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cans deterrence
SEEM till llUUruv
2,499,919
Patented Oct. 22.1%46
UNITED STATES ‘PATENT’ OFFICE
2,409,919
LOW DENSITY GRANULAR OR POWDER
EXPLOSIVES AND THEIR MANUFAC
John Whetstone, West Kilbride, Scotland, assign
or to imperial Chemical Industries Limited, a
corporation of Great Britain
No Drawing. Application September V19, 1942, Se
rial N0. 458,993. In Great Britain September
15, 1941
'9 Claims.
2
1
velocity of ‘detonation and their negative oxygen
balance are usually higher than is desirable for
The present invention relates to granular det
onating explosive compositions of the kind in
which the granules individually comprise am
monium nitrate and aneasily fusible .organic ex
commercial blasting purposes.
:The fusion temperature of ammonium nitrate
plosive compound in a state of intimate admix 5 is too high to enable it to be safely melted With
fusible organic explosive compounds. but it can
ture. The invention relates more particularly to
be reduced by the __inclusion of additional materi
the provision of new or improved granular ex
als such as salts having Water of crystallisation,
plosive compositions as aforesaid that have low
and by various salts and organic materials that
density characteristics, and to an improved proc
ess for the production of low density granular ex 10 .form ‘eutectic mixtures with it. In the manufac
.ture of mst?XpMsWe charges. such materials,
plosives suitable ‘for commercial blasting purposes.
usually pf an oxidising or ,reducinacillaracter,
Blasting explosive powders containing am
.h e been included .in molten compositions com
monium nitrate ‘and organic explosive compounds
ins ammonium nitrate and organic explosive
are :usually manufactured by grinding the solid
. pounds. with the object of minimising the
ammonium nitrate ‘and the organic explosive to
content of the organic explcsire compound re
gethenieven when, as in the case of fusible aro
quired to yield a composition that can conven
matic nitro-compounds such as TNT, the or
ientlylbe loaded. These compositions containing
ganic explosive compound is easily fusible. Any
additional ingredients of the composition are in
ammonium nitrate in ya more, or less completely
operation. Prolonged grinding is required inor
that the Jigui?ed inorganic salts and the molten
der'to produce an explosive satisfactorily sensitive
to initiation by a. commercial ,detonator. Granu
‘organic explosive constitute two immiscible liq
uids that can. onlvhecoarscly dispersed byagita
mom-9f thelngeltso that the resulting mixture
troduced during or subsequent ‘to the grinding 20 fused condition, however, suffer from the defect
lated compositions made from the resulting pow
clers ordinarily show a bulk density of about-0.9
to [1.15 grams, per cubic'centimetre when ‘car
25 sceliegateslrapidly hetero it solidi?es. and the re
sulting cast explosive charges are of lower sen
Sitiveness toinitiation than those made by coat
ing the solid oxidising salts with molten organic
explosive and ,mayfail to propagate their detona
.tridged.underlarpressure of 75 lbsaper square inch.
Low density ammonium nitrate blasting ex
plosive powdersof the kind in which the low-den
.
sity ,is not occasioned by the useof low density 30 tionpmnerly1111 the preparation of cast explosive charges
vegetable tissue, von- the contrary, are made by
lightly mixing ammonium nitrate crystal aggre
such as arellsedfor ?lling containers, for example
shells or other projectiles, grenades, ,mines and
gates .of vlow density with the solid oxidisable in
the'likchithas been .proposedto emulsify with the
gredient's. The low density ammonium nitrate
crystal aggregates facilitate the attainment of 35 aid of an?mulsifyingagent a highlyexplosive or
a composition initially sensitive to detonation, but
ganic compound .or compounds in a .melt of ‘an
must not be .brokendown, and low density blast
oxidising salt or salts, for instance ammonium
ing powders of this kind frequently suffer from
the defect that the granules constituting them
nitrate with or without metallic nitrates.
Ac
cordingto this proposal, the emulsifying agent
are .so .fragile that they disintegrate .very easily v40 maybe a, colloidal ‘substance soluble or swellable
Whenjostled, egg. .in transport, or on storage, and
by water .a-ndcapable of increasing the viscosity
thereby .become denser and less sensitive.
of the melt, andthe-formation of the saline melt
Military explosives containing ‘ammonium ni
into which the highexplosive organic'compound,
trate and aromatic nitro-compoundscan be made
instance TNT,‘ is incorporated, may be as
bycoating solid ammonium nitrate with the fused 45 for
sisted by ‘the ‘presence of ahydrated salt, an ‘or
ganic' amidegor a small ‘proportion of water, "the
tions so '.{obtained being compressed; or cast, or
aromaticv nitro-compound,-the explosive composi
cast and compressed into ,the ammunition in
which they are to be used. They are, however,
seldom sensitive to initiation by ordinary det
onators, and in reflecting their detonation it is
necessary to employ an intermediate primer or
booster whereby the detonating impulse trans
mitted from thedetonatoris enhanced. The den
resulting ‘emulsi?ed explosives jbeing character
ised by improved sensitiveness to detonation and
50
other advantages as compared with similar com;
positions made ‘.by.a fusion process or partial fu
siOn .process without the use of the emulsifying
agent. ,one vof these advantages is that composi
tions of sulfl?cientjfluidity for loading into am
sity'of-such charges usua1ly exceeds 1.4 and their 55 munition may be obtained at safe workingtem~
ii
~ w
e
.
2,409,919
3
4
peratures, e. g. 80 to 110° C., with a reduced pro
spar, dolomite, or anhydrite, or oxidisable ingre
dients such as metal powders may thus be intro
duced. Fusible or soluble materials, however, can
often be employed provided they do not have the
portion of the fusible high explosive compound.
Massive cast explosive charges produced ac
cording to the method of the aforementioned pro
posal, however, are insufficiently sensitive to be
initiated by an ordinary commercial detonator.
and are unsuitable for commercial blasting pur
poses.
It is an object of the invention to provide
property of readily forming hydrates with water
of crystallisation and are not unduly hygroscopic.
Examples of salts that may be employed in this
way include sodium chloride and sodium nitrate.
Ingredients commonly used in blasting explosive
granular low density ammonium nitrate explo l0 compositions, for instance carbonaceous ingre
sives by a fusion process employing molten fusible
dients, especially those of low density, cooling or
organic explosive compounds, which will be of
?ame-quenching agents, waterproo?ng agents;
suitably high sensitiveness to initiation for com
oxidising salts; noncarbonaceous oxidisable in
mercial blasting purposes, but which will be free
gredients and so forth may also, if desired, be used
from the aforesaid defects of the hitherto known 15 in admixture with the granules obtained after the
low density explosives made from ammonium ni~
emulsion has been congealed and granulated, ad
trate and solid organic explosives or other oxil " ‘van'tageously after they have been dried. In some
disable ingredient of ordinary density.
cases they may be applied as surface coats to the
According to the present invention, in the man
dried granules. It will be understood that the
ufacture of detonating exposives suitable for com 20 composition of the ?nal explosive should be so
mercial blasting purposes, a molten easily fusible
adjusted that it has a desirable oxygen balance,
organic explosive is emulsi?ed, with the assist
taking into account any wrapping or packing ma
ance of an emulsifying agent, in an aqueous me
terial that will be included in the blasting charge.
dium that comprises a saturated solution of am
It is noteworthy that if su?icient water were in
monium nitrate carrying solid ammonium nitrate 25 cluded in the composition to dissolve the whole
in suspension and free from readily hydratable
of the ammonium nitrate at a temperature suit
salts, this medium being adapted to yield a pour
able for emulsi?cation, the emulsion would not
able emulsion at the emulsi?cation temperature;
congeal satisfactorily when subsequently cooled,
the resulting aqueous emulsion is congealed into
so that the granulation of the product would be
solid form and converted into granules, and the 30 impracticable. Although the ?uidity of the am
resulting granules are subsequently dried at a
monium nitrate and of the emulsion as a whole
temperature insu?icient to cause them to soften.
at the emulsi?cation temperature is somewhat
According to another feature of the invention,
in?uenced by the nature and amount of the other
the grist of the granule is made more uniform
non-aqueous ingredient or ingredients, we have
by screening them, and according to a further 35 found that in the case of a blasting explosive
feature of the invention at least the ?ne mate
composition consisting of trinitrotoluene, am
rial rejected as a result of the screening operation
monium nitrate and an emulsifying agent about
is remelted to form a portion of the pourable
3 to 8 per cent. water should be present, so that
emulsion that is congealed and converted into
about 30 to 60 per cent. of the ammonium nitrate
granules in a subsequent preparation.
40 remains undissolved at the emulsi?cation tem
In putting the invention into e?ect, there may
perature.
.
advantageously be employed solid high explosive
The granulation may be carried out by pouring
compounds melting at temperatures not appre
the emulsion into the form of an extended cake
ciably in excess of the boiling point of water, but
or the like, and breaking up the latter mechani
which will remain solid under ordinary hot stor 45 cally into granules when it has congealed. Any
age conditions, for instance trinitrotoluene, tet
particles that are too large or too small may be
ranitroanisol and dinitrobenzene; but there may
screened off before or after the granules have
also be employed mixtures containing high ex
been dried off.
plosives of higher melting points, for example,
The waste from the screening operation may be
hexanitrodiphenylamine, pentaerythrite tetrani 50 utilised in forming another batch of emulsion,
trate, polynitronaphthalenes or the like, with eas
advantageously with the addition of a little water,
ily fusible or even liquid explosive compositions
since a certain amount of drying may have taken
in suitable proportions to yield mixtures that
place by the time the congealed granules have
will be solid at hot storage temperatures but liqui
been screened. The size of the granules may be
fy at temperatures not substantially above the 55 controlled by varying the intensity of the me
boiling point of water. It is usually convenient
chanical action in breaking up the congealed cake.
to carry out the emulsi?cation at a temperature
The bulk density of the resulting explosive de
between about 80° and 110° C.
pends amongst other factors on the size‘of the
As emulsifying agents there are advantageously
granules, but it will be understood that the in
employed colloidal substances j soluble or swell 60 vention includes not only explosive compositions
able by water and capable of increasing the vis
of coarsely granular form, but also explosive comé'
cosity of the hot aqueous ammonium nitrate solu
positions in which the granules are small, and
tion, for instance agar-agar, sodium alginate', car
which may be described as powders.
' ‘
rageen moss extract, ?our, dextrin, sodium cellu
The granular explosives made according to the
lose glycolate, starch and Various gums. The 65 present invention are characterised by possess
quantity of the emulsifying agent required will
usually liebetween 0.3 per cent and 0.7 per cent
of the dry weight of the emulsion. The emulsi
?cation may be assisted by agitation.‘
If desired, ingredients of various types com 70
monly employed in the manufacture of explosive
compositions may be introduced into the compo
ing desirably low density characteristics, but the
granules of which they are composed are never
theless of a robust character which enables them
to maintain their desirably low density charac
teristics during transport and storage. These ex
plosives also possess other desirable properties,
more particularly, excellent or improved sensi?
sition of the emulsion, in which case they are
tiveness to initiation and low velocity of detona
preferably of an insoluble and infusible typel.
tion. They may be used in quarrying or mining
Cooling or quenching ingredients such as ?uor 75 and are especially suitable on account "of their
DKUDD KU'LKEHUE
DZ. tJ‘JJLUDWE, I’ llluw LUiiHrv
23876155!!! lluunv
.' & MATCH ,COFv'lPOSi’HOiiS
2,409,919
5
low density characteristics for use in situations
where it is desired to break up the material to
be blasted without e?ecting an intensive degree
of comminution, for instance in the winning of
lump .coal. They maintain their solidity and low
density at the climatic storage temperatures used
placed in line“ at, varying distances in a common
paper wrapper, the second cartridge is detonated
by the ?rst at a distance of 4" but not at 5".
Ea'ample 3
Amixture of 73.4 parts ammonium nitrate, 5
parts water,‘and 0.4 part agar-agar are warmed
in testing.
until the agar-agar has dissolved and the tem
Y The unusually low density characteristics of
perature has risen to 85° C. 16.2 parts trini
the explosives of the present invention, however,
are due not only to the granulation of the con 10 trotoluene are'stirred in and the mixture is fur-l
gealed emulsion, but also to the evaporationof
' ther heated to 90° C. and agitated until the mol
drying the granules, therefore, the temperature
ten trinitrotoluene has been emulsi?ed. 10 parts
anhydrite, screened to pass a 40 mesh sieve and
must not be sufficient to cause incipient fusion
to be retained on a 60 mesh B. S. Sieve, are
' they should be packed in containers which will
the impulse of a No. 6 mercury fulminate-po
water from the individual, solid granules.
In
of the granules, which would destroy the desired 1,5 then stirred into the mixture which is kept agi-‘
tated. The mixture is then poured on to a cold
porosity, but as the drying proceeds the drying
surface to form a slabv of about 14" thickness
temperature may, if desired, be progressively in
and crushed into small granules after it has con
creased.
.
gealed. It is dried and screened to pass a 20
The dried granules may advantageously be pro
vided with a coating of a waterproof material, 20 mesh B. S. sieve, and the larger particles re
tained on the sieve are sent for remelting. When
but this is not essential. They should be packed
cartridged in waxed paper tubes at a bulk density
in waterproof containers, and if the granules
of 0.8 the resulting explosive detonates under
have not been coated it is often desirable that
resist the entry of water vapour. It is desirable
that the explosive should contain no ingredient
of a marked deliquescent character.
'
When cooling and ?ame-quenching ingredients
are included, explosives of suitable composition
for blasting in ?ery or gassy mines may also be
made in accordance with the presentinvention.
The invention is further illustrated by the fol
lowing examples, in which the parts are parts b
weight.
.
tassium chlorate detonator at a velocity ofvv 2200
metres per second. Its power is about 71 per
cent. of that of blasting gelatine. In the double;
cartridge test described in Example 2 the second
cartridge was detonated by the ?rst at 3" but
30 not at 4".
7
Example 4
The procedure is the same as that of Example
3 except that talc is used_in place of anhydrite.
The properties of the explosive are generally simi
Example 1
35' lar to that of Example 3.
A mixture of 81.5 parts ammonium nitrate, 6
Example '5 parts water and. 0.5 part agar-agar are heated
until the agar-agar has dissolved and the tem
perature has risen to 81 to 85° C. 18 parts trini
trotoluene are stirred in and the mixture is fur
ther heated to 90° C., by which time the trini
trotoluene has melted, and is stirreduntil 'a well
dispersed pourable emulsion has been formed.
The aqueous emulsion is then-poured on to a
cold surface to form a slab of ‘about 1A inch in
thickness, which is crushed into granules after
it has congealed, and is screened. The parti-'
cles passing a No. 16 and retained by a No. 25
B. S. sieve are then dried off at 35 to 45° C. The
resulting explosive when cooled and cartridged
under a pressure of 75 lbs. per square inch has a
The procedure is the same as in Example 3 ex
cept that fiuorspar is used instead ofv anhydrite.
The properties of the explosive are‘ generally simi
lar to that of Example 3. ‘
Example 6
The’procedure isv the same as that of Example
3 except that limestone,_screened to pass a 60
mesh sieve vbut not to be retained one. 100 'mesh'
B. S. sieve, is used instead of anhydrite, and that
the proportions of the ingredients employed are
ammonium nitrate 65.2 parts, agar-agar 0.4 part,
water 5 parts, limestone 20 parts, trinitrotoluene
14.4 parts. When the dried granules are car
bulk density of 0.7. The explosive has a power
tridged under a pressure of 75 lbs. per square inch
amounting to about 85 per cent. of that of blast
in waxed paper containers the bulk density is 0.8,
ing gelatine, reckoned on a weight basis. The, 55 and the explosive detonates under the impulse of
explosive when initiated by a No. 6 mercury
a No. 6 mercury fulminate-potassium chlorate
fulminate potassium chlorate detonator has a
detonator at a velocity of about 1900 metres per
velocity of detonation of about 2400 metres per
second.
'
second.
60
Example 7
Example 2'
The procedure is the same as in Example 1,
except that the cake of congealed aqueous emul
sion is broken up into smaller particles and after
these have been dried they are screened through
a 25 B. S. S. sieve, all the coarser material be
ing appropriately sized to provide a more coarse
The explosive is prepared as described in Ex
ample 3, except that the proportions of ingre
clients employed are as follows: ammonium ni
trate 69.6 parts, agar-agar 0.4 part, water 5 parts,
65 aluminium 15.0 parts, trinitrotoluene 15 parts.
The bulk density of the explosive when cartridged
under a pressure of 75 lbs. per square inch is
about 0.75, and the explosive is initiated under
25 mesh sieve when cartridged at a pressure of
the impulse of a No. 6 fulminate-potassium chlo
75 lbs. per square inch in a, waxed paper car
tridge has a density of 0.8 and detonates under 70 rate detonator with a velocity of about 2300
metres per second. The power of the explosive is
the impulse of a No. 6 mercury fulminate-po
about 90 per cent. that of blasting gelatine. An
tassium chlorate detonator at a velocity of about
explosive of similar composition made by milling
2,900 metres per second. In a test in which two
together the dry ingredients has a density under
1%" x 3" freshly made cartridges of the same
explosive in their waxed paper wrappers are 75 the same cartridging pressure of about 1.1 and
ly granular explosive. The material passing the
2,409,919
.
detonates. with a velocity of 3600: metres per
second.
l
‘ '
'
>
'
I
.
claim:
8
-
'
l. A process for the manufacture of low" density
'
blasting explosives which comprises emulsifying
Example 8
a molten easily fusible organic explosive with
The explosive is prepared according to the
method of Example 3- except that sodium chloride
isfusedinstead oi anhydrite, and the proportions
oi,( the. ingredients: used are-ammonium nitrate
71.6 parts, sodium chloride. 13 parts, Water 4 parts,
agar-agar 0.4 part and trinitrotoluene 15 parts.
Under a cartridging pressure of 75 lbs. per square 10
inch the bulk density of the dried granules is
about 0.9, andvunvder the impulse. of a No. 6 mer
cury fulminate-potassium chlorate detonator, the
resulting’ explosive detonates with a velocity of
the assistance of an emulsifying agent in an
aqueous medium that‘ comprises a saturated solu
tion of ammonium nitrate carrying solid ammo
nium nitrate in suspension and is free from
readily hydratable salts, this medium being
adapted to yield a pourable emulsion at the emul
si?cation temperature, congealing and granulat
ing the resulting aqueous emulsion and drying
the resulting granules. at a temperature insuf?
cient to cause them. to soften.
2. A process as. claimed in claim 1 wherein the
2200 metres per second. An explosive of similar 15 granulation is carried out by pouring the emul
composition made by a. dry milling process when
sion into the form. of an extended cake or the
cartridged under the same- pressure has a density
like and breaking up the latter mechanically
of about 1.1 and a velocity of detonation of about
when it has congealed.
3500 metres per second.
3; A. process- as claimed in claim 1 wherein the
20
fusible: organic explosive comprises an explosive
Example 9
compound melting at a temperature not substan
' The ingredients used for making the explosive
are 'the- same as in Example 8, but the sodium
tially exceeding the. boiling point of Water.
4. A process as claimed in. claim 1 wherein the
chlo'ride'is mixed with the dried granules of the 25 fusible explosive comprises a mixture of com
solidi?ed emulsion containing only the. ammo
pounds thatv fuses at a temperature not substan
tially exceeding the. boiling point. of water, of
nium nitrate, agar-agar and trinitrotoluene in
which one constituent is a compound melting at
stead-‘of being included in the composition of the
a temperature substantially exceeding the boil
aqueous emulsion. The sodium chloride is em
.
ployed in crystalline form passing a 40‘ mesh 30 ing point of water;
and retained by a 60 mesh 13. S. S. sieve. Under
acartridging pressure of 75 lbs. per square inch
the density is about 0.9,. and the velocity of deto
nation is about 2600 metres per second under the
impulse of a No. 6 mercury fulminate-potassium
chlorate detonator.» In the double cartridge test
the second cartridge is initiated by the ?rst at
4" distance but not at 5"’.
.
. 5. A process as claimed in claim 1 wherein
the fusible. explosive comprises trinitrotoluene.
6. A process as claimed in claim 1 wherein
the emulsi?catio-n is carried out at a temperature
between 80° C. and1l0° C.
7. A process. as claimed in claim, 1 wherein
the quantity of emulsifying agent employed
amounts .to from 0.3 to 0.7 per cent. of the dry
weight. of the emulsion.
1 While in the preceding examples there is illus
trated the‘ use of a- No. 6 mercury fulminate
8... Av process as claimed in claim 1 wherein
the emulsion consists of a mixture. of ammonium
potassium chlorate detonator, all of these explo
nitrate, trinitrotol-uene, an emulsifying agent and
sives when freshly made are capable of being
from 3 to 8. per cent. of water» reckoned on the
initiated by a No. 2 mercury fulminate-potassium
weight. of‘ the emulsion.
chlorate detonator.
The hereinbefore quoted
numerical values for bulk density are reckoned
on" the basis that the bulk density of water is
unity,
- 7' 9.. A process as claimed in ‘claim 1 vwherein
the ammonium nitrate composition contains a
metal powder.
JOHN WHETSTONE.
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