explosive compositions formulated in accordance with
the present invention. However, other oxidizin~
salts such as those disclosed in the aorementioned
patents to Bluhm, Wade and Breza may also be
emplo~ed. Oxidizer salts which are useful in the
present invention may be generally characterized as
the alkali metal, ammonium, amine, or alkaline earth
metal salts of nitric acid or of perchloric acid. In
addition to the solution oxidizer salt in the
discontinuous a~ueous emulsion phase, the explosive
compositions of the present invention also include an
oxidizer salt dispersed within the emulsion in a
solid granular form. The solid dispersed oxidizer
salt preferably is nonhygroscopic; that îs, it will
not readily deliquesce in air having a humidity of
60-85% at standard temperature and pressure. Thus,
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11
ammonium perchlorate and sodium nitrate may be
employed to form the solid dispersed phase of
oxidizer salt, sodium perchlorate and ammonium
nitrate should not be 50 employed since they are
highly hygroscopic, It i5 preferred that at least a
portion of the solid dispersed oxidizer salt take the
form of ammonium perchlorate since it is a stronger
oxidizing agent than the non-hygroscopic alkali metal
nitrates~ Where sodium nitrate (or another alkali
metal nitrate) is employed in combination with
ammonium perchlorate to provide the solid dispersed
oxidizer salt, the total salt concentration in the
solid dispersed phase will be somewhat higher than if
ammonium perchlorate were employed alone. Also, the
relative concentration of ammonium perchlorate in the
solid emulsion will normally increase as the emulsion
density increases.
The continuous emulsion phase in the explosive
compositions of the present invention is a solid
carbonaceous fuel which is derived from an oleaginous
liquid which is initially emulsified with the aqueous
solution of oxidizer salt. While the change of the
continuous emulsion phase from the liquid to the
solid state may be by any suitable physical or
chemical mechanism which is compatible with the other
emulsion components, as a practical matter it will be
preferred to form the solid phase by a polymerization
mechanism, Suitable liquid systems which may be
polymerized to form a solid polymeric matrix are
described in greater detail hereinafter.
The final emulsion component essential to the
practice of the present invention is a void cell
dispersion which is present in the emulsion in an
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12
amount to provide a void volum0 of at least 5~. The
void volume may be provided by any suitable means
including particulate solids such as hollow, closed
cells which may be evacuated or gas filled, expanded,
yas-entraining aggregates such as perlite and
vermiculate, or occluded free gas such as air, carbon
dioxide, nitrogen, or hydrogen. Various commercially
available hollow closed-cell materials, which are
commonly referred to as microballoons, microbubbles,
1~ or microspheres, may be employed in the present
invention These may be formed of any suitable
materials such as glass, phenol-formaldehyde resins,
and polyvinylidene chloride (saran) resins. SUCh
hollow closed cell materials normally will be of an
average particle size, i.e., nominal diameter, of
less than 80 microns and a predominant particle size
distribution within the range of about 10-100
microrls. A typical average particle size is within
the range of 30~70 microns. Suitahle hollow closed-
cell products which may be employed in the present
invention are disclosed in the aforementioned patent
to Wade and include saran microspheres having a
diametmer of about 30 microns and a particle density
of about 0.032 g/cc, glass microbubbles having a
particle siæe distribution in the range of about 10-
160 microns and a nominal size within the range of
about 60-70 microns and a density in the range of
about 0.1-0.4 g/cc, and glass microbubbles having a
particle size within the range of about 44-175
microns and a bulk density within the range of 0.15-
0.4 g/cc. Other closed-cell materials include the
phenolformaldehyde microballoons and inorganic
microspheres as disclosed in the aforementioned Wade
patent.
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When plastic particulates, such as saran or
phenolformaldehyde micro balloons are added to
provide the void cell volume, it will be recognized
that these plastics will also serve as supplemental
fuels.
Occluded free gas can be incorporated into the
emulsion by any suitable physical or chemical
procedures. ThuS, gas can be entrained by stirring
or other mechanical agitation or by aeration
techniques involving the in situ injection of air (or
other gas) into the emulsion while in the liquid
state. Chemical procedures include the introduction
of organic or inorganic foaming agents which react or
decompose under the action of an appropriate stimulus
to produce suitable gases such as carbon dioxide,
nitrogen or hydroyen which are entrained within the
emulsion as the continuous phase is solidified.
Thus, suitable chemical foaming agents include
organic oaming agents such as dinitroso compounds or
diisocyanates which, upon heating, decompose to
release nitrogen dioxide and carbon dioxide,
respectively. Inorganic foaming ayents which may be
employed in order to produce occluded free yas within
the emulsion include carbonates, bicarbonates,
2S nitriles and peroxides. Where a chemical gas-
generating or foaming agent is employed, the amount
of chemical to be added to the emulsion can be
determined by measuring the density of the emulsion
without entrained gas, computing the gas generated by
a yiven quantity of foaming agent and then adding the
required amount of foaming agent.
Where the void volume is arrived at through the
use of solid agents such as microballoons,
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14
microspheres and the like, the void cell material may
be added before, during or after the formation of the
li~uid emulsion. Where chemical procedures are
employed, the foamin~ agent should be added during or
after formation of the liquid emulsion. Preferably
such agents are added after emulsification of the
aqueous phase and the oleaglnous phase. Where free
occluded gas is added by physical means such as gas
injection or agitation, this step should be carried
out subsequent to formation of the liquid emulsion.
The choice of materials employed to incorporate
the desired void cell volume into the explosive
composition of the present invention is determined to
some extent by the environment in which the explosive
lS is to be used. In a relatively high pressure
environment, because of hydraulic tamping or
otherwise, the void volume should be provided by
solid materials such as glass or saran
microbal].oons. In lower pressure environments, and
also where it may be desirable to form a flexible
explosive product as described in greater detail
hereinater, the void cell volume may be provided by
occluded ~ree gas.
The quantity o void cell volume introduced into
2~ the emulsion is at least 5 volume percent of the
solid emulsion product. Usually it will be preferred
to provide for a void cell volume of about 10 volume
percent or more. The desired void volume
incorpora~ed into the explosive compositions of the
present invention varies with the water content of
the discontinuous emulsion phase, the cell size of
the discontinuous emulsion phase, and the amount of
s~lid oxidizer salt dlsp~rs~d th ougho~t the
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continuous emulsion phase. In general, the void cell
volume should be increased as the water content of
the composition increases and as the solid oxidizer
salt content, particularly ammonium perchlorate,
decreases. Also, all other things being equal, the
void volume should be increased as the dispersed cell
size of the discontinuous aqueous emulsion phase
increases. As a practical matter, it will usually be
desirable to retain the latter at an average cell
size of about 10 microns or less. Further, it
usually will be preferred to provide sufficient void
volume within the explosive composition to provide a
final composition density within the range of about
0.9-1.2 g/cc.
The continuous carbonaceous fuel phase in the
solid emulsion of the present invention may be
present in an amount within the range of 5-30 weight
percent. The arnount of carbonaceous fuel phase in
the absence of a high explosive sensitizer need not
be limited as in the case of the solid emulsion
compositions disclosed in the aforementioned patent
to ~3reza. Accordin~ly, a preferred application oE
the present invention is in those explosive
compositions having a solid carbonaceous fuel phase
in a concentration greater than 10 weight percent.
~s a practical matter it will usually be preferred to
limit the continuous carbonaceous fuel phase to an
amount of about 20~ or less since greater amounts
normally will be unnecessary in terms of either
product integrity or fuel needs. The amount of
carbonaceous fuel present in the solid emulsion may
also be adjusted downward to compensate for
supplemental fuels which may be present. Such
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supplemental fuels may include plastic particulates,
as described previously, or supplemental fuels in the
aqueous phase or as provided by disbursed metallic
compounds, as described hereinafter.
The water content (in the discontinuous emulsion
phase) of the solid emulsion of the presen~ invention
is somewhat less than the water concentrations
generally called for in the aforementioned Wade and
Breza patents. Preferably, the water concentration
is less than the concentration of the solid
carbonaceous fuel in the continuous emulsion phase in
order to ensure blasting cap sensitivity. For this
same reason it is also preferred that the void cell
volume, expressed as volume percent of the emulsion,
be greater than the water concentration in the
emulsion expressed as a weiyht percent.
The total amount of oxidizer salt (in aqueous
solution and in solid dispersion) employed in the
present invention normally will fall within the range
of 60-90 wei~ht percent. Preferably inorganic
oxidizer salts are employed in both the aqueous
discontinuous phase and in the solid dispersed
phase. The discontinuous emulsion phase may take the
form of an aqueous solution of an inorganic oxidizer
salt selected from the group consisting of alkali
metal, ammoniuml and alkaline-earth metal nitrates
and alkali metal, ammonium, and alkaline-earth metal
perchlorates and mixtures thereof. As noted
previously, it will normally be preferred to employ,
as the discontinuous emulsion phase, an aqueous
solution of an oxidizer salt selected from the group
consisting of ammonium nitrate, sodium nitrates and
mixtures thereof. An especially suitable
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discontinuous phase comprises an aqueous solution of
a mixture of ammonium nitrate and sodium nitrate,
with ammonium nitrate present as the principal
oxidizer component. other water soluble additives
may also be incorporated into the aqueous solution of
oxidizer salt. Examples of such additives include
alcohols, urea, formamides and carbohydrates, such as
sucrose, glucose and fructose, which will function as
supplemental fuels.
While, as noted hereinafter, hygroscopic salts
can in some cases be employed as the dispersed solid
oxidizer salt, it usually will be desirable to employ
a non-hygroscopic salt in this capacity and to employ
a salt which is a strong oxidizing agent in
comparison with the oxidizer salt content in the
aqueous emulsion phase. Preferably the dispersed
oxidizer salt is ammonium perchlorate.
The amount of oxidizer salt dispersed within the
solid emulsion in a solid granular form will vary in
a somewhat inverse relationship with the amount of
oxidizer salt in aqueous solution within the
discontinuous emulsion phase. The amount of solid
dispersed oxidizer salt necessary to provide cap
sensitivity also varies in a somewhat inverse
relationship with respect to the void cell volume of
the solid emulsion. Usually it will be ureferred to
employ solid oxidizer salt dispersed throughout the
emulsion in a concentration of at least 20 weight
percent.
The water-in-oil explosive emulsions of the
present invention may be formulated to provide rigid
nonplastic or nonyielding cast products as in the
case of the explosives disclosed in the
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aforementioned patent to Breza. Alternative product
forms may also be provided in accordance with the
present invention. Thus, in a further embodiment of
the invention, there is provided an explosive product
which, while sufficiently firm to be self-sustaining
is also deformable under an applied stress without
disruption of its integrity. Deformable products of
this nature may be advantageously employed in
circumstances in which they are to be loaded into an
irregularly shaped containment. For example, such
products may be employed in seismic prospecting where
they are loaded into irregularly shaped shot holes.
Flexibility can be imparted to the product by
increasing the occluded gas volume in relationship to
the quantity of the solid carbonaceous fuel providing
the continuous emulsion phase. As the ratio of
occluded yas to the polymerized fuel phase increases,
the avera~e thickness of the polymeric material
between the occluded gas cells decreases resulting in
a less ric~id structure, The flexibilit~ of the
explosive product can also be increased by the
incorporation of suitable plasticizers into the
polymeric uel phase~
In a further embodiment of the invention there is
provided a granular explosive product which, like the
inteyral bu~ flexible product described above, can be
used in environments in which irregular shapes are
called for. This product, which may be prepared as
described in greater detail hereinafter, may be
.
characterized as having an average particle size
within the range of 0~1-5 millimeters. The
granulated explosive product, like the integral
product of the present invention can be
.. : .
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19
advantageously used in wet conditions. In this
regard, the product r though granular in nature,
retains its water repellent characteristics because
of the oleophilic nature of the granules resulting
from the hydrophobic continuous emulsion phase.
As noted previously, it will normally be
preferred, as a practical matter, to rorm the solid
carbonaceous fuel phase by polymerization of the
oleagineous liquid employed to form the liquid
emulsion phase, While the polymeric fuel phase may
be a monopolymer, it conveniently can take the form
of a copolymer produced by cross-linking of an
ethylenically unsaturated homopolymer or copol~mer,
pre0rred cross-linking agents are styrene and other
lS vinyl aromatics either alone or mixed with other
ethylenically unsaturated monomers. In one
embodiment of the invention, the continuous
polymerizable fuel phase comprises an unsaturated
polyester~ Unsaturated polyester resins can be
2~ produced hy reacting a polyhydric carboxylic acid and
a polyhydric alcohol ~or the anhydride of either or
both of the foregoing) at the esterification
temperatures, generally at least lSOC, until the
acid value and the hydroxyl value of the reaction
mixture has been reduced to values corresponding to a
mean weight average molecular weight with the range
of about 1,000 - 10,000. The polyester can be one Or
more , ~ -ethylenically unsaturated polyesters of an
, ~-ethylenically unsaturated carboxylic acid and/or
anhydride thereof copolymerized with a polyhydric
alcohol and/or alkylene oxide.
preferably the polyhydric alcohols utilized are
dihydric alcohols such as ethylene glycol; diethylene
' ~
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glycol; 1,2-propylene glycol; 1,2- or 1,3-dipropylene
glycol; 1,3-propylene glycol; 1,3-butylene glycol;
1,2-butylene glycol; neopentyl glycol; 1,3-
pentanediol; and 1,5-pentanediol. Polyhydric
alcohols of higher order such as trimethylol propane
and pentaerythritol can be used in minor amounts up
to 5% by weight.
The carboxylic acids utilized to produce the
unsaturated polyester resin can be unsaturated or
saturated. Suitable unsaturated carboxylic acids for
utilization in the present invention have from 3 to
36 and preferably about 4 to about 8 carbon atoms.
Examples include maleic acid, fumaric acid, itaconic
acid and their anhydrides. Saturated acids which can
be utilized in the present invention include oxalic
acid, malonic acid, adipic acid, succinic acid, and
glutaric acid. Halogenated acids, such as
tetrachlorophtalic acid, and tetrabromophtalic acid
can also be employed.
A number of unsaturated polyester resins can be
manufactured from known components and methods.
~xamples o unsaturated polyester resins suitable for
use in the present invention are set orth below in
Table I.
TABLE I
Suitable Resins by Parts by Weight
Component Resin A Resin B Resin C
maleic anhydride 1. - 23.1
maleic acid - 1.0
phthalic anhydride 1. - 34.9
propylene glycol copolymers 1.8 2.2 37.7
isophtalic acid - 1.0
toluene diisocyanate -- - 4.3
13~ 39~ (
21
It is preferred that the polyester resins include
dicarboxylic acids as the major acid component. The
, molar ratio of unsaturated acids to saturated acids
should be at least 1:5 in order to provide sufficient
unsaturation for reaction with a copol~nerizable
solvent.
The unsaturated polyester resin is preferably
carried within a monomer solvent to provide the
oleaginous liquid from which the continuous emulsion
phase is derived. suitable monomer solvents include
vinyl toluene, alpha-methyl styrene, acrylonitrile,
ethylacrylate, methacrylate, methylmethacrylate,
vinyl acetate, trialkylcyanuarate, diallylphthalate,
ethylvinyl ether, and mixtures thereof. St~rene is a
preferred solvent due to its cost, availability and
reactivity.
It will be recognized that resins other than
polyesters of the type described above may be
utilized in the invention. For example,
methylacrylates, acetates, butadienes, and acrylate
nitriles ma~ be employed to orm the continuous
emulsion phase. For the purpose o describin~
specific embofliments o the invention, reference will
be made to polyester resins.
The liquid continuous phase, in addition to the
polymerizable materials and oxidizer salts and void
cell materials described previously, may also include
other nonpolymerizable materials such as
plasticizers, emulsifiers, organic die stuffs,
auxiliary fuels and, in some cases, compatible high
explosives. A plasticizer may be incorporated into
the continuous phase in order to increase the
flexibiIity of the final product, as noted
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22
previously. Any suitable plasticizer which is
compatible with the particular resin selected for the
polymerizable component can be used. Plasticizers
and their uses are well known to those skilled in the
art and for a further description thereof reference
is made to Encyclopedia of Chemical Technolo~, Kirk-
othmar, 3rd Edition 1982, John Wiley & Sons, Vol. 18,
pp. 111-183.
Die stuffs which may be used include inorganic
pigments such as titanium dioxide or organic die
stuffs such as phthalocycanines. Die stuffs are
generally incorporated into explosive compositions
for aesthetic rather than functional purposes.
Preferably, emulsifiers and plasticizers are
added to the polymerizable continuous phase prior to
the formation of the liquid emulsion. Fillers and
or~anic die stufs preferably are added after or
durin~ ormation of the liquid emulsion but may be
added to the continuous phase prior to admixture with
the discontinuous phase.
The unsat-lrated resin, e.g. a polyester resin,
cross-links with the monomer~ e.(~. styrene, to
provide the final solid emulsion phase which is a
copolymer of the resin and the monomer. Normally, an
inhibitor is added to the polymeric fuel phase to
prevent the cross-linkiny reaction prior to the
desired time. Any inhibitor known in the polymer
art, which is compatible with the other emulsion
components can be used. Suitable inhibitors include
the quinones and in particular methyl tertiarybutyl
hydroquinone and carus hydroquinone. Another
suitable inhibitor is butylated hydroxytoluene
(BHT). Normally the inhibitors will be employed in
concentrations up to about 2000 ppm.
13~8~
23
In most cases, an initiator will be added to
begin the cross-linking of the polymerizable fuel
phase. SUCh initiators are well known to those
skilled in the art. When a polyester resin is used,
the initiator is preferably one or more organic
peroxides. Initiators which can be used to initiate
cross-linking of polyester resin include
hydroperoxides, diacylperoxides, ketoperoxides or
organic peracids. Peroxides which are soluble in the
polymerizable fuel phase are preferred.
Optionally, an accelerator can be used to
accelerate the decomposition of the initiator system,
thus permitting shorter curing times and/or lower
curing temperatures. The accelerator is selected
lS based upon the type of initiator utilized. Metal
salts such as colbalt naphthenate are suitable
accelerators ~or hydroperoxides, ketoperoxides and
peracids. other suitable accelerators are salts and
soaps o~ metal which have a valence number ~reater
than one. The most commonly utilized accelerators are
colbalt and vanadium salts and soaps,
The time necessary to complete the cross-linking
reaction depends upon a number of factors but is
primarily determined by the type and relative
quantities of the initiator, accelerator and
inhibitor and the processing temperature. Many
colbalt accelerated systems can be superactivated by
the addition of selected amines. For example, a
superactivated system includes methyl ethyl
ketoperoxide, colbalt naphthenate and
dimethylanaline. It is preferred in choosing an
initiator system, whether it be the initiator alone
or in combination with an accelerator and an
13~9~
,. ~. ~,
24
inhibitor, that the decomposition temperature of the
initiation system be lower than the processing
temperature. The initiators and accelerators may be
added to the polymerizable liquid in any suitable
amounts. Preferred ranges oE initiators and
accelerators expressed as weight percent of the
polymerizable fuel phase are: for peroxides, about
0.5~ - 5.0%; for metal salt accelerators about 0.001
- 0.10~ based upon the equivalent amount of metal
concentration relative to the resin content; and for
amine accelerators, about 0.001% to 1.0%.
In some cases, the explosive compositions of the
present invention include an emulsifier which
promotes the formation of a water-in-oil emulsion
between the continuous polymeric fuel phase and the
discontinuous aqueous oxidizer phase. SUCh
emulsifiers may be of any suitable type and include
benzyldimethylamine, trimethylhexamethylenediamine,
isophorenediamine, mor~holine and mixtures thereof,
The amount of emulsiier utilized is de~endent upon
the particular emulsiier selected and the
composition o~ the uel phase and oxidizer phase.
Normally the emulsifier is added to the polymeric
fuel phase in an ~nount within the ran~e of 0.1-2
weight percent.
The solid oxidizer salt can be dispersed
throughout the emulsion by adding it to the liquid
water-in-oil emulsion or by dispersing it within the
oleagineous liquid prior to formation of the water-
in-oil emulsion. The preferred mode usually will be
to add the oxidizer salt to the formed emulsion.
Where the oxidizer salt is added directly to the
emulsion (or to the oil phase prior to
~ ( ~3~9~ t
emulsification) it is preferred that a non-
hygroscopic salt be employed in order to avoid or at
least reduce combination of the salt with water from
the aqueous emulsion phase~
An alternative procedure for incorporating the
solid oxidizer salt into the emulsion is to dissolve
the salt in the a~ueous solution at an elevated
temperature to provide a salt concentration in excess
o~ the saturation point at a lower temperature to
which the explosive composition is then cooled. In
this case, hygroscopic as well as non-hygroscopic
salts may be employed. For example, ammonium nitrate
is soluble in water to a concentration of &8 weight
percent at 90, 80 weight percent at 60C and 70
lS weight percent at 30C. ThUS, a saturated aqueous
solution of ammonium nitrate at 90C may be
emulsified with the oleagineous liquid from which the
carbonaceous fuel phase is derived. AS the emulsion
cools and prior to solidification of the oil phase,
some Oe the oxidizer salt will precipitate fr~l the
a~ueous phase. After the continuous phase has been
cured to eorm the solid emulsion matrix, further
cooling will cause additional oxidizer salt to
precipitate from solution at the interface between
the dispersed emulsion cells and the continuous
emulsion matrix.
The solid emulsion explosive products of the
present invention may incorporate high explosives
similarly as in the case of the solid emulsions
disclosed in the aforementioned patent to.Breza.
Such explosives include pentaeryphritol tetranitrate
tPETN), cyclotrimethylenetrinitramine (RDX) and
cyclotetramethylenetetranitramine (HMX). Such high
: . .
. ' ' ' ' , ' ' '
:
~,;, 130~89~ ~`
explosives, ~here employed, will normally be
incorporated into the explosive product in
concentrations of about 10-40 weight percent.
However, a preferred application of the present
invention is in the formulation of explosive products
which are substantially free of such cap-sensitive
high explosives. SUch explosive free products are
preferred from the standpoint of safety in processing
and handling and because of economic
considerations.
In one set of laboratory experiments carried out
respecting the invention, cap-sensitive solid
emulsion explosive compositions were formulated in
which the void cell volume was provided by the
occluded free gas generated ln situ by a foaming
agent. In each of these procedures, the continuous
carbonaceous fuel phase was derived from a
commercially available polyester and styrene monomer
mixture available fro~ the Ashland Chemical Company,
Polyester Division, Columbus, Ohio under the
trademark AROPOL WEP 662P. The following examples
illustrate this laboratory work.
Example 1
A first preblend was prepared by adding cobalt
naphtanate, cobalt, dimethylaniline and tetrahydro-
1,4-oxazine in respective amounts of 0.5, 6, 0.5, and
1 weight percent to the AROPOL WEP 662P resin
mixture. These additives were mixed into the resin
which then was heated to a temperature within the
range of 80-85C to provide a first preblend of
oleaginous liquid. A second preblend of 90 parts by
weight of an inorganic oxidizer solution comprising
13()~1~39~
.... ~:., (
27
70 parts by weight ammonium nitrate, 10 parts by
weight sodium nitrate, and 10 parts by weight water
was heated to 90C until the ammonium nitrate and
sodium nitrate dissol~ed. The heated oxidiæer
solution was then gradually added to 15 parts by
weight of the heated resin blend in a double blade
Waring blender. A water-in-oil emulsion formed
easily and the emulsion matrix was then transferred
to a conventional cake mixer where N,N-dinitroso
pentaminethylene tetramine (an organic foaming agent)
was added in the amount of 0.14 weight percent (based
upon the weight of the total emulsion. Thereafter,
2~ by weight based on the resin of an initiator
available from Lucidol Pennwalt Company under the
trademark Lupersol DDM-9 (a mixture of 8.8~
methylethylketone peroxide in a plasticizer) was
added and the emulsion was thoroughly admixed.
The prepared emulsion was poured into cylindrical
plastic molds being 2.5 inches (6.4 cm) in diameter
2~ by 6 inches (15.2 cm) in length. The emulsion
explosive contained in the molds was heated on a
steam bath for 10 to lS minutes. This heating
accelerated the curing rate at which the continuous
polymeric uel phase solidified. The dispersion was
removed from the molds. The cooled dispersion was a
solid, cross-linked polyester-styrene copolymer
containing inorganic oxidizer droplets and gas
bubbles uniformly distributed throughout the solid
water-in~oil dispersion structure. The product had a
density of 1.1 grams/cc. The molded unconfined
sample weighing approximately 500 grams was detonated
with a No. 8 electric blastiny cap.
'
:.
13~ 8~
( f :`
28
Several more solid emulsion explosives were made
according to the above procedure and molded into
different sizes. A cylindrical cartridge 1.125
inches in diameter by 6 inches in length having a
density of 1.1 grams/cc was detonated by a No. 8
electric blasting cap when unconfined. A sample
molded into a cylinder 2.5 inches in diameter by 12
inches in length having a density of 1.1 grams/cc was
detonated with a No. 8 cap at a velocity of 4200
m/sec. A cartridge 2.5 inches in diameter by 6
inches in length with a density of 1.1 grams/cc, upon
detonation by a No. 8 cap, impressed a lead bloc~ by
44%.
Example 2
The procedure and formulation of Example 1 was
repeated with the exception that the organic foaming
agent was replaced by an inorganic foaming agent.
Sodium nitrite in the amount of 0.14 weight percent
was added to the liquid emulsion. The product was
molded into cylinders 2.5 inches in diameter by 6
inches in length haviny a density of about 1.1
grams/cc. The cast dispersion explosive detonated
completely Wittl a No. ~ blastinc~ cap,
Example 3
Fifteen parts by weight of the liquid resin
mixture AROPOL WEP 662P was heated to a temperature
of 80 to 85C. No accelerators or emulsifiers were
added to the product prepared in this example. A
second preblend of 90 parts by weight of an oxidizer
solution comprising of 70 parts ammonium nitrate, 10
parts sodium nitrate, and 10 parts water was heated
to about 90C until the ammonium nitrate and sodium
nitrate dissolved. The heated oxidizer solution was
` (" ~3V089
29
gradually added to the heated resin in a double blade
Waring blender. The water-in-oil emulsion formed
easily. The emulsion matrix was then transferred to
a conventional cake mixer. Next, 0.14~ sodium
bicarbonate based upon the weight of the emulsion
matrix was added as an inorganic foaming agent.
Immediately after addition of the foaming agent, 2
weight ~ercent of the initiator Lupersol DDM-9 was
added to the emulsion matrix. The product was placed
in a mold 2 1/2 inches in diameter by 10 inches in
length and heated above a steam bath for about 10 to
about 15 minutes. The cooled solid emulsion
explosive was detonated by a No. 8 cap.
Example 4
The procedure and formulation of Example 1 was
repeated with the exception of the molding of the
product. In this example, while the solid emulsion
product was warm but only ~artially cross-linked, the
~roduc~ was mechanically crumbled into small granules
and rapidly cured on a steam bath. While the
particle size distribution varied over a wide range,
the predominant particle size was about 2-5
millimeters. The resulting granular product was
packed into plastic containers 2~2 inches in diameter
and 6 inches long. One cylinder was loaded to a bulk
density of 0.9 gm/cc and the other was more densely
packed to provide a bulk density of 1.1 gm/cc. Both
products were detonated with a number 8 cap leaving
yood impressions on iron witness plates.
Example 5
In this example, the oleaginous fuel phase was
prepared by mixing 107 parts by weight of the resin
mixture AP~OPOL WEP 662P with 2 parts of morpholine.
The aqueous oxidizer phase comprised 250 parts by
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weight ammonium nitrate, 72 parts by weight sodium
nitrate, and 72 parts by weight water. The two
phases were mixed together and emulsified. After
formation of the emulsion, 350 parts by weiyht of
granular ammonium perchlorate and 2 parts by weight
of methylethylketone peroxide were added to the
emulsion. An organic foaming agent, N,N dinitroso
pentaminethylene tetramine was added to a plurality
of samples in amounts ranging from about 0.1-0.2
weight percent to fonn products having various
occluded gas volumes. The emulsions were then
solidified to produce solid emulsions having
densities ~arying from about 1.0-1.2 gm/cc. Those
products having densities within the range of about
1.0 gm~cc to about 1.2 gm/cc were sensitive to a
number 8 electric blasting cap. In addition these
formulations provided products which were deformable
under moderate stress.
In further experimental work relative to the
invention, a larye number o~ solid explosive
cartridges were formulated using three liquid
emulsion systems. In each liquid emulsion, the
oleaginous liquid was a 98 weight percent polyester
and styrene mixture containing 2 weight percent
morpholine as an emulsifying agent. This oleaginous
liquid wa~s mixed with aqueous solutions of ammonium
nitrate and sodium nitrate to form liquid emulsion
systems identified herein as emulsions I, II and
III. The oil and water phases were heated to
temperatures of about 60 and 80C, respectively, and
then stirred for a suitable period of time, e.g. 1-3
minutes, until relatively homogeneous emulsions were
formed. Emulsion I contained 15~ water 15% sodium
~l30U891 ('
nitrate 50% ammonium nitrate and 20% of the liquid
resin mixture. Emulsion II contained 25~ water, 40%
ammonium nitrate 15~ sodium nitrate, and 20% liquid
resin. Emulsion III contained 15.5% water, 51%
ammonium nitrate, 15.5% sodium nitrate, and 18~
resin. All concentrations given herein are expressed
in terms of weight percent unless designated
otherwise.
After formation of the emulsion, additional
inyredients were incorporated. In most cases, the
added ingredients included saran microballoons and
ammonium perchlorate crystals. After addition of the
microballoons and crystalline ammonium perchlorate,
the liquid emulsion was thoroughly mixed to disperse
the solid additives throughout the emulsion system.
Thereafter methylethylketone peroxide was added in an
amount of about 0.2 - 0.3 weight percent. The
emulsion was again stirred to distribute the initator
throughout the syst~m and then poured into molds to
form cartridges having a diameter of about 2 5/8
inches and a length of 4 1/4 inches. The cartridges
were cured at a temperature of about 90C for about
S-10 minutes and then allowed to cool. The
cartridges were then removed from their molds and
tested with number 8 electric blasting caps.
The results of this set of experiments are
tabulated in Tables II through V. In the tables the
component concentrations are given in weight percents
unless indicated otherwise and the detonation results
are designated as D for complete detonation, P for
partial detonation and F for failure to detonate.
The solid emulsion explosives derived from liquid
Emulsion I are set forth in Tables II and III, and
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.
.
' ~ ' ' '
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32
those derived from liquid emulsions II and III are
set forth in Tables IV and Table V, respectively.
From an examination of the experimental data, it
will be recognized that castings formed from emulsion
II, which resulted in a final formulation having a
water content substantially greater than the resin
content, consistently failed to detonate. ThiS was
true even in those cases in which void-cell volumes
and solid ammonium perchlorate concentrations were
sufficient to cause cap sensitivity of other
formulations having somewhat lower water contents.
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~30~89~
37
The results of the detonation test for the solid
emulsion explosives derived from emulsions I (Tables
II and III) and III (Table V) are set forth in
FIGURES 1 and 2, respectively. The figures are data
point representations of detonation, ~, partial
detonation, ~, and failure to detonate, o, plotted as
a function of the void-cell volume, V, on the
ordinate versus the ammonium perchlorate
concentration, C, on the abscissa. From an
examination of the experimental results plotted in
FIGURES 1 and 2 r it can be seen that there i5 a
region of detonability, as indicated, for example, by
broken line 2 drawn through the partial detonation
points of FIG~RE 1, which is dependent upon void cell
volume and ammonium perchlorate concentration. Where
a substantial quantity of ammonium perchlorate is
present, and so long as the water content is
maintained below the resin content, at least partial
detonation can be achieved with only modest
quantities of the saran microballoon. ThiS is shown,
~or example, b~ test 13 (Table III) and test 28
(Table ~). on the other hand, where ammonium
perchlorate was absent, partial detonation was not
achieved for void-cell volumes ranging rom about 19
percent (test 27) to almost 41 percent (test 5)O In
these casesr detonation was not achieved even thouyh
the water content was less than the resin content and
also less than the void cell content expressed as a
volume percent. The water content was somewhat more
than would normally be considered acceptable. In
this regard, it usually will be preferred to limit
the water content of the solid emulsion explosive to
a value oE about 12 weiyht percent or less.
, :
~ ~3(~89J~
38
It will be noted that in every case in which
complete detonation was achieved, the resin content
was greater than 10% and the water content was less
than the resin content, albeit in some cases by only
a relatively small increment. Also, the void cell
content, expressed as volume percent, was in every
case greater than the weight percent of water in the
solid emulsion.
Further experimental work was carried out
relative to the detonability of additional solid
explosives derived from the emulsions identified
previously as emulsions I, II and III. Thése tests
demonstrated the effect of density (as determined by
void cell content) and showed that detonability could
be achieved for systems having very low resin
concentrations so long as the water content was
maintained at a value below the resin content. The
results of this experimental work are set forth in
Table VI.
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In this set of tests, the explosive compositions were
formulated in accordance with the procedure described
previously except that the explosive compositions
were tested as cartridges 2 1/2 inches in diameter
and 5 inches long. For the experimental work set
forth in Table VI tests 32 through 36 were derived
from emulsion number I, test 37 from emulsion II, and
tests 38 and 39 from emulsion III. The component
concentrations and resul~cs are set forth similarly as
described before. In addition, the density of the
final product is also set forth.
As indicated by Example 3, described previously,
the liquid water-in-oil emulsion from which the solid
product is derived can be prepared without the use of
lS a separate emulsifying agent. This is advantageous
from the standpoint of simplifying the manufacturiny
procedure and also in terms of economics. The liquid
resin system employing in this embodiment of the
invention i5 a polyester and styrene monomer mixture
containing polyester in an amount within the range of
35-45 wei~ht percent and styrene in an amount within
the range of 55~65 weight percent. The polyester
resin should be free of acid groups or have an acid
content of 2.25 weight percent or less of the
polyester. The polyester in the mixture should have
an average mean molecular weight within the range of
1,000-10,000, and a viscosity at room temperature,
about 20-25C, within the range of 125-135
centipoises. The styrene polyester mixture described
above will readily emulsify with the aqueous oxidizer
solution when mixed therewith and agitated at a
temperature within the range of about 60-90C. The
previously described resin mixture available under
(i ~3~89~ ~-
41
the trademark AROPOL WEP, 662P is suitable for
formulating liquid emulsions without the use of
emulsifying agents.
As indicated by the previous Example 4, the solid
emulsion explosives of the present invention, will
retain their cap sensitivity, even though made in a
particulate, unconsolidated form. In a further
embodiment of the invention, explosive compositions
of this character are made by forming the liquid
l~ emulsion from the aqueous solution of oxidizer salt
and polymerizable oleaginous liqulid and subsequently
transforming the emulsion into discrete granules.
Preferably, the granularization step is carried out
after partial polymerization (cross-linking) of the
continuous emulsion phase. ~fter transforming the
material into the granular form, the polymerization
reaction is carried to completion to provide the
granular product. The emulsion may be granularized
by a prilling procedure in which the emulsion is
sprayed from a nozzle through a suitablP medium, e.g.
counter-current flc~wing air, or it can be
mechanically granularized, such as by extruding
through a screen, grinding (of the partially cross-
linked product), or by any other suitable
technique.
Having described specific embodiments of the
present invention, it will be understood that certain
modifications thereof may be suggested to those
skilled in the art and it is intended to cov~r all
such modifications as fall within the scope of the
appended claims.
