US3449180A - Explosive for blasting agent containing microcrystalline lipophilic ammonium nitrate - Google Patents

Description

United States Patent US. Cl. 149-21 9 Claims ABSTRACT OF THE DISCLOSURE An explosive or blasting agent containing ammonium nitrate, the ammonium nitrate comprising at least in part microcrystalline lipophilic ammonium nitrate. The lipophilic ammonium nitrate is produced by crystallizing concentrated or saturated solutions of ammonium nitrate in the presence of salts of primary amino alkanes in the amount of from 0.1 to 5% by weight, having chainlengths ranging from C to C and in the presence of salts of amino alkanoles in the amount of from 0.2 to 5% by weight, at a temperature between 20 and 90 C.

Numerous explosives are already known which contain ammonium nitrate as one component. These already known explosive mixtures consist, e.g., of 0 to 20% water, 3 to 6% hydrocarbons, and balance ammonium nitrate. These conventional explosive mixtures containing ammonium nitrate may additionally contain parafiin, asphalt, tar, wood pulp, sugar, meal, resins, coal, colloids that swell in water, metal powder, i.e., magnesium powder, aluminum powder, purely metallic alloys or alloys of metals and non-metals, i.e., phosphorus, used in a pulverulent or coarse state, or these materials may replace the above-mentioned hydrocarbons.

Explosives or propellants containing inorganic nitrate, particularly ammonium nitrate, are also known which either contain nitrate as one component or are produced therefrom by treating said nitrate with 0.001 to 1.5 g. alkylamine, with at least 6 carbon atoms in the alkyl group per 100 g. of nitrate. This is to obtain a lower plastic viscosity and a lower yield point in the case of plastic explosives, and a greater density in the case of powdery explosives.

It is the aim of the present invention to improve explosives or blasting agents containing ammonium nitrate insofar as to considerably increase their brisance and ignition sensitivity. The present invention relates to explosives or blasting agents containing ammonium nitrate which has been produced by crystallisation from concentrated or saturated solutions of ammonium nitrate in the presence of salts of primary amino alkanes in the amount of 0.1-5% by weight, preferably 0.2-1% by weight, their chain-lengths ranging from C C preferably from C C The object of the present invention is obtained in that the ammonium nitrate used consists entirely or in part of microcrystalline ammonium nitrate crystallised out in the presence of salts of amino alkanoles in the amount of 0.25% by Weight, preferably 0.4-1% by weight, and at a temperature between 20-90 C., having thus lipophilic characteristics. In this manner a lipophilic ammonium nitrate is produced from a mixture consisting of primary alkyl amines and primary to tertiary alkanolamines which is characterized by the fact that the surfaces of the ammonium nitrate crystals thus formed ice show the physical qualities of a carbon chain, whereby it is made possible that these surfaces hold liquid hydrocarbons or other organic liquids in a thermodynamically stable manner by means of adsorption. When using only alkyl amines this adsorption aflinity towards hydrocarbons at room temperature cannot be maintained and preserved in a stable manner.

Another surprising characteristic of the ammonium nitrate according to the invention is the fact that the natural hydrophilic quality is not lost but even increased, apart from the added lipophilic quality, so that the ammonium nitrate produced according to the invention quite unexpectedly has the characteristic of being hydrophilic or lipophilic at the same time and according to desire.

Furthermore, it ought to be mentioned that ammonium nitrate treated with alkyl amine has the tendency to increase its bulk density which is unfavourable or undesired in certain explosive mixtures. However, the ammonium nitrate produced according to the invention does not show such an increase in the bulk density.

Alkyl amines and alkanolamines, or their organic or inorganic salts, are added by agitation to the available or prepared ammonium nitrate solution, either separatel or in the form of a previously prepared mixture. However, it is also possible to add at first a desired organic or mineral acid, as, i.e., acetic acid or nitric acid, to the ammonium nitrate solution, or to add an acid salt to the said solution, as, i.e., zinc nitrate, consequently adding a corresponding stoichiometrical amount of basic amine mixture in-situ for the purpose of producing a salt.

crystallisation may be efiected by means of generally known devices or methods, e.g., crystallising out a solution by cooling with consequent filtration or centrifuging. A residual l-2% moisture is of no importance. The prepared mixtures may also evaporate in a vacuum at a steady temperature, thereby either obtaining a completely dry product, or interrupting the drying process as soon as the water contents has reached a certain percentage, or

simply cooling the solution without separating the mother liquor, just as desired.

Lipophilic ammonium nitrate as such is an explosive relatively insensitive to ignition. Together with insignificant amounts of high explosives or simply by adding 3 to 6% of a hydrocarbon mixture highly brisant explosives or blasting agents are obtained showing characteristics that cannot be obtained with the same compositions made of conventional, crystalline, pulverulent ammonium nitrate. However, the entire oxidizing agent of the explosive composition does not necessarily have to consist of lipophilic ammonium nitrate; a part of it may be replaced by other salts, as, e.g., sodium nitrate or ammonium perchlorate.

In all explosives which contain ammonium nitrate the brisance and ignition sensitivity is increased if at least part of the ammonium nitrate consists of lipophilic ammonium nitrate. Thus, e.g., it was observed that an explosive mixture consisting of conventional ammonium nitrate, 0-3% water, and 3 to 6% hydrocarbons could not be ignited with a detonator No. 6. However, when using microcrystalline, lipophilic ammonium nitrate for an ammonium nitrate, then already those cartridges with a diameter of 20 mm. may be ignited with a detonator No. 6, ignition being efiected throughout a linear row of at least 30 cartridges with a diameter of 20 mm. and a length of mm.

10% by weight of lipophilic ammonium nitrate usually sufiice to improve the eifect and performance of the detonation.

The superiority of the explosives or blasting agents according to the present invention is demonstrated by the following examples. Examples 1 to 3 are a comparison between embodiments with amino alkanes on the one hand and amino alkanes and amino alkanoles on the other hand. Example 4 demonstrates the necessity to observe the temperatures, Example 5 shows the advantageous characteristic which lies in the fact that the explosive or the blasting agent is not only of a lipophilic but also of a hydrophilic nature, which is quite astonishing when considering that these two qualities actually contradict each other. Examples 6 to 10 relate to a comparison between lipophilic ammonium nitrate and conventional ammonium nitrate. Example 11 describes the production of a slurry explosive by using a cooled solution without separating the mother liquir.

EXAMPLE 1 (A) The following mixture is added to 10 kg. of a 80% ammonium nitrate solution with a temperature of 65 C.:

g. n-dodecylamine acetate, 75 g. triethanolamine acetate.

The amine mixture is homogeneously mixed with the solution and subsequently permitted to cool to room temperature and to crystallise out during 24 hours without agitation. The crystals thus obtained are separated out by means of a Buchner funnel and pressed to a large extent. Analysis showed that the obtained ammonium nitrate still contains 3.2% moisture. Without further drying 200 g. fuel oil No. 4 are added to 4.800 g. lipophilic ammonium nitrate by means of a small laboratory mixer.

(B) The same experiment was carried out at same conditions, however using only 25 g. n-dodecylamine acetate. Now the ultimate moisture amounted to 2.8%. Fuel oil No. 4 was also added to this mixture. By using explosive mixtures A and B the usual explosion characteristics of explosives were determined, which had been permitted to age for 1 day, 1 week, and 1 month.

l After one week mixture B was already insensitive towards detonators No. 6 and N0. 8 and the normal explosion characteristics could not be determined which serves as evidence for the fact that the unstable alkylamine coating (in the absence of alkanolamine) begins to decompose alter the cooling of the ammonium nitrate has come to an end. On the other hand mixture A retained its sensitivity and its explosion characterist cs.

EXAMPLE 2 (A) In a small laboratory vacuum evaporator (contents 20 liter) 12 kg. ammonium nitrate were heated in 2.1 1. water to a temperature of 85 C. Furthermore, g. tetradecylamine lactate and 120 g. 2-amino-2-methyl-1- propanol-lactate were added. Said vacuum evaporator was put into a water bath with a constant temperature of 85 C. Evaporation (at first boiling) was carried on for 3% hours, maintaining a vacuum of 80-30 torr. The product obtained contained 0.32% final moisture.

(B) At the same time a second equivalent chemical was prepared, however without the 2-amino-2-methyl-lpropanol-lactate. This ammonium nitrate contained a moisture of 0.22%. This time the ammonium nitrate of chemicals A and B was preserved without mixing and 4% fuel oil No. 4 was added after 1 week, 1 month, and 6 months.

After a 24-hour aging of these explosive mixtures the explosion characteristics were determined.

6 months 1 month 1 week B B B Excavation value according to Trauzl (net cmfi) Upsetting value according to Hess (dual strength steel disc),

Detonation speed according to Dautriche (zinc pipe. 30 mm. 5), m./sec

Detonation transmission (on sand) in 22 mm. e per 175 mm. length, cm

EXAMPLE 3 Two mixtures A and B were prepared according to Example 2, the only difference being that evaporation was interrupted after 3 hours. The final moisture of this ammonium nitrate was determined by analysis as follows:

In both cases explosive mixtures were produced with 4% diesel oil No. 4 after 1 week, 1 month, and 6 months of storage. Again chemical B was found to be insensitive to detonation. For chemical A the figures obtained were the same as in Examples 1 and 2.

The typical characteristic to be observed was that ammonium nitrate B had turned almost completely into conventional ammonium nitrate after one week, said ammonium nitrate B being of the typical sandy and coarse nature and having furthermore a moist feel to it as if 1.25% water had been admixed to a conventional ammonium nitrate.

On the other hand ammonium nitrate A still proved to be pulverulent, dusty, and of a dry feel, in spite of its similar moisture contents, even after 6 months of storage.

EXAMPLE 4 (A) The following solution was prepared in the laboratory vacuum evaporator of Example 2: 12 kg. ammonium nitrate plus 1.3 1. water, at a temperature of 102 C. 30 g. n-dodecyl-amine acetate and g. dimethyl ethanol amine acetate are added. The temperature of the water bath of the evaporator was adjusted at C.

(B) Another experiment was carried out in the following manner: 12 kg. ammonium nitrate are dissolved in 1.65 1. water at a temperature of 92 C., adding then the same amounts of n-dodecylic amine acetate and dimethyl ethanol amine acetate as in A. The temperature of the water bath of the evaporator was adjusted at 95 C.

(C) A third experiment was carried out, using 12 kg. ammonium nitrate in 2.1 1. water at a temperature of 82 C. and adding the same amounts of n-dodecylamineand dimethyl ethanol amine acetate as in A and B. The temperature of the water bath of the evaporator was kept constantly at 85 C. The period of evaporation was adjusted in such a way as to obtain an ammonium nitrate in the three instances A, B, and C, whose moisture contents ranged between 0.25 and 0.35%.

After a 1-day storage of these ammonium nitrate samples 2 kg. mixtures were produced in the following composition:

96% ammonium nitrate, 4% Fuel oil No. 4.

Excavation value according to Trauzl cm. 300 Upsetting value according to Hess (dual strength steel disc) mm 9.5 Detonation speed according to Dautriche (zinc pipe--30 mm. ..m./sec 3150 Detonation transmission on sand, in 22 mm. per 175 mm. length Zero negative For sample C high performance explosion data, as already known, were found out.

After having stored samples A, B, and C for one week these 2 kg.-mixtures were again prepared, consequentlyobserving an insensitivity towards detonators (No. 6 and No. 8) for chemicals A and B. Chemical C showed the same high performance explosion characteristics as before.

After another l-month and 6-month storage of sample C the corresponding explosive materials ofli'ered excellent explosive performances, very much like those of Example 2.

To round off this series of tests the ammonium nitrate chemicals A, B, and C were repeated again, this time however without adding dimethyl ethanolamine acetate. Just as in the case of the examples described above a rapid insensitivity towards detonators of the corresponding 4% fuel oil mixture was observed.

This series of tests also showed the necessity not to exceed an operating temperature of 90 C.

EXAMPLE 5 5 g. conventional ammonium nitrate and 5 g. ammonium nitrate produced according to the process of the present invention were weighed in two scales of 5 cm. diameter in layers as thin as possible, and then spread out. Both scales were then put into an air-tight glass container with a relative moisture of 75% (adjusted by means of a sulphuric acid solution of adequate vapor pressure). After remaining there for 24 hours analysis showed a 2.1% increase of weight in the case of the conventional ammonium nitrate. With the ammonium nitrate produced according to the method of the present invention the moisture pick up amounted to 7.5% increase of weight. This test was repeated in an atmosphere of 100% relative moisture, observing an increase of weight by 3.3% in the first instance (conventional ammonium nitrate) and a complete dissolution of the material in the second instance (lipophilic ammonium nitrate). These comparative tests serve to demonstrate the unexpectedly greater hidrophilic character of the lipophilic ammonium nitrate.

EXAMPLE 6 In an industrial vacuum evaporator with agitators of an available content of 1000 liter the following components were mixed and dissolved:

100 1. water,

600 kg. ammonium nitrate,

3.7 kg. zinc nitrate hexahydrate,

1.5 kg. n-dodecylamine,

6.0 kg. triethanolamine,

0.010 kg. silicone oil (anti-foam agent).

The heating jacket of the evaporator was adjusted at 81- 83 C. After complete dissolution and mixing a vacuum of 6025 torr. was maintained during 3 hours. The ammonium nitrate obtained, which at the discharge had a temperature of 58 C., was packed into sacks, producing thus several tons of material in the same manner, stored and kept for further tests to be described below.

6 The moisture of the lipophilic ammonium nitrate thus obtained ranged between 0.75 and 1.25%.

EXAMPLE 7 Using the lipophilic ammonium nitrate prepared in Example 6 as original substance the following explosive mixtures were prepared:

A B O D Lipophilic ammonium nitrate 96 93 84 73 Fuel oil N o. 4 4 4 4 3 Aluminum 0 6 12 24 For each of these explosive mixtures the following explosion characteristics could be observed:

In this connection it ought to be taken into considerae tion that pure blasting gelatine in the conventional composition 93/7 (93% nitroglycerine and 7% nitrocellulose) has an average excavation value of 560 cm.

The chosen aluminum quality was of a 99.5% purity and showed the following granulation:

Greater than 600 microns: 1%, Greater than 300 microns: 12%, Greater than 150 microns: 38%, Greater than 75 microns: 64%, Greater than 43 microns: 95%.

It is remarkable that extremely high weight strength (excavation value) is obtained neither when using coarser aluminum powder nor when using an extremely pulverulent, pyrotechnical powder. The excavation values for such mixtures containing a larger percentage of aluminum will generally not exceed 500 cm.

EXAMPLE 8 (A) Using the material of Example 6 as original substance 5 tons explosive in the following composition were produced:

96% lipophilic ammonium nitrate, 4% fuel oil No. 2.

(B) On the other hand 5 tons explosive were produced in the same composition, containing however conventional,

finely ground ammonium nitrate.

(C) Furthermore, 5 tons explosive were mixed in the same composition with a basis of porous prilled ammonium nitrate(prills).

On the basis of comparative explosions in an iron-ore mine with bore holes of 12 m. depth and 15 cm. diameter the following conclusion could be drawn:

Supposing the weight strength of mixture C to have a value of 100 according to definition, then mixture B has the value 104, while mixture A reaches the unexpected value of 127.

The differences are even more remarkable when comparing the brisance of these three types. The average volume of the rock fragments obtained by using mixture A is three times smaller than the one obtained when using mixtures B and C. The necessary secondary explosions after a large-scale detonation with mixture A amounted only to 20% of those necessary after a large-scale detonation with mixture B or C.

EXAMPLE 9 Using 288 kg. of the lipophilic ammonium nitrate of Example 6 an explosive mixture was obtained by adding 12 kg. fuel oil No. 4. With a conventional cartridging device this mixture was packed into cartridges of 22 mm. diameter per mm. length.

An approximately 20 m. long straight gutter was prepared on moistened sand. One after the other 100 of the cartridges mentioned above were put into this gutter. The priming cartridge which consists of the same mixture was initiated with a detonator No. 6. As a result the complete detonation of each of the 100 cartridges was observed.

This example serves as evidence for the excellent ignition sensitivity of the explosive based on lipophilic ammonium nitrate without adding brisant explosives.

However, it ought to be mentioned that, in contrast to conventional dynamites, these mixtures are not sensitive to impact. Comparative falling-weight tests with a drop hammer according to Kast showed that this mixture hardly detonates under the impact of a 5 kg. load which is dropped from a height of 1.5 m. Exactly the same result was obtained when using a pure ammonium nitrate sample. As is known, dynamites, even when pulverulent explosives with a low nitroglycerine content, will explode under the impact of a much smaller force.

EXAMPLE 10 Since direct comparative tests between explosive mixtures produced with lipophilic ammonium nitrate n the one hand and conventional ammonium nitrate on the other hand were not possible since the latter are insensitive towards detonators, the following tests were carried out:

94 parts by weight of finest ground ammonium nitrate was mixed with 4 parts by weight of fuel oil (No. 2 or No. 4), together with 2 parts by weight of liquid nitroglycerine. Although nitroglycerine had been added no sensitivity towards detonators could be observed.

With a second mixture of the same composition, containing however 4 parts by weight of nitroglycerine, only a marginal sensitivity towards detonator No. 8 could be observed. The explosion characteristics of such a mixture were the following:

Excavation value according to Trauzl (net cm. 280 Upsetting value according to Hess (dual strength steel disc) mm 4.7 Detonation speed according to Dautriche (zinc pipe-30 mm. m./sec 2450 Detonation transmission on sand, in 22 mm. per 175 mm. length cm Zero negative EXAMPLE 11 The following amounts of material were charged into a heatable agitating container:

kg. hot water (95 C.),

20 kg. of a 50% calcium nitrate solution (room temperature),

70 kg. ammonium nitrate.

At that point a white, comparatively liquid slurry was obtained. A suspension of 700 g. guar flour and 4.3 kg. fuel oil No. 2 was added, followed by another 5 minutes of mixing. A viscous slurry was obtained which showed an ignition sensitivity when using a 500 g. initiator booster (trinit-rotoluol, nitropenta, etc.) and which could be used for large-scale open pit detonations.

I claim: 1. An explosive agent comprising: ammonium nitrate, said ammonium nitrate comprising at least in part microcrystalline lipophilic ammonium nitrate, and

said lipophilic ammonium nitrate having been produced by crystallizing a concentrated solution of ammonium nitrate in the presence of at least one salt of a primary amino alkane in the amount of from 0.1 to 5% by weight, having a chain-length between C and C and of at least one salt of an amino alkanol in the amount of from 0.2 to 5% by weight, at a temperature between 20 and C.

2. The explosive agent, as set forth in claim 1, wherein:

said amount of said salt of a primary amino alkane is from 0.2 to 1% by weight.

3. The explosive agent, as set forth in claim 1, wherein:

said chain-length of said salt of a primary amino alkane is from C12 to C14- 4. The explosive agent, as set forth in claim 1, wherein:

said amount of said salt of an amino alkano is from 0.4 to 1% by weight.

5. The explosive agent of claim 1 containing between 3% and 6% hydrocarbons.

6. The explosive agent of claim 5 containing between about 3% and 6% fuel oil and containing aluminum powder.

7. The explosive agent of claim 1 wherein at least 10% by weight of the total ammonium nitrate content of said explosive agent is said lipophilic ammonium nitrate.

8. The explosive agent of claim 1, 2, 3, 4, 5, or 7, wherein said salt of an amino alkanol is an arnno ethanol or an amino propanol.

9. The explosive agent of claim 5 or 6 wherein at least 10% by weight of the total ammonium nitrate content of said explosive agent is said lipophilic ammonuim nitrate, and wherein said salt of an amino alkanol is a salt of an amino ethanol or an amino propanol.

References Cited UNITED STATES PATENTS 2,976,137 3/1961 Stengel l4946 X 2,978,864 4/1961 Stengel l4946 X 3,039,903 6/1962 Enokssom l4946 X 3,093,522 6/1963 Stengel et al l4946 3,166,452 l/l965 Gordon l4946 3,166,555 1/1965 Gordon l4946 X 3,303,073 2/1967 Graham l4946 X BENJAMIN R. PADGETT, Primary Examiner.

S. J. LECHERT, Assistant Examiner.

US. 01. X.R. 149 43, 44,46

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,449 ,180 June 10 1969 Marcel Vercauteren It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, line 6, "Zundibutchen" should read Zundhutchen Signed and sealed this 5th day of May 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer