A blasting agent comprising ammonium nitrate, fuel, a nitroalkane and bentonite as a thickening agent.

BACKGROUND OF THE INVENTION 
This invention relates to an improved blasting agent. In a particular 
aspect this invention relates to a blasting agent characterized by high 
density with good sensitivity. 
It is known from Lawrence, U.S. Pat. No. 2,325,064, to prepare an explosive 
composition from a nitroalkane of 1-3 carbon atoms, ammonium nitrate and a 
carbonaceous material such as wood flour, ivory meal, coal and the like. 
Such compositions proved satisfactory provided they were used promptly 
after preparation. However, they lost sensitivity with the passage of time 
and, hence, proved unreliable in field use. It was discovered that this 
loss of sensitivity was due to lack of affinity between the ammonium 
nitrate and the nitroalkane, so that the latter collected in the bottom 
portion of the container. The composition, therefore, became insensitive 
to the usual detonating devices. Accordingly, there exists a need for 
providing a means of maintaining a mixture of nitroalkane, ammonium 
nitrate and a carbonaceous material in a relatively homogeneous state. 
Also, advantageously the composition should have a high density so that it 
will sink in wet bore holes, i.e. holes having an appreciable water level. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide an improved blasting agent. 
It is another object of this invention to provide an improved blasting 
agent having a high density with good sensitivity. 
Other objects of this invention will be apparent to those skilled in the 
art from the description herein. 
It is the discovery of this invention to provide an improved blasting agent 
comprising ammonium nitrate, a nitroalkane, fuel oil and bentonite as a 
thickener therefor. The composition is characterized by high density, good 
sensitivity, and retains sensitivity well. 
DETAILED DESCRIPTION 
The blasting agent of this invention comprises ammonium nitrate in an 
amount of about 86% by weight mixed with about 10% by weight of a fuel 
composition and about 4% of a thickening agent therefor. It is understood 
that these quantities are the preferred quantities. It is not intended 
they be precise and considerable variation therefrom is permissible 
without adversely affecting the sensitivity. For example, the fuel may 
vary form about 8 to about 14%, and the bentonite may vary from about 2 to 
about 8%; the remainder being ammonium nitrate. 
The fuel component of the blasting agent comprises a mixture of nitroalkane 
of 1 to 3 carbon atoms and fuel oil in a ratio of from about 1:1 by weight 
to about 4:1. The nitroalkane can be nitromethane, nitroethane, or 
preferably nitropropane, or mixtures thereof. Either 1-nitropropane or 
2-nitropropane may be used with equally good results. When nitromethane is 
used as the nitroalkane, the mixture is sufficiently shock sensitive to be 
classified as an explosive by Department of Transportation tests. When 
nitroalkanes of 2-3 carbon atoms are used, the sensitivity is that of 
nitro-carbo-nitrates. 
The fuel oil useful in the practice of this invention is known in the art 
and any type of such oil is suitable. The invention is not limited to any 
particular type or grade. However, the grade known as No. 2 is commonly 
used in the art and is suitable for the practice of this invention. 
The ammonium nitrate used in the practice of this invention is a mixture of 
low density, explosive grade ammonium nitrate prills, as known in the art, 
and comminuted material. The comminuted ammonium nitrate can be used in an 
amount of from 20% to 80% of the total, preferably 50% by weight. 
The bentonite used in the practice of this invention can be either the 
Southern or the Western type in an amount of about 2 to about 8% of the 
total composition, preferably about 4%. Preferably, the bentonite is 
comminuted, e.g. about -200 mesh. The bentonite is primarily useful in 
preventing the liquid fuel component from draining off the ammonium 
nitrate solids and puddling in the bottom of the bag. In the absence of 
bentonite, this puddling develops rather rapidly on standing and the 
mixture becomes insensitive, failing to detonate when initiation is 
attempted. The bentonite has the added advantages contributing to a higher 
density mixture and tending to stabilize it to shock without unduly 
desensitizing it. 
The composition of this invention is readily prepared by mixing the 
ingredients in a conventional manner and discharging the mixture into 
suitable containers, e.g. plastic bags. 
The composition is especially useful in bore holes. It is heavier than 
water, so if water collects in the bore hole, the blasting agent sinks 
without difficulty. It can be detonated by the usual boosters and primers, 
as known in the art, preferably a cast primer. Also at least two primers 
should be used in each column of blasting agent, and under extremely 
severe loading conditions, or where powder column separations ae possible, 
additional primers should be used to preclude cutoffs. 
The composition has a detonation rate, 5 in. diameter unconfined, of 11,250 
feet per second and a detonation pressure of 34 Kbar. It is not cap 
sensitive and is not detonated by the impact of a 30 calibre rifle bullet. 
Typically it will have the following composition and properties. 
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Ammonium nitrate 86% 
Whole prills 43% 
Ground prills 43% 
Nitroalkane 5% 
Fuel oil 5% 
Bentonite 4% 
Total 100% 
Specific gravity, min. 1.10 
Density 1.22 
Rate of detonation* 11,250 fps 
Detonation pressure* 34 Kbar 
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*5 in. diameter unconfined 
It is an embodiment of this invention to provide a finished, packaged 
blasting agent comprising the blasting agent described hereinbefore 
packaged in a nylon bag of from 4 to 8 inches in diameter. The nylon is at 
least 1.25 mil thickness, there being no upper limit as to thickness. 
However, 1 mil thickness nylon film is relatively easily torn and 
punctured and because heavier gauge nylon is relatively expensive, it is 
preferred to employ the nylon bag in conjunction with polyethylene. The 
nylon can be laminated to the polyethylene or it can merely be formed into 
a bag heat sealed at one end and inserted in a polyethylene bag, also heat 
sealed at one end. Such a packaging system wherein the nylon is of from 1 
to 2 mil and the polyethylene is from 4-5 mil has proven very successful. 
Nylon is the only film so far discovered which will contain nitroalkanes 
for a satisfactory shelf-life period. All others tested have apertures and 
voids, which, though microscopic, are sufficient to permit the nitroalkane 
to evaporate and the blasting agent thereby becomes insensitive and 
useless.

The invention will be better understood with reference to the following 
examples. It is understood, however, that the examples are intended only 
to illustrate the invention, and it is not intended that the invention be 
limited thereby. 
EXAMPLE 1 
A sample of explosive grade, uncoated, prilled ammonium nitrate was ground 
through a 1/8inch screen manufactured by the Gruendler Corporation. The 
comminuted material was mixed wth unground prills in a 1:1 by weight 
ratio. The mixture had the following screen analysis: 
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+18 58.75% 
+35 16.25% 
+60 12.5% 
+80 3.75% 
+120 3.75% 
+230 3.75% 
-230 1.25% 
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The mixed ammonium nitrate, 86 g, was then mixed with No 2 fuel oil 2.8 g, 
2-nitropropane 6.5 g and 200-mesh bentonite 4.7 g. The mixture had a 
standard density of 1.32 and after standing 24 hours was sensitive to the 
shock of 20 g of Pentolite (a mixture of pentaerythritol tetranitrate and 
trinitrotoluene). The unconfined rate of detonation in a 3-inch diameter 
column was 2691 m/sec (8826 ft/sec) and in a 1.5".times.12" pipe, it was 
3355.5 m/sec (11,006 ft/sec). 
The mixture was used to fill a four and one-half inch diameter nylon bag of 
1.25 mil thichness, heat sealed on one end and encased in a 4 mil 
polyethylene bag. The 2-NP and fuel oil did not drain away and pool at the 
bottom and the mixture retained good sensitivity on standing. A similar 
mixture but wthout the bentonite was prepared and similarly packaged in a 
nylon bag with polyethylene outer bag. Upon standing a brief period, the 
liquid portion drained away from the ammonium nitrate in the upper portion 
of the bag and puddled in the bottom of the bag. The mixture was 
insensitive and did not detonate on initiation. 
EXAMPLE 2 
The experiment of Example 1 was repeated in all essential details except 
that a 1:1 mixture by weight of 1-nitropropane (1-NP) and 2-nitropropane 
(2-NP) was used in place of 2-NP alone. The resulting mixture was 
satisfactory in all respects. 
EXAMPLE 3 
The experiment of Example 1 was repeated in all essential details except 
that 1-nitropropane was substituted for the 2-nitropropane. The resulting 
mixture was satisfactory in all respects. 
EXAMPLE 4 
The experiment of Example 1 was repeated in all essential details except 
that nitroethane was substituted for the 2-nitropropane. The resulting 
mixture was satisfactory in all respects. 
EXAMPLE 5 
The experiment of Example 1 is repeated in all essential details except 
that the 2-nitropropane and fuel oil are used in equal parts by weight. 
The resulting mixture was satisfactory in all respects. 
EXAMPLE 6 
The experiment of Example 1 is repeated in all essential details except 
that nitromethane is used as the nitroalkane. The resulting mixture is 
satisfactory in all respects. It is sensitive to the shock of a No. 8 cap.